Electrolyte and secondary battery using the same

Abstract

Provided are: an electrolyte solution which is capable of improving the life of a secondary battery provided with a silicon negative electrode and suppressing an increase in resistance thereof; and a secondary battery using the electrolyte solution. This electrolyte solution is used in a battery provided with an electrode having a negative electrode material, the negative electrode material containing elemental silicon and elemental carbon, and the electrolyte solution containing less than 10 mass% of a fluoroether represented by general formula (1). HCF2CF2-O-R (1) (In the formula, R is a fluoroalkyl group. ).

Description

Technical Field

[0001] The present disclosure relates to an electrolytic solution and a secondary battery using the same. Background Art

[0002] It is reported that the use of fluorinated ethers represented by 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether as a solvent for lithium-ion battery electrolyte can improve the life of the battery in the high voltage region (Non-patent prior art document 1). Specifically, the following contents are disclosed: lithium metal is used for the negative electrode and LiNi is used for the positive electrode. 0.5 Mn 1.5 O4, various fluoroethers such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether are mixed with propylene carbonate and used as a solvent, thereby improving the high voltage operating characteristics.

[0003] In addition, it is reported that the life of a silicon negative electrode can be improved by using fluoroethylene carbonate as an additive (Non-Patent Prior Art Document 2).

[0004] Prior art literature Non-patent literature Non-patent document 1: Journal of the Electrochemical Society, 164(1) A6412-A6416 (2017) Non-patent document 2: Journal of the Electrochemical Society, 163(8) A1705-A1716 (2016) Summary of the invention

[0005] Technical problem to be solved by the invention An object of the present disclosure is to provide an electrolyte solution capable of improving the life of a secondary battery having a silicon negative electrode and suppressing an increase in its resistance, and a secondary battery using the electrolyte solution.

[0006] Technical solutions for solving technical problems The present invention discloses an electrolyte solution, characterized in that it is used for a battery having an electrode with a negative electrode material, wherein the negative electrode material contains silicon and carbon, and the electrolyte solution contains less than 10% by mass of a fluorinated ether represented by the following general formula (1).

[0007] HCF2CF2-OR (1) (In the formula, R is a fluorinated alkyl group.) Preferably, the fluorinated ether represented by the general formula (1) is at least one fluorinated ether selected from the group consisting of the fluorinated ethers represented by the following general formulas (2) to (4).

[0008] HCF2CF2-O-CH2CF2CF2H (2) HCF2CF2-O-CH2CF2CF3 (3) HCF2CF2-O-CH2CF3 (4) Preferably, the negative electrode material contains Si and / or SiOa (0<a<2), and a carbon compound.

[0009] The present disclosure also provides a secondary battery including the above-mentioned electrolyte solution.

[0010] Preferably, in the above secondary battery, the negative electrode material contains Si and / or SiOa (0<a<2), and a carbon compound.

[0011] Effects of the Invention The present disclosure can provide an electrolyte solution that can improve the life of a secondary battery having a silicon negative electrode and suppress the increase in resistance. In addition, a secondary battery using the electrolyte solution of the present disclosure has an improved battery life and suppressed resistance increase. DETAILED DESCRIPTION

[0012] Hereinafter, the present disclosure will be described in detail.

[0013] The electrolyte disclosed herein is characterized in that it is an electrolyte suitable for use in a battery having an electrode having a negative electrode material, the negative electrode material containing silicon and carbon, and contains less than 10% by mass of a fluorinated ether represented by the following general formula (1).

[0014] HCF2CF2-OR (1) (In the formula, R is a fluorinated alkyl group.) The present disclosure relates to an electrolyte for use in a secondary battery including the silicon negative electrode as described above.

[0015] The present disclosure uses a specific amount of the above-mentioned specific fluorinated ether as an additive in an electrolyte for a lithium ion secondary battery, thereby forming lithium fluoride (LiF) as a reduction film on a silicon negative electrode, and through this formation, a significant improvement in life and suppression of resistance increase are achieved.

[0016] The lower limit of the LiF formed is preferably 3.0 m g / cm 2 , and more preferably 3.1 m g / cm 2 , particularly preferably 3.2 m g / cm 2 The upper limit is preferably 4.1 m g / cm 2 , and more preferably 3.9 m g / cm 2When the amount of LiF formed on the negative electrode is too small, the life characteristics may not be sufficiently improved. When the amount of LiF formed on the negative electrode is too large, the resistance tends to increase.

[0017] (Fluorinated ether) The electrolyte solution disclosed herein contains less than 10% by mass of the fluoroether represented by the following general formula (1).

[0018] HCF2CF2-OR (1) (In the formula, R is a fluorinated alkyl group.) The fluoroalkyl group is preferably a fluoroalkyl group having 1 to 10 carbon atoms, and more preferably a fluoroalkyl group having 2 to 6 carbon atoms.

[0019] If the number of carbon atoms in the fluoroalkyl group is too small, the boiling point tends to be low, and if the number of carbon atoms is too large, the viscosity tends to be high.

[0020] The fluorine content of the fluoroether is preferably 40 to 75% by mass. When the fluorine content is within this range, the balance between non-flammability and compatibility is particularly excellent. In addition, it is also preferred from the viewpoint of good oxidation resistance and safety.

[0021] The lower limit of the fluorine content is more preferably 45% by mass, further preferably 50% by mass, and particularly preferably 55% by mass, and the upper limit is more preferably 70% by mass, further preferably 69% by mass.

[0022] The fluorine content of the fluoroether (I) is a value calculated according to {(number of fluorine atoms×19) / molecular weight of the fluoroether (I)}×100(%) based on the structural formula of the fluoroether (I).

[0023] Examples of R include -CH2CF2CF3, -CF2CFHCF3, -CF2CF2CF2H, -CH2CF2CF2H, -CH2CH2CF2CF3, -CH2CF2CFHCF3, -CF2CF2CF2CF2H, -CH2CF2CF2CF2H, -CH2CH2CF2CF2H, -CH2CF(CF3)CF2H, -CF2CF2H, -CH2CF2H, -CH2CF3, and -CF2CH3.

[0024] Specific examples of the above-mentioned fluoroether (I) include: HCF2CF2-O-CH2CF2CF2H, HCF2CF2-O-CH2CF2CF3, HCF2CF2-O-CH2CF3, HCF2CF2-O-CF2CFHCF3, HCF2CF2-O-CF2CF2CF2H, HCF2CF2-O-CH2CH2CF2CF3, HCF2CF2-O-CH2CF2CFHCF3, HCF2CF2-O-CF2CF2CF2CF2H, HCF2CF2-O-CF2CF2CF2CF2H, HCF2CF2-O-CH2CF2CF2CF2H, HCF2CF2-O-CH2CH2CF2CF2H, HCF2CF2-O-CH2CF(CF3)CF2H, HCF2CF2-O-CF2CF2H, HCF2CF2-O-CH2CF2H, etc.

[0025] The fluorinated ether represented by the general formula (1) is particularly preferably at least one fluorinated ether selected from the group consisting of fluorinated ethers represented by the following general formulas (2) to (4).

[0026] HCF2CF2-O-CH2CF2CF2H (2) HCF2CF2-O-CH2CF2CF3 (3) HCF2CF2-O-CH2CF3 (4) In particular, by including the fluoroether represented by the above general formula (2) to (4) as an additive in the electrolyte, lithium fluoride (LiF) can be formed as a reducing film on the silicon negative electrode; its formation is beneficial in greatly improving the life and suppressing the increase in resistance.

[0027] The content of the above-mentioned fluoroether needs to be less than 10% by mass in the electrolyte. By being set within this range, it can be used as a good electrolyte. That is, if the content becomes more, the viscosity of the electrolyte becomes higher, and the ion conductivity decreases, so the life of the battery decreases.

[0028] The upper limit of the content of the fluoroether is preferably 9.0% by mass, more preferably 5.0% by mass.

[0029] The lower limit of the content of the fluoroether is preferably 0.001% by mass, more preferably 0.01% by mass.

[0030] The electrolyte solution of the present disclosure preferably contains a solvent.

[0031] The solvent preferably contains at least one selected from the group consisting of carbonate esters and carboxylic acid esters.

[0032] The carbonate ester mentioned above may be a cyclic carbonate ester or a chain carbonate ester.

[0033] The cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate.

[0034] 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.

[0035] Among them, as the above-mentioned non-fluorinated saturated cyclic carbonate, from the viewpoint of high dielectric constant and suitable viscosity, it is preferably selected from at least one of 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.

[0036] The above-mentioned non-fluorinated saturated cyclic carbonate may be used alone or in combination of two or more in any ratio.

[0037] When the non-fluorinated saturated cyclic carbonate is contained, the content of the non-fluorinated saturated cyclic carbonate is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and further preferably 15 to 50% by volume based on the solvent.

[0038] The fluorinated cyclic carbonate is a cyclic carbonate having a fluorine atom. A solvent containing a fluorinated cyclic carbonate can be preferably used even at a high voltage.

[0039] 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.

[0040] The fluorinated cyclic carbonate may be a fluorinated saturated cyclic carbonate or a fluorinated unsaturated cyclic carbonate.

[0041] The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate having a fluorine atom, and specifically, the following general formula (A) can be cited: [Chemistry 1]

[0042] (Where X 1 ~X 4 are the same or different, and represent -H, -CH3, -C2H5, -F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond. 1 ~X 4At 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.

[0043] When the electrolyte solution of the present disclosure 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 stable and excellent charge and discharge characteristics can be obtained.

[0044] In addition, in this specification, an "ether bond" is a bond represented by -O-.

[0045] From the viewpoint of good dielectric constant and oxidation resistance, X 1 ~X 4 One or two of them are -F, a fluoroalkyl group which may have an ether bond, or a fluoroalkoxy group which may have an ether bond.

[0046] From the perspective of being able to expect a decrease in viscosity at low temperatures, an increase in flash point, and even an improvement in 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).

[0047] The fluoroalkyl group (a) is a group obtained by replacing at least one hydrogen atom of an alkyl group 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 particularly preferably 1-5.

[0048] 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, or even the viscosity may be increased.

[0049] Among the fluoroalkyl groups (a), examples of the fluoroalkyl group having 1 carbon atom include CFH2-, CF2H-, and CF3-. In particular, CF2H- or CF3- is preferred in terms of high temperature storage characteristics, and CF3- is most preferred.

[0050] Among the fluoroalkyl groups (a), the group having 2 or more carbon atoms preferably includes the following general formula (a-1) from the viewpoint of good solubility of the electrolyte salt: R 1 -R 2 - (a-1) (Where R 1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; R 2is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; wherein R 1 and R 2 At least one of them has a fluorine atom. ) is a fluorinated alkyl group represented by.

[0051] It should be noted that R 1 and R 2 It may also contain atoms other than carbon atoms, hydrogen atoms and fluorine atoms.

[0052] 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.

[0053] As R 1 Specifically, examples of the linear or branched alkyl group include CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, [Chemistry 2] , wait.

[0054] 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.

[0055] In addition, in R 1 In the case of a branched alkyl group having a fluorine atom, preferably: [Chemistry 3]

[0056] [Chemistry 4] , etc. However, if there are side chains such as CH3- and CF3-, the viscosity tends to be high, so the number thereof is preferably small (1) or zero.

[0057] 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. Some 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.

[0058] (i) The smallest structural unit of a straight chain: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2- (ii) The smallest structural unit of a branched chain: [Chemistry 5]

[0059] 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.

[0060] 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.

[0061] In R 2 In the case of a branched chain, it is a group containing at least one of the above-mentioned 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. b In the case of CF3, X a These units can further improve the solubility of the electrolyte salt.

[0062] Preferred fluoroalkyl groups (a) include CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CHF-, CH3CF2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-, [Chemistry 6]

[0063] [Chemistry 7] , wait.

[0064] The above-mentioned fluoroalkyl group (b) having an ether bond is a group obtained by replacing at least one of the hydrogen atoms possessed by the alkyl group having an ether bond with a fluorine atom. The number of carbon atoms of the above-mentioned fluoroalkyl group (b) having an ether bond is preferably 2 to 17. If the number of carbon atoms is too large, the viscosity of the above-mentioned fluorinated saturated cyclic carbonate becomes higher; 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 compatibility with other solvents are reduced. From this viewpoint, the number of carbon atoms of the above-mentioned fluoroalkyl group (b) having an ether bond is more preferably 2 to 10, and further preferably 2 to 7.

[0065] The alkylene group constituting the ether portion of the fluoroalkyl group (b) having an ether bond may be a linear or branched alkylene group. Some examples of the minimum structural unit constituting such a linear or branched alkylene group are shown below.

[0066] (i) The smallest structural unit of a straight chain: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2- (ii) The smallest structural unit of a branched chain: [Chemistry 8]

[0067] The alkylene group may be composed of these minimum structural units alone, or may be composed of linear (i) groups, branched (ii) groups, or a combination of a linear (i) group and a branched (ii) group. Preferred specific examples are described below.

[0068] 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.

[0069] As further preferred fluorinated alkyl groups (b) having an ether bond, there can be mentioned general formula (b-1): R 3 -(OR 4 ) n1 - (b-1) (Where R 3 is an alkyl group which may have a fluorine atom and preferably has 1 to 6 carbon atoms; R 4 is an alkylene group which may have a fluorine atom and preferably has 1 to 4 carbon atoms; n1 is an integer of 1 to 3; wherein R 3 and R 4At least one of which has a fluorine atom).

[0070] As R 3 and R 4 The following groups can be exemplified, and these groups can be appropriately combined to form the fluorinated alkyl group (b) having an ether bond represented by the above general formula (b-1), but the group is not limited to these groups.

[0071] (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).

[0072] When n2 is 0, as R 3 , examples include CH3-, CF3-, HCF2- and H2CF-.

[0073] As a specific example when 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.

[0074] As n2 is 1, and R 3 The branched group includes: [Chemistry 9] , wait.

[0075] Among them, if there is a side chain such as CH3- or CF3-, the viscosity tends to be high, so R is more preferred. 3 It is a straight chain group.

[0076] (2) In the above general formula (b-1), -(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.

[0077] As R 4 Preferred specific examples include the following linear or branched groups.

[0078] 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.

[0079] Examples of the branched group include: [Chemistry 10] , wait.

[0080] The fluoroalkoxy group (c) is a group in which at least one of the hydrogen atoms in an alkoxy group is replaced by a fluorine atom. The fluoroalkoxy group (c) preferably has 1 to 17 carbon atoms, and more preferably has 1 to 6 carbon atoms.

[0081] As the fluoroalkoxy group (c), the general formula: X 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 contains a fluorine atom).

[0082] Specific examples of the fluoroalkoxy group (c) include: 1 The exemplified fluoroalkoxy group is a group in which an oxygen atom is bonded to the terminal of an alkyl group.

[0083] The fluorine content of the fluoroalkyl (a), the fluoroalkyl (b) and the fluoroalkoxy (c) in the above-mentioned fluorinated saturated cyclic carbonate is preferably more than 10 mass %. If the fluorine content is too low, then the effect of the viscosity under the low temperature, the effect of the rising flash point may not be fully obtained. From this viewpoint, the above-mentioned fluorine content is more preferably more than 12 mass %, more preferably more than 15 mass %. The upper limit is usually 76 mass %.

[0084] The fluorine content of the fluoroalkyl group (a), the fluoroalkyl group having an ether bond (b), and the fluoroalkoxy group (c) is a value calculated according to {(number of fluorine atoms×19) / formula weight of each group}×100(%) based on the structural formula of each group.

[0085] In addition, 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.

[0086] The fluorine content of the fluorinated saturated cyclic carbonate is a value calculated according to {(number of fluorine atoms×19) / molecular weight of fluorinated saturated cyclic carbonate}×100(%) based on the structural formula of the fluorinated saturated cyclic carbonate.

[0087] Specific examples of the fluorinated saturated cyclic carbonate include the following.

[0088] As X 1 ~X 4 Specific examples of the fluorinated saturated cyclic carbonate wherein at least one of the -F groups is: [Chemistry 11] , Etc. These compounds have high withstand voltage and good solubility of electrolyte salt.

[0089] In addition, you can also use [Chemistry 12] , wait.

[0090] 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: [Chemistry 13]

[0091] [Chemistry 14]

[0092] [Chemistry 15] , wait.

[0093] 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 are all -H include: [Chemistry 16]

[0094] [Chemistry 17]

[0095] [Chemistry 18]

[0096] [Chemistry 19]

[0097] [Chemistry 20]

[0098] [Chemistry 21] , wait.

[0099] Among them, the fluorinated saturated cyclic carbonate is preferably any one of the following compounds.

[0100] [Chemistry 22]

[0101] [Chemistry 23]

[0102] Examples of the fluorinated saturated cyclic carbonates include trans-4,5-difluoro-1,3-dioxolane-2-one, 5-(1,1-difluoroethyl)-4,4-difluoro-1,3-dioxolane-2-one, 4-methylene-1,3-dioxolane-2-one, 4-methyl-5-trifluoromethyl-1,3-dioxolane-2-one, 4-ethyl-5-fluoro-1,3-dioxolane-2-one, 4-ethyl-5,5-difluoro-1 ,3-dioxolane-2-one, 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.

[0103] Among these, the fluorinated saturated cyclic carbonate is more preferably fluorinated ethylene carbonate, difluoroethylene carbonate, trifluoromethylethylene carbonate (3,3,3-trifluoropropylene carbonate), or 2,2,3,3,3-pentafluoropropylethylene carbonate.

[0104] 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 obtained by being substituted with a substituent having an aromatic ring or a carbon-carbon double bond. Specifically, it can be mentioned: 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.

[0105] The above-mentioned fluorinated cyclic carbonate may be used alone or in combination of two or more in any ratio.

[0106] 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 further preferably 15 to 45% by volume based on the solvent.

[0107] The above-mentioned chain carbonate may be a non-fluorinated chain carbonate or a fluorinated chain carbonate.

[0108] As the above-mentioned non-fluorinated chain carbonate, for example, hydrocarbon chain carbonates such as CH3OCOOCH3 (dimethyl carbonate: DMC), CH3CH2OCOOCH2CH3 (diethyl carbonate: DEC), CH3CH2OCOOCH3 (ethyl methyl carbonate: EMC), CH3OCOOCH2CH2CH3 (methyl propyl carbonate), methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, 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, and ethylphenyl carbonate can be mentioned. Among them, preferably at least one selected from ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate.

[0109] The non-fluorinated chain carbonate esters may be used alone or in combination of two or more in any ratio.

[0110] 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 20 to 85% by volume, and further preferably 30 to 80% by volume based on the solvent.

[0111] The fluorinated chain carbonate is a chain carbonate having a fluorine atom. A solvent containing a fluorinated chain carbonate can be preferably used even at a high voltage.

[0112] Examples of the fluorinated chain carbonate include general formula (B): R 2 OCOOR 7 (B) (Where Rf 2 is a fluoroalkyl group having 1 to 7 carbon atoms, R 7 It is an alkyl group having 1 to 7 carbon atoms and optionally containing a fluorine atom. ) is a compound represented by

[0113] R 2 is a fluoroalkyl group having 1 to 7 carbon atoms, R 7 It is an alkyl group having 1 to 7 carbon atoms and optionally containing a fluorine atom.

[0114] The fluorinated alkyl group is a group in which at least one of the hydrogen atoms of 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.

[0115] 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.

[0116] If the number of carbon atoms is too large, it may sometimes cause problems such as reduced low-temperature characteristics or reduced solubility of the electrolyte salt; if the number of carbon atoms is too small, it may sometimes cause reduced solubility of the electrolyte salt, reduced discharge efficiency, or even increased viscosity.

[0117] 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.

[0118] As the fluorinated alkyl group having 2 or more carbon atoms, the following general formula (d-1) can be preferably exemplified from the viewpoint of good solubility of the electrolyte salt: R 1 -R 2 - (d-1) (Where R 1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; R 2 is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; wherein R 1 and R 2 At least one of them has a fluorine atom).

[0119] It should be noted that R 1 and R 2 It may also contain atoms other than carbon atoms, hydrogen atoms and fluorine atoms.

[0120] 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.

[0121] As R 1 Specifically, examples of the linear or branched alkyl group include CH3-, CF3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, [Chemistry 24] , wait.

[0122] 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.

[0123] In addition, in R 1 In the case of a branched alkyl group having a fluorine atom, preferably: [Chemistry 25]

[0124] [Chemistry 26] , etc. However, if there are side chains such as CH3- and CF3-, the viscosity tends to be high, so the number thereof is preferably small (1) or zero.

[0125] 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.

[0126] (i) The smallest structural unit of a straight chain: -CH2-, -CHF-, -CF2-, -CHCl-, -CFCl-, -CCl2- (ii) The smallest structural unit of a branched chain: [Chemistry 27]

[0127] 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.

[0128] 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 further improving the solubility of the electrolyte salt, -CH2- or -CH2CH2- is more preferred.

[0129] In R 2 In the case of a branched chain, it is a group containing at least one of the above-mentioned 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. b In the case of CF3, X a These groups can further improve the solubility of the electrolyte salt.

[0130] Specific examples of preferred fluoroalkyl groups include CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CH2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-, [Chemistry 28]

[0131] [Chemistry 29] , wait.

[0132] 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, good rate characteristics, and good oxidation resistance, CF3CH2-, CF3CF2CH2-, HCF2CF2CH2-, CFH2-, and CF2H- are more preferred.

[0133] 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 is preferably 1-4, more preferably 1-3.

[0134] 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.

[0135] 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 20% by mass or more, further preferably 30% by mass or more, particularly preferably 35% by mass or more, more preferably 60% by mass or less, and further preferably 50% by mass or less.

[0136] It should be noted that in the present disclosure, the fluorine content is based on the structural formula of the above-mentioned fluorinated chain carbonate. {(number of fluorine atoms × 19) / molecular weight of fluorinated chain carbonate} × 100 (%) Calculated value.

[0137] As the fluorinated chain carbonate, any of the following compounds is preferred from the viewpoint of low viscosity.

[0138] [Chemistry 30]

[0139] As the fluorinated chain carbonate, methyl 2,2,2-trifluoroethyl carbonate (F3CH2COC(=O)OCH3) is particularly preferred.

[0140] The above-mentioned fluorinated chain carbonates may be used alone or in combination of two or more in any ratio.

[0141] When the fluorinated chain carbonate is contained, the content of the fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 20 to 85% by volume, and even more preferably 30 to 80% by volume based on the solvent.

[0142] The carboxylic acid ester may be a cyclic carboxylic acid ester or a chain carboxylic acid ester.

[0143] The cyclic carboxylic acid ester may be a non-fluorinated cyclic carboxylic acid ester or a fluorinated cyclic carboxylic acid ester.

[0144] 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.

[0145] Specific examples of the non-fluorinated saturated cyclic carboxylic acid ester having an alkylene group having 2 to 4 carbon atoms include: β -Propiolactone, c -Butyrolactone, e -Caprolactone, d -Valerolactone, α methyl- c -Butyrolactone. Among them, c -Butyrolactone, d -Valerolactone is particularly preferred from the viewpoint of increasing the degree of lithium ion dissociation and improving the load characteristics.

[0146] The above-mentioned non-fluorinated saturated cyclic carboxylic acid ester may be used alone or in combination of two or more in any ratio.

[0147] 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.

[0148] 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.

[0149] Examples of the non-fluorinated chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, tert-butyl propionate, 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 ethyl 2-(diethylphosphoryl)acetate, isopropyl propionate, isopropyl acetate, ethyl formate, 2-propynylethyl oxalate, isopropyl formate, isopropyl butyrate, isobutyl formate, isobutyl propionate, isobutyl butyrate, isobutyl acetate, and the like.

[0150] Among them, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate are preferred, and ethyl propionate and propyl propionate are particularly preferred.

[0151] The non-fluorinated chain carboxylic acid esters may be used alone or in combination of two or more in any ratio.

[0152] 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 50% by volume, based on the solvent.

[0153] 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 preferably used even at a high voltage.

[0154] 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: R 31 COOR 32 (Where R 31 and R 32 are independently an alkyl group having 1 to 4 carbon atoms and optionally containing a fluorine atom, R 31 and R 32 At least one of them contains a fluorine atom. ) is a fluorinated chain carboxylic acid ester.

[0155] As R 31 and R 32, for example, the following can be cited: 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.

[0156] 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 trifluorobutyrate, tert-butyl trifluoroacetate. , n-butyl trifluoroacetate, methyl tetrafluoro-2-(methoxy)propionate, 2,2-difluoroethyl acetate, 2,2,3,3-tetrafluoropropyl acetate, CH3C(=O)OCH2CF3(2,2,2-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-trifluoropropionic acid-3,3,3 trifluoropropyl ester, 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, etc., one or more thereof.

[0157] 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-difluoroacetic acid butyl ester, 2,2,3,3-tetrafluoropropionic acid methyl ester, 2-(trifluoromethyl)butyric acid ethyl ester CF3CH2C(=O)OCH3, HCF2C(=O)OCH3, HCF2C(=O)OC2H5, CH3C(=O)OCH2CF3, and HCF2C(=O)OCH3, HCF2C(=O)OC2H5, CH3C(=O)OCH2CF3 are particularly preferred.

[0158] The above-mentioned fluorinated chain carboxylic acid esters may be used alone or in combination of two or more in any ratio.

[0159] 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 20 to 85% by volume, and even more preferably 30 to 80% by volume based on the solvent.

[0160] The solvent preferably comprises at least one selected from the cyclic carbonate, the linear carbonate and the linear carboxylic acid ester, more preferably comprises the cyclic carbonate and at least one selected from the linear carbonate and the linear carboxylic acid ester. The cyclic carbonate is preferably a saturated cyclic carbonate.

[0161] 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.

[0162] 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 are measured in total amount, preferably comprising 10 to 100 volume %, more preferably comprising 30 to 100 volume %, further preferably comprising 50 to 100 volume %.

[0163] 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 carboxylic acid ester, the volume ratio of the above-mentioned cyclic carbonate and at least one selected from the above-mentioned linear carbonate and the above-mentioned linear 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.

[0164] In addition, above-mentioned solvent is also preferably comprised and is selected from at least one of above-mentioned non-fluorinated saturated cyclic carbonate, above-mentioned non-fluorinated chain carbonate and above-mentioned non-fluorinated chain carboxylic acid ester, more preferably comprises above-mentioned non-fluorinated saturated cyclic carbonate and is selected from at least one of above-mentioned non-fluorinated chain carbonate and above-mentioned non-fluorinated chain carboxylic acid ester.The electrolyte that contains the solvent of above-mentioned composition can suitably be used for the electrochemical device that uses under lower voltage.

[0165] 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 chain carbonate and the above-mentioned non-fluorinated chain carboxylic acid ester, 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 are measured in total amount, preferably comprising 5 to 100 volume %, more preferably comprising 20 to 100 volume %, further preferably comprising 30 to 100 volume %.

[0166] In the case where the above-mentioned 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.

[0167] In addition, above-mentioned solvent is also preferably comprised 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, more preferably comprised at least one being selected from above-mentioned fluorinated saturated cyclic carbonate and above-mentioned fluorinated chain carbonate and above-mentioned fluorinated chain carboxylic acid ester.The electrolyte that contains the solvent of above-mentioned composition can not only be applicable to the electrochemical device that uses under lower voltage, can also be applicable to the electrochemical device that uses under higher voltage.

[0168] In the case where the above-mentioned solvent contains 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 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 ester are measured in total amount, preferably comprising 5 to 100 volume %, more preferably comprising 10 to 100 volume %, and further preferably comprising 30 to 100 volume %.

[0169] 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.

[0170] In addition, an ionic liquid can also be used as the above-mentioned solvent. "Ionic liquid" refers to a liquid composed of ions composed of a combination of organic cations and anions.

[0171] 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.

[0172] There is no particular limitation on the anions that counteract these organic cations, and for example, PF6 anion, PF3(C2F5)3 anion, PF3(CF3)3 anion, BF4 anion, BF2(CF3)2 anion, BF3(CF3) anion, bisoxalatoborate anion, P(C2O4)F2 anion, Tf(trifluoromethanesulfonyl) anion, Nf(nonafluorobutanesulfonyl) anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethanesulfonyl)imide anion, bis(pentafluoroethanesulfonyl)imide anion, dicyanoamide anion, and halide anion can be used.

[0173] The above-mentioned solvent is preferably a non-aqueous solvent, and the electrolyte disclosed in the present invention is preferably a non-aqueous electrolyte.

[0174] 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.

[0175] The electrolyte of the present disclosure may further contain a compound (5) represented by the general formula (5).

[0176] General formula (5): [Chemistry 31]

[0177] (In the formula, A a+ is a metal ion, a hydrogen ion or an onium ion. a is an integer of 1 to 3, b is an integer of 1 to 3, p is b / a, n203 is an integer of 1 to 4, n201 is an integer of 0 to 8, n202 is 0 or 1, and Z 201 A transition metal, an element of Group III, Group IV or Group V of the periodic table.

[0178] X 201 is O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (the alkylene group, the halogenated alkylene group, the arylene group, and the halogenated arylene group may have a substituent or a heteroatom in their structure. In addition, when n202 is 1 and n203 is 2 to 4, n203 X 201 can be bonded to each other).

[0179] L 201 is a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms (the alkylene group, the halogenated alkylene group, the arylene group, and the halogenated arylene group may have a substituent or a heteroatom in their structure. In addition, when n201 is 2 to 8, n201 L 201 may be bonded to each other to form a ring) or -Z 203 Y 203 .

[0180] Y 201 , Y 202 and Z 203 Each independently is O, S, NY 204 , hydrocarbon group or fluorinated hydrocarbon group. 203 and Y 204Each of them is independently H, F, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms (the alkyl group, the halogenated alkyl group, the aryl group, and the halogenated aryl group may have a substituent or a heteroatom in their structure. When there are multiple Y 203 or Y 204 In the case of , they may be bonded to each other to form a ring).

[0181] As A a＋ , examples include lithium ion, sodium ion, potassium ion, magnesium ion, calcium ion, barium ion, cesium ion, silver ion, zinc ion, copper ion, cobalt ion, iron ion, nickel ion, manganese ion, titanium ion, lead ion, chromium ion, vanadium ion, ruthenium ion, yttrium ion, lanthanide ion, actinide ion, tetrabutylammonium ion, tetraethylammonium ion, tetramethylammonium ion, triethylmethylammonium ion, triethylammonium ion, pyridinium ion, imidazolium ion, hydrogen ion, tetraethylphosphonium ion, tetramethylphosphonium ion, tetraphenylphosphonium ion, triphenylsulfonium ion, triethylsulfonium ion, etc.

[0182] In the case of electrochemical devices, A a＋ Preferred are lithium ions, sodium ions, magnesium ions, tetraalkylammonium ions, and hydrogen ions, and lithium ions are particularly preferred. a+ The valence a of the cation is an integer of 1 to 3. When it is greater than 3, the lattice energy becomes large, so it becomes difficult to dissolve in the solvent. Therefore, when solubility is required, it is more preferably 1. The valence b of the anion is also an integer of 1 to 3, and is particularly preferably 1. The constant p representing the ratio of the cation to the anion is necessarily determined by the ratio of the valences b / a of the two.

[0183] Next, the ligand part of the general formula (5) is described. In this specification, the ligand part of the general formula (5) and Z 201 The bonded organic or inorganic moieties are called ligands.

[0184] Z 201 Preferred are Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf or Sb, more preferred are Al, B or P.

[0185] X 201represents O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms. These alkylene groups and arylene groups may have substituents or heteroatoms in their structures. Specifically, instead of hydrogen on the alkylene group and the arylene group, there may be halogen atoms, chain or cyclic alkyl groups, aryl groups, alkenyl groups, alkoxy groups, aryloxy groups, sulfonyl groups, amino groups, cyano groups, carbonyl groups, acyl groups, amide groups, or hydroxyl groups as substituents. It may also be a structure in which nitrogen, sulfur, or oxygen is introduced to replace carbon on the alkylene group and the arylene group. In addition, when n202 is 1 and n203 is 2 to 4, n203 X 201 As an example, a ligand such as ethylenediaminetetraacetic acid can be mentioned.

[0186] L 201 represents a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms, or -Z 203 Y 203 (About Z 203 , Y 203 The alkyl and aryl groups in this case are also related to X. 201 Similarly, the structure may have a substituent or a heteroatom. In addition, when n201 is 2 to 8, n201 L 201 They may be bonded to each other to form a ring. 201 , preferably a fluorine atom or a cyano group. This is because, in the case of a fluorine atom, the solubility and dissociation degree of the salt of the anionic compound are improved, and this is accompanied by an increase in ionic conductivity. In addition, the oxidation resistance is improved, thereby suppressing the occurrence of side reactions.

[0187] Y 201 , Y 202 and Z 203 Each independently represents O, S, NY 204 , hydrocarbon group or fluorinated hydrocarbon group. 201 and Y 202 Preferably O, S or NY 204 , more preferably O. As a feature of compound (5), there is a 201 and Y 202 and Z 201 bonding, so these ligands and Z 201 The chelate structure is formed. Through the effect of the chelate, the heat resistance, chemical stability and hydrolysis resistance of the compound are improved. The constant n2O2 in the ligand is 0 or 1, but in particular, when n2O2 is 0, the chelate ring is a five-membered ring, so the chelate effect is most strongly exerted, the stability is increased, and it is preferred.

[0188] In addition, in this specification, a fluorinated hydrocarbon group is a group in which at least one hydrogen atom of a hydrocarbon group is replaced by a fluorine atom.

[0189] Y 203 and Y 204 are independently H, F, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms, wherein these alkyl groups and aryl groups may have a substituent or a heteroatom in their structure, and in Y 203 or Y 204 When there are plural groups, they may be bonded to each other to form a ring.

[0190] In addition, the constant n203 related to the number of ligands is an integer of 1 to 4, preferably 1 or 2, and more preferably 2. In addition, the constant n201 related to the number of ligands is an integer of 0 to 8, preferably an integer of 0 to 4, and more preferably 0, 2 or 4. Furthermore, when n203 is 1, n201 is 2, and when n203 is 2, n201 is 0.

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

[0192] As compound (5), preferably, the compound has the general formula: [Chemistry 32]

[0193] (In the formula, A a+ ,a,b,p,n201,Z 201 and L 201 As described above), or the compound of the general formula: [Chemistry 33]

[0194] (In the formula, A a+ ,a,b,p,n201,Z 201 and L 201 As described above).

[0195] Examples of compound (5) include lithium oxalatoborate salts, and examples thereof include the following formula: [Chemistry 34]

[0196] The lithium bis(oxalato)borate (LIBOB) shown in FIG. 1 has the following formula: [Chemistry 35]

[0197] Lithium difluorooxalatoborate (LIDFOB) shown, In addition, examples of compound (5) include the following formula: [Chemistry 36]

[0198] The lithium difluorooxalato phosphate (LIDFOP) shown in the formula is as follows: [Chemistry 37]

[0199] The lithium tetrafluorooxalato phosphate (LITFOP) shown in the following formula: [Chemistry 38]

[0200] The lithium difluorobisoxalato phosphate shown.

[0201] In addition, specific examples of dicarboxylic acid complex salts in which the central element of the complex is boron include: lithium bis(malonate)borate, lithium difluoro(malonate)borate, lithium bis(methylmalonate)borate, lithium difluoro(methylmalonate)borate, lithium bis(dimethylmalonate)borate, lithium difluoro(dimethylmalonate)borate, and the like.

[0202] Specific examples of dicarboxylic acid complex salts in which the central element of the complex is phosphorus include: lithium tris(oxalato)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.

[0203] Specific examples of dicarboxylic acid complex salts in which the central element of the complex is aluminum include LiAl(C2O4)2, LiAlF2(C2O4) and the like.

[0204] Among them, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tri(oxalato)phosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate are more preferably used from the viewpoint of easy availability and contribution to the formation of a stable film-like structure.

[0205] As the compound (5), lithium bis(oxalato)borate is particularly preferred.

[0206] From the viewpoint of obtaining further excellent cycle characteristics, the content of compound (5) is preferably 0.001 mass % or more, more preferably 0.01 mass % or more, and preferably 10 mass % or less, more preferably 3 mass % or less, based on the solvent.

[0207] The electrolyte solution of the present disclosure preferably further comprises an electrolyte salt (but excluding compound (5)). As the electrolyte salt, in addition to alkali metal salts, ammonium salts, and other metal salts other than alkali metal salts (e.g., light metal salts other than alkali 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.

[0208] As electrolyte salts for secondary battery electrolytes, the following compounds can be cited, for example. MPF6, MBF4, MClO4, MAsF6, MB(C6H5)4, MCH3SO3, MCF3SO3, MAlCl4, M2SiF6, MCl, MBr. (In the formula, M is at least one metal selected from Li, Na and K, preferably one metal selected from Li, Na and K, more preferably Li or Na, and further preferably Li.) By using these alkali metal salts, excellent battery capacity, cycle characteristics, storage characteristics, etc. can be obtained. Among them, it is preferred to select at least one of MPF6, MBF4, MClO4 and MAsF6, and MPF6 is more preferred. By using these alkali metal salts, the internal resistance can be further reduced, and a higher effect can be obtained.

[0209] As the electrolyte salt of the electrolyte solution for secondary batteries, lithium salt is preferred.

[0210] As the lithium salt, any lithium salt can be used, and specifically, the following lithium salts can be mentioned. For example, LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiTaF6, LiWF7, LiAsF6, LiAlCl4, LiI, LiBr, LiCl, LiB 10 Cl 10 , Li2SiF6, Li2PFO3, LiPO2F2 and other inorganic lithium salts; Lithium tungstate such as LiWOF5; Lithium carboxylates such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li; Lithium salts having an S=O group, such as FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li, methyl lithium sulfate, ethyl lithium sulfate (C2H5OSO3Li), and 2,2,2-trifluoroethyl lithium sulfate; 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-perfluoroethane disulfonyl imide, lithium cyclic 1,3-perfluoropropane disulfonyl imide, lithium cyclic 1,2-ethane disulfonyl imide, lithium cyclic 1,3-propane disulfonyl imide, lithium cyclic 1,4-perfluorobutane disulfonyl imide, LiN(CF3SO2)(FSO2), LiN(CF3SO2)(C3F7SO2), LiN(CF3SO2)(C4F9SO2), LiN(POF2)2 and other imide lithium salts; Lithium sulfamate compounds such as (CF3CH2)2NSO3Li, (CF3CH2)(CH3)NSO3Li, (CNCH2)2NSO3Li; Methylated lithium salts such as LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3; 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, and fluorine-containing organic lithium salts such as LiSCN, LiB(CN)4, LiB(C6H5)4, Li2(C2O4), LiP(C2O4)3, Li2B 12 F b H 12-b (b is an integer from 0 to 3), etc.

[0211] Among them, from the viewpoint of having the effects of improving output characteristics, high-rate charge and discharge characteristics, high-temperature storage characteristics, cycle characteristics, etc., 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, and at least one lithium salt selected from LiPF6, LiN(FSO2)2 and LiBF4 is most preferred.

[0212] These electrolyte salts can be used alone or in combination of two or more. When two or more are used in combination, preferred examples are the combination of LiPF6 and LiBF4; and the combination of LiPF6 and LiPO2F2, C2H5OSO3Li or FSO3Li, which have the effect of improving high temperature storage characteristics, load characteristics, and cycle characteristics.

[0213] In this case, the amount of LiBF4, LiPO2F2, C2H5OSO3Li or FSO3Li contained in 100% by mass of the electrolyte as a whole is not limited and is arbitrary as long as it does not significantly impair the effects of the present disclosure. It is usually 0.01% by mass or more, preferably 0.1% by mass or more, relative to the electrolyte of the present disclosure; in addition, it 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.

[0214] In addition, another example is the use of an inorganic lithium salt and an organic lithium salt, which have the effect of inhibiting degradation 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 overall 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.

[0215] The concentration of these electrolyte salts in the electrolyte is not particularly limited as long as it does not impair the effect of the present disclosure. From the viewpoint of making the conductivity of the electrolyte in 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, and further preferably 0.5 mol / L or more; and preferably 3 mol / L or less, more preferably 2.5 mol / L or less, and further preferably 2.0 mol / L or less.

[0216] 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 increases, so the conductivity may decrease, and the battery performance may decrease.

[0217] The electrolyte of the present disclosure may further comprise general formula (6): [Chemistry 39]

[0218] (Where X 21 is a group containing at least H or C; n21 is an integer from 1 to 3; Y 21 and Z 21 are the same or different and are groups containing at least H, C, O or F; n22 is 0 or 1; Y 21 and Z 21 The electrolyte solution containing the compound (6) is unlikely to further decrease the capacity retention rate and further increase the amount of gas generated even when stored at high temperatures.

[0219] When n21 is 2 or 3, 2 or 3 X 21 Can be the same or different.

[0220] 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.

[0221] 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 Z 21 As described above).

[0222] As Y21 , preferably at least one selected from H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-.

[0223] As Z 21 , preferably at least one selected from H-, F-, CH3-, CH3CH2-, CH3CH2CH2-, CF3-, CF3CF2-, CH2FCH2- and CF3CF2CF2-.

[0224] 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.

[0225] Next, a specific example of compound (6) is described. It should be noted that in the following examples, "analogs" 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 the present disclosure, for example, dimers, trimers and tetramers composed of multiple acid anhydrides; or substances with the same number of carbon atoms in the substituent but with structural isomers such as branching, substances with different positions of the substituent bonded to the acid anhydride, etc.

[0226] Specific examples of the acid anhydride forming a five-membered ring structure include succinic anhydride, methylsuccinic anhydride (4-methylsuccinic anhydride), dimethylsuccinic anhydride (4,4-dimethylsuccinic anhydride, 4,5-dimethylsuccinic anhydride, etc.), 4,4,5-trimethylsuccinic anhydride, 4,4,5,5-tetramethylsuccinic anhydride, 4-vinylsuccinic anhydride, 4,5-divinylsuccinic anhydride, phenylsuccinic anhydride (4-phenylsuccinic anhydride), 4,5 -diphenylsuccinic anhydride, 4,4-diphenylsuccinic anhydride, citraconic anhydride, maleic anhydride, methylmaleic anhydride (4-methylmaleic anhydride), 4,5-dimethylmaleic anhydride, phenylmaleic anhydride (4-phenylmaleic anhydride), 4,5-diphenylmaleic anhydride, itaconic anhydride, 5-methylitaconic anhydride, 5,5-dimethylitaconic anhydride, phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, and the like, and the like.

[0227] Specific examples of the acid anhydride forming a six-membered ring structure include cyclohexanedicarboxylic anhydride (cyclohexane-1,2-dicarboxylic anhydride, etc.), 4-cyclohexene-1,2-dicarboxylic anhydride, glutaric anhydride, glutaconic anhydride, 2-phenylglutaric anhydride, and the like, and analogs thereof.

[0228] Specific examples of other acid anhydrides forming a ring structure include 5-norbornene-2,3-dicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, pyromellitic anhydride, diglycolic anhydride, and analogs thereof.

[0229] Specific examples of the acid anhydride forming a ring structure and substituted with a halogen atom include monofluorosuccinic anhydride (such as 4-fluorosuccinic anhydride), 4,4-difluorosuccinic anhydride, 4,5-difluorosuccinic anhydride, 4,4,5-trifluorosuccinic anhydride, trifluoromethylsuccinic anhydride, tetrafluorosuccinic anhydride (4,4,5,5-tetrafluorosuccinic anhydride), 4-fluoromaleic anhydride, 4,5-difluoromaleic anhydride, trifluoromethylmaleic anhydride, 5-fluoroitaconic anhydride, 5,5-difluoroitaconic anhydride, and analogs thereof.

[0230] Among them, preferred examples of compound (6) include glutaric anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic anhydride, 4-cyclohexene-1,2-dicarboxylic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, phenylsuccinic anhydride, 2-phenylglutaric anhydride, maleic anhydride, methylmaleic anhydride, trifluoromethylmaleic anhydride, phenylmaleic anhydride, succinic anhydride, methylsuccinic anhydride, dimethylsuccinic anhydride, trifluoromethylsuccinic anhydride, monofluorosuccinic anhydride, and tetrafluorosuccinic anhydride; more preferred examples include maleic anhydride, methylmaleic anhydride, trifluoromethylmaleic anhydride, succinic anhydride, methylsuccinic anhydride, trifluoromethylsuccinic anhydride, and tetrafluorosuccinic anhydride; and even more preferred examples include maleic anhydride and succinic anhydride.

[0231] Compound (6) is preferably selected from the general formula (7): [Chemistry 40]

[0232] (Where X 31 ~X 34 The same or different, being a group containing at least H, C, O or F) and the general formula (8): [Chemistry 41]

[0233] (Where X 41 and X 42 The compound (8) is a group which is the same or different and contains at least H, C, O or F.

[0234] 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 34The number of carbon atoms in is preferably 1-10, more preferably 1-3.

[0235] 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-.

[0236] As X 41 and X 42 , which are the same or different, are preferably at least one selected from an alkyl group, a fluoroalkyl group, an alkenyl group and a fluoroalkenyl group. 41 and X 42 The number of carbon atoms in is preferably 1-10, more preferably 1-3.

[0237] 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-.

[0238] The compound (7) is preferably any one of the following compounds.

[0239] [Chemistry 42]

[0240] The compound (8) is preferably any one of the following compounds.

[0241] [Chemistry 43]

[0242] The electrolyte preferably contains 0.0001 to 15% by mass of compound (6) relative to the electrolyte, from the viewpoint that the capacity retention rate is not likely to be further reduced and the amount of gas generated is not likely to be further increased even when stored at high temperatures. The content of compound (6) is more preferably 0.01 to 10% by mass, further preferably 0.1 to 5% by mass, and particularly preferably 0.1 to 3.0% by mass.

[0243] In the case where the above-mentioned electrolyte contains both compounds (7) and (8), from the viewpoint that the capacity retention rate is not likely to be further reduced and the amount of gas generated is not likely to be further increased when stored at high temperatures, the above-mentioned electrolyte preferably contains 0.08 to 2.50 mass % of compound (7) and 0.02 to 1.50 mass % of compound (8) relative to the above-mentioned electrolyte, and more preferably contains 0.80 to 2.50 mass % of compound (7) and 0.08 to 1.50 mass % of compound (8).

[0244] The electrolyte solution of the present disclosure may contain at least one selected from the group consisting of nitrile compounds represented by the following general formulae (9a), (9b), and (9c).

[0245] [Chemistry 44]

[0246] (Where R a and R b Each independently represents a hydrogen atom, a cyano group (CN), a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are replaced by halogen atoms. n represents an integer of 1 to 10. [Chemistry 45]

[0247] (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 of an alkyl group are replaced by 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 the hydrogen atoms of an alkyl group are replaced by halogen atoms. m represents an integer of 1 to 10. [Chemistry 46]

[0248] (Where R f , R g , R h and R i Each independently represents a group containing a cyano group (CN), a hydrogen atom (H), a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are replaced by halogen atoms. f , R g , R h and R iAt least one of the groups is a group containing a cyano group. l represents an integer of 1 to 3.) This can improve the high temperature storage characteristics of the electrochemical device. The above-mentioned nitrile compounds may be used alone or in any combination and ratio.

[0249] In the above general formula (9a), 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 the hydrogen atoms of an alkyl group are substituted with a halogen atom.

[0250] 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.

[0251] The alkyl group is preferably an alkyl group having 1 to 5 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group.

[0252] Examples of the group in which at least a part of hydrogen atoms of an alkyl group are substituted with halogen atoms include groups in which at least a part of hydrogen atoms of the above-mentioned alkyl group are substituted with the above-mentioned halogen atoms.

[0253] In R a and R b In the case of an alkyl group or a group in which at least a part of the hydrogen atoms of an alkyl group are replaced by halogen atoms, R a and R b They may be bonded to each other to form a ring structure (for example, a cyclohexane ring).

[0254] R a and R b A hydrogen atom or an alkyl group is preferred.

[0255] In the above general formula (9a), 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. n is preferably an integer of 1-7, and more preferably an integer of 2-5.

[0256] As the nitrile compound represented by the general formula (9a), dinitriles and trinitriles are preferred.

[0257] 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, dicyclohexane-1,1-dicarbonitrile, dicyclohexane-2,2-dicarbonitrile, dicyclohexane-3,3-dicarbonitrile, 2,5-dimethyl-2,5-hexane dicarbonitrile, 2,3-diisobutyl-2,3-dimethyl succinonitrile, 2,2-diisobutyl-2,3-dimethyl succinonitrile, Butyl-3,3-dimethylsuccinonitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyano octane, 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.

[0258] Specific examples of the trinitriles include pentaerythritol, propane tricarbonitrile, 1,3,5-hexane tricarbonitrile, 1,3,6-hexane tricarbonitrile, heptane tricarbonitrile, 1,2,3-propane tricarbonitrile, 1,3,5-pentane tricarbonitrile, cyclohexane tricarbonitrile, tricyanoethylamine, tricyanoethoxypropane, tricyanoethylene, tris(2-cyanoethyl)amine, and the like. 1,3,6-hexane tricarbonitrile and cyclohexane tricarbonitrile are particularly preferred, and cyclohexane tricarbonitrile is most preferred.

[0259] In the above general formula (9b), R c is a hydrogen atom, a halogen atom, an alkyl group, a group in which at least a part of the hydrogen atoms of an alkyl group are replaced by 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 of an alkyl group are substituted with halogen atoms.

[0260] Examples of the halogen atom, the alkyl group, and the group in which at least a part of hydrogen atoms of the alkyl group is substituted with a halogen atom include the groups exemplified for the above general formula (9a).

[0261] The above NC-R c1 -X c1 -R in c1 The alkylene group is preferably an alkylene group having 1 to 3 carbon atoms.

[0262] 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 the hydrogen atoms of an alkyl group are substituted with halogen atoms.

[0263] 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 of an 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 of an alkyl group are substituted with a fluorine atom.

[0264] In R d and R e In the case of an alkyl group or a group in which at least a part of the hydrogen atoms of the alkyl group are replaced by halogen atoms, R d and R e They may be bonded to each other to form a ring structure (for example, a cyclohexane ring).

[0265] In the above general formula (9b), 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 m is preferably an integer of 2-7, and more preferably an integer of 2-5.

[0266] Examples of the nitrile compound represented by the general formula (9b) include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 3-methoxypropionitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanecarbonitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3′-oxydipropionitrile, 3,3′-thiodipropionitrile, pentafluoropropionitrile, methoxyacetonitrile, and benzonitrile. Among them, 3,3,3-trifluoropropionitrile is particularly preferred.

[0267] In the above general formula (9c), R f , R g , R hand R i Each is independently a group containing a cyano group (CN), a hydrogen atom, a halogen atom, an alkyl group, or a group in which at least a part of the hydrogen atoms of an alkyl group are substituted with a halogen atom.

[0268] Examples of the halogen atom, the alkyl group, and the group in which at least a part of hydrogen atoms of the alkyl group is substituted with a halogen atom include the groups exemplified for the above general formula (9a).

[0269] 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 replaced by a cyano group. Examples of the alkyl group in this case include the groups exemplified for the above general formula (9a).

[0270] 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.

[0271] In the above general formula (9c), 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 The same is true. l is preferably an integer of 1-2.

[0272] Examples of the nitrile compound represented by the general formula (9c) include 3-hexenedinitrile, 2,4-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-hexenedinitrile and 2,4-hexenedinitrile, and particularly preferred is 3-hexenedinitrile.

[0273] 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 1.0% by mass.

[0274] The electrolyte of the present disclosure may contain a compound having an isocyanate group (hereinafter, sometimes referred to as "isocyanate"). The isocyanate is not particularly limited, and any isocyanate can be used. Examples of isocyanates include monoisocyanates, diisocyanates, triisocyanates, and the like.

[0275] Specific examples of the monoisocyanates include isocyanatomethane, isocyanatoethane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1-isocyanatoheptane, 1-isocyanatooctane, 1-isocyanatononane, 1-isocyanatodecane, isocyanatocyclohexane, methoxycarbonyl isocyanate, ethoxycarbonyl isocyanate, propoxycarbonyl isocyanate, butoxycarbonyl isocyanate, methoxysulfonyl isocyanate, ethoxysulfonyl isocyanate, propoxysulfonyl isocyanate, butoxysulfonyl isocyanate, fluorosulfonyl isocyanate, methyl isocyanate, butyl isocyanate, phenyl isocyanate, 2-isocyanoethyl acrylate, 2-isocyanoethyl methacrylate, and ethyl isocyanate.

[0276] 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, 1,4-diisocyanato- 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 enediisocyanate), 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 esters, 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, and the like.

[0277] 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.

[0278] 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 industrially readily available and can suppress the manufacturing cost of the electrolyte to a low level, so they are preferred. In addition, from a technical point of view, they can also contribute to the formation of a stable film-like structure and are more preferably used.

[0279] The content of isocyanate is not particularly limited, and can be arbitrary as long as it does not significantly damage the effect of the present disclosure. It is preferably 0.001% by mass or more and 1.0% by mass or less relative to the electrolyte. If the content of isocyanate is above the lower limit, it is possible to bring a sufficient effect of improving the cycle characteristics of the non-aqueous electrolyte secondary battery. 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% by mass or more, further preferably 0.1% by mass or more, and particularly preferably 0.2% by mass or more; and, more preferably 0.8% by mass or less, further preferably 0.7% by mass or less, and particularly preferably 0.6% by mass or less.

[0280] The electrolyte of the present disclosure may further include 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.

[0281] 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.

[0282] Specific examples of the unsaturated cyclic sulfonic acid ester 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-1,4-sultone, etc.

[0283] Among them, from the viewpoint of being easy to obtain and contributing to forming 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 may be any content as long as the effect of the present disclosure is not significantly impaired, but is preferably 0.001 mass % or more and 3.0 mass % or less relative to the electrolyte.

[0284] If the content of the cyclic sulfonate is above the lower limit, the non-aqueous electrolyte secondary battery can be sufficiently improved in terms of cycle characteristics. In addition, if it is below the upper limit, the increase in the manufacturing cost of the non-aqueous electrolyte secondary battery can be avoided. The content of the cyclic sulfonate is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, and particularly preferably 0.2% by mass or more; and more preferably 2.5% by mass or less, further preferably 2.0% by mass or less, and particularly preferably 1.8% by mass or less.

[0285] The electrolyte solution of the present disclosure may further contain polyoxyethylene having a weight average molecular weight of 2000 to 4000 and having -OH, -OCOOH or -COOH at the terminal.

[0286] By including such a compound, the stability of the electrode interface is improved, and the characteristics of the electrochemical device can be improved.

[0287] Examples of the polyoxyethylene include polyoxyethylene monool, polyoxyethylene formic acid, polyoxyethylene diol, polyoxyethylene dicarboxylic acid, polyoxyethylene triol, polyoxyethylene trimaric acid, etc. These may be used alone or in combination of two or more.

[0288] Among them, a mixture of polyoxyethylene monoalcohol and polyoxyethylene diol, and a mixture of polyvinyl formic acid and polyethylene dicarboxylic acid are preferred in terms of further improving the characteristics of the electrochemical device.

[0289] 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.

[0290] The weight average molecular weight can be measured in terms of polystyrene by gel permeation chromatography (GPC).

[0291] 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.

[0292] The content of the polyoxyethylene is more preferably 5×10 -6 mol / kg or more.

[0293] The electrolyte solution disclosed in the present invention may further contain a fluorinated saturated cyclic carbonate, an unsaturated cyclic carbonate, an overcharge prevention agent, other known auxiliary agents, etc. as additives, thereby suppressing the degradation of the characteristics of the electrochemical device.

[0294] As the fluorinated saturated cyclic carbonate, the compound shown in the above-mentioned general formula (A) can be cited. Among them, preferably fluorinated ethylene carbonate, difluoroethylene carbonate, monofluoromethyl ethylene carbonate, trifluoromethyl ethylene carbonate, 2,2,3,3,3-pentafluoropropyl ethylene carbonate (4-(2,2,3,3,3-pentafluoropropyl)-[1,3]dioxolane-2-one). The fluorinated saturated cyclic carbonate can be used alone or in any combination and ratio.

[0295] 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.

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

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

[0298] Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate. 5-ethynylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, 4-methyl-5-allylethylene carbonate, 4-methylene-1,3-dioxolane-2-one, 4,5-dimethylene-1,3-dioxolane-2-one, 4-methyl-5-allylethylene carbonate, and the like.

[0299] 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 can form a more stable interface protection film, so it is particularly preferred, and vinylene carbonate is most preferably used.

[0300] The molecular weight of unsaturated cyclic carbonate is not particularly limited, as long as the effect of the present disclosure is not significantly damaged, then it can be any molecular weight.Molecular weight is preferably more than 50 and below 250.If within the scope, then easily ensure that the unsaturated cyclic carbonate is relative to the solubility of electrolyte, easily give full play to the effect of the present disclosure.The molecular weight of unsaturated cyclic carbonate is more preferably more than 80, in addition, more preferably below 150.

[0301] 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.

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

[0303] The content of the above-mentioned unsaturated cyclic carbonate is not particularly limited, as long as the effect of the present disclosure is not significantly damaged, then it can be any content. The content of the above-mentioned unsaturated cyclic carbonate is preferably more than 0.001 mass % in 100 mass % of electrolyte, more preferably more than 0.01 mass %, and more preferably more than 0.1 mass %. In addition, the above-mentioned content is preferably less than 5 mass %, more preferably less than 4 mass %, and more preferably less than 3 mass %. As long as it is within the above range, 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 high temperature storage characteristics to reduce, the gas generation amount to become more, and the discharge capacity retention rate to reduce such a situation.

[0304] As the unsaturated cyclic carbonate, in addition to the above-mentioned non-fluorinated unsaturated cyclic carbonate, a fluorinated unsaturated cyclic carbonate can also be preferably used.

[0305] Fluorinated unsaturated cyclic carbonate is a cyclic carbonate with unsaturated bonds and fluorine atoms. As long as the quantity of the fluorine atoms possessed by the fluorinated unsaturated cyclic carbonate is more than 1, there is no particular restriction. Wherein, the fluorine atoms are generally below 6, preferably below 4, most preferably 1 or 2.

[0306] 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.

[0307] 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.

[0308] 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.

[0309] Among them, as the fluorinated unsaturated cyclic carbonate, the following compounds are more preferably used because they form a stable interface protective film: 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-allylcarbonate Ethylene 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.

[0310] The molecular weight of fluorinated unsaturated cyclic carbonate is not particularly limited, and can be any molecular weight as long as the effect of the present disclosure is not significantly damaged. The molecular weight is preferably more than 50, and is below 500. As long as it is the scope, it is easy to ensure the solubility of fluorinated unsaturated cyclic carbonate relative to electrolyte.

[0311] The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and any known method can be selected for production. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

[0312] Fluorinated unsaturated cyclic carbonate can be used alone as one, or in any combination and ratio and in combination with more than two. In addition, the content of fluorinated unsaturated cyclic carbonate is not particularly limited, as long as the effect of the present disclosure is not significantly damaged, it is any content. The content of fluorinated unsaturated cyclic carbonate is usually in 100% by mass of electrolyte, preferably more than 0.001% by mass, more preferably more than 0.01% by mass, more preferably more than 0.1% by mass, and preferably less than 5% by mass, more preferably less than 4% by mass, more preferably less than 3% by mass. As long as it is within the 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 reduction of high temperature storage characteristics, the increase of gas generation, and the reduction of discharge capacity retention rate.

[0313] The electrolyte solution of the present disclosure may further contain a compound having a triple bond. The compound may be any compound as long as it has one or more triple bonds in the molecule, and its type is not particularly limited.

[0314] Specific examples of the compound having a triple bond include the following compounds.

[0315] 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 the like hydrocarbon compounds; 2-propynyl methyl carbonate, 2-propynyl ethyl carbonate, 2-propynyl propyl carbonate, 2-propynyl butyl carbonate, 2-propynyl phenyl carbonate, 2-propynyl cyclohexyl carbonate, di(2-propynyl) carbonate, 1-methyl-2-propynyl methyl carbonate, 1,1-dimethyl-2-propynyl methyl carbonate, 2-butynyl methyl carbonate, 3-butynyl methyl carbonate, 2-pentynyl methyl carbonate, Monocarbonates such as 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; 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, ethyl acrylate Ester, propyl acrylate, vinyl acrylate, 2-propylene acrylate, 2-butylene acrylate, 3-butylene acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl methacrylate, 2-propylene methacrylate, 2-butylene methacrylate, 3-butylene methacrylate, methyl 2-propiolate, ethyl 2-propiolate, propyl 2-propiolate, vinyl 2-propiolate, 2-propylene 2-propiolate, 2-butylene 2-propiolate, 3-butylene 2-propiolate, 2-butylene 2-Butynoic acid methyl ester, 2-butynoic acid ethyl ester, 2-butynoic acid propyl ester, 2-butynoic acid vinyl ester, 2-butynoic acid 2-propenyl ester, 2-butynoic acid 2-butenyl ester, 2-butynoic acid 3-butynoic acid methyl ester, 3-butynoic acid ethyl ester, 3-butynoic acid propyl ester, 3-butynoic acid vinyl ester, 3-butynoic acid 2-propenyl ester, 3-butynoic acid 2-butenyl ester, 3-butynoic acid 3-butynoic acid methyl ester, 2-pentynoic acid ethyl ester, 2-pentynoic acid propyl ester, 2-pentynoic acid vinyl ester, 2-pentynoic acid 2-propenyl ester, 2-pentynoic acid Monocarboxylic acid esters such as 2-butenyl acetyloate, 3-butenyl acetyloate, methyl 3-pentynoate, ethyl 3-pentynoate, propyl 3-pentynoate, vinyl 3-pentynoate, 2-propenyl 3-pentynoate, 2-butenyl 3-pentynoate, 3-butenyl 3-pentynoate, methyl 4-pentynoate, ethyl 4-pentynoate, propyl 4-pentynoate, vinyl 4-pentynoate, 2-propenyl 4-pentynoate, 2-butenyl 4-pentynoate, and 3-butenyl 4-pentynoate; fumaric acid esters, methyl pivalate, and ethyl pivalate; 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; Oxalic acid diesters such as 2-propynyl methyl oxalate, 2-propynyl ethyl oxalate, 2-propynyl propyl oxalate, 2-propynyl vinyl oxalate, 2-propynyl allyl oxalate, di(2-propynyl) oxalate, 2-butynyl methyl oxalate, 2-butynyl ethyl oxalate, 2-butynyl propyl oxalate, 2-butynyl vinyl oxalate, 2-butynyl allyl oxalate, di(2-butynyl) oxalate, 3-butynyl methyl oxalate, 3-butynyl ethyl oxalate, 3-butynyl propyl oxalate, 3-butynyl vinyl oxalate, 3-butynyl allyl oxalate, and di(3-butynyl) oxalate; 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; 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 , 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; 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) (2-propenyl) methylphosphonate, (3-butenyl) (2-propenyl) (2-propenyl) methylphosphonate, (1,1-dimethyl-2-propynyl) (2-propenyl) methylphosphonate, (3-butenyl) (1,1-dimethyl-2-propynyl) (2-propenyl) methylphosphonate, (2-propynyl) (2-propenyl) ethylphosphonate, (3-butenyl) (2-propenyl) (2-propenyl) ethylphosphonate, (1,1-dimethyl-2-propynyl) (2-propenyl) ethylphosphonate and (3-butenyl) (1,1-dimethyl-2-propynyl) (1,1-dimethyl-2-propynyl) ethylphosphonate; 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; Among these, compounds having an alkynyloxy group are preferred because they can form a negative electrode coating more stably in an electrolyte solution.

[0316] 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, 2-propynyl methyl oxalate, and di(2-propynyl) oxalate are particularly preferred.

[0317] The above-mentioned compound with triple bond can be used alone as one, or in any combination and ratio and more than two. The compound with triple bond is not limited to the overall amount of the electrolyte disclosed in the present invention, as long as it does not significantly damage the effect of the present invention, and relative to the electrolyte disclosed in the present invention, containing usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, 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.

[0318] In the electrolyte solution of the present disclosure, an overcharge inhibitor may be used in order to effectively suppress battery rupture or ignition when an electrochemical device using the electrolyte solution is overcharged or the like.

[0319] 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 anisole; aromatic compounds such as 2-fluorobiphenyl, 4-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene; Benzene, fluorotoluene, trifluorotoluene and other partially fluorinated aromatic compounds; 2,4-difluoroanisole, 2,5-difluoroanisole, 1,6-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and other fluorinated anisole compounds; 3-propylphenyl acetate, 2-ethylphenyl acetate, benzylphenyl acetate, methylphenyl acetate, benzyl acetate, phenethylphenyl acetate and other aromatic acetates; diphenyl carbonate, methylphenyl carbonate and other aromatic carbonates; toluene, xylene and other toluene derivatives; 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl, o-cyclohexylbiphenyl and other unsubstituted or alkyl-substituted biphenyl derivatives; Among them, preferred are aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partial hydrogenation of 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 kinds in combination, in particular, from the viewpoint of the balance between the overcharge prevention characteristic and the high temperature storage characteristic, a combination of cyclohexylbenzene and tert-butylbenzene or tert-amylbenzene is preferred; or at least one of oxygen-free aromatic compounds selected from biphenyl, alkylbiphenyl, terphenyl, partial hydrogenation of terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, etc. and at least one of oxygen-containing aromatic compounds selected from diphenyl ether, dibenzofuran, etc. are used in combination.

[0320] In the electrolyte used in the present disclosure, carboxylic anhydride (but excluding compound (6)) may also be used. The compound represented by the following general formula (10) is preferred. The method for producing carboxylic anhydride is not particularly limited, and any known method can be selected for production.

[0321] General formula (10): [Chemistry 47]

[0322] (In general formula (10), R 61 , R 62Each independently represents a hydrocarbon group having 1 to 15 carbon atoms which may have a substituent. 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, it can also be an aromatic hydrocarbon group, and it can also be a group formed by bonding an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group can be a saturated hydrocarbon group, and it can also 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. In addition, it can also be a group formed 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 or different.

[0323] 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 main purpose of the present disclosure. 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 the above-mentioned substituents, or may have two or more. When having two or more substituents, these substituents may be the same or different from each other.

[0324] R 61 , R 62 The number of carbon atoms of each hydrocarbon group is usually 1 or more and usually 15 or less, preferably 12 or less, more preferably 10 or less, and further preferably 9 or less. 1 With R 2 When the two hydrocarbon groups are bonded to each other to form a divalent hydrocarbon group, the number of carbon atoms in the divalent hydrocarbon group is usually 1 or more and usually 15 or less, preferably 13 or less, more preferably 10 or less, and further preferably 8 or less. 61 , R 62 When the hydrocarbon group has a substituent containing a carbon atom, it is preferred that R including the substituent 61 , R 62 The total number of carbon atoms satisfies the above range.

[0325] Next, specific examples of the acid anhydride represented by the above general formula (10) are described. It should be noted that in the following examples, "analogs" refer to acid anhydrides obtained by replacing a part of the structure of the exemplified acid anhydride with other structures within the scope of the present disclosure, for example, dimers, trimers and tetramers composed of multiple acid anhydrides, or substances with the same number of carbon atoms of the substituent but with structural isomers such as branched chains, substances with different positions of the substituent bonded to the acid anhydride, etc.

[0326] First, the following is an example of R 61 , R 62 Specific examples of the same acid anhydride.

[0327] 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.

[0328] 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.

[0329] As R 61 , R 62 Specific examples of the acid anhydride which is an alkenyl group 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.

[0330] 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.

[0331] As R 61 , R 62 Specific examples of the acid anhydride which is an aryl group include benzoic anhydride, 4-methylbenzoic anhydride, 4-ethylbenzoic anhydride, 4-tert-butylbenzoic anhydride, 2-methylbenzoic anhydride, 2,4,6-trimethylbenzoic anhydride, 1-naphthoic anhydride, 2-naphthoic anhydride, and the like, and analogs thereof.

[0332] In addition, as R 61 , R 62 Examples of acid anhydrides substituted with halogen atoms include acid anhydrides mainly substituted with fluorine atoms. However, 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.

[0333] As R 61 , R 62 Examples of the acid anhydride of the chain alkyl group substituted with a halogen atom include fluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, 2-fluoropropionic anhydride, 2,2-difluoropropionic anhydride, 2,3-difluoropropionic anhydride, 2,2,3-trifluoropropionic anhydride, 2,3,3-trifluoropropionic anhydride, 2,2,3,3-tetrapropionic anhydride, 2,3,3,3-tetrapropionic anhydride, 3-fluoropropionic anhydride, 3,3-difluoropropionic anhydride, 3,3,3-trifluoropropionic anhydride, perfluoropropionic anhydride, and the like, and analogs thereof.

[0334] 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.

[0335] 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.

[0336] As R 61 , R 62 Examples of the anhydride of the alkynyl group substituted with a halogen atom include 3-fluoro-2-propiolic anhydride, 3-(4-fluorophenyl)-2-propiolic anhydride, 3-(2,3,4,5,6-pentafluorophenyl)-2-propiolic anhydride, 4-fluoro-2-butynoic anhydride, 4,4-difluoro-2-butynoic anhydride, 4,4,4-trifluoro-2-butynoic anhydride, and the like, and analogs thereof.

[0337] 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.

[0338] As R 61 , R 62 Examples of acid anhydrides containing 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.

[0339] Next, the following is an example of R 61 , R 62 Specific examples of acid anhydrides that are different from each other.

[0340] As R 61 , R 62 , all combinations of the above-mentioned examples and their analogs can be considered, and representative examples are given below.

[0341] Examples of combinations of chain alkyl groups include acetic propionic anhydride, acetic butyric anhydride, butyric propionic anhydride, and acetic 2-methylpropionic anhydride.

[0342] Examples of the combination of a chain alkyl group and a cyclic alkyl group include acetic cyclopentane anhydride, acetic cyclohexane anhydride, and cyclopentane propionic anhydride.

[0343] 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.

[0344] Examples of the combination of a chain alkyl group and an alkynyl group include acetic anhydride propiolic acid, acetic anhydride 2-butiolic acid, acetic anhydride 3-butiolic acid, acetic anhydride 3-phenylpropiolic acid, and propiolic anhydride.

[0345] 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.

[0346] 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.

[0347] Examples of combinations of cyclic alkyl groups include cyclopentanecarboxylic acid and cyclohexanecarboxylic anhydride.

[0348] Examples of the combination of a cyclic alkyl group and an alkenyl group include cyclopentane acrylic acid anhydride, 3-cyclopentane methacrylic acid anhydride, 3-cyclopentane butylene acrylic acid anhydride, and cyclohexane acrylic acid anhydride.

[0349] Examples of the combination of a cyclic alkyl group and an alkynyl group include propiolic acid cyclopentane anhydride, 2-butynoic acid cyclopentane anhydride, and propiolic acid cyclohexane anhydride.

[0350] Examples of the combination of a cyclic alkyl group and an aryl group include benzoic acid cyclopentane anhydride, 4-methylbenzoic acid cyclopentane anhydride, and benzoic acid cyclohexane anhydride.

[0351] 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.

[0352] 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.

[0353] 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.

[0354] 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.

[0355] 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.

[0356] Examples of combinations of alkynyl groups include propiolic acid 2-butynoic anhydride, propiolic acid 3-butynoic anhydride, and 2-butynoic acid 3-butynoic anhydride.

[0357] 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.

[0358] 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.

[0359] Examples of combinations of aryl groups include 4-methylbenzoic anhydride benzoic acid, 1-naphthoic anhydride benzoic acid, and 1-naphthoic anhydride 4-methylbenzoic acid.

[0360] 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.

[0361] Examples of combinations 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.

[0362] Among the acid anhydrides forming a chain structure, acetic anhydride, propionic anhydride, 2-methylpropionic anhydride, cyclopentanecarboxylic anhydride, cyclohexanecarboxylic anhydride, acrylic anhydride, 2-methacrylic anhydride, 3-methacrylic anhydride, 2,3-dimethylacrylic anhydride, 3,3-dimethylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, propiolic anhydride, 2-butynoic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, 4-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride, trifluoroacetic anhydride, 3,3,3 -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.

[0363] These compounds form a film having excellent durability by appropriately forming a bond with lithium oxalate salt, and are particularly preferred from the viewpoint of being able to improve charge and discharge rate characteristics, input and output characteristics, and impedance characteristics after a durability test.

[0364] It should be noted that the molecular weight of the carboxylic anhydride is not limited and can be any as long as the effect of the present disclosure is not significantly impaired, and is usually 90 or more, preferably 95 or more; on the other hand, it is usually 300 or less, preferably 200 or less. If the molecular weight of the carboxylic anhydride is within the above range, the viscosity of the electrolyte can be suppressed from increasing, and the film density is optimized, so that the durability can be appropriately improved.

[0365] The method for producing the carboxylic anhydride is not particularly limited, and any known method can be selected to produce the carboxylic anhydride. The non-aqueous electrolyte solution of the present disclosure may contain any one of the carboxylic anhydrides described above, or two or more of them may be contained in any combination and ratio.

[0366] In addition, the content of the above-mentioned carboxylic anhydride relative to the electrolyte of the present disclosure is not particularly limited, and can be arbitrary as long as it does not significantly damage the effect of the present disclosure. It is desirable to contain a concentration of usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less relative to the electrolyte of the present disclosure. If the content of the carboxylic anhydride is within the above range, it is easy to play the effect of improving the cycle characteristics, and the reactivity is good, therefore, it is easy to improve the battery characteristics.

[0367] Other known additives may be used in the electrolyte of the present invention. Examples of other additives 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; 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; Carbonate compounds such as erythritan carbonate, spirobis-dimethylene carbonate, and methoxyethyl-methyl carbonate; Ether compounds such as dioxolane, dioxane, 2,5,8,11-tetraoxadodecane, 2,5,8,11,14-pentaoxapentadecane, ethoxymethoxyethane, trimethoxymethane, glyme, and ethylmonoglyme; Ketone compounds such as dimethyl ketone, diethyl ketone, 3-pentanone, etc. Anhydrides such as 2-allylsuccinic anhydride; Ester compounds such as dimethyl oxalate, diethyl oxalate, ethyl methyl oxalate, di(2-propynyl) oxalate, methyl 2-propynyl 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; Acetamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide and other amide compounds; Ethylene sulfate, vinylene sulfate, ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, cyclobutene sulfone, diphenyl sulfone, N,N-dimethyl methanesulfonamide, N,N-diethyl methanesulfonamide, methyl vinylsulfonate, ethyl vinylsulfonate, allyl vinylsulfonate, propargyl vinylsulfonate, methyl allylsulfonate, ethyl allylsulfonate, 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, (butylenesulfonate sulfur-containing compounds such as 2-(2-(methylsulfonyloxy)propionic acid 2-propynyl ester, 5,5-dimethyl-1,2-oxathiolane-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, etc.; Nitrogen-containing compounds such as 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, N-methylsuccinimide, nitromethane, nitroethane, and ethylenediamine; Trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, ethyl diethylphosphonoacetate, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide, bis(2,2-difluoroethyl) 2,2,2-trifluoroethyl phosphate, bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate, (2,2,2-trifluoroethyl) methyl ester, 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, phosphorus 2-(dimethoxyphosphoryl)acetate methyl ester, 2-(dimethylphosphoryl)acetate methyl ester, 2-(diethoxyphosphoryl)acetate methyl ester, 2-(diethylphosphoryl)acetate methyl ester, methylenebisphosphonic acid methyl ester, methylenebisphosphonic acid ethyl ester, ethylenebisphosphonic acid methyl ester, ethylenebisphosphonic acid ethyl ester, butylenebisphosphonic acid methyl ester, butylenebisphosphonic acid ethyl ester, 2-(dimethoxyphosphoryl)acetate 2-propynyl ester, 2-(dimethyl Phosphorus-containing compounds such as 2-(trimethylsilyl) phosphate, tris(triethylsilyl) phosphate, tris(tert-butyldimethylsilyl) phosphate, tris(trimethoxysilyl) phosphate, tris(trimethylsilyl) phosphite, tris(triethylsilyl) phosphite, tris(tert-butyldimethylsilyl) phosphite, tris(trimethoxysilyl) phosphite, tris(trimethylsilyl) phosphite, tris(triethylsilyl) phosphite, tris(tert-butyldimethylsilyl) phosphite, tris(trimethoxysilyl) phosphite, and trimethylsilyl polyphosphate; Boron-containing compounds such as tris(trimethylsilyl) borate and tris(trimethoxysilyl) borate; 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, and tetramethylsilane; Etc. 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.

[0368] As the above-mentioned other auxiliary agents, phosphorus-containing compounds are preferred, and tris(trimethylsilyl) phosphate and tris(trimethylsilyl) phosphite are preferred.

[0369] The amount of other auxiliary agents is not particularly limited, and any amount can be used as long as the effect of the present disclosure is not significantly impaired. The amount of other auxiliary agents in 100% by mass of the electrolyte is preferably 0.01% by mass or more, and 5% by mass or less. As long as 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 reduced 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 more preferably 1% by mass or less.

[0370] Without prejudice to the effects of the present invention, the electrolyte of the present invention may further contain ether compounds that are not fluoroethers represented by the above general formula (1), cyclic and chain carboxylates, nitrogen-containing compounds, boron-containing compounds, organic silicon compounds, non-flammable (flame retardant) agents, surfactants, high dielectric constant additives, cycle characteristics and rate characteristics improvers, sulfone compounds, etc. as additives.

[0371] As the ether compound, chain ethers having 2 to 10 carbon atoms and cyclic ethers having 3 to 6 carbon atoms are preferred.

[0372] 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.

[0373] Furthermore, the ether compound may contain other fluorinated ethers in addition to the fluorinated ether represented by the above formula (1).

[0374] Examples of such fluoroethers include the following general formula (I): R 4 -O-Rf 5 (I) (Where Rf 4 and Rf 5 are the same or different and are an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms. 3 and Rf 4 At least one of them is a fluoroalkyl group, excluding the fluoroether represented by the above formula (1). The fluoroether (I) shown.

[0375] By containing the fluoroether (I), the flame retardancy of the electrolyte solution can be improved, and the stability and safety at high temperature and high voltage can be improved.

[0376] In the above general formula (I), as long as Rf 4 and Rf 5 At least one of the alkyl groups may be a fluoroalkyl group having 1 to 10 carbon atoms. However, from the viewpoint of further improving the flame retardancy of the electrolyte and the stability and safety at high temperature and high voltage, Rf is preferably 3 and Rf 4 At the same time, it is a fluorinated alkyl group having 1 to 10 carbon atoms. In this case, Rf 3 and Rf 4 They can be the same or different from each other.

[0377] Among them, Rf is more preferred 4 and Rf 5 Same or different, Rf 4 is a fluoroalkyl group having 3 to 6 carbon atoms, and Rf 5 It is a fluorinated alkyl group having 2 to 6 carbon atoms.

[0378] If Rf 4 and Rf 5 If the total number of carbon atoms of Rf is too small, the boiling point of the fluoroether becomes too low; in addition, if Rf 4 or Rf 5 If the number of carbon atoms in the electrolyte is too large, the solubility of the electrolyte salt decreases, and the compatibility with other solvents begins to be adversely affected. In addition, the viscosity increases, so the rate characteristics decrease. 4 The number of carbon atoms is 3 or 4, Rf 5 When the number of carbon atoms is 2 or 3, it is advantageous in that the boiling point and rate characteristics are excellent.

[0379] The fluorine content of the fluoroether (I) is preferably 40 to 75% by mass. When the fluorine content is within this range, the balance between non-flammability and compatibility is particularly excellent. In addition, it is also preferred from the viewpoint of good oxidation resistance and safety.

[0380] The lower limit of the fluorine content is more preferably 45% by mass, further preferably 50% by mass, and particularly preferably 55% by mass, and the upper limit is more preferably 70% by mass, further preferably 66% by mass.

[0381] The fluorine content of the fluoroether (I) is a value calculated according to {(number of fluorine atoms×19) / molecular weight of the fluoroether (I)}×100(%) based on the structural formula of the fluoroether (I).

[0382] As Rf 4, for example, CF3CF2CH2-, CF3CFHCF2-, HCF2CF2CF2-, HCF2CF2CH2-, CF3CF2CH2CH2-, CF3CFHCF2CH2-, HCF2CF2CF2CF2-, HCF2CF2CF2CH2-, HCF2CF2CH2CH2-, HCF2CF(CF3)CH2-, etc. can be cited. In addition, as Rf 5 For example, -CH2CF2CF3, -CF2CFHCF3, -CF2CF2CF2H, -CH2CF2CF2H, -CH2CH2CF2CF3, -CH2CF2CFHCF3, -CF2CF2CF2CF2H, -CH2CF2CF2CF2H, -CH2CH2CF2CF2H, -CH2CF(CF3)CF2H, -CF2CF2H, -CH2CF2H, -CF2CH3, etc. can be mentioned.

[0383] Specific examples of the fluoroether (I) include 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.

[0384] Among them, when HCF2- or CF3CFH- is contained at one or both ends, the polarizability is excellent and a fluoroether (I) with a high boiling point can be formed.

[0385] The boiling point of the fluoroether (I) is preferably 67 to 120° C., more preferably 80° C. or higher, and even more preferably 90° C. or higher.

[0386] Examples of such fluoroether (I) include one or more of CF3CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, HCF2CF2CH2OCF2CFHCF3, HCF2CF2CH2OCH2CF2CF2H, and CF3CFHCF2CH2OCF2CFHCF3.

[0387] 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) and CF3CF2CH2OCF2CFHCF3 (boiling point 82°C), and HCF2CF2CH2OCF2CFHCF3 (boiling point 106°C) is more preferred.

[0388] 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.

[0389] Among them, as the above-mentioned ether compound, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, and crown ether are preferred in terms of high solvating ability for lithium ions and improved ion dissociation degree; dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred in terms of low viscosity and providing high ion conductivity.

[0390] Examples of the cyclic carboxylic acid esters include those having a total carbon number of 3 to 12 in the structural formula. Specifically, c -Butyrolactone, c -Valerolactone, c -Caprolactone, e -caprolactone, 3-methyl- c Among them, from the perspective of improving the characteristics of electrochemical devices due to the improvement of the degree of lithium ion dissociation, c -Butyrolactone is particularly preferred.

[0391] As the amount of the cyclic carboxylic acid ester of the additive, it is usually preferably more than 0.1% by mass in 100% by mass of the solvent, more preferably more than 1% by mass. If it is within this range, it is easy to improve the conductivity of the electrolyte and improve the large current discharge characteristics of the electrochemical device. In addition, the amount of the cyclic carboxylic acid ester is preferably less than 10% by mass, more preferably less than 5% by mass. By setting the upper limit like this, it is easy to make the viscosity of the electrolyte within an appropriate range, avoid the reduction of conductivity, suppress the increase of the negative electrode resistance, and make the large current discharge characteristics of the electrochemical device within a good range.

[0392] In addition, as the above-mentioned cyclic carboxylic acid ester, a fluorinated cyclic carboxylic acid ester (fluorinated lactone) can also be used appropriately. As the fluorinated lactone, for example, the following formula (C) can be mentioned: [Chemistry 48]

[0393] (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 which is a fluorinated alkyl group) The fluorinated lactones shown.

[0394] As X 15 ~X 20 The fluorinated alkyl group may be, for example, -CFH2, -CF2H, -CF3, -CH2CF3, -CF2CF3, -CH2CF2CF3, -CF(CF3)2, etc. From the viewpoint of high oxidation resistance and the effect of improving safety, -CH2CF3 and -CH2CF2CF3 are preferred.

[0395] If X 15 ~X 20 At least one of them is a fluoroalkyl group, then -H, -F, -Cl, -CH3 or a fluoroalkyl group may be present on X 15 ~X 20 The substitution may be performed at only one site or at multiple sites. From the viewpoint of good solubility of the electrolyte salt, the substitution is preferably performed at 1 to 3 sites, and more preferably at 1 to 2 sites.

[0396] 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, among which -CH2CF3 and -CH2CF2CF3 are preferred. 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.

[0397] As the fluorine-containing lactone, in addition to the fluorine-containing lactone represented by the above formula, for example, the following formula (D) can also be mentioned: [Chemistry 49]

[0398] (In the formula, either A or B is CX 226 X 227 (X226 and X 227 Rf is the same or different, and is -H, -F, -Cl, -CF3, -CH3 or an alkylene group in which the hydrogen atom may be replaced 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 225 The same or different, all are -H, -F, -Cl or an alkyl group in which the hydrogen atom may be replaced by a halogen atom and may contain a heteroatom in the chain; n = 0 or 1) The fluorinated lactones shown.

[0399] As the fluorine-containing lactone represented by formula (D), the following formula (E) is preferably mentioned from the viewpoint of easy synthesis and good chemical stability: [Chemistry 50]

[0400] (In the formula, A, B, Rf 12 , X 221 , X 222 and X 223 Same as formula (D) The 5-membered ring structure shown; further, according to the combination of A and B, there is the following formula (F): [Chemistry 51]

[0401] (Where Rf 12 , X 221 , X 222 , X 223 , X 226 and X 227 Same as formula (D) The fluorinated lactone shown, and the following formula (G): [Chemistry 52]

[0402] (Where Rf 12 , X 221 , X 222 , X 223 , X 226 and X 227 Same as formula (D) The fluorinated lactones shown.

[0403] Among these substances, from the viewpoint of being able to exert excellent properties such as high dielectric constant and high withstand voltage, and improving the properties of the electrolyte solution in the present disclosure in terms of good solubility of the electrolyte salt and effective reduction of the internal resistance, the following can be cited: [Chemistry 53]

[0404] wait.

[0405] By containing a fluorinated cyclic carboxylic acid ester, effects such as improvement in ion conductivity, improvement in safety, and improvement in stability at high temperatures can be obtained.

[0406] Examples of the chain carboxylic acid ester include chain carboxylic acid esters having a total carbon atom count of 3 to 7 in the structural formula. 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.

[0407] Among them, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, and the like are preferred from the viewpoint of improving ion conductivity by reducing viscosity.

[0408] 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.

[0409] Examples of the boron-containing compound include boric acid esters such as trimethyl borate and triethyl borate, boric acid ethers, and alkylboranes.

[0410] Examples of the organic silicon-containing compound include (CH3)4-Si, (CH3)3-Si-Si(CH3)3, and silicone oil.

[0411] As the above-mentioned incombustible (flame retardant) agent, phosphate ester or phosphazene compound can be cited. As the above-mentioned phosphate ester, for example, fluorine-containing alkyl phosphate, non-fluorine-based alkyl phosphate, aryl phosphate, etc. can be cited. Among them, fluorine-containing alkyl phosphate is preferred in terms of being able to exert a non-combustible effect in a small amount.

[0412] Examples of the phosphazene compounds include methoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, dimethylaminopentafluorocyclotriphosphazene, diethylaminopentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene.

[0413] Specific examples of the fluorine-containing alkyl phosphate include fluorine-containing dialkyl phosphate disclosed in Japanese Patent Application Laid-Open No. 11-233141, cyclic alkyl phosphate disclosed in Japanese Patent Application Laid-Open No. 11-283669, and fluorine-containing trialkyl phosphate.

[0414] 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.

[0415] The surfactant may be any of a cationic surfactant, anionic surfactant, nonionic surfactant, and amphoteric surfactant. From the viewpoint of good cycle characteristics and rate characteristics, a surfactant containing a fluorine atom is preferred.

[0416] As such a fluorine atom-containing surfactant, for example, the following formula (30) is preferred: R 6 COO - M + (30) (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' are the same or different, and are H or an alkyl group with 1 to 3 carbon atoms)) The fluorinated carboxylate shown in the following formula (40): R 7 SO3 - M + (40) (Where Rf 7 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' are the same or different, and are H or an alkyl group with 1 to 3 carbon atoms)) Fluorinated sulfonates, etc.

[0417] The content of the surfactant in the electrolyte is preferably 0.01 to 2% by mass from the viewpoint of being able to reduce the surface tension of the electrolyte without reducing the charge-discharge cycle characteristics.

[0418] Examples of the dielectric constant-enhancing additive include sulfolane, methyl sulfolane, c -Butyrolactone, c -Valerolactone, etc.

[0419] Examples of the cycle characteristics and rate characteristics improving agent include methyl acetate, ethyl acetate, tetrahydrofuran, and 1,4-dioxane.

[0420] In addition, the electrolyte solution of the present disclosure may be further combined with a polymer material to form a gel electrolyte solution in a gel state (plasticized).

[0421] As such polymer materials, there can be cited conventionally known polyoxyethylene, polyoxypropylene, and their modified bodies (Japanese Patent Publication No. 8-222270, Japanese Patent Publication No. 2002-100405); polyacrylate polymers, polyacrylonitrile, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer and other fluororesins (Japanese Patent Publication No. 4-506726, Japanese Patent Publication No. 8-507407, Japanese Patent Publication No. 10-294131); composites of these fluororesins and hydrocarbon resins (Japanese Patent Publication No. 11-35765, Japanese Patent Publication No. 11-86630), etc. In particular, polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer are preferably used as polymer materials for gel electrolytes.

[0422] Furthermore, the electrolyte solution of the present disclosure may contain an ion conductive compound described in Japanese Patent Application No. 2004-301934.

[0423] The ion-conductive compound is an amorphous fluorinated polyether compound having a fluorinated group in a side chain represented by formula (101): A-(D)-B (101) [Wherein, D is formula (201): -(D1) n -(FAE) m -(AE) p -(Y) q - (201) (wherein D1 is an ether unit having a fluorine-containing ether group in the side chain represented by formula (10a): [Chemistry 54]

[0424] (wherein, Rf is a fluorinated ether group that may have a crosslinkable functional group, R 10 is a group or bond that bonds Rf to the main chain); FAE is an ether unit having a fluorinated alkyl group in the side chain represented by formula (10b): [Chemistry 55]

[0425] (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); AE is an ether unit represented by formula (10c): [Chemistry 56]

[0426] (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); Y is a unit comprising at least one of the formulae (10d-1) to (10d-3): [Chemistry 57] ; 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 particularly specified); A and B are the same or different and are hydrogen atoms, alkyl groups which may contain fluorine atoms and / or crosslinking functional groups, phenyl groups which may contain fluorine atoms and / or crosslinking functional groups, -COOH groups, -OR (R is a hydrogen atom or an alkyl group which may contain fluorine atoms and / or crosslinking functional groups), ester groups or carbonate groups (wherein, when the end of D is an oxygen atom, A and B are not -COOH groups, -OR, ester groups or carbonate groups).].

[0427] The electrolyte solution of the present disclosure may further 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.

[0428] 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.

[0429] As sulfolanes, sulfolane and / or sulfolane derivatives (hereinafter, including sulfolane, sometimes referred to as "sulfolanes") are preferred. As sulfolane derivatives, substances in which one or more of the hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are replaced by fluorine atoms or alkyl groups are preferred.

[0430] 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.

[0431] Examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n-butyl methyl sulfone, n-butyl ethyl sulfone, tert-butyl methyl sulfone, tert-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl Trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, bis(trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl n-propyl sulfone, difluoromethyl n-propyl sulfone, trifluoromethyl n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl n-butyl sulfone, trifluoroethyl tert-butyl sulfone, pentafluoroethyl n-butyl sulfone, pentafluoroethyl tert-butyl sulfone, etc.

[0432] Among them, 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, trifluoromethyl tert-butyl sulfone and the like are preferred from the viewpoint of high ion conductivity and high input and output.

[0433] The content of the sulfone compound is not particularly limited, and can be any value as long as it does not significantly damage the effect of the present disclosure. In the above-mentioned solvent 100 volume %, it is usually 0.3 volume % or more, preferably 0.5 volume % or more, and more preferably 1 volume % or more; and it is usually 40 volume % or less, preferably 35 volume % or less, and more preferably 30 volume % or less. If the content of the sulfone compound is within the above 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 can be within an appropriate range, the conductivity can be avoided from being reduced, and the input and output characteristics and charge and discharge rate characteristics of the non-aqueous electrolyte secondary battery can be within a suitable range.

[0434] From the viewpoint of improving output characteristics, the electrolyte of the present disclosure preferably further contains as an additive at least one compound (11) selected from lithium fluorophosphate salts (excluding LiPF6) and lithium salts having an S═O group.

[0435] When the compound (11) is used as an additive, it is preferable to use a compound other than the compound (11) as the electrolyte salt.

[0436] Examples of the lithium fluorophosphate salts include monofluoro lithium phosphate (LiPO 3 F), difluoro lithium phosphate (LiPO 2 F 2 ), and the like.

[0437] Examples of the lithium salts having an S═O group include lithium monofluorosulfonate (FSO3Li), lithium methyl sulfate (CH3OSO3Li), lithium ethyl sulfate (C2H5OSO3Li), and 2,2,2-trifluoroethyl lithium sulfate.

[0438] Among the compounds (11), LiPO2F2, FSO3Li and C2H5OSO3Li are preferred.

[0439] The content of the compound (11) 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.

[0440] Other additives may be further mixed into the electrolyte solution of the present disclosure as needed. Examples of other additives include metal oxides and glass.

[0441] The content of hydrogen fluoride (HF) in the electrolyte disclosed in the present invention is preferably 5 to 200 ppm. By containing HF, the film formation of the above-mentioned additives can be promoted. If the HF content is too little, the film forming ability on the negative electrode is reduced, and there is a tendency for the characteristics of the electrochemical device to be reduced. In addition, if the HF content is too much, there is a tendency for the oxidation resistance of the electrolyte to be reduced due to the influence of HF. Even if the electrolyte disclosed in the present invention contains HF in the above range, it will not reduce the high temperature storage property and capacity recovery rate of the electrochemical device.

[0442] The HF content is more preferably 10 ppm or more, and further preferably 20 ppm or more. Furthermore, the HF content is more preferably 100 ppm or less, further preferably 80 ppm or less, and particularly preferably 50 ppm or less.

[0443] The HF content can be determined by neutralization titration.

[0444] The electrolyte of the present disclosure can be prepared by any method using the above-mentioned components.

[0445] The electrolyte of the present disclosure has the characteristic of suppressing electrodeposition of alkali metals and can be suitably used in a secondary battery having an electrode having a negative electrode material containing silicon and carbon. A secondary battery having such a negative electrode, a positive electrode and the electrolyte of the present disclosure is also an aspect of the present disclosure.

[0446] <Negative electrode> In the present disclosure, the negative electrode preferably includes a negative electrode material layer and a current collector.

[0447] In the present disclosure, the negative electrode material contains silicon and carbon, and particularly preferably contains Si and / or SiOa (0<a<2), and a carbon compound.

[0448] In the present disclosure, the “negative electrode material” refers to a material that contributes to electrical conductivity, and refers to the negative electrode active material and / or the conductive auxiliary agent described in detail below.

[0449] (Negative electrode active material) The negative electrode active material used in the present disclosure preferably contains silicon as a constituent element. By including silicon as a constituent element, a high-capacity battery can be produced.

[0450] As particles containing silicon, preferably silicon particles (Si), silicon oxide particles represented by the general formula SiOa (0 < a < 2), particles having a structure in which silicon particles are dispersed in a silicon-based compound, or mixtures thereof (hereinafter, they are sometimes collectively referred to as "silicon-containing particles"). By using them, a negative electrode mixture for lithium ion secondary batteries having higher initial charge and discharge efficiency, high capacity, and excellent cycle characteristics can be obtained.

[0451] Among them, at least one selected from Si and SiOa (0<a<2) is preferred.

[0452] Silicon oxide in the present disclosure is a general term for amorphous silicon oxides, and silicon oxide before disproportionation is represented by the general formula SiOa (0<a<2). a is preferably 0.5≤a≤1.6, more preferably 0.8≤a<1.6, and further preferably 0.8≤a<1.3.

[0453] This silicon oxide can be obtained, for example, by heating a mixture of silicon dioxide and metallic silicon to generate silicon monoxide gas, and then cooling and precipitating the gas.

[0454] The particles having a structure in which silicon microparticles are dispersed in a silicon-based compound can be obtained, for example, by a method of calcining a mixture of silicon microparticles and a silicon-based compound, or by heat-treating silicon oxide particles before disproportionation represented by the general formula SiOa in an inert, non-oxidizing atmosphere such as argon at a temperature of 400°C or more, preferably 800 to 1100°C, to obtain a disproportionation reaction. In particular, the material obtained by the latter method is preferred because the silicon microcrystals can be uniformly dispersed. By the disproportionation reaction as described above, the size of the silicon nanoparticles can be 1 to 100 nm. It should be noted that the silicon oxide in the particles having a structure in which silicon nanoparticles are dispersed in silicon oxide is preferably silicon dioxide.

[0455] It should be noted that it was possible to confirm, using a transmission electron microscope, that silicon nanoparticles (crystals) were dispersed in amorphous silicon oxide.

[0456] The physical properties of the silicon-containing particles can be appropriately selected according to the target composite particles. For example, the average particle size is preferably 0.1 to 50 m m, the lower limit is more preferably 0.2 m m or more, more preferably 0.5 m The upper limit is more preferably 30 m m or less, more preferably 20 m In addition, the average particle size in the present invention is represented by the weight average particle size obtained by the particle size distribution measurement based on the laser diffraction method.

[0457] The BET specific surface area of ​​the silicon-containing particles is preferably 0.5 to 100 m2 / g, more preferably 1 to 20 m 2 / g. If the BET specific surface area is 0.5m 2 / g or more, there is no need to worry about the decrease in adhesion when applied to the electrode and the decrease in battery characteristics. 2 / g or less, the proportion of silicon dioxide on the particle surface becomes large, and when used as a negative electrode material for a lithium ion secondary battery, the battery capacity does not decrease.

[0458] In addition, the silicon-containing particles may be coated with carbon to impart conductivity, thereby improving battery characteristics. Methods for imparting conductivity include mixing with conductive particles such as graphite, coating the surface of the silicon-containing particles with a carbon coating, and a combination of the two. A coating method using a carbon coating is preferred, and a chemical vapor deposition (CVD) method is more preferred as a coating method.

[0459] In addition, as the negative electrode active material, a carbon compound such as graphite powder may be used together with Si and / or SiOa (0<a<2).

[0460] Examples of the carbon compound include natural graphite, artificial carbonaceous materials, artificial graphite materials, thermal decomposition products of organic materials such as natural graphite, coal-based coke, petroleum-based coke, coal-based asphalt, petroleum-based asphalt, or materials obtained by oxidation treatment of these asphalts, needle coke, pitch coke and carbon materials obtained by partially graphitizing these asphalts, furnace black, acetylene black, Ketjen black, and asphalt-based carbon fibers, and carbonizable organic materials (for example, coal tar pitch ranging from soft pitch to hard pitch, or coal-based heavy oils such as dry distillation liquefied oil; straight-run heavy oils such as atmospheric residual oil and vacuum residual oil; decomposed petroleum heavy oils such as ethylene tar produced as a by-product during thermal decomposition of crude oil, naphtha, etc.; and aromatic hydrocarbons such as acenaphthylene, decacyclene, anthracene, and phenanthrene; N-ring compounds such as phenazine and acridine; thiophene, bithiazine, and dithiophene. S-ring compounds such as phene; polyphenylenes such as biphenyl and terphenyl; polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, and their insoluble products; nitrogen-containing organic polymers such as polyacrylonitrile and polypyrrole; sulfur-containing organic polymers such as polythiophene and polystyrene; natural polymers such as polysaccharides represented by cellulose, lignin, mannan, polygalacturonic acid, chitosan, and sucrose; thermoplastic resins such as polyphenylene sulfide and polyphenylene ether; thermosetting resins such as furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin) and their carbides, or solutions obtained by dissolving carbonizable organic matter in low molecular weight organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and their carbides} carbonaceous materials obtained by heat treatment at least once in the range of 400 to 3200°C, etc.

[0461] Regarding the carbon compound, for example, the average particle size is preferably 1 to 100 m m, the lower limit is more preferably 3 m m or more, more preferably 5 m The upper limit is more preferably 80 m m or less, more preferably 20 m In addition, the average particle diameter in this disclosure is represented by the weight average particle diameter obtained by the particle size distribution measurement based on the laser diffraction method.

[0462] The BET specific surface area of ​​the carbon compound is preferably 0.1 to 50 m 2 / g, more preferably 1 to 20 m 2 / g. If the BET specific surface area is 0.1m 2 / g or more, there is no need to worry about the decrease in adhesion when applied to the electrode and the decrease in battery characteristics. 2 / g or less, the battery capacity will not decrease when used as a negative electrode material for a lithium ion secondary battery.

[0463] The mass ratio of the silicon-containing particles to the carbon compound is preferably 1 / 99 to 99 / 1, more preferably 5 / 95 to 95 / 5, and further preferably 10 / 90 to 90 / 10.

[0464] The mass ratio of Si and / or SiOa (0<a<2) to the carbon compound is preferably 1 / 99 to 99 / 1, more preferably 5 / 95 to 95 / 5, and further preferably 10 / 90 to 90 / 10.

[0465] The content of the negative electrode active material in the negative electrode material layer is preferably 80.0 to 99.9% by mass, more preferably 90.0 to 99.0% by mass, based on the mass of the solid content in the negative electrode mixture.

[0466] The content of the silicon-containing particles in the negative electrode material layer is preferably 20 to 40% by mass, more preferably 25 to 35% by mass, relative to the mass of the solid content in the negative electrode mixture.

[0467] The content of the carbon compound in the negative electrode material layer is preferably 40 to 60% by mass, more preferably 65 to 75% by mass, relative to the mass of the solid content in the negative electrode mixture.

[0468] (Conductive additive) The negative electrode material layer may further contain a conductive aid. In particular, when the negative electrode active material does not contain a carbon compound, it is preferable to contain a conductive aid.

[0469] As the conductive auxiliary agent, any known conductive material can be used. Specific examples include metal materials such as copper and nickel; graphites such as natural graphite and artificial graphite; carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; and carbon compounds such as amorphous carbon such as needle coke, carbon nanotubes, fullerene, and VGCF. It should be noted that these can be used alone or in any combination and ratio.

[0470] The conductive additive preferably has an average particle size of 0.05 to 100 m m, the lower limit is more preferably 0.1 m m or more, more preferably 0.15 m The upper limit is more preferably 10 m m or less, more preferably 5 m In addition, the average particle size in the present invention is represented by the weight average particle size obtained by the particle size distribution measurement based on the laser diffraction method.

[0471] The BET specific surface area of ​​the conductive additive is preferably 0.1 to 1000 m 2 / g, more preferably 0.5 to 500 m 2 / g.

[0472] As described above, the carbon compound can be used as an active material and can also be used as a conductive auxiliary agent.

[0473] The conductive aid is generally 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more in the negative electrode material layer, and is generally used in an amount containing 50% by mass or less, preferably 30% by mass or less, and more preferably 15% by mass or less. If the content is below this range, the conductivity is sometimes insufficient. On the contrary, if the content is above this range, the battery capacity is sometimes reduced.

[0474] (Binder) The negative electrode material layer preferably contains a binder.

[0475] The binder preferably contains a fluorine-containing copolymer containing vinylidene fluoride (VdF) units and other monomer units except VdF.

[0476] The other monomers may be fluorinated monomers or non-fluorinated monomers.

[0477] Examples of the fluorinated monomer (excluding VdF) include tetrafluoroethylene (TFE), vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene (CTFE), fluoroalkyl vinyl ether, hexafluoropropylene (HFP), (perfluoroalkyl)ethylene, 2,3,3,3-tetrafluoropropylene, and trans-1,3,3,3-tetrafluoropropylene.

[0478] The fluoroalkyl vinyl ether is preferably a fluoroalkyl vinyl ether having a fluoroalkyl group having 1 to 5 carbon atoms, and more preferably at least one selected from perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether).

[0479] The fluorinated monomer is preferably at least one selected from TFE, CTFE, 2,3,3,3-tetrafluoropropylene, HFP and fluoroalkyl vinyl ether, more preferably at least one selected from TFE and HFP, and particularly preferably TFE.

[0480] The fluorinated monomer (excluding VdF) may or may not have a polar group.

[0481] Examples of the non-fluorinated monomer include non-fluorinated monomers having no polar group such as ethylene and propylene, and non-fluorinated monomers having a polar group (hereinafter sometimes referred to as polar group-containing monomers).

[0482] When a non-fluorinated monomer having a polar group is used as the non-fluorinated monomer, a polar group is introduced into the fluorinated copolymer, thereby obtaining further excellent adhesion between the coating layer and the metal foil. As the polar group, it is preferably at least one selected from a carbonyl-containing group, an epoxy group, a hydroxyl group, a sulfonic acid group, a sulfuric acid group, a phosphoric acid group, an amino group, an amide group and an alkoxy group, more preferably at least one selected from a carbonyl-containing group, an epoxy group and a hydroxyl group, and further preferably a carbonyl-containing group.

[0483] The above-mentioned hydroxyl group does not include a hydroxyl group constituting a part of the above-mentioned carbonyl-containing group. In addition, the above-mentioned amino group refers to a monovalent functional group formed by removing hydrogen from ammonia, a primary amine or a secondary amine.

[0484] The above-mentioned carbonyl-containing group refers to a functional group having a carbonyl group (-C(=O)-). As the above-mentioned carbonyl-containing group, a group represented by the general formula: -COOR (R represents a hydrogen atom, an alkyl group or a hydroxyalkyl group) or a carboxylic anhydride group is preferred, and a group represented by the general formula: -COOR is more preferred. The number of carbon atoms of the alkyl group and the hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and further preferably 1 to 3. As the group represented by the general formula: -COOR, specifically, -COOCH2CH2OH, -COOCH2CH(CH3)OH, -COOCH(CH3)CH2OH, -COOH, -COOCH3, -COOC2H5, etc. can be cited.

[0485] When the group represented by the general formula: -COOR is -COOH or includes -COOH, -COOH may be a carboxylate such as a metal carboxylate or an ammonium carboxylate.

[0486] In addition, the carbonyl-containing group may be General formula: -X-COOR (X is an atomic group with a molecular weight of 500 or less and a main chain consisting of 1 to 20 atoms, and R is a hydrogen atom, an alkyl group or a hydroxyalkyl group). The number of carbon atoms in the alkyl group and the hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and even more preferably 1 to 3.

[0487] As the above-mentioned amide group, a group represented by the general formula: -CO-NRR' (R and R' independently represent a hydrogen atom or a substituted or unsubstituted alkyl group), or a bond represented by the general formula: -CO-NR''- (R'' represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted phenyl group is preferred.

[0488] Examples of the polar group-containing monomer include: (meth) hydroxyalkyl acrylates such as hydroxyethyl acrylate and 2-hydroxypropyl acrylate; alkylene malonates such as dimethyl methylene malonate; vinyl carboxyalkyl ethers such as vinyl carboxymethyl ether and vinyl carboxyethyl ether; (meth) carboxyalkyl acrylates such as 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate; (meth) acryloyloxyalkyl dicarboxylates such as monoacryloxyethyl succinate, monoacryloxypropyl succinate, monomethacryloxyethyl succinate, monoacryloxyethyl phthalate, and monomethacryloxyethyl phthalate; and monoesters of unsaturated dibasic acids such as monomethyl maleate, monoethyl maleate, monomethyl citraconic acid, and monoethyl citraconic acid. General formula (50): [Chemistry 58]

[0489] (Where R 11 ~R 13 R independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 14 represents a single bond or a hydrocarbon group having 1 to 8 carbon atoms. 1 represents inorganic cations and / or organic cations. ) The monomer (50) shown; Unsaturated dibasic acids such as maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, etc.; etc.

[0490] As the polar group-containing monomer unit which may be contained in the fluorinated copolymer, a unit based on a monomer (50) represented by the general formula (50) is preferred.

[0491] In the general formula (50), Y1 represents an inorganic cation and / or an organic cation. Examples of inorganic cations include cations such as H, Li, Na, K, Mg, Ca, Al, and Fe. Examples of organic cations include NH4, NH3R 15 NH2R 15 2. NHR 153. NR 15 4(R 15 and independently represent an alkyl group having 1 to 4 carbon atoms. ) and other cations. As Y1, H, Li, Na, K, Mg, Ca, Al, NH4 are preferred, H, Li, Na, K, Mg, Al, NH4 are more preferred, H, Li, Al, NH4 are further preferred, and H is particularly preferred. It should be noted that, for convenience, symbols and valences are omitted in the description of specific examples of inorganic cations and organic cations.

[0492] In the general formula (50), R 11 ~R 13 R independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. The hydrocarbon group is a monovalent hydrocarbon group. The number of carbon atoms of the hydrocarbon group is preferably 4 or less. Examples of the hydrocarbon group include alkyl, alkenyl, and alkynyl groups having the above-mentioned carbon atoms, and methyl or ethyl is preferred. 11 and R 12 R 13 Preferred is a hydrogen atom or a methyl group.

[0493] In the general formula (50), R 14 represents a single bond or a hydrocarbon group having 1 to 8 carbon atoms. The above hydrocarbon group is a divalent hydrocarbon group. The number of carbon atoms of the above hydrocarbon group is preferably 4 or less. Examples of the above hydrocarbon group include alkylene groups and alkenylene groups having the above carbon atoms, among which at least one selected from the group consisting of methylene, ethylene, ethylidene, propylidene and isopropylidene is preferred, and methylene is more preferred.

[0494] The monomer (50) is preferably at least one selected from (meth)acrylic acid and salts thereof, vinylacetic acid (3-butenoic acid) and salts thereof, 3-pentenoic acid and salts thereof, 4-pentenoic acid and salts thereof, 3-hexenoic acid and salts thereof, 4-heptenoic acid and salts thereof, and 5-hexenoic acid and salts thereof.

[0495] As the other monomer, at least one selected from the group consisting of TFE, CTFE, (meth)acrylic acid, 2,3,3,3-tetrafluoropropylene, HFP and fluoroalkyl vinyl ether is preferred. (Meth)acrylic acid includes acrylic acid and methacrylic acid.

[0496] The content of other monomer units in the fluorinated copolymer is preferably 0.0001 to 50.0 mol %, more preferably 0.01 mol % or more, further preferably 0.10 mol % or more, more preferably 45.0 mol % or less, further preferably 40.0 mol % or less, particularly preferably 35.0 mol % or less, based on all monomer units.

[0497] The content of the VdF unit in the fluorinated copolymer is 50.0 to 99.9999 mol %, more preferably 55.0 mol % or more, further preferably 60.0 mol % or more, particularly preferably 65.0 mol % or more, more preferably 99.99 mol % or less, further preferably 99.90 mol % or less, based on all monomer units.

[0498] When the fluorinated copolymer contains a fluorinated monomer unit as another monomer unit, the content of the fluorinated monomer unit is preferably 0.0001 to 50.0 mol %, more preferably 2.0 mol % or more, further preferably 3.0 mol % or more, particularly preferably 4.0 mol % or more, more preferably 45.0 mol % or less, further preferably 40.0 mol % or less, particularly preferably 35.0 mol % or less, relative to all monomer units.

[0499] When the fluorinated copolymer contains a fluorinated monomer unit as another monomer unit, the content of the VdF unit of the fluorinated copolymer is 50.0 to 99.999 mol %, more preferably 55.0 mol % or more, further preferably 60.0 mol % or more, particularly preferably 65.0 mol % or more, more preferably 98.0 mol % or less, further preferably 97.0 mol % or less, particularly preferably 96.0 mol % or less, relative to all the monomer units.

[0500] When the fluorinated copolymer contains non-fluorinated monomer units such as polar group-containing monomers as other monomer units, the content of the non-fluorinated monomer units is preferably 0.0001 to 50.0 mol %, more preferably 0.01 mol % or more, further preferably 0.10 mol % or more, more preferably 5.0 mol % or less, further preferably 3.0 mol % or less, and particularly preferably 1.5 mol % or less relative to all monomer units.

[0501] When the fluorinated copolymer contains non-fluorinated monomer units as other monomer units, the content of the VdF unit of the fluorinated copolymer is preferably 50.0 to 99.999 mol %, more preferably 95.0 mol % or more, further preferably 97.0 mol % or more, particularly preferably 98.5 mol % or more; more preferably 99.99 mol % or less, further preferably 99.90 mol % or less, relative to all monomer units.

[0502] In the present disclosure, the composition of the fluorinated copolymer can be determined, for example, by 19F-NMR testing. In addition, when the fluorinated copolymer contains a polar group-containing monomer unit as other monomer units, the content of the polar group-containing monomer unit, for example, when the polar group is an acid group such as a carboxylic acid, can be determined by acid-base titration of the acid group.

[0503] The weight average molecular weight (in terms of polystyrene) of the fluorinated copolymer is preferably 10,000 to 3,000,000, more preferably 30,000 or more, further preferably 50,000 or more, particularly preferably 200,000 or more; more preferably 2,400,000 or less, further preferably 2,200,000 or less, particularly preferably 2,000,000 or less. The weight average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.

[0504] The number average molecular weight (in terms of polystyrene) of the fluorinated copolymer is preferably 7,000 to 1,500,000, more preferably 21,000 or more, further preferably 35,000 or more, more preferably 1,400,000 or less, further preferably 1,200,000 or less, particularly preferably 1,100,000 or less. The number average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.

[0505] Examples of the fluorinated copolymer include VdF / (meth)acrylic acid copolymers, VdF / TFE copolymers, VdF / HFP copolymers, VdF / fluoroalkyl vinyl ether copolymers, VdF / TFE / HFP copolymers, VdF / 2,3,3,3-tetrafluoropropylene copolymers, VdF / TFE / 2,3,3,3-tetrafluoropropylene copolymers, VdF / TFE / (meth)acrylic acid copolymers, VdF / HFP / (meth)acrylic acid copolymers, VdF / CTFE copolymers, VdF / TFE / 4- Pentenoic acid copolymer, VdF / TFE / 3-butenoic acid copolymer, VdF / TFE / HFP / (meth)acrylic acid copolymer, VdF / TFE / HFP / 4-pentenoic acid copolymer, VdF / TFE / HFP / 3-butenoic acid copolymer, VdF / TFE / 2-carboxyethyl acrylate copolymer, VdF / TFE / HFP / 2-carboxyethyl acrylate copolymer, VdF / TFE / monoacryloyloxyethyl succinate copolymer, VdF / TFE / HFP / monoacryloyloxyethyl succinate copolymer, etc.

[0506] The fluorinated copolymer is preferably at least one selected from the group consisting of VdF / TFE copolymer, VdF / CTFE copolymer, VdF / (meth)acrylic acid copolymer, VdF / 2,3,3,3-tetrafluoropropylene copolymer, VdF / HFP copolymer and VdF / fluoroalkyl vinyl ether copolymer.

[0507] The VdF / TFE copolymer contains VdF units and TFE units. By using the VdF / TFE copolymer as a copolymer, a negative electrode mixture can be formed very easily, and a negative electrode mixture with excellent slurry stability can be obtained, and a coating layer with excellent softness can be formed. As the content of the VdF unit, relative to all monomer units of the VdF / TFE copolymer, it is preferably 50.0 to 95.0 mol%, more preferably 55.0 mol% or more, and further preferably 60.0 mol% or more; more preferably 92.0 mol% or less, and further preferably 89.0 mol% or less. As the content of the TFE unit, relative to all monomer units of the VdF / TFE copolymer, it is preferably 50.0 to 5.0 mol%, more preferably 45.0 mol% or less, and further preferably 40.0 mol% or less; more preferably 8.0 mol% or more, and further preferably 11.0 mol% or more.

[0508] The VdF / TFE copolymer may also include units based on monomers copolymerizable with VdF and TFE (wherein, excluding VdF and TFE) in addition to VdF units and TFE units. From the viewpoint of resistance to electrolyte swelling, the content of units based on monomers copolymerizable with VdF and TFE is preferably less than 3.0 mol % relative to all monomer units of the VdF / TFE copolymer.

[0509] Examples of the monomer copolymerizable with VdF and TFE include the above-mentioned fluorinated monomers, the above-mentioned non-fluorinated monomers, etc. The monomer copolymerizable with VdF and TFE is preferably at least one selected from fluorinated monomers and polar group-containing monomers, and more preferably at least one selected from HFP, 2,3,3,3-tetrafluoropropylene, and monomer (4).

[0510] The weight average molecular weight (polystyrene equivalent) of the VdF / TFE copolymer is preferably 50,000 to 2,000,000, more preferably 80,000 to 1,700,000, and even more preferably 100,000 to 1,500,000.

[0511] The number average molecular weight (polystyrene equivalent) of the VdF / TFE copolymer is 35,000 to 1,400,000, more preferably 40,000 to 1,300,000, and even more preferably 50,000 to 1,200,000.

[0512] The VdF / CTFE copolymer contains VdF units and CTFE units. By using the VdF / CTFE copolymer as a copolymer, a negative electrode mixture can be formed very easily, and a coating layer that is extremely firmly bonded to the metal foil can be formed. As the content of the VdF unit, relative to all monomer units of the VdF / CTFE copolymer, it is preferably 80.0 to 98.0 mol%, more preferably 85.0 mol% or more, and further preferably 90.0 mol% or more; more preferably 97.5 mol% or less, and further preferably 97.0 mol% or less. As the content of the CTFE unit, relative to all monomer units of the VdF / CTFE copolymer, it is preferably 20.0 to 2.0 mol%, more preferably 15.0 mol% or less, and further preferably 10.0 mol% or less; more preferably 2.5 mol% or more, and further preferably 3.0 mol% or more.

[0513] In addition to VdF units and CTFE units, VdF / CTFE copolymers may also include units based on monomers copolymerizable with VdF and CTFE (wherein, VdF and CTFE are not included). From the viewpoint of resistance to electrolyte swelling, the content of units based on monomers copolymerizable with VdF and CTFE is preferably 3.0 mol% or less relative to all monomer units of the VdF / CTFE copolymer.

[0514] Examples of the monomer copolymerizable with VdF and CTFE include the above-mentioned fluorinated monomers, the above-mentioned non-fluorinated monomers, etc. The monomer copolymerizable with VdF and CTFE is preferably at least one selected from fluorinated monomers and polar group-containing monomers, more preferably at least one selected from TFE, HFP, 2,3,3,3-tetrafluoropropylene and monomer (4), and even more preferably TFE.

[0515] The weight average molecular weight (polystyrene equivalent) of the VdF / CTFE copolymer is preferably 50,000 to 2,000,000, more preferably 80,000 to 1,700,000, and even more preferably 100,000 to 1,500,000.

[0516] The number average molecular weight (polystyrene equivalent) of the VdF / CTFE copolymer is preferably 35,000 to 1,400,000, more preferably 40,000 to 1,300,000, and even more preferably 50,000 to 1,200,000.

[0517] The VdF / (meth)acrylic acid copolymer contains a VdF unit and a (meth)acrylic acid unit. By using the VdF / (meth)acrylic acid copolymer as a copolymer, a negative electrode mixture can be formed very easily, and a coating layer that is extremely firmly bonded to the metal foil can be formed. The content of the (meth)acrylic acid unit is preferably 0.0001 to 5.0 mol %, more preferably 0.01 to 3.0 mol %, and further preferably 0.10 to 1.5 mol % relative to the total monomer units.

[0518] The content of the VdF unit in the VdF / (meth)acrylic acid copolymer is preferably 95.0 to 99.9999 mol %, more preferably 97.0 to 99.99 mol %, and further preferably 98.5 to 99.90 mol % based on all monomer units.

[0519] The weight average molecular weight (polystyrene equivalent) of the VdF / (meth)acrylic acid copolymer is preferably 50,000 to 3,000,000, more preferably 80,000 or more, further preferably 100,000 or more, particularly preferably 200,000 or more; more preferably 2,400,000 or less, further preferably 2,200,000 or less, particularly preferably 2,000,000 or less.

[0520] The number average molecular weight (polystyrene equivalent) of the VdF / (meth)acrylic acid copolymer is preferably 20,000 to 1,500,000, more preferably 40,000 or more, further preferably 70,000 or more, particularly preferably 140,000 or more; more preferably 1,400,000 or less, further preferably 1,200,000 or less, particularly preferably 1,100,000 or less.

[0521] The VdF / 2,3,3,3-tetrafluoropropylene copolymer contains VdF units and 2,3,3,3-tetrafluoropropylene units. By using the VdF / 2,3,3,3-tetrafluoropropylene copolymer as a copolymer, it is very easy to form a negative electrode mixture, and it is possible to form a coating layer with excellent flexibility and conductivity. As for the content of the VdF unit, relative to all monomer units of the VdF / 2,3,3,3-tetrafluoropropylene copolymer, it is preferably 50.0 to 98.0 mol%, more preferably 55.0 mol% or more, further preferably 60.0 mol% or more, and particularly preferably 65.0 mol% or more; more preferably 97.0 mol% or less, and further preferably 96.0 mol% or less. The content of the 2,3,3,3-tetrafluoropropylene unit is preferably 2.0 to 50.0 mol %, more preferably 3.0 mol % or more, further preferably 4.0 mol % or more, more preferably 45.0 mol % or less, further preferably 40.0 mol % or less, and particularly preferably 35.0 mol % or less, relative to all monomer units of the VdF / TFE copolymer.

[0522] The VdF / 2,3,3,3-tetrafluoropropylene copolymer may further include units based on monomers copolymerizable with VdF and 2,3,3,3-tetrafluoropropylene (excluding VdF and 2,3,3,3-tetrafluoropropylene) in addition to VdF units and 2,3,3,3-tetrafluoropropylene units. From the viewpoint of resistance to swelling of the electrolyte, the content of the units based on monomers copolymerizable with VdF and 2,3,3,3-tetrafluoropropylene is preferably 3.0 mol% or less relative to all monomer units of the VdF / 2,3,3,3-tetrafluoropropylene copolymer.

[0523] Examples of monomers copolymerizable with VdF and 2,3,3,3-tetrafluoropropylene include the above-mentioned fluorinated monomers, the above-mentioned non-fluorinated monomers, etc. Examples of monomers copolymerizable with VdF and 2,3,3,3-tetrafluoropropylene include at least one selected from fluorinated monomers and polar group-containing monomers, and more preferably at least one selected from TFE, HFP, and monomer (50).

[0524] The weight average molecular weight (polystyrene equivalent) of the VdF / 2,3,3,3-tetrafluoropropylene copolymer is preferably 10,000 to 2,000,000, more preferably 30,000 to 1,700,000, and even more preferably 5,000 to 1,500,000.

[0525] The number average molecular weight (polystyrene equivalent) of the VdF / 2,3,3,3-tetrafluoropropylene copolymer is preferably 7,000 to 1,400,000, more preferably 21,000 to 1,300,000, and even more preferably 35,000 to 1,200,000.

[0526] The VdF / HFP copolymer contains VdF units and HFP units. By using the VdF / HFP copolymer as a copolymer, a negative electrode mixture can be formed very easily, and a coating layer that is extremely firmly bonded to the metal foil can be formed. As the content of the VdF unit, relative to all monomer units of the VdF / HFP copolymer, it is preferably 80.0 to 98.0 mol%, more preferably 83.0 mol% or more, further preferably 85.0 mol% or more, more preferably 97.0 mol% or less, and further preferably 96.0 mol% or less. As the content of the HFP unit, relative to all monomer units of the VdF / HFP copolymer, it is preferably 20.0 to 2.0 mol%, more preferably 17.0 mol% or less, and further preferably 15.0 mol% or less; more preferably 3.0 mol% or more, and further preferably 4.0 mol% or more.

[0527] The VdF / HFP copolymer may also include units based on monomers (wherein, excluding VdF and HFP) that can copolymerize with VdF and HFP, in addition to VdF units and HFP units. From the viewpoint of resistance to electrolyte swelling, the content of units based on monomers that can copolymerize with VdF and HFP is preferably less than 3.0 mol % relative to all monomer units of the VdF / HFP copolymer.

[0528] Examples of the monomer copolymerizable with VdF and HFP include the above-mentioned fluorinated monomers, the above-mentioned non-fluorinated monomers, etc. The monomer copolymerizable with VdF and HFP is preferably at least one selected from fluorinated monomers and polar group-containing monomers, more preferably at least one selected from TFE, 2,3,3,3-tetrafluoropropylene and monomer (50), and still more preferably monomer (50).

[0529] The weight average molecular weight (polystyrene equivalent) of the VdF / HFP copolymer is preferably 50,000 to 2,000,000, more preferably 80,000 to 1,700,000, and even more preferably 100,000 to 1,500,000.

[0530] The number average molecular weight (polystyrene equivalent) of the VdF / HFP copolymer is preferably 35,000 to 1,400,000, more preferably 40,000 to 1,300,000, and even more preferably 50,000 to 1,200,000.

[0531] The VdF / fluoroalkyl vinyl ether copolymer contains VdF units and fluoroalkyl vinyl ether units. As the content of the VdF unit, relative to all the monomer units of the VdF / fluoroalkyl vinyl ether copolymer, it is preferably 80.0 to 98.0 mol%, more preferably 83.0 mol% or more, and further preferably 85.0 mol% or more; more preferably 97.0 mol% or less, and further preferably 96.0 mol% or less. As the content of the fluoroalkyl vinyl ether unit, relative to all the monomer units of the VdF / fluoroalkyl vinyl ether copolymer, it is preferably 20.0 to 2.0 mol%, more preferably 17.0 mol% or less, and further preferably 15.0 mol% or less; more preferably 3.0 mol% or more, and further preferably 4.0 mol% or more.

[0532] VdF / fluoroalkyl vinyl ether copolymers may also include units based on monomers copolymerizable with VdF and fluoroalkyl vinyl ether (wherein, excluding VdF and fluoroalkyl vinyl ether) in addition to VdF units and fluoroalkyl vinyl ether units. From the viewpoint of resistance to electrolyte swelling, the content of units based on monomers copolymerizable with VdF and fluoroalkyl vinyl ether is preferably less than 3.0 mol% relative to all monomer units of VdF / fluoroalkyl vinyl ether copolymers.

[0533] Examples of monomers copolymerizable with VdF and fluoroalkyl vinyl ether include the above-mentioned fluorinated monomers, the above-mentioned non-fluorinated monomers, etc. Examples of monomers copolymerizable with VdF and fluoroalkyl vinyl ether include at least one selected from fluorinated monomers and polar group-containing monomers, more preferably at least one selected from TFE, 2,3,3,3-tetrafluoropropylene and monomer (4), and still more preferably monomer (50).

[0534] The weight average molecular weight (polystyrene equivalent) of the VdF / fluoroalkyl vinyl ether copolymer is preferably 50,000 to 2,000,000, more preferably 80,000 to 1,700,000, and even more preferably 100,000 to 1,500,000.

[0535] The number average molecular weight (polystyrene equivalent) of the VdF / fluoroalkyl vinyl ether copolymer is preferably 35,000 to 1,400,000, more preferably 40,000 to 1,300,000, and even more preferably 50,000 to 1,200,000.

[0536] The binder preferably further contains polyvinylidene fluoride (PVdF). PVdF is a polymer containing VdF units, and is a polymer different from the above-mentioned fluorine-containing copolymer. PVdF may be a VdF homopolymer consisting only of VdF units, or a polymer containing VdF units and units based on a monomer copolymerizable with VdF.

[0537] In the above PVdF, the monomer copolymerizable with VdF is preferably a monomer other than tetrafluoroethylene (TFE). That is, PVdF preferably does not contain a TFE unit.

[0538] In the above-mentioned PVdF, as the monomer that can be copolymerized with VdF, fluorinated monomers, non-fluorinated monomers, etc. can be mentioned, preferably fluorinated monomers. As the above-mentioned fluorinated monomers, vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene (CTFE), fluoroalkyl vinyl ether, hexafluoropropylene (HFP), (perfluoroalkyl) ethylene, 2,3,3,3-tetrafluoropropylene, trans-1,3,3,3-tetrafluoropropylene, etc. can be mentioned. As the above-mentioned non-fluorinated monomers, ethylene, propylene, etc. can be mentioned.

[0539] In the above PVdF, the monomer copolymerizable with VdF is preferably at least one fluorinated monomer selected from CTFE, fluoroalkyl vinyl ether, HFP and 2,3,3,3-tetrafluoropropylene, and more preferably at least one fluorinated monomer selected from CTFE, HFP and fluoroalkyl vinyl ether.

[0540] In the above PVdF, the content of the monomer units copolymerizable with VdF is preferably 0 to 5.0 mol %, more preferably 0 to 3.0 mol %, relative to all monomer units. In the above PVdF, the content of the fluorinated monomer units copolymerizable with VdF is preferably less than 5.0 mol %, more preferably less than 3.0 mol %, and further preferably less than 1.0 mol %, relative to all monomer units.

[0541] In the present disclosure, the composition of PVdF can be, for example, 19 F-NMR test was used to determine the

[0542] The PVdF may have a polar group. As the polar group, there is no particular limitation as long as it is a polar functional group, preferably at least one selected from a carbonyl-containing group, an epoxy group, a hydroxyl group, a sulfonic acid group, a sulfuric acid group, a phosphoric acid group, an amino group, an amide group and an alkoxy group, more preferably at least one selected from a carbonyl-containing group, an epoxy group and a hydroxyl group, and further preferably a carbonyl-containing group. The hydroxyl group does not include a hydroxyl group that constitutes a part of the carbonyl-containing group. In addition, the amino group refers to a monovalent functional group formed by removing hydrogen from ammonia, a primary amine or a secondary amine.

[0543] The above-mentioned carbonyl-containing group refers to a functional group having a carbonyl group (-C(=O)-). As the above-mentioned carbonyl-containing group, a group represented by the general formula: -COOR (R represents a hydrogen atom, an alkyl group or a hydroxyalkyl group) or a carboxylic anhydride group is preferred, and a group represented by the general formula: -COOR is more preferred. The number of carbon atoms of the alkyl group and the hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and further preferably 1 to 3. As the group represented by the general formula: -COOR, specifically, -COOCH2CH2OH, -COOCH2CH(CH3)OH, -COOCH(CH3)CH2OH, -COOH, -COOCH3, -COOC2H5, etc. can be mentioned. When the group represented by the general formula: -COOR is -COOH or contains -COOH, -COOH can be a carboxylate such as a metal carboxylate or an ammonium carboxylate.

[0544] In addition, as the above-mentioned carbonyl-containing group, a group represented by the general formula: -X-COOR (the main chain of X is composed of 2 to 15 atoms, and the molecular weight of the atomic group represented by X is preferably 350 or less. R represents a hydrogen atom, an alkyl group or a hydroxyalkyl group) is preferred. The number of carbon atoms in the alkyl group and the hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and further preferably 1 to 3.

[0545] As the above-mentioned amide group, a group represented by the general formula: -CO-NRR' (R and R' independently represent a hydrogen atom or a substituted or unsubstituted alkyl group), or a bond represented by the general formula: -CO-NR''- (R'' represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted phenyl group is preferred.

[0546] The polar group can be introduced into PVdF by polymerizing VdF with the above-mentioned monomer having a polar group (hereinafter referred to as a polar group-containing monomer), or by reacting PVdF with the above-mentioned compound having a polar group. However, from the viewpoint of productivity, it is preferred to polymerize VdF with the above-mentioned polar group-containing monomer.

[0547] When VdF and the above-mentioned polar group-containing monomer are polymerized, PVdF containing VdF units and polar group-containing monomer units can be obtained. That is, PVdF preferably contains the above-mentioned polar group-containing monomer units. The content of the above-mentioned polar group-containing monomer units is preferably 0.001 to 5.0 mol%, more preferably 0.01 to 3.0 mol%, and further preferably 0.10 to 1.5 mol% relative to the total monomer units.

[0548] In the present disclosure, the content of the polar group-containing monomer unit in PVdF can be measured by acid-base titration of the acid group, for example, when the polar group is an acid group such as carboxylic acid.

[0549] Examples of the polar group-containing monomer include: hydroxyalkyl (meth)acrylates such as hydroxyethyl acrylate and 2-hydroxypropyl acrylate; unsaturated monobasic acids such as (meth)acrylic acid, crotonic acid, vinylacetic acid (3-butenoic acid), 3-pentenoic acid, 4-pentenoic acid, 3-hexenoic acid, and 4-heptenoic acid; unsaturated dibasic acids such as maleic acid, maleic anhydride, citraconic acid, and citraconic anhydride; alkylene malonates such as dimethyl methylene malonate; vinyl carboxymethyl ether, vinyl carboxyethyl ether, and the like. carboxyalkyl (meth)acrylates such as 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate; (meth)acryloxyalkyl dicarboxylates such as monoacryloxyethyl succinate, monomethacryloxyethyl succinate, monoacryloxyethyl phthalate, monoacryloxypropyl succinate, and monomethacryloxyethyl phthalate; monoesters of unsaturated dibasic acids such as monomethyl maleate, monoethyl maleate, monomethyl citraconic acid, and monoethyl citraconic acid; and the like.

[0550] When PVdF is reacted with the above-mentioned compound having a polar group and the above-mentioned polar group is introduced into PVdF, as the above-mentioned compound having a polar group, the above-mentioned polar group-containing monomer or a silane-based coupling agent or a titanate-based coupling agent containing a group reactive with PVdF and a hydrolyzable group can be used. As the above-mentioned hydrolyzable group, an alkoxy group is preferably used. When a coupling agent is used, it can be added to PVdF by reacting with PVdF dissolved or swollen in a solvent.

[0551] As PVdF, it is also possible to use a substance obtained by further reacting the partially dehydrofluorinated PVdF with an oxidant after the partial dehydrofluorination treatment. As the above-mentioned oxidant, hydrogen peroxide, hypochlorite, palladium halide, chromium halide, alkali permanganate, peroxide, alkyl peroxide, alkyl persulfate, etc. can be enumerated.

[0552] The content of the VdF unit of PVdF is preferably more than 95.0 mol%, more preferably more than 97.0 mol%, and further preferably more than 99.0 mol% relative to all monomer units. In addition, the content of the VdF unit of PVdF is preferably 95.0 to 99.999 mol%, more preferably more than 97.0 mol%, and further preferably more than 98.5 mol%; more preferably less than 99.99 mol%, and further preferably less than 99.90 mol%.

[0553] The weight average molecular weight (polystyrene conversion) of PVdF is preferably 50,000 to 3,000,000, more preferably 80,000 or more, further preferably 100,000 or more, particularly preferably 200,000 or more; more preferably 2,400,000 or less, further preferably 2,200,000 or less, particularly preferably 2,000,000 or less. The weight average molecular weight can be measured by gel permeation chromatography (GPC) using N,N-dimethylformamide as a solvent. In addition, the weight average molecular weight of PVdF can be 1,000,000 or more, or 1,500,000 or more.

[0554] The number average molecular weight (polystyrene equivalent) of PVdF is preferably 20,000 to 1,500,000, more preferably 40,000 or more, further preferably 70,000 or more, particularly preferably 140,000 or more, more preferably 1,400,000 or less, further preferably 1,200,000 or less, particularly preferably 1,100,000 or less.

[0555] The number average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as a solvent.

[0556] The melting point of PVdF is preferably 100 to 240° C. The melting point can be determined using a differential scanning calorimeter (DSC) apparatus as a temperature corresponding to a maximum value in a heat of fusion curve when the temperature is increased at a rate of 10° C. / min.

[0557] When the binder contains PVdF and a fluorinated copolymer, the mass ratio of PVdF to the fluorinated copolymer in the binder (PVdF / fluorinated copolymer) is preferably 99 / 1 to 1 / 99, more preferably 97 / 3 to 3 / 97, further preferably 95 / 5 to 5 / 95, further preferably 90 / 10 to 10 / 90, particularly preferably 85 / 15 to 15 / 85, and most preferably 80 / 20 to 40 / 60.

[0558] The binder may contain other polymers besides PVdF and the fluorine-containing copolymer. Examples of other polymers include polymethacrylate, polymethyl methacrylate, polyacrylonitrile, polyimide, polyamide, polyamideimide, polycarbonate, styrene rubber, butadiene rubber and the like.

[0559] The content of the fluorinated copolymer in the binder is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, particularly preferably 10% by mass or more, most preferably 15% by mass or more, and may be 100% by mass or less, based on the mass of the binder.

[0560] The content of the binder in the negative electrode mixture prepared when forming the negative electrode material layer is preferably 0.1 to 20% by mass, more preferably 0.2 to 10% by mass, and even more preferably 0.5 to 7% by mass, based on the mass of the solid content in the negative electrode mixture.

[0561] (Solvent) The negative electrode mixture preferably contains a solvent. Examples of the solvent include water and an organic solvent. An organic solvent is preferred because it can significantly reduce the possibility of water remaining in the negative electrode material layer when the negative electrode mixture is used to form the negative electrode material layer.

[0562] Examples of the organic solvent include nitrogen-containing organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and dimethylformamide; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; β -Methoxy-N,N-dimethylpropionamide, β -n-Butoxy-N,N-dimethylpropionamide, β -n-hexyloxy-N,N-dimethylpropionamide, etc. β -Alkoxypropionamides; and low-boiling general-purpose organic solvents such as mixed solvents thereof.

[0563] As the organic solvent, a solvent represented by the general formula (60) can also be used.

[0564] General formula (60): [Chemistry 59]

[0565] (Where R 1 , R 2 and R 3 are independently H or a monovalent substituent, wherein R 1 , R 2 and R 3 The total number of carbon atoms is 6 or more, R 1 , R 2 and R 3 At least one of R is an organic group having a carbonyl group. 1 , R 2 and R 3 Any two of them can be bonded to form a ring. ) The solvent represented by the general formula (60) is preferably at least one selected from 3-methoxy-N,N-dimethylpropionamide, N-ethyl-2-pyrrolidone (NEP), N-butyl-2-pyrrolidone (NBP), acryloylmorpholine, N-cyclohexyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 3-butoxy-N,N-dimethylpropionamide, N,N,N′,N′-tetraethyl urea, N,N-dimethylacetoacetamide, N-octyl-2-pyrrolidone and N,N-diethylacetamide.

[0566] As the solvent, water or at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and the solvent represented by the general formula (1) is preferred from the viewpoint of excellent coating properties, and N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropionamide, N-ethyl-2-pyrrolidone (NEP), N-butyl-2-pyrrolidone (NBP), acryloylmorpholine, N-cyclohexyl-2-pyrrolidone, N-vinyl- At least one selected from the group consisting of 2-pyrrolidone, 3-butoxy-N,N-dimethylpropionamide, N,N,N′,N′-tetraethylurea, N,N-dimethylacetoacetamide, N-octyl-2-pyrrolidone and N,N-diethylacetamide, more preferably at least one selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, N-ethyl-2-pyrrolidone and N-butyl-2-pyrrolidone, and particularly preferably at least one selected from the group consisting of N-methyl-2-pyrrolidone and N,N-dimethylacetamide.

[0567] The amount of the solvent in the negative electrode mixture can be determined in consideration of the coating properties on the current collector, the thin film forming properties after drying, etc. Usually, the ratio of the binder to the solvent is 0.5:99.5 to 20:80 in terms of mass ratio.

[0568] (Other ingredients) The negative electrode mixture of the present disclosure may further contain other components such as a leveling agent and a reinforcing material.

[0569] The negative electrode mixture can be prepared, for example, by mixing a binder and a solvent, adding a negative electrode active material to the obtained mixture, and further mixing. Then, the obtained negative electrode mixture is evenly coated on a current collector such as a metal foil or a metal mesh, dried, and pressed as needed to form a thin negative electrode material layer on the current collector to prepare a thin film electrode. In addition, the negative electrode mixture can also be prepared by first mixing a negative electrode active material and a binder, and then adding a solvent.

[0570] The negative electrode of the present disclosure comprises a negative electrode material layer and a current collector. The negative electrode material layer is formed using the negative electrode mixture described above and can be disposed on one side or both sides of the current collector.

[0571] Examples of the current collector included in the negative electrode of the present disclosure include metal foils or metal meshes of iron, stainless steel, copper, aluminum, nickel, titanium, and the like, and carbon materials such as carbon cloth and carbon paper. Among them, copper foil is preferred.

[0572] The negative electrode of the present disclosure can be appropriately manufactured by a manufacturing method of applying the negative electrode mixture of the present disclosure to a current collector. After the negative electrode mixture is applied, the coating film can be further dried, optionally heat-treated, and the obtained dry coating film can be pressed.

[0573] As the shape of the current collector, in the case of metal materials, metal foil, metal cylinder, metal coil, metal plate, expanded metal mesh, punched metal mesh, foamed metal, etc. can be cited; in the case of carbon materials, carbon plate, carbon film, carbon cylinder, etc. can be cited. Among them, metal foil is preferred. It should be noted that the film can be appropriately formed into a mesh shape. The thickness of the film is arbitrary, usually 1 m m or more, preferably 3 m m or more, more preferably 5 m m or more; and usually 1 mm or less, preferably 100 m m or less, more preferably 50 m If the film is thinner than this range, the strength required as a current collector may be insufficient. On the other hand, if the film is thicker than this range, the handling properties may be impaired.

[0574] The thickness of the negative electrode plate is designed to match the positive electrode plate used, and there is no particular restriction. However, the thickness of the mixture layer after deducting the thickness of the core metal foil is preferably 15 m m or more, preferably 20 m m or more, more preferably 30 m m or more; and usually 300 m m or less, preferably 280 m m or less, more preferably 250 m m or less.

[0575] <Positive electrode> The positive electrode is preferably composed of a positive electrode active material layer containing a positive electrode active material and a current collector.

[0576] As the above-mentioned positive electrode active material, there is no particular restriction as long as it is a material that can electrochemically absorb and release alkali metal ions. For example, it is preferably a material containing an alkali metal and at least one transition metal. As a specific example, transition metal composite oxides containing alkali metals and transition metal phosphate compounds containing alkali metals can be cited. Among them, as the positive electrode active material, transition metal composite oxides containing alkali metals that can generate high voltage are particularly preferred. As the above-mentioned alkali metal ions, lithium ions, sodium ions, potassium ions, etc. can be cited. In a preferred embodiment, the alkali metal ions can be lithium ions. That is, in this embodiment, the alkali metal ion secondary battery is a lithium ion secondary battery.

[0577] Examples of the alkali metal-containing transition metal composite oxide include Formula (3-1): MaMn 2-b M 1 b O4 (wherein, M is at least one metal selected from Li, Na and K; 0.9≤a; 0≤b≤1.5; M 1 A lithium-manganese spinel composite oxide represented by at least one metal selected from Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge, Formula (3-2): MNi 1-c M 2 c O2 (wherein, M is at least one metal selected from Li, Na and K; 0≤c≤0.5; M 2 A lithium-nickel composite oxide represented by at least one metal selected from Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge, or Formula (3-3): MCo 1-d M3 d O2 (wherein, M is at least one metal selected from Li, Na and K; 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.

[0578] Among the above, M is preferably one metal selected from Li, Na and K, more preferably Li or Na, and further preferably Li.

[0579] Among them, MCoO2, MMnO2, MNiO2, MMn2O4, MNi 0.8 Co 0.15 Al 0.05 O2, or MNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., preferably a compound represented by the following formula (3-4).

[0580] MNi h Co i Mn j M 5 k O2 (3-4) (Where M 5 represents at least one selected from Fe, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge, (h+i+j+k)=1.0, 0≤h≤1.0, 0≤i≤1.0, 0≤j≤1.5, 0≤k≤0.2.) Examples of the alkali metal-containing transition metal phosphate compound include the following formula (70): M e M 4 f (PO4) g (wherein, M is at least one metal selected from Li, Na and K, M 4 represents at least one selected from V, Ti, Cr, Mn, Fe, Co, Ni and Cu, 0.5≤e≤3, 1≤f≤2, 1≤g≤3. ) Among the above, M is preferably a metal selected from Li, Na and K, more preferably Li or Na, and further preferably Li.

[0581] As the transition metal in the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferred. As specific examples, there can be mentioned iron phosphates such as LiFePO4, Li3Fe2(PO4)3, LiFeP2O7; cobalt phosphates such as LiCoPO4; lithium-containing transition metal phosphate compounds formed 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.

[0582] As the lithium-containing transition metal phosphate compound, one having an olivine structure is preferred.

[0583] As other positive electrode active materials, MFePO4, MNi 0.8 Co 0.2 O2, M 1.2 Fe 0.4 Mn 0.4 O2、MNi 0.5 Mn 1.5 O4, MV3O6, M2MnO3, etc. Especially MNi 0.5 Mn 1.5 Positive electrode active materials such as O4 are preferred in that the crystal structure will not be destroyed when the secondary battery is operated at a voltage exceeding 4.4V or a voltage above 4.6V. Therefore, electrochemical devices such as secondary batteries using positive electrode materials including the positive electrode active materials exemplified above are not easy to reduce residual capacity and change resistance increase rate even when stored at high temperatures, and battery performance is not easy to deteriorate even when operated at high voltages, so they are preferred.

[0584] As other positive electrode active materials, M2MnO3 and MM 6 O2 (wherein, M is at least one metal selected from Li, Na and K, M 6 Solid solution materials of transition metals such as Co, Ni, Mn, Fe, etc.

[0585] As the solid solution material, for example, a general formula Mx[Mn(1-y)M 7 Here, M in the formula is at least one metal selected from Li, Na and K, and M 7 It is composed of at least one metal element other than M and Mn, for example, one or more elements selected from Co, Ni, Fe, Ti, Mo, W, Cr, Zr and Sn. In addition, the values ​​of x, y and z in the formula are in the range of 1<x<2, 0≤y<1, 1.5<z<3. 1.2Mn 0.5 Co 0.14 Ni 0.14 A manganese-containing solid solution material such as Li2MnO3 having LiNiO2 or LiCoO2 as a solid solution in a matrix is ​​preferred from the viewpoint of being able to provide an alkali metal ion secondary battery having a high energy density.

[0586] 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 use the above-mentioned positive electrode active material and lithium phosphate in mixture. As the amount of lithium phosphate used, the lower limit is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5% by mass or more, relative to the total of the above-mentioned positive electrode active material and lithium phosphate; the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less.

[0587] In addition, a material obtained by attaching a substance having a different composition to the surface of the above-mentioned positive electrode active material can be used. Examples of the surface-attached substance include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; and carbon.

[0588] These surface-attached substances can be attached to the surface of the positive electrode active material by, for example, dissolving or suspending in a solvent, impregnating and adding to the positive electrode active material, and drying, dissolving or suspending a surface-attached substance precursor in a solvent, impregnating and adding to the positive electrode active material, and then reacting by heating, etc., adding to the positive electrode active material precursor and sintering at the same time, etc. It should be noted that in the case of attaching carbon, a method of mechanically attaching the carbon in the form of, for example, activated carbon can also be used.

[0589] As the amount of the surface-attached substance, relative to the positive electrode active material, in terms of mass, as the lower limit, preferably 0.1ppm or more, more preferably 1ppm or more, and further preferably 10ppm or more; as the upper limit, preferably 20% or less, more preferably 10% or less, and further preferably 5% or less. The surface-attached substance can inhibit the oxidation reaction of the electrolyte on the surface of the positive electrode active material, and can improve the battery life, but when the amount of its attachment is too small, its effect cannot be fully manifested, and when it is too much, it hinders the entry and exit of lithium ions, so sometimes the resistance increases.

[0590] The shape of the particles of the positive electrode active material may be block, polyhedral, spherical, ellipsoidal, plate, needle, columnar, etc. Primary particles may be aggregated to form secondary particles.

[0591] The tap density of the positive electrode active material is preferably 0.5 g / cm 3 More preferably, 0.8 g / cm 3 More preferably, 1.0 g / cm 3 Above. If the tap density of the positive electrode active material is lower than the above lower limit, the amount of dispersion medium required when the positive electrode active material layer is formed increases, and the required amount of conductive material and binder increases. Sometimes, the filling rate of the positive electrode active material into the positive electrode active material layer is restricted, and the battery capacity is restricted. By using a composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. Generally, the larger the tap density, the better. There is no particular upper limit. However, if it is too large, sometimes the diffusion of lithium ions using the electrolyte in the positive electrode active material layer as a medium is limited, and the load characteristics are sometimes easily reduced. Therefore, the upper limit is preferably 4.0g / cm 3 Below, more preferably 3.7 g / cm 3 Below, more preferably 3.5 g / cm 3 the following.

[0592] It should be noted that in the present disclosure, the tap density is determined as follows: 5 g to 10 g of the positive electrode active material powder is placed in a 10 ml glass measuring cylinder and tapped 200 times with an amplitude of about 20 mm. The powder packing density (tap density) at this time is g / cm 3 As the tap density.

[0593] The median diameter d50 of the positive electrode active material particles (secondary particle diameter when primary particles aggregate to form secondary particles) is preferably 0.3 m m or more, more preferably 0.5 m m or more, more preferably 0.8 m m or more, most preferably 1.0 m m or more; and preferably 30 m m or less, more preferably 27 m m or less, more preferably 25 m m or less, preferably 22 mm or less. If it is lower than the above lower limit, sometimes a product with a high tap density cannot be obtained; if it is greater than the upper limit, the diffusion of lithium in the particles will take time, so sometimes the battery performance is reduced, or when the positive electrode of the battery is made, that is, when the active material and the conductive material, the adhesive, etc. are slurried with a solvent and coated into a film, sometimes problems such as pulling out stripes occur. Here, the filling property when making the positive electrode can be further improved by mixing two or more of the above-mentioned positive electrode active materials with different median diameters d50.

[0594] It should be noted that in the present disclosure, the median diameter d50 is measured using a known laser diffraction / scattering particle size distribution measuring device. When using LA-920 manufactured by HORIBA as a particle size distribution meter, using a 0.1% by mass sodium hexametaphosphate aqueous solution as a dispersion medium used during measurement, after 5 minutes of ultrasonic dispersion, the measured refractive index is set to 1.24 for measurement.

[0595] When the primary particles aggregate to form secondary particles, the average primary particle size of the positive electrode active material is preferably 0.05 m m or more, more preferably 0.1 m m or more, more preferably 0.2 m m or more; the upper limit is preferably 5 m m or less, more preferably 4 m m or less, more preferably 3 m m or less, preferably 2 m m or less. When the above upper limit is exceeded, it is difficult to form spherical secondary particles, which sometimes has an adverse effect on the powder filling property; or the specific surface area is greatly reduced, so the possibility of reduced battery performance such as output characteristics becomes higher. On the contrary, if it is below the above lower limit, crystals are usually not developed, so sometimes problems such as poor reversibility of charge and discharge occur.

[0596] It should be noted that in the present disclosure, the primary particle size can be measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph with a magnification of 10,000 times, for any 50 primary particles, the longest value of the line segment intercepted by the left and right boundaries of the primary particles to the straight line in the horizontal direction is obtained, and the average value is obtained.

[0597] 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 2If the BET specific surface area is smaller than this range, the battery performance is likely to be reduced, while if it is larger than this range, it is difficult to increase the tap density, and sometimes problems may arise in the coating property when the positive electrode active material layer is formed.

[0598] In addition, in the present disclosure, the BET specific surface area is defined as a value measured by the following method: using a surface area meter (e.g., a fully automatic surface area measuring device manufactured by Ohkura Riken Co. Ltd.), after pre-drying the sample at 150° C. for 30 minutes under nitrogen flow, using a nitrogen-helium mixed gas in which the relative pressure of nitrogen relative to atmospheric pressure is accurately adjusted to 0.3, the sample is measured by a nitrogen adsorption BET 1-point method based on a gas flow method.

[0599] When the secondary battery of the present disclosure 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.

[0600] The particles of the positive electrode active material preferably have an average particle size of 40 m m or less, and containing 0.5 to 7.0% by volume of an average primary particle size of 1 m The particles are smaller than 1 m. m Microparticles with a diameter of 1 μm or less have a larger contact area with the electrolyte, which can accelerate the diffusion of lithium ions between the electrode and the electrolyte, and as a result, can improve the output performance of the battery.

[0601] As the manufacturing method of the positive electrode active material, a conventional method as a manufacturing method of an inorganic compound is used. In particular, in order to make a spherical or ellipsoidal active material, various methods can be considered, for example, the following method can be cited: the raw material of the transition metal is dissolved or crushed and dispersed in a solvent such as water, pH is adjusted while stirring, a spherical precursor is made and recovered, and after drying it as needed, LiOH, Li2CO3, LiNO3 and other Li sources are added, and the active material is obtained by calcining at high temperature.

[0602] In order to manufacture the positive electrode, the above-mentioned positive electrode active materials can be used alone, or two or more of them with different compositions can be used in any combination or ratio. As a preferred combination in this case, LiCoO2, LiNi 0.33 Co 0.33 Mn 0.33 O2, such as LiMn2O4 or a combination of substances in which a portion of Mn is replaced by other transition metals, or LiCoO2 or a combination of substances in which a portion of Co is replaced by other transition metals.

[0603] From the viewpoint of increasing the battery capacity, the content of the positive electrode active material is preferably 50 to 99.5% by mass, more preferably 80 to 99% by mass, of the positive electrode mixture.

[0604] In addition, the content of the 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, then sometimes the capacity is insufficient. On the contrary, if the content is too high, then sometimes the strength of the positive electrode is insufficient.

[0605] The positive electrode mixture preferably further includes a binder, a thickener, a conductive material, a solvent, and the like.

[0606] As the above-mentioned binder, any binder 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, for example, 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 their hydrogenates; thermoplastic elastomer polymers such as EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-styrene copolymers, styrene-isoprene-styrene block copolymers or their hydrogenates; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, propylene- α -olefin copolymers and other soft resin-like polymers; polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride copolymers, tetrafluoroethylene-ethylene copolymers and other fluorine-based polymers; polymer compositions having ion conductivity of alkali metal ions (especially lithium ions), etc. These may be used alone or in any combination and ratio.

[0607] About the content of binder, as the ratio of binder in positive electrode active material layer, it is usually 0.1 mass % or more, preferably 1 mass % or more, more preferably 1.5 mass % or more; and, it is usually 80 mass % or less, preferably 60 mass % or less, more preferably 40 mass % or less, most preferably 10 mass % or less. If the ratio of binder is too low, the positive electrode active material cannot be fully maintained, the mechanical strength of the positive electrode is insufficient, and the battery performance such as cycle characteristics is sometimes deteriorated. On the other hand, if it is too high, it sometimes leads to a reduction in battery capacity and conductivity.

[0608] 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.

[0609] The ratio of thickener to active material is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more; and, usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If it is lower than this range, the coating property is sometimes significantly reduced. If it is greater than this range, the proportion of active material in the positive electrode active material layer is reduced, sometimes resulting in a problem of reduced battery capacity or an increased resistance between positive electrode active materials.

[0610] 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, ketjen black, channel black, furnace black, lamp black, and thermal black; carbon materials such as amorphous carbon such as needle coke, carbon nanotubes, fullerene, and VGCF, etc., can be cited. It should be noted that these can be used alone or in any combination and ratio. Two or more kinds can be used in combination.

[0611] The conductive material is usually 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; and is usually used in an amount containing 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 is sometimes insufficient. On the contrary, if the content is higher than this range, the battery capacity is sometimes reduced.

[0612] As a solvent for forming the slurry, as long as it is a solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as needed, its type is not particularly limited, and any of an aqueous solvent and an organic solvent can be used. As an aqueous solvent, for example, water, a mixed solvent of alcohol and water, etc. can be cited. As an organic solvent, for example, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide, etc.

[0613] Examples of the material of the positive electrode current collector include metals such as aluminum, titanium, tantalum, stainless steel, nickel, or their alloys; and carbon materials such as carbon cloth and carbon paper. Among them, metal materials are preferred, and aluminum or its alloys are particularly preferred.

[0614] As the shape of the current collector, in the case of metal materials, metal foil, metal cylinder, metal coil, metal plate, expanded metal mesh, punched metal mesh, foamed metal, etc. can be cited; in the case of carbon materials, carbon plate, carbon film, carbon cylinder, etc. can be cited. Among them, metal foil is preferred. It should be noted that the film can be appropriately formed into a mesh shape. The thickness of the film is arbitrary, usually 1 m m or more, preferably 3 m m or more, more preferably 5 m m or more; and usually 1 mm or less, preferably 100 m m or less, more preferably 50 m If the film is thinner than this range, the strength required as a current collector may be insufficient. On the other hand, if the film is thicker than this range, the handling properties may be impaired.

[0615] In addition, coating a conductive additive on the surface of the current collector is preferred from the viewpoint of reducing the contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive additive include carbon or noble metals such as gold, platinum, and silver.

[0616] The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but the value of (the thickness of the positive electrode active material layer on one side when the electrolyte is to be injected) / (the thickness of the current collector) is preferably 20 or less, more preferably 15 or less, and most preferably 10 or less; and preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. If it is greater than this range, the current collector sometimes generates heat due to Joule heat during high current density charging and discharging. If it is less than this range, the volume ratio of the current collector to the positive electrode active material increases, and sometimes the capacity of the battery decreases.

[0617] The positive electrode can be manufactured by conventional methods, for example, by adding the above-mentioned binder, thickener, conductive material, solvent, etc. to the above-mentioned positive electrode active material to prepare a slurry-like positive electrode mixture, coating the slurry on a current collector, drying it, and then pressing it to achieve high density.

[0618] The density increase can be achieved by hand pressing, roll pressing, etc. The density of the positive electrode active material layer is preferably 1.5 g / cm 3 More preferably 2 g / cm 3 More preferably, 2.2 g / cm 3 More than; and, preferably 5g / cm 3Below, more preferably 4.5g / cm 3 Below, more preferably 4g / cm 3 If the range is exceeded, the permeability of the electrolyte to the interface of the current collector / active material is reduced, and the charge and discharge characteristics at high current density are reduced, and sometimes high output cannot be obtained. In addition, if it is below this range, the conductivity between the active materials is reduced, the battery resistance is increased, and sometimes high output cannot be obtained.

[0619] In the case of using the electrolyte disclosed in the present invention, from the viewpoint of high output and improved stability at high temperature, it is preferred that the area of ​​the positive electrode active material layer is increased relative to 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. 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 other than the protruding portion of the terminal in the case of a bottomed rectangular parallelepiped shape. In the case of a bottomed cylindrical shape, it is the geometric surface area of ​​the shell portion filled with the power generation element other than the protruding portion of the terminal 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 the positive electrode mixture layer is formed on both sides with a current collector foil, it refers to the sum of the areas of each face calculated separately.

[0620] The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the lower limit of the thickness of the mixed layer obtained by deducting the thickness of the core metal foil is preferably 10 μm for one side of the current collector. m m or more, more preferably 20 m m or more; and preferably 500 m m or less, more preferably 450 m m or less.

[0621] In addition, a material obtained by attaching a substance having a different composition to the surface of the positive electrode plate may be used. Examples of the surface-attached substance include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate; and carbon.

[0622] <Isolator> The secondary battery of the present disclosure preferably further includes a separator.

[0623] The material and shape of the separator are not particularly limited as long as they are stable in the electrolyte and have excellent liquid retention, and known materials or shapes can be used. Among them, it is preferred that the separator is formed of a material that is stable to the electrolyte disclosed in the present invention, and can use a porous sheet or non-woven fabric-like article with excellent liquid retention, such as resin, glass fiber, inorganic material, etc.

[0624] As materials for resin and glass fiber separators, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters, etc. can be used. Polypropylene / polyethylene double-layer membranes, polypropylene / polyethylene / polypropylene three-layer membranes, etc., these materials can be used alone or in any combination and ratio. Among them, considering the permeability of the electrolyte or the good 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.

[0625] The thickness of the spacer is arbitrary, but is usually 1 m m or more, preferably 5 m m or more, more preferably 8 m m or more; and, usually 50 m m or less, preferably 40 m m or less, more preferably 30 m If the separator is too thin than the above range, the insulation and mechanical strength may be reduced. In addition, if it is too thick 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.

[0626] 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, but is usually 20% or more, preferably 35% or more, and more preferably 45% or more; and is usually 90% or less, preferably 85% or less, and 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.

[0627] The average pore size of the separator is also arbitrary, but is usually 0.5 m m or less, preferably 0.2 m m or less; and, usually 0.05 m If the average pore size is larger than the above range, short circuits are likely to occur. If the average pore size is smaller than the above range, the film resistance may increase and the rate characteristics may decrease.

[0628] On the other hand, as inorganic materials, for example, oxides such as aluminum oxide and silicon dioxide; nitrides such as aluminum nitride and silicon nitride; sulfates such as barium sulfate and calcium sulfate can be used, and materials in the form of particles or fibers can be used.

[0629] As the form, nonwoven fabric, woven fabric, microporous membrane or other film-like shapes can be used. In the case of a film-like shape, a pore size of 0.01 to 1 m m, thickness 5~50 m In addition to the above-mentioned independent film shape, a separator can also be used in which a composite porous layer containing the above-mentioned inorganic particles is formed on the surface of the positive electrode and / or the negative electrode using a resin binder. For example, a separator can be used in which 90% of the particles with a diameter of less than 1 μm are formed on both sides of the positive electrode using a fluororesin as a binder. m m of aluminum oxide particles are formed into a porous layer.

[0630] <Battery Design> The electrode group may be any one of an electrode group of a laminated structure formed by separating the positive electrode plate and the negative electrode plate from the separator, and an electrode group of a structure formed by spirally winding the positive electrode plate and the negative electrode plate from the separator. The proportion of the volume of the electrode group in the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more; and is usually 90% or less, preferably 80% or less.

[0631] If the electrode group occupancy rate is lower than the above range, the battery capacity will be reduced. If it is higher than the above range, the void space will be less, and the components will expand due to the high temperature of the battery, or the vapor pressure of the liquid component of the electrolyte will increase, resulting in an increase in internal pressure, which will reduce various characteristics of the battery such as repeated charge and discharge performance and high-temperature storage, and sometimes even cause the air release valve used to release the internal pressure to work.

[0632] The current collecting structure is not particularly limited, but in order to more effectively realize the effect of the electrolyte disclosed in the present invention to improve the charge-discharge characteristics of high current density, it is preferred to adopt a structure that reduces the resistance of the wiring portion and the bonding portion. When the internal resistance is reduced like this, the effect obtained by using the electrolyte disclosed in the present invention can be particularly well exerted.

[0633] 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 to the terminal. When the area of ​​a single electrode increases, since the internal resistance increases, it is also suitable to set multiple terminals in the electrode to reduce the resistance. In the case where the electrode group has the above-mentioned winding structure, multiple lead structures are set on the positive electrode and the negative electrode respectively, and the internal resistance can be reduced by bundling them to the terminals.

[0634] The material of the outer package case is not particularly limited as long as it is stable with respect to the electrolyte used. Specifically, metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, and magnesium alloys can be used, or laminated films (laminated films) of resin and aluminum foil. From the viewpoint of weight reduction, metals such as aluminum or aluminum alloys and laminated films are preferably used.

[0635] In the case of an outer package case using metals, examples include an outer package case formed by laser welding, resistance welding, or ultrasonic welding to melt and join the metals to form a sealed and airtight structure; or an outer package case formed by using the above metals via a resin sealing gasket to form a caulked structure (Japanese: かしめ構造). In the case of an outer package case using the above laminated film, examples include an outer package case formed by heat-sealing the resin layers to form a sealed and airtight structure. In order to improve the sealing performance, a resin different from the resin used in the laminated film can be sandwiched between the above resin layers. In particular, when the resin layers are heat-sealed via a current collector terminal to form a sealed structure, a metal-resin joint is formed, so a resin having a polar group or a modified resin into which a polar group is introduced is preferably used as the spacer resin.

[0636] The shape of the secondary battery of the present disclosure is arbitrary, and examples include cylindrical, square, laminated, coin-shaped, and large-sized shapes. It should be noted that the shapes and configurations of the positive electrode, negative electrode, and separator can be changed according to the shape of each battery.

[0637] Examples Hereinafter, the present disclosure will be described by way of examples, but the present disclosure is not limited to these examples.

[0638] In the following examples, unless otherwise specified, "parts" and "%" represent "parts by weight" and "wt%", respectively.

[0639] The following shows the fluorinated ethers (A-1) to (A-3) used.

[0640] (A-1) HCF2CF2OCH2CF2CF2H (A-2) HCF2CF2OCH2CF2CF3 (A-3) HCF2CF2OCH2CF3 The following shows the additives used.

[0641] VC: Vinylene carbonate Succinic anhydride Maleic anhydride Adiponitrile FEC: Fluoroethylene carbonate VEC: Vinyl ethyl carbonate DFEC: difluoroethylene carbonate CH3CH2OSO3Li FSO3Li Et2NSO3Li (CF3CH2)2NSO3L (CF3CH2)(CH3)NSO3Li (CNCH2)2NSO3Li Tris(trimethylsilyl) phosphate Tris(triethylsilyl) phosphate Tri(tert-butyldimethylsilyl) phosphate Tris(trimethylsilyl) phosphite Tris(triethylsilyl) phosphite Tris(tert-butyldimethylsilyl) phosphite (Example 1) [Preparation of electrolyte] 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 achieve a concentration of 1.0 mol / L to prepare a basic electrolyte.

[0642] 0.001 mass % of the fluoroether (A-1) was added to the above-mentioned basic electrolyte solution, followed by mixing, thereby preparing a non-aqueous electrolyte solution.

[0643] [Production of negative electrode] Silicon oxide powder (SiO) (average particle size 20 m m, BET specific surface area 2.7m 2 / g) and graphite powder (average particle size 5 m m, BET specific surface area 20m 2 / g) (mass ratio: 30 / 70) 94 mass % and polyvinylidene fluoride (PVdF) 6 mass % as a binder were mixed, and N-methyl-2-pyrrolidone (NMP) was added and mixed to form a slurry. The obtained slurry was applied to a 15 thick m A negative electrode current collector made of a copper foil of 1000 μm was prepared, dried, cut into a predetermined electrode size, and rolled using a roll press to produce a negative electrode having a negative electrode material layer formed on the negative electrode current collector.

[0644] [Production of positive electrode] Add LiNi as the positive electrode active material 0.8 Mn 0.1 Co 0.197 parts by mass of O2 (NMC811), 1.5 parts by mass of acetylene black as a conductive aid, and 1.5 parts by mass of polyvinylidene fluoride (8% by mass NMP solution) as a binder were mixed with a disperser and slurried. The obtained slurry was applied to a 20 mm thick m The aluminum foil was dried and rolled using a press machine, and then cut into a shape having a coated portion (positive electrode material layer) of 50 mm in width and 30 mm in length and an uncoated portion of 5 mm in width and 9 mm in length to prepare a positive electrode.

[0645] [Battery production] The produced negative electrode having a negative electrode material layer on one surface was cut into a shape having a coated portion (negative electrode material layer) of 52 mm in width and 32 mm in length and an uncoated portion of 5 mm in width and 9 mm in length to prepare a negative electrode.

[0646] The positive electrode and the negative electrode are separated by a 20 mm thick m The positive electrode and the negative electrode are placed opposite to each other through a microporous polyethylene film (separator) of m, and the non-aqueous electrolyte obtained above is injected. After the non-aqueous electrolyte fully penetrates the separator, etc., it is sealed and pre-charged and aged to produce an aluminum laminate battery (lithium-ion secondary battery).

[0647] (Measurement of battery characteristics) [Cycle characteristics] The obtained aluminum laminate battery was subjected to constant current-constant voltage charging (hereinafter referred to as CC / CV charging) (0.1C cutoff) to 4.2V at a current equivalent to 0.2C at 25°C, and then discharged to 3V at a constant current of 0.2C, which was regarded as one cycle, and three cycles were implemented. Then, at 45°C, CC / CV charging (0.1C cutoff) was performed to 4.2V at a current equivalent to 1.0C, and then discharged to 3V at a constant current of 1.0C, which was regarded as one cycle, and the initial discharge capacity was calculated from the discharge capacity. The cycle was repeated again to determine the discharge capacity after 300 cycles. The ratio of the discharge capacity after 300 cycles to the initial discharge capacity was calculated and used as the capacity retention rate (%).

[0648] Capacity retention rate (%) = (discharge capacity after 300 cycles) ÷ (initial discharge capacity at 1.0C) × 100 The results are shown as relative values ​​with the result of Comparative Example 1 being set to 1.

[0649] [IV resistance] The battery was charged to SOC 50%, and discharged at 1, 3, and 5C rates to measure the voltage drop (V). The resistance value was calculated from the slope using the calculation formula V=IR based on the obtained voltage and current values. The value of Comparative Example 1 was set to 1, and the relative values ​​were recorded in the attached table of the examples.

[0650] The above SOC indicates the state of charge, and SOC 100% is the capacity when charged to 4.2 V. For example, SOC 50% indicates half the capacity of SOC 100%.

[0651] [LiF amount] After the test, the battery was disassembled, the negative electrode was removed, a predetermined amount of water was added, the solution was stirred, and the solution was filtered. The amount of F in the filtered solution was calculated by ion chromatography, and the obtained value was converted to LiF.

[0652] (Examples 2 to 37) A nonaqueous electrolyte was prepared in the same manner as in Example 1 except that the type and amount of additives in the electrolyte were changed as shown in Table 1, and a battery was produced and various evaluations were performed.

[0653] The results are shown in Table 1.

[0654] (Comparative Example 1) A nonaqueous electrolyte was prepared in the same manner as in Example 1 except that no additive was used, and a battery was produced and various evaluations were performed.

[0655] The results are shown in Table 1.

[0656] (Comparative Example 2) A nonaqueous electrolyte was prepared in the same manner as in Example 1 except that the additives were changed as shown in Table 1, and a battery was produced and various evaluations were performed.

[0657] The results are shown in Table 1.

[0658] [Table 1]

[0659] According to the examples in Table 1, by using the electrolytic solutions obtained in the examples, the cycle characteristics of the secondary battery are improved and the increase in IV resistance is suppressed.

[0660] Industrial Applicability The secondary battery using the electrolyte solution of the present disclosure can be used as various power sources such as a portable power source and a power source for automobiles.

Claims

1. An electrolyte, characterized in that: A battery having an electrode with a negative electrode material, wherein the negative electrode material comprises silicon and carbon, The electrolyte solution contains less than 10% by mass of a fluoroether represented by the following general formula (1), HCF2CF2-OR (1) In formula (1), R is a fluoroalkyl group.

2. The electrolyte according to claim 1, wherein The fluoroether represented by the general formula (1) is at least one fluoroether selected from the group consisting of the fluoroethers represented by the following general formulas (2) to (4), HCF2CF2-O-CH2CF2CF2H (2) HCF2CF2-O-CH2CF2CF3 (3) HCF2CF2-O-CH2CF3 (4).

3. The electrolyte according to claim 1 or 2, wherein The negative electrode material contains Si and / or SiOa, and a carbon compound, wherein 0<a<2.

4. A secondary battery, characterized in that: A method of manufacturing the electrolytic solution according to claim 1 or 2.

5. The secondary battery according to claim 4, wherein The negative electrode material of the secondary battery contains Si and / or SiOa, and a carbon compound, wherein 0<a<2.

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