Slurry composition for manufacturing solid-state batteries and method for manufacturing all-solid-state batteries

Abstract

To provide a slurry composition for manufacturing a high-performance solid-state battery, which is capable of suppressing the gelation of a slurry even when the slurry composition contains an inorganic powder containing an alkali metal, and is also excellent in sinterability.SOLUTION: A slurry composition for manufacturing a solid-state battery includes an organic solvent, and an inorganic powder containing binder resin and alkali metal, and the organic solvent is at least one selected from the group consisting of aromatic compounds, aliphatic hydrocarbons and alicyclic hydrocarbons, and the binder resin is at least one selected from the group consisting of polystyrene resins and polypropylene resins.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a slurry composition for manufacturing solid-state batteries and a method for manufacturing all-solid-state batteries. [Background technology]

[0002] Lithium-ion batteries are widely used as power sources for many electronic devices due to their high energy density and excellent charge-discharge cycle characteristics. However, lithium-ion batteries contain flammable organic solvents, leading to frequent accidents such as leakage and explosions. Therefore, in recent years, all-solid-state lithium-ion batteries (hereinafter also called "all-solid-state batteries") using inorganic solid electrolytes have been investigated. In the manufacture of all-solid-state batteries, a process called the wet method is used, in which a slurry composition of inorganic electrolyte and binder resin dispersed in an organic solvent is coated and dried to produce inorganic powder sheets of uniform thickness. These sheets are then stacked to form a battery, and the binder resin is removed by firing. The binder resin is necessary for controlling the thickness during coating and for lamination of the sheets, but if it remains in the laminate, it creates electrical resistance and negatively affects the performance of the battery, so it must be removed by firing. For this reason, acrylic resin, which has particularly excellent degreasing properties, and polyvinyl acetal resin, which has excellent dispersibility of inorganic powders and sheet strength, are used as binder resins.

[0003] Furthermore, in recent years, interfacial resistance between the electrolyte and the active material has become a problem in achieving high performance in all-solid-state batteries. To solve this problem, for example, Patent Document 1 discloses the use of an active material having a resistance layer formation suppression coating layer that suppresses the formation of high-resistance regions. Furthermore, Patent Document 2 discloses that, in order to reduce interfacial resistance, oxide particles having a neutralization product on part or all of the surface of oxide particles containing an alkaline compound are used. Furthermore, Patent Document 3 discloses a solid electrolyte slurry in which garnet-type solid electrolyte particles and compound particles containing lithium and boron are dispersed in a dispersion medium as a dispersed phase. [Prior art documents]

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, since a compound containing an alkali metal is used to coat the active material, when it is made into a slurry composition, the slurry becomes strongly alkaline, and there is a problem that the binder resin gels. In addition, in Patent Document 2, surface treatment is performed to coat the oxide particles with a neutralization product, but even with such a method, the resulting slurry shows strong alkalinity, and the problem of gelation of the binder resin occurs. Furthermore, in Patent Document 3, in order to suppress the decomposition of the compound containing lithium and boron by moisture, the moisture content in the organic solvent as the dispersion medium must be reduced to 0.007% by mass or less, and it is necessary to manage the entire production equipment in a completely dry state, which causes a problem that the production equipment costs a great deal, and a slurry that can be manufactured more simply is required.

[0006] An object of the present invention is to provide a slurry composition for manufacturing a solid-state battery that can suppress the gelation of a slurry even when an inorganic powder containing an alkali metal is included, has excellent sinterability, and can produce an inorganic powder sheet with low residue, and can manufacture a high-performance all-solid-state battery. Another object is to provide a method for manufacturing an all-solid-state battery using the slurry composition for manufacturing a solid-state battery.

Means for Solving the Problems

[0007] The present invention relates to a slurry composition for manufacturing a solid-state battery, which contains an organic solvent, a binder resin, and inorganic powder containing an alkali metal. The organic solvent is at least one selected from the group consisting of aromatic compounds, aliphatic hydrocarbons, and alicyclic hydrocarbons. The binder resin is at least one selected from the group consisting of polystyrene-based resins and polypropylene-based resins. The present invention will be described in detail below.

[0008] The inventors of the present invention have found that by combining specific organic solvents and binder resins, gelation of the binder resin can be suppressed even in a configuration containing inorganic powder containing an alkali metal. Further, by using such a slurry composition, it has been found that an inorganic powder sheet excellent in sinterability can be produced, and a high-performance all-solid-state battery can be manufactured, thus completing the present invention.

[0009] <Binder resin> The slurry composition for manufacturing a solid-state battery of the present invention contains a binder resin. The above binder resin is at least one selected from the group consisting of polystyrene-based resins and polypropylene-based resins. Polystyrene-based resins and polypropylene-based resins contain a large number of branched structures in the main chain carbon, and decomposition starts from the branches in a high-temperature environment of 300°C or higher. Therefore, they can be decomposed at a relatively low temperature in an air atmosphere compared to polyethylene without branches. On the other hand, although acrylic resins and polyvinyl acetal resins also have a branched structure in the main chain, ester groups and acetal groups containing oxygen are not preferable because they are easily saponified in an alkaline environment. Polystyrene-based resins and polypropylene-based resins are stable even in an alkaline environment and do not have functional groups that hydrolyze. Therefore, a slurry using these resins does not gel or have a sudden viscosity change even in a configuration containing inorganic powder containing an alkali metal, and an inorganic powder sheet can be manufactured by coating.

[0010] The polystyrene resin may be a copolymer of styrene and other monomers, but a styrene homopolymer is preferred. Examples of styrene homopolymers include general-purpose polystyrene (GPPS) having an atactic structure and syndiotactic polystyrene having a syndiotactic structure. Furthermore, examples of copolymers of styrene with other monomers include high-impact polystyrene (HIPS), styrene-butadiene copolymer, styrene-(meth)acrylic acid copolymer, styrene-acrylonitrile copolymer (SAN), and acrylonitrile-butadiene-styrene copolymer (ABS). Among these, GPPS is preferable because it does not contain any other resin components. Furthermore, while there are injection-molded and extruded grades of GPPS, the extruded grade is preferred. Injection-molded grades are designed with a branched structure to reduce entanglement of branched chains. Using a linear grade with fewer branches improves the handling of the inorganic powder sheet.

[0011] Specifically, the polystyrene resins used include XC-315 (manufactured by DIC Corporation), CR-3500 (manufactured by DIC Corporation), NormalFlow (manufactured by Toyo Engineering Corporation), etc.

[0012] The above-mentioned polypropylene resin may be a copolymer of propylene and other monomers, but a propylene homopolymer is preferred. Other monomers copolymerizable with propylene include, for example, α-olefins such as butene-1 and hexene-1. The polymerization form is not particularly limited and may be a random copolymer, a block copolymer, or the like.

[0013] Specifically, the polypropylene resins mentioned above include Novatec MA3H (manufactured by Nippon Polypropylene Co., Ltd.), Novatec EA9 (manufactured by Nippon Polypropylene Co., Ltd.), Novatec FY4 (manufactured by Nippon Polypropylene Co., Ltd.), etc.

[0014] The binder resin can be an ethylene-modified or carboxylic acid-modified polystyrene resin or a polypropylene resin, as long as the sinterability does not deteriorate. By modifying the inorganic powder with ethylene, the affinity with plasticizers is increased, improving the windability and break elongation of the inorganic powder sheet. Furthermore, by modifying it with carboxylic acid, the dispersibility of the inorganic powder can be improved. The introduction rate of the modified structure in the binder resin is preferably 0 mol% or more, more preferably 0.1 mol% or more, even more preferably 0.5% or more, preferably 10 mol% or less, more preferably 8 mol% or less, and even more preferably 5 mol% or less. If the introduction rate of the modified structure in the binder resin is within the above range, sinterability can be sufficiently maintained.

[0015] The above binder resin preferably has a melt flow index (MFR value) of 10 g / 10 min or less according to ISO-1133. The MFR value is preferably 8 g / 10 min or less, more preferably 6 g / 10 min or less, and even more preferably 4 g / 10 min or less. The lower limit is not particularly limited, but for example, it is 0 g / 10 min or more. If the above MFR value is below the above upper limit, the strength of the resulting inorganic powder sheet can be sufficiently increased, resulting in excellent handling properties and the ability to produce thinner inorganic powder sheets.

[0016] The binder resin content in the slurry composition for manufacturing solid batteries of the present invention is preferably 1% by weight or more, more preferably 2% by weight or more, even more preferably 4% by weight or more, preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 8% by weight or less.

[0017] <organic solvents> The slurry composition for manufacturing solid-state batteries of the present invention contains an organic solvent. The above organic solvent is at least one selected from the group consisting of aromatic compounds, aliphatic hydrocarbons, and alicyclic hydrocarbons. It is preferable that the inorganic powder sheet contains the above-mentioned organic solvent, as this provides excellent coating properties, drying properties, and dispersibility of the inorganic powder when the inorganic powder sheet is manufactured.

[0018] Examples of the above aromatic compounds include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, methylbenzylxylene, alkylbenzenes such as 1,4-dimethyl-2-(1-phenylethyl)benzene and ethylbenzene, aromatic alcohols such as phenol, benzyl alcohol and cresol, and aromatic ketones such as acetophenone. Examples of the aliphatic hydrocarbons mentioned above include hexane, n-heptane, isopentane, n-octane, n-nonane, n-decane, and other olefinic solvents such as normal paraffins, isoparaffins, α-olefins, and isobutylene derivatives. Aromatic compounds include aromatic hydrocarbons and aromatic alcohols. Examples of the above-mentioned alicyclic hydrocarbons include limonene, dipentene, terpinene, nethol, synene, orange flavor, terpinolene, phellandrene, mentadiene, terebene, dihydrocymene, mothlene, isoterpinene, critomene, cautusin, cajeptene, oilimene, pinene, turpentine, menthane, pinan, terpene, cyclohexane, alkylcyclohexane such as methylcyclohexane, and others. Among these, toluene, benzyl alcohol, methylcyclohexane, xylene, ethylbenzene, and isoparaffin are preferred. These organic solvents may be used individually or in combination of two or more.

[0019] The boiling point of the above organic solvent is preferably 100°C or higher, more preferably 110°C or higher, preferably 240°C or lower, more preferably 220°C or lower, even more preferably 200°C or lower, and even more preferably 190°C or lower. If the boiling point is above the lower limit, evaporation will not occur too quickly, further improving handling. If the boiling point is below the upper limit, the residue of organic solvents on the inorganic powder sheet can be reduced, improving the sheet strength and further enhancing printability.

[0020] The content of the organic solvent in the slurry composition for manufacturing solid batteries of the present invention is preferably 20% by weight or more, more preferably 30% by weight or more, even more preferably 40% by weight or more, preferably 70% by weight or less, and more preferably 60% by weight or less.

[0021] The slurry composition for manufacturing solid batteries of the present invention may contain other solvents such as aliphatic alcohols in addition to the organic solvents mentioned above.

[0022] The content of the organic solvent in the slurry composition for solid-state battery manufacturing of the present invention is not particularly limited, but a preferred lower limit is 10% by weight and a preferred upper limit is 60% by weight. By keeping it within this range, coating properties and the dispersibility of inorganic powders can be improved.

[0023] <Inorganic powder> The slurry composition for manufacturing solid batteries of the present invention contains inorganic powder. The above inorganic powder contains alkali metals. By including the above-mentioned inorganic powder, the characteristics of the resulting battery can be significantly enhanced. The alkali metals mentioned above are lithium, sodium, potassium, rubidium, cesium, and francium, with lithium being preferred.

[0024] Examples of inorganic powders containing the alkali metals mentioned above include sulfide materials such as Li2S-P2S5, Li2S-GeS2, Li2S-GeS2-P2S5, Li2S-SiS2, Li2S-B2S3, and Li3PO4-P2S5. Materials obtained by adding lithium halides to the above sulfide materials (e.g., LiI-Li2S-P2S5, LiCl-LiI-Li2S-P2S5, LiBr-LiI-Li2S-P2S5, LiI-Li2S-SiS2, LiI-Li2S-B2S3, etc.) are also included. Among these, sulfide-based inorganic powders of the Li2S-P2S5 system are preferred because they do not contain expensive rare earth elements and possess high ionic conductivity. Furthermore, in order to design a battery with a large capacity, it is preferable to use an active material consisting of an alkali metal oxide containing Li. Specifically, Li7La3Zr2O 12 Examples include lithium lanthanum zirconium-containing composite oxides (LLZ series), Al-doped LLZO, lithium lanthanum titanium-containing composite oxides (LLT series), Al-doped LLT series, lithium phosphate series, and other composite oxide materials. Other examples include lithium cobalt oxide, lithium nickel oxide, lithium-nickel-cobalt-aluminum oxide, lithium-nickel-manganese-cobalt oxide, and lithium-manganese-nickel compounds.

[0025] The inorganic powder described above may be coated with a lithium metal compound. The lithium metal compound used for coating is not particularly limited and includes, for example, lithium niobate, lithium titanate, lithium silicate, lithium borosilicate, lithium boric acid, lithium phosphoric acid, lithium phosphorous acid, and lithium phosphorous acid.

[0026] The content of the inorganic powder in the slurry composition for manufacturing solid batteries of the present invention is not particularly limited, but a preferred lower limit is 10% by weight, a more preferred lower limit is 20% by weight, an even more preferred lower limit is 30% by weight, a preferred upper limit is 90% by weight, a more preferred upper limit is 80% by weight, an even more preferred upper limit is 70% by weight, an even more preferred upper limit is 60% by weight, and a particularly preferred upper limit is 50% by weight. By setting the content above the lower limit, it is possible to obtain a composition with sufficient viscosity and excellent coating properties, and by setting the content below the upper limit, it is possible to obtain a composition with excellent dispersibility of the inorganic powder.

[0027] <Other> The slurry composition for manufacturing solid batteries of the present invention may further contain a plasticizer. Examples of the plasticizers mentioned above include 1,3-di-tert-butyltoluene, α-methylstyrene dimer, low molecular weight polyolefin wax, and liquid polyolefin. Aromatic plasticizers such as dioctyl phthalate and dibutyl phthalate can also be used.

[0028] The boiling point of the plasticizer is preferably 240°C or higher and less than 390°C. Setting the boiling point above 240°C facilitates evaporation during the drying process, preventing residue in the molded article. Setting it below 390°C prevents the generation of residual carbon. Note that the boiling point refers to the boiling point at atmospheric pressure.

[0029] The content of the plasticizer in the slurry composition for manufacturing solid batteries of the present invention is not particularly limited, but a preferred lower limit is 0.1% by weight, a more preferred lower limit is 0.5% by weight, a preferred upper limit is 3.0% by weight, and a more preferred upper limit is 2.0% by weight. By keeping the content within these ranges, the amount of plasticizer residue after firing can be reduced.

[0030] The slurry composition for manufacturing solid-state batteries of the present invention may further contain sintering aids such as organic peroxides. Examples of the above-mentioned organic peroxides include 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, and 2,3-dimethyl-2,3-diphenylbutane. The above organic peroxide preferably has a 10-hour half-life temperature of 150°C or higher.

[0031] The slurry composition for manufacturing solid batteries of the present invention may further contain additives such as surfactants. The above-mentioned surfactants are not particularly limited and include, for example, cationic surfactants, anionic surfactants, and nonionic surfactants. The above nonionic surfactant is not particularly limited, but it is preferable that it is a nonionic surfactant with an HLB value of 10 or more and 20 or less. Here, the HLB value is used as an indicator of the hydrophilicity and lipophilicity of a surfactant, and several calculation methods have been proposed. For example, for ester-based surfactants, the saponification value is S and the acid value of the fatty acid constituting the surfactant is A, and the HLB value is defined as 20 (1-S / A). Specifically, nonionic surfactants having polyethylene oxide obtained by adding alkylene ether to a fatty acid chain are preferred, and specifically, for example, polyoxyethylene lauryl ether and polyoxyethylene cetyl ether are preferably used. Although the above nonionic surfactant has good thermal decomposition properties, if it is added in large quantities, the thermal decomposition properties of the slurry composition for solid battery manufacturing may decrease, so the preferred upper limit of the content is 5% by weight.

[0032] The pH of the slurry composition for manufacturing solid batteries of the present invention is preferably 11 or higher. A pH of 11 or higher can significantly improve the performance of the resulting battery. The above pH can be confirmed, for example, by using pH test paper.

[0033] The viscosity of the slurry composition for manufacturing solid batteries of the present invention is not particularly limited, but a preferred lower limit of viscosity is 0.1 Pa·s and a preferred upper limit is 100 Pa·s when measured at 20°C using a B-type viscometer with a probe rotation speed of 5 rpm. By setting the viscosity to 0.1 Pa·s or higher, the inorganic powder sheet obtained after coating by die-coating printing or the like can maintain its predetermined shape. Furthermore, by setting the viscosity to 100 Pa·s or lower, problems such as the die coating marks not disappearing can be prevented, resulting in excellent printability.

[0034] The method for preparing the slurry composition for solid-state battery manufacturing of the present invention is not particularly limited, and conventionally known stirring methods can be used. Specifically, for example, a method can be used to stir the binder resin, the inorganic powder, the organic solvent, and other components such as plasticizers added as needed using a three-roll stirrer, a high-speed stirrer, or the like.

[0035] An inorganic powder sheet can be manufactured by coating the slurry composition for solid-state battery manufacturing of the present invention onto a support film that has been treated with a single-sided release agent, drying the organic solvent, and forming it into a sheet. The inorganic powder sheet described above preferably has a thickness of 1 to 20 μm.

[0036] Examples of methods for producing the inorganic powder sheet include a method of uniformly forming a coating film on a support film using a coating method such as a roll coater, die coater, squeeze coater, or curtain coater with the slurry composition for solid battery manufacturing of the present invention.

[0037] The support film used in manufacturing the above-mentioned inorganic powder sheet is preferably a resin film that is heat-resistant, solvent-resistant, and flexible. The flexibility of the support film allows the slurry composition for solid-state battery manufacturing to be applied to its surface using a roll coater, blade coater, etc., and the resulting inorganic powder sheet-forming film can be stored and supplied in a rolled state.

[0038] Examples of resins used to form the above-mentioned support film include polyethylene terephthalate, polyester, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, polyfluoroethylene and other fluororesins, nylon, cellulose, and the like. The thickness of the above-mentioned support film is preferably, for example, 20 to 100 μm. Furthermore, it is preferable that the surface of the support film be treated with a release agent, which facilitates the peeling operation of the support film during the transfer process.

[0039] An inorganic powder sheet can be manufactured by coating and drying the slurry composition for solid-state battery manufacturing of the present invention. Furthermore, an all-solid-state battery can be manufactured by firing the inorganic powder sheet. In addition, a multilayer ceramic capacitor can be manufactured by using the slurry composition for solid-state battery manufacturing and the inorganic powder sheet of the present invention as a dielectric green sheet and electrode paste, respectively.

[0040] A method for manufacturing the above-mentioned all-solid-state battery includes the steps of: forming an electrode active material layer slurry containing an electrode active material and an electrode active material layer binder to produce an electrode active material sheet; laminating the electrode active material sheet and the inorganic powder sheet of the present invention to produce a laminate; and firing the laminate.

[0041] The electrode active material is not particularly limited, and examples include glass powder, ceramic powder, phosphor nanoparticles, silicon oxide, metal nanoparticles, etc.

[0042] The above-mentioned glass powder is not particularly limited and includes, for example, glass powders such as bismuth oxide glass, silicate glass, lead glass, zinc glass, and boron glass, as well as glass powders of various silicon oxides such as CaO-Al2O3-SiO2 system, MgO-Al2O3-SiO2 system, and LiO2-Al2O3-SiO2 system. Furthermore, the above glass powders include SnO-B2O3-P2O5-Al2O3 mixture, PbO-B2O3-SiO2 mixture, BaO-ZnO-B2O3-SiO2 mixture, ZnO-Bi2O3-B2O3-SiO2 mixture, Bi2O3-B2O3-BaO-CuO mixture, Bi2O3-ZnO-B2O3-Al2O3-SrO mixture, ZnO-Bi2O3-B2O3 mixture, Bi2O3-SiO2 mixture, P2O5-Na2O-CaO-BaO-Al2O3-B2O3 mixture, P2O5-SnO mixture, P2O5-SnO-B2O3 mixture, P2 Other mixtures such as O5-SnO-SiO2, CuO-P2O5-RO, SiO2-B2O3-ZnO-Na2O-Li2O-NaF-V2O5, P2O5-ZnO-SnO-R2O-RO, B2O3-SiO2-ZnO, B2O3-SiO2-Al2O3-ZrO2, SiO2-B2O3-ZnO-R2O-RO, SiO2-B2O3-Al2O3-RO-R2O, SrO-ZnO-P2O5, SrO-ZnO-P2O5, BaO-ZnO-B2O3-SiO2, etc. can also be used. Note that R is an element selected from the group consisting of Zn, Ba, Ca, Mg, Sr, Sn, Ni, Fe, and Mn. In particular, lead-free glass powders such as PbO-B2O3-SiO2 mixtures, BaO-ZnO-B2O3-SiO2 mixtures, or ZnO-Bi2O3-B2O3-SiO2 mixtures are preferred.

[0043] The above ceramic powders are not particularly limited and include, for example, alumina, ferrite, zirconia, zircon, barium zirconate, calcium zirconate, titanium oxide, barium titanate, strontium titanate, calcium titanate, magnesium titanate, zinc titanate, lanthanum titanate, neodymium titanate, lead zirconate titanate, alumina nitride, silicon nitride, boron nitride, boron carbide, barium stanate, calcium stanate, magnesium silicate, mullite, steatite, cordierite, forsterite, and the like. In addition, ITO, FTO, niobium oxide, vanadium oxide, tungsten oxide, lanthanum strontium manganite, lanthanum strontium cobalt ferrite, yttrium-stabilized zirconia, gadolinium-doped ceria, nickel oxide, lanthanum chromite, etc. can also be used. The phosphor fine particles are not particularly limited. For example, as the phosphor material, blue phosphor materials, red phosphor materials, green phosphor materials, etc. conventionally known as phosphor materials for displays are used. As the blue phosphor material, for example, MgAl 10 O 17 :Eu, Y2SiO5:Ce-based, CaWO4:Pb-based, BaMgAl 14 O 23 :Eu-based, BaMgAl 16 O 27 :Eu-based, BaMg2Al 14 O 23 :Eu-based, BaMg2Al 14 O 27 :Eu-based, ZnS:(Ag,Cd)-based ones are used. As the red phosphor material, for example, Y2O3:Eu-based, Y2SiO5:Eu-based, Y3Al5O 12 :Eu-based, Zn3(PO4)2:Mn-based, YBO3:Eu-based, (Y,Gd)BO3:Eu-based, GdBO3:Eu-based, ScBO3:Eu-based, LuBO3:Eu-based ones are used. As the green phosphor material, for example, Zn2SiO4:Mn-based, BaAl 12 O 19 :Mn-based, SrAl 13 O 19 :Mn-based, CaAl 12 O 19 :Mn-based, YBO3:Tb-based, BaMgAl 14 O 23 :Mn-based, LuBO3:Tb-based, GdBO3:Tb-based, ScBO3:Tb-based, Sr6Si3O3Cl4:Eu-based ones are used. In addition, ZnO:Zn-based, ZnS:(Cu,Al)-based, ZnS:Ag-based, Y2O2S:Eu-based, ZnS:Zn-based, (Y,Cd)BO3:Eu-based, BaMgAl 12 O 23 :Eu-based ones can also be used.

[0044] The above-mentioned metal nanoparticles are not particularly limited and include, for example, powders made of copper, nickel, palladium, platinum, gold, silver, aluminum, tungsten, or alloys thereof. Furthermore, metals such as copper and iron, which have good adsorption properties with carboxyl groups, amino groups, amide groups, etc., and are easily oxidized, can also be suitably used. These metal powders may be used individually or in combination of two or more types. In addition to metal complexes, various types of carbon black, carbon nanotubes, etc., may also be used.

[0045] The above electrode active material preferably contains lithium or titanium. Specifically, for example, low-melting-point glass such as LiO2·Al2O3·SiO2-based inorganic glass, Li2S-M x S y Lithium sulfur-based glasses such as (M=B, Si, Ge, P), lithium cobalt composite oxides such as LiCoO2, lithium manganese composite oxides such as LiMnO4, lithium nickel composite oxides, lithium vanadium composite oxides, lithium zirconium composite oxides, lithium hafnium composite oxides, lithium silicate (Li 3.5 Si 0.5 P 0.5 O4), lithium titanium phosphate (LiTi2(PO4)3), lithium titanate (Li4Ti5O 12 ), Li 4 / 3 Ti 5 / 3 O4, lithium germanium phosphate (LiGe2(PO4)3), Li2-SiS glass, Li4GeS4-Li3PS4 glass, LiSiO3, LiMn2O4, Li2S-P2S5 glass / ceramics, Li2O-SiO2, Li2O-V2O5-SiO2, LiS-SiS2-Li4SiO4 glass, ion-conductive oxides such as LiPON, lithium oxide compounds such as Li2O-P2O5-B2O3 and Li2O-GeO2Ba, Li x Al y Ti z (PO4)3-type glass, La x Li y TiO z Glass system, Li x Ge y Pz O4-based glass, Li7La3Zr2O 12 Glass system, Li v Si w P x S y Cl z Lithium niobium oxides such as LiNbO3, lithium alumina compounds such as Li-β-alumina, Li 14 Examples include lithium zinc oxides such as Zn(GeO4)4.

[0046] As the binder for the electrode active material layer mentioned above, polystyrene resins, polypropylene resins, and (meth)acrylic resins can be used.

[0047] Methods for laminating the electrode active material sheet and the inorganic powder sheet of the present invention include methods such as heat pressing, thermal lamination, etc., after each has been formed into a sheet.

[0048] In the firing process described above, the preferred lower limit of the heating temperature is 250°C, and the preferred upper limit is 600°C.

[0049] By the above manufacturing method, an all-solid-state battery can be obtained. The above-mentioned all-solid-state battery preferably has a structure in which a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer are stacked. A method for manufacturing an all-solid-state battery, comprising the steps of obtaining an inorganic powder sheet using the slurry composition for manufacturing solid-state batteries of the present invention, and firing the inorganic powder sheet at a temperature of 600°C or lower, is also one of the present inventions.

[0050] A method for manufacturing the above-mentioned multilayer ceramic capacitor includes the steps of printing a conductive paste onto the inorganic powder sheet, drying it to produce a dielectric sheet, and laminating the dielectric sheets.

[0051] The conductive paste described above contains conductive powder. The material of the conductive powder described above is not particularly limited as long as it is a conductive material, and examples include nickel, palladium, platinum, gold, silver, copper, and alloys thereof. These conductive powders may be used individually or in combination of two or more types.

[0052] The method for printing the conductive paste described above is not particularly limited and includes, for example, screen printing, die-coating, offset printing, gravure printing, and inkjet printing.

[0053] In the above-described method for manufacturing multilayer ceramic capacitors, a multilayer ceramic capacitor is obtained by stacking dielectric sheets on which the conductive paste is printed. [Effects of the Invention]

[0054] According to the present invention, even when the slurry contains an inorganic powder containing an alkali metal, gelation of the slurry can be suppressed, and it also exhibits excellent sinterability, enabling the production of a low-residue inorganic powder sheet and providing a slurry composition for manufacturing high-performance all-solid-state batteries. Furthermore, a method for manufacturing an all-solid-state battery using this slurry composition can be provided. [Modes for carrying out the invention]

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0056] (Example 1) In a separable flask equipped with a Liebig condenser, a temperature-adjustable oil bath, and a stirring blade, 100 parts by weight of polystyrene resin (polystyrene homopolymer, DIC Corporation, XC-315, MFR value 3.2 g / 10 min) as a binder resin and 1000 parts by weight of toluene (boiling point 110°C) as an organic solvent were added. The oil bath was then heated to 80°C and stirred for 6 hours to dissolve the polystyrene resin. A vacuum pump and solvent trap were set up, and the solution was treated with the vacuum pump for 1 hour to recover trace amounts of unreacted monomers and toluene containing water, thereby obtaining a polystyrene resin solution with a resin solids content of 12% by weight. The resin solids content was evaluated by the drying method. 33.3 parts by weight (4 parts by weight of resin) of the obtained polystyrene resin solution were weighed into a poly container for a high-speed stirrer, and organic solvents were added to achieve the formulation shown in Table 1. 1,3-di-tert-butyltoluene was added as a plasticizer, and the sealed container was rotated at high speed to uniformly mix the resin solution. To the resulting resin solution, Li7La3Zr2O was added as a conductive inorganic powder. 12 40 parts by weight of (LLZ manufactured by Toyoshima Seisakusho Co., Ltd.) were added, and the inorganic powder was dispersed by rotating the container at high speed while it was sealed, in order to prepare a slurry composition.

[0057] (Examples 2-6, Comparative Examples 1, 3-4) A slurry composition was obtained in the same manner as in Example 1, except that the type and formulation of the binder resin, organic solvent, and plasticizer were changed as shown in Table 1. The following organic solvents, binder resins, and plasticizers were used. <organic solvents> Benzyl alcohol (boiling point 205°C) Ethylcyclohexane (boiling point 160°C) Xylene (boiling point 139°C) Ethylbenzene (boiling point 136°C) Liquid paraffin NAS-3 (boiling point 195°C), manufactured by NOF Corporation. Butyl acetate (boiling point 126°C) <Binder resin> CR-3500: Polystyrene homopolymer, manufactured by DIC Corporation. NormalFlow: Polystyrene homopolymer, manufactured by Toyo Engineering Corporation. Novatec FY4: Polypropylene homopolymer, manufactured by Nippon Polypropylene Co., Ltd. Novatec EA9: Polypropylene homopolymer, manufactured by Nippon Polypropylene Co., Ltd. Novatec MA3H: Polypropylene homopolymer, manufactured by Nippon Polypropylene Co., Ltd. Esrec BM-S: Polyvinyl acetal resin, manufactured by Sekisui Chemical Co., Ltd. HighFlow: Polystyrene homopolymer, manufactured by Toyo Engineering Corporation. <Plasticizer> α-methylstyrene dimer Dioctyl phthalate Excellex 07500: Liquid polyolefin, manufactured by Mitsui Chemicals, Inc. Unitol P-801: Hydroxyl-modified polyolefin, manufactured by Mitsui Chemicals, Inc. Lucant HC-40: Ethylene-α-olefin copolymer, manufactured by Mitsui Chemicals, Inc. Dibutyl phthalate

[0058] (Comparative Example 2) In a separable flask equipped with a condenser, a temperature-adjustable oil bath, a nitrogen inlet tube, and a stirring blade, 100 parts by weight of methyl methacrylate (MMA) as a monomer and 100 parts by weight of butyl acetate as an organic solvent were added. The oil bath was set to 80°C, and Perloyl L (manufactured by NOF Corporation) was added as a polymerization initiator to polymerize the monomer. When the resin solids content was evaluated using the drying method, it was confirmed that the monomer had polymerized to almost 100%. After dilution with the addition of 600 parts by weight of butyl acetate, the butyl acetate containing trace amounts of unreacted monomer and water was recovered in the same manner as in Example 1 to obtain a resin solution with a resin solids content of 15% by weight. 40 parts by weight (6 parts by weight) of the resin solution were weighed into a poly container for a high-speed stirrer, and organic solvents were added to achieve the formulation shown in Table 1. Dibutyl phthalate was added as a plasticizer, and the sealed container was rotated at high speed to uniformly mix the resin solution. To the resulting resin solution, Li7La3Zr2O was added as a conductive inorganic powder. 12 40 parts by weight of (LLZ manufactured by Toyoshima Seisakusho Co., Ltd.) were added, and the inorganic powder was dispersed by rotating the container at high speed while it was sealed, in order to prepare a slurry composition.

[0059] <Rating> The binder resins used in the examples and comparative examples, and the slurry compositions obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 1 and 2.

[0060] (1) MFR value The MFR was measured in accordance with ISO 1133. Note that ISO 1133 specifies measurement conditions depending on the type of resin, and the measurement was performed under the following conditions. Polystyrene resin: Temperature 200℃, Load 5kg Polypropylene resin: Temperature 230℃, Load 16kg Polyvinyl acetal resin: Temperature 150℃, Load 5kg Polymethyl methacrylate: Temperature 230°C, load 3.8kg

[0061] (2) pH of the slurry composition The obtained slurry composition was applied to pH test paper (manufactured by Advantec Co., Ltd.) using a dropper, and the pH of the slurry composition was measured from the degree of color change and evaluated according to the following criteria. A low pH indicates a low amount of alkali metal in the slurry composition, suggesting inferior battery performance. ○: The slurry composition was strongly alkaline, with a pH of 11 or higher. ×: The slurry composition was not strongly alkaline, with a pH of less than 11.

[0062] (3) Gelation of the slurry composition The resulting slurry composition was opened in a poly container for a high-speed stirrer in a room adjusted to a dew point of -30°C. The slurry was then stirred with a spatula to check its gelation state, which was evaluated according to the following criteria. ○: The slurry was fluid, and no solidified material was observed. △: The slurry was fluid but solidified within 1 hour. ×: The slurry had already gelled when the container was opened.

[0063] (4) Printability of slurry composition For the slurry compositions that showed fluidity in "(3) Gelation of Slurry Composition," an applicator was used to coat a Teflon® sheet fixed on a glass plate in a dry room with a dew point of -30°C, and the resulting inorganic powder sheet was dried for 30 minutes in a forced-air oven set to 120°C. The sheet was then evaluated according to the following criteria. If the printability is excellent, a uniform sheet can be produced, and it can be said that a high-performance all-solid-state battery can be manufactured. ○: A sheet with a smooth and dense coating surface was produced. △: Problems such as smudging, bleed, and blurring were observed. ×: It did not exhibit fluidity and could not be printed. Or, it had poor fluidity and could not be coated with a uniform thickness.

[0064] (5) Handling of inorganic powder sheets The Teflon® sheet was peeled off the inorganic powder sheet obtained in "(4) Printability of Slurry Composition," and the inorganic powder sheet was placed on a ceramic plate for firing using tweezers. The condition of the sheet was visually inspected and evaluated according to the following criteria. If the sheet has good handling properties, it is easier to fabricate electrodes and thus easier to manufacture batteries. ○: No cracks or fractures were observed in the test specimen. △: Some cracks were observed, but the sheet shape was maintained, making it possible to conduct firing tests. ×: The slurry did not exhibit fluidity, making it impossible to produce an inorganic powder sheet. Alternatively, the sheet broke into small pieces and became pulverized.

[0065] (6) Sinterability of inorganic powder sheets In "(5) Handling of Inorganic Powder Sheets," inorganic powder sheets placed on ceramic plates were fired in an electric furnace. The firing conditions were degreasing at 600°C for 30 minutes, followed by firing at 1000°C for 5 hours. The cross-section of the sheet after firing was observed with an electron microscope and evaluated according to the following criteria. High sinterability indicates that a uniform sheet with fewer impurities can be produced, which can lead to the production of higher-performance all-solid-state batteries. ○: A dense inorganic powder sintered body was obtained, free from voids and firing residue (soot). △: Some firing residue (soot) was observed. ×: Inorganic powder sheets could not be fabricated. Alternatively, voids or cavities due to calcination residue (soot) were observed in some places.

[0066] [Table 1]

[0067] [Table 2]

[0068] In Comparative Examples 1 and 2, gelation and rapid thickening occurred, making it impossible to produce good sheets. In Comparative Example 3, no decrease in fluidity due to gelation was observed, but the printed and dried sheets were finely cracked and could not maintain their sheet shape. Furthermore, in Comparative Example 4, although no decrease in fluidity due to gelation was observed, applicator marks remained during printing, repellency occurred in the film, and voids and air pockets formed after sintering. When these slurry compositions were used, it was not possible to densely laminate sheets, and high-performance all-solid-state batteries could not be produced. On the other hand, in Examples 1 to 6, even when containing a large amount of alkali metal, gelation of the slurry composition was suppressed, and printability was good. In addition, although some cracking was observed in some areas, there were no voids or soot after sintering, and dense sheets could be produced. When such slurry compositions are used, sheets can be densely laminated, and it can be said that higher-performance all-solid-state batteries can be produced. [Industrial applicability]

[0069] According to the present invention, even when the slurry contains an inorganic powder containing an alkali metal, gelation of the slurry can be suppressed, and it also exhibits excellent sinterability, enabling the production of a low-residue inorganic powder sheet and providing a slurry composition for manufacturing high-performance all-solid-state batteries. Furthermore, a method for manufacturing an all-solid-state battery using this slurry composition can be provided.

Claims

1. A slurry composition for producing an all-solid-state battery, wherein the binder resin is removed by firing an inorganic powder sheet, which has been coated onto a support film that has been subjected to a single-sided release treatment, at a degreasing temperature of 600°C or lower, It contains an organic solvent, a binder resin, and an inorganic powder containing an alkali metal. The organic solvent is at least one selected from the group consisting of aromatic compounds, aliphatic hydrocarbons, and alicyclic hydrocarbons. The binder resin is at least one selected from the group consisting of styrene homopolymers and propylene homopolymers. A slurry composition for manufacturing solid batteries, wherein the MFR value of the binder resin is 10 g / 10 min or less.

2. A slurry composition for manufacturing solid batteries according to claim 1, wherein the pH is 11 or higher.

3. The slurry composition for manufacturing solid batteries according to claim 1 or 2, wherein the inorganic powder contains lithium.

4. A method for manufacturing an all-solid-state battery, comprising the steps of: obtaining an inorganic powder sheet using a slurry composition for manufacturing solid-state batteries according to any one of claims 1 to 3; and firing the inorganic powder sheet at a temperature of 600°C or lower.

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