JP6939905B2 - Electrolytes, electrochemical devices, lithium-ion secondary batteries and modules - Google Patents

Description

The present invention relates to electrolytes, electrochemical devices, lithium ion secondary batteries and modules.

With the recent weight reduction and miniaturization of electrical products, the development of electrochemical devices such as lithium ion secondary batteries having high energy density is being promoted. Further, as the application fields of electrochemical devices such as lithium ion secondary batteries expand, improvement of characteristics is required. Especially in the future, when lithium-ion secondary batteries are used for automobiles, improvement of battery characteristics will become more and more important.

Patent Document 1 describes at least two aprotons containing a cathode, an anode containing a carbon material having a crystallinity> 0.8, a first solvent having a high dielectric constant, and a second solvent having a low viscosity. A lithium storage battery containing a mixture of a sex organic solvent and an electrolytic solution composed of a lithium salt, wherein the electrolytic solution contains at least one unsaturated bond and is 1 V higher than lithium to form a mobilized layer. Described are storage batteries that further contain a soluble compound of the same type as at least one of the solvents that can be reduced at the anode at potential.

Patent Document 2 describes a charging method for initial charging a non-aqueous electrolyte secondary battery including a negative electrode and a positive electrode and an electrolyte containing a plurality of types of non-aqueous solvents. Also consists of one or more non-aqueous solvents having a noble reduction potential, and the negative electrode potential is set to a potential at which one of the non-aqueous solvents having a noble reduction potential than the above main solvent is reduced and decomposed and the main solvent is not reduced and decomposed. Described is a method of charging a non-aqueous electrolyte secondary battery, which comprises charging for the first time by two or more stages of charging steps including a first charging step of keeping.

Patent Document 3 describes an electrolyte for an alkali metal ion secondary battery containing an anode of a carbonaceous material capable of reversibly mixing alkali metal ions, and is a fluoroethylene carbonate, an alkali metal salt dissolved therein. And electrolytes containing solutions of propylene carbonate are described.

（式中、Ｒｆ^１は含フッ素エーテル基（Ｉａ）、または含フッ素アルコキシ基（Ｉｂ）；Ｘ^１、Ｘ^２およびＸ^３はいずれもＨ）で示される環状カーボネート（Ｉ）と電解質塩（ＩＩ）とを含む電解液が記載されている。In Patent Document 4, the formula (I):

(In the formula, Rf ¹ is a fluorine-containing ether group (Ia) or a fluorine-containing alkoxy group (Ib); X ¹ , X ² and X ³ are all H), and the cyclic carbonate (I) and the electrolyte salt (II). ) And the electrolyte is described.

Japanese Unexamined Patent Publication No. 8-0455545 Japanese Unexamined Patent Publication No. 2001-325988 Special Table 2001-501355 Patent No. 4591505

The present invention has been made in view of the above situation, and provides an electrolytic solution that provides an electrochemical device having low resistance, excellent cycle characteristics, and less gas generation, and an electrochemical device including the electrolytic solution. The purpose is to do.

（式中、Ｒ^１０１及びＲ^１０２は、同一又は異なって、エーテル結合を有してもよい、直鎖状又は分岐鎖状の炭素数１〜３のアルキル基である。Ｒ^１０１とＲ^１０２とは互いに結合していてもよい。）で示される化合物（１）を含むことを特徴とする電解液である。The present invention has the following general formula (1):

(In the formula, R ¹⁰¹ and R ¹⁰² are linear or branched alkyl groups having 1 to 3 carbon atoms, which may have the same or different ether bonds. R ¹⁰¹ and R ¹⁰² Is an electrolytic solution containing the compound (1) represented by (which may be bonded to each other).

The content of compound (1) is preferably 0.001 to 15% by mass with respect to the above electrolytic solution.

In the general formula (1), R ¹⁰¹ and R ¹⁰² are preferably the same or different, and are preferably _{-CH 3} or -CH ₂ CH _3.

The electrolytic solution preferably further contains a solvent (however, excluding compound (1)).

The electrolytic solution preferably further contains an electrolyte salt.

The present invention is also an electrochemical device characterized by comprising the above-mentioned electrolytic solution.

The present invention is also a lithium ion secondary battery, which comprises the above electrolytic solution.

The present invention is also a module including the electrochemical device or the lithium ion secondary battery.

According to the electrolytic solution of the present invention, an electrochemical device having low resistance, excellent cycle characteristics, and less gas generation can be obtained. The electrochemical device of the present invention has low resistance, excellent cycle characteristics, and is less likely to generate gas.

Hereinafter, the present invention will be specifically described.

で示される化合物（１）を含む。この特徴により、本発明の電解液は、低抵抗で、サイクル特性に優れ、かつガスが発生しにくい電気化学デバイスを与えることができる。The electrolytic solution of the present invention is the following general formula (1):

Includes compound (1) represented by. Due to this feature, the electrolytic solution of the present invention can provide an electrochemical device having low resistance, excellent cycle characteristics, and less gas generation.

In the general formula (1), R ¹⁰¹ and R ¹⁰² are linear or branched alkyl groups having 1 to 3 carbon atoms, which may have the same or different ether bonds.
The alkyl groups as R ¹⁰¹ and R ¹⁰² preferably have 1 to 2 carbon atoms. The alkyl group may have a fluorine atom.
R ¹⁰¹ and R ¹⁰² may be coupled (form a ring) to each other.

Examples of R ¹⁰¹ and R ¹⁰² include -CH ₃ (Me), -CH ₂ CH ₃ (Et), -CF ₃ , and -CH ₂ CF _3. Of these, -CH ₃ and -CH ₂ CH ₃ are preferable.

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

As the compound (1), the compound represented by the following formula is particularly preferable.

As the compound (1), one type may be used alone, or two or more types may be used in combination.

（式中、Ｒ^１０１及びＲ^１０２は、同一又は異なって、エーテル結合を有してもよい、直鎖状又は分岐鎖状の炭素数１〜３のアルキル基である。Ｒ^１０１とＲ^１０２とは互いに結合していてもよい。）で示される化合物（１１）をヒドロキシ化して、下記一般式（１２）：

（式中、Ｒ^１０１及びＲ^１０２は上記と同じである。）で示される化合物（１２）を得る工程（１）、及び、
化合物（１２）とトリホスゲンとを反応させて、上記一般式（１）で示される化合物（１）を得る工程（２）を含む製造方法により、好適に製造することができる。Compound (1) has the following general formula (11):

(In the formula, R ¹⁰¹ and R ¹⁰² are linear or branched alkyl groups having 1 to 3 carbon atoms, which may have the same or different ether bonds. R ¹⁰¹ and R ¹⁰² May be bonded to each other.) The compound (11) represented by the formula (11) is hydroxyated to form the following general formula (12):

(In the formula, R ¹⁰¹ and R ¹⁰² are the same as above.) The step (1) for obtaining the compound (12) represented by the above, and
It can be suitably produced by a production method including the step (2) of reacting the compound (12) with triphosgene to obtain the compound (1) represented by the above general formula (1).

R ¹⁰¹ and R ¹⁰² are as described above.

In step (1), compound (11) is hydroxyated to obtain compound (12).
The hydroxylation of step (1) can be carried out, for example, by reacting compound (11) with a hydroxy agent. Examples of the hydroxylating agent include potassium permanganate, osmium tetroxide, sodium periodate, ruthenium oxide and the like. Alternatively, the compound (11) may be epoxidized with a peroxide (sodium hypochlorite, peracetic acid) or the like, and then a ring-opening reaction may be carried out by hydrolysis.

In the above-mentioned hydroxylation, it is preferable to use 1.0 to 1.5 mol, more preferably 1.0 to 1.2 mol of the above-mentioned hydroxyting agent with respect to 1 mol of the compound (11).

The above hydroxylation can be carried out in a solvent. As the solvent, water or an organic solvent can be used.
Examples of the organic solvent include non-aromatic hydrocarbon solvents such as pentane, hexane, heptane, octane, cyclohexane, decahydronaphthalene, n-decane, isododecane and tridecane; benzene, toluene, xylene, tetraline, veratrol, diethylbenzene and methylnaphthalene. , Nitrobenzene, o-nitrotoluene, mesitylene, inden, diphenylsulfide and other aromatic hydrocarbon solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, propiophenone, diisobutyl ketone, isophorone and other ketone solvents; Halogenized hydrocarbon solvents; ether solvents such as diethyl ether, tetrahydrofuran, diisopropyl ether, methyl t-butyl ether, dioxane, dimethoxyethane, diglime, phenetol, 1,1-dimethoxycyclohexane, diisoamyl ether; methanol, ethanol, propanol, Alcohol solvents such as butanol, t-butanol, pentanol; ethyl acetate, isopropyl acetate, diethyl malonate, 3-methoxy-3-methylbutyl acetate, γ-butyrolactone, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, Ester solvents such as diethyl carbonate, α-acetyl-γ-butyrolactone; nitrile solvents such as acetonitrile and benzonitrile; sulfoxide solvents such as dimethyl sulfoxide and sulfolane; and N, N-dimethylformamide, N, N-dimethylacetamide, N -Methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylacrylamide, N, N-dimethylacetoacetamide, N, N-diethylformamide, N, N-diethylacetamide and other amide solvents Can be mentioned.
Of these, water is preferable.

The hydroxylation temperature is preferably 60 to 120 ° C, more preferably 80 to 100 ° C.

The hydroxylation time is preferably 1 to 10 hours, more preferably 1 to 5 hours.

In step (2), compound (12) is reacted with triphosgene to obtain compound (1).
In the reaction of step (2), 0.35 to 1 mol of triphosgene is preferably used, and more preferably 0.35 to 0.5 mol is used with respect to 1 mol of compound (12).

The reaction of step (2) can be carried out in a solvent. As the solvent, an organic solvent is preferable, and a non-aromatic hydrocarbon solvent such as pentane, hexane, heptane, octane, cyclohexane, decahydronaphthalene, n-decane, isododecane, and tridecane; benzene, toluene, and xylene. , Tetraline, veratrol, diethylbenzene, methylnaphthalene, nitrobenzene, o-nitrotoluene, mecitylene, inden, diphenylsulfide and other aromatic hydrocarbon solvents; acetone, methylethylketone, methylisobutylketone, acetophenone, propiophenone, diisobutylketone, isophorone and the like. Ketone solvent; halogenated hydrocarbon solvent such as dichloromethane, chloroform, chlorobenzene, etc .; diethyl ether, tetrahydrofuran, diisopropyl ether, methyl t-butyl ether, dioxane, dimethoxyethane, diglime, phenetol, 1,1-dimethoxycyclohexane, diisoamyl ether, etc. Ether solvent; alcohol solvent such as methanol, ethanol, propanol, butanol, t-butanol, pentanol; ethyl acetate, isopropyl acetate, diethyl malonate, 3-methoxy-3-methylbutyl acetate, γ-butyrolactone, ethylene carbonate, propylene Ester solvents such as carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, α-acetyl-γ-butyrolactone; nitrile solvents such as acetonitrile and benzonitrile; sulfoxide solvents such as dimethyl sulfoxide and sulfolane; and N, N-dimethylformamide , N, N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylacrylamide, N, N-dimethylacetacetamide, N, N-diethylformamide, N, N − An amide solvent such as diethylacetamide can be mentioned.
Of these, an amide solvent and a halogenated hydrocarbon solvent are preferable.

The reaction temperature in step (2) is preferably −120 to 0 ° C., more preferably −78 to −40 ° C.

The reaction time of the step (2) is preferably 0.5 to 6 hours, more preferably 0.5 to 2 hours.

In the above production method, after the completion of each step, the product may be separated and purified by distilling off the solvent, column chromatography, distillation, recrystallization and the like.

The electrolytic solution of the present invention preferably contains 0.001 to 15% by mass of compound (1) with respect to the electrolytic solution. When the content of the compound (1) is within the above range, an electrochemical device having a lower resistance, more excellent cycle characteristics, and less gas generation can be obtained. The content of the compound (1) is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, and particularly preferably 0.5% by mass or more. Further, 10% by mass or less is more preferable, and 5% by mass or less is further preferable.

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

The solvent preferably contains at least one selected from the group consisting of carbonates and carboxylic acid esters.

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

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

Examples of the non-fluorinated cyclic carbonate include non-fluorinated saturated cyclic carbonates, preferably non-fluorinated saturated alkylene carbonates having an alkylene group having 2 to 6 carbon atoms, and non-fluorine having an alkylene group having 2 to 4 carbon atoms. Saturated alkylene carbonate is more preferred.

Among them, the non-fluorinated saturated cyclic carbonate has a high dielectric constant and a suitable viscosity, and thus ethylene carbonate, propylene carbonate, cis-2,3-pentylene carbonate, cis-2,3-butylene carbonate. , 2,3-Pentylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 1,2-butylene carbonate and at least one selected from the group consisting of butylene carbonate are preferable.

As the non-fluorinated saturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

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

The fluorinated cyclic carbonate is a cyclic carbonate having a fluorine atom. The solvent containing the fluorinated cyclic carbonate can be suitably used even under a high voltage.
In addition, in this specification, "high voltage" means a voltage of 4.2V or more. The upper limit of "high voltage" is preferably 4.9V.

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

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

（式中、Ｘ^１〜Ｘ^４は同じか又は異なり、それぞれ−Ｈ、−ＣＨ_３、−Ｃ_２Ｈ_５、−Ｆ、エーテル結合を有してもよいフッ素化アルキル基、又は、エーテル結合を有してもよいフッ素化アルコキシ基を表す。ただし、Ｘ^１〜Ｘ^４の少なくとも１つは、−Ｆ、エーテル結合を有してもよいフッ素化アルキル基、又は、エーテル結合を有してもよいフッ素化アルコキシ基である。）で示される化合物が挙げられる。上記フッ素化アルキル基とは、−ＣＦ_３、−ＣＦ_２Ｈ、−ＣＨ_２Ｆ等である。

(In the formula, X ^{1 to} X ⁴ are the same or different, and each has -H, -CH ₃ , -C ₂ H ₅ , -F, a fluorinated alkyl group which may have an ether bond, or an ether bond. a represents an even better fluorinated alkoxy group. provided that at least one of X ¹ to X ⁴ are, -F, good fluorinated alkyl group which may have an ether bond, or may have an ether bond It is a good fluorinated alkoxy group.). The fluorinated alkyl group is -CF ₃ , -CF ₂ H, -CH ₂ F, or the like.

When the above-mentioned fluorinated saturated cyclic carbonate is contained, when the electrolytic solution of the present invention is applied to a high-voltage lithium ion secondary battery or the like, the oxidation resistance of the electrolytic solution is improved, and stable and excellent charge / discharge characteristics can be obtained.
In the present specification, the “ether bond” is a bond represented by −O−.

Dielectric constant, the oxidation resistance is good point, X ¹ one to X ⁴ or two, -F, good fluorinated alkyl group which may have an ether bond, or may have an ether bond It is preferably a fluorinated alkoxy group.

Decrease in viscosity at low temperatures, increased flash point, since the more can be expected to improve the solubility of an electrolyte salt, X ¹ to X ⁴ are, -H, -F, a fluorinated alkyl group (a), an ether bond It is preferably a fluorinated alkyl group (b) or a fluorinated alkoxy group (c).

The fluorinated alkyl group (a) is obtained by substituting at least one hydrogen atom of the alkyl group with a fluorine atom. The fluorinated alkyl group (a) preferably has 1 to 20 carbon atoms, more preferably 1 to 17 carbon atoms, further preferably 1 to 7 carbon atoms, and particularly preferably 1 to 5 carbon atoms.
If the carbon number is too large, the low temperature characteristics may be deteriorated or the solubility of the electrolyte salt may be lowered. If the carbon number is too small, the solubility of the electrolyte salt may be lowered, the discharge efficiency may be lowered, and further, the solubility of the electrolyte salt may be lowered. Increased viscosity may be seen.

Among the above fluorinated alkyl groups (a), those having 1 carbon atom include CFH _2- , CF ₂ H-, and CF _3- . In particular, CF ₂ H − or CF ₃ − is preferable in terms of high temperature storage characteristics, and CF ₃ − is most preferable.

Among the above fluorinated alkyl groups (a), those having 2 or more carbon atoms are selected from the following general formula (a-1):
R ¹ − R ² − (a-1)
(In the formula, R ¹ is an alkyl group having 1 or more carbon ^{atoms which may have a fluorine atom; R 2} is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; however, R ¹ and The ^{alkyl fluorinated group represented by (at least one of R 2} has a fluorine atom) can be preferably exemplified from the viewpoint of good solubility of the electrolyte salt.
In addition, R ¹ and R ² may further have other atoms other than carbon atom, hydrogen atom and fluorine atom.

R ¹ is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. As R 1, a linear or branched alkyl group having ^{1 to 16 carbon atoms is preferable.} The ^{number of carbon atoms of R 1} is more preferably 1 to 6, and even more preferably 1 to 3.

As R ¹ , specifically, as a linear or branched alkyl group, CH ₃ −, CH ₃ CH ₂ −, CH ₃ CH ₂ CH ₂ −, CH ₃ CH ₂ CH ₂ CH ₂ −,

And so on.

When R ¹ is a linear alkyl group having a fluorine atom, CF _3- , CF ₃ CH _2- , CF ₃ CF _2- , CF ₃ CH ₂ CH _2- , CF ₃ CF ₂ CH _2- , CF ₃ CF ₂ CF _2- , CF ₃ CH ₂ CF _2- , CF ₃ CH ₂ CH ₂ CH _2- , CF ₃ CF ₂ CH ₂ CH _2- , CF ₃ CH ₂ CF ₂ CH _2- , CF ₃ CF ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CF ₂ −, CF ₃ CF ₂ CH ₂ CF ₂ −, CF ₃ CH ₂ CH ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CH ₂ CH ₂ − , CF ₃ CH ₂ CF ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CH ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH ₂ −, HCF ₂ −, HCF ₂ CH ₂ − , HCF ₂ CF ₂ −, HCF ₂ CH ₂ CH ₂ −, HCF ₂ CF ₂ CH ₂ −, HCF ₂ CH ₂ CF ₂ −, HCF ₂ CF ₂ CH ₂ CH ₂ −, HCF ₂ CH ₂ CF ₂ CH ₂ − , HCF ₂ CF ₂ CF ₂ CF _2- , HCF ₂ CF ₂ CH ₂ CH ₂ CH _2- , HCF ₂ CH ₂ CF ₂ CH ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF ₂ CH ₂ CH _2- , FCH _2- , FCH ₂ CH _2- , FCH ₂ CF _2- , FCH ₂ CF ₂ CH _2- , FCH ₂ CF ₂ CF _2- , CH ₃ CF ₂ CH _2- , CH ₃ CF ₂ CF ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ −, CH ₃ CF ₂ CF ₂ CF ₂ −, CH ₃ CH ₂ CF ₂ CF ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ CH ₂ − , CH ₃ CF ₂ CF ₂ CF ₂ CH ₂ −, CH ₃ CF ₂ CF ₂ CH ₂ CH ₂ −, CH ₃ CH ₂ CF ₂ CF ₂ CH ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH _2- , HCFClCF ₂ CH _2- , HCF ₂ CFClCH _2- , HCF ₂ CFClCF ₂ CFClCH _2- , HCFClCF ₂ CFClCF ₂ CH _2- and the like can be mentioned.

When R ¹ is a branched-chain alkyl group having a fluorine atom,

Etc. are preferably mentioned. However, _{if it has a branch of CH 3-} or CF _3- , the viscosity tends to be high, so the number is more preferably small (1) or zero.

R ² is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom. R ² may be linear or branched. An example of the smallest structural unit constituting such a linear or branched alkylene group is shown below. R ² is composed of these alone or in combination.

(I) Linear minimum structural unit:
_{-CH 2 -, - CHF -,} - CF 2 -, - CHCl -, - CFCl -, - CCl 2 -

(Ii) Branched chain minimum structural unit:

Among the above examples, it is preferable to be composed of a constituent unit containing no Cl because the dehydrochloric acid reaction by a base does not occur and it is more stable.

When R ² is linear, it is composed of only the linear minimum structural unit described above, and among them, −CH ₂ −, _{−CH 2} CH ₂ − or −CF ₂₋ is preferable. _{-CH 2-} or -CH ₂ CH ₂ --is more preferable from the viewpoint that the solubility of the electrolyte salt can be further improved.

When R ² is in the form of a branched chain, it contains at least one of the above-mentioned minimum structural units in the form of a branched chain, and the general formula-(CX ^a X ^b )-(X ^a is H, F). , CH ₃ or CF ₃ ; X ^b is CH ₃ or CF _3. However, when X ^b is CF ₃ , X ^a is H or CH ₃ ). These can further improve the solubility of the electrolyte salt in particular.

Preferred alkyl fluorinated groups (a) include, for example, CF ₃ CF _2- , HCF ₂ CF _2- , H ₂ CFCF _2- , CH ₃ CF _2- , CF ₃ CHF-, CH ₃ CF _2- , CF ₃ CF. ₂ CF _2- , HCF ₂ CF ₂ CF _2- , H ₂ CFCF ₂ CF _2- , CH ₃ CF ₂ CF _2- ,

And so on.

The fluorinated alkyl group (b) having an ether bond is one in which at least one hydrogen atom of the alkyl group having an ether bond is replaced with a fluorine atom. The fluorinated alkyl group (b) having an ether bond preferably has 2 to 17 carbon atoms. If the number of carbon atoms is too large, the viscosity of the fluorinated saturated cyclic carbonate becomes high, and the number of fluorine-containing groups increases, so that the solubility of the electrolyte salt decreases due to the decrease in the dielectric constant and the compatibility with other solvents. May be seen to decrease. From this viewpoint, the number of carbon atoms of the fluorinated alkyl group (b) having an ether bond is more preferably 2 to 10, and even more preferably 2 to 7.

The alkylene group constituting the ether portion of the fluorinated alkyl group (b) having an ether bond may be a linear or branched alkylene group. An example of the smallest structural unit constituting such a linear or branched alkylene group is shown below.

(I) Linear minimum structural unit:
_{-CH 2 -, - CHF -,} - CF 2 -, - CHCl -, - CFCl -, - CCl 2 -

(Ii) Branched chain minimum structural unit:

The alkylene group may be composed of these minimum structural units alone, and may be linear (i) or branched chain (ii) or linear (i) and branched chain (ii). It may be composed of combinations. Preferred specific examples will be described later.

Among the above examples, it is preferable to be composed of a constituent unit containing no Cl because the dehydrochloric acid reaction by a base does not occur and it is more stable.

As a fluorinated alkyl group (b) having a more preferable ether bond, the general formula (b-1):
R ^3- (OR ⁴ ) _n1- (b-1)
(In the formula, R ³ may have a fluorine atom, preferably an alkyl group having 1 to 6 carbon atoms; R ⁴ may have a fluorine atom, preferably an alkylene having 1 to 4 carbon atoms. group; n1 is an integer of 1 to 3; provided that at least one of ^{R 3} and ^{R 4} include those represented by and has a fluorine atom).

Examples of R ³ and R ⁴ include the following, and these can be appropriately combined to form a fluorinated alkyl group (b) having an ether bond represented by the above general formula (b-1). , Not limited to these.

(1) As R ³ , the general formula: X ^c ₃ C- (R ⁵ ) _{n 2-} (three X ^c are the same or different, and all are H or F; R ⁵ is a fluorine atom having 1 to 5 carbon atoms. An alkylene group that may have; n2 is preferably an alkyl group represented by 0 or 1).

When n2 is 0, examples of ^{R 3} include CH _3- , CF _3- , HCF _2-, and H _{2 CF-.}

As a specific example when n2 is 1, assuming that R ³ is linear, CF ₃ CH _2- , CF ₃ CF _2- , CF ₃ CH ₂ CH _2- , CF ₃ CF ₂ CH _2- , CF ₃ CF ₂ CF _2- , CF ₃ CH ₂ CF _2- , CF ₃ CH ₂ CH ₂ CH _2- , CF ₃ CF ₂ CH ₂ CH _2- , CF ₃ CH ₂ CF ₂ CH _2- , CF ₃ CF ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CF ₂ −, CF ₃ CF ₂ CH ₂ CF ₂ −, CF ₃ CH ₂ CH ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CH ₂ CH ₂ −, CF ₃ CH ₂ CF ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CH ₂ CH ₂ CH _2- , CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ CH _2- , CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH _2- , HCF ₂ CH _2- , HCF ₂ CF _2- , HCF ₂ CH ₂ CH _2- , HCF ₂ CF ₂ CH _2- , HCF ₂ CH ₂ CF _2- , HCF ₂ CF ₂ CH ₂ CH _2- , HCF ₂ CH ₂ CF ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF _2- , HCF ₂ CF ₂ CH ₂ CH ₂ CH _2- , HCF ₂ CH ₂ CF ₂ CH ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF ₂ CH ₂ CH _2- , FCH ₂ CH _2- , FCH ₂ CF _2- , FCH ₂ CF ₂ CH _2- , CH ₃ CF _2- , CH ₃ CH _2- , CH ₃ CF ₂ CH _2- , CH ₃ CF ₂ CF _2- , CH ₃ CH ₂ CH _2- , CH ₃ CF ₂ CH ₂ CF _2- , CH ₃ CF ₂ CF ₂ CF _2- , CH ₃ CH ₂ CF ₂ CF _2- , CH ₃ CH ₂ CH ₂ CH _2- , CH ₃ CF ₂ CH ₂ CF ₂ CH ₂ −, CH ₃ CF ₂ CF ₂ CF ₂ CH ₂ −, CH ₃ CF ₂ CF ₂ CH ₂ CH ₂ −, CH ₃ CH ₂ CF ₂ CF ₂ CH ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ Examples thereof include CH ₂ CH ₂ −, CH ₃ CH ₂ CF ₂ CF ₂ CH ₂ CH ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH _{2 −.}

n2 is 1, and as R ³ is branched, the

And so on.

However, _{if it has a branch of CH 3-} or CF _3- , the viscosity tends to be high, so that R ³ is linear is more preferable.

^{(2) In − (OR 4} ) _n1 − of the above general formula (b-1), n1 is an integer of 1 to 3, preferably 1 or 2. When n1 = 2 or 3, R ⁴ may be the same or different.

As ^{a preferable specific example of R 4} , the following linear or branched chain can be exemplified.

As those _{linear, -CH 2 -, - CHF -} , - CF 2 -, - CH 2 CH 2 -, - CF 2 CH 2 -, - CF 2 CF 2 -, - CH 2 CF 2 -, -CH ₂ CH ₂ CH _2- , -CH ₂ CH ₂ CF _2- , -CH ₂ CF ₂ CH _2- , -CH ₂ CF ₂ CF _2- , -CF ₂ CH ₂ CH _2- , -CF ₂ CF ₂ CH _2- , −CF ₂ CH ₂ CF _2- , −CF ₂ CF ₂ CF _2-, etc. can be exemplified.

As a branched chain,

And so on.

The fluorinated alkoxy group (c) is obtained by substituting at least one hydrogen atom of the alkoxy group with a fluorine atom. The fluorinated alkoxy group (c) preferably has 1 to 17 carbon atoms. More preferably, it has 1 to 6 carbon atoms.

The fluorinated alkoxy group (c) has a general formula: X ^d ₃ C- (R ⁶ ) _n3- O- (three X ^d are the same or different, and H or F; R ⁶ is preferably the number of carbon atoms. alkylene group which may have 1 to 5 fluorine atoms; n3 is 0 or 1; with the proviso that one of the three X ^d is a fluorinated alkoxy group represented by contains fluorine atom) are particularly preferred.

Specific examples of the fluorinated alkoxy group (c), a fluorinated alkoxy group terminal oxygen atom is bonded to an alkyl group exemplified as R ¹ in formula (a-1) can be mentioned.

The fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) in the fluorinated saturated cyclic carbonate is preferably 10% by mass or more. If the fluorine content is too low, the effect of lowering the viscosity at low temperature and the effect of raising the flash point may not be sufficiently obtained. From this viewpoint, the fluorine content is more preferably 12% by mass or more, and further preferably 15% by mass or more. The upper limit is usually 76% by mass.
The fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) is determined by {(the number of fluorine atoms) based on the structural formula of each group. It is a value calculated by × 19) / formula amount of each group} × 100 (%).

Further, from the viewpoint of good dielectric constant and oxidation resistance, the fluorine content of the entire fluorinated saturated cyclic carbonate is preferably 10% by mass or more, more preferably 15% by mass or more. The upper limit is usually 76% by mass.
The fluorine content of the fluorinated saturated cyclic carbonate is determined by {(number of fluorine atoms × 19) / molecular weight of the fluorinated saturated cyclic carbonate} × 100 (%) based on the structural formula of the fluorinated saturated cyclic carbonate. It is a calculated value.

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

As a specific example of a fluorinated saturated cyclic carbonate in which at least one of ^{X 1 to} X ^{4 is -F,}

等が挙げられる。これらの化合物は、耐電圧が高く、電解質塩の溶解性も良好である。

And so on. These compounds have a high withstand voltage and good solubility of electrolyte salts.

other,

Etc. can also be used.

As a specific example of the fluorinated saturated cyclic carbonate in which at least one of ^{X 1 to} X ^{4 is a fluorinated alkyl group (a) and the rest are all −H,}

And so on.

Specific Example of Fluorinated Saturated Cyclic Carbonate in which at least one of X ^{1 to} X ⁴ is a fluorinated alkyl group (b) having an ether bond or a fluorinated alkoxy group (c), and the rest are all −H. as,

And so on.

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

Other examples of the fluorinated saturated cyclic carbonate include trans-4,5-difluoro-1,3-dioxolane-2-one, 5- (1,1-difluoroethyl) -4,4-difluoro-1, 3-Dioxolane-2-one, 4-methylene-1,3-dioxolan-2-one, 4-methyl-5-trifluoromethyl-1,3-dioxolan-2-one, 4-ethyl-5-fluoro- 1,3-Dioxolan-2-one, 4-ethyl-5,5-difluoro-1,3-dioxolan-2-one, 4-ethyl-4,5-difluoro-1,3-dioxolan-2-one, 4-Ethyl-4,5,5-trifluoro-1,3-dioxolan-2-one, 4,4-difluoro-5-methyl-1,3-dioxolan-2-one, 4-fluoro-5-methyl -1,3-Dioxolan-2-one, 4-fluoro-5-trifluoromethyl-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one and the like can be mentioned. ..

Examples of the fluorinated saturated cyclic carbonate include fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethylethylene carbonate (3,3,3-trifluoropropylene carbonate), and 2,2,3,3,3-pentafluoro. Propylethylene carbonate is more preferred.

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

The above-mentioned fluorinated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

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

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

Examples of the non-fluorinated chain carbonate include CH ₃ OCOOCH ₃ (dimethyl carbonate: DMC), CH ₃ CH ₂ OCOOCH ₂ CH ₃ (diethyl carbonate: DEC), and CH ₃ CH ₂ OCOOCH ₃ (ethyl methyl carbonate: EMC). ), CH ₃ OCOOCH ₂ CH ₂ CH ₃ (methylpropyl carbonate), methylbutyl carbonate, ethylpropyl carbonate, ethylbutyl carbonate, dipropyl carbonate, dibutyl carbonate, methylisopropyl carbonate, methyl-2-phenylphenyl carbonate, phenyl-2 Hydrocarbon-based chain carbonates such as −phenylphenyl carbonate, trans-2,3-pentylene carbonate, trans-2,3-butylene carbonate, and ethylphenyl carbonate can be mentioned. Among them, at least one selected from the group consisting of ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate is preferable.

As the non-fluorinated chain carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

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

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

The fluorinated chain carbonate has the general formula (B):
Rf ² OCOOR ⁷ (B)
(In the formula, Rf ² is a fluorinated alkyl group ^{having 1 to 7 carbon atoms, and R 7} is an alkyl group which may contain a fluorine atom having 1 to 7 carbon atoms.) Can be mentioned.

Rf ² is a fluorinated alkyl group having 1 to 7 carbon atoms, and R ⁷ is an alkyl group which may contain a fluorine atom having 1 to 7 carbon atoms.
The above-mentioned fluorinated alkyl group is obtained by substituting at least one hydrogen atom of the alkyl group with a fluorine atom. When R ⁷ is an alkyl group containing a fluorine atom, it becomes a fluorinated alkyl group.
Rf ² and R ⁷ preferably have 1 to 7 carbon atoms, and more preferably 1 to 2 carbon atoms in that they have low viscosity.
If the carbon number is too large, the low temperature characteristics may be deteriorated or the solubility of the electrolyte salt may be lowered. If the carbon number is too small, the solubility of the electrolyte salt may be lowered, the discharge efficiency may be lowered, and further, the solubility of the electrolyte salt may be lowered. Increased viscosity may be seen.

Examples of the fluorinated alkyl group having 1 carbon atom include CFH _2- , CF ₂ H-, and CF _3- . In particular, CFH _2- or CF ₃ -is preferable in terms of high-temperature storage characteristics.

Examples of the fluorinated alkyl group having 2 or more carbon atoms include the following general formula (d-1):
R ¹ − R ² − (d-1)
(In the formula, R ¹ is an alkyl group having 1 or more carbon ^{atoms which may have a fluorine atom; R 2} is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; however, R ¹ and The ^{alkyl fluorinated group represented by (at least one of R 2} has a fluorine atom) can be preferably exemplified from the viewpoint of good solubility of the electrolyte salt.
In addition, R ¹ and R ² may further have other atoms other than carbon atom, hydrogen atom and fluorine atom.

R ¹ is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. As R ¹ , a linear or branched alkyl group having 1 to 6 carbon atoms is preferable. The ^{number of carbon atoms of R 1} is more preferably 1 to 3.

As R ¹ , specifically, as a linear or branched alkyl group, CH _3- , CF _3- , CH ₃ CH _2- , CH ₃ CH ₂ CH _2- , CH ₃ CH ₂ CH ₂ CH. _2- ,

And so on.

When R ¹ is a linear alkyl group having a fluorine atom, CF _3- , CF ₃ CH _2- , CF ₃ CF _2- , CF ₃ CH ₂ CH _2- , CF ₃ CF ₂ CH _2- , CF ₃ CF ₂ CF _2- , CF ₃ CH ₂ CF _2- , CF ₃ CH ₂ CH ₂ CH _2- , CF ₃ CF ₂ CH ₂ CH _2- , CF ₃ CH ₂ CF ₂ CH _2- , CF ₃ CF ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CF ₂ −, CF ₃ CF ₂ CH ₂ CF ₂ −, CF ₃ CH ₂ CH ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CH ₂ CH ₂ − , CF ₃ CH ₂ CF ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CH ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ CH ₂ −, CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH ₂ −, HCF ₂ −, HCF ₂ CH ₂ − , HCF ₂ CF ₂ −, HCF ₂ CH ₂ CH ₂ −, HCF ₂ CF ₂ CH ₂ −, HCF ₂ CH ₂ CF ₂ −, HCF ₂ CF ₂ CH ₂ CH ₂ −, HCF ₂ CH ₂ CF ₂ CH ₂ − , HCF ₂ CF ₂ CF ₂ CF _2- , HCF ₂ CF ₂ CH ₂ CH ₂ CH _2- , HCF ₂ CH ₂ CF ₂ CH ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF ₂ CH ₂ CH _2- , FCH _2- , FCH ₂ CH _2- , FCH ₂ CF _2- , FCH ₂ CF ₂ CH _2- , FCH ₂ CF ₂ CF _2- , CH ₃ CF ₂ CH _2- , CH ₃ CF ₂ CF ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ −, CH ₃ CF ₂ CF ₂ CF ₂ −, CH ₃ CH ₂ CF ₂ CF ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ CH ₂ − , CH ₃ CF ₂ CF ₂ CF ₂ CH ₂ −, CH ₃ CF ₂ CF ₂ CH ₂ CH ₂ −, CH ₃ CH ₂ CF ₂ CF ₂ CH ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH ₂ −, CH ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH _2- , HCFClCF ₂ CH _2- , HCF ₂ CFClCH _2- , HCF ₂ CFClCF ₂ CFClCH _2- , HCFClCF ₂ CFClCF ₂ CH _2- and the like can be mentioned.

When R ¹ is a branched-chain alkyl group having a fluorine atom,

Etc. are preferably mentioned. However, _{if it has a branch of CH 3-} or CF _3- , the viscosity tends to be high, so the number is more preferably small (1) or zero.

R ² is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom. R ² may be linear or branched. An example of the smallest structural unit constituting such a linear or branched alkylene group is shown below. R ² is composed of these alone or in combination.

(I) Linear minimum structural unit:
_{-CH 2 -, - CHF -,} - CF 2 -, - CHCl -, - CFCl -, - CCl 2 -

(Ii) Branched chain minimum structural unit:

Among the above examples, it is preferable to be composed of a constituent unit containing no Cl because the dehydrochloric acid reaction by a base does not occur and it is more stable.

When R ² is linear, it is composed of only the linear minimum structural unit described above, and among them, −CH ₂ −, _{−CH 2} CH ₂ − or −CF ₂₋ is preferable. _{-CH 2-} or -CH ₂ CH ₂ --is more preferable from the viewpoint that the solubility of the electrolyte salt can be further improved.

When R ² is in the form of a branched chain, it contains at least one of the above-mentioned minimum structural units in the form of a branched chain, and the general formula-(CX ^a X ^b )-(X ^a is H, F). , CH ₃ or CF ₃ ; X ^b is CH ₃ or CF _3. However, when X ^b is CF ₃ , X ^a is H or CH ₃ ). These can further improve the solubility of the electrolyte salt in particular.

Specific preferred alkyl fluorinated groups include, for example, CF ₃ CF _2- , HCF ₂ CF _2- , H ₂ CFCF _2- , CH ₃ CF _2- , CF ₃ CH _2- , CF ₃ CF ₂ CF. _2- , HCF ₂ CF ₂ CF _2- , H ₂ CFCF ₂ CF _2- , CH ₃ CF ₂ CF _2- ,

And so on.

Among them, as the fluorinated alkyl groups of ^{Rf 2} and R ⁷ _{, CF 3-} , CF ₃ CF _2- , (CF ₃ ) ₂ CH-, CF ₃ CH _2- , C ₂ F ₅ CH _2- , CF ₃ CF ₂ CH _2- , HCF ₂ CF ₂ CH _2- , CF ₃ CFHCF ₂ CH _2- , CFH _2- , CF ₂ H- are preferable, and they have high flame retardancy and good rate characteristics and oxidation resistance. , CF ₃ CH _2- , CF ₃ CF ₂ CH _2- , HCF ₂ CF ₂ CH _2- , CFH _2- , CF ₂ H- are more preferable.

When R ⁷ is an alkyl group containing no fluorine atom, it is an alkyl group having 1 to 7 carbon atoms. R ⁷ preferably has 1 to 4 carbon atoms, and more preferably 1 to 3 carbon atoms in that it has a low viscosity.

Examples of the alkyl group containing no fluorine atom include CH ₃ −, CH ₃ CH ₂ −, (CH ₃ ) ₂ CH −, C ₃ H ₇ − and the like. _{Of these, CH 3} − and CH ₃ CH ₂ − are preferable because of their low viscosity and good rate characteristics.

The fluorinated chain carbonate preferably has a fluorine content of 15 to 70% by mass. When the fluorine content is in the above range, the compatibility with the solvent and the solubility of the salt can be maintained. The fluorine content is more preferably 20% by mass or more, further preferably 30% by mass or more, particularly preferably 35% by mass or more, further preferably 60% by mass or less, still more preferably 50% by mass or less.
In the present invention, the fluorine content is determined based on the structural formula of the fluorinated chain carbonate.
{(Number of fluorine atoms x 19) / Molecular weight of fluorinated chain carbonate} x 100 (%)
It is a value calculated by.

The fluorinated chain carbonate is preferably one of the following compounds in terms of low viscosity.

Examples of the fluorinated chain carbonate include methyl 2,2,2-trifluoroethyl carbonate (F ₃ CH ₂ COC (= O) OCH ₃ ) and fluoromethyl methyl carbonate (FH ₂ COC (= O) OCH ₃ ). Especially preferable.

The above-mentioned fluorinated chain carbonate may be used alone or in combination of two or more in any combination and ratio.

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

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

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

Examples of the non-fluorinated cyclic carboxylic acid ester include a non-fluorinated saturated cyclic carboxylic acid ester, and a non-fluorinated saturated cyclic carboxylic acid ester having an alkylene group having 2 to 4 carbon atoms is preferable.

Specific examples of the non-fluorinated saturated cyclic carboxylic acid ester having an alkylene group having 2 to 4 carbon atoms include β-propiolactone, γ-butyrolactone, ε-caprolactone, δ-valerolactone, and α-methyl-γ-. Butyrolactone can be mentioned. Of these, γ-butyrolactone and δ-valerolactone are particularly preferable from the viewpoint of improving the degree of lithium ion dissociation and improving the load characteristics.

As the non-fluorinated saturated cyclic carboxylic acid ester, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

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

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

Examples of the non-fluorinated chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, tert-butyl propionate, and tert. -Butylbutyrate, sec-butylpropionate, sec-butylbutyrate, n-butylbutyrate, methyl pyrophosphate, ethyl pyrophosphate, tert-butylformate, tert-butylacetate, sec-butylformate, sec -Butyl acetate, n-hexyl pivalate, n-propyl formate, n-propyl acetate, n-butyl formate, n-butyl pivalate, n-octyl pivalate, ethyl 2- (dimethoxyphosphoryl) acetate, ethyl 2- ( Dimethylphosphoryl) acetate, ethyl2- (diethoxyphosphoryl) acetate, ethyl2- (diethylphosphoryl) acetate, isopropylpropionate, isopropylacetate, ethylformate, ethyl2-propynyloxalate, isopropylformate, isopropylbutyl Examples thereof include rate, isobutylformate, isobutylpropionate, isobutylbutyrate, isobutylacetate and the like.

Of these, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate are preferable, and ethyl propionate and propyl propionate are particularly preferable.

As the non-fluorinated chain carboxylic acid ester, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

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

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

The fluorinated chain carboxylic acid ester has the following general formula:
R ³¹ COOR ³²
(In the formula, R ³¹ and R ³² are alkyl groups which may contain fluorine atoms having 1 to 4 carbon atoms independently of each other, and ^{at least one of R 31} and R ³² contains a fluorine atom.) The fluorinated chain carboxylic acid ester shown is preferable from the viewpoint of good compatibility with other solvents and oxidation resistance.

Examples of R ³¹ and R ³² include a methyl group (-CH ₃ ), an ethyl group (-CH ₂ CH ₃ ), a propyl group (-CH ₂ CH ₂ CH ₃ ), and an isopropyl group (-CH (CH ₃ ) ₂ ). , Normal butyl group (-CH ₂ CH ₂ CH ₂ CH ₃ ), tertiary butyl group (-C (CH ₃ ) ₃ ) and other non-fluorinated alkyl groups; -CF ₃ , -CF ₂ H, -CFH ₂ , -CF ₂ CF ₃ , -CF ₂ CF ₂ H, -CF ₂ CFH ₂ , -CH ₂ CF ₃ , -CH ₂ CF ₂ H, -CH ₂ CFH ₂ , -CF ₂ CF ₂ CF ₃ , -CF ₂ CF ₂ CF ₂ H, -CF ₂ CF ₂ CFH ₂ , -CH ₂ CF ₂ CF ₃ , -CH ₂ CF ₂ CF ₂ H, -CH ₂ CF ₂ CFH ₂ , -CH ₂ CH ₂ CF ₃ , -CH ₂ CH ₂ CF ₂ H, -CH ₂ CH ₂ CFH ₂ , -CF (CF ₃ ) ₂ , -CF (CF ₂ H) ₂ , -CF (CFH ₂ ) ₂ , -CH (CF ₃ ) ₂ , -CH (CF) ₂ H) ₂ , -CH (CFH ₂ ) ₂ , -CF (OCH ₃ ) CF ₃ , -CF ₂ CF ₂ CF ₂ CF ₃ , -CF ₂ CF ₂ CF ₂ CF ₂ H, -CF ₂ CF ₂ CF ₂ CFH ₂ , -CH ₂ CF ₂ CF ₂ CF ₃ , -CH ₂ CF ₂ CF ₂ CF ₂ H, -CH ₂ CF ₂ CF ₂ CFH ₂ , -CH ₂ CH ₂ CF ₂ CF ₃ , -CH ₂ CH ₂ CF ₂ CF ₂ H, -CH ₂ CH ₂ CF ₂ CFH ₂ , -CH ₂ CH ₂ CH ₂ CF ₃ , -CH ₂ CH ₂ CH ₂ CF ₂ H, -CH ₂ CH ₂ CH ₂ CFH ₂ , -CF (CF) ₃ ) CF ₂ CF ₃ , -CF (CF ₂ H) CF ₂ CF ₃ , -CF (CFH ₂ ) CF ₂ CF ₃ , -CF (CF ₃ ) CF ₂ CF ₂ H, -CF (CF ₃ ) CF ₂ CFH ₂ , -CF (CF ₃ ) CH ₂ CF ₃ , -CF (CF ₃ ) CH ₂ CF ₂ H, -CF (CF ₃ ) CH ₂ CFH ₂ , -CH (CF ₃ ) CF ₂ CF ₃ , -CH (C F ₂ H) CF ₂ CF ₃ , -CH (CFH ₂ ) CF ₂ CF ₃ , -CH (CF ₃ ) CF ₂ CF ₂ H, -CH (CF ₃ ) CF ₂ CFH ₂ , -CH (CF ₃ ) CH ₂ CF ₃ , -CH (CF ₃ ) CH ₂ CF ₂ H, -CH (CF ₃ ) CH ₂ CFH ₂ , -CF ₂ CF (CF ₃ ) CF ₃ , -CF ₂ CF (CF ₂ H) CF ₃ , -CF ₂ CF (CFH ₂ ) CF ₃ , -CF ₂ CF (CF ₃ ) CF ₂ H, -CF ₂ CF (CF ₃ ) CFH ₂ , -CH ₂ CF (CF ₃ ) CF ₃ , -CH ₂ CF ( CF ₂ H) CF ₃ , -CH ₂ CF (CFH ₂ ) CF ₃ , -CH ₂ CF (CF ₃ ) CF ₂ H, -CH ₂ CF (CF ₃ ) CFH ₂ , -CH ₂ CH (CF ₃ ) CF ₃ , -CH ₂ CH (CF ₂ H) CF ₃ , -CH ₂ CH (CFH ₂ ) CF ₃ , -CH ₂ CH (CF ₃ ) CF ₂ H, -CH ₂ CH (CF ₃ ) CFH ₂ , -CF ₂ CH (CF ₃ ) CF ₃ , -CF ₂ CH (CF ₂ H) CF ₃ , -CF ₂ CH (CFH ₂ ) CF ₃ , -CF ₂ CH (CF ₃ ) CF ₂ H, -CF ₂ CH (CF) ₃ ) Examples thereof include fluorinated alkyl groups such as _{CFH 2} , -C (CF ₃ ) ₃ , -C (CF ₂ H) ₃ , and -C (CFH ₂ ) _3. Among them, methyl group, ethyl group, -CF ₃ , -CF ₂ H, -CF ₂ CF ₃ , -CH ₂ CF ₃ , -CH ₂ CF ₂ H, -CH ₂ CFH ₂ , -CH ₂ CH ₂ CF ₃ , -CH ₂ CF ₂ CF ₃ , -CH ₂ CF ₂ CF ₂ H, and -CH ₂ CF ₂ CFH ₂ are particularly preferable because they have good compatibility with other solvents, viscosity, and oxidation resistance.

Specific examples of the fluorinated chain carboxylic acid ester include CF ₃ CH ₂ C (= O) OCH ₃ (methyl 3,3,3-trifluoropropionate) and HCF ₂ C (= O) OCH ₃ (. Methyl difluoroacetate), HCF ₂ C (= O) OC ₂ H ₅ (ethyl difluoroacetate), CF ₃ C (= O) OCH ₂ CH ₂ CF ₃ , CF ₃ C (= O) OCH ₂ C ₂ F ₅ , CF ₃ C (= O) OCH ₂ CF ₂ CF ₂ H (trifluoroacetic acid 2,2,3,3-tetrafluoropropyl), CF ₃ C (= O) OCH ₂ CF ₃ , CF ₃ C (= O) OCH (CF ₃ ) ₂ , ethyl pentafluorobutyrate, methyl pentafluoropropionate, ethyl pentafluoropropionate, methyl heptafluoroisobutyrate, isopropyl trifluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, trifluoroacetic acid n-butyl, methyl tetrafluoro-2- (methoxy) propionate, 2,2-difluoroethyl acetate, 2,2,3,3-tetrafluoropropyl acetate, CH ₃ C (= O) OCH ₂ CF ₃ (acetic acid) 2,2,2-trifluoroethyl), 1H, 1H-heptafluorobutyl acetate, methyl 4,4,4-trifluorobutyrate, ethyl 4,4,4-trifluorobutyrate, 3,3,3-trifluoro Ethyl propionate, 3,3,3-trifluoropropionic acid 3,3,3 trifluoropropyl, ethyl 3- (trifluoromethyl) butyrate, methyl 2,3,3,3-tetrafluoropropionate, 2,2 -Butyl difluoroacetate, methyl 2,2,3,3-tetrafluoropropionate, methyl 2- (trifluoromethyl) -3,3,3-trifluoropropionate, methyl heptafluorobutyrate, etc. The above can be exemplified.
Among them, CF ₃ CH ₂ C (= O) OCH ₃ , HCF ₂ C (= O) OCH ₃ , HCF ₂ C (= O) OC ₂ H ₅ , CF ₃ C (= O) OCH ₂ C ₂ F ₅ , CF ₃ C (= O) OCH ₂ CF ₂ CF ₂ H, CF ₃ C (= O) OCH ₂ CF ₃ , CF ₃ C (= O) OCH (CF ₃ ) ₂ , ethyl pentafluorobutyrate, pentafluoropropionic acid Methyl, ethyl pentafluoropropionate, methyl heptafluoroisobutyrate, isopropyl trifluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, n-butyl trifluoroacetate, methyl tetrafluoro-2- (methoxy) propionate, 2,2-Difluoroethyl acetate, 2,2,3,3-tetrafluoropropyl acetate, CH ₃ C (= O) OCH ₂ CF ₃ , 1H, 1H-heptafluorobutyl acetate, 4,4,4-trifluoro Methyl butyrate, ethyl 4,4,4-trifluorobutyrate, ethyl 3,3,3-trifluoropropionate, 3,3,3-trifluoropropionic acid 3,3,3-trifluoropropyl, 3- (tri) Ethylfluoromethyl) butyrate, methyl 2,3,3,3-tetrafluoropropionate, butyl 2,2-difluoroacetate, methyl 2,2,3,3-tetrafluoropropionate, 2- (trifluoromethyl)- Methyl 3,3,3-trifluoropropionate and methyl heptafluorobutyrate are preferable from the viewpoint of good compatibility with other solvents and rate characteristics, and CF ₃ CH ₂ C (= O) OCH ₃ and HCF ₂ C ( = O) OCH ₃ , HCF ₂ C (= O) OC ₂ H ₅ , CH ₃ C (= O) OCH ₂ CF ₃ is more preferred, HCF ₂ C (= O) OCH ₃ , HCF ₂ C (= O) OC ₂ H ₅ and CH ₃ C (= O) OCH ₂ CF ₃ are particularly preferred.

The above-mentioned fluorinated chain carboxylic acid ester may be used alone or in combination of two or more in any combination and ratio.

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

The solvent preferably contains at least one selected from the group consisting of the cyclic carbonate, the chain carbonate and the chain carboxylic acid ester, and the cyclic carbonate, the chain carbonate and the chain carboxylic acid. It is more preferable to include at least one selected from the group consisting of esters. The cyclic carbonate is preferably a saturated cyclic carbonate.
According to the electrolytic solution containing the solvent having the above composition, an electrochemical device having a lower resistance, more excellent cycle characteristics, and less gas generation can be obtained.

When the solvent contains the cyclic carbonate and at least one selected from the group consisting of the chain carbonate and the chain carboxylic acid ester, the cyclic carbonate, the chain carbonate and the chain carboxylic acid ester In total, it preferably contains 10 to 100% by volume, more preferably 30 to 100% by volume, and even more preferably 50 to 100% by volume, with at least one selected from the group consisting of.

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

The solvent also preferably contains at least one selected from the group consisting of the non-fluorinated saturated cyclic carbonate, the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester, and the non-fluorinated one. It is more preferable to contain a saturated cyclic carbonate and at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester. The electrolytic solution containing the solvent having the above composition can be suitably used for an electrochemical device used at a relatively low voltage.

When the solvent contains the non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester, the non-fluorinated saturated cyclic carbonate. The carbonate and at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester are preferably contained in a total of 5 to 100% by volume, preferably 20 to 100% by volume. It is more preferably contained, and more preferably 30 to 100% by volume.

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

The solvent also preferably contains at least one selected from the group consisting of the fluorinated saturated cyclic carbonate, the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester, and the fluorinated saturated cyclic carbonate. And at least one selected from the group consisting of the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester. The electrolytic solution containing the solvent having the above composition can be suitably used not only for an electrochemical device used at a relatively low voltage but also for an electrochemical device used at a relatively high voltage.

When the solvent contains the fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester, the fluorinated saturated cyclic carbonate and the above The total content of at least one selected from the group consisting of the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester is preferably 5 to 100% by volume, more preferably 10 to 100% by volume. It is more preferable to contain 30 to 100% by volume.

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

An ionic liquid can also be used as the solvent. An "ionic liquid" is a liquid composed of ions in which an organic cation and an anion are combined.

The organic cation is not particularly limited, and examples thereof include imidazolium ions such as dialkyl imidazolium cations and trialkyl imidazolium cations; tetraalkylammonium ions; alkylpyridinium ions; dialkylpyrridinium ions; and dialkylpiperidinium ions. ..

The anions that serve as counters for these organic cations are not particularly limited, but are, for example, PF ₆ anions, PF ₃ (C ₂ F ₅ ) ₃ anions, PF ₃ (CF ₃ ) ₃ anions, BF ₄ anions, and BF ₂ ( CF ₃ ) ₂ anion, BF ₃ (CF ₃ ) anion, bisoxalate borate anion, P (C ₂ O ₄ ) F ₂ anion, Tf (trifluoromethanesulfonyl) anion, Nf (nonafluorobutanesulfonyl) anion, bis ( Fluorosulfonyl) imide anion, bis (trifluoromethanesulfonyl) imide anion, bis (pentafluoroethanesulfonyl) imide anion, dicyanoamine anion, and halide anion can be used.

The solvent is preferably a non-aqueous solvent, and the electrolytic solution of the present invention is preferably a non-aqueous electrolytic solution.
The content of the solvent is preferably 70 to 99.999% by mass, more preferably 80% by mass or more, and more preferably 92% by mass or less in the electrolytic solution.

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

（式中、Ａ^ａ＋は金属イオン、水素イオン又はオニウムイオン。ａは１〜３の整数、ｂは１〜３の整数、ｐはｂ／ａ、ｎ２０３は１〜４の整数、ｎ２０１は０〜８の整数、ｎ２０２は０又は１、Ｚ^２０１は遷移金属、周期律表のＩＩＩ族、ＩＶ族又はＶ族の元素。
Ｘ^２０１は、Ｏ、Ｓ、炭素数１〜１０のアルキレン基、炭素数１〜１０のハロゲン化アルキレン基、炭素数６〜２０のアリーレン基又は炭素数６〜２０のハロゲン化アリーレン基（アルキレン基、ハロゲン化アルキレン基、アリーレン基、及び、ハロゲン化アリーレン基はその構造中に置換基、ヘテロ原子を持っていてもよく、またｎ２０２が１でｎ２０３が２〜４のときにはｎ２０３個のＸ^２０１はそれぞれが結合していてもよい）。
Ｌ^２０１は、ハロゲン原子、シアノ基、炭素数１〜１０のアルキル基、炭素数１〜１０のハロゲン化アルキル基、炭素数６〜２０のアリール基、炭素数６〜２０のハロゲン化アリール基（アルキレン基、ハロゲン化アルキレン基、アリーレン基、及び、ハロゲン化アリーレン基はその構造中に置換基、ヘテロ原子を持っていてもよく、またｎ２０１が２〜８のときにはｎ２０１個のＬ^２０１はそれぞれが結合して環を形成してもよい）又は−Ｚ^２０３Ｙ^２０３。
Ｙ^２０１、Ｙ^２０２及びＺ^２０３は、それぞれ独立でＯ、Ｓ、ＮＹ^２０４、炭化水素基又はフッ素化炭化水素基。Ｙ^２０３及びＹ^２０４は、それぞれ独立でＨ、Ｆ、炭素数１〜１０のアルキル基、炭素数１〜１０のハロゲン化アルキル基、炭素数６〜２０のアリール基又は炭素数６〜２０のハロゲン化アリール基（アルキル基、ハロゲン化アルキル基、アリール基及びハロゲン化アリール基はその構造中に置換基、ヘテロ原子を持っていてもよく、Ｙ^２０３又はＹ^２０４が複数個存在する場合にはそれぞれが結合して環を形成してもよい）。）General formula (5):

(In the formula, A ^{a +} is a metal ion, a hydrogen ion or an onium ion. A is an integer of 1 to 3, b is an integer of 1 to 3, p is b / a, n203 is an integer of 1 to 4, and n201 is 0 to 0. An integer of 8, n202 is 0 or 1, Z ²⁰¹ is a transition metal, and an element of Group III, Group IV or Group V of the periodic table.
X ²⁰¹ is O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (alkylene group). , a halogenated alkylene group, an arylene group, and halogenated arylene group substituent in its structure, n203 amino ^{X 201} when the may have a hetero atom, and n202 is at 1 n203 is 2 to 4 Each may be combined).
L ²⁰¹ is a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, an alkyl halide group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aryl halide group having 6 to 20 carbon atoms ( alkylene group, a halogenated alkylene group, an arylene group, and halogenated arylene group substituent in its structure, may have a hetero atom, and when n201 is 2 to 8, respectively n201 amino L ²⁰¹ May be combined to form a ring) or -Z ²⁰³ Y ²⁰³ .
Y ²⁰¹ , Y ²⁰² and Z ²⁰³ are independently O, S, NY ²⁰⁴ , hydrocarbon groups or fluorinated hydrocarbon groups, respectively. Y ²⁰³ and Y ²⁰⁴ are independently H, F, an alkyl group having 1 to 10 carbon atoms, an alkyl halide group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogen having 6 to 20 carbon atoms. The aryl group (alkyl group, alkyl halide group, aryl group and aryl halide group may have a substituent and a hetero atom in the structure, respectively, when a plurality of ^{Y 203} or Y ^{204 are present, respectively.} May combine to form a ring). )

A ^{a +} includes lithium ion, sodium ion, potassium ion, magnesium ion, calcium ion, barium ion, cesium ion, silver ion, zinc ion, copper ion, cobalt ion, iron ion, nickel ion, manganese ion, titanium ion, etc. Lead ion, chromium ion, vanadium ion, ruthenium ion, ittrium ion, lanthanoid ion, actinoid ion, tetrabutylammonium ion, tetraethylammonium ion, tetramethylammonium ion, triethylmethylammonium ion, triethylammonium ion, pyridinium ion, imidazolium ion , Hydrogen ion, tetraethylphosphonium ion, tetramethylphosphonium ion, tetraphenylphosphonium ion, triphenylsulfonium ion, triethylsulfonium ion and the like.

When used in applications such as electrochemical devices, A ^{a +} is preferably lithium ion, sodium ion, magnesium ion, tetraalkylammonium ion, or hydrogen ion, and lithium ion is particularly preferable. The valence a of the cation of A ^{a +} is an integer of 1 to 3. If it is larger than 3, the crystal lattice energy becomes large, which causes a problem that it becomes difficult to dissolve in a solvent. Therefore, 1 is more preferable when solubility is required. The valence b of the anion is also an integer of 1 to 3, and 1 is particularly preferable. The constant p representing the ratio of cations and anions is inevitably determined by the ratio b / a of the valences of both.

Next, the ligand portion of the general formula (5) will be described. ^{In the present specification, the organic or inorganic moiety bound to Z 201} in the general formula (5) is referred to as a ligand.

Z ²⁰¹ is preferably Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf or Sb, and Al. , B or P is more preferable.

X ²⁰¹ represents O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms. These alkylene groups and arylene groups may have substituents and heteroatoms in their structures. Specifically, instead of hydrogen on an alkylene group and an arylene group, a halogen atom, a chain or cyclic alkyl group, an aryl group, an alkenyl group, an alkoxy group, an aryloxy group, a sulfonyl group, an amino group, a cyano group, or a carbonyl group. It may have a group, an acyl group, an amide group, or a hydroxyl group as a substituent, or it may have a structure in which nitrogen, sulfur, or oxygen is introduced instead of carbon on alkylene and arylene. Also when n202 is 1 in n203 is 2 to 4, n203 amino ^{X 201} may be bonded respectively. Such examples include ligands such as ethylenediaminetetraacetic acid.

L ²⁰¹ is a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, an alkyl halide group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryl halide group having 6 to 20 carbon atoms, or the like. -Z ²⁰³ Y ²⁰³ (Z ²⁰³ and Y ²⁰³ will be described later). ^{Similar to X 201} , the alkyl group and aryl group here may also have a substituent and a hetero atom in the structure, and when n ²⁰¹ is 2 to 8, n 201 L 201 are bonded to each other. May form a ring. As L ²⁰¹ , a fluorine atom or a cyano group is preferable. This is because, in the case of a fluorine atom, the solubility and dissociation degree of the salt of the anionic compound are improved, and the ionic conductivity is improved accordingly. In addition, the oxidation resistance is improved, which can suppress the occurrence of side reactions.

Y ²⁰¹ , Y ²⁰² and Z ²⁰³ independently represent O, S, NY ²⁰⁴ , hydrocarbon groups or fluorinated hydrocarbon groups. Y ²⁰¹ and Y ²⁰² are preferably O, S or NY ²⁰⁴ , and more preferably O. Since the compound (5) has a bond with ^{Z 201 by Y 201} and Y ²⁰² in the same ligand, these ligands form a chelate structure with ^{Z 201.} Due to the effect of this chelate, the heat resistance, chemical stability, and hydrolysis resistance of this compound are improved. The constant n202 in this ligand is 0 or 1, but in particular, when it is 0, the chelating ring becomes a five-membered ring, so that the chelating effect is most strongly exerted and the stability is increased, which is preferable.
In the present specification, the fluorinated hydrocarbon group is a group in which at least one hydrogen atom of the hydrocarbon group is replaced with a fluorine atom.

Y ²⁰³ and Y ²⁰⁴ are independently H, F, an alkyl group having 1 to 10 carbon atoms, an alkyl halide group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. It is an aryl halide group, and these alkyl groups and aryl groups may have a substituent or a hetero atom in the structure, and ^{when a plurality of Y 203} or Y ²⁰⁴ are present, each of them is bonded. May form a ring.

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

In the general formula (5), the alkyl group, the alkyl halide group, the aryl group, and the aryl halide group include those having other functional groups such as a branch, a hydroxyl group, and an ether bond.

（式中、Ａ^ａ＋、ａ、ｂ、ｐ、ｎ２０１、Ｚ^２０１及びＬ^２０１は上述したとおり）で示される化合物、又は、一般式：

（式中、Ａ^ａ＋、ａ、ｂ、ｐ、ｎ２０１、Ｚ^２０１及びＬ^２０１は上述したとおり）で示される化合物であることが好ましい。The compound (5) has a general formula:

(In the formula, A ^{a +} , a, b, p, n201, Z ²⁰¹ and L ²⁰¹ are as described above), or a general formula:

(In the formula, A ^{a +} , a, b, p, n201, Z ²⁰¹ and L ²⁰¹ are as described above).

で示されるリチウムビス（オキサラト）ボレート（ＬＩＢＯＢ）、下記式：

で示されるリチウムジフルオロオキサラトボレート（ＬＩＤＦＯＢ）、Examples of the compound (5) include lithium oxalatoborate salts, which have the following formula:

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

Lithium difluorooxalatoborate (LIDFOB), indicated by

で示されるリチウムジフルオロオキサラトホスファナイト（ＬＩＤＦＯＰ）、下記式：

で示されるリチウムテトラフルオロオキサラトホスファナイト（ＬＩＴＦＯＰ）、下記式：

で示されるリチウムビス（オキサラト）ジフルオロホスファナイト等が挙げられる。The compound (5) also includes the following formula:

Lithium difluorooxalatphosphanite (LIDFOP) represented by, the following formula:

Lithium tetrafluorooxalatphosphanite (LITFOP) represented by, the following formula:

Examples thereof include lithium bis (oxalate) difluorophosphanite represented by.

Other specific examples of the dicarboxylic acid complex salt in which the central element of the complex is boron include lithium bis (malonato) borate, lithium difluoro (malonato) borate, lithium bis (methylmalonato) borate, lithium difluoro (methylmalonato) borate, and lithium bis (. Examples thereof include dimethylmalonato) borate and lithium difluoro (dimethylmalonato) borate.

Specific examples of the dicarboxylic acid complex salt in which the central element of the complex is phosphorus include lithium tris (oxalat) phosphate, lithium tris (malonato) phosphate, lithium difluorobis (malonato) phosphate, lithium tetrafluoro (malonato) phosphate, and lithium tris (lithium tris (malonato) phosphate. Methylmalonato) phosphate, lithium difluorobis (methylmalonato) phosphate, lithium tetrafluoro (methylmalonato) phosphate, lithiumtris (dimethylmalonato) phosphate, lithium difluorobis (dimethylmalonato) phosphate, lithium tetrafluoro (dimethylmalonato) phosphate, etc. Can be mentioned.

Specific examples of the dicarboxylic acid complex salt in which the complex center element is aluminum include LiAl (C ₂ O ₄ ) ₂ , _{LiAl F 2} (C ₂ O ₄ ) and the like.

Among them, lithium bis (oxalate) oxalate, lithium difluoro (oxalate) oxalate, lithium tris (oxalate) oxalate, lithium difluorobis (oxalate) oxalate, and lithium tetrafluoro (oxalate) oxalate are easily available and have a stable film-like structure. It is more preferably used because it can contribute to the formation of an object.

The content of compound (5) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and 10% by mass, based on the above solvent, because even more excellent cycle characteristics can be obtained. % Or less is preferable, and 3% by mass or less is more preferable.

The electrolytic solution of the present invention preferably further contains an electrolyte salt (however, excluding compound (5)). As the electrolyte salt, in addition to lithium salt, ammonium salt and metal salt, liquid salt (ionic liquid), inorganic polymer type salt, organic polymer type salt and the like can be used in the electrolyte solution. Any one can be used.

As the electrolyte salt of the electrolytic solution for a lithium ion secondary battery, a lithium salt is preferable.
Any of the above lithium salts can be used, and specific examples thereof include the following. For _{example, LiPF 6, LiBF 4, LiClO} 4, LiAlF 4, LiSbF 6, LiTaF 6, LiWF 7, LiAsF 6, LiAlCl 4, LiI, LiBr, LiCl, LiB 10 Cl 10, Li 2 SiF 6, Li 2 PFO 3, Inorganic lithium salts such as LiPO ₂ F _2;
Lithium tungstates such as LiWOF _5;
HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF ₃ CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ Lithium carboxylic acid salts such as CO ₂ Li, CF ₃ CF ₂ CF ₂ CF ₂ CO _{2 Li;}
FSO ₃ Li, CH ₃ SO ₃ Li, CH ₂ FSO ₃ Li, CHF ₂ SO ₃ Li, CF ₃ SO ₃ Li, CF ₃ CF ₂ SO ₃ Li, CF ₃ CF ₂ CF ₂ SO ₃ Li, CF ₃ CF ₂ CF ₂ CF ₂ SO ₃ Li, lithium methyl sulfate, lithium ethyl sulfate (C ₂ H ₅ OSO ₃ Li), lithium 2,2,2-trifluoroethyl sulfate and other lithium salts having an S = O group;
LiN (FCO) ₂ , LiN (FCO) (FSO ₂ ), LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO) ₂ ) _2. Lithium bisperfluoroethanesulfonylimide, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, lithium cyclic 1,2-ethanedisulfonylimide, lithium Cyclic 1,3-propanedisulfonylimide, lithium cyclic 1,4-perfluorobutanedisulfonylimide, LiN (CF ₃ SO ₂ ) (FSO ₂ ), LiN (CF ₃ SO ₂ ) (C ₃ F ₇ SO ₂ ) , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (POF ₂ ) _{2 and} other lithium imide salts;
Lithiummethide salts such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) _3;
In addition, the formula: LiPF _a (C _n F _{2n + 1} ) _6-a (in the formula, a is an integer of 0 to 5 and n is an integer of 1 to 6) (for example, LiPF ₃ (C). ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (iso-C ₃ F ₇ ) ₃ , LiPF ₅ (iso-C ₃ F ₇ ), 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 ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiBF ₃ C ₃ F ₇ , 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, LiSCN, LiB (CN) 4} , LiB (C ₆ H ₅ ) ₄ , Li ₂ (C ₂ O ₄ ), LiP (C ₂ O ₄ ) ₃ , Li ₂ B ₁₂ F _b H _12-b (b is an integer of 0 to 3), etc. Can be mentioned.

Among them, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiTaF ₆ , LiPO ₂ F ₂ , FSO ₃ Li, CF ₃ SO ₃ Li, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN ( CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Lithium cyclic 1,2-perfluoroethanedisulfonylimide, Lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) ₃ Etc. are particularly preferable because they have the effect of improving output characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, etc., and at least one selected from the group consisting of _{LiPF 6} , LiN (FSO ₂ ) ₂ and LiBF _4. Lithium salt is most preferable.

These electrolyte salts may be used alone or in combination of two or more. Preferred examples of the combined use of two or more types are the combined use of LiPF ₆ and LiBF ₄ , the combined use of LiPF ₆ and FSO ₃ Li, and the combined use of LiPF ₆ and LiPO ₂ F ₂ , which are load characteristics and cycle characteristics. Has the effect of improving.

_{In this case, the blending amount of LiBF 4} , FSO ₃ Li or LiPO ₂ F ₂ with respect to 100% by mass of the entire electrolytic solution is not limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but with respect to the electrolytic solution of the present invention. It is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less.

Another example is the combined use of an inorganic lithium salt and an organic lithium salt, and the combined use of both has an effect of suppressing deterioration due to high temperature storage. Organolithium salts include CF ₃ SO ₃ Li, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) _2. , Lithium Cyclic 1,2-Perfluoroethanedisulfonylimide, Lithium Cyclic 1,3-Perfluoropropanedisulfonylimide, LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO) ₂ ) ₃ , LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) _3, etc. are preferable. In this case, the ratio of the organic lithium salt to 100% by mass of the entire electrolytic solution is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and preferably 30% by mass or less, particularly. It is preferably 20% by mass or less.

The concentration of these electrolyte salts in the electrolytic solution is not particularly limited as long as the effects of the present invention are not impaired. The total molar concentration of lithium in the electrolytic solution is preferably 0.3 mol / L or more, more preferably 0.4 mol / L, from the viewpoint of keeping the electric conductivity of the electrolytic solution in a good range and ensuring good battery performance. As mentioned above, it is more preferably 0.5 mol / L or more, preferably 3 mol / L or less, more preferably 2.5 mol / L or less, still more preferably 2.0 mol / L or less.

If the total molar concentration of lithium is too low, the electrical conductivity of the electrolyte may be insufficient, while if the concentration is too high, the electrical conductivity may decrease due to the increase in viscosity, resulting in poor battery performance. May be done.

As the electrolyte salt of the electrolytic solution for the electric double layer capacitor, an ammonium salt is preferable.
Examples of the ammonium salt include the following (IIa) to (IIe).
(IIa) Tetraalkyl Quaternary Ammonium Salt General Formula (IIa):

（式中、Ｒ^１ａ、Ｒ^２ａ、Ｒ^３ａ及びＲ^４ａは同じか又は異なり、いずれも炭素数１〜６のエーテル結合を含んでいてもよいアルキル基；Ｘ⁻はアニオン）
で示されるテトラアルキル４級アンモニウム塩が好ましく例示できる。また、このアンモニウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４の含フッ素アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(In the formula, R ^1a , R ^2a , R ^3a and R ^4a are the same or different, and all of them may contain an ether bond having 1 to 6 carbon atoms; X ⁻ is an anion).
The tetraalkyl quaternary ammonium salt represented by is preferably exemplified. Further, it is also preferable that a part or all of the hydrogen atoms of this ammonium salt are substituted with a fluorine atom and / or a fluorine-containing alkyl group having 1 to 4 carbon atoms from the viewpoint of improving oxidation resistance.

As a specific example, the general formula (IIa-1):

（式中、Ｒ^１ａ、Ｒ^２ａ及びＸ⁻は前記と同じ；ｘ及びｙは同じか又は異なり０〜４の整数で、かつｘ＋ｙ＝４）
で示されるテトラアルキル４級アンモニウム塩、一般式（ＩＩａ−２）：

(In the equation, R ^1a , R ^2a and X ⁻ are the same as above; x and y are the same or different integers from 0 to 4, and x + y = 4).
Tetraalkyl quaternary ammonium salt represented by, general formula (IIa-2):

（式中、Ｒ^５ａは炭素数１〜６のアルキル基；Ｒ^６ａは炭素数１〜６の２価の炭化水素基；Ｒ^７ａは炭素数１〜４のアルキル基；ｚは１又は２；Ｘ⁻はアニオン）
で示されるアルキルエーテル基含有トリアルキルアンモニウム塩、
等が挙げられる。アルキルエーテル基を導入することにより、粘性の低下を図ることができる。

(In the formula, R ^5a is an alkyl group having 1 to 6 carbon atoms; R ^6a is a divalent hydrocarbon group having 1 to 6 carbon atoms; R ^7a is an alkyl group having 1 to 4 carbon atoms; z is 1 or 2; X ^- is an anion)
Alkyl ether group-containing trialkylammonium salt, indicated by
And so on. By introducing an alkyl ether group, the viscosity can be reduced.

The anion X ⁻ may be an inorganic anion or an organic anion. The inorganic anions such as _{^{AlCl 4 -, BF 4 -,}} PF 6 -, AsF 6 -, TaF 6 -, I -, SbF 6 - and the like. Examples of the organic anion include bisoxalatoborate anion, difluorooxalatoborate anion, tetrafluorooxalatophosphate anion, difluorobisoxalatphosphate anion, CF ₃ COO ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ). ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ^{− and the} like can be mentioned.

Among these, from the oxidation resistance and ion dissociation viewpoint of _{^{good, BF 4 -, PF 6 -}} , AsF 6 -, SbF 6 - are preferred.

Suitable specific examples of the tetraalkyl quaternary ammonium salt include Et ₄ NBF ₄ , Et ₄ NClO ₄ , Et ₄ NPF ₆ , Et ₄ NAsF ₆ , Et ₄ NSbF ₆ , Et ₄ NCF ₃ SO ₃ and Et ₄ N. _{CF 3 SO 2) 2 N,} Et 4 NC 4 F 9 SO 3, Et 3 MeNBF 4, Et 3 MeNClO 4, Et 3 MeNPF 6, Et 3 MeNAsF 6, Et 3 MeNSbF 6, Et 3 MeNCF 3 SO 3, Et _{3 MeN (CF 3 SO 2)} 2 N, may be used _{Et 3 MeNC 4 F 9 SO 3} , in _{particular, Et 4 NBF 4, Et 4} NPF 6, Et 4 NSbF 6, Et 4 NAsF 6, Et 3 MeNBF 4 , N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium salt and the like.

(IIb) Spiro ring bipyrrolidinium salt General formula (IIb-1):

（式中、Ｒ^８ａ及びＲ^９ａは同じか又は異なり、いずれも炭素数１〜４のアルキル基；Ｘ⁻はアニオン；ｎ１は０〜５の整数；ｎ２は０〜５の整数）
で示されるスピロ環ビピロリジニウム塩、一般式（ＩＩｂ−２）：

(In the formula, R ^8a and R ^9a are the same or different, and both are alkyl groups having 1 to 4 carbon atoms; X ⁻ is an anion; n1 is an integer of 0 to 5; n2 is an integer of 0 to 5).
Spiro ring bipyrrolidinium salt represented by, general formula (IIb-2):

（式中、Ｒ^１０ａ及びＲ^１１ａは同じか又は異なり、いずれも炭素数１〜４のアルキル基；Ｘ⁻はアニオン；ｎ３は０〜５の整数；ｎ４は０〜５の整数）
で示されるスピロ環ビピロリジニウム塩、又は、一般式（ＩＩｂ−３）：

(In the formula, R ^10a and R ^11a are the same or different, and both are alkyl groups having 1 to 4 carbon atoms; X ⁻ is an anion; n3 is an integer of 0 to 5; n4 is an integer of 0 to 5).
Spiro ring bipyrrolidinium salt represented by, or general formula (IIb-3):

（式中、Ｒ^１２ａ及びＲ^１３ａは同じか又は異なり、いずれも炭素数１〜４のアルキル基；Ｘ⁻はアニオン；ｎ５は０〜５の整数；ｎ６は０〜５の整数）
で示されるスピロ環ビピロリジニウム塩が好ましく挙げられる。また、このスピロ環ビピロリジニウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４の含フッ素アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(In the formula, R ^12a and R ^13a are the same or different, and both are alkyl groups having 1 to 4 carbon atoms; X ⁻ is an anion; n5 is an integer of 0 to 5; n6 is an integer of 0 to 5).
The spiro ring bipyrrolidinium salt represented by is preferably mentioned. Further, it is also preferable that a part or all of the hydrogen atoms of the spiro-ring bipyrrolidinium salt are substituted with fluorine atoms and / or fluorine-containing alkyl groups having 1 to 4 carbon atoms from the viewpoint of improving oxidation resistance.

Preferred specific examples of anion X ⁻ are the same as in the case of (IIa). Among them, high dissociative, terms the internal resistance is low under a high _{voltage, BF 4 -, PF 6 -} , (CF 3 SO 2) 2 N- or _{(C 2 F 5 SO 2)} 2 N- is preferable.

等が挙げられる。Preferred specific examples of the spiro ring bipyrrolidinium salt include, for example,

And so on.

This spiro ring bipyrrolidinium salt is excellent in solvent solubility, oxidation resistance, and ionic conductivity.

(IIc) Imidazole salt general formula (IIc):

（式中、Ｒ^１４ａ及びＲ^１５ａは同じか又は異なり、いずれも炭素数１〜６のアルキル基；Ｘ⁻はアニオン）
で示されるイミダゾリウム塩が好ましく例示できる。また、このイミダゾリウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４の含フッ素アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(In the formula, R ^14a and R ^15a are the same or different, and both are alkyl groups having 1 to 6 carbon atoms; X ⁻ is an anion).
The imidazolium salt represented by is preferably exemplified. Further, it is also preferable that a part or all of the hydrogen atoms of this imidazolium salt are substituted with fluorine atoms and / or fluorine-containing alkyl groups having 1 to 4 carbon atoms from the viewpoint of improving oxidation resistance.

Preferred specific examples of anion X ⁻ are the same as in (IIa).

As a preferable specific example, for example

等が挙げられる。

And so on.

This imidazolium salt is excellent in that it has low viscosity and good solubility.

(IId): N-alkylpyridinium salt general formula (IId):

（式中、Ｒ^１６ａは炭素数１〜６のアルキル基；Ｘ⁻はアニオン）
で示されるＮ−アルキルピリジニウム塩が好ましく例示できる。また、このＮ−アルキルピリジニウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４の含フッ素アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(In the formula, R ^16a is an alkyl group having 1 to 6 carbon atoms; X ⁻ is an anion).
The N-alkylpyridinium salt represented by is preferably exemplified. Further, it is also preferable that a part or all of the hydrogen atom of this N-alkylpyridinium salt is substituted with a fluorine atom and / or a fluorine-containing alkyl group having 1 to 4 carbon atoms from the viewpoint of improving oxidation resistance.

Preferred specific examples of anion X ⁻ are the same as in (IIa).

As a preferable specific example, for example

等が挙げられる。

And so on.

This N-alkylpyridinium salt is excellent in that it has low viscosity and good solubility.

(IIe) N, N-dialkylpyrrolidinium salt General formula (IIe):

（式中、Ｒ^１７ａ及びＲ^１８ａは同じか又は異なり、いずれも炭素数１〜６のアルキル基；Ｘ⁻はアニオン）
で示されるＮ，Ｎ−ジアルキルピロリジニウム塩が好ましく例示できる。また、このＮ，Ｎ−ジアルキルピロリジニウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４の含フッ素アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(In the formula, R ^17a and R ^18a are the same or different, and both are alkyl groups having 1 to 6 carbon atoms; X ⁻ is an anion).
The N, N-dialkylpyrrolidinium salt represented by is preferably exemplified. Further, the oxidation resistance is also improved when a part or all of the hydrogen atoms of the N, N-dialkylpyrrolidinium salt are substituted with fluorine atoms and / or fluorine-containing alkyl groups having 1 to 4 carbon atoms. It is preferable from the point of view.

Preferred specific examples of anion X ⁻ are the same as in (IIa).

As a preferable specific example, for example

等が挙げられる。

And so on.

This N, N-dialkylpyrrolidinium salt is excellent in that it has low viscosity and good solubility.

Of these ammonium salts, (IIa), (IIb) and (IIc) are preferable in terms of good solubility, oxidation resistance and ionic conductivity, and further.

（式中、Ｍｅはメチル基；Ｅｔはエチル基；Ｘ⁻、ｘ、ｙは式（ＩＩａ−１）と同じ）
が好ましい。

(In the formula, Me is a methyl group; Et is an ethyl group; X ⁻ , x, y are the same as in formula (IIa-1))
Is preferable.

Further, a lithium salt may be used as the electrolyte salt for the electric double layer capacitor. Examples of the lithium _{salt, LiPF 6, LiBF 4, LiN} (FSO 2) 2, LiAsF 6, LiSbF 6, LiN (SO 2 C 2 H 5) 2 is preferred.
Magnesium salts may be used to further improve the volume. As the magnesium salt, for example, Mg (ClO ₄ ) ₂ , Mg (OOC ₂ H ₅ ) _{2, and the} like are preferable.

When the electrolyte salt is the above-mentioned ammonium salt, the concentration is preferably 0.7 mol / liter or more. If it is less than 0.7 mol / liter, not only the low temperature characteristics deteriorate, but also the initial internal resistance may increase. The concentration of the electrolyte salt is more preferably 0.9 mol / liter or more.
The upper limit of the concentration is preferably 2.0 mol / liter or less, and more preferably 1.5 mol / liter or less in terms of low temperature characteristics.
When the ammonium salt is triethylmethylammonium tetrafluoride (TEMABF ₄ ), the concentration thereof is preferably 0.7 to 1.5 mol / liter in terms of excellent low temperature characteristics.
Further, in the case of spirobipyrrolidinium tetrafluoride (SBPBF ₄ ), it is preferably 0.7 to 2.0 mol / liter.

（式中、Ｘ^２１は少なくともＨ又はＣを含む基、ｎ２１は１〜３の整数、Ｙ^２１及びＺ^２１は、同じか又は異なり、少なくともＨ、Ｃ、Ｏ又はＦを含む基、ｎ２２は０又は１、Ｙ^２１及びＺ^２１はお互いに結合して環を形成してもよい。）で示される化合物（２）を更に含むことが好ましい。上記電解液が化合物（２）を含むと、高温で保管した場合でも、容量保持率が一層低下しにくく、ガスの発生量が更に増加しにくい。The electrolytic solution of the present invention has the general formula (2):

(In the formula, X ²¹ is a group containing at least H or C, n ^{21 is an integer of 1-3, Y 21} and Z 21 are the same or different and contain at least H, C, O or F, n 22 is 0. Alternatively, 1, Y ²¹ and Z ²¹ may be bonded to each other to form a ring), and it is preferable that the compound (2) further contained. When the electrolytic solution contains the compound (2), the capacity retention rate is less likely to decrease and the amount of gas generated is less likely to increase even when stored at a high temperature.

If n21 is 2 or 3, two or three X ²¹ may be different even in the same.
When a ^{plurality of Y 21} and Z ²¹ are present, the plurality of Y ²¹ and Z ²¹ may be the same or different.

The X ^{21, -CY 21 Z 21} - represented by ^(wherein, as ^{Y 21} and ^{Z 21} are described above) - ^{(wherein Y 21} and ^{Z 21} are as defined above) or ^-CY 21 = ^{CZ 21} The group is preferred.

Y ²¹ includes H-, F-, CH _3- , CH ₃ CH _2- , CH ₃ CH ₂ CH _2- , CF _3- , CF ₃ CF _2- , CH ₂ FCH _2- and CF ₃ CF ₂ CF. _At least one selected from the group consisting of 2 − is preferable.
As Z ²¹ , H-, F-, CH _3- , CH ₃ CH _2- , CH ₃ CH ₂ CH _2- , CF _3- , CF ₃ CF _2- , CH ₂ FCH _2- and CF ₃ CF ₂ CF _At least one selected from the group consisting of 2 − is preferable.

Alternatively, Y ²¹ and Z ²¹ can be bonded to each other to form a carbocycle or heterocycle which may contain unsaturated bonds and may have aromaticity. The number of carbon atoms in the ring is preferably 3 to 20.

Next, a specific example of the compound (2) will be described. In the following examples, the "related material" refers to an acid anhydride obtained by replacing a part of the structure of the exemplified acid anhydride with another structure within a range not contrary to the gist of the present invention. For example, dimers, trimerics and tetramers composed of a plurality of acid anhydrides, or isostructural heterogeneous substances having the same number of carbon atoms but having a branched chain, and the substituents are acids. Examples thereof include those having different sites that bind to the anhydride.

Specific examples of the acid anhydride forming a 5-membered ring structure include succinic anhydride, methylsuccinic anhydride (4-methylsuccinic anhydride), and dimethylsuccinic anhydride (4,4-dimethylsuccinic anhydride). , 4,5-Dimethylsuccinic anhydride, etc.), 4,4,5-trimethylsuccinic anhydride, 4,4,5,5-tetramethylsuccinic anhydride, 4-vinylsuccinic anhydride, 4,5 − Divinyl succinic anhydride, phenylsuccinic anhydride (4-phenylsuccinic anhydride), 4,5-diphenylsuccinic anhydride, 4,4-diphenylsuccinic anhydride, citraconic anhydride, maleic anhydride, Methylmaleic anhydride (4-methylmaleic anhydride), 4,5-dimethylmaleic anhydride, phenylmaleic anhydride (4-phenylmaleic anhydride), 4,5-diphenylmaleic anhydride, Itaconic acid anhydride, 5-methylitaconic acid anhydride, 5,5-dimethylitaconic acid anhydride, phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride and the like, and their analogs and the like. Be done.

Specific examples of the acid anhydride forming a 6-membered ring structure include cyclohexanedicarboxylic acid anhydride (cyclohexane-1,2-dicarboxylic acid anhydride, etc.), 4-cyclohexene-1,2-dicarboxylic acid anhydride, and the like. Examples thereof include glutacon anhydride, glutaconic anhydride, 2-phenylglutaric acid anhydride and the like, and their analogs.

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

Specific examples of the acid anhydride that forms a cyclic structure and is substituted with a halogen atom include monofluorosuccinic anhydride (4-fluorosuccinic anhydride, etc.), 4,4-difluorosuccinic anhydride, and 4 , 5-Difluorosuccinate anhydride, 4,4,5-trifluorosuccinate anhydride, trifluoromethylsuccinic anhydride, tetrafluorosuccinate anhydride (4,5,5-tetrafluorosuccinate anhydride) ), 4-Fluoromaleic anhydride, 4,5-difluoromaleic anhydride, trifluoromethylmaleic anhydride, 5-fluoroitaconic anhydride, 5,5-difluoroitaconic anhydride, etc., and them. Anhydrides and the like can be mentioned.

Examples of the compound (2) include glutacon anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic acid anhydride, cyclohexanedicarboxylic acid anhydride, cyclopentanetetracarboxylic dianhydride, and 4-cyclohexene. 1,2-dicarboxylic acid anhydride, 3,4,5,6-tetrahydrophthalic acid anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride, phenylsuccinic anhydride, 2-phenylglutaric acid anhydride, Maleic anhydride, methylmaleic anhydride, trifluoromethylmaleic anhydride, phenylmaleic anhydride, succinic anhydride, methylsuccinic anhydride, dimethylsuccinic anhydride, trifluoromethylsuccinic anhydride, monofluorosuccinate Acid anhydride, tetrafluorosuccinic anhydride and the like are preferable, and maleic anhydride, methyl maleic anhydride, trifluoromethyl maleic anhydride, succinic anhydride, methyl succinic anhydride, trifluoromethyl succinic anhydride, tetra. Fluorosuccinic anhydride is more preferable, and maleic anhydride and succinic anhydride are even more preferable.

Compound (2) is represented by the general formula (3):

（式中、Ｘ^３１〜Ｘ^３４は、同じか又は異なり、少なくともＨ、Ｃ、Ｏ又はＦを含む基）で示される化合物（３）、及び、一般式（４）：

Compound (3) represented by (in the formula, X ^{31 to} X ³⁴ are groups which are the same or different and contain at least H, C, O or F), and general formula (4):

（式中、Ｘ^４１及びＸ^４２は、同じか又は異なり、少なくともＨ、Ｃ、Ｏ又はＦを含む基）で示される化合物（４）からなる群より選択される少なくとも１種であることが好ましい。

(In the formula, X ⁴¹ and X ⁴² are the same or different, and preferably at least one selected from the group consisting of the compound (4) represented by the compound (group containing at least H, C, O or F). ..

As X ^{31 to} X ³⁴ , at least one selected from the group consisting of an alkyl group, a fluorinated alkyl group, an alkenyl group and a fluorinated alkenyl group is preferable. The carbon number of X ^{31 to} X ³⁴ is preferably 1 to 10, and more preferably 1 to 3.

X ^{31 to} X ³⁴ are the same or different, H-, F-, CH _3- , CH ₃ CH _2- , CH ₃ CH ₂ CH _2- , CF _3- , CF ₃ CF _2- , CH ₂ FCH. ₂ - and _CF 3 _CF 2 CF ₂ - at least one member selected from the group consisting of is more preferable.

As X ⁴¹ and X ⁴² , at least one selected from the group consisting of an alkyl group, a fluorinated alkyl group, an alkenyl group and a fluorinated alkenyl group is preferable. The carbon number of X ⁴¹ and X ⁴² is preferably 1 to 10, and more preferably 1 to 3.

X ⁴¹ and X ⁴² are the same or different, H-, F-, CH _3- , CH ₃ CH _2- , CH ₃ CH ₂ CH _2- , CF _3- , CF ₃ CF _2- , CH ₂ FCH. ₂ - and _CF 3 _CF 2 CF ₂ - at least one member selected from the group consisting of is more preferable.

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

Compound (4) is preferably any of the following compounds.

Even when the electrolytic solution is stored at a high temperature, the capacity retention rate is less likely to decrease and the amount of gas generated is less likely to increase. 2) is preferably included. The content of the compound (2) is more preferably 0.01 to 10% by mass, further preferably 0.1 to 3% by mass, and particularly preferably 0.1 to 1.0% by mass.

When the electrolytic solution contains both the compounds (3) and (4), the capacity retention rate is less likely to decrease and the amount of gas generated is less likely to increase even when stored at a high temperature. It is preferable to contain 0.08 to 2.50% by mass of the compound (3) and 0.02 to 1.50% by mass of the compound (4) with respect to the above electrolytic solution, and 0.80 to 2.50% by mass. It is more preferable to contain the mass% of the compound (3) and the compound (4) of 0.08 to 1.50% by mass.

（式中、Ｒ^ａ及びＲ^ｂは、それぞれ独立して、水素原子、シアノ基（ＣＮ）、ハロゲン原子、アルキル基、又は、アルキル基の少なくとも一部の水素原子をハロゲン原子で置換した基を表す。ｎは１〜１０の整数を表す。）

（式中、Ｒ^ｃは、水素原子、ハロゲン原子、アルキル基、アルキル基の少なくとも一部の水素原子をハロゲン原子で置換した基、又は、ＮＣ−Ｒ^ｃ１−Ｘ^ｃ１−（Ｒ^ｃ１はアルキレン基、Ｘ^ｃ１は酸素原子又は硫黄原子を表す。）で表される基を表す。Ｒ^ｄ及びＲ^ｅは、それぞれ独立して、水素原子、ハロゲン原子、アルキル基、又は、アルキル基の少なくとも一部の水素原子をハロゲン原子で置換した基を表す。ｍは１〜１０の整数を表す。）

（式中、Ｒ^ｆ、Ｒ^ｇ、Ｒ^ｈ及びＲ^ｉは、それぞれ独立して、シアノ基（ＣＮ）を含む基、水素原子（Ｈ）、ハロゲン原子、アルキル基、又は、アルキル基の少なくとも一部の水素原子をハロゲン原子で置換した基を表す。ただし、Ｒ^ｆ、Ｒ^ｇ、Ｒ^ｈ及びＲ^ｉのうち少なくとも１つはシアノ基を含む基である。ｌは１〜３の整数を表す。）
これにより、電気化学デバイスの高温保存特性を向上させることができる。上記ニトリル化合物を単独で用いてもよく、２種以上を任意の組み合わせ及び比率で併用してもよい。The electrolytic solution of the present invention may contain at least one selected from the group consisting of nitrile compounds represented by the following general formulas (1a), (1b) and (1c).

(In the formula, ^Ra and R ^b are independent hydrogen atoms, cyano groups (CN), halogen atoms, alkyl groups, or groups in which at least a part of the hydrogen atoms of the alkyl groups are replaced with halogen atoms. Represents. N represents an integer of 1 to 10.)

(In the formula, R ^c is a hydrogen atom, a halogen atom, an alkyl group, a group in which at least a part of the hydrogen atom of the alkyl group is replaced with a halogen atom, or NC-R ^c1- X ^c1- (R ^c1 is an alkylene group). , X ^c1 is .R ^d and R ^e represents a group represented by an oxygen atom or a sulfur atom.) are each independently a hydrogen atom, a halogen atom, an alkyl group, or at least a portion of the alkyl group Represents a group in which the hydrogen atom of is replaced with a halogen atom. M represents an integer of 1 to 10.)

(In the formula, R ^f , R ^g , R ^h and ^Ri are each independently at least one of a group containing a cyano group (CN), a hydrogen atom (H), a halogen atom, an alkyl group, or an alkyl group. the part hydrogen atoms represents a group obtained by substituting a halogen atom. However, at least one of ^{R f,} R ^g, R ^h and R ⁱ is a group containing a cyano group .l represents an integer of 1 to 3 .)
This makes it possible to improve the high temperature storage characteristics of the electrochemical device. The above nitrile compounds may be used alone, or two or more thereof may be used in any combination and ratio.

In the above general formula (1a), ^Ra and R ^b independently use a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or at least a part of the hydrogen atom of the alkyl group as a halogen atom. It is a substituted group.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Of these, a fluorine atom is preferable.
The alkyl group preferably has 1 to 5 carbon atoms. 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 tert-butyl group and the like.
Examples of the group in which at least a part of the hydrogen atom of the alkyl group is replaced with a halogen atom include a group in which at least a part of the hydrogen atom of the above-mentioned alkyl group is replaced with the above-mentioned halogen atom.
When R ^a and R ^b are an alkyl group or a group in which at least a part of hydrogen atoms of the alkyl group is replaced with a halogen atom, ^Ra and R ^b are bonded to each other to form a ring structure (for example, a cyclohexane ring). ) May be formed.
R ^a and R ^b are preferably hydrogen atoms or alkyl groups.

In the above general formula (1a), n is an integer of 1 to 10. When n is 2 or more, n pieces of R ^a may be the same for all, it may be at least partially different. The same applies to ^{R b.} n is preferably an integer of 1 to 7, and more preferably an integer of 2 to 5.

As the nitrile compound represented by the general formula (1a), dinitrile and tricarbonitrile are preferable.
Specific examples of dinitrile include malononitrile, succinonitrile, glutaronitrile, adipoinitrile, pimeronitrile, suberonitrile, azeranitrile, sebaconitrile, undecandinitrile, dodecandinitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, and tert-butyl. Marononitrile, 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-di Carbonitrile, 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-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2, 2,4,4-Tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6 −Dicyanoheptan, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3' -(Ethethylenedioxy) dipropionitrile, 3,3'-(ethylenedithio) dipropionitrile, 3,9-bis (2-cyanoethyl) -2,4,8,10-tetraoxaspiro [5,5] Examples thereof include undecane, butanenitrile, and phthalonitrile. Of these, particularly preferred are succinonitrile, glutaronitrile, and adiponitrile.
Specific examples of the tricarbonitrile include pentantricarbonitrile, propantricarbonitrile, 1,3,5-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile, heptanetricarbonitrile, 1, Examples thereof include 2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, cyclohexanetricarbonitrile, triscyanoethylamine, triscyanoethoxypropane, tricyanoethylene, tris (2-cyanoethyl) amine and the like. Preferred are 1,3,6-hexanetricarbonitrile, cyclohexanetricarbonitrile, and most preferred are cyclohexanetricarbonitrile.

In the above general formula (1b), R ^c is a hydrogen atom, a halogen atom, an alkyl group, a group in which at least a part of hydrogen atoms of the alkyl group is replaced with a halogen atom, or NC-R ^c1- X ^c1- (R). ^c1 is an alkylene group, X ^c1 is an oxygen atom or a sulfur atom), and R ^d and ^Re are independently hydrogen atoms, halogen atoms, alkyl groups, or alkyl groups. It is a group in which at least a part of hydrogen atoms are replaced with halogen atoms.
Examples of the halogen atom, the alkyl group, and the group in which at least a part of the hydrogen atom of the alkyl group is replaced with the halogen atom include those exemplified by the above general formula (1a).
The ^{NC-R c1 -X} c1 - in ^{R c1} is an alkylene group. As the alkylene group, an alkylene group having 1 to 3 carbon atoms is preferable.
It is preferable that R ^c , R ^d and ^Re are independently hydrogen atoms, halogen atoms, alkyl groups, or groups in which at least a part of the hydrogen atoms of the alkyl groups are substituted with halogen atoms.
At ^{least one of R c} , R ^d and ^Re is preferably a halogen atom or a group in which at least a part of the hydrogen atom of the alkyl group is replaced with a halogen atom, and at least a fluorine atom or an alkyl group. More preferably, it is a group in which some hydrogen atoms are replaced with fluorine atoms.
When R ^d and ^Re are an alkyl group or a group in which at least a part of the hydrogen atom of the alkyl group is replaced with a halogen atom, R ^d and ^Re are bonded to each other to form a ring structure (for example, a cyclohexane ring). ) May be formed.

In the above general formula (1b), m is an integer of 1 to 10. When m is 2 or more, ^{all m R ds} may be the same, or at least a part thereof may be different. The same applies to the R ^e. m is preferably an integer of 2 to 7, and more preferably an integer of 2 to 5.

Examples of the nitrile compound represented by the general formula (1b) include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 3-methoxypropionitrile, and 2-methylbutyro. Nitrile, trimethylnitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, fluoronitrile, difluoronitrile, trifluoronitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-Difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, Examples thereof include 3,3'-thiodipropionitrile, pentafluoropropionitrile, methoxynitrile, and benzonitrile. Of these, 3,3,3-trifluoropropionitrile is particularly preferred.

In the general formula ^{(1c), R f, R} g, R h and ^{R i} are each independently, a group containing a cyano group (CN), a hydrogen atom, a halogen atom, an alkyl group, or at least an alkyl group It is a group in which some hydrogen atoms are replaced with halogen atoms.
Examples of the halogen atom, the alkyl group, and the group in which at least a part of the hydrogen atom of the alkyl group is replaced with the halogen atom include those exemplified by the above general formula (1a).
Examples of the group containing a cyano group include a cyano group and a group in which at least a part of hydrogen atoms of an alkyl group is replaced with a cyano group. Examples of the alkyl group in this case include those exemplified for the above general formula (1a).
^{R f,} R g, at least one of ^{R h} and ^{R i} is a group containing a cyano group. Preferably is that R ^{f, R g,} at least two of R ^h and R ⁱ is a group containing a cyano group, more preferably, is that R ^h and R ⁱ is a group containing a cyano group .. When R ^h and R ⁱ are groups containing a cyano group, R ^f and R ^g are preferably hydrogen atoms.

In the above general formula (1c), l is an integer of 1 to 3. When l is 2 or more, ^{all l R fs} may be the same, or at least a part thereof may be different. The same applies to ^{R g.} l is preferably an integer of 1 to 2.

Examples of the nitrile compound represented by the general formula (1c) include 3-hexendinitrile, mucononitrile, maleonitrile, fumaronitrile, acrylonitrile, methacrylonitrile, crotononitrile, 3-methylcrotononitrile, and 2-methyl-2-. Butenenitrile, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, 2-hexenenitrile and the like are exemplified, and 3-hexenedinitrile and mucononitrile are preferable, and 3-hexenedinitrile is particularly preferable. Nitrile is preferred.

The content of the nitrile compound is preferably 0.2 to 7% by mass with respect to the electrolytic solution. As a result, the high-voltage storage characteristics and safety of the electrochemical device can be further improved. The lower limit of the total content of the nitrile compounds is more preferably 0.3% by mass, further preferably 0.5% by mass. The upper limit is more preferably 5% by mass, further preferably 2% by mass, and particularly preferably 0.5% by mass.

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

Specific examples of monoisocyanates include isocyanatomethane, isocyanatoetane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1-isocyanatoheptane, 1-isocyanate. Natooctane, 1-isocyanatononane, 1-isocyanatodecane, isocyanatocyclohexane, methoxycarbonyl isocyanate, ethoxycarbonyl isocyanate, propoxycarbonyl isocyanate, butoxycarbonyl isocyanate, methoxysulfonyl isocyanate, ethoxysulfonyl isocyanate, propoxysulfonyl isocyanate, butoxysulfonyl isocyanate , Fluorosulfonyl isocyanate, methyl isocyanate, butyl isocyanate, phenylisocyanate, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, ethyl isocyanate and the like.

Specific examples of diisocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, and 1,8-diisocyanate. Natooctane, 1,9-diisocyanatononan, 1,10-diisocyanatodecane, 1,3-diisocyanatopropene, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane , 1,4-Diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato -3-Hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluorohexane, toluenediisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane , 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanato Cyclohexane, dicyclohexylmethane-1,1'-diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, bicyclo [2.2] .1] Heptane-2,5-diylbis (methyl = isocyanate), bicyclo [2.2.1] heptane-2,6-diylbis (methyl = isocyanate), 2,4,4-trimethylhexamethylene diisocyanate, Examples thereof include 2,2,4-trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, 1,4-phenylenediocyanate, octamethylene diisocyanate, and tetramethylene diisocyanate.

Specific examples of triisocyanates include 1,6,11-triisocyanatoundecane, 4-isocyanatomethyl-1,8-octamethylene diisocyanate, 1,3,5-triisocyanatemethylbenzene, 1,3,5. -Tris (6-isocyanatohexa-1-yl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 4- (isocyanatomethyl) octamethylene = diisocyanate, etc. Can be mentioned.

Among them, 1,6-diisocyanatohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,3,5-tris (6-isocyanatohexa-1-yl) -1,3,5-triazine- 2,4,6 (1H, 3H, 5H) -trione, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate are industrially readily available. Therefore, it is preferable in that the production cost of the electrolytic solution can be suppressed to a low level, and it can contribute to the formation of a stable film-like structure from a technical point of view, and is more preferably used.

The content of isocyanate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired, but is preferably 0.001% by mass or more and 1.0% by mass or less with respect to the electrolytic solution. When the isocyanate content is at least this lower limit, it is possible to bring about a sufficient effect of improving the cycle characteristics in the non-aqueous electrolyte secondary battery. Further, when it is not more than this upper limit, it is possible to avoid an increase in the initial resistance of the non-aqueous electrolyte secondary battery. The content of isocyanate is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, still more preferably 0.8% by mass or less, still more preferable. Is 0.7% by mass or less, particularly preferably 0.6% by mass or less.

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

Specific examples of the saturated cyclic sulfonic acid ester include 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone. , 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1,3-butane sultone, 1,4-butane sultone, 1-fluoro- 1,4-Butansultone, 2-fluoro-1,4-butansultone, 3-fluoro-1,4-butansultone, 4-fluoro-1,4-butansultone, 1-methyl-1,4-butansultone, 2-methyl- Examples thereof include 1,4-butanesultone, 3-methyl-1,4-butansultone, 4-methyl-1,4-butansultone, and 2,4-butansultone.

Specific examples of the unsaturated cyclic sulfonic acid ester include 1-propen-1,3-sulton, 2-propen-1,3-sulton, 1-fluoro-1-propen-1,3-sulton, 2-fluoro-. 1-Propen-1,3-Sulton, 3-Fluoro-1-Propen-1,3-Sulton, 1-Fluoro-2-Propen-1,3-Sulton, 2-Fluoro-2-Propen-1,3- Sulton, 3-fluoro-2-propen-1,3-sulton, 1-methyl-1-propen-1,3-sulton, 2-methyl-1-propen-1,3-sulton, 3-methyl-1- Propen-1,3-sulton, 1-methyl-2-propen-1,3-sulton, 2-methyl-2-propen-1,3-sulton, 3-methyl-2-propen-1,3-sulton, 1-Butene-1,4-Sulton, 2-Butene-1,4-Sulton, 3-Butene-1,4-Sulton, 1-Fluoro-1-Butene-1,4-Sulton, 2-Fluoro-1- Butene-1,4-sulton, 3-fluoro-1-butene-1,4-sulton, 4-fluoro-1-butene-1,4-sulton, 1-fluoro-2-butene-1,4-sulton, 2-Fluoro-2-butene-1,4-sulton, 3-fluoro-2-butene-1,4-sulton, 4-fluoro-2-butene-1,4-sulton, 1,3-propensulton, 1 −Fluoro-3-butene-1,4-sulton, 2-fluoro-3-butene-1,4-sulton, 3-fluoro-3-butene-1,4-sulton, 4-fluoro-3-butene-1 , 4-Sulton, 1-Methyl-1-butene-1,4-Sulton, 2-Methyl-1-butene-1,4-Sulton, 3-Methyl-1-Butene-1,4-Sulton, 4-Methyl -1-Butene-1,4-Sulton, 1-Methyl-2-Butene-1,4-Sulton, 2-Methyl-2-Butene-1,4-Sulton, 3-Methyl-2-Butene-1,4 -Sulton, 4-methyl-2-butene-1,4-sulton, 1-methyl-3-butene-1,4-sulton, 2-methyl-3-butene-1,4-sulton, 3-methyl-3 -Butene-1,4-sulton, 4-methyl-3-butene-14-sulton and the like can be mentioned.

Among them, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1,3- Sultone is more preferably used because it is easily available and can contribute to the formation of a stable film-like structure. The content of the cyclic sulfonic acid ester is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is preferably 0.001% by mass or more and 3.0% by mass or less with respect to the electrolytic solution. be.

When the content of the cyclic sulfonic acid ester is not more than this lower limit, a sufficient effect of improving the cycle characteristics can be brought to the non-aqueous electrolyte secondary battery. Further, when it is not more than this upper limit, it is possible to avoid an increase in the manufacturing cost of the non-aqueous electrolyte secondary battery. The content of the cyclic sulfonic acid ester is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and even more preferably 2.5% by mass or less. It is more preferably 2.0% by mass or less, and particularly preferably 1.8% by mass or less.

The electrolytic solution of the present invention may further contain polyethylene oxide having a weight average molecular weight of 2000 to 4000 and having -OH, -OCOOH, or -COOH at the end.
By containing such a compound, the stability of the electrode interface can be improved and the characteristics of the electrochemical device can be improved.
Examples of the polyethylene oxide include polyethylene oxide monool, polyethylene oxide carboxylic acid, polyethylene oxide diol, polyethylene oxide dicarboxylic acid, polyethylene oxide triol, and polyethylene oxide tricarboxylic acid. These may be used alone or in combination of two or more.
Among them, a mixture of polyethylene oxide monool and polyethylene oxide diol and a mixture of polyethylene carboxylic acid and polyethylene dicarboxylic acid are preferable in that the characteristics of the electrochemical device are improved.

If the weight average molecular weight of the polyethylene oxide is too small, it may be easily oxidatively decomposed. The weight average molecular weight is more preferably 3000 to 4000.
The weight average molecular weight can be measured by polystyrene conversion by gel permeation chromatography (GPC) method.

The content of the polyethylene oxide ^{is preferably 1 × 10 -6} to 1 × 10 ⁻² mol / kg in the electrolytic solution. If the content of the polyethylene oxide is too high, the characteristics of the electrochemical device may be impaired.
The content of the polyethylene oxide ^{is more preferably 5 × 10-6} mol / kg or more.

The electrolytic solution of the present invention may further contain a fluorinated saturated cyclic carbonate, an unsaturated cyclic carbonate, an overcharge inhibitor, other known auxiliaries and the like as additives. As a result, deterioration of the characteristics of the electrochemical device can be suppressed.

Examples of the fluorinated saturated cyclic carbonate include the compound represented by the above-mentioned general formula (A). Of these, fluoroethylene carbonate, difluoroethylene carbonate, monofluoromethylethylene carbonate, and trifluoromethylethylene carbonate are preferable. As the fluorinated saturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of the fluorinated saturated cyclic carbonate is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, and 0.1 to 3 with respect to the electrolytic solution. It is more preferably mass%.

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

Examples of vinylene carbonates include vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinylvinylene carbonate, 4,5-divinylvinylene carbonate, allylvinylene carbonate, 4 , 5-Diallyl vinylene carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluoro Examples thereof include vinylene carbonate, ethynylethylene carbonate, propargylethylene carbonate, methylvinylene carbonate, dimethylvinylene carbonate and the like.

Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinylethylene carbonate, and 4-methyl-5. Vinyl ethylene carbonate, 4-allyl-5-vinylethylene carbonate, ethynylethylene carbonate, 4,5-dietinylethylene carbonate, 4-methyl-5-ethynylethylene carbonate, 4-vinyl-5-ethynylethylene carbonate, 4-allyl -5-Ethynylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate , 4-Methyl-5-allylethylene carbonate, 4-methylene-1,3-dioxolan-2-one, 4,5-dimethylene-1,3-dioxolan-2-one, 4-methyl-5-allylethylenecarbonate And so on.

Among them, the unsaturated cyclic carbonates include vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, vinylvinylene carbonate, 4,5-vinylvinylene carbonate, allylvinylene carbonate, 4,5-diallylvinylene carbonate, and vinyl. Ethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5-vinylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, 4-methyl-5-allylethylene carbonate, 4-allyl-5-vinyl Preferably, ethylene carbonate, ethynyl ethylene carbonate, 4,5-dietinyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, and 4-vinyl-5-ethynyl ethylene carbonate. Further, vinylene carbonate, vinylethylene carbonate, and ethynylethylene carbonate are particularly preferable because they form a more stable interfacial protective film, and vinylene carbonate is most preferable.

The molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. Within this range, the solubility of the unsaturated cyclic carbonate in the electrolytic solution can be easily ensured, and the effect of the present invention can be sufficiently exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more, and more preferably 150 or less.

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

As the unsaturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the unsaturated cyclic carbonate is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and further preferably 0.1% by mass or more in 100% by mass of the electrolytic solution. The content is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. Within the above range, the electrochemical device using the electrolytic solution is likely to exhibit a sufficient effect of improving the cycle characteristics, the high temperature storage characteristics are lowered, the amount of gas generated is increased, and the discharge capacity retention rate is lowered. It is easy to avoid such a situation.

As the unsaturated cyclic carbonate, in addition to the non-fluorinated unsaturated cyclic carbonate as described above, a fluorinated unsaturated cyclic carbonate can also be preferably used.
Fluorinated unsaturated cyclic carbonates are cyclic carbonates having unsaturated bonds and fluorine atoms. The number of fluorine atoms contained in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the number of fluorine atoms is usually 6 or less, preferably 4 or less, and one or two are most preferable.

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

Examples of the fluorinated vinylene carbonate derivative include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, and 4-fluoro-5-. Examples include vinyl vinylene carbonate and the like.

Examples of the fluorinated ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon double bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, and 4-fluoro-5. -Vinyl ethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate , 4,5-Difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate , 4,5-Difluoro-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5 -Difluoro-4-phenylethylene carbonate and the like can be mentioned.

Among them, as the fluorinated unsaturated cyclic carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4- Fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-Difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4- Fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate form a stable interface protection film, so that it is more effective. It is preferably used.

The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 500 or less. Within this range, it is easy to secure the solubility of the fluorinated unsaturated cyclic carbonate in the electrolytic solution.

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

As the fluorinated unsaturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The content of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the fluorinated unsaturated cyclic carbonate is usually 0.001% by mass or more, more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more in 100% by mass of the electrolytic solution. Further, it is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. Within this range, the electrochemical device using the electrolytic solution is likely to exhibit a sufficient effect of improving the cycle characteristics, the high temperature storage characteristics are lowered, the amount of gas generated is increased, and the discharge capacity retention rate is lowered. It is easy to avoid such a situation.

The electrolytic solution of the present invention may contain a compound having a triple bond. The type of the compound is not particularly limited as long as it is a compound having one or more triple bonds in the molecule.
Specific examples of the compound having a triple bond include the following compounds.
1-Pentyne, 2-Pentyne, 1-Hexyne, 2-Hexyne, 3-Hexyne, 1-Heptyne, 2-Heptyne, 3-Heptyne, 1-Octyne, 2-Octyne, 3-Octyne, 4-Octyne, 1- Nonin, 2-nonin, 3-nonin, 4-nonin, 1-dodecin, 2-dodecin, 3-dodecin, 4-dodecin, 5-dodecin, phenylacetylene, 1-phenyl-1-propine, 1-phenyl-2 -Propin, 1-phenyl-1-butyne, 4-phenyl-1-butyne, 4-phenyl-1-butyne, 1-phenyl-1-pentyne, 5-phenyl-1-pentyne, 1-phenyl-1-hexyne , 6-Phenyl-1-hexyne, diphenylacetylene, 4-ethynyltoluene, dicyclohexylacetylene and other hydrocarbon compounds;

2-Propynylmethyl carbonate, 2-propynylethyl carbonate, 2-propynylpropyl carbonate, 2-propynylbutyl carbonate, 2-propynylphenyl carbonate, 2-propynylcyclohexyl carbonate, di-2-propynyl carbonate, 1-methyl-2-propynyl Methyl carbonate, 1,1-dimethyl-2-propynyl methyl carbonate, 2-butynyl methyl carbonate, 3-butynyl methyl carbonate, 2-pentynyl methyl carbonate, 3-pentynyl methyl carbonate, 4-pentynyl methyl carbonate, etc. Monocarbonate; 2-butin-1,4-diol dimethyldicarbonate, 2-butin-1,4-diol diethyldicarbonate, 2-butin-1,4-diol dipropyldicarbonate, 2-butin-1, Dicarbonates such as 4-diol dibutyl dicarbonate, 2-butin-1,4-diol diphenyl dicarbonate, 2-butin-1,4-diol dicyclohexyl dicarbonate;

2-propynyl acetate, 2-propynyl propionate, 2-propynyl butyrate, 2-propynyl benzoate, 2-propynyl cyclohexylcarboxylic acid, 1,1-dimethyl-2-propynyl acetate, 1,1-dimethyl-2-propionic acid Propinyl, butyric acid 1,1-dimethyl-2-propynyl, benzoate 1,1-dimethyl-2-propynyl, cyclohexylcarboxylic acid 1,1-dimethyl-2-propynyl, 2-butynyl acetate, 3-butynyl acetate, 2 acetate -Pentinyl, 3-pentynyl acetate, 4-pentynyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, vinyl acrylate, 2-propenyl acrylate, 2-butenyl acrylate, 3-butenyl acrylate, methyl methacrylate , Ethyl methacrylate, propyl methacrylate, vinyl methacrylate, 2-propenyl methacrylate, 2-butenyl methacrylate, 3-butenyl methacrylate, methyl 2-propate, ethyl 2-propate, propyl 2-propate, 2 -Vinyl propate, 2-propenyl 2-propenyl, 2-butenyl 2-propate, 3-butenyl 2-propate, methyl 2-butanoate, ethyl 2-butanoate, propyl 2-butinate, 2-butin Vinyl acid, 2-propenyl 2-propenyl, 2-butenyl 2-butenyl, 3-butenyl 2-butenyl, methyl 3-butanoate, ethyl 3-butanoate, propyl 3-butanoate, vinyl 3-butynate , 3-propenyl 3-butanoate, 2-butenyl 3-butenyl, 3-butenyl 3-butenyl, methyl 2-pentate, ethyl 2-pentate, propyl 2-pentate, vinyl 2-pentate, 2 -2-propenyl pentate, 2-butenyl 2-pentinate, 3-butenyl 2-pentanoate, methyl 3-pentate, ethyl 3-pentate, propyl 3-pentate, vinyl 3-pentinate, 3-pentyne 2-propenyl acid, 2-butenyl 3-pentate, 3-butenyl 3-pentate, methyl 4-pentate, ethyl 4-pentate, propyl 4-pentate, vinyl 4-pentate, 2-pentanoate 2 -Monocarboxylic acid esters such as propenyl, 2-butenyl 4-pentanoate, 3-butenyl 4-pentanoate, fumaric acid ester, methyl trimethylacetate, ethyl trimethylacetate;

2-Butin-1,4-diol diacetate, 2-butyne-1,4-diol dipropionate, 2-butyne-1,4-diol dibutyrate, 2-butyne-1,4-diol dibenzoate, 2 -Butin-1,4-diol dicyclohexanecarboxylate, hexahydrobenzo [1,3,2] dioxathiolane-2-oxide (1,2-cyclohexanediol, 2,2-dioxide-1,2-oxathiolan-4- Dicarboxylic acid esters such as ylacetate, 2,2-dioxide-1,2-oxathiolane-4-ylacetate;

Methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, propyl 2-propynyl oxalate, 2-propynyl vinyl oxalate, allyl 2-propynyl oxalate, di-2-propynyl oxalate, 2-butynyl methyl oxalate, oxalate 2-Butinylethyl oxalate, 2-butynylpropyl oxalate, 2-butynylvinyl oxalate, allyl 2-butynyl oxalate, di-2-butynyl oxalate, 3-butynylmethyl oxalate, 3-butynylethyl oxalate, 3-butyl oxalate Oxalic acid diesters such as butynylpropyl, 3-butynylvinyl oxalate, allyl-3-butynyl oxalate, di-3-butynyl oxalate;

Methyl (2-propynyl) (vinyl) phosphine oxide, divinyl (2-propynyl) phosphine oxide, di (2-propynyl) (vinyl) phosphine oxide, di (2-propenyl) 2 (-propynyl) phosphine oxide, di (2) Phosphine oxides such as −propynyl) (2-propenyl) phosphine oxide, di (3-butenyl) (2-propynyl) phosphine oxide, and di (2-propynyl) (3-butenyl) phosphine oxide;

2-propynyl methyl (2-propenyl) phosphinic acid, 2-propynyl 2-butenyl (methyl) phosphinic acid, 2-propynyl di (2-propenyl) phosphinic acid, 2-propynyl di (3-butenyl) phosphinic acid, methyl ( 2-Propenyl) phosphinic acid 1,1-dimethyl-2-propynyl, 2-butenyl (methyl) phosphinic acid 1,1-dimethyl-2-propynyl, di (2-propenyl) phosphinic acid 1,1-dimethyl-2- Propinyl and di (3-butenyl) phosphinic acid 1,1-dimethyl-2-propynyl, methyl (2-propynyl) phosphinic acid 2-propenyl, methyl (2-propynyl) phosphinic acid 3-butenyl, di (2-propynyl) ) Phosphine such as 2-propenyl phosphinic acid, 3-butenyl di (2-propynyl) phosphinic acid, 2-propenyl 2-propenyl (2-propenyl) phosphinic acid, and 3-butenyl phosphinyl (2-propenyl) phosphinic acid. Acid ester;

Methyl 2-propenyl phosphonate 2-propynyl, 2-propynyl phosphonate (2-propynyl), 2-propenyl phosphonic acid (2-propynyl) (2-propenyl), 3-butenyl phosphonic acid (3-butenyl) (2-propynyl) ), 2-Propenylphosphonic acid (1,1-dimethyl-2-propynyl) (methyl), 2-butenylphosphonic acid (1,1-dimethyl-2-propinyl) (methyl), 2-propenylphosphonic acid (1,1) -Dimethyl-2-propynyl) (2-propenyl), and 3-butenylphosphonic acid (3-butenyl) (1,1-dimethyl-2-propynyl), methylphosphonic acid (2-propynyl) (2-propenyl), methylphosphonic acid (3-Butenyl) (2-propynyl), methylphosphonic acid (1,1-dimethyl-2-propynyl) (2-propenyl), methylphosphonic acid (3-butenyl) (1,1-dimethyl-2-propynyl), ethyl Phosphonate (2-propynyl) (2-propenyl), ethylphosphonic acid (3-butenyl) (2-propynyl), ethylphosphonic acid (1,1-dimethyl-2-propynyl) (2-propenyl), and ethylphosphon Phosphonate esters such as acid (3-butenyl) (1,1-dimethyl-2-propynyl);

Phosphoric acid (methyl) (2-propenyl) (2-propynyl), phosphoric acid (ethyl) (2-propenyl) (2-propynyl), phosphoric acid (2-butenyl) (methyl) (2-propynyl), phosphoric acid (2-Butenyl) (Ethyl) (2-Propinyl), Phosphoric Acid (1,1-dimethyl-2-Propinyl) (Methyl) (2-Propenyl), Phosphoric Acid (1,1-dimethyl-2-Propinyl) ( Ethyl) (2-propenyl), phosphoric acid (2-butenyl) (1,1-dimethyl-2-propynyl) (methyl), and phosphoric acid (2-butenyl) (ethyl) (1,1-dimethyl-2- Phosphate esters such as propynyl);

Of these, a compound having an alkynyloxy group is preferable because it forms a negative electrode film more stably in the electrolytic solution.

In addition, 2-propynyl methyl carbonate, di-2-propynyl carbonate, 2-butyne-1,4-diol dimethyl dicarbonate, 2-propynyl acetate, 2-butyne-1,4-diol diacetate, methyl oxalate 2- Compounds such as propynyl and di-2-propynyl oxalate are particularly preferable from the viewpoint of improving storage characteristics.

As the compound having a triple bond, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The amount of the compound having a triple bond to the entire electrolytic solution of the present invention is not limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by mass or more with respect to the electrolytic solution of the present invention. The content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less. When the above range is satisfied, the effects such as output characteristics, load characteristics, cycle characteristics, and high temperature storage characteristics are further improved.

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

Examples of the overcharge inhibitor include unsubstituted or alkyl-substituted terphenyl derivatives such as biphenyl, o-terphenyl, m-terphenyl, and p-terphenyl, and unsubstituted or alkyl-substituted terphenyl derivatives. Partial hydride, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3-trimethyl-3-phenylindane, cyclopentylbenzene, cyclohexylbenzene, cumene, 1,3- Aromatic compounds such as diisopropylbenzene, 1,4-diisopropylbenzene, t-butylbenzene, t-amylbenzene, t-hexylbenzene, anisole; 2-fluorobiphenyl, 4-fluorobiphenyl, o-cyclohexylfluorobenzene, p- Partial fluorides of the above aromatic compounds such as cyclohexylfluorobenzene, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzenefluorobenzene, fluorotoluene, benzotrifluoride; 2,4-difluoroanisole, 2,5-difluoroanisole, 1 , 6-Difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and other fluorine-containing anisole compounds; 3-propylphenylacetate, 2-ethylphenylacetate, benzylphenylacetate, methylphenylacetate, benzylacetate, phenethyl Aromatic acetates such as phenylacetate; aromatic carbonates such as diphenyl carbonate and methylphenyl carbonate, toluene derivatives such as toluene and xylene, 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl, o-cyclohexylbiphenyl and the like. Examples thereof include a biphenyl derivative which is unsubstituted or substituted with an alkyl group. Among them, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydride of terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether and dibenzofuran, diphenylcyclohexane, 1,1,3-trimethyl. -3-Phenylindan, 3-propylphenylacetate, 2-ethylphenylacetate, benzylphenylacetate, methylphenylacetate, benzylacetate, diphenylcarbonate, methylphenylcarbonate and the like are preferable. These may be used alone or in combination of two or more. When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, a partially hydride of biphenyl, alkylbiphenyl, terphenyl, terphenyl, cyclohexylbenzene, t-butylbenzene, etc. Overcharge prevention characteristics and high temperature storage characteristics are to be used in combination with at least one selected from oxygen-free aromatic compounds such as t-amylbenzene and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran. It is preferable from the viewpoint of the balance of.

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

（一般式（６）中、Ｒ^６１、Ｒ^６２はそれぞれ独立に、置換基を有していてもよい、炭素数１以上１５以下の炭化水素基を表す。）

(In the general formula (6), R ⁶¹ and R ⁶² each independently represent a hydrocarbon group having 1 or more and 15 or less carbon atoms, which may have a substituent.)

The types of R ⁶¹ and R ⁶² are not particularly limited as long as they are monovalent hydrocarbon groups. For example, it may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, or may be a bond of an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated hydrocarbon group and may contain an unsaturated bond (carbon-carbon double bond or carbon-carbon triple bond). Further, the aliphatic hydrocarbon group may be chain-like or cyclic, and in the case of chain-like, it may be linear or branched-chain. Further, it may be a combination of a chain and a ring. In addition, R ⁶¹ and R ⁶² may be the same as each other or may be different from each other.

When ^{the hydrocarbon groups of R 61} and R ⁶² have a substituent, the type of the substituent is not particularly limited as long as it is not contrary to the gist of the present invention, and examples thereof include a fluorine atom, a chlorine atom and a bromine atom. , Halogen atom such as iodine atom, preferably fluorine atom. Alternatively, examples of the substituent other than the logene atom include a substituent having a functional group such as an ester group, a cyano group, a carbonyl group and an ether group, and a cyano group and a carbonyl group are preferable. The hydrocarbon groups of R ⁶¹ and R ⁶² may have only one of these substituents, or may have two or more of them. If they have two or more substituents, they may be the same or different from each other.

The carbon number of each hydrocarbon group of R ⁶¹ and R ⁶² is usually 1 or more, and is usually 15 or less, preferably 12 or less, more preferably 10 or less, and further preferably 9 or less. When R ¹ and R ² are bonded to each other to form a divalent hydrocarbon group, the number of carbon atoms of the divalent hydrocarbon group is usually 1 or more, and usually 15 or less, preferably 15 or less. It is 13 or less, more preferably 10 or less, still more preferably 8 or less. When ^{the hydrocarbon groups of R 61} and R ⁶² have a substituent containing a carbon atom, it is preferable that the total number of carbon atoms of ^{R 61} and R ^{62 including the substituent satisfies the above range.}

Next, a specific example of the acid anhydride represented by the general formula (6) will be described. In the following examples, the "related material" refers to an acid anhydride obtained by replacing a part of the structure of the exemplified acid anhydride with another structure within a range not contrary to the gist of the present invention. For example, dimers, trimerics and tetramers composed of a plurality of acid anhydrides, or isostructural heterogeneous substances having the same number of carbon atoms but having a branched chain, and the substituents are acids. Examples thereof include those having different sites that bind to the anhydride.

First, specific examples of acid anhydrides in which ^{R 61} and R ^{62 are the same are given below.}

Specific examples of acid anhydrides in which R ⁶¹ and R ⁶² are chain alkyl groups include acetic anhydride, propionic acid anhydride, butanoic anhydride, 2-methylpropionic acid anhydride, and 2,2-dimethylpropionic acid anhydride. , 2-Methylbutanoic anhydride, 3-Methylbutanoic anhydride, 2,2-dimethylbutanoic anhydride, 2,3-dimethylbutanoic anhydride, 3,3-dimethylbutanoic anhydride, 2,2 3-trimethylbutanoic anhydride, 2,3,3-trimethylbutanoic anhydride, 2,2,3,3-tetramethylbutanoic anhydride, 2-ethylbutanoic anhydride, etc., and their analogs, etc. Can be mentioned.

Specific examples of the acid anhydride in which R ⁶¹ and R ⁶² are cyclic alkyl groups include cyclopropanecarboxylic acid anhydride, cyclopentanecarboxylic acid anhydride, cyclohexanecarboxylic acid anhydride, and their analogs. ..

Specific examples of acid anhydrides in which R ⁶¹ and R ⁶² are alkenyl groups include acrylate anhydrides, 2-methyl acrylate anhydrides, 3-methyl acrylate anhydrides, and 2,3-dimethyl acrylate anhydrides. 3,3-Dimethylacrylic anhydride, 2,3,3-trimethylacrylic anhydride, 2-phenylacrylic anhydride, 3-phenylacrylic anhydride, 2,3-diphenylacrylic anhydride, 3, 3-Diphenylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, 2,2-dimethyl-3-butenoic anhydride, 3-methyl-3-tenic anhydride, 2-Methyl-3-methyl-3-butenoic anhydride, 2,2-dimethyl-3-methyl-3-butenoic anhydride, 3-pentenoic anhydride, 4-pentenoic anhydride, 2-cyclopentencarboxylic acid Examples thereof include acid anhydrides, 3-cyclopentenecarboxylic acid anhydrides, 4-cyclopentenecarboxylic acid anhydrides and the like, and their analogs.

Specific examples of acid anhydrides in which R ⁶¹ and R ⁶² are alkynyl groups include propic acid anhydride, 3-phenylpropic acid anhydride, 2-butanoic acid anhydride, 2-pentanoic acid anhydride, and 3-butanoic acid. Anhydrides, 3-pentanoic anhydrides, 4-pentanoic anhydrides and the like, and their analogs and the like can be mentioned.

Specific examples of acid anhydrides in which R ⁶¹ and R ⁶² are aryl groups include benzoic acid anhydride, 4-methylbenzoic acid anhydride, 4-ethylbenzoic acid anhydride, 4-tert-butyl benzoic acid anhydride, and the like. Examples thereof include 2-methylbenzoic acid anhydride, 2,4,6-trimethylbenzoic acid anhydride, 1-naphthalenecarboxylic acid anhydride, 2-naphthalenecarboxylic acid anhydride and the like, and analogs thereof.

Further, ^{as an example of an acid anhydride in which R 61} and R ⁶² are substituted with a halogen atom, an example of an acid anhydride in which R 61 and R 62 are mainly substituted with a fluorine atom is given below, and some or all of these fluorine atoms are used. Acid anhydrides obtained by substituting chlorine atoms, bromine atoms, and iodine atoms are also included in the exemplary compounds.

Examples of acid anhydrides in which R ⁶¹ and R ⁶² are chain alkyl groups substituted with halogen atoms include fluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, 2-fluoropropionic anhydride, and the like. 2,2-Difluoropropionic anhydride, 2,3-difluoropropionic anhydride, 2,2,3-trifluoropropionic anhydride, 2,3,3-trifluoropropionic anhydride, 2,2 3,3-Tetrapropionic anhydride, 2,3,3,3-tetrapropionic anhydride, 3-fluoropropionic anhydride, 3,3-difluoropropionic anhydride, 3,3,3-trifluoro Propionic anhydride, perfluoropropionic anhydride and the like, and their analogs and the like can be mentioned.

Examples of acid anhydrides in which R ⁶¹ and R ⁶² are cyclic alkyl groups substituted with halogen atoms include 2-fluorocyclopentanecarboxylic acid anhydride, 3-fluorocyclopentanecarboxylic acid anhydride, and 4-fluorocyclopentane. Examples thereof include carboxylic acid anhydrides and the like, and their analogs.

Examples of acid anhydrides in which R ⁶¹ and R ⁶² are alkenyl groups substituted with halogen atoms include 2-fluoroacrylic acid anhydride, 3-fluoroacrylic acid anhydride, 2,3-difluoroacrylic acid anhydride, and so on. 3,3-Difluoroacrylic anhydride, 2,3,3-trifluoroacrylic anhydride, 2- (trifluoromethyl) acrylic anhydride, 3- (trifluoromethyl) acrylic anhydride, 2,3 -Bis (trifluoromethyl) acrylate anhydride, 2,3,3-tris (trifluoromethyl) acrylate anhydride, 2- (4-fluorophenyl) acrylate anhydride, 3- (4-fluorophenyl) Acrylic acid anhydride, 2,3-bis (4-fluorophenyl) acrylic acid anhydride, 3,3-bis (4-fluorophenyl) acrylic acid anhydride, 2-fluoro-3-butenoic acid anhydride, 2, 2-Difluoro-3-butenoic anhydride, 3-fluoro-2-butenoic anhydride, 4-fluoro-3-butenoic anhydride, 3,4-difluoro-3-butenoic anhydride, 3,3 Examples thereof include 4-trifluoro-3-butenoic anhydride and the like, and their analogs.

Examples of acid anhydrides in which R ⁶¹ and R ⁶² are alkynyl groups substituted with halogen atoms include 3-fluoro-2-propic acid anhydride and 3- (4-fluorophenyl) -2-propic acid anhydride. , 3- (2,3,4,5,6-pentafluorophenyl) -2-proponic acid anhydride, 4-fluoro-2-butanoic acid anhydride, 4,4-difluoro-2-butanoic acid anhydride, Examples thereof include 4,4,4-trifluoro-2-butanoic acid anhydrides and the like, and their analogs.

Examples of acid anhydrides in which R ⁶¹ and R ⁶² are aryl groups substituted with halogen atoms include 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, 4 -Trifluoromethylbenzoic anhydride and the like, and their analogs and the like can be mentioned.

Examples of acid anhydrides in which R ⁶¹ and R ⁶² have a substituent having a functional group such as an ester, a nitrile, a ketone, an ether, etc. Ethyl oxalic anhydride, 2-cyanoacetate anhydride, 2-oxopropionic acid anhydride, 3-oxobutanoic acid anhydride, 4-acetylbenzoic acid anhydride, methoxyacetic anhydride, 4-methoxybenzoic acid anhydride, etc. And their relatives and the like.

Subsequently, ^{specific examples of acid anhydrides in which R 61} and R ⁶² are different from each other are given below.

As R ⁶¹ and R ⁶² , the above-mentioned examples and all combinations of their analogs can be considered, and typical examples are given below.

Examples of combinations of chain alkyl groups include propionic anhydride, butanoic anhydride, propionic butanoate, 2-methylpropionic anhydride, and the like.

Examples of the combination of the chain alkyl group and the cyclic alkyl group include cyclopentanoic acid anhydride, cyclohexanoic acid acetate anhydride, propionic acid anhydride and the like.

Examples of the combination of the chain alkyl group and the alkenyl group include acrylate anhydride, 3-methylacrylic acetate anhydride, 3-butenoic acid anhydride, propionic acrylate anhydride and the like.

Examples of combinations of chain alkyl groups and alkynyl groups include propic acid acetate anhydride, 2-butynic acid acetate anhydride, 3-butynic acid acetate anhydride, 3-phenylpropic acid acetate anhydride propionic acid propionic acid anhydride. , Etc. can be mentioned.

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

Examples of combinations of chain alkyl groups and functional hydrocarbon groups include fluoroacetic acid anhydride, trifluoroacetic acid anhydride, 4-fluorobenzoic acid anhydride, fluoropropionic acid anhydride, alkyl acetate. Examples thereof include oxalic acid anhydride, 2-cyanoacetic acid anhydride, 2-oxopropionic acid acetate anhydride, methoxyacetic acid acetate anhydride, and propionic acid methoxyacetic acid anhydride.

Examples of combinations of cyclic alkyl groups include cyclopentanoic acid cyclohexaneic anhydride and the like.

Examples of combinations of cyclic alkyl groups and alkenyl groups include cyclopentanoic anhydride, 3-methylacrylic acid cyclopentanoic anhydride, 3-butenoic acid cyclopentanoic anhydride, cyclohexanoic acid anhydride, and the like. Can be mentioned.

Examples of the combination of the cyclic alkyl group and the alkynyl group include cyclopentanoic anhydride, 2-butyrate cyclopentanoic anhydride, cyclohexaneic anhydride, and the like.

Examples of the combination of the cyclic alkyl group and the aryl group include cyclopentanoic acid anhydride, 4-methylbenzoic acid cyclopentanoic acid anhydride, cyclohexaneic acid anhydride, and the like.

Examples of combinations of cyclic alkyl groups and hydrocarbon groups having functional groups include cyclopentanoic anhydride, cyclopentanoic acid trifluoroacetic anhydride, cyclopentanoic 2-cyanoacetic anhydride, and methoxyacetic acid cyclopentanoate. Anhydride, cyclohexanoic acid fluoroacetic anhydride, and the like can be mentioned.

Examples of combinations of alkenyl groups include 2-methylacrylic acid anhydride, 3-methylacrylic acid anhydride, 3-butenoic acid anhydride, and 3-methylacrylic acid anhydride, 2-methylacrylic acid. Things, etc. can be mentioned.

Examples of the combination of the alkenyl group and the alkynyl group include acrylic acid propic acid anhydride, acrylic acid 2-butynic acid anhydride, 2-methylacrylic acid propynic acid anhydride, and the like.

Examples of the combination of the alkenyl group and the aryl group include acrylic acid benzoic anhydride, 4-methylbenzoic anhydride, 2-methylacrylic anhydride, and the like.

Examples of combinations of an alkenyl group and a hydrocarbon group having a functional group include fluoroacetic acid anhydride, trifluoroacetic acid anhydride, 2-cyanoacetic acid anhydride, methoxyacetic acid anhydride, 2-. Examples thereof include methyl acrylate fluoroacetic acid anhydride.

Examples of combinations of alkynyl groups include propanoic acid 2-butanoic acid anhydride, propanoic acid 3-butynic acid anhydride, 2-butanoic acid 3-butynic acid anhydride, and the like.

Examples of the combination of the alkynyl group and the aryl group include benzoic acid propic acid anhydride, 4-methylbenzoic acid propic acid anhydride, benzoic acid 2-butynic acid anhydride, and the like.

Examples of combinations of an alkynyl group and a hydrocarbon group having a functional group include fluoroacetic anhydride, trifluoroacetic anhydride, 2-cyanoacetic anhydride, 2-cyanoacetic anhydride, methoxyacetic anhydride, 2-. Fluoroacetic anhydride, butynate, and the like can be mentioned.

Examples of combinations of aryl groups include 4-methylbenzoic acid anhydride, 1-naphthalenecarboxylic acid anhydride, 4-methylbenzoic acid 1-naphthalenecarboxylic acid anhydride, and the like.

Examples of combinations of an aryl group and a hydrocarbon group having a functional group include fluoroacetic anhydride, trifluoroacetic anhydride, 2-cyanoacetic anhydride, 2-cyanoacetic anhydride, methoxyacetic anhydride, 4-. Fluoroacetic anhydride of methylbenzoate, and the like can be mentioned.

Examples of combinations of hydrocarbon groups having functional groups include fluoroacetate trifluoroacetic acid anhydride, fluoroacetic acid 2-cyanoacetic acid anhydride, fluoroacetate methoxyacetic acid anhydride, trifluoroacetic acid 2-cyanoacetic acid anhydride, and the like. Can be mentioned.

Among the acid anhydrides forming the above chain structure, acrylic acids such as acetic anhydride, propionic acid anhydride, 2-methylpropionic acid anhydride, cyclopentanecarboxylic acid anhydride, cyclohexanecarboxylic acid anhydride and the like are preferable. Anhydride, 2-methylacrylic acid anhydride, 3-methylacrylic acid anhydride, 2,3-dimethylacrylic acid anhydride, 3,3-dimethylacrylic acid anhydride, 3-butenoic acid anhydride, 2-methyl- 3-butenoic acid anhydride, propic acid anhydride, 2-butanoic acid anhydride, benzoic acid anhydride, 2-methylbenzoic acid anhydride, 4-methylbenzoic acid anhydride, 4-tert-butylbenzoic acid anhydride, Trifluoroacetate anhydride, 3,3,3-trifluoropropionic acid anhydride, 2- (trifluoromethyl) acrylic acid anhydride, 2- (4-fluorophenyl) acrylic acid anhydride, 4-fluorobenzoic acid anhydride 2,3,4,5,6-pentafluorobenzoic anhydride, methoxygic acid anhydride, ethoxygalic acid anhydride, more preferably acrylic acid anhydride, 2-methylacrylic acid anhydride, 3 -Methylacrylic acid anhydride, benzoic acid anhydride, 2-methylbenzoic acid anhydride, 4-methylbenzoic acid anhydride, 4-tert-butyl benzoic acid anhydride, 4-fluorobenzoic acid anhydride, 2,3 4,5,6-pentafluorobenzoic anhydride, methoxygic acid anhydride, ethoxygic acid anhydride.

These compounds can improve the charge / discharge rate characteristics, input / output characteristics, and impedance characteristics, especially after the durability test, by appropriately forming a bond with the lithium oxalate salt to form a film having excellent durability. It is preferable from the viewpoint of being able to do it.

The molecular weight of the carboxylic acid anhydride is not limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 90 or more, preferably 95 or more, while usually 300 or less, preferably 200 or less. be. When the molecular weight of the carboxylic acid anhydride is within the above range, an increase in the viscosity of the electrolytic solution can be suppressed, and the film density is optimized, so that the durability can be appropriately improved.

Further, the method for producing the carboxylic acid anhydride is not particularly limited, and a known method can be arbitrarily selected for production. As the carboxylic acid anhydride described above, any one of them may be contained alone in the non-aqueous electrolyte solution of the present invention, or two or more of them may be coexisted in any combination and ratio.

The content of the carboxylic acid anhydride in the electrolytic solution of the present invention is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01 mass by mass with respect to the electrolytic solution of the present invention. % Or more, preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less. When the content of the carboxylic acid anhydride is within the above range, the effect of improving the cycle characteristics is likely to be exhibited, and the reactivity is preferable, so that the battery characteristics are likely to be improved.

Other known auxiliaries can be used in the electrolytic solution of the present invention. Other auxiliaries include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9. -Divinyl-2,4,8,10-Spyro compounds such as tetraoxaspiro [5.5] undecane; ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan , Sulfolene, ethylene sulfate, vinylene sulfate, diphenylsulfon, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, acetamide, N-methylformamide, N, N-dimethylformamide, N, N-dimethylacetamide , Methyl vinyl sulfonate, ethyl vinyl sulfonate, allyl vinyl sulfonate, propargyl vinyl sulfonate, methyl allyl sulfonate, ethyl allyl sulfonate, allyl allyl sulfonate, propargyl allyl sulfonate, 1,2-bis (vinyl sulfonate) Roxy) ethane, propanedisulfonic acid anhydride, sulfobutyric acid anhydride, sulfobenzoic acid anhydride, sulfopropionic acid anhydride, ethanedisulfonic acid anhydride, methylenemethanedisulfonate, 2-propynyl methanesulfonic acid, pentensulfite, pentafluorophenylmethanesulfonate, Propylene Sulfate, Propylene Sulfite, Propane Salton, Butylene Sulfite, Butane-2,3-Diyl Dimethane Sulfonate, 2-Butin-1,4-Diyl Dimethane Sulfonate, 2-Phenylbicyclohexyl, 2-Butin-1 , 4-Diyldiformate, 2-propynyl vinyl sulfonic acid, bis (2-vinylsulfonylethyl) ether, 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, 2- (methane) Sulfonyloxy) 2-propynyl propionate, 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, 3-sulfo-propionic acid anhydride trimethylene methanedisulfonate 2-methyl tetrahydrofuran, trimethylene Methandisulfonate, tetramethylene sulfoxide, dimethylenemethanedisulfonate, difluoroethylmethylsulfonate, divinylsulfon, 1,2-bis (vinylsulfonyl) ethane, methyl ethylenebisphosphonate, ethylenebisphos Sulfur-containing compounds such as ethyl phonate and ethylene sulfate; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N- Nitrogen-containing compounds such as methylsuccinimide, nitromethane, nitroethane, thiophene 1-oxide, ethylenediamine; trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, methylphosphonic acid Dimethyl, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, ethyl diethylphosphonoacetate, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide, bis phosphate (2,2-difluoro) Ethyl) 2,2,2-trifluoroethyl, bis phosphate (2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl, bis phosphate (2,2,2-trifluoropropyl) Ethyl) Methyl, bis (2,2,2-trifluoroethyl) ethyl, bis phosphate (2,2,2-trifluoroethyl) 2,2-difluoroethyl bis phosphate (2,2,2-) Trifluoroethyl) 2,2,3,3-tetrafluoropropyl, tributyl phosphate, tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3) -Hexafluoropropan-2-yl), trioctyl phosphate, 2-phenylphenyldimethyl phosphate, 2-phenylphenyldiethyl phosphate, (2,2,2-trifluoroethyl) (2,2,3) 3-Tetrafluoropropyl) methyl, phosphate triester, methyl methylenebisphosphonate, ethyl methylenebisphosphonate, methyl2- (dimethoxyphosphoryl) acetate, methyl2- (dimethylphosphoryl) acetate, methyl2- (diethoxyphosphoryl) acetate , Methyl 2- (diethylphosphoryl) acetate, methyl butylenebisphosphonate, ethyl butylenebisphosphonate, 2-propynyl 2- (dimethoxyphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2- (diethoxy) Phospholyl) acetate, 2-propynyl 2- (diethylphosphoryl) acetate, tris (trimethylsilyl) phosphate, tris (trimethylsilyl) phosphate Phosphoric compounds such as ite, tris (triethylsilyl) phosphate, tris (triethylsilyl) phosphite; heptane, octane, nonane, decane, cycloheptane, methylformate, methyl2-propynyloxalate, 2-propynyl methacrylate , Dimethyl malonate, malonic acid ester, pentane, benzene, furan, naphthalene, 2,5,8,11-tetraoxadodecane, 2,5,8,11,14-pentaoxapentadecane, 3-pentanone, 2-phenyl Hydrocarbon compounds such as bicyclohexyl, 3-allyl anhydride succinic acid, ethoxymethoxyethane, trimethoxymethane, cyclohexane; fluorobenzene, difluorobenzene, hexafluorobenzene, benzotrifluoride, monofluorobenzene, 1-fluoro-2-cyclohexyl Fluorophilic aromatic compounds such as benzene, 1-fluoro-4-tert-butylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-2-cyclohexylbenzene, fluorinated biphenyl; tris borate (trimethylsilyl), boro Tris (trimethoxysilyl) acid, tris (trimethylsilyl) phosphate, tris (trimethoxysilyl) phosphate, dimethoxyaluminoxytrimethoxysilane, diethoxyaluminoxytriethoxysilane, dipropoxyaluminoxytriethoxysilane, dibutoxyalumino Silane compounds such as xitrimethoxysilane, dibutoxyaluminoxytriethoxysilane, titanium tetrakis (trimethylsiloxide), titaniumtetrakis (triethylsiloxide), tris phosphite (trimethylsilyl), trimethylsilyl polyphosphate, tetramethylsilane; dimethyl Oxalate, dioxolane, dioxane, dimethyl ketone, diethyl ketone, diethyl oxalate, di (2-propynyl) oxalate, dimethyl succinate, di (2-propynyl) glutarate, 2-propynyl formate, ethyl formate, glyme, ethyl mono Examples thereof include oxygen-containing compounds such as glyme, ethylmethyloxalate, and ethylformate. These may be used alone or in combination of two or more. By adding these auxiliaries, the capacity retention characteristics and cycle characteristics after high temperature storage can be improved.
As the other auxiliary agent, a phosphorus-containing compound is preferable, and tris (trimethylsilyl) phosphate is preferable.

The blending amount of the other auxiliary agents is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The other auxiliary agent is preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the electrolytic solution. Within this range, the effects of other auxiliaries are likely to be sufficiently exhibited, and it is easy to avoid situations such as deterioration of battery characteristics such as high load discharge characteristics. The blending amount of the other auxiliary agent is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, still more preferably 3% by mass or less, still more preferably 1% by mass or less. ..

The electrolytic solution of the present invention contains cyclic and chain carboxylic acid esters, ether compounds, nitrogen-containing compounds, boron-containing compounds, organic silicon-containing compounds, nonflammable (flame-retardant) agents, and surfactants as long as the effects of the present invention are not impaired. An activator, a high dielectricing additive, a cycle property and rate property improving agent, a sulfone compound and the like may be further contained as an additive.

Examples of the cyclic carboxylic acid ester include those having a total number of carbon atoms of 3 to 12 in the structural formula. Specific examples thereof include gamma-butyrolactone, gamma-valerolactone, gamma caprolactone, epsilon caprolactone, 3-methyl-γ-butyrolactone and the like. Of these, gamma-butyrolactone is particularly preferable from the viewpoint of improving the characteristics of the electrochemical device due to the improvement in the degree of lithium ion dissociation.

The blending amount of the cyclic carboxylic acid ester as an additive is usually 0.1% by mass or more, more preferably 1% by mass or more, based on 100% by mass of the solvent. Within this range, the electrical conductivity of the electrolytic solution can be improved, and the large-current discharge characteristics of the electrochemical device can be easily improved. The blending amount of the cyclic carboxylic acid ester is preferably 10% by mass or less, more preferably 5% by mass or less. By setting the upper limit in this way, the viscosity of the electrolytic solution is set to an appropriate range, the decrease in electrical conductivity is avoided, the increase in negative electrode resistance is suppressed, and the large current discharge characteristics of the electrochemical device are set to a good range. Make it easier.

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

(In the formula, X ^{15 to} X ²⁰ are the same or different, all of which are -H, -F, -Cl, -CH ₃ or fluorinated alkyl groups; where at least one of ^{X 15 to} X ^{20 is alkyl fluorinated.} Is the basis)
Fluorine-containing lactones indicated by.

Examples of the fluorinated alkyl groups in X ^{15 to} X ²⁰ _{include -CFH 2} , -CF ₂ H, -CF ₃ , -CH ₂ CF ₃ , -CF ₂ CF ₃ , -CH ₂ CF ₂ CF ₃ , and -CF. (CF ₃ ) _{2 and the like are mentioned, and -CH 2} CF ₃ and -CH ₂ CF ₂ CF ₃ are preferable from the viewpoint of high oxidation resistance and safety improving effect.

If ^{at least one of X 15 to} X ²⁰ is a fluorinated alkyl group, then the -H, -F, -Cl, -CH ₃ or fluorinated alkyl group is replaced with only one of ^{X 15 to} X ^20. It may be replaced with a plurality of places. It is preferably 1 to 3 locations, more preferably 1 to 2 locations from the viewpoint of good solubility of the electrolyte salt.

But it is not fluorinated alkyl group substituted position particularly limited to, since the synthesis yields ^{good, X 17} and / or ^{X 18} is, in particular ^{X 17} or ^{X 18} is a fluorinated alkyl group, inter alia _-CH 2 CF ₃ , -CH ₂ CF ₂ CF ₃ is preferable. ^{X 15 to} X ²⁰ other than the fluorinated alkyl group are −H, −F, −Cl or CH ₃ , and −H is particularly preferable from the viewpoint of good solubility of the electrolyte salt.

As the fluorine-containing lactone, in addition to those represented by the above formula, for example, the following formula (D):

(In the formula, either A or B is CX ²²⁶ X ²²⁷ (X ²²⁶ and X ²²⁷ are the same or different, and both have -H, -F, -Cl, -CF ₃ , -CH ₃ or a hydrogen atom. An alkylene group that may be substituted with a halogen atom or may contain a heteroatom in the chain), while the other is an oxygen atom; Rf ¹² may have an ether bond fluorinated alkyl group or fluorinated. Alkoxy groups; X ²²¹ and X ²²² are the same or different, both -H, -F, -Cl, -CF ₃ or CH ₃ ; X ^{223 to} X ²²⁵ are the same or different, both -H, -F. , -Cl or an alkyl group in which the hydrogen atom may be substituted with a halogen atom or a hetero atom may be contained in the chain; n = 0 or 1)
Fluorine-containing lactones and the like shown by are also mentioned.

The fluorine-containing lactone represented by the formula (D) includes the following formula (E):

(In the formula, A, B, Rf ¹² , X ²²¹ and X ²²² and X ²²³ are the same as in the formula (D)).
The 5-membered ring structure represented by (1) is preferably cited from the viewpoint of easy synthesis and good chemical stability. Further, depending on the combination of A and B, the following formula (F):

(In the equation, Rf ¹² , X ²²¹ and X ²²² , X ²²³ , X ²²⁶ and X ²²⁷ are the same as in equation (D)).
Fluorine-containing lactone represented by and the following formula (G):

(In the equation, Rf ¹² , X ²²¹ and X ²²² , X ²²³ , X ²²⁶ and X ²²⁷ are the same as in equation (D)).
There is a fluorine-containing lactone indicated by.

Among these, excellent characteristics such as high dielectric constant and high withstand voltage can be exhibited in particular, and in addition, the characteristics as an electrolytic solution in the present invention are improved in that the solubility of the electrolyte salt and the reduction of internal resistance are good. from,

等が挙げられる。
フッ素化環状カルボン酸エステルを含有させることにより、イオン伝導度の向上、安全性の向上、高温時の安定性向上といった効果が得られる。

And so on.
By containing the fluorinated cyclic carboxylic acid ester, effects such as improvement of ionic conductivity, improvement of safety, and improvement of stability at high temperature can be obtained.

Examples of the chain carboxylic acid ester include those having a total carbon number of 3 to 7 in the structural formula. Specifically, methyl acetate, ethyl acetate, -n-propyl acetate, isopropyl acetate, -n-butyl acetate, isobutyl acetate, -t-butyl acetate, methyl propionate, ethyl propionate, -n-propyl propionate, Isobutyl propionate, -n-butyl propionate, methylbutyrate, isobutyl propionate, -t-butyl propionate, methyl butyrate, ethyl butyrate, -n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, iso Examples thereof include -n-propyl butyrate and isopropyl isobutyrate.

Among them, methyl acetate, ethyl acetate, -n-propyl acetate, -n-butyl acetate, methyl propionate, ethyl propionate, -n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate and the like are ions due to a decrease in viscosity. It is preferable from the viewpoint of improving conductivity.

As the ether compound, a chain ether having 2 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms are preferable.
Examples of the chain ether having 2 to 10 carbon atoms include dimethyl ether, diethyl ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, diethoxymethane, dimethoxyethane, methoxyethoxyethane, diethoxyethane, and ethylene glycol di-n. Examples thereof include -propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol, diethylene glycol dimethyl ether, pentaethylene glycol, triethylene glycol dimethyl ether, triethylene glycol, tetraethylene glycol, tetraethylene glycol dimethyl ether and diisopropyl ether.

Further, as the ether compound, fluorinated ether can also be preferably used.
The fluorinated ether has the following general formula (I):
Rf ^3- O-Rf ⁴ (I)
(In the formula, Rf ³ and Rf ⁴ are the same or different, and are an alkyl group having 1 to 10 carbon atoms or a fluorinated alkyl group having 1 to 10 carbon atoms. However, at least one of ^{Rf 3} and Rf ^{4 is fluorine.} It is an alkylated group.)
Fluorinated ether (I) represented by. By containing the fluorinated ether (I), the flame retardancy of the electrolytic solution is improved, and the stability and safety at high temperature and high voltage are improved.

In the above general formula (I), ^{at least one of Rf 3} and Rf ⁴ may be a fluorinated alkyl group having 1 to 10 carbon atoms, but the electrolyte is flame-retardant, stable at high temperature and high voltage, and safe. From the viewpoint of further improving the properties, ^{it is preferable that both Rf 3} and Rf ⁴ are fluorinated alkyl groups having 1 to 10 carbon atoms. In this case, Rf ³ and Rf ⁴ may be the same or different from each other.
Among them, Rf ³ and Rf ⁴ are the same or different, Rf ³ is a fluorinated alkyl group having 3 to 6 carbon atoms, and Rf ⁴ is a fluorinated alkyl group having 2 to 6 carbon atoms. More preferred.

If ^{the total carbon number of Rf 3} and Rf ⁴ is too small, the boiling point of the fluorinated ether becomes too low, and if ^{the carbon number of Rf 3} or Rf ⁴ is too large, the solubility of the electrolyte salt decreases, and other solvents The compatibility with the solvent also begins to be adversely affected, and the viscosity increases, so that the rate characteristics decrease. When ^{the carbon number of Rf 3} is 3 or 4, and ^{the carbon number of Rf 4} is 2 or 3, it is advantageous in that it is excellent in boiling point and rate characteristics.

The fluorinated ether (I) preferably has a fluorine content of 40 to 75% by mass. When the fluorine content is in this range, the balance between nonflammability and compatibility becomes particularly excellent. It is also preferable from the viewpoint of good oxidation resistance and safety.
The lower limit of the fluorine content is more preferably 45% by mass, further preferably 50% by mass, and particularly preferably 55% by mass. The upper limit is more preferably 70% by mass, further preferably 66% by mass.
The fluorine content of the fluorinated ether (I) is {(number of fluorine atoms × 19) / molecular weight of the fluorinated ether (I)} × 100 (%) based on the structural formula of the fluorinated ether (I). ) Is the value calculated by.

The Rf ^3, for _{example, CF 3 CF 2 CH 2 -} , CF 3 CFHCF 2 -, HCF 2 CF 2 CF 2 -, HCF 2 CF 2 CH 2 -, CF 3 CF 2 CH 2 CH 2 -, CF 3 CFHCF ₂ CH ₂ −, HCF ₂ CF ₂ CF ₂ CF ₂ −, HCF ₂ CF ₂ CF ₂ CH ₂ −, HCF ₂ CF ₂ CH ₂ CH ₂ −, HCF ₂ CF (CF ₃ ) CH ₂ − and the like can be mentioned. As Rf ⁴ , for example, -CH ₂ CF ₂ CF ₃ , -CF ₂ CFHCF ₃ , -CF ₂ CF ₂ CF ₂ H, -CH ₂ CF ₂ CF ₂ H, -CH ₂ CH ₂ CF ₂ CF ₃ , -CH ₂ CF ₂ CFHCF ₃ , -CF ₂ CF ₂ CF ₂ CF ₂ H, -CH ₂ CF ₂ CF ₂ CF ₂ H, -CH ₂ CH ₂ CF ₂ CF ₂ H, -CH ₂ CF (CF ₃ ) Examples thereof include CF ₂ H, -CF ₂ CF ₂ H, -CH ₂ CF ₂ H, and -CF ₂ CH _3.

Specific examples of the fluorinated ether (I) include, for example, HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H, CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , CF. ₃ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , C ₆ F ₁₃ OCH ₃ , C ₆ F ₁₃ OC ₂ H ₅ , C ₈ F ₁₇ OCH ₃ , C ₈ F ₁₇ OC ₂ H ₅ , CF ₃ CFHCF ₂ CH (CH ₃₎ ) OCF ₂ CFHCF ₃ , HCF ₂ CF ₂ OCH (C ₂ H ₅ ) ₂ , HCF ₂ CF ₂ OC ₄ H ₉ , HCF ₂ CF ₂ OCH ₂ CH (C ₂ H ₅ ) ₂ , HCF ₂ CF ₂ OCH ₂ CH (CH ₃ ) _{2 and the} like can be mentioned.

_{Among them, those containing HCF 2-} or CF ₃ CFH- at one end or both ends are excellent in polarity and can give fluorinated ether (I) having a high boiling point. The boiling point of the fluorinated ether (I) is preferably 67 to 120 ° C. It is more preferably 80 ° C. or higher, and even more preferably 90 ° C. or higher.

Examples of such fluorinated ether (I) include CF ₃ CH ₂ OCF ₂ CFHCF ₃ , CF ₃ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , HCF ₂ CF ₂ CH. ₂ OCH ₂ CF ₂ CF ₂ H, CF ₃ CFHCF ₂ CH ₂ OCF ₂ CFHCF ₃ , HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H, CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H, etc. The above can be mentioned.
_{Among them, HCF 2} CF ₂ CH ₂ OCF ₂ CFHCF ₃ (boiling point 106 ° C) and CF ₃ CF ₂ CH are advantageous in that they have a high boiling point, compatibility with other solvents, and solubility of electrolyte salts. Selected from the group consisting of ₂ OCF _{2 CFHCF 3} (boiling point 82 ° C), HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H (boiling point 92 ° C) and CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H (boiling point 68 ° C). at least it is at least one that is _preferably selected from the group consisting of _{HCF 2 CF 2 CH 2 OCF 2} CFHCF 3 ( boiling point 106 ° C.) and _{HCF 2 CF 2 CH 2 OCF 2} CF 2 H ( boiling point 92 ° C.) It is more preferable that it is one kind.

Cyclic ethers having 3 to 6 carbon atoms include 1,2-dioxane, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, and meta. Formaldehyde, 2-methyl-1,3-dioxolane, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2- (trifluoroethyl) dioxolane 2,2, -bis (trifluoromethyl) -1, Examples thereof include 3-dioxolane and the like, and fluorinated compounds thereof. Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, and crown ether have high solvability to lithium ions and have a high degree of ion dissociation. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferable in terms of improvement, and particularly preferably because they have low viscosity and give high ionic conductivity.

Examples of the nitrogen-containing compound include nitriles, fluorine-containing nitriles, carboxylic acid amides, fluorine-containing carboxylic acid amides, sulfonic acid amides, and fluorine-containing sulfonic acid amides, acetamides, and formamides. Further, 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxadiridinone, 1,3-dimethyl-2-imidazolidinone, N-methylsuccinimide and the like can also be used. However, the nitrile compounds represented by the general formulas (1a), (1b) and (1c) are not included in the nitrogen-containing compounds.

Examples of the boron-containing compound include borate esters such as trimethylborate and triethylborate, borate ether, and alkyl borate.

Examples of the organosilicon-containing compound include (CH ₃ ) ₄ -Si, (CH ₃ ) ₃ -Si-Si (CH ₃ ) ₃ , and silicon oil.

Examples of the non-flammable (flame retardant) agent include phosphoric acid esters and phosphazene compounds. Examples of the phosphoric acid ester include a fluorine-containing alkyl phosphoric acid ester, a non-fluorine-based alkyl phosphoric acid ester, and an aryl phosphoric acid ester. Of these, a fluorine-containing alkyl phosphate is preferable because it can exert a non-combustible effect even in a small amount.

The phosphazene compounds include, for example, methoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, dimethylaminopentafluorocyclotriphosphazene, diethylaminopentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, ethoxyheptafluorocyclotetraphosphazene and the like. Can be mentioned.

Specific examples of the fluorine-containing alkyl phosphate ester include the fluorine-containing dialkyl phosphoric acid ester described in JP-A-11-233141 and the cyclic alkyl phosphate ester described in JP-A-11-283669. , Or a fluorine-containing trialkyl phosphate ester and the like.

Examples of the non-flammable (flame retardant) agent include (CH ₃ O) ₃ P = O, (CF ₃ CH ₂ O) ₃ P = O, (HCF ₂ CH ₂ O) ₃ P = O, (CF ₃ CF _2). CH ₂ ) ₃ P = O, (HCF ₂ CF ₂ CH ₂ ) ₃ P = O and the like are preferable.

The surfactant may be any of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant, but the fluorine atom is good in cycle characteristics and rate characteristics. It is preferable that it contains.

Examples of the surfactant containing such a fluorine atom include the following formula (30):
Rf ⁵ COO ⁻ M ⁺ (30)
(Wherein, Rf ⁵ is a fluorine-containing alkyl group which may contain an ether bond having 3 to 10 carbon atoms; ^{M +} is ^{Li +,} Na +, ^{K +} or NHR _'3 ⁺ (R' are the same or different , Both are H or alkyl groups with 1 to 3 carbon atoms)
Fluorine-containing carboxylate represented by, and the following formula (40):
Rf ⁶ SO ₃ ^- M ⁺ (40)
(Wherein, Rf ⁶ is a fluorine-containing alkyl group which may contain an ether bond having 3 to 10 carbon atoms; ^{M +} is ^{Li +,} Na +, ^{K +} or NHR _'3 ⁺ (R' are the same or different , Both are H or alkyl groups with 1 to 3 carbon atoms)
A fluorine-containing sulfonate represented by is preferable.

The content of the surfactant is preferably 0.01 to 2% by mass in the electrolytic solution from the viewpoint that the surface tension of the electrolytic solution can be reduced without deteriorating the charge / discharge cycle characteristics.

Examples of the high-dielectric additive include sulfolane, methyl sulfolane, γ-butyrolactone, γ-valerolactone and the like.

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

Further, the electrolytic solution of the present invention may be further combined with a polymer material to form a gel-like (plasticized) gel electrolytic solution.

Examples of such polymer materials include conventionally known polyethylene oxides and polypropylene oxides and modified products thereof (Japanese Patent Laid-Open Nos. 8-222270 and 2002-100405); polyacrylate-based polymers, polyacrylonitrile, and polyvinylidene fluoride. , Fluororesin such as vinylidene fluoride-hexafluoropropylene copolymer (Japanese Patent Laid-Open No. 4-506726, Japanese Patent Application Laid-Open No. 8-507407, Japanese Patent Application Laid-Open No. 10-294131); Examples thereof include a composite with a resin (Japanese Patent Laid-Open No. 11-35765, Japanese Patent Application Laid-Open No. 11-86630) and the like. In particular, it is desirable to use polyvinylidene fluoride or vinylidene fluoride-hexafluoropropylene copolymer as a polymer material for a gel electrolyte.

In addition, the electrolytic solution of the present invention may also contain the ionic conductive compound described in Japanese Patent Application No. 2004-301934.

This ionic conductive compound has the formula (101):
A- (D) -B (101)
[In the formula, D is the formula (201):
− (D1) _n − (FAE) _m − (AE) _p − (Y) _q − (201)
(In the formula, D1 is the formula (2a):

(Wherein, Rf is a fluorine-containing ether group which may have a crosslinkable functional group; groups R ¹⁰ couples Rf main chain or a bond)
An ether unit having a fluorine-containing ether group in the side chain indicated by;
FAE is the formula (2b):

(Wherein, Rfa is hydrogen atom, a crosslinkable good fluorinated alkyl group optionally having a functional group; R ¹¹ couples Rfa main chain group or a bond)
An ether unit having an alkyl fluorinated group in the side chain indicated by;
AE is the formula (2c):

(In the formula, R ¹³ has a hydrogen atom, an alkyl group which may have a crosslinkable functional group, an aliphatic ring hydrocarbon group which may have a crosslinkable functional group, or a crosslinkable functional group. May be aromatic hydrocarbon group; R ¹² is a group or bond that binds the main chain to ^{R 13)}
Ether unit indicated by;
Y is the formula (2d-1) to (2d-3):

A unit containing at least one of;
n is an integer from 0 to 200; m is an integer from 0 to 200; p is an integer from 0 to 10000; q is an integer from 1 to 100; where n + m is not 0 and the combination order of D1, FAE, AE and Y is Not specified);
A and B are the same or different, an alkyl group which may contain a hydrogen atom, a fluorine atom and / or a crosslinkable functional group, a phenyl group which may contain a fluorine atom and / or a crosslinkable functional group, -COOH. A group, -OR (R is an alkyl group that may contain a hydrogen atom or a fluorine atom and / or a crosslinkable functional group), an ester group or a carbonate group (provided that D is an oxygen atom, a -COOH group, -OR, not ester group and carbonate group)]
It is an amorphous fluorine-containing polyether compound having a fluorine-containing group in the side chain represented by.

The electrolytic solution of the present invention may contain a sulfone compound. As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2.

Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones, which are monosulfone compounds; and trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones, which are disulfone compounds. Among them, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable, from the viewpoint of dielectric constant and viscosity.

As the sulfolanes, sulfolanes and / or sulfolane derivatives (hereinafter, sulfolanes may be abbreviated as "sulfolanes") are preferable. The sulfolane derivative is preferably one in which one or more hydrogen atoms bonded on the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group.

Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-Difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methyl Sulfolane, 4-fluoro-2-methyl sulfolane, 5-fluoro-3-methyl sulfolane, 5-fluoro-2-methyl sulfolane, 2-fluoromethyl sulfolane, 3-fluoromethyl sulfolane, 2-difluoromethyl sulfolane, 3-difluoro Methyl sulfolane, 2-trifluoromethyl sulfolane, 3-trifluoromethyl sulfolane, 2-fluoro-3- (trifluoromethyl) sulfolane, 3-fluoro-3- (trifluoromethyl) sulfolane, 4-fluoro-3- ( Trifluoromethyl) sulfolane, 3-sulforene, 5-fluoro-3- (trifluoromethyl) sulfolane and the like are preferable because they have high ionic conductivity and high input / output.

Examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, and n-. Butylmethylsulfone, n-butylethylsulfone, t-butylmethylsulfone, t-butylethylsulfone, monofluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone, monofluoroethylmethylsulfone, difluoroethylmethylsulfone, Trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di (tri) Fluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl-n-propyl sulfone, difluoromethyl-n-propyl sulfone, trifluoromethyl-n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone , Trifluoroethyl-n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl-n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, penta Fluoroethyl-n-butyl sulfone, pentafluoroethyl-t-butyl sulfone and the like can be mentioned.

Among them, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone. , Monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoro Ethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, trifluoromethyl-n-butyl sulfone, trifluoromethyl-t -Butyl sulfone or the like is preferable because it has high ionic conductivity and high input / output.

The content of the sulfone compound is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3% by volume or more, preferably 0.5% by volume or more in 100% by volume of the above solvent. , More preferably 1% by volume or more, and usually 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less. When the content of the sulfone compound is within the above range, the effect of improving durability such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the non-aqueous electrolyte solution is set within an appropriate range to reduce the electrical conductivity. Can be avoided, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery can be set in an appropriate range.

The electrolytic solution of the present disclosure is at least one selected from the group consisting of lithium _{fluorophosphate salts (excluding LiPF 6} ) and lithium salts having an S = O group as additives from the viewpoint of improving output characteristics. It is also preferable to contain the compound (7) of.
When compound (7) is used as an additive, it is preferable to use a compound other than compound (7) as the above-mentioned electrolyte salt.

Examples of the lithium fluorophosphate salts include lithium monofluorophosphate (LiPO ₃ F) and lithium difluorophosphate (LiPO ₂ F ₂ ).
Examples of the lithium salts having an S = O group include lithium monofluorosulfonate (FSO ₃ Li), lithium methyl sulfate (CH ₃ OSO ₃ Li), lithium ethyl sulfate (C ₂ H ₅ OSO ₃ Li), 2, 2 , 2-Trifluoroethyl lithium sulfate and the like.
As the compound (7), LiPO ₂ F ₂ , FSO ₃ Li, and C ₂ H ₅ OSO ₃ Li are particularly preferable.

The content of the compound (7) is preferably 0.001 to 20% by mass, more preferably 0.01 to 15% by mass, and 0.1 to 10% by mass with respect to the electrolytic solution. It is more preferably 0.1 to 7% by mass, and particularly preferably 0.1 to 7% by mass.

If necessary, other additives may be added to the electrolytic solution of the present invention. Examples of other additives include metal oxides, glass and the like.

The electrolytic solution of the present invention preferably has a hydrogen fluoride (HF) content of 5 to 200 ppm. By containing HF, film formation of the above-mentioned additives can be promoted. If the HF content is too low, the film forming ability on the negative electrode tends to decrease, and the characteristics of the electrochemical device tend to deteriorate. Further, if the HF content is too large, the oxidation resistance of the electrolytic solution tends to decrease due to the influence of HF. Even if the electrolytic solution of the present invention contains HF in the above range, it does not reduce the high-temperature storage recovery capacity rate of the electrochemical device.
The content of HF is more preferably 10 ppm or more, further preferably 20 ppm or more. The HF content is also more preferably 100 ppm or less, further preferably 80 ppm or less, and particularly preferably 50 ppm or less.
The content of HF can be measured by the neutralization titration method.

The electrolytic solution of the present invention may be prepared by any method using the above-mentioned components.

The electrolytic solution of the present invention can be suitably applied to an electrochemical device such as a lithium ion secondary battery, a lithium ion capacitor, a hybrid capacitor, and an electric double layer capacitor. Hereinafter, a non-aqueous electrolyte battery using the electrolyte of the present invention will be described.
The non-aqueous electrolyte battery can adopt a known structure, and typically includes a positive electrode and a positive electrode capable of occluding and releasing ions (for example, lithium ions), and the electrolytic solution of the present invention. An electrochemical device including such an electrolytic solution of the present invention is also one of the present inventions.

Electrochemical devices include lithium ion secondary batteries, lithium ion capacitors, capacitors (hybrid capacitors, electric double layer capacitors), radical batteries, solar cells (particularly dye-sensitized solar cells), lithium ion primary batteries, fuel cells, etc. Examples thereof include various electrochemical sensors, electrochromic elements, electrochemical switching elements, aluminum electrolytic capacitors, and tantalum electrolytic capacitors, and lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors are suitable.
A module including the above electrochemical device is also one of the present inventions.

The present invention is also a lithium ion secondary battery comprising the electrolytic solution of the present invention.
The lithium ion secondary battery preferably includes a positive electrode, a negative electrode, and the above-mentioned electrolytic solution.

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

The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. For example, a lithium-containing transition metal composite oxide, a lithium-containing transition metal phosphoric acid compound, a sulfide, or a conductive material is used. Examples include sex polymers. Among them, as the positive electrode active material, a lithium-containing transition metal composite oxide and a lithium-containing transition metal phosphoric acid compound are preferable, and a lithium-containing transition metal composite oxide that produces a high voltage is particularly preferable.

The transition metal of the lithium-containing transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples thereof include a lithium-cobalt composite oxide such _{as LiCoO 2 or LiNiO 2.} Lithium-nickel composite oxides, LimnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{4, and} other lithium-manganese composite oxides, and some of the transition metal atoms that are the main constituents of these lithium transition metal composite oxides are Na. Substitute with other elements such as K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W And so on. Specific examples of the substituted ones include, for example, LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O. ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiNi _0.45 Co _0.10 Al _0.45 O ₂ , LiMn _{1. 8} Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _{4, and the} like can be mentioned.

Among them, as the lithium-containing transition metal composite oxide, LiMn _1.5 Ni _0.5 O ₄ and LiNi _0.5 Co _0.2 Mn _0.3 O ₂ have high energy densities even when the voltage is high. LiNi _0.6 Co _0.2 Mn _0.2 O ₂ is preferable.

The transition metal of the lithium-containing transition metal phosphoric acid compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples thereof include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). _3. Iron phosphates such as _{LiFeP 2} O _{7 , cobalt phosphates such as LiCoPO 4} , and some of the transition metal atoms that are the main constituents of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn. , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other elements.

Examples of the lithium-containing transition metal composite oxide include, for example.
Formula: Li _a Mn _2-b M ¹ _b O ₄ (in the formula, 0.9 ≦ a; 0 ≦ b ≦ 1.5; M ¹ is Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, Lithium-manganese spinel composite oxide represented by (at least one metal selected from the group consisting of V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge),
Formula: LiNi _1-c M ² _c O ₂ (in the formula, 0 ≦ c ≦ 0.5; M ² is Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Lithium-nickel composite oxide represented by (at least one metal selected from the group consisting of Sr, B, Ga, In, Si and Ge), or
Formula: LiCo _1-d M ³ _d O ₂ (in the formula, 0 ≦ d ≦ 0.5; M ³ is Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Examples thereof include a lithium-cobalt composite oxide represented by (at least one metal selected from the group consisting of Sr, B, Ga, In, Si and Ge).

_{Among them, LiCoO 2} , LiMnO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ from the viewpoint of providing a high-energy density and high-output lithium-ion secondary battery. , Or LiNi _1/3 Co _1/3 Mn _1/3 O ₂ is preferable.

Other positive electrode active materials include LiFePO ₄ , LiNi _0.8 Co _0.2 O ₂ , Li _1.2 Fe _0.4 Mn _0.4 O ₂ , LiNi _0.5 Mn _0.5 O ₂ , and LiV _3. O _{6 and the} like can be mentioned.

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 including Pb, Ag, Cu). Examples thereof include a sulphide compound having a three-dimensional skeletal structure. In addition, elemental sulfur, _{organic lithium sulfide represented by LiS x} , and the like can also be mentioned.

Examples of the conductive polymer include a p-doping type conductive polymer and an n-doping type conductive polymer. Examples of the conductive polymer include polyacetylene-based, polyphenylene-based, heterocyclic polymers, ionic polymers, rudder and network-like polymers.

Further, it is preferable to include lithium phosphate in the positive electrode active material because the continuous charging characteristics are improved. The use of lithium phosphate is not limited, but it is preferable to use a mixture of the above-mentioned positive electrode active material and lithium phosphate. The lower limit of the amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass, based on the total of the positive electrode active material and lithium phosphate. % Or more, and the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less.

Further, a substance having a composition different from that of the positive electrode active material may be used on the surface thereof. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide and other oxides, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate. , Sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, magnesium carbonate, carbon and the like.

These surface adhering substances are, for example, dissolved or suspended in a solvent and impregnated with the positive electrode active material and dried, and after the surface adhering substance precursor is dissolved or suspended in a solvent and impregnated with the positive electrode active material. It can be adhered to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing at the same time, or the like. When carbon is attached, a method of mechanically attaching the carbon substance later in the form of activated carbon or the like can also be used.

The amount of the surface adhering substance is preferably 0.1 ppm or more, more preferably 1 ppm or more, further preferably 10 ppm or more, and the upper limit is preferably 20% or less, more preferably 20% or less, in terms of mass with respect to the positive electrode active material. Is used at 10% or less, more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material and improve the battery life, but if the adhering amount is too small, the effect is not sufficiently exhibited and is often present. If it is too much, the resistance may increase because it blocks the ingress and egress of lithium ions.

Examples of the shape of the particles of the positive electrode active material include a mass, a polyhedron, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, and a columnar shape as conventionally used. Further, the primary particles may be aggregated to form secondary particles.

The tap density of the positive electrode active material is preferably 0.5 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and further preferably 1.0 g / cm ³ or more. When the tap density of the positive electrode active material is less than the above lower limit, the amount of the dispersion medium required for forming the positive electrode active material layer increases, and the required amount of the conductive material and the binder increases, so that the positive electrode to the positive electrode active material layer is formed. The filling rate of the active material is restricted, and the battery capacity may be restricted. By using the composite oxide powder having a high tap density, a high density positive electrode active material layer can be formed. Generally, the larger the tap density is, the more preferable it is, and there is no particular upper limit. However, if it is too large, the diffusion of lithium ions using the electrolytic solution as a medium in the positive electrode active material layer becomes rate-determining, and the load characteristics may be easily deteriorated. The upper limit is preferably 4.0 g / cm ³ or less, more preferably 3.7 g / cm ³ or less, and further preferably 3.5 g / cm ³ or less.
^{In the present invention, the tap density is the powder packing density (tap density) g / cm 3} when 5 to 10 g of positive electrode active material powder is placed in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm. Ask as.

The median diameter d50 of the particles of the positive electrode active material (secondary particle diameter when the primary particles are aggregated to form secondary particles) is preferably 0.3 μm or more, more preferably 0.5 μm or more, still more preferably. Is 0.8 μm or more, most preferably 1.0 μm or more, and preferably 30 μm or less, more preferably 27 μm or less, still more preferably 25 μm or less, and most preferably 22 μm or less. If it falls below the above lower limit, a high tap density product may not be obtained, and if it exceeds the upper limit, it takes time to diffuse lithium in the particles, resulting in deterioration of battery performance or making a positive electrode of the battery, that is, an active material. When a conductive material, a binder, or the like is slurried with a solvent and applied in a thin film form, problems such as streaks may occur. Here, by mixing two or more kinds of the positive electrode active materials having different median diameters d50, the filling property at the time of producing the positive electrode can be further improved.

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

When the primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, still more preferably 0. It is 2 μm or more, and the upper limit is preferably 5 μm or less, more preferably 4 μm or less, still more preferably 3 μm or less, and most preferably 2 μm or less. If it exceeds the above upper limit, it is difficult to form spherical secondary particles, which adversely affects the powder filling property and greatly reduces the specific surface area, so that there is a high possibility that the battery performance such as output characteristics is deteriorated. be. On the contrary, if it is less than the above lower limit, problems such as inferior reversibility of charge / discharge may occur because the crystal is usually underdeveloped.

In the present invention, the primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles, and the average value is taken. Be done.

BET specific surface area of the positive electrode active material is preferably 0.1 m ² / g or more, more preferably 0.2 m ² / g or more, further preferably 0.3 m ² / g or more, and the upper limit is preferably ^{50 m} 2 / It is g or less, more preferably 40 m ² / g or less, ^{still more preferably 30 m 2} / g or less. If the BET specific surface area is smaller than this range, the battery performance tends to deteriorate, and if it is large, the tap density does not easily increase, and a problem may easily occur in the coatability at the time of forming the positive electrode active material layer.

In the present invention, the BET specific surface area is large after pre-drying the sample at 150 ° C. for 30 minutes under nitrogen flow using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.). It is defined by the value measured by the nitrogen adsorption BET 1-point method by the gas flow method using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen with respect to the atmospheric pressure is 0.3.

When the lithium ion secondary battery of the present invention is used as a large lithium ion secondary battery for a hybrid vehicle or a distributed power source, high output is required. Therefore, the particles of the positive electrode active material are mainly secondary particles. Is preferable.
The particles of the positive electrode active material preferably contain 0.5 to 7.0% by volume of fine particles having an average particle size of secondary particles of 40 μm or less and an average primary particle size of 1 μm or less. By containing fine particles having an average primary particle size of 1 μm or less, the contact area with the electrolytic solution is increased, and the diffusion of lithium ions between the electrode and the electrolytic solution can be made faster, and as a result, the battery Output performance can be improved.

As a method for producing a positive electrode active material, a general method is used as a method for producing an inorganic compound. In particular, various methods can be considered for producing spherical or elliptical spherical active materials. For example, the raw material of the transition metal is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring. A method of obtaining an active material by preparing and recovering a spherical precursor, drying the precursor as necessary, _{adding a Li source such as LiOH, Li 2} CO ₃ , or LiNO ₃ and firing at a high temperature can be mentioned. ..

For the production of the positive electrode, the positive electrode active material may be used alone, or two or more kinds having different compositions may be used in any combination or ratio. In this case, a preferable combination is LiCoO ₂ and _{LiMn 2} O ₄ such as _{LiNi 0.33} Co _0.33 Mn _0.33 O _2, or a combination in which a part of this Mn is replaced with another transition metal or the like. Alternatively, a combination with LiCoO ₂ or a part of this Co substituted with another transition metal or the like can be mentioned.

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

The positive electrode mixture preferably further contains a binder, a thickener, and a conductive material.
As the binder, any material can be used as long as it is a material that is safe for the solvent and electrolytic solution used in electrode production, and for example, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, and fragrance. Resin-based polymers such as group polyamide, chitosan, alginic acid, polyacrylic acid, polyimide, cellulose, nitrocellulose; SBR (styrene / butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile / butadiene rubber), ethylene -Rubber polymer such as propylene rubber; styrene / butadiene / styrene block copolymer or hydrogen additive thereof; EPDM (ethylene / propylene / diene ternary copolymer), styrene / ethylene / butadiene / styrene copolymer, Thermoplastic elastomeric polymers such as styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymers, propylene / α-olefins Soft resinous polymers such as copolymers; fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride copolymers, tetrafluoroethylene / ethylene copolymers; alkali metal ions (particularly lithium ions) Examples thereof include polymer compositions having ionic conductivity. These may be used alone or in any combination and ratio of two or more.

The content of the binder is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1.5% by mass or more, as the proportion of the binder in the positive electrode active material layer, and also. It is usually 80% by mass or less, preferably 60% by mass or less, more preferably 40% by mass or less, and most preferably 10% by mass or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained, the mechanical strength of the positive electrode is insufficient, and the battery performance such as cycle characteristics may be deteriorated. On the other hand, if it is too high, it may lead to a decrease in battery capacity and conductivity.

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

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

As the conductive material, a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite (graphite), carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and needle coke. , Carbon nanotubes, fullerene, carbon materials such as amorphous carbon such as VGCF, and the like. It should be noted that one of these may be used alone, or two or more thereof may be used in any combination and ratio. The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and usually 50% by mass or less, preferably 30% by mass in the positive electrode active material layer. It is used so as to contain% or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. On the contrary, if the content is higher than this range, the battery capacity may decrease.

The solvent for forming the slurry is particularly selected 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 required. There is no limitation, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, a mixed medium of alcohol and water, and the like. Examples of the organic solvent include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; and ketones such as acetone, methyl ethyl ketone and cyclohexanone. Classes; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine, N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) , Dimethylformamides, dimethylacetamides and the like; aprotonic polar solvents such as hexamethylphosphalamides and dimethylsulfoxides and the like.

Examples of the material of the current collector for the positive electrode include metals such as aluminum, titanium, tantalum, stainless steel and nickel, or metal materials such as alloys thereof; carbon materials such as carbon cloth and carbon paper. Of these, metal materials, especially aluminum or alloys thereof, are preferable.

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foamed metal, etc. in the case of metal material, and carbon plate, carbon in the case of carbon material. Examples include a thin film and a carbon column. Of these, a metal thin film is preferable. The thin film may be formed in a mesh shape as appropriate. The thickness of the thin film is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thin film is thinner than this range, the strength required as a current collector may be insufficient. On the contrary, if the thin film is thicker than this range, the handleability may be impaired.

It is also preferable that the surface of the current collector is coated with a conductive auxiliary agent from the viewpoint of reducing the electrical contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive auxiliary agent include carbon and precious metals such as gold, platinum, and silver.

The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but the value of (thickness of the positive electrode active material layer on one side immediately before the electrolyte injection) / (thickness of the current collector) is 20. It is preferably less than or equal to, more preferably 15 or less, most preferably 10 or less, and preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. If it exceeds this range, the current collector may generate heat due to Joule heat during high current density charging / discharging. Below this range, the volume ratio of the current collector to the positive electrode active material may increase and the capacity of the battery may decrease.

The positive electrode may be produced by a conventional method. For example, the above-mentioned binder, thickener, conductive material, solvent, etc. are added to the above-mentioned positive electrode active material to form a slurry-like positive electrode mixture, which is applied to a current collector, dried, and then pressed to obtain a high density. There is a method of densifying.

The high density can be achieved by a hand press, a roller press, or the like. The density of the positive electrode active material layer is preferably 1.5 g / cm ³ or more, more preferably 2 g / cm ³ or more, further preferably 2.2 g / cm ³ or more, and preferably 5 g / cm ³ or less. The range is more preferably 4.5 g / cm ³ or less, still more preferably 4 g / cm ³ or less. If it exceeds this range, the permeability of the electrolytic solution to the vicinity of the current collector / active material interface is lowered, and the charge / discharge characteristics particularly at a high current density are lowered, and high output may not be obtained. If it is lower than that, the conductivity between the active materials decreases, the battery resistance increases, and high output may not be obtained.

When the electrolytic solution of the present invention is used, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery outer case from the viewpoint of improving the stability at high output and high temperature. Specifically, the total area of the electrode areas of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more, and more preferably 40 times or more in terms of area ratio. The outer surface area of the battery outer case is the total area calculated from the vertical, horizontal, and thickness dimensions of the case part filled with power generation elements excluding the protruding part of the terminal in the case of a bottomed square shape. say. In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in a structure in which the positive electrode mixture layer is formed on both sides via a current collector foil. , Refers to the sum of the areas calculated separately for each surface.

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 mixture layer obtained by subtracting the metal leaf thickness of the core material is preferable as the lower limit with respect to one side of the current collector. Is 10 μm or more, more preferably 20 μm or more, and preferably 500 μm or less, more preferably 450 μm or less.

Further, a substance having a composition different from that attached to the surface of the positive electrode plate may be used. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide and other oxides, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate. , Sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, magnesium carbonate, carbon and the like.

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

The negative electrode material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbon materials, alloy-based materials, lithium-containing metal composite oxide materials, conductive polymers, and the like. These may be used individually by 1 type, and may be used in combination of 2 or more types arbitrarily.

The negative electrode active material is a carbonaceous material that can occlude and release lithium such as thermal decomposition products of organic substances and artificial graphite and natural graphite under various thermal decomposition conditions; and occludes and releases lithium such as tin oxide and silicon oxide. Possible metal oxide materials; lithium metals; various lithium alloys; lithium-containing metal composite oxide materials and the like can be mentioned. Two or more kinds of these negative electrode active materials may be mixed and used.

As a carbonaceous material capable of storing and releasing lithium, artificial graphite or purified natural graphite produced by high-temperature treatment of easy-to-graphite pitch obtained from various raw materials, or surface treatment of these graphites with pitch or other organic substances. The carbonaceous material and the negative electrode active material layer obtained by subjecting natural graphite, artificial graphite, artificial carbonaceous material, and artificial graphite material to heat treatment at least once in the range of 400 to 3200 ° C. are preferable. A carbonaceous material consisting of at least two or more different crystalline carbonaceous materials and / or having an interface in which the different crystalline carbonaceous materials are in contact, the negative electrode active material layer has at least two or more different orientations. A material selected from a carbonaceous material having an interface in contact with the carbonaceous material is more preferable because it has a good balance between initial irreversible capacitance and high current density charge / discharge characteristics. In addition, one of these carbon materials may be used alone, or two or more of these carbon materials may be used in any combination and ratio.

As the carbonaceous material obtained by heat-treating the above-mentioned artificial carbonaceous substance and artificial graphite substance at least once in the range of 400 to 3200 ° C., coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, and these pitches are oxidized. Treated, needle coke, pitch coke and partially graphitized carbon agents, furnace black, acetylene black, thermal decomposition products of organic substances such as pitch carbon fibers, carbonizable organic substances and carbonized products thereof, or carbonizable Examples thereof include solutions in which various organic substances are dissolved in low molecular weight organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and carbonized products thereof.

As the metal material used as the negative electrode active material (excluding lithium titanium composite oxide), if lithium can be stored and released, lithium alone, a single metal and alloy forming a lithium alloy, or oxidation thereof. It may be any compound such as a substance, a carbide, a nitride, a silicide, a sulfide or a phosphor, and is not particularly limited. The elemental metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements, and more preferably aluminum, silicon and tin (hereinafter, abbreviated as "specific metal element"). ) Is a single metal and 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.

As the negative electrode active material having at least one atom selected from the specific metal element, the metal single compound of any one specific metal element, the alloy consisting of two or more specific metal elements, or one or two or more specific ones are specified. Alloys consisting of metal elements and other one or more metal elements, compounds containing one or more specific metal elements, and oxides, carbides, nitrides, and silicates of the compounds. , Complex compounds such as sulfides or phosphors. By using these metal simple substances, alloys or metal compounds as the negative electrode active material, it is possible to increase the capacity of the battery.

In addition, a compound in which these composite compounds are complicatedly bonded to several kinds of elements such as elemental metals, alloys or non-metal elements can also be mentioned. Specifically, for example, in silicon and tin, an alloy of these elements and a metal that does not act as a negative electrode can be used. For example, in the case of tin, it is possible to use a complex compound containing 5 to 6 kinds of elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not act as a negative electrode, and a non-metal element. can.

Specifically, Si alone, SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₆ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , _{TaSi 2} , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), LiSiO or tin alone, SnSiO ₃ , LiSnO, Mg ₂ Sn, SnO _w (0 <w ≦ 2) can be mentioned.
Further, a composite material containing Si or Sn as the first constituent element and the second and third constituent elements in addition to the first constituent element can be mentioned. The second constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium and zirconium. The third constituent element is, for example, at least one of boron, carbon, aluminum and phosphorus.
In particular, since high battery capacity and excellent battery characteristics can be obtained, as the metal material, silicon or tin alone (may contain a trace amount of impurities), SiO _v (0 <v ≦ 2), SnO _w (0). ≦ w ≦ 2), Si—Co—C composite material, Si—Ni—C composite material, Sn—Co—C composite material, Sn—Ni—C composite material are preferable.

The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can store and release lithium, but a material containing titanium and lithium is preferable from the viewpoint of high current density charge / discharge characteristics. More preferably, a lithium-containing composite metal oxide material containing titanium is preferable, and a composite oxide of lithium and titanium (hereinafter, abbreviated as "lithium titanium composite oxide") is preferable. That is, it is particularly preferable to use a lithium-titanium composite oxide having a spinel structure contained in the negative electrode active material for an electrolytic solution battery because the output resistance is greatly reduced.

The lithium-titanium composite oxide has a general formula:
Li _x Ti _y M _z O ₄
[In the formula, M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb. ]
It is preferably a compound represented by.
Among the above compositions,
(I) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(Ii) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(Iii) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because it has a good balance of battery performance.

Particularly preferred representative compositions of the compounds are Li _4/3 Ti _5/3 O ₄ for (i), Li ₁ Ti ₂ O ₄ for (ii), and Li _4/5 Ti _11/5 O for (iii). It is _4. As for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.

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

Examples of the binder include the same binders that can be used for the positive electrode described above. The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, 15% by mass. It is more preferably mass% or less, further preferably 10 mass% or less, and particularly preferably 8 mass% or less. If the ratio of the binder to the negative electrode active material exceeds the above range, the ratio of the binder whose amount does not contribute to the battery capacity increases, which may lead to a decrease in the battery capacity. Further, if it falls below the above range, the strength of the negative electrode may decrease.

In particular, when a rubbery polymer typified by SBR is contained in the main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more. , 0.6% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, and further preferably 2% by mass or less. When a fluoropolymer represented by polyvinylidene fluoride is contained in the main component, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and further 3% by mass or more. It is preferable, and usually it is 15% by mass or less, preferably 10% by mass or less, and further preferably 8% by mass or less.

Examples of the thickener include the same thickeners that can be used for the positive electrode described above. The ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, further preferably 0.6% by mass or more, and usually 5% by mass or less. It is preferably 3% by mass or less, and more preferably 2% by mass or less. If the ratio of the thickener to the negative electrode active material is less than the above range, the coatability may be significantly reduced. On the other hand, if it exceeds the above range, the ratio of the negative electrode active material to the negative electrode active material layer decreases, which may cause a problem that the capacity of the battery decreases and an increase in resistance between the negative electrode active materials.

Examples of the conductive material of the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black.

The solvent for forming the slurry is particularly selected as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and the conductive material used as needed. There is no limitation, and either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-. Examples thereof include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene and hexane.

Examples of the material of the current collector for the negative electrode include copper, nickel, stainless steel and the like. Of these, copper foil is preferable from the viewpoint of easy processing into a thin film and cost.

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

The negative electrode may be manufactured by a conventional method. For example, there is a method in which the above-mentioned binder, thickener, conductive material, solvent and the like are added to the above-mentioned negative electrode material to form a slurry, which is applied to a current collector, dried and then pressed to increase the density. .. When an alloy material is used, a method of forming a thin film layer (negative electrode active material layer) containing the 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.

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 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 electrolytic solution near the current collector / negative electrode active material interface. High current density charge / discharge characteristics may deteriorate due to a decrease in permeability. On the other hand, 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.

The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited, but the thickness of the mixture layer after subtracting the metal leaf thickness of the core material is usually 15 μm or more, preferably 20 μm or more. , More preferably 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

Further, a substance having a composition different from that attached to the surface of the negative electrode plate may be used. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide and other oxides, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate. , Sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, magnesium carbonate and the like.

<Separator>
The lithium ion secondary battery of the present invention preferably further includes a separator.
The material and shape of the separator are not particularly limited as long as they are stable in the electrolytic solution and have excellent liquid retention properties, and known ones can be used. Among them, resins, glass fibers, inorganic substances, etc., which are formed of a material stable to the 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. 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. One of these materials, such as polypropylene / polyethylene two-layer film and polypropylene / polyethylene / polypropylene three-layer film, may be used alone, or two or more of them may be used in any combination and ratio. Among them, the separator is preferably a porous sheet or a non-woven fabric made of a polyolefin such as polyethylene or polypropylene because it has good permeability of the electrolytic solution and a good shutdown effect.

The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 8 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 electrolytic solution 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 further 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 fabric, 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 independent thin film shape described above, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, alumina particles having a 90% particle size of less than 1 μm may be formed on both sides of the positive electrode by using a fluororesin as a binder to form a porous layer.

<Battery design>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are formed via 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.

The current collecting structure is not particularly limited, but in order to more effectively improve the charge / discharge characteristics of high current density by the electrolytic solution of the present invention, it is necessary to use a structure that reduces the resistance of the wiring portion and the joint portion. preferable. When the internal resistance is reduced in this way, the effect of using the electrolytic solution of the present invention is particularly well exhibited.

When the electrode group has the above-mentioned laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to the terminals is preferably used. When the area of one electrode becomes large, the internal resistance becomes large. Therefore, it is also preferably used to reduce the resistance by providing a plurality of terminals in the electrode. In the case where the electrode group has the above-mentioned wound structure, the internal resistance can be reduced by providing a plurality of lead structures on the positive electrode and the negative electrode and bundling them in the terminals.

The material of the outer case is not particularly limited as long as it is a substance stable to the electrolytic solution used. Specifically, a nickel-plated steel plate, stainless steel, aluminum or aluminum alloy, metals such as magnesium alloy, or a laminated film (laminated film) of resin and aluminum foil is 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 collecting terminal to form a closed structure, the metal and the resin are bonded to each other. Resin is preferably used.

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

A module including the lithium ion secondary battery of the present invention is also one of the present inventions.

Further, the positive electrode, the negative electrode, and the above-mentioned electrolytic solution are provided, the positive electrode includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, and the positive electrode active material is characterized by containing Mn. The lithium ion secondary battery is also one of the preferred embodiments. Since the positive electrode active material layer containing the positive electrode active material containing Mn is provided, the lithium ion secondary battery is more excellent in high temperature storage characteristics.

_{As the positive electrode active material containing Mn, LiMn 1.5} Ni _0.5 O ₄ and LiNi _0.5 Co _0.2 Mn ₀ can be provided because a lithium ion secondary battery having high energy density and high output can be provided. _.3 O ₂ and LiNi _0.6 Co _0.2 Mn _0.2 O ₂ are preferable.

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

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

As the binder, any material can be used as long as it is a material that is safe for the solvent and electrolytic solution used in the manufacture of the electrode. For example, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene can be used. , SBR (styrene / butadiene rubber), isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, polyethylene terephthalate, polymethylmethacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, NBR (Acrylonitrile-butadiene rubber), fluororubber, ethylene-propylene rubber, styrene / butadiene / styrene block copolymer or hydrogen additive thereof, EPDM (ethylene / propylene / diene ternary copolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene / isoprene / styrene block copolymer or hydrogen additive thereof, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer , Fluorinated polyvinylidene fluoride, tetrafluoroethylene / ethylene copolymer, polymer composition having ionic conductivity of alkali metal ions (particularly lithium ions) and the like. 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 content of the binder is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1.5% by mass or more, as the proportion of the binder in the positive electrode active material layer, and also. It is usually 80% by mass or less, preferably 60% by mass or less, more preferably 40% by mass or less, and most preferably 10% by mass or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained, the mechanical strength of the positive electrode is insufficient, and the battery performance such as cycle characteristics may be deteriorated. On the other hand, if it is too high, it may lead to a decrease in battery capacity and conductivity.

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

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

As the conductive material, a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel, graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, and carbon materials such as amorphous carbon such as needle coke. It should be noted that one of these may be used alone, or two or more thereof may be used in any combination and ratio. The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and usually 50% by mass or less, preferably 30% by mass in the positive electrode active material layer. It is used so as to contain% or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. On the contrary, if the content is higher than this range, the battery capacity may decrease.

The positive electrode current collector is preferably made of a valve metal or an alloy thereof because the high temperature storage characteristics are further improved. Examples of the valve metal include aluminum, titanium, tantalum, and chromium. It is more preferable that the positive electrode current collector is made of aluminum or an alloy of aluminum.

Since the high-temperature storage characteristics of the lithium-ion secondary battery are further improved, the portion of the portion electrically connected to the positive electrode current collector that comes into contact with the electrolytic solution is also made of a valve metal or an alloy thereof. It is preferably configured. In particular, the battery outer case and the parts of the lead wires and safety valves housed in the battery outer case that are electrically connected to the positive electrode current collector and that come into contact with the non-aqueous electrolytic solution are made of valve metal or. It is preferably composed of the alloy. Stainless steel coated with a valve metal or an alloy thereof may be used.

The method for producing the positive electrode is as described above. For example, the above-mentioned binder, thickener, conductive material, solvent and the like are added to the above-mentioned positive electrode active material to prepare a slurry-like positive electrode mixture, which is used as described above. Examples thereof include a method in which the electrode is applied to a positive electrode current collector, dried, and then pressed to increase the density.

The configuration of the negative electrode is as described above.

The electric double layer capacitor may include a positive electrode, a negative electrode, and the above-mentioned electrolytic solution.
In the electric double layer capacitor, at least one of the positive electrode and the negative electrode is a polarizable electrode, and the following electrodes described in detail in JP-A-9-7896 can be used as the polarizable electrode and the non-polarizing electrode.

The polarizable electrode mainly composed of activated carbon used in the present invention preferably contains an activated carbon having a large specific surface area and a conductive agent such as carbon black that imparts electron conductivity. The polar electrode can be formed by various methods. For example, a polarized electrode made of activated carbon and carbon black can be formed by mixing activated carbon powder, carbon black, and a phenolic resin, and firing and activating them in an inert gas atmosphere and a steam atmosphere after press molding. Preferably, the polarizing electrode is bonded to the current collector with a conductive adhesive or the like.

Alternatively, activated carbon powder, carbon black and a binder can be kneaded in the presence of alcohol to form a sheet and dried to obtain a polar electrode. For this binder, for example, polytetrafluoroethylene is used. Alternatively, activated carbon powder, carbon black, a binder and a solvent may be mixed to form a slurry, and this slurry may be coated on a metal foil of a current collector and dried to form a polar electrode integrated with the current collector. can.

A polarization electrode mainly composed of activated carbon may be used for both electrodes to form an electric double layer capacitor, but a configuration using a non-polarizing electrode on one side, for example, a positive electrode mainly composed of a battery active material such as a metal oxide and activated carbon. A configuration that combines a negative electrode of a polarized electrode mainly composed of A configuration in combination with a polar positive electrode is also possible.

Further, a carbonaceous material such as carbon black, graphite, expanded graphite, porous carbon, carbon nanotube, carbon nanohorn, or Ketjen black may be used instead of or in combination with activated carbon.

The non-polarizing electrode is preferably mainly composed of a carbon material capable of reversibly occluding and releasing lithium ions, and an electrode having lithium ions occluded in this carbon material is used for the electrode. In this case, a lithium salt is used as the electrolyte. According to the electric double layer capacitor of this configuration, a higher withstand voltage exceeding 4V can be obtained.

The solvent used for preparing the slurry in the preparation of the electrode is preferably one in which a binder is dissolved, and N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, and phthal are used according to the type of the binder. Dimethyl acetate, ethanol, methanol, butanol or water are appropriately selected.

Examples of the activated carbon used for the polarization electrode include phenol resin-based activated carbon, palm-based activated carbon, petroleum coke-based activated carbon, and the like. Of these, petroleum coke-based activated carbon or phenol resin-based activated carbon is preferably used because a large capacity can be obtained. Further, the activated carbon activation treatment method includes a steam activation treatment method, a molten KOH activation treatment method, and the like, and it is preferable to use the activated carbon by the molten KOH activation treatment method in that a larger capacity can be obtained.

Preferred conductive agents used for the polarization electrode include carbon black, Ketjen black, acetylene black, natural graphite, artificial graphite, metal fiber, conductive titanium oxide, and ruthenium oxide. The mixing amount of the conductive agent such as carbon black used for the polarization electrode is 1 to 1 in the total amount with activated carbon because good conductivity (low internal resistance) is obtained and the capacity of the product decreases if it is too large. It is preferably 50% by mass.

As the activated carbon used for the polar electrode, activated carbon having an average particle size of 20 μm or less and a specific surface area of 1500 to 3000 m ² / g is used so that an electric double layer capacitor having a large capacity and low internal resistance can be obtained. Is preferable. Further, as preferable carbon materials for forming an electrode mainly composed of a carbon material capable of reversibly occluding and releasing lithium ions, natural graphite, artificial graphite, graphitized mesocarbon globules, graphitized whiskers, and air layer Examples thereof include a calcined product of grown carbon fiber, a furfuryl alcohol resin, and a calcined product of novolak resin.

The current collector may be chemically or electrochemically corrosion resistant. Stainless steel, aluminum, titanium or tantalum can be preferably used as the current collector of the polar electrode mainly composed of activated carbon. Of these, stainless steel or aluminum is a particularly preferable material in terms of both characteristics and price of the obtained electric double layer capacitor. Stainless steel, copper or nickel is preferably used as the current collector of the electrode mainly composed of a carbon material capable of reversibly occluding and releasing lithium ions.

Further, in order to store lithium ions in advance in a carbon material capable of reversibly storing and releasing lithium ions, (1) powdered lithium is mixed with a carbon material capable of reversibly storing and releasing lithium ions. Method of leaving, (2) A lithium foil is placed on an electrode formed of a carbon material and a binder that can reversibly store and release lithium ions, and this electrode is placed in a state of being in electrical contact with the electrode as a lithium salt. A method of ionizing lithium by immersing it in an electrolytic solution in which lithium ions are dissolved and incorporating lithium ions into a carbon material. (3) Formed by a carbon material and a binder capable of reversibly storing and releasing lithium ions. The electrode is placed on the minus side, the lithium metal is placed on the plus side, and the lithium salt is immersed in a non-aqueous electrolyte solution as an electrolyte, and an electric current is applied to electrochemically incorporate lithium into the carbon material in an ionized state. There is a way.

As the electric double layer capacitor, a wound type electric double layer capacitor, a laminated type electric double layer capacitor, a coin type electric double layer capacitor and the like are generally known, and the above electric double layer capacitor can also be of these types. ..

For example, in a winding type electric double layer capacitor, a positive electrode and a negative electrode composed of a laminate (electrode) of a current collector and an electrode layer are wound via a separator to produce a winding element, and the winding element is made of aluminum. It is assembled by putting it in a case such as the above, filling it with an electrolytic solution, preferably a non-aqueous electrolytic solution, and then sealing it with a rubber sealing body.

As the separator, a conventionally known material and composition can be used. For example, polyethylene porous film, polytetrafluoroethylene, polypropylene fiber, glass fiber, non-woven fabric of cellulose fiber and the like can be mentioned.

Further, by a known method, a laminated electric double layer capacitor in which a sheet-shaped positive electrode and a negative electrode are laminated via an electrolytic solution and a separator, or a coin-shaped positive electrode and a negative electrode are formed into a coin type via an electrolytic solution and a separator by fixing with a gasket. It can also be a configured coin-type electric double layer capacitor.

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

Next, the present invention will be described with reference to examples, but the present invention is not limited to such examples.

Synthesis Example 1: Synthesis of compound (I) 4-dimethoxymethyl-1,3 dioxolane-2-one 3,3-Dimethoxypropene (5.1 g, 50 mmol) and 60 ml of water were mixed, and potassium permanganate was mixed at 0 ° C. The aqueous solution in which the solution was dissolved was added dropwise. The solution was stirred at 95 ° C. for 1 hour and then filtered. Potassium carbonate was added to the filtrate. The liquid was separated and the aqueous phase was extracted with ethyl acetate. It was dried and concentrated to obtain 3,3-dimethoxypropane-1,2-diol. 3,3-dimethoxy-1,2-diol _(0.5g, 3.67mmol), DMF0.05ml, mixed CH ₂ Cl 2 4 ml, after nitrogen substitution, triphosgene at -78 ° C. (0.44 g, 1.47 mmol) CH ₂ Cl ₂ solution 5 ml was added dropwise. After returning to room temperature, the solution was poured into ice water. The organic layer was extracted 3 times with a 10 wt% citric acid aqueous solution. The organic layer was dried and concentrated to obtain 0.17 g of the target product.

Synthesis Example 2: Synthesis of compound (II) 4,4-diethoxymethyl-1,3 dioxolan-2-one 3,3-diethoxypropane-1 instead of 3,3-dimethoxypropane-1,2-diol , 2-diol (3.00 g, 18.3 mmol) was used, and synthesis was carried out in the same manner as in Synthesis Example 1 to obtain the desired product.

Examples and Comparative Examples shown in Table 1 [4.2V class lithium ion secondary battery characteristics]
(Preparation of electrolyte)
A mixed solvent of EC (ethylene carbonate), EMC (ethylmethyl carbonate) and DMC (dimethyl carbonate) (volume ratio: EC / EMC / DMC = 30/30/40) was used as the solvent for the non-aqueous electrolyte solution, and the supporting electrolyte was used. LiPF ₆ was dissolved to a concentration of 1.0 mol / liter. Additives were added to this standard electrolyte as shown in Table 1 to obtain a non-aqueous electrolyte. The content of each additive in each table indicates the ratio to the finally obtained electrolytic solution.

(Manufacturing of aluminum-laminated lithium-ion secondary battery)
[Preparation of positive electrode]
_{90% by mass of Li (Ni 1/3} Mn _1/3 Co _1/3 ) O ₂ (LNMO) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and polyvinylidene fluoride (polyvinylidene fluoride) as a binder. PVdF) 5% by mass was mixed in an N-methylpyrrolidone solvent to form a slurry. The obtained slurry was applied to one side of a 15 μm-thick aluminum foil coated with a conductive auxiliary agent in advance, dried, and rolled by a press machine. The size of the active material layer was 50 mm in width and 50 mm in length. It was cut into a shape having an uncoated portion of 30 mm, a width of 5 mm, and a length of 9 mm to obtain a positive electrode.

[Preparation of negative electrode]
98 parts by mass of carbonaceous material (graphite), 1 part by mass of aqueous dispersion of sodium carboxymethyl cellulose (concentration of sodium carboxymethyl cellulose 1% by mass) and aqueous dispersion of styrene-butadiene rubber (styrene-styrene-) as a thickener and binder. 1 part by mass (concentration of butadiene rubber 50% by mass) was added, and the mixture was mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil having a thickness of 10 μm, dried, and rolled by a press. The size of the active material layer was 52 mm in width, 32 mm in length, and 5 mm in width and 9 mm in length. It was cut out into a shape having a portion and used as a negative electrode.

[Making aluminum laminated cells]
The positive electrode and the negative electrode are opposed to each other through a microporous polyethylene film (separator) having a thickness of 20 μm, and the non-aqueous electrolyte solution obtained above is injected. After permeation, it was sealed, precharged, and aged to prepare a lithium ion secondary battery.

(Measurement of battery characteristics)
[Cycle capacity retention rate]
With the lithium ion secondary battery sandwiched between plates and pressurized, constant current-constant voltage charging up to 4.2V with a current equivalent to 1C at 60 ° C. (hereinafter referred to as CC / CV charging) (hereinafter referred to as CC / CV charging). After (0.1C cut), the battery was discharged to 3V with a constant current of 1C, and this was set as one cycle, and the initial discharge capacity was obtained from the discharge capacity of the third cycle. Here, 1C represents a current value for discharging the reference capacity of the battery in 1 hour, and 0.2C represents, for example, 1/5 of the current value. The cycle was performed again, and the discharge capacity after 150 cycles was measured. The ratio of the discharge capacity after 150 cycles to the initial discharge capacity was determined, and this was taken as the cycle capacity retention rate (%).
(Discharge capacity after 150 cycles) ÷ (Initial discharge capacity) x 100 = Capacity retention rate (%)

[Gas generation amount]
The volume of the produced lithium ion secondary battery and the volume of the lithium ion secondary battery after 150 cycles were measured, and the amount of gas generated (ml) was calculated by the following formula.
Volume after 150 cycles-Initial volume = Gas generation (ml)

[Evaluation of IV resistance]
The lithium ion secondary battery for which the evaluation of the initial discharge capacity was completed was charged at 25 ° C. with a constant current of 1 C so as to have a capacity half of the initial discharge capacity. This was discharged at 25 ° C. at 2.0 C, and the voltage at 10 seconds was measured. The resistance was calculated from the voltage drop during discharge and used as the IV resistance.

The results are shown in Table 1.

ＶＣ：ビニレンカーボネート
ＦＥＣ：フルオロエチレンカーボネート
ＬｉＢＯＢ：リチウムビス（オキサラト）ボレート
ＶＥＣ：ビニルエチレンカーボネート
ＭＡ：無水コハク酸The compounds in Table 1 are shown below.

VC: Vinylene carbonate FEC: Fluoroethylene carbonate LiBOB: Lithium bis (oxalate) borate VEC: Vinyl ethylene carbonate MA: Succinic anhydride

Examples and Comparative Examples shown in Table 2 [Characteristics of 4.9V class lithium ion secondary battery]
[Preparation of electrolyte]
Each component was mixed so as to have the composition shown in Table 2, and LiPF ₆ was added thereto at a concentration of 1.0 mol / liter to obtain a non-aqueous electrolytic solution.

(Preparation of positive electrode)
_{LiNi 0.5} Mn _1.5 O _{4 is} used as the positive electrode active material, acetylene black is used as the conductive material, and N-methyl-2-pyrrolidone dispersion of polyvinylidene fluoride (PVdF) is used as the binder, and these are mixed and slurryed. A shaped positive electrode mixture slurry was prepared. The solid content ratio of the positive electrode active material, the conductive material, and the binder was 92/3/5 (mass ratio). This slurry was applied to one side of a 15 μm aluminum foil, dried, and rolled and pressed with a press. The size of the active material layer was 50 mm in width, 30 mm in length, and 5 mm in width and 9 mm in length. It was cut into a shape having a work part and used as a positive electrode.

(Preparation of negative electrode)
It was prepared in the same manner as in the examples shown in Table 1.

(Manufacturing of aluminum laminated cell)
It was prepared in the same manner as in the examples shown in Table 1.

(Measurement of battery characteristics)
[Cycle capacity retention rate]
With the lithium ion secondary battery sandwiched between plates and pressurized, constant current-constant voltage charging (hereinafter referred to as CC / CV charging) up to 4.9 V with a current corresponding to 1C at 60 ° C. (hereinafter referred to as CC / CV charging) ( After (0.1C cut), the battery was discharged to 3V with a constant current of 1C, and this was set as one cycle, and the initial discharge capacity was obtained from the discharge capacity of the third cycle. The cycle was performed again, and the discharge capacity after 200 cycles was measured. The ratio of the discharge capacity after 200 cycles to the initial discharge capacity was determined, and this was taken as the cycle capacity retention rate (%).
(Discharge capacity after 200 cycles) ÷ (Initial discharge capacity) x 100 = Capacity retention rate (%)

[Gas generation amount]
The volume of the produced lithium ion secondary battery and the volume of the lithium ion secondary battery after 200 cycles were measured, and the amount of gas generated (ml) was calculated by the following formula.
Volume after 200 cycles-Initial volume = Gas generation (ml)

[Evaluation of IV resistance]
The battery for which the evaluation of the initial discharge capacity was completed was charged at 25 ° C. with a constant current of 1 C so as to have a capacity half of the initial discharge capacity. This was discharged at 25 ° C. at 2.0 C, and the voltage at 10 seconds was measured. The resistance was calculated from the voltage drop during discharge and used as the IV resistance.

The results are shown in Table 2.

ＶＣ：ビニレンカーボネート
ＦＥＣ：フルオロエチレンカーボネート
ＶＥＣ：ビニルエチレンカーボネート
ＭＡ：無水コハク酸

The compounds in Table 2 are shown below.

VC: Vinylene carbonate FEC: Fluoroethylene carbonate VEC: Vinyl ethylene carbonate MA: Succinic anhydride

Claims (7)

The following general formula (1):

(In the formula, R ¹⁰¹ and R ¹⁰² are linear or branched alkyl groups having 1 to 3 carbon atoms, which may have the same or different ether bonds. R ¹⁰¹ and R ¹⁰² is an including electrolyte compound (1) represented by each other may be bonded to.), the content of the compound (1) is, with respect to the electrolyte, at 0.001 wt% electrolyte, characterized in that. The electrolytic solution according to claim 1 , wherein in the general formula (1), R ¹⁰¹ and R ¹⁰² are the same or different, and are -CH ₃ or -CH ₂ CH _3. The electrolytic solution according to claim 1 or 2 , further comprising a solvent (excluding compound (1)). The electrolytic solution according to claim 1, 2 or 3 , further comprising an electrolyte salt. An electrochemical device comprising the electrolytic solution according to claim 1, 2, 3 or 4. A lithium ion secondary battery comprising the electrolytic solution according to claim 1, 2, 3 or 4. A module comprising the electrochemical device according to claim 5 or the lithium ion secondary battery according to claim 6.