Method for manufacturing sulfide solid electrolyte

Abstract

Provided is a method for manufacturing a sulfide solid electrolyte, the method efficiently manufacturing a sulfide solid electrolyte having high ion conductance, using a liquid-phase method. The method includes: mixing a complexing agent and a raw material composition including lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain an electrolyte precursor-containing product that allows easy mass production and includes an electrolyte precursor powder; and then heating the product in a heated air stream.

Description

Method for producing sulfide solid electrolyte

[0001] The present invention relates to a method for producing a 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 to be used as their power sources has become increasingly important. Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents, but by making batteries all-solid-state, flammable organic solvents are not used in the battery, safety devices can be simplified, and manufacturing costs and productivity are excellent. Therefore, batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed.

[0003] Methods for producing a solid electrolyte used in a solid electrolyte layer are roughly divided into solid-phase methods and liquid-phase methods, and liquid-phase methods include homogeneous methods in which a solid electrolyte material is completely dissolved in a solvent, and heterogeneous methods in which the solid electrolyte material is not completely dissolved and a solid-liquid coexistence suspension is formed. For example, among the liquid-phase methods, a homogeneous method in which a solid electrolyte is dissolved in a solvent and reprecipitated is known (see, for example, Patent Document 1), and a heterogeneous method in which a solid electrolyte raw material such as lithium sulfide is reacted in a solvent containing a polar aprotic solvent (see, for example, Patent Documents 2 and 3 and Non-Patent Document 1).

[0004] Further, a method for producing a solid electrolyte is also known, which includes using a specific compound having an amino group as a complexing agent and mixing the complexing agent with a solid electrolyte raw material to prepare an electrolyte precursor (see, for example, Patent Document 4), and a method for producing a solid electrolyte is also known, which includes drying a slurry containing a complexing agent and an electrolyte precursor by fluidized drying using media particles (see, for example, Patent Document 5).

[0005] Japanese Patent Application Publication No. 2014-191899 International Publication No. 2014 / 192309 Pamphlet International Publication No. 2018 / 054709 Pamphlet International Publication No. 2020 / 105737 Pamphlet International Publication No. 2021 / 230189 Pamphlet

[0006] “CHEMISTRY OF MATERIALS”, 2017, No. 29, pp. 1830-1835

[0007] The present invention has been made in view of the above circumstances, and aims to provide a production method for efficiently producing a sulfide solid electrolyte having high ionic conductivity while employing a liquid phase method, which is also easy to mass-produce.

[0008] The method for producing a sulfide solid electrolyte according to the present invention includes: mixing a raw material containing material that includes lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with a complexing agent to obtain an electrolyte precursor containing material; and then heating the material in a heated air stream.

[0009] According to the present invention, it is possible to provide a production method that employs a liquid phase method to efficiently produce a sulfide solid electrolyte having high ionic conductivity and that is easy to mass-produce.

[0010] FIG. 1 is a flow diagram of an apparatus equipped with a flash dryer and a bag filter used in Example 1. FIG. 2 is an X-ray diffraction spectrum of the crystalline sulfide solid electrolyte obtained in Example 3. FIG. 3 is an X-ray diffraction spectrum of the crystalline sulfide solid electrolyte obtained in Examples 3 to 8. FIG. 4 is an X-ray diffraction spectrum of the crystalline sulfide solid electrolyte obtained in Comparative Examples 1 and 2. FIG. 5 is a flow diagram of an apparatus equipped with a fluidized bed dryer and a bag filter used in Comparative Example 3. FIG. 6 is an X-ray diffraction spectrum of the crystalline sulfide solid electrolyte obtained in Comparative Example 3, Examples 3 and 6. FIG. 7 is an X-ray diffraction spectrum of the crystalline sulfide solid electrolyte obtained in Examples 9 to 15.

[0011] 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.

[0012] (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.

[0013] In recent years, liquid-phase synthesis has attracted attention as a method for the practical application of all-solid-state batteries, not only for its versatility and applicability, but also for its ease of mass synthesis. While liquid-phase synthesis offers the aforementioned advantages, it suffers from the drawback of being difficult to achieve high ionic conductivity compared to solid-phase synthesis due to the dissolution of the solid electrolyte, which can lead to partial decomposition and loss of solid electrolyte components during precipitation. For example, in homogeneous synthesis, the raw materials and solid electrolyte are completely dissolved once, resulting in uniform dispersion of the components in the solution. However, in the subsequent precipitation process, precipitation proceeds according to the specific solubility of each component, making it extremely difficult to maintain the dispersion state of the components during precipitation. As a result, the components separate and precipitate. Furthermore, in homogeneous synthesis, the affinity between the solvent and lithium becomes too strong, making it difficult to remove the solvent even after drying after precipitation. For these reasons, homogeneous synthesis suffers from the drawback of significantly reducing the ionic conductivity of the solid electrolyte. Furthermore, in heterogeneous synthesis, where solid and liquid coexistence occurs, partial dissolution of the solid electrolyte leads to separation due to the elution of specific components, making it difficult to obtain the desired solid electrolyte.

[0014] Furthermore, regarding the liquid phase method (heterogeneous method), a step of removing the complexing agent is required in the method of producing a sulfide solid electrolyte via an electrolyte precursor using a complexing agent, as described in, for example, Patent Document 4. The present inventors focused on a method of removing the complexing agent in the method of producing a sulfide solid electrolyte via an electrolyte precursor using a complexing agent.

[0015] In the manufacturing method described in Patent Document 4, the complexing agent is removed by drying a slurry-like electrolyte precursor-containing material under vacuum and at room temperature to form a powdered electrolyte precursor, and then heating the electrolyte precursor under vacuum at 120°C (see, for example, Example 1). Specifically, this is done using a jacket-type heater (such as a vibration dryer) under vacuum. Thus, when a complexing agent is used, the complexing agent cannot be removed from the electrolyte precursor by simple drying, and heating is performed using a jacket-type heater (such as a vibration dryer). However, while such a heater can remove the complexing agent, the inner wall surface of the heater may become locally hot, causing aggregation of halogen compounds contained in the solid electrolyte and resulting in deterioration of the solid electrolyte. Therefore, there are limitations on the temperature conditions for removing the complexing agent, leaving room for improvement in terms of efficient solid electrolyte production. Furthermore, with the increasing demand for sulfide solid electrolytes, there is a need for mass production. However, in the conventional method, heating is performed under vacuum, and the complexing agent is removed in an environment where heat is transferred only when the powder comes into contact with the inner wall surface (heat transfer surface) of the jacket-type heater. This has a significant impact on the size of the equipment, and there were concerns that it would not be possible to adequately address the issue.

[0016] Regarding the removal of the complexing agent, no complexing agent is used in Patent Documents 1 to 3. Furthermore, although the use of a solvent during the reaction of the solid electrolyte raw materials is envisioned, no consideration is given to a method for removing the solvent. In the manufacturing method described in Patent Document 5, a slurry containing a complexing agent and an electrolyte precursor is dried by fluidized drying using media particles. However, even in the manufacturing method described in Patent Document 5, the complexing agent is not removed from the electrolyte precursor by drying the slurry. Therefore, the complexing agent is removed from the dried electrolyte precursor by heating at 110°C under vacuum, as in the manufacturing method described in Patent Document 4 (Example 1, etc.), specifically, by using a jacket-type heater (such as a vibration dryer) under vacuum. As a result, the same problems as those in the manufacturing method described in Patent Document 4 arise.

[0017] Therefore, the present inventors have investigated methods for removing the complexing agent from an electrolyte precursor formed from a complexing agent and a solid electrolyte raw material, and have found that the complexing agent can be removed from the electrolyte precursor contained in the electrolyte precursor-containing material by supplying the electrolyte precursor-containing material into a heated air flow. Removing the complexing agent from the electrolyte precursor by heating in the heated air flow makes it possible to suppress deterioration of the solid electrolyte due to contact between the solid electrolyte powder and the wall surface of a jacket-type heater (such as a vibration dryer) that becomes locally hot.

[0018] Furthermore, since heating is performed using a heated airflow, it is expected that the complexing agent can be removed from the electrolyte precursor-containing material regardless of the scale as long as the supply amount of the heated airflow, particularly the flow rate, is maintained within a certain range. Therefore, there is also the advantage that it is easy to accommodate larger equipment.

[0019] Based on the above findings, the present inventors have discovered that in a method for producing a sulfide solid electrolyte by a liquid-phase method (heterogeneous method) in which a complexing agent is reacted with a solid electrolyte raw material, by removing the complexing agent from the electrolyte precursor powder by heating in a heated air flow, a sulfide solid electrolyte with high ionic conductivity can be efficiently obtained and mass production can be facilitated, while still employing the liquid-phase method.

[0020] (Regarding various aspects of the present embodiment) A method for producing a sulfide solid electrolyte according to a first aspect of the present embodiment is a method for producing a sulfide solid electrolyte, the method comprising: mixing a raw material inclusion containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with a complexing agent to obtain an electrolyte precursor inclusion; and subsequently heating the mixture in a heated air stream.

[0021] In the method for producing a sulfide solid electrolyte of this embodiment, the electrolyte precursor-containing material obtained by mixing the solid electrolyte raw material and the complexing agent may contain, in addition to the electrolyte precursor, the complexing agent and solid electrolyte raw material that did not contribute to the formation of the electrolyte precursor, and the solvent. In the method for producing a sulfide solid electrolyte of this embodiment, the complexing agent can be removed from the electrolyte precursor by heating in a heated air flow. Furthermore, if the electrolyte precursor contains a complexing agent or solvent that does not contribute to the formation of the electrolyte precursor and remains, these can also be removed.

[0022] The electrolyte precursor is a precursor of the sulfide solid electrolyte obtained by the manufacturing method of this embodiment, and can become a sulfide solid electrolyte by removing the complexing agent. Here, the complexing agent is a complexing agent, i.e., an agent capable of forming a complex, and refers to a compound that easily forms a complex with the solid electrolyte raw material contained in the raw material inclusions. Therefore, since the electrolyte precursor is obtained by mixing the raw material inclusions with the complexing agent, it can be said to be a complex formed by the solid electrolyte raw material via the complexing agent, more specifically.

[0023] The manufacturing method of this embodiment includes heating the electrolyte precursor-containing material in a heated air stream after obtaining the electrolyte precursor-containing material. The heating step may be performed after obtaining the electrolyte precursor-containing material. The heating target in the heating step is the electrolyte precursor-containing material, or, if drying, as described below, the electrolyte precursor (hereinafter, the electrolyte precursor-containing material and the electrolyte precursor may be collectively referred to as the "heating target"). When heating the electrolyte precursor-containing material to remove the complexing agent from the electrolyte precursor, it is essential to heat the electrolyte precursor-containing material, particularly the electrolyte precursor contained in the electrolyte precursor-containing material, in a heated air stream. The heated air stream has the functions of drying by temperature (heat) and air stream, dispersing the heated material, and removing the complexing agent by air stream. These functions are believed to enable efficient removal of the complexing agent from the electrolyte precursor. The heated material, such as the electrolyte precursor-containing material, is dispersed in the heated air stream by direct contact with the heated air stream, thereby increasing the contact area between the electrolyte precursor and the heated air stream. Therefore, the complexing agent contained in the electrolyte precursor can be efficiently heated. Furthermore, the heated airflow allows the complexing agent to be quickly separated and removed, and thus suppresses the re-formation of a complex between the electrolyte precursor from which the complexing agent has been removed and the complexing agent (hereinafter also simply referred to as "complex re-formation"), as well as the generation of impurities between the electrolyte precursor and the complexing agent (hereinafter also simply referred to as "impurity generation").This allows for the production of a high-quality sulfide solid electrolyte with few impurities and high ionic conductivity.

[0024] A second aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the first aspect, further comprising drying the electrolyte precursor-containing material.

[0025] In the manufacturing method of this embodiment, when considering the removal of the complexing agent contained in the electrolyte precursor, it is important to directly heat the electrolyte precursor in the heated air stream. As a preliminary step to heating in the heated air stream, the electrolyte precursor-containing material is dried to remove the remaining complexing agent that does not contribute to the formation of the electrolyte precursor and the solvent used as needed, thereby isolating the electrolyte precursor as a powder, which can then be heated in the heated air stream. By drying, the complexing agent contained in the electrolyte precursor can be heated more directly, making it possible to more efficiently separate and remove the complexing agent. As a result, the regeneration of complexes and the generation of impurities are suppressed, making it easier to more efficiently obtain a sulfide solid electrolyte with fewer impurities, high quality, and high ionic conductivity.

[0026] On the other hand, in the conventional method of heating under vacuum using a jacket-type heater, heat is transferred only by contacting the electrolyte precursor with the inner wall surface of the heater, which clearly results in poor contact efficiency and low thermal conduction efficiency. Therefore, it can be said that the production method of this embodiment makes it easier to obtain a sulfide solid electrolyte more efficiently than the conventional method.

[0027] As described above, the main purpose of drying in the manufacturing method of this embodiment is to remove the remaining complexing agent and optional solvent that do not contribute to the formation of the electrolyte precursor from the electrolyte precursor-containing material. Therefore, the removal of the complexing agent from the electrolyte precursor is not achieved by drying, but rather by heating in a heated air stream. On the other hand, the remaining complexing agent and optional solvent can be removed by heating in a heated air stream. It goes without saying that the complexing agent can also be removed from the electrolyte precursor by heating the electrolyte precursor-containing material in a heated air stream.

[0028] A third aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the first or second aspect, wherein the temperature of the heated airflow is 100°C or higher and 180°C or lower.

[0029] As described above, the complexing agent contained in the electrolyte precursor is easily separated and removed from the electrolyte precursor due to the temperature (heat) of the heated airflow and the action of the airflow. Here, by setting the temperature of the heated airflow within the above temperature range, heating is promoted, particularly due to the action of the temperature (heat) of the heated airflow, making it easy to separate and remove the complexing agent from the electrolyte precursor. Furthermore, since the separated gaseous complexing agent is easily discharged to the outside of the system together with the heated airflow, regeneration of complexes and generation of impurities by the separated complexing agent are suppressed, making it easy to obtain a sulfide solid electrolyte with few impurities, high quality, and high ionic conductivity.

[0030] A method for producing a sulfide solid electrolyte according to a fourth aspect of the present embodiment is any one of the first to third aspects, further comprising the step of: supplying the heated airflow at a rate of 0.1 m ３ / min or more 500m ３ / minutes or less.

[0031] By using a heated airflow at a supply rate within the above range, the action of the heated airflow enables more efficient dispersion of the heated object and separation and removal of the complexing agent. This suppresses the re-formation of complexes and the generation of impurities, making it easier to more efficiently obtain a sulfide solid electrolyte with fewer impurities, high quality, and high ionic conductivity. Furthermore, by limiting the supply rate of the heated airflow to a certain range, mass production becomes easier.

[0032] A fifth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to fourth aspects, wherein the flow velocity of the heated airflow is 5 m / s or more and 35 m / s or less.

[0033] As described above, the complexing agent contained in the electrolyte precursor is easily separated and removed from the electrolyte precursor due to the temperature (heat) of the heated airflow and the action of the airflow. Here, by setting the flow rate of the heated airflow within the above temperature range, it is possible to more efficiently promote the separation and removal of the complexing agent, particularly due to the action of the heated airflow. Furthermore, since the separated gaseous complexing agent is easily discharged to the outside of the system together with the heated airflow, regeneration of the complex and generation of impurities by the separated complexing agent are suppressed, making it easier to obtain a sulfide solid electrolyte with few impurities, high quality, and high ionic conductivity.

[0034] A sixth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to fifth aspects, wherein the heating in the heated air flow is carried out for 0.1 seconds to 1 minute.

[0035] In the manufacturing method of this embodiment, the complexing agent contained in the electrolyte precursor can be efficiently removed by heating with a heated airflow, and therefore, heating with a heated airflow can be performed for a short time of 0.1 seconds to 1 minute.

[0036] A seventh aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the second to sixth aspects, wherein the drying is carried out under normal pressure or reduced pressure at a temperature of 5°C or higher and 110°C or lower.

[0037] As conditions for drying the electrolyte precursor-containing material, by changing the pressure condition from normal pressure to reduced pressure and the temperature condition from 5°C to 110°C, the electrolyte precursor-containing material can be dried more efficiently and the electrolyte precursor can be obtained.

[0038] The method for producing a sulfide solid electrolyte according to an eighth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the second to seventh aspects, further comprising further heating after the heating in the heated air flow.

[0039] By heating in the heated air flow, the complexing agent is removed from the electrolyte precursor, and an amorphous sulfide solid electrolyte is obtained. By further heating this electrolyte precursor, in addition to heating in the heated air flow, a crystalline sulfide solid electrolyte is obtained. The production method of this embodiment makes it possible to produce an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte as desired.

[0040] A method for producing a sulfide solid electrolyte according to a ninth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to eighth aspects, except that the complexing agent is a compound having an amino group. Also, a method for producing a sulfide solid electrolyte according to a tenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to ninth aspects, except that the complexing agent is a compound having at least two tertiary amino groups in the molecule.

[0041] In the manufacturing method of this embodiment, the complexing agent is a solvent that has the property of forming a complex with the solid electrolyte raw material contained in the raw material content, as described above. As described below, compounds having heteroatoms are likely to form complexes with the solid electrolyte raw material, making them preferred complexing agents. In particular, compounds having nitrogen atoms as heteroatoms and nitrogen atoms as amino groups not only more easily form complexes, but also more easily incorporate halogen atoms, which are difficult to incorporate in complex formation, making it easier to maintain a uniform dispersion state of the solid electrolyte raw material. Therefore, higher ionic conductivity is more likely to be obtained.

[0042] Furthermore, when a compound having an amino group is used as a complexing agent, in addition to the above properties, it also has the property of being easily separated and removed from the electrolyte precursor, which suppresses the re-formation of the complex and the generation of impurities, making it easier to obtain a sulfide solid electrolyte with high quality, low impurities, and high ionic conductivity in an extremely efficient manner.

[0043] The method for producing a sulfide solid electrolyte according to an eleventh aspect of the present embodiment is the same as any of the first to tenth aspects, except that no media particles are used in the heating in the heated airflow.

[0044] As described above, in the production method of this embodiment, it is essential to heat the electrolyte precursor in a heated air stream, and it is preferable not to use media particles. This can prevent excessive contact with the heated air stream due to adhesion of the electrolyte precursor to the media particles, and can prevent deterioration of the amorphous sulfide solid electrolyte due to deterioration of the electrolyte precursor, making it easier to obtain high ionic conductivity. In the production method of this embodiment, heating in a heated air stream simply means heating with a heated air stream, which allows the complexing agent to be efficiently removed from the electrolyte precursor, making it possible to efficiently produce a sulfide solid electrolyte with high ionic conductivity.

[0045] A twelfth aspect of the present embodiment relates to the method for producing a sulfide solid electrolyte according to any one of the first to eleventh aspects, wherein the sulfide solid electrolyte has a thiolicon region II crystal structure.

[0046] In the manufacturing method of this embodiment, it is possible to manufacture a desired sulfide solid electrolyte by changing the type and compounding ratio of the solid electrolyte raw materials contained in the raw material inclusions. A sulfide solid electrolyte having a thiolicon region II crystal structure is known as a sulfide solid electrolyte with extremely high ionic conductivity, and is preferable as the sulfide solid electrolyte to be obtained by the manufacturing method of this embodiment.

[0047] (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 solid electrolyte in this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and has ionic conductivity due to the lithium atoms.

[0048] 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.

[0049] [Method for Producing Sulfide Solid Electrolyte] A method for producing a sulfide solid electrolyte according to the present embodiment includes: mixing a raw material containing material including lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with a complexing agent to obtain an electrolyte precursor containing material; and then heating the material in a heated air stream.

[0050] [Obtaining an electrolyte precursor-containing material] The manufacturing method of this embodiment includes mixing a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with a complexing agent to obtain an electrolyte precursor-containing material. The manufacturing method of this embodiment will first be described, starting with the raw material containing material.

[0051] (Raw material contents) The raw material contents used in this embodiment contain lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and more specifically, are contents containing compounds containing one or more selected from the group consisting of these atoms (hereinafter also referred to as "solid electrolyte raw materials"). The raw material contents used in this embodiment preferably contain two or more solid electrolyte raw materials.

[0052] Examples of the solid electrolyte raw material contained in the raw material content include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides; various phosphorus fluorides (PF ３ , P.F. ５ ), various phosphorus chlorides (PCl ３ , PCl ５ , P ２ Cl ４ ), various phosphorus bromides (PBr ３ , PBr ５ ), various phosphorus iodides (PI ３ , P ２ I ４ ) and the like; phosphorus halides such as thiophosphoryl fluoride (PSF ３ ), thiophosphoryl chloride (PSCl ３ ), thiophosphoryl bromide (PSBr ３ ), thiophosphoryl iodide (PSI ３ ), thiophosphoryl fluoride dichloride (PSCl ２ F), thiophosphoryl fluoride dibromide (PSBr ２ a 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.

[0053] 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, SnS２ 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.

[0054] Among the above, lithium sulfide, diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides, fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ Preferred examples of the solid electrolyte raw materials include a halogen atom such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide, and a lithium halide such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide. When oxygen atoms are introduced into the solid electrolyte, preferred examples of the solid electrolyte raw materials include a combination of lithium sulfide, phosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, phosphorus pentasulfide, and a halogen atom. Preferred examples of the lithium halide include lithium bromide and lithium iodide, and preferred examples of the halogen atom include bromine and iodine.

[0055] In this embodiment, PS ４ Li containing structure ３ P.S. ４ can also be used as part of the raw material. ３ P.S. ４ This is prepared by manufacturing or the like and used as a raw material. ３ P.S. ４The content is preferably 60 to 100 mol %, more preferably 65 to 90 mol %, and even more preferably 70 to 80 mol %.

[0056] Also, Li ３ P.S. ４ When using a halogen atom, Li ３ P.S. ４ The content of the halogen element is preferably 1 to 50 mol %, more preferably 10 to 40 mol %, even more preferably 20 to 30 mol %, and even more preferably 22 to 28 mol %.

[0057] The lithium sulfide used in this embodiment 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.

[0058] When lithium sulfide, diphosphorus pentasulfide, and lithium halide are used as solid electrolyte raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 65 to 85 mol%, more preferably 70 to 82 mol%, and even more preferably 74 to 80 mol%, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. When lithium sulfide, diphosphorus pentasulfide, lithium halide, and other solid electrolyte raw materials used as needed are used, the content of lithium sulfide and diphosphorus pentasulfide to the total is preferably 50 to 99 mol%, more preferably 55 to 85 mol%, and even more preferably 60 to 80 mol%.

[0059] When lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ionic conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 80 mol%, even more preferably 35 to 80 mol%, and particularly preferably 45 to 70 mol%. When lithium bromide and lithium chloride are used in combination as the lithium halide, from the viewpoint of improving ionic conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium chloride is preferably 1 to 99 mol%, more preferably 15 to 75 mol%, even more preferably 25 to 60 mol%, and particularly preferably 35 to 45 mol%.

[0060] When a halogen element is used as a solid electrolyte raw material, and lithium sulfide and diphosphorus pentasulfide are used, the ratio of the number of moles of lithium sulfide excluding the same number of moles of lithium sulfide as the halogen element to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the halogen element is preferably within the range of 60 to 90%, more preferably within the range of 65 to 85%, even more preferably within the range of 68 to 82%, even more preferably within the range of 72 to 78%, and particularly preferably within the range of 73 to 77%. This is because higher ionic conductivity can be obtained with these ratios. Furthermore, from the same viewpoint, when lithium sulfide, diphosphorus pentasulfide, and a halogen element are used, the content of the halogen element relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the halogen element is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0061] When lithium sulfide, diphosphorus pentasulfide, a halogen element, and a lithium halide are used, the content of the halogen element (α mol %) and the content of the lithium halide (β mol %) relative to the total amount thereof preferably satisfy the following formula (2), more preferably satisfy the following formula (3), even more preferably satisfy the following formula (4), and even more preferably satisfy the following formula (5): 2≦2α+β≦100 (2) 4≦2α+β≦80 (3) 6≦2α+β≦50 (4) 6≦2α+β≦30 (5)

[0062] When two types of halogens are used as simple substances, the molar number of one halogen atom in the substance is A1, and the molar number of the other halogen atom in the substance is A2, and the ratio A1:A2 is preferably 1 to 99:99 to 1, more preferably 10:90 to 90:10, even more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

[0063] When two kinds of halogen elements are used, and the two kinds of halogen elements are bromine and iodine, where A1 is the number of moles of bromine and A2 is the number of moles of iodine, A1:A2 is preferably 1:99 to 99:1, more preferably 20:80 to 80:20, even more preferably 35:65 to 80:20, and even more preferably 45:55 to 70:30. When the two kinds of halogen elements are bromine and chlorine, B1 is the number of moles of bromine and B2 is the number of moles of chlorine, and B1:B2 is preferably 1:99 to 99:1, more preferably 15:85 to 75:25, even more preferably 25:75 to 60:40, and even more preferably 35:45 to 65:55.

[0064] (Complexing Agent) As described above, the complexing agent is a compound that easily forms a complex with the solid electrolyte raw material contained in the raw material content. For example, lithium sulfide and diphosphorus pentasulfide, which are preferably used as solid electrolyte raw materials, and Lithium ion complexes obtained when these are used, are used. ３ P.S. ４ and a solid electrolyte raw material containing a halogen atom (hereinafter, these are also collectively referred to as "solid electrolyte raw material, etc.").

[0065] The complexing agent can be any agent having the above properties, and is particularly preferably a compound containing an atom having a high affinity with lithium atoms, such as a heteroatom such as a nitrogen atom, an oxygen atom, or a chlorine atom, and more preferably a compound having a group containing such a heteroatom, because such a heteroatom or group containing such a heteroatom can coordinate (bond) with lithium.

[0066] It is believed that the heteroatoms present in the molecules of the complexing agent have a high affinity for lithium atoms and have the property of easily bonding with the solid electrolyte raw material, etc. to form a complex (hereinafter also simply referred to as a "complex"). Therefore, by mixing the solid electrolyte raw material with the complexing agent, a complex is formed, which makes it easier to maintain the uniform dispersion state of the solid electrolyte raw material, particularly the dispersion state of the halogen atoms, and as a result, it is believed that a sulfide solid electrolyte with high ionic conductivity can be obtained.

[0067] The ability of the complexing agent to form a complex with the solid electrolyte raw material, etc., can be directly confirmed by, for example, an infrared absorption spectrum measured by FT-IR analysis (diffuse reflectance method). When a powder obtained by stirring tetramethylethylenediamine (hereinafter also simply referred to as "TMEDA"), which is one of the preferred complexing agents, and lithium iodide (LiI) and the complexing agent itself are analyzed by FT-IR analysis (diffuse reflectance method), the spectrum of TMEDA itself is different from that of the complexing agent itself, particularly in the range of 1000 to 1250 cm －１ In addition, considering that it is known that a LiI-TMEDA complex is formed by stirring and mixing TMEDA and lithium iodide (for example, Aust. J. Chem., 1988, 41, 1925-34, particularly Fig. 2), it is reasonable to consider that a LiI-TMEDA complex is formed.

[0068] Also, for example, a complexing agent (TMEDA) and Li ３ P.S. ４ The powder obtained by stirring the above mixture was analyzed by FT-IR analysis (diffuse reflectance method) in the same manner as above. The spectrum of TMEDA itself was found to have a peak at 1000 to 1250 cm－１ It can be seen that the spectrum of the LiI-TMEDA complex is similar to that of the LiI-TMEDA complex, while the peaks derived from the C-N stretching vibration in the spectrum are different. ３ P.S. ４ In the production method of this embodiment, the raw material ingredients and the complexing agent are mixed to obtain a complex, which is used as an electrolyte precursor, and the complexing agent is removed from the powder of the electrolyte precursor in a heated air stream, thereby producing a sulfide solid electrolyte.

[0069] The complexing agent preferably has at least two heteroatoms capable of coordinating (bonding) in the molecule, and more preferably has a group containing at least two heteroatoms in the molecule. By having a group containing at least two heteroatoms in the molecule, the solid electrolyte raw material and the like can be bonded via at least two heteroatoms in the molecule. Furthermore, among heteroatoms, a nitrogen atom is preferred, and the group containing a nitrogen atom is preferably an amino group. In other words, an amine compound is preferred as the complexing agent.

[0070] The amine compound is not particularly limited as long as it has an amino group in the molecule and can promote the formation of a complex, but a compound having at least two amino groups in the molecule is preferred. By having such a structure, the solid electrolyte raw materials and the like can be bonded via at least two nitrogen atoms in the molecule to form a complex.

[0071] Examples of such amine compounds include aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, and these can be used alone or in combination.

[0072] More specifically, typical and preferred examples of the aliphatic amine include aliphatic primary diamines such as ethylenediamine, diaminopropane, and diaminobutane; aliphatic secondary diamines such as N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyldiaminopropane, and N,N'-diethyldiaminopropane; and aliphatic tertiary diamines such as N,N,N',N'-tetramethyldiaminomethane, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyldiaminopropane, N,N,N',N'-tetraethyldiaminopropane, N,N,N',N'-tetramethyldiaminobutane, N,N,N',N'-tetramethyldiaminopentane, and N,N,N',N'-tetramethyldiaminohexane. In the examples given in this specification, for example, in the case of diaminobutane, unless otherwise specified, all isomers of butane, such as linear and branched isomers, are included in addition to isomers relating to the position of the amino group, such as 1,2-diaminobutane, 1,3-diaminobutane, and 1,4-diaminobutane.

[0073] The number of carbon atoms in the aliphatic amine is preferably 2 or more, more preferably 4 or more, and even more preferably 6 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. The number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic amine is preferably 2 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0074] Representative preferred examples of the alicyclic amine include alicyclic primary diamines such as cyclopropanediamine and cyclohexanediamine; alicyclic secondary diamines such as bisaminomethylcyclohexane; and alicyclic tertiary diamines such as N,N,N',N'-tetramethyl-cyclohexanediamine and bis(ethylmethylamino)cyclohexane. Representative preferred examples of the heterocyclic amine include heterocyclic primary diamines such as isophoronediamine; heterocyclic secondary diamines such as piperazine and dipiperidylpropane; and heterocyclic tertiary diamines such as N,N-dimethylpiperazine and bismethylpiperidylpropane. The number of carbon atoms in the alicyclic amine and heterocyclic amine is preferably 3 or more, more preferably 4 or more, and preferably 16 or less, more preferably 14 or less.

[0075] Representative preferred examples of aromatic amines include aromatic primary diamines such as phenyldiamine, tolylenediamine, and naphthalenediamine; aromatic secondary diamines such as N-methylphenylenediamine, N,N'-dimethylphenylenediamine, N,N'-bismethylphenylphenylenediamine, N,N'-dimethylnaphthalenediamine, and N-naphthylethylenediamine; and aromatic tertiary diamines such as N,N-dimethylphenylenediamine, N,N,N',N'-tetramethylphenylenediamine, N,N,N',N'-tetramethyldiaminodiphenylmethane, and N,N,N',N'-tetramethylnaphthalenediamine. The number of carbon atoms in the aromatic amine is preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more, with the upper limit being preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.

[0076] The amine compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom. Although diamine is given as a specific example, it goes without saying that the amine compound that can be used in this embodiment is not limited to diamine, and examples thereof include aliphatic monoamines corresponding to various diamines such as trimethylamine, triethylamine, ethyldimethylamine, and the above-mentioned aliphatic diamines, piperidine compounds such as piperidine, methylpiperidine, and tetramethylpiperidine, pyridine compounds such as pyridine and picoline, morpholine compounds such as morpholine, methylmorpholine, and thiomorpholine, imidazole compounds such as imidazole and methylimidazole, and the above-mentioned alicyclic diamines. In addition to monoamines such as alicyclic monoamines such as the corresponding monoamines, heterocyclic monoamines corresponding to the above heterocyclic diamines, and aromatic monoamines corresponding to the above aromatic diamines, polyamines having three or more amino groups, such as diethylenetriamine, N,N',N''-trimethyldiethylenetriamine, N,N,N',N'',N''-pentamethyldiethylenetriamine, triethylenetetramine, N,N'-bis[(dimethylamino)ethyl]-N,N'-dimethylethylenediamine, hexamethylenetetramine, and tetraethylenepentamine, can also be used.

[0077] Among the above, from the viewpoint of obtaining higher ionic conductivity, a tertiary amine having a tertiary amino group as the amino group is preferred, a tertiary diamine having two tertiary amino groups is more preferred, a tertiary diamine having two tertiary amino groups at both ends is even more preferred, and an aliphatic tertiary diamine having tertiary amino groups at both ends is even more preferred. Among the above amine compounds, the aliphatic tertiary diamine having tertiary amino groups at both ends is preferably tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, or tetraethyldiaminopropane, and in consideration of ease of availability, etc., tetramethylethylenediamine or tetramethyldiaminopropane is preferred.

[0078] Furthermore, compounds having a nitrogen atom as a heteroatom and a group other than an amino group, such as a nitro group or an amide group, can also provide the same effect.

[0079] In the production method of this embodiment, the complexing agent is preferably not only the compound containing a nitrogen atom as a heteroatom but also a compound containing an oxygen atom. As the compound containing an oxygen atom, a compound having one or more functional groups selected from an ether group and an ester group as the group containing an oxygen atom is preferred, and among these, a compound having an ether group is particularly preferred. That is, as the complexing agent containing an oxygen atom, an ether compound is particularly preferred.

[0080] Examples of the ether compound include aliphatic ethers, alicyclic ethers, heterocyclic ethers, and aromatic ethers, and these compounds may be used alone or in combination.

[0081] More specifically, examples of aliphatic ethers include monoethers such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, and tert-butyl methyl ether; diethers such as dimethoxymethane, dimethoxyethane, diethoxymethane, and diethoxyethane; polyethers having three or more ether groups such as diethylene glycol dimethyl ether (diglyme) and triethylene oxide glycol dimethyl ether (triglyme); and ethers containing hydroxyl groups such as diethylene glycol and triethylene glycol. The number of carbon atoms in the aliphatic ether is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more, with the upper limit being preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. Furthermore, the number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic ether is preferably 1 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0082] Examples of alicyclic ethers include ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, dioxane, dioxolane, etc., and examples of heterocyclic ethers include furan, benzofuran, benzopyran, dioxene, dioxine, morpholine, methoxyindole, hydroxymethyldimethoxypyridine, etc. The number of carbon atoms in the alicyclic ether and heterocyclic ether is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0083] Examples of aromatic ethers include methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, diphenyl ether, benzyl phenyl ether, naphthyl ether, etc. The number of carbon atoms in the aromatic ether is preferably 7 or more, more preferably 8 or more, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.

[0084] The ether compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom.

[0085] Among the above ether compounds, aliphatic ethers are preferred, and dimethoxyethane and tetrahydrofuran are more preferred, from the viewpoint of obtaining higher ionic conductivity.

[0086] Examples of the ester compound include ester compounds such as aliphatic esters, alicyclic esters, heterocyclic esters, and aromatic esters, and these can be used alone or in combination.

[0087] More specifically, examples of aliphatic esters include formate esters such as methyl formate, ethyl formate, and triethyl formate; acetate esters such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and isobutyl acetate; propionate esters such as methyl propionate, ethyl propionate, propyl propionate, and butyl propionate; oxalate esters such as dimethyl oxalate and diethyl oxalate; malonate esters such as dimethyl malonate and diethyl malonate; and succinate esters such as dimethyl succinate and diethyl succinate.

[0088] The number of carbon atoms in the aliphatic ester is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more, with the upper limit being preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. The number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic ester is preferably 1 or more, more preferably 2 or more, and the upper limit being preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0089] Examples of alicyclic esters include methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, dimethyl cyclohexanedicarboxylate, dibutyl cyclohexanedicarboxylate, and dibutyl cyclohexenedicarboxylate. Examples of heterocyclic esters include methyl pyridinecarboxylate, ethyl pyridinecarboxylate, propyl pyridinecarboxylate, methyl pyrimidinecarboxylate, ethyl pyrimidinecarboxylate, and lactones such as acetolactone, propiolactone, butyrolactone, and valerolactone.

[0090] The number of carbon atoms in the alicyclic ester and heterocyclic ester is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0091] Examples of aromatic esters include benzoic acid esters such as methyl benzoate, ethyl benzoate, propyl benzoate, and butyl benzoate; phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, and dicyclohexyl phthalate; and trimellitic acid esters such as trimethyl trimellitate, triethyl trimellitate, tripropyl trimellitate, tributyl trimellitate, and trioctyl trimellitate.

[0092] The aromatic ester preferably has 8 or more carbon atoms, more preferably 9 or more carbon atoms, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.

[0093] The ester compound used in this embodiment may be substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, or a cyano group, or with a halogen atom.

[0094] Among the above ester compounds, from the viewpoint of obtaining higher ionic conductivity, aliphatic esters are preferred, acetate esters are more preferred, and ethyl acetate is particularly preferred.

[0095] From the viewpoint of efficiently forming a complex, the molar ratio of the amount of complexing agent added to the total molar amount of lithium atoms contained in the raw material content is preferably 0.1 or more and 2.0 or less, more preferably 0.5 or more and 1.5 or less, even more preferably 0.8 or more and 1.2 or less, and most preferably 1.0.

[0096] (Mixing) In the manufacturing method of this embodiment, the solid electrolyte raw material is mixed with a complexing agent. In this embodiment, the solid electrolyte raw material and the complexing agent may be mixed in either a solid or liquid form. However, since the solid electrolyte raw material contains a solid and the complexing agent is liquid, they are usually mixed in a form in which the solid solid electrolyte raw material is present in a liquid complexing agent. Furthermore, when mixing the raw material and the complexing agent, a solvent may be further mixed as needed. Hereinafter, in the description of mixing the raw material and the complexing agent, unless otherwise specified, the complexing agent also includes the solvent used as needed.

[0097] The method for mixing the solid electrolyte raw material and the complexing agent is not particularly limited. The solid electrolyte raw material and the complexing agent may be mixed in a device capable of mixing the solid electrolyte raw material and the complexing agent. For example, supplying the complexing agent into a tank, operating the stirring blades, and then gradually adding the solid electrolyte raw material is preferable because it results in a good mixed state of the solid electrolyte raw material and improves the dispersibility of the raw material. However, when a halogen is used as the solid electrolyte raw material, the solid electrolyte raw material may not be solid. Specifically, fluorine and chlorine are gases, and bromine is liquid at room temperature and normal pressure. In such cases, for example, if the solid electrolyte raw material is liquid, it may be supplied into the tank together with the complexing agent separately from the other solid solid electrolyte raw materials. Alternatively, if the solid electrolyte raw material is gas, it may be supplied by blowing into the complexing agent mixed with the solid solid electrolyte raw material.

[0098] The manufacturing method of this embodiment is characterized by including mixing a solid electrolyte raw material with a complexing agent. That is, since mixing the solid electrolyte raw material with the complexing agent is sufficient and grinding is not required, the solid electrolyte can be manufactured without using equipment commonly referred to as a grinder, such as a media-type grinder such as a ball mill or a bead mill, which is typically used for grinding solid electrolyte raw materials. In this manufacturing method of this embodiment, simply mixing the solid electrolyte raw material with the complexing agent allows the solid electrolyte raw material and the complexing agent contained in the raw material contents to mix and form a complex, i.e., an electrolyte precursor. Note that the mixture of the raw material and the complexing agent may be ground in a grinder to shorten the mixing time to obtain the complex or to achieve finer powder, but as mentioned above, it is preferable not to use a grinder. On the other hand, the electrolyte precursor may be ground in a grinder.

[0099] An example of an apparatus for mixing the solid electrolyte raw material and the complexing agent is a mechanical agitation mixer equipped with an agitator blade in a tank. Examples of mechanical agitation mixers include high-speed agitation mixers and double-arm mixers. High-speed agitation mixers are preferred from the viewpoint of improving the uniformity of the solid electrolyte raw material in the mixture of the solid electrolyte raw material and the complexing agent and achieving higher ionic conductivity. Examples of high-speed agitation mixers include vertical-axis rotary mixers and horizontal-axis rotary mixers. Either type of mixer may be used.

[0100] Examples of the shape of the impeller used in a mechanical stirring mixer include anchor type, blade type, arm type, ribbon type, multi-stage blade type, double arm type, shovel type, double-shaft blade type, flat blade type, and C-type blade type. From the viewpoint of improving the uniformity of the solid electrolyte raw material and obtaining higher ionic conductivity, the shovel type, flat blade type, and C-type blade type are preferred. Furthermore, in a mechanical stirring mixer, it is preferable to install a circulation line that discharges the material to be stirred outside the mixer and then returns it to the mixer. This allows raw materials with a high specific gravity, such as lithium halide, to be stirred without settling or stagnation, enabling more uniform mixing.

[0101] The location of the circulation line is not particularly limited, but it is preferably installed at a location where it discharges from the bottom of the mixer and returns to the top of the mixer. This makes it easier to uniformly mix the solid electrolyte raw material, which tends to settle, by using convection caused by circulation. Furthermore, it is preferable that the return port is located below the liquid surface of the material to be mixed. This can prevent the material to be mixed from splashing and adhering to the wall surfaces inside the mixer.

[0102] The temperature conditions when mixing the solid electrolyte raw material and the complexing agent are not particularly limited and are, for example, −30 to 100° C., preferably −10 to 50° C., and more preferably about room temperature (23° C.) (for example, about room temperature ±5° C.). The mixing time is about 0.1 to 150 hours, and from the viewpoint of more uniform mixing and obtaining higher ionic conductivity, it is preferably 1 to 120 hours, more preferably 4 to 100 hours, and even more preferably 8 to 80 hours.

[0103] By mixing the solid electrolyte raw materials with the complexing agent, a complex is formed between the solid electrolyte raw materials and the complexing agent. More specifically, the complex is considered to be formed by the interaction of the lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms contained in the solid electrolyte raw materials with the complexing agent, with and / or without the complexing agent being interposed between these atoms. That is, in the production method of this embodiment, the complex obtained by mixing the solid electrolyte raw materials with the complexing agent can be said to be composed of the complexing agent, lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. The complex obtained in this embodiment is not completely soluble in the liquid complexing agent but is usually solid, resulting in a suspension in which the complex is suspended in the complexing agent and an optional solvent. Therefore, the production method of the solid electrolyte of this embodiment corresponds to a heterogeneous system in a so-called liquid-phase method.

[0104] (Solvent) In this embodiment, a solvent may be further added when mixing the solid electrolyte raw materials and the complexing agent. When a solid complex is formed in a liquid complexing agent, if the complex is easily soluble in the complexing agent, separation of the components may occur. Therefore, by using a solvent in which the complex is insoluble, elution of components in the electrolyte precursor can be suppressed. Furthermore, mixing the solid electrolyte raw materials and the complexing agent using a solvent promotes complex formation, allowing each main component to be more evenly present, and an electrolyte precursor can be obtained in which the dispersion state of the solid electrolyte raw materials, particularly the dispersion state of the halogen atoms, is uniformly maintained. As a result, the effect of obtaining high ionic conductivity is more easily achieved.

[0105] The method for producing a solid electrolyte according to this embodiment is a so-called heterogeneous method, in which the complex is preferably precipitated without being completely dissolved in the liquid complexing agent. The solubility of the complex can be adjusted by adding a solvent. Halogen atoms, in particular, tend to dissolve from the complex, so adding a solvent can suppress the dissolution of halogen atoms and obtain the desired complex. As a result, a sulfide solid electrolyte having high ionic conductivity can be easily obtained via an electrolyte precursor in which components such as solid electrolyte raw materials, particularly solid electrolyte raw materials containing halogen atoms, are uniformly dispersed.

[0106] A preferred example of a solvent having such properties is a solvent having a solubility parameter of 10 or less. In this specification, the solubility parameter is a value δ ((cal / cm)) calculated by the following formula (1), which is described in various documents, such as "Chemical Handbook" (published in 2004, revised 5th edition, Maruzen Co., Ltd.). ３ ) １／２ ) and is also called the Hildebrand parameter or SP value.

[0107] (In equation (1), ΔH is the molar heat of heat, R is the gas constant, T is the temperature, and V is the molar volume.)

[0108] By using a solvent with a solubility parameter of 10 or less, the solid electrolyte raw materials, particularly halogen atoms, raw materials containing halogen atoms such as lithium halide, and further components containing halogen atoms that constitute a complex (e.g., an aggregate formed by bonding lithium halide and a complexing agent), can be made to be relatively difficult to dissolve compared to the complexing agent. This makes it easier to fix halogen atoms in the complex, and halogen atoms are present in a well-dispersed state in the resulting electrolyte precursor and further in the solid electrolyte, making it easier to obtain a solid electrolyte with high ionic conductivity. In other words, the solvent used in this embodiment preferably has the property of not dissolving the complex. From the same perspective, the solubility parameter of the solvent is preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 8.5 or less.

[0109] More specifically, the solvent used in the present embodiment can be a wide variety of solvents that have conventionally been used in the production of solid electrolytes. Examples of the solvent include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; solvents containing carbon atoms such as alcohol-based solvents, ester-based solvents, aldehyde-based solvents, ketone-based solvents, ether-based solvents having 4 or more carbon atoms on one side, and solvents containing carbon atoms and heteroatoms; and among these, a solvent may be appropriately selected from those preferably having a solubility parameter within the above-mentioned range.

[0110] More specifically, aliphatic hydrocarbon solvents such as hexane (7.3), pentane (7.0), 2-ethylhexane, heptane (7.4), octane (7.5), decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane (8.2) and methylcyclohexane; benzene, toluene (8.8), xylene (8.8), mesitylene, ethylbenzene (8.8), tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene (9.5), chlorotoluene (8.8), and bromobenzene. Examples of suitable solvents include aromatic hydrocarbon solvents; alcohol solvents such as ethanol (12.7) and butanol (11.4); aldehyde solvents such as formaldehyde, acetaldehyde (10.3), and dimethylformamide (12.1); ketone solvents such as acetone (9.9) and methyl ethyl ketone; ether solvents such as dibutyl ether, cyclopentyl methyl ether (8.4), tert-butyl methyl ether, and anisole; and solvents containing carbon atoms and heteroatoms such as acetonitrile (11.9), dimethyl sulfoxide, and carbon disulfide. The values ​​in parentheses in the above examples are SP values. Furthermore, the above examples are merely examples, and for example, solvents having isomers may include all isomers. Furthermore, solvents substituted with halogen atoms, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents may also include those substituted with aliphatic groups such as alkyl groups.

[0111] Among these solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether-based solvents are preferred, and from the viewpoint of obtaining more stable and high ionic conductivity, heptane, cyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole are more preferred, diethyl ether, diisopropyl ether, and dibutyl ether are even more preferred, and diisopropyl ether and dibutyl ether are still more preferred, and cyclohexane is particularly preferred. The solvent used in this embodiment is preferably an organic solvent exemplified above, and is an organic solvent different from the complexing agent. In this embodiment, these solvents may be used alone or in combination.

[0112] [Drying] The production method of this embodiment may include drying the electrolyte precursor-containing material after obtaining the electrolyte precursor-containing material. In removing the complexing agent, the electrolyte precursor obtained by drying the electrolyte precursor-containing material is heated in a heated air stream, whereby the electrolyte precursor can be heated more directly, and therefore the complexing agent can be separated and removed more efficiently.

[0113] Drying methods include filtration using a glass filter or the like, solid-liquid separation by decantation, and solid-liquid separation using a centrifuge, etc. Specifically, solid-liquid separation can be easily performed by decantation, in which the suspension is transferred to a container, and after the solid has settled, the complexing agent and the solvent used as needed are removed as a supernatant, or by filtration using a glass filter having a pore size of about 10 to 200 μm, preferably 20 to 150 μm.

[0114] It can also be dried by heating using a dryer or the like. The drying of the electrolyte precursor-containing material may be carried out under any pressure condition, such as under pressure, normal pressure, or reduced pressure, and is preferably carried out under normal pressure or reduced pressure. In particular, considering drying at a lower temperature, it is preferable to dry under reduced pressure, or even under vacuum, using a vacuum pump or the like. The temperature condition for drying may be a temperature equal to or higher than the boiling point of the remaining complexing agent or the solvent used as needed. Since the temperature condition can vary depending on the type of complexing agent and solvent used, it is not possible to generalize the specific temperature condition, but it is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, with the upper limit being preferably 110°C or lower, more preferably 85°C or lower, and even more preferably 70°C or lower.

[0115] As for the pressure conditions, as described above, normal pressure or reduced pressure is preferable. When reduced pressure is used, specifically, the pressure is preferably 85 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less. The lower limit may be a vacuum (0 kPa). In consideration of ease of pressure adjustment, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more.

[0116] In the production method of this embodiment, when drying is performed, drying may be performed while heating after the solid-liquid separation. Furthermore, in the production method of this embodiment, drying may or may not be performed. That is, in the production method of this embodiment, the heating target to be heated in the heated air flow may be the electrolyte precursor-containing material or the electrolyte precursor obtained by drying. Furthermore, as described above, the electrolyte precursor is preferred as the heating target because it can be heated more directly.

[0117] [Heating in a heated air stream] The production method of this embodiment includes heating in a heated air stream following obtaining the electrolyte precursor-containing material. The electrolyte precursor-containing material obtained in obtaining the electrolyte precursor-containing material, and further the electrolyte precursor if the drying has been performed (hereinafter, the electrolyte precursor-containing material and the electrolyte precursor may be collectively referred to as "object to be heated"), are heated in a heated air stream to remove the complexing agent from the electrolyte precursor, i.e., by removing the complexing agent from the complex formed by the solid electrolyte raw material and the like and the complexing agent, a sulfide solid electrolyte is obtained.

[0118] More specifically, heating in a heated air stream can be performed by supplying the object to be heated into an air stream through which heated gas flows, and for example, a commercially available device known as a flash dryer can be used. A flash dryer is a device that can heat the object to be heated by the heated air stream by supplying the object to be heated into a pipe through which the heated air stream is supplied, and a direct hot air type flash dryer in which the heated air stream and the object to be heated come into direct contact with each other is preferred.

[0119] 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.

[0120] As the flash dryer, a flash dryer having a structure capable of heating an object to be heated while swirling a heated airflow, such as 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), is preferably used. The adoption of such a structure can suppress adhesion of the electrolyte precursor to the inner wall, and can also utilize the mass difference between the electrolyte precursor from which the complexing agent has been removed and the electrolyte precursor in which the complexing agent remains to perform classification by centrifugal force, thereby enabling more efficient removal of the complexing agent. Furthermore, the flash dryer can be made more compact, thereby saving space.

[0121] Another preferred flash dryer is a type of flash dryer (also referred to as a "vertical-tube flash dryer") that uses a vertical long tube long enough to maintain the required length for heating, and introduces heated airflow from below the vertical long tube to heat the material while co-flowing with it. Using a vertical long-tube flash dryer allows the flow direction of the material and 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, since this type of dryer can accommodate 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.

[0122] 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.

[0123] The flash dryers described above are primarily suitable for use in a distribution system, but it is also possible to carry out flash drying in a batch system using, for example, a container-type flash dryer. For example, a heated airflow can be introduced from the bottom of the container to heat the object to be heated. In this case, if a constriction on the nozzle is provided at the inlet of the heated airflow, the flow rate can be increased to introduce the heated airflow, allowing the object to be heated while being mixed and stirred, thereby improving drying efficiency. When using a batch system, there are no limitations on the type of flash dryer, and any flash dryer can be used, such as the cylindrical container-type flash dryer described above.

[0124] In the case of the batch type, it is possible to arbitrarily set the heating object per batch, the amount and temperature of the heated airflow, and the heating time. Therefore, it is possible to arbitrarily set the operating conditions depending on the state of the heating object, the degree of removal of the complexing agent from the heating object (electrolyte precursor), etc. In addition, by monitoring the change in the concentration of the complexing agent contained in the heated airflow discharged from the flash dryer, it is possible to easily adjust the operation, such as determining whether drying is complete, which provides excellent operational controllability.

[0125] It is preferable not to use media particles when heating in a heated air stream. By not using media particles such as ceramic balls or zirconia beads, excessive contact with the heated air stream due to adhesion of the electrolyte precursor to the media particles can be suppressed, and deterioration of the amorphous sulfide solid electrolyte due to deterioration of the electrolyte precursor can be suppressed. As a result, ionic conductivity is improved.

[0126] (Heated Air Stream) The gas used for the heated air stream can be any gas, and can include, for example, inert gases such as nitrogen and argon, as well as various gases such as air. Nitrogen and air are preferably used in consideration of cost, and nitrogen is preferred in consideration 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 of the quality of the sulfide solid electrolyte due to moisture contained in the gas.

[0127] The temperature of the heated airflow is not particularly limited as long as it can heat the electrolyte precursor to a temperature sufficient to remove the complexing agent, and cannot be generally determined because it varies depending on the type of complexing agent. However, it is preferably 100°C or higher, more preferably 105°C or higher, and even more preferably 110°C or higher, with the upper limit being preferably 180°C or lower, more preferably 170°C or lower, even more preferably 160°C or lower, and still more preferably 155°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. Within the above range, the complexing agent can be removed more efficiently.

[0128] Since the temperature of the heated airflow decreases when the electrolyte precursor is heated, for example, when the above-mentioned flash dryer is used, the outlet temperature from the flash dryer is lower than the supply temperature to the flash dryer (the temperature of the heated airflow). The outlet temperature is usually 3°C or more lower than the supply temperature, and can be 5°C or more lower, or even 10°C or more lower, although this cannot be generalized because it varies depending on the scale of the flash dryer, etc.

[0129] Furthermore, the temperature of the electrolyte precursor is lower than that of the heated air stream because the heating time in the heated air stream is short and the temperature does not usually reach that of the heated air stream. The temperature of the electrolyte precursor after heating in the heated air stream (i.e., the temperature of the sulfide solid electrolyte from which the complexing agent has been removed from the electrolyte precursor) is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, with the upper limit being preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower.

[0130] The amount of heated airflow to be supplied is not particularly limited as long as it is supplied to an extent that the complexing agent can be removed from the electrolyte precursor. Although it cannot be generalized because it varies depending on the type of complexing agent, the scale of the flash dryer to be used, etc., it is preferably 0.1 m 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, the complexing agent can be removed more efficiently.

[0131] The supply amount of the heated airflow is not particularly limited as long as it is supplied to an extent that the complexing agent can be removed from the electrolyte precursor. Although it cannot be generalized because it varies depending on the type of complexing agent, the scale of the flash dryer used, etc., it is preferable to use a ratio of the supply amount of the electrolyte precursor (g / min) to 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 The following is the result.

[0132] The flow rate of the heated airflow is not particularly limited as long as it is supplied at a rate that can remove the complexing agent from the electrolyte precursor, and cannot be generalized because it varies depending on the type of complexing agent, the scale of the flash dryer used, etc., 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, the complexing agent can be removed more efficiently.

[0133] The heating time in the heated airflow is not particularly limited as long as it is supplied to an extent that the complexing agent can be removed from the electrolyte precursor. While this cannot be generalized because it varies depending on the type of complexing agent, the scale of the flash dryer used, and the like, the upper limit is preferably 1 minute or less, more preferably 50 seconds or less, even more preferably 40 seconds or less, even more preferably 15 seconds or less, and particularly preferably 5 seconds or less. The lower limit is typically 0.05 seconds or more, preferably 0.1 seconds or more, and more preferably 0.2 seconds or more. Thus, the heating time in the heated airflow is extremely short. Therefore, for example, the electrolyte precursor is not exposed to high-temperature conditions for a long period of time, heat-induced deterioration can be suppressed, and a sulfide solid electrolyte having high ionic conductivity can be obtained.

[0134] (Content of Complexing Agent) By heating in the heated air flow, the complexing agent can be removed from the electrolyte precursor, and the electrolyte precursor becomes an amorphous sulfide solid electrolyte. However, not all of the complexing agent may be removed from the electrolyte precursor, resulting in some complexing agent remaining in the amorphous sulfide solid electrolyte. In this case, the content of the complexing agent contained in the sulfide solid electrolyte is preferably 0% by mass, i.e., no complexing agent is contained at all. However, from the viewpoint of efficiently obtaining a sulfide solid electrolyte with high ionic conductivity, the content is typically 50% by mass or less, further 45% by mass or less, 35% by mass or less, 25% by mass or less, 15% by mass or less, 10% by mass or less, or 5% by mass or less, with the lower limit being approximately 0.1% by mass or more.

[0135] Furthermore, when a solvent is used, the solvent may remain, as with the complexing agent. In this case, the content of the solvent is also within the same range as the content of the complexing agent. In this specification, the content of the complexing agent contained in the sulfide solid electrolyte and the content of the solvent used as needed are measured by dissolving the powder obtained in the examples etc. in a mixed solution of water and pentanol using a gas chromatography (GC) apparatus, and the content of the complexing agent and the high-boiling-point solvent were quantified using an absolute calibration curve (GC calibration curve method).

[0136] (Powder Recovery) The manufacturing method of this embodiment preferably includes recovering the powder obtained by heating in the heated air stream after the heating. By heating the object to be heated in the heated air stream, the object becomes a powder in which the complexing agent has been removed from the electrolyte precursor, i.e., a powder of the amorphous sulfide solid electrolyte. After heating in the heated air stream, this powder in which the complexing agent has been removed from the electrolyte precursor (powder of the amorphous sulfide solid electrolyte) exists in a state of suspension in the heated air stream. Therefore, in terms of the manufacturing process, it is preferable to recover the powder that exists in a state of suspension in the heated air stream and then perform crystallization by heating, as described below.

[0137] A bag filter is preferably used to recover the powder suspended in the heated airflow from the viewpoint of efficient collection. The heated airflow containing the powder (powder of amorphous sulfide solid electrolyte) from which the complexing agent has been removed from the electrolyte precursor after heating in the heated airflow is supplied to the bag filter, whereby the powder (powder of amorphous sulfide solid electrolyte) from which the complexing agent has been removed from the electrolyte precursor can be recovered. For example, when a flash dryer is used, the powder can be recovered by connecting a bag filter downstream of the flash dryer.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] [Heating] The manufacturing method of this embodiment can include further heating after the heating in the heated air flow. By heating in the heated air flow, an amorphous sulfide solid electrolyte is obtained from the electrolyte precursor. When a crystalline sulfide solid electrolyte is to be obtained, the amorphous sulfide solid electrolyte can be converted into a crystalline sulfide solid electrolyte by further heating (hereinafter also referred to as "post-heating") in addition to heating in the heated air flow.

[0142] Furthermore, the amorphous sulfide solid electrolyte obtained by heating in the above-mentioned heated air flow may contain a complexing agent and a solvent used as needed. Further, post-heating reduces the content of the complexing agent and solvent remaining in the amorphous sulfide solid electrolyte, thereby improving the quality of the sulfide-based solid electrolyte and making it easier to obtain high ionic conductivity. In addition, heating in the above-mentioned heated air flow may result in the electrolyte precursor remaining without becoming an amorphous sulfide solid electrolyte. In this case, post-heating can remove the complexing agent from the electrolyte precursor, and a crystalline sulfide solid electrolyte can be obtained via the amorphous sulfide solid electrolyte.

[0143] The heating temperature for post-heating is not particularly limited as long as it is higher than the temperature of the electrolyte precursor from which the complexing agent has been removed by heating in the heated air stream (i.e., the sulfide solid electrolyte), and for example, the heating temperature may be determined depending on the structure of the crystalline solid electrolyte obtained by heating the amorphous sulfide solid electrolyte obtained by removing the complexing agent from the electrolyte precursor. Here, the "temperature of the electrolyte precursor from which the complexing agent has been removed by heating in the heated air stream (i.e., the sulfide solid electrolyte)" refers to the temperature of the sulfide solid electrolyte at the outlet of the flash dryer, for example, when a flash dryer is used.

[0144] More specifically, the heating temperature for the post-heating is preferably set in the range of 5° C. or higher, more preferably 10° C. or higher, and even more preferably 20° C. or higher, starting from the peak top temperature of the exothermic peak observed on the lowest temperature side when the amorphous solid electrolyte is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) at a temperature increase rate of 10° C. / min, and the upper limit is not particularly limited, but may be about 40° C. or lower. By setting the temperature in this range, not only can a crystalline solid electrolyte be obtained more efficiently and reliably, but the contents of the complexing agent and the solvent used as needed remaining in the sulfide solid electrolyte can be reduced, and by reducing the content of the electrolyte precursor, the purity of the sulfide solid electrolyte can also be improved.

[0145] The heating temperature for post-heating cannot be generally defined because it varies depending on the structure of the crystalline solid electrolyte to be obtained. However, it is usually preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. There is no particular upper limit, but it is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0146] The heating time for post-heating is not particularly limited as long as it is a time that allows a desired crystalline solid electrolyte to be obtained, but is, for example, preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.

[0147] Post-heating can be performed at normal pressure, but can also be performed under reduced pressure or even under vacuum to reduce the heating temperature. When heating under a reduced pressure, the pressure is preferably 85 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less. The lower limit may be vacuum (0 kPa), and considering ease of pressure adjustment, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more. When the pressure condition is within the above range, the heating conditions can be made mild, and the size of the apparatus can be prevented from increasing.

[0148] Furthermore, post-heating is preferably carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere) because this can prevent deterioration (e.g., oxidation) of the crystalline solid electrolyte. The method of post-heating is not particularly limited, and examples thereof include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, and a firing furnace. Furthermore, industrially, a horizontal dryer or a horizontal vibration fluidized dryer having a heating means and a feeding mechanism can also be used, and the method may be selected depending on the amount of heat to be processed.

[0149] (Amorphous sulfide solid electrolyte) The sulfide solid electrolyte obtained by the production method of this embodiment can be either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte, as desired. That is, if post-heating is not performed, an amorphous sulfide solid electrolyte is obtained, and if post-heating is performed, a crystalline sulfide solid electrolyte is obtained.

[0150] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and representative examples thereof include Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ -LiI-LiBr, etc., 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.

[0151] 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.

[0152] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment is, for example, Li ２ S-P ２ S ５ In 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%.

[0153] 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 having a thiolisiconregion II type crystal structure described below and having higher ionic conductivity.

[0154] 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, 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. As described above, the sulfide solid electrolyte obtained by the production method of this embodiment does not use a jacket-type heater (such as a vibration dryer) that has conventionally been used to remove complexing agents, and therefore the generation of secondary particles due to aggregation of primary particles is suppressed, resulting in a small average particle size within the above range. Therefore, the production method of this embodiment does not require a pulverization (atomization) treatment.

[0155] (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).

[0156] 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 ４ Thio-LISICON Region II crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４This indicates that the thio-LISICON region II type has a similar crystal structure.

[0157] 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.

[0158] 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 Ge１－ｘ P ｘ S ４ Diffraction peaks of a crystal structure similar to that of thio-LISICON Region II type appear, for example, at 2θ=20.2° and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0159] The above Li ７ P.S. ６ A preferred example of the crystalline sulfide solid electrolyte is an argyrodite-type crystal structure having a structural skeleton in which part of P is substituted with Si. The composition formula of the argyrodite-type crystal structure is, for example, the composition formula Li ７－ｘ P １－ｙ Si ｙ S ６ and Li ７＋ｘ P １－ｙ Si ｙ S ６ (x is −0.6 to 0.6, y is 0.1 to 0.6) The argyrodite-type crystal structure represented by this composition formula is a cubic or orthorhombic crystal, preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°.

[0160] The composition formula of the argyrodite-type crystal structure is Li ７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ (0.8≦x≦1.7, 0<y≦−0.25x+0.5) is also included. The argyrodite-type crystal structure represented by this composition formula is preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The composition formula of the argyrodite-type crystal structure is preferably the composition formula Li ７－ｘ P.S. ６－ｘ Ha ｘ(Ha is Cl or Br, and x is preferably 0.2 to 1.8). The argyrodite-type crystal structure represented by this composition formula is preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, it has peaks that appear mainly at 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Note that these peak positions may vary within a range of ±0.5°.

[0161] (Content of Complexing Agent) After the removal, further heating reduces the content of complexing agent contained in the crystalline sulfide solid electrolyte to be lower than the content of complexing agent contained in the amorphous sulfide solid electrolyte. The content of complexing agent contained in the crystalline sulfide solid electrolyte is preferably 0% by mass, i.e., no complexing agent is contained at all. However, from the viewpoint of efficiently obtaining a sulfide solid electrolyte with high ionic conductivity, the content is usually 10% by mass or less, further 8% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, with the lower limit being approximately 0.01% by mass or more.

[0162] 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.

[0163] 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. As described above, the sulfide solid electrolyte obtained by the production method of this embodiment does not use a jacket-type heater (such as a vibration dryer) that has conventionally been used to remove complexing agents, and therefore the generation of secondary particles due to aggregation of primary particles is suppressed, resulting in a small average particle size within the above range. Therefore, the production method of this embodiment does not require a pulverization (atomization) treatment.

[0164] 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, and 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.

[0165] (Applications) The sulfide solid electrolyte obtained by the manufacturing method of this embodiment has high ionic conductivity and excellent battery performance, and is therefore suitable for use in batteries. The sulfide solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer. Each layer may be manufactured by a known method.

[0166] 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.

[0167] 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.

[0168] (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

[0169] (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

[0170] (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).

[0171] (Preparation Example: Preparation of Electrolyte Precursor) The electrolyte precursors 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.

[0172] 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.

[0173] (Flash Dryer) The electrolyte precursor powder obtained in the above Preparation Example was heated in a heated airflow using an apparatus having the configuration shown in the schematic diagram of an apparatus used for heating in a heated airflow in FIG. 1 . The apparatus shown in FIG. 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 airflow, as well as a mixer for pneumatically transporting the object to be heated by the gas. Although not shown, a feeder capable of supplying the object to be heated in powder or slurry form may also be provided (not shown). In the apparatus shown in FIG. 1 , the electrolyte precursor (the object to be heated) is pneumatically transported by gas to the bottom of the flash dryer, and the 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 (amorphous sulfide powder) 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. Then, the powder (amorphous sulfide powder) from which the complexing agent has been removed from the electrolyte precursor is collected by a bag filter, and the heated airflow after the powder has been collected is exhausted as is.

[0174] (Example 1) Nitrogen heated to 115°C was used as a heated airflow in a flash dryer. ３ The feed of the electrolyte precursor powder to the flash dryer was started at a rate of 10.5 L / min. Then, using a table feeder, the resulting electrolyte precursor powder was fed at a rate of 4.2 g / min. The powder was then pneumatically transferred to the flash dryer using 10.5 L / min of nitrogen. The object to be heated (electrolyte precursor powder) was heated in a heated airflow using the flash dryer. The heated airflow discharged from the flash dryer was supplied to a bag filter, and the powder (amorphous sulfide solid electrolyte) from which the complexing agent had been removed was recovered. This process continued for 50 minutes (i.e., the operation time was 50 minutes). The temperature of the heated airflow at the outlet of the flash dryer was 109°C, and the temperature of the heated airflow at the inlet of the bag filter was 61°C. The content of the complexing agent in the recovered powder (amorphous sulfide solid electrolyte) was 43% by mass.

[0175] The resulting powder (amorphous sulfide solid electrolyte) from which the complexing agent was removed was heated (post-heated) in a Schlenk flask at 110°C for 2 hours and then at 160°C for 2 hours, thereby obtaining a crystalline sulfide solid electrolyte.

[0176] Examples 2 and 3 Powder was recovered in the same manner as in Example 1, except that the temperature and supply rate of the heated airflow supplied to the flash dryer, the operating time, and the supply rate of the electrolyte precursor powder were set to the values ​​shown in Table 1. The outlet temperature of the flash dryer, the inlet temperature of the bag filter, and the content of the complexing agent contained in the recovered powder (amorphous sulfide solid electrolyte) are shown in Table 1. The ionic conductivity of the crystalline sulfide solid electrolyte obtained in Example 3 was measured and found to be 4.0 (mS / cm). Powder XRD diffraction measurement was also performed on the crystalline sulfide solid electrolyte obtained in Example 3. The X-ray diffraction spectra are shown in Figures 2 and 3. As shown in Figures 2 and 3, crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the crystalline sulfide solid electrolyte had a thiolicon region II crystal structure.

[0177] Examples 4 to 8 Powders were recovered in the same manner as in Example 1, except that the temperature and supply rate of the heated airflow supplied to the flash dryer, the operating time, and the supply rate of the electrolyte precursor powder were set to the values ​​shown in Table 1. The outlet temperature of the flash dryer, the inlet temperature of the bag filter, and the content of the complexing agent contained in the recovered powder (amorphous sulfide solid electrolyte) are shown in Table 1. Powder XRD diffraction measurements were also performed on the crystalline sulfide solid electrolytes obtained in Examples 4 to 8. 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 electrolytes were crystalline sulfide solid electrolytes having a thiolicon region II crystal structure.

[0178]

[0179] The results of the examples confirmed that heating in a heated air stream can reduce the content of complexing agent at the outlet of the flash dryer in an extremely short time, resulting in a high-quality sulfide solid electrolyte with few impurities and high ionic conductivity. It was also confirmed that the higher the supply temperature of the heated air stream, the lower the content of complexing agent at the outlet of the flash dryer, and that the higher the supply rate of the heated air stream relative to the electrolyte precursor, the lower the content of complexing agent at the outlet of the flash dryer. Using this as a guide, the operating conditions can be adjusted depending on the performance required of the sulfide solid electrolyte.

[0180] Comparative Example 1 350 g of the electrolyte precursor powder obtained in the above Preparation Example was heated at 110°C under vacuum for 7 hours using a vibration dryer ("VH-10 (model number)", manufactured by Chuo Kakoki Co., Ltd.) to obtain an amorphous sulfide solid electrolyte, which was then further heated at 170°C under vacuum for 2 hours to obtain a crystalline sulfide solid electrolyte. Powder XRD diffraction measurement was performed on the obtained crystalline sulfide solid electrolyte. The X-ray diffraction spectrum is shown in FIG. 4.

[0181] Comparative Example 2 A crystalline sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1, except that the amount of the electrolyte precursor powder was changed from 350 g to 550 g. Powder XRD diffraction measurement was performed on the obtained crystalline sulfide solid electrolyte. The X-ray diffraction spectrum is shown in FIG.

[0182] According to the results of FIG. 4, the crystalline sulfide solid electrolytes obtained in Comparative Examples 1 and 2 exhibited crystallization peaks at 2θ = 20.2° and 23.6°, indicating that they had a thiolicon region II crystal structure. However, a crystallization peak due to halogen atoms (lithium bromide) was detected at 2θ = 28°, indicating that the electrolyte contained a large amount of impurities and was not of high quality. Furthermore, the ionic conductivity of Comparative Example 1 was 3.7 (mS / cm), confirming that the ionic conductivity was reduced due to the large amount of impurities. Since the X-ray diffraction spectrum of Comparative Example 2 clearly indicated a large amount of impurities and low ionic conductivity, the ionic conductivity was not measured. Furthermore, since Comparative Example 2, which contained a larger amount of electrolyte precursor, exhibited a larger crystallization peak at 2θ = 28°, it was also confirmed that mass production would be difficult if heating in the heated airflow employed in the manufacturing method of this embodiment was not performed.

[0183] Comparative Example 3 A crystalline sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the slurry obtained in Preparation Example was used, and the apparatus equipped with the fluidized bed dryer and bag filter shown in FIG. 1 was replaced with an apparatus equipped with a fluidized bed dryer and bag filter using media particles shown in FIG. 5. The nitrogen supply temperature to the fluidized bed dryer was 147°C, and the supply rate was 2.4 m / s (the flow rate at 147°C at the cross section of the fluidized bed of a 98 mm diameter medium (media particles)). The slurry was supplied so that the temperature of the fluid containing the gas and powder extracted from the top of the fluidized bed dryer was 110°C. Ceramic particles with a particle size of 2 mm were used as the medium media particles, and the ceramic particle packing rate was 30% by volume with respect to the volume of the fluidized bed dryer. After the fluidized bed dryer reached a steady state, drying was continued for 48 hours, and the powder recovered in the bag filter was heated in a vacuum at 110°C for 2 hours and then further heated in a vacuum at 180°C for 2 hours to obtain a crystalline solid electrolyte. The obtained crystalline sulfide solid electrolyte was subjected to powder XRD diffraction measurement. The X-ray diffraction spectrum is shown in Figure 6. For comparison, Figure 6 also shows the X-ray diffraction spectra of Examples 3 and 6.

[0184] Examples 9 to 15 Powders were recovered in the same manner as in Example 1, except that the temperature and supply rate of the heated airflow supplied to the flash dryer, the operating time, and the supply rate of the electrolyte precursor powder were set to the values ​​shown in Table 2. The outlet temperature of the flash dryer, the inlet temperature of the bag filter, and the content of the complexing agent contained in the recovered powder (amorphous sulfide solid electrolyte) are shown in Table 2. Powder XRD diffraction measurements were also performed on the crystalline sulfide solid electrolytes obtained in Examples 9 to 15. The X-ray diffraction spectrum is shown in FIG. 7. As shown in FIG. 7, crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the electrolytes were crystalline sulfide solid electrolytes having a thiolicon region II crystal structure.

[0185]

[0186] Examples 9 to 15 are examples in which the supply amount of electrolyte precursor was increased compared to Examples 1 to 8. The results of Examples 9 to 15 confirmed that even when the scale was increased, by performing heating in the heated airflow while maintaining the supply amount of the heated airflow, particularly the flow rate, within a certain range, the content of the complexing agent at the outlet of the flash dryer could be reduced in an extremely short time, and a high-quality sulfide solid electrolyte with few impurities and high ionic conductivity could be obtained.

[0187] 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, since heating is performed using a heated airflow, the complexing agent can be removed from the electrolyte precursor-containing material regardless of the scale as long as the supply amount of the heated airflow, particularly the flow rate, is maintained within a certain range, making it easy to adapt. 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.

Claims

1. A raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms is mixed with a complexing agent to obtain an electrolyte precursor-containing material. Next, heat in a heated airflow. A method for producing a sulfide solid electrolyte containing a sulfide.

2. A method for producing a sulfide solid electrolyte according to claim 1, comprising drying the electrolyte precursor-containing material.

3. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the temperature of the heated airflow is 100°C or higher and 180°C or lower.

4. The amount of heated air supplied is 0.1 m ３ Over 500m per minute ３ A method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the rate is less than or equal to / min.

5. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the flow velocity of the heated airflow is 5 m / s or more and 35 m / s or less.

6. A method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heating in the heated airflow is performed for 0.1 seconds or more and 1 minute or less.

7. The method for producing a sulfide solid electrolyte according to claim 2, wherein the drying is performed under normal pressure or reduced pressure at a temperature of 5°C to 110°C.

8. A method for producing a sulfide solid electrolyte according to claim 1 or 2, comprising heating in the aforementioned heated air stream, followed by further heating.

9. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the complexing agent is a compound having an amino group.

10. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the complexing agent is a compound having at least two tertiary amino groups in its molecule.

11. A method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein media particles are not used when heating in the aforementioned heated airflow.

12. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the sulfide solid electrolyte has a thiolysicon region type II crystal structure.