Inorganic solid electrolyte dispersion and method for producing inorganic solid electrolyte dispersion

Abstract

To provide an inorganic solid electrolyte dispersion in which an inorganic solid electrolyte in an inorganic solid electrolyte dispersion has uniform dispersibility and also has long-term dispersion retainability.SOLUTION: There is provided an inorganic solid electrolyte dispersion in which an inorganic solid electrolyte powder used as a solid electrolyte in an all-solid-state battery is dispersed in a solvent, wherein the median diameter (D50) of the inorganic solid electrolyte powder obtained from a volume-based particle size distribution measured by a laser diffraction particle size distribution method is 6.5 μm or less and the standard deviation (σ50) based on the medium diameter (D50) is 3.5 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an inorganic solid electrolyte dispersion and a method for producing the inorganic solid electrolyte dispersion. [Background technology]

[0002] Conventionally, batteries such as lithium-ion batteries (batteries using liquid electrolyte materials) have a structure in which the positive electrode material (Ni, Mn, Co, LiCoO2, etc.) and the negative electrode material (graphite, etc.) are separated by a separator (porous resin), with a liquid binder (polymer material) sandwiched in the gap. To date, there has been intensive research into improvements to the positive electrode material, negative electrode material, separator, and binder themselves, as well as improvements to the battery packaging method.

[0003] In recent years, efforts have been made to use inorganic solid electrolytes instead of liquid binders (electrolyte materials) in liquid electrolyte materials, which require a liquid. This eliminates the need for separators, increases the degree of freedom for charge movement between the positive and negative electrode materials to generate electricity, and improves current output efficiency. Batteries that use positive and negative electrode materials and inorganic solid electrolytes are called all-solid-state batteries because they are all composed of solids. Oxide-based solid electrolytes and sulfide-based solid electrolytes are being considered as inorganic solid electrolytes for use in all-solid-state batteries.

[0004] For example, Patent Document 1 discloses a solid electrolyte composition that combines an inorganic solid electrolyte with acid-modified cellulose nanofibers. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6714172 Summary of the Invention [Problem to be solved by the invention]

[0006] While there have been many studies aimed at improving battery characteristics by making various improvements and modifications to solid electrolyte materials, as in Patent Document 1, there have not yet been many studies on solid electrolyte materials that can improve productivity in manufacturing all-solid-state batteries.

[0007] For example, even if a solid electrolyte material is expected to improve battery characteristics, if the dispersibility of the solid electrolyte material is not uniform in a coating liquid (inorganic solid electrolyte dispersion) for coating the electrode material or the like, or if the dispersibility decreases during storage for a certain period of time from immediately after preparation of the coating liquid until coating, this may reduce productivity in manufacturing all-solid-state batteries.

[0008] Therefore, an object of the present invention is to provide an inorganic solid electrolyte dispersion in which the inorganic solid electrolyte is uniformly dispersed and can maintain its dispersion for a long period of time, and a method for producing the same. [Means for solving the problem]

[0009] As a result of intensive research to solve the above problems, the present inventors have come up with the following invention and found that the above problems can be solved.

[0010] [1] An inorganic solid electrolyte dispersion obtained by dispersing an inorganic solid electrolyte powder used for a solid electrolyte of an all-solid-state battery in a solvent, wherein the inorganic solid electrolyte powder has a median diameter (D50) of 6.5 μm or less, as obtained from a volume-based particle size distribution measured by a laser diffraction particle size distribution measurement method, and a standard deviation (σ50) based on the median diameter (D50) of 3.5 μm or less. [2] The inorganic solid electrolyte dispersion according to [1], wherein the content of zirconia in the inorganic solid electrolyte dispersion is 23 mass % or less. [3] A method for producing an inorganic solid electrolyte dispersion, comprising producing the inorganic solid electrolyte dispersion according to [1] or [2] using a wet atomization device. [4] The method for producing an inorganic solid electrolyte dispersion according to [3], wherein the chamber and nozzle of the wet atomization device are made of ceramic. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an inorganic solid electrolyte dispersion in which the inorganic solid electrolyte is uniformly dispersed and can maintain its dispersion for a long period of time, and a method for producing the same. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a wet atomization device according to an embodiment of the present invention. [Figure 2] These are electron microscope photographs, where (a) is an electron microscope photograph of an untreated inorganic solid electrolyte dispersion (oxide-based), and (b) is an electron microscope photograph of an inorganic solid electrolyte dispersion (oxide-based) that had been processed 50 times with an atomizer. [Figure 3] Photographs showing the precipitation state: (a) is a photograph showing the precipitation state of an untreated inorganic solid electrolyte dispersion (oxide-based); (b) is a photograph of an inorganic solid electrolyte dispersion (oxide-based) after 20 passes through a micronizer and 48 hours have passed. [Figure 4] These are electron microscope photographs, where (a) is an electron microscope photograph of an untreated inorganic solid electrolyte dispersion (sulfide-based), and (b) is an electron microscope photograph of an inorganic solid electrolyte dispersion (sulfide-based) after 20 passes through a microparticle processing device. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described.

[0014] [Inorganic solid electrolyte dispersion] The inorganic solid electrolyte dispersion according to this embodiment is prepared by dispersing an inorganic solid electrolyte powder used as a solid electrolyte material for an all-solid-state battery in a solvent.

[0015] (Inorganic solid electrolyte powder) The inorganic solid electrolyte in the inorganic solid electrolyte powder according to this embodiment refers to an inorganic solid electrolyte, and a solid electrolyte refers to a solid electrolyte capable of transferring ions therein. Because it does not contain an organic substance as the primary ion-conducting material, it is clearly distinguished from organic solid electrolytes (polymer electrolytes such as polyethylene oxide (PEO) and organic electrolyte salts such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)). Furthermore, because inorganic solid electrolytes are solid in the steady state, they are typically not dissociated or liberated into cations and anions. In this respect, they are also clearly distinguished from electrolytic solutions or inorganic electrolyte salts (e.g., LiPF, LiBF, LiFSI, LiCl) in which cations and anions are dissociated or liberated within a polymer. The inorganic solid electrolyte is not particularly limited as long as it has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, but generally does not have electronic conductivity.

[0016] The inorganic solid electrolyte powder has a median diameter (D50) obtained from a volume-based particle size distribution measured by a laser diffraction particle size distribution measurement method of 6.5 μm or less, preferably 5 μm or less, more preferably 3.5 μm or less, and even more preferably 2.5 μm or less, and preferably 2 μm or less, and more preferably 1 μm or less. In practice, the median diameter (D50) is 0.1 μm or more.

[0017] Furthermore, the standard deviation (σ50) based on the median diameter (D50) is 3.5 μm or less, preferably 2 μm or less, with the lower limit being practically about 0.1 μm. If the standard deviation (σ50) exceeds 3.5 μm, it may become difficult to obtain uniform dispersion, and the long-term dispersion retention may be easily reduced.

[0018] Inorganic solid electrolytes include (i) oxide-based inorganic solid electrolytes and (ii) sulfide-based inorganic solid electrolytes as typical examples. In terms of high ionic conductivity and ease of interfacial bonding between particles, sulfide-based inorganic solid electrolytes are preferred. Also, in terms of low cost, oxide-based solid electrolytes are preferred. When the all-solid-state battery according to this embodiment is an all-solid-state lithium-ion secondary battery, the inorganic solid electrolyte preferably has ionic conductivity for lithium ions.

[0019] (i) Oxide-based inorganic solid electrolyte The oxide-based inorganic solid electrolyte preferably contains oxygen atoms (O), has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and has electron insulation. The oxide-based inorganic solid electrolyte preferably has an ionic conductivity of 1×10 -6 S / cm or more, more preferably 5×10 -6 S / cm or more, and particularly preferably 1×10 -5 S / cm or more. The upper limit is not particularly limited, but it is practical to be 1×10 -1 S / cm or less.

[0020] Specific compound examples include, for example, Li xa La ya TiO3 [xa = 0.3 to 0.7, ya = 0.3 to 0.7] (LLT), Li xb La yb Zr zb Mbb mb O nb (Mbb is at least one element of Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, Sn; xb satisfies 5 ≤ xb ≤ 10, yb satisfies 1 ≤ yb ≤ 4, zb satisfies 1 ≤ zb ≤ 4, mb satisfies 0 ≤ mb ≤ 2, and nb satisfies 5 ≤ nb ≤ 20.) Li xc B yc Mcc zc O nc (Mcc is at least one element of C, S, Al, Si, Ga, Ge, In, Sn; xc satisfies 0 < xc ≤ 5, yc satisfies 0 < yc ≤ 1, zc satisfies 0 < zc ≤ 1, and nc satisfies 0 < nc ≤ 6.) Lixd (Al,Ga) yd (Ti,Ge) zd Si ad P md O nd (where 1≦xd≦3, 0≦yd≦1, 0≦zd≦2, 0≦ad≦1, 1≦md≦7, 3≦nd≦13), Li (3-2xe) Mee xe DeeO (xe represents a number of 0 or more and 0.1 or less, Mee represents a divalent metal atom, and Dee represents a halogen atom or a combination of two or more halogen atoms), Li xf Si yf O zf (1≦xf≦5, 0 <yf≦3、1≦zf≦10)、Li xg S yg O zg (1≦xg≦3, 0 <yg≦2、1≦zg≦10)、Li3BO3-Li2SO4、Li2O-B2O3-P2O5、Li2O-SiO2、Li6BaLa2Ta2O 12 , LiPO (4-3 / 2w) N w (w<1), Li with LISICON (Lithium superionic conductor) type crystal structure 3.5 Zn 0.25 GeO4, La with perovskite crystal structure 0.55 Li 0.35 TiO3, LiTi2P3O with NASICON (sodium superionic conductor) type crystal structure 12 , Li 1+xh+yh (Al,Ga) xh (Ti,Ge) 2-xh Si yh P 3-yh O 12 (where 0≦xh≦1, 0≦yh≦1), Li7La3Zr2O with a garnet-type crystal structure 12 (LLZ), Li 6.25 La3Zr2Al 0.25 O 12(LLZO), etc. Also desirable are phosphorus compounds containing Li, P, and O. Examples include lithium phosphate (Li3PO4), LiPON, LiPOD1 (wherein D1 is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc.), etc. Also preferably used are LiAlON (wherein A1 is at least one selected from Si, B, Ge, Al, C, Ga, etc.).

[0021] (ii) Sulfide-based inorganic solid electrolyte The sulfide-based inorganic solid electrolyte is preferably a compound that contains sulfur atoms (S), has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation. The sulfide-based inorganic solid electrolyte preferably contains at least Li, S, and P as elements and has lithium ion conductivity, but may contain elements other than Li, S, and P depending on the purpose or case.

[0022] An example of the sulfide-based inorganic solid electrolyte is a lithium ion conductive sulfide-based inorganic solid electrolyte that satisfies the composition represented by the following formula (1).

[0023] L a1 M b1 P c1 S d1 A e1 ...Equation (1) In the formula, L represents an element selected from Li, Na, and K, and Li is preferred. M represents an element selected from B, Zn, Sn, Si, Cu, Ga, Sb, Al, and Ge. A represents an element selected from I, Br, Cl, and F. a1 to e1 represent the composition ratio of each element, and a1:b1:c1:d1:e1 satisfies the ratio 1-12:0-5:1:2-12:0-10. a1 is preferably 1-9, and more preferably 1.5-7.5. b1 is preferably 0-3, and more preferably 0-1. d1 is preferably 2.5-10, and more preferably 3.0-8.5. e1 is preferably 0-5, and more preferably 0-3.

[0024] The composition ratio of each element can be controlled by adjusting the compounding ratio of raw material compounds when producing the sulfide-based inorganic solid electrolyte, as described below.

[0025] The sulfide-based inorganic solid electrolyte may be amorphous (glass) or crystallized (glass-ceramic), or may be only partially crystallized. For example, a Li-PS-based glass containing Li, P, and S, or a Li-PS-based glass-ceramic containing Li, P, and S may be used. The sulfide-based inorganic solid electrolyte can be produced by reacting at least two or more raw materials selected from the group consisting of lithium sulfide (LiS), phosphorus sulfide (e.g., diphosphorus pentasulfide (PS)), elemental phosphorus, elemental sulfur, sodium sulfide, hydrogen sulfide, lithium halides (e.g., LiI, LiBr, LiCl), and sulfides of the elements represented by M above (e.g., SiS, SnS, GeS).

[0026] In the Li-PS glass and Li-PS glass ceramics, the ratio of Li2S to P2S5 is preferably 60:40 to 90:10, more preferably 68:32 to 78:22, in terms of the molar ratio of Li2S:P2S5. By setting the ratio of Li2S to P2S5 within this range, the lithium ion conductivity can be increased. Specifically, the lithium ion conductivity is preferably 1×10 -4 S / cm or more, preferably 1×10 -3 S / cm or more. There is no upper limit, but it is 1×10 -1 It is practical to have a value of S / cm or less.

[0027] Specific examples of sulfide-based inorganic solid electrolytes, including combinations of raw materials, are shown below: Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-H2S, Li2S-P2S5-H2S-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, and Li2S-P2S5-Al2S3 , Li2S-GeS2, Li2S-GeS2-ZnS, Li2S-Ga2S3, Li2S-GeS2-Ga2S3, Li2S-GeS2-P2S5, Li2S-GeS2-Sb2S5, Li2S-GeS2-Al2S3, Li2S-SiS2, L i2S-Al2S3, Li2S-SiS2-Al2S3, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4, Li 10 GeP2S 12 , Li 10 SnP2S 12 However, the mixing ratio of each raw material is not important. As a method for synthesizing a sulfide-based inorganic solid electrolyte material using such a raw material composition, for example, an amorphization method can be mentioned. Examples of the amorphization method include a mechanical milling method, a solution method, and a melt quenching method. This is because processing at room temperature becomes possible, and the manufacturing process can be simplified.

[0028] (solvent) In the inorganic solid electrolyte material dispersion, the inorganic solid electrolyte powder is dispersed in a solvent. The solvent preferably contains a non-aqueous dispersion medium. When the inorganic solid electrolyte material dispersion contains a non-aqueous dispersion medium, decomposition and deterioration of the inorganic solid electrolyte particles can be prevented, and surface oxidation of the particles can be suppressed. Furthermore, when biomass nanofibers are mixed with the inorganic solid electrolyte particles, they are more likely to be mixed uniformly.

[0029] In this embodiment, the phrase "the solvent in the inorganic solid electrolyte material dispersion contains a non-aqueous dispersion medium" includes not only a form in which the solvent contains only a non-aqueous dispersion medium (no aqueous dispersion medium), but also a form in which the solvent contains an aqueous dispersion medium, provided that in a form in which the solvent contains an aqueous dispersion medium, the water content in the solvent does not exceed 50 ppm.

[0030] The non-aqueous dispersion medium generally refers to a non-aqueous dispersion medium other than water, and includes a non-aqueous dispersion medium containing water (a mixed dispersion of water and a non-aqueous dispersion medium) as long as the water content in the solvent is 50 ppm or less.

[0031] Such a non-aqueous dispersion medium may be any medium capable of dispersing each component contained in the inorganic solid electrolyte material dispersion, and examples thereof include various organic solvents. Examples of organic solvents that can be used as the non-aqueous dispersion medium include alcohol compound solvents, ether compound solvents, amide compound solvents, amino compound solvents, ketone compound solvents, aromatic compound solvents, aliphatic compound solvents, nitrile compound solvents, and ester compound solvents. Among these, amide compound solvents, hydrocarbon compound solvents (aromatic compound solvents and aliphatic compound solvents), ether compound solvents, ketone compound solvents, and ester compound solvents are preferred.

[0032] Examples of alcohol compound solvents include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 2-butanol, ethylene glycol, propylene glycol, 1,6-hexanediol, cyclohexanediol, 1,3-butanediol, and 1,4-butanediol.

[0033] Examples of ether compound solvents include alkylene glycols (triethylene glycol, etc.), alkylene glycol monoalkyl ethers (ethylene glycol monomethyl ether, etc.), alkylene glycol dialkyl ethers (ethylene glycol dimethyl ether, etc.), dialkyl ethers (diisopropyl ether, dibutyl ether, etc.), and cyclic ethers (tetrahydrofuran, dioxane (including 1,2-, 1,3-, and 1,4-isomers), etc.).

[0034] Examples of amide compound solvents include N,N-dimethylformamide, N-methyl-2-pyrrolidone, 2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, 2-pyrrolidinone, ε-caprolactam, formamide, N-methylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpropanamide, and hexamethylphosphoric triamide.

[0035] Examples of the amino compound solvent include triethylamine, diisopropylethylamine, and tributylamine. Examples of ketone compound solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, cycloheptanone, dipropyl ketone, dibutyl ketone, diisopropyl ketone, diisobutyl ketone, isobutyl propyl ketone, sec-butyl propyl ketone, pentyl propyl ketone, and butyl propyl ketone.

[0036] Examples of aromatic compound solvents include benzene, toluene, and xylene. Examples of the aliphatic compound solvent include hexane, heptane, octane, decane, cyclohexane, cyclooctane, paraffin, gasoline, naphtha, kerosene, and diesel. Examples of nitrile compound solvents include acetonitrile, propylonitrile, and isobutyronitrile. Examples of ester compound solvents include ethyl acetate, butyl acetate, propyl acetate, propyl butyrate, isopropyl butyrate, butyl butyrate, isobutyl butyrate, butyl pentanoate, ethyl isobutyrate, propyl isobutyrate, isopropyl isobutyrate, isobutyl isobutyrate, propyl pivalate, isopropyl pivalate, butyl pivalate, and isobutyl pivalate.

[0037] The non-aqueous dispersion medium contained in the solvent may be one type or two or more types, and preferably two or more types. When the solvent contains two or more non-aqueous dispersion media, a combination of two or more non-aqueous dispersion media selected from the group consisting of hydrocarbon compound solvents, ether compound solvents, ketone compound solvents and ester compound solvents is preferred.

[0038] In consideration of productivity, the content of the inorganic solid electrolyte powder in the inorganic solid electrolyte material dispersion is preferably 1 to 20 mass %, more preferably 1 to 15 mass %, and even more preferably 1 to 10 mass %.

[0039] Biomass nanofibers can also be added to the inorganic solid electrolyte material dispersion. Examples of biomass nanofibers include cellulose nanofibers, chitin nanofibers, chitosan nanofibers, and silk nanofibers. The average fiber diameter of the biomass nanofibers is preferably 10 to 100 nm, more preferably 10 to 40 nm, and even more preferably 10 to 25 nm. The average length of the biomass nanofibers is preferably 0.5 to 100 μm, and more preferably 1 to 30 μm.

[0040] [Method for producing inorganic solid electrolyte dispersion] The method for producing an inorganic solid electrolyte dispersion according to this embodiment is a method for producing the above-described inorganic solid electrolyte aqueous dispersion of the present invention using a wet atomization apparatus.

[0041] (Wet type atomization equipment) FIG. 1 is a schematic diagram showing the general configuration of a wet atomization device used in this embodiment. As shown in FIG. 1, the wet atomization apparatus 1 has a raw material tank 2, a liquid supply pump 3, a pressure intensifier 4, a high-pressure filter 5, a chamber 6, and a heat exchanger 7. The raw material tank 2 stores a slurry of inorganic solid electrolyte powder. The liquid supply pump 3 supplies the inorganic solid electrolyte powder from the raw material tank 2 to the pressure intensifier 4. The pressure intensifier 4 pressurizes the inorganic solid electrolyte powder supplied from the liquid supply pump 3. The high-pressure filter 5 filters out coarse particles from the pressurized inorganic solid electrolyte powder. The chamber 6 performs atomization by high-pressure spraying of the inorganic solid electrolyte powder from a nozzle (not shown) at a spray pressure of 100 to 245 MPa and a spray velocity of 440 to 700 m / s.

[0042] Furthermore, the wet atomization apparatus 1 for processing inorganic solid electrolyte powder requires higher airtightness than when processing ordinary raw materials. When processing an oxide-based solid electrolyte material dispersion, for example, airtightness is required to prevent oxidation of the inorganic solid electrolyte powder. Furthermore, when processing a sulfide-based solid electrolyte dispersion, for example, airtightness is required to prevent the release of highly toxic gases to the outside even if they are generated by the inorganic solid electrolyte powder (oxide-based) reacting with moisture or water. Furthermore, when processing inorganic solid electrolyte powder (sulfide-based), there are cases where internal gas management is required. Therefore, the wet atomization apparatus 1 is required to have a structure that circulates the internal gas while ensuring airtightness.

[0043] The wet atomization apparatus 1 of this embodiment is ensured to be airtight by covering it with a glove box or the like. Furthermore, the wet atomization apparatus 1 can be provided with an inert gas supply unit 8a and a gas circulation purification unit 9, which can ensure the safety of the gas inside the glove box. An oxygen concentration meter 14 and a moisture concentration meter 15 may be provided to adjust the ventilation and amount of inert gas or the like.

[0044] Furthermore, it is preferable to use ceramics for the chamber 6 and the nozzle (not shown) rather than conventional metals such as stainless steel. This provides superior abrasion resistance and solvent resistance compared to metals such as stainless steel, and minimizes contamination. As a result, a dispersion containing zirconia of 23 mass% or less can be obtained. The chamber 6 may be a system in which inorganic solid electrolyte powder is atomized by colliding it from a nozzle against a ball, or a system in which inorganic solid electrolyte powder is atomized by colliding it with other inorganic solid electrolyte powders from two or more nozzles.

[0045] (Method of manufacturing inorganic solid electrolyte dispersion using a wet atomization device) The method for producing an inorganic solid electrolyte dispersion using a wet atomization device will be described in detail below.

[0046] In a wet-type atomization apparatus 1 partitioned by a glove box or the like, a mixture of inorganic solid electrolyte powder and a solvent is charged into a raw material tank 2. Next, the inorganic solid electrolyte powder in the raw material tank 2 is supplied to the pressure boosting chamber of the pressure booster 4 via the liquid supply pump 3. The supplied inorganic solid electrolyte powder is pressurized by the pressure booster 4. The pressurized inorganic solid electrolyte powder passes through a high-pressure filter 5, and is then supplied to a chamber 6 and sprayed. The atomization treatment can be repeated as many times as necessary, for example, about 1 to 50 times, preferably about 1 to 40 times, more preferably about 1 to 30 times, even more preferably about 1 to 20 times, and particularly preferably about 1 to 10 times.

[0047] [Manufacturing method for all-solid-state batteries] The method for producing an all-solid-state battery using the inorganic solid electrolyte dispersion of this embodiment is not particularly limited as long as it includes a step of forming a solid electrolyte-containing layer using the inorganic solid electrolyte dispersion. The solid electrolyte-containing layer can be formed, for example, by applying the dispersion to a substrate to form a coating layer, and then drying the coating layer.

[0048] In the inorganic solid electrolyte dispersion of this embodiment, the inorganic solid electrolyte particles are uniformly dispersed in the dispersion, so that the concentration of the inorganic solid electrolyte particles is less likely to be uneven during coating. Furthermore, the dispersion maintains its dispersion for a long period of time, so that re-dispersion is not required even if a certain amount of time has passed between the preparation of the dispersion and coating. As a result, productivity in manufacturing all-solid-state batteries can be improved.

[0049] Examples of substrates used for coating include current collectors and transfer sheets. Examples of transfer sheets include resin sheets such as fluorine-based resin sheets and metal sheets. Examples of coating methods include common methods such as doctor blade coating, die coating, gravure coating, spray coating, electrostatic coating, and bar coating.

[0050] The drying temperature is, for example, 40°C or higher, and preferably 60 to 220°C. Examples of methods for drying the coating layer include common methods such as warm air / hot air drying, infrared drying, reduced pressure drying, and dielectric heating drying. Examples of drying atmospheres include inert gas atmospheres such as Ar gas atmosphere and nitrogen gas atmosphere. Furthermore, drying may be carried out under atmospheric pressure or reduced pressure. [Example]

[0051] (Experimental Example A: Comparative Examples 1 and 2, Examples 1 to 5) The organic solvent (N-methyl-2-pyrrolidone) is used as the solvent, and inorganic solid electrolyte particles (oxide system) LLZO(Li 6.25 La3Zr2Al 0.25 O 12 ) were mixed to a concentration of 5% by mass to prepare a 50 ml mixed solution. This mixed solution was subjected to wet atomization treatment using a wet atomization apparatus (manufactured by Sugino Machine Co., Ltd., device name "Starburst", except that the chamber and nozzle were made of ceramic (zirconia)) at a pressure of 200 MPa with a nozzle of 0.12 mm for the number of passes shown in Table 1, to prepare an inorganic solid electrolyte aqueous dispersion. For comparison, a mixed solution (number of passes: 0) that was not subjected to wet atomization treatment was also prepared.

[0052] Next, the particle size distribution of each dispersion and mixed liquid was measured, and the median diameter (D50) and its standard deviation (σ50) were calculated. The measuring instrument used was the LA-960 laser diffraction / scattering particle size distribution analyzer manufactured by Horiba, Ltd. The results are shown in Table 1. The dispersion state (uniform dispersion) of the inorganic solid electrolyte particles in each dispersion and the mixed solution was observed immediately after the wet atomization treatment. Furthermore, the dispersion state (long-term dispersion retention) was also observed 48 hours after the wet atomization treatment. The results are shown in Table 1. The evaluation criteria for each observation were as follows: Uniform dispersion and long-term dispersion retention A: Inorganic solid electrolyte particles are dispersed and the whole is cloudy B: The center is cloudy due to the dispersion of inorganic solid electrolyte particles, but the top is slightly transparent or there is some solid matter accumulated at the bottom, and the dispersion is not as good as A. C: The inorganic solid electrolyte particles are separated into a dispersed layer and a transparent layer where they are not dispersed, and are not dispersed as well as in B.

[0053] [Table 1]

[0054] Here, electron microscope photographs were taken (at the same magnification) of a mixed solution that was not subjected to wet atomization treatment (Comparative Example 1) and an inorganic solid electrolyte dispersion that was subjected to 50 passes of wet atomization treatment (Example 5). The electron microscope used was an S-2380N electron microscope manufactured by Hitachi, Ltd. In the micrograph of Comparative Example 1, as shown in Figure 2(a), coarse particles were partially aggregated. In the micrograph of Example 5, as shown in Figure 2(b), fine particles were uniformly dispersed.

[0055] Furthermore, as shown in FIG. 3, a photograph showing the dispersion state of Comparative Example 1 (FIG. 3(a)) and a photograph showing the dispersion state of Example 2 after 48 hours have elapsed (FIG. 3(b)) show that in Example 2, dispersibility was maintained even after 48 hours have elapsed.

[0056] (Experimental Example B: Comparative Example 3, Examples 6 to 10) Inorganic solid electrolyte aqueous dispersions were prepared in the same manner as in Experimental Example A, except that the pressure in the wet atomization treatment was set to 220 Pa. For each of the prepared inorganic solid electrolyte aqueous dispersions, the particle size distribution was measured in the same manner as in Experimental Example A, and the median diameter (D50) and its standard deviation (σ50) were determined. In addition, the uniform dispersion and long-term dispersion retention were evaluated. The results are shown in Table 2.

[0057] [Table 2]

[0058] (Experimental Example C: Comparative Examples 4 and 5, Examples 11 to 15) The organic solvent (butyl butyrate) is used as the solvent, and inorganic solid electrolyte particles (sulfide-based) are mixed with LSPS (Li 10 SnP2S 12 ) were mixed to a concentration of 5% by mass to prepare a 20 ml mixed solution. This mixed solution was subjected to wet atomization treatment using a wet atomization device (manufactured by Sugino Machine Co., Ltd., device name "Starburst") at a pressure of 200 MPa with a nozzle of 0.12 mm for the number of passes shown in Table 3, to prepare an inorganic solid electrolyte aqueous dispersion. For comparison, a mixed solution (number of passes: 0) that was not subjected to wet atomization treatment was also prepared.

[0059] The particle size distribution of each of the mixed solutions and the prepared inorganic solid electrolyte aqueous dispersions was measured in the same manner as in Experimental Example A, and the median diameter (D50) and its standard deviation (σ50) were determined. Furthermore, the uniform dispersion and long-term dispersion retention were evaluated. The results are shown in Table 3.

[0060] [Table 3]

[0061] Here, electron microscope photographs were taken (at the same magnification) of a mixed solution that was not subjected to wet atomization treatment (Comparative Example 3) and an inorganic solid electrolyte dispersion that was subjected to 20 passes of wet atomization treatment (Example 12). The electron microscope used was an S-2380N electron microscope manufactured by Hitachi, Ltd. In the micrograph of Comparative Example 3, as shown in Figure 4(a), coarse particles were partially aggregated. In the micrograph of Example 5, as shown in Figure 4(b), fine particles were uniformly dispersed.

[0062] From the above, it can be seen that the inorganic solid electrolyte dispersion of this example has improved performance in terms of non-aggregation (uniform dispersion) and dispersion retention.

[0063] (Verification of the amount of contamination in inorganic solid electrolyte dispersions) The wet atomization equipment uses a ceramic (zirconia) chamber and nozzle, and the amount of zirconia component (Zr) before and after treatment was verified. The amount of ceramic component (Zr) in the inorganic solid electrolyte dispersion of Example 5 and the mixed solution of Comparative Example 1 was measured using an inductively coupled plasma optical emission spectrometer. The inductively coupled plasma optical emission spectrometer used was an ICP-OES 5110 model manufactured by Algilent. As a result, the amount of zirconia in the mixed solution of Comparative Example 1 was 20 mass %, while the amount of zirconia in Example 5 was 23 mass %. Considering measurement errors, these zirconia amounts show that contamination was minimized.

[0064] As described above, the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be modified appropriately within the scope of the gist of the invention. [Explanation of symbols]

[0065] 1 Wet atomization device 2 Raw material tank 3. Liquid supply pump 4. Booster 5 High-pressure filter 6 chambers 7 Heat exchanger 8 Inert gas supply source 9 Gas Circulation and Purification Section 14 Oxygen concentration meter 15 Moisture concentration meter

Claims

1. An inorganic solid electrolyte dispersion obtained by dispersing an inorganic solid electrolyte powder used for a solid electrolyte of an all-solid-state battery in a solvent, an inorganic solid electrolyte dispersion, wherein the inorganic solid electrolyte powder has a median diameter (D50) of 0.75 μm or more and 1.51 μm or less, the standard deviation (σ50) based on the median diameter (D50) being 3.5 μm or less, and the content of the inorganic solid electrolyte powder in the inorganic solid electrolyte material dispersion is 1 to 20 mass %.

2. 2. The inorganic solid electrolyte dispersion according to claim 1, wherein the content of zirconia in the inorganic solid electrolyte dispersion is 23 mass % or less.

3. A method for producing an inorganic solid electrolyte dispersion, comprising producing the inorganic solid electrolyte dispersion according to claim 1 or 2 using a wet atomization device.

4. 4. The method for producing an inorganic solid electrolyte dispersion according to claim 3, wherein the chamber and nozzle of the wet atomization device are made of ceramic.

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