Sulfide solid electrolyte manufacturing method

Abstract

Provided is a sulfide solid electrolyte manufacturing method comprising: obtaining a sulfide solid electrolyte for mechanical processing which includes lithium, sulfur, and phosphorus atoms and which, when the morphology of the sulfide solid electrolyte is adjusted by mechanical processing and conveyed by a screw feeder, is less likely to cause adhesion and deposition of the sulfide solid electrolyte on a screw and can be stably supplied; performing mechanical processing on the sulfide solid electrolyte for mechanical processing in a solvent; and conveying the sulfide solid electrolyte after the mechanical processing by a screw feeder provided with a shaftless screw.

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 for use as their power sources has become increasingly important. Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents. However, because these electrolytes are liquid and flammable, safety concerns regarding leakage, fire, and the like 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 have only increased. Therefore, all-solid-state batteries in which the electrolyte is replaced with a solid electrolyte have been developed because such batteries eliminate the use of flammable organic solvents, simplify safety devices, and offer superior manufacturing costs and productivity.

[0003] From the viewpoint of the performance and manufacturing of all-solid-state lithium batteries, solid electrolytes with small particle diameters are required. In all-solid-state lithium batteries, the cathode material, anode material, and electrolyte are all solid, so a small particle diameter of the solid electrolyte facilitates the formation of contact interfaces between the solid electrolyte particles and between the active material and the solid electrolyte, which has the advantage of improving the paths for ionic conduction and electronic conduction.

[0004] Patent Literature 1 discloses a sulfide solid electrolyte and a processing method therefor, in which the morphology is easily adjusted by performing at least one mechanical treatment selected from crushing and granulation, focusing on adjusting the morphology, such as particle size, when the sulfide solid electrolyte is used as a cathode material, an anode material, or an electrolyte layer.

[0005] International Publication No. 2020 / 105736

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a method for producing a sulfide solid electrolyte that is less likely to adhere to or deposit on a screw when conveying a sulfide solid electrolyte whose morphology has been adjusted by mechanical treatment using a screw feeder, and that can stably supply the sulfide solid electrolyte.

[0007] A method for producing a sulfide solid electrolyte according to the present invention includes: obtaining a sulfide solid electrolyte for mechanical treatment that contains lithium atoms, sulfur atoms, and phosphorus atoms; subjecting the sulfide solid electrolyte for mechanical treatment to mechanical treatment in a solvent; and transporting the sulfide solid electrolyte after the mechanical treatment by a screw feeder equipped with a shaftless screw.

[0008] According to the present invention, it is possible to provide a method for producing a sulfide solid electrolyte that is less likely to adhere to or deposit on a screw when conveying a sulfide solid electrolyte whose morphology has been adjusted by mechanical treatment using a screw feeder, and that can stably supply the sulfide solid electrolyte.

[0009] Fig. 1 is a cross-sectional schematic diagram of an example of a screw feeder used in a method for producing a sulfide solid electrolyte according to the present embodiment. Fig. 2 is a cross-sectional schematic diagram of a screw feeder equipped with a shaft-equipped screw used in a comparative example and a reference example.

[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. In recent years, efforts have been made to mass-produce solid electrolytes. Under these circumstances, stable supply and transport of solid electrolytes to destinations is an urgent issue, as it directly contributes to improving the production efficiency of solid electrolytes. When using solid electrolytes, mechanical processing and classification are generally performed to adjust the morphology to suit the destination process. A screw feeder is used to supply solid electrolytes whose morphology has been adjusted by mechanical processing to the destination. However, problems have occurred with screw feeders, such as a decrease in the amount of solid electrolyte supplied or an inability to supply solid electrolyte. The inventors conducted extensive research into this phenomenon and found that morphology-adjusted solid electrolytes have high adhesive strength, and in screws with blades on the shaft, the solid electrolyte adheres and accumulates on the shaft, filling the grooves between the shaft and the blades, making it difficult to supply the solid electrolyte. The phenomenon of the solid electrolyte filling up the screw grooves does not occur when raw materials or powder of a solid electrolyte whose morphology has not been adjusted are fed by a screw feeder, and is specific to solid electrolytes whose morphology has been adjusted. Therefore, the inventors investigated the shape of the screw of the screw feeder.

[0012] The above-mentioned Patent Document 1 does not consider the above problem.

[0013] Based on the above investigations, the present inventors have found that when a sulfide solid electrolyte whose morphology has been adjusted by mechanical treatment is conveyed by a screw feeder, by using a screw without a shaft as the screw of the screw feeder, adhesion and deposition of the sulfide solid electrolyte on the screw is less likely to occur, and the sulfide solid electrolyte can be stably supplied.

[0014] (Regarding Various Forms of the Present Embodiment) A method for producing a sulfide solid electrolyte according to a first form of the present embodiment is a method for producing a sulfide solid electrolyte, the method including: obtaining a sulfide solid electrolyte for mechanical treatment that contains lithium atoms, sulfur atoms, and phosphorus atoms; subjecting the sulfide solid electrolyte for mechanical treatment to mechanical treatment in a solvent; and transporting the sulfide solid electrolyte after the mechanical treatment by a screw feeder equipped with a shaftless screw.

[0015] As used herein, the term "sulfide solid electrolyte" refers to an electrolyte that contains sulfur atoms and maintains a solid state at 25°C under a nitrogen atmosphere. The sulfide solid electrolyte of this embodiment contains lithium atoms, sulfur atoms, and phosphorus 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. In this specification, the term "sulfide solid electrolyte for mechanical treatment" refers to a sulfide solid electrolyte before being subjected to mechanical treatment to adjust its morphology, and can be used as is as a 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 the method for producing a sulfide solid electrolyte of this embodiment (hereinafter also simply referred to as the "production method of this embodiment"), as described above, when a sulfide solid electrolyte whose morphology has been adjusted by mechanical treatment is conveyed by a screw feeder, a shaftless screw is used as the screw of the screw feeder. This makes it difficult for the sulfide solid electrolyte to adhere to or deposit on the screw, and allows for a stable supply of the sulfide solid electrolyte. In this specification, "morphology" refers to various properties of the sulfide solid electrolyte, and in particular refers to the average particle size and specific surface area, which are properties required for the production of a sulfide solid electrolyte. In the production method of this embodiment, the "morphology" is adjusted by mechanical treatment.

[0018] A second aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the first aspect, wherein the shaftless screw is used in at least a portion that comes into contact with the sulfide solid electrolyte after the mechanical treatment.

[0019] The shaftless screw preferably does not have a shaft at least in a portion that comes into contact with the sulfide solid electrolyte after mechanical treatment, which makes it difficult for the sulfide solid electrolyte to adhere to or accumulate on the screw and allows for a more stable supply of the sulfide solid electrolyte.

[0020] A third aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the first or second aspect, wherein the shaftless screw has a shaft at one end or both ends, and does not have a shaft in a portion that comes into contact with the sulfide solid electrolyte after the mechanical treatment.

[0021] The shaftless screw does not have a shaft in the portion that comes into contact with the sulfide solid electrolyte after mechanical treatment, but has a shaft at one end or both ends, thereby making it possible to further increase the durability of the screw while exhibiting the effects of the present invention.

[0022] 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 mechanical treatment is at least one treatment selected from crushing and granulation.

[0023] In the production method of this embodiment, the sulfide solid electrolyte for mechanical treatment is subjected to the above-described mechanical treatment in a solvent, whereby the sulfide solid electrolyte can be easily adjusted to have a desired morphology, such as a desired particle size.

[0024] A fifth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to fourth aspects, wherein the mechanical treatment is carried out using a stirrer or a pulverizer.

[0025] By carrying out the mechanical treatment using a stirrer or a pulverizer, the sulfide solid electrolyte can be easily adjusted to have a desired morphology, such as a desired particle size.

[0026] A sixth aspect of the present embodiment is directed to the method for producing a sulfide solid electrolyte of any one of the first to fifth aspects, wherein the sulfide solid electrolyte for mechanical treatment further contains a halogen atom.

[0027] A sulfide solid electrolyte containing halogen atoms has higher ionic conductivity than a sulfide solid electrolyte not containing halogen atoms. Therefore, by including halogen atoms, it is possible to produce a sulfide solid electrolyte having higher ionic conductivity.

[0028] A seventh aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to sixth aspects, wherein the solvent includes an ether-based solvent.

[0029] In the manufacturing method of this embodiment, by using an ether-based solvent as the solvent, it is possible to easily adjust the morphology of the sulfide solid electrolyte, such as the desired particle size.

[0030] The method for producing a sulfide solid electrolyte according to an eighth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to seventh aspects, wherein the sulfide solid electrolyte for mechanical treatment is amorphous or crystalline.

[0031] In the manufacturing method of this embodiment, it is possible to manufacture an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte as desired.

[0032] A ninth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to eighth aspects, further comprising heating the mechanically treated sulfide solid electrolyte transported by the screw feeder equipped with the shaftless screw in a heated air stream.

[0033] The sulfide solid electrolyte is dispersed in the heated airflow by coming into direct contact with the heated airflow, increasing the contact area between the sulfide solid electrolyte and the heated airflow. This allows the solvent contained in the sulfide solid electrolyte to be heated efficiently. Furthermore, the solvent can be quickly removed by the heated airflow.

[0034] A tenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte of the ninth aspect, wherein the temperature of the heated airflow is 150°C or higher and 250°C or lower.

[0035] By setting the temperature of the heated airflow within the above temperature range, a crystalline sulfide solid electrolyte can be obtained more efficiently and reliably. The production method of this embodiment can produce an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte as desired.

[0036] A method for producing a sulfide solid electrolyte according to an eleventh aspect of the present embodiment is the same as the ninth or tenth aspect, wherein the supply amount of the heated airflow is 0.1 m ３ / min or more 500m ３ / minutes or less.

[0037] By using the heated airflow in an amount within the above range, the action of the heated airflow enables more efficient dispersion of the sulfide solid electrolyte and removal of the solvent.

[0038] A method for producing a sulfide solid electrolyte according to a twelfth aspect of the present embodiment is, in any one of the first to eleventh aspects, wherein the sulfide solid electrolyte for mechanical treatment is obtained by a step including mixing a raw material inclusion containing lithium atoms, sulfur atoms, and phosphorus atoms with a complexing agent.

[0039] By using a complexing agent, it becomes easier to maintain the dispersion state of the raw material ingredients uniformly, and as a result, it becomes easier to obtain a sulfide solid electrolyte having high ionic conductivity.

[0040] A thirteenth aspect of the present embodiment is the method for producing a sulfide solid electrolyte of the twelfth aspect, wherein the raw material contents further include a halogen atom.

[0041] When the raw material contains halogen atoms, the resulting sulfide solid electrolyte contains halogen atoms. A sulfide solid electrolyte containing halogen atoms has higher ionic conductivity than a sulfide solid electrolyte that does not contain halogen atoms. Therefore, by containing halogen atoms, it is possible to produce a sulfide solid electrolyte with higher ionic conductivity.

[0042] An apparatus for producing a sulfide solid electrolyte according to a fourteenth aspect of the present embodiment is an apparatus for producing a sulfide solid electrolyte, comprising: a device for mechanically treating a sulfide solid electrolyte for mechanical treatment in a solvent; and a screw feeder equipped with a shaftless screw for transporting the sulfide solid electrolyte after the mechanical treatment.

[0043] As described above, in the sulfide solid electrolyte production apparatus of the present embodiment, when the sulfide solid electrolyte whose morphology has been adjusted by mechanical treatment is transported by a screw feeder, the screw feeder has a screw without a shaft, which makes it difficult for the sulfide solid electrolyte to adhere to or accumulate on the screw, and enables a stable supply of the sulfide solid electrolyte.

[0044] A sulfide solid electrolyte manufacturing apparatus according to a fifteenth aspect of the present embodiment is the fourteenth aspect, wherein the equipment for performing the mechanical treatment is a stirrer or a pulverizer.

[0045] By using a stirrer or a pulverizer as the equipment for performing the mechanical treatment, the sulfide solid electrolyte can be easily adjusted to have a desired morphology, such as a desired particle size.

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

[0047] [Method for Producing Sulfide Solid Electrolyte] The method for producing a sulfide solid electrolyte of the present embodiment includes: obtaining a sulfide solid electrolyte for mechanical treatment that contains lithium atoms, sulfur atoms, and phosphorus atoms; subjecting the sulfide solid electrolyte for mechanical treatment to mechanical treatment in a solvent; and transporting the sulfide solid electrolyte after the mechanical treatment by a screw feeder equipped with a shaftless screw.

[0048] [Obtaining a sulfide solid electrolyte for mechanical treatment containing lithium atoms, sulfur atoms, and phosphorus atoms] The method for obtaining a sulfide solid electrolyte for mechanical treatment containing lithium atoms, sulfur atoms, and phosphorus atoms is not particularly limited. However, from the viewpoint of easily obtaining a sulfide solid electrolyte with high ionic conductivity, it is preferable to obtain the sulfide solid electrolyte by a process including mixing a raw material containing lithium atoms, sulfur atoms, and phosphorus atoms with a complexing agent. The process preferably includes mixing the raw material containing material with a complexing agent to obtain an electrolyte precursor containing material, drying the electrolyte precursor containing material to obtain an electrolyte precursor, and heating the electrolyte precursor to obtain a sulfide solid electrolyte.

[0049] (Raw material inclusions) The raw material inclusions used in this embodiment contain lithium atoms, sulfur atoms, and phosphorus atoms. Furthermore, from the viewpoint of improving ionic conductivity, the raw material inclusions used in this embodiment preferably further contain halogen atoms. More specifically, the raw material inclusions are inclusions containing substances containing these atoms (hereinafter also referred to as "solid electrolyte raw materials"), and preferably contain two or more solid electrolyte raw materials.

[0050] 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; raw materials containing at least two atoms selected from the above-mentioned atoms, and fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ Representative examples of the raw material include a halogen element such as halogen, phosphorus, sulfur, and the like; and a raw material consisting of one atom selected from the above-mentioned elements.

[0051] Among the above, examples of the solid electrolyte raw material containing lithium atoms, sulfur atoms, and phosphorus atoms include lithium sulfide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５Among the phosphorus sulfides, diphosphorus pentasulfide is preferred.

[0052] Among the above, either a simple halogen or a lithium halide can be preferably used as the solid electrolyte raw material containing a halogen atom. As the halogen atom contained in the raw material, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom is preferred, and a chlorine atom, a bromine atom, or an iodine atom is more preferred.

[0053] As the solid electrolyte raw material, those containing these halogen atoms are preferable. Therefore, as the halogen element, chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ ) is more preferred, and as the lithium halide, lithium chloride, lithium bromide, and lithium iodide are more preferred.

[0054] Furthermore, it is preferable to select the solid electrolyte raw material containing a halogen atom according to the type of sulfide solid electrolyte to be obtained. For example, when a sulfide solid electrolyte having a thiolithium region II crystal structure is to be obtained, bromine (Br ２ ), iodine (I ２ ) is more preferred, and among the lithium halides, lithium bromide and lithium iodide are more preferred. When a sulfide solid electrolyte having an argyrodite-type crystal structure is to be obtained, among the above-mentioned halogen elements, chlorine (Cl ２ ), bromine (Br ２ Among the lithium halides, lithium chloride and lithium bromide are more preferred. These halogen atom-containing solid electrolyte raw materials may be used alone or in combination of two or more kinds, and it is preferred to use two or more kinds in combination.

[0055] Preferred examples of the combination of solid electrolyte raw materials contained in the raw material inclusions include a combination of lithium sulfide, phosphorus sulfide, and lithium halide, a combination of lithium sulfide, phosphorus sulfide, and a simple halogen, and a combination of lithium sulfide, phosphorus sulfide, lithium halide, and a simple halogen. More preferred examples include a combination of lithium sulfide, phosphorus pentasulfide, and a lithium halide, and a combination of lithium sulfide, phosphorus pentasulfide, and a simple halogen. In the above combinations, preferred lithium halides are lithium chloride, lithium bromide, and lithium iodide, and preferred simple halogens are chlorine, bromine, and iodine. As mentioned above, the solid electrolyte raw material containing halogen atoms can be selected depending on the type of sulfide solid electrolyte to be obtained.

[0056] The raw material contains a solid electrolyte raw material containing at least two kinds of atoms selected from the above-mentioned atoms. Examples of solid electrolyte raw materials other than the above include 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 F) and the like.

[0057] Examples of solid electrolyte raw materials other than those mentioned above that are contained in the raw material inclusion include solid electrolyte raw materials that contain at least one atom selected from the above atoms and also contain atoms other than the atoms mentioned above, 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 When oxygen atoms are introduced into a sulfide solid electrolyte, phosphoric acid compounds such as lithium oxide, lithium hydroxide, and lithium phosphate are preferred.

[0058] 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.

[0059] When the raw material contains lithium sulfide, diphosphorus pentasulfide, and lithium halide, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, and even more preferably 74 mol% or more, from the viewpoint of more efficiently obtaining the desired sulfide solid electrolyte, and the upper limit is preferably 85 mol% or less, more preferably 83 mol% or less, and even more preferably 80 mol% or less. The range is typically preferably 60 to 85 mol%, more preferably 65 to 83 mol%, even more preferably 70 to 80 mol%, and even more preferably 74 to 80 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II type crystal structure, in addition to the above ranges, particularly 74 to 78.5 mol%, 74 to 78 mol%, and 74 to 76 mol% are preferred, and when attempting to obtain a sulfide solid electrolyte having an argyrodite type crystal structure, in addition to the above ranges, particularly 76 to 83 mol%, 77 to 80 mol%, and 78 to 80 mol% are preferred.

[0060] When the raw material content includes lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed, the content of lithium sulfide and diphosphorus pentasulfide relative to the total is preferably 50 mol% or more, more preferably 55 mol% or more, and even more preferably 60 mol% or more, with the upper limit being preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, and still more preferably 80 mol% or less. The range is typically preferably 50 to 100 mol%, more preferably 55 to 90 mol%, even more preferably 60 to 85 mol%, and even more preferably 60 to 80 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II type crystal structure, in addition to the above ranges, particularly 65 to 90 mol%, 70 to 85 mol%, and 75 to 83 mol% are preferred, and when attempting to obtain a sulfide solid electrolyte having an argyrodite type crystal structure, in addition to the above ranges, particularly 50 to 78 mol%, 55 to 70 mol%, and 55 to 65 mol% are preferred.

[0061] When the raw material contains a combination of lithium bromide and lithium iodide as lithium halides, 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 mol% or more, more preferably 20 mol% or more, even more preferably 35 mol% or more, and even more preferably 45 mol% or more, with the upper limit being preferably 99 mol% or less, more preferably 90 mol% or less, even more preferably 75 mol% or less, and even more preferably 60 mol% or less. The range is typically preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 35 to 75 mol%, and even more preferably 45 to 60 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having a thiolicon region II crystal structure, in addition to the above range, 40 to 75 mol%, 40 to 65 mol%, and 45 to 55 mol% are particularly preferred.

[0062] Furthermore, when the raw material contains a combination of lithium bromide and lithium chloride 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 chloride is preferably 1 mol% or more, more preferably 15 mol% or more, even more preferably 25 mol% or more, and even more preferably 35 mol% or more, with the upper limit being preferably 99 mol% or less, more preferably 75 mol% or less, even more preferably 60 mol% or less, and even more preferably 45 mol% or less. The range is typically preferably 1 to 99 mol%, more preferably 15 to 75 mol%, even more preferably 25 to 60 mol%, and even more preferably 35 to 45 mol%. Furthermore, when attempting to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure, in addition to the above range, 25 to 45 mol% or 35 to 40 mol% is particularly preferred.

[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 the raw material contains lithium sulfide, diphosphorus pentasulfide, an elemental halogen, and a lithium halide, the content of the elemental halogen (α mol %) and the content of the lithium halide (β mol %) relative to the total amount of lithium sulfide, diphosphorus pentasulfide, the elemental halogen, and the lithium halide preferably satisfy the following formula (2), more preferably satisfy the following formula (3), even more preferably satisfy the following formula (4), and still 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)

[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 kinds of halogen atoms, and the two kinds of halogen atoms are bromine and iodine, then, if the number of moles of bromine is A1 and the number of moles of iodine is A2, the ratio A1:A2 is preferably 1:99 to 99:1, more preferably 20:80 to 80:20, even more preferably 35:65 to 80:20, and even more preferably 45:55 to 70:30. When the two kinds of halogen atoms are bromine and chlorine, then, if the number of moles of bromine is B1 and the number of moles of chlorine is B2, the ratio 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 35:65 to 60:40.

[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] (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. ４and 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.

[0071] The complexing agent preferably has at least two heteroatoms capable of coordinating (bonding) in the molecule, and more preferably has a group containing at least two heteroatoms in the molecule. By having a group containing at least two heteroatoms in the molecule, the 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] (Solvent) When mixing the raw material inclusions and the complexing agent, a solvent may be added. 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, the elution of components in the electrolyte precursor can be suppressed. In addition, mixing the raw material inclusions 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 raw material inclusions, particularly the dispersion state of the halogen atoms, is uniformly maintained. As a result, the effect of obtaining high ionic conductivity is easily achieved.

[0081] The method for producing a sulfide solid electrolyte according to this embodiment is a so-called heterogeneous method, and it is preferable that the complex does not completely dissolve in the liquid complexing agent but precipitates. The solubility of the complex can be adjusted by adding a solvent. Halogen elements, in particular, tend to dissolve from the complex, so adding a solvent can suppress the dissolution of halogen elements 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 dispersed.

[0082] 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.

[0083]

[0084] (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.)

[0085] By using a solvent with a solubility parameter of 10 or less, halogen atoms, raw materials containing halogen atoms such as lithium halide, and even halogen-containing components constituting the co-crystal contained in the complex (e.g., an aggregate formed by bonding lithium halide and a complexing agent) can be made relatively less soluble compared to the complexing agent. This makes it easier to fix the halogen atoms in the complex, and the halogen atoms are present in a well-dispersed state in the resulting electrolyte precursor and further in the sulfide solid electrolyte, making it easier to obtain a sulfide 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.

[0086] More specifically, the solvent used in this embodiment can be a wide variety of solvents that have conventionally been used in the production of sulfide solid electrolytes, and examples thereof include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; solvents containing carbon atoms such as alcohol solvents, ester solvents, aldehyde solvents, ketone solvents, ether solvents having 4 or more carbon atoms on one side, and solvents containing carbon atoms and heteroatoms; etc. Among these, solvents may be appropriately selected, preferably those having a solubility parameter within the above range.

[0087] 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 such as ethanol (12.7), butanol (11.4), and other alcohol-based solvents; aldehyde-based solvents such as formaldehyde, acetaldehyde (10.3), and dimethylformamide (12.1); ketone-based solvents such as acetone (9.9), methyl ethyl ketone, and other ether-based solvents such as dibutyl ether, cyclopentyl methyl ether (8.4), tert-butyl methyl ether, and anisole; and solvents containing carbon atoms and hetero atoms such as acetonitrile (11.9), dimethyl sulfoxide, and carbon disulfide. The values ​​in parentheses in the above examples are SP values.

[0088] 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, cyclohexane, diethyl ether, diisopropyl ether, and dibutyl ether are even 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.

[0089] (Mixing) The manufacturing method of this embodiment preferably includes mixing a raw material inclusion with a complexing agent to obtain an electrolyte precursor inclusion. In this embodiment, the raw material inclusion and the complexing agent may be mixed in either a solid or liquid form. However, since the raw material inclusion typically contains a solid and the complexing agent is liquid, they are mixed in a form in which the solid raw material is present in the liquid complexing agent. Furthermore, when mixing the raw material inclusion and the complexing agent, a solvent may be further mixed as needed. Hereinafter, in the sections describing the mixing of the raw material inclusion and the complexing agent, unless otherwise specified, it is assumed that a solvent may also be further mixed as needed.

[0090] There are no particular limitations on the method for mixing the raw material inclusions, the complexing agent, and the solvent. The raw material and the complexing agent contained in the raw material inclusions can be mixed in a device capable of mixing the raw material inclusions and the complexing agent. For example, the complexing agent is supplied to a tank, the stirring blade is activated, and then the raw material is gradually added while stirring and mixing, which is preferable because it results in a good mixing state of the raw materials and improves the dispersibility of the raw materials. Furthermore, when a halogen element is used as a raw material, the raw material may not be solid. Specifically, at room temperature and normal pressure, fluorine and chlorine are gases, and bromine is liquid. For example, if the raw material is liquid, it can be supplied into the tank together with the complexing agent separately from other solid raw materials. Alternatively, if the raw material is gas, it can be supplied by blowing it into the complexing agent mixed with the solid raw material.

[0091] The mixing of the raw material ingredients with the complexing agent may be performed using a stirrer, or may be performed using a device generally called a pulverizer, such as a media-type pulverizer such as a ball mill or a bead mill, which is used for pulverizing solid raw materials, or may be performed using both a stirrer and a pulverizer. In the production method of this embodiment, a complex can be formed simply by mixing the raw material and the complexing agent using a stirrer, but in order to shorten the mixing time for obtaining the complex or to achieve fine powder, the mixture of the raw material and the complexing agent may be pulverized using a pulverizer.

[0092] A specific example of the agitator is a mechanical agitation mixer equipped with a stirring blade in a tank. Examples of mechanical agitation mixers include high-speed agitation mixers and double-arm mixers, and high-speed agitation mixers are preferably used from the viewpoint of improving the uniformity of the raw materials in the mixture of the raw materials and the complexing agent and obtaining higher ionic conductivity. Examples of high-speed agitation mixers include vertical-axis rotary mixers and horizontal-axis rotary mixers, and either type of mixer may be used.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] The temperature conditions when mixing the raw material ingredients 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 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.

[0097] (Drying) The manufacturing method of this embodiment may include drying the electrolyte precursor-containing material (usually a suspension) obtained as described above. This results in an electrolyte precursor powder. By drying the material in advance, it becomes possible to efficiently perform heating.

[0098] 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.

[0099] 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 is easily performed by decantation, in which the electrolyte precursor-containing material is transferred to a container, and after the solid has precipitated, 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.

[0100] It can also be dried by heating using a dryer or the like. The drying of the electrolyte precursor-containing material may be carried out under any pressure condition, such as under pressure, normal pressure, or reduced pressure, and is preferably carried out under normal pressure or reduced pressure. In particular, considering drying at a lower temperature, it is preferable to dry under reduced pressure, or even under vacuum, using a vacuum pump or the like. The temperature condition for drying may be a temperature equal to or higher than the boiling point of the remaining complexing agent or the solvent used as needed. Since the temperature condition can vary depending on the type of complexing agent and solvent used, it is not possible to generalize the specific temperature condition, but it is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, with the upper limit being preferably 110°C or lower, more preferably 85°C or lower, and even more preferably 70°C or lower.

[0101] As for the pressure conditions, as described above, normal pressure or reduced pressure is preferable. When reduced pressure is used, specifically, the pressure is preferably 85 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less. The lower limit may be a vacuum (0 kPa). In consideration of ease of pressure adjustment, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more.

[0102] (Heating) The manufacturing method of this embodiment preferably includes heating the electrolyte precursor obtained as described above to obtain a sulfide solid electrolyte (sulfide solid electrolyte for mechanical treatment). The electrolyte precursor is a precursor of a sulfide solid electrolyte, and can become a sulfide solid electrolyte by removing the complexing agent. The complexing agent is removed by heating the electrolyte precursor. By including heating the electrolyte precursor in this manner, the complexing agent in the electrolyte precursor is removed, and a sulfide solid electrolyte containing lithium atoms, sulfur atoms, and phosphorus atoms is obtained. Furthermore, in the manufacturing method of this embodiment, crystallization can be achieved by adjusting the heating temperature during heating, and the sulfide solid electrolyte can be converted into a crystalline sulfide solid electrolyte. The sulfide solid electrolyte obtained by the heating may be an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte.

[0103] The heating temperature for removing the complexing agent is not particularly limited as long as the complexing agent can be removed, and may be any temperature at which an amorphous sulfide solid electrolyte is obtained. The temperature at which the amorphous sulfide solid electrolyte is obtained can be determined depending on the structure of the crystalline sulfide solid electrolyte obtained by heating the amorphous sulfide solid electrolyte (or electrolyte precursor). 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 less, more preferably 10 ° C. or less, and even more preferably 20 ° C. or less, starting from the peak top temperature of the exothermic peak observed at the lowest temperature. The lower limit is not particularly limited as long as it is equal to or higher than the boiling point of the complexing agent, and may be set to about −40 ° C. or more, the peak top temperature of the exothermic peak observed at the lowest temperature. By setting the temperature range in this way, the complexing agent is more efficiently and reliably removed from the electrolyte precursor, and an amorphous sulfide solid electrolyte is obtained.

[0104] The heating temperature for removing the complexing agent cannot be generally defined because it varies depending on the structure of the resulting crystalline sulfide solid electrolyte. However, it is usually preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. The lower limit is not particularly limited as long as it is equal to or higher than the boiling point of the complexing agent, and is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher.

[0105] Heating to remove the complexing agent can be carried out at normal pressure, but can also be carried out under reduced pressure or even under vacuum to reduce the heating temperature. When heating under 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.

[0106] The heating time for removing the complexing agent is not particularly limited as long as it is a time that can remove the complexing agent, 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.

[0107] Furthermore, the heating for removing the complexing agent is preferably carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere), because this can prevent deterioration of the sulfide solid electrolyte (e.g., deterioration due to oxidation).

[0108] The heating method for removing the complexing agent is not particularly limited, and examples thereof include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, and a calcination furnace. Industrially, a horizontal dryer or a horizontal vibration fluidized dryer having a heating means and a feeding mechanism can also be used, and the type can be selected depending on the amount of heat to be processed. In addition to the above-mentioned equipment, it is also possible to use dryers of various types, such as a pneumatic dryer, a medium fluidized dryer equipped with a mechanism for fluidizing a medium such as media particles with a gas, and a spray dryer. Using these dryers with airflow allows for efficient production of a sulfide solid electrolyte having a small average particle size.

[0109] By heating as described above, the complexing agent can be removed from the electrolyte precursor, and the electrolyte precursor becomes an amorphous sulfide solid electrolyte. However, not all of the complexing agent may be removed from the electrolyte precursor, resulting in some of the complexing agent remaining in the amorphous sulfide solid electrolyte. In this case, the content of the complexing agent in the sulfide solid electrolyte is preferably 0% by mass, i.e., no complexing agent is contained at all. However, from the viewpoint of efficiently obtaining a sulfide solid electrolyte with high ionic conductivity, the content is usually 50% by mass or less, further 45% by mass or less, 40% by mass or less, 35% by mass or less, or 25% by mass or less, with the lower limit being approximately 0.1% by mass or more.

[0110] 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 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 can be measured using a gas chromatography (GC) apparatus.

[0111] In the production method of this embodiment, heating for crystallization may be performed as desired following the heating for removing the complexing agent. An amorphous sulfide solid electrolyte is obtained by the heating for removing the complexing agent. This can be converted into a crystalline sulfide solid electrolyte by heating for crystallization.

[0112] The heating temperature for crystallization is not particularly limited as long as it is a temperature at which a crystalline sulfide solid electrolyte can be obtained, and cannot be generally determined because it can vary depending on the crystalline structure of the resulting crystalline sulfide solid electrolyte, but is preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher, with the upper limit being preferably 600°C or lower, more preferably 500°C or lower, even more preferably 325°C or lower, and still more preferably 250°C or lower. Representative numerical ranges are preferably 130 to 600°C, 140 to 600°C, 140 to 500°C, 150 to 325°C, or 150 to 250°C.

[0113] The heating time, pressure conditions, heating in an inert gas atmosphere, and heating method for the crystallization can be the same as those described above for the heating for removing the complexing agent.

[0114] (Amorphous sulfide solid electrolyte) The amorphous sulfide solid electrolyte produced in the manufacturing method of this embodiment contains lithium atoms, phosphorus atoms, and sulfur atoms, and preferably halogen atoms. Representative examples include Li, ２ S-P ２ S ５ Sulfide 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, Li２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ -LiI-LiBr, etc., sulfide 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 sulfide solid electrolyte such as LiI is preferable. 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 sulfide 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 sulfide 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 optical emission spectrometer.

[0115] 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.

[0116] 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.

[0117] (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).

[0118] 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 The sulfide solid electrolyte obtained by the production method of this embodiment contains lithium atoms, phosphorus atoms, and sulfur atoms, and preferably halogen atoms, and therefore, the term "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 ４However, 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 has a thiolisiconregion II type crystal structure formed by lithium atoms, phosphorus atoms, and sulfur atoms, preferably halogen atoms. The same applies to the argyrodite type crystal structure described below.

[0119] In X-ray diffraction measurement using CuKα radiation, Li ３ P.S. ４ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°. ４ P ２ S ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°. ７ P.S. ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°. ７ P ３ S １１ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ The diffraction peaks of the thio-LISICON Region II crystal structure appear, for example, at 2θ=20.1°, 23.9°, and 29.5°, and Li ４－ｘ Ge １－ｘ P ｘ S 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°.

[0120] 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.

[0121] 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°.

[0122] 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°.

[0123] 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.

[0124] 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.

[0125] [Mechanical Treatment of Sulfide Solid Electrolyte for Mechanical Treatment in a Solvent] The production method of this embodiment includes mechanically treating the sulfide solid electrolyte obtained as described above in a solvent. This allows the sulfide solid electrolyte to be adjusted to a desired morphology. From the viewpoint of more easily adjusting the desired morphology, the mechanical treatment is preferably at least one treatment selected from crushing and granulation, and is more preferably performed using a stirrer or a grinder.

[0126] Examples of the agitator include the mechanical agitation mixer provided with agitating blades in a tank, which has been exemplified as the mixing device described above. Examples of the mechanical agitation mixer include a high-speed agitation mixer and a double-arm mixer, and any type can be used, but from the viewpoint of more easily adjusting the desired morphology, a high-speed agitation mixer is preferred. More specifically, as described above, examples of the high-speed agitation mixer include a vertical shaft rotary mixer and a horizontal shaft rotary mixer, as well as various devices such as a high-speed swirling thin film agitator and a high-speed shear agitator. Among these, from the viewpoint of more easily adjusting the desired morphology, a high-speed swirling thin film agitator (also referred to as a "thin film swirling high-speed mixer") is preferred.

[0127] Examples of the grinding machine include a media-type grinding machine. Media-type grinding machines are broadly classified into container-driven grinding machines and media-agitation grinding machines. Examples of container-driven grinding machines include agitation tanks, grinding tanks, or combinations thereof, such as ball mills and bead mills. As ball mills and bead mills, any of various types, such as rotary, rolling, vibrating, and planetary types, can be used. Examples of the media-agitation grinding machine include impact grinders such as cutter mills, hammer mills, and pin mills; tower-type grinders such as tower mills; agitation tank-type grinders such as attritors, aquamizers, and sand grinders; flow-through tank-type grinders such as Viscomills and pearl mills; flow-through pipe-type grinders; annular-type grinders such as Coball mills; and continuous dynamic-type grinders.

[0128] The particle size of the media such as beads and balls used in a bead mill, ball mill, etc. may be appropriately determined taking into consideration the desired morphology as well as the type and scale of the equipment used, but is usually preferably 0.01 mm or more, more preferably 0.015 mm or more, even more preferably 0.02 mm or more, and still more preferably 0.04 mm or more, with the upper limit being preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1 mm or less, and still more preferably 0.8 mm or less. Examples of the material of the media include metals such as stainless steel, chrome steel, and tungsten carbide; ceramics such as zirconia and silicon nitride; and minerals such as agate.

[0129] The treatment time for the mechanical treatment may be determined appropriately taking into consideration the desired morphology as well as the type and scale of the equipment used, but is typically preferably at least 5 seconds, more preferably at least 30 seconds, even more preferably at least 3 minutes, and even more preferably at least 15 minutes, with the upper limit being preferably at most 5 hours, more preferably at most 3 hours, even more preferably at most 2 hours, and even more preferably at most 1.5 hours. The peripheral speed of the rotating body in the mechanical treatment (the rotational speed of an apparatus such as a bead mill or ball mill) may be determined appropriately taking into consideration the desired morphology as well as the type and scale of the equipment used, but is typically preferably at least 0.5 m / s, more preferably at least 1 m / s, even more preferably at least 2 m / s, and even more preferably at least 3 m / s, with the upper limit being preferably at most 55 m / s, more preferably at most 40 m / s, even more preferably at most 25 m / s, and even more preferably at most 15 m / s. The peripheral speed may be the same or may be changed during the treatment.

[0130] As the solvent, a wide variety of solvents conventionally used in the production of sulfide solid electrolytes can be used. From the viewpoint of easily adjusting the sulfide solid electrolyte to a desired morphology, the solvent is preferably an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, an aromatic hydrocarbon solvent, or an ether-based solvent, with heptane, cyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, or anisole being more preferred. From the same viewpoint, the solvent preferably contains an ether-based solvent, with diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, tert-butyl methyl ether, or anisole being more preferred, with dibutyl ether being even more preferred. These solvents may be used alone or in combination of two or more. The amount of solvent used may be such that the content of the sulfide solid electrolyte relative to the total amount of the sulfide solid electrolyte and the solvent is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and the upper limit is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less.

[0131] The average particle size (D ５０ ) can be adjusted as desired, but is usually 0.05 μm or more, preferably 0.07 μm or more, more preferably 0.1 μm or more, and even more preferably 0.15 μm or more, and the upper limit is usually 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, and still more preferably 10 μm or less.

[0132] The specific surface area of ​​the sulfide solid electrolyte measured by the BET method can also be adjusted as desired, but is usually 0.1 m ２ / g or more, preferably 0.3m ２ / g or more, more preferably 0.5m ２ / g or more, more preferably 1m ２ / g or more, and the upper limit is usually 70m ２ / g or less, preferably 50m ２ / g or less, more preferably 45m ２ / g or less, more preferably 40m ２ / g or less. In this specification, the specific surface area is a value measured by the BET method (gas adsorption method), and either nitrogen (nitrogen method) or krypton (krypton method) may be used as the gas, and is measured by appropriately selecting depending on the size of the specific surface area. The specific surface area can be measured using, for example, a commercially available device such as a gas adsorption measuring device (e.g., AUTOSORB6 (manufactured by Sysmex Corporation)).

[0133] [Transporting the Mechanically Treated Sulfide Solid Electrolyte by a Screw Feeder Equipped with a Shaftless Screw] The production method of this embodiment includes transporting the mechanically treated sulfide solid electrolyte by a screw feeder equipped with a shaftless screw. The sulfide solid electrolyte whose morphology has been adjusted by the mechanical treatment has high adhesive strength. In the production method of this embodiment, when transporting the mechanically treated sulfide solid electrolyte to the next step, a screw feeder equipped with a shaftless screw is used, which makes it difficult for the sulfide solid electrolyte to adhere to or accumulate on the screw, and allows for a stable supply of the sulfide solid electrolyte.

[0134] FIG. 1 is a cross-sectional schematic diagram of an example of a screw feeder used in the production method of this embodiment. The screw feeder 10 includes a supply port 2 on the upper surface of one end of a casing 1, a discharge port 3 on the lower surface of the other end, and a shaftless screw 4 inside the casing 1. The shaftless screw 4 is connected to a motor 5 provided outside the casing 1, and is rotated by the motor 5. The sulfide solid electrolyte enters the casing 1 through the supply port 2 and is transported to the discharge port 3 along the axial direction of the shaftless screw 4 by the rotation of the shaftless screw 4. From the viewpoint of achieving the effects of the present invention, the shaftless screw 4 is only required to be used in at least a portion that comes into contact with the sulfide solid electrolyte. In FIG. 1, it is preferable that the screw has no shaft between the supply port 2 and the discharge port 3. The amount of sulfide solid electrolyte supplied can be adjusted by appropriately adjusting the screw diameter and the spiral winding pitch of the shaftless screw 4.

[0135] As long as the shaftless screw 4 does not have a shaft in a portion that comes into contact with the sulfide solid electrolyte, it may have a shaft 6 at both ends as shown in Fig. 1 or at one end as shown in Fig. 2. By having a shaft at one or both ends of the shaftless screw 4, the durability of the screw can be further increased. Whether the shaftless screw 4 has a shaft at one end or at both ends is determined appropriately depending on the length (axial direction) of the screw.

[0136] [Heating the sulfide solid electrolyte transported by a screw feeder equipped with a shaftless screw in a heated air stream] The production method of this embodiment preferably includes heating the sulfide solid electrolyte transported by the screw feeder in a heated air stream, thereby removing the solvent used in the mechanical treatment from the sulfide solid electrolyte.

[0137] More specifically, heating in a heated air stream can be performed by supplying the sulfide solid electrolyte into an air stream through which heated gas flows. For example, commercially available dryers such as spray dryers, fluidized bed dryers, and flash dryers can be used. Examples of spray dryers include those in which the sulfide solid electrolyte is sprayed from a spray nozzle together with heated gas and, if necessary, brought into contact with separately heated gas. A fluidized bed dryer is a device that dries the sulfide solid electrolyte while fluidizing it with hot air. A flash dryer is a device that can heat the sulfide solid electrolyte with a heated air stream by supplying the sulfide solid electrolyte into a pipe through which a heated air stream is supplied. A direct hot air type flash dryer in which the heated air stream directly contacts the sulfide solid electrolyte is preferred.

[0138] Flash dryers are primarily suitable for use in flow systems, but it is also possible to perform flash drying in a batch system using, for example, a container-type flash dryer. For example, a heated airflow may be introduced from the bottom of the container to heat the sulfide solid electrolyte. In this case, if a constriction on the nozzle is provided at the inlet for the heated airflow, the flow rate can be increased to introduce the heated airflow, allowing the sulfide solid electrolyte to be heated while being mixed and stirred, thereby improving drying efficiency.

[0139] It is preferable not to use media particles when heating in a heated airflow. By not using media particles such as ceramic balls or zirconia beads, excessive contact with the heated airflow due to adhesion of the sulfide solid electrolyte to the media particles can be suppressed, and deterioration of the sulfide solid electrolyte can be suppressed. As a result, ionic conductivity is improved.

[0140] (Heated Air Stream) The gas used for the heated air stream can be any gas, and can include, for example, inert gases such as nitrogen and argon, as well as various gases such as air. Nitrogen and air are preferably used in consideration of cost, and nitrogen is preferred in consideration of improving ionic conductivity. These gases may be used alone or in combination. The dew point temperature of the gas is preferably −10° C. or lower, more preferably −20° C. or lower, and even more preferably −30° C. or lower, from the viewpoint of suppressing deterioration of the quality of the sulfide solid electrolyte due to moisture contained in the gas.

[0141] Because crystalline sulfide solid electrolytes have higher ionic conductivity than amorphous sulfide solid electrolytes, the sulfide solid electrolyte obtained by the manufacturing method of this embodiment is preferably a crystalline sulfide solid electrolyte. Here, when the sulfide solid electrolyte for mechanical treatment is a crystalline sulfide solid electrolyte, some or all of the sulfide solid electrolyte may be vitrified (amorphized) even though the energy required for the mechanical treatment is relatively small. Therefore, whether the sulfide solid electrolyte for mechanical treatment is an amorphous or crystalline sulfide solid electrolyte, it can be crystallized by adjusting the temperature of the heated airflow, and it is preferable to convert the amorphous sulfide solid electrolyte into a crystalline sulfide solid electrolyte.

[0142] The temperature of the heated air stream is preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher, from the viewpoint of removing the solvent from the sulfide solid electrolyte and more efficiently and reliably obtaining a crystalline sulfide solid electrolyte. The upper limit is preferably 600°C or lower, more preferably 500°C or lower, even more preferably 325°C or lower, and still more preferably 250°C or lower. Typical numerical ranges are preferably 130 to 600°C, 140 to 600°C, 140 to 500°C, 150 to 325°C, or 150 to 250°C. Here, the temperature of the heated air stream is the supply temperature of the heated air stream, and, for example, when the above-mentioned dryer is used, it is the supply temperature to the dryer.

[0143] Since the temperature of the heated airflow decreases when the sulfide solid electrolyte is heated, when the above-mentioned dryer is used, for example, the outlet temperature from the dryer is lower than the supply temperature to the dryer (the temperature of the heated airflow). The outlet temperature cannot be generalized because it varies depending on the scale of the flash dryer, etc., but it can be usually 3°C or more lower, further 5°C or more lower, or even 10°C or more lower than the supply temperature.

[0144] Furthermore, the temperature of the sulfide solid electrolyte is lower than that of the heated air stream because the heating time in the heated air stream is short and the temperature does not usually reach that of the heated air stream. The temperature of the sulfide solid electrolyte after heating in the heated air stream (i.e., the temperature of the sulfide solid electrolyte from which the solvent has been removed) is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, with the upper limit being preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower.

[0145] The amount of heated airflow to be supplied is not particularly limited as long as it is supplied to an extent that the solvent can be removed from the sulfide solid electrolyte. Although it cannot be generalized because it may vary depending on the type of solvent, the scale of the flash dryer to be used, etc., from the viewpoint of obtaining a crystalline sulfide solid electrolyte more efficiently and reliably, 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 solvent can be removed more efficiently.

[0146] The flow rate of the heated air stream is not particularly limited as long as it is supplied to an extent that the solvent can be removed from the sulfide solid electrolyte, and cannot be generalized because it can vary depending on the type of solvent, the scale of the dryer used, etc., but from the viewpoint of more efficiently and reliably obtaining a crystalline sulfide solid electrolyte, it 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 solvent can be removed more efficiently.

[0147] The heating time in the heated air stream is not particularly limited as long as the solvent is supplied to an extent that the solvent can be removed from the sulfide solid electrolyte. While this cannot be generalized because it varies depending on the type of solvent, the size of the dryer used, and the like, from the viewpoint of obtaining a crystalline sulfide solid electrolyte more efficiently and reliably, the upper limit is preferably 1 minute or less, more preferably 50 seconds or less, even more preferably 40 seconds or less, even more preferably 15 seconds or less, and particularly preferably 5 seconds or less. The lower limit is typically 0.05 seconds or more, preferably 0.1 seconds or more, and more preferably 0.2 seconds or more. Thus, the heating time in the heated air stream is extremely short. Therefore, for example, the sulfide solid electrolyte is not exposed to high-temperature conditions for a long period of time, heat-induced deterioration can be suppressed, and a sulfide solid electrolyte having high ionic conductivity can be obtained.

[0148] The crystal structure of the crystalline sulfide solid electrolyte obtained in this manner is the same as that described above in the section (Crystalline sulfide solid electrolyte).

[0149] [Apparatus for Producing Sulfide Solid Electrolyte] The apparatus for producing a sulfide solid electrolyte of the present embodiment is a production apparatus including: a device for performing mechanical treatment on a sulfide solid electrolyte for mechanical treatment in a solvent; and a screw feeder equipped with a shaftless screw for transporting the sulfide solid electrolyte after the mechanical treatment.

[0150] The equipment for performing the mechanical treatment is preferably a stirrer or a pulverizer from the viewpoint of easily adjusting the morphology of the sulfide solid electrolyte, such as the desired particle size. Specific examples and preferred examples of the stirrer and pulverizer are the same as those described in the manufacturing method of this embodiment. Furthermore, the screw feeder equipped with a shaftless screw is the same as that described in the manufacturing method of this embodiment.

[0151] (Applications) The sulfide solid electrolyte obtained by the manufacturing method 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.

[0152] (Electrode Mixture) When the sulfide solid electrolyte obtained by the manufacturing method of this embodiment is used as an electrode mixture, it can be used as an electrode mixture containing the sulfide solid electrolyte and an electrode active material. As the electrode active material, a positive electrode active material or a negative electrode active material is adopted depending on whether the electrode mixture is used for a positive electrode or a negative electrode. As the positive electrode active material and the negative electrode active material, materials conventionally used as these active materials can be used. In addition to the sulfide solid electrolyte and the electrode active material, other components such as a conductive material and a binder may be included.

[0153] (Lithium-ion battery) When the sulfide solid electrolyte obtained by the manufacturing method of this embodiment is used as a battery, it can be used as a lithium-ion battery containing at least one selected from the sulfide solid electrolyte and the electrode mixture. Furthermore, the battery preferably uses a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer, and a known current collector can be used. For example, a layer in which a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu, is coated with Au or the like can be used.

[0154] 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.

[0155] Example 1: 14.7 g of lithium sulfide, 23.6 g of diphosphorus pentasulfide, 4.6 g of lithium bromide, and 7.1 g of lithium iodide were introduced into a 1 L reactor equipped with a stirring blade under a nitrogen atmosphere. After rotating the stirring blade, 467 mL of cyclohexane as a solvent and 111 mL of N,N,N',N'-tetramethylethylenediamine (TMEDA) as a complexing agent were added, and stirring was continued for 72 hours. Next, 428 mL of cyclohexane was added, and the mixture was milled for 3 hours using a circulating bead mill ("Star Mill LMZ015 (product name)" manufactured by Ashizawa Finetech Co., Ltd.) under specified conditions (bead material: zirconia, bead diameter: 0.5 mmφ, bead amount: 456 g, pump flow rate: 650 mL / min, peripheral speed: 8 m / s, mill jacket temperature: 20°C). The resulting slurry was dried under vacuum (room temperature: 23°C) to obtain a powdered electrolyte precursor. The electrolyte precursor powder was then heated in vacuum at 120°C for 2 hours, and further heated at 160°C for 2 hours, to obtain a white powder of a crystalline sulfide solid electrolyte (sulfide solid electrolyte for mechanical treatment).

[0156] Next, 30.0 g of the white powder obtained above, 313 g of heptane, and 157 g of dibutyl ether were added to a 0.5 L reactor equipped with an agitator blade under a nitrogen atmosphere. After rotating the agitator blade, a microbead-compatible bead mill capable of circulating ("UAM-015 (model number)", manufactured by Hiroshima Metal & Machinery Co., Ltd.) was used under specified conditions (bead material: zirconia, bead diameter: 0.05 mmφ, bead usage amount: 391 g, pump flow rate: 150 mL / min, peripheral speed: 8 m / s, mill jacket temperature: 20 ° C.) for 25 minutes under the specified conditions (bead material: zirconia, bead diameter: 0.05 mmφ, bead usage amount: 391 g, pump flow rate: 150 mL / min, peripheral speed: 8 m / s, mill jacket temperature: 20 ° C.) and a first pulverization treatment was performed. Next, the peripheral speed was changed to 12 m / s, and a second pulverization treatment was performed for 25 minutes. The resulting slurry was dried under vacuum (room temperature: 23 ° C.) to obtain a white powder of amorphous sulfide solid electrolyte (sulfide solid electrolyte after mechanical treatment).

[0157] The obtained amorphous sulfide solid electrolyte was supplied into the casing 1 from the supply port 2 of the screw feeder 10 shown in Figure 1, and the screw feeder 10 was operated for 4 hours. It was confirmed that the supply amount of the amorphous sulfide solid electrolyte did not decrease and that it could be supplied stably. Furthermore, no adhesion or deposition of the amorphous sulfide solid electrolyte on the shaftless screw 4 was confirmed.

[0158] Comparative Example 1 The amorphous sulfide solid electrolyte obtained in Example 1 was supplied into a casing 11 from a supply port 12 of a screw feeder 20 equipped with a shaft screw 14 shown in Figure 3, and the screw feeder 20 was operated, but the amount of powder discharged from the discharge port 13 gradually decreased, and after 30 minutes, no powder was discharged from the discharge port 13. It was also confirmed that the amorphous sulfide solid electrolyte had adhered and accumulated on the shaft 16 of the shaft screw 14.

[0159] Reference Example 1 Lithium sulfide, a solid electrolyte raw material, was supplied into the casing 11 from the supply port 12 of the screw feeder 20 equipped with the shaft screw 14 shown in Figure 3 and the screw feeder 20 was operated for two hours, but it was confirmed that the supply amount of lithium sulfide did not decrease and that stable supply was possible. In addition, no adhesion or deposition of lithium sulfide was confirmed on the shaft 16 of the shaft screw 14.

[0160] The powder of electrolyte precursor obtained in Example 1 was supplied into the casing 11 from the supply port 12 of a screw feeder 20 equipped with a shaft screw 14 shown in Figure 3, and the screw feeder 20 was operated for two hours. It was confirmed that the supply amount of the electrolyte precursor did not decrease and that stable supply was possible. Furthermore, no adhesion or deposition of the electrolyte precursor was confirmed on the shaft 16 of the shaft screw 14.

[0161] Reference Example 3 The crystalline sulfide solid electrolyte obtained in Example 1 was supplied into the casing 11 from the supply port 12 of a screw feeder 20 equipped with a shaft screw 14 shown in Figure 3, and the screw feeder 20 was operated for two hours. It was confirmed that the supply amount of the crystalline sulfide solid electrolyte did not decrease and that stable supply was possible. Furthermore, no adhesion or deposition of the crystalline sulfide solid electrolyte was confirmed on the shaft 16 of the shaft screw 14.

[0162] In the method for producing a sulfide solid electrolyte according to the present embodiment, when a solid electrolyte whose morphology has been adjusted by mechanical processing is conveyed by a screw feeder, adhesion and deposition of the solid electrolyte on the screw are unlikely to occur, and the solid electrolyte can be stably supplied. The sulfide solid electrolyte thus obtained 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.

[0163] 1, 11 Casing 2, 12 Supply port 3, 13 Discharge port 4 Shaftless screw 5, 15 Motor 6, 16 Shaft 10, 20 Screw feeder 14 Shaft-equipped screw L Between supply port and discharge port

Claims

1. A method for producing a sulfide solid electrolyte, comprising: obtaining a sulfide solid electrolyte for mechanical treatment, the sulfide solid electrolyte containing lithium atoms, sulfur atoms, and phosphorus atoms; subjecting the sulfide solid electrolyte for mechanical treatment to a mechanical treatment in a solvent; and transporting the sulfide solid electrolyte after the mechanical treatment by a screw feeder equipped with a shaftless screw.

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein the shaftless screw is used in at least a portion that comes into contact with the sulfide solid electrolyte after the mechanical treatment.

3. A method for producing a sulfide solid electrolyte as described in claim 1 or 2, wherein the shaftless screw has a shaft at one or both ends, and does not have a shaft in a portion that comes into contact with the sulfide solid electrolyte after the mechanical treatment.

4. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, wherein the mechanical treatment is at least one treatment selected from the group consisting of crushing and granulation.

5. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 4, wherein the mechanical treatment is carried out using a stirrer or a grinder.

6. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 5, wherein the sulfide solid electrolyte for mechanical treatment further contains a halogen atom.

7. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 6, wherein the solvent includes an ether-based solvent.

8. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 7, wherein the sulfide solid electrolyte for mechanical treatment is amorphous or crystalline.

9. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 8, comprising heating the sulfide solid electrolyte after the mechanical treatment, which is transported by the screw feeder equipped with the shaftless screw, in a heated air stream.

10. The method for producing a sulfide solid electrolyte according to claim 9, wherein the temperature of the heated air flow is 150°C or higher and 250°C or lower.

11. The supply volume of the heated air flow is 0.1 m ３ / min or more 500m ３ The method for producing a sulfide solid electrolyte according to claim 9 or 10, wherein the reaction time is 1000 s / min or less.

12. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 11, wherein the sulfide solid electrolyte for mechanical treatment is obtained by a process including mixing a raw material content including lithium atoms, sulfur atoms, and phosphorus atoms with a complexing agent.

13. The method for producing a sulfide solid electrolyte according to claim 12, wherein the raw material contents further include a halogen atom.

14. An apparatus for producing a sulfide solid electrolyte, comprising: a device for mechanically treating a sulfide solid electrolyte in a solvent; and a screw feeder equipped with a shaftless screw for transporting the sulfide solid electrolyte after the mechanical treatment.

15. The apparatus for producing a sulfide solid electrolyte according to claim 14, wherein the device for performing the mechanical treatment is a stirrer or a grinder.

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