Additive for electrolytic solution, compound and method for manufacturing same, electrolytic solution, and electric power storage device

Abstract

The present disclosure relates to an additive for an electrolytic solution, the additive containing a compound that is expressed by formula (1). [In formula (1), M indicates a group 13 element of the periodic table, and each of R1 to R3 independently indicates a C1-6 alkyl group that may be substituted, a C2-6 alkenyl group that may be substituted, a C2-6 alkynyl group that may be substituted, an aryl group that may be substituted, or a C1-6 alkoxy group that may be substituted.]

Description

Additive for electrolyte, compound and method for producing the same, electrolyte, and electricity storage device

[0001] The present disclosure relates to an additive for an electrolyte, a compound and a method for producing the same, an electrolyte, and an electricity storage device.

[0002] In recent years, with growing interest in solving environmental problems and realizing a sustainable, recycling-based society, development of electricity storage devices, typified by nonaqueous electrolyte secondary batteries, has been widely underway. Among electricity storage devices, lithium ion batteries exhibit high voltage and energy density and are therefore used as power sources for notebook computers, mobile phones, etc. In order to improve the battery performance of these nonaqueous electrolyte secondary batteries, various additives are sometimes added to the nonaqueous electrolyte (e.g., Patent Documents 1 and 2).

[0003] JP-A-5-74486 JP-A-63-102173

[0004] However, even when these conventionally known methods are used, there is still room for improvement in the battery characteristics of the electricity storage device.

[0005] One aspect of the present disclosure is to provide a novel electrolyte additive that improves the battery characteristics of an electricity storage device containing an electrolyte. Another aspect of the present disclosure is to provide an electrolyte using the electrolyte additive and an electricity storage device using the electrolyte. Another aspect of the present disclosure is to provide a compound suitable as an electrolyte additive and a method for producing the compound.

[0006] The present disclosure includes the following aspects: [1] An additive for an electrolyte solution, comprising a compound represented by the following formula (1): [In formula (1), M represents an element of Group 13 of the periodic table, and R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.] [2] An additive for an electrolyte solution, comprising a metal complex of a compound represented by the following formula (1) and an alkali metal salt compound: [In formula (1), M represents an element of Group 13 of the periodic table, and R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.] [3] The electrolyte additive according to [2], wherein the alkali metal salt compound is a lithium salt compound. [4] The electrolyte additive according to any one of [1] to [3], wherein M is a boron atom or an aluminum atom. [5] The electrolyte additive according to any one of [1] to [4], wherein M is a boron atom. [6] R １ ~R ３ [7] The additive for an electrolyte solution according to any one of [1] to [5], wherein R are each independently an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, or an optionally substituted aryl group. １ ~R ３ are each independently an unsubstituted methyl group, an unsubstituted ethyl group, an unsubstituted vinyl group, an unsubstituted allyl group, or an unsubstituted phenyl group, and M is a boron atom. [8] The additive for an electrolyte solution according to any one of [1] to [6], [In formula (1), M represents an element of Group 13 of the periodic table, and R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.] ３ [in formula (2), M represents an element of group 13 of the periodic table, and X represents a halogen atom], and a compound represented by formula (3): R ４ SO ３ H [In formula (3), R ４(wherein R represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.) to obtain a compound represented by formula (1), and the compound represented by HX produced as a by-product in the reaction step is removed. [9] An electrolyte solution containing the electrolyte solution additive according to any one of [1] to [7] and a non-aqueous solvent.

[10] The electrolyte solution according to [9], wherein the non-aqueous solvent contains a cyclic carbonate and / or a chain carbonate.

[11] An electricity storage device comprising the electrolyte solution according to [9] or

[10] , a positive electrode, and a negative electrode.

[12] A compound represented by formula (1): [In formula (1), M represents an element of Group 13 of the periodic table, and R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.]

[13] The compound according to

[12] , wherein M is a boron atom.

[14] R １ ~R ３ are each independently an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, or an optionally substituted aryl group.

[0007] According to one aspect of the present disclosure, there is provided a novel additive for an electrolyte solution that improves the battery characteristics of an electricity storage device containing the electrolyte solution. According to one aspect of the present disclosure, there are provided an electrolyte solution using the additive for the electrolyte solution and an electricity storage device using the electrolyte solution.

[0008] An electrolyte solution including an additive according to one aspect of the present disclosure can improve the battery characteristics of an electricity storage device.

[0009] According to one aspect of the present disclosure, there is provided a method for efficiently producing a compound suitable as an additive for an electrolyte.

[0010] FIG. 1 is a cross-sectional view illustrating an embodiment of an electricity storage device. １９ FIG. 1 is a diagram showing the results of F-NMR measurement.

[0011] Hereinafter, several embodiments according to one aspect of the present invention will be described in detail. In the numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in a certain stage can be arbitrarily combined with the upper or lower limit of a numerical range in another stage. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples.

[0012] <Compound> An example of the compound is a compound represented by the following formula (1) (hereinafter also referred to as "compound (1)"). Compound (1) can be suitably used, for example, as an additive for an electrolyte solution.

[0013] In formula (1), M represents an element of Group 13 of the periodic table. Examples of the element of Group 13 of the periodic table include a boron atom, an aluminum atom, a gallium atom, an indium atom, and a thallium atom. From the viewpoint of further improving solubility in the electrolyte, M may be a boron atom or an aluminum atom, or may be a boron atom.

[0014] In formula (1), R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.

[0015] In formula (1), R １ ~R ３ may all be the same group, and R １ ~R ３ In view of ease of synthesis, R １ ~R ３ may all be the same group.

[0016] In this specification, the term "optionally substituted" means that one or more hydrogen atoms of each group may be substituted with a substituent. Examples of the substituent include a halogen atom. Examples of the halogen atom include an iodine atom, a bromine atom, a chlorine atom, and a fluorine atom.

[0017] R １ , R ２ and R ３ In the alkyl group, alkenyl group, alkynyl group, aryl group, and alkoxy group in R, one or more hydrogen atoms of each group may be substituted with a halogen atom. The halogen atom may be a fluorine atom. １ , R ２ and R ３ When one or more of the hydrogen atoms in each group represented by the formula (I) are substituted with a fluorine atom, the battery resistance can be further reduced.

[0018] In formula (1), R １ , R ２ and R ３ The number of carbon atoms in the alkyl group may be 1 to 3, or 1 to 2. The alkyl group may be linear or branched. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, a sec-pentyl group, a neopentyl group, an n-hexyl group, an isohexyl group, a trifluoromethyl group, and a difluoroethyl group. The alkyl group may be a methyl group optionally substituted with a halogen atom, or an ethyl group optionally substituted with a halogen atom, or may be an unsubstituted methyl group or an unsubstituted ethyl group. When the alkyl group is an unsubstituted methyl group or an unsubstituted ethyl group, the battery resistance is more likely to be reduced.

[0019] In formula (1), R １ , R ２ and R ３The number of carbon atoms in the alkenyl group may be 2 to 5, or 2 to 4. The alkenyl group may be linear or branched. Examples of the alkenyl group include a vinyl group, an allyl group, a methallyl group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, an isobutenyl group, a 1-pentenyl group, a 2-pentenyl group, a 3-pentenyl group, a 4-pentenyl group, an isopentenyl group, a 1-hexenyl group, a 2-hexenyl group, a 3-hexenyl group, a 4-hexenyl group, a 5-hexenyl group, an isohexenyl group, and a 1,1-difluoro-1-propenyl group.

[0020] The alkenyl group may be a vinyl group optionally substituted with a halogen atom, an allyl group optionally substituted with a halogen atom, or a methallyl group optionally substituted with a halogen atom. When the alkenyl group is an allyl group optionally substituted with a halogen atom, or a methallyl group optionally substituted with a halogen atom, a stronger solid electrolyte interface (SEI) is more likely to be formed. Furthermore, when the alkenyl group is a vinyl group optionally substituted with a halogen atom, or an allyl group optionally substituted with a halogen atom, the battery resistance is more likely to be reduced.

[0021] In formula (1), R １ , R ２ and R ３ The number of carbon atoms in the alkynyl group may be 3 to 4. The alkynyl group may be linear or branched. Examples of the alkynyl group include an ethynyl group, a 1-propynyl group, a 2-propynyl group, a 1-butynyl group, a 2-butynyl group, a 3-butynyl group, an isobutynyl group, a 1-pentynyl group, a 2-pentynyl group, a 3-pentynyl group, a 4-pentynyl group, an isopentynyl group, a 1-hexynyl group, a 2-hexynyl group, a 3-hexynyl group, a 4-hexynyl group, a 5-hexynyl group, and an isohexynyl group.

[0022] The alkynyl group may be a 2-propynyl group optionally substituted with a halogen atom. When the alkynyl group is a 2-propynyl group optionally substituted with a halogen atom, a stronger SEI is likely to be formed.

[0023] In formula (1), R １ , R ２ and R ３ The number of carbon atoms of the aryl group as R may be 6 to 10. １ , R ２ and R ３ Examples of the optionally substituted aryl group as the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a hexafluorophenyl group. The aryl may be an optionally substituted phenyl group or an unsubstituted phenyl group. When the aryl group is an unsubstituted phenyl group, the battery resistance is more likely to be reduced.

[0024] In formula (1), R １ , R ２ and R ３ The number of carbon atoms in the alkoxy group may be 1 to 3, or 1 to 2. The alkoxy group may be linear or branched. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentoxy group, an n-hexoxy group, and a 2,2,2-trifluoroethoxy group.

[0025] Examples of compound (1) include compounds represented by the following formulas (1-1), (1-2), (1-3), (1-4), (1-5), (1-6) and (1-7).

[0026] Compound (1) may be a compound represented by formula (1-1), (1-2), (1-3), (1-4), or (1-6). When compound (1) is a compound represented by formula (1-3) or (1-6), an increase in the resistance of the electricity storage device when used at high temperatures can be easily suppressed.

[0027] An example of a method for producing compound (1) is, for example, a method for producing a compound of formula (2): MX ３ and a compound represented by formula (3): R ４ SO ３ H (hereinafter also referred to as "compound (3)") to obtain compound (1).

[0028] In the compound (2), M has the same meaning as M in the formula (1), and X represents a halogen atom. ３ , BCl ３ , B.F. ３ etc.

[0029] In compound (3), R ４ is R in formula (1) １ , R ２ and R ３ Examples of compound (3) include methanesulfonic acid, ethanesulfonic acid, n-propylsulfonic acid, isopropylsulfonic acid, n-butanesulfonic acid, perfluorobutanesulfonic acid, isobutylsulfonic acid, tert-butylsulfonic acid, n-pentanesulfonic acid, isopentylsulfonic acid, tert-pentylsulfonic acid, sec-pentylsulfonic acid, neopentylsulfonic acid, n-hexanesulfonic acid, isohexylsulfonic acid, trifluoromethanesulfonic acid, difluoroethanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, methallyl sulfonic acid, 1-butenesulfonic acid, 2-butenesulfonic acid, 3-butenesulfonic acid, isobutenesulfonic acid, 1-pentenesulfonic acid, 2-pentenesulfonic acid, 3-pentenesulfonic acid, 4-pentenesulfonic acid, Sulfonic acid, isopentene sulfonic acid, 1-hexene sulfonic acid, 2-hexene sulfonic acid, 3-hexene sulfonic acid, 4-hexene sulfonic acid, 5-hexene sulfonic acid, isohexene sulfonic acid, 2,2-difluoro-1-propene sulfonic acid, 1-propyne sulfonic acid, 2-propyne sulfonic acid, 1-butyne sulfonic acid, 2-butyne sulfonic acid, 3-butyne sulfonic acid, isobutyne sulfonic acid, 1-pentyne sulfonic acid, 2-pentyne sulfonic acid, 3-pentyne sulfonic acid, 4-pentyne sulfonic acid, isopentyne sulfonic acid, 1-hexyne sulfonic acid, 2-hexyne sulfonic acid, 3-hexyne sulfonic acid, 4-hexyne sulfonic acid, 5-hexyne sulfonic acid, isohexyne sulfonic acid, p-toluene sulfonic acid, benzene sulfonic acid, and the like.

[0030] In the reaction step, compound (2) and compound (3) may be reacted in a reaction solution containing compound (2), compound (3), and a solvent. The solvent can be appropriately selected depending on the types of compound (2) and compound (3). The solvent may be an organic solvent. Examples of the solvent include halogenated solvents such as dichloromethane and chloroform, aromatic solvents such as toluene and xylene, aliphatic solvents such as n-hexane, isohexane, cyclohexane, and n-heptane, aprotic polar solvents such as acetonitrile and sulfolane, ether solvents such as diethyl ether and tetrahydrofuran, and carbonate solvents such as dimethyl carbonate, diethyl carbonate, ethylene carbonate, and ethyl methyl carbonate.

[0031] In the reaction step, the by-product HX is removed. This makes it possible to suppress the complexation of compound (1) with the by-product HX. By suppressing the complexation, it is possible to suppress the generation of gas originating from active hydrogen (hydrogen atoms in HX) when the electricity storage device is used. Furthermore, when the by-product HX is removed, the reaction time in the reaction step is shortened and the generation of impurities is easily suppressed.

[0032] In the reaction step, methods for removing the by-product HX include increasing the reaction temperature to remove dissolved HX, and blowing in an inert gas (for example, nitrogen gas).

[0033] The temperature of the reaction solution (reaction temperature) when reacting compound (2) with compound (3) can be appropriately set depending on the type of solvent, etc. The reaction temperature may be, for example, 30°C or higher, 35°C or higher, or 40°C or higher, and may be the reflux temperature or lower. The reaction temperature may be, for example, 30°C or higher, 35°C or higher, or 40°C or higher, and the reflux temperature or lower. The reaction temperature may be changed continuously or stepwise.

[0034] The time for which the reaction temperature is maintained (reaction time) can be appropriately set depending on the types of compounds (2) and (3), etc. The reaction time may be, for example, 3 hours or more, 10 hours or more, 12 hours or more, or 14 hours or more, and may be 30 hours or less, 25 hours or less, 20 hours or less, or 15 hours or less.

[0035] The reaction step may be carried out under an inert gas atmosphere. The reaction step may be carried out with stirring.

[0036] After the reaction, post-treatment may be carried out as necessary, which may include precipitating compound (1) as crystals, separating the crystals of compound (1) by filtration, drying compound (1), etc.

[0037] <Electrolyte Additive> An example of the electrolyte additive includes the compound (1). The electrolyte additive may further include an alkali metal salt compound in addition to the compound (1). The alkali metal salt compound can also function as an electrolyte in the electrolyte.

[0038] Alkali metal salt compounds include lithium salt compounds, sodium salt compounds, and potassium salt compounds.

[0039] Lithium salt compounds include LiBr, LiCl, LiI, LiSCN, and LiBF. ４ , LiAsF ４ , LiClO ４ , and LiPF ６ Examples include:

[0040] Sodium salt compounds include NaBr, NaCl, NaI, NaSCN, and NaBF ４ , NaAsF ４ , NaClO ４ , and NaPF ６ Examples include:

[0041] Potassium salt compounds include KBr, KCl, KI, KSCN, and KBF ４ , KAsF ４ , KClO ４ , and KPF ６ Examples include:

[0042] The alkali metal salt compound may be a lithium salt compound from the viewpoint of improving the ionic conductivity of the electrolyte, and LiPF ６ It may be.

[0043] An example of an electrolyte additive is a metal complex of compound (1) and an alkali metal salt compound. When compound (1) becomes a metal complex, the anionic character of compound (1) is enhanced, which is thought to result in easier interaction with the positive electrode.

[0044] Examples of a method for forming a metal complex include a method in which a reaction mixture containing compound (1), an alkali metal salt compound, and a solvent capable of dissolving these compounds is stirred, heated, and / or pressurized.

[0045] In addition to compound (1) and the alkali metal salt compound, the electrolyte additive may, as needed, include anode protectants, cathode protectants, flame retardants, overcharge inhibitors, nitrile compounds, isocyanate compounds, compounds having an acetylene-1,2-diyl group (-C≡C-), compounds having a sulfonyl group (>S(=O)2) (excluding the compound represented by formula (1)), phosphate ester compounds, acid anhydrides, cyclic phosphazene compounds, cyclic dioxazole compounds, boroxine derivatives, ionic compounds, and compounds containing silicon atoms. These other components may be included in the electrolyte together with compound (1) and the alkali metal salt compound as additives for improving the characteristics of the electricity storage device.

[0046] Examples of nitrile compounds include acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and sebaconitrile. The nitrile compound may be succinonitrile, adiponitrile, or a combination thereof.

[0047] Examples of the isocyanate compound include methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate.

[0048] Examples of compounds having an acetylene-1,2-diyl group (—C≡C—) include 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl 2-(methanesulfonyloxy)propionate, di(2-propynyl)oxalate, methyl-2-propynyl oxalate, ethyl-2-propynyl oxalate, di(2-propynyl) glutarate, 2-butyne-1,4-diyldimethanesulfonate, 2-butyne-1,4-diyldiformate, and 2,4-hexadiyn-1,6-diyldimethanesulfonate.

[0049] Examples of compounds having a sulfonyl group (>S(=O)2) include sultones such as 1,3-propane sultone (PS), 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propene sultone, 2,2-dioxide-1,2-oxathiolan-4-yl acetate, and 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, ethylene sulfite, ethylene sulfate, and hexahydrobenzo[1,3,2]dioxathiolan-2-oxide (1,2 cyclic sulfites such as butane-2,3-diyldimethanesulfonate, butane-1,4-diyldimethanesulfonate, methylenemethane disulfonate, and 1,3-propanedisulfonic acid anhydride; divinyl sulfone; 1,2-bis(vinylsulfonyl)ethane; and bis(2-vinylsulfonylethyl)ether.

[0050] Examples of the phosphate ester compound include trimethyl phosphate, tributyl phosphate, trioctyl phosphate, tris(2,2,2-trifluoroethyl phosphate), bis(2,2,2-trifluoroethyl)methyl phosphate, bis(2,2,2-trifluoroethyl)ethyl phosphate, bis(2,2,2-trifluoroethyl)2,2-difluoroethyl phosphate, bis(2,2,2-trifluoroethyl)2,2,3,3-tetrafluoropropyl phosphate, bis(2,2-difluoroethyl)2,2,2-trifluoroethyl phosphate, bis(2,2,3,3-tetrafluoropropyl)2,2,2-trifluoroethyl phosphate, (2,2,2-trifluoroethyl)(2,2,3,3-tetrafluoropropyl)methyl phosphate, tris(1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate, methyl methylenebisphosphonate, and methylenebisphosphonate. Examples of suitable phosphoric acid salts include ethyl sulfonate, methyl ethylene bisphosphonate, ethyl ethylene bisphosphonate, methyl butylene bisphosphonate, ethyl butylene bisphosphonate, methyl 2-(dimethylphosphoryl)acetate, ethyl 2-(dimethylphosphoryl)acetate, methyl 2-(diethylphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate, 2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl 2-(diethylphosphoryl)acetate, methyl 2-(dimethoxyphosphoryl)acetate, ethyl 2-(dimethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate, 2-propynyl 2-(dimethoxyphosphoryl)acetate, 2-propynyl 2-(diethoxyphosphoryl)acetate, methyl pyrophosphate, and ethyl pyrophosphate.

[0051] Examples of acid anhydrides include acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, 3-allylsuccinic anhydride, glutaric anhydride, itaconic anhydride, and 3-sulfo-propionic anhydride.

[0052] Examples of cyclic phosphazene compounds include methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene.

[0053] Examples of cyclic dioxazole compounds include 3-phenyl-1,4,2-dioxazol-5-one, 3-(2-fluorophenyl)-1,4,2-dioxazol-5-one, 3-(3-fluorophenyl)-1,4,2-dioxazol-5-one, 3-(4-fluorophenyl)-1,4,2-dioxazol-5-one, 3-(4-methoxyphenyl)-1,4,2-dioxazol-5-one, 3-(2-thienyl)-1,4,2-dioxazol-5-one, 3-(2,3,4,5,6-pentafluorophenyl)-1,4,2-dioxazol-5-one, 3-[4-(trifluoromethyl)phenyl]-1,4,2-dioxazol-5-one, and 3-(4-nitrophenyl)-1,4,2-dioxazol-5-one.

[0054] Examples of boroxine derivatives include boroxine, trimethylboroxine, trimethoxyboroxine, triethylboroxine, triethoxyboroxine, triisopropylboroxine, triisopropoxyboroxine, tri-n-propylboroxine, tri-n-propoxyboroxine, tri-n-butylboroxine, tri-n-butyloxyboroxine, triphenylboroxine, triphenoxyboroxine, tricyclohexylboroxine, and tricyclohexoxyboroxine.

[0055] Examples of the ionic compound include lithium difluorophosphate, lithium bisoxalatoborate (LiBOB), lithium tetrafluoro(oxalato)phosphate (LiTFOP), lithium difluorooxalatoborate (LiDFOB), lithium difluorobisoxalatophosphate (LiDFOP), lithium tetrafluoroborate, lithium bisfluorosulfonylimide, lithium tetrafluoro(oxalato)phosphate, lithium salts having a phosphate skeleton such as Li2PO3F, lithium trifluoro((methanesulfonyl)oxy)borate, lithium pentafluoro((methanesulfonyl)oxy)phosphate, lithium Examples of the lithium salts include lithium salts having an S(═O) group such as lithium methyl sulfate, lithium ethyl sulfate, lithium 2,2,2-trifluoroethyl sulfate, and lithium fluorosulfonate; sodium difluorophosphate, sodium bisoxalatoborate, sodium tetrafluoro(oxalato)phosphate, sodium difluorobis(oxalato)phosphate, sodium difluorooxalatoborate, potassium difluorophosphate, potassium bisoxalatoborate, potassium tetrafluoro(oxalato)phosphate, potassium difluorobis(oxalato)phosphate, and potassium difluorooxalatoborate.

[0056] Examples of compounds containing silicon atoms include hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, hexaphenylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, trimethylfluorosilane, triethylfluorosilane, tripropylfluorosilane, phenyldimethylfluorosilane, triphenylfluorosilane, vinyldimethylfluorosilane, vinyldiethylfluorosilane, vinyldiphenylfluorosilane, divinyldifluorosilane, divinyldimethylsilane, trimethoxyfluorosilane, triethoxyfluorosilane, dimethyldifluorosilane, diethyldifluorosilane, trivinylfluorosilane, trivinylmethylsilane, ethylvinyldifluorosilane, methyltrifluorosilane, ethyltrifluorosilane, Examples of suitable alkylsilanes include hexamethyldisiloxane, 1,3-diethyltetramethyldisiloxane, hexaethyldisiloxane, octamethyltrisiloxane, methoxytrimethylsilane, ethoxytrimethylsilane, dimethoxydimethylsilane, trimethoxymethylsilane, tetramethoxysilane, tetravinylsilane, tetraallylsilane, tetrabutenylsilane, bis(trimethylsilyl)peroxide, trimethylsilyl acetate, triethylsilyl acetate, trimethylsilyl propionate, trimethylsilyl methacrylate, trimethylsilyl trifluoroacetate, trimethylsilyl methanesulfonate, trimethylsilyl ethanesulfonate, triethylsilyl methanesulfonate, trimethylsilyl fluoromethanesulfonate, bis(trimethylsilyl)sulfate, tris(trimethylsiloxy)boron, tris(trimethylsilyl)phosphate, and tris(trimethylsilyl)phosphite.

[0057] <Electrolyte> An example of the electrolyte contains an electrolyte additive and a non-aqueous solvent. The electrolyte contains compound (1) or a metal complex of compound (1) and an alkali metal salt compound.

[0058] The content of compound (1) may be 0.05% by mass or more, 0.10% by mass or more, 0.15% by mass or more, 0.20% by mass or more, 0.25% by mass or more, 0.30% by mass or more, 0.35% by mass or more, 0.40% by mass or more, or 0.45% by mass or more, based on the total mass of the electrolyte solution. The content of compound (1) may be 5.0% by mass or less, 4.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, 0.80% by mass or less, or 0.60% by mass or less, based on the total mass of the electrolyte solution. The content of compound (1) may be, for example, 0.05 to 5% by mass, based on the total mass of the electrolyte solution. When the content of compound (1) is within the above-mentioned range, it is easier to further suppress an increase in the initial resistance of the electricity storage device. When a plurality of types of compounds (1) are contained, the content of compound (1) means the total amount of these plurality of types of compounds (1).

[0059] When the electrolyte additive contains a metal complex of compound (1) and an alkali metal salt compound, the content of the metal complex may be 0.075% by mass or more, 0.15% by mass or more, 0.20% by mass or more, 0.25% by mass or more, 0.30% by mass or more, 0.35% by mass or more, 0.40% by mass or more, 0.45% by mass or more, or 0.50% by mass or more, based on the total mass of the electrolyte. The content of the metal complex may be 8.0% by mass or less, 7.0% by mass or less, 6.0% by mass or less, 5.0% by mass or less, 4.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, 0.80% by mass or less, or 0.60% by mass or less, based on the total mass of the electrolyte. The content of the metal complex may be, for example, 0.075 to 8% by mass, based on the total mass of the electrolyte. When the content of the metal complex is within the above range, an increase in the initial resistance of the electricity storage device can be further suppressed. When multiple types of metal complexes are contained, the content of the metal complex means the total amount of these multiple types of metal complexes.

[0060] (Non-aqueous solvent) The non-aqueous solvent may be an aprotic solvent from the viewpoint of keeping the viscosity of the electrolyte low, etc. The non-aqueous solvent may contain at least one selected from the group consisting of cyclic carbonates, chain carbonates, aliphatic carboxylic acid esters, lactones, lactams, cyclic ethers, chain ethers, sulfones, nitriles, and halogen derivatives thereof. The non-aqueous solvent may contain at least one of cyclic carbonates and chain carbonates, or may contain a combination of cyclic carbonates and chain carbonates.

[0061] Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, and fluoroethylene carbonate. Examples of linear carbonates include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of aliphatic carboxylic acid esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, and methyl trimethylacetate. An example of a lactone is γ-butyrolactone. Examples of lactams include ε-caprolactam and N-methylpyrrolidone. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1,3-dioxolane. Examples of linear ethers include 1,2-diethoxyethane and ethoxymethoxyethane. An example of a sulfone is sulfolane. An example of a nitrile is acetonitrile. Examples of the halogen derivative include halogen derivatives of cyclic carbonates such as 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one, etc. These may be used alone or in combination of two or more.

[0062] The content of the non-aqueous solvent may be, for example, 70% by mass to 99% by mass based on the total mass of the electrolyte solution.

[0063] (Electrolyte) The electrolytic solution may further contain an electrolyte. The electrolyte may contain a lithium salt that serves as an ion source of lithium ions. The lithium salt may be LiAlCl４ , LiBF ４ , LiPF ６ , LiClO ４ , lithium bistrifluoromethanesulfonimide (LiTFSi), lithium bisfluorosulfonimide (LiFSi), LiAsF ６ and LiSbF ６ These may be used alone or in combination of two or more. The electrolyte may be LiBF ４ and / or LiPF ６ The electrolyte may comprise LiBF ４ and / or LiPF ６ When the electrolyte contains the compound, the ionic conductivity of the electrolyte can be increased, and further, due to its oxidation-reduction resistance, deterioration of the performance of the secondary battery caused by long-term use can be suppressed.

[0064] When the electrolyte additive contains a metal complex of compound (1) and an alkali metal salt compound, the alkali metal salt compound may or may not function as an electrolyte in the electrolyte. When the alkali metal salt compound functions as an electrolyte, the electrolyte additive does not need to contain any electrolyte other than the alkali metal salt compound contained in the electrolyte additive.

[0065] The concentration of the electrolyte may be 0.1 mol / L or more, or 0.5 mol / L or more, and may be 2.0 mol / L or less, or 1.5 mol / L or less, based on the total volume of the electrolyte solution. The concentration of the electrolyte may be 0.1 mol / L or more and 2.0 mol / L or less, or 1.5 mol / L or less, based on the total volume of the electrolyte solution, or 0.5 mol / L or more and 2.0 mol / L or less, or 1.5 mol / L or less. The concentration of the electrolyte is the total amount of electrolyte in the electrolyte solution, and includes the content of alkali metal salt compounds that may be contained in electrolyte additives.

[0066] The electrolytic solution can be produced, for example, by a method including a step of dissolving an additive for the electrolytic solution together with other components added as necessary in a non-aqueous solvent.

[0067] <Electricity storage device> The above-described electrolytic solution is used for an electricity storage device. The electricity storage device is composed of the above-described electrolytic solution, a positive electrode, and a negative electrode. The electricity storage device may be a nonaqueous electrolyte secondary battery (lithium ion battery) or an electric double layer capacitor (lithium ion capacitor).

[0068] Fig. 1 is a cross-sectional view schematically illustrating an example of a nonaqueous electrolyte secondary battery (e.g., a lithium ion battery) that is an electricity storage device. The nonaqueous electrolyte secondary battery 1 shown in Fig. 1 includes alternately stacked negative electrodes 4 and positive electrodes 9, a nonaqueous electrolyte 5 disposed between the negative electrodes 4 and the positive electrodes 9, and a separator 6 disposed in the electrolyte 5. Here, the multiple negative electrodes 4 and positive electrodes 9 are stacked such that a major surface of the negative electrode 4 faces a major surface of the positive electrode 9 via the separator 6. In Fig. 1, some of the repeated structures are omitted. The electrolyte 5 is the electrolyte described above.

[0069] (Positive Electrode) The positive electrode 9 has a positive electrode current collector 8 and positive electrode active material layers 7 provided on both sides of the positive electrode current collector 8 .

[0070] The positive electrode active material layer 7 contains a positive electrode active material. The positive electrode active material may be a lithium-containing composite oxide. Examples of the lithium-containing composite oxide include LiMnO ２ , LiFeO ２ , LiCoO ２ , LiMn ２ O ４ , Li ２ FeSiO ４ , LiNi ｘ Co ｙ M ｚ O ２ (wherein 0.01<x<1, 0≦y<1, 0≦z<1, and x+y+z=1, and M is at least one element selected from the group consisting of Mn, V, Mg, Mo, Nb, Fe, Cu, and Al), LiFePO ４ , and LiMn （１－ｘ） Fe ｘ P.O. ４ (where 0<x<1). ｘ Co ｙ M ｚ O ２ is LiNi ｘ１Co ｙ１ M １ ｚ１ O ２ (However, M １ is Mn, and 0.35<x1<1, 0≦y1<1, 0≦z1<1, and x1+y1+z1=1.), or LiNi ｘ２ Co ｙ２ M ２ ｚ２ O ２ (However, M ２ is an element selected from V, Mg, Mo, Nb, Fe, Cu, and Al, and 0.01<x2<1, 0≦y2<1, 0≦z2<1, and x2+y2+z2=1. ｘ Co ｙ M ｚ O ２ As the lithium-containing composite oxide represented by the formula: LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．６ Co ０．２ Mn ０．２ O ２ , and LiNi ０．８ Co ０．１ Mn ０．１ O ２ The positive electrode active material is LiNi ０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．６ Co ０．２ Mn ０．２ O ２ , LiNi ０．８ Co ０．１ Mn ０．１ O ２ , LiNi ｘ１ Co ｙ１ M １ ｚ１ O ２ (However, M １ , x1, y1 and z1 are as defined above.), LiNi ｘ２ Co ｙ２ M ２ ｚ２O ２ (However, M ２ , x2, y2 and z2 are as defined above.), or LiFePO ４ It may be.

[0071] The positive electrode current collector 8 may contain an electronically conductive material. Examples of the electronically conductive material include conductive materials such as carbon, titanium, chromium, molybdenum, ruthenium, rhodium, tantalum, tungsten, osmium, iridium, platinum, gold, and aluminum, and alloys containing two or more conductive materials (e.g., stainless steel). The material of the positive electrode current collector 8 may be carbon, aluminum, or stainless steel from the viewpoints of high electronic conductivity, stability in the electrolyte, and oxidation resistance, or may be aluminum from the viewpoint of cost.

[0072] The positive electrode current collector 8 may be a foil (foil-like). When the positive electrode current collector 8 is a foil, the positive electrode current collector 8 may have a primer layer on its surface in order to further increase capacity. When the positive electrode current collector 8 has a primer layer, the adhesion between the positive electrode active material layer 7 and the positive electrode current collector 8 can be improved.

[0073] The positive electrode current collector 8 may have a three-dimensional shape. Examples of the positive electrode current collector 8 having a three-dimensional shape include foam metal, mesh, woven fabric, nonwoven fabric, and expanded. When the positive electrode current collector 8 has a three-dimensional shape, even if the adhesion between the material (e.g., binder) used to fabricate the electrode and the positive electrode current collector 8 is low, an electrode with a high capacity density can be fabricated, thereby improving the high-rate charge / discharge characteristics.

[0074] (Negative Electrode) The negative electrode 4 has a negative electrode current collector 3 and a negative electrode active material layer 2 provided on both sides of the negative electrode current collector 3 .

[0075] The negative electrode current collector 3 may contain a metal such as aluminum, copper, nickel, or stainless steel. From the viewpoints of ease of processing and cost, the negative electrode current collector 3 may contain copper. The negative electrode current collector 3 may be in the form of a foil (foil-like). The surface of the negative electrode current collector 3 may be roughened.

[0076] The negative electrode active material layer 2 includes a negative electrode active material. The negative electrode active material is a material capable of absorbing and releasing lithium. Examples of the negative electrode active material include carbon materials such as graphite and amorphous carbon, oxide materials such as indium oxide, silicon oxide, tin oxide, lithium titanate, zinc oxide, and lithium oxide, lithium metal, and metal materials capable of forming an alloy with lithium. Examples of metal materials capable of forming an alloy with lithium include copper, tin, silicon, cobalt, manganese, iron, antimony, and silver, and these metals may contain two or more types. The negative electrode active material may be a carbon material such as graphite or amorphous carbon, or silicon oxide.

[0077] From the viewpoint of achieving a high energy density, the negative electrode active material may include a carbon material such as graphite and a Si-based active material selected from Si, a Si alloy, a Si oxide, and the like. From the viewpoint of achieving both cycle characteristics and a high energy density, the negative electrode active material may include graphite and a Si-based active material. In these cases, the mass ratio of the Si-based active material to the total mass of the carbon material and the Si-based active material may be, at the lower limit, 0.5% by mass or more, 1% by mass or more, or 2% by mass or more, and may be, at the upper limit, 95% by mass or less, 50% by mass or less, or 40% by mass or less. The mass ratio of the Si-based active material to the total mass of the carbon material and the Si-based active material may be, at the lower limit, 0.5% by mass or more and 95% by mass or less, 50% by mass or less, or 40% by mass or less; at the lower limit, 1% by mass or more and 95% by mass or less, 50% by mass or less, or 40% by mass or less; or at the lower limit, 2% by mass or more and 95% by mass or less, 50% by mass or less, or 40% by mass or less.

[0078] (Other Components) The positive electrode active material layer 7 and the negative electrode active material layer 2 may further contain a binder. Examples of binders include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer rubber (SBR), carboxymethyl cellulose (CMC), polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide, polyacrylic acid, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, polymethacrylic acid, and copolymers thereof. The positive electrode active material layer 7 and the negative electrode active material layer 2 may contain the same or different binders. When the positive electrode active material layer 7 contains a binder, the binder contained in the positive electrode active material layer 7 may be polyvinylidene fluoride (PVDF). When the negative electrode active material layer 2 contains a binder, the binder contained in the negative electrode active material layer 2 may be SBR, polyacrylic acid, or a copolymer containing these, from the viewpoint of further improving cycle characteristics.

[0079] The positive electrode active material layer 7 and the negative electrode active material layer 2 may further contain a conductive additive. The conductive additive may be a substance containing a conductive material such as carbon. Examples of the carbon-containing substance include carbonaceous particles such as graphite, carbon black, acetylene black, and ketjen black, as well as carbon fiber.

[0080] The separator 6 may be a porous film. The porous film may contain, for example, a resin selected from the group consisting of polyethylene, polypropylene, and fluororesin. The separator 6 may be a single layer or may have multiple layers.

[0081] The specific configuration of each member constituting the electricity storage device of the present invention, such as the shape and thickness, can be appropriately determined by a person skilled in the art. The configuration of the electricity storage device is not limited to the embodiment shown in FIG. 1 and can be appropriately modified.

[0082] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0083] 1. Synthesis of Compounds (Synthesis Example 1) Dichloromethane and 25 g (0.1 mol) of boron tribromide were charged into a four-neck flask equipped with a stirring seal, a thermometer, a condenser connected to an alkali trap, and a dropping funnel. The mixed solution was heated to 30°C, and 29 g (0.3 mol) of methanesulfonic acid was added dropwise while stirring. After the dropwise addition was completed, the reaction solution was heated to 40°C and stirred for 15 hours to remove the generated HBr from the system. The reaction solution was then cooled to room temperature (25°C) to precipitate crystals, and the resulting slurry was then heated to 40°C and stirred for 15 hours. ２ The crystals obtained by filtration under atmospheric pressure were dried under reduced pressure to obtain a compound represented by the following formula (1-1) (compound (1-1)). The yield was 55% based on boron tribromide. １ H-NMR (400MHz): δ = 2.4ppm (s), １３ C-NMR (100 MHz): 34.3 ppm Measurement solvent: DMSO-d6)

[0084] Synthesis Example 2 Boron tribromide and methanesulfonic acid were reacted according to the following procedure, without removing the generated HBr from the system. Dichloromethane and 25 g (0.1 mol) of boron tribromide were charged into a four-neck flask equipped with a stirring seal, a thermometer, a condenser connected to an alkali trap, and a dropping funnel. The mixed solution was cooled in an ice bath, and 29 g (0.3 mol) of methanesulfonic acid was added dropwise while stirring. After the dropwise addition was completed, the reaction solution was stirred at room temperature for 48 hours. The reaction solution changed from a paste to a slurry during stirring. This slurry was then heated in a N ２ The crystals obtained by filtration under atmospheric pressure were dried under reduced pressure to obtain a crude product. １ When analyzed by H-NMR, in addition to a signal similar to that in Synthesis Example 1 that is expected to be that of compound (1-1), multiple signals that appear to be impurities were confirmed around 2.9 to 3.1 ppm (measurement solvent: DMSO-d6).

[0085] (Synthesis Example 3) A reaction to obtain compound (1-1) was carried out under the following conditions without using boron tribromide. Toluene, 3 g (0.05 mol) of boric acid, and 15 g (0.15 mol) of methanesulfonic acid were charged into a four-necked flask equipped with a ball stopper, a stirring seal, a thermometer, and a Dean-Stark apparatus. The reaction solution was heated to 110°C, and the reaction was carried out for 5 hours while removing water generated in the Dean-Stark apparatus and refluxing the solvent. After completion of the reaction, the upper layer, toluene, was removed from the reaction solution which separated into two layers, and the lower layer was collected. Regarding this lower layer, １ When H-NMR was measured, only the signal of the raw material methanesulfonic acid was detected, and the target product was not obtained.

[0086] From the above results, it was confirmed that by using boron tribromide and performing an operation of removing the generated HBr from the system, compound (1-1) can be obtained in a shorter time while suppressing the generation of impurities.

[0087] Synthesis Example 4: 50 g of dichloromethane and 25 g (0.1 mol) of boron tribromide were charged into a four-neck flask equipped with a stirring seal, a thermometer, a condenser connected to an alkali trap, and a dropping funnel. The mixed solution was heated to 30°C, and 33 g (0.3 mol) of ethanesulfonic acid was added dropwise over 4 hours while stirring. After the dropwise addition was completed, the reaction solution was heated to 40°C and stirred for 15 hours to remove the generated HBr from the system. Thereafter, the reaction solution was cooled to room temperature (25°C), and the slurry that precipitated crystals was dissolved in N ２ The crystals obtained by filtration under atmospheric pressure were dried under reduced pressure to obtain a compound represented by formula (1-2) (compound (1-2)). The yield was 15% based on boron tribromide. １ H-NMR (400MHz): δ = 1.31 ppm (t), δ = 3.10 ppm (q), measurement solvent: DMSO-d6)

[0088] Synthesis Example 5: 50 g of dichloromethane and 25 g (0.1 mol) of boron tribromide were charged into a four-neck flask equipped with a stirring seal, a thermometer, a condenser connected to an alkali trap, and a dropping funnel. The mixed solution was heated to 30°C, and 47 g (0.3 mol) of benzenesulfonic acid was added dropwise over 4 hours while stirring. After the dropwise addition was completed, the reaction solution was heated to 40°C and stirred for 15 hours to remove the generated HBr from the system. Thereafter, the reaction solution was cooled to room temperature (25°C), and the slurry that precipitated crystals was dissolved in N ２ The crystals obtained by filtration under atmospheric pressure were dried under reduced pressure to obtain a compound represented by formula (1-6) (compound (1-6)). The yield was 13% based on boron tribromide. １ H-NMR (400MHz): δ = 7.31-7.37ppm (m), δ = 7.60-7.64 (m), measurement solvent: DMSO-d6)

[0089] Synthesis Example 6: 50 g of dichloromethane and 25 g (0.1 mol) of boron tribromide were charged into a four-neck flask equipped with a stirring seal, a thermometer, a condenser connected to an alkali trap, and a dropping funnel. The mixed solution was heated to 30°C, and 37 g (0.3 mol) of allylsulfonic acid was added dropwise over 4 hours while stirring. After the dropwise addition was completed, the reaction solution was heated to 40°C and stirred for 15 hours to remove the generated HBr from the system. The reaction solution was then cooled to room temperature (25°C), and the resulting slurry was dissolved in N ２ The crystals obtained by filtration under atmospheric pressure were dried under reduced pressure to obtain a compound represented by formula (1-4) (compound (1-4)). The yield was 15% based on boron tribromide. １ H-NMR (400MHz): δ = 3.25 ppm (t), δ = 5.09 ppm (t), δ = 5.75-5.87 (m), measurement solvent: DMSO-d6)

[0090] Synthesis Example 7: 50 g of dichloromethane and 25 g (0.1 mol) of boron tribromide were charged into a four-neck flask equipped with a stirring seal, a thermometer, a condenser connected to an alkali trap, and a dropping funnel. The mixed solution was heated to 30°C, and 32 g (0.3 mol) of vinyl sulfonic acid was added dropwise over 4 hours while stirring. After the dropwise addition was completed, the reaction solution was heated to 40°C and stirred for 15 hours to remove the generated HBr from the system. The reaction solution was then cooled to room temperature (25°C), and the resulting slurry was dissolved in N ２ The crystals obtained by filtration under atmospheric pressure were dried under reduced pressure to obtain a compound represented by formula (1-3) (compound (1-3)). The yield was 6% based on boron tribromide. １ H-NMR (400MHz): δ = 5.33 ppm (q), δ = 5.64 ppm (q), δ = 6.45 ppm (q), measurement solvent: DMSO-d6)

[0091] 2. Preparation of Electrolyte Solution (Example 1) Synthesis of Metal Complex At room temperature, 13.2 ml of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were placed in a 100 ml Teflon (registered trademark) flask with a lid at a volume ratio of EC:EMC = 30:70, and LiPF ６ Then, 0.17 g (0.56 mmol) of the compound (1-1) obtained in Synthesis Example 1 was added, and the mixture was stirred at 25° C. for 20 minutes until the cloudy solution became a transparent, homogeneous solution, thereby obtaining the compound (1-1) and LiPF ６ A metal complex of compound (1-1) and LiPF was obtained. ６ The formation of metal complexes with １９ This was confirmed by F-NMR. １９ F-NMR was measured under the conditions of using benzotrifluoride as a standard substance and DMSO-d6 as a solvent. １９ The results of F-NMR measurements are shown, where a represents the compound (1-1) and LiPF ６ a shows the measurement results of the metal complex with LiPF before metal complex formation. ６ These are the measurement results.

[0092] The EC / EMC solution containing the metal complex was used as the electrolyte solution. The content of the metal complex was 1.5% by mass based on the total mass of the electrolyte solution.

[0093] Example 2 Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of EC:EMC=30:70 to obtain a mixed non-aqueous solvent. LiPF 6 was added as an electrolyte to the obtained mixed non-aqueous solvent. ６ was dissolved to obtain LiPF at a concentration of 1 mol / L. ６ The resulting LiPF solution was prepared. ６ The compound (1-2) was added to the solution and dissolved therein to obtain an electrolyte solution. The content of the compound (1-2) was 1 mass % based on the total mass of the electrolyte solution.

[0094] Example 3 Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of EC:EMC=30:70 to obtain a mixed non-aqueous solvent. LiPF 6 was added as an electrolyte to the obtained mixed non-aqueous solvent. ６ was dissolved to obtain LiPF at a concentration of 1 mol / L. ６ The resulting LiPF solution was prepared. ６ The compound (1-6) was added to the solution and dissolved therein to obtain an electrolyte solution. The content of the compound (1-6) was 1 mass % based on the total mass of the electrolyte solution.

[0095] Example 4 Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of EC:EMC=30:70 to obtain a mixed non-aqueous solvent. LiPF 6 was added as an electrolyte to the obtained mixed non-aqueous solvent. ６ was dissolved to obtain LiPF at a concentration of 1 mol / L. ６ The resulting LiPF solution was prepared. ６ The compound (1-4) was added to the solution and dissolved therein to obtain an electrolyte solution. The content of the compound (1-4) was 1% by mass based on the total mass of the electrolyte solution.

[0096] Example 5 Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of EC:EMC=30:70 to obtain a mixed non-aqueous solvent. LiPF 6 was added as an electrolyte to the obtained mixed non-aqueous solvent. ６ was dissolved to obtain LiPF at a concentration of 1 mol / L. ６The resulting LiPF solution was prepared. ６ The compound (1-3) was added to the solution and dissolved therein to obtain an electrolyte solution. The content of the compound (1-3) was 1 mass % based on the total mass of the electrolyte solution.

[0097] Comparative Example 1 Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of EC:EMC=30:70 to obtain a mixed non-aqueous solvent. LiPF 6 was added as an electrolyte to the obtained mixed non-aqueous solvent. ６ was dissolved to obtain LiPF at a concentration of 1 mol / L. ６ A solution was prepared.

[0098] (Comparative Example 2) LiPF obtained in Comparative Example 1 ６ 1,3-propane sultone (PS) was added to the solution to a concentration of 1 mass % and dissolved to obtain an electrolyte solution.

[0099] (Comparative Example 3) LiPF obtained in Comparative Example 1 ６ Vinylene carbonate (VC) was added to the solution so as to be 1% by mass and dissolved therein to obtain an electrolyte solution.

[0100] 3. Fabrication of a Non-Aqueous Electrolyte Secondary Battery A positive electrode sheet (manufactured by Yayama Co., Ltd.) containing a lithium-containing composite oxide and a negative electrode sheet (manufactured by Yayama Co., Ltd.) containing graphite were prepared. The positive electrode sheet had an aluminum foil (thickness: 20 μm) as a positive electrode current collector and positive electrode active material layers formed on both sides of the aluminum foil. The positive electrode active material layer contained a lithium-containing composite oxide (LiNi) as a positive electrode active material. ０．５ Co ０．２ Mn ０．３ O ２The negative electrode sheet contained carbon black (CB) and carbon (KS) as conductivity imparting agents, and polyvinylidene fluoride (PVDF) as a binder. The mass ratio of these was lithium-containing composite oxide:CB:KS:PVDF = 92:2.5:2.5:3. The negative electrode sheet had copper foil (thickness 10 μm) as a negative electrode current collector and negative electrode active material layers formed on both sides thereof. The negative electrode active material layer contained graphite (Gr) as a negative electrode active material, and sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) as binders. The mass ratio of these was Gr:CMC:SBR = 98:1:1. The negative electrode sheets and positive electrode sheets were alternately stacked with propylene separators interposed between them to produce a battery element having a total of 13 layers as electrodes: 7 layers of negative electrode sheets and 6 layers of positive electrode sheets.

[0101] The fabricated battery element was inserted into a bag formed from a laminate film having aluminum (40 μm thick) and resin layers covering both sides thereof, so that the ends of the positive electrode sheet and the negative electrode sheet protruded from the bag. Next, each electrolyte solution obtained in each Example or Comparative Example was added to the bag, and the bag was vacuum-sealed to obtain a sheet-like nonaqueous electrolyte secondary battery. To improve adhesion between the electrodes, the sheet-like nonaqueous electrolyte secondary battery was sandwiched between glass plates and pressure was applied.

[0102] 4. Battery Performance Evaluation (Aging Process) Each nonaqueous electrolyte secondary battery was charged at 25°C for 1 hour at a current corresponding to 0.1 C and then held at 25°C for 10 hours. Subsequently, each nonaqueous electrolyte secondary battery was charged at 25°C for 5 hours at a current corresponding to 0.1 C and held at 45°C for 24 hours. Thereafter, each nonaqueous electrolyte secondary battery was discharged to 3 V at a current corresponding to 0.1 C at 25°C, and then degassed. Each nonaqueous electrolyte secondary battery was then aged by repeating three cycles of charging at 25°C to 4.2 V at a current corresponding to 0.2 C and discharging to 3 V at a current corresponding to 0.2 C, three cycles of charging at 25°C to 4.2 V at a current corresponding to 0.5 C and discharging to 3.0 V at a current corresponding to 0.5 C, and three cycles of charging at 1 C to 4.2 V and discharging to 3.0 V at a current corresponding to 1 C, thereby stabilizing each nonaqueous electrolyte secondary battery. The battery was charged to 4.2 V at a current corresponding to 1 C and discharged to 3.0 V at a current corresponding to 1 C. The discharge capacity measured at the third cycle was taken as the "discharge capacity after aging."

[0103] (Initial DCR Measurement) Each nonaqueous electrolyte secondary battery after aging was charged at 25° C. with a current equivalent to 1 C to 50% of the discharge capacity after aging, and then discharged at a current equivalent to 0.2 C at −10° C., and the change in battery voltage during this period was measured. Thereafter, with a 10-minute pause, charging and discharging were repeated while changing the discharge current (discharge rate) to 0.5 C, 1.0 C, and 2.0 C, and the change in voltage when this was measured was measured, and the DCR (Ω) was calculated from this value as “initial DCR (Ω).”

[0104] The DCR is a value equivalent to the resistance value of the battery, and it can be said that the lower the DCR value, the higher the output characteristics of the battery.

[0105] (DCR Measurement After High-Temperature Storage Test (DCR After Storage)) After the initial DCR measurement, each lithium ion battery was charged to 4.2 V at 1 C at 25° C. and then held at 60° C. for 30 days. Thereafter, each nonaqueous electrolyte secondary battery was cooled to 25° C. and discharged to 3 V at a current equivalent to 1 C. Next, the cycle of charging to 4.2 V at 25° C. at a current equivalent to 1 C and discharging to 3.0 V at a current equivalent to 1 C was repeated for two cycles, and the discharge capacity at the second cycle was designated as the "discharge capacity after storage."

[0106] After the high-temperature storage test, each nonaqueous electrolyte secondary battery was charged at 25°C with a current equivalent to 1 C to 50% of the post-storage discharge capacity, and then discharged at a current equivalent to 0.2 C at -10°C, and the change in battery voltage was observed. After that, with a 10-minute pause, the battery was repeatedly charged and discharged while changing the discharge current (discharge rate) to 0.5 C, 1.0 C, and 2.0 C, and the change in voltage was read, and the DCR (Ω) was calculated as "post-storage DCR (Ω)" from that value. The results are shown in Table 1.

[0107] The "DCR value difference" in Table 1 was calculated using the following formula: (DCR difference) = (DCR after storage (Ω)) - (initial DCR (Ω))

[0108]

[0109] According to one aspect of the present invention, there is provided a nonaqueous electrolyte secondary battery that has excellent storage stability at high temperatures, such as suppressing an increase in DCR even when the battery is stored at high temperatures for 30 days. Such a nonaqueous electrolyte secondary battery can contribute to solving environmental problems from the viewpoint of reducing waste by extending the battery life, and has extremely high industrial applicability.

[0110] DESCRIPTION OF SYMBOLS 1... Non-aqueous electrolyte secondary battery, 2... Negative electrode active material layer, 3... Negative electrode current collector, 4... Negative electrode, 5... Non-aqueous electrolyte, 6... Separator, 7... Positive electrode active material layer, 8... Positive electrode current collector, 9... Positive electrode.

Claims

1. An additive for an electrolyte solution, comprising a compound represented by the following formula (1): [In formula (1), M represents an element of Group 13 of the periodic table, and R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.] 2. An additive for an electrolyte solution, comprising a metal complex of a compound represented by the following formula (1) and an alkali metal salt compound: [In formula (1), M represents an element of Group 13 of the periodic table, and R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.] 3. The electrolyte additive according to claim 2, wherein the alkali metal salt compound is a lithium salt compound.

4. The electrolyte additive according to any one of claims 1 to 3, wherein M is a boron atom or an aluminum atom.

5. The electrolyte additive according to any one of claims 1 to 3, wherein M is a boron atom.

6. R １ ~R ３ are each independently an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, or an optionally substituted aryl group. The additive for an electrolyte solution according to any one of claims 1 to 3.

7. R １ ~R ３ are each independently an unsubstituted methyl group, an unsubstituted ethyl group, an unsubstituted vinyl group, an unsubstituted allyl group, or an unsubstituted phenyl group, and M is a boron atom. The additive for an electrolyte solution according to any one of claims 1 to 3.

8. The following formula (1): [In formula (1), M represents an element of Group 13 of the periodic table, and R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.] ３ [in formula (2), M represents an element of group 13 of the periodic table, and X represents a halogen atom], and a compound represented by formula (3): R ４ SO ３ H [In formula (3), R ４ represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.] with 9. An electrolyte solution comprising the electrolyte additive according to any one of claims 1 to 3 and a non-aqueous solvent.

10. An electricity storage device comprising the electrolyte solution according to claim 9, a positive electrode, and a negative electrode.

11. A compound represented by the following formula (1): [In formula (1), M represents an element of Group 13 of the periodic table, and R １ ~R ３ each independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, an optionally substituted alkynyl group having 2 to 6 carbon atoms, an optionally substituted aryl group, or an optionally substituted alkoxy group having 1 to 6 carbon atoms.] 12. The compound of claim 11, wherein M is a boron atom.

13. R １ ~R ３ are each independently an optionally substituted alkyl group having 1 to 6 carbon atoms, an optionally substituted alkenyl group having 2 to 6 carbon atoms, or an optionally substituted aryl group.

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