Method for producing sulfide solid electrolyte

Abstract

To provide a method for efficiently producing a sulfide solid electrolyte using a liquid-phase method.SOLUTION: There is provided a method for producing a sulfide solid electrolyte not using a pulverizer in reacting raw materials, the method comprising stirring in a reactor a raw material containing lithium sulfide, a phosphorus compound and a halogen compound, and a complexing agent, discharging outside the reactor through a discharging port provided in the reactor a fluid containing contents in the reactor, and returning to the reactor through a returning port provided in the reactor the fluid containing the discharged contents, thereby circulating the fluid containing the contents.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a sulfide solid electrolyte. [Background technology]

[0002] With the recent rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as their power sources has become increasingly important. Conventionally, batteries used for such applications have used electrolytes containing flammable organic solvents, but by making batteries all-solid-state, flammable organic solvents are not used in the battery, safety devices can be simplified, and manufacturing costs and productivity are excellent. Therefore, batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed.

[0003] Methods for producing solid electrolytes used in solid electrolyte layers are broadly divided into solid-phase methods and liquid-phase methods. Liquid-phase methods include homogeneous methods, in which the solid electrolyte material is completely dissolved in a solvent, and heterogeneous methods, in which the solid electrolyte material is not completely dissolved but is instead a solid-liquid coexistence suspension. For example, a known solid-phase method involves mechanically milling raw materials such as lithium sulfide and diphosphorus pentasulfide using a device such as a ball mill or a bead mill, followed by heat treatment as needed to produce an amorphous or crystalline solid electrolyte (see, for example, Patent Document 1). According to this method, a solid electrolyte is obtained by applying mechanical stress to raw materials such as lithium sulfide to promote solid-solid reactions.

[0004] On the other hand, among the liquid phase methods, a homogeneous method in which a solid electrolyte is dissolved in a solvent and reprecipitated is known (see, for example, Patent Document 2), and a heterogeneous method in which a solid electrolyte raw material such as lithium sulfide is reacted in a solvent containing a polar aprotic solvent (see Patent Documents 3 and 4, and Non-Patent Document 1). For example, Patent Document 4 discloses a method for producing a solid electrolyte with a Li4PS4I structure, which includes a step of using dimethoxyethane (DME) and combining it with the Li3PS4 structure to obtain Li3PS4·DME. The ionic conductivity of the obtained solid electrolyte is 5.5 × 10 -5S / cm (3.9 × 10 for calcium doped -4 S / cm). Patent Document 5 discloses a solid electrolyte production apparatus that combines a pulverization synthesis means (specifically, a pulverizer) that pulverizes and reacts raw materials such as lithium sulfide in a solvent, and a synthesis means (specifically, a reaction vessel equipped with stirring blades) that reacts raw materials such as lithium sulfide in a solvent, and a method for producing a solid electrolyte using the apparatus. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 159667 Brochure [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-191899 [Patent Document 3] International Publication No. 2014 / 192309 Brochure [Patent Document 4] International Publication No. 2018 / 054709 Brochure [Patent Document 5] Japanese Patent Application Laid-Open No. 2015-207521 [Non-patent literature]

[0006] [Non-Patent Document 1] “CHEMISTRY OF MATERIALS”, 2017, No. 29, pp. 1830-1835 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a production method that can efficiently produce a sulfide solid electrolyte using a liquid phase method. [Means for solving the problem]

[0008] As a result of extensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention. 1. By stirring not only the raw materials for the sulfide solid electrolyte but also the complexing agent in the reaction vessel, the reaction of the raw materials can be promoted without the need for crushing. 2. In this case, by providing a mechanism for circulating the fluid containing the contents of the reaction vessel to the outside of the reaction vessel, it is possible to prevent raw materials with a high specific gravity, such as lithium halide, from settling and stagnating at the bottom of the reaction vessel, particularly directly below the rotating shaft of the stirring blades, without having to stir the fluid containing the contents so vigorously that it splashes and adheres to the inner wall of the reaction vessel. This prevents deviations in the composition of the sulfide solid electrolyte due to their lack of contribution to the reaction, efficiently promotes the reaction, and produces a sulfide solid electrolyte with high ionic conductivity.

[0009] The mechanism by which the decrease in the reaction efficiency of Li2S and P2S5 can be suppressed by suppressing the precipitation of lithium halide, which has a high specific gravity, is not clear, but it is thought to be as follows. Lithium sulfide (Li2S) does not normally form complexes with complexing agents such as tetramethylethylenediamine (TMEDA), but rather reacts with nearby diphosphorus pentasulfide (P2S5) via TMEDA to form Li3PS4. On the other hand, lithium halides have the property of readily forming complexes with complexing agents. Therefore, the presence of lithium halides near Li2S increases the TMEDA concentration near Li2S, which is thought to promote the reaction with P2S5. Conversely, if the lithium halide precipitates and its concentration in the reaction field decreases, the aforementioned reaction promotion effect is not achieved, and the reaction efficiency of Li2S and P2S5 is thought to plateau.

[0010] The present inventors have found that the above-mentioned problems can be solved by the following invention, which was completed based on the findings. [1] A method for producing a sulfide solid electrolyte that does not use a pulverizer when reacting raw materials, comprising: stirring raw materials including lithium sulfide, a phosphorus compound, and a halogen compound with a complexing agent in a reaction vessel; extracting a fluid containing contents resulting from the reaction in the reaction vessel to the outside of the reaction vessel through an outlet provided in the reaction vessel; and returning the extracted fluid containing contents to the reaction vessel through a return port provided in the reaction vessel, thereby circulating the fluid containing the contents. [2] The raw material contains two or more solid compounds, and the difference in density between the most dense compound and the least dense compound is 1.0 g / cm 3 The method for producing a sulfide solid electrolyte according to [1] above. [3] The method for producing a sulfide solid electrolyte according to [1] above, wherein the circulation amount per minute of the fluid containing the contents is 0.01 to 5.0 times the volume of the fluid containing the contents in the reaction vessel. [4] The method for producing a sulfide solid electrolyte according to the above [1], wherein the capacity of the reaction vessel is 30 L or more. [5] The method for producing a sulfide solid electrolyte according to [3] above, wherein the circulation amount per minute of the fluid containing the contents is 3.5 L / min or more and 100 L / min or less. [6] The method for producing a sulfide solid electrolyte according to the above [1], in which the fluid containing the contents is not subjected to a pulverization step. [7] The method for producing a sulfide solid electrolyte according to the above [1], wherein the withdrawal port is installed at the bottom of the reaction vessel. [8] The method for producing a sulfide solid electrolyte according to [1] above, wherein the return port is installed below the liquid level of the fluid containing the contents in the reaction vessel. [9] The method for producing a sulfide solid electrolyte according to the above [1], wherein the temperature inside the reaction vessel is controlled.

[10] The method for producing a sulfide solid electrolyte according to the above [1], wherein the compound containing a halogen element is at least one selected from the group consisting of lithium bromide (LiBr), lithium iodide (LiI), and lithium chloride (LiCl).

[11] The method for producing a sulfide solid electrolyte according to the above [1], wherein the compound containing a halogen element is at least one selected from bromine (Br2) and iodine (I2).

[12] The method for producing a sulfide solid electrolyte according to the above [1], wherein the complexing agent contains a nitrogen atom.

[13] The method for producing a sulfide solid electrolyte according to the above [1], wherein the complexing agent has two or more amino groups.

[14] The method for producing a sulfide solid electrolyte according to the above [1], wherein the complexing agent is tetramethylethylenediamine. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a production method that can efficiently produce a sulfide solid electrolyte using a liquid phase method. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a flow diagram illustrating an example of a preferred embodiment of a flow including a reaction vessel used in the production method of the present embodiment. [Figure 2] 1 shows X-ray diffraction spectra of the reaction product (electrolyte precursor), amorphous sulfide solid electrolyte, and crystalline sulfide solid electrolyte obtained in Example 3. [Figure 3] 1 shows X-ray diffraction spectra of raw materials used in the examples. [Figure 4] 1 is an X-ray diffraction spectrum of an amorphous sulfide solid electrolyte obtained in an example. [Figure 5] 1 is an X-ray diffraction spectrum of an amorphous sulfide solid electrolyte obtained in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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 of values ​​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.

[0014] (Findings Obtained by the Inventors to Achieve the Invention) As a result of extensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention. In recent years, efforts have been made to commercialize all-solid-state batteries by enlarging the reactor capacity (mass production) for industrial production, for example, to 30 L or more, and liquid-phase synthesis has attracted attention as a method that allows for simple, large-scale synthesis in addition to versatility and applicability. However, the conventional solid-phase method involving mechanical milling, etc., disclosed in Patent Document 1, is centered on solid-phase reactions and is able to easily obtain a solid electrolyte with high purity, thereby achieving high ionic conductivity. However, the liquid-phase methods disclosed in Patent Documents 2 to 4 and Non-Patent Document 1, etc., dissolve the solid electrolyte, which causes decomposition or loss of some of the solid electrolyte components during precipitation, making it more difficult to achieve high ionic conductivity compared to solid-phase synthesis methods. For example, in the homogeneous method, the raw materials and solid electrolyte are completely dissolved, allowing the components to be uniformly dispersed in the solution. However, in the subsequent precipitation process, precipitation proceeds according to the specific solubility of each component, making it extremely difficult to maintain the dispersion of the components. As a result, each component separates and precipitates. Furthermore, in the homogeneous method, the affinity between the solvent and lithium becomes too strong, making it difficult to remove the solvent even when dried after precipitation. For these reasons, it has been discovered that the homogeneous method has the problem of significantly reducing the ionic conductivity of the solid electrolyte. Furthermore, it has been found that even in the heterogeneous solid-liquid coexistence method, a portion of the solid electrolyte dissolves, causing separation due to elution of specific components, making it difficult to obtain the desired solid electrolyte.

[0015] Furthermore, in the homogeneous and heterogeneous liquid-phase processes described above, the reaction is typically carried out using a stirring device, such as a stirrer equipped with a stirring blade. The inventors discovered that by mixing the raw materials for the sulfide solid electrolyte with a complexing agent, it is possible to promote the reaction between the raw materials in the liquid phase without mechanical milling or other processes. However, as the equipment was enlarged to a certain extent for industrial production, they discovered that the reaction rate of Li2S and P2S5, which are part of the solid electrolyte raw materials, reached a plateau with normal stirring alone, resulting in a significant decrease in production efficiency. Further investigation into this phenomenon by the inventors surprisingly revealed that one of the causes was the precipitation of lithium halide during stirring. However, a fluid containing an electrolyte material and a solvent (hereinafter also simply referred to as "fluid") usually has high viscosity and adhesive properties, although this depends on the concentration of the solid electrolyte material. Therefore, when stirring the fluid to prevent the lithium halide from settling, extremely strong stirring is required, and the fluid splashes and adheres to the inner wall of the reaction vessel. As a result, a deviation in the composition of the solid electrolyte occurs, and it has become clear during the study of upsizing (mass production) for the aforementioned industrial production that this leads to a decrease in the ionic conductivity of the solid electrolyte.

[0016] It was also confirmed that even when strong stirring was performed using a stirring blade or the like, lithium halide has a large specific gravity and ultimately settles and stagnates at the bottom of the reaction vessel, particularly directly below the rotating shaft of the stirring blade or the like. The above-mentioned issues became apparent only when attempts were made to mass-produce sulfide solid electrolytes using a liquid phase method, and were previously completely unrecognized phenomena.

[0017] Furthermore, the apparatus disclosed in Patent Document 5 is based on the premise that the reaction is promoted by pulverizing and synthesizing the raw materials in the reaction vessel, and therefore the above-mentioned problems in the reaction vessel are unlikely to occur. However, since pulverization and synthesis are essential, there is still room for improvement in production efficiency. Based on the above findings, the present inventors have arrived at the invention described below, which relates to a production method capable of efficiently producing a sulfide solid electrolyte using a liquid phase method.

[0018] [Method for producing sulfide solid electrolyte] The method for producing a sulfide solid electrolyte of the present embodiment is a production method that does not use a pulverizer when reacting raw materials with each other, and is characterized in that raw materials including lithium sulfide, a phosphorus compound, and a halogen compound are stirred and reacted with a complexing agent in a reaction tank, a fluid containing the contents produced by the reaction in the reaction tank is withdrawn to the outside of the reaction tank through an outlet installed in the reaction tank, and the withdrawn fluid containing the contents is returned to the reaction tank through a return port installed in the reaction tank, thereby circulating the fluid containing the contents.

[0019] The fluid containing the contents of the reaction vessel includes lithium-containing compounds (e.g., lithium sulfide) and other solids as raw materials. Because the complexing agent is liquid, the fluid typically contains the liquid complexing agent, the reactant between the raw materials and the complexing agent, unreacted raw materials, and the reactant resulting from the reaction between the raw materials and the unreacted raw materials, as well as a solvent, etc., forming a slurry containing solids and liquids. The "reactant between the raw materials and the complexing agent" refers to a reaction product obtained by stirring the raw materials and the complexing agent. The lithium, sulfur, phosphorus, and halogen atoms contained in the raw materials react with the complexing agent, and these atoms are considered to be in the form of a complex in which they are directly bonded (coordinated) with each other, with or without the aid of the complexing agent. Note that the "reactant" is distinct from both the raw materials and the "sulfide solid electrolyte," and should be distinguished from these, as will be discussed later. In this embodiment, the reaction between the raw materials is accelerated by passing through the reaction product of the raw materials and the complexing agent, and it is possible to efficiently produce a sulfide solid electrolyte.

[0020] By circulating the fluid containing the contents, the amount of raw materials that do not contribute to the reaction, which settles and stagnates at the bottom of the reaction vessel without being stirred by a stirring device such as a stirrer, can be reduced, and compositional deviations in the resulting sulfide solid electrolyte can be suppressed. Furthermore, since this circulation generates convection in the fluid containing the contents in the reaction vessel, even if stirring by a stirring device such as a stirrer with stirring blades is limited to a degree that does not cause splashing of the fluid, a uniform dispersion state of the raw materials in the fluid can be ensured. This makes it possible to promote reactions between the raw materials and the complexing agent, and even reactions between the raw materials themselves, while suppressing compositional deviations in the sulfide solid electrolyte due to splashing. In this way, a sulfide solid electrolyte with high ionic conductivity can be obtained more efficiently using a liquid-phase method.

[0021] In this specification, the term "solid electrolyte" refers to an electrolyte that remains solid at 25° C. under a nitrogen atmosphere. The "sulfide solid electrolyte" obtained by the production method of this embodiment is a solid electrolyte that contains lithium, sulfur, phosphorus, and halogen elements and has ionic conductivity attributable to lithium.

[0022] The term "sulfide solid electrolyte" includes both a crystalline sulfide solid electrolyte having a crystalline structure obtained by the manufacturing method of this embodiment and an amorphous sulfide solid electrolyte. In this specification, a crystalline sulfide solid electrolyte is a solid electrolyte in which a peak derived from the solid electrolyte is observed in the X-ray diffraction pattern in X-ray diffraction measurement, regardless of whether or not a peak derived from the raw material of the solid electrolyte is present. That is, a 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 include an amorphous sulfide solid electrolyte in part. Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating an amorphous solid electrolyte to a temperature above the crystallization temperature. In this specification, the amorphous sulfide solid electrolyte refers to one in which the X-ray diffraction pattern in X-ray diffraction measurement is a halo pattern in which no peaks other than those derived from the material are observed, and it does not matter whether or not there are peaks derived from the raw materials of the solid electrolyte.

[0023] (raw materials) The raw materials used in this embodiment are two or more selected from compounds containing at least one element of lithium, sulfur, phosphorus, and a halogen element, and include lithium sulfide, a phosphorus compound, and a halogen compound. That is, in this embodiment, the raw materials used are two or more compounds containing at least one element of lithium, sulfur, phosphorus, and a halogen element, and include lithium sulfide, a phosphorus compound, and a halogen compound. As described above, the solid electrolyte in this embodiment contains lithium, sulfur, phosphorus, and a halogen element because raw materials containing lithium, sulfur, phosphorus, and a halogen element are used as the two or more compounds.

[0024] Compounds that can be used as raw materials include those containing at least one element selected from the group consisting of lithium, sulfur, phosphorus, and halogen elements, i.e., lithium sulfide, phosphorus compounds, and halogen compounds. More specifically, lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide (all of which are halogen compounds); phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5); phosphorus halides such as various phosphorus fluorides (PF3, PF5), various phosphorus chlorides (PCl3, PCl5, P2Cl4), various phosphorus bromides (PBr3, PBr5), and various phosphorus iodides (PI3, P2I4); thiophosphoryl fluoride (PSF3), thiophosphoryl chloride (PSCl3), and bromides (PBr5). Representative examples of the starting material include raw materials consisting of at least two elements selected from the above four elements, such as thiophosphoryl halides (all of which correspond to phosphorus compounds), such as thiophosphoryl chloride (PSBr3), thiophosphoryl iodide (PSI3), thiophosphoryl fluoride dichloride (PSCl2F), and thiophosphoryl fluoride dibromide (PSBr2F); and elemental halogens (which correspond to halogen compounds), such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), preferably bromine (Br2) and iodine (I2).

[0025] Compounds that can be used as raw materials other than those mentioned above include, for example, compounds that contain at least one element selected from the above four elements and also contain an element other than the four elements, 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; metal sulfides such as silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, tin sulfide (SnS, SnS2), aluminum sulfide, and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate (all of which fall under the category of phosphorus compounds); and sodium iodide. Halides of alkali metals other than lithium, such as sodium halides such as sodium fluoride, sodium chloride, and sodium bromide (which fall under the category of halogen compounds); metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides, and bismuth halides (which fall under the category of halogen compounds); phosphorus oxyhalides such as phosphorus oxychloride (POCl3) and phosphorus oxybromide (POBr3) (which fall under both phosphorus compounds and halogen compounds); and the like.

[0026] In this embodiment, from the viewpoint of more easily obtaining a sulfide solid electrolyte having high ionic conductivity, preferred compounds usable as raw materials include lithium sulfide, phosphorus sulfides such as diphosphorus trisulfide (PS) and diphosphorus pentasulfide (PS), halogen elements such as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide. Preferred combinations of compounds usable as raw materials include lithium sulfide, diphosphorus pentasulfide, and lithium halides, and lithium sulfide, diphosphorus pentasulfide, and halogen elements. Preferred lithium halides include lithium bromide, lithium iodide, and lithium chloride, and preferred halogen elements include bromine and iodine. The lithium halides and halogen elements mentioned above can be used alone or in combination.

[0027] In this embodiment, examples of compounds that can be used as raw materials include solid electrolytes such as Li3PS4 that contain a PS4 structure, etc. By using, as a raw material, a structure containing lithium such as Li3PS4 that exists as a main structure in the solid electrolyte obtained by the production method of this embodiment, the constituent ratio of the structure can be increased, and ionic conductivity is more likely to be improved, compared to when a compound such as the lithium sulfide described above is used as a raw material and a sulfide solid electrolyte is formed while being synthesized by a reaction between compounds. By first preparing a solid electrolyte containing the above structure, for example by manufacturing it, and then using it as a raw material, the structure and a raw material containing halogen atoms, such as a simple halogen or lithium halide, are bonded (coordinated) with or without a complexing agent, and a reaction product in which halogen atoms are dispersed and fixed is more easily obtained. As a result, a sulfide solid electrolyte with high ionic conductivity is obtained.

[0028] In this embodiment, examples of solid electrolytes that can be used as raw material compounds include amorphous sulfide solid electrolytes having a Li3PS4 molecular structure (also referred to as "amorphous Li3PS4") and crystalline sulfide solid electrolytes (also referred to as "crystalline Li3PS4"). In consideration of improving ionic conductivity, amorphous sulfide solid electrolytes that do not contain a Li4P2S7 structure or crystalline sulfide solid electrolytes are preferred. These solid electrolytes can be produced by conventional production methods such as mechanical milling, slurry production, and melt quenching, or commercially available products can also be used. In addition, an amorphous sulfide solid electrolyte is preferable. The dispersibility of halogen atoms in the reactant is improved, which facilitates bonding between the halogen atoms and lithium atoms, sulfur atoms, and phosphorus atoms in the solid electrolyte, thereby accelerating the reaction between the raw materials, resulting in a sulfide solid electrolyte with higher ionic conductivity.

[0029] When the above solid electrolyte is used as the compound, the content of the amorphous sulfide solid electrolyte having a Li3PS4 structure relative to the total amount of raw materials is preferably 60 to 100 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 80 mol%. When a solid electrolyte having a Li3PS4 structure or the like and a halogen element are used, the content of the halogen element relative to the amorphous sulfide solid electrolyte having a Li3PS4 structure or the like is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0030] In the present embodiment, when lithium sulfide is used as the compound containing an alkali metal, the lithium sulfide is preferably in the form of particles. The average particle size of lithium sulfide particles (D 50 ) is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.5 μm or more and 100 μm or less, and even more preferably 1 μm or more and 20 μm or less. 50 ) is the particle size at which 50% of the total particle size is obtained by accumulating the particle size distribution curve from the smallest particle size, and the volume distribution is the average particle size that can be measured using, for example, 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, i.e., within the same range as that of the lithium sulfide particles.

[0031] When lithium sulfide, diphosphorus pentasulfide, and lithium halide are used as raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 70 to 80 mol%, more preferably 72 to 78 mol%, and even more preferably 74 to 76 mol%, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. When lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as needed are used, the content of lithium sulfide and diphosphorus pentasulfide relative to the total of these is preferably 60 to 100 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 80 mol%. Furthermore, when lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ionic conductivity, the proportion of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, still more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0032] When using a halogen element as a raw material, for example, 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%. This is because these ratios result in higher ionic conductivity. From the same viewpoint, when lithium sulfide, diphosphorus pentasulfide, and a halogen element are used, the content of the halogen element relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the halogen element is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0033] When lithium sulfide, diphosphorus pentasulfide, an elemental halogen, and a lithium halide are used, the content of the elemental halogen (α mol %) and the content of the lithium halide (β mol %) relative to the total amount of these preferably satisfy the following formula (2), more preferably satisfy the following formula (3), even more preferably satisfy the following formula (4), and even more preferably satisfy the following formula (5). 2≦2α+β≦100…(2) 4≦2α+β≦80 …(3) 6≦2α+β≦50 …(4) 6≦2α+β≦30 …(5)

[0034] When two kinds of halogens are used as simple substances, the molar number of one halogen element in the substance is A1, and the molar number of the other halogen element in the substance is A2. 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.

[0035] Furthermore, when the two types of halogen atoms are bromine and iodine, where the number of moles of bromine is B1 and the number of moles of iodine is B2, the ratio B1:B2 is preferably 1 to 99:99 to 1, more preferably 15:85 to 90:10, even more preferably 20:80 to 80:20, still more preferably 30:70 to 75:25, and particularly preferably 35:65 to 75:25.

[0036] When two or more solid compounds are used as raw materials, the difference in density between the compound with the highest density and the compound with the lowest density in the fluid containing the contents of the reaction vessel is preferably 1.0 g / cm from the viewpoint of ease of production. 3 More preferably, 1.5 g / cm 3 More preferably, 1.8 g / cm 3 More preferably, 2.0 g / cm 3 From the same viewpoint, the upper limit is preferably 3.5 g / cm. 3 or less, more preferably 3.0 g / cm 3 More preferably 2.8 g / cm or less 3 More preferably, 2.6 g / cm or less 3 In the production method of this embodiment, even when raw materials having such a difference in density are used, by circulating the fluid containing the contents, it is possible to prevent the raw material having a high specific gravity, such as lithium halide, from settling and stagnating at the bottom of the reaction tank or the like.

[0037] (complexing agent) The method for producing a sulfide solid electrolyte of this embodiment uses a complexing agent. In this specification, the term "complexing agent" refers to a substance that forms a reactant by reacting with a raw material, more specifically, a substance that can form a complex with lithium atoms and has the property of interacting with a compound containing lithium, such as a sulfide or halide, contained in the raw material to promote the formation of a reactant. The complexing agent can be used without any particular limitation as long as it has the above-mentioned properties, and is particularly preferably a compound containing an atom with high affinity to lithium atoms, such as a heteroatom such as a nitrogen atom, an oxygen atom, or a chlorine atom, and more preferably a compound containing a group containing these heteroatoms.Among these heteroatoms, nitrogen atom is preferred.This is because these heteroatoms and groups containing the heteroatoms are easily coordinated (bonded) with lithium atoms.

[0038] The complexing agent has heteroatoms in its molecules that have a high affinity for lithium atoms. It is believed to have the property of easily forming aggregates with lithium-containing structures, such as Li3PS4, which typically contain the PS4 structure and are present as the main structure in the sulfide solid electrolyte obtained by the manufacturing method of this embodiment, as well as with lithium-containing raw materials, such as lithium halides. Therefore, by stirring the raw materials with the complexing agent, lithium-containing structures, such as the PS4 structure, or aggregates mediated by the complexing agent, and lithium-containing raw materials, such as lithium halides, or aggregates mediated by the complexing agent, are uniformly present, resulting in a reaction product in which halogen atoms are more dispersed and fixed. This is believed to result in a sulfide solid electrolyte with high ionic conductivity. It is also believed to have the secondary effect of suppressing the generation of hydrogen sulfide.

[0039] Therefore, the complexing agent used in this embodiment 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, a lithium-containing structure such as Li3PS4 having a PS4 structure can be bonded to a lithium-containing compound such as lithium halide via at least two heteroatoms in the molecule. This bond allows the halogen atoms to be more dispersed and fixed in the reaction mixture, resulting in a solid electrolyte with high ionic conductivity. As mentioned above, nitrogen atoms are preferred among heteroatoms, and amino groups are preferred as groups containing nitrogen atoms, that is, amine compounds are preferred as complexing agents.

[0040] 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 in exhibiting the function of the complexing agent.

[0041] Representative 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. 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, with the upper limit being preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. The number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic amine is preferably 2 or more, and the upper limit being preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0042] Typical 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. Typical 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 the upper limit is preferably 16 or less, more preferably 14 or less.

[0043] Representative preferred examples of the aromatic amine 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 aromatic amine preferably has 6 or more carbon atoms, more preferably 7 or more carbon atoms, and even more preferably 8 or more carbon atoms, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.

[0044] 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 diamines have been given as specific examples, it goes without saying that the amine compounds that can be used in the production method of this embodiment are not limited to diamines, and examples thereof include aliphatic monoamines corresponding to various diamines such as trimethylamine, triethylamine, ethyldimethylamine, and the above-mentioned aliphatic diamines, as well as 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 monoamines corresponding to the above heterocyclic diamines; 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.

[0045] Among the above, from the viewpoint of obtaining higher ionic conductivity, an amine compound having two or more amino groups is preferred, and a diamine having two amino groups is particularly preferred. From the same viewpoint, a tertiary diamine having two tertiary amino groups is more preferable, a tertiary diamine having two tertiary amino groups at both ends is even more preferable, and an aliphatic tertiary diamine having tertiary amino groups at both ends is even more preferable. Among the above amine compounds, the aliphatic tertiary diamine having tertiary amino groups at both ends is preferably tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, or tetraethyldiaminopropane, and taking into consideration ease of availability, etc., tetramethylethylenediamine or tetramethyldiaminopropane is preferable, with tetramethylethylenediamine being particularly preferable.

[0046] As complexing agents other than the above-mentioned amine compounds, compounds having a group containing a heteroatom such as an oxygen atom or a halogen atom such as a chlorine atom have a high affinity with lithium atoms and are exemplified as complexing agents other than the above-mentioned amine compounds. Furthermore, compounds having a group other than an amino group, such as a nitro group or an amide group, containing a nitrogen atom as a heteroatom, can also achieve the same effect. However, in the production method of this embodiment, complexing agents other than the amine compounds function as complexing agents when used alone, but when used in combination with an amine compound, the amine compound predominantly functions as the complexing agent described above, so that the complexing agent does not substantially function as a complexing agent and may function as a solvent, as described below.

[0047] Examples of the other complexing agents include alcohol solvents such as ethanol and butanol; ester solvents such as ethyl acetate and butyl acetate; aldehyde solvents such as formaldehyde, acetaldehyde, and dimethylformamide; ketone solvents such as acetone and methyl ethyl ketone; ether solvents such as diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole; halogen atom-containing aromatic hydrocarbon solvents such as trifluoromethylbenzene, nitrobenzene, chlorobenzene, chlorotoluene, and bromobenzene; and solvents containing carbon atoms and heteroatoms such as acetonitrile, dimethyl sulfoxide, and carbon disulfide. Among these, ether solvents are preferred, with diethyl ether, diisopropyl ether, dibutyl ether, and tetrahydrofuran being more preferred, and diethyl ether, diisopropyl ether, and dibutyl ether being even more preferred.

[0048] In the present embodiment, the content of the amine compound in the complexing agent is preferably as high as possible, and specifically, it is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass, i.e., it is particularly preferred that the entire amount of the complexing agent is an amine compound.

[0049] (solvent) In this embodiment, since the fluid containing the contents is usually highly viscous as described above, a solvent can be used to reduce the viscosity of the fluid and facilitate stirring. Stirring the raw material and complexing agent using a solvent reduces the viscosity, facilitating stirring. This promotes the formation of reaction products involving lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and facilitates the uniform distribution of lithium-containing structures such as PS4 structures or aggregates via the complexing agent, and lithium-containing raw materials such as lithium halides or aggregates via the complexing agent. This results in a reaction product in which the halogen atoms are more dispersed and fixed, thereby making it easier to achieve the effect of achieving high ionic conductivity.

[0050] The manufacturing method of this embodiment uses a fluid that is a slurry, which is a so-called heterogeneous method, and therefore it is preferable that the reactant does not completely dissolve in the liquid complexing agent but precipitates. The solubility of the reactant can also be adjusted by using a solvent together with the complexing agent. Halogen atoms in particular tend to leach out of the reactant, so adding a solvent can suppress the leach-out of halogen atoms, making it easier to obtain the desired reactant. As a result, a crystalline sulfide solid electrolyte with high ionic conductivity can be obtained via the reactant in which components such as halogens are dispersed.

[0051] More specifically, the solvent that can be used in combination with the above-mentioned complexing agent can be a wide variety of solvents that have conventionally been used in the production of 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-based solvents, ester-based solvents, aldehyde-based solvents, ketone-based solvents, ether-based solvents, and solvents containing carbon atoms and heteroatoms; and the like. It is also possible to use solvents from those exemplified as complexing agents.

[0052] More specifically, examples of the solvent include aliphatic hydrocarbon solvents such as hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene, chlorotoluene, and bromobenzene; alcohol-based solvents such as ethanol and butanol; ester-based solvents such as ethyl acetate and butyl acetate; aldehyde-based solvents such as formaldehyde, acetaldehyde, and dimethylformamide; ketone-based solvents such as acetone and methyl ethyl ketone; ether-based solvents such as diethyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole; and solvents containing carbon atoms and hetero atoms such as acetonitrile, dimethyl sulfoxide, and carbon disulfide.

[0053] 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, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and ether-based solvents are more preferred, alicyclic hydrocarbon solvents and ether-based solvents are even more preferred, and alicyclic hydrocarbon solvents are even more preferred. More specific solvents include heptane, cyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole, and heptane, cyclohexane, diethyl ether, diisopropyl ether, and dibutyl ether are more preferred, and cyclohexane, diisopropyl ether, and dibutyl ether are even more preferred, with cyclohexane being particularly preferred. In this embodiment, these solvents may be used alone or in combination.

[0054] Some of these solvents, for example, ether solvents having a heteroatom, can also be used as the complexing agent. As mentioned above, when an amine compound is used as a complexing agent, the amine compound predominantly functions as the complexing agent, and therefore the ether solvent does not substantially function as a complexing agent, but may function as a solvent. The ether solvents described as solvents function as a solvent when an amine compound is used as a complexing agent, and may function as a complexing agent when an amine compound is not used. Therefore, ether solvents are also exemplified as solvents. Therefore, for example, when an amine compound and an ether-based solvent are used in combination, the amine compound may be treated as a complexing agent, and the ether-based solvent may be treated as another solvent. In addition to the ether-based solvent, the solvents exemplified as complexing agents and solvents may also be treated in the same manner.

[0055] When a solvent is used, the content of the complexing agent relative to the total amount of the complexing agent and the solvent is preferably 1.5% by mass or more, more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and the upper limit is preferably 65.0% by mass or less, more preferably 50.0% by mass or less, even more preferably 35.0% by mass or less, and still more preferably 25.0% by mass or less.

[0056] (stirring) The stirring of the raw materials and the complexing agent is usually carried out in the form of a slurry in which the solid raw materials are present in the liquid complexing agent, since the raw materials contain solids and the complexing agent is liquid. By stirring the raw materials and the complexing agent, the raw materials and the complexing agent are reacted to obtain a reaction product. Here, as will be described later, the "reactant" is a reaction product in which the complexing agent reacts with lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and these atoms are bonded (coordinated) to each other directly with or without the aid of a complexing agent. This includes not only the reaction product of the raw materials and the complexing agent, but also the reaction product in which raw materials react with each other.

[0057] The amount of raw material used per 1 L of complexing agent varies depending on the volume of the fluid in the reaction vessel and cannot be generalized, but is usually preferably 5 g or more, more preferably 30 g or more, even more preferably 50 g or more, still more preferably 100 g or more, and particularly preferably 250 g or more, with the upper limit being preferably 800 g or less, more preferably 700 g or less, even more preferably 600 g or less, and still more preferably 500 g or less. When the content of raw material is within the above range, the raw material is easily stirred, the raw material is more uniformly dispersed, and the reaction between the raw material and the complexing agent is promoted, making it easier to efficiently obtain the reaction product, and further the sulfide solid electrolyte.

[0058] In the manufacturing method of this embodiment, for example, when reacting raw materials with a complexing agent by stirring them, it is necessary not to use a pulverizer. In the manufacturing method of this embodiment, the reaction between raw materials occurs mainly by stirring the raw materials with a complexing agent in a reaction vessel, but it is also necessary not to use a pulverizer when reacting raw materials with each other, not only in a reaction vessel but also outside the reaction vessel. Therefore, it is necessary not to use a pulverizer when stirring the raw materials with a complexing agent in a reaction vessel, and it is also necessary not to use a pulverizer when reacting raw materials with each other, not only in a reaction vessel but also outside the reaction vessel. The stirring of the raw materials and the complexing agent is not particularly limited except that a pulverizer is not used as described above, and the raw materials and the complexing agent may be placed in a device capable of stirring the raw materials and the complexing agent and stirred. For example, it is preferable to supply the complexing agent into a reaction vessel, operate the stirring blades, and then gradually add two or more compounds used as raw materials, since this makes the raw materials more uniformly dispersed. Furthermore, when a halogen element is used as a raw material, the raw material may contain a compound that is not solid. Specifically, at room temperature and normal pressure, fluorine and chlorine are gaseous, and bromine is liquid. For example, if the raw material is liquid, it may be supplied into a reaction vessel together with a complexing agent separately from other solid raw materials. If the raw material is gaseous, it may be supplied by blowing it into a mixture of a complexing agent and a solid raw material.

[0059] The production method of this embodiment is characterized by stirring the raw materials and the complexing agent to cause a reaction, and does not require the use of equipment generally referred to as 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. If a "pulverizer" is used to stir the raw materials and the complexing agent, the cost of the pulverizer increases, especially when attempting to increase the size (mass production), and the increased initial investment increases the cost of the sulfide solid electrolyte, resulting in the inconvenience of being unable to efficiently supply the sulfide solid electrolyte. "Stirring without using a pulverizer" literally means not using a pulverizer. In the manufacturing method of this embodiment, "stirring" essentially involves "mixing" that occurs, but it can be said to mean stirring to a degree that does not result in "pulverization" of solids such as lithium-containing compounds (e.g., lithium sulfide) used as raw materials. In this specification, "pulverizers" include pulverizers exemplified as pulverizers that can be used to pulverize the reactants and electrolyte precursors described below. In the manufacturing method of this embodiment, a pulverizer is not used when stirring the raw materials and the complexing agent, and a pulverizer can be used in processes other than the stirring.

[0060] In the method for producing a sulfide solid electrolyte of this embodiment, the raw materials and the complexing agent can react with each other to form a reactant by simply stirring them without using a "pulverizer." This makes it possible to obtain a sulfide solid electrolyte more efficiently than when pulverization is performed. Therefore, in the production method of this embodiment, the fluid containing the contents of the reaction vessel does not need to be subjected to a pulverization step. In this way, the ability to easily obtain a reactant without the pulverization step can be said to be one of the advantages of the production method of this embodiment. In the production method of this embodiment, it is preferable not to perform pulverization during the reaction between the raw materials and the complexing agent or during the circulation of the fluid containing the contents of the reaction vessel. However, the reactant may be pulverized using a pulverizer to finely pulverize it.

[0061] An example of an apparatus for stirring the raw materials and complexing agent is a mechanical stirring mixer equipped with stirring blades in a reaction vessel for stirring (which may also be referred to as mixing by stirring or stirring mixing). Examples of mechanical stirring mixers include high-speed stirring mixers and double-arm mixers, and high-speed stirring mixers are preferably used from the viewpoint of promoting the reaction between the raw materials and the complexing agent by making the dispersion state of the raw materials more uniform through fluid convection, thereby obtaining higher ionic conductivity. Examples of high-speed stirring mixers include vertical-axis rotary mixers and horizontal-axis rotary mixers, and either type of mixer may be used. When the raw materials and the complexing agent are stirred using these mixers, "pulverization" of the raw materials and the complexing agent may occur, but the process is essentially focused on "mixing," so the above-mentioned problems associated with using a "pulverizer" do not occur. On the other hand, when a "pulverizer" is used, "mixing" may occur, but the process is essentially focused on "pulverization," so the above-mentioned problems occur.

[0062] Examples of the shape of the stirring blade used in the mechanical stirring mixer include blade type, arm type, anchor type, paddle type, full zone 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 making the dispersion state of the raw materials in the fluid more uniform and obtaining higher ionic conductivity, the shovel type, flat blade type, C-type blade type, anchor type, paddle type, full zone type, etc. are preferred, with the anchor type, paddle type, and full zone type being more preferred.

[0063] When a mechanical stirring mixer is used, the rotation speed of the stirring blades can be adjusted appropriately depending on the volume, temperature, shape of the stirring blades, etc. of the fluid in the reaction vessel, but is not particularly limited. Generally, it is sufficient to set the rotation speed at about 5 rpm to 400 rpm. From the viewpoints of suppressing deviations in composition due to fluid splashing, etc., making the dispersion state of the raw materials more uniform through fluid convection, and promoting the reaction between the raw materials and the complexing agent, the rotation speed is preferably 10 rpm to 300 rpm, more preferably 15 rpm to 250 rpm, and even more preferably 20 rpm to 200 rpm.

[0064] In the production method of this embodiment, it is preferable to control the temperature in the reaction vessel, that is, to control the temperature when stirring the raw materials and the complexing agent. By controlling the temperature, the reaction between the raw materials and the complexing agent is promoted, and a sulfide solid electrolyte with high ionic conductivity can be obtained more efficiently. The temperature conditions when stirring the raw materials and complexing agent are not particularly limited, and are, for example, usually −30 to 120° C., preferably −10 to 100° C., more preferably 0 to 80° C., and even more preferably 10 to 60° C. The stirring time is usually 0.1 to 500 hours, and from the viewpoint of making the raw materials more uniformly dispersed and promoting the reaction between the raw materials and the complexing agent, is preferably 1 to 450 hours, more preferably 10 to 425 hours, even more preferably 20 to 400 hours, and still more preferably 40 to 375 hours.

[0065] By stirring the raw materials and the complexing agent, a reaction product is obtained in which the lithium, sulfur, phosphorus, and halogen atoms contained in the raw materials are directly bonded to each other via the complexing agent due to the interaction between these atoms and the complexing agent. It is also believed that some of these atoms are directly bonded to each other without the complexing agent. That is, in the manufacturing method of this embodiment, the reaction product of the raw materials and the complexing agent obtained by stirring the raw materials and the complexing agent is composed of the complexing agent, lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. In this embodiment, the resulting reaction product is not completely soluble in the liquid complexing agent but is usually solid, so the fluid containing the contents is a slurry. Furthermore, the fluid containing the contents may contain, in addition to the reactants, unreacted raw materials, the complexing agent itself that does not contribute to the reactants, and, if necessary, a solvent. Therefore, the use of a slurry in the production method of this embodiment means that it corresponds to a heterogeneous system in a so-called liquid phase method.

[0066] In the production method of this embodiment, before stirring the raw materials and the complexing agent, the raw materials may be stirred with the above-mentioned solvent to form a slurry in advance. By dispersing the raw materials in the solvent as a slurry in advance, good contact between the raw materials and the complexing agent can be achieved immediately after the start of stirring, and the reaction due to stirring between the raw materials and the complexing agent can be promoted. In this case, the amount of solvent used is preferably 0.1 L or more, more preferably 0.3 L or more, even more preferably 0.5 L or more, and still more preferably 0.75 L or more per 100 g of raw material, and the upper limit is preferably 5.0 L or less, more preferably 4.0 L or less, even more preferably 3.0 L or less, and still more preferably 2.5 L or less.

[0067] (circulation) In the production method of this embodiment, it is necessary to circulate the fluid containing the contents by withdrawing it from the reaction vessel through an outlet provided in the reaction vessel and returning it to the reaction vessel through a return port provided in the reaction vessel. As described above, this circulation suppresses settling and stagnation of reactants and the like in the fluid at the bottom of the reaction vessel, reducing the amount of raw materials that do not contribute to the reaction. Furthermore, by generating convection in the fluid containing the contents in the reaction vessel, it is possible to ensure a uniform dispersion of the raw materials in the fluid even when stirring is performed to a degree that does not cause splashing of the fluid. Therefore, it is possible to promote the reaction while suppressing compositional deviations in the sulfide solid electrolyte, and it is possible to more efficiently obtain a sulfide solid electrolyte having high ionic conductivity using a liquid phase method.

[0068] Hereinafter, the circulation of fluids, including the outlet and return ports provided in the reaction tank, will be described with reference to a flow diagram showing an example of a preferred embodiment of a flow including a reaction tank used in the production method of this embodiment shown in FIG. 1 shows a reaction tank 1 equipped with an outlet 2 and a return port 3, which is equipped with an agitator 4 having agitating blades 5, and a flow in which a fluid containing the contents extracted from the outlet 2 passes through a circulation line 12 by a pump 11 and is returned to the return port 3. Valves 13a and 13b are provided on the suction side and discharge side of the pump 11, respectively.

[0069] The reaction vessel is not particularly limited as long as it is provided with an outlet and return port and a stirrer capable of stirring the fluid in the reaction vessel. For example, the material constituting the reaction vessel may be appropriately selected from metal, glass, resin, etc., depending on the capacity of the reaction vessel, the required pressure resistance, heat resistance, etc. For example, if the capacity is up to about 10 L, a glass Schlenk flask, separable flask, etc. may be used, and if the capacity exceeds 10 L, a metal vessel equipped with an outlet and return port, etc. may be used. The capacity of the reaction vessel may be appropriately selected depending on the amount of the desired sulfide solid electrolyte, and is not particularly limited. It is usually selected from about 0.1 L to 100 L, preferably 0.3 L to 50 L. When aiming for large-scale (mass production) for industrial production, the capacity is preferably 30 L or more, more preferably 100 L or more, even more preferably 500 L or more, and even more preferably 600 L or more. There is no particular upper limit as long as industrial production is possible. For example, it can be in the range of 100 kL or less, 50 kL or less, or 10 kL or less.

[0070] The outlet to be installed in the reaction vessel need only be located at a position that allows the fluid containing the contents of the reaction vessel to be extracted, i.e., located below the liquid level of the fluid. Considering that the specific gravity of unreacted raw materials and reactants in the fluid is high and they tend to settle and stagnate at the bottom of the reaction vessel, particularly directly below the rotating shaft of the stirring blades, the outlet is preferably located at the bottom of the reaction vessel, more preferably below the stirring blades, and even more preferably at the bottom (lowest part) of the reaction vessel. Figure 1 shows an embodiment in which the outlet 2 is installed at the bottom of the reaction vessel 1.

[0071] The return port to be installed in the reaction tank may be installed at any location without any particular limitation, and may be installed either above or below the liquid level of the fluid in the reaction tank. When installed above the liquid level of the fluid, it is preferable to install it on the side of the reaction tank so that the fluid is returned to the reaction tank along the wall surface of the reaction tank from the viewpoint of suppressing splashing of the fluid. From the viewpoint of efficiently generating convection of the fluid in the reaction tank and suppressing splashing of the fluid and adhesion of the fluid to the wall surface of the reaction tank, the return port is preferably installed below the liquid level of the fluid, more preferably below the liquid level of the fluid and above the location where the withdrawal port is installed. Figure 2 shows an embodiment in which the return port 3 is installed below the liquid level of the fluid in the reaction tank 1 and above the withdrawal port 2. Unless the return port is provided at the top of the reaction tank, it will be provided on the side as shown in Figure 1. The return port may further be provided with an inner tube so that the fluid withdrawn to the outside of the reaction tank is returned to the fluid inside the reaction tank.

[0072] The amount of fluid circulated per minute cannot be generalized because it varies depending on the volume of the fluid in the reaction tank. However, from the viewpoint of efficiently generating convection in the fluid and suppressing splashing of the fluid and adhesion of the fluid to the wall surfaces in the reaction tank, the amount of fluid circulated per minute is preferably at least 0.01 times, more preferably at least 0.03 times, and even more preferably at least 0.05 times the volume of the fluid in the reaction tank, with the upper limit being preferably at most 5.0 times, more preferably at most 3.0 times, and even more preferably at most 2.0 times. For example, when the volume of the fluid in the reaction vessel is more than 1.0 L at a laboratory level to a small to medium industrial production scale, the circulation rate of the fluid per minute is preferably 0.01 times or more, more preferably 0.03 times or more, and even more preferably 0.05 times or more of the volume of the fluid in the reaction vessel, with no particular upper limit, and usually 5.0 times or less. Also, for example, when the volume of the fluid in the reaction vessel is less than 1.0 L at a laboratory level, the circulation rate of the fluid per minute is preferably 0.1 times or more, more preferably 0.5 times or more, even more preferably 0.75 times or more, and even more preferably 1.0 times or more of the volume of the fluid in the reaction vessel, with no particular upper limit, and usually 5.0 times or less.

[0073] When the volume of the fluid in the reaction tank is increased (mass production) for industrial production, for example, to 30 L or more, the amount of fluid circulated per minute is preferably 0.01 times or more, more preferably 0.02 times or more, of the volume of the fluid in the reaction tank, and there is no particular upper limit, and it is usually set to 5.0 times or less. In this case, the amount of fluid circulated per minute cannot be generalized as the absolute amount varies depending on the volume of the fluid, but is preferably 3.5 L / min or more, more preferably 5.0 L / min or more, and even more preferably 10 L / min or more, and there is no particular upper limit, so it should usually be set to 100 L / min or less.

[0074] For circulating the fluid, a pump 11 can be used as needed, as shown in Figure 1. There are no particular restrictions on the type of pump, and it can be selected appropriately from centrifugal, mixed flow, axial flow, positive displacement, etc., taking into consideration the amount of fluid circulated, the required head, etc. Furthermore, if the reactants contained in the fluid or the unreacted raw materials cause wear on the impeller in the case of a centrifugal pump or the piston in the case of a positive displacement pump, it is also possible to use a pump that is resistant to fluids containing solids, such as a slurry pump, gravel pump, or sand pump. The circulation amount may be constantly adjusted by using, for example, valve 13b on the discharge side of pump 11 shown in FIG. 1 as a flow rate control valve, or a pump capable of flow rate control may be selected.

[0075] To control the temperature inside the reaction tank, a heater or cooler may be provided inside or outside the reaction tank depending on the desired temperature. For example, when heating a fluid inside the reaction tank, a jacket-type heater may be provided outside the reaction tank, a shell-and-tube or electric heat exchanger may be provided inside the reaction tank, or a heat exchanger may be provided in the fluid circulation line.

[0076] The agitator 4 that agitates the raw materials and the complexing agent in the reaction vessel, and the agitating blades 5 that are provided when a mechanical agitation mixer is used as the agitator, are as described above.

[0077] 1 shows a configuration in which the raw materials and the complexing agent are supplied from the top of the reaction vessel, but this is not limiting and they may be supplied separately. For example, when the raw materials and the solvent are stirred to form a slurry in advance as described above, the slurry may be transferred from a slurry preparation device into the reaction vessel, and the complexing agent may be supplied separately into the reaction vessel. Furthermore, although not shown in Fig. 1, when the fluid in the reaction vessel is subjected to treatments such as pulverization, drying, heating, etc., a pipe for supplying the fluid to the apparatus may be provided, for example, on the discharge side of pump 11 shown in Fig. 1. This allows the reaction by stirring the raw materials and complexing agent, as well as treatments such as pulverization, drying, and heating, to be carried out continuously, making it possible to produce a sulfide solid electrolyte more efficiently, which is industrially advantageous. When a continuous system is used, the supply amounts of the complexing agent and raw materials may be adjusted depending on the supply amounts of fluids to other apparatuses.

[0078] (Crushing) In the production method of this embodiment, if desired, the reactant obtained by the stirring or the amorphous or crystalline sulfide solid electrolyte obtained after drying the fluid containing the contents described below may be pulverized. Pulverizing the reactant or electrolyte precursor allows a sulfide solid electrolyte with a small particle size to be obtained while suppressing a decrease in ionic conductivity, and is therefore effective when a small particle size is desired. The pulverization of the reactant, the electrolyte precursor, in this embodiment is not performed to obtain an amorphous or crystalline sulfide solid electrolyte by reacting raw materials with mechanical stress as disclosed in, for example, Patent Document 5, but is performed solely for the purpose of atomization.

[0079] The mill used to pulverize the reactants and electrolyte precursor is not particularly limited as long as it can pulverize particles, and for example, a media-type mill using a milling medium can be used. Among media-type mills, considering that the reactants are mainly in a liquid state accompanied by liquids such as a complexing agent and a solvent, or in a slurry state, a wet mill that can handle wet pulverization is preferred. These mills not only pulverize but also essentially mix at the same time, i.e., pulverization and mixing are performed.

[0080] Representative examples of wet mills include wet bead mills, wet ball mills, and wet vibration mills, with wet bead mills using beads as milling media being preferred because they allow for flexible adjustment of milling conditions and are suitable for smaller particle sizes. Alternatively, dry mills such as dry media mills (e.g., dry bead mills, dry ball mills, and dry vibration mills) and dry non-media mills (e.g., jet mills) can also be used.

[0081] As a mill used to mill the reactants and electrolyte precursor, a machine capable of milling an object using ultrasonic waves, such as a machine called an ultrasonic mill, ultrasonic homogenizer, or probe ultrasonic mill, can be used.

[0082] The average particle size (D 50 ) is determined appropriately as desired, but is usually 0.01 μm or more and 50 μm or less, preferably 0.03 μm or more and 5 μm or less, and more preferably 0.05 μm or more and 3 μm or less. By setting the average particle size in this range, it is possible to meet the demand for a sulfide solid electrolyte having a small particle size, that is, an average particle size of 1 μm or less.

[0083] The pulverization can be carried out after drying the fluid containing the contents and forming it into a powder (electrolyte precursor) as described above. In this case, it is preferable to use any of the dry grinders among the grinders exemplified above as grinders that can be used in the manufacturing method of this embodiment. Other matters related to grinding, such as grinding conditions, are the same as those for grinding a fluid containing the contents, and the average particle size of the reactant and electrolyte precursor obtained by grinding is also the same as above.

[0084] (Dry) The manufacturing method of this embodiment may include drying the fluid (usually a slurry) containing the reactants, thereby obtaining a powder of the electrolyte precursor, i.e., the reactants and the electrolyte precursor are substantially the same thing. By drying the fluid containing the contents, it becomes possible to perform heating more efficiently. Note that drying and the subsequent heating may be performed in the same process.

[0085] Drying of the fluid containing the contents can be carried out at a temperature that depends on the amount of remaining complexing agent (complexing agent not incorporated into the reactant) and the type of solvent used if necessary, for example, at a temperature equal to or higher than the boiling point of the complexing agent. Alternatively, the complexing agent and the solvent used as needed can be evaporated 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) (for example, about room temperature ±5°C). Unlike complexing agents, solvents are less likely to be incorporated into the reaction product, and therefore the amount of solvent that can be contained in the reaction product is usually 3% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less.

[0086] As described above, the reactant is a complexing agent reacted with lithium, sulfur, phosphorus, and halogen atoms, and these atoms are directly bonded (coordinated) with one another with or without the aid of a complexing agent. In X-ray diffraction measurements, peaks distinct from those derived from the raw materials are observed in the X-ray diffraction pattern. This reaction product includes cocrystals composed of a complexing agent and lithium, sulfur, phosphorus, and halogen atoms. Simply stirring the raw material compounds results in peaks distinct from those derived from the raw materials. However, stirring the raw materials and the complexing agent results in peaks distinct from those derived from the raw materials. Therefore, the reactant (cocrystal) has a structure distinct from that of the raw material compounds themselves. This is specifically confirmed in the Examples. Examples of X-ray diffraction patterns of the electrolyte precursor obtained by drying the reactant (cocrystal) and the raw materials, such as lithium sulfide, are shown in Figures 2 and 3, respectively. As mentioned above, the electrolyte precursor is essentially the same as the reactant. Therefore, the electrolyte precursor also contains a co-crystal. The peaks in the X-ray diffraction pattern are due to the co-crystal, and therefore the electrolyte precursor and the reactant (co-crystal) show essentially the same peaks. The X-ray diffraction pattern shows that the reactant (co-crystal) has a specific crystal structure. Furthermore, the diffraction pattern does not include the diffraction patterns of any of the raw materials, such as lithium sulfide shown in Figure 3, or the amorphous and crystalline Li3PS4 shown for reference. This shows that the reactant (co-crystal) has a crystal structure different from that of the raw materials.

[0087] The reactant (co-crystal) is characterized by having a structure different from that of the crystalline sulfide solid electrolyte. This is also specifically confirmed in the Examples. Figure 2 also shows the X-ray diffraction pattern of the crystalline sulfide solid electrolyte, which shows that it differs from the diffraction pattern of the reactant (co-crystal). Note that the reactant (co-crystal) has a specific crystal structure and is different from the amorphous sulfide solid electrolyte, which has a broad pattern as shown in Figure 2.

[0088] The cocrystal is composed of a complexing agent, a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom, and is typically presumed to form a complex structure in which the lithium atom is directly bonded to other atoms with or without the intervention of a complexing agent. Here, whether the complexing agent forms a co-crystal can be confirmed by, for example, gas chromatography analysis. Specifically, the complexing agent contained in the co-crystal can be quantified by dissolving the reactant powder in methanol and performing gas chromatography analysis of the resulting methanol solution. The content of the complexing agent in the reaction product varies depending on the molecular weight of the complexing agent, but is usually about 10% by mass to 70% by mass, preferably 15% by mass to 65% by mass.

[0089] In the production method of this embodiment, it is preferable to form a co-crystal containing halogen atoms in order to improve ionic conductivity. By using a complexing agent, a lithium-containing structure such as a PS4 structure and a lithium-containing compound such as a lithium halide used as a raw material are bonded (coordinated) via the complexing agent, making it easier to obtain a co-crystal in which the halogen atoms are more dispersed and fixed, thereby improving ionic conductivity.

[0090] The fact that halogen atoms in the reactant form a co-crystal can be confirmed by checking that a predetermined amount of halogen atoms is still present in the reactant even after solid-liquid separation of a fluid containing the reactant. This is because halogen atoms that do not form a co-crystal are more easily dissolved than halogen atoms that form a co-crystal and are discharged into the liquid during solid-liquid separation. Furthermore, this can also be confirmed by checking that the proportion of halogen atoms in the reactant or sulfide solid electrolyte is not significantly reduced compared to the proportion of halogen atoms supplied from the raw materials, as determined by composition analysis of the reactant or sulfide solid electrolyte using inductively coupled plasma atomic emission spectroscopy (ICP). The amount of halogen atoms remaining in the reaction product is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more, based on the charged composition. The upper limit of the amount of halogen atoms remaining in the reaction product is 100% by mass.

[0091] (heating) The method for producing a sulfide solid electrolyte of this embodiment preferably includes heating the reactant or the electrolyte precursor obtained by the drying to obtain an amorphous sulfide solid electrolyte, or heating the reactant, the electrolyte precursor, or the amorphous sulfide solid electrolyte to obtain a crystalline sulfide solid electrolyte. By heating, the complexing agent in the reactant or the electrolyte precursor is removed, and an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms is obtained. Furthermore, the reactant or the electrolyte precursor heated by this heating may be a pulverized product of the reactant or the electrolyte precursor obtained by the pulverization described above. Here, the removal of the complexing agent from the reactant and electrolyte precursor is supported by the fact that it is clear from the results of X-ray diffraction patterns, gas chromatography analysis, etc. that the complexing agent forms a co-crystal with the reactant and electrolyte precursor, and also by the fact that the sulfide solid electrolyte obtained by removing the complexing agent by heating the reactant and electrolyte precursor has the same X-ray diffraction pattern as the sulfide solid electrolyte obtained by a conventional method without using a complexing agent.

[0092] In the production method of this embodiment, the crystalline sulfide solid electrolyte may be obtained by heating the reactants and the electrolyte precursor, or by heating the reactants and the electrolyte precursor to obtain an amorphous sulfide solid electrolyte, and then heating the amorphous sulfide solid electrolyte. In other words, the production method of this embodiment can also produce an amorphous sulfide solid electrolyte.

[0093] In the production method of this embodiment, whether to obtain an amorphous sulfide solid electrolyte, a crystalline sulfide solid electrolyte, or an amorphous sulfide solid electrolyte and then a crystalline sulfide solid electrolyte, or to obtain a crystalline sulfide solid electrolyte directly from a reactant or electrolyte precursor, is appropriately selected as desired, and can be adjusted by the heating temperature, heating time, etc. The heating temperature for obtaining an amorphous sulfide solid electrolyte cannot be generally defined because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is generally preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. There is no particular lower limit, but it is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 105°C or higher.

[0094] The heating temperature for obtaining a crystalline sulfide solid electrolyte cannot be generally defined because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is generally preferably 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C or higher. There is no particular upper limit, but it is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0095] The heating time is not particularly limited as long as it is a time that allows the desired amorphous sulfide solid electrolyte or crystalline sulfide solid electrolyte to be obtained, and is usually from 1 minute to 24 hours. Furthermore, the heating is preferably carried out in an inert gas atmosphere (for example, a nitrogen atmosphere or an argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum).

[0096] (Amorphous sulfide solid electrolyte) The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains lithium, sulfur, phosphorus, and a halogen element. Representative examples include solid electrolytes composed of lithium sulfide, phosphorus sulfide, and a lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr; and solid electrolytes further containing other elements such as oxygen and silicon, such as Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI. From the viewpoint of obtaining higher ionic conductivity, solid electrolytes composed of lithium sulfide, phosphorus sulfide, and a lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr, are preferred. The types of elements constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0097] When the amorphous sulfide solid electrolyte obtained by the production method of this embodiment contains at least Li2S-P2S5, the molar ratio of Li2S to P2S5 is preferably 65-85:15-35, more preferably 70-80:20-30, and even more preferably 72-78:22-28, from the viewpoint of obtaining higher ionic conductivity. When the amorphous sulfide solid electrolyte produced by the production method of this embodiment is, for example, Li2S-P2S5-LiI-LiBr, the total content of lithium sulfide and diphosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%. The ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0098] In the amorphous sulfide solid electrolyte obtained by the production method of this embodiment, the compounding ratio (molar ratio) of lithium element, sulfur element, phosphorus element, and halogen element is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.6, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.05-0.5, and still more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.08-0.4. When bromine and iodine are used in combination as the halogen elements, the compounding ratio (molar ratio) of lithium, sulfur, phosphorus, bromine, and iodine is preferably 1.0-1.8:1.0-2.0:0.1-0.8:0.01-0.3:0.01-0.3, more preferably 1.1-1.7:1.2-1.8:0.2-0.6:0.02-0.25:0.02-0.25, more preferably 1.2-1.6:1.3-1.7:0.25-0.5:0.03-0.2:0.03-0.2, and even more preferably 1.35-1.45:1.4-1.7:0.3-0.45:0.04-0.18:0.04-0.18. By setting the compounding ratio (molar ratio) of lithium element, sulfur element, phosphorus element and halogen element within the above range, it becomes easier to obtain a solid electrolyte having a thiolithium region II type crystal structure described below and having higher ionic conductivity.

[0099] The residual Li2S content of the amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment is typically 15.0% or less, preferably 10.0% or less, more preferably 7.5% or less, and even more preferably 5.5% or less. The residual Li2S content is determined by the method described in the Examples and refers to the amount of unreacted Li2S in the reaction field when Li2S is used as a raw material. This value serves as an indicator of the progress of the raw material reaction, more specifically, the progress of the raw material becoming a constituent of the sulfide solid electrolyte. In other words, the smaller the residual Li2S content, the less unreacted Li2S there is, indicating that Li2S contributes more to the formation of the sulfide solid electrolyte. Therefore, the smaller the residual Li2S content of the amorphous sulfide solid electrolyte, the better, and it is typically about 0.5% or more.

[0100] The shape of the amorphous 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.

[0101] (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 solid electrolyte to a crystallization temperature or higher, and its crystal structure may be Li3PS4 crystal structure, Li4P2S6 crystal structure, Li7PS6 crystal structure, Li7P3S 11 Examples of such a crystal structure include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0102] Also, Li 4-x Ge 1-x P x S4-type 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 Examples of such a crystal structure include a crystal structure similar to the S4-based 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, since it can provide higher ionic conductivity. Here, the "thio-LISICON Region II type crystal structure" refers to a structure in which Li 4-x Ge 1-x P x S4-type thio-LISICON Region II crystal structure, Li 4-x Ge 1-x P xThis indicates that the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment has either the thio-LISICON Region II type or a crystal structure similar to that of the S4-based thio-LISICON Region II type. The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may have the thio-LISICON Region II type crystal structure or may have it as the main crystal. However, from the viewpoint of obtaining higher ionic conductivity, it is preferable that it has it as the main crystal. In this specification, "having it as the main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or more, preferably 90% or more, and more preferably 95% or more. Furthermore, from the viewpoint of obtaining higher ionic conductivity, it is preferable that the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment does not contain crystalline Li3PS4 (β-Li3PS4).

[0103] In X-ray diffraction measurements using CuKα radiation, the diffraction peaks of the Li3PS4 crystal structure appear, for example, at 2θ = 17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, the diffraction peaks of the Li4P2S6 crystal structure appear, for example, at 2θ = 16.9°, 27.1°, and 32.5°, and the diffraction peaks of the Li7PS6 crystal structure appear, for example, at 2θ = 15.3°, 25.2°, 29.6°, and 31.0°, and the diffraction peaks of the Li7P3S 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°. 4-x Ge 1-x P x The diffraction peaks of the S4 thio-LISICON Region II crystal structure appear, for example, at 2θ = 20.1°, 23.9°, and 29.5°. 4-x Ge 1-x P x Diffraction peaks of a crystal structure similar to the S4 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°.

[0104] As described above, when a thiolischicon region II-type crystal structure is obtained in the present embodiment, it is preferable that it does not contain crystalline Li3PS4 (β-Li3PS4). Fig. 2 shows an example of X-ray diffraction measurement of the crystalline sulfide solid electrolyte obtained by the production method of the present embodiment. Fig. 3 shows an example of X-ray diffraction measurement of crystalline Li3PS4 (β-Li3PS4). As can be understood from Figs. 2 and 3, the sulfide solid electrolyte obtained by the production method of the present embodiment does not have diffraction peaks at 2θ = 17.5° and 26.1° found in crystalline Li3PS4, or even if it has them, the detected peaks are extremely small compared to the diffraction peaks of the thiolischicon region II-type crystal structure.

[0105] Having the above-mentioned structural framework of Li7PS6 and substituting part of P with Si, the composition formula Li 7-x P 1-y Si y S6 and Li 7+x P 1-y Si y The crystal structure represented by S6 (x is -0.6 to 0.6, y is 0.1 to 0.6) is cubic or orthorhombic, preferably cubic, and in X-ray diffraction measurement using CuKα rays, mainly peaks appear at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. The above composition formula Li 7-x-2y PS 6-x-y Cl x (0.8 ≦ x ≦ 1.7, 0 < y ≦ -0.25x + 0.5) is preferably cubic, and in X-ray diffraction measurement using CuKα rays, mainly peaks appear at positions of 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. Also, the above composition formula Li 7-x PS 6-x Ha xThe crystal structure represented by the formula (where Ha is Cl or Br, and x is preferably 0.2 to 1.8) is preferably a cubic crystal, and in X-ray diffraction measurement using CuKα radiation, has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°. These peak positions may vary within a range of ±0.5°.

[0106] 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.

[0107] The sulfide solid electrolyte obtained by the manufacturing method of this embodiment has high ionic conductivity and excellent battery performance, and is therefore suitable for use in batteries. It is particularly suitable when lithium element is used as the conductive species. 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.

[0108] The battery preferably includes 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 of a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu, coated with Au or the like can be used. [Example]

[0109] 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.

[0110] Example 1 In a Schlenk tube (volume: 500 mL) equipped with a stirrer, 13.60 g of lithium sulfide (LiS), 21.93 g of diphosphorus pentasulfide (P2S5), 4.28 g of lithium bromide (LiBr), and 6.60 g of lithium iodide (LiI) were introduced under a nitrogen atmosphere. After rotating the stirrer, 400 mL of cyclohexane was added to obtain a cyclohexane slurry containing lithium sulfide, diphosphorus pentasulfide, lithium bromide, and lithium iodide as raw materials and cyclohexane as a solvent. The raw materials and complexing agent were stirred using an apparatus having the configuration shown in Figure 1. In this apparatus, the reaction vessel was a separable flask (volume: 500 mL), and the stirring blade was an anchor-type stirring blade. The extraction port was installed at the bottom of the separable flask, and the return port was installed below the liquid level of the fluid in the reaction vessel. The resulting cyclohexane slurry was transferred to a reaction vessel, and 103 mL of tetramethylethylenediamine (TMEDA) was added as a complexing agent. The stirring speed of the stirring blade was set to 200 rpm, and the pump flow rate was set to 550 mL / min. While circulating the fluid in the reaction vessel, stirring of the fluid in the reaction vessel was initiated. The temperature inside the reaction vessel was kept at room temperature (23°C). After 360 hours (stirring time) from the start of the stirring, the resulting fluid was dried under reduced pressure at room temperature to obtain a powdered electrolyte precursor. The mixture was then heated under reduced pressure at 110°C for 2 hours to remove the complexing agent contained in the electrolyte precursor, yielding an amorphous solid electrolyte. The obtained amorphous sulfide solid electrolyte was subjected to powder X-ray diffraction (XRD) measurement by the following method. The remaining amount of Li2S in the amorphous sulfide solid electrolyte was calculated to be 4%. In addition, among the solid compounds used as raw materials, lithium sulfide, diphosphorus pentasulfide, lithium bromide, and lithium iodide, lithium iodide (density: 4.08 g / cm3) had the highest density. 3 ) and the lowest density lithium sulfide (density: 1.66 g / cm 3 ) and the density difference is 2.42 g / cm 3 Furthermore, composition analysis was performed by ICP analysis (inductively coupled plasma atomic emission spectroscopy). The experimental conditions for Example 1 are shown in Table 1, the measurement results are shown in Table 2, and the results of XRD measurement are shown in Figure 4.

[0111] Furthermore, the amorphous sulfide solid electrolyte was heated at 200°C under reduced pressure for 2 hours to obtain a crystalline sulfide solid electrolyte. The obtained crystalline solid electrolyte was subjected to XRD measurement in the same manner as the amorphous solid electrolyte described above. Crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in the X-ray diffraction spectrum of the crystalline solid electrolyte. The crystalline solid electrolyte had a thiolithiregion II crystal structure and did not have diffraction peaks at 2θ = 17.5° and 26.1°. The ionic conductivity was measured to be 2.5 x 10 -3 (S / cm), confirming that the material had high ionic conductivity. The results are shown in Table 2.

[0112] (Powder XRD diffraction and measurement of remaining Li2S) Powder X-ray diffraction (XRD) measurement and calculation of the remaining amount of Li2S were carried out as follows. Powders of the electrolyte precursor and amorphous sulfide solid electrolyte obtained in the examples and comparative examples were filled into a groove 20 mm in diameter and 0.2 mm deep and leveled with glass to prepare a sample. This sample was sealed with Kapton film for XRD and measured under the following conditions without exposing it to air. Powder X-ray diffraction (XRD) of the raw materials used in the examples was also performed in the same manner as for the amorphous sulfide solid electrolyte. The Li2S residual amount refers to the amount of unreacted Li2S in the reaction field when lithium sulfide (Li2S) is used as the raw material. It is a numerical value that serves as an indicator for understanding the progress of the raw material reaction, more specifically, the progress of the raw material becoming a constituent of the sulfide solid electrolyte. In other words, the smaller the Li2S residual amount, the less unreacted Li2S there is, indicating that Li2S contributes more to the formation of the sulfide solid electrolyte. Measurement equipment: D2 PHASER, manufactured by Bruker Tube voltage: 30kV Tube current: 10mA X-ray wavelength: Cu-Kα ray (1.5418Å) Optical system: Concentration method Slit configuration: Soller slit 4°, divergence slit 1 mm, Kβ filter (Ni plate) Detector: Semiconductor detector Measurement range: 2θ=10-60deg Step width, scan speed: 0.05deg, 0.05deg / sec

[0113] The remaining amount of Li2S was analyzed using Excel Solver's function to confirm the remaining amount of raw material from the above measurement results. The 2θ of the raw data was designated A, the peak intensity B, the baseline used in the calculation, and the glass intensity C and D, respectively. When calculating the peak intensity for the baseline, the following empirical calculations were made based on the measurement system for each 2θ. C=-45.72*A+4600-457.2 The glass strength D was calculated using the following formula, where the peak angles are E, F, G, and H, the widths are I, J, K, and L, and the strengths are M, N, O, and P.

number

[0114] Furthermore, the background correction data for calculation is Q as follows: Q=BC The peak position of the raw material Li2S at the beginning of the reaction and the calculated peak shift of the Li2S peak are designated as R, and R is added to all peaks and reflected in the above Q. In addition, the peak intensity of Li2S at the beginning of the reaction is designated as S, and the peak intensity was fitted by multiplying the peak intensity S at the beginning of the reaction by a coefficient T. If the total residual of the fitting is designated as U, it is obtained as follows.

number

[0115] In calculations using the solver function, E, F, G, H, I, J, K, L, M, N, O, P, R, and T were used as variables, and calculations were performed so that U was minimized using GRG nonlinearity, and the remaining amount of Li2S was fitted.

[0116] In this example, the ionic conductivity was measured as follows. From the obtained crystalline sulfide solid electrolyte, a 10 mm diameter (cross-sectional area S: 0.785 cm 2) and a height (L) of 0.1 to 0.3 cm were molded into circular pellets to serve as samples. Electrode terminals were attached to the top and bottom of the samples, and measurements were made at 25°C using the AC impedance method (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV). A Cole-Cole plot was obtained. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high-frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following equation: R=ρ(L / S) σ=1 / ρ

[0117] Example 2 15.87 g of lithium sulfide (LiS) was introduced into a 500 mL Schlenk flask equipped with a stirrer under a nitrogen atmosphere. After rotating the stirrer, 300 mL of cyclohexane was added, followed by 6.26 g of iodine (I). The mixture was stirred at room temperature for 2 hours. 3.94 g of bromine (Br) was then added, and the mixture was stirred at room temperature for 12 hours, followed by further stirring at 50 °C for 3 hours. The slurry was allowed to settle, and 190 mL of the supernatant was removed. Then, 190 mL of cyclohexane was added and decanted. Decantation was performed three times to wash away sulfur molecules by-produced by the reaction of lithium sulfide, bromine, and iodine, yielding a cyclohexane slurry containing lithium sulfide, lithium bromide, and lithium iodide as raw materials. To the obtained cyclohexane slurry, 21.93 g of diphosphorus pentasulfide (P2S5) and 100 mL of cyclohexane were added (total amount of cyclohexane was 400 mL), and the mixture was transferred to the reaction vessel of the apparatus used in Example 1, and 103 mL of tetramethylethylenediamine (TMEDA) as a complexing agent was added. The fluid in the reaction vessel contained lithium sulfide, diphosphorus pentasulfide, lithium bromide, and lithium iodide as raw materials, TMEDA as a complexing agent, and cyclohexane as a solvent. The stirring speed of the stirring blade was set to 200 rpm, and the pump flow rate was set to 550 mL / min. The stirring of the fluid in the reaction vessel was started while circulating the fluid in the reaction vessel. The temperature in the reaction vessel was set to room temperature (23°C). After 300 hours (stirring time) from the start of the stirring, the resulting fluid was dried under reduced pressure at room temperature to obtain a powdered electrolyte precursor. The mixture was then heated under reduced pressure at 110°C for 2 hours to remove the complexing agent contained in the electrolyte precursor, yielding an amorphous solid electrolyte.

[0118] The obtained amorphous solid electrolyte was subjected to powder X-ray diffraction (XRD) measurement by the method described above. The remaining amount of Li2S in the amorphous sulfide solid electrolyte was calculated and found to be 2%. Furthermore, composition analysis was performed by ICP analysis (inductively coupled plasma atomic emission spectroscopy). The experimental conditions for Example 2 are shown in Table 1, the measurement results in Table 2, and the XRD measurement results in Figure 4. Next, a crystalline sulfide solid electrolyte was obtained in the same manner as in Example 1. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 2.1 × 10 -3 (S / cm), confirming that the material had high ionic conductivity. The results are shown in Table 2.

[0119] Example 3 In a Schlenk tube (volume: 5000 mL) equipped with a stirrer, 439.5 g of lithium sulfide (LiS), 708.6 g of diphosphorus pentasulfide (P2S5), 138.5 g of lithium bromide (LiBr), and 213.4 g of lithium iodide (LiI) were introduced under a nitrogen atmosphere. After rotating the stirrer, 4 L of cyclohexane was added to obtain a cyclohexane slurry containing lithium sulfide, diphosphorus pentasulfide, lithium bromide, and lithium iodide as raw materials and cyclohexane as a solvent. The raw materials and complexing agent were stirred using an apparatus having the configuration shown in Figure 1. In this apparatus, the reaction vessel had a capacity of 40 L and the stirring blade was an anchor-type stirring blade. The withdrawal port was installed at the bottom of the separable flask, and the return port was installed below the liquid level of the fluid in the reaction vessel. The resulting cyclohexane slurry was transferred to a reactor, and an additional 27 L of cyclohexane was added (total amount of cyclohexane: 31.0 L). Also, 3.33 L of tetramethylethylenediamine (TMEDA) as a complexing agent was added. The stirring speed of the impeller was set to 80 rpm, and the pump flow rate was set to 3 L / min. While circulating the fluid in the reactor, stirring of the fluid in the reactor was initiated. The temperature inside the reactor was set to 30°C. After 210 hours (stirring time) from the start of stirring, the resulting fluid was dried under reduced pressure at room temperature to obtain a powdered electrolyte precursor. The mixture was then heated under reduced pressure at 110°C for 2 hours to remove the complexing agent contained in the electrolyte precursor, yielding an amorphous solid electrolyte. The obtained electrolyte precursor and amorphous solid electrolyte were subjected to powder X-ray diffraction (XRD) measurement. The remaining amount of Li2S in the amorphous sulfide solid electrolyte was calculated and found to be 2%. Furthermore, composition analysis was performed using ICP analysis (inductively coupled plasma atomic emission spectroscopy). The experimental conditions for Example 3 are shown in Table 1, the measurement results in Table 2, and the XRD measurement results in Figure 2.

[0120] Next, a crystalline sulfide solid electrolyte was obtained in the same manner as in Example 1. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 3.9 × 10 -3 (S / cm), confirming that the material had high ionic conductivity. The results are shown in Table 2. The X-ray diffraction spectrum of the electrolyte precursor showed peaks distinct from those derived from the raw materials used, and exhibited an X-ray diffraction pattern distinct from that of the amorphous sulfide solid electrolyte and the crystalline sulfide solid electrolyte. Powder X-ray diffraction (XRD) measurements were also performed on the raw materials used in the examples (lithium bromide, lithium iodide, lithium sulfide, and diphosphorus pentasulfide), as well as amorphous Li3PS4 and crystalline Li3PS4 prepared for reference X-ray diffraction patterns. The resulting X-ray diffraction spectra are shown in Figure 3. The X-ray diffraction spectrum of the electrolyte precursor also exhibited an X-ray diffraction pattern distinct from that of the raw materials.

[0121] Example 4 An electrolyte precursor and an amorphous sulfide solid electrolyte were obtained in the same manner as in Example 3, except that the stirring blades in the apparatus were changed from anchor-type stirring blades to inclined paddle-type stirring blades and the stirring time was set to 230 hours. Powder X-ray diffraction (XRD) measurement was performed on the obtained amorphous sulfide solid electrolyte. The remaining amount of Li2S in the amorphous sulfide solid electrolyte was calculated to be 5%. Furthermore, composition analysis was performed using ICP analysis (inductively coupled plasma atomic emission spectroscopy). The experimental conditions for Example 4 are shown in Table 1, the measurement results in Table 2, and the results of the XRD measurement in Figure 4. Next, a crystalline sulfide solid electrolyte was obtained in the same manner as in Example 1. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 2.0 × 10 -3 (S / cm), confirming that the material had high ionic conductivity. The results are shown in Table 2.

[0122] Example 5 In a Schlenk tube (volume: 5000 mL) equipped with a stirrer, 439.5 g of lithium sulfide (LiS), 708.6 g of diphosphorus pentasulfide (P2S5), 138.5 g of lithium bromide (LiBr), and 213.4 g of lithium iodide (LiI) were introduced under a nitrogen atmosphere. After rotating the stirrer, 4 L of cyclohexane was added to obtain a cyclohexane slurry containing lithium sulfide, diphosphorus pentasulfide, lithium bromide, and lithium iodide as raw materials and cyclohexane as a solvent. The raw materials and complexing agent were stirred using an apparatus having the configuration shown in Figure 1. In this apparatus, the reaction vessel had a capacity of 40 L and the stirring blade was an anchor-type stirring blade. The withdrawal port was installed at the bottom of the separable flask, and the return port was installed below the liquid level of the fluid in the reaction vessel. The resulting cyclohexane slurry was transferred to a reactor, and an additional 27 L of cyclohexane was added (total amount of cyclohexane: 31.0 L). Also, 3.33 L of tetramethylethylenediamine (TMEDA) as a complexing agent was added. The stirring speed of the impeller was set to 80 rpm, and the pump flow rate was set to 3 L / min. While circulating the fluid in the reactor, stirring of the fluid in the reactor was initiated. The temperature inside the reactor was set to 50°C. After 165 hours (stirring time) from the start of stirring, the resulting fluid was dried under reduced pressure at room temperature to obtain a powdered electrolyte precursor. The mixture was then heated under reduced pressure at 110°C for 2 hours to remove the complexing agent contained in the electrolyte precursor, yielding an amorphous solid electrolyte.

[0123] The obtained amorphous solid electrolyte was subjected to powder X-ray diffraction (XRD) measurement. The remaining amount of Li2S in the amorphous sulfide solid electrolyte was calculated and found to be 2%. Furthermore, composition analysis was performed by ICP analysis (inductively coupled plasma atomic emission spectroscopy). The experimental conditions for Example 5 are shown in Table 1, the measurement results in Table 2, and the results of the XRD measurement in Figure 4. Next, a crystalline sulfide solid electrolyte was obtained in the same manner as in Example 1. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 3.6 × 10 -3 (S / cm), confirming that the material had high ionic conductivity. The results are shown in Table 2.

[0124] (Comparative Example 1) An electrolyte precursor, an amorphous sulfide solid electrolyte, and a crystalline sulfide solid electrolyte were obtained in the same manner as in Example 1, except that the fluid was not circulated and the stirring time was set to 200 hours. For the obtained amorphous sulfide solid electrolyte, XRD measurement, calculation of the remaining amount of LiS, composition analysis by ICP analysis, and ionic conductivity measurement were carried out in the same manner as in Example 1. The experimental conditions for Comparative Example 1 are shown in Table 1, the measurement results are shown in Table 2, and the results of the XRD measurement are shown in FIG. 5.

[0125] (Comparative Example 2) An electrolyte precursor, an amorphous sulfide solid electrolyte, and a crystalline sulfide solid electrolyte were obtained in the same manner as in Example 1, except that no fluid was circulated, the stirring blades were inclined paddle-type, and the stirring time was 310 hours. For the obtained amorphous sulfide solid electrolyte, XRD measurement, calculation of the remaining LiS amount, composition analysis by ICP analysis, and ionic conductivity measurement were carried out in the same manner as in Example 1. The experimental conditions for Comparative Example 2 are shown in Table 1, the measurement results in Table 2, and the results of the XRD measurement in FIG. 5.

[0126] (Comparative Example 3) In a Schlenk tube (volume: 5000 mL) equipped with a stirrer, 161.1 g of lithium sulfide (LiS), 259.9 g of diphosphorus pentasulfide (P2S5), 50.8 g of lithium bromide (LiBr), and 78.2 g of lithium iodide (LiI) were introduced under a nitrogen atmosphere. After rotating the stirrer, 3 L of cyclohexane was added to obtain a cyclohexane slurry containing lithium sulfide, diphosphorus pentasulfide, lithium bromide, and lithium iodide as raw materials and cyclohexane as a solvent. The raw materials and complexing agent were stirred using an apparatus having the configuration shown in Figure 1. In this apparatus, the reaction vessel had a capacity of 6 L and the stirring blade was a full-zone type stirring blade. The withdrawal port was installed at the bottom of the separable flask, and the return port was installed below the liquid level of the fluid in the reaction vessel. The resulting cyclohexane slurry was transferred to a reaction vessel, and an additional 2.2 L of cyclohexane was added (total amount of cyclohexane: 5.2 L). Also, 1.22 L of tetramethylethylenediamine (TMEDA) as a complexing agent was added. The stirring speed of the stirring blade was set to 100 rpm, and stirring of the fluid in the reaction vessel was initiated. The temperature inside the reaction vessel was kept at room temperature (23°C). After 200 hours (stirring time) from the start of stirring, the resulting fluid was dried under reduced pressure at room temperature to obtain a powdered electrolyte precursor. The mixture was then heated under reduced pressure at 110°C for 2 hours to remove the complexing agent contained in the electrolyte precursor, yielding an amorphous solid electrolyte. The obtained amorphous solid electrolyte was subjected to powder X-ray diffraction (XRD) measurement. The remaining amount of Li2S in the amorphous sulfide solid electrolyte was calculated and found to be 20%. Furthermore, composition analysis was performed by ICP analysis (inductively coupled plasma atomic emission spectroscopy). The experimental conditions for Comparative Example 3 are shown in Table 1, the measurement results in Table 2, and the results of XRD measurement in Figure 5.

[0127] [Table 1]

[0128] The raw materials used in this example and listed in Table 1 are as follows. Li2S: Lithium sulfide (density: 1.66 g / cm 3 ) P2S5: Diphosphorus pentasulfide (density: 2.09 g / cm 3 ) LiBr: Lithium bromide (density: 3.46 g / cm 3 ) LiI: Lithium iodide (density: 4.08 g / cm 3 ) Br2: Bromine I2: Iodine

[0129] The complexing agents and solvents used in this example and shown in Table 1 are as follows: TMEDA: Tetramethylethylenediamine (N,N,N',N'-tetramethylethylenediamine) cyc-Hex: Cyclohexane

[0130] [Table 2]

[0131] The results of the above examples show that circulating the fluid containing the contents reduces the amount of remaining Li2S and promotes the reaction of the raw materials. Furthermore, the results of composition analysis confirm that the raw materials are essentially the same as those used, with almost no deviation in composition. This confirms that the manufacturing method of this embodiment efficiently produces a sulfide solid electrolyte using a liquid-phase method, and that the resulting sulfide solid electrolyte has high ionic conductivity. Furthermore, a comparison of Examples 3 and 4 confirms that the type of impeller affects the amount of remaining Li2S, with anchor-type impellers being able to produce a slightly lower amount of remaining Li2S than inclined paddle-type impellers. On the other hand, in the comparative examples, the fluid was not circulated, and therefore the remaining amount of Li2S was 20% or more in all cases, indicating that the reaction of the raw materials had not progressed. Furthermore, the results of composition analysis confirmed that there was a deviation in the composition of lithium iodide, particularly in comparative examples 1 and 2. From this, although the ionic conductivity of the sulfide solid electrolyte obtained in the comparative examples was not measured, it is clear that it was not as good as that of the examples. In the comparative examples, the high remaining amount of Li2S and the deviation in the composition of lithium iodide are thought to be mainly due to the settling and retention of unreacted raw materials at the bottom of the reaction vessel, and the fact that good convection conditions were not achieved in the reaction vessel due to the lack of circulation, which prevented the reaction from progressing.

[0132] Example 6 5.86 kg of lithium sulfide (LiS), 9.45 kg of diphosphorus pentasulfide (P2S5), 1.85 kg of lithium bromide (LiBr), and 2.85 kg of lithium iodide (LiI) were introduced into a pressure-resistant reactor (made of stainless steel) equipped with a stirrer under a nitrogen atmosphere. 443 L of cyclohexane was added, yielding a cyclohexane slurry containing lithium sulfide, diphosphorus pentasulfide, lithium bromide, and lithium iodide as raw materials and cyclohexane as a solvent. The raw material and complexing agent were mixed using an apparatus having the configuration shown in Figure 1. In this apparatus, the reaction vessel had a capacity of 600 L and the mixing blades were anchor-type mixing blades. The withdrawal port was installed at the bottom of the reaction vessel, and the return port was installed below the liquid level in the reaction vessel. 45 L of tetramethylethylenediamine (TMEDA) was added as a complexing agent, and the stirring speed of the stirring blade was set to 80 rpm. The pump flow rate for circulating the slurry was set to 45 L / min. While circulating the fluid in the reactor, stirring of the fluid in the reactor was initiated. The temperature inside the reactor was set to 30°C. After 159 hours (stirring time) from the start of stirring, the resulting fluid was dried under reduced pressure at room temperature to obtain a powdered electrolyte precursor. The mixture was then heated under reduced pressure at 110°C for 2 hours to remove the complexing agent contained in the electrolyte precursor, yielding an amorphous solid electrolyte. The obtained amorphous solid electrolyte was subjected to powder X-ray diffraction (XRD) measurement. The remaining amount of Li2S in the amorphous sulfide solid electrolyte was calculated and found to be 6.5%. Furthermore, composition analysis was performed by ICP analysis (inductively coupled plasma atomic emission spectroscopy). The experimental conditions for Example 6 are shown in Table 3, and the measurement results are shown in Table 4.

[0133] Next, a crystalline sulfide solid electrolyte was obtained in the same manner as in Example 1. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 3.8 × 10 -3 (S / cm), confirming that the material had high ionic conductivity. The results are shown in Table 4.

[0134] [Table 3]

[0135] [Table 4]

[0136] From the results of Example 6, even when the reaction vessel had a capacity of 600 L, which is large enough for industrial production (mass production), the residual amount of Li2S was small at 6.5%, and the reaction of the raw materials was progressing. Furthermore, the results of composition analysis showed that the raw materials were almost the same as those used, with almost no deviation in composition. It was confirmed that the production method of this embodiment can efficiently produce a sulfide solid electrolyte using a liquid phase method. Furthermore, the ionic conductivity of the obtained sulfide solid electrolyte was 3.8 × 10 -3(S / cm), and it was confirmed that the ion conductivity was superior to that of the smaller scale cases of Examples 1 to 5 above. [Industrial Applicability]

[0137] According to the production method of this embodiment, a sulfide solid electrolyte can be efficiently produced using a liquid phase method. The crystalline sulfide solid electrolyte obtained by the production method of this embodiment is suitable for use in batteries, particularly batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones. [Explanation of symbols]

[0138] 1. Reaction tank 2.Extraction port 3.Return port 4. Mixer 5. Mixing blade 11. Pump 12.Circulation Line 13. Valve

Claims

1. A reaction vessel is provided with an outlet and a return port, The reaction tank includes a circulation line for extracting a fluid containing the contents of the reaction tank from the extraction port to the outside of the reaction tank and returning the fluid from the return port, and a stirrer having an agitator blade. Sulfide solid electrolyte manufacturing equipment.

2. The apparatus for producing a sulfide solid electrolyte according to claim 1 , wherein the return port is installed below a liquid level of the fluid.

3. 3. The apparatus for producing a sulfide solid electrolyte according to claim 1, wherein the return port is located below a liquid level of the fluid and above a location where the withdrawal port is located.

4. The sulfide solid electrolyte manufacturing apparatus according to any one of claims 1 to 3, wherein the withdrawal port is installed below a liquid level of a fluid containing contents in the reaction tank.

5. The sulfide solid electrolyte manufacturing apparatus according to any one of claims 1 to 4, wherein the withdrawal port is installed at a bottom of the reaction vessel.

6. 6. The manufacturing apparatus according to claim 1, further comprising a device for controlling the temperature inside the reaction vessel, in at least one of the reaction vessel and the circulation line.

7. The manufacturing apparatus according to any one of claims 1 to 6, wherein the reaction vessel and the circulation line are not equipped with a pulverizer.

8. The manufacturing apparatus according to any one of claims 1 to 7, further comprising a pump in the circulation line for extracting a fluid containing the contents of the reaction tank from the extraction port to the outside of the reaction tank and returning it from the return port.

9. 9. The manufacturing apparatus according to claim 1, wherein the circulation line has a flow rate control valve that controls the circulation rate of the fluid containing the contents of the reaction vessel.

10. 10. The apparatus for producing a sulfide solid electrolyte according to any one of claims 1 to 9, wherein the fluid containing the contents in the reaction tank is obtained by stirring raw materials containing lithium sulfide, a phosphorus compound, and a halogen compound and a complexing agent using the stirrer.

11. A method for producing a sulfide solid electrolyte, using the production apparatus according to any one of claims 1 to 10.

12. 12. The method for producing a sulfide solid electrolyte according to claim 11, wherein the raw materials containing lithium sulfide, a phosphorus compound, and a halogen compound and the complexing agent are stirred in a reaction tank of the production apparatus, and the content in the reaction tank is not subjected to a pulverization step.

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