JP7504675B2 - Non-aqueous electrolyte and non-aqueous electrolyte battery using the same - Google Patents

Description

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

2. Description of the Related Art With the rapid advancement of portable electronic devices such as mobile phones and notebook personal computers, there is an increasing demand for higher capacity batteries used as their main power sources or backup power sources. As a result, non-aqueous electrolyte batteries such as lithium-ion secondary batteries, which have a higher energy density than nickel-cadmium batteries and nickel-metal hydride batteries, are attracting attention.
_{Representative examples of the electrolyte for lithium ion secondary batteries include non-aqueous electrolytes in which electrolytes such as LiPF6, LiBF4, LiN(CF3SO2)2, and LiCF3(CF2)3SO3 are dissolved in a mixed solvent of} a high dielectric constant solvent such as ethylene carbonate or propylene carbonate, and a low viscosity solvent such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.

The negative electrode active material used in lithium ion secondary batteries is mainly a carbonaceous material capable of absorbing and releasing lithium ions, with representative examples including natural graphite, artificial graphite, and amorphous carbon. Furthermore, metal or alloy-based negative electrodes using silicon, tin, and the like, with the aim of achieving higher capacity, are also known. The positive electrode active material is mainly a transition metal composite oxide capable of absorbing and releasing lithium ions, with representative examples of transition metals including cobalt, nickel, manganese, and iron.

In non-aqueous electrolyte secondary batteries using such non-aqueous electrolytes, the reactivity differs depending on the composition of the non-aqueous electrolyte, and the battery characteristics change significantly depending on the non-aqueous electrolyte. Various studies have been conducted on non-aqueous solvents and electrolytes to improve the battery characteristics such as storage characteristics of non-aqueous electrolyte secondary batteries and to increase the safety of the battery during overcharging.

Patent Document 1 studies how to improve the discharge capacity retention rate after high-temperature continuous charging in a lithium battery comprising a positive electrode using lithium cobalt oxide as an active material, a negative electrode using silicon as an active material, and a non-aqueous electrolyte by incorporating halogenated ethylene carbonate and a specific phosphate ester in the electrolyte.
In Patent Document 2, in a lithium battery comprising a positive electrode using lithium cobalt oxide as an active material, a negative electrode using carbon or silicon as an active material, and a non-aqueous electrolyte, a study is conducted on improving swelling of the battery during high-temperature storage by adding a compound having a sulfone structure to the electrolyte together with a phosphoric acid ester.

JP 2007-115583 A JP 2008-41635 A

However, in recent years, there has been an increasing demand for improved performance in lithium non-aqueous electrolyte batteries, and although there is a demand for batteries to have high levels of performance in all areas, including high-temperature storage characteristics, energy density, output characteristics, life span, high-speed charge/discharge characteristics, and low-temperature characteristics, this has not yet been achieved. In particular, there are issues such as a decrease in rate characteristics due to high density, high negative electrode resistance after high-temperature storage tests, and a decrease in power capacity after high-temperature storage.

Patent Document 1 discloses that the use of an electrolyte solution containing a specific phosphate ester such as triphenyl phosphate and a halogenated ethylene carbonate such as fluoroethylene carbonate improves the discharge capacity after a cycle test. However, even when these specific halogenated ethylene carbonate and phosphate ester compounds are combined, there is still room for improvement in the rate characteristics and the negative electrode resistance at low temperatures after high-temperature storage.
Patent Document 2 discloses that the swelling of a battery during high-temperature storage can be improved by using an electrolyte solution containing a specific phosphate ester and a compound having a sulfone structure. However, even when this electrolyte solution is used, there is still room for improvement in the rate characteristics, the negative electrode resistance at low temperatures after high-temperature storage, and the decrease in power capacity after high-temperature storage.

The present invention has been made in consideration of the above-mentioned problems. That is, the objective of the present invention is to provide a nonaqueous electrolyte and a nonaqueous electrolyte battery that can improve the rate characteristics and the increase in negative electrode resistance at low temperatures after high-temperature storage in a nonaqueous electrolyte battery.

After extensive research, the inventors of the present invention discovered that the above problems could be solved by adding a specific compound to the electrolyte, which led to the completion of the present invention.

（式（Ａ）中、Ｒ^１～Ｒ^５のすべてが水素原子である。）
（ｂ）前記炭素数４以下の鎖状カルボン酸エステルは酢酸メチルであることを特徴とする（ａ）に記載の非水系電解液。
（ｃ）前記式（Ａ）で表される化合物の濃度が、非水系電解液の全量に対して０．００１質量％以上５質量％以下である、（ａ）又は（ｂ）に記載の非水系電解液。
（ｄ）前記炭素数４以下の鎖状カルボン酸エステルの含有量が、非水系電解液の溶媒全量に対して５体積％以上９０体積％以下である、（ａ）～（ｃ）のいずれかに記載の非水系電解液。
（ｅ）更に、炭素－炭素不飽和結合を有する環状カーボネートおよびフッ素原子を有する環状カーボネートからなる群より選ばれる１種以上の化合物を含有することを特徴とする（ａ）～（ｄ）のいずれかに記載の非水系電解液。
（ｆ）前記、炭素－炭素不飽和結合を有する環状カーボネートおよびフッ素原子を有する環状カーボネートからなる群より選ばれる１種以上の化合物の総含有量が、非水系電解液の全量に対して０．００１質量％以上５質量％以下である、（ｅ）に記載の非水系電解液。
（ｇ）リチウムイオンを吸蔵及び放出可能な正極と、リチウムイオンを吸蔵及び放出可能
な負極と、非水系電解液とを備えた非水系電解液電池であって、該非水系電解液が、（ａ）～（ｆ）のいずれかに記載の非水系電解液であることを特徴とする非水系電解液電池。 The gist of the present invention is as follows.
(a) A nonaqueous electrolyte solution for a nonaqueous electrolyte battery having a positive electrode and a negative electrode capable of absorbing and releasing metal ions, the nonaqueous electrolyte solution containing, together with an alkali metal salt and a nonaqueous solvent, (1) a compound represented by the following formula (A), and (2) a chain carboxylate ester having 4 or less carbon atoms:

(In formula (A), all of R ¹ to R ⁵ are hydrogen atoms.)
(b) The nonaqueous electrolyte according to (a), wherein the chain carboxylate having 4 or less carbon atoms is methyl acetate.
(c) The nonaqueous electrolyte solution according to (a) or (b), wherein the concentration of the compound represented by formula (A) is 0.001% by mass or more and 5% by mass or less with respect to the total amount of the nonaqueous electrolyte solution.
(d) The nonaqueous electrolyte solution according to any one of (a) to (c), wherein the content of the chain carboxylate having 4 or less carbon atoms is 5 vol % or more and 90 vol % or less with respect to the total amount of the solvent in the nonaqueous electrolyte solution.
(e) The nonaqueous electrolyte solution according to any one of (a) to (d), further comprising one or more compounds selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and cyclic carbonates having a fluorine atom.
(f) The nonaqueous electrolyte solution according to (e), wherein the total content of the one or more compounds selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and cyclic carbonates having a fluorine atom is 0.001% by mass or more and 5% by mass or less with respect to the total amount of the nonaqueous electrolyte solution.
(g) A nonaqueous electrolyte battery comprising a positive electrode capable of absorbing and releasing lithium ions, a negative electrode capable of absorbing and releasing lithium ions, and a nonaqueous electrolyte, wherein the nonaqueous electrolyte is the nonaqueous electrolyte according to any one of (a) to (f).

According to the present invention, it is possible to provide a nonaqueous electrolyte battery that realizes a battery having excellent rate characteristics and suppression of an increase in negative electrode resistance at low temperatures after high-temperature storage, and a nonaqueous electrolyte battery that uses the nonaqueous electrolyte.
Furthermore, the nonaqueous electrolyte according to one embodiment of the present invention can improve the rate characteristics, open circuit voltage after high-temperature storage, capacity retention rate, and negative electrode resistance at low temperatures of a nonaqueous electrolyte battery.
The action and principle by which a nonaqueous electrolyte battery produced using the nonaqueous electrolyte of the present invention and the nonaqueous electrolyte battery of the present invention become a secondary battery improved in terms of rate characteristics, open circuit voltage after high-temperature storage (hereinafter sometimes referred to as OCV), capacity retention rate, and negative electrode resistance at low temperatures is not clear, but is thought to be as follows. However, the present invention is not limited to the action and principle described below.

A chain carboxylate having 4 or less carbon atoms has a low viscosity and a high dielectric constant compared to a chain carbonate. Therefore, an electrolyte containing a chain carboxylate having 4 or less carbon atoms can realize a battery having excellent lithium ion conductivity and rate characteristics compared to a conventional electrolyte containing only a chain carbonate. However, since a chain carboxylate having 4 or less carbon atoms has a lower oxidation resistance than a chain carbonate, it is continuously decomposed on the positive electrode surface by charging and discharging or high-temperature storage, and therefore the OCV and remaining capacity of the battery after high-temperature storage are reduced. At the same time, it alters the positive electrode surface, increasing the resistance of the positive electrode. As a result, the rate characteristics of the battery are reduced. In addition, the components oxidized and decomposed by the chain carboxylate having 4 or less carbon atoms at the positive electrode diffuse in the electrolyte and reach the negative electrode surface. The oxidized and decomposed components that reach the negative electrode surface cause reductive decomposition on the negative electrode surface, increasing the resistance of the negative electrode. In a negative electrode with increased resistance, the acceptance of lithium ions at low temperatures is reduced, and lithium electrodeposition and the like are more likely to occur.
The compound represented by formula (A) has an aromatic ring, which is an easily oxidizable site, in the molecule. Therefore, the above site undergoes an oxidation reaction on the positive electrode, and the compound represented by formula (A) generates a cation on the aromatic ring when it is oxidized and decomposed. The cation quickly reacts with the chain carboxylate ester having 4 or less carbon atoms to form a protective film on the surface of the positive electrode, suppressing the continuous oxidative decomposition of the chain carboxylate ester having 4 or less carbon atoms on the surface of the positive electrode. Therefore, it is possible to suppress the decrease in OCV after high-temperature storage of the battery and improve the decrease in remaining capacity. At the same time, it is estimated that the rate characteristics are improved because the deterioration of the positive electrode surface can be suppressed. In addition, it is estimated that the suppression of the continuous decomposition of the chain carboxylate ester having 4 or less carbon atoms at the positive electrode reduces the oxidative decomposition components that go around to the negative electrode, and the increase in the negative electrode resistance at low temperatures after high-temperature storage of the battery is suppressed. It is estimated that when R ¹ to R ⁵ of the compound represented by formula (A) are other than hydrogen atoms, that is, when the compound has a substituent on the aromatic ring, the substituent is oxidized and no cation is generated on the aromatic ring, so that the desired reaction does not occur.

The following describes an embodiment of the present invention, but the present invention is not limited to the following embodiment and can be modified in any manner without departing from the gist of the present invention.
In addition, "wt%", "ppm by weight", and "parts by weight" are synonymous with "% by mass", "ppm by mass", and "parts by mass", respectively. In addition, when simply written as "ppm", it means "ppm by mass".

1. Nonaqueous Electrolyte Solution 1-1. Nonaqueous Electrolyte Solution of the Present Invention The nonaqueous electrolyte solution of the present invention is characterized by containing, in addition to an alkali metal salt and a nonaqueous solvent, (1) a compound represented by the following formula (A), and (2) a chain carboxylate ester having 4 or less carbon atoms:

1-1-1. Compound represented by formula (A)

(In formula (A), all of R ¹ to R ⁵ are hydrogen atoms.)

In the present invention, a compound represented by formula (A) is used, specifically a compound having the following structure: This is because the steric hindrance of the aromatic ring is small, and the reaction with a chain carboxylate having 4 or less carbon atoms proceeds favorably.

There is no limit to the concentration of the compound represented by formula (A) relative to the total amount of the nonaqueous electrolyte of the present invention, and it can be any concentration as long as it does not significantly impair the effects of the present invention. However, it is usually 0.001 mass% or more, preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.1 mass% or more, and particularly preferably 0.3 mass% or more, relative to the total amount of the nonaqueous electrolyte of the present invention, and is usually 5.0 mass% or less, preferably 4.5 mass% or less, more preferably 4.0 mass% or less, even more preferably 3.5 mass% or less, and particularly preferably 3.0 mass% or less. If the concentration is within the above range, the reactivity of the compound represented by formula (A) on the electrode and the reactivity with base components such as reduction products of the electrolyte generated on the electrode can be adjusted to a preferred range, making it possible to optimize the battery characteristics.

In addition, when the concentration of the compound represented by formula (A) falls within the above range, the effects of high temperature properties, etc. are further improved.

The method of blending the compound represented by formula (A) in the electrolyte of the present invention is not particularly limited. In addition to the method of directly adding the compound to the electrolyte, there is a method of generating the compound in a battery or in the electrolyte. Examples of the method of generating the compound include a method of adding a compound other than this compound and generating the compound by oxidizing, reducing, or hydrolyzing a battery component such as the electrolyte. Furthermore, there is also a method of generating the compound by producing a battery and applying an electrical load such as charging and discharging.

1-1-2. Chain carboxylate esters having 4 or less carbon atoms Examples of chain carboxylate esters having 4 or less carbon atoms include methyl acetate, ethyl acetate, and methyl propionate. Among these, methyl acetate is more preferable from the viewpoint of improving the diffusion of substances by reducing the viscosity.

The content of the chain carboxylate ester having 4 or less carbon atoms is usually preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 15% by volume or more, and particularly preferably 20% by volume or more, based on the total amount of the solvent in the nonaqueous electrolyte (100% by volume). By setting the lower limit in this way, the diffusion of metal ions such as lithium ions in the nonaqueous electrolyte is improved, and the performance of the nonaqueous electrolyte battery can be easily improved so that it can be safely disposed of. In addition, the content of the chain carboxylate ester is preferably 90% by volume or less, more preferably 80% by volume or less, even more preferably 70% by volume or less, and particularly preferably 60% by volume or less, based on the total amount of the solvent in the nonaqueous electrolyte (100% by volume). By setting the upper limit in this way, the amount of polymerizable compounds that hinder the diffusion of substances can be suppressed, and the nonaqueous electrolyte battery can be safely disposed of.
The chain carboxylate ester having 4 or less carbon atoms may be used alone or in any combination and ratio of two or more. When two or more chain carboxylate esters having 4 or less carbon atoms are used in combination, the total amount of the chain carboxylate esters having 4 or less carbon atoms should be within the above range.

1-2. Electrolytes <alkali metal salts>
As the electrolyte in the non-aqueous electrolyte solution, an alkali metal salt is used, and usually a lithium salt is used. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used, and specifically, the following can be mentioned.

These include lithium fluoroborates, lithium fluorophosphates, lithium tungstates, lithium carboxylates, lithium sulfonates, lithium imide salts, lithium methide salts, lithium oxalate salts, and fluorine-containing organic lithium salts.

Among them, the lithium fluoroborate salts include LiBF ₄ ; the lithium fluorophosphate salts include LiPF _6, Li ₂ PO ₃ F, and LiPO ₂ F ₂ ; the lithium sulfonate salts include LiFSO ₃ and CH ₃ SO ₃ Li; the lithium imide salts include LiN(FSO ₂ ) ₂ , LiN(FSO ₂ )(CF ₃ SO ₂ ), LiN(CF ₃ SO ₂ ) ₂ , and LiN(C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethane disulfonylimide, and lithium cyclic 1,3-perfluoropropane disulfonylimide; and the lithium methide salts include LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) ₃ , and LiC(C ₂ F ₅ SO ₂ ) ₃ ; as the lithium oxalate salts, lithium difluorooxalatoborate, lithium bis(oxalato)borate, lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, lithium tris(oxalato)phosphate, etc. are more preferred because they have the effect of improving low-temperature output characteristics, high-rate charge/discharge characteristics, impedance characteristics, high-temperature storage characteristics, cycle characteristics, etc. More preferred are _LiPF6 , LiN( _FSO2 ) ₂ , lithium bis(oxalato)borate, and _LiFSO3 , and particularly preferred is _LiPF6 . The above lithium salts may be used alone or in combination of two or more.

Preferred examples of the combination of two or more of these lithium salts include _LiPF6 and LiN( _FSO2 ) ₂ , _LiPF6 and _LiBF4 , LiPF6 and LiN( _CF3SO2 )2, and _LiPF6 and LiN( _CF3SO2 ) ₂ .
Examples of the combination include _iBF4 and LiN( _FSO2 ) ₂ , and _LiBF4 , _LiPF6 , and LiN( _FSO2 ) ₂ . Among these, the combination of _LiPF6 and LiN( _FSO2 ) ₂ , _LiPF6 and LiBF4, _{LiBF4 , LiPF6} , and LiN( _FSO2 ) ₂ is preferable, and has the effect of improving the load characteristics and cycle characteristics.

The concentration of these lithium salts in the nonaqueous electrolyte is not particularly limited as long as the effects of the present invention are not impaired; however, from the viewpoint of keeping the electrical conductivity of the electrolyte in a good range and ensuring good battery performance, the total molar concentration of lithium in the nonaqueous electrolyte is preferably 0.3 mol/L or more, more preferably 0.4 mol/L or more, even more preferably 0.5 mol/L or more, and is preferably 3 mol/L or less, more preferably 2.5 mol/L or less, even more preferably 2.0 mol/L or less.
When the total molar concentration of lithium is within the above range, the electrical conductivity of the electrolyte becomes sufficient, and a decrease in electrical conductivity due to an increase in viscosity and a resulting decrease in battery performance are prevented.

1-3. Nonaqueous Solvent There is no particular limitation on the nonaqueous solvent in the present invention, and known organic solvents can be used. Examples of these include fluorine atom-free cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates having 5 or more carbon atoms, ether compounds, and sulfone compounds. There is no particular limitation on the combination of two or more organic solvents, and examples thereof include fluorine atom-free cyclic carbonates and chain carboxylates having 5 or more carbon atoms, cyclic carboxylates and chain carbonates, and fluorine atom-free cyclic carbonates, chain carbonates and chain carboxylates having 5 or more carbon atoms. Among these, fluorine atom-free cyclic carbonates and chain carbonates, and saturated cyclic carbonates, chain carbonates and chain carboxylates having 5 or more carbon atoms are preferred.

<Fluorine-free cyclic carbonate>
Examples of cyclic carbonates not containing fluorine atoms include cyclic carbonates having an alkylene group having 2 to 4 carbon atoms.
Specific examples of fluorine-free cyclic carbonates having an alkylene group with 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are particularly preferred from the viewpoint of improving battery characteristics due to the improvement in the degree of dissociation of lithium ions.

The fluorine-free cyclic carbonate may be used alone or in any combination of two or more kinds in any ratio.
The amount of the cyclic carbonate having no fluorine atom is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention, but is usually 3% by volume or more, preferably 5% by volume or more, and more preferably 10% by volume or more in 100% by volume of the nonaqueous solvent. By setting it in this range, the decrease in electrical conductivity due to the decrease in the dielectric constant of the nonaqueous electrolyte can be avoided, and the large current discharge characteristics, stability to the negative electrode, and cycle characteristics of the nonaqueous electrolyte battery can be easily set in a good range. In addition, it is 95% by volume or less, more preferably 90% by volume or less, even more preferably 85% by volume or less, and particularly preferably 80% by volume or less. By setting it in this range, the viscosity of the nonaqueous electrolyte can be set in an appropriate range, the decrease in ion conductivity can be suppressed, and the load characteristics of the nonaqueous electrolyte battery can be easily set in a good range.

<Chain carbonate>
As the chain carbonate, a chain carbonate having 3 to 7 carbon atoms is preferable, and a dialkyl carbonate having 3 to 7 carbon atoms is more preferable.
Specific examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl-n-propyl carbonate. Dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferred.
Furthermore, chain carbonates having fluorine atoms (hereinafter, sometimes referred to as "fluorinated chain carbonates") can also be suitably used.

The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, and preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or different carbons.
Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives such as fluoromethyl methyl carbonate, fluorinated ethyl methyl carbonate derivatives such as 2-fluoroethyl methyl carbonate, and fluorinated diethyl carbonate derivatives such as ethyl-(2-fluoroethyl) carbonate.

The chain carbonate may be used alone or in any combination of two or more kinds in any ratio.
The amount of the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 15% by volume or more, even more preferably 20% by volume or more, and particularly preferably 25% by volume or more, based on 100% by volume of the nonaqueous solvent. By setting the lower limit in this way, the viscosity of the nonaqueous electrolyte is set to an appropriate range, the decrease in ion conductivity is suppressed, and the large current discharge characteristics of the nonaqueous electrolyte battery are easily set to a good range. In addition, the chain carbonate is preferably 90% by volume or less, more preferably 85% by volume or less, and particularly preferably 80% by volume or less, based on 100% by volume of the nonaqueous solvent. By setting the upper limit in this way, the decrease in electrical conductivity due to the decrease in the dielectric constant of the nonaqueous electrolyte is avoided, and the large current discharge characteristics of the nonaqueous electrolyte battery are easily set to a good range.

<Chain Carboxylic Acid Ester Having 5 or More Carbon Atoms>
The chain carboxylate having 5 or more carbon atoms is not particularly limited as long as it has 5 or more carbon atoms. Specific examples include butyl acetate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, methyl valerate, methyl isobutyrate, ethyl isobutyrate, and methyl pivalate. Chain carboxylates in which some of the hydrogen atoms of the above-mentioned compounds are replaced with fluorine can also be used suitably.
The amount of the chain carboxylate having 5 or more carbon atoms is usually 1 vol% or more, preferably 5 vol% or more, more preferably 15 vol% or more in 100 vol% of the nonaqueous solvent. In this range, the electrical conductivity of the nonaqueous electrolyte is improved, and the large current discharge characteristics of the nonaqueous electrolyte battery are easily improved. In addition, the amount of the chain carboxylate having 5 or more carbon atoms is usually 70 vol% or less, preferably 50 vol% or less, more preferably 40 vol% or less. By setting the upper limit in this way, the viscosity of the nonaqueous electrolyte is in an appropriate range, a decrease in electrical conductivity is avoided, an increase in the negative electrode resistance is suppressed, and the large current discharge characteristics of the nonaqueous electrolyte battery are easily in a good range.

<Cyclic Carboxylic Acid Ester>
The cyclic carboxylic acid ester preferably has 3 to 12 carbon atoms.
Specific examples include gamma-butyrolactone, gamma-valerolactone, gamma-caprolactone, epsilon-caprolactone, etc. Among these, gamma-butyrolactone is particularly preferred from the viewpoint of improving the battery characteristics resulting from the improvement in the degree of dissociation of lithium ions.

The cyclic carboxylate ester may be used alone or in any combination of two or more kinds in any ratio.
The amount of the cyclic carboxylate is usually 5% by volume or more, more preferably 10% by volume or more, based on 100% by volume of the nonaqueous solvent. In this range, the electrical conductivity of the nonaqueous electrolyte is improved, and the large-current discharge characteristics of the nonaqueous electrolyte battery are easily improved. In addition, the amount of the cyclic carboxylate is preferably 50% by volume or less, more preferably 40% by volume or less. By setting the upper limit in this way, the viscosity of the nonaqueous electrolyte is in an appropriate range, a decrease in electrical conductivity is avoided, an increase in the negative electrode resistance is suppressed, and the large-current discharge characteristics of the nonaqueous electrolyte battery are easily in a good range.

<Ether compounds>
Preferred ether compounds include chain ethers having 3 to 10 carbon atoms, such as dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether, and cyclic ethers having 3 to 6 carbon atoms, such as tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, and 1,4-dioxane. Some of the hydrogen atoms in the above-mentioned ether compounds may be substituted with fluorine.
Among these, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether are preferred in that they have a high ability to solvate lithium ions and improve ion dissociation properties, and dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred because they have a low viscosity and provide high ionic conductivity.

The ether-based compounds may be used alone or in any combination of two or more in any ratio.
The amount of the ether-based compound is usually, based on 100 volume% of the nonaqueous solvent, preferably 5 vol% or more, more preferably 10 vol% or more, even more preferably 15 vol% or more, and preferably 70 vol% or less, more preferably 60 vol% or less, even more preferably 50 vol% or less.

Within this range, it is easy to ensure the effect of improving ionic conductivity due to the improved degree of lithium ion dissociation of the ether-based compound and the reduced viscosity, and when the negative electrode active material is a carbonaceous material, it is easy to avoid a situation in which the ether-based compound is co-intercalated with the lithium ion, resulting in a decrease in capacity.

<Sulfone-based compounds>
The sulfone-based compound is preferably a cyclic sulfone having 3 to 6 carbon atoms, or a chain sulfone having 2 to 6 carbon atoms. The number of sulfonyl groups in one molecule of the sulfone-based compound is preferably 1 or 2.

Examples of cyclic sulfones having 3 to 6 carbon atoms include:
Monosulfone compounds such as trimethylene sulfones, tetramethylene sulfones, pentamethylene sulfones, and hexamethylene sulfones;
Examples of disulfone compounds include trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones.

Among these, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.
The sulfolane is preferably sulfolane and/or a sulfolane derivative (hereinafter, sulfolane may also be referred to as "sulfolane"). The sulfolane derivative is preferably one in which one or more hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group.

Among these, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,3-difluorosulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, etc. are preferred because of their high ionic conductivity and high input/output characteristics.

Examples of chain sulfones having 2 to 6 carbon atoms include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, and pentafluoroethyl methyl sulfone. Among these, dimethyl sulfone, ethyl methyl sulfone, and monofluoromethyl methyl sulfone are preferred because of their high ionic conductivity and high input/output characteristics.

The sulfone-based compounds may be used alone or in any combination of two or more in any ratio.
The amount of the sulfone-based compound is usually, based on 100 volume% of the nonaqueous solvent, preferably 0.3 vol% or more, more preferably 1 vol% or more, even more preferably 5 vol% or more, and preferably 40 vol% or less, more preferably 35 vol% or less, even more preferably 30 vol% or less.
Within this range, the effect of improving durability such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the nonaqueous electrolyte can be set within an appropriate range, making it possible to avoid a decrease in electrical conductivity, and making it easy to avoid a situation in which the charge/discharge capacity retention rate decreases when charging/discharging the nonaqueous electrolyte battery at a high current density.

1-5. Auxiliary Agent In the nonaqueous electrolyte solution of the present invention, in addition to the compound represented by formula (A) and the chain carboxylate having 4 or less carbon atoms, an auxiliary agent may be appropriately used depending on the purpose. As the auxiliary agent, any conventionally known agent may be used. The auxiliary agent may be used alone or in any combination and ratio of two or more types.

Examples of the auxiliary agent that may be contained in the non-aqueous electrolyte solution include cyclic carbonates having carbon-carbon unsaturated bonds, cyclic carbonates having fluorine atoms, compounds having an isocyanato group (isocyanate group), sulfur-containing organic compounds, phosphorus-containing organic compounds other than the compound represented by formula (A), organic compounds having a cyano group, silicon-containing compounds, aromatic compounds other than the compound represented by formula (A), fluorine-free carboxylic acid esters having 5 or more carbon atoms, cyclic compounds having ether bonds, carboxylic acid anhydrides, borates, oxalates, monofluorophosphates, difluorophosphates, fluorosulfonates, etc. Examples of sulfur-containing organic compounds, phosphorus-containing organic compounds other than the compound represented by formula (A), organic compounds having a cyano group, silicon-containing compounds, aromatic compounds other than the compound represented by formula (A), fluorine-free carboxylic acid esters having 5 or more carbon atoms, cyclic compounds having ether bonds, carboxylic acid anhydrides, borates, oxalates, monofluorophosphates, difluorophosphates, and fluorosulfonates include, for example, compounds described in International Publication No. 2015/111676. The cyclic compound having an ether bond can be used as an auxiliary in a non-aqueous electrolyte, and also includes those that can be used as a non-aqueous solvent as shown in 1-3. When the cyclic compound having an ether bond is used as an auxiliary, it is used in an amount of less than 4 mass%. Borates, oxalates, monofluorophosphates, difluorophosphates, and fluorosulfonates can be used as auxiliary in a non-aqueous electrolyte, and also includes those that can be used as an electrolyte as shown in 1-2. When these compounds are used as auxiliary, they are used in an amount of less than 3 mass%.
In particular, from the viewpoint of improving battery characteristics, the nonaqueous electrolyte solution according to one embodiment of the present invention preferably further contains one or more selected from the group consisting of a cyclic carbonate having a carbon-carbon unsaturated bond and a cyclic carbonate having a fluorine atom, and it is particularly preferable that the nonaqueous electrolyte solution further contains a cyclic carbonate having a carbon-carbon unsaturated bond and a cyclic carbonate having a fluorine atom.
The compound represented by formula (A) undergoes an oxidation reaction on the active material to form active radicals and cations within the structure. In addition, the cyclic carbonate having a carbon-carbon unsaturated bond and the cyclic carbonate having a fluorine atom have radical and cation receptor sites within the structure. Therefore, it is considered that a composite coating is formed.
Therefore, the reaction of the electrolyte on the surface of the active material is more suppressed than when each compound is added alone, and the battery characteristics are improved.

<Cyclic carbonate having carbon-carbon unsaturated bond>
The cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter, sometimes referred to as "unsaturated cyclic carbonate") is not particularly limited, and any unsaturated carbonate can be used as long as it is a cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond. Note that cyclic carbonates having an aromatic ring are also included in the unsaturated cyclic carbonate.

Examples of the unsaturated cyclic carbonate include vinylene carbonates, catechol carbonates, and ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond, or a carbon-carbon triple bond.
Vinylene carbonates include:
Examples of the vinylene carbonate include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-divinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, and 4-allyl-5-fluoro vinylene carbonate.

Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond include:
Examples of the ethylene carbonate include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl-5-ethynyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, 4-phenyl-5-vinyl ethylene carbonate, 4-allyl-5-phenyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, and 4-methyl-5-allyl ethylene carbonate.

Among them, preferred unsaturated cyclic carbonates are
vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, and 4-vinyl-5-ethynyl ethylene carbonate.

Furthermore, vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are particularly preferred since they form a more stable interface protective film.
The molecular weight of the unsaturated cyclic carbonate is not particularly limited, and may be any as long as it does not significantly impair the effects of the present invention. The molecular weight is preferably 80 or more and 250 or less. In this range, the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolyte is easily ensured, and the effects of the present invention are easily fully exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 85 or more, and more preferably 150 or less. The method for producing the unsaturated cyclic carbonate is not particularly limited, and it is possible to produce it by arbitrarily selecting a known method.

The unsaturated cyclic carbonate may be used alone or in any combination and ratio of two or more kinds. The amount of the unsaturated cyclic carbonate is not particularly limited and may be any amount as long as it does not significantly impair the effects of the present invention. In 100% by mass of the nonaqueous electrolyte, the amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, particularly preferably 2% by mass or less. Within this range, the nonaqueous electrolyte battery is likely to exhibit a sufficient cycle characteristic improvement effect, and it is also easy to avoid situations such as a decrease in high-temperature storage characteristics, an increase in the amount of gas generated, and a decrease in the discharge capacity retention rate.

<Fluorine Atom-Containing Cyclic Carbonate>
Examples of cyclic carbonate compounds having fluorine atoms include fluorinated cyclic carbonates having an alkylene group having 2 to 6 carbon atoms, and derivatives thereof, such as fluorinated ethylene carbonate and derivatives thereof. Examples of derivatives of fluorinated ethylene carbonate include fluorinated ethylene carbonate substituted with an alkyl group (e.g., an alkyl group having 1 to 4 carbon atoms). Among these, ethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferred.

in particular,
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.

Among these, at least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate is more preferred in that it provides high ion conductivity and favorably forms an interface protective film.
The fluorine atom-containing cyclic carbonate compound may be used alone or in any combination of two or more kinds in any ratio.

The cyclic carbonate compound having a fluorine atom may be used alone, or two or more may be used in any combination and ratio. The amount of the halogenated cyclic carbonate in the non-aqueous electrolyte of the present invention is not limited, and is arbitrary as long as it does not significantly impair the effects of the present invention. In 100% by mass of the non-aqueous electrolyte, the amount is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more. Also, the amount is usually 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. However, monofluoroethylene carbonate may be used as a solvent, and in that case, the amount is not limited to the above content. In this specification, a cyclic carbonate having a fluorine atom and an unsaturated bond is classified as an unsaturated cyclic carbonate.

2. Non-aqueous electrolyte battery configuration The non-aqueous electrolyte of the present invention is suitable for use as an electrolyte for secondary batteries, such as lithium secondary batteries, among non-aqueous electrolyte batteries. Hereinafter, a non-aqueous electrolyte battery using the non-aqueous electrolyte of the present invention will be described.
The nonaqueous electrolyte battery of the present invention can have a known structure and typically comprises a negative electrode and a positive electrode capable of absorbing and releasing ions (e.g., lithium ions), and the nonaqueous electrolyte of the present invention described above.

2-1. Negative Electrode The negative electrode refers to an electrode having a negative electrode active material on at least a part of the surface of a current collector.
The negative electrode active material used in the negative electrode will be described below.
There are no particular limitations on the negative electrode active material, so long as it is capable of electrochemically absorbing and releasing lithium ions.
Specific examples include carbonaceous materials, metal particles that can be alloyed with Li, lithium-containing metal composite oxide materials, and mixtures thereof. Among these, it is preferable to use carbonaceous materials, metal particles that can be alloyed with Li, and mixtures of metal particles that can be alloyed with Li and graphite particles, because they have good cycle characteristics and safety and also have excellent continuous charging characteristics. These may be used alone or in any combination of two or more.

<Carbonaceous materials>
Examples of the carbonaceous material include natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite, and resin-coated graphite. Of these, natural graphite is preferred. The carbonaceous material may be used alone or in any combination and ratio of two or more.
Examples of natural graphite include scaly graphite, scaly graphite, and/or graphite particles obtained by treating such graphite as a raw material with a process such as spheroidization or densification. Among these, from the viewpoint of particle packing and charge/discharge rate characteristics, spherical or ellipsoidal graphite particles that have been subjected to a spheroidization process are particularly preferred.
The average particle size (d50) of the graphite particles is usually 1 μm or more and usually 100 μm or less.

<Physical properties of carbonaceous materials>
The carbonaceous material as the negative electrode active material preferably satisfies at least one of the characteristics such as the physical properties and shape shown in the following (1) to (4), and particularly preferably satisfies a plurality of the characteristics simultaneously.
(1) X-ray parameters The d value (interlayer distance) of the lattice plane (002 plane) of the carbonaceous material determined by X-ray diffraction according to the Gakushin method is usually 0.335 nm or more and 0.360 nm or less. The crystallite size (Lc) of the carbonaceous material determined by X-ray diffraction according to the Gakushin method is 1.0 nm or more.
(2) Volume-Based Average Particle Size The volume-based average particle size of a carbonaceous material is a volume-based average particle size (median diameter) determined by a laser diffraction/scattering method, and is usually 1 μm or more and 100 μm or less.
(3) Raman R value and Raman half width The Raman R value of a carbonaceous material is a value measured by using an argon ion laser Raman spectroscopy, and is usually 0.01 or more and 1.5 or less.
Further, the Raman half-width of the carbonaceous material around 1580 cm ^-1 is not particularly limited, but is usually 10 cm ^-1 or more and 100 cm ^-1 or less.
(4) BET Specific Surface Area The BET specific surface area of a carbonaceous material is the value of the specific surface area measured by the BET method, and is usually 0.1 m ² ·g ^-1 or more and 100 m ² ·g ^-1 or less.
The negative electrode active material may contain two or more carbonaceous materials having different properties, the properties being one or more characteristics selected from the group consisting of X-ray diffraction parameters, median diameter, Raman R value, and BET specific surface area.
Preferred examples include a case where the volume-based particle size distribution is not symmetrical about the median size, where two or more types of carbonaceous materials having different Raman R values are contained, and where X-ray parameters are different.

<Metal particles that can be alloyed with Li>
Any conventionally known metal particles that can be alloyed with Li can be used, but from the standpoint of capacity and cycle life, it is preferable that the metal particles are, for example, a metal selected from the group consisting of Sb, Si, Sn, Al, As, and Zn, or a compound thereof.
Examples of the metal compound include metal oxides, metal nitrides, and metal carbides. In addition, an alloy consisting of two or more metals may be used. Among them, metal Si (hereinafter sometimes referred to as Si) or a metal Si compound is preferable in terms of increasing capacity.
In this specification, Si or Si metal compounds are collectively referred to as Si compounds. Specific examples of Si compounds include _SiOx , _SiNx , _SiCx , and _SiZxOy (Z=C, N). As the Si compound, Si metal oxide ( _{SiOx )} is preferred because it has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals are preferred because they allow easy ingress and egress of alkali ions such as lithium ions and allow high capacity to be obtained.
This general formula, SiO _x , can be obtained by using silicon dioxide (SiO ₂ ) and Si as raw materials, and the value of x is usually 0<x<2.
The average particle size (d50) of metal particles that can be alloyed with Li is usually 0.01 μm or more and 10 μm or less from the viewpoint of cycle life.

<Mixture of metal particles capable of being alloyed with Li and graphite particles>
The mixture of metal particles capable of being alloyed with Li and graphite particles used as the negative electrode active material may be a mixture in which the above-mentioned metal particles capable of being alloyed with Li and the above-mentioned graphite particles are mixed in the state of independent particles, or it may be a composite in which the metal particles capable of being alloyed with Li are present on the surface or inside of the graphite particles.
The content of the metal particles capable of forming an alloy with Li relative to the total content of the metal particles capable of forming an alloy with Li and the graphite particles is usually 1 mass % or more and 99 mass % or less.

<Lithium-containing metal composite oxide material>
The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it is capable of absorbing and releasing lithium ions. From the viewpoint of high current density charge/discharge characteristics, however, a lithium-containing metal composite oxide material containing titanium is preferred, a composite oxide of lithium and titanium (hereinafter sometimes abbreviated as "lithium titanium composite oxide") is more preferred, and a lithium titanium composite oxide having a spinel structure is particularly preferred since it significantly reduces the output resistance.
Furthermore, the lithium and titanium of the lithium titanium composite oxide may be substituted with other metal elements, for example, at least one element selected from the group consisting of Al, Ga, Cu and Zn.
As _the lithium titanium composite oxide, Li4 _{/ 3Ti5/ 3O4} , _Li1Ti2O4 and Li4/ _{5Ti11 / 5O4} are preferred. Also, as the lithium titanium composite oxide in which part of the lithium titanium is replaced with another element, for example, Li4 _/ 3Ti4 _{/ 3Al1/3O4 is preferred} .

<Negative electrode configuration and manufacturing method>
The negative electrode may be manufactured by any known method as long as it does not significantly impair the effects of the present invention. For example, the negative electrode may be formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to the negative electrode active material to form a slurry, applying the slurry to a current collector, drying the slurry, and pressing the current collector.

<Current collector>
Any known current collector can be used to hold the negative electrode active material. Examples of the current collector for the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel, and copper is particularly preferred from the standpoints of ease of processing and cost.

<binder>
There are no particular limitations on the binder that binds the negative electrode active material, so long as it is a material that is stable to the non-aqueous electrolyte solution and the solvent used in producing the electrode.
Specific examples include rubber-like polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), and ethylene-propylene rubber; fluorine-based polymers such as polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and tetrafluoroethylene-ethylene copolymers. These may be used alone or in any combination and ratio of two or more.
The ratio of the binder to the negative electrode active material is usually 0.1% by mass or more and 20% by mass or less.
In particular, when a rubber-like polymer such as SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass to 5% by mass, and when a fluorine-based polymer such as polyvinylidene fluoride is contained as a main component, the ratio of the binder to the negative electrode active material is usually 1% by mass to 15% by mass.

<Thickener>
The thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, but specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, etc. These may be used alone or in any combination and ratio of two or more.
When a thickener is used, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more and 5% by mass or less.

<Electrode Density>
The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is usually 1 g·cm ⁻³ or more and 2.2 g·cm ⁻³ or less.

<Thickness of negative electrode plate>
The thickness of the negative electrode plate is designed to match the positive electrode plate to be used and is not particularly limited, but the thickness of the composite layer minus the thickness of the metal foil of the core material is usually 15 μm or more and 300 μm or less.

<Surface coating of negative electrode plate>
In addition, a material having a different composition from the negative electrode active material may be attached to the surface of the negative electrode plate (surface-attached material). Examples of the surface-attached material include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate.

2-2. Positive Electrode The positive electrode refers to a current collector having a positive electrode active material on at least a portion of its surface.
<Positive electrode active material>
The positive electrode active material (lithium transition metal compound) used in the positive electrode will be described below.
<Lithium transition metal compounds>
The lithium transition metal compound is a compound having a structure capable of desorbing and inserting lithium ions, and examples thereof include sulfides, phosphate compounds, silicate compounds, borate compounds, lithium transition metal composite oxides, etc. Among these, lithium transition metal composite oxides are preferred.
The lithium transition metal composite oxide includes those having a spinel structure that allows three-dimensional diffusion and those having a layered structure that allows two-dimensional diffusion of lithium ions. Those having a spinel structure are generally represented as Li _x M ₂ O ₄ (M is at least one transition metal), and specifically include LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O ₄ , and LiCoVO _4. Those having a layered structure are generally represented as Li _x MO ₂ (M is at least one transition metal, and x is usually 1 to 1.5). _{Specifically , LiCoO2 , LiNiO2 , LiNi0.85Co0.10Al0.05O2 , LiNi0.80Co0.15Al0.05O2 , LiNi0.33Co0.33Mn0.33O2 , Li1.05Ni0.33Co0.33Mn0.33O2 , LiNi0.5Co0.2Mn0.3O2 , Li1.05Ni0.5Co0.2Mn0.3O2 , LiNi0.6Co0.2Mn0.2O2 , LiNi ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 0.8Co0.1Mn0.1O2 , etc. ​}

Among these, lithium transition metal composite oxides having a layered structure are preferred, and transition metal oxides represented by the following composition formula (F) are more preferred.
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ ... (F)
(In the composition formula (F), the numerical values are 0.9≦a1≦1.1, 0.3≦b1≦0.9, 0.01≦c1≦0.5, and 0.0≦d1≦0.5, and 0.5≦b1+c1 and b1+c1+d1=1 are satisfied. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)
In the composition formula (F), it is preferable that d1 has a value of 0.1≦d1≦0.5.

In particular, a transition metal oxide represented by the following composition formula (F') is preferable.
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ ... (F ')
(In formula (F'), the numerical values are 0.90≦a1≦1.10, 0.50≦b1≦0.98, 0.01≦c1<0.50, and 0.01≦d1<0.50, and b1+c1+d1=1 is satisfied. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.)

_{Specific examples} of suitable lithium transition metal oxides represented _{by composition} formula _{( F ' ) include LiNi0.85Co0.10Al0.05O2 , LiNi0.80Co0.15Al0.05O2 , LiNi0.5Co0.2Mn0.3O2 , Li1.05Ni0.50Co0.20Mn0.30O2 , LiNi0.6Co0.2Mn0.2O2 , LiNi0.8Co0.1Mn0.1O2 , and the like .}
In each composition formula, M is preferably Mn or Al, because this increases the structural stability of the transition metal oxide and suppresses structural deterioration during repeated charge and discharge.

Introduction of foreign elements
Furthermore, the lithium transition metal composite oxide may contain elements (foreign elements) other than the elements contained in the above composition formula.

Surface coating
The positive electrode active material may have a surface to which a substance (surface-attached substance) of a different composition is attached. Examples of the surface-attached substance include oxides such as aluminum oxide, sulfates such as lithium sulfate, and carbonates such as lithium carbonate. Carbonates are preferred because they improve the affinity between the compound represented by formula (A) and the chain carboxylate having 4 or less carbon atoms and the positive electrode.
These surface-adhering substances can be attached to the surface of the positive electrode active material, for example, by dissolving or suspending them in a solvent, adding them to the positive electrode active material by immersion, and drying.
The amount of the surface-attached substance is preferably 1 μmol/g or more, more preferably 10 μmol/g or more, and usually 1 mmol/g or less, by mass relative to the positive electrode active material.
In this specification, a positive electrode active material having a substance of a different composition attached to its surface is also referred to as a "positive electrode active material".

<blend>
These positive electrode active materials may be used alone or in any combination of two or more in any ratio.

<Positive electrode configuration and manufacturing method>
The configuration and manufacturing method of the positive electrode are described below. In this embodiment, the positive electrode using the positive electrode active material can be manufactured by a conventional method. That is, the positive electrode active material and the binder, and if necessary, the conductive material and the thickener, etc. are mixed in a dry state to form a sheet, which is then pressed onto the positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry, which is then applied to the positive electrode current collector and dried to form a positive electrode active material layer on the current collector, thereby obtaining a positive electrode. In addition, for example, the above-mentioned positive electrode active material may be roll-formed into a sheet electrode, or may be compression-formed into a pellet electrode.
Hereinafter, the case where the slurry is applied to the positive electrode current collector and then dried will be described.

<Active material content>
The content of the positive electrode active material in the positive electrode active material layer is usually 80% by mass or more and 98% by mass or less.

<Density of Positive Electrode Active Material Layer>
In order to increase the packing density of the positive electrode active material, the positive electrode active material layer obtained by coating and drying is preferably compacted by a hand press, a roller press, etc. The density of the positive electrode active material layer is usually 1.5 g/ ^cm3 or more, preferably 3.0 g/ ^cm3 or more, more preferably 3.3 g/ ^cm3 , and is usually 3.8 g/ ^cm3 or less.

Conductive material
As the conductive material, any known conductive material can be used. Specific examples include metal materials such as copper and nickel. The conductive material may be used alone or in any combination and ratio of two or more. The conductive material is usually used in an amount of 0.01% by mass or more and 50% by mass or less in the positive electrode active material layer.

<Binding Agent>
The binder used in producing the positive electrode active material layer is not particularly limited, and in the case of a coating method, the type is not particularly limited as long as it is a material that is dissolved or dispersed in the liquid medium used in producing the electrode. In view of weather resistance, chemical resistance, heat resistance, flame retardancy, and the like, preferred are fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; and CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide.
In addition, mixtures, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, etc. of the above polymers can also be used. The binder may be used alone or in any combination and ratio of two or more kinds.
Furthermore, when a resin is used as a binder, the weight average molecular weight of the resin is optional as long as it does not significantly impair the effects of the present invention, but is usually from 10,000 to 3,000,000. When the molecular weight is in this range, the strength of the electrode is improved, and the electrode can be suitably formed.
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.

Liquid medium
The liquid medium for forming the slurry is not particularly limited in type as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, the conductive material, the binder, and the thickener used as needed, and either an aqueous solvent or an organic solvent may be used.

<Current collector>
The material of the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum. Among them, aluminum is preferable.
The shape of the current collector may be a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, a foamed metal, etc. Among these, a metal thin film is preferable. The metal thin film may be appropriately formed into a mesh shape.

<Positive electrode plate thickness>
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer minus the thickness of the metal foil of the core material is usually 10 μm or more and 500 μm or less on one side of the current collector.

<Surface coating of positive electrode plate>
Furthermore, the positive electrode plate may have a substance of a different composition attached to its surface, and the same substance as the above-mentioned surface-attached substance may be used.

2-3. Separator A separator is usually placed between the positive and negative electrodes to prevent short circuits. In this case, the non-aqueous electrolyte is usually impregnated into the separator before use.
There are no particular limitations on the material and shape of the separator, and any known material can be used as long as it does not significantly impair the effects of the present invention.

<material>
The material of the separator is not particularly limited as long as it is a material stable against a non-aqueous electrolyte solution, but preferably includes, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, sulfates such as barium sulfate and calcium sulfate, inorganic materials such as glass filters made of glass fibers, and resins such as polyolefins, more preferably polyolefins, and particularly preferably polyethylene and polypropylene. These materials may be used alone or in any combination and ratio of two or more. The above materials may also be used in a laminated state.

<form>
The form is not particularly limited, but preferably, a thin film such as a nonwoven fabric, a woven fabric, or a microporous film is used. In the thin film form, a separator having a pore size of 0.01 to 1 μm and a thickness of 1 to 50 μm is preferably used. In addition to the above independent thin film form, a separator may be used in which a composite porous layer containing the above inorganic particles is formed on the surface layer of the positive electrode and/or negative electrode using a resin binder. The separator is preferably a microporous film or a nonwoven fabric because of its excellent liquid retention.

<Porosity>
When a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is not limited, but is usually 20% or more and 90% or less.

<Air permeability>
The characteristics of a separator in a non-aqueous electrolyte battery can be understood by its Gurley value. The Gurley value indicates the difficulty of air passing through the film in the thickness direction, and is expressed as the number of seconds required for 100 ml of air to pass through the film. The Gurley value of a separator is arbitrary, but is usually 10 to 1000 seconds/100 ml.

2-4. Battery design (electrode group)
The electrode group may have a laminated structure in which the positive electrode plate and the negative electrode plate are sandwiched between the separator, or a structure in which the positive electrode plate and the negative electrode plate are spirally wound with the separator between them. 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 and 90% or less.

Current collection structure
In the case where the electrode group has the above-mentioned laminated structure, a structure in which the metal core parts of the electrode layers are bundled and welded to a terminal is preferably used. A structure in which multiple terminals are provided in the electrode to reduce resistance is also preferably used. In the case where the electrode group has the above-mentioned wound structure, the internal resistance can be reduced by providing multiple lead structures on each of the positive electrode and the negative electrode and bundling them to a terminal.

<Protection element>
As the protective element, a PTC (Positive Temperature Coefficient) element whose resistance increases when abnormal heat generation or excessive current flows, a temperature fuse, a thermistor, a valve (current cutoff valve) that cuts off the current flowing in the circuit due to a sudden increase in the internal pressure or temperature of the battery when abnormal heat generation occurs, etc. It is preferable to select the above protective element under conditions that do not operate during normal use at high current, and it is more preferable to design it so that abnormal heat generation or thermal runaway does not occur even without the protective element.

<Exterior body>
A non-aqueous electrolyte battery is usually constructed by housing the above-mentioned non-aqueous electrolyte, a negative electrode, a positive electrode, a separator, etc. in an exterior body (exterior case). There are no limitations on this exterior body, and any known exterior body can be used as long as it does not significantly impair the effects of the present invention.
The material of the exterior case is not particularly limited as long as it is a substance that is stable against the non-aqueous electrolyte solution used, but from the viewpoint of weight reduction, metals such as aluminum or aluminum alloys, and laminate films are preferably used.
Examples of exterior cases using the above metals include those in which the metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed, airtight structure, and those in which the above metals are used with a resin gasket in between to form a crimped structure.

<shape>
The shape of the exterior case is also arbitrary, and may be, for example, cylindrical, rectangular, laminated, coin-shaped, large, or the like.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.
The compounds used in the present examples and comparative examples are shown below.

Example 1
[Preparation of non-aqueous electrolyte]
Under a dry argon atmosphere, a mixture (volume ratio 20:40:40) of ethylene carbonate (hereinafter referred to as EC), dimethyl carbonate (hereinafter referred to as DMC), and methyl acetate (hereinafter referred to as MA) was used as a non-aqueous solvent, and LiPF ₆ that had been thoroughly dried as an electrolyte was dissolved at a concentration of 1.3 mol / L in the non-aqueous electrolyte solution. Further, 1.0 mass% of vinylene carbonate (hereinafter referred to as VC) was added to the entire non-aqueous electrolyte solution, 2.0 mass% of monofluoroethylene carbonate (hereinafter referred to as FEC) was added to the entire non-aqueous electrolyte solution, and 3.0 mass% of compound 1 was added to the entire non-aqueous electrolyte solution to prepare the non-aqueous electrolyte solution of Example 1.

[Preparation of Positive Electrode]
97 parts by mass of nickel-containing transition metal oxide ( _{LiNi0.85Co0.10Al0.05O2} ) as a positive _electrode active material _, 1.5 parts by mass of acetylene black as a conductive material, and 1.5 parts by mass of polyvinylidene fluoride ( _PVdF ) as a binder were mixed in N-methylpyrrolidone solvent with a disperser to form a slurry. This was uniformly applied to both sides of an aluminum foil with a thickness of 21 μm, dried, and pressed to form a positive electrode.

[Preparation of negative electrode]
A natural graphite powder was used as the negative electrode active material, an aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose: 1% by mass) as a thickener, and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber: 50% by mass) as a binder, and the mixture was mixed with a disperser to form a slurry. This slurry was uniformly applied to one side of a copper foil having a thickness of 12 μm, dried, and then pressed to form a negative electrode. Note that the negative electrode after drying was prepared so that the mass ratio of natural graphite: sodium carboxymethylcellulose: styrene-butadiene rubber was 98:1:1.

[Manufacture of non-aqueous electrolyte battery (pouch type)]
The above positive electrode, negative electrode, and polypropylene separator were laminated in this order to prepare a battery element.
This battery element was inserted into a bag made of a laminate film in which both sides of aluminum (40 μm thick) were covered with a resin layer so that the positive and negative terminals were protruding, and then the nonaqueous electrolyte of Example 1 was injected into the bag and vacuum sealed to prepare a pouch-type battery, which was the nonaqueous electrolyte battery of Example 1.

Example 2
In a dry argon atmosphere, a mixture of EC, DMC, EMC, and MA (volume ratio 20:60:10:10) was used as a non-aqueous solvent, and _LiPF6 that had been thoroughly dried was dissolved as an electrolyte at a concentration of 1.3 mol/L in the non-aqueous electrolyte solution. Further, VC was added in an amount of 1.0 mass% relative to the entire non-aqueous electrolyte solution, FEC was added in an amount of 2.0 mass% relative to the entire non-aqueous electrolyte solution, and Compound 1 was added in an amount of 0.3 mass% relative to the entire non-aqueous electrolyte solution to prepare a non-aqueous electrolyte solution of Example 2.
A nonaqueous electrolyte battery of Example 2 was fabricated in the same manner as in Example 1, except that the nonaqueous electrolyte of Example 2 was used.

Example 3
Under a dry argon atmosphere, a mixture of EC, DMC, EMC, and methyl propionate (hereinafter referred to as MP) (volume ratio 20:60:10:10) was used as a non-aqueous solvent, and LiPF ₆ that had been thoroughly dried was dissolved as an electrolyte at a concentration of 1.3 mol/L in the non-aqueous electrolyte solution. Further, VC was added in an amount of 1.0% by mass relative to the entire non-aqueous electrolyte solution, FEC was added in an amount of 2.0% by mass relative to the entire non-aqueous electrolyte solution, and Compound 1 was added in an amount of 3.0% by mass relative to the entire non-aqueous electrolyte solution to prepare a non-aqueous electrolyte solution of Example 3.
A nonaqueous electrolyte battery of Example 3 was fabricated in the same manner as in Example 1, except that the nonaqueous electrolyte of Example 3 was used.

<Comparative Example 1>
A nonaqueous electrolyte battery of Comparative Example 1 was produced in the same manner as in Example 1, except that the content of Compound 1 relative to the total amount of the nonaqueous electrolyte was 2.0 mass % and DMC was used instead of methyl acetate.

<Comparative Example 2>
A nonaqueous electrolyte battery of Comparative Example 2 was fabricated in the same manner as in Comparative Example 1, except that the content of Compound 1 relative to the total amount of the nonaqueous electrolyte was 4.0 mass %.

<Comparative Example 3>
A nonaqueous electrolyte battery of Comparative Example 3 was fabricated in the same manner as in Example 1, except that Compound 1 was not added.

<Comparative Example 4>
A nonaqueous electrolyte battery of Comparative Example 4 was produced in the same manner as in Example 2, except that Compound 2 was added in place of Compound 1 so that the content thereof was 3.0 mass % relative to the total amount of the nonaqueous electrolyte.

<Comparative Example 5>
A nonaqueous electrolyte battery of Comparative Example 5 was produced in the same manner as in Example 3, except that Compound 2 was added in place of Compound 1 such that the content thereof was 3.0 mass % relative to the total amount of the nonaqueous electrolyte.

<Evaluation of non-aqueous electrolyte batteries>
[Rate characteristics]
Each of the nonaqueous electrolyte batteries thus fabricated was sandwiched between glass plates to enhance adhesion between the electrodes, and charged at 25° C. for 4 hours at a constant current equivalent to 0.05 C, and then discharged to 2.5 V at a constant current of 0.2 C. Here, 1 C represents the current value at which the battery's reference capacity is discharged in 1 hour, 0.5 C represents 1/2 that current value, and 0.2 C represents 1/5 that current value.
Next, the battery was charged to 4.1 V at a constant current equivalent to 0.1 C, discharged to 2.5 V at a constant current of 0.2 C, further charged to 4.1 V at a constant current equivalent to 0.2 C, discharged to 2.5 V at a constant current of 0.2 C, and then constant current-constant voltage charging (0.05 C cut) was performed at 0.2 C to 4.1 V. After that, after 3 days at 45 ° C, the battery was discharged to 2.5 V at a constant current of 0.2 C. Thereafter, the charging conditions were unified to constant current-constant voltage charging (0.05 C cut) to 4.2 V at 0.2 C, and the 1 C discharge capacity and 0.05 C discharge capacity up to 2.5 V were measured. 100 × (1 C discharge capacity / 0.05 C discharge capacity) was used as the rate characteristic. Table 1 shows the composition and rate characteristic evaluation results of Examples 1 to 3 and Comparative Examples 1 to 5.

[Negative electrode resistance at low temperature after high temperature storage]
After measuring the rate characteristics, the battery was charged again to 4.2 V and left at 85 ° C. for 3 days. The battery was then discharged to 2.5 V at a constant current of 0.2 C, and charged at a constant current and constant voltage of 0.2 C to 4.2 V (0.05 C cut), and then the AC impedance was measured at an open circuit voltage at 0 ° C., with a voltage amplitude of 10 mV and a frequency in the range of 0.1 to 20,000 Hz. The imaginary part at a frequency of 15.9 Hz was taken as the negative electrode resistance at low temperatures. The smaller the negative electrode resistance at low temperatures, the smoother the acceptance of lithium cations at the negative electrode, and it is expected that lithium electrodeposition and the like can be suppressed. Table 1 shows the evaluation results of the compositions of Example 1 and Comparative Examples 1 to 3 and the negative electrode resistance at low temperatures.

From Table 1, it is clear that when a nonaqueous electrolyte containing a compound represented by formula (A) and a chain carboxylic acid ester having 4 or less carbon atoms is used (Examples 1 to 3), the rate characteristics of the nonaqueous electrolyte battery and the negative electrode resistance at low temperatures after high-temperature storage can be improved at the same time, compared to when they are not used (Comparative Examples 1 to 5).

Example 4
Under a dry argon atmosphere, a mixture of EC, DMC, EMC, and MA (volume ratio 20:60:10:10) was used as a non-aqueous solvent, and LiPF ₆ , which had been thoroughly dried as an electrolyte, was dissolved at a concentration of 1.3 mol / L in the non-aqueous electrolyte solution, and VC was added at 1.0 mass% relative to the entire non-aqueous electrolyte solution, FEC at 2.0 mass% relative to the entire non-aqueous electrolyte solution, and Compound 1 at 0.5 mass% relative to the entire non-aqueous electrolyte solution to prepare the non-aqueous electrolyte solution of Example 4. A non-aqueous electrolyte battery of Example 4 was produced in the same manner as in Example 1, except that the non-aqueous electrolyte solution of Example 4 was used.

Example 5
A nonaqueous electrolyte battery of Example 5 was produced in the same manner as in Example 4, except that the content of Compound 1 relative to the total amount of the nonaqueous electrolyte was 0.3 mass %.

Example 6
A nonaqueous electrolyte battery of Example 6 was produced in the same manner as in Example 4, except that the content of Compound 1 relative to the total amount of the nonaqueous electrolyte was 3.0 mass % and MP was used instead of methyl acetate.

<Comparative Example 6>
A nonaqueous electrolyte battery of Comparative Example 6 was produced in the same manner as in Example 4, except that Compound 2 was added in place of Compound 1 such that the content thereof was 3.0 mass % relative to the total amount of the nonaqueous electrolyte.

<Comparative Example 7>
A nonaqueous electrolyte battery of Comparative Example 7 was produced in the same manner as in Example 6, except that Compound 2 was used in place of Compound 1 in a content of 3.0 mass % relative to the total amount of the nonaqueous electrolyte.

<Evaluation of non-aqueous electrolyte batteries>
[OCV after high temperature storage]
Each of the nonaqueous electrolyte batteries thus fabricated was sandwiched between glass plates to enhance adhesion between the electrodes, and charged at a constant current equivalent to 0.05 C for 4 hours at 25° C., and then discharged to 2.5 V at a constant current of 0.2 C. Here, 1 C represents the current value at which the battery's reference capacity is discharged in 1 hour, 0.5 C represents 1/2 that current value, and 0.2 C represents 1/5 that current value.
Next, the battery was charged to 4.1 V at a constant current equivalent to 0.1 C, discharged to 2.5 V at a constant current of 0.2 C, further charged to 4.1 V at a constant current equivalent to 0.2 C, discharged to 2.5 V at a constant current of 0.2 C, and then constant current-constant voltage charging (0.05 C cut) was performed at 0.2 C to 4.1 V. After that, after 3 days at 45 ° C, it was discharged to 2.5 V at a constant current of 0.2 C. Thereafter, the charging conditions were unified to constant current-constant voltage charging (0.05 C cut) to 4.2 V at 0.2 C, and the 1 C discharge capacity and 0.05 C discharge capacity up to 2.5 V were measured. After that, it was charged again to 4.2 V and left at 85 ° C for 3 days. After that, it was cooled to 25 ° C, and the open circuit voltage was measured. The voltage of Comparative Example 6 is taken as the reference voltage of 0 V, and the difference in open circuit voltage between Comparative Example 6 and Examples 4 to 6 and Comparative Example 7 is shown as the OCV (ΔV) after high-temperature storage in Table 2. Note that a higher OCV after high-temperature storage means that self-discharge during high-temperature storage is more suppressed, and a desired power capacity can be obtained.

[Remaining capacity rate]
For the nonaqueous electrolyte batteries of Examples 4 to 6 and Comparative Examples 6 and 7, the OCV after high-temperature storage was measured, and then the batteries were discharged to 2.5 V at a constant current of 0.2 C. This discharge capacity was divided by the 0.2 C capacity before high-temperature storage, and multiplied by 100 to obtain the remaining capacity rate (%) shown in Table 2. Note that a higher remaining capacity rate means that self-discharge during high-temperature storage is more suppressed, and a desired power capacity can be obtained.

[Negative electrode resistance at low temperature after high temperature storage]
After measuring the capacity residual rate, constant current-constant voltage charging (0.05C cut) was performed at 0.2C up to 4.2V, and then AC impedance was measured at 0°C, with a voltage amplitude of 10mV and a frequency range of 0.1 to 20000Hz, at open circuit voltage. The imaginary part at a frequency of 15.9Hz was taken as the negative electrode resistance at low temperature. Table 2 shows the relative values (%) of Examples 4 to 6 and Comparative Example 7 when Comparative Example 6 is taken as 100. The smaller the negative electrode resistance at low temperature, the smoother the acceptance of lithium cations in the negative electrode, and it is expected that lithium electrodeposition and the like can be suppressed.

From Table 2, it is clear that when a nonaqueous electrolyte containing a compound represented by formula (A) and a chain carboxylic acid ester having 4 or less carbon atoms is used (Examples 4 to 6), the decrease in OCV after high-temperature storage of a nonaqueous electrolyte battery is suppressed, the negative electrode resistance at low temperatures after high-temperature storage is reduced, and the decrease in the remaining capacity rate after high-temperature storage can be suppressed compared to when not using the compound represented by formula (A) and a chain carboxylic acid ester having 4 or less carbon atoms (Comparative Examples 6 to 7).

Claims (5)

A nonaqueous electrolyte solution for a nonaqueous electrolyte battery having a positive electrode and a negative electrode capable of absorbing and releasing metal ions, the nonaqueous electrolyte solution containing, together with an alkali metal salt and a nonaqueous solvent, (1) a compound represented by the following formula (A) in an amount of 0.001 mass % or more and 5 mass % or less, based on a total amount of the nonaqueous electrolyte solution, and (2) a chain carboxylate ester having 4 or less carbon atoms in an amount of 5 volume % or more and 90 volume % or less, based on a total amount of the solvent of the nonaqueous electrolyte solution:

(In formula (A), all of R ¹ to R ⁵ are hydrogen atoms.) The nonaqueous electrolyte solution according to claim 1, characterized in that the chain carboxylic acid ester having 4 or less carbon atoms is methyl acetate. 3. The nonaqueous electrolyte solution according to claim 1, further comprising one or more compounds selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and cyclic carbonates having a fluorine atom. The nonaqueous electrolyte solution according to claim 3, wherein a total content of the one or more compounds selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond and cyclic carbonates having a fluorine atom is 0.001% by mass or more and 5% by mass or less with respect to a total amount of the nonaqueous electrolyte solution. 5. A nonaqueous electrolyte battery comprising a positive electrode capable of absorbing and releasing lithium ions, a negative electrode capable of absorbing and releasing lithium ions, and a nonaqueous electrolyte, wherein the nonaqueous electrolyte is the nonaqueous electrolyte according to claim 1 .