WO2025206230A1 - Sulfide solid electrolyte production method - Google Patents

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

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

With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as power sources for these devices has become increasingly important. Among these, lithium-ion batteries have attracted attention due to their high energy density.
Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents, which necessitates the installation of safety devices to suppress temperature rises in the event of a short circuit, as well as improvements in the structure and materials to prevent short circuits.In response to this, all-solid-state batteries that use a solid electrolyte layer instead of the electrolyte can be developed, as this eliminates the need for flammable organic solvents in the battery, simplifies safety devices, and is superior in manufacturing cost and productivity.

Methods for manufacturing solid electrolytes used in solid electrolyte layers are broadly divided into solid-phase methods and liquid-phase methods. Liquid-phase methods are further divided into homogeneous methods, in which the solid electrolyte material is completely dissolved in a solvent, and heterogeneous methods, in which the solid electrolyte material is not completely dissolved but is left as a solid-liquid coexistence suspension. For example, Patent Documents 1 and 2 propose methods in which raw materials are brought into contact with a hydrocarbon organic solvent or subjected to mechanical milling.

International Publication No. 2009/047977 JP 2017-112100 A

The present invention aims to provide a method for producing a sulfide solid electrolyte, in which solid electrolyte raw materials are first heated to obtain a calcined product, and then further heated to obtain a sulfide solid electrolyte, that can efficiently produce a sulfide solid electrolyte with superior ionic conductivity.

The method for producing a sulfide solid electrolyte according to the present invention includes the steps of:
heating a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a calcined product;
a method for producing a sulfide solid electrolyte, the method comprising: subjecting the calcined product to an amorphization treatment to obtain an amorphized product; and heating the amorphized product.
is.

The present invention provides a method for producing a sulfide solid electrolyte in which solid electrolyte raw materials are first heated to obtain a calcined product, and then further heated to obtain a sulfide solid electrolyte, thereby efficiently producing a sulfide solid electrolyte with superior ionic conductivity.

1 is 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 calcined product used in Comparative Example 1. 1 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Example 1. 1 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 1. 1 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Example 2. 1 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 2. 1 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Example 3. 1 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 3. 1 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Example 4. 1 is an X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 4.

An embodiment of the present invention (hereinafter sometimes referred to as "this embodiment") will be described below. Note that in this specification, the upper and lower limits of numerical ranges expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values in the examples can also be used as the upper and lower limits.

(Findings gained by the inventors to arrive at the present invention)
As a result of extensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention.
The manufacturing methods described in Patent Documents 1 and 2 do not pay any attention to the fact that the raw material content is calcined, and then further subjected to an amorphization treatment before heating, and they do not disclose at all that the ionic conductivity of the resulting sulfide solid electrolyte is improved by performing an amorphization treatment on the calcined product of the raw material content.

In this specification, the term "solid electrolyte" refers to an electrolyte that remains solid at 25°C under a nitrogen atmosphere. The "sulfide solid electrolyte" obtained by the manufacturing 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.

As used herein, the term "sulfide solid electrolyte" includes both crystalline sulfide solid electrolytes and amorphous sulfide solid electrolytes. A crystalline sulfide solid electrolyte is a solid electrolyte in which peaks derived from the solid electrolyte are observed in the X-ray diffraction pattern in X-ray diffraction measurement, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present. In other words, a crystalline sulfide solid electrolyte contains a crystalline structure derived from the solid electrolyte, and the crystalline structure may be partially or entirely 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 contain amorphous sulfide solid electrolyte (also referred to as "glass component") as part of it. Therefore, crystalline sulfide solid electrolytes include so-called glass ceramics, which are obtained by heating an amorphous solid electrolyte (glass component) above its crystallization temperature.

In addition, in this specification, an amorphous sulfide solid electrolyte (glass component) refers to one in which the X-ray diffraction pattern in X-ray diffraction measurement is a halo pattern in which no peaks other than those derived from the material are observed, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present.

[Method for producing sulfide solid electrolyte]
A method for producing a sulfide solid electrolyte according to a first aspect of the present embodiment includes the steps of:
heating a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a calcined product;
a method for producing a sulfide solid electrolyte, the method comprising: subjecting the calcined product to an amorphization treatment to obtain an amorphized product; and heating the amorphized product.
is.

In a conventional method for producing a sulfide solid electrolyte, a raw material mixture containing multiple types of solid electrolyte raw materials is mechanically treated by pulverization, then calcined, and then fired to gradually promote crystallization, resulting in the production of 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 deliberately subjecting the calcined product obtained by the above-mentioned calcination to an amorphization treatment and then calcining the product.

A second aspect of this embodiment is as follows:
a method for producing a sulfide solid electrolyte according to a first embodiment, wherein the raw material content is heated in a sealed state in a pressure-resistant container when the raw material content is heated to obtain a calcined product;
is.

By using a pressure-resistant 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 promoted efficiently.

A third aspect of this embodiment is as follows:
the method for producing a sulfide solid electrolyte according to the first or second aspect, wherein the raw material content is heated in the presence of a solvent when the raw material content is heated to obtain a calcined product;
is.

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 promoted efficiently.

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

Specific examples of amorphization treatments include mechanical treatment and melt-quenching treatment, and a specific example of mechanical treatment is pulverization treatment. In such mechanical treatments, setting the integrated power to a certain level or higher enables sufficient amorphization treatment, which is preferable from the perspective of improving the ionic conductivity of the resulting sulfide solid electrolyte.

A seventh aspect of this embodiment is as follows:
the method for producing a sulfide solid electrolyte according to any one of the first to sixth aspects, wherein the amorphous product has an intensity ratio (I _18.2 /I 44.8 ) of a peak intensity (I _18.2 ) at 2θ=18.2±0.3° to a peak intensity (I _44.8 ) at 2θ= _44.8 ±0.5° in X-ray diffraction measurement using CuKα radiation of 0.2 or less;
is.

The amorphous material obtained by the amorphization treatment has a low ratio _of crystalline _Li3PS4 , represented by the peak intensity ( _I18.2 ) at 2θ=18.2±0.3°. On the other hand, the peak intensity ( _I44.8 ) at _2θ =44.8±0.5° derived from the raw material lithium sulfide ( _Li2S ) can be used as an index for comparing the peak intensity derived from this crystalline _Li3PS4 . Therefore, when the intensity ratio ( _I18.2 / _I44.8 ) is within the above range, the amorphous material obtained by the amorphization treatment can be said to be sufficiently amorphized, and it becomes easier to obtain a sulfide solid electrolyte with higher ionic conductivity.

An eighth aspect of this embodiment is as follows:
The method for producing a sulfide solid electrolyte according to any one of the first to seventh aspects, wherein the amorphous material does not contain crystalline Li ₃ PS _4;
is.

The amorphous material obtained by the amorphization treatment has a low ratio _of crystalline _Li3PS4 , represented by the peak intensity ( _I18.2 ) at 2θ=18.2±0.3°. On the other hand, the peak intensity ( _I44.8 ) at _2θ =44.8±0.5° derived from the raw material lithium sulfide ( _Li2S ) can be used as an index for comparing the peak intensity derived from this crystalline _Li3PS4 . Therefore, when the intensity ratio ( _I18.2 / _I44.8 ) is within the above range, the amorphous material obtained by the amorphization treatment can be said to be sufficiently amorphized, and it becomes easier to obtain a sulfide solid electrolyte with higher ionic conductivity.

A ninth aspect of this 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;
is.

The amorphous material can be heated in the presence or absence of a solvent, but heating in the presence of a solvent makes it difficult for particles to bond together during crystallization, resulting in a sulfide solid electrolyte with smaller particle sizes.

A tenth aspect of this embodiment is as follows:
The method for producing a sulfide solid electrolyte according to any one of the first to ninth aspects, wherein the raw material content is a pre-mixture of at least lithium sulfide, phosphorus sulfide, and lithium halide;
is.

Specific examples of the raw material ingredients that are preferably used include 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, making it possible to efficiently obtain a sulfide solid electrolyte with excellent ionic conductivity.

An eleventh aspect of this embodiment is:
The method for producing a sulfide solid electrolyte according to any one of first to tenth aspects, wherein the sulfide solid electrolyte is a crystalline sulfide solid electrolyte having an argyrodite-type crystal structure;
is.
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 content is heated at a heating temperature of 150°C or higher and 300°C or lower;
is.
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 heating temperature of 250°C or higher and 500°C or lower;
is.

As mentioned above, sulfide solid electrolytes with an argyrodite-type crystal structure are known as solid electrolytes with high ionic conductivity, but conventional manufacturing methods require firing at high temperatures of around 400°C. However, with 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 then used to produce a sulfide solid electrolyte with an argyrodite-type crystal structure that is relatively highly crystalline under lower temperature conditions.

[Heating raw material components to obtain 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.

(Raw material content)
The raw material inclusions contain lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. The raw material inclusions are not particularly limited as long as they contain these atoms, and examples include inclusions containing a compound containing at least one atom selected from these atoms, either singly or in combination as a raw material. 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.

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; phosphorus sulfides such as diphosphorus trisulfide (P ₂ S ₃ ) and diphosphorus pentasulfide (P ₂ S ₅ ); phosphorus halides such as various phosphorus fluorides (PF ₃ , PF ₅ ), various phosphorus chlorides (PCl ₃ , PCl ₅ , P ₂ Cl ₄ ), various phosphorus bromides (PBr ₃ , PBr ₅ ), and various phosphorus iodides (PI ₃ , P ₂ I ₄ ); thiophosphoryl fluoride (PSF ₃ Representative examples of the starting material include raw materials consisting of at least two elements selected from the above four elements, such as thiophosphoryl halides such as thiophosphoryl chloride (PSCl ₃ ), thiophosphoryl bromide (PSBr ₃ ), thiophosphoryl iodide (PSI ₃ ), thiophosphoryl dichloride fluoride (PSCl ₂ F), and thiophosphoryl dibromide fluoride (PSBr ₂ F); and elemental halogens such as fluorine (F ₂ ), chlorine (Cl ₂ ), bromine (Br ₂ ), and iodine (I ₂ ), preferably bromine (Br ₂ ) and iodine (I ₂ ).

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; metal sulfides such as silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, tin sulfide (SnS, SnS ₂ ), 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; and phosphorus oxyhalides such as phosphorus oxychloride (POCl ₃ ) and phosphorus oxybromide (POBr ₃ ).

In this embodiment, the halogen atom can vary depending on the sulfide solid electrolyte to be obtained, but from the viewpoint of more easily obtaining a sulfide solid electrolyte having high ionic conductivity, a chlorine atom, a bromine atom, or an iodine atom is preferred among halogen atoms. These atoms may be used alone or in combination.
Furthermore, for example, when a sulfide solid electrolyte having a thiolicon region II type crystal structure, which will be described later, is to be obtained, a bromine atom or an iodine atom is more preferable, and when a sulfide solid electrolyte having an argyrodite type crystal structure is to be obtained, a chlorine atom or a bromine atom is more preferable.

In this embodiment, from the viewpoint of more easily obtaining a sulfide solid electrolyte having high ionic conductivity, compounds that can be used as raw materials are preferably, among the above, alkali metal sulfides such as lithium sulfide and sodium sulfide; phosphorus sulfides such as diphosphorus trisulfide (P ₂ S ₃ ) and diphosphorus pentasulfide (P ₂ S ₅ ); elemental halogens such as fluorine (F ₂ ), chlorine (Cl ₂ ), bromine (Br ₂ ), and iodine (I ₂ ); and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; and, among alkali metal sulfides, lithium sulfide is preferred, and among phosphorus sulfides, diphosphorus pentasulfide is preferred.

As mentioned above, raw materials containing halogen atoms vary depending on the sulfide solid electrolyte to be obtained, so it is not possible to generalize, but among the halogen elements, chlorine (Cl ₂ ), bromine (Br ₂ ), and iodine (I ₂ ) are preferred, and among the lithium halides, lithium chloride, lithium bromide, and lithium iodide are preferred. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II crystal structure, bromine (Br ₂ ) and iodine (I ₂ ) are more preferred as the halogen elements, and lithium bromide and lithium iodide are more preferred as the lithium halides. Furthermore, when attempting to obtain a sulfide solid electrolyte having an argyrodite crystal structure, chlorine (Cl ₂ ) and bromine (Br ₂ ) are more preferred as the halogen elements, and lithium chloride and lithium bromide are more preferred as the lithium halides.

In the present embodiment, preferred examples of compounds that can be used as raw materials include sulfide solid electrolytes such as _Li3PS4 that contain a _{PS4 unit} or the like. When a structure containing lithium such as _Li3PS4 that exists as the main structure in the _sulfide solid electrolyte obtained by the production method of the present embodiment is used as a raw material, the effect of improving ionic conductivity due to the amorphization treatment is more likely to be achieved.

The raw sulfide solid electrolyte may be amorphous or crystalline, or may contain both amorphous and crystalline components. However, it is preferable to use a crystalline one in which a peak attributable to the _Li3PS4 structure is observed at 2θ = 17.0° to 19.0° in X-ray diffraction measurement using _CuKα radiation. In either case, when a compound containing halogen atoms is used as a raw material, the dispersibility of the halogen atoms is improved, making it easier for bonds to form between the halogen atoms and the lithium atoms, sulfur atoms, and phosphorus atoms in the solid electrolyte. As a result, a sulfide solid electrolyte with higher ionic conductivity can be obtained.

In this embodiment, when lithium sulfide is used as the raw material, the lithium sulfide is preferably in the form of particles.
The average particle size ( _D50 ) of the lithium sulfide particles is preferably 10 μm or more and 2000 μm or less, more preferably 30 μm or more and 1500 μm or less, and even more preferably 50 μm or more and 1000 μm or less. In this specification, the average particle size ( _D50 ) is the particle size at which 50% of the total particle size is reached when a particle size distribution integral curve is drawn and the particle size is sequentially integrated from the smallest particle, and the volume distribution refers to the average particle size that can be measured using, for example, a laser diffraction/scattering particle size distribution measuring device. Furthermore, among the above-mentioned examples of raw materials, solid raw materials preferably have an average particle size similar to that of the lithium sulfide particles, that is, preferably within the same range as the average particle size of the lithium sulfide particles. The particle size of the raw material compound may be adjusted by pulverization or the like, as necessary.

As the raw material components, it is preferable to use a crude mixture containing lithium sulfide, phosphorus sulfide, and lithium halide.
When lithium sulfide, diphosphorus pentasulfide, and 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. 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.

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, and even more preferably 60 mol% or more, with the upper limit being preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 80 mol% or less, and even more preferably 70 mol% or less.

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.
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.

(crude mixture)
The phosphorus sulfide in the crude mixture containing lithium sulfide, phosphorus sulfide, and lithium halide 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. When a sulfide solid electrolyte having a _Li3PS4 structure is to be obtained using lithium sulfide and diphosphorus pentasulfide _, they may be used in a molar ratio of 3:1.
Furthermore, when another sulfide solid electrolyte is to be obtained, it is sufficient to use a molar ratio corresponding to the sulfide solid electrolyte, and when a sulfide solid electrolyte containing a halogen atom is to be obtained, it is sufficient to use a raw material compound containing a halogen atom corresponding to the sulfide solid electrolyte. The molar ratio corresponding to the sulfide solid electrolyte, the raw material compound to be used, etc. are the same as those explained above for the raw material contents.

The compounds contained in the crude mixture may be crushed before use. Crushing may be performed using any of the crushers described above as being usable in obtaining the mixture. For example, a pin mill, preferably a pin mill equipped with a constant volume feeder, may be used.

(Mixing and grinding)
It is believed that the compounds contained in the crude mixture mainly form fine crystals. This is because the mixing and grinding 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 raw sulfide solid electrolyte.

The crude mixture can be mixed and pulverized using any of the pulverizers described above as being usable in obtaining the mixture, with media-type pulverizers such as ball mills and bead mills being preferred. It is also possible to use kneaders such as single- or multi-screw kneaders.

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

The crude mixture and solvent typically form a slurry (suspension). The content of the crude mixture in the slurry to be mixed and pulverized may be selected appropriately from within the range of the content of the amorphous material relative to the total amount of the amorphous material and organic solvent in the mixture when the amorphous material is heated, as described below.

[Obtaining the calcined product]
The manufacturing method of this embodiment includes heating the raw material inclusions to obtain a calcined product. The calcination promotes a reaction between the solid electrolyte raw materials contained in the raw material inclusions, thereby obtaining the calcined product.

The calcination method is not particularly limited, but examples include methods using a hot plate, autoclave, vacuum heating device, argon gas atmosphere furnace, or firing furnace. Other methods include 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, on an industrial scale, a horizontal dryer or horizontal vibrating fluidized dryer equipped with a heating means and a feed mechanism. The calcination method can be selected depending on the processing volume to be calcined, but it is preferable to heat the material in a sealed pressure-resistant container such as an autoclave.

The heating temperature and time for calcination cannot be generalized as they can vary depending on the composition of the calcined product and whether an amorphous or crystalline calcined product is desired, but 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.

Furthermore, the heating time is preferably 0.1 hours or more, more preferably 0.2 hours or more, and even more preferably 0.25 hours or more, with the upper limit being preferably 8 hours or less, more preferably 6 hours or less, and even more preferably 4 hours or less.

The calcination of the raw material contents is preferably carried out in an inert gas atmosphere (e.g., nitrogen atmosphere, argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum). An inert gas atmosphere containing hydrogen gas may also be used, as this prevents deterioration (e.g., oxidation) of the raw material contents.

In addition, the calcination of the raw material components may be carried out in the presence of a solvent, with the type and amount of solvent being the same as those used when heating the amorphous material, as described below.

The calcined product thus obtained is expected to be a sulfide solid electrolyte having a molecular structure _{of Li3PS4} , but this will vary depending on the blending 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.

[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, and examples thereof include mechanical treatment, melt quenching, and the like. A specific example of the mechanical treatment is pulverization treatment. More specifically, the pulverization treatment is preferably carried out by mechanical milling, and even more specifically, it is preferably carried out using a media-type pulverizer such as a ball mill or a bead mill.

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, from the viewpoint of efficient amorphization, the amount of 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.

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

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

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 mm or more, preferably 0.1 mm or more, more preferably 0.3 mm or more, with the upper limit being usually 5.0 mm or less, preferably 3.0 mm or less, more preferably 2.0 mm or less. The diameter of the balls is usually 2.0 mm or more, preferably 2.5 mm or more, more preferably 3.0 mm or more, with the upper limit being usually 20.0 mm or less, preferably 15.0 mm or less, more preferably 10.0 mm 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.

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 generally determined, but is usually 10 rpm or more, preferably 20 rpm or more, and more preferably 50 rpm or more, and the upper limit is 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.
The grinding 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, and the upper limit is usually 100 hours or less, preferably 72 hours or less, more preferably 48 hours or less, and even more preferably 36 hours or less.

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.
The treatment time for the amorphization treatment is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more, and the upper limit is usually 100 hours or less, preferably 50 hours or less, more preferably 20 hours or less, and even more preferably 10 hours or less.

The pulverization treatment is preferably performed with an integrated power of 0.5 Wh/g or more, from the viewpoint of sufficiently amorphizing the material to be treated and improving the ionic conductivity of the resulting sulfide solid electrolyte. Similarly, the integrated power in the 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 for calculating the integrated power is the same as that used in the examples described later.

The amorphization treatment is preferably carried out until the intensity ratio (I 18.2 /I 44.8 ) of the peak intensity (I _18.2 ) at 2θ=18.2±0.3° to the peak intensity (I _44.8 ) at 2θ= _44.8 ± _0.5 °, as measured by X-ray diffraction using CuKα radiation, of the amorphized product after the amorphization treatment is 0.2 or less, more preferably 0.10 or less, and even more preferably 0.05 or less.
In the X-ray diffraction measurement using CuKα radiation, the peak at 2θ = 18.2 ± 0.3° is derived from crystalline Li ₃ PS ₄ , and the peak at 2θ = 44.8 ± 0.5° is derived from the raw material lithium sulfide (Li ₂ S). Therefore, when the ratio of these peak intensities (I _18.2 /I _44.8 ) is within the above range, the ratio of crystalline Li ₃ PS ₄ is small, that is, it can be said that the material is sufficiently amorphized. When the amorphized material is heated as described below, the reaction between the solid electrolyte raw materials is more likely to proceed, which is thought to improve the ionic conductivity of the resulting sulfide solid electrolyte.

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

The heating of the amorphous material may be carried out in one step or in multiple steps, but for example, it can be carried out in two steps of calcination and firing.
The heating temperature and time for calcination 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, a _PS4 structure is formed, and halogens are easily incorporated into the argyrodite-type crystal structure. Since the raw material mixture of fine crystals is calcined in a solution, it is possible to form crystals containing a _PS4 structure at a relatively low temperature.
The heating device used for calcination is not particularly limited. 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.

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

The amorphous material or its calcined product can be heated either in the presence or absence of a solvent. When heating in a solvent, the solvent can be an organic solvent, as described below. The amorphous material or its calcined product is dispersed in the solvent to form a slurry, and then heated.

There are no particular limitations on the heating device used to heat the amorphous material or its calcined product, 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 heated slurry is not particularly limited, but the solvent can be distilled off under normal pressure or reduced pressure. In addition, filtration can be used in combination to further increase productivity.

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.

Furthermore, when heating the amorphous material or its calcined product, the heating is preferably carried out 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.

(organic solvent)
As the organic solvent used when heating the amorphous material or the calcined material thereof, a wide range 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.

Examples of the aliphatic hydrocarbon solvent 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 the alicyclic hydrocarbon solvent include saturated alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, and 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.

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

Preferred examples of ether solvents 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).

Preferred examples of ester solvents 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.

Further preferred solvents include alcohol-based solvents such as ethanol and butanol; aldehyde-based solvents such as formaldehyde, acetaldehyde and dimethylformamide; and ketone-based solvents such as acetone and methyl ethyl ketone.

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, or a nitrile group.
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.

Furthermore, 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 nitrogen atoms such as dimethylformamide and nitrobenzene.

Preferred examples of the solvent containing a halogen atom as a hetero atom include dichloromethane, chlorobenzene, trifluoromethylbenzene, chlorobenzene, chlorotoluene, and bromobenzene.
Preferred examples of the solvent containing a sulfur atom include dimethyl sulfoxide and carbon disulfide.

The amount of organic solvent used is such that the total content of the amorphous material relative to the total amount of the amorphous 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 even 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 even more preferably 12% by mass or less. When the amount of organic solvent used is within the above range, the amorphous material is more likely to be maintained uniformly in the organic solvent, allowing for more efficient production of the sulfide solid electrolyte.

Among the organic solvents listed above, those with a boiling point of 50°C or higher are preferred for use in the manufacturing method of this embodiment. A boiling point of 50°C or higher suppresses the amount of organic solvent volatilizing when the amorphized material is selectively heated, allows the amorphized material to be more uniformly maintained in the organic solvent, and makes it possible to reduce the amount of organic solvent used. From this perspective, the boiling point of the organic solvent is more preferably 65°C or higher, even more preferably 75°C or higher, even more preferably 100°C or higher, and particularly preferably 200°C or higher.

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 aromatic ether solvents mentioned above), ester solvents (excluding the aromatic ester solvents mentioned above), solvents having an amino group (amine solvents), and solvents containing a halogen atom are more preferred. Of these, it is more preferred to use at least one solvent selected from aromatic solvents having an aromatic ring and alicyclic solvents, and it is particularly preferred to use a combination of at least one solvent selected from aromatic hydrocarbon solvents and at least one solvent selected from aromatic ether solvents.

Aromatic solvents are preferably aromatic hydrocarbon solvents and aromatic ether solvents. Furthermore, aromatic hydrocarbon solvents are preferably benzene, toluene, xylene, biphenyl, naphthalene, and tetrahydronaphthalene (tetralin, cyclohexylbenzene), and aromatic ether solvents are preferably diphenyl ether (diphenyl oxide).

The aliphatic hydrocarbons are preferably pentane and hexane, and the alicyclic hydrocarbons are preferably cyclohexane.
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.

As the solvent having an amino group (amine solvent), aliphatic amines and heterocyclic amines are preferred, and among these, triethylamine and pyridine are preferred.
Moreover, dichloromethane is preferred as the solvent containing a halogen atom.

[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.

(Amorphous sulfide solid electrolyte)
The amorphous sulfide solid electrolyte obtained by the production method of this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. Typical examples include sulfide solid electrolytes composed of lithium sulfide _, phosphorus sulfide, and lithium halide, such as Li ₂ S-P ₂ S ₅ -LiI, Li ₂ S-P ₂ S ₅ -LiCl, Li ₂ S-P ₂ S 5 -LiBr, and Li 2 _S -P 2 _{S 5} -LiI-LiBr; and sulfide solid electrolytes containing other atoms such as oxygen atoms and silicon atoms, such as Li ₂ S-P ₂ S ₅ -Li ₂ O-LiI and Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, are preferred. From the viewpoint of obtaining higher ionic conductivity, preferred examples of _the solid electrolyte include _those composed _of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li ₂ S—P ₂ S ₅ —LiI, Li ₂ S—P ₂ S ₅ —LiCl, Li ₂ S—P ₂ S 5 —LiBr, and Li 2 S—P 2 S ₅ —LiI-LiBr.
The types of elements constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

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.

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

(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 examples of the crystal structure include the Li ₃ PS ₄ crystal structure, the Li ₄ P ₂ S ₆ crystal structure, the Li ₇ PS ₆ crystal structure, the Li ₇ P ₃ S ₁₁ crystal structure, and a crystal structure having peaks near 2θ = 20.2 ° and near 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 crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment preferably includes the following argyrodite-type crystal structure and thiolicon region II-type crystal structure.

The crystal structure has the structural skeleton of Li ₇ PS ₆ and is represented by the composition formula Li _7−x P _1−y Si _y S ₆ and Li _7+x P _1−y Si _y S ₆ (x is −0.6 to 0.6, y is 0.1 to 0.6), in which a portion of P is substituted with Si. The crystal structure is a cubic or orthorhombic crystal, preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, it has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The crystal structure represented by the above composition formula Li7 _{-x-2yPS6 -x-yClx (} 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°. The crystal structure represented by the composition formula Li7 _{-xPS6 - xHax} (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, it has peaks that appear mainly at 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. These crystal structures that basically have the structural skeleton _{of Li7PS6} are also called argyrodite-type crystal structures.
These peak positions may vary within a range of ±0.5°.

Other examples include Li _4-x Ge _1-x P _x S ₄ based thio-LISICON Region II type crystal structures (see Kanno et al., Journal of The Electrochemical Society, 148(7)A742-746(2001)), and crystal structures similar to Li _4-x Ge _1-x P _x S ₄ based thio-LISICON Region II type crystal structures (see Solid State Ionics, 177(2006), 2721-2725).

In this specification, the term "thiolisicon region II type crystal structure" refers to either a Li4 _{-xGe1 - xPxS4- based} thiolisicon region II (thio-LISICON Region II) type crystal structure or a crystal structure similar to the Li4 _{-xGe1 -xPxS4 -} based thiolisicon _region II (thio-LISICON Region II) type. The thiolisicon region II type crystal structure and the similar crystal structure are very similar to each other because their diffraction peaks are similar, as will be described later. Therefore, it is technically reasonable to treat the "thiolisicon region II type crystal structure" as including both the thiolisicon region II type crystal structure and the similar crystal structure.

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 preferably does not contain crystalline Li ₃ PS ₄ (β-Li ₃ PS ₄ ).

The notation of the crystal structure as "Li4 _{-xGe1 -xPxS4- based thio} -LISICON Region II type" means that at the time of discovery in the above document, the crystal structure was composed of the atoms in question, namely, Li, Ge, P and S atoms. The sulfide solid electrolyte obtained by the manufacturing method of this embodiment has a thio-LISICON Region II type crystal structure, which means that the "Li4 _{-xGe1 -xPxS4- based} thio-LISICON _Region II type" crystal structure (including similar crystal structures) is formed by the atoms (Li, P, S, and halogen atoms) contained in the raw material inclusions, thereby exhibiting the same diffraction peaks as the "Li4 _{-xGe1 - xPxS4} - _based thio-LISICON Region II type" crystal structure (including similar crystal structures). The same applies to the argyrodite type crystal structure described above.

In X-ray diffraction measurements using CuKα radiation, the diffraction peaks of the Li ₃ PS ₄ crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°; the diffraction peaks of the Li ₄ P ₂ S ₆ crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°; the diffraction peaks of the Li ₇ PS ₆ crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°; the diffraction peaks of the Li ₇ P ₃ S ₁₁ 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 the diffraction peaks of the Li _4-x Ge _1-x P Diffraction peaks of the _Li4 - _xGe1 -xPxS4 thiolicon region II (thio-LISICON Region II) crystal structure appear, for example, at 2θ = 20.1°, 23.9°, and 29.5°, and diffraction peaks of a crystal structure similar to the Li4 _{-xGe1 -xPxS4 thiolicon region} II (thio-LISICON Region II) crystal structure appear, for example, at 2θ = 20.2° and 23.6°. These peak positions may vary within a range of ±0.5°.

As described above, when a thiolisiconregion II type crystal structure is obtained in this embodiment, it is preferable that the sulfide solid _electrolyte does not contain crystalline _Li3PS4 (β- _Li3PS4 ). The sulfide solid electrolyte obtained by the production method of this embodiment does not have the diffraction peaks at 2θ = 17.5° _and 26.1° seen in crystalline _Li3PS4 , or _even if it does have them, the peaks detected are extremely small compared to the diffraction peaks of the thiolisiconregion II type crystal structure.

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

(Applications of sulfide solid electrolytes)
The sulfide solid electrolyte obtained by the manufacturing 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 manufacturing method of this embodiment may be used in any of the positive electrode layer, negative electrode layer, and electrolyte layer. Each layer can be manufactured by a known method.

Furthermore, it is preferable that the above battery use a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer, and known current collectors can be used. For example, a layer of a material that reacts with the above solid electrolyte, such as Au, Pt, Al, Ti, or Cu, coated with Au or the like can be used.

The present invention will now be described in detail using examples, but the present invention is not limited to these examples in any way.

(Preparation Example 1: Preparation of raw 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 "100UPZ", manufactured by Hosokawa Micron Corporation) (feeding rate: 80 g/min, disk rotation speed: 18,000 rpm).
Furthermore, diphosphorus pentasulfide (P ₂ S ₅ , manufactured by Italmatch Japan), 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. Here, the addition rate of diphosphorus pentasulfide (P ₂ S ₅ ) was 140 g/min, the addition rate of lithium bromide (LiBr) was 230 g/min, and the addition rate of lithium chloride (LiCl) was 250 g/min, and the rotation speed of the disk was 18,000 rpm for all of them.

Next, in a glove box with a nitrogen atmosphere, each of the compounds ground as described above was weighed out so that the molar ratio of each compound was Li ₂ S:P ₂ S ₅ :LiBr:LiCl=47.5:12.5:15.0:25.0, totaling 110 g, and the resulting mixture was placed in a glass container, and the container was shaken to roughly mix.
The crudely mixed raw material contents (crude mixture) were subjected to powder XRD measurement using the method _described below. The results are shown in Figure 1. At this point, two diffraction peaks near 2θ = 18.2° cannot be confirmed, confirming that the _Li3PS4 structure has not been formed. The gentle peak near 2θ = 20.0° is the result of detecting the Kapton film.
110 g of the crudely 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% by mass relative to the raw material) under a nitrogen atmosphere to obtain a slurry of approximately 10% by 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.

400 mL of the raw material mixture obtained above was placed in an autoclave (500 mL capacity, made of SUS316) equipped with a stirrer and a heating oil bath, and heated at 200°C for 2 hours while stirring at 350 rpm. After treatment, the mixture was dried under reduced pressure to remove the solvent and obtain a calcined product.

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 performed using a Fritsch planetary ball mill. First, milling was performed twice for 5 minutes at a rotation speed of 150 rpm (positive and negative rotation). Subsequently, milling was performed for a total of 5 hours, with one hour of rotation at 370 rpm (positive and negative rotation). Powder XRD analysis of this sample (amorphized product) confirmed that it had been amorphized. The powder XRD analysis results are shown in Figure 2. In addition, the intensity ratio (I _{18.0 /I 45.0 ) of the peak intensity (I 18.0} ) at 2θ=18.0±0.3° to the peak intensity (I _45.0 ) at 2θ=45.0± _0.3 ° in X-ray diffraction measurement using _CuKα radiation of the amorphous material was 0.

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. Specifically, an _Al2O3 sagger (999-60S, manufactured by Tokyo Glass Instruments Co., Ltd.) was placed in the _electric 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 door of the electric furnace 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 allowed to cool slowly, yielding a sulfide solid electrolyte.
The obtained sulfide solid electrolyte powder was subjected to powder XRD measurement by 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 confirmed.
The ionic conductivity of the obtained sulfide solid electrolyte was measured by the method described below and was found to be 6.7 mS/cm.

(Measurement of ionic conductivity)
In this example, the ionic conductivity was measured as follows.
A circular pellet with a diameter of 10 mm (cross-sectional area S: 0.785 cm ² ) and a height (L) of 0.1 to 0.3 cm was molded from the sulfide solid electrolyte 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

(Powder X-ray Diffraction (XRD) Measurement)
In this specification, powder X-ray diffraction (XRD) measurements were 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 exposing it to air.
Measuring device: M03xhf (model number, manufactured by Mac Science Co., Ltd.)
Tube voltage: 40 kV
Tube current: 40mA
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

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 peak intensity corrected for the background, C be the target peak, D be the peak position in the range used for calculation (C ± 0.5°), 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/E2)+(1-A)×exp(-1×(D-C)2/E2)}+F}
The H values were summed within the range of the peak C ±0.5° to be calculated, and the sum was minimized with GRG nonlinearity using the solver function of spreadsheet software Excel (Microsoft) to determine the peak intensity.
In this way, the peak intensity (I _18.2 ) at 2θ = 18.2 ± 0.3° and the peak intensity (I _44.8 ) at 2θ = 44.8 ± 0.5° were determined, and the ratio (I _18.2 /I _44.8 ) of the peak intensity (I _18.2 ) to the peak intensity (I _44.8 ) was calculated.
The half-width parameter 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 the GRG nonlinear solver function. The half-width parameter was calculated using the following equation.
Half-width (FMHM) = E × 2 × (ln4) (1/2)

(cumulative power)
The integrated power E (unit: Wh/g) was calculated using the following formula, where _P0 (unit: W) is the average air power of each machine when the calcined material (the material to be pulverized) is not included, P (unit: W) is the average instantaneous power required to process the calcined material in each machine, t (unit: h) is the total processing time, and M (unit: g) is the total weight of the calcined material to be processed.
E=(P−P ₀ )×t/M

(Comparative Example 1)
Powder XRD measurement was carried out on the calcined product obtained in Preparation Example 1. The results are shown in Figure 2. The intensity ratio (I _18.2 /I _44.8 ) of the peak intensity (I _18.2 ) at 2θ = 18.2 ± 0.3° of the raw sulfide solid electrolyte to the peak intensity (I _44.8 ) at 2θ = 44.8 ± 0.5° was 4.21.
Next, the calcined product was heated in an electric furnace in a glove box under a nitrogen atmosphere without being subjected to mechanical milling, and the same procedure as in Example 1 was repeated to obtain a sulfide solid electrolyte.
The obtained sulfide solid electrolyte powder was subjected to powder XRD diffraction measurement, and the results are shown in FIG.
The ionic conductivity was measured by the following method and was found to be 4.4 mS/cm.

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.
The obtained sulfide solid electrolyte powder was subjected to powder XRD diffraction measurement, and the results are shown in FIG.
The ionic conductivity was measured by the following method and was found to be 8.4 mS/cm.

(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.
The obtained sulfide solid electrolyte powder was subjected to powder XRD diffraction measurement, and the results are shown in FIG.
The ionic conductivity was measured by the following method and was found to be 6.2 mS/cm.

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.
The obtained sulfide solid electrolyte powder was subjected to powder XRD diffraction measurement, and the results are shown in FIG.
The ionic conductivity was measured by the following method and was found to be 8.6 mS/cm.

(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.
The obtained sulfide solid electrolyte powder was subjected to powder XRD diffraction measurement, and the results are shown in FIG.
The ionic conductivity was measured by the following method and was found to be 7.1 mS/cm.

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.
The obtained sulfide solid electrolyte powder was subjected to powder XRD diffraction measurement, and the results are shown in FIG.
The ionic conductivity was measured by the following method and was found to be 9.1 mS/cm.

(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.
The obtained sulfide solid electrolyte powder was subjected to powder XRD diffraction measurement, and the results are shown in FIG.
The ionic conductivity was measured by the following method and was found to be 7.2 mS/cm.

The manufacturing conditions for Examples 1 to 4 and Comparative Examples 1 to 4, as well as the XRD measurement results and ionic conductivity of the resulting sulfide solid electrolytes, are shown in Table 1 below.

As is clear from a comparison between Examples 1 to 4 and Comparative Examples 1 to 4, in which the calcined product obtained in Production Example 1 was pulverized, the ionic conductivity of the final sulfide solid electrolyte obtained was excellent. In contrast, in Comparative Examples 1 to 4, in which the calcined product obtained in Production Examples 1 to 4 was heated without being pulverized, the ionic conductivity of the final sulfide solid electrolyte obtained was lower.

The manufacturing method of this embodiment employs a liquid phase method, reduces the heating temperature, and suppresses granulation due to heating, allowing for the efficient production of a sulfide solid electrolyte that maintains particle size. The sulfide solid electrolyte obtained by this manufacturing 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 (13)

heating a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain a calcined product;
a method for producing a sulfide solid electrolyte, the method comprising: subjecting the calcined product to an amorphization treatment to obtain an amorphized product; and heating the amorphized product. The method for producing a sulfide solid electrolyte according to claim 1, wherein when the raw material content is heated to obtain the calcined product, the raw material content is heated in a sealed pressure-resistant container. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein when the raw material content is heated to obtain the calcined product, the raw material content is heated in the presence of a solvent. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, wherein the amorphization treatment is a mechanical treatment or a melt-quenching treatment. The method for producing a sulfide solid electrolyte according to claim 4, wherein the mechanical treatment is a pulverization treatment. The method for producing a sulfide solid electrolyte according to claim 5, wherein the integrated power consumption in the pulverization process is 0.5 Wh/g or more. 7. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 6, wherein the amorphous product has a peak intensity (I _18.2 ) at 2θ = 18.2 ± 0.3° by X-ray diffraction measurement using CuKα rays, and an intensity ratio (I _18.2 /I _44.8 ) of the peak intensity (I _44.8 ) at 2θ = 44.8 ± 0.5° is 0.2 or less. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 7, wherein the amorphous material does not contain crystalline Li ₃ PS ₄ . 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. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 9, wherein the raw material content is a premix of at least lithium sulfide, phosphorus sulfide, and lithium halide. The 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. 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 temperature of 150°C or higher and 300°C or lower. 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.