Method for manufacturing sulfide solid electrolyte

Abstract

Provided is a method for manufacturing a sulfide solid electrolyte, the method enabling efficient manufacture of a sulfide solid electrolyte having high ion conductance while using a liquid-phase method, and easy mass production, the method including: mixing a complexing agent and a raw material composition including lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms to obtain an electrolyte precursor composition; and then heating in a solvent that has a higher boiling point than the boiling point of the complexing agent.

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 solvent having a boiling point higher than the boiling point of the complexing agent.

[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] 1 is an X-ray diffraction spectrum of the powder obtained in Example 1. FIG. 2 is a SEM (scanning electron microscope) photograph of the crystalline sulfide solid electrolyte obtained in Example 1. FIG. 3 is an X-ray diffraction spectrum of the powder obtained in Example 1 and Comparative Examples 1 and 2. FIG. 4 is an X-ray diffraction spectrum of the powder obtained in Examples 1 and 2. FIG. 5 is an X-ray diffraction spectrum of the powder obtained in Examples 1, 3 and 4. FIG. 6 is a SEM (scanning electron microscope) photograph of the crystalline sulfide solid electrolyte obtained in Comparative Example 3. FIG. 7 is a particle size distribution of the powder obtained in Examples 1 and 2 and Comparative Examples 3 and 4. FIG. 8 is an X-ray diffraction spectrum of the powder obtained in Example 5.

[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 also 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, allowing the components to be uniformly dispersed in the liquid. 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 problem of significantly reducing the ionic conductivity of the solid electrolyte. Furthermore, in heterogeneous synthesis, where solid and liquid coexistence occurs, the solid electrolyte is partially dissolved, resulting in 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. 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. This limits the temperature conditions for removing the complexing agent, leaving room for improvement in terms of efficient solid electrolyte production. Furthermore, during heating for complexing agent removal and crystallization, secondary particles formed by aggregation of primary particles with an average particle size of approximately 0.1 µm are generated, which increases the oil absorption of the solid electrolyte, and may require pulverization (atomization) of the crystallized solid electrolyte. Furthermore, with the increasing demand for sulfide solid electrolytes, there is a need for mass production. However, with conventional methods, the complexing agent is removed in an environment where heating is performed under vacuum, and heat is only transferred when the powder comes into contact with the inner wall surface (heat transfer surface) of a jacket-type heater. This significantly increases the size of the equipment, and there are concerns that it may not be possible to adequately respond to the demand.

[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 heating the electrolyte precursor-containing material in a solvent having a boiling point higher than that of the complexing agent. Removing the complexing agent from the electrolyte precursor by heating in a solvent 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, it was found that the dissolution of part of the solid electrolyte suppresses separation due to the elution of specific components. This is a surprising and unexpected effect in a liquid phase, an environment where elution of specific components is likely to occur. Another advantage is that heating in the liquid phase is sufficient, making it easy to accommodate larger devices.

[0019] Based on the above findings, the 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 solvent having a boiling point higher than that of the complexing agent, a sulfide solid electrolyte with high ionic conductivity can be efficiently obtained and mass production can be facilitated, even while 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, comprising: 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 subsequently heating the material in a solvent having a boiling point higher than that of the complexing agent.

[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, along with 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 solvent (hereinafter simply referred to as a "high-boiling point solvent") having a boiling point higher than that of the complexing agent contained in the electrolyte precursor in the electrolyte precursor-containing material. It is believed that heating in a solvent having a boiling point higher than that of the complexing agent makes the complexing agent more fluid, allowing it to separate and be removed from the electrolyte precursor.

[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 high-boiling point solvent after obtaining the electrolyte precursor-containing material. The heating may be performed after obtaining the electrolyte precursor-containing material, and the heating target in the heating is the electrolyte precursor-containing material, or, in the case of drying, the electrolyte precursor, as described below. 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 high-boiling point solvent. Direct contact between the electrolyte precursor in the electrolyte precursor-containing material and the high-boiling point solvent efficiently heats and rapidly removes the complexing agent contained in the electrolyte precursor. This suppresses the re-formation of a complex between the electrolyte precursor from which the complexing agent has been removed and the complexing agent, as well as the generation of impurities between the electrolyte precursor and the complexing agent, resulting in a 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, wherein the heating temperature of the solvent is set to a temperature higher than the boiling point of the complexing agent.

[0025] As described above, the complexing agent contained in the electrolyte precursor becomes more fluid when heated and is removed from the electrolyte precursor. Here, by heating the high-boiling-point solvent above the boiling point of the complexing agent, the complexing agent volatilizes, making it easier to separate from the electrolyte precursor. Furthermore, the separated gaseous complexing agent is more likely to escape from the high-boiling-point solvent and be discharged to the outside of the system, making it less likely for the separated complexing agent to remain in the high-boiling-point solvent. This suppresses the re-formation of complexes with the complexing agent removed from the electrolyte precursor, due to the complexing agent remaining in the electrolyte precursor as well as the complexing agent remaining in the high-boiling-point solvent, and the generation of impurities. This makes it easier to obtain a sulfide solid electrolyte with fewer impurities and high quality and high ionic conductivity.

[0026] A method for producing a sulfide solid electrolyte according to a third aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to the first or second aspect, wherein the heating in the solvent causes the solvent to boil.

[0027] Boiling the high-boiling solvent not only facilitates separation of the complexing agent from the electrolyte precursor, but also promotes rapid separation because the high-boiling solvent is discharged out of the system together with the vapor of the high-boiling solvent produced by boiling. As a result, re-formation of the complex with the powder from which the complexing agent has been removed from the electrolyte precursor 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.

[0028] A fourth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the third aspect, wherein a solvent having a boiling point higher than that of the complexing agent is separately prepared, and the electrolyte precursor-containing material is mixed with the separately prepared solvent to form a mixture, which is then added to the solvent used for heating.

[0029] The method for supplying the electrolyte precursor-containing material involves mixing a high-boiling-point solvent, prepared separately from the high-boiling-point solvent used in the heating step, with the electrolyte precursor-containing material and adding the resulting mixture to the high-boiling-point solvent used in the heating step. As described in detail below, the mixture is preferably added to a heated high-boiling-point solvent, preferably a boiled high-boiling-point solvent. Unlike a method in which the electrolyte precursor is added to a preheated high-boiling-point solvent and then heated, this method allows the electrolyte precursor to be heated instantaneously to the target temperature while gradually controlling the amount of electrolyte precursor added. This suppresses the re-formation of complexes with the powder from which the complexing agent has been removed 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. The separately prepared high-boiling-point solvent may be the same type as the high-boiling-point solvent used in the heating step, or a different type. Using the same type of solvent is preferred from the perspective of more efficiently obtaining a sulfide solid electrolyte with fewer impurities, high quality, and high ionic conductivity.

[0030] 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 an amount of the solvent used per 1 g of a supplied amount of the electrolyte precursor contained in the electrolyte precursor-containing material is 20 mL or more and 2000 mL or less.

[0031] Using the high-boiling-point solvent in an amount within the above range enables more efficient separation and removal of the complexing agent. This suppresses the re-formation of complexes with the powder from which the complexing agent has been removed from the electrolyte precursor, as well as the generation of impurities. This makes it easier to obtain a sulfide solid electrolyte with fewer impurities, high quality, and high ionic conductivity. Furthermore, limiting the amount of the high-boiling-point solvent used to a certain range makes it easier to accommodate mass production.

[0032] A method for producing a sulfide solid electrolyte according to a sixth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to fifth aspects, further comprising drying the electrolyte precursor-containing material.

[0033] As described above, in the manufacturing method of this embodiment, it is essential to heat the electrolyte precursor in a high-boiling-point solvent. As a preliminary step, an electrolyte precursor-containing material containing the electrolyte precursor and a solvent is dried, and the solvent is removed to isolate the electrolyte precursor as a powder. This can be heated in a high-boiling-point solvent, thereby more directly heating the electrolyte precursor. This allows the complexing agent contained in the electrolyte precursor to be more efficiently separated and removed. As a result, regeneration of the complex with the electrolyte precursor from which the complexing agent has been removed 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. 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, resulting in poor contact efficiency and low thermal conduction efficiency. Therefore, the manufacturing method of this embodiment can more efficiently obtain a sulfide solid electrolyte compared to the conventional method.

[0034] As described above, the main purpose of drying in the manufacturing method of this embodiment is to remove the solvent from the electrolyte precursor-containing material, and it can also remove any remaining complexing agent that does not contribute to the formation of the electrolyte precursor. Therefore, in the manufacturing method of this embodiment, the complexing agent is removed from the electrolyte precursor not by drying, but only by heating in a high-boiling point solvent. Needless to say, the complexing agent can also be removed from the electrolyte precursor by heating the electrolyte precursor-containing material in a high-boiling point solvent.

[0035] A seventh aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the sixth aspect, 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.

[0036] 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 a powder of the electrolyte precursor can be obtained.

[0037] 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 first to seventh aspects, further comprising, after heating in the solvent, further heating at a temperature higher than the heating temperature in the solvent.

[0038] By heating in the solvent, the complexing agent is removed from the electrolyte precursor, and an amorphous sulfide solid electrolyte is obtained. By further heating this at a temperature higher than the heating temperature in the solvent, 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.

[0039] 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.

[0040] In the sulfide solid electrolyte 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 inclusion, as described above. As described below, a compound having a heteroatom is likely to form a complex with the solid electrolyte raw material, and is a preferred compound as a complexing agent. In particular, a compound having a nitrogen atom as a heteroatom and further a nitrogen atom as an amino group not only makes it easier to form a complex, but also makes it easier to incorporate halogen atoms, which are difficult to incorporate in the formation of a complex, 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.

[0041] Furthermore, when a compound having an amino group is used as a complexing agent, in addition to the above-mentioned properties, it also has the property of being easily separated and removed from the electrolyte precursor, which suppresses the re-formation of a complex with the powder from which the complexing agent has been removed and the generation of impurities, making it easier to obtain a sulfide solid electrolyte with high quality, high ionic conductivity, and few impurities in an extremely efficient manner.

[0042] A method for producing a sulfide solid electrolyte according to an eleventh aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to tenth aspects above, wherein the solvent is a hydrocarbon solvent containing no heteroatoms. A method for producing a sulfide solid electrolyte according to a twelfth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to eleventh aspects above, wherein the solvent is at least one organic solvent selected from aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents. A method for producing a sulfide solid electrolyte according to a thirteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to the twelfth aspect above, wherein the organic solvent has a carbon number of 8 or more.

[0043] As described above, compounds having heteroatoms have the property of easily forming complexes with the solid electrolyte raw materials. By using a hydrocarbon solvent that does not contain heteroatoms as the high-boiling-point solvent, the formation of complexes between the high-boiling-point solvent and the electrolyte precursor is suppressed, thereby suppressing the generation of impurities and making it easier to efficiently obtain a sulfide solid electrolyte that is high in quality, has few impurities, and has high ionic conductivity.

[0044] Furthermore, in consideration of suppressing the generation of impurities and the ease of selecting a solvent having a boiling point higher than that of the complexing agent, the high-boiling-point solvent is preferably at least one organic solvent selected from aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents, and preferably has 8 or more carbon atoms.

[0045] A method for producing a sulfide solid electrolyte according to a fourteenth aspect of the present embodiment is the same as any one of the first to thirteenth aspects, except that no pulverization treatment is performed after heating in the solvent.

[0046] The electrolyte precursor obtained using a complexing agent inherently has a small average particle size. However, as described above, when heating for removing the complexing agent and crystallizing the electrolyte precursor, a jacket-type heater (such as a vibration dryer) is used, which generates secondary particles and increases the oil absorption, which can lead to pulverization (atomization). However, according to the production method of this embodiment, the use of a jacket-type heater (such as a vibration dryer) does not result in the generation of secondary particles, and therefore, there is no need for a pulverization (atomization) process. This significantly contributes to energy savings in the production of sulfide solid electrolytes, making it possible to more efficiently produce sulfide solid electrolytes.

[0047] A fifteenth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to fourteenth aspects, wherein the heating in the solvent removes a complexing agent from the electrolyte precursor contained in the electrolyte precursor-containing material. By heating in the solvent, the complexing agent can be removed from the electrolyte precursor contained in the electrolyte precursor-containing material, and the electrolyte precursor can be converted into a sulfide solid electrolyte.

[0048] A method for producing a sulfide solid electrolyte according to a sixteenth aspect of the present embodiment is any one of the first to fifteenth aspects, wherein the sulfide solid electrolyte has a thiolicon region II crystal structure.

[0049] 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.

[0050] (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.

[0051] 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.

[0052] [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 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 solvent having a boiling point higher than that of the complexing agent.

[0053] [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.

[0054] (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.

[0055] 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.

[0056] Examples of usable solid electrolyte raw materials other than those mentioned above include solid electrolyte raw materials containing at least one atom selected from the above four types of atoms and also containing atoms other than the four types of atoms, more specifically lithium compounds such as lithium oxide, lithium hydroxide, and lithium carbonate; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, and tin sulfide (SnS, SnS ２ metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium such as sodium halides such as sodium iodide, sodium fluoride, sodium chloride and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides and bismuth halides; phosphorus oxychloride (POCl ３ ), phosphorus oxybromide (POBr ３ ) and the like; and the like.

[0057] 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.

[0058] 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. ４ The content is preferably 60 to 100 mol %, more preferably 65 to 90 mol %, and even more preferably 70 to 80 mol %.

[0059] 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 %.

[0060] 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.

[0061] 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 70 to 80 mol%, more preferably 72 to 78 mol%, and even more preferably 74 to 78 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 100 mol%, more preferably 55 to 85 mol%, and even more preferably 60 to 75 mol%. Furthermore, 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%, still more preferably 30 to 70 mol%, and particularly preferably 40 to 60 mol%.

[0062] 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%.

[0063] 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)

[0064] 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.

[0065] Furthermore, when the two kinds of halogen elements are bromine and iodine, where the number of moles of bromine is B1 and the number of moles of iodine is B2, the ratio B1:B2 is preferably 1 to 99:99 to 1, more preferably 15:85 to 90:10, even more preferably 20:80 to 80:20, still more preferably 30:70 to 75:25, and particularly preferably 35:65 to 75:25.

[0066] (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.").

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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 electrolyte precursor powder using a high-boiling point solvent, thereby producing a sulfide solid electrolyte.

[0071] 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.

[0072] 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.

[0073] Examples of such amine compounds include aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, and these can be used alone or in combination.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] Among the above ether compounds, aliphatic ethers are preferred, and dimethoxyethane and tetrahydrofuran are more preferred, from the viewpoint of obtaining higher ionic conductivity.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] (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 a solvent added as needed.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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, so a suspension of the complex is obtained in which the complex is suspended in the complex and a solvent added as needed. Therefore, the production method of the solid electrolyte of this embodiment corresponds to a heterogeneous system in a so-called liquid-phase method.

[0106] (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.

[0107] 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.

[0108] 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.

[0109] (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.)

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] [Drying] The manufacturing 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 high-boiling point solvent, whereby the electrolyte precursor can be heated more directly, and therefore the complexing agent can be separated and removed more efficiently.

[0115] 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 added as necessary 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.

[0116] 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 above the boiling point of the solvent. Since the specific temperature condition can vary depending on the type of complexing agent and solvent used, it is not possible to generalize, 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.

[0117] 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). Considering the ease of adjusting the pressure, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more.

[0118] 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 of heating in the high-boiling point solvent 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 heat the electrolyte precursor more directly.

[0119] [Heating in a Solvent] The manufacturing method of this embodiment includes heating the electrolyte precursor-containing material in a solvent having a boiling point higher than that of the complexing agent after obtaining the electrolyte precursor-containing material. The electrolyte precursor-containing material obtained in obtaining the electrolyte precursor-containing material, or the electrolyte precursor if the drying has been performed, is heated in a high-boiling point solvent to remove the complexing agent from the electrolyte precursor, i.e., to remove the complexing agent from the complex formed by the solid electrolyte raw material and the complexing agent, thereby obtaining a sulfide solid electrolyte. This phenomenon can be referred to as "decomplexation" because it decomposes the complex (electrolyte precursor), or as "decomplexation" because it removes the complexing agent from the complex (electrolyte precursor).

[0120] (Solvent Having a Boiling Point Higher than that of the Complexing Agent) The solvent (high-boiling solvent) having a boiling point higher than that of the complexing agent used in the production method of this embodiment is not particularly limited as long as it has a boiling point higher than that of the complexing agent contained in the electrolyte precursor. However, as described above, considering that solvents having heteroatoms have the property of easily forming complexes with the solid electrolyte raw material, it is preferable that the high-boiling solvent be a hydrocarbon solvent that does not contain heteroatoms.

[0121] The hydrocarbon solvent may be selected from the organic solvents exemplified as solvents that can be used in obtaining the electrolyte precursor-containing material, and a solvent having a boiling point higher than that of the complexing agent may be used. Preferably, the hydrocarbon solvent is an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, or an aromatic hydrocarbon solvent, and more preferably, an aliphatic hydrocarbon solvent or an alicyclic hydrocarbon solvent.

[0122] Considering that the high-boiling solvent is likely to have a boiling point higher than that of the complexing agent, the carbon number of the high-boiling solvent is preferably 8 or more, more preferably 9 or more, and the upper limit is preferably 24 or less, more preferably 20 or less, and even more preferably 16 or less, as an aliphatic hydrocarbon solvent.

[0123] Aliphatic hydrocarbon solvents preferably used as high-boiling point solvents include, for example, octane, 2-ethylhexane, decane, undecane, dodecane, tridecane, etc. Note that these are merely examples, and while 2-ethylhexane is an isomer of octane, all isomers of such isomers may be included. Furthermore, perfluorooctane and other isomers substituted with halogen atoms may also be included.

[0124] Furthermore, examples of alicyclic hydrocarbon solvents that are preferably used as high-boiling point solvents include cyclopentane-based hydrocarbon solvents such as trimethylcyclopentane (C8, 105°C), methylethylcyclopentane (C8, 149°C), propylcyclopentane (C8, unknown), and butylcyclopentane (C9, 157°C); dimethylcyclohexane (C8, 118 to 120°C), ethylcyclohexane (C8, 130 to 132°C), propylcyclohexane (C9, 155°C); Representative preferred solvents include cyclohexane-based hydrocarbon solvents such as isopropylcyclohexane (C9, 155°C) and butylcyclohexane (C10, 178-180°C); cycloheptane-based hydrocarbon solvents such as methylcycloheptane (C8, 145°C) and ethylcycloheptane (C9, 145°C); cyclooctane-based hydrocarbon solvents such as cyclooctane (C8, 151°C) and dimethylcyclooctane (C10, 158-159°C); cyclononane, cyclodecane, etc. Note that these are merely examples, and solvents having isomers such as isopropylcyclohexane in relation to propylcyclohexane may also include all isomers. Furthermore, solvents substituted with halogen atoms, and alicyclic hydrocarbon solvents substituted with aliphatic groups such as alkyl groups, may also be included. The high-boiling point solvents listed above may be used singly or in combination.

[0125] (Heating) In the manufacturing method of this embodiment, the electrolyte precursor-containing material, or the electrolyte precursor if the drying has been performed (hereinafter, these are also collectively referred to as "electrolyte precursor-containing material, etc."), is heated in a high-boiling point solvent, thereby removing the complexing agent from the electrolyte precursor.

[0126] The heating conditions for the high-boiling solvent are not particularly limited as long as the complexing agent is heated to a degree that makes it easy to flow and separates it from the electrolyte precursor and can be removed. The heating temperature for the high-boiling solvent cannot be generalized because it can vary depending on the pressure conditions. Therefore, based on the boiling point of the complexing agent, the heating temperature is preferably -50°C or higher relative to the boiling point of the complexing agent. From the viewpoint of more efficient removal of the complexing agent, the heating temperature is preferably 0°C (i.e., the boiling point of the complexing agent) or higher, more preferably greater than 0°C (i.e., the boiling point of the complexing agent). Furthermore, from the viewpoint of more stable removal of the complexing agent, the heating temperature is preferably 1°C or higher, more preferably 3°C or higher, even more preferably 5°C or higher, and even more preferably 10°C or higher relative to the boiling point of the complexing agent.

[0127] In terms of the heating conditions for the high-boiling solvent, it is effective to heat the high-boiling solvent to a temperature above the boiling point of the complexing agent in order to more efficiently remove the complexing agent, because, as described above, heating the high-boiling solvent above the boiling point of the complexing agent volatilizes the complexing agent, making it easier to separate it from the electrolyte precursor.

[0128] Furthermore, as a heating condition for the high-boiling point solvent, it is preferable to boil the high-boiling point solvent. That is, it is preferable that the high-boiling point solvent is heated to a temperature equal to or higher than the boiling point of the high-boiling point solvent. By boiling the high-boiling point solvent, as described above, not only is the complexing agent easily separated from the electrolyte precursor, but the high-boiling point solvent is also discharged out of the system together with the vapor of the high-boiling point solvent produced by boiling, thereby promoting rapid separation.

[0129] The heating conditions for the high-boiling point solvent cannot be generalized because they may vary depending on the pressure conditions as described above, but are preferably 60° C. or higher, more preferably 65° C. or higher, even more preferably 70° C. or higher, and still more preferably 75° C. or higher, with the upper limit being preferably 130° C. or lower, more preferably 120° C. or lower, and even more preferably 115° C. or lower. Heating within the above temperature range allows for efficient removal of the complexing agent.

[0130] Regarding the heating conditions for the high-boiling point solvent, the pressure conditions are preferably 100 kPa or less, more preferably 85 kPa or less, and even more preferably 70 kPa or less, and 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. When the pressure conditions are within the above range, the heating conditions can be made mild, and an increase in the size of the apparatus can be suppressed.

[0131] (Heating Method) The method for heating the electrolyte precursor-containing material, etc. in a high-boiling point solvent is not particularly limited as long as it can be heated in a high-boiling point solvent. For example, the electrolyte precursor-containing material, etc. may be supplied to a heated high-boiling point solvent, or the electrolyte precursor-containing material, etc. may be supplied to a high-boiling point solvent and then heated.

[0132] Alternatively, for example, a high-boiling solvent may be prepared separately from the high-boiling solvent used for heating, and the electrolyte precursor-containing material or the like may be mixed with the separately prepared high-boiling solvent to form a mixture, and this mixture may be added to the high-boiling solvent used for heating the electrolyte precursor-containing material or the like. In this case, the mixture may be added to a heated high-boiling solvent used for heating the electrolyte precursor-containing material or the like, or the mixture may be added to a boiled high-boiling solvent. Furthermore, the mixture may be heated after being added to the high-boiling solvent used for heating the electrolyte precursor-containing material or the like, or may be heated to a boil. In either case, from the viewpoint of more efficiently removing the complexing agent, it is preferable to boil the high-boiling solvent used for heating.

[0133] The content of the electrolyte precursor in the mixture of the electrolyte precursor-containing material and the separately prepared high-boiling-point solvent is preferably 1 mass % or more, more preferably 5 mass % or more, even more preferably 10 mass % or more, and even more preferably 20 mass % or more, based on the total amount of the mixture, and the upper limit is preferably 50 mass % or less, more preferably 40 mass % or less. When the content is within the above range, the mixture is easy to handle and can be easily added to the high-boiling-point solvent used for heating.

[0134] The high-boiling-point solvent (high-boiling-point solvent used to form a mixture containing an electrolyte precursor) prepared separately from the high-boiling-point solvent for heating may be appropriately selected from the solvents exemplified above as the high-boiling-point solvent for heating, and may be the same type of solvent as the high-boiling-point solvent for heating, or a different type of solvent. From the viewpoint of more efficiently obtaining a sulfide solid electrolyte with few impurities, high quality, and high ionic conductivity, it is preferable to use the same type of solvent. Using the same type of solvent also makes it easier to recycle the solvent through separation and purification treatment.

[0135] In the production method of this embodiment, the amount of the high-boiling-point solvent for heating used per gram of supplied amount of electrolyte precursor contained in the electrolyte precursor-containing material is preferably 20 mL or more, more preferably 100 mL or more, and even more preferably 150 mL or more, with the upper limit being preferably 2000 mL or less, more preferably 1500 mL or less, and even more preferably 1000 mL or less. When the amount of the high-boiling-point solvent for heating used is within the above range, a sulfide solid electrolyte with few impurities, high quality, and high ionic conductivity can be obtained more efficiently, and disposal of the solvent becomes easier.

[0136] Since the high-boiling-point solvent for heating is itself heated, a portion of it may volatilize and decrease. On the other hand, it can be said that the amount of the high-boiling-point solvent used for heating is preferably a certain amount or more relative to the amount of electrolyte precursor supplied. In the manufacturing method of this embodiment, if the high-boiling-point solvent decreases during heating, it is preferable to add a high-boiling-point solvent. Adding a high-boiling-point solvent can replenish the reduced high-boiling-point solvent, and more efficiently obtain a sulfide solid electrolyte with fewer impurities, high quality, and high ionic conductivity. There are no particular limitations on the method for adding the high-boiling-point solvent. As described above, for example, the high-boiling-point solvent may be added alone, or a mixture of the high-boiling-point solvent and the electrolyte precursor-containing material may be added.

[0137] (Content of Complexing Agent) By heating in the above-mentioned solvent, 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 of the 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 usually 20% by mass or less, further 17.5% by mass or less, 15% by mass or less, or 10% by mass or less, with the lower limit being approximately 0.1% by mass or more.

[0138] Similarly to the complexing agent, the high-boiling solvent may also remain. In this case, the content of the high-boiling solvent is also in the same range as the content of the complexing agent.

[0139] (Constant-rate drying period and falling-rate drying period) The heating in the solvent of the manufacturing method of this embodiment can be classified into two periods based on the temperature of the electrolyte precursor and the state of complexing agent removal. The first is the constant-rate drying period, in which the entire surface of the electrolyte precursor powder is covered with complexing agent, the surface and core temperatures of the electrolyte precursor are maintained constant, and the amount of complexing agent contained in the electrolyte precursor decreases linearly with time. During the constant-rate drying period, the complexing agent contained in the electrolyte precursor reaches its limit content, and the content of complexing agent typically decreases to about 25 mass%.

[0140] The second is a falling-rate drying period, in which, after the constant-rate drying period, the surface temperature of the electrolyte precursor rises to the temperature of the high-boiling-point solvent, and the core temperature of the powder also gradually rises, eventually approaching the temperature of the high-boiling-point solvent. During the falling-rate drying period, the complexing agent contained in the electrolyte precursor reaches an equilibrium content, and the content of the complexing agent does not decrease any further at this temperature. After the falling-rate drying period, the content of the complexing agent contained in the electrolyte precursor decreases to the numerical range described above for the content of the complexing agent contained in the sulfide solid electrolyte.

[0141] In the production method of this embodiment, the heating in a solvent is preferably performed in a high-boiling point solvent, but a part of the heating in a solvent may be performed in a high-boiling point solvent. When a part of the heating in a solvent is performed in a high-boiling point solvent, it is preferable to perform the heating in the high-boiling point solvent at least during the constant rate drying period.

[0142] The duration of the constant-rate drying period cannot be generalized because it varies depending on the type and content of the complexing agent contained in the electrolyte precursor, but it is usually 10 minutes or more, preferably 45 minutes or more, with an upper limit of usually 1 hour 30 minutes or less, more preferably 1 hour 15 minutes, from the start of heating in the solvent. The duration of the falling-rate drying period is usually 10 minutes or more, preferably 45 minutes or more, with an upper limit of usually 6 hours or less, preferably 5 hours or less, more preferably 4 hours or less.

[0143] [Heating] The production method of this embodiment may include, after heating in the solvent, further heating at a temperature higher than the heating temperature in the solvent. By heating in the solvent, 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 at a temperature higher than the heating temperature in the solvent (hereinafter also referred to as "post-heating").

[0144] Furthermore, the amorphous sulfide solid electrolyte obtained by heating in the above-mentioned solvent may contain residual complexing agents and high-boiling-point solvents. Furthermore, post-heating reduces the content of the complexing agents and high-boiling-point solvents 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 solvent 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.

[0145] The heating temperature is not particularly limited as long as it is a temperature higher than the heating temperature in heating in a solvent. For example, the heating temperature can be determined depending on the structure of the crystalline solid electrolyte obtained by heating an amorphous sulfide solid electrolyte obtained by removing the complexing agent from the electrolyte precursor. Specifically, 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. The heating temperature is preferably set to 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 at the lowest temperature. The upper limit is not particularly limited, but it can 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 content of complexing agent and high-boiling point solvent 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.

[0146] The heating temperature cannot be generally defined because it varies depending on the structure of the crystalline solid electrolyte to be obtained. However, it is generally 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.

[0147] The heating time 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.

[0148] Heating can be carried out at normal pressure, but in order to reduce the heating temperature, it can also be carried out under a reduced pressure atmosphere or even a vacuum atmosphere. When heating is carried out under a reduced pressure atmosphere, the pressure condition 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 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. When the pressure condition is within the above range, the heating condition can be made mild, and the size of the apparatus can be prevented from increasing.

[0149] Furthermore, 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 heating method is not particularly limited, and examples thereof include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, and a baking 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.

[0150] Post-heating can also be carried out in a high-boiling point solvent. The heating temperature in post-heating (crystallization) is higher than the heating temperature in the above-mentioned solvent. Therefore, after removing the complexing agent by heating in the solvent, the pressure can be restored with an inert gas or the like, making it possible to heat in a boiling state at a predetermined temperature. This allows heating in the solvent and crystallization by post-heating to be carried out continuously in the same device, making it a very efficient heating method.

[0151] (Amorphous sulfide solid electrolyte) The sulfide solid electrolyte obtained by the manufacturing method of this embodiment can be either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte, as desired, as described above. 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 ２S-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.

[0152] 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.

[0153] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment is, for example, Li ２ S-P２ 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%.

[0154] 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.

[0155] 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 for removing complexing agents and heating for crystallization, 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.

[0156] (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 structures include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0157] 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 ４Examples 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 ４ This indicates that the thio-LISICON region II type has a similar crystal structure.

[0158] 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.

[0159] 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 ６Diffraction peaks of the crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°. ７ P.S. ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°. ７ P ３ S １１ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ The diffraction peaks of the thio-LISICON Region II crystal structure appear, for example, at 2θ=20.1°, 23.9°, and 29.5°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ Diffraction peaks of a crystal structure similar to that of thio-LISICON Region II type appear, for example, at 2θ=20.2° and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0160] 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°.

[0161] 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°.

[0162] Further heating after the removal reduces the content of the complexing agent in the crystalline sulfide solid electrolyte to be less than the content of the complexing agent in the amorphous sulfide solid electrolyte. The content of the complexing agent 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, or even 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.

[0163] In addition, like the complexing agent, the high-boiling solvent may also remain. In this case, the content of the high-boiling solvent is also in the same range as the content of the complexing agent. In this specification, the contents of the complexing agent and the high-boiling solvent contained in the sulfide solid electrolyte were measured using a gas chromatography (GC) apparatus after dissolving the powder obtained in the examples etc. in a mixed solution of water and pentanol, and the contents of the complexing agent and the high-boiling solvent were quantified using an absolute calibration curve (GC calibration curve method).

[0164] 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.

[0165] The specific surface area of ​​the sulfide solid electrolyte obtained by the production method of this embodiment is usually 10 m ２ / g or more, even 15m ２ / g or more, 20m ２ / g or more, 25m ２ / g or more. There is no particular upper limit. ２ In this specification, the specific surface area is a value measured by the BET method (gas adsorption method), and either nitrogen (nitrogen method) or krypton (krypton method) may be used as the gas, and is measured by appropriately selecting depending on the size of the specific surface area.

[0166] [Sulfide Solid Electrolyte] The sulfide solid electrolyte of the present embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, halogen atoms, a complexing agent, and a solvent having a boiling point higher than that of the complexing agent, and the particle size distribution measured by laser diffraction / scattering particle size distribution measurement has peaks at a peak position of 0.5 μm or less and a peak position of more than 0.5 μm, and the volume fraction of the peak at the peak position of 0.5 μm or less is smaller than the volume fraction of the peak at the peak position of more than 0.5 μm.

[0167] The sulfide solid electrolyte of this embodiment can be produced by the above-described method for producing a sulfide solid electrolyte of this embodiment, and from the viewpoint of more efficient production, it is preferable to produce it by the above-described method for producing a sulfide solid electrolyte of this embodiment. That is, the sulfide solid electrolyte of this embodiment is a sulfide solid electrolyte with improved ionic conductivity.

[0168] The sulfide solid electrolyte of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. These atoms are derived from the solid electrolyte raw material contained in the raw material inclusions used in the production method of this embodiment.

[0169] The sulfide solid electrolyte of this embodiment also contains a complexing agent and a solvent (high-boiling solvent) having a boiling point higher than that of the complexing agent. The complexing agent and high-boiling solvent are used in the manufacturing process and can be said to be characteristics of the sulfide solid electrolyte obtained by the manufacturing method of this embodiment. The complexing agent and the solvent having a boiling point higher than that of the complexing agent are the same as those described in the manufacturing method of this embodiment. The contents of the complexing agent and high-boiling solvent contained in the sulfide solid electrolyte of this embodiment are also as described above.

[0170] (Particle Size Distribution Peak) The sulfide solid electrolyte of this embodiment has the following particle size distribution characteristics: the particle size distribution measured by laser diffraction / scattering particle size distribution measurement has two peaks at 0.5 μm or less and at a peak position exceeding 0.5 μm, and the volume fraction of the peak at 0.5 μm or less is smaller than the volume fraction of the peak at 0.5 μm or less. In this specification, the particle size distribution measured by laser diffraction / scattering particle size distribution measurement is a particle size distribution measured on a volume basis. As described above, such particle size distribution characteristics, i.e., the particle size distribution having two peaks and a large volume fraction of the peak with a smaller particle size, are unique to sulfide solid electrolytes obtained by heating in a high-boiling point solvent to remove the complexing agent, and cannot be observed in sulfide solid electrolytes obtained by a conventional liquid-phase method (heterogeneous method).

[0171] The sulfide solid electrolyte of this embodiment may be either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte. Preferred examples of the amorphous sulfide solid electrolyte and crystalline sulfide solid electrolyte that can be the sulfide solid electrolyte of this embodiment include the amorphous sulfide solid electrolyte and crystalline sulfide solid electrolyte described above as being obtained by the manufacturing method of this embodiment. Crystalline sulfide solid electrolytes that have a thiolicon region II crystal structure or an argyrodite crystal structure can achieve high ionic conductivity.

[0172] The average particle size (D ５０ ) is as described above as the properties of the sulfide solid electrolyte obtained by the production method of this embodiment, and 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. Considering use in a positive electrode, a negative electrode, and an electrolyte layer, the thickness is preferably 0.03 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more, with the upper limit being preferably 5.0 μm or less, more preferably 1.0 μm or less, and even more preferably 0.5 μm or less.

[0173] The specific surface area of ​​the sulfide solid electrolyte of this embodiment is as described above as a property of the sulfide solid electrolyte obtained by the production method of this embodiment.

[0174] (Applications) The sulfide solid electrolyte 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 produced by a known method.

[0175] 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.

[0176] [Electrode Mixture] The electrode mix using the sulfide solid electrolyte of this embodiment is an electrode mix containing the sulfide solid electrolyte of this embodiment and an electrode active material.

[0177] (Electrode Active Material) As the electrode active material, a positive electrode active material or a negative electrode active material is adopted depending on whether the electrode mixture is used for a positive electrode or a negative electrode.

[0178] The positive electrode active material can be any material that can promote a battery chemical reaction involving the movement of lithium ions due to atoms that are used to exhibit ionic conductivity, preferably lithium atoms, in relation to the negative electrode active material. Examples of such positive electrode active materials that can insert and extract lithium ions include oxide-based positive electrode active materials and sulfide-based positive electrode active materials.

[0179] Oxide-based positive electrode active materials include LMO (lithium manganese oxide), LCO (lithium cobalt oxide), NMC (lithium nickel manganese cobalt oxide), NCA (lithium nickel cobalt aluminate), LNCO (lithium nickel cobalt oxide), and olivine-type compounds (LiMeNPO ４ , Me=Fe, Co, Ni, Mn) and other lithium-containing transition metal composite oxides are preferred. Examples of sulfide-based positive electrode active materials include titanium sulfide (TiS ２ ), molybdenum sulfide (MoS ２ ), iron sulfide (FeS, FeS ２ ), copper sulfide (CuS), nickel sulfide (Ni ３ S ２ In addition to the above positive electrode active materials, niobium selenide (NbSe) ３ The positive electrode active material may be used alone or in combination of two or more.

[0180] The negative electrode active material can be any atom that exhibits ionic conductivity, preferably a metal capable of forming an alloy with lithium atoms, its oxide, or an alloy of the metal with lithium atoms, as long as it can promote a battery chemical reaction involving the migration of lithium ions due to lithium atoms. As such a negative electrode active material capable of inserting and extracting lithium ions, any material known in the battery field as a negative electrode active material can be used without limitation. Examples of such a negative electrode active material include metals that can form alloys with metallic lithium or metallic lithium, such as metallic lithium, metallic indium, metallic aluminum, metallic silicon, and metallic tin, oxides of these metals, and alloys of these metals with metallic lithium.

[0181] The electrode active material may have a coating layer on its surface. Examples of materials for forming the coating layer include ion conductors such as nitrides, oxides, or composites of atoms that exhibit ionic conductivity in the sulfide solid electrolyte, preferably lithium atoms. Specifically, lithium nitride (Li ３ N), Li ４ GeO ４ The main structure is, for example, Li ４－２ｘ Zn ｘ GeO ４ Conductors having a lysicone-type crystal structure such as Li ３ P.O. ４ For example, Li ４－ｘ Ge １－ｘ P ｘ S ４ Conductors having a thiolicon-type crystal structure such as La ２／３－ｘ Li ３ｘ TiO ３ Conductors having a perovskite crystal structure such as LiTi ２ (P.O. ４ ) ３ Conductors having a NASICON type crystal structure such as Li ｙ Ti ３－ｙ O ４ (0<y<3), Li ４ Ti ５ O １２Lithium titanate (LTO), LiNbO ３ , LiTaO ３ Lithium metal oxides of metals belonging to Group 5 of the periodic table, such as Li ２ Alumni ２ O ３ -P ２ O ５ system, Li ２ Alumni ２ O ３ -ZnO-based, Li ２ O-Al ２ O ３ -SiO ２ -P ２ O ５ -TiO ２ Examples of suitable conductors include oxide-based conductors such as those based on ZnO.

[0182] An electrode active material having a coating layer can be obtained, for example, by applying a solution containing various atoms constituting the material forming the coating layer to the surface of the electrode active material and then baking the electrode active material after application, preferably at 200°C to 400°C. Here, the solution containing various atoms may be, for example, a solution containing alkoxides of various metals such as lithium ethoxide, titanium isopropoxide, niobium isopropoxide, or tantalum isopropoxide. In this case, the solvent may be an alcoholic solvent such as ethanol or butanol; an aliphatic hydrocarbon solvent such as hexane, heptane, or octane; or an aromatic hydrocarbon solvent such as benzene, toluene, or xylene. The application may be performed by immersion, spray coating, or the like.

[0183] From the viewpoint of improving production efficiency and battery performance, the firing temperature is preferably 200°C or higher and 400°C or lower, more preferably 250°C or higher and 390°C or lower, and the firing time is usually about 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0184] The coverage of the coating layer is preferably 90% or more, more preferably 95% or more, and even more preferably 100% based on the surface area of ​​the electrode active material, i.e., the entire surface is preferably covered. The thickness of the coating layer is preferably 1 nm or more, more preferably 2 nm or more, and the upper limit is preferably 30 nm or less, more preferably 25 nm or less. The thickness of the coating layer can be measured by cross-sectional observation using a transmission electron microscope (TEM), and the coverage can be calculated from the thickness of the coating layer, elemental analysis value, and BET specific surface area.

[0185] (Other Components) The electrode mixture using the sulfide solid electrolyte of this embodiment may contain other components such as a conductive material, a binder, etc. in addition to the sulfide solid electrolyte and electrode active material. That is, the manufacturing method of the electrode mixture of this embodiment may use other components such as a conductive material, a binder, etc. in addition to the sulfide solid electrolyte and electrode active material. When mixing the sulfide solid electrolyte and the electrode active material, the other components such as a conductive material, a binder, etc. may be added to and mixed with the sulfide solid electrolyte and the electrode active material. From the viewpoint of improving battery performance by improving electronic conductivity, examples of the conductive material include carbon-based materials such as artificial graphite, graphite carbon fiber, resin-calcined carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads, furfuryl alcohol resin-calcined carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon.

[0186] The use of a binder improves the strength of the produced positive and negative electrodes. The binder is not particularly limited as long as it can impart functions such as binding property and flexibility, and examples thereof include fluorine-based polymers such as polytetrafluoroethylene and polyvinylidene fluoride, thermoplastic elastomers such as butylene rubber and styrene-butadiene rubber, acrylic resins, acrylic polyol resins, polyvinyl acetal resins, polyvinyl butyral resins, and silicone resins.

[0187] The compounding ratio (mass ratio) of the electrode active material to the sulfide solid electrolyte in the electrode mixture is preferably 99.5:0.5 to 40:60, more preferably 99:1 to 50:50, and even more preferably 98:2 to 60:40, in order to improve battery performance and in consideration of production efficiency.

[0188] When a conductive material is contained, the content of the conductive material in the electrode mixture is not particularly limited, but in consideration of improving battery performance and manufacturing efficiency, it is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, with the upper limit being preferably 10% by mass or less, preferably 8% by mass or less, and even more preferably 5% by mass or less. Furthermore, when a binder is contained, the content of the binder in the electrode mixture is not particularly limited, but in consideration of improving battery performance and manufacturing efficiency, it is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, with the upper limit being preferably 20% by mass or less, preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0189] [Lithium-ion battery] The lithium-ion battery using the sulfide solid electrolyte of this embodiment is a lithium-ion battery including at least one selected from the sulfide solid electrolyte of this embodiment and the electrode mixture.

[0190] The lithium ion battery using the sulfide solid electrolyte of this embodiment is not particularly limited in its configuration as long as it contains the sulfide solid electrolyte of this embodiment and an electrode composite containing the sulfide solid electrolyte, and may have the configuration of a commonly used lithium ion battery.

[0191] A lithium ion battery using the sulfide solid electrolyte of this embodiment preferably includes, for example, a positive electrode layer, a negative electrode layer, an electrolyte layer, and a current collector. The positive electrode layer and the negative electrode layer preferably use an electrode mixture using the sulfide solid electrolyte of this embodiment, and the electrolyte layer preferably uses the sulfide solid electrolyte of this embodiment.

[0192] The current collector may be a known material, for example, a layer of Au or the like coated with a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu.

[0193] 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.

[0194] (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

[0195] (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

[0196] (Measurement of Specific Surface Area) The specific surface area was measured by the BET method using nitrogen adsorption using a gas adsorption amount measuring device.

[0197] (Measurement of the Content of Complexing Agent and Solvent in Sulfide Solid Electrolyte) The contents of complexing agent and solvent in the sulfide solid electrolyte were measured using a gas chromatograph (GC). The measurement outline involved measuring powder of sulfide solid electrolyte, etc., decomposed in a mixture of water and pentanol (pentanol content in the mixture: 90% by volume) using GC, and quantifying the complexing agent and solvent using an absolute calibration curve. First, 0.1 g of sample was precisely weighed and placed in a vial. 10 ml of a mixture of water and pentanol 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, 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 solvent to be used and adjusting the volume to 50 ml of a mixture of water and pentanol (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 and solvent 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).

[0198] (Measurement of particle size distribution) Measurement was performed using a laser diffraction / scattering particle size distribution analyzer ("Partica LA-950 (model number)" manufactured by Horiba, Ltd.). Specifically, a mixture of dehydrated toluene (manufactured by Wako Pure Chemical Industries, special grade) and tertiary butyl alcohol (manufactured by Wako Pure Chemical Industries, special grade) in a mass ratio of 93.8:6.2 was used as the dispersion medium. 50 mL of the dispersion medium was injected into the flow cell of the device and circulated, and then the powder to be measured was added and subjected to ultrasonic treatment, after which the particle size distribution was measured. In addition, the average particle size (D ５０ ) was the particle size at which the particle size distribution reached 50% (volume basis) of the total when the particle size distribution curve was drawn and the particle size was accumulated in order from the smallest particle size.

[0199] (Measurement of Complex Weight Ratio) The complex weight ratio was measured from the weight loss rate using a thermogravimetric analyzer (TG apparatus). The powders (samples) to be measured in each of the Examples and Comparative Examples were subjected to vacuum drying at 80°C for 1 hour as a pretreatment for removing the solvent. After the pretreatment, 20 mg of the sample was heated from room temperature (23°C) to 600°C at a rate of 10°C / min under a nitrogen stream. The value calculated from the weight change before and after the treatment using the following formula was taken as the complex weight ratio in the powder. Complex weight ratio (wt%) = (weight before heating - weight after heating) / weight before heating x 100

[0200] Example 1: 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 were introduced into a 1-liter reactor equipped with an agitator under a nitrogen atmosphere. 100 mL of tetramethylethylenediamine (TMEDA, boiling point: 120°C) as a complexing agent and 800 mL of cyclohexane as a solvent were added, and the agitator was operated to mix the mixture at 30°C for 72 hours by stirring. 456 g of zirconia balls (diameter: 0.5 mmφ) (bead filling rate relative to the milling chamber: 80%) were placed in a circulating bead mill ("Labostar Mini LMZ015 (trade name)" manufactured by Ashizawa Finetech Co., Ltd.). Pulverization was performed for 60 minutes while circulating between the reactor and the milling chamber under the following conditions: pump flow rate: 550 mL / min, peripheral speed: 8 m / s, mill jacket temperature: 20°C, to obtain a slurry of an electrolyte precursor (complex). The resulting slurry was then immediately dried under vacuum at room temperature (23°C) to obtain a powder of the electrolyte precursor (complex). The complex weight ratio of the resulting powder was measured by the above-mentioned method and found to be 53 wt%.

[0201] The resulting electrolyte precursor powder was subjected to vacuum drying at 70°C for 5 hours in a vibration dryer (manufactured by Chuo Kakoki Co., Ltd.) to perform constant-rate drying. The complex weight ratio of the resulting powder was measured using the above-mentioned method and found to be 22 wt%. 3.5 g of this powder was mixed with 225 mL of normal decane (boiling point: 174°C) to prepare a normal decane slurry of the electrolyte precursor. Next, 200 mL of normal decane (boiling point: 174°C) was placed in a 500 mL flask equipped with a thermometer and a stirrer. The flask was then evacuated using a vacuum pump and a pressure reduction controller, and the mixture was immersed in an oil bath and heated to a boiling state at 100°C and 8 kPa. The normal decane slurry of the electrolyte precursor was then gradually added to the flask to maintain a constant liquid level in the flask. Further, normal decane was gradually added and maintained in this state for 1 hour, followed by heating to 110°C (the pressure inside the flask was 13 kPa, and normal decane was boiling). This state was maintained for 1 hour, and falling-rate drying was performed to remove the complexing agent. During this process, the high-boiling point solvent and complexing agent that had evaporated in the flask were cooled and recovered using a circulating cooler. After the complexing agent was removed, the temperature inside the flask was increased from 110°C to 160°C at a heating rate of 20°C / hour (the pressure inside the flask was gradually restored to 68 kPa with nitrogen), and crystallization was performed. As with the falling-rate drying, normal decane was supplied to the flask as needed to maintain a constant liquid level in the flask. The normal decane was then dried under vacuum at 90°C for 1 hour, and the complex weight ratio of the resulting powder was measured using the method described above, resulting in a value of 4 wt%.

[0202] XRD measurement was performed on the powder obtained after crystallization. Crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the product was a crystalline sulfide solid electrolyte with a thiolicon region II crystal structure. The results are shown in Figure 1. The ionic conductivity was measured to be 2.4 (mS / cm), and the specific surface area was 31 (m ２ / g). The contents of the complexing agent and decane contained in the crystalline sulfide solid electrolyte were 0.8 mass% and 0.03 mass%, respectively. The crystalline sulfide solid electrolyte after crystallization was observed using a scanning electron microscope (SEM). A photograph taken with a scanning electron microscope (SEM) is shown in Figure 2.

[0203] XRD measurements were also performed on the powder before removal of the complexing agent (electrolyte precursor powder) and the powder after constant-rate drying for complexing agent removal. The X-ray diffraction spectrum of the powder obtained after constant-rate drying for complexing agent removal showed no peaks derived from the electrolyte precursor powder or raw materials, and showed a halo pattern, confirming that it was an amorphous sulfide solid electrolyte. The results of XRD measurements of the electrolyte precursor powder and the powder after constant-rate drying are shown in Figure 1. The results of XRD measurements of the powder before removal of the complexing agent (electrolyte precursor powder) are also shown in Figure 3, and the results of XRD measurements of the crystalline sulfide solid electrolyte are also shown in Figures 4 and 5.

[0204] Example 2 As in Example 1, normal decane was heated to 90°C in a flask (the pressure was 5 kPa, and the normal decane was boiling). Subsequently, normal decane slurry was gradually added, and this state was maintained for 1 hour. Subsequently, the normal decane was heated to 110°C (the pressure inside the flask was restored to 13 kPa, and the normal decane was boiling). This state was maintained for 1 hour, and then falling-rate drying was performed to remove the complexing agent. During this process, the high-boiling-point solvent and complexing agent that had evaporated in the flask were cooled and recovered using a circulating cooler. Furthermore, normal decane was supplied to the flask as needed to maintain a constant liquid level in the flask. After the complexing agent was removed, the normal decane was dried under vacuum at 90°C for 1 hour. The complex weight ratio of the resulting powder was measured using the method described above, and was found to be 12 wt%. Furthermore, the powder after removing the complexing agent was transferred to a Lab Schlenk and heated at 160 ° C for 2 hours (under a vacuum atmosphere) while evacuating with a vacuum pump to crystallize, resulting in a crystalline sulfide solid electrolyte powder. XRD measurement of the resulting crystalline sulfide solid electrolyte powder was performed, and crystallization peaks were detected mainly at 2θ = 20.2 ° and 23.6 ° in the X-ray diffraction spectrum, confirming that the resulting crystalline sulfide solid electrolyte had a thiolicon region II crystal structure. The results are shown in Figure 4. XRD measurement of the powder after falling-rate drying was also performed. The results are shown in Figure 4.

[0205] Example 3: In Example 2, constant-rate drying was performed using an electrolyte precursor (complex) powder (complex weight ratio: 53 wt %) by heating to 80°C (pressure was 4 kPa, and normal decane was boiling), and this state was maintained for 1 hour. Subsequently, the process up to falling-rate drying was performed in the same manner as in Example 2. The normal decane was then dried under vacuum conditions at 90°C for 1 hour, and the complex weight ratio of the obtained powder was measured using the above-mentioned method, which was 8.5 wt %. Furthermore, the obtained powder was transferred to a Lab Schlenk and heated at 110°C for 2 hours while evacuating with a vacuum pump (under a vacuum atmosphere), to obtain a powder. The complex weight ratio of the obtained powder was measured using the above-mentioned method, which was 6.4 wt %. Furthermore, XRD measurement was performed on the powder obtained by heating. Crystallization peaks due to the thiolisiconregion II crystal structure were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, but slight peaks were detected at these angles. However, the product was confirmed to be an amorphous sulfide solid electrolyte with a halo pattern. These results are shown in Figure 5. XRD measurement was also performed on the powder after falling-rate drying. The results are shown in Figure 5.

[0206] Example 4 The powder obtained by removing the complexing agent in Example 3 was transferred to a Lab Schlenk tube and heated at 160°C for 2 hours (under a vacuum atmosphere) while evacuating with a vacuum pump to crystallize the powder. The complex weight ratio of the obtained powder was measured using the method described above and found to be 2.3% by weight. Furthermore, XRD measurement revealed that crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the resulting powder was a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure. The results are shown in Figure 5.

[0207] The ionic conductivity of the resulting crystalline sulfide solid electrolyte was measured and found to be 1.5 (mS / cm). The contents of the complexing agent and decane contained in the crystalline sulfide solid electrolyte were 0.8% by mass and 0.03% by mass, respectively.

[0208] Comparative Example 1: An electrolyte precursor powder (complex weight ratio: 53 wt %) was obtained in the same manner as in Example 1. The obtained powder was mixed with 225 mL of heptane (boiling point: 98°C) to prepare a heptane slurry of the electrolyte precursor. Next, 200 mL of heptane (boiling point: 98°C) was placed in a 500 mL flask equipped with a thermometer and a stirrer, and the mixture was brought to a boil at 80°C under 57 kPa. While further heating, the heptane slurry of the electrolyte precursor was gradually added to the flask, the pressure was returned to normal pressure, and the temperature was raised to 100°C (the heptane reached a boiling state). This state was maintained for 2 hours to remove the complexing agent. The solvent and complexing agent evaporated in the flask were cooled and recovered using a circulating cooler. Furthermore, to maintain a constant liquid level in the flask, heptane was supplied to the flask as needed, and constant-rate drying was performed to remove the complexing agent. The heptane was then dried under vacuum at 80°C for 1 hour, and the complex weight ratio of the resulting powder was measured using the method described above, resulting in a value of 22% by weight. The resulting powder was transferred to a Lab Schlenk tube and heated at 110°C for 2 hours while being evacuated with a vacuum pump (under a vacuum atmosphere), resulting in falling-rate drying, yielding a powder. XRD measurements were performed on the powder after constant-rate drying and the powder after falling-rate drying, confirming peaks due to various impurities. These results are shown in Figure 3.

[0209] (Comparative Example 2) The powder obtained in Comparative Example 1 was further crystallized by heating at 160°C for 2 hours in a Lab Schlenk flask while evacuating with a vacuum pump (under a vacuum atmosphere) to obtain a powder. When the powder obtained by crystallization was subjected to XRD measurement, slight crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, which could be said to have a thiolicon region II crystal structure, but peaks due to various impurities were also confirmed. The results are shown in Figure 3.

[0210] Comparative Example 3: An electrolyte precursor (complex) powder was obtained in the same manner as in Example 1. The complex weight ratio of the obtained powder was measured using the method described above and found to be 53% by weight. The obtained powder was further dried at 110°C under reduced pressure for 6 hours, and then crystallized by heating at 160°C under reduced pressure for 2 hours to obtain a crystalline powder. The obtained crystalline powder was observed using a scanning electron microscope (SEM). A photograph taken with the scanning electron microscope (SEM) is shown in FIG. 6.

[0211] (Comparative Example 4) 100 g of the crystalline powder obtained in Comparative Example 3 was introduced into a 3-liter reactor equipped with an agitator blade, and 2144 mL of heptane and 138 mL of diisopropyl ether (DiPE) were added and stirred for 10 minutes to obtain a slurry. The obtained slurry was subjected to a 3-pass crushing process using a microbead mill ("MAX Nano Getter (trade name)", manufactured by Ashizawa Finetech Co., Ltd.) capable of circulating operation under specified conditions (bead diameter: 0.05 mmφ, bead usage: 1573 g (bead filling amount relative to the crushing chamber: 65%), pump flow rate: 1000 mL / min, peripheral speed 6 m / s). Furthermore, the slurry crushed by the microbead mill was dried under vacuum at room temperature (23 ° C.) to obtain a crushed powder.

[0212] The particle size distributions of the crystalline sulfide solid electrolyte powders obtained in Examples 1 and 2, the crystallized powder obtained in Comparative Example 3, and the powder obtained in Comparative Example 4 were measured by the above-described method. The measurement results are shown in FIG.

[0213] According to the results of Figure 7, the powders of Examples 1 and 2 have peaks at a peak position of 0.5 μm or less and a peak position greater than 0.5 μm, and it was confirmed that the volume fraction of the peak at the peak position of 0.5 μm or less is smaller than the volume fraction of the peak at the peak position greater than 0.5 μm. On the other hand, the powder after crystallization of Comparative Example 3 has two peaks like the powder of Example 1, but it was confirmed that the volume fraction of the peak at the peak position of 0.5 μm or less is larger than the volume fraction of the peak at the peak position greater than 0.5 μm. Furthermore, from the results of Figure 7, it was also confirmed that the shape of the peak at the peak position of 0.5 μm or less is sharper than the shape of the peak at the peak position greater than 0.5 μm, and the half-width of the peak at the peak position of 0.5 μm or less is smaller than the half-width of the peak at the peak position greater than 0.5 μm.

[0214] 7, it was confirmed that the powder of Comparative Example 4 obtained by pulverizing (atomizing) the powder of Comparative Example 3 had the same particle size distribution as the powders of Examples 1 and 2. This shows that the powder of Example 1 has a particle size distribution that could not be obtained without pulverizing (atomizing) by the conventional liquid phase method (heterogeneous method), even without pulverizing (atomizing).

[0215] Furthermore, from the above particle size distribution measurement, the average particle size (D ５０ ) were 0.15 μm and 0.12 μm, respectively, and the average particle diameter (D ５０ ) was 3.0 μm, and the average particle size (D ５０ The average particle size (D ５０ ) is the average particle size (D ５０ ), this is supported by the fact that the crystalline sulfide solid electrolyte obtained in Example 1 hardly agglomerated ( FIG. 2 ), and that the crystallized powder of Comparative Example 3 agglomerated a lot, resulting in the generation of secondary particles ( FIG. 6 ).

[0216] Example 5: An electrolyte precursor (complex) powder (complex weight ratio was 53 wt %) was obtained in the same manner as in Example 1. 3.5 g of the obtained electrolyte precursor (powder) was mixed with 225 mL of normal decane (boiling point: 174°C) to prepare a normal decane slurry of the electrolyte precursor. Normal decane was heated to 80°C in a flask (pressure was 4 kPa, and the normal decane reached a boiling state), and then the normal decane slurry was gradually added. This state was maintained for 1 hour, and constant-rate drying was performed. During this process, the high-boiling-point solvent and complexing agent that had evaporated in the flask were cooled and recovered using a circulating cooler. Furthermore, normal decane was supplied to the flask as needed to maintain a constant liquid level in the flask, and this state was maintained to obtain a slurry. Next, the obtained slurry was collected, and normal decane was heated to 110°C in a flask (the pressure was 13 kPa, and the normal decane was boiling), and then the slurry was gradually added and held for 1 hour, thereby performing falling-rate drying. Note that the liquid level in the flask was also kept constant during the drying process.

[0217] Furthermore, this slurry was recovered, and normal decane was heated to 160°C in a flask (the pressure was 68 kPa, and normal decane was boiling), and then this slurry was gradually added and maintained for 1 hour, thereby causing crystallization. Note that the liquid level in the flask was also kept constant during the experiment. Thereafter, the normal decane was dried under vacuum conditions at 90°C for 1 hour, and the complex weight ratio of the obtained powder was measured by the above-mentioned method, which was found to be 2.7 wt%.

[0218] XRD measurement of the powder obtained after crystallization revealed that crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the resulting electrolyte was a crystalline sulfide solid electrolyte having a thiolicon region II crystal structure. The results are shown in Figure 8. The ionic conductivity was measured and found to be 1.3 (mS / cm).

[0219] According to the method for producing a sulfide solid electrolyte of this embodiment, a sulfide solid electrolyte with high ionic conductivity can be efficiently produced. Furthermore, the amount of complexing agent that can be removed can be increased simply by increasing the amount of high-boiling-point solvent used, making it easy to adapt to mass production. 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. mixing a raw material containing a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom with a complexing agent to obtain an electrolyte precursor containing material; then heating in a solvent having a boiling point higher than that of the complexing agent; A method for producing a sulfide solid electrolyte, comprising:

2. The method for producing a sulfide solid electrolyte according to claim 1 , wherein the heating temperature of the solvent is higher than the boiling point of the complexing agent.

3. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heating in the solvent causes the solvent to boil.

4. 4. The method for producing a sulfide solid electrolyte according to claim 3, wherein a solvent having a boiling point higher than a boiling point of the complexing agent is separately prepared, and the electrolyte precursor-containing material is mixed with the separately prepared solvent to form a mixture, which is then added to the solvent used for heating.

5. 3. The method for producing a sulfide solid electrolyte according to claim 1, wherein an amount of the solvent used per 1 g of the supplied amount of the electrolyte precursor contained in the electrolyte precursor-containing material is 20 mL or more and 2000 mL or less.

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

7. The method for producing a sulfide solid electrolyte according to claim 6, wherein the drying is carried out at a temperature of 5°C or higher and 110°C or lower under normal pressure or reduced pressure.

8. 3. The method for producing a sulfide solid electrolyte according to claim 1, further comprising, after heating in the solvent, further heating at a temperature higher than the heating temperature in the solvent.

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

11. 3. The method for producing a sulfide solid electrolyte according to claim 1, wherein the solvent is a hydrocarbon solvent containing no heteroatoms.

12. 3. The method for producing a sulfide solid electrolyte according to claim 1, wherein the solvent is at least one organic solvent selected from aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents.

13. The method for producing a sulfide solid electrolyte according to claim 12, wherein the organic solvent has 8 or more carbon atoms.

14. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein after heating in the solvent, no pulverization treatment is performed.

15. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein a complexing agent is removed from the electrolyte precursor contained in the electrolyte precursor-containing material by heating in the solvent.

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