阅读说明：本技术 电解液、电化学装置及电子装置 (Electrolyte solution, electrochemical device, and electronic device ) 是由 彭谢学 郑建明 唐超 于 2020-12-30 设计创作，主要内容包括：本申请提供了一种电解液、电化学装置以及电子装置。所述电解液包括式(I-A)表示的化合物中的至少一种；其中,式(I-A)中由圆弧及与圆弧相连的直线构成的整体表示共价键；n独立地选自3到10的整数,A～(11)和A～(12)各自独立地选自不存在、式(I-B)、式(I-C)或式(I-D),并且A～(11)、A～(12)至少一个选自式(I-B)。所述电化学装置包括正极片、负极片、隔离膜以及所述电解液。所述电解液可以显著改善所述电化学装置的循环性能、高温存储性能和浮充性能。(The application provides an electrolyte, an electrochemical device and an electronic device. The electrolyte includes at least one of compounds represented by formula (I-A); wherein the whole consisting of the circular arc and the straight line connected with the circular arc in the formula (I-A) represents a covalent bond; n is independently selected from an integer of 3 to 10, A 11 And A 12 Each independently selected from absent, formula (I-B), formula (I-C) or formula (I-D), and A 11 、A 12 At least one is selected from the formula (I-B). The electrochemical device comprises a positive plate, a negative plate, an isolating membrane and the electrolyte. The electrolyte can significantly improve cycle performance, high-temperature storage performance, and float charge performance of the electrochemical device.)

1. An electrolyte comprising at least one of the compounds represented by formula (I-A);

wherein the whole consisting of the circular arc and the straight line connected with the circular arc in the formula (I-A) represents a covalent bond; n is independently selected from an integer of 3 to 10, A¹¹And A¹²Each independently selected from absent, formula (I-B), formula (I-C) or formula (I-D), and A¹¹、A¹²At least one is selected from formula (I-B);

wherein the content of the first and second substances,

represents a binding site to an adjacent atom;

R¹¹independently selected from the group consisting of a covalent single bond, a covalent double bond, an oxygen atom, a substituted or unsubstituted C₁-C₁₀Alkylene of (a), substituted or unsubstituted C₁-C₁₀Alkylene oxide of (a), substituted or unsubstituted C₂-C₁₀Wherein, when substituted, the substituent comprises halogen(ii) a Only when R is¹¹Selected from covalent double bonds, A¹¹And A¹²One of which is selected from absent;

R¹²、R¹³and R¹⁴Each independently selected from the group consisting of a covalent single bond, substituted or unsubstituted C₁-C₁₀Alkylene of (a), substituted or unsubstituted C₂-C₁₀Alkenylene group of (a), substituted or unsubstituted C₆-C₁₀Arylene of (a), substituted or unsubstituted C₃-C₁₀Wherein, when substituted, the substituent comprises a halogen;

R¹⁵independently selected from hydrogen, halogen, substituted or unsubstituted C₁-C₁₀Alkyl, substituted or unsubstituted C₂-C₁₀Alkenyl of (a), substituted or unsubstituted C₂-C₁₀Alkynyl, substituted or unsubstituted C₆-C₁₀Aryl, substituted or unsubstituted C₃-C₁₀Wherein, when substituted, the substituent comprises a halogen.

2. The electrolyte solution according to claim 1, wherein the compound represented by formula (I-a) includes at least one of compounds represented by formulae (I-1) to (I-30);

3. the electrolyte according to claim 1, wherein the compound represented by the formula (I-a) is contained in the electrolyte in an amount of 0.1 to 10% by mass based on the mass of the electrolyte.

4. The electrolyte of claim 1, further comprising at least one of a boron-based lithium salt, a compound containing a sulfur-oxygen double bond, a polynitrile compound, and a phosphate lithium salt.

5. The electrolyte solution according to claim 4, satisfying at least one of the following conditions (a) to (c):

(a) based on the mass of the electrolyte, the mass percentage content of the boron lithium salt in the electrolyte is 0.1-1%;

(b) the mass percentage content of the compound containing the sulfur-oxygen double bond in the electrolyte is 0.01-10%, preferably 0.1-8%;

(c) in the electrolytic solution, the mass ratio of the compound represented by the formula (I-A) to the polynitrile compound is less than 5.

6. The electrolyte of claim 4, the lithium boron salt comprising at least one of a compound represented by formula (II-A);

wherein B in the formula (II-A) is a boron atom, A²¹、A²²、A²³、A²⁴Each independently selected from one of halogen, formula (II-B), formula (II-C) or formula (II-D);

wherein the content of the first and second substances,

is shown andbinding sites for adjacent atoms;

binding site of formula (II-C)The O atom to which it is attached is bonded to the B atom in formula (II-A) and to the binding site in formula (II-C)The C atom to which it is attached is bonded to the B atom in formula (II-A) or to the C atom in another substituent;

x is 0 or 1;

R²¹、R²³each independently selected from substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₂-C₆Wherein, when substituted, the substituents include halogen;

R²²independently selected from substituted or unsubstituted C₁-C₆Alkylene of (a), substituted or unsubstituted C₂-C₆Wherein, when substituted, the substituent comprises halogen.

7. The electrolyte of claim 4, wherein the boron-based lithium salt comprises at least one of lithium tetrafluoroborate, lithium dioxalate, and lithium difluorooxalate borate.

8. The electrolyte according to claim 4, wherein the compound containing a double sulfur-oxygen bond comprises at least one of compounds represented by formula (III-A);

wherein the content of the first and second substances,

R³¹and R³²Each independently selected from substituted or unsubstituted C₁-C₅Alkyl, substituted or unsubstituted C₁-C₅Alkylene of (a), substituted orUnsubstituted C₂-C₁₀Alkenyl of (a), substituted or unsubstituted C₂-C₁₀Alkynyl, substituted or unsubstituted C₃-C₁₀An alicyclic group of (A), substituted or unsubstituted C₆-C₁₀Aryl of (a); wherein, when substituted, the substituent comprises at least one of a halogen and a heteroatom-containing functional group; wherein R is³¹And R³²Can bond and form a ring structure.

9. The electrolyte solution according to claim 8, wherein the compound represented by formula (III-a) includes at least one of compounds represented by formulae (III-1) to (III-16);

10. the electrolyte of claim 4, wherein:

the polynitrile compound comprises at least one of 1, 2-bis (2-cyanoethoxy) ethane, adiponitrile, 1,2, 3-tris (2-cyanoethoxy) propane or 1,3, 6-hexanetrinitrile;

the phosphate lithium salt compound comprises at least one of lithium difluorophosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate.

11. An electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte according to any one of claims 1 to 10.

12. An electronic device comprising the electrochemical device of claim 11.

Technical Field

The present application relates to the field of electrochemistry, and in particular, to an electrolyte, an electrochemical device, and an electronic device.

Background

Electrochemical devices, such as lithium ion batteries, have high energy density, high power density, and stable service life, and are widely used in mobile electronic devices (including mobile phones, notebooks, cameras, and other electronic products). In recent years, electrochemical devices have been rapidly developed with the development of mobile electronic devices, and the demand for electrochemical devices is expected to continue to increase with the rise of the industries of energy storage devices, power tools, and electric automobiles in the next few years. However, with the rapid development of technology and the diversity of market demands, more demands have been made on electrochemical devices of electronic products, such as thinner, lighter, more diversified shapes, higher safety performance, higher power performance, etc.

In order to increase the energy density of an electrochemical device, in addition to increasing the compacted density and gram volume of positive and negative electrode materials of the electrochemical device, increasing the working voltage of the electrochemical device is also one of important methods for increasing the energy density of a battery, however, increasing the charging voltage accelerates the decomposition of an electrolyte, which leads to the problems of shortening the cycle life of the electrochemical device and the like.

Disclosure of Invention

In some embodiments, the present application provides an electrolyte comprising at least one of the compounds represented by formula (I-a);

wherein the whole consisting of the circular arc and the straight line connected with the circular arc in the formula (I-A) represents a covalent bond; n is independently selected from an integer of 3 to 10, A¹¹And A¹²Each independently selected from absent, formula (I-B), formula (I-C) or formula (I-D), and A¹¹、A¹²At least one is selected from formula (I-B);

wherein the content of the first and second substances,represents a binding site to an adjacent atom;

R¹¹independently selected from the group consisting of a covalent single bond, a covalent double bond, an oxygen atom, a substituted or unsubstituted C₁-C₁₀Alkylene of (a), substituted or unsubstituted C₁-C₁₀Alkylene oxide of (a), substituted or unsubstituted C₂-C₁₀Wherein, when substituted, the substituents include halogen; only when R is¹¹Selected from covalent double bonds, A¹¹And A¹²One of which is selected from absent;

R¹²、R¹³and R¹⁴Each independently selected from the group consisting of a covalent single bond, substituted or unsubstituted C₁-C₁₀Alkylene of (a), substituted or unsubstituted C₂-C₁₀Alkenylene group of (a), substituted or unsubstituted C₆-C₁₀Arylene of (a), substituted or unsubstituted C₃-C₁₀Wherein, when substituted, the substituent comprises a halogen;

R¹⁵independently selected from hydrogen, halogen, substituted or unsubstituted C₁-C₁₀Alkyl, substituted or unsubstituted C₂-C₁₀Alkenyl of (a), substituted or unsubstituted C₂-C₁₀Alkynyl, substituted or unsubstituted C₆-C₁₀Aryl, substituted or unsubstituted C₃-C₁₀Wherein, when substituted, the substituent comprises a halogen.

In some embodiments, the compound represented by formula (I-A) includes at least one of compounds represented by formulae (I-1) to (I-30);

in some embodiments, the compound represented by formula (I-a) is present in the electrolyte in an amount of 0.1% to 10% by mass, based on the mass of the electrolyte.

In some embodiments, the electrolyte further includes at least one of a boron-based lithium salt, a sulfur-oxygen double bond-containing compound, a polynitrile compound, and a phosphate lithium salt-based compound.

In some embodiments, the boron-based lithium salt is present in the electrolyte in an amount of 0.1 to 1% by mass, based on the mass of the electrolyte.

In some embodiments, the sulfur oxygen double bond-containing compound is present in the electrolyte in an amount of 0.01 to 10% by mass, preferably 0.1 to 8% by mass, based on the mass of the electrolyte.

In some embodiments, in the electrolyte, a mass ratio of the compound represented by the formula (I-a) to the polynitrile compound is less than 5.

In some embodiments, the lithium boron-based salt comprises at least one of the compounds represented by formula (II-a);

wherein B in the formula (II-A) is a boron atom, A²¹、A²²、A²³、A²⁴Each independently selected from one of halogen, formula (II-B), formula (II-C) or formula (II-D);

wherein the content of the first and second substances,represents a binding site to an adjacent atom; binding site of formula (II-C)The O atom to which it is attached is bonded to the B atom in formula (II-A) and to the binding site in formula (II-C)The C atom to which it is attached is bonded to the B atom in formula (II-A) or to the C atom in another substituent; x is 0 or 1; r²¹、R²³Each independently selected from substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₂-C₆Wherein, when substituted, the substituents include halogen; r²²Independently selected from substituted or unsubstituted C₁-C₆Alkylene of (a), substituted or unsubstituted C₂-C₆Wherein, when substituted, the substituent comprises halogen.

In some embodiments, the compound represented by formula (II-a) comprises at least one of lithium tetrafluoroborate, lithium dioxalate, lithium difluorooxalate borate.

In some embodiments, the compound containing a double sulfur-oxygen bond comprises at least one of the compounds represented by formula (III-A);

wherein R is³¹And R³²Each independently selected from substituted or unsubstituted C₁-C₅Alkyl, substituted or unsubstituted C₁-C₅Alkylene of (a), substituted or unsubstituted C₂-C₁₀Alkenyl of (a), substituted or unsubstituted C₂-C₁₀Alkynyl, substituted or unsubstituted C₃-C₁₀An alicyclic group of (A), substituted or unsubstituted C₆-C₁₀Aryl of (a); wherein, when substituted, the substituent comprises at least one of a halogen and a heteroatom-containing functional group; wherein R is³¹And R³²Can bond and form a ring structure.

In some embodiments, the compound represented by formula (III-A) comprises at least one of the compounds represented by formulae (III-1) to (III-16);

in some embodiments, the polynitrile compound comprises at least one of 1, 2-bis (2-cyanoethoxy) ethane, adiponitrile, 1,2, 3-tris (2-cyanoethoxy) propane, or 1,3, 6-hexanetrinitrile; the phosphate lithium salt compound comprises at least one of lithium difluorophosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate.

In some embodiments, the present application also provides an electrochemical device comprising a positive electrode tab, a negative electrode tab, a separator, and the electrolyte described herein.

In some embodiments, the present application further provides an electronic device comprising an electrochemical device as described herein.

The electrolyte can significantly improve the cycle performance, high-temperature storage performance and float charge performance of the electrochemical device.

Detailed Description

It is to be understood that the disclosed embodiments are merely exemplary of the application that may be embodied in various forms and that specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present application.

In the description of the present application, unless otherwise expressly specified or limited, the terms "additive a", "additive B", "additive C", "additive D", "additive E", and the like are used for illustrative purposes only and are not to be construed as indicating or implying relative importance or relationship to each other. In the description of the present application, unless otherwise expressly specified or limited, the letters and numbers in the terms "formula I-A", "formula I-B", "formula I-1", "formula II-A", "formula II-B", "formula II-1", and the like, are used for labeling purposes only and are not to be construed as indicating or implying relative importance, existence of relationship, or chemical elements.

In the description of the present application, unless otherwise indicated, the functional groups of all compounds may be substituted or unsubstituted.

In the description of the present application, an alkylene group is a divalent group formed by losing one hydrogen atom from an alkyl group, an alkenylene group is a divalent group formed by losing one hydrogen atom from an alkenyl group, an alkynylene group is a divalent group formed by losing one hydrogen atom from an alkynyl group, an alkyleneoxy group is a divalent group formed by losing one hydrogen atom from an alkoxy group, and an arylene group is a divalent group formed by losing one hydrogen atom from an aryl group. In the description of the present application, subunit structures not explicitly described are to be read in light of the description in this paragraph.

In the description of the present application, the term "alicyclic hydrocarbon group" means a cyclic hydrocarbon having aliphatic properties, and containing a closed carbon ring in the molecule.

In the description of this application, the term "heteroatom" means an atom other than C, H. In some embodiments, the heteroatoms include at least one of B, N, O, Si, P, S. In the description of the present application, the term "heteroatom-containing functional group" refers to a functional group that includes at least one heteroatom.

The electrolyte solution, electrochemical device and electronic device according to the present invention will be described in detail below.

[ electrolyte ]

The electrolyte of the present application is first explained.

< additive A >

In some embodiments, the electrolyte comprises an additive A, wherein the additive A is at least one of the compounds represented by the formula (I-A);

wherein the whole consisting of the circular arc and the straight line connected with the circular arc in the formula (I-A) represents a covalent bond; n is independently selected from an integer of 3 to 10, A¹¹And A¹²Each independently selected from absent, formula (I-B), formula (I-C) or formula (I-D), and A¹¹、A¹²At least one is selected from formula (I-B);

wherein the content of the first and second substances,represents a binding site to an adjacent atom;

R¹¹independently selected from the group consisting of a covalent single bond, a covalent double bond, an oxygen atom, a substituted or unsubstituted C₁-C₁₀Alkylene of (a), substituted or unsubstituted C₁-C₁₀Alkylene oxide of (a), substituted or unsubstituted C₂-C₁₀Wherein, when substituted, the substituents include halogen; only when R is¹¹Selected from covalent double bonds, A¹¹And A¹²One of which is selected from absent; r¹²、R¹³And R¹⁴Each independently selected from the group consisting of a covalent single bond, substituted or unsubstituted C₁-C₁₀Alkylene of (a), substituted or unsubstituted C₂-C₁₀Alkenylene group of (a), substituted or unsubstituted C₆-C₁₀Arylene of (a), substituted or unsubstituted C₃-C₁₀Wherein, when substituted, the substituent comprises a halogen; r¹⁵Independently selected from hydrogen, halogen, substituted or unsubstituted C₁-C₁₀Alkyl, substituted or unsubstituted C₂-C₁₀Alkenyl of (a), substituted or unsubstituted C₂-C₁₀Alkynyl of (A), bySubstituted or unsubstituted C₆-C₁₀Aryl, substituted or unsubstituted C₃-C₁₀Wherein, when substituted, the substituent comprises a halogen.

In the electrolyte of the present application, the additive a is a cyclic ether cyano (-CN) functional compound. The cyclic ether cyano (-CN) functional group compound can form a complex with the transition metal to stabilize the transition metal on the surface of the positive active material; in addition, the cyclic ether polycyano (-CN) functional group compound can be oxidized to form a film, so that the compound can play a role in double protection, further inhibit the continuous decomposition of the electrolyte and inhibit high-temperature gas generation. Therefore, the inclusion of the additive a in the electrolyte can significantly improve the cycle performance, high-temperature storage performance, and float charge performance of an electrochemical device using the electrolyte.

In some embodiments, additive A comprises at least one of the compounds represented by formulas (I-1) to (I-40);

in some embodiments, the additive a is present in an amount of 0.1% to 10% by mass, based on the mass of the electrolyte. When the additive a is present in the above range by mass, the high-temperature storage performance and the float charge performance of the electrochemical device can be further improved. In some embodiments, the mass percentage of additive a may be 0.2%, 0.3%, 0.4%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%.

When the electrolyte contains the additive a, in some embodiments, the electrolyte may further include at least one of a boron lithium salt (denoted as additive B), a compound containing a sulfur-oxygen double bond (denoted as additive C), a polynitrile compound (denoted as additive D), and a phosphate lithium salt compound (denoted as additive E), and the electrochemical performance of the electrochemical device may be further improved by using the additive a and the additives in combination in the electrolyte.

< additive B >

In some embodiments, additive B is at least one of the compounds represented by formula (II-a);

wherein B in the formula (II-A) is a boron atom, A²¹、A²²、A²³、A²⁴Each independently selected from one of halogen, formula (II-B), formula (II-C) or formula (II-D);

wherein the content of the first and second substances,represents a binding site to an adjacent atom; binding site of formula (II-C)The O atom to which it is attached is bonded to the B atom in formula (II-A) and to the binding site in formula (II-C)The C atom to which it is attached is bonded to the B atom in formula (II-A) or to the C atom in another substituent; x is 0 or 1;

R²¹、R²³each independently selected from substituted or unsubstituted C₁-C₆Alkyl, substituted or unsubstituted C₂-C₆Wherein, when substituted, the substituents include halogen; r²²Independently selected from substituted or unsubstituted C₁-C₆Alkylene of (a), substituted or unsubstituted C₂-C₆Wherein, when substituted, the substituent comprises halogen.

When the additive A and the additive B are simultaneously added into the electrolyte, the high-temperature storage performance is further improved, probably because the additive A can act with transition metal on the surface of the anode, and the additive B can form a film on the surface of the anode, and the additive A and the additive B can be used cooperatively to further inhibit the decomposition of the electrolyte and reduce the gas generation effect.

In some embodiments, additive B comprises lithium tetrafluoroborate (LiBF)₄) At least one of lithium bis (oxalato) borate (LiBOB) and lithium difluoro (oxalato) borate (lidob).

In some embodiments, the additive B is present in the electrolyte in an amount of 0.1 to 1% by mass, based on the mass of the electrolyte. In some embodiments, the additive B may be present in the electrolyte in an amount of 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.9% by mass, based on the mass of the electrolyte.

< additive C >

In some embodiments, additive C is at least one of the compounds represented by formula (III-a);

wherein R is³¹And R³²Each independently selected from substituted or unsubstituted C₁-C₅Alkyl, substituted or unsubstituted C₁-C₅Alkylene of (a), substituted or unsubstituted C₂-C₁₀Alkenyl of (a), substituted or unsubstituted C₂-C₁₀Alkynyl, substituted or unsubstituted C₃-C₁₀With or without cycloaliphatic radicalsSubstituted C₆-C₁₀Aryl of (a); wherein, when substituted, the substituent comprises at least one of a halogen and a heteroatom-containing functional group; wherein R is³¹And R³²Can bond and form a ring structure.

The antioxidant capacity of the additive C is strong, the interface of the anode can be protected, and on the other hand, an interface film can be formed on the surface of the cathode, so that the protection of the active material is further enhanced.

In some embodiments, additive C comprises at least one of the compounds represented by formulas (III-1) to (III-16);

in some embodiments, the additive C is present in the electrolyte in an amount of 0.01 to 10% by mass, preferably 0.1 to 8% by mass, based on the total mass of the electrolyte. In some embodiments, the additive C may be present in the electrolyte in a mass percentage of 0.05%, 0.07%, 0.09%, 0.3%, 0.5%, 0.7%, 0.9%, 1.0%, 1.3%, 1.5%, 2.0%, 2.3%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5%, 7%, 9% based on the total mass of the electrolyte.

< additive D >

In some embodiments, additive D comprises at least one of 1,2, 3-tris (2-cyanoethoxy) propane (TCEP), 1,3, 6-Hexanetrinitrile (HTCN), 1, 2-bis (2-cyanoethoxy) ethane (done), Adiponitrile (AND).

In some embodiments, the additive D is present in the electrolyte in an amount of 0.1 to 10% by mass, based on the mass of the electrolyte. In some embodiments, the additive D may be present in the electrolyte in an amount of 0.3%, 0.5%, 0.7%, 0.9%, 1.0%, 1.3%, 1.5%, 2.0%, 2.3%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5%, 7%, 9% by mass, based on the mass of the electrolyte.

< additive E >

In some embodiments, additive E comprises lithium difluorophosphate (LiPO)₂F₂) Lithium difluorobis (oxalato) phosphate (LiDFOP), and lithium tetrafluoro (oxalato) phosphate (LiTFOP).

In some embodiments, the additive E is present in the electrolyte in an amount of 0.1 to 1% by mass, based on the mass of the electrolyte. In some embodiments, the additive E may be present in the electrolyte in an amount of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.9% by mass, based on the mass of the electrolyte.

< additive F >

In some embodiments, the electrolyte may further include a cyclic carbonate compound (denoted as additive F). In some embodiments, additive F comprises at least one of the compounds represented by formula (IV-a);

wherein R is³Selected from substituted or unsubstituted C₁-C₆Alkylene, substituted or unsubstituted C₂-C₆An alkenylene group; wherein, when substituted, the substituent group comprises halogen and C₁-C₆Alkyl radical, C₂-C₆At least one alkenyl group.

The cyclic carbonate (additive F) can assist in enhancing the SEI film forming stability of the negative electrode, increase the flexibility of an SEI film, further increase the protection effect on the negative electrode active material, and reduce the interface contact probability of the negative electrode active material and the electrolyte, so that the impedance increase caused by byproduct accumulation in the circulation process of the electrochemical device is improved.

In some embodiments, additive F comprises at least one of the compounds represented by formulas (IV-1) to (IV-8);

in some embodiments, the additive F is present in the electrolyte in an amount of 0.01% to 30%, preferably 0.1% to 10%, by mass based on the mass of the electrolyte.

[ organic solvent ]

In some embodiments, the electrolyte further comprises an organic solvent. The organic solvent is an organic solvent known in the art to be suitable for an electrochemical device, and for example, a nonaqueous organic solvent is generally used. In some embodiments, the non-aqueous organic solvent comprises at least one of a carbonate-based solvent, a carboxylate-based solvent, an ether-based solvent, or other aprotic solvent.

In some embodiments, the carbonate-based solvent comprises at least one of a chain carbonate, a cyclic carbonate. In some embodiments, the carbonate-based solvent comprises at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate.

In some embodiments, the carboxylate-based solvent comprises at least one of methyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, 2-difluoroethyl acetate, ethyl 2, 2-difluoroacetate, γ -butyrolactone, valerolactone, butyrolactone.

In some embodiments, the ether-based solvent comprises at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, 2-methyl tetrahydrofuran.

In some embodiments, the non-aqueous organic solvent comprises a cyclic aprotic solvent and a chain aprotic solvent. In some embodiments, the mass ratio of the cyclic aprotic solvent to the chain-like aprotic solvent of the nonaqueous organic solvent is 20:80 to 60: 40.

In the present application, one kind of non-aqueous organic solvent or a mixture of plural kinds of non-aqueous organic solvents may be used as the organic solvent in the electrolyte, and when a mixed solvent is used, the mixing ratio may be controlled according to the performance of the electrochemical device.

[ electrolyte salt ]

In some embodiments, the electrolyte further comprises an electrolyte salt. The electrolyte salt is well known in the art as an electrolyte salt suitable for an electrochemical device. For different electrochemical devices, suitable electrolyte salts may be selected. For example, for lithium ion batteries, lithium salts are commonly used as electrolyte salts.

In some embodiments, the lithium salt comprises at least one of an organic lithium salt or an inorganic lithium salt.

In some embodiments, the lithium salt used in the present application comprises at least one of fluorine, boron, and phosphorus.

In some embodiments, the lithium salt of the present application comprises lithium hexafluorophosphate (LiPF)₆) Lithium hexafluoroantimonate (LiSbF)₆) Lithium hexafluoroarsenate (LiAsF)₆) Lithium perfluorobutylsulfonate (LiC)₄F₉SO₃) Lithium perchlorate (LiClO)₄) Lithium aluminate (LiAlO)₂) Lithium aluminum tetrachloride (LiAlCl)₄) Lithium bis (sulfonimide) (LiN (C)_yF_2y+1SO₂)(C_zF_2z+1SO₂) Wherein y and z are natural numbers), lithium chloride (LiCl), lithium fluoride (LiF).

In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5 to 3mol/L based on the total volume of the electrolyte. In still other embodiments, the concentration of the lithium salt in the electrolyte is 0.5 to 2mol/L based on the total volume of the electrolyte. In still other embodiments, the concentration of the lithium salt in the electrolyte is 0.8 to 1.5mol/L based on the total volume of the electrolyte.

[ electrochemical device ]

Next, the electrochemical device of the present application will be described.

The electrochemical device of the present application is, for example, a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor. The secondary battery is, for example, a lithium secondary battery including, but not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

In some embodiments, the electrochemical device comprises a positive electrode tab, a negative electrode tab, a separator, and an electrolyte as described herein before.

< Positive electrode sheet >

The positive electrode tab is a positive electrode tab known in the art that can be used in an electrochemical device. In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. In some embodiments, the positive electrode active material layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

(i) Positive electrode active material

The positive electrode active material may be any conventionally known material capable of reversibly intercalating and deintercalating active ions, which is known in the art and can be used as a positive electrode active material for an electrochemical device. In some embodiments, the positive active material contains a composite oxide containing lithium and at least one selected from cobalt, manganese, and nickel.

In some embodiments, the positive active material comprises LiCoO₂、LiNiO₂、LiMnO₂、LiMn₂O₄、Li(Ni_aCo_bMn_c)O₂(0<a<1，0<b<1，0<c<1，a+b+c＝1)、LiMn₂O₄LiNi_1-yCo_yO₂、LiCo_l-yMn_yO₂、LiNi_{l- y}Mn_yO₂(0<y<1)、Li(Ni_aMn_bCo_c)O₄(0<a<2，0<b<2，0<c<2，a+b+c＝2)、LiMn_2-zNi_zO₄、LiMn_2-zCo_zO₄(0<z<2)、Li(Ni_aCo_bAl_c)O₂(0<a<1，0<b<1，0<c<1，a+b+c＝1)、LiCoPO₄And LiFePO₄At least one kind of (a) or a mixture of two or more kinds of (b). In some embodiments, the positive active material may include a sulfide, a selenide, a halide, and the like, in addition to the above-described oxide.

In some embodiments, the positive active material may have a coating layer on a surface thereof, or may be mixed with a compound having a coating layer. In some embodiments, the coating layer may comprise at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, a oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. In some embodiments, the compound used for the cladding layer may be amorphous or crystalline. In some embodiments, the cladding element for the cladding layer may comprise Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may be formed by any method as long as the properties of the positive electrode active material are not adversely affected by the inclusion of the coating element in the compound. In some embodiments, the method may comprise any coating method known to those skilled in the art, such as spraying, dipping, and the like.

(ii) Positive electrode conductive agent

In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent. The positive electrode conductive agent is used for providing conductivity for the positive electrode, and can improve the conductivity of the positive electrode. The positive electrode conductive agent is a conductive material known in the art that can be used as a positive electrode active material layer. The positive electrode conductive agent may be selected from any conductive material as long as it does not cause a chemical change. In some embodiments, the positive electrode conductive agent includes at least one of a carbon-based material (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber), a metal-based material (e.g., metal powder or metal fiber including copper, nickel, aluminum, silver, etc.), a conductive polymer (e.g., a polyphenylene derivative).

(iii) Positive electrode binder

In some embodiments, the positive electrode active material layer further comprises a positive electrode binder. The positive electrode binder is a binder known in the art that can be used as a positive electrode active material layer. The positive electrode binder may improve binding properties between the positive electrode active material particles and the positive electrode current collector. In some embodiments, the positive electrode binder comprises at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy, nylon.

(iv) Positive current collector

In some embodiments, the positive current collector is a metal, such as, but not limited to, aluminum foil.

In some embodiments, the structure of the positive electrode tab is a structure of a positive electrode tab that can be used in an electrochemical device, which is well known in the art.

In some embodiments, the method for preparing the positive electrode sheet is a method for preparing a positive electrode sheet that can be used for an electrochemical device, which is well known in the art. In some embodiments, in the preparation of the positive electrode slurry, a positive electrode active material, a binder, and if necessary, a conductive material and a thickener are generally added and dissolved or dispersed in a solvent to prepare a positive electrode slurry. The solvent is evaporated during the drying process. The solvent is a solvent known in the art that can be used as the positive electrode active material layer, and is, for example, but not limited to, N-methylpyrrolidone (NMP).

< negative electrode sheet >

The negative electrode tab is a negative electrode tab known in the art that may be used in an electrochemical device. In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. In some embodiments, the anode active material layer includes an anode active material, an anode conductive agent, and an anode binder.

(i) Negative electrode active material

The negative electrode active material may be any conventionally known material capable of intercalating and deintercalating active ions or any conventionally known material capable of doping and dedoping active ions, which is known in the art and can be used as a negative electrode active material for an electrochemical device.

In some embodiments, the negative active material comprises at least one of lithium metal, a lithium metal alloy, a material capable of doping/dedoping lithium, a transition metal oxide, and a carbon material.

(a) Lithium metal alloy

In some embodiments, the lithium metal alloy comprises lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, or Sn.

(b) Material capable of doping/dedoping lithium

In some embodiments, the material that reversibly intercalates/deintercalates lithium ions may be a carbon material.

In some embodiments, the material capable of doping/dedoping lithium comprises Si, SiO_x(0<x<2) Si/C composite, Si-Q alloy (wherein Q is not Si and is an alkali metal, alkaline earth metal, group 13 to group 16 element, transition element, rare earth element or combination thereof), Sn, SnO₂At least one of Sn/C composite, Sn-R alloy (wherein R is not Sn and is an alkali metal, an alkaline earth metal, a group 13 to group 16 element, a transition element, a rare earth element, or a combination thereof).

In some embodiments, exemplary elements of Q and R may be at least one of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po.

In some embodiments, the SiO_x(0<x<2) Is a porous silicon-based negative electrode active material, porous SiO_xThe average particle diameter D50 of the particles is 1 μm to 20 μm. In some embodiments, the SiO is measured at the surface_xThe average diameter of pores in the particles is 30nm to 500nm, SiO_xThe specific surface area of the particles was 5m²G to 50m²(ii) in terms of/g. In some embodiments, the SiO_xThe particulate silicon-based negative electrode active material may further contain Li₂SiO₃And Li₄SiO₄At least one of (1).

In some embodiments, the carbon in the Si/C composite is not agglomerated and dispersed in bulk inside the Si particles, but is uniformly dispersed in an atomic state inside the Si particles. In some embodiments, the molar ratio of C and Si, i.e., n (C)/n (Si), may be in a range of greater than 0 and less than 18. In some embodiments, the percentage of carbon in the Si/C composite may be 1% to 50% relative to the total weight of the Si/C composite. In some embodiments, the Si/C composite may have a particle size of 10nm to 100 μm.

(c) Transition metal oxide

In some embodiments, the transition metal oxide comprises at least one of vanadium oxide, lithium vanadium oxide.

(d) Carbon material

The carbon material may be selected from various carbon materials known in the art to be used as a carbon-based negative electrode active material for an electrochemical device. In some embodiments, the carbon material comprises at least one of crystalline carbon, amorphous carbon. In some embodiments, the crystalline carbon is natural graphite or artificial graphite. In some embodiments, the crystalline carbon is amorphous, platy, platelet, spherical, or fibrous in shape. In some embodiments, the crystalline carbon is low crystalline carbon or high crystalline carbon. In some embodiments, the low crystalline carbon comprises at least one of soft carbon, hard carbon. In some embodiments, the high crystalline carbon comprises at least one of natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microbeads, mesophase pitch, and high temperature calcined carbon. In some embodiments, the high temperature calcined carbon is petroleum or coke derived from coal tar pitch. In some embodiments, the amorphous carbon comprises at least one of soft carbon, hard carbon, mesophase pitch carbonization products, fired coke.

(ii) Negative electrode conductive agent

In some embodiments, the negative electrode active material layer further includes a negative electrode conductive agent. The negative electrode conductive agent is used for providing conductivity to the negative electrode, and can improve the conductivity of the negative electrode. The negative electrode conductive agent is a conductive material known in the art that can be used as a negative electrode active material layer. The negative electrode conductive agent may be selected from any conductive material as long as it does not cause a chemical change. In some embodiments, the negative electrode conductive agent includes at least one of a carbon-based material (e.g., natural graphite, artificial graphite, conductive carbon black, acetylene black, ketjen black, carbon fiber), a metal-based material (e.g., metal powder or metal fiber including copper, nickel, aluminum, silver, etc.), a conductive polymer (e.g., a polyphenylene derivative).

(iii) Negative electrode binder

In some embodiments, the anode active material layer further includes an anode binder. The binder may comprise various polymeric binders. In some embodiments, the negative electrode binder comprises at least one of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy, nylon.

(iv) Negative current collector

In some embodiments, the negative current collector is a metal such as, but not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or combinations thereof.

In some embodiments, the structure of the negative electrode sheet is a structure of a negative electrode sheet that may be used in an electrochemical device, as is well known in the art.

In some embodiments, the method of preparing the negative electrode sheet is a method of preparing a negative electrode sheet that may be used for an electrochemical device, which is well known in the art. In some embodiments, in the preparation of the negative electrode slurry, a negative electrode active material, a binder, and if necessary, a conductive material and a thickener are generally added and then dissolved or dispersed in a solvent to prepare a negative electrode slurry. The solvent is evaporated during the drying process. The solvent is a solvent known in the art, such as, but not limited to, water, which can be used as the negative electrode active material layer. The thickener is a thickener known in the art that can be used as the anode active material layer, and is, for example, but not limited to, sodium carboxymethyl cellulose.

< isolation film >

The separator is a separator known in the art that can be used for an electrochemical device, such as, but not limited to, polyolefin porous films. In some embodiments, the polyolefin-based porous membrane comprises a single or multilayer membrane composed of one or more of Polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methyl methacrylate copolymer.

In some embodiments, the polyolefin-based porous film is coated with a coating. In some embodiments, the coating comprises an organic coating and an inorganic coating. In some embodiments, the organic coating comprises at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyimide, acrylonitrile-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, acrylic acid-styrene copolymer, polydimethylsiloxane, sodium polyacrylate, sodium carboxymethylcellulose. In some embodiments, the inorganic coating comprises SiO₂、Al₂O₃、CaO、TiO₂、ZnO₂、MgO、ZrO₂And SnO₂At least one of (1).

The form and thickness of the separator are not particularly limited. The method for preparing the separator is a method for preparing a separator that can be used in an electrochemical device, which is well known in the art.

< outer case >

In some embodiments, the electrochemical device further comprises an overwrap housing. The outer packaging case is a well known outer packaging case in the art that can be used for electrochemical devices and is stable to the electrolyte used, such as, but not limited to, a metal-based outer packaging case.

[ electronic device ]

Finally, the electronic device of the present application is explained.

The electronic device of the present application is any electronic device such as, but not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handy cleaner, a portable CD player, a mini disc, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery, and a lithium ion capacitor. Note that the electrochemical device of the present application is applicable to an energy storage power station, a marine vehicle, and an air vehicle, in addition to the above-exemplified electronic devices. The air transport carrier device comprises an air transport carrier device in the atmosphere and an air transport carrier device outside the atmosphere.

In some embodiments, the electronic device comprises an electrochemical device as described herein.

The present application is further illustrated below with reference to examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.

In the following examples and comparative examples, the reagents, materials and instruments used were commercially available or synthetically obtained, unless otherwise specified, and the additives specifically used were as follows.

Additive A:

3,3' - (cyclopentane-1, 1-diylbis (oxy)) dipropionitrile3,3' - (cyclopentane-1, 2-diylbis (oxy)) dipropionitrile3,3' - (cyclopentane-1, 2, 3-triyltris (oxy)) tripropyl cyanide3,3',3 ", 3" ',3 "", 3 "" ' - (cyclohexane-1, 2,3,4,5, 6-hexylhexa (oxy)) hexapropionitrile

(3,3' - ((cyclohexane-1, 2, 3-Triyltris (methylene)) tris (oxy)) tripropyl cyanide

And (3) an additive B:

lithium tetrafluoroborate (LiBF)₄) Two, twoLithium fluorooxalate borate (liddob);

and (3) an additive C:

2, 4-Butanesulfonic acid lactone1, 3-propane sultoneVinyl sulfate ester

And (3) an additive D:

1,2, 3-tris (2-cyanoethoxy) propane1,3, 6-Hexanetricarbonitrile1, 2-bis (2-cyanoethoxy) ethaneAdiponitrile

And (3) an additive E:

lithium difluorophosphate (LiPO)₂F₂) Lithium tetrafluoro oxalate phosphate (litfo).

And (3) an additive F:

fluoroethylene carbonateVinylene carbonate

The lithium ion batteries of examples 1 to 63 and comparative examples 1 to 6 were each prepared as follows

(1) Preparation of the electrolyte

At water content<10ppIn an argon atmosphere glove box of m, Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), Ethyl Propionate (EP) and Propyl Propionate (PP) are uniformly mixed according to a mass ratio of 1:1:1:1:1, and then fully dried lithium salt LiPF is added₆(1M) is dissolved in the nonaqueous solvent to form a base electrolyte. Additives of a certain mass were added to the base electrolyte to prepare electrolytes of examples 1 to 63 and comparative examples 1 to 6.

(2) Preparation of positive plate

Mixing anode active material LCO (molecular formula is LiCoO)₂) The conductive carbon black and the adhesive polyvinylidene fluoride (PVDF for short) are fully stirred and mixed in a proper amount of N-methyl pyrrolidone (NMP for short) solvent according to the weight ratio of 97.9:0.9:1.2 to form uniform anode slurry; and coating the slurry on an Al foil of a positive current collector, drying and cold pressing to obtain the positive plate.

(3) Preparation of negative plate

Fully stirring and mixing a negative electrode active material graphite, a binder Styrene Butadiene Rubber (SBR) and a thickener sodium carboxymethyl cellulose (CMC) in a proper amount of deionized water solvent according to a weight ratio of 97.4:1.4:1.2 to form uniform negative electrode slurry; and coating the slurry on a Cu foil of a negative current collector, drying and cold pressing to obtain the negative plate.

(4) Preparation of the separator

A single layer PE porous polymer film was used as the separator.

(5) Preparation of lithium ion battery

Stacking the prepared positive plate, the prepared isolating membrane and the prepared negative plate in sequence to enable the isolating membrane to be positioned between the positive plate and the negative plate to play an isolating role, and then winding to obtain an electrode assembly; and (3) placing the electrode assembly in an outer packaging foil, leaving a liquid injection port, injecting the prepared electrolyte into the dried battery, and performing vacuum packaging, standing, formation, shaping and other processes to complete the preparation of the lithium ion battery.

The performance test procedure of the lithium ion battery is explained next.

4.45V high-temperature storage performance test

The cell was charged at 25 ℃ to 4.45V at a constant current of 0.5C, then charged at constant voltage to a current of 0.05C, and the thickness of the lithium ion cell was tested and recorded as d₀(ii) a The plate was placed in an oven at 85 ℃ for 24h, and the thickness at this time was monitored and recorded as d. Thickness expansion rate (%) after 24h of high-temperature storage of lithium ion battery (d-d)₀)/d₀X 100%, the thickness expansion rate exceeds 50%, and the test is stopped.

4.5V high-temperature storage performance test

Charging the battery at 25 deg.C with 0.5C constant current to 4.5V, then charging at constant voltage to current of 0.05C, testing the thickness of the lithium ion battery and recording as d₀(ii) a The plate was placed in an oven at 85 ℃ for 24h, and the thickness at this time was monitored and recorded as d. Thickness expansion rate (%) after 24h of high-temperature storage of lithium ion battery (d-d)₀)/d₀X 100%, the thickness expansion rate exceeds 50%, and the test is stopped.

Float performance test

The cell was discharged at 25 ℃ to 3.0V at 0.5C, charged to 4.45V at 0.5C, charged to 0.05C at constant voltage at 4.45V, and the thickness of the lithium ion cell was tested and recorded as d₀Placing the lithium ion battery in a 45 ℃ oven, charging at a constant voltage of 4.45V for 42 days, monitoring the thickness change, recording the thickness as d, and obtaining the thickness expansion rate (%) of the lithium ion battery float charge (d-d)₀)/d₀×100％。

The kinds and contents of additives used in the electrolytes of the lithium ion batteries of examples 1 to 63 and comparative examples 1 to 6, and the results of performance tests of the lithium ion batteries are shown in tables 1 to 2, in which the contents of the respective additives are mass percentages calculated based on the mass of the electrolyte.

TABLE 1

Note: the blank space in table 1 indicates that the compound was not added.

As can be seen from the performance test results of examples 1 to 45 and comparative examples 1 to 5 of Table 1, the addition of compounds I to 18 improves the high-temperature storage performance of lithium ion batteries to various degrees under electrochemical systems having different charge cut-off voltages. Within a certain concentration range, along with the increase of the content of the compound I-18, the improvement effect on the high-temperature storage performance is obvious, on one hand, the improvement effect is not obvious when the content of the compound I-18 is too large (exceeds the range), on the other hand, the electrolyte dynamics is influenced, other performances are possibly influenced, and on the other hand, the action effect is not obvious when the content of the compound I-18 is too small. The compounds I-4, I-6, I-7 and I-32 have certain improvement on high-temperature storage performance under different charge cut-off voltage systems.

When the additive C (a compound containing a sulfur-oxygen double bond functional group) and/or the additive B (a boron lithium salt compound) is added into the additive A, the high-temperature storage performance of the lithium ion battery under different charge cut-off voltages is further improved. The possible reason is that the compound containing the sulfur-oxygen double bond functional group can form a protective film on the surfaces of the anode and the cathode, so that the decomposition of the electrolyte is further inhibited, and the high-temperature performance of the battery is improved; the boron lithium salt such as lithium tetrafluoroborate and lithium difluorooxalate borate can form a fluorine-containing solid interface film on the surface of the negative electrode, reduce the reaction of FEC and the negative electrode, thereby inhibiting the generation of gas and improving the high-temperature performance of the battery.

TABLE 2

Note: the blank part in table 2 indicates that the compound was not added.

As can be seen from the results of the performance tests of examples 4, 7 to 8, 11 to 12, 46 to 63 and comparative example 6 of Table 2, the use of additive A in combination with additive C (a compound having a thiol double bond functional group) and/or additive D (a polynitrile compound) can significantly improve the float charge performance of a lithium ion battery. The reason is probably that the compound containing the sulfur-oxygen double bond functional group can form a protective film on the surfaces of the anode and the cathode to further inhibit the decomposition of the electrolyte, the additive D can interact with the surface of the anode to reduce the contact between the electrolyte and the surface of the anode and inhibit the decomposition of the electrolyte, and the combined use can strengthen the protection of an interface, so that the floating charge performance of the lithium ion battery can be obviously improved. In addition, the combined use of the additive A and the additive D can effectively reduce the influence of the additive A on the dynamics of the battery and play a role in balancing the performance.

The lithium ion batteries of examples 64 to 83 and comparative examples 7 to 9 were each prepared as follows

(1) Preparation of the electrolyte

At water content<In a 10ppm argon atmosphere glove box, Ethylene Carbonate (EC), Propylene Carbonate (PC) and diethyl carbonate (DEC) are uniformly mixed according to a mass ratio of 3:3:4, and then fully dried lithium salt LiPF is added₆(1M) is dissolved in the nonaqueous solvent to form a base electrolyte. The electrolytes of examples 64 to 83 and comparative examples 7 to 9 were prepared by adding additives to the base electrolyte in a predetermined amount.

(2) Preparation of positive plate

A positive electrode active material NCM811 (molecular formula LiNi)_0.8Mn_0.1Co_0.1O₂) Fully stirring and mixing acetylene black serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder in a proper amount of N-methylpyrrolidone (NMP) solvent according to a weight ratio of 96:2:2 to form uniform positive electrode slurry; and coating the slurry on an Al foil of a positive current collector, drying and cold pressing to obtain the positive plate.

(3) Preparation of negative plate

The negative electrode sheet was prepared in the same manner as in examples 1 to 63.

(4) Preparation of the separator

Preparation of the separator was prepared as in examples 1-63.

(5) Preparation of lithium ion battery

Preparation of lithium ion batteries the preparation of lithium ion batteries of examples 1-63 was performed.

The performance test procedure of the lithium ion battery is explained next.

85 ℃ high temperature storage Performance test

The cell was charged at 25 ℃ to 4.25V at a constant current of 0.5C, then charged at constant voltage to a current of 0.05C, and the thickness of the lithium ion cell was tested and recorded as d₀(ii) a The plate was placed in an oven at 85 ℃ for 24h, and the thickness at this time was monitored and recorded as d. Thickness expansion rate (%) after 24h of high-temperature storage of lithium ion battery (d-d)₀)/d₀X 100%, the thickness expansion rate exceeds 50%, and the test is stopped.

The kinds and contents of the additives used in the electrolytes of the lithium ion batteries of examples 64 to 83 and comparative examples 7 to 9, and the results of the performance test of the lithium ion batteries are shown in table 3, wherein the contents of the respective additives are mass percentages calculated based on the mass of the electrolyte.

TABLE 3

Note: the blank part in table 3 indicates that the compound was not added.

As can be seen by comparing examples 64 to 83 with comparative examples 7 to 9, the high-temperature storage properties can be further improved by adding both additives (C and E). This is probably because the compound having a functional group containing a sulfur-oxygen double bond can form a protective film on the surfaces of the positive and negative electrodes to inhibit decomposition of the electrolyte, lithium difluorophosphate (LiPO)₂F₂) And lithium tetrafluoro oxalate phosphate (LiTFOP) as a positive electrode film-forming additive, which can inhibit oxidative decomposition of the electrolyte and can enhance interfacial protection when used in combinationFurther inhibit the decomposition of the electrolyte and reduce the gas generation, thereby improving the high-temperature storage performance.

Although the present application has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.