JP2009163939A - Non-aqueous electrolytic solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolytic solution capable of improving low-temperature characteristics, cycle characteristics, and rate characteristics, with improved safety, and suitable for an electrochemical device such as a lithium ion secondary battery. <P>SOLUTION: The non-aqueous electrolytic solution comprises an electrolytic salt dissolving solvent (I) containing a fluorine-contained solvent (IA), at least one of a compound (II) selected from a group of a specific cyclic siloxane compound (IIA), a specific fluoro-silane compound (IIB), and a specific compound (IIC), and an electrolyte salt (III). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte suitable for use in electrochemical devices such as lithium ion secondary batteries.

  In recent years, with the miniaturization of electronic devices, the demand for higher capacity for secondary batteries has increased, and lithium ion secondary batteries with higher energy density than nickel-cadmium batteries and nickel-hydrogen batteries have attracted attention. ing.

Examples of the electrolyte solution for the lithium ion secondary battery include LiPF ₆ , LiBF ₄ , LiClO ₄ , LICF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ (CF ₂ ) ₃ SO _{3, and the} like. The electrolyte is a cyclic carbonate such as ethylene carbonate or propylene carbonate; a chain carbonate such as dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate; a cyclic ester such as γ-butyrolactone or γ-valerolactone; Chain esters; Cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and tetrahydropyran; Chain ethers such as dimethoxyethane and dimethoxymethane; Non-water such as sulfur-containing organic solvents such as sulfolane and diethylsulfone Nonaqueous electrolyte prepared by dissolving the medium is used.

  In such a lithium ion secondary battery using a non-aqueous electrolyte solution, the reactivity and ion conductivity differ depending on the composition of the non-aqueous electrolyte solution, so that the battery characteristics vary greatly depending on the non-aqueous electrolyte solution. Further, as a characteristic of the battery, there is a problem that the internal resistance becomes high in a low temperature environment, and the discharge capacity is reduced when discharging is performed at a constant discharge rate (hereinafter abbreviated as “rate”). Thus, while lithium ion secondary batteries are used in various electronic devices, as well as automobiles and power tools, there has been a demand for an electrolyte solution that does not degrade performance even in a low temperature environment.

  For example, in Patent Document 1, 2-methyltetrahydrofuran, 1,2-dimethoxyethane, 4-methyl-1,3-dioxolane and the like are mixed in a mixed solvent of ethylene carbonate and diethyl carbonate to improve low-temperature characteristics. Proposed. However, with these methods, it was not possible to obtain sufficient characteristics when batteries were used in severe cold regions such as -20 ° C and -30 ° C.

  Patent Document 2 uses a non-aqueous electrolyte solution containing a cyclic siloxane or a reaction product thereof, and Patent Document 3 uses a non-aqueous electrolyte solution containing a silicon compound having a specific structure. It is described that both the input / output characteristics and the cycle characteristics can be improved. However, although these methods are effective, they have not yet obtained a secondary battery having sufficient characteristics.

  In order to solve these problems, Patent Documents 4 and 5 disclose a method of adding a specific silicon-containing compound to a solvent containing a chain carboxylic acid ester or ethylene carbonate. However, in these methods, the use of a fluorine-containing solvent as a solvent is not considered, and the silicon compound has a low flash point, so that there is a problem that the ignitability increases.

JP-A-3-55770 JP 2004-71458 A JP 2004-87459 A JP 2007-141831 A JP 2007-149656 A

  An object of the present invention is to provide a non-aqueous electrolyte suitable for electrochemical devices such as lithium ion secondary batteries, which can improve low temperature characteristics, cycle characteristics and rate characteristics and improve safety. To do.

（式中、Ｒ¹およびＲ²は同じかまたは異なり、いずれも炭素数１〜１２の有機基；ｎは３〜１０の整数である）
で示される環状シロキサン化合物、
（ＩＩＢ）式（ＩＩＢ）：
ＳｉＦ_xＲ³ _pＲ⁴ _qＲ⁵ _r
（式中、Ｒ³〜Ｒ⁵は同じかまたは異なり、いずれも炭素数１〜１２の有機基；ｘは１〜３の整数；ｐ、ｑおよびｒは同じかまたは異なり、いずれも０〜３の整数；ただし、１≦ｐ＋ｑ＋ｒ≦３である）
で示されるフルオロシラン化合物、および
（ＩＩＣ）式（ＩＩＣ）：

（式中、Ｒ⁶〜Ｒ⁸は同じかまたは異なり、いずれも炭素数１〜１２の有機基；ＡはＨ、Ｃ、Ｎ、Ｏ、Ｆ、Ｓ、ＳｉおよびＰよりなる群から選ばれる少なくとも１種の元素から構成される基である）
で示される化合物
よりなる群から選ばれる少なくとも１種の化合物、ならびに
（ＩＩＩ）電解質塩
を含有する非水系電解液に関する。 The present invention
(I) (IA) Solvent for dissolving electrolyte salt containing fluorine-containing solvent,
(II) (IIA) Formula (IIA):

(Wherein, R ¹ and R ² are the same or different and both are organic groups having 1 to 12 carbon atoms; n is an integer of 3 to 10)
A cyclic siloxane compound represented by:
(IIB) Formula (IIB):
SiF _x R ³ _p R ⁴ _q R ⁵ _r
(Wherein R ^{3 to} R ⁵ are the same or different and all are organic groups having 1 to 12 carbon atoms; x is an integer of 1 to 3; p, q and r are the same or different, and all are 0 to 3) An integer of 1; however, 1 ≦ p + q + r ≦ 3)
And (IIC) Formula (IIC):

(Wherein R ^{6 to} R ⁸ are the same or different and all are organic groups having 1 to 12 carbon atoms; A is at least selected from the group consisting of H, C, N, O, F, S, Si and P) It is a group composed of one kind of element)
And (III) a nonaqueous electrolytic solution containing an electrolyte salt.

The fluorine-containing solvent (IA) is
(IA1) fluorinated ether,
It is preferably at least one selected from the group consisting of (IA2) fluorine-containing ester and (IA3) fluorine-containing carbonate.

The fluorine-containing solvent (IA) is
(IA1a) fluorine-containing chain ether,
(IA2a) fluorine-containing chain ester,
(IA2b) fluorine-containing cyclic ester,
It is preferably at least one selected from the group consisting of (IA3a) fluorine-containing chain carbonate and (IA3b) fluorine-containing cyclic carbonate.

The electrolyte salt (III) is
(III-1) It is preferably at least one electrolyte salt selected from the group consisting of LiPF ₆ and LiBF ₄ .

The electrolyte salt (III) is
(III-2a) It is preferable to include at least one electrolyte salt selected from the group consisting of LiN (SO ₂ CF ₃ ) ₂ and LiN (SO ₂ C ₂ F ₅ ) ₂ .

The electrolyte salt (III-2a) is preferably LiN (SO ₂ CF ₃ ) ₂ .

The electrolyte salt (III) is
further,
(III-2b) It is preferable to include at least one electrolyte salt selected from the group consisting of LiPF ₆ and LiBF ₄ .

  The non-aqueous electrolyte solution is preferably for a lithium ion secondary battery.

  Moreover, this invention relates to an electrochemical device provided with the said non-aqueous electrolyte solution.

  Furthermore, this invention relates to a lithium ion secondary battery provided with the said non-aqueous electrolyte solution.

  The lithium ion secondary battery preferably further includes a positive electrode, a negative electrode, and a separator.

  In the lithium ion secondary battery, the positive electrode active material used for the positive electrode is selected from the group consisting of cobalt complex oxide, nickel complex oxide, manganese complex oxide, iron complex oxide, and vanadium complex oxide. It is preferably at least one selected.

  The negative electrode active material used for the negative electrode is preferably a carbon material.

  According to the present invention, by containing a fluorine-containing solvent, a specific compound and an electrolyte salt, it is possible to improve low temperature characteristics, cycle characteristics and rate characteristics and improve safety, such as a lithium ion secondary battery. A non-aqueous electrolyte suitable for an electrochemical device can be provided.

  The nonaqueous electrolytic solution of the present invention contains a solvent (I) for dissolving an electrolyte salt, a specific compound (II) and an electrolyte salt (III).

  The solvent (I) for dissolving the electrolyte salt contains the fluorine-containing solvent (A) from the viewpoint of improving safety, low temperature characteristics, cycle characteristics, and oxidation resistance.

  The fluorine-containing solvent (IA) may be a conventionally known one, but is selected from the group consisting of a fluorine-containing ether (IA1), a fluorine-containing ester (IA2) and a fluorine-containing carbonate (IA3) from the viewpoint of excellent battery characteristics. It is preferable that it is at least one kind.

  Examples of the fluorinated ether (IA1) include a fluorinated chain ether (IA1a). For example, JP-A-8-37024, JP-A-9-97627, JP-A-11-26015, JP2000-2000A. Examples thereof include compounds described in JP-A No. -294281, JP-A No. 2001-52737, JP-A No. 11-307123, and the like.

Among them, the formula (IA1a):
Rf ¹ ORf ²
(In the formula, Rf ¹ is a fluorine-containing alkyl group having 3 to 6 carbon atoms; Rf ² is a fluorine-containing alkyl group having 2 to 6 carbon atoms)
Is preferable from the viewpoint of good compatibility with other solvents and an appropriate boiling point.

Particularly Rf ^1, _{e.g., HCF 2 CF 2 CH 2 -} , HCF 2 CF 2 CF 2 CH 2 -, HCF 2 CF 2 CF 2 CF 2 CH 2 -, C 2 F 5 CH 2 -, CF 3 CFHCF 2 _{CH 2 -, HCF 2 CF (} CF 3) CH 2 -, C 2 F 5 CH 2 CH 2 -, CF 3 CH 2 CH 2 - can be exemplified fluorine-containing alkyl group having 3 to 6 carbon atoms such as, also, Examples of Rf ² include —CF ₂ CF ₂ H, —CF ₂ CFHCF ₃ , —CF ₂ CF ₂ CF ₂ H, —CH ₂ CH ₂ CF ₃ , —CH ₂ CFHCF ₃ , —CH ₂ CH ₂ C _2. fluorine-containing alkyl group having 2 to 6 carbon atoms, such as F ₅ can be exemplified. Among them, Rf ¹ is a fluorine-containing alkyl group having 3 to 4 carbon atoms, and particularly preferably from ionic conductivity viewpoint of satisfactory Rf ² is a fluorine-containing alkyl group having 2 to 3 carbon atoms.

Specific examples of the fluorine-containing ether (IA1a) include, for example, HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H, C ₂ F ₅ CH ₂ OCF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , C _{One or more of 2} F ₅ CH ₂ OCF ₂ CFHCF ₃ , HCF ₂ CF ₂ CH ₂ OCH ₂ CFHCF ₃ , C ₂ F ₅ CH ₂ OCH ₂ CFHCF _{3 and the} like can be exemplified, and among them, HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H, C ₂ F ₅ CH ₂ OCF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , C ₂ F ₅ CH ₂ OCF ₂ CFHCF ₃ are compatible with other solvents. It is particularly preferable from the viewpoint of good and rate characteristics.

  Examples of the fluorinated ester (IA2) include a fluorinated chain ester (IA2a) and a fluorinated cyclic ester (IA2b).

As the fluorine-containing chain ester (IA2a), the formula (IA2a):
Rf ³ COORf ⁴
(In the formula, Rf ³ is an alkyl group which may contain a fluorine atom having 1 to 2 carbon atoms; Rf ⁴ is an alkyl group which may contain a fluorine atom having 1 to ⁴ carbon atoms; provided that Rf ³ and Rf (At least one of ⁴ is a fluorine-containing alkyl group)
Is preferable from the viewpoint of high flame retardancy and good compatibility with other solvents.

The Rf ^3, _{e.g., HCF 2 -, CF 3 -} , C 2 F 5 -, HCF 2 CF 2 -, HCF 2 -, CH 3 CF 2 -, CF 3 CH 2 -, CH 3 -, C 2 H _5- and the like can be exemplified, and among them, CF _3- , HCF _2- , and CF ₃ -are particularly preferable from the viewpoint of good rate characteristics.

Examples of Rf ⁴ include —CF ₃ , —C ₂ F ₅ , —CH ₂ CF ₃ , —CH ₂ CH ₂ CF ₃ , —CH (CF ₃ ) ₂ , —CH ₂ CF ₂ CFHCF ₃ , —CH _{2. C 2 F 5, -CH 2 CF} 2 CF 2 H, -CH 2 CH 2 C 2 F 5, or fluorine-containing alkyl groups such as _{-CH 2 C 3 F 7, -CH} 3, -C 2 H 5, - Non-fluorinated alkyl groups such as C ₃ H ₇ and —CH (CH ₃ ) CH ₃ can be exemplified, among which —CH ₂ CF ₃ , —CH ₂ C ₂ F ₅ , —CH (CF ₃ ) ₂ , —CH ₂ CF ₂ CF ₂ H, —CH ₃ , and —C ₂ H ₅ are particularly preferred from the viewpoint of good compatibility with other solvents.

As specific examples of the fluorine-containing chain ester (IA2a),
1. Those in which both Rf ³ and Rf ⁴ are fluorine-containing alkyl groups:
_{CF 3 COOCH 2 CF 3, CF} 3 COOCH 2 C 2 F 5, CF 3 COOCH 2 CF 2 CF 2 H, HCF 2 COOCH 2 CF 3, HCF 2 COOCH 2 C 2 F 5, HCF 2 COOCF 2 CF 2 H
2. Rf ³ is a fluorine-containing alkyl group and Rf ⁴ is a non-fluorinated alkyl group:
CF ₃ COOCH ₃ , CF ₃ COOC ₂ H ₅ , HCF ₂ COOCH ₃ , HCF ₂ COOC ₂ H ₅ , CH ₃ CF ₂ COOCH ₃ , CH ₃ CF ₂ COOC ₂ H ₅ , C ₂ F ₅ COOCH ₃ , C ₂ F ₅ COOC ₂ H ₅
3. Rf ³ is a non-fluorinated alkyl group and Rf ⁴ is a fluorine-containing alkyl group:
_{CH 3 COOCH 2 CF 3, CH} 3 COOCH 2 C 2 F 5, CH 3 COOCH 2 CF 2 CF 2 H, C 2 H 5 COOCH 2 CF 3, C 2 H 5 COOCH 2 C 2 F 5, C 2 H 5 COOCH ₂ CF ₂ CF ₂ H
1 type or 2 types or more can be illustrated, and among these, 2. 2. Rf ³ is a fluorinated alkyl group, Rf ⁴ is a non-fluorinated alkyl group, and Rf ³ is preferably a non-fluorinated alkyl group, and Rf ⁴ is preferably a fluorine-containing alkyl group. Among them, CF ₃ COOCH ₃ , CF ₃ COOC ₂ H ₅ , HCF ₂ COOCH ₃ , HCF ₂ COOC ₂ H ₅ , CH ₃ COOCH ₂ CF ₃ and CH ₃ COOCH ₂ C ₂ F ₅ are particularly preferred from the viewpoints of compatibility with other solvents and good rate characteristics.

  By containing the fluorine-containing cyclic ester (IA2b), the effect of improving the rate characteristics by improving the dielectric constant and improving the oxidation resistance by improving the oxidation potential can be obtained.

（式中、Ｘ¹〜Ｘ⁶は同じかまたは異なり、いずれも水素原子、フッ素原子、塩素原子、−ＣＨ₃または含フッ素アルキル基；ただし、Ｘ¹〜Ｘ⁶の少なくとも１つは含フッ素メチル基である）
で示される含フッ素ラクトン（ＩＡ２ｂ１）があげられる。 As fluorine-containing cyclic ester (IA2b), for example, formula (IA2b1):

(In the formula, X ^{1 to} X ⁶ are the same or different and all are hydrogen atom, fluorine atom, chlorine atom, —CH ₃ or fluorine-containing alkyl group; provided that at least one of X ^{1 to} X ⁶ is fluorine-containing methyl Base)
And a fluorine-containing lactone (IA2b1) represented by

Examples of the fluorine-containing alkyl group in X ^{1 to} X ⁶ include —CH ₂ F, —CHF ₂ , —CF ₃ , —CH ₂ CF ₃ , —C ₂ F ₅ , —CH ₂ C ₂ F ₅ , —CF ( CF ₃ ) _{2 and the} like, and —CF ₃ and —CH ₂ CF ₃ are preferable from the viewpoint of good voltage resistance.

In the fluorine-containing alkyl group, all of X ^{1 to} X ⁶ may be substituted, or only one may be substituted. Especially, it is preferable from the point with the favorable solubility of electrolyte salt to substitute 1-3, especially 1-2.

The substitution position of the fluorine-containing alkyl group is not particularly limited, X ³ and / or X ⁴ are, in particular, X ³ or X ⁴ is a fluorine-containing methyl group, it is inter alia -CF _3, a good synthesis yield This is preferable. X ^{1 to} X ⁶ other than the fluorine-containing alkyl group are a hydrogen atom, a fluorine atom, a chlorine atom or —CH ₃ , and a hydrogen atom is particularly preferable from the viewpoint of good solubility of the electrolyte salt.

（式中、ＡおよびＢはいずれか一方がＣＸ¹²Ｘ¹³（Ｘ¹²およびＸ¹³は同じかまたは異なり、いずれも水素原子、フッ素原子、塩素原子、−ＣＦ₃、−ＣＨ₃または水素原子がハロゲン原子で置換されていてもよくヘテロ原子を鎖中に含んでいてもよいアルキル基である）であり、他方は酸素原子；Ｒｆ⁵は含フッ素エーテル基、含フッ素アルコキシ基または炭素数２以上の含フッ素アルキル基；Ｘ⁷およびＸ⁸は同じかまたは異なり、いずれも水素原子、フッ素原子、塩素原子、−ＣＦ₃または−ＣＨ₃；Ｘ⁹〜Ｘ¹¹は同じかまたは異なり、いずれも水素原子、フッ素原子、塩素原子または水素原子がハロゲン原子で置換されていてもよくヘテロ原子を鎖中に含んでいてもよいアルキル基；ｍは０または１である）
で示される含フッ素ラクトン（ＩＡ２ｂ２）などもあげられる。 As the fluorine-containing lactone (IA2b1), in addition to those represented by the formula (IA2b1), for example, the formula (IA2b2):

(In the formula, either one of A and B is CX ¹² X ¹³ (X ¹² and X ¹³ are the same or different, and each is a hydrogen atom, a fluorine atom, a chlorine atom, —CF ₃ , —CH ₃ or a hydrogen atom) And the other is an oxygen atom; Rf ⁵ is a fluorine-containing ether group, a fluorine-containing alkoxy group, or a carbon number of 2 or more. X ⁷ and X ⁸ are the same or different, all are hydrogen atoms, fluorine atoms, chlorine atoms, —CF ₃ or —CH ₃ ; X ^{9 to} X ¹¹ are the same or different and both are hydrogen An atom, a fluorine atom, a chlorine atom or a hydrogen atom, which may be substituted with a halogen atom and may contain a hetero atom in the chain; m is 0 or 1)
And a fluorine-containing lactone (IA2b2) represented by

（式中、Ａ、Ｂ、Ｒｆ⁵、Ｘ⁷、Ｘ⁸およびＸ⁹は式（Ａ２ｂ２）と同じである）
で示される５員環構造を有する含フッ素ラクトン（ＩＡ２ｂ２ａ）が、合成が容易である点、化学的安定性が良好な点から好ましい。 As the fluorine-containing lactone (IA2b2) represented by the formula (IA2b2), the formula (IA2b2a):

(Wherein A, B, Rf ⁵ , X ⁷ , X ⁸ and X ⁹ are the same as those in formula (A2b2))
The fluorine-containing lactone (IA2b2a) having a five-membered ring structure represented by is preferable from the viewpoint of easy synthesis and good chemical stability.

（式中、Ｒｆ⁵、Ｘ⁷、Ｘ⁸、Ｘ⁹、Ｘ¹²およびＸ¹³は式（Ａ２ｂ２ａ）と同じ）
で示される含フッ素ラクトン（ＩＡ２ｂ２ａ−１）と、式（ＩＡ２ｂ２ａ−２）：

（式中、Ｒｆ⁵、Ｘ⁷、Ｘ⁸、Ｘ⁹、Ｘ¹²およびＸ¹³は式（ＩＡ２ｂ２ａ）と同じ）
で示される含フッ素ラクトン（ＩＡ２ｂ２ａ−２）がある。 The fluorine-containing lactone (IA2b2a) represented by the formula (IA2b2a) has a formula (IA2b2a-1):

(Wherein Rf ⁵ , X ⁷ , X ⁸ , X ⁹ , X ¹² and X ¹³ are the same as those in formula (A2b2a))
And a fluorine-containing lactone (IA2b2a-1) represented by formula (IA2b2a-2):

(Wherein Rf ⁵ , X ⁷ , X ⁸ , X ⁹ , X ¹² and X ¹³ are the same as those in formula (IA2b2a))
There exists fluorine-containing lactone (IA2b2a-2) shown by these.

が好ましい。 Among these, the point that the excellent characteristics such as high dielectric constant and high withstand voltage can be exhibited especially, and the characteristics as the 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

Is preferred.

なども使用できる。 In addition, as the fluorine-containing cyclic ester (IA2b),

Etc. can also be used.

As the fluorine-containing chain carbonate (IA3a), for example, the formula (A3a):
Rf ⁶ OCOORf ⁷
(Wherein Rf ⁶ is a fluorine-containing alkyl group having 1 to 4 carbon atoms; Rf ⁷ is an alkyl group optionally containing a fluorine atom having 1 to 4 carbon atoms)
Is preferable from the viewpoints of high flame retardancy and good rate characteristics.

Examples of Rf ⁶ include CF ₃ −, C ₂ F ₅ —, (CF ₃ ) ₂ CH—, CF ₃ CH ₂ —, C ₂ F ₅ CH ₂ —, HCF ₂ CF ₂ CH ₂ —, CF ₃ CFHCF. ₂ CH ₂ — and the like can be exemplified, and as Rf ⁷ , for example, —CF ₃ , —C ₂ F ₅ , —CH (CF ₃ ) ₂ , —CH ₂ CF ₃ , —CH ₂ C ₂ F ₅ , —CH Fluorine-containing alkyl groups such as ₂ CF ₂ CF ₂ H and —CH ₂ CF ₂ CFHCF _3, and non-fluorinated alkyl groups such as —CH ₃ , —C ₂ H ₅ , —C ₃ H ₇ , and —CH (CH ₃ ) ₂ Examples are groups. Among them, as Rf ⁶ , CF ₃ —, CF ₃ CH ₂ —, C ₂ F ₅ CH ₂ — is used, and as Rf ⁷ , —CF ₃ , —CH ₂ CF ₃ , —CH ₂ C ₂ F ₅ , — CH ₃ and —C ₂ H ₅ are particularly preferable from the viewpoints of suitable viscosity, good compatibility with other solvents, and good rate characteristics.

Specific examples of the fluorine-containing chain carbonate (IA3a) include, for example, CF ₃ OCOOCF ₃ , CF ₃ CH ₂ OCOOCH ₂ CF ₃ , C ₂ F ₅ CH ₂ OCOOCH ₂ C ₂ F ₅ , C ₂ F ₅ CH ₂ OCOOCH ₃ , one or more fluorine-containing chain carbonates such as CF ₃ CH ₂ OCOOCH ₃ , CF ₃ CH ₂ OCOOCH ₃ , CF ₃ CH ₂ OCOOC ₂ H _5, etc., among which CF ₃ OCOOCF ₃ , CF ₃ CH ₂ OCOOCH ₂ CF ₃ , C ₂ F ₅ CH ₂ OCOOCH ₂ C ₂ F ₅ , CF ₃ CH ₂ OCOOCH ₃ , CF ₃ CH ₂ OCOOC ₂ H ₅ are suitable for viscosity, flame retardant, other solvents It is particularly preferred from the viewpoint of good compatibility with the above and rate characteristics. Further, for example, compounds described in JP-A-6-21992, JP-A-2000-327634, JP-A-2001-256983 and the like can also be exemplified.

  By containing the fluorinated cyclic carbonate (IA3b), an effect of increasing the dielectric constant and an effect of improving the oxidation resistance can be obtained.

（式中、Ｘ¹⁴〜Ｘ¹⁷は同じかまたは異なり、いずれも−Ｈ、−Ｆ、−ＣＦ₃、−ＣＨＦ₂、−ＣＨ₂Ｆ、−Ｃ₂Ｆ_5、−ＣＨ₂ＣＦ₃または−ＣＨ₂ＯＣＨ₂Ｃ₂Ｆ₅；ただし、Ｘ¹⁴〜Ｘ¹⁷の少なくとも１つは−Ｆ、−ＣＦ₃、−Ｃ₂Ｆ_5、−ＣＨ₂ＣＦ₃または−ＣＨ₂ＯＣＨ₂Ｃ₂Ｆ₅である）
で示されるものである。 The fluorine-containing cyclic carbonate (IA3b) has the formula (IA3b):

(In the formula, X ^{14 to} X ¹⁷ are the same or different and all are —H, —F, —CF ₃ , —CHF ₂ , —CH ₂ F, —C ₂ F _5, —CH ₂ CF ₃ or —CH. ₂ OCH ₂ C ₂ F ₅ ; provided that at least one of X ^{14 to} X ¹⁷ is —F, —CF ₃ , —C ₂ F _5, —CH ₂ CF _3, or —CH ₂ OCH ₂ C ₂ F ₅ . )
It is shown by.

X ¹⁴ to X ¹⁷ _{are, -H, -F, -CF 3,} -CHF 2, -CH 2 F, -C 2 F 5, a -CH ₂ CF ₃ or _{-CH 2 OCH 2 C 2 F 5} , -F, -CF ₃ , and -CH ₂ CF ₃ are preferred from the viewpoint of good dielectric constant and viscosity and excellent compatibility with other solvents.

In formula _{(IA3b), -F, -CF 3} , -C 2 F 5, -CH 2 CF 3 or -CH ₂ OCH ₂ C ₂ F ₅ may be substituted on all of the X ¹⁴ to X ¹⁷ And it may be substituted at only one place. Among these, from the point that the dielectric constant and oxidation resistance are good, the number of substitution sites is preferably 1 to 2.

  Among the fluorine-containing cyclic carbonates (IA3b), the lithium ion 2 in the present invention is particularly advantageous in that it has excellent characteristics such as a high dielectric constant and a high withstand voltage, as well as good solubility of the electrolyte salt and reduction of internal resistance. From the viewpoint of improving the characteristics as a secondary battery, the following are preferable.

などがあげられる。 As the fluorine-containing cyclic carbonate (IA3b) having a high withstand voltage and good solubility of the electrolyte salt, for example,

Etc.

なども使用できる。 In addition, as the fluorine-containing cyclic carbonate (IA3b),

Etc. can also be used.

  Among the above fluorinated solvents (IA), the fluorinated chain ether (IA1a) and the fluorinated chain ester (IA2a) are improved in that oxidation resistance, reduction resistance, low temperature characteristics, safety and rate characteristics are improved. ), Fluorine-containing cyclic carbonate (IA3b) is preferable, and fluorine-containing chain ether (IA1a) is preferable.

  When the fluorine-containing chain ether (IA1a) is used as the fluorine-containing solvent (IA), the fluorine-containing chain ether (IA1a) is contained in an amount of 20 to 80% by volume based on the whole electrolyte salt dissolving solvent (I). It is preferable. When the amount of the fluorinated chain ether (IA1a) decreases, the safety tends to deteriorate, and when it increases, the rate characteristics tend to deteriorate. In view of a good balance between safety and rate characteristics, it is preferably contained in an amount of 20 to 60% by volume, particularly 20 to 50% by volume.

  Moreover, when using a fluorine-containing cyclic carbonate (IA3b) as a fluorine-containing solvent (IA), 5-50 volume% of fluorine-containing cyclic carbonate (IA3b) is contained with respect to the whole solvent (I) for electrolyte salt melt | dissolution. It is preferable. When the amount of the fluorinated cyclic carbonate (IA3b) decreases, the cycle characteristics tend to deteriorate, and when it increases, the viscosity increases and the rate characteristics tend to deteriorate. From the viewpoint of a good balance between the cycle characteristics and the rate characteristics, 5 to 40% by volume, particularly 5 to 30% by volume is further preferable.

  Further, when the fluorine-containing chain ester (IA2a) is used as the fluorine-containing solvent (IA), the fluorine-containing chain ester (IA2a) is 1 to 20% by volume with respect to the whole electrolyte salt dissolving solvent (I). It is preferably included. When the amount of the fluorine-containing chain ester (IA2a) decreases, the coating of the fluorine-containing carbonate Li salt on the negative electrode becomes thin and the safety tends to deteriorate. When the amount increases, the coating becomes too thick, and cycle characteristics and rate characteristics Tend to get worse. In view of a good balance between safety, rate characteristics, and cycle characteristics, it is preferably contained in an amount of 1 to 10% by volume, particularly 1 to 5% by volume.

  In addition, as the fluorine-containing solvent (IA), at least one fluorine-containing solvent selected from the group consisting of monofluorobenzene, hexafluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, and pentafluorobenzene, Fluorine-containing sulfolane derivatives and the like can also be used, and these can be contained within a range not impairing the effects of the present invention.

  In addition to the fluorine-containing solvent (IA), the electrolyte salt dissolving solvent (I) can also contain a non-fluorinated solvent (IB).

  Examples of the non-fluorine solvent (IB) include non-fluorine ethers (IB1) such as non-fluorine chain ethers (IB1a), non-fluorine chain esters (IB2a), and non-fluorine cyclic esters (IB2b). Non-fluorinated carbonates (IB3) such as non-fluorinated esters (IB2), non-fluorinated chain carbonates (IB3a), and non-fluorinated cyclic carbonates (IB3b).

As the non-fluorine chain ether (IB1a), the formula (IB1a1):
R ⁹ OR ¹⁰
Or formula (IB1a2):
R ⁹ —O—R ¹⁰ —O—R ¹¹
(Wherein R ⁹ , R ¹⁰ and R ¹¹ are the same or different and all are alkyl groups having 3 to 6 carbon atoms)
Is preferable from the viewpoint of low viscosity and good oxidation resistance.

  Specific examples include, for example, dipropyl ether, dibutyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, etc. Among them, 1,2-dimethoxyethane, 1,2-diethoxyethane are preferable. From the viewpoint of good cycle characteristics.

  Use of the non-fluorine chain ester (IB2a) has an advantage that the low temperature characteristics can be improved.

As the non-fluorine chain ester (IB2a), the formula (IB2a):
R ¹² COOR ¹³
(Wherein R ¹² and R ¹³ are the same or different, R ¹² is an alkyl group having 1 to 2 carbon atoms; R ¹³ is an alkyl group having 1 to 4 carbon atoms)
Is preferable from the viewpoint of low viscosity, high dielectric constant, and low surface tension.

  Preferable specific examples of the non-fluorine chain ester (IB2a) include, for example, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate and the like. Among them, methyl acetate, ethyl acetate Methyl propionate is preferable because it has low viscosity, low surface tension, and improves cycle characteristics. However, there is a difficulty that oxidation resistance is low.

  When the non-fluorinated cyclic ester (IB2b) is used, effects such as improvement in solubility of the electrolyte salt (III), improvement in oxidation resistance, ion dissociation, and rate characteristics can be obtained.

  Examples of the non-fluorine-based cyclic ester (IB2b) include γ-butyrolactone, γ-valerolactone, β-butyrolactone, β-propiolactone, δ-valerolactone, ε-caprolactone, and the like. Butyrolactone and γ-valerolactone are preferred because of their good ion dissociation and dielectric constant.

  Use of non-fluorinated chain carbonate (IB3a) has an advantage that the low-temperature characteristics can be improved.

As the non-fluorine chain carbonate (IB3a), the formula (IB3a):
R ¹⁴ OCOOR ¹⁵
(Wherein, R ¹⁴ and R ¹⁵ are the same or different and both are alkyl groups having 1 to 4 carbon atoms)
Is preferable from the viewpoint of low viscosity and good compatibility with other solvents.

  Specific examples of the non-fluorine chain carbonate (IB3a) include, for example, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, etc. Among them, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and the like. The compatibility with the solvent and the rate characteristic are preferable from the viewpoint of good.

  When non-fluorine-based cyclic carbonate (IB3b) is used, effects such as improved solubility of the electrolyte salt (III) and improved ion dissociation can be obtained.

  As the non-fluorine-based cyclic carbonate (IB3b), at least one selected from the group consisting of ethylene carbonate and propylene carbonate is preferable from the viewpoint of good ion dissociation, low viscosity, and dielectric constant.

  In addition, as non-fluorinated solvents (IB), cyclohexylbenzene, biphenyl, etc. can be used when safety improvement, especially overcharge safety improvement is required, and vinylene carbonate has improved cycle characteristics. Can be used if necessary.

  Among the above non-fluorinated solvents (IB), non-fluorinated chain carbonates (IB3a), non-fluorine-based carbonates (IB3a), non-fluorinated solvents (IB3a), Fluorine-based cyclic carbonate (IB3b) is preferable, and a combination of non-fluorine-based chain carbonate (IB3a) and non-fluorine-based cyclic carbonate (IB3b) is preferable.

  These non-fluorinated solvents (IB) can be contained within the scope of the present invention, and specifically, the non-fluorinated chain carbonate (IB3a) in the electrolyte salt dissolving solvent (I). It is preferable that 10-40 volume% and 10-40 volume% of non-fluorine-type cyclic carbonate (IB3b) are included.

  By using the specific compound (II) in combination with the fluorinated solvent (IA), the surface tension can be lowered to lower the interface resistance, and the low temperature characteristics, cycle characteristics, rate characteristics and safety can be improved.

  The specific compound (II) is at least one compound selected from the group consisting of a specific cyclic siloxane compound (IIA), a specific fluorosilane compound (IIB), and a specific compound (IIC).

（式中、Ｒ¹およびＲ²は同じかまたは異なり、いずれも炭素数１〜１２の有機基；ｎは３〜１０の整数である）
で示されるものである。 The cyclic siloxane compound (IIA) has the formula (IIA):

(Wherein, R ¹ and R ² are the same or different and both are organic groups having 1 to 12 carbon atoms; n is an integer of 3 to 10)
It is shown by.

In formula (IIA), R ¹ and R ² are the same or different, and each is an organic group having 1 to 12 carbon atoms, and examples of R ¹ and R ² include a methyl group, an ethyl group, an n-propyl group, Chain alkyl groups such as isopropyl group, butyl group, isobutyl group, sec-butyl group and t-butyl group; cyclic alkyl groups such as cyclohexyl group and norbornanyl group; vinyl group, 1-propenyl group, allyl group, butenyl group, Alkenyl groups such as 1,3-butadienyl group; alkynyl groups such as ethynyl group, propynyl group and butynyl group; halogenated alkyl groups such as trifluoromethyl group; alkyls having a saturated heterocyclic group such as 3-pyrrolidinopropyl group Group; aryl group such as phenyl group optionally having alkyl substituent; aralkyl such as phenylmethyl group and phenylethyl group ; Trialkylsilyl group such as trimethylsilyl group; and trialkylsiloxy groups such as trimethylsiloxy groups.

Among them, those having a smaller number of carbon atoms are more likely to exhibit characteristics, and organic groups having 1 to 6 carbon atoms are preferable. Also, the alkenyl group acts on the electrolyte solution and the electrode surface coating to improve input / output characteristics, and the aryl group is preferable because it captures radicals generated in the battery during charge / discharge and improves the overall battery performance. . Therefore, R ¹ and R ² are particularly preferably a methyl group, a vinyl group or a phenyl group.

  In the formula (IIA), n is an integer of 3 to 10, preferably an integer of 3 to 6, and particularly preferably 3 or 4.

  Specific examples of the cyclic siloxane compound (IIA) include, for example, hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, hexaphenylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotri Examples include cyclotrisiloxane such as siloxane, cyclotetrasiloxane such as octamethylcyclotetrasiloxane, cyclopentasiloxane such as decamethylcyclopentasiloxane, and the like. Of these, cyclotrisiloxane is particularly preferred.

The fluorosilane compound (IIB) has the formula (IIB):
SiF _x R ³ _p R ⁴ _q R ⁵ _r
(Wherein R ^{3 to} R ⁵ are the same or different and all are organic groups having 1 to 12 carbon atoms; x is an integer of 1 to 3; p, q and r are the same or different, and all are 0 to 3) An integer of 1; however, 1 ≦ p + q + r ≦ 3)
It is shown by.

In formula (IIB), R ^{3 to} R ⁵ are the same or different and all are organic groups having 1 to 12 carbon atoms. Specific examples of R ^{3 to} R ⁵ are R ¹ and R in formula (IIA). ^{This is the same} as that exemplified as the ^second specific example.

  Specific examples of the fluorosilane compound (IIB) include, for example, trimethylfluorosilane, triethylfluorosilane, tripropylfluorosilane, phenyldimethylfluorosilane, triphenylfluorosilane, vinyldimethylfluorosilane, vinyldiethylfluorosilane, vinyldiphenylfluoro. In addition to monofluorosilanes such as silane, trimethoxyfluorosilane, and triethoxyfluorosilane, difluorosilanes such as dimethyldifluorosilane, diethyldifluorosilane, divinyldifluorosilane, and ethylvinyldifluorosilane; methyltrifluorosilane, ethyltrifluoro Examples also include trifluorosilanes such as silane.

  Since the fluorosilane compound (IIB) volatilizes when the boiling point is low, it may be difficult to contain a predetermined amount in the electrolytic solution. Moreover, even if it is made to contain in electrolyte solution, there exists a possibility that it may volatilize on the conditions that the heat_generation | fever of a battery by charging / discharging or external environment becomes high temperature. Accordingly, those having a boiling point of 50 ° C. or higher at 1 atm are preferable, and those having a boiling point of 60 ° C. or higher are particularly preferable.

  Similarly to the cyclic siloxane compound (IIA), the organic group having a smaller number of carbon atoms is more effective, and the alkenyl group having 1 to 6 carbon atoms acts on the electrolyte solution or the electrode surface coating. The output characteristics are improved, and the aryl group has the action of capturing radicals generated in the battery during charge / discharge and improving the overall battery performance. Therefore, from this viewpoint, the organic group is preferably a methyl group, a vinyl group or a phenyl group. Specific examples of the fluorosilane compound (IIB) include trimethylfluorosilane, vinyldimethylfluorosilane, phenyldimethylfluorosilane, vinyldiphenyl. Particularly preferred is fluorosilane.

（式中、Ｒ⁶〜Ｒ⁸は同じかまたは異なり、いずれも炭素数１〜１２の有機基；ＡはＨ、Ｃ、Ｎ、Ｏ、Ｆ、Ｓ、ＳｉおよびＰよりなる群から選ばれる少なくとも１種の元素から構成される基である）
で示されるものである。 Compound (IIC) has the formula (IIC):

(Wherein R ^{6 to} R ⁸ are the same or different and all are organic groups having 1 to 12 carbon atoms; A is at least selected from the group consisting of H, C, N, O, F, S, Si and P) It is a group composed of one kind of element)
It is shown by.

In formula (IIC), R ^{6 to} R ⁸ are the same or different and are all organic groups having 1 to 12 carbon atoms, and specific examples thereof are those exemplified as specific examples of R ^{1 to} R ^5. It is the same.

  In the formula (IIC), A is not particularly limited as long as it is a group composed of at least one element selected from the group consisting of H, C, N, O, F, S, Si and P. As the element directly bonded to the oxygen atom in (IIC), C, S, Si or P is preferable. Examples of the existence form of these atoms include a chain alkyl group, a cyclic alkyl group, an alkenyl group, an alkynyl group, a halogenated alkyl group, a carbonyl group, a sulfonyl group, a trialkylsilyl group, a bosphoryl group, and a phosphinyl group. Those are preferred.

  The molecular weight of compound (IIC) is preferably 1000 or less, particularly preferably 800 or less, and more preferably 500 or less.

  Specific examples of the compound (IIC) include, for example, siloxane compounds such as hexamethyldisiloxane, 1,3-diethyltetramethyldisiloxane, hexaethyldisiloxane, octamethyltrisiloxane; methoxytrimethylsilane, ethoxytrimethylsilane, and the like. Alkoxysilanes; peroxides such as bis (trimethylsilyl) peroxide; carboxylic acid esters such as trimethylsilyl acetate, triethylsilyl acetate, trimethylsilyl propionate, trimethylsilyl methacrylate, trimethylsilyl trifluoroacetate; trimethylsilyl methanesulfonate, ethane Sulfonic acid esters such as trimethylsilyl sulfonate, triethylsilyl methanesulfonate, trimethylsilyl fluoromethanesulfonate; bis (tri Sulfates such as Chirushiriru) sulfates; boric acid esters such as tris (trimethylsiloxy) boron; tris (trimethylsilyl) phosphate, tris (trimethylsilyl) phosphite phosphoric acid or phosphorous acid esters such as phosphites and the like are exemplified.

  Of these, siloxane compounds, sulfonic acid esters, and sulfuric acid esters are preferable, and siloxane compounds and sulfonic acid esters are particularly preferable. The siloxane compound is preferably hexamethyldisiloxane, the sulfonic acid ester is preferably trimethylsilyl methanesulfonate, and the sulfuric acid ester is preferably bis (trimethylsilyl) sulfate.

  The specific compound (II), that is, the cyclic siloxane compound (IIA), the fluorosilane compound (IIB) and the compound (IIC) may be used alone or in combination of two or more in any combination and ratio May be. Moreover, even if it is in the compound classified into said each by specific compound (II), 1 type may be used independently and 2 or more types may be used together by arbitrary combinations and a ratio.

  The compounding amount of these specific compounds (II) is preferably 10 ppm or more (0.001% by mass or more) in total in the non-aqueous electrolyte solution of the present invention, more preferably 0.01% by mass or more, Preferably it is 0.05 mass% or more, Most preferably, it is 0.1 mass% or more. The upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less. If the concentration of the specific compound (II) is too low, the effect of improving the low-temperature characteristics may be difficult to obtain, whereas if the concentration is too high, the charge / discharge efficiency may be reduced.

  In addition, when these specific compounds (II) are actually used as non-aqueous electrolytes for the production of secondary batteries, even if the battery is disassembled and the non-aqueous electrolyte is taken out again, the content thereof is remarkably high. Since it often decreases, it is considered that the present invention includes at least the specific compound (II) that can be detected from the nonaqueous electrolyte extracted from the battery.

  In addition, surfactant (D) and phosphate ester (E) can be blended as optional components.

  By blending the surfactant (D), the capacity of the battery can be increased. Further, when used in combination with the specific compound (II), the interfacial resistance with the electrode can be further lowered, so that discharge at a higher rate is possible. The blending amount of the surfactant (D) is 5% by mass or less with respect to the entire electrolyte salt dissolving solvent (I) from the viewpoint of reducing the surface tension of the electrolytic solution without reducing the charge / discharge cycle characteristics. Further, it is preferably 3% by mass or less, particularly preferably 0.05 to 2% by mass.

  As the surfactant (D), any of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant may be used. However, the fluorine-containing surfactant has cycle characteristics and rate characteristics. Is preferable from the viewpoint of good.

For example, the formula (D1):
Rf ⁸ COO ^- M ⁺
(Wherein Rf ⁸ is a fluorine-containing alkyl group or fluorine-containing ether group having 4 to 20 carbon atoms; M ⁺ is an alkali metal cation or NHR ′ ₃ ⁺ (the three R ′ are the same or different, and all are H or carbon 1 to 3 alkyl groups))
A fluorine-containing carboxylate (D1) represented by
Formula (D2):
Rf ⁹ SO ₃ ^- M ⁺
(Wherein Rf ⁹ is the same as Rf ⁸ and M ⁺ is the same as in formula (D1)).
Fluorine-containing sulfonate (D2)
1 type or 2 types or more can be illustrated preferably.

As Rf ⁸ and Rf ⁹ , a fluorine-containing alkyl group having 4 to 20 carbon atoms is preferable from the viewpoint of a good degree of reducing the surface tension of the electrolytic solution, and in particular, a fluorine-containing alkyl group having 4 to 8 carbon atoms is soluble. From the point which is excellent in it.

As the alkali metal in M ⁺ , Li, Na, and K are preferable, and when M ⁺ is NHR ′ ₃ ⁺ , NH ₄ ⁺ is preferable.

Specific examples of the fluorine-containing carboxylate (D1) include, for example, C ₄ F ₉ COO ^— NH ₄ ⁺ , C ₅ F ₁₁ COO ^— NH ₄ ⁺ , C ₆ F ₁₃ COO ^— NH ₄ ⁺ , C ₇ F _{15 ^{COO - NH 4 +, C 8}} F 17 COO - NH 4 +, C 9 F 19 COO - NH 4 +, C 4 F 9 COO - NH (CH 3) 3 +, C 5 F 11 COO - NH (CH 3 ^{_{) 3 +, C 6 F 13}} COO - NH (CH 3) 3 +, C 7 F 15 COO - NH (CH 3) 3 +, C 8 F 17 COO - NH (CH 3) 3 +, C 9 F 19 ^{_{COO - NH (CH 3) 3}} +, C 4 F 9 COO - Li +, C 5 F 11 COO - Li +, C 6 F 13 COO - Li +, C 7 F 15 COO - Li +, C 8 F 17 _{^{COO - Li +, C 9 F}} 19 COO - Li +, CF 3 O [CF (CF 3) CF 2 O] s -CF (CF 3) COO - NH 4 + (s: 0~3 integer), C _{Three F 7 OCF (CF 3) COO} - NH 4 +, C 3 F 7 OCF (CF 3) CF 2 OCF (CF 3) COO - NH 4 +, CF 3 O [CF (CF 3) CF 2 O] s - CF (CF ₃ ) COO ^— NH (CH ₃ ) ₃ ⁺ (s: integer from 0 to 3), C ₃ F ₇ OCF (CF ₃ ) COO ^— NH (CH ₃ ) ₃ ⁺ , C ₃ F ₇ OCF (CF _{3) CF 2 OCF (CF 3} ) COO - NH (CH 3) 3 +, CF 3 O [CF (CF 3) CF 2 O] s -CF (CF 3) COO - Li + (s: 0~3 of Integers), C ₃ F ₇ OCF (CF ₃ ) COO ⁻ Li ⁺ , C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COO ⁻ Li ⁺ , among others, electrolyte salt dissolving solvents C ₅ F ₁₁ COO ^— NH ₄ ⁺ , C ₇ F ₁₅ COO ^— NH ₄ ⁺ , C ₅ F from the point of good solubility in (I) and surface tension reduction effect ^{_{11 COO - Li +, C 6}} F 13 COO - Li +, C 3 F 7 OCF (CF 3) COO - NH 4 +, C 3 F 7 OCF (CF 3) CF 2 OCF (CF 3) COO - NH 4 ^{_{+, C 3 F 7 OCF (}} CF 3) COO - Li +, C 3 F 7 OCF (CF 3) CF 2 OCF (CF 3) COO - Li + is preferred.

Specific examples of the fluorine-containing sulfonate (D2), ^{_{e.g., C 4 F 9 SO 3 -}} NH 4 +, C 5 F 11 SO 3 - NH 4 +, C 6 F 13 SO 3 - NH 4 +, C _{^{7 F 15 SO 3 - NH 4}} +, C 8 F 17 SO 3 - NH 4 +, C 9 F 19 SO 3 - NH 4 +, C 4 F 9 SO 3 - NH (CH 3) 3 +, C 5 F ₁₁ SO ₃ ^- NH (CH ₃ ) ₃ ⁺ , C ₆ F ₁₃ SO ₃ ^- NH (CH ₃ ) ₃ ⁺ , C ₇ F ₁₅ SO ₃ ^- NH (CH ₃ ) ₃ ⁺ , C ₈ F ₁₇ SO ₃ ^- NH (CH ₃ ) ₃ ⁺ , C ₉ F ₁₉ SO ₃ ^- NH (CH ₃ ) ₃ ⁺ , C ₄ F ₉ SO ₃ ^- Li ⁺ , C ₅ F ₁₁ SO ₃ ^- Li ⁺ , C ₆ F ₁₃ SO ₃ ^- Li _{^{+, C 7 F 15 SO 3}} - Li +, C 8 F 17 SO 3 - Li +, C 9 F 19 SO 3 - Li +, C 3 F 7 OC (CF 3) FCF 2 OC (CF 3) FSO 3 _{^{- NH 4 +, C 3 F}} 7 OC (CF 3) FCF 2 OC (CF 3 _{) FCF 2 OC (CF 3)} FSO 3 - NH 4 +, HCF 2 CF 2 OCF 2 CF 2 SO 3 - NH 4 +, CF 3 CFHCF 2 OCF 2 CF 2 SO 3 - NH 4 +, C 3 F 7 OC ^{_{(CF 3) FSO 3 - NH}} 4 +, C 3 F 7 OC (CF 3) FCF 2 OC (CF 3) FSO 3 - NH (CH 3) 3 +, C 3 F 7 OC (CF 3) FCF 2 OC _{(CF 3) FCF 2 OC (} CF 3) FSO 3 - NH (CH 3) 3 +, HCF 2 CF 2 OCF 2 CF 2 SO 3 - NH (CH 3) 3 +, CF 3 CFHCF 2 OCF 2 CF 2 SO _{^{3 - NH (CH 3) 3}} +, C 3 F 7 OC (CF 3) FSO 3 - NH (CH 3) 3 +, C 3 F 7 OC (CF 3) FCF 2 OC (CF 3) FSO 3 - Li _{^{+, C 3 F 7 OC (}} CF 3) FCF 2 OC (CF 3) FCF 2 OC (CF 3) FSO 3 - Li +, HCF 2 CF 2 OCF ₂ CF ₂ SO ₃ ^- Li ⁺ , CF ₃ CFHCF ₂ OCF ₂ CF ₂ SO ₃ ^- Li ⁺ , C ₃ F ₇ OC (CF ₃ ) FSO ₃ ^- Li ^+, etc. C ₄ F ₉ SO ₃ ^- NH ₄ ⁺ , C ₆ F ₁₃ SO ₃ ^- NH ₄ ⁺ , C ₈ F ₁₇ SO ₃ ^- NH ₄ ⁺ , C ₄ F from the point that the effect of reducing solubility and surface tension is good _{^{9 SO 3 - Li +, C}} 6 F 13 SO 3 - Li +, C 8 F 17 SO 3 - Li +, C 3 F 7 OC (CF 3) FCF 2 OC (CF 3) FSO 3 - NH 4 +, _{C 3 F 7 OC (CF 3} ) FCF 2 OC (CF 3) FSO 3 - Li +, C 3 F 7 OC (CF 3) FSO 3 - NH 4 +, C 3 F 7 OC (CF 3) FSO 3 - Li ⁺ is preferred.

  By blending the phosphoric ester (E), nonflammability (non-ignition property) can be imparted. Ignition can be prevented when the blending amount is 3% by volume or less in the electrolyte salt dissolving solvent (I).

  Examples of the phosphate ester (E) include a fluorine-containing alkyl phosphate ester (E1), a non-fluorine alkyl phosphate ester (E2), and an aryl phosphate ester (E3). ) Is high because it contributes to the incombustibility of the electrolyte, and a small amount is preferable because of its incombustible effect.

（式中、Ｒｆ¹⁰〜Ｒｆ¹²は同じかまたは異なり、いずれも炭素数１〜３の含フッ素アルキル基である）
で示される含フッ素トリアルキルリン酸エステル（Ｅ１ｃ）があげられる。 Examples of the fluorine-containing alkyl phosphate ester (E1) include a fluorine-containing dialkyl phosphate ester (E1a) described in JP-A No. 11-233141 and a cyclic alkyl phosphate ester described in JP-A No. 11-283669. In addition to (E1b), formula (E1c):

(In the formula, Rf ^{10 to} Rf ¹² are the same or different and all are fluorine-containing alkyl groups having 1 to 3 carbon atoms)
And a fluorine-containing trialkyl phosphate ester (E1c) represented by

  The fluorine-containing trialkyl phosphate ester (E1c) has a high ability to impart nonflammability, and also has good compatibility with the fluorine-containing solvent (IA). It is possible to prevent ignition even when the content is less than or equal to 1%, or even less than 1% by volume.

As the fluorine-containing trialkyl phosphate ester (E1c), in the formula (E1c), Rf ^{10 to} Rf ¹² are the same or different, and any of CF ₃ —, C ₂ F ₅ —, CF ₃ CH ₂ —, HCF _{2 is used.} CF ₂ — or CF ₃ CFHCF ₂ — is preferred, and in particular, tri2,2,3,3,3-trifluoroethyl phosphate, Rf ^{10 to} Rf where Rf ^{10 to} Rf ¹² are all CF ₃ —. Tri 2,2,3,3,3-pentafluoropropyl phosphate in which all ¹² are C ₂ F _5- , Tri 2,2, phosphate in which Rf ^{10 to} Rf ¹² are all HCF ₂ CF _2- 3,3-tetrafluoropropyl is preferred.

  Next, the electrolyte salt (III) will be described.

  In order to ensure practical performance as a lithium ion secondary battery, the concentration of the electrolyte salt (III) is required to be 0.5 mol / liter or more, further 0.8 mol / liter or more. Yes. The upper limit is usually 1.5 mol / liter. The solvent (I) for dissolving an electrolyte salt used in the present invention has a solubility capable of satisfying these requirements for the concentration of the electrolyte salt (III).

The electrolyte salt (III-1) used in the electrolytic solution of the present invention in the first embodiment is LiPF ₆ or LiBF ₄ that is frequently used in lithium ion secondary batteries.

Next, the electrolyte salt (III-2) used in the electrolytic solution of the present invention in the second aspect is selected from the group consisting of LiN (SO ₂ CF ₃ ) ₂ and LiN (SO ₂ C ₂ F ₅ ) _2. It contains at least one electrolyte salt (III-2a).

  The electrolyte (III-2a) is excellent in terms of dissociation of the electrolyte salt, particularly solubility in the fluorinated solvent (A), and the concentration in the electrolytic solution is 0.1 mol / liter or more. By containing this electrolyte salt (III-2a), the ionic conductivity of the nonaqueous electrolytic solution can be improved. The upper limit is usually 1.5 mol / liter.

In the present invention, the electrolyte (III-2a) may be blended singly, but when at least one electrolyte salt (III-2b) selected from the group consisting of LiPF ₆ and LiBF ₄ is used in combination, aluminum is further added. The effect of preventing corrosion on the current collector and cell metal is obtained. When used in combination, the electrolyte salt (III-2b) concentration is 0.1 mol / liter or more. The upper limit is usually 0.9 mol / liter.

  Further, when used in combination, the electrolyte salt (III-2a) concentration is 0.1-0.9 mol / liter, the electrolyte salt (III-2b) concentration is 0.1-0.9 mol / liter, and the electrolyte salt (III -2b) Concentration / (electrolyte salt (III-2a) concentration) of 1/9 to 9/1 is excellent in cycle characteristics based on corrosion resistance to metals, improvement effect of Coulomb efficiency, and ion conductivity. This is preferable.

  Next, preferred formulations of the non-aqueous electrolyte solution of the present invention are specifically shown, but the present invention is not limited to these.

(Prescription 1)
(I) Solvent for dissolving electrolyte salt (IA) Fluorine-containing solvent Type: HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H
Blending amount: 40% by volume
(IB) Non-fluorinated solvent Type: Ethylene carbonate Amount: 20% by volume
(IB) Non-fluorinated solvent Type: Dimethyl carbonate Amount: 40% by volume
(II) Specific compound Type: Hexamethylcyclotrisiloxane Amount: 0.3% by mass
(D) Surfactant _{Type: C 3 F 7 OCF (CF} 3) CF 2 OCF (CF 3) COO - Li +
Blending amount: 0.1% by mass
(III) Electrolyte salt Type: LiPF ₆
Concentration: 1.0 mol / liter

(Prescription 2)
(I) Solvent for dissolving electrolyte salt (IA) Fluorine-containing solvent Type: HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H
Blending amount: 40% by volume
(IB) Non-fluorinated solvent Type: Ethylene carbonate Amount: 20% by volume
(IB) Non-fluorinated solvent Type: Dimethyl carbonate Amount: 40% by volume
(II) Specific compound Type: Trimethylfluorosilane Amount: 0.3% by mass
(D) Surfactant _{Type: C 3 F 7 OCF (CF} 3) CF 2 OCF (CF 3) COO - Li +
Blending amount: 0.1% by mass
(III) Electrolyte salt Type: LiPF ₆
Concentration: 1.0 mol / liter

(Prescription 3)
(I) Solvent for dissolving electrolyte salt (IA) Fluorine-containing solvent Type: HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H
Blending amount: 40% by volume
(IB) Non-fluorinated solvent Type: Ethylene carbonate Amount: 20% by volume
(IB) Non-fluorinated solvent Type: Dimethyl carbonate Amount: 40% by volume
(II) Specific compound Type: Hexamethyldisiloxane Amount: 0.3% by mass
(D) Surfactant _{Type: C 3 F 7 OCF (CF} 3) CF 2 OCF (CF 3) COO - Li +
Blending amount: 0.1% by mass
(III) Electrolyte salt Type: LiPF ₆
Concentration: 1.0 mol / liter

配合量：１０体積％
（ＩＢ）非フッ素系溶媒
種類：エチレンカーボネート
配合量：１２体積％
（ＩＢ）非フッ素系溶媒
種類：ジメチルカーボネート
配合量：３５体積％
（ＩＩ）特定の化合物
種類：ヘキサメチルトリシロキサン
配合量：０．３質量％
（Ｄ）界面活性剤
種類：Ｃ₃Ｆ₇ＯＣＦ（ＣＦ₃）ＣＦ₂ＯＣＦ（ＣＦ₃）ＣＯＯ^-Ｌｉ⁺
配合量：０．１質量％
（Ｅ）リン酸エステル
種類：（ＣＦ₃ＣＨ₂Ｏ）₃Ｐ＝Ｏ
配合量：３体積％
（ＩＩＩ）電解質塩
種類：ＬｉＰＦ₆
濃度：１．０モル／リットル (Prescription 4)
(I) Solvent for dissolving electrolyte salt (IA) Fluorine-containing solvent Type: HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H
Blending amount: 40% by volume
(IA) Fluorine-containing solvent

Compounding amount: 10% by volume
(IB) Non-fluorinated solvent Type: Ethylene carbonate Amount: 12% by volume
(IB) Non-fluorinated solvent Type: Dimethyl carbonate Amount: 35% by volume
(II) Specific compound Type: Hexamethyltrisiloxane Amount: 0.3% by mass
(D) Surfactant _{Type: C 3 F 7 OCF (CF} 3) CF 2 OCF (CF 3) COO - Li +
Blending amount: 0.1% by mass
(E) Phosphate ester Type: (CF ₃ CH ₂ O) ₃ P═O
Blending amount: 3% by volume
(III) Electrolyte salt Type: LiPF ₆
Concentration: 1.0 mol / liter

  The non-aqueous electrolyte of the present invention as described above includes, for example, an electrolytic capacitor, an electric double layer capacitor, a battery charged / discharged by charge transfer of ions, a solid display element such as electroluminescence, a current sensor, a gas sensor, etc. It can be used for sensors.

  Among them, it is preferable to use as a positive electrode, a negative electrode, a separator, and a lithium ion secondary battery provided with the nonaqueous electrolytic solution of the present invention. In particular, the positive electrode active material used for the positive electrode is a cobalt-based composite oxide. And at least one selected from the group consisting of nickel-based composite oxides, manganese-based composite oxides, iron-based composite oxides, and vanadium-based composite oxides. This is preferable.

An example of the cobalt-based composite oxide is LiCoO ₂ , an example of the nickel-based composite oxide is LiNiO ₂ , and an example of the manganese-based composite oxide is LiMnO ₂ . In addition, a CoNi composite oxide represented by LiCo _x Ni _1-x O ₂ (0 <x <1) or a CoMn composite oxide represented by LiCo _x Mn _1-x O ₂ (0 <x <1) Or a composite oxide of NiMn represented by LiNi _x Mn _1-x O ₂ (0 <x <1), LiNi _x Mn _2-x O ₄ (0 <x <2), or LiNi _1-xy Co _x Mn _{y O 2 (0 <x <} 1,0 <y <1,0 <x + y <1) may be a composite oxide of NiCoMn represented by. In these lithium-containing composite oxides, a part of metal elements such as Co, Ni, and Mn may be substituted with one or more metal elements such as Mg, Al, Zr, Ti, and Cr. .

In addition, examples of the iron-based composite oxide include LiFeO ₂ and LiFePO ₄ , and examples of the vanadium-based composite oxide include V ₂ O ₅ .

  As the positive electrode active material, among the above complex oxides, a nickel complex oxide or a cobalt complex oxide is preferable because the capacity can be increased. In particular, in a small lithium ion secondary battery, it is desirable to use a cobalt-based composite oxide from the viewpoint of high energy density and safety.

  In the present invention, particularly when used in a large-sized lithium ion secondary battery for a hybrid vehicle or a distributed power source, a high output is required. Therefore, the particles of the positive electrode active material are mainly secondary particles. It is preferable to contain 0.5 to 7.0% by volume of fine particles having an average particle diameter of 40 μm or less and an average primary particle diameter of 1 μm or less.

  Inclusion of fine particles having an average primary particle size of 1 μm or less increases the contact area with the non-aqueous electrolyte and enables faster diffusion of lithium ions between the electrode and the electrolyte to improve output performance. Can do.

Examples of the negative electrode active material used for the negative electrode in the present invention include carbon materials, and also include metal oxides and metal nitrides capable of inserting lithium ions. Examples of carbon materials include natural graphite, artificial graphite, pyrolytic carbons, cokes, mesocarbon microbeads, carbon fibers, activated carbon, and pitch-coated graphite. Metal oxides capable of inserting lithium ions include tin and Examples of the metal compound containing silicon include tin oxide and silicon oxide. Examples of the metal nitride include Li _2.6 Co _0.4 N.

  The separator that can be used in the present invention is not particularly limited, and is a microporous polyethylene film, a microporous polypropylene film, a microporous ethylene-propylene copolymer film, a microporous polypropylene / polyethylene bilayer film, a microporous polypropylene / polyethylene / Examples thereof include a polypropylene three-layer film.

  In addition, since the electrolytic solution of the present invention is nonflammable, it is particularly useful as an electrolytic solution for the above-described hybrid vehicle and a large-sized lithium ion secondary battery for a distributed power source. It is also useful as a non-aqueous electrolyte solution.

  Next, the present invention will be specifically described based on examples, but the present invention is not limited to such examples.

  In addition, each compound used in the following Examples and Comparative Examples is as follows.

含フッ素鎖状カーボネート（ＩＡ３ａ）
（ＩＡ３ａ）：ＣＦ₃ＯＣＯＯＣＦ₃
含フッ素環状カーボネート（ＩＡ３ｂ）
（ＩＡ３ｂ）：ＣＦ₃−ＥＣ

Ingredient (IA)
Fluorine-containing chain ether (IA1a)
(IA1a-1): HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H
(IA1a-2): C ₂ F ₅ CH ₂ OCF ₂ CF ₂ H
(IA1a-3): HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃
Fluorine-containing chain ester (IA2a)
(IA2a): HCF ₂ COOCH ₃
Fluorine-containing cyclic ester (IA2b)
(IA2b): CF ₃ -γ-butyrolactone

Fluorine-containing chain carbonate (IA3a)
(IA3a): CF ₃ OCOOCF ₃
Fluorine-containing cyclic carbonate (IA3b)
(IA3b): CF ₃ -EC

Ingredient (IB)
Non-fluorine chain ether (IB1a)
(IB1a): 1,2-dimethoxyethane non-fluorine chain ester (IB2a)
(IB2a): methyl propionate non-fluorinated cyclic ester (IB2b)
(IB2b): γ-butyrolactone non-fluorinated chain carbonate (IB3a)
(IB3a-1): Dimethyl carbonate (IB3a-2): Ethyl methyl carbonate (IB3a-3): Diethyl carbonate Non-fluorinated cyclic carbonate (IB3b)
(IB3b): ethylene carbonate

Ingredient (II)
Cyclic siloxane compound (IIA)
(IIA): Hexamethylcyclotrisiloxane fluorosilane compound (IIB)
(IIB): Trimethylfluorosilane compound (IIC)
(IIC-1): Hexamethyldisiloxane (IIC-2): Trimethylsilyl methanesulfonate

Ingredient (D)
Fluorinated carboxylate (D1)
_{(D1-1): C 3 F 7} OCF (CF 3) CF 2 OCF (CF 3) COO - NH 4 +
_{(D1-2): C 3 F 7} OCF (CF 3) CF 2 OCF (CF 3) COO - Li +
Fluorinated sulfonate (D2)
(D2): C ₄ F ₉ SO ₃ ^- NH ₄ ⁺

Ingredient (E)
Fluorine-containing trialkyl phosphate (E1c)
(E1c): (CF ₃ CH ₂ O) ₃ P═O

Example 1
Mixing HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H as component (IA) and dimethyl carbonate and ethylene carbonate as component (IB) in a ratio of 40/20/40% by volume to dissolve this electrolyte salt LiPF ₆ as an electrolyte salt (III) is further added to the organic solvent so as to have a concentration of 1.0 mol / liter, and the mixture is sufficiently stirred at 25 ° C. Further, hexamethylcyclotrisiloxane is added as a component (II) to a concentration of 0.001. 3% by mass was added to prepare the electrolytic solution of the present invention.

Examples 2-29
In the same manner as in Example 1, component (I), component (II), electrolyte salt (III), component (D), and component (E) were blended in the composition ratios shown in Tables 1 to 4, and the electrolyte of the present invention. An organic solvent for dissolving the salt was prepared.

Comparative Examples 1-3
In the same manner as in Example 1, the component (I), the component (II) and the electrolyte salt (III) shown in Table 4 were mixed to prepare a comparative electrolytic solution having the composition shown in Table 4.

Test 1 (Cylindrical battery production)
A cylindrical secondary battery was produced by the following method.

(Preparation of positive electrode)
A positive electrode active material prepared by mixing LiCoO ₂ , carbon black, and polyvinylidene fluoride (manufactured by Kureha Chemical Co., Ltd., trade name KF-1000) at 85/7/8 (mass% ratio) is dispersed in N-methyl-2-pyrrolidone. Then, the slurry is applied uniformly on a positive electrode current collector (aluminum foil having a thickness of 15 μm), dried to form a positive electrode mixture layer, and then compression-molded with a roller press and then cut. The lead body was then welded to produce a strip-shaped positive electrode.

(Preparation of negative electrode)
Styrene-butadiene rubber dispersed with distilled water is added to artificial graphite powder (manufactured by Temcal Co., Ltd., trade name KS-44) so that the solid content becomes 6% by mass, and mixed with a disperser to form a slurry. Is uniformly coated on a negative electrode current collector (copper foil having a thickness of 10 μm), dried to form a negative electrode mixture layer, then compression-molded by a roller press, cut, dried, and lead body Were welded to produce a strip-shaped negative electrode.

  The belt-like positive electrode was overlapped on the belt-like negative electrode with a microporous polyethylene film having a thickness of 20 μm and wound in a spiral shape to obtain a laminated electrode body having a spiral winding structure. In that case, it wound so that the rough surface side of the positive electrode current collector could be the outer peripheral side. Thereafter, the electrode body was filled in a bottomed cylindrical battery case having an outer diameter of 18 mm, and the positive and negative lead bodies were welded.

  Next, the electrolyte solutions of Examples 1 to 29 and Comparative Examples 1 to 4 are injected into the battery case, and after the electrolyte solution sufficiently permeates the separator and the like, it is sealed, precharged, aged, and cylindrical. A non-aqueous secondary battery was prepared.

Test 2 (discharge capacity)
When the charge / discharge current is represented by C, measurement is performed under the following charge / discharge measurement conditions with 1500 mA as 1C. The evaluation was performed using an index with the result of the discharge capacity of Comparative Example 1 as 100.
Charging / Discharging Condition Charging: Holds until the charging current reaches 1 / 10C at 1.0C and 4.2V (CC / CV charging)
Discharge: 1C, 3.0Vcut (CC discharge)

Test 3 (rate characteristics)
Regarding charging, the battery was charged at 1.0 C · 4.2 V under the above conditions until the charging current became 1/10 C, discharged to 3.0 V at a current equivalent to 0.2 C, and the discharge capacity was determined. Subsequently, the battery was charged at 1.0 C / 4.2 V until the charging current became 1/10 C, and discharged at a current equivalent to 2 C until 3.0 V, and the discharge capacity was determined. The rate characteristics were evaluated from the ratio between the discharge capacity at 2C and the discharge capacity at 0.2C. For the rate characteristic, a value obtained by the following calculation formula is described as the rate characteristic.
Rate characteristic (%) = 2C discharge capacity (mAh) /0.2C discharge capacity (mAh) × 100

Test 4 (cycle characteristics)
As for the cycle characteristics, a charge / discharge test is performed under the above charge / discharge conditions, and a discharge capacity of 50 cycles is measured. For the cycle characteristics, the value obtained by the following calculation formula is described as the cycle retention rate.
Cycle maintenance ratio (%) = 50 cycle discharge capacity (mAh) / 1 cycle discharge capacity (mAh) × 100

Test 5 (low temperature characteristics)
With respect to the low temperature characteristics, the battery was charged at 1.0 C and 4.2 V at 25 ° C. under the above charge / discharge conditions until the charge current became 1/10 C, and discharged to 3.0 V at a current of 0.2 C to obtain the discharge capacity. Subsequently, the battery was charged at 1.0 C and 4.2 V at 25 ° C. until the charging current became 1/10 C, left at −20 ° C. for 4 hours, discharged to 3.0 V at a current of 0.2 C, and the capacity was determined.
The low temperature characteristics were evaluated from the ratio of the capacity at −20 ° C. and the discharge capacity at 25 ° C.
For the low temperature characteristics, values obtained by the following calculation formula are described as the low temperature characteristics.
Low temperature characteristics (%) = discharge capacity at −20 ° C./discharge capacity at 25 ° C. × 100

Test 6 (Overcharge test)
The cylindrical batteries of Examples and Comparative Examples were each discharged to 3.0 V at a current value equivalent to 1 CmA, overcharged at a current value equivalent to 3 CmA with 12 V as the upper limit voltage, and the presence or absence of ignition / rupture was examined. The results are shown in Tables 1-4.

Claims (13)

(I) (IA) Solvent for dissolving electrolyte salt containing fluorine-containing solvent,
(II) (IIA) Formula (IIA):

(Wherein, R ¹ and R ² are the same or different and both are organic groups having 1 to 12 carbon atoms; n is an integer of 3 to 10)
A cyclic siloxane compound represented by:
(IIB) Formula (IIB):
SiF _x R ³ _p R ⁴ _q R ⁵ _r
(Wherein R ^{3 to} R ⁵ are the same or different and all are organic groups having 1 to 12 carbon atoms; x is an integer of 1 to 3; p, q and r are the same or different, and all are 0 to 3) An integer of 1; however, 1 ≦ p + q + r ≦ 3)
And (IIC) Formula (IIC):

(Wherein R ^{6 to} R ⁸ are the same or different and all are organic groups having 1 to 12 carbon atoms; A is at least selected from the group consisting of H, C, N, O, F, S, Si and P) It is a group composed of one kind of element)
A nonaqueous electrolytic solution containing at least one compound selected from the group consisting of the compounds represented by (III) and (III) an electrolyte salt. Fluorine-containing solvent (IA)
(IA1) fluorinated ether,
The nonaqueous electrolytic solution according to claim 1, which is at least one selected from the group consisting of (IA2) a fluorinated ester and (IA3) a fluorinated carbonate. Fluorine-containing solvent (IA)
(IA1a) fluorine-containing chain ether,
(IA2a) fluorine-containing chain ester,
(IA2b) fluorine-containing cyclic ester,
The nonaqueous electrolytic solution according to claim 1 or 2, which is at least one selected from the group consisting of (IA3a) a fluorine-containing chain carbonate and (IA3b) a fluorine-containing cyclic carbonate. The electrolyte salt (III)
(III-1) a non-aqueous electrolyte solution according to claim 1 which is LiPF _6, and at least one electrolyte salt selected from the group consisting of LiBF _4. The electrolyte salt (III)
(III-2a) LiN (SO 2 CF 3) 2 and _{LiN (SO 2 C 2 F 5} ) non according to claim 1 comprising at least one electrolyte salt selected from the group consisting of ₂ Aqueous electrolyte. The non-aqueous electrolyte solution according to claim 5, wherein the electrolyte salt (III-2a) is LiN (SO ₂ CF ₃ ) ₂ . further,
(III-2b) The nonaqueous electrolyte solution according to claim 5 or 6, comprising at least one electrolyte salt selected from the group consisting of LiPF ₆ and LiBF ₄ . The nonaqueous electrolytic solution according to claim 1, which is for a lithium ion secondary battery. An electrochemical device comprising the non-aqueous electrolyte solution according to claim 1. A lithium ion secondary battery comprising the non-aqueous electrolyte solution according to claim 1. Furthermore, the lithium ion secondary battery of Claim 10 provided with a positive electrode, a negative electrode, and a separator. The positive electrode active material used for the positive electrode is at least one selected from the group consisting of cobalt-based composite oxide, nickel-based composite oxide, manganese-based composite oxide, iron-based composite oxide, and vanadium-based composite oxide. Item 12. A lithium ion secondary battery according to Item 11. The lithium ion secondary battery according to claim 11 or 12, wherein the negative electrode active material used for the negative electrode is a carbon material.