JP6760445B2 - Non-aqueous electrolyte solution and non-aqueous electrolyte secondary battery using it - Google Patents

Description

The present invention relates to a non-aqueous electrolyte solution and a non-aqueous electrolyte solution secondary battery using the same.

With the rapid progress of electronic devices, the demand for higher capacity for secondary batteries is increasing, and non-aqueous electrolyte batteries such as lithium-ion secondary batteries with high energy density are widely used and actively researched. Has been done.
The electrolyte used in a non-aqueous electrolyte battery is generally mainly composed of an electrolyte and a non-aqueous solvent. As the electrolytic solution of the lithium ion secondary battery, a non-aqueous electrolytic solution obtained by dissolving an electrolyte such as LiPF _{6 in} a mixed solvent of a high dielectric constant solvent such as cyclic carbonate and a low viscosity solvent such as chain carbonate is used. Has been done.

When a lithium ion secondary battery is repeatedly charged and discharged, the electrolyte decomposes on the electrodes and the materials constituting the battery deteriorate, resulting in a decrease in the capacity of the battery. In some cases, the safety against swelling, ignition, explosion, etc. of the battery may be reduced.
So far, a method of improving the battery characteristics of a lithium ion secondary battery by using a specific non-aqueous electrolytic solution has been proposed. For example, in Patent Document 1, the reaction between the lithium metal and the electrolytic solution is suppressed by using an electrolytic solution containing maleimide or a derivative thereof, and the self-discharge rate when the lithium battery is stored at 60 ° C. for 2 months. Has been reported to improve. Patent Document 2 reports that the charge / discharge efficiency of a silicon negative electrode is improved by using an electrolytic solution containing a compound such as maleimide and vinylene carbonate. Patent Document 3 reports that the charge / discharge efficiency of a battery is improved by using a maleimide compound and an electrolytic solution containing 0.05% by weight to 5% by weight of a chemical species containing a hydroxyl group having a molecular weight of less than 1000. Has been done.

Japanese Unexamined Patent Publication No. 11-219723 Japanese Patent Application Laid-Open No. 2009-302058 Japanese Unexamined Patent Publication No. 2012-174680

In the non-aqueous electrolyte secondary battery, the present invention suppresses a decrease in the battery voltage when the battery is used in a high temperature environment, improves the recovery capacity rate, and improves the remaining / recovery capacity rate during continuous charging. An object of the present invention is to provide a non-aqueous electrolyte solution capable of producing an excellent battery and a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte solution.

The inventions described in Patent Documents 1 to 3 certainly contribute to the improvement of the characteristics of a part of the battery, but the effect is not satisfactory, and further improvement is required.
As a result of repeating various studies in order to solve the above-mentioned problems, the present inventor has found that the above-mentioned problems can be solved, and has completed the present invention.

That is, the gist of the present invention is
[1]
A non-aqueous electrolyte solution having a positive electrode having a positive electrode active material capable of occluding / releasing metal ions and a negative electrode having a negative electrode active material capable of occluding / releasing metal ions A non-aqueous electrolyte solution used in a secondary battery. ,
The non-aqueous electrolyte solution contains a bismaleimide compound and contains
At least one compound selected from carbonate having a halogen atom, a nitrile compound, a compound having an S = O bond, a compound having an isocyanato group, a compound represented by the formula (X), a difluorophosphate, and a dicarboxylic acid ester. A non-aqueous electrolyte solution characterized by containing.

(R ⁴³ , R ⁴⁴ , and R ⁴⁵ represent organic groups that may independently have a halogen atom, a cyano group, an ester group, and an ether group, respectively.)
[2]
The non-aqueous electrolyte solution according to [1], wherein the bismaleimide compound is a compound represented by any of the following formulas (1) to (6).

(In the formula, R ^{1 to} R ⁴ independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)

(In the formula, R ^{5 to} R ⁸ independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)

(In the formula, R ^{9 to} R ¹² independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)

(In the formula, R ^{13 to} R ²² independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)

(In the formula, R ^{23 to} R ⁴⁰ independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)

(R ⁴¹ and R ⁴² independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group, and n represents an integer of 1 or more.)
[3]
The content of the bismaleimide compound having the structure represented by any of the formulas (1) to (6) is 0.01% by mass or more and 5% by mass or less in the non-aqueous electrolytic solution []. The non-aqueous electrolyte solution according to 1] or [2].
[4]
The non-aqueous electrolyte solution according to any one of [1] to [3], wherein the water content in the non-aqueous electrolyte solution is 40 ppm or less.
[5]
The non-aqueous electrolyte solution according to any one of [1] to [4], wherein the carbonate having a halogen atom is at least one of fluoroethylene carbonate and difluoroethylene carbonate.
[6]
The nitrile compound is at least one of succinonitrile, glutaronitrile, adiponitrile, pimeronitrile, sevaconitrile, valeronitrile, octanenitrile, decanenitrile, lauronitrile, and crotononitrile [1] to [1] to [ The non-aqueous electrolyte solution according to any one of 5].
[7]
The compound having an S = O bond is characterized by being at least one of propane sultone, propensultone, ethylene sulfate, lithium fluorosulfonate, lithium bis (trifluoromethylsulfonyl) amide, and lithium bis (fluorosulfonyl) amide. The non-aqueous electrolyte solution according to any one of [1] to [6].
[8]
The non-item according to any one of [1] to [7], wherein the compound having an isocyanato group is at least one of hexamethylene diisocyanate and 1,3-bis (isocyanatomethyl) cyclohexane. Aqueous electrolyte.
[9]
The non-aqueous electrolyte solution according to any one of [1] to [8], wherein the compound represented by the formula (X) is at least one of the following compounds.

[10]
The non-aqueous electrolysis according to any one of [1] to [9], wherein the difluorophosphate is at least one of lithium difluorophosphate, sodium difluorophosphate, and potassium difluorophosphate. liquid.
[11]
The dicarboxylic acid ester is at least one of malonic acid ester, methyl malonic acid ester, ethyl malonic acid ester, propyl malonic acid ester, butyl malonic acid ester, succinic acid ester, adipic acid ester, fumaric acid ester, and maleic acid ester. The non-aqueous electrolyte solution according to any one of [1] to [10], which is characterized by being present.
[12]
A non-aqueous electrolyte secondary battery including a positive electrode having a positive electrode active material capable of storing and releasing metal ions, a negative electrode having a negative electrode active material capable of storing and releasing metal ions, and a non-aqueous electrolyte solution. A non-aqueous electrolyte secondary battery according to any one of [1] to [11], wherein the non-aqueous electrolyte solution is used.

According to the present invention, an excellent non-aqueous electrolyte solution that suppresses a decrease in battery voltage when a battery is used in a high temperature environment, improves the recovery capacity rate, and improves the residual / recovery capacity rate during continuous charging. The next battery can be obtained.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the description described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents as long as the gist described in the claims is not exceeded.
[1. Non-aqueous electrolyte solution]
The non-aqueous electrolyte solution of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the electrolyte, like a general non-aqueous electrolyte solution.
Its main feature is that it contains both a bismaleimide compound and a specific compound.

[1-1. Bismaleimide compound]
The bismaleimide compound described in the claims is not particularly limited, and examples thereof include the following.
1-1-1. Compound of formula (1)

(In the formula, R ^{1 to} R ⁴ independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom is most preferable because it has a large effect of improving battery characteristics.

Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and an aryl group. Among these, an alkyl group is most preferable because of its moderate reactivity and low resistance.
The carbon number of each of the hydrocarbon group and the alkoxy group is not particularly limited as long as the effect of the present invention is not impaired, but is usually 1 or more, preferably 2 or more, and usually 10 or less, preferably 5 or less, and further. It is preferably 3 or less. This is because if the number of carbon atoms is too large, intramolecular steric hindrance becomes large and the reaction on the electrode surface is unlikely to occur.

Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a t-amyl group and the like. Examples of the alkenyl group include a vinyl group, an allyl group, a 1-propenyl group, a 1-butenyl group and the like. Examples of the alkynyl group include an ethynyl group and a propynyl group. Examples of the aryl group include a phenyl group, a 2-tolyl group, a 3-tolyl group, a 4-tolyl group, a benzyl group, a 4-t-butylphenyl group, a 4-t-amylphenyl group and the like. Of these, a methyl group, an ethyl group, a propyl group, an isopropyl group, a t-butyl group, and a t-amyl group are preferable, and a methyl group, an ethyl group, and a propyl group are particularly preferable because they have moderate reactivity and low resistance. .. Specific examples of the compound of the formula (1) include the following. Among these, compound 1-0, compound 1-1, compound 1-2, and compound 1-5 are preferable.

1-1-2. Compound of formula (2)

(In the formula, R ^{5 to} R ⁸ independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)
The contents of R ^{5 to} R ⁸ described above are the same as the contents of R ^{1 to} R ⁴ described in the equation (1).
Specific examples of the compound of the formula (2) include the following. Among these, Compound 2-0, Compound 2-1 and Compound 2-2, and Compound 2-4 are preferable because they have appropriate reactivity on the positive electrode surface and can appropriately exhibit the effects of the present invention.

1-1-3. Compound of formula (3)

(In the formula, R ^{9 to} R ¹² independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)
The contents of R ^{9 to} R ¹² described above are the same as the contents of R ^{1 to} R ⁴ described in the equation (1).
Specific examples of the compound of the formula (3) include the following. Among these, compound 3-0, compound 3-1 and compound 3-2 are preferable because they have appropriate reactivity on the positive electrode surface and can appropriately exhibit the effects of the present invention.

1-1-4. Compound of formula (4)

(In the formula, R ^{13 to} R ²² independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)
The contents of R ^{13 to} R ²² described above are the same as the contents of R ^{1 to} R ⁴ described in the equation (1).
Specific examples of the compound of the formula (4) include the following. In addition, Me represents a methyl group. Among these, compound 4-0, compound 4-1 and compound 4-2, compound 4-8, compound 4-10 and compound 4-11 are preferable.

1-1-5. Compound of formula (5)

(In the formula, R ^{23 to} R ⁴⁰ independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group.)
The contents of R ^{23 to} R ⁴⁰ described above are the same as the contents of R ^{1 to} R ⁴ described in the equation (1).
Specific examples of the compound of the formula (5) include the following. Among these, compound 5-2 is preferable because it has an appropriate reactivity on the surface of the positive electrode and can appropriately exhibit the effects of the present invention.

1-1-6. Compound of formula (6)

(R ⁴¹ and R ⁴² independently represent a hydrogen atom, a halogen atom, a hydrocarbon group, and an alkoxy group, and n represents an integer of 1 or more.)
Examples of the halogen atoms of R ⁴¹ and R ⁴² include fluorine, chlorine, bromine and iodine. Of these, fluorine is preferable because it is stable against reactions in the battery. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and an aryl group. Examples of the alkyl group include an alkyl group having 1 to 10 carbon atoms, and an alkyl group having 1 to 5 carbon atoms is particularly preferable. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a t-amyl group and the like. Examples of the alkenyl group include a vinyl group, an allyl group, a 1-propenyl group, a 1-butenyl group and the like. Examples of the alkynyl group include an ethynyl group and a propynyl group. Examples of the aryl group include a phenyl group, a 2-tolyl group, a 3-tolyl group, a 4-tolyl group, a benzyl group, a 4-t-butylphenyl group, a 4-t-amylphenyl group and the like. Of these, a methyl group, an ethyl group, a propyl group, an isopropyl group, a t-butyl group, and a t-amyl group are preferable, and in particular, a methyl group, an ethyl group, and a propyl group have moderate reactivity of the compound and resistance. Is preferable because it is low. Examples of the alkoxy group include an alkoxy group having 1 to 10 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms is particularly preferable. Specific examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a t-butoxy group, a methoxymethyl group, an ethoxyethyl group and the like. If the alkoxy group is a methoxy group or an ethoxy group, the reactivity of the compound Is preferable because it is moderate and has low resistance.

As R ⁴¹ and R ⁴² , a hydrogen atom, a fluorine atom, a methyl group, and an ethyl group are particularly preferable because the reactivity of the compound is appropriate and the resistance is low.
n is an integer of 1 or more, preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, while usually 20 or less, preferably 15 or less, more preferably 12 or less. Within the above range, the distance between the two maleimides is appropriate, so that the stability of the compound is high, and the reactivity on the positive electrode surface is appropriate, so that the effects of the present invention can be appropriately exhibited, which is preferable.

Specific compounds of formula (2) include

And so on.
Among the above, compounds 6-1 to 6-6 are preferable, and compounds 6-1 and 6-3 and 6-4 are particularly preferable because the film formed by them is stable.
Among the above compounds, the compound of the formula (4) and the compound of the formula (5) are more preferable, and the compound of the formula (4) is further preferable, in order to form a film capable of widely protecting the electrode.
When the above compound is used, by forming a uniform film on the surface of the negative electrode, the effect of suppressing the capacity decrease at high temperature and suppressing the capacity decrease at the time of continuous charging is great. These may be used alone or in combination of two or more.

When the above compound is used, it is preferably contained in a non-aqueous electrolytic solution in an amount of 0.01% by mass or more, more preferably 0.03% by mass or more, and most preferably 0.05% by mass or more. Further, it is preferably used in a content of 5% by mass or less, more preferably in a content of 3% by mass or less, particularly preferably in a content of 1% by mass or less, and a content of 0.5% by mass or less. Most preferably used in. By using the above content, it is possible to sufficiently obtain the effect of improving the high temperature storage characteristic and the continuous charging characteristic, and to suppress an unnecessary increase in resistance.

The amount of water in the non-aqueous electrolyte solution is not particularly limited, but is preferably 40 ppm or less, more preferably 30 ppm or less, and particularly preferably 20 ppm or less. Further, it is preferably 1 ppm or more, more preferably 2 ppm or more, and particularly preferably 3 ppm or more. Within the above range, the generation of acid in the electrolytic solution can be suppressed, and the process in the production of the electrolytic solution can be relatively simplified.

In the present invention, in addition to the above bismaleimide compound, a carbonate having a halogen atom, a nitrile compound, a compound having an S = O bond, a compound having an isocyanato group, a compound represented by the formula (X), and a difluorophosphate. , It is characterized by containing at least one compound selected from dicarboxylic acid esters.

(R ⁴³ , R ⁴⁴ , and R ⁴⁵ represent organic groups that may independently have a halogen atom, a cyano group, an ester group, and an ether group, respectively.)
In the present invention, at least one selected from a carbonate having a halogen atom, a nitrile compound, a compound having an S = O bond, a compound having an isocyanato group, a compound represented by the formula (X), a difluorophosphate, and a dicarboxylic acid ester. Compounds may be referred to as "other compounds".

[1-2. Carbonate with halogen atom]
The carbonate having a halogen atom is not particularly limited, and examples thereof include the following.
Examples of the halogen atom of the carbonate having a halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Among these, a fluorine atom and a chlorine atom are preferable, and a fluorine atom is particularly preferable.

As the carbonate having a fluorine atom, a chain carbonate having a fluorine atom and a cyclic carbonate having a fluorine atom are preferable, and as the chain carbonate having a fluorine atom, for example, fluoromethylmethyl carbonate, difluoromethylmethylcarbonate, trifluoromethylmethyl Examples thereof include carbonate, trifluoroethyl methyl carbonate, and bis (trifluoroethyl) carbonate. Of these, trifluoroethyl methyl carbonate and bis (trifluoroethyl) carbonate are preferable because they easily form a stable film and have high compound stability.

Examples of the cyclic carbonate having a fluorine atom include a fluorinated product of a cyclic carbonate having an alkylene group having 2 or more and 6 or less carbon atoms, and a derivative thereof. For example, a fluorinated product of ethylene carbonate (hereinafter referred to as “fluorinated ethylene carbonate”). (May be described), and derivatives thereof. Examples of the derivative of the fluorinated product of ethylene carbonate include a fluorinated product of ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms). Of these, fluorinated ethylene carbonate having a fluorine content of 1 or more and 8 or less, and a derivative thereof are preferable.

Examples of the fluorinated ethylene carbonate having 1 to 8 fluorines and its derivative include monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4, 5-Difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene Carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate , 4,5-Difluoro-4,5-dimethylethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate and the like.

Of these, monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate are preferable because they give high ionic conductivity to the electrolytic solution and easily form a stable interface protection film. These may be used alone or in combination of two or more.
The content of the carbonate having a halogen atom is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and most preferably 0.5% by mass or more. Further, it is preferably used in a content of 15% by mass or less, more preferably used in a content of 10% by mass or less, and most preferably used in a content of 7% by mass or less. By using the above content, the effect of improving high temperature storage characteristics and continuous charging characteristics can be sufficiently obtained.

[1-3. Nitrile compound]
The nitrile compound is not particularly limited, and examples thereof include the following.
Examples of the nitrile compound include
Acetonitrile, propionitrile, butyronitrile, valeronitrile, hexanenitrile, heptanenitrile, octanenitrile, nonanenitrile, decanenitrile, lauronitrile, tridecanenitrile, tetradecanenitrile, hexadecanenitrile, pentadecanenitrile, heptadecanenitrile, octadecanenitrile, nona Decanenitrile, Icosannitrile, Crotononitrile, Methacronitrile, Acrylonitrile, methoxyacrylonitrile, Marononitrile, Scusinonitrile, Glutaronitrile, Adiponitrile, Pimeronitrile, Suberonitrile, Azelanitrile, Sevaconitrile, Undecandinitrile, Dodecandinitrile, Methylmalono Nitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile, 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, 2,3,3
-Trimethylsuccinonitrile, 2,2,3,3-tetramethylsuccinonitrile, 2,3-diethyl-2,3-dimethylsuccinonitrile, 2,2-diethyl-3,3-dimethylsuccinonitrile, Bicyclohexyl-1,1-dicarbonitrile, bicyclohexyl-2,2-dicarbonitrile, bicyclohexyl-3,3-dicarbonitrile, 2,5-dimethyl-2,5-hexanedicarbonitrile, 2, 3-Diisobutyl-2,3-dimethylsuccinonitrile, 2,2-diisobutyl-3,3-dimethylsuccinonitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglue Taronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3 , 4-Tetramethylglutaronitrile, maleonitrile, fumaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2 -Dizianobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3'-(ethylenedioxy) dipropionitrile, 3,3'-(ethylenedithio) dipropionitrile and 3,9- Examples thereof include bis (2-cyanoethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane.

Of these, mononitrile, dinitrile, trinitrile, and tetranitrile are preferable. This is because if the number of nitriles is too large, the toxicity of the compound increases. The carbon number of the mononitrile is usually 2 or more, preferably 3 or more, more preferably 4 or more, while usually 20 or less, preferably 18 or less, more preferably 11 or less. The carbon number of the dinitrile is usually 3 or more, preferably 4 or more, more preferably 5 or more, while usually 20 or less, preferably 10 or less, more preferably 8 or less. The carbon number of trinitrile is usually 4 or more, preferably 5 or more, more preferably 6 or more, while usually 20 or less, preferably 18 or less, more preferably 11 or less. The number of carbon atoms of tetranitrile is usually 5 or more, preferably 6 or more, more preferably 7 or more, while usually 20 or less, preferably 18 or less, more preferably 11 or less. Within this range, the protective effect of the electrode is large and the increase in viscosity can be suppressed.

Of these, valeronitrile, octanenitrile, lauronitrile, tridecanenitrile, tetradecanenitrile, hexadecanenitrile, pentadecanenitrile, heptadecanenitrile, octadecanenitrile, nonadecannitrile, crotononitrile, acrylonitrile, methoxyacrylonitrile, malononitrile, succino Nitrile, Glutaronitrile, Adiponitrile, Pimeronitrile, Suberonitrile, Azelanitrile, Sevaconitrile, Undecandinitrile, Dodecandinitrile and 3,9-bis (2-cyanoethyl) -2,4,8,10-Tetraoxaspiro [5,5 ] Undecane and fumaronitrile are preferable from the viewpoint of improving storage characteristics. In addition, Valeronitrile, Octanenitrile, Lauronitrile, Succinonitrile, Glutaronitrile, Adiponitrile, Pimeronitrile, Suberonitrile, and 3,9-bis (2-cyanoethyl) -2,4,8,10-Tetraoxaspiro [5] , 5] Undecane is more preferable because it has a particularly excellent effect of improving storage characteristics and is less deteriorated by a side reaction at the electrode. Generally, the smaller the molecular weight of a nitrile compound, the larger the proportion of cyano groups in one molecule, and the higher the viscosity of the molecule, while the larger the molecular weight, the higher the boiling point of the compound. Therefore, from the viewpoint of improving work efficiency, Valeronitrile, Octanenitrile, Lauronitrile, Succinonitrile, Adiponitrile and Pimeronitrile are more preferable. These may be used alone or in combination of two or more.

The content of the nitrile compound is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and most preferably 0.5% by mass or more. Further, it is preferably used in a content of 6% by mass or less, more preferably used in a content of 5% by mass or less, and most preferably used in a content of 4% by mass or less. By using the above content, it is possible to sufficiently obtain the effect of improving the high temperature storage characteristic and the continuous charging characteristic, and it is possible to suppress an unnecessary increase in resistance.

[1-4. Compound with S = O bond]
The compound having an S = O bond is not particularly limited, and examples thereof include the following.
Examples of the compound having an S = O bond include a chain sulfonic acid ester, a cyclic sulfonic acid ester, a chain sulfate ester, a cyclic sulfate ester, a chain sulfite ester, a cyclic sulfite ester, a chain sulfone, and a cyclic sulfone. Be done. Of these, chain sulfonic acid esters, cyclic sulfonic acid esters, chain sulfate esters, and cyclic sulfate esters are preferable because they have a large effect of suppressing a voltage drop during high-temperature storage.

Examples of the chain sulfonic acid ester include the following.
Fluorosulfuric acid esters such as methyl fluorosulfonate and ethyl fluorosulfonate;
Methyl methanesulfonate, ethyl methanesulfonate, 2-propinyl methanesulfonate, 3-butynyl methanesulfonate, busulfan, methyl 2- (methanesulfonyloxy) propionate, ethyl 2- (methanesulfonyloxy) propionate, 2- 2-Propinyl (methanesulfonyloxy) propionate, 3-butynyl 2- (methanesulfonyloxy) propionate, methyl methanesulfonyloxyacetate, ethyl methanesulfonyloxyacetate, 2-propinyl methanesulfonyloxyacetic acid and 3-butynyl methanesulfonyloxyacetic acid Methansulfonic acid esters such as butynyl;
Methyl vinyl sulfonate, ethyl vinyl sulfonate, allyl vinyl sulfonate, propargyl vinyl sulfonate, methyl allyl sulfonate, ethyl allyl sulfonate, allyl allyl sulfonate, propargyl allyl sulfonate and 1,2-bis (vinyl sulfonate) ) Alkenyl sulfonic acid ester such as ethane;
Methoxycarbonylmethyl methanedisulfonic acid, ethoxycarbonylmethyl methanedisulfonic acid, 1-methoxycarbonylethyl methanedisulfonic acid, 1-ethoxycarbonylethyl methanedisulfonic acid, methoxycarbonylmethyl 1,2-ethanedisulfonic acid, 1,2-ethanedisulfonic acid Ethoxycarbonylmethyl, 1,2-ethanedisulfonic acid 1-methoxycarbonylethyl, 1,2-ethanedisulfonic acid 1-ethoxycarbonylethyl, 1,3-propanedisulfonic acid methoxycarbonylmethyl, 1,3-propanedisulfonic acid ethoxycarbonyl Methyl, 1-methoxycarbonylethyl 1,3-propanedisulfonic acid, 1-ethoxycarbonylethyl 1,3-propanedisulfonic acid, methoxycarbonylmethyl 1,3-butanedisulfonic acid, ethoxycarbonylmethyl 1,3-butanedisulfonic acid, Alkyl disulfonic acid esters such as 1,3-butanedisulfonic acid 1-methoxycarbonylethyl and 1,3-butanedisulfonic acid 1-ethoxycarbonylethyl;
Examples of the cyclic sulfonic acid ester include the following.

1,3-Propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone , 2-Methyl-1,3-Propane Sultone, 3-Methyl-1,3-Propane Sultone, 1-Propen-1,3-Sultone, 2-Propen-1,3-Sultone, 1-Fluoro-1-Propen -1,3-sultone, 2-fluoro-1-propen-1,3-sultone, 3-fluoro-1-propen-1,3-sultone, 1-fluoro-2-propen-1,3-sultone, 2 -Fluoro-2-propen-1,3-sultone, 3-fluoro-2-propen-1,3-sultone, 1-methyl-1-propen-1,3-sultone, 2-methyl-1-propen-1 , 3-Sultone, 3-Methyl-1-propen-1,3-Sultone, 1-Methyl-2-Propen-1,3-Sultone, 2-Methyl-2-Propen-1,3-Sultone, 3-Methyl Sultone compounds such as -2-propen-1,3-sultone, 1,4-butane sultone and 1,5-pentane sultone;
Disulfonate compounds such as methylene methane disulfonate and ethylene methane disulfonate;
Examples of the chain sulfate ester include the following.

Dialkyl sulphate compounds such as dimethyl sulphate, ethyl methyl sulphate and diethyl sulphate.
Examples of the cyclic sulfate ester include the following.
1,2-Ethylene sulphate, 1,2-propylene sulphate, 1,3-propylene sulphate, 1,2-butylene sulphate, 1,3-butylen sulphate, 1,4-butylen sulphate, 1, An alkylene sulfate compound such as 2-pentylene sulphate, 1,3-pentylene sulphate, 1,4-pentylene sulphate and 1,5-pentylene sulphate.

Examples of the chain sulfite ester include the following.
Dialkylsulfite compounds such as dimethylsulfite, ethylmethylsulfite and diethylsulfite.
Examples of the cyclic sulfite ester include the following.
1,2-Ethylene sulphite, 1,2-propylene sulphite, 1,3-propylene sulphite, 1,2-butylene sulphite, 1,3-butylen sulphite, 1,4-butylensulfite, 1, An alkylene sulfite compound such as 2-pentylene sulphite, 1,3-pentylene sulphite, 1,4-pentylene sulphite and 1,5-pentylene sulphite.

Examples of the chain sulfone include the following.
Dialkyl sulfone compounds such as dimethyl sulfone and diethyl sulfone Examples of the cyclic sulfone include the following.
An alkylene sulfone compound such as sulfolane, methyl sulfolane, and 4,5-dimethyl sulfolane, and an alkynylene sulfone compound such as sulfolene.

Of these, methyl 2- (methanesulfonyloxy) propionate, ethyl 2- (methanesulfonyloxy) propionate, 2-propynyl 2- (methanesulfonyloxy) propionate, 1-methoxycarbonylethyl propandisulfonic acid, propandisulfone 1-ethoxycarbonylethyl acid, 1-methoxycarbonylethyl butanedisulfonic acid, 1-ethoxycarbonylethyl butanedisulfonic acid, 1,3-propanesulton, 1-propen-1,3-sulton, 1,4-butanesulton, 1, 2-Ethylene sulphate, 1,2-ethylene sulphite, methyl methanesulfonate and ethyl methanesulphonate are preferable from the viewpoint of improving storage characteristics, and 1-methoxycarbonylethyl propanodisulfonate, 1-ethoxycarbonylethyl propanedisulfonic acid, 1-methoxycarbonylethyl butanedisulfonic acid, 1-ethoxycarbonylethyl butanedisulfonic acid, 1,3-propanesulton, 1-propen-1,3-sulton, 1,2-ethylenesulfate, 1,2-ethylenesulfite Is more preferable, and 1,3-propane sulton and 1-propen-1,3-sulton are even more preferable. These may be used alone or in combination of two or more.

The content of the compound having an S = O bond is preferably 0.01% by mass or more, preferably 0.1.
It is more preferably contained in an amount of 0.5% by mass or more, and most preferably 0.5% by mass or more.
Further, it is preferably used in a content of 5% by mass or less, more preferably used in a content of 4% by mass or less, and most preferably used in a content of 3% by mass or less. By using the above content, it is possible to sufficiently obtain the effect of improving the high temperature storage characteristic and the continuous charging characteristic, and it is possible to suppress an unnecessary increase in resistance.

[1-5. Compound having isocyanato group (N = C = O group)]
The compound having an isocyanato group (N = C = O group) is not particularly limited, and examples thereof include the following.
Examples of the organic compound having an isocyanate group include methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, tertiary butyl isocyanate, pentyl isocyanate hexyl isocyanate, cyclohexyl isocyanate, vinyl isocyanate, allyl isocyanate, ethynyl isocyanate, propargyl isocyanate and phenyl. Organic compounds having one isocyanate group such as isocyanate and fluorophenyl isocyanate;
Monomethylene diisocyanate, dimethylene diisocyanis, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanis, decamethylene diisocyanate, dodecamethylene diisocyanate, 1,3-diisosia Natopropane, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5 -Diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluoro Hexamethylene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis (isosyanatomethyl) cyclohexane, 1,3-bis (isosianatomethyl) cyclohexane, 1,4-bis (isosianatomethyl) cyclohexane, 1, 2-Diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexamethylene-1,1'-diisocyanate, dicyclohexamethylene-2,2'-diisocyanate, dicyclohexylmethane-3, 3'-diisocyanis, dicyclohexamethylene-
4,4'-Diisocyanate, bicyclo [2.2.1] heptane-2,5-diylbis (
Methyl isocyanate), bicyclo [2.2.1] heptane-2,6-diylbis (methylisocyanate), isophorone diisocyanate, carbonyl diisocyanate, 1,4-diisocyanatobutane-1,4-dione, 1,5- Organic compounds having two isocyanate groups such as diisocyanatopentane-1,5-dione, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate;
And so on.

Of these, monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, 1, 3-Bis (isocyanatomethyl) cyclohexane, dicyclohexamethylene-4,4'-diisocyanis, bicyclo [2.2.1]
Heptane-2,5-diylbis (methylisocyanate), bicyclo [2.2.1] heptane-2,6-diylbis (methylisocyanate), isophorone diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2 , 4,4-trimethylhexamethylene diisocyanate and other organic compounds having two isocyanate groups are preferable from the viewpoint of improving storage characteristics, such as hexamethylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, and dicyclohexylmethane-4. , 4'-diisocyanate, bicyclo [
2.2.1] Heptane-2,5-diylbis (methylisocyanate), bicyclo [2.2.1] heptane-2,6-diylbis (methylisocyanate), isophorone diisocyanate, 2,2,4-trimethylhexa Methylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate are more preferable, 1,3-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane-4,4'-diisocyanate, bicyclo [2.2.1]. ] Heptane-2,5-diylbis (methylisocyanate), bicyclo [2.2.1] heptane-2,6-diylbis (methylisocyanate) are more preferred. These may be used alone or in combination of two or more.

The content of the compound having an isocyanato group (N = C = O group) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and most preferably 0.2% by mass or more. Further, it is preferably used in a content of 5% by mass or less, more preferably used in a content of 3% by mass or less, and most preferably used in a content of 2% by mass or less. By using the above content, it is possible to sufficiently obtain the effect of improving the high temperature storage characteristic and the continuous charging characteristic, and it is possible to suppress an unnecessary increase in resistance.

[1-6. Compound represented by formula (X)]

(R ⁴³ , R ⁴⁴ , and R ⁴⁵ represent organic groups that may independently have a halogen atom, a cyano group, an ester group, and an ether group, respectively.)
The compound represented by the formula (X) is not particularly limited, and examples thereof include the following.
Examples of the halogen atom represented by R ⁴³ , R ⁴⁴ , and R ⁴⁵ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and among these, a fluorine atom is most preferable because it has a large effect of improving battery characteristics. Organic groups that may have a halogen atom, a cyano group, an ester group, or an ether group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a t-amyl group, and a vinyl. Group, allyl group, 1-propenyl group, 1-butenyl group, ethynyl group, propynyl group, phenyl group, 2-tolyl group, 3-tolyl group, 4-tolyl group, benzyl group, 4-t-butylphenyl group, Hydrocarbon group such as 4-t-amylphenyl group, fluorinated hydrocarbon group such as fluoromethyl group, trifluoromethyl group, trifluoroethyl group, cyanomethyl group, cyanoethyl group, cyanopropyl group, cyanobutyl group, cyanopentyl group , Cyan hydrocarbon groups such as cyanohexyl group, ethoxycarbonyl group, ethoxycarbonylmethyl group, 1-ethoxycarbonylethyl group, acetoxy group, acetoxymethyl group, 1-acetoxyethyl group, acryloyl group, acryloylmethyl group, 1-acryloyl Examples thereof include an organic group having an ester group such as an ethyl group, an organic group having an ethyl group such as a methoxy group, an ethoxy group, a methoxymethyl group, an ethoxymethyl group, a methoxyethyl group and an ethoxyethyl group.

Examples of the compound represented by the formula (X) include the following.
Trivinyl isocyanurate, tri (1-propenyl) isocyanurate, triallyl isocyanurate, trimetalyl isocyanurate, methyldiallyl isocyanurate, ethyldiallyl isocyanurate, diethylallylyl isocyanurate, diethylvinyl isocyanurate, tri (propargyl) isocyanurate , Tris (2-acryloxymethyl) isocyanurate, tris (2-acryloxyethyl) isocyanurate, tris (2-methacryloxymethyl) isocyanurate, tris (2-methacryloxyethyl) isocyanurate, ε-caprolactone-modified tris -(2-Acryloxyethyl) isocyanurate, among which triallyl isocyanurate, trimetalyl isocyanurate, tris (2-acryloxyethyl) isocyanurate, tris (2-methacryloxyethyl) isocyanurate, ε-caprolactone. Modified tris- (2-acryloxyethyl) isocyanurate is preferable, and triallyl isocyanurate and tris (2-acryloxyethyl) isocyanurate are particularly preferable because they have a large effect of improving continuous charging characteristics. These may be used alone or in combination of two or more.

The content of the compound represented by the formula (1) is preferably 0.01% by mass or more, preferably 0.1.
It is more preferably contained in an amount of 0.2% by mass or more, and most preferably 0.2% by mass or more.
Further, it is preferably used in a content of 5% by mass or less, more preferably used in a content of 3% by mass or less, and most preferably used in a content of 2% by mass or less. By using the above content, it is possible to sufficiently obtain the effect of improving the high temperature storage characteristic and the continuous charging characteristic, and to suppress an unnecessary increase in resistance.

[1-7. Monofluorophosphate, difluorophosphate]
The monofluorophosphate and difluorophosphate are not particularly limited, and examples thereof include the following.
For example, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate, ammonium difluorophosphate and the like can be mentioned, and among them, lithium difluorophosphate is particularly preferable because it has a large effect of improving continuous charging characteristics. These may be used alone or in combination of two or more.

The content of difluorophosphate is preferably 0.01% by mass or more, preferably 0.1% by mass.
It is more preferably contained in an amount of 0.2% by mass or more, and most preferably 0.2% by mass or more. Further, it is preferably used in a content of 3% by mass or less, more preferably in a content of 2% by mass or less, and most preferably in an amount of 1.5% by mass or less. By using the above content, the effect of improving high temperature storage characteristics and continuous charging characteristics can be sufficiently obtained.

[1-8. Dicarboxylic acid ester]
The dicarboxylic acid ester is not particularly limited, and examples thereof include the following.
Maronic acid ester and its derivatives, succinic acid ester and its derivatives, adipic acid ester and its derivatives, fumaric acid ester and its derivatives, maleic acid ester and its derivatives, phthalates and its derivatives, terephthalates and its derivatives.

Examples of malonic acid esters and their derivatives include the following.
Dimethyl malonate, diethyl malonate, diethyl methylmalonate, diethyl ethylmalonate, diethyl butyl malonate, divinyl malonate, diallyl malonate, dipropargyl malonate.
Examples of the succinic acid ester and its derivative include the following.

Diethyl succinate, diethyl succinate, diethyl methyl succinate, diethyl dimethyl succinate, diethyl tetramethylsuccinate, divinyl succinate, diallyl succinate, dipropargyl succinate.
Examples of the adipate ester and its derivative include the following.
Dimethyl adipate, diethyl adipic acid, diethyl methyl adipate, diethyl dimethyl adipate, diethyl tetramethyl adipate, divinyl adipic acid, diallyl adipate, dipropargyl adipate.

Examples of the fumaric acid ester and its derivative include the following.
Dimethyl fumarate, diethyl fumarate, diethyl methyl fumarate.
Examples of maleic acid esters and their derivatives include the following.
Dimethyl maleate, diethyl maleate, diethyl methyl maleate.
Examples of the phthalate ester and its derivative include the following.

Dimethyl phthalate, diethyl phthalate, di2-ethylhexyl phthalate.
Examples of the terephthalic acid ester and its derivative include the following.
Dimethyl terephthalate, diethyl terephthalate, di2-ethylhexyl terephthalate.
Among these, diethyl methylmalonic acid, diethyl ethylmalonate, and diethyl butylmalonate are particularly preferable because they have a large effect of improving high-temperature storage characteristics. These may be used alone or in combination of two or more.

The content of the dicarboxylic acid ester is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and most preferably 0.5% by mass or more. Further, it is preferably used in a content of 5% by mass or less, more preferably used in a content of 4% by mass or less, and most preferably used in a content of 3% by mass or less. By using the above content, the effect of improving high temperature storage characteristics and continuous charging characteristics can be sufficiently obtained.

According to the gist of the present invention, the desired effect can be exhibited by using the bismaleimide compound in combination with the above-mentioned "other compounds". The mechanism of action is not clear, but according to various studies so far, after the bismaleimide compound forms a film on the negative electrode surface in the first charge, "other compounds" further react on the negative electrode, so each is independent. It is considered that the negative electrode surface coating becomes much stronger than when used in. Bismaleimide also reacts on the surface of the positive electrode, but the reaction of "other compounds" on the surface of the positive electrode or the interaction with the metal contained in the positive electrode is strengthened, or the surface of the positive electrode of "other compounds". By covering the part that does not reach the reaction above or the interaction with the metal contained in the positive electrode, the voltage drop in a high temperature environment is suppressed, the recovery capacity rate is improved, and the residue during continuous charging・ It is thought that the recovery capacity rate will improve.

[1-9. Electrolytes〕
There is no limitation on the electrolyte used for the non-aqueous electrolyte solution of the present invention, and any known electrolyte can be used as long as it is used as an electrolyte in the target non-aqueous electrolyte secondary battery. When the non-aqueous electrolyte solution of the present invention is used in a lithium secondary battery, a lithium salt is usually used as the electrolyte.

Specific examples of the electrolyte include inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiSO ₃ F, and LiN (FSO ₂ ) ₂ .
LiCF ₃ SO ₃ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Lithium cyclic 1,3-hexafluoropropanedisulfonylimide, Lithium cyclic 1,2-tetrafluoroethanedisulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C) ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF) ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) _{2 and} other fluorine-containing organic lithium salts;
Examples thereof include dicarboxylic acid complex lithium salts such as lithium bis (oxalate) borate, lithium difluorooxalato borate, lithium tris (oxalat) phosphate, lithium difluorobis (oxalat) phosphate, and lithium tetrafluoro (oxalat) phosphate.

Of these, LiPF ₆ , LiBF ₄ , LiSO ₃ F, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (from the viewpoint of solubility / dissociation in non-aqueous solvent, electrical conductivity, and obtained battery characteristics). CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Lithium bis (oxalat) borate, lithium difluorooxalat borate, lithium tris (oxalate) phosphate, lithium difluorobis ( Oxalato) phosphate and lithium tetrafluoro (oxalat) phosphate are preferable, and LiPF ₆ and LiBF ₄ are particularly preferable.

In addition, one type of electrolyte may be used alone, or two or more types may be used in any combination and ratio. Above all, when two kinds of specific inorganic lithium salts are used in combination, or when an inorganic lithium salt and a fluorine-containing organic lithium salt are used in combination, gas generation during trickle charging is suppressed and deterioration after high temperature storage is suppressed. Therefore, it is preferable. In particular, the combined use of LiPF ₆ and LiBF ₄ , the use of inorganic lithium salts such as LiPF ₆ and LiBF ₄ , and LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) _2, etc. It is preferable to use it in combination with a fluorine-containing organic lithium salt.

Further, when LiPF ₆ and LiBF ₄ are used in combination, it is preferable that LiBF ₄ is usually contained in a ratio of 0.01% by mass or more and 50% by mass or less with respect to the entire electrolyte. The above ratio is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, while preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less. Most preferably, it is 3% by mass or less. When the ratio is in the above range, the desired effect can be easily obtained, and the low degree of dissociation of LiBF ₄ suppresses the increase in the resistance of the electrolytic solution.

On the other hand, inorganic lithium salts such as LiPF ₆ and LiBF ₄ , inorganic lithium salts such as LiSO ₃ F and LiN (FSO ₂ ) ₂ , LiCF ₃ SO ₃ and LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F) ₅ SO ₂ ) ₂ , Lithium cyclic 1,3-hexafluoropropanedisulfonylimide, Lithium cyclic 1,2-tetrafluoroethanedisulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC ( CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ ( Fluorine-containing organic lithium salts such as CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ , and lithium bis (oxalate) Use in combination with a dicarboxylic acid complex lithium salt such as borate, lithium tris (oxalate) phosphate, lithium difluorooxalat borate, lithium tri (oxalate) phosphate, lithium difluorobis (oxalat) phosphate, lithium tetrafluoro (oxalat) phosphate, etc. In this case, the ratio of the inorganic lithium salt to the total electrolyte is usually 70% by mass or more, preferably 80% by mass or more, more preferably 85% by mass or more, and usually 99% by mass or less, preferably 95% by mass or less. ..

The concentration of the lithium salt in the non-aqueous electrolyte solution of the present invention is arbitrary as long as the gist of the present invention is not impaired, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0. It is 8 mol / L or more. Further, it is usually in the range of 3 mol / L or less, preferably 2 mol / L or less, more preferably 1.8 mol / L or less, and further preferably 1.6 mol / L or less. When the concentration of the lithium salt is within the above range, the electrical conductivity of the non-aqueous electrolyte solution becomes sufficient, and the electrical conductivity decreases due to the increase in viscosity. The non-aqueous electrolyte solution using the non-aqueous electrolyte solution of the present invention (2) Suppress the deterioration of the performance of the next battery.

[1-10. Non-aqueous solvent]
As the non-aqueous solvent contained in the non-aqueous electrolyte solution of the present invention, a solvent of a conventionally known non-aqueous electrolyte solution can be appropriately selected and used. Examples of commonly used non-aqueous solvents include cyclic carbonates, chain carbonates, chain and cyclic carboxylic acid esters, chain and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, aromatic fluorine-containing solvents and the like. Can be mentioned.

Examples of the cyclic carbonate include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and the cyclic carbonate usually has 3 or more and 6 or less carbon atoms. Among these, ethylene carbonate and propylene carbonate are preferable because they have a high dielectric constant, so that the electrolyte is easily dissolved, and the cycle characteristics are good when a non-aqueous electrolyte secondary battery is used.

Examples of the chain carbonate include chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate, and the alkyl groups constituting the chain carbonate. The number of carbon atoms is preferably 1 or more and 5 or less, and particularly preferably 1 or more and 4 or less. Of these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable from the viewpoint of improving battery characteristics. In addition, chain carbonates in which a part of hydrogen of the alkyl group is replaced with fluorine can also be mentioned. The chain carbonates substituted with fluorine include bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) carbonate, bis (2-fluoroethyl) carbonate, and bis (2,2-difluoroethyl). Examples thereof include carbonate, bis (2,2,2-trifluoroethyl) carbonate, 2-fluoroethylmethyl carbonate, 2,2-difluoroethylmethyl carbonate, 2,2,2-trifluoroethylmethyl carbonate and the like.

Examples of the chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and propionic acid. Chains in which isopropyl, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, ethyl pivalate, etc. and some of the hydrogens of these compounds are replaced with fluorine. State carboxylic acid ester can be mentioned. Examples of the chain carboxylic acid ester substituted with fluorine include methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetic acid. Among these, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, methyl pentanoate, methyl isobutyrate, ethyl isobutyrate, and methyl pivalate are batteries. It is preferable from the viewpoint of improving the characteristics.

Examples of the cyclic carboxylic acid ester include γ-butyrolactone, γ-valerolactone and the like, and cyclic carboxylic acid ester in which a part of hydrogen of these compounds is replaced with fluorine. Of these, γ-butyrolactone is more preferable.
As the chain ether, dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1 Examples thereof include −ethoxymethoxyethane, 1,2-ethoxymethoxyethane and the like, and chain ethers in which a part of hydrogen of these compounds is replaced with fluorine. As a chain ether substituted with fluorine, bis (trifluoroethoxy) ethane, ethoxytrifluoroethoxyethane, methoxytrifluoroethoxyethane, 1,1,1,2,2,3,4,5,5-deca Fluoro-3-methoxy-4-trifluoromethyl-pentane, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-ethoxy-4-trifluoromethyl-pentane, 1 , 1,1,2,2,3,4,5,5,5-decafluoro-3-propoxy-4-trifluoromethyl-pentane, 1,1,2,2-tetrafluoroethyl-2,2, Examples thereof include 3,3-tetrafluoropropyl ether and 2,2-difluoroethyl-2,2,3,3-tetrafluoropropyl ether. Of these, 1,2-dimethoxyethane and 1,2-diethoxyethane are more preferable.

Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane and the like, and cyclic ether in which a part of hydrogen of these compounds is replaced with fluorine.
Examples of the phosphorus-containing organic solvent include trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, and triethyl phosphite. Examples thereof include triphenyl phosphite, trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide and the like, and phosphorus-containing organic solvents in which a part of hydrogen of these compounds is replaced with fluorine. Examples of the phosphorus-containing organic solvent substituted with fluorine include tris phosphate (2,2,2-trifluoroethyl) and tris phosphate (2,2,3,3,3-pentafluoropropyl).

Examples of the sulfur-containing organic solvent include sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, dimethylsulfoxide, methyl methanesulfonate, ethyl methanesulfonate, and methyl ethanesulfonate. , Ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, dibutyl sulfate and the like, and sulfur-containing organic solvents in which a part of hydrogen of these compounds is replaced with fluorine.

Examples of the aromatic fluorine-containing solvent include fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, benzotrifluoride and the like.
Among the above-mentioned non-aqueous solvents, it is preferable to use ethylene carbonate and / or propylene carbonate which are cyclic carbonates, and further, the combined use of these and chain carbonate can achieve both high conductivity and low viscosity of the electrolytic solution. Is preferable.

One type of non-aqueous solvent may be used alone, or two or more types may be used in any combination and ratio. When two or more kinds are used in combination, for example, when a cyclic carbonate and a chain carbonate are used in combination, the preferable content of the chain carbonate in the non-aqueous solvent is usually 20% by volume or more, preferably 40% by volume or more. Further, it is usually 95% by volume or less, preferably 90% by volume or less. On the other hand, the preferable content of the cyclic carbonate in the non-aqueous solvent is usually 5% by volume or more, preferably 10% by volume or more, and usually 80% by volume or less, preferably 60% by volume or less. When the ratio of the chain carbonate is in the above range, the increase in the viscosity of the non-aqueous electrolyte solution is suppressed, and the decrease in the electric conductivity of the non-aqueous electrolyte solution due to the decrease in the dissociation degree of the lithium salt which is the electrolyte is suppressed. In the present specification, the volume of the non-aqueous solvent is a measured value at 25 ° C., but for a solid at 25 ° C. such as ethylene carbonate, the measured value at the melting point is used.

[1-11. Other additives]
The non-aqueous electrolyte solution of the present invention may contain various additives as long as the effects of the present invention are not significantly impaired. As the additive, conventionally known additives can be arbitrarily used. As the additive, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

(Overcharge inhibitor)
Specific examples of the overcharge inhibitor include alkylbiphenyls such as 2-methylbiphenyl and 2-ethylbiphenyl, terphenyl, and partially hydrides of terphenyl, cyclohexylbenzene, cis-1-propyl-4-phenylcyclohexane, and trans. -1-propyl-4-phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1-butyl-4-phenylcyclohexane, diphenyl ether, dibenzofuran, ethylphenyl carbonate, tris (2-t-amylphenyl) phosphate , Tris (3-
t-amylphenyl) phosphate, tris (4-t-amylphenyl) phosphate, tris (2-cyclohexylphenyl) phosphate, tris (3-cyclohexylphenyl) phosphate, tris (4-cyclohexylphenyl) phosphate, triphenyl phosphate, tri Aromatic compounds such as triryl phosphate, tri (t-butylphenyl) phosphate, methylphenyl carbonate, diphenyl carbonate; 2-fluorobiphenyl, 3-fluorobiphenyl, 4-fluorobiphenyl, 4,4'-difluorobiphenyl, 2,4 Partially fluorinated of aromatic compounds such as −difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5- Examples thereof include fluorine-containing anisole compounds such as difluoroanisole.

The content of these overcharge inhibitors in the non-aqueous electrolyte solution is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5. It is mass% or more, and usually 5 mass% or less, preferably 3 mass% or less, and more preferably 2 mass% or less. When the concentration is in the above range, the desired effect of the overcharge inhibitor is likely to be exhibited, and deterioration of battery characteristics such as high temperature storage characteristics is suppressed. By containing an overcharge inhibitor in the non-aqueous electrolyte solution, it is possible to suppress the explosion and ignition of the non-aqueous electrolyte secondary battery due to overcharging, and the safety of the non-aqueous electrolyte secondary battery is improved. preferable.

Other auxiliaries include vinylene carbonate, vinylethylene carbonate, ethynylethylene carbonate, erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate, methoxyethyl-ethyl carbonate, ethoxyethyl-methyl carbonate, ethoxyethyl. Carbonate compounds such as −ethyl carbonate; 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane and the like. Spiro compounds; nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsucciimide. Compounds; Hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, t-butylcyclohexane, dicyclohexyl; methyldimethylphosphinate, ethyldimethylphosphinate, ethyl Phosphorus-containing compounds such as diethylphosphinate, trimethylphosphonoformate, triethylphosphonoformate, trimethylphosphonoacetate, triethylphosphonoacetate, trimethyl-3-phosphonopropionate, triethyl-3-phosphonopropionate , Succinic anhydride, methyl succinic anhydride, 4,4-dimethyl succinic anhydride, 4,5-dimethyl succinic anhydride, maleic anhydride, citraconic anhydride, maleic anhydride, phenyl maleic anhydride, diphenyl maleic anhydride , Succinic anhydride, cyclohexane 1,2-dicarboxylic acid anhydride, acetic anhydride, propionic anhydride, acrylic anhydride, methacrylic anhydride and other acid anhydrides. Of these, vinylene carbonate, vinylethylene carbonate, succinic anhydride, maleic anhydride, and methacrylic anhydride are preferable from the viewpoint of improving cycle characteristics and high-temperature storage characteristics. These may be used alone or in combination of two or more.

The content of these auxiliaries in the non-aqueous electrolyte solution is not particularly limited, but is usually 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.2% by mass or more. It is usually 8% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less. It is preferable to add these auxiliaries from the viewpoint of improving the capacity retention characteristics and cycle characteristics after high temperature storage. When this concentration is in the above range, the effect of the auxiliary agent is likely to be exhibited, and deterioration of battery characteristics such as high rate load discharge characteristics is suppressed.

[2. Negative electrode]
The negative electrode active material used for the negative electrode will be described below. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like. One of these may be used alone, or two or more thereof may be arbitrarily combined and used in combination.

<Negative electrode active material>
Examples of the negative electrode active material include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like.
Examples of the carbonaceous material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite. ..

(1) Examples of natural graphite include scaly graphite, scaly graphite, soil graphite, and / or graphite particles obtained by subjecting these graphites to spheroidization, densification, or the like. Among these, spherical or ellipsoidal graphite that has been subjected to a spheroidizing treatment is particularly preferable from the viewpoint of particle packing property and charge / discharge rate characteristics.
As the device used for the spheroidizing process, for example, a device that repeatedly applies mechanical actions such as compression, friction, and shearing force including the interaction of particles mainly with impact force to the particles can be used. Specifically, it has a rotor with a large number of blades installed inside the casing, and by rotating the rotor at high speed, mechanical actions such as impact compression, friction, and shearing force are applied to the carbon material introduced inside. , And a device that performs the spheroidizing process is preferable. Further, it is preferable that the carbon material has a mechanism for repeatedly giving a mechanical action by circulating the carbon material.

For example, in the case of sphericalizing using the above-mentioned device, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and 50 to 100 m / sec. It is more preferable to do so. Further, although the treatment can be carried out simply by passing a carbonaceous material, it is preferable to circulate or retain in the apparatus for 30 seconds or more, and to circulate or retain in the apparatus for 1 minute or more. More preferred.

(2) As artificial graphite, coal tar pitch, coal-based heavy oil, atmospheric residual oil, petroleum-based heavy oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, etc. Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene silfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin are usually used in the range of 2500 ° C or higher and usually 3200 ° C or lower. Examples thereof include those produced by graphitization at temperature, crushing and / or classifying as necessary. At this time, a silicon-containing compound, a boron-containing compound, or the like can also be used as a graphitization catalyst. In addition, artificial graphite obtained by graphitizing mesocarbon microbeads separated in a pitch heat treatment process can be mentioned. Further, artificial graphite of granulated particles composed of primary particles can also be mentioned. For example, by mixing mesocarbon microbeads, graphitizable carbon material powder such as coke with graphitizable binder such as tar and pitch, and graphitizing catalyst, graphitizing and pulverizing if necessary. Examples thereof include graphite particles obtained by assembling or bonding a plurality of flat particles so that the orientation planes are non-parallel.

(3) As the amorphous carbon, an amorphous carbon that uses an easily graphitizable carbon precursor such as tar or pitch as a raw material and is heat-treated at least once in a temperature range (range of 400 to 2200 ° C.) where graphitization does not occur. Examples thereof include amorphous carbon particles that have been heat-treated using particles or a non-graphitizable carbon precursor such as a resin as a raw material.
(4) The carbon-coated graphite can be obtained by mixing natural graphite and / or artificial graphite with a carbon precursor which is an organic compound such as tar, pitch or resin, and heat-treating it once or more in the range of 400 to 2300 ° C. Examples thereof include a carbon graphite composite in which natural graphite and / or artificial graphite is used as nuclear graphite and amorphous carbon is coated on the nuclear graphite. The form of the composite may be a coating of the entire surface or a part thereof, or a composite of a plurality of primary particles using carbon derived from the carbon precursor as a binder. Carbon can also be deposited (CVD) on the graphite surface by reacting natural graphite and / or artificial graphite with hydrocarbon gases such as benzene, toluene, methane, propane, and aromatic volatiles at high temperatures. Graphite composites can also be obtained.

(5) As the graphite-coated graphite, natural graphite and / or artificial graphite is mixed with a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin, and once in the range of about 2400 to 3200 ° C. Examples thereof include graphite-coated graphite in which natural graphite and / or artificial graphite obtained by the above heat treatment is used as nuclear graphite, and graphite is coated on the entire or a part of the surface of the nuclear graphite.
(6) As the resin-coated graphite, natural graphite and / or artificial graphite obtained by mixing natural graphite and / or artificial graphite and resin or the like and drying at a temperature of less than 400 ° C. is used as nuclear graphite, and the resin or the like is nuclear graphite. Examples thereof include resin-coated graphite coating the above.

Further, as the carbonaceous materials (1) to (6), one kind may be used alone, or two or more kinds may be used in any combination and ratio.
Examples of the organic compounds such as tar, pitch and resin used in (2) to (5) above include coal-based heavy oil, DC-based heavy oil, decomposition-based petroleum heavy oil, aromatic hydrocarbons, and N-ring compounds. , S-ring compounds, polyphenylenes, synthetic organic polymers, natural polymers, thermoplastic resins, thermosetting resins, and other carbonizable organic compounds selected from the group. Further, the raw material organic compound may be used by being dissolved in a low molecular weight organic solvent in order to adjust the viscosity at the time of mixing.

Further, as the natural graphite and / or the artificial graphite which is a raw material of the nuclear graphite, the natural graphite which has been subjected to the spheroidizing treatment is preferable.
As an alloy-based material used as a negative electrode active material, if lithium can be occluded and released, lithium alone, a single metal and alloy forming a lithium alloy, or their oxides, carbides, nitrides, silicides, and sulfides. It may be either a substance or a compound such as a phosphate, and is not particularly limited. The elemental metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / semi-metal elements (that is, excluding carbon), and more preferably elemental metals of aluminum, silicon and tin. An alloy or compound containing these atoms. One of these may be used alone, or two or more thereof may be used in any combination and ratio.

<Physical properties of carbonaceous materials>
When a carbonaceous material is used as the negative electrode active material, it is desirable that it has the following physical properties.
(X-ray parameter)
The d value (interlayer distance) of the lattice planes (002 planes) determined by X-ray diffraction of carbonaceous materials is usually 0.335 nm or more, and usually 0.360 nm or less, 0.350 nm. The following is preferable, and 0.345 nm or less is more preferable. The crystallite size (Lc) of the carbonaceous material determined by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

(Volume-based average particle size)
The volume-based average particle size of the carbonaceous material is the volume-based average particle size (median diameter) determined by the laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and 7 μm. The above is particularly preferable, and usually 100 μm or less, 50 μm or less is preferable, 40 μm or less is more preferable, 30 μm or less is further preferable, and 25 μm or less is particularly preferable.

If the volume-based average particle size falls below the above range, the irreversible capacity may increase, resulting in a loss of initial battery capacity. On the other hand, if it exceeds the above range, a non-uniform coating surface is likely to occur when the electrode is produced by coating, which may not be desirable in the battery manufacturing process.
The volume-based average particle size is measured by dispersing carbon powder in a 0.2 mass% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This is performed using a meter (for example, LA-700 manufactured by HORIBA, Ltd.). The median diameter obtained by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

(Raman R value)
The Raman R value of the carbonaceous material is a value measured by laser Raman spectroscopy, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1. It is 5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

If the Raman R value is less than the above range, the crystallinity of the particle surface becomes too high, and the number of sites where Li enters between layers may decrease due to charging and discharging. That is, the charge acceptability may decrease. Further, when the negative electrode is densified by pressing after being applied to the current collector, the crystals tend to be oriented in the direction parallel to the electrode plate, which may lead to deterioration of the load characteristics.
On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte solution is increased, and the efficiency may be lowered and the gas generation may be increased.

To measure the Raman spectrum, a Raman spectroscope (for example, a Raman spectroscope manufactured by Nippon Spectroscopy Co., Ltd.) is used to naturally drop the sample into the measurement cell and fill it, and then the surface of the sample in the cell is filled with an argon ion laser beam (or semiconductor). This is performed by rotating the cell in a plane perpendicular to the laser beam while irradiating the cell (laser beam). The resulting Raman spectrum, the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and measuring the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity ratio _{R (R = I B / I} A) Is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention.

The Raman measurement conditions described above are as follows.
-Laser wavelength: Ar ion laser 514.5 nm (semiconductor laser 532 nm)
-Measurement range: 1100 cm ^{-1 to} 1730 cm ^-1
・ Raman R value: Background processing,
・ Smoothing processing: Simple average, convolution 5 points

(BET specific surface area)
BET specific surface area of the carbonaceous material is a value of the measured specific surface area using the BET method is usually 0.1 m ² · ^{g -1} or more, 0.7 m ² · ^{g -1} or more, 1. 0 m ² · ^{g -1} or more, and particularly preferably 1.5 m ² · ^{g -1} or more, generally not more than 100 m ² · ^{g -1,} preferably ^{25 m} 2 · ^{g -1} or less, 15 m ² · g ^-1 more preferably less, ^{10 m} 2 · ^{g -1} or less are especially preferred.

If the value of the BET specific surface area is less than this range, the acceptability of lithium tends to deteriorate during charging when used as a negative electrode material, and lithium tends to precipitate on the electrode surface, which may reduce stability. On the other hand, if it exceeds this range, the reactivity with the non-aqueous electrolyte solution increases when used as the negative electrode material, gas generation tends to increase, and it may be difficult to obtain a preferable battery.

To measure the specific surface area by the BET method, a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken) is used to pre-dry the sample at 350 ° C. for 15 minutes under nitrogen flow, and then to atmospheric pressure. This is performed by the nitrogen adsorption BET 1-point method by the gas flow method using a nitrogen helium mixed gas accurately adjusted so that the relative pressure value of nitrogen is 0.3.

(Circularity)
When the circularity is measured as the degree of sphere of the carbonaceous material, it is preferably within the following range. The circularity is defined by "circularity = (peripheral length of a corresponding circle having the same area as the projected particle shape) / (actual peripheral length of the projected particle shape)", and is theoretical when the circularity is 1. Become a true sphere.
The circularity of the particles in which the particle size of the carbonaceous material is in the range of 3 to 40 μm is preferably closer to 1, and preferably 0.1 or more, particularly 0.5 or more, more preferably 0.8 or more. 0.85 or more is more preferable, and 0.9 or more is particularly preferable. The high current density charge / discharge characteristics improve as the circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between the particles is increased, and the high current density charge / discharge characteristics for a short time may be lowered.

The circularity is measured using a flow-type particle image analyzer (for example, FPIA manufactured by Sysmex Corporation). About 0.2 g of the sample was dispersed in a 0.2 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and ultrasonic waves of 28 kHz were irradiated at an output of 60 W for 1 minute. , The detection range is specified as 0.6 to 400 μm, and the measurement is performed on particles having a particle size in the range of 3 to 40 μm.

The method for improving the circularity is not particularly limited, but a spherical shape obtained by subjecting it to a spherical shape is preferable because the shape of the interparticle voids when the electrode body is formed is adjusted. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying shearing force and compressive force, and a mechanical / physical treatment method of granulating a plurality of fine particles by the adhesive force of the binder or the particles themselves. Can be mentioned.

(Tap density)
The tap density of the carbonaceous material is usually 0.1 g · cm ^-3 or more, preferably 0.5 g · cm ^-3 or more, more preferably 0.7 g · cm ^-3 or more, and 1 g · cm ^-3 or more. It is particularly preferable, 2 g · cm ^-3 or less is preferable, 1.8 g · cm ^-3 or less is further preferable, and 1.6 g · cm ^-3 or less is particularly preferable. If the tap density is lower than the above range, the filling density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds the above range, the voids between the particles in the electrode become too small, it becomes difficult to secure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

To measure the tap density, pass through a sieve with a mesh size of 300 μm, drop the sample into a tapping cell of 20 cm ³ to fill the sample up to the upper end surface of the cell, and then use a powder density measuring device (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap denser), tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample.

(Orientation ratio)
The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. If the orientation ratio is less than the above range, the high-density charge / discharge characteristics may deteriorate. The upper limit of the above range is the theoretical upper limit of the orientation ratio of the carbonaceous material.
The orientation ratio is measured by X-ray diffraction after pressure molding the sample. A molded product obtained by filling 0.47 g of a sample into a molding machine having a diameter of 17 mm and compressing it at 58.8 MN · m- ² was set using clay so as to be flush with the surface of the sample holder for measurement. Measure X-ray diffraction. From the peak intensities of (110) diffraction and (004) diffraction of the obtained carbon, the ratio expressed by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated.
The X-ray diffraction measurement conditions are as follows. In addition, "2θ" indicates a diffraction angle.

・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degrees Light receiving slit = 0.15 mm
Scattering slit = 0.5 degrees ・ Measurement range and step angle / measurement time:
(110) Surface: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree / 60 seconds (004) Surface: 52 degrees ≤ 2θ ≤ 57 degrees 1 degree / 60 seconds

(Aspect ratio (powder))
The aspect ratio of the carbonaceous material is usually 1 or more, usually 10 or less, preferably 8 or less, and even more preferably 5 or less. If the aspect ratio exceeds the above range, streaks or a uniform coated surface cannot be obtained at the time of electrode plate formation, and the high current density charge / discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the carbonaceous material.

The aspect ratio is measured by magnifying and observing the particles of the carbonaceous material with a scanning electron microscope. Arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted for each of them, and the carbonaceous material particles are observed three-dimensionally. The longest diameter A and the shortest diameter B orthogonal to the diameter A are measured, and the average value of A / B is obtained.

<Construction and manufacturing method of negative electrode>
Any known method can be used for producing the electrode as long as the effect of the present invention is not significantly impaired. For example, a binder, a solvent, and if necessary, a thickener, a conductive material, a filler, and the like are added to a negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed to form a slurry. Can be done.
Further, when an alloy-based material is used, a method of forming a thin film layer (negative electrode active material layer) containing the above-mentioned negative electrode active material by a method such as a vapor deposition method, a sputtering method, or a plating method is also used.

(Electrode density)
The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the negative electrode active material existing on the current collector is preferably 1 g · cm ^-3 or more, and 1.2 g · cm ^-3 or more. Is more preferable, 1.3 g · cm ^-3 or more is particularly preferable, 2.2 g · cm ^-3 or less is preferable, 2.1 g · cm ^-3 or less is more preferable, and 2.0 g · cm ^-3 or less is more preferable. More preferably, 1.9 g · cm ^-3 or less is particularly preferable. If the density of the negative electrode active material existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous system near the current collector / negative electrode active material interface High current density charge / discharge characteristics may deteriorate due to a decrease in the permeability of the electrolytic solution. Further, if it falls below the above range, the conductivity between the negative electrode active materials may decrease, the battery resistance may increase, and the capacity per unit volume may decrease.

[3. Positive electrode]
<Positive electrode active material>
The positive electrode active material (lithium transition metal compound) used for the positive electrode will be described below.
<Lithium transition metal compound>
The lithium transition metal compound is a compound having a structure capable of desorbing and inserting Li ions, and examples thereof include sulfides, phosphate compounds, and lithium transition metal composite oxides. As the sulfide, a compound having a two-dimensional layered structure such as TiS ₂ or MoS ₂ or a strong compound represented by the general formula Me _x Mo ₆ S ₈ (Me is various transition metals such as Pb, Ag, and Cu). Examples thereof include a sulphide compound having a three-dimensional skeletal structure. Examples of the phosphate compound include those belonging to the olivine structure, which are generally represented by LiMePO ₄ (Me is at least one transition metal), and specifically, LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , Examples thereof include LiMnPO ₄ . Examples of the lithium transition metal composite oxide include those belonging to a spinel structure capable of three-dimensional diffusion and a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally represented as LiMe ₂ O ₄ (Me is at least one transition metal), and specifically LiMn ₂ O ₄ , LiCo MnO ₄ , LiNi _0.5 Mn _1.5 O. ₄ , LiCoVO _{4 and the} like can be mentioned. Those having a layered structure are generally represented as LiMeO ₂ (Me is at least one transition metal). Specifically, LiCoO ₂ , LiNiO ₂ , LiNi _1-x Co _x O ₂ , LiNi _1-x-y Co _x Mn _y O ₂ , LiNi _0.5 Mn _0.5 O ₂ , Li _1.2 Cr _{0. 4 Mn 0.4 O 2, Li 1.2} Cr 0.4 Ti 0.4 O 2, such as LiMnO ₂ and the like.

(composition)
Further, the lithium-containing transition metal compound may be, for example, a lithium transition metal compound represented by the following composition formula (A) or (B).
1) In the case of a lithium transition metal compound represented by the following composition formula (A) Li _{1 + x} MO ₂ ... (A)
However, x is usually 0 or more and 0.5 or less. M is an element composed of Ni and Mn, or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more and 5 or less. The Ni / M molar ratio is usually 0 or more and 0.5 or less. The Co / M molar ratio is usually 0 or more and 0.5 or less. The rich portion of Li represented by x may be replaced with the transition metal site M.

In the above composition formula (A), the atomic ratio of the amount of oxygen is described as 2 for convenience, but there may be some non-stoichiometric ratio. Further, x in the above composition formula is a charged composition at the production stage of the lithium transition metal compound. Batteries on the market are usually aged after the batteries are assembled. Therefore, the amount of Li in the positive electrode may be missing due to charging and discharging. In that case, in composition analysis, x when discharged to 3 V may be measured to be −0.65 or more and 1 or less.

Further, the lithium transition metal compound is excellent in battery characteristics when it is fired by high-temperature firing in an oxygen-containing gas atmosphere in order to enhance the crystallinity of the positive electrode active material.
Further, the lithium transition metal compound represented by the composition formula (A) may be a solid solution with Li ₂ MO ₃ called a 213 layer as shown in the general formula (A') below.
αLi ₂ MO ₃・ (1-α) LiM'O ₂ ... (A')
In the general formula, α is a number satisfying 0 <α <1.

M is at least one metallic element average oxidation number of 4 ^+, specifically, at least one metal element Mn, Zr, Ti, Ru, selected from the group consisting of Re and Pt.
M 'is at least one metallic element average oxidation number of 3 ^+, preferably, V, Mn, Fe, at least one metallic element selected from the group consisting of Co and Ni, more preferably , Mn, Co and Ni, at least one metal element selected from the group.

2) In the case of a lithium transition metal-based compound represented by the following general formula (B) Li [Li _a M _b Mn _2-ba-a ] O _{4 + δ} ... (B) However, M is Ni, Cr, It is an element composed of at least one of transition metals selected from Fe, Co, Cu, Zr, Al and Mg.
The value of b is usually 0.4 or more and 0.6 or less.

When the value of b is in this range, the energy density per unit weight of the lithium transition metal compound is high.
Further, the value of a is usually 0 or more and 0.3 or less. Further, a in the above composition formula is a charged composition at the production stage of the lithium transition metal compound. Batteries on the market are usually aged after the batteries are assembled. Therefore, the amount of Li in the positive electrode may be missing due to charging and discharging. In that case, in composition analysis, a when discharged to 3 V may be measured to be −0.65 or more and 1 or less.

When the value of a is in this range, the energy density per unit weight of the lithium transition metal compound is not significantly impaired, and good load characteristics can be obtained.
Further, the value of δ is usually in the range of ± 0.5.
When the value of δ is in this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode manufactured by using this lithium transition metal compound are good.

Here, the chemical meaning of the lithium composition in the lithium nickel-manganese-based composite oxide, which is the composition of the lithium transition metal-based compound, will be described in more detail below.
To determine the composition formulas a and b of the lithium transition metal compound, each transition metal and lithium are analyzed by an inductively coupled plasma emission spectrophotometer (ICP-AES) to determine the ratio of Li / Ni / Mn. It is calculated by.

From a structural point of view, it is considered that lithium related to a is replaced with the same transition metal site. Here, due to the lithium related to a, the average valence of M and manganese becomes larger than 3.5 valence due to the principle of charge neutrality.
Further, the lithium transition metal compound may be fluorine-substituted, and is described as LiMn ₂ O _4-x F _2x .

(blend)
Specific examples of the lithium transition metal-based compound having the above composition include, for example, Li _{1 + x} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + x} Ni _0.85 Co _0.10 Al _0.05 O ₂ , Li _{1 + x} Ni. _0.33 Mn _0.33 Co _0.33 O ₂ , Li _{1 + x} Ni _0.45 Mn _0.45 Co _0.1 O ₂ , Li _{1 + x} Mn _1.8 Al _0.2 O ₄ , Li _{1 + x} Mn _1.5 Examples include Ni _0.5 O _{4 and the} like. One of these lithium transition metal compounds may be used alone, or two or more thereof may be blended and used.

(Introduction of different elements)
Further, a foreign element may be introduced into the lithium transition metal compound. As different elements, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te , Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi , N, F, S, Cl, Br, I, As, Ge, P, Pb, Sb, Si and Sn are selected from any one or more. These different elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a simple substance or a compound on the particle surface or grain boundaries thereof. It may be unevenly distributed.

<Construction and manufacturing method of positive electrode for lithium secondary battery>
The positive electrode for a lithium secondary battery is formed by forming a positive electrode active material layer containing the above-mentioned lithium transition metal compound powder for a positive electrode material for a lithium secondary battery and a binder on a current collector.
For the positive electrode active material layer, is the positive electrode material, the binder, and the conductive material and the thickener used as needed mixed in a dry manner to form a sheet, which is then pressure-bonded to the positive electrode current collector? Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to a positive electrode current collector and dried.

As the material of the positive electrode current collector, a metal material such as aluminum, stainless steel, nickel plating, titanium, or tantalum, or a carbon material such as carbon cloth or carbon paper is usually used. As for the shape, in the case of metal material, metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foam metal, etc., and in the case of carbon material, carbon plate, carbon thin film, carbon column. And so on. The thin film may be formed in a mesh shape as appropriate.

When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but it is usually preferably in the range of 1 μm or more and 100 mm or less. If it is thinner than the above range, the strength required for the current collector may be insufficient, while if it is thicker than the above range, the handleability may be impaired.
The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that is stable to the liquid medium used in the production of the electrode may be used. Resin-based polymers such as polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, ethylene -Rubber polymer such as propylene rubber, styrene-butadiene-styrene block copolymer and its hydrogen additive, EPDM (ethylene-propylene-diene ternary copolymer), styrene-ethylene-butadiene-ethylene copolymer, Thermoplastic elastomeric polymers such as styrene / isoprene styrene block copolymer and its hydrogenated additives, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin Soft resinous polymers such as polymers, fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, and alkali metal ions (particularly lithium ions) Examples thereof include a polymer composition having ionic conductivity. In addition, as these substances, 1 type may be used alone, and 2 or more types may be used together in arbitrary combinations and ratios.

The proportion of the binder in the positive electrode active material layer is usually 0.1% by mass or more and 80% by mass or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained and the mechanical strength of the positive electrode may be insufficient, which may deteriorate the battery performance such as cycle characteristics. On the other hand, if it is too high, It may lead to a decrease in battery capacity and conductivity.
The positive electrode active material layer usually contains a conductive material in order to increase conductivity. The type is not particularly limited, but specific examples include metallic materials such as copper and nickel, graphite such as natural graphite and artificial graphite (graphite), carbon black such as acetylene black, and amorphous carbon such as needle coke. Carbon material can be mentioned. In addition, as these substances, 1 type may be used alone, and 2 or more types may be used together in arbitrary combinations and ratios. The ratio of the conductive material in the positive electrode active material layer is usually 0.01% by mass or more and 50% by mass or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and conversely, if it is too high, the battery capacity may decrease.

As the liquid medium for forming the slurry, a lithium transition metal compound powder as a positive electrode material, a binder, and a conductive material and a thickener used as needed can be dissolved or dispersed. As long as it is a solvent, the type thereof is not particularly limited, and either an aqueous solvent or an organic solvent may be used. Examples of aqueous solvents include water and alcohol, and examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N. , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to. In particular, when an aqueous solvent is used, a dispersant is added together with the thickener, and a latex such as SBR is used to make a slurry. In addition, as these solvents, 1 type may be used alone, and 2 or more types may be used together in arbitrary combinations and ratios.

The content ratio of the lithium transition metal compound powder as the positive electrode material in the positive electrode active material layer is usually 10% by mass or more and 99.9% by mass or less. If the proportion of the lithium transition metal compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.
The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

The electrode density of the positive electrode after pressing is usually 2.2 g / cm ³ or more and 4.2 g / cm ³ or less.
The positive electrode active material layer obtained by coating and drying is preferably compacted by a roller press or the like in order to increase the packing density of the positive electrode active material.

[4. Separator]
A separator is usually interposed between the positive electrode and the negative electrode to prevent a short circuit. In this case, the non-aqueous electrolyte solution of the present invention is usually used by impregnating this separator.
The material and shape of the separator are not particularly limited, and any known separator can be used as long as the effects of the present invention are not significantly impaired. Among them, resins, glass fibers, inorganic substances and the like formed of a material stable to the non-aqueous electrolytic solution of the present invention are used, and a porous sheet or a non-woven fabric-like material having excellent liquid retention property is used. Is preferable.

As the material of the resin and the glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyether sulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferable, and polyolefins are more preferable. One of these materials may be used alone, or two or more of these materials may be used in any combination and ratio.

The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, further preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, further preferably 30 μm or less. If the separator is too thin than the above range, the insulating property and mechanical strength may decrease. Further, if it is too thick than the above range, not only the battery performance such as rate characteristics may be deteriorated, but also the energy density of the non-aqueous electrolyte secondary battery as a whole may be lowered.

Further, when a porous material such as a porous sheet or a non-woven fabric is used as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, still more preferably 45% or more. Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too small than the above range, the film resistance tends to increase and the rate characteristics tend to deteriorate. On the other hand, if it is larger than the above range, the mechanical strength of the separator tends to decrease and the insulating property tends to decrease.

The average pore size of the separator is also arbitrary, but is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. If the average pore diameter exceeds the above range, a short circuit is likely to occur. Further, if it falls below the above range, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used, and those having a particle shape or a fiber shape are used. Used.

As the form, a thin film such as a non-woven fabric, a woven cloth, or a microporous film is used. As the thin film shape, a thin film having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the above-mentioned independent thin film shape, a separator obtained by forming a composite porous layer containing the above-mentioned inorganic particles on the surface layer of the positive electrode and / or the negative electrode by using a resin binder can be used. For example, alumina particles having a 90% particle size of less than 1 μm are formed on both sides of the positive electrode by using a fluororesin as a binder to form a porous layer.

The characteristics of the separator in the non-electrolyte liquid secondary battery can be grasped by the galley value. The gullet value indicates the difficulty of passing air in the film thickness direction, and is represented by the number of seconds required for 100 ml of air to pass through the film. Therefore, the smaller the value, the easier it is to pass through, and the larger the value. It means that it is harder to pass through. That is, the smaller the value, the better the communication in the thickness direction of the film, and the larger the value, the poorer the communication in the thickness direction of the film. The communication property is the degree of connection of holes in the film thickness direction. If the galley value of the separator of the present invention is low, it can be used for various purposes. For example, when used as a separator for a non-aqueous lithium secondary battery, a low galley value means that lithium ions can be easily transferred, which is preferable because the battery performance is excellent. The galley value of the separator is arbitrary, but is preferably 10 to 1000 seconds / 100 ml, more preferably 15 to 800 seconds / 100 ml, and even more preferably 20 to 500 seconds / 100 ml. When the galley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.

[5. Battery design]
<Electrode group>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are formed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are spirally wound through the separator. Either may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. ..

When the electrode group occupancy rate is less than the above range, the battery capacity becomes small. Further, if it exceeds the above range, the void space is small, and the internal pressure rises due to the expansion of the member due to the high temperature of the battery and the increase of the vapor pressure of the liquid component of the electrolyte, and the charge / discharge repetition performance as a battery. In some cases, various characteristics such as high temperature storage may be deteriorated, and a gas discharge valve that releases internal pressure to the outside may operate.

<Exterior case>
The material of the outer case is not particularly limited as long as it is a substance stable to the non-aqueous electrolyte solution used. Specifically, nickel-plated steel plates, stainless steel, aluminum or aluminum alloys, metals such as magnesium alloys, or laminated films (laminated films) of resin and aluminum foil are used. From the viewpoint of weight reduction, aluminum or aluminum alloy metal or laminated film is preferably used.

In the outer case using metals, the metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed and sealed structure, or the above metals are used to form a caulking structure via a resin gasket. Things can be mentioned. Examples of the outer case using the above-mentioned laminated film include a case in which resin layers are heat-sealed to form a sealed and sealed structure. In order to improve the sealing property, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when the resin layer is heat-sealed via the current collector terminal to form a closed structure, the metal and the resin are bonded to each other. Therefore, a resin having a polar group or a modification in which a polar group is introduced as an intervening resin is introduced. Resin is preferably used.

<Protective element>
As a protective element, PTC (Positive Temperature Coafficient), which increases resistance when abnormal heat generation or excessive current flows, a thermal fuse, thermistor, and cuts off the current flowing in the circuit due to a sudden rise in battery internal pressure or internal temperature during abnormal heat generation. A valve (current cutoff valve) or the like can be used. It is preferable to select the protective element under conditions that do not operate under normal use with a high current, and it is more preferable to design the protective element so as not to cause abnormal heat generation or thermal runaway even without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually configured by accommodating the above-mentioned non-aqueous electrolyte, negative electrode, positive electrode, separator and the like inside the exterior. As the exterior body is not particularly limited, known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.
The shape of the exterior body is also arbitrary, and may be any of, for example, a cylindrical type, a square type, a laminated type, a coin type, and a large size.

<Battery voltage>
The non-aqueous electrolyte secondary battery of the present invention is usually used at a battery voltage of 4.3 V or higher. The battery voltage is preferably 4.3 V or higher, more preferably 4.35 V or higher, and most preferably 4.4 V or higher. This is because the energy density of the battery can be increased by increasing the battery voltage. On the other hand, when the battery voltage is increased, the potential of the positive electrode is increased, which causes a problem that side reactions on the surface of the positive electrode are increased. The above problem can be solved by using the electrolytic solution and the battery of the present invention, but if the voltage is too high, the amount of side reaction on the positive electrode surface becomes too large and the battery characteristics are deteriorated. Therefore, the upper limit of the battery voltage is preferably 5 V or less, more preferably 4.8 V or less, and most preferably 4.6 V or less.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded.

<Preparation of non-aqueous electrolyte solution>
In a dry argon atmosphere, with respect to a non-aqueous solvent in which ethylene carbonate (hereinafter EC), ethyl methyl carbonate (hereinafter EMC) and diethyl carbonate (hereinafter DEC) are mixed at 30% by volume, 40% by volume and 30% by volume, respectively. , LiPF ₆ was dissolved to 1.2M. To this, 2% by mass of vinylene carbonate was added to prepare a non-aqueous electrolyte solution.

[Examples 1-1 to 1-2, Comparative Examples 1-1 to 1-4]
A non-aqueous electrolyte solution was prepared by adding a predetermined amount of bismaleimide and / or other compounds as an additive to the non-aqueous electrolyte solution under a dry argon atmosphere. The types and amounts of additives used are as shown in Table 1.

<Manufacturing of negative electrode>
To 98 parts by mass of graphite powder as a negative electrode active material, 1 part by mass of an aqueous dispersion of sodium carboxymethyl cellulose and 1 part by mass of an aqueous dispersion of styrene-butadiene rubber were added as a thickener and a binder, respectively, and mixed with a disperser. And made into a slurry. The obtained slurry was applied to one side of a copper foil, dried and pressed to prepare a negative electrode. The prepared negative electrode was dried under reduced pressure at 60 ° C. for 12 hours before use.

<Preparation of positive electrode>
To 96.8 parts by mass of lithium cobalt oxide as a positive electrode active material, 1.6 parts by mass of a conductive additive and 1.6 parts by mass of a binder (pVDF) were added and mixed with a disperser to form a slurry. The obtained slurry was applied to both sides of the aluminum foil, dried and pressed to prepare a positive electrode. The prepared positive electrode was dried under reduced pressure at 80 ° C. for 12 hours before use.

<Battery production>
The above positive electrode, negative electrode, and polyethylene separator were laminated in this order of negative electrode, separator, positive electrode, separator, and negative electrode to prepare a battery element. After inserting this battery element into a bag made of a laminated film in which both sides of aluminum (thickness 40 μm) are coated with a resin layer while projecting positive and negative electrode terminals, 0.4 mL of non-aqueous electrolyte solution is placed in the bag. It was injected and vacuum-sealed to prepare a sheet-shaped battery. Further, in order to improve the adhesion between the electrodes, a sheet-shaped battery was sandwiched between glass plates and pressurized.

<Characteristic evaluation test 1>
Test 1.60 ° C. High temperature storage test The battery prepared as described above was charged to 4.4 V at 25 ° C., discharged to 3 V, and conditioned until the capacity became stable. Then, the battery charged to 4.4 V was left for 10 days in an environment of 60 ° C. At this time, the recovery capacity rate (%) and the voltage drop rate (%) were measured. The capacity before the test is defined as the capacity when the battery is discharged to 3 V at 0.2 C at 25 ° C. after the test, then recharged to 4.4 V and then discharged to 3 V at 0.2 C again. The ratio of the recovery capacity to the recovery capacity is defined as the recovery capacity ratio. Further, the difference between the voltage before the test and the voltage after the test is defined as the voltage drop, and the ratio to the voltage drop in Comparative Example 1-1 is defined as the voltage drop rate (the smaller the value, the better).

From the results in Table 1, the following can be seen. The voltage drop rate increased in Comparative Example 1-2 containing only "other compounds" as opposed to Comparative Example 1-1 which did not contain bismaleimide and "other compounds" specified in the present invention. Further, Comparative Example 1-3 containing only bismaleimide.
In 1 and 1-4, the voltage drop rate and the recovery capacity rate were improved to some extent, but the effect was limited. On the other hand, when Examples 1-1 and 1-2 using the electrolytic solution of the present invention were used, both the voltage drop rate and the recovery capacity rate had a large improvement effect.

<Preparation of non-aqueous electrolyte solution>
In a dry argon atmosphere, with respect to a non-aqueous solvent in which ethylene carbonate (hereinafter EC), ethyl methyl carbonate (hereinafter EMC) and diethyl carbonate (hereinafter DEC) are mixed at 30% by volume, 40% by volume and 30% by volume, respectively. , LiPF ₆ was dissolved to 1.2M. To this, 2% by mass of vinylene carbonate was added to prepare a non-aqueous electrolyte solution.

[Example 2-1 to Example 2-3, Comparative Example 2-1 to Comparative Example 2-4]
A non-aqueous electrolyte solution was prepared by adding a predetermined amount of bismaleimide and / or other compounds as an additive to the non-aqueous electrolyte solution under a dry argon atmosphere. The types and amounts of additives used are as shown in Table 2.
<Manufacturing of negative electrode, positive electrode, battery>
The same electrodes as those used in Example 1-1 were used.

<Characteristic evaluation test 2>
Test 2. Continuous Charge Test The battery prepared as described above was charged to 4.4 V at 25 ° C., discharged to 3 V, and conditioned until the capacity became stable. Then, the battery charged to 4.4 V was charged in an environment of 60 ° C. for 14 days so as to keep it at 4.4 V (continuous charging). The recovery capacity rate (%) at this time was measured. The capacity before the test is defined as the capacity when the battery is discharged to 3 V at 0.2 C at 25 ° C. after the test, then recharged to 4.4 V and then discharged to 3 V at 0.2 C again. The ratio of the recovery capacity to the recovery capacity is defined as the recovery capacity ratio.

From the results in Table 2, the following can be seen. Compared with Comparative Example 2-1 which does not contain bismaleimide and "other compounds" specified in the present invention, Comparative Example 2-2 containing only "other compounds" improved the residual / recovery volume ratio. The effect was small. On the other hand, when Examples 2-1 to 2-3 using the electrolytic solution of the present invention were used, the effect of improving the residual / recovery volume ratio was large. Here, since the residual / recovery volume ratio was not improved in Comparative Examples 2-3 and 2-4 containing only bismaleimide, it was found that the electrolytic solution of the present invention had a specific effect.

<Preparation of non-aqueous electrolyte solution>
In a dry argon atmosphere, with respect to a non-aqueous solvent in which ethylene carbonate (hereinafter EC), ethyl methyl carbonate (hereinafter EMC) and diethyl carbonate (hereinafter DEC) are mixed at 30% by volume, 40% by volume and 30% by volume, respectively. , LiPF ₆ was dissolved to 1.2M. To this, 2% by mass of vinylene carbonate was added to prepare a non-aqueous electrolyte solution.

[Examples 3-1 to 3-3, Comparative Examples 3-1 to 3-5]
A non-aqueous electrolyte solution was prepared by adding a predetermined amount of bismaleimide and / or other compounds as an additive to the non-aqueous electrolyte solution under a dry argon atmosphere. The types and amounts of additives used are as shown in Table 3.
<Manufacturing of negative electrode, positive electrode, battery>
The same electrodes as those used in Example 1-1 were used.

<Characteristic evaluation test 2>
Test 3.80 ° C. High temperature charging test The battery prepared as described above was charged to 4.4V at 25 ° C., discharged to 3V, and conditioned until the capacity became stable. Then, the battery charged to 4.4 V was left in an environment of 80 ° C. for 3 days. The voltage drop rate (%) at this time was measured. The difference between the voltage before the test and the voltage after the test is defined as the voltage drop, and the ratio to the voltage drop in Comparative Example 3-1 is defined as the voltage drop rate (the smaller the value, the better).

From the results in Table 3, the following can be seen. The voltage drop rate deteriorated in Comparative Example 3-2 containing only "other compounds", as opposed to Comparative Example 3-1 containing no bismaleimide and "other compounds" specified in the present invention. Further, in Comparative Example 3-3, Comparative Example 3-4, and Comparative Example 3-5 containing only bismaleimide, the voltage drop rate was improved, but the effect was limited. On the other hand, when Example 3-1, Example 3-2, and Example 3-3 using the electrolytic solution of the present invention were used, the effect of improving the voltage drop rate was large.

According to the non-aqueous electrolyte solution of the present invention, the decomposition of the electrolyte solution of the non-aqueous electrolyte secondary battery is suppressed, the decrease in the battery voltage when the battery is used in a high temperature environment is suppressed, and the recovery capacity rate is improved. It is possible to manufacture a non-aqueous electrolyte secondary battery having a high energy density and an improved residual / recovery charge rate during continuous charging. Therefore, it can be suitably used in various fields such as electronic devices in which a non-aqueous electrolyte secondary battery is used.

The application of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and it can be used in various known applications. Specific examples include laptops, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copies, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, mini disks, transceivers. , Electronic notebook, calculator, memory card, portable tape recorder, radio, backup power supply, motor, car, bike, motorized bicycle, bicycle, lighting equipment, toys, game equipment, clock, power tool, strobe, camera, large household Examples include storage batteries and lithium ion capacitors.

Claims (6)

A non-aqueous electrolyte solution having a positive electrode having a positive electrode active material capable of occluding / releasing metal ions and a negative electrode having a negative electrode active material capable of occluding / releasing metal ions A non-aqueous electrolyte solution used in a secondary battery. ,
The non-aqueous electrolyte solution contains a bismaleimide compound in an amount of 0.01% by mass or more and 3% by mass or less.
In addition, it contains 0.01% by mass or more and 10% by mass or less of fluoroethylene carbonate.
A non-aqueous electrolyte solution, wherein the bismaleimide compound is a compound of the following formula (4).

(In the formula, R ^{13 to} R ²² independently represent a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms.) The non-aqueous electrolysis according to claim 1, wherein the bismaleimide compound is the following compound 4-0, compound 4-1, compound 4-2, compound 4-8, compound 4-10, or compound 4-11. liquid.

The non-aqueous electrolyte solution according to claim 1 or 2, wherein the water content in the non-aqueous electrolyte solution is 40 ppm or less. Further, the nitrile compound is contained in an amount of 0.01% by mass or more and 4% by mass or less, and the nitrile compound is valeronitrile, octanenitrile, lauronitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronitrile, suberonitrile, or 3,9-. The non-aqueous electrolyte solution according to any one of claims 1 to 3, which is a bis (2-cyanoethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane. The non-aqueous electrolyte solution according to claim 4, wherein the nitrile compound is adiponitrile. A non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of occluding / releasing metal ions, a negative electrode having a negative electrode active material capable of occluding / releasing metal ions, and a non-aqueous electrolyte solution.
A non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the non-aqueous electrolyte secondary battery is used.