JP2015191738A - Electrolyte and electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an electrolyte that is adaptable to increases in the voltage of electrochemical devices and that can improve the high temperature storage characteristics, high temperature cycle characteristics, load characteristics and safety of electrochemical devices; and an electrochemical device.SOLUTION: An electrolyte comprises: a solvent including a fluorinated saturated cyclic carbonate, a fluorinated chain carbonate, and a fluorinated ether; at least one sultone compound selected from the group consisting of sultone compounds having an extremely limited structure; and an electrolyte salt.

Description

The present invention relates to an electrolytic solution and an electrochemical device.

With the recent reduction in weight and size of electrical products, development of electrochemical devices such as lithium ion secondary batteries having a high energy density is in progress. Further, improvement in characteristics is demanded as an application field of electrochemical devices such as lithium ion secondary batteries expands. In particular, in the future, when lithium ion secondary batteries are used in vehicles, improvement of battery characteristics will become increasingly important.

Lithium ion secondary batteries require various characteristics such as initial capacity, rate characteristics, cycle characteristics, high temperature storage characteristics, low temperature characteristics, continuous charge characteristics, self-discharge characteristics, and overcharge prevention characteristics. In order to improve, methods for incorporating various additives into the electrolytic solution have been studied.

Patent Document 1, in R ¹ OCOOR 2 ^(wherein R ¹ represents an alkyl group or a halogen atom-substituted alkyl group, R ² represents an alkyl group or a halogen atom-substituted alkyl group does not have a hydrogen on the β position.) Non-aqueous electrolytes containing the carbonates represented are described. Further, when the β-position hydrogen of at least one alkyl group of the carbonate ester is substituted, the carbonate ester has improved chemical stability, reduced reactivity with metallic lithium, and improved oxidation resistance, at least one of them. It is described that a battery using an electrolytic solution containing a carbonic acid ester substituted with a β-position hydrogen of the alkyl group has improved safety and, in addition, improved charge / discharge cycle life.

In Patent Document 2, in a nonaqueous electrolytic solution comprising a nonaqueous solvent containing a fluorinated carbonate, a cyclic carbonate, and a chain carbonate, and an electrolyte, R ¹ OCOOR ² (wherein R ¹ and R ² may be the same or different from each other, one is a hydrocarbon group having 1 to 4 carbon atoms in which one or more hydrogen atoms are substituted with fluorine atoms, and the other is 1 to 4 carbon atoms. Or a hydrocarbon group of 1 to 4 in which one or more hydrogen atoms are substituted with fluorine atoms.) Can be used.

（式中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５及びＲ_６は、それぞれ独立に水素原子、炭素数１〜６のアルキル基、または炭素数１〜６のフッ素原子置換アルキル基を表す。） Patent Document 3 discloses a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode mainly composed of lithium metal or a substance capable of occluding and releasing lithium, and a non-aqueous electrolyte. A non-aqueous electrolyte secondary battery characterized in that it contains a γ-sultone compound represented by the general formula (I) is described. Moreover, since the said (gamma) -sultone compound is added in nonaqueous electrolyte, the fall of the discharge capacity which arises at the time of a charge / discharge cycle can be suppressed, and it can describe that a charge / discharge cycle characteristic can be improved. .

Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a fluorine atom-substituted alkyl group having 1 to 6 carbon atoms. Represents.)

In Patent Document 4, the nonaqueous solvent contains a fluorinated solvent composed of a chain fluorinated carbonate and a fluorinated ethylene carbonate, and the total amount of the fluorinated solvent in the nonaqueous solvent is in the range of 50 to 100 wt%. A water electrolyte is described. Further, it is described that when this non-aqueous electrolyte is used, a capacity reduction accompanying the charge / discharge cycle is remarkably small, and a high energy density lithium secondary battery free from gas generation during charge storage can be obtained.

Japanese Patent Application Laid-Open No. 07-006786 JP-A-11-307120 JP 2000-235866 A International Publication No. 2007/043526

When an electrochemical device such as a lithium ion secondary battery is applied to an application requiring a large capacity power source such as a vehicle, it is necessary to increase the voltage in order to achieve a higher energy density. For this reason, there is a need for an electrolytic solution that can cope with a higher voltage and that can improve various characteristics of the electrochemical device, and there is a concern about a decrease in safety due to a higher voltage.

The present invention has been made in view of the above-described current situation, can cope with the high voltage of electrochemical devices, and can improve the high temperature storage characteristics, high temperature cycle characteristics, load characteristics, and safety of electrochemical devices. It is an object to provide an electrolytic solution and an electrochemical device that can be used.

The inventors of the present invention provide an electrolyte obtained by adding a specific fluorinated ether to a solvent containing all of a fluorinated saturated cyclic carbonate, a fluorinated chain carbonate, and a fluorinated ether. The present inventors have found that storage characteristics, high temperature cycle characteristics, load characteristics, and safety are improved, and the present invention has been achieved.

That is, the present invention includes a solvent containing a fluorinated saturated cyclic carbonate, a fluorinated chain carbonate, and a fluorinated ether, a sultone compound represented by the general formula (1), and a sultone compound represented by the general formula (2). An electrolytic solution comprising at least one sultone compound selected from the group consisting of an electrolyte salt and an electrolyte salt.

（一般式（１）において、Ｒ^１、Ｒ^２及びＲ^３は、それぞれ独立に、水素原子、フッ素原子、炭素数１〜３の非フッ素化アルキル基又は炭素数１〜３のフッ素化アルキル基を表す。） General formula (1):

(In General formula (1), R < ¹ >, R < ² > and R < ³ > are respectively independently a hydrogen atom, a fluorine atom, a C1-C3 non-fluorinated alkyl group, or a C1-C3 fluorinated alkyl group. Represents.)

（一般式（２）において、Ｒ^４、Ｒ^５、Ｒ^６及びＲ^７は、それぞれ独立に、水素原子、フッ素原子、炭素数１〜３の非フッ素化アルキル基又は炭素数１〜３のフッ素化アルキル基を表す。） General formula (2):

(In General Formula (2), R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a hydrogen atom, a fluorine atom, a non-fluorinated alkyl group having 1 to 3 carbon atoms or a fluorine having 1 to 3 carbon atoms. Represents an alkyl group.)

The fluorine content of the fluorinated chain carbonate is preferably 33 to 70% by mass.

The fluorine content of the fluorinated ether is preferably 50 to 75% by mass.

The fluorinated saturated cyclic carbonate is preferably 3 to 94% by volume, the fluorinated chain carbonate is 94 to 3% by volume, and the fluorinated ether is preferably 3 to 40% by volume with respect to the solvent.

The total amount of the fluorinated saturated cyclic carbonate, the fluorinated chain carbonate, and the fluorinated ether is preferably 9 to 100% by volume with respect to the solvent.

It is preferable that the said sultone compound is 0.2-7 mass% with respect to the said electrolyte solution.

The present invention is also an electrochemical device comprising the above-described electrolytic solution.

The present invention is also a lithium ion secondary battery comprising the above electrolyte solution.

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

According to the electrolytic solution of the present invention, it is possible to cope with the high voltage of the electrochemical device, and to improve the high temperature storage characteristics, high temperature cycle characteristics, load characteristics, and safety of the electrochemical devices. The electrochemical device provided with the electrolytic solution has excellent high-temperature storage characteristics, high-temperature cycle characteristics, load characteristics, and safety, and is therefore suitable for applications such as in-vehicle use.

Hereinafter, the present invention will be specifically described.

The electrolytic solution of the present invention contains a solvent.

The solvent includes a fluorinated saturated cyclic carbonate.

The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate having a fluorine atom. 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、−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。）で表されるフッ素化飽和環状カーボネート（Ａ）が挙げられる。
上記フッ素化飽和環状カーボネート（Ａ）を含むと、本発明の電解液をリチウムイオン二次電池等に適用した場合に、負極に安定な被膜を形成することができ、負極での電解液の副反応を充分に抑制することができる。その結果、極めて安定で優れた充放電特性が得られる。
なお、本明細書中で「エーテル結合」は、−Ｏ−で表される結合である。

(In the formula, X ^{1 to} X ⁴ are the same or different and are each —H, —CH ₃ , —F, a fluorinated alkyl group that may have an ether bond, or a fluorine that may have an ether bond. Wherein at least one of X ^{1 to} X ⁴ is —F, a fluorinated alkyl group that may have an ether bond, or a fluorinated alkoxy group that may have an ether bond. Fluorinated saturated cyclic carbonate (A) represented by:
When the fluorinated saturated cyclic carbonate (A) is contained, when the electrolytic solution of the present invention is applied to a lithium ion secondary battery or the like, a stable film can be formed on the negative electrode, and the secondary solution of the electrolytic solution at the negative electrode can be formed. The reaction can be sufficiently suppressed. As a result, extremely stable and excellent charge / discharge characteristics can be obtained.
In the present specification, the “ether bond” is a bond represented by —O—.

In the general formula (A), from the viewpoint of good dielectric constant and oxidation resistance, one or two of X ^{1 to} X ⁴ are —F, a fluorinated alkyl group that may have an ether bond, or A fluorinated alkoxy group which may have an ether bond is preferable.

In the above general formula (A), X ^{1 to} X ⁴ can be represented by —H, —F, fluorinated alkyl, since it can be expected to decrease the viscosity at low temperature, increase the flash point, and further improve the solubility of the electrolyte salt. The group (a), a fluorinated alkyl group (b) having an ether bond, or a fluorinated alkoxy group (c) is preferred.

The fluorinated alkyl group (a) is obtained by substituting at least one hydrogen atom of the alkyl group with a fluorine atom. 1-20 are preferable, as for carbon number of a fluorinated alkyl group (a), 2-17 are more preferable, 2-7 are still more preferable, and 2-5 are especially preferable.
If the carbon number is too large, the low-temperature characteristics may be lowered or the solubility of the electrolyte salt may be lowered. If the carbon number is too small, the solubility of the electrolyte salt is lowered, the discharge efficiency is lowered, and further, An increase in viscosity may be observed.

Among the fluorinated alkyl groups (a), those having 1 carbon include CFH ₂ —, CF ₂ H—, and CF ₃ —.

Among the fluorinated alkyl groups (a), those having 2 or more carbon atoms include the following general formula (a-1):
R ¹ -R ^2- (a-1)
(Wherein 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; provided that R ¹ and A fluorinated alkyl 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.
R ¹ and R ² may further have other atoms other than the carbon atom, the hydrogen atom, and the fluorine atom.

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

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 —,

Etc.

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 C F 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 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 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 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 alkyl group having a fluorine atom,

Etc. are preferable. However, since the viscosity tends to be high when having a branch of —CH ₃ or —CF ₃ , the number thereof is preferably small (one) 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 minimum 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 minimum structural unit:

In addition, among the above examples, it is preferable that the base is composed of a constitutional unit that does not contain Cl, because de-HCl reaction with a base does not occur and is more stable.

When R ² is linear, it is composed of only the above-mentioned linear minimum structural unit, and among them, —CH ₂ —, —CH ₂ CH ₂ — or CF ₂ — is preferable. From the viewpoint that the solubility of the electrolyte salt can be further improved, —CH ₂ — or —CH ₂ CH ₂ — is more preferable.

When R ² is branched, it comprises at least one of the aforementioned branched minimum structural units, and R ² is represented by 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, provided that when X ^b is CF ₃ , X ^a is H or CH ₃ . In particular, the solubility of the electrolyte salt can be further improved.

Preferred examples of the fluorinated alkyl group (a) include CF ₃ CF ₂ —, HCF ₂ CF ₂ —, H ₂ CFCF ₂ —, CH ₃ CF ₂ —, CF ₃ CF ₂ CF ₂ —, and HCF ₂ CF ₂ CF _{2. -, H 2 CFCF 2 CF 2} -, CH 3 CF 2 CF 2 -,

Etc.

The fluorinated alkyl group (b) having an ether bond is obtained by substituting at least one hydrogen atom of the alkyl group having an ether bond with a fluorine atom. The fluorinated alkyl group (b) having an ether bond preferably has 2 to 17 carbon atoms. If the number of carbons is too large, the viscosity of the fluorinated saturated cyclic carbonate (A) increases, and the fluorine-containing group increases, so that the solubility of the electrolyte salt decreases due to a decrease in the dielectric constant, A decrease in compatibility may be observed. In this respect, the fluorinated alkyl group (b) having an ether bond preferably has 2 to 10 carbon atoms, and more preferably 2 to 7 carbon atoms.

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 minimum 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 minimum structural unit:

The alkylene group may be composed of these minimum structural units alone, and may be linear (i), branched (ii), or linear (i) and branched (ii). You may comprise by the combination. Preferred specific examples will be described later.

In addition, among the above examples, it is preferable that the base is composed of a constitutional unit that does not contain Cl, because de-HCl reaction with a base does not occur and is more stable.

As the 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 alkylene having 1 to 4 carbon atoms. N1 is an integer of 1 to 3; provided that at least one of R ³ and R ⁴ has a fluorine atom).

Examples of R ³ and R ⁴ include the following, and these can be combined as appropriate to form a fluorinated alkyl group (b) having an ether bond represented by the general formula (b-1). However, it is not limited to these.

(1) As R ³ , the general formula: X ^c ₃ C— (R ⁵ ) _n2 — (three X ^c are the same or different, and each is H or F; R ⁵ represents a fluorine atom having 1 to ⁵ carbon atoms. An alkylene group which may have; n2 is preferably an alkyl group represented by 0 or 1).

When n2 is 0, R ³ includes CH ₃ —, CF ₃ —, HCF ₂ —, and H ₂ CF—.

Specific examples when n2 is 1 include those in which 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 H 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 -, FCH 2 CF 2 CH 2 -, CH 3 CF 2 -, CH 3 CH 2 -, _{H 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 CH 2 -, CH 3 CF 2 CH 2 CF 2 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 - and the like.

n2 is 1, and as R ³ is branched, the

Etc.

However, since the viscosity is likely to increase when a branch such as —CH ₃ or —CF ₃ is present, it is more preferable that R ³ is linear.

(2) In — (OR ⁴ ) _n1 — in the general formula (b-1), n1 is an integer of 1 to 3, and preferably 1 or 2. When n1 = 2 or 3, R ⁴ may be the same or different.

Preferable specific examples of R ⁴ include the following linear or branched ones.

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 — and the like can be exemplified.

As a branched chain,

Etc.

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 is C1-C6.

As the fluorinated alkoxy group (c), the general ^{_{formula: X d 3 C- (R 6}} ) n3 -O- (3 single ^{X d} is either the same or different H or F; ^{R 6} is preferably the number of carbon atoms A fluorinated alkoxy group represented by an alkylene group optionally having 1 to 5 fluorine atoms; n3 is 0 or 1; but any one of three X ^ds contains a fluorine atom is particularly preferable.

Specific examples of the fluorinated alkoxy group (c) include a fluorinated alkoxy group in which an oxygen atom is bonded to the terminal of the alkyl group exemplified as R ¹ in the general formula (a-1).

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 (A) is preferably 10% by mass or more. If the fluorine content is too low, the effect of lowering the viscosity at low temperatures and the effect of increasing the flash point may not be sufficiently obtained. From this viewpoint, the fluorine content is more preferably 20% by mass or more, and further preferably 30% by mass or more. The upper limit is usually 85% 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 based on {(number of fluorine atoms) based on the structural formula of each group. × 19) / Formula amount of each group} × 100 (%).

Moreover, 5 mass% or more is preferable and, as for the fluorine content rate of the whole fluorinated saturated cyclic carbonate (A), 10 mass% or more is more preferable. The upper limit is usually 76% by mass. From the viewpoint of good dielectric constant and oxidation resistance, the fluorine content of the entire fluorinated saturated cyclic carbonate (A) is preferably 10 to 70% by mass, more preferably 15 to 60% by mass.
The fluorine content of the fluorinated saturated cyclic carbonate (A) is determined based on the structural formula of the fluorinated saturated cyclic carbonate (A) {(number of fluorine atoms × 19) / of the fluorinated saturated cyclic carbonate (A). Molecular weight} × 100 (%)

Specific examples of the fluorinated saturated cyclic carbonate (A) include the following.

In the above general formula (A), as a specific example of the fluorinated saturated cyclic carbonate (A) 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。

Etc. These compounds have a high withstand voltage and good solubility of the electrolyte salt.

other,

Etc. can also be used.

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

Etc.

In the general formula (A), at least one of X ^{1 to} X ⁴ is a fluorinated alkyl group (b) or a fluorinated alkoxy group (c) having an ether bond, and the rest are all —H. As a specific example of the fluorinated saturated cyclic carbonate (A),

Etc.

The fluorinated saturated cyclic carbonate (A) is not limited to the specific examples described above. Moreover, the said fluorinated saturated cyclic carbonate (A) may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

As the fluorinated saturated cyclic carbonate (A), fluoroethylene carbonate and difluoroethylene carbonate are preferable.

The solvent includes a fluorinated chain carbonate.

The fluorinated chain carbonate is a chain carbonate having a fluorine atom and has a fluorine content of 10 to 70.0% by mass. An electrolytic solution containing a fluorinated chain carbonate having a fluorine content in the above range can improve the high-temperature storage characteristics and cycle characteristics of the electrochemical device. The lower limit of the fluorine content is preferably 25% by mass, more preferably 30.0% by mass. The upper limit of the fluorine content is preferably 60.0% by mass, and more preferably 55.0% by mass.

The fluorine content is a value calculated from {(number of fluorine atoms × 19) / molecular weight of fluorinated chain carbonate} × 100 (%) based on the structural formula of the fluorinated chain carbonate.

Examples of the fluorinated chain carbonate include the general formula (B):
Rf ¹ OCOORf ² (B)
(In the formula, Rf ¹ and Rf ² are the same or different, and may be a fluorine atom or an alkyl group having 1 to 11 carbon atoms which may have an ether bond. However, Rf ¹ And Rf ^{2 is} a fluorine-containing alkyl group having 1 to 11 carbon atoms which may have an ether bond.), The fluorine-containing carbonate has high flame retardancy and has rate characteristics and oxidation resistance. From the viewpoint of good properties. Rf ¹ and Rf ² preferably have 1 to 5 carbon atoms.

The Rf ¹ and Rf ^2, for _{example, CF 3 -, CF 3 CH} 2 -, H 2 CFCH 2 -, HCF 2 CF 2 CH 2 -, CF 3 CF 2 CH 2 -, (CF 3) 2 CH-, Fluorine-containing alkyl groups such as H (CF ₂ CF ₂ ) ₂ CH ₂ — and CF ₃ —CF ₂ —, C ₃ F ₇ OCF (CF ₃ ) CH ₂ —, C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF _{(CF 3) CH 2 -,} C 2 F 5 OCF (CF 3) CH 2 -, CF 3 OCF (CF 3) CH 2 -, C 2 F 5 OC (CF 3) 2 CH 2 - the ether bond such as Examples thereof include fluorine-containing alkyl groups such as CH ₃ —, C ₂ H ₅ —, C ₃ H ₇ —, and C ₄ H ₅ —.
From these groups, a combination in which the fluorine content of the fluorinated chain carbonate is within the above range may be selected.

Specific examples of the fluorinated chain carbonate include H ₂ CFCH ₂ OCOOCH ₃ , HCF ₂ CH ₂ OCOOCH ₃ , (CF ₃ CH ₂ O) ₂ CO, (HCF ₂ CF ₂ CH ₂ O) ₂ CO, (CF _{3 CF 2 CH 2 O) 2} CO, ((CF 3) 2 CHO) 2 CO, (H (CF 2 CF 2) 2 CH 2 O) 2 CO, (C 3 F 7 OCF (CF 3) CF 2 OCF (CF ₃ ) CH ₂ O) ₂ CO, (C ₃ F ₇ OCF (CF ₃ ) CH ₂ O) ₂ CO, CH ₃ OCOOCH ₂ CF ₂ CF ₃ , CH ₃ OCOOCH ₂ CF ₂ CF ₂ H, C ₂ H ₅ OCOOCH ₂ CF ₂ CF ₂ H, CH ₃ OCOOCH ₂ CF ₃ , C ₂ H ₅ OCOOCH ₂ CF ₃ , CF ₃ CF ₂ CH ₂ OCOOCH ₂ CF ₂ C Examples thereof include F ₂ H, C ₃ F ₇ OCF (CF ₃ ) CH ₂ OCOOC ₃ H ₇ , HCF ₂ CF ₂ CH ₂ OCOOC ₃ H ₇ , (CF ₃ ) ₂ CHOOCOOCH ₃ , and CH ₃ OCOOCF ₃ .

Among the fluorinated chain carbonates, (CF ₃ CH ₂ O) ₂ CO, (HCF ₂ CF ₂ CH ₂ O) ₂ CO, (CF ₃ CF ₂ CH ₂ O) ₂ CO, ((CF ₃ ) ₂ CHO) ₂ CO, (H (CF ₂ CF ₂ ) ₂ CH ₂ O) ₂ CO, (C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) CH ₂ O) ₂ CO, (C ₃ F ₇ OCF (CF ₃ ) CH ₂ O) ₂ CO, CH ₃ OCOOCH ₂ CF ₂ CF ₃ , CH ₃ OCOOCH ₂ CF ₂ CF ₂ H, C ₂ H ₅ OCOOCH ₂ CF ₂ CF ₂ H, CH ₃ OCOOCH ₂ CF _{3, C 2 H 5 OCOOCH 2} CF 3, CF 3 CF 2 CH 2 OCOOCH 2 CF 2 CF 2 H, C 3 F 7 OCF (CF 3) CH 2 OCOOC 3 H 7, _{CF 2 CF 2 CH 2 OCOOC 3} H 7, (CF 3) 2 CHOCOOCH 3, _and, at least one selected from the group consisting of CH ₃ OCOOCF 3 are preferred.

The solvent includes a fluorinated ether.

Examples of the fluorinated ether include 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, provided that at least one of Rf ³ and Rf ⁴ is fluorine. A fluorinated ether (I) represented by formula (1). By containing 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 general formula (I), at least one of Rf ³ and Rf ⁴ may be a fluorinated alkyl group having 1 to 10 carbon atoms. However, the flame retardancy of the electrolyte solution, stability at high temperature and high voltage, safety From the viewpoint of further improving the properties, it is preferable that Rf ³ and Rf ⁴ are both 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. It is preferable.

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 As a result, adverse effects are also exerted on the compatibility, and the rate characteristic (viscosity) decreases because the viscosity increases. When Rf ³ has 3 or 4 carbon atoms and Rf ⁴ has 2 or 3 carbon atoms, it is advantageous in that it has excellent boiling point and rate characteristics.

The fluorinated ether preferably has a fluorine content of 50 to 75% by mass. When the fluorinated ether has a fluorine content in this range, the high temperature storage characteristics, high temperature cycle characteristics, load characteristics, and safety of the electrochemical device can be further improved.
The lower limit of the fluorine content is more preferably 55% by mass, still more preferably 60% by mass, and particularly preferably 65% by mass. The upper limit is more preferably 70% by mass and even more preferably 68% by mass.

The fluorine content is a value calculated from {(number of fluorine atoms × 19) / molecular weight of fluorinated ether (I)} × 100 (%) based on the structural formula of fluorinated ether.

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. As the 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 ) _{CF 2 H, -CF 2 CF 2} H, -CH 2 CF 2 H, or the like _-CF 2 CH ₃ and the like. From these groups, a combination in which the fluorine content of the fluorinated ether falls within the above range may be selected.

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} or the like can be mentioned.

Among them, HCF ₂ at one or both ends - or _CF 3 -CFH- is excellent polarizable those containing, can give a high boiling point fluorinated ethers (I). The boiling point of the fluorinated ether (I) is preferably 67 to 120 ° C. More preferably, it is 80 degreeC or more, More preferably, it is 90 degreeC or more.

Examples of such a 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 , and 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 1 type of H, etc. or two The above is mentioned.
Of these, HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ (boiling point 106 ° C.), CF ₃ CF ₂ CH is advantageous because of its high boiling point, compatibility with other solvents, and good solubility of the electrolyte salt. 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.). And at least one 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.). One type is more preferable.

In the electrolytic solution of the present invention, the fluorinated saturated cyclic carbonate is preferably 3 to 94% by volume, the fluorinated chain carbonate is 3 to 94% by volume, and the fluorinated ether is preferably 3 to 40% by volume with respect to the solvent. When the content of each component is within the above range, the high temperature storage characteristics, high temperature cycle characteristics, load characteristics, and safety of the electrochemical device can be further improved. More preferably, the solvent is 3 to 50% by volume of fluorinated saturated cyclic carbonate, 5 to 94% by volume of fluorinated chain carbonate, and 3 to 40% by volume of fluorinated ether. More preferably, it is 5 to 40% by volume, 10 to 60% by volume of fluorinated chain carbonate, and 3 to 30% by volume of fluorinated ether.
The total amount of the fluorinated saturated cyclic carbonate, the fluorinated chain carbonate and the fluorinated ether need not be 100% by volume, and the solvent may contain components other than these as described later.

In the electrolytic solution of the present invention, the total amount of fluorinated saturated cyclic carbonate, fluorinated chain carbonate and fluorinated ether is preferably 9 to 100% by volume with respect to the solvent. When the total amount of the fluorinated saturated cyclic carbonate and the fluorinated chain carbonate is within the above range, the electrolytic solution is more suitable for a high voltage electrochemical device. The total amount of fluorinated saturated cyclic carbonate and fluorinated chain carbonate is more preferably 20 to 95% by volume.

The solvent may contain other components other than the fluorinated saturated cyclic carbonate, fluorinated chain carbonate, and fluorinated ether. Examples of other components include non-fluorinated saturated cyclic carbonate and non-fluorinated chain carbonate.

The solvent in the present invention may further contain a non-fluorinated saturated cyclic carbonate and / or a non-fluorinated chain carbonate.

Examples of the non-fluorinated saturated cyclic carbonate include non-fluorinated saturated cyclic carbonates having an alkylene group having 2 to 4 carbon atoms.

Specific examples of the non-fluorinated saturated cyclic carbonate having an alkylene group having 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, and butylene carbonate. Of these, ethylene carbonate and propylene carbonate are particularly preferred from the viewpoint of improving the degree of lithium ion dissociation and load characteristics.

A non-fluorinated saturated cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

Examples of the non-fluorinated chain carbonate include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, Examples include isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate.

Among these, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. It is.

A non-fluorinated chain carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

When using the said other component, it is preferable to set it as 5-94 volume% with respect to a solvent. The lower limit of the content of other components may be 30% by volume or 20% by volume.

The solvent is preferably a non-aqueous solvent, and the electrolytic solution of the present invention is preferably a non-aqueous electrolytic solution.

The electrolytic solution of the present invention contains at least one sultone compound selected from the group consisting of a sultone compound represented by the general formula (1) and a sultone compound represented by the general formula (2).

（一般式（１）において、Ｒ^１、Ｒ^２及びＲ^３は、それぞれ独立に、水素原子、フッ素原子、炭素数１〜３の非フッ素化アルキル基又は炭素数１〜３のフッ素化アルキル基を表す。） General formula (1):

(In General formula (1), R < ¹ >, R < ² > and R < ³ > are respectively independently a hydrogen atom, a fluorine atom, a C1-C3 non-fluorinated alkyl group, or a C1-C3 fluorinated alkyl group. Represents.)

（一般式（２）において、Ｒ^４、Ｒ^５、Ｒ^６及びＲ^７は、それぞれ独立に、水素原子、フッ素原子、炭素数１〜３の非フッ素化アルキル基又は炭素数１〜３のフッ素化アルキル基を表す。） General formula (2):

(In General Formula (2), R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a hydrogen atom, a fluorine atom, a non-fluorinated alkyl group having 1 to 3 carbon atoms or a fluorine having 1 to 3 carbon atoms. Represents an alkyl group.)

Specific examples of the sultone compound represented by the general formula (1) include 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, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1 -Propene-1,3-sultone, 1-fluoromethyl-1,3-propane sultone, 2-trifluoromethyl-1,3-propane sultone, 3-trifluoromethyl-1,3-propane sultone, 1-methyl -1,3-propane sultone, 1,2-di (trifluoromethyl) -1,3-propane sultone, 1,1-di (trifluoromethyl) -1,3-propanes , 1-trifluoroethyl-1,3-propane sultone, 2-trifluoroethyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, etc. are mentioned, and in particular, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1 1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1,3-sultone, and 2-methyl-1,3-propane sultone are preferable.

Specific examples of the sultone compound represented by the general formula (2) include 1,4-butane sultone, 1-butene-1,4-sultone, 3-butene-1,4-sultone, 1-fluoromethyl-1, 4-butane sultone, 2-trifluoromethyl-1,4-butane sultone, 3-trifluoromethyl-1,4-butane sultone, 4-trifluoromethyl-1,4-butane sultone, 1-methyl-1,4-butane sultone, 2-methyl-1,4-butane sultone, 3-methyl-1,4-butane sultone, 4-methyl-1,4-butane sultone, 1,2-di (trifluoromethyl) -1,4-butane sultone, 1,1 -Di (trifluoromethyl) -1,4-butane sultone, 1-trifluoroethyl-1,4-butane sultone, 2-trifluoroethyl-1,4- Examples thereof include tan sultone, 1-fluoro-1,4-butane sultone, 3-fluoro-1,4-butane sultone, and particularly 1,4-butane sultone, 1-butene-1,4-sultone, and 3-butene-1,4. -Sultone, 1-fluoromethyl-1,4-butane sultone and 2-methyl-1,4-butane sultone are preferred.

Among the sultone compounds mentioned above, in particular, 1,3-propane sultone, 1,4-butane sultone, 1-propene-1,3-sultone, 1-butene-1,4-sultone, 3-butene-1,4 -Sultone is preferred.

It is preferable that content of the said sultone compound is 0.2-7 mass% with respect to electrolyte solution. Thereby, the high temperature storage characteristic of an electrochemical device can be improved further. As for the minimum of content of the said sultone compound, 0.5 mass% is more preferable, and 1 mass% is still more preferable. The upper limit is more preferably 5% by mass, and further preferably 2% by mass.

The electrolytic solution of the present invention contains an electrolyte salt.
As the above electrolyte salt, in addition to lithium salt, ammonium salt, metal salt, liquid salt (ionic liquid), inorganic polymer type salt, organic polymer type salt, etc. can be used for electrolyte solution. Any thing can be used.

As an electrolyte salt of the electrolyte solution for a lithium ion secondary battery, a lithium salt is preferable.
For _{example, LiPF 6, LiBF 4, LiClO} 4, LiAlF 4, LiSbF 6, inorganic lithium salts LiTaF 6, LiWF ₇ and the like;
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 Carboxylic acid lithium 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 Sulfonic acid lithium salts such as CF ₂ CF ₂ SO ₃ Li;
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 imide salts such as lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) ;
Lithium metide salts such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ ;
Lithium oxalatoborate salts such as lithium difluorooxalatoborate and lithium bis (oxalato) borate;
Lithium oxalate phosphate salts such as lithium tetrafluorooxalatophosphate, lithium difluorobis (oxalato) phosphate, lithium tris (oxalato) phosphate;
In addition, a salt represented by the formula: LiPF _a (C _n F _{2n + 1} ) _6-a (wherein, a is an integer of 0 to 5 and n is an integer of 1 to 6) (for example, 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 Fluorine-containing organic materials such as ₃ C ₃ F ₇ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ Lithium salts; and the like.

Among them, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiTaF ₆ , FSO ₃ Li, CF ₃ SO ₃ Li, LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , Lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium difluorobis (oxalato) phosphate, LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) _{3 and the} like are particularly preferable because they have an effect of improving output characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like.

These lithium salts may be used alone or in combination of two or more. A preferable example in the case of using two or more types in combination is a combination of LiPF ₆ and LiBF ₄ or LiPF ₆ and FSO ₃ Li, which has an effect of improving load characteristics and cycle characteristics.

In this case, there is no limit to the amount of LiBF ₄ or FSO ₃ Li based on 100% by mass of the entire electrolyte, and it is optional as long as the effects of the present invention are not significantly impaired. 0.01 mass% or more, preferably 0.1 mass% or more, and usually 30 mass% or less, preferably 20 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 the effect of suppressing deterioration due to high-temperature storage. As the organic lithium salt, 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-perfluoropropane disulfonylimide, LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium tetrafluorooxalate phosphate, lithium difluorobisoxalatophosphate, LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ LiPF ₃ (C ₂ F ₅ ) ₃ or the like is preferable. In this case, the ratio of the organic lithium salt to 100% by mass of the entire electrolyte is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and preferably 30% by mass or less, particularly Preferably it is 20 mass% or less.

The concentration of these lithium salts in the electrolytic solution is not particularly limited as long as the effects of the present invention are not impaired. From the viewpoint of ensuring the electric conductivity of the electrolytic solution in a good range and ensuring good battery performance, the total molar concentration of lithium in the electrolytic solution is preferably 0.3 mol / L or more, more preferably 0.4 mol / L. As mentioned above, More preferably, it is 0.5 mol / L or more, Preferably it is 3 mol / L or less, More preferably, it is 2.5 mol / L or less, More preferably, it is 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. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, resulting in decreased battery performance. There is a case.

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 (IIa) to (IIe) below.
(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。

(Wherein R ^1a , R ^2a , R ^3a and R ^4a are the same or different, and all are alkyl groups optionally containing an ether bond having 1 to 6 carbon atoms; X ⁻ is an anion) Preferred examples include quaternary ammonium salts. In addition, the ammonium salt in which part or all of the hydrogen atoms are substituted with a fluorine atom and / or a fluorine-containing alkyl group having 1 to 4 carbon atoms is preferable from the viewpoint of improving oxidation resistance.

As a specific example, 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）：

(Wherein R ^1a , R ^2a and X ⁻ are the same as above; x and y are the same or different and are integers of 0 to 4 and x + y = 4), a tetraalkyl quaternary ammonium salt represented by the 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、粘性の低下が図ることができる。

(Wherein 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 alkyl ether group containing trialkylammonium salt represented by the anion),
Etc. By introducing an alkyl ether group, the viscosity can be lowered.

The anion X ⁻ may be an inorganic anion or an organic anion. Examples of the inorganic anion include AlCl ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , TaF ₆ ⁻ , I ⁻ and SbF ₆ ⁻ . Examples of the organic anion include CF ₃ COO ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ^{− and the} like.

Among these, BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , and SbF ₆ ⁻ are preferable from the viewpoint of good oxidation resistance and ion dissociation.

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 , 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, etc. It is done.

(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）：

(Wherein 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) Spirocyclic bipyrrolidinium salt, 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）：

(Wherein, 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 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。

(Wherein 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) Spiro ring bipyrrolidinium salts are preferred. Moreover, it is preferable from the point which oxidation resistance improves what part or all of the hydrogen atom of this spiro ring bipyrrolidinium salt is substituted by the fluorine atom and / or the C1-C4 fluorine-containing alkyl group.

Preferred examples of the anion X ⁻ are the same as in the case of (IIa). Among them, BF ₄ −, PF ₆ −, (CF ₃ SO ₂ ) ₂ N— or (C ₂ F ₅ SO ₂ ) ₂ N− is preferable because of its high dissociation property and low internal resistance under high voltage. preferable.

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

Etc.

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

(IIc) Imidazolium 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 shown by can be illustrated preferably. Moreover, it is preferable from the point which oxidation resistance improves what part or all of the hydrogen atom of this imidazolium salt substituted by the fluorine atom and / or the C1-C4 fluorine-containing alkyl group.

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

As a preferable specific example, for example,

等が挙げられる。

Etc.

This imidazolium salt is excellent in terms of 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。

(Wherein R ^16a is an alkyl group having 1 to 6 carbon atoms; X ⁻ is an anion)
An N-alkylpyridinium salt represented by the formula is preferably exemplified. Moreover, what substituted a part or all of the hydrogen atom of this N-alkyl pyridinium salt by the fluorine atom and / or the C1-C4 fluorine-containing alkyl group is preferable from the point which oxidation resistance improves.

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

As a preferable specific example, for example,

等が挙げられる。

Etc.

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。

(Wherein, 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)
N, N-dialkylpyrrolidinium salts represented by Also, oxidation resistance of the N, N-dialkylpyrrolidinium salt in which part or all of the hydrogen atoms are substituted with fluorine atoms and / or fluorine-containing alkyl groups having 1 to 4 carbon atoms is improved. It is preferable from the point.

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

As a preferable specific example, for example,

等が挙げられる。

Etc.

This N, N-dialkylpyrrolidinium salt is excellent in terms of low viscosity and good solubility.

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

（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。

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

Moreover, you may use lithium salt as electrolyte salt for electrical double layer capacitors. Examples of the lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiSbF 6, LiN (SO 2 C 2 H 5) 2 is preferred.
In order to further improve the capacity, a magnesium salt may be used. 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 ammonium salt, the concentration is preferably 0.6 mol / liter or more. If it is less than 0.6 mol / liter, not only the low-temperature characteristics are deteriorated, but also the initial internal resistance is increased. The concentration of the electrolyte salt is preferably 0.9 mol / liter or more.
The upper limit of the concentration is preferably 3.0 mol / liter or less, more preferably 2 mol / liter or less, from the viewpoint of low temperature characteristics.
When the ammonium salt is triethylmethylammonium tetrafluoroborate (TEMABF ₄ ), the concentration is preferably 0.8 to 1.9 mol / liter in terms of excellent low temperature characteristics.
In the case of spirobipyrrolidinium tetrafluoroborate (SBPBF ₄ ), it is preferably 0.7 to 2.0 mol / liter.

The electrolytic solution of the present invention preferably further contains a polyethylene oxide having a weight average molecular weight of 2000 to 4000 and having —OH, —OCOOH, or —COOH at the terminal.
By containing such a compound, the stability of the electrode interface is 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.
Of these, 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 become better.

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

The polyethylene oxide content is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / kg in the electrolytic solution. When there is too much content of the said polyethylene oxide, there exists a possibility of impairing the characteristic of an electrochemical device.
The polyethylene oxide content is more preferably 5 × 10 ⁻⁶ mol / kg or more.

The electrolytic solution of the present invention may further contain an unsaturated cyclic carbonate, an overcharge inhibitor, other known auxiliaries, and the like. Thereby, the fall of the characteristic of an electrochemical device can be suppressed.

Examples of the unsaturated cyclic carbonate include vinylene carbonates, aromatic carbonates, ethylene carbonates substituted with a substituent having a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, Catechol carbonates etc. are mentioned.

As vinylene carbonates, vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-divinyl vinylene carbonate, allyl vinylene carbonate, 4 , 5-diallyl vinylene carbonate, 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluoro Examples include vinylene carbonate.

Specific examples of the ethylene carbonate 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, 4-methyl-5- Vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl -5-ethynylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate 4,5 diallyl carbonate, 4-methyl-5-allyl carbonate and the like.

Among these, as the unsaturated cyclic carbonate, vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl Ethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5-vinylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, 4-methyl-5-allylethylene carbonate, 4-allyl-5-vinyl Ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ether Ren carbonate is preferred. Vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are particularly preferable because they form a more stable interface protective film.

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 80 or more and 250 or less. If it is this range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will fully be expressed easily. The molecular weight of the unsaturated cyclic carbonate is more preferably 85 or more, and more preferably 150 or less.

The production method of the unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.

An unsaturated cyclic carbonate may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a 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 still more preferably 0.1% by mass or more in 100% by mass of the solvent in the present invention. The content is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. If it is within the above range, the electrochemical device using the electrolytic solution is likely to exhibit a sufficient cycle characteristic improving effect, the high-temperature storage characteristic is lowered, the amount of gas generation is increased, and the discharge capacity maintenance ratio 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 suitably used.
The fluorinated unsaturated cyclic carbonate is a cyclic carbonate having an unsaturated bond and a fluorine atom. 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 most preferably 1 or 2 fluorine atoms.

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

Fluorinated vinylene carbonate derivatives include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-5- And vinyl vinylene carbonate.

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, 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-diflu B-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4- Examples thereof include phenylethylene carbonate.

Among them, examples of the fluorinated unsaturated cyclic carbonate include 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, -Fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate form a stable interface protective film, More 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 250 or less. If it is this range, it will be easy to ensure the solubility of the fluorinated unsaturated cyclic carbonate with respect to electrolyte solution, and the effect of this invention will be easy to be expressed.

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

A fluorinated unsaturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types by arbitrary combinations and ratios. Further, 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 in 100% by mass of the electrolytic solution, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass or more. Moreover, it is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. Within this range, the electrochemical device using the electrolytic solution is likely to exhibit a sufficient cycle characteristic improvement effect, and the high-temperature storage characteristic is reduced, the amount of gas generated is increased, and the discharge capacity maintenance rate is reduced. It is easy to avoid such a situation.

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

As an overcharge inhibitor, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partially fluorinated products of the above aromatic compounds such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like And a fluorine-containing anisole compound. Of these, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, terphenyl partially hydrogenated, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran 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, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, Using at least one selected from aromatic compounds not containing oxygen, such as t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like is an overcharge prevention property and a high temperature storage property. From the standpoint of balance.

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; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, anhydrous Carboxylic anhydrides such as itaconic acid, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; 2,4,8,10-tetraoxaspiro [5.5 ] Spiro compounds such as undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane; ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, Ethyl methanesulfonate, busulfan Sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, methyl vinylsulfonate, ethyl vinylsulfonate, allyl vinylsulfonate, propargyl vinylsulfonate, methyl allylsulfonate, allylsulfone Sulfur-containing compounds such as ethyl acrylate, allyl sulfonate, propargyl allyl sulfonate, 1,2-bis (vinylsulfonoxy) ethane; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl Nitrogen-containing compounds such as 2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate , Triphenyl phosphate Phosphorus-containing compounds such as dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, ethyl diethylphosphonoacetate, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide; heptane, Examples include hydrocarbon compounds such as octane, nonane, decane, and cycloheptane, and fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene, and benzotrifluoride. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high temperature storage can be improved.

The blending amount of 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 can be sufficiently exhibited, and it is easy to avoid a situation in which battery characteristics such as high-load discharge characteristics deteriorate. The blending amount of other auxiliaries is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 3% by mass or less, still more preferably 1% by mass or less. .

The electrolyte solution of the present invention is cyclic and chain carboxylic acid ester, non-fluorinated ether compound, nitrogen-containing compound, boron-containing compound, organosilicon-containing compound, non-flammable (flame retardant) as long as the effects of the present invention are not impaired. An agent, a surfactant, a high dielectric additive, a cycle characteristic and rate characteristic improver, and the like may be further contained.

Examples of the cyclic carboxylic acid ester include those having 3 to 12 total carbon atoms in the structural formula. Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, isopsilon caprolactone, and the like. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving the characteristics of the electrochemical device derived from the improvement of the degree of lithium ion dissociation.

The compounding quantity of cyclic carboxylic acid ester is 100 mass% of solvent normally, Preferably it is 0.1 mass% or more, More preferably, it is 1 mass% or more. Within this range, the electrical conductivity of the electrolytic solution is improved, and the large current discharge characteristics of the electrochemical device are easily improved. Moreover, the compounding quantity of cyclic carboxylic acid ester becomes like this. Preferably it is 10 mass% or less, More preferably, it is 5 mass% or less. By setting the upper limit in this way, the viscosity of the electrolytic solution is set in 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 in a favorable range. Make it easier.

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

(Wherein X ^{15 to} X ²⁰ are the same or different and all are —H, —F, —Cl, —CH ₃ or a fluorinated alkyl group; provided that at least one of X ^{15 to} X ²⁰ is a fluorinated alkyl. A fluorine-containing lactone represented by the following formula:

Examples of the fluorinated alkyl group for 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 , —CF (CF ₃ ) _{2 and the} like are mentioned, and —CH ₂ CF ₃ and —CH ₂ CF ₂ CF ₃ are preferred from the viewpoint of high oxidation resistance and an effect of improving safety.

If at least one of X ^{15 to} X ²⁰ is a fluorinated alkyl group, —H, —F, —Cl, —CH ₃ or the fluorinated alkyl group is substituted at only one position of X ^{15 to} X ^20. Alternatively, a plurality of locations may be substituted. Preferably, the number of the electrolyte salt is 1 to 3 and preferably 1 to 2 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 one of A and B is CX ²⁶ X ²⁷ (X ²⁶ and X ²⁷ are the same or different, and all are —H, —F, —Cl, —CF ₃ , —CH ₃ or a hydrogen atom) An alkylene group which may be substituted with a halogen atom and may contain a hetero atom in the chain), the other is an oxygen atom; Rf ¹² is a fluorinated alkyl group or a fluorinated group which may have an ether bond An alkoxy group; X ²¹ and X ²² are the same or different; all are —H, —F, —Cl, —CF ₃ or CH ₃ ; X ^{23 to} X ²⁵ are the same or different and both are —H, —F , -Cl or an alkyl group in which a hydrogen atom may be substituted with a halogen atom and may contain a hetero atom in the chain; and a fluorine-containing lactone represented by n = 0 or 1).

As the fluorine-containing lactone represented by the formula (D), the following formula (E):

(Wherein, A, B, Rf ¹² , X ²¹ , X ²² and X ²³ are the same as those in formula (D)), the chemical stability of the 5-membered ring structure is easy to synthesize. It is preferably mentioned from a favorable point, and further, by the combination of A and B, the following formula (F):

(Wherein, Rf ¹² , X ²¹ , X ²² , X ²³ , X ²⁶ and X ²⁷ are the same as those in formula (D)), and the following formula (G):

(Wherein Rf ¹² , X ²¹ , X ²² , X ²³ , X ²⁶ and X ²⁷ are the same as those in formula (D)).

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

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。

Etc.
By including the fluorinated cyclic carboxylic acid ester, effects such as improvement in ionic conductivity, improvement in safety, and improvement in stability at high temperatures can be obtained.

Examples of the chain carboxylic acid ester include those having 3 to 7 carbon atoms in the structural formula. Specifically, methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-t-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate , Isobutyric acid-n-propyl, isobutyric acid isopropyl and the like.

Among them, methyl acetate, ethyl acetate, acetate-n-propyl, acetate-n-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. are ions due to viscosity reduction. It is preferable from the viewpoint of improvement of conductivity.

Moreover, fluorinated chain carboxylic acid ester can also be used suitably. As the fluorine-containing ester, the following formula (H):
Rf ¹⁰ COORf ¹¹ (H)
(Wherein Rf ¹⁰ is a fluorinated alkyl group having 1 to 2 carbon atoms and Rf ¹¹ is a fluorinated alkyl group having 1 to 4 carbon atoms), the flame-retardant property is high, And it is preferable from the viewpoint of good compatibility with other solvents and oxidation resistance.

Examples of Rf ¹⁰ include CF _3- , CF ₃ CF _2- , HCF ₂ CF _2- , HCF _2- , CH ₃ CF _2- , CF ₃ CH _2-, and the like, among others CF _3- , CF ₃ CF ₂ − is particularly preferable from the viewpoint of good rate characteristics.

Examples of Rf ¹¹ include CF ₃ , —CF ₂ CF ₃ , —CH (CF ₃ ) ₂ , —CH ₂ CF ₃ , —CH ₂ CH ₂ CF ₃ , —CH ₂ CF ₂ CFHCF ₃ , —CH ₂ C _2. Examples include F ₅ , —CH ₂ CF ₂ CF ₂ H, —CH ₂ CH ₂ C ₂ F ₅ , —CH ₂ CF ₂ CF ₃ , —CH ₂ CF ₂ CF ₂ CF _3, etc., among others —CH ₂ CF ₃ , —CH (CF ₃ ) ₂ —CH ₂ C ₂ F ₅ , —CH ₂ CF ₂ CF ₂ H are particularly preferred from the viewpoint of good compatibility with other solvents.

Specific examples of the fluorinated chain carboxylic acid ester include, for example, CF ₃ C (═O) OCH ₂ CF ₃ , CF ₃ C (═O) OCH ₂ CH ₂ CF ₃ , and CF ₃ C (═O) OCH ₂ C. _{One or more of 2} F ₅ , CF ₃ C (═O) OCH ₂ CF ₂ CF ₂ H, CF ₃ C (═O) OCH (CF ₃ ) _2, etc. can be exemplified, among which 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 However, the compatibility with other solvents and the rate characteristics are particularly preferable.

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

Examples of the cyclic ether having 3 to 6 carbon atoms include 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane and the like. Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions and improve the degree of ion dissociation. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferable because they have low viscosity and give high ionic conductivity.

Examples of the nitrogen-containing compound include nitrile, fluorine-containing nitrile, carboxylic acid amide, fluorine-containing carboxylic acid amide, sulfonic acid amide, and fluorine-containing sulfonic acid amide. In addition, 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxaziridinone, 1,3-dimethyl-2-imidazolidinone, N-methylsuccinimide and the like can also be used.

Examples of the boron-containing compound include boric acid esters such as trimethyl borate and triethyl borate, boric ether, and alkyl borate.

Examples of the organosilicon-containing compound include (CH ₃ ) ₄ —Si, (CH ₃ ) ₃ —Si—Si (CH ₃ ) _{3, and the} like.

Examples of the incombustible (flame retardant) agent include phosphate esters and phosphazene compounds. Examples of the phosphate ester include fluorine-containing alkyl phosphate esters, non-fluorinated alkyl phosphate esters, and aryl phosphate esters. Especially, it is preferable that it is a fluorine-containing alkyl phosphate ester at the point which can exhibit a nonflammable effect in a small quantity.

Specific examples of the fluorine-containing alkyl phosphate ester include fluorine-containing dialkyl phosphate esters described in JP-A No. 11-233141 and cyclic alkyl phosphate esters described in JP-A No. 11-283669. Or fluorine-containing trialkyl phosphate ester etc. are mentioned.

As the non-flammable (flame retardant) agent, (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. From the viewpoint of good cycle characteristics and rate characteristics, a fluorine atom It is preferable that it contains.

As such a surfactant containing a fluorine atom, for example, the following formula (3):
Rf ⁵ COO ⁻ M ⁺ (3)
(In the formula, Rf ⁵ is a fluorine-containing alkyl group that may contain an ether bond having 3 to 10 carbon atoms; M ⁺ is Li ⁺ , Na ⁺ , K ⁺ or NHR ′ ₃ ⁺ (R ′ is the same or different; , Each of which is H or an alkyl group having 1 to 3 carbon atoms), or a fluorine-containing carboxylate represented by the following formula (4):
Rf ⁶ SO ₃ ⁻ M ⁺ (4)
(In the formula, 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 ′ is the same or different; These are preferably fluorine-containing sulfonates represented by H) or an alkyl group having 1 to 3 carbon atoms.

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 reducing the charge / discharge cycle characteristics.

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

Examples of the cycle characteristic and rate characteristic 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 (plasticized) gel electrolytic solution.

Examples of such a polymer material include conventionally known polyethylene oxide and polypropylene oxide, modified products thereof (JP-A-8-222270 and JP-A-2002-1000040); polyacrylate polymers, polyacrylonitrile, and polyvinylidene fluoride. , Fluororesins such as vinylidene fluoride-hexafluoropropylene copolymer (JP-A-4-506726, JP-A-8-507407, JP-A-10-294131); these fluororesins and hydrocarbons Examples include composites with resins (Japanese Patent Laid-Open Nos. 11-35765 and 11-86630). In particular, it is desirable to use polyvinylidene fluoride or a vinylidene fluoride-hexafluoropropylene copolymer as the polymer material for the gel electrolyte.

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

This ion conductive compound has the formula (1-1):
A- (D) -B (1-1)
[Wherein D represents the formula (2-1):
-(D1) _n- (FAE) _m- (AE) _p- (Y) _q- (2-1)
(In the formula, D1 represents the formula (2a):

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

(Wherein, Rfa is hydrogen atom, a crosslinkable functional group which may have a fluorinated alkyl group; R ¹¹ is a group or a bond that binds the Rfa main chain) fluorinated alkyl group in the side chain represented by Ether units having:
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 cyclic hydrocarbon group which may have a crosslinkable functional group, or a crosslinkable functional group. An aromatic hydrocarbon group which may be present; R ¹² is an ether unit represented by R ¹³ and a group or a bond which bonds the main chain;
Y represents formulas (2d-1) to (2d-3):

A unit comprising at least one of
n is an integer of 0 to 200; m is an integer of 0 to 200; p is an integer of 0 to 10000; q is an integer of 1 to 100; provided that n + m is not 0, and the bonding order of D1, FAE, AE and Y is Not specified);
A and B are the same or different and are a hydrogen atom, a fluorine atom and / or an alkyl group which may contain a crosslinkable functional group, a phenyl group which may contain a fluorine atom and / or a crosslinkable functional group, -COOH A group, —OR (wherein R is a hydrogen atom or a fluorine atom and / or an alkyl group which may contain a crosslinkable functional group), an ester group or a carbonate group (provided that when D is an oxygen atom, a —COOH group, -OR, not an ester group or a carbonate group)].

You may mix | blend another additive with the electrolyte solution of this invention as needed. Examples of other additives include metal oxide and glass.

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

The electrolytic solution of the present invention contains a fluorinated saturated cyclic carbonate, a fluorinated chain carbonate, a solvent containing a fluorinated ether, and a sultone compound having a very limited structure. For this reason, the electrical device which has the outstanding high temperature storage characteristic, high temperature cycling characteristic, load characteristic, and safety | security can be manufactured using the electrolyte solution of this invention. The electrolyte solution of the present invention can be suitably applied to electrochemical devices such as lithium ion secondary batteries and electric double layer capacitors. An electrochemical device comprising the electrolytic solution of the present invention is also one aspect of the present invention.

Electrochemical devices include lithium ion secondary batteries, capacitors (electric double layer capacitors), radical batteries, solar cells (especially dye-sensitized solar cells), fuel cells, various electrochemical sensors, electrochromic devices, and electrochemical switching. Examples thereof include an element, an aluminum electrolytic capacitor, a tantalum electrolytic capacitor, and a lithium ion secondary battery and an electric double layer capacitor are preferable.
A module including the electrochemical device is also one aspect of the present invention.

The present invention is also a lithium ion secondary battery including the electrolytic solution of the present invention. The lithium ion secondary battery of this invention is equipped with a positive electrode, a negative electrode, and the above-mentioned electrolyte solution.

<Negative electrode>
First, the negative electrode active material used for the negative electrode will be described. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.

(Negative electrode active material)
Examples of the negative electrode active material include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like.

As a carbonaceous material used as a negative electrode active material,
(1) natural graphite,
(2) a carbonaceous material obtained by heat-treating an artificial carbonaceous material and an artificial graphite material at least once in the range of 400 to 3200 ° C;
(3) a carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different crystallinities and / or has an interface in contact with the different crystalline carbonaceous materials,
(4) A carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different orientations and / or has an interface in contact with the carbonaceous materials having different orientations,
Is preferably a good balance between initial irreversible capacity and high current density charge / discharge characteristics. Moreover, the carbonaceous materials (1) to (4) may be used alone or in combination of two or more in any combination and ratio.

Examples of the artificial carbonaceous material and artificial graphite material of (2) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, those obtained by oxidizing these pitches, needle coke, pitch coke and Carbon materials that are partially graphitized, furnace black, acetylene black, organic pyrolysis products such as pitch-based carbon fibers, carbonizable organic materials and their carbides, or carbonizable organic materials are benzene, toluene, xylene, quinoline And a solution dissolved in a low-molecular organic solvent such as n-hexane, and carbides thereof.

As an alloy material used as the negative electrode active material, as long as lithium can be occluded / released, lithium alone, simple metals and alloys forming lithium alloys, or oxides, carbides, nitrides, silicides, sulfides thereof Any of compounds such as products or phosphides may be used and is not particularly limited. The single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements (that is, excluding carbon), more preferably aluminum, silicon and tin (hereinafter referred to as “ Simple metals) and alloys or compounds containing these atoms (sometimes abbreviated as “specific metal elements”). These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

As a negative electrode active material having at least one kind of atom selected from a specific metal element, a metal simple substance of any one specific metal element, an alloy composed of two or more specific metal elements, one type or two or more specific types Alloys comprising metal elements and one or more other metal elements, as well as compounds containing one or more specific metal elements, and oxides, carbides, nitrides and silicides of the compounds And composite compounds such as sulfides or phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

In addition, a compound in which these complex compounds are complexly bonded to several kinds of elements such as a simple metal, an alloy, or a nonmetallic element is also included. Specifically, for example, in silicon and tin, an alloy of these elements and a metal that does not operate as a negative electrode can be used. For example, in the case of tin, 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 operate as a negative electrode, and a nonmetallic element may be used. it can.

Among these negative electrode active materials, since the capacity per unit mass is large when a battery is formed, any one simple metal of a specific metal element, an alloy of two or more specific metal elements, oxidation of a specific metal element In particular, silicon and / or tin metal simple substance, alloy, oxide, carbide, nitride and the like are preferable from the viewpoint of capacity per unit mass and environmental load.

The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but a material containing titanium and lithium is preferable from the viewpoint of high current density charge / discharge characteristics, A lithium-containing composite metal oxide material containing titanium is more preferable, and a composite oxide of lithium and titanium (hereinafter sometimes abbreviated as “lithium titanium composite oxide”). That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in an anode active material for electrochemical devices because the output resistance is greatly reduced.

In addition, lithium or titanium of the lithium titanium composite oxide is at least selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. Those substituted with one element are also preferred.

The metal oxide is a lithium titanium composite oxide represented by the general formula (J). In the general formula (J), 0.7 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.3, It is preferable that 0 ≦ z ≦ 1.6 because the structure upon doping and dedoping of lithium ions is stable.

_{Li x Ti y M z O 4} (J)
[In General Formula (J), 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. ]
Among the compositions represented by the general formula (J),
(A) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(B) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(C) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because of a good balance of battery performance.

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

<Configuration and production method of negative electrode>
Any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired. For example, a binder (binder), a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. are added to the negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can be formed.

In the case of using an alloy-based material, a method of forming a thin film layer (negative electrode active material layer) containing the above-described negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.

(Binder)
The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the electrolyte and the solvent used in manufacturing the electrode.

Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. And a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

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. The following is more preferable, 10 mass% or less is still more preferable, and 8 mass% or less is especially preferable. When the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio from which the amount of binders does not contribute to battery capacity may increase, and the fall of battery capacity may be caused. On the other hand, below the above range, the strength of the negative electrode may be reduced.

In particular, when a rubbery polymer typified by SBR is contained as a 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, and 0 .6% by mass or more is more preferable, and usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. Moreover, when the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. Preferably, it is usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

(Slurry forming solvent)
The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.

Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Examples include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.

In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in accordance with the thickener and make a slurry using a latex such as SBR. In addition, these solvent may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

(Current collector)
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.

In addition, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, or the like when the current collector is a metal material. Among them, a metal thin film is preferable, and a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.

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

(Thickness ratio between current collector and negative electrode active material layer)
The thickness ratio of the current collector and the negative electrode active material layer is not particularly limited, but the value of “(negative electrode active material layer thickness on one side just before electrolyte injection) / (current collector thickness)” 150 or less is preferable, 20 or less is more preferable, 10 or less is particularly preferable, 0.1 or more is preferable, 0.4 or more is more preferable, and 1 or more is particularly preferable. When the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease.

<Positive electrode>
(Positive electrode active material)
Below, the positive electrode active material used for a positive electrode is described. The positive electrode active material used in the present invention is preferably a lithium transition gold compound powder having a function capable of inserting / extracting lithium ions that satisfies any of the following three conditions.
1. Lithium transition metal compound powder having a pH of 10.8 or higher.
2. A lithium transition metal compound powder containing a compound having at least one element selected from Mo, W, Nb, Ta and Re and a compound having a B element and / or a Bi element.
3. Lithium transition metal compound powder having a peak at a pore radius of 80 nm or more and less than 800 nm.

(Lithium transition metal compound)
The lithium transition metal compound is a compound having a structure capable of desorbing and inserting Li ions, and examples thereof include sulfides, phosphate compounds, and lithium transition metal composite oxides. Examples of sulfides include compounds having a two-dimensional layered structure such as TiS ₂ and MoS ₂ , and solid compounds represented by the general formula Me _x Mo ₆ S ₈ (Me is various transition metals including Pb, Ag, and Cu). Examples thereof include a chevrel compound having a three-dimensional skeleton structure. Examples of the phosphate compound include those belonging to the olivine structure, and are generally represented by LiMePO ₄ (Me is at least one or more transition metals), specifically LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO _4, and the like. Examples of the lithium transition metal composite oxide include spinel structures capable of three-dimensional diffusion and those belonging to a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally expressed as LiMe ₂ O ₄ (Me is at least one transition metal), specifically, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O. ₄ , LiCoVO _{4 and the} like. Those having a layered structure are generally expressed as LiMeO ₂ (Me is at least one or more transition metals), specifically, LiCoO ₂ , LiNiO ₂ , LiNi _1-x Co _x O ₂ , LiNi _{1-x. -y Co x Mn y O 2,} LiNi 0.5 Mn 0.5 O 2, Li 1.2 Cr 0.4 Mn 0.4 O 2, Li 1.2 Cr 0.4 Ti 0.4 O 2, Examples include LiMnO ₂ .

Of these, lithium nickel manganese cobalt based composite oxide or LiCoO ₂ is preferable.

The lithium transition metal compound powder preferably has an olivine structure, a spinel structure, or a layered structure from the viewpoint of lithium ion diffusion. Of these, those having a layered structure are particularly preferred.

Further, a foreign element may be introduced into the lithium transition metal compound powder. As the different elements, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te , Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi , N, F, S, Cl, Br, or I. These foreign elements may be incorporated into the crystal structure of the lithium nickel manganese cobalt composite oxide, or may not be incorporated into the crystal structure of the lithium nickel manganese cobalt composite oxide. It may be unevenly distributed as a single substance or a compound in the boundary.

(Additive)
In the present invention, a compound (hereinafter also referred to as “additive element 1”) having at least one element selected from Mo, W, Nb, Ta and Re (hereinafter also referred to as “additive element 1”), In addition, a compound having at least one element selected from B and Bi (hereinafter also referred to as “additive element 2”) (hereinafter also referred to as “additive 2”) may be used.

Among these additive elements 1, the additive element 1 is preferably Mo or W, and most preferably W, because the effect is great. Among these additive elements 2, the additive element 2 is preferably B from the viewpoint of being inexpensive and available as an industrial raw material and being a light element.

The type of the compound having additive element 1 (additive 1) is not particularly limited as long as the effect of the present invention is exhibited, but an oxide is usually used.

Exemplary compounds of the additive _{1, MoO, MoO 2, MoO} 3, MoO x, Mo 2 O 3, Mo 2 O 5, Li 2 MoO 4, WO, WO 2, WO 3, WO x, W 2 O 3 , W ₂ O ₅ , W ₁₈ O ₄₉ , W ₂₀ O ₅₈ , W ₂₄ O ₇₀ , W ₂₅ O ₇₃ , W ₄₀ O ₁₁₈ , Li ₂ WO ₄ , NbO, NbO ₂ , Nb ₂ O ₃ , Nb ₂ O ₅ Nb ₂ O ₅ .nH ₂ O, LiNbO ₃ , Ta ₂ O, Ta ₂ O ₅ , LiTaO ₃ , ReO ₂ , ReO ₃ , Re ₂ O ₃ , Re ₂ O _7, etc. From the viewpoint of easy availability or inclusion of lithium, MoO ₃ , Li ₂ MoO ₄ , WO ₃ , Li ₂ WO ₄ are preferable, and WO ₃ is particularly preferable. These additional additives 1 may be used individually by 1 type, and 2 or more types may be mixed and used for them.

The type of the compound containing additive element 2 (additive 2) is not particularly limited as long as it exhibits the effects of the present invention, but usually boric acid, oxo acid salts, oxides , Hydroxides and the like are used. Among these additives 2, boric acid and oxides are preferable, and boric acid is particularly preferable because it can be obtained at low cost as an industrial raw material.

Examples of the additive 2 include BO, B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₅ , B ₆ O, B ₇ O, B ₁₃ O ₂ , LiBO ₂ , LiB ₅ O ₈ , and Li ₂ B. ₄ O ₇ , HBO ₂ , H ₃ BO ₃ , B (OH) ₃ , B (OH) ₄ , BiBO ₃ , Bi ₂ O ₃ , Bi ₂ O ₅ , Bi (OH) _{3 and the} like are listed as industrial raw materials. From the viewpoint of being relatively inexpensive and easily available, B ₂ O ₃ , H ₃ BO ₃ , and Bi ₂ O ₃ are preferable, and H ₃ BO ₃ is particularly preferable. These additives 2 may be used alone or in a combination of two or more.

Further, the range of the total amount of additive 1 and additive 2 is usually 0.1 mol% or more, preferably 0, as the lower limit with respect to the total molar amount of transition metal elements constituting the main component. 0.3 mol% or more, more preferably 0.5 mol% or more, particularly preferably 1.0 mol% or more, and the upper limit is usually less than 8 mol%, preferably 5 mol% or less, more preferably 4 mol% or less. Especially preferably, it is 3 mol% or less. If the lower limit is not reached, the above effect may not be obtained. If the upper limit is exceeded, battery performance may be reduced.

(Method for producing positive electrode active material)
As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. In particular, various methods are conceivable for preparing a spherical or elliptical active material. For example, a transition metal source material is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring. And a spherical precursor is prepared and recovered, and dried as necessary. Then, a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ is added, and the active material is obtained by baking at a high temperature. .

For the production of the positive electrode, the positive electrode active material may be used alone, or one or more of the different compositions may be used in any combination or ratio. As a preferable combination in this case, a combination of LiCoO ₂ and LiMn ₂ O ₄ such as LiNi _0.33 Co _0.33 Mn _0.33 O ₂ or a part of this Mn substituted with another transition metal or the like Or a combination with LiCoO ₂ or a part of this Co substituted with another transition metal or the like.

(Production of lithium transition metal compound powder)
The method for producing the lithium transition metal compound powder is not limited to a specific production method, but the lithium compound, at least one transition metal compound selected from Mn, Co and Ni, and the above-mentioned addition A slurry preparation step of pulverizing the agent in a liquid medium and obtaining a slurry in which these are uniformly dispersed, a spray drying step of spray drying the obtained slurry, and a firing step of firing the obtained spray dried body Is preferably produced by a production method comprising

For example, a lithium nickel manganese cobalt based composite oxide powder will be described as an example. A lithium compound, a nickel compound, a manganese compound, a cobalt compound, and a slurry in which the above additives are dispersed in a liquid medium are spray-dried. The spray-dried body thus obtained can be produced by firing in an oxygen-containing gas atmosphere.

Below, the manufacturing method of lithium nickel manganese cobalt type complex oxide powder which is a suitable aspect of this invention is mentioned as an example, and the manufacturing method of lithium transition metal type compound powder is demonstrated in detail.

I) Slurry preparation process Among the raw material compounds used in the preparation of the slurry for producing the lithium transition metal compound powder, the lithium compounds include Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ , LiOH, LiOH · H _2. Examples include O, LiH, LiF, LiCl, LiBr, LiI, CH ₃ OOLi, Li ₂ O, Li ₂ SO ₄ , dicarboxylic acid Li, citric acid Li, fatty acid Li, and alkyl lithium. Among these lithium compounds, lithium compounds that do not contain nitrogen, sulfur, or halogen atoms are preferred because they do not generate harmful substances such as SO _x and NO _x during the firing treatment. It is a compound that tends to form voids by generating cracked gas in the secondary particles of the spray-dried powder by generating cracked gas. Taking these points into consideration, Li ₂ CO ₃ , LiOH, LiOH.H ₂ O is preferable, and Li ₂ CO ₃ is particularly preferable. These lithium compounds may be used individually by 1 type, and may use 2 or more types together.

Moreover, as a nickel compound, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , 2NiCO ₃ .3Ni (OH) ₂ .4H ₂ O, NiC ₂ O ₄ .2H ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, NiSO ₄ , NiSO ₄ .6H ₂ O, nickel fatty acid, nickel halide and the like. Among these, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , 2NiCO ₃ .3Ni (OH) ₂ .4H ₂ O, NiC are used in that no harmful substances such as SO _X and NO _X are generated during the firing process. Nickel compounds such as ₂ O ₄ .2H ₂ O are preferred. Further, from the viewpoint that it can be obtained as an industrial raw material at a low cost and from the viewpoint of high reactivity, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , and further, a decomposition gas is generated at the time of firing. Ni (OH) ₂ , NiOOH, and NiCO ₃ are particularly preferable from the viewpoint of easily forming voids in the secondary particles. These nickel compounds may be used individually by 1 type, and may use 2 or more types together.

In addition, manganese compounds such as Mn ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ , manganese oxide, MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate, fatty acid manganese And manganese salts such as oxyhydroxide, manganese chloride and the like. Among these manganese compounds, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , and MnCO ₃ do not generate gases such as SO _X and NO _X during firing, and can be obtained at low cost as industrial raw materials. Therefore, it is preferable. These manganese compounds may be used individually by 1 type, and may use 2 or more types together.

Further, as the cobalt compound, Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , Co ₃ O ₄ , Co (OCOCH ₃ ) ₂ .4H ₂ O, CoCl ₂ , Co (NO ₃ ) ₂ .6H ₂ O, Co (SO ₄ ) ₂ · 7H ₂ O, CoCO _{3 and the} like. Among them, Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , Co ₃ O ₄ , and CoCO ₃ are preferable, and more preferably, from the viewpoint that no harmful substances such as SO _X and NO _X are generated during the firing process. Co (OH) ₂ and CoOOH are industrially inexpensively available and highly reactive. In addition, Co (OH) ₂ , CoOOH, and CoCO ₃ are particularly preferable from the viewpoint of easily forming voids in the secondary particles of the spray-dried powder due to generation of decomposition gas during firing. These cobalt compounds may be used individually by 1 type, and may use 2 or more types together.

In addition to the above Li, Ni, Mn, and Co raw material compounds, other elements are substituted to introduce the above-mentioned foreign elements, and voids in secondary particles formed by spray drying described later are efficiently formed. It is possible to use a group of compounds intended to be used. In addition, the addition stage of the compound used for the purpose of efficiently forming the voids of the secondary particles used here can be selected either before or after mixing the raw materials depending on the property. It is. In particular, it is preferable to add a compound which is easily decomposed due to mechanical shear stress applied by the mixing step after the mixing step. The additive is as described above.

The method for mixing the raw materials is not particularly limited, and may be wet or dry. For example, a method using an apparatus such as a ball mill, a vibration mill, or a bead mill can be used. Wet mixing in which the raw material compound is mixed in a liquid medium such as water or alcohol is preferable because more uniform mixing is possible and the reactivity of the mixture can be increased in the firing step.

The mixing time varies depending on the mixing method, but it is sufficient that the raw materials are uniformly mixed at the particle level. For example, a ball mill (wet or dry type) usually takes about 1 to 2 days, and a bead mill (wet continuous method) residence time. Is usually about 0.1 to 6 hours.

In the raw material mixing stage, it is preferable that the raw material is pulverized in parallel. As the degree of pulverization, the particle diameter of the raw material particles after pulverization is an index, but the average particle diameter (median diameter) is usually 0.6 μm or less, preferably 0.55 μm or less, more preferably 0.52 μm or less, most preferably Preferably, it is 0.5 μm or less. If the average particle size of the pulverized raw material particles is too large, the reactivity in the firing process is lowered, and the composition is difficult to homogenize. However, making particles smaller than necessary leads to an increase in the cost of pulverization, so that the average particle size is usually 0.01 μm or more, preferably 0.02 μm or more, more preferably 0.05 μm or more. That's fine. A means for realizing such a degree of pulverization is not particularly limited, but a wet pulverization method is preferable. Specific examples include dyno mill.

The median diameter of the pulverized particles in the slurry was measured by using a known laser diffraction / scattering particle size distribution measuring apparatus with a refractive index of 1.24 and a particle diameter reference set to a volume reference. . As a dispersion medium used in the measurement, a 0.1 wt% sodium hexametaphosphate aqueous solution was used, and measurement was performed after ultrasonic dispersion (output 30 W, frequency 22.5 kHz) for 5 minutes.

II) Spray drying process After the wet mixing, it is then usually subjected to a drying process. The drying method is not particularly limited, but spray drying is preferable from the viewpoints of uniformity of the generated particulate matter, powder fluidity, powder handling performance, and efficient production of dry particles.

(Spray-dried powder)
In the method for producing a lithium transition metal-based compound powder such as the lithium nickel manganese cobalt-based composite oxide powder, the slurry obtained by wet-grinding the raw material compound and the above-mentioned additive is spray-dried, A powder obtained by agglomerating primary particles to form secondary particles is obtained. Examples of the method for confirming the shape characteristics of the spray-dried powder obtained by agglomerating primary particles to form secondary particles include SEM observation and cross-sectional SEM observation.

III) Firing step The spray-dried powder obtained in the above-described spray drying step is then calcined as a calcining precursor.

This firing condition depends on the composition and the lithium compound raw material used, but as a tendency, if the firing temperature is too high, primary particles grow excessively, sintering between the particles proceeds too much, and the specific surface area becomes small. Pass. On the other hand, if it is too low, heterogeneous phases are mixed, and the lattice distortion increases without developing the crystal structure. Moreover, the specific surface area becomes too large. The firing temperature is usually 1000 ° C. or higher, preferably 1010 ° C. or higher, more preferably 1025 ° C. or higher, most preferably 1050 ° C. or higher, preferably 1250 ° C. or lower, more preferably 1200 ° C. or lower, still more preferably 1175 ° C. It is as follows.

For firing, for example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln or the like can be used. The firing process is usually divided into three parts: temperature increase, maximum temperature retention, and temperature decrease. The second maximum temperature holding portion is not necessarily limited to one time, and may include two or more stages depending on the purpose, which means that aggregation is eliminated to the extent that secondary particles are not destroyed. The temperature raising / maximum temperature holding / temperature lowering step may be repeated twice or more with a crushing step or a pulverization step which means crushing to primary particles or even fine powder.

When firing is performed in two stages, the first stage is preferably maintained at a temperature not lower than the temperature at which the Li raw material begins to decompose and below the melting temperature. For example, when lithium carbonate is used, the first stage is preferably maintained at 400 ° C. or higher. More preferably, it is 450 ° C. or higher, more preferably 500 ° C. or higher, most preferably 550 ° C. or higher, usually 950 ° C. or lower, more preferably 900 ° C. or lower, still more preferably 880 ° C. or lower, most preferably 850 ° C. or lower. is there.

In the temperature raising step up to the maximum temperature holding step, the temperature in the furnace is usually raised at a temperature raising rate of 1 ° C./min to 20 ° C./min. Even if this rate of temperature rise is too slow, it takes time and is industrially disadvantageous. However, if it is too fast, the furnace temperature does not follow the set temperature depending on the furnace. The rate of temperature rise is preferably 2 ° C./min or more, more preferably 3 ° C./min or more, preferably 18 ° C./min or less, more preferably 15 ° C./min or less.

Although the holding time in the maximum temperature holding step varies depending on the temperature, it is usually 15 minutes or longer, preferably 30 minutes or longer, more preferably 45 minutes or longer, most preferably 1 hour or longer within the above-mentioned temperature range. Time or less, preferably 12 hours or less, more preferably 9 hours or less, and most preferably 6 hours or less. If the firing time is too short, it becomes difficult to obtain a lithium-transition metal compound powder with good crystallinity, and it is not practical to be too long. If the firing time is too long, it will be disadvantageous because it will be necessary to crush afterwards or it will be difficult to crush.

In the temperature lowering step, the temperature in the furnace is normally decreased at a temperature decreasing rate of 0.1 ° C./min or more and 20 ° C./min or less. If the temperature lowering rate is too slow, it takes time and is industrially disadvantageous, but if it is too fast, the uniformity of the target product tends to be lost or the deterioration of the container tends to be accelerated. The temperature lowering rate is preferably 1 ° C./min or more, more preferably 3 ° C./min or more, and preferably 15 ° C./min or less.

Since the firing atmosphere has an appropriate oxygen partial pressure region depending on the composition of the lithium transition metal-based compound powder to be obtained, appropriate various gas atmospheres for satisfying the oxygen partial pressure region are used. Examples of the gas atmosphere include oxygen, air, nitrogen, argon, hydrogen, carbon dioxide, and a mixed gas thereof. An oxygen-containing gas atmosphere such as air can be used for the lithium nickel manganese cobalt based composite oxide powder. Usually, the atmosphere has an oxygen concentration of 1% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and 100% by volume or less, preferably 50% by volume or less, more preferably 25% by volume or less.

In such a production method, in order to produce a lithium transition metal-based compound powder, for example, a lithium nickel manganese cobalt-based composite oxide powder having the specific composition, the lithium compound , Nickel compound, manganese compound, cobalt compound, and additive, in preparing a slurry dispersed in a liquid medium, by adjusting the mixing ratio of each compound, the target Li / Ni / Mn / Co The molar ratio of can be controlled.

According to the lithium transition metal-based compound powder such as lithium nickel manganese cobalt-based composite oxide powder obtained in this way, the lithium secondary battery having a high capacity, excellent low-temperature output characteristics and storage characteristics, and good performance balance. A positive electrode material for a secondary battery is provided.

<Configuration and manufacturing method of positive electrode>
The structure of the positive electrode will be described below. The positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be performed by a conventional method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.

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. Moreover, an upper limit becomes like this. Preferably it is 99 mass% or less, More preferably, it is 98 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. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

(Binder)
The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used during electrode production may be used. The same binder as that used in the production of the negative electrode described above can be used. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1.5% by mass or more, and 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. When the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, battery capacity and conductivity may be reduced.

(Slurry forming solvent)
As the solvent for forming the slurry, the positive electrode active material, the conductive material, the binder, and a solvent that can dissolve or disperse the thickener that is used as necessary are particularly suitable for the type. There is no restriction, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) Amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.

(Current collector)
The material of the positive electrode current collector is not particularly limited, and a known material can be arbitrarily used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. A thin film, a carbon cylinder, etc. are mentioned.

Moreover, it is also preferable from the viewpoint of reducing the electronic contact resistance between the current collector and the positive electrode active material layer that a conductive additive is applied to the surface of the current collector. Examples of the conductive assistant include noble metals such as carbon, 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 electrolyte injection) / (thickness of the current collector) is 20 The lower limit is preferably 15 or less, most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the positive electrode active material increases and the battery capacity may decrease.

<Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the electrolytic solution of the present invention is usually used by impregnating this separator.

The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Among them, a resin, glass fiber, inorganic material, etc., which is formed of a material that is stable with respect to the electrolytic solution of the present invention, is used, and it is preferable to use a porous sheet or a nonwoven fabric-like material excellent in liquid retention. .

As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

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, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if the thickness is too thick, the battery performance such as rate characteristics may be lowered, and the energy density of the electrochemical device as a whole may be lowered.

Furthermore, when a porous material such as a porous sheet or nonwoven fabric is used as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Moreover, it is 90% or less normally, 85% or less is preferable and 75% or less is still more preferable. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.

On the other hand, as inorganic materials, 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. Used.

As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the above-mentioned independent thin film shape, 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, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

Hereinafter, the battery design will be described.
<Electrode group>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape through the separator. Either is acceptable. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, a gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

<Current collection structure>
The current collecting structure is not particularly limited, but in order to more effectively realize the high current density charge / discharge characteristics by the electrolytic solution of the present invention, it is necessary to make the structure that reduces the resistance of the wiring part and the joint part. preferable. Thus, when internal resistance is reduced, the effect using the electrolyte solution of this invention is exhibited especially favorable.

When the electrode group has a laminated structure, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

<Exterior case>
The material of the outer case is not particularly limited as long as it is a material that is stable with respect to the electrolytic solution used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

In an exterior case using metals, the metal is welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the exterior case using a laminate film include a sealed and sealed structure formed by thermally fusing resin layers together. In order to improve the sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

<Protective element>
Protection elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed so as not to cause abnormal heat generation or thermal runaway even without the protective element.

<Exterior body>
The electrochemical device of the present invention is usually configured by housing the above electrolyte, negative electrode, positive electrode, separator, and the like in an outer package. This exterior body is not particularly limited, and any known one can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.

The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like. In addition, the shape and structure of a positive electrode, a negative electrode, and a separator can be changed and used according to the shape of each battery.

As described above, the electrolytic solution of the present invention is excellent in battery characteristics with suppressed gas generation. Therefore, it is particularly useful as an electrolyte for electrochemical devices such as large lithium ion secondary batteries for hybrid vehicles and distributed power supplies, and as an electrolyte for electrochemical devices such as small lithium ion secondary batteries. Is also useful. A module including the lithium ion secondary battery of the present invention is also one aspect of the present invention.

The present invention may also be an electric double layer capacitor including a positive electrode, a negative electrode, and the above-described electrolytic solution.
In the electric double layer capacitor of the present invention, 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 are used as the polarizable electrode and the nonpolarizable electrode. it can.

The polarizable electrode mainly composed of activated carbon used in the present invention preferably contains a non-activated carbon having a large specific surface area and a conductive agent such as carbon black imparting electron conductivity. The polarizable electrode can be formed by various methods. For example, a polarizable 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 in an inert gas atmosphere and a water vapor atmosphere after press molding. Preferably, the polarizable electrode is joined 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, formed into a sheet, and dried to form a polarizable electrode. For example, polytetrafluoroethylene is used as the binder. In addition, activated carbon powder, carbon black, binder and solvent are mixed to form a slurry, and this slurry is coated on the metal foil of the current collector and dried to obtain a polarizable electrode integrated with the current collector. it can.

An electric double layer capacitor may be formed by using a polarizable electrode mainly composed of activated carbon for both electrodes, but a configuration using a non-polarizable 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 structure combining a polarizable electrode negative electrode mainly composed of carbon, a negative electrode mainly composed of a carbon material capable of reversibly occluding and releasing lithium ions, or a negative electrode composed mainly of lithium metal or lithium alloy and activated carbon. A combination with a polar electrode is also possible.

Further, carbonaceous materials such as carbon black, graphite, expanded graphite, porous carbon, carbon nanotube, carbon nanohorn, and ketjen black may be used instead of or in combination with activated carbon.

The non-polarizable electrode is preferably composed mainly of a carbon material capable of reversibly occluding and releasing lithium ions, and an electrode obtained by occluding lithium ions 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 having this configuration, a higher withstand voltage exceeding 4 V can be obtained.

The solvent used for preparing the slurry in the preparation of the electrode is preferably a solvent that dissolves the binder. According to the type of the binder, N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, phthalate Dimethyl acid, ethanol, methanol, butanol or water is appropriately selected.

Examples of the activated carbon used for the polarizable electrode include phenol resin activated carbon, coconut shell activated carbon, petroleum coke activated carbon and the like. Among these, it is preferable to use petroleum coke activated carbon or phenol resin activated carbon in that a large capacity can be obtained. Activated carbon activation treatment methods include a steam activation treatment method, a molten KOH activation treatment method, and the like, and it is preferable to use activated carbon by a molten KOH activation treatment method in terms of obtaining a larger capacity.

Preferred conductive agents used for the polarizable 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 polarizable electrode is so that good conductivity (low internal resistance) is obtained, and if it is too much, the product capacity is reduced. It is preferable to set it as 50 mass%.

Moreover, as the activated carbon used for the polarizable 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 as to obtain a large capacity and low internal resistance electric double layer capacitor. Is preferred. Further, as a preferable carbon material for constituting an electrode mainly composed of a carbon material capable of reversibly inserting and extracting lithium ions, natural graphite, artificial graphite, graphitized mesocarbon spherule, graphitized whisker, gas layer Examples include a grown carbon fiber, a fired product of furfuryl alcohol resin, and a fired product of novolac resin.

The current collector is only required to be chemically and electrochemically corrosion resistant. As the current collector of the polarizable electrode mainly composed of activated carbon, stainless steel, aluminum, titanium or tantalum can be preferably used. Of these, stainless steel or aluminum is a particularly preferable material in terms of both characteristics and cost of the obtained electric double layer capacitor. As the current collector of the electrode mainly composed of a carbon material capable of reversibly inserting and extracting lithium ions, stainless steel, copper or nickel is preferably used.

In addition, in order to preliminarily store lithium ions in a carbon material capable of reversibly inserting and extracting lithium ions, (1) mixing powdered lithium with a carbon material capable of reversibly inserting and extracting lithium ions. (2) A lithium foil is placed on an electrode formed of a carbon material capable of reversibly occluding and releasing lithium ions and a binder, and the electrode is in contact with the lithium salt. A method in which lithium is ionized by immersing it in an electrolyte solution in which lithium is ionized and lithium ions are taken into the carbon material; (3) formed by a carbon material and a binder capable of reversibly inserting and extracting lithium ions; Place the electrode on the negative side, place lithium metal on the positive side, immerse it in a non-aqueous electrolyte containing lithium salt as an electrolyte, and pass an electric current to make an electrochemical carbon material A method of incorporating in a state in which lithium has been ionized.

As the electric double layer capacitor, a wound type electric double layer capacitor, a laminate type electric double layer capacitor, a coin type electric double layer capacitor, etc. are generally known, and the electric double layer capacitor of the present invention is also in these types. Can do.

For example, in a wound electric double layer capacitor, a positive electrode and a negative electrode made of a laminate (electrode) of a current collector and an electrode layer are wound through a separator to produce a wound element, and the wound element is made of aluminum. And then filled with an electrolytic solution, preferably a non-aqueous electrolytic solution, and then sealed and sealed with a rubber sealing body.

As the separator, conventionally known materials and structures can be used in the present invention. For example, a polyethylene porous membrane, polypropylene fiber, glass fiber, cellulose fiber non-woven fabric and the like can be mentioned.

In addition, by a known method, a laminate type electric double layer capacitor in which a sheet-like positive electrode and a negative electrode are laminated via an electrolytic solution and a separator, and a positive electrode and a negative electrode are formed into a coin shape by fixing with a gasket and the electrolytic solution and the separator. A configured coin type electric double layer capacitor can also be used.

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

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

Examples 1-15, Comparative Examples 1-5
(Preparation of electrolyte)
In a dry argon atmosphere, chain carbonate and cyclic carbonate are mixed in the proportions shown in Table 1, and dried LiPF ₆ is added to the solution to a concentration of 1.0 mol / liter, and non-aqueous electrolysis is performed. A liquid was obtained. A sultone compound was further added to this non-aqueous electrolyte. The blending ratio of the sultone compound was expressed by mass% with respect to the electrolytic solution.
A: CF ₃ CH ₂ OCOOCH ₃ (fluorine content: 36.1%)
B: CF ₃ CH ₂ OCOOCH ₂ CF ₃ (fluorine content: 50.4%)
_{C: (C 3 F 7 OCF} (CF 3) CH 2 O) 2 CO ( fluorine content of 65.1%)
D: HCF ₂ CH ₂ OCOOCH ₃ (fluorine content: 27.1%)
a: HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H (fluorine content: 65.5%)
b: CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H (fluorine content: 67.3%)
c: HCF ₂ CH ₂ CH ₂ OC ₄ H ₉ (fluorine content: 43.6%)
FEC: monofluoroethylene carbonate EMC: ethyl methyl carbonate EC: ethylene carbonate PS: 1,3-propane sultone BS: 1,4-butane sultone

(Production of coin-type battery)
Positive electrode in which LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , carbon black, and polyvinylidene fluoride (trade name: KF-7200, manufactured by Kureha Chemical Co., Ltd.) are mixed at 92/3/5 (mass ratio). A positive electrode mixture slurry was prepared by dispersing the active material in N-methyl-2-pyrrolidone to form a slurry. The obtained positive electrode mixture slurry is uniformly applied on an aluminum current collector, dried to form a positive electrode mixture layer (thickness 50 μm), and then compression molded by a roller press machine to form a positive electrode laminate. Manufactured. The positive electrode laminate was punched into a diameter of 1.6 mm with a punching machine to produce a circular positive electrode.

Separately, styrene-butadiene rubber dispersed with distilled water was added to artificial graphite powder so as to have a solid content of 6% by mass, and mixed with a disperser to form a slurry. A negative electrode current collector (thickness 10 μm) On the copper foil) and dried to form a negative electrode mixture layer. After that, compression molding was performed with a roller press machine, and a circular negative electrode was produced with a punching machine having a diameter of 1.6 mm.

The above-mentioned circular positive electrode is opposed to the positive electrode and the negative electrode through a microporous polyethylene film (separator) having a thickness of 20 μm, and the non-aqueous electrolyte obtained above is injected. After permeation, it was sealed, precharged and aged to produce a coin-type lithium ion secondary battery.

(Measurement of battery characteristics)
About the obtained coin-type lithium ion secondary battery, the high temperature cycling characteristic and the high temperature storage characteristic were investigated in the following way.

Charge / Discharge Condition Charging: Holds the charge current at 1 / 10C at 0.5C and 4.4V (CC / CV charge)
Discharge: 0.5C 3.0Vcut (CC discharge)

(Load characteristics)
Charge and discharge at 25 ° C. under charge / discharge conditions (charge at 1.0 C at a predetermined voltage until the charge current becomes 1/10 C, and discharge to 3.0 V at a current equivalent to 0.2 C). The test is performed under discharge conditions (charging is performed at a predetermined voltage at 1.0 C until the charging current becomes 1/10 C, and discharging is performed to 3.0 V at a current equivalent to 2 C).
The load characteristics were calculated using the following formula.

(High temperature cycle characteristics)
About the high temperature cycle test, it charged / discharged 100 times by said charging / discharging conditions at 60 degreeC, and measured the high temperature cycle characteristic. The capacity retention rate was calculated using the following formula.

(High temperature storage characteristics)
For high-temperature storage characteristics, charge / discharge is performed under the above charge / discharge conditions (charging at 1.0 C until a charging current becomes 1/10 C at a predetermined voltage, and discharging to 3.0 V at a current equivalent to 1 C), The discharge capacity was examined. Then, it charged again on said charging conditions, and preserve | saved for one day in a 85 degreeC thermostat. The battery after storage was discharged at 25 ° C. under the above discharge conditions to a discharge end voltage of 3 V, and the remaining capacity was measured. After further charging under the above charge conditions, the discharge end voltage at a constant current under the above discharge conditions. The recovery capacity was measured by discharging to 3V. Table 1 shows the recovery capacity ratio when the discharge capacity before storage is 100.

(Nail penetration safety)
After performing the above charging conditions (charging at 1.0 C at a predetermined voltage until the charging current becomes 1/10 C), a test was conducted to determine whether a 3 mm diameter nail was stabbed to ignite and smoke. The results are shown in Table 1.

In Comparative Examples 3 and 4, the high temperature cycle characteristics and the high temperature storage characteristics are improved, but the nail penetration safety is poor. Most of the compositions given in the examples clear the nail penetration test and have a good balance of high-temperature storage characteristics, high-temperature cycle characteristics, and load characteristics.

Claims (9)

Fluorinated saturated cyclic carbonate, fluorinated chain carbonate, solvent containing fluorinated ether, sultone compound represented by general formula (1) and sultone compound represented by general formula (2) An electrolyte solution comprising at least one sultone compound and an electrolyte salt.
General formula (1):

(In General formula (1), R < ¹ >, R < ² > and R < ³ > are respectively independently a hydrogen atom, a fluorine atom, a C1-C3 non-fluorinated alkyl group, or a C1-C3 fluorinated alkyl group. Represents.)
General formula (2):

(In General Formula (2), R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a hydrogen atom, a fluorine atom, a non-fluorinated alkyl group having 1 to 3 carbon atoms or a fluorine having 1 to 3 carbon atoms. Represents an alkyl group.) The electrolytic solution according to claim 1, wherein the fluorine content of the fluorinated chain carbonate is 33 to 70% by mass. The electrolytic solution according to claim 1 or 2, wherein the fluorine content of the fluorinated ether is 50 to 75% by mass. The electrolytic solution according to claim 1, 2 or 3, wherein the fluorinated saturated cyclic carbonate is 3 to 94% by volume, the fluorinated chain carbonate is 94 to 3% by volume, and the fluorinated ether is 3 to 40% by volume with respect to the solvent. . The electrolytic solution according to claim 1, 2, 3, or 4, wherein a total amount of the fluorinated saturated cyclic carbonate, the fluorinated chain carbonate, and the fluorinated ether is from 9 to 100% by volume based on the solvent. The electrolytic solution according to claim 1, 2, 3, 4, or 5, wherein the sultone compound is 0.2 to 7% by mass relative to the electrolytic solution. An electrochemical device comprising the electrolytic solution according to claim 1, 2, 3, 4, 5 or 6. A lithium ion secondary battery comprising the electrolytic solution according to claim 1, 2, 3, 4, 5 or 6. A module comprising the electrochemical device according to claim 7 or the lithium ion secondary battery according to claim 8.