Sulfide solid electrolyte manufacturing system and manufacturing method

Abstract

A sulfide solid electrolyte manufacturing system comprising: a mixing device that mixes a sulfide solid electrolyte starting material–containing material, a solvent, and a complexing agent to obtain an electrolyte precursor–containing material; a drying device that dries the electrolyte precursor–containing material to obtain an electrolyte precursor; a decomplexing device that removes the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; a separation device that separates the solvent and the complexing agent from at least one fluid which is selected from among a fluid (I) that is supplied from the drying device and contains at least one selected from among the solvent and the complexing agent and a fluid (II) that is supplied from the decomplexing device and contains at least one selected from among the solvent and the complexing agent; and a supply line (1) that supplies the solvent and the complexing agent separated by the separation device to the mixing device.

Description

Sulfide solid electrolyte manufacturing system and manufacturing method

[0001] The present invention relates to a sulfide solid electrolyte production system and production method.

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

[0003] Methods for producing solid electrolytes used in solid electrolyte layers are roughly divided into solid-phase methods and liquid-phase methods. In recent years, in order to commercialize all-solid-state batteries, the liquid-phase method has attracted attention as a method that can be easily synthesized in large quantities, in addition to being versatile and applicable. For example, Patent Document 1 discloses a method for producing a solid electrolyte, which includes reacting raw materials containing at least lithium, sulfur, and phosphorus in a solvent to obtain a solid electrolyte-containing liquid, subjecting the solid electrolyte-containing liquid to solid-liquid separation, and removing a sulfur-containing compound from the liquid obtained by the solid-liquid separation. Patent Document 2 discloses a method for producing a solid electrolyte, which includes mixing a raw material containing lithium, sulfur, phosphorus, and a halogen element with a complexing agent containing a compound having at least two tertiary amino groups in its molecule.

[0004] JP 2019-574000 A, WO 2020 / 105737 Pamphlet

[0005] The present invention has been made in view of the above circumstances, and aims to provide a sulfide solid electrolyte production system and a sulfide solid electrolyte production method that reuse solvents and complexing agents that have conventionally been discarded, thereby improving production efficiency.

[0006] The sulfide solid electrolyte production system according to the present invention comprises: a mixing device that mixes a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content; a drying device that dries the electrolyte precursor content to obtain an electrolyte precursor; a decomplexing device that removes the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; a separation device that separates the solvent and the complexing agent from at least one fluid selected from fluid (I) containing at least one selected from the solvent and the complexing agent and supplied from the drying device, and fluid (II) containing at least one selected from the solvent and the complexing agent and supplied from the decomplexing device; and a supply line (1) that supplies the solvent and the complexing agent separated in the separation device to the mixing device.

[0007] The method for producing a sulfide solid electrolyte according to the present invention includes: mixing a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content; drying the electrolyte precursor content to obtain an electrolyte precursor; removing the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; separating the solvent and the complexing agent from a fluid (I) containing at least one selected from the solvent and the complexing agent discharged in the process of obtaining the electrolyte precursor, and a fluid (II) containing at least one selected from the solvent and the complexing agent discharged in the process of obtaining the sulfide solid electrolyte; and reusing the separated solvent and complexing agent in the process of obtaining the electrolyte precursor content.

[0008] According to the present invention, it is possible to provide a sulfide solid electrolyte production system and a sulfide solid electrolyte production method that reuse solvents and complexing agents that have conventionally been discarded, thereby improving production efficiency.

[0009] FIG. 1 is a diagram illustrating an example of a sulfide solid electrolyte production system according to an embodiment of the present invention.

[0010] 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 range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​in the examples can also be used as the upper and lower limit values.

[0011] (Findings Obtained by the Inventors to Achieve the Present Invention) The inventors conducted extensive research to solve the above-mentioned problems, and as a result, discovered the following and completed the present invention. Conventionally, solvents and complexing agents used in the production of solid electrolytes have been discarded. However, as the production equipment becomes larger, the amounts of solvents and complexing agents discarded increase, leading to increased environmental impact and increased production costs. Therefore, the inventors investigated the recovery and reuse of solvents and complexing agents. Specifically, because the solvents and complexing agents used in the production of solid electrolytes are discharged as gases, they investigated methods for separating the solvents and complexing agents from fluids containing the gaseous solvents and complexing agents.

[0012] The above-mentioned Patent Document 1 describes the reuse of the liquid obtained by solid-liquid separation after removing sulfur-containing compounds from the liquid, but does not consider the recovery and reuse of the solvent and complexing agent when a complexing agent is further used. Furthermore, the above-mentioned Patent Document 2 does not consider the above-mentioned problem. Based on the above considerations, the present inventors have discovered that by separating the solvent and the complexing agent from a fluid containing the solvent and the complexing agent, respectively, discharged during the production process of a solid electrolyte, the solvent and the complexing agent that were previously discarded can be reused, thereby improving production efficiency.

[0013] (Regarding Various Forms of the Present Embodiment) A sulfide solid electrolyte production system according to a first embodiment of the present embodiment is a sulfide solid electrolyte production system including: a mixing device that mixes a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content; a drying device that dries the electrolyte precursor content to obtain an electrolyte precursor; a decomplexing device that removes the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; a separation device that separates the solvent and the complexing agent from at least one fluid selected from fluid (I) containing at least one selected from the solvent and the complexing agent and supplied from the drying device, and fluid (II) containing at least one selected from the solvent and the complexing agent and supplied from the decomplexing device; and a supply line (1) that supplies the solvent and the complexing agent separated in the separation device to the mixing device.

[0014] The electrolyte precursor-containing material obtained by mixing the raw material inclusions, the solvent, and the complexing agent may contain, along with the electrolyte precursor, the complexing agent and the raw material inclusions that did not contribute to the formation of the electrolyte precursor, and the solvent. The electrolyte precursor is a precursor of a sulfide solid electrolyte obtained by drying the electrolyte precursor inclusions, more specifically, a precursor obtained by mixing the raw material inclusions and the complexing agent, which can become a sulfide solid electrolyte by removing the complexing agent. Furthermore, the complexing agent is a complexing agent, i.e., an agent that can form a complex, and refers to a compound that easily forms a complex with the raw material inclusions. Therefore, since the electrolyte precursor is obtained by mixing the raw material inclusions and the complexing agent, it can be said to be a complex formed by the raw material inclusions via the complexing agent.

[0015] In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state at 25°C under a nitrogen atmosphere. In this embodiment, the sulfide solid electrolyte is a solid electrolyte that contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms and has ionic conductivity due to the lithium atoms. The term "sulfide solid electrolyte" includes both a crystalline sulfide solid electrolyte having a crystal structure obtained by the production method of this embodiment and an amorphous sulfide solid electrolyte.

[0016] As used herein, the term "crystalline sulfide solid electrolyte" refers to a solid electrolyte in which peaks derived from the solid electrolyte are observed in an X-ray diffraction pattern obtained by X-ray diffraction measurement, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present. That is, the crystalline sulfide 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 the crystalline sulfide solid electrolyte has the X-ray diffraction pattern described above, it may also contain an amorphous sulfide solid electrolyte as a portion thereof. Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating an amorphous sulfide solid electrolyte to a temperature equal to or higher than the crystallization temperature. Furthermore, as used herein, the term "amorphous sulfide solid electrolyte" refers to an X-ray diffraction pattern obtained by X-ray diffraction measurement that exhibits a halo pattern in which substantially no peaks other than those derived from the raw materials are observed, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present.

[0017] In this specification, the term "raw material-containing material" refers to a solid electrolyte raw material used in producing a sulfide solid electrolyte, and refers to an element or compound containing a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom, or a mixture thereof.

[0018] In this specification, the term "fluid" refers to a gas or liquid containing at least one selected from a solvent and a complexing agent.

[0019] As described above, in the sulfide solid electrolyte production system of this embodiment, the solvent and complexing agent used when drying the electrolyte precursor-containing material to obtain the electrolyte precursor and when removing the complexing agent from the electrolyte precursor to obtain the sulfide solid electrolyte are discharged as gases. Therefore, by separating the solvent and complexing agent from a fluid containing at least one selected from gaseous solvents and complexing agents and supplying them to a mixing device, it is possible to reuse the solvent and complexing agent that have conventionally been discarded, and the production efficiency of the sulfide solid electrolyte can be improved.

[0020] A sulfide solid electrolyte production system according to a second aspect of the present embodiment is the same as that of the first aspect, except that the separation device includes one or more absorption towers and one or more distillation towers.

[0021] By providing the separation unit with one or more absorption towers and one or more distillation towers, it is possible to efficiently separate a larger amount of solvent and complexing agent from the fluid supplied from the drying unit and the decomplexing unit, thereby making it possible to reuse a larger amount of solvent and complexing agent and further improve the production efficiency of the sulfide solid electrolyte.

[0022] A sulfide solid electrolyte production system according to a third aspect of the present embodiment is the same as the second aspect, except that it further includes a supply line (2-1) that supplies the fluid (I) from the drying device to the distillation column.

[0023] By providing a supply line (2-1) connecting the drying device and the distillation column, when the electrolyte precursor-containing material is dried to obtain the electrolyte precursor, the fluid (I) containing at least one selected from the remaining solvent and complexing agent can be supplied directly from the drying device to the distillation column. Therefore, the solvent and complexing agent can be separated more efficiently, and by reusing them, the production efficiency of the sulfide solid electrolyte can be further improved.

[0024] A sulfide solid electrolyte production system according to a fourth aspect of the present embodiment is the second or third aspect, further comprising a supply line (3-1) for supplying the fluid (II) from the decomplexing device to the distillation column.

[0025] By providing a supply line (3-1) connecting the decomplexing device and the distillation column, when the complexing agent is removed from the electrolyte precursor to obtain a sulfide solid electrolyte, the fluid (II) containing at least one selected from the remaining solvent and complexing agent can be supplied directly from the decomplexing device to the distillation column. This allows for more efficient separation of the solvent and complexing agent, and by reusing them, the production efficiency of the sulfide solid electrolyte can be further improved.

[0026] A sulfide solid electrolyte production system according to a fifth aspect of the present embodiment is the same as that of the second aspect, except that the fluid (I) contains a solvent, a complexing agent, and an atmospheric gas, and further includes a supply line (2-2) that supplies the fluid (I) from the drying device to the absorption tower and the distillation tower in this order.

[0027] By providing a supply line (2-2) connecting the drying device, the absorption tower, and the distillation tower in this order, when the electrolyte precursor-containing material is dried to obtain the electrolyte precursor, the fluid (I) containing at least one selected from the remaining solvent and complexing agent and the atmospheric gas can be supplied directly from the drying device to the absorption tower and the distillation tower. Therefore, the solvent, the complexing agent, and the atmospheric gas can be separated more efficiently, and by reusing them, the production efficiency of the sulfide solid electrolyte can be further improved.

[0028] A sulfide solid electrolyte production system according to a sixth aspect of the present embodiment is the same as that of the second aspect, except that the fluid (II) contains a solvent, a complexing agent, and an atmospheric gas, and further includes a supply line (3-2) that supplies the fluid (II) from the decomplexing device to the absorption tower and the distillation tower in this order.

[0029] By providing a supply line (3-2) connecting the decomplexer, the absorption tower, and the distillation tower in this order, when removing the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte, the fluid (II) containing at least one selected from the remaining solvent and the complexing agent and the atmospheric gas can be supplied directly from the decomplexer to the absorption tower and the distillation tower. Therefore, the solvent, the complexing agent, and the atmospheric gas can be separated more efficiently, and by reusing them, the production efficiency of the sulfide solid electrolyte can be further improved.

[0030] A sulfide solid electrolyte production system according to a seventh aspect of the present embodiment is the same as any one of the second, fifth, and sixth aspects, except that the absorption liquid in the absorption tower is the solvent. A sulfide solid electrolyte production system according to an eighth aspect of the present embodiment is the same as the seventh aspect, except that the solvent is a hydrocarbon solvent.

[0031] By using the solvent used in this embodiment, preferably a hydrocarbon solvent, as the absorption liquid in the absorption tower, it is not necessary to separate the absorption liquid from the solvent and complexing agent, which facilitates distillation in the subsequent distillation tower. Therefore, the solvent and complexing agent can be separated more efficiently, and by reusing them, the production efficiency of the sulfide solid electrolyte can be further improved.

[0032] A sulfide solid electrolyte production system according to a ninth aspect of the present embodiment is the sulfide solid electrolyte production system of any one of the first to eighth aspects, wherein the complexing agent is an amine compound.

[0033] When the complexing agent is an amine compound, it easily forms an electrolyte precursor together with the raw materials contained in the raw material inclusions, and is easily separated and removed from the electrolyte precursor, making it easier to obtain a high-quality sulfide solid electrolyte with few impurities extremely efficiently.

[0034] A sulfide solid electrolyte production system according to a tenth aspect of the present embodiment is the sulfide solid electrolyte production system of any one of the first to ninth aspects, wherein the drying device and the decomposition device include at least one device selected from a vacuum drying device and an air flow drying device.

[0035] When the drying device and the decomplexing device are provided with at least one device selected from a vacuum drying device and an airflow drying device, the electrolyte precursor or the sulfide solid electrolyte can be obtained more efficiently.

[0036] A method for producing a sulfide solid electrolyte according to an eleventh aspect of the present embodiment includes: mixing a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content; drying the electrolyte precursor content to obtain an electrolyte precursor; removing the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; separating the solvent and the complexing agent from fluid (I) containing at least one selected from the solvent and the complexing agent, which is discharged in the process of obtaining the electrolyte precursor, and fluid (II) containing at least one selected from the solvent and the complexing agent, which is discharged in the process of obtaining the sulfide solid electrolyte; and reusing the separated solvent and the complexing agent in the process of obtaining the electrolyte precursor content.

[0037] In the method for producing a sulfide solid electrolyte of this embodiment, as described above, the solvent and complexing agent used when drying the electrolyte precursor-containing material to obtain the electrolyte precursor and when removing the complexing agent from the electrolyte precursor to obtain the sulfide solid electrolyte are discharged as gas. Therefore, by separating the solvent and complexing agent from a fluid containing at least one selected from gaseous solvents and complexing agents, the solvent and complexing agent that have conventionally been discarded can be reused to obtain the electrolyte precursor-containing material, thereby improving the production efficiency of the sulfide solid electrolyte.

[0038] A twelfth aspect of this embodiment is the method for producing a sulfide solid electrolyte according to the eleventh aspect, wherein the separating step is at least one selected from the group consisting of cooling at least one fluid selected from the fluid (I) and the fluid (II), distilling the resulting liquid, and separating the liquid into the solvent and the complexing agent, and wherein the at least one fluid selected from the fluid (I) and the fluid (II) contains a solvent, a complexing agent, and an atmospheric gas, and contacting the at least one fluid selected from the fluid (I) and the fluid (II) with an absorbing liquid to separate the liquid into an absorbing liquid containing the solvent and the complexing agent and the atmospheric gas, and then distilling the absorbing liquid to separate the liquid into the solvent and the complexing agent.

[0039] In the method for producing a sulfide solid electrolyte of the present embodiment, by employing the above separation method, the solvent and the complexing agent can be separated more efficiently, and by reusing them, the production efficiency of the sulfide solid electrolyte can be further improved.

[0040] A method for producing a sulfide solid electrolyte according to a thirteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to the twelfth aspect, wherein the absorption liquid is the solvent. A method for producing a sulfide solid electrolyte according to a fourteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to the thirteenth aspect, wherein the solvent is a hydrocarbon solvent.

[0041] By using the solvent used in this embodiment, preferably a hydrocarbon solvent, as the absorbing liquid, it is not necessary to separate the absorbing liquid from the solvent and complexing agent, which facilitates distillation. Therefore, the solvent and complexing agent can be separated more efficiently, and by reusing them, the production efficiency of the sulfide solid electrolyte can be further improved.

[0042] A method for producing a sulfide solid electrolyte according to a fifteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the eleventh to fourteenth aspects, wherein the complexing agent is an amine compound.

[0043] When the complexing agent is an amine compound, it is easy to form an electrolyte precursor together with the raw materials contained in the raw material inclusions, and is easy to separate and remove from the electrolyte precursor, making it easy to obtain a high-quality sulfide solid electrolyte with few impurities extremely efficiently.

[0044] A sixteenth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the twelfth to fifteenth aspects, wherein at least one selected from the fluid (I) and the fluid (II) contains a solvent, a complexing agent, and an atmospheric gas; the at least one selected from the fluid (I) and the fluid (II) is brought into contact with an absorbing liquid to separate the absorbing liquid containing the solvent and the complexing agent and the atmospheric gas, and then the atmospheric gas is reused in obtaining the sulfide solid electrolyte.

[0045] In the method for producing a sulfide solid electrolyte of the present embodiment, the atmospheric gas is separated from a fluid containing a solvent, a complexing agent, and the atmospheric gas, and is reused in obtaining the sulfide solid electrolyte, thereby further improving the production efficiency of the sulfide solid electrolyte.

[0046] The sulfide solid electrolyte production system and sulfide solid electrolyte production method of this embodiment will be described in more detail below in accordance with the above aspects.

[0047] [Sulfide Solid Electrolyte Production System] The sulfide solid electrolyte production system of the present embodiment is a sulfide solid electrolyte production system including: a mixing device that mixes a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content; a drying device that dries the electrolyte precursor content to obtain an electrolyte precursor; a decomplexing device that removes the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; a separation device that separates the solvent and the complexing agent from at least one fluid selected from fluid (I) containing at least one selected from the solvent and the complexing agent and supplied from the drying device, and fluid (II) containing at least one selected from the solvent and the complexing agent and supplied from the decomplexing device; and a supply line (1) that supplies the solvent and the complexing agent separated in the separation device to the mixing device.

[0048] FIG. 1 is a diagram illustrating an example of a sulfide solid electrolyte production system according to this embodiment. As shown in FIG. 1 , the sulfide solid electrolyte production system 100 according to this embodiment includes a mixer 10, a dryer 20, a decomplexer 30, and a separator 40. The separator 40 may include one or more absorption towers 50 and one or more distillation towers 60. In the mixer 10, a raw material content of the sulfide solid electrolyte, a solvent, and a complexing agent are mixed to obtain an electrolyte precursor content. The obtained electrolyte precursor content is supplied to a dryer 20, where the electrolyte precursor content is dried to obtain an electrolyte precursor. The obtained electrolyte precursor is supplied to a decomplexer 30, where the complexing agent is removed from the electrolyte precursor to obtain a sulfide solid electrolyte.

[0049] Fluid (I), which contains at least one selected from the solvent and the complexing agent remaining in the drying apparatus 20 after the drying, is supplied to the distillation column 60 through a supply line (2-1) connecting the drying apparatus 20 and the distillation column 60. When the fluid (I) contains a solvent, a complexing agent, and an atmospheric gas, the fluid (I) is supplied to the absorption column 50 and the distillation column 60 in this order through a supply line (2-2) connecting the drying apparatus 20 and the absorption column 50 and the distillation column 60.

[0050] Fluid (II), which contains at least one selected from a solvent and a complexing agent remaining in the decomplexing unit 30 after the complexing agent has been removed from the electrolyte precursor, is supplied to the distillation unit 60 through a supply line (3-1) connecting the decomplexing unit 30 and the distillation unit 60. When the fluid (II) contains a solvent, a complexing agent, and an atmospheric gas, the fluid (II) is supplied to the absorption unit 50 and the distillation unit 60 in this order through a supply line (3-2) connecting the decomplexing unit 30 and the absorption unit 50 and the distillation unit 60.

[0051] In FIG. 1 , the supply line (3-1) is a separate supply line from the supply line (2-1), but the supply line (3-1) may merge with the supply line (2-1) between the decomposition unit 30 and the distillation column 60. Similarly, the supply line (2-2) may merge with the supply line (3-2) between the drying unit 20 and the absorption column 50.

[0052] At least one fluid selected from fluid (I) and fluid (II) is separated into a solvent and a complexing agent in at least one separation device 40 selected from an absorption tower 50 and a distillation tower 60. The separated solvent and complexing agent are supplied to the mixer 10 through a supply line (1) connecting the separation device 40 and the mixer 10. In addition, the atmospheric gas separated in the absorption tower 50 may be reused in the decomplexer 30 through a supply line (4) connecting the absorption tower 50 and the decomplexer 30.

[0053] (Mixing Apparatus) The mixing apparatus 10 is an apparatus that mixes a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content. The mixing apparatus 10 is not particularly limited, and may be a batch type or a continuous type. When the mixing apparatus 10 is a continuous type, it is preferable that the mixing apparatus 10 is equipped with a line that supplies the obtained electrolyte precursor content to the drying apparatus 20.

[0054] Examples of the mixing device include a mechanical agitation mixer equipped with an agitator blade in a tank. Examples of the mechanical agitation mixer include a high-speed agitation mixer and a double-arm mixer. From the viewpoint of improving the uniformity of the raw materials in the mixture of the raw material ingredients and the solvent, and from the viewpoint of improving the uniformity of the raw materials in the mixture of the raw material ingredients, the solvent, and the complexing agent, a high-speed agitation mixer is preferably used. Examples of the high-speed agitation mixer include a vertical axis rotary mixer and a horizontal axis rotary mixer, and either type of mixer may be used.

[0055] 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, C-type blade type, etc., and from the viewpoint of improving the uniformity of the raw materials in the raw material content, the shovel type, flat blade type, C-type blade type, etc. are preferred. In addition, a mechanical stirring mixer may be provided with a circulation line that discharges the material to be stirred outside the mixer and then returns it to the mixer. This allows the heavy raw materials to be stirred without settling or stagnating, enabling more uniform mixing.

[0056] The location of the circulation line is not particularly limited, but it is preferable to install it in 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 raw materials in the raw material-containing mixture, which tend 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 surface inside the mixer.

[0057] (Raw material contents) The raw material contents used in this embodiment contain raw materials for the sulfide solid electrolyte, that is, contain lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. For example, a substance containing at least one selected from lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms can be used alone or in combination.

[0058] Such substances include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ) and other phosphorus sulfides; various phosphorus fluorides (PF ３ , P.F. ５ ), various phosphorus chlorides (PCl ３ , PCl ５ , P ２ Cl ４ ), various phosphorus bromides (PBr ３ , PBr ５ ), various phosphorus iodides (PI ３ , P ２ I ４ ) and the like; phosphorus halides such as thiophosphoryl fluoride (PSF ３ ), thiophosphoryl chloride (PSCl ３ ), thiophosphoryl bromide (PSBr ３ ), thiophosphoryl iodide (PSI ３ ), thiophosphoryl fluoride dichloride (PSCl ２ F), thiophosphoryl fluoride dibromide (PSBr ２ Representative examples include starting materials comprising at least two types of atoms selected from the above four types of atoms, such as thiophosphoryl halides such as F).

[0059] Examples of materials that can be used as raw materials other than those mentioned above include raw materials that contain at least one atom selected from the above four types of atoms and also contain atoms other than the four types of atoms, more specifically, lithium compounds such as lithium oxide, lithium hydroxide, and lithium carbonate; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, and tin sulfide (SnS, SnS２ metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium such as sodium halides such as sodium iodide, sodium fluoride, sodium chloride and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides and bismuth halides; phosphorus oxychloride (POCl ３ ), phosphorus oxybromide (POBr ３ ) and the like; and the like.

[0060] 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 combination of raw materials include a combination of lithium sulfide, diphosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, diphosphorus pentasulfide, and a single halogen atom, and preferred examples of the lithium halide include lithium bromide and lithium iodide, and preferred examples of the single halogen atom include bromine and iodine.

[0061] The lithium sulfide used in this embodiment is preferably in the form of particles. ５０ In this specification, the average particle size (D 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% (volume basis) of the total, and the volume distribution can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer. Furthermore, among the above-mentioned examples of raw materials, solid raw materials preferably have an average particle size similar to that of the lithium sulfide particles. That is, raw materials within the same range as the average particle size of the lithium sulfide particles are preferred.

[0062] When the raw material contains lithium sulfide, diphosphorus pentasulfide, and lithium halide, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 70 to 80 mol%, more preferably 72 to 78 mol%, and even more preferably 74 to 78 mol%, from the viewpoint of more efficiently obtaining a desired sulfide solid electrolyte. When the raw material contains lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed, the content of lithium sulfide and diphosphorus pentasulfide to the total is preferably 50 to 95 mol%, more preferably 55 to 85 mol%, and even more preferably 60 to 75 mol%. Furthermore, when the raw material content contains a combination of lithium bromide and lithium iodide as the lithium halide, from the viewpoint of more efficiently obtaining the desired sulfide solid electrolyte, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 80 mol%, still more preferably 30 to 70 mol%, and particularly preferably 40 to 60 mol%.

[0063] When the raw material content includes a halogen element as a raw material, and includes lithium sulfide and diphosphorus pentasulfide, the ratio of the number of moles of lithium sulfide excluding the same number of moles of lithium sulfide as the halogen element to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the halogen element is preferably within the range of 60 to 90%, more preferably within the range of 65 to 85%, even more preferably within the range of 68 to 82%, even more preferably within the range of 72 to 78%, and particularly preferably within the range of 73 to 77%. These ratios allow the desired sulfide solid electrolyte to be obtained more efficiently.

[0064] From the same viewpoint, when the raw material contains lithium sulfide, diphosphorus pentasulfide, and an elemental halogen, the content of the elemental halogen relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the elemental halogen is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and still more preferably 3 to 15 mol%.

[0065] When lithium sulfide, diphosphorus pentasulfide, a halogen element, and a lithium halide are used, the content of the halogen element (α mol %) and the content of the lithium halide (β mol %) relative to the total amount thereof preferably satisfy the following formula (1), more preferably satisfy the following formula (2), even more preferably satisfy the following formula (3), and even more preferably satisfy the following formula (4): 2≦2α+β≦100 (1) 4≦2α+β≦80 (2) 6≦2α+β≦50 (3) 6≦2α+β≦30 (4)

[0066] When the raw material contains two types of halogen as simple substances, the mole number of one halogen atom in the substance is A1, and the mole 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.

[0067] When the raw material contains two types of halogen atoms, and the two types of halogen atoms are bromine and iodine, the ratio B1:B2 is preferably 1:99 to 99:1, more preferably 15:85 to 90:10, even more preferably 20:80 to 80:20, still more preferably 30:70 to 75:25, and particularly preferably 35:65 to 75:25, where B1 is the number of moles of bromine and B2 is the number of moles of iodine.

[0068] In this embodiment, Li 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 %.

[0069] Also, Li ３ P.S. ４ When using a halogen atom, Li ３ P.S. ４ The content of the halogen element is preferably 1 to 50 mol %, more preferably 10 to 40 mol %, even more preferably 20 to 30 mol %, and even more preferably 22 to 28 mol %.

[0070] (Solvent) The solvent used in this embodiment is not particularly limited as long as it has a boiling point different from that of the complexing agent described below, and any solvent that has been conventionally used in the production of sulfide solid electrolytes can be used. Examples of the solvent include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents.

[0071] Examples of aliphatic hydrocarbon solvents include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, tridecane, etc., examples of alicyclic hydrocarbon solvents include cyclohexane, methylcyclohexane, etc., and examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, etc. Among these, from the viewpoint of further promoting the formation of the electrolyte precursor, alicyclic hydrocarbon solvents and aromatic hydrocarbon solvents are preferred, and cyclohexane, toluene, and ethylbenzene are more preferred.

[0072] The solvent used in this embodiment is preferably one of the solvents exemplified above, and is a solvent different from the complexing agent described below. In this embodiment, these solvents may be used alone or in combination of two or more.

[0073] (Complexing Agent) The complexing agent is a compound that easily forms a complex with the raw material contained in the raw material content. For example, lithium sulfide and diphosphorus pentasulfide, which are preferably used as the raw material, and Li obtained when these are used, ３ P.S. ４ and a compound capable of forming a complex with a raw material containing a halogen atom. The complexing agent is not particularly limited as long as it has the above-described properties. Compounds containing atoms with high affinity for lithium atoms, such as heteroatoms like nitrogen, oxygen, and chlorine atoms, are particularly preferred, and compounds containing groups containing these heteroatoms are more preferred. This is because these heteroatoms and groups containing the heteroatoms can coordinate (bond) with lithium.

[0074] 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 raw materials contained in the raw material-containing substance can be bonded via at least two heteroatoms in the molecule. Furthermore, among heteroatoms, nitrogen atoms are preferred, and amino groups are preferred as groups containing nitrogen atoms. In other words, amine compounds are preferred as complexing agents.

[0075] The amine compound is not particularly limited as long as it has an amino group in the molecule, as long as it 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 above-mentioned raw materials can be bonded via at least two nitrogen atoms in the molecule to form a complex. Examples of such amine compounds include aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, which can be used alone or in combination. Among these, aliphatic amines are preferred from the viewpoint of ease of manifesting the function of the complexing agent.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] Among the above, from the viewpoint of obtaining a sulfide solid electrolyte more efficiently, 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.

[0082] 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.

[0083] (Drying Device) The drying device 20 is a device that dries the electrolyte precursor-containing material to obtain an electrolyte precursor, and removes remaining solvent and complexing agent that do not contribute to the formation of the electrolyte precursor. The drying device 20 is not particularly limited and may be a batch type or a continuous type. When the drying device 20 is a continuous type, it is preferable that the drying device 20 is equipped with a line that supplies the obtained electrolyte precursor to the decomplexing device 30. Examples of the drying device 20 include a vacuum drying device, an airflow drying device, a band drying device, a spray drying device, a low-temperature drying device, and a rotary drying device. Among these, from the viewpoint of obtaining the electrolyte precursor more efficiently, it is preferable that the drying device 20 is equipped with at least one device selected from a vacuum drying device and an airflow drying device.

[0084] The vacuum drying equipment is not particularly limited, and examples thereof include an equipment in which an electrolyte precursor-containing material (material to be dried) in a sealed vacuum chamber is heated by a heater or other heating device, and a gaseous fluid in the vacuum chamber is exhausted by a vacuum pump. Examples of the gas flow drying equipment include an equipment in which heated gas is supplied to a drying tube (which may be a cylindrical tank), and the electrolyte precursor-containing material (material to be dried) is supplied to the drying tube.

[0085] From the viewpoint of more efficiently separating the solvent and the complexing agent from the fluid (I) in the separation device described later, the drying device 20 preferably includes a supply line (2-1) connected to the distillation column 60 described later, and preferably includes a supply line (2-2) connected to the absorption column 50 described later. In addition, it is preferable to include a cooler between the drying device 20 and the distillation column 60 to cool the fluid (I).

[0086] The electrolyte precursor obtained in the drying apparatus 20 is supplied to the decomplexing apparatus 30. Furthermore, the fluid (I) containing at least one selected from a solvent and a complexing agent remaining in the drying apparatus 20 is supplied to the separation apparatus 40. Here, when the fluid (I) contains a solvent, a complexing agent, and an atmospheric gas, the fluid (I) is preferably supplied to the absorption tower 50 through a supply line (2-2) connecting the drying apparatus 20 and the absorption tower 50. Furthermore, when the fluid (I) contains at least one selected from a solvent and a complexing agent but does not contain an atmospheric gas, the fluid (I) is preferably cooled by a cooler and then supplied as a liquid to the distillation tower 60 through a supply line (2-1) connecting the drying apparatus 20 and the distillation tower 60.

[0087] (Decomplexing Apparatus) The decomplexing apparatus 30 is an apparatus for removing a complexing agent from an electrolyte precursor to obtain a sulfide solid electrolyte. The decomplexing apparatus 30 is not particularly limited, and examples thereof include dryers such as a vacuum dryer, an airflow dryer, and a band dryer, as well as various heaters such as a hot plate, a vacuum heating apparatus, an argon gas atmosphere furnace, a calcination furnace, and a vacuum calcination furnace. In particular, from the viewpoint of obtaining a sulfide solid electrolyte more efficiently, it is preferable that the decomplexing apparatus 30 includes at least one type of equipment selected from a vacuum dryer and an airflow dryer. The vacuum dryer and the airflow dryer described above in the section (Drying Apparatus) can be used.

[0088] From the viewpoint of more efficiently separating the solvent and complexing agent from the fluid (II) in the separation device described below, the decomplexing device 30 preferably includes a supply line (3-1) connected to the distillation column 60 described below, and a supply line (3-2) connected to the absorption column 50 described below. In addition, it is preferable to include a chiller between the decomplexing device 30 and the distillation column 60 to cool the fluid (II).

[0089] Fluid (II), which contains at least one selected from a solvent and a complexing agent remaining in the decomplexing unit 30, is supplied to the separation unit 40. When fluid (II) contains a solvent, a complexing agent, and an atmospheric gas, it is preferable that fluid (II) be supplied to the absorption tower 50 through a supply line (3-2) connecting the decomplexing unit 30 and the absorption tower 50. When fluid (II) contains at least one selected from a solvent and a complexing agent but does not contain an atmospheric gas, it is preferable that fluid (II) be cooled by a cooling device and then supplied as a liquid to the distillation tower 60 through a supply line (3-1) connecting the decomplexing unit 30 and the distillation tower 60.

[0090] (Separation Device) The separation device 40 is a device that separates a solvent and a complexing agent from a fluid containing at least one selected from a solvent and a complexing agent remaining in the drying device 20 and the decomplexing device 30. Examples of the separation device 40 include an adsorption tower, an absorption tower 50, and a distillation tower 60. Among these, from the viewpoints of more efficiently separating the solvent and the complexing agent and reducing equipment costs, the absorption tower 50 and the distillation tower 60 are preferred. From the viewpoints of further improving the production efficiency of the sulfide solid electrolyte, the separation device 40 preferably includes one or more absorption towers 50 and one or more distillation towers 60.

[0091] (Absorption Tower) The absorption tower 50 is a device that separates a fluid (gas) containing a solvent, a complexing agent, and an atmospheric gas into an absorption liquid containing the solvent and the complexing agent, and the atmospheric gas. The fluid introduced into the absorption tower 50 comes into gas-liquid contact with the absorption liquid supplied from the top of the absorption tower 50, whereby the solvent and complexing agent contained in the fluid are absorbed by the absorption liquid and separated from the atmospheric gas. The absorption liquid containing the solvent and the complexing agent is supplied to the distillation tower 60 through a supply line (2-2) or (3-2) connecting the absorption tower 50 and the distillation tower 60. The absorption tower 50 preferably includes a supply line (4) connected to the decomplexer 30. The atmospheric gas separated in the absorption tower 50 is preferably reused in the decomplexer 30 through the supply line (4) from the viewpoint of more efficiently obtaining a sulfide solid electrolyte. The solvent and complexing agent can be separated from the fluid more efficiently by appropriately adjusting the temperature, pressure, concentration, amount used, and circulation flow rate of the absorbing solution in the absorption tower 50 .

[0092] The number of absorption towers 50 is appropriately selected depending on the conditions, and may be one, or two or more.

[0093] From the viewpoint of separating the solvent and the complexing agent more efficiently, the temperature inside the absorption tower 50 (tower bottom temperature) is preferably −10 to 100° C., more preferably 0 to 90° C., and even more preferably 10 to 80° C.

[0094] The pressure inside the absorption tower 50 may be normal pressure or may be increased. From the viewpoint of separating the solvent and the complexing agent more efficiently, the pressure applied when increasing the pressure is preferably 1 to 1000 kPa, more preferably 10 to 800 kPa, and even more preferably 50 to 500 kPa.

[0095] (Absorption liquid) The absorption liquid is not particularly limited as long as it can absorb the solvent and the complexing agent, but from the viewpoint of obtaining a sulfide solid electrolyte more efficiently, the above-mentioned solvents are preferred, and hydrocarbon solvents are more preferred. Preferred examples of the solvent and hydrocarbon solvent are the same as the preferred examples listed in the above section (Solvent).

[0096] (Atmospheric Gas) Examples of the atmospheric gas include inert gases such as nitrogen and argon, air, etc. Among these, nitrogen and argon are preferred, and nitrogen is more preferred.

[0097] (Distillation Column) The distillation column 60 is an apparatus that separates the solvent and the complexing agent from a liquid containing the solvent and the complexing agent by utilizing the difference in boiling points. Examples of the distillation column 60 include a plate column having multiple internal trays and a packed column filled with packing for gas-liquid contact. The distillation column 60 may be provided with a circulation line for circulating the liquid containing the solvent and the complexing agent so that the liquid containing the solvent and the complexing agent in the distillation column 60 is extracted from the bottom of the distillation column 60 and returned to the distillation column 60. The circulation line may also be provided with a heat exchanger that heats the liquid containing the solvent and the complexing agent by heat exchange between the liquid containing the solvent and the complexing agent flowing through the circulation line and a heat medium. A liquid containing the solvent and the complexing agent is introduced into the distillation column 60, a liquid containing a high-boiling point component (complexing agent) is extracted from the bottom of the column, and a low-boiling point component (solvent) is discharged from the top of the column and cooled to obtain a liquid (condensate). By appropriately adjusting the temperature, pressure, distillation time (residence time), etc. in the distillation column 60, the solvent and complexing agent can be separated more efficiently from the liquid containing the solvent and complexing agent.

[0098] The number of distillation columns 60 is appropriately selected depending on the conditions, and may be one or two or more.

[0099] The temperature inside the distillation column 60 (column bottom temperature) is preferably 30 to 200°C, more preferably 50 to 150°C, and even more preferably 70 to 140°C, from the viewpoint of separating the solvent and the complexing agent more efficiently.

[0100] The pressure inside the distillation column 60 may be reduced, normal, or increased. From the viewpoint of more efficiently separating the solvent and the complexing agent, the pressure inside the column is preferably 1 to 1,000 kPa, more preferably 10 to 800 kPa, and even more preferably 50 to 500 kPa.

[0101] The distillation time (residence time) cannot be generally defined because it varies depending on the size of the distillation column, etc., but is usually 0.1 to 150 hours, preferably 0.5 to 100 hours, and more preferably 1 to 50 hours.

[0102] (Supply Line (1)) The solvent and complexing agent separated in the separation device 40 are supplied to the mixer 10 through the supply line (1) connecting the separation device 40 and the mixer 10, and are reused for mixing with the raw material contents. The supply line (1) may be provided to connect the absorption tower 50 and the mixer 10, or the absorption liquid containing the solvent and complexing agent separated in the absorption tower 50 may be directly supplied to the mixer 10. Alternatively, the supply line (1) may be provided to connect the distillation tower 60 and the mixer 10, or the solvent and complexing agent separated in the distillation tower 60 may be supplied to the mixer 10.

[0103] [Method for Producing Sulfide Solid Electrolyte] The method for producing a sulfide solid electrolyte of the present embodiment includes: mixing a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content; drying the electrolyte precursor content to obtain an electrolyte precursor; removing the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; separating the solvent and the complexing agent from fluid (I) containing at least one selected from the solvent and the complexing agent, which is discharged in the process of obtaining the electrolyte precursor, and fluid (II) containing at least one selected from the solvent and the complexing agent, which is discharged in the process of obtaining the sulfide solid electrolyte; and reusing the separated solvent and complexing agent in the process of obtaining the electrolyte precursor content.

[0104] The manufacturing method of this embodiment can be easily implemented by the manufacturing system of this embodiment described above.

[0105] (Obtaining Electrolyte Precursor Inclusions) The method for producing a sulfide solid electrolyte of this embodiment includes mixing a raw material inclusion for a sulfide solid electrolyte with a solvent and a complexing agent to obtain an electrolyte precursor inclusion. There are no particular limitations on the method for mixing the raw material inclusions, the solvent, and the complexing agent. The raw material, solvent, and complexing agent contained in the raw material inclusions may be mixed in an apparatus capable of mixing the raw material inclusions, the solvent, and the complexing agent. For example, supplying the solvent and complexing agent to a tank, operating the stirring blade, and then gradually adding the raw material while stirring and mixing is preferable, as this results in a good mixing state of the raw material inclusions and improves the dispersibility of the raw material. Furthermore, when a halogen element is used as a raw material, the raw material may not be solid. Specifically, fluorine and chlorine are gases, and bromine is liquid at room temperature and normal pressure. For example, if the raw material is liquid, it may be supplied to the tank together with the solvent and complexing agent separately from other solid raw materials. Alternatively, if the raw material is gas, it may be supplied by blowing into the solvent, complexing agent, and solid raw material.

[0106] As an apparatus for mixing the raw material ingredients, the solvent, and the complexing agent, the apparatus described above in the section (Mixing Apparatus) can be used.

[0107] The content of the raw materials in the raw material-containing mixture may be determined based on the total amount of the complexing agent and the solvent, 1 L. The content of the complexing agent relative to the total amount of the complexing agent and the solvent is preferably 10 to 65% by mass, more preferably 15 to 60% by mass, and even more preferably 20 to 55% by mass.

[0108] The temperature conditions when mixing the raw material ingredients, solvent, and 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 making it easier to obtain an electrolyte precursor, it is preferably 1 to 120 hours, more preferably 4 to 100 hours, and even more preferably 8 to 80 hours.

[0109] (Obtaining Electrolyte Precursor) The method for producing a sulfide solid electrolyte of this embodiment includes drying the electrolyte precursor-containing material to obtain the electrolyte precursor. By drying the electrolyte precursor-containing material (usually a suspension), a powder of the electrolyte precursor is obtained, and the complexing agent can be efficiently removed from the electrolyte precursor, as described below.

[0110] As the device for drying the electrolyte precursor-containing material, the device described above in the section (Drying device) can be used.

[0111] Drying can be performed on the electrolyte precursor-containing material at a temperature appropriate for the type of remaining complexing agent (complexing agent not incorporated into the electrolyte precursor) and solvent. For example, drying can be performed at a temperature equal to or higher than the boiling point of the complexing agent or solvent. Furthermore, drying can be performed by volatilizing the complexing agent and solvent by drying under reduced pressure (vacuum drying) using a vacuum pump or the like at typically 5 to 100°C, preferably 10 to 85°C, more preferably 15 to 70°C, and even more preferably at about room temperature (23°C) (e.g., about room temperature ±5°C). Furthermore, unlike the complexing agent that constitutes the electrolyte precursor, the solvent is less likely to form the electrolyte precursor. Therefore, the amount of solvent that may remain in the electrolyte precursor is typically 3% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less.

[0112] (Obtaining Sulfide Solid Electrolyte) The method for producing a sulfide solid electrolyte of this embodiment includes removing a complexing agent from the above-mentioned electrolyte precursor to obtain a sulfide solid electrolyte. As an apparatus for removing a complexing agent from the electrolyte precursor, the apparatus described in the above section (Decomplexing Apparatus) can be used. As a method for removing a complexing agent from the electrolyte precursor, heating can be mentioned. By heating the electrolyte precursor, the complexing agent in the electrolyte precursor is removed, and an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms can be obtained.

[0113] In the method for producing a sulfide solid electrolyte of this embodiment, whether to obtain an amorphous sulfide solid electrolyte, a crystalline sulfide solid electrolyte, or an amorphous sulfide solid electrolyte and then a crystalline sulfide solid electrolyte, or a crystalline sulfide solid electrolyte directly from an electrolyte precursor is appropriately selected as desired and can be adjusted by the heating temperature, heating time, etc. Furthermore, the heating may be performed in one step or in two or more steps.

[0114] The heating temperature of the electrolyte precursor may be determined depending on the structure of the crystalline sulfide solid electrolyte obtained by heating the amorphous sulfide solid electrolyte (or electrolyte precursor), for example, when obtaining an amorphous sulfide solid electrolyte. Specifically, the amorphous sulfide solid electrolyte (or electrolyte precursor) is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA device) at a temperature increase rate of 10 ° C. / min. The heating temperature is preferably set to 5 ° C. or less, more preferably 10 ° C. or less, and even more preferably 20 ° C. or less, starting from the temperature of the exothermic peak observed at the lowest temperature. There is no particular restriction on the lower limit, but it may be set to about −40 ° C. or more, which is the temperature of the exothermic peak observed at the lowest temperature. By setting the temperature range, an amorphous sulfide solid electrolyte can be obtained more efficiently and reliably. The heating temperature for obtaining an amorphous sulfide solid electrolyte cannot be generally defined because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is usually preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. There is no particular lower limit, but it is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher.

[0115] Furthermore, when a crystalline sulfide solid electrolyte is obtained by heating an amorphous sulfide solid electrolyte or directly from an electrolyte precursor, the heating temperature can be determined depending on the structure of the crystalline sulfide solid electrolyte, and is preferably higher than the heating temperature for obtaining an amorphous sulfide solid electrolyte. Specifically, the amorphous sulfide solid electrolyte (or electrolyte precursor) is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) at a temperature increase rate of 10°C / min. The temperature is preferably set to 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, starting from the peak top temperature of the exothermic peak observed at the lowest temperature. There is no particular upper limit, but it is preferably about 40°C or lower. By setting the temperature range in this way, a crystalline sulfide solid electrolyte can be obtained more efficiently and reliably. The heating temperature for obtaining a crystalline sulfide solid electrolyte cannot be generally defined because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is usually preferably 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C or higher. There is no particular upper limit, but it is preferably 450°C or lower, more preferably 300°C or lower, even more preferably 280°C or lower, and still more preferably 250°C or lower.

[0116] The heating time is not particularly limited as long as it is a time that allows a desired amorphous sulfide solid electrolyte or crystalline sulfide 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.

[0117] Furthermore, the heating is preferably carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum), because this can prevent deterioration (e.g., oxidation) of the crystalline sulfide solid electrolyte.

[0118] (Amorphous sulfide solid electrolyte) The amorphous sulfide solid electrolyte produced in the manufacturing method of this embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and representative examples thereof include Li,２ S-P ２ S ５ Solid electrolytes composed of lithium sulfide and phosphorus sulfide 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 -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, and Li ２ S-P ２ S ５ A solid electrolyte composed of lithium sulfide, phosphorus sulfide, and two types of lithium halides, such as LiI-LiBr, is more preferred. The types of atoms constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0119] In the amorphous sulfide solid electrolyte, the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms is preferably 1.0 to 1.8: 0.1 to 0.8: 1.0 to 2.0: 0.01 to 0.6, more preferably 1.1 to 1.7: 0.2 to 0.6: 1.2 to 1.8: 0.05 to 0.5, and even more preferably 1.2 to 1.6: 0.25 to 0.5: 1.3 to 1.7: 0.08 to 0.4. Furthermore, when bromine and iodine, or bromine and chlorine are used in combination as halogen atoms, the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, bromine, and iodine (or chlorine) is preferably 1.0 to 1.8: 0.1 to 0.8: 1.0 to 2.0: 0.01 to 0.3: 0.01 to 0.3, more preferably 1.1 to 1.7: 0.2 to 0.6: 1.2 to 1.8: 0.02 to 0.25: 0.02 to 0.25, even more preferably 1.2 to 1.6: 0.25 to 0.5: 1.3 to 1.7: 0.03 to 0.2: 0.03 to 0.2, and still more preferably 1.35 to 1.45: 0.3 to 0.45: 1.4 to 1.7: 0.04 to 0.18: 0.04 to 0.18.

[0120] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle size (D ５０ ) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm.

[0121] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may be a so-called glass ceramic obtained by heating an amorphous sulfide solid electrolyte to a crystallization temperature or higher, and its crystalline structure may be Li ３ P.S. ４ Crystal structure, Li ４ P ２ S ６ Crystal structure, Li ７ P.S. ６ Crystal structure, Li ７ P ３ S １１ Examples of such structures include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0122] Li４－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 thio-LISICON region II type has a similar crystal structure.

[0123] In X-ray diffraction measurement using CuKα radiation, Li ３ P.S. ４ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°. ４ P ２ S ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°. ７ P.S. ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°. ７ P ３ S １１Diffraction 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°.

[0124] 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.

[0125] 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 Siｙ 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°.

[0126] 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, it has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The 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°. These peak positions may vary within a range of ±0.5°.

[0127] The composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms in the crystalline sulfide solid electrolyte is the same as the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms in the above-mentioned amorphous sulfide solid electrolyte.

[0128] The shape of the crystalline sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D ５０) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm.

[0129] (Separating Solvent and Complexing Agent) The method for producing a sulfide solid electrolyte of the present embodiment includes separating the solvent and the complexing agent from fluid (I) containing at least one selected from a solvent and a complexing agent discharged in obtaining the electrolyte precursor, and fluid (II) containing at least one selected from a solvent and a complexing agent discharged in obtaining the sulfide solid electrolyte.

[0130] Methods for separating the solvent and complexing agent from the above fluids (I) and (II) include, for example, absorption, pressure swing adsorption (PSA), distillation, and membrane separation. Among these, absorption and distillation are preferred from the viewpoint of more efficient separation of the solvent and complexing agent and reduction of equipment costs. Absorption and distillation may be combined. In absorption, a gaseous fluid is contacted with an absorption liquid, and the solvent and complexing agent are absorbed into the absorption liquid for separation. In distillation, the gaseous fluid is cooled, and the solvent and complexing agent are separated from the resulting liquid by utilizing the difference in boiling points.

[0131] The absorbing liquid may be the same as the solvent described above. When the absorbing liquid is the same solvent as the solvent, the absorbing liquid is reused together with the solvent to obtain the electrolyte precursor-containing material after separating the solvent and the complexing agent.

[0132] The separation method may be appropriately selected depending on the fluid used for separation. For example, when the fluid (I) and the fluid (II) contain a solvent, a complexing agent, and an atmospheric gas, it is preferable to contact at least one selected from the fluids (I) and (II) with an absorption liquid by an absorption method, separate the absorption liquid containing the solvent and the complexing agent from the atmospheric gas, and then distill the absorption liquid by a distillation method to separate the solvent and the complexing agent. Furthermore, when the fluid (I) and the fluid (II) contain at least one selected from a solvent and a complexing agent, but do not contain an atmospheric gas, it is preferable to cool at least one fluid selected from the fluids (I) and (II) by a distillation method, distill the resulting liquid, and separate it into the solvent and the complexing agent.

[0133] Furthermore, it is preferable to reuse the atmospheric gas separated by the absorption method in the above step (obtaining a sulfide solid electrolyte) from the viewpoint of obtaining a sulfide solid electrolyte more efficiently.

[0134] (Reuse of Solvent and Complexing Agent) The method for producing a sulfide solid electrolyte of this embodiment includes reusing the separated solvent and complexing agent in obtaining an electrolyte precursor-containing material. The solvent and complexing agent separated by the distillation method are reused in the above (obtaining an electrolyte precursor-containing material). In addition, the absorption liquid containing the solvent and complexing agent obtained by the absorption method may be reused in the above (obtaining an electrolyte precursor-containing material).

[0135] The sulfide solid electrolyte production system and sulfide solid electrolyte production method of the present embodiment can reuse solvents and complexing agents that have conventionally been discarded, thereby improving the production efficiency of sulfide solid electrolytes, and the resulting sulfide solid electrolyte is suitable for use in batteries, particularly in batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones, as well as in automotive applications.

[0136] 100: Sulfide solid electrolyte production system 10: Mixing device 20: Drying device 30: Decomposition device 40: Separation device 50: Absorption tower 60: Distillation tower 1: Supply line (1) 2-1: Supply line (2-1) 2-2: Supply line (2-2) 3-1: Supply line (3-1) 3-2: Supply line (3-2) 4: Supply line (4)

Claims

1. A sulfide solid electrolyte production system comprising: a mixing device that mixes a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content; a drying device that dries the electrolyte precursor content to obtain an electrolyte precursor; a decomplexing device that removes the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; a separation device that separates the solvent and the complexing agent from at least one fluid selected from a fluid (I) containing at least one selected from the solvent and the complexing agent supplied from the drying device, and a fluid (II) containing at least one selected from the solvent and the complexing agent supplied from the decomplexing device; and a supply line (1) that supplies the solvent and the complexing agent separated in the separation device to the mixing device.

2. The sulfide solid electrolyte production system according to claim 1, wherein the separation device comprises one or more absorption towers and one or more distillation towers.

3. The sulfide solid electrolyte production system according to claim 2, further comprising a supply line (2-1) for supplying the fluid (I) from the drying device to the distillation column.

4. The sulfide solid electrolyte production system according to claim 2 or 3, further comprising a supply line (3-1) for supplying the fluid (II) from the decomposition device to the distillation column.

5. The sulfide solid electrolyte production system according to claim 2, wherein the fluid (I) contains a solvent, a complexing agent, and an atmospheric gas, and further comprising a supply line (2-2) for supplying the fluid (I) from the drying device to the absorption tower and the distillation tower in this order.

6. The sulfide solid electrolyte production system according to claim 2, wherein the fluid (II) contains a solvent, a complexing agent, and an atmospheric gas, and further comprising a supply line (3-2) for supplying the fluid (II) from the decomplexer to the absorption tower and the distillation tower in this order.

7. A sulfide solid electrolyte production system according to any one of claims 2, 5 and 6, wherein the solvent is an absorption liquid in the absorption tower.

8. The sulfide solid electrolyte production system according to claim 7, wherein the solvent is a hydrocarbon solvent.

9. The sulfide solid electrolyte production system according to any one of claims 1 to 8, wherein the complexing agent is an amine compound.

10. A sulfide solid electrolyte production system according to any one of claims 1 to 9, wherein the drying device and the decomposition device comprise at least one type of device selected from a vacuum drying device and an air flow drying device.

11. A method for producing a sulfide solid electrolyte, comprising: mixing a raw material content of a sulfide solid electrolyte, a solvent, and a complexing agent to obtain an electrolyte precursor content; drying the electrolyte precursor content to obtain an electrolyte precursor; removing the complexing agent from the electrolyte precursor to obtain a sulfide solid electrolyte; separating the solvent and the complexing agent from a fluid (I) containing at least one selected from the solvent and the complexing agent discharged in obtaining the electrolyte precursor, and a fluid (II) containing at least one selected from the solvent and the complexing agent discharged in obtaining the sulfide solid electrolyte; and reusing the separated solvent and complexing agent in obtaining the electrolyte precursor content.

12. The method for producing a sulfide solid electrolyte according to claim 11, wherein the separating step is at least one selected from the group consisting of: cooling at least one fluid selected from the fluid (I) and the fluid (II), distilling the resulting liquid, and separating the liquid into the solvent and the complexing agent; and wherein the at least one fluid selected from the fluid (I) and the fluid (II) contains a solvent, a complexing agent, and an atmospheric gas, contacting the at least one fluid selected from the fluid (I) and the fluid (II) with an absorbing liquid to separate the liquid into an absorbing liquid containing the solvent and the complexing agent and the atmospheric gas, and then distilling the absorbing liquid to separate the liquid into the solvent and the complexing agent.

13. The method for producing a sulfide solid electrolyte according to claim 12, wherein the absorption liquid is the solvent.

14. The method for producing a sulfide solid electrolyte according to claim 13, wherein the solvent is a hydrocarbon solvent.

15. A method for producing a sulfide solid electrolyte according to any one of claims 11 to 14, wherein the complexing agent is an amine compound.

16. A method for producing a sulfide solid electrolyte according to any one of claims 12 to 15, wherein at least one selected from the fluid (I) and the fluid (II) contains a solvent, a complexing agent, and an atmospheric gas, and the at least one selected from the fluid (I) and the fluid (II) is brought into contact with an absorbing liquid to separate the absorbing liquid containing the solvent and the complexing agent and the atmospheric gas, and then the atmospheric gas is reused in obtaining the sulfide solid electrolyte.