Electrolyte for lithium-ion secondary battery, lithium-ion secondary battery and component

Abstract

The present invention provides an electrolyte solution, etc., which can reduce the resistance of a lithium ion secondary battery and improve the storage characteristics. The electrolyte solution for a lithium ion secondary battery of the present invention is characterized by comprising the general formula (1) (in the general formula (1), R 1 and R 2 are independently methyl, ethyl, propyl or butyl. ) is the compound (1). #imgabs0#

Description

Technical Field

[0001] The invention relates to an electrolyte for a lithium ion secondary battery, a lithium ion secondary battery and a component. Background Art

[0002] With the recent trend of lightweight and miniaturization of electronic products, the development of electrochemical devices such as lithium-ion secondary batteries with high energy density is being promoted. In addition, with the expansion of the application fields of electrochemical devices such as lithium-ion secondary batteries, the improvement of characteristics is expected. In particular, when lithium-ion secondary batteries are used in automotive applications in the future, the improvement of battery characteristics becomes increasingly important.

[0003] On the other hand, research has also been conducted on capacitors with the purpose of improving characteristics. For example, Patent Document 1 describes an electrolyte solution for electrolytic capacitors, characterized in that it uses a quaternary ammonium salt or quaternary phosphonium salt containing a specific boron anion as a solute.

[0004] Furthermore, Patent Document 2 describes an electrolyte solution for an electric double layer capacitor containing ethyltrimethylammonium tetrafluoroborate and a specific imidazolium tetrafluoroborate.

[0005] Furthermore, Patent Document 3 describes a non-aqueous electrolyte solution to which lithium difluorophosphate or the like is added.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 1-194313

[0009] Patent Document 2: Japanese Patent Application Publication No. 2012-74528

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 11-67270 Summary of the invention

[0011] Technical problem to be solved by the invention

[0012] An object of the present invention is to provide an electrolyte solution that can reduce the resistance of a lithium ion secondary battery and improve the storage characteristics, and a lithium ion secondary battery having the electrolyte solution.

[0013] Means for solving technical problems

[0014] The present invention relates to an electrolyte for a lithium ion secondary battery, characterized in that it comprises a compound (1) represented by the general formula (1):

[0015] [Chemistry 1]

[0016]

[0017] (In general formula (1), R 1 and R 2 are independently methyl, ethyl, propyl or butyl. ).

[0018] The above compound (1) is preferably of the formula:

[0019] [Chemistry 2]

[0020]

[0021] The compound (1-a) shown.

[0022] The content of the compound (1) is preferably 0.01 to 10% by mass based on the electrolyte solution.

[0023] The present invention also relates to an electrolyte for a lithium ion secondary battery, characterized in that it contains an imidazolium cation (1-1) represented by the general formula (1-1):

[0024] [Chemistry 3]

[0025]

[0026] (In general formula (1-1), R 1 and R 2 are independently methyl, ethyl, propyl or butyl. ),

[0027] and difluorophosphate ion.

[0028] The present invention also relates to a lithium ion secondary battery, characterized by comprising the above-mentioned electrolyte.

[0029] The present invention also relates to a component, characterized by comprising the above-mentioned lithium-ion secondary battery.

[0030] Effects of the Invention

[0031] According to the present invention, it is possible to provide an electrolyte solution capable of reducing the resistance of a lithium ion secondary battery and improving storage characteristics, and a lithium ion secondary battery having the electrolyte solution. DETAILED DESCRIPTION

[0032] The present invention is described in detail below.

[0033] The present invention relates to an electrolyte for a lithium ion secondary battery (hereinafter also referred to as a first electrolyte), characterized in that it contains a compound (1) represented by the general formula (1):

[0034] [Chemistry 4]

[0035]

[0036] (In general formula (1), R1 and R 2 are independently methyl, ethyl, propyl or butyl. ).

[0037] The first electrolyte solution of the present invention has the above characteristics, and can reduce the resistance of the lithium ion secondary battery and improve the storage characteristics (for example, the recovery capacity after high-temperature storage).

[0038] In the general formula (1), R 1 and R 2 Each of the above alkyl groups is independently an alkyl group having 1 to 4 carbon atoms and may have an ether bond. Examples of the above alkyl group include methyl, ethyl, propyl, and butyl. 1 and R 2 At least one of them is methyl; preferably R 1 and R 2 One of them is methyl and the other is ethyl, propyl or butyl.

[0039] As compound (1), among them, it is preferably selected from formula (1-a):

[0040] [Chemistry 5]

[0041]

[0042] The compound (1-a) and formula (1-b) are shown:

[0043] [Chemistry 6]

[0044]

[0045] At least one of the compounds (1-b) shown above is more preferably the compound (1-a).

[0046] The compound (1) may be used alone or in combination of two or more.

[0047] In the first electrolyte solution, the content of the compound (1) is preferably 0.01 to 10% by mass relative to the electrolyte solution. When the content of the compound (1) is within the above range, the resistance of the lithium ion secondary battery can be further reduced and the storage characteristics can be further improved.

[0048] The content of the compound (1) is preferably 0.1% by mass or more, further preferably 0.5% by mass or more, and more preferably 5.0% by mass or less, further preferably 3.0% by mass or less, and particularly preferably 2.0% by mass or less, relative to the electrolyte solution.

[0049] The present invention also relates to an electrolyte for a lithium ion secondary battery (hereinafter also referred to as a second electrolyte), characterized in that it comprises the general formula (1-1):

[0050] [Chemistry 7]

[0051]

[0052] (In general formula (1-1), R 1 and R 2 are independently methyl, ethyl, propyl or butyl. ) The imidazolium cation (1-1) and difluorophosphate ion (PO2F2 - ).

[0053] The second electrolyte solution of the present invention has the above-mentioned characteristics, and can reduce the resistance of the lithium ion secondary battery and improve the storage characteristics (for example, the recovery capacity after high-temperature storage).

[0054] In the general formula (1-1), R 1 and R 2 R is independently methyl, ethyl, propyl or butyl. 1 and R 2 Preferred combinations are the same as those described for the general formula (1).

[0055] As the imidazolium cation (1-1), preferably selected from

[0056] [Chemistry 8]

[0057]

[0058] The imidazolium cation (1-1a) shown, and

[0059] [Chemistry 9]

[0060]

[0061] At least one of the imidazolium cations (1-1b) shown above is preferably the imidazolium cation (1-1a).

[0062] The molar ratio (a / b) of the content (a) of the imidazolium cation (1-1) to the content (b) of the difluorophosphate ion in the second electrolyte is preferably 0.001 to 20. By setting the molar ratio (a / b) within the above range, the resistance of the lithium ion secondary battery can be further reduced, and the storage characteristics can be further improved.

[0063] The molar ratio (a / b) is more preferably 0.01 or more, further preferably 0.1 or more, and particularly preferably 0.9 or more. Furthermore, it is more preferably 13 or less, further preferably 3 or less, and particularly preferably 1.1 or less.

[0064] In the second electrolyte solution, the content of the imidazolium cation (1-1) is preferably 0.0005 to 15% by mass based on the mass of the electrolyte solution.

[0065] The content of the imidazolium cation (1-1) and difluorophosphate ion can be measured by NMR or gas chromatography.

[0066] As the ion source for providing each ion contained in the second electrolyte solution, a compound containing each ion and soluble in the solvent constituting the electrolyte solution can be used. Each of the above ion sources can be used alone or in combination of two or more.

[0067] Examples of the ion source of the imidazolium cation (1-1) include the above-mentioned compound (1) and a compound containing the imidazolium cation (1-1) and a counter anion (except for a difluorophosphate ion).

[0068] As the above-mentioned counter anion (except difluorophosphate ion), PF6 - 、N(FSO2)2 - 、N(CF3SO2)2 - 、ClO4 - , Cl - 、BF4 - etc., among which PF6 is preferred - .

[0069] Examples of the ion source of difluorophosphate ions include the above-mentioned compound (1) and a compound containing a difluorophosphate ion and a counter cation (except the imidazolium cation (1-1)).

[0070] Examples of the counter cation (except for the imidazolium cation (1-1)) include Li + , ammonium cation, pyridinium cation, pyrrolidinium cation, piperidinium cation, etc., among which Li + .

[0071] In order to further reduce the resistance of the lithium ion secondary battery and further improve the storage characteristics, it is preferred to use the compound (1) as an ion source for both the imidazolium cation (1-1) and the difluorophosphate ion.

[0072] Compound (1) can be prepared by, for example, comprising the following general formula:

[0073] [Chemistry 10]

[0074]

[0075] (Where R 1 and R 2 The method can be suitably produced by the step of reacting an imidazolium chloride with lithium difluorophosphate as described above.

[0076] The above reaction can be carried out in a solvent. As the above solvent, an organic solvent is preferred, and examples thereof include non-aromatic hydrocarbon solvents, aromatic hydrocarbon solvents, ketone solvents, halogenated hydrocarbon solvents, ether solvents, ester solvents, nitrile solvents, sulfoxide solvents, and amide solvents. Specifically, non-aromatic hydrocarbon solvents such as pentane, hexane, heptane, octane, cyclohexane, decahydronaphthalene, n-decane, isododecane, and tridecane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, tetrahydronaphthalene, veratrol, diethylbenzene, methylnaphthalene, nitrobenzene, o-nitrotoluene, mesitylene, indene, and diphenyl sulfide; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, propiophenone, diisobutyl ketone, and isophorone; halogenated hydrocarbon solvents such as dichloromethane, carbon tetrachloride, chloroform, and chlorobenzene; diethyl ether, tetrahydrofuran, diisopropyl ether, methyl tert-butyl ether, dioxane, dimethoxyethane, diethylene glycol dimethyl ether, phenethyl ether, 1,1-dimethyl Ether solvents such as oxycyclohexane and diisoamyl ether; ester solvents such as ethyl acetate, isopropyl acetate, diethyl malonate, 3-methoxy-3-methylbutyl acetate, γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, α-acetyl-γ-butyrolactone; nitrile solvents such as acetonitrile and benzonitrile; sulfoxide solvents such as dimethyl sulfoxide and cyclopentane; and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, N,N-dimethylacrylamide, N,N-dimethylacetoacetamide, N,N-diethylformamide, N,N-diethylacetamide, etc.

[0077] The above solvents may be used alone or in combination of two or more.

[0078] The reaction temperature is preferably 0 to 50°C, more preferably 10 to 30°C.

[0079] The reaction time is preferably 1 to 50 hours, more preferably 10 to 30 hours.

[0080] The above-mentioned production method may further include steps such as an ion exchange step, a filtration step, and a concentration step.

[0081] The electrolyte solutions (first and second electrolyte solutions) of the present invention preferably contain a solvent.

[0082] The solvent preferably contains at least one selected from the group consisting of carbonate esters and carboxylic acid esters.

[0083] The carbonate ester mentioned above may be a cyclic carbonate ester or a chain carbonate ester.

[0084] The cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate.

[0085] Examples of the non-fluorinated cyclic carbonate include non-fluorinated saturated cyclic carbonates, preferably non-fluorinated saturated alkylene carbonates having an alkylene group having 2 to 6 carbon atoms, and more preferably non-fluorinated saturated alkylene carbonates having an alkylene group having 2 to 4 carbon atoms.

[0086] Among them, as the above-mentioned unfluorinated saturated cyclic carbonate, in terms of high dielectric constant and suitable viscosity, it is preferably at least one selected from ethylene carbonate, propylene carbonate, cis-2,3-pentylene carbonate, cis-2,3-butylene carbonate, 2,3-pentylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 1,2-butylene carbonate and butylene carbonate.

[0087] The above-mentioned non-fluorinated saturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0088] 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 even more preferably 15 to 45% by volume based on the solvent.

[0089] The fluorinated cyclic carbonate is a cyclic carbonate having a fluorine atom. A solvent containing the fluorinated cyclic carbonate can be suitably used even at a high voltage.

[0090] 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.

[0091] The fluorinated cyclic carbonate may be a fluorinated saturated cyclic carbonate or a fluorinated unsaturated cyclic carbonate.

[0092] The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate having a fluorine atom, and specifically, the following general formula (A) can be cited:

[0093] [Chemistry 11]

[0094]

[0095] (Where X 1 ~X 4 are 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; wherein X 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 refers to -CF3, -CF2H, -CH2F, etc.

[0096] When the electrolyte solution of the present invention is used in a high-voltage lithium ion secondary battery or the like, the electrolyte solution containing the fluorinated saturated cyclic carbonate has improved oxidation resistance and can provide stable and excellent charge and discharge characteristics.

[0097] In addition, in this specification, an "ether bond" is a bond represented by -O-.

[0098] 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.

[0099] In order to reduce the viscosity at low temperature, increase the flash point, and further improve the solubility of the electrolyte salt, X 1 ~X 4 Preferred are -H, -F, a fluoroalkyl group (a), a fluoroalkyl group having an ether bond (b), or a fluoroalkoxy group (c).

[0100] The fluoroalkyl group (a) is a group in which at least one of the hydrogen atoms in the alkyl group is substituted with a fluorine atom. The number of carbon atoms in the fluoroalkyl group (a) is preferably 1-20, more preferably 1-17, further preferably 1-7, and further more preferably 1-5.

[0101] 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.

[0102] Among the fluoroalkyl groups (a), the group having 1 carbon atom may include CFH2-, CF2H-, and CF3-. In particular, CF2H- or CF3- is preferred in terms of high temperature storage characteristics, and CF3- is most preferred.

[0103] Among the above-mentioned fluoroalkyl groups (a), as a group having 2 or more carbon atoms, from the viewpoint of good solubility of the electrolyte salt, the following general formula (a-1) can be preferably exemplified:

[0104] R 1 -R 2 -(a-1)

[0105] (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; however, R 1 and R 2 At least one of them has a fluorine atom).

[0106] It should be noted that R 1 and R 2 Further, it may have atoms other than carbon atoms, hydrogen atoms and fluorine atoms.

[0107] 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.

[0108] As R 1 Specifically, examples of the linear or branched alkyl group include CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-,

[0109] [Chemistry 12]

[0110]

[0111] wait.

[0112] In addition, in R 1In the case of a straight-chain alkyl group having a fluorine atom, examples include CF3-, CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2 CH2-, CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3CF2C F2CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2CF2 CH2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, HCF2CF2C F2CF2CH2CH2-, FCH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, FCH2CF2CF2-, CH3CF2CH2-, CH3CF2CF2-, CH3CF2CH2CF2-, CH3 CF2CF2CF2-, CH3CH2CF2CF2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2C H2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, HCFClCF2CH2-, HCF2CFClCH2-, HCF2CFClCF2CFClCH2-, HFCClCF2CFClCF2CH2-, etc.

[0113] In addition, in R 1 In the case of a branched alkyl group having a fluorine atom, preferably:

[0114] [Chemistry 13]

[0115]

[0116] [Chemistry 14]

[0117]

[0118] However, if there are side chains such as CH3- and CF3-, the viscosity tends to be high, so the number is more preferably small (1) or zero.

[0119] 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 them individually or in combination.

[0120] (i) The smallest structural unit of a straight chain:

[0121] -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0122] (ii) The smallest structural unit of a branched chain:

[0123] [Chemistry 15]

[0124]

[0125] Among the above examples, it is preferred that the structure be composed of a structural unit containing no Cl, since the structure does not cause a dehydrochlorination reaction by a base and is more stable.

[0126] In R 2 In the case of a linear chain, it is composed only of the above-mentioned linear minimum structural unit, among which -CH2-, -CH2CH2- or -CF2- are preferred. From the viewpoint of being able to further improve the solubility of the electrolyte salt, -CH2- or -CH2CH2- is more preferred.

[0127] In R 2 In the case of a branched chain, it contains at least one of the branched chain minimum structural units, and the general formula can be preferably exemplified as follows: -(CX a X b )-(X a is H, F, CH3 or CF3; X b is CH3 or CF3; wherein, in X b In the case of CF3, X a It is a unit represented by H or CH3). It can further improve the solubility of the electrolyte salt.

[0128] Preferred fluoroalkyl groups (a) include CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CHF-, CH3CF2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-,

[0129] [Chemistry 16]

[0130]

[0131] [Chemistry 17]

[0132]

[0133] wait.

[0134] The fluoroalkyl group (b) having an ether bond is a group obtained by replacing at least one of the hydrogen atoms of the alkyl group having an ether bond with 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, due to the increase in the number of fluorinated groups, it is sometimes observed that the solubility of the electrolyte salt caused by the decrease in the dielectric constant and the decrease in its compatibility with other solvents are reduced. From this viewpoint, the number of carbon atoms of the fluoroalkyl group (b) having an ether bond is more preferably 2 to 10, and further preferably 2 to 7.

[0135] The alkylene group constituting the ether portion of the fluoroalkyl group (b) having an ether bond may be a linear or branched alkylene group. Examples of the minimum structural unit constituting such a linear or branched alkylene group are shown below.

[0136] (i) The smallest structural unit of a straight chain:

[0137] -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0138] (ii) The smallest structural unit of a branched chain:

[0139] [Chemistry 18]

[0140]

[0141] The alkylene group may be composed of one 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.

[0142] Among the above examples, it is preferred that the structure be composed of a structural unit containing no Cl, since the structure does not cause a dehydrochlorination reaction by a base and is more stable.

[0143] As further preferred fluorinated alkyl groups (b) having an ether bond, there can be mentioned general formula (b-1):

[0144] R 3 -(OR 4 ) n1 - (b-1)

[0145] (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 which has a fluorine atom).

[0146] 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 present invention is not limited to these groups.

[0147] (1) As R 3 , preferably the general formula: X c 3C-(R 5 ) n2 -(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 an alkyl group represented by 0 or 1).

[0148] When n2 is 0, as R 3 , examples include CH3-, CF3-, HCF2- and H2CF-.

[0149] As a specific example of the case where n2 is 1, R 3It is a straight-chain group, and examples thereof include CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2CH2-, CF3CF2CH2CH2CH2 -, CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3C F2CF2CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2C F2CH2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, HCF2CF2CF2CF2CH2CH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, CH3CF2-, CH3CH2-, CH3CF2CH2-, CH3CF2CF2-, CH3CH2 CH2-, CH3CF2CH2CF2-, CH3CF2CF2CF2-, CH3CH2CF2CF2-, CH3CH2CH2CH2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2CH2CF2CH2CH2-, CH3CH2CF2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, etc.

[0150] As n2 is 1, and R 3 For branched groups, examples include

[0151] [Chemistry 19]

[0152]

[0153] wait.

[0154] However, if there are side chains such as CH3- and CF3-, the viscosity tends to increase, so R 3 A straight-chain group is more preferred.

[0155] (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.

[0156] As R 4 Preferred specific examples include the following linear or branched groups.

[0157] Examples of the straight-chain group include -CH2-, -CHF-, -CF2-, -CH2CH2-, -CF2CH2-, -CF2CF2-, -CH2CF2-, -CH2CH2CH2-, -CH2CH2CF2-, -CH2CF2CH2-, -CH2CF2CF2-, -CF2CH2CH2-, -CF2CF2CH2-, -CF2CH2CF2-, -CF2CH2CF2-, -CF2CH2CF2- and the like.

[0158] Examples of branched groups include:

[0159] [Chemistry 20]

[0160]

[0161] wait.

[0162] The fluoroalkoxy group (c) is a group in which at least one of the hydrogen atoms in 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.

[0163] As the fluoroalkoxy group (c), a particularly preferred group is a group of the general formula: d 3C-(R 6 ) n3 -O-(3 X d Same or different, both H or F; R 6 Preferably, it is an alkylene group having 1 to 5 carbon atoms and optionally having a fluorine atom; n3 is 0 or 1; wherein 3 X d At least one of them is a fluorine atom).

[0164] Specific examples of the fluoroalkoxy group (c) include: 1 The alkyl group exemplified is a fluoroalkoxy group in which an oxygen atom is bonded to the terminal.

[0165] The fluorine content of the fluoroalkyl (a), the fluoroalkyl (b) and the fluoroalkoxy (c) with ether bond in the above-mentioned fluorinated saturated cyclic carbonate is preferably more than 10 mass %. If the fluorine content is too low, it is possible to fully obtain the viscosity reduction effect and the rising effect of the flash point at low temperatures. 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 %.

[0166] The fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group having an ether bond (b) and the fluorinated alkoxy 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.

[0167] 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.

[0168] 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.

[0169] Specific examples of the fluorinated saturated cyclic carbonate include the following.

[0170] As X 1 ~X 4 Specific examples of the fluorinated saturated cyclic carbonate wherein at least one of the carbonyl groups is -F include:

[0171] [Chemistry 21]

[0172]

[0173] Etc. These compounds have high withstand voltage and good solubility in electrolyte salts.

[0174] In addition, you can also use:

[0175] [Chemistry 22]

[0176]

[0177] wait.

[0178] As X 1 ~X 4 Specific examples of fluorinated saturated cyclic carbonates in which at least one of the fluorinated alkyl groups (a) is a fluorinated alkyl group and all the others are -H include:

[0179] [Chemistry 23]

[0180]

[0181] [Chemistry 24]

[0182]

[0183] [Chemistry 25]

[0184]

[0185] wait.

[0186] As X 1 ~X 4 Specific examples of the fluorinated saturated cyclic carbonate in which at least one of the fluorinated alkyl groups (b) or the fluorinated alkoxy group (c) having an ether bond and the rest of the fluorinated saturated cyclic carbonates are -H include:

[0187] [Chemistry 26]

[0188]

[0189] [Chemistry 27]

[0190]

[0191] [Chemistry 28]

[0192]

[0193] [Chemistry 29]

[0194]

[0195] [Chemistry 30]

[0196]

[0197] [Chemistry 31]

[0198]

[0199] wait.

[0200] Among them, the fluorinated saturated cyclic carbonate is preferably any one of the following compounds.

[0201] [Chemistry 32]

[0202]

[0203] [Chemistry 33]

[0204]

[0205] Examples of the fluorinated saturated cyclic carbonates include, in addition to 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. 3-dioxolane-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, etc.

[0206] Among these, the fluorinated saturated cyclic carbonate is more preferably fluoroethylene carbonate, difluoroethylene carbonate, trifluoromethylethylene carbonate (3,3,3-trifluoropropylene carbonate), or 2,2,3,3,3-pentafluoropropylethylene carbonate.

[0207] The above-mentioned 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 by a substituent having an aromatic ring or a carbon-carbon double bond. Specifically, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate, etc. can be mentioned.

[0208] The above-mentioned fluorinated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0209] When the fluorinated cyclic carbonate is contained, the content of the fluorinated cyclic carbonate is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and even more preferably 15 to 45% by volume based on the solvent.

[0210] The above-mentioned chain carbonate may be a non-fluorinated chain carbonate or a fluorinated chain carbonate.

[0211] As the above-mentioned non-fluorinated chain carbonate, for example, 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, dipropyl carbonate, dibutyl carbonate, methyl isopropyl carbonate, methyl-2-phenylphenyl carbonate, phenyl-2-phenylphenyl carbonate, trans-2,3-pentylene carbonate, trans-2,3-butylene carbonate, ethyl phenyl carbonate and other hydrocarbon chain carbonates can be mentioned. Among them, preferably at least one selected from ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate.

[0212] The non-fluorinated linear carbonates may be used alone or in combination of two or more in any combination and ratio.

[0213] When the non-fluorinated linear carbonate is contained, the content of the non-fluorinated linear 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.

[0214] The fluorinated chain carbonate is a chain carbonate having a fluorine atom. A solvent containing the fluorinated chain carbonate can be suitably used even at a high voltage.

[0215] Examples of the fluorinated chain carbonate include those of the general formula (B):

[0216] R 2 OCOOR 7 (B)

[0217] (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 which may contain fluorine atoms. ) is a compound represented by

[0218] 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 which may contain a fluorine atom.

[0219] 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 In the case of an alkyl group containing a fluorine atom, it is a fluorinated alkyl group.

[0220] From the perspective of low viscosity, Rf 2 and R 7 The number of carbon atoms in is preferably 1-7, more preferably 1-2.

[0221] If the number of carbon atoms is too large, the low-temperature characteristics may be reduced or the solubility in the electrolyte salt may be reduced. If the number of carbon atoms is too small, the solubility in the electrolyte salt may be reduced, the discharge efficiency may be reduced, and the viscosity may be increased.

[0222] Examples of the fluorinated alkyl group having 1 carbon atom include CFH2-, CF2H-, CF3-, etc. In particular, CFH2- or CF3- is preferred in terms of high temperature storage characteristics.

[0223] As the fluorinated alkyl group having 2 or more carbon atoms, from the viewpoint of good solubility in electrolyte salt, the following general formula (d-1) can be preferably exemplified:

[0224] R 1 -R 2 - (d-1)

[0225] (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; however, R 1 and R 2 At least one of them has a fluorine atom).

[0226] It should be noted that R 1 and R 2 Further, it may have atoms other than carbon atoms, hydrogen atoms and fluorine atoms.

[0227] 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 is more preferably 1-3.

[0228] As R 1 Specifically, examples of the linear or branched alkyl group include CH3-, CF3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-,

[0229] [Chemistry 34]

[0230]

[0231] wait.

[0232] In addition, in R 1In the case of a straight-chain alkyl group having a fluorine atom, examples include CF3-, CF3CH2-, CF3CF2-, CF3CH2CH2-, CF3CF2CH2-, CF3CF2CF2-, CF3CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2-, CF3CH2CF2CH2-, CF3CF2CF2CH2-, CF3CF2CF2CF2-, CF3CF2CH2CF2-, CF3CH2CH2CH2-, CF3CF2CH2CH2 CH2-, CF3CH2CF2CH2CH2-, CF3CF2CF2CH2CH2-, CF3CF2CF2CF2CH2-, CF3CF2CH2CF2CH2-, CF3CF2CH2CH2CH2CH2-, CF3CF2C F2CF2CH2CH2-, CF3CF2CH2CF2CH2CH2-, HCF2-, HCF2CH2-, HCF2CF2-, HCF2CH2CH2-, HCF2CF2CH2-, HCF2CH2CF2-, HCF2CF2 CH2CH2-, HCF2CH2CF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CH2CH2CH2-, HCF2CH2CF2CH2CH2-, HCF2CF2CF2CF2CH2-, HCF2CF2C F2CF2CH2CH2-, FCH2-, FCH2CH2-, FCH2CF2-, FCH2CF2CH2-, FCH2CF2CF2-, CH3CF2CH2-, CH3CF2CF2-, CH3CF2CH2CF2-, CH3 CF2CF2CF2-, CH3CH2CF2CF2-, CH3CF2CH2CF2CH2-, CH3CF2CF2CF2CH2-, CH3CF2CF2CH2CH2-, CH3CH2CF2CF2CH2-, CH3CF2C H2CF2CH2CH2-, CH3CF2CH2CF2CH2CH2-, HCFClCF2CH2-, HCF2CFClCH2-, HCF2CFClCF2CFClCH2-, HFCClCF2CFClCF2CH2-, etc.

[0233] In addition, in R 1 In the case of a branched alkyl group having a fluorine atom, preferably:

[0234] [Chemistry 35]

[0235]

[0236] [Chemistry 36]

[0237]

[0238] However, if there are side chains such as CH3- and CF3-, the viscosity tends to be high, so the number is more preferably small (1) or zero.

[0239] 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. Examples of the minimum structural unit constituting such a linear or branched alkylene group are shown below. 2 It is composed of them individually or in combination.

[0240] (i) The smallest structural unit of a straight chain:

[0241] -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2-

[0242] (ii) The smallest structural unit of a branched chain:

[0243] [Chemistry 37]

[0244]

[0245] Among the above examples, it is preferred that the structure be composed of a structural unit containing no Cl, since the structure does not cause a dehydrochlorination reaction by a base and is more stable.

[0246] In R 2 In the case of a linear chain, it is composed only of the above-mentioned linear minimum structural unit, among which -CH2-, -CH2CH2- or -CF2- are preferred. From the viewpoint of being able to further improve the solubility of the electrolyte salt, -CH2- or -CH2CH2- is more preferred.

[0247] In R 2 In the case of a branched chain, it contains at least one of the branched chain minimum structural units, and the general formula can be preferably exemplified as follows: -(CX a X b )-(X a is H, F, CH3 or CF3; X b is CH3 or CF3; wherein, in X b In the case of CF3, X a It is a unit represented by H or CH3). It can further improve the solubility of the electrolyte salt.

[0248] Preferred fluoroalkyl groups include, for example, CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CH2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-,

[0249] [Chemistry 38]

[0250]

[0251] [Chemistry 39]

[0252]

[0253] wait.

[0254] 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-. From the viewpoint of high flame retardancy, rate characteristics and good oxidation resistance, CF3CH2-, CF3CF2CH2-, HCF2CF2CH2-, CFH2-, and CF2H- are more preferred.

[0255] In R 7 In the case of an alkyl group not containing a fluorine atom, it is an alkyl group having 1 to 7 carbon atoms. 7 The number of carbon atoms in the moiety is preferably 1-4, more preferably 1-3.

[0256] Examples of the alkyl group not containing a fluorine atom include CH3-, CH3CH2-, (CH3)2CH-, C3H7-, etc. Among them, CH3- and CH3CH2- are preferred from the viewpoint of low viscosity and good rate characteristics.

[0257] The fluorine content of the above-mentioned fluorinated linear carbonate is preferably 15 to 70% by mass. If the fluorine content is within the above range, the compatibility with the solvent and the solubility of the salt can be maintained. The above-mentioned fluorine content is more preferably more than 20% by mass, more preferably more than 30% by mass, particularly preferably more than 35% by mass, more preferably less than 60% by mass, more preferably less than 50% by mass.

[0258] It should be noted that the fluorine content in the present invention is based on the structural formula of the above-mentioned fluorinated chain carbonate.

[0259] {(number of fluorine atoms × 19) / molecular weight of fluorinated chain carbonate} × 100 (%)

[0260] The calculated value.

[0261] As the fluorinated chain carbonate, any of the following compounds is preferred in terms of low viscosity.

[0262] [Chemistry 40]

[0263]

[0264] As the fluorinated chain carbonate ester, methyl carbonate 2,2,2-trifluoroethyl (F3CH2COC(=O)OCH3) is particularly preferred.

[0265] The non-fluorinated linear carbonates may be used alone or in combination of two or more in any combination and ratio.

[0266] When the fluorinated chain carbonate is contained, the content of the fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and even more preferably 50 to 80% by volume based on the solvent.

[0267] The carboxylic acid ester may be a cyclic carboxylic acid ester or a chain carboxylic acid ester.

[0268] The cyclic carboxylic acid ester may be a non-fluorinated cyclic carboxylic acid ester or a fluorinated cyclic carboxylic acid ester.

[0269] Examples of the non-fluorinated cyclic carboxylic acid ester include non-fluorinated saturated cyclic carboxylic acid esters, and non-fluorinated saturated cyclic carboxylic acid esters having an alkylene group having 2 to 4 carbon atoms are preferred.

[0270] Specific examples of the non-fluorinated saturated cyclic carboxylic acid ester having an alkylene group having 2 to 4 carbon atoms include β-propiolactone, γ-butyrolactone, ε-caprolactone, δ-valerolactone, and α-methyl-γ-butyrolactone. Among them, γ-butyrolactone and δ-valerolactone are particularly preferred from the viewpoint of improving the degree of lithium ion dissociation and the load characteristics.

[0271] The above-mentioned non-fluorinated saturated cyclic carboxylic acid ester may be used alone or in combination of two or more in any combination and ratio.

[0272] When the non-fluorinated saturated cyclic carboxylic acid ester is contained, the content of the non-fluorinated saturated cyclic carboxylic acid ester is preferably 0 to 90% by volume, 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.

[0273] The chain carboxylate may be a non-fluorinated chain carboxylate or a fluorinated chain carboxylate. When the solvent contains the chain carboxylate, an increase in resistance of the electrolyte after high-temperature storage can be further suppressed.

[0274] Examples of the unfluorinated linear carboxylic acid esters 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, 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, methyl 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, and the like.

[0275] Among them, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate are preferred, and ethyl propionate and propyl propionate are particularly preferred.

[0276] The non-fluorinated chain carboxylic acid esters may be used alone or in combination of two or more in any combination and ratio.

[0277] When the non-fluorinated chain carboxylic acid ester is contained, the content of the non-fluorinated chain carboxylic acid ester is preferably 0 to 90% by volume, 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.

[0278] The fluorinated chain carboxylic acid ester is a chain carboxylic acid ester having a fluorine atom. A solvent containing the fluorinated chain carboxylic acid ester can be suitably used even at a high voltage.

[0279] As the fluorinated chain carboxylic acid ester, the following general formula is preferred from the viewpoint of good compatibility with other solvents and good oxidation resistance:

[0280] R 31 COOR 32

[0281] (Where R 31 and R 32 are independently an alkyl group having 1 to 4 carbon atoms and which may contain a fluorine atom, R 31 and R 32 At least one of them contains a fluorine atom. ) is a fluorinated chain carboxylic acid ester.

[0282] As R 31 and R 32, examples of which include unfluorinated alkyl groups such as methyl (-CH3), ethyl (-CH2CH3), propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), tert-butyl (-C(CH3)3); -CF3, -CF2H, -CFH2, -CF2CF3, -CF2CF2H, -CF2CFH2, -CH2CF3, -CH2CF2H, -CH2CFH2, -CF2CF2CF3, -CF2CF2CF2H, -CF2CF2CFH2, -CH2CF2CF3, -CH2CF2CF2H, -CH2CF2CFH2, -CH2CH2CF3, -CH2CH2CF2H, -CH2CH2CFH2, -CF(CF3)2, -CF(CF2H)2, -CF(CFH2)2, -CH(CF3)2, -CH(CF2H)2, -CH(CFH2)2, -CF(OCH3)CF3, -CF2CF2CF2CF3, -CF2CF2CF2CF2H, -CF2CF2CF2CFH2, -CH2CF2CF2CF3, -CH2CF2CF2CF2H, -CH2CF2CF2CFH2, -CH2CH2CF2CF3, -CH2CH2CF2CF2H, -CH2CH2CF2CFH2, -CH2CH2CH2CF3, -CH2CH2CH2CF2H, -CH2CH2CH2CFH2, -CF(CF3)CF2CF3, -CF(CF2H)CF2CF3, -CF(CFH2)CF2CF3, -CF(CF3)CF2CF2H, -CF(CF3)CF2CFH2, -CF(CF3)CH2CF3, -CF(CF3)CH2CF2H, -CF(CF3)CH2CFH2, -CH(CF3)CF2CF3, -CH(CF2H)CF2CF3, -CH(CFH2)CF2CF3, -CH(CF3)CF2CF2H, -CH(CF3)CF2CFH2, -CH(CF3)CH2CF3, -CH(CF3)CH2CF2H, -CH(CF3)CH2CFH2, -CF2CF(CF3)CF3, -CF2CF(CF2H)CF3, -CF2CF(CFH2)CF3, -CF2CF(CF3)CF2H, -CF2CF(CF3)CFH2, -CH2CF(CF3)CF3, -CH2CF(CF2H)CF3, -CH2CF(CFH2)CF3, -CH2CF(CF3)CF2H, -CH2CF(CF3)CFH2, -CH2CH(CF3)CF3, -CH2CH(CF2H)CF3, -CH2CH(CFH2)CF3, -CH2CH(CF3)CF2H,-CH2CH(CF3)CFH2, -CF2CH(CF3)CF3, -CF2CH(CF2H)CF3, -CF2CH(CFH2)CF3, -CF2CH(CF3)CF2H, -CF2CH(CF3)CFH2, -C(CF3)3, -C(CF2H)3, -C(CFH2)3 and other fluoroalkyl groups. Among them, methyl, ethyl, -CF3, -CF2H, -CF2CF3, -CH2CF3, -CH2CF2H, -CH2CFH2, -CH2CH2CF3, -CH2CF2CF3, -CH2CF2CF2H, -CH2CF2CFH2 are particularly preferred from the viewpoint of good compatibility with other solvents, viscosity and oxidation resistance.

[0283] Specific examples of the fluorinated chain carboxylic acid esters include CF3CH2C(=O)OCH3(3,3,3-trifluoropropionic acid methyl ester), HCF2C(=O)OCH3(difluoroacetic acid methyl ester), HCF2C(=O)OC2H5(difluoroacetic acid ethyl ester), CF3C(=O)OCH2CH2CF3, CF3C(=O)OCH2C2F5, CF3C(=O)OCH2CF2CF2H(trifluoroacetic acid 2,2,3,3-tetrafluoropropyl ester), CF3C(=O)OCH2CF3, CF3C(=O)OCH(CF3)2, ethyl pentafluorobutyrate, methyl pentafluoropropionate, ethyl pentafluoropropionate, methyl heptafluoroisobutyrate, isopropyl trifluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, One or more of butyl ester, n-butyl trifluoroacetate, methyl tetrafluoro-2-(methoxy)propionate, 2,2-difluoroethyl acetate, 2,2,3,3-tetrafluoropropyl acetate, CH3C(=O)OCH2CF3 (2,2,2-trifluoroethyl acetate), 2,2,3,3,4,4,4-heptafluorobutyl acetate, methyl 4,4,4-trifluorobutyrate, ethyl 4,4,4-trifluorobutyrate, ethyl 3,3,3-trifluoropropionate, 3,3,3-trifluoropropyl 3,3,3-trifluoropropionate, ethyl 3-(trifluoromethyl)butyrate, methyl 2,3,3,3-tetrafluoropropionate, butyl 2,2-difluoroacetate, methyl 2,2,3,3-tetrafluoropropionate, methyl 2-(trifluoromethyl)-3,3,3-trifluoropropionate, methyl heptafluorobutyrate, and the like.

[0284] Among them, from the viewpoint of good compatibility with other solvents and good rate characteristics, preferred are CF3CH2C(=O)OCH3, HCF2C(=O)OCH3, HCF2C(=O)OC2H5, CF3C(=O)OCH2C2F5, CF3C(=O)OCH2CF2CF2H, CF3C(=O)OCH2CF3, CF3C(=O)OCH(CF3)2, ethyl pentafluorobutyrate, methyl pentafluoropropionate, ethyl pentafluoropropionate, methyl heptafluoroisobutyrate, isopropyl trifluorobutyrate, ethyl trifluoroacetate, tert-butyl trifluoroacetate, n-butyl trifluoroacetate, methyl tetrafluoro-2-(methoxy)propionate, 2,2-difluoroethyl acetate, 2,2,3,3-tetrafluoropropyl acetate, CH3C(=O)OCH2CF3, 2,2,3, 3,4,4,4-heptafluorobutyl ester, 4,4,4-trifluorobutyric acid methyl ester, 4,4,4-trifluorobutyric acid ethyl 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-difluorobutyl acetate, 2,2,3,3-tetrafluoropropionic acid methyl ester, 2-(trifluoromethyl) -3,3,3-trifluoropropionic acid methyl ester, heptafluorobutyric acid methyl ester, more preferably CF3CH2C(=O)OCH3, HCF2C(=O)OCH3, HCF2C(=O)OC2H5, CH3C(=O)OCH2CF3, particularly preferably HCF2C(=O)OCH3, HCF2C(=O)OC2H5, CH3C(=O)OCH2CF3.

[0285] The above-mentioned fluorinated chain carboxylic acid esters may be used alone or in combination of two or more in any combination and ratio.

[0286] When the fluorinated chain carboxylic acid ester is contained, the content of the fluorinated chain carboxylic acid ester is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and even more preferably 50 to 80% by volume based on the solvent.

[0287] The above-mentioned solvent preferably comprises at least one selected from the above-mentioned cyclic carbonate, the above-mentioned chain carbonate and the above-mentioned chain carboxylic acid ester, and more preferably comprises the above-mentioned cyclic carbonate and at least one selected from the above-mentioned chain carbonate and the above-mentioned chain carboxylic acid ester. The above-mentioned cyclic carbonate is preferably a saturated cyclic carbonate.

[0288] The electrolyte solution containing the solvent of the above composition can further improve the high-temperature storage characteristics and cycle characteristics of the electrochemical device.

[0289] In the case where the above-mentioned solvent comprises the above-mentioned cyclic carbonate, and at least one selected from the above-mentioned linear carbonate and the above-mentioned linear carboxylate, the above-mentioned cyclic carbonate, and at least one selected from the above-mentioned linear carbonate and the above-mentioned linear carboxylate preferably comprise 10 to 100 volume %, more preferably comprise 30 to 100 volume %, further preferably comprise 50 to 100 volume % in total.

[0290] Under the situation that above-mentioned solvent comprises above-mentioned cyclic carbonate, and at least one being selected from above-mentioned linear carbonate and above-mentioned linear carboxylate, as above-mentioned cyclic carbonate and at least one volume ratio being selected from above-mentioned linear carbonate and above-mentioned linear carboxylate, preferably 5 / 95~95 / 5, more preferably more than 10 / 90, further preferably more than 15 / 85, particularly preferably more than 20 / 80, more preferably below 90 / 10, further preferably below 60 / 40, particularly preferably below 50 / 50.

[0291] Above-mentioned solvent also preferably comprises at least one being selected from above-mentioned non-fluorinated saturated cyclic carbonate, above-mentioned non-fluorinated linear carbonate and above-mentioned non-fluorinated linear carboxylic acid ester in addition, more preferably comprises above-mentioned non-fluorinated saturated cyclic carbonate and at least one being selected from above-mentioned non-fluorinated linear carbonate and above-mentioned non-fluorinated linear carboxylic acid ester.The electrolyte that contains the solvent of above-mentioned composition can be used for the electrochemical device that uses under lower voltage compatibly.

[0292] In the case where the above-mentioned solvent comprises the above-mentioned non-fluorinated saturated cyclic carbonate, and at least one selected from the above-mentioned non-fluorinated linear carbonate and the above-mentioned non-fluorinated linear carboxylate, the above-mentioned non-fluorinated saturated cyclic carbonate, and at least one selected from the above-mentioned non-fluorinated linear carbonate and the above-mentioned non-fluorinated linear carboxylate preferably comprise 5 to 100 volume %, more preferably comprise 20 to 100 volume %, further preferably comprise 30 to 100 volume % in total.

[0293] In the case where the electrolyte comprises the above-mentioned non-fluorinated saturated cyclic carbonate, and at least one selected from the above-mentioned non-fluorinated chain carbonate and the above-mentioned non-fluorinated chain carboxylic acid ester, the volume ratio of the above-mentioned non-fluorinated saturated cyclic carbonate to at least one selected from the above-mentioned non-fluorinated chain carbonate and the above-mentioned non-fluorinated chain carboxylic acid ester is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 or more, further preferably 15 / 85 or more, particularly preferably 20 / 80 or more, more preferably 90 / 10 or less, further preferably 60 / 40 or less, particularly preferably 50 / 50 or less.

[0294] Above-mentioned solvent also preferably comprises at least one being selected from above-mentioned fluorinated saturated cyclic carbonate, above-mentioned fluorinated chain carbonate and above-mentioned fluorinated chain carboxylic acid ester in addition, more preferably comprises above-mentioned fluorinated saturated cyclic carbonate and at least one being selected from above-mentioned fluorinated chain carbonate and above-mentioned fluorinated chain carboxylic acid ester.The electrolyte that contains the solvent of above-mentioned composition not only can be suitable for the electrochemical device that uses under lower voltage, can also be suitable for the electrochemical device that uses under higher voltage.

[0295] In the case where the above-mentioned solvent comprises the above-mentioned fluorinated saturated cyclic carbonate, and at least one selected from the above-mentioned fluorinated chain carbonate and the above-mentioned fluorinated chain carboxylic acid ester, the above-mentioned fluorinated saturated cyclic carbonate, and at least one selected from the above-mentioned fluorinated chain carbonate and the above-mentioned fluorinated chain carboxylic acid ester comprise 5 to 100 volume %, more preferably comprise 10 to 100 volume %, further preferably comprise 30 to 100 volume %.

[0296] In the case where the above-mentioned solvent comprises the above-mentioned fluorinated saturated cyclic carbonate, and at least one selected from the above-mentioned fluorinated chain carbonate and the above-mentioned fluorinated chain carboxylic acid ester, the volume ratio of the above-mentioned fluorinated saturated cyclic carbonate and at least one selected from the above-mentioned fluorinated chain carbonate and the above-mentioned fluorinated chain carboxylic acid ester 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, particularly preferably less than 50 / 50.

[0297] In addition, as the above-mentioned solvent, an ionic liquid can also be used. The "ionic liquid" refers to a liquid containing ions obtained by combining an organic cation and an anion.

[0298] 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.

[0299] The counter anions of these organic cations are not particularly limited and, for example, PF6 anion, PF3(C2F5)3 anion, PF3(CF3)3 anion, BF4 anion, BF2(CF3)2 anion, BF3(CF3) anion, P(C2O4)F2 anion, Tf(trifluoromethanesulfonyl) anion, Nf(nonafluorobutanesulfonyl) anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethanesulfonyl)imide anion, bis(pentafluoroethanesulfonyl)imide anion, dicyanamide anion, and halide anion can be used.

[0300] The above-mentioned solvent is preferably a non-aqueous solvent, and the electrolyte of the present invention is preferably a non-aqueous electrolyte.

[0301] The content of the solvent in the electrolyte is preferably 70 to 99.999% by mass, more preferably 80% by mass or more, and more preferably 92% by mass or less.

[0302] The electrolyte solution of the present invention may further contain the following compound (5). Examples of the compound (5) include

[0303] The following formula:

[0304] [Chemistry 41]

[0305]

[0306] Lithium difluorooxalatoborate (LIDFOB) as shown;

[0307] The following formula:

[0308] [Chemistry 42]

[0309]

[0310] The lithium difluorooxalate phosphate (LIDFOP) shown in the following formula:

[0311] [Chemistry 43]

[0312]

[0313] The lithium tetrafluorooxalate phosphate (LITFOP) shown in the following formula:

[0314] [Chemistry 44]

[0315]

[0316] As shown, lithium difluorobis(oxalate)phosphate, etc.

[0317] Examples of compound (5) 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.

[0318] Compound (5) also includes lithium tris(oxalate)phosphate, lithium tris(malonate)phosphate, lithium difluorobis(malonate)phosphate, lithium tetrafluoro(malonate)phosphate, lithium tris(methylmalonate)phosphate, lithium difluorobis(methylmalonate)phosphate, lithium tetrafluoro(methylmalonate)phosphate, lithium tris(dimethylmalonate)phosphate, lithium difluorobis(dimethylmalonate)phosphate, lithium tetrafluoro(dimethylmalonate)phosphate, and the like.

[0319] Other examples of compound (5) include LiAl(C2O4)2, LiAlF2(C2O4) and the like.

[0320] Among them, lithium difluorooxalatoborate, lithium trioxalatephosphate, lithium difluorobisoxalatephosphate, and lithium tetrafluorooxalatephosphate are more preferably used from the viewpoint of easy availability and the ability to contribute to the formation of a stable film-like structure.

[0321] The content of the compound (5) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and preferably 10% by mass or less, more preferably 3% by mass or less, based on the solvent, from the viewpoint of obtaining further excellent cycle characteristics.

[0322] The electrolyte solution of the present invention preferably further comprises an electrolyte salt (except compound (1) and compound (5)). As the electrolyte salt, in addition to lithium salts, ammonium salts, and metal salts, any salt that can be used in an electrolyte solution, such as a liquid salt (ionic liquid), an inorganic polymer salt, or an organic polymer salt, can be used.

[0323] As the electrolyte salt of the electrolyte solution for lithium ion secondary batteries, a lithium salt is preferable.

[0324] As the lithium salt, any salt can be used, and specifically, the following substances 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;

[0325] Lithium tungstate such as LiWOF5;

[0326] Lithium carboxylates such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li;

[0327] Lithium salts having an S=O group, such as FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li, methyl lithium sulfate, ethyl lithium sulfate (C2H5OSO3Li), and 2,2,2-trifluoroethyl lithium sulfate;

[0328] 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), LiN(POF2)2 and other imide lithium salts;

[0329] Methyl lithium salts such as LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3;

[0330] In addition, the formula: 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.

[0331] Among them, LiPF6, LiBF4, LiSbF6, LiTaF6, LiPO2F2, FSO3Li, 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 because they have the effects of improving output characteristics, high-rate charge and discharge characteristics, high-temperature storage characteristics, cycle characteristics, etc., and the most preferred is at least one lithium salt selected from LiPF6, LiN(FSO2)2 and LiBF4.

[0332] These electrolyte salts can be used alone or in combination of two or more. A preferred example of the combination of two or more is the combination of LiPF6 and LiBF4; the combination of LiPF6 and LiPO2F2, C2H5OSO3Li or FSO3Li has the effect of improving high temperature storage characteristics, load characteristics, and cycle characteristics.

[0333] In this case, the amount of LiBF4, LiPO2F2, C2H5OSO3Li or FSO3Li relative to 100% by mass of the entire electrolyte is not limited, and is arbitrary 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, relative to the electrolyte of the present invention, 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.

[0334] In addition, other examples are the combined use of inorganic lithium salts and organic lithium salts, and the combined use of the two has the effect of suppressing the 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. In this case, the ratio of the organic lithium salt to the total 100% by mass of the 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.

[0335] 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 viewpoint of setting the conductivity of the electrolyte to 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, in addition, preferably 3 mol / L or less, more preferably 2.5 mol / L or less, further preferably 2.0 mol / L or less.

[0336] If the total molar concentration of lithium is too low, the conductivity of the electrolyte may be insufficient. On the other hand, if the concentration is too high, the viscosity may increase, resulting in a decrease in conductivity and a decrease in battery performance.

[0337] The electrolyte of the present invention preferably further comprises the general formula (2):

[0338] [Chemistry 45]

[0339]

[0340] (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 The electrolyte solution containing the compound (2) is less likely to decrease the capacity retention rate and less likely to increase the amount of gas generated even when stored at high temperatures.

[0341] In n 21 If it is 2 or 3, then 2 or 3 X 21 Can be the same or different.

[0342] In the presence of multiple Y 21 and Z 21 In the case of multiple Y 21 and Z 21 Can be the same or different.

[0343] As X 21 , preferably -CY 21 Z 21 -(where Y 21 and Z 21 as above) or -CY 21 =CZ 21 -(where Y 21 and Z21 As described above).

[0344] As Y 21 , preferably at least one selected from H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-.

[0345] As Z 21 , preferably at least one selected from H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-.

[0346] Or, Y 21 and Z 21 They may be bonded to each other to include an unsaturated bond, and may form a carbocyclic ring or a heterocyclic ring which may have aromaticity. The number of carbon atoms in the ring is preferably 3 to 20.

[0347] Next, a specific example of compound (2) is described. It should be noted that in the following examples, "analogues" refer to an acid anhydride obtained by replacing a part of the structure of the exemplified acid anhydride with another structure within the scope of not violating the gist of the present invention, and examples thereof include dimers, trimers and tetramers containing multiple acid anhydrides, or structural isomers having the same number of carbon atoms of the substituent but with branches, etc., and substances in which the substituent is bonded to the acid anhydride at different positions.

[0348] Specific examples of the acid anhydride forming a 5-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 ... 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.

[0349] Specific examples of the acid anhydride forming a 6-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.

[0350] Specific examples of the acid anhydride forming other cyclic structures include 5-norbornene-2,3-dicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, pyromellitic anhydride, diglycolic anhydride, and analogs thereof.

[0351] Specific examples of the acid anhydride which is substituted with a halogen atom while forming a cyclic structure 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 analogs thereof.

[0352] Among them, preferred compounds (2) are 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, and tetrafluorosuccinic anhydride; more preferred compounds are maleic anhydride, methylmaleic anhydride, trifluoromethylmaleic anhydride, succinic anhydride, methylsuccinic anhydride, trifluoromethylsuccinic anhydride, and tetrafluoromethylsuccinic anhydride; and even more preferred compounds are maleic anhydride and succinic anhydride.

[0353] Compound (2) is preferably selected from the general formula (3):

[0354] [Chemistry 46]

[0355]

[0356] (Where X 31 ~X 34 The same or different, being a group containing at least H, C, O or F), and the compound (3) represented by the general formula (4):

[0357] [Chemistry 47]

[0358]

[0359] (Where X 41 and X 42 The compound (4) is a group which is the same or different and contains at least H, C, O or F.

[0360] 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.

[0361] 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-.

[0362] As X 41 ~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.

[0363] 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-.

[0364] The compound (3) is preferably any one of the following compounds.

[0365] [Chemistry 48]

[0366]

[0367] The compound (4) is preferably any one of the following compounds.

[0368] [Chemistry 49]

[0369]

[0370] The electrolyte solution preferably contains 0.0001 to 15% by mass of compound (2) even when stored at high temperatures, because the capacity retention rate is less likely to decrease and the amount of gas generated is less likely to increase. The content of compound (2) is 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.

[0371] In the case where the above-mentioned electrolyte contains both compounds (3) and (4), the capacity retention rate is less likely to decrease and the amount of gas generated is less likely to increase even when stored at high temperatures. Therefore, the above-mentioned 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 above-mentioned electrolyte, and more preferably contains 0.80 to 2.50 mass % of compound (3) and 0.08 to 1.50 mass % of compound (4).

[0372] The electrolyte solution of the present invention may contain at least one selected from the group consisting of nitrile compounds represented by the following general formulae (1a), (1b) and (1c).

[0373] [Chemistry 50]

[0374]

[0375] (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 in an alkyl group are substituted by halogen atoms; n represents an integer of 1 to 10.

[0376] [Chemistry 51]

[0377]

[0378] (Where R c represents a hydrogen atom, a halogen atom, an alkyl group, a group in which at least a part of the hydrogen atoms in the alkyl group are substituted with halogen atoms, or 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 hydrogen atoms in an alkyl group is substituted with a halogen atom. m represents an integer of 1 to 10. )

[0379] [Chemistry 52]

[0380]

[0381] (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 in the alkyl group are replaced by halogen atoms; wherein R f , Rg , R h and R i At least one of them is a group containing a cyano group. (l represents an integer of 1 to 3).

[0382] 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 combination and ratio.

[0383] In the above general formula (1a), R a and R b Each is independently a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms in an alkyl group is substituted with a halogen atom.

[0384] 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.

[0385] The alkyl group preferably has a carbon number of 1 to 5. 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.

[0386] Examples of the group in which at least a part of hydrogen atoms in an alkyl group are substituted with halogen atoms include groups in which at least a part of hydrogen atoms in the above-mentioned alkyl group are substituted with the above-mentioned halogen atoms.

[0387] In R a and R b In the case of an alkyl group or a group in which at least a part of hydrogen atoms in an alkyl group are substituted with halogen atoms, R a and R b They may be bonded to each other to form a ring structure (eg, a cyclohexane ring).

[0388] R a and R b A hydrogen atom or an alkyl group is preferred.

[0389] In the above general formula (1a), n is an integer of 1 to 10. When n is 2 or more, n R a They may all be the same or at least partly different. b The same is true for n. n is preferably an integer of 1-7, and more preferably an integer of 2-5.

[0390] As the nitrile compound represented by the general formula (1a), dinitrile and tricarbonitrile are preferred.

[0391] Specific examples of dinitriles include malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, octanonitrile, azelaic acid, sebacononitrile, 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-di Isobutyl-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-dicyanopentane, Cyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,3'-(ethylenedioxy)dipropionitrile, 3,3'-(ethylenedisulfide)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.

[0392] Specific examples of the trinitriles include pentaerythritol, propanetricarbonitrile, 1,3,5-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile, heptanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, cyclohexanetricarboxylic acid, tricyanoethylamine, tricyanoethoxypropane, tricyanoethylene, tris(2-cyanoethyl)amine, and the like. Particularly preferred are 1,3,6-hexanetricarboxylic acid and cyclohexanetricarboxylic acid, and most preferred is cyclohexanetricarboxylic acid.

[0393] In the above general formula (1b), R c is a hydrogen atom, a halogen atom, an alkyl group, a group in which at least a part of the hydrogen atoms in the alkyl group are substituted with halogen atoms, or NC-R c1 -X c1 -(R c1 represents an alkylene group, X c1 represents an oxygen atom or a sulfur atom. ) represented by a group, R d and R e Each is independently a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms in an alkyl group are substituted with halogen atoms.

[0394] Examples of the halogen atom, the alkyl group, and the group in which at least a part of hydrogen atoms in the alkyl group is substituted with a halogen atom include the groups exemplified for the above general formula (1a).

[0395] The above NC-R c1 -X c1 -R in c1 The alkylene group is preferably an alkylene group having 1 to 3 carbon atoms.

[0396] R c , R d and R e Each of them is independently preferably a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of hydrogen atoms in an alkyl group is substituted with a halogen atom.

[0397] 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 hydrogen atoms in 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 hydrogen atoms in the alkyl group are substituted with a fluorine atom.

[0398] In R d and R e In the case of an alkyl group or a group in which at least a part of hydrogen atoms in an alkyl group are substituted with halogen atoms, R d and R e They may be bonded to each other to form a ring structure (eg, a cyclohexane ring).

[0399] In the above general formula (1b), m is an integer of 1 to 10. When m is 2 or more, m R d They may all be the same or at least partly different. e The same is true for m. m is preferably an integer of 2-7, more preferably an integer of 2-5.

[0400] Examples of the nitrile compound represented by the general formula (1b) include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 3-methoxypropionitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, 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.

[0401] In the above general formula (1c), R f , Rg , 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 hydrogen atoms in an alkyl group is substituted with a halogen atom.

[0402] Examples of the halogen atom, the alkyl group, and the group in which at least a part of hydrogen atoms in the alkyl group is substituted with a halogen atom include the groups exemplified for the above general formula (1a).

[0403] Examples of the group containing a cyano group include, in addition to the cyano group, a group in which at least a part of hydrogen atoms in an alkyl group is substituted with a cyano group. Examples of the alkyl group in this case include the groups exemplified for the above general formula (1a).

[0404] R f , R g , R h and R i At least one of them is a group containing a cyano group. 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 In the case of a group containing a cyano group, R f and R g Preferred is a hydrogen atom.

[0405] In the above general formula (1c), l is an integer of 1 to 3. When l is 2 or more, one R f They may all be the same or at least partly different. g , and the same is true. l is preferably an integer of 1 to 2.

[0406] Examples of the nitrile compound represented by the general formula (1c) include 3-hexenedicononitrile, mucononitrile, maleonitrile, fumaric acid nitrile, acrylonitrile, methacrylonitrile, crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitrile, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, and 2-hexenenitrile. Preferred are 3-hexenedicononitrile and mucononitrile, and particularly preferred is 3-hexenedicononitrile.

[0407] 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, 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.

[0408] The electrolyte of the present invention may contain a compound having an isocyanate group (hereinafter sometimes referred to as "isocyanate"). The isocyanate is not particularly limited, and any isocyanate may be used. Examples of isocyanates include monoisocyanates, diisocyanates, triisocyanates, and the like.

[0409] Specific examples of 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.

[0410] Specific examples of diisocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1,8-diisocyanatooctane, 1,9-diisocyanatononane, 1,10-diisocyanatodecane, 1,3-diisocyanatopropylene, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, and 1,4-diisocyanato-2-propene. 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluorohexane, 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, 2,5-bis(isocyanatemethyl)bicyclo[2.2.1]heptane, 2,6-bis(isocyanatemethyl)bicyclo[2.2.1]heptane, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, 1,4-phenylene diisocyanate, octamethylene diisocyanate, tetramethylene diisocyanate, etc.

[0411] Specific examples of triisocyanates include 1,6,11-triisocyanatoundecane, 4-isocyanatomethyl-1,8-octamethylene diisocyanate, 1,3,5-triisocyanatomethylbenzene, 1,3,5-tris(6-isocyanatohexane-1-yl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 4-(isocyanatomethyl)octamethylene diisocyanate.

[0412] Among them, 1,6-diisocyanatohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,3,5-tris(6-isocyanatohexane-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 easily available industrially and can keep the manufacturing cost of the electrolyte low, so they are preferred. In addition, from a technical point of view, they can also help form a stable film-like structure and are more suitable for use.

[0413] The content of isocyanate is not particularly limited, as long as the effect of the present invention is not significantly damaged, it is arbitrary, preferably 0.001 mass % or more and 1.0 mass % or less relative to the electrolyte. If the content of isocyanate is above the lower limit, the non-aqueous electrolyte secondary battery can be made to have sufficient cycle characteristics to improve the effect. In addition, if it is below the upper limit, the initial resistance increase 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, particularly preferably 0.6 mass % or less.

[0414] The electrolyte of the present invention may contain a cyclic sulfonic acid ester. The cyclic sulfonic acid ester is not particularly limited, and any cyclic sulfonic acid ester 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.

[0415] 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.

[0416] 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-propene-1,3-sultone, 1-methyl-2-propene-1,3-sultone, 2-methyl-2-propene-1,3-sultone, 3-methyl-2-propene-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.

[0417] Among them, from the viewpoint of easy acquisition and the ability to contribute to the formation of a stable film-like structure, 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. The content of the cyclic sulfonic acid ester is not particularly limited, and is any content that does not significantly impair the effects of the present invention, and is preferably 0.001 mass % or more and 3.0 mass % or less relative to the electrolyte.

[0418] If the content of the cyclic sulfonate is greater than or equal to the lower limit, the non-aqueous electrolyte secondary battery can have a sufficient effect of improving the cycle characteristics. In addition, if it is less than or equal to the upper limit, an increase in the manufacturing cost of the non-aqueous electrolyte secondary battery can be avoided. The content of the cyclic sulfonate is more preferably greater than or equal to 0.01 mass%, further preferably greater than or equal to 0.1 mass%, particularly preferably greater than or equal to 0.2 mass%, and more preferably less than or equal to 2.5 mass%, further preferably less than or equal to 2.0 mass%, particularly preferably less than or equal to 1.8 mass%.

[0419] The electrolyte solution of the present invention may further contain polyoxyethylene having a weight average molecular weight of 2,000 to 4,000 and having -OH, -OCOOH, or -COOH at the terminal.

[0420] By including such a compound, the stability of the electrode interface is improved, and the characteristics of the electrochemical device can be improved.

[0421] Examples of the polyoxyethylene include polyoxyethylene monoalcohol, polyoxyethylene carboxylic acid, polyoxyethylene diol, polyoxyethylene dicarboxylic acid, polyoxyethylene triol, polyoxyethylene tricarboxylic acid, etc. These may be used alone or in combination of two or more.

[0422] Among them, a mixture of polyoxyethylene monoalcohol and polyoxyethylene diol, and a mixture of polyoxyethylene carboxylic acid and polyoxyethylene dicarboxylic acid are preferred in that the characteristics of the electrochemical device are further improved.

[0423] If the weight average molecular weight of the polyoxyethylene is too small, it may be easily oxidatively decomposed. The weight average molecular weight is more preferably 3,000 to 4,000.

[0424] The weight average molecular weight can be measured in terms of polystyrene by gel permeation chromatography (GPC).

[0425] The content of the above-mentioned polyoxyethylene in the electrolyte is preferably 1×10 -6 ~1×10 -2 If the content of the above-mentioned polyoxyethylene is too high, the characteristics of the electrochemical device may be impaired.

[0426] The content of the polyoxyethylene is more preferably 5×10 -6 mol / kg or more.

[0427] The electrolyte solution of the present invention may further contain, as additives, a fluorinated saturated cyclic carbonate, 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.

[0428] As fluorinated saturated cyclic carbonate, the compound shown in the above-mentioned general formula (A) can be cited. Among them, preferably fluoroethylene carbonate, difluoroethylene carbonate, monofluoromethyl ethylene carbonate, trifluoromethyl ethylene carbonate, 2,2,3,3,3-pentafluoropropyl ethylene carbonate (4-(2,2,3,3,3-pentafluoro-propyl)-[1,3] dioxolane-2-one). Fluorinated saturated cyclic carbonate can be used alone or in any combination and ratio.

[0429] The content of the fluorinated saturated cyclic carbonate is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.1 to 3% by mass, based on the electrolytic solution.

[0430] 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, vinyl carbonates, allyl carbonates, and catechol carbonates.

[0431] 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 vinylene carbonate, propargyl vinylene carbonate, methyl vinylene carbonate, and dimethyl vinylene carbonate.

[0432] 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-vinyl ethylene carbonate, 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, and the like.

[0433] Wherein, as unsaturated cyclic carbonate, 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, 4-vinyl-5-ethynyl ethylene carbonate. In addition, vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are particularly preferred because they can form a further stable interface protection film, and are most preferably vinylene carbonate.

[0434] The molecular weight of unsaturated cyclic carbonate is not particularly limited, as long as the effect of the present invention is not significantly damaged, and is arbitrarily.Molecular weight is preferably more than 50 and below 250.As long as it is this scope, then it is easy to ensure that the unsaturated cyclic carbonate is to the solubility of electrolyte, easily fully shows the effect of the present invention.The molecular weight of unsaturated cyclic carbonate is more preferably more than 80, in addition, more preferably below 150.

[0435] The method for producing the unsaturated cyclic carbonate is not particularly limited, and the unsaturated cyclic carbonate can be produced by arbitrarily selecting a known method.

[0436] The unsaturated cyclic carbonate may be used alone or in combination of two or more in any combination and ratio.

[0437] 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 %, more preferably more than 0.01 mass %, more preferably more than 0.1 mass % in 100 mass % of electrolyte. In addition, the above-mentioned content is preferably below 5 mass %, more preferably below 4 mass %, more preferably below 3 mass %. If it is within the above-mentioned scope, the electrochemical device using the electrolyte is easy to show sufficient cycle characteristics to improve the effect, in addition, it is easy to avoid the situation of high temperature preservation characteristic reduction, gas generation amount becoming more, discharge capacity retention rate reduction and the like.

[0438] As the unsaturated cyclic carbonate, in addition to the above-mentioned non-fluorinated unsaturated cyclic carbonate, a fluorinated unsaturated cyclic carbonate can also be preferably used.

[0439] Fluorinated unsaturated cyclic carbonate is a cyclic carbonate with unsaturated bonds and fluorine atoms. As long as the number of fluorine atoms possessed by fluorinated unsaturated cyclic carbonate is more than 1, there is no particular restriction. Wherein, the fluorine atoms are usually less than 6, preferably less than 4, most preferably 1 or 2.

[0440] 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.

[0441] Examples of the fluorinated vinylene carbonate derivatives 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.

[0442] Examples of the fluoroethylene carbonate derivative 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.

[0443] Among them, as the fluorinated unsaturated cyclic carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4 ,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, and 4,5-difluoro-4,5-diallylethylene carbonate are more suitable for use because they form a stable interface protective film.

[0444] 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 in addition below 500.If it is the scope, then easily ensure the solubility of fluorinated unsaturated cyclic carbonate to electrolyte.

[0445] The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and any known method can be selected to produce the fluorinated unsaturated cyclic carbonate. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

[0446] Fluorinated unsaturated cyclic carbonate can be used alone as one, or two or more can be used in any combination and ratio combination. 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 0.001 mass %, more preferably more than 0.01 mass %, more preferably more than 0.1 mass %, in electrolyte 100 mass %, in addition, preferably less than 5 mass %, more preferably less than 4 mass %, more preferably less than 3 mass %. If within the scope, the electrochemical device using electrolyte is easy to show sufficient cycle characteristics to improve the effect, in addition, it is easy to avoid the situation of high temperature storage characteristics reduction, gas generation amount becoming more, discharge capacity retention rate reduction and the like.

[0447] 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.

[0448] Specific examples of the compound having a triple bond include the following compounds.

[0449] 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;

[0450] 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, carbon Monocarbonates such as 3-pentynyl methyl carbonate and 4-pentynyl methyl carbonate; dicarbonates such as 2-butyne-1,4-diol dimethyl dicarbonate, 2-butyne-1,4-diol diethyl dicarbonate, 2-butyne-1,4-diol dipropyl dicarbonate, 2-butyne-1,4-diol dibutyl dicarbonate, 2-butyne-1,4-diol diphenyl dicarbonate and 2-butyne-1,4-diol dicyclohexyl dicarbonate;

[0451] 2-Propynyl acetate, 2-propynyl propionate, 2-propynyl butyrate, 2-propynyl benzoate, 2-propynyl cyclohexanecarboxylate, 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 cyclohexanecarboxylate, 2-butynyl acetate, 3-butynyl acetate, 2-pentynyl acetate, 3-pentynyl acetate, 4-pentynyl acetate, methyl acrylate, propylene glycol Ethyl acrylate, propyl acrylate, vinyl acrylate, 2-propenyl acrylate, 2-butenyl acrylate, 3-butenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl methacrylate, 2-propenyl methacrylate, 2-butenyl methacrylate, 3-butenyl methacrylate, methyl 2-propiolate, ethyl 2-propiolate, propyl 2-propiolate, vinyl 2-propiolate, 2-propenyl 2-propiolate, 2-butenyl 2-propiolate, 3-butenyl 2-propiolate , methyl 2-butynoate, ethyl 2-butynoate, propyl 2-butynoate, vinyl 2-butynoate, 2-propenyl 2-butynoate, 2-butenyl 2-butynoate, 3-butenyl 2-butynoate, methyl 3-butynoate, ethyl 3-butynoate, propyl 3-butynoate, vinyl 3-butynoate, 2-propenyl 3-butynoate, 2-butenyl 3-butynoate, methyl 2-pentynoate, ethyl 2-pentynoate, propyl 2-pentynoate, vinyl 2-pentynoate, 2-propenyl 2-pentynoate, 2 - monocarboxylic acid esters such as 2-butenyl pentynoate, 3-butenyl 2-pentynoate, 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, 3-butenyl 4-pentynoate, fumaric acid esters, methyl pivalate, ethyl pivalate;

[0452] dicarboxylic acid esters such as 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-dioxo-1,2-oxathiolane-4-yl acetate, 2,2-dioxo-1,2-oxathiolane-4-yl acetate;

[0453] 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 oxalate, and di-3-butynyl oxalate;

[0454] Phosphine oxides such as methyl(2-propynyl)(vinyl)phosphine oxide, divinyl(2-propynyl)phosphine oxide, di(2-propynyl)(vinyl)phosphine oxide, di(2-propenyl)(2-propynyl)phosphine oxide, di(2-propenyl)(2-propynyl)phosphine oxide, di(3-butenyl)(2-propynyl)phosphine oxide, and di(2-propynyl)(3-butenyl)phosphine oxide;

[0455] 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 Esters, and phosphinates such as 1,1-dimethyl-2-propynyl di(3-butenyl)phosphinate, 2-propenyl methyl(2-propynyl)phosphinate, 3-butenyl methyl(2-propynyl)phosphinate, 2-propenyl di(2-propynyl)phosphinate, 3-butenyl di(2-propynyl)phosphinate, 2-propenyl 2-propynyl(2-propenyl)phosphinate, and 3-butenyl 2-propynyl(2-propenyl)phosphinate;

[0456] 2-propenylphosphonic acid (methyl) (2-propynyl) ester, 2-butenylphosphonic acid (methyl) (2-propynyl) ester, 2-propenylphosphonic acid (2-propynyl) (2-propenyl) ester, 3-butenylphosphonic acid (3-butenyl) (2-propynyl) ester, 2-propenylphosphonic acid (1,1-dimethyl-2-propynyl) (methyl) ester, 2-propenylphosphonic acid (1,1-dimethyl-2-propynyl) (methyl) ester, 2-propenylphosphonic acid (1,1-dimethyl-2-propynyl) (2-propenyl) ester, and 3-butenylphosphonic acid (3-butenyl) (1,1-dimethyl-2-propynyl) (2-propenyl) ester. Phosphonic acid esters such as (1,1-dimethyl-2-propynyl) methylphosphonate, (2-propynyl) methylphosphonate, (3-butenyl) methylphosphonate, (2-propynyl) methylphosphonate, (1,1-dimethyl-2-propynyl) methylphosphonate, (3-butenyl) methylphosphonate, (1,1-dimethyl-2-propynyl) ethylphosphonate, (2-propynyl) ethylphosphonate, (3-butenyl) ethylphosphonate, (2-propynyl) ethylphosphonate, (1,1-dimethyl-2-propynyl) ethylphosphonate and (3-butenyl) ethylphosphonate;

[0457] 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.

[0458] Among these, compounds having an alkynyloxy group are preferred because they can form a negative electrode coating more stably in an electrolyte solution.

[0459] Furthermore, from the viewpoint of improving storage characteristics, 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, methyl 2-propynyl oxalate, and di-2-propynyl oxalate are particularly preferred.

[0460] The above-mentioned compound with triple bond can be used alone as one, or two or more can be used in any combination and ratio. The compound with triple bond of the present invention is not limited to the overall amount of the electrolyte, as long as it does not significantly damage the effect of the present invention, and is arbitrary, 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, and more preferably 1% by mass or less. When the above range is met, the effects of output characteristics, load characteristics, cycle characteristics, high temperature storage characteristics, etc. are further improved.

[0461] The electrolyte solution of the present invention may contain an overcharge preventer in order to effectively suppress battery rupture and ignition when an electrochemical device using the electrolyte solution reaches an overcharge state or the like.

[0462] 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, isopropylbenzene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene, tert-butylbenzene, tert-amylbenzene, tert-hexylbenzene, and aromatic compounds such as anisole; 2-fluorobiphenyl, 4-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, Partial fluorides of the above aromatic compounds such as fluorotoluene and trifluoromethylbenzene; fluorinated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 1,6-difluoroanisole, 2,6-difluoroanisole and 3,5-difluoroanisole; aromatic acetates such as 3-propylphenyl acetate, 2-ethylphenyl acetate, benzylphenyl acetate, methylphenyl acetate, benzyl acetate and phenethylphenyl acetate; aromatic carbonates such as diphenyl carbonate and methyl benzene 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, methyl benzene carbonate, etc. They can be used alone or in combination of two or more. In the case of using two or more in combination, in particular, a combination of cyclohexylbenzene with tert-butylbenzene or tert-amylbenzene; and at least one selected from oxygen-free aromatic compounds such as 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 is preferably used in combination from the viewpoint of balancing the overcharge prevention characteristics and the high temperature storage characteristics.

[0463] In the electrolyte used in the present invention, carboxylic anhydride (except compound (2)) can be used. A compound represented by the following general formula (6) is preferred. The method for producing carboxylic anhydride is not particularly limited, and any known method can be selected for production.

[0464] [Chemistry 53]

[0465]

[0466] (In general formula (6), R 61 , R 62Each independently represents a hydrocarbon group having 1 to 15 carbon atoms which may have a substituent.)

[0467] R 61 , R 62 As long as 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 obtained 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, and in the case of a chain-shaped group, it can be straight-chain or branched. Furthermore, it can be a group obtained by bonding a chain-shaped group and a ring-shaped group. It should be noted that R 61 and R 62 They can be the same as each other or different.

[0468] In addition, in 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.

[0469] 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. 61 and R 62 When the two hydrocarbon groups are bonded 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, R including the substituent 61 , R 62 The total number of carbon atoms preferably satisfies the above range.

[0470] 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 another structure within the scope that does not violate the main purpose of the present invention, and examples include dimers, trimers and tetramers containing multiple acid anhydrides, or structural isomers with the same number of carbon atoms of the substituent but with branches, etc., and substances with different positions of the substituent bonded to the acid anhydride, etc.

[0471] First, the following is an example of R 61 , R 62 Specific examples of the same acid anhydride.

[0472] 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.

[0473] As R 61 , R 62 Specific examples of the acid anhydride having a cyclic alkyl group include cyclopropanecarboxylic anhydride, cyclopentanecarboxylic anhydride, cyclohexanecarboxylic anhydride and the like, and analogs thereof.

[0474] 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 analogs thereof.

[0475] 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 analogs thereof.

[0476] As R 61 , R 62 Specific examples of the acid anhydride which is an aromatic group include benzoic anhydride, 4-methylbenzoic anhydride, 4-ethylbenzoic anhydride, 4-tert-butylbenzoic anhydride, 2-methylbenzoic anhydride, 2,4,6-trimethylbenzoic anhydride, 1-naphthoic anhydride, 2-naphthoic anhydride and the like, and analogs thereof.

[0477] In addition, as R 61 , R 62 As examples of acid anhydrides substituted with halogen atoms, examples of acid anhydrides substituted with fluorine atoms are mainly given below, 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 exemplified compounds.

[0478] 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-tetrafluoropropionic anhydride, 2,3,3,3-tetrafluoropropionic anhydride, 3-fluoropropionic anhydride, 3,3-difluoropropionic anhydride, 3,3,3-trifluoropropionic anhydride, perfluoropropionic anhydride and the like, and analogs thereof.

[0479] As R 61 , R 62 Examples of the acid anhydride of a cyclic alkyl group substituted with a halogen atom include 2-fluorocyclopentanecarboxylic anhydride, 3-fluorocyclopentanecarboxylic anhydride, 4-fluorocyclopentanecarboxylic anhydride and the like, and analogs thereof.

[0480] 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.

[0481] As R 61 , R62 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.

[0482] 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 analogs thereof.

[0483] As R 61 , R 62 Examples of acid anhydrides 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 analogs thereof.

[0484] Next, the following is an example of R 61 , R 62 Specific examples of acid anhydrides that are different from each other.

[0485] As R 61 , R 62 All combinations of the above-mentioned examples and their analogs can be considered, and representative examples are given below.

[0486] Examples of combinations of chain alkyl groups include acetic propionic anhydride, acetic butyric anhydride, butyric propionic anhydride, and acetic 2-methylpropionic anhydride.

[0487] Examples of the combination of a chain alkyl group and a cyclic alkyl group include acetic cyclopentanecarboxylic anhydride, acetic cyclohexanecarboxylic anhydride, and cyclopentanecarboxylic propionic anhydride.

[0488] 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.

[0489] Examples of the combination of a chain alkyl group and an alkynyl group include acetic anhydride propiolic acid, acetic 2-butiolic acid, acetic anhydride 3-butiolic acid, acetic 3-phenylpropiolic acid, propiolic acid, and the like.

[0490] Examples of the combination of a chain alkyl group and an aryl group include acetic anhydride benzoic acid, acetic 4-methylbenzoic acid, acetic 1-naphthoic acid, and benzoic acid propionic anhydride.

[0491] 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.

[0492] Examples of combinations of cyclic alkyl groups include cyclopentanecarboxylic acid and cyclohexanecarboxylic anhydride.

[0493] Examples of the combination of a cyclic alkyl group and an alkenyl group include acrylic acid cyclopentanecarboxylic anhydride, 3-methacrylic acid cyclopentanecarboxylic anhydride, 3-butenoic acid cyclopentanecarboxylic anhydride, acrylic acid cyclohexanecarboxylic anhydride, and the like.

[0494] Examples of the combination of a cyclic alkyl group and an alkynyl group include propiolic acid cyclopentanecarboxylic anhydride, 2-butynoic acid cyclopentanecarboxylic anhydride, and propiolic acid cyclohexanecarboxylic anhydride.

[0495] Examples of the combination of a cyclic alkyl group and an aryl group include benzoic acid cyclopentanecarboxylic anhydride, 4-methylbenzoic acid cyclopentanecarboxylic anhydride, and benzoic acid cyclohexanecarboxylic anhydride.

[0496] 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.

[0497] 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.

[0498] 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.

[0499] 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.

[0500] 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.

[0501] Examples of combinations of alkynyl groups include propiolic acid 2-butynoic anhydride, propiolic acid 3-butynoic anhydride, and 2-butynoic acid 3-butynoic anhydride.

[0502] 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.

[0503] 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.

[0504] Examples of combinations of aryl groups include 4-methylbenzoic anhydride benzoic acid, 1-naphthoic anhydride benzoic acid, and 1-naphthoic anhydride 4-methylbenzoic acid.

[0505] 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.

[0506] 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.

[0507] Among the acid anhydrides forming the above-mentioned 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- trifluoropropionic anhydride, 2-(trifluoromethyl)acrylic anhydride, 2-(4-fluorophenyl)acrylic anhydride, 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, methoxyformic anhydride, ethoxyformic anhydride; more preferably 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, ethoxyformic anhydride.

[0508] These compounds are preferred because they can appropriately form a bond with lithium oxalate salt to form a coating film having excellent durability, and can particularly improve charge and discharge rate characteristics, input and output characteristics, and impedance characteristics after a durability test.

[0509] It should be noted that the molecular weight of the carboxylic anhydride is not limited and is arbitrary as long as the effect of the present invention is not significantly impaired, and 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 coating density can be appropriately adjusted, so that the durability can be appropriately improved.

[0510] In addition, the method for producing the carboxylic anhydride is not particularly limited, and any known method can be selected to produce the carboxylic anhydride. The carboxylic anhydride described above may be contained in the non-aqueous electrolyte of the present invention alone or in combination of two or more in any combination and ratio.

[0511] In addition, the above-mentioned carboxylic anhydride of the present invention is not particularly limited relative to the content of the electrolyte, as long as the effect of the present invention is not significantly damaged, and it is arbitrary. Relative to the electrolyte of the present invention, it is expected to be generally 0.01 mass % or more, preferably 0.1 mass % or more, and generally 5 mass % or less, preferably 3 mass % or less. If the content of carboxylic anhydride is within the above range, it is easy to show the effect of improving the cycle characteristics, and the reactivity is suitable, so the battery characteristics are easily improved.

[0512] In the electrolyte of the present invention, other known auxiliary agents can be used. Examples of other auxiliary agents include hydrocarbon compounds such as pentane, heptane, octane, nonane, decane, cycloheptane, benzene, furan, naphthalene, 2-phenylbicyclohexane, cyclohexane, 2,4,8,10-tetraoxaspiro[5.5]undecane, and 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane;

[0513] Fluorinated aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene, trifluorotoluene, monofluorobenzene, 1-fluoro-2-cyclohexylbenzene, 1-fluoro-4-tert-butylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-2-cyclohexylbenzene, and fluorobiphenyl;

[0514] Carbonate compounds such as 1,4-anhydride erythritol carbonate, spirobis-dimethylene carbonate, and methoxyethyl-methyl carbonate;

[0515] Ether compounds such as dioxolane, dioxane, 2,5,8,11-tetraoxadodecane, 2,5,8,11,14-pentaoxadecane, ethoxymethoxyethane, trimethoxymethane, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether (ethyl monoglyme);

[0516] Ketone compounds such as dimethyl ketone, diethyl ketone, 3-pentanone, etc.

[0517] Anhydrides such as 2-allylsuccinic anhydride;

[0518] Ester compounds such as dimethyl oxalate, diethyl oxalate, ethyl methyl oxalate, di(2-propynyl) oxalate, 2-propynyl methyl oxalate, dimethyl succinate, di(2-propynyl) glutarate, methyl formate, ethyl formate, 2-propynyl formate, 2-butyne-1,4-diyl dicarboxylate, 2-propynyl methacrylate, and dimethyl malonate;

[0519] Acetamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide and other amide compounds;

[0520] Ethylene sulfate, vinylene sulfate, ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, cyclobutene sulfone, diphenyl sulfone, N,N-dimethylmethanesulfonamide, N,N-diethylmethanesulfonamide, methyl vinylsulfonate, ethyl vinylsulfonate, allyl vinylsulfonate, propargyl vinylsulfonate, methyl allylsulfonate, ethyl allylsulfonate, allyl allylsulfonate, propargyl allylsulfonate, 1,2-bis(vinylsulfonyloxy)ethane, propanedisulfonic anhydride, sulfobutyric anhydride, sulfobenzoic anhydride, sulfopropionic anhydride, ethanedisulfonic anhydride, methylene methanedisulfonate, 2-propynyl methanesulfonate, amyl sulfite, pentafluorophenyl methanesulfonate, propylene sulfate, propylene sulfite, propane sultone, butylene sulfite, butane -2,3-dimethyl dimethanesulfonate, 2-butyne-1,4-dimethyl dimethanesulfonate, 2-propynyl vinylsulfonate, bis(2-vinylsulfonylethyl) ether, 5-vinyl-hexahydro-1,3,2-benzodioxathiole-2-oxide, 2-propynyl 2-(methylsulfonyloxy)propionate, 5,5-dimethyl-1,2-oxathiole-4-one 2,2-dioxide, 3-sulfo-propionic anhydride methanedisulfonic acid trimethylene ester 2-methyltetrahydrofuran, methanedisulfonic acid trimethylene ester, tetramethylene sulfoxide, methanedisulfonic acid dimethylene ester, difluoroethyl methyl sulfone, divinyl sulfone, 1,2-bis(vinylsulfonyl)ethane, methyl ethanedisulfonate, ethyl ethanedisulfonate, ethylene sulfate, thiophene 1-oxide and other sulfur-containing compounds;

[0521] 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and nitrogen-containing compounds such as N-methylsuccinimide, nitromethane, nitroethane, and ethylenediamine;

[0522] Trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, diethylphosphinoacetic acid ethyl ester, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide, bis(2,2-difluoroethyl) 2,2,2-trifluoroethyl phosphate, bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate Fluoroethyl ester, 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, tri(2,2,2-trifluoroethyl) phosphate, tri(1,1,1,3,3,3-hexafluoropropane-2-yl) phosphate, trioctyl phosphate, 2-phenylphenyl dimethyl phosphate, 2-phenylphenyl diethyl phosphate, (2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoropropyl) methyl phosphate, 2-(dimethoxyphosphoryl) methyl acetate, 2-(dimethylphosphoryl) methyl acetate, 2-(diethoxyphosphoryl) methyl acetate, 2-(diethylphosphoryl) methyl acetate, methylene bisphosphonic acid methyl, methylene bisphosphonic acid ethyl, ethylene bisphosphonic acid methyl, ethylene bisphosphonic acid ethyl, butylene bisphosphonic acid methyl, butylene bisphosphonic acid ethyl, 2-(di Phosphorus-containing compounds such as 2-(methoxyphosphoryl)acetate, 2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl 2-(diethoxyphosphoryl)acetate, 2-propynyl 2-(diethylphosphoryl)acetate, tris(trimethylsilyl)phosphate, tris(triethylsilyl)phosphate, tris(trimethoxysilyl)phosphate, tris(trimethylsilyl)phosphite, tris(triethylsilyl)phosphite, tris(trimethoxysilyl)phosphite, and trimethylsilyl polyphosphate;

[0523] Boron-containing compounds such as tris(trimethylsilyl) borate and tris(trimethoxysilyl) borate;

[0524] Silane compounds such as bis(trimethyl)aluminum orthosilicate, bis(triethyl)aluminum orthosilicate, bis(propanol)triethylaluminum orthosilicate, bis(butanol)trimethylaluminum orthosilicate, bis(trimethylsiloxy)titanium, tetra(triethylsiloxy)titanium, tetramethylsilane, etc.; etc.

[0525] These may be used alone or in combination of two or more. By adding these auxiliary agents, the capacity retention characteristics after high-temperature storage and the cycle characteristics can be improved.

[0526] Among these other auxiliary agents, phosphorus-containing compounds are preferred, and tris(trimethylsilyl) phosphate and tris(trimethylsilyl) phosphite are preferred.

[0527] The amount of other auxiliary agents is not particularly limited, and is arbitrary as long as it does not significantly impair the effect of the present invention. The amount of other auxiliary agents in 100% by mass of the electrolyte is preferably 0.01% by mass or more, and further preferably 5% by mass or less. If it is within this range, it is easy to fully demonstrate the effects of other auxiliary agents, and it is also easy to avoid situations such as reduction in battery characteristics such as high-load discharge characteristics. 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 further preferably 1% by mass or less.

[0528] The electrolyte of the present invention may further contain cyclic and chain carboxylates, ether compounds, nitrogen-containing compounds, boron-containing compounds, organic silicon-containing compounds, non-flammable (flame retardants), surfactants, high dielectric constant additives, cycle characteristics and rate characteristics improvers, sulfone compounds, etc. as additives without damaging the effects of the present invention.

[0529] Examples of the cyclic carboxylic acid esters include those having a total carbon number of 3 to 12 in the structural formula. Specifically, examples include γ-butyrolactone, γ-valerolactone, γ-caprolactone, ε-caprolactone, 3-methyl-γ-butyrolactone, etc. Among them, γ-butyrolactone is particularly preferred because it can increase the degree of lithium ion dissociation and thus improve the characteristics of the electrochemical device.

[0530] The amount of the cyclic carboxylic acid ester as an additive is usually in 100% by mass of the solvent, preferably 0.1% by mass or more, more preferably 1% by mass or more. If it is within this range, the conductivity of the electrolyte is improved, and the large current discharge characteristics of the electrochemical device are easily improved. In addition, the amount of the cyclic carboxylic acid ester is preferably 10% by mass or less, more preferably 5% by mass or less. By setting the upper limit like this, the viscosity of the electrolyte is in an appropriate range, the reduction of the conductivity is avoided, the increase of the negative electrode resistance is suppressed, and the large current discharge characteristics of the electrochemical device are easily set to a good range.

[0531] In addition, as the above-mentioned cyclic carboxylic acid ester, a fluorinated cyclic carboxylic acid ester (fluorinated lactone) can also be suitably used. As the fluorinated lactone, for example, the fluorinated lactone represented by the following formula (C) can be cited:

[0532] [Chemistry 54]

[0533]

[0534] (Where X 15 ~X 20 are the same or different, all are -H, -F, -Cl, -CH3 or fluoroalkyl; wherein X 15 ~X 20 At least one of them is a fluorinated alkyl group).

[0535] As X 15 ~X 20 The fluorinated alkyl group may be, for example, -CFH2, -CF2H, -CF3, -CH2CF3, -CF2CF3, -CH2CF2CF3, -CF(CF3)2, and from the viewpoint of high oxidation resistance and safety improvement effect, -CH2CF3 and -CH2CF2CF3 are preferred.

[0536] If X 15 ~X 20 At least one of the following 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 made at one position or at multiple positions. From the viewpoint of good solubility of the electrolyte salt, the substitution is preferably made at 1 to 3 positions, more preferably at 1 to 2 positions.

[0537] The substitution position of the fluoroalkyl group is not particularly limited, but from the viewpoint of good synthesis yield, X 17 and / or X 18 , especially X 17 or X 18 is a fluoroalkyl group, preferably -CH2CF3 or -CH2CF2CF3. 15 ~X 20 It is -H, -F, -Cl or CH 3 , and is preferably -H from the viewpoint of good solubility of the electrolyte salt.

[0538] As the fluorinated lactone, in addition to the substance represented by the above formula, for example, the fluorinated lactone represented by the following formula (D) can be mentioned:

[0539] [Chemistry 55]

[0540]

[0541] (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 alkyl 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 are -H, -F, -Cl, -CF3 or CH3; X 223 ~X 225The same or different, all are -H, -F, -Cl or an alkyl group in which the hydrogen atom may be substituted by a halogen atom and may contain a heteroatom in the chain; n=0 or 1).

[0542] As the fluorine-containing lactone represented by formula (D), from the viewpoint of easy synthesis and good chemical stability, a 5-membered ring structure represented by the following formula (E) can be preferably mentioned:

[0543] [Chemistry 56]

[0544]

[0545] (In the formula, A, B, Rf 12 , X 221 , X 222 and X 223 Same as formula (D),

[0546] Further according to the combination of A and B, there is a fluorine-containing lactone represented by the following formula (F):

[0547] [Chemistry 57]

[0548]

[0549] (Where Rf 12 , X 221 , X 222 , X 223 , X 226 and X 227 Same as formula (D)), and

[0550] The fluorinated lactone represented by the following formula (G):

[0551] [Chemistry 58]

[0552]

[0553] (Where Rf 12 , X 221 , X 222 , X 223 , X 226 and X 227 Same as formula (D)).

[0554] Among these, from the viewpoint of being able to exert excellent properties such as high dielectric constant and high withstand voltage, and from the viewpoint of improving the properties of the electrolyte solution in the present invention in terms of good solubility of the electrolyte salt and reduction of the internal resistance, the following can be cited:

[0555] [Chemistry 59]

[0556]

[0557] wait.

[0558] By containing the fluorinated cyclic carboxylic acid ester, effects such as improved ion conductivity, improved safety, and improved stability at high temperatures are obtained.

[0559] Examples of the chain carboxylic acid esters include those 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, isopropyl isobutyrate, and the like.

[0560] Among them, from the viewpoint of improving ion conductivity by reducing viscosity, 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.

[0561] As the ether compound, chain ethers having 2 to 10 carbon atoms and cyclic ethers having 3 to 6 carbon atoms are preferred.

[0562] 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.

[0563] Furthermore, as the above-mentioned ether compound, fluorinated ether can also be preferably used.

[0564] Examples of the fluorinated ether include fluorinated ether (I) represented by the following general formula (I):

[0565] R 3 -O-Rf 4 (I)

[0566] (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; wherein Rf 3 and Rf 4 At least one of them is a fluoroalkyl group).

[0567] 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.

[0568] 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 fluorinated alkyl groups having 1 to 10 carbon atoms. In this case, Rf 3 and Rf 4 They can be the same or different from each other.

[0569] 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.

[0570] If Rf 3 and Rf 4 If the total number of carbon atoms is too small, the boiling point of the fluoroether is 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 its compatibility with other solvents begins to be negatively 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.

[0571] 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 flame retardancy and compatibility is particularly excellent. In addition, it is also preferred from the viewpoint of good oxidation resistance and safety.

[0572] The lower limit of the fluorine content is more preferably 45 mass %, further preferably 50 mass %, particularly preferably 55 mass %, and the upper limit is more preferably 70 mass %, further preferably 66 mass %.

[0573] 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).

[0574] As Rf 3, for example, CF3CF2CH2-, CF3CFHCF2-, HCF2CF2CF2-, HCF2CF2CH2-, CF3CF2CH2CH2-, CF3CFHCF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CF2CH2-, HCF2CF2CH2CH2-, HCF2CF(CF3)CH2-, etc. can be mentioned. 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.

[0575] Specific examples of the fluoroether (I) include HCF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CF2H, HCF2CF2CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, C6F 13 OCH3、C6F 13 OC2H5、C8F 17 OCH3、C8F 17 OC2H5, CF3CFHCF2CH(CH3)OCF2CFHCF3, HCF2CF2OCH(C2H5)2, HCF2CF2OC4H9, HCF2CF2OCH2CH(C2H5)2, HCF2CF2OCH2CH(CH3)2, etc.

[0576] Among them, those containing HCF2- or CF3CFH- at one or both ends have excellent polarizability and can give fluoroether (I) with a 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.

[0577] Examples of such fluoroether (I) include one or more of CF3CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, HCF2CF2CH2OCF2CFHCF3, HCF2CF2CH2OCH2CF2CF2H, CF3CFHCF2CH2OCF2CFHCF3, HCF2CF2CH2OCF2CF2H, and CF3CF2CH2OCF2CF2H.

[0578] Among them, from the viewpoint of advantages in terms of high boiling point, compatibility with other solvents and good solubility of electrolyte salts, it is preferred to be 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).

[0579] 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 in terms of their high solvating ability for lithium ions and improved ion dissociation degree. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred in terms of their low viscosity and high ion conductivity.

[0580] 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 compounds represented by the general formulas (1a), (1b), and (1c) are not included in the nitrogen-containing compound.

[0581] Examples of the boron-containing compound include boric acid esters such as trimethyl borate and triethyl borate, boric acid ethers, and alkylboranes.

[0582] Examples of the organic silicon-containing compound include (CH3)4-Si, (CH3)3-Si-Si(CH3)3, and silicone oil.

[0583] As the above-mentioned incombustible (flame retardant) agent, phosphate esters and phosphazene compounds can be cited. As the above-mentioned phosphate esters, for example, fluorinated alkyl phosphate esters, non-fluorinated alkyl phosphate esters, aryl phosphate esters, etc. can be cited. Among them, fluorinated alkyl phosphate esters are preferred in terms of being able to exert flame retardant effects in a small amount.

[0584] Examples of the phosphazene compounds include methoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, dimethylaminopentafluorocyclotriphosphazene, diethylaminopentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene.

[0585] 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.

[0586] 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.

[0587] The surfactant may be any of a cationic surfactant, anionic surfactant, nonionic surfactant, and amphoteric surfactant. From the viewpoint of improving cycle characteristics and rate characteristics, the surfactant preferably contains a fluorine atom.

[0588] As such a surfactant containing a fluorine atom, for example, a fluorine-containing carboxylate represented by the following formula (30) is preferred:

[0589] R 5 COO - M + (30)

[0590] (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)),

[0591] The fluorine-containing sulfonate represented by the following formula (40):

[0592] R 6 SO3 - M + (40)

[0593] (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's are the same or different and are H or an alkyl group having 1 to 3 carbon atoms)) and the like.

[0594] The content of the surfactant is preferably 0.01 to 2% by mass in the electrolyte solution from the viewpoint of being able to reduce the surface tension of the electrolyte solution without deteriorating the charge-discharge cycle characteristics.

[0595] Examples of the dielectric constant-enhancing additive include sulfolane, methyl sulfolane, γ-butyrolactone, and γ-valerolactone.

[0596] Examples of the cycle characteristics and rate characteristics improving agent include methyl acetate, ethyl acetate, tetrahydrofuran, and 1,4-dioxane.

[0597] 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).

[0598] As the polymer material, there can be cited conventionally known polyoxyethylene, polyoxypropylene, their modified products (Japanese Patent Publication No. 8-222270, Japanese Patent Publication No. 2002-100405); polyacrylate polymers, polyacrylonitrile; fluororesins such as polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer (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. In particular, it is expected that polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer are used as polymer materials for gel electrolytes.

[0599] In addition, the electrolyte solution of the present invention may contain an ion conductive compound described in Japanese Patent Application No. 2004-301934.

[0600] The ion conductive compound is an amorphous fluorinated polyether compound having a fluorinated group in the side chain represented by formula (101):

[0601] A-(D)-B (101)

[0602] [Wherein, D is formula (201):

[0603] -(D1) n -(FAE)m -(AE) p -(Y) q - (201)

[0604] (wherein D1 is an ether unit having a fluorine-containing ether group in the side chain represented by formula (2a):

[0605] [Chemistry 60]

[0606]

[0607] (wherein, Rf is a fluorinated ether group having a crosslinkable functional group; R 10 is a group or bond that bonds Rf to the main chain);

[0608] FAE is an ether unit having a fluorinated alkyl group on the side chain represented by formula (2b):

[0609] [Chemistry 61]

[0610]

[0611] (wherein, Rfa is a hydrogen atom or a fluoroalkyl group which may have a crosslinkable functional group; R 11 is a group or bond that bonds Rfa to the main chain);

[0612] AE is an ether unit represented by formula (2c):

[0613] [Chemistry 62]

[0614]

[0615] (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 To R 13 Groups or bonds bonded to the main chain);

[0616] Y is a unit comprising at least one of the formulae (2d-1) to (2d-3):

[0617] [Chemistry 63]

[0618]

[0619] 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 limited);

[0620] 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 end of D is an oxygen atom, it is not a -COOH group, -OR, an ester group or a carbonate group)].

[0621] 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.

[0622] 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.

[0623] As sulfolanes, preferably sulfolane and / or sulfolane derivatives (hereinafter, including sulfolane, sometimes referred to as "sulfolanes"). As sulfolane derivatives, preferably one or more of the hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted by fluorine atoms or alkyl groups.

[0624] 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-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoromethylsulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 2-fluoro-3-(trifluoromethyl)sulfolane, 3-fluoro-3-(trifluoromethyl)sulfolane, 4-fluoro-3-(trifluoromethyl)sulfolane, 3-cyclobutene sulfolane, 5-fluoro-3-(trifluoromethyl)sulfolane, and the like.

[0625] 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, Fluoromethyl 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.

[0626] 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.

[0627] 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 %, usually 0.3 volume % or more, preferably 0.5 volume % or more, more preferably 1 volume % or more, in addition, usually 40 volume % or less, preferably 35 volume % or less, 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, 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 in an appropriate range.

[0628] From the viewpoint of improving output characteristics, the electrolyte of the present invention preferably contains, as an additive, at least one compound (7) selected from lithium fluorophosphate salts (excluding LiPF6 and LiPO2F2) and lithium salts having an S═O group.

[0629] When the compound (7) is used as an additive, it is preferable to use a compound other than the compound (7) as the electrolyte salt.

[0630] Examples of the lithium fluorophosphate salts include lithium monofluorophosphate (LiPO 3 F) and the like.

[0631] Examples of the lithium salts having an S═O group include lithium monofluorosulfonate (FSO 3 Li), lithium methyl sulfate (CH 3 OSO 3 Li), lithium ethyl sulfate (C 2 H 5 OSO 3 Li), and 2,2,2-trifluoroethyl lithium sulfate.

[0632] Among the compounds (7), FSO3Li and C2H5OSO3Li are preferred.

[0633] The content of the compound (7) is preferably 0.001 to 20% by mass, more preferably 0.01 to 15% by mass, further preferably 0.1 to 10% by mass, and particularly preferably 0.1 to 7% by mass, based on the above-mentioned electrolyte solution.

[0634] The electrolyte solution of the present invention may further contain other additives as required. Examples of other additives include metal oxides and glass.

[0635] The electrolyte of the present invention preferably contains at least one selected from the group consisting of unsaturated cyclic carbonate, fluorinated saturated cyclic carbonate, lithium salt having an S=O group, imide lithium salt, nitrile compound, cyclic sulfonate and compound (2) as an additive. By containing these additives, the resistance of the lithium ion secondary battery can be further reduced, and the storage characteristics can be further improved.

[0636] The above-mentioned additive is preferably selected from unsaturated cyclic carbonates, fluorinated saturated cyclic carbonates, lithium sulfonate compounds, alkyl lithium sulfate compounds, (C m F 2m+1 SO2)(C n F 2n+1 SO2)NLi (m and n are integers of 0 to 5), a lithium imide salt represented by the general formula (1a), a nitrile compound represented by a saturated cyclic sulfonate, an unsaturated cyclic sulfonate, compound (3) and compound (4), and more preferably at least one selected from vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, FSO3Li, C2H5OSO3Li, LiN(FSO2)2, LiN(CF3SO2)2, adiponitrile, succinonitrile, glutaronitrile, 1,3-propane sultone, 1-propylene-1,3-sultone, succinic anhydride and maleic anhydride.

[0637] The content of the additive is preferably 0.001 to 5% by mass relative to the electrolyte, 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 3% by mass or less, further preferably 1% by mass or less.

[0638] The electrolyte of the present invention preferably contains 1 to 1000 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 that the film forming ability on the negative electrode is reduced and the characteristics of the electrochemical device are reduced. In addition, if the HF content is too much, there is a tendency that the oxidation resistance of the electrolyte is reduced 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 and recovery capacity rate of the electrochemical device.

[0639] The HF content is more preferably 5 ppm or more, further preferably 10 ppm or more, and particularly preferably 20 ppm or more. The HF content is further more preferably 200 ppm or less, further preferably 100 ppm or less, further preferably 80 ppm or less, and particularly preferably 50 ppm.

[0640] The HF content can be determined by neutralization titration.

[0641] The electrolyte solution of the present invention can be prepared by any method using the above-mentioned components.

[0642] The electrolyte solution of the present invention is an electrolyte solution for lithium ion secondary batteries.

[0643] The present invention also relates to a lithium ion secondary battery comprising the electrolyte of the present invention.

[0644] The lithium ion secondary battery of the present invention preferably comprises a positive electrode, a negative electrode, and the above-mentioned electrolyte solution.

[0645] <Positive electrode>

[0646] The positive electrode is composed of a positive electrode active material layer containing a positive electrode active material and a current collector.

[0647] 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, sulfur-based materials, 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.

[0648] 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 materials obtained by replacing part of the transition metal atoms as the main body of these lithium transition metal composite oxides with 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. As specific examples of the replaced materials, for example, 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 0.8 Co 0.1 Mn 0.1 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.

[0649] Among them, the lithium-containing transition metal composite oxide is preferably LiMn which has a high energy density even when a high voltage is reached. 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 Among them, LiMn is particularly preferred in the case of a high voltage of 4.4 V or more. 1.5 Ni 0.5 O4.

[0650] The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. Specific examples include iron phosphates such as LiFePO4, Li3Fe2(PO4)3, LiFeP2O7; cobalt phosphates such as LiCoPO4; substances obtained by replacing a part of the transition metal atoms serving as the main body of these lithium transition metal phosphate compounds with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.

[0651] Examples of the lithium-containing transition metal composite oxide include

[0652] 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,

[0653] 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

[0654] Formula: LiCo 1-d M 3 d O2(where 0≤d≤0.5; M 3 The present invention relates to 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.

[0655] 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.

[0656] 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, Li2MnO3, etc.

[0657] As the sulfur-based material, a material containing a sulfur atom can be exemplified, preferably at least one selected from elemental sulfur, metal sulfide and organic sulfur compound, and more preferably elemental sulfur. The metal sulfide can be a metal polysulfide. The organic sulfur compound can be an organic polysulfide.

[0658] Examples of the metal sulfide include LiS x (0<x≤8) represented by the compound; Li2S x (0<x≤8); compounds with two-dimensional layered structures such as TiS2 and MoS2; compounds with the general formula Me x Chevrel compounds having a strong three-dimensional skeleton structure represented by Mo6S8 (Me is various transition metals including Pb, Ag, and Cu), etc.

[0659] Examples of the organic sulfur compound include carbon sulfur compounds and the like.

[0660] The above-mentioned organic sulfur compound is sometimes supported on a material having pores such as carbon and used as a carbon composite material. From the viewpoint of further excellent cycle performance and further reduced overvoltage, the content of sulfur contained in the carbon composite material is preferably 10 to 99 mass %, more preferably 20 mass % or more, further preferably 30 mass % or more, particularly preferably 40 mass % or more, and preferably 85 mass % or less, relative to the above-mentioned carbon composite material.

[0661] When the positive electrode active material is the sulfur single substance, the content of sulfur contained in the positive electrode active material is equal to the content of the sulfur single substance.

[0662] 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.

[0663] In addition, if lithium phosphate is included in the positive electrode active material, the continuous charging characteristics are improved, so it is preferred. There is no restriction on the use of lithium phosphate, 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.

[0664] In addition, the surface of the positive electrode active material may be attached with a material having a different composition from the positive electrode active material. 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.

[0665] These surface-attached substances can be attached to the surface of the positive electrode active material by, for example, the following methods: a method of dissolving or suspending the surface-attached substance in a solvent, adding it to the positive electrode active material by infiltration, and drying; a method of dissolving or suspending a surface-attached substance precursor in a solvent, adding it to the positive electrode active material by infiltration, and then reacting it by heating, etc.; a method of adding it to the positive electrode active material precursor and calcining it at the same time, etc. It should be noted that in the case of attaching carbon, a method of mechanically attaching carbon in the form of activated carbon, etc., can also be used.

[0666] 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, as the lower limit, and preferably 20% or less, more preferably 10% or less, and further preferably 5% or less, as the upper limit, relative to the above-mentioned positive electrode active material. 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; however, if the amount of the attached substance is too small, the effect cannot be fully manifested, and if it is too much, it will hinder the entry and exit of lithium ions, so sometimes the resistance increases.

[0667] The shape of the particles of the positive electrode active material may be block, polyhedron, sphere, ellipsoid, plate, needle, column, etc. The primary particles may be aggregated to form secondary particles.

[0668] 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 3Above. If the tap density of the positive electrode active material is lower than the above lower limit, the amount of dispersion medium required when the positive electrode active material layer is formed increases, and the necessary amounts of conductive materials and binders increase at the same time. Sometimes, the filling rate of the positive electrode active material in the positive electrode active material layer is limited, and the battery capacity is limited. By using a composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. Generally speaking, 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 using the electrolyte in the positive electrode active material layer as a medium becomes a rate-determining factor, and sometimes the load characteristics are easily reduced. Therefore, the upper limit is preferably 4.0 g / cm 3 Below, more preferably 3.7 g / cm 3 Below, more preferably 3.5 g / cm 3 the following.

[0669] It should be noted that in the present invention, as the tap density, 5 to 10 g of the positive electrode active material powder was placed in a 10 ml glass measuring cylinder and tapped 200 times with an amplitude of about 20 mm to obtain the powder packing density (tap density) g / cm 3 .

[0670] The median particle size d50 of the particles of the positive electrode active material (secondary particle size in the case where 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 higher than the upper limit, the diffusion of lithium in the particles takes time, which sometimes leads to a reduction in battery performance, or when the positive electrode of the battery is made, that is, when the active material and the conductive material, the binder, etc. are slurried with a solvent and coated into a film, problems such as pulling out stripes occur. Here, by mixing two or more of the above-mentioned positive electrode active materials with different median particle sizes d50, the filling property during the production of the positive electrode can be further improved.

[0671] It should be noted that in the present invention, median particle diameter d50 is measured by known laser diffraction / scattering particle size distribution measuring device. When using HORIBA company's 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, a refractive index of 1.24 is set to measure.

[0672] In the case where the primary particles agglomerate 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 powder filling property, or because the specific surface area is greatly reduced, the possibility of reduced battery performance such as output characteristics becomes higher. On the contrary, if it is lower than the above lower limit, the reversibility of charge and discharge is sometimes deteriorated due to the underdeveloped crystals.

[0673] It should be noted that in the present invention, the average primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph with a magnification of 10,000 times, the longest value of the intercept of the left and right boundaries of the primary particles to the horizontal straight line is obtained for any 50 primary particles, and the average value is obtained.

[0674] 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 40m 2 / 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, and if it is larger than this range, it is difficult to increase the tap density, which may cause problems in coating properties when forming the positive electrode active material layer.

[0675] It should be noted that in the present invention, a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.) is used to pre-dry the sample at 150°C for 30 minutes under nitrogen flow, and then a nitrogen-helium mixed gas that has been precisely adjusted so that the relative pressure of nitrogen relative to atmospheric pressure reaches 0.3 is used to measure the sample by the nitrogen adsorption BET one-point method using the gas flow method, and the measured value is defined as the BET specific surface area.

[0676] 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 output is required, and therefore the particles of the positive electrode active material preferably mainly contain secondary particles.

[0677] The particles of the positive electrode active material preferably include secondary particles with an average particle size of 40 μm or less and 0.5 to 7.0 volume % of microparticles with a primary particle size of 1 μm or less. By containing microparticles with a primary particle size of 1 μm or less, the contact area with the electrolyte becomes larger, and the diffusion of lithium ions between the electrode and the electrolyte can be made faster, resulting in the improvement of the output performance of the battery.

[0678] As the manufacturing method of positive electrode active material, the conventional method of manufacturing method of inorganic compound can be used. In particular, when making spherical or ellipsoidal active material, various methods can be considered, for example, the raw material of transition metal is dissolved or crushed and dispersed in a solvent such as water, pH is adjusted while stirring to make a spherical precursor, after drying as needed, LiOH, Li2CO3, LiNO3 and other Li sources are added and calcined at high temperature to obtain the method of active material, etc.

[0679] In order to manufacture the positive electrode, the positive electrode active material can be used alone or in any combination or ratio. As a preferred combination in this case, LiCoO2 and LiNi 0.33 Co 0.33 Mn 0.33 O2 and LiMn2O4, or a combination of substances in which a portion of Mn is replaced by other transition metals, etc.; or a combination of substances in which a portion of Co is replaced by other transition metals, etc. with LiCoO2.

[0680] 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, 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, 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 battery capacity sometimes becomes insufficient. On the contrary, if the content is too high, the strength of the positive electrode is sometimes insufficient.

[0681] The positive electrode mixture preferably further includes a binder, a thickener, and a conductive material.

[0682] As the above-mentioned binder, any material 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. or its hydrogenated product; thermoplastic elastomer polymers such as EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymer, styrene-isoprene-styrene block copolymer or its hydrogenated product; soft resin 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.

[0683] As the ratio of the binder in the positive electrode active material layer, the content of the binder is usually more than 0.1 mass %, preferably more than 1 mass %, more preferably more than 1.5 mass %, in addition, usually less than 80 mass %, preferably less than 60 mass %, more preferably less than 40 mass %, most preferably less than 10 mass %. If the ratio of the binder is too low, the positive electrode active material cannot be fully maintained, and the mechanical strength of the positive electrode is sometimes insufficient, so that the battery performance such as cycle characteristics is deteriorated. On the other hand, if too high, sometimes the reduction of battery capacity and conductivity is caused.

[0684] 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.

[0685] 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 proportion of active material in the positive electrode active material layer is reduced, and sometimes the problem of reduced capacity of battery and increased resistance between positive electrode active materials are generated.

[0686] 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, 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. It should be noted that they can be used alone or in any combination and ratio. The conductive material is usually used in a content of 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 1% by mass or more in the positive electrode active material layer; in addition, it is usually used in a content of 50% by mass or less, preferably 30% by mass or less, and more preferably 15% by mass or less. If the content is lower than this range, the conductivity sometimes becomes insufficient. On the contrary, if the content is higher than this range, the battery capacity sometimes decreases.

[0687] 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, a mixed solvent of water, 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.

[0688] 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, particularly aluminum or alloys thereof, are preferred.

[0689] As the shape of the current collector, in the case of metal materials, metal foil, metal cylinder, metal coil, metal plate, metal film, porous metal (expanded metal), punching metal, foamed metal, etc. can be cited. In the case of carbon materials, carbon plates, carbon films, carbon cylinders, etc. can be cited. Among these, metal films are preferably used. It should be noted that the film can be appropriately formed into a mesh shape. The thickness of the film is arbitrary, but is usually more than 1 μm, preferably more than 3 μm, and more preferably more than 5 μm. In addition, it is usually less than 1 mm, preferably less than 100 μm, and 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 is impaired.

[0690] In addition, from the viewpoint of reducing the contact resistance between the current collector and the positive electrode active material layer, it is preferable to apply a conductive additive on the surface of the current collector. Examples of the conductive additive include carbon; and precious metals such as gold, platinum, and silver.

[0691] 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 is injected) / (the thickness of the current collector) is preferably less than 20, more preferably less than 15, and most preferably less than 10. In addition, it is 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 Joules 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.

[0692] The positive electrode can be manufactured by conventional methods. For example, a method can be cited in which the above-mentioned binder, thickener, conductive material, solvent, etc. are added to the above-mentioned positive electrode active material to prepare a slurry-like positive electrode mixture, which is applied to a current collector and pressed after drying to make it high-density.

[0693] The density increase can be achieved by hand pressing, roller 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 3 If the value is greater than this range, the permeability of the electrolyte to the interface of the current collector / active material is sometimes reduced, and the charge-discharge characteristics under high current density are reduced, and high output cannot be obtained. In addition, if the value is less than this range, the conductivity between active materials is sometimes reduced, the battery resistance is increased, and high output cannot be obtained.

[0694] In the case of using the electrolyte of the present invention, from the viewpoint of high output and improved stability at high temperature, the area of ​​the positive electrode active material layer is preferably larger than the surface area of ​​the battery outer casing. Specifically, the sum of the electrode areas of the positive electrode is preferably 15 times or more, and more preferably 40 times or more relative to the surface area of ​​the outer packaging of the secondary battery in terms of area ratio. In the case of a bottomed rectangular parallelepiped shape, the surface area of ​​the battery outer casing refers to the total area calculated from the length, width and thickness of the shell portion filled with the power generation element except the protruding portion of the terminal. In the case of a bottomed cylindrical shape, it is the geometric surface area when the shell portion filled with the power generation element except the protruding portion 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 a structure in which a positive electrode mixture layer is formed on both sides separated by a current collector foil, it refers to the sum of the areas of each face calculated separately.

[0695] The thickness of the positive electrode plate is not particularly limited. From the perspective of high capacity and high output, the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core material is preferably 10 μm or more, more preferably 20 μm or more, relative to a single side of the current collector, as a lower limit. In addition, it is preferably 500 μm or less, more preferably 450 μm or less.

[0696] In addition, the surface of the positive electrode plate may be attached with a substance having a different composition. 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.

[0697] <Negative electrode>

[0698] The negative electrode is composed of a negative electrode active material layer containing a negative electrode active material and a current collector.

[0699] As the negative electrode material, there is no particular limitation as long as it is a material that 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 any combination of two or more.

[0700] Examples of the negative electrode active material include thermal decomposition products of organic matter under various thermal decomposition conditions, 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; metal composite oxide materials containing lithium, etc. These negative electrode active materials can be used in combination of two or more.

[0701] As a carbonaceous material capable of absorbing and releasing lithium, it is preferred that artificial graphite or refined natural graphite is manufactured by high-temperature treatment of graphitizable pitch obtained from various raw materials, or a material obtained by carbonizing these graphites after surface treatment with organic matter such as pitch; from the viewpoint of a good balance between initial irreversible capacity and high current density charge and discharge characteristics, it is more preferred to be selected from the following materials: natural graphite; artificial graphite; carbonaceous materials obtained by heat-treating artificial carbonaceous materials and artificial graphite materials at a temperature in the range of 400 to 3200°C for one or more times; a carbonaceous material in which the negative electrode active material layer contains at least two or more carbonaceous materials with different crystallinity and / or a contact interface with the carbonaceous materials with different crystallinity; a carbonaceous material in which the negative electrode active material layer has at least two or more carbonaceous materials with different orientations. In addition, these carbon materials can be used alone or in combination of two or more in any combination and ratio.

[0702] 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 partially graphitizing them, furnace black, acetylene black, asphalt-based carbon fibers and other organic materials thermal decomposition 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.

[0703] 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 a single metal and alloy forming a lithium alloy, it is preferably a material containing metal and semi-metal elements of Groups 13 and 14, 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 any combination and ratio.

[0704] As the negative electrode active material having at least one atom selected from the specific metal element, it is possible to cite a metal single substance of any specific metal element, an alloy containing two or more specific metal elements, an alloy containing one or more specific metal elements and other one or more metal elements, and a compound containing one or more specific metal elements and its oxide, carbide, nitride, silicide, sulfide or phosphide and other composite compounds. By using these metal single substances, alloys or metal compounds as negative electrode active materials, it is possible to achieve high capacity of the battery.

[0705] In addition, compounds formed 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, for example, in the case of silicon and tin, alloys of these elements and metals that do not work as negative electrodes can be used. For example, in the case of tin, a complex compound containing 5 to 6 elements such as a combination of tin and a metal that acts as a negative electrode other than silicon, and a further metal that does not work as a negative electrode and a non-metallic element can also be used.

[0706] 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).

[0707] In addition, a composite material containing Si or Sn as a first constituent element and 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.

[0708] In particular, in order to obtain 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.

[0709] As the lithium-containing metal composite oxide material used as the negative electrode active material, there is no particular limitation 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 or used in the negative electrode active material for an electrolyte battery, the output resistance can be greatly reduced, so it is particularly preferred.

[0710] The lithium titanium composite oxide is preferably of the general formula:

[0711] Li x Ti y M z O4

[0712] [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]

[0713] The compounds shown.

[0714] Among the above components,

[0715] (i)1.2≤x≤1.4, 1.5≤y≤1.7, z=0

[0716] (ii)0.9≤x≤1.1,1.9≤y≤2.1, z=0

[0717] (iii)0.7≤x≤0.9, 2.1≤y≤2.3, z=0

[0718] The structure of is particularly preferred because it has a good balance in battery performance.

[0719] Regarding the particularly preferred representative composition of the above compound, in (i) Li 4 / 3 Ti 5 / 3 O4, (ii) Li1Ti2O4, (iii) 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 structure.

[0720] The negative electrode mixture preferably further includes a binder, a thickener, and a conductive material.

[0721] As the above-mentioned binder, the same substances as the above-mentioned 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, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, further 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 exceeds the above range, since the amount of the binder does not help the battery capacity, the binder ratio increases, and there is a situation where the battery capacity is reduced. In addition, if it is lower than the above range, it sometimes leads to a reduction in the strength of the negative electrode.

[0722] In particular, in the case of a rubber-like polymer represented by SBR in the main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, 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 a fluorine-based polymer represented by polyvinylidene fluoride in 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.

[0723] As the above-mentioned thickener, the same substance as the thickener 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, there is a problem of reduced capacity of the battery, and sometimes the resistance between the negative electrode active materials increases.

[0724] 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.

[0725] 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.

[0726] 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.

[0727] 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.

[0728] 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.

[0729] The manufacture of the negative electrode can be carried out according to conventional methods. For example, it can be mentioned that: the above-mentioned binder, thickener, conductive material, solvent, etc. are added to the above-mentioned negative electrode material to make a slurry, apply it on the current collector, and press it after drying to make it high-density. 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. is also used.

[0730] 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 current collector is greater than the above range, the negative electrode active material particles may be destroyed, sometimes resulting in an increase in the initial irreversible capacity and a deterioration in the high current density charge and discharge characteristics caused by the reduced permeability of the electrolyte to the current collector / negative electrode active material interface. In addition, if it is lower than the above range, sometimes the conductivity between the negative electrode active materials is reduced, the battery resistance is increased, and the capacity per unit volume is reduced.

[0731] The thickness of the negative electrode plate is designed to match the positive electrode plate used, and there is no particular restriction. The thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core material is expected to be usually 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.

[0732] In addition, the surface of the negative electrode plate may be attached with a substance having a different composition. 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; and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

[0733] <Isolator>

[0734] The lithium ion secondary battery of the present invention preferably further comprises a separator.

[0735] The material and shape of the separator are not particularly limited as long as the electrolyte is stable and has excellent liquid retention, and known materials can be used. Among them, it is preferably formed using a material that is stable relative to the electrolyte of the present invention, and resin, glass fiber, inorganic material, etc. can be used, and a porous sheet or non-woven fabric-like material with excellent liquid retention can be used.

[0736] As materials for resin and glass fiber separators, polyolefins such as polyethylene and polypropylene, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, glass filters, etc. can be used. Polypropylene / polyethylene two-layer membrane, polypropylene / polyethylene / polypropylene three-layer membrane, etc., these materials can be used alone or in any combination and ratio. Among them, in terms of good permeability of the electrolyte and shutdown 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.

[0737] 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 and 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.

[0738] Furthermore, when a porous material 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.

[0739] 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 circuits are likely to occur. In addition, if it is lower than the above range, the film resistance sometimes increases and the rate characteristics decrease.

[0740] On the other hand, as inorganic materials, oxides such as aluminum oxide and silicon dioxide; nitrides such as aluminum nitride and silicon nitride; sulfates such as barium sulfate and calcium sulfate are used, and materials in the form of particles or fibers are used.

[0741] As the form, a material in the form of a thin film, such as a nonwoven fabric, a woven fabric, or a microporous film, can be used. In the case of a thin film, 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 shapes, the following separators can also be used: separators made by forming a composite porous layer containing particles of the above-mentioned inorganic substance on the surface of the positive electrode and / or the negative electrode using a resin binder. For example, a porous layer can be formed on both sides of the positive electrode using fluororesin as a binder to form aluminum oxide particles with a particle size of 90% less than 1 μm.

[0742] <Battery Design>

[0743] The electrode group may be a laminated structure in which the positive electrode plate and the negative electrode plate are sandwiched by the separator; or a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape with the separator sandwiched therebetween. 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.

[0744] If the electrode group occupancy rate is lower than the above range, the battery capacity becomes smaller. In addition, if it is higher than the above range, there is sometimes less void space, the battery reaches a high temperature and the components expand, or the vapor pressure of the liquid component of the electrolyte increases, thereby increasing the internal pressure, or reducing various characteristics of the battery such as repeated electrical performance and high-temperature storage, thereby activating the gas release valve that releases the internal pressure to the outside.

[0745] The current collecting structure is not particularly limited. In order to more effectively realize the improvement of the charge-discharge characteristics of the high current density utilizing the electrolyte of the present invention, it is preferably set to a structure that reduces the resistance of the wiring portion and the junction portion. When reducing the internal resistance like this, the effect of using the electrolyte of the present invention can be particularly well exerted.

[0746] In the case where 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 into terminals. When the area of ​​a piece of electrode increases, the internal resistance increases, so it is also suitable to use a means of reducing the resistance by providing multiple terminals in the electrode. In the case where the electrode group has the above-mentioned winding structure, the internal resistance can be reduced by providing multiple wire structures at the positive electrode and the negative electrode respectively and bundling them into terminals.

[0747] 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 are used. From the viewpoint of lightweight, metals such as aluminum or aluminum alloys and laminated films are preferably used.

[0748] In the case of using a metal outer shell, an outer shell having a sealed and airtight structure formed by welding metals to each other through laser welding, resistance welding, or ultrasonic welding can be cited; or an outer shell having a caulking and riveting structure (the Japanese original text of "caulking and riveting" is "かしめ") structure made of the above-mentioned metals through a resin sealing gasket can be cited. In the outer shell using the above-mentioned laminated film, an outer shell having a sealed and airtight structure formed by heat-melting resin layers to each other can be cited. In order to improve the sealing performance, a resin different from the resin used in the laminated film can be spaced between the above-mentioned resin layers. In particular, when the resin layers are heat-melted through the current collecting terminals to form a closed structure, a bond between the metal and the resin is formed, so as the resin for the interval, a resin having a polar group or a modified resin introduced with a polar group is suitable.

[0749] The lithium ion secondary battery of the present invention may have any shape, such as cylindrical, rectangular, laminated, coin, or large shapes. The shape and structure of the positive electrode, negative electrode, and separator may be changed according to the shape of each battery.

[0750] In addition, as one of the suitable embodiments, 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 current 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.

[0751] 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 output. 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.

[0752] 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 battery capacity sometimes becomes insufficient. On the contrary, if the content is too high, the strength of the positive electrode is sometimes insufficient.

[0753] The positive electrode active material layer may further include a conductive material, a thickener, and a binder.

[0754] As the above-mentioned binder, any substance can be used as long as it is a material that is safe for the solvent and electrolyte used in the manufacture of the electrode, 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, 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 (particularly 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.

[0755] The content of binder is based on the ratio of binder in positive electrode active material layer, usually 0.1 mass %, preferably 1 mass %, more preferably 1.5 mass %, in addition, usually 80 mass %, preferably 60 mass %, more preferably 40 mass %, most preferably 10 mass %. If the ratio of binder is too low, the mechanical strength of positive electrode is insufficient sometimes, positive electrode active material cannot be fully maintained, and battery performance such as cycle characteristics is deteriorated. On the other hand, if too high, battery capacity and conductivity are sometimes reduced.

[0756] 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.

[0757] 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 proportion of active material in the positive electrode active material layer is reduced, and sometimes the problem of reduced capacity of battery and increased resistance between positive electrode active materials are generated.

[0758] As the above-mentioned conductive material, any known conductive material can be used. As specific examples, metal materials such as copper and nickel; graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, amorphous carbons such as needle coke, and the like can be cited. It should be noted that they can be used alone or in any combination and ratio. The conductive material is used in the positive electrode active material layer at a content of usually 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 1% by mass or more. In addition, it is used at a content of usually 50% by mass or less, preferably 30% by mass or less, and more preferably 15% by mass or less. If the content is lower than this range, the conductivity sometimes becomes insufficient. On the contrary, if the content is higher than this range, the battery capacity sometimes decreases.

[0759] 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, chromium, etc. The positive electrode current collector is more preferably composed of aluminum or an aluminum alloy.

[0760] From the viewpoint of further improving the high temperature storage characteristics, the lithium ion secondary battery is preferably composed of a valve metal or its alloy for the portion in contact with the electrolyte among the portion electrically connected to the positive electrode current collector. In particular, the portion of the battery outer casing, and the wire, safety valve, etc. contained in the battery outer casing that is electrically connected to the positive electrode current collector and in contact with the non-aqueous electrolyte is preferably composed of a valve metal or its alloy. Stainless steel covered with a valve metal or its alloy may also be used.

[0761] The manufacturing method of the above-mentioned positive electrode is as described above. For example, it can be cited as: adding the above-mentioned binder, thickener, conductive material, solvent, etc. to the above-mentioned positive electrode active material to form a slurry-like positive electrode mixture, coating it on the above-mentioned positive electrode collector, and pressing it after drying to make it high-density.

[0762] The negative electrode has the same structure as described above.

[0763] A module including the lithium ion secondary battery of the present invention is also one of the present invention.

[0764] The electrolyte solution of the present invention is useful as an electrolyte solution for large lithium ion secondary batteries for hybrid vehicles and distributed power sources.

[0765] Example

[0766] Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to the described Examples.

[0767] Synthesis example 1

[0768] 1-Ethyl-3-methylimidazolium chloride and lithium difluorophosphate were dissolved in an acetone / acetonitrile (volume ratio 1:1) solvent at a molar ratio of 1:1, and stirred for 24 hours with a stirrer. Then, the mixture was filtered and concentrated to obtain the target compound (I) represented by the following formula.

[0769] [Chemistry 64]

[0770]

[0771] (Preparation of Electrolyte)

[0772] Examples 1 to 27 and Comparative Examples 1 to 3

[0773] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 30 / 40 / 30, and LiPF6 was added to the mixture to reach a concentration of 1.0 mol / L to prepare a basic electrolyte. Further, each component described in Table 1 was added to the basic electrolyte in the amount described in Table 1 to obtain a non-aqueous electrolyte.

[0774] (Manufacturing of aluminum laminated lithium-ion secondary battery)

[0775] [Production of positive electrode]

[0776] LiNi as the positive electrode active material 0.8 Co 0.1 Mn 0.1 93 mass % of O2 (NMC), 3 mass % of acetylene black as a conductive material, and 4 mass % of polyvinylidene fluoride (PVdF) as a binder were mixed in N-methylpyrrolidone solvent and slurried. The obtained slurry was coated on one side of a 15 μm thick aluminum foil pre-coated with a conductive auxiliary agent, dried, rolled with a press, and then cut into a shape with an active material layer of 50 mm wide and 30 mm long, and an uncoated portion of 5 mm wide and 9 mm long, as a positive electrode.

[0777] [Production of negative electrode]

[0778] To 98 parts by mass of carbonaceous material (graphite), 1 part by mass of an aqueous dispersion of sodium carboxymethylcellulose (the concentration of sodium carboxymethylcellulose is 1% by mass) and 1 part by mass of an aqueous dispersion of styrene-butadiene rubber (the concentration of styrene-butadiene rubber is 50% by mass) were added as thickeners and binders, and mixed with a dispenser to form a slurry. The obtained slurry was coated on a copper foil with a thickness of 10 μm, dried, rolled with a press, and then cut into an active material layer with a size of 52 mm wide and 32 mm long, and a shape of an uncoated portion with a width of 5 mm and a length of 9 mm, as a negative electrode.

[0779] [Manufacturing of aluminum laminated battery cells]

[0780] The positive electrode and the negative electrode are placed opposite to each other with a microporous polyethylene film (separator) having a thickness of 20 μm therebetween, and the non-aqueous electrolyte obtained above is injected. After the non-aqueous electrolyte fully penetrates the separator, etc., the film is sealed, pre-charged, and aged to produce a lithium-ion secondary battery.

[0781] (Measurement of battery characteristics)

[0782] [Recovery capacity after saving]

[0783] In a state where the secondary battery manufactured as described above is clamped by plates and pressurized, constant current-constant voltage charging (hereinafter referred to as CC / CV charging) (0.1C cut-off) is performed at 25°C with a current equivalent to 0.2C to 4.2V, and then discharged to 3V at a constant current of 0.2C. This is regarded as one cycle, and the initial discharge capacity is calculated from the discharge capacity of the third cycle. Here, 1C refers to the current value when the reference capacity of the battery is discharged in 1 hour, for example, 0.2C refers to the current value of 1 / 5 thereof. CC / CV charging (0.1C cut-off) is performed again at 0.2C to 4.2V, and high temperature storage is performed at 60°C for 3 days. After the battery is fully cooled, it is discharged to 3V at 0.2C at 25°C. Thereafter, it is charged at 0.2C (CC / CV charging (0.1C cut-off)) to 4.2V, discharged to 3V at 0.2C, and the discharge capacity is measured. This discharge capacity is the recovery capacity after high temperature storage. The value of Comparative Example 1 was set to 1 and the calculation was performed.

[0784] The results are shown in Table 1.

[0785] [Evaluation of IV resistance]

[0786] The battery after the evaluation of the initial discharge capacity was charged at 1C constant current at 25°C to half of the initial discharge capacity. It was discharged at 1.0C and the voltage was measured when it was discharged for 10 seconds. The resistance was calculated from the decrease in voltage during discharge and recorded as IV resistance. The value of Comparative Example 1 was calculated as 1.

[0787] The results are shown in Table 1.

[0788] [Table 1]

[0789]

[0790] The meanings of the codes in the above table are as follows.

[0791] (I)

[0792] [Chemistry 65]

[0793]

[0794] (II):

[0795] [Chemistry 66]

[0796]

[0797] (III)

[0798] [Chemistry 67]

[0799]

[0800] A: Vinylene carbonate

[0801] B: Vinyl ethylene carbonate

[0802] C: Ethylene fluorocarbonate

[0803] D: Ethylene difluorocarbonate

[0804] E: FSO3Li

[0805] F: CH3CH2OSO3Li

[0806] G: Lithium bis(fluorosulfonyl)imide (LiFSI)

[0807] H: Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)

[0808] I: Adiponitrile

[0809] J: Succinonitrile

[0810] K: Glutaronitrile

[0811] L: Propane sultone

[0812] M: Propylene sultone

[0813] N: Succinic anhydride

[0814] O: Maleic anhydride

[0815] a / b: molar ratio of the content of imidazolium cation (a) to the content of difluorophosphate ion (b)

Claims

1. An electrolyte for a lithium ion secondary battery, characterized in that: It contains a compound (1-a) represented by the following formula:

2. The electrolyte according to claim 1, wherein The content of the compound (1-a) is 0.01 to 10% by mass based on the electrolyte solution.

3. An electrolyte for a lithium ion secondary battery, characterized in that: Include The following formula: The imidazolium cation (1-1a) and difluorophosphate ion shown, The molar ratio a / b of the content a of the imidazolium cation (1-1a) to the content b of the difluorophosphate ion is 0.9 to 1.

1.

4. The electrolyte according to claim 3, wherein The content of the imidazolium cation (1-1a) is 0.0005 to 15% by mass relative to the electrolyte solution.

5. The electrolyte according to any one of claims 1 to 4, wherein The electrolyte further includes a solvent, and the solvent includes at least one selected from cyclic carbonate, chain carbonate and chain carboxylic acid ester.

6. A lithium ion secondary battery, characterized in that: An electrolyte solution according to any one of claims 1 to 5.

7. A component, characterized in that A lithium ion secondary battery according to claim 6.

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