Method for producing sulfide solid electrolyte

Abstract

Provided is a method for producing a sulfide solid electrolyte which is capable of more efficiently producing a sulfide solid electrolyte that has a higher ion conductivity, and which can be easily suited to mass production, the method comprising: obtaining an electrolyte precursor by mixing a starting material-containing material and a complexing agent; heating the electrolyte precursor with use of a flow through heater so as to obtain a powder; transferring the powder from the flow through heater to a separation device through a transfer pipe; and collecting the transferred powder by means of the separation device. The method for producing a sulfide solid electrolyte includes heating the transfer pipe during the transfer.

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 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, development is being carried out on batteries in which the electrolyte is replaced with a solid electrolyte layer, so-called all-solid-state batteries.

[0003] Methods for producing solid electrolytes used in solid electrolyte layers are broadly divided into solid-phase methods and liquid-phase methods. Liquid-phase methods include homogeneous methods, in which the solid electrolyte material is completely dissolved in a solvent, and heterogeneous methods, in which the solid electrolyte material is not completely dissolved but is instead a solid-liquid coexistence suspension. In recent years, studies on mass production of solid electrolytes have been progressing, and liquid-phase methods using complexing agents have attracted attention as a method that is easily adaptable to scale-up. For example, a solid production method is known that uses a specific compound having an amino group as a complexing agent and mixes the complexing agent with a solid electrolyte raw material to prepare an electrolyte precursor (see, for example, Patent Document 1), and a solid electrolyte production method is known that includes drying a slurry containing the complexing agent and the electrolyte precursor by fluidized drying using media particles (see, for example, Patent Document 2).

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

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

[0006] The method for producing a sulfide solid electrolyte according to the present invention includes: mixing a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with a complexing agent to obtain an electrolyte precursor; heating the electrolyte precursor using a flow-through heater to obtain a powder; transferring the powder from the flow-through heater to a separation device through a transfer pipe; and collecting the transferred powder with the separation device, wherein the transferring step includes heating the transfer pipe.

[0007] According to the present invention, it is possible to more efficiently produce a sulfide solid electrolyte having high ionic conductivity, and it is also possible to provide a method for producing a sulfide solid electrolyte that is easily adaptable to mass production.

[0008] 1 is a flow diagram of an apparatus equipped with a flash dryer and a bag filter used in Example 1. 2 is an X-ray diffraction spectrum of the crystalline sulfide solid electrolyte obtained in Examples 1 to 3. 3 is an X-ray diffraction spectrum of the crystalline sulfide solid electrolyte obtained in Comparative Examples 1 to 3.

[0009] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. In this specification, the upper and lower limit values ​​of a numerical range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​of the examples can also be used as the upper and lower limit values. Furthermore, preferred specifications can be arbitrarily adopted. In other words, one preferred specification can be adopted in combination with one or more other preferred specifications. It can be said that a combination of preferred items is more preferable.

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

[0011] In recent years, as research into the practical application of all-solid-state batteries has progressed, mass production of sulfide solid electrolytes has become an urgent issue, and studies on improving production efficiency have been ongoing. The inventors have focused on the development of liquid-phase methods, which are relatively easy to scale up, particularly heterogeneous methods that use complexing agents during the reaction of solid electrolyte raw materials. During the development, it has been discovered that when performing decomplexation to remove the complexing agent from an electrolyte precursor obtained by mixing the solid electrolyte raw material with the complexing agent, performing the decomposition at higher temperatures leads to improved efficiency. On the other hand, separation devices such as bag filters are used to collect the powdered solid electrolyte obtained by the decomposition. However, separation devices such as bag filters have an upper limit on their operating temperature due to material constraints. Therefore, it has been found that there are limitations on increasing the decomposition temperature.

[0012] Therefore, the inventors focused on the temperature of a fluid containing a solid electrolyte from a heating device, such as a dryer, used for complex decomposition to a separation device. The fluid containing a solid electrolyte contains an amorphous sulfide solid electrolyte, but may contain an amorphous sulfide solid electrolyte with a remaining complexing agent (which may be said to be in a state where complex decomposition is in progress), or an electrolyte precursor. The temperature of the fluid containing a solid electrolyte was lowered in the transfer piping from the heating device for complex decomposition to the separation device, but the inventors found that by maintaining this temperature, complex decomposition further progressed and solid electrolyte was produced more efficiently.

[0013] The above-mentioned Patent Document 1 focuses on the complexing agent used to form an electrolyte precursor, focusing on the fact that the elution of halogen atoms can be suppressed, thereby attempting to obtain a sulfide solid electrolyte with high ionic conductivity. Furthermore, the above-mentioned Patent Document 2 focuses on the fact that a slurry containing a complexing agent and an electrolyte precursor is instantaneously dried by fluidized drying using media particles, thereby suppressing a degradation reaction in which components that are easily eluted from the solid electrolyte or electrolyte precursor into the solvent, thereby attempting to obtain a solid electrolyte with high ionic conductivity. However, neither Patent Document 1 focuses on the temperature from the time of decomplexation to remove the complexing agent from the electrolyte precursor to the separation device that collects the powdered solid electrolyte, nor does it focus on maintaining that temperature to promote decomplexation and more efficiently produce a solid electrolyte.

[0014] Based on the above findings, the inventors continued their development and found that a simple method of carrying out decomplexation to remove the complexing agent from the electrolyte precursor and then maintaining the temperature up to a separation device for collecting the powdered solid electrolyte allows the decomplexation to proceed, thereby enabling more efficient production of a solid electrolyte. Furthermore, since the production method of the present invention employs a reaction between the raw material ingredients and the complexing agent (liquid-phase method) and heating using a flow-through heater, it is easy to scale up and can be easily adapted to mass production.

[0015] (Regarding various aspects of the present embodiment) A method for producing a sulfide solid electrolyte according to a first aspect of the present 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; heating the electrolyte precursor using a flow-through heater to obtain a powder; transferring the powder from the flow-through heater to a separation device through a transfer pipe; and collecting the transferred powder with the separation device, wherein the transferring step includes heating the transfer pipe.

[0016] In the method for producing a sulfide solid electrolyte of this embodiment, the electrolyte precursor obtained by mixing a solid electrolyte raw material and a complexing agent contains the complexing agent, and a sulfide solid electrolyte powder is obtained by removing the complexing agent from the electrolyte precursor. Decomplexation to remove the complexing agent from the electrolyte precursor is performed using a flow-through heater. Furthermore, the electrolyte precursor obtained by the above mixing may contain, together with the electrolyte precursor, the complexing agent and solid electrolyte raw material that did not contribute to the formation of the electrolyte precursor, as well as a solvent used as needed. In the method for producing a sulfide solid electrolyte of this embodiment, heating in a heated air flow not only removes the complexing agent from the electrolyte precursor, but also removes any remaining complexing agent and solvent that did not contribute to the formation of the electrolyte precursor.

[0017] 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.

[0018] The manufacturing method of this embodiment includes obtaining an electrolyte precursor, followed by heating using a flow-through heater to obtain a powder. The object to be heated in the heating step is the electrolyte precursor. As described above, the electrolyte precursor may be a substance containing a complexing agent that did not contribute to the formation of the electrolyte precursor, an optional solvent, etc. Furthermore, when the electrolyte precursor is a substance containing a complexing agent and a solvent, etc., obtained by the above mixing and then dried as described below, the electrolyte precursor becomes a powder (hereinafter, in this specification, the electrolyte precursor, as well as the substance containing a complexing agent that did not contribute to the formation of the electrolyte precursor, an optional solvent, etc., may be collectively referred to as the "object to be heated").

[0019] When heating the electrolyte precursor to remove the complexing agent from the electrolyte precursor, it is essential to heat the electrolyte precursor using a flow-type heater. Heating using a flow-type heater has the functions of drying by temperature (heat) and flow, and dispersing the heated object and removing the complexing agent by flow. These functions are thought to enable efficient removal of the complexing agent from the electrolyte precursor. By heating the heated object while flowing, i.e., by heating while moving, the heated object is dispersed within the heater, allowing the complexing agent contained in the electrolyte precursor to be efficiently heated. Furthermore, by flowing the heated object, the complexing agent can be quickly separated and removed. Furthermore, regeneration of a complex between the electrolyte precursor from which the complexing agent has been removed and the complexing agent (hereinafter also simply referred to as "complex regeneration") and generation of impurities between the electrolyte precursor and the complexing agent (hereinafter also simply referred to as "impurity generation") are suppressed, resulting in a sulfide solid electrolyte with few impurities and high quality and high ionic conductivity.

[0020] As described above, to efficiently carry out the complexation, it is preferable to carry out the complexation at as high a temperature as possible. However, due to material limitations of the separation device used to recover the powder obtained by heating, there is a constraint that the temperature cannot be sufficiently increased, and it has been found that there is room for improvement in terms of further promoting the complexation. Therefore, focusing on the fact that the temperature of the fluid containing the solid electrolyte discharged from the flow-type heater decreases in the transfer pipe that transfers the fluid to the separation device, the transfer pipe was heated to suppress the decrease in the temperature of the fluid. As a result, the complexation of the electrolyte precursor remaining in the fluid, from which the complexing agent was not removed by heating in the flow-type heater, and the complexation of the amorphous sulfide solid electrolyte containing the complexing agent further progressed, resulting in more efficient production of the solid electrolyte. Thus, the production method of this embodiment makes it possible to more efficiently produce a sulfide solid electrolyte with high ionic conductivity.

[0021] A method for producing a sulfide solid electrolyte according to a second aspect of the present embodiment is the same as the first aspect, except that the heating temperature of the transfer pipe is 80°C or higher and 180°C or lower. A method for producing a sulfide solid electrolyte according to a third aspect of the present embodiment is the same as the first or second aspect, except that the heating temperature in obtaining the powder is 80°C or higher and 180°C or lower.

[0022] By setting the heating temperature of the transfer piping to 80° C. or higher and 180° C. or lower, it is possible to efficiently suppress a decrease in the temperature of the solid electrolyte-containing fluid in the transfer piping, and more efficiently obtain a sulfide solid electrolyte having high ionic conductivity. Furthermore, by setting the heating temperature for obtaining the powder, i.e., the heating temperature in the flow-through heater, to 80° C. or higher and 180° C. or lower, it is possible to more efficiently proceed with complex decomposition in the flow-through heater.

[0023] A fourth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to third aspects, wherein the flow-type heater is a heater selected from a flash dryer, a spray dryer, and a fluidized bed dryer. A fifth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the fourth aspect, wherein the flow-type heater is a flash dryer.

[0024] In the production method of this embodiment, the type of flow-type heater is not particularly limited, but by employing a heater of a type known as a flash dryer, a spray dryer, or a fluidized bed dryer, it is possible to more efficiently proceed with decomposition, and as a result, a sulfide solid electrolyte having high ionic conductivity can be more efficiently obtained. Furthermore, among these dryers, a flash dryer is most preferable in that it more efficiently proceeds with decomposition, thereby more efficiently obtaining a sulfide solid electrolyte having high ionic conductivity.

[0025] A sixth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to fifth aspects, further comprising heating the powder collected by the collection.

[0026] By heating with the flow-through heater, the complexing agent is removed from the electrolyte precursor, and an amorphous sulfide solid electrolyte is obtained. That is, the powder collected by collection can be said to be an amorphous sulfide solid electrolyte. By further heating this, in addition to heating with the flow-through heater, a crystalline sulfide solid electrolyte is obtained. With the production method of this embodiment, it is possible to produce an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte as desired.

[0027] (Solid Electrolyte) In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state under a nitrogen atmosphere at 25° C. The sulfide solid electrolyte in this embodiment is a solid electrolyte that contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms and has ionic conductivity due to the lithium atoms.

[0028] 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.

[0029] [Method for Producing Sulfide Solid Electrolyte] The method for producing a sulfide solid electrolyte of the present 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; heating the electrolyte precursor using a flow-through heater to obtain a powder; transferring the powder from the flow-through heater to a separator through a transfer pipe; and collecting the transferred powder using the separator, wherein the transfer pipe is heated.

[0030] [Obtaining an Electrolyte Precursor] The manufacturing method of this embodiment includes mixing a raw material content containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with a complexing agent to obtain an electrolyte precursor. The manufacturing method of this embodiment will first be described, starting with the raw material content.

[0031] (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.

[0032] 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 (PSF３ ), 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.

[0033] 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.

[0034] 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 halogen molecules such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide, and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide. When oxygen atoms are introduced into the solid electrolyte, preferred are phosphate compounds such as lithium oxide, lithium hydroxide, and lithium phosphate. Preferred combinations of solid electrolyte raw materials include lithium sulfide, phosphorus pentasulfide, and lithium halides, and lithium sulfide, phosphorus pentasulfide, and halogen molecules. Preferred lithium halides are lithium bromide and lithium iodide, and preferred halogen molecules are bromine and iodine.

[0035] 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 %.

[0036] Also, Li ３ P.S. ４ When using halogen molecules, Li ３ P.S. ４ The content of halogen molecules relative to the total amount 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 %.

[0037] 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.

[0038] When lithium sulfide, diphosphorus pentasulfide, and lithium halide are used as solid electrolyte raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 65 to 85 mol%, more preferably 70 to 82 mol%, and even more preferably 74 to 80 mol%, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. When lithium sulfide, diphosphorus pentasulfide, lithium halide, and other solid electrolyte raw materials used as needed are used, the content of lithium sulfide and diphosphorus pentasulfide to the total is preferably 50 to 99 mol%, more preferably 55 to 85 mol%, and even more preferably 60 to 80 mol%.

[0039] When lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ionic conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 80 mol%, even more preferably 35 to 80 mol%, and particularly preferably 45 to 70 mol%. When lithium bromide and lithium chloride are used in combination as the lithium halide, from the viewpoint of improving ionic conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium chloride is preferably 1 to 99 mol%, more preferably 15 to 75 mol%, even more preferably 25 to 60 mol%, and particularly preferably 35 to 45 mol%.

[0040] When halogen molecules are used as solid electrolyte raw materials, 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 number of moles of halogen molecules to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the number of moles of halogen molecules 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 halogen molecules are used, the content of halogen molecules relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and halogen molecules 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%.

[0041] When lithium sulfide, diphosphorus pentasulfide, halogen molecules, and lithium halide are used, the content of halogen molecules (α mol %) and the content of 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)

[0042] When two types of halogens are used as molecules, 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.

[0043] When two types of halogen molecules are used, and the two types of halogen molecules are bromine and iodine, where A1 is the number of moles of bromine and A2 is the number of moles of iodine, A1:A2 is preferably 1:99 to 99:1, more preferably 20:80 to 80:20, even more preferably 35:65 to 80:20, and even more preferably 45:55 to 70:30. When the two types of halogen molecules are bromine and chlorine, B1 is the number of moles of bromine and B2 is the number of moles of chlorine, and B1:B2 is preferably 1:99 to 99:1, more preferably 15:85 to 75:25, even more preferably 25:75 to 60:40, and even more preferably 35:45 to 65:55.

[0044] (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.").

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Also, for example, a complexing agent (TMEDA) and Li ３ P.S. ４ The powder obtained by stirring the above mixture was analyzed by FT-IR analysis (diffuse reflectance method) in the same manner as above. The spectrum of TMEDA itself was found to have a peak at 1000 to 1250 cm －１ It can be seen that the spectrum of the LiI-TMEDA complex is similar to that of the LiI-TMEDA complex, while the peaks derived from the C-N stretching vibration in the spectrum are different. ３ P.S. ４ In the production method of this embodiment, the raw material ingredients and the complexing agent are mixed to obtain a complex, which is used as an electrolyte precursor, and the complexing agent is removed from the powder of the electrolyte precursor in a heated air stream, thereby producing a sulfide solid electrolyte.

[0049] 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.

[0050] 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.

[0051] Examples of such amine compounds include aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, and these can be used alone or in combination.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] Among the above ether compounds, aliphatic ethers are preferred, and dimethoxyethane and tetrahydrofuran are more preferred, from the viewpoint of obtaining higher ionic conductivity.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] (Mixing) In the manufacturing method of this embodiment, the solid electrolyte raw material is mixed with a complexing agent. In this embodiment, the solid electrolyte raw material and the complexing agent may be mixed in either a solid or liquid form. However, since the solid electrolyte raw material contains a solid and the complexing agent is liquid, they are usually mixed in a form in which the solid solid electrolyte raw material is present in a liquid complexing agent. Furthermore, when mixing the raw material and the complexing agent, a solvent may be further mixed as needed. Hereinafter, in the description of mixing the raw material and the complexing agent, unless otherwise specified, the complexing agent also includes the solvent used as needed.

[0077] 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 them. 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 halogen molecules are 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] By mixing the solid electrolyte raw materials with the complexing agent, a complex is formed between the solid electrolyte raw materials and the complexing agent. More specifically, the complex is considered to be formed by the interaction of the lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms contained in the solid electrolyte raw materials with the complexing agent, with and / or without the complexing agent being interposed between these atoms. That is, in the production method of this embodiment, the complex obtained by mixing the solid electrolyte raw materials with the complexing agent can be said to be composed of the complexing agent, lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. The complex obtained in this embodiment is not completely soluble in the liquid complexing agent but is usually solid, resulting in a suspension in which the complex is suspended in the complexing agent and an optional solvent. Therefore, the production method of the solid electrolyte of this embodiment corresponds to a heterogeneous system in a so-called liquid-phase method.

[0084] (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.

[0085] 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.

[0086] 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.

[0087] (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.)

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] [Drying] The manufacturing method of this embodiment may include drying the electrolyte precursor after obtaining the electrolyte precursor. The electrolyte precursor obtained by the above mixing may contain a complexing agent and solid electrolyte raw material that did not contribute to the formation of the electrolyte precursor, as well as a solvent used as needed. In such cases, it is preferable to include drying. Drying allows the remaining complexing agent that did not contribute to the formation of the electrolyte precursor and the solvent used as needed to be removed in advance. By removing the remaining complexing agent and the solvent used as needed in advance in this way, the electrolyte precursor can be heated more directly, making it possible to separate and remove the complexing agent more efficiently.

[0093] Drying methods include filtration using a glass filter or the like, solid-liquid separation by decantation, and solid-liquid separation using a centrifuge, etc. Specifically, solid-liquid separation can be easily performed by decantation, in which the suspension is transferred to a container, and after the solid has settled, the complexing agent and the solvent used as needed are removed as a supernatant, or by filtration using a glass filter having a pore size of about 10 to 200 μm, preferably 20 to 150 μm.

[0094] Drying can also be performed by heating using a dryer or the like. The drying of the electrolyte precursor may be performed under any pressure condition, such as under pressure, normal pressure, or reduced pressure, and is preferably performed under normal pressure or reduced pressure. In particular, considering drying at a lower temperature, drying under reduced pressure, or even under vacuum, using a vacuum pump or the like is preferable. The temperature condition for drying may be a temperature equal to or higher than the boiling point of the remaining complexing agent or the solvent used as needed. Since the 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.

[0095] 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.

[0096] 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. For example, when the electrolyte precursor obtained by the above mixing is a mixture containing a residual complexing agent and an optional solvent, the object to be heated in the fluidized bed dryer may be the mixture, or the electrolyte precursor powder obtained by drying the mixture. Furthermore, as described above, the electrolyte precursor is preferred as the object to be heated because it can be heated more directly.

[0097] [Heating with a Flow-Type Heater to Obtain Powder] The production method of this embodiment includes heating the electrolyte precursor obtained by the above mixing with a flow-type heater to obtain a powder. By heating the electrolyte precursor obtained in the step of obtaining the electrolyte precursor with the flow-type heater, the complexing agent is removed from the electrolyte precursor, i.e., the complexing agent is removed from the complex formed between the solid electrolyte raw materials and the complexing agent, thereby obtaining a sulfide solid electrolyte.

[0098] (Flow-type heater) More specifically, heating with a flow-type heater can be performed by supplying the object to be heated to a flow-type heater, and for example, a heating device commercially available as a flow-type heater can be used. A flow-type heater is a heater that can heat the object to be heated while circulating it within the heater (also referred to as "while moving it within the heater"). The object to be heated that is supplied to the flow-type heater is heated within the flow-type heater and then discharged.

[0099] The flow-type heater can be any heater that can heat an object to be heated while flowing it through, and preferred examples thereof include a flash dryer, a spray dryer, and a fluidized bed dryer. Among these, a flash dryer is preferred.

[0100] The spray dryer is a type of dryer that dries a liquid fluid (including a slurry) by spraying the fluid from a spray nozzle into a drying gas having a predetermined temperature, and commercially available spray dryers, spray driers, etc. can be used. Examples of fluidized bed dryers include medium fluidized bed dryers that use a medium (for example, commercially available as "slurry dryers"), as well as band fluidized bed dryers that use a band conveyor. Details of flash dryers will be described later.

[0101] The heating temperature in obtaining the powder, i.e., the heating temperature in the flow-through heater, is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, with the upper limit being preferably 180°C or lower, more preferably 165°C or lower, and even more preferably 150°C or lower. When the heating temperature is within the above range, the complexing agent can be more efficiently removed from the electrolyte precursor while protecting the separation device. Here, when a flow-through heater is used, a difference occurs between the heating temperature and the temperature of the object to be heated. The "heating temperature in obtaining the powder" means the "heating temperature in the flow-through heater."

[0102] (Flash Dryer) In the manufacturing method of this embodiment, it is preferable to use a flash dryer. By using a flash dryer, the object to be heated comes into direct contact with the heated airflow and is dispersed in the heated airflow, thereby increasing the contact area between the electrolyte precursor and the heated airflow. This allows the complexing agent contained in the electrolyte precursor to be efficiently heated. Furthermore, the heated airflow allows the complexing agent to be quickly separated and removed. Furthermore, since the regeneration of complexes and the generation of impurities are suppressed, it is easier to obtain a sulfide solid electrolyte with few impurities, high quality, and high ionic conductivity.

[0103] An airflow dryer is a device that can heat an object to be heated by the heated airflow by supplying the object to be heated into a pipe through which the heated airflow is supplied. A direct hot air type airflow dryer in which the heated airflow comes into direct contact with the object to be heated is preferred.

[0104] A preferred example of an airflow dryer is an airflow dryer equipped with a cylindrical container-shaped heating section (also referred to as a "cylindrical container-type airflow dryer"), as shown in FIG. 1. When the heating section is a cylindrical container, the cross-sectional area of ​​the flow path for the heated object and heated airflow is increased, so that even if the heated object adheres to the inner wall surface and solidifies, or the cross-sectional area of ​​the flow path is reduced due to such adhesion and solidification, the influence of flow disturbance and blockage on fluctuations can be suppressed. As a result, stable drying can be easily performed. Furthermore, compared to other types described below, this type is suitable for large-volume processing, facilitates long-term operation, and is easy to maintain, as it is easy to visually inspect and open and clean.

[0105] As the flash dryer, a flash dryer having a structure capable of heating an object to be heated while swirling a heated airflow, such as a flash dryer provided with a dispersion plate so that the heated airflow swirls within the piping, or a flash dryer in which at least a portion of the piping has a circular or semicircular shape (also referred to as a "circular flash dryer" or a "semicircular flash dryer," respectively), is preferably used. The adoption of such a structure can suppress adhesion of the electrolyte precursor to the inner wall, and can also utilize the mass difference between the electrolyte precursor from which the complexing agent has been removed and the electrolyte precursor in which the complexing agent remains to perform classification by centrifugal force, thereby enabling more efficient removal of the complexing agent. Furthermore, the flash dryer can be made more compact, thereby saving space.

[0106] Another preferred flash dryer is a type of flash dryer (also referred to as a "vertical-tube flash dryer") that uses a vertical long tube long enough to maintain the required length for heating, and introduces heated airflow from below the vertical long tube to heat the material while co-flowing with it. Using a vertical long-tube flash dryer allows the flow direction of the material and heated airflow to be limited to an upward direction, thereby adapting to changes in the flow rate, particle size, density, etc. of the material, facilitating stable drying. Furthermore, due to its simple structure, even if the material adheres to the inner wall, it can be easily removed, making it suitable for long-term operation. Furthermore, since this type of dryer can accommodate increases in processing volume and drying capacity by simply extending the vertical dimension, it requires a smaller installation area than other types, providing advantages in terms of equipment installation.

[0107] In a vertical long-tube type flash dryer, the diameter of the vertical long tube portion may be the same, or may be different and have some wider or narrower portions in order to adjust the heating condition of the object to be heated.

[0108] It is preferable not to use media particles when heating with a flow-type heater. By not using media particles such as ceramic balls or zirconia beads, excessive contact with the heated air flow due to adhesion of the electrolyte precursor to the media particles can be suppressed, and deterioration of the amorphous sulfide solid electrolyte due to deterioration of the electrolyte precursor can be suppressed. As a result, ionic conductivity is improved.

[0109] When using a flash dryer, the gas used in the heated gas stream for heating the object to be heated can be any gas, and various gases such as inert gases such as nitrogen and argon, and air can be used. Nitrogen and air are preferably used in terms of cost, and nitrogen is preferred in terms of improving ionic conductivity. These gases may be used alone or in combination. The dew point temperature of the gas is preferably −10° C. or lower, more preferably −20° C. or lower, and even more preferably −30° C. or lower, from the viewpoint of suppressing deterioration in the quality of the sulfide solid electrolyte due to moisture contained in the gas.

[0110] The temperature of the heated airflow is not particularly limited as long as it can heat the electrolyte precursor to a temperature sufficient to remove the complexing agent. While this temperature cannot be generalized because it varies depending on the type of complexing agent, it is preferable to set the temperature within the range of the heating temperature used to obtain the powder. Here, the temperature of the heated airflow is the supply temperature of the heated airflow, e.g., when the above-mentioned flash dryer is used, it is the supply temperature to the flash dryer. Within the above range, the complexing agent can be removed more efficiently.

[0111] Since the temperature of the heated airflow decreases when the electrolyte precursor is heated, for example, when the above-mentioned flash dryer is used, the temperature of the heated airflow discharged from the flash dryer is lower than the supply temperature (temperature of the heated airflow) to the flash dryer. The outlet temperature is usually 3°C or more lower than the supply temperature, and can be 5°C or more lower, or even 10°C or more lower, although this cannot be generalized because it varies depending on the scale of the flash dryer, etc.

[0112] Furthermore, the temperature of the electrolyte precursor is lower than the temperature of the heated air stream because the heating time in the heated air stream is short and the temperature does not usually reach the temperature of the heated air stream. This applies not only to flash dryers but also to other flow-type heaters, and the temperature of the electrolyte precursor is lower than the temperature in the flow-type heater. The temperature of the electrolyte precursor after heating with the flow-type heater (i.e., the temperature of the sulfide solid electrolyte from which the complexing agent has been removed from the electrolyte precursor) is preferably 40°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, with the upper limit being preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower.

[0113] The amount of heated airflow to be supplied is not particularly limited as long as it is supplied to an extent that the complexing agent can be removed from the electrolyte precursor. Although it cannot be generalized because it varies depending on the type of complexing agent, the scale of the flash dryer to be used, etc., it is preferably 0.1 m ３ / min or more, more preferably 0.3 m ３ / min or more, more preferably 0.5 m ３ / min or more, and the upper limit is preferably 500m ３ / min or less, more preferably 475m ３ / min or less, more preferably 450m ３ Within the above range, the complexing agent can be removed more efficiently.

[0114] The supply amount of the heated airflow is not particularly limited as long as it is supplied to an extent that the complexing agent can be removed from the electrolyte precursor. Although it cannot be generalized because it varies depending on the type of complexing agent, the scale of the flash dryer used, etc., it is preferable to use a ratio of the supply amount of the electrolyte precursor (g / min) to the supply amount of the heated airflow (m ３ / min), preferably 1.0 g / m ３ More preferably, 1.5 g / m ３ More preferably, 2.0 g / m ３ The upper limit is preferably 50.0 g / m ３ The following is the result.

[0115] The flow rate of the heated airflow is not particularly limited as long as it is supplied at a rate that can remove the complexing agent from the electrolyte precursor, and cannot be generalized because it varies depending on the type of complexing agent, the scale of the flash dryer used, etc., but is preferably 5 m / s or more, more preferably 7.5 m / s or more, and even more preferably 9 m / s or more, with the upper limit being preferably 35 m / s or less, more preferably 30 m / s or less, and even more preferably 25 m / s or less. Within the above range, the complexing agent can be removed more efficiently.

[0116] The heating time in the heated air stream is not particularly limited as long as it is supplied to an extent that the complexing agent can be removed from the electrolyte precursor, and cannot be generally determined because it varies depending on the type of complexing agent, the scale of the flash dryer used, etc., but the upper limit is preferably 1 minute or less, more preferably 50 seconds or less, even more preferably 40 seconds or less, still more preferably 15 seconds or less, and particularly preferably 5 seconds or less. The lower limit is usually 0.05 seconds or more, preferably 0.1 seconds or more, and more preferably 0.2 seconds or more.

[0117] In this way, the heating time in the heated air stream is extremely short. Therefore, for example, the electrolyte precursor is not exposed to high temperature conditions for a long time, and thermal degradation can be suppressed, resulting in a sulfide solid electrolyte having high ionic conductivity. Even when other flow-type heaters (preferably the above-mentioned spray dryer and fluidized bed dryer) are used, the heating time can be shortened because they are flow-type. Therefore, similar to the flash dryer, thermal degradation can be suppressed, resulting in a sulfide solid electrolyte having high ionic conductivity.

[0118] (Complexing Agent Content) Heating with the fluidized bed heater can remove the complexing agent from the electrolyte precursor, converting the electrolyte precursor into an amorphous sulfide solid electrolyte. However, there are cases where not all of the complexing agent is removed from the electrolyte precursor, resulting in the electrolyte precursor remaining, or where the complexing agent remains in the amorphous sulfide solid electrolyte. In these cases, the content of the complexing agent contained in the sulfide solid electrolyte is preferably 0% by mass, i.e., no complexing agent is contained at all. However, from the viewpoint of efficiently obtaining a sulfide solid electrolyte with high ionic conductivity, the content is typically 50% by mass or less, further 45% by mass or less, 35% by mass or less, 25% by mass or less, 15% by mass or less, 10% by mass or less, or 5% by mass or less, with the lower limit being approximately 0.1% by mass or more.

[0119] Furthermore, when a solvent is used, the solvent may remain, as with the complexing agent. In this case, the content of the solvent is also within the same range as the content of the complexing agent. In this specification, the content of the complexing agent contained in the sulfide solid electrolyte and the content of the solvent used as needed are measured by dissolving the powder obtained in the examples etc. in a mixed solution of water and pentanol using a gas chromatography (GC) apparatus, and the content of the complexing agent and the high-boiling-point solvent were quantified using an absolute calibration curve (GC calibration curve method).

[0120] [Transferring and Heating the Transfer Pipe] The production method of this embodiment includes transferring the powder obtained by heating using the flow-type heater from the flow-type heater to a separation device through a transfer pipe, and also includes heating the transfer pipe during the transfer. When transferring the powder obtained by heating using the flow-type heater to the separation device through the transfer pipe, heating the transfer pipe can suppress a decrease in the temperature of the powder transferred from the flow-type heater to the separation device. The powder transferred from the flow-type heater may contain, in addition to the amorphous sulfide solid electrolyte obtained by decomposition of the electrolyte precursor as described above, an amorphous sulfide solid electrolyte with a remaining complexing agent (which can also be said to be in a state where decomposition is in progress), or the electrolyte precursor itself. By heating the transfer pipe and suppressing a decrease in the temperature of the powder, the decomposition proceeds, and the sulfide solid electrolyte can be obtained more efficiently.

[0121] The powder obtained by heating using a flow-type heater can be transferred from the flow-type heater to the separation device via a transfer pipe, and there are no limitations on the method. For example, when a flash dryer is used as the flow-type heater, the powder is transferred along with the heated airflow, i.e., as a fluid containing the powder and the heated airflow. Furthermore, when another flow-type heater is used, the powder discharged from the flow-type heater can be transferred by means such as air transport. Therefore, the powder discharged from the flow-type heater can be supplied to the separation device via a transfer pipe either as powder or as a fluid containing the powder.

[0122] There are no limitations on the method for heating the transfer pipe as long as it can heat the transfer pipe, and examples of such methods include installing a heat insulating material, using a heater for heating pipes such as a jacket heater, or using a commercially available product for heat retention, etc. Furthermore, as the jacket heater, a steam jacket that uses steam as a heating medium, an electric heating jacket that uses electricity, etc. can be used.

[0123] The heating temperature of the transfer pipe may be set to a level that can suppress a decrease in the temperature of the powder or powder-containing fluid discharged from the flow-through heater, and may be set appropriately depending on the temperature of the powder (or powder-containing fluid) discharged from the flow-through heater. Alternatively, the heating temperature may be set so that the temperature of the powder (or powder-containing fluid) discharged from the flow-through heater is equal to or lower than the limit value of the supply temperature to the downstream separation device.

[0124] The supply temperature of the powder or powder-containing fluid discharged from the flow-through heater to the separation device cannot be generally determined because the limiting value of the supply temperature varies depending on the device used for the separation device, but is preferably 150°C or lower, with the lower limit being preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. The heating temperature of the transfer piping can be adjusted so that the supply temperature of the powder or powder-containing fluid discharged from the flow-through heater to the separation device is the above-mentioned temperature, but cannot be generally set, and is, for example, preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, with the upper limit being preferably 180°C or lower, more preferably 165°C or lower, and even more preferably 150°C or lower.

[0125] [Collecting by Separator] The manufacturing method of this embodiment includes collecting the powder transferred by the above-described transfer in a separator. The powder or a fluid containing the powder discharged from the flow-through heater is supplied to a separator in a state in which the temperature drop in the transfer pipe is suppressed and decomplexation has progressed, and the powder is collected in the separator. The powder collected in the separator is a powder obtained by removing the complexing agent from the electrolyte precursor, i.e., a powder of an amorphous sulfide solid electrolyte. This powder obtained by removing the complexing agent from the electrolyte precursor (amorphous sulfide solid electrolyte powder) exists suspended in the heated airflow, for example, when a flash dryer is used as the flow-through heater. That is, the powder (amorphous sulfide solid electrolyte powder) exists suspended in the fluid containing the powder and the heated airflow. Therefore, by collecting the powder discharged from the flow-through heater in a separator, it can be used as an amorphous sulfide solid electrolyte. Furthermore, if necessary, it can be used as a crystalline sulfide solid electrolyte by crystallizing it by heating, as described below.

[0126] (Separation Device) As a separation device used for collecting the powder supplied via the flow-type heater and the transfer pipe, a bag filter is preferably used from the viewpoint of efficiently collecting the powder. For example, when a flash dryer is used as the flow-type heater, the powder (powder of the amorphous sulfide solid electrolyte) from which the complexing agent has been removed from the electrolyte precursor and a fluid containing a heated airflow are supplied to the bag filter, whereby the powder (powder of the amorphous sulfide solid electrolyte) from which the complexing agent has been removed from the electrolyte precursor can be collected.

[0127] The filter used in the bag filter can be any filter made of materials such as polypropylene, nylon, acrylic, polyester, cotton, wool, heat-resistant nylon, polyamide / polyimide, PPS (polyphenylene sulfide), glass fiber, and PTFE (polytetrafluoroethylene), and functional filters such as electrostatic filters can also be used. Among these, filters made of heat-resistant nylon, polyamide / polyimide, PPS (polyphenylene sulfide), glass fiber, and PTFE (polytetrafluoroethylene) are preferred, and filters made of heat-resistant nylon, PPS (polyphenylene sulfide), and PTFE (polytetrafluoroethylene) are more preferred, with filters made of PTFE (polytetrafluoroethylene) being particularly preferred.

[0128] The bag filter may also have a brushing means, for example, preferably a pulsating counter pressure type or a pulse jet type, with the pulse jet type being particularly preferred.

[0129] An induced draft fan may be provided in the line from the exhaust port of the bag filter to forcibly exhaust the gas exhausted from the exhaust port. By exhausting the gas with an induced draft fan or the like, filtration in the bag filter proceeds smoothly, and the slurry can be dried in a shorter time.

[0130] [Heating] The production method of this embodiment can include heating the powder collected by the separation device. The powder collected by the separation device is an amorphous sulfide solid electrolyte obtained by further progressing decomposition in the transfer piping. When a crystalline sulfide solid electrolyte is to be obtained, it is preferable to convert the amorphous sulfide solid electrolyte into a crystalline sulfide solid electrolyte by further heating (hereinafter also referred to as "post-heating") in addition to the heating by the circulation heater.

[0131] Furthermore, the powder collected by the separation device may contain, in addition to the amorphous sulfide solid electrolyte, an electrolyte precursor, an amorphous sulfide solid electrolyte with a remaining complexing agent (which may be considered to be in a state where decomplexation is in progress), and possibly even remaining complexing agents and solvents used as needed. Furthermore, post-heating not only converts the amorphous sulfide solid electrolyte into a crystalline sulfide solid electrolyte as described above, but also promotes decomplexation of the electrolyte precursor and reduces the content of complexing agent remaining in the amorphous sulfide solid electrolyte, thereby converting the resulting amorphous sulfide solid electrolyte into a crystalline sulfide solid electrolyte. Furthermore, it is also possible to remove the remaining complexing agent that did not contribute to the formation of the electrolyte precursor, as well as the solvent used as needed. Therefore, the quality of the sulfide solid electrolyte obtained by the manufacturing method of this embodiment is improved, making it easier to obtain high ionic conductivity.

[0132] The heating temperature of the post-heating is not particularly limited as long as it is higher than the temperature of the powder obtained by heating using the above-mentioned flow-through heater, and can be determined, for example, 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. Here, "a temperature higher than the temperature of the powder obtained by heating using a flow-through heater" means the temperature of the powder at the outlet of the fluidized bed heater.

[0133] More specifically, the heating temperature for post-heating is preferably set in the range of 5° C. or higher, more preferably 10° C. or higher, and even more preferably 20° C. or higher, starting from the peak top temperature of the exothermic peak observed on the lowest temperature side when the powder, i.e., 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 upper limit is not particularly limited, but may be about 40° C. or lower. By setting the temperature range in this way, not only can a crystalline solid electrolyte be obtained more efficiently and reliably, but the quality of the sulfide solid electrolyte is improved and high ionic conductivity can be easily obtained.

[0134] The heating temperature for post-heating cannot be generally defined because it varies depending on the structure of the crystalline solid electrolyte to be obtained. However, it is usually preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. There is no particular upper limit, but it is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0135] The heating time for post-heating is not particularly limited as long as it is a time that allows a desired crystalline solid electrolyte to be obtained, but is, for example, preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.

[0136] Post-heating can be performed at normal pressure, but can also be performed under reduced pressure or even under vacuum to reduce the heating temperature. When heating under a reduced pressure, the pressure is preferably 85 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less. The lower limit may be vacuum (0 kPa), and considering ease of pressure adjustment, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more. When the pressure condition is within the above range, the heating conditions can be made mild, and the size of the apparatus can be prevented from increasing.

[0137] Furthermore, post-heating is preferably carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere) because this can prevent deterioration (e.g., oxidation) of the crystalline solid electrolyte. The method of post-heating is not particularly limited, and examples thereof include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, and a firing furnace. Furthermore, industrially, a horizontal dryer or a horizontal vibration fluidized dryer having a heating means and a feeding mechanism can also be used, and the method may be selected depending on the amount of heat to be processed.

[0138] (Amorphous sulfide solid electrolyte) The sulfide solid electrolyte obtained by the production method of this embodiment can be either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte, as desired. That is, if post-heating is not performed, an amorphous sulfide solid electrolyte is obtained, and if post-heating is performed, a crystalline sulfide solid electrolyte is obtained.

[0139] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and representative examples thereof include Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ -LiI-LiBr, etc., solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide; and solid electrolytes further containing other atoms such as oxygen atoms and silicon atoms, for example, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-SiS ２ -P ２ S ５ In order to obtain higher ionic conductivity, a solid electrolyte such as Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ A solid electrolyte composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiI-LiBr, is preferred. The types of atoms constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0140] 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.

[0141] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment is, for example, Li ２ S-P ２ S ５ In the case of -LiI-LiBr, the total content of lithium sulfide and diphosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%. The ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0142] In the amorphous sulfide solid electrolyte obtained by the production method of this embodiment, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms is preferably 1.0 to 1.8: 1.0 to 2.0: 0.1 to 0.8: 0.01 to 0.6, more preferably 1.1 to 1.7: 1.2 to 1.8: 0.2 to 0.6: 0.05 to 0.5, and even more preferably 1.2 to 1.6: 1.3 to 1.7: 0.25 to 0.5: 0.08 to 0.4. Further, when bromine and iodine are used in combination as halogen atoms, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine, and iodine is preferably 1.0 to 1.8: 1.0 to 2.0: 0.1 to 0.8: 0.01 to 0.3: 0.01 to 0.3, more preferably 1.1 to 1.7: 1.2 to 1.8: 0.2 to 0.6: 0.02 to 0.25: 0.02 to 0.25, more preferably 1.2 to 1.6: 1.3 to 1.7: 0.25 to 0.5: 0.03 to 0.2: 0.03 to 0.2, and even more preferably 1.35 to 1.45: 1.4 to 1.7: 0.3 to 0.45: 0.04 to 0.18: 0.04 to 0.18. By setting the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above range, it becomes easier to obtain a solid electrolyte with higher ionic conductivity having a thiolisiconregion II type crystal structure, an argyrodite type crystal structure, or the like, which will be described later.

[0143] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle size (D ５０ ) is, for example, 0.01 μm or more, further 0.03 μm or more, 0.05 μm or more, or 0.1 μm or more, and the upper limit is 5 μm or less, further 3.0 μm or less, 1.5 μm or less, 1.0 μm or less, or 0.5 μm or less.

[0144] (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 ６Crystal 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).

[0145] Li ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure (Kanno et al., Journal of the Electrochemical Society, 148(7)A742-746(2001)), Li ４－ｘ Ge １－ｘ P ｘ S ４ Examples of the crystal structure include a crystal structure similar to the thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725). The crystal structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is preferably the thio-LISICON Region II type crystal structure among the above, in that higher ionic conductivity can be obtained. Here, the "thio-LISICON Region II type crystal structure" refers to a crystal structure in which Li ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４ This indicates that the thiolisicon region II type crystal structure has a similar crystal structure to the thiolisicon region II type. As will be described later, the thiolisicon region II type crystal structure and the similar crystal structure have similar diffraction peaks, and are therefore very close to each other. Therefore, it is technically appropriate to treat the "thiolisicon region II type crystal structure" as including the thiolisicon region II type crystal structure and the similar crystal structure. Here, the above "Li４－ｘ Ge １－ｘ P ｘ S ４ The notation of the crystal structure "thio-LISICON Region II type" means that the crystal structure was found in the above document to be composed of Li, Ge, P, and S atoms. The sulfide solid electrolyte obtained by the production method of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and therefore, is not a "Li ４－ｘ Ge １－ｘ P ｘ S ４ "Li in thio-LISICON Region II type" ４－ｘ Ge １－ｘ P ｘ S ４ However, when the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has the same diffraction peak as the above-mentioned "thiolisiconregion II type crystal structure" (including the above-mentioned "similar crystal structure"), it can be said that the sulfide solid electrolyte obtained by the manufacturing method of this embodiment has a thiolisiconregion II type crystal structure formed by lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. The same applies to the argyrodite type crystal structure described below.

[0146] 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.

[0147] In X-ray diffraction measurement using CuKα radiation, Li３ P.S. ４ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°. ４ P ２ S ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°. ７ P.S. ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°. ７ P ３ S １１ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ The diffraction peaks of the thio-LISICON Region II crystal structure appear, for example, at 2θ=20.1°, 23.9°, and 29.5°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ Diffraction peaks of a crystal structure similar to that of thio-LISICON Region II type appear, for example, at 2θ=20.2° and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0148] 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°.

[0149] 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°.

[0150] Furthermore, the atomic composition ratios contained in the crystalline sulfide solid electrolyte are preferably those according to the composition formulas corresponding to the various crystal structures, and are within the range of the atomic composition ratios of the amorphous sulfide solid electrolyte. When the atomic composition ratios are within the range, it is easy to form a thiosilicon region II type crystal structure or an argyrodite type crystal structure, among the above crystal structures.

[0151] (Complexing Agent Content) By heating the powder collected by the separation device, the content of complexing agent contained in the crystalline sulfide solid electrolyte is reduced to be lower than the content of complexing agent contained in the amorphous sulfide solid electrolyte. The content of complexing agent contained in the crystalline sulfide solid electrolyte is preferably 0% by mass, i.e., no complexing agent is contained at all. However, from the viewpoint of efficiently obtaining a sulfide solid electrolyte with high ionic conductivity, the content is usually 10% by mass or less, 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.

[0152] Similarly to the complexing agent, when a solvent is used, the solvent may also remain. In this case, the content of the solvent is also in the same range as the content of the complexing agent.

[0153] 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 such, 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 been conventionally used to remove complexing agents, but uses a flow-type heater. Therefore, the generation of secondary particles due to aggregation of primary particles is suppressed, and the average particle size is small within the above range. Using a flow-type heater to heat the electrolyte precursor and heating the transfer piping also has the effect of reducing the average particle size. Therefore, the production method of this embodiment does not require a pulverization (atomization) treatment.

[0154] 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. ２In 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.

[0155] (Applications) The sulfide solid electrolyte obtained by the manufacturing method of this embodiment has high ionic conductivity and excellent battery performance, and is therefore suitable for use in batteries. A battery using the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is also called a lithium ion battery, and a battery using the sulfide solid electrolyte in an electrolyte layer, as described below, is called an all-solid-state battery. The sulfide solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer. Each layer can be manufactured by a known method.

[0156] 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.

[0157] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0158] (Measurement of Powder XRD Diffraction) Powder X-ray diffraction (XRD) measurement was carried out as follows. The sulfide solid electrolyte powder obtained in the Examples and Comparative Examples was filled into a groove 20 mm in diameter and 0.2 mm deep, and leveled with glass to prepare a sample. This sample was sealed with Kapton film for XRD and measured under the following conditions without being exposed to air. Measurement device: D2 PHASER, manufactured by Bruker Corporation Tube voltage: 30 kV Tube current: 10 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: focusing method Slit configuration: Soller slit 4°, divergence slit 1 mm, Kβ filter (Ni plate) used Detector: semiconductor detector Measurement range: 2θ = 10-60 deg Step width, scan speed: 0.05 deg, 0.05 deg / sec

[0159] (Measurement of Ion Conductivity) In the present example, the measurement of ion conductivity was carried out as follows. A 10 mm diameter (cross-sectional area S: 0.785 cm ) sample was taken from the crystalline solid electrolyte obtained in the examples and comparative examples. ２ ), and a height (L) of 0.1 to 0.3 cm were molded into a circular pellet to prepare a sample. Electrode terminals were attached to the top and bottom of the sample, and measurements were made at 25°C using an AC impedance method (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high-frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following formula: R = ρ (L / S) σ = 1 / ρ

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

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

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

[0163] (Flash Dryer) The electrolyte precursor powder obtained in the above Preparation Example was heated in a heated airflow using an apparatus having the configuration shown in the schematic diagram of an apparatus used for heating in a heated airflow in FIG. 1 . The apparatus shown in FIG. 1 is an apparatus mainly comprising a flash dryer (a cylindrical vessel-type flash dryer) and a bag filter, and is equipped with a blower and heater for supplying the heated airflow, as well as a mixer for pneumatically transporting the object to be heated by the gas. Although not shown, a feeder capable of supplying the object to be heated in powder or slurry form may also be provided (not shown). In the apparatus shown in FIG. 1 , the electrolyte precursor (the object to be heated) is pneumatically transported by gas to the bottom of the flash dryer, and the heated airflow generated by heating the gas with a heater is supplied from the bottom of the flash dryer. The object to be heated in the heated airflow in the flash dryer becomes a powder (amorphous sulfide powder) in which the complexing agent has been removed from the electrolyte precursor, and the heated airflow containing this is supplied to a downstream bag filter. Then, the powder (amorphous sulfide powder) from which the complexing agent has been removed from the electrolyte precursor is collected by a bag filter, and the heated airflow after the powder has been collected is exhausted as is.

[0164] (Example 1) Using the above-mentioned flash dryer, nitrogen heated to 135°C was used as a heated airflow, and the airflow was 3 m ３ The supply of the material to be heated (electrolyte precursor powder) to the flash dryer was started at a rate of 100.5 g / min using a table feeder. The material to be heated (electrolyte precursor powder) was heated in a heated air stream using the flash dryer, and the heated air stream discharged from the flash dryer was supplied to a bag filter of a separation device through a transfer pipe, and the powder (amorphous sulfide solid electrolyte) containing the complexing agent removed from the electrolyte precursor was collected. This process continued for 20 minutes (i.e., the operation time was 20 minutes). Here, an electric heating jacket was attached to the transfer pipe, and heating was performed at a heating temperature set to 125°C. The temperature of the heated air stream at the outlet of the flash dryer was 123°C, and the temperature of the heated air stream at the inlet of the bag filter was 122°C. The contents of the complexing agent contained in the powder (amorphous sulfide solid electrolyte) at the inlet of the flash dryer and at the inlet of the bag filter after passing through the transfer piping were 55.0% by mass and 20.4% by mass, respectively.

[0165] The resulting powder (amorphous sulfide solid electrolyte) from which the complexing agent was removed was heated (post-heated) in a Schlenk flask at 110°C for 2 hours and then at 160°C for 2 hours, thereby obtaining a crystalline sulfide solid electrolyte.

[0166] The ionic conductivity of the crystalline sulfide solid electrolyte obtained in Example 1 was measured and found to be 4.0 (mS / cm). Furthermore, powder XRD diffraction measurements were performed on the crystalline sulfide solid electrolyte obtained in Example 1. The X-ray diffraction spectrum is shown in FIG. 2. As shown in FIG. 2, crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the crystalline sulfide solid electrolyte had a thiolicon region II crystal structure.

[0167] Examples 2 and 3 Amorphous sulfide solid electrolytes and crystalline sulfide solid electrolytes were obtained in the same manner as in Example 1, except that the supply amount of the heated object (electrolyte precursor powder), the supply temperature of the heated airflow, and the heating temperature of the transfer piping were set to the conditions shown in Table 1. The content of the complexing agent in the obtained sulfide solid electrolyte was measured. The results and the amount of complexing agent removed are shown in Table 1. In addition, powder XRD diffraction measurements were performed on the crystalline sulfide solid electrolytes obtained in Examples 2 and 3. The X-ray diffraction spectrum is shown in FIG. 2. As shown in FIG. 2, crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the crystalline sulfide solid electrolytes had a thiolicon region II crystal structure.

[0168] Comparative Examples 1 to 3 Amorphous sulfide solid electrolytes and crystalline sulfide solid electrolytes were obtained in the same manner as in Example 1, except that the transfer piping was not heated, and the supply rate of the heated object (electrolyte precursor powder), the supply temperature of the heated airflow, and the heating temperature of the transfer piping were set to the conditions shown in Table 1. The content of the complexing agent in the obtained sulfide solid electrolyte was measured. The results and the amount of complexing agent removed are shown in Table 1. Powder XRD diffraction measurements were also performed on the crystalline sulfide solid electrolytes obtained in Comparative Examples 1 to 3. The X-ray diffraction spectra are shown in FIG. 3. As shown in FIG. 3, crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum, confirming that the crystalline sulfide solid electrolytes had a thiolicon region II crystal structure.

[0169]

[0170] From the results of the Examples and Comparative Examples, it was confirmed that the method for producing a sulfide solid electrolyte of the present embodiment can more efficiently produce a sulfide solid electrolyte having high ionic conductivity and can also be easily adapted for mass production. Specifically, the above Examples and Comparative Examples can be considered as follows.

[0171] The above Examples and Comparative Examples have the same supply temperature of the heated airflow, and can be compared between Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3. For example, when comparing Example 1 and Comparative Example 1, although the supply rates of the electrolyte precursor were 100.5 g / min and 78.5 g / min, respectively, which was 28.0% higher in Example 1, the content of the complexing agent at the outlet of the flash dryer (after passing through the heated transfer piping) was 20.4 mass% and 22.4 mass%, respectively, which was greater in Example 1, and as a result, the removal amounts of the complexing agent were 43.7 g / min and 33.0 g / min, respectively, confirming an improvement of 32.6%. A comparison between Example 2 and Comparative Example 2 confirmed that the amount of complexing agent removed was improved by 36.0%, even though the supply amount of electrolyte precursor was 25.8% greater in Example 2, and a comparison between Example 3 and Comparative Example 3 confirmed that the amount of complexing agent removed was improved by 23.3%, even though the supply amount of electrolyte precursor was 13.7% greater in Example 3. Thus, it was confirmed that heating the transfer piping can increase the amount of complexing agent removed, i.e., increase the production amount of sulfide solid electrolyte, despite the large supply amount of electrolyte precursor.

[0172] Furthermore, as a result of powder XRD diffraction measurement, it was confirmed that the sulfide solid electrolyte obtained in the examples has a thiolicon region II type crystal structure and has high ionic conductivity.

[0173] According to the method for producing a sulfide solid electrolyte of this embodiment, a sulfide solid electrolyte with high ionic conductivity can be efficiently produced. Furthermore, the method can easily accommodate mass production of sulfide solid electrolytes. Therefore, the sulfide solid electrolyte of this embodiment obtained by the production method of this embodiment is suitable for use in batteries, particularly batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones, and particularly all-solid-state batteries.

Claims

1. Obtaining an electrolyte precursor by mixing a raw material inclusion containing a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom with a complexing agent; obtaining a powder by heating the electrolyte precursor using a flow-through heater; transferring the powder from the flow-through heater to a separator through a transfer pipe; and collecting the transferred powder by the separator, including heating the transfer pipe in the transferring step, a method for producing a sulfide solid electrolyte.

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein the heating temperature of the transfer pipe is 80°C or higher and 180°C or lower.

3. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heating temperature in obtaining the powder is 80°C or higher and 180°C or lower.

4. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, wherein the flow-through heater is a heater selected from a pneumatic dryer, a spray dryer, and a fluidized bed dryer.

5. The method for producing a sulfide solid electrolyte according to claim 4, wherein the flow-through heater is a pneumatic dryer.

6. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 5, including heating the powder collected by the collecting step.

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