Carbonaceous material dispersion for all-solid lithium ion secondary battery and electrode slurry for all-solid lithium ion secondary battery

Abstract

A carbonaceous material dispersion, which is a carbonaceous material dispersion for a full solid lithium ion secondary battery formed by dispersing a carbonaceous material and a dispersant in a dispersion medium, characterized in that the dispersion medium contains at least an ester-based solvent, the dispersant contains at least polyvinyl butyral, the blending amount of the carbonaceous material in the dispersion is 10 to 25 mass% relative to the total mass of the dispersion, in addition, the blending amount of the dispersant relative to the mass of the carbonaceous material is 5 mass% to 40 mass%, and the viscosity of the carbonaceous material dispersion at 25°C is 500 mPa·s or less. When used as an electrically conductive aid for a full solid lithium ion secondary battery, deterioration of the solid electrolyte can be suppressed, the carbonaceous material is highly concentrated and uniformly dispersed, and when mixed with an electrode active material, the solid components can be dispersed at low viscosity and high concentration, which contributes to good electrical conductivity of the secondary battery.

Description

Technical Field

[0001] This invention relates to a carbonaceous material dispersion for all-solid-state lithium-ion secondary batteries and an electrode slurry for all-solid-state lithium-ion secondary batteries. More specifically, this invention relates to a carbonaceous material dispersion for all-solid-state lithium-ion secondary batteries that, when used as a conductive additive in all-solid-state lithium-ion secondary batteries, can suppress the deterioration of the solid electrolyte, exhibits a high concentration and uniform dispersion of the carbonaceous material, and, when mixed with electrode active materials, achieves low viscosity and high concentration dispersion of the solid components; and an electrode slurry for all-solid-state lithium-ion secondary batteries using the carbonaceous material dispersion for all-solid-state lithium-ion secondary batteries. Background Technology

[0002] In recent years, high-capacity, high-output lithium-ion secondary batteries have been widely used in many fields, including portable personal computers, smartphones, mobile phones and other electronic devices, as well as electric vehicles and hybrid vehicles.

[0003] In lithium-ion secondary batteries, electrolytes that use flammable organic solvents or similar substances in the dilution solvent have been used as the medium for ion movement. In batteries that use such electrolytes, problems such as electrolyte leakage, fire, and explosion may occur.

[0004] To address this issue, an all-solid-state lithium-ion secondary battery is being developed, using a solid electrolyte instead of a liquid electrolyte, and with all other components composed entirely of solids. The solid electrolyte and the extremely low charge-movement resistance of lithium ions in an all-solid-state lithium-ion secondary battery reduce the battery's internal resistance. Furthermore, because the electrolyte is solid, the risk of fire is reduced, leakage is prevented, and corrosion-induced performance degradation is less likely.

[0005] An all-solid-state lithium-ion secondary battery has: a positive electrode layer and a negative electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the electrolyte is composed of a solid.

[0006] As a solid electrolyte layer, when only electrode active materials are used to form the electrode layer through powder molding, the electrolyte is solid, making it difficult for the electrolyte to penetrate into the interior of the electrode layer. This reduces the interface between the electrode active materials and the electrolyte, leading to a decrease in battery performance. Furthermore, because the electrode layer is made of solid material, it lacks flexibility and processability, resulting in poor operability.

[0007] To address this problem, the following solution is proposed: forming an electrode layer using a slurry prepared by dispersing electrode active material, solid electrolyte material, and binder in a solvent.

[0008] Furthermore, conventional lithium-ion secondary batteries have used electrode slurries in the following ways: electrode slurries formed by dispersing active materials and conductive additives in a polymer solution in which polyvinylidene fluoride (PVDF) is dissolved as a binder in N-methyl-2-pyrrolidone (NMP) solvent; and electrode slurries formed by dispersing active materials and conductive additives in an aqueous solution in which styrene-butadiene rubber (SBR) is emulsified as a binder in an aqueous solvent, and then adding thickeners such as carboxymethyl cellulose (CMC). However, in all-solid-state lithium-ion secondary batteries, if the solid electrolyte is exposed to a highly polar solvent, the ionic conductivity decreases, and sufficient battery performance cannot be obtained. Therefore, NMP and water cannot be used as solvents for the electrode slurries used in electrode fabrication.

[0009] For example, in Patent Document 1, a slurry for forming a positive electrode compound layer in an all-solid-state lithium-ion secondary battery, comprising a positive electrode active material, a solid electrolyte material, a binder, a conductive agent, and a solvent, is proposed. The following combination is used: the binder is a styrene-containing binder resin such as styrene-butadiene rubber (SBR) or styrene-ethylene-butene-styrene block copolymer (SEBS); the conductive agent is carbon fiber; and the solvent is a non-polar solvent such as heptane, toluene, or xylene. Furthermore, the following is shown: This results in a positive electrode current collector that improves conductivity and enables the formation of a flexible and strong positive electrode compound layer.

[0010] However, the following was also reported: when carbon black is used instead of expensive carbon fiber as a conductive agent, for example, if a styrene-containing binder resin is used as the adhesive, the resistance increases compared to a positive electrode binder layer with only silicone polymers added.

[0011] Furthermore, in Patent Document 2, a slurry for forming a negative electrode layer of an all-solid-state lithium-ion secondary battery, comprising a negative electrode active material, a solid electrolyte material, a binder, a conductive agent, and a solvent, is proposed. This slurry comprises the following components: a negative electrode active material containing Si; a solid electrolyte containing a sulfide solid electrolyte; a conductive material composed of a fibrous carbonaceous material having a six-membered carbon ring; a binder composed of a polymer compound having an aromatic ring, such as SBR or SEBS; and at least one solvent selected from the group consisting of 1,3,5-trimethylbenzene, isopropylbenzene, and methyl phenyl ether. In addition, it is disclosed that the binder may contain polymer compounds other than those having aromatic rings, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), butene rubber (BR), polyvinyl butyral (PVB), and acrylic resin, within a range of 5% by mass or less. Furthermore, the following is shown: With this combination, when using a negative electrode active material containing Si, during repeated charge-discharge cycles of the negative electrode compound, the portion of poor contact between the conductive material and the negative electrode active material caused by repeated charge-discharge is suppressed, and the increase in internal resistance can be suppressed.

[0012] However, the following was also reported: In this case, considering the dispersibility when using carbon fibers with six-membered carbon rings as conductive agents, even when using adhesives composed of aromatic ring polymers such as SBR and SEBS, and solvents with aromatic rings such as 1,3,5-trimethylbenzene, isopropylbenzene, and methyl phenyl ether, and using flake-like carbonaceous materials as conductive agents, the increase in internal resistance could not be suppressed, even when both the adhesive and solvent were made of aromatic ring materials.

[0013] In addition, Patent Document 3 proposes the following scheme: for example, using polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl acetate, polymethyl methacrylate, polyethylene, etc. as adhesive materials, and using aromatic hydrocarbons such as toluene, xylene, decahydronaphthalene, tetrahydronaphthalene, hexane, pentane, ethylhexane, heptane, decane, cyclohexane, etc., and unsaturated hydrocarbons such as hexene, heptene, cyclohexene, etc. as solvents, and forming a positive electrode binder layer by wet mechanical chemical treatment.

[0014] Furthermore, Patent Document 4 discloses the following: In the preparation of slurry for all-solid-state lithium-ion secondary batteries, conventionally, butyl butyrate, heptane, etc., are used as low-polarity solvents. However, due to insufficient affinity with PVDF, the molecular chains of PVDF cannot be fully extended in the solvent, which cannot sufficiently increase the viscosity of the electrode slurry, and the electrode slurry cannot be uniformly coated, resulting in non-uniformity within the electrode and a decrease in battery performance. To solve these problems, acrylic copolymers with a specified structure are used as binders, and solvents such as butyl ether (butyl butyrate, butyl propionate, butyl valerate) and alkane solvents (hexane, cyclohexane, heptane, cycloheptane, octane, cyclooctane) are used.

[0015] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2010-262764 Patent Document 2: Japanese Patent Application Publication No. 2019-125481 Patent Document 3: Japanese Patent Application Publication No. 2013-222501 Patent Document 4: Japanese Patent Application Publication No. 2020-21581 Summary of the Invention The technical problem that the invention aims to solve However, when using the combination of solvent and binder in the prior art as an electrode slurry for all-solid-state lithium-ion secondary batteries, or as a carbonaceous material dispersion formed by dispersing the carbonaceous material used to prepare the electrode slurry for all-solid-state lithium-ion secondary batteries in a solvent, the problem of solid electrolyte degradation occurs. In addition, it is difficult to disperse the carbonaceous material at a high concentration and uniformly in the slurry or dispersion. When mixed with the electrode active material, it is not possible to disperse the solid components at a low viscosity and high concentration, and it is not possible to sufficiently improve the charge-discharge characteristics, cycle characteristics, electrode conductivity, and other characteristics of the obtained all-solid-state lithium-ion secondary battery, especially its conductivity.

[0016] Therefore, the technical problem of the present invention is to provide a carbonaceous material dispersion for an all-solid-state lithium-ion secondary battery and an electrode slurry for an all-solid-state lithium-ion secondary battery that can solve the above-mentioned technical problems. Furthermore, the technical problem of the present invention is to provide a carbonaceous material dispersion for an all-solid-state lithium-ion secondary battery that, when used as a conductive additive for an all-solid-state lithium-ion secondary battery, can suppress the deterioration of the solid electrolyte, exhibits high concentration and uniform dispersion of the carbonaceous material, and demonstrates excellent conductivity, as well as an electrode slurry for an all-solid-state lithium-ion secondary battery using the carbonaceous material dispersion for an all-solid-state lithium-ion secondary battery.

[0017] Solutions for solving technical problems In order to solve the above-mentioned technical problems, the inventors of this invention, through dedicated exploration and research, discovered the following and realized the present invention: As a carbonaceous material dispersion for all-solid-state lithium-ion secondary batteries, a dispersant containing at least polyvinyl butyral is added in a specified proportion to the carbonaceous material, especially carbon black, as a dispersant, and an ester solvent is used as a solvent. This can suppress the deterioration of the solid electrolyte, and the carbonaceous material is highly concentrated and uniformly dispersed, thus exhibiting excellent conductivity.

[0018] In other words, the present invention, which solves the above-mentioned technical problems, is a carbonaceous material dispersion. This carbonaceous material dispersion is an all-solid-state carbonaceous material dispersion for lithium-ion secondary batteries formed by dispersing carbonaceous material and a dispersant in a dispersion medium. Its characteristics are that the dispersion medium contains at least an ester solvent, the dispersant contains at least polyvinyl butyral, the amount of carbonaceous material in the dispersion is 10-25% by mass relative to the total mass of the dispersion, and the amount of dispersant is 5-40% by mass relative to the mass of the carbonaceous material. The viscosity of the carbonaceous material dispersion at 25°C is 500 mPa. Below s.

[0019] In one embodiment of the carbonaceous material dispersion involved in the present invention, a carbonaceous material dispersion is shown, characterized in that the amount of dispersant is 5% by mass or more and less than 20% by mass relative to the mass of the carbonaceous material.

[0020] In another embodiment of the carbonaceous material dispersion involved in the present invention, a carbonaceous material dispersion is shown, characterized in that the amount of dispersant is 20% to 40% by mass relative to the mass of the carbonaceous material.

[0021] In one embodiment of the carbonaceous material dispersion according to the present invention, a carbonaceous material dispersion is shown, characterized in that the viscoelasticity of the carbonaceous material dispersion at 25°C has a shear rate of 10–1000 s. -1 It has a minimum value within the range.

[0022] In one embodiment of the carbonaceous material dispersion of the present invention, a carbonaceous material dispersion is shown, wherein the dispersion medium contains 10% by mass or more of an ester solvent in the total amount of the dispersion medium.

[0023] In one embodiment of the carbonaceous material dispersion according to the present invention, a carbonaceous material dispersion is shown, wherein the ester solvent is at least one selected from the group consisting of propyl acetate, butyl butyrate, butyl valerate, butyl hexanoate, pentyl butyrate, pentyl valerate, pentyl hexanoate, hexyl butyrate, hexyl valerate, and hexyl hexanoate.

[0024] In one embodiment of the carbonaceous material dispersion involved in the present invention, a carbonaceous material dispersion is shown, wherein the ester solvent is butyl butyrate.

[0025] In one embodiment of the carbonaceous material dispersion involved in the present invention, a carbonaceous material dispersion is shown, wherein the carbonaceous material is carbon black.

[0026] In one embodiment of the carbonaceous material dispersion involved in the present invention, a carbonaceous material dispersion is further shown, wherein the carbon black is acetylene black.

[0027] In one embodiment of the carbonaceous material dispersions involved in this invention, a carbonaceous material dispersion is shown, which further contains a pH adjuster.

[0028] Furthermore, the present invention, which solves the above-mentioned technical problems, is also an all-solid-state electrode slurry for lithium-ion secondary batteries. This all-solid-state electrode slurry for lithium-ion secondary batteries incorporates carbonaceous materials, dispersants, binder resins, and either positive or negative electrode active materials in a dispersion medium. Its characteristic is that… The dispersion medium contains at least an ester solvent, the dispersant contains at least polyvinyl butyral, and the amount of dispersant in the solids of the slurry is 5 to 40% by mass relative to the mass of the carbonaceous material.

[0029] In one embodiment of the all-solid-state lithium-ion secondary battery electrode slurry involved in the present invention, a carbonaceous material dispersion is shown, characterized in that the amount of dispersant is 5% by mass or more and less than 20% by mass relative to the mass of the carbonaceous material.

[0030] In one embodiment of the all-solid-state electrode slurry for lithium-ion secondary batteries according to the present invention, an all-solid-state electrode slurry for lithium-ion secondary batteries is shown. When the solid content concentration of the slurry is 65-75% by mass, the viscosity of the slurry at 25°C is 500-5000 mPa. s.

[0031] In one embodiment of the all-solid-state lithium-ion secondary battery electrode slurry involved in the present invention, a carbonaceous material dispersion is shown, characterized in that the amount of dispersant is 20 to 40 by mass relative to the mass of the carbonaceous material.

[0032] In one embodiment of the all-solid-state electrode slurry for lithium-ion secondary batteries according to the present invention, an all-solid-state electrode slurry for lithium-ion secondary batteries is shown. When the solid content concentration of the slurry is 77-87% by mass, the viscosity of the slurry at 25°C is 1000-10000 mPa. s.

[0033] Invention Effects According to the present invention, since a carbonaceous material dispersion that can suppress the deterioration of the solid electrolyte when used as a conductive additive for an all-solid lithium-ion secondary battery, exhibits excellent conductivity with high concentration and uniform dispersion of carbonaceous material, and an electrode slurry for an all-solid lithium-ion secondary battery using the carbonaceous material dispersion, it is possible to manufacture a secondary battery with excellent and stable performance in terms of charge-discharge characteristics, cycle characteristics, electrode conductivity, etc. Detailed Implementation

[0034] The present invention will now be described in detail based on its embodiments.

[0035] <Carbonized material dispersions> The first aspect of the present invention relates to a carbonaceous material dispersion for an all-solid-state lithium-ion secondary battery, which is formed by dispersing carbonaceous material and a dispersant in a dispersion medium. The dispersion medium is characterized by containing at least an ester solvent, the dispersant containing at least polyvinyl butyral, the amount of carbonaceous material in the dispersion being 10-25% by mass relative to the total mass of the dispersion, and the amount of dispersant being 5-40% by mass relative to the mass of the carbonaceous material. The viscosity of the carbonaceous material dispersion at 25°C is 500 mPa. Below s.

[0036] First, the components constituting the carbonaceous material dispersion for all-solid-state lithium-ion secondary batteries involved in the first aspect will be explained.

[0037] (Carbon-based materials) The carbonaceous material used need only be conductive and in granular form; there are no particular limitations. However, examples include carbon black (CB), carbon nanotubes (CNT), carbon nanofibers (CNF), graphene, fullerene, natural graphite, artificial graphite, non-graphitizable carbon, coke, and graphite. These materials can be used alone or in combination. CB is particularly preferred. Furthermore, examples of CB include furnace black, Ketjen black, channel black, acetylene black, and thermally cracked black; any one of these can be used. For example, acetylene black is preferred because it inherently has a low metal content during manufacturing.

[0038] In addition, carbon black that has undergone oxidation treatment or graphitization treatment can also be used. The oxidation treatment of carbon black involves high-temperature treatment of carbon black in air or secondary treatment using nitric acid, nitrogen dioxide, ozone, etc., such as directly introducing (covalently bonding) oxygen-containing polar functional groups such as phenol groups, quinone groups, carboxyl groups, and carbonyl groups onto the surface of carbon black to improve its dispersibility.

[0039] Additionally, depending on the requirements, carbonaceous materials may be subjected to dry magnetic separation to remove metallic impurities mixed in before the manufacture of the carbonaceous material dispersion, and / or, after the carbonaceous materials are dispersed in an ester solvent to prepare a dispersion, they may be subjected to wet magnetic separation.

[0040] In this specification, the "powdered" form of the carbonaceous material used as a raw material dispersed in the dispersion medium is simply a form that can be dispersed in the ester solvents described below, and is not particularly limited thereto. Furthermore, the shape is not particularly limited and is not limited to approximately spherical; it may include elliptical, flake-like, needle-like, short fibrous, or amorphous forms.

[0041] Furthermore, regarding carbon black, as explained on the website of the Carbon Black Association, the smallest indestructible unit of carbon black is an aggregate (primary aggregate), a part of which (domain) is usually called a particle. This particle is considered to be the smallest unit defined in nanomaterials, but it is also only a part of the aggregate. Aggregates form agglomerates (secondary aggregates) through physical forces such as intermolecular forces. Moreover, to prevent scattering and improve handling, carbon black products are mostly transported and sold in the form of processed granules such as droplets after compression and granulation.

[0042] For example, it may include a primary aggregate having an average particle size of about 10 to 100 nm, a secondary aggregate having an average particle size of about 0.1 to 100 μm formed by agglomeration of the primary aggregate, or, further considering operability, processed particles having an average particle size of about 500 to 5000 μm formed by compression or granulation.

[0043] Furthermore, from the perspective of carbon black conductivity, conductive carbon microparticles are preferably aggregates with chain-like or cluster-like structures formed by primary particles being interconnected to a certain extent. The interconnection of these primary particles within the aggregate, also known as the structure, can be assessed by measuring particle size distribution (dynamic light scattering or laser diffraction / light scattering) or observing with an electron microscope (either scanning or transmission electron microscopy). Such a structure can efficiently form conductive pathways between electrode active material particles. Therefore, it is possible to impart excellent conductivity to the electrode active material layer with a smaller amount of material used.

[0044] (Dispersion medium) The dispersion medium constituting the all-solid-state carbonaceous material dispersion for lithium-ion secondary batteries according to the first aspect of the present invention contains at least an ester solvent. The ester solvent is used because, as described below, the dispersant in the all-solid-state carbonaceous material dispersion for lithium-ion secondary batteries according to the first aspect of the present invention is primarily polyvinyl butyral, and the ester solvent exhibits good solubility in this polyvinyl butyral, is hydrophobic, and has low reactivity with the solid electrolyte.

[0045] Furthermore, for the dispersion medium involved in this invention, any dispersion medium that exhibits good solubility in the aforementioned polyvinyl butyral as a dispersant is acceptable. There is no particular limitation on the proportion of ester solvent in the dispersion medium; however, to obtain a good dispersion, it is preferable, for example, to contain at least 10% by mass of the total dispersion medium, and more preferably at least 20% by mass of the total dispersion medium. Of course, it is a preferred embodiment where the entire dispersion medium (100% by mass) is composed of ester solvent.

[0046] Furthermore, as an ester solvent, there are no particular limitations on the type of ester solvent used, as long as it exhibits good solubility in polyvinyl butyral and low reactivity with solid electrolytes. For example, an ester solvent containing R... 1 -COOR 2 (R in the formula) 1 R is a C1-C8 hydrocarbon group. 2 (A carboxylic acid ester represented by an alkyl group of C2 to C8.)

[0047] Specifically, for example, the following solvents can be used alone or in combination of two or more of the following solvents: propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, hexyl propionate, heptyl propionate, octyl propionate, ethyl butyrate, propyl butyrate, butyl butyrate, pentyl butyrate, hexyl butyrate, heptyl butyrate, octyl butyrate, ethyl valerate, propyl valerate, butyl valerate, pentyl valerate, heptyl valerate, octyl valerate, ethyl heptate, propyl heptate, butyl heptate, pentyl heptate, heptyl heptate, octyl heptate, ethyl heptate, propyl heptate, butyl heptate, pentyl heptate, heptyl heptate, octyl heptate, ethyl octate, propyl octate, butyl octate, pentyl octate, heptyl octate, octyl octate, etc.

[0048] Among them, propyl acetate, butyl butyrate, butyl valerate, butyl hexanoate, pentyl butyrate, pentyl valerate, pentyl hexanoate, hexyl butyrate, hexyl valerate, and hexyl hexanoate are preferred, with butyl butyrate being particularly preferred.

[0049] Furthermore, regarding the dispersion medium involved in this invention, there are no particular limitations as long as it does not significantly impair the solubility of the resin component of the ester solvent or its dispersibility with carbonaceous materials. However, non-polar solvents are preferred. Using a non-polar solvent can prevent the decrease in the ionic conductivity of the solid electrolyte that occurs when using polar solvents such as water or NMP.

[0050] As the dispersion medium involved in this invention, there is no particular limitation on nonpolar solvents that can be used with the aforementioned ester solvents. However, specifically, it may include, for example, non-aqueous linear and / or branched or cyclic alkanes with 4 to 30 carbon atoms, such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, methyl ester cyclohexane, etc.; linear and / or branched and / or cyclic halogenated alkanes with 1 to 30 carbon atoms, such as dichloromethane, chloroform, tetrachloromethane, dichloroethane, trichloroethane, tetrachloroethane, chlorocyclohexane, etc.; and aromatic compounds with 6 to 22 carbon atoms, such as benzene and toluene. Xylene, mesitylene, etc.; hydrogenated aromatic compounds with 10 to 22 carbon atoms, such as tetrahydronaphthalene, cis-decahydronaphthalene, and trans-decahydronaphthalene; halogenated aromatic compounds with 6 to 22 carbon atoms, such as chlorobenzene, fluorobenzene, dichlorobenzene or difluorobenzene, trichlorobenzene or trifluorobenzene, chloronaphthalene or fluoronaphthalene, etc.; straight-chain and / or branched and / or cyclic ethers, such as diethyl ether, dipropyl ether, tert-butyl methyl ether, tert-amyl methyl ether, tert-amyl ethyl ether, dimethoxyethane, diethoxyethane, methoxybenzene, methylthiobenzene, ethoxybenzene, petroleum ether, etc.; straight-chain and / or branched and / or cyclic ketones, such as acetone, trichloroacetone, butanone, pentanone, etc. Ketones, heptanone, octanone, nonanone, cyclopentanone, cyclohexanone, acetophenone, acetylacetone, etc.; straight-chain and / or branched and / or cyclic nitroalkanes, such as nitromethane, nitrobenzene, nitrocyclohexane, etc.; nitroaromatic compounds with 6 to 22 carbon atoms, such as nitrobenzene, etc.; straight-chain and / or branched and / or cyclic amines, preferably tert-butylamine, diaminoethane, diethylamine, triethylamine, tributylamine, pyrrolidine, piperidine, morpholine, N-methylaniline, and N,N-dimethylaniline, etc.; hexamethyldisilane, diphenyldimethylsilane, chlorophenyltrimethylsilane, phenyltrimethylsilane, phenethyltri(trimethylsiloxy)silane, phenyltri(trimethylsiloxy)silane, etc. Silicone oils including silanes, polydimethylsiloxanes, tetraphenyltetramethyltrisiloxanes, poly(3,3,3-trifluoropropylsiloxane), 3,5,7-triphenylmethylpentanesiloxanes, 3,5-diphenyloctamethyltetrasiloxanes, 1,1,5,5-tetraphenyl-1, 3,3,5-tetramethyl-trisiloxanes, and hexamethylcyclotrisiloxanes; fluorinated solvents, such as hydrofluoroethers, dichlorofluoromethane, 1,1,1,2-tetrafluoroethane, pentafluoroethane, difluoromethane, trifluoromethane, 1,1,1,2,3,3,3-heptafluoropropane, 1,1-difluoroethane, 1,1,1,3,3,3-hexafluoropropane, octafluoropropane, etc.; or mixtures of the above non-polar solvents in any proportion.

[0051] As non-polar solvents, cyclohexane, n-hexane, benzene, toluene, xylene, etc. are particularly preferred.

[0052] The dispersion medium involved in this invention is preferably composed only of the above-mentioned ester solvents, or a mixture of ester solvents and non-polar solvents, wherein the content of the ester solvent in the mixture is 10% by mass or more and less than 100% by mass, and the content of the non-polar solvent is 0% by mass or more and less than 90% by mass (totaling 100% by mass).

[0053] (Dispersant) The dispersant in the all-solid lithium-ion secondary battery carbonaceous material dispersion constituting the first aspect of the present invention contains at least polyvinyl butyral.

[0054] In one embodiment, polyvinyl butyral is preferably the main component of the dispersant, particularly preferably 80% by mass or more, and even more preferably all of the dispersant, i.e., 100% by mass, is polyvinyl butyral. In the carbonaceous material dispersion for all-solid-state lithium-ion secondary batteries, by using polyvinyl butyral as a dispersant in combination with the aforementioned ester solvent as the dispersion medium, good dispersibility of the carbonaceous material in the carbonaceous material dispersion can be obtained, achieving low viscosity. Furthermore, as described below, in the preparation of the electrode slurry for all-solid-state lithium-ion secondary batteries, when mixed with the electrode active material, the solid components can be dispersed with low viscosity and high concentration. Moreover, it moderately increases the viscosity of the slurry, reduces the settling velocity of the electrode active material, carbonaceous material, and other materials constituting the electrode, and allows the slurry to be uniformly coated on the current collector. Furthermore, it enables adhesion between active materials, between active materials and conductive additives, and between conductive additives and other materials constituting the electrode with appropriate strength, adhesion, and conductivity.

[0055] Polyvinyl butyral is not particularly limited, but if the hydroxyl content is low, specifically, for example, the hydroxyl content in the polymer is 5% by mass or more and 25% by mass or less, more preferably 10% by mass or more and 20% by mass or less, and even more preferably 12.5% ​​by mass or more and 17.5% by mass or less, then the solubility relative to the aforementioned ester solvents used as dispersion media is good, and therefore preferred. Furthermore, although not particularly limited, it is preferred that the acetic acid group content of polyvinyl butyral is about 1% by mass. Regarding viscosity, it is preferred that the solution viscosity of a 10% by mass ethanol solution of polyvinyl butyral, measured at 20°C according to DIN 53015, is 10 to 100 mPa. s, especially preferably 20-60 mPa Approximately s.

[0056] Regarding dispersants, other dispersants that can be used in conjunction with polyvinyl butyral may include, for example, resin-based dispersants other than polyvinyl butyral, surfactants exemplified below, etc.

[0057] (Other resin-based dispersants) As a resin-based dispersant other than polyvinyl butyral, polyvinyl butyral, polyvinyl acetate, polyester resin, epoxy resin, polyether resin, alkyd resin, polyurethane resin, etc., can be used. When the above-mentioned resin-based components are combined with polyvinyl butyral in addition to polyvinyl butyral, the proportions are: polyvinyl butyral is 80% by mass or more and less than 100% by mass, and the proportions of the other components are less than 20% by mass and more than 0% by mass (totaling 100% by mass). If the amount of other components is less than 20% by mass, the viscosity of the carbonaceous material dispersion according to the present invention at 25°C can be maintained at a desired value, specifically, for example, 500 mPa. Below s, and when the prepared slurry is finally coated onto the current collector, it can improve the adhesion between active materials, between active materials and conductive additives, and between conductive additives and other materials constituting the electrode.

[0058] (pH adjuster) In the all-solid-state carbonaceous material dispersion for lithium-ion secondary batteries according to the first aspect of the present invention, a pH adjuster may be added as needed.

[0059] pH adjusters can be exemplified by tertiary amines, secondary amines, primary amines, cyclic amines, and alkanoylamines or amino alcohols that are compounds having an amino and hydroxyl group in an alkane skeleton, or amine compounds such as diethylene glycol ammonium salts, tris(hydroxymethyl)aminomethane (THAM), morpholine, etc. Although not particularly limited, 2-methylaminoethanol, 2-amino-1-butanol, 4-ethylamino-1-butanol, triethylamine, 2-amino-2-ethyl-1,3-propanediol (AEPD), 2-amino-2-methyl-1-propanol (AMP), THAM, etc. are particularly preferred.

[0060] (surfactant) In the all-solid-state carbonaceous material dispersion for lithium-ion secondary batteries according to the first aspect of the present invention, a surfactant may be used as a dispersant as needed.

[0061] Surfactants are not specifically limited, but examples include anionic surfactants such as sodium dodecylbenzenesulfonate and sodium dodecyl sulfate, cationic surfactants such as tetramethylammonium chloride, and nonionic surfactants such as polyoxyethylene alkyl ether compounds and polyoxyethylene fatty acid ester compounds.

[0062] As a dispersant, when the other components mentioned above are combined in addition to polyvinyl butyral, the proportions are as follows: polyvinyl butyral is 80% by mass or more and less than 100% by mass, and the other components are less than 20% by mass and more than 0% by mass (totaling 100% by mass). If the amount of other components is less than 20% by mass, the viscosity of the carbonaceous material dispersion according to the present invention at 25°C can be maintained at a desired value, specifically, for example, 500 mPa. Below s, and when the prepared slurry is finally coated onto the current collector, it can improve the adhesion between active materials, between active materials and conductive additives, and between conductive additives and other materials constituting the electrode.

[0063] (The proportions in the dispersion) In the all-solid-state carbonaceous material dispersion for lithium-ion secondary batteries according to the first aspect of the present invention, the following adjustments are made: in a dispersion medium containing at least an ester solvent, the carbonaceous material is 10-25% by mass, more preferably 12-18% by mass, relative to the total mass of the dispersion; and the amount of dispersant is 5-40% by mass relative to the mass of the carbonaceous material (i.e., 100% by mass of the carbonaceous material), preferably 5% or more and less than 20% by mass, more preferably 6% or more and less than 12% by mass. If the amounts of carbonaceous material and dispersant are maintained within these ranges, a dispersion containing a high concentration of carbonaceous material with good dispersibility and low viscosity can be formed. Furthermore, if the concentration of carbonaceous material is less than the above proportions, the energy required to remove the solvent during product manufacturing increases, as does the transportation cost of the dispersion and the cost of the solvent. Conversely, if the concentration of carbonaceous material is greater than the above proportions, sufficient flowability is difficult to obtain, resulting in poor operability. Furthermore, if the concentration of the dispersant is less than the above-mentioned proportion, it will be difficult to obtain flowability; if the concentration of the dispersant is more than the above-mentioned proportion, there is a concern that the conductivity of the final product will decrease due to the increased proportion of insulating components in the dispersion. In addition, if it is desired to improve the adhesion of the final product, it can be adjusted in such a way that the amount of dispersant relative to the mass of the carbonaceous material (i.e., 100% by mass relative to the mass of the carbonaceous material) is preferably 20 to 40% by mass, more preferably 25 to 35% by mass.

[0064] Furthermore, as described above, when a pH adjuster is added, the amount of the pH adjuster is set to 0.01 to 5% relative to the total amount of the dispersion, more preferably to about 0.05 to 3%. By adding a pH adjuster within this range, better dispersibility of the carbonaceous material can be obtained.

[0065] (Viscosity of the dispersion) Then, by performing the above-described combination and proportions of the composition, for example, the following exemplified dispersion treatment, the viscosity of the carbonaceous material dispersion according to the present invention at 25°C can be made to be 500 mPa. Below s, preferably 50–300 mPa Approximately s.

[0066] Furthermore, in this specification, the viscosity of the carbonaceous material dispersion refers to the value measured immediately after thorough stirring of the dispersion with a spatula (e.g., for one minute) at a test temperature of 25°C and a rotor speed of 60 rpm using a Type B viscometer.

[0067] The carbonaceous material dispersion involved in this invention has the above-specified combination and proportion, exhibiting the specified viscosity. Therefore, the carbonaceous material is dispersed at a high concentration and uniformly, showing stable fluidity. When mixed with electrode active materials to prepare an all-solid lithium-ion secondary battery electrode slurry, the electrode active materials can be dispersed at a high concentration with a moderately low viscosity suitable for construction.

[0068] This characteristic can be objectively evaluated through the following aspects: For example, the viscoelasticity of the carbonaceous material dispersion involved in this invention at 25°C is within the range of 10–1000 s. -1 The range is more preferably 10–500s. -1 The range is further preferably 10–100s. -1 It has a minimum value within the range.

[0069] Furthermore, in this specification, the viscoelasticity of the carbonaceous material dispersion refers to the following: when the dispersion is kept at a temperature of 25°C, and the shear rate is increased from 0.1 s⁻¹... -1 Change to 1000s -1 When using a rheometer to measure shear viscosity, the value is indicated by the range of shear rates that represent the minimum viscosity.

[0070] (Manufacturing of carbonaceous material dispersions) The method for manufacturing the carbonaceous material dispersion for all-solid lithium-ion secondary batteries according to the first aspect of the present invention is not particularly limited. The carbonaceous material and the dispersant are added and stirred in an ester solvent as a dispersion medium in the proportion specified above, and then dispersed.

[0071] There are no particular limitations on the dispersing device; a disperser commonly used for pigment dispersion, etc., can be used. For example, examples include dispersers, homogenizers, planetary mixers, homogenizers (such as M-Technic's "CLEARMIX", PRIMIX's "FILMICS", and Silverson's "ABRAMIX"), paint conditioners (manufactured by Red Devil), paint mixers (such as PUC's "PUC Paint Mixer" and IKA's "Paint Mixer MK"), cone mills (such as IKA's "Cone Mill MKO"), ball mills, sand mills (such as Shinmaru Enterprises' "Dino Mill"), grinding mills, bead mills (such as Eirich's "DCP Mill"), media dispersers such as sand mills, wet jet mills (such as GenusPY, SuginoMachine's "Star Burst", and Nanozer's "Nanomizer"), and M-Technic's "CLEAR" mill. Media-free dispersers such as the "SS-5" and "MICROS" manufactured by Nara Machinery Co., Ltd., and other roller mills, but not limited to these.

[0072] Preferably, the carbonaceous material is dispersed and prepared by a media mill, particularly a media mill using beads with an average particle size of 0.05 to 2 mm. More preferably, the material is dispersed using a shear-type dispersion device, as described in detail below, before being dispersed by the media mill, thereby completing the preparation.

[0073] Furthermore, regarding the particle size of the beads used in the media mill, if it is too small, there is a concern that fine fragments of carbonaceous materials, such as primary aggregates of carbon black, may break, and the dispersion process requires excessive energy. Additionally, due to operational difficulties, an average particle size of 0.05 mm or more is preferred, particularly 0.5 mm or more. However, if the beads are too large, there are concerns that the number of beads per unit volume decreases, resulting in reduced dispersion efficiency, insufficient pulverization of the carbonaceous materials, and the carbonaceous materials existing in a state with a large aspect ratio, which prevents the achievement of liquid properties in coatings and coating agents. Therefore, an average bead diameter of 2 mm or less is preferred, particularly 1.5 mm or less.

[0074] The material of the dispersion media beads used in media mills is not particularly limited. Examples include alumina, zirconium oxide, steel, chromium steel, and glass. However, considering factors such as product contamination and the magnitude of kinetic energy due to specific gravity, zirconium oxide beads are preferred.

[0075] There are no particular restrictions on the shape of the beads, but spherical beads are generally used.

[0076] There are no particular limitations on the structure of media mills; various known media mills can be used. Specifically, various known grinding mills, sand mills, bead mills, etc., can be listed.

[0077] Furthermore, the filling ratio of the beads into the container can be determined based on the container, stirring mechanism, and structure, and there is no particular limitation. However, if the ratio is too low, there is a concern that it may not be able to fully pulverize or cut the carbonaceous material. If the ratio is too high, there are concerns that the rotation requires greater driving force, and that wear of the beads will increase contamination of the processed medium. Therefore, it is preferable to set the filling ratio of the beads to, for example, about 70-85% of the effective volume of the container.

[0078] In addition, the operating conditions such as processing time, shaft rotation speed, container pressure, and motor load depend on the amount of carbonaceous material and the characteristics of the resin to be dispersed, especially its viscosity and compatibility with the carbonaceous material. These can be set appropriately according to the purpose.

[0079] Alternatively, pre-dispersion can be performed using other stirring devices, such as shear mixers, homogenizers, etc., before dispersion treatment through the media mill.

[0080] By performing dispersion treatment in this manner, a sample with a viscosity of 500 mPa at 25°C was prepared. Below s, preferably 50-300 mPa A dispersion of approximately s.

[0081] <Electrode slurry for all-solid-state lithium-ion secondary batteries> The carbonaceous material dispersion described in detail above, which contains the following electrode active substances, can be prepared as an electrode slurry.

[0082] That is, the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention is an all-solid-state electrode slurry for lithium-ion secondary batteries formed by combining carbonaceous materials, dispersants, binder resins and positive or negative active materials in a dispersion medium. The dispersion medium contains at least an ester solvent, the dispersant contains at least polyvinyl butyral, and in the solid component of the slurry, the amount of dispersant is 5 to 40 by mass relative to the mass of the carbonaceous materials.

[0083] In a preferred embodiment of the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention, the amount of dispersant in the solid component of the slurry is preferably 5% by mass or more and less than 20% by mass relative to the mass of the carbonaceous material, more preferably 6% by mass or more and less than 12% by mass.

[0084] In another embodiment of the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention, the amount of dispersant in the solid component of the slurry is 20 to 40% by mass relative to the mass of the carbonaceous material, more preferably 25 to 35% by mass.

[0085] Furthermore, the manufacturing process and the order of addition of each component of the all-solid-state lithium-ion secondary battery electrode slurry involved in the second aspect of the present invention are not limited. For example, it can be set in any of the following ways: (a) a method of manufacturing an all-solid-state lithium-ion secondary battery electrode slurry by dispersing and mixing all components at once; (b) a method of manufacturing an all-solid-state lithium-ion secondary battery electrode slurry by combining a positive electrode active material or a negative electrode active material with the carbonaceous material dispersion involved in the first aspect of the present invention after preparation; (c) a method of manufacturing an all-solid-state lithium-ion secondary battery electrode slurry by preparing a carbonaceous material dispersion in a portion of a dispersion medium and an electrode active material dispersion in a portion of a dispersion medium, and mixing the carbonaceous material dispersion and the electrode active material dispersion.

[0086] (Dispersion media, carbonaceous materials, dispersants, and pH adjusters) The dispersion medium, carbonaceous material, and dispersant in the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention are the same as those described in the carbonaceous material dispersion according to the first aspect of the present invention, and are omitted here to avoid repetition. Furthermore, the pH adjuster described above may also be added to the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention, similarly to the carbonaceous material dispersion according to the first aspect of the present invention, as needed.

[0087] (Electrode active material) In the all-solid-state lithium-ion secondary battery electrode slurry according to the second aspect of the present invention, there are no particular limitations on the positive electrode active material that can be used, but metal compounds such as metal oxides and metal sulfides that can be doped or intercalated with lithium ions, as well as conductive polymers, can be used.

[0088] For example, examples could include oxides of transition metals such as Fe, Co, Ni, and Mn, complex oxides with lithium, and inorganic compounds such as transition metal sulfides. Specifically, examples could include MnO, V₂O₅, and V₆O. 13 The materials include transition metal oxide powders such as TiO2, layered lithium nickelate, lithium cobalt oxide, lithium manganese oxide, and spinel-structured lithium manganese oxide composite oxide powders, lithium iron phosphate materials as olivine-structured phosphate compounds, and transition metal sulfide powders such as TiS2 and FeS. Additionally, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Furthermore, the aforementioned inorganic and organic compounds can be mixed and used.

[0089] On the other hand, in the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention, the negative electrode active material that can be used is not particularly limited as long as it can be doped or intercalated with lithium ions. For example, metallic Li, alloys such as tin alloys, silicon alloys, and lead alloys, etc., can be listed. X Fe2O3, Li X Fe3O4, Li X WO2, lithium titanate, lithium vanadate, lithium silicate and other metal oxides, conductive polymers such as polyacetylene and poly-p-phenylene oxide, amorphous carbon materials such as soft carbon and hard carbon, graphitized carbon materials and other artificial graphite, or carbon powders such as natural graphite, carbon black, mesophase carbon black, resin sintered carbon materials, vapor-grown carbon fibers, carbon fibers and other carbon materials. These negative electrode active materials can be used individually or in combination.

[0090] The average particle size of these electrode active materials is preferably in the range of 0.05 to 100 μm, more preferably in the range of 0.1 to 50 μm. The average particle size of the electrode active materials mentioned in this specification refers to the average particle size measured using an electron microscope.

[0091] (Adhesive resin) In the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention, the binder resin incorporated in the dispersion medium is not particularly limited, but polymers that are not soluble in water can be used. Specifically, for example, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, polyamide, polyamide-imide, butadiene rubber, isobutylene rubber, styrene-butadiene rubber, ethylene propylene rubber, and nitrile rubber can be used. Among these, styrene-butadiene rubber is particularly preferred. In addition, sometimes the same dispersant as the resin-based dispersant that can be incorporated in the carbonaceous material dispersion according to the first aspect of the present invention can also function as a binder resin.

[0092] As an apparatus for manufacturing the electrode slurry, the same apparatus used in preparing the dispersion of the present invention described above can be used.

[0093] In one embodiment of the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention, by using the components specified above, when the solid component concentration of the slurry is 65 to 75% by mass (for example, when the amount of dispersant relative to the mass of the carbonaceous material is 5% to 20% by mass or more), the viscosity of the slurry at 25°C can be made to be 500 to 5000 mPa. s, preferably 1000~4000mPa s can improve workability.

[0094] In one embodiment of the all-solid-state electrode slurry for lithium-ion secondary batteries according to the second aspect of the present invention, by using the components specified above, when the solid component concentration of the slurry is 77 to 87% by mass (for example, when the amount of dispersant is 20 to 40% by mass relative to the mass of the carbonaceous material), the viscosity of the slurry at 25°C can be made to be 1000 to 10000 mPa. s, more preferably 1000-5000 mPa s can improve workability.

[0095]

Example

[0096] Example 1 The dispersion was prepared by mixing 100% by mass of butyl butyrate (manufactured by Tokyo Chemical Industry Co., Ltd.) as the dispersion medium, 1.5% by mass of polyvinyl butyral (S-LEC BL, manufactured by Sekisui Chemicals Co., Ltd.) as the dispersant (10% by mass relative to acetylene black), 15% by mass of acetylene black (Denka Black granules, manufactured by DENKA Co., Ltd.), and 1% by mass of 2-amino-2-ethyl ester-1,3-propanediol, and then dispersed using a laboratory bead mill (manufactured by AIMEX Co., Ltd.).

[0097] Furthermore, regarding the dispersion process using a bead mill, zirconia beads with a diameter of 1 mm were used. The bead filling rate in the container was 30% of the effective volume of the container, resulting in a dispersion-to-bead volume ratio of approximately 1:1. Dispersion was carried out in the container at approximately 2000 rpm until the viscosity reached 100 mPa. Approximately s.

[0098] After dispersing the carbonaceous material dispersion (acetylene black dispersion) prepared in this way, it was allowed to stand for more than 24 hours, and then the viscosity at 25°C was measured, which yielded a result of 104 mPa. s. Measurements were taken using a Type B viscometer (Toki Sangyo Co., Ltd., "TVB-15M") at a measurement temperature of 25°C and a Type B viscometer rotor speed of 60 rpm, immediately after thoroughly dispersing the composition with a spatula. Rotor No. 21 was used. Then, a rheometer (Malvern) was used. The "Kinexus" manufactured by PANalytica enables shearing speeds from 0.1 s⁻¹ to... -1 Change to 1000s -1 Measure the shear viscosity and confirm that the minimum viscosity is within 10s. -1 ~1000s -1 Range (250s) -1 ).

[0099] Four parts of the prepared carbonaceous material dispersion were mixed with 18 parts of an adhesive solution formed by dissolving styrene-butadiene rubber in 10% by mass butyl butyrate. The mixture was then homogenized using a rotary-rotating defoamer to prepare a coating paste. The paste was applied to a glass plate using a plasterer (manufactured by YOSHIMITSU Seiki Co., Ltd.) and dried at 100°C under reduced pressure for two hours to obtain a coating film (30 μm thick after drying). The resistance was measured using a low resistivity meter (Loresta-GX, manufactured by Mitsubishi Chemical Analytech Co., Ltd.), and the result was 1211 Ω, indicating good conductivity.

[0100] Example 2 Compared to the 10.0 g carbonaceous material dispersion prepared in Example 1 above, LiNi, as the positive electrode active material, was combined with a total solid content concentration of 65% by mass. 1 / 3 Co 1 / 3 Mn 1 / 3 30.0g of O2 powder (manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd., with a particle size of 1 to several μm), an adhesive solution formed by dissolving styrene-butadiene rubber in 10% by mass of butyl butyrate, and butyl butyrate were mixed using a rotary stirring defoamer at a rotation speed of 1200 rpm for five minutes, resulting in a slurry exhibiting fluidity.

[0101] Here, the rheometer described above was used to measure whether the obtained slurry for forming the positive electrode mixture layer reached a suitable viscosity during coating. The rheometer measurement conditions were a constant temperature of 25°C and a shear rate of 10 s. -1 The average value of the slurry is obtained by measuring 5 points every 60 seconds.

[0102] As a result, the viscosity of the slurry was 3746 mPa. s.

[0103] Example 3 The dispersion was prepared by mixing a total mass of 100% by mass, a dispersion medium of butyl butyrate of 83.2% by mass, a dispersion agent of 0.8% by mass of polyvinyl butyral (S-LECBL, manufactured by Sekisui Chemicals Co., Ltd.) (relative to 5.3% by mass of acetylene black), a dispersion agent of 15% by mass of acetylene black (Denka Black (trade name) granules, manufactured by DENKA Co., Ltd.), and a dispersion of 1% by mass of 2-amino-2-ethyl ester-1,3-propanediol, and then dispersed using a bead mill.

[0104] Furthermore, regarding the conditions for dispersion treatment via a bead mill, in addition to dispersing until the viscosity becomes 300 mPa... Except for about s, the conditions are the same as in Example 1.

[0105] The viscosity of the carbonaceous material dispersion (acetylene black dispersion) prepared in this manner was measured using the same method as in Example 1. The result was that the viscosity of the dispersion was 345 mPa. Then, as in Example 1, the shear rate was adjusted from 0.1 s using a rheometer. -1 Change to 1000s -1 Measure the shear viscosity and confirm that the minimum viscosity is within 10s. -1 ~1000s -1 Range (630s) -1 ).

[0106] Then, as in Example 1, a dry coating was prepared, and the resistance value was measured to be 1079Ω, showing good conductivity.

[0107] Example 4 The dispersion is prepared by mixing a total mass of 100% by mass, a dispersion medium of butyl butyrate of 81.5% by mass, a dispersion agent of 2.5% by mass of polyvinyl butyral (S-LECBL, manufactured by Sekisui Chemicals Co., Ltd.) (16.7% by mass relative to acetylene black), a dispersion agent of 15% by mass of acetylene black (Denka Black (trade name) granules, manufactured by DENKA Co., Ltd.), and a dispersion of 1% by mass of 2-amino-2-ethyl ester-1,3-propanediol, and then dispersed by a bead mill.

[0108] Furthermore, the conditions for dispersion treatment by bead milling are the same as those in Example 1.

[0109] The viscosity of the carbonaceous material dispersion (acetylene black dispersion) prepared in this manner was measured using the same method as in Example 1. The result was that the viscosity of the dispersion was 79 mPa. s.

[0110] Then, as in Example 1, the shear rate was increased from 0.1 s using a rheometer. -1 Change to 1000s -1 Measure the shear viscosity and confirm that the minimum viscosity is within 10s. -1 ~1000s -1 Range (250s) -1 ).

[0111] Then, as in Example 1, a dried coating was prepared, and the resistance value was measured to be 1371Ω, showing good conductivity.

[0112] Comparative Examples 1-2 Except that cellulose acetate or polyvinylpyrrolidone (both manufactured by Kanto Chemical Co., Ltd.) were used instead of polyvinyl butyral as the dispersant in Example 1, the dispersion process was performed using a bead mill, just like in Example 1.

[0113] However, in either case, the resin component did not dissolve smoothly into butyl butyrate, which served as the dispersion medium, and a uniform dispersion of acetylene black was not obtained.

[0114] Comparative Example 3 The dispersion was prepared by mixing a total mass of 100% by mass, a dispersion medium of butyl butyrate of 83.4% by mass, a dispersion agent of 0.6% by mass of polyvinyl butyral (S-LECBL, manufactured by Sekisui Chemicals Co., Ltd.) (4% by mass relative to acetylene black), a dispersion agent of 15% by mass of acetylene black (Denka Black (trade name) granules, manufactured by DENKA Co., Ltd.), and a dispersion of 1% by mass of 2-amino-2-ethyl ester-1,3-propanediol. The dispersion was then dispersed using a bead mill, but the dispersion did not exhibit sufficient flowability.

[0115] Example 5 The dispersion was prepared in the following proportions: total mass of 100% by mass; butyl butyrate as the dispersion medium of 81% by mass; polyvinyl butyral (S-LECBL, manufactured by Sekisui Chemicals Co., Ltd.) as the dispersant of 3% by mass (relative to 20% by mass of acetylene black); acetylene black (Denka Black granules, manufactured by DENKA Co., Ltd.) of 15% by mass; and 2-amino-2-ethyl ester-1,3-propanediol of 1% by mass. The mixture was then dispersed using a bead mill. Furthermore, the dispersion conditions using the bead mill were the same as those in Example 1.

[0116] The viscosity of the carbonaceous material dispersion (acetylene black dispersion) prepared in this manner was measured using the same method as in Example 1. The result was that the viscosity of the dispersion was 137 mPa. Then, as in Example 1, the shear rate was increased from 0.1 s using a rheometer. -1 Change to 1000s -1 The shear viscosity was measured, and the result showed that the minimum viscosity was within 10 s. -1 ~1000s -1 Range (250s) -1 ).

[0117] Then, as in Example 1, a dried coating was prepared, and the resistance value was measured to be 1953Ω, which is slightly lower than that in Examples 1 and 3.

[0118] Example 6 The dispersion was prepared by mixing a total mass of 100% by mass, a dispersion medium of 79% by mass of butyl butyrate (manufactured by Tokyo Chemical Industry Co., Ltd.), a dispersion agent of 5% by mass of polyvinyl butyral (S-LECBL, manufactured by Sekisui Chemicals Co., Ltd., which is 33.3% by mass relative to acetylene black), a dispersion medium of 15% by mass of acetylene black (Denka Black (trade name) granules, manufactured by DENKA Co., Ltd.), and a dispersion medium of 1% by mass of 2-amino-2-ethyl ester-1,3-propanediol, and then dispersed using a laboratory bead mill (manufactured by AIMEX Co., Ltd.).

[0119] Furthermore, regarding the dispersion process using a bead mill, zirconia beads with a diameter of 1 mm were used. The bead filling rate in the container was 30% of the effective volume of the container, resulting in a dispersion-to-bead volume ratio of approximately 1:1. Dispersion was carried out in the container at approximately 2000 rpm until the viscosity reached 100 mPa. Approximately s.

[0120] After dispersing the carbonaceous material dispersion (acetylene black dispersion) prepared in this way, it was allowed to stand for more than 24 hours, and then the viscosity at 25°C was measured, which yielded a value of 86 mPa. s. Measurements were taken using a Type B viscometer (Toki Sangyo Co., Ltd., "TVB-15M") at a measurement temperature of 25°C and a Type B viscometer rotor speed of 60 rpm, immediately after thoroughly dispersing the composition with a spatula. Rotor No. 21 was used. Then, a rheometer (Malvern) was used. The "Kinexus" manufactured by PANalytica enables shearing speeds from 0.1 s⁻¹ to... -1 Change to 1000s -1 Measure the shear viscosity and confirm that the minimum viscosity is within 10s. -1 ~1000s -1 Range (90s) -1 ).

[0121] Example 7 Compared to the 10.0 g carbonaceous material dispersion prepared in Example 6 above, LiNi, as the positive electrode active material, was added with a total solid content concentration of 80% by mass. 1 / 3 Co 1 / 3 Mn 1 / 3 32.0g of O2 powder (manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd., with a particle size of 1 to several μm) and butyl butyrate were mixed using a rotary defoamer with a rotation speed of 1200 rpm for five minutes. The mixture became a slurry with good fluidity.

[0122] Here, the rheometer described above was used to measure whether the obtained slurry for forming the positive electrode mixture layer reached a suitable viscosity during coating. The rheometer measurement conditions were a constant 25°C and a shear rate of 10 s. -1 The average value of five measurements taken every 60 seconds is used as the viscosity of the slurry.

[0123] As a result, the viscosity of the slurry was 1228 mPa. s.

[0124] Example 8 The dispersion is prepared by mixing a total mass of 100% by mass, a dispersion medium of butyl butyrate of 78% by mass, a resin composition of polyvinyl butyral (S-LECBL, manufactured by Sekisui Chemicals Co., Ltd.) of 6% by mass (relative to 40.0% by mass of acetylene black), a dispersion medium of 15% by mass of acetylene black (Denka Black (trade name) granules, manufactured by DENKA Co., Ltd.), and a resin composition of 2-amino-2-ethyl ester-1,3-propanediol of 1% by mass, and then dispersed using a bead mill.

[0125] Furthermore, the conditions for dispersion treatment using a bead mill are the same as those in Example 6.

[0126] The viscosity of the carbonaceous material dispersion (acetylene black dispersion) prepared in this manner was measured using the same method as in Example 5. The result was that the viscosity of the dispersion was 106 mPa. s.

[0127] Then, as in Example 6, the shear rate was increased from 0.1 s using a rheometer. -1 Change to 1000s -1 Measure the shear viscosity and confirm that the minimum viscosity is within 10s. -1 ~1000s -1 Range (160s) -1 ).

[0128] Comparative Examples 4-5 Except that cellulose acetate or polyvinylpyrrolidone (both manufactured by Kanto Chemical Co., Ltd.) were used instead of polyvinyl butyral as the resin composition in Example 6, the dispersion process was performed using a bead mill, just like in Example 1.

[0129] However, in either case, the resin component did not dissolve smoothly into butyl butyrate, which served as the dispersion medium, and a uniform dispersion of acetylene black was not obtained.

[0130] Example 9 The dispersion is prepared by mixing a total mass of 100% by mass, a dispersion medium of butyl butyrate of 82% by mass, a resin composition of polyvinyl butyral (S-LECBL, manufactured by Sekisui Chemicals Co., Ltd.) of 2% by mass (relative to 13.3% by mass of acetylene black), a resin composition of acetylene black (Denka Black (trade name) granules, manufactured by DENKA Co., Ltd.) of 15% by mass, and a resin composition of 2-amino-2-ethyl ester-1,3-propanediol of 1% by mass, and then dispersed using a bead mill.

[0131] Furthermore, the conditions for dispersion processing using a bead mill are the same as those in Example 6.

[0132] The viscosity of the carbonaceous material dispersion (acetylene black dispersion) prepared in this manner was measured using the same method as in Example 5. The result was that the viscosity of the dispersion was 72 mPa. s.

[0133] Then, as in Example 6, the shear rate was increased from 0.1 s using a rheometer. -1 Change to 1000s -1The shear viscosity was measured, and the minimum viscosity was found at 10s. -1 ~1000s -1 Range (250s) -1 ).

[0134] Example 10 Under the same conditions as in Example 7, the carbonaceous material dispersion prepared in Example 9 was combined with a positive electrode active material and treated using a rotary-rotational stirring defoamer. Subsequently, butyl butyrate was added under the same conditions as in Example 7, and the mixture was treated again using a rotary-rotational stirring defoamer. The result was that the mixture did not exhibit sufficient fluidity. However, by adding butyl butyrate and treating the mixture using a rotary-rotational stirring defoamer until sufficient fluidity was exhibited, a fluid slurry with a solids content of 75% by mass was obtained.

[0135] Comparative Example 6 The dispersion was prepared by mixing a mixture with a total mass of 100% by mass, butyl butyrate as the dispersion medium at 76% by mass, polyvinyl butyral (S-LECBL, manufactured by Sekisui Chemicals Co., Ltd.) as the resin composition at 8% by mass (relative to 53.3% by mass of acetylene black), acetylene black (Denka Black granules, manufactured by DENKA Co., Ltd.) at 15% by mass, and 2-amino-2-ethyl ester-1,3-propanediol at 1% by mass, and then dispersed using a bead mill. Furthermore, the dispersion conditions using the bead mill were the same as those in Example 6.

[0136] The viscosity of the carbonaceous material dispersion (acetylene black dispersion) prepared in this manner was measured using the same method as in Example 6. The result was that the viscosity of the dispersion was 93 mPa. Then, as in Example 6, the shear rate was increased from 0.1 s using a rheometer. -1 Change to 1000s -1 The shear viscosity was measured, and the result was that the minimum viscosity was outside the measurement range.

Claims

1. A carbonaceous material dispersion, wherein the carbonaceous material dispersion is an all-solid-state carbonaceous material dispersion for lithium-ion secondary batteries in which carbonaceous material and a dispersant are dispersed in a dispersion medium, characterized in that, The dispersion medium contains at least an ester solvent, and the dispersant is polyvinyl butyral. The amount of carbonaceous material in the dispersion is 10–25% by mass relative to the total mass of the dispersion, and the amount of dispersant is 25–35% by mass relative to the mass of the carbonaceous material. The viscosity of the carbonaceous material dispersion at 25°C is 500 mPa. Below s; The viscoelasticity of the carbonaceous material dispersion at 25°C is within the range of 10–100 s⁻¹. -1 It has a minimum value within the range.

2. The carbonaceous material dispersion according to claim 1, The dispersion medium contains at least 10% by mass of ester solvents in the total dispersion medium.

3. The carbonaceous material dispersion according to claim 1, The ester solvent is selected from at least one of the following groups: propyl acetate, butyl butyrate, butyl valerate, butyl hexanoate, pentyl butyrate, pentyl valerate, pentyl hexanoate, hexyl butyrate, hexyl valerate, and hexyl hexanoate.

4. The carbonaceous material dispersion according to claim 3, The ester solvent is butyl butyrate.

5. The carbonaceous material dispersion according to claim 1, The carbonaceous material is carbon black.

6. The carbonaceous material dispersion according to claim 5, Carbon black is acetylene black.

7. The carbonaceous material dispersion according to claim 1, The carbonaceous material dispersion also contains a pH adjuster.

8. An all-solid-state electrode slurry for lithium-ion secondary batteries, wherein the all-solid-state electrode slurry for lithium-ion secondary batteries incorporates carbonaceous materials, dispersants, binder resins, and positive or negative electrode active materials in a dispersion medium, characterized in that... The dispersion medium contains at least an ester solvent, and the dispersant is polyvinyl butyral. Furthermore, in the solids component of the slurry, the amount of dispersant relative to the mass of the carbonaceous material is 25-35% by mass. The carbonaceous material dispersion formed by dispersing the carbonaceous material and dispersant in the dispersion medium has a viscosity of 500 mPa at 25°C. Below s, the viscoelasticity of a carbonaceous material dispersion formed by dispersing carbonaceous material and a dispersant in a dispersion medium at 25°C is measured at shear rates of 10–100 s. -1 It has a minimum value within the range.

9. The all-solid-state electrode slurry for lithium-ion secondary batteries according to claim 8, When the solids concentration of the slurry is 77–87% by mass, the viscosity of the slurry at 25°C is 1000–10000 mPa. s.