Electrolyte solution, electrochemical device, lithium ion secondary battery, and assembly

文档序号：1246841 发布日期：2020-08-18 浏览：6次中文

阅读说明：本技术 电解液、电化学器件、锂离子二次电池及组件 (Electrolyte solution, electrochemical device, lithium ion secondary battery, and assembly ) 是由桑岛佳子山内昭佳铃木悠希林航太郎仲村尚子山田贵哉下冈俊晴山本祯洋山崎于 2019-01-09 设计创作，主要内容包括：本发明提供能够提高电化学器件的高温保存特性和循环特性的电解液。上述电解液含有通式(1-1)(式中,R101为可以被氟代的碳原子数1～7的烷基等,在结构中也可以含有O等。)以及通式(1-2)(式中,R102和R103(i)相互独立地为H、F、可以被氟代的碳原子数1～7的烷基等,或者(ii)为相互连结而与氮原子一起形成5元或6元杂环的烃基,在结构中也可以含有O等。)表示的化合物中的至少1种。<Image he="693" wi="700" file="DDA0002567037320000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The invention provides an electrolyte solution capable of improving high-temperature storage characteristics and cycle characteristics of an electrochemical device. The above electricityThe electrolyte solution contains a compound represented by the general formula (1-1) (wherein R is 101 The fluorinated alkyl group has 1 to 7 carbon atoms and may contain O or the like in the structure. ) And general formula (1-2) (wherein R 102 And R 103 (i) H, F independently of each other, a C1-7 alkyl group which may be fluorinated, or (ii) a hydrocarbon group which is linked to each other to form a 5-or 6-membered heterocyclic ring together with the nitrogen atom, and may contain O or the like in the structure. ) At least 1 of the compounds represented.)

1. An electrolytic solution characterized by containing at least 1 selected from the group consisting of compounds represented by the following general formulae (1-1) and (1-2),

general formula (1-1):

in the formula, R¹⁰¹A fluorinated or non-fluorinated alkyl group having 1 to 7 carbon atoms, a fluorinated or non-fluorinated alkenyl group having 2 to 8 carbon atoms, a fluorinated or non-fluorinated alkynyl group having 2 to 9 carbon atoms, or a fluorinated or non-fluorinated aryl group having 6 to 12 carbon atoms, and may contain at least one member selected from the group consisting of O, Si, S and N in the structure;

general formula (1-2):

in the formula, R¹⁰²And R¹⁰³(i) H, F, a fluorinated or non-fluorinated alkyl group having 1 to 7 carbon atoms, a fluorinated or non-fluorinated alkenyl group having 2 to 7 carbon atoms, a fluorinated or non-fluorinated alkynyl group having 2 to 9 carbon atoms, or a fluorinated or non-fluorinated aryl group having 5 to 12 carbon atoms, or (ii) a hydrocarbon group which is linked to each other to form a 5-or 6-membered heterocyclic ring together with the nitrogen atom; r¹⁰²And R¹⁰³At least 1 selected from O, S and N is contained or not contained in the structure.

2. An electrochemical device comprising the electrolyte solution according to claim 1.

3. A lithium ion secondary battery comprising the electrolyte solution according to claim 1.

4. An assembly comprising the electrochemical device according to claim 2 or the lithium-ion secondary battery according to claim 3.

5. A compound represented by the following general formula (11):

in the formula, R¹¹¹Is a fluoroalkenyl group having 2 to 7 carbon atoms, a fluoroalkynyl group having 2 to 7 carbon atoms, a non-fluorinated alkynyl group having 5 to 9 carbon atoms, or a fluorinated or non-fluorinated aryl group having 6 to 12 carbon atoms, and may or may not contain at least 1 selected from O and Si in the structure.

6. A compound represented by the following general formula (12):

in the formula, R¹¹²And R¹¹³(i) Independently of each other, F, a non-fluorinated alkyl group having 1 to 7 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, a fluorinated or non-fluorinated alkenyl group having 3 to 7 carbon atoms or a fluorinated or non-fluorinated alkynyl group having 3 to 7 carbon atoms, and R¹¹²And R¹¹³At least one of F, a non-fluorinated alkyl group having 3 to 7 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, a fluorinated or non-fluorinated alkenyl group having 3 to 7 carbon atoms, or a fluorinated or non-fluorinated alkynyl group having 3 to 7 carbon atoms, or (ii) a hydrocarbon group which is linked to each other to form a 5-or 6-membered heterocyclic ring together with a nitrogen atom; r¹¹²And R¹¹³At least 1 selected from O, S and N is contained or not contained in the structure.

Technical Field

The invention relates to an electrolyte, an electrochemical device, a lithium ion secondary battery and a module.

Background

With the recent weight reduction and size reduction of electric products, development of electrochemical devices such as lithium ion secondary batteries having high energy density has been advanced. In addition, as the application field of electrochemical devices such as lithium ion secondary batteries is expanded, improvement of characteristics is required. In particular, when a lithium ion secondary battery is used for vehicle-mounted applications in the future, improvement of battery characteristics is becoming more and more important.

Patent document 1 describes an electrolytic solution containing a compound such as methyl acrylate.

Patent document 2 describes an electrolytic solution containing a compound such as N, N-dimethylacrylamide.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. 2001-185212

[ patent document 2] Japanese patent laid-open No. 2003-86246

Disclosure of Invention

[ problem to be solved by the invention ]

The invention aims to provide an electrolyte solution capable of improving high-temperature storage characteristics and cycle characteristics of an electrochemical device, and an electrochemical device provided with the electrolyte solution.

It is also an object of the present invention to provide novel fluoroacrylate compounds and fluoroacrylamide compounds.

[ MEANS FOR SOLVING PROBLEMS ] to solve the problems

The present invention relates to an electrolyte solution characterized by containing at least 1 selected from the compounds represented by the following general formulae (1-1) and (1-2).

General formula (1-1):

[ CHEM 1]

(in the formula, R¹⁰¹An optionally fluorinated alkyl group having 1 to 7 carbon atoms, an optionally fluorinated alkenyl group having 2 to 8 carbon atoms, an optionally fluorinated alkynyl group having 2 to 9 carbon atoms, or an optionally fluorinated aryl group having 6 to 12 carbon atomsIn the structure, at least one selected from O, Si, S and N may be contained. )

General formula (1-2):

[ CHEM 2]

(in the formula, R¹⁰²And R¹⁰³(i) H, F, an alkyl group having 1 to 7 carbon atoms which may be fluorinated, an alkenyl group having 2 to 7 carbon atoms which may be fluorinated, an alkynyl group having 2 to 9 carbon atoms which may be fluorinated, or an aryl group having 5 to 12 carbon atoms which may be fluorinated, or (ii) a hydrocarbon group which is linked to each other to form a 5-or 6-membered heterocyclic ring together with the nitrogen atom. R¹⁰²And R¹⁰³At least 1 selected from O, S and N may be contained in the structure. )

The present invention also relates to an electrochemical device comprising the electrolyte solution.

The present invention also relates to a lithium ion secondary battery comprising the above electrolyte solution.

The present invention also relates to a module provided with the electrochemical device or the lithium-ion secondary battery.

The present invention relates to a compound represented by the following general formula (11):

[ CHEM 3]

(in the formula, R¹¹¹The fluorinated alkyl group may have a fluoroalkenyl group having 2 to 7 carbon atoms, a fluoroalkynyl group having 2 to 7 carbon atoms, an unfluorinated alkynyl group having 5 to 9 carbon atoms, or an aryl group having 6 to 12 carbon atoms which may be fluorinated, and may contain at least 1 selected from O and Si in the structure. ).

The present invention relates to a compound represented by the following general formula (12):

[ CHEM 4 ]

(in the formula, R¹¹²And R¹¹³(i) Independently of each other, F, a non-fluorinated alkyl group having 1 to 7 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, an alkenyl group having 3 to 7 carbon atoms which may be fluorinated, or an alkynyl group having 3 to 7 carbon atoms which may be fluorinated, and R¹¹²And R¹¹³At least one of F, a non-fluorinated alkyl group having 3 to 7 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, an alkenyl group having 3 to 7 carbon atoms which may be fluorinated, or an alkynyl group having 3 to 7 carbon atoms which may be fluorinated, or (ii) a hydrocarbon group which is linked to each other to form a 5-or 6-membered heterocyclic ring together with a nitrogen atom. R¹¹²And R¹¹³At least 1 selected from O, S and N may be contained in the structure. ).

[ Effect of the invention ]

The electrolyte solution of the present invention can improve high-temperature storage characteristics and cycle characteristics of an electrochemical device. The electrochemical device having the electrolyte solution is excellent in high-temperature storage characteristics and cycle characteristics.

In addition, according to the present invention, a novel fluoroacrylate compound and fluoroacrylamide compound can be provided.

Detailed Description

The present invention will be specifically described below.

The electrolyte solution of the present invention is characterized by containing at least 1 kind (hereinafter, also referred to as compound (1)) selected from compounds represented by the following general formulae (1-1) and (1-2).

General formula (1-1):

[ CHEM 5]

General formula (1-2):

[ CHEM 6 ]

By virtue of the above features, the electrolyte of the present invention can improve high-temperature storage characteristics and cycle characteristics of an electrochemical device.

In addition, in order to improve the characteristics of nonaqueous electrolyte secondary batteries, electrolytes containing various additives, such as: vinylene carbonate and its derivatives (Japanese patent application laid-open No. 8-45545), and halogen atom-substituted cyclic carbonates (International patent publication No. 98/15024). However, in the electrolyte solution containing these compounds, the compounds are reductively decomposed on the surface of the negative electrode to form a coating, and excessive decomposition of the electrolyte solution is suppressed by the coating, which has the effect of improving the charge-discharge cycle, while there is a problem that a large amount of gas is generated when the secondary battery is stored under high-temperature environment and high-voltage condition, or when the charge-discharge cycle is repeated. The electrolyte solution of the present invention contains the compound (1), and thus can suppress the amount of gas generated during high-temperature storage or during charge and discharge cycles, and can improve battery characteristics.

The compound (1) is at least 1 compound selected from the group consisting of the compound (1-1) represented by the general formula (1-1) and the compound (1-2) represented by the general formula (1-2).

In the general formula (1-1), R¹⁰¹The fluorinated alkyl group has 1 to 7 carbon atoms, 2 to 8 carbon atoms, 2 to 9 carbon atoms or 6 to 12 carbon atoms, and may be fluorinated, and may contain at least one selected from the group consisting of O, Si, S and N.

As R¹⁰¹The alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms.

The alkyl group may be a non-fluorinated alkyl group or a fluorinated alkyl group, and may contain at least 1 selected from the group consisting of O, Si, S and N in the structure. The alkyl group may have a ring structure. The ring may be aromatic.

As R¹⁰¹Examples of the alkyl group in (1) include a methyl group (-CH)₃) Ethyl (-CH)₂CH₃) Propyl (-CH)₂CH₂CH₃) Isopropyl (-CH (CH)₃)₂) N-butyl (-CH)₂CH₂CH₂CH₃) And the like non-fluorinated alkyl groups; -CF₃、-CF₂H、-CFH₂、-CF₂CF₃、-CF₂CF₂H、-CF₂CFH₂、-CH₂CF₃、-CH₂CF₂H、-CH₂CFH₂、-CF₂CF₂CF₃、-CF₂CF₂CF₂H、-CF₂CF₂CFH₂、-CH₂CF₂CF₃、-CH₂CF₂CF₂H、-CH₂CF₂CFH₂、-CH₂CH₂CF₃、-CH₂CH₂CF₂H、-CH₂CH₂CFH₂、-CF(CF₃)₂、-CF(CF₂H)₂、-CF(CFH₂)₂、-CH(CF₃)₂、-CH(CF₂H)₂、-CH(CFH₂)₂、-CH₂CF(CF₃)OC₃F₇、-CH₂CF₂OCF₃Isofluoroalkyl groups; -CH₂Si(CH₃)₃or-CH₂CH₂Si(CH₃)₃And trialkylsilylalkyl groups.

Further, there may be mentioned a cycloalkyl group and an alkyl group having an aromatic ring, each of which is represented by the following formula and may have a structure containing at least 1 kind selected from O, Si, S and N.

[ CHEM 7 ]

Among the above alkyl groups, preferred are methyl, ethyl and-CH₂CF₃、-CH₂CF₂H、-CH₂CFH₂、-CH₂CF₂CF₃、-CH₂CF₂CF₂H、-CH₂CF₂CFH₂、-CH₂Si(CH₃)3。

AsR¹⁰¹The number of carbon atoms of the alkenyl group is preferably 2 to 6, more preferably 2 to 5.

The alkenyl group may be a non-fluorinated alkenyl group or a fluorinated alkenyl group, and may contain at least 1 selected from O, Si, S and N in the structure.

As R¹⁰¹Examples of the alkenyl group in (1) include a vinyl group (-CH ═ CH)₂) 1-propenyl (-CH ═ CH-CH)₃) 1-methylethenyl (-C (CH)₃)＝CH₂) 2-propenyl (-CH)₂-CH＝CH₂) 1-butenyl (-CH ═ CH-CH)₂CH₃) 2-methyl-1-propenyl (-CH ═ C (CH)₃)-CH₃) 1-methyl-1-propenyl (-C (CH)₃)＝CH-CH₃) 1-ethylvinyl (-C (CH)₂CH₃)＝CH₂) 2-butenyl (-CH)₂-CH＝CH-CH₃) 2-methyl-2-propenyl (-CH)₂-C(CH₃)＝CH₂) 1-methyl-2-propenyl (-CH (CH)₃)-CH＝CH₂) 3-butenyl (-CH)₂CH₂-CH＝CH₂) 1-methylene-2-propenyl (-CH)₂)-CH＝CH₂)1, 3-butadienyl (-CH ═ CH)₂)2, 3-butadienyl (-CH)₂-CH＝C＝CH₂) 1-methyl-1, 2-allenyl (-C (CH)₃)＝C＝CH₂)1, 2-butadienyl (-CH ═ C ═ CH-CH)₃) 2-pentenyl (-CH)₂-CH＝CH-CH₂CH₃) 2-ethyl-2-propenyl (-CH)₂-C(CH₂CH₃)＝CH₂) 1-ethyl-2-propenyl (-CH (CH)₂CH₃)-CH＝CH₂) 3-pentenyl (-CH)₂CH₂-CH＝CH-CH₃) And groups in which at least 1 hydrogen atom is replaced by a fluorine atom.

Further, there may be mentioned cycloalkenyl groups represented by the following formulae, and groups in which at least 1 hydrogen atom is replaced with a fluorine atom.

[ CHEM 8 ]

As the above alkenyl group, among them, 2-propenyl (-CH) is preferable₂-CH＝CH₂) 3-butenyl (-CH)₂CH₂-CH＝CH₂) 2-butenyl (-CH)₂-CH＝CH-CH₃) 2-methyl-2-propenyl (-CH)₂-C(CH₃)＝CH₂) 2-pentenyl (-CH)₂-CH＝CH-CH₂CH₃)，

[ CHEM 9 ]

And those in which at least 1 hydrogen atom is replaced by a fluorine atom, more preferably 2-propenyl (-CH)₂-CH＝CH₂) 2-butenyl (-CH)₂-CH＝CH-CH₃) 2-pentenyl (-CH)₂-CH＝CH-CH₂CH₃，

[ CHEM 10 ]

And those in which at least 1 hydrogen atom is replaced by a fluorine atom.

As R¹⁰¹The alkynyl group in the above-mentioned (C) is preferably 3 to 9, more preferably 3 to 4 or 6 to 9.

The alkynyl group may be a non-fluorinated alkynyl group or a fluorinated alkynyl group, and may contain at least 1 kind selected from O, Si, S and N in the structure.

As R¹⁰¹Examples of the alkynyl group in (1) include an ethynyl group (-C.ident.CH) and a 1-propynyl group (-C.ident.C-CH)₃) 2-propynyl (-CH)₂-C.ident.CH), 1-butynyl (-C.ident.C-CH)₂CH₃) 2-butynyl (-CH)₂-C≡C-CH₃) 3-butynyl (-CH)₂CH₂-C.ident.CH), 1-pentynyl (-C.ident.C-CH)₂CH₂CH₃) 2-pentynyl (-CH)₂-C≡C-CH₂CH₃) 3-pentynyl (-CH)₂CH₂-C≡C-CH₃) 4-pentynyl (-CH)₂CH₂CH₂-C≡CH)，-CH₂-C≡C-TMS、-CH₂-C≡C-TES、-CH₂-C≡C-TBDMS、-CH₂-C≡C-Si(OCH₃)₃、-CH₂-C≡C-Si(OC₂H₅)₃And groups in which at least 1 hydrogen atom is replaced by a fluorine atom.

TMS represents-Si (CH)₃)₃TES represents-Si (C)₂H₅)₃TBDMS represents-Si (CH)₃)₂C(CH₃)₃。

As the alkynyl group, among them, 2-propynyl (-CH) is preferred₂-C ≡ CH), 2-butynyl (-CH)₂-C≡C-CH₃)，-CH₂-C≡C-TMS、-CH₂-C.ident.C-TBDMS and groups thereof in which at least 1 hydrogen atom is replaced by a fluorine atom, more preferably 2-propynyl (-CH)₂-C≡CH)、-CH₂-C≡CF、-CH₂-C≡C-CF₃、-CH₂-C≡C-TMS、-CH₂-C≡C-TBDMS。

As R¹⁰¹The aryl group in (2) is a group obtained by removing 1 hydrogen atom from an aromatic ring, and preferably contains a 6-membered aromatic hydrocarbon ring, and is preferably monocyclic or bicyclic.

The aryl group may be a non-fluorinated aryl group or a fluorinated aryl group, and may contain at least 1 selected from O, Si, S and N in the structure.

Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a methoxybenzyl group, a naphthyl group, and the like, and these groups may or may not have a fluorine atom. Among them, preferred is a phenyl group which may have a fluorine atom, and more preferred is a phenyl group which does not have a fluorine atom.

As R¹⁰¹The preferred one is an alkenyl group which may be fluorinated or an alkynyl group which may be fluorinated.

Examples of the compound (1-1) include compounds represented by the following formulae.

[ CHEM 11 ]

[ CHEM 12 ]

[ CHEM 13 ]

Among the compounds (1-1), preferred is a compound represented by the following formula.

[ CHEM 14 ]

[ CHEM 15 ]

Among the compounds (1-1), the compounds represented by the following formulae are particularly preferred.

[ CHEM 16 ]

Among the compounds (1-1), the compound (11) characterized by the following general formula (11) is a novel compound. The present invention also relates to compound (11).

[ CHEM 17 ]

In the general formula (11), R¹¹¹Is a C2-7 fluoroalkenyl group, a C2-7 fluoroalkynyl group, a C5-9 non-fluorinated alkynyl group, or a fluorinated alkynyl groupThe aryl group having 6 to 12 carbon atoms of (1) may contain at least 1 kind selected from O and Si in the structure.

As R¹¹¹The number of carbon atoms of the fluoroalkenyl group is preferably 2 to 6, more preferably 2 to 5.

The fluoroalkenyl group may contain at least 1 selected from O and Si in the structure.

As R¹¹¹Examples of the above-mentioned fluoroalkenyl group include those in which at least 1 hydrogen atom is replaced by a fluorine atom: vinyl (-CH ═ CH)₂) 1-propenyl (-CH ═ CH-CH)₃) 1-methylethenyl (-C (CH)₃)＝CH₂) 2-propenyl (-CH)₂-CH＝CH₂) 1-butenyl (-CH ═ CH-CH)₂CH₃) 2-methyl-1-propenyl (-CH ═ C (CH)₃)-CH₃) 1-methyl-1-propenyl (-C (CH)₃)＝CH-CH₃) 1-ethylvinyl (-C (CH)₂CH₃)＝CH₂) 2-butenyl (-CH)₂-CH＝CH-CH₃) 2-methyl-2-propenyl (-CH)₂-C(CH₃)＝CH₂) 1-methyl-2-propenyl (-CH (CH)₃)-CH＝CH₂) 3-butenyl (-CH)₂CH₂-CH＝CH₂) 1-methylene-2-propenyl (-CH)₂)-CH＝CH₂)1, 3-butadienyl (-CH ═ CH)₂)2, 3-butadienyl (-CH)₂-CH＝C＝CH₂) 1-methyl-1, 2-allenyl (-C (CH)₃)＝C＝CH₂)1, 2-butadienyl (-CH ═ C ═ CH-CH)₃) 2-pentenyl (-CH)₂-CH＝CH-CH₂CH₃) 2-ethyl-2-propenyl (-CH)₂-C(CH₂CH₃)＝CH₂) 1-ethyl-2-propenyl (-CH (CH)₂CH₃)-CH＝CH₂) And 3-pentenyl (-CH)₂CH₂-CH＝CH-CH₃)。

Among the above fluoroalkenyl groups, 2-propenyl (-CH) is preferred₂-CH＝CH₂) 2-butenyl (-CH)₂-CH＝CH-CH₃) And 2-pentenyl (-CH)₂-CH＝CH-CH₂CH₃) InAnd at least 1 hydrogen atom is substituted by a fluorine atom.

As R¹¹¹The number of carbon atoms of the above-mentioned fluoroalkynyl group is preferably 2 to 6, more preferably 3 to 5.

The above-mentioned fluoroalkynyl group may contain at least 1 selected from O and Si in the structure.

As R¹¹¹Examples of the above-mentioned fluoroalkynyl group include those in which at least 1 hydrogen atom is replaced by a fluorine atom: ethynyl (-C ≡ CH), 1-propynyl (-C ≡ C-CH)₃) 2-propynyl (-CH)₂-C.ident.CH), 1-butynyl (-C.ident.C-CH)₂CH₃) 2-butynyl (-CH)₂-C≡C-CH₃) 3-butynyl (-CH)₂CH₂-C.ident.CH), 1-pentynyl (-C.ident.C-CH)₂CH₂CH₃) 2-pentynyl (-CH)₂-C≡C-CH₂CH₃) 3-pentynyl (-CH)₂CH₂-C≡C-CH₃) And 4-pentynyl (-CH)₂CH₂CH₂-C≡CH)。

Among the above-mentioned fluorinated alkynyl groups, 2-propynyl (-CH) is preferable₂-C ≡ CH) and 2-butynyl (-CH)₂-C≡C-CH₃) In (2), a group in which at least 1 hydrogen atom is substituted with a fluorine atom is more preferably-CH₂-C≡CF、-CH₂-C≡C-CF₃。

As R¹¹¹The non-fluorinated alkynyl group in (1) may contain at least 1 selected from O and Si in the structure.

As R¹¹¹As the above-mentioned non-fluorinated alkynyl group, 1-pentynyl (-C.ident.C-CH) may be mentioned₂CH₂CH₃) 2-pentynyl (-CH)₂-C≡C-CH₂CH₃) 3-pentynyl (-CH)₂CH₂-C≡C-CH₃) 4-pentynyl (-CH)₂CH₂CH₂-C≡CH)，-CH₂-C≡C-TMS、-CH₂-C≡C-TES、-CH₂-C≡C-TBDMS、-CH₂-C≡C-Si(OCH₃)₃、-CH₂-C≡C-Si(OC₂H₅)₃And the like.

As aboveFluorinated alkynyl group, among them, 2-pentynyl (-CH) is preferable₂-C≡C-CH₂CH₃) 3-pentynyl (-CH)₂CH₂-C≡C-CH₃)、-CH₂-C≡C-TMS、-CH₂-C≡C-TBDMS。

As R¹¹¹The aryl group in (2) is a group obtained by removing 1 hydrogen atom from an aromatic ring, and preferably contains a 6-membered aromatic hydrocarbon ring, and is preferably monocyclic or bicyclic.

The aryl group may be a non-fluorinated aryl group or a fluorinated aryl group, and may contain at least 1 selected from O and Si in the structure.

As R¹¹¹The fluorinated alkenyl group and the non-fluorinated alkynyl group are preferable.

Examples of the compound (11) include compounds represented by the following formulae.

[ CHEM 18 ]

[ CHEM 19 ]

Among the compounds (11), preferred is a compound represented by the following formula.

[ CHEM 20 ]

The compound (11) is preferably produced by a production method including the step (1-1) of reacting the compound (a) represented by the following general formula (a) with the compound (b) represented by the following general formula (b) to obtain the compound (11) represented by the above general formula (11), but the production method is not limited thereto.

General formula (a):

[ CHEM 21 ]

(in the formula, X¹⁰¹Is a halogen atom. )

General formula (b): r¹¹¹-OH (in the formula, R)¹¹¹As described above. .

In the general formula (a), X¹⁰¹Is a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and among them, a fluorine atom is preferable.

In the reaction in the step (1-1), the compound (b) is preferably used in an amount of 0.5 to 2.0mol, more preferably 0.7 to 1.3 mol, and still more preferably 0.9 to 1.1 mol, based on 1 mol of the compound (a).

The reaction in the step (1-1) is preferably carried out in the presence of a base. Examples of the base include amines and inorganic bases.

Examples of the amine include triethylamine, tri (N-propyl) amine, tri (N-butyl) amine, diisopropylethylamine, cyclohexyldimethylamine, pyridine, lutidine, γ -collidine, N, N-dimethylaniline, N-methylpiperidine, N-methylpyrrolidine, N-methylmorpholine, 1, 8-diazabicyclo [5.4.0] -7-undecene (DBU), 1, 5-diazabicyclo [4.3.0] -5-nonene, 1, 4-diazabicyclo [2.2.2] octane (DABCO), 4-Dimethylaminopyridine (DMAP), and proton sponge.

Examples of the inorganic base include lithium hydroxide, potassium hydroxide, sodium hydroxide, calcium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, cesium carbonate, cesium hydrogencarbonate, lithium hydrogencarbonate, cesium fluoride, potassium fluoride, sodium fluoride, lithium chloride, lithium bromide, and the like.

Among the bases, amines are preferable, and triethylamine and pyridine are more preferable.

The base is preferably used in an amount of 1.0 to 2.0mol, more preferably 1.0 to 1.2 mol, based on 1 mol of the compound (a).

The reaction in the step (1-1) can be carried out with or without a solvent. When the reaction is carried out in a solvent, the solvent is preferably an organic solvent, and examples thereof include non-aromatic hydrocarbon solvents such as pentane, hexane, heptane, octane, cyclohexane, decalin, n-decane, isododecane, tridecane, and the like; aromatic hydrocarbon solvents such as benzene, toluene, xylene, tetralin, veratrole, diethylbenzene, methylnaphthalene, nitrobenzene, o-nitrotoluene, mesitylene, indene, and diphenyl sulfide; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, propiophenone, diisobutyl ketone, and isophorone; halogenated hydrocarbon solvents such as dichloromethane, carbon tetrachloride, chloroform, chlorobenzene, and the like; ether solvents such as diethyl ether, tetrahydrofuran, diisopropyl ether, methyl tert-butyl ether, dioxane, dimethoxyethane, diglyme, phenetole, 1-dimethoxycyclohexane, and diisoamyl ether; ester solvents such as ethyl acetate, isopropyl acetate, diethyl malonate, 3-methoxy-3-methylbutyl acetate, gamma-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, alpha-acetyl-gamma-butyrolactone and the like; nitrile solvents such as acetonitrile and benzonitrile; sulfoxide solvents such as dimethyl sulfoxide and sulfolane; and amide solvents such as N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, 1, 3-dimethyl-2-imidazolidinone, N-dimethylacrylamide, N-dimethylacetamide, N-diethylformamide, and N, N-diethylacetamide.

Among them, halogenated hydrocarbon solvents are preferable, and dichloromethane, carbon tetrachloride and chloroform are more preferable.

The reaction temperature in the step (1-1) is preferably-10 to 70 ℃, more preferably 0 to 25 ℃, and still more preferably 0 to 10 ℃.

The reaction time in the step (1-1) is preferably 0.1 to 72 hours, more preferably 0.1 to 24 hours, and still more preferably 0.1 to 12 hours.

After completion of each step, the product can be isolated and purified by distillation of the solvent, distillation, column chromatography, recrystallization, or the like.

In the general formula (1-2), R¹⁰²And R¹⁰³(i) H, F, an alkyl group having 1 to 7 carbon atoms which may be fluorinated, an alkenyl group having 2 to 7 carbon atoms which may be fluorinated, an alkynyl group having 2 to 9 carbon atoms which may be fluorinated, or an aryl group having 5 to 12 carbon atoms which may be fluorinated, or (ii) a hydrocarbon group which is linked to each other to form a 5-or 6-membered heterocyclic ring together with the nitrogen atom. R¹⁰²And R¹⁰³At least 1 selected from O, S and N may be contained in the structure.

As R¹⁰²And R¹⁰³The alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms.

The alkyl group may be a non-fluorinated alkyl group or a fluorinated alkyl group, and may contain at least 1 selected from O, S and N in the structure.

As R¹⁰²And R¹⁰³Examples of the alkyl group in (1) include a methyl group (-CH)₃) Ethyl (-CH)₂CH₃) Propyl (-CH)₂CH₂CH₃) Isopropyl (-CH (CH)₃)₂) N-butyl (-CH)₂CH₂CH₂CH₃) T-butyl (-C (CH))₃)₃) Isopropyl (-CH (CH)₃)₂) Cyclopropyl (-CHCH)₂CH₂) And the like non-fluorinated alkyl groups; -CF₃、-CF₂H、-CFH₂、-CF₂CF₃、-CF₂CF₂H、-CF₂CFH₂、-CH₂CF₃、-CH₂CF₂H、-CH₂CFH₂、-CF₂CF₂CF₃、-CF₂CF₂CF₂H、-CF₂CF₂CFH₂、-CH₂CF₂CF₃、-CH₂CF₂CF₂H、-CH₂CF₂CFH₂、-CH₂CH₂CF₃、-CH₂CH₂CF₂H、-CH₂CH₂CFH₂、-CF(CF₃)₂、-CF(CF₂H)₂、-CF(CFH₂)₂、-CH(CF₃)₂、-CH(CF₂H)₂、-CH(CFH₂)₂、-CH₂CF(CF₃)OC₃F₇、-CH₂CF₂OCF₃And fluoroalkyl groups.

Among the above alkyl groups, preferred are methyl, ethyl, isopropyl, tert-butyl and-CH₂CF₃。

As R¹⁰²And R¹⁰³The number of carbon atoms of the alkenyl group is preferably 2 to 5, more preferably 3 to 5.

The alkenyl group may be a non-fluorinated alkenyl group or a fluorinated alkenyl group, and may contain at least 1 selected from O, S and N in the structure.

As R¹⁰²And R¹⁰³Examples of the alkenyl group in (1) include a vinyl group (-CH ═ CH)₂) 1-propenyl (-CH ═ CH-CH)₃) 1-methylethenyl (-C (CH)₃)＝CH₂) 2-propenyl (-CH)₂-CH＝CH₂) 1-butenyl (-CH ═ CH-CH)₂CH₃) 2-methyl-1-propenyl (-CH ═ C (CH)₃)-CH₃) 1-methyl-1-propenyl (-C (CH)₃)＝CH-CH₃) 1-ethylvinyl (-C (CH)₂CH₃)＝CH₂) 2-butenyl (-CH)₂-CH＝CH-CH₃) 2-methyl-2-propenyl (-CH)₂-C(CH₃)＝CH₂) 1-methyl-2-propenyl (-CH (CH)₃)-CH＝CH₂) 3-butenyl (-CH)₂CH₂-CH＝CH₂) 1-methylene-2-propenyl (-C (═ CH)₂)-CH＝CH₂)1, 3-butadienyl (-CH ═ CH)₂)2, 3-butadienyl (-CH)₂-CH＝C＝CH₂) 1-methyl-1, 2-allenyl (-C (CH)₃)＝C＝CH₂)1, 2-butadienyl (-CH ═ C ═ CH-CH)₃) 2-pentenyl (-CH)₂-CH＝CH-CH₂CH₃) 2-ethyl-2-propenyl (-CH)₂-C(CH₂CH₃)＝CH₂) 1-ethyl-2-propenyl (-CH (CH)₂CH₃)-CH＝CH₂) 3-pentenyl (-C)H₂CH₂-CH＝CH-CH₃) And groups in which at least 1 hydrogen atom is replaced with a fluorine atom.

Among the above alkenyl groups, 2-propenyl (-CH) is preferred₂-CH＝CH₂) And 2-propenyl group in which at least 1 hydrogen atom is replaced by a fluorine atom, and more preferably 2-propenyl group (-CH)₂-CH＝CH₂)。

As R¹⁰²And R¹⁰³The alkynyl group in the above-mentioned publication preferably has 2 to 5 carbon atoms, more preferably 3 to 5 carbon atoms.

The alkynyl group may be a non-fluorinated alkynyl group or a fluorinated alkynyl group, and may contain at least 1 selected from O, S and N in the structure.

As R¹⁰²And R¹⁰³Examples of the alkynyl group in (1) include an ethynyl group (-C.ident.CH) and a 1-propynyl group (-C.ident.C-CH)₃) 2-propynyl (-CH)₂-C.ident.CH), 1-butynyl (-C.ident.C-CH)₂CH₃) 2-butynyl (-CH)₂-C≡C-CH₃) 3-butynyl (-CH)₂CH₂-C.ident.CH), 1-pentynyl (-C.ident.C-CH)₂CH₂CH₃) 2-pentynyl (-CH)₂-C≡C-CH₂CH₃) 3-pentynyl (-CH)₂CH₂-C≡C-CH₃) 4-pentynyl (-CH)₂CH₂CH₂-C ≡ CH), a group in which at least 1 hydrogen atom in these groups is substituted with a fluorine atom, and the like.

As the alkynyl group, among them, 2-propynyl (-CH) is preferred₂-C ≡ CH), 2-butynyl (-CH)₂-C≡C-CH₃) And a group in which at least 1 hydrogen atom in these groups is substituted with a fluorine atom, more preferably 2-propynyl (-CH)₂-C≡CH)。

As R¹⁰²And R¹⁰³The aryl group in (2) is a group obtained by removing 1 hydrogen atom from an aromatic ring, and preferably contains a 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring, and is preferably monocyclic or bicyclic.

The aryl group may be a non-fluorinated aryl group or a fluorinated aryl group, and may contain at least 1 selected from O, S and N in the structure.

Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a methoxybenzyl group, a naphthyl group, and a pyridyl group, and these groups may or may not have a fluorine atom. Among them, preferred are a phenyl group which may have a fluorine atom and a pyridyl group which may have a fluorine atom, and more preferred are a phenyl group which does not have a fluorine atom and a pyridyl group which does not have a fluorine atom.

As R¹⁰²And R¹⁰³The above hydrocarbon groups are linked to each other to form a 5-or 6-membered heterocyclic ring together with a nitrogen atom (nitrogen atom in the amide bond in the general formula (1-2)). The heterocyclic ring is preferably a non-aromatic heterocyclic ring. The number of carbon atoms of the hydrocarbon group is preferably 3 to 5, more preferably 4 to 5. The hydrocarbon group may contain at least 1 selected from O, S and N in the structure.

Examples of the hydrocarbon group include a group which forms a pyrrolidine ring together with the nitrogen atom, a group which forms a piperidine ring together with the nitrogen atom, a group which forms an oxazolidine ring together with the nitrogen atom, a group which forms a morpholine ring together with the nitrogen atom, a group which forms a thiazole ring together with the nitrogen atom, a group which forms a 2, 5-dihydro-1H-pyrrole ring together with the nitrogen atom, a group which forms a pyrrole-2, 5-dione ring together with the nitrogen atom, and a group which forms a 4, 5-dihydro-1H-imidazole ring together with the nitrogen atom. Among them, preferred are a group forming a pyrrolidine ring together with the nitrogen atom, a group forming a piperidine ring together with the nitrogen atom, a group forming a morpholine ring together with the nitrogen atom, a group forming a 2, 5-dihydro-1H-pyrrole ring together with the nitrogen atom, and a group forming a pyrrole-2, 5-dione ring together with the nitrogen atom.

R¹⁰²And R¹⁰³Both are preferably H and a group other than the above-mentioned aryl group.

R¹⁰²And R¹⁰³Preferably, no unsaturated bond is contained. In this case, the increase in resistance after the high-temperature storage of the electrolyte can be further suppressed.

R¹⁰²And R¹⁰³May be the same or different.

Examples of the compound (1-2) include compounds represented by the following formulae.

[ CHEM 22 ]

Among the compounds (1-2), preferred is a compound represented by the following formula.

[ CHEM 23 ]

Among the compounds (1-2), the compound (12) characterized by the following general formula (12) is a novel compound.

General formula (12):

[ CHEM 24 ]

The present invention also relates to compound (12).

In the general formula (12), R¹¹²And R¹¹³(i) Independently of each other, F, a non-fluorinated alkyl group having 1 to 7 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, an alkenyl group having 3 to 7 carbon atoms which may be fluorinated, or an alkynyl group having 3 to 7 carbon atoms which may be fluorinated, and R¹¹²And R¹¹³At least one of F, a non-fluorinated alkyl group having 3 to 7 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, an alkenyl group having 3 to 7 carbon atoms which may be fluorinated, or an alkynyl group having 3 to 7 carbon atoms which may be fluorinated, or (ii) a hydrocarbon group which is linked to each other to form a 5-or 6-membered heterocyclic ring together with the nitrogen atom. R¹¹²And R¹¹³At least 1 selected from O, S and N may be contained in the structure.

As R¹¹²And R¹¹³The non-fluorinated alkyl group has preferably 1 to 6 carbon atoms, more preferably 1 to 5 carbon atoms. The above-mentioned non-fluorinated alkyl group may have an ether bond in the structure.

As aboveExamples of the fluorinated alkyl group include a methyl group (-CH)₃) Ethyl (-CH)₂CH₃) Propyl (-CH)₂CH₂CH₃) Isopropyl (-CH (CH)₃)₂) Cyclopropyl (-CHCH)₂CH₂) N-butyl (-CH)₂CH₂CH₂CH₃) T-butyl (-C (CH))₃)₃) And the like. Among them, methyl, ethyl, isopropyl, and tert-butyl are preferable.

As R¹¹²And R¹¹³The fluoroalkyl group preferably has 1 to 4 carbon atoms, and more preferably 1 to 3 carbon atoms. The fluoroalkyl group may have an ether bond in the structure.

Examples of the fluoroalkyl group include-CF₃、-CF₂H、-CFH₂、-CF₂CF₃、-CF₂CF₂H、-CF₂CFH₂、-CH₂CF₃、-CH₂CF₂H、-CH₂CFH₂、-CF₂CF₂CF₃、-CF₂CF₂CF₂H、-CF₂CF₂CFH₂、-CH₂CF₂CF₃、-CH₂CF₂CF₂H、-CH₂CF₂CFH₂、-CH₂CH₂CF₃、-CH₂CH₂CF₂H、-CH₂CH₂CFH₂、-CF(CF₃)₂、-CF(CF₂H)₂、-CF(CFH₂)₂、-CH(CF₃)₂、-CH(CF₂H)₂、-CH(CFH₂)₂、-CH₂CF(CF₃)OC₃F₇、-CH₂CF₂OCF₃And the like. Among them, preferred is-CH₂CF₃。

As R¹¹²And R¹¹³The number of carbon atoms of the alkenyl group is preferably 3 to 5, more preferably 3 to 4.

The alkenyl group may be an unsubstituted or fluorinated alkenyl group, or may have an ether bond in the structure.

As R¹¹²And R¹¹³Examples of the alkenyl group in (1) include a 1-propenyl group (-CH-CH)₃) 1-methylethenyl (-C (CH)₃)＝CH₂) 2-propenyl (-CH)₂-CH＝CH₂) 1-butenyl (-CH ═ CH-CH)₂CH₃) 2-methyl-1-propenyl (-CH ═ C (CH)₃)-CH₃) 1-methyl-1-propenyl (-C (CH)₃)＝CH-CH₃) 1-ethylvinyl (-C (CH)₂CH₃)＝CH₂) 2-butenyl (-CH)₂-CH＝CH-CH₃) 2-methyl-2-propenyl (-CH)₂-C(CH₃)＝CH₂) 1-methyl-2-propenyl (-CH (CH)₃)-CH＝CH₂) 3-butenyl (-CH)₂CH₂-CH＝CH₂) 1-methylene-2-propenyl (-C (═ CH)₂)-CH＝CH₂)1, 3-butadienyl (-CH ═ CH)₂)2, 3-butadienyl (-CH)₂-CH＝C＝CH₂) 1-methyl-1, 2-allenyl (-C (CH)₃)＝C＝CH₂)1, 2-butadienyl (-CH ═ C ═ CH-CH)₃) 2-pentenyl (-CH)₂-CH＝CH-CH₂CH₃) 2-ethyl-2-propenyl (-CH)₂-C(CH₂CH₃)＝CH₂) 1-ethyl-2-propenyl (-CH (CH)₂CH₃)-CH＝CH₂) 3-pentenyl (-CH)₂CH₂-CH＝CH-CH₃) And groups in which at least 1 hydrogen atom is replaced with a fluorine atom.

As R¹¹²And R¹¹³The alkynyl group in (b) preferably has 3 to 5 carbon atoms, more preferably 3 to 4 carbon atoms.

The alkynyl group may be a non-fluorinated alkynyl group, a fluorinated alkynyl group, or an alkynyl group having an ether bond in the structure.

As R¹¹²And R¹¹³As the above-mentioned alkynyl group, 1-propynyl (-C.ident.C-CH) may be mentioned₃) 2-propynyl (-CH)₂-C.ident.CH), 1-butynyl (-C.ident.C-CH)₂CH₃) 2-butynyl (-CH)₂-C≡C-CH₃) 3-butynyl (-CH)₂CH₂-C.ident.CH), 1-pentynyl (-C.ident.C-CH)₂CH₂CH₃) 2-pentynyl (-CH)₂-C≡C-CH₂CH₃) 3-pentynyl (-CH)₂CH₂-C≡C-CH₃) 4-pentynyl (-CH)₂CH₂CH₂-C.ident.CH), and a group in which at least 1 hydrogen atom in these groups is replaced by a fluorine atom, and the like

As the alkynyl group, among them, 2-propynyl (-CH) is preferred₂-C≡CH)。

As R¹¹²And R¹¹³The above hydrocarbon groups in (2) are linked to each other to form a 5-or 6-membered heterocyclic ring together with a nitrogen atom (nitrogen atom in the amide bond in the general formula (12)). The heterocyclic ring is preferably a non-aromatic heterocyclic ring. The number of carbon atoms of the hydrocarbon group is preferably 3 to 5, more preferably 4 to 5. The hydrocarbon group may contain at least 1 selected from O, S and N in the structure.

R¹¹²And R¹¹³Preferably at least one of F, the fluoroalkyl group and the fluoroalkyl group isAlkenyl or alkynyl as described above.

R¹¹²And R¹¹³May be the same or different.

Examples of the compound (12) include compounds represented by the following formulae.

[ CHEM 25 ]

Among the compounds (12), preferred is a compound represented by the following formula.

[ CHEM 26 ]

The compound (12) is preferably produced by the production method of step (1-2) in which the compound (12) represented by the above general formula (12) is obtained by reacting the compound (a) represented by the following general formula (a) with the compound (c) represented by the following general formula (c), but the production method is not limited thereto.

General formula (a):

[ CHEM 27 ]

(in the formula, X¹⁰¹Is a halogen atom. )

General formula (c):

[ CHEM 28 ]

(in the formula, R¹¹²And R¹¹³As described above. .

In the reaction in the step (1-2), the compound (c) is preferably used in an amount of 0.5 to 4.0 mol, more preferably 0.7 to 3.0 mol, and still more preferably 0.9 to 2.2 mol, based on 1 mol of the compound (a).

The reaction in the step (1-2) is preferably carried out in the presence of a base. Examples of the base include amines and inorganic bases.

Among the above bases, amines are preferable, and the compound (c) as a reaction raw material and amines other than the compound (c) may be used in combination or may not be used in combination. The amine other than the compound (c) is preferably triethylamine or pyridine.

When a base other than the compound (c) is used in combination as the base, the amount of the base is preferably 1.0 to 2.0mol, more preferably 1.0 to 1.2 mol, based on 1 mol of the compound (a).

The reaction in the step (1-2) can be carried out with or without a solvent. When the reaction is carried out in a solvent, the solvent is preferably an organic solvent, and examples thereof include non-aromatic hydrocarbon solvents such as pentane, hexane, heptane, octane, cyclohexane, decalin, n-decane, isododecane, tridecane, and the like; aromatic hydrocarbon solvents such as benzene, toluene, xylene, tetralin, veratrole, diethylbenzene, methylnaphthalene, nitrobenzene, o-nitrotoluene, mesitylene, indene, and diphenyl sulfide; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, propiophenone, diisobutyl ketone, and isophorone; halogenated hydrocarbon solvents such as dichloromethane, carbon tetrachloride, chloroform, chlorobenzene, and the like; ether solvents such as diethyl ether, tetrahydrofuran, diisopropyl ether, methyl tert-butyl ether, dioxane, dimethoxyethane, diglyme, phenetole, 1-dimethoxycyclohexane, and diisoamyl ether; ester solvents such as ethyl acetate, isopropyl acetate, diethyl malonate, 3-methoxy-3-methylbutyl acetate, gamma-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate alpha-acetyl-gamma-butyrolactone and the like; nitrile solvents such as acetonitrile and benzonitrile; sulfoxide solvents such as dimethyl sulfoxide and sulfolane; and amide solvents such as N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, 1, 3-dimethyl-2-imidazolidinone, N-dimethylacrylamide, N-dimethylacetamide, N-diethylformamide, and N, N-diethylacetamide.

Among them, halogenated hydrocarbon solvents are preferable, and dichloromethane, carbon tetrachloride and chloroform are more preferable.

The reaction temperature in the step (1-2) is preferably-10 to 70 ℃, more preferably 0 to 25 ℃, and still more preferably 0 to 10 ℃.

The reaction time in the step (1-2) is preferably 0.1 to 72 hours, more preferably 0.1 to 24 hours, and still more preferably 0.1 to 12 hours.

After completion of each step, the product can be isolated and purified by distillation of the solvent, distillation, column chromatography, recrystallization, or the like.

The compound (1) may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The electrolyte solution of the present invention preferably contains 0.001 to 10 mass% of the compound (1) relative to the electrolyte solution. When the content of the compound (1) is within the above range, the high-temperature storage characteristics and the cycle characteristics of the electrochemical device can be further improved. The content of the compound (1) is more preferably 0.005% by mass or more, still more preferably 0.01% by mass or more, and particularly preferably 0.1% by mass or more. Further, it is more preferably 7% by mass or less, still more preferably 5% by mass or less, and particularly preferably 3% by mass or less.

The electrolyte solution of the present invention preferably contains a solvent (excluding the compound (1)).

The solvent preferably contains at least 1 selected from the group consisting of carbonates and carboxylates.

The carbonate may be a cyclic carbonate or a chain carbonate.

The cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate.

The non-fluorinated cyclic carbonate includes a non-fluorinated saturated cyclic carbonate, preferably a non-fluorinated saturated alkylene carbonate having an alkylene group with 2 to 6 carbon atoms, and more preferably a non-fluorinated saturated alkylene carbonate having an alkylene group with 2 to 4 carbon atoms.

Among them, the non-fluorinated saturated cyclic carbonate is preferably at least 1 of ethylene carbonate, propylene carbonate, 2, 3-pentenyl cis-carbonate, 2, 3-butenyl cis-carbonate, 2, 3-pentenyl 2, 3-butenyl carbonate, 1, 2-pentenyl carbonate, 1, 2-butenyl carbonate and butenyl carbonate, from the viewpoint of high dielectric constant and suitable viscosity.

The above-mentioned non-fluorinated saturated cyclic carbonates may be used alone in 1 kind, or may be used in combination in 2 or more kinds in an arbitrary combination and ratio.

When the non-fluorinated saturated cyclic carbonate is contained, the content of the non-fluorinated saturated cyclic carbonate is preferably 5 to 90 vol%, more preferably 10 to 60 vol%, and still more preferably 15 to 45 vol% with respect to the solvent.

The fluorinated cyclic carbonate is a cyclic carbonate having a fluorine atom. The fluorinated cyclic carbonate-containing solvent can be suitably used even at a high voltage.

In the present specification, "high voltage" means a voltage of 4.2V or more. In addition, the upper limit of the "high voltage" is preferably 4.9V.

The fluorinated cyclic carbonate may be a fluorinated saturated cyclic carbonate or a fluorinated unsaturated cyclic carbonate.

The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate having a fluorine atom, and specifically, a compound represented by the following general formula (a):

[ CHEM 29 ]

(in the formula, X¹～X⁴The same or different, each represents-H, -CH₃、-C₂H₅F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond. Wherein, X¹～X⁴At least 1 of them is-F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond. ). Said fluoroalkyl is-CF₃、-CF₂H、-CH₂F, and the like.

When the electrolyte solution of the present invention is applied to a high-voltage lithium ion secondary battery or the like, the oxidation resistance of the electrolyte solution is improved and stable and excellent charge and discharge characteristics can be obtained if the fluorinated saturated cyclic carbonate is contained.

In the present specification, the "ether bond" is a bond represented by-O-.

X is a compound having a good dielectric constant and good oxidation resistance¹～X⁴1 or 2 of them is preferably-F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond.

X is expected to decrease the viscosity at low temperature, increase the flash point, and improve the solubility of the electrolyte salt¹～X⁴Preferred is-H, -F, fluoroalkyl (a), fluoroalkyl (b) having an ether bond, or fluoroalkoxy (c).

The fluoroalkyl group (a) is a group in which at least 1 of the hydrogen atoms of the alkyl group is substituted with a fluorine atom. The number of carbon atoms of the fluoroalkyl group (a) is preferably 1 to 20, more preferably 1 to 17, further preferably 1 to 7, and particularly preferably 1 to 5.

If the number of carbon atoms is too large, the low temperature characteristics may be degraded, or the solubility of the electrolyte salt may be degraded, and if the number of carbon atoms is too small, the solubility of the electrolyte salt may be degraded, the discharge efficiency may be degraded, or the viscosity may be increased.

The fluoroalkyl group (a) having 1 carbon atom is exemplified by CFH₂-、CF₂H-、CF₃-. In terms of high-temperature storage characteristics, CF is particularly preferred₂H-or CF₃-, most preferably CF₃-。

The fluoroalkyl group (a) having 2 or more carbon atoms is preferably a fluoroalkyl group represented by the following general formula (a-1) because it is excellent in solubility of an electrolyte salt.

R¹-R²- (a-1)

(in the formula, R¹An alkyl group having 1 or more carbon atoms which may have a fluorine atom; r²An alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; wherein R is¹And R²Has a fluorine atom).

In addition, R is¹And R²Further, the compound may have other atoms than carbon, hydrogen and fluorine atoms.

R¹An alkyl group having 1 or more carbon atoms which may have a fluorine atom. As R¹Preferably, the alkyl group is a linear or branched alkyl group having 1 to 16 carbon atoms. As R¹The number of carbon atoms of (2) is more preferably 1 to 6, and still more preferably 1 to 3.

As R¹Specifically, the linear or branched alkyl group may include CH₃-、CH₃CH₂-、CH₃CH₂CH₂-、CH₃CH₂CH₂CH₂-、

[ CHEM 30 ]

And the like.

In addition, in R¹To have fluorineIn the case of an atomic linear alkyl group, CF is mentioned₃-、CF₃CH₂-、CF₃CF₂-、CF₃CH₂CH₂-、CF₃CF₂CH₂-、CF₃CF₂CF₂-、CF₃CH₂CF₂-、CF₃CH₂CH₂CH₂-、CF₃CF₂CH₂CH₂-、CF₃CH₂CF₂CH₂-、CF₃CF₂CF₂CH₂-、CF₃CF₂CF₂CF₂-、CF₃CF₂CH₂CF₂-、CF₃CH₂CH₂CH₂CH₂-、CF₃CF₂CH₂CH₂CH₂-、CF₃CH₂CF₂CH₂CH₂-、CF₃CF₂CF₂CH₂CH₂-、CF₃CF₂CF₂CF₂CH₂-、CF₃CF₂CH₂CF₂CH₂-、CF₃CF₂CH₂CH₂CH₂CH₂-、CF₃CF₂CF₂CF₂CH₂CH₂-、CF₃CF₂CH₂CF₂CH₂CH₂-、HCF₂-、HCF₂CH₂-、HCF₂CF₂-、HCF₂CH₂CH₂-、HCF₂CF₂CH₂-、HCF₂CH₂CF₂-、HCF₂CF₂CH₂CH₂-、HCF₂CH₂CF₂CH₂-、HCF₂CF₂CF₂CF₂-、HCF₂CF₂CH₂CH₂CH₂-、HCF₂CH₂CF₂CH₂CH₂-、HCF₂CF₂CF₂CF₂CH₂-、HCF₂CF₂CF₂CF₂CH₂CH₂-、FCH₂-、FCH₂CH₂-、FCH₂CF₂-、FCH₂CF₂CH₂-、FCH₂CF₂CF₂-、CH₃CF₂CH₂-、CH₃CF₂CF₂-、CH₃CF₂CH₂CF₂-、CH₃CF₂CF₂CF₂-、CH₃CH₂CF₂CF₂-、CH₃CF₂CH₂CF₂CH₂-、CH₃CF₂CF₂CF₂CH₂-、CH₃CF₂CF₂CH₂CH₂-、CH₃CH₂CF₂CF₂CH₂-、CH₃CF₂CH₂CF₂CH₂CH₂-、CH₃CF₂CH₂CF₂CH₂CH₂-、HCFClCF₂CH₂-、HCF₂CFClCH₂-、HCF₂CFClCF₂CFClCH₂-、HCFClCF₂CFClCF₂CH₂-and the like.

In addition, in R¹When the alkyl group is a branched alkyl group having a fluorine atom, preferred examples thereof include

[ CHEM 31 ]

[ CHEM 32 ]

And the like. Wherein, if having CH₃-、CF₃Such a branched chain tends to increase the viscosity, and therefore, the number thereof is more preferably small (1) or zero.

R²The alkylene group has 1 to 3 carbon atoms and may have a fluorine atom. R²May be linearIt may be branched. Examples of the minimum structural unit constituting such a linear or branched alkylene group are shown below. R²Consisting of these alone or in combination.

(i) Linear minimum structural unit:

-CH₂-、-CHF-、-CF₂-、-CHCl-、-CFCl-、-CCl₂-

(ii) branched minimum structural unit:

[ CHEM 33 ]

In the above examples, it is preferable that the compound is composed of a structural unit containing no Cl from the viewpoint of not causing HCl removal reaction by alkali and being more stable.

At R²When the chain is linear, it is composed of only the above-mentioned linear minimum structural unit, and among them, -CH is preferable₂-、-CH₂CH₂-or-CF₂-. From the viewpoint of further improving the solubility of the electrolyte salt, — CH is more preferable₂-or-CH₂CH₂-。

At R²When the branched chain structure contains at least 1 branched chain minimum structural unit, the general formula- (CX)^aX^b)-(X^aIs H, F, CH₃Or CF₃；X^bIs CH₃Or CF₃. Wherein, in X^bIs CF₃In the case of (A), X^aIs H or CH₃) The unit shown. These elements can in particular further increase the solubility of the electrolyte salt.

Preferable fluoroalkyl group (a) includes, for example, CF₃CF₂-、HCF₂CF₂-，H₂CFCF₂-、CH₃CF₂-、CF₃CHF-、CH₃CF₂-、CF₃CF₂CF₂-、HCF₂CF₂CF₂-、H₂CFCF₂CF₂-、CH₃CF₂CF₂-、

[ CHEM 34 ]

[ CHEM 35 ]

And the like.

The fluoroalkyl group (b) having an ether bond is a group in which at least 1 of the hydrogen atoms of the alkyl group having an ether bond is substituted with a fluorine atom. The number of carbon atoms of the fluoroalkyl group (b) having an ether bond is preferably 2 to 17. If the number of carbon atoms is too large, the viscosity of the fluorinated saturated cyclic carbonate becomes high, and further, since the number of fluorine-containing groups becomes large, the solubility of the electrolyte salt is lowered due to the lowering of the dielectric constant, and the compatibility with other solvents is sometimes observed to be lowered. From this viewpoint, the number of carbon atoms of the fluoroalkyl group (b) having an ether bond is more preferably 2 to 10, and still more preferably 2 to 7.

The alkylene group constituting the ether moiety of the fluoroalkyl group (b) having an ether bond may be a linear or branched alkylene group. Examples of the minimum structural unit constituting such a linear or branched alkylene group are shown below.

(i) Linear minimum structural unit:

-CH₂-、-CHF-、-CF₂-、-CHCl-、-CFCl-、-CCl₂-

(ii) branched minimum structural unit:

[ CHEM 36 ]

The alkylene group may be composed of one of these minimum structural units alone, or may be composed of a plurality of linear (i) s, a plurality of branched (ii) s, or a combination of linear (i) s and branched (ii) s. Specific examples of the preferable examples are described later.

In the above examples, it is preferable that the compound is composed of a structural unit containing no Cl from the viewpoint of not causing HCl removal reaction by alkali and being more stable.

A more preferred fluoroalkyl group (b) having an ether bond is a group represented by the general formula (b-1).

R³-(OR⁴)_n1- (b-1)

(in the formula, R³An alkyl group which may have a fluorine atom and preferably has 1 to 6 carbon atoms; r⁴An alkylene group which may have a fluorine atom, preferably having 1 to 4 carbon atoms; n1 is an integer of 1-3; wherein R is³And R⁴At least 1 of which has fluorine atoms).

As R³And R⁴Examples of the fluoroalkyl group having an ether bond (b) represented by the general formula (b-1) include the following groups, and the fluoroalkyl groups can be combined as appropriate to form the fluoroalkyl group.

(1) As R³Preferably of the general formula: x^c ₃C-(R⁵)_n2- (3X)^cThe same or different, are H or F; r⁵An alkylene group having 1 to 5 carbon atoms and optionally having a fluorine atom; n2 represents an alkyl group represented by 0 or 1).

When n2 is 0, R is³Examples thereof are CH₃-、CF₃-、HCF₂-and H₂CF-。

As a specific example when n2 is 1, R is³As the linear group, CF can be exemplified₃CH₂-、CF₃CF₂-、CF₃CH₂CH₂-、CF₃CF₂CH₂-、CF₃CF₂CF₂-、CF₃CH₂CF₂-、CF₃CH₂CH₂CH₂-、CF₃CF₂CH₂CH₂-、CF₃CH₂CF₂CH₂-、CF₃CF₂CF₂CH₂-、CF₃CF₂CF₂CF₂-、CF₃CF₂CH₂CF₂-、CF₃CH₂CH₂CH₂CH₂-、CF₃CF₂CH₂CH₂CH₂-、CF₃CH₂CF₂CH₂CH₂-、CF₃CF₂CF₂CH₂CH₂-、CF₃CF₂CF₂CF₂CH₂-、CF₃CF₂CH₂CF₂CH₂-、CF₃CF₂CH₂CH₂CH₂CH₂-、CF₃CF₂CF₂CF₂CH₂CH₂-、CF₃CF₂CH₂CF₂CH₂CH₂-、HCF₂CH₂-、HCF₂CF₂-、HCF₂CH₂CH₂-、HCF₂CF₂CH₂-、HCF₂CH₂CF₂-、HCF₂CF₂CH₂CH₂-、HCF₂CH₂CF₂CH₂-、HCF₂CF₂CF₂CF₂-、HCF₂CF₂CH₂CH₂CH₂-、HCF₂CH₂CF₂CH₂CH₂-、HCF₂CF₂CF₂CF₂CH₂-、HCF₂CF₂CF₂CF₂CH₂CH₂-、FCH₂CH₂-、FCH₂CF₂-、FCH₂CF₂CH₂-、CH₃CF₂-、CH₃CH₂-、CH₃CF₂CH₂-、CH₃CF₂CF₂-、CH₃CH₂CH₂-、CH₃CF₂CH₂CF₂-、CH₃CF₂CF₂CF₂-、CH₃CH₂CF₂CF₂-、CH₃CH₂CH₂CH₂-、CH₃CF₂CH₂CF₂CH₂-、CH₃CF₂CF₂CF₂CH₂-、CH₃CF₂CF₂CH₂CH₂-、CH₃CH₂CF₂CF₂CH₂-、CH₃CF₂CH₂CF₂CH₂CH₂-、CH₃CH₂CF₂CF₂CH₂CH₂-、CH₃CF₂CH₂CF₂CH₂CH₂-and the like.

N2 is 1, and R³Examples of the branched group include

[ CHEM 37 ]

And the like.

Wherein, if having CH₃-、CF₃Since the viscosity tends to be high due to such a branch, R³More preferably, the group is linear.

(2) - (OR) of the above general formula (b-1)⁴)_n1In the formula (I), n1 is an integer of 1-3, preferably 1 or 2. When n1 is 2 or 3, R is⁴May be the same or different.

As R⁴Specific preferred examples of (3) include the following linear or branched groups.

Examples of the linear group include-CH₂-、-CHF-、-CF₂-、-CH₂CH₂-、-CF₂CH₂-、-CF₂CF₂-、-CH₂CF₂-、-CH₂CH₂CH₂-、-CH₂CH₂CF₂-、-CH₂CF₂CH₂-、-CH₂CF₂CF₂-、-CF₂CH₂CH₂-、-CF₂CF₂CH₂-、-CF₂CH₂CF₂-、-CF₂CF₂CF₂-and the like.

Examples of the branched group include

[ CHEM 38 ]

And the like.

The fluoroalkoxy group (c) is a group in which at least 1 of the hydrogen atoms of the alkoxy group is replaced with a fluorine atom. The fluoroalkoxy group (c) preferably has 1 to 17 carbon atoms. The number of carbon atoms is more preferably 1 to 6.

The fluoroalkoxy group (c) is particularly preferably represented by the general formula: x^d ₃C-(R⁶)_n3-O- (3X)^dThe same or different, are H or F; r⁶Preferably an alkylene group having 1 to 5 carbon atoms and optionally having a fluorine atom; n3 is 0 or 1; wherein, 3X^dAt least one of which is a fluorine atom).

Specific examples of the fluoroalkoxy group (c) include R in the general formula (a-1)¹Examples of the "fluoroalkoxy group" include fluoroalkoxy groups in which an oxygen atom is bonded to the terminal of an alkyl group.

The fluorine content of the fluoroalkyl group (a), the fluoroalkyl group (b) having an ether bond, and the fluoroalkoxy group (c) in the fluorinated saturated cyclic carbonate is preferably 10% by mass or more. If the fluorine content is too low, the effect of lowering the viscosity at low temperatures and the effect of increasing the flash point may not be sufficiently obtained. From this viewpoint, the fluorine content is more preferably 12% by mass or more, and still more preferably 15% by mass or more. The upper limit is usually 76 mass%.

The fluorine content of the fluoroalkyl group (a), the fluoroalkyl group (b) having an ether bond, and the fluoroalkoxy group (c) is a value calculated by [ (the number of fluorine atoms × 19)/the formula amount of each group ] × 100 (%) based on the structural formula of each group.

The fluorine content of the fluorinated saturated cyclic carbonate as a whole is preferably 10 mass% or more, more preferably 15 mass% or more, from the viewpoint of satisfactory dielectric constant and oxidation resistance. The upper limit is usually 76 mass%.

The fluorine content of the fluorinated saturated cyclic carbonate is a value calculated from [ (the number of fluorine atoms × 19)/the molecular weight of the fluorinated saturated cyclic carbonate ] × 100 (%) based on the structural formula of the fluorinated saturated cyclic carbonate.

Specific examples of the fluorinated saturated cyclic carbonate include the following.

As X¹～X⁴Specific examples of the fluorinated saturated cyclic carbonate in which at least 1 is-F include

[ CHEM 39 ]

And the like. These compounds have high withstand voltage and good solubility of the electrolyte salt.

In addition, it is also possible to use

[ CHEM 40 ]

And the like.

As X¹～X⁴Specific examples of fluorinated saturated cyclic carbonates in which at least 1 of the cyclic carbonates is a fluoroalkyl group (a) and the remainder is all-H are mentioned

[ CHEM 41 ]

[ CHEM 42 ]

[ CHEM 43 ]

And the like.

As X¹～X⁴Specific examples of the fluorinated saturated cyclic carbonate in which at least 1 of the (a) s is a fluoroalkyl group (b) or a fluoroalkoxy group (c) having an ether bond and the remainder is all-H include

[ CHEM 44 ]

[ CHEM 45 ]

[ CHEM 46 ]

[ CHEM 47 ]

[ CHEM 48 ]

[ CHEM 49 ]

And the like.

Among these, the fluorinated saturated cyclic carbonate is preferably any of the following compounds.

[ CHEM 50 ]

[ CHEM 51 ]

Examples of the fluorinated saturated cyclic carbonate include trans-4, 5-difluoro-1, 3-dioxolan-2-one, 5- (1, 1-difluoroethyl) -4, 4-difluoro-1, 3-dioxolan-2-one, 4-methylene-1, 3-dioxolan-2-one, 4-methyl-5-trifluoromethyl-1, 3-dioxolan-2-one, 4-ethyl-5-fluoro-1, 3-dioxolan-2-one, 4-ethyl-5, 5-difluoro-1, 3-dioxolan-2-one, 4-ethyl-4, 5-difluoro-1, 3-dioxolan-2-one, 4-ethyl-4, 5, 5-trifluoro-1, 3-dioxolan-2-one, 4-difluoro-5-methyl-1, 3-dioxolan-2-one, 4-fluoro-5-trifluoromethyl-1, 3-dioxolan-2-one, 4-difluoro-1, 3-dioxolan-2-one, and the like.

Among the fluorinated saturated cyclic carbonates, fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethyl ethylene carbonate (3, 3, 3-trifluoropropylene carbonate) and 2,2,3,3, 3-pentafluoropropylethylene carbonate are more preferable.

The fluorinated unsaturated cyclic carbonate is a cyclic carbonate having an unsaturated bond and a fluorine atom, and a fluoroethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond is preferable. Specific examples thereof include 4, 4-difluoro-5-phenylethylene carbonate, 4, 5-difluoro-4-phenylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-difluoro-4-vinylethylene carbonate, 4-difluoro-4-allylethylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4, 5-diallylethylene carbonate, 4, 5-difluoro-4-vinylethylene carbonate, 4, 5-difluoro-4, 5-divinylethylene carbonate, and the like, 4, 5-difluoro-4, 5-diallylcarbonate ethylene and the like.

The fluorinated cyclic carbonate may be used alone in 1 kind, or may be used in combination of 2 or more kinds in any combination and ratio.

When the fluorinated cyclic carbonate is contained, the content of the fluorinated cyclic carbonate is preferably 5 to 90 vol%, more preferably 10 to 60 vol%, and still more preferably 15 to 45 vol% with respect to the solvent.

The chain carbonate may be a non-fluorinated chain carbonate or a fluorinated chain carbonate.

Examples of the non-fluorinated chain carbonate include CH₃OCOOCH₃(dimethyl carbonate: DMC), CH₃CH₂OCOOCH₂CH₃(diethyl carbonate: DEC), CH₃CH₂OCOOCH₃(methyl Ethyl carbonate: EMC), CH₃OCOOCH₂CH₂CH₃Hydrocarbon chain carbonates such as (methylpropyl carbonate), methylbutyl carbonate, ethylpropyl carbonate, ethylbutyl carbonate, dipropyl carbonate, dibutyl carbonate, methylisopropyl carbonate, methyl-2-phenylphenyl carbonate, phenyl-2-phenylphenyl carbonate, trans-2, 3-pentenyl carbonate, trans-2, 3-butenyl carbonate, and ethyl benzenecarbonate. Among them, at least 1 kind selected from the group consisting of ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate is preferable.

The above-mentioned non-fluorinated chain carbonate may be used alone in 1 kind, or may be used in combination in 2 or more kinds in an arbitrary combination and ratio.

When the non-fluorinated chain carbonate is contained, the content of the non-fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and still more preferably 50 to 80% by volume with respect to the solvent.

The fluorinated chain carbonate is a chain carbonate having a fluorine atom. The solvent containing the fluorinated chain carbonate can be suitably used even under a high voltage.

Examples of the fluorinated chain carbonate include compounds represented by the general formula (B):

Rf²OCOOR⁷(B)

(wherein Rf²Is a C1-7 fluoroalkyl group, R⁷An alkyl group having 1 to 7 carbon atoms and optionally containing a fluorine atom. ).

Rf²Is a C1-7 fluoroalkyl group, R⁷An alkyl group having 1 to 7 carbon atoms and optionally containing a fluorine atom.

The fluoroalkyl group is a group in which at least 1 of the hydrogen atoms of the alkyl group is replaced with a fluorine atom. At R⁷In the case of an alkyl group containing a fluorine atom, the alkyl group is a fluoroalkyl group.

From the aspect of low viscosity, Rf²And R⁷The number of carbon atoms of (A) is preferably 1 to 7, more preferably 1 to 2.

If the number of carbon atoms is too large, the low-temperature characteristics may be degraded, or the solubility of the electrolyte salt may be degraded; if the number of carbon atoms is too small, the solubility of the electrolyte salt may be lowered, the discharge efficiency may be lowered, and the viscosity may be increased.

The fluoroalkyl group having 1 carbon atom may be CFH₂-、CF₂H-、CF₃-and the like. Particularly, CFH is preferable in terms of high-temperature storage characteristics₂-or CF₃-。

The fluoroalkyl group having 2 or more carbon atoms is preferably represented by the following general formula (d-1) in view of good solubility of the electrolyte salt:

R¹-R²- (d-1)

In addition, R is¹And R²It may further have other atoms than carbon atoms, hydrogen atoms and fluorine atoms.

R¹An alkyl group having 1 or more carbon atoms which may have a fluorine atom. As R¹Preferably, the alkyl group is a linear or branched alkyl group having 1 to 6 carbon atoms. As R¹The number of carbon atoms of (2) is more preferably 1 to 3.

As R¹Specifically, the linear or branched alkyl group may include CH₃-、CF₃-、CH₃CH₂-、CH₃CH₂CH₂-、CH₃CH₂CH₂CH₂-、

[ CHEM 52 ]

And the like.

In addition, in R¹In the case of a linear alkyl group having a fluorine atom, CF is mentioned₃-、CF₃CH₂-、CF₃CF₂-、CF₃CH₂CH₂-、CF₃CF₂CH₂-、CF₃CF₂CF₂-、CF₃CH₂CF₂-、CF₃CH₂CH₂CH₂-、CF₃CF₂CH₂CH₂-、CF₃CH₂CF₂CH₂-、CF₃CF₂CF₂CH₂-、CF₃CF₂CF₂CF₂-、CF₃CF₂CH₂CF₂-、CF₃CH₂CH₂CH₂CH₂-、CF₃CF₂CH₂CH₂CH₂-、CF₃CH₂CF₂CH₂CH₂-、CF₃CF₂CF₂CH₂CH₂-、CF₃CF₂CF₂CF₂CH₂-、CF₃CF₂CH₂CF₂CH₂-、CF₃CF₂CH₂CH₂CH₂CH₂-、CF₃CF₂CF₂CF₂CH₂CH₂-、CF₃CF₂CH₂CF₂CH₂CH₂-、HCF₂-、HCF₂CH₂-、HCF₂CF₂-、HCF₂CH₂CH₂-、HCF₂CF₂CH₂-、HCF₂CH₂CF₂-、HCF₂CF₂CH₂CH₂-、HCF₂CH₂CF₂CH₂-、HCF₂CF₂CF₂CF₂-、HCF₂CF₂CH₂CH₂CH₂-、HCF₂CH₂CF₂CH₂CH₂-、HCF₂CF₂CF₂CF₂CH₂-、HCF₂CF₂CF₂CF₂CH₂CH₂-、FCH₂-、FCH₂CH₂-、FCH₂CF₂-、FCH₂CF₂CH₂-、FCH₂CF₂CF₂-、CH₃CF₂CH₂-、CH₃CF₂CF₂-、CH₃CF₂CH₂CF₂-、CH₃CF₂CF₂CF₂-、CH₃CH₂CF₂CF₂-、CH₃CF₂CH₂CF₂CH₂-、CH₃CF₂CF₂CF₂CH₂-、CH₃CF₂CF₂CH₂CH₂-、CH₃CH₂CF₂CF₂CH₂-、CH₃CF₂CH₂CF₂CH₂CH₂-、CH₃CF₂CH₂CF₂CH₂CH₂-、HCFClCF₂CH₂-、HCF₂CFClCH₂-、HCF₂CFClCF₂CFClCH₂-、HCFClCF₂CFClCF₂CH₂-and the like.

In addition, in R¹When the alkyl group is a branched alkyl group having a fluorine atom, preferred examples thereof include

[ CHEM 53 ]

[ CHEM 54 ]

And the like. Wherein, if having CH₃-、CF₃Such a branched chain tends to increase the viscosity, and therefore, the number thereof is more preferably small (1) or zero.

R²The alkylene group has 1 to 3 carbon atoms and may have a fluorine atom. R²The polymer may be linear or branched. Examples of the minimum structural unit constituting such a linear or branched alkylene group are shown below. R²Consisting of them alone or in combination.

(i) Linear minimum structural unit:

-CH₂-、-CHF-、-CF₂-、-CHCl-、-CFCl-、-CCl₂-

(ii) branched minimum structural unit:

[ CHEM 55 ]

In the above examples, it is preferable that the compound is composed of a structural unit containing no Cl from the viewpoint of not causing HCl removal reaction by alkali and being more stable.

At R²When the chain is linear, it is preferably composed of only the above-mentioned linear minimum structural unit, among them, -CH₂-、CH₂CH₂-or-CF₂-. From the viewpoint of further improving the solubility of the electrolyte salt, — CH is more preferable₂-or-CH₂CH₂-。

At R²When the branched chain is a branched chain, it contains at least 1 branched chain minimum structural unit, and preferable examples thereof include those of the general formula- (CX)^aX^b)-(X^aIs H, F, CH₃Or CF₃；X^bIs CH₃Or CF₃. Wherein, in X^bIs CF₃In the case of (A), X^aIs H or CH₃) The unit shown. These units can be further improved in particularSolubility of the electrolyte salt.

Specific examples of the preferred fluoroalkyl group include CF₃CF₂-、HCF₂CF₂-、H₂CFCF₂-、CH₃CF₂-、CF₃CH₂-、CF₃CF₂CF₂-、HCF₂CF₂CF₂-、H₂CFCF₂CF₂-、CH₃CF₂CF₂-

[ CHEM 56 ]

[ CHEM 57 ]

And the like.

Wherein, as Rf²And R⁷Is preferably CF, is₃-、CF₃CF₂-、(CF₃)₂CH-，CF₃CH₂-、C₂F₅CH₂-、CF₃CF₂CH₂-、HCF₂CF₂CH₂-、CF₃CFHCF₂CH₂-、CFH₂-、CF₂H-is more preferably CF in view of high flame retardancy, good rate characteristics and good oxidation resistance₃CH₂-、CF₃CF₂CH₂-、HCF₂CF₂CH₂-、CFH₂-、CF₂H-。

At R⁷When the alkyl group is an alkyl group containing no fluorine atom, the alkyl group has 1 to 7 carbon atoms. From the aspect of low viscosity, R⁷The number of carbon atoms of (A) is preferably 1 to 4, more preferably 1 to 3.

Examples of the alkyl group not containing a fluorine atom include CH₃-、CH₃CH₂-、(CH₃)₂CH-、C₃H₇-and the like. Among them, CH is preferable in view of low viscosity and good rate characteristics₃-、CH₃CH₂-。

The fluorine content of the fluorinated chain carbonate is preferably 15 to 70% by mass. When the fluorine content is in the above range, the compatibility with the solvent and the solubility of the salt can be maintained. The fluorine content is more preferably 20% by mass or more, still more preferably 30% by mass or more, particularly preferably 35% by mass or more, still more preferably 60% by mass or less, and still more preferably 50% by mass or less.

In the present invention, the fluorine content is determined by the structural formula of the fluorinated chain carbonate

A value calculated by { (the number of fluorine atoms X19)/the molecular weight of a fluorinated chain carbonate }. times.100 (%).

The fluorinated chain carbonate is preferably any of the following compounds in view of low viscosity.

[ CHEM 58 ]

The fluorinated chain carbonate is particularly preferably methyl 2,2, 2-trifluoroethyl carbonate (F)₃CH₂COC(＝O)OCH₃)。

The fluorinated chain carbonate may be used alone in 1 kind, or may be used in combination in 2 or more kinds in any combination and ratio.

When the fluorinated chain carbonate is contained, the content of the fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and still more preferably 50 to 80% by volume with respect to the solvent.

The carboxylic acid ester may be a cyclic carboxylic acid ester or a chain carboxylic acid ester.

The cyclic carboxylic acid ester may be a non-fluorinated cyclic carboxylic acid ester or a fluorinated cyclic carboxylic acid ester.

The non-fluorinated cyclic carboxylic acid ester includes a non-fluorinated saturated cyclic carboxylic acid ester, and preferably a non-fluorinated saturated cyclic carboxylic acid ester having an alkylene group having 2 to 4 carbon atoms.

Specific examples of the non-fluorinated saturated cyclic carboxylic acid ester having an alkylene group having 2 to 4 carbon atoms include β -propiolactone, γ -butyrolactone, -caprolactone, -valerolactone, and α methyl- γ -butyrolactone. Among them, γ -butyrolactone and-valerolactone are particularly preferable from the viewpoint of improving the degree of dissociation of lithium ions and improving the load characteristics.

The above-mentioned non-fluorinated saturated cyclic carboxylic acid ester may be used alone in 1 kind, or may be used in combination in 2 or more kinds in an arbitrary combination and ratio.

When the non-fluorinated saturated cyclic carboxylic acid ester is contained, the content of the non-fluorinated saturated cyclic carboxylic acid ester is preferably 0 to 90% by volume, more preferably 0.001 to 90% by volume, still more preferably 1 to 60% by volume, and particularly preferably 5 to 40% by volume, based on the solvent.

The chain carboxylic acid ester may be a non-fluorinated chain carboxylic acid ester or a fluorinated chain carboxylic acid ester. When the solvent contains the chain carboxylic acid ester, the increase in resistance after high-temperature storage of the electrolyte can be further suppressed.

Examples of the non-fluorinated chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, tert-butyl butyrate, sec-butyl propionate, sec-butyl butyrate, n-butyl butyrate, methyl pyrophosphate, ethyl pyrophosphate, tert-butyl formate, tert-butyl acetate, sec-butyl formate, sec-butyl acetate, n-hexyl pivalate, n-propyl formate, n-propyl acetate, n-butyl formate, n-butyl pivalate, n-octyl pivalate, ethyl 2- (dimethoxyphosphoryl) acetate, ethyl 2- (dimethylphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethylphosphoryl) acetate, isopropyl propionate, isopropyl acetate, ethyl formate, monoethyl mono-2-propynyl oxalate, methyl acetate, ethyl propionate, and ethyl propionate, Isopropyl formate, isopropyl butyrate, isobutyl formate, isobutyl propionate, isobutyl butyrate, isobutyl acetate, and the like.

Among them, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate are preferable, and ethyl propionate and propyl propionate are particularly preferable.

The above-mentioned non-fluorinated chain carboxylic acid ester may be used alone in 1 kind, or may be used in combination in 2 or more kinds in an arbitrary combination and ratio.

When the non-fluorinated chain carboxylic acid ester is contained, the content of the non-fluorinated chain carboxylic acid ester is preferably 0 to 90% by volume, more preferably 0.001 to 90% by volume, further preferably 1 to 60% by volume, and particularly preferably 5 to 40% by volume, based on the solvent.

The fluorinated chain carboxylic acid ester is a chain carboxylic acid ester having a fluorine atom. The solvent containing the fluorinated chain carboxylic acid ester can be suitably used even under a high voltage.

The fluorinated chain carboxylic acid ester is preferably represented by the following general formula:

R³¹COOR³²

(in the formula, R³¹And R³²Independently of each other, a C1-4 alkyl group which may contain a fluorine atom, R³¹And R³²At least one of which contains a fluorine atom. ) The fluorinated chain carboxylic acid ester is shown.

As R³¹And R³²Examples thereof include a methyl group (-CH)₃) Ethyl (-CH)₂CH₃) Propyl (-CH)₂CH₂CH₃) Isopropyl (-CH (CH)₃)₂) N-butyl (-CH)₂CH₂CH₂CH₃) T-butyl (-C (CH))₃)₃) And the like non-fluorinated alkyl groups; -CF₃、-CF₂H、-CFH₂、-CF₂CF₃、-CF₂CF₂H、-CF₂CFH₂、-CH₂CF₃、-CH₂CF₂H、-CH₂CFH₂、-CF₂CF₂CF₃、-CF₂CF₂CF₂H、-CF₂CF₂CFH₂、-CH₂CF₂CF₃、-CH₂CF₂CF₂H、-CH₂CF₂CFH₂、-CH₂CH₂CF₃、-CH₂CH₂CF₂H、-CH₂CH₂CFH₂、-CF(CF₃)₂、-CF(CF₂H)₂、-CF(CFH₂)₂、-CH(CF₃)₂、-CH(CF₂H)₂、-CH(CFH₂)₂、-CF(OCH₃)CF₃、-CF₂CF₂CF₂CF₃、-CF₂CF₂CF₂CF₂H、-CF₂CF₂CF₂CFH₂、-CH₂CF₂CF₂CF₃、-CH₂CF₂CF₂CF₂H、-CH₂CF₂CF₂CFH₂、-CH₂CH₂CF₂CF₃、-CH₂CH₂CF₂CF₂H、-CH₂CH₂CF₂CFH₂、-CH₂CH₂CH₂CF₃、-CH₂CH₂CH₂CF₂H、-CH₂CH₂CH₂CFH₂、-CF(CF₃)CF₂CF₃、-CF(CF₂H)CF₂CF₃、-CF(CFH₂)CF₂CF₃、-CF(CF₃)CF₂CF₂H、-CF(CF₃)CF₂CFH₂、-CF(CF₃)CH₂CF₃、-CF(CF₃)CH₂CF₂H、-CF(CF₃)CH₂CFH₂、-CH(CF₃)CF₂CF₃、-CH(CF₂H)CF₂CF₃、-CH(CFH₂)CF₂CF₃、-CH(CF₃)CF₂CF₂H、-CH(CF₃)CF₂CFH₂、-CH(CF₃)CH₂CF₃、-CH(CF₃)CH₂CF₂H、-CH(CF₃)CH₂CFH₂、-CF₂CF(CF₃)CF₃、-CF₂CF(CF₂H)CF₃、-CF₂CF(CFH₂)CF₃、-CF₂CF(CF₃)CF₂H、-CF₂CF(CF₃)CFH₂、-CH₂CF(CF₃)CF₃、-CH₂CF(CF₂H)CF₃、-CH₂CF(CFH₂)CF₃、-CH₂CF(CF₃)CF₂H、-CH₂CF(CF₃)CFH₂、-CH₂CH(CF₃)CF₃、-CH₂CH(CF₂H)CF₃、-CH₂CH(CFH₂)CF₃、-CH₂CH(CF₃)CF₂H、-CH₂CH(CF₃)CFH₂、-CF₂CH(CF₃)CF₃、-CF₂CH(CF₂H)CF₃、-CF₂CH(CFH₂)CF₃、-CF₂CH(CF₃)CF₂H、-CF₂CH(CF₃)CFH₂、-C(CF₃)₃、-C(CF₂H)₃、-C(CFH₂)₃And fluoroalkyl groups. Among them, methyl, ethyl and-CF are particularly preferable from the viewpoint of good compatibility with other solvents, viscosity and oxidation resistance₃、-CF₂H、-CF₂CF₃、-CH₂CF₃、-CH₂CF₂H、-CH₂CFH₂、-CH₂CH₂CF₃、-CH₂CF₂CF₃、-CH₂CF₂CF₂H、-CH₂CF₂CFH₂。

Specific examples of the fluorinated chain carboxylic acid ester include 1 or 2 or more of the following: CF (compact flash)₃CH₂C(＝O)OCH₃(3, 3, 3-Trifluoropropionic acid methyl ester), HCF₂C(＝O)OCH₃(methyl difluoroacetate), HCF₂C(＝O)OC₂H₅(Ethyldifluoroacetate), CF₃C(＝O)OCH₂CH₂CF₃、CF₃C(＝O)OCH₂C₂H₅、CF₃C(＝O)OCH₂CF₂CF₂H (trifluoroacetic acid-2, 2,3, 3-tetrafluoropropyl ester), CF₃C(＝O)OCH₂CF₃、CF₃C(＝O)OCH(CF₃)₂Ethyl pentafluorobutyrate, methyl pentafluoropropionate, ethyl pentafluoropropionate, methyl heptafluoroisobutyrate, isopropyl trifluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, n-butyl trifluoroacetate, methyl tetrafluoro-2- (methoxy) propionate, 2-difluoroethyl acetate, 2,3, 3-tetrafluoropropyl acetate, CH₃C(＝O)OCH₂CF₃(2, 2, 2-trifluoroethyl acetate), 2,2,3,3,4,4, 4-heptafluorobutyl acetate, 4,4, 4-trifluorobutanoic acid methyl ester, 4,4, 4-trifluorobutanoic acid ethyl ester, 3,3, 3-trifluoropropionic acid ethyl ester, 3,3, 3-trifluoropropyl 3, 3- (trifluoromethyl) butanoic acid ethyl ester, 2,3,3, 3-tetrafluoropropionic acid methyl ester, 2, 2-difluoroacetic acid butyl ester, 2,2,3, 3-tetrafluoropropionic acid methyl ester, 2- (trifluoromethyl) -3, 3, 3-trifluoropropionic acid methyl ester, heptafluorobutyric acid methyl ester, etc.

Among them, from the viewpoint of good compatibility with other solvents and rate characteristics, CF is preferable₃CH₂C(＝O)OCH₃、HCF₂C(＝O)OCH₃、HCF₂C(＝O)OC₂H₅、CF₃C(＝O)OCH₂C₂F₅、CF₃C(＝O)OCH₂CF₂CF₂H、CF₃C(＝O)OCH₂CF₃、CF₃C(＝O)OCH(CF₃)₂Ethyl pentafluorobutyrate, methyl pentafluoropropionate, ethyl pentafluoropropionate, methyl heptafluoroisobutyrate, isopropyl trifluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, n-butyl trifluoroacetate, methyl tetrafluoro-2- (methoxy) propionate, 2-difluoroethyl acetate, 2,3, 3-tetrafluoropropyl acetate, CH₃C(＝O)OCH₂CF₃2,2,3,3,4,4, 4-heptafluorobutyl acetate, methyl 4,4, 4-trifluorobutyrate, ethyl 3,3, 3-trifluoropropionate, 3,3, 3-trifluoropropyl 3, 3- (trifluoromethyl) butyrate, 2,methyl 3,3, 3-tetrafluoropropionate, butyl 2, 2-difluoroacetate, methyl 2,2,3, 3-tetrafluoropropionate, methyl 2- (trifluoromethyl) -3, 3, 3-trifluoropropionate, methyl heptafluorobutyrate, and more preferably CF₃CH₂C(＝O)OCH₃、HCF₂C(＝O)OCH₃、HCF₂C(＝O)OC₂H₅、CH₃C(＝O)OCH₂CF₃Particularly preferred is HCF₂C(＝O)OCH₃、HCF₂C(＝O)OC₂H₅、CH₃C(＝O)OCF₂CF₃。

The fluorinated chain carboxylic acid ester may be used alone in 1 kind, or may be used in combination in 2 or more kinds in an arbitrary combination and ratio.

When the fluorinated chain carboxylic ester is contained, the content of the fluorinated chain carboxylic ester is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and still more preferably 50 to 80% by volume with respect to the solvent.

The solvent preferably contains at least 1 selected from the group consisting of the cyclic carbonate, the chain carbonate, and the chain carboxylate, and more preferably contains the cyclic carbonate and at least 1 selected from the group consisting of the chain carbonate and the chain carboxylate. The cyclic carbonate is preferably a saturated cyclic carbonate.

The electrolyte solution containing the solvent having the above composition can further improve the high-temperature storage characteristics and cycle characteristics of the electrochemical device.

When the solvent contains the cyclic carbonate and at least 1 selected from the chain carbonate and the chain carboxylate, the total amount of the cyclic carbonate and at least 1 selected from the chain carbonate and the chain carboxylate is preferably 10 to 100 vol%, more preferably 30 to 100 vol%, and still more preferably 50 to 100 vol%.

When the solvent contains the cyclic carbonate and at least 1 selected from the chain carbonate and the chain carboxylic ester, the volume ratio of the cyclic carbonate to the at least 1 selected from the chain carbonate and the chain carboxylic ester is preferably 5/95 to 95/5, more preferably 10/90 or more, further preferably 15/85 or more, particularly preferably 20/80 or more, more preferably 90/10 or less, further preferably 60/40 or less, and particularly preferably 50/50 or less.

The solvent preferably contains at least 1 kind selected from the group consisting of the non-fluorinated saturated cyclic carbonate, the non-fluorinated chain carbonate and the non-fluorinated chain carboxylate, and more preferably contains at least 1 kind selected from the group consisting of the non-fluorinated saturated cyclic carbonate and the non-fluorinated chain carbonate. The electrolyte solution containing the solvent of the above composition can be suitably used for an electrochemical device used at a relatively low voltage.

When the solvent contains the non-fluorinated saturated cyclic carbonate and at least 1 selected from the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester, the total amount of the non-fluorinated saturated cyclic carbonate and at least 1 selected from the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester is preferably 5 to 100 vol%, more preferably 20 to 100 vol%, and still more preferably 30 to 100 vol%.

When the electrolyte solution contains the non-fluorinated saturated cyclic carbonate and at least 1 selected from the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic ester, the volume ratio of the non-fluorinated saturated cyclic carbonate to at least 1 selected from the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic ester is preferably 5/95 to 95/5, more preferably 10/90 or more, further preferably 15/85 or more, particularly preferably 20/80 or more, more preferably 90/10 or less, further preferably 60/40 or less, and particularly preferably 50/50 or less.

The solvent preferably contains at least 1 kind selected from the fluorinated saturated cyclic carbonate, the fluorinated chain carbonate, and the fluorinated chain carboxylate, and more preferably contains at least 1 kind selected from the fluorinated saturated cyclic carbonate and the fluorinated chain carbonate. The electrolyte solution containing the solvent of the above composition can be suitably used not only for an electrochemical device used at a relatively low voltage but also for an electrochemical device used at a relatively high voltage.

When the solvent contains the fluorinated saturated cyclic carbonate and at least 1 selected from the fluorinated chain carbonate and the fluorinated chain carboxylate, the total amount of the fluorinated saturated cyclic carbonate and at least 1 selected from the fluorinated chain carbonate and the fluorinated chain carboxylate is preferably 5 to 100% by volume, more preferably 10 to 100% by volume, and still more preferably 30 to 100% by volume.

When the solvent contains the fluorinated saturated cyclic carbonate and at least 1 selected from the fluorinated chain carbonate and the fluorinated chain carboxylic ester, the volume ratio of the fluorinated saturated cyclic carbonate to the at least 1 selected from the fluorinated chain carbonate and the fluorinated chain carboxylic ester is preferably 5/95 to 95/5, more preferably 10/90 or more, further preferably 15/85 or more, particularly preferably 20/80 or more, more preferably 90/10 or less, further preferably 60/40 or less, and particularly preferably 50/50 or less.

In addition, as the solvent, an ionic liquid may be used. "ionic liquid" refers to a liquid composed of ions combining organic cations and anions.

The organic cation is not particularly limited, and examples thereof include imidazolium ions such as dialkylimidazolium cations and trialkylimidazolium cations; a tetraalkylammonium ion; an alkylpyridinium ion; a dialkyl pyrrolidinium ion; and a dialkylpiperidinium ion.

The anion that is a counter-ion of these organic cations is not particularly limited, and for example, PF can be used₆Anion, PF₃(C₂F₅)₃Anion, PF₃(CF₃)₃Anion, BF₄Anion, BF₂(CF₃)₂Anion, BF₃(CF₃) Anion, bis (oxalato) borate anion, P (C)₂O₄)F₂Anion, Tf (trifluoromethanesulfonic acid)Acyl) anion, Nf (nonafluorobutanesulfonyl) anion bis (fluorosulfonyl) imide anion, bis (trifluoromethanesulfonyl) imide anion, bis (pentafluoroethanesulfonyl) imide anion, dicyanamide anion, halide anion.

The solvent is preferably a nonaqueous solvent, and the electrolyte solution of the present invention is preferably a nonaqueous electrolyte solution.

The content of the solvent in the electrolyte is preferably 70 to 99.999% by mass, more preferably 80% by mass or more, and still more preferably 92% by mass or less.

The electrolyte solution of the present invention may further contain a compound (5) represented by general formula (5).

General formula (5):

[ CHEMICAL 59 ]

(in the formula, A)^a+Is a metal ion, a hydrogen ion or an onium ion. a is an integer of 1 to 3, b is an integer of 1 to 3, p is b/a, n203 is an integer of 1 to 4, n201 is an integer of 0 to 8, n202 is 0 or 1, Z²⁰¹Is a transition metal, an element of group III, group IV or group V of the periodic Table of the elements.

X²⁰¹O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms or a halogenated arylene group having 6 to 20 carbon atoms (the alkylene group, the halogenated alkylene group, the arylene group and the halogenated arylene group may have a substituent or a hetero atom in their structure), and when n202 is 1 and n203 is 2 to 4, n 203X atoms²⁰¹May be separately bonded).

L²⁰¹Halogen atom, cyano group, alkyl group having 1 to 10 carbon atoms, haloalkyl group having 1 to 10 carbon atoms, aryl group having 6 to 20 carbon atoms, haloaryl group having 6 to 20 carbon atoms (alkylene group, haloalkylene group, arylene group, and haloarylene group may have a substituent or a hetero atom in the structure thereof), and when n201 is 2 to 8, n 201L²⁰¹May be bonded to form a ring) or-Z²⁰³Y²⁰³。

Y²⁰¹、Y²⁰²And Z²⁰³Each independently is O, S, NY²⁰⁴A hydrocarbon group or a fluorinated hydrocarbon group. Y is²⁰³And Y²⁰⁴H, F, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or a haloaryl group having 6 to 20 carbon atoms (the alkyl group, haloalkyl group, aryl group and haloaryl group may have a substituent or a hetero atom in their structure, and a plurality of Y's may be present²⁰³And Z²⁰⁴In the case of (b), they may be bonded to form a ring).

A^a+Represents lithium ion, sodium ion, potassium ion, magnesium ion, calcium ion, barium ion, cesium ion, silver ion, zinc ion, copper ion, cobalt ion, iron ion, nickel ion, manganese ion, titanium ion, lead ion, chromium ion, vanadium ion, ruthenium ion, yttrium ion, lanthanide ion, actinide ion, tetrabutylammonium ion, tetraethylammonium ion, tetramethylammonium ion, triethylmethylammonium ion, triethylammonium ion, pyridinium ion, imidazolium ion, hydrogen ion, tetraethylphosphonium ion, tetramethylphosphonium ion, tetraphenylphosphonium ion, triphenylsulfonium ion, triethylsulfonium ion, or the like.

In the case of use in electrochemical devices and the like, A^a+Lithium ion, sodium ion, magnesium ion, tetraalkylammonium ion, and hydrogen ion are preferable, and lithium ion is particularly preferable. A. the^a+The valence a of the cation (2) is an integer of 1 to 3. In the case of more than 3, the lattice energy becomes large, thus causing a problem of difficulty in dissolution in a solvent. Therefore, when the solubility is required, 1 is more preferable. The valence b of the anion is also an integer of 1 to 3, and 1 is particularly preferred. The constant p representing the ratio of cation to anion is necessarily determined by the ratio b/a of the valences of the two.

Next, a part of the ligand of the general formula (5) will be described. In the present specification, Z is a group represented by the general formula (5)²⁰¹The bound organic or inorganic moiety is referred to as a ligand.

Z²⁰¹Preferably Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf or Sb, more preferably Al, B or P.

X²⁰¹O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms or a halogenated arylene group having 6 to 20 carbon atoms. These alkylene groups and arylene groups may have a substituent or a hetero atom in their structure. Specifically, the hydrogen atoms in the alkylene group and the arylene group may be replaced by halogen atoms, linear or cyclic alkyl groups, aryl groups, alkenyl groups, alkoxy groups, aryloxy groups, sulfonyl groups, amino groups, cyano groups, carbonyl groups, acyl groups, amide groups, or hydroxyl groups, or nitrogen, sulfur, or oxygen may be introduced in place of carbon atoms in the alkylene group and the arylene group. In addition, when n202 is 1 and n203 is 2 to 4, n 203X²⁰¹Or may be bonded separately. Examples of such a ligand include a ligand such as ethylenediaminetetraacetic acid.

L²⁰¹Represents a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms or-Z²⁰³Y²⁰³(with respect to Z)²⁰³、Y²⁰³As will be described later). The alkyl and aryl radicals here may also be reacted with X²⁰¹Similarly, the structure may have a substituent or hetero atom, and when n201 is 2 to 8, n 201L' s²⁰¹The two may be bonded to form a ring. As L²⁰¹Preferably a fluorine atom or a cyano group. This is because, in the case of a fluorine atom, the solubility and dissociation degree of the salt of the anionic compound are improved, and the ion conductivity is improved. In addition, the oxidation resistance is improved, and thus the occurrence of side reactions can be suppressed.

Y²⁰¹、Y²⁰²And Z²⁰³Each independently representing O, S, NY²⁰⁴A hydrocarbon group or a fluorinated hydrocarbon group. Y is²⁰¹And Y²⁰²Preferably O, S or NY²⁰⁴More preferably, O. The compound (5) is characterized in that Y is present in the same ligand²⁰¹And Y²⁰²Formed with Z²⁰¹Thus these ligands are bonded to Z²⁰¹Forming a chelate structure. The chelating effect improves the heat resistance, chemical stability, and hydrolysis resistance of the compound.The constant n202 in the ligand is 0 or 1, and particularly in the case of 0, the chelate ring is a five-membered ring, and therefore the chelate effect is exhibited most strongly, and the stability is increased, which is preferable.

In the present specification, a fluorinated hydrocarbon group is a group in which at least 1 of hydrogen atoms of a hydrocarbon group is substituted with a fluorine atom.

Y²⁰³And Y²⁰⁴H, F, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or a haloaryl group having 6 to 20 carbon atoms, each independently, wherein the alkyl group and the aryl group may have a substituent or a hetero atom in the structure thereof, and a plurality of Y's may be present²⁰³Or Y²⁰⁴In the case of (3), the two may be bonded to form a ring.

The constant n203 relating to the number of ligands is an integer of 1 to 4, preferably 1 or 2, and more preferably 2. The constant n201 relating to the number of ligands is an integer of 0 to 8, preferably an integer of 0 to 4, and more preferably 0, 2, or 4. Further, it is preferable that n201 is 2 when n203 is 1, and n201 is 0 when n203 is 2.

In the general formula (5), the alkyl group, the haloalkyl group, the aryl group and the haloaryl group also include groups having other functional groups such as a branched chain, a hydroxyl group and an ether bond.

As compound (5), preferred is a compound of the formula:

[ CHEM 60 ]

(in the formula, A)^a+、a、b、p、n201、Z²⁰¹And L²⁰¹As shown above), or a compound of formula (la):

[ CHEM 61 ]

(in the formula, A)^a+、a、b、p、n201、Z²⁰¹And L²⁰¹As shown above).

The compound (5) is a lithium oxalato borate salt, and the following chemical formula:

[ CHEM 62 ]

Lithium bis (oxalato) borate (LIBOB) represented by the following formula:

[ CHEM 63 ]

Lithium difluorooxalato borate (LIDFOB) as shown,

as the compound (5), there may be mentioned the following formula:

[ CHEM 64 ]

Lithium difluorooxalate phosphate (LIDFOP), the following formula:

[ CHEM 65 ]

Lithium tetrafluorooxalate phosphate (LITFOP), the following formula:

[ CHEM 66 ]

Lithium bis (oxalato) difluorophosphate, etc.

Specific examples of the dicarboxylic acid complex salt in which boron is a central element of the complex include lithium bis (malonate) borate, lithium difluoro (malonate) borate, lithium bis (methylmalonate) borate, lithium difluoro (methylmalonate) borate, lithium bis (dimethylmalonate) borate, lithium difluoro (dimethylmalonate) borate, and the like.

Specific examples of the dicarboxylic acid complex salt in which phosphorus is the central element of the complex include lithium tris (oxalato) phosphate, lithium tris (malonato) phosphate, lithium difluorobis (malonato) phosphate, lithium tetrafluoro (malonato) phosphate, lithium tris (methylmalonate) phosphate, lithium difluorobis (methylmalonate) phosphate, lithium tetrafluoro (methylmalonate) phosphate, lithium tris (dimethylmalonate) phosphate, lithium difluorobis (dimethylmalonate) phosphate, lithium tetrafluoro (dimethylmalonate) phosphate, and the like.

Specific examples of the dicarboxylic acid complex salt in which the central element of the complex is aluminum include LiAl (C)₂O₄)₂、LiAlF₂(C₂O₄) And the like.

Among these, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium tris (oxalate) phosphate, lithium difluoro (oxalate) phosphate, and lithium tetrafluoro (oxalate) phosphate are more preferably used in terms of easy availability and contribution to the formation of a stable film-like structure.

As the compound (5), lithium bis (oxalato) borate is particularly preferable.

The content of the compound (5) is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, preferably 10 mass% or less, and more preferably 3 mass% or less with respect to the solvent, from the viewpoint of obtaining more excellent cycle characteristics.

The electrolytic solution of the present invention preferably further contains an electrolyte salt (excluding the compound (5)). As the electrolyte salt, any electrolyte salt that can be used in an electrolytic solution, such as a liquid salt (ionic liquid), an inorganic polymer salt, and an organic polymer salt, can be used in addition to a lithium salt, an ammonium salt, and a metal salt.

As the electrolyte salt of the electrolyte solution for a lithium ion secondary battery, a lithium salt is preferable.

As the lithium salt, any lithium salt can be used, and specific examples thereof include the following lithium salts. Examples thereof include: LiPF₆、LiBF₄、LiClO₄、LiAlF₄、LiSbF₆、LiTaF₆，LiWF₇、LiAsF₆，LiAlCl₄，LiI、LiBr、LiCl、LiB₁₀Cl₁₀、Li₂SiF₆、Li₂PFO₃、LiPO₂F₂Inorganic lithium salts;

LiWOF₅lithium tungstate species;

HCO₂Li、CH₃CO₂Li、CH₂FCO₂Li、CHF₂CO₂Li、CF₃CO₂Li、CF₃CH₂CO₂Li、CF₃CF₂CO₂Li、CF₃CF₂CF₂CO₂Li、CF₃CF₂CF₂CF₂CO₂lithium carboxylates such as Li;

FSO₃Li、CH₃SO₃Li、CH₂FSO₃Li、CHF₂SO₃Li、CF₃SO₃Li、CF₃CF₂SO₃Li、CF₃CF₂CF₂SO₃Li、CF₃CF₂CF₂CF₂SO₃li, lithium methylsulfate, lithium ethylsulfate (C)₂H₅OSO₃Lithium salts having S ═ O groups such as Li), lithium 2,2, 2-trifluoroethyl sulfate, and the like;

LiN(FCO)₂、LiN(FCO)(FSO₂)、LiN(FSO₂)₂、LiN(FSO₂)(CF₃SO₂)、LiN(CF₃SO₂)₂、LiN(C₂F₅SO₂)₂lithium bis (perfluoroethanesulfonyl) imide, lithium cyclic 1, 2-perfluoroethanedisulfonyl imide, lithium cyclic 1, 3-perfluoropropanedisulfonyl imide, lithium cyclic 1, 2-ethanedidisulfonyl imide, lithium cyclic 1, 3-propanedisulfonyl imide, lithium cyclic 1, 4-perfluorobutanedisulfonyl imide, LiN (CF)₃SO₂)(FSO₂)、LiN(CF₃SO₂)(C₃F₇SO₂)、LiN(CF₃SO₂)(C₄F₉SO₂)、LiN(POF₂)₂Lithium imide salts;

LiC(FSO₂)₃、LiC(CF₃SO₂)₃、LiC(C₂F₅SO₂)₃and the like methyllithium salts;

in addition, there may be mentioned the formula: LiPF_a(C_nF_2n+1)_6-a(wherein a is an integer of 0 to 5 and n is an integer of 1 to 6) or a salt thereof (e.g., LiPF₃(C₂F₅)₃、LiPF₃(CF₃)₃、LiPF₃(iso-C₃F₇)₃、LiPF₅(iso-C₃F₇)、LiPF₄(CF₃)₂、LiPF₄(C₂F₅)₂)、LiPF₄(CF₃SO₂)₂、LiPF₄(C₂F₅SO₂)₂、LiBF₃CF₃、LiBF₃C₂F₅、LiBF₃C₃F₇、LiBF₂(CF₃)₂、LiBF₂(C₂F₅)₂、LiBF₂(CF₃SO₂)₂、LiBF₂(C₂F₅SO₂)₂And fluorine-containing organic lithium salts, LiSCN, LiB (CN)₄、LiB(C₆H₅)₄、Li₂(C₂O₄)、LiP(C₂O₄)₃、Li₂B₁₂F_bH_12-b(b is an integer of 0 to 3), and the like.

Among these, LiPF is particularly preferable in terms of having an effect of improving output characteristics, high-rate charge/discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like₆、LiBF₄、LiSbF₆、LiTaF₆、LiPO₂F₂、FSO₃Li，CF₃SO₃Li、LiN(FSO₂)₂、LiN(FSO₂)(CF₃SO₂)、LiN(CF₃SO₂)₂、LiN(C₂F₅SO₂)₂Lithium cyclic 1, 2-perfluoroethane disulfonimide, lithium cyclic 1, 3-perfluoropropane disulfonimide, and LiC (FS)O₂)₃、LiC(CF₃SO₂)₃、LiC(C₂F₅SO₂)₃、LiBF₃CF₃、LiBF₃C₂F₅、LiPF₃(CF₃)₃、LiPF₃(C₂F₅)₃Etc., most preferably selected from LiPF₆、LiN(FSO₂)₂And LiBF₄At least 1 lithium salt of (1).

These electrolyte salts may be used alone, or 2 or more kinds thereof may be used in combination. LiPF is a preferred example of a combination of 2 or more species₆And LiBF₄Or, LiPF₆With LiPO₂F₂、C₂H₅OSO₃Li or FSO₃The use of Li in combination has the effect of improving high-temperature storage characteristics, load characteristics, and cycle characteristics.

In this case, the LiBF was 100 mass% based on the entire electrolyte₄、LiPO₂F₂、C₂H₅OSO₃Li or FSO₃The amount of Li to be added is not limited, and is arbitrary as long as the effect of the present invention is not significantly impaired, and is usually 0.01 mass% or more, preferably 0.1 mass% or more, and is usually 30 mass% or less, preferably 20 mass% or less, more preferably 10 mass% or less, and further preferably 5 mass% or less with respect to the electrolyte solution of the present invention.

In addition, another example is a combination of an inorganic lithium salt and an organic lithium salt, and the combination of these two has an effect of suppressing deterioration due to high-temperature storage. As the organic lithium salt, CF is preferable₃SO₃Li、LiN(FSO₂)₂、LiN(FSO₂)(CF₃SO₂)、LiN(CF₃SO₂)₂、LiN(C₂F₅SO₂)₂Lithium cyclic 1, 2-perfluoroethane disulfonimide, lithium cyclic 1, 3-perfluoropropane disulfonimide, and LiC (FSO)₂)₃、LiC(CF₃SO₂)₃、LiC(C₂F₅SO₂)₃、LiBF₃CF₃、LiBF₃C₂F₅、LiPF₃(CF₃)₃、LiPF₃(C₂F₅)₃And the like. In this case, the proportion of the organic lithium salt is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and further preferably 30% by mass or less, particularly preferably 20% by mass or less, relative to 100% by mass of the entire electrolyte solution.

The concentration of these electrolyte salts in the electrolytic solution is not particularly limited as long as the effects of the present invention are not impaired. From the viewpoint of ensuring good battery performance by setting the electrical conductivity of the electrolytic solution within a good range, the total molar concentration of lithium in the electrolytic solution is preferably 0.3mol/L or more, more preferably 0.4mol/L or more, further preferably 0.5mol/L or more, and further preferably 3mol/L or less, more preferably 2.5mol/L or less, further preferably 2.0mol/L or less.

If the total molar concentration of lithium is too low, the conductivity of the electrolytic solution may be insufficient, while if the concentration is too high, the conductivity may be lowered due to an increase in viscosity, and the battery performance may be lowered.

The electrolyte salt of the electrolyte solution for an electric double layer capacitor is preferably an ammonium salt.

The ammonium salt includes the following (IIa) to (IIe).

(IIa) tetraalkylammonium salt

Preferred examples may include general formula (IIa):

[ CHEM 67 ]

(in the formula, R^1a、R^2a、R^3aAnd R^4aThe alkyl groups are the same or different and are C1-C6 alkyl groups which can contain ether bonds; x^-Is an anion).

In addition, from the viewpoint of improving oxidation resistance, the ammonium salt is also preferably one in which a part or all of the hydrogen atoms of the ammonium salt are substituted with fluorine atoms and/or fluoroalkyl groups having 1 to 4 carbon atoms.

Specific examples thereof include those represented by the general formula (IIa-1):

[ CHEM 68 ]

(in the formula, R^1a、R^2aAnd X^-The same as above; a tetraalkylammonium salt wherein x and y are the same or different and each is an integer of 0 to 4, and x + y is 4),

General formula (IIa-2):

[ CHEM 69 ]

(in the formula, R^5aIs an alkyl group having 1 to 6 carbon atoms; r^6aIs a C1-6 2-valent hydrocarbon group; r^7aIs an alkyl group having 1 to 4 carbon atoms; z is 1 or 2; x^-Anionic), and the like.

By introducing an alkyl ether group, the viscosity can be reduced.

Anion X^-May be an inorganic anion or an organic anion. Examples of the inorganic anion include AlCl₄ ^-、BF₄ ^-、PF₆ ^-、AsF₆ ^-、TaF₆ ^-、I^-、SbF₆ ^-. Examples of the organic anion include bis (oxalato) borate anion, difluoro (oxalato) borate anion, tetrafluoro (oxalato) phosphate anion, difluoro (oxalato) phosphate anion, and CF₃COO^-、CF₃SO₃ ^-、(CF₃SO₂)₂N^-、(C₂F₅SO₂)₂N^-And the like.

Among them, BF is preferable from the viewpoint of good oxidation resistance and ion dissociation property₄ ^-、PF₆ ^-、AsF₆ ^-、SbF₆ ^-。

Preferable specific example of the tetraalkylammonium salt is Et₄NBF₄、Et₄NClO₄，Et₄NPF₆、Et₄NAsF₆、Et₄NSbF₆、Et₄NCF₃SO₃、Et₄N(CF₃SO₂)₂N、Et₄NC₄F₉SO₃、Et₃MeNBF₄、Et₃MeNClO₄、Et₃MeNPF₆、Et₃MeNAsF₆、Et₃MeNSbF₆、Et₃MeNCF₃SO₃、Et₃MeN(CF₃SO₂)₂N、Et₃MeNC₄F₉SO₃That is, Et can be specifically mentioned₄NBF₄、Et₄NPF₆、Et₄NSbF₆、Et₄NAsF₆、Et₃MeNBF₄And N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium salts.

(IIb) Spirocyclic bispyrrolidinium salts

Preferred examples thereof include those of the general formula (IIb-1):

[ CHEM 70 ]

(in the formula, R^8aAnd R^9aThe alkyl groups are the same or different and are all alkyl groups with 1-4 carbon atoms; x^-Is an anion; n1 is an integer of 0-5; n2 is an integer of 0 to 5) is used as the solvent,

General formula (IIb-2):

[ CHEM 71 ]

(in the formula, R^10aAnd R^11aThe alkyl groups are the same or different and are all alkyl groups with 1-4 carbon atoms;X^-is an anion; n3 is an integer of 0-5; n4 is an integer of 0 to 5), or

General formula (IIb-3):

[ CHEM 72 ]

(in the formula, R^12aAnd R^13aThe alkyl groups are the same or different and are all alkyl groups with 1-4 carbon atoms; x^-Is an anion; n5 is an integer of 0-5; n6 is an integer of 0 to 5).

In addition, from the viewpoint of improving oxidation resistance, the spiro-bispyrrolidinium salt is preferably one in which some or all of the hydrogen atoms of the spiro-bispyrrolidinium salt are substituted with fluorine atoms and/or fluoroalkyl groups having 1 to 4 carbon atoms.

Anion X^-The preferable specific example of (3) is the same as that of (IIa). Among them, BF is preferable in view of high dissociation and low internal resistance at high voltage₄-、PF₆-、(CF₃SO₂)₂N-or (C)₂F₅SO₂)₂N-。

Preferred specific examples of the spirocyclic bispyrrolidinium salt include, for example,

[ CHEM 73 ]

And the like.

The spirocyclic bispyrrolidinium salt is excellent in solubility in a solvent, oxidation resistance and ion conductivity.

(IIc) imidazolium salts

There may be exemplified general formula (IIc):

[ CHEM 74 ]

(in the formula, wherein,R^14aand R^15aThe alkyl groups are the same or different and are all alkyl groups with 1-6 carbon atoms; x^-Is an anion).

In addition, from the viewpoint of improving oxidation resistance, the imidazolium salt is preferably one in which a part or all of the hydrogen atoms are substituted with fluorine atoms and/or fluoroalkyl groups having 1 to 4 carbon atoms.

Anion X^-Preferred specific examples of (3) are the same as those of (IIa).

Specific preferred examples thereof include

[ CHEM 75 ]

And the like.

The imidazolium salt is excellent in low viscosity and good solubility.

(IId): n-alkylpyridinium salts

There can be preferably exemplified the general formula (IId):

[ CHEM 76 ]

(in the formula, R^16aIs an alkyl group having 1 to 6 carbon atoms; x^-Is an anion).

In addition, from the viewpoint of improving oxidation resistance, the N-alkylpyridinium salt is preferably one in which some or all of the hydrogen atoms are substituted with fluorine atoms and/or fluoroalkyl groups having 1 to 4 carbon atoms.

Anion X^-Preferred specific examples of (3) are the same as those of (IIa).

Specific preferred examples thereof include

[ CHEM 77 ]

And the like.

The N-alkylpyridinium salt is excellent in low viscosity and good solubility.

(IIe) N, N-dialkylpyrrolidinium salts

There may be preferably exemplified general formula (IIe):

[ CHEM 78 ]

(in the formula, R^17aAnd R^18aThe alkyl groups are the same or different and are all alkyl groups with 1-6 carbon atoms; x^-Is an anion) is used.

In addition, from the viewpoint of improving oxidation resistance, the N, N-dialkyl pyrrolidinium salt is preferably one in which a part or all of hydrogen atoms are substituted with fluorine atoms and/or fluorine-containing alkyl groups having 1 to 4 carbon atoms.

Anion X^-Preferred specific examples of (3) are the same as those of (IIa).

Specific preferred examples thereof include

[ CHEM 79 ]

[ CHEM 80 ]

And the like.

The N, N-dialkylpyrrolidinium salt is excellent in low viscosity and good solubility.

Among these ammonium salts, (IIa), (IIb) and (IIc) are preferable, and (IIb) and (IIc) are more preferable, from the viewpoint of good solubility, oxidation resistance and ion conductivity

[ CHEMICAL 81 ]

(wherein Me is methyl; Et is ethyl; X^-X and y are the same as those in formula (IIa-1).

As the electrolyte salt for the electric double layer capacitor, a lithium salt may be used. The lithium salt is preferably LiPF, for example₆、LiBF₄、LiN(FSO₂)₂、LiAsF₆、LiSbF₆、LiN(SO₂C₂H₅)₂。

To further increase capacity, magnesium salts may also be used. The magnesium salt is preferably, for example, Mg (ClO)₄)₂、Mg(OOC₂H₅)₂And the like.

When the electrolyte salt is the above ammonium salt, the concentration is preferably 0.7 mol/l or more. If it is less than 0.7 mol/liter, there is a risk that not only the low-temperature characteristics are deteriorated but also the initial internal resistance becomes high. The concentration of the electrolyte salt is more preferably 0.9 mol/l or more.

From the viewpoint of low-temperature characteristics, the upper limit of the concentration is preferably 2.0 mol/liter or less, and more preferably 1.5 mol/liter or less.

The ammonium salt is triethylmethylammonium Tetrafluoroborate (TEMABF)₄) In the case of (2), the concentration is preferably 0.7 to 1.5 mol/liter in view of excellent low-temperature characteristics.

In addition, the spiro-bis-pyrrolidinium tetrafluoroborate (SBPBF)₄) In the case of (3), it is preferably 0.7 to 2.0 mol/liter.

The electrolyte of the present invention preferably further contains a compound represented by the general formula (2):

[ CHEM 82 ]

(in the formula, X²¹Is a group containing at least H or C, n21 is an integer of 1 to 3, Y²¹And Z²¹Identical or different, is a radical containing at least H, C, O or F, n22 is 0 or 1, Y²¹And Z²¹May be bonded to each other to form a ring. ) The compound (2) shown below. If the above electrolysis is carried outWhen the liquid contains the compound (2), the capacity retention rate is less likely to be further reduced and the amount of gas generated is less likely to be further increased even when stored at high temperatures.

In the case where n21 is 2 or 3, 2 or 3X' s²¹May be the same or different.

In the presence of a plurality of Y²¹And Z²¹In the case of (2), a plurality of Y's present²¹And Z²¹May be the same or different.

As X²¹Preferably is-CY²¹Z²¹- (in, Y)²¹And Z²¹As shown above) or-CY²¹＝CZ²¹- (in, Y)²¹And Z²¹As shown above).

As Y²¹Preferably selected from H-, F-, CH₃-、CH₃CH₂-、CH₃CH₂CH₂-、CF₃-、CF₃CF₂-、CH₂FCH₂And CF₃CF₂CF₂At least 1 of (A) - (B).

As Z²¹Preferably selected from H-, F-, CH₃-、CH₃CH₂-、CH₃CH₂CH₂-、CF₃-、CF₃CF₂-、CH₂FCH₂And CF₃CF₂CF₂At least 1 of (A) - (B).

Or, Y²¹And Z²¹Can be bonded to each other to form a carbocyclic or heterocyclic ring which may contain unsaturated bonds and may also have aromatic properties. The number of carbon atoms in the ring is preferably 3 to 20.

Next, specific examples of the compound (2) will be described. In the following examples, "analog" refers to an acid anhydride obtained by replacing a part of the structure of an acid anhydride exemplified by the examples with another structure within a range not departing from the gist of the present invention, and examples thereof include dimers, trimers, tetramers, and the like containing a plurality of acid anhydrides; or a structural isomer having a branched chain or the like, for example, although the number of carbon atoms of the substituent is the same, or a site to which the substituent and the acid anhydride are bonded is different.

Specific examples of the acid anhydride forming the five-membered ring structure include succinic anhydride, methylsuccinic anhydride (4-methylsuccinic anhydride), dimethylsuccinic anhydride (4, 4-dimethylsuccinic anhydride, 4, 5-dimethylsuccinic anhydride, etc.), 4, 5-trimethylsuccinic anhydride, 4,5, 5-tetramethylsuccinic anhydride, 4-vinylsuccinic anhydride, 4, 5-divinylsuccinic anhydride, phenylsuccinic anhydride (4-phenylsuccinic anhydride), 4, 5-diphenylsuccinic anhydride, 4-diphenylsuccinic anhydride, citraconic anhydride, maleic anhydride, methylmaleic anhydride (4-methylmaleic anhydride), 4, 5-dimethylmaleic anhydride, phenylmaleic anhydride (4-phenylmaleic anhydride), 4, 5-diphenylmaleic anhydride, etc, Itaconic anhydride, 5-methyl itaconic anhydride, 5-dimethyl itaconic anhydride, phthalic anhydride, 3,4, 5, 6-tetrahydrophthalic anhydride, and the like.

Specific examples of the acid anhydride forming a six-membered ring structure include cyclohexanedicarboxylic anhydride (cyclohexane-1, 2-dicarboxylic anhydride, etc.), 4-cyclohexene-1, 2-dicarboxylic anhydride, glutaric anhydride, glutaconic anhydride, 2-phenylpentanoic anhydride, etc., and the like.

Specific examples of other acid anhydrides having a cyclic structure include 5-norbornene-2, 3-dicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, pyromellitic anhydride, diglycolic anhydride, and the like.

Specific examples of the acid anhydride having a cyclic structure and substituted with a halogen atom include monofluorosuccinic anhydride (e.g., 4-fluorosuccinic anhydride), 4-difluorosuccinic anhydride, 4, 5-difluorosuccinic anhydride, 4, 5-trifluorosuccinic anhydride, trifluoromethylsuccinic anhydride, tetrafluorosuccinic anhydride (4, 4,5, 5-tetrafluorosuccinic anhydride), 4-fluoromaleic anhydride, 4, 5-difluoromaleic anhydride, trifluoromethylmaleic anhydride, 5-fluoroitaconic anhydride, 5, 5-difluoroitaconic anhydride, and the like.

Among the compounds (2), preferred are glutaric anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, 4-cyclohexene-1, 2-dicarboxylic anhydride, 3,4, 5, 6-tetrahydrophthalic anhydride, 5-norbornene-2, 3-dicarboxylic anhydride, phenylsuccinic anhydride, 2-phenylpentanedioic anhydride, maleic anhydride, methylmaleic anhydride, trifluoromethylmaleic anhydride, phenylmaleic anhydride, succinic anhydride, methylsuccinic anhydride, dimethylsuccinic anhydride, trifluoromethylsuccinic anhydride, monofluorosuccinic anhydride, and tetrafluorosuccinic anhydride, and more preferred are maleic anhydride, methylmaleic anhydride, trifluoromethylmaleic anhydride, succinic anhydride, methylsuccinic anhydride, trifluoromethylsuccinic anhydride, and mixtures thereof, Tetrafluorosuccinic anhydride, and maleic anhydride and succinic anhydride are more preferable.

The compound (2) is preferably selected from the general formula (3):

[ CHEM 83 ]

(in the formula, X³¹～X³⁴Same or different, a group containing at least H, C, O or F), and a general formula (4):

[ CHEM 84 ]

(in the formula, X⁴¹And X⁴²The same or different, a group containing at least H, C, O or F).

As X³¹～X³⁴The same or different, preferably at least 1 selected from the group consisting of alkyl, fluoroalkyl, alkenyl and fluoroalkenyl. X³¹～X³⁴The number of carbon atoms of (A) is preferably 1 to 10, more preferably 1 to 3.

As X³¹～X³⁴Identical or different, more preferably selected from H-, F-, CH₃-、CH₃CH₂-、CH₃CH₂CH₂-、CF₃-、CF₃CF₂-、CH₂FCH₂And CF₃CF₂CF₂At least 1 of (A) - (B).

As X⁴¹And X⁴²The same or different, preferably at least 1 selected from the group consisting of alkyl, fluoroalkyl, alkenyl and fluoroalkenyl. X⁴¹And X⁴²The number of carbon atoms of (A) is preferably 1 to 10, more preferably 1 to 3.

As X⁴¹And X⁴²Identical or different, more preferably selected from H-, F-, CH₃-、CH₃CH₂-、CH₃CH₂CH₂-、CF₃-、CF₃CF₂-、CH₂FCH₂And CF₃CF₂CF₂At least 1 of (A) - (B).

The compound (3) is preferably any one of the following compounds.

[ CHEM 85 ]

The compound (4) is preferably any one of the following compounds.

[ CHEM 86 ]

The electrolyte solution preferably contains 0.0001 to 15 mass% of the compound (2) relative to the electrolyte solution so that the capacity retention rate is not liable to be further reduced and the amount of gas generated is not liable to be further increased even when the electrolyte solution is stored at a high temperature. The content of the compound (2) is more preferably 0.01 to 10% by mass, still more preferably 0.1 to 3% by mass, and particularly preferably 0.1 to 1.0% by mass.

In the case where the electrolyte solution contains both the compounds (3) and (4), the electrolyte solution preferably contains 0.08 to 2.50 mass% of the compound (3) and 0.02 to 1.50 mass% of the compound (4), and more preferably contains 0.80 to 2.50 mass% of the compound (3) and 0.08 to 1.50 mass% of the compound (4), in terms of not being liable to further decrease the capacity retention rate and not liable to further increase the amount of gas generated even when stored at high temperature.

The electrolyte solution of the present invention may contain at least 1 kind selected from nitrile compounds represented by the following general formulae (1a), (1b) and (1 c).

[ CHEM 87 ]

(in the formula, R^aAnd R^bEach independently represents a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms of an alkyl group is substituted by a halogen atom. n represents an integer of 1 to 10. )

[ CHEM 88 ]

(in the formula, R^cRepresents a hydrogen atom, a halogen atom, an alkyl group, a group in which at least a part of the hydrogen atoms of the alkyl group is substituted by a halogen atom, or NC-R^c1-X^c1-(R^c1Represents an alkylene group, X^c1Represents an oxygen atom or a sulfur atom. ) The group shown. R^dAnd R^eEach independently represents a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms of an alkyl group is substituted by a halogen atom. m represents an integer of 1 to 10. )

[ CHEM 89 ]

(in the formula, R^f、R^g、R^hAnd RⁱEach independently represents a cyano group (CN) -containing group, a hydrogen atom (H), a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom. Wherein R is^f、R^g、R^hAnd RⁱAt least 1 of which is a cyano-containing group. l represents an integer of 1 to 3. )

This improves the high-temperature storage characteristics of the electrochemical device. The nitrile compounds can be used alone, or in any combination and ratio of 2 or more.

In the above general formula (1a), R^aAnd R^bEach independently represents a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among them, fluorine atoms are preferable.

The alkyl group is preferably an alkyl group having 1 to 5 carbon atoms. Specific examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tert-butyl.

Examples of the group in which at least a part of hydrogen atoms of the alkyl group is substituted with a halogen atom include a group in which at least a part of hydrogen atoms of the alkyl group is substituted with the halogen atom.

At R^aAnd R^bIn the case of an alkyl group or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom, R^aAnd R^bMay be bonded to each other to form a ring structure (e.g., cyclohexane ring).

R^aAnd R^bPreferably a hydrogen atom or an alkyl group.

In the general formula (1a), n is an integer of 1 to 10. When n is 2 or more, n R^aMay be all the same or at least partially different. With respect to R^bThe same applies. n is preferably an integer of 1 to 7, more preferably an integer of 2 to 5.

As the nitrile compound represented by the above general formula (1a), dinitriles and trinitriles are preferable.

Specific examples of the dinitrile include malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile, sebaconitrile, undecanedionitrile, dodecanedinitrile, methyl malononitrile, ethyl malononitrile, isopropyl malononitrile, t-butyl malononitrile, methyl succinonitrile, 2-dimethyl succinonitrile, 2,3, 3-trimethyl succinonitrile, 2,3, 3-tetramethyl succinonitrile, 2, 3-diethyl-2, 3-dimethyl succinonitrile, 2-diethyl-3, 3-dimethyl succinonitrile, bicyclohexane-1, 1-dicarbonitrile, bicyclohexane-2, 2-dicarbonitrile, bicyclohexane-3, 3-dicarbonitrile, 2, 5-dimethyl-2, 5-hexanedicarboxylic acid nitrile, 2, 3-diisobutyl-2, 3-dimethylsuccinonitrile, 2-diisobutyl-3, 3-dimethylsuccinonitrile, 2-methylglutaronitrile, 2, 3-dimethylglutaronitrile, 2, 4-dimethylglutaronitrile, 2,3, 3-tetramethylglutaronitrile, 2, 4, 4-tetramethylglutaronitrile, 2,3, 4-tetramethylglutaronitrile, 2,3,3, 4-tetramethylglutaronitrile, 1, 4-dicyanopentane, 2, 6-dicyanoheptane, 2, 7-dicyanooctane, 2, 8-dicyanononane, 1, 6-dicyanodecane, 1, 2-dicyanobenzene, 1, 3-dicyanobenzene, 1, 4-dicyanobenzene, 3, 3'- (ethylenedioxy) dipropionitrile, 3' - (ethylenedithio) dipropionitrile, 3, 9-bis (2-cyanoethyl) -2, 4, 8, 10-tetraoxaspiro [5, 5] undecane, butyronitrile, phthalonitrile, and the like. Among them, succinonitrile, glutaronitrile, and adiponitrile are particularly preferable.

Specific examples of the trinitrile include valeronitrile, propionitrile, 1, 3, 5-hexanetricarbonitrile, 1, 3, 6-hexanetricarbonitrile, heptacarbonitrile, 1, 2, 3-propanetricitrile, 1, 3, 5-pentacarbonitrile, cyclohexanetricarbonitrile, tricyanoethylamine, tricyanoethylpropane, tricyanoethylene, tris (2-cyanoethyl) amine and the like, and 1, 3, 6-hexanetricarbonitrile and cyclohexanetricarbonitrile are particularly preferable, and cyclohexanetricarbonitrile is most preferable.

In the above general formula (1b), R^cRepresents a hydrogen atom, a halogen atom, an alkyl group, a group in which at least a part of the hydrogen atoms of the alkyl group is substituted by a halogen atom, or NC-R^c1-X^c1-(R^c1Represents an alkylene group, X^c1Represents an oxygen atom or a sulfur atom. ) A group represented by R^dAnd R^eEach independently represents a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom.

Examples of the halogen atom, the alkyl group and the group in which at least a part of hydrogen atoms of the alkyl group is substituted with a halogen atom include the groups exemplified for the above general formula (1 a).

NC-R as described above^c1-X^c1R in (A-C)^c1Is an alkylene group. The alkylene group is preferably an alkylene group having 1 to 3 carbon atoms.

R^c、R^dAnd R^eEach of which is independently preferably a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom.

R^c、R^dAnd R^eAt least one of (a) and (b) is preferably a halogen atom or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom, and more preferably a fluorine atom or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom.

At R^dAnd R^eIn the case of an alkyl group or a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a halogen atom, R^dAnd R^eThe ring structures (for example, cyclohexane rings) may be bonded to each other.

In the general formula (1b), m is an integer of 1 to 10. When m is 2 or more, m R^dMay be all the same or at least partially different. For R^eAs well as so. m is preferably an integer of 2 to 7, more preferably an integer of 2 to 5.

The nitrile compound represented by the above general formula (1b) includes acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 3-methoxypropionitrile, 2-methylbutyronitrile, trimethylacetonitrile, capronitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2-difluoropropionitrile, 2, 3-difluoropropionitrile, 3, 3-difluoropropionitrile, 2, 3-trifluoropropionitrile, 3,3 '-oxydiproponitrile, 3, 3' -thiodipropionitrile, pentafluoropropionitrile, methoxyacetonitrile, benzonitrile and the like. Among them, 3,3, 3-trifluoropropionitrile is particularly preferable.

In the above general formula (1c), R^f、R^g、R^hAnd RⁱEach independently represents a cyano group (CN) -containing group, a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of the alkyl group is substituted with a halogen atom.

Examples of the cyano group-containing group include groups in which at least a part of hydrogen atoms of an alkyl group is substituted with a cyano group, in addition to a cyano group. Examples of the alkyl group in this case include the alkyl groups exemplified for the general formula (1 a).

R^f、R^g、R^hAnd RⁱAt least 1 of which is a cyano-containing group. Preferably R^f、R^g、R^hAnd RⁱAt least 2 of which are cyano-containing groups, more preferably R^hAnd RⁱIs a cyano-containing group. At R^hAnd RⁱIn the case of a cyano-containing group, R^fAnd R^gPreferably a hydrogen atom.

In the general formula (1c), l is an integer of 1 to 3. In the case where l is 2 or more, l R^fMay be all the same or at least partially different. For R^gAs well as so. l is preferably an integer of 1 to 2.

Examples of the nitrile compound represented by the above general formula (1c) include 3-hexenedionitrile, hexadienedinitrile (Mucononitril), maleonitrile, fumaronitrile, acrylonitrile, methacrylonitrile, crotononitrile, 3-methylcrotonitrile, 2-methyl-2-butenenitrile, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, and 2-hexenenitrile, and 3-hexenedionitrile and hexadienedinitrile are preferable, and 3-hexenedionitrile are particularly preferable.

The content of the nitrile compound is preferably 0.2 to 7% by mass relative to the electrolyte. This can further improve the high-temperature storage characteristics and safety of the electrochemical device at high voltage. The lower limit of the total content of the nitrile compounds is more preferably 0.3% by mass, and still more preferably 0.5% by mass. The upper limit is more preferably 5% by mass, still more preferably 2% by mass, and particularly preferably 0.5% by mass.

The electrolytic solution of the present invention may contain a compound having an isocyanate group (hereinafter, may be simply referred to as "isocyanate"). The isocyanate is not particularly limited, and any isocyanate may be used. Examples of the isocyanate include monoisocyanates, diisocyanates, and triisocyanates.

Specific examples of the monoisocyanates include isocyanatomethane, isocyanatoethane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1-isocyanatoheptane, 1-isocyanatooctane, 1-isocyanatononane, 1-isocyanatodecane, isocyanatocyclohexane, methoxycarbonylisocyanate, ethoxycarbonyl isocyanate, propoxycarbonylisocyanate, butoxycarbonylisocyanate, methoxysulfonyl isocyanate, ethoxysulfonyl isocyanate, propoxysulfonylisocyanate, butoxysulfonylisocyanate, fluorosulfonyl isocyanate, methyl isocyanate, butyl isocyanate, phenyl isocyanate, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, methyl isocyanate, ethyl isocyanate, ethyl isocyanate, and the like.

Specific examples of the diisocyanates include 1, 4-diisocyanatobutane, 1, 5-diisocyanatopentane, 1, 6-diisocyanatohexane, 1, 7-diisocyanatoheptane, 1, 8-diisocyanatooctane, 1, 9-diisocyanatononane, 1, 10-diisocyanatodecane, 1, 3-diisocyanatopropene, 1, 4-diisocyanato-2-butene, 1, 4-diisocyanato-2-fluorobutane, 1, 4-diisocyanato-2, 3-difluorobutane, 1, 5-diisocyanato-2-pentene, 1, 5-diisocyanato-2-methylpentane, 1, 6-diisocyanato-2-hexene, 1, 6-diisocyanato-3-hexene, 1, 6-diisocyanato-3-fluorohexane, 1, 6-diisocyanato-3, 4-difluorohexane, tolylene diisocyanate, xylene diisocyanate, toluene diisocyanate, 1, 2-bis (isocyanatomethyl) cyclohexane, 1, 3-bis (isocyanatomethyl) cyclohexane, 1, 4-bis (isocyanatomethyl) cyclohexane, 1, 2-diisocyanatocyclohexane, 1, 3-diisocyanatocyclohexane, 1, 4-diisocyanatocyclohexane, dicyclohexylmethane-1, 1 '-diisocyanate, dicyclohexylmethane-2, 2' -diisocyanate, dicyclohexylmethane-3, 3 '-diisocyanate, dicyclohexylmethane-4, 4' -diisocyanate, isophorone diisocyanate, 2, 5-bis (isocyanotomethyl) bicyclo [2.2.1] heptane, 2, 6-bis (isocyanotomethyl) bicyclo [2.2.1] heptane, 2, 4, 4-trimethylhexamethylene diisocyanate, 2, 4-trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, 1, 4-phenylene diisocyanate, octamethylene diisocyanate, tetramethylene diisocyanate, and the like.

Specific examples of the triisocyanates include 1, 6, 11-triisocyanatoundecane, 4-isocyanatomethyl-1, 8-octamethylene diisocyanate, 1, 3, 5-triisocyanatomethylbenzene, 1, 3, 5-tris (6-isocyanatohexane-1-yl) -1, 3, 5-triazine-2, 4, 6(1H, 3H, 5H) -trione, and 4- (isocyanatomethyl) octamethylene ═ diisocyanate.

Among them, 1, 6-diisocyanatohexane, 1, 3-bis (isocyanatomethyl) cyclohexane, 1, 3, 5-tris (6-isocyanatohex-1-yl) -1, 3, 5-triazine-2, 4, 6(1H, 3H, 5H) -trione, 2, 4, 4-trimethylhexamethylene diisocyanate, and 2,2, 4-trimethylhexamethylene diisocyanate are industrially easily available and can suppress the production cost of an electrolyte solution, and therefore, it is preferable and also contributes to the formation of a stable film-like structure from the technical viewpoint, and it is more preferable to use.

The content of the isocyanate is not particularly limited, and may be any as long as the effect of the present invention is not significantly impaired, and is preferably 0.001 mass% or more and 1.0 mass% or less with respect to the electrolyte solution. When the content of isocyanate is not less than the lower limit, a sufficient effect of improving cycle characteristics can be exerted on the nonaqueous electrolyte secondary battery. If the amount is less than the upper limit, the initial resistance of the nonaqueous electrolyte secondary battery can be prevented from increasing. The content of the isocyanate is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and further preferably 0.8% by mass or less, further preferably 0.7% by mass or less, particularly preferably 0.6% by mass or less.

The electrolyte of the present invention may contain a cyclic sulfonic acid ester. The cyclic sulfonic acid ester is not particularly limited, and any cyclic sulfonic acid ester can be used. Examples of the cyclic sulfonic acid ester include saturated cyclic sulfonic acid esters, unsaturated cyclic sulfonic acid esters, saturated cyclic disulfonic acid esters, and unsaturated cyclic disulfonic acid esters.

Specific examples of the saturated cyclic sulfonic acid ester include 1, 3-propane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, 3-fluoro-1, 3-propane sultone, 1-methyl-1, 3-propane sultone, 2-methyl-1, 3-propane sultone, 3-methyl-1, 3-propane sultone, 1, 3-butane sultone, 1, 4-butane sultone, 1-fluoro-1, 4-butane sultone, 2-fluoro-1, 4-butane sultone, 3-fluoro-1, 4-butane sultone, 4-fluoro-1, 4-butane sultone, 1-methyl-1, 4-butane sultone, 2-methyl-1, 4-butane sultone, 3-methyl-1, 4-butane sultone, 4-methyl-1, 4-butane sultone, 2, 4-butane sultone, and the like.

Specific examples of the unsaturated cyclic sulfonic acid ester include 1-propene-1, 3-sultone, 2-propene-1, 3-sultone, 1-fluoro-1-propene-1, 3-sultone, 2-fluoro-1-propene-1, 3-sultone, 3-fluoro-1-propene-1, 3-sultone, 1-fluoro-2-propene-1, 3-sultone, 2-fluoro-2-propene-1, 3-sultone, 3-fluoro-2-propene-1, 3-sultone, 1-methyl-1-propene-1, 3-sultone, 2-methyl-1-propene-1, 3-sultone, 3-methyl-1-propene-1, 3-sultone, 1-methyl-2-propene-1, 3-sultone, 2-methyl-2-propene-1, 3-sultone, 3-methyl-2-propene-1, 3-sultone, 1-butene-1, 4-sultone, 2-butene-1, 4-sultone, 3-butene-1, 4-sultone, 1-fluoro-1-butene-1, 4-sultone, 2-fluoro-1-butene-1, 4-sultone, 3-fluoro-1-butene-1, 4-sultone, 4-fluoro-1-butene-1, 4-sultone, 1-fluoro-2-butene-1, 4-sultone, 2-fluoro-2-butene-1, 4-sultone, 3-fluoro-2-butene-1, 4-sultone, 4-fluoro-2-butene-1, 4-sultone, 1, 3-propene sultone, 1-fluoro-3-butene-1, 4-sultone, 2-fluoro-3-butene-1, 4-sultone, 3-fluoro-3-butene-1, 4-sultone, 4-fluoro-3-butene-1, 4-sultone, 1-methyl-1-butene-1, 4-sultone, 2-methyl-1-butene-1, 4-sultone, 3-methyl-1-butene-1, 4-sultone, 4-methyl-1-butene-1, 4-sultone, 1-methyl-2-butene-1, 4-sultone, 2-methyl-2-butene-1, 4-sultone, 3-methyl-2-butene-1, 4-sultone, 4-methyl-2-butene-1, 4-sultone, 1-methyl-3-butene-1, 4-sultone, 2-methyl-3-butene-1, 4-sultone, 3-methyl-3-butene-1, 4-sultone, 4-methyl-3-butene-1, 4-sultone, and the like.

Among them, 1, 3-propane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, 3-fluoro-1, 3-propane sultone, and 1-propene-1, 3-sultone are more preferably used from the viewpoint of ease of obtaining and contribution to forming a stable film-like structure. The content of the cyclic sulfonic acid ester is not particularly limited, and may be any as long as the effect of the present invention is not significantly impaired, and is preferably 0.001 mass% or more and 3.0 mass% or less with respect to the electrolyte solution.

When the content of the cyclic sulfonic acid ester is not less than the lower limit, a sufficient effect of improving the cycle characteristics can be obtained for the nonaqueous electrolyte secondary battery. If the amount is less than the upper limit, the production cost of the nonaqueous electrolyte secondary battery can be prevented from increasing. The content of the cyclic sulfonic acid ester is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and further preferably 2.5% by mass or less, further preferably 2.0% by mass or less, particularly preferably 1.8% by mass or less.

The electrolyte can also contain polyoxyethylene with the weight-average molecular weight of 2000-4000 and the tail end of-OH, -OCOOH or-COOH.

By containing such a compound, the stability of the electrode interface is improved, and the characteristics of the electrochemical device can be improved.

Examples of the polyoxyethylene include polyoxyethylene monol, polyoxyethylene carboxylic acid, polyoxyethylene glycol, polyoxyethylene dicarboxylic acid, polyoxyethylene triol, and polyoxyethylene tricarboxylic acid. These can be used alone, also can be used in combination of more than 2.

Among them, from the viewpoint of improving the characteristics of the electrochemical device, a mixture of polyoxyethylene monol and polyoxyethylene glycol and a mixture of polyethylene carboxylic acid and polyethylene dicarboxylic acid are preferable.

If the weight average molecular weight of the polyoxyethylene is too small, it may be easily oxidized and decomposed. The weight average molecular weight is more preferably 3000 to 4000.

The weight average molecular weight can be measured in terms of polystyrene by a Gel Permeation Chromatography (GPC) method.

The content of the polyoxyethylene in the electrolyte is preferably 1 × 10^-6～1×10^-2mol/kg. If the polyoxyethylene content is too high, the characteristics of the electrochemical device may be impaired.

The polyoxyethylene content is more preferably 5 × 10^-6mol/kg or more.

The electrolyte solution of the present invention may further contain a fluorinated saturated cyclic carbonate, an unsaturated cyclic carbonate, an overcharge inhibitor, other known additives, and the like as additives. This can suppress the deterioration of the characteristics of the electrochemical device.

Examples of the fluorinated saturated cyclic carbonate include compounds represented by the above general formula (A). Among them, preferred are fluoroethylene carbonate, difluoroethylene carbonate, monofluoromethyl ethylene carbonate, trifluoromethyl ethylene carbonate, and 2,2,3,3, 3-pentafluoropropyl ethylene carbonate (4- (2, 2,3,3, 3-pentafluoropropyl) - [1, 3] dioxolan-2-one). The fluorinated saturated cyclic carbonate may be used alone in 1 kind, or may be used in combination of 2 or more kinds in any combination and ratio.

The content of the fluorinated saturated cyclic carbonate is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, and still more preferably 0.1 to 3% by mass, based on the electrolyte solution.

Examples of the unsaturated cyclic carbonate include vinylene carbonates, vinyl carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond, or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, and catechol carbonates.

Examples of the vinylene carbonates include vinylene carbonate, methylvinylene carbonate, 4, 5-dimethylvinylene carbonate, phenylvinylene carbonate, 4, 5-diphenylvinylene carbonate, vinyl vinylene carbonate, 4, 5-divinylvinylene carbonate, allylvinylene carbonate, 4, 5-diallylvinylene carbonate, 4-fluoroethylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluorocarbon vinylene carbonate, ethynylethylene carbonate, propargylethylene carbonate, methylvinylene carbonate, dimethylvinylene carbonate, and the like.

Specific examples of the vinyl carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4, 5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynylethylene carbonate, 4, 5-diacetylene ethylene carbonate, 4-methyl-5-ethynylethylene carbonate, 4-vinyl-5-ethynylethylene carbonate, 4-allyl-5-ethynylethylene carbonate, phenyl ethylene carbonate, 4, 5-diphenyl ethylene carbonate, 4-phenyl-5-vinyl ethylene carbonate, 4-allyl-5-phenyl ethylene carbonate, and the like, Allyl ethylene carbonate, 4, 5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, 4-methylene-1, 3-dioxolan-2-one, 4, 5-dimethylene-1, 3-dioxolan-2-one, 4-methyl-5-allyl ethylene carbonate, and the like.

Among these, preferable unsaturated cyclic carbonates are vinylene carbonate, vinylene methyl carbonate, 4, 5-dimethylethylene carbonate, vinylene carbonate, 4, 5-vinylene carbonate, allylvinylene carbonate, 4, 5-diallylvinylene carbonate, vinylene carbonate, 4, 5-divinylethylene carbonate, 4-methyl-5-vinylene carbonate, allylethylene carbonate, 4, 5-diallylethylene carbonate, 4-methyl-5-allylethylene carbonate, 4-allyl-5-vinylene carbonate, ethynylethylene carbonate, 4, 5-diacetyleneethylene carbonate, 4-methyl-5-ethynylethylene carbonate, vinylene carbonate, vinyl carbonate, vinylene, 4-vinyl-5-ethynyl ethylene carbonate. In addition, vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are particularly preferable because they form a stable interface protection film, and vinylene carbonate is most preferable.

The molecular weight of the unsaturated cyclic carbonate is not particularly limited, and may be any as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. When the amount is within this range, the solubility of the unsaturated cyclic carbonate in the electrolyte solution can be easily ensured, and the effects of the present invention can be easily and sufficiently exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more, and further more preferably 150 or less.

The method for producing the unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected for production.

The unsaturated cyclic carbonate may be used alone in 1 kind, or may be used in combination of 2 or more kinds in any combination and ratio.

The content of the above-mentioned unsaturated cyclic carbonate is not particularly limited and may be any as long as the effect of the present invention is not significantly impaired. The content of the unsaturated cyclic carbonate is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, and further preferably 0.1 mass% or more, based on 100 mass% of the electrolyte solution. The content is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. When the amount is within the above range, the electrochemical device using the electrolyte solution is likely to exhibit a sufficient effect of improving cycle characteristics, and it is also likely to avoid a decrease in high-temperature storage characteristics, an increase in the amount of gas generated, a decrease in the discharge capacity retention rate, and the like.

As the unsaturated cyclic carbonate, in addition to the above-mentioned non-fluorinated unsaturated cyclic carbonate, a fluorinated unsaturated cyclic carbonate can be preferably used.

The fluorinated unsaturated cyclic carbonate is a cyclic carbonate having an unsaturated bond and a fluorine atom. The number of fluorine atoms contained in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the fluorine atom is usually 6 or less, preferably 4 or less, and most preferably 1 or 2.

Examples of the fluorinated unsaturated cyclic carbonate include fluoroethylene carbonate derivatives, fluoroethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon double bond, and the like.

Examples of the fluoroethylene carbonate derivative include 4-fluoroethylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-allyl-5-fluoroethylene carbonate, and 4-fluoro-5-vinylvinylene carbonate.

Examples of the fluoroethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond include 4-fluoro-4-vinyl ethylene carbonate, 4-fluoro-4-allyl ethylene carbonate, 4-fluoro-5-vinyl ethylene carbonate, 4-fluoro-5-allyl ethylene carbonate, 4-difluoro-4-vinyl ethylene carbonate, 4-difluoro-4-allyl ethylene carbonate, 4, 5-difluoro-4-vinyl ethylene carbonate, 4, 5-difluoro-4-allyl ethylene carbonate, 4-fluoro-4, 5-divinyl ethylene carbonate, 4-fluoro-4, 5-diallyl ethylene carbonate, and mixtures thereof, Ethylene 4, 5-difluoro-4, 5-divinylcarbonate, ethylene 4, 5-difluoro-4, 5-diallylcarbonate, ethylene 4-fluoro-4-phenylcarbonate, ethylene 4-fluoro-5-phenylcarbonate, ethylene 4, 4-difluoro-5-phenylcarbonate, ethylene 4, 5-difluoro-4-phenylcarbonate, and the like.

Wherein the fluorinated unsaturated cyclic carbonate includes 4-fluoroethylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylene carbonate, 4-allyl-5-fluoroethylene carbonate, 4-fluoro-4-vinylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylene carbonate, 4-fluoro-5-allylethylene carbonate, 4-difluoro-4-vinylene carbonate, 4-difluoro-4-allylethylene carbonate, 4, 5-difluoro-4-vinylene carbonate, 4, 5-difluoro-4-allylethylene carbonate, and mixtures thereof, 4-fluoro-4, 5-divinylethylene carbonate, 4-fluoro-4, 5-diallylethylene carbonate, 4, 5-difluoro-4, 5-divinylethylene carbonate, 4, 5-difluoro-4, 5-diallylethylene carbonate can be used more preferably because they form a stable interface protective film.

The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited, and may be any as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 500 or less. When the amount is within this range, the solubility of the fluorinated unsaturated cyclic carbonate in the electrolyte solution can be easily ensured.

The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected for production. The molecular weight is more preferably 100 or more, and still more preferably 200 or less.

The fluorinated unsaturated cyclic carbonate may be used alone in 1 kind, or may be used in combination of 2 or more kinds in any combination and ratio. In addition, the content of the fluorinated unsaturated cyclic carbonate is not particularly limited, and may be any as long as the effect of the present invention is not significantly impaired. The content of the fluorinated unsaturated cyclic carbonate is usually preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and still more preferably 0.1% by mass or more, and further preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less in 100% by mass of the electrolytic solution. Within this range, the electrochemical device using the electrolyte solution is likely to exhibit a sufficient effect of improving cycle characteristics, and the deterioration of high-temperature storage characteristics, an increase in the amount of gas generated, a decrease in the discharge capacity retention rate, and the like are likely to be avoided.

The electrolyte of the present invention may also contain a compound having a triple bond. The compound is not limited in its kind as long as it has 1 or more triple bonds in the molecule.

Specific examples of the compound having a triple bond include the following compounds.

1-pentyne, 2-pentyne, 1-hexyne, 2-hexyne, 3-hexyne, 1-heptyne, 2-heptyne, 3-heptyne, 1-octyne, 2-octyne, 3-octyne, 4-octyne, 1-nonyne, 2-nonyne, 3-nonyne, 4-nonyne, 1-dodecyne, 2-dodecyne, 3-dodecyne, 4-dodecyne, 5-dodecyne, phenylacetylene, 1-phenyl-1-propyne, 1-phenyl-2-propyne, 1-phenyl-1-butyne, 4-phenyl-1-butyne, 1-phenyl-1-pentyne, 5-phenyl-1-pentyne, Hydrocarbon compounds such as 1-phenyl-1-hexyne, 6-phenyl-1-hexyne, diphenylacetylene, 4-ethynyltoluene, and dicyclohexylacetylene;

monocarbonates such as 2-propynyl methyl carbonate, 2-propynyl ethyl carbonate, 2-propynyl propyl carbonate, 2-propynyl butyl carbonate, 2-propynyl phenyl carbonate, 2-propynyl cyclohexyl carbonate, bis (2-propynyl) carbonate, 1-methyl-2-propynyl methyl carbonate, 1-dimethyl-2-propynyl methyl carbonate, 2-butynyl methyl carbonate, 3-butynyl methyl carbonate, 2-pentynyl methyl carbonate, 3-pentynyl methyl carbonate and 4-pentynyl methyl carbonate; dicarbonates such as 2-butyne-1, 4-diol dimethyl dicarbonate, 2-butyne-1, 4-diol diethyl dicarbonate, 2-butyne-1, 4-diol dipropyl dicarbonate, 2-butyne-1, 4-diol dibutyl dicarbonate, 2-butyne-1, 4-diol diphenyl dicarbonate and 2-butyne-1, 4-diol dicyclohexyl dicarbonate;

2-propynyl acetate, 2-propynyl propionate, 2-propynyl butyrate, 2-propynyl benzoate, 2-propynyl cyclohexanoate, 1-dimethyl-2-propynyl acetate, 1-dimethyl-2-propynyl propionate, 1-dimethyl-2-propynyl butyrate, 1-dimethyl-2-propynyl benzoate, 1-dimethyl-2-propynyl cyclohexanoate, 2-butynyl acetate, 3-butynyl acetate, 2-pentynyl acetate, 3-pentynyl acetate, 4-pentynyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, vinyl acrylate, 2-propenyl acrylate, 2-butenyl acrylate, methyl acrylate, ethyl acrylate, 2-propenyl acrylate, 2-butenyl acrylate, methyl acrylate, ethyl acrylate, methyl acrylate, 3-butenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl methacrylate, 2-propenyl methacrylate, 2-butenyl methacrylate, 3-butenyl methacrylate, methyl 2-propiolate, ethyl 2-propiolate, propyl 2-propiolate, vinyl 2-propiolate, 2-butenolate 2-propiolate, 3-butenyl 2-propiolate, methyl 2-butynoate, ethyl 2-butynoate, propyl 2-butynoate, vinyl 2-butynoate, 2-propenyl 2-butynoate, 2-butenyl 2-butynoate, 3-butenyl 2-butynoate, methyl 3-butynoate, vinyl 2-propiolate, allyl 2-propiolate, vinyl 2-propiolate, methyl 2-butynoate, vinyl 2-propenyl 2-propiolate, methyl 3-butynoate, vinyl 2, Ethyl 3-butynoate, propyl 3-butynoate, vinyl 3-butynoate, 2-propenyl 3-butynoate, 2-butenyl 3-butynoate, methyl 2-pentynoate, ethyl 2-pentynoate, propyl 2-pentynoate, vinyl 2-pentynoate, 2-propenyl 2-pentynoate, 2-butenyl 2-pentynoate, 3-butenyl 2-pentynoate, methyl 3-pentynoate, ethyl 3-pentynoate, propyl 3-pentynoate, vinyl 3-pentynoate, 2-propenyl 3-pentynoate, 2-butenyl 3-pentynoate, 3-butenyl 3-pentynoate, methyl 4-pentynoate, Monocarboxylic acid esters such as ethyl 4-pentynoate, propyl 4-pentynoate, vinyl 4-pentynoate, 2-propenyl 4-pentynoate, 2-butenyl 4-pentynoate, 3-butenyl 4-pentynoate, fumaric acid esters, methyl pivalate, and ethyl pivalate;

dicarboxylic acid esters such as 2-butyne-1, 4-diol diacetate, 2-butyne-1, 4-diol dipropionate, 2-butyne-1, 4-diol dibutyrate, 2-butyne-1, 4-diol dibenzoate, 2-butyne-1, 4-diol dicyclohexyl formate, hexahydrobenzo [1, 3, 2] dioxothiolane-2-oxide (1, 2-cyclohexanediol, 2-dioxo-1, 2-oxothiolan-4-ylacetate, and 2, 2-dioxo-1, 2-oxothiolan-4-ylacetate);

oxalic acid diesters such as monomethylpropinyl oxalate, monoethyl-2-propinyl oxalate, monopropylmono-2-propinyl oxalate, monoethyl-2-propinyl oxalate, monoallyl-2-propinyl oxalate, di-2-propinyl oxalate, monomethyl-2-butynyl oxalate, monoethyl-2-butynyl oxalate, monopropyl-2-butynyl oxalate, monoethyl-2-butynyl oxalate, monoallyl-2-butynyl oxalate, di-2-butynyl oxalate, monomethyl-3-butynyl oxalate, monoethyl-3-butynyl oxalate, monopropyl-3-butynyl oxalate, monoethyl-3-butynyl oxalate, monoallyl-3-butynyl oxalate, di-3-butynyl oxalate;

phosphine oxides such as methyl (2-propynyl) (vinyl) phosphine oxide, divinyl (2-propynyl) phosphine oxide, bis (2-propynyl) (vinyl) phosphine oxide, bis (2-propenyl) (2-propynyl) phosphine oxide, bis (2-propynyl) (2-propenyl) phosphine oxide, bis (3-butenyl) (2-propynyl) phosphine oxide, and bis (2-propynyl) (3-butenyl) phosphine oxide;

2-propynyl methyl (2-propenyl) phosphinate, 2-propynyl 2-butenyl (methyl) phosphinate, 2-propynyl bis (2-propenyl) phosphinate, 2-propynyl bis (3-butenyl) phosphinate, 1-dimethyl-2-propynyl methyl (2-propenyl) phosphinate, 1-dimethyl-2-propynyl 2-butenyl (methyl) phosphinate, 1-dimethyl-2-propynyl bis (2-propenyl) phosphinate, 1-dimethyl-2-propynyl bis (3-butenyl) phosphinate, 1-dimethyl-2-propynyl methyl (2-propynyl) phosphinate, 2-propenyl methyl (2-propynyl) phosphinate, 3-butenyl methyl (2-propynyl) phosphinate, Phosphinates such as 2-propenyl bis (2-propynyl) phosphinate, 3-butenyl bis (2-propynyl) phosphinate, 2-propenyl 2-propynyl (2-propenyl) phosphinate and 3-butenyl 2-propynyl (2-propenyl) phosphinate;

2-Propenylphosphonic acid (methyl) (2-propynyl) ester, 2-butenylphosphonic acid (methyl) (2-propynyl) ester, 2-propenylphosphonic acid (2-propynyl) (2-propenyl) ester, 3-butenylphosphonic acid (3-butenyl) (2-propynyl) ester, 2-propenylphosphonic acid (1, 1-dimethyl-2-propynyl) (methyl) ester, 2-butenylphosphonic acid (1, 1-dimethyl-2-propynyl) (methyl) ester, 2-propenylphosphonic acid (1, 1-dimethyl-2-propynyl) (2-propenyl) ester, 3-butenylphosphonic acid (3-butenyl) (1, 1-dimethyl-2-propynyl) ester, 2-butenylphosphonic acid (3-butenyl) ester, Phosphonates such as (2-propynyl) (2-propenyl) methylphosphonate, (3-butenyl) (2-propynyl) methylphosphonate, (1, 1-dimethyl-2-propynyl) (2-propenyl) methylphosphonate, (3-butenyl) (1, 1-dimethyl-2-propynyl) methylphosphonate, (2-propynyl) (2-propenyl) ethylphosphonate, (3-butenyl) (2-propynyl) ethylphosphonate, (1, 1-dimethyl-2-propynyl) (2-propenyl) ethylphosphonate, and (3-butenyl) (1, 1-dimethyl-2-propynyl) ethylphosphonate;

(methyl) (2-propenyl) (2-propynyl) phosphate, (ethyl) (2-propenyl) (2-propynyl) phosphate, (2-butenyl) (methyl) (2-propynyl) phosphate, (2-butenyl) (ethyl) (2-propynyl) phosphate, phosphoric acid esters such as (1, 1-dimethyl-2-propynyl) (methyl) (2-propenyl) phosphate, (1, 1-dimethyl-2-propynyl) (ethyl) (2-propenyl) phosphate, (2-butenyl) (1, 1-dimethyl-2-propynyl) (methyl) phosphate and (2-butenyl) (ethyl) (1, 1-dimethyl-2-propynyl) phosphate.

Among them, a compound having an alkynyloxy group is preferable because a negative electrode coating film is formed more stably in an electrolytic solution.

In addition, from the viewpoint of improving the storage characteristics, compounds such as 2-propynyl methyl carbonate, bis (2-propynyl) carbonate, 2-butyne-1, 4-diol dimethyl dicarbonate, 2-propynyl acetate, 2-butyne-1, 4-diol diacetate, monomethylpropynyl oxalate, bis (2-propynyl) oxalate and the like are particularly preferable.

The triple bond-containing compounds may be used alone in 1 kind, or may be used in combination of 2 or more kinds in any combination and ratio. The amount of the compound having a triple bond to be added to the entire electrolyte solution of the present invention is not limited, and may be any amount as long as the effect of the present invention is not significantly impaired, and is usually contained at a concentration of 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and further usually 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, to the electrolyte solution of the present invention. When the above range is satisfied, the effects of the output characteristics, the load characteristics, the cycle characteristics, the high-temperature storage characteristics, and the like are further improved.

In the electrolyte solution of the present invention, an overcharge inhibitor may be used in order to effectively suppress rupture and ignition of a battery when an electrochemical device using the electrolyte solution is in a state of overcharge or the like.

Examples of the anti-overcharge agent include aromatic compounds such as terphenyl derivatives unsubstituted or substituted with an alkyl group, e.g., biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, partial hydrides of terphenyl derivatives unsubstituted or substituted with an alkyl group, cyclohexylbenzene, t-butylbenzene, t-pentylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1, 3-trimethyl-3-phenylindane, cyclopentylbenzene, cyclohexylbenzene, cumene, 1, 3-diisopropylbenzene, 1, 4-diisopropylbenzene, t-butylbenzene, t-pentylbenzene, t-hexylbenzene, anisole, etc.; partial fluoro compounds of the above aromatic compounds such as 2-fluorobiphenyl, 4-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, fluorotoluene, and fluoroform; fluorine-containing anisole compounds such as 2, 4-difluoroanisole, 2, 5-difluoroanisole, 1, 6-difluoroanisole, 2, 6-difluoroanisole and 3, 5-difluoroanisole; aromatic acetates such as 3-propylphenyl acetate, 2-ethylphenyl acetate, benzylphenyl acetate, methylphenyl acetate, benzyl acetate and phenethylphenyl acetate; aromatic carbonates such as diphenyl carbonate and methyl phenyl carbonate; toluene derivatives such as toluene and xylene; and biphenyl derivatives unsubstituted or substituted with an alkyl group, such as 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl, and o-cyclohexylbiphenyl. Among them, preferred are aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partial hydride of terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, etc., diphenylcyclohexane, 1, 3-trimethyl-3-phenylindane, 3-propylphenyl acetate, 2-ethylphenyl acetate, benzylphenyl acetate, methylphenylacetate, benzyl acetate, diphenyl carbonate, methyl phenylcarbonate, etc. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds. In the case of using 2 or more kinds in combination, from the viewpoint of the balance between the overcharge prevention property and the high-temperature storage property, a combination of cyclohexylbenzene and tert-butylbenzene or tert-pentylbenzene is particularly preferable, and at least 1 kind selected from oxygen-free aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partial hydride of terphenyl, cyclohexylbenzene, tert-butylbenzene, and tert-pentylbenzene and at least 1 kind selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran are preferably used in combination.

In the electrolyte solution used in the present invention, carboxylic acid anhydride (excluding the compound (2)) may be used. Preferred is a compound represented by the following general formula (6). The method for producing the carboxylic anhydride is not particularly limited, and a known method can be arbitrarily selected for production.

[ CHEM 90 ]

(in the general formula (6), R⁶¹、R⁶²Each independently represents a hydrocarbon group having 1 to 15 carbon atoms which may have a substituent. )

R⁶¹、R⁶²Any monovalent hydrocarbon group can be usedThere is no particular limitation. For example, the hydrocarbon group may be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded. The aliphatic hydrocarbon group may be a saturated hydrocarbon group or may contain an unsaturated bond (a carbon-carbon double bond or a carbon-carbon triple bond). The aliphatic hydrocarbon group may be linear or branched, and may be linear or cyclic. Further, the group may be a chain or ring-like group. In addition, R is⁶¹And R⁶²May be the same as or different from each other.

In addition, in R⁶¹、R⁶²When the hydrocarbon group of (3) has a substituent, the kind of the substituent is not particularly limited as long as the gist of the present invention is not violated, and examples thereof include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and preferably a fluorine atom. Alternatively, the substituent other than the halogen atom may be a substituent having a functional group such as an ester group, a cyano group, a carbonyl group, or an ether group, and is preferably a cyano group or a carbonyl group. R⁶¹、R⁶²The hydrocarbon group (b) may have only one substituent or two or more substituents. In the case where two or more substituents are present, these substituents may be the same or different from each other.

R⁶¹、R⁶²The number of carbon atoms of each hydrocarbon group is usually 1 or more, and usually 15 or less, preferably 12 or less, more preferably 10 or less, and further preferably 9 or less. At R¹And R²When the divalent hydrocarbon groups are bonded to each other, the number of carbon atoms of the divalent hydrocarbon group is usually 1 or more, and usually 15 or less, preferably 13 or less, more preferably 10 or less, and still more preferably 8 or less. In addition, in R⁶¹、R⁶²When the hydrocarbon group of (3) has a substituent containing a carbon atom, R including the substituent is preferable⁶¹、R⁶²The total number of carbon atoms satisfies the above range.

Next, specific examples of the acid anhydride represented by the above general formula (6) will be described. In the following examples, "analog" refers to an acid anhydride obtained by replacing a part of the structure of an acid anhydride exemplified by the examples with another structure within a range not departing from the gist of the present invention, and examples thereof include dimers, trimers, tetramers, and the like containing a plurality of acid anhydrides; or a substance having the same number of carbon atoms in the substituent but having, for example, a structural isomer such as a branched chain or a site to which the substituent is bonded to an acid anhydride.

First, R is given below⁶¹、R⁶²Specific examples of the same acid anhydride.

As R⁶¹、R⁶²Specific examples of the acid anhydride having a chain alkyl group include acetic anhydride, propionic anhydride, butyric anhydride, 2-methylpropionic anhydride, 2-dimethylpropionic anhydride, 2-methylbutyric anhydride, 3-methylbutyric anhydride, 2-dimethylbutanoic anhydride, 2, 3-dimethylbutanoic anhydride, 3, 3-dimethylbutanoic anhydride, 2, 3-trimethylbutyric anhydride, 2,3, 3-trimethylbutyric anhydride, 2,3, 3-tetramethylbutyric anhydride, 2-ethylbutyric anhydride and the like.

As R⁶¹、R⁶²Specific examples of the acid anhydride having a cyclic alkyl group include cyclopropanecarboxylic anhydride, cyclopentanecarboxylic anhydride, cyclohexanecarboxylic anhydride, and the like.

As R⁶¹、R⁶²Specific examples of the acid anhydride having an alkenyl group include acrylic anhydride, 2-methacrylic anhydride, 3-methacrylic anhydride, 2, 3-dimethylacrylic anhydride, 3, 3-dimethylacrylic anhydride, 2,3, 3-trimethylacrylic anhydride, 2-phenylacrylic anhydride, 3-phenylacrylic anhydride, 2, 3-diphenylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, 2-dimethyl-3-butenoic anhydride, 3-methyl-3-butenoic anhydride, 2-methyl-3-butenoic anhydride, 2-dimethyl-3-methyl-3-butenoic anhydride, 3-pentenoic anhydride, 2-methyl-3-butenoic anhydride, 3-pentenoic anhydride, 2, 3-pentenoic anhydride, 4-pentenoic anhydride, 2-cyclopentenecarboxylic anhydride, 3-cyclopentenecarboxylic anhydride, 4-cyclopentenecarboxylic anhydride, etc., and the like.

As R⁶¹、R⁶²Specific examples of the alkynyl acid anhydride include propynoic acid anhydride, 3-phenylpropanoic acid anhydride, 2-butynoic acid anhydride, 2-pentynoic acid anhydride, 3-butynoic acid anhydride, 3-pentynoic acid anhydride, 4-pentynoic acid anhydride, and the like.

As R⁶¹、R⁶²Specific examples of the aryl acid anhydride include benzoic anhydride, 4-methylbenzoic anhydride, 4-ethylbenzoic anhydride, 4-tert-butylbenzoic anhydride, 2-methylbenzoic anhydride, 2, 4, 6-trimethylbenzoic anhydride, 1-naphthoic anhydride, 2-naphthoic anhydride, and the like.

In addition, as R⁶¹、R⁶²Examples of the acid anhydride substituted with a halogen atom include acid anhydrides substituted with a fluorine atom, but acid anhydrides obtained by replacing a part or all of the fluorine atoms with a chlorine atom, a bromine atom, or an iodine atom are also included in the exemplified compounds.

As R⁶¹、R⁶²Examples of the acid anhydride which is a chain alkyl group substituted with a halogen atom include fluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, 2-fluoropropionic anhydride, 2-difluoropropionic anhydride, 2, 3-difluoropropionic anhydride, 2, 3-trifluoropropionic anhydride, 2,3, 3-trifluoropropionic anhydride, 2,3, 3-tetrafluoropropionic anhydride, 2,3,3, 3-tetrafluoropropionic anhydride, 3-fluoropropionic anhydride, 3, 3-difluoropropionic anhydride, 3,3, 3-trifluoropropionic anhydride, perfluoropropionic anhydride, and the like.

As R⁶¹、R⁶²Examples of the acid anhydride of the cyclic alkyl group substituted with a halogen atom include 2-fluorocyclopentanecarboxylic acid anhydride, 3-fluorocyclopentanecarboxylic acid anhydride, 4-fluorocyclopentanecarboxylic acid anhydride and the like, and the like.

As R⁶¹、R⁶²Examples of the acid anhydride having an alkenyl group substituted with a halogen atom include 2-fluoroacrylic anhydride, 3-fluoroacrylic anhydride, 2, 3-difluoroacrylic anhydride, 3, 3-difluoroacrylic anhydride, 2,3, 3-trifluoropropene anhydride, 2- (trifluoromethyl) acrylic anhydride, 3- (trifluoromethyl) acrylic anhydride, 2, 3-bis (trifluoromethyl) acrylic anhydride, 2,3, 3-tris (trifluoromethyl) acrylic anhydride, 2- (4-fluorophenyl) acrylic anhydride, 3- (4-fluorophenyl) acrylic anhydride, 2, 3-bis (4-fluorophenyl) acrylic anhydride, 3, 3-bis (4-fluorophenyl) acrylic anhydride, 2-fluoro-3-butenoic anhydride, 2-difluoro-3-butenoic anhydride, 2-fluoro-3-butenoic anhydride, 3-trifluoromethyl-propenoic anhydride, 2, 3-bis (4-fluorophenyl) acrylic anhydride, 2-fluoro-3-butenoic, 3-fluoro-2-butenoic anhydride, 4-fluoro-3-butenoic anhydride, 3, 4-difluoro-3-butenoic anhydride, 3, 4-trifluoro-3-butenoic anhydride and the likeAnd the like thereof.

As R⁶¹、R⁶²Examples of the acid anhydride having an alkynyl group substituted with a halogen atom include 3-fluoro-2-propynoic acid anhydride, 3- (4-fluorophenyl) -2-propynoic acid anhydride, 3- (2, 3,4, 5, 6-pentafluorophenyl) -2-propynoic acid anhydride, 4-fluoro-2-butynoic acid anhydride, 4, 4-difluoro-2-butynoic acid anhydride, 4,4, 4-trifluoro-2-butynoic acid anhydride and the like, and the like.

As R⁶¹、R⁶²Examples of the acid anhydride of the aryl group substituted with a halogen atom include 4-fluorobenzoic anhydride, 2,3, 4,5, 6-pentafluorobenzoic anhydride, 4-trifluoromethylbenzoic anhydride and the like, and the like.

As R⁶¹、R⁶²Examples of the acid anhydride having a substituent having a functional group such as an ester, a nitrile, a ketone, an ether and the like include methoxyformic anhydride, ethoxyformic anhydride, methyloxalic anhydride, ethyloxalic anhydride, 2-cyanoacetic anhydride, 2-oxopropionic anhydride, 3-oxobutyric anhydride, 4-acetylbenzoic anhydride, methoxyacetic anhydride, 4-methoxybenzoic anhydride and the like, and the like.

Next, R is mentioned below⁶¹、R⁶²Specific examples of the acid anhydrides different from each other.

As R⁶¹、R⁶²All combinations of the above-mentioned examples and their analogs are considered, and representative examples are given below.

Examples of the combination of the chain alkyl groups include acetic acid propionic anhydride, acetic acid butyric anhydride, butyric acid propionic anhydride, acetic acid 2-methylpropanoic anhydride, and the like.

Examples of the combination of the chain alkyl group and the cyclic alkyl group include acetic acid cyclopentanecarboxylic anhydride, acetic acid cyclohexanecarboxylic anhydride, and cyclopentanecarboxylic acid propionic anhydride.

Examples of the combination of the chain alkyl group and the alkenyl group include acetic acrylic anhydride, acetic 3-methacrylic anhydride, acetic 3-butenoic anhydride, acrylic propionic anhydride, and the like.

Examples of the combination of the chain alkyl group and the alkynyl group include acetic propynic anhydride, acetic acid 2-butynic anhydride, acetic acid 3-phenyl propynic anhydride, propionic propynic anhydride, and the like.

Examples of the combination of the chain alkyl group and the aryl group include acetic benzoic anhydride, acetic 4-methylbenzoic anhydride, acetic 1-naphthoic anhydride, benzoic propionic anhydride, and the like.

Examples of the combination of the chain alkyl group and the hydrocarbon group having a functional group include acetic acid fluoroacetic anhydride, acetic acid trifluoroacetic anhydride, acetic acid 4-fluorobenzoic anhydride, fluoroacetic acid propionic anhydride, acetic acid alkyl oxalic anhydride, acetic acid 2-cyanoacetic anhydride, acetic acid 2-oxopropionic anhydride, acetic acid methoxyacetic anhydride, and methoxyacetic acid propionic anhydride.

Examples of the combination of the cyclic alkyl groups include cyclopentanecarboxylic acid cyclohexanecarboxylic acid anhydride.

Examples of the combination of the cyclic alkyl group and the alkenyl group include acrylic cyclopentanecarboxylic anhydride, 3-methacrylic cyclopentanecarboxylic anhydride, 3-butenoic cyclopentanecarboxylic anhydride, acrylic cyclohexanecarboxylic anhydride, and the like.

Examples of the combination of the cyclic alkyl group and the alkynyl group include cyclopentanoic anhydride propiolate, 2-butynoic cyclopentecarboxylic anhydride, propiolate cyclohexanecarboxylic anhydride, and the like.

Examples of the combination of the cyclic alkyl group and the aryl group include benzoic acid cyclopentanecarboxylic anhydride, 4-methylbenzoic acid cyclopentanecarboxylic anhydride, benzoic acid cyclohexanecarboxylic anhydride, and the like.

Examples of the combination of the cyclic alkyl group and the hydrocarbon group having a functional group include fluoroacetic cyclopentanecarboxylic acid anhydride, cyclopentanecarboxylic acid trifluoroacetic anhydride, cyclopentanecarboxylic acid 2-cyanoacetic anhydride, cyclopentanecarboxylic acid methoxyacetic anhydride, cyclohexanecarboxylic acid fluoroacetic anhydride, and the like.

Examples of the combination of alkenyl groups include acrylic acid 2-methacrylic anhydride, acrylic acid 3-butenoic anhydride, and 2-methacrylic acid 3-methacrylic anhydride.

Examples of the combination of alkenyl and alkynyl groups include acrylic propynoic anhydride, acrylic 2-butynoic anhydride, 2-methacrylic propynoic anhydride, and the like.

Examples of the combination of the alkenyl group and the aryl group include acrylic benzoic anhydride, acrylic 4-methyl benzoic anhydride, and 2-methyl acrylic benzoic anhydride.

Examples of the combination of an alkenyl group and a hydrocarbon group having a functional group include acrylic acid fluoroanhydride, acrylic acid trifluoroacetic anhydride, acrylic acid 2-cyanoacetic anhydride, acrylic acid methoxyacetic anhydride, and 2-methacrylic acid fluoroanhydride.

Examples of the combination of alkynyl groups include 2-butynoic anhydride propiolate, 3-butynoic anhydride propiolate, and 3-butynoic anhydride 2-butynoic acid.

Examples of the combination of an alkynyl group and an aryl group include propiolic acid anhydride benzoate, propiolic acid anhydride 4-methylbenzoate, 2-butynoic acid anhydride and the like.

Examples of the combination of an alkynyl group and a hydrocarbon group having a functional group include fluoroacetic propiolate, trifluoroacetic propiolate, 2-cyanoacetic propiolate, methoxyacetic propiolate, and 2-butylacetiolate fluoroacetic anhydride.

Examples of the combination of aryl groups include benzoic acid 4-methylbenzoic anhydride, benzoic acid 1-naphthoic anhydride, 4-methylbenzoic acid 1-naphthoic anhydride, and the like.

Examples of the combination of an aryl group and a hydrocarbon group having a functional group include benzoic acid fluoroanhydride, benzoic acid trifluoroacetic anhydride, benzoic acid 2-cyanoacetic anhydride, benzoic acid methoxyacetic anhydride, 4-methylbenzoic acid fluoroanhydride, and the like.

Examples of combinations of the hydrocarbon groups having functional groups include trifluoroacetic anhydride fluoroacetate, 2-cyanoacetic anhydride fluoroacetate, methoxyacetic anhydride fluoroacetate, 2-cyanoacetic anhydride trifluoroacetate, and the like.

Among the acid anhydrides forming the chain structure, preferred are acetic anhydride, propionic anhydride, 2-methylpropanoic anhydride, cyclopentanoic anhydride, cyclohexanecarboxylic anhydride, etc., acrylic anhydride, 2-methacrylic anhydride, 3-methacrylic anhydride, 2, 3-dimethylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, propiolic anhydride, 2-butynoic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride, trifluoroacetic anhydride, 3,3, 3-trifluoropropionic anhydride, 2- (trifluoromethyl) acrylic anhydride, 2- (4-fluorophenyl) acrylic anhydride, 4-fluorobenzoic anhydride, 2,3, 4,5, 6-pentafluorobenzoic anhydride, etc, Methoxy formic anhydride and ethoxy formic anhydride, more preferably acrylic anhydride, 2-methacrylic anhydride, 3-methacrylic anhydride, benzoic anhydride, 2-methyl benzoic anhydride, 4-tert-butyl benzoic anhydride, 4-fluoro benzoic anhydride, 2,3, 4,5, 6-pentafluorobenzoic anhydride, methoxy formic anhydride and ethoxy formic anhydride.

These compounds are preferable in that they form a coating film having excellent durability by appropriately forming a bond with a lithium oxalate salt, and in particular, the charge/discharge rate characteristics, the input/output characteristics, and the impedance characteristics after the durability test can be improved.

The molecular weight of the carboxylic anhydride is not limited, and may be any as long as the effect of the present invention is not significantly impaired, and is usually 90 or more, preferably 95 or more, and on the other hand, is usually 300 or less, preferably 200 or less. When the molecular weight of the carboxylic anhydride is within the above range, the viscosity of the electrolyte solution can be suppressed from increasing, and the film density can be made appropriate, so that the durability can be appropriately improved.

The method for producing the carboxylic anhydride is not particularly limited, and a known method can be arbitrarily selected for production. The carboxylic anhydride described above may be contained in the nonaqueous electrolyte solution of the present invention in any 1 kind alone, or may be contained in any combination and ratio of 2 or more kinds at the same time.

The content of the carboxylic anhydride in the electrolyte solution of the present invention is not particularly limited, and may be any content as long as the effect of the present invention is not significantly impaired, and the carboxylic anhydride is contained in the electrolyte solution of the present invention at a concentration of usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less. When the content of the carboxylic anhydride is within the above range, the effect of improving the cycle characteristics is easily exhibited, and the reactivity is good, so that the battery characteristics are easily improved.

Other known additives can be used in the electrolyte of the present invention. Examples of other auxiliaries include: hydrocarbon compounds such as pentane, heptane, octane, nonane, decane, cycloheptane, benzene, furan, naphthalene, 2-phenylbicyclohexane, cyclohexane, 2, 4, 8, 10-tetraoxaspiro [5.5] undecane, and 3, 9-divinyl-2, 4, 8, 10-tetraoxaspiro [5.5] undecane;

fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene, phenylfluoroform, monofluorobenzene, 1-fluoro-2-cyclohexylbenzene, 1-fluoro-4-tert-butylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-2-cyclohexylbenzene, fluorobiphenyl and the like;

carbonate compounds such as 1, 4-anhydroerythritol carbonate (erythroritan carbonate), spirobis-dimethylene carbonate, and methoxyethyl-methyl carbonate;

ether compounds such as dioxolane, dioxane, 2,5, 8, 11-tetraoxadodecane, 2,5, 8, 11, 14-pentaoxapentadecane, ethoxymethoxyethane, trimethoxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether (ethyl monoglyme);

ketone compounds such as dimethyl ketone, diethyl ketone, and 3-pentanone;

anhydrides such as 2-allyl succinic anhydride;

ester compounds such as dimethyl oxalate, diethyl oxalate, ethyl methyl oxalate, di (2-propynyl) oxalate, monomethylene-2-propynyl oxalate, dimethyl succinate, di (2-propynyl) glutarate, methyl formate, ethyl formate, 2-propynyl formate, 2-butyne-1, 4-diyl dicarboxylate, 2-propynyl methacrylate and dimethyl malonate;

amide compounds such as acetamide, N-methylformamide, N-dimethylformamide, and N, N-dimethylacetamide;

vinyl sulfate, vinylene sulfate, vinyl sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N-dimethylmethanesulfonamide, N-diethylmethanesulfonamide, methyl vinylsulfonate, ethyl vinylsulfonate, allyl vinylsulfonate, propargyl vinylsulfonate, methyl allylsulfonate, ethyl allylsulfonate, allyl allylsulfonate, propargyl allylsulfonate, 1, 2-bis (vinylsulfonyloxy) ethane, propanedisulfonic anhydride, sulfobutyric anhydride, sulfobenzoic anhydride, sulfopropionic anhydride, ethanedisulfonic anhydride, methylene methanedisulfonate, methanesulfonic acid-2-propyn-1-ol, pentylene sulfite, pentafluorophenyl methanesulfonate, allyl sulfate, allyl sulfite, methyl acetate, ethyl methanesulfonate, propyonate, sulfolane, methyl methanesulfonate, propynyl acetate, sulfolane, methyl sulfonate, allyl sulfate, allyl, Propane sultone, butylene sulfite, butane-2, 3-diyldimethane sulfonate, 2-butyne-1, 4-diyldimethane sulfonate, 2-propynyl vinylsulfonate, bis (2-vinylsulfonylethyl) ether, 5-vinyl-hexahydro-1, 3, 2-benzodioxolane-2-oxide, 2-propynyl 2- (methylsulfonyloxy) propionate, 2-oxo-5, 5-dimethyl-1, 2-oxathiolan-4-one 2, 2-dioxide, 3-sulfo-propionic anhydride, trimethylene methanedisulfonate, 2-methyltetrahydrofuran, trimethylene methanedisulfonate, tetramethylene sulfoxide, methylene disulfonate, methylene difluoroethylmethylsulfone, dimethylene sulfone, dimethylene disulfonate, dimethylene sulfone, dimethylene disulfide, dimethylene sulfide, dimethyl, Sulfur-containing compounds such as divinyl sulfone, 1, 2-bis (vinylsulfonyl) ethane, ethanedisulfonic acid methyl ester, ethanedisulfonic acid ethyl ester, vinyl sulfate, and thiophene 1-oxide;

nitrogen-containing compounds such as 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1, 3-dimethyl-2-imidazolidinone, N-methylsuccinimide, nitromethane, nitroethane, and ethylenediamine;

trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, ethyl diethylphosphonoacetate, methyl dimethylphosphonate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide, bis (2, 2-difluoroethyl) 2,2, 2-trifluoroethyl phosphate, bis (2, 2,3, 3-tetrafluoropropyl) 2,2, 2-trifluoroethyl phosphate, bis (2, 2, 2-trifluoroethyl) methyl phosphate, bis (2, 2, 2-trifluoroethyl) ethyl phosphate, bis (2, 2, 2-trifluoroethyl) 2, 2-difluoroethyl phosphate, bis (2, 2, 2-trifluoroethyl) 2,2,3, 3-tetrafluoropropyl ester, tributyl phosphate, tris (2, 2, 2-trifluoroethyl) phosphate, tris (1, 1, 1, 3,3, 3-hexafluoropropan-2-yl) phosphate, trioctyl phosphate, 2-phenylphenyldimethyl phosphate, 2-phenylphenyldiethyl phosphate, 2,2, 2-trifluoroethyl) (2, 2,3, 3-tetrafluoropropyl) methyl phosphate, 2- (dimethoxyphosphoryl) methyl acetate, 2- (dimethylphosphoryl) methyl acetate, 2- (diethoxyphosphoryl) methyl acetate, 2- (diethylphosphoryl) methyl acetate, methylenebisphosphonic acid methyl ester, methylenebisphosphonic acid ethyl ester, ethylenebisphosphonic acid methyl ester, ethylenebisphosphonic acid ethyl ester, butylenediphosphonic acid methyl ester, butylenediphosphonic acid ethyl ester, ethylenebisphosphonic acid methyl ester, Phosphorus-containing compounds such as 2-propinyl 2- (dimethoxyphosphoryl) acetate, 2-propinyl 2- (dimethylphosphoryl) acetate, 2-propinyl 2- (diethoxyphosphoryl) acetate, 2-propinyl 2- (diethylphosphoryl) acetate, tris (trimethylsilyl) phosphate, tris (triethylsilyl) phosphate, tris (trimethoxysilyl) phosphate, tris (trimethylsilyl) phosphite, tris (triethylsilyl) phosphite, tris (trimethoxysilyl) phosphite, and trimethylsilyl polyphosphate;

boron-containing compounds such as tris (trimethylsilyl) borate and tris (trimethoxysilyl) borate;

silane compounds such as biscresol trimethyl aluminum orthosilicate, bisethanolyl triethyl aluminum orthosilicate, bispropanol triethyl aluminum orthosilicate, bisbutanolyl trimethyl aluminum orthosilicate, bisbutanoyl triethyl aluminum orthosilicate, tetrakis (trimethylsiloxy) titanium, tetrakis (triethylsiloxy) titanium, tetramethylsilane, and the like;

and the like. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds. By adding these additives, the capacity retention characteristics and cycle characteristics after high-temperature storage can be improved.

Among the above-mentioned other assistants, preferred are phosphorus-containing compounds, and preferred are tris (trimethylsilyl) phosphate and tris (trimethylsilyl) phosphite.

The compounding amount of the other additives is not particularly limited, and may be any as long as the effects of the present invention are not significantly impaired. The other auxiliary agent is preferably 0.01 mass% or more and 5 mass% or less based on 100 mass% of the electrolyte solution. When the amount is within this range, the effects of other additives are easily exhibited sufficiently, and the battery characteristics such as high-load discharge characteristics are easily prevented from being deteriorated. The amount of the other auxiliary is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, and further preferably 3% by mass or less, further preferably 1% by mass or less.

The electrolyte solution of the present invention may further contain, as additives, cyclic and chain carboxylic acid esters, ether compounds, nitrogen-containing compounds, boron-containing compounds, organic silicon-containing compounds, non-combustible (flame retardant) agents, surfactants, high dielectric constant additives, cycle characteristic and rate characteristic improving agents, sulfone compounds, and the like, within a range that does not impair the effects of the present invention.

The cyclic carboxylic acid ester includes cyclic carboxylic acid esters having 3 to 12 total carbon atoms in the structural formula. Specific examples thereof include γ -butyrolactone, γ -valerolactone, γ -caprolactone, 3-methyl- γ -butyrolactone and the like. Among these, γ -butyrolactone is particularly preferable because it can improve the dissociation degree of lithium ions, thereby improving the characteristics of the electrochemical device.

The amount of the cyclic carboxylic acid ester as an additive is usually preferably 0.1% by mass or more, and more preferably 1% by mass or more, per 100% by mass of the solvent. Within this range, the conductivity of the electrolyte solution can be improved, and the large current discharge characteristics of the electrochemical device can be easily improved. The amount of the cyclic carboxylic acid ester is preferably 10% by mass or less, and more preferably 5% by mass or less. By setting the upper limit in this manner, the viscosity of the electrolyte solution is brought into an appropriate range, and thus, the decrease in conductivity is avoided, the increase in the negative electrode resistance is suppressed, and the large-current discharge characteristic of the electrochemical device is easily brought into a favorable range.

Further, as the cyclic carboxylic acid ester, fluorinated cyclic carboxylic acid ester (fluorinated lactone) can also be preferably used. Examples of the fluorine-containing lactone include the following formula (C):

[ CHEM 91 ]

(in the formula, X¹⁵～X²⁰The same or different are-H, -F, -Cl, -CH₃Or a fluoroalkyl group; wherein, X¹⁵～X²⁰At least 1 of which is a fluoroalkyl group).

As X¹⁵～X²⁰The fluoroalkyl group in (1) includes, for example, -CFH₂、-CF₂H、-CF₃、-CH₂CF₃、-CF₂CF₃、-CH₂CF₂CF₃、-CF(CF₃)₂For example, the compound is preferably-CH because of its high oxidation resistance and safety-improving effect₂CF₃or-CH₂CF₂CF₃。

If X is¹⁵～X²⁰At least 1 of which is fluoroalkyl, then-H, -F, -Cl, -CH₃Or fluoroalkyl may be present only at X¹⁵～X²⁰The substitution at 1 position may be carried out at a plurality of positions. From the viewpoint of good solubility of the electrolyte salt, the number of sites is preferably 1 to 3, and more preferably 1 to 2.

The position of substitution of the fluoroalkyl group is not particularly limited, and X is a group represented by formula (I) in view of good synthesis yield¹⁷And/or X¹⁸In particular X¹⁷Or X¹⁸Is fluoroalkyl, of which-CH is preferred₂CF₃or-CH₂CF₂CF₃. X other than fluoroalkyl¹⁵～X²⁰is-H, -F, -Cl or CH₃In particular, the electrolyte salt is preferably-H, because it has good solubility.

Examples of the fluorinated lactone include, in addition to the compounds represented by the above formula, fluorinated lactones represented by the following formula (D):

[ CHEM 92 ]

(wherein any one of A and B is CX²²⁶X²²⁷(X²²⁶And X²²⁷Are the same or different and are each-H, -F, -Cl, -CF₃、-CH₃Or a group in which a hydrogen atom may be substituted with a halogen atom or a hetero atom may be contained in the chainAlkyl) and the other is an oxygen atom; rf¹²Is a fluoroalkyl group or a fluoroalkoxy group which may have an ether bond; x²²¹And X²²²Are the same or different and are each-H, -F, -Cl, -CF₃Or CH₃；X²²³～X²²⁵The same or different, are-H, -F, -Cl, or an alkyl group in which the hydrogen atom may be substituted by a halogen atom and which may contain a heteroatom in the chain; n is 0 or 1).

The fluorinated lactone represented by the formula (D) is preferably represented by the following formula (E) from the viewpoint of easy synthesis and good chemical stability:

[ CHEM 93 ]

(in the formula, A, B, Rf¹²、X²²¹、X²²²And X²²³Same as formula (D)

The 5-membered ring structure shown, further, according to a combination of A and B, comprises the following formula (F):

[ CHEM 94 ]

(wherein Rf¹²、X²²¹、X²²²、X²²³、X²²⁶And X²²⁷Same as formula (D)

A fluorine-containing lactone represented by the following formula (G):

[ CHEM 95 ]

(wherein Rf¹²、X²²¹、X²²²、X²²³、X²²⁶And X²²⁷Same as formula (D)

The fluorine-containing lactone is represented.

Among them, from the viewpoint of exhibiting excellent characteristics such as a high dielectric constant and a high withstand voltage, and from the viewpoint of improving the characteristics as the electrolytic solution in the present invention in terms of satisfactory reduction in solubility and internal resistance of the electrolyte salt, there can be mentioned

[ CHEM 96 ]

And the like.

By containing the fluorinated cyclic carboxylic acid ester, the effects of improving the ionic conductivity, improving the safety, and improving the stability at high temperatures can be obtained.

The chain carboxylic acid ester includes a chain carboxylic acid ester having 3 to 7 total carbon atoms in the structural formula. Specific examples thereof include methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isobutyl propionate, n-butyl propionate, methyl butyrate, isobutyl propionate, tert-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, n-propyl isobutyrate, isopropyl isobutyrate, and the like.

Among them, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate and the like are preferable from the viewpoint of improvement in ionic conductivity due to reduction in viscosity.

The ether compound is preferably a chain ether having 2 to 10 carbon atoms or a cyclic ether having 3 to 6 carbon atoms.

Examples of the chain ether having 2 to 10 carbon atoms include dimethyl ether, diethyl ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, diethoxymethane, dimethoxyethane, methoxyethoxyethane, diethoxyethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, pentaethylene glycol, triethylene glycol dimethyl ether, triethylene glycol, tetraethylene glycol dimethyl ether, and diisopropyl ether.

Further, as the ether compound, a fluoroether may also be preferably used.

Examples of the fluoroether include the following general formula (I):

Rf³-O-Rf⁴(I)

(wherein Rf³And Rf⁴The same or different, and is an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms. Wherein, Rf³And Rf⁴Is a fluoroalkyl group. ) The fluoroether (I) shown.

The fluorinated ether (I) improves the flame retardancy of the electrolyte solution, and improves the stability and safety at high temperature and high voltage.

In the above general formula (I), Rf³And Rf⁴At least one of them may be a fluoroalkyl group having 1 to 10 carbon atoms, and Rf is preferable from the viewpoint of further improving the flame retardancy of the electrolyte, the stability at high temperature and high voltage, and the safety³And Rf⁴And a fluoroalkyl group having 1 to 10 carbon atoms. In this case, Rf³And Rf⁴May be the same or different from each other.

Among them, Rf is more preferable³And Rf⁴Identical or different, Rf³Is a C3-6 fluoroalkyl group and Rf⁴Is a C2-6 fluoroalkyl group.

If Rf³And Rf⁴If the total number of carbon atoms is too small, the boiling point of the fluoroether becomes too low, and if Rf is too low³Or Rf⁴When the number of carbon atoms (b) is too large, the solubility of the electrolyte salt is lowered, and the compatibility with other solvents also starts to be adversely affected. At Rf³Has 3 or 4 carbon atoms, Rf⁴When the number of carbon atoms of (2) or (3) is 2, it is advantageous in that the boiling point and rate characteristics are excellent.

The fluorine content of the fluoroether (I) is preferably 40 to 75% by mass. When the fluorine content is in this range, the balance between incombustibility and compatibility is particularly excellent. Further, it is preferable from the viewpoint of oxidation resistance and good safety.

The lower limit of the fluorine content is more preferably 45% by mass, still more preferably 50% by mass, and particularly preferably 55% by mass. The upper limit is more preferably 70% by mass, and still more preferably 66% by mass.

The fluorine content of the fluoroether (I) is a value calculated from { (the number of fluorine atoms X19)/the molecular weight of the fluoroether (I) } 100 (%) based on the structural formula of the fluoroether (I).

As Rf³For example, CF₃CF₂CH₂-、CF₃CFHCF₂-、HCF₂CF₂CF₂-，HCF₂CF₂CH₂-、CF₃CF₂CH₂CH₂-、CF₃CFHCF₂CH₂-、HCF₂CF₂CF₂CF₂-、HCF₂CF₂CF₂CH₂-、HCF₂CF₂CH₂CH₂-、HCF₂CF(CF₃)CH₂-and the like. Further, as Rf⁴For example, may include-CH₂CF₂CF₃、-CF₂CFHCF₃、-CF₂CF₂CF₂H，-CH₂CF₂CF₂H、-CH₂CH₂CF₂CF₃、-CH₂CF₂CFHCF₃、-CF₂CF₂CF₂CF₂H、-CH₂CF₂CF₂CF₂H、-CH₂CH₂CF₂CF₂H、-CH₂CF(CF₃)CF₂H、-CF₂CF₂H、-CH₂CF₂H、-CF₂CH₃And the like.

Specific examples of the fluoroether (I) include HCF₂CF₂CH₂OCF₂CF₂H、CF₃CF₂CH₂OCF₂CF₂H、HCF₂CF₂CH₂OCF₂CFHCF₃、CF₃CF₂CH₂OCF₂CFHCF₃、C₆F₁₃OCH₃、C₆F₁₃OC₂H₅、C₈F₁₇OCH₃、C₈F₁₇OC₂H₅、CF₃CFHCF₂CH(CH₃)OCF₂CFHCF₃、HCF₂CF₂OCH(C₂H₅)₂、HCF₂CF₂OC₄H₉、HCF₂CF₂OCH₂CH(C₂H₅)₂、HCF₂CF₂OCH₂CH(CH₃)₂And the like.

Wherein the HCF is contained at one or both ends₂-or CF₃CFH-has excellent material polarizability and can form fluoroether (I) having a high boiling point. The boiling point of the fluoroether (I) is preferably 67 to 120 ℃. More preferably 80 ℃ or higher, and still more preferably 90 ℃ or higher.

Examples of the fluoroether (I) include CF₃CH₂OCF₂CFHCF₃、CF₃CF₂CH₂OCF₂CFHCF₃、HCF₂CF₂CH₂OCF₂CFHCF₃、HCF₂CF₂CH₂OCH₂CF₂CF₂H、CF₃CFHCF₂CH₂OCF₂CFHCF₃、HCF₂CF₂CH₂OCF₂CF₂H、CF₃CF₂CH₂OCF₂CF₂H, etc. 1 or 2 or more.

Among them, HCF is preferably selected from the group consisting of HCF, which is advantageous in view of high boiling point, compatibility with other solvents, and good solubility of the electrolyte salt₂CF₂CH₂OCF₂CFHCF₃(boiling point 106 ℃ C.), CF₃CF₂CH₂OCF₂CFHCF₃(boiling point 82 ℃ C.), HCF₂CF₂CH₂OCF₂CF₂H (boiling point 92 ℃ C.) and CF₃CF₂CH₂OCF₂CF₂At least 1 of H (boiling point 68 ℃), more preferably selected from HCF₂CF₂CH₂OCF₂CFHCF₃(boiling point 106 ℃ C.) and HCF₂CF₂CH₂OCF₂CF₂At least 1 of H (boiling point 92 ℃ C.).

Examples of the cyclic ether having 3 to 6 carbon atoms include 1, 2-dioxane, 1, 3-dioxane, 2-methyl-1, 3-dioxane, 4-methyl-1, 3-dioxane, 1, 4-dioxane, trioxymethylene, 2-methyl-1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 2- (trifluoroethyl) dioxolane, 2-bis (trifluoromethyl) -1, 3-dioxolane, and fluoro compounds thereof. Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol n-propyl ether, ethylene glycol n-butyl ether, diethylene glycol dimethyl ether, and crown ether are preferable from the viewpoints of high solvating ability for lithium ions and improvement of ion dissociation degree; dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferable from the viewpoint of low viscosity and high ion conductivity.

Examples of the nitrogen-containing compound include nitriles, fluorine-containing nitriles, carboxylic acid amides, fluorine-containing carboxylic acid amides, sulfonic acid amides, fluorine-containing sulfonic acid amides, acetamides, and formamides. In addition, 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1, 3-dimethyl-2-imidazolidinone, N-methylsuccinimide, and the like can also be used. Wherein the nitrile compounds represented by the above general formulae (1a), (1b) and (1c) are not contained in the above nitrogen-containing compound.

Examples of the boron-containing compound include boric acid esters such as trimethyl borate and triethyl borate, boric acid ethers, and alkylboranes.

Examples of the organic silicon-containing compound include (CH)₃)₄-Si、(CH₃)₃-Si-Si(CH₃)₃Silicon oil, etc.

Examples of the non-combustible (flame retardant) agent include phosphate esters and phosphazene compounds. Examples of the phosphate ester include a fluorine-containing alkyl phosphate ester, a non-fluorine-containing alkyl phosphate ester, and an aryl phosphate ester. Among them, fluorine-containing alkyl phosphate esters are preferable because a small amount of the phosphate esters can exhibit a non-combustible effect.

Examples of the phosphazene compound include methoxy pentafluorocyclotriphosphazene, phenoxy pentafluorocyclotriphosphazene, dimethylamino pentafluorocyclotriphosphazene, diethylaminopentafluorocyclotriphosphazene, ethoxy pentafluorocyclotriphosphazene, and ethoxy heptafluorocyclotetraphosphazene.

Specific examples of the fluorine-containing alkyl phosphate include a fluorine-containing dialkyl phosphate described in Japanese patent application laid-open No. 11-233141, a cyclic alkyl phosphate described in Japanese patent application laid-open No. 11-283669, and a fluorine-containing trialkyl phosphate.

The above-mentioned incombustible (flame retardant) agent is preferably (CH)₃O)₃P＝O、(CF₃CH₂O)₃P＝O、(HCF₂CH₂O)₃P＝O、(CF₃CF₂CH₂)₃P＝O、(HCF₂CF₂CH₂)₃P ═ O, and the like.

The surfactant may be any of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant, but a surfactant containing a fluorine atom is preferable in terms of good cycle characteristics and rate characteristics.

Such a surfactant containing a fluorine atom is preferably represented by the following formula (30):

Rf⁵COO^-M⁺(30)

(wherein Rf⁵A fluorine-containing alkyl group having 3 to 10 carbon atoms and optionally containing an ether bond; m⁺Is Li⁺、Na⁺、K⁺Or NHR'₃ ⁺(R' are the same or different and are each H or an alkyl group having 1 to 3 carbon atoms)

A fluorine-containing carboxylic acid salt represented by the following formula (40):

Rf⁶SO₃ ^-M⁺(40)

(in the formula，Rf⁶A fluorine-containing alkyl group having 3 to 10 carbon atoms and optionally containing an ether bond; m⁺Is Li⁺、Na⁺、K⁺Or NHR'₃ ⁺(R' are the same or different and are each H or an alkyl group having 1 to 3 carbon atoms)

The fluorine-containing sulfonate shown below, and the like.

The content of the surfactant is preferably 0.01 to 2% by mass in the electrolyte solution, in view of reducing the surface tension of the electrolyte solution without reducing the charge-discharge cycle characteristics.

Examples of the high dielectric constant additive include sulfolane, methylsulfolane, γ -butyrolactone, and γ -valerolactone.

Examples of the cycle characteristics and rate characteristics improving agent include methyl acetate, ethyl acetate, tetrahydrofuran, and 1, 4-dioxane.

The electrolyte of the present invention may be combined with a polymer material to form a gel-like (plasticized) electrolyte.

The polymer material may include conventionally known polyoxyethylene and polyoxypropylene, and modified products thereof (Japanese patent application laid-open No. 8-222270 and Japanese patent application laid-open No. 2002-100405); and fluororesins such as polyacrylate polymers, polyacrylonitrile, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene copolymers (Japanese patent application laid-open No. 4-506726, Japanese patent application laid-open No. 8-507407, and Japanese patent application laid-open No. 10-294131; composites of these fluororesins with hydrocarbon resins (Japanese patent application laid-open No. 11-35765, and Japanese patent application laid-open No. 11-86630), and the like, and polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymers are particularly preferably used as the polymer material for the gel electrolyte.

The electrolyte solution of the present invention may contain an ion-conductive compound described in Japanese patent application laid-open No. 2004-301934.

The ion-conductive compound is an amorphous fluorine-containing polyether compound having a fluorine-containing group in a side chain, represented by formula (101):

A-(D)-B (101)

[ in the formula, D is formula (201):

-(D1)_n-(FAE)_m-(AE)_p-(Y)_q- (201)

(wherein D1 represents an ether unit having a fluorine-containing ether group in the side chain represented by the formula (2 a):

[ CHEM 97 ]

(wherein Rf is a fluorine-containing ether group which may have a crosslinkable functional group; R¹⁰Is a group or bond bonding Rf to the main chain);

FAE is an ether unit having a fluoroalkyl group in a side chain represented by the formula (2 b):

[ CHEM 98 ]

(wherein Rfa is a hydrogen atom, a fluoroalkyl group which may have a crosslinkable functional group; R¹¹Is a group or bond linking Rfa to the main chain);

AE is an ether unit represented by formula (2 c):

[ CHEM 99 ]

(in the formula, R¹³A hydrogen atom, an alkyl group which may have a crosslinkable functional group, an alicyclic hydrocarbon group which may have a crosslinkable functional group, or an aromatic hydrocarbon group which may have a crosslinkable functional group; r¹²To be R¹³A group or bond bonded to the main chain);

y is a unit containing at least 1 of the formulae (2d-1) to (2 d-3):

[ CHEM 100 ]

n is an integer of 0 to 200; m is an integer of 0 to 200; p is an integer of 0 to 10000; q is an integer of 1 to 100; wherein n + m is not 0, and the bonding order of D1, FAE, AE and Y is not specified);

a and B are the same OR different and are a hydrogen atom, an alkyl group which may have a fluorine atom and/OR a crosslinkable functional group, a phenyl group which may have a fluorine atom and/OR a crosslinkable functional group, -COOH group, -OR (R is a hydrogen atom OR an alkyl group which may have a fluorine atom and/OR a crosslinkable functional group), an ester group OR a carbonate group (wherein, in the case where D is an oxygen atom at the terminal, it is not-COOH group, -OR, ester group OR carbonate group) ].

The electrolyte of the present invention may contain a sulfone compound. The sulfone compound is preferably a cyclic sulfone having 3 to 6 carbon atoms or a chain sulfone having 2 to 6 carbon atoms. The number of sulfonyl groups in 1 molecule is preferably 1 or 2.

Examples of the cyclic sulfone include polysulfone compounds, i.e., trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones; the disulfone compounds include trimethylene disulfones, tetramethylene disulfones, hexamethylene disulfones, and the like. Among these, tetramethylene sulfones, tetramethylene disulfides, hexamethylene sulfones, and hexamethylene disulfides are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable, from the viewpoint of dielectric constant and viscosity.

The sulfolane is preferably sulfolane and/or a sulfolane derivative (hereinafter, including sulfolane, it may be abbreviated as "sulfolane"). The sulfolane derivative is preferably a sulfolane derivative in which 1 or more of hydrogen atoms bonded to carbon atoms constituting a sulfolane ring are substituted with a fluorine atom or an alkyl group.

Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2-difluorosulfolane, 2, 3-difluorosulfolane, 2, 4-difluorosulfolane, 2, 5-difluorosulfolane, 3, 4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methylsulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-methylsulfolane, 2-methylsulfolane, or 2-fluoro-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoromethylsulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 2-fluoro-3- (trifluoromethyl) sulfolane, 3-fluoro-3- (trifluoromethyl) sulfolane, 4-fluoro-3- (trifluoromethyl) sulfolane, 3-sulfolene, 5-fluoro-3- (trifluoromethyl) sulfolane, and the like.

Further, examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n-butyl methyl sulfone, n-butyl ethyl sulfone, tert-butyl methyl sulfone, tert-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, bis (trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl n-propyl sulfone, difluoromethyl n-propyl sulfone, trifluoromethyl n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, Trifluoromethyl isopropyl sulfone, trifluoroethyl n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl n-butyl sulfone, trifluoroethyl t-butyl sulfone, pentafluoroethyl n-butyl sulfone, pentafluoroethyl t-butyl sulfone, and the like.

Among them, from the viewpoint of high ionic conductivity and high input/output, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl-isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, trifluoromethyl-n-butyl sulfone, trifluoromethyl-t-butyl sulfone, and the like are preferable.

The content of the sulfone compound is not particularly limited, and may be any as long as the effect of the present invention is not significantly impaired, and is usually 0.3 vol% or more, preferably 0.5 vol% or more, more preferably 1 vol% or more, and is usually 40 vol% or less, preferably 35 vol% or less, more preferably 30 vol% or less, of 100 vol% of the solvent. When the content of the sulfone compound is in the above range, the effect of improving durability such as cycle characteristics and storage characteristics is easily obtained, and the viscosity of the nonaqueous electrolyte solution is set to an appropriate range, so that the decrease in conductivity can be avoided, and the input/output characteristics and the charge/discharge rate characteristics of the nonaqueous electrolyte secondary battery can be set to an appropriate range.

From the viewpoint of improving the output characteristics, the electrolyte solution of the present invention preferably further contains a lithium fluorophosphate (not including LiPF)₆) And at least 1 compound (7) among lithium salts having an S ═ O group as an additive.

When the compound (7) is used as an additive, it is preferable to use a compound other than the compound (7) as the electrolyte salt.

The lithium fluorophosphate salt includes lithium monofluorophosphate (LiPO)₃F) Lithium difluorophosphate (LiPO)₂F₂) And the like.

Examples of the lithium salt having S ═ O group include lithium monofluorosulfonate (FSO)₃Li), lithium methylsulfate (CH)₃OSO₃Li), lithium ethylsulfate (C)₂H₅OSO₃Li), lithium 2,2, 2-trifluoroethyl sulfate, and the like.

Among these, LiPO is preferable as the compound (7)₂F₂、FSO₃Li、C₂H₅OSO₃Li。

The content of the compound (7) is preferably 0.001 to 20% by mass, more preferably 0.01 to 15% by mass, even more preferably 0.1 to 10% by mass, and particularly preferably 0.1 to 7% by mass, relative to the electrolyte.

The electrolyte of the present invention may further contain other additives as required. Examples of the other additives include metal oxides and glass.

The electrolyte of the present invention preferably contains 5 to 200ppm of Hydrogen Fluoride (HF). The addition of HF promotes the formation of a coating film of the additive. If the HF content is too small, the capability of forming a coating on the negative electrode tends to be lowered, and the characteristics of the electrochemical device tend to be lowered. In addition, if the HF content is too high, the oxidation resistance of the electrolytic solution tends to be lowered by the influence of HF. The electrolyte solution of the present invention does not lower the high-temperature storage stability and recovery capacity rate of the electrochemical device even when it contains HF in the above-mentioned range.

The content of HF is more preferably 10ppm or more, and still more preferably 20ppm or more. The content of HF is more preferably 100ppm or less, still more preferably 80ppm or less, and particularly preferably 50ppm or less.

The HF content can be determined by neutralization titration.

The electrolyte of the present invention can be prepared by any method using the above-mentioned components.

The electrolyte solution of the present invention can be preferably applied to electrochemical devices such as lithium ion secondary batteries, lithium ion capacitors, hybrid capacitors, and electric double layer capacitors. Hereinafter, a nonaqueous electrolyte battery using the electrolyte of the present invention will be described.

The nonaqueous electrolyte battery may have a known structure, and typically includes a positive electrode and a positive electrode capable of absorbing and releasing ions (for example, lithium ions), and the electrolyte solution of the present invention. Such an electrochemical device comprising the electrolyte solution of the present invention is also one aspect of the present invention.

Examples of the electrochemical device include a lithium ion secondary battery, a lithium ion capacitor, a capacitor (a hybrid capacitor, an electric double layer capacitor), a radical battery, a solar cell (particularly, a dye-sensitized solar cell), a lithium ion primary battery, a fuel cell, various electrochemical sensors, an electrochromic element, an electrochemical switching element, an aluminum electrolytic capacitor, a tantalum electrolytic capacitor, and the like, and preferably a lithium ion secondary battery, a lithium ion capacitor, an electric double layer capacitor.

An assembly having the electrochemical device is also one aspect of the present invention.

The present invention also relates to a lithium ion secondary battery comprising the electrolyte of the present invention.

The lithium ion secondary battery preferably includes a positive electrode, a negative electrode, and the electrolyte solution.

< Positive electrode >

The positive electrode is composed of a positive electrode active material layer containing a positive electrode active material and a current collector.

The positive electrode active material is not particularly limited as long as it can electrochemically absorb and release lithium ions, and examples thereof include lithium-containing transition metal composite oxides, lithium-containing transition metal phosphate compounds, sulfides, and conductive polymers. Among them, the positive electrode active material is preferably a lithium-containing transition metal composite oxide or a lithium-containing transition metal phosphate compound, and particularly preferably a lithium-containing transition metal composite oxide that generates a high voltage.

The transition metal of the lithium-containing transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples thereof include LiCoO₂Lithium-cobalt composite oxide, LiNiO₂Lithium-nickel composite oxide, LiMnO₂、LiMn₂O₄、Li₂MnO₄And lithium-manganese complex oxides in which a part of transition metal atoms that are the main component of these lithium transition metal complex oxides is replaced with another element such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, and the like. As a specific example of the substance formed in place of the latter, LiNi can be mentioned_0.5Mn_0.5O₂、LiNi_0.85Co_0.10Al_0.05O₂、LiNi_0.5Co_0.2Mn_0.3O₂、LiNi_0.6Co_0.2Mn_0.2O₂、LiNi_0.33Co_0.33Mn_0.33O₂、LiNi_0.45Co_0.10Al_0.45O₂、LiMn_1.8Al_0.2O₄、LiMn_1.5Ni_0.5O₄And the like.

Among these, LiMn having a high energy density even at a high voltage is preferable as the lithium-containing transition metal composite oxide_1.5Ni_0.5O₄、LiNi_0.5Co_0.2Mn_0.3O₂、LiNi_0.6Co_0.2Mn_0.2O₂。

The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples thereof include LiFePO₄、Li₃Fe₂(PO₄)₃、LiFeP₂O₇Iso-phosphates of iron, LiCoPO₄Cobalt phosphates, and those obtained by substituting other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, and Si for a part of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds.

Examples of the lithium-containing transition metal composite oxide include

Formula (II): li_aMn_2-bM¹ _bO₄(wherein a is 0.9. ltoreq. a; b is 0. ltoreq. b.ltoreq.1.5; M¹At least one metal selected from the group consisting of Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge),

formula (II): LiNi_1-cM² _cO₂(wherein c is 0. ltoreq. c is 0.ltoreq.0.5; M²At least one metal selected from among Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge), or,

formula (II): LiCo_1-dM³ _dO₂(wherein d is 0. ltoreq. d.ltoreq.0.5; M³At least 1 metal selected from the group consisting of Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge).

Among these, LiCoO is preferable from the viewpoint of providing a lithium ion secondary battery having high energy density and high output₂、LiMnO₂、LiNiO₂、LiMn₂O₄、LiNi_0.8Co_0.15Al_0.05O₂Or LiNi_1/3Co_1/3Mn_1/3O₂。

As another positive electrode active material, LiFePO can be mentioned₄、LiNi_0.8Co_0.2O₂、Li_1.2Fe_0.4Mn_0.4O₂、LiNi_0.5Mn_0.5O₂、LiV₃O₆And the like.

As the sulfide, TiS can be mentioned₂、MoS₂Compounds having a two-dimensional layered structure, represented by the general formula Me_xMo₆S₈And Chevrel compounds having a strong three-dimensional skeleton structure represented by (Me is various transition metals represented by Pb, Ag, and Cu). Further, elemental sulfur or LiS_xThe organic lithium sulfide shown above.

Examples of the conductive polymer include a p-doped conductive polymer and an n-doped conductive polymer. Examples of the conductive polymer include polyacetylene-based, polyphenylene-based, heterocyclic polymer, ionic polymer, ladder-shaped and network-shaped polymer, and the like.

Further, if the positive electrode active material contains lithium phosphate, the continuous charging characteristics are improved, which is preferable. The use of lithium phosphate is not limited, and the above-mentioned positive electrode active material and lithium phosphate are preferably used in combination. The lower limit of the amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less, relative to the total amount of the positive electrode active material and the lithium phosphate.

In addition, a material in which a substance having a different composition is attached to the surface of the positive electrode active material may be used. Examples of the surface-adhering substance include oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boria, antimony oxide, and bismuth oxide, sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

These surface-attached substances can be added by, for example, dissolving or suspending them in a solvent, impregnating the positive electrode active material with the solution, and drying the solution; a method in which a precursor of a surface-attached substance is dissolved or suspended in a solvent, then the solution is added by dipping to the positive electrode active material, and then the solution is reacted by heating or the like; and is attached to the surface of the positive electrode active material by a method of adding the precursor to the positive electrode active material and simultaneously sintering the precursor. In the case of carbon adhesion, a method of subsequently mechanically adhering carbon in the form of activated carbon or the like may be used.

The amount of the surface-adhering substance is preferably 0.1ppm or more, more preferably 1ppm or more, and still more preferably 10ppm or more, as a lower limit, and preferably 20% or less, more preferably 10% or less, and still more preferably 5% or less, by mass, based on the positive electrode active material. The surface-attached substance can suppress the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material, and can improve the battery life, but when the amount of the attached substance is too small, the effect cannot be sufficiently exhibited, and when the amount of the attached substance is too large, the introduction and removal of lithium ions are inhibited, and thus the resistance is increased.

Examples of the shape of the particles of the positive electrode active material include a block shape, a polyhedral shape, a spherical shape, an ellipsoidal shape, a plate shape, a needle shape, a columnar shape, and the like, which have been conventionally used. In addition, the primary particles may be aggregated to form secondary particles.

The tap density of the positive electrode active material is preferably 0.5g/cm³Above, more preferably 0.8g/cm³Above, more preferably 1.0g/cm³The above. If the tap density of the positive electrode active material is less than the lower limit, the amount of the dispersion medium required for forming the positive electrode active material layer increases, the amount of the conductive material or the binder required increases, the filling rate of the positive electrode active material in the positive electrode active material layer is limited, and the battery capacity is limitedAnd (4) about. By using the composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. While there is no particular upper limit as the tap density is generally higher, if it is too high, the diffusion of lithium ions using the electrolyte as a medium in the positive electrode active material layer may be restricted, and the load characteristics may be easily lowered, so the upper limit is preferably 4.0g/cm³Hereinafter, more preferably 3.7g/cm³Hereinafter, more preferably 3.5g/cm³The following.

In the present invention, 5 to 10g of the positive electrode active material powder was charged into a 10ml glass measuring cylinder with respect to tap density, and the powder was tapped at an amplitude of about 20mm for 200 times to obtain a powder packing density (tap density) g/cm³To obtain the final product.

The median particle diameter d50 of the particles of the positive electrode active material (secondary particle diameter in the case where the primary particles are aggregated to form secondary particles) is preferably 0.3 μm or more, more preferably 0.5 μm or more, even more preferably 0.8 μm or more, and most preferably 1.0 μm or more, and is preferably 30 μm or less, more preferably 27 μm or less, even more preferably 25 μm or less, and most preferably 22 μm or less. If the amount is less than the lower limit, a high tap density product may not be obtained, and if the amount exceeds the upper limit, it takes time for lithium in the particles to diffuse, which may cause problems such as deterioration of battery performance, and occurrence of a pull-out stripe in the case of manufacturing a positive electrode for a battery, that is, in the case of forming an active material into a slurry with a solvent, a conductive material, a binder, or the like, and applying the slurry in a thin film. Here, by mixing two or more kinds of the positive electrode active materials having different median particle diameters d50, the filling property at the time of producing the positive electrode can be further improved.

In the present invention, the median particle diameter d50 is measured by a known laser diffraction/scattering particle size distribution measuring apparatus. When LA-920 manufactured by HORIBA Inc. was used as a particle size distribution meter, a 0.1 mass% aqueous solution of sodium hexametaphosphate was used as a dispersion medium used for measurement, and the refractive index was set to 1.24 after 5 minutes of ultrasonic dispersion for measurement.

When the primary particles are aggregated to form the secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more, and the upper limit is preferably 5 μm or less, more preferably 4 μm or less, even more preferably 3 μm or less, and most preferably 2 μm or less. If the amount exceeds the upper limit, spherical secondary particles are difficult to form, and the powder filling property is adversely affected, or the specific surface area is greatly reduced, so that the possibility of deterioration in battery performance such as output characteristics may be high. On the other hand, if the amount is less than the lower limit, there is a possibility that the crystal is not developed, which causes a problem of poor charge/discharge reversibility.

In the present invention, the primary particle diameter can be measured by observation using a Scanning Electron Microscope (SEM). Specifically, in a photograph of 10000 times magnification, the longest value of the intercept of the left and right boundary lines of the primary particle with respect to the straight line in the horizontal direction is obtained for any 50 primary particles, and the longest value is obtained by averaging.

The BET specific surface area of the positive electrode active material is preferably 0.1m²A value of at least one per gram, more preferably 0.2m²A value of at least one per gram, more preferably 0.3m²A maximum of 50m or more in terms of/g²A ratio of 40m or less per gram²A ratio of 30m or less per gram²The ratio of the carbon atoms to the carbon atoms is less than g. When the BET specific surface area is less than this range, the battery performance tends to be lowered, and when it is more than this range, the tap density tends to be difficult to increase, and there may be a problem in coatability at the time of formation of the positive electrode active material layer.

In the present invention, the BET specific surface area is defined by a value measured by a nitrogen adsorption BET1 point method by a gas flow method using a nitrogen helium mixed gas in which a sample is pre-dried at 150 ℃ for 30 minutes under a nitrogen gas flow using a surface area meter (for example, a full-automatic surface area measuring device manufactured by university research corporation) and then the relative pressure of nitrogen to the atmospheric pressure is accurately adjusted to 0.3.

In the case where the lithium ion secondary battery of the present invention is used as a large lithium ion secondary battery for a hybrid vehicle or a distributed power supply, high output is required, and therefore, the particles of the positive electrode active material are preferably mainly secondary particles.

The particles of the positive electrode active material preferably contain secondary particles having an average particle diameter of 40 μm or less and 0.5 to 7.0 vol% of fine particles having an average primary particle diameter of 1 μm or less. By containing fine particles having an average primary particle diameter of 1 μm or less, the contact area with the electrolyte solution becomes large, and diffusion of lithium ions between the electrode and the electrolyte solution can be further accelerated, and as a result, the output performance of the battery can be improved.

As the method for producing the positive electrode active material, a general method as a method for producing an inorganic compound can be used. In particular, various methods are conceivable for producing spherical or ellipsoidal active substances, and examples thereof include: dissolving or pulverizing and dispersing a transition metal raw material in a solvent such as water, adjusting pH under stirring to prepare a recovered spherical precursor, drying the precursor if necessary, and adding LiOH and Li₂CO₃、LiNO₃And a method of obtaining an active material by firing the Li source at a high temperature.

The positive electrode active material may be used alone or 2 or more kinds of materials having different compositions may be used in combination or ratio. In this case, a preferable combination is LiCoO₂And LiNi_0.33Co_0.33Mn_0.33O₂Equal LiMn₂O₄Or a combination of a substance in which a part of Mn is replaced with another transition metal or the like, or LiCoO₂Or a combination of substances in which a part of Co is replaced with another transition metal or the like.

The content of the positive electrode active material is preferably 50 to 99.5% by mass, more preferably 80 to 99% by mass of the positive electrode mixture, from the viewpoint of high battery capacity. The content of the positive electrode active material in the positive electrode active material layer is preferably 80 mass% or more, more preferably 82 mass% or more, and particularly preferably 84 mass% or more. The upper limit is preferably 99 mass% or less, and more preferably 98 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the capacitance may become insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

The positive electrode mixture preferably further contains a binder, a thickener, and a conductive material.

As the binder, any binder can be used as long as it is safe for the solvent and the electrolyte used in the production of the electrode, and examples thereof include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, chitosan, alginic acid, polyacrylic acid, polyimide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), ethylene-propylene rubber, and the like; styrene-butadiene-styrene block copolymers or hydrogenated products thereof; thermoplastic elastomer polymers such as EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer, and hydrogenated product thereof; soft resinous polymers such as syndiotactic-1, 2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers and propylene- α -olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride copolymers, and tetrafluoroethylene-ethylene copolymers; and a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). These can be used alone in 1 kind, also can be in any combination and ratio and use more than 2.

The content of the binder is usually 0.1 mass% or more, preferably 1 mass% or more, more preferably 1.5 mass% or more, and usually 80 mass% or less, preferably 60 mass% or less, more preferably 40 mass% or less, and most preferably 10 mass% or less, in terms of the proportion of the binder in the positive electrode active material layer. If the proportion of the binder is too low, the mechanical strength of the positive electrode may be insufficient, and the positive electrode active material may not be sufficiently retained, thereby deteriorating battery performance such as cycle characteristics. On the other hand, if it is too high, the battery capacity and conductivity may be lowered.

Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, polyvinylpyrrolidone, and salts thereof. One kind may be used alone, or two or more kinds may be used in combination in any combination and ratio.

The proportion of the thickener to the active material is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and is usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If the amount is less than this range, the coatability may be significantly reduced. If the amount exceeds this range, the proportion of the active material in the positive electrode active material layer decreases, which may cause a problem of decrease in the capacity of the battery or a problem of increase in the resistance between the positive electrode active materials.

As the conductive material, a known conductive material can be used as desired. Specific examples thereof include metal materials such as copper and nickel; graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, and carbon materials such as amorphous carbon including needle coke, carbon nanotubes, fullerene and VGCF. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds in any combination and ratio. The conductive material is used in the positive electrode active material layer in a content of usually 0.01 mass% or more, preferably 0.1 mass% or more, and more preferably 1 mass% or more, and in a content of usually 50 mass% or less, preferably 30 mass% or less, and more preferably 15 mass% or less. If the content is less than this range, the conductivity may become insufficient. On the contrary, if the content is higher than the range, the battery capacity may be lowered.

The solvent used for forming the slurry is not particularly limited in kind as long as it can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as needed, and any of an aqueous solvent and an organic solvent can be used. Examples of the aqueous solvent include water, and a mixed solvent of an alcohol and water. Examples of the organic solvent include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and Tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethylsulfoxide.

Examples of the material of the positive electrode current collector include metal materials such as aluminum, titanium, tantalum, stainless steel, and nickel, or alloys thereof; carbon cloth, carbon paper, and the like. Among them, a metal material, particularly aluminum or an alloy thereof, is preferable.

As the shape of the current collector, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, a porous metal mesh (expanded metal), a punching metal, a foamed metal, and the like can be given, and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder, and the like can be given. Among them, a metal thin film is preferable. The film may be appropriately formed into a mesh shape. The thickness of the film is arbitrary, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and is usually 1mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the film is thinner than this range, the strength required as a current collector may be insufficient. On the contrary, if the film is thicker than this range, the workability may be impaired.

In addition, it is preferable that the surface of the current collector is coated with a conductive assistant in order to reduce the electrical contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive assistant include: carbon; noble metals such as gold, platinum, and silver.

The ratio of the current collector to the thickness of the positive electrode active material layer is not particularly limited, and the value of (the thickness of the positive electrode active material layer on one side immediately before electrolyte injection)/(the thickness of the current collector) is preferably 20 or less, more preferably 15 or less, most preferably 10 or less, and is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. If the amount exceeds this range, heat generation by joule heat may occur in the current collector during high current density charge and discharge. If the amount is less than this range, the volume ratio of the current collector to the positive electrode active material increases, and the capacity of the battery may decrease.

The positive electrode may be produced by a conventional method. For example, a method of adding the binder, the thickener, the conductive material, the solvent, and the like to the positive electrode active material to prepare a slurry-like positive electrode mixture, applying the slurry-like positive electrode mixture to a current collector, drying the applied current collector, and pressing the dried current collector to increase the density of the current collector can be cited.

The densification may be performed by hand pressing, rolling, or the like. The density of the positive electrode active material layer is preferably 1.5g/cm³Above, more preferably 2g/cm³Above, more preferably 2.2g/cm³The above is preferably 5g/cm³Hereinafter, more preferably 4.5g/cm³Hereinafter, more preferably 4g/cm³The following ranges. If the amount exceeds this range, the permeability of the electrolyte solution into the vicinity of the current collector/active material interface decreases, and particularly, the charge-discharge characteristics at a high current density decrease, and thus, a high output may not be obtained. If the amount is less than this range, the conductivity between the active materials decreases, the battery resistance increases, and a high output may not be obtained.

In the case of using the electrolyte solution of the present invention, the area of the positive electrode active material layer is preferably larger than the outer surface area of the battery outer case from the viewpoint of high output and improved stability at high temperatures. Specifically, the total electrode area of the positive electrode is preferably 15 times or more, and more preferably 40 times or more, in terms of an area ratio to the surface area of the exterior of the secondary battery. The external surface area of the battery outer case is: in the case of the bottomed square shape, the total area found is calculated from the dimensions of the length, width, and thickness of the case portion filled with the power generating element, excluding the protruding portion of the terminal. In the case of a bottomed cylindrical shape, the geometric surface area is obtained when the case portion filled with the power generating element other than the protruding portion of the terminal is made substantially cylindrical. The total of the electrode areas of the positive electrode means the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material; in the structure in which the positive electrode mixture layers are formed on both surfaces of the current collector foil, the total area of the surfaces is calculated.

The thickness of the positive electrode is not particularly limited, and from the viewpoint of high capacity and high output, the lower limit of the thickness of the mixture layer obtained by subtracting the thickness of the metal foil of the core material is preferably 10 μm or more, more preferably 20 μm or more, and further preferably 500 μm or less, more preferably 450 μm or less, with respect to one surface of the current collector.

In addition, a material having a different composition from the positive electrode plate may be adhered to the surface of the positive electrode plate. Examples of the surface-adhering substance include oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boria, antimony oxide, and bismuth oxide, sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

< negative electrode >

The negative electrode is composed of a negative electrode active material layer containing a negative electrode active material and a current collector.

The negative electrode material is not particularly limited as long as it can electrochemically absorb and release lithium ions. Specific examples thereof include carbon materials, alloy materials, lithium-containing metal composite oxide materials, conductive polymers, and the like. These may be used alone in 1 kind, or may be used in any combination of 2 or more kinds.

Examples of the negative electrode active material include carbonaceous materials capable of absorbing and releasing lithium, such as thermally decomposed organic materials under various thermal decomposition conditions, artificial graphite, and natural graphite; metal oxide materials capable of absorbing and releasing lithium, such as tin oxide and silicon oxide; lithium metal; various lithium alloys; metal composite oxide materials containing lithium, and the like. These negative electrode active materials may be used in combination of 2 or more.

Preferred carbonaceous materials capable of absorbing and releasing lithium include artificial graphite or purified natural graphite produced by subjecting graphitizable pitch obtained from various raw materials to high-temperature treatment, and those obtained by subjecting these graphites to surface treatment with an organic substance such as pitch and then carbonizing the graphite; from the viewpoint of a good balance between initial irreversible capacity and high current density charge/discharge characteristics, the material is more preferably selected from the following materials: natural graphite; artificial graphite; heat-treating the artificial carbonaceous material and the artificial graphite material at 400-3200 ℃ for more than 1 time to obtain a carbonaceous material; a carbonaceous material in which at least 2 or more carbonaceous materials having different crystallinities and/or a carbonaceous contact interface having the different crystallinities are contained in the negative electrode active material layer; and a carbonaceous material for providing the negative electrode active material layer with a carbonaceous contact interface having at least 2 or more different orientations. These carbon materials may be used alone in 1 kind, or may be used in combination in 2 or more kinds at an arbitrary combination and ratio.

Examples of the carbonaceous material obtained by heat-treating the artificial carbonaceous material and the artificial graphite material at 400 to 3200 ℃ for 1 or more times include coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, carbonaceous material obtained by oxidizing these pitches, needle coke, pitch coke, carbon agents obtained by partially graphitizing these, thermal decomposition products of organic substances such as furnace black, acetylene black, pitch-based carbon fibers, carbonizable organic substances and carbides thereof, solutions obtained by dissolving carbonizable organic substances in low-molecular-weight organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and carbides thereof.

The metal material used as the negative electrode active material (excluding the lithium titanium composite oxide) is not particularly limited as long as it can absorb and release lithium, and may be any of a simple substance of lithium, a simple substance metal and an alloy forming a lithium alloy, or a compound of the above, such as an oxide, a carbide, a nitride, a silicide, a sulfide, or a phosphide. As the elemental metal and the alloy forming the lithium alloy, a material containing metal and semimetal elements of groups 13 and 14 is preferable, and elemental metals of aluminum, silicon, and tin (hereinafter, simply referred to as "specific metal elements") and alloys or compounds containing these atoms are more preferable. These can be used alone in 1 kind, also can be in any combination and ratio and use more than 2.

Examples of the negative electrode active material having at least 1 atom selected from the specific metal elements include a simple metal substance of any 1 specific metal element, an alloy containing 2 or more specific metal elements, an alloy containing 1 or 2 or more specific metal elements and 1 or 2 or more other metal elements, and a compound containing 1 or 2 or more specific metal elements and a composite compound such as an oxide, carbide, nitride, silicide, sulfide, or phosphide of the compound. By using these simple metals, alloys, or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

Further, there may be mentioned compounds in which these complex compounds are complexly bonded to a plurality of elements such as a simple metal, an alloy or a nonmetallic element. Specifically, for example, in the case of silicon or tin, an alloy of these elements with a metal which does not operate as a negative electrode can be used. For example, in the case of tin, a complex compound containing 5 to 6 elements, such as tin and a metal other than silicon which functions as a negative electrode, and further a combination of a metal which does not function as a negative electrode and a nonmetal element, may be used.

Specifically, the Si is simple substance or SiB₄、SiB₆、Mg₂Si、Ni₂Si、TiSi₂、MoSi₂、CoSi₂、NiSi₂、CaSi₂、CrSi₂、Cu₆Si、FeSi₂、MnSi₂、NbSi₂、TaSi₂、VSi₂、WSi₂、ZnSi₂、SiC、Si₃N₄、Si₂N₂O、SiO_v(0<v is less than or equal to 2), LiSiO, or Sn simple substance, SnSiO₃、LiSnO、Mg₂Sn、SnO_w(0<w≤2)。

Further, a composite material containing Si or Sn as the 1 st constituent element and the 2 nd and 3 rd constituent elements in addition thereto is exemplified. The 2 nd constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, and zirconium. The 3 rd constituent element is, for example, at least one of boron, carbon, aluminum, and phosphorus.

In particular, from the obtainable heightFrom the viewpoint of battery capacity and excellent battery characteristics, the metal material is preferably a simple substance of silicon or tin (which may contain a trace amount of impurities), or SiO_v(0<v≤2)、SnO_w(w is more than or equal to 0 and less than or equal to 2), Si-Co-C composite materials, Si-Ni-C composite materials, Sn-Co-C composite materials and Sn-Ni-C composite materials.

The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can absorb and release lithium, and is preferably a material containing titanium and lithium, more preferably a lithium-containing metal composite oxide material containing titanium, and even more preferably a composite oxide of lithium and titanium (hereinafter simply referred to as "lithium-titanium composite oxide") in terms of high current density charge-discharge characteristics. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in the negative electrode active material for an electrolyte battery because the output resistance is greatly reduced.

The lithium titanium composite oxide is preferably represented by the general formula:

Li_xTi_yM_zO₄

[ wherein M represents at least 1 element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb. ]

The compound shown in the specification.

In the above composition, because

(i)1.2≤x≤1.4、1.5≤y≤1.7、z＝0

(ii)0.9≤x≤1.1、1.9≤y≤2.1、z＝0

(iii)0.7≤x≤0.9、2.1≤y≤2.3、z＝0

The structure (2) is particularly preferable because the balance of battery performance is good.

A particularly preferred representative composition of the above compounds, in (i), is Li_4/3Ti_5/3O₄In (ii) is Li₁Ti₂O₄In (iii) is Li_4/5Ti_11/5O₄. In addition, for the structure where Z ≠ 0, for example, Li can be cited_4/3Ti_4/3Al_1/3O₄As a preferred configuration.

The negative electrode mixture preferably further contains a binder, a thickener, and a conductive material.

Examples of the binder include the same binders as those usable for the positive electrode. The proportion of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 0.6% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 8% by mass or less. If the ratio of the binder to the anode active material exceeds the above range, the amount of the binder does not contribute to the battery capacity, and therefore the binder ratio may increase, resulting in a decrease in the battery capacity. If the content is less than the above range, the strength of the negative electrode may be reduced.

In particular, when a rubbery polymer represented by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When a fluorine-based polymer represented by polyvinylidene fluoride is contained as a main component, the proportion of the fluorine-based polymer to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more, and is usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

Examples of the thickener include the same thickeners as those usable for the positive electrode. The proportion of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 0.6% by mass or more, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. If the ratio of the thickener to the negative electrode active material is less than the above range, coatability may be significantly reduced. If the amount exceeds the above range, the proportion of the negative electrode active material in the negative electrode active material layer decreases, which may result in a decrease in the capacity of the battery or an increase in the resistance between the negative electrode active materials.

As the conductive material of the negative electrode, metal materials such as copper and nickel can be mentioned; carbon materials such as graphite and carbon black.

The solvent used for forming the slurry is not particularly limited as long as it can dissolve or disperse the negative electrode active material, the binder, and the thickener and the conductive material used as needed, and any of an aqueous solvent and an organic solvent can be used.

Examples of the aqueous solvent include water and alcohol, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N-dimethylaminopropylamine, Tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphoramide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, and hexane.

Examples of the material of the current collector for the negative electrode include copper, nickel, and stainless steel. Among these, copper foil is preferable in terms of easy processing into a film and cost.

The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, usually 100 μm or less, preferably 50 μm or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be excessively reduced, and if it is too thin, handling may be difficult.

The negative electrode may be produced by a conventional method. For example, the negative electrode material may be added with the binder, thickener, conductive material, solvent, etc. to prepare a slurry, and the slurry may be applied to a current collector, dried, and then pressed to increase the density. When an alloy material is used, a method of forming a thin film layer (negative electrode active material layer) containing the negative electrode active material by a method such as vapor deposition, sputtering, or plating may be used.

Electrode structure for electrically polarizing negative electrode active materialThe density of the negative electrode active material present on the current collector is preferably, but not particularly limited to, 1g · cm^-3More preferably 1.2 g/cm^-3Above, 1.3 g/cm is particularly preferable^-3The above is preferably 2.2 g/cm^-3Hereinafter, more preferably 2.1 g/cm^-3Hereinafter, more preferably 2.0 g/cm^-3The concentration is preferably 1.9 g/cm or less^-3The following. If the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles may be broken, resulting in an increase in initial irreversible capacity and a deterioration in high current density charge/discharge characteristics due to a decrease in the permeability of the electrolyte solution to the vicinity of the current collector/negative electrode active material interface. If the content is less than the above range, the conductivity between the negative electrode active materials may decrease, the battery resistance may increase, and the capacity per unit volume may decrease.

The thickness of the negative electrode plate is not particularly limited, and is designed according to the positive electrode plate to be used, and the thickness of the mixture layer obtained by subtracting the thickness of the metal foil of the core material is desirably generally 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and is generally 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

In addition, a material in which a substance having a different composition from that of the negative electrode plate is attached to the surface of the negative electrode plate may be used. Examples of the surface-adhering substance include oxides such as alumina, silica, titania, zirconia, magnesia, calcium oxide, boria, antimony oxide, and bismuth oxide, sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate, and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

< spacers >

The lithium ion secondary battery of the present invention preferably further comprises a separator.

The material and shape of the separator are not particularly limited as long as they are stable in an electrolytic solution and have excellent liquid retention properties, and known materials and shapes can be used. Among them, a porous sheet or a nonwoven fabric-like article which is made of a material stable to the electrolyte solution of the present invention, can use a resin, glass fiber, an inorganic substance, etc., and has excellent liquid retention properties is preferably used.

Examples of the material for the resin and glass fiber spacer include polyolefins such as polyethylene and polypropylene, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, and glass filters. Polypropylene/polyethylene 2 film, polypropylene/polyethylene/polypropylene 3 film, and the like, and these materials may be used alone in 1 kind, or may be used in combination of 2 or more kinds at any combination and ratio. Among them, the separator is preferably a porous sheet or a nonwoven fabric made of polyolefin such as polyethylene or polypropylene, in view of its excellent permeability and shutdown (shutdown) effects of the electrolyte.

The thickness of the separator is arbitrary, and is usually 1 μm or more, preferably 5 μm or more, and more preferably 8 μm or more, and is usually 50 μm or less, preferably 40 μm or less, and more preferably 30 μm or less. If the spacer is too thin than the above range, insulation properties and mechanical strength may be reduced. Further, if the separator is too thick than the above range, not only the battery performance such as rate characteristics may be degraded, but also the energy density of the entire electrolytic solution battery may be degraded.

Further, when a porous material such as a porous sheet or a nonwoven fabric is used as the separator, the porosity of the separator is arbitrary, and is usually 20% or more, preferably 35% or more, and more preferably 45% or more, and is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too small as compared with the above range, the membrane resistance tends to be large, and the rate characteristics tend to be deteriorated. If the amount is too large, the mechanical strength of the separator tends to be low, and the insulation tends to be low.

The average pore diameter of the separator is also arbitrary, and is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. If the average pore diameter exceeds the above range, short circuits are liable to occur. If the ratio is less than the above range, the film resistance may become large, and the rate characteristics may be deteriorated.

On the other hand, as the material of the inorganic substance, for example, an oxide such as alumina or silica, a nitride such as aluminum nitride or silicon nitride, a sulfate such as barium sulfate or calcium sulfate, or a particle-shaped or fiber-shaped material can be used.

As the form, a film-shaped material such as a nonwoven fabric, a woven fabric, a microporous film, or the like can be used. In the case of a thin film, it is preferable to use a material having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm. In addition to the above independent thin film shape, a separator in which a composite porous layer containing the inorganic particles is formed on the surface layer of the positive electrode and/or the negative electrode using a resin binder may be used. For example, alumina particles having a particle size of 90% less than 1 μm are formed as a porous layer on both surfaces of the positive electrode using a fluororesin as a binder.

< design of Battery >

The electrode group may be any of a laminated electrode group in which the positive electrode plate and the negative electrode plate are laminated with the separator interposed therebetween, and a spirally wound electrode group in which the positive electrode plate and the negative electrode plate are wound with the separator interposed therebetween. The ratio of the volume of the electrode group in the internal volume of the battery (hereinafter referred to as electrode group occupancy) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less.

If the electrode group occupancy is lower than the above range, the battery capacity becomes small. If the amount exceeds the above range, the void space is small, and when the battery becomes high in temperature, the components expand, the vapor pressure of the liquid component of the electrolyte increases, the internal pressure increases, various characteristics such as the charge and discharge repeatability and high-temperature storage as the battery deteriorate, and a gas release valve for releasing the internal pressure to the outside may be operated.

The current collecting structure is not particularly limited, and in order to more effectively improve the charge-discharge characteristics at a high current density by the electrolyte solution of the present invention, it is preferable to reduce the resistance of the wiring portion and the junction portion. When the internal resistance is reduced in this manner, the effect of using the electrolyte solution of the present invention can be particularly exhibited.

In the case where the electrode group has the above-described laminated structure, it is preferable to use a structure in which the metal core portions of the respective electrode layers are bundled and welded as terminals. When the area of one electrode is increased, the internal resistance is increased, and therefore, it is also preferable to use a means for reducing the resistance by providing a plurality of terminals in the electrode. In the case where the electrode group has the above-described wound structure, the internal resistance can be reduced by providing a plurality of lead structures in each of the positive electrode and the negative electrode and bundling the lead structures into terminals.

The material of the outer case is not particularly limited as long as it is stable to the electrolyte solution used. Specifically, a metal such as nickel-plated steel sheet, stainless steel, aluminum, an aluminum alloy, or a magnesium alloy, or a laminated film (laminated film) of a resin and an aluminum foil can be used. From the viewpoint of weight reduction, a metal or laminated film of aluminum or an aluminum alloy is preferably used.

When a metal-based outer case is used, there may be mentioned an outer case having a hermetically sealed structure formed by welding metals to each other by laser welding, resistance welding or ultrasonic welding, or an outer case having a structure formed by caulking (the japanese language "かしめ" for caulking and riveting ") using the above-mentioned metal-based material through a resin gasket. In the case of an outer case using the laminate film, an outer case having a hermetically sealed structure formed by thermally welding resin layers to each other may be used. In order to improve the sealing property, a resin different from the resin used for the laminate film may be present between the above resin layers. In particular, when the resin layer is thermally welded through the current collecting terminal to form a sealed structure, since the metal and the resin are bonded to each other, it is preferable to use a resin having a polar group and a modified resin into which a polar group is introduced as the resin interposed therebetween.

The shape of the lithium ion secondary battery of the present invention is arbitrary, and examples thereof include a cylindrical shape, a square shape, a laminated shape, a coin shape, a large size shape, and the like. The shapes and configurations of the positive electrode, the negative electrode, and the separator may be changed according to the shape of each battery.

In addition, a module including the lithium ion secondary battery of the present invention is also one aspect of the present invention.

A lithium ion secondary battery according to a preferred embodiment is provided with a positive electrode, a negative electrode, and the electrolyte solution, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, and the positive electrode active material contains Mn. The lithium ion secondary battery has more excellent high-temperature storage characteristics because the lithium ion secondary battery includes a positive electrode active material layer containing a positive electrode active material containing Mn.

The Mn-containing positive electrode active material is preferably LiMn in that it can provide a lithium ion secondary battery having high energy density and high output_1.5Ni_0.5O₄、LiNi_0.5Co_0.2Mn_0.3O₂、LiNi_0.6Co_0.2Mn_0.2O₂。

The content of the positive electrode active material in the positive electrode active material layer is preferably 80 mass% or more, more preferably 82 mass% or more, and particularly preferably 84 mass% or more. The upper limit is preferably 99 mass% or less, and more preferably 98 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the capacitance may become insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

The positive electrode active material layer may further contain a conductive material, a thickener, and a binder.

As the binder, any binder can be used as long as it is safe for a solvent or an electrolyte used in the production of an electrode, and examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, NBR (acrylonitrile-butadiene rubber), fluororubber, ethylene-propylene rubber, a styrene-butadiene-styrene block copolymer or a hydride thereof, EPDM (ethylene-propylene-diene terpolymer), a styrene-ethylene-butadiene-ethylene copolymer, a polymer of ethylene-propylene-styrene copolymer, a polymer of ethylene-, Styrene-isoprene-styrene block copolymers or hydrogenated products thereof, syndiotactic-1, 2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, propylene- α -olefin copolymers, fluorinated polyvinylidene fluoride, tetrafluoroethylene-ethylene copolymers, polymer compositions having ion conductivity for alkali metal ions (particularly lithium ions), and the like. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds in any combination and ratio.

Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. One kind may be used alone, or two or more kinds may be used in combination in any combination and ratio.

As the conductive material, a known conductive material can be used as desired. Specific examples thereof include metal materials such as copper and nickel; and carbon materials such as graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. These may be used alone in 1 kind, or may be used in combination of 2 or more kinds in any combination and ratio. The conductive material is used so as to be contained in the positive electrode active material layer by usually 0.01 mass% or more, preferably 0.1 mass% or more, and more preferably 1 mass% or more, and is used so as to be contained by usually 50 mass% or less, preferably 30 mass% or less, and more preferably 15 mass% or less. If the content is less than this range, the conductivity may become insufficient. On the contrary, if the content is higher than the range, the battery capacity may be lowered.

In order to further improve the high-temperature storage characteristics, the positive electrode current collector is preferably made of a valve metal or an alloy thereof. Examples of the valve metal include aluminum, titanium, tantalum, and chromium. The positive electrode current collector is more preferably made of aluminum or an alloy of aluminum.

In the lithium ion secondary battery, from the viewpoint of further improving the high-temperature storage characteristics, a portion of the portion electrically connected to the positive electrode current collector, which is in contact with the electrolyte solution, is preferably made of a valve metal or an alloy thereof. In particular, the battery outer case, and the portion of the lead wire, the safety valve, or the like housed in the battery outer case, which is electrically connected to the positive electrode current collector and is in contact with the nonaqueous electrolytic solution, are preferably made of a valve metal or an alloy thereof. Stainless steel covered with valve metal or alloys thereof may also be used.

As described above, the method for producing the positive electrode includes, for example, a method in which the binder, the thickener, the conductive material, the solvent, and the like are added to the positive electrode active material to prepare a slurry-like positive electrode mixture, and the slurry-like positive electrode mixture is applied to the positive electrode current collector, dried, and then pressed to increase the density.

The negative electrode has the above-described structure.

The electric double layer capacitor may include a positive electrode, a negative electrode, and the electrolyte solution.

In the electric double layer capacitor, at least one of the positive electrode and the negative electrode is a polarizable electrode, and as the polarizable electrode and the non-polarizable electrode, the following electrodes described in detail in japanese patent application laid-open No. 9-7896 can be used.

The polarizable electrodes mainly composed of activated carbon used in the present invention preferably contain non-activated carbon having a large specific surface area and a conductive material such as carbon black that imparts electron conductivity. The polarizing electrode may be formed by various methods. For example, a polarizable electrode containing activated carbon and carbon black can be formed by mixing activated carbon powder, carbon black, and a phenolic resin, press-molding the mixture, and then sintering and activating the mixture in an inert gas atmosphere and a water vapor atmosphere. The polarizable electrodes are preferably bonded to the current collector with a conductive adhesive or the like.

Alternatively, the polarizing electrode may be produced by kneading activated carbon powder, carbon black and a binder in the presence of an alcohol, molding the kneaded mixture into a sheet, and drying the sheet. Polytetrafluoroethylene, for example, can be used as the binder. Alternatively, the activated carbon powder, carbon black, a binder and a solvent may be mixed to prepare a slurry, and the slurry may be applied to a metal foil of a current collector and dried to prepare a polarizable electrode integrated with the current collector.

The electric double layer capacitor may be formed by using a polarizable electrode mainly composed of activated carbon for both electrodes, or may be formed by using a non-polarizable electrode on one side, and for example, may be formed by combining a positive electrode mainly composed of a battery active material such as a metal oxide and a negative electrode mainly composed of activated carbon, or may be formed by combining a negative electrode mainly composed of a carbon material capable of reversibly absorbing and desorbing lithium ions, or a negative electrode composed of a lithium metal or a lithium alloy and a polarized positive electrode mainly composed of activated carbon.

Carbon black, graphite, expanded graphite, porous carbon, carbon nanotubes, carbon nanohorns, ketjen black, and other carbonaceous materials may be used instead of or in combination with activated carbon.

The non-polarized electrode is preferably made mainly of a carbon material capable of reversibly absorbing and desorbing lithium ions, and a material obtained by absorbing lithium ions in the carbon material is used for the electrode. In this case, the electrolyte may use a lithium salt. According to the electric double layer capacitor having this configuration, a higher withstand voltage exceeding 4V can be obtained.

The solvent used for preparing the slurry for producing the electrode is preferably a solvent in which a binder is dissolved, and N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, dimethyl phthalate, ethanol, methanol, butanol, or water may be appropriately selected depending on the type of the binder.

The activated carbon used for the polarizing electrode includes phenol resin-based activated carbon, coconut shell-based activated carbon, petroleum coke-based activated carbon, and the like. Among them, petroleum coke-based activated carbon and phenol resin-based activated carbon are preferably used in view of obtaining a large capacity. The activated carbon activation treatment method includes a steam activation treatment method, a molten KOH activation treatment method, and the like, and it is preferable to use activated carbon subjected to the molten KOH activation treatment method in order to obtain a larger capacity.

Examples of a preferable conductive material used for the polarizable electrodes include carbon black, ketjen black, acetylene black, natural graphite, artificial graphite, metal fibers, conductive titanium oxide, and ruthenium oxide. The amount of the conductive material such as carbon black used for the polarizing electrode is preferably 1 to 50% by mass in total with the activated carbon, because the capacity of the product is reduced if the amount is too large in order to obtain good conductivity (low internal resistance).

In addition, as the activated carbon used in the polarizable electrode, in order to obtain an electric double layer capacitor having a large capacity and a low internal resistance, it is preferable to use activated carbon having an average particle diameter of 20 μm or less and a specific surface area of 1500 to 3000m²Per gram of activated carbon. Further, preferred carbon materials for constituting the electrode mainly composed of a carbon material capable of reversibly absorbing and desorbing lithium ions include natural graphite, artificial graphite, graphitized mesophase carbon spherules, graphitized whiskers, vapor grown carbon fibers, a fired product of furfuryl alcohol resin, and a fired product of Novolak resin.

The current collector may be any current collector having chemical and electrochemical corrosion resistance. As the current collector of the polarizable electrode mainly composed of activated carbon, stainless steel, aluminum, titanium, or tantalum can be preferably used. Among them, stainless steel or aluminum is a particularly preferable material in terms of both the characteristics and the price of the resulting electric double layer capacitor. As the current collector of the electrode mainly composed of a carbon material capable of reversibly absorbing and desorbing lithium ions, stainless steel, copper, or nickel is preferably used.

In addition, in order to allow a carbon material capable of reversibly absorbing and desorbing lithium ions to absorb lithium ions in advance, there is a method of: (1) a method of mixing powdery lithium in a carbon material capable of reversibly absorbing and desorbing lithium ions in advance, (2) a method of placing a lithium foil on an electrode comprising a carbon material capable of reversibly absorbing and desorbing lithium ions and a binder, and bringing the lithium foil into electrical contact with the electrode, and in this state, immersing the electrode in an electrolyte solution in which a lithium salt is dissolved to ionize lithium and incorporate lithium ions into the carbon material, and (3) a method of placing an electrode comprising a carbon material capable of reversibly absorbing and desorbing lithium ions and a binder on a negative electrode side, placing a lithium metal on a positive electrode side, immersing the electrode in a nonaqueous electrolyte solution in which a lithium salt is an electrolyte, and applying an electric current to electrochemically incorporate lithium into the carbon material in an ionized state.

As electric double layer capacitors, there are generally known wound electric double layer capacitors, laminated electric double layer capacitors, coin-type electric double layer capacitors, and the like, and these types of electric double layer capacitors can be used.

For example, a wound electric double layer capacitor is assembled by: a wound element is produced by winding a positive electrode and a negative electrode of a laminate (electrode) including a current collector and an electrode layer with a separator interposed therebetween, and the wound element is put into a case made of aluminum or the like, filled with an electrolyte solution, preferably a nonaqueous electrolyte solution, and then sealed with a sealing member made of rubber.

As the spacer, a conventionally known material and a spacer having a structure can be used. For example, porous polyethylene film, polytetrafluoroethylene, polypropylene fiber, glass fiber, nonwoven fabric of cellulose fiber, and the like can be mentioned.

Alternatively, a laminated electric double layer capacitor in which sheet-like positive and negative electrodes are laminated with an electrolyte and a separator interposed therebetween, and a coin-type electric double layer capacitor in which positive and negative electrodes are fixed with a gasket with an electrolyte and a separator interposed therebetween may be manufactured by a known method.

The electrolyte solution of the present invention is useful as an electrolyte solution for a large lithium ion secondary battery for a hybrid vehicle or a distributed power supply, or an electrolyte solution for an electric double layer capacitor.

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Electrolyte solution, electrochemical device, lithium ion secondary battery, and assembly

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