Method for producing sulfide solid electrolyte

Abstract

To provide a method for producing sulfide solid electrolyte with high productivity and a small particle size.SOLUTION: A method for producing sulfide solid electrolyte includes: mixing raw material contents that include lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with a solvent to obtain a precursor-containing mixture; and supplying the precursor-containing mixture to a liquid or gas medium that has been heated to a higher temperature than the boiling point of the solvent, thereby evaporating the solvent. For the ratio between the raw material contents and the solvent, the raw material contents are 4.0 g or less relative to 100 ml of the solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a sulfide solid electrolyte. [Background technology]

[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. Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents, but by making batteries all-solid-state, flammable organic solvents are not used in the battery, safety devices can be simplified, and manufacturing costs and productivity are excellent. Therefore, batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed.

[0003] As a method for producing a solid electrolyte, Patent Document 1 discloses a method in which a liquid containing a solid electrolyte raw material and a solvent is supplied to a high-temperature medium, and the solvent is evaporated to precipitate an argyrodite-type crystal structure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2019-169459 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a method for producing a sulfide solid electrolyte with excellent productivity and small particle size. [Means for solving the problem]

[0006] The method for producing a sulfide solid electrolyte according to the present invention includes the steps of: a method for producing a sulfide solid electrolyte, comprising: mixing a raw material containing material, which contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, with a solvent to obtain a precursor-containing mixture; and supplying the precursor-containing mixture to a liquid or gas medium heated to a temperature higher than the boiling point of the solvent to evaporate the solvent, wherein the ratio of the raw material containing material to the solvent is 4.0 g or less per 100 ml of solvent; is. [Effects of the Invention]

[0007] According to the present invention, a method for producing a sulfide solid electrolyte having a small particle size can be provided, which is excellent in productivity. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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 numerical 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. Furthermore, preferred specifications can be arbitrarily adopted. In other words, one preferred specification can be adopted in combination with one or more other preferred specifications. It can be said that a combination of preferred items is more preferable.

[0009] (Findings Obtained by the Inventors to Achieve the Invention) As a result of extensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention.

[0010] The method described in Patent Document 1 discloses a method in which a liquid containing a solid electrolyte raw material and a solvent is supplied to a high-temperature medium and the solvent is evaporated to precipitate an argyrodite-type crystal structure, but does not disclose that changing the concentration of the solid electrolyte material changes the particle size of the resulting solid electrolyte. In response to this, the present inventors have discovered that a sulfide solid electrolyte having small particle diameters can be produced by setting the concentration of the solid electrolyte material at a certain level or less.

[0011] (Various aspects of this embodiment) A method for producing a sulfide solid electrolyte according to a first aspect of the present embodiment includes the steps of: a method for producing a sulfide solid electrolyte, comprising: mixing a raw material containing material, which contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, with a solvent to obtain a precursor-containing mixture; and supplying the precursor-containing mixture to a liquid or gas medium heated to a temperature higher than the boiling point of the solvent to evaporate the solvent, wherein the ratio of the raw material containing material to the solvent is 4.0 g or less per 100 ml of solvent; is.

[0012] In the method for producing a sulfide solid electrolyte of the present embodiment, by supplying a precursor-containing mixture to a medium heated to a high temperature, it is possible to synthesize a particulate solid electrolyte while removing the solvent, and this method has excellent productivity. Furthermore, in the method for producing a sulfide solid electrolyte of this embodiment, by setting the ratio of the raw material contents to the solvent to a certain level or less, the concentration of solids such as the precursor and unreacted raw materials in the precursor-containing mixture supplied to the medium is reduced, and it is thought that this results in a sulfide solid electrolyte having a small particle size when the solvent is evaporated.

[0013] In the manufacturing method of this embodiment, the term "precursor" refers to a precursor of a solid electrolyte that becomes a sulfide solid electrolyte by evaporating the solvent. By mixing the raw material ingredients with the solvent, the solid electrolyte raw materials are uniformly mixed via the solvent, and in some cases, they may further react with each other to form a structure similar to the sulfide solid electrolyte, becoming a precursor. By removing the solvent from this, it is thought that the reaction between the raw materials progresses and the sulfide solid electrolyte is formed. Furthermore, in the production method of the present embodiment, the solvent contained in the precursor-containing mixture is removed by contact with the medium heated to a high temperature, and the precursor is converted into a sulfide solid electrolyte and appears in the medium. Furthermore, in the production method of this embodiment, the "precursor-containing mixture" is a mixture containing at least the precursor and a solvent, and may further contain unreacted raw materials and the like.

[0014] 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 solvent contains an alcohol solvent. That is it.

[0015] When the solvent contains an alcohol solvent, the raw materials are more likely to be dispersed more uniformly, and therefore the electrolyte precursor can be obtained more efficiently, resulting in improved production efficiency and making it possible to easily produce a high-quality sulfide solid electrolyte.

[0016] A method for producing a sulfide solid electrolyte according to a third aspect of the present embodiment is the same as the first or second aspect, The solvent contains a complexing agent. That is it. Since alcohol solvents may react with the electrolyte raw materials or the synthesized solid electrolyte itself, thereby reducing ionic conductivity, it is desirable for the solvent to contain a complexing agent or a hydrocarbon solvent, as described below, in order to achieve the desired ratio of solvent to raw material contents.

[0017] Here, the complexing agent refers to a compound capable of forming a complex. When the solvent contains a complexing agent, the formation of the complex is promoted, and the solid electrolyte raw materials are more likely to be uniformly dispersed. Therefore, all of the raw materials contained in the raw material inclusions are more likely to contribute to the formation of the sulfide solid electrolyte, and as a result, a sulfide solid electrolyte having higher ionic conductivity is more likely to be obtained.

[0018] A method for producing a sulfide solid electrolyte according to a fourth aspect of the present embodiment is the same as the third aspect, except that: the complexing agent is an ether compound; That is it.

[0019] Use of an ether compound as a complexing agent is preferable because it promotes the formation of a complex, improves production efficiency, and makes it easier to obtain a sulfide solid electrolyte with higher ionic conductivity.

[0020] A method for producing a sulfide solid electrolyte according to a fifth aspect of the present embodiment is the same as any of the first to fourth aspects, except that: The solvent contains a hydrocarbon solvent. That is it.

[0021] It is preferable that the solvent contains a hydrocarbon solvent, from the viewpoint of maintaining high ionic conductivity when the amount of solids in the precursor-containing mixture is small.

[0022] A method for producing a sulfide solid electrolyte according to a sixth aspect of the present embodiment is the same as any of the first to fifth aspects, except that: The halogen atom is at least one selected from a chlorine atom, a bromine atom, and an iodine atom. That is it.

[0023] The halogen atoms contained in the raw material may vary depending on the sulfide solid electrolyte to be obtained, but are preferably selected from, for example, chlorine atoms, bromine atoms, and iodine atoms.

[0024] A method for producing a sulfide solid electrolyte according to a seventh aspect of the present embodiment is the same as any of the first to sixth aspects, except that: The ratio of the raw material content to the solvent is 1.5 g or more of raw material content per 100 ml of solvent; That is it.

[0025] In this embodiment, as described above, the ratio of the raw material ingredients to the solvent needs to be a certain level or less. However, from the viewpoint of improving productivity and the ionic conductivity of the resulting sulfide solid electrolyte, it is preferable that the ratio of the raw material ingredients be a certain level or more.

[0026] The method for producing a sulfide solid electrolyte according to an eighth aspect of the present embodiment is the same as any one of the first to seventh aspects, except that: The precursor-containing mixture is supplied to the liquid medium by injection, dropwise addition or spraying. That is it.

[0027] A specific example of evaporating the solvent from the precursor-containing mixture is to inject, dropwise add, or spray the precursor-containing mixture into a liquid medium. Since the medium is heated to a high temperature, the precursor-containing mixture comes into contact with the medium, and the solvent contained in the precursor-containing mixture evaporates, resulting in the deposition of a sulfide solid electrolyte in the medium.

[0028] A method for producing a sulfide solid electrolyte according to a ninth aspect of the present embodiment is the same as any of the first to eighth aspects, except that: The medium is a hydrocarbon compound having 10 to 40 carbon atoms. That is it.

[0029] The medium used in this embodiment may be a liquid medium or a gaseous medium. However, it is preferable to use a liquid medium in which the solubility of the sulfide solid electrolyte is low, so that the sulfide solid electrolyte can be efficiently precipitated. For example, it is preferable to use a hydrocarbon compound having 10 to 40 carbon atoms.

[0030] (solid electrolyte) In this specification, the term "solid electrolyte" refers to an electrolyte that remains solid at 25° C. under a nitrogen atmosphere. The solid electrolyte in this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and has ionic conductivity due to the lithium atoms.

[0031] The term "solid electrolyte" includes both amorphous solid electrolytes and crystalline solid electrolytes. In this specification, a crystalline solid electrolyte refers to a solid electrolyte in which a peak derived from the 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 the raw material of the solid electrolyte is present. That is, a crystalline solid electrolyte includes a crystalline structure derived from the solid electrolyte, and a part of the crystalline structure may be derived from the solid electrolyte, or the entire crystalline structure may be derived from the solid electrolyte. Furthermore, as long as the crystalline solid electrolyte has the X-ray diffraction pattern described above, it may also include an amorphous solid electrolyte in part. Therefore, a crystalline solid electrolyte includes so-called glass ceramics obtained by heating an amorphous solid electrolyte to a temperature equal to or higher than the crystallization temperature. In addition, in this specification, an amorphous solid electrolyte refers to an amorphous solid electrolyte that has a halo pattern in which peaks other than those derived from the material are substantially not observed in an X-ray diffraction pattern obtained by X-ray diffraction measurement, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present.

[0032] [Method for producing sulfide solid electrolyte] The method for producing the sulfide solid electrolyte of this embodiment includes the steps of: a method for producing a sulfide solid electrolyte, comprising: mixing a raw material containing material, which contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, with a solvent to obtain a precursor-containing mixture; and supplying the precursor-containing mixture to a liquid or gas medium heated to a temperature higher than the boiling point of the solvent to evaporate the solvent, wherein the ratio of the raw material containing material to the solvent is 4.0 g or less per 100 ml of solvent; is.

[0033] Obtaining a Precursor-Containing Mixture The manufacturing method of this embodiment includes mixing a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with a solvent to obtain a precursor-containing mixture. The manufacturing method of this embodiment will be described first starting with the ingredients contained in the raw materials.

[0034] (Raw material content) The raw material inclusions used in this embodiment contain lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and more specifically, are inclusions containing a substance containing one or more atoms selected from the group consisting of these atoms (hereinafter also referred to as a "solid electrolyte raw material"). As the halogen atoms, chlorine atoms, bromine atoms, and iodine atoms are preferred, and chlorine atoms and bromine atoms are more preferred. It is preferable that the raw material inclusions contain at least two types of halogen atoms.

[0035] Examples of raw materials contained in the raw material content include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; phosphorus sulfides such as diphosphorus trisulfide (P2S3) and diphosphorus pentasulfide (P2S5); phosphorus halides such as various phosphorus fluorides (PF3, PF5), various phosphorus chlorides (PCl3, PCl5, P2Cl4), various phosphorus bromides (PBr3, PBr5), and various phosphorus iodides (PI3, P2I4); thiophosphoryl fluoride (PSF3), thiophosphite chloride, and the like. Representative examples include raw materials consisting of at least two atoms selected from the above four types of atoms, such as thiophosphoryl halides such as thiophosphoryl (PSCl3), thiophosphoryl bromide (PSBr3), thiophosphoryl iodide (PSI3), thiophosphoryl fluoride dichloride (PSCl2F), and thiophosphoryl fluoride dibromide (PSBr2F); and elemental halogens such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), preferably chlorine (Cl2) and bromine (Br2).

[0036] 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 above four types of atoms and also contain atoms other than the four types of atoms, 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; metal sulfides such as silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, tin sulfide (SnS, SnS), aluminum sulfide, and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium, 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; and phosphorus oxyhalides such as phosphorus oxychloride (POCl) and phosphorus oxybromide (POBr).

[0037] Among the above, preferred raw materials contained in the raw material-containing substance are lithium sulfide, phosphorus sulfides such as diphosphorus trisulfide (P2S3) and diphosphorus pentasulfide (P2S5), elemental halogens such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide. Furthermore, when oxygen atoms are introduced into the solid electrolyte, preferred are lithium oxide, lithium hydroxide, and phosphate compounds such as lithium phosphate.

[0038] The halogen atom is preferably a chlorine atom, a bromine atom, or an iodine atom, and at least one selected from these is preferred. Therefore, the lithium halide is preferably lithium chloride, lithium bromide, or lithium iodide, and the halogen element is preferably chlorine (Cl2), bromine (Br2), or iodine (I2), which may be used alone or in combination.

[0039] 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 simple halogen. Preferred lithium halides include lithium chloride, lithium bromide, and lithium iodide, and preferred simple halogens include chlorine, bromine, and iodine.

[0040] In this embodiment, Li3PS4 containing the PS4 structure can be used as part of the raw material. Specifically, Li3PS4 is prepared in advance by manufacturing or the like, and then used as the raw material. The content of Li3PS4 relative to the total amount of the raw materials is preferably 60 to 100 mol %, more preferably 65 to 90 mol %, and even more preferably 70 to 80 mol %.

[0041] When Li3PS4 and a simple halogen are used, the content of the simple halogen relative to Li3PS4 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 %.

[0042] The lithium sulfide used in this embodiment is preferably in the form of particles. The average particle size of lithium sulfide particles (D 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% (by volume) of the total, and the volume distribution refers to the average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device. 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, i.e., within the same range as that of the lithium sulfide particles.

[0043] When lithium sulfide, diphosphorus pentasulfide, and lithium halide are used as raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 70 to 82 mol%, more preferably 72 to 80 mol%, and even more preferably 74 to 80 mol%, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. When lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed are used, the content of lithium sulfide and diphosphorus pentasulfide relative to the total of these is preferably 50 to 100 mol%, more preferably 55 to 85 mol%, and even more preferably 60 to 80 mol%.

[0044] When lithium chloride and lithium bromide are used in combination as the lithium halide, from the viewpoint of improving ionic conductivity, the proportion of lithium chloride to the total of lithium chloride and lithium bromide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, still more preferably 40 to 80 mol%, and particularly preferably 50 to 75 mol%.

[0045] When a halogen element is used as a raw material, and lithium sulfide and diphosphorus pentasulfide are used, the ratio of the number of moles of lithium sulfide excluding the same number of moles of lithium sulfide as the halogen element to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the halogen element 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%. This is because higher ionic conductivity can be obtained at these ratios. From the same viewpoint, when lithium sulfide, diphosphorus pentasulfide, and a halogen element are used, the content of the halogen element relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the halogen element is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0046] When lithium sulfide, diphosphorus pentasulfide, a halogen element, and a lithium halide are used, the content of the halogen element (α mol %) and the content of the lithium halide (β mol %) relative to the total amount thereof preferably satisfy the following formula (2), more preferably satisfy the following formula (3), even more preferably satisfy the following formula (4), and even 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)

[0047] When two types of halogens are used as simple substances, the molar number of one halogen atom in the substance is A1, and the molar number of the other halogen atom in the substance is A2. 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.

[0048] (solvent) The solvent used in this embodiment can be a wide variety of solvents that have conventionally been used in the production of solid electrolytes, and examples thereof include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; solvents containing carbon atoms such as alcohol solvents, ester solvents, aldehyde solvents, ketone solvents, ether solvents, and solvents containing carbon atoms and heteroatoms; and the like. Any of these may be appropriately selected and used.

[0049] More specifically, examples of the solvent include aliphatic hydrocarbon solvents such as hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene, chlorotoluene, and bromobenzene; alcohol solvents such as ethanol and butanol; aldehyde solvents such as formaldehyde, acetaldehyde, and dimethylformamide; ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as dibutyl ether, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole; and solvents containing carbon atoms and hetero atoms such as acetonitrile, dimethyl sulfoxide, and carbon disulfide.

[0050] Among these solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether-based solvents are preferred, and from the viewpoint of obtaining a more stable and high ionic conductivity, heptane, cyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole are more preferred, diethyl ether, diisopropyl ether, and dibutyl ether are even more preferred, and diisopropyl ether and dibutyl ether are still more preferred, and cyclohexane is particularly preferred. In this embodiment, these solvents may be used alone or in combination.

[0051] The solvent used in this embodiment preferably contains an alcohol solvent as described below as a part thereof.

[0052] (alcohol solvent) Examples of alcohol solvents include primary and secondary aliphatic alcohols such as methanol, ethanol, isopropanol, butanol, and 2-ethylhexyl alcohol; polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, and hexanediol; alicyclic alcohols such as cyclopentanol, cyclohexanol, and cyclopentylmethanol; aromatic alcohols such as butylphenol, benzyl alcohol, phenethyl alcohol, naphthol, and diphenylmethanol; and alkoxy alcohols such as methoxyethanol, propoxyethanol, and butoxyethanol. Of the various solvents mentioned above, the alcohol solvent is preferably an aliphatic alcohol, more preferably a primary aliphatic alcohol, further preferably methanol or ethanol, and particularly preferably ethanol.

[0053] The solvent used in the present embodiment preferably contains the complexing agent and an alcohol solvent from the viewpoint of promoting the reaction of the solid electrolyte raw materials, and more preferably contains a complexing agent, an alcohol, and a hydrocarbon solvent from the viewpoint of improving the ionic conductivity of the resulting sulfide solid electrolyte while promoting the reaction of the solid electrolyte raw materials.

[0054] The solvent used in this embodiment preferably contains a complexing agent, which will be described below, as a part thereof.

[0055] (complexing agent) As described above, the complexing agent is a compound that easily forms a complex with the solid electrolyte raw material contained in the raw material inclusions, and is, for example, a compound that can form a complex with lithium sulfide and diphosphorus pentasulfide, which are preferably used as solid electrolyte raw materials, Li3PS4 obtained when these are used, and solid electrolyte raw materials containing halogen atoms (hereinafter, these are also collectively referred to as "solid electrolyte raw materials, etc.").

[0056] The complexing agent can be any compound having the above properties without any particular limitation, and is preferably a compound containing an atom having a high affinity with lithium atoms, such as a heteroatom such as a nitrogen atom, an oxygen atom, or a chlorine atom, and more preferably a compound having a group containing such a heteroatom, because such a heteroatom or group containing such a heteroatom can coordinate (bond) with lithium.

[0057] It is believed that the heteroatoms present in the complexing agent molecules have a high affinity for lithium atoms and have the property of easily bonding with the solid electrolyte raw materials, etc. to form a complex (hereinafter also simply referred to as a "complex"). Therefore, by mixing the solid electrolyte raw materials with the complexing agent, a complex is formed, which makes it easier to maintain the uniform dispersion state of the solid electrolyte raw materials, particularly the dispersion state of the halogen atoms, and as a result, it is believed that a sulfide solid electrolyte with high ionic conductivity can be obtained.

[0058] Whether the complexing agent is capable of forming a complex with the solid electrolyte raw material or the like can be directly confirmed by an infrared absorption spectrum measured by, for example, FT-IR analysis (diffuse reflectance method).

[0059] In the production method of this embodiment, the complexing agent is preferably a compound containing an oxygen atom as a heteroatom. The compound containing an oxygen atom is preferably a compound having one or more functional groups selected from an ether group and an ester group as the group containing an oxygen atom, and among these, a compound having an ether group is particularly preferred. That is, an ether compound is particularly preferred as the complexing agent containing an oxygen atom.

[0060] Examples of the ether compound include aliphatic ethers, alicyclic ethers, heterocyclic ethers, and aromatic ethers, and these compounds may be used alone or in combination.

[0061] More specifically, examples of aliphatic ethers include monoethers such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, and tert-butyl methyl ether; diethers such as dimethoxymethane, dimethoxyethane, diethoxymethane, and diethoxyethane; polyethers having three or more ether groups such as diethylene glycol dimethyl ether (diglyme) and triethylene oxide glycol dimethyl ether (triglyme); and ethers containing hydroxyl groups such as diethylene glycol and triethylene glycol. The aliphatic ether preferably has 2 or more carbon atoms, more preferably 3 or more carbon atoms, and even more preferably 4 or more carbon atoms, and the upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less carbon atoms. The number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic ether is preferably 1 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0062] Examples of alicyclic ethers include ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, dioxane, and dioxolane. Examples of heterocyclic ethers include furan, benzofuran, benzopyran, dioxene, dioxin, morpholine, methoxyindole, and hydroxymethyldimethoxypyridine. The number of carbon atoms in the alicyclic ether and heterocyclic ether is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0063] Examples of aromatic ethers include methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, diphenyl ether, benzyl phenyl ether, and naphthyl ether. The aromatic ether preferably has 7 or more carbon atoms, more preferably 8 or more carbon atoms, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.

[0064] The ether compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom.

[0065] Among the above ether compounds, aliphatic ethers are preferred, and dimethoxyethane and tetrahydrofuran are more preferred, from the viewpoint of obtaining higher ionic conductivity.

[0066] Examples of the ester compound include ester compounds such as aliphatic esters, alicyclic esters, heterocyclic esters, and aromatic esters, and these can be used alone or in combination.

[0067] More specifically, examples of aliphatic esters include formate esters such as methyl formate, ethyl formate, and triethyl formate; acetate esters such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and isobutyl acetate; propionate esters such as methyl propionate, ethyl propionate, propyl propionate, and butyl propionate; oxalate esters such as dimethyl oxalate and diethyl oxalate; malonate esters such as dimethyl malonate and diethyl malonate; and succinate esters such as dimethyl succinate and diethyl succinate.

[0068] The number of carbon atoms in the aliphatic ester is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more, with the upper limit being preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. The number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic ester is preferably 1 or more, more preferably 2 or more, and the upper limit being preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0069] Examples of alicyclic esters include methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, dimethyl cyclohexanedicarboxylate, dibutyl cyclohexanedicarboxylate, and dibutyl cyclohexenedicarboxylate. Examples of heterocyclic esters include methyl pyridinecarboxylate, ethyl pyridinecarboxylate, propyl pyridinecarboxylate, methyl pyrimidinecarboxylate, ethyl pyrimidinecarboxylate, and lactones such as acetolactone, propiolactone, butyrolactone, and valerolactone.

[0070] The number of carbon atoms in the alicyclic ester and heterocyclic ester is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0071] Examples of aromatic esters include benzoic acid esters such as methyl benzoate, ethyl benzoate, propyl benzoate, and butyl benzoate; phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, and dicyclohexyl phthalate; and trimellitic acid esters such as trimethyl trimellitate, triethyl trimellitate, tripropyl trimellitate, tributyl trimellitate, and trioctyl trimellitate.

[0072] The aromatic ester preferably has 8 or more carbon atoms, more preferably 9 or more carbon atoms, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.

[0073] The ester compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom.

[0074] Among the above ester compounds, from the viewpoint of obtaining higher ionic conductivity, aliphatic esters are preferred, acetate esters are more preferred, and ethyl acetate is particularly preferred.

[0075] The ratio of the complexing agent to the alcohol solvent in the solvent is preferably 1.0 to 30 times, more preferably 1.5 to 15 times, further preferably 2.0 to 10 times, and particularly preferably 2.2 to 5.0 times, in terms of volume ratio of alcohol to complexing agent. The ratio of the total amount of the complexing agent and the alcohol solvent in the solvent is preferably 10 to 100% by volume, more preferably 20 to 80% by volume, and even more preferably 25 to 60% by volume, based on the total amount of the solvent.

[0076] (mixture) In the manufacturing method of this embodiment, the precursor-containing mixture is obtained by mixing the above-mentioned raw material ingredients with a solvent. Here, the ratio of the raw material content to the solvent needs to be 4.0 g or less of the raw material content per 100 ml of solvent from the viewpoint of obtaining a sulfide solid electrolyte with a small particle size, and further taking productivity into consideration, the ratio is preferably 0.5 g or more and 3.5 g or less of the raw material content per 100 ml of solvent, and more preferably 0.8 g or more and 3.0 g or less of the raw material content per 100 ml of solvent. In addition, from the viewpoint of improving the ionic conductivity of the resulting sulfide solid electrolyte, the ratio of the raw material ingredients to the solvent is preferably 1.5 g or more of the raw material ingredients per 100 ml of solvent.

[0077] There is no particular limitation on the method for mixing the raw material ingredients and the solvent, and the raw material ingredients and the solvent may be mixed by being charged into a device capable of mixing the raw material ingredients and the solvent. However, when a halogen element is used as the solid electrolyte raw material, the solid electrolyte raw material may not be solid, specifically, fluorine and chlorine are gaseous, and bromine is liquid, at room temperature and normal pressure. In such a case, for example, when the solid electrolyte raw material is liquid, it may be supplied into the tank together with a solvent separately from other solid solid electrolyte raw materials, or when the solid electrolyte raw material is gas, it may be supplied by blowing into a mixture of a solvent and a solid solid electrolyte raw material.

[0078] When the solvent contains multiple components, there is no particular limitation on the order in which the components are added, and for example, after first mixing the complexing agent and the raw material contents, an alcohol can be added and mixed, and if necessary, a solvent component such as a hydrocarbon solvent can be added and mixed. It is also desirable to add the alcohol after adding the complexing agent or hydrocarbon solvent, and more preferably to add the hydrocarbon solvent, complexing agent, and alcohol in this order.

[0079] The manufacturing method of this embodiment is characterized by including mixing raw material ingredients with a solvent. At this time, mixing can be performed by 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 electrolyte raw materials, to obtain a mixture containing a precursor of the solid electrolyte (precursor-containing mixture). In order to shorten the mixing time for obtaining the precursor or to obtain fine powder, the raw material ingredients and the solvent may be mixed together or may be pulverized by a pulverizer after being mixed.

[0080] An example of an apparatus for mixing the raw material ingredients and the solvent is a mechanical agitation mixer equipped with an agitator blade in a tank. Examples of mechanical agitation mixers include high-speed agitation mixers and double-arm mixers, and high-speed agitation mixers are preferably used from the viewpoint of improving the uniformity of the solid electrolyte raw material in the mixture of the solid electrolyte raw material and the solvent and obtaining higher ionic conductivity. Examples of high-speed agitation mixers include vertical-axis rotary mixers and horizontal-axis rotary mixers, and either type of mixer may be used.

[0081] The shapes of the impellers used in mechanically stirred mixers include anchor, blade, arm, ribbon, multi-blade, double-arm, shovel, double-shaft, flat, and C-shaped blades. From the viewpoint of improving the uniformity of the solid electrolyte raw materials and achieving higher ionic conductivity, the shovel, flat, and C-shaped blades are preferred. Mechanically stirred mixers may also be equipped with a circulation line that discharges the material to be stirred outside the mixer and then returns it to the mixer. This allows heavy raw materials to be stirred without settling or stagnation, enabling more uniform mixing.

[0082] The location of the circulation line is not particularly limited, but it is preferably installed at 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 solid electrolyte raw material, which tends 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 surfaces inside the mixer.

[0083] The temperature conditions when mixing the solid electrolyte raw material and the complexing agent are not particularly limited and are, for example, −30 to 100° C., preferably −10 to 50° C., and more preferably about room temperature (23° C.) (for example, about room temperature ±5° C.) The mixing time is about 0.1 to 150 hours, and from the viewpoint of more uniform mixing and obtaining higher ionic conductivity, is preferably 1 to 120 hours, more preferably 4 to 100 hours, and even more preferably 8 to 80 hours.

[0084] When a complexing agent is used as a solvent, mixing the solid electrolyte raw material with the complexing agent forms a complex between the solid electrolyte raw material, etc., and the complexing agent. More specifically, the complex is considered to be formed by the interaction of the complexing agent with lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms contained in the solid electrolyte raw material, which are directly bonded to each other with or without the aid of the complexing agent. That is, in the production method of this embodiment, the complex obtained by mixing the solid electrolyte raw material with the complexing agent can be said to be composed of the complexing agent, lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. The complex obtained in this embodiment is not completely soluble in the complexing agent, which is a liquid, but is usually a solid, so that a suspension of the complex in a solvent containing the complex is obtained.

[0085] Feeding the precursor-containing mixture into a heated medium The manufacturing method of this embodiment is as follows: supplying the precursor-containing mixture to a liquid or gas medium heated above the boiling point of the solvent to evaporate the solvent; Includes: The precursor-containing mixture is supplied to a medium heated to a temperature higher than the boiling point of the solvent, thereby removing the solvent from the precursor-containing mixture, thereby obtaining a particulate sulfide solid electrolyte.

[0086] (A medium heated above the boiling point of the solvent) The medium used in the manufacturing method of this embodiment, which is heated to a temperature higher than the boiling point of the solvent, may be either a gas or a liquid, but when a liquid medium is used, a high-boiling-point liquid medium having a boiling point higher than that of the solvent is used. The high-boiling liquid medium is preferably one that does not react with or dissolve the resulting particulate sulfide solid electrolyte, and therefore, a hydrocarbon compound is preferably used.

[0087] The hydrocarbon compound used as the medium may be selected from those exemplified as solvents that can be used in obtaining the precursor-containing mixture, and one having a higher boiling point may be used. Preferred examples include those described as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents, and more preferred examples include those described as aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents.

[0088] Considering that the high-boiling liquid medium is likely to have a boiling point higher than that of the solvent, the carbon number of the high-boiling liquid medium is preferably 8 or more, more preferably 10 or more, and the upper limit is preferably 40 or less, more preferably 20 or less, and even more preferably 16 or less, such as an aliphatic hydrocarbon compound.

[0089] Examples of aliphatic hydrocarbon compounds that are preferably used as high-boiling point liquid solvents include aliphatic hydrocarbon compounds such as octane, 2-ethylhexane, decane, undecane, dodecane, and tridecane. The high-boiling liquid medium may be used alone or in combination of two or more of the above-mentioned examples.

[0090] Specific examples of the gas medium include inert gases such as nitrogen and argon, but hydrogen sulfide and mixtures of hydrogen sulfide and inert gases can also be used.

[0091] (heating) In the manufacturing method of this embodiment, the medium is heated to a temperature higher than the boiling point of the solvent. When the solvent is a mixture of multiple components, the boiling point of the solvent refers to the boiling point of the component with the highest boiling point among the components contained in the solvent, excluding the boiling points of minor components contained in the solvent at a ratio of 3% by mass or less. The medium is preferably heated to a temperature 20° C. or higher than the boiling point of the solvent, more preferably 40° C. or higher, and even more preferably 60° C. or higher.

[0092] When the medium is a liquid, the specific temperature to which the medium is heated is preferably 120°C or higher and 500°C or lower, more preferably 150°C or higher and 450°C or lower, and even more preferably 170°C or higher and 400°C or lower, from the viewpoint of efficiently evaporating the solvent while suppressing decomposition of the precursor-containing mixture. When the medium is a gas, the specific temperature to which the medium is heated is preferably 120°C or higher and 700°C or lower, more preferably 150°C or higher and 600°C or lower, and even more preferably 170°C or higher and 500°C or lower, for the same reasons as above.

[0093] The pressure conditions when the precursor-containing mixture is supplied to the heated medium are not particularly limited, but from the viewpoint of efficiently removing the solvent, normal pressure or reduced pressure is preferred.

[0094] (Method of supply) Specific methods for supplying the precursor-containing mixture to the medium include injection, dripping, and spraying. From the viewpoint of atomizing the resulting sulfide solid electrolyte, it is preferable to reduce the amount of precursor contained in one drop. Therefore, it is preferable to supply the precursor-containing mixture to the medium by dripping or spraying. More specific examples include injection or dripping using a tube pump, and spraying using a microspray. Here, in order to atomize and homogenize the solid electrolyte, it is preferable to supply the precursor-containing mixture in small amounts at a constant rate. The supply amount can be appropriately adjusted depending on the medium used, temperature, etc., but when the precursor-containing mixture is added dropwise to the medium, it is preferable to supply the precursor-containing mixture in a rate of, for example, about 0.1 to 10 mL / min per supply port.

[0095] (Recovery of sulfide solid electrolyte) In the production method of this embodiment, the sulfide solid electrolyte is obtained by evaporating the solvent from the precursor-containing mixture as described above. However, when a liquid medium is used, the medium may be further removed. Since the liquid medium has a high boiling point, it is preferable to remove it by solid-liquid separation such as filtration, centrifugation, decantation, etc. Furthermore, the sulfide solid electrolyte obtained in this manner may be washed by repeatedly adding a low-boiling point solvent and removing the solvent by solid-liquid separation, or may be further subjected to a drying treatment.

[0096] (Firing) In the manufacturing method of this embodiment, the sulfide solid electrolyte obtained as described above may be used as is, or may further include calcining the sulfide solid electrolyte. By calcining the sulfide solid electrolyte obtained as described above, a crystalline structure is formed or the crystallinity is improved, thereby obtaining a high-quality sulfide solid electrolyte.

[0097] The heating temperature for firing is usually preferably 130° C. or higher, more preferably 140° C. or higher, and even more preferably 150° C. or higher, with the upper limit being preferably 700° C. or lower, more preferably 600° C. or lower, and even more preferably 500° C. or lower. The firing temperature refers to the maximum temperature during firing. The firing time is usually 1 minute to 24 hours, preferably 10 minutes to 20 hours, more preferably 30 minutes to 16 hours, and even more preferably 1 hour to 12 hours. The firing time refers to the time during which the heating temperature is maintained during firing.

[0098] 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.

[0099] (Amorphous sulfide solid electrolyte) The sulfide solid electrolyte obtained by the manufacturing method of this embodiment is either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte. The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. Representative examples include solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr; and solid electrolytes further containing other atoms such as oxygen atoms and silicon atoms, such as Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI. From the viewpoint of obtaining higher ionic conductivity, amorphous sulfide solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr, are preferred. The types of atoms constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0100] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may be a so-called glass ceramic obtained by heating an amorphous sulfide solid electrolyte to a crystallization temperature or higher, and its crystal structure may be Li3PS4 crystal structure, Li4P2S6 crystal structure, Li7PS6 crystal structure, Li7P3S 11 Examples of such a crystal structure include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0101] Li 4-x Ge 1-x P x S4-type thio-LISICON Region II crystal structure (Kanno et al., Journal of the Electrochemical Society, 148(7)A742-746(2001)), Li 4-x Ge 1-x P xExamples of such a crystal structure include a crystal structure similar to the S4-based thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725). The crystal structure of the crystalline sulfide solid electrolyte obtained by the method for producing a solid electrolyte of this embodiment is preferably the thio-LISICON Region II type crystal structure among the above, since it can provide higher ionic conductivity. Here, the "thio-LISICON Region II type crystal structure" refers to a structure in which Li 4-x Ge 1-x P x S4-type thio-LISICON Region II crystal structure, Li 4-x Ge 1-x P x This indicates that the crystal structure is either S4-type thio-LISICON Region II type or similar.

[0102] The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may contain the thiolicon region II crystal structure or may contain it as the main crystal. However, from the viewpoint of obtaining higher ionic conductivity, it is preferable that it contains it as the main crystal. In this specification, "containing it as the main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or more, preferably 90% or more, and more preferably 95% or more. Furthermore, from the viewpoint of obtaining higher ionic conductivity, it is preferable that the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment does not contain crystalline Li3PS4 (β-Li3PS4).

[0103] In X-ray diffraction measurements using CuKα radiation, the diffraction peaks of the Li3PS4 crystal structure appear, for example, at 2θ = 17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, the diffraction peaks of the Li4P2S6 crystal structure appear, for example, at 2θ = 16.9°, 27.1°, and 32.5°, and the diffraction peaks of the Li7PS6 crystal structure appear, for example, at 2θ = 15.3°, 25.2°, 29.6°, and 31.0°, and the diffraction peaks of the Li7P3S 11Diffraction peaks of the crystal structure appear, for example, at 2θ = 17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°. 4-x Ge 1-x P x The diffraction peaks of the S4 thio-LISICON Region II crystal structure appear, for example, at 2θ = 20.1°, 23.9°, and 29.5°. 4-x Ge 1-x P x Diffraction peaks of a crystal structure similar to the S4 thio-LISICON Region II type appear, for example, at 2θ = 20.2 and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0104] A preferred example of the solid electrolyte is a crystalline sulfide having an argyrodite-type crystal structure in which the structural skeleton of the above Li7PS6 is present and part of the P is substituted with Si. The composition formula of the argyrodite crystal structure is, for example, Li 7-x P 1-y Si y S6 and Li 7+x P 1-y Si y S6 (x is −0.6 to 0.6, y is 0.1 to 0.6). The argyrodite-type crystal structure represented by this composition formula is a cubic or orthorhombic crystal, preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°.

[0105] The composition formula of the argyrodite crystal structure is Li 7-x-2y PS 6-x-y Cl x(0.8 ≦ x ≦ 1.7, 0 < y ≦ -0.25x + 0.5) is also cited. The alditol-type crystal structure represented by this composition formula is preferably cubic, and in X-ray diffraction measurement using CuKα rays, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Also, as the composition formula of the alditol-type crystal structure, the composition formula Li 7-x PS 6-x Ha x (where Ha is Cl or Br, and x is preferably 0.2 to 1.8) is also cited. The alditol-type crystal structure represented by this composition formula is preferably cubic, and in X-ray diffraction measurement using CuKα rays, it mainly has peaks appearing at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Regarding these peak positions, they may shift within a range of ±0.5°.

[0106] (Properties of sulfide solid electrolyte) The shape of the sulfide solid electrolyte obtained by the manufacturing method of this embodiment is particulate. As the average particle diameter (D 50 ) of the particulate sulfide solid electrolyte, for example, it is 0.01 μm or more, further 0.03 μm or more, 0.05 μm or more, 0.1 μm or more, and preferably 10 μm or less as the upper limit, more preferably 7.0 μm or less, and even more preferably 4.0 μm or less. Thus, the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has a small average particle diameter within the above range by setting the ratio of the raw material inclusion and the solvent to a certain value or less. Therefore, in the manufacturing method of this embodiment, a pulverization (atomization) treatment may not be performed.

[0107] (Applications) The sulfide solid electrolyte obtained by the production method of this embodiment has excellent coating suitability and can be used in battery production without using a solvent, etc., and can efficiently exhibit excellent battery performance. In addition, since it has high ionic conductivity and excellent battery performance, it is suitable for use in batteries. The sulfide solid electrolyte obtained by the manufacturing method of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer. Each of these layers can be manufactured by a known method.

[0108] 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. For example, a layer of a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu, coated with Au or the like can be used. [Example]

[0109] 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.

[0110] (Measurement of particle size distribution) Measurements were performed using a laser diffraction / scattering particle size distribution analyzer (Partica LA-950 (model number), manufactured by Horiba, Ltd.). Specifically, a mixture of dehydrated toluene (manufactured by Wako Pure Chemical Industries, special grade) and tertiary butyl alcohol (manufactured by Wako Pure Chemical Industries, special grade) in a mass ratio of 93.8:6.2 was used as the dispersion medium. 50 mL of the dispersion medium was injected into the flow cell of the device and circulated, after which the powder to be measured was added and ultrasonicated, after which the particle size distribution was measured. In addition, the average particle size (D 50 ) was the particle size at which the particle size distribution reached 50% (volume basis) of the total when the particle size distribution curve was drawn and the particle size was accumulated in order from the smallest particle size.

[0111] (Measurement of ionic conductivity) The sulfide solid electrolyte powders obtained in the examples and comparative examples were used to prepare a ceramic tube with a diameter of 6 to 10 mm (cross-sectional area S: 0.283 to 0.785 cm).2 ) and a height (L) of 0.1 to 0.3 cm were molded into circular pellets to serve as samples. Electrode terminals were attached to the top and bottom of the samples, and measurements were made at 25°C using the AC impedance method (frequency range: 1 MHz to 0.1 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high-frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following equation: R=ρ(L / S) σ=1 / ρ

[0112] Example 1 0.597 g of lithium sulfide, 0.759 g of diphosphorus pentasulfide, 0.289 g of lithium chloride, and 0.356 g of lithium bromide were weighed in an anaerobic glove box, and 10 mL of tetrahydrofuran (THF) was added and stirred for 24 hours to prepare a stock solution. 70 mL of ethanol was then added to this stock solution to obtain a precursor-containing mixture (ratio of raw material content to solvent: 2.5 g of raw material content per 100 mL of solvent). 480 mL of tridecane was placed in a separable flask equipped with a stirrer and a condenser, the atmosphere in the flask was replaced with nitrogen gas, and the temperature of the tridecane was raised to and maintained at 210°C.

[0113] Using a tube pump, the precursor-containing mixture was added dropwise to the tridecane in the separable flask at a rate of approximately 1 mL / min. As a result, the solvents (THF and ethanol) contained in the precursor-containing mixture evaporated, and solids precipitated in the tridecane, forming a slurry.

[0114] The slurry consisting of tridecane and solids was cooled to 100°C, and then the solids were separated by decantation. Toluene was added to the separated solids, and then decantation was performed again to separate the solids. This washing procedure was repeated three times. The solids were then vacuum dried at 150°C to recover the sulfide solid electrolyte. The particle size distribution of the recovered solids was confirmed, and the average particle size (D 50 ) was 8.3 μm.

[0115] The obtained solid was calcined at 430°C for 8 hours.

[0116] Example 2 The solid content was recovered in the same manner as in Example 1, except that 200 mL of ethanol was added to the raw solution to obtain a precursor-containing mixture, and a sulfide solid electrolyte was obtained (ratio of raw material content to solvent: 0.95 g of raw material content to 100 mL of solvent). Average particle size of solids (D 50 ) was 2.5 μm, and the ionic conductivity of the sulfide solid electrolyte was 0.27 mS / cm.

[0117] Example 3 0.597 g of lithium sulfide, 0.759 g of diphosphorus pentasulfide, 0.289 g of lithium chloride, and 0.356 g of lithium bromide were weighed in an anaerobic glove box, and 10 mL of toluene and 10 mL of tetrahydrofuran (THF) were added in that order. The mixture was stirred for 72 hours to prepare a stock solution. The solids were recovered in the same manner as in Example 1, except that 30 mL of ethanol was added to the stock solution, followed by an additional 50 mL of toluene to obtain a precursor-containing mixture. A sulfide solid electrolyte was obtained. (Ratio of raw material content to solvent: 2.0 g of raw material content per 100 mL of solvent.) Average particle size of solids (D 50 ) was 5.8 μm, and the ionic conductivity of the sulfide solid electrolyte was 3.9 mS / cm.

[0118] (Comparative Example 1) The solid content was recovered in the same manner as in Example 1, except that 30 mL of ethanol was added to the stock solution to obtain a precursor-containing mixture, and a sulfide solid electrolyte was obtained (ratio of raw material content to solvent: 5.0 g of raw material content to 100 mL of solvent). Average particle size of solids (D 50 ) was 14 μm, and the ionic conductivity of the sulfide solid electrolyte was 3.9 mS / cm.

[0119] The solvents used in Examples 1 to 3 and Comparative Example 1, the ratios of the raw material ingredients to the solvent, and the properties of the resulting sulfide solid electrolytes are shown in Table 1 below.

[0120] [Table 1]

[0121] As is clear from the comparison between Examples 1 to 3 and Comparative Example 1, in Examples 1 to 3 in which the ratio of the raw material content to the solvent was 4.0 g or less per 100 ml of solvent, the average particle size (D 50 ) has become smaller. In Example 3, in which the solvent contained toluene, the average particle size (D 50 ) has become smaller. [Industrial Applicability]

[0122] The sulfide solid electrolyte obtained by the production method of this embodiment is suitable for use in batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones.

Claims

1. A method for producing a sulfide solid electrolyte, comprising: mixing a raw material-containing substance containing lithium atoms, phosphorus atoms, sulfur atoms and halogen atoms with a solvent to obtain a precursor-containing mixture; and supplying the precursor-containing mixture to a medium that is a liquid or gas heated to a temperature higher than the boiling point of the solvent to evaporate the solvent, wherein the ratio of the raw material-containing substance to the solvent is 4.0 g or less of the raw material-containing substance per 100 ml of the solvent.

2. The method for producing a sulfide solid electrolyte according to Claim 1, wherein the solvent contains an alcohol solvent.

3. The method for producing a sulfide solid electrolyte according to Claim 1 or 2, wherein the solvent contains a complexing agent.

4. The method for producing a sulfide solid electrolyte according to Claim 3, wherein the complexing agent is an ether compound.

5. The method for producing a sulfide solid electrolyte according to Claim 1 or 2, wherein the solvent contains a hydrocarbon solvent.

6. The method for producing a sulfide solid electrolyte according to Claim 1 or 2, wherein the halogen atom is one or more selected from chlorine atoms, bromine atoms and iodine atoms.

7. The method for producing a sulfide solid electrolyte according to Claim 1 or 2, wherein the ratio of the raw material-containing substance to the solvent is 1.5 g or more of the raw material-containing substance per 100 ml of the solvent.

8. The method for producing a sulfide solid electrolyte according to Claim 1 or 2, wherein the precursor-containing mixture is supplied by injecting, dropping or spraying it into the liquid medium.

9. The method for producing a sulfide solid electrolyte according to Claim 1 or 2, wherein the medium is a hydrocarbon compound having 10 to 40 carbon atoms.