Electrolyte for fluoride battery, polymer electrolyte, and fluoride battery

Abstract

A purpose of the present disclosure is to provide an electrolyte for a flame-retardant fluoride battery having low volatility, a polymer electrolyte in which said electrolyte for a fluoride battery is used, and a fluoride battery. The present disclosure is an electrolyte solution for a fluoride battery, the electrolyte solution containing a fluoropolyether and a fluoride salt.

Description

Electrolyte for fluoride battery, polymer electrolyte, and fluoride battery

[0001] The present disclosure relates to an electrolyte for a fluoride battery, a polymer electrolyte, and a fluoride battery.

[0002] With the recent trend toward lighter and smaller electrical appliances, electrochemical devices with high energy density have been developed.

[0003] Fluoride ion batteries, which are one type of electrochemical device, use fluoride ions (F － ) as a charge carrier and is capable of high voltage, and various studies are currently underway (see, for example, Patent Documents 1 and 2).

[0004] JP 2014-501434 A JP 2022-128927 A

[0005] The electrolyte solutions described in Patent Documents 1 and 2 are highly volatile and highly flammable, and therefore there is room for improvement in terms of ease of handling in a high-temperature environment.

[0006] An object of the present disclosure is to provide a low-volatility and flame-retardant electrolyte solution for a fluoride battery, as well as a polymer electrolyte and a fluoride battery using the electrolyte solution for a fluoride battery.

[0007] The present disclosure (1) is an electrolyte for a fluoride battery, which contains a fluoropolyether and a fluoride salt.

[0008] The present disclosure (2) is the electrolyte solution for a fluoride battery according to the present disclosure (1), wherein the fluoropolyether is at least one of the fluoropolyethers represented by the following formulas (1) to (4): (1) R １ -O-Ra １ -Rb １ -O-Ra １ -R １ (2) R ２ -Rb ２ -O-Ra ２ -Rb ２ -R ２ (3) R ３ -Rb ３ -O-Ra ３ -R ３ (4) R ４ -Rb ４ -R ４(In the formula, Ra １ ~Ra ３ are each independently a group containing a fluorine-free alkylene unit and / or a fluorine-free oxyalkylene unit, １ ~Ra ３ Each oxyalkylene unit is independently —CH ２ CH ２ O- or -CH ２ CH(J)O—, each J is independently an alkyl group or an aryl group, and Rb １ ~Rb ４ are each independently a fluoropolyether group represented by the following formula (5), １ ~R ３ are each independently a hydrogen atom, a hydroxyl group, a fluorine atom, an alkyl group having 1 to 3 carbon atoms, an aryl group, or a fluoroalkyl group having 1 to 3 carbon atoms, ４ are each independently a fluorine atom, a hydrogen atom, a hydroxyl group, an aldehyde group, a carboxylic acid group, an alkyl ester group having 1 to 10 carbon atoms, an amide group which may have a substituent, or an amino group which may have a substituent. １ -Rf-O-Rf ２ - (wherein, Rf １ and Rf ２ are each independently an alkylene group having 1 to 16 carbon atoms which may be substituted with a fluorine atom, and Rf is a divalent fluoropolyether group.

[0009] The present disclosure (3) is １ ~Ra ３ are each independently a polyoxyalkylene group represented by the following formula (Ra-I): —(CH ２ CH ２ O)r(CH ２ CH (CH ３ )O)s(CH ２ CH (CH ２ CH ３ )O)t(CH ２CH(Ph)O)u- (wherein r, s, t, and u each independently represent an integer of 0 or 1 or greater, and r+s+t+u is 4 to 50.)

[0010] The present disclosure (4) is １ ~Ra ３ The electrolyte solution for a fluoride battery according to the present disclosure (2) or (3), wherein the number average molecular weight of

[0011] The present disclosure (5) is the electrolyte solution for a fluoride battery according to any one of the present disclosures (2) to (4), wherein each Rf is independently a fluoropolyether group represented by the following formula (Rf-I): Formula (Rf-I): -(OC ６ F １２ ) a-(OC ５ F １０ ) b-(OC ４ F ８ ) c-(OC ３ Rc ６ ) d-(OC ２ F ４ ) e-(OCF ２ )f- (In the formula, each Rc is independently a hydrogen atom, a fluorine atom, or a chlorine atom; each a, b, c, d, e, and f is independently an integer of 0 to 200; the sum of a, b, c, d, e, and f is 1 or more; the order of the repeating units assigned with a, b, c, d, e, or f is arbitrary; and when all Rc's are hydrogen atoms or chlorine atoms, at least one of a, b, c, e, and f is 1 or more.)

[0012] The present disclosure (6) is the electrolyte solution for a fluoride battery according to any one of the present disclosures (2) to (5), wherein each Rf is independently a group represented by the following formula (Rf-II) or the following formula (Rf-I-II): Formula (Rf-II): -(OC ３ F ６ ) d-(OC ２ F ４ )e- (wherein d is an integer of 1 to 200, and e is 0 or 1) Formula (Rf-I-II): -(OC ４ F ８ ) c-(OC ３ F ６ ) d-(OC ２ F４ ) e-(OCF ２ )f- (In the formula, c and d each independently represent an integer of 0 to 30, e and f each independently represent an integer of 1 to 200, the sum of c, d, e and f is 2 or more, and the order of the repeating units assigned with c, d, e or f is arbitrary.)

[0013] The present disclosure (7) is １ ~R ３ are each independently a methyl group, an ethyl group, a trifluoromethyl group, or a pentafluoroethyl group.

[0014] The present disclosure (8) is the electrolyte solution for a fluoride battery according to any one of the present disclosures (1) to (7), in which the fluoride salt is ammonium fluoride or a metal fluoride.

[0015] The present disclosure (9) is the electrolyte solution for a fluoride battery according to the present disclosure (8), wherein the ammonium fluoride is an alkylammonium fluoride having a neopentyl group.

[0016] The present disclosure (10) is the electrolyte solution for a fluoride battery according to any one of the present disclosures (1) to (9), wherein the content of the fluoride salt is 0.1 to 10 mass %.

[0017] The present disclosure (11) is an electrolyte solution for a fluoride battery according to any one of the present disclosures (1) to (10), which is liquid at 25°C.

[0018] The present disclosure (12) has an ionic conductivity of 1.0 × 10 －９ ~1.0 x 10 －４ The electrolyte solution for a fluoride battery according to any one of the present disclosures (1) to (11), wherein the solubility is 0.05 S / cm.

[0019] The present disclosure (13) is a polymer electrolyte containing the electrolyte solution for a fluoride battery according to any one of the present disclosures (1) to (12).

[0020] The present disclosure (14) is a fluoride battery comprising the electrolyte solution for a fluoride battery according to any one of the present disclosures (1) to (12) or the polymer electrolyte according to the present disclosure (13).

[0021] According to the present disclosure, it is possible to provide a low-volatility and flame-retardant electrolyte solution for a fluoride battery, as well as a polymer electrolyte and a fluoride battery using the electrolyte solution for a fluoride battery.

[0022] The present disclosure will be specifically described below.

[0023] Composition The present disclosure relates to an electrolyte for a fluoride battery comprising a fluoropolyether and a fluoride salt.

[0024] The electrolyte solution of the present disclosure has the above-described configuration, and therefore can achieve low volatility and flame retardancy.

[0025] As the fluoropolyether, at least one of the compounds represented by the following formulas (1) to (4) can be suitably used. １ ~Rb ４ Furthermore, the compounds of the following formulas (1) to (3) can achieve low volatility and flame retardancy by the moiety Ra １ ~Ra ３ The part (1) R improves the solubility of the fluoride salt. １ -O-Ra １ -Rb １ -O-Ra １ -R １ (2) R ２ -Rb ２ -O-Ra ２ -Rb ２ -R ２ (3) R ３ -Rb ３ -O-Ra ３ -R ３ (4) R ４ -Rb ４ -R ４ (In the formula, Ra １ ~Ra ３ are each independently a group containing a fluorine-free alkylene unit and / or a fluorine-free oxyalkylene unit, １ ~Ra ３ Each oxyalkylene unit is independently —CH ２ CH ２ O- or -CH ２ CH(J)O—, each J is independently an alkyl group or an aryl group, and Rb１ ~Rb ４ are each independently a fluoropolyether group represented by the following formula (5), １ ~R ３ are each independently a hydrogen atom, a hydroxyl group, a fluorine atom, an alkyl group having 1 to 3 carbon atoms, an aryl group, or a fluoroalkyl group having 1 to 3 carbon atoms, ４ are each independently a fluorine atom, a hydrogen atom, a hydroxyl group, an aldehyde group, a carboxylic acid group, an alkyl ester group having 1 to 10 carbon atoms, an amide group which may have a substituent, or an amino group which may have a substituent. １ -Rf-O-Rf ２ - (wherein, Rf １ and Rf ２ are each independently an alkylene group having 1 to 16 carbon atoms which may be substituted with a fluorine atom, and Rf is a divalent fluoropolyether group.

[0026] Ra １ ~Ra ３ The alkylene unit may be linear or branched, but is preferably linear, and preferably has 1 to 3 carbon atoms.

[0027] Ra １ ~Ra ３ The oxyalkylene unit is -CH ２ In the case of CH(J)O-, the alkyl group for J may be linear or branched, but is preferably linear. The alkyl group for J preferably has 1 to 3 carbon atoms. Examples of the aryl group for J include a phenyl group, a 4-nitrophenyl group, a 4-acetylaminophenyl group, and a 4-methanesulfonylphenyl group.

[0028] Ra １ ~Ra ３ In the formula (I), the total number of fluorine-free alkylene units and fluorine-free oxyalkylene units is preferably 4 to 50.

[0029] Ra １ ~Ra ３Each of the groups preferably independently contains at least an oxyalkylene unit, and is more preferably a polyoxyalkylene group represented by the following formula (Ra-I): (Ra-I): —(CH ２ CH ２ O)r-(CH ２ CH (CH ３ )O)s-(CH ２ CH (CH ２ CH ３ )O)t-(CH ２ CH(Ph)O)u- (wherein r, s, t, and u each independently represent an integer of 0 or 1 or greater, and r+s+t+u is 4 to 50.)

[0030] In the above formula (Ra-I), r is preferably 1 or more, more preferably 2 or more, and preferably 30 or less, more preferably 20 or less. s, t, and u are preferably 10 or less, more preferably 5 or less, and even more preferably 0. r+s+t+u is preferably 1 or more, more preferably 2 or more, and preferably 20 or less, more preferably 10 or less.

[0031] Ra １ ~Ra ３ The number average molecular weight of the polymer is preferably 40 or more, more preferably 100 or more, and is preferably 4000 or less, more preferably 1000 or less. １ ~Ra ３ The number average molecular weight of １ This is a value measured by H-NMR.

[0032] Rb １ ~Rb ４ In the formula (5), Rf １ and Rf ２ The alkylene group of Rf may be linear or branched, but is preferably linear. １ and Rf ２ The alkylene group of Rf is preferably a fluorine-substituted alkylene group substituted with a fluorine atom. １ and Rf ２ The alkylene group preferably has 1 to 3 carbon atoms.

[0033] Rb １ ~Rb ４ In the above formula (5), Rf may have a ring structure.

[0034] Rb １ ~Rb ４ In the formula (5), Rf is preferably a fluoropolyether group represented by the following formula (Rf-I): Formula (Rf-I): -(OC ６ F １２ ) a-(OC ５ F １０ ) b-(OC ４ F ８ ) c-(OC ３ Rc ６ ) d-(OC ２ F ４ ) e-(OCF ２ )f- (In the formula, each Rc is independently a hydrogen atom, a fluorine atom, or a chlorine atom; each a, b, c, d, e, and f is independently an integer of 0 to 200; the sum of a, b, c, d, e, and f is 1 or more; the order of the repeating units assigned with a, b, c, d, e, or f is arbitrary; and when all Rc's are hydrogen atoms or chlorine atoms, at least one of a, b, c, e, and f is 1 or more.)

[0035] Rc is preferably a hydrogen atom or a fluorine atom, more preferably a fluorine atom, That is, Rf in formula (5) is preferably a perfluoropolyether group.

[0036] Preferably, a, b, c, d, e and f are each independently an integer of 0 to 100.

[0037] The sum of a, b, c, d, e, and f is preferably 5 or more, more preferably 10 or more, and may be 15 or more or 20 or more. The sum of a, b, c, d, e, and f is preferably 100 or less, more preferably 60 or less, and may be 50 or less or 30 or less.

[0038] Each repeating unit to which a, b, c, d, e, or f is assigned may be linear or branched. ６ F １２)- is, for example, -(OCF ２ CF ２ CF ２ CF ２ CF ２ CF ２ )-,-(OCF(CF ３ )CF ２ CF ２ CF ２ CF ２ ) -, -(OCF ２ CF (CF ３ )CF ２ CF ２ CF ２ ) -, -(OCF ２ CF ２ CF (CF ３ )CF ２ CF ２ ) -, -(OCF ２ CF ２ CF ２ CF (CF ３ )CF ２ ) -, -(OCF ２ CF ２ CF ２ CF ２ CF (CF ３ ))-. ５ F １０ )- is, for example, -(OCF ２ CF ２ CF ２ CF ２ CF ２ )-,-(OCF(CF ３ )CF ２ CF ２ CF ２ ) -, -(OCF ２ CF (CF ３ )CF ２ CF ２ ) -, -(OCF ２ CF ２ CF (CF ３ )CF ２ ) -, -(OCF ２ CF ２ CF ２ CF (CF ３ ))-. ４ F ８ )- is, for example, -(OCF２ CF ２ CF ２ CF ２ )-,-(OCF(CF ３ )CF ２ CF ２ ) -, -(OCF ２ CF (CF ３ )CF ２ ) -, -(OCF ２ CF ２ CF (CF ３ )) -, -(OC(CF ３ ) 2CF ２ ) -, -(OCF ２ C (CF ３ )2)-,-(OCF(CF ３ )CF(CF ３ ))-,-(OCF(C2F5)CF ２ ) -, -(OCF ２ CF(C2F5))-. ３ F ６ )-(that is, in the above formula (Rf-I), when all Rc's are fluorine atoms), can be represented by, for example, -(OCF ２ CF ２ CF ２ )-,-(OCF(CF ３ )CF ２ ) -, -(OCF ２ CF (CF ３ ))-. ２ F ４ )- is, for example, -(OCF ２ CF ２ )-,-(OCF(CF ３ ))-.

[0039] Rf may be a group represented by any one of the following formulae (Rf-II) to (Rf-IV): Formula (Rf-II): -(OC ３ F ６ ) d-(OC ２ F ４ )e- (wherein d is an integer of 1 to 200, and e is 0 or 1) Formula (Rf-I-II): -(OC ４ F ８ ) c-(OC ３ F ６) d-(OC ２ F ４ ) e-(OCF ２ )f- (wherein c and d each independently represent an integer of 0 to 30, e and f each independently represent an integer of 1 to 200, the sum of c, d, e and f is 2 or more, and the order of the repeating units assigned with c, d, e or f is arbitrary.) Formula (Rf-I-III): -(R ２０ -R ２１ ) g- (wherein, R ２０ is OCF ２ or O.C. ２ F ４ and R ２１ is O.C. ２ F ４ , O.C. ３ F ６ , O.C. ４ F ８ , O.C. ５ F １０ and O.C. ６ F １２ or a combination of two or three groups selected from these groups, and g is an integer of 2 to 100.) Formula (Rf-I-IV): -(OC ６ F １２ ) a-(OC ５ F １０ ) b-(OC ４ F ８ ) c-(OC ３ F ６ ) d-(OC ２ F ４ ) e-(OCF ２ )f- (wherein e is an integer of 1 to 200, a, b, c, d and f each independently are an integer of 0 to 200, and the order of the repeating units to which a, b, c, d, e or f is assigned is arbitrary.) Formula (Rf-IV): -(OC ６ F １２ ) a-(OC ５ F １０ ) b-(OC ４ F ８ ) c-(OC ３ F ６ ) d-(OC ２ F ４ ) e-(OCF ２)f- (wherein f is an integer of 1 to 200, a, b, c, d, and e each independently are an integer of 0 to 200, and the order of the repeating units assigned a, b, c, d, e, or f is arbitrary.)

[0040] In the above formula (Rf-II), d may be preferably 5 to 200, more preferably 10 to 100, and even more preferably 10 to 30. The above formula (Rf-II) is preferably -(OCF ２ CF ２ CF ２ ) d- or -(OCF(CF ３ )CF ２ ) d- is a group represented by the formula:

[0041] In the above formula (Rf-I-II), e and f are each independently an integer of preferably 5 to 200, more preferably 10 to 200. The sum of c, d, e and f is preferably 5 or more, more preferably 10 or more, and may be 15 or more or 20 or more. The above formula (Rf-I-II) is preferably -(OCF ２ CF ２ CF ２ CF ２ )c-(OCF ２ CF ２ CF ２ ) d-(OCF ２ CF ２ ) e-(OCF ２ )f-, or a group represented by -(OC ２ F ４ ) e-(OCF ２ )f-, and more preferably, -(OC ２ F ４ ) e-(OCF ２ )f- is a group represented by the formula:

[0042] In the above formula (Rf-I-III), R ２０ is preferably OC ２ F ４ and R ２１ is preferably OC ２ F ４ , O.C. ３ F ６ and O.C. ４ F８ or a combination of two or three groups independently selected from these groups, more preferably OC ３ F ６ and O.C. ４ F ８ is a group selected from ２ F ４ , O.C. ３ F ６ and O.C. ４ F ８ Examples of the combination of two or three groups independently selected from the group consisting of, but not limited to, -OC ２ F ４ O.C. ３ F ６ -, -OC ２ F ４ O.C. ４ F ８ -, -OC ３ F ６ O.C. ２ F ４ -, -OC ３ F ６ O.C. ３ F ６ -, -OC ３ F ６ O.C. ４ F ８ -, -OC4F8OC ４ F ８ -, -OC ４ F ８ O.C. ３ F ６ -, -OC ４ F ８ O.C. ２ F ４ -, -OC ２ F ４ OC2F4OC ３ F ６ -, -OC ２ F ４ O.C. ２ F ４ O.C. ４ F ８ -, -OC ２ F ４ O.C. ３ F ６ OC2F4-, -OC ２ F ４ O.C.３ F ６ O.C. ３ F ６ -, -OC ２ F ４ O.C. ４ F ８ O.C. ２ F ４ -, -OC ３ F ６ O.C. ２ F ４ O.C. ２ F ４ -, -OC ３ F ６ O.C. ２ F ４ O.C. ３ F ６ -, -OC ３ F ６ OC3F6OC ２ F ４ - and -OC ４ F ８ O.C. ２ F ４ O.C. ２ F ４ In the above formula (Rf-I-III), g is preferably an integer of 3 or more, more preferably an integer of 5 or more. The above g is preferably an integer of 50 or less. In the above formula (Rf-I-III), OC ２ F ４ , O.C. ３ F ６ , O.C. ４ F ８ , O.C. ５ F １０ , and O.C. ６ F １２ may be either a straight chain or a branched chain, and is preferably a straight chain. In this embodiment, the above formula (Rf-I-III) is preferably —(OC ２ F ４ -OC ３ F ６ ) g- or -(OC ２ F ４ -OC ４ F ８ ) g-.

[0043] In the above formula (Rf-I-IV), e is preferably an integer of 1 to 100, more preferably an integer of 5 to 100. The sum of a, b, c, d, e, and f is preferably 5 or more, more preferably 10 or more, for example, 10 to 100.

[0044] In the above formula (Rf-IV), f is preferably an integer of 1 to 100, more preferably an integer of 5 to 100. The sum of a, b, c, d, e, and f is preferably 5 or more, more preferably 10 or more, for example, 10 to 100.

[0045] In Rf, the ratio of e to f (hereinafter referred to as the "e / f ratio") may be 0.5 to 4, preferably 0.6 to 3, more preferably 0.7 to 2, and even more preferably 0.8 to 1.4. By setting the e / f ratio to 4 or less, lubricity and chemical stability are further improved. The smaller the e / f ratio, the more improved the lubricity. On the other hand, by setting the e / f ratio to 0.5 or more, the stability of the compound can be further increased. The larger the e / f ratio, the more improved the stability of the fluoropolyether structure. In this case, the e / f ratio is preferably 0.8 or more.

[0046] Rf is represented by the following formula (Rf-I-VI): -(OCF ２ CF ２ CF ２ )a-(OCF(CF ３ )CF ２ ) b-(OCF ２ CF(CF3))c-(OCF ２ CF ２ )d-(OCF(CF ３ ))e-(OCF ２ )f- (wherein a, b, c, d, e, and f each independently represent an integer of 0 to 200, the sum of a, b, c, d, e, and f is 1 or more, and the order of the repeating units assigned with a, b, c, d, e, or f is arbitrary).

[0047] Rf is represented by the following formula (Rf-I-VII): -(OCF ２ CF ２ )d-(OCF(CF ３ ))e-(OCF ２)f- (wherein d, e, and f each independently represent an integer of 0 to 200, the sum of d, e, and f is 1 or more, and the order of the repeating units to which d, e, or f is added is arbitrary.) When Rf is this group, it is thought that an increase in the number of ether bonds facilitates coordination of salt cations, thereby improving salt solubility.

[0048] In Rf, the ratio of d to f (hereinafter referred to as the "d / f ratio") may be 0.5 to 4, preferably 0.6 to 3, more preferably 0.7 to 2, and even more preferably 0.8 to 1.4. By setting the d / f ratio to 4 or less, lubricity and chemical stability are further improved. The smaller the d / f ratio, the more improved the lubricity. On the other hand, by setting the d / f ratio to 0.5 or more, the stability of the compound can be further increased. The larger the d / f ratio, the more improved the stability of the fluoropolyether structure. In this case, the d / f ratio is preferably 0.8 or more.

[0049] Each Rf is preferably independently a group represented by the above formula (Rf-II) or (Rf-I-II), and more preferably a group represented by the above formula (Rf-I-II).

[0050] The number average molecular weight of Rf is not particularly limited, but is, for example, 500 to 30,000, preferably 1,500 to 30,000, and more preferably 2,000 to 10,000. １９ This is a value measured by F-NMR.

[0051] R １ ~R ３ The alkyl group and fluoroalkyl group of R may be linear or branched, but are preferably linear. １ ~R ３ Examples of the aryl group include a phenyl group, a 4-nitrophenyl group, a 4-acetylaminophenyl group, and a 4-methanesulfonylphenyl group.

[0052] R １ ~R ３are each independently preferably an alkyl group having 1 to 3 carbon atoms or a fluoroalkyl group having 1 to 3 carbon atoms, more preferably a methyl group, an ethyl group, a trifluoromethyl group or a pentafluoroethyl group, and even more preferably a methyl group, a trifluoromethyl group or a pentafluoroethyl group.

[0053] R ４ The alkyl ester group may be linear or branched.

[0054] R ４ Examples of the substituent that the amide group or amino group may have include an alkyl group, an alkoxy group, and a hydroxy group.

[0055] R ４ are each independently preferably a fluorine atom, a hydrogen atom, a hydroxyl group, an aldehyde group, a carboxylic acid group, an alkyl ester group having 1 to 10 carbon atoms, an amide group which may have a substituent, or an amino group which may have a substituent, and more preferably a fluorine atom. ４ is a fluorine atom, R ４ -Rb ４ and Rb ４ -R ４ , that is, R ４ -Rf １ and Rf ２ -R ４ are each independently -CF ３ , -CF ２ CF ３ , and -CF ２ CF ２ CF ３ It may be a group selected from the group consisting of:

[0056] The fluoropolyether is particularly preferably the fluoropolyether represented by the formula (1) above, since it has good ionic conductivity and the like.

[0057] The fluoropolyether is preferably a liquid at any temperature between 25° C. and 80° C. because it has good ionic conductivity and the like. Examples of a form "liquid at any temperature between 25° C. and 80° C." include a form that is solid at 25° C. and liquid at 50° C., and a form that is solid at 50° C. and liquid at 80° C. Normally, there is no form that is liquid at low temperatures and solid at high temperatures, and therefore this is not included in the form "liquid at any temperature between 25° C. and 80° C.."

[0058] In the electrolyte solution for a fluoride ion battery of the present disclosure, the content of the fluoropolyether is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. The upper limit is not particularly limited, but is usually 99% by mass or less, preferably 98% by mass or less.

[0059] The fluoride salt is not particularly limited as long as it generates fluoride ions, and may be an organic fluoride salt or an inorganic fluoride salt. The fluoride salt may also be an ionic liquid. More specifically, ammonium fluoride, metal fluorides, etc. may be used. These may be used alone or in combination of two or more. Ammonium fluoride is preferred because of its good solubility.

[0060] Specific examples of the metal fluorides include alkali or alkaline earth fluorides (e.g., LiF, NaF, KF, CsF, MgF ２ , BaF ２ ), transition metal fluorides (e.g., VF ４ , FeF ３ , MoF ６ , PdF ２ , AgF), main group metal fluorides (e.g., AlF ３ , PbF ４ , BiF ３ ), lanthanide or actinide fluorides (e.g., LaF ３ , YbF ３ , U.F. ５ The metal fluoride is preferably LiF, NaF, KF, or CsF.

[0061] Examples of the ammonium fluoride include ammonium hydrogen fluoride, alkyl ammonium fluoride, etc. Alkyl ammonium fluoride is preferred because of its good solubility.

[0062] The alkylammonium fluoride is N ＋ -Rx ４ Preferably, Rx has a cation represented by the formula: Each Rx is independently an alkyl group or a fluoroalkyl group, and preferably an alkyl group. The number of carbon atoms in Rx is, for example, 1 to 10, and may be 5 or less, or 3 or less. The alkyl ammonium fluoride is preferably tetramethylammonium fluoride or tetrabutylammonium fluoride.

[0063] The alkyl group and fluoroalkyl group in the alkylammonium fluoride may be linear or branched, but preferably at least one is branched, and more preferably both branched and linear. The number of carbon atoms in the alkyl group and fluoroalkyl group is preferably 1 or more, and preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. The number of carbon atoms in the linear alkyl group and linear fluoroalkyl group is preferably 1 or more, and preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. The number of carbon atoms in the branched alkyl group and branched fluoroalkyl group is preferably 1 or more, more preferably 3 or more, and even more preferably 4 or more, and preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less.

[0064] The alkylammonium fluoride is preferably an alkylammonium fluoride having a branched alkyl group having 5 carbon atoms, more preferably an alkylammonium fluoride having a neopentyl group, further preferably trimethylneopentylammonium fluoride or dimethyldineopentylammonium fluoride, and particularly preferably trimethylneopentylammonium fluoride.

[0065] In the electrolyte solution for a fluoride battery of the present disclosure, the content of the fluoride salt is preferably 0.1% by mass or more, more preferably 1% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less.

[0066] In the electrolyte solution for a fluoride battery of the present disclosure, the fluoropolyether is usually used as a solvent. The content of the fluoropolyether relative to the solvent is preferably 70% by volume or more, more preferably 80% by volume or more, and even more preferably 90% by volume or more. The upper limit is not particularly limited, and may be 100% by mass.

[0067] The fluoride battery electrolyte solution of the present disclosure may use solvents other than the fluoropolyethers. Examples of solvents other than the fluoropolyethers include conventionally known non-aqueous solvents for fluoride ion batteries, such as carbonate-based solvents, ester-based solvents, ether-based solvents, and fluorobenzene-based solvents. Examples of carbonate-based solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, as well as linear carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Examples of ester-based solvents include cyclic esters such as γ-butyrolactone and γ-valerolactone, and linear esters such as methyl acetate and ethyl acetate. Examples of ether-based solvents include cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, and linear ethers such as dimethoxyethane and glyme-based compounds. Examples of glyme-based compounds include diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Examples of fluorobenzene-based solvents include 1,3-difluorobenzene, 1,2,4-trifluorobenzene, and 1,2,3,4-tetrafluorobenzene. These may be used alone or in combination of two or more. In the present disclosure, ether-based solvents are preferred, chain ethers are more preferred, and glyme-based compounds are even more preferred.

[0068] The fluoride battery electrolyte of the present disclosure may contain at least one anion acceptor selected from the group consisting of tris(hexafluoroisopropyl)borate, tris(pentafluorophenyl)borane, difluorophenylboroxine, trifluorophenylboroxine, bis(trifluoromethyl)phenylboroxine, trifluoromethylphenylboroxine, triphenylboroxine, trimethoxyboroxine, fluorobis(2,4,6-trimethylphenyl)borane, 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine, N,N-diethyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline, and fluoro(trifluoromethyl)phenylboroxine. These anion acceptors are believed to reversibly bind to fluoride ions in solution, thereby increasing the amount of fluoride salt dissolved in the solution. Furthermore, it is believed that the reversible complex formation between these anion acceptors and fluoride ions reduces the amount of free fluoride ions in the solution, improving the stability of the cycle characteristics.

[0069] In the electrolyte solution for a fluoride battery of the present disclosure, the content of the anion acceptor is preferably 0.001 to 20 mass %, more preferably 0.01 to 15 mass %, even more preferably 0.1 to 10 mass %, and particularly preferably 0.1 to 7 mass %, relative to the electrolyte solution.

[0070] The electrolyte solution may further contain polyethylene oxide having a weight-average molecular weight of 2000 to 4000 and having —OH, —OCOOH, or —COOH at its terminal. The inclusion of such a compound improves the stability of the electrode interface, thereby improving the characteristics of the fluoride battery. Examples of the polyethylene oxide include polyethylene oxide monool, polyethylene oxide carboxylic acid, polyethylene oxide diol, polyethylene oxide dicarboxylic acid, polyethylene oxide triol, and polyethylene oxide tricarboxylic acid. These may be used alone or in combination of two or more. Among these, a mixture of polyethylene oxide monool and polyethylene oxide diol, and a mixture of polyethylene carboxylic acid and polyethylene dicarboxylic acid are preferred, in terms of improving the characteristics of the fluoride battery.

[0071] If the weight-average molecular weight of the polyethylene oxide is too small, it may be susceptible to oxidative decomposition. The weight-average molecular weight is more preferably 3,000 to 4,000. The weight-average molecular weight can be measured in terms of polystyrene by gel permeation chromatography (GPC).

[0072] The content of the polyethylene oxide in the electrolyte is 1×10 －６ ~1 x 10 －２ If the content of polyethylene oxide is too high, the characteristics of the fluoride battery may be impaired. The content of polyethylene oxide is preferably 5×10 －６ It is more preferably mol / kg or more.

[0073] The electrolyte for a fluoride battery of the present disclosure is preferably a liquid at 25°C.

[0074] The ionic conductivity of the electrolyte for a fluoride battery of the present disclosure is preferably 1.0×10 －９ S / cm or more, more preferably 1.0×10 －８ S / cm or more, more preferably 1.0×10 －７ The upper limit is not particularly limited, but is preferably 1.0 × 10 －４The ionic conductivity can be measured at 25° C. using a SevenCompact S230 manufactured by Mettler Toledo.

[0075] The F ion transport number of the fluoride battery electrolyte of the present disclosure is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. The upper limit is not particularly limited, but is preferably 0.8 or less. The F ion transport number is determined by pulsed magnetic field gradient NMR measurement using F ions as the target nuclide (Science 362, 1144-1148 (2018)).

[0076] <Polymer Electrolyte> The present disclosure also relates to a polymer electrolyte comprising the fluoride battery electrolyte of the present disclosure.

[0077] The polymer electrolyte of the present disclosure may be, for example, a gel electrolyte in which a polymer material is plasticized with the electrolyte solution for a fluoride battery of the present disclosure.

[0078] Examples of the polymer material include conventionally known polyethylene oxide, polypropylene oxide, and modified products thereof (Japanese Patent Application Laid-Open Nos. 8-222270 and 2002-100405); fluororesins such as polyacrylate polymers, polyacrylonitrile, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene copolymers (Japanese Patent Application Laid-Open Nos. 4-506726, 8-507407, and 10-294131); and composites of these fluororesins with hydrocarbon resins (Japanese Patent Application Laid-Open Nos. 11-35765 and 11-86630). Polyvinylidene fluoride is particularly preferred.

[0079] <Fluoride Battery> The present disclosure also relates to a fluoride battery including the fluoride battery electrolyte solution of the present disclosure or the polymer electrolyte of the present disclosure.

[0080] The fluoride battery of the present disclosure preferably includes a positive electrode, a negative electrode, etc., and is particularly preferably a fluoride ion secondary battery including these.

[0081] As the positive electrode active material used in the positive electrode, for example, a metal that forms a metal fluoride can be used, and specific examples include Au, Pt, S, Ag, Fe, Co, Ni, Cu, Cr, Mo, W, V, Sb, Bi, Sn, In, Ce, Pb, etc. These may be used alone or in combination of two or more. Furthermore, it may be an alloy of two or more metals, or a fluoride of these metals. The positive electrode active material may be, for example, a foil, a compact, or one formed by a vapor deposition method.

[0082] The content of the positive electrode active material is preferably 50 to 99.5% by mass of the electrode mixture, more preferably 80 to 99% by mass, in terms of high battery capacity. The content 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.

[0083] The negative electrode active material used in the negative electrode can be, for example, a material that absorbs and releases carrier ions, and may be a material that adsorbs and desorbs carrier ions like a capacitor, or a material that inserts and desorbs carrier ions like an ion secondary battery. Specific examples include precious metals such as Pt, Au, and Ag; lithium metal; carbonaceous materials such as artificial graphite, graphite carbon fiber, resin-baked carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-baked carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon; silicon-containing compounds such as silicon alloys; Li ４ Ti ５ O １２ ; etc.

[0084] In order to increase the capacity of the resulting electrode mixture, the content of the negative electrode active material is preferably 40% by mass or more, more preferably 50% by mass or more, and particularly preferably 60% by mass or more, of the electrode mixture, and the upper limit is preferably 99% by mass or less, more preferably 98% by mass or less.

[0085] The positive electrode current collector is not particularly limited as long as it is a conductor and has a redox potential nobler than that of the positive electrode active material, and examples thereof include C, Au, Pt, Ag, Co, Mo, Cu, W, V, Sb, Bi, Sn, Ni, Pb, Fe, Cr, Zn, In, Ti, Ga, Mn, Al, Zr, etc. The negative electrode current collector can be the same as the positive electrode current collector.

[0086] The electrode mixture constituting the positive electrode or the negative electrode may contain a conductive additive. Examples of the conductive additive include, but are not limited to, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and carbon materials such as amorphous carbon such as fullerene and VGCF. These may be used alone or in any combination and ratio of two or more.

[0087] The conductive additive is used in an amount of usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more in the electrode mixture, and usually 50% by mass or less, preferably 30% by mass or less, more preferably 15% by mass or less.

[0088] The electrode mixture may contain a binder, which is not particularly limited, and examples thereof include polymer compositions such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), EPDM (ethylene-propylene-diene terpolymer), polyvinylidene fluoride, and tetrafluoroethylene.

[0089] The binder is used in an amount of usually 1.0% by mass or more, preferably 1.3% by mass or more, more preferably 1.6% by mass or more, and usually 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less, based on the electrode active material.

[0090] The positive electrode and the negative electrode may be produced by a conventional method, for example, a method in which a slurry containing an electrode composition is prepared, applied to a current collector, and dried.

[0091] The thicknesses of the positive electrode and the negative electrode are not particularly limited. However, from the viewpoint of high capacity and high output, the thickness of the mixture layer minus the thickness of the metal foil of the current collector is, as a lower limit, preferably 10 μm or more, more preferably 20 μm or more, and also preferably 500 μm or less, more preferably 450 μm or less, on one side of the current collector.

[0092] A secondary battery containing the electrolyte solution for a fluoride 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 solution and has excellent liquid retention properties, and any known separator can be used. Among these, it is preferable to use a material that is stable to the electrolyte solution, 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.

[0093] 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 of two or more. Among these, the separator is preferably a porous sheet or nonwoven fabric made from a polyolefin such as polyethylene or polypropylene, due to its excellent electrolyte permeability and shutdown effect.

[0094] The material of the outer case is not particularly limited as long as it is a substance that is stable against the electrolyte used. Specifically, metals such as nickel-plated steel sheet, stainless steel, aluminum or aluminum alloy, magnesium alloy, or a laminate film of resin and aluminum foil (laminate film) can be used. From the viewpoint of weight reduction, metals such as aluminum or aluminum alloy and laminate film are preferably used.

[0095] The shape of the secondary battery using the above-mentioned electrolyte solution 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.

[0096] 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.

[0097] Next, the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0098] The following compounds were used. Compounds 1-1 to 1-4 were liquid at 25°C. <Compound 1-1> CH ３ O (CH ２ CH ２ O) ｘ１ CH ２ CF ２ (OCF ２ CF ２ ) ｙ (OCF ２ ) ｚ OCF ２ CH ２ O (CH ２ CH ２ O) ｘ２ CH ３ (x1:4, y: average 12.3, z: average 10.2, x2:4, (CH ２ CH ２ O) ｘ１ Number average molecular weight: 176, (CH ２ CH ２ O) ｘ２ Number average molecular weight: 176) <Compound 1-2> Compound having the same structure as Compound 1-1 (x1: average 8.4, y: average 12.3, z: average 10.2, x2: average 8.4, (CH ２ CH ２ O) ｘ１ Number average molecular weight: 400, (CH ２ CH ２ O) ｘ２ Number average molecular weight: 400) <Compound 1-3> CF ２ (CF ３ )CF ２ (OCF (CF３ )CF ２ ) ｘ OCF (CF ３ ) CH ２ O (CH ２ CH ２ O) ｙ CH ２ C (CF ３ ) F (OCF ２ C (CF ３ ) F) ｚ OCF ２ C (CF ３ ) F ２ (x: average 7, y: average 4.1, z: average 7, (CH ２ CH ２ O) ｙ Number average molecular weight: 200) <Compound 1-4> CF ２ (CF ３ )CF ２ (OCF (CF ３ )CF ２ ) ｘ OCF (CF ３ ) CH ２ O (CH ２ CH ２ O) ｙ CH ３ (x: average 7, y: 4, (CH ２ CH ２ O) ｙ Number average molecular weight: 176)

[0099] <Compound 2-1> Ethyl methyl carbonate (EMC, manufactured by Kishida Chemical Co., Ltd., boiling point 108°C, flash point 22°C) <Compound 2-2> Tetrafluoroethyl trifluoroethyl ether (Tokyo Chemical Industry Co., Ltd., boiling point 56°C, no flash point) <Compound 2-3> Triethylene glycol dimethyl ether (Tokyo Chemical Industry Co., Ltd., boiling point 216°C, flash point 108°C)

[0100] <LiF> Lithium fluoride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) <NaF> Sodium fluoride (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) <KF> Potassium fluoride (manufactured by Tokyo Chemical Industry Co., Ltd.) <CsF> Cesium fluoride (manufactured by Tokyo Chemical Industry Co., Ltd.) <TMAF> Tetramethylammonium fluoride (manufactured by Sigma-Aldrich) <TBAF> Tetrabutylammonium fluoride (manufactured by Sigma-Aldrich) <NpAF> Trimethylneopentylammonium fluoride (Synthesis Example 6 below)

[0101] Synthesis Example 1 Synthesis of Compound 1-1 600 mg of sodium hydroxide (FUJIFILM Wako Pure Chemical Industries, Ltd., 15.3 mmol), 30 g of 1,3-bis(trifluoromethyl)benzene (Tokyo Chemical Industry Co., Ltd.), and 10 g of fluoropolyether alcohol terminated at both ends (Solvay, Fomblin D2, 5.1 mmol) were added to a nitrogen-substituted reaction vessel, followed by heating and stirring at 70°C for 3 hours. The internal temperature was raised to 65°C, and 5.5 g of triethylene glycol-2-bromoethyl methyl ether (Tokyo Chemical Industry Co., Ltd., 20.4 mmol) was added dropwise from a dropping funnel over 10 minutes, followed by heating and stirring for 6 hours. After returning to room temperature, 5 ml of 1N hydrochloric acid was added to the reaction solution and stirred for 3 hours. This solution was washed four times with pure water, and 2 g of magnesium sulfate was added to the separated organic layer and dried. The magnesium sulfate was removed by filtration, and the volatiles were removed from the treated solution by distillation. Compound 1-1 was obtained by further drying at 100°C for 3 hours.

[0102] Synthesis Example 2 Synthesis of Tosylated Polyethylene Glycol Monomethyl Ether 8.0 g of polyethylene glycol monomethyl ether 400 (Tokyo Chemical Industry Co., Ltd., average molecular weight 380-420, 20.0 mmol), 25 mL of tetrahydrofuran (Tokyo Chemical Industry Co., Ltd.), and 4.7 g of p-toluenesulfonyl chloride (Tokyo Chemical Industry Co., Ltd., 25 mmol) were added to a nitrogen-purged reaction vessel and stirred until homogeneous. A solution of 3.4 g of potassium hydroxide (Fujifilm Wako Pure Chemical Industries, Ltd., 60 mmol) in 10 mL of pure water was added to the reaction vessel in an ice-water bath. After stirring for 10 minutes, the ice-water bath was removed and the mixture was stirred at room temperature for 12 hours. The reaction solution was poured into a mixture of 30 mL of ice-water and 60 mL of methylene chloride, and the aqueous layer was extracted three times with methylene chloride. 8 g of magnesium sulfate was added to the separated organic layer and the mixture was dried. The magnesium sulfate was removed by filtration, and the volatiles were removed from the treated solution by distillation to obtain a tosylated polyethylene glycol monomethyl ether.

[0103] (Synthesis Example 3) Synthesis of Compound 1-2 Compound 1-2 was obtained by reacting the tosylated polyethylene glycol monomethyl ether synthesized in Synthesis Example 2 in place of triethylene glycol-2-bromoethyl methyl ether under the reaction conditions of Synthesis Example 1.

[0104] Synthesis Example 4 Synthesis of Compound 1-3 600 mg of sodium hydroxide (FUJIFILM Wako Pure Chemical Industries, Ltd., 15.3 mmol), 30 g of 1,3-bis(trifluoromethyl)benzene (Tokyo Chemical Industry Co., Ltd.), and 7.7 g of fluoropolyether monoterminated alcohol (Unichem Co., Ltd., perfluoropolyether modified product, molecular weight 1500, 5.1 mmol) were added to a nitrogen-purged reaction vessel, and the mixture was heated and stirred at 70°C for 3 hours. The internal temperature was raised to 65°C, and 1.3 g (2.5 mmol) of the polyethylene glycol with both terminal tosylation obtained in Synthesis Example 9 was dissolved in 5 g of 1,3-bis(trifluoromethyl)benzene and added dropwise from the dropping funnel over 10 minutes. The mixture was heated and stirred for 6 hours. After returning to room temperature, 5 ml of 1N hydrochloric acid was added to the reaction solution, and the mixture was stirred for 3 hours. This solution was washed four times with pure water, and 2 g of magnesium sulfate was added to the separated organic layer and dried. The magnesium sulfate was removed by filtration, and the volatile matter was distilled off from the treated solution, which was then dried at 100° C. for 3 hours to obtain compound 1-3.

[0105] Synthesis Example 5 Synthesis of Compound 1-4 A nitrogen-purged reaction vessel was charged with 600 mg of sodium hydroxide (FUJIFILM Wako Pure Chemical Industries, Ltd., 15.3 mmol), 30 g of 1,3-bis(trifluoromethyl)benzene (Tokyo Chemical Industry Co., Ltd.), and 5.1 g of fluoropolyether monoterminated alcohol (Unichem Co., Ltd., perfluoropolyether modified, molecular weight 1500, 5.1 mmol), followed by heating and stirring at 70°C for 3 hours. The internal temperature was raised to 65°C, and 2.8 g of triethylene glycol-2-bromoethyl methyl ether (Tokyo Chemical Industry Co., Ltd., 10.0 mmol) was added dropwise from the dropping funnel over 10 minutes, followed by heating and stirring for 6 hours. After returning to room temperature, 5 ml of 1N hydrochloric acid was added to the reaction solution and the mixture was stirred for 3 hours. This solution was washed four times with pure water, and 2 g of magnesium sulfate was added to the separated organic layer and dried. The magnesium sulfate was removed by filtration, and the volatile matter was distilled off from the treated solution, which was then dried at 100° C. for 3 hours to obtain compound 1-4.

[0106] Synthesis Example 6: Synthesis of NpAF Trimethylneopentylammonium iodide was prepared by adding sodium carbonate (28.7 g) to a pear-shaped flask containing a magnetically stirred solution of methyl iodide (20 mL) and neopentylamine (11.8 mL) in ethanol (200 mL). After magnetic stirring at room temperature for over 20 hours, the mixture was suspended in ethanol (500 mL), filtered, and the solvent was removed using a hot stirrer. The resulting solid was then recrystallized from isopropanol (170 mL). The resulting crystals were dried in vacuo to obtain trimethylneopentylammonium iodide. The resulting trimethylneopentylammonium iodide (2 g), fluoride ion exchange resin (3.5 g), and methanol (30 mL) were placed in a PTFE beaker and allowed to stand for 30 minutes. The solution was then filtered, and the filtrate was heated to 60°C using a hot stirrer to remove the solvent. After solvent removal, a highly viscous solution was obtained. Isopropanol (6 mL) was added to the resulting solution, and the solution was dried under vacuum at 60°C to obtain brown crystals. The resulting crystals were transferred to a glove box, and after adding isopropanol (2 mL) in the glove box, the crystals were transferred to a sealable drying container and dried under vacuum at 60°C for one day. The above drying procedure was repeated twice. The resulting crystals were transferred to a sealable drying container and dried under vacuum at 80°C for one day, to obtain white crystalline NpAF.

[0107] <Experiment 1> Examples 1 to 4, Comparative Examples 1 to 3 (Preparation of Electrolyte Compositions Containing Fluoride Salt) Lithium fluoride (LiF, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the compounds listed in Table 1 and stirred at 45°C for 24 hours to obtain compositions containing 5% by mass of fluoride salt. The obtained compositions were pressure-filtered using a membrane filter (DISMIC 25HP045AN) to obtain samples for evaluation.

[0108] (Volatility Test) Approximately 5 g of a sample was weighed into an aluminum cup and heated in a thermostatic bath at 100°C for 5 hours. The mass of the sample on the aluminum cup was then weighed, and the mass loss rate of the sample was calculated using the following formula: (Sample mass loss rate) = 1 - (mass after heating) / (mass before heating) If the mass loss rate was 10% or less, it was evaluated as ◯ (low volatility), and if it was more than 10%, it was evaluated as × (high volatility).

[0109] (Non-flammability test) The non-flammability (non-ignition property) of the composition was examined by the following method. (Sample preparation) A strip of cellulose paper (15 mm wide, 320 mm long, 0.04 mm thick) was thoroughly immersed in the composition produced in the above Examples or Comparative Examples, and then removed to serve as a sample. (Test method) The sample was fixed to a metal stand, and a lighter flame was brought close to one end of the sample and held there for 1 second to check for ignition. The evaluation criteria were ○ if the sample did not ignite (non-flammable) or if it ignited but the flame quickly went out (self-extinguishing), and × if it ignited and continued to burn.

[0110] (Measurement of Ionic Conductivity) Ionic conductivity was measured using a SevenCompact S230 manufactured by Mettler Toledo at 25° C. The measuring instrument was calibrated in advance using a standard solution of 12.88 mS / cm before use.

[0111]

[0112] <Experiment 2> Examples 5 to 11 (Preparation of Electrolyte Compositions Containing Fluoride Salts) Compound 1-1 and the fluoride salts shown in Table 2 were added to give a salt concentration of 5 mass %, and the mixture was stirred at 45° C. for 24 hours to obtain compositions. The obtained compositions were pressure-filtered using a membrane filter (DISMIC 25HP045AN) to obtain samples for evaluation.

[0113] The ionic conductivity, volatility, and non-flammability were evaluated in the same manner as in Experiment 1.

[0114]

Claims

1. A fluoride battery electrolyte comprising a fluoropolyether and a fluoride salt.

2. The electrolyte for a fluoride battery according to claim 1, wherein the fluoropolyether is at least one of the following formulas (1) to (4): (1) R １ -O-Ra １ -Rb １ -O-Ra １ -R １ (2) R ２ -Rb ２ -O-Ra ２ -Rb ２ -R ２ (3) R ３ -Rb ３ -O-Ra ３ -R ３ (4) R ４ -Rb ４ -R ４ (In the formula, Ra １ ~Ra ３ each independently represents a group containing an alkylene unit not containing fluorine and / or an oxyalkylene unit not containing fluorine, １ ~Ra ３ Each oxyalkylene unit is independently —CH ２ CH ２ O- or -CH ２ CH(J)O-, each J is independently an alkyl group or an aryl group, and Rb １ ~Rb ４ R is each independently a fluoropolyether group represented by the following formula (5): １ ~R ３ are each independently a hydrogen atom, a hydroxyl group, a fluorine atom, an alkyl group having 1 to 3 carbon atoms, an aryl group, or a fluoroalkyl group having 1 to 3 carbon atoms; R ４ are each independently a fluorine atom, a hydrogen atom, a hydroxyl group, an aldehyde group, a carboxylic acid group, an alkyl ester group having 1 to 10 carbon atoms, an amide group which may have a substituent, or an amino group which may have a substituent. １ -Rf-O-Rf ２ - (wherein, Rf １ and Rf ２ are each independently an alkylene group having 1 to 16 carbon atoms which may be substituted by a fluorine atom, and Rf is a divalent fluoropolyether group.

3. The above Ra １ ~Ra ３ The electrolyte for a fluoride battery according to claim 2, wherein each of the groups is independently a polyoxyalkylene group represented by the following formula (Ra-I): -(CH ２ CH ２ O)r(CH ２ CH (CH ３ )O)s(CH ２ CH (CH ２ CH ３ )O)t(CH ２ CH(Ph)O)u- (wherein r, s, t and u are each independently an integer of 0 or 1 or more, and r+s+t+u is 4 to 50.) 4. The above Ra １ ~Ra ３ 4. The electrolyte for a fluoride battery according to claim 2 or 3, wherein the number average molecular weight of said electrolyte is 40 to 4,000.

5. The electrolyte for a fluoride battery according to any one of claims 2 to 4, wherein each Rf is independently a fluoropolyether group represented by the following formula (Rf-I): Formula (Rf-I): -(OC ６ F １２ ) a-(OC ５ F １０ ) b-(OC ４ F ８ )c-(OC ３ Rc ６ ) d-(OC ２ F ４ ) e-(OCF ２ )f- (In the formula, Rc is each independently a hydrogen atom, a fluorine atom or a chlorine atom; a, b, c, d, e and f are each independently an integer from 0 to 200; the sum of a, b, c, d, e and f is 1 or more; the order of the repeating units to which a, b, c, d, e or f is assigned is arbitrary; and when all Rc are hydrogen atoms or chlorine atoms, at least one of a, b, c, e and f is 1 or more.) 6. The electrolyte for a fluoride battery according to any one of claims 2 to 5, wherein each Rf is independently a group represented by the following formula (Rf-II) or the following formula (Rf-I-II): ３ F ６ ) d-(OC ２ F ４ )e- (wherein, d is an integer of 1 to 200, and e is 0 or 1.) Formula (Rf-I-II): -(OC ４ F ８ )c-(OC ３ F ６ ) d-(OC ２ F ４ ) e-(OCF ２ )f- (In the formula, c and d each independently represent an integer of 0 to 30, e and f each independently represent an integer of 1 to 200, the sum of c, d, e and f is 2 or more, and the order of each repeating unit to which c, d, e or f is added is arbitrary.) 7. The above R １ ~R ３ The electrolyte for a fluoride battery according to any one of claims 2 to 6, wherein each of the is independently a methyl group, an ethyl group, a trifluoromethyl group, or a pentafluoroethyl group.

8. The electrolyte for a fluoride battery according to any one of claims 1 to 7, wherein the fluoride salt is ammonium fluoride or a metal fluoride.

9. The electrolyte for a fluoride battery according to claim 8, wherein said ammonium fluoride is an alkylammonium fluoride having a neopentyl group.

10. The electrolyte for a fluoride battery according to any one of claims 1 to 9, wherein the content of the fluoride salt is 0.1 to 10 mass %.

11. The electrolyte for a fluoride battery according to any one of claims 1 to 10, which is liquid at 25°C.

12. Ion conductivity is 1.0 x 10 －９ ~1.0 x 10 －４ The electrolyte for a fluoride battery according to any one of claims 1 to 11, wherein the fluoride concentration is 1.0 S / cm.

13. A polymer electrolyte comprising the electrolyte solution for a fluoride battery according to any one of claims 1 to 12.

14. A fluoride battery comprising the electrolyte for a fluoride battery according to any one of claims 1 to 12 or the polymer electrolyte according to claim 13.

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