Method for producing sulfide solid electrolyte having argyrodite crystal structure

Abstract

This method for producing a sulfide solid electrolyte having an argyrodite crystal structure includes: mixing a raw material-containing substance in a solvent to obtain an intermediate-containing substance; drying the intermediate-containing substance through fluidized drying using medium particles as media to obtain an intermediate; and firing the intermediate.

Description

Method for producing sulfide solid electrolyte having argyrodite-type crystal structure

[0001] The present invention relates to a method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure.

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as their power sources has become increasingly important. Among these batteries, lithium-ion batteries have attracted attention due to their high energy density.

[0003] Currently available lithium-ion batteries use electrolytes containing flammable organic solvents, which necessitates the installation of safety devices to suppress temperature rise during short circuits, as well as improvements in structure and materials to prevent short circuits. In particular, for automotive applications, there is a demand for higher capacity and higher output, making it increasingly important to consider safety aspects of batteries that use conventional electrolytes. In contrast, lithium-ion batteries, which use solid electrolytes and are completely solid-state, do not use flammable organic solvents within the battery, which allows for simplified safety devices and is thought to be superior in terms of manufacturing cost and productivity.

[0004] Sulfide solid electrolytes are known as solid electrolytes used in lithium-ion batteries. Various crystal structures of sulfide solid electrolytes are known, one of which is the argyrodite-type crystal structure. Sulfide solid electrolytes having the argyrodite-type crystal structure are known to have high stability and high ionic conductivity.

[0005] As a method for producing a sulfide solid electrolyte, for example, Patent Document 1 describes a method for producing a solid electrolyte having an argyrodite-type crystal structure, which includes heat-treating a raw material mixture containing lithium, sulfur, phosphorus, and a halogen in a solvent using a pressure-resistant container or under reflux, removing the solvent, and firing the treated product obtained by the heat treatment. Furthermore, Patent Document 2 describes a method for producing a solid electrolyte, which includes drying a slurry containing a solid electrolyte containing at least an alkali metal, sulfur atoms, and phosphorus atoms as constituent atoms or a precursor of the solid electrolyte and a polar solvent by fluidized drying using media particles as a medium.

[0006] JP 2020-95953 A International Publication No. 2021 / 230189 Pamphlet

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure in which the proportion of coarse particles is reduced after firing.

[0008] The method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to the present invention includes: mixing raw material inclusions in a solvent to obtain an intermediate inclusion; drying the intermediate inclusion by fluidized drying using media particles as a medium to obtain an intermediate; and calcining the intermediate.

[0009] According to the present invention, it is possible to provide a method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure in which the proportion of coarse particles is reduced after firing.

[0010] 1 is a flow diagram illustrating an example of a dryer used in the manufacturing method of the present embodiment; 2 is a volume-based particle size distribution of dried powders (intermediates) obtained in Examples and Comparative Examples; 3 is a volume-based particle size distribution of sulfide solid electrolytes obtained in Examples and Comparative Examples;

[0011] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. In this specification, the upper and lower limit values ​​of a range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​in the examples can also be used as the upper and lower limit values.

[0012] (Findings Obtained by the Inventors to Achieve the Present Invention) The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found the following, which has led to the completion of the present invention.

[0013] Sulfide solid electrolytes having a stable phase crystal structure, such as an argyrodite-type crystal structure, require heat treatment (calcination) at high temperatures (e.g., 400°C) during production. During this process, particles of the solid electrolyte raw material aggregate and sinter, resulting in the production of a solid electrolyte containing coarse particles with a particle size of 20 μm or more. Since both electrode materials and separator materials are applied as inks made from solid electrolyte powder during the battery manufacturing process, the presence of coarse particles in the solid electrolyte hinders uniform application. Therefore, it is necessary for the solid electrolyte to be free of coarse particles. One possible method for reducing the coarse particles contained in the solid electrolyte is to remove them from the solid electrolyte by classifying it using a classifier after calcination. However, the lower the proportion of coarse particles contained in the solid electrolyte obtained after calcination, the higher the yield of the separator material and electrode material that will be produced. Therefore, from the perspective of production costs, it is desirable to reduce the proportion of coarse particles contained in the solid electrolyte obtained after calcination.

[0014] The inventors have found that, although there is no difference in the volumetric particle size distribution of the dried powder (intermediate after drying) depending on the type of dryer used to dry an intermediate-containing material obtained by mixing raw material contents in a solvent, there is a difference in the volumetric particle size distribution of the calcined powder (solid electrolyte) obtained after calcining the dried powder. For example, as shown in the comparative example, the calcined powder (solid electrolyte) obtained after calcining the dried powder dried using a conical dryer has a broad volumetric particle size distribution, and the solid electrolyte contains a large proportion of coarse particles with a particle size of 20 μm or more. From this, it is inferred that the dried powder obtained by drying using a conical dryer is a powder that is prone to generating coarse particles during or after calcination. In contrast, the calcined powder (solid electrolyte) obtained after calcining the dried powder dried by fluidized drying using media particles as a medium has a sharp volumetric particle size distribution with one peak in the particle size range of 1 to 10 μm, and the solid electrolyte contains a small proportion of coarse particles with a particle size of 20 μm or more.

[0015] Patent Document 1 does not address the above-mentioned problem. Furthermore, in the manufacturing method of Patent Document 1, the raw material mixture is heat-treated in a solvent, and then the solvent is removed by drying under reduced pressure. Therefore, the proportion of coarse particles contained in the solid electrolyte obtained after firing is high, and there is room for improvement. In the manufacturing method of Patent Document 2, heat treatment (firing) at a high temperature (e.g., 400°C) is not performed, and therefore the problem of coarse particles due to firing is not addressed.

[0016] Based on the above investigations, the inventors have discovered that by mixing the raw material inclusions in a solvent and drying the intermediate inclusions by fluidized drying using media particles as a medium, a sulfide solid electrolyte having an argyrodite-type crystal structure with a reduced proportion of coarse particles can be obtained after firing.

[0017] (Regarding various forms of the present embodiment) A method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure (hereinafter also simply referred to as a "sulfide solid electrolyte") according to a first form of the present embodiment is a method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure, comprising: mixing raw material inclusions in a solvent to obtain an intermediate inclusion; drying the intermediate inclusions by fluidized drying using media particles as a medium to obtain an intermediate; and calcining the intermediate.

[0018] In the method for producing a sulfide solid electrolyte of this embodiment, the intermediate-containing material obtained by mixing the raw material-containing materials in a solvent may contain the solvent and the raw material-containing materials together with the intermediate. Here, the "intermediate" is a product of a reaction between the raw materials to be mixed, and is different from the raw materials contained in the raw material-containing material and the sulfide solid electrolyte having an argyrodite-type crystal structure obtained by the production method of this embodiment. As will be described later, the intermediate is a compound containing Li ３ P.S. ４ The presence of the "intermediate" can be confirmed, for example, by analyzing the "intermediate" by FT-IR (diffuse reflectance spectroscopy) and detecting a peak different from that of the raw material and the sulfide solid electrolyte, or by detecting a similar peak by powder X-ray diffraction (XRD) measurement.

[0019] In the method for producing a sulfide solid electrolyte of this embodiment, as described above, an intermediate inclusion obtained by mixing raw material inclusions in a solvent is dried by fluidized drying using media particles as a medium, whereby a sulfide solid electrolyte having an argyrodite-type crystal structure in which the proportion of coarse particles is reduced after firing can be obtained.

[0020] A method for producing a sulfide solid electrolyte according to a second aspect of the present embodiment is the same as the first aspect, except that the intermediate-containing material and the intermediate are not Li ３ P.S. ４ It includes:

[0021] In the method for producing a sulfide solid electrolyte of this embodiment, the intermediate-containing material and the intermediate are Li ３ P.S. ４By including the sulfide solid electrolyte, it becomes easier to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure, and it also becomes easier to obtain a sulfide solid electrolyte having a smaller particle size.

[0022] A method for producing a sulfide solid electrolyte according to a third aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to the first or second aspect above, except that the mixing is performed under heating. A method for producing a sulfide solid electrolyte according to a fourth aspect is the method for producing a sulfide solid electrolyte according to the third aspect above, except that the heating is performed under pressure. A method for producing a sulfide solid electrolyte according to a fifth aspect is the method for producing a sulfide solid electrolyte according to the third or fourth aspect above, except that the heating is performed using an autoclave.

[0023] In the method for producing a sulfide solid electrolyte of this embodiment, the mixing is carried out under heating, particularly under heating and pressure, particularly using an autoclave, so that the reaction between the raw materials contained in the raw material content proceeds quickly. For example, when lithium sulfide and phosphorus sulfide (diphosphorus pentasulfide) are used as raw materials, Li is contained in the intermediate content. ３ P.S. ４ is easily formed, and the sulfide solid electrolyte can be obtained more efficiently.

[0024] A sixth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the third to fifth aspects, wherein the heating is performed at a heating temperature of 150°C or higher and lower than 300°C.

[0025] In the method for producing a sulfide solid electrolyte of this embodiment, when the raw material contents are mixed in the solvent, heating is performed within the above temperature range. For example, when lithium sulfide and phosphorus sulfide (diphosphorus pentasulfide) are used as raw materials, Li is contained in the intermediate contents. ３ P.S. ４ is easily formed, and the sulfide solid electrolyte can be obtained more efficiently.

[0026] A seventh aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to sixth aspects, wherein the raw material contents contain, as constituent atoms, an alkali metal, a sulfur atom, a phosphorus atom, and a halogen atom.

[0027] In the method for producing a sulfide solid electrolyte of the present embodiment, the raw material inclusions contain the above-described constituent atoms, which makes it easier to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure and further improves ionic conductivity.

[0028] The method for producing a sulfide solid electrolyte according to an eighth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to seventh aspects, wherein the solvent is a hydrocarbon solvent.

[0029] In the method for producing a sulfide solid electrolyte of the present embodiment, by using a hydrocarbon solvent as the solvent, the proportion of coarse particles can be further reduced, and the sulfide solid electrolyte can be obtained more efficiently.

[0030] A ninth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to eighth aspects, wherein the fluidized drying is performed using a fluidized medium dryer having a mechanism for fluidizing the media particles with a gas.

[0031] In the method for producing a sulfide solid electrolyte of this embodiment, fluidized drying is performed using a medium fluidized dryer having a mechanism for fluidizing media particles with a gas, whereby the object to be dried is dried while being appropriately pulverized, which not only enables efficient drying but also makes it easier to obtain a sulfide solid electrolyte with a reduced proportion of coarse particles.

[0032] A tenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to ninth aspects, wherein the media particles are ceramic balls.

[0033] In the method for producing a sulfide solid electrolyte of this embodiment, by using ceramic balls as media particles, it is possible to further improve drying efficiency and fluidity, and also to further reduce the proportion of coarse particles.

[0034] The method for producing a sulfide solid electrolyte according to an eleventh aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to the ninth or tenth aspect, wherein the gas is an inert gas.

[0035] In the method for producing a sulfide solid electrolyte of the present embodiment, by using an inert gas as the gas for fluidizing the media particles, it is possible to suppress deterioration due to oxidation of the intermediate contained in the intermediate-containing material, and also to further reduce the proportion of coarse particles.

[0036] A method for producing a sulfide solid electrolyte according to a twelfth aspect of the present embodiment is any one of the ninth to eleventh aspects, wherein the gas is heated.

[0037] In the method for producing a sulfide solid electrolyte of the present embodiment, if the gas for fluidizing the media particles is heated, the intermediate-containing material can be dried more efficiently and the proportion of coarse particles can be further reduced.

[0038] A thirteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte of any one of the first to twelfth aspects, wherein the drying is performed in a circulating manner.

[0039] In the method for producing a sulfide solid electrolyte of the present embodiment, by performing fluidized drying using media particles in a circulating manner, the intermediate-containing material can be dried more efficiently and the proportion of coarse particles can be further reduced.

[0040] A fourteenth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to thirteenth aspects, wherein the firing is carried out at a heating temperature of 300°C or higher and 500°C or lower.

[0041] In the method for producing a sulfide solid electrolyte of this embodiment, by firing the intermediate within the above temperature range, a sulfide solid electrolyte having an argyrodite-type crystal structure is easily obtained.

[0042] (Sulfide Solid Electrolyte) In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state at 25° C. under a nitrogen atmosphere. The sulfide solid electrolyte in this embodiment is a sulfide solid electrolyte having an argyrodite-type crystal structure, and preferably contains an alkali metal, a sulfur atom, a phosphorus atom, and a halogen atom, more preferably contains a lithium atom as the alkali metal, and has ionic conductivity attributable to the lithium atom.

[0043] The term "sulfide solid electrolyte" includes crystalline sulfide solid electrolytes. In this specification, a crystalline sulfide solid electrolyte refers to a sulfide solid electrolyte in which a peak derived from a solid electrolyte is observed in an X-ray diffraction pattern in an X-ray diffraction measurement, regardless of whether or not a peak derived from a raw material of the sulfide solid electrolyte is present. In other words, a crystalline sulfide solid electrolyte includes a crystal structure derived from a solid electrolyte, and a part of the crystal structure may be derived from the solid electrolyte, or the entire crystal structure may be derived from the solid electrolyte.

[0044] The method for producing the sulfide solid electrolyte of this embodiment will be described in more detail below in accordance with the above aspects.

[0045] [Method for Producing a Sulfide Solid Electrolyte Having an Argyrodite-Type Crystal Structure] The method for producing a sulfide solid electrolyte of the present embodiment is a method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure, comprising: mixing raw material inclusions in a solvent to obtain an intermediate inclusion; drying the intermediate inclusion by fluidized drying using media particles as a medium to obtain an intermediate; and calcining the intermediate.

[0046] (Raw material containing substance) The raw material containing substance used in this embodiment preferably contains an alkali metal, a sulfur atom, a phosphorus atom, and a halogen atom as constituent atoms, and more preferably contains a lithium atom as the alkali metal. As the raw material containing substance, for example, a substance containing at least one selected from a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom can be used alone or in combination.

[0047] Such substances include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides; various phosphorus fluorides (PF ３ , P.F. ５ ), various phosphorus chlorides (PCl ３ , PCl ５ , P ２ Cl ４ ), various phosphorus bromides (PBr ３ , PBr ５ ), various phosphorus iodides (PI ３ , P ２ I ４ ) and the like; phosphorus halides such as thiophosphoryl fluoride (PSF ３ ), thiophosphoryl chloride (PSCl ３ ), thiophosphoryl bromide (PSBr ３ ), thiophosphoryl iodide (PSI ３ ), thiophosphoryl fluoride dichloride (PSCl ２ F), thiophosphoryl fluoride dibromide (PSBr ２ a source material consisting of at least two atoms selected from the above four types of atoms, such as thiophosphoryl halides, e.g., fluorine (F); ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ ), preferably chlorine (Cl ２ ), bromine (Br ２ ) are typical examples.

[0048] Examples of materials that can be used as raw materials other than those mentioned above include raw materials that contain at least one atom selected from the alkali metals, sulfur atoms, phosphorus atoms, and halogen elements mentioned above, and also contain atoms other than the atoms mentioned above, more specifically, lithium compounds such as lithium oxide, lithium hydroxide, and lithium carbonate; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, and tin sulfide (SnS, SnS ２metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium such as sodium halides such as sodium iodide, sodium fluoride, sodium chloride and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides and bismuth halides; phosphorus oxychloride (POCl ３ ), phosphorus oxybromide (POBr ３ ) and the like; and the like.

[0049] In this embodiment, from the viewpoint of more easily obtaining a sulfide solid electrolyte having an argyrodite-type crystal structure with high ionic conductivity, the raw materials are selected from the above-mentioned materials, such as lithium sulfide and diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides, fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ Preferred examples of the combination of raw materials include a combination of lithium sulfide, diphosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, diphosphorus pentasulfide, and a single halogen atom, and lithium bromide and lithium iodide are preferred as the lithium halide, and lithium bromide and lithium iodide are preferred as the single halogen atom.

[0050] In this embodiment, Li ３ P.S. ４ A sulfide solid electrolyte such as Li can also be used as a raw material. ３ P.S. ４ By using Li ３ P.S. ４ Since it is easy to obtain an intermediate, it is possible to more easily obtain a sulfide solid electrolyte having an argyrodite-type crystal structure. ３P.S. ４ In this case, the raw material combination of the sulfide solid electrolyte contained in the raw material inclusions is ３ P.S. ４ and the lithium halide, Li ３ P.S. ４ and the above-mentioned elemental halogens, Li ３ P.S. ４ and the lithium halide and the elemental halogen.

[0051] In the present embodiment, when lithium sulfide is used as the compound containing an alkali metal, the lithium sulfide is preferably in the form of particles. ５０ ) is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.5 μm or more and 100 μm or less, and even more preferably 1 μm or more and 20 μm or less. ５０ ) is the particle size at which, when a particle size distribution cumulative curve is drawn, the cumulative total, starting from the smallest particle size, reaches 50% (volume basis) of the total, and the volume distribution can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer. Furthermore, among the above-mentioned examples of raw materials, solid raw materials preferably have an average particle size similar to that of the lithium sulfide particles. That is, raw materials within the same range as the average particle size of the lithium sulfide particles are preferred.

[0052] When the raw material contains lithium sulfide, diphosphorus pentasulfide, and lithium halide, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 65 to 85 mol%, more preferably 70 to 83 mol%, even more preferably 74 to 83 mol%, even more preferably 76 to 83 mol%, even more preferably 77 to 80 mol%, and particularly preferably 78 to 80 mol%. When the raw material contains lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed, the content of lithium sulfide and diphosphorus pentasulfide to the total is preferably 50 to 95 mol%, more preferably 50 to 90 mol%, even more preferably 55 to 85 mol%, even more preferably 55 to 78 mol%, even more preferably 58 to 70 mol%, and particularly preferably 60 to 65 mol%. Furthermore, when the raw material content contains a combination of lithium bromide and lithium chloride as the lithium halide, from the viewpoint of more easily obtaining a sulfide solid electrolyte having an argyrodite-type crystal structure, the ratio of lithium bromide to the total of lithium bromide and lithium chloride is preferably 1 to 99 mol%, more preferably 15 to 75 mol%, even more preferably 25 to 60 mol%, still more preferably 25 to 45 mol%, and particularly preferably 35 to 40 mol%.

[0053] When the raw material content includes an elemental halogen as a raw material, including lithium sulfide and diphosphorus pentasulfide, the ratio of the number of moles of lithium sulfide excluding the same number of moles of lithium sulfide as the elemental halogen to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the elemental halogen is preferably within the range of 60 to 90%, more preferably within the range of 65 to 85%, even more preferably within the range of 68 to 82%, even more preferably within the range of 72 to 78%, and particularly preferably within the range of 73 to 77%. These ratios make it easier to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure.

[0054] From the same viewpoint, when the raw material contains lithium sulfide, diphosphorus pentasulfide, and an elemental halogen, the content of the elemental halogen relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the elemental halogen is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and still more preferably 3 to 15 mol%.

[0055] When the raw material contains lithium sulfide, diphosphorus pentasulfide, an elemental halogen, and a lithium halide, the content of the elemental halogen (α mol %) and the content of the lithium halide (β mol %) relative to the total amount of lithium sulfide, diphosphorus pentasulfide, the elemental halogen, and the lithium halide preferably satisfy the following formula (2), more preferably satisfy the following formula (3), even more preferably satisfy the following formula (4), and still more preferably satisfy the following formula (5): 2≦2α+β≦100 (2) 4≦2α+β≦80 (3) 6≦2α+β≦50 (4) 6≦2α+β≦30 (5)

[0056] When the raw material contains two types of halogen as simple substances, the mole number of one halogen atom in the substance is A1, and the mole number of the other halogen atom in the substance is A2, and the ratio A1:A2 is preferably 1 to 99:99 to 1, more preferably 10:90 to 90:10, even more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

[0057] When the raw material contains two kinds of halogen atoms, and the two kinds of halogen atoms are bromine and chlorine, the ratio B1:B2 is preferably 1:99 to 99:1, more preferably 15:85 to 75:25, even more preferably 25:75 to 60:40, and even more preferably 35:65 to 65:35, where B1 is the number of moles of bromine and B2 is the number of moles of chlorine.

[0058] In addition, the raw material contains Li ３ P.S. ４ If the raw material contains Li, the total amount of the raw material contained in the raw material ３ P.S. ４The content of Li is preferably 60 to 100 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 80 mol%. ３ P.S. ４ Li may be prepared by manufacturing, and in this case, it can be obtained by reacting lithium sulfide with diphosphorus pentasulfide in a molar ratio of 3:1. ３ P.S. ４ When using lithium sulfide and diphosphorus pentasulfide, the compounding ratio with other raw materials such as lithium halide and elemental halogen may be the same as that when lithium sulfide and diphosphorus pentasulfide are used. For example, when lithium sulfide and diphosphorus pentasulfide are reacted in a molar ratio of 3:1, 2 moles of Li ３ P.S. ４ Therefore, 2 moles of Li ３ P.S. ４ corresponds to a total of 4 moles of lithium sulfide and diphosphorus pentasulfide. Therefore, in the compounding ratio when using the above lithium sulfide and diphosphorus pentasulfide, the number of moles of lithium sulfide and diphosphorus pentasulfide is ３ P.S. ４ It can be applied as twice the amount of Li ３ P.S. ４ When using a halogen atom, Li ３ P.S. ４ The amount of the halogen element to be used is preferably 1 to 50 mol %, more preferably 10 to 40 mol %, even more preferably 20 to 30 mol %, and even more preferably 22 to 28 mol %.

[0059] (Solvent) As the solvent used in the present embodiment, a wide variety of solvents that have conventionally been used in the production of sulfide solid electrolytes can be used. Preferred examples thereof include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents, and among these, aromatic hydrocarbon solvents are preferred.

[0060] Examples of aliphatic hydrocarbon solvents include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane. Examples of alicyclic hydrocarbon solvents include cyclohexane and methylcyclohexane. Examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, and nitrobenzene.

[0061] Other examples include solvents containing heteroatoms such as nitrogen atoms, oxygen atoms, sulfur atoms, and halogen atoms. Heteroatoms have a high affinity for lithium atoms and tend to bond with the raw materials of the sulfide solid electrolyte contained in the raw material inclusions to form complexes. Therefore, solvents containing heteroatoms are compounds (hereinafter also referred to as "complexing agents") that can coordinate (bond) with the lithium atoms contained in the raw material inclusions to form complexes. Mixing the raw materials of the sulfide solid electrolyte with the complexing agent forms a complex, which makes it easier to maintain a uniform dispersion state of the raw materials of the sulfide solid electrolyte, particularly the dispersion state of the halogen atoms. As a result, it is believed that a sulfide solid electrolyte with high ionic conductivity can be obtained.

[0062] Examples of solvents containing nitrogen atoms include solvents having an amino group.Preferred examples of solvents having an amino group include aliphatic amines such as ethylenediamine, diaminopropane, dimethylethylenediamine, diethylethylenediamine, dimethyldiaminopropane, tetramethyldiaminomethane, tetramethylethylenediamine (TMEDA), tetramethyldiaminopropane (TMPDA), tetraethylethylenediamine, and tetraethyldiaminopropane; alicyclic amines such as cyclopropanediamine, cyclohexanediamine, and bisaminomethylcyclohexane; heterocyclic amines such as isophoronediamine, piperazine, dipiperidylpropane, and dimethylpiperazine; and aromatic amines such as phenyldiamine, tolylenediamine, naphthalenediamine, methylphenylenediamine, dimethylnaphthalenediamine, dimethylphenylenediamine, tetramethylphenylenediamine, and tetramethylnaphthalenediamine.Nitrile solvents such as acetonitrile and acrylonitrile; and solvents containing nitrogen atoms such as dimethylformamide, nitrobenzene, and dimethylacetamide are also preferred.

[0063] Preferred examples of the complexing agent include solvents containing an oxygen atom as a heteroatom, such as ether solvents, ester solvents, alcohol solvents, aldehyde solvents, and ketone solvents.

[0064] Preferred examples of the ether solvent include aliphatic ethers such as dimethyl ether, diethyl ether, tert-butyl methyl ether, dimethoxymethane, dimethoxyethane, diethylene glycol dimethyl ether (diglyme), triethylene oxide glycol dimethyl ether (triglyme), diethylene glycol, and triethylene glycol; alicyclic ethers such as ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, and dioxane; heterocyclic ethers such as furan, benzofuran, and benzopyran; and aromatic ethers such as methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, and diphenyl ether.

[0065] Preferred examples of the ester solvent include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, and isopropyl acetate; aliphatic esters such as methyl propionate, ethyl propionate, dimethyl oxalate, diethyl oxalate, dimethyl malonate, diethyl malonate, dimethyl succinate, and diethyl succinate; alicyclic esters such as methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, and dimethyl cyclohexanedicarboxylate; heterocyclic esters such as methyl pyridinecarboxylate, methyl pyrimidinecarboxylate, acetolactone, propiolactone, butyrolactone, and valerolactone; and aromatic esters such as methyl benzoate, ethyl benzoate, dimethyl phthalate, diethyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, trimethyl trimellitate, and triethyl trimellitate.

[0066] Preferred examples of the solvent include alcohol solvents such as ethanol and butanol; aldehyde solvents such as formaldehyde, acetaldehyde and dimethylformamide; and ketone solvents such as acetone and methyl ethyl ketone.

[0067] Preferred examples of solvents containing a halogen atom as a heteroatom include chloroform, carbon tetrachloride, dichloromethane, chlorobenzene, dichlorobenzene, trifluoromethylbenzene, chlorotoluene, bromobenzene, etc. Preferred examples of solvents containing a sulfur atom include dimethyl sulfoxide, carbon disulfide, etc.

[0068] (Mixing) The production method of this embodiment includes mixing the raw material-containing materials in the solvent to obtain an intermediate-containing material.

[0069] There are no particular limitations on the method for mixing the raw material inclusions with the solvent; the raw materials and solvent contained in the raw material inclusions can be mixed by adding them to a device capable of mixing the raw material inclusions with the solvent. For example, supplying the solvent into a tank, operating the stirring blade, and then gradually adding the raw materials while stirring and mixing is preferable, as this results in a good mixing state of the raw material inclusions and improves the dispersibility of the raw materials. Furthermore, when a halogen element is used as the raw material, the raw material may not be solid; specifically, at room temperature and normal pressure, fluorine and chlorine are gases, and bromine is liquid. For example, if the raw material is liquid, it can be supplied into the tank together with the solvent separately from other solid raw materials. Alternatively, if the raw material is gas, it can be supplied by blowing it into the solvent mixed with the solid raw material.

[0070] In the manufacturing method of this embodiment, when mixing the raw material inclusions and the solvent, mixing can be performed using a method that does not use equipment generally called a pulverizer, such as a media-type pulverizer such as a ball mill or a bead mill, which is used for pulverizing solid raw materials, to obtain a mixture containing an intermediate of the sulfide solid electrolyte (intermediate-containing material). Note that in order to shorten the mixing time for obtaining the intermediate-containing material or to achieve finer powder, the raw material inclusions and the like may be pulverized in a pulverizer when mixing them or after they have been mixed.

[0071] As an apparatus for mixing the raw material ingredients and the solvent, for example, a mechanical stirring mixer equipped with stirring blades in a tank can be mentioned. Examples of the mechanical stirring mixer include a high-speed stirring mixer and a double-arm mixer, and from the viewpoint of improving the uniformity of the raw materials in the mixture of the raw material ingredients and the solvent, a high-speed stirring mixer is preferably used. In addition, examples of the high-speed stirring mixer include a vertical shaft rotary mixer and a horizontal shaft rotary mixer, and either type of mixer can be used.

[0072] Examples of the shape of the impeller used in a mechanical stirring mixer include anchor type, blade type, arm type, ribbon type, multi-stage blade type, double arm type, shovel type, double-shaft blade type, flat blade type, C-type blade type, etc., and from the viewpoint of improving the uniformity of the raw materials in the raw material content, the shovel type, flat blade type, C-type blade type, etc. are preferred. In addition, a mechanical stirring mixer may be provided with a circulation line that discharges the material to be stirred outside the mixer and then returns it to the mixer. This allows the heavy raw materials to be stirred without settling or stagnating, enabling more uniform mixing.

[0073] The location of the circulation line is not particularly limited, but it is preferable to install it in a location where it discharges from the bottom of the mixer and returns to the top of the mixer. This makes it easier to uniformly mix the raw materials in the raw material-containing mixture, which tend to settle, by using convection caused by circulation. Furthermore, it is preferable that the return port is located below the liquid surface of the material to be mixed. This can prevent the material to be mixed from splashing and adhering to the wall surface inside the mixer.

[0074] In the manufacturing method of this embodiment, the intermediate inclusion obtained by mixing the raw material inclusion and the solvent contains Li, from the viewpoint of making the particle size of the obtained sulfide solid electrolyte smaller and further reducing the proportion of coarse particles. ３ P.S. ４ Preferably, the mixing is carried out under heating, and more preferably under pressure. By carrying out the mixing under heating or under heating and pressure, Li ３ P.S. ４ It becomes easier to obtain intermediate compounds containing

[0075] The heating temperature is not particularly limited as long as the intermediate-containing material can be efficiently obtained. ３ P.S. ４ From the viewpoint of efficiently obtaining an intermediate-containing material containing Li, the temperature is preferably 150°C or higher and lower than 300°C, more preferably 160°C or higher and 275°C or lower, even more preferably 165°C or higher and 225°C or lower, and even more preferably 170°C or higher and 200°C or lower. ３ P.S. ４ It is possible to produce an intermediate containing

[0076] The heating time is not particularly limited as long as the intermediate-containing substance can be efficiently obtained. ３ P.S. ４ From the viewpoint of efficiently obtaining an intermediate-containing product containing the compound, the time is preferably from 10 minutes to 24 hours, more preferably from 30 minutes to 18 hours, even more preferably from 1 hour to 12 hours, and even more preferably from 2 hours to 10 hours.

[0077] The heating may be carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum). This is because deterioration (e.g., oxidation) of the intermediate obtained by the heating can be prevented. The heating method is not particularly limited, and examples thereof include methods using a hot plate, an autoclave, a vacuum heating device, an argon gas atmosphere furnace, and a calcination furnace. Among these, an autoclave is preferred from the viewpoint of more efficiently obtaining the intermediate-containing material and further reducing the proportion of coarse particles, and an autoclave equipped with a stirrer and a heating mechanism may also be used. Furthermore, industrially, a horizontal dryer or a horizontal vibration fluidized dryer having a heating means and a feeding mechanism can also be used, and the method may be selected depending on the amount of processing to be heated.

[0078] The Li preferably contained in the intermediate compound thus obtained ３ P.S. ４ The structure is solid ３１ It can be observed by P-NMR measurement, and PS ４ ３－ From the viewpoint of ionic conductivity, the crystal structure consisting of phosphorus atoms and sulfur atoms is PS ４ ３－ Structures other than the structure, e.g., P ２ S ７ ４－ Structure, P ２ S ６ ４－ Structure (P ｘ S ｙ ａ－ According to the above synthesis method, it is preferable that such a PS ４ ３－It becomes easier to obtain an intermediate containing a structure.

[0079] (Drying) The manufacturing method of this embodiment includes drying the intermediate-containing material obtained by the above method by fluidized drying using media particles as a medium to obtain an intermediate. The inventors have found that by drying the intermediate-containing material by fluidized drying using media particles as a medium to obtain an intermediate, the proportion of coarse particles contained in the sulfide solid electrolyte obtained by calcining the intermediate, as described below, is reduced. This is presumably because, in fluidized drying using a medium, the intermediate-containing material to be dried flows, thereby uniformly dispersing the intermediates contained in the intermediate-containing material and suppressing aggregation.

[0080] Furthermore, in fluidized drying using a medium, the intermediate-containing material flows, increasing the heat transfer area of ​​the intermediate-containing material, promoting rapid and uniform heat conduction, and thus enabling drying in a short time. Therefore, high-temperature drying is not necessary for uniform drying, and even if high-temperature drying is performed, drying for a short time is sufficient. This makes it possible to minimize the elution of halogen atoms due to the thermal history caused by high-temperature drying, and also makes it possible to suppress quality deterioration such as a decrease in ionic conductivity. Furthermore, there is no need to select low-temperature drying to suppress the thermal history caused by high-temperature drying, and long drying times are not required, resulting in excellent productivity. Furthermore, since the intermediate-containing material is fluidized using a medium, it can be dried uniformly, almost regardless of the viscosity of the intermediate-containing material, and can therefore be used with intermediate-containing materials of a wide range of viscosities.

[0081] The fluidized-bed drying is preferably carried out using a fluidized-bed dryer having a mechanism for fluidizing media particles with a gas. By using a fluidized-bed dryer, the proportion of coarse particles contained in the sulfide solid electrolyte obtained by the calcination process described below can be further reduced. The fluidized-bed dryer can be any device that can dry the intermediate-containing material to be dried while fluidizing it with media particles serving as a medium. It is also possible to use a commercially available fluidized-bed dryer in which media particles are contained as a medium and the media particles are dried while flowing. Commercially available fluidized-bed dryers include the SFD-mini (manufactured by Okawara Manufacturing Co., Ltd.) and MSD (manufactured by Nara Machinery Manufacturing Co., Ltd.).

[0082] A preferred embodiment of a drying apparatus capable of performing fluidized drying using a medium that can be used in this embodiment will be described with reference to Fig. 1. The drying apparatus shown in Fig. 1 includes a medium fluidized dryer that can perform fluidized drying by fluidizing media particles as a medium, and a bag filter for recovering the powder intermediate from the gas and powder obtained by drying, i.e., the fluid containing the intermediate contained in the intermediate-containing material, discharged by the dryer.

[0083] The medium fluidization dryer shown in Figure 1 is a type that uses media particles as a medium, and is an apparatus in which the media particles in the dryer are fluidized by gas, and intermediate inclusions are supplied into the fluidized bed of media particles and dried. When intermediate inclusions are supplied into the fluidized bed of media particles, the intermediate inclusions flow, increasing the heat transfer area and enabling shorter drying times. The dryer has a partition plate, preferably having multiple vents, for supplying gas. By having the partition plate, the media particles that serve as the medium do not stagnate at the bottom, but rather form a fluidized bed by convection within the dryer due to the gas supplied into the dryer through the vents.

[0084] An outlet is provided above the fluidized medium dryer for discharging the gas supplied from below and the powder contained in the intermediate-containing material, i.e., the fluid containing the intermediate, and the fluid discharged from the outlet is supplied to a bag filter. The bag filter is equipped with multiple filters, and the powder in the fluid is collected by the filters and recovered as an intermediate, and the gas in the fluid is exhausted from an outlet above the bag filter.

[0085] In a medium fluidized dryer, media particles are used as the medium, and a form in which the media particles are kept in a fluidized state by a gas, as shown in Figure 1, is effective. As the gas, it is preferable to use an inert gas such as nitrogen or argon from the viewpoint of suppressing deterioration due to oxidation of the intermediate and further reducing the proportion of coarse particles, and it is more preferable to use nitrogen from the viewpoint of cost.

[0086] As the media particles, it is preferable to use ceramic balls from the viewpoint of further improving drying efficiency and fluidity and further reducing the proportion of coarse particles. The particle size of the media particles cannot be generally specified because it varies depending on the size of the medium fluidized dryer, but it is usually sufficient to use particles of about 0.5 mm to 5.0 mm, and considering drying efficiency, fluidity, etc., it is preferably 1.0 mm to 4.0 mm. Furthermore, when the particle size of the media particles is within the above range, it is possible to suppress exhaust to the outside of the dryer along with a fluid containing gas and an intermediate contained in the dried intermediate-containing material, thereby reducing the amount captured by the bag filter.

[0087] When a gas is used to fluidize the medium, it is preferable that the gas is heated. In the case of a medium fluidized dryer of the type shown in Figure 1, the gas also serves as a heat source for drying the intermediate-containing material, so a heated gas is used. It is also preferable that the media particles are heated. In the case of a medium fluidized dryer of the type shown in Figure 1, the media particles are in a heated state by the heated gas, and the intermediate-containing material is heated by the gas and by the media particles heated by the gas, allowing drying in an extremely short time and further reducing the proportion of coarse particles.

[0088] Furthermore, there are no particular restrictions on the opening size of the ventilation hole in the partition plate, as long as it is smaller than the particle size of the media particles so that the media particles do not fall to the bottom; for example, it may be approximately 0.1 mm or more and 3 mm or less. Considering the ease of supplying the medium (gas) from below, the opening size is preferably 0.3 mm or more and 2.5 mm or less, and more preferably 0.5 mm or more and 2.0 mm or less.

[0089] The drying temperature in this drying can be set according to the type of solvent contained in the intermediate-containing material. For example, the drying can be performed at a temperature equal to or higher than the boiling point of the solvent. As described above, the drying temperature varies depending on the boiling point of the solvent used, and therefore cannot be generally specified. However, the drying temperature is usually about 50 to 150°C, preferably 55 to 130°C, more preferably 60 to 100°C, and even more preferably 65 to 80°C.

[0090] 1 is used, the gas supply temperature is usually about 60 to 240°C, and from the viewpoint of drying in a shorter time, it is preferably 70 to 230°C, more preferably 90 to 220°C, and even more preferably 100 to 210°C, and the linear velocity of the gas is usually about 0.5 to 10.0 m / s based on the supply temperature, and from the viewpoint of maintaining good fluidity of the media particles, it is preferably 1.0 to 8.0 m / s, more preferably 1.5 to 7.0 m / s, and even more preferably 3.0 to 6.0 m / s. The linear velocity of the gas is the volumetric flow rate relative to the cross-sectional area of ​​the fluidized bed of the media particles as the medium, in a direction perpendicular to the flow direction of the gas (which can also be said to be the cross-sectional area of ​​the container that stores the media particles in the dryer, in a direction perpendicular to the flow direction of the gas).

[0091] The temperature of the fluid at the outlet of the medium-fluidized dryer is usually about 50 to 120°C, and from the same viewpoint, it is preferably 55 to 100°C, more preferably 60 to 90°C, and even more preferably 65 to 80°C. Within the above range, the drying temperature in the medium-fluidized dryer is easily set within the above-mentioned preferred drying temperature range. The temperature of the fluid can be adjusted by the linear velocity and temperature of the gas, the supply amount of the intermediate-containing substance, etc., and is easily adjusted by the supply amount of the intermediate-containing substance.

[0092] In the production method of this embodiment, the main drying may be performed in a circulating manner. By performing the main drying in a circulating manner, the intermediate-containing material can be dried more efficiently and the proportion of coarse particles can be further reduced.

[0093] In the production method of this embodiment, a bag filter is preferably used as shown in FIG. 1 from the viewpoint of efficiently collecting the powder obtained by drying, that is, the intermediate.

[0094] The filter used in the bag filter can be any filter made of materials such as polypropylene, nylon, acrylic, polyester, cotton, wool, heat-resistant nylon, polyamide / polyimide, PPS (polyphenylene sulfide), glass fiber, and PTFE (polytetrafluoroethylene), and functional filters such as electrostatic filters can also be used. Among these, filters made of heat-resistant nylon, polyamide / polyimide, PPS (polyphenylene sulfide), glass fiber, and PTFE (polytetrafluoroethylene) are preferred, and filters made of heat-resistant nylon, PPS (polyphenylene sulfide), and PTFE (polytetrafluoroethylene) are more preferred, with filters made of PTFE (polytetrafluoroethylene) being particularly preferred.

[0095] The bag filter may also have a brushing means, for example, preferably a pulsating counter pressure type or a pulse jet type, with the pulse jet type being particularly preferred.

[0096] An induced draft fan may be provided in the line from the exhaust port of the bag filter to forcibly exhaust the gas exhausted from the exhaust port. By exhausting the gas using an induced draft fan or the like, filtration in the bag filter proceeds smoothly and a stable fluidized bed of media particles is obtained in the media fluidized dryer, allowing the intermediate-containing material to be dried in a shorter time.

[0097] (Caustic Treatment) The production method of this embodiment includes calcining the intermediate obtained by the above method. By calcining the intermediate, an argyrodite-type crystal structure is formed and the crystallinity is improved, resulting in a high-quality sulfide solid electrolyte having an argyrodite-type crystal structure.

[0098] The heating temperature and time during firing can be adjusted appropriately taking into consideration the composition of the intermediate, etc. For example, the heating temperature is preferably 300°C or higher and 500°C or lower, more preferably 320°C or higher and 480°C or lower, even more preferably 350°C or higher and 450°C or lower, and even more preferably 380°C or higher and 430°C or lower. The heating temperature refers to the maximum temperature during firing. The firing time is preferably 1 minute to 10 hours, more preferably 10 minutes to 8 hours, even more preferably 30 minutes to 6 hours, and even more preferably 1 hour to 4 hours. The firing time refers to the time during which the heating temperature during firing is maintained. The firing may be performed while supplying an inert gas such as nitrogen gas or argon gas.

[0099] The calcination method is not particularly limited, and examples thereof include a method using a vacuum heating device, a calcination furnace, etc. Furthermore, industrially, a horizontal dryer having a heating means and a feeding mechanism, a horizontal vibration fluidized dryer, etc. may also be used, and the method may be selected depending on the amount of heat to be processed.

[0100] (Sulfide Solid Electrolyte) The sulfide solid electrolyte obtained by the above production method is a sulfide solid electrolyte having an argyrodite-type crystal structure.

[0101] The argyrodite crystal structure is ７ P.S. ６ The argyrodite-type crystal structure has a structural skeleton basically as shown in the figure, with some of the P substituted with Si. The composition formula of the argyrodite-type crystal structure is, for example, Li ７－ｘ P １－ｙ Si ｙ S ６ and Li ７＋ｘ P １－ｙ Si ｙ S ６ (x is -0.6 to 0.6, y is 0.1 to 0.6). The argyrodite-type crystal structure represented by these composition formulas is a cubic or orthorhombic crystal, preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, it has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The composition formula of the argyrodite-type crystal structure is Li７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ (0.8≦x≦1.7, 0<y≦−0.25x+0.5). The argyrodite-type crystal structure represented by this composition formula is preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, it has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The composition formula of the argyrodite-type crystal structure is preferably Li ７－ｘ P.S. ６－ｘ Ha ｘ (Ha is Cl or Br, and x is preferably 0.2 to 1.8). The argyrodite-type crystal structure represented by this composition formula is preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, it has peaks that appear mainly at 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. These peak positions may vary within a range of ±0.5°.

[0102] The shape of the sulfide solid electrolyte having an argyrodite-type crystal structure obtained by the production method of this embodiment is not particularly limited, and may be, for example, particulate. The particulate sulfide solid electrolyte preferably has a mode diameter in a volumetric particle size distribution of 7.5 to 50.0 μm, more preferably 8.0 to 30.0 μm. When the mode diameter is within the above range, a sulfide solid electrolyte having a reduced proportion of coarse particles is easily obtained. The mode diameter is determined as the peak value of the particle size distribution. The half-width of the mode diameter in the volumetric particle size distribution is preferably 5.0 to 12.0 μm, more preferably 6.0 to 11.0 μm. When the half-width is within the above range, a sulfide solid electrolyte having a reduced proportion of coarse particles is easily obtained. In this specification, the term "half-width" refers to the peak width at 50% height of the mode diameter, and a smaller half-width indicates a more uniform particle size. The mode diameter and half width can be measured, for example, using a laser diffraction particle size distribution analyzer, specifically by the method described in the Examples.

[0103] (Applications) The sulfide solid electrolyte having an argyrodite-type crystal structure obtained by the method for producing a sulfide solid electrolyte of this embodiment is a sulfide solid electrolyte with a reduced proportion of coarse particles, as described above, and therefore has excellent coatability when made into an ink, making it suitable for use as an electrode material and separator material for lithium-ion batteries. The sulfide solid electrolyte obtained by the method for producing a sulfide solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer. Each layer may be produced by a known method.

[0104] The battery preferably includes a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer, and a known current collector can be used, such as a layer of Au, Pt, Al, Ti, or Cu, which reacts with the solid electrolyte, coated with Au or the like.

[0105] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0106] (Measurement of volumetric particle size distribution) In the present examples, the volumetric particle size distribution was measured as follows. For the dry powders (intermediates) and sulfide solid electrolytes obtained in the examples and comparative examples, the volumetric particle size distributions were measured using a laser diffraction particle size distribution analyzer under the following measurement conditions, and the mode diameter and half width were calculated. The measurement results are shown in Table 1. The volumetric particle size distribution of the dry powder (intermediate) is shown in Figure 2, and the volumetric particle size distribution of the sulfide solid electrolyte is shown in Figure 3.

[0107] (Measurement conditions) Measuring device: Laser diffraction particle size distribution measuring device (LA-950V2 Model A2, manufactured by Horiba, Ltd.) Measurement standard: Volume Analysis conditions: Sphericity and refractive index 70% Particle size measurement range: 0.01 μm or more and 5000 μm or less

[0108] (Example 1) (Mixing) As raw materials, lithium sulfide, diphosphorus pentasulfide, lithium bromide, and lithium chloride were mixed in a molar ratio of Li: ２ S:P ２ S ５The mixture was weighed to a ratio of 47.5:12.5:15.0:25.0, and placed in a stainless steel container. The container was stirred with a stirring blade to obtain a raw material-containing material. After adding dehydrated toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent to a reactor equipped with a stirring blade, the raw material-containing material was added under a nitrogen atmosphere, and the raw material-containing material was dispersed in the solvent to obtain a slurry of approximately 15% by mass. While maintaining the nitrogen atmosphere, the slurry was mixed and pulverized using a bead mill (LMZ015, manufactured by Ashizawa Finetech Co., Ltd.). The slurry obtained above was placed in an autoclave (capacity 500 mL, made of SUS316) equipped with a stirrer and a temperature-controlling jacket, and heated at 180 ° C. for 4 hours while stirring at a rotation speed of 70 rpm to obtain an intermediate-containing material.

[0109] (Drying) Next, using a fluidized drying device (SFD-mini, manufactured by Okawara Manufacturing Co., Ltd.) having a media fluidized dryer and a bag filter configured as shown in FIG. 1, the gas was supplied to the fluidized dryer at a temperature of 170°C, the linear velocity of the gas in the drying chamber was 3.0 to 3.5 m / s, and the intermediate-containing material was supplied so that the temperature of the fluid containing the gas and powder extracted from the top of the media fluidized dryer was 130°C. Ceramic particles with a particle size of 1.5 to 3.0 mm were used as the media particles. Nitrogen was used as the gas for fluidizing the media particles. Drying was carried out after the operation of the media fluidized dryer reached a steady state, and the dried powder (intermediate) was collected using a bag filter.

[0110] (Firing) The dried powder (intermediate) obtained above was heated in an electric furnace (F-1404-A, manufactured by Tokyo Glass Instruments Co., Ltd.) in a glove box under a nitrogen atmosphere. ２ O ３The dried powder (intermediate) was placed in a sagger (999-60S, manufactured by Tokyo Glass Instruments Co., Ltd.) and then placed in an electric furnace preheated to 410°C and heated for 2 hours. The sagger was then removed from the electric furnace and slowly cooled to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure. Powder X-ray diffraction (XRD) measurement using an X-ray diffraction (XRD) device (D2 PHASER, manufactured by BRUKER Corporation) confirmed that the obtained sulfide solid electrolyte had an argyrodite-type crystal structure, as evidenced by the appearance of diffraction peaks at 2θ = 25.5 ± 1.0 deg and 29.9 ± 1.0 deg.

[0111] Comparative Example 1 After obtaining an intermediate-containing material by the same procedure as in (mixing) of Example 1, the intermediate-containing material was dried for 12 hours at a heat medium temperature of 140°C using a conical dryer (Nauta Mixer (registered trademark) DBX-50RWV, manufactured by Hosokawa Micron Corporation) to obtain a dried powder (intermediate). The obtained dried powder (intermediate) was subjected to the same procedure as in (calcination) of Example 1 to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure.

[0112] Comparative Example 2 After obtaining an intermediate-containing material by the same operation as in (mixing) of Example 1, the intermediate-containing material was dried for 12 hours at a heat medium temperature of 140°C using a conical dryer (Nauta Mixer (registered trademark) DBX-50RWV, manufactured by Hosokawa Micron Corporation) to obtain a dry powder (intermediate). The obtained dry powder (intermediate) was classified using a sieve with a mesh size of 710 μm to remove agglomerates. The dry powder (intermediate) from which the agglomerates had been removed was subjected to the same operation as in (calcination) of Example 1 to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure.

[0113]

[0114] FIG. 2 shows the volumetric particle size distribution of the dried powder (intermediate) obtained in Example 1 and Comparative Examples 1 and 2, and FIG. 3 shows the volumetric particle size distribution of the sulfide solid electrolyte obtained in Example 1 and Comparative Examples 1 and 2. As shown in FIG. 2 , no difference was observed in the volumetric particle size distribution between Example 1, in which the intermediate inclusion obtained by mixing the raw material inclusions in a solvent was dried using a fluidized bed dryer, and Comparative Examples 1 and 2, in which the intermediate inclusions were dried using a conical dryer. Similarly, the mode diameters of Example 1 and Comparative Examples 1 and 2 were comparable, and the half-widths of Example 1 and Comparative Examples 1 and 2 were also comparable. On the other hand, as shown in FIG. 3 , the volumetric particle size distribution of the sulfide solid electrolyte obtained in Example 1 had a sharp shape with one peak in the particle size range of 1 to 10 μm, and the proportion of coarse particles with a particle size of 20 μm or more contained in the sulfide solid electrolyte was low. In contrast, the volume-based particle size distributions of the sulfide solid electrolytes obtained in Comparative Examples 1 and 2 were both broad, and the sulfide solid electrolyte contained a large proportion of coarse particles with particle sizes of 20 μm or more. The results of Comparative Example 2 indicate that sieving the dried powder (intermediate) before firing does not reduce the proportion of coarse particles with particle sizes of 20 μm or more contained in the resulting sulfide solid electrolyte. Furthermore, the mode diameter of the sulfide solid electrolyte obtained in Example 1 was larger than the mode diameters of the sulfide solid electrolytes obtained in Comparative Examples 1 and 2, while the half-width of the sulfide solid electrolyte obtained in Example 1 was smaller than the half-width of the sulfide solid electrolytes obtained in Comparative Examples 1 and 2. This also indicates that the sulfide solid electrolyte obtained in Example 1 had a reduced proportion of coarse particles with particle sizes of 20 μm or more.

[0115] According to the manufacturing method of this embodiment, a sulfide solid electrolyte having an argyrodite-type crystal structure with a reduced proportion of coarse particles can be obtained. The obtained sulfide solid electrolyte has excellent coatability when made into an ink, and is therefore suitable for use as an electrode material and a separator material for lithium-ion batteries.

Claims

1. A method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure, comprising: mixing a raw material inclusion in a solvent to obtain an intermediate inclusion; drying the intermediate inclusion by fluidized drying using media particles as a medium to obtain an intermediate; and calcining the intermediate.

2. The intermediate-containing material and the intermediate are Li ３ P.S. ４ A method for producing the sulfide solid electrolyte having an argyrodite-type crystal structure according to claim 1, comprising:

3. A method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to claim 1 or 2, wherein the mixing is carried out under heating.

4. The method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to claim 3, wherein the heating is carried out under pressure.

5. The method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to claim 3 or 4, wherein the heating is carried out using an autoclave.

6. The method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to any one of claims 3 to 5, wherein the heating is carried out at a heating temperature of 150°C or higher and lower than 300°C.

7. A method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to any one of claims 1 to 6, wherein the raw material contains, as constituent atoms, an alkali metal, a sulfur atom, a phosphorus atom, and a halogen atom.

8. A method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to any one of claims 1 to 7, wherein the solvent is a hydrocarbon solvent.

9. A method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to any one of claims 1 to 8, wherein the fluidized drying is carried out using a media fluidized dryer having a mechanism for fluidizing the media particles with a gas.

10. A method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to any one of claims 1 to 9, wherein the media particles are ceramic balls.

11. The method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to claim 9 or 10, wherein the gas is an inert gas.

12. The method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to any one of claims 9 to 11, wherein the gas is heated.

13. The method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to any one of claims 1 to 12, wherein the drying is carried out in a circulating manner.

14. A method for producing a sulfide solid electrolyte having an argyrodite-type crystal structure according to any one of claims 1 to 13, wherein the firing is carried out at a heating temperature of 300°C or higher and 500°C or lower.

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