Electrolyte for secondary battery, and secondary battery

Abstract

A secondary battery is provided with a positive electrode, a negative electrode, and an electrolyte solution containing a thiazole-type compound. The thiazole-type compound contains a compound represented by formula (1) and / or a compound represented by formula (2).

Description

Technical Field

[0001] The present technology relates to an electrolyte for a secondary battery and a secondary battery. Background Art

[0002] As various electronic devices such as mobile phones become popular, secondary batteries are being developed as small, lightweight power sources with high energy density. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte (electrolyte for secondary batteries), and various studies have been conducted on the structure of the secondary battery.

[0003] Specifically, the electrolyte solution contains a benzotriazole derivative having a specific structure (for example, see Patent Documents 1 and 2). In addition, the electrolyte solution contains a benzothiazole derivative having a specific structure (for example, see Patent Documents 3 and 4).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2001-273927

[0007] Patent Document 2: Japanese Patent Application No. 2013-513923

[0008] Patent Document 3: Japanese Patent No. 6056721

[0009] Patent Document 4: International Publication No. 2019 / 181278 Pamphlet Summary of the invention

[0010] Various studies have been conducted on the structure of secondary batteries, but the battery characteristics of the secondary batteries are still insufficient and thus there is room for improvement.

[0011] There is a demand for an electrolyte solution for a secondary battery and a secondary battery that can provide excellent battery characteristics.

[0012] An electrolyte solution for a secondary battery according to an embodiment of the present technology includes an electrolyte of a thiazole-type compound including at least one of a compound represented by formula (1) and a compound represented by formula (2).

[0013] ,

[0014] (R1 to R15 are each hydrogen, fluorine, amino, silylalkyl, aminoalkyl, alkyl, cycloalkyl, aryl, alkoxy, alkylthio, fluorinated alkyl, fluorinated cycloalkyl, fluorinated aryl, fluorinated alkoxy, fluorinated alkylthio, and any one of monovalent bonding groups formed by two or more of these groups being bonded to each other.).

[0015] A secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode, and an electrolyte solution having the same structure as that of the electrolyte solution for a secondary battery according to an embodiment of the present technology described above.

[0016] According to a secondary battery electrolyte or a secondary battery according to an embodiment of the present technology, the secondary battery electrolyte contains a thiazole-type compound containing at least one of a compound represented by formula (1) and a compound represented by formula (2), so that excellent battery characteristics can be obtained.

[0017] It should be noted 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 It is a cross-sectional view showing the structure of a secondary battery in one embodiment of the present technology.

[0019] Figure 2 Yes means Figure 1 A cross-sectional view of the structure of a battery element is shown.

[0020] Figure 3 It is a block diagram showing the structure of an application example of a secondary battery. DETAILED DESCRIPTION

[0021] Hereinafter, one embodiment of the present technology will be described in detail with reference to the drawings. It should be noted that the order of the description is as follows.

[0022] 1. Electrolyte for secondary batteries

[0023] 1-1. Structure

[0024] 1-2. Manufacturing method

[0025] 1-3. Function and effect

[0026] 2. Secondary battery

[0027] 2-1. Structure

[0028] 2-2. Action

[0029] 2-3. Manufacturing method

[0030] 2-4. Actions and effects

[0031] 3. Modifications

[0032] 4. Uses of secondary batteries

[0033] <1. Electrolyte for secondary batteries>

[0034] First, an electrolyte solution for a secondary battery (hereinafter simply referred to as “electrolyte solution”) according to an embodiment of the present technology will be described.

[0035] <1-1. Structure>

[0036] The electrolyte described here is a liquid electrolyte used in a secondary battery as an electrochemical device. In addition, the electrolyte can also be used in other electrochemical devices other than secondary batteries. Specific examples of other electrochemical devices are primary batteries and capacitors.

[0037] [Thiazole type compounds]

[0038] The electrolyte solution contains any one or two or more of thiazole-type compounds. The thiazole-type compound is a compound containing a condensed ring formed by condensation of naphthalene and thiazole.

[0039] Specifically, the thiazole-type compound includes one or both of a compound represented by formula (1) and a compound represented by formula (2).

[0040] ,

[0041] (R1 to R15 are each hydrogen, fluorine, amino, silylalkyl, aminoalkyl, alkyl, cycloalkyl, aryl, alkoxy, alkylthio, fluorinated alkyl, fluorinated cycloalkyl, fluorinated aryl, fluorinated alkoxy, fluorinated alkylthio, and any one of monovalent bonding groups formed by two or more of these groups being bonded to each other.).

[0042] Hereinafter, the compound represented by formula (1) is referred to as a “first thiazole-type compound”, and the compound represented by formula (2) is referred to as a “second thiazole-type compound”.

[0043] As shown in formula (1), the first thiazole type compound is a compound including one fused ring. As shown in formula (2), the second thiazole type compound is a compound including two fused rings, and the two fused rings are indirectly bonded to each other via a disulfide bond (-SS-).

[0044] The electrolyte includes a thiazole compound because, when the secondary battery using the electrolyte is charged and discharged, a good coating derived from the thiazole compound is formed on the surface of the negative electrode. The coating has a dense film structure and is electrochemically stable. Thus, the surface of the negative electrode is electrochemically protected using the coating, so the decomposition reaction of the electrolyte on the negative electrode surface can be suppressed. Therefore, even if charging and discharging are repeated, the reduction of discharge capacity can be suppressed.

[0045] (structure)

[0046] R1 to R15 are not particularly limited as long as they are any of hydrogen (-H), fluorine (-F), amino (-NH2), silylalkyl, aminoalkyl, alkyl, cycloalkyl, aryl, alkoxy, alkylthio, fluorinated alkyl, fluorinated cycloalkyl, fluorinated aryl, fluorinated alkoxy, fluorinated alkylthio and bonding groups as described above.

[0047] The number of carbon atoms in the alkyl group is not particularly limited, and specific examples of the alkyl group include methyl, ethyl, propyl, and butyl groups. The alkyl group may be chain-like or branched.

[0048] The number of carbon atoms in the cycloalkyl group is not particularly limited. Specific examples of the cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl.

[0049] The number of carbon atoms in the aryl group is not particularly limited, and specific examples of the aryl group include phenylene and naphthylene.

[0050] The number of carbon atoms in the alkoxy group is not particularly limited, and specific examples of the alkoxy group include methoxy, ethoxy, and propoxy. The alkoxy group may be chain-like or branched.

[0051] The number of carbon atoms in the alkylthio group is not particularly limited, and specific examples of the alkylthio group include a methylthio group and an ethylthio group. It should be noted that, before confirmation, an alkylthio group is a group in which an oxygen atom in an alkoxy group is substituted with a sulfur atom.

[0052] The silylalkyl group is a group in which three hydrogen atoms in a silyl group (-SiH3) are replaced by an alkyl group. The details of the alkyl group are as described above. Specific examples of the silylalkyl group include trimethylsilyl and the like.

[0053] The aminoalkyl group is a group in which two hydrogen atoms in an amino group are replaced by an alkyl group. The details of the alkyl group are as described above. Specific examples of the aminoalkyl group include dimethylamino and the like.

[0054] A fluorinated alkyl group is a group in which one or more hydrogen atoms in an alkyl group are replaced by fluorine. A fluorinated cycloalkyl group is a group in which one or more hydrogen atoms in a cycloalkyl group are replaced by fluorine. A fluorinated aryl group is a group in which one or more hydrogen atoms in an aryl group are replaced by fluorine. A fluorinated alkoxy group is a group in which one or more hydrogen atoms in an alkoxy group are replaced by fluorine. A fluorinated alkylthio group is a group in which one or more hydrogen atoms in an alkylthio group are replaced by fluorine.

[0055] The bonding group is a monovalent group formed by mutually bonding two or more of hydrogen, fluorine, amino, silylalkyl, aminoalkyl, alkyl, cycloalkyl, aryl, alkoxy, alkylthio, fluorinated alkyl, fluorinated cycloalkyl, fluorinated aryl, fluorinated alkoxy, and fluorinated alkylthio. The type of the bonding group is not particularly limited, and specifically, it is a group formed by mutually bonding an alkyl and an amino group (a group formed by mutually bonding an alkylene group and an amino group), a group formed by mutually bonding an alkyl and a silylalkyl group (a group formed by mutually bonding an alkylene group and a silyl group), and a group formed by mutually bonding an alkyl and an aminoalkyl group (a group formed by mutually bonding an alkylene group and an aminoalkyl group).

[0056] (Specific example)

[0057] Specific examples of the thiazole type compound are described below.

[0058] Specific examples of the first thiazole-type compound include compounds represented by Formula (1-1) to Formula (1-31), and the like.

[0059]

[0060]

[0061]

[0062] Specific examples of the second thiazole-type compound include compounds represented by formulae (2-1) to (2-24), and the like.

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] (content)

[0069] The content of the thiazole compound in the electrolyte solution is not particularly limited, but is preferably 0.001% by weight to 5% by weight. This is because a sufficiently good film can be formed, and thus the decomposition reaction of the electrolyte solution can be sufficiently suppressed.

[0070] It should be noted that, when the electrolyte solution contains both the first thiazole type compound and the second thiazole type compound, the content of the thiazole type compound is the sum of the content of the first thiazole type compound and the content of the second thiazole type compound.

[0071] It should be noted that, when determining the content of the thiazole-type compound, the secondary battery is disassembled, the electrolyte is recovered, and then the electrolyte is analyzed to calculate the content of the thiazole-type compound. The analysis method of the electrolyte is not particularly limited, and specifically, it is any one or more of high-frequency inductively coupled plasma (ICP) emission spectrometry, nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS).

[0072] [Solvent]

[0073] It should be noted that the electrolyte solution may further contain a solvent. The solvent contains any one or two or more of non-aqueous solvents (organic solvents), and the electrolyte solution containing the non-aqueous solvent is a so-called non-aqueous electrolyte solution.

[0074] The non-aqueous solvent is an ester, an ether, or the like, and more specifically, a carbonate-based compound, a carboxylate-based compound, a lactone-based compound, or the like.

[0075] The carbonate-based compound is a cyclic carbonate, a chain carbonate, etc. Specific examples of the cyclic carbonate are ethylene carbonate and propylene carbonate, etc. Specific examples of the chain carbonate are dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc.

[0076] The carboxylate ester compound is a chain carboxylate, etc. Specific examples of the chain carboxylate are methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, ethyl trimethylacetate, methyl butyrate, ethyl butyrate, and the like.

[0077] The lactone compound is lactone, etc. Specific examples of lactone are γ-butyrolactone and γ-valerolactone.

[0078] It should be noted that the ether may also be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, and the like.

[0079] (Electrolyte Salt)

[0080] In addition, the electrolytic solution may further contain an electrolyte salt. The electrolyte salt is a light metal salt such as a lithium salt.

[0081] Specific examples of lithium salts are lithium hexafluorophosphate (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), lithium bis(oxalate)borate (LiB(C2O4)2), lithium difluorooxalatoborate (LiBF2(C2O4)), lithium difluorobis(oxalato)borate (LiPF2(C2O4)2), lithium tetrafluorooxalatophosphate (LiPF4(C2O4)), lithium monofluorophosphate (Li2PFO3) and lithium difluorophosphate (LiPF2O2).

[0082] The content of the electrolyte salt is not particularly limited, but is specifically 0.3 mol / kg to 3.0 mol / kg relative to the solvent, because high ion conductivity can be obtained.

[0083] (additive)

[0084] It should be noted that the electrolyte may further contain any one or two or more of the additives.

[0085] (Unsaturated cyclic carbonates, fluorinated cyclic carbonates, and cyanated cyclic carbonates)

[0086] Specifically, additive is any one or more than two of unsaturated cyclic carbonate, fluorinated cyclic carbonate and cyanided cyclic carbonate. This is because the electrochemical stability of the electrolyte can be improved. Thus, the decomposition reaction of the electrolyte can be further suppressed during the charge and discharge of the secondary battery, even if therefore repeated charge and discharge can further suppress the reduction of discharge capacity.

[0087] The unsaturated cyclic carbonate is a cyclic carbonate containing an unsaturated carbon bond (carbon-carbon double bond). The number of unsaturated carbon bonds is not particularly limited, and may be only one or may be two or more.

[0088] The unsaturated cyclic carbonate includes any one or two or more of a vinylene carbonate compound, a vinyl ethylene carbonate compound, and a methylene ethylene carbonate compound.

[0089] The vinylene carbonate compound is an unsaturated cyclic carbonate having a vinylene carbonate-type structure. Specific examples of the vinylene carbonate compound include vinylene carbonate (1,3-dioxol-2-one), methyl vinylene carbonate (4-methyl-1,3-dioxol-2-one), ethyl vinylene 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.

[0090] The vinyl ethylene carbonate-based compound is an unsaturated cyclic carbonate having a vinyl ethylene carbonate-type structure. Specific examples of the vinyl ethylene carbonate-based compound include vinyl ethylene carbonate (4-vinyl-1,3-dioxolane-2-one), 4-methyl-4-vinyl-1,3-dioxolane-2-one, 4-ethyl-4-vinyl-1,3-dioxolane-2-one, 4-n-propyl-4-vinyl-1,3-dioxolane-2-one, 5-methyl-4-vinyl-1,3-dioxolane-2-one, 4,4-divinyl-1,3-dioxolane-2-one, and 4,5-divinyl-1,3-dioxolane-2-one.

[0091] The methylene ethylene carbonate compound is an unsaturated cyclic carbonate having a methylene ethylene carbonate-type structure. Specific examples of the methylene ethylene carbonate compound are methylene ethylene carbonate (4-methylene-1,3-dioxolane-2-one), 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one, and 4,4-diethyl-5-methylene-1,3-dioxolane-2-one. Here, as the methylene ethylene carbonate compound, a compound having only one methylene group is exemplified, but the methylene ethylene carbonate compound may also have two or more methylene groups.

[0092] It should be noted that the cyclic carbonate containing an unsaturated carbon bond does not correspond to any of the fluorinated cyclic carbonate and the cyanated cyclic carbonate, but corresponds to an unsaturated cyclic carbonate.

[0093] Fluorinated cyclic carbonate is a cyclic carbonate containing fluorine as a constituent element. The number of fluorine is not particularly limited, and therefore can be only 1, or can be more than 2. That is, fluorinated cyclic carbonate is a compound in which one or more hydrogens in the cyclic carbonate are substituted with fluorine.

[0094] Specific examples of the fluorinated cyclic carbonate are fluoroethylene carbonate (4-fluoro-1,3-dioxolane-2-one) and difluoroethylene carbonate (4,5-difluoro-1,3-dioxolane-2-one).

[0095] It should be noted that the cyclic carbonate containing fluorine as a constituent element does not correspond to any of the unsaturated cyclic carbonate and the cyanated cyclic carbonate, but corresponds to the fluorinated cyclic carbonate.

[0096] Cyclic cyanide carbonate is a cyclic carbonate containing a cyano group. The number of cyano groups is not particularly limited, and therefore may be only one, or may be more than two. That is, cyclic cyanide carbonate is a compound in which one or more hydrogens in the cyclic carbonate are replaced by a cyano group.

[0097] Specific examples of the cyanated cyclic carbonate are ethylene cyanocarbonate (4-cyano-1,3-dioxolane-2-one) and ethylene dicyanocarbonate (4,5-dicyano-1,3-dioxolane-2-one).

[0098] It should be noted that the cyano group-containing cyclic carbonate does not correspond to any of the unsaturated cyclic carbonate and the fluorinated cyclic carbonate, but corresponds to the cyanated cyclic carbonate.

[0099] (sulfonates, sulfates, sulfites, dicarboxylic anhydrides, disulfonic anhydrides, sulfonic anhydrides and sulfobenzoic acid imides)

[0100] In addition, the additive is any one or more of sulfonic acid ester, sulfuric acid ester, sulfite, dicarboxylic anhydride, disulfonic anhydride, sulfonic acid carboxylic anhydride and sulfobenzoic acid imide. This is because the electrochemical stability of the electrolyte can be improved. Thus, the decomposition reaction of the electrolyte can be further suppressed during the charge and discharge of the secondary battery, so even if the charge and discharge are repeated, the reduction of the discharge capacity can be further suppressed.

[0101] Specific examples of the sulfonic acid esters are 1,3-propane sultone, 1-propylene-1,3-sultone, 1,4-butane sultone, 2,4-butane sultone, propargyl methanesulfonate, and the like.

[0102] Specific examples of the sulfuric acid ester include 1,3,2-dioxazolothiophene 2,2-dioxide, 1,3,2-dioxathiinane 2,2-dioxide, 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxazolothiophene, and the like.

[0103] Specific examples of the sulfite ester include 1,3-propane sultone, 1-propylene-1,3-sultone, 1,4-butane sultone, 2,4-butane sultone, propargyl methanesulfonate, etc. Specific examples of the sulfite ester include 1,3,2-dioxazolothiophene 2-oxide and 4-methyl-1,3,2-dioxazolothiophene 2-oxide, etc.

[0104] Specific examples of dicarboxylic anhydrides include 1,4-dioxane-2,6-dione, succinic anhydride, and glutaric anhydride.

[0105] Specific examples of the disulfonic anhydride include 1,2-ethanedisulfonic anhydride, 1,3-propanedisulfonic anhydride, hexafluoro1,3-propanedisulfonic anhydride, and the like.

[0106] Specific examples of the sulfonic acid anhydride are 2-sulfobenzoic anhydride and 2,2-dioxooxazolidin-5-one.

[0107] Specific examples of the sulfobenzoic acid imide are o-sulfonylbenzoimide and N-methylsaccharin, and the like.

[0108] (Nitrile compounds)

[0109] In addition, the additive is a nitrile compound. This is because the electrochemical stability of the electrolyte can be improved. Thus, the decomposition reaction of the electrolyte can be further suppressed during charge and discharge, so even if repeated charge and discharge, the reduction of the discharge capacity can be further suppressed. In this case, the generation of gas caused by the decomposition reaction of the electrolyte can also be suppressed.

[0110] The nitrile compound is a compound containing one or more cyano groups (-CN). Specific examples of the nitrile compound are octanonitrile, benzonitrile, phthalonitrile, succinonitrile, glutaronitrile, adiponitrile, sebaconitrile, 1,3,6-hexanetrinitrile, 3,3'-oxydipropionitrile, 3-butoxypropionitrile, ethylene glycol dipropionitrile ether, 1,2,2,3-tetracyanopropane, tetracyanopropane, fumaric acid nitrile, 7,7,8,8-tetracyanoquinodimethane, cyclopentanecarbonitrile, 1,3,5-cyclohexanetrinitrile, and 1,3-bis(dicyanomethylidene)indane.

[0111] In addition, the above-mentioned cyanated cyclic carbonate is removed from the nitrile compound described herein.

[0112] <1-2. Manufacturing method>

[0113] When the electrolytic solution is produced, an electrolyte salt is added to a solvent, and then the thiazole type compound is added to the solvent. Thus, the electrolyte salt and the thiazole type compound are dissolved or dispersed in the solvent, respectively, to prepare the electrolytic solution.

[0114] <1-3. Functions and effects>

[0115] According to the electrolyte, the electrolyte contains a thiazole type compound.

[0116] In this case, as described above, when the secondary battery using the electrolyte is charged and discharged, a good coating derived from the thiazole compound is formed on the surface of the negative electrode, so the coating is used to electrochemically protect the surface of the negative electrode. Thus, the decomposition reaction of the electrolyte on the surface of the negative electrode can be suppressed, so even if the charge and discharge are repeated, the reduction of the discharge capacity can be suppressed. Therefore, a secondary battery with excellent battery characteristics can be realized.

[0117] In particular, when the content of the thiazole compound in the electrolyte is 0.001 wt % to 5 wt %, a sufficiently good film can be formed. Therefore, the decomposition reaction of the electrolyte can be sufficiently suppressed, and thus a higher effect can be obtained.

[0118] In addition, when the electrolyte solution contains any one or two or more of unsaturated cyclic carbonate, fluorinated cyclic carbonate, and cyanated cyclic carbonate, the decomposition reaction of the electrolyte solution can be further suppressed, so that a higher effect can be obtained.

[0119] In addition, if the electrolyte solution contains any one or two or more of sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic anhydrides, and sulfobenzoic acid imides, the decomposition reaction of the electrolyte solution can be further suppressed, thereby achieving a higher effect.

[0120] <2. Secondary batteries>

[0121] Next, a secondary battery according to an embodiment of the present technology using the above-mentioned electrolytic solution will be described.

[0122] The secondary battery described here is a secondary battery that obtains battery capacity by intercalation and deintercalation of electrode reaction substances, and includes a positive electrode, a negative electrode, and an electrolyte solution.

[0123] The charge capacity of the negative electrode is preferably greater than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of ​​the negative electrode is preferably greater than the electrochemical capacity per unit area of ​​the positive electrode. This is to prevent the electrode reaction material from precipitating on the surface of the negative electrode during the charging process.

[0124] The type of electrode reaction material is not particularly limited, and specifically, it is a light metal such as an alkali metal and an alkaline earth metal. The alkali metal is lithium, sodium, and potassium, and the alkaline earth metal is beryllium, magnesium, and calcium.

[0125] In the following, the case where the electrode reaction material is lithium is taken as an example. A secondary battery that obtains battery capacity by inserting and extracting lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is inserted and extracted in an ionic state.

[0126] <2-1. Structure>

[0127] Figure 1 shows a cross-sectional structure of a secondary battery, and Figure 2 Shows Figure 1 The cross-sectional structure of the battery element 20 is shown.

[0128] like Figure 1 as well as Figure 2 As shown, the secondary battery mainly includes a battery can 11, a pair of insulating plates 12, 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 accommodated in the cylindrical battery can 11.

[0129] [Battery can]

[0130] like Figure 1 As shown, the battery can 11 is a storage component for storing battery elements 20 and the like. Since the battery can 11 has an open end and a closed end, it has a hollow structure. In addition, the battery can 11 includes any one or more of metal materials such as iron, aluminum, iron alloy, and aluminum alloy. It should be noted that the surface of the battery can 11 may also be plated with a metal material such as nickel.

[0131] The battery cover 14, the safety valve mechanism 15, and the thermistor element (PTC element) 16 are riveted to one open end of the battery can 11 via a gasket 17. Thus, the battery can 11 is sealed by the battery cover 14. Here, the battery cover 14 is made of the same material as the material of the battery can 11. The safety valve mechanism 15 and the PTC element 16 are respectively provided inside the battery cover 14, and the safety valve mechanism 15 is electrically connected to the battery cover 14 via the PTC element 16. The gasket 17 is made of an insulating material, and asphalt or the like may be applied to the surface of the gasket 17.

[0132] In the safety valve mechanism 15, when the internal pressure of the battery can 11 reaches a certain level or more due to internal short circuit, external heating, etc., the disc plate 15A turns over, thereby cutting off the electrical connection between the battery cover 14 and the battery element 20. In order to prevent abnormal heating caused by a large current, the resistance of the PTC element 16 increases as the temperature rises.

[0133] [Insulation board]

[0134] like Figure 1 As shown, the insulating plates 12 and 13 are arranged to face each other with the battery element 20 interposed therebetween. Thus, the battery element 20 is sandwiched between the insulating plates 12 and 13.

[0135] [Battery components]

[0136] like Figure 1 as well as Figure 2As shown, the battery element 20 is a power generation element including a positive electrode 21 , a negative electrode 22 , a separator 23 , and an electrolyte solution (not shown).

[0137] The battery element 20 is a so-called wound electrode body. That is, the positive electrode 21 and the negative electrode 22 are stacked on each other with the separator 23 interposed therebetween, and are wound so as to face each other with the separator 23 interposed therebetween. The center pin 24 is inserted into a space 20S provided at the winding center of the battery element 20. In addition, the center pin 24 may be omitted.

[0138] (positive electrode)

[0139] like Figure 2 As shown, the positive electrode 21 includes a positive electrode collector 21A and a positive electrode active material layer 21B.

[0140] The positive electrode current collector 21A has a pair of surfaces provided with a positive electrode active material layer 21B. The positive electrode current collector 21A is made of a conductive material such as a metal material, and a specific example of the conductive material is aluminum.

[0141] The positive electrode active material layer 21B includes any one or more of the positive electrode active materials that insert and remove lithium. In addition, the positive electrode active material layer 21B may further include any one or more 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, and specifically, it is a coating method or the like.

[0142] Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode collector 21A, so the positive electrode 21 includes two positive electrode active material layers 21B. Alternatively, the positive electrode active material layer 21B may be provided only on one side of the positive electrode collector 21A on the side of the positive electrode 21 facing the negative electrode 22, so the positive electrode 21 includes only one positive electrode active material layer 21B.

[0143] The type of positive electrode active material is not particularly limited, specifically, it is a lithium-containing compound, etc. The lithium-containing compound is a compound containing one or more transition metal elements as constituent elements together with lithium, and may further contain one or more other elements as constituent elements. The types of other elements are not particularly limited as long as they are elements other than lithium and transition metal elements, specifically, they are elements belonging to Groups 2 to 15 in the long-period periodic table. The type of lithium-containing compound is not particularly limited, specifically, it is an oxide, a phosphate compound, a silicate compound, a boric acid compound, etc.

[0144] Specific examples of oxides are LiNiO2, LiCoO2, LiCo 0.98 Al 0.01 Mg 0.01 O2、LiNi 0.5 Co0.2 Mn 0.3 O2 and LiMn2O4. Specific examples of phosphate compounds are LiFePO4, LiMnPO4 and LiFe 0.5 Mn 0.5 PO4, etc.

[0145] The positive electrode binder includes any one or more of materials such as synthetic rubber and polymer compounds. Specific examples of synthetic rubber are styrene-butadiene rubber, fluorine rubber, and EPDM rubber. Specific examples of polymer compounds are polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

[0146] The positive electrode conductive agent includes any one or two or more conductive materials such as carbon materials, metal materials, and conductive polymer compounds. Specific examples of the carbon material include graphite, carbon black, acetylene black, and Ketjen black.

[0147] (negative electrode)

[0148] like Figure 2 As shown, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B.

[0149] The negative electrode current collector 22A has a pair of surfaces provided with the negative electrode active material layer 22B. The negative electrode current collector 22A includes a conductive material such as a metal material, and a specific example of the conductive material is copper.

[0150] The negative electrode active material layer 22B contains any one or more of the negative electrode active materials that insert and release lithium. In addition, the negative electrode active material layer 22B may further contain any one or more 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, and specifically, it is any one or more of a coating method, a gas phase method, a liquid phase method, a thermal spraying method, and a sintering method (sintering method).

[0151] Here, since the negative electrode active material layer 22B is provided on both sides of the negative electrode collector 22A, the negative electrode 22 includes two negative electrode active material layers 22B. Alternatively, the negative electrode active material layer 22B may be provided only on one side of the negative electrode collector 22A on the side of the negative electrode 22 facing the positive electrode 21, so that the negative electrode 22 includes only one negative electrode active material layer 22B.

[0152] The type of negative electrode active material is not particularly limited, and specifically, it is a carbon material, a metal-based material, etc. This is because a high energy density can be obtained.

[0153] Specific examples of the carbon material include easily graphitizable carbon, hardly graphitizable carbon, and graphite (natural graphite and artificial graphite).

[0154] Metallic materials are materials containing any one or more of metal elements and semi-metal elements that can form alloys with lithium as constituent elements. Specific examples of the metal elements and semi-metal elements are silicon and tin. The metal material can be a monomer, an alloy, a compound, a mixture of two or more thereof, or a material containing two or more phases thereof. Specific examples of metal materials are TiSi2 and SiO x (0<x≤2, or 0.2<x<1.4), etc.

[0155] The "monomer" described here refers only to a general monomer, and therefore may contain trace impurities. That is, the purity of the monomer is not necessarily limited to 100%. In addition, the "alloy" described here includes not only materials containing two or more metal elements as constituent elements, but also materials containing one or more metal elements and one or more semi-metal elements as constituent elements. In addition, the "alloy" may also contain one or more non-metal elements as constituent elements.

[0156] Among them, the negative electrode material preferably contains a metal material, and more preferably contains a silicon-containing material. This is because a sufficiently high energy density can be obtained, and the decomposition reaction of the electrolyte can be fully suppressed by using a thiazole-type compound. The silicon-containing material is a material containing silicon as a constituent element. As described above, the silicon-containing material can be a single substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more thereof, or a material containing two or more phases thereof.

[0157] The alloy of silicon contains any one or two or more of metal elements such as tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium as constituent elements other than silicon. The compound of silicon contains any one or two or more of non-metal elements such as carbon and oxygen as constituent elements other than silicon. In addition, the compound of silicon may further contain any one or two or more of a series of metal elements described in relation to the alloy of silicon as constituent elements other than silicon.

[0158] Specific examples of silicon alloys include, in addition to the above-mentioned TiSi2, SiB4, SiB6, Mg2Si, Ni2Si, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, and SiC, etc. In addition, the composition of the silicon alloy (mixing ratio of silicon and metal elements) can be changed arbitrarily.

[0159] Specific examples of silicon compounds include the above-mentioned SiO xIn addition, there are Si3N4, Si2N2O and LiSiO.

[0160] In particular, the negative electrode active material preferably contains both a carbon material and a silicon-containing material, because during charge and discharge, the negative electrode active material layer 22B can be prevented from being damaged or falling off while maintaining the battery capacity.

[0161] In detail, the silicon-containing material as a metal-based material has the advantage of high theoretical capacity, but has the risk point of being prone to violent expansion and contraction during charging and discharging. On the other hand, the carbon material has the risk point of low theoretical capacity, but has the advantage of being difficult to expand and contract during charging and discharging. Therefore, by using carbon materials and silicon-containing materials in combination, it is possible to suppress the expansion and contraction of the negative electrode active material layer 22B during charging and discharging while obtaining a high theoretical capacity. Thus, as described above, it is possible to prevent the damage and shedding of the negative electrode active material layer 22B while ensuring the battery capacity.

[0162] The details about the negative electrode binder are the same as those about the positive electrode binder, and the details about the negative electrode conductor are the same as those about the positive electrode conductor.

[0163] (Diaphragm)

[0164] like Figure 2 As shown, the separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows lithium ions to pass therethrough while preventing contact (short circuit) between the positive electrode 21 and the negative electrode 22. The separator 23 is made of a polymer compound such as polyethylene.

[0165] (Electrolyte)

[0166] The electrolyte solution is impregnated in each of the positive electrode 21, the negative electrode 22, and the separator 23, and has the above-mentioned structure. That is, the electrolyte solution contains a thiazole type compound.

[0167] [Positive lead and negative lead]

[0168] like Figure 1 as well as Figure 2 As shown, the positive electrode lead 25 is connected to the positive electrode collector 21A of the positive electrode 21 and is made of a conductive material such as aluminum. The positive electrode lead 25 is electrically connected to the battery cover 14 via the safety valve mechanism 15 .

[0169] like Figure 1 as well as Figure 2 As shown, the negative electrode lead 26 is connected to the negative electrode current collector 22A of the negative electrode 22 and is made of a conductive material such as nickel. The negative electrode lead 26 is electrically connected to the battery can 11 .

[0170] <2-2. Action>

[0171] The secondary battery operates as follows during charge and discharge.

[0172] During charge, lithium is extracted from the positive electrode 21 in the battery element 20, and the lithium is inserted into the negative electrode 22 via the electrolyte. On the other hand, during discharge, lithium is extracted from the negative electrode 22 in the battery element 20, and the lithium is inserted into the positive electrode 21 via the electrolyte. During these charge and discharge, lithium is inserted and extracted in an ionic state.

[0173] <2-3. Manufacturing method>

[0174] When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are prepared by the following steps, and the secondary battery is assembled using the positive electrode 21, the negative electrode 22 and the electrolyte, and then the assembled secondary battery is stabilized. It should be noted that the steps for preparing the electrolyte are as described above.

[0175] [Production of positive electrode]

[0176] First, a positive electrode mixture is prepared by mixing a positive electrode active material, a positive electrode binder and a positive electrode conductive agent with each other. Next, a paste-like positive electrode mixture slurry is prepared by putting the positive electrode mixture into a solvent. The solvent can be an aqueous solvent or an organic solvent. Next, the positive electrode mixture slurry is applied on both sides of the positive electrode collector 21A to form a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B can be compression molded using a roller press or the like. In this case, the positive electrode active material layer 21B can be heated or compression molded repeatedly. Thus, a positive electrode active material layer 21B is formed on both sides of the positive electrode collector 21A, thereby making a positive electrode 21.

[0177] [Production of negative electrode]

[0178] The negative electrode 22 is formed by the same steps as the steps for making the positive electrode 21 described above. Specifically, first, a mixture (negative electrode mixture) in which a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent are mixed with each other is put into a solvent to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to both sides of the negative electrode collector 22A to form a negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B can be compression molded. Thus, the negative electrode active material layer 22B is formed on both sides of the negative electrode collector 22A, thereby manufacturing the negative electrode 22.

[0179] [Assembly of secondary battery]

[0180] First, the positive electrode lead 25 is connected to the positive electrode collector 21A of the positive electrode 21 by a joining method such as welding, and the negative electrode lead 26 is connected to the negative electrode collector 22A of the negative electrode 22 by a joining method such as welding. Next, the positive electrode 21 and the negative electrode 22 are stacked on each other with the separator 23 interposed therebetween, and then the positive electrode 21, the negative electrode 22 and the separator 23 are wound to produce a wound body (not shown) having a space 20S. The wound body has the same structure as the battery element 20 except that the positive electrode 21, the negative electrode 22 and the separator 23 are not impregnated with an electrolyte. Next, the center pin 24 is inserted into the space 20S of the wound body.

[0181] Next, the wound body and the insulating plates 12 and 13 are stored in the battery can 11 while the wound body is sandwiched by the insulating plates 12 and 13. In this case, the positive electrode lead 25 is connected to the safety valve mechanism 15 by a joining method such as welding, and the negative electrode lead 26 is connected to the battery can 11 by a joining method such as welding. Next, the electrolyte is injected into the battery can 11, thereby impregnating the wound body. Thus, the electrolyte is impregnated into each of the positive electrode 21, the negative electrode 22 and the separator 23, thereby manufacturing the battery element 20.

[0182] Finally, the battery cover 14, the safety valve mechanism 15, and the PTC element 16 are housed inside the battery can 11, and then the battery can 11 is caulked via the gasket 17. Thus, the battery cover 14, the safety valve mechanism 15, and the PTC element 16 are fixed to the battery can 11, and the battery element 20 is sealed inside the battery can 11, thereby assembling the secondary battery.

[0183] [Stabilization of secondary batteries]

[0184] The assembled secondary battery is charged and discharged. Various conditions such as the ambient temperature, the number of charge and discharge times (cycle number), and the charge and discharge conditions can be set arbitrarily. Thus, a coating is formed on the surface of each of the positive electrode 21 and the negative electrode 22, so that the state of the battery element 20 is electrochemically stabilized. Thus, the secondary battery is completed.

[0185] <2-4. Functions and effects>

[0186] According to the secondary battery, the electrolyte has the above-mentioned structure. In this case, due to the above-mentioned reasons, even if charging and discharging are repeated, the decomposition reaction of the electrolyte on the surface of the negative electrode 22 can be suppressed, so the reduction of the discharge capacity can be suppressed. Therefore, excellent battery characteristics can be obtained.

[0187] In particular, if the negative electrode 22 contains a silicon-containing material as a negative electrode active material, a sufficiently high energy density can be obtained, and the decomposition reaction of the electrolyte can be sufficiently suppressed by the thiazole type compound, so that a higher effect can be obtained.

[0188] Furthermore, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing insertion and extraction of lithium, and thus a higher effect can be obtained.

[0189] Other actions and effects of the secondary battery are the same as those of the above-mentioned electrolyte solution.

[0190] <3. Modifications>

[0191] As described below, the structure of the secondary battery described above can be modified as appropriate. In addition, any two or more of the series of modified examples described below can be combined with each other.

[0192] [Modification 1]

[0193] The case where the battery structure of the secondary battery is a cylindrical type has been described above, but although not specifically illustrated here, the type of battery structure is not particularly limited, and may be a laminated film type, a square type, a coin type, a button type, or the like.

[0194] [Modification 2]

[0195] The separator 23 which is a porous film is used. However, although not specifically shown here, a laminated separator including a polymer compound layer may also be used.

[0196] Specifically, the laminated separator includes a porous film having a pair of faces and a polymer compound layer disposed on one or both faces of the porous film. This is because the adhesion of the separator to each of the positive electrode 21 and the negative electrode 22 is improved, so the positional deviation (winding deviation) of the battery element 20 is suppressed. Thus, even if a decomposition reaction of the electrolyte occurs, the expansion of the secondary battery can be suppressed. The polymer compound layer includes a polymer compound such as polyvinylidene fluoride. This is because polymer compounds such as polyvinylidene fluoride have excellent physical strength and are electrochemically stable.

[0197] It should be noted that one or both of the porous film and the polymer compound layer may include any one or more of the plurality of insulating particles. This is because when the secondary battery generates heat, the plurality of insulating particles promote heat dissipation, thereby improving the safety (heat resistance) of the secondary battery. The plurality of insulating particles include one or both of an inorganic material and a resin material. Specific examples of inorganic materials are aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials are acrylic resins and styrene resins.

[0198] When a laminated separator is produced, 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, a plurality of insulating particles may be added to the precursor solution as required.

[0199] Even when the laminated separator is used, the same effect can be obtained because lithium can move between the positive electrode 21 and the negative electrode 22. In this case, the safety of the secondary battery is improved as described above, so a higher effect can be obtained.

[0200] [Variation 3]

[0201] An electrolyte solution is used as a liquid electrolyte. However, although not specifically shown here, an electrolyte layer as a gel electrolyte may also be used.

[0202] In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are stacked on each other via the separator 23 and the electrolyte layer, and the positive electrode 21, the negative electrode 22, the separator 23 and the electrolyte layer are wound. The electrolyte layer is interposed between the positive electrode 21 and the separator 23, and between the negative electrode 22 and the separator 23.

[0203] Specifically, the electrolyte layer includes an electrolyte and a polymer compound, and the electrolyte is maintained by the polymer compound. This is because leakage of the electrolyte can be prevented. The structure of the electrolyte is as described above. The polymer compound includes polyvinylidene fluoride, etc. In the case of forming the electrolyte layer, a precursor solution including an electrolyte, a polymer compound, and a solvent is prepared, and then the precursor solution is applied to one or both sides of each of the positive electrode 21 and the negative electrode 22.

[0204] Even when the electrolyte layer is used, lithium can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer, so the same effect can be obtained. In this case, in particular, as described above, since leakage of the electrolyte can be prevented, a higher effect can be obtained.

[0205] <3. Applications of secondary batteries>

[0206] The purpose (application example) of the secondary battery is not particularly limited. In electronic devices and electric vehicles, the secondary battery used as a power source can be a main power source or an auxiliary power source. The main power source is the power source that is used preferentially, regardless of the presence or absence of other power sources. The auxiliary power source can be a power source that is used instead of the main power source, or a power source that is switched from the main power source.

[0207] Specific examples of the uses of secondary batteries are as follows. Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, stereo headphones, portable radios, and portable information terminals. Storage devices such as backup power supplies and memory cards. Power tools such as electric drills and electric saws. Battery packs mounted on electronic devices, etc. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric vehicles (including hybrid vehicles). Power storage systems such as household or industrial battery systems that store electricity in advance in case of emergencies. In these uses, one secondary battery or multiple secondary batteries can be used.

[0208] The battery pack may use a single cell or a battery pack. An electric vehicle is a vehicle that uses a secondary battery as a driving power source to operate (drive), or it may be a hybrid vehicle that also has other driving sources besides the secondary battery. In a home power storage system, the power stored in the secondary battery as a power storage source can be used for home electrical products, etc.

[0209] Here, an example of application of the secondary battery will be described in detail. The configuration of the application example described below is just an example and can be modified as appropriate.

[0210] Figure 3 The module structure of the battery pack is shown. The battery pack described here is a battery pack using one secondary battery (so-called soft pack), and is mounted in electronic devices such as smartphones.

[0211] like Figure 3 As shown in FIG. 1 , the battery pack includes a power source 51 and a circuit board 52 . The 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 .

[0212] The power source 51 includes a secondary battery. In the secondary battery, the positive lead is connected to the positive terminal 53, and the negative lead is connected to the negative terminal 54. The power source 51 can be connected to the outside via the positive terminal 53 and the negative terminal 54, so it can be charged and discharged. The circuit substrate 52 includes a control unit 56, a switch 57, a PTC element 58 and a temperature detection unit 59. In addition, the PTC element 58 can also be omitted.

[0213] The control unit 56 includes a central processing unit (CPU) and a memory, etc., and controls the operation of the entire battery pack. The control unit 56 detects and controls the use state of the power source 51 as needed.

[0214] It should be noted that when the voltage of the power source 51 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, the control unit 56 cuts off the switch 57 to prevent the charging current from flowing through the current path of the power source 51. The overcharge detection voltage is not particularly limited, but is specifically 4.20V±0.05V, and the overdischarge detection voltage is not particularly limited, but is specifically 2.40V±0.1V.

[0215] The switch 57 includes a charge control switch, a discharge control switch, a charge diode, a discharge diode, etc., and switches the connection between the power supply 51 and the external device according to the instruction of the control unit 56. The switch 57 includes a field effect transistor (MOSFET) using a metal oxide semiconductor, etc., and the charge and discharge current is detected based on the on-resistance of the switch 57.

[0216] The temperature detection unit 59 includes a temperature detection element such as a thermistor. The temperature detection unit 59 uses the temperature detection terminal 55 to measure the temperature of the power supply 51, 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 when abnormal heat is generated, and when the control unit 56 performs correction processing when calculating the remaining capacity.

[0217] Example

[0218] Embodiments of the present technology will be described.

[0219] <Examples 1 to 25 and Comparative Examples 1 and 2>

[0220] As described below, after the secondary battery was manufactured, the battery characteristics of the secondary battery were evaluated.

[0221] [Manufacturing of Secondary Batteries]

[0222] Through the following steps, the Figure 1 as well as Figure 2 The cylindrical lithium-ion secondary battery shown.

[0223] (Production of positive electrode)

[0224] First, 94 parts by mass of a positive electrode active material (lithium cobalt oxide (LiCoO2) containing a lithium compound (oxide)), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 3 parts by mass of a positive electrode conductor (acetylene black) are mixed together to form a positive electrode mixture. Next, the positive electrode mixture is put into a solvent (N-methyl-2-pyrrolidone as an organic solvent), and then the solvent is stirred to prepare a paste-like positive electrode mixture slurry. Next, the positive electrode mixture slurry is applied to both sides of the positive electrode collector 21A (a strip-shaped aluminum foil with a thickness of 12 μm) using a coating device, and then the positive electrode mixture slurry is dried to form a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B is compression-molded using a roller press. Thus, the positive electrode 21 is produced.

[0225] (Production of negative electrode)

[0226] Here, two types of negative electrodes 22 were produced.

[0227] In the case of making the first negative electrode 22, first, 93 parts by mass of a negative electrode active material (63 parts by mass of artificial graphite as a carbon material and 30 parts by mass of silicon oxide as a metal material (silicon-containing material)) and 7 parts by mass of a negative electrode binder (polyvinylidene fluoride) are mixed with each other to form a negative electrode mixture. Next, the negative electrode mixture is put into a solvent (N-methyl-2-pyrrolidone as an organic solvent), and then the solvent is stirred to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to both sides of the negative electrode collector 22A (strip-shaped copper foil with a thickness of 15 μm) using a coating device, and then the negative electrode mixture slurry is dried to form a negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B is compression-molded using a roller press. Thus, the negative electrode 22 is made.

[0228] When preparing the second negative electrode 22 , the same steps as those for preparing the first negative electrode 22 were used except that 93 parts by mass of a negative electrode active material (artificial graphite as a carbon material) and 7 parts by mass of a negative electrode binder (polyvinylidene fluoride) were mixed with each other to obtain a negative electrode mixture.

[0229] (Preparation of electrolyte)

[0230] A solvent (ethylene carbonate as a cyclic carbonate and dimethyl carbonate as a chain carbonate) was prepared. The mixing ratio (weight ratio) of the solvent was ethylene carbonate: dimethyl carbonate = 20:80. Next, an electrolyte salt (LiPF6 as a lithium salt) was added to the solvent, and the solvent was stirred. The content of the electrolyte salt was 1.2 mol / kg relative to the solvent. Finally, a thiazole-type compound was added to the solvent to which the electrolyte salt was added, and the solvent was stirred. The classification and types of thiazole-type compounds are shown in Tables 1 and 2. Thus, an electrolyte solution was prepared.

[0231] For comparison, an electrolyte solution was prepared by the same procedure except that the thiazole-type compound was not used.

[0232] The meanings of the "classification" shown in Tables 1 and 2 are as follows: "First" means that the first thiazole type compound is used, and "Second" means that the second thiazole type compound is used.

[0233] (Assembly of secondary batteries)

[0234] First, the cathode lead 25 (aluminum foil) is welded to the cathode current collector 21A of the cathode 21 , and the anode lead 26 (copper foil) is welded to the anode current collector 22A of the anode 22 .

[0235] Next, the positive electrode 21 and the negative electrode 22 were stacked with the separator 23 (microporous polyethylene film with a thickness of 15 μm) interposed therebetween, and then the positive electrode 21, the negative electrode 22 and the separator 23 were wound to produce a wound body having a space 20S. Next, the center pin 24 was inserted into the space 20S of the wound body.

[0236] Next, the insulating plates 12 and 13 are housed together with the wound body in the battery can 11. In this case, the positive electrode lead 25 is welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to the battery can 11. Next, the electrolyte is injected into the battery can 11. Thus, the electrolyte is impregnated into the wound body, and the battery element 20 is manufactured.

[0237] Finally, the battery cover 14, the safety valve mechanism 15, and the PTC element 16 are housed in the battery can 11, and then the battery can 11 is caulked via the gasket 17. Thus, the battery can 11 is sealed, and the secondary battery is assembled.

[0238] (Stabilization of secondary batteries)

[0239] The secondary battery was charged and discharged for 1 cycle in a normal temperature environment (temperature = 23°C). When 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 the voltage of 4.2V until the current reached 0.05C. When discharging, constant current discharge was performed at a current of 0.1C until the voltage reached 3.0V. 0.1C refers to the current value that completely discharges the battery capacity (theoretical capacity) within 10 hours, and 0.05C refers to the current value that completely discharges the battery capacity within 20 hours.

[0240] Thus, since the coating is formed on the surface of each of the positive electrode 21 and the negative electrode 22, the state of the battery element 20 is electrochemically stabilized. Thus, the secondary battery is completed.

[0241] It should be noted that after the secondary battery was completed, the content (weight %) of the thiazole compound in the electrolyte was measured using ICP emission spectrometry. The results are shown in Tables 1 and 2.

[0242] [Evaluation of battery characteristics]

[0243] Cycle characteristics were evaluated as battery characteristics by the procedure described below, and the results shown in Tables 1 and 2 were obtained.

[0244] First, the secondary battery was charged in a high temperature environment (temperature = 50°C), and then the charged secondary battery was left to stand in the same environment (standing time = 5 hours). During charging, constant current charging was performed at a current of 1C until the voltage reached 4.2V, and then constant voltage charging was performed at the voltage of 4.2V until the current reached 0.05C. 1C refers to the current value that completely discharges the battery capacity within 1 hour.

[0245] Next, the secondary battery was discharged in the same environment to measure the discharge capacity (discharge capacity of the first cycle). During discharge, constant current discharge was performed at a current of 3C until the voltage reached 3.0 V. 3C is the current value that completely discharges the battery capacity in 1 / 3 hour.

[0246] Next, the secondary battery was repeatedly charged and discharged in the same environment until the number of cycles reached 100, and the discharge capacity (discharge capacity at the 100th cycle) was measured. The charge and discharge conditions after the second cycle were the same as those for the first cycle.

[0247] Finally, based on the calculation formula: capacity retention rate (%)=(discharge capacity at the 100th cycle / discharge capacity at the 1st cycle)×100, the capacity retention rate, which is an index for evaluating the cycle characteristics, was calculated.

[0248] [Table 1]

[0249]

[0250] [Table 2]

[0251]

[0252] [Investigation]

[0253] As shown in Tables 1 and 2, the capacity retention rate varies depending on the structure of the electrolyte solution.

[0254] Specifically, in the case where the electrolyte solution contained the thiazole-type compound (Examples 1 to 25), the capacity retention rate increased compared to the case where the electrolyte solution did not contain the thiazole-type compound (Comparative Examples 1 and 2).

[0255] In particular, when the electrolytic solution contained a thiazole-type compound, the tendency described below was obtained.

[0256] First, a high capacity maintenance rate is obtained regardless of the type of the thiazole-type compound (the first thiazole-type compound and the second thiazole-type compound).

[0257] Second, if the content of the thiazole-type compound in the electrolyte is 0.001 wt % to 5 wt %, the capacity retention rate is further increased.

[0258] Third, when the negative electrode active material includes a silicon-containing material, the capacity retention rate increases compared to when the negative electrode active material does not include a silicon-containing material (when the negative electrode active material includes a carbon material). Specifically, when the negative electrode active material does not include a silicon-containing material, the capacity retention rate increases by about 26%, whereas when the negative electrode active material includes a silicon-containing material, the capacity retention rate increases by about 66%.

[0259] <Examples 26 to 31>

[0260] A secondary battery was prepared by the same procedure as in Example 4, except that the electrolyte contained an additive (unsaturated cyclic carbonate, fluorinated cyclic carbonate, or cyanated cyclic carbonate) as shown in Table 3, and then the battery characteristics were evaluated. The classification, type, and content (weight %) of the additive are shown in Table 3.

[0261] Specifically, vinylene carbonate (VC) was used as the unsaturated cyclic carbonate, fluoroethylene carbonate (FEC) was used as the fluorinated cyclic carbonate, and cyanoethylene carbonate (CEC) was used as the cyanated cyclic carbonate.

[0262] [Table 3]

[0263]

[0264] As shown in Table 3, when the electrolyte solution contained an additive (unsaturated cyclic carbonate, fluorinated cyclic carbonate, or cyanated cyclic carbonate) (Examples 26 to 31), the capacity retention rate was further increased compared to the case where the electrolyte solution did not contain the additive (Example 4).

[0265] <Examples 32 to 51>

[0266] As shown in Tables 4 and 5, a secondary battery was produced by the same procedure as in Example 4 except that the electrolyte contained an additive (sulfonic acid ester, sulfuric acid ester, sulfurous acid ester, dicarboxylic acid anhydride, disulfonic acid anhydride, sulfonic acid carboxylic acid anhydride or sulfobenzoic acid imide), and then the battery characteristics were evaluated. The classification, type and content (weight %) of the additive are shown in Tables 4 and 5.

[0267] Specifically, as the sulfonic acid ester, 1,3-propane sultone (PS), 1-propylene-1,3-sultone (PRS), 1,4-butane sultone (BS1), 2,4-butane sultone (BS2), and propargyl methanesulfonate (MSP) were used.

[0268] As the sulfuric acid ester, 1,3,2-dioxazolothiophene 2,2-dioxide (OTO), 1,3,2-dioxathiinane 2,2-dioxide (OTA), and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxazolothiophene (SOTO) were used.

[0269] As the sulfite, 1,3,2-dioxazolothiophene 2-oxide (DTO) and 4-methyl-1,3,2-dioxazolothiophene 2-oxide (MDTO) were used.

[0270] As dicarboxylic anhydrides, 1,4-dioxane-2,6-dione (DOD), succinic anhydride (SA), and glutaric anhydride (GA) were used.

[0271] As the disulfonic anhydride, 1,2-ethanedisulfonic anhydride (ESA), 1,3-propanedisulfonic anhydride (PSA), and hexafluoro-1,3-propanedisulfonic anhydride (FPSA) were used.

[0272] As the sulfonic acid anhydride, 2-sulfobenzoic anhydride (SBA) and 2,2-dioxooxazolidin-5-one (DOTO) were used.

[0273] As the sulfobenzoic acid imide, o-sulfophthalimide (SBI) and N-methylsaccharin (NMS) were used.

[0274] [Table 4]

[0275]

[0276] [Table 5]

[0277]

[0278] As shown in Tables 4 and 5, when the electrolyte solution contains an additive (sulfonate, sulfate, sulfite, dicarboxylic anhydride, disulfonic anhydride, sulfonic acid carboxylic anhydride or sulfobenzoic acid imide) (Examples 32 to 51), the capacity retention rate is further increased compared to the case where the electrolyte solution does not contain the additive (Example 3).

[0279] [Summarize]

[0280] From the results shown in Tables 1 to 5, it can be seen that when the electrolyte contains the thiazole-type compound, a high capacity retention rate is obtained. Therefore, the cycle characteristics are improved, and thus excellent battery characteristics are obtained in the secondary battery.

[0281] As mentioned above, although the present technology has been described by taking one embodiment and one example, the structure of the present technology is not limited to the structure described in one embodiment and one example, and various modifications are possible.

[0282] Specifically, the case where the element structure of the battery element is a winding type is described. However, the element structure of the battery element is not particularly limited, and thus other element structures such as a stacking type and a repeatedly folded type may be used. In the stacking type, the positive electrode and the negative electrode are alternately stacked with a separator, and in the repeatedly folded type, the positive electrode and the negative electrode are folded into a Z shape with the separator interposed therebetween.

[0283] In addition, the case where the electrode reaction material is lithium is described, but the electrode reaction material is not particularly limited. Specifically, as described above, the electrode reaction material can be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium and calcium. In addition, the electrode reaction material can also be other light metals such as aluminum.

[0284] The effects described in this specification are merely examples, and therefore the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects can also be obtained with respect to the present technology.

[0285] It should be noted that the present technology can also adopt the following structures.

[0286] <1> A secondary battery comprising:

[0287] positive electrode;

[0288] a negative electrode; and

[0289] An electrolyte solution comprising a thiazole-type compound,

[0290] The thiazole-type compound includes at least one of a compound represented by formula (1) and a compound represented by formula (2).

[0291] ,

[0292] (R1 to R15 are each hydrogen, fluorine, amino, silylalkyl, aminoalkyl, alkyl, cycloalkyl, aryl, alkoxy, alkylthio, fluorinated alkyl, fluorinated cycloalkyl, fluorinated aryl, fluorinated alkoxy, fluorinated alkylthio, and any one of monovalent bonding groups formed by two or more of these groups being bonded to each other.).

[0293] <2> The secondary battery according to <1>,

[0294] The negative electrode comprises a negative electrode active material,

[0295] The negative electrode active material includes a silicon-containing material.

[0296] <3> The secondary battery according to <1> or <2>,

[0297] The content of the thiazole-type compound in the electrolyte is 0.001 wt % or more and 5 wt % or less.

[0298] <4> The secondary battery according to any one of <1> to <3>,

[0299] The electrolyte further comprises at least one of an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, and a cyanated cyclic carbonate.

[0300] <5> The secondary battery according to any one of <1> to <4>,

[0301] The electrolyte further comprises at least one of sulfonic acid esters, sulfates, sulfites, dicarboxylic anhydrides, disulfonic anhydrides, sulfonic acid carboxylic anhydrides, and sulfobenzoic acid imides.

[0302] <6> The secondary battery according to any one of <1> to <5>,

[0303] It is a lithium-ion secondary battery.

[0304] <7> An electrolyte for a secondary battery,

[0305] Contains thiazole-type compounds,

[0306] The thiazole-type compound includes at least one of a compound represented by formula (1) and a compound represented by formula (2).

[0307] ,

[0308] (R1 to R15 are each hydrogen, fluorine, amino, silylalkyl, aminoalkyl, alkyl, cycloalkyl, aryl, alkoxy, alkylthio, fluorinated alkyl, fluorinated cycloalkyl, fluorinated aryl, fluorinated alkoxy, fluorinated alkylthio, and any one of monovalent bonding groups formed by two or more of these groups being bonded to each other.).

Claims

1. A secondary battery comprising: positive electrode; a negative electrode; and An electrolyte solution comprising a thiazole-type compound, The thiazole compound includes at least one of a compound represented by formula (1) and a compound represented by formula (2), ， in, R1 to R15 are each hydrogen, fluorine, amino, silylalkyl, aminoalkyl, alkyl, cycloalkyl, aryl, alkoxy, alkylthio, fluorinated alkyl, fluorinated cycloalkyl, fluorinated aryl, fluorinated alkoxy, fluorinated alkylthio, and any one of monovalent bonding groups in which two or more thereof are bonded to each other.

2. The secondary battery according to claim 1, wherein The negative electrode comprises a negative electrode active material, The negative electrode active material includes a silicon-containing material.

3. The secondary battery according to claim 1 or 2, wherein: The content of the thiazole-type compound in the electrolyte is 0.001 wt % or more and 5 wt % or less.

4. The secondary battery according to any one of claims 1 to 3, wherein The electrolyte further comprises at least one of an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, and a cyanated cyclic carbonate.

5. The secondary battery according to any one of claims 1 to 4, wherein The electrolyte further comprises at least one of sulfonic acid esters, sulfates, sulfites, dicarboxylic anhydrides, disulfonic anhydrides, sulfonic acid carboxylic anhydrides, and sulfobenzoic acid imides.

6. The secondary battery according to any one of claims 1 to 5, wherein The secondary battery is a lithium ion secondary battery.

7. An electrolyte for a secondary battery, comprising a thiazole compound, The thiazole compound includes at least one of a compound represented by formula (1) and a compound represented by formula (2), ， in, R1 to R15 are each hydrogen, fluorine, amino, silylalkyl, aminoalkyl, alkyl, cycloalkyl, aryl, alkoxy, alkylthio, fluorinated alkyl, fluorinated cycloalkyl, fluorinated aryl, fluorinated alkoxy, fluorinated alkylthio, and any one of monovalent bonding groups in which two or more thereof are bonded to each other.

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