Composition for electrolyte solution, electrochemical device, secondary battery, and lithium-ion secondary battery

Abstract

The present disclosure provides: a composition for an electrolyte solution, which can suppress gas generation during high-temperature storage; and an electrochemical device, a secondary battery and a lithium-ion secondary battery, each of which uses this composition for an electrolyte solution. More specifically, the present disclosure is a composition for an electrolyte solution, wherein the composition contains a compound (A) represented by formula (A). (A) Rf1-O-CH2-CH2-O-R1 (In the formula, Rf1 is 1-6 C fluoroalkyl group, and R1 is H, Li, Na, K or Cs).

Description

statement Title of invention: Electrolyte composition, electrochemical device, secondary battery, and lithium ion secondary battery Technical Field The present disclosure relates to an electrolyte composition, an electrochemical device, a secondary battery, and a lithium ion secondary battery. Background technology In recent years, with the trend toward lighter and smaller electrical appliances, the development of electrochemical devices such as lithium-ion secondary batteries with high energy density has been progressing. Furthermore, as the fields of application of electrochemical devices such as lithium-ion secondary batteries expand, improvements in their characteristics are desired. In particular, when lithium-ion secondary batteries are used in automobiles in the future, improvements in battery characteristics will become increasingly important. Patent Document 1 describes an electrolyte solution for lithium metal secondary batteries that contains a specific lithium salt and a non-aqueous solvent. Prior art documents Patent documents

[0004] Patent Document 1: Special Publication No. 2022-552481 Summary of the Invention Problems that the invention aims to solve An object of the present disclosure is to provide an electrolyte composition that can suppress gas generation during high-temperature storage, as well as an electrochemical device, a secondary battery, and a lithium-ion secondary battery that use the electrolyte composition. Means to solve the problem The present disclosure (1) is a composition for an electrolyte solution containing a compound (A) represented by the following formula (A): (A) Rf1-O-CH2-CH2-O-R1 (In the formula, Rf1 is a fluoroalkyl group having 1 to 6 carbon atoms, and R1 is H, Li, Na, K, or Cs.)

[0007] The present disclosure (2) provides that Rf1 is HCF2-CF2 one, HCF2-CF2-CH2-, HCF2-CH2-, CF3-CF2-CH2-, or The composition for an electrolyte solution according to the present disclosure (1) is CF3-CHF-CF2-.

[0008] The present disclosure (3) is the composition for an electrolyte solution according to the present disclosure (1) or (2), wherein R1 is H or Li.

[0009] The present disclosure (4) is the composition for an electrolyte solution according to any one of the present disclosures (1) to (3), wherein the content of the compound (A) is 0.0001 to 30,000 ppm relative to the composition for an electrolyte solution.

[0010] The present disclosure (5) relates to the compound (A), HCF2-CF2-O-CH2-CH2-OH, HCF2-CF2-O-CH2-CH2-OLi, CF3-CHF-CF2-O-CH2-CH2-OH, and The composition for an electrolyte solution according to any one of the present disclosures (1) to (4) is at least one selected from the group consisting of CF3-CHF-CF2-O-CH2-CH2-OLi.

[0011] The present disclosure (6) is a composition for an electrolyte solution according to any one of the present disclosures (1) to (5), which contains a fluorinated ether (E) represented by the following formula (E): (E) Rf2-O-R2 (In the formula, Rf2 is a fluoroalkyl group having 1 to 5 carbon atoms, and R2 is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group for R2 may have an ether bond and / or fluorine.)

[0012] The present disclosure (7) is the composition for an electrolyte solution according to the present disclosure (6), wherein Rf2 is HCF2-CF2-.

[0013] The present disclosure (8) provides that R2 is -CH2-CH2-O-CF2-CF2H, or -CH2-CH2-O-CF2-CHF-CF3 The composition for an electrolyte solution according to the present disclosure (6) or (7),

[0014] The present disclosure (9) is characterized in that the fluorinated ether (E) is HCF2-CF2-O-CH2-CH2-O-CF2-CF2H, and CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3 The composition for an electrolyte solution according to any one of the present disclosures (6) to (8) is at least one selected from the group consisting of:

[0015] The present disclosure (10) is a composition for an electrolyte solution according to any one of the present disclosures (6) to (9), wherein the content of the fluorinated ether (E) is 0.01 to 99 mass% relative to the composition for an electrolyte solution.

[0016] The present disclosure (11) is a composition for an electrolyte solution according to any one of the present disclosures (1) to (10), which contains at least one lithium salt selected from the group consisting of LiPF6, LiFSI, and LiTFSI.

[0017] The present disclosure (12) relates to the compound (A), HCF2-CF2-O-CH2-CH2-OH, HCF2-CF2-O-CH2-CH2-OLi, CF3-CHF-CF2-O-CH2-CH2-OH, and CF3-CHF-CF2-O-CH2-CH2-OLi, the content of the compound (A) is 0.003 to 30,000 ppm relative to the electrolyte solution composition; HCF2-CF2-O-CH2-CH2-O-CF2-CF2H, and CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3 At least one fluorinated ether (E) selected from the group consisting of In the composition for an electrolyte solution according to any one of the present disclosures (1) to (11), the content of the fluorinated ether (E) is 0.5 to 50 mass % relative to the composition for an electrolyte solution.

[0018] The present disclosure (13) is a secondary battery comprising the electrolyte solution composition according to the present disclosure (12) and lithium metal as a negative electrode active material.

[0019] The present disclosure (14) relates to a compound (A), HCF2-CF2-O-CH2-CH2-OH, HCF2-CF2-O-CH2-CH2-OLi, CF3-CHF-CF2-O-CH2-CH2-OH, and CF3-CHF-CF2-O-CH2-CH2-OLi, the content of the compound (A) is 0.01 to 30,000 ppm relative to the electrolyte solution composition; HCF2-CF2-O-CH2-CH2-O-CF2-CF2H, and CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3 At least one fluorinated ether (E) selected from the group consisting of In the composition for an electrolyte solution according to any one of the present disclosures (1) to (11), the content of the fluorinated ether (E) is 40 to 95 mass % relative to the composition for an electrolyte solution.

[0020] The present disclosure (15) is a secondary battery comprising the composition for an electrolyte solution according to the present disclosure (14) and a silicon material as a negative electrode active material.

[0021] The present disclosure (16) is a composition for an electrolyte solution according to any one of the present disclosures (1) to (12) and (14), which is for a secondary battery.

[0022] The present disclosure (17) is an electrochemical device including the composition for an electrolyte solution according to any one of the present disclosures (1) to (12) and (14).

[0023] The present disclosure (18) is a secondary battery containing the composition for an electrolyte solution according to any one of the present disclosures (1) to (12) and (14).

[0024] The present disclosure (19) is a lithium ion secondary battery containing the composition for an electrolyte solution according to any one of the present disclosures (1) to (12) and (14). Effect of the invention According to the present disclosure, it is possible to provide an electrolyte solution composition that can suppress gas generation during high-temperature storage, as well as an electrochemical device, a secondary battery, and a lithium-ion secondary battery that use the electrolyte solution composition. MODE FOR CARRYING OUT THE INVENTION

[0026] The present disclosure will now be described in detail. The present disclosure relates to a composition for an electrolyte solution containing a compound (A) represented by the following formula (A): (A) Rf1-O-CH2-CH2-O-R1 (In the formula, Rf1 is a fluoroalkyl group having 1 to 6 carbon atoms, and R1 is H, Li, Na, K, or Cs.) The composition of the present disclosure, containing compound (A), can suppress gas generation during high-temperature storage in an electrochemical device. This effect is presumably brought about by the fact that compound (A) is adsorbed to defect sites in the positive electrode, thereby suppressing side reactions at the positive electrode / electrolyte interface. The composition of the present disclosure is used in an electrolyte solution, and may be either an electrolyte solution or a constituent component (additive, etc.) of an electrolyte solution. Furthermore, the composition of the present disclosure can be suitably used in electrochemical devices (particularly secondary batteries such as lithium ion secondary batteries). In the formula (A), Rf1 is a fluoroalkyl group having 1 to 6 carbon atoms. The number of carbon atoms in the fluoroalkyl group is preferably 1 to 4, more preferably 1 to 3, still more preferably 2 or 3, and particularly preferably 2. The fluoroalkyl group may be linear or branched, but is preferably linear. Rf1 is preferably HCF2-CF2-, HCF2-CF2-CH2-, HCF2-CH2-, CF3-CF2-CH2-, or CF3-CHF-CF2-, and more preferably HCF2-CF2- or CF3-CHF-CF2- from the viewpoint of suppressing gas generation during high-temperature storage. In the formula (A), R1 is H, Li, Na, K or Cs. From the viewpoint of suppressing gas generation during high-temperature storage, H, Li, Na and K are preferred, and H and Li are more preferred.

[0032] As the compound (A), in particular, from the viewpoint of suppressing gas generation during high-temperature storage, HCF2-CF2-O-CH2-CH2-OH, HCF2-CF2-CH2-O-CH2-CH2-OH, HCF2-CH2-O-CH2-CH2-OH, CF3-CF2-CH2-O-CH2-CH2-OH, CF3-CHF-CF2-O-CH2-CH2-OH, CF3-CHF-CF2-O-CH2-CH2-OLi, HCF2-CF2-O-CH2-CH2-OLi, HCF2-CF2-O-CH2-CH2-OK, is preferred, HCF2-CF2-O-CH2-CH2-OH, HCF2-CF2-O-CH2-CH2-OLi, CF3-CHF-CF2-O-CH2-CH2-OH, CF3-CHF-CF2-O-CH2-CH2-OLi, is more preferred, HCF2-CF2-O-CH2-CH2-OH, CF3-CHF-CF2-O-CH2-CH2-OH, is more preferred.

[0033] The compound (A) may be used alone or in combination of two or more kinds.

[0034] In the composition of the present disclosure, the content of compound (A) is preferably 0.0001 ppm or more and 30,000 ppm or less relative to the composition of the present disclosure. In order to further suppress gas generation during high-temperature storage, the content of compound (A) in the composition of the present disclosure is more preferably 0.003 ppm or more, even more preferably 0.01 ppm or more, and particularly preferably 0.1 ppm or more, and is more preferably 20,000 ppm or less, even more preferably 10,000 ppm or less, even more preferably 7,000 ppm or less, and particularly preferably 5,000 ppm or less.

[0035] The composition of the present disclosure preferably contains a fluorinated ether (E) represented by the following formula (E): (E) Rf2-O-R2 (In the formula, Rf2 is a fluoroalkyl group having 1 to 5 carbon atoms, and R2 is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group for R2 may have an ether bond and / or fluorine.) The combined use of compound (A) and fluorinated ether (E) can further suppress gas generation during high-temperature storage. This effect is presumably due to the high oxidation resistance of the fluorinated ether (E) and the adsorption of compound (A) to the positive electrode, which suppresses side reactions at the positive electrode / electrolyte interface. In the formula (E), Rf2 is a fluoroalkyl group having 1 to 6 carbon atoms. The number of carbon atoms in the fluoroalkyl group is preferably 1 to 4, more preferably 1 to 3, still more preferably 1 or 2, and particularly preferably 2. The fluoroalkyl group may be linear or branched, but is preferably linear. Rf2 is preferably CF₃-, CF₂H-, CFH₂-, CF₃-CF₂-, CF₃-CH₂-, HCF₂-CH₂-, HCF₂-CF₂-, FCH₂-CH₂-, CF₃-CH₂-CH₂-, CF₃-CF ... HCF₂-CF₂-CH₂-, FCH₂-CF₂-CH₂-, HCF₂-CF₂-CF₂-CH₂-, and HCF₂-CF₂-CF₂-CF₂-CH₂-. HCF₂-CF₂-CF₂- is more preferred from the viewpoint of suppressing gas generation during high-temperature storage.

[0038] In formula (E), R2 is H or an alkyl group having 1 to 6 carbon atoms. The number of carbon atoms in the alkyl group is preferably 1 to 4, more preferably 1 to 3, and still more preferably 3. The alkyl group may be linear or branched, but is preferably linear. The alkyl group may have an ether bond and / or fluorine, but preferably has an ether bond and fluorine. As R2, -CF3, -CF2H, -CFH2, -CH3, -CH2-CH3, -CF2-CF3, -CH2-CF3, -CH2-CF2H, -CH2-CFH2, -CH2-CH2-CH3, -CH2-CH2-CF3, -CH2-CF2-CF3, -CH2-CF2-CF2H, -CH2-CF2-CFH2, -CH2-CF2-CF2-CF2-CF2H, -CH2-CH2-O-CF2-CF2H, -CH2-CH2-O-CF2-CHF-CF3 is preferred, and from the viewpoint of suppressing gas generation during high-temperature storage, -CH2-CH2-O-CF2-CF2H and -CH2-CH2-O-CF2-CHF-CF3 are more preferred.

[0039] As the fluorinated ether (E), in particular, from the viewpoint of suppressing gas generation during high-temperature storage, HCF2-CF2-O-CH2-CF2-O-CF2-CF2H, HCF2-CF2-CH2-O-CH2-CH2-CH2-CF2-CF2H, HCF2-CH2-O-CH2-CH2-O-CH2-CF2H, HCF2-CF2-O-CH2-CH2-O-CF2-CF2H, CF3-CF2-CH2-O-CH2-CH2-O-CH2-CF2-CF3, CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3, HCF2-CF2-CH2-O-CF2-CF2H, is preferred, HCF2-CF2-O-CH2-CH2-O-CF2-CF2H, CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3, is more preferred.

[0040] The fluorinated ether (E) may be used alone or in combination of two or more kinds. When two kinds of fluorinated ethers (E) are used in combination, it is preferable to combine HCF2-CF2-O-CH2-CH2-O-CF2-CF2H with HCF2-CF2-CH2-O-CF2-CF2H.

[0041] In the composition of the present disclosure, the content of the fluorinated ether (E) is preferably 0.01% by mass or more and 99% by mass or less, based on the composition of the present disclosure. When the composition of the present disclosure is used as a negative electrode active material in a secondary battery containing a silicon material, the content of the fluorinated ether (E) relative to the composition of the present disclosure is more preferably 10% by mass or more, even more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more, and is more preferably 95% by mass or less, even more preferably 90% by mass or less, even more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less, in order to further suppress gas generation during high-temperature storage. When the composition of the present disclosure is used in a secondary battery containing a metal material (particularly lithium metal) as a negative electrode active material, the content of the fluorinated ether (E) relative to the composition of the present disclosure is more preferably 0.5% by mass or more, even more preferably 2% by mass or more, even more preferably 10% by mass or more, and particularly preferably 20% by mass or more, and is more preferably 80% by mass or less, even more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less, in order to further suppress gas generation during high-temperature storage. In the composition of the present disclosure, the content of the compound (A) is preferably 0.00000001 mass % or more and 5 mass % or less relative to the content of the fluorinated ether (E). When the composition of the present disclosure is used as a negative electrode active material in a secondary battery containing a silicon material, the content of compound (A) relative to the content of fluorinated ether (E) is more preferably 0.0000001% by mass or more, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, even more preferably 0.06% by mass or less, and particularly preferably 0.03% by mass or less, in order to further suppress gas generation during high-temperature storage. When the composition of the present disclosure is used as a negative electrode active material in a secondary battery containing a metal material (particularly lithium metal), the content of compound (A) relative to the content of fluorinated ether (E) is more preferably 0.00000003% by mass or more, even more preferably 0.0000003% by mass or more, and is more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.05% by mass or less, in order to further suppress gas generation during high-temperature storage.

[0043] The composition of the present disclosure preferably contains a solvent. The fluorinated ether (E) can be used as the solvent, but the composition may further contain a solvent other than the fluorinated ether (E).

[0044] The solvent preferably contains at least one selected from the group consisting of carbonates and carboxylic acid esters.

[0045] The carbonate may be a cyclic carbonate or a chain carbonate.

[0046] The cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate.

[0047] The non-fluorinated cyclic carbonate may be a non-fluorinated saturated cyclic carbonate, preferably a non-fluorinated saturated alkylene carbonate having an alkylene group with 2 to 6 carbon atoms, more preferably a non-fluorinated saturated alkylene carbonate having an alkylene group with 2 to 4 carbon atoms.

[0048] Among these, the non-fluorinated saturated cyclic carbonate is preferably at least one selected from the group consisting 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, as these have a high dielectric constant and suitable viscosity.

[0049] The non-fluorinated saturated cyclic carbonates may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0050] When the non-fluorinated saturated cyclic carbonate is contained, the content of the non-fluorinated saturated cyclic carbonate relative to the solvent is preferably 5 to 90% by volume, more preferably 10 to 60% by volume, and even more preferably 15 to 45% by volume.

[0051] The fluorinated cyclic carbonate is a cyclic carbonate having a fluorine atom. A solvent containing the fluorinated cyclic carbonate can be suitably used even under high voltage. In this specification, the term "high voltage" refers to a voltage of 4.2 V or higher. The upper limit of the "high voltage" is preferably 5.5 V, and more preferably 5.0 V.

[0052] The fluorinated cyclic carbonate may be a fluorinated saturated cyclic carbonate or a fluorinated unsaturated cyclic carbonate.

[0053] The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate having a fluorine atom, and specifically, is represented by the following general formula (A):

[0054] [C1] (A) XXCCX3X4 (wherein X1 to X4 are the same or different and each represent -H, -CH3, -C2H5, -F, a fluorinated alkyl group which may have an ether bond, or a fluorinated alkoxy group which may have an ether bond, provided that at least one of X1 to X4 is -F, a fluorinated alkyl group which may have an ether bond, or a fluorinated alkoxy group which may have an ether bond.) Examples of the fluorinated alkyl group include -CF3, -CF2H, -CH2F, etc.

[0055] When the composition of the present disclosure contains the above-mentioned fluorinated saturated cyclic carbonate, the oxidation resistance of the electrolyte is improved and stable and excellent charge / discharge characteristics are obtained when the composition is applied to a high-voltage lithium ion secondary battery or the like. In this specification, an "ether bond" is a bond represented by --O--.

[0056] From the viewpoint of good dielectric constant and oxidation resistance, it is preferable that one or two of X1 to X4 is -F, a fluorinated alkyl group which may have an ether bond, or a fluorinated alkoxy group which may have an ether bond.

[0057] X1 to X4 are preferably -H, -F, a fluorinated alkyl group (a), a fluorinated alkyl group having an ether bond (b), or a fluorinated alkoxy group (c), because this is expected to reduce viscosity at low temperatures, increase the flash point, and further improve the solubility of the electrolyte salt. The fluorinated alkyl group (a) is an alkyl group in which at least one hydrogen atom has been substituted with a fluorine atom. The fluorinated alkyl group (a) preferably has 1 to 20 carbon atoms, more preferably 1 to 17, still more preferably 1 to 7, and particularly preferably 1 to 5. If the number of carbon atoms is too large, there is a risk that the low-temperature characteristics and the solubility of the electrolyte salt may be reduced, whereas if the number of carbon atoms is too small, there may be a reduction in the solubility of the electrolyte salt, a reduction in discharge efficiency, and even an increase in viscosity.

[0059] Among the above fluorinated alkyl groups (a), those having one carbon atom include CFH2-, CF2H-, and CF3-. In particular, CF2H- or CF3- is preferred in terms of high-temperature storage properties, and CF3- is most preferred.

[0060] The above fluorinated chain carbonates may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0061] When the fluorinated chain carbonate is contained, the content of the fluorinated chain carbonate is preferably 10 to 90 mass %, more preferably 40 to 85 mass %, and even more preferably 50 to 80 mass % relative to the composition.

[0062] The fluorinated chain carbonate is a chain carbonate having fluorine atoms. A solvent containing the fluorinated chain carbonate can be suitably used even under high voltage.

[0063] The above-mentioned fluorinated chain carbonates include those represented by the general formula (B): Rf2OCOOR7 (B) (wherein Rf2 is a fluorinated alkyl group having 1 to 7 carbon atoms, and R7 is an alkyl group having 1 to 7 carbon atoms which may contain a fluorine atom).

[0064] Rf² is a fluorinated alkyl group having 1 to 7 carbon atoms, and R7 is an alkyl group having 1 to 7 carbon atoms which may contain a fluorine atom. The fluorinated alkyl group is an alkyl group in which at least one hydrogen atom has been substituted with a fluorine atom. When R7 is an alkyl group containing a fluorine atom, it becomes a fluorinated alkyl group. Rf2 and R7 preferably have 1 to 7 carbon atoms, more preferably 1 or 2, in terms of low viscosity. If the number of carbon atoms is too large, there is a risk that the low-temperature characteristics and the solubility of the electrolyte salt may be reduced, whereas if the number of carbon atoms is too small, there may be a reduction in the solubility of the electrolyte salt, a reduction in discharge efficiency, and even an increase in viscosity.

[0065] Examples of the fluorinated alkyl group having one carbon atom include CFH2-, CF2H-, CF3-, etc. In particular, CFH2- or CF3- is preferred in terms of high-temperature storage properties.

[0066] Examples of the fluorinated alkyl group having two or more carbon atoms include a group represented by the following general formula (d-1): Rd1-Rd2- (d-1) (wherein Rd1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; Rd2 is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; provided that at least one of Rd1 and Rd2 has a fluorine atom) is a preferred example from the viewpoint of good solubility of the electrolyte salt. R1 and Rd2 may further have atoms other than carbon atoms, hydrogen atoms and fluorine atoms. Rd1 is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. Rd1 is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and more preferably 1 to 3 carbon atoms.

[0068] Specific examples of preferred fluorinated alkyl groups include CF3CF2-, HCF2CF2-, H2CFCF2-, CH3CF2-, CF3CH2-, CF3CF2CF2-, HCF2CF2CF2-, H2CFCF2CF2-, CH3CF2CF2-,

[0069] Among these, the fluorinated alkyl groups for Rf2 and R7 are preferably CF3-, CF3CF2-, (CF3)2CH-, CF3CH2-, C2F5CH2-, CF3CF2CH2-, HCF2CF2CH2-, CF3CFHCF2CH2-, CFH2-, and CF2H-, and from the viewpoints of high flame retardancy and good rate characteristics and oxidation resistance, CF3CH2-, CF3CF2CH2-, HCF2CF2CH2-, CFH2-, and CF2H- are more preferred.

[0070] When R7 is an alkyl group containing no fluorine atom, it is an alkyl group having a carbon number of 1 to 7. R7 preferably has a carbon number of 1 to 4, more preferably 1 to 3, in terms of low viscosity.

[0071] Examples of the alkyl group not containing a fluorine atom include CH3-, CH3CH2-, (CH3)2CH-, C3H7-, etc. Among these, CH3- and CH3CH2- are preferred in terms of low viscosity and good rate characteristics.

[0072] The fluorine content of the fluorinated chain carbonate is preferably 15 to 70% by mass. When the fluorine content is within the above range, compatibility with solvents and solubility of salts can be maintained. The fluorine content is more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 35% by mass or more, more preferably 60% by mass or less, and even more preferably 50% by mass or less. In the present disclosure, the fluorine content is determined based on the structural formula of the fluorinated chain carbonate as follows: {(number of fluorine atoms x 19) / molecular weight of fluorinated chain carbonate} x 100(%) This is the value calculated by

[0073] The fluorinated chain carbonate is preferably any of the following compounds, because it has low viscosity.

[0074] [Case 2] F₂CH₂C-0-0-0-CHo FaCF₂CH₂C-O-8-O-CH, F₂CH₂C-0--0-CH2CH3 HF2OF₂CH₂C-0-0-0-CH3 F3CF2CH2C-OCO-CH2CH3 HF2CF2CH2C-OCO-CH2CH3 FaCH2C-0-8-o-CH2CF3 F3CH2C-o---CH2CF2CF3 -8-o-CH₂OF₂OF2H F3CF2CH2C-о-с-о-CH2CF2CF2H F3CF2CH2C-0-CO-CH2CF2CF3 HF2CF2CH2C-0-CO-CH2CF2CF2H F3CH2C-OCO-CH2CF2CF2H HF2CH2C-OCO-CH3 FH₂C-0-0-0-CH2 HF2C-0-0-0-CH3

[0075] As the above-mentioned fluorinated chain carbonate, methyl 2,2,2-trifluoroethyl carbonate (F3CH2COC(=O)OCH3) is particularly preferable.

[0076] The above fluorinated chain carbonates may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0077] When the fluorinated chain carbonate is contained, the content of the fluorinated chain carbonate is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and even more preferably 50 to 80% by volume, relative to the solvent. The solvent preferably contains at least one selected from the group consisting of the cyclic carbonate, the chain carbonate, and the chain carboxylic acid ester, and more preferably contains the cyclic carbonate and at least one selected from the group consisting of the chain carbonate and the chain carboxylic acid ester. The cyclic carbonate is preferably a saturated cyclic carbonate. A composition containing the solvent having the above composition can further suppress gas generation during high-temperature storage of an electrochemical device.

[0079] When the solvent contains the cyclic carbonate and at least one selected from the group consisting of the chain carbonate and the chain carboxylic acid ester, the cyclic carbonate and at least one selected from the group consisting of the chain carbonate and the chain carboxylic acid ester preferably account for 10 to 100 mass %, more preferably 30 to 100 mass %, and even more preferably 50 to 100 mass %, of the composition.

[0080] When the solvent contains the cyclic carbonate and at least one selected from the group consisting of the chain carbonate and the chain carboxylic acid ester, the mass ratio of the cyclic carbonate to the at least one selected from the group consisting of the chain carbonate and the chain carboxylic acid ester is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 or more, even more preferably 15 / 85 or more, particularly preferably 20 / 80 or more, more preferably 90 / 10 or less, even more preferably 60 / 40 or less, and particularly preferably 50 / 50 or less.

[0081] The solvent also preferably contains at least one selected from the group consisting of the non-fluorinated saturated cyclic carbonate, the non-fluorinated chain carbonate, and the non-fluorinated chain carboxylic acid ester, and more preferably contains the non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester. An electrolyte solution containing a solvent of the above composition can be suitably used in electrochemical devices used at relatively low voltages.

[0082] When the solvent contains the non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester, the non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester preferably account for 5 to 100 mass%, more preferably 20 to 100 mass%, and even more preferably 30 to 100 mass%, of the composition.

[0083] When the solvent contains the non-fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester, the mass ratio of the non-fluorinated saturated cyclic carbonate to the at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 or more, even more preferably 15 / 85 or more, particularly preferably 20 / 80 or more, more preferably 90 / 10 or less, even more preferably 60 / 40 or less, and particularly preferably 50 / 50 or less.

[0084] The solvent also preferably contains at least one selected from the group consisting of the fluorinated saturated cyclic carbonate, the fluorinated chain carbonate, and the fluorinated chain carboxylic acid ester, and more preferably contains the fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester. An electrolytic solution containing a solvent of the above composition can be suitably used not only in electrochemical devices used at relatively low voltages, but also in electrochemical devices used at relatively high voltages.

[0085] When the solvent contains the fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester, the total amount of the fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester is preferably 10 to 100 mass%, more preferably 30 to 100 mass%, and even more preferably 50 to 100 mass%, based on the composition.

[0086] When the solvent contains the fluorinated saturated cyclic carbonate and at least one selected from the group consisting of the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester, the mass ratio of the fluorinated saturated cyclic carbonate to the at least one selected from the group consisting of the fluorinated chain carbonate and the fluorinated chain carboxylic acid ester is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 or more, even more preferably 15 / 85 or more, particularly preferably 20 / 80 or more, more preferably 90 / 10 or less, even more preferably 60 / 40 or less, and particularly preferably 50 / 50 or less.

[0087] The solvent is preferably a non-aqueous solvent, and the composition of the present disclosure is preferably a composition for a non-aqueous electrolyte solution. The content of the solvent in the electrolytic solution is preferably 70 to 99.999% by mass, more preferably 80% by mass or more, and more preferably 92% by mass or less.

[0088] The composition of the present disclosure preferably further contains an electrolyte salt. As the electrolyte salt, any salt that can be used in an electrolytic solution, such as a lithium salt, an ammonium salt, a metal salt, a liquid salt (ionic liquid), an inorganic polymer salt, or an organic polymer salt, can be used.

[0089] As the electrolyte salt for the electrolyte solution for lithium ion secondary batteries, a lithium salt is preferred. Any lithium salt can be used, and specific examples thereof include inorganic lithium salts such as LiPF6, LiBF4, LiCIO4, LiAIF4, LiSbF6, LiTaF6, LiWF7, LiAsF6, LiAICI4, LiI, LiBr, LiCl, LiB10C110, Li2SiF6, Li2PFO3, and LiPO2F2; Lithium tungstates such as LiWOF5; Lithium carboxylates such as HCO₂Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, CF3CF2CF2CF2CO2Li; Lithium salts with an S=O group, such as FSO₃Li, CH3SO₃Li, CH2FSO₃Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li, lithium methyl sulfate, lithium ethyl sulfate (C2H5OSO3Li), and lithium 2,2,2-trifluoroethyl sulfate; Lithium imide salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2) (CF3SO2), iN(CF3SO2)2, LiN(C2F5SO2)2, lithium bisperfluoroethanesulfonylimide, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, lithium cyclic 1,2-ethanedisulfonylimide, lithium cyclic 1,3-propanedisulfonylimide, lithium cyclic 1,4-perfluorobutanedisulfonylimide, LiN(CF3SO2) (FSO₂), LiN(CF3SO2) (C3F7SO₂), LiN(CF3SO2) (C4F9SO2), and LiN(POF2)2; Lithium methide salts such as LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3; Other examples include salts represented by the formula: LiPFa(CF2n+1)6-a (wherein a is an integer of 0 to 5, and n is an integer of 1 to 6) (e.g., 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, L Fluorine-containing organic lithium salts such as iBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2, LiSCN, LiB(CN)4, LiB(C6H5)4, Li2(C2O4), LiP(C2O4)3, and Li2B12FbH12-b (b is an integer of 0 to 3), etc.

[0090] Among these, LiPF6, LiBF4, LiSbF6, LiTaF6, LiPO2F2, FSO3Li, CF3SO3Li, iN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, and the like are preferred because they have the effect of improving output characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like. LiPF6, LiN(FSO2) At least one lithium salt selected from the group consisting of LiPF6, LiFSI, and LiTFSI is particularly preferred.

[0091] These electrolyte salts may be used alone or in combination of two or more. A preferred example of a combination of two or more is a combination of LiPF6 and LiBF4, or a combination of LiPF6 and LiPO2F2, C2H5OSO3Li, or FSO3Li, which has the effect of improving high-temperature storage characteristics, load characteristics, and cycle characteristics.

[0092] In this case, there is no limit to the amount of LiBF4, LiPO2F2, C2H5OSO3Li or FSO3Li blended relative to 100% by mass of the entire electrolyte solution, and it can be any amount as long as it does not significantly impair the effects of the present disclosure. However, it is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to the electrolyte solution. Another example is the combined use of an inorganic lithium salt and an organic lithium salt, which has the effect of suppressing deterioration due to high-temperature storage. Preferred organic lithium salts include CF3SO3Li, LiN(FSO2)2(LIFSI), LiN(FSO2)(CF3SO2), LiN(CF3SO2)2(LITFSI), LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, and LiPF3(C2F5)3. In this case, the proportion of the organic lithium salt relative to 100% by mass of the entire electrolyte solution is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and is preferably 30% by mass or less, particularly preferably 20% by mass or less. The concentration of these electrolyte salts in the electrolyte solution is not particularly limited as long as it does not impair the effects of the present disclosure. In order to maintain the electrical conductivity of the electrolyte solution in a good range and ensure good battery performance, the total molar concentration of lithium in the electrolyte solution is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, even more preferably 0.5 mol / L or more, particularly preferably 1.0 mol / L or more, and is preferably 3 mol / L or less, more preferably 2.5 mol / L or less, even more preferably 2.0 mol / L or less.

[0095] If the total molar concentration of lithium is too low, the electrical conductivity of the electrolyte may be insufficient, whereas if the concentration is too high, the electrical conductivity may decrease due to increased viscosity, which may result in reduced battery performance.

[0096] The ether compound is preferably a chain ether having 2 to 10 carbon atoms or a cyclic ether having 3 to 6 carbon atoms. Examples of chain ethers 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.

[0097] Examples of cyclic ethers 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, metaformaldehyde, 2-methyl-1,3-dioxolane, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-(trifluoroethyl)dioxolane, 2,2-bis(trifluoromethyl)-1,3-dioxolane, and fluorinated compounds thereof. Among these, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, and crown ether are preferred in that they have a high ability to solvate lithium ions and improve the degree of ionic dissociation, and dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred because they have low viscosity and provide high ionic conductivity.

[0098] As the ether compound, fluorinated ethers other than the fluorinated ether (E) can also be suitably used.

[0099] The compositions of the present disclosure may be prepared by any method using the ingredients described above. The composition of the present disclosure can be suitably applied to, for example, electrochemical devices such as secondary batteries such as lithium ion secondary batteries, lithium ion capacitors, hybrid capacitors, electric double layer capacitors, etc. A nonaqueous electrolyte battery using the composition of the present disclosure will be described below. The nonaqueous electrolyte battery can have a known structure and typically includes a positive electrode and a negative electrode capable of absorbing and releasing ions (e.g., lithium ions) and the composition (electrolyte) of the present disclosure. An electrochemical device including the composition (electrolyte) of the present disclosure also constitutes the present disclosure.

[0101] Examples of electrochemical devices include secondary batteries such as lithium ion secondary batteries, lithium ion capacitors, capacitors (hybrid capacitors, electric double layer capacitors), radical batteries, solar cells (particularly dye-sensitized solar cells), lithium ion primary batteries, fuel cells, various electrochemical sensors, electrochromic elements, electrochemical switching elements, aluminum electrolytic capacitors, and tantalum electrolytic capacitors, with secondary batteries such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors being preferred. The present disclosure also includes a module including the electrochemical device.

[0102] The present disclosure also relates to a secondary battery comprising the composition (electrolyte) of the present disclosure. The secondary battery preferably comprises a positive electrode, a negative electrode, and the above-mentioned electrolyte solution. The secondary battery is preferably a lithium ion secondary battery.

[0103] <Positive electrode> The positive electrode is composed of a positive electrode active material layer containing a positive electrode active material and a current collector. The positive electrode active material is not particularly limited as long as it can electrochemically absorb and release lithium ions, and examples thereof include lithium-containing transition metal composite oxides, lithium-containing transition metal phosphate compounds, sulfur-based materials, conductive polymers, etc. Among these, lithium-containing transition metal composite oxides and lithium-containing transition metal phosphate compounds are preferred as the positive electrode active material, and lithium-containing transition metal composite oxides that generate high voltage are particularly preferred.

[0105] The transition metal of the lithium-containing transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc., and specific examples include lithium-cobalt composite oxides such as LiCoO2, lithium-nickel composite oxides such as LiNiO2, lithium-manganese composite oxides such as LiMnO2, LiMn2O4, and Li2MnO4, and lithium transition metal composite oxides in which some of the transition metal atoms that form the main components of these lithium transition metal composite oxides have been replaced with other elements such as Na, K, B, F, AI, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. Specific examples of substituted compounds include LiNi0.5Mn0.5O2, LiNi0.85C00.10A10.0502, LiNi0.5C00.2Mn0.302, LiNi0.6Co0.2Mn0.2O2, LiNi0.33Co0.33Mn0.3302, LiNi0.8C00.1Mn0.102, LiNi0.45C00.10A10.4502, LiMn1.8A10.204, and LiMn1.5Ni0.504.

[0106] Among these, LiMn1.5Ni0.504, LiNi0.5Co0.2Mn0.302, and LiNi0.6Co0.2Mn0.2O2 are preferred as the lithium-containing transition metal composite oxides, as they have high energy density even at high voltages. Of these, LiMn1.5Ni0.504 is preferred for high voltages of 4.4 V or higher.

[0107] Among these, LiNiO.6Co0.2Mn0.2O2, LiNi0.8C00.1Mn0.102, and LiNi0.85C00.10A10.05O2 are preferred as the lithium-containing transition metal composite oxides, since they can provide a high-capacity lithium ion secondary battery.

[0108] Preferable transition metals in lithium-containing transition metal phosphate compounds include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc., and specific examples include iron phosphates such as LiFePO4, Li3Fe2(PO4)3, and LiFeP2O7, cobalt phosphates such as LiCoPO4, and lithium transition metal phosphate compounds in which some of the transition metal atoms that make up the main components of these compounds have been substituted with other elements such as AI, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, and Si.

[0109] Examples of the lithium-containing transition metal composite oxide include a lithium manganese spinel composite oxide represented by the formula: LiaMn2-bM1bO4 (wherein 0.9≤a; 0≤b≤1.5; M' is at least one metal selected from the group consisting of Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge); A lithium-nickel composite oxide represented by the formula: LiNi₁-cM²cO₂ (wherein 0≦c≦0.5; M² is at least one metal selected from the group consisting of Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge), or Examples include lithium-cobalt composite oxides represented by the formula: LiC01-gM3gO2 (wherein 0≦d≦0.5; M3 is at least one metal selected from the group consisting of Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge).

[0110] Among these, LiCoO2, LiMnO2, LiNiO2, LiMn2O4, LiNi0.8Co0.15A10.0502, or LiNi1 / 3Co1 / 3Mn1 / 3O2 are preferred in terms of providing a lithium ion secondary battery with high energy density and high output.

[0111] Other examples of the positive electrode active material include LiFePO4, LiNi0.8C00.2O2, Li1.2Fe0.4Mn0.4O2, LiNi0.5Mn0.5O2, LiV3O6, and Li2MnO3.

[0112] The content of the positive electrode active material is preferably 50 to 99.5% by mass of the positive electrode mixture, more preferably 80 to 99% by mass, in terms of high battery capacity. The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. The upper limit is preferably 99% by mass or less, more preferably 98% by mass or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electrical capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

[0113] The positive electrode mixture preferably further contains a binder, a thickener, and a conductive material. Any material can be used as the binder as long as it is safe for the solvents and electrolytes used in the production of the electrodes. Examples of such binders include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, chitosan, alginic acid, polyacrylic acid, polyimide, cellulose, and nitrocellulose; rubber-like 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 hydrogenated products thereof; and EPDM (ethylene-propylene glycol dimethyl ether (EPDM)). Examples of suitable polymers include thermoplastic elastomeric polymers such as styrene-ethylene-butadiene-styrene terpolymers, styrene-ethylene-butadiene-styrene copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products thereof; soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorine-containing polymers such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride copolymers, and tetrafluoroethylene-ethylene copolymers; and polymer compositions having ionic conductivity for alkali metal ions (particularly lithium ions). These may be used alone or in any combination and ratio of two or more. The content of the binder, expressed as the proportion of the binder in the positive electrode active material layer, is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1.2% by mass or more, and usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, and most preferably 10% by mass or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently held, resulting in insufficient mechanical strength of the positive electrode and possibly deteriorating battery performance such as cycle characteristics. On the other hand, if the proportion is too high, this may lead to a decrease in battery capacity and conductivity.

[0115] Any known conductive material can be used as the conductive material. Specific examples include metal materials such as copper, nickel, and gold; graphite (e.g., natural graphite and artificial graphite); carbon black (e.g., acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black); and carbon materials such as needle coke, carbon nanotubes, fullerenes, and amorphous carbon (e.g., VGCF). These materials may be used alone or in any combination and ratio of two or more. The conductive material is typically contained in the positive electrode active material layer in an amount of at least 0.01% by mass, preferably at least 0.1% by mass, and more preferably at least 1% by mass, and typically at most 50% by mass, preferably at most 30% by mass, and more preferably at most 15% by mass. A content below this range may result in insufficient conductivity. Conversely, a content above this range may result in a decrease in battery capacity.

[0116] The solvent for forming the slurry is not particularly limited as long as it can dissolve or disperse the positive electrode active material, conductive material, binder, and thickener used as needed, and either an aqueous solvent or an organic solvent can be used. Examples of aqueous solvents include water and a mixture of alcohol and water. Examples of organic solvents include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), N-butylpyrrolidone (NBP), 3-methoxy-N,N-dimethylpropionamide, dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide.

[0117] Examples of materials for the positive electrode current collector include metals such as aluminum, titanium, tantalum, stainless steel, and nickel, or metal materials such as alloys thereof, and carbon materials such as carbon cloth and carbon paper. Among these, metal materials, particularly aluminum or its alloys, are preferred.

[0118] The shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, expanded metal, punched metal, or foamed metal, for a metal material; or, for a carbon material, a carbon plate, a carbon thin film, or a carbon cylinder. Of these, a metal thin film is preferred. The thin film may be formed into a mesh-like shape as appropriate. The thickness of the thin film is optional, but is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less. If the thin film is thinner than this range, the strength required as a current collector may be insufficient. Conversely, if the thin film is thicker than this range, handling may be impaired.

[0119] It is also preferable that a conductive assistant is applied to the surface of the current collector from the viewpoint of reducing the electrical contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive assistant include carbon and noble metals such as gold, platinum, and silver.

[0120] The positive electrode can be manufactured by a conventional method. For example, a method can be mentioned in which the above-mentioned positive electrode active material is added with the above-mentioned binder, thickener, conductive material, solvent, etc. to form a slurry-like positive electrode mixture, which is applied to a current collector, dried, and then pressed to increase the density.

[0121] <Negative electrode> The negative electrode is composed of a negative electrode active material layer containing a negative electrode active material and a current collector.

[0122] The above-mentioned negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbon materials, silicon materials, metal materials, conductive polymers, etc. These may be used alone or in any combination of two or more.

[0123] Examples of the above-mentioned carbon materials include natural graphite, artificial graphite, and those obtained by carbonizing these graphites after surface treatment with pitch or other organic substances. These may be used alone or in any combination of two or more.

[0124] The above-mentioned silicon material may be a single silicon or a composite material containing silicon and one or more other constituent elements (such as cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, zirconium, boron, carbon, aluminum, phosphorus, etc.). These may be used alone or in any combination of two or more. From the viewpoint of obtaining excellent battery capacity, the above-mentioned silicon materials are preferably SiO√(0 < v ≦ 2), SnO㎢(0 ≦ w ≦ 2), Si-Co-C composite material, and Si-Ni-C composite material.

[0125] It is preferable to use the above-mentioned silicon material in combination with the above-mentioned carbon material. In this case, the mass ratio is preferably silicon material:carbon material = 1 to 20:99 to 80.

[0126] Examples of the metal material include metal materials containing metal elements such as lithium and tin. The metal material may be a simple metal, or a compound such as an alloy, oxide, carbide, nitride, silicide, sulfide, or phosphide. These may be used alone or in any combination of two or more. From the viewpoint of obtaining an excellent battery capacity, metal materials containing lithium are preferred as the metal material, and lithium metal (simple lithium metal) is more preferred.

[0127] From the viewpoint of high current density charge / discharge characteristics, the lithium-containing metal material is preferably a material containing lithium and titanium, and more preferably a composite oxide of lithium and titanium (hereinafter abbreviated as "lithium titanium composite oxide").

[0128] The lithium titanium composite oxide may be a compound represented by the general formula: LixTiyMzO4 [In the formula, M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb.] It is preferable that the compound is represented by the following formula: Among the above compositions, (i)1.2≤x≤1.4, 1.5≤y≤1.7, z= 0 (ii)0.9≤x≤1.1, 1.9≤y≤2.1, z= 0 (iii)0.7≤x≤0.9, 2.1≤y≤2.3, z=0 The structure of is particularly preferred because it has a good balance of battery performance.

[0129] Particularly preferred representative compositions of the above compounds are (i) Li4 / 3Ti5 / 3O4, (ii) Li1Ti2O4, and (iii) Li4 / 5Ti11 / 5O4. As for the structure where Z≠0, for example, Li4 / 3Ti4 / 3Al1 / 3O4 is preferred.

[0130] The negative electrode mixture preferably further contains a binder, a thickener, and a conductive material.

[0131] Examples of the binder include the same binders as those usable for the positive electrode described above. The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 0.6% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less, and particularly preferably 8% by mass or less. If the ratio of the binder to the negative electrode active material exceeds the above range, the ratio of the binder that does not contribute to the battery capacity increases, which may result in a decrease in battery capacity. On the other hand, if the ratio is below the above range, the strength of the negative electrode may be reduced.

[0132] In particular, when a rubber-like polymer such as SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Also, when a fluorine-based polymer such as polyvinylidene fluoride is contained as a main component, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and usually 15% by mass or less, preferably 10% by mass or less, more preferably 8% by mass or less.

[0133] Examples of conductive materials for the negative electrode include metal materials such as copper and nickel; and carbon materials such as graphite and carbon black.

[0134] The solvent for forming the slurry is not particularly limited as long as it is capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as needed, and either an aqueous solvent or an organic solvent may be used. Examples of aqueous solvents include water and alcohol, and examples of organic solvents include N-methylpyrrolidone (NMP), N-butylpyrrolidone (NBP), 3-methoxy-N,N-dimethylpropionamide, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, and hexane.

[0135] Examples of materials for the negative electrode current collector include copper, nickel, stainless steel, etc. Among these, copper foil is preferred from the viewpoints of ease of processing into a thin film and cost.

[0136] The negative electrode may be manufactured by a conventional method. For example, the negative electrode material may be prepared by adding the binder, thickener, conductive material, solvent, etc., to form a slurry, which is then applied to a current collector, dried, and pressed to increase density. When an alloy material is used, a thin film layer (negative electrode active material layer) containing the negative electrode active material may be formed by a vapor deposition method, a sputtering method, a plating method, or the like.

[0137] <Separator> The secondary battery of the present disclosure preferably further includes a separator. The material and shape of the separator are not particularly limited as long as they are stable to the electrolyte solution and have excellent liquid retention properties, and any known separator can be used. Among them, it is preferable to use a material that is stable to the electrolyte solution, such as a resin, glass fiber, or inorganic material, and that is in the form of a porous sheet or nonwoven fabric, which has excellent liquid retention properties.

[0138] Examples of materials that can be used for the resin or glass fiber separator include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and glass filters. These materials may be used alone or in any combination and ratio, such as polypropylene / polyethylene two-layer films and polypropylene / polyethylene / polypropylene three-layer films. Among these, porous sheets or nonwoven fabrics made from polyolefins such as polyethylene and polypropylene are preferred for the separator, due to their excellent electrolyte permeability and shutdown effect.

[0139] On the other hand, inorganic materials include, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate, and these are used in particulate or fibrous form.

[0140] The separator may be in the form of a thin film such as a nonwoven fabric, a woven fabric, or a microporous film. A thin film having a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the above-mentioned independent thin film, a separator may be used in which a composite porous layer containing the above-mentioned inorganic particles is formed on the surface layer of the positive electrode and / or negative electrode using a resin binder. For example, a porous layer may be formed on both sides of the positive electrode using alumina particles with a 90% particle size of less than 1 μm and a fluororesin as a binder. The secondary battery of the present disclosure may have any shape, such as a cylindrical shape, a square shape, a laminated shape, a coin shape, a large shape, etc. The shapes and configurations of the positive electrode, negative electrode, and separator can be changed according to the shape of each battery.

[0142] A module including the secondary battery of the present disclosure also constitutes the present disclosure.

[0143] The present disclosure also includes an electric double layer capacitor comprising the composition of the present disclosure. The electric double layer capacitor may include a positive electrode, a negative electrode, and the above-mentioned electrolyte solution. In the electric double layer capacitor, at least one of the positive electrode and the negative electrode is a polarizable electrode, and the following electrodes described in detail in Japanese Patent Application Laid-Open No. 9-7896 can be used as the polarizable electrode and non-polarizable electrode.

[0144] The composition of the present disclosure is useful as an electrolyte solution for large-scale lithium-ion secondary batteries for hybrid automobiles and distributed power sources, and for electric double layer capacitors.

[0145] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. Example

[0146] Next, the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0147] (Fabrication and Evaluation of Lithium Metal Secondary Batteries) [Preparation of electrolyte] The materials were mixed in the proportions shown in Table 1 to obtain a non-aqueous electrolyte solution.

[0148] [Preparation of Positive Electrode] 97% by mass of Li(Ni0.8Mn0.1C00.1)O2 (NMC811) as the positive electrode active material, 1.5% by mass of acetylene black as the conductive material, and 1.5% by mass of polyvinylidene fluoride (PVdF) as the binder were mixed in N-methylpyrrolidone solvent to form a slurry. The resulting slurry was applied to a 15 μm thick aluminum foil current collector, dried, and then compression-molded using a press. The electrode was cut into shapes with a width of 30 mm, a length of 30 mm, and an uncoated portion of 4 mm width and 5 mm length to form a positive electrode.

[0149] [Preparation of negative electrode] A 0.15 mm thick lithium foil was cut into a width of 32 mm and a length of 32 mm as the negative electrode active material, and then rolled with a PTFE roll onto a copper mesh having terminal sections of 33 mm wide, 33 mm long, and 4 mm wide, 5 mm long to form a negative electrode.

[0150] [Preparation of Laminated Cell] A battery element was fabricated by laminating the positive and negative electrodes fabricated as described above with a polypropylene separator in the order negative electrode, separator, positive electrode. This battery element was inserted into a bag made of a laminate film in which both sides of an aluminum sheet (40 µm thick) were coated with a resin layer, with the positive and negative electrode terminals protruding. After that, the electrolyte solutions of the Examples and Comparative Examples in Table 1 were poured into the bag, which was then vacuum-sealed to fabricate a pouch-type lithium metal secondary battery.

[0151] [Cycle Test] The laminated cell manufactured as described above was subjected to constant current-constant voltage charging (hereinafter referred to as CC / CV charging) at 25°C to 4.15 V at a current equivalent to 0.2 C (cut at 0.05 C), and then discharged to 3.0 V at a constant current of 0.2 C. This constitutes one cycle, and five cycles of formation cycles were performed. Subsequently, 200 cycles of 0.5 C constant current-constant voltage charging and constant current discharging (between 4.15 and 3.0 V) were performed in a thermostatic bath at 40°C. The ratio of the discharge capacity at the 200th cycle to the discharge capacity at the 1st cycle at 40°C was determined and defined as the cycle capacity retention rate (%). (Discharge capacity after 200 cycles) / (Discharge capacity at 1st cycle) x 100 = Cycle capacity retention rate (%)

[0152] [Evaluation of gas generation amount] The volume of the battery before and after the cycle test was measured by Archimedes' method, and the amount of gas generated was calculated from the change in volume before and after the cycle. (Battery volume after cycle test) - (Battery volume before cycle test) = Amount of gas generated (ml)

[0153]

[0154] (Fabrication and Evaluation of Lithium-Ion Secondary Batteries) [Preparation of electrolyte] The materials were mixed in the proportions shown in Table 2 to obtain a non-aqueous electrolyte solution.

[0155] [Preparation of Positive Electrode] A positive electrode mixture slurry was prepared by mixing LiNi◦.5Mn1.504 as the positive electrode active material, acetylene black as the conductive material, and an N-methyl-2-pyrrolidone dispersion of polyvinylidene fluoride (PVdF) as the binder, with the solids ratio of the active material, conductive material, and binder being 92 / 3 / 5 (mass %). The obtained positive electrode mixture slurry was uniformly applied onto an aluminum foil current collector having a thickness of 15 μm, dried, and then compression-molded using a press to form a positive electrode.

[0156] [Preparation of negative electrode] The negative electrode active materials were artificial graphite powder, SiO powder, an aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose: 1% by mass) as a thickener, and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber: 50% by mass) as a binder. The solids ratio of the artificial graphite powder, SiO powder, thickener, and binder was 82.45 / 14.55 / 1.5 / 1.5 (mass%). A negative electrode mixture slurry was prepared by mixing the mixture in an aqueous solvent. The mixture was uniformly applied to a 10 μm thick copper foil, dried, and then compressed using a press to form a negative electrode.

[0157] [Preparation of Laminated Cell] A battery element was fabricated by laminating the positive and negative electrodes fabricated as described above with a polypropylene separator in the order negative electrode, separator, positive electrode. This battery element was inserted into a bag made of a laminate film in which both sides of an aluminum sheet (40 µm thick) were coated with a resin layer, with the positive and negative electrode terminals protruding. After that, the electrolyte solutions of the Examples and Comparative Examples in Table 2 were poured into the bag, which was then vacuum-sealed to fabricate a pouch-type lithium-ion secondary battery.

[0158] [Cycle Test] The laminated cell manufactured as described above was subjected to CC / CV charging (0.05C cut) at 25°C at a current equivalent to 0.1C up to 4.9V, followed by discharging to 3.0V at a constant current of 0.1C. This cycle constitutes one cycle, and five cycles of formation cycles were performed. Subsequently, 200 cycles of 0.5C constant current-constant voltage charging and constant current discharging (4.9-3.0V) were performed in a 40°C thermostatic chamber. The ratio of the discharge capacity at the 200th cycle to the discharge capacity at the 1st cycle at 40°C was determined and defined as the cycle capacity retention rate (%). (Discharge capacity after 200 cycles) / (Discharge capacity at 1st cycle) x 100 = Cycle capacity retention rate (%)

[0159] [Evaluation of gas generation amount] The volume of the battery before and after the cycle test was measured by Archimedes' method, and the amount of gas generated was calculated from the change in volume before and after the cycle. (Battery volume after cycle test) - (Battery volume before cycle test) = Amount of gas generated (ml)

[0160] The abbreviations in the table are as follows: <Compound (A)> A-1:HCF2-CF2-O-CH2-CH2-OH A-2: HCF2-CF2-CH2-O-CH2-CH2-OH A-3:HCF2-CH2-O-CH2-CH2-OH A-4: CF3-CF2-CH2-O-CH2-CH2-OH A-5:CF3-CHF-CF2-O-CH2-CH2-ОН A-6:HCF2-CF2-O-CH2-CH2-OLi A-7:HCF2-CF2-O-CH2-CH2-OK A-8:HCF2-CF2-O-CH2-CH2-ONa A-9:HCF2-CF2-O-CH2-CH2-OCs A-10:CF3-CHF-CF2-O-CH2-CH2-OLi <Fluorinated ether (E)> E-1:HCF2-CF2-O-CH2-CH2-O-CF2-CF2H E-2:HCF2-CF2-CH2-O-CH2-CH2-CH2-CF2-CF2H E-3:HCF2-CH2-O-CH2-CH2-O-CH2-CF2H E-4:CF3-CF2-CH2-O-CH2-CH2-O-CH2-CF2-CF3 E-5:CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3 E-6:HCF2-CF2-CH2-O-CF2-CF2H <Other solvent components> DME:CH3-O-CH2-CH2-O-CH3 EC: Ethylene carbonate DMC: Dimethyl carbonate FEC: Fluoroethylene carbonate TFMEC: Trifluoromethylethylene carbonate TFEMC: CF3-CH2-COO-CH₃ (trifluoroethyl methyl carbonate) <Lithium salt> LiFSI: Lithium bis(fluorosulfonyl)imide LiTFSI: Lithium bis(trifluoromethanesulfonyl)imide LiPF6: Lithium hexafluorophosphate

Claims

1. An electrolyte composition comprising a compound (A) represented by the following formula (A): (A) Rf¹-O-CH2-CH2-O-R1 (In the formula, Rf1 is a fluoroalkyl group having 1 to 6 carbon atoms, and R1 is H, Li, Na, K, or Cs.)

2. The Rf1 is HCF2-CF2 one, HCF2-CF2-CH2-, HCF2-CH2-, CF3-CF2-CH2-, or 2. The electrolyte composition according to claim 1, which is CF3-CHF-CF2-.

3. 3. The composition for an electrolyte solution according to claim 1, wherein R1 is H or Li.

4. 4. The composition for an electrolyte solution according to claim 1, wherein the content of the compound (A) is 0.0001 to 30,000 ppm relative to the composition for an electrolyte solution.

5. The compound (A) is HCF2-CF2-O-CH2-CH2-OH, HCF2-CF2-O-CH2-CH2-OLi, CF3-CHF-CF2-O-CH2-CH2-OH, and 5. The composition for an electrolyte solution according to claim 1, which is at least one selected from the group consisting of CF3-CHF-CF2-O-CH2-CH2-OLi.

6. 6. The composition for an electrolytic solution according to claim 1, which contains a fluorinated ether (E) represented by the following formula (E): wherein R 1 is an integer of 1 to 5; (E) Rf2-O-R2 (In the formula, Rf2 is a fluoroalkyl group having 1 to 5 carbon atoms, and R2 is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group for R2 may have an ether bond and / or fluorine.)

7. 7. The composition for an electrolyte solution according to claim 6, wherein Rf2 is HCF2-CF2-.

8. The R2 is -CH2-CH2-O-CF2-CF2H, or -CH2-CH2-O-CF2-CHF-CF3 8. The composition for an electrolyte solution according to claim 6, wherein

9. The fluorinated ether (E) is HCF2-CF2-O-CH2-CH2-O-CF2-CF2H, and CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3 9. The composition for an electrolyte solution according to claim 6, which is at least one selected from the group consisting of:

10. 10. The composition for an electrolyte solution according to claim 6, wherein the content of the fluorinated ether (E) is 0.01 to 99% by mass based on the composition for an electrolyte solution.

11. 11. The composition for an electrolyte solution according to claim 1, which contains at least one lithium salt selected from the group consisting of LiPF6, LiFSI, and LiTFSI.

12. The compound (A) is HCF2-CF2-O-CH2-CH2-OH, HCF2-CF2-O-CH2-CH2-OLi, CF3-CHF-CF2-O-CH2-CH2-OH, and CF3-CHF-CF2-O-CH2-CH2-OLi, the content of the compound (A) is 0.003 to 30,000 ppm relative to the electrolyte solution composition; HCF2-CF2-O-CH2-CH2-O-CF2-CF2H, and CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3 At least one fluorinated ether (E) selected from the group consisting of 12. The composition for an electrolyte solution according to claim 1, wherein the content of the fluorinated ether (E) is 0.5 to 50% by mass based on the composition for an electrolyte solution.

13. 13. A secondary battery comprising the electrolyte solution composition according to claim 12 and lithium metal as a negative electrode active material.

14. Compound (A) is HCF2-CF2-O-CH2-CH2-OH, HCF2-CF2-O-CH2-CH2-OLi, CF3-CHF-CF2-O-CH2-CH2-OH, and CF3-CHF-CF2-O-CH2-CH2-OLi, the content of the compound (A) is 0.01 to 30,000 ppm relative to the electrolyte solution composition; HCF2-CF2-O-CH2-CH2-O-CF2-CF2H, and CF3-CHF-CF2-O-CH2-CH2-O-CF2-CHF-CF3 At least one fluorinated ether (E) selected from the group consisting of 12. The composition for an electrolyte solution according to claim 1, wherein the content of the fluorinated ether (E) is 40 to 95 mass % based on the mass of the composition for an electrolyte solution.

15. 15. A secondary battery comprising the electrolyte solution composition according to claim 14 and a silicon material as a negative electrode active material.

16. 15. The composition for an electrolyte solution according to claim 1, which is for a secondary battery.

17. 15. An electrochemical device comprising the composition for an electrolyte solution according to claim 1.

18. A secondary battery comprising the electrolyte solution composition according to any one of claims 1 to 12 and 14.

19. 15. A lithium ion secondary battery comprising the composition for an electrolyte solution according to claim 1.

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