Electrolyte for secondary battery and power storage device

Abstract

The present disclosure relates to an electrolytic solution for a secondary battery, the electrolytic solution containing: a first compound represented by formula (1); and at least one second compound selected from the group consisting of compounds represented by formula (2-1), compounds represented by formula (2-2), and compounds represented by formula (2-3).

Description

Electrolyte for secondary battery and power storage device

[0001] The present disclosure relates to an electrolyte for a secondary battery and an electricity storage device.

[0002] The use of electrolytes containing various additives has been investigated for energy storage devices such as lithium-ion batteries. When an electrolyte contains additives, the additives may decompose during the initial charge / discharge cycle, forming a film called a solid electrolyte interface (SEI) on the electrode surface. The formation of such an SEI prevents degradation of energy storage devices, such as nonaqueous electrolyte secondary batteries, during repeated charge / discharge cycles, and contributes to improving battery performance.

[0003] Among these, lithium-ion batteries are required to have high output power, particularly for use in automobiles.

[0004] For example, Patent Document 1 discloses that adding 1,3-propane sultone (PS) to an electrolyte improves the charge / discharge cycle characteristics of a lithium secondary battery. Patent Document 2 discloses that adding a vinylene carbonate (VC) derivative as an additive improves the discharge characteristics of a lithium secondary battery. Patent Document 3 also discloses an additive for an electrolyte containing a specific cyclic sulfone compound, which can improve cycle characteristics and suppress gas generation.

[0005] JP-A No. 63-102173 JP-A No. 5-74486 International Publication No. 2017 / 043576

[0006] However, conventional electrolytes using additives have the problem that the initial resistance increases during the SEI formation process during initial charge and discharge, resulting in a decrease in battery output.

[0007] One aspect of the present disclosure relates to an electrolyte solution that can suppress an increase in the initial resistance of an electricity storage device. Another aspect of the present disclosure relates to an electricity storage device using the electrolyte solution.

[0008] The present disclosure encompasses the following aspects: [1] An electrolyte solution for a secondary battery, comprising a first compound represented by the following formula (1) and at least one second compound selected from the group consisting of a compound represented by the following formula (2-1), a compound represented by the following formula (2-2), and a compound represented by the following formula (2-3): [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.] [In formula (2-1), Z １ represents a group in which one or more hydrogen atoms of an alkylene group having 1 to 3 carbon atoms have been substituted with a halogen atom, an alkyl group, a halogenated alkyl group, or an alkenyl group, or an optionally substituted alkenylene group having 2 to 4 carbon atoms.] [In formula (2-2), Y represents an alkylene group having 1 to 3 carbon atoms which may be substituted, or an alkenylene group having 2 to 4 carbon atoms which may be substituted, J represents an oxygen atom or a single bond, and m represents 1 or 2.] [In formula (2-3), Q is a group that forms a ring structure together with the sulfur atom of the sulfonyl group and represents an optionally substituted alkylene group having 4 to 6 carbon atoms or an optionally substituted alkenylene group having 4 to 6 carbon atoms, and X represents a group represented by the following formula (2a) or (2b)] [In formula (2a) or formula (2b), R ａeach independently represent an alkyl group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, an alkenyl group having 2 to 4 carbon atoms which may be substituted with a fluorine atom, an alkynyl group having 2 to 4 carbon atoms which may be substituted with a fluorine atom, an aryl group having 6 to 10 carbon atoms which may be substituted with a fluorine atom, a hydroxy group, or a lithium oxy group.] [2] The electrolyte solution for a secondary battery according to [1], wherein the second compound comprises a compound represented by formula (2-1). [3] The electrolyte solution for a secondary battery according to [1] or [2], wherein the second compound comprises a compound represented by formula (2-2). [4] The electrolyte solution for a secondary battery according to any one of [1] to [3], wherein the second compound comprises a compound represented by formula (2-3). [5] The electrolyte solution for a secondary battery according to any one of [1] to [4], wherein M is a boron atom or an aluminum atom. [6] The electrolyte solution for a secondary battery according to any one of [1] to [5], wherein M is a boron atom. [7] R １ ~R ３ are each independently an optionally substituted alkyl group having 1 to 6 carbon atoms. [8] The electrolyte solution for a secondary battery according to any one of [1] to [7], further containing a cyclic carbonate and / or a chain carbonate different from the second compound. [9] An electricity storage device comprising the electrolyte solution for a secondary battery according to any one of [1] to [8], a positive electrode, and a negative electrode.

[0009] According to one aspect of the present disclosure, it is possible to provide an electrolyte solution that can suppress an increase in the initial resistance of an electricity storage device. According to another aspect of the present disclosure, it is possible to provide an electricity storage device using the electrolyte solution.

[0010] FIG. 1 is a cross-sectional view illustrating an embodiment of an electricity storage device.

[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] [Electrolyte for Secondary Battery] An example of an electrolyte for a secondary battery contains a first compound and a second compound.

[0013] <First Compound> The first compound is a compound represented by the following formula (1) (hereinafter "compound (1)"). When the electrolytic solution contains the first compound, an increase in the initial resistance of the electricity storage device is suppressed. When the electrolytic solution contains the first compound, an increase in the resistance after cycling relative to the initial resistance can also be suppressed.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] R １ , R ２ and R ３In 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.

[0019] 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.

[0020] In formula (1), R １ , R ２ and R ３ The 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.

[0021] 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.

[0022] 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 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.

[0023] 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.

[0024] 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 aryl groups as include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a hexafluorophenyl group.

[0025] In formula (1), R １ , R ２ and R ３The 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.

[0026] 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).

[0027] In the electrolyte solution, one type of compound may be used as the compound (1), or two or more types of compounds may be used in combination.

[0028] The total content of the first compounds 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 amount of the electrolyte solution. The total content of the first compounds 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, 1.0% by mass or less, 0.80% by mass or less, or 0.60% by mass or less, based on the total amount of the electrolyte solution. The total content of the first compounds may be, for example, 0.05 to 5% by mass, based on the total amount of the electrolyte solution. When the content of the first compounds is within the above-mentioned range, an increase in the initial resistance of the electricity storage device is further easily suppressed.

[0029] Compound (1) can be, for example, MX ３ (wherein M is as defined above, and X represents a halogen atom), and ４ SO ３ H (wherein, R ４ is the above R １ ~R ３ The compound represented by the formula (I) can be obtained by a method comprising reacting a compound represented by the formula (I) with

[0030] <Second Compound> The second compound is at least one compound selected from the group consisting of a compound represented by formula (2-1) (hereinafter referred to as "compound (2-1)"), a compound represented by formula (2-2) (hereinafter referred to as "compound (2-2)"), and a compound represented by formula (2-3) (hereinafter referred to as "compound (2-3)").

[0031] [Compound (2-1)] The compound (2-1) is a cyclic carbonate represented by the following formula (2-1).

[0032] In formula (2-1), Z １ represents a group in which one or more hydrogen atoms of an alkylene group having 1 to 3 carbon atoms have been substituted with a halogen atom, an alkyl group, a halogenated alkyl group, or an alkenyl group (hereinafter also referred to as a "substituted alkylene group"), or an alkenylene group having 2 to 4 carbon atoms which may be substituted. Z １ is a group that forms a ring structure together with the carbonate group (—O—C(═O)—O—). １ From the viewpoint of facilitating the formation of a stronger SEI, may be a substituted alkylene group having 2 to 3 carbon atoms or an optionally substituted alkenylene group having 2 to 3 carbon atoms.

[0033] Z １ The number of carbon atoms in the substituted alkylene group represented by Z is 1 to 3, may be 2 to 3, or may be 2. １ The number of carbon atoms in the substituted alkylene group as Z １ is the number of carbon atoms constituting the ring of the group represented by １ The number of carbon atoms in the substituents is not included.

[0034] Z １In the substituted alkylene group as defined above, one or more of the hydrogen atoms bonded to the carbon atoms constituting the ring are substituted with a halogen atom, an alkyl group, a halogenated alkyl group, or an alkenyl group. The halogen atom may be the halogen atom described above. The halogen atom may be a fluorine atom. The alkyl group may be the alkyl group described above. The number of carbon atoms in the alkyl group may be 1 to 6. The alkyl group may be a methyl group. The halogenated alkyl group is a group in which one or more hydrogen atoms in the alkyl group described above are substituted with a halogen atom. The halogenated alkyl group may be a trifluoromethyl group. The alkenyl group may be the alkenyl group described above. The number of carbon atoms in the alkenyl group may be 2 to 6. The alkenyl group is a vinyl group (CH ２ ═CH—).

[0035] Z １ Examples of the substituted alkylene group include -CHF-CH ２ -, -CHF-CHF-, -CHF-CF ２ -, -CF ２ -CF ２ -, -CH(CH ３ )-CH ２ -, -CH(CF ３ )-CH ２ -, -CH(CF ３ )-CH(CF ３ ) - and -CH(CH=CH ２ )-CH ２ - are listed.

[0036] Z １ The number of carbon atoms in the alkenylene group represented by Z is 2 to 4, and may be 2 to 3, or may be 2. １ The number of carbon atoms in the alkenylene group as Z １ is the number of carbon atoms constituting the ring of the group represented by １ When contains a substituent, the number of carbon atoms of the substituent is not included.

[0037] Z １ Examples of the alkenylene group having 2 to 4 carbon atoms include -CH=CH-, -CH=CH-CH ２ -, -CH=CH-CH ２ -CH ２- and -CH ２ -CH=CH-CH ２ - is mentioned. １ The alkenylene group having 2 to 4 carbon atoms as the alkyl group may have a halogen atom, an alkyl group, a halogenated alkyl group, or an alkenyl group as a substituent, or may not have a substituent.

[0038] The compound (2-1) may be a compound represented by the following formula (2-1A) or (2-1B).

[0039] In formula (2-1A) or (2-1B), X １ ~X ６ each independently represents a hydrogen atom, a halogen atom, an alkyl group, a halogenated alkyl group, or an alkenyl group. The halogen atom, the alkyl group, the halogenated alkyl group, and the alkenyl group are the same as those in the above Z １ In the compound represented by formula (2-1A), X １ ~X ４ In the compound represented by formula (2-1B), one or more of X is a halogen atom, an alkyl group, a halogenated alkyl group, or an alkenyl group. ５ ~X ６ may each be a hydrogen atom.

[0040] Specific examples of the compound (2-1) include compounds represented by the following formulas (2-1a), (2-1b), (2-1c), (2-1d), (2-1e), (2-1f), (2-1g), (2-1h), and (2-1i). From the viewpoint of being able to better protect the negative electrode, the compound (2-1) may be a compound represented by formula (2-1a) or a compound represented by formula (2-1i).

[0041] [Compound (2-2)] The compound (2-2) is a cyclic sulfone represented by the following formula (2-2).

[0042] In formula (2-2), Y represents an alkylene group having 1 to 3 carbon atoms which may be substituted, or an alkenylene group having 2 to 4 carbon atoms which may be substituted.

[0043] The number of carbon atoms in the alkylene group represented by Y is 1 to 3, may be 2 to 3, or may be 2. The number of carbon atoms in the alkylene group represented by Y is the number of carbon atoms constituting the ring in the group represented by Y, and when Y contains a substituent, the number of carbon atoms in the substituent is not included. Examples of the alkylene group represented by Y include -CH ２ -, -CH ２ -CH ２ - and -CH ２ -CH ２ -CH ２ In the alkylene group represented by Y, one or more of the hydrogen atoms bonded to the carbon atoms constituting the ring may be substituted with a substituent, or may not be substituted. Examples of the substituent include Z １ Examples of the substituent in the formula (I) include the groups exemplified above.

[0044] In formula (2-2), J represents an oxygen atom or a single bond. m represents 1 or 2. From the viewpoint of facilitating the formation of an SEI, Y may be an optionally substituted alkylene group having 2 to 3 carbon atoms or an optionally substituted alkenylene group having 2 to 3 carbon atoms, J may be an oxygen atom, and m may be 2.

[0045] The compound (2-2) may be a compound represented by the following formula (2-2A), (2-2B) or (2-2C): In formula (2-2A), (2-2B) or (2-2C), m is defined as above.

[0046] Specific examples of the compound (2-2) include compounds represented by the following formulas (2-2a), (2-2b), (2-2c), and (2-2d): From the viewpoint of being able to better protect the negative electrode, the compound (2-2) may be a compound represented by formula (2-2a) or a compound represented by formula (2-2c).

[0047]

[0048] [Compound (2-3)] The compound (2-3) is a cyclic sulfone represented by the following formula (2-3).

[0049] In formula (2-3), Q is a group that forms a ring structure together with the sulfur atom of the sulfonyl group, and represents an optionally substituted alkylene group having 4 to 6 carbon atoms or an optionally substituted alkenylene group having 4 to 6 carbon atoms.

[0050] The number of carbon atoms in the alkylene group having 4 to 6 carbon atoms and the alkenylene group having 4 to 6 carbon atoms represented by Q may be 4, from the viewpoint of facilitating the formation of a stronger SEI.

[0051] Examples of the alkylene group having 4 to 6 carbon atoms represented by Q include a tetramethylene group, a pentamethylene group, and a hexamethylene group.

[0052] The alkenylene group having 4 to 6 carbon atoms represented by Q is —CH═CHCH ２ CH ２ -, -CH ２ CH=CHCH ２ -, -CH=CHCH ２ CH ２ CH ２ -, -CH ２ CH=CHCH ２ CH ２ -, -CH=CHCH ２ CH ２ CH ２ CH ２ -, -CH ２ CH=CHCH ２ CH ２ CH ２ - and -CH ２ CH ２ CH=CHCH ２ CH ２ - are listed.

[0053] A group represented by -X is bonded to a carbon atom at any position in the alkylene group and alkenylene group represented by Q. The alkylene group and alkenylene group represented by Q may further have a substituent other than the group represented by -X.

[0054] X represents a group represented by the following formula (2a) or (2b).

[0055] In formula (2a) or formula (2b), R ａeach independently represents an alkyl group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, an alkenyl group having 2 to 4 carbon atoms which may be substituted with a fluorine atom, an alkynyl group having 2 to 4 carbon atoms which may be substituted with a fluorine atom, an aryl group having 6 to 10 carbon atoms which may be substituted with a fluorine atom, a hydroxy group (—OH), or a lithium oxy group (—OLi).

[0056] In formula (2a) or formula (2b), R ａ The number of carbon atoms in the alkyl group may be 1 to 4, 1 to 3, or 1 to 2. The alkyl group may be linear or branched. The alkyl group may be a methyl group optionally substituted with a fluorine atom, or an unsubstituted methyl group. 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, a trifluoromethyl group, and a 1,1,1-trifluoroethyl group.

[0057] In formula (2a) or (2b), R ａ The alkenyl group as represented by the formula (I) has 2 to 4 carbon atoms. The alkenyl group may be linear or branched. Examples of the alkenyl group include a vinyl group, an allyl group, a methallyl group (2-methylallyl group), a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, an isobutenyl group, and a 1,1-difluoro-1-propenyl group. The alkenyl group may be a vinyl group optionally substituted with a fluorine atom, an allyl group optionally substituted with a fluorine atom, or a methallyl group optionally substituted with a fluorine atom.

[0058] In formula (2a) or formula (2b), R ａ The number of carbon atoms in the alkynyl group as defined above is 2 to 4, and may be 3 to 4. The alkynyl group may be linear or branched. Examples of the alkynyl group include a 1-propynyl group, a 2-propynyl group, a 1-butynyl group, a 2-butynyl group, and a 3-butynyl group. The alkynyl group may be a 2-propynyl group optionally substituted with a fluorine atom.

[0059] In formula (2a) or (2b), R ａThe aryl group as the aryl group has 6 to 10 carbon atoms. Examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tosyl group, a xylyl group, a naphthyl group, a fluorophenyl group, a pentafluorophenyl group, and a hexafluorophenyl group. The aryl group may be a phenyl group optionally substituted with a fluorine atom, and may be a phenyl group, a 4-fluorophenyl group, or a pentafluorophenyl group.

[0060] The compound (2-3) may be a compound represented by the following formula (2-3A): In formula (2-3A), X is defined as above.

[0061] Specific examples of the compound (2-3) include compounds represented by the following formulas (2-3a), (2-3b), (2-3c), (2-3d), (2-3e), (2-3f), (2-3g), (2-3h), and (2-3i). From the viewpoint of being able to better protect the negative electrode, the compound (2-3) may be a compound represented by formula (2-3a) or formula (2-3e).

[0062] The second compound may be at least one selected from the group consisting of compounds (2-1) and (2-2), or may be compound (2-1), because including the second compound simultaneously with the first compound improves the effect of suppressing an increase in the initial resistance of the electricity storage device and the effect of suppressing an increase in the resistance after cycling. Furthermore, the second compound may be compound (2-3), because including the second compound simultaneously with the first compound improves the effect of improving the cycle capacity retention rate of the electricity storage device.

[0063] The second compound may be a commercially available product. For example, compound (2-1) may be produced according to the method described in JP-A-2010-138157 or JP-A-11-180974, compound (2-2) may be produced according to the method described in JP-A-2001-52738, and compound (2-3) may be produced according to the method described in WO 2019 / 088127.

[0064] The content of the second compound 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 amount of the electrolyte solution. The content of the second compound may be 10.0% by mass or less, 9.0% by mass or less, 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, 1.0% by mass or less, 0.80% by mass or less, or 0.60% by mass or less, based on the total amount of the electrolyte solution. The content of the second compound may be, for example, 0.05 to 5% by mass, based on the total amount of the electrolyte solution. When the content of the second compound is within the above-mentioned range, an increase in the initial resistance of the electricity storage device is further easily suppressed.

[0065] When the second compound is two or more compounds selected from the group consisting of the compound (2-1), the compound (2-2), and the compound (2-3), the content of the second compound is the content of each of the second compounds.

[0066] The ratio of the content of the first compound to the content of the second compound (content of the first compound:content of the second compound) may be 1:0.1 to 1:20, or 1:0.25 to 1:5, in mass ratio. When the second compound is two or more compounds selected from compound (2-1), compound (2-2), and compound (2-3), the content ratio is the ratio of the respective contents of the two or more second compounds (the content of compound (2-1), compound (2-2), or compound (2-3)). This makes the effect of the combination of the first compound and the second compound more pronounced.

[0067] The total content of the first compound and the second compound may be 0.1% by mass to 15% by mass based on the total amount of the electrolyte. If the total content of the first compound and the second compound is 15% by mass or less, there is little risk of a thick SEI being formed on the electrode and increasing resistance. If the total content of the first compound and the second compound is 0.1% by mass or more, the effect of improving resistance characteristics is further enhanced.

[0068] From the same viewpoint, when the electrolytic solution contains, as the second compound, two compounds selected from the group consisting of the compound represented by formula (2-1), the compound represented by formula (2-2), and the compound represented by formula (2-3), the total content of the first compound and the second compound may be 0.1% by mass to 15% by mass based on the total amount of the electrolytic solution.

[0069] Further, from the same viewpoint, when the electrolytic solution contains three types of compounds represented by the formula (2-1), the formula (2-2), and the formula (2-3) as the second compound, the total content of the first compound and the second compound may be 0.5% by mass to 15% by mass based on the total amount of the electrolytic solution.

[0070] <Non-aqueous solvent> The electrolyte solution may further contain a compound different from the first compound and the second compound as a non-aqueous solvent. Part or all of the second compound may also serve as the non-aqueous solvent.

[0071] 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.

[0072] The electrolyte may contain, as a non-aqueous solvent, a cyclic carbonate of a different kind from the cyclic carbonate added as an additive, such as ethylene carbonate, propylene carbonate, butylene carbonate, and fluoroethylene carbonate.

[0073] 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.

[0074] 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.

[0075] <Electrolyte> The electrolytic solution contains an electrolyte. The electrolyte may contain a lithium salt that serves as an ion source of lithium ions. The lithium salt is LiAlCl ４ , 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 ６When 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.

[0076] 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.

[0077] <Other Components> The electrolytic solution may contain other components different from the first compound, the second compound, the non-aqueous solvent, and the electrolyte. Examples of the other components include a negative electrode protector, a positive electrode protector, a flame retardant, an overcharge inhibitor, a nitrile compound, an isocyanate compound, a compound having an acetylene-1,2-diyl group (—C≡C—), a phosphate ester compound, an acid anhydride, a cyclic phosphazene compound, a cyclic dioxazole compound, a boroxine derivative, a compound containing a silicon atom, and an alkali metal salt compound (e.g., a lithium salt compound).

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] Examples of cyclic phosphazene compounds include methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] Examples of lithium salt compounds 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, Li ２ P.O. ３ Examples of lithium salts include lithium salts having a phosphate skeleton such as F, and lithium salts having an S(═O) group such as lithium trifluoro((methanesulfonyl)oxy)borate, lithium pentafluoro((methanesulfonyl)oxy)phosphate, lithium methyl sulfate, lithium ethyl sulfate, lithium 2,2,2-trifluoroethyl sulfate, and lithium fluorosulfonate.

[0088] Other examples of alkali metal salt compounds include sodium difluorophosphate, potassium difluorophosphate, sodium bisoxalatoborate, potassium bisoxalatoborate, sodium tetrafluoro(oxalato)phosphate, potassium tetrafluoro(oxalato)phosphate, sodium difluorobis(oxalato)phosphate, potassium difluorobis(oxalato)phosphate, sodium difluorooxalatoborate, and potassium difluorooxalatoborate.

[0089] [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).

[0090] 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, an electrolyte 5 disposed between the negative electrodes 4 and the positive electrodes 9, and a separator 6 disposed in the electrolyte 5. 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. The nonaqueous electrolyte secondary battery 1 has three layers of negative electrodes 4 and two layers of positive electrodes 9. The electrolyte 5 is the above-described electrolyte for a secondary battery.

[0091] (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 .

[0092] 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 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 , LiNi ０．８ Co ０．１ Mn ０．１ O ２ , 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).

[0093] 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.

[0094] 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.

[0095] 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.

[0096] (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 .

[0097] 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.

[0098] 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.

[0099] 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.

[0100] (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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0105] 1. Synthesis of Compounds (Synthesis Example 1) 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 29 g (0.3 mol) of methanesulfonic 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, 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 the compound represented by formula (1-1). The yield was 55 mol% based on boron tribromide. １ H-NMR (400MHz): δ = 2.4ppm (s), １３ C-NMR (100 MHz): 34.3 ppm, measurement solvent: DMSO-d6)

[0106] Synthesis Example 2: 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. The reaction solution was then cooled to room temperature, 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 (1-2) (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)

[0107] Synthesis Example 3 3-sulfolene (236.3 g, 2.0 mol) and 500 mL of water were placed in a 2 L four-neck flask equipped with a stirrer, a condenser, and a thermometer, and the temperature was raised to 40°C to prepare a homogeneous solution. Sodium hydroxide (104.0 g, 2.6 mol) was added to the solution, and the solution was stirred for 10 hours while maintaining the temperature at 40°C. The flask was then cooled in an ice bath. Concentrated sulfuric acid (130.10 g, 1.3 mol) was added dropwise to the resulting reaction solution over 30 minutes to acidify the reaction solution. The reaction solution was concentrated to precipitate a solid, and the precipitated solid was filtered off. The resulting filtrate was then concentrated to obtain 3-hydroxysulfolane (250.59 g, yield 92% based on 3-sulfolene).

[0108] Next, 3-hydroxysulfolane (5.4 g, 40 mmol) synthesized by the above method, methanesulfonyl chloride (5.4 g, 44 mmol), and 20 mL of acetonitrile were placed in a 200 mL four-neck flask equipped with a stirrer, a condenser, a thermometer, and a dropping funnel. The flask was cooled in an ice bath, and triethylamine (4.0 g, 40 mmol) was added dropwise while stirring the reaction solution in the flask. After the dropwise addition was completed, the reaction solution was stirred for 1 hour while maintaining the temperature at 0 to 5°C. Water was then added to the reaction solution, and the precipitated white solid was collected by filtration. The collected solid was washed with methanol and then dried under reduced pressure to obtain a white solid compound (compound represented by formula (2-3a)) (7.0 g, yield 82% relative to 3-hydroxysulfolane).

[0109] Synthesis Example 4 Sodium 2-methyl-2-propene-1-sulfonate (8.04 g, 50 mmol), N,N-dimethylformamide (0.37 g, 5 mmol), and 30 mL of dichloromethane were placed in a 200 mL four-neck flask equipped with a stirrer, a condenser, a thermometer, and a dropping funnel. While stirring the reaction solution in the flask at room temperature (25°C), thionyl chloride (7.14 g, 60 mmol) was added dropwise. After the dropwise addition was completed, the reaction solution was stirred for 24 hours while maintaining the temperature at 20 to 25°C. Water was then added to the reaction solution, the mixture was separated, and the oil layer was concentrated to obtain 2-methyl-2-propene-1-sulfonic acid chloride (7.73 g, yield 100% relative to sodium 2-methyl-2-propene-1-sulfonate).

[0110] Next, a 200 mL four-neck flask equipped with a stirrer, condenser, thermometer, and dropping funnel was charged with 3-hydroxysulfolane (5.45 g, 40 mmol) obtained in the same manner as in (Synthesis Example 3), 2-methyl-2-propene-1-sulfonic acid chloride (6.80 g, 44 mmol) obtained above, and 20 mL of acetonitrile. The flask was cooled in an ice bath, and triethylamine (4.05 g, 40 mmol) was added dropwise while stirring the reaction solution in the flask. After the addition was completed, the reaction solution was stirred for 1 hour while maintaining the temperature at 0 to 5°C. Water was then added, and the precipitated white solid was filtered off. The obtained solid was washed with methanol and then dried under reduced pressure to obtain a white solid compound (compound represented by formula (2-3e)) (5.84 g, 50% yield based on 3-hydroxysulfolane).

[0111] 2. Preparation of Electrolyte for Secondary Battery The following components were prepared to prepare an electrolyte. First Compound (1-1): Compound represented by formula (1-1) obtained in Synthesis Example 1. (1-2): Compound represented by formula (1-2) obtained in Synthesis Example 2. Second Compound (2-1a): Fluoroethylene carbonate manufactured by Kishida Chemical Co., Ltd. (hereinafter referred to as "FEC") (2-1i): Vinylene carbonate manufactured by Sigma-Aldrich (hereinafter referred to as "VC") (2-2a): 1,3-propane sultone manufactured by Tokyo Chemical Industry Co., Ltd. (hereinafter referred to as "PS") (2-2c): 1,3,2-dioxathiolane 2,2-dioxide manufactured by Tokyo Chemical Industry Co., Ltd. (hereinafter referred to as "ESA") (2-3a): Compound represented by formula (2-3a) obtained in Synthesis Example 3. (2-3e): Compound represented by formula (2-3e) obtained in Synthesis Example 4.

[0112] 2. Preparation of Electrolyte Solution Production 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 1.0 mol / L. ６ A solution was obtained.

[0113] Example 1 LiPF obtained in Production Example 1 ６ 0.05 g of the compound represented by formula (1-1) and 0.05 g of FEC were further dissolved in 9.90 g of the solution to prepare an electrolyte solution. In the electrolyte solution, the concentration of the compound represented by formula (1-1) was 0.5 mass% based on the total mass of the electrolyte solution, and the concentration of FEC was 0.5 mass% based on the total mass of the electrolyte solution.

[0114] Example 2 An electrolyte solution was prepared in the same manner as in Example 1, except that 0.05 g of FEC was changed to 0.05 g of VC in Example 1. In the electrolyte solution, the concentration of the compound represented by formula (1-1) was 0.5 mass% based on the total mass of the electrolyte solution, and the concentration of VC was 0.5 mass% based on the total mass of the electrolyte solution.

[0115] Example 3 LiPF obtained in Production Example 1 ６0.05 g of the compound represented by formula (1-2) and 0.05 g of VC were further dissolved in 9.90 g of the solution to prepare an electrolyte solution. In the electrolyte solution, the concentration of the compound represented by formula (1-2) was 0.5 mass % based on the total mass of the electrolyte solution, and the concentration of VC was 0.5 mass % based on the total mass of the electrolyte solution.

[0116] Example 4 An electrolyte solution was prepared in the same manner as in Example 1, except that 0.05 g of FEC was changed to 0.05 g of ESA. In the electrolyte solution, the concentration of the compound represented by formula (1-1) was 0.5 mass% based on the total mass of the electrolyte solution, and the concentration of ESA was 0.5 mass% based on the total mass of the electrolyte solution.

[0117] Example 5 An electrolyte solution was prepared in the same manner as in Example 1, except that 0.05 g of FEC in Example 1 was changed to 0.05 g of the compound represented by formula (2-3a). In the electrolyte solution, the concentration of the compound represented by formula (1-1) was 0.5 mass% based on the total mass of the electrolyte solution, and the concentration of the compound represented by formula (2-3a) was 0.5 mass% based on the total mass of the electrolyte solution.

[0118] Example 6 An electrolyte solution was prepared in the same manner as in Example 1, except that 0.05 g of FEC in Example 1 was changed to 0.05 g of the compound represented by formula (2-3e). In the electrolyte solution, the concentration of the compound represented by formula (1-1) was 0.5 mass% based on the total mass of the electrolyte solution, and the concentration of the compound represented by formula (2-3e) was 0.5 mass% based on the total mass of the electrolyte solution.

[0119] Example 7 LiPF obtained in Production Example 1 ６ 0.10 g of the compound represented by formula (1-1) and 0.10 g of ESA were further dissolved in 9.80 g of the solution to prepare an electrolyte solution. In the electrolyte solution, the concentration of the compound represented by formula (1-1) was 1.0 mass % based on the total mass of the electrolyte solution, and the concentration of ESA was 1.0 mass % based on the total mass of the electrolyte solution.

[0120] Example 8 An electrolyte solution was prepared in the same manner as in Example 7, except that 0.10 g of ESA was changed to 0.10 g of PS. In the electrolyte solution, the concentration of the compound represented by formula (1-1) was 1.0 mass% based on the total mass of the electrolyte solution, and the concentration of PS was 1.0 mass% based on the total mass of the electrolyte solution.

[0121] Comparative Example 1 LiPF obtained in Production Example 1 ６ 0.05 g of FEC was dissolved in 9.95 g of the solution to prepare an electrolyte solution having a concentration of 0.5 mass % based on the total mass of the electrolyte solution.

[0122] Comparative Example 2 An electrolyte solution was prepared in the same manner as in Comparative Example 1, except that 0.05 g of FEC was changed to 0.05 g of VC. In the electrolyte solution, the concentration of FEC was 0.5 mass% based on the total mass of the electrolyte solution.

[0123] Comparative Example 3 An electrolyte solution was prepared in the same manner as in Comparative Example 1, except that 0.05 g of FEC was changed to 0.05 g of ESA. In the electrolyte solution, the concentration of FEC was 0.5 mass% based on the total mass of the electrolyte solution.

[0124] Comparative Example 4 An electrolyte solution was prepared in the same manner as in Comparative Example 1, except that 0.05 g of FEC was changed to 0.05 g of the compound represented by formula (2-3a). In the electrolyte solution, the concentration of the compound represented by formula (2-3a) was 0.5 mass% based on the total mass of the electrolyte solution.

[0125] Comparative Example 5 An electrolyte solution was prepared in the same manner as in Comparative Example 1, except that 0.05 g of FEC in Comparative Example 1 was changed to 0.05 g of the compound represented by formula (2-3e). In the electrolyte solution, the concentration of the compound represented by formula (2-3e) was 0.5 mass% based on the total mass of the electrolyte solution.

[0126] Comparative Example 6 LiPF obtained in Production Example 1 ６ 0.10 g of ESA was dissolved in 9.90 g of the solution to prepare an electrolyte solution having a concentration of 1.0 mass % based on the total mass of the electrolyte solution.

[0127] Comparative Example 7 An electrolyte solution was prepared in the same manner as in Comparative Example 1, except that 0.10 g of ESA was changed to 0.10 g of PS in Comparative Example 6. In the electrolyte solution, the concentration of PS was 1.0 mass% based on the total mass of the electrolyte solution.

[0128] 3. Evaluation <Preparation of non-aqueous electrolyte secondary battery> A positive electrode sheet containing a lithium-containing composite oxide (manufactured by JFE Techno Research Corporation) and a negative electrode sheet containing graphite (manufactured by Yayama Co., Ltd.) 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. ０．８ Co ０．１ Mn ０．１ O ２ The negative electrode sheet contained lithium-containing composite oxide (Li-O), acetylene black (AB) as a conductive additive, and vinylidene fluoride (PVDF) as a binder. The mass ratio of these was lithium-containing composite oxide:AB:PVDF = 95:2:3. 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 of the copper foil. 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 polypropylene separators interposed between them to produce a battery element having a total of five layers as electrodes: three layers of negative electrode sheets and two layers of positive electrode sheets.

[0129] The battery element prepared by the above method was inserted into a bag formed from a laminate film having aluminum foil (40 μm thick) and resin layers covering both sides of the foil, so that the ends of the positive electrode sheet and the negative electrode sheet protruded from the bag. Furthermore, the electrolyte prepared in each Comparative Example and Example was added to the bag, and the bag was vacuum-sealed to obtain a sheet-shaped nonaqueous electrolyte secondary battery. To increase the adhesion between the electrodes, the sheet-shaped electrolyte secondary battery was sandwiched between glass plates and pressure was applied.

[0130] <Evaluation of Initial Characteristics> 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 then 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. Thereafter, each nonaqueous electrolyte secondary battery was 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. During this aging, the ratio of the discharge capacity to the charge capacity measured in the first cycle of charging 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 was expressed as a percentage and designated "initial charge / discharge efficiency." Furthermore, the discharge capacity measured in the third cycle of charging to 4.2 V at a current corresponding to 1 C and discharging to 3.0 V at a current corresponding to 1 C was designated "discharge capacity after aging."

[0131] (Measurement of Initial DCR) 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 was measured during this period. After that, 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 was measured, and the DCR (Ω) was calculated from this value as “initial DCR (Ω).”

[0132] The DCR is a value corresponding to the resistance value of a battery, and it can be said that the lower the DCR value, the higher the output characteristics of the battery. Furthermore, the ratio of the initial DCR of a secondary battery containing both the first compound and the second compound to the initial DCR of a secondary battery not containing the first compound, expressed as a percentage, was defined as the "initial DCR ratio (%)." It can be said that the lower the initial DCR ratio, the greater the effect of reducing the initial DCR when the first compound and the second compound are used in combination.

[0133] (Post-cycling DCR) After the initial DCR measurement, each nonaqueous electrolyte secondary battery was charged to 4.2 V at 45°C with a current corresponding to 2 C and discharged to 3 V at a current corresponding to 2 C for 400 cycles. Then, at 25°C, 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 for three cycles. The discharge capacity measured in the third cycle was designated the "post-cycling discharge capacity." Subsequently, the battery was charged to 50% of the post-cycling discharge capacity at 25°C with a current corresponding to 1 C, and then discharged at -10°C with a current corresponding to 0.2 C, and the change in battery voltage during this period was measured. After that, the battery was repeatedly charged and discharged with a 10-minute pause, while the discharge current (discharge rate) was changed to 0.5 C, 1.0 C, and 2.0 C. The change in voltage was measured, and the DCR (Ω) was calculated from this value as the "post-cycling DCR (Ω)."

[0134] The ratio of the DCR after cycling to the initial DCR, expressed as a percentage, was defined as the "DCR increase rate (%)." A lower DCR increase rate can be said to be more effective in suppressing the increase in resistance during repeated use of the nonaqueous electrolyte secondary battery, i.e., the cycle deterioration of the battery.

[0135]

[0136] Tables 1 and 2 show the concentrations of each additive in the electrolyte solutions of each Example and Comparative Example, and the evaluation results of battery performance. It was confirmed that the electrolyte solutions containing the compound represented by formula (1-1) or formula (1-2) and the second compound had a reduced initial DCR compared to electrolyte solutions not containing the compound represented by formula (1-1) or formula (1-2), and provided high-power secondary batteries.

[0137] In an electrolyte solution containing the compound represented by formula (1-1) or formula (1-2) and the second compound, an improvement in initial charge-discharge efficiency was observed compared to an electrolyte solution not containing formula (1-1) or formula (1-2), and it was confirmed that by reducing side reactions during the aging process, the loss of lithium ions involved in reactions in the secondary battery can be suppressed.

[0138]

[0139] Table 3 shows the concentrations of the first and second compounds in the electrolyte solution and the evaluation results of the DCR. As shown in Table 3, in the electrolyte solution containing the compound represented by formula (1-1) and the second compound, the increase in the DCR after cycling relative to the initial DCR was also suppressed compared to the electrolyte solution not containing the first compound, confirming that the cycle deterioration of the secondary battery can be suppressed.

[0140] According to one aspect of the present invention, there is provided a nonaqueous electrolyte secondary battery having excellent output characteristics, such as a reduced initial DCR after battery fabrication. 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.

[0141] DESCRIPTION OF SYMBOLS 1... Non-aqueous electrolyte secondary battery, 2... Negative electrode active material layer, 3... Negative electrode current collector, 4... Negative electrode, 5... Electrolyte, 6... Separator, 7... Positive electrode active material layer, 8... Positive electrode current collector, 9... Positive electrode.

Claims

1. An electrolyte solution for a secondary battery, comprising: a first compound represented by the following formula (1); and at least one second compound selected from the group consisting of a compound represented by the following formula (2-1), a compound represented by the following formula (2-2), and a compound represented by the following formula (2-3). [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.] [In formula (2-1), Z １ represents a group in which one or more hydrogen atoms of an alkylene group having 1 to 3 carbon atoms have been substituted with a halogen atom, an alkyl group, a halogenated alkyl group, or an alkenyl group, or an optionally substituted alkenylene group having 2 to 4 carbon atoms.] [In formula (2-2), Y represents an alkylene group having 1 to 3 carbon atoms which may be substituted, or an alkenylene group having 2 to 4 carbon atoms which may be substituted, J represents an oxygen atom or a single bond, and m represents 1 or 2.] [In formula (2-3), Q is a group that forms a ring structure together with the sulfur atom of the sulfonyl group and represents an optionally substituted alkylene group having 4 to 6 carbon atoms or an optionally substituted alkenylene group having 4 to 6 carbon atoms, and X represents a group represented by the following formula (2a) or (2b)] [In formula (2a) or formula (2b), R ａ each independently represents an alkyl group having 1 to 4 carbon atoms which may be substituted with a fluorine atom, an alkenyl group having 2 to 4 carbon atoms which may be substituted with a fluorine atom, an alkynyl group having 2 to 4 carbon atoms which may be substituted with a fluorine atom, an aryl group having 6 to 10 carbon atoms which may be substituted with a fluorine atom, a hydroxy group, or a lithium oxy group.] 2. The electrolyte solution for a secondary battery according to claim 1, wherein the second compound includes a compound represented by formula (2-1).

3. The electrolyte solution for a secondary battery according to claim 1, wherein the second compound includes a compound represented by formula (2-2).

4. The electrolyte solution for a secondary battery according to claim 1, wherein the second compound includes a compound represented by formula (2-3).

5. The electrolyte for a secondary battery according to claim 1, wherein M is a boron atom or an aluminum atom.

6. The electrolyte for a secondary battery according to claim 1, wherein M is a boron atom.

7. R １ ~R ３ 2. The electrolyte solution for a secondary battery according to claim 1, wherein each of the groups independently represents an optionally substituted alkyl group having 1 to 6 carbon atoms.

8. The electrolyte solution for a secondary battery according to claim 1, further comprising a cyclic carbonate and / or a chain carbonate different from the second compound.

9. An electricity storage device comprising the secondary battery electrolyte solution according to any one of claims 1 to 8, a positive electrode, and a negative electrode.

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