Secondary battery electrolyte and secondary battery

Abstract

A secondary battery according to the present invention comprises a positive electrode, a negative electrode, and an electrolyte that contains a thiazole compound. The thiazole compound contains at least a compound represented by formula (1) and / or a compound represented by formula (2).

Description

Electrolyte for secondary battery and secondary battery

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

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as small, lightweight power sources that can provide high energy density. These secondary batteries contain a positive electrode, a negative electrode, and an electrolyte (secondary battery electrolyte), and various studies have been conducted on the configuration of these secondary batteries.

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

[0004] Japanese Patent Publication No. 2001-273927 Japanese Patent Publication No. 2013-513923 Japanese Patent No. 6056721 International Publication No. 2019 / 181278 Pamphlet

[0005] Although various studies have been conducted on the configuration of secondary batteries, the battery characteristics of the secondary batteries are still insufficient and there is room for improvement.

[0006] There is a demand for an electrolyte solution for a secondary battery and a secondary battery that can provide excellent battery characteristics.

[0007] An electrolyte solution for a secondary battery according to one embodiment of the present technology includes a thiazole-type compound, and the thiazole-type compound includes at least one of a compound represented by formula (1) and a compound represented by formula (2).

[0008] (Each of R1 to R15 is any one of hydrogen, fluorine, an amino group, a silylalkyl group, an aminoalkyl group, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an alkylthio group, a fluorinated alkyl group, a fluorinated cycloalkyl group, a fluorinated aryl group, a fluorinated alkoxy group, a fluorinated alkylthio group, and a monovalent bonding group in which two or more of these groups are bonded to each other.)

[0009] A secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode, and an electrolyte solution, and the electrolyte solution has a configuration similar to that of the electrolyte solution for a secondary battery according to the embodiment of the present technology described above.

[0010] According to the secondary battery electrolyte or secondary battery of one embodiment of the present technology, the secondary battery electrolyte contains a thiazole-type compound, and the thiazole-type compound contains at least one of the compound shown in formula (1) and the compound shown in formula (2), so that excellent battery characteristics can be obtained.

[0011] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below.

[0012] It is a cross-sectional view showing the configuration of a secondary battery according to an embodiment of the present technology.It is a cross-sectional view showing the configuration of a battery element shown in Figure 1.It is a block diagram showing the configuration of an application example of a secondary battery.

[0013] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order: 1. Electrolyte for secondary battery 1-1. Configuration 1-2. Manufacturing method 1-3. Action and effect 2. Secondary battery 2-1. Configuration 2-2. Operation 2-3. Manufacturing method 2-4. Action and effect 3. Modification 4. Use of secondary battery

[0014] 1. Electrolyte for Secondary Battery First, an electrolyte for a secondary battery (hereinafter simply referred to as "electrolyte") according to an embodiment of the present technology will be described.

[0015] <1-1. Configuration> The electrolytic solution described here is a liquid electrolyte used in a secondary battery, which is an electrochemical device. However, the electrolytic solution may also be used in electrochemical devices other than secondary batteries. Specific examples of other electrochemical devices include primary batteries and capacitors.

[0016] [Thiazole-Type Compound] The electrolyte solution contains one or more thiazole-type compounds, which are compounds containing a fused ring formed by condensing naphthalene and thiazole.

[0017] Specifically, the thiazole-type compound includes one or both of a compound represented by formula (1) and a compound represented by formula (2).

[0018] (Each of R1 to R15 is any one of hydrogen, fluorine, an amino group, a silylalkyl group, an aminoalkyl group, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an alkylthio group, a fluorinated alkyl group, a fluorinated cycloalkyl group, a fluorinated aryl group, a fluorinated alkoxy group, a fluorinated alkylthio group, and a monovalent bonding group in which two or more of these groups are bonded to each other.)

[0019] Hereinafter, the compound shown in formula (1) will be referred to as a "first thiazole-type compound," and the compound shown in formula (2) will be referred to as a "second thiazole-type compound."

[0020] The first thiazole-type compound is a compound containing one fused ring as shown in formula (1). The second thiazole-type compound is a compound containing two fused rings as shown in formula (2), in which the two fused rings are indirectly bonded to each other via a dithio bond (-S-S-).

[0021] The electrolyte solution contains a thiazole-type compound because a good coating derived from the thiazole-type compound forms on the surface of the negative electrode during charge and discharge of a secondary battery using the electrolyte solution. This coating has a dense film structure and is electrochemically stable. As a result, the surface of the negative electrode is electrochemically protected by the coating, which suppresses the decomposition reaction of the electrolyte on the surface of the negative electrode. Therefore, even with repeated charge and discharge, the decrease in discharge capacity is suppressed.

[0022] (Configuration) As described above, each of R1 to R15 is hydrogen (—H), fluorine (—F), an amino group (—NH 2 ), a silylalkyl group, an aminoalkyl group, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an alkylthio group, a fluorinated alkyl group, a fluorinated cycloalkyl group, a fluorinated aryl group, a fluorinated alkoxy group, a fluorinated alkylthio group, and a bonding group.

[0023] The number of carbon atoms of the alkyl group is not particularly limited, and specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group, etc. However, the alkyl group may be linear or branched.

[0024] The number of carbon atoms in the cycloalkyl group is not particularly limited, and specific examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

[0025] 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.

[0026] The number of carbon atoms in the alkoxy group is not particularly limited, and specific examples of the alkoxy group include a methoxy group, an ethoxy group, and a propoxy group, etc. However, the alkoxy group may be linear or branched.

[0027] 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. For clarity, an alkylthio group is a group in which the oxygen atom in an alkoxy group is substituted with a sulfur atom.

[0028] The silylalkyl group is a silyl group (—SiH 3 The details of the alkyl group are as described above. A specific example of a silylalkyl group is a trimethylsilyl group.

[0029] An aminoalkyl group is a group in which two hydrogen atoms contained in an amino group are substituted with alkyl groups, and details regarding the alkyl are as described above. A specific example of an aminoalkyl group is a dimethylamino group.

[0030] A fluorinated alkyl group is a group in which one or more hydrogen atoms contained in an alkyl group are substituted with fluorine. A fluorinated cycloalkyl group is a group in which one or more hydrogen atoms contained in a cycloalkyl group are substituted with fluorine. A fluorinated aryl group is a group in which one or more hydrogen atoms contained in an aryl group are substituted with fluorine. A fluorinated alkoxy group is a group in which one or more hydrogen atoms contained in an alkoxy group are substituted with fluorine. A fluorinated alkylthio group is a group in which one or more hydrogen atoms contained in an alkylthio group are substituted with fluorine.

[0031] The bonding group is a monovalent group in which two or more of hydrogen, fluorine, amino group, silylalkyl group, aminoalkyl group, alkyl group, cycloalkyl group, aryl group, alkoxy group, alkylthio group, fluorinated alkyl group, fluorinated cycloalkyl group, fluorinated aryl group, fluorinated alkoxy group and fluorinated alkylthio group are bonded to each other. The type of bonding group is not particularly limited, but specifically includes a group in which an alkyl group and an amino group are bonded to each other (a group in which an alkylene group and an amino group are bonded to each other), a group in which an alkyl group and a silylalkyl group are bonded to each other (a group in which an alkylene group and a silylalkyl group are bonded to each other), and a group in which an alkyl group and an aminoalkyl group are bonded to each other (a group in which an alkylene group and an aminoalkyl group are bonded to each other).

[0032] (Specific Examples) Specific examples of the thiazole-type compound are as follows.

[0033] Specific examples of the first thiazole type compound include compounds represented by formulas (1-1) to (1-31).

[0034]

[0035]

[0036]

[0037] Specific examples of the second thiazole type compound include compounds represented by formulas (2-1) to (2-24).

[0038]

[0039]

[0040]

[0041]

[0042]

[0043] (Content) The content of the thiazole-type compound in the electrolyte solution is not particularly limited, but is preferably 0.001% by weight to 5% by weight, because a sufficiently good coating film is formed, and the decomposition reaction of the electrolyte solution is sufficiently suppressed.

[0044] In addition, when the electrolyte solution contains both the first thiazole type compound and the second thiazole type compound, the content of the thiazole type compound described above is the sum of the content of the first thiazole type compound and the content of the second thiazole type compound.

[0045] In addition, when measuring the content of thiazole-type compounds, the secondary battery is disassembled to recover the electrolyte, and the electrolyte is then analyzed to calculate the content of the thiazole-type compounds. The method for analyzing the electrolyte is not particularly limited, but specifically, any one or more of inductively coupled plasma (ICP) atomic emission spectroscopy, nuclear magnetic resonance spectroscopy (NMR), and gas chromatography mass spectrometry (GC-MS) can be used.

[0046] [Solvent] The electrolytic solution may further contain a solvent. The solvent contains one or more non-aqueous solvents (organic solvents), and the electrolytic solution containing the non-aqueous solvent is a so-called non-aqueous electrolytic solution.

[0047] The non-aqueous solvent is an ester, an ether, or the like, more specifically, a carbonate ester compound, a carboxylic acid ester compound, a lactone compound, or the like.

[0048] Carbonate compounds include cyclic carbonates and chain carbonates. Specific examples of cyclic carbonates include ethylene carbonate and propylene carbonate. Specific examples of chain carbonates include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0049] The carboxylic acid ester compound is a chain carboxylic acid ester, etc. Specific examples of the chain carboxylic acid ester include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, ethyl trimethylacetate, methyl butyrate, and ethyl butyrate.

[0050] The lactone compound is lactone, etc. Specific examples of lactone include γ-butyrolactone and γ-valerolactone.

[0051] The ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, or the like.

[0052] (Electrolyte Salt) The electrolytic solution may further contain an electrolyte salt, which is a light metal salt such as a lithium salt.

[0053] A specific example of the lithium salt is lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(fluorosulfonyl)imide (LiN(FSO 2 ) 2 ), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF 3 SO 2 ) 3 ), lithium bis(oxalato)borate (LiB(C 2 O 4 ) 2 ), lithium difluorooxalatoborate (LiBF 2 (C2 O 4 )), lithium difluorodi(oxalato)borate (LiPF 2 (C 2 O 4 ) 2 ), lithium tetrafluorooxalatophosphate (LiPF 4 (C 2 O 4 )), lithium monofluorophosphate (Li 2 PFO 3 ) and lithium difluorophosphate (LiPF 2 O 2 ) etc.

[0054] The content of the electrolyte salt is not particularly limited, but specifically, it is 0.3 mol / kg to 3.0 mol / kg relative to the solvent, because high ionic conductivity can be obtained.

[0055] (Additives) The electrolytic solution may further contain one or more additives.

[0056] (Unsaturated cyclic carbonate, fluorinated cyclic carbonate, and cyanized cyclic carbonate) Specifically, the additive is one or more of unsaturated cyclic carbonate, fluorinated cyclic carbonate, and cyanized cyclic carbonate. This is because the electrochemical stability of the electrolyte is improved. This further suppresses the decomposition reaction of the electrolyte during charge and discharge of the secondary battery, thereby further suppressing the decrease in discharge capacity even when charge and discharge are repeated.

[0057] 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 one or two or more.

[0058] The unsaturated cyclic carbonate contains one or more of a vinylene carbonate compound, a vinylethylene carbonate compound, and a methyleneethylene carbonate compound.

[0059] Vinylene carbonate compounds are unsaturated cyclic carbonates having a vinylene carbonate 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.

[0060] The vinylethylene carbonate compound is an unsaturated cyclic carbonate ester having a vinylethylene carbonate type structure. Specific examples of the vinylethylene carbonate compound include vinylethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, 4-ethyl-4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolan-2-one, 4,4-divinyl-1,3-dioxolan-2-one, and 4,5-divinyl-1,3-dioxolan-2-one.

[0061] Methylene ethylene carbonate compounds are unsaturated cyclic carbonates having a methylene ethylene carbonate structure. Specific examples of methylene ethylene carbonate compounds include methylene ethylene carbonate (4-methylene-1,3-dioxolan-2-one), 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl-5-methylene-1,3-dioxolan-2-one. While compounds having only one methylene group have been exemplified as methylene ethylene carbonate compounds here, the methylene ethylene carbonate compounds may have two or more methylene groups.

[0062] It should be noted that a cyclic carbonate containing an unsaturated carbon bond does not fall under either a fluorinated cyclic carbonate or a cyanated cyclic carbonate, but falls under an unsaturated cyclic carbonate.

[0063] A fluorinated cyclic ester carbonate is a cyclic ester carbonate containing fluorine as a constituent element. The number of fluorine atoms is not particularly limited, and may be one or two or more. That is, a fluorinated cyclic ester carbonate is a compound in which one or two or more hydrogen atoms in a cyclic ester carbonate are substituted with fluorine atoms.

[0064] Specific examples of fluorinated cyclic carbonates include ethylene fluorocarbonate (4-fluoro-1,3-dioxolan-2-one) and ethylene difluorocarbonate (4,5-difluoro-1,3-dioxolan-2-one).

[0065] It should be noted that a cyclic carbonate containing fluorine as a constituent element does not fall into either the category of an unsaturated cyclic carbonate or a cyanated cyclic carbonate, but falls into the category of a fluorinated cyclic carbonate.

[0066] A cyanated cyclic carbonate is a cyclic carbonate containing a cyano group. The number of cyano groups is not particularly limited and may be one or two or more. That is, a cyanated cyclic carbonate is a compound in which one or more hydrogen atoms of a cyclic carbonate are substituted with a cyano group.

[0067] Specific examples of cyanated cyclic carbonates include ethylene cyanocarbonate (4-cyano-1,3-dioxolan-2-one) and ethylene dicyanocarbonate (4,5-dicyano-1,3-dioxolan-2-one).

[0068] It should be noted that a cyclic carbonate containing a cyano group does not fall into either the category of an unsaturated cyclic carbonate or a fluorinated cyclic carbonate, but falls into the category of a cyanated cyclic carbonate.

[0069] (Sulfonate esters, sulfate esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic acid anhydrides, and sulfobenzoimide) The additive is one or more of sulfonate esters, sulfate esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic acid anhydrides, and sulfobenzoimide. This is because the electrochemical stability of the electrolyte is improved. This further suppresses the decomposition reaction of the electrolyte during charge and discharge of the secondary battery, thereby further suppressing the decrease in discharge capacity even when charge and discharge are repeated.

[0070] Specific examples of sulfonic acid esters include 1,3-propane sultone, 1-propene-1,3-sultone, 1,4-butane sultone, 2,4-butane sultone, and methanesulfonic acid propargyl ester.

[0071] Specific examples of sulfate esters include 1,3,2-dioxathiolane 2,2-dioxide, 1,3,2-dioxathiane 2,2-dioxide, and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane.

[0072] Specific examples of sulfites include 1,3-propane sultone, 1-propene-1,3-sultone, 1,4-butane sultone, 2,4-butane sultone, and methanesulfonic acid propargyl ester. Specific examples of sulfites include 1,3,2-dioxathiolane 2-oxide and 4-methyl-1,3,2-dioxathiolane 2-oxide.

[0073] Specific examples of dicarboxylic acid anhydrides include 1,4-dioxane-2,6-dione, succinic anhydride, and glutaric anhydride.

[0074] Specific examples of disulfonic acid anhydrides include 1,2-ethanedisulfonic acid anhydride, 1,3-propanedisulfonic acid anhydride, and hexafluoro-1,3-propanedisulfonic acid anhydride.

[0075] Specific examples of sulfonic acid carboxylic acid anhydrides include 2-sulfobenzoic acid anhydride and 2,2-dioxooxathiolan-5-one.

[0076] Specific examples of sulfobenzoimides include o-sulfobenzimide and N-methylsaccharin.

[0077] (Nitrile Compound) The additive is a nitrile compound. This is because the electrochemical stability of the electrolyte is improved. This further suppresses the decomposition reaction of the electrolyte during charge and discharge, thereby further suppressing the decrease in discharge capacity even when charge and discharge are repeated. In this case, gas generation due to the decomposition reaction of the electrolyte is also suppressed.

[0078] The nitrile compound is a compound containing one or more cyano groups (—CN). Specific examples of the nitrile compound include octanenitrile, benzonitrile, phthalonitrile, succinonitrile, glutaronitrile, adiponitrile, sebaconitrile, 1,3,6-hexanetricarbonitrile, 3,3′-oxydipropionitrile, 3-butoxypropionitrile, ethylene glycol bispropionitrile ether, 1,2,2,3-tetracyanopropane, tetracyanopropane, fumaronitrile, 7,7,8,8-tetracyanoquinodimethane, cyclopentanecarbonitrile, 1,3,5-cyclohexanetricarbonitrile, and 1,3-bis(dicyanomethylidene)indane.

[0079] However, the above-mentioned cyanated cyclic carbonate is excluded from the nitrile compounds described here.

[0080] <1-2. Manufacturing Method> When manufacturing an electrolytic solution, an electrolyte salt is added to a solvent, and then a thiazole-type compound is added to the solvent. As a result, the electrolyte salt and the thiazole-type compound are each dissolved or dispersed in the solvent, and an electrolytic solution is prepared.

[0081] <1-3. Actions and Effects> According to this electrolyte, the electrolyte contains a thiazole-type compound.

[0082] In this case, as described above, during charging and discharging of a secondary battery using an electrolyte solution, a good coating derived from the thiazole-type compound is formed on the surface of the negative electrode, and the surface of the negative electrode is electrochemically protected using this coating. This suppresses the decomposition reaction of the electrolyte solution on the surface of the negative electrode, thereby suppressing the decrease in discharge capacity even when charging and discharging are repeated. Therefore, a secondary battery with excellent battery characteristics can be realized.

[0083] In particular, if the content of the thiazole-type compound in the electrolyte is 0.001% by weight to 5% by weight, a sufficiently good coating film is formed, and the decomposition reaction of the electrolyte is sufficiently suppressed, thereby achieving a higher effect.

[0084] Furthermore, if the electrolyte solution contains one or more of unsaturated cyclic carbonates, fluorinated cyclic carbonates, and cyanated cyclic carbonates, the decomposition reaction of the electrolyte solution is further suppressed, thereby achieving a greater effect.

[0085] Furthermore, if the electrolyte solution contains one or more of sulfonic acid esters, sulfate esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic acid anhydrides, and sulfobenzoic acid imides, the decomposition reaction of the electrolyte solution is further suppressed, thereby achieving a greater effect.

[0086] 2. Secondary Battery Next, a secondary battery using the above-described electrolytic solution according to an embodiment of the present technology will be described.

[0087] The secondary battery described here is a secondary battery that obtains battery capacity by utilizing the absorption and desorption of electrode reactants, and is equipped with a positive electrode, a negative electrode, and an electrolyte.

[0088] The charge capacity of the negative electrode is preferably larger than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of ​​the negative electrode is preferably larger than the electrochemical capacity per unit area of ​​the positive electrode. This is to prevent deposition of electrode reactants on the surface of the negative electrode during charging.

[0089] The type of electrode reactant is not particularly limited, but specifically includes light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, and alkaline earth metals include beryllium, magnesium, and calcium.

[0090] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

[0091] 2-1. Structure FIG. 1 shows a cross-sectional structure of a secondary battery, and FIG. 2 shows a cross-sectional structure of a battery element 20 shown in FIG.

[0092] 1 and 2, this secondary battery mainly includes a battery can 11, a pair of insulating plates 12 and 13, a battery element 20, a positive electrode lead 25, and a negative electrode lead 26. The secondary battery described here is a cylindrical secondary battery in which the battery element 20 is housed inside the cylindrical battery can 11.

[0093] [Battery Can] As shown in FIG. 1 , the battery can 11 is a housing member that houses the battery element 20 and other components. The battery can 11 has an open end and a closed end, and thus has a hollow structure. The battery can 11 contains one or more metal materials such as iron, aluminum, iron alloys, and aluminum alloys. The surface of the battery can 11 may be plated with a metal material such as nickel.

[0094] A battery lid 14, a safety valve mechanism 15, and a thermosensitive resistor (PTC element) 16 are crimped to one open end of the battery can 11 via a gasket 17. This seals the battery can 11 with the battery lid 14. Here, the battery lid 14 contains the same material as the material from which the battery can 11 is formed. The safety valve mechanism 15 and the PTC element 16 are each provided inside the battery lid 14, and the safety valve mechanism 15 is electrically connected to the battery lid 14 via the PTC element 16. The gasket 17 contains an insulating material, and the surface of the gasket 17 may be coated with asphalt or the like.

[0095] In this safety valve mechanism 15, when the internal pressure of the battery can 11 reaches a certain level due to an internal short circuit, external heating, or the like, the disk plate 15A reverses, thereby cutting off the electrical connection between the battery lid 14 and the battery element 20. To prevent abnormal heat generation due to a large current, the electrical resistance of the PTC element 16 increases with increasing temperature.

[0096] 1, the insulating plates 12 and 13 are arranged to face each other with the battery element 20 interposed therebetween.

[0097] [Battery Element] As shown in FIGS. 1 and 2, the battery element 20 is a power generating element including a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown).

[0098] This battery element 20 is a so-called wound electrode body. That is, the positive electrode 21 and the negative electrode 22 are stacked on top of each other with a separator 23 interposed therebetween, and are wound while facing each other with the separator 23 interposed therebetween. A center pin 24 is inserted into a space 20S provided at the center of the winding of the battery element 20. However, the center pin 24 may be omitted.

[0099] (Positive Electrode) As shown in FIG. 2, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B.

[0100] The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. The positive electrode current collector 21A contains a conductive material such as a metal material, and a specific example of the conductive material is aluminum.

[0101] The positive electrode active material layer 21B contains one or more types of positive electrode active materials that absorb and release lithium. However, the positive electrode active material layer 21B may further contain one or more types of other materials such as a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically includes a coating method.

[0102] Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A, and therefore the positive electrode 21 includes two positive electrode active material layers 21B. However, since the positive electrode active material layer 21B is provided on only one side of the positive electrode current collector 21A on the side where the positive electrode 21 faces the negative electrode 22, the positive electrode 21 may include only one positive electrode active material layer 21B.

[0103] The type of positive electrode active material is not particularly limited, but specifically includes a lithium-containing compound. This lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements, and may further include one or more other elements as constituent elements. The type of other element is not particularly limited as long as it is an element other than lithium and transition metal elements, but specifically includes elements belonging to Groups 2 to 15 of the long period periodic table. The type of lithium-containing compound is not particularly limited, but specifically includes oxides, phosphate compounds, silicate compounds, borate compounds, and the like.

[0104] A specific example of the oxide is LiNiO 2 , LiCoO 2 , LiCo 0.98 Al 0.01 Mg 0.01 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 and LiMn 2 O 4 Specific examples of phosphate compounds include LiFePO 4 , LiMnPO 4 and LiFe 0.5 Mn 0.5 P.O. 4 And so on.

[0105] The positive electrode binder contains one or more of materials such as synthetic rubber and polymer compounds. Specific examples of synthetic rubber include styrene-butadiene rubber, fluorine-containing rubber, and ethylene-propylene-diene. Specific examples of polymer compounds include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

[0106] The positive electrode conductive agent contains one or more conductive materials such as a carbon material, a metal material, and a conductive polymer compound, and specific examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black.

[0107] (Negative Electrode) As shown in FIG. 2, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B.

[0108] 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 contains a conductive material such as a metal material, and a specific example of the conductive material is copper.

[0109] The negative electrode active material layer 22B includes one or more types of negative electrode active materials that absorb and release lithium. However, the negative electrode active material layer 22B may further include one or more types 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 includes one or more types of a coating method, a vapor phase method, a liquid phase method, a thermal spraying method, and a firing method (sintering method).

[0110] Here, the anode active material layer 22B is provided on both sides of the anode current collector 22A, and therefore the anode 22 includes two anode active material layers 22B. However, since the anode active material layer 22B is provided on only one side of the anode current collector 22A on the side where the anode 22 faces the cathode 21, the anode 22 may include only one anode active material layer 22B.

[0111] The type of negative electrode active material is not particularly limited, but specific examples include carbon materials and metal-based materials, because high energy density can be obtained.

[0112] Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite).

[0113] The metallic material is a material containing, as a constituent element, one or more of metallic elements and semi-metallic elements that can form an alloy with lithium, and specific examples of the metallic element and semi-metallic element include silicon and tin. The metallic material may be a simple substance, an alloy, a compound, a mixture of two or more of these, or a material containing two or more of these phases. Specific examples of metallic materials include TiSi 2 and SiO x (0<x≦2 or 0.2<x<1.4), etc.

[0114] The "element" described here refers to a general element, and may contain trace amounts of impurities. In other words, the purity of the element is not necessarily limited to 100%. Furthermore, 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 metalloid elements as constituent elements. Furthermore, the "alloy" may contain one or more non-metal elements as constituent elements.

[0115] Among these, the negative electrode material preferably contains a metal-based 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 sufficiently suppressed by utilizing a thiazole-type compound. This silicon-containing material is a material containing silicon as a constituent element. As described above, the silicon-containing material may be silicon alone, a silicon alloy, a silicon compound, a mixture of two or more of these, or a material containing two or more of these phases.

[0116] Silicon alloys contain, as constituent elements other than silicon, any one or more of metal elements such as tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. Silicon compounds contain, as constituent elements other than silicon, any one or more of non-metal elements such as carbon and oxygen. However, silicon compounds may also contain, as constituent elements other than silicon, any one or more of the metal elements described for silicon alloys.

[0117] Specific examples of silicon alloys include the above-mentioned TiSi 2 In addition, SiB 4 , SiB 6 , Mg 2 Si, Ni 2 Si, MoSi 2 , CoSi 2 , NiSi 2 , CaSi 2 , CrSi 2 , Cu 5 Si, FeSi 2 , MnSi 2 , NbSi 2 , TaSi 2 , VSi 2 , WSi 2 , ZnSi 2 and SiC, etc. However, the composition of the silicon alloy (the mixture ratio of silicon and metal elements) can be changed as desired.

[0118] Specific examples of silicon compounds include the above-mentioned SiO x Others, Si 3 N 4 , Si 2 N 2 O and LiSiO, etc.

[0119] In particular, it is preferable that the negative electrode active material contains both a carbon material and a silicon-containing material, because this prevents damage and separation of the negative electrode active material layer 22B while ensuring the battery capacity during charging and discharging.

[0120] Specifically, silicon-containing materials, which are metal-based materials, have the advantage of high theoretical capacity, but the drawback is that they tend to expand and contract significantly during charging and discharging. On the other hand, carbon materials have the drawback of low theoretical capacity, but the drawback is that they tend not to expand and contract during charging and discharging. Therefore, by using a carbon material and a silicon-containing material in combination, a high theoretical capacity can be obtained while suppressing the expansion and contraction of the anode active material layer 22B during charging and discharging. As a result, as described above, the battery capacity is guaranteed while preventing damage and detachment of the anode active material layer 22B.

[0121] The details regarding the negative electrode binder are the same as those regarding the positive electrode binder, and the details regarding the negative electrode conductive agent are the same as those regarding the positive electrode conductive agent.

[0122] 2, 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 through while preventing contact (short circuit) between the positive electrode 21 and the negative electrode 22. The separator 23 contains a polymer compound such as polyethylene.

[0123] (Electrolyte) The electrolyte is impregnated into each of the positive electrode 21, the negative electrode 22, and the separator 23, and has the above-described structure. That is, the electrolyte contains a thiazole-type compound.

[0124] 1 and 2, the positive electrode lead 25 is connected to the positive electrode current collector 21A of the positive electrode 21, and contains a conductive material such as aluminum. The positive electrode lead 25 is electrically connected to the battery lid 14 via the safety valve mechanism 15.

[0125] 1 and 2, the negative electrode lead 26 is connected to the negative electrode current collector 22A of the negative electrode 22 and contains a conductive material such as nickel. The negative electrode lead 26 is electrically connected to the battery can 11.

[0126] <2-2. Operation> The secondary battery operates as follows during charging and discharging.

[0127] During charging, lithium is released from the positive electrode 21 of the battery element 20 and is absorbed into the negative electrode 22 via the electrolyte. During discharging, lithium is released from the negative electrode 22 of the battery element 20 and is absorbed into the positive electrode 21 via the electrolyte. During charging and discharging, lithium is absorbed and released in an ionic state.

[0128] <2-3. Manufacturing Method> When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are prepared according to the procedure described below as an example, and the secondary battery is assembled using an electrolyte together with the positive electrode 21 and the negative electrode 22, and then the assembled secondary battery is subjected to a stabilization process. The procedure for preparing the electrolyte is as described above.

[0129] [Fabrication of Positive Electrode] First, a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent are mixed together to form a positive electrode mixture. The positive electrode mixture is then poured into a solvent to prepare a paste-like positive electrode mixture slurry. This solvent may be an aqueous solvent or an organic solvent. The positive electrode mixture slurry is then applied to both surfaces of the positive electrode current collector 21A to form the positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B may be compression-molded using a roll press or the like. In this case, the positive electrode active material layer 21B may be heated, or the compression molding may be repeated multiple times. This results in the positive electrode active material layer 21B being formed on both surfaces of the positive electrode current collector 21A, thereby fabricating the positive electrode 21.

[0130] [Fabrication of Negative Electrode] The negative electrode 22 is formed by the same procedure as the fabrication procedure for the positive electrode 21 described above. Specifically, first, a mixture (negative electrode mixture) of a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent is mixed together and poured into a solvent to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 22A to form the negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B may be compression-molded. As a result, the negative electrode active material layer 22B is formed on both surfaces of the negative electrode current collector 22A, and the negative electrode 22 is fabricated.

[0131] [Assembly of Secondary Battery] First, a positive electrode lead 25 is connected to the positive electrode current collector 21A of the positive electrode 21 using a joining method such as welding, and a negative electrode lead 26 is connected to the negative electrode current collector 22A of the negative electrode 22 using a joining method such as welding. Next, the positive electrode 21 and the negative electrode 22 are stacked together with the separator 23 interposed therebetween, and the positive electrode 21, the negative electrode 22, and the separator 23 are then wound to produce a wound body (not shown) having a space 20S. This wound body has a configuration similar to that of 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, a center pin 24 is inserted into the space 20S of the wound body.

[0132] Next, with the wound body sandwiched between insulating plates 12 and 13, the wound body and insulating plates 12 and 13 are housed inside battery can 11. In this case, the positive electrode lead 25 is connected to safety valve mechanism 15 using a joining method such as welding, and the negative electrode lead 26 is connected to battery can 11 using a joining method such as welding. Next, an electrolyte solution is injected into the inside of battery can 11, thereby impregnating the wound body with the electrolyte solution. As a result, the positive electrode 21, the negative electrode 22, and the separator 23 are each impregnated with the electrolyte solution, and battery element 20 is produced.

[0133] Finally, the battery lid 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 crimped via the gasket 17. As a result, the battery lid 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 a secondary battery.

[0134] [Stabilization of Secondary Battery] The assembled secondary battery is charged and discharged. Various conditions, such as the ambient temperature, the number of charge / discharge cycles (number of cycles), and the charge / discharge conditions, can be set as desired. This forms a coating on the surface of each of the positive electrode 21 and the negative electrode 22, electrochemically stabilizing the state of the battery element 20. This completes the secondary battery.

[0135] <2-4. Actions and Effects> In this secondary battery, the electrolyte has the above-described structure. In this case, for the reasons described above, even if charging and discharging are repeated, the decomposition reaction of the electrolyte on the surface of the negative electrode 22 is suppressed, and therefore, the decrease in discharge capacity is suppressed. Therefore, excellent battery characteristics can be obtained.

[0136] In particular, if the negative electrode 22 contains a silicon-containing material as the negative electrode active material, a sufficiently high energy density can be obtained, and the decomposition reaction of the electrolyte can be sufficiently suppressed by using a thiazole-type compound, thereby achieving even greater effects.

[0137] Furthermore, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium, and therefore a greater effect can be obtained.

[0138] Other functions and effects of this secondary battery are similar to those of the above-mentioned electrolyte solution.

[0139] 3. Modifications The configuration of the secondary battery described above can be modified as appropriate, as described below. However, any two or more of the modifications described below may be combined with each other.

[0140] [Variation 1] The secondary battery has been described as having a cylindrical battery structure. However, although not specifically illustrated here, the type of battery structure is not particularly limited, and may be a laminate film type, a square type, a coin type, a button type, or the like.

[0141] [Modification 2] A porous film separator 23 is used. However, although not specifically shown here, a laminated separator including a polymer compound layer may also be used.

[0142] Specifically, the laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer provided on one or both surfaces of the porous membrane. This is because the separator improves adhesion to each of the positive electrode 21 and the negative electrode 22, thereby suppressing misalignment (winding misalignment) of the battery element 20. This suppresses swelling of the secondary battery even if a decomposition reaction of the electrolyte solution occurs. 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.

[0143] One or both of the porous film and the polymer compound layer may contain one or more types of insulating particles. This is because the insulating particles promote heat dissipation when the secondary battery generates heat, thereby improving the safety (heat resistance) of the secondary battery. The insulating particles contain one or both of an inorganic material and a resin material. Specific examples of inorganic materials include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials include acrylic resin and styrene resin.

[0144] 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 film. In this case, multiple insulating particles may be added to the precursor solution as needed.

[0145] Even when this laminated separator is used, the same effect can be obtained because lithium becomes movable between the positive electrode 21 and the negative electrode 22. In this case, as described above, the safety of the secondary battery is particularly improved, and therefore, a greater effect can be obtained.

[0146] [Modification 3] An electrolytic solution that is a liquid electrolyte is used. However, although not specifically shown here, an electrolyte layer that is a gel electrolyte may also be used.

[0147] In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are stacked 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 together. The electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23.

[0148] Specifically, the electrolyte layer contains a polymer compound together with an electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented. The composition of the electrolytic solution is as described above. The polymer compound contains polyvinylidene fluoride, etc. When forming the electrolyte layer, a precursor solution containing the electrolytic solution, the polymer compound, a solvent, etc. is prepared, and then the precursor solution is applied to one or both surfaces of each of the positive electrode 21 and the negative electrode 22.

[0149] Even when this electrolyte layer is used, the same effect can be obtained because lithium can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer. In this case, particularly, leakage of the electrolyte solution is prevented as described above, so that a greater effect can be obtained.

[0150] 3. Uses of Secondary Batteries There are no particular limitations on the uses (application examples) of secondary batteries. Secondary batteries used as power sources may be the main power source or auxiliary power source in electronic devices, electric vehicles, and the like. 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 may be a power source used in place of the main power source or a power source that can be switched from the main power source.

[0151] Specific examples of uses for secondary batteries are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, headphone stereos, portable radios, and portable information terminals. Storage devices such as backup power supplies and memory cards. Power tools such as power drills and power saws. Battery packs installed in electronic devices. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric cars (including hybrid cars). Power storage systems such as home or industrial battery systems that store power in preparation for emergencies. In these uses, one secondary battery may be used, or multiple secondary batteries may be used.

[0152] The battery pack may use a single cell or a battery pack. The electric vehicle is a vehicle that operates (travels) using a secondary battery as a driving power source, and may be a hybrid vehicle that also has a driving source other than the secondary battery. In a home power storage system, power stored in a secondary battery, which is a power storage source, can be used to power home electrical appliances, etc.

[0153] Here, an example of an application of the secondary battery will be specifically described. The configuration of the application described below is merely an example and can be modified as appropriate.

[0154] Fig. 3 shows the block diagram of a battery pack. The battery pack described here is a battery pack (a so-called soft pack) that uses one secondary battery, and is installed in electronic devices such as smartphones.

[0155] 3, the battery pack includes a power supply 51 and a circuit board 52. The circuit board 52 is connected to the power supply 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55.

[0156] The power source 51 includes one secondary battery. The positive electrode lead of this secondary battery is connected to a positive electrode terminal 53, and the negative electrode lead is connected to a negative electrode terminal 54. The power source 51 can be connected to the outside via the positive electrode terminal 53 and the negative electrode terminal 54, and is therefore capable of charging and discharging. The circuit board 52 includes a control unit 56, a switch 57, a PTC element 58, and a temperature detection unit 59. However, the PTC element 58 may be omitted.

[0157] The control unit 56 includes a central processing unit (CPU) and memory, and controls the operation of the entire battery pack. The control unit 56 detects and controls the usage state of the power source 51 as necessary.

[0158] When the voltage of power supply 51 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, control unit 56 turns off switch 57 to prevent charging current from flowing through the current path of power supply 51. The overcharge detection voltage is not particularly limited, but specifically, it is 4.20 V±0.05 V, and the overdischarge detection voltage is not particularly limited, but specifically, it is 2.40 V±0.1 V.

[0159] Switch 57 includes a charge control switch, a discharge control switch, a charge diode, a discharge diode, etc., and switches between the connection and disconnection of power supply 51 and an external device in response to instructions from control unit 56. Switch 57 includes a metal oxide semiconductor field effect transistor (MOSFET), etc., and the charge / discharge current is detected based on the ON resistance of switch 57.

[0160] Temperature detection unit 59 includes a temperature detection element such as a thermistor. Temperature detection unit 59 measures the temperature of power supply 51 using temperature detection terminal 55 and outputs the temperature measurement result to control unit 56. The temperature measurement result measured by temperature detection unit 59 is used when control unit 56 performs charge / discharge control in the event of abnormal heat generation and when control unit 56 performs correction processing when calculating the remaining capacity.

[0161] An embodiment of the present technology will be described.

[0162] Examples 1 to 25 and Comparative Examples 1 and 2 As will be described below, secondary batteries were manufactured, and then the battery characteristics of the secondary batteries were evaluated.

[0163] [Manufacturing of Secondary Battery] A cylindrical lithium ion secondary battery shown in FIGS. 1 and 2 was manufactured by the procedure described below.

[0164] (Fabrication of Positive Electrode) First, a positive electrode active material (lithium-containing compound (oxide) lithium cobalt oxide (LiCoO 2 )), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 3 parts by mass of a positive electrode conductive agent (acetylene black) were mixed together to prepare a positive electrode mixture. Subsequently, the positive electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the solvent was stirred to prepare a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was applied to both sides of a positive electrode current collector 21A (a strip-shaped aluminum foil having a thickness of 12 μm) using a coating device, and the positive electrode mixture slurry was then dried to form a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B was compression-molded using a roll press. Thus, the positive electrode 21 was produced.

[0165] (Fabrication of Negative Electrode) Here, two types of negative electrodes 22 were fabricated.

[0166] When preparing the first type of negative electrode 22, first, 93 parts by mass of negative electrode active material (63 parts by mass of artificial graphite, which is a carbon material, and 30 parts by mass of silicon oxide, which is a metal-based material (silicon-containing material)) and 7 parts by mass of a negative electrode binder (polyvinylidene fluoride) were mixed together to prepare a negative electrode mixture. Next, the negative electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, which is an organic solvent), and the solvent was stirred to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to both sides of the negative electrode current collector 22A (a strip-shaped copper foil having a thickness of 15 μm) using a coating device, and the negative electrode mixture slurry was then dried to form a negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B was compression-molded using a roll press. This produced the negative electrode 22.

[0167] When preparing the second type of negative electrode 22, the same procedure as that for preparing the first type of negative electrode 22 was used, except that 93 parts by mass of a negative electrode active material (artificial graphite, which is a carbon material) and 7 parts by mass of a negative electrode binder (polyvinylidene fluoride) were mixed together to obtain a negative electrode mixture.

[0168] (Preparation of Electrolyte Solution) A solvent (ethylene carbonate, which is a cyclic carbonate ester, and dimethyl carbonate, which is a chain carbonate ester) was prepared. The mixing ratio (weight ratio) of the solvent was ethylene carbonate:dimethyl carbonate = 20:80. Next, an electrolyte salt (LiPF , which is a lithium salt) was added to the solvent. 6 ) 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 had been added, and the solvent was stirred. The classification and types of thiazole-type compounds are as shown in Tables 1 and 2. In this way, an electrolytic solution was prepared.

[0169] For comparison, an electrolyte solution was prepared in the same manner except that the thiazole compound was not used.

[0170] The meaning of the "classification" shown in Tables 1 and 2 is as follows: "First" indicates that a first thiazole-type compound was used, and "Second" indicates that a second thiazole-type compound was used.

[0171] (Assembly of Secondary Battery) First, a positive electrode lead 25 (aluminum foil) was welded to the positive electrode current collector 21 A of the positive electrode 21 , and a negative electrode lead 26 (copper foil) was welded to the negative electrode current collector 22 A of the negative electrode 22 .

[0172] Next, the positive electrode 21 and the negative electrode 22 were stacked together with a separator 23 (a microporous polyethylene film having a thickness of 15 μm) interposed therebetween, and then the positive electrode 21, the negative electrode 22, and the separator 23 were wound together to produce a wound body having a space 20S. Next, a center pin 24 was inserted into the space 20S of the wound body.

[0173] Next, the insulating plates 12 and 13 were housed together with the wound body inside the battery can 11. In this case, the positive electrode lead 25 was welded to the safety valve mechanism 15, and the negative electrode lead 26 was welded to the battery can 11. Next, the electrolyte was injected into the battery can 11. As a result, the wound body was impregnated with the electrolyte, and the battery element 20 was produced.

[0174] Finally, the battery lid 14, the safety valve mechanism 15, and the PTC element 16 were housed inside the battery can 11, and then the battery can 11 was crimped via the gasket 17. This sealed the battery can 11, and thus the secondary battery was assembled.

[0175] (Stabilization of Secondary Battery) The secondary battery was subjected to one cycle of charge and discharge in a room temperature environment (temperature = 23°C). During charging, the battery was charged at a constant current of 0.1 C until the voltage reached 4.2 V, and then charged at a constant voltage of 0.05 C at the same voltage of 4.2 V. During discharging, the battery was discharged at a constant current of 0.1 C until the voltage reached 3.0 V. 0.1 C is the current value at which the battery capacity (theoretical capacity) is fully discharged in 10 hours, and 0.05 C is the current value at which the battery capacity is fully discharged in 20 hours.

[0176] As a result, a coating was formed on the surface of each of the positive electrode 21 and the negative electrode 22, electrochemically stabilizing the state of the battery element 20. Thus, the secondary battery was completed.

[0177] After the secondary battery was completed, the content (wt %) of the thiazole-type compound in the electrolyte was measured using ICP atomic emission spectroscopy. The results are shown in Tables 1 and 2.

[0178] [Evaluation of Battery Characteristics] The cycle characteristics were evaluated as the battery characteristics according to the procedure described below, and the results shown in Tables 1 and 2 were obtained.

[0179] 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, the battery was charged at a constant current of 1 C until the voltage reached 4.2 V, and then at the same voltage of 4.2 V, the battery was charged at a constant voltage of 0.05 C. 1 C is the current value at which the battery capacity is fully discharged in 1 hour.

[0180] Subsequently, the secondary battery was discharged in the same environment to measure the discharge capacity (discharge capacity at the first cycle). During discharge, the secondary battery was discharged at a constant current of 3 C until the voltage reached 3.0 V. 3 C is the current value at which the battery capacity is fully discharged in 1 / 3 of an hour.

[0181] Subsequently, the discharge capacity (discharge capacity at the 100th cycle) of the secondary battery was measured by repeatedly charging and discharging the battery in the same environment until the number of cycles reached 100. The charge and discharge conditions for the second and subsequent cycles were the same as those for the first cycle.

[0182] Finally, the capacity retention rate, which is an index for evaluating cycle characteristics, was calculated based on the formula: capacity retention rate (%)=(discharge capacity at 100th cycle / discharge capacity at 1st cycle)×100.

[0183]

[0184]

[0185] [Discussion] As shown in Tables 1 and 2, the capacity retention rate varied depending on the composition of the electrolyte solution.

[0186] Specifically, when the electrolyte solution contained a thiazole-type compound (Examples 1 to 25), the capacity retention rate increased compared to when the electrolyte solution did not contain a thiazole-type compound (Comparative Examples 1 and 2).

[0187] In particular, when the electrolyte solution contained a thiazole-type compound, the following tendency was observed.

[0188] First, a high capacity retention rate was obtained regardless of the type of thiazole-type compound (first thiazole-type compound and second thiazole-type compound).

[0189] Secondly, when the content of the thiazole type compound in the electrolyte solution was 0.001 wt % to 5 wt %, the capacity retention rate was further increased.

[0190] Third, when the negative electrode active material contained a silicon-containing material, the increase rate of the capacity retention rate was greater than when the negative electrode active material did not contain a silicon-containing material (when the negative electrode active material contained a carbon material). Specifically, the increase rate of the capacity retention rate when the negative electrode active material did not contain a silicon-containing material was about 26%, whereas the increase rate of the capacity retention rate when the negative electrode active material contained a silicon-containing material was about 66%.

[0191] Examples 26 to 31 Secondary batteries were fabricated and their battery characteristics were evaluated in the same manner as in Example 4, except that an additive (unsaturated cyclic ester carbonate, fluorinated cyclic ester carbonate, or cyanated cyclic ester carbonate) was added to the electrolyte solution as shown in Table 3. The classification, type, and content (wt %) of the additive are as shown in Table 3.

[0192] 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.

[0193]

[0194] 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 increased more than when the electrolyte solution did not contain an additive (Example 4).

[0195] Examples 32 to 51 Secondary batteries were fabricated and their battery characteristics were evaluated in the same manner as in Example 4, except that additives (sulfonic acid ester, sulfate ester, sulfite ester, dicarboxylic acid anhydride, disulfonic acid anhydride, sulfonic acid carboxylic acid anhydride, or sulfobenzoic acid imide) were added to the electrolyte solution as shown in Tables 4 and 5. The classification, type, and content (wt %) of the additives are as shown in Tables 4 and 5.

[0196] Specifically, 1,3-propane sultone (PS), 1-propene-1,3-sultone (PRS), 1,4-butane sultone (BS1), 2,4-butane sultone (BS2), and methanesulfonic acid propargyl ester (MSP) were used as sulfonate esters.

[0197] As sulfates, 1,3,2-dioxathiolane 2,2-dioxide (OTO), 1,3,2-dioxathiane 2,2-dioxide (OTA), and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane (SOTO) were used.

[0198] As sulfites, 1,3,2-dioxathiolane 2-oxide (DTO) and 4-methyl-1,3,2-dioxathiolane 2-oxide (MDTO) were used.

[0199] As dicarboxylic acid anhydrides, 1,4-dioxane-2,6-dione (DOD), succinic anhydride (SA) and glutaric anhydride (GA) were used.

[0200] As the disulfonic acid anhydrides, 1,2-ethanedisulfonic acid anhydride (ESA), 1,3-propanedisulfonic acid anhydride (PSA) and hexafluoro-1,3-propanedisulfonic acid anhydride (FPSA) were used.

[0201] As sulfonic acid carboxylic acid anhydrides, 2-sulfobenzoic anhydride (SBA) and 2,2-dioxooxathiolan-5-one (DOTO) were used.

[0202] As sulfobenzoic acid imides, o-sulfobenzimide (SBI) and N-methylsaccharin (NMS) were used.

[0203]

[0204]

[0205] As shown in Tables 4 and 5, when the electrolyte solution contained an additive (sulfonic acid ester, sulfate ester, sulfite ester, dicarboxylic acid anhydride, disulfonic acid anhydride, sulfonic acid carboxylic acid anhydride, or sulfobenzoic acid imide) (Examples 32 to 51), the capacity retention rate was increased more than when the electrolyte solution did not contain an additive (Example 3).

[0206] [Summary] From the results shown in Tables 1 to 5, it can be seen that when the electrolyte solution contains a thiazole-type compound, a high capacity retention rate is obtained. Therefore, the cycle characteristics are improved, and excellent battery characteristics are obtained in the secondary battery.

[0207] The present technology has been described above with reference to an embodiment and examples. However, the configuration of the present technology is not limited to the configuration described in the embodiment and examples, and can be modified in various ways.

[0208] Specifically, the battery element has been described as having a wound structure. However, the structure of the battery element is not particularly limited, and other structures such as a stacked structure and a zigzag structure may also be used. In the stacked structure, positive and negative electrodes are alternately stacked with a separator interposed therebetween, while in the zigzag structure, the positive and negative electrodes are folded in a zigzag pattern while facing each other with the separator interposed therebetween.

[0209] Although the electrode reactant is lithium in the above description, the electrode reactant is not particularly limited. Specifically, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. Alternatively, the electrode reactant may be other light metals such as aluminum.

[0210] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

[0211] The present technology may also be configured as follows: <1> A secondary battery comprising: a positive electrode; a negative electrode; and an electrolyte solution containing a thiazole-type compound, wherein the thiazole-type compound includes at least one of a compound represented by formula (1) and a compound represented by formula (2). (Each of R1 to R15 is any one of hydrogen, fluorine, an amino group, a silylalkyl group, an aminoalkyl group, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an alkylthio group, a fluorinated alkyl group, a fluorinated cycloalkyl group, a fluorinated aryl group, a fluorinated alkoxy group, a fluorinated alkylthio group, and a monovalent bonding group in which two or more of them are bonded to each other.) <2> The secondary battery according to <1>, wherein the negative electrode includes a negative electrode active material, and the negative electrode active material includes a silicon-containing material. <3> The secondary battery according to <1> or <2>, wherein the content of the thiazole-type compound in the electrolyte solution is 0.001% by weight or more and 5% by weight or less. <4> The secondary battery according to any one of <1> to <3>, wherein the electrolyte solution further includes 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 <1> to <4>, wherein the electrolyte solution further contains at least one of a sulfonic acid ester, a sulfate ester, a sulfite ester, a dicarboxylic acid anhydride, a disulfonic acid anhydride, a sulfonic acid carboxylic acid anhydride, and a sulfobenzoic acid imide. <6> The secondary battery according to any one of <1> to <5>, wherein the secondary battery is a lithium ion secondary battery. <7> An electrolyte solution for a secondary battery, comprising a thiazole-type compound, wherein the thiazole-type compound includes at least one of a compound represented by formula (1) and a compound represented by formula (2). (Each of R1 to R15 is any one of hydrogen, fluorine, an amino group, a silylalkyl group, an aminoalkyl group, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an alkylthio group, a fluorinated alkyl group, a fluorinated cycloalkyl group, a fluorinated aryl group, a fluorinated alkoxy group, a fluorinated alkylthio group, and a monovalent bonding group in which two or more of these groups are bonded to each other.)

Claims

1. A positive electrode, a negative electrode, and an electrolytic solution containing a thiazole-type compound are provided, wherein the thiazole-type compound contains at least one of a compound represented by formula (1) and a compound represented by formula (2), a secondary battery. 【Chemical 1】 (Each of R1 to R15 is any one of hydrogen, fluorine, an amino group, a silylalkyl group, an aminoalkyl group, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an alkylthio group, a fluorinated alkyl group, a fluorinated cycloalkyl group, a fluorinated aryl group, a fluorinated alkoxy group, a fluorinated alkylthio group, and a monovalent linking group in which two or more of them are bonded to each other.)

2. The negative electrode contains a negative electrode active material, and the negative electrode active material contains a silicon-containing material, The secondary battery according to claim 1.

3. The content of the thiazole-type compound in the electrolytic solution is 0.001% by weight or more and 5% by weight or less, The secondary battery according to claim 1.

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

5. The electrolytic solution further contains at least one of a sulfonic acid ester, a sulfuric acid ester, a sulfurous acid ester, a dicarboxylic acid anhydride, a disulfonic acid anhydride, a sulfonic acid carboxylic acid anhydride, and a sulfobenzoimide, The secondary battery according to any one of claims 1 to 3.

6. It is a lithium ion secondary battery, The secondary battery according to any one of claims 1 to 3.

7. An electrolytic solution for a secondary battery containing a thiazole-type compound, wherein the thiazole-type compound contains at least one of a compound represented by formula (1) and a compound represented by formula (2), An electrolytic solution for a secondary battery. 【Chemical 2】 (Each of R1 to R15 is any one of hydrogen, fluorine, an amino group, a silylalkyl group, an aminoalkyl group, an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group, an alkylthio group, a fluorinated alkyl group, a fluorinated cycloalkyl group, a fluorinated aryl group, a fluorinated alkoxy group, a fluorinated alkylthio group, and a monovalent linking group in which two or more of them are bonded to each other.)

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