Electrode active material layer, electrode including electrode active material layer, and method for manufacturing electrode active material layer

Abstract

The present invention relates to an electrode active material layer containing fibers, a binder, and an electrode active material, wherein the fibers include fibers having a fiber diameter of 1-15 μm, the coefficient CV of variation of the fiber length of the fibers is 0-0.30, and the surface roughness Sa of the electrode active material layer is 0-10 μm.

Description

Electrode active material layer, electrode including said electrode active material layer, and method for producing said electrode active material layer

[0001] The present invention relates to an electrode active material layer, an electrode including the electrode active material layer, and a method for producing the electrode active material layer.

[0002] In recent years, the use of portable terminals such as mobile phones, notebook computers, and pad-type information terminal devices has become increasingly widespread. Portable terminals are required to be more portable, and as they rapidly become smaller, thinner, lighter, and more powerful, batteries used in portable terminals are also required to be smaller, thinner, lighter, and more powerful. Lithium-ion secondary batteries are widely used as non-aqueous electrolyte secondary batteries for power sources in such portable terminals.

[0003] In lithium-ion secondary batteries, lithium ions are inserted into and extracted from the pores of the active material during charge and discharge, which causes the active material to expand and contract. This expansion and contraction of the active material is thought to be one of the causes of battery performance degradation, including peeling of the electrode material from the current collector and the generation of voids between the active material, resulting in reduced conductivity. To prevent this degradation in battery performance, attempts have been made to add fibers to the electrodes.

[0004] For example, in Patent Document 1, in an electrode slurry containing a specified cellulose fiber, a carboxymethyl group-containing cellulose ether or its salt, and an electrode active material, the specified cellulose fiber follows the expansion and contraction of the electrode, thereby improving the adhesion of the electrode active material to the current collector.

[0005] In Patent Document 2, the flexibility of the electrode plate is improved by including a fibrous resin mainly composed of polyvinyl alcohol resin as a binder in the active material and conductive material, thereby suppressing internal short circuits due to peeling of the conductive material.

[0006] International Publication No. 2018-135353 Japanese Patent Application Laid-Open No. 2023-87359

[0007] On the other hand, when fibers are added to an electrode, it is difficult to distribute the fibers uniformly throughout the electrode, which generally results in a decrease in the surface smoothness of the electrode material and a decrease in battery performance. The cellulose nanofibers described in Patent Document 1 are fine fibers that can maintain the surface smoothness of the electrode material to a certain extent, but they only follow the expansion and contraction of the electrode and do not suppress the expansion and contraction of the active material itself, so there is a limit to the improvement in battery performance.

[0008] In Patent Document 2, when sufficient stirring is performed to uniformly disperse the fibrous resin in the electrode, the stirring can cause foaming of the binder, making it unsuitable for producing electrodes.

[0009] Therefore, an object of the present invention is to provide an electrode active material layer and an electrode including the electrode active material layer, in which, when the expansion and contraction of the active material itself is suppressed using fibers, the fibers can be uniformly distributed throughout the electrode active material layer, and a high discharge capacity retention rate can be achieved when used in a battery.

[0010] The present inventors conducted extensive research to solve the above-mentioned problems, and as a result, they have completed the present invention. That is, the present invention includes the following preferred embodiments. [1] An electrode active material layer comprising fibers, a binder, and an electrode active material, wherein the fibers have a fiber diameter of 1 to 15 μm, the fiber length coefficient of variation CV of the fibers is 0 to 0.30, and the surface roughness Sa of the electrode active material layer is 0 to 10 μm. [2] The electrode active material layer according to [1], wherein the fiber length is 0.1 to 5 mm. [3] The electrode active material layer according to [1] or [2], wherein the fiber content in the electrode active material layer is 0.008 to 1.2 vol %. [4] The electrode active material layer according to any one of [1] to [3], wherein the binder content is more than 0.1 mass % based on the total mass of the electrode active material layer. [5] The electrode active material layer according to any one of [1] to [4], wherein the ratio (B / A) of the fiber length B of the fibers to the average particle diameter A of the electrode active material in the electrode active material layer is 3 to 1700. [6] The electrode active material layer according to any one of [1] to [5], wherein the fibers are selected from the group consisting of synthetic fibers, semi-synthetic fibers, recycled fibers, and inorganic fibers. [7] The electrode active material layer according to any one of [1] to [6], wherein the fibers are straight fibers. [8] The electrode active material layer according to any one of [1] to [7], wherein the fibers do not contain pulp fibers. [9] The electrode active material layer according to any one of [1] to [8], wherein the electrode active material layer is for a negative electrode.

[10] The electrode active material layer according to any one of [1] to [9], wherein the electrode active material contains a silicon-based active material.

[11] An electrode comprising the electrode active material layer according to any one of [1] to

[10] and a current collector.

[12] The electrode according to

[11] , wherein the coefficient of variation CV of the electrode weight is 0 to 0.03.

[13] A method for producing an electrode active material layer according to any one of [1] to

[10] , comprising: (1) a step of preparing an electrode composition containing fibers, a binder, and an electrode active material; and (2) a step of applying the electrode composition to a current collector and drying it to form an electrode active material layer.

[14] (1) A method for producing an electrode active material layer according to

[13] , wherein, in the step of preparing an electrode composition, the binder is added last among the components contained in the electrode composition, and the fibers are added and kneaded immediately before the addition of the binder.

[0011] According to the present invention, it is possible to provide an electrode active material layer and an electrode including the electrode active material layer, in which, when fibers are used to suppress expansion and contraction of the active material, the fibers are uniformly distributed throughout the electrode active material layer, and when used in a battery, a high discharge capacity retention rate can be achieved.

[0012] Hereinafter, embodiments of the present invention will be described in detail. Note that the following description is for illustrating embodiments of the present invention, and is not intended to limit the present invention to the following embodiments.

[0013] <Electrode active material layer> The electrode active material layer of this embodiment includes fibers, a binder, and an electrode active material, the fibers having a fiber diameter of 1 to 15 μm, the fiber length variation coefficient CV of the fibers being 0 to 0.30, and the surface roughness Sa of the electrode active material layer being 0 to 10 μm. The electrode active material layer of this embodiment is formed by applying a composition for forming an electrode active material layer containing fibers, a binder, and an electrode active material (hereinafter also simply referred to as an "electrode composition") to, for example, a current collector, and drying the composition.

[0014] The mechanism by which the electrode active material layer of this embodiment maintains good surface smoothness and provides a high discharge capacity retention rate when used in a battery is unclear, but is presumed to be as follows. The fibers added to the electrode active material layer serve to connect and reinforce the active material. This is thought to allow lithium ions to be inserted and removed from the voids of the active material during charge and discharge, maintaining the shape of the active material even when the active material expands and contracts, thereby suppressing expansion of the active material. However, fibers, particularly hydrophobic fibers among inorganic, natural, and organic fibers, are typically difficult to distribute uniformly throughout the electrode active material layer due to aggregation, entanglement with the active material, or breakage, which can lead to a risk of degraded battery performance. However, by adjusting the fiber diameter, fiber length coefficient of variation (CV), and surface smoothness of the electrode active material layer within appropriate ranges, the fibers can be uniformly dispersed within the electrode active material layer, forming electrolyte passages and improving the electrolyte permeability of an electrode including the electrode active material layer of this embodiment. As a result, the resistance of a battery including the electrode active material layer of this embodiment is likely to be low, and the battery capacity is likely to be large. Furthermore, when the fibers are uniformly dispersed in the electrode active material layer, the expansion of the active material can be suppressed uniformly throughout the electrode material. Therefore, the present inventors have found that an electrode including the electrode active material layer can achieve a high discharge capacity retention rate. Therefore, this embodiment also includes an electrode including the electrode active material layer.

[0015] [Fibers] The fibers contained in the electrode active material layer of this embodiment have a fiber diameter of 1 to 15 μm. The fiber diameter of the fibers is 1 μm or more, from the viewpoints of easily obtaining the reinforcing effect of the active material by the fibers and easily suppressing electrode expansion. If the fiber diameter is less than 1 μm, electrode expansion tends to be difficult to suppress. Furthermore, from the viewpoint of maintaining the smoothness of the electrode active material layer derived from the fibers, which can be a cause of reduced battery performance, the fiber diameter is 15 μm or less. If the fiber diameter is more than 15 μm, unevenness tends to occur on the electrode surface, making it difficult to obtain an electrode with a uniform surface. In the electrode active material layer of this embodiment, the fiber diameter is preferably 2 to 11 μm, more preferably 3 to 9 μm, and even more preferably 4 to 8 μm. The fiber diameter of the fibers used as a raw material for the electrode composition can be adjusted within the above range by appropriately changing the spinning conditions (e.g., spinning temperature, nozzle diameter, etc.). The fiber diameter in the electrode composition does not substantially change even after kneading. The fiber diameter can be determined, for example, by the method described in the Examples below.

[0016] The fiber length variation coefficient CV of the fibers contained in the electrode active material layer of this embodiment is 0 to 0.30. The fiber length variation coefficient CV of the fibers is 0.30 or less, from the viewpoint of facilitating uniform dispersion of the fibers in the electrode active material layer. Furthermore, when the fiber length variation coefficient CV is 0.30 or less, the fiber length is uniform, and the expansion suppression of the active material can be uniformly achieved throughout the electrode material. When the fiber length variation coefficient CV of the fibers exceeds 0.30, the fiber length varies, causing localized viscosity changes in the slurry, which tends to make it difficult to uniformly disperse the fibers in the electrode active material layer. Furthermore, since fibers with different fiber lengths are expected to have different effects on suppressing the expansion of the active material, even if the fibers are uniformly dispersed, it is difficult to achieve a uniform expansion suppression effect throughout the electrode material. In the electrode active material layer of this embodiment, the fiber length variation coefficient CV of the fibers is preferably 0 to 0.28, more preferably 0 to 0.25, and even more preferably 0 to 0.20. The method for adjusting the coefficient of variation CV of the fiber length of the fibers contained in the electrode active material layer of this embodiment to fall within the above range is not limited in any way, but for example, when an electrode active material layer is produced by the method for producing an electrode active material layer described below, the coefficient of variation CV of the fiber length can be adjusted by adjusting the order of addition of the fibers and binder and the kneading conditions. The coefficient of variation CV of the fiber length can be calculated, for example, from the fiber length measured with a microscope, as described below.

[0017] The surface roughness Sa of the electrode active material layer of this embodiment is 0 to 10 μm. When the surface roughness Sa of the electrode active material layer of this embodiment is 10 μm or less, the surface of the electrode active material layer is smooth, and when the electrode active material layer is used in a battery, a large contact area with the separator can be ensured, resulting in a uniform battery reaction and improved battery performance. Furthermore, when the fibers are uniformly distributed within the electrode active material layer, the surface roughness Sa of the electrode active material layer can be said to be 10 μm or less. When the surface roughness Sa of the electrode active material layer exceeds 10 μm, the surface irregularities are large, reducing the contact area with the separator, and therefore, a uniform battery reaction tends not to occur. The surface roughness Sa of the electrode active material layer of this embodiment is preferably 0 to 8 μm, more preferably 0 to 5 μm, and even more preferably 0 to 3 μm. The method for adjusting the surface roughness Sa of the electrode active material layer of this embodiment to be within the above range is not limited in any way, but for example, when the electrode active material layer is manufactured by the manufacturing method of the electrode active material layer described below, the surface roughness Sa can be adjusted by adjusting the order of adding the fiber and the binder and the kneading conditions. The surface roughness Sa of the electrode active material layer can be calculated, for example, by a one-shot 3D shape measuring device as described below.

[0018] The fiber length of the fibers contained in the electrode active material layer is preferably 0.1 to 5 mm. When the fiber length is 0.1 to 5 mm, the fibers can be uniformly dispersed within the electrode, thereby suppressing electrode expansion. Furthermore, the electrode composition has better coatability, allowing for the production of a uniform electrode with no weight variations. When the fiber length is less than 0.1 mm, the reinforcing effect of the fibers on the electrode material is difficult to obtain, and electrode expansion suppression tends to be insufficient. This can lead to peeling of the electrode material from the current collector plate, resulting in deterioration of battery performance. On the other hand, when the fiber length is 0.1 mm or more, expansion and contraction of the active material can be effectively suppressed, and the reinforcing effect of the fibers on the electrode material can be easily obtained. Furthermore, when the fiber length exceeds 5 mm, the fibers tend to entangle with each other in the electrode composition, forming fibrous clumps, which can deteriorate the stability and coatability of the composition. The fiber length is more preferably 0.1 to 4.5 mm, even more preferably 0.15 to 4 mm, even more preferably 0.2 to 3.5 mm, particularly preferably 0.3 to 3.5 mm, and particularly preferably 0.4 to 3.5 mm, and may be 0.5 to 3.5 mm. The method for adjusting the fiber length within the above range is not particularly limited. For example, when an electrode active material layer is produced by the method for producing an electrode active material layer described below, the fiber length can be adjusted by adjusting the order of addition of the fibers and binder and the kneading conditions. The fiber length of the fibers contained in the electrode active material layer can be calculated, for example, as described below, by observing the fibers contained in the electrode composition after kneading with a microscope and averaging the lengths of 50 fibers.

[0019] The fiber content (fiber volume content) in the electrode active material layer is preferably 0.008 to 1.2 vol%, more preferably 0.01 to 1.15 vol%, even more preferably 0.025 to 1.1 vol%, even more preferably 0.05 to 1.05 vol%, and particularly preferably 0.1 to 1.05 vol%, and may be, for example, 0.13 to 1.05 vol%, 0.15 to 1.05 vol%, or 0.2 to 1.05 vol%. When the fiber volume content is within the above range, expansion of the electrode obtained from the electrode active material layer can be further suppressed. The fiber volume content can be calculated by dividing the content of each component in the electrode composition relative to the total mass of the electrode composition by the specific gravity of the component to determine the volume of each component, and then dividing the fiber volume by the sum of the volumes determined from the sum of the volumes of the components [fiber content in the electrode composition (fiber volume content) = fiber volume / sum of volumes].

[0020] The fibers contained in the electrode active material layer of this embodiment are preferably selected from the group consisting of synthetic fibers, semi-synthetic fibers, recycled fibers, and inorganic fibers. Examples of synthetic fibers include polypropylene fibers, polyolefin fibers, acrylic fibers, polyvinyl alcohol (hereinafter sometimes referred to as "PVA") fibers, ethylene-vinyl alcohol copolymer fibers, polyamide fibers, polyimide fibers, and polyester fibers. Examples of semi-synthetic fibers include acetate fibers and triacetate fibers. Examples of recycled fibers include rayon, cupra, lyocell, and polynosic. Examples of inorganic fibers include glass fibers, carbon fibers, ceramic fibers, and metal fibers. Among these, from the viewpoint of preventing fiber breakage and enabling the production of a uniform electrode, the fibers are preferably synthetic fibers, semi-synthetic fibers, or recycled fibers, and more preferably contain at least one selected from the group consisting of polypropylene fibers, PVA fibers, polyester fibers, ethylene-vinyl alcohol copolymer fibers, polyamide fibers, polyimide fibers, acetate fibers, triacetate fibers, rayon, cupra, lyocell, and polynosic. From the viewpoint of hydrophilicity and excellent electrolyte permeability, it is even more preferable to contain at least one selected from the group consisting of PVA fibers, polyamide fibers, acetate fibers, triacetate fibers, rayon, cupra, lyocell, and polynosic.

[0021] Examples of glass fibers include E glass, S glass, C glass, ECR glass, and AR glass.

[0022] The polymer constituting the polypropylene-based fiber is not particularly limited, and examples thereof include propylene homopolymers, copolymers of propylene and other olefins, etc. Furthermore, the copolymers of propylene and other olefins may be either block copolymers or random copolymers.

[0023] The polymer constituting the PVA-based fiber is not particularly limited as long as it contains a vinyl alcohol unit as a main component, and may contain other structural units (modifying units) as desired, as long as the effects of this embodiment are not impaired. Examples of such modifying units include α-olefins such as propylene, 1-butene, isobutene, and 1-hexene; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, phthalic acid, phthalic anhydride, maleic acid, maleic anhydride, itaconic acid, and itaconic anhydride, and their salts or C1-18 alkyl esters thereof; acrylamides such as acrylamide, C1-18 N-alkylacrylamide, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine, its acid salts, and quaternary salts thereof; methacrylamides such as methacrylamide, C1-18 N-alkylmethacrylamide, N,N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid and its salts, methacrylamidepropyldimethylamine, its acid salts, and quaternary salts thereof; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, and N-vinylacetamide; acrylonitrile vinyl cyanides such as vinyl ether, methacrylonitrile, etc.; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, etc.; allyl acetate; allyl ethers such as propyl allyl ether, butyl allyl ether, hexyl allyl ether, etc.; vinyl halides such as vinyl chloride, vinyl fluoride, vinyl bromide, etc.; vinylidene halides such as vinylidene chloride, vinylidene fluoride, etc.; trimethoxyvinylsilane vinyl silanes such as silane; compounds having an oxyalkylene group such as polyoxyalkylene allyl ether; isopropenyl acetate; hydroxy group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, and 3-methyl-3-buten-1-ol; compounds having a carboxyl group derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride, and the like;Examples of the modifying unit include monomers having a sulfonic acid group derived from ethylene sulfonic acid, allyl sulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc.; and compounds having a cationic group derived from vinyloxyethyl trimethylammonium chloride, vinyloxybutyl trimethylammonium chloride, vinyloxyethyl dimethylamine, vinyloxymethyl diethylamine, N-acrylamidomethyl trimethylammonium chloride, N-acrylamidoethyl trimethylammonium chloride, N-acrylamidodimethylamine, allyl trimethylammonium chloride, methallyl trimethylammonium chloride, dimethylallylamine, allylethylamine, etc. These modifying units may be used alone or in combination of two or more. The method for introducing such a modifying unit may be a copolymerization method or a post-reaction method.

[0024] The molar ratio of the modifying unit to the vinyl alcohol unit [(vinyl alcohol unit) / (modifying unit)] is, for example, 85 / 15 to 100 / 0, preferably 88 / 12 to 100 / 0, more preferably 90 / 10 to 100 / 0. １３ It can be determined by C-NMR (nuclear magnetic resonance spectroscopy) or the like.

[0025] The number average molecular weight of the PVA-based polymer is not particularly limited, but from the viewpoint of the handleability of the resulting fiber, it is preferably 20,000 or more, more preferably 70,000 or more, and preferably 250,000 or less, more preferably 200,000 or less. The number average molecular weight can be determined, for example, by gel permeation chromatography (GPC) using polymethyl methacrylate as a standard substance.

[0026] The viscosity-average degree of polymerization of the PVA-based polymer is not particularly limited, but from the viewpoint of the handleability of the resulting fiber, it is preferably 500 or more, more preferably 1,700 or more, and preferably 5,000 or less, more preferably 4,000 or less. The viscosity-average degree of polymerization can be measured, for example, based on JIS K 6726:1994 "Testing Methods for Polyvinyl Alcohol." Specifically, when the saponification degree is less than 99.5 mol%, the viscosity-average degree of polymerization can be calculated from the intrinsic viscosity [η] (liters / g) measured in water at 30°C for PVA saponified to a saponification degree of 99.5 mol% or more, using the following formula: Viscosity-average degree of polymerization = ([η] x 10 ４ / 8.29) （１／０．６２）

[0027] The degree of saponification of the PVA-based polymer can be appropriately selected depending on the purpose and is not particularly limited. However, from the viewpoint of the handleability of the resulting fiber, the degree of saponification is, for example, 88 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more. The upper limit of the degree of saponification is 100 mol% or less. The degree of saponification can be determined, for example, according to JIS K 6726:1994.

[0028] The tensile strength of the PVA-based fiber is preferably 2 cN / dtex or more, more preferably 3 cN / dtex or more. The upper limit of the tensile strength is not particularly limited, but is, for example, 50 cN / dtex or less. The elongation is preferably 50% or less, more preferably 30% or less. The elongation is usually 2% or more. When the tensile strength and elongation of the PVA-based fiber are within the above ranges, expansion of the electrode obtained from the electrode composition can be further suppressed. The tensile strength and elongation of the PVA-based fiber can be measured, for example, according to JIS L 1013:2021.

[0029] The PVA-based polymer constituting the PVA-based fiber may contain only one type of polymer, or may contain two or more polymers differing in one or more of the above-described types of modifying units, their molar ratios, degrees of polymerization, degrees of saponification, etc., or may contain a polymer other than the above-described PVA-based polymer. Furthermore, the PVA-based fiber may be a composite spun fiber with another polymer (e.g., a core-sheath fiber).

[0030] Examples of polymers constituting polyester-based fibers include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polypropylene terephthalate (PPT), polylactic acid (PLA), etc. Among these, PET or PBT is preferred because it easily achieves both good coatability of the electrode composition and suppression of expansion of the electrode obtained from the composition.

[0031] The polyester polymer may be a modified polyester polymer modified with a monomer such as isophthalic acid, as long as the effect of this embodiment is not impaired. The proportion of the modifying monomer in the modified polyester polymer is usually 0.1 to 30 mol %, preferably 0.5 to 20 mol %, and more preferably 1 to 15 mol %.

[0032] The number average molecular weight of the polyester-based polymer is not particularly limited, but from the viewpoint of the handleability of the resulting fiber, it is usually 4,000 to 15,000, and preferably 6,000 to 10,000. The number average molecular weight of the polyester-based polymer can be determined in the same manner as the number average molecular weight of the PVA-based polymer.

[0033] The tensile strength of the polyester fiber is preferably 2 cN / dtex or more, more preferably 3 cN / dtex or more. The upper limit of the tensile strength is not particularly limited, but is, for example, 50 cN / dtex or less. The elongation is preferably 400% or less, more preferably 100% or less, and even more preferably 50% or less. The elongation is usually 2% or more. When the tensile strength and elongation of the polyester fiber are within the above ranges, expansion of the electrode obtained from the electrode composition can be further suppressed. The tensile strength and elongation of the polyester fiber can be measured, for example, according to JIS L 1013:2021.

[0034] The polymer constituting the ethylene-vinyl alcohol copolymer fiber contains, for example, 10 to 70 mol %, preferably 30 to 50 mol %, of ethylene units, and the remainder may be vinyl alcohol units alone or may consist of vinyl alcohol and other vinyl monomer units. When the polymer consists of vinyl alcohol and other vinyl monomer units, it is usually preferred that the amount of vinyl alcohol units is greater than the amount of other vinyl monomer units.

[0035] The ethylene-vinyl alcohol copolymer can be obtained by saponifying the vinyl acetate portion of an ethylene / vinyl acetate copolymer, and the degree of saponification of the vinyl alcohol unit in the ethylene-vinyl alcohol copolymer is, for example, 90 to 99.99 mol%, preferably 95 to 99.98 mol%, and more preferably 96 to 99.97 mol%.

[0036] The number average molecular weight of the ethylene-vinyl alcohol copolymer is not particularly limited, but from the viewpoint of the handleability of the resulting fiber, it is preferably 5,000 to 25,000, more preferably 8,000 to 20,000. The number average molecular weight of the ethylene-vinyl alcohol copolymer can be determined in the same manner as the number average molecular weight of the PVA polymer.

[0037] Examples of polymers that constitute polyamide-based fibers include aliphatic polyamides (e.g., polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 610, polyamide 612, and polyamide 9C), semi-aromatic polyamides (e.g., polyamide 9T) synthesized from aromatic dicarboxylic acids and aliphatic diamines, and wholly aromatic polyamides synthesized from aromatic dicarboxylic acids and aromatic diamines, such as polyparaphenylene terephthalamide.

[0038] Examples of polymers constituting polyimide fibers include polyimide polymers obtained by reacting an aromatic diamine compound (e.g., paraphenylenediamine (PPD)) with a tetracarboxylic acid compound (e.g., pyromellitic dianhydride (PMDA)), polyetherimide polymers containing ether units and cyclic imide units as repeating units, and polyamideimide polymers.

[0039] From the viewpoint of easily dispersing the fibers uniformly in the electrode active material layer, the fibers are preferably straight fibers. In this specification, straight fibers are fibers that can maintain the shape before being added to the slurry without bending or curving in the electrode. If the fibers are not straight fibers, for example, fibers that are bent like pulp fibers, it is difficult to obtain a uniform electrode active material layer because the fiber length and fiber diameter cannot be made constant to the extent necessary to achieve the effects of this embodiment. Preferably, the fibers do not contain pulp fibers.

[0040] The polymer may contain additives such as antifoaming agents, flame retardants, antifreeze agents, pH adjusters, opacifying agents, colorants, oils, and special functional agents depending on the purpose, as long as the effects of the present embodiment are not impaired. These additives may be contained alone or in combination.

[0041] The aspect ratio of the fibers contained in the electrode active material layer [ratio of fiber diameter to fiber length (fiber length / fiber diameter)] is preferably 5 to 1,000, more preferably 10 to 800, even more preferably 20 to 600, and even more preferably 30 to 400. When the aspect ratio of the fibers is within the above range, the coatability of the electrode composition is improved, and expansion of the electrode obtained from the electrode composition can be further suppressed.

[0042] The cross-sectional shape of the fibers contained in the electrode active material layer is not particularly limited. The cross-sectional shape of the fibers may be, for example, circular, or irregular shapes such as oval, triangular, rectangular, rhombic, star-shaped, flat, or snowman-shaped. They may also be hollow. When the fibers have irregular cross sections, the fiber diameter may be calculated by converting them into a perfect circle.

[0043] [Binder] The binder contained in the electrode active material layer preferably contains at least one selected from the group consisting of synthetic resin-based binders, natural resin-based binders, semi-synthetic resin-based binders, silicate-based binders, phosphate-based binders, sol-based binders, and cement-based binders. Among these, synthetic resin-based binders are more preferred because they are more likely to suppress expansion of an electrode including an electrode active material layer obtained from the electrode composition.

[0044] Examples of synthetic resin binders include polyvinylidene fluoride (PVDF), PVA-based binders, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, polyamideimide, polyimide, styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, epoxy resin, nylon, copolymers of propylene and olefins having 2 to 8 carbon atoms, sodium polyacrylate, polyacrylic acid, and acrylic binders such as copolymers of (meth)acrylic acid and (meth)acrylic acid alkyl esters. Among these, SBR, acrylic binders, and PVA binders are preferred because they are more likely to suppress expansion of an electrode containing an electrode active material layer obtained from the electrode composition.

[0045] Examples of natural resin binders include glue, starch, and lacquer.

[0046] Examples of the semi-synthetic resin binder include diacetyl cellulose and nitrile cellulose.

[0047] Examples of silicate binders include Li ２ O.nSiO ２ , Na ２ O.nSiO ２ , K. ２ O.nSiO ２ etc.

[0048] Examples of the phosphate binder include aluminum phosphate and magnesium phosphate.

[0049] An example of the sol-based binder is fumed silica.

[0050] Examples of cement binders include portland cement and alumina cement.

[0051] The binder may be used alone or in combination of two or more. The content of the binder can be adjusted appropriately depending on the type of binder. In a preferred embodiment, the binder contained in the electrode active material layer is preferably more than 0.1 mass%, more preferably more than 0.1 mass% and not more than 20 mass%, even more preferably 0.2 to 15 mass%, and even more preferably 0.2 to 12 mass%, based on the total mass of the electrode active material layer. When the binder content is more than 0.1 mass% relative to the total mass of the electrode active material layer, the adhesion of the active material is improved, which is advantageous from the viewpoint of maintaining the durability of the battery. Furthermore, when the binder content is 20 mass% or less relative to the total mass of the electrode active material layer, the discharge capacity is likely to be improved.

[0052] The number average molecular weight of the PVA-based binder is not particularly limited, but from the viewpoint of ease of handling of the electrode composition, it is, for example, 20,000 or more, more preferably 70,000 or more, and preferably 250,000 or less, more preferably 200,000 or less. The number average molecular weight can be determined, for example, by gel permeation chromatography (GPC) using polymethyl methacrylate as a standard substance.

[0053] The viscosity-average degree of polymerization of the PVA-based binder is not particularly limited, but from the viewpoint of the ease of handling of the electrode composition, it is, for example, 500 or more, preferably 1,500 or more, and for example, 5,000 or less, preferably 4,500 or less. The viscosity-average degree of polymerization can be measured, for example, based on JIS K 6726:1994 "Test Method for Polyvinyl Alcohol." Specifically, when the degree of saponification is less than 99.5 mol%, the viscosity-average degree of polymerization can be calculated from the intrinsic viscosity [η] (liters / g) measured in water at 30°C for PVA saponified to a degree of saponification of 99.5 mol% or more, using the following formula: Viscosity-average degree of polymerization = ([η] x 10 ４ / 8.29) （１／０．６２）

[0054] The saponification degree of the PVA-based binder can also be appropriately selected depending on the purpose and is not particularly limited, but from the viewpoint of the handleability of the electrode composition, the saponification degree is, for example, 80 mol% or more, preferably 85 mol% or more. The upper limit of the saponification degree is 100 mol% or less. The saponification degree can be determined, for example, according to JIS K 6726:1994.

[0055] The PVA binder used in this embodiment may be an unmodified PVA consisting of only vinyl alcohol units, or may be modified with at least one monomer selected from the group consisting of carboxylic acids having unsaturated double bonds, alkyl esters of the carboxylic acids, acid anhydrides of the carboxylic acids, salts of the carboxylic acids, and silyl compounds having unsaturated double bonds. Examples of such monomers include maleic acid, monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, maleic anhydride, citraconic acid, monomethyl citraconic acid, dimethyl citraconic acid, diethyl citraconic acid, citraconic anhydride, fumaric acid, monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, diethyl fumarate, itaconic acid, monomethyl itaconate, dimethyl itaconate, monoethyl itaconate, diethyl itaconate, itaconic anhydride, acrylic acid ... Preferred are methyl acrylate, ethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, monomethyl maleate, dimethyl maleate, monomethyl citraconic acid, monomethyl fumarate, monomethyl itaconate, itaconic anhydride, methyl acrylate, methyl methacrylate, and vinyltrimethoxysilane, and examples thereof include monomethyl maleate, dimethyl maleate, monomethyl fumarate, itaconic anhydride, methyl acrylate, methyl methacrylate, and vinyltrimethoxysilane.

[0056] The number average molecular weight and viscosity average degree of polymerization of the SBR-based binder used in this embodiment are not particularly limited, but from the viewpoint of the handleability of the resulting electrode composition, the number average molecular weight is preferably from 20,000 to 300,000, and the viscosity average degree of polymerization is preferably from 100 to 1,500. The number average molecular weight and viscosity average degree of polymerization of the SBR-based binder can be determined by the same method as that for the number average molecular weight and viscosity average degree of polymerization of the PVA-based binder.

[0057] [Electrode active material] The electrode active material layer contains an electrode active material. The electrode active material layer may be used for either a positive electrode or a negative electrode. Alternatively, it may be used for both a positive electrode and a negative electrode. Therefore, the electrode active material may be either a positive electrode active material or a negative electrode active material. The electrode active material layer is preferably for a negative electrode.

[0058] In the electrode active material layer, the fiber content (mass) is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.15 parts by mass or more, relative to 100 parts by mass of the electrode active material, from the viewpoints of easily exerting the reinforcing effect of the fibers and easily suppressing electrode expansion. Furthermore, from the viewpoints of easily suppressing entanglement of fibers during kneading of the electrode composition and easily improving the uniformity of the composition, the fiber content is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, even more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less. Therefore, the fiber content is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 6 parts by mass, and even more preferably 0.15 to 4 parts by mass, relative to 100 parts by mass of the electrode active material.

[0059] In a preferred embodiment, the binder contained in the electrode active material layer is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, and even more preferably 0.2 to 12 parts by mass, per 100 parts by mass of the electrode active material. When the binder content is 0.1 parts by mass or more per 100 parts by mass of the electrode active material, the adhesion of the active material to the current collector is improved, which is advantageous from the viewpoint of maintaining the durability of the applied battery. Furthermore, when the binder content is 20 parts by mass or less per 100 parts by mass of the active material, the discharge capacity is likely to be improved.

[0060] The negative electrode active material may be, for example, a material that has been conventionally used as a negative electrode active material for non-aqueous electrolyte batteries, and examples thereof include carbonaceous materials such as amorphous carbon, artificial graphite, natural graphite (graphite), mesocarbon microbeads (MCMB), pitch-based carbon fiber, carbon black, activated carbon, carbon fiber, hard carbon, soft carbon, mesoporous carbon, and conductive polymers such as polyacene; ｘ , SiC, and silicon-based active materials such as SiO ｘ , SnO ｘ and LiTiO ｘ other metal oxides, lithium metals such as lithium alloys, TiS ２ and LiTiS ２ and composite materials of metal oxides and carbonaceous materials, etc. These negative electrode active materials can be used alone or in combination of two or more.

[0061] Among the above, from the viewpoint of improving the battery capacity of the battery obtained from the electrode active material layer, SiO ｘ It is preferable to use silicon-based active materials such as SiC, hard carbon, and lithium metal such as lithium titanate (LTO).

[0062] When the electrode active material layer is used for a negative electrode, the content of the negative electrode active material in the electrode active material layer is not particularly limited and can be adjusted appropriately depending on the type of active material used, but is, for example, 80 to 99.9 mass%, preferably 85 to 98 mass%, relative to the total mass of the electrode active material layer. Furthermore, the content of the above-mentioned preferred negative electrode active material in the electrode active material layer is not particularly limited and can be adjusted appropriately depending on the type of active material used, but is, for example, 0.1 to 50 mass%, preferably 0.5 to 40 mass%, more preferably 1 to 35 mass%, relative to the total mass of the electrode active material layer.

[0063] The positive electrode active material may be, for example, a material that has been conventionally used as a positive electrode active material for non-aqueous electrolyte batteries. ２ , TiS ３, amorphous MoS ３ , Cu ２ V ２ O ３ , amorphous V ２ O-P ２ O ５ , MoO ３ , V ２ O ５ and V ６ O １３ transition metal oxides such as lithium-containing cobalt oxide (LiCoO ２ ), lithium-containing nickel oxide (LiNiO ２ ), lithium manganese oxide (LiMn ２ O ４ ), Co—Ni—Mn lithium-containing composite oxide, Ni—Mn—Al lithium-containing composite oxide, Ni—Co—Al lithium-containing composite oxide, olivine-type lithium iron phosphate (LiFePO ４ ), olivine-type lithium manganese phosphate (LiMnPO ４ ), Li １＋ｘ Mn ２－ｘ O ４ (0<X<2) Lithium-excess spinel compound represented by Li[Ni ０．１７ Li ０．２ Co ０．０７ Mn ０．５６ ]O ２ , LiNi ０．５ Mn １．５ O ４ and the like, sulfur, organic radicals such as compounds and polymers having a nitroxyl radical, compounds and polymers having an oxy radical, compounds and polymers having a nitrogen radical, and compounds and polymers having a fulvalene skeleton. These positive electrode active materials can be used alone or in combination of two or more.

[0064] Among the above, from the viewpoint of improving the battery capacity of the battery obtained from the electrode active material layer, LiCoO ２ LiNiO ２ Co—Ni—Mn lithium-containing composite oxides, for example, LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi０．５ Co ０．２ Mn ０．３ O ２ , LiNi ０．８ Co ０．１ Mn ０．１ O ２ Lithium-containing composite oxides of Ni-Co-Al, for example, LiNi ０．８ Co ０．１ Al ０．１ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ It is preferable to use the following.

[0065] When the electrode active material layer is used for a positive electrode, the content of the positive electrode active material in the electrode active material layer is not particularly limited and can be appropriately adjusted depending on the type of active material used, but is, for example, 80 to 99.9 mass %, preferably 85 to 98 mass %, relative to the total mass of the electrode active material layer.

[0066] The particle size of the electrode active material contained in the electrode active material layer is not particularly limited and can be adjusted appropriately depending on the type of electrode active material used, but when a carbonaceous material such as amorphous carbon, artificial graphite, natural graphite (graphite), mesocarbon microbeads (MCMB), pitch-based carbon fiber, carbon black, activated carbon, carbon fiber, hard carbon, soft carbon, mesoporous carbon, and conductive polymers such as polyacene is used as the electrode active material, the average particle size of the electrode active material is preferably 3 to 100 μm, more preferably 5 to 80 μm, and even more preferably 7 to 50 μm from the viewpoint of improving the energy density of the battery. The particle size of the active material can be measured, for example, by laser diffraction scattering, image analysis using an electron microscope, X-ray CT, etc.

[0067] The particle size of the electrode active material contained in the electrode active material layer is not particularly limited and can be adjusted appropriately depending on the type of electrode active material used. ｘ Silicon-based active materials such as SiO, SiC, and Si ｘ , SnO ｘ and LiTiO ｘWhen a composite metal oxide represented by the formula (I) is used, the average particle size of the electrode active material is preferably 0.001 to 40 μm, more preferably 0.005 to 35 μm, and even more preferably 0.01 to 30 μm, from the viewpoint of improving the energy density of the battery. The particle size of the active material can be measured, for example, by a laser diffraction scattering method, image analysis using an electron microscope, X-ray CT, or the like.

[0068] In the electrode active material layer, the ratio (B / A) of the fiber length B to the average particle diameter A of the electrode active material is preferably 3 or more, more preferably 5 or more, and even more preferably 7 or more, from the viewpoint of reinforcing the active materials. It is also preferably 1700 or less, more preferably 1400 or less, even more preferably 1100 or less, and particularly preferably 900 or less, and may be, for example, 500 or less. In one embodiment of this embodiment, the ratio (B / A) of the fiber length B to the average particle diameter A of the electrode active material in the electrode active material layer is preferably 3 to 1700, more preferably 5 to 1400, even more preferably 7 to 1100, and even more preferably 7 to 900, and may be, for example, 7 to 500. When the electrode active material contained in the electrode active material layer is composed of two or more electrode active materials, the average particle diameter A is the average particle diameter of the electrode active material with the largest average particle diameter. The average particle diameter A of the electrode active material is determined by measuring the particle diameter by laser diffraction scattering method, and the D ５０ The ratio (B / A) of the fiber length B (μm) of the fibers to the average particle diameter A (μm) of the electrode active material in the electrode active material layer can be determined, for example, by the method described in the Examples below.

[0069] [Conductive Aid] The electrode active material layer may contain a conductive aid. The conductive aid is used to increase the output of the non-aqueous electrolyte battery and can be appropriately selected depending on whether it is used in the positive electrode or negative electrode. Examples of conductive aids include carbon-based materials such as graphite, acetylene black, carbon black, carbon nanotubes, ketjen black, and vapor-grown carbon fiber (VGCF); metal-based materials such as metal powders of copper, nickel, aluminum, and silver; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination of two or more.

[0070] The amount of the conductive additive contained in the electrode active material layer is not particularly limited and can be adjusted appropriately depending on the type of conductive additive used, but is, for example, 0.1 to 20 mass %, more preferably 0.5 to 10 mass %, relative to the total mass of the electrode active material layer. By setting the amount of the conductive additive within this range, the dispersion of the conductive additive in the electrode composition is not impaired, and the expected conductivity is likely to be obtained.

[0071] <Method for Manufacturing Electrode Active Material Layer> The electrode active material layer of this embodiment may be manufactured by any manufacturing method as long as the above-described characteristics are satisfied. The electrode active material layer of this embodiment can be obtained, for example, by preparing an electrode composition, applying the obtained electrode composition to a current collector, and drying it. Alternatively, an electrode can be obtained by forming an electrode active material layer on the current collector. The electrode active material layer of this embodiment and an electrode including the electrode active material layer can be manufactured by, for example, a manufacturing method including: (1) a step of preparing an electrode composition including fibers, a binder, and an electrode active material; and (2) a step of applying the electrode composition to a current collector and drying to form an electrode active material layer, wherein, in the step of preparing the electrode composition, the binder is preferably added last among the components contained in the electrode composition, and the fibers are added and kneaded immediately before the addition of the binder.

[0072] The electrode composition can be prepared, for example, by mixing fibers, a binder, and an electrode active material, and, if necessary, a conductive aid, a solvent, and other additives.

[0073] [Solvent] The electrode composition may contain a solvent. The solvent is preferably one that can dissolve the binder described above and can be appropriately selected depending on the binder used. Examples of the solvent include water; alcohols such as methanol, ethanol, propanol, and 2-propanol; cyclic ethers such as tetrahydrofuran and 1,4-dioxane; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; cyclic amides such as N-methylpyrrolidone and N-ethylpyrrolidone; sulfoxides such as dimethyl sulfoxide; hydrocarbons such as n-dodecane; esters such as γ-butyrolactone and methyl lactate; and sulfoxides / sulfones such as dimethyl sulfoxide and sulfolane. These may be used alone or in combination of two or more.

[0074] In this embodiment, the amount of solvent contained in the electrode composition is not particularly limited, and may be adjusted appropriately depending on the type and amount of the binder used, the desired viscosity of the composition, and the like.

[0075] [Other Additives] The electrode composition may contain additives, if necessary, that can impart viscosity, toughness, etc. to the composition. Such additives are not particularly limited, and examples that can be used include various alcohols, particularly polyvinyl alcohol and modified products thereof; celluloses such as CMC; polysaccharides; polyethers such as polyethylene glycol and polypropylene glycol; polyamines; pyrrolidones; and maleic acids.

[0076] Among other additives, the electrode composition may contain a thickener, which is likely to improve the thixotropy of the composition. The solid content of the thickener, which is optionally blended into the composition, is preferably 0.1 to 3 mass %, more preferably 0.5 to 2 mass %, based on the total mass of the solid content of the composition.

[0077] In the process of preparing an electrode composition, it is important to uniformly disperse the fibers in the composition. To achieve this, sufficient fiber mixing is required. However, if the mixing time is too long, fiber re-aggregation and entanglement with each other or with the active material may occur. Furthermore, when hard, brittle fibers such as glass fibers are mixed with a high solids content at the initial stage of mixing, high shear forces and / or long shear history can cause fiber breakage, which can cause fiber length variations and hinder the maintenance of appropriate fiber length. Therefore, it is preferable to add the fibers to the electrode composition at a time not too early, for example, toward the end of the mixing process.

[0078] In the process of preparing the electrode composition, if the kneading time of the binder is too long, foaming bubbles may occur, which may cause unevenness in the electrode active material layer, resulting in a decrease in battery performance. Therefore, among the components contained in the electrode composition, it is preferable to add the binder not too early, for example, towards the end of the process. Furthermore, adding the binder after the addition of the fibers can ensure sufficient agitation of the fibers to uniformly disperse the fibers in the electrode composition while also suppressing foaming of the binder. Therefore, it is more preferable to add the binder after the addition of the fibers.

[0079] In one embodiment of this embodiment, a portion of the fibers or binder may be added to the first half. Fibers with hydrophilic groups, in particular, have good compatibility with the aqueous slurry and suppress aggregation in the slurry. Therefore, even if a portion of the fibers is added to the first half, they can be uniformly dispersed in the electrode composition. Furthermore, foaming of the binder can be suppressed by using an antifoaming agent or by relaxing the kneading conditions.

[0080] The electrode composition is preferably prepared, for example, in the following order: (i) kneading components contained in the electrode composition other than the fibers and binder, such as an electrode active material, and if necessary, a conductive aid, a solvent, and a thickener; (ii) adding fibers and kneading; and (iii) adding a binder and kneading.

[0081] First, in (i), the components contained in the electrode composition other than the fibers and the binder, such as the electrode active material, and optionally the conductive additive and thickener, are kneaded together. In this process, the thickener may be added in multiple batches to adhere to the surface of the active material, from the viewpoint of reducing the frequency of collisions between the active material and the binder and improving the dispersibility of the active material in the slurry.

[0082] Next, in step (ii), fibers are added to the mixture obtained in step (i) and kneaded. By not adding the fibers initially, but adding them after the components other than the fibers and binder have been thoroughly kneaded in step (i), the kneading time for the fibers can be set appropriately, and re-aggregation of the fibers, entanglement of the fibers with each other or between the fibers and the active material, and / or fiber breakage that may occur during long-term kneading can be suppressed.

[0083] Finally, in step (iii), a binder is added to the mixture obtained in step (ii) and kneaded. Adding the binder last ensures sufficient kneading of the fibers to uniformly disperse them in the electrode composition, while also suppressing foaming of the binder.

[0084] The kneading method in the above steps (i) to (iii) is not particularly limited, and any mixing method can be used. Examples of kneading devices used in the kneading methods include stirring, rotating, and shaking types, and preferably a stirring planetary mixer. The kneading in the above steps (i) to (iii) can be carried out, for example, at room temperature.

[0085] The kneading time in (i) above may be selected appropriately depending on the type or amount of the mixed liquid in (i). From the viewpoint of improving the dispersibility of each component in the mixed liquid, for example, kneading may be performed multiple times at 1500 to 2500 rpm for 1 to 5 minutes. The kneading time in (ii) above may be selected appropriately depending on the type or amount of the mixed liquid in (ii). From the viewpoint of improving the dispersibility of the fibers, for example, kneading may be performed multiple times at 1500 to 2500 rpm for 1 to 5 minutes. The kneading time in (iii) above may be selected appropriately depending on the type or amount of the mixed liquid in (iii). From the viewpoint of suppressing foaming of the binder, for example, kneading may be performed for 1 to 5 minutes at 1500 to 2500 rpm, followed by kneading in a degassing mode at 1700 to 2700 rpm for 1 to 5 minutes.

[0086] In order to maintain good surface smoothness of the electrode active material layer, it is preferable to stir the fibers in a slurry containing the electrode active material and a solvent in the step of preparing the electrode composition. If the fibers are stirred without adding a solvent in the step of preparing the electrode composition, the good surface smoothness of the electrode active material layer tends to be difficult to maintain.

[0087] [Electrode] As described above, the electrode active material layer of the present embodiment can be formed on the current collector by, for example, applying and drying the electrode composition to the current collector, thereby forming an electrode. This embodiment also covers an electrode including the electrode active material layer and the current collector of the present embodiment.

[0088] The method for applying the electrode composition to the current collector is not particularly limited, and known methods can be used. Specific examples include doctor blade coating, dipping, reverse roll coating, direct roll coating, gravure coating, extrusion coating, and brush coating. In this case, the electrode composition may be applied to only one side of the current collector, or may be applied to both sides. The thickness of the electrode composition film on the current collector after application and before drying may be appropriately set depending on the thickness of the electrode to be obtained after drying, but is generally an amount that is preferably 0.005 to 5 mm, more preferably 0.01 to 2 mm.

[0089] The current collector to which the electrode composition is applied is not particularly limited as long as it is made of a material that is electrically conductive and electrochemically durable. For example, metal materials such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum can be used. These materials may be used alone or in combination of two or more types in any ratio. The shape of the current collector is not particularly limited, but it is usually preferably in the form of a sheet having a thickness of about 0.001 to 0.5 mm.

[0090] The method for drying the electrode composition on the current collector is not particularly limited and any known method can be used, such as drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. By drying the electrode composition on the current collector in this manner, the electrode active material layer of this embodiment is formed, and an electrode can be obtained. The drying temperature and drying time may be appropriately determined depending on the composition of the electrode composition and the thickness of the electrode composition film on the current collector after application and before drying.

[0091] After the drying step, the electrode may be subjected to a pressure treatment. Examples of a method for applying pressure to the electrode include die pressing and roll pressing. The pressure treatment can improve the adhesion between the electrode composition and the current collector. The pressure temperature and pressure time may be appropriately determined depending on the composition of the electrode composition.

[0092] From the viewpoint of battery design and battery manufacturing, the coefficient of variation CV of the electrode weight is preferably 0 to 0.03, more preferably 0 to 0.025, and even more preferably 0 to 0.02. The coefficient of variation CV of the electrode weight corresponds to the weight unevenness of the electrode, and it can be said that the smaller the coefficient of variation CV of the electrode weight, the less uneven the coating of the electrode composition and the more suppressed the variation in the battery capacity of the final battery product. There are no particular limitations on the method for adjusting the coefficient of variation CV of the electrode weight within the above range. For example, when an electrode active material layer is manufactured by the above-mentioned manufacturing method of an electrode active material layer, it can be adjusted by adjusting the solids concentration and slurry viscosity of the final slurry. The coefficient of variation CV of the electrode weight can be determined, for example, by the method described in the Examples below.

[0093] [Battery] A non-aqueous electrolyte battery can be formed by arranging the electrodes (positive electrode and negative electrode) facing each other, if necessary with a separator interposed therebetween, and immersing the electrodes in an electrolyte solution.

[0094] The separator that can be present between the positive electrode and the negative electrode may be polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof. Alternatively, a mixed multilayer film such as a two-layer separator of polyethylene / polypropylene, a three-layer separator of polyethylene / polypropylene / polyethylene, or a three-layer separator of polypropylene / polyethylene / polypropylene, or a glass nonwoven fabric may be used.

[0095] The electrolytic solution is an electrolyte dissolved in a solvent, and may be in liquid or gel form as long as it is one used in ordinary non-aqueous electrolyte batteries. An appropriate electrolyte may be selected depending on the type of negative electrode active material and positive electrode active material, so as to exhibit the function of the battery. Specific examples of the electrolyte include LiClO. ４ , LiBF ６ , LiPF ６ , LiCF ３ SO ３ , LiCF ３ CO ２ , LiAsF ６ , LiSbF ６ , LiB １０ Cl １０ , LiAlCl ４ , LiCl, LiBr, LiB(C ２ H ５ ) ４ , C.F. ３ SO ３ Li, C.H. ３ SO ３ Li, LiCF ３ SO ３ , LiC ４ F ９ SO ３ , Li(CF ３ SO ２ ) ２ N, LiN (C ｘ F ２ｘ＋１ SO ２ ) (C ｙ F ２ｙ＋１ SO ２) (x and y are natural numbers), LiI, LiB (C ２ O ４ ) ２ (lithium bis(oxalato)borate [LiBOB]), lower aliphatic lithium carboxylates, and the like.

[0096] The solvent (electrolyte solution solvent) for dissolving the electrolyte is not particularly limited. Specific examples include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, vinylene carbonate, and ethyl methyl carbonate; lactones such as γ-butyl lactone; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; and olefins such as 1,3-dioxolane and 4-methyl-1,3-dioxolane. Examples of suitable electrolytes include xolanes; nitrogen-containing compounds such as acetonitrile and nitromethane; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate; inorganic acid esters such as triethyl phosphate, dimethyl carbonate, and diethyl carbonate; diglymes; triglymes; sulfolanes; oxazolidinones such as 3-methyl-2-oxazolidinone; and sultones such as 1,3-propane sultone, 1,4-butane sultone, and naphtha sultone, and these can be used alone or in combination of two or more. When a gelled electrolyte is used, a nitrile polymer, an acrylic polymer, a fluorine-based polymer, an alkylene oxide polymer, or the like can be added as a gelling agent.

[0097] The method for producing a nonaqueous electrolyte battery is not particularly limited, but for example, a negative electrode and a positive electrode are stacked with a separator interposed therebetween, and the stacked electrodes are rolled or folded according to the shape of the battery, placed in a battery container, and an electrolyte is poured in and sealed. The shape of the battery may be any of the known types such as a coin type, button type, sheet type, cylindrical type, prismatic type, flat type, etc.

[0098] Hereinafter, the present embodiment will be described in more detail based on examples and comparative examples, but the present embodiment is not limited to the following examples.

[0099] [Fiber length and fiber diameter] The fiber length of the fibers used in the examples and comparative examples was measured by measuring the fiber lengths of 100 randomly selected fibers, and the average of the measured values ​​was used as the fiber length. The fiber diameter of 30 randomly selected fibers was measured by microscopic observation, and the average of the measured values ​​was used as the fiber diameter.

[0100] [Fiber length / average particle diameter of electrode active material] From the fiber length and the average particle diameter of the electrode active material measured above, the ratio (B / A) of the fiber length B of the fibers to the average particle diameter A of the electrode active material in the electrode active material layer was calculated. When the electrode active material layer contains two or more types of electrode active materials, the average particle diameter A is calculated from the one with the largest average particle diameter. The average particle diameter A of the electrode active material was calculated by measuring the particle diameter by a laser diffraction scattering method, and ５０ was requested as follows.

[0101] [Specific Gravity] The specific gravity of the fibers used in the examples and comparative examples was measured in accordance with the density gradient tube method described in 8.17.2 of JIS L 1013:2021 ("Testing methods for chemical fiber filaments").

[0102] [Aqueous Dispersion of SBR Binder] As the binder, an SBR binder (TRD2001 manufactured by JSR, specific gravity: 0.95) was used. In the example, an aqueous dispersion of the SBR binder (solid content concentration: 48.4 mass%) was used.

[0103] [Aqueous Solution of Thickener] CMC (Cellogen VSH-6, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., specific gravity: 1.6) was used as the thickener. In the example, the CMC was dissolved in water as a solvent to prepare a solution with a solid content of 1.5% by mass.

[0104] [Preparation of Nonaqueous Electrolyte Battery Electrode Composition] (Example 1) 89.78% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) as an electrode active material, 4.99% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, and 111.3% by mass of the above CMC aqueous solution with a solids concentration of 1.5% by mass as a thickener (amount equivalent to 1.67% by mass as solids) were placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Next, 0.25% by mass of PVA fiber (specific gravity: 1.28, fiber length: 2 mm, fiber diameter: 5 μm) was added and kneaded. Next, 6.85% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0105] (Example 2) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) as an electrode active material 2:8 mixture 89.55% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.98% by mass as a conductive additive, 110.7% by mass of the above CMC aqueous solution having a solid content concentration of 1.5% by mass as a thickener (amount to be 1.66% by mass as solids) was placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.50% by mass of PVA fiber (specific gravity: 1.28, fiber length: 2 mm, fiber diameter: 5 μm) was added and kneaded. Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0106] (Example 3) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) as an electrode active material 2:8 mixture 89.55% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.98% by mass as a conductive additive, 110.7% by mass of the above CMC aqueous solution having a solid content concentration of 1.5% by mass as a thickener (amount to be 1.66% by mass as solids) was placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.50% by mass of PVA fiber (specific gravity: 1.28, fiber length: 0.5 mm, fiber diameter: 7 μm) was added and kneaded. Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0107] (Example 4) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) as an electrode active material 2:8 mixture 89.55% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.98% by mass as a conductive additive, 110.7% by mass of the above CMC aqueous solution having a solid content concentration of 1.5% by mass as a thickener (amount to be 1.66% by mass as solids) was placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.50% by mass of PVA fiber (specific gravity: 1.28, fiber length: 3 mm, fiber diameter: 7 μm) was added and kneaded. Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0108] (Example 5) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) as an electrode active material and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) 2:8 mixture 89.84 mass%, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.99 parts by mass as a conductive additive, 111.3 mass% of the above CMC aqueous solution having a solid content concentration of 1.5 mass% as a thickener (amount to 1.67 mass% as solids) was added to a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.18 mass% of PP fiber (specific gravity: 0.91, fiber length: 3 mm, fiber diameter: 7 μm) was added and kneaded. Next, 6.85% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0109] (Example 6) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) as an electrode active material and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) 2:8 mixture 89.68 mass%, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.98 parts by mass as a conductive additive, 110.7 mass% of the above CMC aqueous solution having a solid content concentration of 1.5 mass% as a thickener (amount to be 1.66 mass% as solids) was put into a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.36 mass% of PP fiber (specific gravity: 0.91, fiber length: 3 mm, fiber diameter: 7 μm) was added and kneaded. Next, 6.85% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0110] (Example 7) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) as an electrode active material and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) 2:8 mixture 89.55% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.98% by mass as a conductive additive, 110.7% by mass of the above CMC aqueous solution having a solid content concentration of 1.5% by mass as a thickener (amount to 1.66% by mass as solids) was placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.49% by mass of glass fiber (specific gravity: 2.50, fiber length: 3 mm, fiber diameter: 6.5 μm) was added and kneaded. Next, 6.85% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0111] (Example 8) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) as an electrode active material and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) 2:8 mixture 89.13% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.95% by mass as a conductive additive, 110.0% by mass of the above CMC aqueous solution having a solid content concentration of 1.5% by mass as a thickener (amount to be 1.65% by mass as solids) was placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.98% by mass of glass fiber (specific gravity: 2.50, fiber length: 3 mm, fiber diameter: 6.5 μm) was added and kneaded. Next, 6.81% by mass of the above SBR binder aqueous dispersion having a solid content of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0112] (Example 9) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) as an electrode active material and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) 2:8 mixture 90.19% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.98% by mass as a conductive additive, 83.3% by mass of the above CMC aqueous solution having a solid content concentration of 1.5% by mass as a thickener (amount to be 1.25% by mass as solids) was placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.25% by mass of PVA fiber (specific gravity: 1.28, fiber length: 2 mm, fiber diameter: 5 μm) was added and kneaded. Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0113] (Example 10) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) as an electrode active material and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) 2:8 mixture 90.61% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.98% by mass as a conductive additive, 56.0% by mass of the above CMC aqueous solution having a solid content concentration of 1.5% by mass as a thickener (amount to be 0.84% ​​by mass as solids) was placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.25% by mass of PVA fiber (specific gravity: 1.28, fiber length: 2 mm, fiber diameter: 5 μm) was added and kneaded. Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0114] (Example 11) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) as an electrode active material and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) 2:8 mixture 91.02% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.98% by mass as a conductive additive, CMC solid content concentration 1.5% by mass of the above CMC aqueous solution 28.0% by mass (amount to 0.42% by mass as solids) as a thickener was put into a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.25% by mass of PVA fiber (specific gravity: 1.28, fiber length: 2 mm, fiber diameter: 5 μm) was added and kneaded. Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0115] (Comparative Example 1) 89.84% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle diameter: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle diameter: 13 μm) as an electrode active material, 4.99% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, 111.3% by mass of an aqueous solution of the above CMC having a solid content of 1.5% by mass as a thickener (amount equivalent to 1.67% by mass as a solid content), and 0.18% by mass of PP fiber (specific gravity: 0.91, fiber length: 3 mm, fiber diameter: 7 μm) were added to a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Next, 6.85% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0116] (Comparative Example 2) 89.68% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle diameter: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle diameter: 13 μm) as an electrode active material, 4.98% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, 111.3% by mass of an aqueous solution of the above CMC having a solid content of 1.5% by mass as a thickener (amount equivalent to 1.67% by mass as a solid content), and 0.36% by mass of PP fiber (specific gravity: 0.91, fiber length: 3 mm, fiber diameter: 7 μm) were added to a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Next, 6.85% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0117] (Comparative Example 3) 89.56% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle diameter: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle diameter: 13 μm) as an electrode active material, 4.98% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, 110.7% by mass of an aqueous solution of the above CMC having a solid content of 1.5% by mass as a thickener (amount equivalent to 1.66% by mass as a solid content), and 0.49% by mass of glass fiber (specific gravity: 2.50, fiber length: 3 mm, fiber diameter: 6.5 μm) were placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0118] (Comparative Example 4) 89.13% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle diameter: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle diameter: 13 μm) as an electrode active material, 4.95% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, 110.0% by mass of an aqueous solution of the above CMC having a solid content of 1.5% by mass as a thickener (amount equivalent to 1.65% by mass as a solid content), and 0.98% by mass of glass fiber (specific gravity: 2.50, fiber length: 3 mm, fiber diameter: 6.5 μm) were added to a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Next, 6.81% by mass of the above SBR binder aqueous dispersion having a solid content of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0119] (Comparative Example 5) 89.47% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle diameter: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle diameter: 13 μm) as an electrode active material, 4.97% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, 110.7% by mass of an aqueous solution of the above CMC having a solid content of 1.5% by mass as a thickener (amount equivalent to 1.66% by mass as a solid content), and 0.59% by mass of pulp fiber (LBKP, specific gravity: 1.50, fiber length: 2 mm, fiber diameter: 20 μm) were added to a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0120] (Comparative Example 6) 89.33% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle diameter: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle diameter: 13 μm) as an electrode active material, 4.96% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, 110.7% by mass of an aqueous solution of the above CMC having a solid content of 1.5% by mass as a thickener (amount equivalent to 1.66% by mass as a solid content), and 0.75% by mass of PVA fiber (specific gravity: 1.28, fiber length: 2 mm, fiber diameter: 5 μm) were added to a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Next, 6.84% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0121] (Comparative Example 7) 90% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) as an electrode active material, 5% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, and 111.3% by mass of the above CMC aqueous solution having a solids concentration of 1.5% by mass as a thickener (amount equivalent to 1.67% by mass as solids) were placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 6.88% by mass of the above SBR binder aqueous dispersion having a solids concentration of 48.4% by mass was added and kneaded to obtain a composition for a nonaqueous electrolyte battery electrode.

[0122] (Comparative Example 8) SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) as an electrode active material and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) 2:8 mixture 89.74% by mass, carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) 4.99% by mass as a conductive additive, 111.3% by mass of the above CMC aqueous solution having a solid content concentration of 1.5% by mass as a thickener (amount to 1.67% by mass as solids) was placed in a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Then, 0.29% by mass of pulp fiber (LBKP, specific gravity: 1.50, fiber length: 2 mm, fiber diameter: 25 μm) was added and kneaded. Next, 6.85% by mass of the above SBR binder aqueous dispersion having a solid content concentration of 48.4% by mass was added and kneaded to obtain a composition for a non-aqueous electrolyte battery electrode.

[0123] (Comparative Example 9) 89.74% by mass of a 2:8 mixture of SiOx (BSO-1, manufactured by BTR, specific gravity: 2.2, average particle size: 5 μm) and artificial graphite (G49, manufactured by Zichen, specific gravity: 2.2, average particle size: 13 μm) as an electrode active material, 4.99% by mass of carbon black (SuperP, manufactured by MTI Corporation, specific gravity: 1.8) as a conductive additive, and 111.3% by mass of an aqueous solution of the above CMC having a solids concentration of 1.5% by mass as a thickener (amount equivalent to 1.67% by mass as a solids content) were charged into a dedicated container and kneaded using a planetary mixer (ARE-310, manufactured by Thinky Corporation). Next, 0.29% by mass of beaten pulp fiber (LBKP, beating degree: CSF 140 ml, specific gravity: 1.50, average fiber length: 0.3 mm, average fiber diameter: 18 μm) was added and kneaded, followed by 6.85% by mass of the above SBR binder aqueous dispersion with a solid content concentration of 48.4% by mass, and kneading to obtain a composition for a nonaqueous electrolyte battery electrode.

[0124] [Fabrication of Electrode] The nonaqueous electrolyte battery electrode compositions obtained in Examples 1 to 11 and Comparative Examples 1 to 9 were coated onto a copper foil current collector (thickness: 15 μm) using a coating machine (manufactured by Imoto Machinery Co., Ltd.). The coating was dried in a hot air dryer at 80°C for 30 minutes to form an electrode active material layer on the current collector. The active material layer was then rolled using a roll press (manufactured by Hosen Co., Ltd.). After that, a lithium ion secondary battery negative electrode (φ14 mm) was punched out, and secondary drying was performed at 120°C for 3 hours under reduced pressure to fabricate a lithium ion secondary battery negative electrode.

[0125] <Evaluation of the properties of the electrode active material layer> [Surface smoothness] An arbitrary location (measurement range: 24 mm × 18 mm) of the electrode after rolling treatment was photographed using a one-shot 3D shape measuring instrument (Keyence, VR-3000). The surface roughness (Sa) (unit: μm) of the electrode surface was calculated using an analysis tool built into the instrument. The surface roughness (Sa) of the electrode surface was calculated over a predetermined calculation measurement range: 20 mm × 15 mm.

[0126] [Presence or absence of bubbles in electrode active material layer] Five arbitrary locations on the electrode (measurement range: 79 mm × 59 mm) were observed using a microscope. The number of bubbles in the measurement field of view was measured, and the average value for the five locations was calculated. If the average number of bubbles in the five locations was 5 or more, it was judged as "bubbles present," and if it was less than 5, it was judged as "no bubbles present." Note that if there were aggregates or streaks in the electrode active material layer, measurement was difficult and therefore not possible.

[0127] [Presence or Absence of Bubbles in Electrode Composition] The presence or absence of bubbles in the electrode composition obtained after kneading was visually confirmed to determine the presence or absence of bubbles.

[0128] [Fiber length and fiber length variation after kneading] Fibers were filtered and extracted from the kneaded nonaqueous electrolyte battery electrode composition, and 50 fibers were randomly selected and their lengths were measured using a microscope (manufactured by Keyence Corporation). The CV value was calculated using the average length and standard deviation of the 50 selected fibers using the following formula.

[0129] <Electrode Evaluation> [Electrode Weight Unevenness] Fifteen randomly selected locations (φ14 mm) were punched out from the rolled electrode. The weights of the 15 electrodes were measured, and the CV value was calculated from the average weight and standard deviation using the following formula.

[0130] [Fabrication of Lithium-Ion Secondary Battery] The negative electrode for a lithium-ion secondary battery obtained according to the above procedure was transferred to a glove box (manufactured by Miwa Seisakusho Co., Ltd.) under an argon gas atmosphere. Metallic lithium foil (thickness 0.2 mm, φ15 mm) was used as the positive electrode, glass nonwoven fabric (TGP-020A) was used as the separator, and lithium hexafluorophosphate (LiPF ) in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) was used as the electrolyte. ６ EC / EMC / DMC=1 / 1 / 1 volume %, vinylene carbonate (VC)=1 mass % was used for injection. A coin battery (2032 type) which is a lithium ion secondary battery having a similar configuration was fabricated.

[0131] <Battery Performance Evaluation> [Discharge Capacity Retention Rate] A rate test was performed on the coin batteries prepared according to the above procedure using a commercially available charge / discharge tester (TOSCAT3100, manufactured by Toyo Systems). The resistance value when a current of 0.5 mA was applied for 3 seconds before the initial charge was defined as the DC resistance. Charging was performed at a constant current of 0.2 C to 5 mV, followed by constant voltage charging at 5 mV to a current of 0.02 mA relative to the lithium potential. Discharging was performed at a constant current of 0.2 C to 1.5 V relative to the lithium potential. The coin batteries were placed in a thermostatic chamber at 25°C and subjected to one initial charge / discharge cycle under the above conditions. After aging, five charge / discharge cycles were performed. In the five-cycle charge / discharge evaluation after aging, the discharge capacity retention rate was defined as the percentage ratio of the discharge capacity at the fifth cycle to the discharge capacity at the first cycle.

[0132] Table 1 shows the evaluation results of the electrode active material layers obtained in the examples and comparative examples, and the electrodes and batteries obtained from the electrode active material layers.

[0133] In Comparative Examples 1 and 2, only electrode compositions containing numerous aggregates due to fiber aggregation were obtained. Therefore, in Comparative Examples 1 and 2, it was difficult to measure the number of bubbles in the electrode composition, the fiber length in the electrode active material layer, and the number of bubbles. Furthermore, electrodes worthy of battery evaluation could not be produced. In Comparative Examples 3 and 4, it was difficult to measure the number of bubbles in the electrode active material layer due to uneven viscosity of the electrode composition caused by fiber length variations due to fiber breakage, resulting in streaking during coating. Furthermore, it was impossible to produce electrodes worthy of battery evaluation due to uneven fiber length and streaking during coating caused by fiber breakage.

[0134] In Comparative Examples 8 and 9, only electrode compositions containing numerous aggregates due to fiber aggregation were obtained, making it difficult to measure the fiber length in the electrode active material layer.

[0135]

Claims

1. An electrode active material layer comprising fibers, a binder, and an electrode active material, wherein the fibers have a fiber diameter of 1 to 15 μm, the fiber length coefficient of variation CV of the fibers is 0 to 0.30, and the surface roughness Sa of the electrode active material layer is 0 to 10 μm.

2. The electrode active material layer according to claim 1, wherein the fiber length is 0.1 to 5 mm.

3. The electrode active material layer according to claim 1, wherein the fiber content in the electrode active material layer is 0.008 to 1.2% by volume.

4. The electrode active material layer according to claim 1, wherein the binder content is more than 0.1 mass % based on the total mass of the electrode active material layer.

5. The electrode active material layer according to claim 1, wherein the ratio (B / A) of the fiber length B of the fibers to the average particle diameter A of the electrode active material in the electrode active material layer is 3 to 1,700.

6. The electrode active material layer according to claim 1, wherein the fibers are selected from the group consisting of synthetic fibers, semi-synthetic fibers, recycled fibers, and inorganic fibers.

7. The electrode active material layer according to claim 1, wherein the fibers are straight fibers.

8. The electrode active material layer according to claim 1, wherein the fibers do not include pulp fibers.

9. The electrode active material layer according to claim 1, which is for a negative electrode.

10. The electrode active material layer according to claim 1, wherein the electrode active material comprises a silicon-based active material.

11. An electrode comprising the electrode active material layer according to any one of claims 1 to 10 and a current collector.

12. The electrode according to claim 11, wherein the coefficient of variation CV of the electrode weight is 0 to 0.

03.

13. A method for producing an electrode active material layer according to any one of claims 1 to 10, comprising: (1) a step of preparing an electrode composition containing fibers, a binder, and an electrode active material; and (2) a step of applying the electrode composition to a current collector and drying it to form an electrode active material layer.

14. A method for producing an electrode active material layer according to claim 13, wherein (1) in the step of preparing an electrode composition, among the components contained in the electrode composition, the binder is added last, and the fibers are added and kneaded immediately before the addition of the binder.

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