Composition for electrode, electrode, and battery

Abstract

A composition for batteries according to the present disclosure contains a polymer (A). The polymer (A) contains a structural unit (a). The constituent unit (a) is derived from a compound having a five-membered or six-membered nitrogen-containing heterocyclic structure, wherein the nitrogen-containing heterocyclic structure contains an unsaturated bond. The proportion of the structural unit (a) in the polymer (A) relative to the total of all structural units constituting the polymer (A) is greater than 50 mol%.

Description

Technical Field

[0001] This disclosure relates to compositions for electrodes, electrodes, and batteries. Background Technology

[0002] Lithium-ion rechargeable batteries have attracted attention as high-energy-density batteries.

[0003] Patent Document 1 discloses a coating solution for manufacturing electrodes in batteries. The coating solution disclosed in Patent Document 1 contains a solvent, a binder, a carbon-based substance, and a polymer having a five-membered ring structure containing nitrogen. The content of the aforementioned polymer is between 1 ppm and 10,000 ppm relative to the total mass of the coating solution. Patent Document 1 specifically discloses a copolymer of polyvinylpyrrolidone and polyvinylimidazolium (monomer ratio of 50:50) as the aforementioned polymer. The coating solution disclosed in Patent Document 1 is used as a raw material for the electrode material layer of a battery.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2004-63423 Summary of the Invention

[0005] The problem that the invention aims to solve For batteries, there is a requirement for electrode compositions that can suppress the increase in resistance (hereinafter also referred to as "resistance after high-temperature storage") after long-term (e.g., 28 days) storage in a high-temperature environment (e.g., 60°C).

[0006] In view of the above, the object of this disclosure is to provide an electrode composition, an electrode, and a battery that can suppress the increase in resistance of a battery after high-temperature storage.

[0007] Methods for solving problems The means to solve the above problems include the following methods.

[0008] <1> An electrode composition containing a polymer (A). The aforementioned polymer (A) contains structural units (a) derived from compounds having a five- or six-membered nitrogen-containing heterocyclic structure and the aforementioned nitrogen-containing heterocyclic structure containing unsaturated bonds. The proportion of the aforementioned structural unit (a) in the aforementioned polymer (A) is greater than 50 moles relative to the total of all structural units constituting the aforementioned polymer (A).

[0009] <2> As mentioned above <1> The electrode composition wherein the proportion of the aforementioned structural unit (a) is 60 mol% or more.

[0010] <3> As mentioned above <1> or <2> The electrode composition wherein the aforementioned structural unit (a) comprises a structural unit derived from vinylimidazole.

[0011] <4> As mentioned above <1> ~ <3> The electrode composition described in any one of the above statements further comprises an active substance (B) and a binder (C).

[0012] <5> As mentioned above <4> The electrode composition wherein the aforementioned active material (B) comprises a carbon-based compound.

[0013] <6> As mentioned above <1> ~ <5> The electrode composition according to any one of the following, wherein the content of the aforementioned polymer (A) relative to the solid component of the electrode composition is 0.01% to 1.0% by mass.

[0014] <7> Electrodes, comprising: Current collector, and The foregoing <1> ~ <6> The solid form of the electrode composition described in any one of the above statements.

[0015] <8> The battery has the aforementioned <7> The aforementioned electrode.

[0016] According to this disclosure, electrode compositions, electrodes, and batteries are available that can suppress the increase in resistance of batteries after high-temperature storage. Attached Figure Description

[0017] [ Figure 1 ] Figure 1 This is a simplified cross-sectional view of a laminated battery, which is an example of a battery as described in this disclosure. Detailed Implementation

[0018] In this specification, the numerical range represented by "~" refers to the range including the values ​​before and after "~" as the lower and upper limits.

[0019] In this specification, the amounts of each component in the composition refer to the total amount of the various substances present in the composition, unless otherwise specified. In the case of the presence of multiple substances belonging to each component in the composition, the amounts refer to the total amount of the multiple substances present in the composition.

[0020] In this specification, "(meth)acrylate" means acrylate or methacrylate.

[0021] (1) Electrode composition The electrode composition disclosed herein (hereinafter also referred to as the "electrode composition") contains a polymer (A). The polymer (A) comprises a structural unit (a). The structural unit (a) is derived from a compound having a five- or six-membered nitrogen-containing heterocyclic structure and the aforementioned nitrogen-containing heterocyclic structure contains an unsaturated bond (hereinafter also referred to as "monomer (a)"). The proportion of structural unit (a) in the polymer (A) relative to the total number of all structural units constituting the polymer (A) (hereinafter also referred to as "proportion of structural unit (a)") is greater than 50 moles.

[0022] The term "unsaturated bond" refers to a double or triple bond.

[0023] The term "heterocyclic structure" refers to a ring structure composed of carbon atoms and heteroatoms (such as nitrogen, oxygen, or sulfur).

[0024] In this public document, “content” and “amount added” are considered to be substantially the same.

[0025] Because the electrode composition of this disclosure has the above-described structure, it is possible to suppress the increase in resistance of the battery after high-temperature storage.

[0026] The electrode composition disclosed herein can be used as a raw material for electrodes. Details regarding the electrodes are described later.

[0027] (1.1) Polymer (A) The electrode composition contains a polymer (A). Therefore, when the electrode composition contains an active material (B), the polymer (A) adsorbs and / or coats the surface of the active material (B), thereby suppressing the decomposition reaction of the electrolyte on the surface of the active material (B) during battery fabrication. As a result, the electrode composition can suppress the increase in resistance after the battery is stored at high temperatures.

[0028] The weight-average molecular weight of polymer (A) is not particularly limited, but is preferably 0.1 million or more, more preferably 0.5 million or more, and even more preferably 10,000 or more. The weight-average molecular weight of polymer (A) is preferably 1 million or less, more preferably 800,000 or less, and even more preferably 500,000 or less. The weight-average molecular weight can be determined using, for example, a gel permeation chromatography Alliance GPC-2000 manufactured by Waters Corporation.

[0029] The content of the aforementioned polymer (A) relative to the solid component of the electrode composition (hereinafter also referred to as "the content of polymer (A)") is not particularly limited, but is preferably 0.01% to 1.0% by mass. As a result, the electrode composition can further suppress the increase in resistance of the battery after high-temperature storage.

[0030] From the viewpoint of further suppressing the increase in resistance of the battery after high-temperature storage, the content of polymer (A) is more preferably 0.05% to 0.8% by mass, more preferably 0.1% to 0.6% by mass, and particularly preferably 0.2% to 0.4% by mass.

[0031] The term "solid composition of the electrode composition" refers to the total mass after removing the solvent (D) from the electrode composition when the electrode composition contains the solvent (D) described later, and the total mass of the electrode composition when the electrode composition does not contain the solvent (D).

[0032] (1.1.1) Structural unit (a) The polymer (A) contains structural unit (a). Structural unit (a) originates from monomer (a).

[0033] Among the monomers (a), examples of compounds having a five-membered nitrogen-containing heterocyclic structure containing unsaturated bonds include vinylimidazole, vinylpyrrole, vinylindole, vinylpyrazole, vinylbenzimidazole, vinyl-1H-indazole, vinylpyrroleline, vinylpyrazoline, vinyltriazole, vinyltetrazole, vinyloxazole, vinyloxazoline, vinylisooxazole, vinylisooxazoline, vinylthiazole, or vinylthiazoline.

[0034] Among the monomers (a), examples of compounds having a six-membered nitrogen-containing heterocyclic structure containing unsaturated bonds include vinylquinoline, vinylpyridine, vinylquinoline, or vinyltriazine.

[0035] Monomer (a) can be used alone or in combination of two or more.

[0036] The structural unit (a) preferably comprises a structural unit derived from vinylimidazole, more preferably a structural unit derived from vinylimidazole. Thus, the electrode composition can further suppress the increase in resistance of the battery after high-temperature storage.

[0037] (1.1.2) Structural unit (b) Polymer (A) may or may not contain structural unit (b). Structural unit (b) is derived from a compound capable of copolymerizing with monomer (a) (wherein, monomer (a) is excluded) (hereinafter also referred to as "monomer (b)"). When polymer (A) does not contain structural unit (b), polymer (A) may be a homopolymer of monomer (a) (structural unit (a) percentage: 100 mol%). When polymer (A) contains structural unit (b), polymer (A) may be a copolymer of monomer (a) and monomer (b).

[0038] By including structural unit (b) in the polymer (A), when the electrode composition contains active material (B), the polymer (A) adsorbs and / or coats the surface of the active material (B), thereby suppressing the decomposition reaction of the electrolyte on the surface of the active material (B) during battery fabrication. As a result, the electrode composition tends to further suppress the increase in resistance after high-temperature storage of the battery. This is presumably because, compared to the case where the polymer (A) does not contain structural unit (b), the polymer (A) containing structural unit (b) is more easily adsorbed onto the surface of the active material (B) and functions as a protective coating layer.

[0039] Monomer (b) can be any compound that can copolymerize with monomer (a), and there are no particular limitations. Examples of monomer (b) include unsaturated monomers with carboxyl groups, their salts, alkyl methacrylates, unsaturated monomers with acidic phosphate groups, (meth)acrylamide and its derivatives, ether sulfate type ammonium salts, or unsaturated monomers with carbonyl groups.

[0040] Examples of unsaturated monomers having a carboxyl group and their salts include, for example, (meth)acrylic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, crotonic acid, or acrylamide glycolic acid. Examples of salts include alkali metal salts (e.g., sodium or potassium), alkaline earth metal salts (e.g., calcium or magnesium), ammonium salts, or organic amine salts (monoethanolamine or triethanolamine, etc.).

[0041] Examples of alkyl methacrylates include, for example, hydroxyethyl methacrylate, methyl methacrylate, ethyl methacrylate, (N,N-dimethylaminoethyl) methacrylate, (N,N-diethylaminoethyl) methacrylate, or aminoethyl methacrylate.

[0042] Examples of unsaturated monomers with acidic phosphate groups include 2-(meth)acryloyloxyethyl phosphate, 2-(meth)acryloyloxypropyl phosphate, 2-(meth)acryloyloxy-3-chloropropyl phosphate, or 2-(meth)acryloyloxyethylphenyl phosphate.

[0043] Examples of (meth)acrylamide and its derivatives include, for example, (meth)acrylamide, methylene bis(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, or N,N-dimethyl(meth)acrylamide.

[0044] Ether sulfate type ammonium salts are commercially available. Examples of commercially available ether sulfate type ammonium salts include products from ADEKA Corporation (e.g., "SR-10", "SR-020", "SR-1025", or "SR-3025").

[0045] Examples of unsaturated monomers with carbonyl groups include vinylpyrrolidone, acrolein, diacetone (meth)acrylamide, vinyl methyl ketone, vinyl ethyl ketone, or vinyl butyl ketone.

[0046] The proportion of structural unit (a) is greater than 50 mol%. The proportion of structural unit (a) is preferably 60 mol% or more. The proportion of structural unit (a) is more preferably 60 mol% to 100 mol%, more preferably 70 mol% or more and less than 100 mol%, particularly preferably 80 mol% or more and less than 100 mol%, more preferably 80 mol% to 99 mol%, and more preferably 85 mol% to 99 mol%. By making the proportion of structural unit (a) within the above range, the electrode composition can suppress the increase in resistance of the battery after high-temperature storage, compared to cases where the proportion of structural unit (a) is not within the above range.

[0047] In the case that polymer (A) does not contain structural unit (b), the proportion of structural unit (a) can be 100 moles.

[0048] When the polymer (A) contains structural unit (b), the proportion of structural unit (a) and the proportion of structural unit (b) in the polymer (A) relative to the total of all structural units constituting the polymer (A) (hereinafter also referred to as "proportion of structural unit (b)") are preferably within the following ranges.

[0049] From the viewpoint of further suppressing the increase in resistance of the battery after high-temperature storage, the proportion of structural unit (a) is preferably 60 mol% or more and less than 100 mol%, more preferably 70 mol% or more and less than 100 mol%, more preferably 80 mol% or more and less than 100 mol%, particularly preferably 80 mol% to 99 mol%, and more preferably 85 mol% to 99 mol.

[0050] The proportion of structural unit (b) can be appropriately selected according to the type of structural unit (b) (i.e., the type of monomer (b)). The proportion of structural unit (b) is preferably greater than 0 mol%. From the viewpoint of further suppressing the increase in resistance of the battery after high-temperature storage, it is preferably greater than 0 mol% and less than 40 mol%, more preferably greater than 0 mol% and less than 30 mol%, more preferably greater than 0 mol% and less than 20 mol%, particularly preferably 1 mol% to 20 mol%, and more preferably 1 mol% to 15 mol%.

[0051] (1.2) Active substance (B) The electrode composition may contain an active substance (B). Thus, the solid form of the electrode composition functions as an electrode additive material layer. The term "electrode additive material layer" refers to at least one of a negative electrode additive material layer and a positive electrode additive material layer.

[0052] The active material (B) can be either the negative electrode active material (B1) or the positive electrode active material (B2).

[0053] The shape of the active material (B) is not particularly limited, and examples include fibrous, spherical, or flake-like forms. When the active material (B) is in particulate form, the particle size is not particularly limited. The particle size of the negative electrode active material (B1) is preferably 5 μm to 20 μm. The particle size of the positive electrode active material (B2) is preferably 5 μm to 15 μm.

[0054] The primary particle size of the positive electrode active material (B2) is preferably 2.0 μm or less, more preferably 0.2 μm to 1.0 μm.

[0055] The particle size of the active substance (B) is expressed as the cumulative 50% by volume of the particle size (particle size distribution D50, median particle size) in the volume-based particle size distribution measured using a particle size distribution measuring device based on laser diffraction scattering.

[0056] When the electrode composition contains an active substance (B), the content of the active substance (B) is not particularly limited, but is preferably 10% to 99.9% by mass, more preferably 30% to 99% by mass, even more preferably 50% to 99% by mass, and particularly preferably 70% to 99% by mass, relative to the solid component of the electrode composition.

[0057] The active material (B) can be appropriately selected according to the type of battery and the intended use of the electrode composition, and can be a known active material.

[0058] The active material (B) in the case where the battery is a lithium-ion secondary battery and the solid part of the electrode composition is used in the electrode compound material layer will be described below.

[0059] (1.2.1) Negative electrode active material (B1) The negative electrode active material (B1) can be any substance that can absorb and release lithium ions, and there are no particular restrictions. Examples of negative electrode active materials (B1) include carbon-based compounds, silicon oxide, metals (e.g., silicon, tin, or lithium), alloys (e.g., silicon alloys, tin alloys, or lithium alloys), or lithium titanate.

[0060] The term "carbon-based compound" refers to carbon materials with a volume resistivity of less than 40 Ω·cm, preferably less than 3 Ω·cm, at 20°C.

[0061] The term "silicon oxide" refers to the compound represented by the formula (1) below.

[0062] Formula (1): SiO X [In formula (1), X represents 0.5 or more and less than 1.6.] Examples of carbon-based compounds include, for example, graphite or amorphous carbon materials. Examples of graphite include, for example, synthetic graphite or natural graphite (e.g., flake graphite, block graphite, or earthy graphite). Examples of amorphous carbon materials include, for example, hard carbon, coke, mesophase carbon microspheres (MCMB) obtained by sintering at temperatures below 1500°C, or mesophase pitch carbon fibers (MCF).

[0063] Silica can be coated with amorphous carbon. Silica can also be a known compound. For information on silica, please refer to International Publication No. 2013 / 094668, Japanese Patent Application Publication No. 2016-143642, etc.

[0064] The negative electrode active material (B1) can be used alone or in combination of two or more.

[0065] The negative electrode active material (B1) preferably contains a carbon-based compound, and more preferably a carbon-based compound. Therefore, compared with the case where the negative electrode active material (B1) does not contain a carbon-based compound, it is possible to simultaneously achieve high energy density and charge-discharge cycle durability of the battery.

[0066] (1.2.2) Positive electrode active material (B2) As the positive electrode active material (B2), any material that can absorb and release lithium ions is acceptable, without any particular limitation. It can be appropriately adjusted according to the application of the lithium-ion secondary battery.

[0067] Examples of positive electrode active materials (B2) include, for example, the first oxide and the second oxide.

[0068] The first oxide uses lithium (Li) and nickel (Ni) as its constituent metal elements.

[0069] The second oxide comprises at least one metallic element selected from Li, Ni, and other metallic elements besides Li and Ni. Examples of metallic elements other than Li and Ni include transition metals and typical metallic elements. Preferably, the metallic element other than Li and Ni is included in the second oxide in a proportion equal to or less than that of Ni in terms of atomic number. The metallic element other than Li and Ni can be, for example, at least one selected from the group consisting of Co, Mn, Al, Cr, Fe, V, Mg, Ca, Na, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce.

[0070] The positive electrode active material (B2) can be used alone or in combination of two or more.

[0071] The positive electrode active material (B2) preferably comprises a lithium-containing composite oxide (hereinafter sometimes referred to as "NCM") represented by the following formula (X). The lithium-containing composite oxide (X) has the following advantages: high energy density per unit volume and excellent thermal stability.

[0072] LiNi a Co b Mn c O2… Formula (X) In equation (X), a, b and c are each independently greater than 0 and less than 1, and the sum of a, b and c is 0.99~1.00.

[0073] As a specific example of NCM, LiNi can be cited. 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, or LiNi 0.8 Co 0.1 Mn 0.1 O2, etc.

[0074] The positive electrode active material (B2) may also contain a lithium-containing composite oxide (hereinafter sometimes referred to as "NCA") represented by the following formula (Y).

[0075] Li t Ni 1-x-y Co x Al y O2... formula (Y) In formula (Y), t is 0.95~1.15, x is 0~0.3, y is 0.01~0.2, and the sum of x and y is less than 0.5.

[0076] As a specific example of NCA, LiNi can be cited. 0.8 Co 0.15 Al 0.05 O2, etc.

[0077] (1.3) Adhesive (C) The electrode composition may include a binder (C). Thus, when the electrode composition includes an active substance (B) and an electrode compound material layer is formed on the current collector, the binder (C) can bond the active substance (B) to the electrode current collector.

[0078] Examples of binders (C) include, for example, carboxymethyl cellulose (CMC), polyvinyl acetate, polymethyl methacrylate, nitrocellulose, fluoropolymers, or rubber particles.

[0079] Examples of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and vinylidene fluoride-hexafluoropropylene copolymer.

[0080] Examples of rubber particles include styrene-butadiene rubber (SBR) particles and acrylonitrile rubber particles.

[0081] The adhesive (C) can be used alone or in combination of two or more.

[0082] When the electrode composition contains a binder (C), the content of the binder (C) is not particularly limited, but is preferably 0.1% to 4% by mass relative to the solid components of the battery composition.

[0083] (1.4) Solvent (D) Electrode compositions may contain a solvent (D).

[0084] Examples of solvents (D) include water and water-miscible liquid media. If the solvent (D) in the electrode composition includes a water-miscible liquid media, the coating properties of the electrode composition onto the electrode current collector are improved. Examples of water-miscible liquid media include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, amides (e.g., N-methylpyrrolidone), carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, phosphate esters, ethers, or nitriles. When the electrode composition contains a positive electrode active material (B2) and a solvent (D), N-methylpyrrolidone is preferably used as the solvent (D).

[0085] When the electrode composition contains a solvent (D), the proportion of the total amount of solid components relative to the total amount of the electrode composition (hereinafter also referred to as "solid component concentration") is not particularly limited, but is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more. The solid component concentration is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, and particularly preferably 70% by mass or less.

[0086] (1.5) Conductive additive (E) Electrode compositions may contain conductive additives (E).

[0087] The conductive additive (E) can be any known conductive additive. Preferably, a conductive carbon material is preferred. Examples of conductive carbon materials include carbon black, conductive carbon fibers, or fullerenes. Examples of conductive carbon fibers include carbon nanotubes, carbon nanofibers, or carbon fibers. Examples of natural graphite include, for example, flake graphite, block graphite, or amorphous graphite.

[0088] Conductive additives (E) can be used alone or in combination of two or more.

[0089] The conductive additive (E) can be a commercially available product. Commercially available carbon black products include, for example, "Super P" (manufactured by TIMCAL). Commercially available flake graphite products include "KS-6" (manufactured by TIMREX).

[0090] The content of the conductive additive (E) is not particularly limited, but is preferably 0.05% to 5% by mass relative to the solid component of the electrode composition.

[0091] (1.6) Additives (F) Electrode compositions may contain additives (F). Therefore, depending on the type of additive (F), various functions can be imparted to the electrode composition. Examples of additives (F) include thickeners, surfactants, dispersants, wetting agents, and defoamers.

[0092] (1.7) Preferred composition The preferred electrode composition includes, in addition to the polymer (A), an active material (B) and a binder (C). Thus, the solid component of the electrode composition functions as the electrode binder material layer of the battery.

[0093] When the electrode composition further comprises an active material (B) and a binder (C), the active material (B) preferably comprises a carbon-based compound, more preferably a carbon-based compound. By including a carbon-based compound in the active material (B), both high energy density and charge-discharge cycle durability of the battery can be achieved compared to the case where the active material (B) does not contain a carbon-based compound.

[0094] (2) Electrode The electrodes of this disclosure include current collectors and solids of the electrode composition of this disclosure.

[0095] The term "electrode" refers to at least one of the positive and negative terminals of a battery.

[0096] The term "solid substance of electrode composition" refers to a substance that is solid at room temperature (23°C) and obtained by removing the solvent (D) from the electrode composition when the electrode composition contains a solvent (D). It also refers to a substance that is solid at room temperature (23°C) and constituted by the electrode composition when the electrode composition does not contain a solvent (D). When the electrode composition contains a solvent (D), the solid substance of the electrode composition is formed, for example, by coating the electrode composition onto a current collector and drying it. When the electrode composition does not contain a solvent (D), the solid substance of the electrode composition is formed, for example, by coating a molten portion of the electrode composition onto a current collector and cooling it.

[0097] Because the electrodes of this disclosure have the above-described configuration, it is possible to suppress the increase in resistance of the battery after high-temperature storage.

[0098] The solid form of the electrode layer composition can be formed on at least one main surface of the current collector.

[0099] The function of the solid form of the electrode composition depends on the raw materials of the electrode composition. When the electrode composition contains an active substance (B), the solid form of the electrode composition can function as an electrode additive material layer. When the electrode composition does not contain an active substance (B), the solid form of the electrode composition can function as a base coating layer between the current collector and the electrode additive material layer. The following explains the case where the solid form of the electrode composition functions as an electrode additive material layer.

[0100] (2.1) Negative electrode The negative electrode comprises a current collector (hereinafter also referred to as "negative electrode current collector") and a negative electrode flux material layer. The negative electrode flux material layer is formed on at least one main surface of the negative electrode current collector.

[0101] Materials used as negative current collectors include, for example, copper, aluminum, nickel, stainless steel (SUS), or nickel-plated steel.

[0102] The negative electrode binder material layer is a solid form of the electrode composition of this disclosure. Specifically, the negative electrode binder material layer preferably contains a polymer (A), a negative electrode active material (B1), and a binder (C). The negative electrode binder material layer may further contain at least one of a conductive additive (E) and an additive (F), if necessary.

[0103] (2.2) Positive electrode The positive electrode comprises a current collector (hereinafter also referred to as "positive current collector") and a positive electrode flux layer. The positive electrode flux layer is formed on at least one main surface of the positive current collector.

[0104] Materials used as positive current collectors include, for example, aluminum, nickel, stainless steel (SUS), or copper. "Aluminum" includes pure aluminum or aluminum alloys.

[0105] The positive electrode binder material layer is a solid form of the electrode composition of this disclosure. Specifically, the positive electrode binder material layer preferably contains a polymer (A), a positive electrode active material (B2), and a binder (C). The positive electrode binder material layer may further contain at least one of a conductive additive (E) and an additive (F), if necessary.

[0106] (3) Battery The battery described in this disclosure has the electrodes described in this disclosure.

[0107] Because the battery of this disclosure has the above-described configuration, the increase in resistance after high-temperature storage is suppressed.

[0108] In the battery disclosed herein, the electrodes are at least one of a positive electrode and a negative electrode. There is no particular limitation on the type of battery, which may be appropriately selected according to the intended use of the battery. Examples of battery types include, for instance, lithium-ion secondary batteries, manganese batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-zinc batteries, sodium-sulfur batteries, zinc-halogen batteries, or redox flow batteries.

[0109] The following description uses lithium-ion secondary batteries as an example of batteries in this disclosure.

[0110] (3.1) Lithium-ion secondary battery The lithium-ion secondary battery has the electrodes described in this disclosure.

[0111] Lithium-ion rechargeable batteries typically consist of an outer casing, a positive electrode, a negative electrode, a separator, and an electrolyte. The outer casing houses the positive electrode, negative electrode, separator, and non-aqueous electrolyte. The separator separates the positive and negative electrodes.

[0112] In the lithium-ion secondary battery of this disclosure, at least one of the positive electrode and the negative electrode is an electrode of this disclosure. If one of the positive electrode and the negative electrode of the lithium-ion secondary battery of this disclosure is an electrode of this disclosure, the other of the positive electrode and the negative electrode may be a known electrode that can be used in lithium-ion secondary batteries.

[0113] The following describes the situation of the positive and negative electrodes in this disclosure.

[0114] (3.1.1) Outer packaging There are no particular limitations on the shape of the outer packaging; it can be appropriately selected based on the intended use of the lithium-ion secondary battery. Examples of outer packaging include packaging containing a laminated film or packaging consisting of a battery case and a battery case lid.

[0115] (3.1.2) Positive and negative electrodes Positive poles represent the positive poles of this publication. Negative poles represent the negative poles of this publication.

[0116] (3.1.3) Diaphragm For example, a porous resin sheet can be used as a separator. The material of the porous resin sheet can be resin or nonwoven fabric containing the resin. Examples of resins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyester, cellulose, or polyamide. The separator is preferably a porous resin sheet with a single-layer or multi-layer structure. The porous resin sheet is primarily composed of one or more polyolefin resins. The separator thickness is preferably 5 μm to 30 μm. The separator is preferably disposed between the positive and negative electrodes.

[0117] (3.1.4) Non-aqueous electrolyte Non-aqueous electrolytes contain electrolytes and non-aqueous solvents.

[0118] (3.1.4.1) Electrolytes The electrolyte preferably contains at least one of a lithium salt containing fluorine (hereinafter, sometimes referred to as "fluorinated lithium salt") and a lithium salt not containing fluorine.

[0119] Examples of fluorinated lithium salts include inorganic acid anionic salts and organic acid anionic salts.

[0120] Examples of inorganic acid anionic salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), or lithium hexafluorotantalate (LiTaF6).

[0121] Examples of anionic salts of organic acids include lithium trifluoromethanesulfonate (LiCF3SO3).

[0122] Among them, LiPF6 is particularly preferred as a fluorinated lithium salt.

[0123] Examples of fluorine-free lithium salts include lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), or lithium decachloroborate (Li2B). 10 Cl 10 )wait.

[0124] When the electrolyte contains a fluorinated lithium salt, the proportion of the fluorinated lithium salt relative to the total amount of electrolyte is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass.

[0125] When the fluorinated lithium salt contains lithium hexafluorophosphate (LiPF6), the content of lithium hexafluorophosphate (LiPF6) is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, relative to the total amount of electrolyte.

[0126] When the non-aqueous electrolyte contains an electrolyte, the concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.1 mol / L to 3 mol / L, more preferably 0.5 mol / L to 2 mol / L.

[0127] When the non-aqueous electrolyte contains lithium hexafluorophosphate (LiPF6), the concentration of lithium hexafluorophosphate (LiPF6) in the non-aqueous electrolyte is preferably 0.1 mol / L to 3 mol / L, more preferably 0.5 mol / L to 2 mol / L.

[0128] (3.1.4.2) Non-aqueous solvents Non-aqueous electrolytes typically contain non-aqueous solvents.

[0129] Examples of non-aqueous solvents include, for example, cyclic carbonates, fluorinated cyclic carbonates, chain carbonates, fluorinated chain carbonates, aliphatic carboxylic acid esters, fluorinated aliphatic carboxylic acid esters, γ-lactones, fluorinated γ-lactones, cyclic ethers, fluorinated cyclic ethers, chain ethers, fluorinated chain ethers, nitriles, amides, lactams, nitromethane, nitrobenzene, sulfolane, trimethyl phosphate, dimethyl sulfoxide, or dimethyl sulfoxide phosphate. One non-aqueous solvent can be used alone or in combination of two or more.

[0130] Examples of cyclic carbonates include, for example, ethylene carbonate (EC), propylene carbonate (PC), or butyl carbonate (BC).

[0131] Examples of fluorinated cyclic carbonates include, for example, ethylene fluorocarbonate (FEC), ethylene difluorocarbonate (DFEC), or propylene trifluorocarbonate.

[0132] Examples of chain carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or dipropyl carbonate (DPC).

[0133] Examples of fluorinated chain carbonates include, for example, 2,2,2-trifluoroethyl methyl carbonate.

[0134] Examples of aliphatic carboxylic acid esters include methyl formate, methyl acetate, methyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylbutyrate, ethyl formate, ethyl acetate, ethyl propionate, ethyl butyrate, ethyl isobutyrate, or ethyl trimethylbutyrate.

[0135] Examples of fluorinated aliphatic carboxylic acid esters include, for example, methyl difluoroacetate, methyl 3,3,3-trifluoropropionate, ethyl difluoroacetate, or 2,2,2-trifluoroethyl acetate.

[0136] Examples of γ-lactones include, for example, γ-butyrolactone or γ-valerolactone.

[0137] Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxane, 4-methyl-1,3-dioxane, 1,3-dioxane, or 1,4-dioxane.

[0138] Examples of chain ethers include, for example, 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, or 1,2-dibutoxyethane.

[0139] Examples of fluorinated chain ethers include HCF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CF2H, HCF2CF2CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, and C6F. 13 OCH3, C6F 13 OC2H5, C8F 17 OCH3, C8F 17 OC2H5, CF3CFHCF2CH(CH3)OCF2CFHCF3, HCF2CF2OCH(C2H5)2, HCF2CF2OC4H9, HCF2CF2OCH2CH(C2H5)2, or HCF2CF2OCH2CH(CH3)2, etc.

[0140] Examples of nitrile compounds include acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, or 3-methoxypropionitrile.

[0141] Examples of amides include, for example, N,N-dimethylformamide.

[0142] Examples of lactams include, for example, N-methylpyrrolidone, N-methyloxazolidinone, or N,N'-dimethylimidazolinone.

[0143] The non-aqueous solvent preferably comprises at least one selected from the group consisting of cyclic carbonates, fluorinated cyclic carbonates, chain carbonates, and fluorinated chain carbonates. In this case, the total proportion of the cyclic carbonates, fluorinated cyclic carbonates, chain carbonates, and fluorinated chain carbonates relative to the total amount of the non-aqueous solvent is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass.

[0144] The non-aqueous solvent preferably includes at least one selected from the group consisting of cyclic carbonates and chain carbonates. In this case, the total proportion of cyclic carbonates and chain carbonates in the non-aqueous solvent is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, relative to the total amount of the non-aqueous solvent.

[0145] The content of non-aqueous solvent is preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 90% by mass or less, relative to the total amount of non-aqueous electrolyte.

[0146] The content of non-aqueous solvent is preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the total amount of non-aqueous electrolyte.

[0147] From the viewpoint of further improving the dissociation property of the electrolyte and the mobility of ions, the intrinsic viscosity of the non-aqueous solvent is preferably below 10.0 mPa·s at 25°C.

[0148] (3.1.4.3) Electrolyte additives Non-aqueous solvents can contain electrolyte additives. This makes it difficult for side reactions, which are not part of the original battery reaction, to occur during the charge-discharge cycle of a lithium-ion secondary battery. The battery reaction refers to the reaction in which lithium ions are inserted into and out of the positive and negative electrodes. Side reactions include the reductive decomposition of the non-aqueous electrolyte caused by the negative electrode, the oxidative decomposition of the non-aqueous electrolyte caused by the positive electrode, and the dissolution of metal elements from the positive electrode active material.

[0149] There are no particular restrictions on the use of electrolyte additives; any known electrolyte additives may be used, for example, the additives described in Japanese Patent Application Publication No. 2019-153443 may be used.

[0150] (3.2) An example of a lithium-ion secondary battery Reference Figure 1 An example of a lithium-ion secondary battery involved in the embodiments of this disclosure will be specifically described. Figure 1 This is a cross-sectional view of the lithium-ion secondary battery 1 according to the embodiments of this disclosure.

[0151] The lithium-ion secondary battery 1 described in this disclosure is a stacked type. For example... Figure 1 As shown, the lithium-ion secondary battery 1 includes a battery element 10, a positive electrode lead 21, a negative electrode lead 22, and an outer packaging body 30. The battery element 10 is sealed inside the outer packaging body 30. The outer packaging body 30 is formed of a laminated film. The positive electrode lead 21 and the negative electrode lead 22 are respectively mounted on the battery element 10. The positive electrode lead 21 and the negative electrode lead 22 extend from the inside of the outer packaging body 30 towards the outside and in opposite directions.

[0152] like Figure 1 As shown, the battery element 10 is formed by stacking a positive electrode 11, a separator 13, and a negative electrode 12. The positive electrode 11 is formed by forming a positive electrode flux layer 11B on the two main surfaces of the positive electrode current collector 11A. The negative electrode 12 is formed by forming a negative electrode flux layer 12B on the two main surfaces of the negative electrode current collector 12A.

[0153] like Figure 1 As shown, the positive electrode additive material layer 11B formed on one main surface of the positive electrode current collector 11A of the positive electrode 11 and the negative electrode additive material layer 12B formed on one main surface of the negative electrode current collector 12A of the negative electrode 12 adjacent to the positive electrode 11 are opposite each other through the separator 13.

[0154] A non-aqueous electrolyte is injected inside the outer packaging 30. The non-aqueous electrolyte permeates into the positive electrode flux layer 11B, the separator 13, and the negative electrode flux layer 12B. In the lithium-ion secondary battery 1, a single cell layer 14 is formed by adjacent positive electrode flux layer 11B, separator 13, and negative electrode flux layer 12B.

[0155] In this embodiment, the lithium-ion secondary battery 1 is a stacked type, but this disclosure is not limited to this; the lithium-ion secondary battery 1 can also be, for example, a wound type. A wound type is formed by overlapping and winding the positive electrode, separator, negative electrode, and separator in this order. Wound types include cylindrical and square types.

[0156] In this embodiment, such as Figure 1As shown, the positive lead 21 and the negative lead 22 protrude from the inside of the outer packaging 30 in opposite directions relative to the outer packaging 30, but this disclosure is not limited to this. For example, the positive lead and the negative lead may also protrude from the inside of the outer packaging 30 in the same direction relative to the outer packaging 30.

[0157] Example The following illustrates embodiments of this disclosure, but this disclosure is not limited to these embodiments. Hereinafter, "amount added" refers to the content relative to the total amount of the final non-aqueous electrolyte, and "wt%" refers to mass%.

[0158] [1] Aggregation Example [1.1] Polymerization Example 1 (Polyvinylpyrrolidone homopolymer) A reaction vessel equipped with a stirrer, reflux condenser, dropping device, and thermometer was prepared. 75 parts by mass of 1-vinylpyrrolidone (x) and 75 parts by mass of distilled water were mixed to prepare a monomer aqueous solution. 309.5 parts by mass of distilled water were added to the reaction vessel, and the temperature was raised to 80°C while stirring to induce nitrogen replacement. Maintaining the internal temperature at 80°C, 1.3 parts by mass of 4,4'-azobis(4-cyanopentanoic acid) was added as a polymerization initiator, and the monomer aqueous solution was continuously added dropwise to the reactor over 2 hours. After the addition was completed, the mixture was allowed to mature for 6 hours. The resulting aqueous solution was cooled to room temperature, and distilled water was added to the aqueous solution to obtain a polymer aqueous solution. The solid content concentration of the polymer aqueous solution was 14.8% by weight.

[0159] The aqueous polymer solution of Polymerization Example 1 contains a polyvinylpyrrolidone homopolymer. The 1-vinylpyrrolidone monomer (b) of the polyvinylpyrrolidone homopolymer does not have a five- or six-membered nitrogen-containing heterocyclic structure containing unsaturated bonds.

[0160] [1.2] Polymerization Example 2 (Polyvinylimidazolium homopolymer) The 1-vinylpyrrolidone was replaced with 1-vinylimidazole as monomer (a), and otherwise the same procedure as in polymerization example 1 was followed to obtain an aqueous polymer solution.

[0161] The polymer aqueous solution of polymerization example 2 contains a polyvinylimidazolium homopolymer as the polymer (A). The 1-vinylimidazolium monomer (a) of the polyvinylimidazolium homopolymer has a five-membered nitrogen-containing heterocyclic structure containing unsaturated bonds. Therefore, the polyvinylimidazolium homopolymer of polymerization example 2 has structural unit (a).

[0162] [1.3] Polymerization Example 3 (Polyvinylimidazolium homopolymer) A reaction vessel equipped with a stirrer, reflux condenser, dropping device, and thermometer was prepared. 75 parts by mass of 1-vinylimidazolium (monomer a) and 75 parts by mass of distilled water were mixed to prepare a monomer aqueous solution. 279.5 parts by mass of distilled water and 2.5 parts by mass of a 35% hydrochloric acid aqueous solution were added to the reaction vessel, and the temperature was raised to 80°C while stirring to induce nitrogen replacement. Maintaining the internal temperature at 80°C, 1.3 parts by mass of 4,4'-azobis(4-cyanopentanoic acid) was added as a polymerization initiator, and the monomer aqueous solution was continuously added dropwise to the reactor over 2 hours. After the addition was completed, the mixture was allowed to mature for 6 hours. The resulting aqueous solution was cooled to room temperature, and distilled water was added to the aqueous solution to obtain a polymer aqueous solution. The solid content concentration of the polymer aqueous solution was 14.8% by weight.

[0163] The polymer aqueous solution of polymerization example 3 contains a polyvinylimidazolium homopolymer as the polymer (A). Therefore, the polyvinylimidazolium homopolymer of polymerization example 3 has structural unit (a).

[0164] [1.4] Polymerization Example 4 (Polyvinylimidazolium copolymer) A reaction vessel equipped with a stirrer, reflux condenser, dropping device, and thermometer was prepared. An aqueous monomer solution was prepared by mixing 67.5 parts by mass of 1-vinylimidazolium (monomer a), 7.5 parts by mass of 2-hydroxyethyl methacrylate (monomer b), and 75 parts by mass of distilled water. 309.5 parts by mass of distilled water were added to the reaction vessel, and the temperature was raised to 80°C while stirring to induce nitrogen replacement. Maintaining the internal temperature at 80°C, 1.3 parts by mass of 4,4'-azobis(4-cyanopentanoic acid) was added as a polymerization initiator. The aqueous monomer solution was continuously added dropwise to the reactor over 2 hours. After the addition was completed, the mixture was allowed to mature for 6 hours. The resulting aqueous solution was cooled to room temperature, and distilled water was added to the aqueous solution to obtain a polymer aqueous solution. The solid content concentration of the polymer aqueous solution was 14.8% by weight.

[0165] The polymer aqueous solution of polymerization example 3 contains a polyvinylimidazolium copolymer as a polymer (A). The 1-vinylimidazolium monomer (a) of the polyvinylimidazolium copolymer has a five-membered nitrogen-containing heterocyclic structure containing unsaturated bonds. Therefore, the polyvinylimidazolium copolymer of polymerization example 4 has structural unit (a).

[0166] [1.5] Polymerization Examples 5 to 12 (Polyvinylimidazolium copolymers) The 2-hydroxyethyl methacrylate used as monomer (b) was changed to monomer (b) listed in Table 1, and the ratio of monomer (a) to monomer (b) was changed to the ratio shown in Table 1. Otherwise, the same procedure as in polymerization example 4 was followed to obtain a water-soluble polymer.

[0167] The polymer aqueous solution of polymerization example 5 contains a polyvinylimidazolium copolymer. The 1-vinylimidazolium monomer (a) of the polyvinylimidazolium copolymer has a five-membered nitrogen-containing heterocyclic structure containing unsaturated bonds, but the proportion of monomer (a) is not greater than 50%.

[0168] The aqueous solutions of the polymers in polymerization Examples 6 to 12 contain a polyvinylimidazolium copolymer as a polymer (A). The 1-vinylimidazolium monomer (a) of the polyvinylimidazolium copolymer has a five-membered nitrogen-containing heterocyclic structure containing unsaturated bonds. Therefore, the polyvinylimidazolium copolymers of polymerization Examples 5 to 12 have structural unit (a).

[0169] [2] Example 1 [2.1] Electrode Composition A 5L planetary disperser was used for slurry preparation.

[0170] 960 parts by mass of natural graphite as the negative electrode active material (B1) and "Super-P" (material: conductive carbon, BET specific surface area: 62 m²) as a conductive additive (E). 2 To 10 parts by mass of carboxymethyl cellulose (CMC), add 450 parts by mass of a "1%-CMC aqueous solution" as a binder (C) and solvent (D), mix for 30 minutes to obtain a mixture. The term "1% by mass aqueous solution of carboxymethyl cellulose (CMC)" refers to an aqueous solution in which the mass percentage of CMC as a binder (C) is 1% relative to the total amount of the aqueous solution.

[0171] Add 300 parts by mass of 1%-CMC aqueous solution to the obtained mixture, mix for 30 minutes, then add 250 parts by mass of 1%-CMC aqueous solution and mix for another 30 minutes.

[0172] Add 200 parts by mass of the polymer aqueous solution of Polymer Example 2, which serves as the polymer (A) and solvent (D), to the obtained mixture, and mix for 30 minutes.

[0173] 50 parts by weight of styrene-butadiene rubber (SBR) (40% emulsion) as binder (C) were added to the obtained mixture, and after mixing for 30 minutes, vacuum degassing was performed for 30 minutes. This yielded a negative electrode slurry (i.e., an electrode composition). The solid content concentration of the negative electrode slurry was 44%.

[0174] [2.2] Lithium-ion secondary batteries (layered batteries) As a lithium-ion secondary battery, a stacked battery for evaluating the heating rate is manufactured as described below.

[0175] [2.2.1] Negative electrode A die-casting machine was used in the slurry application process.

[0176] The coating weight after drying was 11.0 mg / cm³. 2 The aforementioned negative electrode mixture slurry was coated onto a portion of one side of a copper foil (10 μm thick), which serves as the negative electrode current collector, and then dried. Next, on a portion of the opposite side (uncoated side) of the copper foil, a coating was applied at a mass of 11.0 mg / cm³. 2 The above-mentioned negative electrode mixture slurry is applied in the manner described above and then dried.

[0177] In a vacuum drying oven, copper foil thus obtained was coated on both sides at 120°C (coating amount totaling 22.0 mg / cm² on both sides). 2 Dry for 12 hours.

[0178] Using a small pressurizer, the pressurized density was adjusted to 1.45 ± 0.05 g / cm³. 3 The dried copper foil on both sides is then subjected to pressure.

[0179] The electrode was cut to obtain the electrode coating area (31mm×42mm) and leave blank space for electrode tab welding.

[0180] The copper foil coated on both sides after pressure is cut to obtain a coated portion (42mm × 31mm) and leave the tabs uncoated. This yields the negative electrode.

[0181] [2.2.2] Positive electrode A 5L planetary disperser was used for slurry preparation.

[0182] NMC532 (i.e., LiNi) will be used as the positive electrode active material. 0.5 Mn 0.3 Co 0.2 After mixing 920 parts by weight of O2, 20 parts by weight of "Super-P" (conductive carbon manufactured by TIMCAL) as a conductive additive, and 20 parts by weight of "KS-6" (flake graphite manufactured by TIMREX) as a conductive additive for 10 minutes, 100 parts by weight of N-methylpyrrolidone (NMP) are added and the mixture is further mixed for 20 minutes.

[0183] Next, 150 parts by mass of "8%-PVDF solution" (PVDF W#7200 manufactured by Kureha dissolved in NMP) were added and mixed for 30 minutes. Then, another 150 parts by mass of the aforementioned 8%-PVDF solution were added and mixed for another 30 minutes. "8%-PVDF solution" refers to a solution containing 8% PVDF (PVDF W#7200 manufactured by Kureha Corporation) by mass relative to the total amount of PVDF solution (solution: NMP). Then, 200 parts by mass of the aforementioned 8%-PVDF solution were added and mixed for 30 minutes. Next, 80 parts by mass of a solution dissolved in NMP were added and mixed for 30 minutes. Finally, 27 parts by mass of NMP were added to adjust the viscosity, and the mixture was mixed for 30 minutes, followed by 30 minutes of vacuum degassing.

[0184] Through the above methods, a positive electrode mixture slurry with a solid component concentration of 60% was obtained.

[0185] A die-casting machine was used in the slurry application process.

[0186] The coating weight after drying was 19.0 mg / cm³. 2 The aforementioned positive electrode slurry was coated onto a portion of one side of an aluminum foil (20 μm thick, 200 mm wide) serving as the positive electrode current collector, and then dried. Next, on a portion of the opposite side (uncoated side), a coating of 19.0 mg / cm³ was applied. 2 The above-mentioned positive electrode mixture slurry is coated onto aluminum foil and then dried.

[0187] In a vacuum drying oven, the resulting double-sided coated aluminum foil was dried at 130°C (coating weight totaling 38.0 mg / cm² on both sides). 2 Dry for 12 hours.

[0188] Using a 35-ton press, the pressurized density was set to 2.9 ± 0.05 g / cm³. 3 The dried aluminum foil on both sides is then subjected to pressure.

[0189] The aluminum foil coated on both sides after being pressurized is cut to obtain the positive electrode by leaving the coated part (40mm×29mm) and the electrode tab weld blank.

[0190] [2.2.3] Non-aqueous electrolyte Ethyl carbonate (hereinafter EC) and methyl ethyl carbonate (EMC) are mixed at a volume ratio of EC:EMC = 30:70 to obtain a mixed solvent that can be used as a non-aqueous solvent.

[0191] In the above mixed solvent, LiPF6, as the electrolyte, is dissolved at a concentration of 1 mol / L (hereinafter also referred to as "1M") in the final non-aqueous electrolyte. Next, vinylene carbonate (VC), as an additive, is dissolved at a concentration of 0.5% by mass relative to the final non-aqueous electrolyte. Thus, a non-aqueous electrolyte is obtained.

[0192] [2.2.4] Stacked battery precursor As a diaphragm, a porous polyethylene membrane (50mm×50mm) with a porosity of 45% and a thickness of 25μm was prepared.

[0193] The negative electrode (surface), separator, positive electrode (back / surface), separator, and negative electrode (surface) are sequentially overlapped and fixed to obtain a laminate with 5 positive electrode layers and 6 negative electrode layers. Using an ultrasonic bonding machine, aluminum tabs are bonded to the blank portion of the positive electrode of the obtained laminate as positive electrode tabs, and nickel tabs are bonded to the blank portion of the negative electrode as negative electrode tabs. The laminate with the positive and negative electrode tabs is clamped in a laminated sheet, and three sides are heat-sealed to obtain a laminated battery precursor. The battery capacity of the aforementioned battery precursor is converted to 350mAh based on the discharge capacity.

[0194] Using a vacuum dryer, the interior of the laminate obtained above was dried under reduced pressure at 70°C for 12 hours. After the laminate was dried under reduced pressure, 1.20 ± 0.05 parts by mass of the above-mentioned non-aqueous electrolyte was injected into the remaining side that had not been heated and sealed. Then, the remaining side was heated and sealed while vacuum suction was performed to obtain the tandem battery precursor (i.e., the tandem battery before charging and discharging).

[0195] [2.2.5] Stacked battery The aforementioned stacked battery precursor was kept at 25°C for 24 hours under atmospheric conditions, then charged with a constant current of 0.1C for 3 hours (0.1C-CC), and then rested at 25°C for 12 hours.

[0196] Next, the rested tandem battery precursor is charged with constant current and constant voltage at 0.1C (0.1C-CCCV) to 4.2V (SOC100%), and after resting for 30 minutes, it is discharged with constant current at 0.1C (0.1C-CC) to 2.8V to obtain the tandem battery.

[0197] [2.3] Evaluation [2.3.1] Battery resistance (relative value) after high-temperature storage For stacked batteries, the following evaluation of battery resistance is performed.

[0198] The battery was charged to a constant voltage of 4.2V at room temperature, and then discharged at a constant current of 0.1C at room temperature. The first potential drop was measured 10 seconds after the start of discharge.

[0199] Similarly, the activated battery was charged to a constant voltage of 4.2V at room temperature, and then discharged at a constant current of 0.2C at room temperature. The second potential drop was measured 10 seconds after the start of discharge.

[0200] The activated battery was charged to a constant voltage of 4.2V at room temperature, and then discharged at a constant current of 0.5C at room temperature. The third potential drop was measured 10 seconds after the start of discharge.

[0201] The activated battery was charged to a constant voltage of 4.2V at room temperature, and then discharged at a constant current of 1.0C at room temperature. The fourth potential drop was measured 10 seconds after the start of discharge.

[0202] The battery resistance (DC resistance; DC-IR) during the initial discharge phase is calculated based on the potential drop from the first to the fourth potential drop at each current rate.

[0203] The following evaluation is conducted for stacked batteries.

[0204] Charge the battery to a constant voltage of 4.2V at room temperature and store it in a constant temperature and humidity bath at 60℃ for 28 days.

[0205] After storing the battery, let it stand at room temperature for 2 hours before evaluating its resistance (DC resistance; DC-IR).

[0206] Calculate the rate of increase in battery resistance based on the battery resistance before and after storage.

[0207] The resistance increase rate of Example 1, obtained later as Comparative Example 1, was calculated as 100, and this was taken as the resistance increase rate (relative value) after storage. The permissible resistance increase rate (relative value) after storage is less than 100.

[0208] [2.3.2] Nail puncture test (relative value) For stacked batteries, the following nail penetration test is conducted as an evaluation of the rate of internal heat generation during a short circuit.

[0209] The stacked battery prepared above was charged at a constant current and constant voltage of 0.1C (0.1C-CCCV) to 4.2V (SOC 100%), and then subjected to a nail puncture test. A nail with a diameter of 3mm, a length of 15mm, a front end angle of 30°, and a bottomed hole with a diameter of 0.6mm was covered using a MACOR (registered trademark) sheath. Next, a sheath-type K thermocouple (product number: IP10-K-0.5-200) with a sheath diameter of 0.5mm and a sheath length of 200mm was inserted near the front end of the nail to obtain the nail puncture test fixture.

[0210] A nail penetration test fixture and a stacked battery were fixed on a nail penetration test apparatus (Toyo System TYS-94DM45). The nail was driven into the center of the battery (cell) at a speed of 1 mm / s, short-circuiting the positive and negative terminals inside the battery container. The internal temperature of the battery, measured by the nail penetration test fixture, and the surface temperature, measured by a thermocouple mounted on the battery surface, were measured over time.

[0211] The rate of battery heating was calculated based on the results obtained from the aforementioned nail penetration test, as shown below. After the short circuit, the time it takes for the battery's internal temperature to rise by 0.2°C is defined as the heating start time T0 (seconds), and one second after T0 is defined as T1 (seconds). The battery's internal temperature at T0 is defined as H0 (°C), and the battery's internal temperature at T1 is defined as H1 (°C). The heating rate immediately after the short circuit is calculated using the following formula.

[0212] Heating rate = (H1 - H0) / (T1 - T0) The heating rate of Example 1, obtained later as 100, was calculated and used as the nail puncture test (relative value).

[0213] [3] Examples 2 to 11 and Comparative Examples 1 to 4 The type and amount of polymer were changed as described in Table 1. Otherwise, the evaluation was performed using the same method as in Example 1. It should be noted that the nail penetration test was not performed for Comparative Examples 2-3 and Examples 2-3, 5-11.

[0214] [Table 1] In Table 1, "ether sulfate type ammonium salt" refers to REASOAP "SR-10" manufactured by ADEKA Corporation. "Amount added" refers to the mass ratio of the polymer (A) relative to the solid component of the negative electrode mixture slurry (i.e., the electrode composition).

[0215] The electrode compositions of Comparative Examples 1 to 3 do not contain polymer (A). In Comparative Example 4, the proportion of structural unit (a) is not greater than 50 mol%. Therefore, the resistance increase rate (relative value) after storage of Comparative Examples 1 to 4 is not less than 100. As a result, it can be seen that the electrode compositions of Comparative Examples 1 to 4 are not electrode compositions capable of suppressing the increase in resistance of the battery after high-temperature storage.

[0216] The electrode compositions of Examples 1 to 11 contain polymer (A). The proportion of polymer (A) is greater than 50 mol%. Therefore, the resistance increase rate (relative value) after storage of Examples 1 to 11 is less than 100. As a result, it can be seen that the electrode compositions of Examples 1 to 11 are electrode compositions capable of suppressing the increase in resistance of batteries after high-temperature storage.

[0217] The full disclosure of Japanese Patent Application 2023-122890, filed on July 27, 2023, is incorporated herein by reference.

[0218] All documents, patent applications and technical standards described in this specification are incorporated herein by reference to the extent that each document, patent application and technical standard is incorporated by reference to the extent that it is specifically and separately described.

Claims

1. An electrode composition containing a polymer (A). The polymer (A) contains structural units (a) from compounds having a five- or six-membered nitrogen-containing heterocyclic structure and the nitrogen-containing heterocyclic structure comprising unsaturated bonds. The proportion of the structural unit (a) in the polymer (A) is greater than 50 moles relative to the total number of all structural units constituting the polymer (A).

2. The electrode composition according to claim 1, wherein, The proportion of the structural unit (a) is 60 mol% or more.

3. The electrode composition according to claim 1 or claim 2, wherein, The structural unit (a) comprises a structural unit derived from vinylimidazole.

4. The electrode composition according to any one of claims 1 to 3, further comprising an active substance (B) and a binder (C).

5. The electrode composition according to claim 4, wherein, The active substance (B) comprises carbon-based compounds.

6. The electrode composition according to any one of claims 1 to 5, wherein, The content of the polymer (A) relative to the solid component of the electrode composition is 0.01% to 1.0% by mass.

7. An electrode comprising: Current collector, and The solid form of the electrode composition according to any one of claims 1 to 6.

8. A battery having the electrodes as described in claim 7.

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