Method for producing sulfide solid electrolyte

Abstract

The present invention provides a method for producing a sulfide solid electrolyte by irradiating a solid electrolyte starting material with microwaves, the method including: obtaining an amorphous product by subjecting a starting material-containing material that contains a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom, or a calcined product that is obtained by heating the starting material-containing material to an amorphization treatment; and performing microwave irradiation on a mixture of the amorphous product and an organic solvent. With the method, it is possible to efficiently produce a sulfide solid electrolyte that has more excellent ionic conductivity, while maintaining particle diameters by suppressing granulation due to heating.

Description

Method for producing sulfide solid electrolyte

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

[0002] In recent years, the rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones has placed great importance on the development of batteries to be used as their power sources. Lithium-ion batteries, in particular, have attracted attention due to their high energy density. Traditionally, batteries used for such applications have used electrolytes containing flammable organic solvents, necessitating the installation of safety devices to suppress temperature rise during short circuits, as well as improvements in the structure and materials to prevent short circuits. In response to these issues, all-solid-state batteries that use a solid electrolyte and are completely solid-state can be developed without the use of flammable organic solvents, simplify safety devices, and offer superior manufacturing costs and productivity. Therefore, all-solid-state batteries that use a solid electrolyte layer instead of the electrolyte are being developed.

[0003] Methods for producing a solid electrolyte used in a solid electrolyte layer are roughly divided into a solid phase method and a liquid phase method, and the liquid phase method includes a homogeneous method in which a solid electrolyte material is completely dissolved in a solvent, and a heterogeneous method in which a solid electrolyte material is not completely dissolved and a solid-liquid coexistence suspension is formed (for example, Patent Document 1). Also, as another method for producing a solid electrolyte, Patent Document 2 discloses a method in which lithium sulfide and diphosphorus pentasulfide are irradiated with microwaves in an organic solvent to produce amorphous Li ３ P.S. ４ Furthermore, Patent Document 3 discloses a method for producing a sulfide solid electrolyte by irradiating a mixture of raw material components containing halogen atoms in an organic solvent with microwaves.

[0004] International Publication No. 2021 / 54412 Patent Publication No. 2020-15661 International Publication No. 2023 / 140178 Pamphlet

[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 by irradiating a solid electrolyte raw material with microwaves, which method can efficiently produce a sulfide solid electrolyte having superior ionic conductivity while suppressing granulation due to heating and maintaining particle size.

[0006] The method for producing a sulfide solid electrolyte according to the present invention includes: subjecting a raw material-containing material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, or a calcined product obtained by heating the raw material-containing material, to an amorphization treatment to obtain an amorphized material; and irradiating a mixture of the amorphized material and an organic solvent with microwaves.

[0007] According to the present invention, in a production method for obtaining a sulfide solid electrolyte by irradiating a solid electrolyte raw material with microwaves, it is possible to provide a production method for a sulfide solid electrolyte, which can efficiently produce a sulfide solid electrolyte having superior ionic conductivity while suppressing granulation due to heating and maintaining particle size.

[0008] 1 shows an X-ray diffraction spectrum of the raw material content after crude mixing obtained in Preparation Example 1. 1 shows X-ray diffraction spectra of the amorphous material obtained in Example 1 and the raw material sulfide solid electrolyte used in Comparative Example 1. 1 shows X-ray diffraction spectra of the sulfide solid electrolytes obtained in Example 1 and Comparative Example 1.

[0009] 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 by "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.

[0010] (Findings Obtained by the Inventor to Achieve the Present Invention) As a result of intensive research to solve the above-mentioned problems, the inventors have found the following and have completed the present invention. Patent Documents 1 and 2 disclose methods for producing a sulfide solid electrolyte by irradiating a raw material with microwaves. In particular, the production method described in Patent Document 2 discloses that by irradiating a mixture of raw material ingredients in an organic solvent with microwaves, the heating temperature can be kept low and granulation due to heating can be suppressed.

[0011] Although the average particle size of solid electrolytes is adjusted depending on the application, it is undesirable for the average particle size to increase due to granulation. Therefore, as described in Patent Document 2, suppressing granulation during the production stage of solid electrolytes is considered to be one of the major challenges. Granulation of solid electrolytes tends to be particularly pronounced in production methods that employ microwave irradiation, and research and development of methods to suppress this is important. Through extensive research, the present inventors have discovered that performing an amorphization treatment during mixing of raw material components not only suppresses granulation but also unexpectedly improves the ionic conductivity of the resulting sulfide solid electrolyte.

[0012] In this specification, the term "solid electrolyte" refers to an electrolyte that remains solid at 25° C. under a nitrogen atmosphere. The term "sulfide solid electrolyte" obtained by the production method of this embodiment refers to a solid electrolyte that contains alkali metal atoms, sulfur atoms, phosphorus atoms, and halogen atoms and has ionic conductivity due to alkali metal atoms such as lithium atoms.

[0013] In this specification, the term "sulfide solid electrolyte" includes both crystalline sulfide solid electrolytes and amorphous sulfide solid electrolytes. In this specification, a crystalline sulfide solid electrolyte is a solid electrolyte in which a peak derived from the solid electrolyte is observed in the X-ray diffraction pattern in 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 sulfide solid electrolyte includes a crystalline structure derived from the solid electrolyte, and a portion 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 sulfide solid electrolyte has the X-ray diffraction pattern described above, it may also include an amorphous sulfide solid electrolyte (also referred to as a "glass component") as a portion thereof. Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating an amorphous solid electrolyte (glass component) to a temperature above the crystallization temperature.

[0014] In this specification, the amorphous sulfide solid electrolyte (glass component) refers to a solid electrolyte in which the X-ray diffraction pattern is a halo pattern in which no peaks other than those derived from the material are observed in X-ray diffraction measurement, and it does not matter whether or not there are peaks derived from the raw materials of the solid electrolyte.

[0015] [Method for Producing Sulfide Solid Electrolyte] A method for producing a sulfide solid electrolyte according to a first aspect of the present embodiment is a method for producing a sulfide solid electrolyte, the method comprising: subjecting a raw material-containing material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, or a calcined product obtained by heating the raw material-containing material, to an amorphization treatment to obtain an amorphized material; and irradiating a mixture of the amorphized material and an organic solvent with microwaves.

[0016] In the past, when a sulfide solid electrolyte was produced by irradiating a raw material inclusion containing multiple solid electrolyte raw materials with microwaves, the solid electrolyte raw materials were simply mixed. The present inventors discovered that the ionic conductivity of the resulting sulfide solid electrolyte was improved by subjecting the raw material inclusion to an amorphization treatment and then irradiating it with microwaves.

[0017] A second aspect of this embodiment is the method for producing a sulfide solid electrolyte according to the first aspect, in which the amorphization treatment is performed on a calcined product of the raw material inclusions. A third aspect of this embodiment is the method for producing a sulfide solid electrolyte according to the first or second aspect, in which the raw material inclusions are heated in a sealed state in a pressure-resistant vessel when obtaining the calcined product. A fourth aspect of this embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to third aspects, in which the raw material inclusions are heated in the presence of a solvent when obtaining the calcined product.

[0018] By using the calcined product of the raw material contents as the target of the amorphization treatment, it becomes easier to obtain a sulfide solid electrolyte having higher ionic conductivity. As a method for obtaining the calcined product, a method in which the raw material contents are heated in a sealed state in a pressure-resistant vessel is preferable, and heating in the presence of a solvent is also preferable.

[0019] A fifth aspect of this embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to fourth aspects, wherein the amorphization treatment is a mechanical treatment or a melt-quenching treatment. A sixth aspect of this embodiment is the method for producing a sulfide solid electrolyte according to the fifth aspect, wherein the mechanical treatment is a pulverization treatment. A seventh aspect of this embodiment is the method for producing a sulfide solid electrolyte according to the sixth aspect, wherein an integrated power in the pulverization treatment is 0.5 Wh / g or more.

[0020] In the present embodiment, the amorphization treatment is preferably a mechanical treatment or a melt-quenching treatment, and more preferably a mechanical treatment. In the mechanical treatment, setting the integrated power to a certain level or more enables sufficient amorphization treatment, which is preferable from the viewpoint of improving the ionic conductivity of the resulting sulfide solid electrolyte.

[0021] In an eighth aspect of this embodiment, the amorphous material is characterized by a peak intensity (I １８．２ ) at 2θ=44.8±0.5° (I ４４．８ ) to the intensity ratio (I １８．２ / I ４４．８The method for producing a sulfide solid electrolyte according to any one of the first to seventh aspects, wherein the amorphous material is crystalline Li ３ P.S. ４ The method for producing a sulfide solid electrolyte according to any one of the first to eighth aspects, wherein the sulfide solid electrolyte does not contain:

[0022] The amorphous material obtained by the amorphization treatment has a peak intensity (I １８．２ ) Crystalline Li ３ P.S. ４ On the other hand, the ratio of this crystalline Li ３ P.S. ４ As an index for comparing the peak intensities derived from the raw material lithium sulfide (Li ２ The peak intensity (I) at 2θ = 44.8 ± 0.5° derived from ４４．８ ) can be used. Therefore, the intensity ratio (I １８．２ / I ４４．８ ) is within the above range, the amorphized material obtained by the amorphization treatment can be said to be sufficiently amorphized, and it becomes easier to obtain a sulfide solid electrolyte having higher ionic conductivity.

[0023] 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 amorphization treatment of the raw material contents is carried out in the absence of the organic solvent or in a state in which the amount of the organic solvent added is 30 mass % or less relative to the total amount of the raw material contents.

[0024] The amorphization treatment can be carried out efficiently by setting the ratio of the raw material ingredients to the organic solvent within the above range.

[0025] An eleventh aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to tenth aspects, wherein the organic solvent has a dielectric loss factor at 25° C. of 10.0 or less.

[0026] In an eleventh aspect of this embodiment, an organic solvent having a predetermined dielectric loss factor is used. When a substance is exposed to an electromagnetic field irradiated with microwaves, the energy loss is the sum of conductive loss, dielectric loss, and magnetic loss. When a liquid is exposed to an electromagnetic field irradiated with microwaves, dielectric loss occurs, converting the energy of the electric field into thermal energy and generating heat. In other words, the lower the dielectric loss, the more efficiently the energy irradiated with microwaves can be consumed by the raw material.

[0027] The dielectric loss factor is proportional to the dielectric loss, and the dielectric loss factor and the dielectric loss have the following relationship: Dielectric loss = πfε ０ ε” |E| ２ (f: frequency (1 / sec), ε ０ : dielectric constant of vacuum, ε": dielectric loss factor of material, |E|: electric field (V / m)

[0028] Thus, the dielectric loss factor is an index of the ease of heating by microwaves, and the smaller the dielectric loss factor, the smaller the dielectric loss. Therefore, when the dielectric loss factor of the organic solvent used in the production method of this embodiment is 10.0 or less, the raw material contents can be heated more selectively, and therefore the sulfide solid electrolyte can be produced more efficiently.

[0029] A twelfth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to eleventh aspects, wherein the boiling point of the organic solvent is 50° C. or higher.

[0030] The higher the boiling point of the organic solvent, the more the amount of the organic solvent that volatilizes when the raw material content is selectively heated can be suppressed, and the raw material content can be more uniformly maintained in the organic solvent. Therefore, it is easier to selectively heat the raw material content and it is possible to reduce the amount of organic solvent used.

[0031] A thirteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to twelfth aspects, wherein the organic solvent is at least one selected from aromatic solvents and alicyclic solvents.

[0032] Aromatic solvents and alicyclic solvents tend to satisfy the properties, i.e., the dielectric loss factor and boiling point, required in the fourth and fifth embodiments, and therefore enable the sulfide solid electrolyte to be produced more efficiently.

[0033] A fourteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to thirteenth aspects, wherein the content of the amorphous material contained in the mixture is 1% by mass or more and 20% by mass or less.

[0034] In the fourteenth embodiment, the content of the amorphous material contained in the mixture is set to a predetermined range, so that the amount of the organic solvent used can be reduced, and the sulfide solid electrolyte can be produced more efficiently.

[0035] A fifteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to fourteenth aspects, wherein the microwave irradiation is performed and the mixture is heated at 150°C or higher and 360°C or lower.

[0036] In the fifteenth embodiment, the temperature of the mixture is heated to within a predetermined range. As described above, for example, to produce a sulfide solid electrolyte having an argyrodite-type crystal structure, conventional production methods require firing at a high temperature of approximately 400°C. However, according to the production method of this embodiment, it is possible to produce a sulfide solid electrolyte having an argyrodite-type crystal structure even under relatively low temperatures of 150°C or higher and 360°C or lower.

[0037] In a sixteenth aspect of this embodiment, the raw material contains Li ３ P.S. ４ The method for producing a sulfide solid electrolyte according to any one of the first to fifteenth aspects, wherein the starting sulfide solid electrolyte has a structure:

[0038] The sixteenth embodiment is a method for producing a ferroelectric material containing Li as a raw material ingredient. ３ P.S. ４ The raw material sulfide solid electrolyte having the structure is used. Such raw material components can be obtained by reacting a crude mixture containing specific compounds such as lithium sulfide, phosphorus sulfide, and lithium halide, and Li ３ P.S.４ Because of the crystallinity derived from the structure, the effect of improving ionic conductivity due to the amorphization treatment is more likely to be realized.

[0039] A seventeenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to sixteenth aspects, wherein the sulfide solid electrolyte is a crystalline sulfide solid electrolyte having an argyrodite-type crystal structure.

[0040] As described above, conventional manufacturing methods for a sulfide solid electrolyte having an argyrodite-type crystal structure require firing at a high temperature of approximately 400°C. However, the manufacturing method of this embodiment makes it possible to reduce the heating temperature to, for example, 150°C or higher and 360°C or lower. In other words, when manufacturing a sulfide solid electrolyte having an argyrodite-type crystal structure, the advantages of the manufacturing method of this embodiment can be more effectively utilized.

[0041] [Amorphization Treatment] The manufacturing method of this embodiment includes subjecting a raw material containing material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, or a calcined product obtained by heating the raw material containing material (hereinafter, sometimes referred to as "calcined product"), to an amorphization treatment to obtain an amorphized product. The amorphization treatment is not particularly limited as long as it amorphizes the raw material containing material or the calcined product. Examples of the amorphization treatment include mechanical milling (mechanical processing) and melt quenching. Mechanical milling is preferred, and more specifically, it is preferably performed using a media-type mill such as a ball mill or a bead mill. The amorphization treatment can be performed in the same manner as the milling used to obtain the mixture described below. The milling time is typically 0.5 hours or more, preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more. The upper limit is typically 100 hours or less, preferably 50 hours or less, more preferably 30 hours or less, and even more preferably 10 hours or less.

[0042] In the above-mentioned pulverization treatment, it is preferable to set the integrated power of the pulverization treatment to 0.5 Wh / g or more from the viewpoint of sufficiently amorphizing the treatment object and improving the ionic conductivity of the resulting sulfide solid electrolyte. Similarly, the integrated power in the above-mentioned reprocessing treatment is more preferably 1.0 Wh / g or more, even more preferably 2.5 Wh / g or more, and particularly preferably 3.0 Wh / g or more. The method of calculating the integrated power is the same as that used in the examples described later.

[0043] The amorphization treatment is carried out by measuring the peak intensity (I) at 2θ=18.2±0.3° in X-ray diffraction measurement using CuKα rays of the amorphized material after the amorphization treatment. １８．２ ) at 2θ=44.8±0.5° (I ４４．８ ) to the intensity ratio (I １８．２ / I ４４．８ ) is preferably carried out until it is 0.2 or less, more preferably until it is 0.10 or less, and even more preferably until it is 0.05 or less. The peak at 2θ=18.2±0.3° in the X-ray diffraction measurement using CuKα rays is the peak of crystalline Li ３ P.S. ４ The peak at 2θ=44.8±0.5° is due to the raw material lithium sulfide (Li ２ Therefore, the ratio of these peak intensities (I １８．２ / I ４４．８ ) is within the above range, crystalline Li ３ P.S. ４ The ratio of is small, that is, it can be said that the solid electrolyte raw materials are sufficiently amorphous, and when microwave irradiation is performed as described below, the reaction between the solid electrolyte raw materials is likely to proceed, which is thought to improve the ionic conductivity of the resulting sulfide solid electrolyte.

[0044] (Raw material inclusions) The raw material inclusions contain lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. There are no particular limitations on the raw material inclusions as long as they contain these atoms, and examples include inclusions containing a compound containing at least one atom selected from these atoms as a raw material, either alone or in combination. The inclusions preferably contain two or more substances selected from substances containing at least one atom selected from lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. Therefore, the sulfide solid electrolyte obtained by the production method of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms.

[0045] Compounds that can be used as raw materials contain at least one atom of a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom, and more specifically, alkali metal sulfides such as lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; alkali metal halides such as lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; and sodium halides such as sodium iodide, sodium fluoride, sodium chloride, and sodium bromide; 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 ２a raw material consisting of at least two elements selected from the above four elements, such as thiophosphoryl halides, e.g., fluorine (F); ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ ), preferably bromine (Br ２ ), iodine (I ２ ) are typical examples.

[0046] Compounds that can be used as raw materials other than those mentioned above include, for example, compounds containing at least one atom selected from the above four types of atoms and also containing atoms other than the four types of atoms, more specifically, lithium compounds such as lithium oxide, lithium hydroxide, and lithium carbonate; silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, and tin sulfide (SnS, SnS ２ metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; 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.

[0047] In this embodiment, the halogen atom can vary depending on the sulfide solid electrolyte to be obtained, and therefore cannot be generalized. However, from the viewpoint of more easily obtaining a sulfide solid electrolyte having high ionic conductivity, among halogen atoms, chlorine atoms, bromine atoms, and iodine atoms are preferred. These atoms may be used alone or in combination. Furthermore, for example, when a sulfide solid electrolyte having a thiolicon region II crystal structure, which will be described later, is to be obtained, bromine atoms and iodine atoms are more preferred. Furthermore, when a sulfide solid electrolyte having an argyrodite crystal structure is to be obtained, chlorine atoms and bromine atoms are more preferred.

[0048] In this embodiment, from the viewpoint of more easily obtaining a sulfide solid electrolyte having high ionic conductivity, examples of compounds that can be used as raw materials include, among the above, alkali metal sulfides such as lithium sulfide and sodium sulfide, 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 Among the alkali metal sulfides, lithium sulfide is preferred, and among the phosphorus sulfides, diphosphorus pentasulfide is preferred.

[0049] As mentioned above, raw materials containing halogen atoms can vary depending on the sulfide solid electrolyte to be obtained, so it is difficult to generalize. However, among the halogen elements, chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ ) is preferred, and among the lithium halides, lithium chloride, lithium bromide, and lithium iodide are preferred. Furthermore, when a sulfide solid electrolyte having a thiolithium region II crystal structure is to be obtained, bromine (Br ２ ), iodine (I ２ ) is more preferable, and lithium bromide and lithium iodide are more preferable as lithium halides. In addition, when a sulfide solid electrolyte having an argyrodite-type crystal structure is to be obtained, chlorine (Cl ２ ), bromine (Br ２ ) is more preferred, and as the lithium halide, lithium chloride and lithium bromide are more preferred.

[0050] In this embodiment, compounds that can be used as raw materials include PS ４ Li including units etc. ３ P.S. ４ The sulfide solid electrolyte obtained by the production method of this embodiment has a main structure containing Li. ３P.S. ４ When a structure containing lithium such as Li is used as a raw material, the effect of improving ionic conductivity due to the amorphous treatment is easily achieved. ３ P.S. ４ It is preferable to use a raw sulfide solid electrolyte having the structure, and such a raw sulfide solid electrolyte can be obtained, for example, by reacting a crude mixture containing lithium sulfide, phosphorus sulfide, and lithium halide.

[0051] The raw material sulfide solid electrolyte is a sulfide solid electrolyte that can be used as a compound used as a raw material, and has a molecular structure of Li ３ P.S. ４ Crystalline raw sulfide solid electrolytes having the structure are preferred, and those containing halogen atoms are more preferred. When the raw material inclusions contain the raw sulfide solid electrolyte as a raw material, higher Joule heating is obtained due to the ionic conductivity of the raw sulfide solid electrolyte, which makes it easier to promote the reaction, improves the crystallinity of the resulting sulfide solid electrolyte, and makes it easier to obtain a sulfide solid electrolyte with higher ionic conductivity. In addition, in consideration of obtaining high ionic conductivity, the raw sulfide solid electrolyte is preferably Li ４ P ２ S ７ An amorphous or crystalline sulfide solid electrolyte that does not contain a structure is preferred. These raw sulfide solid electrolytes can be produced by conventional production methods such as mechanical milling, slurry method, and melt quenching method, or commercially available products can also be used.

[0052] The raw sulfide solid electrolyte may be amorphous or crystalline, or may contain both amorphous and crystalline materials. However, in X-ray diffraction measurement using CuKα rays, Li ３ P.S. ４It is preferable to use a crystalline compound in which a peak due to the structure is observed. In any case, when a compound containing halogen atoms is used as a raw material, the dispersibility of the halogen atoms is improved, and bonding between the halogen atoms and lithium atoms, sulfur atoms, and phosphorus atoms in the solid electrolyte is more likely to occur, resulting in a sulfide solid electrolyte having higher ionic conductivity.

[0053] In this embodiment, when lithium sulfide is used as a raw material, the lithium sulfide is preferably in the form of particles. ５０ In this specification, the average particle size (D ５０ ) is the particle size at which 50% of the total particle size is reached when the particle size distribution integral curve is drawn and the integral is calculated sequentially from the smallest particle size, and the volume distribution is the average particle size that can be measured using, for example, 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, i.e., within the same range as that of the lithium sulfide particles. The particle size of the raw material compound may be adjusted by pulverization or the like, as necessary.

[0054] 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 cannot be generalized because it varies depending on the sulfide solid electrolyte to be obtained. However, from the viewpoint of obtaining higher chemical stability and high ionic conductivity, the ratio is preferably 60 mol% or more, more preferably 65 mol% or more, and even more preferably 68 mol% or more, with the upper limit being preferably 85 mol% or less, more preferably 83 mol% or less, and even more preferably 80 mol% or less.

[0055] 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 55 mol% or more, more preferably 58 mol% or more, even more preferably 60 mol% or more, and the upper limit is preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 80 mol% or less, and still more preferably 70 mol% or less.

[0056] When lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of obtaining high ionic conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 mol% or more, more preferably 20 mol% or more, even more preferably 40 mol% or more, still more preferably 50 mol% or more, and the upper limit is preferably 99 mol% or less, more preferably 90 mol% or less, even more preferably 80 mol% or less, and still more preferably 70 mol% or less. Furthermore, when lithium bromide and lithium chloride are used in combination as the lithium halide, the ratio of lithium bromide to the total of lithium bromide and lithium chloride is the same as the ratio of lithium bromide to the total of lithium bromide and lithium iodide described above.

[0057] The amorphization treatment of the raw material content can be carried out in the presence or absence of an organic solvent. That is, at least a part of the organic solvent can be mixed with the raw material content and then the amorphization treatment can be carried out. When the amorphization treatment is carried out in the presence of an organic solvent, from the viewpoint of efficient amorphization, the amount of the organic solvent added relative to the total amount of the raw material content is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0058] [Production of Raw Material Sulfide Solid Electrolyte] As described above, the raw material contains a material having a molecular structure of Li ３ P.S. ４ A raw sulfide solid electrolyte having a structure such as Li is preferably used. Hereinafter, a method for producing the raw sulfide solid electrolyte used in the raw material inclusion will be described, focusing mainly on the molecular structure of Li. ３ P.S. ４A sulfide solid electrolyte (lithium thiophosphate) having the structure will be described.

[0059] The raw material content can be obtained by reacting a crude mixture containing specific compounds such as lithium sulfide, phosphorus sulfide, and lithium halide, and Li ３ P.S. ４ In addition to the structure, the crude mixture may contain one or more raw material components selected from lithium sulfide, phosphorus sulfide, and lithium halide.

[0060] The raw sulfide solid electrolyte can be produced by a conventional production method such as a mechanical milling method, a slurry method, or a melt quenching method, and preferably can be produced by a production method including: calcining a crude mixture containing lithium sulfide, phosphorus sulfide, and a lithium halide to obtain a calcined product.

[0061] (Crude Mixture) In the crude mixture containing lithium sulfide, phosphorus sulfide, and lithium halide, phosphorus sulfide is preferably diphosphorus pentasulfide. The amounts of lithium sulfide and phosphorus sulfide used in the crude mixture may be appropriately determined depending on the sulfide solid electrolyte to be obtained. ３ P.S. ４ When a sulfide solid electrolyte having the structure is to be obtained, the molar ratio may be 3:1. When another sulfide solid electrolyte is to be obtained, the molar ratio may be used according to the sulfide solid electrolyte, and when a sulfide solid electrolyte containing a halogen atom is to be obtained, a raw material compound containing a halogen atom according to the sulfide solid electrolyte may be used. The molar ratio according to the sulfide solid electrolyte, the raw material compound to be used, and the like are the same as those described above for the raw material contents.

[0062] The compounds contained in the crude mixture may be crushed in advance. The crushing may be performed using a crusher described as a crusher that can be used to obtain the above mixture, and it is preferable to use, for example, a pin mill, particularly a pin mill having a constant volume feeder.

[0063] (Mixing and pulverization) It is believed that the compounds contained in the crude mixture mainly form fine crystals. This is because the mixing and pulverization of the raw material compounds promotes the atomization of the compounds contained in the crude mixture. It is also believed that some of the raw material compounds react to form a raw material sulfide solid electrolyte.

[0064] The crude mixture may be mixed and pulverized using any of the pulverizers described above as being usable in obtaining the mixture, and media-type pulverizers such as ball mills and bead mills are preferred. Alternatively, kneaders such as single-screw or multi-screw kneaders may also be used.

[0065] The solvent used in the mixing and grinding is preferably an organic solvent, which may be appropriately selected from the organic solvents used in obtaining the mixture described below.

[0066] The crude mixture and the solvent usually form a slurry (suspension). The content of the crude mixture in the slurry to be mixed and pulverized may be appropriately selected from the range of the content of the amorphous material in the mixture to obtain the mixture described below.

[0067] (Causticizing) The method for producing a raw sulfide solid electrolyte may include mixing and pulverizing the crude mixture of raw material components as needed, and then heating (hereinafter also referred to as "calcining") to obtain a calcined product. Calcining promotes the reaction of the raw material compounds contained in the crude mixture to produce the raw sulfide solid electrolyte, and also removes the solvent, thereby obtaining a powdered raw sulfide solid electrolyte. In other words, the calcined product obtained by calcining becomes the raw sulfide solid electrolyte.

[0068] The calcination method is not particularly limited, and examples thereof include methods using a hot plate, autoclave, vacuum heating device, argon gas atmosphere furnace, calcination furnace, etc. Also, methods using shear-type dryers such as FM mixers and Nauta mixers, stationary furnaces such as hearth kilns, rotary furnaces such as rotary kilns, and industrially, horizontal dryers and horizontal vibration fluidized dryers having a heating means and a feeding mechanism can also be used. The calcination method may be selected depending on the processing amount to be calcined, but it is preferable to heat the mixture in a sealed pressure-resistant container such as an autoclave. Furthermore, the calcination of the raw material content may be carried out in the presence or absence of a solvent, but it is preferably carried out in the presence of a solvent.

[0069] The heating temperature and time in the calcination cannot be generalized because they vary depending on the composition of the calcined product and whether an amorphous or crystalline calcined product is intended to be obtained. For example, the heating temperature is preferably 150°C or higher, more preferably 160°C or higher, and even more preferably 170°C or higher, with the upper limit being preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0070] As described above, the raw sulfide solid electrolyte may be either amorphous or crystalline, but is preferably crystalline from the viewpoint of finally obtaining a sulfide solid electrolyte having higher ionic conductivity. Therefore, the heating temperature in the calcination is preferably a temperature at which a crystalline raw sulfide solid electrolyte is obtained, and may be determined by the method starting from the crystallization temperature, as described above for the heating temperature by microwave irradiation.

[0071] The heating time is preferably 0.1 hour or more, more preferably 0.2 hour or more, and even more preferably 0.25 hour or more, and the upper limit is preferably 8 hours or less, more preferably 6 hours or less, and even more preferably 4 hours or less.

[0072] The calcination is preferably 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). An inert gas atmosphere containing hydrogen gas may also be used, as this can prevent deterioration (e.g., oxidation) of the raw material sulfide solid electrolyte.

[0073] Furthermore, drying may be carried out before calcination. By drying, the solvent contained in the crude mixture can be removed in advance. The drying method may be the same as that used for drying the fluid obtained by microwave irradiation.

[0074] The raw material sulfide solid electrolyte obtained by the above manufacturing method has a molecular structure mainly consisting of Li ３ P.S. ４ However, it goes without saying that when the compounding ratio (molar ratio) of the raw materials used in the crude mixture is changed, or when a raw material compound containing a halogen atom is used, a sulfide solid electrolyte corresponding to the change can be obtained.

[0075] Molecular structure: Li ３ P.S. ４ In the case of a raw material sulfide solid electrolyte having the argyrodite-type crystal structure, calcination at the above-mentioned preferred heating temperature results in a crystalline sulfide solid electrolyte. Furthermore, for example, when the raw material blending ratio is such that a sulfide solid electrolyte having the argyrodite-type crystal structure described below is obtained, the calcined product is considered to be merely a precursor that can produce a sulfide solid electrolyte having the argyrodite-type crystal structure by microwave irradiation.

[0076] [Microwave Irradiation] In the production method of this embodiment, the mixture of the amorphized material and the organic solvent is irradiated with microwaves.

[0077] (Organic Solvent) As the organic solvent, a wide variety of solvents that have conventionally been used in the production of solid electrolytes can be used, and examples thereof include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents.

[0078] Examples of aliphatic hydrocarbon solvents include saturated aliphatic hydrocarbons such as pentane, hexane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane, as well as unsaturated aliphatic hydrocarbons corresponding to the above saturated aliphatic hydrocarbons such as pentene and hexene. Examples of alicyclic hydrocarbon solvents include saturated alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, as well as unsaturated alicyclic hydrocarbons such as cyclohexene and methylcyclohexene. Examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, biphenyl, naphthalene, tetrahydronaphthalene (tetralin, cyclohexylbenzene), decalin (decahydronaphthalene), anthracene, and the like.

[0079] In addition to the above hydrocarbon solvents, examples of the solvent include solvents containing heteroatoms such as atoms other than carbon and hydrogen atoms, for example, nitrogen atoms, oxygen atoms, sulfur atoms, halogen atoms, etc. Preferred examples of the solvent containing an oxygen atom as a heteroatom include ether solvents, ester solvents, alcohol solvents, aldehyde solvents, and ketone solvents.

[0080] 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 (diphenyl oxide).

[0081] 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.

[0082] 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.

[0083] Examples of solvents containing a nitrogen atom as a heteroatom include solvents having a group containing a nitrogen element, such as an amino group, an amide group, a nitro group, a nitrile group, etc. For example, preferred examples of solvents having an amino group (amine solvents) include aliphatic amines such as diethylamine, triethylamine, ethylenediamine, diaminopropane, dimethylethylenediamine, diethylethylenediamine, dimethyldiaminopropane, tetramethyldiaminomethane, tetramethylethylenediamine (TMEDA), and tetramethyldiaminopropane (TMPDA); alicyclic amines such as cyclopropanediamine, cyclohexanediamine, and bisaminomethylcyclohexane; heterocyclic amines such as isophoronediamine, pyridine, methylpyridine, dimethylpyridine, methylethylpyridine, piperazine, dipiperidylpropane, and dimethylpiperazine; and aromatic amines such as phenyldiamine, tolylenediamine, naphthalenediamine, methylphenylenediamine, dimethylnaphthalenediamine, dimethylphenylenediamine, tetramethylphenylenediamine, tetramethylnaphthalenediamine, and dimethylaniline.

[0084] Preferred examples of solvents having a nitrile group (nitrile solvents) include acetonitrile, propionitrile, 3-chloropropionitrile, benzonitrile, 4-fluorobenzonitrile, tert-butyronitrile, isobutyronitrile, acrylonitrile, cyclohexylnitrile, capronitrile, isocapronitrile, malononitrile, and fumaronitrile. Other preferred examples include solvents containing a nitrogen atom, such as dimethylformamide and nitrobenzene.

[0085] Preferred examples of solvents containing a halogen atom as a heteroatom include dichloromethane, chlorobenzene, trifluoromethylbenzene, chlorobenzene, chlorotoluene, bromobenzene, etc. Preferred examples of solvents containing a sulfur atom include dimethyl sulfoxide, carbon disulfide, etc.

[0086] The amount of organic solvent used is such that the content of the total amount of the amorphized material relative to the total amount of the amorphized material and the organic solvent is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and still more preferably 8% by mass or more, with the upper limit being preferably 20% by mass or less, more preferably 17% by mass or less, even more preferably 15% by mass or less, and still more preferably 12% by mass or less. When the amount of organic solvent used is within the above range, the amorphized material is more likely to be maintained uniformly in the organic solvent, and therefore the amorphized material is more likely to be selectively heated by microwave irradiation, allowing the sulfide solid electrolyte to be produced more efficiently.

[0087] (Dielectric Loss Factor and Boiling Point of Organic Solvent) Among the above organic solvents, the organic solvent used in the production method of this embodiment is preferably one with a dielectric loss factor of 10.0 or less at 25°C. By using an organic solvent with a dielectric loss factor of 10.0 or less, the amorphous material can be heated more selectively, thereby making it possible to produce a sulfide solid electrolyte more efficiently. From this perspective, the dielectric loss factor of the organic solvent is more preferably 8.0 or less, even more preferably 5.0 or less, even more preferably 1.0 or less, and particularly preferably 0.5 or less. There is no particular lower limit, and the dielectric loss factor is usually 0.01 or more. The dielectric loss factor in this specification is the dielectric loss factor at 25°C at 2.45 GHz, and is a measured value measured according to a conventional method. For example, the relative permittivity and dielectric loss tangent can be measured using a dielectric constant measurement device (e.g., various devices such as an LCR meter, an impedance material analyzer, a network analyzer, a TDR measurement device, or a pulse THz spectroscopy device) and the dielectric loss factor can be calculated.

[0088] Among the above organic solvents, the organic solvent used in the production method of this embodiment is preferably one having a boiling point of 50° C. or higher. A boiling point of 50° C. or higher suppresses the amount of volatilization of the organic solvent when the amorphized material is selectively heated, and also allows the amorphized material to be more uniformly maintained in the organic solvent, making it easier to selectively heat the amorphized material and enabling a reduction in the amount of organic solvent used. From these perspectives, the boiling point of the organic solvent is more preferably 65° C. or higher, even more preferably 75° C. or higher, still more preferably 100° C. or higher, and particularly preferably 200° C. or higher.

[0089] As the organic solvent, among the organic solvents exemplified above, aromatic solvents having an aromatic ring such as aromatic hydrocarbon solvents, aromatic ether solvents, and aromatic ester solvents, as well as aliphatic hydrocarbons, alicyclic hydrocarbons, ether solvents (excluding the above-mentioned aromatic ether solvents), ester solvents (excluding the above-mentioned aromatic ester solvents), solvents having an amino group (amine solvents), and solvents containing a halogen atom are more preferred, and among these, it is more preferred to use at least one selected from aromatic solvents having an aromatic ring and alicyclic solvents, and it is particularly preferred to use a combination of at least one selected from aromatic hydrocarbon solvents and at least one selected from aromatic ether solvents. These organic solvents are likely to satisfy the above-mentioned dielectric loss factor and boiling point conditions, and are easy to selectively heat the amorphous material, making it possible to more efficiently produce a sulfide solid electrolyte.

[0090] The aromatic solvent is preferably an aromatic hydrocarbon solvent or an aromatic ether solvent, and the aromatic hydrocarbon solvent is preferably benzene, toluene, xylene, biphenyl, naphthalene, tetrahydronaphthalene (tetralin, cyclohexylbenzene), or decalin (decahydronaphthalene), and the aromatic ether solvent is preferably diphenyl ether (diphenyl oxide).

[0091] As the aliphatic hydrocarbon, pentane and hexane are preferred, and as the alicyclic hydrocarbon, cyclohexane is preferred. As the ether solvent (excluding the above-mentioned aromatic ether solvents), aliphatic ethers and alicyclic ethers are preferred, with diethyl ether and tetrahydrofuran being particularly preferred. As the ester solvent (excluding the above-mentioned aromatic ester solvents), aliphatic esters are preferred, with ethyl acetate being particularly preferred.

[0092] As the solvent having an amino group (amine solvent), aliphatic amines and heterocyclic amines are preferred, and triethylamine and pyridine are particularly preferred. As the solvent containing a halogen atom, dichloromethane is preferred.

[0093] [Mixing] In the manufacturing method of this embodiment, microwave irradiation is performed on a mixture of the amorphized material and an organic solvent. This mixture can be obtained by mixing at least a portion of the organic solvent with an amorphized material obtained by amorphizing the raw material content in advance. Alternatively, the raw material content and a portion or all of the organic solvent can be pre-mixed and then amorphized in the presence of the organic solvent, resulting in a mixture of the amorphized material and the organic solvent. Therefore, in the manufacturing method of this embodiment, the raw material content is mixed with the organic solvent, or the amorphized material is mixed with the organic solvent. Below, the mixing of the amorphized material and the organic solvent is described in detail as an example. However, by replacing "amorphized material" with "raw material content," the details of the mixing of the raw material content and the organic solvent can be described.

[0094] The mixture obtained by mixing the amorphized material with the organic solvent becomes a slurry (suspension) in which the amorphized material is dispersed in the organic solvent. By mixing them to form a mixture, the amorphized material can be more uniformly maintained in the organic solvent, making it easier to selectively heat the amorphized material, and enabling the efficient production of a sulfide solid electrolyte.

[0095] Mixing the amorphous material with an organic solvent to obtain a mixture can be carried out using, for example, a mixer. It can also be carried out using a stirrer, a pulverizer, or the like. Mixing of the raw materials can occur using a stirrer, and pulverization of the raw materials occurs using a pulverizer, but mixing also occurs at the same time. In other words, it can be said that the mixture can be obtained by subjecting the amorphous material to stirring, mixing, pulverization, or a combination of these processes in an organic solvent. In the production method of this embodiment, mixing can be carried out using a stirrer, a mixer, or a pulverizer. However, from the viewpoint of efficiently obtaining a slurry (suspension) in which the raw material ingredients are dispersed in the organic solvent, it is preferable to use either a stirrer or a mixer, and it is more preferable to use a mixer.

[0096] Examples of the stirrer or mixer include a mechanical stirring mixer that is equipped with stirring blades in a reaction vessel and can stir (also referred to as mixing by stirring or stirring and mixing). Examples of the mechanical stirring mixer include a high-speed stirring mixer and a double-arm mixer. Examples of the high-speed stirring mixer include a vertical-axis rotary mixer and a horizontal-axis rotary mixer, and either type of mixer may be used.

[0097] Examples of the shape of the stirring blade used in the mechanical stirring mixer include blade type, arm type, anchor type, paddle type, full zone 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 promoting the reaction of the raw materials more efficiently, the shovel type, flat blade type, C-type blade type, anchor type, paddle type, full zone type, etc. are preferred, with the anchor type, paddle type, and full zone type being more preferred.

[0098] When a mechanical stirring mixer is used, the rotation speed of the stirring blades can be adjusted appropriately depending on the volume of the fluid in the reaction vessel, the temperature, the shape of the stirring blades, etc., and is not particularly limited. However, it is usually sufficient to set the rotation speed at about 5 rpm or more and 400 rpm or less. From the viewpoint of more efficiently promoting the reaction of the raw materials, the rotation speed is preferably 10 rpm or more and 300 rpm or less, more preferably 15 rpm or more and 250 rpm or less, and even more preferably 20 rpm or more and 200 rpm or less.

[0099] The temperature conditions when mixing is performed using a mixer are not particularly limited, and are, for example, usually −30 to 120° C., preferably −10 to 100° C., more preferably 0 to 80° C., and even more preferably 10 to 60° C. The mixing time is usually 0.1 to 500 hours, and from the viewpoint of making the amorphized product more uniformly dispersed and promoting the reaction, is preferably 1 to 450 hours, more preferably 10 to 425 hours, even more preferably 20 to 400 hours, and still more preferably 40 to 375 hours.

[0100] As the pulverizer, for example, a media-type pulverizer using a pulverizing medium can be used. Media-type pulverizers are broadly classified into container-driven pulverizers and media-agitation pulverizers. Examples of container-driven pulverizers include agitation tanks, pulverization tanks, and combinations thereof, such as ball mills and bead mills. Examples of media-agitation pulverizers include impact pulverizers such as cutter mills, hammer mills, and pin mills; tower-type pulverizers such as tower mills; agitation tank pulverizers such as attritors, aquamizers, and sand grinders; flow-tank pulverizers such as Viscomill and pearl mills; flow-tube pulverizers; annular pulverizers such as Coball mills; continuous dynamic pulverizers; and single- or multi-shaft kneaders. Among these, considering the ease of adjusting the particle size of the sulfide solid electrolyte finally obtained, the ball mills and bead mills exemplified as container-driven pulverizers are preferred, and planetary pulverizers are particularly preferred.

[0101] These pulverizers can be appropriately selected depending on the desired scale, etc. For relatively small scales, container-driven pulverizers such as ball mills and bead mills can be used, while for large scales or mass production, other types of pulverizers may be used.

[0102] Furthermore, as will be described later, when the mixture is in a liquid state involving a liquid such as a solvent or in a slurry state during mixing, a wet mill that can handle wet milling is preferred. Typical examples of wet mills include wet bead mills, wet ball mills, and wet vibration mills. Wet bead mills that use beads as milling media are preferred because they allow for free adjustment of milling conditions and are easily adaptable to smaller particle sizes. Dry mills, such as dry media mills (e.g., dry bead mills, dry ball mills, and dry vibration mills) and dry non-media mills (e.g., jet mills), can also be used.

[0103] Furthermore, when the material to be mixed is in a liquid state or a slurry state, a flow-through mill that can perform a circulation operation to circulate the material as needed can also be used. Specifically, a mill that circulates the material between a mill (pulverizing mixer) that pulverizes the slurry and a temperature holding tank (reaction vessel) can be used.

[0104] The size of the beads or balls used in the ball mill or bead mill may be appropriately selected depending on the desired particle size, processing amount, etc. For example, the diameter of the beads is usually 0.05 mmφ or more, preferably 0.1 mmφ or more, more preferably 0.3 mmφ or more, with the upper limit being usually 5.0 mmφ or less, preferably 3.0 mmφ or less, more preferably 2.0 mmφ or less. The diameter of the balls is usually 2.0 mmφ or more, preferably 2.5 mmφ or more, more preferably 3.0 mmφ or more, with the upper limit being usually 20.0 mmφ or less, preferably 15.0 mmφ or less, more preferably 10.0 mmφ or less. Examples of materials include metals such as stainless steel, chrome steel, and tungsten carbide; ceramics such as zirconia and silicon nitride; and minerals such as agate.

[0105] Furthermore, when a ball mill or a bead mill is used, the rotation speed varies depending on the scale of the treatment and cannot be generalized, but is usually 10 rpm or more, preferably 20 rpm or more, more preferably 50 rpm or more, with the upper limit being usually 1,000 rpm or less, preferably 900 rpm or less, more preferably 800 rpm or less, and even more preferably 700 rpm or less. Furthermore, the milling time in this case varies depending on the scale of the treatment and cannot be generalized, but is usually 0.5 hours or more, preferably 1 hour or more, more preferably 5 hours or more, and even more preferably 10 hours or more, with the upper limit being usually 100 hours or less, preferably 72 hours or less, more preferably 48 hours or less, and even more preferably 36 hours or less.

[0106] By selecting the size and material of the medium (beads, balls) used, the rotor rotation speed, time, etc., it is possible to perform mixing, stirring, pulverization, or a combination of these processes, and it is possible to adjust the particle size, etc. of the resulting sulfide.

[0107] The content of the amorphized material in the mixture obtained by mixing is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and still more preferably 8% by mass or more, with the upper limit being preferably 20% by mass or less, more preferably 17% by mass or less, even more preferably 15% by mass or less, and still more preferably 12% by mass or less. When the content of the amorphized material is within the above range, the amorphized material is more likely to be maintained uniformly in the organic solvent, and therefore the amorphized material is more likely to be selectively heated by microwave irradiation, allowing the sulfide solid electrolyte to be produced more efficiently.

[0108] [Microwave Irradiation] In the production method of this embodiment, it is necessary to irradiate the mixture obtained by the above-mentioned mixing with microwaves. By irradiating the mixture containing the raw material ingredients and the organic solvent with microwaves, the amorphous material is selectively heated, and a sulfide solid electrolyte is obtained.

[0109] As a microwave generator for irradiating microwaves, for example, an irradiation device equipped with a high-frequency oscillator for emitting microwaves can be used, and if the scale is small, a commercially available microwave oven or the like can also be used.

[0110] The microwave frequency is not particularly limited as long as it is within the range of about 0.3 GHz or more and 3000 GHz or less. In consideration of more efficient heating of the raw material contents and ease of obtaining microwave generators, the frequency is preferably 0.5 GHz or more, more preferably 1.0 GHz or more, and even more preferably 1.5 GHz or more, with the upper limit being preferably 100 GHz or less, more preferably 10.0 GHz or less, and even more preferably 6.0 GHz or less.

[0111] The output power cannot be generalized because it varies depending on the type of organic solvent contained in the mixture to be irradiated with microwaves, the amount of the mixture, etc., but in consideration of more efficiently heating the raw material contents, the output power is preferably 10 W or more, more preferably 50 W or more, and even more preferably 100 W or more, with the upper limit being preferably 500 kW or less, more preferably 300 kW or less, and even more preferably 200 kW or less.

[0112] Although the microwave irradiation time cannot be generalized because it varies depending on the type of organic solvent contained in the mixture to be irradiated with microwaves, the amount of the mixture, etc., in consideration of more efficient heating of the amorphized product, it is preferably 1 minute or more, more preferably 2 minutes or more, and even more preferably 3 minutes or more, with the upper limit being preferably 360 minutes or less, more preferably 300 minutes or less, and even more preferably 240 minutes or less. Furthermore, with regard to the heating temperature, the irradiation time during which the temperature is maintained at the highest temperature is preferably 1 minute or more, more preferably 2 minutes or more, and even more preferably 3 minutes or more, with the upper limit being preferably 240 minutes or less, more preferably 210 minutes or less, even more preferably 190 minutes or less, and even more preferably 180 minutes or less.

[0113] The heating temperature by microwave irradiation cannot be generally determined because it varies depending on the composition of the sulfide solid electrolyte to be obtained, and whether an amorphous or crystalline sulfide solid electrolyte is to be obtained. However, the temperature of the mixture is preferably 150°C or higher, more preferably 200°C or higher, and even more preferably 230°C or higher, with the upper limit being preferably 360°C or lower, more preferably 350°C or lower, even more preferably 310°C or lower, and still more preferably 300°C or lower.

[0114] The heating temperature by microwave irradiation can vary depending on the composition of the sulfide solid electrolyte to be obtained, whether it is amorphous or crystalline, as described above. That is, the heating temperature by microwave irradiation can control whether the sulfide solid electrolyte to be obtained is amorphous or crystalline.

[0115] For example, the temperature required for crystallization of the resulting raw sulfide solid electrolyte, i.e., the amorphous sulfide solid electrolyte, is determined by subjecting the amorphous sulfide solid electrolyte to differential thermal analysis (DTA) at a temperature increase rate of 10°C / min using a differential thermal analyzer (DTA device), and the peak top temperature of the exothermic peak observed at the lowest temperature is determined as the crystallization temperature. If the raw material contents in the mixture obtained by the above mixing, which are to be heated by microwave irradiation, are heated to a temperature higher than the crystallization temperature, a crystalline sulfide solid electrolyte is obtained, and if the raw material contents are heated to a temperature lower than the crystallization temperature, an amorphous sulfide solid electrolyte is obtained.

[0116] When producing a crystalline sulfide solid electrolyte, from the viewpoint of obtaining a crystalline sulfide solid electrolyte more stably and efficiently, the temperature of the amorphous material is preferably in the range of 5 ° C. or more, more preferably 10 ° C. or more, and even more preferably 20 ° C. or more relative to the crystallization temperature. There is no particular limitation as to the upper limit, but it may be about 40 ° C. or less. On the other hand, when producing an amorphous sulfide solid electrolyte, from the viewpoint of obtaining a crystalline sulfide solid electrolyte more stably and efficiently, the temperature of the amorphous material is preferably in the range of 5 ° C. or less, more preferably 10 ° C. or less, and even more preferably 20 ° C. or less relative to the crystallization temperature. It may be set to be equal to or higher than the boiling point of the organic solvent contained in the mixture. The lower limit is not particularly limited as long as it is equal to or higher than the boiling point of the organic solvent contained in the mixture. For example, it may be set to be equal to or higher than the temperature of the exothermic peak observed at the lowest temperature side -40 ° C.

[0117] In the production method of this embodiment, since the amorphized material is selectively heated as described above, the temperature of the raw material content itself is considered to be higher than the temperature of the organic solvent (considered to be the same as the temperature of the mixture.) Therefore, in the production method of this embodiment, although the temperature of the mixture obtained by the above mixing can be known, the temperature of the amorphized material in the mixture is indirectly known from the temperature of the mixture.

[0118] According to the examples described below, a sulfide solid electrolyte having an argyrodite-type crystal structure is obtained by setting the temperature of the mixture at 300°C. Considering that, as mentioned above, a sulfide solid electrolyte having an argyrodite-type crystal structure requires firing at a high temperature of about 400°C according to conventional methods, the temperature of the amorphous material itself can be considered to be the temperature of the mixture + about 100°C. Strictly speaking, this can vary depending on the type and content of the organic solvent in the mixture, but it is advisable to determine whether the temperature of the amorphous material itself has reached the crystallization temperature and set the heating temperature based on the temperature of the mixture + 100°C as a guide.

[0119] [Drying] The manufacturing method of this embodiment may include drying the fluid obtained by the microwave irradiation. The obtained fluid contains the sulfide solid electrolyte produced by the microwave irradiation, the remaining organic solvent, etc., and is usually in the form of a slurry (suspension). Therefore, by drying the fluid, a powder of the sulfide solid electrolyte is obtained.

[0120] Drying can be performed by irradiating the mixture with microwaves and drying the resulting fluid at a temperature that depends on the type of solvent, typically at 5 to 200°C, preferably 10 to 190°C, and more preferably 15 to 180°C, under reduced pressure (vacuum drying) using a vacuum pump or the like to volatilize the solvent.

[0121] Drying may be carried out by filtering the fluid using a glass filter or the like, by solid-liquid separation by decantation, or by solid-liquid separation using a centrifugal separator or the like.

[0122] The drying may be carried out by any of the above-mentioned reduced pressure drying (vacuum drying), filtration, and solid-liquid separation. For example, reduced pressure drying (vacuum drying) may be carried out after filtration or solid-liquid separation.

[0123] [Sulfide Solid Electrolyte] The sulfide solid electrolyte obtained by the manufacturing method of this embodiment is either an amorphous sulfide solid electrolyte (glass component) or a crystalline sulfide solid electrolyte. Whether it is amorphous or crystalline can be adjusted by the heating temperature by microwave irradiation.

[0124] (Amorphous 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, and representative examples thereof include Li, ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５- LiI-LiBr, etc., sulfide solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide; ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-SiS ２ -P ２ S ５ In order to obtain higher ionic conductivity, a sulfide solid electrolyte such as LiI is preferable. ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ A preferred example is a solid electrolyte composed of lithium sulfide, phosphorus sulfide, and a lithium halide, such as LiI-LiBr. The types of elements constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0125] In the solid electrolyte (amorphous solid electrolyte and crystalline solid electrolyte) obtained by the method for producing a solid electrolyte of this embodiment, the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms is preferably 1.0 to 1.8:0.1 to 0.8:1.0 to 2.0:0.01 to 0.6, more preferably 1.1 to 1.7:0.2 to 0.6:1.2 to 1.8:0.05 to 0.5, and even more preferably 1.2 to 1.6:0.25 to 0.5:1.3 to 1.7:0.08 to 0.4. Furthermore, when bromine and iodine, or bromine and chlorine are used in combination as halogen atoms, the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, bromine, and iodine or chlorine is preferably 1.0 to 1.8: 0.1 to 0.8: 1.0 to 2.0: 0.01 to 0.3: 0.01 to 0.3, more preferably 1.1 to 1.7: 0.2 to 0.6: 1.2 to 1.8: 0.02 to 0.25: 0.02 to 0.25, even more preferably 1.2 to 1.6: 0.25 to 0.5: 1.3 to 1.7: 0.03 to 0.2: 0.03 to 0.2, and still more preferably 1.35 to 1.45: 0.3 to 0.45: 1.4 to 1.7: 0.04 to 0.18: 0.04 to 0.18. By setting the composition ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above range, it becomes easier to obtain a solid electrolyte having a higher ionic conductivity and a crystal structure described below, particularly a thiolisiconregion II crystal structure or an argyrodite crystal structure.

[0126] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle size (D ５０ ) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm.

[0127] (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 solid electrolyte to a crystallization temperature or higher, and its crystalline structure may be Li ３ P.S. ４ Crystal structure, Li ４ P ２ S ６ Crystal structure, Li ７P.S. ６ Crystal structure, Li ７ P ３ S １１ Examples of the crystalline sulfide solid electrolyte obtained by the production method of this embodiment include a crystalline structure having peaks at 2θ = 20.2° and 23.6° in X-ray diffraction measurement using CuKα rays (for example, JP 2013-16423 A). In addition, from the viewpoint of obtaining higher ionic conductivity, the following argyrodite-type crystalline structure and thiolicon region II-type crystalline structure are preferred.

[0128] The above Li ７ P.S. ６ The structural skeleton of the compound has the composition formula Li ７－ｘ P １－ｙ Si ｙ S ６ and Li ７＋ｘ P １－ｙ Si ｙ S ６ The crystal structure represented by the formula (x is -0.6 to 0.6, y is 0.1 to 0.6) 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°. ７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ The crystal structure represented by (0.8≦x≦1.7, 0<y≦−0.25x+0.5) is 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°. ７－ｘ P.S. ６－ｘ Ha ｘ The crystal structure represented by the formula (where Ha is Cl or Br, and x is preferably 0.2 to 1.8) is 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°. ７ P.S.６ A crystal structure basically having the structural skeleton shown in the figure is also called an argyrodite-type crystal structure. Note that the positions of these peaks may vary within a range of ±0.5°.

[0129] Also, Li ４－ｘ Ge １－ｘ P ｘ S ４ 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 ｘ S ４ Also included are crystal structures similar to the thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725).

[0130] As used herein, the term "thiolicon region II crystal structure" refers to a Li ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４ This indicates that the thiolisicon region II type crystal structure has a similar crystal structure to the thiolisicon region II type. As will be described later, the thiolisicon region II type crystal structure and the similar crystal structure have similar diffraction peaks, and are therefore very close to each other. Therefore, it is technically reasonable to treat the "thiolisicon region II type crystal structure" as including the thiolisicon region II type crystal structure and the similar crystal structure.

[0131] The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may have the above-mentioned thiolicon region II type crystal structure or may have it as the main crystal, but from the viewpoint of obtaining higher ionic conductivity, it is preferable that it has it as the main crystal. In this specification, "having it as the main crystal" means that the proportion of the target crystal structure among the crystal structures is 80% or more, preferably 90% or more, and more preferably 95% or more. Furthermore, from the viewpoint of obtaining higher ionic conductivity, the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment has crystalline Li ３ P.S. ４ (β-Li ３ P.S. ４ ) is preferably not included.

[0132] The above "Li ４－ｘ Ge １－ｘ P ｘ S ４ The notation of the crystal structure "thio-LISICON Region II type" means that the crystal structure was composed of the atoms in question, namely, Li, Ge, P, and S atoms, at the time of discovery in the above document. The fact that the sulfide solid electrolyte obtained by the production method of this embodiment has a thio-LISICON Region II type crystal structure means that the above "Li ４－ｘ Ge １－ｘ P ｘ S ４ The crystal structure of "thio-LISICON Region II type" (including the above-mentioned similar crystal structure) is formed by each atom (Li, P, S and halogen atoms) contained in the raw material content, thereby forming the above-mentioned "Li ４－ｘ Ge １－ｘ P ｘ S ４ This means that the crystal structure exhibits the same diffraction peaks as the "thio-LISICON Region II type" crystal structure (including the above-mentioned similar crystal structures). The same applies to the argyrodite type crystal structure described below.

[0133] In X-ray diffraction measurement using CuKα radiation, Li３ P.S. ４ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°. ４ P ２ S ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°. ７ P.S. ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°. ７ P ３ S １１ Diffraction 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°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ The diffraction peaks of the thio-LISICON Region II crystal structure appear, for example, at 2θ=20.1°, 23.9°, and 29.5°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ Diffraction peaks of a crystal structure similar to that of 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°.

[0134] As described above, in this embodiment, when the thiolicon region II crystal structure is obtained, crystalline Li ３ P.S. ４ (β-Li ３ P.S. ４ The sulfide solid electrolyte obtained by the production method of this embodiment preferably does not contain crystalline Li ３ P.S. ４ The diffraction peaks at 2θ=17.5° and 26.1° seen in the thiolicon region II crystal structure are not present, or even if they are present, they are extremely small peaks compared to the diffraction peaks of the thiolicon region II crystal structure.

[0135] The shape of the crystalline sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D ５０ ) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm.

[0136] (Uses of sulfide solid electrolyte) The sulfide solid electrolyte obtained by the production method of this embodiment has high ionic conductivity and excellent battery performance, and is therefore suitable for use in batteries. The sulfide solid electrolyte obtained by the production method of this embodiment may be used in any of a positive electrode layer, a negative electrode layer, and an electrolyte layer. Each layer can be produced by a known method.

[0137] The battery preferably includes a current collector in addition to the positive electrode layer, the electrolyte layer, and the 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.

[0138] 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.

[0139] (Preparation Example 1: Preparation of Raw Material Sulfide Solid Electrolyte) Lithium sulfide (Li ２ S) was pulverized under a nitrogen atmosphere using a pin mill equipped with a constant volume feeder (model number "100UPZ", manufactured by Hosokawa Micron Corporation) (feeding rate: 80 g / min, disk rotation speed: 18,000 rpm). ２ S ５ Lithium bromide (LiBr, manufactured by Honjo Chemical Co., Ltd.), and lithium chloride (LiCl, manufactured by Honjo Chemical Co., Ltd.) were also pulverized using the pin mill. ２ S ５ The charging rates of lithium bromide (LiBr) and lithium chloride (LiCl) were 140 g / min, 230 g / min, and 250 g / min, respectively, and the rotation speed of the disk was 18,000 rpm.

[0140] Next, in a glove box under a nitrogen atmosphere, each compound pulverized as described above was mixed with a mixture of 100% ammonium hydroxide and 100% ammonium hydroxide in a molar ratio of Li ２ S:P ２ S ５ The raw materials were mixed in a ratio of 47.5:12.5:15.0:25.0, and a total of 110 g was weighed out and placed in a glass container. The container was shaken to roughly mix the raw material contents. The crude mixture was subjected to powder XRD analysis using the method described below. The results are shown in Figure 1. At this point, two diffraction peaks near 2θ = 18.2° could not be confirmed, so Li ３ P.S. ４ It can be confirmed that no structure was formed. The gentle peak near 2θ = 20.0° was detected by Kapton film. 110 g of the roughly mixed raw material was dispersed in a mixed solvent of 720 mL of dehydrated toluene (manufactured by Wako Pure Chemical Industries, Ltd.) and 2.9 mL of dehydrated isobutyronitrile (manufactured by Kishida Chemical Co., Ltd.) (2 mass% relative to the raw material) under a nitrogen atmosphere to obtain a slurry of approximately 10 mass%. The slurry was mixed and pulverized using a bead mill (LMZ015, manufactured by Ashizawa Finetech Co., Ltd.) while maintaining the nitrogen atmosphere. Specifically, 456 g of zirconia beads with a diameter of 0.5 mm were used as the milling medium, and the bead mill was operated at a peripheral speed of 12 m / s and a flow rate of 500 mL / min. The slurry was introduced into the mill and circulated for 1 hour to obtain a raw material mixture.

[0141] 400 mL of the mixture of raw materials obtained above was placed in an autoclave (volume: 500 mL, made of SUS316) equipped with a stirrer and a heating oil bath, and heat-treated at 200° C. for 2 hours while stirring at a rotation speed of 350 rpm. After the treatment, the mixture was dried under reduced pressure to distill off the solvent, and a calcined product was obtained.

[0142] Example 1 2.0 g of the calcined product obtained in Preparation Example 1 was placed in a 45 ml zirconia pot, and ten 10 mm diameter zirconia balls were added. Mechanical milling was carried out using a Fritsch planetary ball mill. First, milling was carried out twice for 5 minutes at a rotation speed of 150 rpm (positive and negative rotation). Then, milling was carried out for a total of 5 hours by rotating the mill at 370 rpm for 1 hour each time with positive and negative rotation. Powder XRD measurement was carried out on this sample (amorphized product), and it was confirmed that the product had been amorphized. The powder XRD measurement results are shown in Figure 2. The peak intensity (I) at 2θ = 18.2 ± 0.3° was measured by X-ray diffraction measurement using CuKα radiation for the amorphized product. １８．２ ) at 2θ=44.8±0.5° (I ４４．８ ) to the intensity ratio (I １８．２ / I ４４．８ ) was 0. 1.5 g of this sample was weighed out and mixed with 13.5 g of a solvent containing biphenyl and diphenyl oxide ("DAWTHERM A Heat Medium (trade name)", manufactured by Dow Chemical Japan Co., Ltd., biphenyl content: 27% by mass) to obtain a mixture (slurry concentration: 10% by mass). The obtained mixture was placed in a microwave irradiation device ("Discover 2.0 (model number)", manufactured by CEM), and microwave irradiation (frequency: 2.45 GHz) was initiated. The mixture was maintained at 300°C for 30 minutes, and then the microwave irradiation was stopped. The obtained fluid was dried under vacuum at 180°C for 4 hours to obtain a sulfide solid electrolyte powder. The obtained sulfide solid electrolyte powder was subjected to powder XRD measurement using the method described below. The results are shown in Figure 3. 3, diffraction peaks at 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°, which are attributable to the argyrodite-type crystal structure, can be seen. Furthermore, the ionic conductivity of the obtained sulfide solid electrolyte was measured by the method described below, and was found to be 3.3 mS / cm.

[0143] Example 2 A sulfide solid electrolyte powder was obtained in the same manner as in Example 1, except that the milling time of the calcined product was changed to 10 hours. The peak intensity (I １８．２ ) at 2θ=44.8±0.5° (I ４４．８ ) to the intensity ratio (I １８．２ / I ４４．８ ) was 0. The ionic conductivity of the obtained sulfide solid electrolyte powder was measured by the following method and was found to be 3.7 mS / cm.

[0144] Example 3 A sulfide solid electrolyte powder was obtained in the same manner as in Example 1, except that the milling time of the calcined product was changed to 20 hours. The peak intensity (I １８．２ ) at 2θ=44.8±0.5° (I ４４．８ ) to the intensity ratio (I １８．２ / I ４４．８ ) was 0. The ionic conductivity of the obtained sulfide solid electrolyte powder was measured by the following method and was found to be 3.6 mS / cm.

[0145] Comparative Example 1 Powder XRD measurement was carried out on the raw sulfide solid electrolyte obtained in Preparation Example 1. The results are shown in FIG. 2. The peak intensity (I １８．２ ) at 2θ=44.8±0.5° (I ４４．８ ) to the intensity ratio (I １８．２ / I ４４．８) was 4.21. 1.5 g of the raw sulfide solid electrolyte was weighed out and mixed with 13.5 g of a solvent containing biphenyl and diphenyl oxide ("DAWTHERM A Heat Medium (trade name)", manufactured by Dow Chemical Japan Co., Ltd., biphenyl content: 27% by mass) to obtain a mixture (slurry concentration: 10% by mass). The resulting mixture was placed in a microwave irradiation device ("Discover 2.0 (model number)", manufactured by CEM), and microwave irradiation (frequency: 2.45 GHz) was initiated. The mixture was maintained at 300°C for 30 minutes, and then the microwave irradiation was stopped. The resulting mixture was dried under vacuum at 180°C for 4 hours to obtain a sulfide solid electrolyte powder. The resulting sulfide solid electrolyte powder was subjected to powder XRD diffraction measurement using the following method. The results are shown in Figure 3. 3, diffraction peaks at 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°, which are attributable to the argyrodite-type crystal structure, were confirmed. Furthermore, the ionic conductivity was measured by the following method and was found to be 1.6 mS / cm.

[0146] (Measurement of Ion Conductivity) In this example, the measurement of ion conductivity was carried out as follows. A 10 mm diameter (cross-sectional area S: 0.785 cm ２ ), and a height (L) of 0.1 to 0.3 cm were molded into a circular pellet to prepare a sample. Electrode terminals were attached to the top and bottom of the sample, and measurements were made at 25°C using an AC impedance method (frequency range: 1 MHz to 100 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 defined as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following formula: R = ρ (L / S) σ = 1 / ρ

[0147] (Powder X-ray Diffraction (XRD) Measurement) In this specification, powder X-ray diffraction (XRD) measurement was carried out as follows. The powders obtained in the examples and comparative examples were filled into a groove 20 mm in diameter and 0.2 mm deep, and leveled with glass to prepare a sample. This sample was sealed with Kapton film for XRD and measured under the following conditions without being exposed to air. Measuring device: M03xhf (model number, manufactured by Mac Science Co., Ltd.) Tube voltage: 40 kV Tube current: 40 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: focusing method Slit configuration: divergence slit 0.5°, scattering slit 0.5°, receiving slit 0.3 mm, monochromator used Detector: semiconductor detector Measurement range: 2θ = 10-60 deg Step width, scan speed: 0.05 deg, 10 seconds / step

[0148] The peak intensities at 2θ = 18.2 ± 0.3° and 44.8 ± 0.5° were calculated using the following method. The half-width was calculated using a range of ±0.3° of the target peak. Let A be the ratio of the Lorentz function (0 ≦ A ≦ 1), B be the background-corrected peak intensity, C be the target peak, D be the peak position in the range (C ± 0.5°) used for calculation, E be the half-width parameter, F be the background, and G be the intensity of each peak in the peak range used for calculation. When the variables are A, B, C, D, E, and F, the following is calculated for each peak position: H = G - {B × {A / (1 + (D - C) 2 / E 2 ) + (1 - A) × exp(-1 × (D - C) 2 / E 2 )} + F} The H values ​​within the range of C ± 0.5° of the peak to be calculated were summed, and the sum was minimized using the GRG nonlinear solver function in the spreadsheet software Excel (Microsoft) to determine the peak intensity. In this way, the peak intensity (I １８．２ ) and the peak intensity at 2θ = 44.8 ± 0.5° (I ４４．８ ) and the peak intensity (I １８．２ ) peak intensity (I ４４．８ ) to the ratio (I １８．２ / I ４４．８) was calculated. In addition, the half-width at 2θ = 30 ± 0.3° (FMHM) was calculated by summing H within the range of the target peak C ± 0.5° and minimizing it with GRG nonlinearity using the solver function to find the half-width parameter. The half-width parameter was used to calculate the following equation: Half-width (FMHM) = E × 2 × (ln4) (1 / 2)

[0149] (Integrated power) The integrated power E (unit: Wh / g) is the average air power of each machine when the calcined material (object to be pulverized) is not included. ０ (unit: W), the average instantaneous power required to process the calcined material in each machine is P (unit: W), the total processing time is t (unit: h), and the total weight of the calcined material to be processed is M (unit: g), and the following formula was used to calculate E = (P - P ０ ) x t / M

[0150] The production conditions in Examples 1 to 3 and Comparative Example 1, as well as the results of XRD measurement and ionic conductivity of the obtained sulfide solid electrolytes, are shown in Table 1 below.

[0151]

[0152] As is clear from a comparison between Examples 1 to 3 and Comparative Example 1, in Examples 1 to 3 in which the raw sulfide solid electrolyte obtained in Production Example 1 was subjected to a pulverization treatment, the ionic conductivity of the sulfide solid electrolyte finally obtained was excellent. In contrast, in Comparative Example 1 in which the raw sulfide solid electrolyte obtained in Production Example 1 was subjected to microwave heating without being pulverized, the ionic conductivity of the sulfide solid electrolyte finally obtained was lower. Furthermore, the sulfide solid electrolytes obtained in Examples 1 to 3 had lower 30° half-widths derived from argyrodite-type crystals compared to that obtained in Comparative Example 1. It is believed that the amorphization treatment facilitates the formation of argyrodite-type crystallites even at low firing temperatures, thereby improving ionic conductivity.

[0153] According to the production method of this embodiment, a liquid phase method is employed, the heating temperature is reduced, and granulation due to heating is suppressed, thereby enabling efficient production of a sulfide solid electrolyte that maintains particle size. The sulfide solid electrolyte obtained by the production method of this embodiment is suitable for use in batteries, particularly 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: subjecting a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, or a calcined product obtained by heating the raw material, to an amorphization treatment to obtain an amorphized product; and irradiating a mixture of the amorphized product and an organic solvent with microwaves.

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein the amorphous treatment is carried out on a calcined product of the raw material components.

3. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the raw material content is heated in a sealed pressure vessel when the calcined product is obtained.

4. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, wherein the raw material content is heated in the presence of a solvent when the calcined product is obtained.

5. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 4, wherein the amorphization treatment is a mechanical treatment or a melt-quenching treatment.

6. The method for producing a sulfide solid electrolyte according to claim 5, wherein the mechanical treatment is a pulverization treatment.

7. The method for producing a sulfide solid electrolyte according to claim 6, wherein the integrated power consumption in the pulverization treatment is 0.5 Wh / g or more.

8. The peak intensity (I) at 2θ=18.2±0.3° in X-ray diffraction measurement of the amorphous material using CuKα radiation １８．２ ) at 2θ=44.8±0.5° (I ４４．８ ) to the intensity ratio (I １８．２ / I ４４．８ 8. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 7, wherein the value of (a) is 0.2 or less.

9. The amorphous material is crystalline Li ３ P.S. ４ The method for producing a sulfide solid electrolyte according to any one of claims 1 to 8, wherein the sulfide solid electrolyte does not contain 10. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 9, wherein the amorphization treatment of the raw material contents is carried out in the absence of the organic solvent or in a state in which the amount of the organic solvent added is 30 mass% or less relative to the total amount of the raw material contents.

11. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 10, wherein the organic solvent has a dielectric loss factor of 10.0 or less at 25°C.

12. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 11, wherein the boiling point of the organic solvent is 50°C or higher.

13. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 12, wherein the organic solvent is at least one selected from the group consisting of aromatic solvents and alicyclic solvents.

14. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 13, wherein the content of amorphous material in the mixture is 1% by mass or more and 20% by mass or less.

15. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 14, wherein the mixture is heated to 150°C or higher and 360°C or lower by microwave irradiation.

16. The raw material contains Li ３ P.S. ４ The method for producing a sulfide solid electrolyte according to any one of claims 1 to 15, wherein the raw material sulfide solid electrolyte has a structure.

17. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 16, wherein the sulfide solid electrolyte is a crystalline sulfide solid electrolyte having an argyrodite-type crystal structure.

Images