Secondary battery

Abstract

A secondary battery is provided with a positive electrode, a negative electrode containing a negative electrode active material, and an electrolyte solution containing a thiazole-type compound. The negative electrode active material includes a central part into which the electrode reaction material is inserted and removed, and a covering part which covers the surface of the central part and which contains, as a constituent element, at least one of nickel, iron, and copper. The thiazole-type compound includes at least one of a compound represented by formula (1), a compound represented by formula (2), a compound represented by formula (3), and a compound represented by formula (4).

Description

Technical Field

[0001] The present technology relates to a secondary battery. Background Art

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

[0003] Specifically, the electrolyte contains a benzotriazole derivative having a specific structure (see, for example, Patent Documents 1 and 2). In addition, the electrolyte contains a benzothiazole derivative having a specific structure (see, for example, 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 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 configuration of secondary batteries, but the battery characteristics of such secondary batteries are still insufficient and thus there is room for improvement.

[0011] A secondary battery having excellent battery characteristics is desired.

[0012] A secondary battery according to an embodiment of the present technology comprises a positive electrode, a negative electrode containing a negative electrode active material, and an electrolyte containing a thiazole-type compound. The negative electrode active material comprises a central portion in which an electrode reaction material is embedded and released and a covering portion covering the surface of the central portion, wherein the covering portion comprises at least one of nickel, iron, and copper as a constituent element. The thiazole-type compound comprises at least one of a compound represented by formula (1), a compound represented by formula (2), a compound represented by formula (3), and a compound represented by formula (4).

[0013] [Chemical formula 1]

[0014] Chemical formula 1

[0015]

[0016] (R1 to R28 are each hydrogen, fluorine, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, alkoxy, fluoroalkyl, fluoroalkenyl, fluoroalkynyl, fluorocycloalkyl, fluoroaryl, fluoroalkoxy, amino, carboxylate, and monovalent bonding groups of two or more of these groups bonded to each other.)

[0017] In addition, the details of each of the "carboxylate group" and the "monovalent bonding group" will be described later.

[0018] According to the secondary battery of one embodiment of the present technology, the negative electrode active material includes the core portion and the covering portion, the covering portion contains at least one of nickel, iron, and copper as a constituent element, and the electrolyte contains the thiazole type compound, so excellent battery characteristics can be obtained.

[0019] In addition, 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 below. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a cross-sectional view showing the structure of a secondary battery in one embodiment of the present technology.

[0021] Figure 2 It is shown Figure 1 A cross-sectional view showing the structure of a battery element.

[0022] Figure 3 It is a cross-sectional view schematically showing the structure of the negative electrode active material in an enlarged manner.

[0023] Figure 4 It is a block diagram showing the configuration of an application example of a secondary battery. DETAILED DESCRIPTION

[0024] Hereinafter, one embodiment of the present technology will be described with reference to the attached Figure 1 The order of description is as follows.

[0025] 1. Secondary battery

[0026] 1-1. Overall composition

[0027] 1-2. Detailed composition of electrolyte

[0028] 1-3. Action

[0029] 1-4. Manufacturing method

[0030] 1-5. Function and effect

[0031] 2. Modifications

[0032] 3. Uses of secondary batteries

[0033] <1. Secondary batteries>

[0034] First, a secondary battery according to an embodiment of the present technology will be described.

[0035] 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.

[0036] In this secondary battery, the charge capacity of the negative electrode is greater than the discharge capacity of the positive electrode. That is, 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 because the electrode reaction material is prevented from precipitating on the surface of the negative electrode during charging.

[0037] 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.

[0038] Hereinafter, 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.

[0039] <1-1. Overall structure>

[0040] 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. Figure 3 The cross-sectional structure of the negative electrode active material 220 which is the main part of the negative electrode 22 is schematically shown in an enlarged manner.

[0041] 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.

[0042] [Battery can]

[0043] like Figure 1 As shown, the battery can 11 is a storage component for storing the battery element 20 and the like. The battery can 11 has an open end and a closed other end, and thus has a hollow structure. In addition, the battery can 11 contains any one or more of metal materials such as iron, aluminum, iron alloy, and aluminum alloy. In addition, the surface of the battery can 11 may be plated with a metal material such as nickel.

[0044] The battery cover 14, the safety valve mechanism 15, and the thermistor element (PTC element) 16 are fastened to the 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.

[0045] In the safety valve mechanism 15, if the internal pressure of the battery can 11 reaches a certain level or above due to internal short circuit or external heating, the disc plate 15A turns over to cut 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.

[0046] [Insulation board]

[0047] 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.

[0048] [Battery components]

[0049] like Figure 1 as well as Figure 2 As 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).

[0050] 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 while facing each other with the separator 23 interposed therebetween. The center pin 24 is inserted into a winding center space 20S provided at the winding center of the battery element 20. However, the center pin 24 may be omitted.

[0051] (positive electrode)

[0052] like Figure 2 As shown, the positive electrode 21 includes a positive electrode collector 21A and a positive electrode active material layer 21B.

[0053] 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.

[0054] The positive electrode active material layer 21B contains any one or two or more of the positive electrode active materials that insert and release lithium. However, the positive electrode active material layer 21B may further contain any one or two 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.

[0055] 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. However, the positive electrode active material layer 21B may be provided only on one side of the positive electrode collector 21A on the side opposite to the negative electrode 22 of the positive electrode 21, so the positive electrode 21 includes only one positive electrode active material layer 21B.

[0056] The type of positive electrode active material is not particularly limited, and specifically, it is a lithium-containing compound, etc. The lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements, 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, and 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, and specifically, it is an oxide, a phosphate compound, a silicate compound, a boric acid compound, etc.

[0057] Specific examples of oxides are LiNiO2, LiCoO2, LiCo 0.98 Al 0.01 Mg 0.01 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2 and LiMn2O4. Specific examples of phosphate compounds are LiFePO4, LiMnPO4 and LiFe 0.5 Mn 0.5 PO4, etc.

[0058] 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.

[0059] The positive electrode conductive agent contains any one or two or more conductive materials such as carbon materials, and specific examples of the carbon materials are graphite, carbon black, acetylene black, and Ketjen black, etc. However, the conductive material may also be a metal material or a polymer compound.

[0060] In addition, as described later, the covering portion 222 in the negative electrode active material 220 includes a covering element as a constituent element, and the covering element includes any one or more of nickel, iron and copper. In the case where the supply source of the covering element is the positive electrode 21, the positive electrode active material layer 21B further includes a covering metal powder, and the covering metal powder may also include any one or more of nickel powder, iron powder and copper powder. The covering metal powder is a powdered metal material containing the covering element as a constituent element. The content of the covering metal powder in the positive electrode active material layer 21B is not particularly limited, and can therefore be set arbitrarily.

[0061] (negative electrode)

[0062] like Figure 2 As shown, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B.

[0063] The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. 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.

[0064] The negative electrode active material layer 22B contains any one or more of the negative electrode active materials that insert and release lithium. However, 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 spraying method, and a sintering method (sintering method).

[0065] Here, the negative electrode active material layer 22B is provided on both sides of the negative electrode collector 22A, so the negative electrode 22 includes two negative electrode active material layers 22B. However, 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 opposite to the positive electrode 21, so the negative electrode 22 includes only one negative electrode active material layer 22B.

[0066] More specifically, if Figure 3 As shown, the negative electrode active material layer 22B includes a plurality of granular negative electrode active materials (negative electrode active materials 220), and the negative electrode active material 220 includes a core portion 221 and a covering portion 222. Figure 3 In FIG. 1 , only one negative electrode active material 220 is shown.

[0067] The center portion 221 includes any one or more of the materials capable of inserting and removing lithium, and the materials are carbon materials and metal materials. This is because a high energy density can be obtained. Thus, the negative electrode material can include only carbon materials, only metal materials, or both carbon materials and metal materials.

[0068] Specific examples of the carbon material include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite).

[0069] 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.

[0070] Among them, the negative electrode material preferably includes a metal-based material, and the metal-based material preferably includes silicon as a constituent element, because a sufficiently high energy density can be obtained.

[0071] The details of the negative electrode binder are the same as those of the positive electrode binder, and the details of the negative electrode conductive agent are the same as those of the positive electrode conductive agent.

[0072] The covering portion 222 covers the surface of the central portion 221. However, the covering portion 222 may cover the entire surface of the central portion 221, or may cover only a portion of the surface of the central portion 221. In the latter case, a plurality of covering portions 222 may cover the surface of the central portion 221 at a plurality of locations separated from each other.

[0073] As described later, the cover 222 is formed by performing a stabilization treatment on the assembled secondary battery in the manufacturing process of the secondary battery. The stabilization treatment is the so-called initial charge and discharge treatment, which is performed to electrochemically stabilize the state of the assembled secondary battery. As described later, the conditions of the stabilization treatment can be set arbitrarily. That is, the number of charge and discharge in the stabilization treatment is not limited to one time, and can also be two or more times.

[0074] In the stabilization treatment, the cover 222 is formed to cover the surface of the reactive center 221, so the reactivity of the surface of the center 221 is reduced by the cover 222. As a result, the reactivity of the surface of the negative electrode active material 220 is reduced, thereby suppressing the decomposition reaction of the electrolyte on the surface of the negative electrode active material 220. Therefore, during subsequent charge and discharge, the decomposition reaction of the electrolyte is also suppressed, so the state of the secondary battery is electrochemically stabilized.

[0075] In addition, during the stabilization treatment, the coating 222 may be formed not only on the surface of the core 221 but also on the surface of the positive electrode active material. This is because the decomposition reaction of the electrolyte on the surface of the positive electrode active material is also suppressed.

[0076] In particular, as described above, the covering portion 222 includes a covering element as a constituent element, and the covering element includes any one or more of nickel, iron, and copper. The state of the covering element in the covering portion 222 is not particularly limited, and thus it may be a monomer, a compound, an alloy, or two or more thereof. However, a monomer may also contain any amount of impurities, and therefore the purity of the monomer is not necessarily limited to 100%.

[0077] The reason why the covering part 222 contains the covering element as a constituent element is that the physical strength of the covering part 222 is improved, and therefore the covering part 222 is easily maintained even if charge and discharge are repeated. Thus, even if charge and discharge are repeated, the decomposition reaction of the electrolyte is suppressed, thereby suppressing the reduction of the discharge capacity.

[0078] In addition, the method of making the covering part 222 contain the covering element as a constituent element, in other words, the supply source of the covering element is not particularly limited. In addition, the details of the supply source of the covering element will be described later.

[0079] (Diaphragm)

[0080] 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.

[0081] (Electrolyte)

[0082] The electrolyte is a liquid electrolyte. The electrolyte is impregnated in each of the positive electrode 21, the negative electrode 22, and the separator 23, and contains a thiazole-type compound. The detailed structure of the electrolyte will be described later.

[0083] [Positive lead and negative lead]

[0084] 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 .

[0085] like Figure 1 as well as Figure 2As 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 .

[0086] <1-2. Detailed composition of electrolyte>

[0087] The details of the composition of the electrolyte solution are as follows.

[0088] [Thiazole type compounds]

[0089] As described above, the electrolyte solution contains one or more of the thiazole type compounds. The thiazole type compound is a compound having a thiazole type structure, and is a so-called thiazole derivative.

[0090] Specifically, the thiazole-type compound includes any one or two or more of a compound represented by formula (1), a compound represented by formula (2), a compound represented by formula (3), and a compound represented by formula (4).

[0091] Hereinafter, the compound represented by formula (1) is referred to as a “first thiazole-type compound”, the compound represented by formula (2) is referred to as a “second thiazole-type compound”, the compound represented by formula (3) is referred to as a “third thiazole-type compound”, and the compound represented by formula (4) is referred to as a “fourth thiazole-type compound”.

[0092] [Chemical formula 2]

[0093] Chemical formula 2

[0094]

[0095] (R1 to R28 are each hydrogen, fluorine, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, alkoxy, fluoroalkyl, fluoroalkenyl, fluoroalkynyl, fluorocycloalkyl, fluoroaryl, fluoroalkoxy, amino, carboxylate, and monovalent bonding groups of two or more of these groups bonded to each other.)

[0096] As shown in formula (1), the first thiazole type compound is a compound containing one benzene ring. As shown in formula (2), the second thiazole type compound is a compound containing two benzene rings. As shown in formula (3), the third thiazole type compound is a compound in which two first thiazole type compounds are indirectly bonded to each other via a disulfide bond (-SS-). As shown in formula (4), the fourth thiazole type compound is a compound in which two first thiazole type compounds are directly bonded to each other and the carbon-carbon double bond in each of the two thiazole rings disappears.

[0097] The electrolyte contains the thiazole type compound because the physical strength of the cover 222 is significantly improved by the synergistic effect of the cover element contained as a constituent element in the cover 222 and the thiazole type compound, so that even if charge and discharge are repeated, it is easy to maintain the cover 222. Therefore, even if charge and discharge are repeated, the decomposition reaction of the electrolyte is suppressed, thereby suppressing the reduction of the discharge capacity.

[0098] (constitute)

[0099] As described above, R1 to R28 are not particularly limited as long as they are each hydrogen (-H), fluorine (-F), alkyl, alkenyl, alkynyl, cycloalkyl, aryl, alkoxy, fluoroalkyl, fluoroalkenyl, fluoroalkynyl, fluorocycloalkyl, fluoroaryl, fluoroalkoxy, amino (-NH2), carboxylate, and monovalent bonding groups.

[0100] The number of carbon atoms in the alkyl group is not particularly limited, and specific examples of the alkyl group include methyl, ethyl, and propyl groups, etc. The alkyl group may be chain-shaped or branched.

[0101] The number of carbon atoms in the alkenyl group is not particularly limited, and specific examples of the alkenyl group include vinyl and allyl groups, etc. The alkenyl group may be chain-shaped or branched.

[0102] The number of carbon atoms in the alkynyl group is not particularly limited, and specific examples of the alkynyl group include ethynyl and propargyl, etc. The alkenyl group may be chain-shaped or branched.

[0103] 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.

[0104] The number of carbon atoms in the aryl group is not particularly limited, and specific examples of the aryl group include a phenylene group and a naphthylene group.

[0105] 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, etc. The alkoxy group may be chain-shaped or branched.

[0106] A fluoroalkyl group is a group in which one or more hydrogen atoms contained in an alkyl group are replaced by fluorine. A fluoroalkenyl group is a group in which one or more hydrogen atoms contained in an alkenyl group are replaced by fluorine. A fluoroalkynyl group is a group in which one or more hydrogen atoms contained in an alkynyl group are replaced by fluorine. A fluorocycloalkyl group is a group in which one or more hydrogen atoms contained in a cycloalkyl group are replaced by fluorine. A fluoroaryl group is a group in which one or more hydrogen atoms contained in an aryl group are replaced by fluorine. A fluoroalkoxy group is a group in which one or more hydrogen atoms contained in an alkoxy group are replaced by fluorine.

[0107] The carboxylate group is a group represented by -C(=O)-O-R30 (R30 is an alkyl group), and the details of the alkyl group are as described above. Specific examples of the carboxylate group are methyl carboxylate group (-C(=O)-O-CH3) and ethyl carboxylate group (-C(=O)-O-C2H5).

[0108] The type of the monovalent bonding group is not particularly limited. Specific examples of the monovalent bonding group include a group in which an alkyl group and a carboxylate group are bonded to each other (a group in which an alkylene group and a carboxylate group are bonded to each other), and more specifically, -CH2-C(=O)-O-CH3.

[0109] (Specific example)

[0110] Specific examples of the thiazole type compound are described below.

[0111] Specific examples of the first thiazole-type compound include compounds represented by Formula (1-1) to Formula (1-27).

[0112] [Chemical formula 3]

[0113] Chemical formula 3

[0114]

[0115] [Chemical formula 4]

[0116] Chemical formula 4

[0117]

[0118] Specific examples of the second thiazole-type compound include compounds represented by Formula (2-1) to Formula (2-31), and the like.

[0119] [Chemical formula 5]

[0120] Chemical formula 5

[0121]

[0122] [Chemical formula 6]

[0123] Chemical formula 6

[0124]

[0125] [Chemical formula 7]

[0126] Chemical formula 7

[0127]

[0128] Specific examples of the third thiazole-type compound include compounds represented by Formula (3-1) to Formula (3-24), and the like.

[0129] [Chemical formula 8]

[0130] Chemical formula 8

[0131]

[0132] [Chemical formula 9]

[0133] Chemical formula 9

[0134]

[0135] [Chemical formula 10]

[0136] Chemical formula 10

[0137]

[0138] [Chemical formula 11]

[0139] Chemical formula 11

[0140]

[0141] [Chemical formula 12]

[0142] Chemical formula 12

[0143]

[0144] Specific examples of the fourth thiazole-type compound include compounds represented by Formula (4-1) to Formula (4-9), and the like.

[0145] [Chemical formula 13]

[0146] Chemical formula 13

[0147]

[0148] [Chemical formula 14]

[0149] Chemical formula 14

[0150]

[0151] (content)

[0152] 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 the physical strength of the coating 222 is sufficiently increased, and thus the decomposition reaction of the electrolyte solution is sufficiently suppressed.

[0153] When the electrolyte solution contains both the first thiazole type compound and the second thiazole type compound, the content of the thiazole type compound in the electrolyte solution is the sum of the content of the first thiazole type compound in the electrolyte solution and the content of the second thiazole type compound in the electrolyte solution.

[0154] In addition, when the content of the thiazole-type compound is measured, the secondary battery is disassembled, the electrolyte is recovered, and 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, 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) are used.

[0155] [Solvent]

[0156] In addition, 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] The lactone compound is lactone, etc. Specific examples of lactone are γ-butyrolactone and γ-valerolactone.

[0161] In addition, the ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, and the like.

[0162] (Electrolyte Salt)

[0163] In addition, the electrolytic solution may further contain an electrolyte salt. The electrolyte salt is a light metal salt such as a lithium salt.

[0164] 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)methylide (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).

[0165] 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.

[0166] (additive)

[0167] In addition, the electrolyte solution may further contain any one or two or more of the additives.

[0168] (Unsaturated cyclic carbonates, fluorinated cyclic carbonates and cyanated cyclic carbonates)

[0169] Specifically, additive is any one or more than two of unsaturated cyclic carbonate, fluorinated cyclic carbonate and cyanide cyclic carbonate. This is because the electrochemical stability of electrolyte improves. Thus, further suppressing the decomposition reaction of electrolyte during the charge and discharge of secondary battery, even if therefore repeatedly carrying out charge and discharge, also further suppressing the reduction of discharge capacity.

[0170] 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.

[0171] 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.

[0172] Vinylene carbonate compounds are unsaturated cyclic carbonates having a vinylene carbonate type structure. Specific examples of vinylene carbonate compounds 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.

[0173] 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.

[0174] Methylene ethylene carbonate compounds are unsaturated cyclic carbonates having a methylene ethylene carbonate type structure. Specific examples of methylene ethylene carbonate compounds 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 methylene ethylene carbonate compounds, compounds having only one methylene group are exemplified, but the methylene ethylene carbonate compounds may also have two or more methylene groups.

[0175] In addition, 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 the unsaturated cyclic carbonate.

[0176] Fluorinated cyclic carbonate is a cyclic carbonate comprising fluorine as a constituent element. The quantity of fluorine is not particularly limited, and therefore can be only one, or can be more than two. That is, fluorinated cyclic carbonate is a compound in which one or more hydrogens in the cyclic carbonate are substituted by fluorine.

[0177] Specific examples of the fluorinated cyclic carbonate include fluoroethylene carbonate (4-fluoro-1,3-dioxolane-2-one) and difluoroethylene carbonate (4,5-difluoro-1,3-dioxolane-2-one).

[0178] In addition, the cyclic carbonate containing fluorine as a constituent element corresponds to neither the unsaturated cyclic carbonate nor the cyanated cyclic carbonate, but corresponds to the fluorinated cyclic carbonate.

[0179] Cyclic cyanide carbonate is a cyclic carbonate containing a cyano group. The number of cyano groups is not particularly limited, so it can be only one, or it can be more than two. That is, cyanide cyclic carbonate is a compound in which one or more hydrogens in the cyclic carbonate are replaced by a cyano group.

[0180] Specific examples of the cyanated cyclic carbonate include ethylene cyanocarbonate (4-cyano-1,3-dioxolane-2-one) and ethylene dicyanocarbonate (4,5-dicyano-1,3-dioxolane-2-one).

[0181] In addition, the cyclic carbonate containing a cyano group does not correspond to any of the unsaturated cyclic carbonate and the fluorinated cyclic carbonate, but corresponds to the cyanated cyclic carbonate.

[0182] (sulfonates, sulfates, sulfites, dicarboxylic anhydrides, disulfonic anhydrides, sulfonic anhydrides and sulfonylbenzamides)

[0183] In addition, the additive is any one or more of sulfonic acid ester, sulfuric acid ester, sulfite, dicarboxylic acid anhydride, disulfonic acid anhydride, sulfonic acid carboxylic acid anhydride and sulfonylbenzimide. This is because the electrochemical stability of the electrolyte is improved. As a result, the decomposition reaction of the electrolyte is further suppressed during the charge and discharge of the secondary battery, and even if the charge and discharge are repeated, the reduction of the discharge capacity is further suppressed.

[0184] Specific examples of the sulfonic acid ester include 1,3-propane sultone, 1-propylene-1,3-sultone, 1,4-butane sultone, 2,4-butane sultone, propargyl methanesulfonate, and the like.

[0185] Specific examples of the sulfuric acid ester include 1,3,2-dioxathiolane 2,2-dioxide, 1,3,2-dioxathiolane 2,2-dioxide, and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane.

[0186] Specific examples of sulfite esters include 1,3-propane sultone, 1-propylene-1,3-sultone, 1,4-butane sultone, 2,4-butane sultone, propargyl methanesulfonate, etc. Specific examples of sulfite esters include 1,3,2-dioxathiolane 2-oxide, 4-methyl-1,3,2-dioxathiolane 2-oxide, etc.

[0187] Specific examples of dicarboxylic anhydrides include 1,4-dioxane-2,6-dione, succinic anhydride, and glutaric anhydride.

[0188] Specific examples of the disulfonic anhydride include 1,2-ethanedisulfonic anhydride, 1,3-propanedisulfonic anhydride, and hexafluoro-1,3-propanedisulfonic anhydride.

[0189] Specific examples of the sulfonic acid anhydride include 2-sulfobenzoic anhydride and 2,2-dioxothiolan-5-one.

[0190] Specific examples of sulfonylbenzimide include o-sulfonylbenzimide and N-methylsaccharin.

[0191] In addition, as described above, the covering portion 222 in the negative electrode active material 220 contains a covering element as a constituent element. When the supply source of the covering element is an electrolyte, the electrolyte may further contain any one or two or more of the covering compounds. The covering compound is a compound containing any one or two or more of nickel, iron and copper as constituent elements. The content of the covering compound in the electrolyte is not particularly limited and can therefore be set arbitrarily.

[0192] The type of the coating compound containing nickel as a constituent element is not particularly limited, and specific examples thereof include nickel acetate, nickel(II) diethyldithiocarbamate, and bis(cyclopentadienyl)nickel.

[0193] The type of the covering compound containing iron as a constituent element is not particularly limited, and specific examples include iron acetate, iron (III) dimethyldithiocarbamate, bis(cyclopentadienyl)iron, tris(1,3-diphenyl-1,3-propanedione)iron, and tris(hexafluoroacetylacetonate)iron (III).

[0194] The type of the coating compound containing copper as a constituent element is not particularly limited, and specific examples include copper acetate, tetrakis(acetonitrile)copper(I) tetrafluoroborate, tetrakis(acetonitrile)copper(I) hexafluorophosphate, copper(II) dimethyldithiocarbamate, copper(II) tetrafluoroborate, and copper(I) thiocyanate.

[0195] (Nitrile compounds)

[0196] In addition, the additive includes a nitrile compound. This is because the electrochemical stability of the electrolyte is improved. Thus, the decomposition reaction of the electrolyte is further suppressed during charge and discharge, so even if charge and discharge are repeated, the reduction of the discharge capacity is further suppressed, and the generation of gas caused by the decomposition reaction of the electrolyte is also suppressed.

[0197] 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-hexanetricarboxylic acid nitrile, 3,3'-oxydipropionitrile, 3-butoxypropionitrile, ethylene glycol dipropionitrile ether, 1,2,2,3-tetracyanopropane, tetracyanopropane, fumaronitrile, 7,7,8,8-tetracyanoquinodimethane, cyclopentanecarbonitrile, 1,3,5-cyclohexanetricarboxylic acid nitrile, and 1,3-bis(dicyanomethylene)indane.

[0198] However, the above-mentioned cyanated cyclic carbonate is excluded from the nitrile compound described here.

[0199] <1-3. Action>

[0200] The secondary battery operates as follows.

[0201] 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.

[0202] <1-4. Manufacturing method>

[0203] When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are produced by the following exemplary steps, and an electrolyte is prepared. Then, a secondary battery is assembled using the positive electrode 21 and the negative electrode 22 and the electrolyte, and the assembled secondary battery is stabilized.

[0204] [Production of positive electrode]

[0205] 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, and then a paste-like positive electrode mixture slurry is prepared by adding the positive electrode mixture to a solvent. The solvent can be an aqueous solvent or an organic solvent. Next, the positive electrode mixture slurry is applied to 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 also be compression molded using a roller press or the like. In this case, the positive electrode active material layer 21B can be heated, or the compression molding can be repeated multiple times. Thus, the positive electrode active material layer 21B is formed on both sides of the positive electrode collector 21A, thereby manufacturing the positive electrode 21.

[0206] When the positive electrode 21 is used as a supply source of the covering element, the positive electrode 21 is produced by the same procedure except that the covering metal powder is further added to the positive electrode mixture.

[0207] [Production of negative electrode]

[0208] First, the negative electrode mixture is prepared by mixing the center portion 221, the negative electrode binder and the negative electrode conductive agent, and then a paste-like negative electrode mixture slurry is prepared by adding the negative electrode mixture to a solvent. The solvent can be an aqueous solvent or an organic solvent. 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 also be compression-molded using a roller press or the like. In this case, the negative electrode active material layer 22B can be heated, or the compression molding can be repeated multiple times.

[0209] Finally, as described later, after the secondary battery is assembled, a stabilization treatment is performed on the assembled secondary battery. Thus, the covering portion 222 including the covering element as a constituent element is formed on the surface of the central portion 221, thereby forming the negative electrode active material 220 including the central portion 221 and the covering portion 222.

[0210] Therefore, the negative electrode active material layer 22B including the negative electrode active material 220 is formed on both surfaces of the negative electrode collector 22A, thereby producing the negative electrode 22 .

[0211] [Preparation of electrolyte]

[0212] When the electrolytic solution is produced, an electrolyte salt is added to a solvent, and then the thiazole compound is added to the solvent. Thus, the electrolyte salt and the thiazole compound are dissolved or dispersed in the solvent, respectively, to prepare the electrolytic solution.

[0213] When an electrolyte solution is used as a supply source of the covering element, the electrolyte solution is prepared by the same procedure except that a covering compound is further added to the solvent.

[0214] [Assembly of secondary battery]

[0215] 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, after the positive electrode 21 and the negative electrode 22 are stacked on each other via the separator 23, the positive electrode 21, the negative electrode 22 and the separator 23 are wound to produce a winding body (not shown) having a winding center space 20S. The winding body has the same structure as the battery element 20 except that the electrolyte is not impregnated in each of the positive electrode 21, the negative electrode 22 and the separator 23. Next, the center pin 24 is inserted into the winding center space 20S of the winding body.

[0216] Next, the winding body and the insulating plates 12 and 13 are stored in the battery can 11 in a state where the winding 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 using a joining method such as welding, and the negative electrode lead 26 is connected to the battery can 11 using a joining method such as welding. Next, an electrolyte is injected into the battery can 11 to impregnate the winding body. In this way, the electrolyte is impregnated in each of the positive electrode 21, the negative electrode 22, and the separator 23, thereby manufacturing the battery element 20.

[0217] Finally, after the battery cover 14, the safety valve mechanism 15, and the PTC element 16 are housed inside the battery can 11, the battery can 11 is tightened 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.

[0218] [Stabilization of secondary batteries]

[0219] The assembled secondary battery is charged and discharged. Various conditions such as the ambient temperature, the number of charge and discharge times (number of cycles), and the charge and discharge conditions can be set arbitrarily.

[0220] In the stabilization process of the secondary battery, as described above, the covering portion 222 including the covering element as a constituent element is formed on the surface of the central portion 221, thereby forming the negative electrode active material 220 including the central portion 221 and the covering portion 222. In this case, a coating may also be formed on the surface of the positive electrode active material.

[0221] Therefore, the state of the secondary battery is electrochemically stabilized, thereby completing the secondary battery.

[0222] <1-5. Functions and effects>

[0223] According to this secondary battery, the negative electrode active material 220 of the negative electrode 22 includes a core portion 221 and a covering portion 222 containing one or more of nickel, iron, and copper as a covering element, and the electrolyte contains a thiazole compound.

[0224] In this case, as described above, the physical strength of the covering portion 222 is improved by the synergistic effect of the covering element and the thiazole-type compound. Thus, even if charge and discharge are repeated, the decomposition reaction of the electrolyte is suppressed, thereby suppressing the reduction of the discharge capacity. Therefore, excellent battery characteristics can be obtained.

[0225] In particular, if the center portion 221 includes a metal-based material including silicon as a constituent element, a sufficiently high energy density can be obtained, and thus a higher effect can be obtained.

[0226] Furthermore, when the content of the thiazole type compound in the electrolyte is 0.001 wt % to 5 wt %, the physical strength of the coating portion 222 is sufficiently improved. Therefore, the decomposition reaction of the electrolyte is sufficiently suppressed, and thus a higher effect can be obtained.

[0227] Furthermore, if the electrolyte solution contains any one or two or more of an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, and a cyanated cyclic carbonate, the decomposition reaction of the electrolyte solution is further suppressed, so that a higher effect can be obtained.

[0228] Furthermore, 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 sulfobenzimide, the decomposition reaction of the electrolyte solution is further suppressed, so that a higher effect can be obtained.

[0229] Furthermore, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by inserting and releasing lithium, so that a higher effect can be obtained.

[0230] <2. Modifications>

[0231] The configuration of the secondary battery can be appropriately modified as described below. However, any two or more of the series of modifications described below can be combined with each other.

[0232] [Modification 1]

[0233] The case where the secondary battery has a cylindrical battery structure is described below, but although not specifically illustrated here, the type of battery structure is not particularly limited, and may be a laminated type, a square type, a coin type, a button type, or the like.

[0234] [Modification 2]

[0235] The separator 23 is a porous film. However, although not specifically shown here, a laminated separator including a polymer compound layer may be used.

[0236] Specifically, the laminated separator includes a porous film having a pair of faces and a polymer compound layer disposed on one or both sides of the porous film. This is because the adhesion of the separator to the positive electrode 21 and the negative electrode 22 is improved, thereby suppressing the positional deviation (winding deviation) of the battery element 20. Thus, even if a decomposition reaction of the electrolyte occurs, the expansion of the secondary battery is suppressed. The polymer compound layer includes a polymer compound such as polyvinylidene fluoride. This is because polyvinylidene fluoride and the like have excellent physical strength and are electrochemically stable.

[0237] In addition, one or both of the porous film and the polymer compound layer may also include any one or more of a plurality of insulating particles. This is because a plurality of insulating particles promote heat dissipation when the secondary battery is heated, so the safety (heat resistance) of the secondary battery is improved. The 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.

[0238] 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 needed.

[0239] When the laminated separator is used, the lithium ions can also move between the positive electrode 21 and the negative electrode 22, so the same effect can be obtained. In this case, the safety of the secondary battery is improved as described above, so a higher effect can be obtained.

[0240] [Variation 3]

[0241] 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.

[0242] In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are stacked on each other with the separator 23 and the electrolyte layer interposed therebetween, 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.

[0243] 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 is prevented. The electrolyte is composed as described above. The polymer compound includes polyvinylidene fluoride, etc. When forming the electrolyte layer, after preparing a precursor solution including an electrolyte, a polymer compound, and a solvent, the precursor solution is applied to one or both sides of each of the positive electrode 21 and the negative electrode 22.

[0244] Even when the electrolyte layer is used, lithium ions 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, leakage of the electrolyte is prevented, so a higher effect can be obtained.

[0245] <3. Applications of secondary batteries>

[0246] The purpose (application example) of the secondary battery is not particularly limited. The secondary battery used as a power source can be a main power source or an auxiliary power source in electronic equipment and electric vehicles. The main power source is a 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 used in place of the power source and is a power source switched from the main power source.

[0247] Specific examples of the use 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; 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.

[0248] 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 a driving source other than the secondary battery. In a home power storage system, the power stored in the secondary battery as a power storage source can be used to use home electrical products, etc.

[0249] 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 appropriately changed.

[0250] Figure 4 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.

[0251] like Figure 4 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 .

[0252] 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 that charging and discharging can be performed. The circuit substrate 52 includes a control unit 56, a switch 57, a PTC element 58, and a temperature detection unit 59. However, the PTC element 58 can also be omitted.

[0253] 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.

[0254] In addition, if 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 so that the charging current does not flow 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.

[0255] 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.

[0256] The temperature detection unit 59 includes a temperature detection element such as a thermistor. The temperature detection unit 59 measures the temperature of the power supply 51 using the temperature detection terminal 55, and outputs the temperature measurement result to the control unit 56. The temperature measurement result measured by the temperature detection unit 59 is used when the control unit 56 performs charge and discharge control in the event of abnormal heating and when the control unit 56 performs correction processing when calculating the remaining capacity.

[0257] Example

[0258] Examples of the present technology will be described.

[0259] <Examples 1 to 48 and Comparative Examples 1 to 24>

[0260] As described below, after the secondary battery was manufactured, the battery characteristics of the secondary battery were evaluated.

[0261] [Manufacturing of Secondary Batteries]

[0262] Through the following steps, the Figure 1 as well as Figure 2 The cylindrical lithium-ion secondary battery shown.

[0263] (Production of positive electrode)

[0264] First, a positive electrode mixture is prepared by mixing 94 parts by mass of a positive electrode active material (lithium cobalt oxide (LiCoO2) as a lithium-containing 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). Next, after adding the positive electrode mixture to a solvent (N-methyl-2-pyrrolidone as an organic solvent), the solvent is stirred to prepare a paste-like positive electrode mixture slurry. Next, after applying the positive electrode mixture slurry on both sides of the positive electrode collector 21A (a strip-shaped aluminum foil with a thickness of 12 μm) using a coating device, 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, a positive electrode 21 is produced.

[0265] In addition, when the positive electrode 21 is used as a supply source of the covering element (nickel (Ni), iron (Fe) and copper (Cu)), the positive electrode 21 is produced by the same steps except that the covering metal powder (nickel powder, iron powder and copper powder, median diameter D50 = 0.2μm) is added to the positive electrode mixture. In this case, part of the positive electrode conductive agent is replaced with the covering metal powder, and the content of the covering metal powder in the positive electrode mixture is 0.0005 parts by mass. In addition, when two or more covering metal powders are used, the contents of the two or more covering metal powders are the same.

[0266] (Production of negative electrode)

[0267] First, 93 parts by mass of the negative electrode active material (center portion 221) and 7 parts by mass of the negative electrode binder (polyvinylidene fluoride) were mixed together to prepare a negative electrode mixture. As the center portion 221, a mixture of 63 parts by mass of artificial graphite as a carbon material and 30 parts by mass of silicon oxide (SiO) as a metal material was used.

[0268] Next, after adding the negative electrode mixture to the solvent (N-methyl-2-pyrrolidone as an organic solvent), the solvent was stirred to prepare a paste-like negative electrode mixture slurry. Next, after applying the negative electrode mixture slurry on both sides of the negative electrode collector 22A (strip-shaped copper foil with a thickness of 15 μm) using a coating device, the negative electrode mixture slurry was dried to form the negative electrode active material layer 22B. Next, the negative electrode active material layer 22B was compression-molded using a roller press.

[0269] Finally, as described later, after assembling the secondary battery, a stabilization treatment of the assembled secondary battery is performed. Thus, a covering portion 222 including a covering element as a constituent element is formed on the surface of the central portion 221, thereby forming a negative electrode active material 220 including the central portion 221 and the covering portion 222. Thus, the negative electrode 22 is manufactured.

[0270] Furthermore, the negative electrode 22 was produced by the same procedure except that only the carbon material was used as the center portion 221 instead of the metal-based material.

[0271] Here, for comparison, the negative electrode 22 was produced by the same procedure except that the covering portion 222 not including the covering element as a constituent element was formed by not using a supply source of the covering element.

[0272] (Preparation of electrolyte)

[0273] 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, type and content (weight %) of the thiazole-type compound are shown in Tables 1 to 5, respectively. Thus, an electrolyte solution was prepared.

[0274] In addition, when an electrolyte is used as a supply source of the covering element, the electrolyte is prepared by the same steps except that the covering compound is added to the solvent to which the thiazole-type compound is added. In this case, bis(cyclopentadienyl)nickel is used as a covering compound containing nickel as a constituent element, bis(cyclopentadienyl)iron is used as a covering compound using iron as a constituent element, and tetra(acetonitrile)copper(I)hexafluorophosphate is used as a covering compound containing copper as a constituent element. In addition, the content of the covering compound in the electrolyte is 0.05% by weight. In addition, when two or more covering compounds are used, the contents of the two or more covering compounds are each the same amount.

[0275] Here, for comparison, an electrolyte solution was prepared by the same procedure except that the thiazole-type compound was not used.

[0276] The meanings of the "classifications" shown in Tables 1 to 5 are as follows: "First" represents the first thiazole type compound, "Second" represents the second thiazole type compound, "Third" represents the third thiazole type compound, and "Fourth" represents the fourth thiazole type compound.

[0277] (Assembly of secondary batteries)

[0278] First, the positive electrode lead 25 (aluminum foil) is welded to the positive electrode collector 21A of the positive electrode 21 , and the negative electrode lead 26 (copper foil) is welded to the negative electrode collector 22A of the negative electrode 22 .

[0279] Next, after the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 (microporous polyethylene film with a thickness of 15 μm) interposed therebetween, the positive electrode 21, the negative electrode 22 and the separator 23 are wound to produce a wound body having a winding center space 20S. Next, the center pin 24 is inserted into the winding center space 20S of the wound body.

[0280] Next, the wound body and the insulating plates 12 and 13 are housed inside 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 in the wound body, and the battery element 20 is manufactured.

[0281] Finally, after the battery cover 14, the safety valve mechanism 15, and the PTC element 16 are housed in the battery can 11, the battery can 11 is tightened via the gasket 17. Thus, the battery can 11 is sealed, and the secondary battery is assembled.

[0282] (Stabilization of secondary batteries)

[0283] The 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 the 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 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.

[0284] Thus, as described above, the covering portion 222 including the covering element as a constituent element is formed on the surface of the core portion 221, thereby forming the negative electrode active material 220. Therefore, the state of the secondary battery is electrochemically stabilized, and the secondary battery is completed.

[0285] In addition, after the secondary battery is completed, the secondary battery is disassembled and the negative electrode active material 220 is recovered. The negative electrode active material 220 is analyzed using a scanning electron microscope (scanning electron microscope SU3800 / SU3900 manufactured by High-Tech Co., Ltd.), an energy dispersive X-ray analyzer (EDS) and an X-ray photoelectron spectrometer (EDX). The results are shown in Tables 1 to 5.

[0286] After the secondary battery was completed, the content (weight %) of the thiazole-type compound in the electrolyte was measured using ICP emission spectrometry. The results are shown in Tables 1 to 5.

[0287] [Evaluation of battery characteristics]

[0288] Cycle characteristics were evaluated as battery characteristics by the procedure described below, and the results shown in Tables 1 to 5 were obtained.

[0289] First, in a high temperature environment (temperature = 50°C), after charging the secondary battery, the charged secondary battery was left standing in the same environment (standing time = 3 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 is the current value that completely discharges the battery capacity within 1 hour.

[0290] 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 refers to the current value that completely discharges the battery capacity in 1 / 3 hour.

[0291] 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.

[0292] 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.

[0293] [Table 1]

[0294]

[0295] [Table 2]

[0296]

[0297] [Table 3]

[0298]

[0299] [Table 4]

[0300]

[0301] [Table 5]

[0302]

[0303] [Investigation]

[0304] As shown in Tables 1 to 5, the capacity retention rate varies depending on the configuration of the secondary battery.

[0305] Specifically, when both a carbon material and a metal-based material were used as the negative electrode active material (Examples 1 to 45 and Comparative Examples 1 to 12), the results described below were obtained.

[0306] Here, the capacity retention rate in the case where the covering portion 222 does not include the covering element as a constituent element and the electrolyte solution does not include the thiazole-type compound (Comparative Example 1) is used as a comparison reference.

[0307] When the coating portion 222 includes the coating element as a constituent element and the electrolyte does not include the thiazole-type compound (Comparative Examples 2 to 11), the capacity retention rate decreases.

[0308] In addition, when the coating portion 222 does not contain the coating element as a constituent element and the electrolyte solution contains a thiazole-type compound (Comparative Example 12), the capacity retention rate increases slightly.

[0309] Considering these results (Comparative Examples 1 to 12), when the covering portion 222 contains the covering element as a constituent element and the electrolyte contains the thiazole-type compound, the capacity retention rate is expected to be maintained substantially the same.

[0310] However, actually, results different from the above expectation were obtained. That is, when the coating portion 222 contained the coating element as a constituent element and the electrolyte contained the thiazole-type compound (Examples 1 to 45), the capacity retention rate increased significantly.

[0311] The reason why the capacity retention rate is significantly increased is considered to be because, as described above, a coating having excellent electrochemical durability is formed on the surface of the negative electrode 22 by the synergistic effect of the coating element and the thiazole-type compound.

[0312] In particular, when the coating portion 222 contained a coating element as a constituent element and the electrolyte contained a thiazole-type compound (Examples 1 to 45), the tendency described below was obtained.

[0313] First, even if any one of the first thiazole type compound, the second thiazole type compound, the third thiazole type compound, and the fourth thiazole type compound is used, a high capacity maintenance rate is obtained. Second, if the content of the thiazole type compound in the electrolyte is 0.001 wt % to 5 wt %, the capacity maintenance rate is further increased. Third, a high capacity maintenance rate is obtained regardless of the type of supply source of the covering element.

[0314] The results described here are not limited to the case where both carbon material and metal-based material are used as negative electrode active materials (Examples 1 to 45 and Comparative Examples 1 to 12), but are also obtained when only carbon material is used as the negative electrode active material (Examples 46 to 48 and Comparative Examples 13 to 24).

[0315] <Examples 49 to 54>

[0316] As shown in Table 6, 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), and then the battery characteristics were evaluated. The classification, type and content (weight %) of the additive are shown in Table 6.

[0317] 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.

[0318] [Table 6]

[0319]

[0320] As shown in Table 6, when the electrolyte solution contained an additive (unsaturated cyclic carbonate, fluorinated cyclic carbonate, or cyanated cyclic carbonate) (Examples 49 to 54), the capacity retention rate was further increased compared to the case where the electrolyte solution did not contain the additive (Example 4).

[0321] <Examples 55 to 74>

[0322] As shown in Tables 7 and 8, a secondary battery was prepared by the same procedure as in Example 4 except that the electrolyte contained an additive (sulfonic acid ester, sulfuric acid ester, sulfite ester, dicarboxylic acid anhydride, disulfonic acid anhydride, sulfonic acid carboxylic acid anhydride or sulfonylbenzimide), and then the battery characteristics were evaluated. The classification, type and content (weight %) of the additive are shown in Tables 7 and 8.

[0323] 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.

[0324] As the sulfuric acid ester, 1,3,2-dioxathiolane 2,2-dioxide (OTO), 1,3,2-dioxathiolane 2,2-dioxide (OTA), and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane (SOTO) were used.

[0325] As the sulfite, 1,3,2-dioxathiolane 2-oxide (DTO) and 4-methyl-1,3,2-dioxathiolane 2-oxide (MDTO) were used.

[0326] As dicarboxylic anhydrides, 1,4-dioxane-2,6-dione (DOD), succinic anhydride (SA), and glutaric anhydride (GA) were used.

[0327] As the disulfonic anhydride, 1,2-ethanedisulfonic anhydride (ESA), 1,3-propanedisulfonic anhydride (PSA), and hexafluoro-1,3-propanedisulfonic anhydride (FPSA) were used.

[0328] As the sulfonic acid anhydride, 2-sulfobenzoic anhydride (SBA) and 2,2-dioxothiol-5-one (DOTO) were used.

[0329] As the sulfobenzimide, o-sulfonylbenzoimide (SBI) and N-methylsaccharin (NMS) were used.

[0330] [Table 7]

[0331]

[0332] [Table 8]

[0333]

[0334] As shown in Tables 7 and 8, when the electrolyte solution contained an additive (sulfonate, sulfate, sulfite, dicarboxylic anhydride, disulfonic anhydride, sulfonic acid anhydride or sulfonylbenzimide) (Examples 55 to 74), the capacity retention rate was further increased compared to the case where the electrolyte solution did not contain the additive (Example 4).

[0335] [Summarize]

[0336] According to the results shown in Tables 1 to 8, if the negative electrode active material 220 of the negative electrode 22 includes a central portion 221 and a covering portion 222, the covering portion 222 includes a covering element as a constituent element, and the electrolyte includes a thiazole-type compound, a high capacity retention rate is obtained, thereby improving the cycle characteristics. Therefore, in a secondary battery using an electrolyte, excellent battery characteristics can be obtained.

[0337] Although the present technology has been described above by taking one embodiment and one example, the configuration of the present technology is not limited to the configuration described in one embodiment and one example, and various modifications are possible.

[0338] 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 therefore other element structures such as a stacking type and a repeatedly folded type may also 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.

[0339] 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.

[0340] 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.

[0341] In addition, the present technology can also adopt the following configurations.

[0342] <1> A secondary battery comprising:

[0343] positive electrode;

[0344] a negative electrode comprising a negative electrode active material; and

[0345] An electrolyte solution comprising a thiazole-type compound,

[0346] The negative electrode active material comprises:

[0347] The central part, where the electrode reaction substances are embedded and de-embedded; and

[0348] a covering portion covering a surface of the central portion,

[0349] The covering portion contains at least one of nickel, iron and copper as a constituent element,

[0350] The thiazole-type compound includes at least one of a compound represented by formula (1), a compound represented by formula (2), a compound represented by formula (3), and a compound represented by formula (4).

[0351] [Chemical formula 15]

[0352] Chemical formula 15

[0353]

[0354] (R1 to R28 are each hydrogen, fluorine, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, alkoxy, fluoroalkyl, fluoroalkenyl, fluoroalkynyl, fluorocycloalkyl, fluoroaryl, fluoroalkoxy, amino, carboxylate, and monovalent bonding groups of two or more of these groups bonded to each other.)

[0355] <2> The secondary battery according to <1>, wherein

[0356] The central portion comprises a metal-based material,

[0357] The metal-based material contains silicon as a constituent element.

[0358] <3> The secondary battery according to <1> or <2>, wherein

[0359] The content of the thiazole-type compound in the electrolyte is 0.001 wt % or more and 5 wt % or less.

[0360] <4> The secondary battery according to any one of <1> to <3>, wherein

[0361] The electrolyte further comprises at least one of unsaturated cyclic carbonate, fluorinated cyclic carbonate and cyanated cyclic carbonate.

[0362] <5> The secondary battery according to any one of <1> to <4>, wherein

[0363] The electrolyte further comprises at least one of sulfonic acid esters, sulfates, sulfites, dicarboxylic anhydrides, disulfonic anhydrides, sulfonic acid carboxylic anhydrides, and sulfonylbenzimide.

[0364] <6> The secondary battery according to any one of <1> to <5>, wherein

[0365] The lithium secondary battery is an ion secondary battery.

Claims

1. A secondary battery comprising: positive electrode; a negative electrode comprising a negative electrode active material; and An electrolyte solution comprising a thiazole-type compound, The negative electrode active material comprises: The center part, where the electrode reaction substances are embedded and de-embedded; as well as a covering portion covering a surface of the central portion, The covering portion contains at least one of nickel, iron and copper as a constituent element, The thiazole-type compound includes at least one of a compound represented by formula (1), a compound represented by formula (2), a compound represented by formula (3), and a compound represented by formula (4), R1 to R28 are each hydrogen, fluorine, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, alkoxy, fluoroalkyl, fluoroalkenyl, fluoroalkynyl, fluorocycloalkyl, fluoroaryl, fluoroalkoxy, amino, carboxylate, 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 central portion comprises a metal-based material, The metal-based material contains silicon as a constituent element.

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 unsaturated cyclic carbonate, fluorinated cyclic carbonate and 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 sulfonylbenzimide.

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

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