Electrolytes for secondary batteries and secondary batteries

Abstract

This secondary battery comprises a positive electrode, a negative electrode, and an electrolyte solution containing a fluorine-containing compound. The fluorine-containing compound includes at least one of compounds respectively expressed in formula (1) to formula (22).

Description

[Technical Field]

[0001] This technology relates to electrolytes for secondary batteries and secondary batteries. [Background technology]

[0002] With the widespread use of various electronic devices such as mobile phones, development is progressing on secondary batteries as a power source that is small, lightweight, and can achieve high energy density.

[0003] This secondary battery includes an electrolyte (electrolyte for secondary batteries) along with a positive electrode and a negative electrode, and various studies have been conducted regarding the configuration of this secondary battery. Specifically, in order to obtain good charge-discharge cycle life characteristics, carbonate esters of alcohols having a specific structure are included in the electrolyte (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-251259 [Overview of the project]

[0005] Although various studies have been conducted on the configuration of secondary batteries, their cycle characteristics are still not sufficient, and there is room for improvement.

[0006] Therefore, there is a need for electrolytes and batteries for secondary batteries that can achieve excellent cycle characteristics.

[0007] An electrolyte for a secondary battery according to one embodiment of this technology contains a fluorine-containing compound, wherein the fluorine-containing compound contains at least one of the compounds represented by formulas (1) to (22).

[0008] [ka] (Each of R1 to R16 is one of the following: hydrogen (H), fluorine (F), a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). However, at least one of R1 to R4 is Expressed by equation (30) It is a fluorine-containing group. At least one of R5 to R10 is Expressed by equation (30) It is a fluorine-containing group. At least one of R11 and R12 is a fluorine-containing group. At least one of R13 to R16 is a fluorine-containing group.

[0009] [ka] (Each of R17 to R38 is one of the following: hydrogen, fluorine, hydrocarbon group, oxygen-containing hydrocarbon group, fluorinated hydrocarbon group, and fluorine-containing group represented by formula (30). However, at least one of R17-R20 is a fluorine-containing group. At least one of R21-R26 is a fluorine-containing group. At least one of R27-R34 is a fluorine-containing group. At least one of R35-R38 is a fluorine-containing group.

[0010] [ka] (Each of R39 to R44 is one of hydrogen, fluorine, a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). Each of R45, R46, and R52 is one of a hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). Each of R47 to R51 is one of hydrogen, fluorine, an alkyl group, an alkoxy group, and a fluorinated alkyl group.) However, at least one of R39 to R44 is a fluorine-containing group. At least one of R45 and R46 is Expressed by equation (30) Fluorine-containing group R201, R202, R204, and R205 are each hydrogen atoms, and R203 is a trifluoromethyl group.Among R47 to R51, at least one is a trifluoromethyl group.)

[0011] [Chemical formula] (Each of R53 to R70 is any one of hydrogen, fluorine, an alkyl group, an alkoxy group, and a fluorinated alkyl group. Each of R71 and R72 is any one of hydrogen, fluorine, a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). However, at least one of R53 to R62 is a trifluoromethyl group. At least one of R63 to R66 is a trifluoromethyl group. At least one of R67 to R70 is a trifluoromethyl group.)

[0012] [Chemical formula] (Each of R73 to R76, R79 to R82, and R85 to R88 is any one of hydrogen, fluorine, an alkyl group, an alkoxy group, and a fluorinated alkyl group. Each of R77, R78, R83, R84, and R89 to R92 is any one of hydrogen, fluorine, a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). However, at least one of R73 to R76 is a trifluoromethyl group. At least one of R79 to R82 is a trifluoromethyl group. At least one of R85 to R88 is a trifluoromethyl group.)

[0013] [Chemical formula] (Each of R93 to R96 and R109 to R116 is any one of hydrogen, fluorine, an alkyl group, an alkoxy group, and a fluorinated alkyl group. Each of R97 to R108, R117, and R118 is any one of hydrogen, fluorine, a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by the formula (30). However, at least one of R93 to R96 is a trifluoromethyl group. At least one of R99 to R102 is Expressed by equation (30) a fluorine-containing group. At least one of R103 to R108 is a fluorine-containing group. At least one of R109 to R112 is a trifluoromethyl group. At least one of R113 to R116 is a trifluoromethyl group.)

[0014]

Chemical Formula

[0015] The secondary battery of one embodiment of the present technology includes a positive electrode, a negative electrode, and an electrolyte, and the electrolyte has the same configuration as the configuration of the electrolyte for the secondary battery of one embodiment of the present technology described above.

[0016] According to the electrolyte for the secondary battery or the secondary battery of one embodiment of the present technology, since the electrolyte for the secondary battery contains a fluorine-containing compound, excellent cycle characteristics can be obtained.

[0017] Note that the effects of the present technology are not necessarily limited to the effects described here, and may be any of a series of effects related to the present technology described later.

Brief Description of the Drawings

[0018] [Figure 1] This is a cross-sectional view showing the configuration of a secondary battery in one embodiment of this technology. [Figure 2] Figure 1 is a cross-sectional view showing the configuration of the battery element. [Figure 3] This is a block diagram showing the configuration of an example application of a secondary battery. [Modes for carrying out the invention]

[0019] An embodiment of this technology will be described in detail below with reference to the drawings. The order of description is as follows. 1. Electrolyte for secondary batteries 1-1. Composition 1-2. Manufacturing method 1-3. Mechanism of Action and Effects 2. Secondary battery 2-1. Composition 2-2.Operation 2-3. Manufacturing method 2-4. Mechanism of Action and Effects 3. Variant 4. Applications of rechargeable batteries

[0020] <1. Electrolyte for secondary batteries> First, we will describe an electrolyte for a secondary battery (hereinafter simply referred to as "electrolyte") according to one embodiment of this technology.

[0021] <1-1. Structure> The electrolyte is used in secondary batteries, which are electrochemical devices. However, the electrolyte may also be used in other electrochemical devices besides secondary batteries. The types of other electrochemical devices are not particularly limited, but specifically include capacitors, etc.

[0022] [Fluorine-containing compounds] This electrolyte contains a fluorine-containing compound, which includes one or more compounds represented by formulas (1) to (22).

[0023] [ka] (Each of R1 to R16 is one of the following: hydrogen, fluorine, hydrocarbon group, oxygen-containing hydrocarbon group, fluorinated hydrocarbon group, and fluorine-containing group represented by formula (30). However, at least one of R1 to R4 is a fluorine-containing group. At least one of R5 to R10 is a fluorine-containing group. At least one of R11 and R12 is a fluorine-containing group. At least one of R13 to R16 is a fluorine-containing group.

[0024] [ka] (Each of R17 to R38 is one of the following: hydrogen, fluorine, hydrocarbon group, oxygen-containing hydrocarbon group, fluorinated hydrocarbon group, and fluorine-containing group represented by formula (30). However, at least one of R17-R20 is a fluorine-containing group. At least one of R21-R26 is a fluorine-containing group. At least one of R27-R34 is a fluorine-containing group. At least one of R35-R38 is a fluorine-containing group.

[0025] [ka] (Each of R39 to R44 is one of hydrogen, fluorine, a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). Each of R45, R46, and R52 is one of a hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). Each of R47 to R51 is one of hydrogen, fluorine, an alkyl group, an alkoxy group, and a fluorinated alkyl group.) However, at least one of R39-R44 is a fluorine-containing group. At least one of R45 and R46 is a fluorine-containing group. At least one of R47-R51 is a trifluoromethyl group.

[0026] [ka] (Each of R53 to R70 is one of hydrogen, fluorine, alkyl group, alkoxy group, and fluorinated alkyl group. Each of R71 and R72 is one of hydrogen, fluorine, hydrocarbon group, oxygen-containing hydrocarbon group, fluorinated hydrocarbon group, and fluorine-containing group represented by formula (30). However, at least one of R53-R62 is a trifluoromethyl group. At least one of R63-R66 is a trifluoromethyl group. At least one of R67-R70 is a trifluoromethyl group.

[0027] [ka] (Each of R73-R76, R79-R82, and R85-R88 is one of hydrogen, fluorine, alkyl group, alkoxy group, and fluorinated alkyl group. Each of R77, R78, R83, R84, and R89-R92 is one of hydrogen, fluorine, hydrocarbon group, oxygen-containing hydrocarbon group, fluorinated hydrocarbon group, and fluorine-containing group represented by formula (30). However, at least one of R73-R76 is a trifluoromethyl group. At least one of R79-R82 is a trifluoromethyl group. At least one of R85-R88 is a trifluoromethyl group.

[0028] [ka] (Each of R93-R96 and R109-R116 is one of hydrogen, fluorine, alkyl group, alkoxy group, and fluorinated alkyl group. Each of R97-R108, R117, and R118 is one of hydrogen, fluorine, hydrocarbon group, oxygen-containing hydrocarbon group, fluorinated hydrocarbon group, and fluorine-containing group represented by formula (30). However, at least one of R93-R96 is a trifluoromethyl group. At least one of R99-R102 is a fluorine-containing group. At least one of R103-R108 is a fluorine-containing group. At least one of R109-R112 is a trifluoromethyl group. At least one of R113-R116 is a trifluoromethyl group.

[0029] [ka] (Each of R201 to R205 is either a hydrogen atom or a trifluoromethyl group. An asterisk (*) indicates an unbonded bond.) However, at least one of R201 to R205 is a trifluoromethyl group.

[0030] As is clear from formulas (1) to (22), this fluorine-containing compound is a compound containing fluorine, and more specifically, a compound containing an aromatic ring (benzene ring) to which one or more trifluoromethyl groups (-CF3) have been introduced.

[0031] The electrolyte contains fluorine-containing compounds because, during the charging and discharging of a secondary battery using this electrolyte, the solvent (described later) decomposes on the electrode surface, along with the benzene ring to which the trifluoromethyl group has been introduced. This results in the formation of a good protective film on the electrode surface derived from the fluorine-containing compounds. This film is electrochemically stable and therefore functions as a protective film on the electrode surface.

[0032] As a result, the decomposition reaction of the electrolyte is suppressed during charging and discharging, and the decrease in discharge capacity is suppressed even if the charging and discharging is repeated. In this case, in particular, because the coating derived from the fluorine-containing compound has excellent electrochemical durability, the decrease in discharge capacity is effectively suppressed even when the secondary battery is charged and discharged in a high-temperature environment.

[0033] The following section provides a detailed explanation of the 22 compounds shown in formulas (1) to (22). Note that each of the compounds shown in formulas (1) to (22) may be one type or two or more types.

[0034] (Compounds containing primary fluorine) The compound shown in formula (1) is a cyclic fluorine-containing compound. Each of R1 to R4 is not particularly limited as long as it is one of hydrogen, fluorine, a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorinated hydrocarbon group, or a fluorine-containing group, but one or more of R1 to R4 are fluorine-containing groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of benzene rings into which the trifluoromethyl group has been introduced is one or more.

[0035] A hydrocarbon group is a monovalent group composed of carbon and hydrogen. This hydrocarbon group may be linear or branched, having one or more side chains. Furthermore, the hydrocarbon group may contain a carbon-carbon double bond (>C=C<) or a carbon-carbon triple bond (-C≡C-).

[0036] In particular, the hydrocarbon group is preferably one of an alkyl group, an alkenyl group, or an alkynyl group, because this ensures the solubility and compatibility of the primary fluorine-containing compound.

[0037] Specific examples of alkyl groups include methyl, ethyl, and propyl groups. Specific examples of alkenyl groups include vinyl, allyl, 2-propenyl, and propa-2-en-1-yl groups. Specific examples of alkynyl groups include ethynyl, propargyl, 2-propynyl, and propa-2-en-1-yl groups.

[0038] The number of carbon atoms in each alkyl group, alkenyl group, and alkynyl group is not particularly limited, but it is preferably 3 or less. That is, the number of carbon atoms in the alkyl group is preferably 1 to 3, and the number of carbon atoms in each of the alkenyl group and alkynyl group is preferably 2 or 3. This is because the solubility and compatibility of the primary fluorine-containing compound are further improved.

[0039] An oxygen-containing hydrocarbon group is a monovalent group composed of carbon, hydrogen, and oxygen. This oxygen-containing hydrocarbon group may be linear or branched, having one or more side chains.

[0040] In particular, the hydrocarbon group is preferably an alkoxy group, as this ensures the solubility and compatibility of the primary fluorine-containing compound. Specific examples of alkoxy groups include methoxy, ethoxy, and propoxy groups.

[0041] The number of carbon atoms in the alkoxy group is not particularly limited, but it is preferably three or less. This is because it improves the solubility and compatibility of the primary fluorine-containing compound.

[0042] A fluorinated hydrocarbon group is a group in which one or more hydrogen atoms of the above-mentioned hydrocarbon groups (alkyl groups, alkenyl groups, or alkynyl groups) are substituted with fluorine.

[0043] The fluorine-containing group is a phenyl group into which a trifluoromethyl group has been introduced, as shown in formula (30). The types of R201 to R205 are not particularly limited as long as they are either hydrogen or a trifluoromethyl group, but one or more of R201 to R205 are trifluoromethyl groups. Therefore, the fluorine-containing group contains one or more trifluoromethyl groups.

[0044] Specific examples of primary fluorine-containing compounds include the compounds represented by formulas (1-1) to (1-11), respectively.

[0045] [ka]

[0046] (Compounds containing fluorine) The compound shown in formula (2) is a cyclic fluorine-containing compound. The details for each of R5 to R10 are the same as the details for each of R1 to R4. However, one or more of R5 to R10 are fluorine-containing groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of benzene rings into which the trifluoromethyl group has been introduced is one or more.

[0047] Specific examples of fluorine-containing compounds include those represented by formulas (2-1) to (2-15), respectively.

[0048] [ka]

[0049] (Third fluorine-containing compound) The compound shown in formula (3) is a trifluorinated compound having a cyclic structure. The details for R11 and R12 are the same as the details for R1 to R4. However, one or both of R11 and R12 are fluorine-containing groups. Thus, the trifluorinated compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of benzene rings into which the trifluoromethyl group has been introduced is one or more.

[0050] Specific examples of tertiary fluorine-containing compounds include the compounds represented by formulas (3-1) to (3-9), respectively.

[0051] [ka]

[0052] (Compounds containing quaternary fluorine) The compound shown in formula (4) is a quaternary fluorine-containing compound having a cyclic structure. The details for each of R13 to R16 are the same as the details for each of R1 to R4. However, one or more of R13 to R16 are fluorine-containing groups. Thus, the quaternary fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of benzene rings into which the trifluoromethyl group has been introduced is one or more.

[0053] Specific examples of quaternary fluorine-containing compounds include the compounds represented by formulas (4-1) to (4-9), respectively.

[0054] [ka]

[0055] (5th fluorine-containing compound) The compound shown in formula (5) is a cyclic fluorine-containing compound. The details for each of R17 to R20 are the same as the details for each of R1 to R4. However, one or more of R17 to R20 are fluorine-containing groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings with introduced trifluoromethyl groups is one or more.

[0056] Specific examples of fluorine-containing compounds include those represented by formulas (5-1) to (5-9), respectively.

[0057] [ka]

[0058] (Compounds containing fluorine hexafluoride) The compound shown in formula (6) is a cyclic fluorine-containing compound. The details for each of R21 to R26 are the same as the details for each of R1 to R4. However, one or more of R21 to R26 are fluorine-containing groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of benzene rings into which the trifluoromethyl group has been introduced is one or more.

[0059] Specific examples of fluorine-hexavalent compounds include those represented by formulas (6-1) to (6-11), respectively.

[0060] [ka]

[0061] (Veteran fluorine-containing compound) The compound shown in formula (7) is a cyclic fluorine-containing compound. The details for each of R27 to R34 are the same as the details for each of R1 to R4. However, one or more of R27 to R34 are fluorine-containing groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of benzene rings into which the trifluoromethyl group has been introduced is one or more.

[0062] Specific examples of fluorine-containing compounds include those represented by formulas (7-1) to (7-12), respectively.

[0063] [ka]

[0064] (Veteran fluorine-containing compound) The compound shown in formula (8) is a cyclic fluorine-containing compound. The details for each of R35 to R38 are the same as the details for each of R1 to R4. However, one or more of R35 to R38 are fluorine-containing groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings with introduced trifluoromethyl groups is one or more.

[0065] Specific examples of fluorine-containing compounds include those represented by formulas (8-1) to (8-9), respectively.

[0066] [ka]

[0067] (Compounds containing fluorine 9) The compound shown in formula (9) is a cyclic fluorine-containing compound. The details for each of R39 to R44 are the same as the details for each of R1 to R4. However, one or more of R39 to R44 are fluorine-containing groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of benzene rings into which the trifluoromethyl group has been introduced is one or more.

[0068] Specific examples of fluorine-containing compounds include those represented by formulas (9-1) to (9-9), respectively.

[0069] [ka]

[0070] (10th fluorine-containing compound) The compound shown in formula (10) is a 10th fluorine-containing compound having a chain-like structure. The details for R45 and R46 are the same as those for R1 to R4, except that hydrogen, fluorine, and oxygen-containing hydrocarbon groups are excluded. However, one or both of R45 and R46 are fluorine-containing groups. Thus, the 10th fluorine-containing compound contains a benzene ring into which a trifluoromethyl group is introduced, and the number of such benzene rings is one or more.

[0071] Specific examples of fluorine-containing compounds include those represented by formulas (10-1) to (10-10), respectively.

[0072] [ka]

[0073] (11th fluorine-containing compound) The compound shown in formula (11) is a cyclic 11th fluorine-containing compound. Each of R47 to R51 is not particularly limited as long as it is one of hydrogen, fluorine, alkyl group, alkoxy group, or fluorinated alkyl, but one or more of R47 to R51 are trifluoromethyl groups. Details regarding R52 are the same as those for R45 and R46, respectively. Thus, the 11th fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of benzene rings into which a trifluoromethyl group has been introduced is one or more.

[0074] Details regarding the alkyl and alkoxy groups are as described above. Furthermore, details regarding the number of carbon atoms in the alkyl and alkoxy groups are as described above. The number of carbon atoms in the alkyl and alkoxy groups is preferably 3 or less, and more specifically, preferably 1 to 3. This is because it improves the solubility and compatibility of the 11th fluorine-containing compound.

[0075] A fluorinated alkyl group is a group in which one or more hydrogen atoms of the alkyl group described above are substituted with fluorine. Details regarding the number of carbon atoms in the alkyl group that determines the number of carbon atoms in a fluorinated alkyl group are as described above.

[0076] Specific examples of 11th fluorine-containing compounds include the compounds represented by formulas (11-1) to (11-11), respectively.

[0077] [ka]

[0078] (Compounds containing 12th fluorine) The compound shown in formula (12) is a cyclic compound containing 12 fluorine. The details for each of R53 to R62 are the same as the details for each of R47 to R51. However, one or more of R53 to R62 are trifluoromethyl groups. Thus, the compound containing 12 fluorine contains benzene rings into which trifluoromethyl groups have been introduced, and the number of such benzene rings is one or more.

[0079] Specific examples of 12-fluorine-containing compounds include the compounds represented by formulas (12-1) to (12-6), respectively.

[0080] [ka]

[0081] (13th fluorine-containing compound) The compound shown in formula (13) is a cyclic fluorine-containing compound. The details for each of R63 to R66 are the same as the details for each of R47 to R51. However, one or more of R63 to R66 are trifluoromethyl groups. Thus, the fluorine-containing compound contains a benzene ring into which trifluoromethyl groups have been introduced, and the number of such benzene rings is one or more.

[0082] Specific examples of 13th fluorine-containing compounds include the compounds represented by formulas (13-1) to (13-6), respectively.

[0083] [ka]

[0084] (14th fluorine-containing compound) The compound shown in formula (14) is a cyclic compound containing 14 fluorine. Details for each of R67 to R70 are the same as those for each of R47 to R51. Details for each of R71 and R72 are the same as those for each of R1 to R4. However, one or more of R67 to R70 are trifluoromethyl groups. Thus, the compound containing 14 fluorine contains benzene rings into which trifluoromethyl groups have been introduced, and the number of benzene rings into which trifluoromethyl groups have been introduced is one or more.

[0085] Specific examples of fluorine-containing compounds include those represented by formulas (14-1) to (14-13), respectively.

[0086] [ka]

[0087] (15th fluorine-containing compound) The compound shown in formula (15) is a cyclic fluorine-containing compound. Details for each of R73 to R76 are the same as those for each of R47 to R51. Details for each of R77 and R78 are the same as those for each of R1 to R4. However, one or more of R73 to R76 are trifluoromethyl groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings is one or more.

[0088] Specific examples of fluorine-containing compounds include those represented by formulas (15-1) to (15-14), respectively.

[0089] [ka]

[0090] (16th fluorine-containing compound) The compound shown in formula (16) is a cyclic fluorine-containing compound. Details for each of R79 to R82 are the same as those for each of R47 to R51. Details for each of R83 and R84 are the same as those for each of R1 to R4. However, one or more of R79 to R82 are trifluoromethyl groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings is one or more.

[0091] Specific examples of fluorine-containing compounds include those represented by formulas (16-1) to (16-15), respectively.

[0092] [ka]

[0093] (17th fluorine-containing compound) The compound shown in formula (17) is a cyclic fluorine-containing compound. Details for each of R85 to R88 are the same as those for each of R47 to R51. Details for each of R89 to R92 are the same as those for each of R1 to R4. However, one or more of R85 to R88 are trifluoromethyl groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings is one or more.

[0094] Specific examples of fluorine-containing compounds include those represented by formulas (17-1) to (17-14), respectively.

[0095] [ka]

[0096] (18th fluorine-containing compound) The compound shown in formula (18) is a cyclic fluorine-containing compound. Details for each of R93 to R96 are the same as those for each of R47 to R51. Details for each of R97 and R98 are the same as those for each of R1 to R4. However, one or more of R93 to R96 are trifluoromethyl groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings is one or more.

[0097] Specific examples of fluorine-containing compounds of the 18th category include compounds represented by formulas (18-1) to (18-15), respectively.

[0098] [ka]

[0099] (19th fluorine-containing compound) The compound shown in formula (19) is a 19th fluorine-containing compound having a cyclic structure. The details for each of R99 to R102 are the same as the details for each of R1 to R4. However, one or more of R99 to R102 are fluorine-containing groups. Thus, the 19th fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings with introduced trifluoromethyl groups is one or more.

[0100] Specific examples of fluorine-containing compounds include those represented by formulas (19-1) to (19-9), respectively.

[0101] [ka]

[0102] (20th fluorine-containing compound) The compound shown in formula (20) is a cyclic fluorine-containing compound. The details for each of R103 to R108 are the same as the details for each of R1 to R4. However, one or more of R103 to R108 are fluorine-containing groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings with introduced trifluoromethyl groups is one or more.

[0103] Specific examples of fluorine-containing compounds include those represented by formulas (20-1) to (20-10), respectively.

[0104] [ka]

[0105] (21st fluorine-containing compound) The compound shown in formula (21) is a cyclic fluorine-containing compound. The details for each of R109 to R112 are the same as the details for each of R47 to R51. However, one or more of R109 to R112 are trifluoromethyl groups. Thus, the fluorine-containing compound contains a benzene ring into which trifluoromethyl groups have been introduced, and the number of such benzene rings is one or more.

[0106] Specific examples of fluorine-21-containing compounds include the compounds represented by formulas (21-1) to (21-5), respectively.

[0107] [ka]

[0108] (22nd fluorine-containing compound) The compound shown in formula (22) is a cyclic fluorine-containing compound. Details for each of R113 to R116 are the same as those for each of R47 to R51. Details for each of R117 and R118 are the same as those for each of R1 to R4. However, one or more of R113 to R116 are trifluoromethyl groups. Thus, the fluorine-containing compound contains a benzene ring into which a trifluoromethyl group has been introduced, and the number of such benzene rings is one or more.

[0109] Specific examples of fluorine-22-containing compounds include those represented by formulas (22-1) to (22-14), respectively.

[0110] [ka]

[0111] (Content) The content of fluorine-containing compounds in the electrolyte is not particularly limited, but is preferably 0.5% to 2.0% by weight. This is because a sufficiently good film derived from the fluorine-containing compounds is formed on the electrode surface, thereby sufficiently suppressing the decomposition reaction of the electrolyte.

[0112] The fluorine-containing compound content described here is the sum of the individual compound contents of the 22 compounds listed above.

[0113] [solvent] Furthermore, the electrolyte may also contain a solvent. This solvent contains one or more non-aqueous solvents (organic solvents), and the electrolyte containing such a non-aqueous solvent is a so-called non-aqueous electrolyte. Non-aqueous solvents include esters and ethers, and more specifically, carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds.

[0114] Carbonate ester compounds include cyclic carbonate esters and linear carbonate esters. Specific examples of cyclic carbonate esters include ethylene carbonate and propylene carbonate. Specific examples of linear carbonate esters include dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate.

[0115] Carboxylic acid ester compounds include chain-like carboxylic acid esters. Specific examples of chain-like carboxylic acid esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, ethyl trimethylacetate, methyl butyrate, and ethyl butyrate.

[0116] Lactone compounds include lactones, among others. Specific examples of lactones include γ-butyrolactone and γ-valerolactone.

[0117] In addition to the lactone compounds mentioned above, ethers may also be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane.

[0118] [Electrolyte salts] Furthermore, the electrolyte may also contain an electrolyte salt. This electrolyte salt is a light metal salt such as a lithium salt. Specific examples of lithium salts include lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3SO2)3), and lithium bis(oxalato)borate (LiB(C2O4)2).

[0119] The electrolyte salt content is not particularly limited, but specifically, it is between 0.3 mol / kg and 3.0 mol / kg relative to the solvent. This is because it allows for high ionic conductivity.

[0120] [Additives] Furthermore, the electrolyte may also contain one or more of the additives.

[0121] (Unsaturated cyclic carbonates, fluorinated cyclic carbonates, and cyanated cyclic carbonates) Specifically, the additives are one or more of the following: unsaturated cyclic carbonate esters, fluorinated cyclic carbonate esters, and cyanated cyclic carbonate esters. This is because it improves the electrochemical stability of the electrolyte. As a result, the decomposition reaction of the electrolyte is further suppressed during the charging and discharging of the secondary battery, and the decrease in discharge capacity is further suppressed even after repeated charging and discharging.

[0122] Unsaturated cyclic carbonate esters are cyclic carbonate esters that have unsaturated carbon bonds (carbon-carbon double bonds). The number of unsaturated carbon bonds is not particularly limited; there may be one or two or more.

[0123] This unsaturated cyclic carbonate ester contains one or more of the following compounds: vinylene carbonate compounds, vinyl ethylene carbonate compounds, and methylene ethylene carbonate compounds.

[0124] Vinylen carbonate compounds are unsaturated cyclic carbonate esters having a vinylene-type structure. Specific examples of vinylene carbonate compounds include vinylene carbonate (1,3-dioxol-2-one), methylvinylene carbonate (4-methyl-1,3-dioxol-2-one), ethylvinylene carbonate (4-ethyl-1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1,3-dioxol-2-one, and 4-trifluoromethyl-1,3-dioxol-2-one.

[0125] Vinyl ethylene carbonate compounds are unsaturated cyclic carbonate esters having a vinyl ethylene carbonate-type structure. Specific examples of vinyl ethylene carbonate compounds include vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, 4-ethyl-4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolan-2-one, 4,4-divinyl-1,3-dioxolan-2-one, and 4,5-divinyl-1,3-dioxolan-2-one.

[0126] Methylene carbonate compounds are unsaturated cyclic carbonate esters having a methylene carbonate-type structure. Specific examples of methylene carbonate compounds include methylene carbonate (4-methylene-1,3-dioxolan-2-one), 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl-5-methylene-1,3-dioxolan-2-one. Here, only compounds having one methylene group are given as examples of methylene carbonate compounds, but these methylene carbonate compounds may have two or more methylene groups.

[0127] Furthermore, cyclic carbonate esters containing unsaturated carbon bonds are classified as unsaturated cyclic carbonate esters, and do not fall under either fluorinated cyclic carbonate esters or cyanated cyclic carbonate esters.

[0128] Fluorinated cyclic carbonates are cyclic carbonates that contain fluorine as a constituent element. The number of fluorine atoms is not particularly limited; there may be one or two or more. In other words, fluorinated cyclic carbonates are compounds in which one or more hydrogen atoms in a cyclic carbonate are substituted with fluorine.

[0129] Specific examples of fluorinated cyclic carbonate esters include fluoroethylene (4-fluoro-1,3-dioxolan-2-one) and difluoroethylene (4,5-difluoro-1,3-dioxolan-2-one).

[0130] Furthermore, cyclic carbonate esters containing fluorine as a constituent element are classified as fluorinated cyclic carbonate esters, and not as unsaturated cyclic carbonate esters or cyanated cyclic carbonate esters.

[0131] A cyanated cyclic carbonate ester is a cyclic carbonate ester having a cyano group. The number of cyano groups is not particularly limited; there may be one or two or more. In other words, a cyanated cyclic carbonate ester is a compound in which one or more hydrogens of a cyclic carbonate ester are substituted with cyano groups.

[0132] Specific examples of cyanated cyclic carbonate esters include ethylene cyanocarbonate (4-cyano-1,3-dioxolan-2-one) and ethylene dicyanocarbonate (4,5-dicyano-1,3-dioxolan-2-one).

[0133] Furthermore, cyclic carbonate esters containing a cyano group are not classified as either unsaturated cyclic carbonate esters or fluorinated cyclic carbonate esters, but rather as cyanated cyclic carbonate esters.

[0134] (Sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, and sulfonic acid carboxylic acid anhydrides) Furthermore, the additives are one or more of the following: sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, and sulfonic acid carboxylic acid anhydrides. This is because it improves the electrochemical stability of the electrolyte. As a result, the decomposition reaction of the electrolyte is further suppressed during charging and discharging of the secondary battery, and the decrease in discharge capacity is further suppressed even after repeated charging and discharging.

[0135] Specific examples of sulfonic acid esters include 1,3-propanesultone, 1-propene-1,3-sultone, 1,4-butanesultone, 2,4-butanesultone, and propargyl methanesulfonate.

[0136] Specific examples of sulfate esters include 1,3,2-dioxathiolane 2,2-dioxide, 1,3,2-dioxatiane 2,2-dioxide, and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane.

[0137] Specific examples of sulfite esters include 1,3-propanesultone, 1-propene-1,3-sultone, 1,4-butanesultone, 2,4-butanesultone, and propargyl methanesulfonic acid. Specific examples of sulfite esters include 1,3,2-dioxathiolane 2-oxide and 4-methyl-1,3,2-dioxathiolane 2-oxide.

[0138] Specific examples of dicarboxylic acid anhydrides include 1,4-dioxan-2,6-dione, succinic anhydride, and glutaric anhydride.

[0139] Specific examples of disulfonic anhydrides include 1,2-ethanedisulfonic anhydride, 1,3-propanedisulfonic anhydride, and hexafluoro1,3-propanedisulfonic anhydride.

[0140] Specific examples of sulfonic acid carboxylic acid anhydrides include 2-sulfobenzoic acid anhydride and 2,2-dioxoxathiolan-5-one.

[0141] (Nitrile compounds) Furthermore, the additive is a nitrile compound. This is because it improves the electrochemical stability of the electrolyte. As a result, the decomposition reaction of the electrolyte is further suppressed during the charging and discharging of the secondary battery, so the decrease in discharge capacity is further suppressed even after repeated charging and discharging, and the generation of gas caused by the decomposition reaction of the electrolyte is also suppressed.

[0142] These nitrile compounds are compounds having one or more cyano groups (-CN). Specific examples of nitrile compounds include octanenitrile, benzonitrile, phthalonitrile, succinonitrile, glutalonitrile, adiponitrile, sebaconitrile, 1,3,6-hexanetricarbonite, 3,3'-oxydipropionitrile, 3-butoxypropionitrile, ethylene glycol bispropionitrile ether, 1,2,2,3-tetracyanopropane, tetracyanopropane, fumaronitrile, 7,7,8,8-tetracyanoquinodimethane, cyclopentanecarbonite, 1,3,5-cyclohexanetricarbonite, and 1,3-bis(dicyanomethylidene)indan.

[0143] However, the cyanated cyclic carbonate esters mentioned above are excluded from the nitrile compounds described here.

[0144] <1-2. Manufacturing method> When preparing an electrolyte solution, an electrolyte salt is added to a solvent, and then a fluorine-containing compound is added to the solvent. This causes the electrolyte salt and the fluorine-containing compound to disperse or dissolve in the solvent, thus preparing the electrolyte solution.

[0145] <1-3. Mechanism and Effects> According to this electrolyte, it contains fluorine-containing compounds, and more specifically, it contains one or more of the 22 types of fluorine-containing compounds (fluorine-containing compounds 1 to 22) mentioned above.

[0146] In this case, unlike when the electrolyte does not contain fluorine-containing compounds or when the electrolyte contains other compounds, as described above, a good film derived from the fluorine-containing compound is formed on the electrode surface. As a result, the decomposition reaction of the electrolyte is suppressed during charging and discharging of the secondary battery using the electrolyte, and the decrease in discharge capacity is suppressed even when charging and discharging is repeated. Therefore, excellent cycle characteristics can be obtained in a secondary battery using an electrolyte.

[0147] The "other compounds" mentioned above are compounds that do not possess the structures of the first fluorine-containing compounds to the second fluorine-containing compounds, but have structures similar to them. Specifically, these include compounds represented by formulas (41-1) and (41-2), respectively.

[0148] [ka]

[0149] In particular, if the number of carbon atoms in each hydrocarbon group (alkyl group, alkenyl group, and alkynyl group) and oxygen-containing hydrocarbon group (alkoxy group) in formula (1), etc., is 3 or less, the solubility and compatibility of fluorine-containing compounds can be ensured, thus achieving a higher effect.

[0150] Furthermore, if the number of carbon atoms in the alkyl group in formula (1), etc., is 3 or less, the solubility and compatibility of the fluorine-containing compound are ensured, thus enabling a higher effect.

[0151] Furthermore, if the fluorine-containing compound content in the electrolyte is between 0.5% and 2.0% by weight, the decomposition reaction of the electrolyte is sufficiently suppressed, thus achieving a higher effect.

[0152] Furthermore, if the electrolyte contains one or more of the following: unsaturated cyclic carbonate esters, fluorinated cyclic carbonate esters, and cyanated cyclic carbonate esters, the decomposition reaction of the electrolyte is further suppressed, resulting in a higher effectiveness.

[0153] Furthermore, if the electrolyte contains one or more of the following: sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, and sulfonic acid carboxylic acid anhydrides, the decomposition reaction of the electrolyte is further suppressed, thus achieving a higher effect.

[0154] Furthermore, if the electrolyte contains nitrile compounds, the decomposition reaction of the electrolyte is further suppressed, and the generation of gases resulting from that decomposition reaction is also suppressed, thus achieving a higher effect.

[0155] <2. Secondary battery> Next, we will explain secondary batteries using the electrolyte described above.

[0156] The secondary battery described here is a secondary battery that obtains its capacity by utilizing the intercalation and deintercalation of electrode reactants, and is equipped with a positive electrode, a negative electrode, and an electrolyte, which is a liquid electrolyte.

[0157] In this secondary battery, the charging capacity of the negative electrode is greater than the discharging capacity of the positive electrode. In other words, the electrochemical capacity per unit area of ​​the negative electrode is set to be greater than the electrochemical capacity per unit area of ​​the positive electrode. This is to prevent the deposition of electrode reactants on the surface of the negative electrode during charging.

[0158] The types of electrode reactants are not particularly limited, but specifically, they are light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, while alkaline earth metals include beryllium, magnesium, and calcium.

[0159] In the following example, we will consider the case where lithium is the electrode reactant. A secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium is a so-called lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

[0160] <2-1. Structure> Figure 1 shows the cross-sectional configuration of a secondary battery, while Figure 2 shows the cross-sectional configuration of the battery element 20 shown in Figure 1. However, only a portion of the battery element 20 is shown in Figure 2.

[0161] As shown in Figures 1 and 2, this secondary battery mainly comprises a battery casing 11, a pair of insulating plates 12 and 13, a battery element 20, a positive electrode lead 25, and a negative electrode lead 26. The secondary battery described here is a cylindrical secondary battery in which the battery element 20 is housed inside a cylindrical battery casing 11.

[0162] [Battery cans, etc.] As shown in Figure 1, the battery casing 11 is a housing member that houses the battery elements 20 and the like. The battery casing 11 has a hollow structure with one end closed and the other end open, and contains one or more types of metal materials such as iron, aluminum, iron alloys, and aluminum alloys. The surface of the battery casing 11 may be plated with a metal material such as nickel.

[0163] The insulating plates 12 and 13 are arranged to face each other via the battery element 20. As a result, the battery element 20 is sandwiched between the insulating plates 12 and 13.

[0164] The open end of the battery can 11 is crimped with a battery cover 14, a safety valve mechanism 15, and a thermal resistance element (PTC element) 16 via a gasket 17. This seals the open end of the battery can 11 with the battery cover 14. The battery cover 14 contains the same material as the battery can 11. The safety valve mechanism 15 and the PTC element 16 are located inside the battery cover 14, with the safety valve mechanism 15 electrically connected to the battery cover 14 via the PTC element 16. The gasket 17 contains an insulating material, and its surface may be coated with asphalt or the like.

[0165] In this safety valve mechanism 15, if the internal pressure of the battery can 11 reaches a certain level due to an internal short circuit or overheating, the disk plate 15A inverts, thereby disconnecting the electrical connection between the battery cover 14 and the battery element 20. To prevent abnormal heat generation caused by high current, the electrical resistance of the PTC element 16 increases in proportion to the rise in temperature.

[0166] [Battery element] As shown in Figures 1 and 2, the battery element 20 is a power generation element that includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown).

[0167] This battery element 20 is a so-called wound electrode body. That is, in the battery element 20, the positive electrode 21 and the negative electrode 22 are stacked on top of each other via a separator 23, and the positive electrode 21, the negative electrode 22, and the separator 23 are wound together. As a result, the positive electrode 21 and the negative electrode 22 are wound facing each other via the separator 23. A center pin 24 is inserted into the winding center space 20S provided at the winding center of the battery element 20. However, the center pin 24 may be omitted.

[0168] (positive electrode) As shown in Figure 2, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B.

[0169] The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. This positive electrode current collector 21A contains a conductive material such as a metal material, a specific example of which is aluminum.

[0170] Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A and contains one or more types of positive electrode active materials capable of intercalating and deintercalating lithium. However, the positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A on the side where the positive electrode 21 faces the negative electrode 22. Furthermore, the positive electrode active material layer 21B may also contain one or more types of other materials such as a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically, it may be one or more types of methods such as coating.

[0171] The type of positive electrode active material is not particularly limited, but specifically, it is a lithium-containing compound. This lithium-containing compound is a compound that contains lithium along with one or more transition metal elements as constituent elements, and may further contain one or more other elements as constituent elements. The type of other element is not particularly limited as long as it is an element other than lithium and the transition metal elements, but specifically, it is an element belonging to groups 2 to 15 of the long-period periodic table. The type of lithium-containing compound is not particularly limited, but specifically, it is an oxide, a phosphoric acid compound, a silicate compound, and a borate compound.

[0172] Specific examples of oxides include LiNiO2, LiCoO2, and LiCo 0.98 Al 0.01 Mg 0.01 O2, LiLiLi 0.5 Co 0.2 Mn 0.3 Examples include O2 and LiMn2O4. Specific examples of phosphorylated compounds include LiFePO4, LiMnPO4, and LiFe 0.5 Mn 0.5 Examples include PO4.

[0173] The positive electrode binder contains one or more of the following: synthetic rubber and polymer compounds. Specific examples of synthetic rubber include styrene-butadiene rubber, fluorine-based rubber, and ethylene-propylenediene. Specific examples of polymer compounds include polyvinylidene fluoride, polyimide, and carboxymethylcellulose.

[0174] The positive electrode conductive agent contains one or more types of conductive materials, such as carbon materials. Specific examples of carbon materials include graphite, carbon black, acetylene black, and Ketjenblack. However, the conductive material may also be a metallic material or a polymer compound.

[0175] (Negative electrode) As shown in Figure 2, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B.

[0176] The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. This negative electrode current collector 22A contains a conductive material such as a metal material, and specific examples of the metal material include copper and the like.

[0177] Here, the negative electrode active material layer 22B is provided on both surfaces of the negative electrode current collector 22A, and contains any one or two or more kinds of negative electrode active materials capable of occluding and releasing lithium. However, the negative electrode active material layer 22B may be provided only on one side of the negative electrode current collector 22A on the side where the negative electrode 22 faces the positive electrode 21. Further, the negative electrode active material layer 22B may further contain any one or two or more kinds of other materials such as a negative electrode binder and a negative electrode conductive agent. The method for forming the negative electrode active material layer 22B is not particularly limited, but specifically, it is any one or two or more kinds of methods such as a coating method, a vapor phase method, a liquid phase method, a spraying method, and a firing method (sintering method).

[0178] The type of the negative electrode active material is not particularly limited, but specifically, it is one or both of a carbon material and a metal-based material, etc. This is because a high energy density can be obtained. Specific examples of the carbon material include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite). The metal-based material is a material containing any one or two or more kinds of metal elements and semi-metal elements capable of forming an alloy with lithium as constituent elements, and specific examples of the metal elements and semi-metal elements include one or both of silicon and tin. This metal-based material may be a single substance, an alloy, a compound, a mixture of two or more thereof, or a material containing two or more phases thereof. Specific examples of the metal-based material include TiSi2 and SiO x (0 < x ≤ 2, or 0.2 < x < 1.4), etc.

[0179] Details regarding each of the negative electrode binder and the negative electrode conductive agent are the same as those regarding each of the positive electrode binder and the positive electrode conductive agent.

[0180] (Separator) As shown in Figure 2, the separator 23 is an insulating porous membrane interposed between the positive electrode 21 and the negative electrode 22, allowing lithium ions to pass through while preventing contact (short circuit) between the positive electrode 21 and the negative electrode 22. This separator 23 contains a polymer compound such as polyethylene.

[0181] (electrolyte) The electrolyte is impregnated into the positive electrode 21, the negative electrode 22, and the separator 23, and has the configuration described above. That is, the electrolyte contains a fluorine-containing compound.

[0182] [Positive lead and negative lead] As shown in Figures 1 and 2, the positive electrode lead 25 is connected to the positive electrode current collector 21A of the positive electrode 21 and contains one or more conductive materials such as aluminum. This positive electrode lead 25 is electrically connected to the battery cover 14 via a safety valve mechanism 15.

[0183] As shown in Figures 1 and 2, the negative electrode lead 26 is connected to the negative electrode current collector 22A of the negative electrode 22 and contains one or more conductive materials such as nickel. This negative electrode lead 26 is electrically connected to the battery can 11.

[0184] <2-2. Operation> The secondary battery operates as follows:

[0185] During charging, lithium is released from the positive electrode 21 of the battery element 20, and this lithium is absorbed into the negative electrode 22 via the electrolyte. Conversely, during discharging, lithium is released from the negative electrode 22 of the battery element 20, and this lithium is absorbed into the positive electrode 21 via the electrolyte. During these charging and discharging processes, lithium is absorbed and released in an ionic state.

[0186] <2-3. Manufacturing method> When manufacturing a secondary battery, the positive electrode 21 and negative electrode 22 are prepared according to the procedure described below, and then the secondary battery is prepared using the positive electrode 21 and negative electrode 22 together with the electrolyte, after which the secondary battery is subjected to a stabilization treatment. The procedure for preparing the electrolyte is as described above.

[0187] [Fabrication of the positive electrode] First, a paste-like positive electrode mixture slurry is prepared by adding a mixture (positive electrode mixture) containing positive electrode active material, positive electrode binder, and positive electrode conductive agent to a solvent. The composition of the positive electrode mixture can be changed as desired. The solvent may be an aqueous solvent or an organic solvent. Next, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 21A to form a positive electrode active material layer 21B. After this, the positive electrode active material layer 21B may be compressed and molded using a roll press or the like. In this case, the positive electrode active material layer 21B may be heated, or the compression molding may be repeated multiple times. As a result, a positive electrode 21 is fabricated as positive electrode active material layers 21B are formed on both sides of the positive electrode current collector 21A.

[0188] [Fabrication of the negative electrode] The negative electrode 22 is formed using the same procedure as that used for the positive electrode 21 described above. Specifically, first, a paste-like negative electrode slurry is prepared by adding a mixture (negative electrode mixture) containing a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent to a solvent. The composition of the negative electrode mixture can be changed as desired. Next, the negative electrode slurry is applied to both sides of the negative electrode current collector 22A to form a negative electrode active material layer 22B. After this, the negative electrode active material layer 22B may be compression molded. As a result, the negative electrode 22 is fabricated by forming a negative electrode active material layer 22B on both sides of the negative electrode current collector 22A.

[0189] [Assembly of rechargeable batteries] First, the positive electrode lead 25 is connected to the positive electrode current collector 21A of the positive electrode 21 using a welding method or the like, and the negative electrode lead 26 is connected to the negative electrode current collector 22A of the negative electrode 22 using a welding method or the like. Next, the positive electrode 21 and the negative electrode 22 are stacked on top of each other via a separator 23, and then the positive electrode 21, the negative electrode 22 and the separator 23 are wound together to form a wound body (not shown) having a winding center space 20S. This wound body has the same configuration as the battery element 20, except that the positive electrode 21, the negative electrode 22 and the separator 23 are not impregnated with electrolyte. Next, a center pin 24 is inserted into the winding center space 20S of the wound body.

[0190] Next, with the wound body sandwiched between the insulating plates 12 and 13, the wound body is housed together with the insulating plates 12 and 13 inside the battery can 11, which has an open end. In this case, the positive electrode lead 25 is connected to the safety valve mechanism 15 using a welding method or the like, and the negative electrode lead 26 is connected to the battery can 11 using a welding method or the like. Subsequently, the electrolyte is injected into the inside of the battery can 11, thereby impregnating the wound body with the electrolyte. As a result, the positive electrode 21, the negative electrode 22, and the separator 23 are each impregnated with the electrolyte, and the battery element 20 is manufactured.

[0191] Finally, the battery cover 14, safety valve mechanism 15, and PTC element 16 are housed inside the battery can 11 which has an open end, and then the open end of the battery can 11 is crimped via the gasket 17. As a result, the battery cover 14, safety valve mechanism 15, and PTC element 16 are fixed to the open end of the battery can 11, and the battery element 20 is sealed inside the battery can 11, thus assembling the secondary battery.

[0192] [Stabilization of secondary batteries] The assembled secondary battery is charged and discharged. Various conditions such as ambient temperature, number of charge / discharge cycles, and charge / discharge conditions can be set arbitrarily. As a result, a coating is formed on the surfaces of the positive electrode 21 and the negative electrode 22, thereby electrochemically stabilizing the state of the secondary battery. In this case, as described above, a good coating derived from the fluorine-containing compound is formed. Thus, the secondary battery is completed.

[0193] <2-4. Action and Effects> This secondary battery is equipped with an electrolyte having the above-described configuration. In this case, for the reasons described above, the decomposition reaction of the electrolyte is suppressed during charging and discharging, so the decrease in discharge capacity is suppressed even when charging and discharging is repeated. Therefore, excellent cycle characteristics can be obtained.

[0194] In particular, if the secondary battery is a lithium-ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the intercalation and deintercalation of lithium, thus achieving a higher level of effectiveness.

[0195] Other functions and effects of this secondary battery are the same as those of the electrolyte described above.

[0196] <3. Variant> The configuration of the secondary battery described above can be modified as appropriate, as explained below. However, the series of modifications described below may be combined with each other.

[0197] [Example 1] The explanation described the case where the battery structure of a secondary battery is cylindrical. However, although not specifically illustrated here, the type of battery structure is not particularly limited, and may include laminate film type, rectangular type, coin type, button type, etc.

[0198] [Differentiation 2] A porous membrane separator 23 was used. However, although not specifically shown in the diagram, a laminated separator containing a polymer compound layer may also be used.

[0199] Specifically, the laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer provided on one or both sides of the porous membrane. This improves the adhesion of the separator to the positive electrode 21 and the negative electrode 22, thereby suppressing misalignment (winding misalignment) of the battery element 20. As a result, swelling of the secondary battery is suppressed even if decomposition reactions of the electrolyte occur. The polymer compound layer contains polymer compounds such as polyvinylidene fluoride. Polyvinylidene fluoride and similar compounds are chosen because they have excellent physical strength and are electrochemically stable.

[0200] Furthermore, one or both of the porous membrane and the polymer compound layer may contain one or more types of insulating particles. This is because the multiple insulating particles promote heat dissipation when the secondary battery generates heat, thereby improving the safety (heat resistance) of the secondary battery. The insulating particles include one or both of inorganic materials and resin materials. Specific examples of inorganic materials include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials include acrylic resin and styrene resin.

[0201] When fabricating a laminated separator, a precursor solution containing a polymer compound and a solvent is prepared, and then the precursor solution is applied to one or both sides of a porous membrane. In this case, if necessary, multiple insulating particles may be added to the precursor solution.

[0202] Even when using this stacked separator, lithium ions can move between the positive electrode 21 and the negative electrode 22, thus achieving a similar effect. In this case, as mentioned above, the safety of the secondary battery is improved, resulting in an even greater effect.

[0203] [Difference 3] A liquid electrolyte solution was used. However, although not specifically illustrated here, a gel-like electrolyte layer may also be used.

[0204] In the battery element 20 using an electrolyte layer, the positive electrode 21 and the negative electrode 22 are stacked on top of each other via a separator 23 and the electrolyte layer, and the positive electrode 21, negative electrode 22, separator 23, and electrolyte layer are wound together. This electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23.

[0205] Specifically, the electrolyte layer contains a polymer compound along with the electrolyte, and the electrolyte is held in place by the polymer compound. This prevents leakage of the electrolyte. The composition of the electrolyte is as described above. The polymer compound includes polyvinylidene fluoride, etc. When forming the electrolyte layer, a precursor solution containing the electrolyte, polymer compound, and solvent is prepared, and then the precursor solution is applied to one or both sides of the positive electrode 21 and the negative electrode 22, respectively.

[0206] Even when this electrolyte layer is used, lithium ions can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer, thus achieving a similar effect. In this case, in particular, as mentioned above, leakage of the electrolyte is prevented, resulting in an even greater effect.

[0207] <4. Applications of rechargeable batteries> The uses (application examples) of secondary batteries are not particularly limited. Secondary batteries used as power sources may be the primary power source or auxiliary power source for electronic devices and electric vehicles. A primary power source is a power source that is used preferentially regardless of the presence or absence of other power sources. An auxiliary power source is a power source used in place of the primary power source, or a power source that can be switched to from the primary power source.

[0208] Specific examples of the uses of secondary batteries are as follows. Electronic devices such as video cameras, digital still cameras, mobile phones, notebook personal computers, headphone stereos, portable radios, and portable information terminals. Storage devices such as backup power supplies and memory cards. Electric tools such as electric drills and electric saws. Battery packs mounted on electronic devices and the like. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles (including hybrid vehicles). Power storage systems such as household or industrial battery systems that store power for emergencies and the like. In these uses, one secondary battery may be used, or a plurality of secondary batteries may be used.

[0209] The battery pack may use a single cell or a battery module. An electric vehicle is a vehicle that operates (runs) using a secondary battery as a driving power source, and may be a hybrid vehicle that also has other driving sources in addition to the secondary battery. In a household power storage system, household electrical appliances and the like can be used using the power stored in the secondary battery, which is the power storage source.

[0210] Here, a specific example of an application example of a secondary battery will be described. The configuration of the application example described below is merely an example and can be changed as appropriate.

[0211] FIG. 3 shows the block configuration of a battery pack. The battery pack described here is a battery pack (so-called soft pack) using one secondary battery, and is mounted on an electronic device typified by a smartphone.

[0212] As shown in FIG. 3, this battery pack includes a power source 51 and a circuit board 52. This circuit board 52 is connected to the power source 51 and includes a positive electrode terminal 53, a negative electrode terminal 54, and a temperature detection terminal 55.

[0213] The power supply 51 includes one secondary battery. In this secondary battery, the positive electrode lead is connected to the positive electrode terminal 53, and the negative electrode lead is connected to the negative electrode terminal 54. Since this power supply 51 can be connected to the outside via the positive electrode terminal 53 and the negative electrode terminal 54, it can be charged and discharged. The circuit board 52 includes a control unit 56, a switch 57, a PTC element 58, and a temperature detection unit 59. However, the PTC element 58 may be omitted.

[0214] The control unit 56 includes a central processing unit (CPU), a memory, etc., and controls the operation of the entire battery pack. This control unit 56 detects and controls the usage state of the power supply 51 as necessary.

[0215] In addition, when the voltage of the power supply 51 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, the control unit 56 disconnects the switch 57 so that no charging current flows through the current path of the power supply 51. The overcharge detection voltage is not particularly limited, but specifically, it is 4.20V ± 0.05V, and the overdischarge detection voltage is not particularly limited, but specifically, it is 2.40V ± 0.1V.

[0216] The switch 57 includes a charge control switch, a discharge control switch, a charging diode, a discharging diode, etc., and switches the connection between the power supply 51 and an external device according to the instruction of the control unit 56. This switch 57 includes a metal oxide semiconductor field effect transistor (MOSFET), etc., and the charge and discharge current is detected based on the ON resistance of the switch 57.

[0217] The temperature detection unit 59 includes a temperature detection element such as a thermistor, measures the temperature of the power supply 51 using the temperature detection terminal 55, and outputs the measurement result of the temperature to the control unit 56. The measurement result of the temperature measured by the temperature detection unit 59 is used when the control unit 56 performs charge and discharge control during abnormal heat generation and when the control unit 56 performs correction processing during calculation of the remaining capacity.

Example

[0218] An example of this technology will be described below.

[0219] <Experimental Examples 1-1 to 1-27 and Comparative Examples 1 to 3> As explained below, after fabricating a secondary battery, its characteristics were evaluated.

[0220] [Manufacturing of secondary batteries] The cylindrical lithium-ion secondary battery shown in Figures 1 and 2 was fabricated using the following procedure.

[0221] (Fabrication of the positive electrode) First, 91 parts by mass of positive electrode active material (lithium cobaltate (LiCoO2)), a lithium-containing compound (oxide), 3 parts by mass of positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of positive electrode conductive agent (graphite) were mixed together to prepare a positive electrode mixture. Next, the positive electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the solvent was stirred to prepare a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was applied to both sides of the positive electrode current collector 21A (a strip of aluminum foil with a thickness of 12 μm) using a coating apparatus, and the positive electrode mixture slurry was dried to form a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B was compressed and molded using a roll press. This completed the production of the positive electrode 21.

[0222] (Fabrication of the negative electrode) First, a negative electrode mixture was prepared by mixing 93 parts by mass of negative electrode active material with 7 parts by mass of negative electrode binder (polyvinylidene fluoride). The negative electrode active material used was a mixture of 63 parts by mass of artificial graphite (a carbon material) and 30 parts by mass of silicon oxide (SiO2) (a metallic material). Next, the negative electrode mixture was added to a solvent (an organic solvent, N-methyl-2-pyrrolidone), and the solvent was stirred to prepare a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was applied to both sides of the negative electrode current collector 22A (a strip of copper foil with a thickness of 15 μm) using a coating apparatus, and the negative electrode mixture slurry was dried to form a negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B was compressed and molded using a roll press. This completed the production of the negative electrode 22.

[0223] (Preparation of electrolyte solution) An electrolyte salt (LiPF6, a lithium salt) was added to a solvent (ethylene carbonate, a cyclic carbonate ester, and dimethyl carbonate, a chain carbonate ester), and the solvent was then stirred. The solvent mixing ratio (by weight) was ethylene carbonate:dimethyl carbonate = 20:80, and the electrolyte salt content was 1.2 mol / kg relative to the solvent. Subsequently, a fluorine-containing compound was added to the solvent to which the electrolyte salt had been added, and the solvent was then stirred. The classification and types of fluorine-containing compounds are shown in Tables 1 and 2. This "classification" indicates whether the fluorine-containing compound is one of the 1st to 22nd fluorine-containing compounds. Thus, an electrolyte solution was prepared.

[0224] For comparison, electrolytes were prepared using the same procedure, except that fluorine-containing compounds were not used. Furthermore, electrolytes were prepared using the same procedure, except that other compounds (the compounds shown in formulas (41-1) and (41-2), respectively) were used instead of fluorine-containing compounds.

[0225] (Assembly of secondary batteries) First, an aluminum positive electrode lead 25 was welded to the positive electrode current collector 21A of the positive electrode 21, and a copper negative electrode lead 26 was welded to the negative electrode current collector 22A of the negative electrode 22.

[0226] Next, the positive electrode 21 and the negative electrode 22 were stacked on top of each other via a separator 23 (a microporous polyethylene film with a thickness of 15 μm), and then the positive electrode 21, the negative electrode 22, and the separator 23 were wound together to create a wound body having a winding center space 20S. Subsequently, a center pin 24 was inserted into the winding center space 20S of the wound body.

[0227] Next, insulating plates 12 and 13 were placed inside the battery can 11, which has an open end, along with the wound material. In this case, the positive electrode lead 25 was welded to the safety valve mechanism 15, and the negative electrode lead 26 was welded to the battery can 11. Subsequently, electrolyte was injected into the battery can 11. As a result, the wound material was impregnated with electrolyte, and the battery element 20 was fabricated.

[0228] Finally, the battery cover 14, safety valve mechanism 15, and PTC element 16 were housed inside the battery can 11, which has an open end, and then the open end of the battery can 11 was crimped via the gasket 17. As a result, the battery can 11 was sealed, and the secondary battery was assembled.

[0229] (Stabilization of secondary batteries) A secondary battery was charged and discharged for one cycle in a normal temperature environment (temperature = 23°C). During charging, constant current charging was performed at a current of 0.1C until the voltage reached 4.2V, and then constant voltage charging was performed at that voltage of 4.2V until the current reached 0.05C. During discharging, constant current discharge was performed at a current of 0.1C until the voltage reached 3.0V. 0.1C is the current value that completely discharges the battery capacity (theoretical capacity) in 10 hours, and 0.05C is the current value that completely discharges the battery capacity in 20 hours. This completed the secondary battery.

[0230] After the completion of the secondary battery, the results of measuring the content (weight %) of the fluorine-containing compound in the electrolyte by high-frequency inductively coupled plasma (ICP) emission spectroscopy are as shown in Tables 1 and 2.

[0231] [Characteristic Evaluation of Secondary Battery] When evaluating the cycle characteristics of the secondary battery, the results shown in Tables 1 and 2 were obtained.

[0232] When examining the cycle characteristics, first, the secondary battery was charged in a high-temperature environment (temperature = 50°C), and then the charged secondary battery was left standing (standing time = 3 hours) in the same environment. During charging, it was charged at a constant current with a current of 1C until the voltage reached 4.2V, and then charged at a constant voltage with that 4.2V voltage until the current reached 0.05C. 1C is the current value that can discharge the battery capacity in 1 hour.

[0233] Subsequently, the secondary battery was discharged in the same environment to measure the discharge capacity (discharge capacity of the first cycle). During discharge, it was discharged at a constant current with a current of 3C until the voltage reached 3.0V. 3C is the current value that can discharge the battery capacity in 10 / 3 hours.

[0234] Subsequently, the secondary battery was repeatedly charged and discharged in the same environment until the number of cycles reached 100 cycles to measure the discharge capacity (discharge capacity of the 100th cycle). The charge-discharge conditions after the second cycle were the same as those of the first cycle.

[0235] Finally, based on the calculation formula of capacity retention rate (%) = (discharge capacity of the 100th cycle / discharge capacity of the first cycle) × 100, the capacity retention rate, which is an index for evaluating cycle characteristics, was calculated.

[0236]

Table 1

[0237]

Table 2

[0238] [Consideration] As shown in Tables 1 and 2, when the electrolyte contained other compounds (Comparative Examples 2 and 3), the volume retention rate increased only slightly compared to when the electrolyte did not contain other compounds (Comparative Example 1).

[0239] In contrast, when the electrolyte contained a fluorine-containing compound (Examples 1-1 to 1-27), the volume retention rate increased significantly compared to when the electrolyte did not contain a fluorine-containing compound (Comparative Example 1).

[0240] In particular, when the electrolyte contained a fluorine-containing compound, the volume retention rate increased more when the fluorine-containing compound content in the electrolyte was between 0.5% and 2.0% by weight.

[0241] <Examples 2-1 to 2-6> As shown in Table 3, secondary batteries were fabricated using the same procedure as above, except that the electrolyte contained an additive (unsaturated cyclic carbonate ester, fluorinated cyclic carbonate ester, or cyanated cyclic carbonate ester). The characteristics (cycle characteristics) of these secondary batteries were then evaluated. The classification, type, and content (weight %) of the additives are shown in Table 3.

[0242] Specifically, vinylene carbonate (VC) was used as the unsaturated cyclic carbonate ester. Ethylene fluorocarbonate (FEC) was used as the fluorinated cyclic carbonate ester. Ethylene cyanocarbonate (CEC) was used as the cyanated cyclic carbonate ester.

[0243] [Table 3]

[0244] As shown in Table 3, when the electrolyte contained additives (unsaturated cyclic carbonate ester, fluorinated cyclic carbonate ester, or cyanated cyclic carbonate ester) (Examples 2-1 to 2-6), the volume retention rate was greater compared to when the electrolyte did not contain additives (Example 1-4).

[0245] <Examples 3-1 to 3-18> As shown in Table 4, secondary batteries were fabricated using the same procedure as above, except that the electrolyte contained additives (sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, or sulfonic acid carboxylic acid anhydrides), and then their characteristics (cycle characteristics) were evaluated. The classification, type, and content (weight %) of the additives are as shown in Table 4.

[0246] Specifically, the sulfonic acid esters used were 1,3-propanesultone (PS), 1-propene-1,3-sultone (PRS), 1,4-butanesultone (BS1), 2,4-butanesultone (BS2), and propargyl methanesulfonic acid ester (MSP).

[0247] As sulfate esters, 1,3,2-dioxathione 2,2-dioxide (OTO), 1,3,2-dioxatian 2,2-dioxide (OTA), and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathione (SOTO) were used.

[0248] As sulfite esters, 1,3,2-dioxathiolane 2-oxide (DTO) and 4-methyl-1,3,2-dioxathiolane 2-oxide (MDTO) were used.

[0249] As dicarboxylic acid anhydrides, 1,4-dioxan-2,6-dione (DOD), succinic anhydride (SA), and glutaric anhydride (GA) were used.

[0250] As disulfonic anhydrides, 1,2-ethanedisulfonic anhydride (ESA), 1,3-propanedisulfonic anhydride (PSA), and hexafluoro-1,3-propanedisulfonic anhydride (FPSA) were used.

[0251] As sulfonic acid carboxylic acid anhydrides, 2-sulfobenzoic acid anhydride (SBA) and 2,2-dioxoxathiolan-5-one (DOTO) were used.

[0252] [Table 4]

[0253] As shown in Table 4, when the electrolyte contained additives (sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, or sulfonic acid carboxylic acid anhydrides) (Examples 3-1 to 3-18), the volume retention rate was greater compared to when the electrolyte did not contain additives (Examples 1-4).

[0254] <Examples 4-1 to 4-18> As shown in Table 5, secondary batteries were fabricated using the same procedure as above, except that an additive (nitrile compound) was included in the electrolyte. The characteristics of these secondary batteries (cycle characteristics and safety) were then evaluated. The classification, type, and content (weight %) of the additives are as shown in Table 5.

[0255] Specifically, the nitrile compounds used were octanenitrile (ON), benzonitrile (BN), phthalonitrile (PN), succinonitrile (SN), glutalonitrile (GN), adiponitrile (AN), sebaconitrile (SBN), 1,3,6-hexanetricarbonite (HCN), 3,3'-oxydipropionitrile (OPN), 3-butoxypropionitrile (BPN), ethylene glycol bispropionitrile ether (EGPN), 1,2,2,3-tetracyanopropane (TCP), tetracyanoethylene (TCE), fumaronitrile (FN), 7,7,8,8-tetracyanoquinodimethane (TCQ), cyclopentanecarbonite (CPCN), 1,3,5-cyclohexanetricarbonite (CHCN), and 1,3-bis(dicyanomethylidene)indan (BCMI).

[0256] Here, as described above, in addition to cycle characteristics, safety was also evaluated as a characteristic of the secondary battery. To investigate safety, the secondary battery was stored in a high-temperature environment (temperature = 80°C), and the time until the safety valve mechanism 15 activated due to the rise in internal pressure of the battery case 11 (operating time) was measured. This operating time is an indicator for evaluating safety (gas generation characteristics) and is a parameter that represents the degree of gas generation suppression. In other words, the longer the operating time, the longer the time until the safety valve mechanism 15 activates, which means that the generation of gas caused by the decomposition reaction of the electrolyte inside the battery case 11 is suppressed.

[0257] In Table 5, the operating time values ​​are shown normalized by setting the operating time measured in Examples 1-4 to 1.0.

[0258] The increase in internal pressure of the battery case 11 indicates that a decomposition reaction of the electrolyte occurred inside the battery case 11, resulting in the generation of gas. Furthermore, the activation of the safety valve mechanism 15 indicates that the electrical connection between the battery cover 14 and the battery element 20 was disconnected.

[0259] [Table 5]

[0260] As shown in Table 5, when the electrolyte contained an additive (nitrile compound) (Examples 4-1 to 4-18), the operating time was extended while maintaining a nearly equivalently high volume retention rate compared to when the electrolyte did not contain an additive (Examples 1-4).

[0261] [summary] The results shown in Tables 1 to 5 indicate that a high capacity retention rate was obtained when the electrolyte contained a fluorine-containing compound. Therefore, excellent cycle characteristics were obtained in the secondary battery using the electrolyte.

[0262] Although the present technology has been described above with reference to one embodiment and one example, the configuration of the present technology is not limited to the configuration described in the one embodiment and one example, and can be modified in various ways.

[0263] Specifically, the case where the element structure of the battery element is of the wound type has been described. However, the element structure of the battery element is not particularly limited, and other element structures such as stacked type and zigzag type may also be used. In the stacked type, the positive electrode and negative electrode are stacked alternately with a separator in between, while in the zigzag type, the positive electrode and negative electrode are folded in a zigzag pattern facing each other with a separator in between.

[0264] Furthermore, while the case where the electrode reactant is lithium has been described, the electrode reactant is not particularly limited. Specifically, as mentioned above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0265] The effects described herein are illustrative only, and therefore the effects of this technology are not limited to those described herein. Accordingly, other effects may be obtained with respect to this technology.

Claims

1. Positive electrode and, The negative electrode and, Electrolyte containing a fluorine-containing compound and Equipped with, The fluorine-containing compound comprises a compound represented by formula (11) in a secondary battery. 【Chemistry 1】 (Each of R47 to R51 is one of hydrogen, fluorine, alkyl group, alkoxy group, and fluorinated alkyl group. At least one of R47 to R51 is a trifluoromethyl group. R52 is one of a hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). The hydrocarbon group is one of an alkenyl group and an alkynyl group. The fluorinated hydrocarbon group is a group in which at least one hydrogen of the hydrocarbon group is substituted with fluorine.) 【Chemistry 2】 (Each of R201 to R205 is either a hydrogen atom or a trifluoromethyl group. An asterisk (*) indicates an unbonded bond.) However, at least one of R201 to R205 is a trifluoromethyl group.

2. Positive electrode and, The negative electrode and, Electrolyte containing a fluorine-containing compound and Equipped with, The fluorine-containing compound comprises a compound represented by formula (12), wherein the secondary battery is a secondary battery. 【Transformation 3】 (Each of R53 to R62 is one of hydrogen, fluorine, alkyl group, alkoxy group, and fluorinated alkyl group.) However, at least one of R53 to R62 is a trifluoromethyl group. At least one of R53 to R62 is either an alkyl group or an alkoxy group.

3. The number of carbon atoms in each of the alkyl group, alkenyl group, alkynyl group, and alkoxy group is 3 or less. The secondary battery according to claim 1.

4. The fluorinated alkyl group is a group in which at least one hydrogen atom of the alkyl group is substituted with fluorine. The number of carbon atoms in the alkyl group is 3 or less. A secondary battery according to claim 1 or claim 2.

5. The content of the fluorine-containing compound in the electrolyte is 0.5% by weight or more and 2.0% by weight or less. A secondary battery according to claim 1 or claim 2.

6. The electrolyte further comprises at least one of unsaturated cyclic carbonate esters, fluorinated cyclic carbonate esters, and cyanated cyclic carbonate esters. A secondary battery according to claim 1 or claim 2.

7. The electrolyte further comprises at least one of sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, and sulfonic acid carboxylic acid anhydrides. A secondary battery according to claim 1 or claim 2.

8. The electrolyte further comprises a nitrile compound. A secondary battery according to claim 1 or claim 2.

9. Lithium-ion rechargeable batteries, A secondary battery according to claim 1 or claim 2.

10. Contains fluorine-containing compounds, The fluorine-containing compound is an electrolyte for a secondary battery, comprising a compound represented by formula (11). 【Chemistry 4】 (Each of R47 to R51 is one of hydrogen, fluorine, alkyl group, alkoxy group, and fluorinated alkyl group. At least one of R47 to R51 is a trifluoromethyl group. R52 is one of a hydrocarbon group, a fluorinated hydrocarbon group, and a fluorine-containing group represented by formula (30). The hydrocarbon group is one of an alkenyl group and an alkynyl group. The fluorinated hydrocarbon group is a group in which at least one hydrogen of the hydrocarbon group is substituted with fluorine.) 【Transformation 5】 (Each of R201 to R205 is either a hydrogen atom or a trifluoromethyl group. An asterisk (*) indicates an unbonded bond.) However, at least one of R201 to R205 is a trifluoromethyl group.

11. Contains fluorine-containing compounds, The fluorine-containing compound is an electrolyte for a secondary battery, comprising a compound represented by formula (12). 【Transformation 6】 (Each of R53 to R62 is one of hydrogen, fluorine, alkyl group, alkoxy group, and fluorinated alkyl group.) However, at least one of R53 to R62 is a trifluoromethyl group. At least one of R53 to R62 is either an alkyl group or an alkoxy group.

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