Sulfide solid electrolyte production method

Abstract

Provided is a sulfide solid electrolyte production method in which a solid electrolyte raw material is once heated to obtain a calcined product and is further heated to obtain a sulfide solid electrolyte. The sulfide solid electrolyte production method includes: obtaining a calcined product by heating a raw material-containing material that contains a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom and from which a sulfide solid electrolyte having more excellent ion conductivity can be efficiently produced; subjecting the calcined product to an amorphization treatment to obtain an amorphous product; and heating the amorphous product.

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 solid-phase methods and liquid-phase methods, and the liquid-phase methods include 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 Documents 1 and 2 propose a method in which raw materials are contacted in a state in which a hydrocarbon organic solvent is added, or a method in which mechanical milling is performed.

[0004] International Publication No. 2009 / 047977 Pamphlet Japanese Patent Application Laid-Open No. 2017-112100

[0005] An object of the present invention is to provide a method for producing a sulfide solid electrolyte, in which a solid electrolyte raw material is once heated to obtain a calcined product, and then further heated to obtain a sulfide solid electrolyte, and the method can efficiently produce a sulfide solid electrolyte having superior ionic conductivity.

[0006] A method for producing a sulfide solid electrolyte according to the present invention includes: heating a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a calcined product; subjecting the calcined product to an amorphization treatment to obtain an amorphized product; and heating the amorphized product.

[0007] According to the present invention, in a production method in which a solid electrolyte raw material is once heated to obtain a calcined product and then further heated to obtain a sulfide solid electrolyte, a sulfide solid electrolyte having superior ionic conductivity can be efficiently produced, and a production method for a sulfide solid electrolyte can be provided.

[0008] 1 is an X-ray diffraction spectrum of the raw material content after crude mixing obtained in Preparation Example 1. FIG. 2 is an X-ray diffraction spectrum of the amorphous material obtained in Example 1 and the calcined product used in Comparative Example 1. FIG. 3 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Example 1. FIG. 4 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 1. FIG. 5 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Example 2. FIG. 6 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 2. FIG. 7 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Example 3. FIG. 8 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 3. FIG. 9 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Example 4. FIG. 10 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 4.

[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 inventor discovered the following and completed the present invention. The manufacturing methods described in Patent Documents 1 and 2 do not pay any attention to the fact that after calcining the raw material inclusions, further amorphization treatment is performed before heating, and they do not disclose anything about the fact that the ionic conductivity of the resulting sulfide solid electrolyte is improved by performing amorphization treatment on the calcined product of the raw material inclusions.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] [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, comprising: heating a raw material-containing material that includes lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a calcined product; subjecting the calcined product to an amorphization treatment to obtain an amorphous product; and heating the amorphous product.

[0015] In a conventional method for producing a sulfide solid electrolyte, a raw material mixture containing multiple solid electrolyte raw materials is mechanically pulverized, then calcined, and then fired to gradually promote crystallization, thereby producing a sulfide solid electrolyte with excellent ionic conductivity. The present inventors have found that the ionic conductivity of the resulting sulfide solid electrolyte can be improved by intentionally subjecting the calcined product obtained by the calcination to an amorphization treatment and then firing the product.

[0016] A second aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to the first aspect, wherein the raw material contents are heated in a sealed state in a pressure-resistant container when the raw material contents are heated to obtain a calcined product.

[0017] By using a pressure vessel when heating the raw material contents to obtain the calcined product, the reaction between the solid electrolyte materials contained in the raw material contents can be efficiently promoted.

[0018] A third aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to the first or second aspect, wherein the raw material contents are heated in the presence of a solvent when the raw material contents are heated to obtain a calcined product.

[0019] By heating the raw material contents in the presence of a solvent, the reaction between the solid electrolyte materials contained in the raw material contents can be efficiently promoted.

[0020] 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 amorphization treatment is a mechanical treatment or a melt-quenching treatment. A fifth aspect of this embodiment is the method for producing a sulfide solid electrolyte according to the fourth aspect, in which the mechanical treatment is a pulverization treatment. A sixth aspect of this embodiment is the method for producing a sulfide solid electrolyte according to the fifth aspect, in which the integrated power in the pulverization treatment is 0.5 Wh / g or more.

[0021] Specific examples of the amorphization treatment include mechanical treatment and melt-quenching treatment, and a specific example of the mechanical treatment is pulverization 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.

[0022] In a seventh 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 ４４．８ ) is 0.2 or less.

[0023] 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.

[0024] In an eighth aspect of this embodiment, 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 seventh aspects, which does not include:

[0025] 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.

[0026] A ninth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to eighth aspects, wherein the amorphous material is heated in the presence or absence of a solvent.

[0027] The amorphous material can be heated in the presence or absence of a solvent. When the amorphous material is heated in the presence of a solvent, the particles are less likely to bond together during crystallization, and the resulting sulfide solid electrolyte has a smaller particle size.

[0028] 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 raw material contents are a premix of at least lithium sulfide, phosphorus sulfide, and lithium halide.

[0029] Specifically, the raw material ingredients are preferably a premix of at least lithium sulfide, phosphorus sulfide, and lithium halide. When the raw material ingredients are such a premix, the reactivity between the solid electrolyte raw materials is improved, and a sulfide solid electrolyte having excellent ionic conductivity can be efficiently obtained.

[0030] An eleventh aspect of this embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to tenth aspects, wherein the sulfide solid electrolyte is a crystalline sulfide solid electrolyte having an argyrodite-type crystal structure. A twelfth aspect of this embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to eleventh aspects, wherein the raw material inclusions are heated at a temperature of 150°C or higher and 300°C or lower. A thirteenth aspect of this embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to twelfth aspects, wherein the amorphous material is heated at a temperature of 250°C or higher and 500°C or lower.

[0031] As described above, sulfide solid electrolytes having an argyrodite-type crystal structure are known as solid electrolytes with high ionic conductivity, but conventional manufacturing methods require firing at a high temperature of about 400° C. However, according to the manufacturing method of this embodiment, the raw material contents are heated once and then subjected to an amorphization treatment, and the resulting amorphous material is made into a sulfide solid electrolyte having an argyrodite-type crystal structure with relatively high crystallinity, which can be manufactured at lower temperature conditions.

[0032] [Heating a raw material containing material to obtain a calcined product] The production method of this embodiment includes heating a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a calcined product.

[0033] (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.

[0034] 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 ２ a 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.

[0035] 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.

[0036] 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.

[0037] 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 ２Among the alkali metal sulfides, lithium sulfide is preferred, and among the phosphorus sulfides, diphosphorus pentasulfide is preferred.

[0038] 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.

[0039] 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. ３ P.S. ４ When a lithium-containing structure such as the above is used as a raw material, the effect of improving ionic conductivity due to the amorphous treatment is more likely to be achieved.

[0040] 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.

[0041] 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.

[0042] As the raw material components, it is preferable to use a crude mixture containing lithium sulfide, phosphorus sulfide, and a lithium halide. When lithium sulfide, diphosphorus pentasulfide, and a lithium halide are used as the raw material components, 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, but from the viewpoint of obtaining higher chemical stability and high ionic conductivity, it 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.

[0043] 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.

[0044] 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.

[0045] (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.

[0046] 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.

[0047] (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.

[0048] 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.

[0049] The mixing and pulverization may be carried out in the presence of a solvent, and the solvent used is preferably an organic solvent, which may be appropriately selected from the organic solvents used in heating the amorphized material described below.

[0050] The crude mixture and the solvent usually form a slurry (suspension), and 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 amorphized material relative to the total amount of the amorphized material and the organic solvent in the mixture when the amorphized material is heated, as described below.

[0051] [Obtaining the Calcined Product] The manufacturing method of this embodiment includes obtaining the calcined product by heating the raw material inclusions. The calcination promotes a reaction between the solid electrolyte raw materials contained in the raw material inclusions, and the calcined product is obtained.

[0052] The method of calcination is not particularly limited, and examples thereof include methods using a hot plate, autoclave, vacuum heating device, argon gas atmosphere furnace, calcination furnace, etc. In addition, methods using a shear-type dryer such as an FM mixer or Nauta mixer, a stationary furnace such as a hearth kiln, or a rotary furnace such as a rotary kiln, and further, industrially, a horizontal dryer having a heating means and a feeding mechanism, a horizontal vibration fluidized dryer, etc. The method of calcination 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.

[0053] 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.

[0054] 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.

[0055] The calcination of the raw material content 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 content.

[0056] The calcination of the raw material-containing material may be carried out in the presence of a solvent, and the type and amount of the solvent are the same as those used when heating the amorphized material, which will be described later.

[0057] The calcined product thus obtained has a molecular structure mainly consisting of Li ３ P.S. ４ A sulfide solid electrolyte having the structure is assumed, but it varies depending on the compounding ratio (molar ratio) of the raw materials used in the raw material inclusions and the type of substance containing halogen atoms contained in the raw material inclusions.

[0058] [Amorphization Treatment] The manufacturing method of this embodiment includes subjecting the calcined product to an amorphization treatment to obtain an amorphized product. The amorphization treatment is not particularly limited as long as it is a method that amorphizes the calcined product, but examples thereof include mechanical treatment, melt quenching, etc. A specific example of the mechanical treatment is pulverization, and more specifically, the pulverization is preferably carried out by mechanical milling, and more specifically, it is preferably carried out using a media-type pulverizer such as a ball mill or a bead mill.

[0059] The amorphization treatment of the calcined product can be carried out in the presence or absence of an organic solvent. That is, the amorphization treatment can be carried out after mixing at least a portion of the organic solvent with the calcined product. When the amorphization treatment is carried out in the presence of an organic solvent, the amount of the organic solvent added relative to the total amount of the calcined product is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, from the viewpoint of efficient amorphization.

[0060] As the mill used in the amorphization treatment, for example, a media-type mill using a grinding medium can be used. Media-type mills are broadly classified into container-driven mills and media-agitated mills. Examples of container-driven mills include agitation tanks, grinding tanks, or combinations thereof, such as ball mills and bead mills. Examples of media-agitated mills include impact mills such as cutter mills, hammer mills, and pin mills; tower-type mills such as tower mills; agitation tank-type mills such as attritors, aquamizers, and sand grinders; flow-tank-type mills such as Viscomills and pearl mills; flow-tube-type mills; annular-type mills such as Coball mills; continuous dynamic-type mills; and single- or multi-screw kneaders. Among these, considering the ease of adjusting the particle size of the resulting amorphized material, the ball mills and bead mills exemplified as container-driven mills are preferred, and planetary-type mills are particularly preferred.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] By selecting the size and material of the medium (beads, balls) used, the rotor rotation speed, time, etc., mixing, stirring, pulverization, or a combination of these processes can be performed, and the particle size, etc. of the resulting sulfide can be adjusted. The treatment time in the amorphization treatment is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more, with the upper limit usually being 100 hours or less, preferably 50 hours or less, more preferably 20 hours or less, and even more preferably 10 hours or less.

[0065] 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.

[0066] 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. ４is small, that is, it can be said that the material is sufficiently amorphized, and when the amorphized material is heated as described below, the reaction between the solid electrolyte raw materials proceeds more easily, which is thought to improve the ionic conductivity of the resulting sulfide solid electrolyte.

[0067] [Heating the Amorphized Material] The manufacturing method of this embodiment includes heating the amorphized material. By heating the amorphized material, a sulfide solid electrolyte, more specifically a crystalline sulfide solid electrolyte, can be obtained.

[0068] The heating of the amorphized material may be carried out in one step or in multiple steps, but can be carried out in two steps, for example, by calcining and firing. The heating temperature and time for calcining when heating the amorphized material can be adjusted appropriately taking into consideration the composition of the amorphized material, etc. For example, the heating temperature is preferably 150°C to 300°C, more preferably 160°C to 280°C, and particularly preferably 170°C to 250°C. The heating time is preferably 0.1 to 8 hours, more preferably 0.2 to 6 hours, and particularly preferably 0.25 to 4 hours. By setting the temperature within the above range, PS ４ The fine crystal raw material mixture is calcined in a solution, and the PS structure is formed at a relatively low temperature. ４ This makes it possible to form crystals containing the structure. There is no particular limitation on the heating device used in the calcination. Examples include shear-type dryers such as FM mixers and Nauta mixers, stationary furnaces such as hearth kilns, and rotary furnaces such as rotary kilns. Drying may be performed before calcination, or drying and calcination may be performed simultaneously. The atmosphere for calcination is not particularly limited, but an inert gas atmosphere such as nitrogen or argon is preferred.

[0069] The heating temperature and time for firing the amorphized material can be appropriately adjusted taking into consideration the composition of the amorphized material or the calcined material, etc. For example, the heating temperature is preferably 250°C to 500°C, more preferably 300°C to 400°C, even more preferably 350°C to 390°C, and particularly preferably 360°C to 380°C. The heating time is preferably 1 to 360 minutes, more preferably 5 to 180 minutes, and particularly preferably 10 to 120 minutes.

[0070] The amorphized material or the calcined material thereof may be heated in the presence or absence of a solvent. When heating in a solvent, the solvent may be, specifically, an organic solvent as described below, and the amorphized material or the calcined material thereof is dispersed in the solvent to form a slurry, and then heated.

[0071] The heating apparatus used to heat the amorphous material or its calcined product is not particularly limited, but if the heating temperature exceeds the boiling point of the solvent used, it is preferable to use an autoclave. The method for removing the solvent from the slurry subjected to the heating is not particularly limited, but the solvent can be distilled off under normal pressure or reduced pressure. Filtration can also be used in combination to further increase productivity.

[0072] The atmosphere in which the amorphous material or its calcined product is heated is not particularly limited, but is preferably an inert gas atmosphere such as nitrogen or argon.

[0073] Furthermore, the amorphous material or the calcined material thereof is preferably heated under reduced pressure, which is preferably 0.1 Pa or more, more preferably 1.0 Pa or more, and even more preferably 5.0 Pa or more from the viewpoint of the apparatus, and is preferably 100.0 Pa or less, more preferably 50.0 Pa or less, and even more preferably 20.0 Pa or less from the viewpoint of obtaining a solid electrolyte having high ionic conductivity.

[0074] (Organic Solvent) As the organic solvent used when heating the amorphous material or the calcined material thereof, a wide range of organic 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.

[0075] 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, and anthracene.

[0076] 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.

[0077] 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).

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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 uniformly maintained in the organic solvent, and the sulfide solid electrolyte can be produced more efficiently.

[0084] 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, allows the amorphized material to be more uniformly maintained in the organic solvent, and enables the amount of organic solvent used to be reduced. From these viewpoints, 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.

[0085] As the organic solvent, of 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.

[0086] 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, or tetrahydronaphthalene (tetralin, cyclohexylbenzene), and the aromatic ether solvent is preferably diphenyl ether (diphenyl oxide).

[0087] 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.

[0088] 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.

[0089] [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 and heating time in the heating step.

[0090] (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 of the solid electrolyte 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.

[0091] 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.

[0092] 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.

[0093] (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.

[0094] 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°.

[0095] 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).

[0096] 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.

[0097] 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.

[0098] 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 crystal structure of the "thio-LISICON Region II type" (including the above-mentioned similar crystal structures). The same applies to the above-mentioned argyrodite-type crystal structure.

[0099] 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°.

[0100] 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.

[0101] 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.

[0102] (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.

[0103] 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.

[0104] 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.

[0105] (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.

[0106] 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.

[0107] 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.

[0108] 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 one 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 results of the powder XRD measurement are shown in Figure 2. The peak intensity (I) at 2θ = 18.0 ± 0.3° was measured by X-ray diffraction measurement using CuKα radiation for the amorphized product. １８．０ ) at 2θ=45.0±0.3° (I ４５．０ ) to the intensity ratio (I １８．０ / I ４５．０ ) was 0.

[0109] The amorphous material thus obtained was heated in an electric furnace (F-1404-A, manufactured by Tokyo Glass Instruments Co., Ltd.) in a glove box under a nitrogen atmosphere. ２ O ３ A sagger (999-60S, manufactured by Tokyo Glass Instruments Co., Ltd.) made of PET was placed in the furnace, and the temperature was raised from room temperature to 340°C over one hour and maintained at 340°C for at least one hour. The electric furnace door was then opened, and the calcined material was quickly poured into the sagger. The door was then immediately closed and the material was heated for one hour. The sagger was then removed from the electric furnace and slowly cooled to obtain a sulfide solid electrolyte. Powder XRD analysis was performed on the obtained sulfide solid electrolyte powder using the method described below. The results are shown in Figure 3. In Figure 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 using the method described below and found to be 6.7 mS / cm.

[0110] (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

[0111] (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

[0112] 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)

[0113] (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

[0114] Comparative Example 1 Powder XRD measurement was carried out on the calcined product obtained in Preparation Example 1. The results are shown in FIG. 2. The peak intensity (I１８．２ ) at 2θ=44.8±0.5° (I ４４．８ ) to the intensity ratio (I １８．２ / I ４４．８ ) was 4.21. Next, a sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the calcined product was heated in an electric furnace in a glove box under a nitrogen atmosphere without being subjected to mechanical milling. Powder XRD diffraction measurement was performed on the obtained sulfide solid electrolyte powder. The results are shown in FIG. 4. In addition, the ionic conductivity was measured by the following method and was found to be 4.4 mS / cm.

[0115] Example 2 A sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the heating temperature in the electric furnace was 360°C. Powder XRD diffraction measurement was performed on the obtained sulfide solid electrolyte powder. The results are shown in Figure 5. In addition, the ionic conductivity was measured by the following method and was found to be 8.4 mS / cm.

[0116] Comparative Example 2 A sulfide solid electrolyte was obtained in the same manner as in Example 2, except that the calcined product obtained in Preparation Example 1 was heated directly in an electric furnace in a glove box under a nitrogen atmosphere without being subjected to mechanical milling. Powder XRD diffraction analysis was performed on the obtained sulfide solid electrolyte powder. The results are shown in FIG. 6 . Furthermore, the ionic conductivity was measured by the following method and was found to be 6.2 mS / cm.

[0117] Example 3 A sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the heating temperature in the electric furnace was 380°C. Powder XRD diffraction measurement was performed on the obtained sulfide solid electrolyte powder. The results are shown in Figure 7. In addition, the ionic conductivity was measured by the following method and was found to be 8.6 mS / cm.

[0118] Comparative Example 3 A sulfide solid electrolyte was obtained in the same manner as in Example 3, except that the calcined product obtained in Preparation Example 1 was heated directly in an electric furnace in a glove box under a nitrogen atmosphere without being subjected to mechanical milling. Powder XRD diffraction analysis was performed on the obtained sulfide solid electrolyte powder. The results are shown in FIG. 8 . Furthermore, the ionic conductivity was measured by the following method and was found to be 7.1 mS / cm.

[0119] Example 4 A sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the heating temperature in the electric furnace was 400°C. Powder XRD diffraction measurement was performed on the obtained sulfide solid electrolyte powder. The results are shown in Figure 9. In addition, the ionic conductivity was measured by the following method and was found to be 9.1 mS / cm.

[0120] Comparative Example 4 A sulfide solid electrolyte was obtained in the same manner as in Example 4, except that the calcined product obtained in Preparation Example 1 was heated directly in an electric furnace in a glove box under a nitrogen atmosphere without being subjected to mechanical milling. Powder XRD diffraction analysis was performed on the obtained sulfide solid electrolyte powder. The results are shown in FIG. 10 . Furthermore, the ionic conductivity was measured by the following method and was found to be 7.2 mS / cm.

[0121] The production conditions in Examples 1 to 4 and Comparative Examples 1 to 4, as well as the results of XRD measurement and ionic conductivity of the obtained sulfide solid electrolytes, are shown in Table 1 below.

[0122]

[0123] As is clear from the comparison between Examples 1 to 4 and Comparative Examples 1 to 4, the ionic conductivity of the sulfide solid electrolyte finally obtained in Examples 1 to 4, in which the calcined product obtained in Production Example 1 was subjected to a pulverization treatment, was excellent. In contrast, the ionic conductivity of the sulfide solid electrolyte finally obtained in Comparative Examples 1 to 4, in which the calcined product obtained in Production Examples 1 to 4 was subjected to heating without being subjected to a pulverization treatment, was lower.

[0124] 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: heating a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a calcined product; subjecting the calcined product to an amorphization treatment to obtain an amorphized product; and heating the amorphized product.

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein the raw material content is heated to obtain the calcined product while the raw material content is sealed in a pressure-resistant container.

3. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the raw material content is heated in the presence of a solvent when the raw material content is heated to obtain the calcined product.

4. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, wherein the amorphous treatment is a mechanical treatment or a melt-quenching treatment.

5. The method for producing a sulfide solid electrolyte according to claim 4, wherein the mechanical treatment is a pulverization treatment.

6. The method for producing a sulfide solid electrolyte according to claim 5, wherein the integrated power consumption in the pulverization treatment is 0.5 Wh / g or more.

7. 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 7. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 6, wherein the value of (a) is 0.2 or less.

8. 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 7, wherein the sulfide solid electrolyte does not contain 9. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 8, wherein the amorphous material is heated in the presence or absence of a solvent.

10. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 9, wherein the raw material contents are a premix of at least lithium sulfide, phosphorus sulfide, and lithium halide.

11. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 10, wherein the sulfide solid electrolyte is a crystalline sulfide solid electrolyte having an argyrodite-type crystal structure.

12. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 11, wherein the raw material content is heated to a heating temperature of 150°C or higher and 300°C or lower.

13. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 12, wherein the amorphous material is heated at a temperature of 250°C or higher and 500°C or lower.

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