Method and apparatus for producing crystalline sulfide solid electrolyte

Abstract

The present invention provides a method for producing a crystalline sulfide solid electrolyte, with which it is possible to more efficiently produce a sulfide solid electrolyte that has a higher ion conductivity, and which can be easily suited to mass production, the method including: obtaining an amorphous sulfide solid electrolyte containing a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom; and heating the amorphous sulfide solid electrolyte in a heated air flow. The present invention also provides an apparatus for producing a crystalline sulfide solid electrolyte.

Description

Crystalline sulfide solid electrolyte manufacturing method and manufacturing device

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

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries for use as their power sources has become increasingly important. Traditionally, batteries used for such applications have used electrolytes containing flammable organic solvents. However, because the electrolytes are liquid and flammable, safety concerns regarding leakage, fire, and other issues have arisen when used in batteries. In particular, for automotive applications, high capacity and high output are required, and safety concerns regarding batteries using conventional electrolytes are becoming increasingly serious. Therefore, all-solid-state batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed because such batteries eliminate the use of flammable organic solvents, simplify safety devices, and offer superior manufacturing costs and productivity.

[0003] Methods for producing solid electrolytes used in solid electrolyte layers are broadly divided into solid-phase methods and liquid-phase methods. Liquid-phase methods include 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 instead a solid-liquid coexistence suspension. In recent years, studies on mass production of solid electrolytes have been progressing, and liquid-phase methods using complexing agents have attracted attention as a method that is easily adaptable to scale-up. For example, a solid production method is known that uses a specific compound having an amino group as a complexing agent and mixes the complexing agent with a solid electrolyte raw material to prepare an electrolyte precursor (see, for example, Patent Document 1), and a solid electrolyte production method is known that includes drying a slurry containing the complexing agent and the electrolyte precursor by fluidized drying using media particles (see, for example, Patent Document 2).

[0004] International Publication No. 2020 / 105737 Pamphlet International Publication No. 2021 / 230189 Pamphlet

[0005] An object of the present invention is to provide a method and apparatus for producing a crystalline sulfide solid electrolyte, which can more efficiently produce a sulfide solid electrolyte having high ionic conductivity and can easily be adapted for mass production.

[0006] The method for producing a crystalline sulfide solid electrolyte according to the present invention is a production method comprising: obtaining an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms; and heating the amorphous sulfide solid electrolyte in a heated air stream.

[0007] According to the present invention, it is possible to provide a method and an apparatus for producing a crystalline sulfide solid electrolyte, which can more efficiently produce a sulfide solid electrolyte having high ionic conductivity and can easily be adapted for mass production.

[0008] Fig. 1 is a flow diagram of an apparatus equipped with an airflow dryer and a bag filter used in Example 1. Fig. 2 is an X-ray diffraction spectrum of the heated powder and the thermally mechanically treated product obtained in Examples 1 and 2. Fig. 3 is an X-ray diffraction spectrum of the powder obtained in Comparative Example 1. Fig. 4 is an X-ray diffraction spectrum of the powder obtained in Comparative Example 2. Fig. 5 is a flow diagram for explaining the manufacturing method of this embodiment. Fig. 6 is a flow diagram for explaining the manufacturing method of another embodiment.

[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 numerical range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​of the examples can also be used as the upper and lower limit values. Furthermore, preferred specifications can be arbitrarily adopted. In other words, one preferred specification can be adopted in combination with one or more other preferred specifications. It can be said that a combination of preferred items is more preferable.

[0010] (Findings Obtained by the Inventors to Achieve the Present Invention) The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found the following, which has led to the completion of the present invention.

[0011] In recent years, as the practical application of all-solid-state batteries has been studied, mass production of sulfide solid electrolytes has become an urgent issue, and studies on improving production efficiency have been ongoing. The present inventors have focused on the development of liquid-phase methods, which are relatively easy to scale up, particularly heterogeneous methods that use a complexing agent during the reaction of solid electrolyte raw materials. The production methods disclosed in Patent Documents 1 and 2 employ a heterogeneous method involving the reaction of solid electrolyte raw materials with a complexing agent, which makes them amenable to scale up. In their efforts to further improve production efficiency, the present inventors focused on the heat-induced crystallization process to obtain crystalline solid electrolytes. In conventional production methods such as those described in Patent Documents 1 and 2, batch-type heating equipment, such as agitator dryers, has been used for heat-induced crystallization as it is easy to operate. However, it has been found that such batch-type heating equipment poses significant concerns when scaling up for mass production. More specifically, it has been found that it is extremely difficult to increase the thermal history of the powder required for crystallization in accordance with the processing scale. This leads to poor crystallization of the solid electrolyte, making it extremely difficult to stably produce a high-quality solid electrolyte that is homogeneous and has high ionic conductivity.

[0012] The inventors further investigated heating methods for crystallization and found that employing heating with a heated air stream is effective. Heating with a heated air stream can significantly shorten the heating time while ensuring uniform thermal history throughout the powder. This suppresses deterioration due to oxidation and other factors resulting from excessive thermal history, and enables the stable production of high-quality solid electrolytes with uniform and high ionic conductivity. Furthermore, while the heating time required for conventional batch processes was several hours, heating with a heated air stream can be reduced to a few seconds to a few minutes, thereby improving the production efficiency of solid electrolytes. Furthermore, the thermal history is easily uniform regardless of the amount of material being heated, making it extremely easy to scale up the process.

[0013] Based on the above findings, the present inventors have established a production method and a production apparatus that can more efficiently produce a sulfide solid electrolyte having high ionic conductivity and that can easily be adapted for mass production.

[0014] (Regarding various aspects of the present embodiment) A method for producing a crystalline sulfide solid electrolyte according to a first aspect of the present embodiment is a method for producing a crystalline sulfide solid electrolyte, the method comprising: obtaining an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms; and heating the amorphous sulfide solid electrolyte in a heated air stream.

[0015] There are no particular limitations on the method for obtaining the amorphous sulfide solid electrolyte in the method for producing a crystalline sulfide solid electrolyte of this embodiment, as long as an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms can be obtained. That is, in the method for producing a crystalline sulfide solid electrolyte of this embodiment, it is particularly important to heat the amorphous sulfide solid electrolyte in a heated air flow. The crystalline sulfide solid electrolyte is obtained by heating the amorphous sulfide solid electrolyte in a heated air flow. In other words, heating the amorphous sulfide solid electrolyte in a heated air flow corresponds to heating for crystallizing the amorphous sulfide solid electrolyte.

[0016] By employing heating in a heated air stream to crystallize the amorphous sulfide solid electrolyte, as described above, it is possible to shorten the heating time while uniformly applying thermal history to the entire powder, thereby suppressing deterioration due to oxidation or the like caused by excessive thermal history. Furthermore, heating in a heated air stream not only enables crystallization in an extremely short time, but also facilitates uniform thermal history depending on the amount of material being heated, making it extremely easy to scale up. As a result, the production method of this embodiment enables more efficient production of a homogeneous sulfide solid electrolyte having high ionic conductivity, and can be a production method that is easily adaptable to mass production.

[0017] A second aspect of the present embodiment is a method for producing a crystalline sulfide solid electrolyte according to the first aspect, wherein the temperature of the heated airflow is 150°C or higher and 250°C or lower.

[0018] Crystallization can be carried out more efficiently by setting the temperature of the heated airflow during crystallization of the amorphous sulfide solid electrolyte to 150° C. or higher and 250° C. or lower, which makes it easier to obtain a more homogeneous crystalline sulfide solid electrolyte having high ionic conductivity.

[0019] A method for producing a crystalline sulfide solid electrolyte according to a third aspect of the present embodiment is the same as the first or second aspect, and further comprises: transferring the heated powder obtained by the heating from a heating device used by heating in the heated airflow to a separation device through a transfer pipe; and collecting the transferred heated powder with a separation device, and heating the transfer pipe.

[0020] The degree of crystallinity of the heated powder can be improved by heating the transfer pipe through which the heated powder obtained by the above heating passes when being supplied to the separation device, which makes it easier to obtain a more homogeneous crystalline sulfide solid electrolyte having high ionic conductivity.

[0021] A fourth aspect of the present embodiment is the method for producing a crystalline sulfide solid electrolyte of the third aspect, wherein the heating temperature of the transfer pipe is 150°C or higher and 250°C or lower.

[0022] By setting the temperature of the heated airflow in the transfer piping when supplying the heated powder to the separation device to 150° C. or higher and 250° C. or lower, the crystallinity of the heated powder can be improved more efficiently, making it easier to obtain a more homogeneous crystalline sulfide solid electrolyte with high ionic conductivity.

[0023] A fifth aspect of the present embodiment is a method for producing a crystalline sulfide solid electrolyte according to the third or fourth aspect, further comprising: mechanically treating the collected material obtained by the collection; and heating the mechanically treated material obtained by the mechanical treatment in a heated air stream.

[0024] The material collected in the separation device is the heated powder obtained by the heating, i.e., a crystalline sulfide solid electrolyte. When the crystalline sulfide solid electrolyte is used for applications such as the electrolyte layer, positive electrode, and negative electrode of a lithium ion battery, it is preferable to adjust the morphology (herein, this means the form (shape) of the solid electrolyte, mainly the average particle size and specific surface area) according to these applications. Adjusting the morphology is preferably performed by mechanical treatment, as this is efficient.

[0025] Furthermore, since the mechanically treated product obtained by the mechanical treatment may be partially amorphous, it is preferable to heat it again in a heated air stream. Heating again in a heated air stream can improve the crystallinity of the heated powder, making it easier to obtain a more homogeneous crystalline sulfide solid electrolyte with high ionic conductivity. Furthermore, if a solvent is used during the mechanical treatment, heating again in a heated air stream can also remove the solvent.

[0026] A sixth aspect of the present embodiment is directed to the method for producing a crystalline sulfide solid electrolyte of the fifth aspect, wherein the temperature of the heated airflow is 150°C or higher and 250°C or lower.

[0027] When the mechanically treated material is heated in a heated air stream, the temperature of the heated air stream is preferably 150°C or higher and 250°C or lower, similar to the temperature in the second embodiment. By heating the heated air stream at a temperature within the above range, crystallization can be carried out more efficiently. Therefore, a crystalline sulfide solid electrolyte that is more homogeneous and has high ionic conductivity is more likely to be obtained. Furthermore, when the mechanical treatment is carried out using a solvent, the solvent can be efficiently removed.

[0028] A seventh aspect of the present embodiment is a method for producing a crystalline sulfide solid electrolyte according to any one of the first to sixth aspects, wherein the heating in the heated air flow is carried out using a flash dryer.

[0029] As long as heating can be performed in a heated air stream, there are no particular limitations on the type of heating equipment used for the heating, but it is preferable to use a flash dryer. The use of a flash dryer makes it easy to stably perform heating in a heated air stream, and therefore the crystallinity of the amorphous sulfide solid electrolyte to be heated and the mechanically treated product can be improved. As a result, a more homogeneous crystalline sulfide solid electrolyte having high ionic conductivity can be more easily obtained.

[0030] The method for producing a crystalline sulfide solid electrolyte according to an eighth aspect of the present embodiment is any one of the first to seventh aspects, wherein the crystalline sulfide solid electrolyte has a thiolicon region II crystal structure.

[0031] A crystalline sulfide solid electrolyte having a thiolisiconregion II crystal structure is known as a solid electrolyte having high ionic conductivity. The solid electrolyte produced by the method for producing a crystalline sulfide solid electrolyte of the present embodiment is not particularly limited as long as it is crystalline, i.e., has a crystalline structure. However, it is preferable to produce a solid electrolyte having high ionic conductivity, such as a crystalline sulfide solid electrolyte having a thiolisiconregion II crystal structure.

[0032] A method for producing a crystalline sulfide solid electrolyte according to a ninth aspect of the present embodiment is a method for producing a crystalline sulfide solid electrolyte comprising the following steps (i) to (iii) in this order, and a method for producing a crystalline sulfide solid electrolyte according to a tenth aspect is the ninth aspect, further comprising the following steps (iv) to (vi) in this order: (i) mixing a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms using a solvent; (ii) drying the fluid obtained by the mixing to remove the solvent; (iii) heating the amorphous sulfide solid electrolyte obtained by removing the solvent in (ii) in a heated air stream; (iv) transferring the heated powder obtained by the heating in (iii) to a separator through a transfer pipe and collecting it in the separator; (v) mechanically treating the collected material obtained by the collection; and (vi) heating the mechanically treated material obtained by the mechanical treatment in a heated air stream.

[0033] The above (i) and (ii) correspond to obtaining the amorphous sulfide solid electrolyte in the first embodiment, and the above (iii) corresponds to heating in a heated air stream in the first embodiment. According to the production method of the ninth embodiment, the amorphous sulfide solid electrolyte in the first embodiment is obtained by performing the above (i) and (ii), thereby more efficiently obtaining the amorphous sulfide solid electrolyte. Furthermore, the production method of the tenth embodiment further includes (iv) and (v) in addition to (i) to (iii) of the production method of the ninth embodiment, and as described in the fifth embodiment, it is easier to obtain a crystalline sulfide solid electrolyte that is more homogeneous and has high ionic conductivity.

[0034] An apparatus for producing a crystalline sulfide solid electrolyte according to an eleventh aspect of the present embodiment is an apparatus including: a production device for an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms; and a heating device for heating the amorphous sulfide solid electrolyte in a heated air flow.

[0035] The manufacturing apparatus according to the eleventh embodiment is equipped with manufacturing equipment and heating equipment for an amorphous sulfide solid electrolyte, and thus can easily carry out the above manufacturing method. Therefore, a sulfide solid electrolyte having high ionic conductivity can be more efficiently manufactured, and mass production can be easily achieved.

[0036] A twelfth aspect of the present invention relates to an apparatus for producing a crystalline sulfide solid electrolyte, wherein the apparatus for producing an amorphous sulfide solid electrolyte is the eleventh aspect, and the apparatus for producing an amorphous sulfide solid electrolyte comprises: a mixing device that mixes a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms using a solvent; and a drying device that dries a fluid obtained in the mixing device to remove the solvent. A thirteenth aspect of the present invention relates to an apparatus for producing a crystalline sulfide solid electrolyte, wherein the apparatus for producing an amorphous sulfide solid electrolyte is the eleventh or twelfth aspect, and further comprises: a separation device that collects the heated powder obtained in the heating device; a mechanical processing device that mechanically processes the collected material obtained in the separation device; a heating device that heats the mechanically processed material obtained by the mechanical processing; and a transfer pipe that transfers the heated powder from the heating device to the separation device.

[0037] In a twelfth embodiment, the amorphous sulfide solid electrolyte manufacturing apparatus includes a mixing device and a drying device for raw material ingredients, thereby enabling the amorphous sulfide solid electrolyte to be manufactured more efficiently. In a thirteenth embodiment, the amorphous sulfide solid electrolyte manufacturing apparatus includes a separation device, a mechanical processing device, a heating device, and a transfer pipe, and the inclusion of the mechanical processing device makes it easier to obtain a crystalline sulfide solid electrolyte that is more homogeneous and has high ionic conductivity.

[0038] (Solid Electrolyte) In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state under a nitrogen atmosphere at 25° C. The sulfide solid electrolyte in this embodiment is a solid electrolyte that contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms and has ionic conductivity due to the lithium atoms.

[0039] The term "solid electrolyte" includes both amorphous solid electrolytes and crystalline solid electrolytes. In this specification, a crystalline solid electrolyte is a solid electrolyte in which peaks derived from the solid electrolyte are observed in an 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. That is, a crystalline 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 a crystalline solid electrolyte has the X-ray diffraction pattern described above, it may also contain an amorphous solid electrolyte in part. Therefore, crystalline solid electrolytes include so-called glass ceramics obtained by heating an amorphous solid electrolyte to a temperature equal to or higher than its crystallization temperature. Furthermore, in this specification, an amorphous solid electrolyte is one in which a halo pattern in an X-ray diffraction pattern in X-ray diffraction measurement is observed in which substantially no peaks other than those derived from the material are present, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present.

[0040] [Method for producing crystalline sulfide solid electrolyte] A method for producing a crystalline sulfide solid electrolyte according to the present embodiment includes: obtaining an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms; and heating the amorphous sulfide solid electrolyte in a heated air stream.

[0041] [Obtaining Amorphous Sulfide Solid Electrolyte] The manufacturing method of this embodiment includes obtaining an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. The manufacturing method of this embodiment will first be described by starting with obtaining the amorphous sulfide solid electrolyte.

[0042] In the production method of this embodiment, there are no particular limitations on the method for obtaining the amorphous sulfide solid electrolyte as long as an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms can be obtained. For example, a preferred production method includes mixing raw material components containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms.

[0043] (Raw material inclusions) The raw material inclusions are those containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and more specifically, are inclusions containing compounds containing at least one atom selected from these atoms (hereinafter also referred to as "solid electrolyte raw materials"). The raw material inclusions preferably contain two or more types of solid electrolyte raw materials.

[0044] Examples of solid electrolyte raw materials contained in the raw material content include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; alkali metal halides such as 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 phosphorus sulfides such as various phosphorus fluorides (PF ３ , P.F. ５ ), various phosphorus chlorides (PCl ３ , PCl ５ , P ２Cl ４ ), various phosphorus bromides (PBr ３ , PBr ５ ), various phosphorus iodides (PI ３ , P ２ I ４ ) and the like; phosphorus halides such as thiophosphoryl fluoride (PSF ３ ), thiophosphoryl chloride (PSCl ３ ), thiophosphoryl bromide (PSBr ３ ), thiophosphoryl iodide (PSI ３ ), thiophosphoryl fluoride dichloride (PSCl ２ F), thiophosphoryl fluoride dibromide (PSBr ２ a source material consisting of at least two atoms selected from the above four types of atoms, such as thiophosphoryl halides, e.g., fluorine (F); ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ ), preferably bromine (Br ２ ), iodine (I ２ ) are typical examples.

[0045] Examples of usable solid electrolyte raw materials other than those mentioned above include solid electrolyte raw materials 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; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, and tin sulfide (SnS, SnS ２ metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium such as sodium halides such as sodium iodide, sodium fluoride, sodium chloride and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides and bismuth halides; phosphorus oxychloride (POCl ３ ), phosphorus oxybromide (POBr ３) and the like; and the like.

[0046] In this embodiment, 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, and bromine atoms and iodine atoms are more preferred. These atoms may be used alone or in combination. For example, in the case of lithium halide, lithium bromide may be used alone, lithium iodide may be used alone, or lithium bromide and lithium iodide may be used in combination.

[0047] From the same viewpoint, among the above compounds, lithium sulfide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ Among the phosphorus sulfides, diphosphorus pentasulfide is preferred. 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.

[0048] In this embodiment, PS ４ Li containing structure ３ P.S. ４ can also be used as a solid electrolyte raw material. ３ P.S. ４ In this case, the combination of the solid electrolyte raw materials contained in the raw material contents may be Li, ３ P.S. ４ and the lithium halide, Li ３ P.S. ４ and the above-mentioned elemental halogens, Li３ P.S. ４ and the lithium halide and the elemental halogen.

[0049] Preferred combinations of compounds that can be used as raw materials include, for example, a combination of lithium sulfide, phosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, phosphorus pentasulfide, and an elemental halogen. Preferred lithium halides include lithium bromide, lithium iodide, and lithium chloride, and preferred elemental halogens include chlorine, bromine, and iodine.

[0050] When lithium sulfide is used as the compound containing lithium atoms, the lithium sulfide is preferably in the form of particles. ５０ ) is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.5 μm or more and 100 μm or less, and even more preferably 1 μm or more and 20 μm or less. ５０ ) is the particle size at which, when a particle size distribution cumulative curve is drawn, the cumulative total, starting from the smallest particle size, reaches 50% (by volume) of the total, and the volume distribution refers to an average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device. Furthermore, among the above-mentioned examples of raw materials, solid raw materials preferably have an average particle size similar to that of the lithium sulfide particles, i.e., within the same range as that of the lithium sulfide particles.

[0051] When the raw material contains lithium sulfide, diphosphorus pentasulfide, and lithium halide, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, and even more preferably 74 mol% or more, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. The upper limit is preferably 85 mol% or less, more preferably 83 mol% or less, and even more preferably 80 mol% or less. In addition, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II crystal structure, in addition to the above range, 74 to 78.5 mol%, 74 to 78 mol%, and 74 to 76 mol% are particularly preferred. When attempting to obtain a sulfide solid electrolyte having an argyrodite crystal structure, in addition to the above range, 76 to 83 mol%, 77 to 80 mol%, and 78 to 80 mol% are particularly preferred.

[0052] When using lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed, the content of lithium sulfide and diphosphorus pentasulfide relative to their total is preferably 50 mol% or more, more preferably 55 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 85 mol% or less, and even more preferably 80 mol% or less. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II crystal structure, in addition to the above ranges, particularly 65 to 90 mol%, 70 to 85 mol%, and 75 to 83 mol% are preferred. When attempting to obtain a sulfide solid electrolyte having an argyrodite crystal structure, in addition to the above ranges, particularly 50 to 78 mol%, 55 to 70 mol%, and 55 to 65 mol% are preferred.

[0053] When the raw material contains a combination of lithium bromide and lithium iodide as lithium halides, from the viewpoint of improving 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 35 mol% or more, still more preferably 45 mol% or more, and the upper limit is preferably 99 mol% or less, more preferably 90 mol% or less, even more preferably 75 mol% or less, and even more preferably 60 mol% or less. Also, when the raw material contains a combination of lithium bromide and lithium chloride as lithium halides, from the viewpoint of improving ionic conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium chloride is preferably 1 mol% or more, more preferably 15 mol% or more, even more preferably 25 mol% or more, still more preferably 35 mol% or more, and the upper limit is preferably 99 mol% or less, more preferably 75 mol% or less, even more preferably 60 mol% or less, and even more preferably 45 mol% or less.

[0054] When the raw material inclusions contain a halogen element as a raw material, including lithium sulfide and diphosphorus pentasulfide, the ratio of the number of moles of lithium sulfide excluding the same number of moles of lithium sulfide as the halogen element to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the halogen element is preferably within the range of 60 to 90%, more preferably within the range of 65 to 85%, even more preferably within the range of 68 to 82%, even more preferably within the range of 72 to 78%, and particularly preferably within the range of 73 to 77%. This is because these ratios result in higher ionic conductivity. Furthermore, from the same viewpoint, when the raw material inclusions contain lithium sulfide, diphosphorus pentasulfide, and a halogen element, the content of the halogen element relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the halogen element is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0055] When the raw material contains lithium sulfide, diphosphorus pentasulfide, an elemental halogen, and a lithium halide, the content of the elemental halogen (α mol %) and the content of the lithium halide (β mol %) relative to the total amount of lithium sulfide, diphosphorus pentasulfide, the elemental halogen, and the lithium halide preferably satisfy the following formula (1), more preferably satisfy the following formula (2), even more preferably satisfy the following formula (3), and still more preferably satisfy the following formula (4): 2≦2α+β≦100 (1) 4≦2α+β≦80 (2) 6≦2α+β≦50 (3) 6≦2α+β≦30 (4)

[0056] In addition, the raw material contains Li ３ P.S. ４ If the raw material contains Li, the total amount of the raw material contained in the raw material ３ P.S. ４ The content is preferably 60 to 100 mol %, more preferably 65 to 90 mol %, and even more preferably 70 to 80 mol %.

[0057] (Mixing) Mixing of two or more raw materials selected from compounds containing at least one atom of lithium atom, sulfur atom, phosphorus atom, and halogen atom can be performed, for example, by using a mixer. It can also be performed using a stirrer, a pulverizer, or the like. Mixing of raw materials can occur using a stirrer, and using a pulverizer causes the raw materials to be pulverized, but mixing also occurs at the same time. In other words, it can be said that the sulfide solid electrolyte used in this embodiment can be produced by stirring, mixing, pulverizing, or a combination of these processes, of two or more raw materials selected from compounds containing at least one atom of lithium atom, sulfur atom, phosphorus atom, and halogen atom.

[0058] Examples of the stirrer or mixer include a mechanical stirring mixer that is equipped with stirring blades in a reaction vessel and can stir (also referred to as mixing by stirring or stirring and mixing). Examples of the mechanical stirring mixer include a high-speed stirring mixer and a double-arm mixer. Examples of the high-speed stirring mixer include a vertical-axis rotary mixer and a horizontal-axis rotary mixer, and either type of mixer may be used.

[0059] When a mechanical stirring mixer is used, the rotation speed of the stirring blades can be adjusted appropriately depending on the volume of the fluid in the reaction vessel, the temperature, the shape of the stirring blades, etc., and is not particularly limited. However, it is usually sufficient to set the rotation speed at about 5 rpm or more and 400 rpm or less. From the viewpoint of more efficiently promoting the reaction of the raw materials, the rotation speed is preferably 10 rpm or more and 300 rpm or less, more preferably 15 rpm or more and 250 rpm or less, and even more preferably 20 rpm or more and 200 rpm or less.

[0060] The temperature conditions when mixing is performed using a mixer are not particularly limited, and are, for example, usually −30 to 120° C., preferably −10 to 100° C., more preferably 0 to 80° C., and even more preferably 10 to 60° C. The mixing time is usually 0.1 to 500 hours, and from the viewpoint of achieving a more uniform dispersion state of the raw materials and promoting the reaction, is preferably 1 to 450 hours, more preferably 10 to 425 hours, even more preferably 20 to 400 hours, and still more preferably 40 to 375 hours.

[0061] The method of mixing with pulverization using a pulverizer has been conventionally adopted as a solid-phase method (mechanical milling method). As the pulverizer, for example, a media-type pulverizer using pulverization media can be used.

[0062] Media-type mills are broadly classified into vessel-driven mills and media-agitation mills. Examples of vessel-driven mills include agitation tanks, grinding tanks, and combinations thereof, such as ball mills and bead mills. Examples of media-agitation 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 sulfide, the ball mills and bead mills exemplified as vessel-driven mills are preferred, and planetary mills are particularly preferred.

[0063] 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.

[0064] Furthermore, as will be described later, when the mixture is in a liquid state involving a liquid such as a solvent or in a slurry state during mixing, a wet mill that can handle wet milling is preferred. Typical examples of wet mills include wet bead mills, wet ball mills, and wet vibration mills. Wet bead mills that use beads as milling media are preferred because they allow for free adjustment of milling conditions and are easily adaptable to smaller particle sizes. Dry mills, such as dry media mills (e.g., dry bead mills, dry ball mills, and dry vibration mills) and dry non-media mills (e.g., jet mills), can also be used.

[0065] Furthermore, when the material to be mixed is in a liquid state or a slurry state, a flow-through mill that can perform a circulation operation to circulate the material as needed can also be used. Specifically, a mill that circulates the material between a mill (pulverizing mixer) that pulverizes the slurry and a temperature holding tank (reaction vessel) can be used.

[0066] 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.

[0067] (Solvent) When mixing the raw materials, a solvent may be added to the raw materials and mixed in. As the solvent, various solvents widely known as organic solvents may be used.

[0068] As the solvent, a wide variety of solvents that have conventionally been used in the production of solid electrolytes can be used, and examples thereof include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents.

[0069] Examples of aliphatic hydrocarbons include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane. Examples of alicyclic hydrocarbons include cyclohexane and methylcyclohexane. Examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, and nitrobenzene.

[0070] In addition to the above hydrocarbon solvents, solvents containing heteroatoms such as atoms other than carbon and hydrogen atoms, such as nitrogen, oxygen, sulfur, and halogen atoms, are also suitable. These solvents have the property of readily forming complexes with compounds containing lithium, phosphorus, sulfur, and halogen atoms, which are used as raw materials (hereinafter, such solvents are also referred to as "complexing agents"). These solvents facilitate the retention of halogen atoms within the structure of the sulfide solid electrolyte, making them useful in terms of achieving higher ionic conductivity. The above complexes can be referred to as electrolyte precursors because they become amorphous sulfide solid electrolytes by removing the complexing agent from the complex via drying, as described below. Examples of such complexing agents containing oxygen atoms as heteroatoms include ether solvents, ester solvents, alcohol solvents, aldehyde solvents, and ketone solvents.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] Examples of complexing agents containing nitrogen atoms as heteroatoms include solvents containing nitrogen atom-containing groups such as amino groups, amide groups, nitro groups, and nitrile groups.For example, preferred examples of solvents containing amino groups include aliphatic amines such as ethylenediamine, diaminopropane, dimethylethylenediamine, diethylethylenediamine, dimethyldiaminopropane, tetramethyldiaminomethane, tetramethylethylenediamine (TMEDA), and tetramethyldiaminopropane (TMPDA); alicyclic amines such as cyclopropanediamine, cyclohexanediamine, and bisaminomethylcyclohexane; heterocyclic amines such as isophoronediamine, piperazine, dipiperidylpropane, and dimethylpiperazine; aromatic amines such as phenyldiamine, tolylenediamine, naphthalenediamine, methylphenylenediamine, dimethylnaphthalenediamine, dimethylphenylenediamine, tetramethylphenylenediamine, and tetramethylnaphthalenediamine.Preferred examples of solvents containing nitrogen atoms include nitrile solvents such as acetonitrile and acrylonitrile; and solvents containing nitrogen atoms such as dimethylformamide, nitrobenzene, and dimethylacetamide.

[0075] Preferred examples of solvents containing a halogen atom as a heteroatom include chloroform, carbon tetrachloride, dichloromethane, chlorobenzene, dichlorobenzene, trifluoromethylbenzene, chlorotoluene, bromobenzene, etc. Preferred examples of solvents containing a sulfur atom include dimethyl sulfoxide, carbon disulfide, etc.

[0076] When a solvent is used, the amount of the solvent used is preferably 100 mL or more, more preferably 200 mL or more, even more preferably 250 mL or more, and still more preferably 300 mL or more per kg of the total amount of the raw materials, and the upper limit is preferably 3000 mL or less, more preferably 2500 mL or less, even more preferably 2000 mL or less, and still more preferably 1550 mL or less. When the amount of the solvent used is within the above range, the raw materials can be reacted efficiently.

[0077] (Drying) When mixing is performed using a solvent, the method may include drying the fluid (usually a slurry) obtained by mixing. When a complexing agent is used as the solvent, the complexing agent is removed from a complex containing the complexing agent (electrolyte precursor). When a complexing agent and a solvent are used in combination, the complexing agent is removed from a complex containing the complexing agent (electrolyte precursor) and the solvent is removed. When a solvent other than the complexing agent is used, the solvent is removed to obtain an amorphous sulfide solid electrolyte. The obtained amorphous sulfide solid electrolyte exhibits ionic conductivity due to lithium atoms.

[0078] Drying can be performed on the fluid obtained by mixing at a temperature appropriate for the type of solvent. For example, drying can be performed at a temperature equal to or higher than the boiling point of the solvent (including the complexing agent). Furthermore, drying can be performed by drying under reduced pressure (vacuum drying) using a vacuum pump or the like, typically at 5 to 100°C, preferably 10 to 85°C, more preferably 15 to 70°C, and even more preferably at about room temperature (23°C) (for example, about room temperature ±5°C), to volatilize the complexing agent and any solvent used as needed. Drying can be performed, for example, using a heated dryer capable of drying by heating and / or reducing pressure to the above-mentioned drying temperature. It is also possible to use a flash dryer, spray dryer, or fluidized dryer capable of heating in a heated air stream, as used to dry the amorphous sulfide solid electrolyte described below. Among these, flash dryers, spray dryers, and fluidized dryers, particularly flash dryers, are preferred.

[0079] Drying may be performed by filtering the fluid obtained by the above mixing using a glass filter or the like, by solid-liquid separation by decantation, or by solid-liquid separation using a centrifuge or the like. When a solvent other than a complexing agent is used, an amorphous sulfide solid electrolyte is obtained by solid-liquid separation. Furthermore, when a complexing agent is used as the solvent, solid-liquid separation is performed, and then drying is performed under the above-mentioned temperature conditions to remove the complexing agent incorporated into the complex (electrolyte precursor). Specifically, solid-liquid separation is easily performed by transferring the fluid to a container, and after the solids contained in the fluid (amorphous sulfide solid electrolyte or complex (electrolyte precursor)) are precipitated, decantation is performed to remove the complexing agent and solvent that form the supernatant, or by filtration using a glass filter with a pore size of, for example, about 10 to 200 μm, preferably 20 to 150 μm.

[0080] The sulfide solid electrolyte obtained by the above-mentioned mixing, or, when a solvent is used, the sulfide solid electrolyte obtained by removing the solvent by the above-mentioned drying, exhibits ionic conductivity due to lithium atoms and is an amorphous sulfide solid electrolyte.

[0081] [Heating in a heated air stream] The manufacturing method of this embodiment includes heating the amorphous sulfide solid electrolyte obtained as described above in a heated air stream, thereby converting the amorphous sulfide solid electrolyte into a crystalline sulfide solid electrolyte. Heating the amorphous sulfide solid electrolyte in a heated air stream not only enables crystallization in an extremely short time as described above, but also makes it easier to make the thermal history uniform depending on the amount of the object to be heated, thereby efficiently obtaining a homogeneous crystalline sulfide solid electrolyte with high ionic conductivity. Furthermore, mass production can be easily achieved.

[0082] The method of heating in a heated air stream is not particularly limited as long as the amorphous sulfide solid electrolyte, which is the object to be heated, can be heated by the heated air stream, and is preferably carried out using a heating device such as a flash dryer, a spray dryer, a fluidized bed dryer, etc. Among these heating devices, a flash dryer is preferred because it allows for more stable and efficient crystallization in a short time and allows heating while maintaining a uniform thermal history regardless of the amount of the object to be heated.

[0083] (Airflow dryer) An airflow dryer is a device that can heat an object to be heated by the heated airflow by supplying the object to be heated into a pipe through which a heated airflow is supplied. A direct hot air type airflow dryer in which the heated airflow comes into direct contact with the object to be heated is preferred.

[0084] A preferred example of an airflow dryer is an airflow dryer equipped with a cylindrical container-shaped heating section (also referred to as a "cylindrical container-type airflow dryer"), as shown in FIG. 1. When the heating section is a cylindrical container, the cross-sectional area of ​​the flow path for the heated object and heated airflow is increased, so that even if the heated object adheres to the inner wall surface and solidifies, or the cross-sectional area of ​​the flow path is reduced due to such adhesion and solidification, the influence of flow disturbance and blockage on fluctuations can be suppressed. As a result, stable drying can be easily performed. Furthermore, compared to other types described below, this type is suitable for large-volume processing, facilitates long-term operation, and is easy to maintain, as it is easy to visually inspect and open and clean.

[0085] As the flash dryer, a flash dryer having a structure capable of heating an object to be heated while swirling a heated airflow is preferably used, for example, a flash dryer provided with a dispersion plate so that the heated airflow swirls within the piping, or a flash dryer in which at least a portion of the piping has a circular or semicircular shape (also referred to as a "circular flash dryer" or a "semicircular flash dryer," respectively). The use of such a structure can suppress adhesion to the inner wall of the amorphous sulfide solid electrolyte to be heated. Furthermore, for example, when a solvent (including a complexing agent) remains in the amorphous sulfide solid electrolyte, the mass difference corresponding to the remaining amount can be utilized to perform centrifugal classification, thereby enabling efficient removal of the remaining solvent (including a complexing agent) and crystallization. Furthermore, the flash dryer can be made more compact, thereby saving space.

[0086] Preferred examples of flash dryers include flash dryers (also referred to as "vertical-tube-type flash dryers") that use a vertical long tube long enough to maintain the required length for heating, introducing a heated airflow from below the vertical long tube and heating the material while co-flowing with the material. Using a vertical long-tube flash dryer allows the flow direction of the material and the heated airflow to be limited to an upward direction, thereby adapting to changes in the flow rate, particle size, density, etc. of the material, facilitating stable drying. Furthermore, due to its simple structure, even if the material adheres to the inner wall, it can be easily removed, making it suitable for long-term operation. Furthermore, because this method accommodates increases in processing volume and drying capacity by simply extending the vertical dimension, it requires a smaller installation area than other types, providing advantages in terms of equipment installation.

[0087] In a vertical long-tube type flash dryer, the diameter of the vertical long tube portion may be the same, or may be different and have some wider or narrower portions in order to adjust the heating condition of the object to be heated.

[0088] The flash dryer can be preferably used regardless of whether the amorphous sulfide solid electrolyte to be heated is in a powder state or in a liquid state (slurry or the like) containing a solvent.

[0089] (Other Heating Equipment) The spray dryer is a dryer of a type that dries a liquid fluid (including a slurry) to be heated by spraying the fluid from a spray nozzle into a heated airflow having a predetermined temperature. As the spray dryer, commercially available spray dryers, spray driers, etc. can be used.

[0090] Examples of fluidized bed dryers include media fluidized bed dryers (commercially available as "slurry dryers," for example), as well as band fluidized bed dryers using a band conveyor. Media used in media fluidized bed dryers include media particles such as ceramic balls and zirconia beads. Media fluidized bed dryers are dryers that heat an object to be heated by a fluidized bed formed by these media particles, and because a heated airflow is used to form the fluidized bed, heating essentially takes place in the heated airflow.

[0091] These spray dryers and fluidized bed dryers can be used whether the amorphous sulfide solid electrolyte to be heated is in a powder state or in a liquid state (slurry, etc.) accompanied by a solvent, but are more suitable in terms of their characteristics when the amorphous sulfide solid electrolyte is in a liquid state (slurry, etc.) accompanied by a solvent.

[0092] The gas used in the heated airflow for heating the object to be heated can be any gas, and various gases such as inert gases such as nitrogen and argon, and air can be used. Nitrogen and air are preferable in terms of cost, and nitrogen is preferred in terms of improving ionic conductivity. These gases may be used alone or in combination. The dew point temperature of the gas is preferably −10° C. or lower, more preferably −20° C. or lower, and even more preferably −30° C. or lower, from the viewpoint of suppressing deterioration in the quality of the sulfide solid electrolyte due to moisture contained in the gas.

[0093] The temperature of the heated airflow during heating is not particularly limited as long as it is set to a level at which the amorphous sulfide solid electrolyte can be crystallized to form a crystalline sulfide solid electrolyte. However, it cannot be generalized because it can vary depending on the type of crystalline sulfide solid electrolyte to be obtained, the type of solvent (including complexing agent) if a solvent is used, the scale of the flash dryer used, etc. The temperature of the heated airflow is, for example, preferably 150°C or higher, more preferably 160°C or higher, and even more preferably 170°C or higher, with the upper limit preferably being 250°C or lower. Here, the temperature of the heated airflow is the supply temperature of the heated airflow, and, for example, when the above-mentioned flash dryer is used, it is the supply temperature to the flash dryer. When the heating temperature is within the above range, crystallization can be performed more efficiently, making it easier to obtain a crystalline sulfide solid electrolyte that is more homogeneous and has high ionic conductivity.

[0094] Furthermore, the temperature of the amorphous sulfide solid electrolyte to be heated is lower than the temperature of the heated air stream because the heating time in the heated air stream is short and the temperature does not usually reach the temperature of the heated air stream. This is also true when using a flash dryer or other dryers such as the above-mentioned spray dryer and fluidized dryer, and the temperature of the heated object is lower than the temperature in these dryers. The temperature of the amorphous sulfide solid electrolyte to be heated by heating in a dryer such as a flash dryer, spray dryer, or fluidized dryer is preferably 140°C or higher, more preferably 150°C or higher, after the heating, and the upper limit is preferably 240°C or lower.

[0095] The supply amount of the heated airflow is not particularly limited as long as it is supplied to an extent that the amorphous sulfide solid electrolyte can be crystallized to form a crystalline sulfide solid electrolyte, and cannot be generalized because it varies depending on the type of crystalline sulfide solid electrolyte to be obtained, the type of solvent (including complexing agent) when a solvent is used, the scale of the flash dryer to be used, etc. The supply amount of the heated airflow is preferably 0.1 m, for example. ３ / min or more, more preferably 0.3 m ３ / min or more, more preferably 0.5 m ３ / min or more, and the upper limit is preferably 500m ３ / min or less, more preferably 475m ３ / min or less, more preferably 450m ３ Within the above range, crystallization can be carried out more efficiently, making it easier to obtain a more homogeneous crystalline sulfide solid electrolyte having high ionic conductivity.

[0096] The supply amount of the heated airflow cannot be generally determined as in the case of the supply amount of the heated airflow described above, but it is preferable to use the ratio of the supply amount of the amorphous sulfide solid electrolyte (g / min) / the supply amount of the heated airflow (m ３ / min), preferably 1.0 g / m ３ More preferably, 1.5 g / m ３ More preferably, 2.0 g / m ３ The upper limit is preferably 50.0 g / m ３ Within the above range, crystallization can be carried out more efficiently, making it easier to obtain a more homogeneous crystalline sulfide solid electrolyte having high ionic conductivity.

[0097] The flow velocity of the heated airflow, like the supply rate of the heated airflow, cannot be generally determined, but is preferably 5 m / s or more, more preferably 7.5 m / s or more, and even more preferably 9 m / s or more, with the upper limit being preferably 35 m / s or less, more preferably 30 m / s or less, and even more preferably 25 m / s or less. Within the above range, crystallization can be carried out more efficiently, making it easier to obtain a more homogeneous crystalline sulfide solid electrolyte having high ionic conductivity.

[0098] The heating time in the heated airflow cannot be generally determined, as with the supply amount of the heated airflow, but the upper limit is preferably 1 minute or less, more preferably 50 seconds or less, even more preferably 40 seconds or less, still more preferably 15 seconds or less, and particularly preferably 5 seconds or less, and the lower limit is usually 0.05 seconds or more, preferably 0.1 seconds or more, and more preferably 0.2 seconds or more.

[0099] In this way, the heating time in the heated air flow is extremely short, and therefore the amorphous sulfide solid electrolyte to be heated is not exposed to high temperature conditions for a long period of time, and thermal degradation can be suppressed, resulting in a crystalline sulfide solid electrolyte with high ionic conductivity.

[0100] [Transporting] The production method of this embodiment preferably includes transferring the heated powder obtained by the heating from a heating device used for heating in the heated airflow to a separation device through a transfer pipe. The heated powder discharged from the heating device, i.e., the crystallized sulfide solid electrolyte, can be recovered as is, but in order to more efficiently produce a crystalline sulfide solid electrolyte, it is preferable to recover it using a separation device described below.

[0101] There are no particular restrictions on the type of transfer piping from the heating equipment to the separation device as long as it can transfer the heated powder. For example, depending on the scale, steel piping such as stainless steel piping or glass piping may be used.

[0102] The heated powder can be transferred from the heating device to the separation device through a transfer pipe, and there are no limitations on the method. Since a device that can be heated in a heated airflow is selected as the heating device, the heated powder is usually transferred together with the heated airflow, i.e., as a fluid containing powder and heated airflow. Therefore, the heated powder can be supplied to the separation device through a transfer pipe as a fluid containing powder.

[0103] Furthermore, it is preferable to heat the transfer piping from the heating equipment to the separation device. Heating the transfer piping can improve the crystallinity of the crystalline sulfide solid electrolyte that becomes the heated powder. There are no limitations on the method for heating the transfer piping as long as it can heat the transfer piping. For example, as shown in FIG. 1 , it is possible to use a transfer piping heating device such as the installation of a heat insulating material, a piping heater such as a jacket heater, or a commercially available product as a heat retention heater. Furthermore, as the jacket heater, a steam jacket that uses steam as a heating medium, an electric heating jacket that uses electricity, or the like can be used.

[0104] The heating temperature of the transfer pipe should be set to a level that can suppress a decrease in the temperature of the heated powder discharged from the heating equipment, but cannot be generalized because it can vary depending on the type of crystalline sulfide solid electrolyte to be obtained, the type of solvent (including complexing agent) if a solvent is used, the scale of the flash dryer used, the supply temperature limit of the device adopted for the separation device, etc. The heating temperature of the transfer pipe is, for example, preferably 150°C or higher, more preferably 160°C or higher, and even more preferably 170°C or higher, with the upper limit preferably being 250°C or lower. When the heating temperature is within the above range, crystallization can be carried out more efficiently, making it easier to obtain a crystalline sulfide solid electrolyte that is more homogeneous and has high ionic conductivity.

[0105] The supply temperature of the heated powder discharged from the heating equipment to the separation device cannot be generally determined because the limit value for the supply temperature may vary depending on the device used in the separation device, but it is preferably 150°C or less, with a lower limit of preferably 50°C or more, more preferably 60°C or more, and even more preferably 70°C or more.

[0106] [Collection by Separation Device] In the manufacturing method of this embodiment, it is preferable to collect the powder transferred by the above-mentioned transfer by a separation device. The heated powder discharged from the heating device that performs heating in the heated air flow is discharged together with the heated air flow as a fluid containing the heated powder and the heated air flow, as described above. By using a separation device, the fluid containing the heated powder and the heated air flow can be separated into the heated powder and the heated air flow, making it easy to selectively collect the heated powder, i.e., the crystalline sulfide solid electrolyte. The material collected by the separation device is the heated powder, i.e., the crystalline sulfide solid electrolyte.

[0107] (Separation device) From the viewpoint of efficiently collecting the powder, a bag filter is preferably used as a separation device used to collect the heated powder supplied via the heating equipment and transfer piping, as shown in Fig. 1. By using a bag filter, the fluid containing the heated powder and heated airflow discharged from the heating equipment can be easily separated into the heated powder and the heated airflow, and the heated powder can be captured and recovered.

[0108] The filter used in the bag filter can be any filter made of materials such as polypropylene, nylon, acrylic, polyester, cotton, wool, heat-resistant nylon, polyamide / polyimide, PPS (polyphenylene sulfide), glass fiber, and PTFE (polytetrafluoroethylene), and functional filters such as electrostatic filters can also be used. Among these, filters made of heat-resistant nylon, polyamide / polyimide, PPS (polyphenylene sulfide), glass fiber, and PTFE (polytetrafluoroethylene) are preferred, and filters made of heat-resistant nylon, PPS (polyphenylene sulfide), and PTFE (polytetrafluoroethylene) are more preferred, with filters made of PTFE (polytetrafluoroethylene) being particularly preferred.

[0109] The bag filter may also have a brushing means, for example, preferably a pulsating counter pressure type or a pulse jet type, with the pulse jet type being particularly preferred.

[0110] An induced draft fan may be provided in the line from the exhaust port of the bag filter to forcibly exhaust the gas exhausted from the exhaust port. By exhausting the gas with an induced draft fan or the like, filtration in the bag filter proceeds smoothly, and the slurry can be dried in a shorter time.

[0111] [Mechanical Treatment] The production method of this embodiment may include mechanically treating the collected material (which is a crystalline sulfide solid electrolyte, as described above) obtained by collection using the separation device. When adjusting the morphology of the crystalline sulfide solid electrolyte obtained by the production method of this embodiment depending on its application, it is efficient to perform the adjustment by mechanical treatment.

[0112] The mechanical treatment method is not particularly limited as long as it includes at least one treatment selected from crushing and granulation, and examples thereof include methods using mechanical treatment equipment such as a stirrer or a grinder. The stirrer may be appropriately selected from the stirrers exemplified as devices that can be used in the mixing process described above. For example, a mechanical stirring mixer equipped with stirring blades in a tank is preferred. Mechanical stirring mixers include high-speed stirring mixers, double-arm mixers, etc., and any type can be used. However, from the viewpoint of more easily adjusting the desired morphology, high-speed stirring mixers are preferred. More specifically, high-speed stirring mixers include, as already mentioned, vertical shaft rotary mixers, horizontal shaft rotary mixers, etc., as well as various devices such as high-speed swirling thin film mixers and high-speed shear mixers. Among these, high-speed swirling thin film mixers (also referred to as "thin film swirling high-speed mixers") are preferred from the viewpoint of more easily adjusting the desired morphology.

[0113] The grinder may be appropriately selected from among the agitators exemplified as devices that can be used in the above-mentioned mixing. For example, a media-type grinder is preferably used. Media-type grinders are broadly classified into container-driven grinders and media-agitating grinders, and either type of grinder is preferably used.

[0114] Morphology adjustment by mechanical treatment can be performed, for example, by changing the operating conditions of the agitator or pulverizer. Morphology adjustment involves reducing the energy applied to the object of mechanical treatment, resulting in crushing (atomization) and a tendency to increase the specific surface area. On the other hand, increasing the applied energy results in granulation (particle growth), which tends to decrease the specific surface area. For example, when using a pulverizer, the amount of energy applied can be adjusted by the circumferential speed of the rotor and the size of the particle diameter of the medium. Crushing can be achieved by rotating the rotor at a low circumferential speed or reducing the particle diameter of the medium, while granulation can be achieved by rotating the rotor at a high circumferential speed or increasing the particle diameter of the medium. Furthermore, the longer the mechanical treatment time, the greater the tendency for granulation (particle growth).

[0115] As mentioned above, morphology adjustment by mechanical treatment can be performed by varying the magnitude of the applied energy, more specifically, the circumferential speed of the rotor and the particle size of the medium. Here, the magnitudes of the applied energy, the circumferential speed of the rotor, and the particle size of the medium can vary depending on the amount of crystalline sulfide solid electrolyte to be treated, shape characteristics such as average particle size, and so a univocal definition is difficult. While the above "magnitude" is a relative term, it is easy to grasp the "magnitude" by actually performing mechanical treatment, and therefore does not require excessive trial and error.

[0116] A solvent may be used when carrying out the mechanical treatment. That is, a fluid obtained by adding a solvent to the collected material may be subjected to the mechanical treatment by the above method. The solvent may be appropriately selected from the solvents exemplified above as solvents that can be used in obtaining the amorphous sulfide solid electrolyte. In consideration of ease of mechanical treatment, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether-based solvents are preferred.

[0117] The amount of solvent used may be such that the content of the collected material relative to the total amount of the collected material and the solvent is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and the upper limit is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less.

[0118] [Heating the Mechanically Treated Product in a Heated Air Stream] The manufacturing method of this embodiment can include heating the mechanically treated product obtained by the above mechanical treatment in a heated air stream. When the collected product obtained by the above collection is mechanically treated, a portion of the collected product may become amorphous due to collisions between the collected product and itself, between the collected product and the agitator blades of the agitator, or between the collected product and the medium of the mill. In such cases, the crystallinity can be improved by heating the mechanically treated product in a heated air stream. Furthermore, when a solvent is used for the mechanical treatment, it is also possible to remove the solvent.

[0119] Heating of the mechanically treated product in the heated air stream can be carried out in the same manner as heating of the amorphous sulfide solid electrolyte in the heated air stream. Therefore, the heating of the mechanically treated product in the heated air stream can be carried out using a heating device such as a flash dryer, a spray dryer, or a fluidized bed dryer, and other heating conditions are also the same. For example, when heating the mechanically treated product in the heated air stream, the temperature of the heated air stream 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 250°C or lower, and the supply rate of the heated air stream is also the same.

[0120] The thermally mechanically treated product obtained by heating the mechanically treated product in a heated air stream becomes a crystalline sulfide solid electrolyte, similar to the heated powder obtained by heating the above-mentioned amorphous sulfide solid electrolyte in a heated air stream.

[0121] (Flow of Method for Producing Crystalline Sulfide Solid Electrolyte) The overall flow of the production method of this embodiment will be described using the flow diagram of FIG. 5. (1A) of FIG. 5 shows the flow of the production method of this embodiment, which includes obtaining an amorphous sulfide solid electrolyte and heating in a heated air stream. Also, (2A) and (3A) of FIG. 5 show an example of a preferred flow of the production method of this embodiment. More specifically, (2A) shows the flow of (1A) including heating in a heated air stream to obtain a heated powder, and collecting the heated powder in a separation device through a transfer pipe. (3A) shows the flow of (2A) including mechanically treating the collected material and heating the mechanically treated material in a heated air stream.

[0122] In (1A) to (3A), obtaining the amorphous sulfide solid electrolyte preferably includes mixing raw material components containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, as described above, and more preferably mixing the raw material components using a solvent. After mixing the raw material components, the fluid obtained by mixing is preferably dried. The solvent can be removed by drying the fluid, resulting in an amorphous sulfide solid electrolyte. When drying the fluid to remove the solvent, the solvent can be removed by drying in a heated air stream, similar to heating the amorphous sulfide solid electrolyte described above in a heated air stream.

[0123] The manufacturing method of this embodiment includes heating the amorphous sulfide solid electrolyte obtained by obtaining the amorphous sulfide solid electrolyte in a heated air stream, thereby obtaining a crystalline sulfide solid electrolyte. The crystalline sulfide solid electrolyte obtained by heating in the heated air stream may be collected as is, as shown in (2A), and used as the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment. Alternatively, the collected material may be mechanically treated to obtain a mechanically treated product, which may be used as a crystalline sulfide solid electrolyte. Alternatively, the mechanically treated product may be further heated in the heated air stream to obtain a crystalline sulfide solid electrolyte. In this way, when the mechanically treated product is heated in the heated air stream, the object to be heated in the heated air stream may be an electrolyte precursor, an amorphous sulfide solid electrolyte, or a crystalline sulfide solid electrolyte (the mechanically treated product).

[0124] [Method for producing crystalline sulfide solid electrolyte] A method for producing a crystalline sulfide solid electrolyte according to another embodiment different from the present embodiment includes the following steps (i) to (iii) in this order. Furthermore, the method for producing a crystalline sulfide solid electrolyte according to another embodiment preferably further includes the following steps (iv) to (vi) in this order. (i) Mixing raw material components containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms using a solvent; (ii) Drying the fluid obtained by the mixing to remove the solvent; (iii) Heating the amorphous sulfide solid electrolyte obtained by removing the solvent in (ii) in a heated air stream; (iv) Transferring the heated powder obtained by the heating in (iii) to a separator through a transfer pipe and collecting it in the separator; (v) Mechanically treating the collected material obtained by the collection; and (vi) Heating the mechanically treated material obtained by the mechanical treatment in a heated air stream.

[0125] FIG. 6 (1B) shows a flow of a production method of another embodiment, which includes mixing the raw material ingredients in a solvent (corresponding to the above (i) and hereinafter simply referred to as "mixing"), removing the solvent by drying (corresponding to the above (ii) and hereinafter simply referred to as "removing the solvent"), and heating in a heated air stream (corresponding to the above (iii)). The amorphous sulfide solid electrolyte can be produced more efficiently by the above-mentioned mixing and solvent removal. Therefore, the production method of another embodiment can be said to be a production method including (i) mixing and (ii) removing the solvent to obtain an amorphous sulfide solid electrolyte, and (iii) heating in a heated air stream.

[0126] The raw material ingredients and solvent in the mixing in (i) above are as described in the manufacturing method of this embodiment. The mixing method and the like are also as described in the manufacturing method of this embodiment. The method of removing the solvent by drying in the solvent removal in (ii) above is also as described in the manufacturing method of this embodiment. Furthermore, the amorphous sulfide solid electrolyte, the method of heating in a heated air stream in the heating in (iii) above are also as described in the manufacturing method of this embodiment.

[0127] 6 (2B) shows an example of a preferred flow of a manufacturing method of another embodiment. More specifically, (2B) shows that the heated powder obtained by heating in a heated air stream in the flow of (1B) is collected in a separation device through a transfer pipe (corresponding to the above (iv) and hereinafter simply referred to as "collecting"), mechanically treating the collected product (corresponding to the above (v) and hereinafter simply referred to as "mechanically treating"), and heating the mechanically treated product in a heated air stream (corresponding to the above (vi) and hereinafter simply referred to as "heating in a heated air stream").

[0128] The transfer piping in (iv) above, the collection method in the collection step, the technique for mechanical treatment in (v) above, the mechanically treated product obtained, and the method for crushing in a heated air stream in (vi) above are as explained in the manufacturing method of this embodiment.

[0129] (Amorphous Sulfide Solid Electrolyte) The amorphous sulfide solid electrolyte used in 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., solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide; and solid electrolytes further containing other atoms such as oxygen atoms and silicon atoms, for example, Li 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 solid electrolyte 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, Li ２ S-P ２ S ５ A solid electrolyte composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiI-LiBr, is preferred. The types of atoms constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0130] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains at least Li ２ S-P ２ S ５ When Li ２ S and P ２ S ５ From the viewpoint of obtaining higher ionic conductivity, the molar ratio of 65-85:15-35 is preferred, 70-80:20-30 is more preferred, and 72-78:22-28 is even more preferred.

[0131] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment is, for example, Li ２ S-P ２ S ５In the case of -LiI-LiBr, the total content of lithium sulfide and diphosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%. The ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0132] In the amorphous sulfide solid electrolyte obtained by the production method of this embodiment, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms is preferably 1.0 to 1.8: 1.0 to 2.0: 0.1 to 0.8: 0.01 to 0.6, more preferably 1.1 to 1.7: 1.2 to 1.8: 0.2 to 0.6: 0.05 to 0.5, and even more preferably 1.2 to 1.6: 1.3 to 1.7: 0.25 to 0.5: 0.08 to 0.4. Further, when bromine and iodine are used in combination as halogen atoms, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine, and iodine is preferably 1.0 to 1.8: 1.0 to 2.0: 0.1 to 0.8: 0.01 to 0.3: 0.01 to 0.3, more preferably 1.1 to 1.7: 1.2 to 1.8: 0.2 to 0.6: 0.02 to 0.25: 0.02 to 0.25, more preferably 1.2 to 1.6: 1.3 to 1.7: 0.25 to 0.5: 0.03 to 0.2: 0.03 to 0.2, and even more preferably 1.35 to 1.45: 1.4 to 1.7: 0.3 to 0.45: 0.04 to 0.18: 0.04 to 0.18. By setting the compounding 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 with higher ionic conductivity having a thiolisiconregion II type crystal structure, which will be described later.

[0133] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle size (D ５０ ) is, for example, 0.01 μm or more, further 0.03 μm or more, 0.05 μm or more, or 0.1 μm or more, and the upper limit is 5 μm or less, further 3.0 μm or less, 1.5 μm or less, 1.0 μm or less, or 0.5 μm or less.

[0134] The amorphous sulfide solid electrolyte used in the manufacturing method of the other embodiment may be the same as the amorphous sulfide solid electrolyte used in the manufacturing method of the present embodiment described above.

[0135] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may be a so-called glass ceramic obtained by heating an amorphous sulfide solid electrolyte to a crystallization temperature or higher, and its crystalline structure may be Li ３ P.S. ４ Crystal structure, Li ４ P ２ S ６ Crystal structure, Li ７ P.S. ６ Crystal structure, Li ７ P ３ S １１ Examples of such a crystal structure include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0136] 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 Examples of the crystal structure include a crystal structure similar to the thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725). The crystal structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is preferably the thio-LISICON Region II type crystal structure among the above, in that higher ionic conductivity can be obtained. Here, the "thio-LISICON Region II type crystal structure" refers to a crystal structure in which Li ４－ｘ Ge １－ｘ P ｘ S ４Thio-LISICON Region II crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４ This indicates that the thio-LISICON region II type has a similar crystal structure.

[0137] Here, 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 found in the above document to be composed of Li, Ge, P, and S atoms. The sulfide solid electrolyte obtained by the production method of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and therefore, is not a "Li ４－ｘ Ge １－ｘ P ｘ S ４ "Li in thio-LISICON Region II type" ４－ｘ Ge １－ｘ P ｘ S ４ However, when the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has the same diffraction peak as the above-mentioned "thiolisiconregion II type crystal structure" (including the above-mentioned "similar crystal structure"), it can be said that the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has a thiolisiconregion II type crystal structure formed by lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms.

[0138] The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may contain the above-mentioned thiolicon region II type crystal structure or may contain it as the main crystal, but from the viewpoint of obtaining higher ionic conductivity, it is preferable that it contains it as the main crystal. In this specification, "containing it as the main crystal" means that the proportion of the target crystal structure 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 contains crystalline Li ３ P.S. ４ (β-Li ３ P.S. ４ ) is preferably not included.

[0139] In X-ray diffraction measurement using CuKα radiation, Li ３ 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 ４Diffraction 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°.

[0140] The atomic composition ratios of the crystalline sulfide solid electrolyte are preferably within the range of the atomic composition ratios of the amorphous sulfide solid electrolyte, which are determined by the composition formulas corresponding to the various crystal structures. When the atomic composition ratios are within the range, the thiolicon region II crystal structure is more likely to be formed.

[0141] (Content of Complexing Agent) In the production method of the present embodiment, when an amorphous sulfide solid electrolyte produced using a complexing agent is used, the content of the complexing agent contained in the crystalline sulfide solid electrolyte obtained by the production method of the present embodiment is preferably 0 mass%, i.e., no complexing agent is contained at all. However, from the viewpoint of efficiently obtaining a sulfide solid electrolyte having high ionic conductivity, the content is usually 10 mass% or less, further 8 mass% or less, 5 mass% or less, 3 mass% or less, or 1 mass% or less, and the lower limit is about 0.01 mass% or more.

[0142] Similarly to the complexing agent, when a solvent is used, the solvent may also remain. In this case, the content of the solvent is also in the same range as the content of the complexing agent.

[0143] The shape of the crystalline sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D ５０) is, for example, 0.01 μm or more, further 0.03 μm or more, 0.05 μm or more, or 0.1 μm or more, with the upper limit being 5 μm or less, further 3.0 μm or less, 1.5 μm or less, 1.0 μm or less, or 0.5 μm or less. The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is crystallized by heating in a heated air flow. Therefore, the generation of secondary particles due to aggregation of primary particles is suppressed, and the average particle size is small within the above range. Heating the amorphous sulfide solid electrolyte in a heated air flow also has the effect of reducing the average particle size. Therefore, in the manufacturing method of this embodiment, among the mechanical treatments, pulverization (atomization) treatment does not need to be performed. As explained above, mechanical treatment may be performed as necessary.

[0144] The specific surface area of ​​the sulfide solid electrolyte obtained by the production method of this embodiment is usually 10 m ２ / g or more, even 15m ２ / g or more, 20m ２ / g or more, 25m ２ / g or more. There is no particular upper limit. ２ In this specification, the specific surface area is a value measured by the BET method (gas adsorption method), and either nitrogen (nitrogen method) or krypton (krypton method) may be used as the gas, and is measured by appropriately selecting depending on the size of the specific surface area.

[0145] The crystalline sulfide solid electrolyte obtained by the production method of another embodiment may be the same as the crystalline sulfide solid electrolyte obtained by the production method of the above-described embodiment.

[0146] (Applications) The crystalline 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. A battery using the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is also called a lithium ion battery, and a battery using the crystalline sulfide solid electrolyte in an electrolyte layer, as described below, is called an all-solid-state battery. The sulfide solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer. Each layer can be manufactured by a known method.

[0147] 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.

[0148] [Apparatus for Producing Crystalline Sulfide Solid Electrolyte] The apparatus for producing a crystalline sulfide solid electrolyte of the present embodiment is a production apparatus including: a production device for an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms; and a heating device for heating the amorphous sulfide solid electrolyte in a heated air flow.

[0149] As the equipment for producing the amorphous sulfide solid electrolyte, any equipment capable of producing the amorphous sulfide solid electrolyte can be used without particular limitation. For example, mixing equipment such as mixers, agitators, and pulverizers, which have been described as equipment that can be used to mix the raw material components, and heating dryers that can dry by heating to a drying temperature and / or reducing the pressure, which have been described as equipment that can be used to dry the fluid obtained by the mixing equipment to remove the solvent, can be preferably used, as well as drying equipment such as flash dryers, spray dryers, and fluidized bed dryers that can dry by heating with a heated airflow, among which flash dryers are preferred. When using equipment that can dry by heating with a heated airflow as the equipment used to remove the solvent, it is preferable to use transfer piping and a separation device, as in the case of the heating equipment for the amorphous sulfide solid electrolyte described below.

[0150] As the drying equipment, it is also possible to use equipment such as a filter using a glass filter or the like, a solid-liquid separator by decantation, or a solid-liquid separator using a centrifugal separator or the like.

[0151] Furthermore, as the heating equipment for heating in the heated air flow provided in the manufacturing apparatus of this embodiment, as described above in the manufacturing method of this embodiment, an air flow dryer, a spray dryer, and a fluidized bed dryer are preferably used, and among these, an air flow dryer is preferred.

[0152] The manufacturing apparatus of this embodiment preferably further includes: a separation device that collects the heated powder obtained by the heating device; a mechanical processing device that mechanically processes the collected material obtained by the separation device; a heating device that heats the mechanically processed material obtained by the mechanical processing; and a transfer pipe that transfers the heated powder from the heating device to the separation device.

[0153] The separation device can be any device that can collect the heated powder obtained by the heating device, and a bag filter is preferably used as described in the manufacturing method of this embodiment. The configuration of the heating device, transfer piping, and separation device (bag filter) is, for example, as shown in Figure 1.

[0154] Any mechanical processing equipment can be used without particular limitations as long as it is capable of performing at least one process selected from crushing and granulation, and as explained in the manufacturing method of this embodiment above, it is preferable to use mechanical processing equipment such as a stirrer or a grinder.

[0155] As described in the production method of this embodiment, the heating equipment for heating the mechanically treated material is preferably equipment capable of heating in a heated air stream, such as a flash dryer, spray dryer, fluidized bed dryer, etc., and among these, a flash dryer is preferably used. Furthermore, when equipment capable of heating in a heated air stream is used as the heating equipment for the mechanically treated material, a separation device such as a transfer pipe for transferring the material to a separation device or a bag filter may be used, similar to the heating equipment used to heat the amorphous sulfide solid electrolyte.

[0156] As described in the manufacturing method of this embodiment, the transfer piping may be steel piping such as stainless steel piping, glass piping, or the like, depending on the scale, etc. The transfer piping is preferably heated by installing a heat insulating material, or by using a heater for heating the piping such as a jacket heater, or a commercially available heater for heat retention, etc.

[0157] 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.

[0158] (Measurement of Powder XRD Diffraction) Powder X-ray diffraction (XRD) measurement was carried out as follows. The sulfide solid electrolyte powder obtained in the Examples and Comparative Examples was 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. Measurement device: D2 PHASER, manufactured by Bruker Corporation Tube voltage: 30 kV Tube current: 10 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: focusing method Slit configuration: Soller slit 4°, divergence slit 1 mm, Kβ filter (Ni plate) used Detector: semiconductor detector Measurement range: 2θ = 10-60 deg Step width, scan speed: 0.05 deg, 0.05 deg / sec

[0159] (Measurement of Ion Conductivity) In the present example, the measurement of ion conductivity was carried out as follows. A 10 mm diameter (cross-sectional area S: 0.785 cm ) sample was taken from the crystalline solid electrolyte obtained in the examples and comparative examples. 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: 5 MHz to 0.5 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high-frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following formula: R = ρ (L / S) σ = 1 / ρ

[0160] (Measurement of the Complexing Agent Content in Sulfide Solid Electrolyte) The complexing agent content in the sulfide solid electrolyte was measured using a gas chromatograph (GC). The measurement outline involved measuring powder of a sulfide solid electrolyte decomposed in a mixture of water and pentanol (pentanol content in the mixture: 90% by volume) using GC, and quantifying the complexing agent using an absolute calibration curve. First, 0.1 g of sample was precisely weighed and placed in a vial. 10 ml of a water and pentanol mixture was added to the vial, and the sample was completely decomposed and dissolved. Approximately 1.5 ml of the dissolved sample was placed in a GC vial, which was then capped and secured with a crimper. The vial was then placed in the GC autosampler and measured. The calibration curve was prepared by weighing 0.5 g of the complexing agent to be used and adjusting the volume to 50 ml of a water and pentanol mixture (equivalent to 10,000 μg / ml). This was diluted to 2500, 1000, 250, 25, and 2.5 μg / ml (standard solutions) and measured by GC. A calibration curve was created using the least squares method from the peak area and the concentration of the standard solution. The GC peak area value of the sample solution was applied to the calibration curve, and the concentration in the sample solution was calculated according to the following formula: Content (mass%) of complexing agent in powder of sulfide solid electrolyte, etc. = [Concentration (μg / ml) determined from the calibration curve × Amount of mixture of water and pentanol used to dissolve the sample (10 ml)] ÷ Sample amount (g).

[0161] (Preparation Example: Preparation of Amorphous Sulfide Solid Electrolyte) The amorphous sulfide solid electrolytes used in the Examples and Comparative Examples were prepared by the following method, where the amounts of the solid electrolyte raw materials, complexing agent, etc. used were adjusted to the amounts required for each Example and Comparative Example while maintaining the same ratios of the amounts used as described in the following methods.

[0162] In a 1-liter reactor equipped with an agitator, 13.19 g of lithium sulfide, 21.26 g of diphosphorus pentasulfide, 4.15 g of lithium bromide, and 6.40 g of lithium iodide (total amount of solid electrolyte raw material: 45 g) were introduced under a nitrogen atmosphere. 100 mL of tetramethylethylenediamine (TMEDA) as a complexing agent and 800 mL of cyclohexane as a solvent were added, and the agitator was operated to mix by stirring at 30 ° C. for 72 hours. 456 g of zirconia balls (diameter: 0.5 mmφ) (bead filling rate relative to the grinding chamber: 80%) were charged into a circulating bead mill ("Labostar Mini LMZ015 (trade name)", manufactured by Ashizawa Finetech Co., Ltd.), and the mixture was circulated between the reactor and the grinding chamber at a pump flow rate of 550 mL / min, a peripheral speed of 8 m / s, and a mill jacket temperature of 20 ° C., followed by grinding for 60 minutes to obtain a slurry of the electrolyte precursor (complex). The resulting slurry was then immediately dried under vacuum at room temperature (23° C.) to obtain a powder of an electrolyte precursor (complex). The content of the complexing agent in the resulting powder of the electrolyte precursor (complex) was 55% by mass.

[0163] The electrolyte precursor powder obtained in the above Preparation Example was heated in a heated air stream using an apparatus having the configuration shown in the schematic diagram of an apparatus used for heating in a heated air stream in Figure 1. The apparatus shown in Figure 1 is an apparatus mainly comprising a flash dryer (a cylindrical vessel-type flash dryer) and a bag filter, and is equipped with a blower and heater for supplying the heated air stream, and a mixer for pneumatically transporting the material to be heated by gas. Furthermore, although not shown, a feeder (not shown) may be provided that can supply the material to be heated in the form of powder or slurry.

[0164] In the apparatus shown in Figure 1, the electrolyte precursor (the object to be heated) is pneumatically transported to the bottom of the flash dryer by a gas, and a heated airflow generated by heating the gas with a heater is supplied from the bottom of the flash dryer. The object to be heated in the heated airflow in the flash dryer becomes a powder (powder of amorphous sulfide solid electrolyte) in which the complexing agent has been removed from the electrolyte precursor, and the heated airflow containing this is supplied to a downstream bag filter. The powder (powder of amorphous sulfide solid electrolyte) in which the complexing agent has been removed from the electrolyte precursor is then recovered in the bag filter, and the heated airflow from which the powder has been recovered is then exhausted as is.

[0165] Using the above-mentioned flash dryer, nitrogen heated to 135°C was used as a heated airflow, and the airflow was 3 m ３ The feed to the flash dryer was started at a rate of 1000 g / min, and then a table feeder was used to feed the material to the flash dryer at a rate of 91.5 g / min. The material to be heated (electrolyte precursor powder) was heated in a heated airflow using the flash dryer, and the heated airflow discharged from the flash dryer was supplied to a bag filter of a separation device through a transfer pipe, and the powder contained in the heated airflow, from which the complexing agent had been removed, was collected. This process continued for 20 minutes (i.e., the operation time was 20 minutes). The collected powder was subjected to powder XRD diffraction measurement, which showed a halo pattern and confirmed that it was an amorphous sulfide solid electrolyte.

[0166] Example 1 The amorphous sulfide solid electrolyte obtained in the above Preparation Example was supplied to an apparatus shown in Fig. 1, which was different from the apparatus used in the above Preparation Example, and heated in a heated air stream in a flash dryer. The heated air stream discharged from the flash dryer was supplied to a bag filter of a separation device through a transfer pipe, and heated powder contained in the heated air stream was collected. Here, nitrogen heated to 220°C was used as the heated air stream, and a flow rate of 2.6 m was used. ３ The supply of the amorphous sulfide solid electrolyte powder to the flash dryer was started at a rate of 36.2 g / min using a table feeder, and the operation was continued for 45 minutes (i.e., the operation time was 45 minutes). The time it took for the amorphous sulfide solid electrolyte to pass through the flash dryer was 0.25 seconds.

[0167] The obtained heated powder was subjected to powder XRD diffraction measurement. The X-ray diffraction spectrum is shown in Figure 2. As shown in Figure 2, crystallization peaks were detected mainly at 2θ = 20.2 ° and 23.6 ° in the X-ray diffraction spectrum, confirming that the product was a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure. The ionic conductivity was measured to be 3.94 mS / cm, and the average particle size was 3.1 μm. The complexing agent contents of the amorphous sulfide solid electrolyte and the crystalline sulfide solid electrolyte were 13.2 mass% and 1.34 mass%, respectively. The outlet temperature of the flash dryer of the heated airflow, the flow rate within the heated dryer, and the inlet temperature of the bag filter for the heated object are as shown in Table 1.

[0168] Example 2 35.0 g of the crystalline sulfide solid electrolyte (the capture product obtained in Example 1) and 547 g of toluene were charged into a 1 L reactor equipped with an agitator under a nitrogen atmosphere. After rotating the agitator, a circulating bead mill ("Star Mill LMZ015 (trade name)" manufactured by Ashizawa Finetech Co., Ltd.) was used for 1 hour of mechanical treatment (bead material: zirconia, bead diameter: 0.3 mmφ, bead amount: 456 g, pump flow rate: 650 mL / min, peripheral speed: 12 m / s, mill jacket temperature: 10°C). The resulting slurry was supplied to the apparatus shown in FIG. 1 , which is separate from the apparatus used in the above Preparation Example and Example 1, and heated in a heated airflow in a flash dryer to heat the mechanically treated product contained in the slurry. The heated airflow (including the mechanically treated product) discharged from the flash dryer was supplied to a bag filter of a separation device through a transfer pipe, and the powder of the heated mechanically treated product contained in the heated airflow was collected. This was continued for 60 minutes (i.e., the operation time was 60 minutes). Here, nitrogen heated to 210°C was used as the heated air flow, and a flow rate of 2.6 m ３ The material was then fed to the flash dryer at a rate of 45.0 g / min using a table feeder, and the time it took for the material to pass through the flash dryer was 0.25 seconds.

[0169] The powder of the obtained thermally mechanically treated product was subjected to powder XRD diffraction measurement. The X-ray diffraction spectrum is shown in Figure 2. As shown in Figure 2, crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the product was a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure. The ionic conductivity was measured to be 3.93 mS / cm, and the average particle size was 1.5 μm. The complexing agent content of the mechanically treated product (crystalline sulfide solid electrolyte) was 1.2 mass%. The outlet temperature of the flash dryer of the heated airflow, the flow rate within the heated dryer, and the inlet temperature of the bag filter for the heated object are as shown in Table 1.

[0170] Comparative Example 1 The procedure was the same as in Example 1, except that the amorphous sulfide solid electrolyte was heated in a Schlenk flask at 110°C for 2 hours and then at 160°C for 2 hours. Powder XRD diffraction measurements were performed on the obtained powder. The X-ray diffraction spectrum is shown in FIG. 3. As shown in FIG. 3, crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the resultant was a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure. The ionic conductivity was measured to be 4.0 mS / cm, and the complexing agent content was 1.2% by mass.

[0171] (Comparative Example 2) Comparative Example 1 was repeated except that heating in the Schlenk flask at 160°C for 1 minute was performed. The obtained powder was subjected to powder XRD diffraction measurement. The X-ray diffraction spectrum is shown in Figure 4. As shown in Figure 4, the X-ray diffraction spectrum showed no crystallization peak and a halo pattern, indicating that an amorphous sulfide solid electrolyte was obtained. The content of the complexing agent was 9.2 mass%.

[0172]

[0173] The results of the Examples confirmed that a crystalline sulfide solid electrolyte can be obtained in as short a time as 0.25 seconds by heating an amorphous sulfide solid electrolyte in a heated air stream. In contrast, the results of Comparative Examples 1 and 2 confirmed that a crystalline sulfide solid electrolyte can be obtained by heating for a total of 4 hours, but not by heating for 1 minute. Thus, it was found that a crystalline sulfide solid electrolyte can be obtained in an extremely short time by heating in a heated air stream in the Examples.

[0174] It was confirmed that the ionic conductivity of the crystalline sulfide solid electrolyte obtained in the examples was higher than that of the crystalline sulfide solid electrolyte obtained in Comparative Example 1. This is thought to be because the crystalline sulfide solid electrolyte obtained in Comparative Example 1 had low ionic conductivity due to deterioration caused by oxidation or the like resulting from excessive thermal history caused by heating for a long period of time. Furthermore, in Comparative Example 2, in which the heating time was shortened, no diffraction peaks that appear due to the formation of a crystalline structure were observed, and no crystalline sulfide solid electrolyte was obtained.

[0175] Furthermore, from the diffraction peak results of Example 2 ( FIG. 2 ), it was confirmed that the crystalline sulfide solid electrolyte obtained in Example 2 had the same diffraction peak as the crystalline sulfide solid electrolyte obtained in Example 1. That is, the mechanically treated collected material obtained in Example 1 may have a smaller average particle size and may be partially amorphous, but the crystalline sulfide solid electrolyte of Example 2 obtained by heating again in a heated air stream was confirmed to be equivalent to the crystalline sulfide solid electrolyte obtained in Example 1.

[0176] According to the method for producing a sulfide solid electrolyte of this embodiment, a sulfide solid electrolyte with high ionic conductivity can be efficiently produced. Furthermore, the method can easily accommodate mass production of sulfide solid electrolytes. Therefore, the sulfide solid electrolyte of this embodiment 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, and particularly all-solid-state batteries.

Claims

1. A method for producing a crystalline sulfide solid electrolyte, comprising obtaining an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and heating the amorphous sulfide solid electrolyte in a heated gas stream.

2. The method for producing a crystalline sulfide solid electrolyte according to claim 1, wherein the temperature of the heated gas stream is 150°C or higher and 250°C or lower.

3. The method for producing a crystalline sulfide solid electrolyte according to claim 1 or 2, comprising transferring the heated powder obtained by the heating to a separation device through a transfer pipe from the heating device used by heating the heated powder in the heated gas stream, and collecting the transferred heated powder by a separation device, wherein the transfer pipe is heated.

4. The method for producing a crystalline sulfide solid electrolyte according to claim 3, wherein the heating temperature of the transfer pipe is 150°C or higher and 250°C or lower.

5. The method for producing a crystalline sulfide solid electrolyte according to claim 3 or 4, comprising mechanically treating the collected material obtained by the collecting, and heating the mechanically treated material obtained by the mechanical treatment in a heated gas stream.

6. The method for producing a crystalline sulfide solid electrolyte according to claim 5, wherein the temperature of the heated gas stream is 150°C or higher and 250°C or lower.

7. The method for producing a crystalline sulfide solid electrolyte according to any one of claims 1 to 6, wherein the heating in the heated gas stream is performed using a fluidized bed dryer.

8. The method for producing a crystalline sulfide solid electrolyte according to any one of claims 1 to 7, wherein the crystalline sulfide solid electrolyte has a thioliicon region II-type crystal structure.

9. A method for producing a crystalline sulfide solid electrolyte having the following (i) to (iii) in order: (i) mixing a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms using a solvent; (ii) drying the fluid obtained by the mixing to remove the solvent; (iii) heating the amorphous sulfide solid electrolyte obtained by removing the solvent in (ii) in a heated gas stream.

10. Further, a method for producing a crystalline sulfide solid electrolyte according to claim 9, comprising the following (iv) to (vi) in this order: (iv) transferring the heated powder obtained by heating in (iii) to a separation device through a transfer pipe and collecting it by the separation device; (v) mechanically treating the collected material obtained by the collecting; (vi) heating the mechanically treated material obtained by the mechanical treatment in a heated air stream 11. A production apparatus for a crystalline sulfide solid electrolyte, comprising a production apparatus for an amorphous sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and a heating apparatus for heating the amorphous sulfide solid electrolyte in a heated air stream 12. The production apparatus for a crystalline sulfide solid electrolyte according to claim 11, wherein the production apparatus for the amorphous sulfide solid electrolyte comprises a mixing apparatus for mixing a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms using a solvent, and a drying apparatus for drying the fluid obtained by the mixing apparatus to remove the solvent 13. Further, a separation device for collecting the heated powder obtained by the heating apparatus, a mechanical treatment device for mechanically treating the collected material obtained by the separation device, a heating apparatus for heating the mechanically treated material obtained by the mechanical treatment, and a transfer pipe for transferring the heated powder from the heating apparatus to the separation device. The production apparatus for a crystalline sulfide solid electrolyte according to claim 11 or 12

Images