Electrolyte solution, electrochemical device, lithium ion secondary battery, and module

Abstract

Provided is an electrolyte solution capable of providing an electrochemical device having low resistance and excellent high-temperature storage characteristics and cycle characteristics. The electrolyte solution is characterized by containing a solvent containing a compound (1) represented by formula (1) CF2OCOOCH3, and lithium fluorosulfonate.

Description

[0001] This application is a divisional application based on the Chinese invention patent application with application number: 201880023982.2, application date: July 31, 2018, and invention name: "Electrolyte, electrochemical device, lithium-ion secondary battery and assembly". Technical Field

[0002] The invention relates to an electrolyte, an electrochemical device, a lithium ion secondary battery and a component. Background Art

[0003] As electrical products have become lighter and smaller in size in recent years, electrochemical devices such as lithium-ion secondary batteries with high energy density are being developed. In addition, as the application fields of electrochemical devices such as lithium-ion secondary batteries expand, improvements in characteristics are required. In particular, when lithium-ion secondary batteries are used for automotive applications in the future, improvements in battery characteristics are becoming increasingly important. Summary of the invention

[0004] Patent Document 1 describes an electrolyte characterized by containing a compound represented by Chemical Formula 1 and a light metal salt represented by Chemical Formula 2. (In the formula, R31 represents a hydrogen group, a fluoro group, or an alkyl group having 1 to 3 carbon atoms or a group in which at least a part of hydrogen is substituted by fluorine, X31 represents a hydrogen group or a fluoro group, and R32 represents an alkyl group having 1 or 2 carbon atoms.) (In the formula, R11 represents a -C(=O)-R21-C(=O)- group (R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group.) or a -C(=O)-C(=O)- group, R12 represents a halogen group, an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, X11 and X12 each represent oxygen (O) or sulfur (S), M11 represents a transition metal element or a Group 3B element, a Group 4B element or a Group 5B element in the short-period periodic table, M21 represents a Group 1A element or a Group 2A element in the short-period periodic table or aluminum (Al), a is an integer of 1 to 4, b is an integer of 0 to 8, and c, d, e and f are integers of 1 to 3 respectively.) Patent Document 2 describes an electrolyte solution characterized by containing a fluorocarboxylic acid ester represented by Chemical Formula 3 and a high dielectric constant solvent. (In the formula, R1 represents a group in which at least a part of hydrogen atoms of an alkyl group having 1 to 5 carbon atoms is replaced by fluorine. R2 represents an alkyl group having 1 to 4 carbon atoms or a group in which at least a part of hydrogen atoms of the alkyl group is replaced by fluorine.)

[0005] Patent Document 3 describes a non-aqueous electrolyte solution comprising an electrolyte salt dissolving solvent (I) and an electrolyte salt (II), wherein the electrolyte salt dissolving solvent (I) comprises a fluorinated ester solvent (A) represented by (A) and a fluorinated solvent (B) other than the fluorinated ester solvent (A). R 1 CFXCOOR 2 (A) (Where R 1 is a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 3 carbon atoms in which the hydrogen atom may be substituted by a fluorine atom; X is a hydrogen atom or a fluorine atom; wherein R 1 When X is a fluorine atom or a perfluoroalkyl group, R 2 is an alkyl group having 1 to 4 carbon atoms. )

[0006] Patent Document 4 describes a nonaqueous electrolyte for a nonaqueous electrolyte secondary battery containing a nonaqueous solvent and an electrolyte, and contains a fluorocarboxylate represented by Chemical Formula 4 and lithium fluorosulfate (LiSO 3 F). (wherein, R1 and R2 are H, F, CH 3－x F x (x is 1, 2, or 3, and they may be the same or different. R3 is an alkyl group having 1 to 3 carbon atoms which may contain fluorine.) Prior art literature Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2005-317446 Patent Document 2: Japanese Patent Application Publication No. 2006-32300 Patent Document 3: Japanese Patent Application Publication No. 2008-257988 Patent Document 4: Japanese Patent Application Publication No. 2017-69184

[0008] However, these techniques are not sufficient to achieve both low resistance of electrochemical devices and improvement of high-temperature storage characteristics and cycle characteristics of electrochemical devices.

[0009] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide an electrolyte solution capable of providing an electrochemical device having low resistance and excellent high-temperature storage characteristics and cycle characteristics, and an electrochemical device including the electrolyte solution.

[0010] The present inventors have found that the above-mentioned problems can be preferably solved when a fluorinated chain ester having a specific structure and further lithium fluorosulfonate are contained, thereby completing the present invention.

[0011] That is, the present invention is an electrolytic solution characterized by containing a solvent containing a compound (1) represented by the formula (1): CF2HCOOCH3 and lithium fluorosulfonate.

[0012] The above solvent preferably further contains a fluorinated cyclic carbonate.

[0013] The above solvent preferably further contains a fluorinated chain carbonate.

[0014] The above-mentioned electrolytic solution preferably further contains a compound (2) represented by the general formula (2). General formula (2): (Where X 21 is a group containing at least H or C, n 21 is an integer from 1 to 3, Y 21 and Z 21 are the same or different and are groups containing at least H, C, O or F, n 22 is 0 or 1, Y 21 and Z 21 They may bond to each other to form a ring.)

[0015] The compound (2) is preferably at least one selected from the group consisting of a compound (3) represented by the general formula (3), a compound (4) represented by the general formula (4), and phthalic anhydride. General formula (3): (Where X 31 ~X 34 The same or different groups contain at least H, C, O or F. General formula (4): (Where X 41 and X 42 The same or different groups contain at least H, C, O or F.

[0016] The present invention is also an electrochemical device characterized by comprising the above-mentioned electrolyte.

[0017] The present invention is also a lithium ion secondary battery characterized by comprising the above-mentioned electrolyte.

[0018] The present invention is also a component, characterized by comprising the above-mentioned electrochemical device or the above-mentioned lithium-ion secondary battery.

[0019] The electrolyte solution of the present invention can provide an electrochemical device having low resistance and excellent high-temperature storage characteristics and cycle characteristics. The electrochemical device having the electrolyte solution has low resistance and excellent high-temperature storage characteristics and cycle characteristics. DETAILED DESCRIPTION

[0020] Hereinafter, the present invention will be described in detail.

[0021] The electrolyte of the present invention contains a solvent containing a compound (1) represented by the formula (1): CF2HCOOCH3 and lithium fluorosulfonate (FSO3Li). By containing the two components of compound (1) and lithium fluorosulfonate, the electrolyte of the present invention can provide an electrochemical device with low resistance and excellent high-temperature storage characteristics and cycle characteristics.

[0022] The content of compound (1) is preferably 10 to 100 volume % relative to the above-mentioned solvent. By making the content of compound (1) the above-mentioned range, it is possible to provide an electrochemical device with further low resistance and better high temperature storage characteristics and cycle characteristics. As the content of compound (1), it is more preferably 15 volume % or more relative to the above-mentioned solvent, and more preferably 20 volume % or more. In addition, it is more preferably 95 volume % or less, more preferably 90 volume % or less, and particularly preferably 85 volume % or less.

[0023] The content of lithium fluorosulfonate is preferably 0.001 to 15% by mass relative to the above-mentioned electrolyte. By making the content of lithium fluorosulfonate within the above-mentioned range, an electrochemical device with further low resistance and better high-temperature storage characteristics and cycle characteristics can be provided. As the content of lithium fluorosulfonate, relative to the above-mentioned electrolyte, it is more preferably 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.5% by mass or more, and particularly preferably 0.8% by mass or more. In addition, it is more preferably 10% by mass or less, more preferably 8% by mass or less, and particularly preferably 5% by mass or less.

[0024] The above solvent preferably further contains a carbonate or an ester (but excluding compound (1)).

[0025] The above-mentioned solvent may contain a cyclic carbonate or a chain carbonate. The cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate. The above-mentioned chain carbonate may be a non-fluorinated chain carbonate or a fluorinated chain carbonate. The solvent preferably contains at least one selected from the group consisting of non-fluorinated saturated cyclic carbonates, fluorinated saturated cyclic carbonates, fluorinated chain carbonates and non-fluorinated chain carbonate esters.

[0026] Examples of the non-fluorinated saturated cyclic carbonate include non-fluorinated saturated cyclic carbonates having an alkylene group having 2 to 4 carbon atoms.

[0027] Among them, as the above-mentioned non-fluorinated saturated cyclic carbonate, from the aspects of high dielectric constant and appropriate viscosity, it is preferably at least one selected from ethylene carbonate, propylene carbonate, dipropyl carbonate, dibutyl carbonate, cis-2,3-pentylene carbonate, cis-2,3-butylene carbonate, 2,3-pentylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 1,2-butylene carbonate, methyl isopropyl carbonate and butylene carbonate.

[0028] The above-mentioned non-fluorinated saturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0029] When the non-fluorinated saturated cyclic carbonate is contained, the content of the non-fluorinated saturated cyclic carbonate is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and further preferably 15 to 45% by volume based on the solvent.

[0030] As the above-mentioned non-fluorinated chain carbonate, for example, hydrocarbon chain carbonates such as CH3OCOOCH3 (dimethyl carbonate: DMC), CH3CH2OCOOCH2CH3 (diethyl carbonate: DEC), CH3CH2OCOOCH3 (ethyl methyl carbonate: EMC), CH3OCOOCH2CH2CH3 (methyl propyl carbonate), methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, methyl-2-phenylphenyl carbonate, phenyl-2-phenylphenyl carbonate, trans-2,3-pentylene carbonate, trans-2,3-butylene carbonate, and ethylphenyl carbonate can be cited. Among them, at least one selected from ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate is preferred.

[0031] The above-mentioned non-fluorinated chain carbonate may be used alone or in combination of two or more in any combination and ratio.

[0032] When the non-fluorinated chain carbonate is contained, the content of the non-fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and even more preferably 50 to 80% by volume based on the solvent.

[0033] The solvent preferably contains both the non-fluorinated chain carbonate and the non-fluorinated cyclic carbonate. The electrolyte solution containing the solvent of this composition can be suitably used in an electrochemical device used at a relatively low voltage.

[0034] The solvent preferably contains 20 to 90% by volume of the non-fluorinated saturated cyclic carbonate and the non-fluorinated chain carbonate in total, more preferably 30 to 85% by volume, and even more preferably 50 to 80% by volume.

[0035] When the above-mentioned electrolyte contains the above-mentioned non-fluorinated cyclic carbonate and the above-mentioned non-fluorinated chain carbonate, the volume ratio of the above-mentioned non-fluorinated cyclic carbonate and the above-mentioned non-fluorinated chain carbonate is preferably 5 / 95 to 95 / 5, more preferably more than 10 / 90, further preferably more than 15 / 85, particularly preferably more than 20 / 80, more preferably less than 90 / 10, further preferably less than 60 / 40.

[0036] When above-mentioned solvent contains at least one selected from above-mentioned non-fluorinated linear carbonate and above-mentioned non-fluorinated cyclic carbonate, electrolyte of the present invention also can contain above-mentioned fluorinated saturated cyclic carbonate as additive.As the content of above-mentioned fluorinated saturated cyclic carbonate at this moment, with respect to above-mentioned solvent, is preferably 0.1~5 mass %.

[0037] The above solvent may contain a cyclic ester or a chain ester (but excluding compound (1)). The cyclic ester may be a non-fluorinated cyclic ester or a fluorinated cyclic ester. The above-mentioned chain carbonate ester may be a non-fluorinated chain ester or a fluorinated chain ester. The solvent preferably contains at least one selected from the group consisting of non-fluorinated saturated cyclic esters, fluorinated saturated cyclic esters, fluorinated chain esters, and non-fluorinated chain esters.

[0038] Examples of the non-fluorinated saturated cyclic ester include non-fluorinated saturated cyclic esters having an alkylene group having 2 to 4 carbon atoms.

[0039] Specific examples of the non-fluorinated saturated cyclic ester having an alkylene group having 2 to 4 carbon atoms include β-propiolactone, γ-butyrolactone, ε-caprolactone, δ-valerolactone, and α-methyl-γ-butyrolactone. Among them, γ-butyrolactone and δ-valerolactone are particularly preferred from the perspective of increasing the degree of lithium ion dissociation and improving the load characteristics.

[0040] The non-fluorinated saturated cyclic ester may be used alone or in combination of two or more in any combination and ratio.

[0041] Examples of the non-fluorinated chain ester include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, tert-butyl propionate, tert-butyl butyrate, sec-butyl propionate, sec-butyl butyrate, n-butyl butyrate, methyl pyrophosphate, ethyl pyrophosphate, tert-butyl formate, tert-butyl acetate, sec-butyl formate, sec-butyl acetate, n-hexyl pivalate, n-propyl formate, n-propyl acetate, n-butyl formate, Butyl ester, n-butyl pivalate, n-octyl pivalate, ethyl 2-(dimethoxyphosphoryl)acetate, ethyl 2-(dimethylphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate, isopropyl propionate, isopropyl acetate, ethyl formate, ethyl 2-propynyl oxalate, isopropyl formate, isopropyl butyrate, isobutyl formate, isobutyl propionate, isobutyl butyrate, isobutyl acetate, etc.

[0042] Among them, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate are preferred, and ethyl propionate and propyl propionate are particularly preferred.

[0043] The non-fluorinated chain ester may be used alone or in combination of two or more in any combination and ratio.

[0044] The amount of the unfluorinated saturated cyclic ester is preferably 0 to 90% by volume, more preferably 0.001 to 90% by volume, further preferably 1 to 60% by volume, particularly preferably 5 to 40% by volume, based on the solvent. The content of the non-fluorinated chain ester is preferably 0 to 90% by volume, more preferably 0.001 to 90% by volume, further preferably 1 to 60% by volume, particularly preferably 5 to 40% by volume, based on the solvent. The total amount of the non-fluorinated saturated cyclic ester and the non-fluorinated chain ester is preferably 0 to 90% by volume, more preferably 1 to 60% by volume, and even more preferably 5 to 40% by volume based on the solvent.

[0045] The solvent preferably contains a fluorinated cyclic carbonate from the viewpoint of being able to be suitably used even at a high voltage. The fluorinated cyclic carbonate may be a fluorinated saturated cyclic carbonate or a fluorinated unsaturated cyclic carbonate. In addition, in this specification, "high voltage" means a voltage of 4.2V or more. In addition, the upper limit of "high voltage" is preferably 4.9V.

[0046] The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate to which a fluorine atom is added, and specific examples thereof include compounds represented by the following general formula (A).

[0047] (Where X 1 ~X 4are the same or different, and each represents -H, -CH3, -C2H5, -F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond. 1 ~X 4 At least one of them is -F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond). The fluoroalkyl group is -CF3, -CF2H, -CH2F, etc.

[0048] When the electrolyte solution of the present invention contains the fluorinated saturated cyclic carbonate, the oxidation resistance of the electrolyte solution is improved when the electrolyte solution of the present invention is used in a high-voltage lithium ion secondary battery or the like, and stable and excellent charge and discharge characteristics can be obtained. In addition, in this specification, an "ether bond" is a bond represented by -O-.

[0049] From the perspective of good dielectric constant and oxidation resistance, X 1 ~X 4 One or two of them are preferably -F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond.

[0050] X is expected to reduce viscosity at low temperatures, increase flash point, and improve solubility of electrolyte salts. 1 ~X 4 Preferred are -H, -F, a fluorinated alkyl group (a), a fluorinated alkyl group having an ether bond (b), or a fluorinated alkoxy group (c).

[0051] The fluoroalkyl group (a) is a group in which at least one hydrogen atom of an alkyl group is substituted with a fluorine atom. The fluoroalkyl group (a) preferably has 1 to 20 carbon atoms, more preferably 1 to 17 carbon atoms, further preferably 1 to 7 carbon atoms, and particularly preferably 1 to 5 carbon atoms. If the number of carbon atoms is too large, low-temperature characteristics may be reduced or the solubility of the electrolyte salt may be reduced. If the number of carbon atoms is too small, the solubility of the electrolyte salt may be reduced, the discharge efficiency may be reduced, and the viscosity may be increased.

[0052] In the above-mentioned fluoroalkyl group (a), the group having 1 carbon atom may be CFH2-, CF2H-, or CF3-. In terms of high temperature storage characteristics, CF2H- or CF3- is particularly preferred, and CF3- is most preferred.

[0053] Among the fluoroalkyl groups (a), as a group having 2 or more carbon atoms, preferably, from the viewpoint of good solubility of the electrolyte salt, a fluoroalkyl group represented by the following general formula (a-1) can be exemplified. R 1 -R 2 -(a-1) (Where R 1is 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; wherein R 1 and R 2 At least one of them has a fluorine atom). It should be noted that R 1 and R 2 It may further contain atoms other than carbon atoms, hydrogen atoms and fluorine atoms.

[0054] R 1 It is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. 1 , preferably a linear or branched alkyl group having 1 to 16 carbon atoms. 1 The number of carbon atoms in the moiety is more preferably 1-6, and even more preferably 1-3.

[0055] As R 1 Specifically, the following groups as straight-chain or branched alkyl groups can be mentioned: CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-,

[0056]

[0057] wait.

[0058] In addition, R 1In the case of a linear alkyl group having a fluorine atom, examples include CF3-, CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CF2CH2CF2-, CF3CH2CH2CH2CH2-, CF3CF2CH2CH2 -, CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3CF2CF2 CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2CF2CH 2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, HCF2CF2CF 2CF2CH2CH2-, FCH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, FCH2CF2CF2-, CH3CF2CH2-, CH3CF2CF2-, CH3CF2CH2CF2-, CH3C F2CF2CF2-, CH3CH2CF2CF2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2C H2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, HCFClCF2CH2-, HCF2CFClCH2-, HCF2CFClCF2CFClCH2-, HFCClCF2CFClCF2CH2-, etc.

[0059] In addition, in R 1 In the case of a branched alkyl group having a fluorine atom, preferably, the following groups are mentioned.

[0060]

[0061]

[0062] However, if there are side chains such as CH3- and CF3-, the viscosity tends to increase, and therefore, the number of side chains is preferably small (one) or zero.

[0063] R 2 It is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom. 2 It may be linear or branched. An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below. 2 It is composed of one or a combination of them.

[0064] (i) The smallest structural unit of a straight chain: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0065] (ii) The smallest structural unit of a branched chain:

[0066]

[0067] In addition, among the above examples, it is preferable to be composed of a structural unit containing no Cl from the viewpoint of not causing a dehydrochlorination reaction by a base and being more stable.

[0068] R 2 When it is linear, it is composed only of the linear minimum structural unit, among which -CH2-, -CH2CH2- or -CF2- are preferred. -CH2- or -CH2CH2- is more preferred because it can further improve the solubility of the electrolyte salt.

[0069] R 2 When it is branched, it contains at least one of the branched minimum structural units, preferably represented by the general formula: a X b )-represented group (X a is H, F, CH3 or CF3; X b is CH3 or CF3. b When it is CF3, X a In particular, they can further improve the solubility of the electrolyte salt.

[0070] Preferred fluorinated alkyl groups (a) include, for example, CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CHF-, CH3CF2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-,

[0071]

[0072]

[0073] wait.

[0074] The fluoroalkyl group (b) having an ether bond is a group in which at least one of the hydrogen atoms of the alkyl group having an ether bond is replaced by a fluorine atom. The fluoroalkyl group (b) having an ether bond preferably has 2 to 17 carbon atoms. If the number of carbon atoms is too large, the viscosity of the fluorinated saturated cyclic carbonate increases. In addition, the number of fluorinated groups increases, so sometimes the solubility of the electrolyte salt due to the decrease in dielectric constant and the decrease in compatibility with other solvents can be seen. From this viewpoint, the number of carbon atoms of the fluoroalkyl group (b) having an ether bond is more preferably 2 to 10, and more preferably 2 to 7.

[0075] The alkylene group constituting the ether portion of the fluoroalkyl 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.

[0076] (i) The smallest structural unit of a straight chain: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0077] (ii) The smallest structural unit of a branched chain:

[0078]

[0079] The alkylene group may be composed of these minimum structural units alone, or may be composed of linear (i) groups, branched (ii) groups, or a combination of a linear (i) group and a branched (ii) group. Preferred specific examples are described below.

[0080] In addition, among the above examples, it is preferable to be composed of a structural unit containing no Cl from the viewpoint of not causing a dehydrochlorination reaction by a base and being more stable.

[0081] As a more preferable fluorinated alkyl group (b) having an ether bond, a group represented by the general formula (b-1) can be mentioned. R 3 -(OR 4 ) n1 -(b-1) (Where R 3 is an alkyl group which may have a fluorine atom and preferably has 1 to 6 carbon atoms; R 4 is an alkylene group which may have a fluorine atom and preferably has 1 to 4 carbon atoms; n1 is an integer of 1 to 3; wherein R 3 and R 4 At least one of them has a fluorine atom)

[0082] As R 3 and R 4 The following groups can be exemplified, and these groups can be appropriately combined to form the fluorinated alkyl group (b) having an ether bond represented by the above general formula (b-1), but the group is not limited to these.

[0083] (1) As R 3 , preferably of the general formula: X c 3C-(R 5 ) n2 - represents an alkyl group (3 X c Same or different, both H or F; R 5 is an alkylene group having 1 to 5 carbon atoms and optionally having a fluorine atom; n2 is 0 or 1).

[0084] When n2 is 0, as R 3 , examples include CH3-, CF3-, HCF2- and H2CF-.

[0085] As a specific example when n2 is 1, R 3As a straight-chain group, CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CF2-, CF3CH2CH2CH2CH2-, CF3CF2CH2CH2-. , CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3CF 2CF2CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2CF 2CH2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, H CF2CF2CF2CF2CH2CH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, CH3CF2-, CH3CH2-, CH3CF2CH2-, CH3CF2CF2-, CH3CH2C H2-, CH3CF2CH2CF2-, CH3CF2CF2CF2-, CH3CH2CF2CF2-, CH3CH2CH2CH2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2CH2CF2CH2CH2-, CH3CH2CF2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, etc.

[0086] As n2 is 1 and R 3 The branched group includes the following groups:

[0087]

[0088] wait.

[0089] However, if there is a side chain such as CH3- or CF3-, the viscosity tends to be high, so R is more preferred. 3 It is a straight chain.

[0090] (2) -(OR 4 ) n1 -, n1 is an integer of 1 to 3, preferably 1 or 2. It should be noted that when n1 = 2 or 3, R 4 Can be the same or different.

[0091] As R 4 Preferred specific examples of include the following linear or branched groups.

[0092] Examples of the linear group include -CH2-, -CHF-, -CF2-, -CH2CH2-, -CF2CH2-, -CF2CF2-, -CH2CF2-, -CH2CH2CH2-, -CH2CH2CF2-, -CH2CF2CH2-, -CF2CH2CH2-, -CF2CF2CH2-, -CF2CH2CF2-, -CF2CH2CF2-, -CF2CH2CF2- and the like.

[0093] Examples of branched groups include the following:

[0094]

[0095] wait.

[0096] The fluoroalkoxy group (c) is a group in which at least one hydrogen atom of an alkoxy group is substituted with a fluorine atom. The fluoroalkoxy group (c) preferably has 1 to 17 carbon atoms, and more preferably has 1 to 6 carbon atoms.

[0097] As the fluoroalkoxy group (c), it is particularly preferred that X d 3C-(R 6 ) n3 -O- represented by fluoroalkoxy (3 X d Same or different, both H or F; R 6 It is preferably an alkylene group having 1 to 5 carbon atoms and optionally having a fluorine atom; n3 is 0 or 1; wherein 3 X d any one of which contains a fluorine atom).

[0098] Specific examples of the fluoroalkoxy group (c) include: 1 The alkyl group exemplified is a fluoroalkoxy group having an oxygen atom bonded to the terminal thereof.

[0099] The fluorine content of the fluoroalkyl (a), the fluoroalkyl (b) and the fluoroalkoxy (c) in the above-mentioned fluorinated saturated cyclic carbonate is preferably more than 10 mass %. If the fluorine content is too low, then there is a possibility that the viscosity reduction effect and the rising effect of the flash point under low temperature can not be fully obtained. From this viewpoint, the above-mentioned fluorine content is more preferably more than 12 mass %, more preferably more than 15 mass %. The upper limit is usually 76 mass %. The fluorine content of the fluoroalkyl group (a), the fluoroalkyl group having an ether bond (b) and the fluoroalkoxy group (c) is a value calculated from {(number of fluorine atoms×19) / formula weight of each group}×100(%) based on the structural formula of each group.

[0100] Furthermore, from the viewpoint of good dielectric constant and oxidation resistance, the fluorine content of the fluorinated saturated cyclic carbonate as a whole is preferably 10% by mass or more, more preferably 15% by mass or more, and the upper limit is usually 76% by mass. The fluorine content of the fluorinated saturated cyclic carbonate is a value calculated from {(number of fluorine atoms×19) / molecular weight of fluorinated saturated cyclic carbonate}×100(%) based on the structural formula of the fluorinated saturated cyclic carbonate.

[0101] Specific examples of the fluorinated saturated cyclic carbonate include the following compounds.

[0102] As X 1 ~X 4 Specific examples of the fluorinated saturated cyclic carbonate ester in which at least one of the atoms in the ester is -F include the following compounds.

[0103] These compounds have high withstand voltage and good solubility of electrolyte salts.

[0104] In addition, the following compounds may also be used:

[0105]

[0106] wait.

[0107] As X 1 ~X 4 Specific examples of the fluorinated saturated cyclic carbonate in which at least one of the fluorinated alkyl groups (a) is a fluorinated alkyl group and all the others are -H include the following compounds:

[0108]

[0109]

[0110]

[0111] wait.

[0112] As X 1 ~X 4 Specific examples of fluorinated saturated cyclic carbonates in which at least one of the fluorinated alkyl groups (b) or fluorinated alkoxy groups (c) having an ether bond and the rest are all -H include the following compounds:

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119] wait.

[0120] Among them, as the fluorinated saturated cyclic carbonate ester, any one of the following compounds is preferred.

[0121]

[0122]

[0123] Among these, the fluorinated saturated cyclic carbonate is more preferably fluorinated ethylene carbonate, difluoroethylene carbonate, trifluoromethylethylene carbonate (3,3,3-trifluoropropylene carbonate), or 2,2,3,3,3-pentafluoropropylethylene carbonate.

[0124] Examples of the fluorinated saturated cyclic carbonates include trans-4,5-difluoro-1,3-dioxolane-2-one, 5-(1,1-difluoroethyl)-4,4-difluoro-1,3-dioxolane-2-one, 4-methylene-1,3-dioxolane-2-one, 4-methyl-5-trifluoromethyl-1,3-dioxolane-2-one, 4-ethyl-5-fluoro-1,3-dioxolane-2-one, 4-ethyl-5,5-difluoro-1,3-dioxolane-2-one, pentane-2-one, 4-ethyl-4,5-difluoro-1,3-dioxolane-2-one, 4-ethyl-4,5,5-trifluoro-1,3-dioxolane-2-one, 4,4-difluoro-5-methyl-1,3-dioxolane-2-one, 4-fluoro-5-methyl-1,3-dioxolane-2-one, 4-fluoro-5-trifluoromethyl-1,3-dioxolane-2-one, 4,4-difluoro-1,3-dioxolane-2-one, trifluoromethyl ethylene carbonate, etc.

[0125] The fluorinated unsaturated cyclic carbonate is a cyclic carbonate having an unsaturated bond and a fluorine atom, and is preferably a fluorinated ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond, and specifically includes 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, and the like.

[0126] It should be noted that the above-mentioned fluorinated cyclic carbonate is not limited to the above-mentioned specific examples. In addition, the above-mentioned fluorinated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0127] The content of the fluorinated cyclic carbonate is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and even more preferably 15 to 45% by volume based on the solvent.

[0128] When above-mentioned solvent contains above-mentioned fluorinated cyclic carbonate, preferably contain compound (1) and the above-mentioned fluorinated cyclic carbonate of 10~100 volume % in total.As above-mentioned content, total more preferably more than 20 volume %, further preferably more than 30 volume %, particularly preferably more than 40 volume %, more preferably below 95 volume %, further preferably below 90 volume %, particularly preferably below 85 volume %.

[0129] When the solvent contains the fluorinated cyclic carbonate, the volume ratio of compound (1) to the fluorinated cyclic carbonate is preferably 10 / 90 to 95 / 5, more preferably 15 / 85 or more, further preferably 20 / 80 or more, particularly preferably 30 / 70 or more, and more preferably 90 / 10 or less.

[0130] From the viewpoint of being able to be suitably used even at a high voltage, the solvent preferably contains a fluorinated chain carbonate.

[0131] Examples of the fluorinated chain carbonate include compounds represented by the general formula (B). R 2 OCOOR 7 (B) (Where Rf 2 is a fluoroalkyl group having 1 to 7 carbon atoms, R 7 It is an alkyl group having 1 to 7 carbon atoms and may contain fluorine atoms.

[0132] R 2 is a fluoroalkyl group having 1 to 7 carbon atoms, R 7 It is an alkyl group having 1 to 7 carbon atoms and which may contain a fluorine atom. The fluorinated alkyl group is a group in which at least one of the hydrogen atoms in the alkyl group is replaced by a fluorine atom. 7 When it is an alkyl group containing a fluorine atom, it is referred to as a fluoroalkyl group. From the perspective of low viscosity, Rf 2 and R 7 The number of carbon atoms is preferably 1-7, more preferably 1-2. If the number of carbon atoms is too large, the low-temperature characteristics may be reduced or the solubility of the electrolyte salt may be reduced. If the number of carbon atoms is too small, the solubility of the electrolyte salt may be reduced, the discharge efficiency may be reduced, and the viscosity may be increased.

[0133] Examples of the fluorinated alkyl group having 1 carbon atom include CFH2-, CF2H-, CF3-, etc. CFH2- or CF3- is particularly preferred in terms of high temperature storage characteristics.

[0134] As the fluorinated alkyl group having 2 or more carbon atoms, preferably, a fluorinated alkyl group represented by the following general formula (d-1) can be exemplified from the viewpoint of good solubility of the electrolyte salt. R 1 -R 2 -(d-1) (Where 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; wherein R 1 and R 2 At least one of them has a fluorine atom) It should be noted that R 1 and R 2 It may further have atoms other than carbon atoms, hydrogen atoms and fluorine atoms.

[0135] R 1 It is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. 1 , preferably a linear or branched alkyl group having 1 to 6 carbon atoms. 1 The number of carbon atoms in the moiety is more preferably 1-6, and even more preferably 1-3.

[0136] As R 1 Specifically, there can be mentioned CH3-, CF3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2-, CH3CH2CH2CH2-,

[0137]

[0138] wait.

[0139] In addition, in R 1 In the case of a linear alkyl group having a fluorine atom, examples include CF3-, CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CF2CH2CF2-, CF3CH2CH2CH2CH2-, CF3CF2CH2CH2 -, CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3CF2CF2 CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2CF2CH 2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, HCF2CF2CF 2CF2CH2CH2-, FCH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, FCH2CF2CF2-, CH3CF2CH2-, CH3CF2CF2-, CH3CF2CH2CF2-, CH3C F2CF2CF2-, CH3CH2CF2CF2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2C H2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, HCFClCF2CH2-, HCF2CFClCH2-, HCF2CFClCF2CFClCH2-, HFCClCF2CFClCF2CH2-, etc.

[0140] In addition, in R 1 In the case of a branched alkyl group having a fluorine atom, preferably, the following groups are mentioned.

[0141]

[0142]

[0143] However, if there is a side chain such as CH3- or CF3-, the viscosity tends to be high, and therefore, the number thereof is preferably small (one) or zero.

[0144] R 2 It is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom. 2 It may be linear or branched. An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below. 2 It is composed of one or a combination of them.

[0145] (i) The smallest structural unit of a straight chain: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0146] (ii) The smallest structural unit of a branched chain:

[0147]

[0148] In addition, among the above examples, it is preferable to be composed of a structural unit containing no Cl from the viewpoint of not causing a dehydrochlorination reaction by a base and being more stable.

[0149] R 2 When it is linear, it is composed only of the linear minimum structural unit, and -CH2-, -CH2CH2- or -CF2- are preferred. -CH2- or -CH2CH2- is more preferred because it can further improve the solubility of the electrolyte salt.

[0150] R 2 When the branched chain is present, it contains at least one of the branched chain minimum structural units, and preferably, the general formula: a X b )-represented group (X a is H, F, CH3 or CF3; X b is CH3 or CF3. b When it is CF3, X a In particular, they can further improve the solubility of the electrolyte salt.

[0151] Specific examples of preferred fluoroalkyl groups include CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CH2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-,

[0152]

[0153]

[0154] wait.

[0155] Among them, as Rf 2 and R 7 The fluorinated alkyl group is preferably CF3-, CF3CF2-, (CF3)2CH-, CF3CH2-, C2F5CH2-, CF3CF2CH2-, HCF2CF2CH2-, CF3CFHCF2CH2-, CFH2-, and CF2H-. In view of high flame retardancy, rate characteristics, and good oxidation resistance, CF3CH2-, CF3CF2CH2-, HCF2CF2CH2-, CFH2-, and CF2H- are more preferred.

[0156] R 7 When it is an alkyl group not containing fluorine atoms, it is an alkyl group having 1 to 7 carbon atoms. 7 The number of carbon atoms in is preferably 1-4, more preferably 1-3.

[0157] Examples of the alkyl group not containing a fluorine atom include CH3-, CH3CH2-, (CH3)2CH-, C3H7-, etc. Among them, CH3- and CH3CH2- are preferred because of their low viscosity and good rate characteristics.

[0158] The preferred fluorine content of the above-mentioned fluorinated linear carbonate is 20~70 mass %.If the fluorine content is the above-mentioned scope, then the compatibility with the solvent and the solubility of the salt can be maintained.The above-mentioned fluorine content is more preferably more than 30 mass %, further preferably more than 35 mass %, more preferably below 60 mass %, further preferably below 50 mass %. In addition, the fluorine content in the present invention is a value calculated according to the following formula based on the structural formula of the above-mentioned fluorinated chain carbonate. {(number of fluorine atoms × 19) / molecular weight of fluorinated chain carbonate} × 100 (%)

[0159] As the fluorinated chain carbonate, any of the following compounds is preferred from the viewpoint of low viscosity.

[0160]

[0161] As the fluorinated chain carbonate, 2,2,2-trifluoroethyl methyl carbonate is more preferable.

[0162] The content of the fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and even more preferably 50 to 80% by volume based on the solvent.

[0163] Above-mentioned solvent preferably contains at least one selected from above-mentioned fluorinated chain carbonate and above-mentioned fluorinated cyclic carbonate, more preferably contains above-mentioned fluorinated chain carbonate and above-mentioned fluorinated cyclic carbonate.The electrolyte that contains the solvent of this composition can be suitably used for the electrochemical device that uses under higher voltage.

[0164] Above-mentioned solvent preferably contains the above-mentioned fluorinated cyclic carbonate and the above-mentioned fluorinated chain carbonate that add up to 10~90 volume %.As above-mentioned content, add up to more than 20 volume %, further be preferably more than 30 volume %, be particularly preferably more than 40 volume %, more preferably below 85 volume %, further be preferably below 80 volume %.

[0165] Above-mentioned solvent contains above-mentioned fluorinated cyclic carbonate and above-mentioned fluorinated chain carbonate under the situation of both; As the volume ratio of above-mentioned fluorinated cyclic carbonate and above-mentioned fluorinated chain carbonate, be preferably 5 / 95~95 / 5; More preferably be more than 10 / 90; Further be preferably more than 20 / 80; Particularly preferably be more than 30 / 70; More preferably be below 80 / 20; Further be preferably below 60 / 40.

[0166] When above-mentioned solvent contains above-mentioned fluorinated cyclic carbonate and above-mentioned fluorinated chain carbonate these two, preferably contain compound (1), above-mentioned fluorinated cyclic carbonate and above-mentioned fluorinated chain carbonate that add up to 10~100 volume %.As above-mentioned content, add up to more preferably more than 20 volume %, further preferably more than 30 volume %, particularly preferably more than 40 volume %, more preferably below 95 volume %, further preferably below 90 volume %, particularly preferably below 85 volume %.

[0167] When the solvent contains both the fluorinated cyclic carbonate and the fluorinated chain carbonate, the volume ratio of compound (1) to the fluorinated cyclic carbonate and the fluorinated chain carbonate is preferably 5 to 45 / 5 to 45 / 10 to 90, more preferably 10 to 40 / 10 to 40 / 20 to 80, further preferably 15 to 40 / 10 to 35 / 25 to 75, and particularly preferably 20 to 40 / 10 to 30 / 30 to 70.

[0168] From the aspect that it can be suitably used even at a high voltage of 4.3 V or more, the above-mentioned solvent also preferably contains a fluorinated chain ester (wherein, compound (1) is not included). As the above-mentioned fluorinated chain ester, from the aspect of good compatibility with other solvents and oxidation resistance, a fluorinated chain ester represented by the following general formula (wherein, compound (1) is not included) is preferred. R 31 COF 32 (Where Rf 31 is a fluoroalkyl group having 1 to 4 carbon atoms, Rf 32 is an alkyl group having 1 to 4 carbon atoms and may contain fluorine atoms)

[0169] As Rf 31 For example, HCF2-, CF3-, CF3CF2-, HCF2CF2-, CH3CF2-, CF3CH2- and the like can be mentioned. Among them, HCF2-, CF3-, CF3CF2-, and CF3CH2- are particularly preferred because of their good viscosity and oxidation resistance.

[0170] As Rf 32 For example, CH3-, C2H5-, CF3-, CF3CF2-, (CF3)2CH-, CF3CH2-, CF3CH2CH2-, CF3CFHCF2CH2-, C2F5CH2-, CF2HCF2CH2-, C2F5CH2CH2-, CF3CF2CH2-, CF3CF2CF2CH2-, etc. can be illustrated. Among them, CH3-, C2H5-, CF3CH2-, and CF3CH2CH2- are particularly preferred in terms of good compatibility with other solvents.

[0171] As specific examples of the above-mentioned fluorinated chain esters, for example, CF3CH2C(=O)OCH3, CF3C(=O)OCH2CH2CF3, CF3C(=O)OCH2C2F5, CF3C(=O)OCH2CF2CF2H, CF3C(=O)OCH2CF3, CF3C(=O)OCH(CF3)2, etc., one or more of which are exemplified, wherein from the perspective of good compatibility with other solvents and rate characteristics, CF3CH2C(=O)OCH3, CF3C(=O)OCH2C2F5, CF3C(=O)OCH2CF2CF2H, CF3C(=O)OCH2CF3, CF3C(=O)OCH(CF3)2, ethyl pentafluorobutyrate, methyl pentafluoropropionate, ethyl pentafluoropropionate, methyl pentafluoroisobutyrate, trifluoromethane, trifluoromethane, trifluoromethane, trifluoroisobutyrate ... Isopropyl fluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, n-butyl trifluoroacetate, 2,2,3,3-tetrafluoropropyl trifluoroacetate, methyl tetrafluoro-2-(methoxy)propionate, methyl difluoroacetate, ethyl difluoroacetate, 2,2-difluoroethyl acetate, 2,2,3,3-tetrafluoropropyl acetate, 2,2,2-trifluoroethyl acetate, 1H,1H-heptafluorobutyl acetate, methyl 4,4,4-trifluorobutyrate, 4 ,4,4-trifluorobutyric acid ethyl ester, 3,3,3-trifluoropropionic acid methyl ester, 3,3,3-trifluoropropionic acid ethyl ester, 3,3,3-trifluoropropionic acid 3,3,3-trifluoropropyl ester, 3-(trifluoromethyl)butyric acid ethyl ester, 2,3,3,3-tetrafluoropropionic acid methyl ester, 2,2-difluoroacetic acid butyl ester, 2,2,3,3-tetrafluoropropionic acid methyl ester, 2-(trifluoromethyl)-3,3,3-trifluoropropionic acid methyl ester, heptafluorobutyric acid methyl ester.

[0172] The content of the fluorinated chain ester (excluding compound (1)) is preferably 5 to 90% by volume, more preferably 15 to 70% by volume, based on the solvent.

[0173] Above-mentioned solvent can also contain at least one fluorinated carbonate selected from above-mentioned fluorinated chain carbonate and above-mentioned fluorinated cyclic carbonate ester and above-mentioned fluorinated chain ester (wherein, do not include compound (1)).The electrolyte containing the solvent of this composition can not only be suitably used for the electrochemical device used under relatively low voltage, but also can be suitably used for the electrochemical device used under the higher voltage more than 4.3V.

[0174] When the above-mentioned solvent contains the above-mentioned fluorinated carbonate and the above-mentioned fluorinated chain ester (wherein, excluding compound (1)), it is preferred to contain 10 to 90% by volume of the above-mentioned fluorinated carbonate and the above-mentioned fluorinated chain ester in total. As the above-mentioned content, the total is more preferably more than 20% by volume, more preferably more than 30% by volume, particularly preferably more than 40% by volume, more preferably less than 85% by volume, and more preferably less than 80% by volume.

[0175] When the solvent contains the fluorinated carbonate and the fluorinated chain ester (excluding compound (1)), the volume ratio of the fluorinated carbonate to the fluorinated chain ester is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 or more, further preferably 20 / 80 or more, particularly preferably 30 / 70 or more, and more preferably 90 / 10 or less.

[0176] In addition, as the above-mentioned solvent, an ionic liquid may also be used. An “ionic liquid” is a liquid formed of ions that are a combination of organic cations and anions.

[0177] The organic cation is not particularly limited, and examples thereof include imidazolium ions such as dialkylimidazolium cations and trialkylimidazolium cations; tetraalkylammonium ions; alkylpyridinium ions; dialkylpyrrolidinium ions; and dialkylpiperidinium ions.

[0178] There is no particular limitation on the anions that serve as counterions to these organic cations, and for example, PF6 anion, PF3(C2F5)3 anion, PF3(CF3)3 anion, BF4 anion, BF2(CF3)2 anion, BF3(CF3) anion, bis(oxalatoborate) anion, P(C2O4)F2 anion, Tf(trifluoromethanesulfonyl) anion, Nf(nonafluorobutanesulfonyl) anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethanesulfonyl)imide anion, bis(pentafluoroethanesulfonyl)imide anion, dicyanoamide anion, and halide anion can be used.

[0179] The above-mentioned solvent is preferably composed only of a compound having fluorine atoms (fluorinated solvent). Furthermore, the above-mentioned solvent is preferably a non-aqueous solvent, and the electrolyte solution of the present invention is preferably a non-aqueous electrolyte solution.

[0180] The electrolytic solution of the present invention may further contain a compound (5) represented by the general formula (5).

[0181] General formula (5): (In the formula, A a+ is a metal ion, a hydrogen ion or an onium ion. a is an integer from 1 to 3, b is an integer from 1 to 3, p is b / a, n 203 is an integer from 1 to 4, n 201 is an integer from 0 to 8, n 202 is 0 or 1, Z 201 It is a transition metal, an element of Group III, Group IV or Group V of the periodic table. X 201O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (the alkylene group, the halogenated alkylene group, the arylene group, and the halogenated arylene group may have a substituent or a heteroatom in their structure, and in addition, 202 is 1, n 203 When n is 2 to 4, 203 X 201 Each can be bonded.) L 201 is a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms (the alkylene group, the halogenated alkylene group, the arylene group, and the halogenated arylene group may have a substituent or a heteroatom in their structure, and in addition, 201 When n is 2 to 8, 201 L 201 may be bonded to form a ring) or -Z 203 Y 203 . Y 201 , Y 202 and Z 203 Each independently is O, S, NY 204 , hydrocarbon group or fluorinated hydrocarbon group. 203 and Y 204 Each of them is independently H, F, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms (the alkyl group, the halogenated alkyl group, the aryl group, and the halogenated aryl group may have a substituent or a heteroatom in their structure. When there are multiple Y 203 or Y 204 When they are bonded to form a ring)

[0182] As A a+ , lithium ion, sodium ion, potassium ion, magnesium ion, calcium ion, barium ion, cesium ion, silver ion, zinc ion, copper ion, cobalt ion, iron ion, nickel ion, manganese ion, titanium ion, lead ion, chromium ion, vanadium ion, ruthenium ion, yttrium ion, lanthanide ion, actinide ion, tetrabutylammonium ion, tetraethylammonium ion, tetramethylammonium ion, triethylmethylammonium ion, triethylammonium ion, pyridinium ion, imidazolium ion, hydrogen ion, tetraethylphosphonium ion, tetramethylphosphonium ion, tetraphenylphosphonium ion, triphenylsulfonium ion, triethylsulfonium ion and the like can be mentioned.

[0183] When used in electrochemical devices, A a+ Preferred are lithium ions, sodium ions, magnesium ions, tetraalkylammonium ions, and hydrogen ions, and lithium ions are particularly preferred. a+The valence a of the cation is an integer of 1 to 3. When it is greater than 3, the lattice energy becomes large, which may cause a problem of difficulty in dissolving in a solvent. Therefore, when solubility is required, it is more preferably 1. The valence b of the anion is also an integer of 1 to 3, and is particularly preferably 1. The constant p representing the ratio of the cation to the anion is necessarily determined by the ratio b / a of the valences of the two.

[0184] Next, the ligand part of the general formula (5) is described. In this specification, the ligand Z in the general formula (5) is 201 The bonded organic or inorganic moieties are called ligands.

[0185] Z 201 Preferred are Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf or Sb, more preferred are Al, B or P.

[0186] X 201 represents O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms. These alkylene groups and arylene groups may have a substituent or a heteroatom in their structure. Specifically, a halogen atom, a chain or cyclic alkyl group, an aryl group, an alkenyl group, an alkoxy group, an aryloxy group, a sulfonyl group, an amino group, a cyano group, a carbonyl group, an acyl group, an amide group, or a hydroxyl group may be used as a substituent to replace the hydrogen on the alkylene group and the arylene group, and a structure in which nitrogen, sulfur, or oxygen is introduced to replace the carbon on the alkylene group and the arylene group may be used. In addition, in n 202 is 1, n 203 When n is 2 to 4, 203 X 201 Each of them can be bonded. As such an example, a ligand such as ethylenediaminetetraacetic acid can be mentioned.

[0187] L 201 represents a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms, or -Z 203 Y 203 (About Z 203 , Y 203 The alkyl and aryl groups may also be 201 Similarly, there are substituents and heteroatoms in its structure. 201 When n is 2 to 8, 201 L 201 Each of them may be bonded to form a ring. 201, preferably a fluorine atom or a cyano group. The reason is that, in the case of a fluorine atom, the solubility and dissociation degree of the salt of the anionic compound are improved, and with this, the ion conductivity is improved. In addition, the oxidation resistance is improved, thereby being able to suppress the occurrence of side reactions.

[0188] Y 201 , Y 202 and Z 203 Each independently represents O, S, NY 204 , hydrocarbon group or fluorinated hydrocarbon group. 201 and Y 202 Preferably O, S or NY 204 , more preferably O. As a feature of compound (5), due to the presence of Y in the same ligand 201 and Y 202 Composed of Z 201 bonds, so these ligands are bound to Z 201 The chelate structure is formed. Through the chelate effect, the heat resistance, chemical stability and hydrolysis resistance of the compound are improved. The constant n in the ligand 202 It is 0 or 1, and is particularly preferred when it is 0 because the chelate ring is a five-membered ring and the chelate effect is most strongly exerted and the stability is increased. In addition, in this specification, a fluorinated hydrocarbon group is a group in which at least one hydrogen atom of a hydrocarbon group is substituted with a fluorine atom.

[0189] Y 203 and Y 204 Each of them is independently H, F, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms. These alkyl groups and aryl groups may have a substituent or a heteroatom in their structure. In addition, when there are multiple Y 203 or Y 204 When , they may be bonded to each other to form a ring.

[0190] In addition, the constant n related to the number of ligands mentioned above 203 is an integer of 1 to 4, preferably 1 or 2, and more preferably 2. In addition, the constant n related to the number of the ligands is 201 is an integer of 0 to 8, preferably an integer of 0 to 4, more preferably 0, 2 or 4. 203 When n is 1 201 Preferably 2, in n 203 When n is 2, 201 Preferably 0.

[0191] In the general formula (5), the alkyl group, the halogenated alkyl group, the aryl group, and the halogenated aryl group also include groups having other functional groups such as branches, hydroxyl groups, and ether bonds.

[0192] As compound (5), a compound represented by the following general formula is preferred: (In the formula, A a+ ,a,b,p,n 201 , Z 201 and L 201 as above), or, (In the formula, A a+ ,a,b,p,n 201 , Z 201 and L 201 as described above).

[0193] Examples of compound (5) include lithium oxalate borate salts, which may be represented by the following formula: Lithium bis(oxalatoborate) (LIBOB) is represented by the following formula: Lithium difluorooxalate borate (LIDFOB)

[0194] Compound (5) also includes compounds represented by the following formula: Lithium difluorooxalate phosphate (LIDFOP) is represented by the following formula: Lithium tetrafluorooxalate phosphate (LITFOP) is represented by the following formula: Representing lithium difluorobis(oxalate)phosphate, etc.

[0195] In addition, specific examples of dicarboxylic acid complex salts in which the central element of the complex is boron include lithium bis(malonate)borate, lithium difluoro(malonate)borate, lithium bis(methylmalonate)borate, lithium difluoro(methylmalonate)borate, lithium bis(dimethylmalonate)borate, lithium difluoro(dimethylmalonate)borate, and the like.

[0196] Specific examples of dicarboxylic acid complex salts in which the central element of the complex is phosphorus include lithium trioxalate phosphate, lithium tri(malonate) phosphate, lithium difluorobis(malonate) phosphate, lithium tetrafluoro(malonate) phosphate, lithium tri(methylmalonate) phosphate, lithium difluorobis(methylmalonate) phosphate, lithium tetrafluoro(methylmalonate) phosphate, lithium tri(dimethylmalonate) phosphate, lithium difluorobis(dimethylmalonate) phosphate, lithium tetrafluoro(dimethylmalonate) phosphate, and the like.

[0197] Specific examples of dicarboxylic acid complex salts in which the central element of the complex is aluminum include LiAl(C2O4)2, LiAlF2(C2O4) and the like.

[0198] Among them, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium trioxalatephosphate, lithium difluorobis(oxalatophosphate), and lithium tetrafluorooxalatephosphate are more preferably used in view of the availability and the contribution to the formation of a stable film-like structure.

[0199] The content of the compound (5) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and is preferably 10% by mass or less, more preferably 3% by mass or less, based on the solvent, in order to obtain better cycle characteristics.

[0200] The electrolyte of the present invention preferably further contains an electrolyte salt (excluding lithium fluorosulfonate (FSO3Li) and compound (5)). As the above-mentioned electrolyte salt, in addition to lithium salts, ammonium salts, and metal salts, any electrolyte salt that can be used in an electrolyte such as a liquid salt (ionic liquid), an inorganic polymer salt, or an organic polymer salt can also be used.

[0201] As the electrolyte salt of the electrolyte solution for lithium ion secondary batteries, lithium salts (excluding lithium fluorosulfonate (FSO3Li) and compound (5)) are preferred. As the lithium salt, any lithium salt can be used, and specifically, the following lithium salts can be mentioned. For example, LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiTaF6, LiWF7, LiAsF6, LiAlCl4, LiI, LiBr, LiCl, LiB 10 Cl 10 , Li2SiF6, Li2PFO3, LiPO2F2 and other inorganic lithium salts; Lithium tungstate such as LiWOF5; Lithium carboxylates such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li; Lithium salts having an S=O group, such as CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li, methyl lithium sulfate, ethyl lithium sulfate, 2,2,2-trifluoroethyl lithium sulfate (excluding lithium fluorosulfonate (FSO3Li)); Lithium imide salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium bis(perfluoroethanesulfonyl imide), lithium cyclic 1,2-perfluoroethanedisulfonyl imide, lithium cyclic 1,3-perfluoropropanedisulfonyl imide, lithium cyclic 1,2-ethanedisulfonyl imide, lithium cyclic 1,3-propanedisulfonyl imide, lithium cyclic 1,4-perfluorobutanedisulfonyl imide, LiN(CF3SO2)(FSO2), LiN(CF3SO2)(C3F7SO2), LiN(CF3SO2)(C4F9SO2), and LiN(POF2)2; Methylated lithium salts such as LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3; In addition, LiPF a (C n F 2n+1 ) 6－a (wherein a is an integer from 0 to 5, and n is an integer from 1 to 6) (for example, LiPF3(C2F5)3, LiPF3(CF3)3, LiPF3(iso-C3F7)3, LiPF5(iso-C3F7), LiPF4(CF3)2, LiPF4(C2F5)2), LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2, etc., fluorine-containing organic lithium salts, LiSCN, LiB(CN)4, LiB(C6H5)4, Li2(C2O4), LiP(C2O4), Li2B 12 F b H 12－b (b is an integer from 0 to 3), etc.

[0202] Among them, from the viewpoint of having the effects of improving power characteristics, high-rate charge and discharge characteristics, high-temperature storage characteristics, cycle characteristics, etc., LiPF6, LiBF4, LiSbF6, LiTaF6, LiPO2F2, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethanedisulfonyl imide lithium, cyclic 1,3-perfluoropropanedisulfonyl imide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, etc. are particularly preferred.

[0203] These electrolyte salts can be used alone or in combination of two or more. A preferred example of using two or more is the combination of LiPF6 and LiBF4, or the combination of LiPF6 and LiPO2F2, which has the effect of improving load characteristics and cycle characteristics.

[0204] At this time, the amount of LiBF4 and LiPO2F2 contained in the electrolyte solution as a whole is not limited, and can be any amount as long as it does not significantly impair the effect of the present invention. It is usually 0.01% by mass or more, preferably 0.1% by mass or more, and is usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less, relative to the electrolyte solution of the present invention.

[0205] In addition, another example is the use of an inorganic lithium salt and an organic lithium salt, which has the effect of inhibiting deterioration caused by high temperature storage. As an organic lithium salt, preferably CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethane disulfonyl imide lithium, cyclic 1,3-perfluoropropane disulfonyl imide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, etc. At this time, the ratio of the organic lithium salt relative 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 20% by mass or less.

[0206] The concentration of these electrolyte salts in the electrolyte is not particularly limited as long as it does not damage the effect of the present invention. From the aspect of making the conductivity of the electrolyte a good range and ensuring good battery performance, the total molar concentration of lithium in the electrolyte is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, further preferably 0.5 mol / L or more, and in addition, preferably 3 mol / L or less, more preferably 2.5 mol / L or less, and further preferably 2.0 mol / L or less.

[0207] When the total molar concentration of lithium is too low, the conductivity of the electrolyte may be insufficient. On the other hand, when the concentration is too high, the conductivity may decrease due to an increase in viscosity, and the battery performance may decrease.

[0208] As the electrolyte salt of the electrolytic solution for an electric double layer capacitor, an ammonium salt is preferable. Examples of the ammonium salt include the following (IIa) to (IIe). (IIa) Tetraalkyl quaternary ammonium salt Preferred examples include tetraalkyl quaternary ammonium salts represented by the general formula (IIa).

[0209] (Where R 1a , R 2a , R 3a and R 4a are the same or different, and are all alkyl groups having 1 to 6 carbon atoms and may contain ether bonds; － for anions) Furthermore, from the viewpoint of improving oxidation resistance, a compound in which a part or all of the hydrogen atoms of the ammonium salt are substituted with fluorine atoms and / or a fluorine-containing alkyl group having 1 to 4 carbon atoms is also preferred.

[0210] As a specific example, the following may be mentioned:

[0211] (Where R 1a , R 2a and X － Same as above; x and y are the same or different, and are integers from 0 to 4, and x+y=4) The tetraalkyl quaternary ammonium salt represented by the general formula (IIa-2):

[0212] (Where 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 －for anions) The alkyl ether group-containing trialkyl ammonium salt represented by the above-mentioned can reduce the viscosity by introducing the alkyl ether group.

[0213] Anion X － It can be an inorganic anion or an organic anion. Examples of inorganic anions include AlCl4 － 、BF4 － PF6 － 、AsF6 － 、TaF6 － ,I － 、SbF6 － Examples of organic anions include bis(oxalatoborate) anions, difluorooxalatoborate anions, tetrafluorooxalatophosphate anions, difluorobis(oxalatophosphate) anions, CF3COO － CF3SO3 － 、(CF3SO2)2N － 、(C2F5SO2)2N － wait.

[0214] Among them, BF4 is preferred from the viewpoint of good oxidation resistance and ion dissociation. － PF6 － 、AsF6 － 、SbF6 － .

[0215] Preferred specific examples of tetraalkylammonium salts include Et4NBF4, Et4NClO4, Et4NPF6, Et4NAsF6, Et4NSbF6, Et4NCF3SO3, Et4N(CF3SO2)2N, Et4NC4F9SO3, Et3MeNBF4, Et3MeNClO4, Et3MeNPF6, Et3MeNAsF6, Et3MeNSbF6, Et3MeNCF3SO3, Et3MeN(CF3SO2)2N, and Et3MeNC4F9SO3. In particular, Et4NBF4, Et4NPF6, Et4NSbF6, Et4NAsF6, Et3MeNBF4, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium salt, and the like can be mentioned.

[0216] (IIb) Spirocyclic Bispyrrolidinium Salt Preferred examples include those represented by the general formula (IIb-1):

[0217] (Where R 8a and R 9a are the same or different and are all alkyl groups with 1 to 4 carbon atoms; －is an anion; n1 is an integer from 0 to 5; n2 is an integer from 0 to 5) The spirocyclic bispyrrolidinium salt represented by the general formula (IIb-2):

[0218] (Where R 10a and R 11a are the same or different and are all alkyl groups with 1 to 4 carbon atoms; － is an anion; n3 is an integer from 0 to 5; n4 is an integer from 0 to 5) A spirocyclic bispyrrolidinium salt represented by the general formula (IIb-3):

[0219] (Where R 12a and R 13a are the same or different and are all alkyl groups with 1 to 4 carbon atoms; － is an anion; n5 is an integer from 0 to 5; n6 is an integer from 0 to 5) In addition, from the viewpoint of improving oxidation resistance, a compound in which a part or all of the hydrogen atoms of the spirobispyrrolidinium salt are substituted with fluorine atoms and / or a fluorine-containing alkyl group having 1 to 4 carbon atoms is also preferred.

[0220] Anion X － The preferred specific examples are the same as those of (IIa). Among them, BF4 is preferred from the perspective of high dissociation and low internal resistance at high voltage. － PF6 － 、(CF3SO2)2N － or (C2F5SO2)2N － .

[0221] Preferred specific examples of the spirobispyrrolidinium salt include the following compounds.

[0222] The spirobispyrrolidinium salt is excellent in solubility in a solvent, oxidation resistance, and ion conductivity.

[0223] (IIc) Imidazolium salt Preferred examples include imidazolium salts represented by general formula (IIc).

[0224] (Where R 14a and R 15a are the same or different and are all alkyl groups with 1 to 6 carbon atoms; － for anions) Furthermore, from the viewpoint of improving oxidation resistance, a compound in which a part or all of the hydrogen atoms of the imidazolium salt are substituted with fluorine atoms and / or a fluorine-containing alkyl group having 1 to 4 carbon atoms is also preferred.

[0225] Anion X － Preferred specific examples are the same as those for (IIa).

[0226] Preferred specific examples include the following compounds.

[0227]

[0228] This imidazolium salt is excellent in that it has low viscosity and good solubility.

[0229] (IId): N-alkylpyridinium salt Preferred examples include N-alkylpyridinium salts represented by general formula (IId).

[0230] (Where R 16a is an alkyl group having 1 to 6 carbon atoms; － for anions) In addition, from the viewpoint of improving oxidation resistance, a compound in which a part or all of the hydrogen atoms of the N-alkylpyridinium salt are substituted with fluorine atoms and / or a fluorine-containing alkyl group having 1 to 4 carbon atoms is also preferred.

[0231] Anion X － Preferred specific examples are the same as those for (IIa).

[0232] Preferred specific examples include the following compounds.

[0233]

[0234] This N-alkylpyridinium salt is excellent in that it has low viscosity and good solubility.

[0235] (IIe) N,N-dialkylpyrrolidinium salt Preferred examples include N,N-dialkylpyrrolidinium salts represented by the general formula (IIe).

[0236] (Where R 17a and R 18a are the same or different and are all alkyl groups with 1 to 6 carbon atoms; － for anions) In addition, from the viewpoint of improving oxidation resistance, a compound in which a part or all of the hydrogen atoms of the N,N-dialkylpyrrolidinium salt are substituted with fluorine atoms and / or a fluorine-containing alkyl group having 1 to 4 carbon atoms is also preferred.

[0237] Anion X － Preferred specific examples are the same as those for (IIa).

[0238] Preferred specific examples include the following compounds.

[0239]

[0240]

[0241] This N,N-dialkylpyrrolidinium salt is excellent in that it has low viscosity and good solubility.

[0242] Among these ammonium salts, (IIa), (IIb) and (IIc) are preferred in terms of good solubility, oxidation resistance and ion conductivity, and more preferred are

[0243] (wherein, Me is methyl; Et is ethyl; X － , x, and y are the same as those in formula (IIa-1)).

[0244] In addition, as the electrolyte salt for the electric double layer capacitor, a lithium salt can be used. As the lithium salt, for example, LiPF6, LiBF4, LiN(FSO2)2, LiAsF6, LiSbF6, LiN(SO2C2H5)2 is preferred. In order to further increase the capacity, a magnesium salt may be used. As the magnesium salt, for example, Mg(ClO4)2, Mg(OOC2H5)2, etc. are preferred.

[0245] When the electrolyte salt is the above-mentioned ammonium salt, the concentration is preferably 0.7 mol / L or more. If it is less than 0.7 mol / L, there is a possibility that not only the low temperature characteristics will deteriorate, but also the initial internal resistance will increase. The concentration of the above-mentioned electrolyte salt is more preferably 0.9 mol / L or more. From the viewpoint of low-temperature characteristics, the upper limit of the above concentration is preferably 2.0 mol / L or less, and more preferably 1.5 mol / L or less. When the ammonium salt is methyltriethylammonium tetrafluoroborate (TEMABF4), the concentration thereof is preferably 0.7 to 1.5 mol / L in terms of excellent low temperature characteristics. In the case of spirobipyrrolidinium tetrafluoroborate (SBPBF4), the concentration is preferably 0.7 to 2.0 mol / L.

[0246] The electrolytic solution of the present invention preferably further contains a compound (2) represented by the general formula (2). (Where X 21 is a group containing at least H or C, n21 is an integer from 1 to 3, Y 21 and Z 21 are the same or different and are groups containing at least H, C, O or F, n 22 is 0 or 1, Y 21 and Z 21 (the compounds may be bonded to each other to form a ring). When the electrolyte solution contains the compound (2), the capacity retention rate is unlikely to further decrease and the amount of gas generated is unlikely to further increase even when stored at high temperatures.

[0247] In n 21 When it is 2 or 3, 2 or 3 X 21 Can be the same or different. In the presence of multiple Y 21 and Z 21 When there are multiple Y 21 and Z 21 Can be the same or different.

[0248] As X 21 , preferably by -CY 21 Z 21 -(where Y 21 and Z 21 as above) or -CY 21 =CZ 21 -(where Y 21 and Z 21 As described above).

[0249] As Y 21 , preferably at least one selected from the group consisting of H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-. As Z 21 , preferably at least one selected from the group consisting of H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-.

[0250] Or, Y 21 and Z 21 They may be bonded to each other to form a carbocyclic ring or a heterocyclic ring which may contain an unsaturated bond and may have aromaticity. The number of carbon atoms in the ring is preferably 3 to 20.

[0251] Next, a specific example of compound (2) is described. It should be noted that in the following examples, "analogs" refer to anhydrides obtained by replacing a part of the structure of the exemplified anhydride with other structures within the scope of not violating the main purpose of the present invention, for example, dimers, trimers and tetramers composed of multiple anhydrides, or structural isomers such as having the same number of carbon atoms in the substituent but with branches, anhydrides in which the substituent is bonded to the anhydride at different locations, etc.

[0252] Specific examples of the acid anhydride having a five-membered ring structure include succinic anhydride, methylsuccinic anhydride (4-methylsuccinic anhydride), dimethylsuccinic anhydride (4,4-dimethylsuccinic anhydride, 4,5-dimethylsuccinic anhydride, etc.), 4,4,5-trimethylsuccinic anhydride, 4,4,5,5-tetramethylsuccinic anhydride, 4-vinylsuccinic anhydride, 4,5-divinylsuccinic anhydride, phenylsuccinic anhydride (4-phenylsuccinic anhydride), 4,5 -diphenylsuccinic anhydride, 4,4-diphenylsuccinic anhydride, citraconic anhydride, maleic anhydride, methylmaleic anhydride (4-methylmaleic anhydride), 4,5-dimethylmaleic anhydride, phenylmaleic anhydride (4-phenylmaleic anhydride), 4,5-diphenylmaleic anhydride, itaconic anhydride, 5-methylitaconic anhydride, 5,5-dimethylitaconic anhydride, phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, and the like, and the like.

[0253] Specific examples of the acid anhydride having a six-membered ring structure include cyclohexanedicarboxylic anhydride (cyclohexane-1,2-dicarboxylic anhydride, etc.), 4-cyclohexene-1,2-dicarboxylic anhydride, glutaric anhydride, glutaconic anhydride, 2-phenylglutaric anhydride, and the like, and analogs thereof.

[0254] Specific examples of the acid anhydride having another cyclic structure include 5-norbornene-2,3-dicarboxylic anhydride, cyclopentanetetracarboxylic anhydride, pyromellitic anhydride, diglycolic anhydride, and the like, and analogs thereof.

[0255] Specific examples of the acid anhydride having a cyclic structure and substituted with a halogen atom include monofluorosuccinic anhydride (such as 4-fluorosuccinic anhydride), 4,4-difluorosuccinic anhydride, 4,5-difluorosuccinic anhydride, 4,4,5-trifluorosuccinic anhydride, trifluoromethylsuccinic anhydride, tetrafluorosuccinic anhydride (4,4,5,5-tetrafluorosuccinic anhydride), 4-fluoromaleic anhydride, 4,5-difluoromaleic anhydride, trifluoromethylmaleic anhydride, 5-fluoroitaconic anhydride, 5,5-difluoroitaconic anhydride, and the like, and analogs thereof.

[0256] Among them, preferred examples of compound (2) include glutaric anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic anhydride, 4-cyclohexene-1,2-dicarboxylic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, phenylsuccinic anhydride, 2-phenylglutaric anhydride, maleic anhydride, methylmaleic anhydride, trifluoromethylmaleic anhydride, phenylmaleic anhydride, succinic anhydride, methylsuccinic anhydride, dimethylsuccinic anhydride, trifluoromethylsuccinic anhydride, monofluorosuccinic anhydride, tetrafluorosuccinic anhydride, and phthalic anhydride. More preferred examples include maleic anhydride, methylmaleic anhydride, trifluoromethylmaleic anhydride, succinic anhydride, methylsuccinic anhydride, trifluoromethylsuccinic anhydride, tetrafluorosuccinic anhydride, and phthalic anhydride.

[0257] The compound (2) is preferably at least one selected from the group consisting of the compound (3) represented by the general formula (3), the compound (4) represented by the general formula (4) and phthalic anhydride, and more preferably at least one selected from the compound (3) and the compound (4).

[0258] General formula (3): (Where X 31 ~X 34 The same or different groups contain at least H, C, O or F. General formula (4):

[0259] (Where X 41 and X 42 The same or different groups contain at least H, C, O or F.

[0260] As X 31 ~X 34 , which are the same or different, are preferably at least one selected from an alkyl group, a fluoroalkyl group, an alkenyl group and a fluoroalkenyl group. 31 ~X 34 The number of carbon atoms in is preferably 1-10, more preferably 1-3.

[0261] As X 31 ~X 34 , the same or different, more preferably at least one selected from H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-.

[0262] As X 41 and X 42 , which are the same or different, are preferably at least one selected from an alkyl group, a fluoroalkyl group, an alkenyl group and a fluoroalkenyl group.41 and X 42 The number of carbon atoms in is preferably 1-10, more preferably 1-3.

[0263] As X 41 and X 42 , the same or different, more preferably at least one selected from H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-.

[0264] As compound (3), any of the following compounds is preferred.

[0265]

[0266] As compound (4), any of the following compounds is preferred.

[0267]

[0268] Even when the electrolyte is stored at high temperature, the capacity retention rate is difficult to further decrease and the amount of gas generated is difficult to further increase. Therefore, it is preferred that the electrolyte contains 0.0001 to 15% by mass of compound (2). The content of compound (2) is more preferably 0.01 to 10% by mass, more preferably 0.1 to 3% by mass, and particularly preferably 0.1 to 1.0% by mass.

[0269] When the electrolyte contains both compounds (3) and (4), the capacity retention rate is unlikely to be further reduced and the amount of gas generated is unlikely to be further increased even when stored at high temperatures. Therefore, the electrolyte preferably contains 0.08 to 2.50 mass % of compound (3) and 0.02 to 1.50 mass % of compound (4) relative to the electrolyte, and more preferably contains 0.80 to 2.50 mass % of compound (3) and 0.08 to 1.50 mass % of compound (4).

[0270] The electrolytic solution of the present invention may further contain at least one selected from the group consisting of nitrile compounds represented by the following general formulae (1a), (1b) and (1c). (Where R a and R b Each independently represents a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are substituted with a halogen atom. n represents an integer of 1 to 10. (Where R crepresents a hydrogen atom, a halogen atom, an alkyl group, a group in which at least part of the hydrogen atoms of an alkyl group are substituted with halogen atoms, or a group consisting of NC—R c1 -X c1 -(R c1 represents an alkylene group, X c1 represents an oxygen atom or a sulfur atom). d and R e Each independently represents a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are substituted with a halogen atom. m represents an integer of 1 to 10. (Where R f , R g , R h and R i Each independently represents a group containing a cyano group (CN), a hydrogen atom (H), a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are substituted with a halogen atom. f , R g , R h and R i At least one of the groups is a group containing a cyano group. l represents an integer of 1 to 3.) This can improve the high temperature storage characteristics of the electrochemical device. The above-mentioned nitrile compounds may be used alone or in combination of two or more in any ratio.

[0271] In the above general formula (1a), R a and R b Each independently represents a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, among which a fluorine atom is preferred. The alkyl group is preferably an alkyl group having 1 to 5 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group. Examples of the group in which at least a part of the hydrogen atoms of the alkyl group are substituted with halogen atoms include groups in which at least a part of the hydrogen atoms of the above-mentioned alkyl group are substituted with the above-mentioned halogen atoms. In R a and R b When it is an alkyl group or a group in which at least part of the hydrogen atoms of the alkyl group are substituted with halogen atoms, R a With R b They may be bonded to each other to form a ring structure (eg, a cyclohexane ring). R a and R bA hydrogen atom or an alkyl group is preferred.

[0272] In the above general formula (1a), n is an integer of 1 to 10. When n is 2 or more, the n Ra may be completely the same or at least partially different. b The same applies. n is preferably an integer of 1-7, and more preferably an integer of 2-5.

[0273] As the nitrile compound represented by the above general formula (1a), dinitriles and trinitriles are preferred. Specific examples of dinitriles include malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, octanonitrile, azelaic acid, sebaconitrile, undecane dicarbonitrile, dodecane dicarbonitrile, methyl malononitrile, ethyl malononitrile, isopropyl malononitrile, tert-butyl malononitrile, methyl succinonitrile, 2,2-dimethyl succinonitrile, 2,3-dimethyl succinonitrile, 2,3,3-trimethyl succinonitrile, 2,2,3,3-tetramethyl succinonitrile, 2,3-diethyl-2,3-dimethyl succinonitrile, 2,2-diethyl-3,3-dimethyl succinonitrile, bicyclohexane-1,1-dicarbonitrile, bicyclohexane-2,2-dicarbonitrile, bicyclohexane-3,3-dicarbonitrile, 2,5-dimethyl-2,5-hexane dicarbonitrile, 2,3-diisobutyl-2,3-dimethyl succinonitrile, 2,2 ... Butyl-3,3-dimethylsuccinonitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7 ...2,3,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, 2,3,3,4- Cyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3'-(ethylenedioxy)dipropionitrile, 3,3'-(ethylenedithio)dipropionitrile, 3,9-bis(2-cyanoethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, butyronitrile, phthalonitrile, etc. Among these, succinonitrile, glutaronitrile, and adiponitrile are particularly preferred. Specific examples of the trinitriles include pentaerythritol, propane tricarbonitrile, 1,3,5-hexane tricarbonitrile, 1,3,6-hexane tricarbonitrile, heptane tricarbonitrile, 1,2,3-propane tricarbonitrile, 1,3,5-pentane tricarbonitrile, cyclohexane tricarbonitrile, tricyanoethylamine, tricyanoethoxypropane, tricyanoethylene, tris(2-cyanoethyl)amine, and the like. 1,3,6-hexane tricarbonitrile and cyclohexane tricarbonitrile are particularly preferred, and cyclohexane tricarbonitrile is most preferred.

[0274] In the above general formula (1b), R c A hydrogen atom, a halogen atom, an alkyl group, a group in which at least part of the hydrogen atoms of an alkyl group are substituted with halogen atoms, or a group consisting of NC-Rc1 -X c1 -(R c1 represents an alkylene group, X c1 represents an oxygen atom or a sulfur atom), R d and R e Each independently represents a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are substituted with a halogen atom. Examples of the halogen atom, the alkyl group, and the group in which at least a part of the hydrogen atoms of the alkyl group are substituted with a halogen atom include the groups exemplified in the above-mentioned general formula (1a). The above NC-R c1 -X c1 -R c1 The alkylene group is preferably an alkylene group having 1 to 3 carbon atoms. R c , R d and R e Preferably, each independently is a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are substituted with a halogen atom. R c , R d and R e At least one of them is preferably a halogen atom or a group in which at least a part of the hydrogen atoms of the alkyl group are substituted with a halogen atom, and more preferably a fluorine atom or a group in which at least a part of the hydrogen atoms of the alkyl group are substituted with a fluorine atom. In R d and R e When it is an alkyl group or a group in which at least part of the hydrogen atoms of the alkyl group are substituted with halogen atoms, R d With R e They may be bonded to each other to form a ring structure (eg, a cyclohexane ring).

[0275] In the above general formula (1b), m is an integer of 1 to 10. When m is 2 or more, m R d They can be completely the same or at least partially different. e m is preferably an integer of 2-7, and more preferably an integer of 2-5.

[0276] Examples of the nitrile compound represented by the general formula (1b) include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauryl nitrile, 3-methoxypropionitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanecarbonitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3'-thiodipropionitrile, pentafluoropropionitrile, methoxyacetonitrile, and benzonitrile. Among these, 3,3,3-trifluoropropionitrile is particularly preferred.

[0277] In the above general formula (1c), R f , R g , R h and R i Each independently represents a group containing a cyano group (CN), a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are substituted with a halogen atom. Examples of the halogen atom, the alkyl group, and the group in which at least a part of the hydrogen atoms of the alkyl group are substituted with a halogen atom include the groups exemplified in the above-mentioned general formula (1a). Examples of the group containing a cyano group include, in addition to a cyano group, a group in which at least a part of hydrogen atoms of an alkyl group is substituted with a cyano group. Examples of the alkyl group in this case include the alkyl groups exemplified in the above general formula (1a). R f , R g , R h and R i At least one of them is a group containing a cyano group. Preferably, R f , R g , R h and R i At least two of them are groups containing a cyano group, and more preferably, R h and R i is a group containing a cyano group. h and R i When R is a group containing a cyano group, f and R g Preferred is a hydrogen atom.

[0278] In the above general formula (1c), l is preferably an integer of 1 to 3. When l is 2 or more, one R f They can be completely the same or at least partially different. g The same is true for l. l is preferably an integer of 1-2.

[0279] Examples of the nitrile compound represented by the general formula (1c) include 3-hexenedinitrile, hexadienedinitrile, maleonitrile, fumaronitrile, acrylonitrile, methacrylonitrile, butenenitrile, 3-methylbutenenitrile, 2-methyl-2-butenenitrile, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, and 2-hexenenitrile. Preferred are 3-hexenedinitrile and hexadienedinitrile, and particularly preferred is 3-hexenedinitrile.

[0280] The content of the nitrile compound is preferably 0.2 to 7% by mass relative to the electrolyte. Thus, the high temperature storage characteristics and safety of the electrochemical device under high voltage can be further improved. The lower limit of the total content of the nitrile compound is more preferably 0.3% by mass, and more preferably 0.5% by mass. The upper limit is more preferably 5% by mass, more preferably 2% by mass, and particularly preferably 0.5% by mass.

[0281] The electrolyte of the present invention may also contain a compound having an isocyanate group (hereinafter, sometimes abbreviated as "isocyanate"). The isocyanate is not particularly limited, and any isocyanate can be used. Examples of isocyanates include monoisocyanates, diisocyanates, triisocyanates, and the like.

[0282] Specific examples of the monoisocyanates include isocyanatomethane, isocyanatoethane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1-isocyanatoheptane, 1-isocyanatooctane, 1-isocyanatononane, 1-isocyanatodecane, isocyanatocyclohexane, methoxycarbonyl isocyanate, ethoxycarbonyl isocyanate, propoxycarbonyl isocyanate, butoxycarbonyl isocyanate, methoxysulfonyl isocyanate, ethoxysulfonyl isocyanate, propoxysulfonyl isocyanate, butoxysulfonyl isocyanate, fluorosulfonyl isocyanate, methyl isocyanate, butyl isocyanate, phenyl isocyanate, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, and ethyl isocyanate.

[0283] Specific examples of diisocyanates include 1,4-diisocyanate butane, 1,5-diisocyanate pentane, 1,6-diisocyanate hexane, 1,7-diisocyanate heptane, 1,8-diisocyanate octane, 1,9-diisocyanate nonane, 1,10-diisocyanate decane, 1,3-diisocyanate propylene, 1,4-diisocyanate-2-butene, 1,4-diisocyanate-2-fluorobutane ... Isocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluorohexane, toluene diisocyanate, xylene diisocyanate, toluene diisocyanate, 1,2-bis(isocyanatomethyl) Cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-1,1'-diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, Isophorone diisocyanate, bicyclo[2.2.1]heptane-2,5-diylbis(methyl=isocyanate), bicyclo[2.2.1]heptane-2,6-diylbis(methyl=isocyanate), 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, 1,4-phenylene diisocyanate, octamethylene diisocyanate, tetramethylene diisocyanate, etc.

[0284] Specific examples of triisocyanates include 1,6,11-triisocyanatoundecane, 4-isocyanatomethyl-1,8-octamethylene diisocyanate, 1,3,5-triisocyanatemethylbenzene, 1,3,5-tris(6-isocyanatohex-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 4-(isocyanatomethyl)octamethylene diisocyanate.

[0285] Among them, 1,6-diisocyanatohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,3,5-tris(6-isocyanatohex-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,4,4-trimethylhexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate are preferred from the viewpoint of being easily available industrially and keeping the production cost of the electrolyte solution low. In addition, from a technical point of view, they also contribute to the formation of a stable film-like structure and are more preferably used.

[0286] The content of isocyanate is not particularly limited, as long as it does not significantly damage the effect of the present invention, it is arbitrary, preferably 0.001 mass % to 1.0 mass % relative to the electrolyte. If the content of isocyanate is above the lower limit, it is possible to bring sufficient cycle characteristics to the non-aqueous electrolyte secondary battery. In addition, if it is below the upper limit, the initial increase in resistance of the non-aqueous electrolyte secondary battery can be avoided. The content of isocyanate is more preferably 0.01 mass % or more, more preferably 0.1 mass % or more, particularly preferably 0.2 mass % or more, in addition, more preferably 0.8 mass % or less, more preferably 0.7 mass % or less, and particularly preferably 0.6 mass % or less.

[0287] The electrolyte of the present invention may also contain a cyclic sulfonic acid ester. The cyclic sulfonic acid ester is not particularly limited, and any cyclic sulfonic acid ester may be used. Examples of the cyclic sulfonic acid ester include saturated cyclic sulfonic acid esters, unsaturated cyclic sulfonic acid esters, saturated cyclic disulfonic acid esters, and unsaturated cyclic disulfonic acid esters.

[0288] Specific examples of the saturated cyclic sulfonic acid esters include 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1,3-butane sultone, 1,4-butane sultone, Sultone, 1-fluoro-1,4-butane sultone, 2-fluoro-1,4-butane sultone, 3-fluoro-1,4-butane sultone, 4-fluoro-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, 2,4-butane sultone, etc.

[0289] Specific examples of the unsaturated cyclic sulfonic acid esters include 1-propylene-1,3-sultone, 2-propylene-1,3-sultone, 1-fluoro-1-propylene-1,3-sultone, 2-fluoro-1-propylene-1,3-sultone, 3-fluoro-1-propylene-1,3-sultone, 1-fluoro-2-propylene-1,3-sultone, 2-fluoro-2-propylene-1,3-sultone, 3-fluoro-2-propylene-1,3-sultone, 1-methyl-1-propylene-1,3-sultone, 2-methyl-1-propylene-1,3-sultone, Esters, 3-methyl-1-propylene-1,3-sultone, 1-methyl-2-propylene-1,3-sultone, 2-methyl-2-propylene-1,3-sultone, 3-methyl-2-propylene-1,3-sultone, 1-butene-1,4-sultone, 2-butene-1,4-sultone, 3-butene-1,4-sultone, 1-fluoro-1-butene-1,4-sultone, 2-fluoro-1-butene-1,4-sultone, 3-fluoro-1-butene-1,4-sultone, 4-fluoro-1-butene-1,4-sultone, 1-Fluoro-2-butene-1,4-sultone, 2-Fluoro-2-butene-1,4-sultone, 3-Fluoro-2-butene-1,4-sultone, 4-Fluoro-2-butene-1,4-sultone, 1,3-Propene sultone, 1-Fluoro-3-butene-1,4-sultone, 2-Fluoro-3-butene-1,4-sultone, 3-Fluoro-3-butene-1,4-sultone, 4-Fluoro-3-butene-1,4-sultone, 1-Methyl-1-butene-1,4-sultone, 2-Methyl-1-butene-1,4-sultone , 3-methyl-1-butene-1,4-sultone, 4-methyl-1-butene-1,4-sultone, 1-methyl-2-butene-1,4-sultone, 2-methyl-2-butene-1,4-sultone, 3-methyl-2-butene-1,4-sultone, 4-methyl-2-butene-1,4-sultone, 1-methyl-3-butene-1,4-sultone, 2-methyl-3-butene-1,4-sultone, 3-methyl-3-butene-1,4-sultone, 4-methyl-3-butene-14-sultone, etc.

[0290] Among them, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, and 1-propylene-1,3-sultone are more preferably used from the viewpoint of the ease of obtaining and the formation of a stable film-like structure. The content of the cyclic sulfonic acid ester is not particularly limited and is arbitrary as long as it does not significantly impair the effect of the present invention, and is preferably 0.001 mass % to 3.0 mass % relative to the electrolyte.

[0291] If the content of the cyclic sulfonate is above the lower limit, the non-aqueous electrolyte secondary battery can be sufficiently improved in terms of cycle characteristics. In addition, if it is below the upper limit, the increase in the manufacturing cost of the non-aqueous electrolyte secondary battery can be avoided. The content of the cyclic sulfonate is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and more preferably 2.5% by mass or less, further preferably 2.0% by mass or less, and particularly preferably 1.8% by mass or less.

[0292] The electrolyte solution of the present invention may further contain polyethylene oxide having a weight average molecular weight of 2000 to 4000 and having -OH, -OCOOH, or -COOH at the terminal. By including 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 monoalcohol, polyethylene oxide carboxylic acid, polyethylene oxide diol, polyethylene oxide dicarboxylic acid, polyethylene oxide triol, polyethylene oxide tricarboxylic acid, etc. These may be used alone or in combination of two or more. Among them, a mixture of polyethylene oxide monoalcohol and polyethylene oxide diol, and a mixture of polyethylene carboxylic acid and polyethylene dicarboxylic acid are preferred because the characteristics of the electrochemical device are better.

[0293] When the weight average molecular weight of the polyethylene oxide is too small, it may be easily oxidatively decomposed. The weight average molecular weight is more preferably 3,000 to 4,000. The weight average molecular weight can be measured in terms of polystyrene by gel permeation chromatography (GPC).

[0294] The content of the polyethylene oxide in the electrolyte is preferably 1×10 －6 ~1×10 －2 If the content of the polyethylene oxide is too high, the characteristics of the electrochemical device may be impaired. The content of the polyethylene oxide is more preferably 5×10 －6 mol / kg or more.

[0295] The electrolyte solution of the present invention may further contain an unsaturated cyclic carbonate, an overcharge prevention agent, other known auxiliary agents, etc. This can suppress the degradation of the characteristics of the electrochemical device.

[0296] Examples of the unsaturated cyclic carbonate include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, ethylene carbonates, allyl carbonates, and catechol carbonates.

[0297] Examples of the vinylene carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-divinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluorovinylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, methyl vinylene carbonate, and dimethyl vinylene carbonate.

[0298] Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl- 5-ethynyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, 4-phenyl-5-vinyl ethylene carbonate, 4-allyl-5-phenyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, 4-methylene-1,3-dioxolane-2-one, 4,5-dimethylene-1,3-dioxolane-2-one, 4-methyl-5-allyl ethylene carbonate, etc.

[0299] Among them, the unsaturated cyclic carbonate is preferably vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, and 4-vinyl-5-ethynyl ethylene carbonate. In addition, vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are particularly preferred because they form a more stable interface protective film.

[0300] The molecular weight of unsaturated cyclic carbonate is not particularly limited, as long as the effect of the present invention is not significantly damaged. The molecular weight is preferably 50 to 250. If it is this range, it is easy to ensure the solubility of the unsaturated cyclic carbonate in the electrolyte, and it is easy to fully embody the effect of the present invention. The molecular weight of the unsaturated cyclic carbonate is more preferably more than 80, and in addition, it is more preferably less than 150.

[0301] The method for producing the unsaturated cyclic carbonate is not particularly limited, and the unsaturated cyclic carbonate can be produced by any known method.

[0302] The unsaturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0303] The content of the above-mentioned unsaturated cyclic carbonate is not particularly limited, as long as the effect of the present invention is not significantly damaged, it is arbitrary. The content of the above-mentioned unsaturated cyclic carbonate is preferably more than 0.001 mass % in 100 mass % of electrolyte, more preferably more than 0.01 mass %, and more preferably more than 0.1 mass %. In addition, the above-mentioned content is preferably less than 5 mass %, more preferably less than 4 mass %, and more preferably less than 3 mass %. If it is within the above-mentioned scope, the electrochemical device using the electrolyte easily embodies sufficient cycle characteristics to improve the effect, in addition, it is easy to avoid the high temperature storage characteristics to reduce, the gas generation amount to become more, and the discharge capacity retention rate to reduce such a situation.

[0304] As the unsaturated cyclic carbonate, in addition to the above-mentioned non-fluorinated unsaturated cyclic carbonate, a fluorinated unsaturated cyclic carbonate can also be suitably used. Fluorinated unsaturated cyclic carbonate is a cyclic carbonate with unsaturated bonds and fluorine atoms. If the quantity of the fluorine atoms possessed by the fluorinated unsaturated cyclic carbonate is more than 1, there is no particular restriction. Wherein the fluorine atoms are generally below 6, are preferably below 4, and most preferably are 1 or 2.

[0305] Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives and fluorinated ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon double bond.

[0306] Examples of the fluorinated vinylene carbonate derivative include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, and 4-fluoro-5-vinylvinylene carbonate.

[0307] Examples of the fluoroethylene carbonate derivatives substituted with a substituent having an aromatic ring or 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-difluoro-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, and the like.

[0308] Among them, as the fluorinated unsaturated cyclic carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate are more preferably used because they can form a stable interface protective film. Ethyl carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate.

[0309] The molecular weight of fluorinated unsaturated cyclic carbonate is not particularly limited, as long as the effect of the present invention is not significantly damaged, and is arbitrary.Molecular weight is preferably more than 50, and below 500.If this scope, then easily ensure the solubility of fluorinated unsaturated cyclic carbonate in electrolyte.

[0310] The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and any known method may be selected for production. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

[0311] Fluorinated unsaturated cyclic carbonate can be used alone as one, or can be used in any combination and ratio as well as more than two. In addition, the content of fluorinated unsaturated cyclic carbonate is not particularly limited, as long as the effect of the present invention is not significantly damaged. The content of fluorinated unsaturated cyclic carbonate is usually preferably more than 0.01% by mass in 100% by mass of electrolyte, more preferably more than 0.1% by mass, more preferably more than 0.2% by mass, in addition, preferably less than 5% by mass, more preferably less than 4% by mass, more preferably less than 3% by mass. If within the scope, the electrochemical device using the electrolyte easily embodies sufficient cycle characteristics to improve the effect, in addition, it is easy to avoid the reduction of high temperature storage characteristics, the increase of gas generation, and the reduction of discharge capacity retention rate.

[0312] The electrolyte solution of the present invention may contain a compound having a triple bond. The type of the compound is not particularly limited as long as it has one or more triple bonds in the molecule. Specific examples of the compound having a triple bond include the following compounds. 1-pentyne, 2-pentyne, 1-hexyne, 2-hexyne, 3-hexyne, 1-heptyne, 2-heptyne, 3-heptyne, 1-octyne, 2-octyne, 3-octyne, 4-octyne, 1-nonyne, 2-nonyne, 3-nonyne, 4-nonyne, 1-dodecyne, 2-dodecyne, 3-dodecyne, 4-dodecyne, 5-dodecyne, phenylacetylene, 1-phenyl-1-propyne, 1-phenyl-2-propyne, 1-phenyl-1-butyne, 4-phenyl-1-butyne, 4-phenyl-1-butyne, 1-phenyl-1-pentyne, 5-phenyl-1-pentyne, 1-phenyl-1-hexyne, 6-phenyl-1-hexyne, diphenylacetylene, 4-ethynyltoluene, dicyclohexylacetylene and other hydrocarbon compounds;

[0313] 2-propynyl methyl carbonate, 2-propynyl ethyl carbonate, 2-propynyl propyl carbonate, 2-propynyl butyl carbonate, 2-propynyl phenyl carbonate, 2-propynyl cyclohexyl carbonate, di-2-propynyl carbonate, 1-methyl-2-propynyl methyl carbonate, 1,1-dimethyl-2-propynyl methyl carbonate, 2-butynyl methyl carbonate, 3-butynyl methyl carbonate, 2-pentynyl methyl carbonate Monocarbonates such as 2-butyne-1,4-diol dicarbonate, 3-pentynyl methyl carbonate, 4-pentynyl methyl carbonate; dicarbonates such as 2-butyne-1,4-diol dicarbonate, diethyl 2-butyne-1,4-diol dicarbonate, dipropyl 2-butyne-1,4-diol dicarbonate, dibutyl 2-butyne-1,4-diol dicarbonate, diphenyl 2-butyne-1,4-diol dicarbonate, and dicyclohexyl 2-butyne-1,4-diol dicarbonate;

[0314] 2-Propynyl acetate, 2-propynyl propionate, 2-propynyl butyrate, 2-propynyl benzoate, 2-propynyl cyclohexylcarboxylate, 1,1-dimethyl-2-propynyl acetate, 1,1-dimethyl-2-propynyl propionate, 1,1-dimethyl-2-propynyl butyrate, 1,1-dimethyl-2-propynyl benzoate, 1,1-dimethyl-2-propynyl cyclohexylcarboxylate, 2-butynyl acetate, 3-butynyl acetate, 2-pentynyl acetate, 3-pentynyl acetate, 4-pentynyl acetate, methyl acrylate, acrylic acid Ethyl acrylate, propyl acrylate, vinyl acrylate, 2-propylene acrylate, 2-butylene acrylate, 3-butylene acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl methacrylate, 2-propylene methacrylate, 2-butylene methacrylate, 3-butylene methacrylate, methyl 2-propiolate, ethyl 2-propiolate, propyl 2-propiolate, vinyl 2-propiolate, 2-propylene 2-propiolate, 2-butylene 2-propiolate, 3-butylene 2-propiolate, 2- Methyl butynoate, ethyl 2-butynoate, propyl 2-butynoate, vinyl 2-butynoate, 2-propene 2-butynoate, 2-butenyl 2-butynoate, 3-butenyl 2-butynoate, methyl 3-butynoate, ethyl 3-butynoate, propyl 3-butynoate, vinyl 3-butynoate, 2-propene 3-butynoate, 2-butenyl 3-butynoate, methyl 2-pentynoate, ethyl 2-pentynoate, propyl 2-pentynoate, vinyl 2-pentynoate, 2-propene 2-pentynoate, 2-pentynoate Monocarboxylic acid esters such as 2-butenyl acetyloate, 3-butenyl acetyloate, methyl 3-pentynoate, ethyl 3-pentynoate, propyl 3-pentynoate, vinyl 3-pentynoate, 2-propenyl 3-pentynoate, 2-butenyl 3-pentynoate, 3-butenyl 3-pentynoate, methyl 4-pentynoate, ethyl 4-pentynoate, propyl 4-pentynoate, vinyl 4-pentynoate, 2-propenyl 4-pentynoate, 2-butenyl 4-pentynoate, and 3-butenyl 4-pentynoate, fumaric acid esters, methyl trimethylacetate, and ethyl trimethylacetate;

[0315] 2-Butyne-1,4-diol diacetate, 2-butyne-1,4-diol dipropionate, 2-butyne-1,4-diol dibutyrate, 2-butyne-1,4-diol dibenzoate, 2-butyne-1,4-diol dicyclohexanecarboxylate, hexahydrobenzo[1,3,2]dioxathiolane-2-oxide (1,2-cyclohexanediol, 2,2-dioxide-1,2-oxathiolane-4-yl acetate, 2,2-dioxide-1,2-oxathiolane-4-yl acetate and other dicarboxylic acid esters;

[0316] Oxalic acid diesters such as 2-propynyl methyl oxalate, 2-propynyl ethyl oxalate, 2-propynyl propyl oxalate, 2-propynyl vinyl oxalate, 2-propynyl allyl oxalate, di-2-propynyl oxalate, 2-butynyl methyl oxalate, 2-butynyl ethyl oxalate, 2-butynyl propyl oxalate, 2-butynyl vinyl oxalate, 2-butynyl allyl oxalate, di-2-butynyl oxalate, 3-butynyl methyl oxalate, 3-butynyl ethyl oxalate, 3-butynyl propyl oxalate, 3-butynyl vinyl oxalate, 3-butynyl allyl oxalate, and di-3-butynyl oxalate;

[0317] Phosphine oxides such as methyl (2-propynyl) (vinyl) phosphine oxide, divinyl (2-propynyl) phosphine oxide, di (2-propynyl) (vinyl) phosphine oxide, di (2-propynyl) 2 (-propynyl) phosphine oxide, di (2-propynyl) (2-propynyl) phosphine oxide, di (3-butenyl) (2-propynyl) phosphine oxide and di (2-propynyl) (3-butenyl) phosphine oxide;

[0318] 2-propynyl methyl (2-propenyl) phosphinate, 2-propynyl 2-butenyl (methyl) phosphinate, 2-propynyl di (2-propenyl) phosphinate, 2-propynyl di (3-butenyl) phosphinate, 1,1-dimethyl-2-propynyl methyl (2-propenyl) phosphinate, 1,1-dimethyl-2-propynyl 2-butenyl (methyl) phosphinate, 1,1-dimethyl-2-propynyl di (2-propenyl) phosphinate Phosphinates such as acetylenic esters and di(3-butenyl)phosphinate 1,1-dimethyl-2-propynyl phosphinate, methyl(2-propynyl)phosphinate 2-propenyl phosphinate, methyl(2-propynyl)phosphinate 3-butenyl phosphinate, di(2-propynyl)phosphinate 2-propenyl phosphinate, di(2-propynyl)phosphinate 3-butenyl phosphinate, 2-propenyl(2-propenyl)phosphinate and 3-butenyl(2-propenyl)phosphinate;

[0319] 2-Propylene phosphonic acid methyl 2-propynyl ester, 2-butenyl phosphonic acid methyl (2-propynyl) ester, 2-propenyl phosphonic acid (2-propynyl) (2-propenyl) ester, 3-butenyl phosphonic acid (3-butenyl) (2-propynyl) ester, 2-propenyl phosphonic acid (1,1-dimethyl-2-propynyl) (methyl) ester, 2-butenyl phosphonic acid (1,1-dimethyl-2-propynyl) (methyl) ester, 2-propenyl phosphonic acid (1,1-dimethyl-2-propynyl) (2-propenyl) ester and 3-butenyl phosphonic acid (3-butenyl) (1,1-dimethyl-2-propynyl) ester , phosphonates such as (2-propynyl)(2-propenyl)methylphosphonate, (3-butenyl)(2-propenyl)methylphosphonate, (1,1-dimethyl-2-propynyl)(2-propenyl)methylphosphonate, (3-butenyl)(1,1-dimethyl-2-propynyl)methylphosphonate, (2-propynyl)(2-propenyl)ethylphosphonate, (3-butenyl)(2-propenyl)ethylphosphonate, (1,1-dimethyl-2-propynyl)(2-propenyl)ethylphosphonate and (3-butenyl)(1,1-dimethyl-2-propynyl)ethylphosphonate;

[0320] Phosphoric acid esters such as (methyl)(2-propenyl)(2-propynyl) phosphate, (ethyl)(2-propenyl)(2-propynyl) phosphate, (2-butenyl)(methyl)(2-propynyl) phosphate, (2-butenyl)(ethyl)(2-propynyl) phosphate, (1,1-dimethyl-2-propynyl)(methyl)(2-propenyl) phosphate, (1,1-dimethyl-2-propynyl)(ethyl)(2-propenyl) phosphate, (2-butenyl)(1,1-dimethyl-2-propynyl)(methyl) phosphate and (2-butenyl)(ethyl)(1,1-dimethyl-2-propynyl) phosphate;

[0321] Among these, compounds having an alkynyloxy group are preferred because they can form a negative electrode coating more stably in an electrolyte solution.

[0322] In addition, compounds such as 2-propynyl methyl carbonate, di-2-propynyl carbonate, 2-butyne-1,4-diol dimethyl dicarbonate, 2-propynyl acetate, 2-butyne-1,4-diol diacetate, 2-propynyl methyl oxalate, and di-2-propynyl oxalate are particularly preferred from the viewpoint of improving storage characteristics.

[0323] The above-mentioned compound with triple bond can be used alone as one, or in any combination and ratio and in combination with more than two. The amount of the compound with triple bond relative to the entire electrolyte of the present invention is not limited, as long as the effect of the present invention is not significantly damaged, relative to the electrolyte of the present invention, with a concentration of usually 0.01% by mass, preferably 0.05% by mass, more preferably 0.1% by mass, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less. When the above range is met, the effects of power characteristics, load characteristics, cycle characteristics, high temperature storage characteristics, etc. are further improved.

[0324] The electrolyte solution of the present invention may contain an overcharge preventer in order to effectively suppress battery rupture or ignition when an electrochemical device using the electrolyte solution becomes overcharged or the like.

[0325] Examples of the overcharge prevention agent include unsubstituted or alkyl-substituted terphenyl derivatives such as biphenyl, o-terphenyl, m-terphenyl, and p-terphenyl, partially hydrogenated products of unsubstituted or alkyl-substituted terphenyl derivatives, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3-trimethyl-3-phenylindane, cyclopentylbenzene, cyclohexylbenzene, cumene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene, tert-butylbenzene, tert-amylbenzene, tert-hexylbenzene, and anisole; aromatic compounds such as 2-fluorobiphenyl, 4-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene. , fluorotoluene, trifluorotoluene and other partially fluorinated aromatic compounds mentioned above; fluorinated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 1,6-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole; aromatic acetates such as 3-propylphenyl acetate, 2-ethylphenyl acetate, benzylphenyl acetate, methylphenyl acetate, benzyl acetate, phenylethylphenyl acetate; aromatic carbonates such as diphenyl carbonate and methylphenyl carbonate, toluene derivatives such as toluene and xylene, unsubstituted or alkyl-substituted biphenyl derivatives such as 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl and o-cyclohexylbiphenyl, etc. Among them, preferred are aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3-trimethyl-3-phenylindane, 3-propylphenyl acetate, 2-ethylphenyl acetate, benzylphenyl acetate, methylphenyl acetate, benzyl acetate, diphenyl carbonate, methylphenyl carbonate, etc. They can be used alone or in combination of two or more. When two or more are used in combination, from the perspective of the balance between the overcharge prevention characteristic and the high temperature storage characteristic, it is particularly preferred to use a combination of cyclohexylbenzene and tert-butylbenzene or tert-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, etc., and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran.

[0326] The electrolyte used in the present invention may also use a carboxylic anhydride (but excluding compound (2)). A compound represented by the following general formula (6) is preferred. The method for producing the carboxylic anhydride is not particularly limited, and any known method may be selected for production.

[0327] (In general formula (6), R 61 , R 62 Each independently represents a hydrocarbon group having 1 to 15 carbon atoms which may have a substituent.

[0328] If R61 , R 62 If it is a monovalent hydrocarbon group, its type is not particularly limited. For example, it can be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, or a group formed by bonding an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group can be a saturated hydrocarbon group, or it can contain an unsaturated bond (carbon-carbon double bond or carbon-carbon triple bond). In addition, the aliphatic hydrocarbon group can be chain-shaped or cyclic. In the case of a chain-shaped group, it can be straight-chain or branched. In addition, it can also be a group formed by bonding a chain and a ring. It should be noted that R 61 and R 62 They can be the same or different.

[0329] In addition, R 61 , R 62 When the hydrocarbon group has a substituent, the type of the substituent is not particularly limited as long as it does not violate the purpose of the present invention. Examples include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, preferably fluorine atoms. Alternatively, as substituents other than halogen atoms, substituents having functional groups such as ester groups, cyano groups, carbonyl groups, and ether groups may be mentioned, preferably cyano groups and carbonyl groups. 61 , R 62 The hydrocarbon group may have only one of these substituents, or may have two or more. When having two or more substituents, these substituents may be the same or different from each other.

[0330] R 61 , R 62 The number of carbon atoms in each hydrocarbon group is usually 1 or more, and is usually 15 or less, preferably 12 or less, more preferably 10 or less, and further preferably 9 or less. 1 With R 2 When they are bonded to each other to form a divalent hydrocarbon group, the number of carbon atoms in the divalent hydrocarbon group is usually 1 or more, and usually 15 or less, preferably 13 or less, more preferably 10 or less, and further preferably 8 or less. 61 , R 62 When the hydrocarbon group has a substituent containing a carbon atom, it is preferred that R including the substituent 61 , R 62 The total number of carbon atoms satisfies the above range.

[0331] Next, specific examples of the acid anhydride represented by the above general formula (6) are described. It should be noted that in the following examples, "analogs" refer to acid anhydrides obtained by replacing a part of the structure of the exemplified acid anhydride with other structures within the scope of not violating the gist of the present invention, for example, dimers, trimers and tetramers formed by multiple acid anhydrides, or acid anhydrides with the same carbon number of substituents but branched isomers, acid anhydrides with different substituent-anhydride bonding sites, etc.

[0332] First, in the following example, R 61 , R 62 Specific examples of the same acid anhydride.

[0333] As R 61 , R 62 Specific examples of the acid anhydride having a chain alkyl group include acetic anhydride, propionic anhydride, butyric anhydride, 2-methylpropionic anhydride, 2,2-dimethylpropionic anhydride, 2-methylbutyric anhydride, 3-methylbutyric anhydride, 2,2-dimethylbutyric anhydride, 2,3-dimethylbutyric anhydride, 3,3-dimethylbutyric anhydride, 2,2,3-trimethylbutyric anhydride, 2,3,3-trimethylbutyric anhydride, 2,2,3,3-tetramethylbutyric anhydride, 2-ethylbutyric anhydride, and the like, and analogs thereof.

[0334] As R 61 , R 62 Specific examples of the acid anhydride of a cyclic alkyl group include cyclopropanecarboxylic anhydride, cyclopentanecarboxylic anhydride, cyclohexanecarboxylic anhydride, and the like, and analogs thereof.

[0335] As R 61 , R 62 Specific examples of the alkenyl acid anhydride include acrylic anhydride, 2-methacrylic anhydride, 3-methacrylic anhydride, 2,3-dimethylacrylic anhydride, 3,3-dimethylacrylic anhydride, 2,3,3-trimethylacrylic anhydride, 2-phenylacrylic anhydride, 3-phenylacrylic anhydride, 2,3-diphenylacrylic anhydride, 3,3-diphenylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, 2,2-dimethyl-3-butenoic anhydride, 3-methyl-3-butenoic anhydride, 2-methyl-3-methyl-3-butenoic anhydride, 2,2-dimethyl-3-methyl-3-butenoic anhydride, 3-pentenoic anhydride, 4-pentenoic anhydride, 2-cyclopentenecarboxylic anhydride, 3-cyclopentenecarboxylic anhydride, 4-cyclopentenecarboxylic anhydride, and the like, and analogs thereof.

[0336] As R 61 , R 62 Specific examples of the acid anhydride which is an alkynyl group include propiolic anhydride, 3-phenylpropiolic anhydride, 2-butynoic anhydride, 2-pentynoic anhydride, 3-butynoic anhydride, 3-pentynoic anhydride, 4-pentynoic anhydride and the like, and the like.

[0337] As R 61 , R 62 Specific examples of the acid anhydride which is an aryl group include benzoic anhydride, 4-methylbenzoic anhydride, 4-ethylbenzoic anhydride, 4-tert-butylbenzoic anhydride, 2-methylbenzoic anhydride, 2,4,6-trimethylbenzoic anhydride, 1-naphthalenecarboxylic anhydride, 2-naphthalenecarboxylic anhydride, and the like, and analogs thereof.

[0338] In addition, as R 61 , R 62 Examples of acid anhydrides substituted with halogen atoms include mainly examples of acid anhydrides substituted with fluorine atoms, but acid anhydrides obtained by replacing part or all of these fluorine atoms with chlorine atoms, bromine atoms, or iodine atoms are also included in the exemplary compounds.

[0339] As R 61 , R 62 Examples of the acid anhydride of the chain alkyl group substituted with a halogen atom include fluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, 2-fluoropropionic anhydride, 2,2-difluoropropionic anhydride, 2,3-difluoropropionic anhydride, 2,2,3-trifluoropropionic anhydride, 2,3,3-trifluoropropionic anhydride, 2,2,3,3-tetrapropionic anhydride, 2,3,3,3-tetrapropionic anhydride, 3-fluoropropionic anhydride, 3,3-difluoropropionic anhydride, 3,3,3-trifluoropropionic anhydride, perfluoropropionic anhydride, and the like, and analogs thereof.

[0340] As R 61 , R 62 Examples of the acid anhydride of the cyclic alkyl group substituted with a halogen atom include 2-fluorocyclopentanecarboxylic anhydride, 3-fluorocyclopentanecarboxylic anhydride, 4-fluorocyclopentanecarboxylic anhydride, and the like, and analogs thereof.

[0341] As R 61 , R 62 Examples of the acid anhydride of the alkenyl group substituted with a halogen atom include 2-fluoroacrylic anhydride, 3-fluoroacrylic anhydride, 2,3-difluoroacrylic anhydride, 3,3-difluoroacrylic anhydride, 2,3,3-trifluoroacrylic anhydride, 2-(trifluoromethyl)acrylic anhydride, 3-(trifluoromethyl)acrylic anhydride, 2,3-bis(trifluoromethyl)acrylic anhydride, 2,3,3-tri(trifluoromethyl)acrylic anhydride, 2-(4-fluorophenyl)acrylic anhydride, 3-(4-fluorophenyl)acrylic anhydride, 2,3-bis(4-fluorophenyl)acrylic anhydride, 3,3-bis(4-fluorophenyl)acrylic anhydride, 2-fluoro-3-butenoic anhydride, 2,2-difluoro-3-butenoic anhydride, 3-fluoro-2-butenoic anhydride, 4-fluoro-3-butenoic anhydride, 3,4-difluoro-3-butenoic anhydride, 3,3,4-trifluoro-3-butenoic anhydride, and analogs thereof.

[0342] As R 61 , R 62 Examples of the anhydride of the alkynyl group substituted with a halogen atom include 3-fluoro-2-propiolic anhydride, 3-(4-fluorophenyl)-2-propiolic anhydride, 3-(2,3,4,5,6-pentafluorophenyl)-2-propiolic anhydride, 4-fluoro-2-butynoic anhydride, 4,4-difluoro-2-butynoic anhydride, 4,4,4-trifluoro-2-butynoic anhydride, and the like, and analogs thereof.

[0343] As R 61 , R 62 Examples of the acid anhydride of the aryl group substituted with a halogen atom include 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, 4-trifluoromethylbenzoic anhydride, and the like, and the like.

[0344] As R 61 , R 62 Examples of the acid anhydride having a substituent having a functional group such as an ester, nitrile, ketone, or ether include methoxyformic anhydride, ethoxyformic anhydride, methyl oxalic anhydride, ethyl oxalic anhydride, 2-cyanoacetic anhydride, 2-oxopropionic anhydride, 3-oxobutyric anhydride, 4-acetylbenzoic anhydride, methoxyacetic anhydride, 4-methoxybenzoic anhydride, and the like, and analogs thereof.

[0345] Next, the following is an example of R 61 , R 62 Specific examples of acid anhydrides that are different from each other.

[0346] The above can be considered as R 61 , R 62 While all combinations of the examples and their analogs are contemplated, representative examples are given below.

[0347] Examples of combinations of chain alkyl groups include acetic propionic anhydride, acetic butyric anhydride, butyric propionic anhydride, and acetic 2-methylpropionic anhydride.

[0348] Examples of the combination of a chain alkyl group and a cyclic alkyl group include acetic cyclopentane anhydride, acetic cyclohexane anhydride, and cyclopentane propionic anhydride.

[0349] Examples of the combination of a chain alkyl group and an alkenyl group include acetic anhydride, acetic anhydride-3-methacrylic anhydride, acetic anhydride-3-butenoic anhydride, and acrylic anhydride-propionic anhydride.

[0350] Examples of the combination of a chain alkyl group and an alkynyl group include acetic anhydride propiolic acid, acetic anhydride 2-butiolic acid, acetic anhydride 3-butiolic acid, acetic anhydride 3-phenylpropiolic acid, and propiolic anhydride propiolic acid.

[0351] Examples of the combination of a chain alkyl group and an aryl group include acetic anhydride benzoic acid, acetic 4-methylbenzoic acid, acetic 1-naphthalenecarboxylic acid anhydride, and benzoic acid propionic anhydride.

[0352] Examples of the combination of a chain alkyl group and a hydrocarbon group having a functional group include acetic fluoroacetic anhydride, acetic trifluoroacetic anhydride, acetic 4-fluorobenzoic anhydride, acetic fluoropropionic anhydride, acetic alkyl oxalic anhydride, acetic 2-cyanoacetic anhydride, acetic 2-oxopropionic anhydride, acetic methoxyacetic anhydride, methoxyacetic propionic anhydride, and the like.

[0353] Examples of combinations of cyclic alkyl groups include cyclopentanecarboxylic acid and cyclohexanecarboxylic anhydride.

[0354] Examples of the combination of a cyclic alkyl group and an alkenyl group include cyclopentane acrylic acid anhydride, 3-cyclopentane methacrylic acid anhydride, 3-cyclopentane butylene acrylic acid anhydride, and cyclohexane acrylic acid anhydride.

[0355] Examples of the combination of a cyclic alkyl group and an alkynyl group include propiolic acid cyclopentane anhydride, 2-butynoic acid cyclopentane anhydride, and propiolic acid cyclohexane anhydride.

[0356] Examples of the combination of a cyclic alkyl group and an aryl group include benzoic acid cyclopentane anhydride, 4-methylbenzoic acid cyclopentane anhydride, and benzoic acid cyclohexane anhydride.

[0357] Examples of the combination of a cyclic alkyl group and a hydrocarbon group having a functional group include fluoroacetic cyclopentanecarboxylic anhydride, cyclopentanecarboxylic trifluoroacetic anhydride, cyclopentanecarboxylic 2-cyanoacetic anhydride, cyclopentanecarboxylic methoxyacetic anhydride, and cyclohexanecarboxylic fluoroacetic anhydride.

[0358] Examples of combinations of alkenyl groups include acrylic acid 2-methacrylic anhydride, acrylic acid 3-methacrylic anhydride, acrylic acid 3-butenoic anhydride, and 2-methacrylic acid 3-methacrylic anhydride.

[0359] Examples of the combination of an alkenyl group and an alkynyl group include acrylic acid propiolic anhydride, acrylic acid 2-butynic anhydride, and 2-methacrylic acid propiolic anhydride.

[0360] Examples of the combination of an alkenyl group and an aryl group include acrylic acid benzoic anhydride, acrylic acid 4-methylbenzoic anhydride, and 2-methacrylic acid benzoic anhydride.

[0361] Examples of the combination of an alkenyl group and a hydrocarbon group having a functional group include acrylic acid fluoroacetic anhydride, acrylic acid trifluoroacetic anhydride, acrylic acid 2-cyanoacetic anhydride, acrylic acid methoxyacetic anhydride, and 2-methacrylic acid fluoroacetic anhydride.

[0362] Examples of combinations of alkynyl groups include propiolic acid 2-butynoic anhydride, propiolic acid 3-butynoic anhydride, and 2-butynoic acid 3-butynoic anhydride.

[0363] Examples of the combination of an alkynyl group and an aryl group include benzoic acid propiolic anhydride, 4-methylbenzoic acid propiolic anhydride, and benzoic acid 2-butynoic anhydride.

[0364] Examples of the combination of an alkynyl group and a hydrocarbon group having a functional group include propiolic acid fluoroacetic anhydride, propiolic acid trifluoroacetic anhydride, propiolic acid 2-cyanoacetic anhydride, propiolic acid methoxyacetic anhydride, and 2-butynoic acid fluoroacetic anhydride.

[0365] Examples of the combination of aryl groups include benzoic acid 4-methylbenzoic anhydride, benzoic acid 1-naphthalenecarboxylic anhydride, and 4-methylbenzoic acid 1-naphthalenecarboxylic anhydride.

[0366] Examples of the combination of an aryl group and a hydrocarbon group having a functional group include benzoic acid fluoroacetic anhydride, benzoic acid trifluoroacetic anhydride, benzoic acid 2-cyanoacetic anhydride, benzoic acid methoxyacetic anhydride, and 4-methylbenzoic acid fluoroacetic anhydride.

[0367] Examples of the combination of hydrocarbon groups having a functional group include fluoroacetic acid trifluoroacetic anhydride, fluoroacetic acid 2-cyanoacetic anhydride, fluoroacetic acid methoxyacetic anhydride, trifluoroacetic acid 2-cyanoacetic anhydride, and the like.

[0368] Among the acid anhydrides having a chain structure, acetic anhydride, propionic anhydride, 2-methylpropionic anhydride, cyclopentanecarboxylic anhydride, cyclohexanecarboxylic anhydride, acrylic anhydride, 2-methacrylic anhydride, 3-methacrylic anhydride, 2,3-dimethylacrylic anhydride, 3,3-dimethylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, propiolic anhydride, 2-butynoic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, 4-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride, trifluoroacetic anhydride, 3,3,3 The anhydride preferably includes 2-(trifluoromethyl)acrylic anhydride, 2-(4-fluorophenyl)acrylic anhydride, 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, methoxyformic anhydride, and ethoxyformic anhydride; and more preferably includes acrylic anhydride, 2-methacrylic anhydride, 3-methacrylic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, 4-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride, 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, methoxyformic anhydride, and ethoxyformic anhydride.

[0369] These compounds are preferred from the viewpoint of forming a film having excellent durability by appropriately forming a bond with lithium oxalate, and in particular being able to improve the charge and discharge rate characteristics, input and output characteristics, and impedance characteristics after a durability test.

[0370] The molecular weight of the carboxylic anhydride is not limited and is arbitrary as long as it does not significantly impair the effects of the present invention, but is usually 90 or more, preferably 95 or more, and is usually 300 or less, preferably 200 or less. If the molecular weight of the carboxylic anhydride is within the above range, the viscosity increase of the electrolyte can be suppressed, and the film density can be made appropriate, so that the durability can be appropriately improved.

[0371] In addition, the method for producing the carboxylic anhydride is not particularly limited, and any known method can be selected for production. The carboxylic anhydride described above may be contained in the non-aqueous electrolyte of the present invention alone or in any combination and ratio.

[0372] In addition, the above-mentioned carboxylic anhydride is not particularly limited in the content of the electrolyte of the present invention, as long as it does not significantly damage the effect of the present invention, it is arbitrary, and it is desirable that, relative to the electrolyte of the present invention, it is usually 0.01 mass %, preferably 0.1 mass % or more, and usually 5 mass %, preferably 3 mass % or less. If the content of carboxylic anhydride is within the above range, it is easy to embody the effect of improving the cycle characteristics, and in addition, the reactivity is good, so the battery characteristics are easily improved.

[0373] The electrolyte of the present invention may use other known auxiliary agents. Examples of other auxiliary agents include carbonate compounds such as anhydroerythritol carbonate, spirobismethylene carbonate, and methoxyethyl-methyl carbonate; spirocyclic compounds such as 2,4,8,10-tetraoxaspiro[5.5]undecane and 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane; ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, cyclobutene sulfone, ethylene sulfate, vinyl sulfate, diphenyl sulfone, N,N-dimethylmethanesulfonamide, N,N-diethylmethanesulfonamide, acetamide, N-methyl N,N-dimethylformamide, N,N-dimethylacetamide, methyl vinyl sulfonate, ethyl vinyl sulfonate, allyl vinyl sulfonate, propargyl vinyl sulfonate, methyl allyl sulfonate, ethyl allyl sulfonate, allyl allyl sulfonate, propargyl allyl sulfonate, 1,2-bis(vinylsulfonyloxy)ethane, propane disulfonic anhydride, sulfobutyric anhydride, sulfobenzoic anhydride, sulfopropionic anhydride, ethane disulfonic anhydride, methylene methane disulfonate, 2-propynyl methanesulfonate, amyl sulfite, pentafluorophenyl methanesulfonate, propylene sulfate, propylene sulfite, propanesulfonic acid Ester, butylene sulfite, butane-2,3-diyl dimethanesulfonate, 2-butyne-1,4-diyl dimethanesulfonate, 2-phenyl bicyclohexane, 2-butyne-1,4-diyl dicarboxylate, 2-propynyl vinyl sulfonate, bis(2-vinylsulfonylethyl) ether, 5-vinyl-hexahydro-1,3,2-benzodioxathiole-2-oxide, 2-propynyl 2-(methylsulfonyloxy)propionate, 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, 3-sulfo-propynyl Acid anhydride trimethylene methane disulfonate 2-methyltetrahydrofuran, trimethylene methane disulfonate, tetramethylene sulfoxide, dimethylene methane disulfonate, difluoroethyl methyl sulfone, divinyl sulfone, 1,2-bis(vinylsulfonyl)ethane, ethylene bisphosphonic acid methyl ester, ethylene bisphosphonic acid ethyl ester, ethylene sulfate and other sulfur-containing compounds; 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide, nitromethane, nitroethane, thiophene 1-oxide, ethylenediamine and other nitrogen-containing compounds;Trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, ethyl diethylphosphonoacetate, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide, bis(2,2-difluoroethyl) 2,2,2-trifluoroethyl phosphate, bis(2,2,3,3- 2,2,2-trifluoroethyl phosphate, bis(2,2,2-trifluoroethyl) methyl phosphate, bis(2,2,2-trifluoroethyl) ethyl phosphate, bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate, bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate, tributyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, tris(1,1,1,3,3,3-hexafluoropropane-2 phosphate, 2-phenylphenyl dimethyl phosphate, 2-phenylphenyl diethyl phosphate, (2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoropropyl) methyl phosphate, triester phosphate, methyl methylenebisphosphonate, ethyl methylenebisphosphonate, methyl 2-(dimethoxyphosphoryl) acetate, methyl 2-(dimethylphosphoryl) acetate, methyl 2-(diethoxyphosphoryl) acetate, methyl 2-(diethylphosphoryl) acetate , methyl butylenebisphosphonate, ethyl butylenebisphosphonate, 2-propynyl 2-(dimethoxyphosphoryl) acetate, 2-propynyl 2-(dimethylphosphoryl) acetate, 2-propynyl 2-(diethoxyphosphoryl) acetate, 2-propynyl 2-(diethylphosphoryl) acetate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) phosphite, tris(triethylsilyl) phosphate, tris(triethylsilyl) phosphite and other phosphorus-containing compounds;Heptane, octane, nonane, decane, cycloheptane, methyl formate, 2-propynyl methyl oxalate, 2-propynyl methacrylate, dimethyl malonate, malonate, pentane, benzene, furan, naphthalene, 2,5,8,11-tetraoxadodecane, 2,5,8,11,14-pentaoxapentadecane, 3-pentanone, 2-phenylbicyclohexane, 3-allylsuccinic anhydride, ethoxymethoxyethane, trimethoxymethane, cyclohexane and other hydrocarbon compounds, fluorobenzene, difluorobenzene, hexafluorobenzene, trifluorotoluene, monofluorobenzene, 1-fluoro-2-cyclohexylbenzene, 1-fluoro-4-tert-butylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-2-cyclohexylbenzene, fluorobiphenyl and other fluorinated aromatic compounds, tris(trimethylsilyl)borate, tris(trimethoxysilyl)borate, tris(trimethylsilyl)borate Silane compounds such as tetra(trimethylsilyl)phosphate, tri(trimethoxysilyl)phosphate, dimethoxyaluminumoxytrimethoxysilane, diethoxyaluminumoxytriethoxysilane, dipropoxyaluminumoxytriethoxysilane, dibutoxyaluminumoxytrimethoxysilane, dibutoxyaluminumoxytriethoxysilane, tetra(trimethylsilyl)titanium, tetra(triethylsilyl)titanium 1, tri(trimethylsilyl)phosphite, trimethylsilylpolyphosphate, tetramethylsilane, and oxygen-containing compounds such as dimethyl oxalate, dioxolane, dioxane, dimethyl ketone, diethyl ketone, diethyl oxalate, di(2-propynyl)oxalate, dimethyl succinate, di(2-propynyl)glutarate, 2-propynyl formate, ethyl formate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethyl methyl oxalate, and ethyl formate. These may be used alone or in combination of two or more. By adding these additives, the capacity retention and cycle characteristics after high temperature storage can be improved.

[0374] Among the other auxiliary agents, phosphorus-containing compounds are preferred, and tris(trimethylsilyl)phosphate is preferred.

[0375] The amount of other auxiliary agents is not particularly limited, and is arbitrary as long as it does not significantly damage the effect of the present invention. The other auxiliary agents are preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the electrolyte. If it is within this range, it is easy to fully reflect the effects of other auxiliary agents, and it is also easy to avoid the situation where the characteristics of the battery such as high-load discharge characteristics are reduced. The amount of other auxiliary agents is more preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and more preferably 3% by mass or less, and more preferably 1% by mass or less.

[0376] The electrolyte of the present invention may further contain cyclic and chain carboxylates, ether compounds, nitrogen-containing compounds, boron-containing compounds, organic silicon compounds, non-flammable (flame retardant) agents, surfactants, high dielectric additives, cycle characteristics and rate characteristics improvers, sulfone compounds, etc. as additives within the range that does not impair the effects of the present invention.

[0377] Examples of the cyclic carboxylic acid ester include compounds having a total carbon number of 3 to 12 in the structural formula. Specifically, examples include γ-butyrolactone, γ-valerolactone, γ-caprolactone, ε-caprolactone, and 3-methyl-γ-butyrolactone. Among them, γ-butyrolactone is particularly preferred from the perspective of improving the characteristics of the electrochemical device due to an increase in the degree of lithium ion dissociation.

[0378] The amount of the cyclic carboxylic acid ester as an additive is usually preferably more than 0.1% by mass in 100% by mass of the solvent, more preferably more than 1% by mass. If it is this range, the conductivity of the electrolyte can be improved, and the large current discharge characteristics of the electrochemical device can be easily improved. In addition, the amount of the cyclic carboxylic acid ester is preferably less than 10% by mass, more preferably less than 5% by mass. By setting the upper limit in this way, the viscosity of the electrolyte is made to be an appropriate range, the reduction of conductivity is avoided, the increase of the negative electrode resistance is suppressed, and the large current discharge characteristics of the electrochemical device are easily made to be a good range.

[0379] Furthermore, as the cyclic carboxylic acid ester, a fluorinated cyclic carboxylic acid ester (fluorinated lactone) can also be preferably used. As the fluorinated lactone, for example, there can be mentioned a fluorinated lactone represented by the following formula (C).

[0380]

[0381] (Where X 15 ~X 20 are the same or different, and are -H, -F, -Cl, -CH3 or fluoroalkyl; wherein X 15 ~X 20 At least one of which is a fluorinated alkyl group)

[0382] As X 15 ~X 20 The fluorinated alkyl group may be, for example, -CFH2, -CF2H, -CF3, -CH2CF3, -CF2CF3, -CH2CF2CF3, -CF(CF3)2, and is preferably -CH2CF3 or -CH2CF2CF3 in view of high oxidation resistance and safety improvement effect.

[0383] If X 15 ~X 20 At least one of them is a fluoroalkyl group, then -H, -F, -Cl, -CH3 or a fluoroalkyl group may be present only in X 15 ~X 20 The substitution may be performed at one site or at multiple sites. From the viewpoint of good solubility of the electrolyte salt, the substitution may be performed at 1 to 3 sites, and more preferably at 1 to 2 sites.

[0384] The substitution position of the fluoroalkyl group is not particularly limited, but from the perspective of good synthesis yield, X 17and / or X 18 , especially X 17 or X 18 is a fluoroalkyl group, among which -CH2CF3 and -CH2CF2CF3 are preferred. X other than a fluoroalkyl group 15 ~X 20 It is -H, -F, -Cl or CH 3 , and -H is particularly preferred from the viewpoint of good solubility of the electrolyte salt.

[0385] Examples of the fluorine-containing lactone include, in addition to the compounds represented by the above formula, fluorine-containing lactone represented by the following formula (D).

[0386]

[0387] (In the formula, either A or B is CX 226 X 227 (X 226 and X 227 Rf is the same or different, and is -H, -F, -Cl, -CF3, -CH3 or an alkylene group in which the hydrogen atom may be substituted by a halogen atom and may contain a heteroatom in the chain, and the other is an oxygen atom; 12 is a fluorinated alkyl or fluorinated alkoxy group which may have an ether bond; X 221 and X 222 The same or different, all are -H, -F, -Cl, -CF3 or CH3; X 223 ~X 225 The same or different, all are -H, -F, -Cl or an alkyl group whose hydrogen atom may be substituted by a halogen atom and may contain a heteroatom in the chain; n = 0 or 1.

[0388] As the fluorine-containing lactone represented by the formula (D), preferably, a five-membered ring structure represented by the following formula (E) is used, from the viewpoint of easy synthesis and good chemical stability.

[0389]

[0390] (In the formula, A, B, Rf 12 , X 221 , X 222 and X 223 Same as formula (D). Furthermore, by combining A and B, there are fluorine-containing lactone represented by the following formula (F) and fluorine-containing lactone represented by the following formula (G).

[0391]

[0392] (Where Rf 12 , X 221 , X 222 , X223 , X 226 and X 227 Same as formula (D).

[0393]

[0394] (Where Rf 12 , X 221 , X 222 , X 223 , X 226 and X 227 Same as formula (D).

[0395] Among these, from the aspect that excellent characteristics such as high dielectric constant and high withstand voltage can be particularly exerted, and the solubility of electrolyte salt and the reduction of internal resistance are good, and the aspect of improving the characteristics of the electrolyte solution in the present invention can be mentioned:

[0396] wait. By containing a fluorinated cyclic carboxylic acid ester, effects such as improvement in ion conductivity, improvement in safety, and improvement in stability at high temperatures can be obtained.

[0397] Examples of the chain carboxylic acid esters include compounds having a total carbon number of 3 to 7 in the structural formula thereof. Specifically, examples include methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isobutyl propionate, n-butyl propionate, methyl butyrate, isobutyl propionate, tert-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, n-propyl isobutyrate, and isopropyl isobutyrate.

[0398] Among them, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, and the like are preferred from the viewpoint of improving ion conductivity due to a decrease in viscosity.

[0399] As the ether compound, chain ethers having 2 to 10 carbon atoms and cyclic ethers having 3 to 6 carbon atoms are preferred. Examples of the chain ether having 2 to 10 carbon atoms include dimethyl ether, diethyl ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, diethoxymethane, dimethoxyethane, methoxyethoxyethane, diethoxyethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol, diethylene glycol dimethyl ether, pentaethylene glycol, triethylene glycol dimethyl ether, triethylene glycol, tetraethylene glycol, tetraethylene glycol dimethyl ether, and diisopropyl ether.

[0400] Furthermore, as the above-mentioned ether compound, fluorinated ether can also be preferably used. Examples of the fluoroether include fluoroether (I) represented by the following general formula (I). R 3 -O-Rf 4 (I) (Where Rf 3 and Rf 4 are the same or different and are alkyl groups having 1 to 10 carbon atoms or fluoroalkyl groups having 1 to 10 carbon atoms. 3 and Rf 4 At least one of them is a fluorinated alkyl group.) By containing the fluoroether (I), the flame retardancy of the electrolyte solution is improved, and the stability and safety at high temperature and high voltage are improved.

[0401] In the above general formula (I), Rf 3 and Rf 4 At least one of the alkyl groups may be a fluoroalkyl group having 1 to 10 carbon atoms. From the viewpoint of further improving the flame retardancy, stability at high temperature and high voltage, and safety of the electrolyte, Rf 3 and Rf 4 Preferably, they are all fluoroalkyl groups having 1 to 10 carbon atoms. 3 and Rf 4 They can be the same or different from each other. Among them, Rf 3 and Rf 4 The same or different, more preferably Rf 3 is a fluoroalkyl group having 3 to 6 carbon atoms and Rf 4 It is a fluorinated alkyl group having 2 to 6 carbon atoms.

[0402] If Rf 3 and Rf 4 If the total number of carbon atoms of Rf is too small, the boiling point of the fluoroether becomes too low. 3 or Rf 4 If the number of carbon atoms in the electrolyte is too large, the solubility of the electrolyte salt decreases, and the compatibility with other solvents begins to be adversely affected. In addition, the viscosity increases, so the rate characteristics decrease. 3 The number of carbon atoms is 3 or 4, Rf 4 When the number of carbon atoms is 2 or 3, it is advantageous in that the boiling point and rate characteristics are excellent.

[0403] The fluorine content of the fluoroether (I) is preferably 40 to 75% by mass. When the fluorine content is within this range, the balance between non-flammability and compatibility is particularly excellent. In addition, it is also preferred from the perspective of good oxidation resistance and safety. The lower limit of the fluorine content is more preferably 45% by mass, further preferably 50% by mass, and particularly preferably 55% by mass, and the upper limit is more preferably 70% by mass, further preferably 66% by mass. The fluorine content of the fluoroether (I) is a value calculated from {(number of fluorine atoms×19) / molecular weight of the fluoroether (I)}×100(%) based on the structural formula of the fluoroether (I).

[0404] As Rf 3 For example, CF3CF2CH2-, CF3CFHCF2-, HCF2CF2CF2-, HCF2CF2CH2-, CF3CF2CH2CH2-, CF3CFHCF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CF2CH2-, HCF2CF2CH2CH2-, HCF2CF(CF3)CH2-, etc. can be cited. In addition, as Rf 4 For example, -CH2CF2CF3, -CF2CFHCF3, -CF2CF2CF2H, -CH2CF2CF2H, -CH2CH2CF2CF3, -CH2CF2CFHCF3, -CF2CF2CF2CF2H, -CH2CF2CF2CF2H, -CH2CH2CF2CF2H, -CH2CF(CF3)CF2H, -CF2CF2H, -CH2CF2H, -CF2CH3, etc. can be mentioned.

[0405] Specific examples of the fluoroether (I) include HCF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CF2H, HCF2CF2CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, C6F 13 OCH3、C6F 13 OC2H5、C8F 17 OCH3、C8F 17 OC2H5, CF3CFHC F2CH(CH3)OCF2CFHCF3, HCF2CF2OCH(C2H5)2, HCF2CF2OC4H9, HCF2CF2OCH2CH(C2H5)2, HCF2CF2OCH2CH(CH3)2, etc.

[0406] Among them, compounds containing HCF2- or CF3CFH- at one or both ends can provide fluoroether (I) with excellent polarizability and high boiling point. The boiling point of fluoroether (I) is preferably 67 to 120°C, more preferably 80°C or higher, and even more preferably 90°C or higher.

[0407] As such fluoroether (I), for example, one or more of CF3CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, HCF2CF2CH2OCF2CFHCF3, HCF2CF2CH2OCH2CF2CF2H, CF3CFHCF2CH2OCF2CFHCF3, HCF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CF2H and the like can be mentioned. Among them, considering the advantages of high boiling point, compatibility with other solvents and good solubility of electrolyte salt, it is preferably at least one selected from HCF2CF2CH2OCF2CFHCF3 (boiling point 106°C), CF3CF2CH2OCF2CFHCF3 (boiling point 82°C), HCF2CF2CH2OCF2CF2H (boiling point 92°C) and CF3CF2CH2OCF2CF2H (boiling point 68°C), and more preferably at least one selected from HCF2CF2CH2OCF2CFHCF3 (boiling point 106°C) and HCF2CF2CH2OCF2CF2H (boiling point 92°C).

[0408] Examples of the cyclic ether having 3 to 6 carbon atoms include 1,2-dioxane, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane, trioxane, 2-methyl-1,3-dioxolane, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-(trifluoroethyl)dioxolane, 2,2-bis(trifluoromethyl)-1,3-dioxolane, and fluorinated compounds thereof. Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, and crown ethers are preferred from the viewpoint of having low viscosity and providing high ion conductivity. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred from the viewpoint of having high solvation ability in lithium ions and improving the degree of ion dissociation.

[0409] Examples of the nitrogen-containing compound include nitrile, fluorine-containing nitrile, carboxylic acid amide, fluorine-containing carboxylic acid amide, sulfonic acid amide, fluorine-containing sulfonic acid amide, acetamide, formamide, etc. In addition, 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, and N-methylsuccinimide, etc. can also be used. However, the nitrile compound represented by the above general formula (1a), (1b) and (1c) is not included in the above nitrogen-containing compound.

[0410] Examples of the boron-containing compound include boric acid esters such as trimethyl borate and triethyl borate, boric acid ethers, and alkylboranes.

[0411] Examples of the organic silicon-containing compound include (CH 3 ) 4 —Si, (CH 3 ) 3 —Si—Si(CH 3 ) 3 , and silicone oil.

[0412] As the above-mentioned incombustible (flame retardant) agent, phosphate esters and phosphazene compounds can be cited. As the above-mentioned phosphate esters, for example, fluorine-containing alkyl phosphate esters, non-fluorine-based alkyl phosphate esters, aryl phosphate esters, etc. can be cited. Among them, from the aspect of being able to exert the incombustible effect in a small amount, fluorine-containing alkyl phosphate esters are preferred.

[0413] Examples of the phosphazene compounds include methoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, dimethylaminopentafluorocyclotriphosphazene, diethylaminopentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene.

[0414] Specific examples of the fluorine-containing alkyl phosphate include fluorine-containing dialkyl phosphates described in Japanese Patent Application Laid-Open No. 11-233141, cyclic alkyl phosphates described in Japanese Patent Application Laid-Open No. 11-283669, and fluorine-containing trialkyl phosphates.

[0415] As the above-mentioned non-combustible (flame retardant) agent, preferred are (CH3O)3P=O, (CF3CH2O)3P=O, (HCF2CH2O)3P=O, (CF3CF2CH2)3P=O, (HCF2CF2CH2)3P=O and the like.

[0416] The surfactant may be any of a cationic surfactant, anionic surfactant, nonionic surfactant, and amphoteric surfactant. From the viewpoint of good cycle characteristics and rate characteristics, the surfactant preferably contains a fluorine atom.

[0417] As such a fluorine atom-containing surfactant, for example, a fluorine-containing carboxylate represented by the following formula (30), a fluorine-containing sulfonate represented by the following formula (40), or the like is preferred. R 5 COO － M + (30) (Where Rf 5 M is a fluorinated alkyl group having 3 to 10 carbon atoms and may contain an ether bond; + For Li + 、Na + , K + or NHR'3 + (R' is the same or different, and is H or an alkyl group having 1 to 3 carbon atoms)) R 6 SO3 － M + (40) (Where Rf 6 M is a fluorinated alkyl group having 3 to 10 carbon atoms and may contain an ether bond; + For Li + 、Na + , K + or NHR'3 + (R' is the same or different, and is H or an alkyl group having 1 to 3 carbon atoms))

[0418] The content of the surfactant in the electrolyte is preferably 0.01 to 2% by mass from the viewpoint of being able to reduce the surface tension of the electrolyte without deteriorating the charge-discharge cycle characteristics.

[0419] Examples of the high dielectric additive include sulfolane, methyl sulfolane, γ-butyrolactone, and γ-valerolactone.

[0420] Examples of the cycle characteristics and rate characteristics improving agent include methyl acetate, ethyl acetate, tetrahydrofuran, and 1,4-dioxane.

[0421] In addition, the electrolyte solution of the present invention may be further combined with a polymer material to form a gel electrolyte solution in a gel state (plasticized).

[0422] As the polymer material, there can be mentioned conventionally known polyethylene oxide, polypropylene oxide, and their modified bodies (Japanese Patent Publication No. 8-222270, Japanese Patent Publication No. 2002-100405); polyacrylate polymers, polyacrylonitrile, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer and other fluororesins (Japanese Patent Publication No. 4-506726, Japanese Patent Publication No. 8-507407, Japanese Patent Publication No. 10-294131); composites of these fluororesins and hydrocarbon resins (Japanese Patent Publication No. 11-35765, Japanese Patent Publication No. 11-86630), etc. It is particularly preferred to use polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer as the polymer material for gel electrolyte.

[0423] Furthermore, the electrolyte solution of the present invention may further contain an ion conductive compound described in Japanese Patent Application No. 2004-301934.

[0424] The ion conductive compound is an amorphous fluorine-containing polyether compound represented by the formula (1-1) and having a fluorine-containing group in a side chain. A-(D)-B(1-1) [Wherein, D is formula (2-1): -(D1) n -(FAE) m -(AE) p - (Y) q-(2-1) (wherein, D1 is an ether unit having a fluorine-containing ether group in the side chain represented by formula (2a),

[0425]

[0426] (wherein, Rf is a fluorine-containing ether group having a crosslinkable functional group; R 10 is a group or connecting bond that bonds Rf to the main chain) FAE is an ether unit having a fluoroalkyl group in the side chain represented by formula (2b);

[0427]

[0428] (wherein, Rfa is a hydrogen atom or a fluoroalkyl group which may have a crosslinkable functional group; R 11 is a group or connecting bond that bonds Rfa to the main chain) AE is an ether unit represented by formula (2c);

[0429]

[0430] (Where R 13 is 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 an aromatic hydrocarbon group which may have a crosslinkable functional group; R 12 For bonding R 13 Groups or bonds to the main chain) Y is a unit containing at least one of formulae (2d-1) to (2d-3);

[0431]

[0432] 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; wherein n+m is not 0, and the bonding order of D1, FAE, AE and Y is not specific); A and B are the same or different and are a hydrogen atom, an alkyl group which may contain a fluorine atom and / or a crosslinkable functional group, a phenyl group which may contain a fluorine atom and / or a crosslinkable functional group, a -COOH group, -OR (R is a hydrogen atom or an alkyl group which may contain a fluorine atom and / or a crosslinkable functional group), an ester group or a carbonate group (wherein, when the terminal of D is an oxygen atom, it is not a -COOH group, -OR, an ester group or a carbonate group)]

[0433] The electrolyte of the present invention may contain a sulfone compound. The sulfone compound is preferably a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms. The number of sulfonyl groups in one molecule is preferably 1 or 2.

[0434] Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones as monosulfone compounds, and trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones as disulfone compounds. Among them, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferred from the viewpoint of dielectric constant and viscosity, and tetramethylene sulfones (sulfolanes) are particularly preferred.

[0435] As sulfolanes, preferably sulfolane and / or sulfolane derivatives (hereinafter, sometimes also including sulfolane and abbreviated as "sulfolanes"). As sulfolane derivatives, preferably one or more of the hydrogen atoms bonded on the carbon atom constituting the sulfolane ring are substituted by fluorine atoms or alkyl groups.

[0436] Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methylsulfolane, 4-fluoro-2-methyl sulfolane, 5-fluoro-3-methyl sulfolane, 5-fluoro-2-methyl sulfolane, 2-fluoromethyl sulfolane, 3-fluoromethyl sulfolane, 2-difluoromethyl sulfolane, 3-difluoromethyl sulfolane, 2-trifluoromethyl sulfolane, 3-trifluoromethyl sulfolane, 2-fluoro-3-(trifluoromethyl) sulfolane, 3-fluoro-3-(trifluoromethyl) sulfolane, 4-fluoro-3-(trifluoromethyl) sulfolane, 3-cyclobutene sulfolane, 5-fluoro-3-(trifluoromethyl) sulfolane, etc.

[0437] Examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n-butyl methyl sulfone, n-butyl ethyl sulfone, tert-butyl methyl sulfone, tert-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl Trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, bis(trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl n-propyl sulfone, difluoromethyl n-propyl sulfone, trifluoromethyl n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl n-butyl sulfone, trifluoroethyl tert-butyl sulfone, pentafluoroethyl n-butyl sulfone, pentafluoroethyl tert-butyl sulfone, etc.

[0438] Among them, preferred are dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, tert-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, trifluoromethyl n-propyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl n-butyl sulfone, trifluoroethyl tert-butyl sulfone, trifluoromethyl n-butyl sulfone, and trifluoromethyl tert-butyl sulfone.

[0439] The content of sulfone compounds is not particularly limited, as long as the effect of the present invention is not significantly damaged, and is arbitrary. In the above-mentioned solvent 100 volume %, it is usually 0.3 volume % or more, preferably 0.5 volume % or more, more preferably 1 volume % or more, and in addition, it is usually 40 volume % or less, preferably 35 volume % or less, and more preferably 30 volume % or less. If the content of sulfone compounds is within the above-mentioned range, it is easy to obtain the effect of improving the durability such as cycle characteristics and storage characteristics. In addition, if the viscosity of the non-aqueous electrolyte is set to an appropriate range, the reduction of conductivity can be avoided, and the input-output characteristics and charge-discharge rate characteristics of the non-aqueous electrolyte secondary battery can be made into an appropriate range.

[0440] The electrolyte solution of the present invention may further contain other additives as required. Examples of other additives include metal oxides and glass.

[0441] In addition, at least one selected from vinylene carbonate, lithium bis(oxalatoborate), lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide, cyclohexanetricarbonitrile, tris(trimethylsilyl)phosphate, LiPO2F2, and a compound represented by the following structural formula may be added. The amount of the compound is preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the electrolyte. The amount of the compound is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 4% by mass or less, further preferably 3% by mass or less.

[0442] The electrolyte of the present invention preferably contains 5 to 200 ppm of hydrogen fluoride (HF). By containing HF, the film formation of the above-mentioned additives can be promoted. If the HF content is too little, there is a tendency for the film forming ability on the negative electrode to decrease, and the characteristics of the electrochemical device to decrease. In addition, if the HF content is too much, there is a tendency for the oxidation resistance of the electrolyte to decrease due to the influence of HF. Even if the electrolyte of the present invention contains HF in the above range, it will not reduce the high temperature storage capacity recovery rate of the electrochemical device. The HF content is more preferably 10 ppm or more, and further preferably 20 ppm or more. In addition, the HF content is more preferably 100 ppm or less, further preferably 80 ppm or less, and particularly preferably 50 ppm or less. The HF content can be determined by neutralization titration.

[0443] The electrolyte solution of the present invention can be prepared by any method using the above-mentioned components.

[0444] The electrolyte solution of the present invention can be suitably applied to electrochemical devices such as lithium ion secondary batteries, lithium ion capacitors, hybrid capacitors, and electric double layer capacitors. A non-aqueous electrolyte battery using the electrolyte solution of the present invention will be described below. The non-aqueous electrolyte battery may have a known structure, and typically comprises a positive electrode capable of absorbing and releasing ions (such as lithium ions) and a positive electrode and the electrolyte of the present invention. Such an electrochemical device comprising the electrolyte of the present invention is also one of the present invention.

[0445] Electrochemical devices include lithium ion secondary batteries, lithium ion capacitors, capacitors (hybrid capacitors, electric double layer capacitors), free radical batteries, solar cells (especially dye-sensitized solar cells), lithium ion primary batteries, fuel cells, various electrochemical sensors, electrochromic elements, electrochemical switching elements, aluminum electrolytic capacitors, tantalum electrolytic capacitors, etc., preferably lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors. A module including the above electrochemical device is also one of the present invention.

[0446] Furthermore, the present invention is also a lithium ion secondary battery comprising the electrolytic solution of the present invention. The lithium ion secondary battery may include a positive electrode, a negative electrode, and the electrolyte solution.

[0447] <Positive electrode> The positive electrode is composed of a positive electrode active material layer containing a positive electrode active material and a current collector.

[0448] As the positive electrode active material, there is no particular limitation as long as it can electrochemically absorb and release lithium ions, and examples thereof include lithium-containing transition metal composite oxides, lithium-containing transition metal phosphate compounds, sulfides, conductive polymers, etc. Among them, as the positive electrode active material, preferably lithium-containing transition metal composite oxides, lithium-containing transition metal phosphate compounds, particularly preferably lithium-containing transition metal composite oxides that produce high voltage.

[0449] As the transition metal of the lithium-containing transition metal composite oxide, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferred. As specific examples, lithium-cobalt composite oxides such as LiCoO2, lithium-nickel composite oxides such as LiNiO2, lithium-manganese composite oxides such as LiMnO2, LiMn2O4, Li2MnO4, and compounds in which part of the transition metal atoms that will become the main body of these lithium transition metal composite oxides are replaced by other elements such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, etc. Specific examples of the substituted compounds include LiNi 0.5 Mn 0.5 O2、LiNi 0.85 Co 0.10 Al 0.05 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.33 Co 0.33 Mn 0.33 O2、LiNi 0.45 Co 0.10 Al 0.45 O2、LiMn 1.8 Al 0.2 O4、LiMn 1.5 Ni 0.5 O4, etc.

[0450] Among them, as the lithium-containing transition metal composite oxide, LiMn having high energy density even at a high voltage of 4.4 V or more is preferred. 1.5 Ni 0.5 O4、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2.

[0451] The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. As specific examples, there can be mentioned iron phosphates such as LiFePO4, Li3Fe2(PO4)3, LiFeP2O7, cobalt phosphates such as LiCoPO4, and compounds in which a part of the transition metal atoms that will become the main body of these lithium transition metal phosphate compounds are replaced by other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.

[0452] Examples of the lithium-containing transition metal composite oxide include By formula: Li a Mn 2－b M 1 b O4 (where 0.9≤a; 0≤b≤1.5; M 1 A lithium-manganese spinel composite oxide represented by at least one metal selected from Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge, Formula: LiNi 1－c M 2 c O2(where 0≤c≤0.5; M 2 A lithium-nickel composite oxide represented by at least one metal selected from Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge, or Formula: LiCo 1－d M 3 d O2(where 0≤d≤0.5; M 3 A lithium-cobalt composite oxide represented by at least one metal selected from Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge.

[0453] Among them, LiCoO2, LiMnO2, LiNiO2, LiMn2O4, LiNi 0.8 Co 0.15 Al 0.05 O2, or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2.

[0454] As other positive electrode active materials, LiFePO4, LiNi 0.8 Co 0.2 O2、Li 1.2 Fe 0.4 Mn 0.4 O2、LiNi 0.5 Mn 0.5 O2, LiV3O6, etc.

[0455] Examples of sulfides include compounds having a two-dimensional layered structure such as TiS2 and MoS2, and compounds having the general formula Me x Mo6S8 (Me is a transition metal represented by Pb, Ag or Cu) and has a strong three-dimensional skeleton structure. In addition, sulfur, LiS x Represented by organic lithium sulfide, etc.

[0456] Examples of the conductive polymer include p-doped conductive polymers and n-doped conductive polymers. Examples of the conductive polymer include polyacetylene-based polymers, polyphenylene-based polymers, heterocyclic polymers, ionic polymers, ladder polymers, and network polymers.

[0457] In addition, if lithium phosphate is included in the positive electrode active material, the continuous charging characteristics are improved, so it is preferred. The use of lithium phosphate is not limited, and it is preferred to mix the above-mentioned positive electrode active material and lithium phosphate. The amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and more preferably 0.5% by mass or more, with respect to the total of the above-mentioned positive electrode active material and lithium phosphate, and the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and more preferably 5% by mass or less.

[0458] In addition, a substance obtained by attaching a substance having a different composition to the surface of the above-mentioned positive electrode active material can be used. Examples of the surface-attached substance include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide, sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

[0459] These surface-attached substances can be attached to the surface of the positive electrode active material by, for example, dissolving or suspending in a solvent, impregnating and adding to the positive electrode active material, and drying, making a surface-attached substance precursor dissolved or suspended in a solvent, impregnating and adding to the positive electrode active material, and then reacting by heating, etc., adding to the positive electrode active material precursor and calcining at the same time, etc. It should be noted that in the case of attaching carbon, a method of mechanically attaching the carbon in the form of, for example, activated carbon can also be used.

[0460] The amount of the surface-attached substance is preferably 0.1 ppm or more, more preferably 1 ppm or more, and further preferably 10 ppm or more, relative to the above-mentioned positive electrode active material, by mass, as a lower limit of use, and preferably 20% or less, more preferably 10% or less, and further preferably 5% or less as an upper limit of use. The surface-attached substance can inhibit the oxidation reaction of the electrolyte on the surface of the positive electrode active material and improve the battery life, but when the amount of the attached substance is too small, the effect cannot be fully manifested, and when it is too much, it hinders the entry and exit of lithium ions, so sometimes the resistance increases.

[0461] The shape of the particles of the positive electrode active material may be block, polyhedron, sphere, ellipsoid, plate, needle, column, etc. as conventionally used. In addition, the primary particles may be aggregated to form secondary particles.

[0462] The tap density of the positive electrode active material is preferably 0.5 g / cm 3 More preferably, 0.8 g / cm 3 More preferably, 1.0 g / cm 3 Above. If the tap density of the positive electrode active material is lower than the above lower limit, the amount of dispersion medium required increases when the positive electrode active material layer is formed, and the amount of conductive material or binder required increases, which restricts the filling rate of the positive electrode active material in the positive electrode active material layer, and sometimes the battery capacity is restricted. By using a composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. Generally, the larger the tap density, the better, and there is no particular upper limit. However, if it is too large, the diffusion of lithium ions in the positive electrode active material layer with the electrolyte as the medium becomes rate-limiting, and sometimes the load characteristics are easily reduced. Therefore, the upper limit is preferably 4.0g / cm 3 Below, more preferably 3.7 g / cm 3 Below, more preferably 3.5 g / cm 3 the following. It should be noted that in the present invention, the tap density is the powder packing density (tap density) when 5 to 10 g of the positive electrode active material powder is added to a 10 ml glass volumetric flask and tapped 200 times with a stroke of about 20 mm. 3 And find out.

[0463] The median diameter d50 of the particles of the positive electrode active material (secondary particle diameter when the primary particles agglomerate to form secondary particles) is preferably 0.3 μm or more, more preferably 0.5 μm or more, further preferably 0.8 μm or more, and most preferably 1.0 μm or more. In addition, it is preferably 30 μm or less, more preferably 27 μm or less, further preferably 25 μm or less, and most preferably 22 μm or less. If it is lower than the above lower limit, it is sometimes impossible to obtain a high tap density product. If it is greater than the upper limit, the diffusion of lithium in the particles takes time, so the battery performance is sometimes reduced; or the positive electrode of the battery is made, that is, the active material and the conductive material or adhesive are slurried in a solvent and coated as a thin film. Problems such as stripes occur. Here, by mixing two or more of the above-mentioned positive electrode active materials with different median diameters d50, the filling property during the production of the positive electrode can be further improved.

[0464] It should be noted that in the present invention, median diameter d50 is measured by known laser diffraction / scattering particle size distribution measuring device. When using HORIBA LA-920 as a particle size distribution meter, as the dispersion medium used during measurement, 0.1% by mass sodium hexametaphosphate aqueous solution is used, and after 5 minutes of ultrasonic dispersion, the refractive index is set to 1.24 and measured.

[0465] When the primary particles are agglomerated to form secondary particles, the average primary particle size of the positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.2 μm or more, and the upper limit is preferably 5 μm or less, more preferably 4 μm or less, further preferably 3 μm or less, and most preferably 2 μm or less. If it is greater than the above upper limit, it is difficult to form spherical secondary particles, which sometimes has a negative impact on the filling property of the powder; or the possibility of reducing battery performance such as power characteristics due to a significant reduction in specific surface area becomes higher. On the contrary, if it is lower than the above lower limit, the crystal is usually not developed, so sometimes problems such as poor reversibility of charge and discharge occur.

[0466] It should be noted that in the present invention, the primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph with a magnification of 10,000 times, for any 50 primary particles, the longest value of the slice based on the left and right boundary lines of the primary particles relative to the straight line in the horizontal direction is obtained, and the average value is obtained.

[0467] The BET specific surface area of ​​the positive electrode active material is preferably 0.1 m 2 / g or more, more preferably 0.2m 2 / g or more, more preferably 0.3m 2 / g or more, and the upper limit is preferably 50m 2 / g or less, more preferably 40m2 / g or less, more preferably 30m 2 If the BET specific surface area is smaller than this range, the battery performance is likely to decrease, while if it is larger, it is difficult to increase the tap density, and problems may occur in coating properties when forming the positive electrode active material layer.

[0468] It should be noted that in the present invention, the BET specific surface area is defined by the following value: using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.), after pre-drying the sample at 150°C for 30 minutes under nitrogen flow, using a nitrogen-helium mixed gas accurately adjusted in such a way that the relative pressure of nitrogen to atmospheric pressure reaches 0.3, the value is measured by the nitrogen adsorption BET single-point method utilizing the gas flow method.

[0469] When the lithium ion secondary battery of the present invention is used as a large lithium ion secondary battery for hybrid vehicles or distributed power sources, high power is required, and therefore the particles of the positive electrode active material preferably mainly contain secondary particles. The particles of the positive electrode active material preferably contain 0.5 to 7.0 volume % of secondary particles having an average particle size of 40 μm or less and an average primary particle size of 1 μm or less. By containing particles having an average primary particle size of 1 μm or less, the contact area with the electrolyte becomes larger, which can accelerate the diffusion of lithium ions between the electrode and the electrolyte, resulting in the ability to improve the power performance of the battery.

[0470] As a method for manufacturing positive electrode active materials, conventional methods for manufacturing inorganic compounds are used. In particular, in order to make spherical or ellipsoidal active materials, various methods are considered, such as the following methods, etc.: the raw material of the transition metal is dissolved or crushed and dispersed in a solvent such as water, pH is adjusted while stirring, a spherical precursor is made and recovered, and after drying it as needed, LiOH, Li2CO3, LiNO3 and other Li sources are added, and calcined at high temperature to obtain an active material.

[0471] In order to manufacture the positive electrode, the above-mentioned positive electrode active materials can be used alone, or two or more of different compositions can be used in any combination or ratio. As a preferred combination in this case, LiCoO2 and LiNi 0.33 Co 0.33 Mn 0.33 O2, etc. A combination of substances obtained by replacing a portion of LiMn2O4 or its Mn with other transition metals, etc.; or a combination of substances obtained by replacing a portion of LiCoO2 or its Co with other transition metals, etc.

[0472] In terms of high battery capacity, the content of the positive electrode active material is preferably 50 to 99.5% by mass of the positive electrode mixture, and more preferably 80 to 99% by mass. In addition, 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. In addition, the upper limit is preferably 99% by mass or less, and more preferably 98% by mass or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the capacity is sometimes insufficient. On the contrary, if the content is too high, the strength of the positive electrode is sometimes insufficient.

[0473] The positive electrode mixture preferably further includes a binder, a thickener, and a conductive material. As the above-mentioned binder, any binder can be used as long as it is a material safe for the solvent and electrolyte used in the manufacture of the electrode, and examples thereof include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, chitosan, alginic acid, polyacrylic acid, polyimide, cellulose, and nitrocellulose; rubber polymers such as SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR (acrylonitrile-butadiene rubber), and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers; Polymers or their hydrogenated products; thermoplastic elastomer-like polymers such as EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer or their hydrogenated products; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene-α-olefin copolymer; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride copolymer, tetrafluoroethylene-ethylene copolymer; polymer compositions having ion conductivity of alkali metal ions (especially lithium ions), etc. These may be used alone or in combination of two or more in any combination and ratio.

[0474] The content of the binder is measured in the ratio of the binder in the positive electrode active material layer, usually 0.1 mass % or more, preferably 1 mass % or more, more preferably 1.5 mass % or more, in addition, usually 80 mass % or less, preferably 60 mass % or less, more preferably 40 mass % or less, most preferably 10 mass % or less. If the ratio of the binder is too low, the positive electrode active material cannot be fully maintained, the mechanical strength of the positive electrode is insufficient, and the battery performance such as the cycle characteristics deteriorates sometimes. On the other hand, if too high, it sometimes leads to a reduction in battery capacity or conductivity.

[0475] Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, polyvinyl pyrrolidone, and salts thereof, etc. One type may be used alone, or two or more types may be used in any combination and ratio.

[0476] The ratio of thickener to active material is usually 0.1 mass %, preferably 0.2 mass %, more preferably 0.3 mass %, in addition, usually 5 mass %, preferably 3 mass %, more preferably 2 mass %. If it is lower than this scope, the coating property is significantly reduced sometimes. If it is greater than this scope, the ratio of active material in positive electrode active material layer is reduced, and the problem of the capacity reduction of battery or the problem of increased resistance between positive electrode active materials is sometimes generated.

[0477] As the above-mentioned conductive material, known conductive materials can be used arbitrarily. As a specific example, metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, etc., carbon materials such as amorphous carbon such as needle coke, carbon nanotubes, fullerene, VGCF, etc. can be cited. It should be noted that they can be used alone, or two or more can be used in any combination and ratio. The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and is usually 50% by mass or less, preferably 30% by mass or less, and more preferably 15% by mass or less in the positive electrode active material layer. If the content is lower than this range, sometimes the conductivity is insufficient. Conversely, if the content is higher than this range, sometimes the battery capacity is reduced.

[0478] As a solvent for forming the slurry, as long as it is a solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as needed, its type is not particularly limited, and any of an aqueous solvent and an organic solvent can be used. As an aqueous solvent, for example, water, a mixed solvent of alcohol and water, etc. can be cited. As an organic solvent, for example, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, 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); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide, etc.

[0479] Examples of the material of the positive electrode current collector include metals such as aluminum, titanium, tantalum, stainless steel, nickel, or alloys thereof; and carbon materials such as carbon cloth and carbon paper. Among them, metal materials are preferred, and aluminum or alloys thereof are particularly preferred.

[0480] As the shape of the current collector, in the case of metal materials, metal foil, metal cylinder, metal coil, metal plate, metal film, extended metal, stamped metal, foamed metal, etc. can be cited, and in the case of carbon materials, carbon plate, carbon film, carbon cylinder, etc. can be cited. Among these, metal film is preferred. It should be noted that the film can be appropriately formed into a mesh. The thickness of the film is arbitrary, usually more than 1 μm, preferably more than 3 μm, more preferably more than 5 μm, and usually less than 1 mm, preferably less than 100 μm, more preferably less than 50 μm. If the film is thinner than this range, the strength required as a current collector is sometimes insufficient. On the contrary, if the film is thicker than this range, sometimes the handling property is impaired.

[0481] In addition, from the viewpoint of reducing the electrical contact resistance between the current collector and the positive electrode active material layer, it is also preferred to apply a conductive additive on the surface of the current collector. Examples of the conductive additive include carbon or precious metals such as gold, platinum, and silver.

[0482] The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, and the value of (the thickness of the positive electrode active material layer on one side before the electrolyte injection) / (the thickness of the current collector) is preferably less than 20, more preferably less than 15, and most preferably less than 10, and preferably more than 0.5, more preferably more than 0.8, and most preferably more than 1. If it is greater than this range, the current collector sometimes generates heat due to Joule heat during high current density charging and discharging. If it is less than this range, the volume ratio of the current collector to the positive electrode active material increases, and sometimes the capacity of the battery decreases.

[0483] The positive electrode can be manufactured according to conventional methods. For example, a method of adding the above-mentioned binder, thickener, conductive material, solvent, etc. to the above-mentioned positive electrode active material to prepare a slurry-like positive electrode mixture, coating the slurry on a collector, drying it, and then pressing it to achieve high density can be cited.

[0484] The density increase can be achieved by hand pressing, roll pressing, etc. The density of the positive electrode active material layer is preferably 1.5 g / cm 3 More preferably, 2 g / cm 3 More preferably, 2.2 g / cm 3 More than 5 g / cm 3 Below, more preferably 4.5g / cm 3 Below, more preferably 4g / cm 3If the value is greater than this range, the permeability of the electrolyte near the collector / active material interface is reduced, and the charge-discharge characteristics at high current density are reduced, and sometimes high power cannot be obtained. In addition, if it is less than this range, the conductivity between active materials is reduced, the battery resistance is increased, and sometimes high power cannot be obtained.

[0485] When the electrolyte of the present invention is used, from the viewpoint of high power and improved stability at high temperature, the area of ​​the positive electrode active material layer is preferably set to be larger than the surface area of ​​the battery outer casing. Specifically, the sum of the electrode areas of the positive electrode relative to the surface area of ​​the outer packaging of the secondary battery is preferably set to 15 times or more, and more preferably 40 times or more in terms of area ratio. The surface area of ​​the battery outer casing refers to the total area calculated by the longitudinal, transverse and thickness dimensions of the shell part filled with the power generation element except the protruding part of the terminal in the case of a bottomed rectangular parallelepiped shape. In the case of a bottomed cylindrical shape, the geometric surface area of ​​the shell part filled with the power generation element except the protruding part of the terminal is approximated as a cylinder. The sum of the electrode areas of the positive electrode refers to the geometric surface area of ​​the positive electrode mixture layer relative to the mixture layer containing the negative electrode active material. In the structure formed by forming the positive electrode mixture layer on both sides separated by the collector foil, it refers to the sum of the areas of each face calculated separately.

[0486] The thickness of the positive electrode plate is not particularly limited. From the perspective of high capacity and high power, for a single side of the collector, the lower limit of the thickness of the composite layer after deducting the thickness of the metal foil of the core material is preferably greater than 10 μm, more preferably greater than 20 μm, and is also preferably less than 500 μm, more preferably less than 450 μm.

[0487] In addition, a positive electrode plate having a material having a different composition attached to the surface of the positive electrode plate may be used. Examples of the surface-attached material include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; and carbon.

[0488] <Negative electrode> The negative electrode is composed of a negative electrode active material layer containing a negative electrode active material and a current collector.

[0489] As the negative electrode material, there is no particular limitation as long as it can electrochemically absorb and release lithium ions. As specific examples, carbon materials, alloy materials, lithium-containing metal composite oxide materials, conductive polymers, etc. can be cited. They can be used alone or in combination of two or more.

[0490] Examples of the negative electrode active material include pyrolysis products of organic matter under various pyrolysis conditions, or carbonaceous materials such as artificial graphite and natural graphite that can absorb and release lithium; metal oxide materials such as tin oxide and silicon oxide that can absorb and release lithium; lithium metal; various lithium alloys; lithium-containing metal composite oxide materials, etc. These negative electrode active materials can be used in combination of two or more.

[0491] As a carbonaceous material capable of absorbing and releasing lithium, it is preferred that artificial graphite or refined natural graphite made by high-temperature treatment of graphitized pitch obtained from various raw materials, or a material obtained by carbonizing these graphites after surface treatment with organic matter other than pitch, selected from natural graphite, artificial graphite, artificial carbonaceous material and artificial graphite material, heat-treated once or more in the range of 400 to 3200 ° C, a carbonaceous material having a negative electrode active material layer containing at least two or more carbonaceous materials with different crystallinity and / or having an interface of carbonaceous materials with different crystallinity, and a carbonaceous material having an interface of carbonaceous materials with at least two or more carbonaceous materials with different orientations in the negative electrode active material layer, and a good balance of the initial irreversible capacity and high current density charge and discharge characteristics of the carbonaceous material. In addition, these carbon materials can be used alone, or two or more can be used in any combination and ratio.

[0492] Examples of the carbonaceous materials obtained by heat-treating the artificial carbonaceous material and the artificial graphite material at a temperature in the range of 400 to 3200° C. for more than one time include coal-based coke, petroleum-based coke, coal-based asphalt, petroleum-based asphalt and materials obtained by oxidation treatment of these asphalts, needle coke, asphalt coke and carbon agents obtained by partial graphitization of these, furnace black, acetylene black, asphalt-based carbon fibers and other organic materials' pyrolysis products, carbonizable organic materials and their carbides, or solutions obtained by dissolving carbonizable organic materials in low molecular weight organic solvents such as benzene, toluene, xylene, quinoline, n-hexane and their carbides, etc.

[0493] As the metal material used as the above-mentioned negative electrode active material (except lithium titanium composite oxide), as long as it can absorb and release lithium, it can be lithium alone, a single metal and alloy forming a lithium alloy, or any of their oxides, carbides, nitrides, silicides, sulfides or phosphides, etc., without special restrictions. As the single metal and alloy forming a lithium alloy, it is preferably a material containing metal and semi-metal elements of Group IIIA and Group IVA, and more preferably a single metal of aluminum, silicon and tin (hereinafter referred to as "specific metal elements") and an alloy or compound containing these atoms. They can be used alone or in combination of two or more in any combination and ratio.

[0494] As the negative electrode active material having at least one atom selected from the specific metal element, any metal single substance of the specific metal element, an alloy comprising two or more specific metal elements, an alloy comprising one or more specific metal elements and other one or more metal elements, and a compound containing one or more specific metal elements and a composite compound such as an oxide, carbide, nitride, silicide, sulfide or phosphide of the compound can be cited. By using these metal single substances, alloys or metal compounds as negative electrode active materials, the high capacity of the battery can be achieved.

[0495] In addition, compounds obtained by complex bonding of these composite compounds with a variety of elements such as metal simple substances, alloys or non-metallic elements can also be cited. Specifically, in the case of silicon or tin, alloys of these elements and metals that do not function as negative electrodes can also be used. For example, in the case of tin, a complex compound containing 5 to 6 elements by combining metals other than tin and silicon that function as negative electrodes, metals that do not function as negative electrodes, and non-metallic elements can also be used.

[0496] Specifically, Si single substance, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu6Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, SiO v (0<v≤2), LiSiO or tin, SnSiO3, LiSnO, Mg2Sn, SnO w (0<w≤2). In addition, a composite material containing Si or Sn as the first constituent element and further containing a second and a third constituent element can be mentioned. The second constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium and zirconium. The third constituent element is, for example, at least one of boron, carbon, aluminum and phosphorus. In particular, from the viewpoint of obtaining a high battery capacity and excellent battery characteristics, the metal material is preferably a simple substance of silicon or tin (which may contain a trace amount of impurities), SiO v (0<v≤2), SnO w (0≤w≤2), Si-Co-C composite material, Si-Ni-C composite material, Sn-Co-C composite material, Sn-Ni-C composite material.

[0497] As the lithium-containing metal composite oxide material used as the negative electrode active material, there is no particular restriction as long as it can absorb and release lithium. From the viewpoint of high current density charge and discharge characteristics, it is preferably a material containing titanium and lithium, more preferably a lithium-containing composite metal oxide material containing titanium, and further preferably a composite oxide of lithium and titanium (hereinafter referred to as "lithium-titanium composite oxide"). That is, if a lithium-titanium composite oxide having a spinel structure is contained and used in the negative electrode active material for an electrolyte battery, the output resistance is greatly reduced, so it is particularly preferred.

[0498] The lithium titanium composite oxide is preferably a compound having the general formula Li x Ti y M z The compound shown by O4. [wherein, 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 above components, (i)1.2≤x≤1.4, 1.5≤y≤1.7, z=0 (ii)0.9≤x≤1.1, 1.9≤y≤2.1, z=0 (iii)0.7≤x≤0.9, 2.1≤y≤2.3, z=0 The structure of is particularly preferred because the balance of battery performance is good.

[0499] A particularly preferred representative composition of the above compound is Li 4 / 3 Ti 5 / 3 O4, in (ii) it is Li1Ti2O4, in (iii) it is Li 4 / 5 Ti 11 / 5 O4. In addition, for the structure of Z≠0, for example, Li 4 / 3 Ti 4 / 3 Al 1 / 3 O4 is the preferred substance.

[0500] The negative electrode mixture preferably further contains a binder, a thickener, and a conductive material.

[0501] As the above-mentioned binder, the same substances as the binder that can be used in the positive electrode can be cited. 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, and particularly preferably 0.6% by mass or more. In addition, it is preferably 20% by mass or less, more preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 8% by mass or less. If the ratio of the binder to the negative electrode active material is greater than the above range, the proportion of the binder that does not contribute to the battery capacity increases, sometimes resulting in a reduction in the battery capacity. In addition, if it is less than the above range, it sometimes results in a reduction in the strength of the negative electrode.

[0502] In particular, in the case of containing a rubber-like polymer represented by SBR as the main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and in addition, it is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. In addition, in the case of containing a fluorine-based polymer represented by polyvinylidene fluoride as the main component, the ratio relative 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, and in addition, it is usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

[0503] As the above-mentioned thickener, the same substances as the thickeners that can be used in the positive electrode can be cited. The ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. If the ratio of the thickener to the negative electrode active material is lower than the above range, the coating property is sometimes significantly reduced. In addition, if it is greater than the above range, the proportion of the negative electrode active material in the negative electrode active material layer is reduced, and sometimes there is a problem of reduced capacity of the battery or increased resistance between the negative electrode active materials.

[0504] Examples of the conductive material of the negative electrode include metal materials such as copper and nickel; and carbon materials such as graphite and carbon black.

[0505] The type of solvent used to form the slurry is not particularly limited as long as it can dissolve or disperse the negative electrode active material, the binder, and, if necessary, the thickener and the conductive material. Both aqueous solvents and organic solvents can be used. Examples of aqueous solvents include water and alcohols, and examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.

[0506] Examples of the material of the negative electrode current collector include copper, nickel, stainless steel, etc. Among them, copper foil is preferred from the viewpoint of easy processing into a thin film and from the viewpoint of cost.

[0507] The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be excessively reduced, while if it is too thin, it may become difficult to handle.

[0508] The manufacture of the negative electrode can be carried out according to conventional methods. For example, a method of adding the above-mentioned binder, thickener, conductive material, solvent, etc. to the above-mentioned negative electrode to make a slurry, applying it on the collector and pressing it after drying to achieve high density can be cited. In addition, when an alloy material is used, a method of forming a thin film layer (negative electrode active material layer) containing the above-mentioned negative electrode active material by means of evaporation, sputtering, plating, etc. can also be used.

[0509] The electrode structure when the negative electrode active material is made into an electrode is not particularly limited. The density of the negative electrode active material on the current collector is preferably 1 g·cm -3 More preferably, 1.2 g·cm -3 More than 1.3 g·cm -3 More than 2.2 g·cm -3 Below, more preferably 2.1 g·cm -3 Below, more preferably 2.0 g·cm -3 Below, particularly preferably 1.9 g·cm -3 Below. If the density of the negative electrode active material on the collector is greater than the above range, the negative electrode active material particles are destroyed, sometimes resulting in an increase in the initial irreversible capacity, or a deterioration in the high current density charge and discharge characteristics caused by a decrease in the permeability of the electrolyte near the collector / negative electrode active material interface. In addition, if it is lower than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and sometimes the capacity per unit volume decreases.

[0510] The thickness of the negative electrode plate is designed accordingly according to the positive electrode plate used, and there is no particular restriction. The thickness of the composite layer after deducting the thickness of the metal foil of the core material is usually expected to be 15 μm or more, preferably 20 μm or more, and more preferably 30 μm or more. In addition, it is usually 300 μm or less, preferably 280 μm or less, and more preferably 250 μm or less.

[0511] In addition, a negative electrode plate having a material having a different composition attached to the surface of the negative electrode plate may be used. Examples of the surface-attached material include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

[0512] <Isolator> The lithium ion secondary battery of the present invention preferably further comprises a separator. The material or shape of the separator is not particularly limited as long as it is stable in the electrolyte and has excellent liquid retention, and known materials or shapes can be used. Among them, resins, glass fibers, inorganic substances, etc. formed of materials that are stable in the electrolyte of the present invention can be used, and preferably porous sheets or non-woven fabrics with excellent liquid retention are used.

[0513] As materials for resin and glass fiber separators, for example, polyolefins such as polyethylene and polypropylene, aramid, polytetrafluoroethylene, polyethersulfone, glass filters, etc. can be used. Polypropylene / polyethylene double-layer membranes, polypropylene / polyethylene / polypropylene three-layer membranes, etc., these materials can be used alone or in any combination and ratio. Among them, considering the good permeability of the electrolyte or the shut-down effect, the above-mentioned separator is preferably a porous sheet or non-woven fabric made of polyolefins such as polyethylene and polypropylene as a raw material.

[0514] The thickness of the separator is arbitrary, 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 thinner than the above range, the insulation or mechanical strength may be reduced. In addition, if it is too thicker than the above range, not only the battery performance such as rate characteristics may be reduced, but also the energy density of the electrolyte battery as a whole may be reduced.

[0515] In addition, when a porous object such as a porous sheet or nonwoven fabric is used as a separator, the porosity of the separator is arbitrary, usually 20% or more, preferably 35% or more, more preferably 45% or more, and usually 90% or less, preferably 85% or less, more preferably 75% or less. If the porosity is too small than the above range, there is a tendency for the membrane resistance to increase and the rate characteristics to deteriorate. In addition, if it is too large than the above range, there is a tendency for the mechanical strength of the separator to decrease and the insulation to decrease.

[0516] In addition, the average pore size of the separator is also arbitrary, usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. If the average pore size is larger than the above range, short circuit is likely to occur. In addition, if it is lower than the above range, the film resistance sometimes increases and the rate characteristics decrease.

[0517] On the other hand, as inorganic materials, for example, oxides such as aluminum oxide and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate can be used, and materials in the form of particles or fibers can be used.

[0518] As the form, a non-woven fabric, a woven fabric, a microporous film or other thin film shape can be used. In the case of a thin film shape, a material with a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is suitable. In addition to the above-mentioned independent thin film shape, a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and / or the negative electrode using a resin binder can also be used. For example, a porous layer can be formed on both sides of the positive electrode using a fluororesin as a binder using aluminum oxide particles with a particle size of 90% less than 1 μm.

[0519] <Battery Design> The electrode group may be any of an electrode group of a laminated structure formed by sandwiching the above-mentioned positive electrode plate and negative electrode plate with the above-mentioned separator, and an electrode group of a structure formed by spirally winding the above-mentioned positive electrode plate and negative electrode plate with the above-mentioned separator. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy) is usually 40% or more, preferably 50% or more, and is usually 90% or less, preferably 80% or less.

[0520] If the electrode group occupancy is lower than the above range, the battery capacity becomes smaller. In addition, if it is higher than the above range, the void space is small, the battery reaches a high temperature, the components expand, or the vapor pressure of the liquid component of the electrolyte increases, so the internal pressure rises, and sometimes the various characteristics of the battery such as repeated charge and discharge performance or high temperature storage are reduced. In addition, the gas release valve that releases the internal pressure to the outside is sometimes operated.

[0521] The current collecting structure is not particularly limited. In order to more effectively realize the charge-discharge characteristics of high current density by utilizing the electrolyte of the present invention, it is preferably set to a structure that reduces the resistance of the wiring part and the joint part. When the internal resistance is reduced like this, the effect of using the electrolyte of the present invention is particularly well exerted.

[0522] When the electrode group has the above-mentioned stacked structure, it is suitable to use a structure formed by bundling the metal core parts of each electrode layer and welding them to the terminal. When the area of ​​a single electrode increases, the internal resistance increases, so it is also suitable to set multiple terminals in the electrode to reduce the resistance. When the electrode group has the above-mentioned winding structure, multiple lead structures are set on the positive electrode and the negative electrode respectively, and the internal resistance can be reduced by bundling them to the terminal.

[0523] The material of the outer casing is not particularly limited as long as it is a material that is stable relative to the electrolyte used. Specifically, metals such as nickel-plated steel plates, stainless steel, aluminum or aluminum alloys, magnesium alloys, or laminated films (laminated films) of resins and aluminum foils can be used. From the viewpoint of lightweight, metals such as aluminum or aluminum alloys and laminated films are suitable.

[0524] In the case of using a metal outer shell, an outer shell formed by welding the metals to each other to form a sealed and closed structure by laser welding, resistance welding, or ultrasonic welding can be cited; or an outer shell formed by a riveted structure using the above-mentioned metal via a resin sealing gasket. In the case of using the above-mentioned laminated film outer shell, an outer shell formed by heat-melting the resin layers to each other to form a sealed and closed structure can be cited. In order to improve the sealing performance, a resin different from the resin used in the laminated film can be sandwiched between the above-mentioned resin layers. In particular, when the resin layers are heat-melted via the collector terminal to form a closed structure, a metal-resin bond is formed, so as a spacer resin, it is suitable to use a resin having a polar group or a modified resin into which a polar group is introduced.

[0525] The lithium ion secondary battery of the present invention may be in any shape, such as cylindrical, rectangular, laminated, coin, or giant shapes. The shape and structure of the positive electrode, negative electrode, and separator may be changed according to the shape of each battery.

[0526] Furthermore, a module including the lithium ion secondary battery of the present invention is also one of the present invention.

[0527] In addition, the following lithium ion secondary battery is also one of the preferred embodiments, wherein the lithium ion secondary battery is characterized in that it has a positive electrode, a negative electrode, and the above-mentioned electrolyte, the above-mentioned positive electrode has a positive electrode collector and a positive electrode active material layer containing a positive electrode active material, and the above-mentioned positive electrode active material contains Mn. Since it has a positive electrode active material layer containing a positive electrode active material containing Mn, the high temperature storage characteristics of the above-mentioned lithium ion secondary battery are further excellent.

[0528] As the Mn-containing positive electrode active material, LiMn is preferred from the viewpoint of being able to provide a lithium ion secondary battery with high energy density and high power. 1.5 Ni 0.5 O4、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2.

[0529] The content of the above-mentioned positive electrode active material in the positive electrode active material layer is preferably 80 mass % or more, more preferably 82 mass % or more, and particularly preferably 84 mass % or more. In addition, the upper limit is preferably 99 mass % or less, more preferably 98 mass % or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the capacitance is sometimes insufficient. On the contrary, if the content is too high, the strength of the positive electrode is sometimes insufficient.

[0530] The positive electrode active material layer may further include a conductive material, a thickener, and a binder.

[0531] As the above-mentioned binder, any binder can be used as long as it is a material that is safe for the solvent or electrolyte used in electrode manufacturing, and examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, NBR (acrylonitrile-butadiene rubber), fluororubber, etc. , ethylene-propylene rubber, styrene-butadiene-styrene block copolymer or its hydrogenated product, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer or its hydrogenated product, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene-α-olefin copolymer, fluorinated polyvinylidene fluoride, tetrafluoroethylene-ethylene copolymer, polymer composition having ion conductivity of alkali metal ions (especially lithium ions), etc. It should be noted that these substances may be used alone or in combination of two or more in any combination and ratio.

[0532] The content of the binder is measured in the ratio of the binder in the positive electrode active material layer, usually 0.1 mass % or more, preferably 1 mass % or more, more preferably 1.5 mass % or more, in addition, usually 80 mass % or less, preferably 60 mass % or less, more preferably 40 mass % or less, most preferably 10 mass % or less. If the ratio of the binder is too low, the positive electrode active material cannot be fully maintained, the mechanical strength of the positive electrode is insufficient, and the battery performance such as the cycle characteristics deteriorates sometimes. On the other hand, if too high, it sometimes leads to a reduction in battery capacity or conductivity.

[0533] Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof, etc. One type may be used alone, or two or more types may be used in any combination and ratio.

[0534] The ratio of thickener to active material is usually 0.1 mass %, preferably 0.2 mass %, more preferably 0.3 mass %, in addition, usually 5 mass %, preferably 3 mass %, more preferably 2 mass %. If it is lower than this scope, the coating property is significantly reduced sometimes. If it is higher than this scope, the ratio of active material in positive electrode active material layer is reduced, and the problem of the capacity reduction of battery or the resistance increase between positive electrode active materials is sometimes generated.

[0535] As the above-mentioned conductive material, any known conductive material can be used. As a specific example, metal materials such as copper and nickel, graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, amorphous carbon such as needle coke and the like can be cited. It should be noted that they can be used alone, or two or more can be used in any combination and ratio. The content of the conductive material is usually used in the positive electrode active material layer. 0.01 mass% or more, preferably 0.1 mass% or more, more preferably 1 mass% or more, in addition, 50 mass% or less, preferably 30 mass% or less, more preferably 15 mass% or less is usually used. If the content is lower than this range, the conductivity is sometimes insufficient. On the contrary, if the content is higher than this range, the battery capacity is sometimes reduced.

[0536] From the viewpoint of further improving the high temperature storage characteristics, the positive electrode current collector is preferably composed of a valve metal or an alloy thereof. Examples of the valve metal include aluminum, titanium, tantalum, and chromium. The positive electrode current collector is more preferably composed of aluminum or an aluminum alloy.

[0537] From the viewpoint of further improving the high temperature storage characteristics, the part of the lithium ion secondary battery electrically connected to the positive electrode collector and in contact with the electrolyte is also preferably composed of a valve metal or its alloy. It is particularly preferred that the battery outer casing, and the lead wire, safety valve, etc. contained in the battery outer casing are electrically connected to the positive electrode collector and in contact with the non-aqueous electrolyte. Stainless steel covered with a valve metal or its alloy can be used. Components

[0538] The manufacturing method of the positive electrode is as described above, and for example, a method of adding the above-mentioned binder, thickener, conductive material, solvent, etc. to the above-mentioned positive electrode active material to prepare a slurry-like positive electrode mixture, applying it on the positive electrode collector and pressing it after drying to achieve high density can be cited.

[0539] The negative electrode has the same structure as described above.

[0540] The electric double layer capacitor may include a positive electrode, a negative electrode, and the electrolyte solution. In the electric double layer capacitor, at least one of the positive electrode and the negative electrode is a polarizable electrode. As the polarizable electrode and the non-polarizable electrode, the following electrodes described in detail in Japanese Patent Application Laid-Open No. 9-7896 can be used.

[0541] The polarized electrode mainly composed of activated carbon used in the present invention preferably comprises inactivated carbon with a large specific surface area and a conductive agent such as carbon black that imparts electronic conductivity. The polarized electrode can be formed by various methods. For example, activated carbon powder, carbon black and phenolic resin are mixed, and after compression molding, they are calcined and activated in an inactive gas atmosphere and a water vapor atmosphere, thereby forming a polarized electrode comprising activated carbon and carbon black. Preferably, the polarized electrode is bonded to the collector with a conductive adhesive or the like.

[0542] In addition, activated carbon powder, carbon black and a binder may be kneaded in the presence of alcohol to form a sheet, and dried to form a polarized electrode. The binder uses, for example, polytetrafluoroethylene. In addition, activated carbon powder, carbon black, a binder and a solvent may be mixed to form a slurry, which is applied to a metal foil of a collector, and dried to form a polarized electrode integrated with the collector.

[0543] Polarized electrodes with activated carbon as the main body can be used at both poles to make a double-layer capacitor, or a non-polarized electrode can be used on one side, for example: a positive electrode with a battery active material such as a metal oxide as the main body and a negative electrode with activated carbon as the main body; a negative electrode with a carbon material that can reversibly absorb and release lithium ions as the main body, or a negative electrode of lithium metal or lithium alloy, and a polarized positive electrode with activated carbon as the main body.

[0544] Furthermore, carbonaceous materials such as carbon black, graphite, expanded graphite, porous carbon, carbon nanotubes, carbon nanohorns, and Ketjen black may be used instead of activated carbon or in combination therewith.

[0545] As a non-polarizable electrode, it is preferred to use a carbon material that can reversibly absorb and release lithium ions as the main body, and the object in which the lithium ions are absorbed in the carbon material is used as the electrode. In this case, a lithium salt is used as the electrolyte. The double-layer capacitor according to this structure can obtain a further higher withstand voltage of more than 4V.

[0546] The solvent used to prepare the slurry in the production of the electrode is preferably a solvent that can dissolve the binder, and N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, dimethyl phthalate, ethanol, methanol, butanol or water is appropriately selected to match the type of binder.

[0547] As the activated carbon used in the polarized electrode, there are phenolic resin activated carbon, coconut shell activated carbon, petroleum coke activated carbon, etc. Among these, in terms of obtaining a large capacity, it is preferred to use petroleum coke activated carbon or phenolic resin activated carbon. In addition, among the activation treatment methods of activated carbon, there are steam activation treatment methods, molten KOH activation treatment methods, etc., and in terms of obtaining a larger capacity, it is preferred to use activated carbon using the molten KOH activation treatment method.

[0548] As the preferred conductive agent used in the polarized electrode, carbon black, Ketjen black, acetylene black, natural graphite, artificial graphite, metal fiber, conductive titanium oxide, ruthenium oxide can be enumerated. In order to obtain good conductivity (low internal resistance), in addition, since the capacity of the product is reduced if too much, the mixed amount of the conductive agent such as the carbon black used in the polarized electrode is preferably set to 1 to 50 mass % in the total amount with the activated carbon.

[0549] In order to obtain an electric double layer capacitor with a large capacity and low internal resistance, it is preferable to use activated carbon having an average particle size of 20 μm or less and a specific surface area of ​​1500 to 3000 m 2 / g of activated carbon. In addition, as preferred carbon materials for forming an electrode mainly composed of a carbon material capable of reversibly absorbing and releasing lithium ions, natural graphite, artificial graphite, graphitized mesoporous carbon microspheres, graphitized whiskers, vapor-grown carbon fibers, a fired product of furfuryl alcohol resin, or a fired product of NOVLAC resin can be cited.

[0550] The collector can be used as long as it has chemical corrosion resistance and electrochemical corrosion resistance. As the collector of the polarized electrode with activated carbon as the main body, stainless steel, aluminum, titanium or tantalum can be preferably used. Among these, stainless steel or aluminum is a particularly preferred material in terms of the characteristics and price of the obtained double-layer capacitor. As the collector of the electrode with a carbon material that can reversibly absorb and detach lithium ions as the main body, stainless steel, copper or nickel is preferably used.

[0551] In addition, in order to pre-absorb lithium ions in a carbon material that can reversibly absorb and desorb lithium ions, there are: (1) a method of pre-mixing powdered lithium in a carbon material that can reversibly absorb and desorb lithium ions; (2) a method of placing lithium foil on an electrode formed by a carbon material that can reversibly absorb and desorb lithium ions and a binder, immersing the electrode in an electrolyte solution in which a lithium salt is dissolved while the electrode is in electrical contact with the electrode, thereby ionizing the lithium and introducing lithium ions into the carbon material; and (3) a method of placing an electrode formed by a carbon material that can reversibly absorb and desorb lithium ions and a binder on the negative side, placing lithium metal on the positive side, immersing the electrodes in a non-aqueous electrolyte solution containing a lithium salt as an electrolyte, and electrochemically introducing lithium in an ionized state into the carbon material by passing current.

[0552] As electric double layer capacitors, generally known are wound electric double layer capacitors, laminated electric double layer capacitors, coin-type electric double layer capacitors, etc., and the electric double layer capacitor may be in these forms.

[0553] For example, a wound electric double-layer capacitor is assembled in the following manner: the positive electrode and the negative electrode of a stack (electrode) including a collector and an electrode layer are wound with an insulator between them to produce a wound element, the wound element is placed in a casing made of aluminum or the like, an electrolyte, preferably a non-aqueous electrolyte, is filled therein, and then sealed with a rubber sealing body to thereby assemble.

[0554] As the separator, conventionally known materials and structures may be used, for example, polyethylene porous membrane, polytetrafluoroethylene, nonwoven fabric of polypropylene fiber, glass fiber, cellulose fiber, etc. may be mentioned.

[0555] In addition, by a known method, a laminated double-layer capacitor can be made by stacking sheet-shaped positive and negative electrodes with an electrolyte and an isolator between them; or a coin-type double-layer capacitor can be made by fixing the positive and negative electrodes with a sealing gasket with an electrolyte and an isolator between them to form a coin shape.

[0556] The electrolyte solution of the present invention is useful as an electrolyte solution for a large lithium ion secondary battery for a hybrid vehicle or a distributed power source, or for an electric double layer capacitor. Example

[0557] Next, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

[0558] Examples and Comparative Examples listed in Table 1 (Preparation of Electrolyte) The components were mixed so as to have the composition shown in Table 1, and LiPF6 was added thereto so as to have a concentration of 1.0 mol / L to obtain a non-aqueous electrolyte solution.

[0559] The components described in Table 1 are as follows. Ingredient(I) I-a: CF2HCOOCH3 I-b: CF3CH2COOCH3

[0560] Ingredient(II) II-a: Fluoroethylene carbonate II-b: 3,3,3-trifluoropropylene carbonate II-c: II-d: Ethylene carbonate

[0561] Component (III) III-a: methyl 2,2,2-trifluoroethyl carbonate III-b: ethyl methyl carbonate III-c: dimethyl carbonate

[0562] Ingredients(IV) IV-a: IV-b: IV-c: IV-d: IV-e: IV-f: IV-g: IV-h:

[0563]

Table 1

[0564] (Manufacturing of aluminum laminated lithium-ion secondary battery) [Production of positive electrode] As the positive electrode active material, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2 90 mass%, acetylene black as a conductive material 5 mass% and polyvinylidene fluoride (PVdF) as a binder 5 mass% were mixed in N-methylpyrrolidone solvent to form a slurry. The obtained slurry was applied to one side of an aluminum foil with a thickness of 15 μm pre-coated with a conductive auxiliary agent, dried, and rolled with a press. The obtained material was cut into a shape with a width of 50 mm and a length of 30 mm as the size of the active material layer and a non-coated portion with a width of 5 mm and a length of 9 mm to prepare a positive electrode.

[0565] [Production of negative electrode] 1 mass part of an aqueous dispersion of sodium carboxymethylcellulose (1 mass % concentration of sodium carboxymethylcellulose) as a thickener and binder and 1 mass part of an aqueous dispersion of styrene-butadiene rubber (50 mass % concentration of styrene-butadiene rubber) were added to 98 mass parts of carbonaceous material (graphite), and mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil with a thickness of 10 μm and dried, and pressed with a press, and the obtained material was cut into a shape with a width of 52 mm and a length of 32 mm as the size of the active material layer and a non-coated portion with a width of 5 mm and a length of 9 mm to prepare a negative electrode.

[0566] [Manufacturing of aluminum laminated batteries] The positive electrode and the negative electrode are placed opposite each other with a microporous polyethylene film (separator) of 20 μm thickness interposed therebetween, and the non-aqueous electrolyte obtained above is injected. After the non-aqueous electrolyte fully penetrates the separator, etc., it is packaged and pre-charged and aged to produce a lithium-ion secondary battery.

[0567] (Measurement of battery characteristics) [Evaluation of IV resistance] After the lithium secondary battery is charged to 4.2V at a constant current equivalent to 0.2C at 25°C while being clamped and pressed by a plate, it is discharged to 3.0V at a constant current of 0.2C. The battery is stabilized by two cycles. The third cycle is charged to 4.2V at a constant current of 0.2C, and then charged at a constant voltage of 4.2V until the current value reaches 0.05C, and discharged to 3.0V at a constant current of 0.2C. Then, after charging to 4.2V at a constant current of 0.2C in the fourth cycle, charging is implemented at a constant voltage of 4.2V until the current value reaches 0.05C, and discharged to 3.0V at a constant current of 0.2C, and the initial discharge capacity is obtained. The lithium secondary battery is charged to half the capacity of the initial discharge capacity at a constant current of 1C at 25°C. It is discharged at 2.0C at 25°C, and the voltage at 10 seconds is measured. The resistance is calculated from the drop in voltage during discharge as IV resistance. The results are shown in Table 2.

[0568] [High temperature storage test] The secondary battery manufactured as described above is charged to 4.2V at 25°C with a current equivalent to 0.5C under constant current-constant voltage charging (hereinafter, marked as CC / CV charging) (0.1C cut-off) and then discharged to 3V at a constant current of 0.5C, which is regarded as one cycle, and the initial discharge capacity is calculated from the discharge capacity of the third cycle. Here, 1C represents the current value of the reference capacity of the battery discharged in 1 hour, for example, 0.5C represents the current value of 1 / 2 thereof. After CC / CV charging (0.1C cut-off) to 4.2V is performed again, it is stored at high temperature at 85°C for 36 hours. After the battery is fully cooled, the volume is measured by the Archimedean method, and the amount of gas generated (gas increase) (ml) is calculated from the volume change before and after storage. Next, it is discharged to 3V at 0.5C at 25°C as the residual capacity. The residual capacity after high-temperature storage is measured, and the ratio of the residual capacity to the initial discharge capacity is calculated, which is taken as the capacity retention rate (%). (Remaining capacity) / (Initial discharge capacity)×100=Capacity retention rate (%) The results are shown in Table 2.

[0569]

Table 2

[0570] Examples and Comparative Examples listed in Table 3 (Preparation of Electrolyte) The components were mixed so as to have the composition shown in Table 3, and LiPF6 was added thereto so as to have a concentration of 1.0 mol / L to obtain a non-aqueous electrolyte solution.

[0571] The components described in Table 3 are as follows. Components (I) to (IV): as shown in Table 1.

[0572] Other ingredients VC: Vinylene carbonate LiBOB: Lithium bis(oxalatoborate) LiTFSI: Lithium bis(trifluoromethanesulfonyl)imide LiFSI: Lithium bis(fluorosulfonyl)imide

[0573]

Table 3

[0574] (Manufacturing of aluminum laminated lithium-ion secondary battery) A lithium ion secondary battery was prepared in the same manner as in Example 1 except that the nonaqueous electrolyte solution described in Table 3 was used.

[0575] (Measurement of battery characteristics) [Evaluation of IV resistance] The lithium secondary battery was charged to 4.35V at a constant current equivalent to 0.2C at 25°C while being clamped and pressed by a plate, and then discharged to 3.0V at a constant current of 0.2C. The battery was stabilized by two cycles. The third cycle was charged to 4.35V at a constant current of 0.2C, and then charged at a constant voltage of 4.35V until the current value reached 0.05C, and discharged to 3.0V at a constant current of 0.2C. Then, after charging to 4.35V at a constant current of 0.2C in the fourth cycle, charging was carried out at a constant voltage of 4.35V until the current value reached 0.05C, and discharged to 3.0V at a constant current of 0.2C, and the initial discharge capacity was obtained. The lithium secondary battery was charged to half the capacity of the initial discharge capacity at a constant current of 1C at 25°C. It was discharged at 2.0C at 25°C, and its voltage at 10 seconds was measured. The resistance was calculated from the voltage drop during discharge and was defined as the IV resistance. The results are shown in Table 4.

[0576] [High temperature cycle characteristics test] The lithium-ion secondary battery manufactured as described above is clamped and pressed with a plate and subjected to constant current-constant voltage charging (hereinafter, marked as CC / CV charging) (0.1C cutoff) at a current equivalent to 1C at 60°C to 4.35V, and then discharged to 3V at a constant current of 1C. This is regarded as one cycle, and the initial discharge capacity is calculated from the discharge capacity of the third cycle. Here, 1C represents the current value of the reference capacity of the battery discharged in 1 hour, for example, 0.2C represents 1 / 5 of its current value. The cycle is repeated again, and the discharge capacity after 200 cycles is measured. The ratio of the discharge capacity after 200 cycles to the initial discharge capacity is calculated and used as the cycle capacity retention rate (%). (Discharge capacity after 200 cycles) ÷ (initial discharge capacity) × 100 = capacity retention rate (%) The results are shown in Table 4.

[0577] [Gas generation] The volume of the manufactured lithium ion secondary battery and the volume of the lithium ion secondary battery after 200 cycles were measured, and the amount of gas generated (gas increase) (ml) was calculated according to the following formula. Volume after 200 cycles - initial volume = gas generation (ml) The results are shown in Table 4.

[0578] [High temperature storage test] The secondary battery manufactured as described above is charged to 4.35V at 25°C with a current equivalent to 0.5C under constant current-constant voltage charging (hereinafter, marked as CC / CV charging) (0.1C cut-off) and then discharged to 3V at a constant current of 0.5C, which is regarded as one cycle, and the initial discharge capacity is calculated from the discharge capacity of the third cycle. Here, 1C represents the current value of the reference capacity of the battery discharged in 1 hour, for example, 0.5C represents the current value of 1 / 2 thereof. After CC / CV charging (0.1C cut-off) to 4.35V is performed again, it is stored at high temperature at 85°C for 24 hours. After the battery is fully cooled, the volume is measured by the Archimedean method, and the amount of gas generated (gas increase) (ml) is calculated from the volume change before and after storage. Then, it is discharged to 3V at 0.5C at 25°C as the residual capacity. The residual capacity after high-temperature storage is measured, and the ratio of the residual capacity to the initial discharge capacity is calculated, which is taken as the capacity retention rate (%). (Remaining capacity) / (Initial discharge capacity)×100=Capacity retention rate (%) The results are shown in Table 4.

[0579]

Table 4

Claims

1. An electrolyte, characterized in that: contain: A solvent comprising a compound (1) represented by the formula (1): CF2HCOOCH3; and Lithium fluorosulfonate.

2. The electrolyte according to claim 1, wherein The solvent further contains a fluorinated cyclic carbonate.

3. The electrolyte according to claim 1 or 2, wherein The solvent further contains a fluorinated chain carbonate.

4. The electrolyte according to claim 1, 2 or 3, wherein The electrolyte further contains a compound (2) represented by the general formula (2), General formula (2): Where, X 21 is a group containing at least H or C, n 21 is an integer from 1 to 3, Y 21 and Z 21 are the same or different and are groups containing at least H, C, O or F, n 22 is 0 or 1, Y 21 and Z 21 They are not bonded to form a ring, or they are bonded to each other to form a ring.

5. The electrolyte according to claim 1, 2, 3 or 4, wherein The compound (2) is at least one selected from the group consisting of a compound (3) represented by the general formula (3), a compound (4) represented by the general formula (4), and phthalic anhydride: General formula (3): Where, X 31 ~X 34 are the same or different and are groups containing at least H, C, O or F, General formula (4): Where, X 41 and X 42 The same or different groups contain at least H, C, O or F.

6. An electrochemical device, characterized in that: An electrolyte solution according to claim 1, 2, 3, 4 or 5.

7. A lithium ion secondary battery, characterized in that: An electrolyte solution according to claim 1, 2, 3, 4 or 5.

8. A component, characterized in that A device comprising the electrochemical device according to claim 6 or the lithium ion secondary battery according to claim 7.

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