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

Abstract

The present disclosure provides: a composition for an electrolyte solution, which can suppress an increase in resistance during low-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. Also provided is a novel composition. More specifically, the present disclosure is a composition for an electrolyte solution, wherein the composition contains a compound (M) represented by formula (M). (M) Rf1 - COOM (In the formula, Rf1 is a 1-6 C fluoroalkyl group, and M is an alkali metal other than Li.)

Description

Electrolyte composition, electrochemical device, secondary battery, lithium ion secondary battery and composition

[0001] The present disclosure relates to an electrolyte composition, an electrochemical device, a secondary battery, a lithium ion secondary battery, and a composition.

[0002] In recent years, the trend toward lighter and smaller electrical appliances has led to the development of electrochemical devices with high energy density, such as lithium-ion secondary batteries. Furthermore, as the range of applications for electrochemical devices such as lithium-ion secondary batteries expands, improvements in their performance are required. In particular, improving battery performance will become increasingly important when lithium-ion secondary batteries are used in automobiles.

[0003] Patent Document 1 describes an electrolyte solution for a lithium metal secondary battery that contains a specific lithium salt and a non-aqueous solvent.

[0004] Special Publication No. 2022-552481

[0005] The present disclosure aims to provide an electrolyte composition that can suppress an increase in resistance during low-temperature storage, as well as an electrochemical device, a secondary battery, and a lithium-ion secondary battery that use the electrolyte composition. Another aim of the present disclosure is to provide a novel composition.

[0006] The present disclosure (1) is a composition for an electrolyte solution containing a compound (M) represented by the following formula (M): (M)Rf １ -COOM (where Rf １ is a fluoroalkyl group having 1 to 6 carbon atoms, and M is an alkali metal other than Li.

[0007] The present disclosure (2) relates to the Rf １ is HCF ２ The composition for an electrolyte solution according to the present disclosure (1) is

[0008] The present disclosure (3) provides that the compound (M) is HCF ２ -COOK and HCF ２ The composition for an electrolyte solution according to the present disclosure (1) or (2) is at least one selected from the group consisting of —COONa.

[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 (M) is 0.0001 to 3 mass% relative to the composition for an electrolyte solution.

[0010] The present disclosure (5) is a composition for an electrolyte solution according to any one of the present disclosures (1) to (4), which contains a fluorinated ether (E) represented by the following formula (E): (E) Rf ２ -OR (wherein, Rf ２ is a fluoroalkyl group having 1 to 6 carbon atoms, and R is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group of R may have an ether bond and / or fluorine.

[0011] The present disclosure (6) relates to the Rf ２ is HCF ２ -CF ２ The composition for an electrolyte solution according to the present disclosure (5) is

[0012] The present disclosure (7) is that the R is —CH ２ -CF ２ -CF ２ H, -CH ２ -CH ２ -CH ３ , or -CH ２ -CH ２ -O-CF ２ -CF ２ The composition for an electrolyte solution according to the present disclosure (5) or (6), wherein H

[0013] The present disclosure (8) provides that the fluorinated ether (E) is HCF ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H, HCF ２ -CF ２ -O-CH ２ -CH ２ -CH ３ , and HCF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２The composition for an electrolyte solution according to any one of the present disclosures (5) to (7) is at least one selected from the group consisting of H 2 .

[0014] The present disclosure (9) is the composition for an electrolyte solution according to any one of the present disclosures (5) to (8), wherein the content of the fluorinated ether (E) is 0.1 to 100% by volume relative to the solvent in the composition for an electrolyte solution.

[0015] The present disclosure (10) is LiPF ６ The composition for an electrolyte solution according to any one of the present disclosures (1) to (9) contains at least one lithium salt selected from the group consisting of LiFSI, LiTFSI, and LiTFSI.

[0016] The present disclosure (11) provides that the compound (M) is HCF ２ -COOK and HCF ２ -COONa, the content of the compound (M) is 0.0001 to 1 mass % relative to the electrolyte solution composition, and HCF ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H, HCF ２ -CF ２ -O-CH ２ -CH ２ -CH ３ , and HCF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ The composition for an electrolyte solution according to any one of the present disclosures (1) to (10), further comprising at least one fluorinated ether (E) selected from the group consisting of H, and the content of the fluorinated ether (E) is 5 to 80% by volume relative to the solvent in the composition for an electrolyte solution.

[0017] The present disclosure (12) is a secondary battery comprising the composition for an electrolyte solution according to the present disclosure (11) and lithium metal as a negative electrode active material.

[0018] The present disclosure (13) provides that the compound (M) is HCF ２-COOK and HCF ２ -COONa, the content of the compound (M) is 0.01 to 0.1 mass % relative to the electrolyte solution composition, and HCF ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H, HCF ２ -CF ２ -O-CH ２ -CH ２ -CH ３ , and HCF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ The composition for an electrolyte solution according to any one of the present disclosures (1) to (10), further comprising at least one fluorinated ether (E) selected from the group consisting of H, and the content of the fluorinated ether (E) is 25 to 30% by volume relative to the solvent in the composition for an electrolyte solution.

[0019] The present disclosure (14) is a secondary battery comprising the composition for an electrolyte solution according to the present disclosure (13) and a silicon material as a negative electrode active material.

[0020] The present disclosure (15) is a composition for an electrolyte solution according to any one of the present disclosures (1) to (11) and (13), which is for a secondary battery.

[0021] The present disclosure (16) is an electrochemical device comprising the composition for an electrolyte solution according to any one of the present disclosures (1) to (11) and (13).

[0022] The present disclosure (17) is a secondary battery containing the composition for an electrolyte solution according to any one of the present disclosures (1) to (11) and (13).

[0023] The present disclosure (18) is a lithium ion secondary battery containing the composition for an electrolyte solution according to any one of the present disclosures (1) to (11) and (13).

[0024] The present disclosure (19) is a composition containing a compound (M) represented by the following formula (M) and a fluorinated ether (E) represented by the following formula (E): (M) Rf１ -COOM (where Rf １ is a fluoroalkyl group having 1 to 6 carbon atoms, and M is an alkali metal other than Li. ２ -OR (wherein, Rf ２ is a fluoroalkyl group having 1 to 6 carbon atoms, and R is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group of R may have an ether bond and / or fluorine.

[0025] According to the present disclosure, it is possible to provide an electrolyte composition that can suppress an increase in resistance during low-temperature storage, as well as an electrochemical device, a secondary battery, and a lithium-ion secondary battery that use the electrolyte composition. Furthermore, according to the present disclosure, it is also possible to provide a novel composition.

[0026] The present disclosure will be specifically described below.

[0027] The present disclosure relates to a composition for an electrolyte solution containing a compound (M) represented by the following formula (M): (M)Rf １ -COOM (where Rf １ is a fluoroalkyl group having 1 to 6 carbon atoms, and M is an alkali metal other than Li.

[0028] The composition of the present disclosure, containing compound (M), can suppress an increase in resistance during low-temperature storage in an electrochemical device. This effect is presumably achieved by the fact that compound (M) is entrained when the solvent in the electrolyte is reduced on the negative electrode to form a protective film, thereby forming a protective film with low resistance.

[0029] The composition of the present disclosure is used in an electrolyte solution, and may be an electrolyte solution or a constituent component (e.g., an additive) of an electrolyte solution. The composition of the present disclosure is also suitable for use in electrochemical devices (particularly secondary batteries such as lithium-ion secondary batteries).

[0030] In formula (M), Rf １is 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, even more preferably 1 or 2, and particularly preferably 1. The fluoroalkyl group may be linear or branched, but is preferably linear. １ As for CF ３ -, HCF ２ -, FCH ２ -, CF ３ -CF ２ -, CF ３ -CH ２ -, HCF ２ -CH ２ -, FCH ２ -CH ２ -, CF ３ -CH ２ -CH ２ -, CF ３ -CF ２ -CH ２ -, HCF ２ -CF ２ -CH ２ -, FCH ２ -CF ２ -CH ２ -, HCF ２ -CF ２ -CF ２ -CF ２ -CH ２ - is preferable, and HCF is preferable from the viewpoint of suppressing the increase in resistance during storage at low temperatures. ２ - is more preferable.

[0031] In formula (M), M is an alkali metal other than Li. When M is an alkali metal other than Li, the alkali metal is contained in the coating film formed on the negative electrode. This reduces the crystallinity of the coating film, making it easier for lithium ions to move. The alkali metal may be any of Na, K, Rb, Cs, and Fr, but Na and K are preferred, and K is more preferred, from the viewpoints of ionization tendency and ion size.

[0032] Among the compounds (M), HCF is preferred from the viewpoint of suppressing the increase in resistance during low-temperature storage. ２ -COONa (sodium difluoroacetate), HCF ２-COOK (potassium difluoroacetate) is preferred, with potassium difluoroacetate being more preferred.

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

[0034] In the composition of the present disclosure, the content of compound (M) is preferably 0.0001% by mass or more and 3% by mass or less relative to the composition of the present disclosure. In order to further suppress an increase in resistance during low-temperature storage, the content of compound (M) is more preferably 0.001% by mass or more, even more preferably 0.01% by mass or more, more preferably 2% by mass or less, even more preferably 1% by mass or less, even more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less.

[0035] The composition of the present disclosure preferably contains a fluorinated ether (E) represented by the following formula (E): (E) Rf ２ -OR (wherein, Rf ２ is a fluoroalkyl group having 1 to 6 carbon atoms, and R is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group of R may have an ether bond and / or fluorine.

[0036] The combined use of the compound (M) and the fluorinated ether (E) can further suppress the increase in resistance during low-temperature storage. This effect is presumably brought about by the fact that the fluorinated ether (E) suppresses the decomposition reaction of the electrolyte, thereby suppressing the formation of an excessive coating, and by the formation of a coating containing the compound (M).

[0037] In formula (E), Rf ２ 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, even more preferably 2 to 3, and particularly preferably 2. The fluoroalkyl group may be linear or branched, but is preferably linear. ２ As for CF ３ -, CF ２ H-, CFH ２ -, CF３ -CF ２ -, CF ３ -CH ２ -, HCF ２ -CH ２ -, HCF ２ -CF ２ -, FCH ２ -CH ２ -, CF ３ -CH ２ -CH ２ -, CF ３ -CF ２ -CH ２ -, HCF ２ -CF ２ -CH ２ -, FCH ２ -CF ２ -CH ２ -, HCF ２ -CF ２ -CF ２ -CF ２ -CH ２ - is preferable, and HCF is preferable from the viewpoint of suppressing the increase in resistance during storage at low temperatures. ２ -CF ２ - is more preferable.

[0038] In formula (E), R 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 even 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 at least fluorine. R is -CF ３ , -CF ２ H, -CFH ２ , -CH ３ , -CH ２ -CH ３ , -CF ２ -CF ３ , -CH ２ -CF ３ , -CH ２ -CF ２ H, —CH ２ -CFH ２ , -CH ２ -CH ２ -CH ３ , -CH２ -CH ２ -CF ３ , -CH ２ -CF ２ -CF ３ , -CH ２ -CF ２ -CF ２ H, —CH ２ -CF ２ -CFH ２ , -CH ２ -CF ２ -CF ２ -CF ２ -CF ２ H, —CH ２ -CH ２ -O-CF ２ -CF ２ H is preferred, and -CH is preferred from the viewpoint of suppressing an increase in resistance during low-temperature storage. ２ -CF ２ -CF ２ H, —CH ２ -CH ２ -CH ３ , -CH ２ -CH ２ -O-CF ２ -CF ２ H is more preferred, and —CH ２ -CF ２ -CF ２ H, —CH ２ -CH ２ -O-CF ２ -CF ２ H is more preferred, and —CH ２ -CF ２ -CF ２ H is particularly preferred.

[0039] As the fluorinated ether (E), HCF is particularly preferred from the viewpoint of suppressing an increase in resistance during storage at low temperatures. ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H, HCF ２ -CF ２ -O-CH ２ -CH ２ -CH ３ , C.F. ２ -CF ２ -O-CH ２-CH ２ -O-CF ２ -CF ２ H is preferred, and HCF ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H, C.F. ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ Furthermore, when the composition of the present disclosure is used in a secondary battery containing a silicon material as a negative electrode active material, HCF ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H is particularly preferred, and when the composition of the present disclosure is used in a secondary battery containing a metal material (particularly lithium metal) as the negative electrode active material, CF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ H is particularly preferred.

[0040] The fluorinated ether (E) may be used alone or in combination of two or more. When two types of fluorinated ether (E) are used in combination, HCF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ H and HCF ２ -CF ２ -CH ２ -O-CF ２ -CF ２ It is preferable to combine H.

[0041] In the composition of the present disclosure, the content of the fluorinated ether (E) is preferably 0.1% by volume or more and 100% by volume or less relative to the solvent in 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) is more preferably 5% by volume or more relative to the solvent, even more preferably 15% by volume or more, particularly preferably 25% by volume or more, and more preferably 80% by volume or less, even more preferably 60% by volume or less, even more preferably 40% by volume or less, particularly preferably 30% by volume or less, in order to further suppress the increase in resistance during low-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 the fluorinated ether (E) relative to the solvent is more preferably 5% by volume or more, even more preferably 10% by volume or more, even more preferably 20% by volume or more, and particularly preferably 30% by volume or more, and is more preferably 80% by volume or less, even more preferably 60% by volume or less, and particularly preferably 50% by volume or less, in order to further suppress an increase in resistance during low-temperature storage.

[0042] 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).

[0043] The solvent preferably contains at least one selected from the group consisting of carbonates and carboxylic acid esters.

[0044] The carbonate may be a cyclic carbonate or a chain carbonate.

[0045] The cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate.

[0046] The non-fluorinated cyclic carbonate may be a non-fluorinated saturated cyclic carbonate, preferably a non-fluorinated saturated alkylene carbonate having an alkylene group having 2 to 6 carbon atoms, more preferably a non-fluorinated saturated alkylene carbonate having an alkylene group having 2 to 4 carbon atoms.

[0047] 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, because of its high dielectric constant and suitable viscosity.

[0048] The non-fluorinated saturated cyclic carbonates may be used alone or in any combination of two or more in any ratio.

[0049] 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.

[0050] The fluorinated cyclic carbonate is a cyclic carbonate having a fluorine atom. A solvent containing a fluorinated cyclic carbonate can be suitably used even under high voltage. In this specification, "high voltage" refers to a voltage of 4.2 V or more. The upper limit of the "high voltage" is preferably 5.5 V, more preferably 5.0 V.

[0051] The fluorinated cyclic carbonate may be a fluorinated saturated cyclic carbonate or a fluorinated unsaturated cyclic carbonate.

[0052] The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate having a fluorine atom, and specifically, is represented by the following general formula (A):

[0053] (In the formula, X １ ~X ４are the same or different, and are —H, —CH ３ , -C ２ H ５ , —F, a fluorinated alkyl group which may have an ether bond, or a fluorinated alkoxy group which may have an ether bond. １ ~X ４ wherein at least one of the groups is —F, a fluorinated alkyl group which may have an ether bond, or a fluorinated alkoxy group which may have an ether bond. The fluorinated alkyl group is a compound represented by the formula: ３ , -CF ２ H, —CH ２ F etc.

[0054] When the composition of the present disclosure contains the 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, etc. In this specification, the term "ether bond" refers to a bond represented by -O-.

[0055] X is a good choice due to its excellent dielectric constant and oxidation resistance. １ ~X ４ It is preferred that one or two of the groups be —F, a fluorinated alkyl group which may have an ether bond, or a fluorinated alkoxy group which may have an ether bond.

[0056] Since it is expected that the viscosity at low temperatures will decrease, the flash point will increase, and the solubility of electrolyte salts will improve, １ ~X ４ is preferably —H, —F, a fluorinated alkyl group (a), a fluorinated alkyl group having an ether bond (b), or a fluorinated alkoxy group (c).

[0057] The fluorinated alkyl group (a) is an alkyl group in which at least one hydrogen atom has been substituted with a fluorine atom. The number of carbon atoms in the fluorinated alkyl group (a) is preferably 1 to 20, more preferably 1 to 17, even more preferably 1 to 7, and particularly preferably 1 to 5. If the number of carbon atoms is too large, there is a risk of deterioration in low-temperature characteristics and deterioration in the solubility of the electrolyte salt. If the number of carbon atoms is too small, there may be deterioration in the solubility of the electrolyte salt, deterioration in discharge efficiency, and even increase in viscosity.

[0058] Among the above fluorinated alkyl groups (a), those having one carbon atom include CFH ２ -, CF ２ H-, CF ３ In particular, CF ２ H- or CF ３ - is preferable in terms of high temperature storage properties, and CF ３ - is most preferred.

[0059] The above fluorinated cyclic carbonates may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0060] When the fluorinated cyclic carbonate is contained, the content of the fluorinated 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.

[0061] The chain carbonate may be a non-fluorinated chain carbonate or a fluorinated chain carbonate.

[0062] Examples of the non-fluorinated chain carbonate include CH ３ OCOOCH ３ (Dimethyl carbonate: DMC), CH ３ CH ２ OCOOCH ２ CH ３ (Diethyl carbonate: DEC), CH ３ CH ２ OCOOCH ３ (Ethyl methyl carbonate: EMC), CH ３ OCOOCH ２ CH２ CH ３ Examples of the carbonate include hydrocarbon chain carbonates such as (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 ethyl phenyl carbonate. Among these, at least one carbonate selected from the group consisting of ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate is preferred.

[0063] The non-fluorinated chain carbonates may be used alone or in any combination of two or more in any ratio.

[0064] When the non-fluorinated chain carbonate is contained, the content of the non-fluorinated chain carbonate relative to the solvent is preferably 10 to 90% by volume, more preferably 40 to 85% by volume, and even more preferably 50 to 80% by volume.

[0065] 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.

[0066] The fluorinated chain carbonate may be a fluorinated chain carbonate represented by the general formula (B): ２ OCOOR ７ (B) (wherein, Rf ２ is a fluorinated alkyl group having 1 to 7 carbon atoms, and R ７ is an alkyl group having 1 to 7 carbon atoms which may contain a fluorine atom.

[0067] Rf ２ is a fluorinated alkyl group having 1 to 7 carbon atoms, and R ７is 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. ７ When Rf is an alkyl group containing a fluorine atom, it becomes a fluorinated alkyl group. ２ and R ７ In terms of low viscosity, the carbon number is preferably 1 to 7, and more preferably 1 to 2. If the carbon number 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 carbon number 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.

[0068] The fluorinated alkyl group having one carbon atom is CFH ２ -, CF ２ H-, CF ３ - etc. In particular, CFH ２ - or CF ３ - is preferable in terms of high-temperature storage properties.

[0069] The fluorinated alkyl group having two or more carbon atoms includes a group represented by the following general formula (d-1): ｄ１ -R ｄ２ - (d-1) (wherein, R ｄ１ is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; R ｄ２ is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; provided that R ｄ１ and R ｄ２ In view of the good solubility of the electrolyte salt, a fluorinated alkyl group represented by the formula: ｄ１ and R ｄ２ may further have atoms other than carbon atoms, hydrogen atoms and fluorine atoms.

[0070] R ｄ１ R is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. ｄ１ R is preferably a linear or branched alkyl group having 1 to 6 carbon atoms. ｄ１ The number of carbon atoms is more preferably 1 to 3.

[0071] Specific examples of preferred fluorinated alkyl groups include CF ３ CF ２ -, HCF ２ CF ２ -, H ２ CFCF ２ -, CH ３ CF ２ -, CF ３ CH ２ -, CF ３ CF ２ CF ２ -, HCF ２ CF ２ CF ２ -, H ２ CFCF ２ CF ２ -, CH ３ CF ２ CF ２ -,

[0072] Among them, Rf ２ and R ７ Examples of the fluorinated alkyl group include CF ３ -, CF ３ CF ２ -, (CF ３ ) ２ CH-, CF ３ CH ２ -, C ２ F ５ CH ２ -, CF ３ CF ２ CH ２ -, HCF ２ CF ２ CH ２ -, CF ３ CFHCF ２ CH ２ -, CFH ２ -, CF ２ H- is preferred, and CF is preferred because of its high flame retardancy, good rate characteristics and oxidation resistance. ３ CH ２ -, CF ３ CF ２ CH ２ -, HCF ２ CF ２ CH ２ -, CFH ２ -, CF ２ H- is more preferred.

[0073] R ７ When R is an alkyl group containing no fluorine atom, it is an alkyl group having 1 to 7 carbon atoms. ７ In terms of low viscosity, the number of carbon atoms is preferably 1 to 4, and more preferably 1 to 3.

[0074] Examples of the alkyl group not containing a fluorine atom include CH ３ -, CH ３ CH ２ -, (CH ３ ) ２ CH-, C ３ H ７ Among them, CH ３ -, CH ３ CH ２ - is preferred.

[0075] The fluorinated chain carbonate preferably has a fluorine content of 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 a value calculated based on the structural formula of the fluorinated chain carbonate by {(number of fluorine atoms × 19) / molecular weight of fluorinated chain carbonate} × 100(%).

[0076] The fluorinated chain carbonate is preferably any one of the following compounds, because it has low viscosity.

[0077]

[0078] The fluorinated chain carbonates include methyl 2,2,2-trifluoroethyl carbonate (F ３ CH ２ COC(=O)OCH ３ ) is particularly preferred.

[0079] The above fluorinated chain carbonates may be used alone or in any combination of two or more in any ratio.

[0080] 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.

[0081] 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 a solvent of the above composition can further suppress an increase in resistance during low-temperature storage of an electrochemical device.

[0082] 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 solvent preferably contains the cyclic carbonate and at least one selected from the group consisting of the chain carbonate and the chain carboxylic acid ester in a total amount of 10 to 100% by volume, more preferably 30 to 100% by volume, and even more preferably 50 to 100% by volume.

[0083] 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 volume 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.

[0084] 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.

[0085] 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 solvent preferably contains the non-fluorinated saturated cyclic carbonate and the at least one selected from the group consisting of the non-fluorinated chain carbonate and the non-fluorinated chain carboxylic acid ester in a total amount of 5 to 100% by volume, more preferably 20 to 100% by volume, and even more preferably 30 to 100% by volume.

[0086] 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 volume 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.

[0087] 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.

[0088] 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 solvent 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 in a total amount of 5 to 100% by volume, more preferably 10 to 100% by volume, and even more preferably 30 to 100% by volume.

[0089] 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 volume 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.

[0090] 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 electrolyte solution is preferably 70 to 99.999 mass %, more preferably 80 mass % or more, and more preferably 92 mass % or less.

[0091] The composition of the present disclosure preferably further contains an electrolyte salt, which may be 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.

[0092] The electrolyte salt of the electrolyte solution for lithium ion secondary batteries is preferably a lithium salt. Any lithium salt can be used, and specific examples include the following: LiPF ６ , LiBF ４ , LiClO ４ , LiAlF ４ , LiSbF ６ , LiTaF ６ , LiWF ７ , LiAsF ６ , LiAlCl ４ , LiI, LiBr, LiCl, LiB １０ Cl １０ , Li ２ SiF ６ , Li ２ PFO ３ , LiPO ２ F ２ Inorganic lithium salts such as LiWOF ５ Lithium tungstates such as HCO ２ Li, C.H. ３ CO ２ Li, C.H. ２ FCO ２ Li, CHF ２ CO ２ Li, CF ３ CO ２ Li, CF ３ CH ２ CO ２ Li, CF ３ CF ２ CO ２ Li, CF ３ CF ２ CF ２ CO ２ Li, CF ３ CF ２ CF ２ CF ２ CO ２ Lithium carboxylate salts such as Li; FSO３ Li, C.H. ３ SO ３ Li, C.H. ２ FSO ３ Li, CHF ２ SO ３ Li, CF ３ SO ３ Li, CF ３ CF ２ SO ３ Li, CF ３ CF ２ CF ２ SO ３ Li, CF ３ CF ２ CF ２ CF ２ SO ３ Li, lithium methyl sulfate, lithium ethyl sulfate (C ２ H ５ OSO ３ Lithium salts having an S=O group such as lithium 2,2,2-trifluoroethyl sulfate; LiN(FCO) ２ , LiN(FCO)(FSO ２ ), LiN(FSO ２ ) ２ , LiN(FSO ２ ) (CF ３ SO ２ ), iN(CF ３ SO ２ ) ２ , LiN(C ２ F ５ SO ２ ) 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(CF ３ SO ２ ) (FSO ２ ), LiN(CF ３ SO ２ ) (C ３ F ７ SO ２), LiN(CF ３ SO ２ ) (C ４ F ９ SO ２ ), LiN (POF ２ ) ２ Lithium imide salts such as LiC(FSO ２ ) ３ , LiC(CF ３ SO ２ ) ３ , LiC(C ２ F ５ SO ２ ) ３ Lithium methide salts such as: ａ (C ｎ F ２ｎ＋１ ) ６－ａ (wherein a is an integer of 0 to 5, and n is an integer of 1 to 6) ３ (C ２ F ５ ) ３ , LiPF ３ (CF ３ ) ３ , LiPF ３ (iso-C ３ F ７ ) ３ , LiPF ５ (iso-C ３ F ７ ), LiPF ４ (CF ３ ) ２ , LiPF ４ (C ２ F ５ ) ２ ), LiPF ４ (CF ３ SO ２ ) ２ , LiPF ４ (C ２ F ５ SO ２ ) ２ , LiBF ３ CF ３ , LiBF ３ C ２ F ５ , LiBF ３ C ３ F ７ , LiBF２ (CF ３ ) ２ , LiBF ２ (C ２ F ５ ) ２ , LiBF ２ (CF ３ SO ２ ) ２ , LiBF ２ (C ２ F ５ SO ２ ) ２ Fluorine-containing organic lithium salts such as LiSCN and LiB(CN) ４ , LiB(C ６ H ５ ) ４ , Li ２ (C ２ O ４ ), LiP(C ２ O ４ ) ３ , Li ２ B １２ F ｂ H １２－ｂ (b is an integer of 0 to 3), etc.

[0093] Among them, LiPF ６ , LiBF ４ , LiSbF ６ , LiTaF ６ , LiPO ２ F ２ , FSO ３ Li, CF ３ SO ３ Li,iN(FSO ２ ) ２ , LiN(FSO ２ ) (CF ３ SO ２ ), LiN(CF ３ SO ２ ) ２ , LiN(C ２ F ５ SO ２ ) ２ , lithium cyclic 1,2-perfluoroethane disulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC(FSO ２ ) ３ , LiC(CF ３ SO２ ) ３ , LiC(C ２ F ５ SO ２ ) ３ , LiBF ３ CF ３ , LiBF ３ C ２ F ５ , LiPF ３ (CF ３ ) ３ , LiPF ３ (C ２ F ５ ) ３ are preferred because they have the effect of improving output characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, etc., and LiPF ６ , LiN(FSO ２ ) ２ (lithium bis(fluorosulfonyl)imide (LIFSI)) and LiN(CF ３ SO ２ ) ２ (lithium bis(trifluoromethanesulfonyl)imide (LITFSI)) is more preferred, and LiPF ６ At least one lithium salt selected from the group consisting of LiFSI, LiTFSI, and LiTFSI is particularly preferred.

[0094] 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 LiPF ６ and LiBF ４ In combination with LiPF ６ and LiPO ２ F ２ , C ２ H ５ OSO ３ Li or FSO ３ When used in combination with Li, it has the effect of improving high-temperature storage characteristics, load characteristics, and cycle characteristics.

[0095] In this case, LiBF relative to 100% by mass of the entire electrolyte ４ , LiPO ２ F ２ , C ２ H ５ OSO ３Li or FSO ３ There is no limitation on the amount of Li to be blended, 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 electrolytic solution.

[0096] 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. ３ SO ３ Li, LiN (FSO ２ ) ２ (LIFSI), LiN(FSO ２ ) (CF ３ SO ２ ), LiN(CF ３ SO ２ ) ２ (LITFSI), LiN(C ２ F ５ SO ２ ) ２ , lithium cyclic 1,2-perfluoroethane disulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC(FSO ２ ) ３ , LiC(CF ３ SO ２ ) ３ , LiC(C ２ F ５ SO ２ ) ３ , LiBF ３ CF ３ , LiBF ３ C ２ F ５ , LiPF ３ (CF ３ ) ３ , LiPF ３ (C ２ F ５ ) ３In 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.

[0097] 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 keep 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, and even more preferably 2.0 mol / L or less.

[0098] 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.

[0099] The composition of the present disclosure may further contain additives such as cyclic and chain carboxylic acid esters, ether compounds, nitrogen-containing compounds, boron-containing compounds, organosilicon-containing compounds, flame-retardant (flame retardant) agents, surfactants, high-dielectric additives, cycle performance and rate performance improvers, and sulfone-based compounds, within the scope of not impairing the effects of the present disclosure.

[0100] 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 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.

[0101] 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 terms of their high ability to solvate lithium ions and improve the degree of ionic dissociation, and particularly preferred are dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and provide high ionic conductivity.

[0102] As the ether compound, fluorinated ethers other than the fluorinated ether (E) can also be suitably used.

[0103] The compositions of the present disclosure may be prepared by any method using the ingredients described above.

[0104] The composition of the present disclosure can be suitably applied to electrochemical devices such as secondary batteries, such as lithium ion secondary batteries, lithium ion capacitors, hybrid capacitors, and electric double layer capacitors. 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 such a composition (electrolyte) of the present disclosure also constitutes the present disclosure.

[0105] Examples of electrochemical devices include secondary batteries such as lithium ion secondary batteries, lithium ion capacitors, capacitors (hybrid capacitors and 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. A module including the above electrochemical device also constitutes one aspect of the present disclosure.

[0106] 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-described electrolyte. The secondary battery is preferably a lithium-ion secondary battery.

[0107] <Positive Electrode> The positive electrode is composed of a positive electrode active material layer containing a positive electrode active material and a current collector.

[0108] 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.

[0109] The transition metal of the lithium-containing transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, or the like, and specific examples thereof include LiCoO ２ Lithium-cobalt composite oxides such as LiNiO ２ Lithium-nickel composite oxides such as LiMnO ２ , LiMn ２ O ４ , Li ２ MnO ４ and lithium manganese composite oxides in which a part of the transition metal atoms that constitute the main component of these lithium transition metal composite oxides has been substituted with other elements such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. Specific examples of the substituted oxides include LiNi ０．５ Mn ０．５ O ２ , LiNi ０．８５ Co ０．１０ Al ０．０５ O ２ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．６ Co ０．２ Mn ０．２ O ２ , LiNi ０．３３ Co ０．３３ Mn ０．３３ O ２ , LiNi ０．８ Co ０．１ Mn ０．１ O ２ , LiNi ０．４５ Co ０．１０ Al ０．４５ O ２ , LiMn １．８ Al ０．２ O ４ , LiMn １．５ Ni ０．５ O ４ etc.

[0110] Among these, the lithium-containing transition metal composite oxide is LiMn, which has a high energy density even when applied at a high voltage. １．５ Ni ０．５ O４ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．６ Co ０．２ Mn ０．２ O ２ Among them, in the case of a high voltage of 4.4 V or more, LiMn １．５ Ni ０．５ O ４ is preferred.

[0111] Among these, the lithium-containing transition metal composite oxide is preferably LiNi because it can provide a high-capacity lithium ion secondary battery. ０．６ Co ０．２ Mn ０．２ O ２ , LiNi ０．８ Co ０．１ Mn ０．１ O ２ , LiNi ０．８５ Co ０．１０ Al ０．０５ O ２ is preferred.

[0112] The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, or the like, and specific examples thereof include LiFePO ４ , Li ３ Fe ２ (P.O. ４ ) ３ , LiFeP ２ O ７ Iron phosphates such as LiCoPO ４ and lithium transition metal phosphate compounds in which a part of the transition metal atoms that constitute the main components of these lithium transition metal phosphate compounds is substituted with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, and Si.

[0113] Examples of the lithium-containing transition metal composite oxide include those represented by the formula: Li ａ Mn ２－ｂ M １ ｂ O ４ (In the formula, 0.9≦a; 0≦b≦1.5; M １is 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-manganese spinel composite oxide represented by the formula: LiNi １－ｃ M ２ ｃ O ２ (In the formula, 0≦c≦0.5; M ２ 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 a lithium-nickel composite oxide represented by the formula: LiCo １－ｄ M ３ ｄ O ２ (In the formula, 0≦d≦0.5; M ３ 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).

[0114] Among these, LiCoO is preferred because it can provide a lithium ion secondary battery with high energy density and high output. ２ , LiMnO ２ , LiNiO ２ , LiMn ２ O ４ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , or LiNi １／３ Co １／３ Mn １／３ O ２ is preferred.

[0115] Other examples of the positive electrode active material include LiFePO ４ , LiNi ０．８ Co ０．２ O ２ , Li １．２ Fe ０．４ Mn ０．４ O ２ , LiNi ０．５ Mn ０．５ O ２ , LiV ３ O６ , Li ２ MnO ３ etc.

[0116] 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.

[0117] 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 solvent and electrolyte used in the electrode production, and examples thereof include resin-based 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; EPDM (ethylene-propylene-diene rubber); Examples of suitable polymers include thermoplastic elastomeric polymers such as styrene-ethylene-butadiene-styrene terpolymers, 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-based 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.

[0118] The content of the binder, 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, which may deteriorate battery performance such as cycle characteristics. On the other hand, if the proportion is too high, it may lead to a decrease in battery capacity and conductivity.

[0119] 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 present in the positive electrode active material layer in an amount of 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 1% by mass or more, and typically 50% by mass or less, preferably 30% by mass or less, and more preferably 15% by mass or less. A content lower than this range may result in insufficient conductivity. Conversely, a content higher than this range may result in a decrease in battery capacity.

[0120] 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 may 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.

[0121] Examples of the material for the positive electrode current collector include metals such as aluminum, titanium, tantalum, stainless steel, and nickel, or alloys thereof; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum or its alloys, are preferred.

[0122] Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, and foamed metal in the case of a metal material, and carbon plate, carbon thin film, and carbon cylinder in the case of a carbon material. Of these, metal thin film is preferred. The thin film may be formed into a mesh 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 is 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.

[0123] In addition, it is also preferable that the surface of the current collector is coated with a conductive additive, from the viewpoint of reducing the electrical contact resistance between the current collector and the positive electrode active material layer. Examples of the conductive additive include carbon and precious metals such as gold, platinum, and silver.

[0124] The positive electrode may be manufactured by a conventional method, for example, by adding the above-mentioned binder, thickener, conductive material, solvent, etc. to the above-mentioned positive electrode active material to form a slurry positive electrode mixture, which is then applied to a current collector, dried, and pressed to increase density.

[0125] <Negative Electrode> The negative electrode is composed of a negative electrode active material layer containing a negative electrode active material and a current collector.

[0126] The negative electrode active material is not particularly limited as long as it can electrochemically absorb 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.

[0127] Examples of the carbon material include natural graphite, artificial graphite, and graphite obtained by subjecting such graphite to surface treatment with pitch or other organic substances and then carbonizing the graphite. These may be used alone or in any combination of two or more.

[0128] The silicon material may be silicon alone or a composite material containing silicon and one or more other constituent elements (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 silicon material may be SiO ｖ (0<v≦2), SnO ｗ (0≦w≦2), Si—Co—C composite materials, and Si—Ni—C composite materials are preferred.

[0129] The silicon material is preferably used in combination with the carbon material, in which case the mass ratio of silicon material to carbon material is preferably 1 to 20:99 to 80.

[0130] 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, a metal material containing lithium is preferred as the metal material, and lithium metal (simple lithium metal) is more preferred.

[0131] The lithium-containing metal material is preferably a material containing lithium and titanium from the viewpoint of high current density charge / discharge characteristics, and more preferably a composite oxide of lithium and titanium (hereinafter abbreviated as "lithium titanium composite oxide").

[0132] The lithium titanium composite oxide may be represented by the general formula: Li ｘ Ti ｙ M ｚ O ４ [wherein M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb.] Among the above compositions, the following structures are particularly preferred because they provide a good balance of battery performance: (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

[0133] A particularly preferred representative composition of the compound is (i) Li ４／３ Ti ５／３ O ４ , (ii) Li １ Ti ２ O ４ , (iii) Li ４／５ Ti １１／５ O ４ In addition, for the structure where Z≠0, for example, Li ４／３ Ti ４／３ Al １／３ O ４ are mentioned as preferred.

[0134] The negative electrode mixture preferably further contains a binder, a thickener, and a conductive material.

[0135] Examples of the binder include the same binders that can be used 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, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, even 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. Furthermore, if the ratio is below the above range, the strength of the negative electrode may be reduced.

[0136] 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, and 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 of the binder 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, and more preferably 8% by mass or less.

[0137] 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.

[0138] 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.

[0139] Examples of the material 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.

[0140] 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.

[0141] <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 it is stable to the electrolyte and has 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, such as resin, glass fiber, or inorganic material, and that is in the form of a porous sheet or nonwoven fabric with excellent liquid retention properties.

[0142] 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.

[0143] 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.

[0144] As for the form, thin film shapes such as nonwoven fabric, woven fabric, and microporous film are used. Thin film shapes with a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the above-mentioned independent thin film shapes, separators can 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 can 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.

[0145] The shape of the secondary battery of the present disclosure is arbitrary, and examples thereof include cylindrical, prismatic, laminated, coin, large, etc. The shapes and configurations of the positive electrode, negative electrode, and separator can be changed according to the shape of each battery.

[0146] The present disclosure also includes a module including the secondary battery of the present disclosure.

[0147] The present disclosure also includes an electric double layer capacitor comprising the composition of the present disclosure. The electric double layer capacitor may comprise a positive electrode, a negative electrode, and the above-described 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, which are described in detail in JP-A-9-7896, can be used as the polarizable electrode and the non-polarizable electrode.

[0148] The composition of the present disclosure is useful as an electrolyte solution for large-scale lithium-ion secondary batteries for hybrid vehicles and distributed power sources, and for electric double-layer capacitors.

[0149] The present disclosure also relates to a composition (second composition of the present disclosure) containing a compound (M) represented by the following formula (M) and a fluorinated ether (E) represented by the following formula (E): (M) Rf １ -COOM (where Rf １ is a fluoroalkyl group having 1 to 6 carbon atoms, and M is an alkali metal other than Li. ２ -OR (wherein, Rf ２ is a fluoroalkyl group having 1 to 6 carbon atoms, and R is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group of R may have an ether bond and / or fluorine.

[0150] The second composition of the present disclosure is a novel composition and can be used as a plating bath solvent, a pharmaceutical intermediate, etc.

[0151] In the second composition of the present disclosure, the form and content of the compound (M) and the fluorinated ether (E) are the same as those described for the composition of the present disclosure.

[0152] 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.

[0153] Next, the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0154] (Fabrication and Evaluation of Lithium Metal Secondary Battery) [Preparation of Electrolyte Solution] Materials were mixed in the proportions shown in Table 1 to obtain non-aqueous electrolyte solutions.

[0155] [Preparation of Positive Electrode] 94% by mass of LiMnO (LMO) as the positive electrode active material, 3% by mass of acetylene black as the conductive material, and 3% 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 15 mm, a length of 20 mm, and an uncoated portion of 5 mm, a length of 9 mm, to form a positive electrode.

[0156] [Preparation of Negative Electrode] A lithium foil having a thickness of 0.15 mm was cut as a negative electrode active material to a width of 16 mm and a length of 21 mm, and then rolled with a PTFE roll onto a Ni mesh having terminal portions of 17 mm in width, 22 mm in length, and 5 mm in width, and 9 mm in length to prepare a negative electrode.

[0157] [Fabrication of Laminated Cells] The cathode and anode prepared as described above were stacked on a polyethylene separator in the order of anode, separator, and cathode to prepare a battery element. This battery element was inserted into a bag made of a laminate film of an aluminum sheet (40 μm thick) coated on both sides with a resin layer, with the cathode and anode terminals protruding. The electrolyte solutions of the Examples and Comparative Examples listed in Table 1 were then poured into the bag, which was then vacuum-sealed to prepare a sheet-shaped lithium metal secondary battery.

[0158] [Low-Temperature 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 4.1 V at a current equivalent to 0.2 C (0.05 C cut), and then discharged to 3.0 V at a constant current of 0.2 C. This constituted one cycle, and five formation cycles were performed. Thereafter, 300 cycles of constant-current-constant-voltage charging at 0.5 C and constant-current discharging (between 4.1 and 3.0 V) were performed in a thermostatic bath at 0°C. The ratio of the discharge capacity at the 300th cycle to the discharge capacity at the first cycle at 0°C was calculated, and this was defined as the cycle capacity retention rate (%). (Discharge capacity at the 300th cycle) / (Discharge capacity at the first cycle) × 100 = cycle capacity retention rate (%)

[0159] [Evaluation of Resistance Increase Rate] The battery was charged at 25°C with a constant current of 0.2 C to half the initial discharge capacity. It was then discharged at 3.0 C at 25°C, and the voltage was measured 10 seconds later. The resistance was calculated from the voltage drop during discharge, and this was taken as the IV resistance. This operation was performed before and after the low-temperature cycle test, and the resistance increase rate (%) was calculated using the following formula: (Resistance after low-temperature cycle test) / (Resistance before low-temperature cycle test) × 100 = Resistance increase rate (%)

[0160]

[0161] (Fabrication and Evaluation of Lithium Ion Secondary Battery) [Preparation of Electrolyte Solution] The materials shown in Table 2 were mixed in the proportions shown in Table 2 to obtain a non-aqueous electrolyte solution.

[0162] [Preparation of Positive Electrode] Li (Ni) as a positive electrode active material ０．５ Mn ０．３ Co ０．２ ) O ２ 98.0% by mass of NMC532, 1.0% by mass of acetylene black as a conductive material, and 1.0% by mass of polyvinylidene fluoride (PVdF) as a 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 40 mm, a length of 45 mm, and an uncoated portion of 5 mm, a length of 9 mm, to form a positive electrode.

[0163] [Preparation of Negative Electrode] SiO powder, natural graphite powder, an aqueous dispersion of sodium carboxymethyl cellulose (concentration of sodium carboxymethyl cellulose: 1% by mass) as a negative electrode active material, and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber: 50% by mass) as a binder were used. SiO powder, natural graphite powder, thickener, and binder were mixed in an aqueous solvent at a solids ratio of 9.6 / 86.4 / 2 / 2 (mass%) to prepare a negative electrode mixture slurry. The resulting slurry was uniformly applied to a 10 μm thick copper foil current collector, dried, and then compressed using a press. The electrode was cut into a shape with a width of 41 mm, a length of 46 mm, and an uncoated portion of 5 mm and 9 mm in length to form a negative electrode.

[0164] [Fabrication of Laminated Cells] The positive and negative electrodes prepared as described above and a polyethylene separator were laminated in this order to fabricate a battery element. 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. The electrolyte solutions of the Examples and Comparative Examples listed in Table 2 were then poured into the bag, which was then vacuum-sealed to fabricate a sheet-like lithium-ion secondary battery.

[0165] [Low-Temperature 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 4.3 V at a current equivalent to 0.5 C (0.05 C cut), and then discharged to 3.0 V at a constant current of 0.5 C. This constituted one cycle, and five formation cycles were performed. Thereafter, 150 cycles of 1 C constant-current-constant-voltage charging and constant-current discharging (between 4.3 and 3.0 V) were performed in a thermostatic chamber at 0°C. The ratio of the discharge capacity at the 150th cycle to the discharge capacity at the first cycle at 0°C was calculated, and this was defined as the cycle capacity retention rate (%). (Discharge capacity at the 150th cycle) / (Discharge capacity at the first cycle) × 100 = cycle capacity retention rate (%)

[0166] [Evaluation of Resistance Increase Rate] The battery was charged at a constant current of 0.5 C at 25°C to half the initial discharge capacity. It was then discharged at 5.0 C at 25°C, and the voltage was measured 20 seconds later. The resistance was calculated from the voltage drop during discharge, and this was taken as the IV resistance. This operation was performed before and after the low-temperature cycle test, and the resistance increase rate (%) was calculated using the following formula: (Resistance after low-temperature cycle test) / (Resistance before low-temperature cycle test) × 100 = Resistance increase rate (%)

[0167]

[0168] The abbreviations in the table are as follows: <Lithium salt> LiPF ６ : Lithium hexafluorophosphate LiFSI: Lithium bis(fluorosulfonyl)imide LiTFSI: Lithium bis(trifluoromethanesulfonyl)imide <Fluorinated ether (E)> E-1: HCF ２ -CF２ -O-CH ２ -CF ２ -CF ２ H, E-2: HCF ２ -CF ２ -O-CH ２ -CH ２ -CH ３ E-3: HCF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ H <Compound (M)> M-1: Potassium difluoroacetate M-2: Sodium difluoroacetate <Other solvent components> EC: Ethylene carbonate EMC: Ethyl methyl carbonate DMC: Dimethyl carbonate DME: CH ３ -O-CH ２ -CH ２ -O-CH ３ FEC: Fluoroethylene carbonate

Claims

1. An electrolyte composition containing a compound (M) represented by the following formula (M): (M) Rf １ -COOM (where Rf １ is a fluoroalkyl group having 1 to 6 carbon atoms, and M is an alkali metal other than Li.

2. The above-mentioned Rf １ is HCF ２ The composition for an electrolyte solution according to claim 1, wherein 3. The compound (M) is HCF ２ -COOK and HCF ２ 3. The composition for an electrolyte solution according to claim 1, wherein the composition is at least one selected from the group consisting of —COONa.

4. The composition for an electrolyte solution according to any one of claims 1 to 3, wherein the content of the compound (M) is 0.0001 to 3 mass % relative to the composition for an electrolyte solution.

5. The composition for an electrolyte solution according to any one of claims 1 to 4, which contains a fluorinated ether (E) represented by the following formula (E): (E) Rf ２ -OR (wherein, Rf ２ is a fluoroalkyl group having 1 to 6 carbon atoms, and R is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group of R may have an ether bond and / or fluorine.

6. The above Rf ２ is HCF ２ -CF ２ The composition for an electrolyte solution according to claim 5, wherein:

7. The R is —CH ２ -CF ２ -CF ２ H, -CH ２ -CH ２ -CH ３ , or -CH ２ -CH ２ -O-CF ２ -CF ２ 7. The electrolyte composition according to claim 5, wherein the electrolyte composition is H 2 .

8. The fluorinated ether (E) is HCF ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H, HCF ２ -CF ２ -O-CH ２ -CH ２ -CH ３ , and HCF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ The composition for an electrolyte solution according to any one of claims 5 to 7, wherein the composition is at least one selected from the group consisting of H 2 .

9. The composition for an electrolyte solution according to any one of claims 5 to 8, wherein the content of the fluorinated ether (E) is 0.1 to 100% by volume relative to the solvent in the composition for an electrolyte solution.

10. LiPF ６ 10. The electrolyte solution composition according to claim 1, which contains at least one lithium salt selected from the group consisting of LiFSI, LiTFSI, and LiTFSI.

11. The compound (M) is HCF ２ -COOK and HCF ２ -COONa, the content of the compound (M) is 0.0001 to 1 mass % relative to the electrolyte solution composition, and HCF ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H, HCF ２ -CF ２ -O-CH ２ -CH ２ -CH ３ , and HCF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ 11. The composition for an electrolyte solution according to claim 1, further comprising at least one fluorinated ether (E) selected from the group consisting of H, and a content of the fluorinated ether (E) is 5 to 80% by volume relative to the solvent in the composition for an electrolyte solution.

12. A secondary battery comprising the electrolyte composition according to claim 11 and lithium metal as the negative electrode active material.

13. The compound (M) is HCF ２ -COOK and HCF ２ -COONa, the content of the compound (M) is 0.01 to 0.1 mass % relative to the electrolyte solution composition, and HCF ２ -CF ２ -O-CH ２ -CF ２ -CF ２ H, HCF ２ -CF ２ -O-CH ２ -CH ２ -CH ３ , and HCF ２ -CF ２ -O-CH ２ -CH ２ -O-CF ２ -CF ２ 11. The composition for an electrolyte solution according to claim 1, further comprising at least one fluorinated ether (E) selected from the group consisting of H, and a content of the fluorinated ether (E) is 25 to 30% by volume relative to the solvent in the composition for an electrolyte solution.

14. A secondary battery comprising the electrolyte composition according to claim 13 and a silicon material as a negative electrode active material.

15. The electrolyte composition according to any one of claims 1 to 11 and 13, which is for use in a secondary battery.

16. An electrochemical device comprising the electrolyte composition according to any one of claims 1 to 11 and 13.

17. A secondary battery comprising the electrolyte composition according to any one of claims 1 to 11 and 13.

18. A lithium ion secondary battery comprising the electrolyte composition according to any one of claims 1 to 11 and 13.

19. A composition containing a compound (M) represented by the following formula (M) and a fluorinated ether (E) represented by the following formula (E): (M) Rf １ -COOM (where Rf １ is a fluoroalkyl group having 1 to 6 carbon atoms, and M is an alkali metal other than Li. ２ -OR (wherein, Rf ２ is a fluoroalkyl group having 1 to 6 carbon atoms, and R is H or an alkyl group having 1 to 6 carbon atoms. The alkyl group of R may have an ether bond and / or fluorine.

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