Electrolytes for secondary batteries and secondary batteries

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

[Technical Field]

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

[0002] With the widespread use of various electronic devices such as mobile phones, development of rechargeable batteries is progressing as a power source that is small, lightweight, and provides high energy density. These rechargeable batteries consist of a positive electrode, a negative electrode, and an electrolyte (electrolyte for rechargeable batteries), and various studies are being conducted on the configuration of these batteries.

[0003] Specifically, a benzotriazole derivative having a particular structure is contained in the electrolyte (see, for example, Patent Documents 1 and 2). Alternatively, a benzothiazole derivative having a particular structure is contained in the electrolyte (see, for example, Patent Documents 3 and 4). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-273927 [Patent Document 2] Special Publication No. 2013-513923 [Patent Document 3] Patent No. 6056721 Specification [Patent Document 4] International Publication No. 2019 / 181278 Brochure [Overview of the project]

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

[0006] There is a need for electrolytes and batteries for secondary batteries that can achieve excellent battery characteristics.

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

[0008] [ka] (Each of R1 to R15 is one of the following: 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, fluorinated alkylthio group, or a monovalent bond group formed by the bonding of two or more of these groups.)

[0009] A secondary battery according to one embodiment of this technology comprises a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte has the same configuration as the electrolyte for the secondary battery according to the above-described embodiment of this technology.

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

[0011] Furthermore, the effects of this technology are not necessarily limited to those described herein, but may include any of the series of effects related to this technology described later. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view showing the configuration of a secondary battery in one embodiment of this technology. [Figure 2] Figure 1 is a cross-sectional view showing the configuration of the battery element. [Figure 3] This is a block diagram showing the configuration of an example application of a secondary battery.

Mode for Carrying Out the Invention

[0013] Hereinafter, regarding one embodiment of the present technology, a detailed description will be given with reference to the drawings. The order of description is as follows. 1. Electrolyte for secondary battery 1-1. Composition 1-2. Manufacturing method 1-3. Action and effect 2. Secondary battery 2-1. Composition 2-2. Operation 2-3. Manufacturing method 2-4. Action and effect 3. Variation 4. Applications of secondary batteries

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

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

[0016] [Thiazole-type compound] The electrolyte contains any one or two or more of thiazole-type compounds. This thiazole-type compound is a compound containing a condensed ring in which naphthalene and thiazole are condensed with each other.

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

[0018] [Chemical formula] (Each of R1 to R15 is one of the following: 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, fluorinated alkylthio group, or a monovalent bond group formed by the bonding of two or more of these groups.)

[0019] In the following, the compound shown in formula (1) will be referred to as the "first thiazole compound," and the compound shown in formula (2) will be referred to as the "second thiazole 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 linked to each other via dithio bonds (-SS-).

[0021] The electrolyte contains thiazole compounds because, during the charging and discharging of a secondary battery using this electrolyte, a good film derived from these thiazole compounds forms on the surface of the negative electrode. This film has a dense structure and is electrochemically stable. As a result, the surface of the negative electrode is electrochemically protected by this film, suppressing the decomposition reaction of the electrolyte on the negative electrode surface. Therefore, even with repeated charging and discharging, the decrease in discharge capacity is suppressed.

[0022] (composition) Each of R1 to R15 is not particularly limited as long as it is any of the following: hydrogen (-H), fluorine (-F), amino group (-NH2), 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, fluorinated alkylthio group, and bonding group, as described above.

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

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

[0025] The number of carbon atoms in an aryl group is not particularly limited; specific examples of aryl groups include phenylene groups and naphthylene groups.

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

[0027] The number of carbon atoms in an alkylthio group is not particularly limited; specific examples of alkylthio groups include methylthio and ethylthio groups. For clarification, an alkylthio group is an alkoxy group in which the oxygen atom is replaced by a sulfur atom.

[0028] A silylalkyl group is a group in which three hydrogen atoms in a silyl group (-SiH3) are replaced by an alkyl group. Details regarding the alkyl group are as described above. A specific example of a silylalkyl group is the trimethylsilyl group.

[0029] An aminoalkyl group is a group in which two hydrogen atoms in an amino group are replaced by an alkyl group. Details regarding the alkyl group are as described above. A specific example of an aminoalkyl group is the dimethylamino group.

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

[0031] The bonding group is a monovalent group formed by bonding two or more of the following groups to each other: 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. The type of bonding group is not particularly limited, but specifically, it is 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 example) Specific examples of thiazole-type compounds are as follows.

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

[0034] [ka]

[0035] [ka]

[0036] [ka]

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

[0038] [ka]

[0039] [ka]

[0040] [ka]

[0041] [ka]

[0042] [ka]

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

[0044] Furthermore, when the electrolyte contains both the first thiazole type compound and the second thiazole type compound, the content of the thiazole type compound is the sum of the content of the first thiazole type compound and the content of the second thiazole type compound.

[0045] When measuring the content of thiazole-type compounds, the electrolyte is recovered by disassembling the secondary battery, and the content of the thiazole-type compounds is calculated by analyzing the electrolyte. The analytical method for the electrolyte is not particularly limited, but specifically, it may be one or more of the following: inductively coupled plasma (ICP) emission spectroscopy, nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectroscopy (GC-MS).

[0046] [solvent] Furthermore, the electrolyte may also contain a solvent. This solvent may contain one or more non-aqueous solvents (organic solvents), and an electrolyte containing such a non-aqueous solvent is a so-called non-aqueous electrolyte.

[0047] Non-aqueous solvents include esters and ethers, and more specifically, carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds.

[0048] Carbonate ester compounds include cyclic carbonate esters and linear carbonate esters. Specific examples of cyclic carbonate esters include ethylene carbonate and propylene carbonate. Specific examples of linear carbonate esters include dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate.

[0049] Carboxylic acid ester compounds include linear carboxylic acid esters. Specific examples of linear carboxylic acid esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, ethyl trimethylacetate, methyl butyrate, and ethyl butyrate.

[0050] Lactone compounds include lactones, among others. Specific examples of lactones include γ-butyrolactone and γ-valerolactone.

[0051] The ethers may also be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane.

[0052] (Electrolyte salts) Furthermore, the electrolyte may also contain an electrolyte salt. This electrolyte salt is a light metal salt, such as a lithium salt.

[0053] Specific examples of lithium salts include lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3SO2)3), lithium bis(oxalato)borate (LiB(C2O4)2), lithium difluorooxalatoborate (LiBF2(C2O4)), lithium difluorodi(oxalato)borate (LiPF2(C2O4)2), lithium tetrafluorooxalatophosphate (LiPF4(C2O4)), lithium monofluorophosphate (Li2PFO3), and lithium difluorophosphate (LiPF2O2).

[0054] The electrolyte salt content is not particularly limited, but specifically, it is between 0.3 mol / kg and 3.0 mol / kg relative to the solvent. This is because it allows for high ionic conductivity.

[0055] (Additives) Furthermore, the electrolyte may also contain one or more of the additives.

[0056] (Unsaturated cyclic carbonates, fluorinated cyclic carbonates, and cyanated cyclic carbonates) Specifically, the additives are one or more of the following: unsaturated cyclic carbonate esters, fluorinated cyclic carbonate esters, and cyanated cyclic carbonate esters. This is because it improves the electrochemical stability of the electrolyte. As a result, the decomposition reaction of the electrolyte is further suppressed during the charging and discharging of the secondary battery, and the decrease in discharge capacity is further suppressed even after repeated charging and discharging.

[0057] Unsaturated cyclic carbonate esters are cyclic carbonate esters that contain unsaturated carbon bonds (carbon-carbon double bonds). The number of unsaturated carbon bonds is not particularly limited; there may be one or two or more.

[0058] This unsaturated cyclic carbonate ester contains one or more of the following compounds: vinylene carbonate compounds, vinyl ethylene carbonate compounds, and methylene ethylene carbonate compounds.

[0059] Vinylen carbonate compounds are unsaturated cyclic carbonate esters having a vinylene-type structure. Specific examples of vinylene carbonate compounds include vinylene carbonate (1,3-dioxol-2-one), methylvinylene carbonate (4-methyl-1,3-dioxol-2-one), ethylvinylene carbonate (4-ethyl-1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1,3-dioxol-2-one, and 4-trifluoromethyl-1,3-dioxol-2-one.

[0060] Vinyl ethylene carbonate compounds are unsaturated cyclic carbonate esters having a vinyl ethylene carbonate-type structure. Specific examples of vinyl ethylene carbonate compounds include vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, 4-ethyl-4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolan-2-one, 4,4-divinyl-1,3-dioxolan-2-one, and 4,5-divinyl-1,3-dioxolan-2-one.

[0061] Methylene carbonate compounds are unsaturated cyclic carbonate esters having a methylene carbonate-type structure. Specific examples of methylene carbonate compounds include methylene carbonate (4-methylene-1,3-dioxolan-2-one), 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl-5-methylene-1,3-dioxolan-2-one. Here, only compounds having one methylene group are given as examples of methylene carbonate compounds, but these methylene carbonate compounds may have two or more methylene groups.

[0062] Furthermore, cyclic carbonate esters containing unsaturated carbon bonds are classified as unsaturated cyclic carbonate esters, and do not fall under either fluorinated cyclic carbonate esters or cyanated cyclic carbonate esters.

[0063] Fluorinated cyclic carbonates are cyclic carbonates that contain fluorine as a constituent element. The number of fluorine atoms is not particularly limited; there may be one or two or more. In other words, fluorinated cyclic carbonates are compounds in which one or more hydrogen atoms in a cyclic carbonate are substituted with fluorine.

[0064] Specific examples of fluorinated cyclic carbonate esters include fluoroethylene (4-fluoro-1,3-dioxolan-2-one) and difluoroethylene (4,5-difluoro-1,3-dioxolan-2-one).

[0065] Furthermore, cyclic carbonate esters containing fluorine as a constituent element are classified as fluorinated cyclic carbonate esters, and not as unsaturated cyclic carbonate esters or cyanated cyclic carbonate esters.

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

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

[0068] Furthermore, cyclic carbonate esters containing a cyano group are classified as cyanated cyclic carbonate esters, and not as unsaturated cyclic carbonate esters or fluorinated cyclic carbonate esters.

[0069] (Sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic acid anhydrides, and sulfobenzoic acid imides) Furthermore, the additives are one or more of the following: sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic acid anhydrides, and sulfobenzoic acid imides. This is because it improves the electrochemical stability of the electrolyte. As a result, the decomposition reaction of the electrolyte is further suppressed during the charging and discharging of the secondary battery, and the decrease in discharge capacity is further suppressed even after repeated charging and discharging.

[0070] Specific examples of sulfonic acid esters include 1,3-propanesultone, 1-propene-1,3-sultone, 1,4-butanesultone, 2,4-butanesultone, and propargyl methanesulfonate.

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

[0072] Specific examples of sulfite esters include 1,3-propanesultone, 1-propene-1,3-sultone, 1,4-butanesultone, 2,4-butanesultone, and propargyl methanesulfonic acid. Specific examples of sulfite esters include 1,3,2-dioxathiolane 2-oxide and 4-methyl-1,3,2-dioxathiolane 2-oxide.

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

[0074] Specific examples of disulfonic anhydrides include 1,2-ethanedisulfonic anhydride, 1,3-propanedisulfonic anhydride, and hexafluoro1,3-propanedisulfonic anhydride.

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

[0076] Specific examples of sulfobenzoic acid imides include o-sulfobenzimide and N-methylsaccharin.

[0077] (Nitrile compounds) Furthermore, the additive is a nitrile compound. This is because it improves the electrochemical stability of the electrolyte. As a result, the decomposition reaction of the electrolyte is further suppressed during charging and discharging, and the decrease in discharge capacity is further suppressed even when charging and discharging is repeated. In this case, the generation of gas caused by the decomposition reaction of the electrolyte is also suppressed.

[0078] These nitrile compounds are compounds containing one or more cyano groups (-CN). Specific examples of nitrile compounds include octanenitrile, benzonitrile, phthalonitrile, succinonitrile, glutalonitrile, adiponitrile, sebaconitrile, 1,3,6-hexanetricarbonite, 3,3'-oxydipropionitrile, 3-butoxypropionitrile, ethylene glycol bispropionitrile ether, 1,2,2,3-tetracyanopropane, tetracyanopropane, fumaronitrile, 7,7,8,8-tetracyanoquinodimethane, cyclopentanecarbonite, 1,3,5-cyclohexanetricarbonite, and 1,3-bis(dicyanomethylidene)indan.

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

[0080] <1-2. Manufacturing method> When preparing an electrolyte, an electrolyte salt is added to the solvent, and then a thiazole compound is added to the solvent. This causes the electrolyte salt and the thiazole compound to dissolve or disperse in the solvent, thus preparing the electrolyte.

[0081] <1-3. Mechanism and Effects> According to this electrolyte, it contains thiazole-type compounds.

[0082] In this case, as described above, during the charging and discharging of a secondary battery using an electrolyte, a good film derived from the thiazole compound is formed on the surface of the negative electrode, and this film electrochemically protects the surface of the negative electrode. As a result, the decomposition reaction of the electrolyte on the surface of the negative electrode is suppressed, and the decrease in discharge capacity is suppressed even when charging and discharging is repeated. Therefore, a secondary battery with excellent battery characteristics can be realized. It is possible.

[0083] In particular, a sufficiently good coating is formed when the thiazole compound content in the electrolyte is between 0.001% and 5% by weight. Therefore, the decomposition reaction of the electrolyte is sufficiently suppressed, and a higher effect can be obtained.

[0084] Furthermore, if the electrolyte contains one or more of the following: unsaturated cyclic carbonate esters, fluorinated cyclic carbonate esters, and cyanated cyclic carbonate esters, the decomposition reaction of the electrolyte is further suppressed, resulting in a higher effectiveness.

[0085] Furthermore, if the electrolyte contains one or more of the following: sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic acid anhydrides, and sulfobenzoic acid imides, the decomposition reaction of the electrolyte is further suppressed, thus achieving a higher effect.

[0086] <2. Secondary battery> Next, we will describe a secondary battery according to one embodiment of this technology using the electrolyte described above.

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

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

[0089] The types of electrode reactants are not particularly limited, but specifically, they are light metals such as alkali metals and alkaline earth metals. Alkali metals include lithium, sodium, and potassium, while alkaline earth metals include beryllium, magnesium, and calcium.

[0090] In the following example, we will consider the case where lithium is the electrode reactant. A secondary battery that obtains battery capacity by utilizing the intercalation and deintercalation of lithium is a so-called lithium-ion secondary battery. In this lithium-ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

[0091] <2-1. Structure> Figure 1 shows the cross-sectional configuration of a secondary battery, while Figure 2 shows the cross-sectional configuration of the battery element 20 shown in Figure 1.

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

[0093] [Battery can] As shown in Figure 1, the battery casing 11 is a housing member that contains the battery elements 20 and the like. The battery casing 11 has an open end and a closed end, thus having a hollow structure. Furthermore, the battery casing 11 contains one or more types of metal materials, such as iron, aluminum, iron alloys, and aluminum alloys. The surface of the battery casing 11 may be plated with a metal material such as nickel.

[0094] At the open end of the battery case 11, a battery cover 14, a safety valve mechanism 15, and a thermal resistance element (PTC element) 16 are crimped via a gasket 17. This seals the battery case 11 with the battery cover 14. Here, the battery cover 14 contains the same material as the forming material of the battery case 11. The safety valve mechanism 15 and the PTC element 16 are located 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 contains an insulating material, and its surface may be coated with asphalt or the like.

[0095] In this safety valve mechanism 15, if the internal pressure of the battery can 11 reaches a certain level due to an internal short circuit or external overheating, the disk plate 15A inverts, thereby disconnecting the electrical connection between the battery cover 14 and the battery element 20. To prevent abnormal heat generation caused by high current, the electrical resistance of the PTC element 16 increases in proportion to the rise in temperature.

[0096] [insulating board] As shown in Figure 1, the insulating plates 12 and 13 are arranged to face each other via the battery element 20. As a result, the battery element 20 is sandwiched between the insulating plates 12 and 13.

[0097] [Battery element] As shown in Figures 1 and 2, the battery element 20 is a power generation element that includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown).

[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 via a separator 23 and are wound facing each other via the separator 23. 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 Figure 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. This positive electrode current collector 21A contains a conductive material such as a metal material, a specific example of which is aluminum.

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

[0102] Here, since the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A, the positive electrode 21 contains two positive electrode active material layers 21B. However, since the positive electrode active material layer 21B is provided only on 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 contain only one positive electrode active material layer 21B.

[0103] The type of positive electrode active material is not particularly limited, but specifically, it is a lithium-containing compound. This lithium-containing compound is a compound that contains lithium along with one or more transition metal elements as constituent elements, and may further contain one or more other elements as constituent elements. The type of other element is not particularly limited as long as it is an element other than lithium and the transition metal elements, but specifically, it is an element belonging to groups 2 to 15 of the long-period periodic table. The type of lithium-containing compound is not particularly limited, but specifically, it is an oxide, a phosphoric acid compound, a silicate compound, and a borate compound.

[0104] Specific examples of oxides include LiNiO2, LiCoO2, and LiCo 0.98 Al 0.01 Mg 0.01 O2, LiLiLi 0.5 Co 0.2 Mn 0.3 Examples include O2 and LiMn2O4. Specific examples of phosphorylated compounds include LiFePO4, LiMnPO4, and LiFe 0.5 Mn 0.5 Examples include PO4.

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

[0106] The positive electrode conductive agent contains one or more conductive materials, such as carbon materials, metallic materials, and conductive polymer compounds. Specific examples of carbon materials include graphite, carbon black, acetylene black, and Ketjen black.

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

[0108] The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. This negative electrode current collector 22A contains a conductive material such as a metallic material, a specific example of which is copper.

[0109] The negative electrode active material layer 22B contains one or more types of negative electrode active materials that intercalate and deintercalate lithium. However, the negative electrode active material layer 22B may further contain one or more types of other materials such as negative electrode binders and negative electrode conductive agents. The method for forming the negative electrode active material layer 22B is not particularly limited, but specifically, it is one or more types of coating, gas phase, liquid phase, thermal spraying, and firing (sintering) methods.

[0110] Here, since the negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A, the negative electrode 22 contains two negative electrode active material layers 22B. However, since the negative electrode active material layer 22B is provided only on one side of the negative electrode current collector 22A on the side where the negative electrode 22 faces the positive electrode 21, the negative electrode 22 may contain only one negative electrode active material layer 22B.

[0111] The type of the negative electrode active material is not particularly limited, and specifically, it is a carbon material, a metal-based material, or the like. This is because a high energy density can be obtained.

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

[0113] The metal-based material is a material containing any one or two or more of metal elements and metalloid elements that can form an alloy with lithium as constituent elements. Specific examples of the metal elements and metalloid elements include silicon and tin. This metal-based material may be a single substance, an alloy, a compound, a mixture of two or more of them, or a material containing two or more phases of them. Specific examples of the metal-based material include TiSi2 and SiO x (0 < x ≤ 2 or 0.2 < x < 1.4), etc.

[0114] The "single substance" described here means only a general single substance, so it may contain trace amounts of impurities. That is, the purity of the single substance is not necessarily limited to 100%. In addition, the "alloy" described here includes not only materials containing two or more metal elements as constituent elements, but also materials containing one or two or more metal elements and one or two or more metalloid elements as constituent elements. Also, the "alloy" may contain one or two or more non-metal elements as constituent elements.

[0115] Among them, it is preferable that the negative electrode material contains a metal-based material, and it is more preferable that it 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 using 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 a single substance of silicon, an alloy of silicon, a compound of silicon, a mixture of two or more of them, or a material containing two or more phases of them.

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

[0117] Specific examples of silicon alloys include, in addition to the TiSi2 mentioned above, SiB4, SiB6, Mg2Si, Ni2Si, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, and SiC. However, the composition of silicon alloys (the mixing ratio of silicon to metal elements) can be arbitrarily changed.

[0118] A specific example of a silicon compound is the SiO mentioned above. x Other examples include Si3N4, Si2N2O, and LiSiO.

[0119] In particular, it is preferable that the negative electrode active material contains both carbon material and silicon-containing material. This is because, during charging and discharging, the battery capacity is ensured while preventing damage and detachment of the negative electrode active material layer 22B.

[0120] In detail, silicon-containing materials, which are metallic materials, have the advantage of high theoretical capacity, but also the concern that they tend to expand and contract drastically during charging and discharging. On the other hand, carbon materials have the concern of low theoretical capacity, but also the advantage that they do not expand and contract easily during charging and discharging. Therefore, by using carbon materials and silicon-containing materials in combination, a high theoretical capacity can be obtained while suppressing the expansion and contraction of the negative electrode active material layer 22B during charging and discharging. As a result, as described above, the battery capacity is ensured while preventing damage and detachment of the negative electrode active material layer 22B.

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

[0122] (Separator) As shown in Figure 2, the separator 23 is an insulating porous membrane interposed between the positive electrode 21 and the negative electrode 22, allowing lithium ions to pass through while preventing contact (short circuit) between the positive electrode 21 and the negative electrode 22. This separator 23 contains a polymer compound such as polyethylene.

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

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

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

[0126] <2-2. Operation> Rechargeable batteries operate as follows during charging and discharging.

[0127] During charging, lithium is released from the positive electrode 21 of the battery element 20, and this lithium is absorbed into the negative electrode 22 via the electrolyte. Conversely, during discharging, lithium is released from the negative electrode 22 of the battery element 20, and this lithium is absorbed into the positive electrode 21 via the electrolyte. During both 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 negative electrode 22 are prepared according to the example procedure described below, and the secondary battery is assembled using the positive electrode 21 and negative electrode 22 together with the electrolyte. After that, the assembled secondary battery is stabilized. The procedure for preparing the electrolyte is as described above.

[0129] [Fabrication of the positive electrode] First, a positive electrode mixture is prepared by mixing the positive electrode active material, positive electrode binder, and positive electrode conductive agent together. Subsequently, a paste-like positive electrode mixture slurry is prepared by adding the positive electrode mixture to a solvent. This solvent may be an aqueous solvent or an organic solvent. Next, the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 21A to form the positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B may be compressed and molded using a roll press or the like. In this case, the positive electrode active material layer 21B may be heated, or the compression molding may be repeated multiple times. As a result, the positive electrode 21 is manufactured by forming the positive electrode active material layer 21B on both sides of the positive electrode current collector 21A.

[0130] [Fabrication of the negative electrode] The negative electrode 22 is formed using the same procedure as the positive electrode 21 described above. Specifically, first, a paste-like negative electrode slurry is prepared by adding a mixture (negative electrode mixture) in which the negative electrode active material, negative electrode binder, and negative electrode conductive agent are mixed together to a solvent. Next, the negative electrode slurry is applied to both sides 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 sides of the negative electrode current collector 22A, and the negative electrode 22 is manufactured.

[0131] [Assembly of rechargeable batteries] First, the positive electrode lead 25 is connected to the positive electrode current collector 21A of the positive electrode 21 using a joining method such as welding, and the 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 on top of each other via a separator 23, and then the positive electrode 21, the negative electrode 22 and the separator 23 are wound together to create a wound body (not shown) with a space 20S. This wound body has the same configuration as the battery element 20, except that the positive electrode 21, the negative electrode 22 and the separator 23 are not impregnated with electrolyte. Next, a center pin 24 is inserted into the space 20S of the wound body.

[0132] Next, with the winding body sandwiched between the insulating plates 12 and 13, the winding body and insulating plates 12 and 13 are housed inside the battery can 11. 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. Subsequently, the electrolyte is injected into the battery can 11, thereby impregnating the winding body with the electrolyte. As a result, the positive electrode 21, the negative electrode 22, and the separator 23 are each impregnated with the electrolyte, and the battery element 20 is manufactured.

[0133] Finally, the battery cover 14, safety valve mechanism 15, and PTC element 16 are placed inside the battery case 11, and then the battery case 11 is crimped via the gasket 17. This fixes the battery cover 14, safety valve mechanism 15, and PTC element 16 to the battery case 11, and also seals the battery element 20 inside the battery case 11, thus assembling the secondary battery.

[0134] [Stabilization of secondary batteries] The assembled secondary battery is then charged and discharged. Various conditions such as ambient temperature, number of charge / discharge cycles, and charge / discharge conditions can be set arbitrarily. As a result, a coating is formed on the surfaces of the positive electrode 21 and the negative electrode 22, thereby electrochemically stabilizing the state of the battery element 20. Thus, the secondary battery is completed.

[0135] <2-4. Action and Effects> In this secondary battery, the electrolyte has the configuration described above. 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 thus 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 utilizing thiazole-type compounds, thus achieving an even higher effect.

[0137] Furthermore, if the secondary battery is a lithium-ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the intercalation and deintercalation of lithium, thus achieving a higher level of efficiency.

[0138] Other functions and effects of this secondary battery are the same as those of the electrolyte described above.

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

[0140] [Example 1] The explanation described the case where the battery structure of a secondary battery is cylindrical. However, although not specifically illustrated here, the type of battery structure is not particularly limited, and may include laminate film type, rectangular type, coin type, button type, etc.

[0141] [Differentiation 2] A porous membrane separator 23 was used. However, although not specifically shown in the diagram, a laminated separator containing a polymer compound layer may also be used.

[0142] Specifically, the laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer provided on one or both sides of the porous membrane. This improves the adhesion of the separator to the positive electrode 21 and the negative electrode 22, thereby suppressing misalignment (winding misalignment) of the battery element 20. As a result, swelling of the secondary battery is suppressed even if decomposition reactions of the electrolyte occur. The polymer compound layer contains a polymer compound such as polyvinylidene fluoride. Polymer compounds such as polyvinylidene fluoride have excellent physical strength and are also electrochemically stable.

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

[0144] When fabricating a laminated separator, a precursor solution containing a polymer compound and a solvent is prepared, and then the precursor solution is applied to one or both sides of a porous membrane. In this case, if necessary, multiple insulating particles may be added to the precursor solution.

[0145] Even when using this stacked separator, lithium can move between the positive electrode 21 and the negative electrode 22, thus achieving a similar effect. In this case, as mentioned above, the safety of the secondary battery is improved, resulting in an even greater effect.

[0146] [Difference 3] A liquid electrolyte solution was used. However, although not specifically illustrated here, a gel-like electrolyte layer may also be used.

[0147] In the battery element 20 using an electrolyte layer, the positive electrode 21 and the negative electrode 22 are stacked on top of each other via a separator 23 and the electrolyte layer, and the positive electrode 21, negative electrode 22, separator 23, and electrolyte layer are wound together. This electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23.

[0148] Specifically, the electrolyte layer contains a polymer compound along with the electrolyte, and the electrolyte is held in place by the polymer compound. This prevents leakage of the electrolyte. The composition of the electrolyte is as described above. The polymer compound includes polyvinylidene fluoride, etc. When forming the electrolyte layer, a precursor solution containing the electrolyte, polymer compound, and solvent is prepared, and then the precursor solution is applied to one or both sides of the positive electrode 21 and the negative electrode 22, respectively.

[0149] Even when this electrolyte layer is used, lithium can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer, thus achieving a similar effect. In this case, in particular, as described above, leakage of the electrolyte is prevented, resulting in an even greater effect.

[0150] <3. Applications of rechargeable batteries> The uses (application examples) of secondary batteries are not particularly limited. Secondary batteries used as power sources may be the primary power source or the auxiliary power source in electronic devices and electric vehicles, etc. A primary power source is a power source that is used preferentially regardless of the presence or absence of other power sources. An auxiliary power source may be a power source used in place of the primary power source, or a power source that can be switched from the primary power source.

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

[0152] The battery pack may use individual cells or a battery pack. An electric vehicle is a vehicle that operates (drives) using a secondary battery as a power source, and may also be a hybrid vehicle equipped with other power sources in addition to the secondary battery. In a household power storage system, the electricity stored in the secondary battery, which is the power storage source, can be used to power household electrical appliances, etc.

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

[0154] Figure 3 shows the block configuration of the battery pack. The battery pack described here is a single rechargeable battery pack (a so-called soft pack) and is installed in electronic devices such as smartphones.

[0155] As shown in Figure 3, this battery pack comprises 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 supply 51 includes one secondary battery. In this secondary battery, the positive lead is connected to the positive terminal 53, and the negative lead is connected to the negative terminal 54. Since the power supply 51 can be connected to the outside via the positive terminal 53 and the negative terminal 54, it can be charged and discharged. The circuit board 52 includes a control unit 56, a switch 57, a PTC element 58, and a temperature detection unit 59. However, the PTC element 58 may be omitted.

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

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

[0159] Switch 57 includes a charge control switch, a discharge control switch, a charging diode, and a discharging diode, and switches the connection between the power supply 51 and external equipment according to the instructions of the control unit 56. This switch 57 includes a field-effect transistor (MOSFET) using a metal oxide semiconductor, and the charge / discharge current is detected based on the ON resistance of switch 57.

[0160] The temperature detection unit 59 includes a temperature detection element such as a thermistor. This 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 / discharge control in the event of abnormal heat generation and when the control unit 56 performs correction processing when calculating the remaining capacity. [Examples]

[0161] An example of this technology will be described below.

[0162] <Examples 1-25 and Comparative Examples 1, 2> As explained below, after manufacturing the rechargeable batteries, their battery characteristics were evaluated.

[0163] [Manufacturing of secondary batteries] The cylindrical lithium-ion secondary batteries shown in Figures 1 and 2 were manufactured using the procedure described below.

[0164] (Fabrication of the positive electrode) First, 94 parts by mass of positive electrode active material (lithium cobaltate (LiCoO2)), a lithium-containing compound (oxide), 3 parts by mass of positive electrode binder (polyvinylidene fluoride), and 3 parts by mass of positive electrode conductive agent (acetylene black) were mixed together to prepare a positive electrode mixture. Next, the positive electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the solvent was stirred to prepare a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was applied to both sides of the positive electrode current collector 21A (a strip of aluminum foil with a thickness of 12 μm) using a coating apparatus, and the positive electrode mixture slurry was dried to form a positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B was compressed and molded using a roll press. This completed the production of the positive electrode 21.

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

[0166] To produce the first type of negative electrode 22, first, 93 parts by mass of negative electrode active material (63 parts by mass of artificial graphite, a carbon material, and 30 parts by mass of silicon oxide, a metallic material (silicon-containing material)) and 7 parts by mass of negative electrode binder (polyvinylidene fluoride) were mixed together to form a negative electrode mixture. Next, the negative electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the solvent was stirred to prepare a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was applied to both sides of the negative electrode current collector 22A (a strip of copper foil with a thickness of 15 μm) using a coating apparatus, and then the negative electrode mixture slurry was dried to form a negative electrode active material layer 22B. Finally, the negative electrode active material layer 22B was compressed and molded using a roll press. This completed the production of the negative electrode 22.

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

[0168] (Preparation of electrolyte solution) Solvents (ethylene carbonate, a cyclic carbonate ester, and dimethyl carbonate, a chain carbonate ester) were prepared. The mixing ratio (by weight) of the solvents was ethylene carbonate:dimethyl carbonate = 20:80. Next, an electrolyte salt (LiPF6, a lithium salt) was added to the solvent, and the solvent was stirred. The electrolyte salt content was 1.2 mol / kg relative to the solvent. Finally, a thiazole 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 compounds are shown in Tables 1 and 2. This completed the preparation of the electrolyte solution.

[0169] For comparison, the electrolyte was prepared using the same procedure, except that a thiazole compound was not used.

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

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

[0172] Next, the positive electrode 21 and the negative electrode 22 were stacked on top of each other via a separator 23 (a microporous polyethylene film with a thickness of 15 μm), and then the positive electrode 21, the negative electrode 22, and the separator 23 were wound together to create a wound body with a space 20S. Subsequently, a center pin 24 was inserted into the space 20S of the wound body.

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

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

[0175] (Stabilization of secondary batteries) A secondary battery was subjected to one charge-discharge cycle in a normal temperature environment (temperature = 23°C). During charging, constant current charging was performed at a current of 0.1C until the voltage reached 4.2V, and then constant voltage charging was performed at that voltage of 4.2V until the current reached 0.05C. During discharging, constant current discharge was performed at a current of 0.1C until the voltage reached 3.0V. 0.1C is the current value required to completely discharge the battery capacity (theoretical capacity) in 10 hours, and 0.05C is the current value required to completely discharge the battery capacity in 20 hours.

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

[0177] Furthermore, after the secondary battery was completed, the content (by weight) of thiazole-type compounds in the electrolyte was measured using ICP emission spectroscopy, and the results are shown in Tables 1 and 2.

[0178] [Evaluation of battery characteristics] The cycle characteristics of the battery were evaluated using 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 undisturbed in the same environment (undisturbed time = 5 hours). During charging, constant current charging was performed at a current of 1C until the voltage reached 4.2V, and then constant voltage charging was performed at that voltage of 4.2V until the current reached 0.05C. 1C is the current value required to completely discharge the battery capacity in one hour.

[0180] Next, the discharge capacity (discharge capacity in the first cycle) was measured by discharging the secondary battery in the same environment. During discharge, a constant current discharge was performed at a current of 3C until the voltage reached 3.0V. 3C is the current value required to completely discharge the battery capacity in 1 / 3 of an hour.

[0181] Next, the secondary battery was repeatedly charged and discharged in the same environment until it reached 100 cycles, and the discharge capacity (discharge capacity at 100 cycles) was measured. 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 (%) was calculated based on the formula: Capacity retention rate (%) = (Discharge capacity at 100 cycles / Discharge capacity at 1 cycle) × 100, which is an indicator for evaluating cycle characteristics.

[0183] [Table 1]

[0184] [Table 2]

[0185] [Consideration] As shown in Tables 1 and 2, the volume retention rate varied depending on the electrolyte composition.

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

[0187] In particular, when the electrolyte contained thiazole-type compounds, the following tendencies were observed.

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

[0189] Secondly, when the content of thiazole-type compounds in the electrolyte was between 0.001% and 5% by weight, the volume retention rate increased further.

[0190] Thirdly, when the negative electrode active material contained a silicon-containing material, the rate of increase in capacity retention was higher compared to 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 rate of increase in capacity retention when the negative electrode active material did not contain a silicon-containing material was approximately 26%, while the rate of increase when the negative electrode active material contained a silicon-containing material was approximately 66%.

[0191] <Examples 26-31> As shown in Table 3, secondary batteries were prepared using the same procedure as in Example 4, except that the electrolyte contained an additive (unsaturated cyclic carbonate ester, fluorinated cyclic carbonate ester, or cyanated cyclic carbonate ester), and then the battery characteristics were evaluated. The classification, type, and content (weight %) of the additives are as shown in Table 3.

[0192] Specifically, vinylene carbonate (VC) was used as the unsaturated cyclic carbonate ester. Ethylene fluorocarbonate (FEC) was used as the fluorinated cyclic carbonate ester. Ethylene cyanocarbonate (CEC) was used as the cyanated cyclic carbonate ester.

[0193] [Table 3]

[0194] As shown in Table 3, when the electrolyte contained an additive (unsaturated cyclic carbonate ester, fluorinated cyclic carbonate ester, or cyanated cyclic carbonate ester) (Examples 26-31), the volume retention rate was greater compared to when the electrolyte did not contain an additive (Example 4).

[0195] <Examples 32-51> As shown in Tables 4 and 5, secondary batteries were prepared using the same procedure as in Example 4, except that the electrolyte contained additives (sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic acid anhydrides, or sulfobenzoic acid imides), and then the battery characteristics were evaluated. The classification, type, and content (weight %) of the additives are as shown in Tables 4 and 5.

[0196] Specifically, the sulfonic acid esters used were 1,3-propanesultone (PS), 1-propene-1,3-sultone (PRS), 1,4-butanesultone (BS1), 2,4-butanesultone (BS2), and propargyl methanesulfonic acid ester (MSP).

[0197] As sulfate esters, 1,3,2-dioxathione 2,2-dioxide (OTO), 1,3,2-dioxatian 2,2-dioxide (OTA), and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathione (SOTO) were used.

[0198] As sulfite esters, 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-dioxan-2,6-dione (DOD), succinic anhydride (SA), and glutaric anhydride (GA) were used.

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

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

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

[0203] [Table 4]

[0204] [Table 5]

[0205] As shown in Tables 4 and 5, when the electrolyte contained additives (sulfonic acid esters, sulfuric acid esters, sulfite esters, dicarboxylic acid anhydrides, disulfonic acid anhydrides, sulfonic acid carboxylic acid anhydrides, or sulfobenzoic acid imides) (Examples 32-51), the volume retention rate was greater compared to when the electrolyte did not contain additives (Example 3).

[0206] [summary] The results shown in Tables 1 to 5 indicate that a high capacity retention rate was obtained when the electrolyte contained a thiazole-type compound. Therefore, the cycle characteristics were improved, resulting in excellent battery characteristics in the secondary battery.

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

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

[0209] Furthermore, while the case where the electrode reactant is lithium has been described, the electrode reactant is not particularly limited. Specifically, as mentioned above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0210] The effects described herein are illustrative only, and therefore the effects of this technology are not limited to those described herein. Accordingly, other effects may be obtained with respect to this technology.

[0211] Furthermore, this technology can also be configured as follows: <1> Positive electrode and, The negative electrode and, Electrolyte containing thiazole-type compounds and Equipped with, The thiazole-type compound comprises at least one of the compound represented by formula (1) and the compound represented by formula (2). Secondary battery. [ka] (Each of R1 to R15 is one of the following: 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, fluorinated alkylthio group, or a monovalent bond group formed by the bonding of two or more of these groups.) <2> The aforementioned negative electrode includes a negative electrode active material. The negative electrode active material includes a silicon-containing material. <1> The secondary battery described above. <3> The content of the thiazole-type compound in the electrolyte is 0.001% by weight or more and 5% by weight or less. <1> or <2> The secondary battery described above. <4> The electrolyte further comprises at least one of unsaturated cyclic carbonates, fluorinated cyclic carbonates, and cyanated cyclic carbonates. <1> or <3> A rechargeable battery as described in one of the following. <5> The electrolyte further comprises at least one of the following: sulfonic acid ester, sulfuric acid ester, sulfite ester, dicarboxylic acid anhydride, disulfonic acid anhydride, sulfonic acid carboxylic acid anhydride, and sulfobenzoic acid imide. <1> or <4> A rechargeable battery as described in one of the following. <6> Lithium-ion rechargeable batteries, <1> or <5> A rechargeable battery as described in one of the following. <7> Contains thiazole-type compounds, The thiazole-type compound comprises at least one of the compound represented by formula (1) and the compound represented by formula (2). Electrolyte for secondary batteries. [ka] (Each of R1 to R15 is one of the following: 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, fluorinated alkylthio group, or a monovalent bond group formed by the bonding of two or more of these groups.)

Claims

1. Positive electrode and, The negative electrode and, Electrolyte containing thiazole-type compounds and Equipped with, The thiazole-type compound comprises at least one of the compound represented by formula (1) and the compound represented by formula (2). Secondary battery. 【Chemistry 1】 (Each of R1 to R15 is one of the following: 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, fluorinated alkylthio group, or a monovalent bond group formed by two or more of these being bonded together.)

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

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

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

5. The electrolyte further comprises at least one of the following: sulfonic acid ester, sulfuric acid ester, sulfite ester, dicarboxylic acid anhydride, disulfonic acid anhydride, sulfonic acid carboxylic acid anhydride, and sulfobenzoic acid imide. A secondary battery according to any one of claims 1 to 3.

6. Lithium-ion rechargeable batteries, A secondary battery according to any one of claims 1 to 3.

7. Contains thiazole-type compounds, The thiazole-type compound comprises at least one of the compound represented by formula (1) and the compound represented by formula (2). Electrolyte for secondary batteries. 【Chemistry 2】 (Each of R1 to R15 is one of the following: 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, fluorinated alkylthio group, or a monovalent bond group formed by two or more of these being bonded together.)

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