阅读说明：本技术 非水电解液二次电池及其制造方法 (Nonaqueous electrolyte secondary battery and method for manufacturing same ) 是由 武弘义 加治佐由姬 阿部正男 植谷庆裕 于 2013-12-10 设计创作，主要内容包括：本发明涉及非水电解液二次电池及其制造方法。一种非水电解液二次电池,其具备正极、负极、配置在上述正极与上述负极之间的隔离体、以及包含具有离子传导性的支持电解质的电解液,上述正极包含导电性聚合物,上述负极包含能够嵌入·脱嵌离子的碳质材料,上述电解液包含负极覆膜形成剂。因此,在正极使用导电性聚合物、负极使用碳质材料的非水电解液二次电池中,能够使重量能量密度变得优异,并且能够有效地抑制电池性能的劣化。(The present invention relates to a nonaqueous electrolyte secondary battery and a method for manufacturing the same. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and an electrolyte solution containing a supporting electrolyte having ion conductivity, wherein the positive electrode contains a conductive polymer, the negative electrode contains a carbonaceous material capable of intercalating and deintercalating ions, and the electrolyte solution contains a negative electrode coating forming agent. Therefore, in a nonaqueous electrolyte secondary battery using a conductive polymer for the positive electrode and a carbonaceous material for the negative electrode, the weight energy density can be made excellent, and the deterioration of the battery performance can be effectively suppressed.)

1. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and an electrolyte solution containing a supporting electrolyte having lithium ion conductivity,

the positive electrode comprises a composite having a layer containing a positive electrode active material, the layer containing the positive electrode active material being composed of a polymer and an optionally contained conductive auxiliary agent, the polymer comprising a conductive polymer and a metal polycarboxylate (a), the conductive polymer comprising at least one selected from the group consisting of polyaniline, a polyaniline derivative, polypyrrole, and a polypyrrole derivative, the metal polycarboxylate (a) being at least one of an alkali metal polycarboxylate and an alkaline earth polycarboxylate, the metal polycarboxylate (a) comprising 1 to 70 parts by weight of the metal polycarboxylate (a) per 100 parts by weight of the conductive polymer,

the negative electrode contains a carbonaceous material capable of intercalating and deintercalating lithium ions,

the electrolyte contains a negative electrode coating forming agent, the negative electrode coating forming agent in the electrolyte is vinylene carbonate represented by the following formula (1), the content ratio of the negative electrode coating forming agent in the electrolyte is in the range of 0.5-10 parts by weight relative to 100 parts by weight of the electrolyte,

2. a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and an electrolyte solution containing a supporting electrolyte having lithium ion conductivity,

the positive electrode comprises a composite having a layer containing a positive electrode active material, the layer containing the positive electrode active material being composed of a polymer and an optionally contained conductive auxiliary agent, the polymer comprising a conductive polymer and a metal polycarboxylate (a), the conductive polymer comprising at least one selected from the group consisting of polyaniline, a polyaniline derivative, polypyrrole, and a polypyrrole derivative, the metal polycarboxylate (a) being at least one of an alkali metal polycarboxylate and an alkaline earth polycarboxylate, the metal polycarboxylate (a) comprising 1 to 70 parts by weight of the metal polycarboxylate (a) per 100 parts by weight of the conductive polymer,

the negative electrode contains a carbonaceous material capable of intercalating and deintercalating lithium ions,

the electrolyte contains a negative electrode coating forming agent, the negative electrode coating forming agent in the electrolyte is fluoroethylene carbonate represented by the following formula (2),

3. the nonaqueous electrolyte secondary battery according to claim 2, wherein a content ratio of the negative electrode coating film forming agent in the electrolyte solution is in a range of 0.1 to 30 parts by weight with respect to 100 parts by weight of the electrolyte solution.

4. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the electrolyte contains lithium hexafluorophosphate as a supporting electrolyte.

5. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the polycarboxylic acid of (a) is at least one selected from the group consisting of polyacrylic acid, polymethacrylic acid, polyvinylbenzoic acid, polyallylbenzoic acid, polymetlylberylbenzoic acid, polymaleic acid, polyfumaric acid, polyaspartic acid, and polyglutamic acid.

6. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the polycarboxylic acid metal salt (a) is a semi-lithium salt of polyacrylic acid.

7. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the positive electrode active material-containing layer contains 5 to 40 parts by weight of the metal polycarboxylate (a) with respect to 100 parts by weight of the conductive polymer.

8. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the polymer constituting the layer containing a positive electrode active material further optionally contains at least one selected from the group consisting of a styrene-butadiene copolymer and polyvinylpyrrolidone.

9. The method for producing a nonaqueous electrolyte secondary battery according to any one of claims 1 to 8, characterized by comprising the following steps (I) to (III):

(I) preparing a positive electrode and a negative electrode, and disposing a separator therebetween to produce a laminate including the positive electrode, the separator, and the negative electrode;

(II) a step of accommodating at least one of the laminates in a battery container;

(III) injecting an electrolyte into the battery container.

Technical Field

The present invention relates to a nonaqueous electrolyte secondary battery and a method for producing the same, and more particularly to a nonaqueous electrolyte secondary battery which has excellent weight energy density and effectively suppresses deterioration of battery performance, and a method for producing the same.

Background

In recent years, with the progress and development of electronic technology in portable PCs, portable telephones, portable information terminals (PDAs), and the like, secondary batteries capable of being repeatedly charged and discharged have been widely used as power storage devices for these electronic devices.

Among such lithium secondary batteries, a secondary battery using a lithium-containing transition metal oxide such as lithium manganate or lithium cobaltate as an electrode active material for a positive electrode and a carbonaceous material capable of intercalating and deintercalating lithium ions for a negative electrode is widely used as a so-called rocking chair type lithium ion secondary battery in which the lithium ion concentration in an electrolyte does not substantially change during charge and discharge. This rocking chair type secondary battery can be reduced in the amount of electrolyte solution and can be made smaller than a so-called reserve type secondary battery, and is also widely used as a power storage device for the above-mentioned electronic devices because it is small in size and has a high energy density.

However, the lithium secondary battery is a secondary battery that obtains electric energy through an electrochemical reaction, and has a disadvantage of low output density due to a slow rate of the electrochemical reaction. Further, since the internal resistance of the secondary battery is high, it is difficult to rapidly discharge and also difficult to rapidly charge the secondary battery. In addition, since the electrochemical reaction accompanying charge and discharge deteriorates the electrode and the electrolyte, the life, i.e., the cycle characteristics are generally not good.

Here, in order to improve the above-described problems, a nonaqueous electrolyte secondary battery using a conductive polymer such as polyaniline having a dopant for a positive electrode active material is also known (patent document 1). However, in general, a secondary battery having a conductive polymer as a positive electrode active material is an anion-mobile type in which anions are doped into a polymer of a positive electrode during charging and are dedoped from the polymer of the positive electrode during discharging, and therefore cannot be configured as a rocking chair type secondary battery as described above. Therefore, a nonaqueous electrolyte secondary battery using a conductive polymer for a positive electrode active material basically requires a large amount of an electrolyte solution, and as a result, there is a problem that it cannot contribute to downsizing of the battery.

In order to solve such a problem, a secondary battery has been proposed in which a positive electrode is made of a conductive polymer having a polymer anion such as polyvinylsulfonic acid as a dopant, and the ion concentration in an electrolyte is substantially not changed by making the conductive polymer cation-mobile (see patent document 2).

Disclosure of Invention

Problems to be solved by the invention

However, the secondary battery of patent document 2 uses a metal such as lithium for the negative electrode. In general, among lithium ion secondary batteries, it is considered preferable to use a carbonaceous material capable of intercalating and deintercalating lithium ions for the negative electrode from the viewpoint of safety and cycle characteristics, and this is also the case with a nonaqueous electrolyte secondary battery in which a conductive polymer is used for the positive electrode, and therefore this point is also considered to be a problem in the secondary battery of patent document 2.

Therefore, the present inventors have made various studies and experiments in advance on a nonaqueous electrolyte secondary battery using a conductive polymer for a positive electrode and a carbonaceous material for a negative electrode, and in this process, have made efforts to improve the deterioration of battery performance, which is a problem in the nonaqueous electrolyte secondary battery having the above-described structure.

The present invention has been made in view of such circumstances, and provides a nonaqueous electrolyte secondary battery which uses a conductive polymer for a positive electrode and a carbonaceous material for a negative electrode, has an excellent weight energy density, and can effectively suppress deterioration of battery performance, and a method for manufacturing the same.

Means for solving the problems

In order to achieve the above object, a first aspect of the present invention is a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and an electrolyte solution containing a supporting electrolyte having ion conductivity; the positive electrode contains a conductive polymer, the negative electrode contains a carbonaceous material capable of intercalating and deintercalating ions, and the electrolyte contains a negative electrode coating forming agent.

A second aspect of the present invention is a method for producing a nonaqueous electrolyte secondary battery according to the first aspect, including the steps (I) to (III) below:

(I) preparing a positive electrode and a negative electrode, and providing a separator therebetween to produce a laminate including the positive electrode, the separator, and the negative electrode;

(II) a step of accommodating at least one of the above-described laminated bodies in a battery container;

(III) injecting an electrolyte into the battery container.

That is, since a polymer positive electrode including a conductive polymer has characteristics such as excellent output density and exhibits a property of trapping an acid in an electrolyte solution depending on the kind of the conductive polymer, a negative electrode including a carbonaceous material is corroded by a side reaction thereof when left to stand for a long time, and as a result, battery performance is deteriorated. The present inventors, having obtained such findings through various experiments, have conducted extensive studies on the nonaqueous electrolyte secondary battery having the above-described configuration in order to solve the deterioration of the battery performance, and as a result, have found that, if a negative electrode film forming agent is contained in the electrolyte, a stable film is formed on the negative electrode side by the action of the negative electrode film forming agent during initial charge and discharge, and therefore, the film can effectively suppress the side reaction caused on the negative electrode side, suppress self-discharge in a discharge state, and prevent the deterioration of the battery performance.

ADVANTAGEOUS EFFECTS OF INVENTION

As described above, the nonaqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution containing a supporting electrolyte having ion conductivity; the positive electrode contains a conductive polymer, the negative electrode contains a carbonaceous material capable of intercalating and deintercalating ions, and the electrolyte contains a negative electrode coating forming agent. Therefore, the weight energy density is excellent, and the deterioration of the battery performance can be effectively suppressed.

In particular, when the electrolyte solution contains lithium hexafluorophosphate as a supporting electrolyte, a film different from the film obtained by the negative electrode film forming agent is further formed on the surface of the negative electrode, and therefore, deterioration of the battery performance can be further suppressed.

In addition, when the positive electrode further contains nitrogen, since acid and the like generated in the electrolyte are adsorbed, deterioration of battery performance can be further suppressed.

In addition, when the negative electrode coating forming agent in the electrolyte is at least one of vinylene carbonate represented by formula (1) and fluoroethylene carbonate represented by formula (2), deterioration of battery performance can be further suppressed.

In addition, when the conductive polymer constituting the positive electrode is at least one selected from the group consisting of polyaniline, a polyaniline derivative, polypyrrole, and a polypyrrole derivative, battery performance such as weight energy density can be further improved.

When the positive electrode further contains the component (a), further improvement in battery performance such as weight energy density can be obtained.

(a) At least one of polycarboxylic acids and polycarboxylic acid metal salts.

In addition, when the polycarboxylic acid of the above (a) is at least one selected from the group consisting of polyacrylic acid, polymethacrylic acid, polyvinylbenzoic acid, polyallylbenzoic acid, polymethacrylbenzoic acid, polymaleic acid, polyfumaric acid, polyaspartic acid, and polyglutamic acid, a further increase in the weight energy density can be obtained.

Further, when the metal polycarboxylate of the above (a) is at least one of an alkali metal polycarboxylate and an alkaline earth polycarboxylate, the effective weight energy density can be improved.

In addition, in the case of the method for producing a nonaqueous electrolyte secondary battery including the steps (I) to (III) described below, a nonaqueous electrolyte secondary battery having excellent weight energy density and less deterioration in battery performance can be obtained.

(I) Preparing a positive electrode and a negative electrode, and disposing a separator therebetween to produce a laminate including the positive electrode, the separator, and the negative electrode;

(II) a step of accommodating at least one of the laminates in a battery container;

(III) injecting an electrolyte into the battery container.

Drawings

Fig. 1 is a graph showing self-discharge characteristics when the vertical axis is a voltage (V) and the horizontal axis is a time (hrs.) in each of the nonaqueous electrolyte secondary batteries of example 1 and comparative example 1.

Fig. 2 is a graph showing self-discharge characteristics when the vertical axis is a voltage (V) and the horizontal axis is a time (hrs.) in each of the nonaqueous electrolyte secondary batteries of example 2 and comparative example 2.

Fig. 3 is a graph showing self-discharge characteristics of the nonaqueous electrolyte secondary batteries of examples 3 to 7 and comparative example 3, where the vertical axis represents voltage (V) and the horizontal axis represents time (hrs).

Fig. 4 is a graph showing self-discharge characteristics of the nonaqueous electrolyte secondary batteries of examples 8 to 10 and comparative example 3, where the vertical axis represents voltage (V) and the horizontal axis represents time (hrs).

Fig. 5 is a graph showing self-discharge characteristics of the nonaqueous electrolyte secondary batteries of examples 11 to 15 and comparative example 4, where the vertical axis represents voltage (V) and the horizontal axis represents time (hrs).

Fig. 6 is a graph showing self-discharge characteristics when the vertical axis is voltage (V) and the horizontal axis is time (hrs) in each of the nonaqueous electrolyte secondary batteries of example 16 and comparative example 5.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail, and the description below is an example of the embodiments of the present invention, and the present invention is not limited to the following.

The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and an electrolyte solution containing a supporting electrolyte having ion conductivity, wherein the positive electrode contains a conductive polymer, the negative electrode contains a carbonaceous material capable of intercalating and deintercalating ions, and the electrolyte solution contains a negative electrode coating forming agent. Here, the "negative electrode coating forming agent" in the present invention refers to a substance that acts to form a coating on the surface of the negative electrode during initial charging. Among them, in general, it is preferable to use a substance that reacts earlier than the electrolyte solvent used at the time of initial charging and that has excellent properties of the formed film.

The following description will be made in order of the above-described members and materials used.

< Positive electrode >

[ conductive Polymer ]

As described above, the positive electrode of the nonaqueous electrolyte secondary battery of the present invention contains a conductive polymer. The conductive polymer in the present invention refers to a group of polymers in which the conductivity of the polymer itself is changed by inserting or extracting ion species into or from the polymer in order to compensate for the change in charge generated or lost by the oxidation reaction or reduction reaction of the polymer main chain.

In such a polymer, a state with high conductivity is referred to as a doped state, and a state with low conductivity is referred to as a dedoped state. Even if a polymer having conductivity loses conductivity due to an oxidation reaction or a reduction reaction and becomes insulating (i.e., in a dedoped state), such a polymer can reversibly have conductivity again due to the oxidation-reduction reaction, and therefore such an insulating polymer in a dedoped state also falls within the category of a conductive polymer in the present invention.

In addition, one of the preferable conductive polymers of the present invention is a polymer having, as a dopant, a protonic acid anion of at least one of the group consisting of an inorganic acid anion, an aliphatic sulfonate anion, an aromatic sulfonate anion, a polymeric sulfonate anion, and a polyvinyl sulfate anion. In addition, as another conductive polymer preferred in the present invention, a dedoped polymer in which the conductive polymer is dedoped is used.

Specific examples of the conductive polymer include: polyacetylene, polypyrrole, polyaniline, polythiophene, polyfuran, polyselenophene, polyisothianaphthene, polyphenylene sulfide, polyphenylene oxide, polyazulene, poly (3, 4-ethylenedioxythiophene), various derivatives thereof, and the like. Among them, polyaniline, a polyaniline derivative, polypyrrole, and a polypyrrole derivative having a large electrochemical capacity are preferably used, and polyaniline and a polyaniline derivative are more preferably used.

In the present invention, the polyaniline refers to a polymer obtained by subjecting aniline to electrolytic polymerization or chemical oxidative polymerization, and the derivative of polyaniline refers to a polymer obtained by subjecting a derivative of aniline to electrolytic polymerization or chemical oxidative polymerization, for example.

Here, as the derivative of aniline, more specifically, there can be exemplified one having at least one substituent such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylaryl group, an arylalkyl group, an alkoxyalkyl group, or the like at a position other than the 4-position of aniline. Preferred specific examples include: ortho-substituted anilines such as o-methylaniline, o-ethylaniline, o-phenylaniline, o-methoxyaniline, and o-ethoxyaniline, and meta-substituted anilines such as m-methylaniline, m-ethylaniline, m-methoxyaniline, m-ethoxyaniline, and m-phenylaniline. These may be used alone or in combination of two or more. In the present invention, p-phenylaminoaniline has a substituent at the 4-position, but polyaniline can be obtained by oxidative polymerization, and therefore, it can be suitably used as an aniline derivative.

Hereinafter, in the present invention, "aniline or a derivative thereof" may be simply referred to as "aniline", and "at least one of polyaniline and a polyaniline derivative" may be simply referred to as "polyaniline". Therefore, even in the case where the polymer constituting the conductive polymer is obtained from an aniline derivative, it is sometimes referred to as "conductive polyaniline".

In the positive electrode of the nonaqueous electrolyte secondary battery of the present invention, it is preferable that the positive electrode contains nitrogen in addition to the conductive polymer. Here, "containing nitrogen" not only means a case where the conductive polymer has an N atom in its molecular structure, but also includes a case where a substance serving as a nitrogen source is separately added to a material. As described above, by containing nitrogen in the positive electrode material, the positive electrode material more effectively adsorbs an acid or the like generated in the electrolytic solution. On the other hand, the positive electrode also preferably further contains at least one (a) of a polycarboxylic acid and a polycarboxylic acid metal salt.

[ regarding at least one (a) of polycarboxylic acid and polycarboxylic acid metal salt ]

In the present invention, the polycarboxylic acid is a polymer having a carboxyl group in the molecule. As the polycarboxylic acid, for example, polyacrylic acid, polymethacrylic acid, polyvinylbenzoic acid, polyallylbenzoic acid, polymethacrylbenzoic acid, polymaleic acid, polyfumaric acid, polyaspartic acid, and polyglutamic acid can be preferably used, and polyacrylic acid and polymethacrylic acid are more preferably used. These may be used alone or in combination of two or more.

The metal salt of polycarboxylic acid is, for example, an alkali metal salt or an alkaline earth metal salt, and these may be used alone or in combination of two or more. The alkali metal salt is preferably a lithium salt or a sodium salt, and the alkaline earth metal salt is preferably a magnesium salt or a calcium salt.

[ outer shape of Positive electrode ]

The positive electrode of the nonaqueous electrolyte secondary battery of the present invention is formed of a composite containing at least the conductive polymer and the component (a), and is preferably formed into a porous sheet. The thickness of the positive electrode is preferably 1 to 500 μm, and more preferably 10 to 300 μm.

The thickness of the positive electrode can be obtained by the following method: the positive electrode was measured using a direct reading thickness meter (manufactured by kawasaki corporation) having a flat plate with a tip shape of 5mm in diameter, and the average of 10 points of the measured values was obtained with respect to the electrode surface. When the positive electrode (porous layer) is provided on the current collector and the composite is formed, the thickness of the composite is measured in the same manner as described above, the average value of the measured values is obtained, and the thickness of the current collector is subtracted to calculate the thickness of the positive electrode.

[ production of Positive electrode ]

The positive electrode of the nonaqueous electrolyte secondary battery of the present invention is produced, for example, as follows. For example, the component (a) is dissolved or dispersed in water, and a conductive additive such as conductive polymer powder and, if necessary, conductive carbon black is added thereto and sufficiently dispersed to prepare a paste having a solution viscosity of about 0.1 to 50Pa · s. By applying this to a current collector and then evaporating water, a sheet electrode can be obtained as a composite (porous sheet) having a layer containing a positive electrode active material on the current collector, the layer containing the conductive polymer, the component (a), and, if necessary, a conductive auxiliary agent.

The conductive aid is preferably a conductive material which has excellent conductivity, is effective for reducing the resistance between active materials of a battery, and does not change in properties depending on the potential applied during discharge of the battery. Generally, conductive carbon black, for example, acetylene black, ketjen black, or the like, carbon fiber, carbon nanotube, or the like fibrous carbon material can be used.

In the material for forming the positive electrode of the nonaqueous electrolyte secondary battery of the present invention, the component (a) is used in an amount of usually 1 to 100 parts by weight, preferably 2 to 70 parts by weight, and most preferably 5 to 40 parts by weight, based on 100 parts by weight of the conductive polymer. That is, when the amount of the component (a) is too small relative to the conductive polymer, a nonaqueous electrolyte secondary battery having excellent energy density tends not to be obtained, whereas when the amount of the component (a) is too large, the weight of the positive electrode increases due to the increase in the weight of the member other than the positive electrode active material, and therefore, considering the weight of the entire battery, a nonaqueous electrolyte secondary battery having high energy density tends not to be obtained.

< negative electrode >

The negative electrode of the nonaqueous electrolyte secondary battery of the present invention is formed of a material containing a carbonaceous material capable of intercalating and deintercalating ions, and a known carbonaceous material used as a negative electrode active material of a lithium ion secondary battery can be used. Specifically, sintered products of coke, pitch, phenol resin, polyimide, cellulose and the like, artificial graphite, natural graphite and the like are mentioned, and among them, artificial graphite and natural graphite are preferably mentioned. These may be used alone or in combination of two or more.

In addition, the carbonaceous material is preferably used as a main component of the negative electrode material. Here, the main component means a component showing the majority of the whole, and includes a case where the whole is composed of only the main component.

< Current collector >

Examples of the material of the current collector include metal foils and meshes of nickel, aluminum, stainless steel, copper, and the like. The positive electrode current collector and the negative electrode current collector may be made of the same material or different materials.

< electrolyte solution >

The electrolyte solution contains a substance containing an electrolyte (supporting electrolyte) and a solvent. In the present invention, the electrolyte solution contains a negative electrode coating forming agent.

The negative electrode coating forming agent is a substance that acts to form a coating on the surface of the negative electrode during initial charging as described above, and among them, it is preferable to use a substance that reacts earlier than a commonly used electrolyte solvent during initial charging to form a coating having excellent properties. Specific examples thereof include: vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone, propylene sulfite, ethylene sulfite, vinyl acetate, vinyl ethylene carbonate, dimethyl sulfate, phenyl ethylene carbonate, phenyl vinylene carbonate, fluoro-gamma-butyrolactone, and the like. These may be used alone or in combination of two or more. Among these, vinylene carbonate and fluoroethylene carbonate are preferable because they have higher film formability for the negative electrode, and thus can further suppress deterioration of battery performance.

The content of the negative electrode coating forming agent in the electrolyte solution is preferably in the range of 0.1 to 30 parts by weight, and more preferably in the range of 0.1 to 20 parts by weight, based on 100 parts by weight of the electrolyte solution. That is, if the content ratio of the negative electrode film forming agent is less than the above range, the film tends to be not formed efficiently, whereas if it exceeds the above range, the film is present in an excess amount more than the amount necessary for forming the film of the negative electrode in the battery, and a side reaction is caused on the electrode, which may cause a decrease in capacity and gas generation.

As the electrolyte constituting the electrolyte solution, for example, a combination of a metal ion such as a lithium ion and a counter ion suitable therefor, for example, a sulfonate ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a hexafluoroarsenate ion, a bis (trifluoromethanesulfonyl) imide ion, a bis (pentafluoroethanesulfonyl) imide ion, a halogen ion, or the like is preferably used. Therefore, as a specific example of such an electrolyte, LiCF can be mentioned₃SO₃、LiClO₄、LiBF₄、LiPF₆、LiAsF₆、LiN(SO₂CF₃)₂、LiN(SO₂C₂F₅)₂And LiCl, and the like, and they may be used alone or in combination of two or more. In particular, the electrolyte contains lithium hexafluorophosphate (LiPF)₆) The supporting electrolyte is preferable because deterioration of battery performance can be further suppressed.

Here, it is known that lithium hexafluorophosphate is decomposed in an electrolytic solution to generate an acid such as hydrofluoric acid. The present inventors confirmed that the hydrofluoric acid present in a small amount in the electrolytic solution forms a coating different from that formed by the negative electrode coating forming agent, and therefore it is considered that the electrochemical stability and efficiency of the carbonaceous material as the negative electrode are further improved by including lithium hexafluorophosphate in the electrolytic solution.

As the solvent constituting the electrolytic solution, for example, a nonaqueous solvent, i.e., an organic solvent, of at least one of carbonates, nitriles, amides, ethers, and the like is used. Specific examples of such organic solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, acetonitrile, propionitrile, N' -dimethylacetamide, N-methyl-2-pyrrolidone, dimethoxyethane, diethoxyethane, and γ -butyrolactone. These may be used alone or in combination of two or more.

As the content of the electrolyte in the electrolytic solution, a usual amount as the electrolyte content of the nonaqueous electrolyte secondary battery can be used. That is, the electrolyte content in the electrolyte solution is generally in the range of 0.1 to 2.5mol/L, preferably 0.5 to 1.5 mol/L. When the amount of the electrolyte is too small, a nonaqueous electrolyte secondary battery having excellent gravimetric energy density tends not to be obtained, while when the amount of the electrolyte is too large, intercalation and deintercalation of ions do not function well, and thus a nonaqueous electrolyte secondary battery having excellent gravimetric energy density tends not to be obtained.

When the separator is used in the nonaqueous electrolyte secondary battery of the present invention, the separator may be any insulating porous sheet that can prevent an electrical short circuit between the positive electrode and the negative electrode disposed to face each other with the separator interposed therebetween, and that is electrochemically stable, has a large ion permeability, and has a certain degree of mechanical strength. Therefore, for example, paper, nonwoven fabric, and a porous film made of a resin such as polypropylene, polyethylene, and polyimide are preferably used, and these may be used alone or in combination of two or more.

< method for producing nonaqueous electrolyte Secondary Battery >

The method for producing a nonaqueous electrolyte secondary battery of the present invention using the above material is characterized by comprising the following steps (I) to (III). The following describes the production method in detail.

(I) And preparing a positive electrode and a negative electrode, and disposing a separator between the positive electrode and the negative electrode to produce a laminate including the positive electrode, the separator, and the negative electrode.

(II) a step of accommodating at least one of the above-described laminated bodies in a battery container.

(III) injecting an electrolyte into the battery container.

Specifically, the separators are stacked so as to be disposed between the positive electrode and the negative electrode, thereby producing a laminate. Next, the laminate is placed in a battery container such as an aluminum laminate package, and then vacuum-dried. Next, an electrolyte solution is injected into the battery container after vacuum drying. Finally, the package as a battery container is sealed, thereby completing the nonaqueous electrolyte secondary battery of the present invention.

< nonaqueous electrolyte Secondary Battery >

The nonaqueous electrolyte secondary battery of the present invention may be formed in various shapes such as a film type, a sheet type, a square type, a cylinder type, a button type, and the like, in addition to the above-described laminate battery.