Method for producing sulfide solid electrolyte

Abstract

The present invention relates to a method for producing a sulfide solid electrolyte, comprising a step of subjecting a slurry to at least one treatment selected from drying and heating. The method comprises: mixing a solid electrolyte raw material containing lithium, sulfur, phosphorus, and a halogen element with a complexing agent in a reaction tank to obtain a complex slurry containing a complex formed by the solid electrolyte raw material and the complexing agent; and transferring the complex slurry to an intermediate tank equipped with a cooling device for cooling.

Description

Technical Field

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

[0002] In recent years, with the rapid spread of information-related devices and communication equipment such as personal computers, video cameras, and mobile phones, the development of batteries used as their power sources has also received significant attention. Batteries used for these applications have traditionally used electrolytes containing flammable organic solvents. However, the elimination of flammable organic solvents in fully solid-state batteries simplifies safety features and improves manufacturing costs and productivity. Consequently, the development of fully solid-state batteries, which replace the electrolyte with a solid electrolyte layer, has been pursued.

[0003] The methods for producing solid electrolytes used in solid electrolyte layers are broadly divided into solid-phase and liquid-phase methods. In recent years, with the goal of practical application of all-solid-state batteries, the liquid-phase method has attracted considerable attention as a method that not only offers versatility and applicability but also allows for easy mass production of solid electrolytes. Liquid-phase methods include homogeneous methods using a solution of the solid electrolyte material, and heterogeneous methods using a suspension (slurry) in which the solid electrolyte material is not completely dissolved but a solid-liquid coexistence occurs.

[0004] In the liquid phase method, a complexing agent solution (or slurry) of a solid electrolyte raw material is generated, and after the solution is dried to obtain a complex crystal, the complex crystal is fired to obtain a solid electrolyte of another crystal (with reference to patent documentation 1). In particular, in order to obtain a uniform solid electrolyte, a uniform method of dissolving the electrolyte completely in a solution state of a solvent has advantages (with reference to non-patent documentation 1). In addition, such a method is not limited to the field of solid electrolytes, but is also studied in the manufacture method of solar cells (with reference to patent documentation 2).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2018 / 054709

[0008] Patent Document 2: Japanese Patent Application No. 2015-526884

[0009] Non-patent literature

[0010] Non-patent document 1: J. Jpn. Soc. Colour Mater., 89〔9〕, 300-305 (2016) Summary of the Invention

[0011] Technical problem to be solved by the invention

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a sulfide solid electrolyte having high ionic conductivity by suppressing a decrease in ionic conductivity during mass production.

[0013] Solutions for solving the above technical problems

[0014] The present inventors have diligently conducted research to solve the above-mentioned technical problems and have found that the technical problems can be solved by the following method for producing a sulfide solid electrolyte, which includes a step of subjecting a slurry to at least one treatment selected from drying and heating. The method comprises: mixing a solid electrolyte raw material containing lithium, sulfur, phosphorus, and a halogen element with a complexing agent in a reaction tank to obtain a complex slurry containing a complex formed by the solid electrolyte raw material and the complexing agent; and transferring the complex slurry to an intermediate tank equipped with a cooling device for cooling.

[0015] Effects of the Invention

[0016] According to the present invention, a production method can be provided that suppresses a decrease in ionic conductivity due to separation of specific components even when a non-uniform method using a slurry is adopted in the production process, thereby obtaining a sulfide solid electrolyte having high ionic conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flowchart illustrating an example of a preferred mode of the production method of this embodiment.

[0018] Figure 2 This is a flowchart illustrating an example of a preferred mode of the production method of this embodiment.

[0019] Figure 3 This is a flowchart illustrating an example of a preferred embodiment of an apparatus used in the production method of this embodiment.

[0020] Figure 4 These are the X-ray diffraction spectra of the sulfide solid electrolytes obtained in Reference Example 1, Example 1, and Comparative Example 1.

[0021] Figure 5 These are the X-ray diffraction spectra of the solid electrolyte raw materials used in the examples, and the amorphous and crystalline Li3PS4 of reference examples 1 and 2.

[0022] Figure 6 These are X-ray diffraction spectra of the complex obtained in Reference Example 1, the amorphous sulfide solid electrolyte, and the crystalline sulfide solid electrolyte. DETAILED DESCRIPTION

[0023] The following describes an embodiment of the present invention (hereinafter sometimes referred to as the "present embodiment"). In addition, in this specification, the upper and lower limits of the numerical ranges of "above", "below", and "to" are numerical values that can be combined arbitrarily, and the numerical values of the examples can also be used as the upper and lower limits.

[0024] (Discovery made by the present inventors to complete the present invention)

[0025] The present inventors have conducted intensive studies to solve the above-mentioned technical problems, and as a result, have found the following matters, thereby completing the present invention.

[0026] In liquid-phase methods, uniform dispersion is achieved by dissolving the raw materials, and therefore research has been conducted on manufacturing conditions that enable dissolution. However, in the synthesis of sulfide solid electrolytes using multi-component raw materials, it is difficult to uniformly dissolve the components of the complexing agent solution or slurry without separation and to perform synthesis. The applicants have conducted research using various complexing agents in heterogeneous methods where solid and liquid coexist. As a general trend, they have found that the ionic conductivity of solid electrolytes tends to decrease when mass production is achieved.

[0027] The inventors have conducted in-depth research on the tendency of ionic conductivity to decrease, and found that, in particular, in the heterogeneous method where solid and liquid coexist, specific components such as halogen elements and lithium elements (hereinafter sometimes referred to as "specific components") derived from preferably used solid electrolyte raw materials, such as lithium bromide and lithium iodide, are prone to separation. If this specific component separates, the desired compound structure cannot be obtained, and therefore the ionic conductivity of the solid electrolyte is sometimes reduced. Furthermore, if mass production is achieved, it is difficult to maintain the dispersed state of each component or suppress the separation of the specific component through a series of manufacturing processes such as the mixing process of the slurry containing the solid electrolyte raw material, making it difficult to obtain a sulfide solid electrolyte with high ionic conductivity having the desired crystal structure.

[0028] As described above, in the manufacture of sulfide solid electrolytes, in order to obtain high ionic conductivity, it is crucial to keep the above-mentioned specific components from separating from the complex, and therefore, a complexing agent is used in the manufacturing method of the present embodiment. On the other hand, it has also been found that even if a complexing agent is used, if the complex is kept in a slurry state, the specific components will separate from the complex over time, resulting in a decrease in ionic conductivity. The situation in which the complex is kept in a slurry state sometimes also occurs in the production of laboratory-level solid electrolytes, but if it is manufactured on a mass production scale in the future, it can be fully anticipated that the situation in which the complex is kept in a slurry state will become long-term due to manufacturing adjustments, equipment failures, etc., thereby resulting in the possibility of a decrease in ionic conductivity. In the manufacturing method of the present embodiment, the complex slurry is stored by cooling, so that the specific components can be suppressed as much as possible from being separated from the complex to obtain high ionic conductivity.

[0029] Therefore, the manufacturing method of this embodiment can not only cope with the situation of obtaining a sulfide solid electrolyte with higher ionic conductivity, but also cope with the situation in which, in the manufacturing process of the sulfide solid electrolyte, after the complex slurry is prepared, the drying, heating, etc. described later cannot be performed within a short period of time, such as within 12 hours, within 6 hours, or within 1 hour. In other words, it can also cope with the situation in which the complex is maintained for a long time in the form of a complex slurry. It can be said that this is an effective manufacturing method.

[0030] In addition, for cooling preservation, it can be considered that the reason that above-mentioned specific component can be retained in complex compound and thus suppress separation is due to, in complex compound, the binding force of the lithium element of the structure of the PS4 structure etc. connected via the heteroelement in the complexing agent and the lithium elements such as lithium halide is maintained, and the chemical stability of the aggregate formed via the complexing agent in the complex slurry is maintained, but its detailed mechanism is still unclear. If completely dissolved or not dissolved at all within a specified temperature range, there is no influence of solubility (such as patent documentation 2).

[0031] However, since the complex slurry of this embodiment is a solid-liquid coexistence, each component of the complex with different solubility is dissolved or not dissolved and contained in the slurry. Since solubility changes with temperature, it is generally considered desirable to maintain the dissolved state of the complex slurry by keeping the temperature of the complex slurry constant. Moreover, in visual observation when the complex slurry is kept for a long time, no changes are observed regardless of whether it is cooled or not. Therefore, it is difficult to identify problems related to the chemical stability of the complex slurry.

[0032] However, surprisingly, in the production method of this embodiment, it was found that simply by performing the simple operation of cooling and storing a complex slurry containing a complex formed by a predetermined element and a complexing agent, the following excellent effects can be achieved: chemical stability of the aggregate formed by the complexing agent in the complex slurry can be obtained, and the separation of bromine and lithium elements from specific components, especially easily separable lithium bromide, can be suppressed, thereby achieving a sulfide solid electrolyte with higher ionic conductivity.

[0033] [Method for producing sulfide solid electrolyte]

[0034] The method for producing a sulfide solid electrolyte according to the present embodiment is a method for producing a sulfide solid electrolyte, comprising a step of subjecting a slurry to at least one treatment selected from drying and heating, and is characterized in that the method comprises: mixing a solid electrolyte raw material containing lithium, sulfur, phosphorus, and a halogen element with a complexing agent in a reaction tank to obtain a complex slurry containing a complex formed by the solid electrolyte raw material and the complexing agent; and transferring the complex slurry to an intermediate tank equipped with a cooling device for cooling.

[0035] "A method for producing a sulfide solid electrolyte comprising a step of subjecting a slurry to at least one treatment selected from drying and heating" indicates that the production method of this embodiment employs a heterogeneous liquid-phase method, i.e., a slurry in which both solid and liquid coexist, using a solvent that does not completely dissolve the solid electrolyte raw material. Furthermore, in this embodiment, the slurry may primarily include a slurry containing the solid electrolyte raw material, a complex slurry containing the complex described later, or a slurry containing at least one selected from the solid electrolyte raw material, a complex, and a sulfide solid electrolyte obtained by reacting a portion of the raw material. Regardless of the type of slurry, the production method of this embodiment employs the heterogeneous liquid-phase method at the point in time when the slurry is present.

[0036] In this specification, a "sulfide solid electrolyte" refers to an electrolyte that contains at least sulfur and remains solid at 25°C in a nitrogen atmosphere. The sulfide solid electrolyte obtained by the production method of this embodiment contains lithium, sulfur, phosphorus, and halogen elements, and has ionic conductivity due to lithium.

[0037] The term "sulfide solid electrolyte" encompasses both crystalline sulfide solid electrolytes and amorphous sulfide solid electrolytes having a crystal structure. In this specification, a crystalline sulfide solid electrolyte refers to a solid electrolyte in which peaks derived from the sulfide solid electrolyte are observed in the X-ray diffraction pattern during X-ray diffraction measurement, regardless of whether these peaks are derived from the raw materials of the solid electrolyte. Specifically, a crystalline sulfide solid electrolyte contains a crystal structure derived from the sulfide solid electrolyte, and may contain a portion or all of the crystal structure derived from the sulfide solid electrolyte. Furthermore, a crystalline sulfide solid electrolyte may also contain a portion of an amorphous sulfide solid electrolyte, as long as it exhibits the aforementioned X-ray diffraction pattern. Therefore, a crystalline sulfide solid electrolyte includes so-called glass ceramics, which are obtained by heating an amorphous sulfide solid electrolyte to a temperature above its crystallization temperature.

[0038] In this specification, an amorphous sulfide solid electrolyte refers to an X-ray diffraction pattern having a halo pattern (hollow pattern) in which substantially no peaks other than peaks derived from the material are observed in X-ray diffraction measurement, regardless of the presence or absence of peaks derived from the raw material of the sulfide solid electrolyte.

[0039] In the method for producing a sulfide solid electrolyte of this embodiment, it is preferred that the following four embodiments be included, depending on whether a solid electrolyte such as Li3PS4 is used as a solid electrolyte raw material or whether a solvent is used. An example of a preferred mode of these four embodiments is shown in Figure 1 (Implementation A and B) and Figure 2 (Embodiments C and D). That is, the manufacturing method of this embodiment preferably includes: (Embodiment A) a manufacturing method using raw materials such as lithium sulfide and phosphorus pentasulfide and a complexing agent; (Embodiment B) a manufacturing method including a solid electrolyte such as Li3PS4 as the main electrolyte structure as a raw material and using a complexing agent; (Embodiment C) a manufacturing method in which a solvent is added to the raw materials such as lithium sulfide and the complexing agent in the above-mentioned embodiment A; (Embodiment D) a manufacturing method in which a solvent is added to the solid electrolyte such as Li3PS4 as the raw material and the complexing agent in the above-mentioned embodiment B.

[0040] Hereinafter, Embodiments A to D will be described in sequence.

[0041] (Implementation A)

[0042] like Figure 1 As shown, embodiment A is a method for producing a sulfide solid electrolyte that includes subjecting a slurry to at least one treatment selected from drying and heating. In this method, which is characterized by mixing a solid electrolyte raw material containing lithium, sulfur, phosphorus, and a halogen element with a complexing agent in a reaction tank, raw materials containing lithium, sulfur, and phosphorus, such as lithium sulfide and phosphorus pentasulfide, and raw materials containing halogen elements, such as lithium bromide and lithium iodide, are used as solid electrolyte raw materials. Mixing the solid electrolyte raw material and the complexing agent in the reaction tank typically produces a complex slurry containing a complex formed between the solid electrolyte raw material and the complexing agent, which is then cooled to produce the sulfide solid electrolyte. Furthermore, in embodiment A, it is preferred that at least one step selected from drying and heating be included after cooling and storage.

[0043] The manufacturing method of this embodiment preferably includes pulverizing the complex, and the complex contained in the complex slurry includes the pulverized complex. In addition, when heating is included after pulverization, cooling and storage are preferably performed after pulverization and before heating, that is, the pulverization is preferably performed during mixing (simultaneously with mixing) or after mixing and before cooling and storage.

[0044] The following description will be based on Embodiment A, but the contents described as “this embodiment” are also applicable to other embodiments.

[0045] (Solid electrolyte raw materials)

[0046] The solid electrolyte raw material used in the present embodiment contains lithium, sulfur, phosphorus, and a halogen element. Specifically, at least one or more raw materials selected from raw materials containing at least one of these elements are used.

[0047] Representative examples of the raw material (compound) of the solid electrolyte raw material, for example, containing at least one of lithium, sulfur, phosphorus and halogen, include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide and lithium iodide; phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5); various phosphorus fluorides (PF3, PF5), various phosphorus chlorides (PCl3, PCl5, P2Cl4), various phosphorus bromides (PBr3, PBr5), various phosphorus iodides (P I3, P2I4) and other phosphorus halides; thiophosphoryl fluoride (PSF3), thiophosphoryl chloride (PSCl3), thiophosphoryl bromide (PSBr3), thiophosphoryl iodide (PSI3), thiophosphoryl fluoride dichloride (PSCl2F), thiophosphoryl fluoride dibromide (PSBr2F) and other thiophosphoryl halides; raw materials composed of at least two elements selected from the above four elements, halogen monomers such as fluorine (F2), chlorine (Cl2), bromine (Br2), iodine (I2), preferably bromine (Br2) and iodine (I2).

[0048] Substances that can be used as raw materials other than the above-mentioned ones include, for example, raw materials containing at least one element selected from the above-mentioned four elements and elements other than the four elements. More specifically, there can be mentioned 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; phosphoric acid compounds such as sodium phosphate and lithium phosphate; alkali metal halides other than lithium such as sodium iodide, sodium fluoride, sodium chloride, and sodium bromide; metal halides such as aluminum halide, silicon halide, germanium halide, arsenic halide, selenium halide, tin halide, antimony halide, tellurium halide, and bismuth halide; halogenated phosphorus oxides such as phosphorus oxychloride (POCl3) and phosphorus oxybromide (POBr3); and the like.

[0049] As a solid electrolyte raw material, it is sufficient to appropriately select a raw material suitable for obtaining the desired crystal structure from the above. From the viewpoint of more easily obtaining a sulfide solid electrolyte with high ionic conductivity, as a raw material, lithium sulfide is preferred among the above; phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5); halogen monomers such as fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2); and lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide.

[0050] As examples of the combination of raw materials, preferably exemplified are combinations of raw materials containing lithium, sulfur and phosphorus elements, such as lithium sulfide and phosphorus pentasulfide, and raw materials containing halogen elements, such as lithium halides; and combinations of raw materials containing lithium, sulfur and phosphorus elements, such as lithium sulfide and phosphorus pentasulfide, and raw materials containing halogen elements, such as halogen monomers. Preferred lithium halides are lithium bromide and lithium iodide, and preferred halogen monomers are chlorine, bromine and iodine, and more preferred are bromine and iodine.

[0051] The lithium sulfide used in embodiment A is preferably in the form of particles.

[0052] The average particle size of lithium sulfide particles (D 50 ) is preferably from 10 μm to 2000 μm, more preferably from 30 μm to 1500 μm, and even more preferably from 50 μm to 1000 μm. In this specification, the average particle size (D 50 ) is the particle size at which the cumulative particle size, starting from the smallest particle size, reaches 50% of the total when a cumulative particle size distribution curve is plotted. The volume distribution is, for example, the average particle size that can be measured using a laser diffraction / scattering particle size distribution measuring instrument. Furthermore, among the substances exemplified as the raw materials above, the solid raw material preferably has an average particle size approximately equivalent to that of the lithium sulfide particles, that is, preferably has an average particle size within the same range as that of the lithium sulfide particles.

[0053] When lithium sulfide, phosphorus pentasulfide, and lithium halide are used as raw materials, from the viewpoint of obtaining higher chemical stability and higher ion conductivity, the ratio of lithium sulfide to the total of lithium sulfide and phosphorus pentasulfide is preferably 70 to 80 mol%, more preferably 72 to 78 mol%, and even more preferably 74 to 76 mol%.

[0054] When lithium sulfide, phosphorus pentasulfide, lithium halide, and other raw materials used as needed are used, the content of lithium sulfide and phosphorus pentasulfide relative to the total of these raw materials is preferably 60 to 100 mol %, more preferably 65 to 90 mol %, and even more preferably 70 to 80 mol %.

[0055] In addition, when lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ion conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, further preferably 40 to 80 mol%, and particularly preferably 45 to 65 mol%.

[0056] When using a halogen monomer as a raw material and lithium sulfide and phosphorus pentasulfide, the ratio of the moles of lithium sulfide obtained by removing the same number of moles of lithium sulfide as the moles of the halogen monomer to the total moles of lithium sulfide and phosphorus pentasulfide obtained by removing the same number of moles of lithium sulfide as the moles of the halogen monomer is preferably in the range of 60-90%, more preferably in the range of 65-85%, even more preferably in the range of 68-82%, even more preferably in the range of 72-78%, and particularly preferably in the range of 73-77%. This is because these ratios can achieve higher ionic conductivity. From the same viewpoint, when using lithium sulfide, phosphorus pentasulfide, and a halogen monomer, the content of the halogen monomer relative to the total amount of lithium sulfide, phosphorus pentasulfide, and the halogen monomer is preferably 1-50 mol%, more preferably 2-40 mol%, even more preferably 3-25 mol%, and even more preferably 3-15 mol%.

[0057] When lithium sulfide, phosphorus pentasulfide, a halogen monomer, and a lithium halide are used, the content of the halogen monomer relative to the total amount of these (α mol%) and the content of the lithium halide relative to the total amount of these (β mol%) preferably satisfy the following formula (2), more preferably satisfy the following formula (3), further preferably satisfy the following formula (4), and even more preferably satisfy the following formula (5).

[0058] 2≤2α+β≤100…(2)

[0059] 4≤2α+β≤80…(3)

[0060] 6≤2α+β≤50…(4)

[0061] 6≤2α+β≤30…(5)

[0062] When used as two halogen monomers, if the number of moles of one halogen element in the substance is set to A1 and the number of moles of the other halogen element in the substance is set to A2, then A1:A2 is preferably 1 to 99:99 to 1, more preferably 10:90 to 90:10, further preferably 20:80 to 80:20, and further preferably 30:70 to 70:30.

[0063] In addition, when the two halogen monomers are bromine and iodine, if the number of moles of bromine is set to B1 and the number of moles of iodine is set to B2, then B1:B2 is preferably 1-99:99-1, more preferably 15:85-90:10, further preferably 20:80-80:20, further preferably 30:70-75:25, and particularly preferably 35:65-75:25.

[0064] (Complexing agent)

[0065] A complexing agent is used in the method for producing a sulfide solid electrolyte according to this embodiment. In this specification, a complexing agent refers to a substance capable of forming a complex with lithium. It is a substance that reacts with lithium-containing sulfides, halides, and the like contained in the solid electrolyte raw material to promote complex formation. Therefore, without a complexing agent, complex formation is difficult, the separation of specific components cannot be suppressed, and high ionic conductivity cannot be achieved.

[0066] As a complexing agent, any compound having the above-mentioned properties can be used without particular limitation. Particularly preferred are compounds containing elements with a high affinity for lithium, such as nitrogen, oxygen, chlorine, and other heteroelements. More preferred are compounds containing groups containing these heteroelements. This is because these heteroelements and groups containing these heteroelements can coordinate (bond) with lithium.

[0067] It is believed that the complexing agent is a substance having the following properties: the heteroelement in its molecule has a high affinity for lithium atoms and is easily bonded to a structure containing lithium, such as Li3PS4, which is a representative structure present as the main structure in the sulfide solid electrolyte obtained by the manufacturing method of this embodiment, or a raw material containing lithium, such as a lithium halide, to form an aggregate. In this embodiment, "a complex formed by a solid electrolyte raw material and a complexing agent" is a general term for these structures and aggregates, preferably formed by a complexing agent, lithium, sulfur, phosphorus, and a halogen element. Therefore, it is believed that by mixing the above-mentioned solid electrolyte raw material with the complexing agent, the structure containing lithium, such as the PS4 structure, or the aggregate via the complexing agent, the raw material containing lithium, such as the lithium halide, or the aggregate via the complexing agent, can be distributed, and a complex in which the halogen element is more dispersed and fixed can be obtained, thereby suppressing the reduction in ionic conductivity caused by the separation of specific components, resulting in a sulfide solid electrolyte with high ionic conductivity.

[0068] Therefore, it is preferred to have at least two heteroelements capable of coordination (bonding) in the molecule, and more preferably to have a group containing at least two heteroelements in the molecule. By having a group containing at least two heteroelements in the molecule, it is possible to make a structure containing lithium such as Li3PS4 containing a PS4 structure and a raw material containing lithium such as a lithium halide bonded via at least two heteroelements in the molecule, so that the halogen element is more dispersedly fixed in the complex, and the reduction in ionic conductivity caused by the separation of these specific components can be suppressed. As a result, a sulfide solid electrolyte with high ionic conductivity can be obtained. In addition, among the heteroelements, nitrogen is preferred, and as a group containing nitrogen, an amino group is preferred, that is, an amine compound is preferred as a complexing agent.

[0069] Amine compounds are not particularly limited, as long as they contain amino groups in the molecule, as they can promote complex formation. However, compounds containing at least two amino groups in the molecule are preferred. This structure allows lithium-containing structures such as Li3PS4, which contain a PS4 structure, to be bonded to lithium-containing raw materials such as lithium halides via at least two nitrogen elements in the molecule. This allows the halogen element to be more dispersed and fixed in the complex, resulting in a sulfide solid electrolyte with high ionic conductivity.

[0070] Examples of such amine compounds include amine compounds such as aliphatic amines, alicyclic amines, heterocyclic amines and aromatic amines, and these amine compounds can be used alone or in combination of two or more.

[0071] More specifically, representative and preferred examples of the aliphatic amine include primary aliphatic diamines such as ethylenediamine, diaminopropane, and diaminobutane; secondary aliphatic diamines such as N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyldiaminopropane, and N,N'-diethyldiaminopropane; tertiary aliphatic 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; and the like. Here, in the examples in this specification, for example, in the case of diaminobutane, unless otherwise specified, all isomers such as linear and branched isomers are included in addition to isomers related to the position of the amino group such as 1,2-diaminobutane, 1,3-diaminobutane, and 1,4-diaminobutane.

[0072] The number of carbon atoms in the aliphatic amine is preferably 2 or more, more preferably 4 or more, and even more preferably 6 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. Furthermore, the number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic amine is preferably 2 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0073] Examples of the alicyclic amine include, for example, primary alicyclic diamines such as cyclopropanediamine and cyclohexanediamine; secondary alicyclic diamines such as bisaminomethylcyclohexane; tertiary alicyclic diamines such as N,N,N',N'-tetramethyl-cyclohexanediamine and bis(ethylmethylamino)cyclohexane; and the like. Examples of the heterocyclic amine include, for example, primary heterocyclic diamines such as isophoronediamine; secondary heterocyclic diamines such as piperazine and dipiperidylpropane; and tertiary heterocyclic diamines such as N,N-dimethylpiperazine and bismethylpiperidylpropane.

[0074] The carbon number of the alicyclic amine or 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.

[0075] In addition, as aromatic amines, representative and preferred examples include aromatic primary diamines such as phenylenediamine, toluenediamine, and naphthalenediamine; aromatic secondary diamines such as N-methylphenylenediamine, N,N'-dimethylphenylenediamine, N,N'-dimethylphenylphenylenediamine, N,N'-dimethylnaphthalenediamine, and N-naphthylethylenediamine; aromatic tertiary diamines such as N,N-dimethylphenylenediamine, N,N,N',N'-tetramethylphenylenediamine, N,N,N',N'-tetramethyldiaminodiphenylmethane, and N,N,N',N'-tetramethylnaphthalenediamine; and the like.

[0076] The number of carbon atoms in the aromatic amine is preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.

[0077] The amine compound used in the present embodiment may be an amine compound substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxy group, a hydroxyl group, a cyano group, or a halogen atom.

[0078] Furthermore, although diamines are exemplified as specific examples, it goes without saying that the amine compounds that can be used in this embodiment are not limited to diamines. For example, in addition to trimethylamine, triethylamine, ethyldimethylamine, aliphatic monoamines corresponding to various diamines such as the above-mentioned aliphatic diamines, piperidine compounds such as piperidine, methylpiperidine, and tetramethylpiperidine, pyridine compounds such as pyridine, morpholine compounds such as morpholine, methylmorpholine, and thiomorpholine, imidazole compounds such as imidazole, methylimidazole, and the like, and cyclohexane compounds corresponding to the above-mentioned alicyclic diamines can be used. In addition to monoamines such as alicyclic monoamines such as the monoamine of the above-mentioned heterocyclic diamines, heterocyclic monoamines corresponding to the above-mentioned heterocyclic diamines, and aromatic monoamines corresponding to the above-mentioned aromatic diamines, polyamines having three or more amino groups such as diethylenetriamine, N,N',N"-trimethyldiethylenetriamine, N,N,N',N",N"-pentamethyldiethylenetriamine, triethylenetetramine, N,N'-bis[(dimethylamino)ethyl]-N,N'-dimethylethylenediamine, hexamethylenetetramine, and tetraethylenepentamine can also be used.

[0079] Among the above, from the perspective of achieving higher ion conductivity, tertiary amines having a tertiary amino group as an amino group are preferred, tertiary diamines having two tertiary amino groups are more preferred, tertiary diamines having two tertiary amino groups at both terminals are further preferred, and aliphatic tertiary diamines having tertiary amino groups at both terminals are even more preferred. Among the above amine compounds, aliphatic tertiary diamines having tertiary amino groups at both terminals are preferred, including tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, and tetraethyldiaminopropane. Considering availability, tetramethylethylenediamine and tetramethyldiaminopropane are preferred.

[0080] As other complexing agents besides amine compounds, for example, compounds having groups containing heteroelements such as oxygen and halogen elements such as chlorine have a high affinity for lithium and can be cited as other complexing agents besides the above-mentioned amine compounds. In addition, compounds having groups other than amino groups containing nitrogen as heteroelements, such as nitro groups and amide groups, can also achieve the same effects.

[0081] 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-containing aromatic hydrocarbon solvents such as trifluorotoluene, 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.

[0082] (mix)

[0083] like Figure 1 As shown in the flowchart of , a solid electrolyte raw material and a complexing agent are mixed in a reaction tank to obtain a complex slurry containing the above-mentioned complex formed by the solid electrolyte raw material and the complexing agent. Since the solid electrolyte raw material contains a solid and the complexing agent is a liquid, in this embodiment, the solid electrolyte raw material and the complexing agent are typically mixed in a slurry-like form in which the solid electrolyte raw material is present in the liquid complexing agent.

[0084] The amount of the solid electrolyte raw material relative to the amount of the complexing agent 1L, and when using a solvent described later, relative to the total amount of the complexing agent and the solvent 1L, is preferably 5g or more, more preferably 10g or more, further preferably 30g or more, and further preferably 45g or more. The upper limit is preferably 500g or less, more preferably 400g or less, further preferably 300g or less, and further preferably 250g or less. If the content of the solid electrolyte raw material is within the above range, the solid electrolyte raw material is easily mixed, the dispersion state of the solid electrolyte raw material is improved, and the reaction between the raw materials is promoted, so it is easy to efficiently obtain a complex, and then it is easy to obtain a solid electrolyte.

[0085] The method for mixing the solid electrolyte raw material and the complexing agent is not particularly limited, as long as at least one raw material (compound) contained in the solid electrolyte raw material and the complexing agent are added to a device capable of mixing the solid electrolyte raw material and the complexing agent in a reaction tank and mixed. For example, if the complexing agent is supplied to Figure 3 In the reaction tank shown, it is preferred to gradually add the solid electrolyte raw material after operating the stirring blade, because this can achieve a good mixing state of the raw materials, improve the dispersibility of the raw materials, and easily obtain a complex.

[0086] Furthermore, when using a halogen monomer as a raw material, the raw material may not be solid. Specifically, at room temperature and pressure, fluorine and chlorine are gases, while bromine is liquid. For example, if the raw material is liquid, it can be supplied to the reaction tank separately from other solid raw materials and together with the complexing agent. Alternatively, if the raw material is gaseous, it can be supplied by blowing the solid electrolyte raw material into the complexing agent.

[0087] The method for producing a sulfide solid electrolyte of this embodiment is characterized in that it comprises mixing a solid electrolyte raw material and a complexing agent in a reaction tank, for example, by using Figure 3The solid electrolyte material can be mixed in a reaction tank equipped with a stirrer as shown. Alternatively, the solid electrolyte material can be produced by a method that does not use equipment commonly referred to as a pulverizer, such as a ball mill or bead mill, that is used to pulverize the solid raw material. In the production method of this embodiment, the solid electrolyte material and the complexing agent are simply mixed in a reaction tank to form a complex, which can then be dried, heated, etc. as needed to obtain a sulfide solid electrolyte.

[0088] As a device for mixing solid electrolyte raw materials and complexing agents, for example, a mechanical stirring mixer having a stirring blade in a reaction tank can be exemplified. Mechanical stirring mixers can exemplify high-speed stirring mixers, double-arm type mixers, etc., and from the viewpoint of efficiently obtaining a uniform complex by improving the uniformity of the raw materials in the mixture of solid electrolyte raw materials and complexing agents to obtain higher ion conductivity, it is preferred to use a high-speed stirring mixer. In addition, as a high-speed stirring mixer, vertical axis rotation type mixers, horizontal axis rotation type mixers, etc. can be exemplified, and any type of mixer can be used.

[0089] The shape of the stirring blade used in the mechanical stirring mixer may be a blade type, an arm type, a belt type, a multi-stage blade type, a double-arm type, a bucket type, a double-shaft blade type, a flat blade type, a C-type blade type, etc. From the viewpoint of efficiently obtaining a uniform complex by improving the uniformity of the raw materials in the mixture of the solid electrolyte raw material and the complexing agent, thereby obtaining higher ion conductivity, the bucket type, the flat blade type, the C-type blade type, etc. are preferred.

[0090] The temperature conditions when mixing the solid electrolyte raw material and the complexing agent are not particularly limited, and are, for example, -30 to 100°C, preferably -10 to 50°C, and more preferably about room temperature (23°C) (for example, about ±5°C at room temperature). In addition, the mixing time is about 0.1 to 150 hours, and from the viewpoint of more uniform mixing and obtaining higher ionic conductivity, it is preferably 0.3 to 120 hours, more preferably 0.5 to 100 hours, and further preferably 0.8 to 80 hours. Therefore, the reaction tank can be equipped with a heating mechanism for heating the fluid in the reaction tank as needed.

[0091] By mixing the solid electrolyte raw material and the complexing agent in the reaction tank, under the action of the lithium element, sulfur element, phosphorus element and halogen element contained in the above raw materials and the complexing agent, a complex obtained by directly bonding these elements to each other via the complexing agent and / or without the complexing agent can be obtained. That is, in the manufacturing method of this embodiment, the complex obtained by mixing the solid electrolyte raw material with the complexing agent is formed by the complexing agent, lithium element, sulfur element, phosphorus element and halogen element, and by mixing the above solid electrolyte raw material and the complexing agent, a complex slurry containing the complex can be obtained. In this embodiment, the complex obtained is not a substance that is completely dissolved relative to the complexing agent as a liquid, but a slurry containing the complex as a solid can be obtained. Therefore, the manufacturing method of this embodiment is equivalent to the so-called heterogeneous system in the liquid phase method. In addition, the slurry can be referred to as a complex slurry containing a complex, but it is considered that it also contains a solid electrolyte raw material, a complexing agent, etc. that do not form a complex, or a solid electrolyte obtained by reacting a portion of the solid electrolyte raw material.

[0092] (Complex)

[0093] As described above, the complex is formed by a complexing agent, a lithium element, a sulfur element, a phosphorus element, and a halogen element. In addition, it is considered that since the complex has the characteristic that a peak different from the peak derived from the raw material can be observed in the X-ray diffraction pattern in the X-ray diffraction measurement, it is preferred that the complex typically has a complex structure in which the lithium element and other elements are directly bonded via a complexing agent and / or not via a complexing agent. By simply mixing the solid electrolyte raw materials, only the peaks derived from the raw materials should be observed. However, by mixing the solid electrolyte raw materials with the complexing agent, peaks different from the peaks derived from the raw materials can be observed, so these complexes obtained by mixing are substances having a structure that is significantly different from the raw materials themselves contained in the solid electrolyte raw materials. This will be specifically confirmed in the examples. In Figures 4 to 6 The following shows an example of measuring X-ray diffraction patterns of various raw materials such as lithium sulfide, complexes, and sulfide solid electrolytes. Figure 6 The X-ray diffraction pattern of the complex shows that it has a predetermined crystal structure. In addition, the diffraction pattern does not contain Figure 5 From the diffraction patterns of any of the raw materials such as lithium sulfide shown, it is understood that the complex has a crystal structure different from that of the raw material.

[0094] Furthermore, the complex is characterized in that it has a structure different from that of the crystalline sulfide solid electrolyte. This will also be specifically confirmed in the examples. Figure 4 The X-ray diffraction pattern of the crystalline sulfide solid electrolyte is also shown in , which shows that it is different from the diffraction pattern of the complex. In addition, the complex has a predetermined crystal structure, which is different from the amorphous solid electrolyte having a wide pattern.

[0095] From the above results, it can be inferred that the complex is formed by the complexing agent, lithium, sulfur, phosphorus and halogen elements, and typically forms a complex structure in which lithium and other elements are directly bonded via the complexing agent and / or without the complexing agent.

[0096] Here, the formation of a complex by the complexing agent can be confirmed by, for example, gas chromatography analysis. Specifically, by dissolving a powder of the complex in methanol and subjecting the resulting methanol solution to gas chromatography analysis, the amount of the complexing agent contained in the complex can be quantified.

[0097] The content of the complexing agent in the complex varies depending on the molecular weight of the complexing agent, but is generally about 10% by mass to 70% by mass, and preferably 15% by mass to 65% by mass.

[0098] In this embodiment, from the perspective of improving ionic conductivity, it is preferred to form a complex containing a halogen element. By using a complexing agent, a lithium-containing structure such as a PS4 structure and a lithium-containing raw material such as a lithium halide are bonded (coordinated) via the complexing agent, thereby easily obtaining a complex in which the halogen element is more dispersed and fixed. This prevents the separation of these specific components and suppresses the reduction of ionic conductivity, thereby achieving high ionic conductivity.

[0099] The presence of a specified amount of halogen in the complex can be confirmed by the presence of a specified amount of halogen even after solid-liquid separation of the complex slurry. This is because halogens that do not form a complex elute more easily than those that do and are discharged into the liquid from solid-liquid separation. Furthermore, compositional analysis of the complex or sulfide solid electrolyte using ICP analysis (inductively coupled plasma emission spectrometry) can be used to confirm that the ratio of halogen in the complex or sulfide solid electrolyte is not significantly lower than that of the halogen supplied from the raw materials.

[0100] The amount of the halogen element retained in the complex is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more relative to the configuration composition. The upper limit of the amount of the halogen element retained in the complex is 100% by mass.

[0101] (cool down)

[0102] The method for producing a sulfide solid electrolyte according to this embodiment includes transferring the complex slurry to an intermediate tank equipped with a cooling device for cooling (since cooling also involves storage, it may be simply referred to as "cooling" or "cooling storage" below). If this cooling storage is not performed, specific components that contribute to the development and improvement of ionic conductivity, such as halogen elements and lithium elements, which are preferably used as solid electrolyte raw materials, such as lithium bromide and lithium iodide, will not be retained in the complex and will separate, resulting in a decrease in the ionic conductivity of the resulting sulfide solid electrolyte.

[0103] As described above, in the manufacture of sulfide solid electrolytes, in order to obtain high ionic conductivity, it is crucial to keep the specific component from separating from the complex, and therefore, a complexing agent is used in the manufacturing method of the present embodiment. On the other hand, it has been found that even if a complexing agent is used, if the complex is kept in a slurry state, the specific component separates from the complex over time, resulting in a decrease in ionic conductivity. The situation in which the complex is kept in a slurry state sometimes also occurs in the production of laboratory-level solid electrolytes, but if it is manufactured on a mass production scale in the future, it can be fully anticipated that the situation in which the complex is kept in a slurry state will be prolonged due to manufacturing adjustments, equipment failures, etc., thereby resulting in the possibility of a decrease in ionic conductivity. In the manufacturing method of the present embodiment, the complex slurry is stored by cooling, so that the specific component can be suppressed as much as possible from being separated from the complex to obtain high ionic conductivity.

[0104] Therefore, the manufacturing method of this embodiment can not only cope with the situation of obtaining a sulfide solid electrolyte with higher ionic conductivity, but also cope with the situation in which, in the manufacturing process of the sulfide solid electrolyte, after the complex slurry is prepared, the drying, heating, etc. described later cannot be performed within a short period of time, such as within 12 hours, within 6 hours, or within 1 hour. In other words, it can also cope with the situation in which the complex is maintained for a long time in the form of a complex slurry. It can be said that this is an effective manufacturing method.

[0105] For being able to make the above-mentioned specific component be retained in complex compound and thus suppress the reason of separation by cooling preservation, it can be considered that it is because, in complex compound, the lithium element of the structure of the PS4 structure etc. connected via the heteroelement in the complexing agent and the binding force of the lithium element such as lithium halide are maintained, the chemical stability of the aggregate formed via the complexing agent in the complex slurry is maintained, but its detailed mechanism is still unclear. If completely dissolved or completely undissolved within a specified temperature range, there is no influence of solubility (such as patent documentation 2). However, since the complex slurry of the present embodiment is solid-liquid coexistence, therefore, each component of the complex compound with different solubility dissolves or is undissolved and is included in the slurry. Because solubility changes due to temperature, it is generally believed that it is desired to keep the temperature of the complex slurry constant to maintain the dissolved state of the complex slurry. And, in the visual observation when keeping the complex slurry for a long time, no matter with or without cooling preservation, no change is observed. Therefore, it is difficult to find the problem related to the chemical stability of the complex slurry. However, surprisingly, in the production method of this embodiment, it was found that simply by performing the simple operation of cooling and storing a complex slurry containing a complex formed by a predetermined element and a complexing agent, the following excellent effects can be achieved: chemical stability of the aggregate formed by the complexing agent in the complex slurry can be obtained, and the separation of bromine and lithium elements from specific components, especially easily separable lithium bromide, can be suppressed, thereby achieving a sulfide solid electrolyte with higher ionic conductivity.

[0106] like Figure 3 As shown, cooling and storage can be carried out after the above-mentioned mixing of the complex slurry can be obtained. In the case of drying described later, it can be carried out before drying. In the case of crushing the complex described later, it is preferably carried out after crushing. For the complex slurry, in the case of heating described later, it is preferably cooled and stored after crushing and before heating. In the case of drying described later, it is preferably cooled and stored after crushing and before drying. In addition, in the case of drying and heating described later, since drying is usually performed first, it is preferably cooled and stored after crushing and before drying. Therefore, in the present embodiment, it is preferably cooled and stored after crushing and before drying or heating the complex slurry. By cooling and storing at such a time, it is possible to more efficiently retain specific components in the complex, suppress the reduction in ionic conductivity caused by separation, and easily obtain a sulfide solid electrolyte with high ionic conductivity.

[0107] exist Figure 3 In the illustrated flow, a configuration is shown in which the complex slurry obtained by mixing in the reaction tank is transferred to an intermediate tank equipped with a cooling device and stored under cooling.

[0108] As an intermediate tank for cooling storage, for example Figure 3 As shown, an intermediate tank having a cooling jacket such as a water cooling jacket on the outer wall of the intermediate tank may be used as a cooling device, and the medium of the cooling jacket may be appropriately determined according to the desired cooling temperature.

[0109] In order to achieve more uniform cooling, Figure 3 As shown, the intermediate tank may be equipped with a mixer (agitator). As the mixer, for example, one appropriately selected from the various mixers exemplified as the mixers that may be equipped in the reaction tank may be used.

[0110] In addition, if Figure 3 As shown, the intermediate tank can be set as a tank different from the reaction tank for performing the above-mentioned mixing. From the perspective of simplifying the device and omitting the labor of transferring the complex slurry, the intermediate tank can be replaced by using a tank equipped with a cooling device in the reaction tank for performing the above-mentioned mixing.

[0111] In this embodiment, the temperature conditions for cold storage are preferably set to be lower than room temperature (23°C), more preferably 20°C or lower, even more preferably 15°C or lower, and even more preferably 10°C or lower. The lower limit is not particularly limited, but is preferably -15°C or higher, more preferably -10°C or higher, even more preferably -5°C or higher, and even more preferably 0°C or higher. When these temperature conditions are set, the specific components are more efficiently retained in the complex, the decrease in ionic conductivity caused by separation is suppressed, and a sulfide solid electrolyte with high ionic conductivity is easily obtained.

[0112] In addition, the cooling storage time is determined by the time the complex slurry is maintained during the production process of the sulfide solid electrolyte. However, from the perspective of suppressing the separation of specific components as much as possible, it is preferably 0.1 hours or more, more preferably 1 hour or more, and even more preferably 12 hours or more. In addition, the upper limit of the cooling storage time is also determined by the time the complex slurry is maintained and is not particularly limited. However, for example, if it is 240 hours or less, an extremely excellent suppression effect on the separation of specific components can be obtained. From the perspective of improving this suppression effect, it is preferably 72 hours or less, more preferably 60 hours or less, even more preferably 48 hours or less, and even more preferably 36 hours or less.

[0113] (crushed)

[0114] The method for producing the sulfide solid electrolyte of this embodiment preferably further includes pulverizing the complex. By pulverizing the complex, a sulfide solid electrolyte having a small particle size can be obtained while suppressing a decrease in ion conductivity.

[0115] The pulverization of the complex in this embodiment is different from the mechanical grinding of the so-called solid phase method, and does not obtain an amorphous or crystalline sulfide solid electrolyte by mechanical stress. As described above, the complex contains a complexing agent, and the structure containing lithium such as the PS4 structure is bonded (coordinated) to the raw material containing lithium such as lithium halide via the complexing agent. In addition, it is believed that if the complex is pulverized, microparticles of the complex can be obtained while maintaining the above-mentioned bonding (coordination) and dispersion. If the complex is heat-treated, the components bonded (coordinated) via the complexing agent are combined while removing the complexing agent, and a reaction to a crystalline sulfide solid electrolyte is likely to occur. Therefore, it is difficult to produce large grain growth caused by the aggregation of particles observed in the synthesis of conventional solid electrolytes, and micronization can be easily performed.

[0116] Furthermore, from the perspectives of all-solid-state battery performance and manufacturing, it is desirable for sulfide solid electrolytes to have a smaller particle size. However, it is not easy to micronize sulfide solid electrolytes by pulverizing them using a bead mill or the like. For example, wet pulverization using a solvent can achieve a certain degree of micronization, but the sulfide solid electrolyte is easily degraded by the solvent and easily aggregates during pulverization, which poses the problem of excessive load on the pulverization. On the other hand, even dry pulverization without a solvent is difficult to micronize to the submicron level. Under such circumstances, the easy process of pulverizing the complex can improve the performance of the all-solid-state battery and increase manufacturing efficiency, which can be a significant advantage.

[0117] Furthermore, by stirring and mixing during the pulverization, it becomes easy to make structures containing lithium such as PS4 structures or aggregates via complexing agents, raw materials containing lithium such as lithium halides or aggregates via complexing agents distributed, thereby obtaining a complex in which the halogen element is more dispersedly fixed. As a result, it is easy to achieve the effect of obtaining higher ion conductivity while micronizing.

[0118] The pulverizer used for pulverizing the complex is not particularly limited as long as it can pulverize particles. For example, a media pulverizer using a pulverizing medium can be used. Among media pulverizers, a wet pulverizer capable of wet pulverization is preferably used, considering that the complex is mainly in a slurry state accompanied by liquids such as a complexing agent and a solvent.

[0119] Representative examples of wet pulverizers include wet bead mills, wet ball mills, and wet vibration mills. Wet bead mills that use beads as the pulverization medium are preferred because they allow for flexible adjustment of pulverization conditions and are easily adaptable to materials with smaller particle sizes. Furthermore, dry pulverizers such as dry bead mills, dry ball mills, and dry vibration mills, and dry non-media pulverizers such as jet mills can also be used.

[0120] In addition, the complex compound pulverized by a pulverizer is usually supplied as a mixture obtained by mixing a solid electrolyte raw material with a complexing agent, and the object mainly supplied in a slurry state, i.e., pulverized by a pulverizer, becomes a complex compound slurry containing a complex compound. Therefore, the pulverizer used in the present embodiment is preferably a flow-through pulverizer, which can carry out a circulation operation of circulating the complex compound slurry as needed. More specifically, it is preferred to use a pulverizer of the form circulated between a pulverizer (pulverizing mixer) and a temperature-maintaining tank (reaction tank) for pulverizing the slurry as described in Japanese Patent Application Laid-Open No. 2010-140893.

[0121] The size of the beads used in the above-mentioned grinder can be appropriately selected according to the desired particle size, processing volume, etc. For example, the diameter of the beads can be set to about 0.05 mmφ or more and 5.0 mmφ or less, preferably 0.1 mmφ or more and 3.0 mmφ or less, and more preferably 0.3 mmφ or more and 1.5 mmφ or less.

[0122] As a pulverizer used for pulverizing the complex, a machine capable of pulverizing an object with ultrasonic waves, for example, a machine called an ultrasonic pulverizer, an ultrasonic homogenizer, a probe ultrasonic pulverizer, or the like can be used.

[0123] In this case, various conditions such as the frequency of the ultrasonic wave can be appropriately selected according to the average particle size of the desired complex, and the frequency can be set, for example, to about 1 kHz to 100 kHz. From the viewpoint of more efficiently pulverizing the complex, it is preferably 3 kHz to 50 kHz, more preferably 5 kHz to 40 kHz, and even more preferably 10 kHz to 30 kHz.

[0124] The output of the ultrasonic pulverizer is generally about 500 to 16,000 W, preferably 600 to 10,000 W, more preferably 750 to 5,000 W, and even more preferably 900 to 1,500 W.

[0125] The average particle size (D 50 ) is appropriately determined according to expectations, and is generally 0.01 μm to 50 μm, preferably 0.03 μm to 5 μm, and more preferably 0.05 μm to 3 μm. By setting it to such an average particle size, it becomes possible to cope with situations where there is a requirement for a small particle size such as an average particle size of 1 μm or less.

[0126] The pulverization time is usually from 0.1 hours to 100 hours. From the viewpoint of efficiently achieving a desired particle size, it is preferably from 0.3 hours to 72 hours, more preferably from 0.5 hours to 48 hours, and even more preferably from 0.8 hours to 24 hours.

[0127] As long as the complex can be crushed, the crushing can be carried out at any time. From the viewpoint of more efficiently making the particle size the desired size, and from the viewpoint of more efficiently retaining the specific components in the complex, suppressing the decrease in ionic conductivity caused by separation, and easily obtaining a sulfide solid electrolyte with high ionic conductivity, it is preferred to crush before cooling and storage, for example, during the above-mentioned mixing (simultaneously with the above-mentioned mixing), or after the above-mentioned mixing, and more preferably after the above-mentioned mixing.

[0128] In addition, when drying is performed as described later, pulverization can also be performed after drying. In this case, among the pulverizers exemplified above as pulverizers that can be used in this production method, any of the dry pulverizers is preferably used. Other pulverization conditions and other matters related to pulverization are the same as those for the pulverization of the complex slurry. In addition, the average particle size of the complex obtained by pulverization is also the same as described above.

[0129] (dry)

[0130] The method for producing a sulfide solid electrolyte according to this embodiment includes a step of subjecting the slurry to at least one treatment selected from drying and heating, that is, a step of drying, heating, or both. In the method according to this embodiment, the slurry is preferably a complex slurry. Therefore, the method according to this embodiment preferably includes a step of subjecting the complex slurry to at least one treatment selected from drying and heating.

[0131] When the slurry is a complex slurry, a configuration including this treatment can yield a complex powder. For example, when obtaining a crystalline sulfide solid electrolyte, heating, described below, is preferred, but prior drying allows for efficient heating. Alternatively, drying and subsequent heating can be performed in the same process.

[0132] As a drying device, any device can be used without particular limitation, and examples thereof include a hot plate, a vacuum heating drying device, an argon atmosphere furnace, and a firing furnace. In addition, in industry, examples thereof include a horizontal dryer having a heating unit and a feeding mechanism, a horizontal vibrating fluidized dryer, and the like.

[0133] The complex slurry can be dried at a temperature appropriate to the type of residual complexing agent (complexing agent not introduced into the complex). For example, it can be dried at a temperature above the boiling point of the complexing agent. Furthermore, it can be dried under reduced pressure (vacuum drying) using a vacuum pump or the like at a temperature of typically 5 to 100°C, preferably 10 to 85°C, more preferably 15 to 70°C, and even more preferably around room temperature (23°C) (e.g., around room temperature ±5°C) to volatilize the complexing agent.

[0134] Alternatively, the complex slurry may be dried by filtration using a glass filter, solid-liquid separation by decantation, or solid-liquid separation using a centrifuge. In this embodiment, after solid-liquid separation, drying may be performed under the above-mentioned temperature conditions.

[0135] Specifically, in solid-liquid separation, the complex slurry is transferred to a container, and after the complex slurry is precipitated, it is easier to remove the complexing agent and solvent that become the supernatant by decantation or by filtering using a glass filter with a pore size of about 10 to 200 μm, preferably 20 to 150 μm.

[0136] (heating)

[0137] The method for producing the sulfide solid electrolyte of this embodiment may include heating the complex. The heating may be performed on the complex slurry, or, when drying is performed, on the complex powder. Alternatively, the complex may be pulverized by the pulverization described above.

[0138] By heating the complex, the complexing agent in the complex is removed, and an amorphous sulfide solid electrolyte containing lithium, sulfur, phosphorus, and halogen elements can be obtained, or a crystalline sulfide solid electrolyte can be further obtained.

[0139] Here, the fact that the complexing agent in the complex is removed can be confirmed by the results of X-ray diffraction patterns, gas chromatography analysis, etc., showing that the complexing agent forms a complex. In addition, this can be confirmed by the fact that the sulfide solid electrolyte obtained by removing the complexing agent by heating the complex is the same as the solid electrolyte obtained by the conventional method without using a complexing agent.

[0140] In the production method of this embodiment, the complex is heated to remove the complexing agent from the complex, thereby obtaining a sulfide solid electrolyte. The less complexing agent in the sulfide solid electrolyte, the better. However, the complexing agent may be contained to the extent that the performance of the solid electrolyte is not impaired. The content of the complexing agent in the sulfide solid electrolyte is generally 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0141] In the production method of this embodiment, in order to obtain a crystalline sulfide solid electrolyte, the complex can be heated to directly obtain the crystalline sulfide solid electrolyte. Alternatively, after heating the complex to obtain an amorphous sulfide solid electrolyte, the amorphous sulfide solid electrolyte can be heated to obtain a crystalline sulfide solid electrolyte. In other words, according to the production method of this embodiment, an amorphous sulfide solid electrolyte can also be produced.

[0142] Conventionally, to obtain a crystalline solid electrolyte with high ionic conductivity, such as a solid electrolyte having a type II crystal structure of a crystalline lithium sulfide superion conductor region, as described later, it was necessary to produce an amorphous solid electrolyte through mechanical pulverization such as mechanical milling or other melt-quenching treatments, followed by heating the amorphous solid electrolyte. However, the production method of this embodiment can produce a crystalline solid electrolyte having a type II crystal structure of a crystalline lithium sulfide superion conductor region without mechanical pulverization or other melt-quenching treatments. In this respect, it is superior to conventional production methods based on mechanical milling and other treatments.

[0143] In the manufacturing method of this embodiment, it is possible to appropriately select, as desired, to obtain an amorphous sulfide solid electrolyte, or a crystalline sulfide solid electrolyte, or to obtain an amorphous sulfide solid electrolyte and then a crystalline sulfide solid electrolyte, or to obtain a crystalline sulfide solid electrolyte directly from a complex, which can be adjusted by heating temperature, heating time, etc.

[0144] The heating temperature of the complex, for example, when obtaining an amorphous sulfide solid electrolyte, can be determined based on the structure of the crystalline sulfide solid electrolyte obtained by heating the amorphous sulfide solid electrolyte (or complex). Specifically, the amorphous sulfide solid electrolyte (or complex) is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) apparatus under a temperature increase condition of 10°C / minute. The starting point is preferably 5°C or less, more preferably 10°C or less, and even more preferably 20°C or less, with the temperature of the peak top of the exothermic peak observed on the lowest temperature side as the starting point. The lower limit is not particularly limited, but can be set to approximately -40°C or more, which is the temperature of the peak top of the exothermic peak observed on the lowest temperature side. By setting the temperature within this range, the amorphous sulfide solid electrolyte can be obtained more efficiently and reliably. The heating temperature for obtaining the amorphous sulfide solid electrolyte varies depending on the structure of the obtained crystalline sulfide solid electrolyte and cannot be generally specified, but is generally preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower. The lower limit is not particularly limited, but is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher.

[0145] In addition, when heating an amorphous sulfide solid electrolyte to obtain a crystalline sulfide solid electrolyte or directly obtaining a crystalline sulfide solid electrolyte from a complex, the heating temperature can be determined according to the structure of the crystalline sulfide solid electrolyte, and is preferably higher than the above-mentioned heating temperature for obtaining the amorphous sulfide solid electrolyte. Specifically, the amorphous sulfide solid electrolyte (or complex) is subjected to differential thermal analysis (DTA) using a differential thermal analyzer (DTA) apparatus under a temperature increase condition of 10°C / minute. The starting point is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, with the upper limit not particularly limited, but can be approximately 40°C or lower. By setting the temperature within this range, a crystalline sulfide solid electrolyte can be obtained more efficiently and reliably. The heating temperature for obtaining the crystalline sulfide solid electrolyte varies depending on the structure of the obtained crystalline sulfide solid electrolyte and cannot be generally specified, but is generally preferably 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C or higher. The upper limit is not particularly limited, but is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0146] The heating time is not particularly limited as long as it is a time that can produce the desired amorphous sulfide solid electrolyte or crystalline sulfide solid electrolyte. For example, it is preferably 1 minute or longer, more preferably 10 minutes or longer, even more preferably 30 minutes or longer, and even more preferably 1 hour or longer. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or shorter, more preferably 10 hours or shorter, even more preferably 5 hours or shorter, and even more preferably 3 hours or shorter.

[0147] Furthermore, heating is preferably performed in an inert gas atmosphere (e.g., nitrogen or argon) or under reduced pressure (particularly in a vacuum). This is because it prevents degradation (e.g., oxidation) of the crystalline sulfide solid electrolyte. The heating method is not particularly limited; examples include methods using a hot plate, a vacuum heater, an argon atmosphere furnace, or a firing furnace. Furthermore, industrially, horizontal dryers equipped with a heating unit and a feed mechanism, such as horizontal vibrating fluidized bed dryers, can also be used. The method can be selected based on the desired heating throughput.

[0148] (Amorphous sulfide solid electrolyte)

[0149] The amorphous sulfide solid electrolyte obtained by the method for producing a sulfide solid electrolyte according to this embodiment contains lithium, sulfur, phosphorus, and a halogen. Representative examples of preferred solid electrolytes include solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr. Solid electrolytes that also contain other elements such as oxygen and silicon include Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI. From the perspective of achieving higher ionic conductivity, solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr, are preferred.

[0150] The types of elements constituting the amorphous sulfide solid electrolyte can be confirmed by, for example, an ICP emission spectrometer.

[0151] When the amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment is an amorphous sulfide solid electrolyte containing at least Li2S-P2S5, from the viewpoint of obtaining higher ion conductivity, 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.

[0152] In the case of the amorphous sulfide solid electrolyte obtained by the production method of this embodiment, for example, Li2S-P2S5-LiI-LiBr, the combined content of lithium sulfide and phosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%. Furthermore, the ratio of lithium bromide to the combined content 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 45 to 65 mol%.

[0153] In the amorphous sulfide solid electrolyte obtained by the production method of this embodiment, the mixing ratio (molar ratio) of lithium element, sulfur element, phosphorus element and halogen element is preferably 1.0 to 1.8:1.0 to 2.0:0.1 to 0.8:0.01 to 0.6, more preferably 1.1 to 1.7:1.2 to 1.8:0.2 to 0.6:0.05 to 0.5, and even more preferably 1.2 to 1.6:1.3 to 1.7:0.25 to 0.5:0.08 to 0.4. In addition, when bromine and iodine are used in combination as halogen elements, the blending ratio (molar ratio) of lithium element, sulfur element, phosphorus element, 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 further preferably 1.35-1.45:1.4-1.7:0.3-0.45:0.04-0.18:0.04-0.18. By setting the blending ratio (molar ratio) of lithium, sulfur, phosphorus and halogen elements within the above range, a sulfide solid electrolyte having a type II crystal structure of the sulfide crystalline lithium superion conductor region described later and higher ionic conductivity can be easily obtained.

[0154] The shape of the amorphous sulfide solid electrolyte is not particularly limited, and may be, for example, a particle shape. The average particle size (D 50 ) For example, it can be exemplified in the range of 0.01 μm to 500 μm and 0.1 to 200 μm.

[0155] (Crystalline Solid Electrolyte)

[0156] The crystalline sulfide solid electrolyte obtained by the method for producing a sulfide solid electrolyte of this embodiment may be a so-called glass ceramic obtained by heating an amorphous sulfide solid electrolyte to a temperature above the crystallization temperature. Examples of its crystal structure include Li3PS4 crystal structure, Li4P2S6 crystal structure, Li7PS6 crystal structure, Li7P3S 11 A crystal structure, a crystal structure having peaks near 2θ=20.2° and 23.6° (for example, Japanese Patent Application Laid-Open No. 2013-16423), and the like.

[0157] In addition, Li 4-x Ge 1-x P x S4 type sulfide crystalline lithium superion conductor region II (thio-LISICONRegion II) type crystal structure (see Kanno et al., Journal of The Electrochemical Society, 148 (7) A742-746 (2001)), and Li 4-x Ge 1-x P x The crystal structure of S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type is similar (see Solid State Ionics, 177 (2006), 2721-2725) and the like.

[0158] From the perspective of obtaining higher ionic conductivity, the crystal structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is preferably a sulfide crystal lithium superion conductor region type II crystal structure among the above. Here, "sulfide crystal lithium superion conductor region type II crystal structure" means Li 4-x Ge 1-x P x S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type crystal structure, and Li 4-x Ge 1-x P xAny crystal structure similar to the S4-type thio-LISICON Region II type. Furthermore, the crystalline sulfide solid electrolyte obtained by the production method of this embodiment may have the aforementioned thio-LISICON Region II crystal structure, or may have the thio-LISICON Region II crystal structure as the main crystal. From the perspective of achieving higher ionic conductivity, it is preferred that the thio-LISICON Region II crystal structure be the main crystal. In this specification, "having the thio-LISICON Region II crystal structure 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 perspective of achieving higher ionic conductivity, the crystalline sulfide solid electrolyte obtained by the production method of this embodiment is preferably a crystalline sulfide solid electrolyte that does not contain crystalline Li3PS4 (β-Li3PS4).

[0159] In the X-ray diffraction measurement using CuKα rays, 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°; 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 The diffraction peaks of the crystal structure appear near 2θ=17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, for example. 4-x Ge 1-x P x The diffraction peaks of the S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) crystal structure appear near 2θ=20.1°, 23.9°, and 29.5°, which are similar to the Li 4-x Ge 1-x P x The diffraction peaks of the S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type-like crystal structure appear near 2θ=20.2 and 23.6°, for example.

[0160] As described above, in the case of obtaining a type II crystal structure of the sulfide crystalline lithium superion conductor region in this embodiment, it is preferable that crystalline Li3PS4 (β-Li3PS4) is not included. Figure 4An example of X-ray diffraction measurement of the crystalline sulfide solid electrolyte obtained by the production method of this embodiment is shown. Figure 5 An example of X-ray diffraction measurement of crystalline Li3PS4 (β-Li3PS4) is shown. Figure 4 as well as Figure 5 The following can be understood: the sulfide solid electrolyte obtained by the manufacturing method of this embodiment does not have the diffraction peaks at 2θ=17.5° and 26.1° that can be observed in crystalline Li3PS4, or even if it has them, only the diffraction peaks that are extremely small compared to the diffraction peaks of the type II crystal structure in the sulfide crystalline lithium superion conductor region are detected.

[0161] The above-mentioned structure skeleton has Li7PS6 and a part of P is replaced by Si with 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 has peaks mainly appearing at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0° in X-ray diffraction measurement using CuKα radiation. 7-x-2y PS 6-x-y Cl x The crystal structure represented by (0.8≤x≤1.7, 0<y≤-0.25x+0.5) is preferably cubic, and in the X-ray diffraction measurement using CuKα rays, it mainly has peaks appearing at positions of 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0° and 52.0°. 7-x PS 6-x Ha x The crystal structure represented by (Ha is Cl or Br, and x is preferably 0.2 to 1.8) is preferably cubic, and in X-ray diffraction measurements using CuKα rays, it mainly has peaks appearing at 2θ = 15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0°.

[0162] In addition, the peak positions of the above-mentioned respective crystal structures can be shifted within a range of ±1.0°.

[0163] The shape of the crystalline sulfide solid electrolyte is not particularly limited, and can be, for example, in the form of particles. The average particle size (D 50 ) For example, it can be exemplified in the range of 0.01 μm to 500 μm and 0.1 to 200 μm.

[0164] (Implementation Method B)

[0165] Next, embodiment B will be described.

[0166] Embodiment B is a method in which, in the production method of this embodiment characterized by mixing a solid electrolyte raw material containing lithium, sulfur, phosphorus, and a halogen element with a complexing agent, a solid electrolyte raw material containing Li3PS4, such as, for example, preferably amorphous Li3PS4 or crystalline Li3PS4, and a complexing agent are used as the solid electrolyte raw material. In the aforementioned embodiment A, the lithium sulfide raw materials react with each other to synthesize a structure containing lithium, such as Li3PS4, which is present as the main structure in the sulfide solid electrolyte obtained by the production method of this embodiment, while also forming a complex. Therefore, it is believed that the composition ratio of the structure is likely to be low.

[0167] Therefore, in embodiment B, a solid electrolyte containing the above-described structure is first prepared and used as a solid electrolyte raw material. This allows the above-described structure, used as the solid electrolyte raw material, to be bonded (coordinated) with a lithium-containing raw material such as a lithium halide via a complexing agent, making it easier to obtain a complex in which the halogen element is dispersed and fixed. As a result, a sulfide solid electrolyte with high ionic conductivity can be obtained. Furthermore, as a secondary effect, the generation of hydrogen sulfide can be suppressed.

[0168] As a solid electrolyte raw material containing lithium, sulfur, and phosphorus that can be used in embodiment B, from the perspective of obtaining higher ion conductivity, an amorphous solid electrolyte or a crystalline solid electrolyte having a PS4 structure as a molecular structure can be exemplified, and preferably amorphous Li3PS4 and crystalline Li3PS4 can be exemplified. In addition, if the generation of hydrogen sulfide is to be suppressed, an amorphous solid electrolyte or a crystalline solid electrolyte that does not contain a P2S7 structure is preferred. These solid electrolytes can be, for example, solid electrolytes produced by conventional manufacturing methods such as mechanical grinding, slurry method, and melt quenching method, or commercially available products can be used.

[0169] In this case, the solid electrolyte containing lithium, sulfur, and phosphorus is preferably an amorphous solid electrolyte. This improves the dispersibility of the halogen in the complex, facilitating bonding between the halogen and the lithium, sulfur, and phosphorus in the solid electrolyte. This results in a sulfide solid electrolyte with higher ionic conductivity.

[0170] In embodiment B, the content of the amorphous solid electrolyte having a PS4 structure and the like relative to the total solid electrolyte raw material is preferably 60 to 100 mol %, more preferably 65 to 90 mol %, and even more preferably 70 to 80 mol %.

[0171] When using an amorphous solid electrolyte having a PS4 structure and a halogen monomer, the content of the halogen monomer relative to the amorphous solid electrolyte having a PS4 structure is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, further preferably 3 to 25 mol%, and further preferably 3 to 15 mol%.

[0172] In addition, the case of using a halogen monomer and a lithium halide, and the case of using two halogen monomers are the same as in the embodiment A.

[0173] In the embodiment B, except for the above-mentioned raw materials, for example, the complexing agent, mixing, cooling and storage, drying, heating, amorphous solid electrolyte, crystalline solid electrolyte, etc. are the same as those described in the above-mentioned embodiment A.

[0174] In the embodiment B, the preferred method of pulverizing the complex, the pulverizer used for pulverization, the pulverization being performed after mixing or after drying, and various conditions related to pulverization are the same as those in the embodiment A.

[0175] (Implementation Methods C and D)

[0176] like Figure 2 As shown in the flowchart of , embodiments C and D differ from embodiments A and B in that a solvent is added to the solid electrolyte raw material and the complexing agent. Embodiments C and D are heterogeneous methods in which solid and liquid coexist. In embodiments A and B, a solid electrolyte precursor is formed in a liquid complexing agent. At this time, if the complex easily dissolves in the complexing agent, separation of the components may sometimes occur. In embodiments C and D, by using a solvent that does not dissolve the complex, elution of the components in the complex can be suppressed.

[0177] (Solvent)

[0178] In the methods for producing a sulfide solid electrolyte according to embodiments C and D, a solvent that does not dissolve the complex is added to the solid electrolyte raw material and the complexing agent, and the solid electrolyte raw material, the complexing agent, and the solvent that does not dissolve the complex are mixed. By mixing the solid electrolyte raw material and the complexing agent using the solvent, the effect of using the complexing agent is promoted, namely, the formation of complexes formed by reacting with lithium, sulfur, phosphorus, and halogen elements is promoted. This facilitates the 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 allows for the formation of complexes in which the halogen element is more dispersed and fixed. As a result, the effect of achieving high ionic conductivity is more easily achieved.

[0179] The production method of this embodiment is a so-called heterogeneous method, in which the complex preferably precipitates incompletely dissolving in the liquid complexing agent. In embodiments C and D, the solubility of the complex can be adjusted by adding a solvent. In particular, since halogen elements readily separate from the complex, the addition of a solvent can suppress this separation, thereby obtaining the desired complex. As a result, a crystalline sulfide solid electrolyte with high ionic conductivity can be obtained via a complex in which components such as halogens are dispersed.

[0180] As a solvent having such properties, a solvent having a solubility parameter of 10 or less can be preferably mentioned. In this specification, the solubility parameter is described in various documents, such as "Chemical Handbook" (published in 2001, 5th revised edition, Maruzen Co., Ltd.), and is a value δ ((cal / cm 3 ) 1 / 2 ), also known as Hildebrand parameter, SP value.

[0181] [Number 1]

[0182]

[0183] (In mathematical formula (1), ΔH is the molar heat, R is the gas constant, T is the temperature, and V is the molar volume.)

[0184] By using a solvent with a solubility parameter of 10 or less, compared to the above-mentioned complexing agent, it has the property of being relatively difficult to dissolve halogen elements, solid electrolyte raw materials containing halogen elements such as lithium halide, and components containing halogen elements that constitute the complex (for example, an aggregate obtained by bonding lithium halide and the complexing agent), etc., it is easy to fix the halogen elements in the complex, and the halogen elements are present in a well-dispersed state in the resulting complex and further in the sulfide solid electrolyte, thereby easily obtaining a sulfide solid electrolyte with high ionic conductivity. That is, the solvent used in this embodiment preferably has the property of not dissolving the complex. From the same viewpoint, the solubility parameter of the solvent is preferably 9.5 or less, more preferably 9.0 or less, and even more preferably 8.5 or less.

[0185] As the solvent used in the manufacturing method of embodiments C and D, more specifically, solvents that have been used in the manufacture of solid electrolytes can be widely adopted, for example, hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents; solvents containing carbon atoms such as alcohol solvents, ester solvents, aldehyde solvents, ketone solvents, ether solvents, solvents containing carbon atoms and heteroatoms; etc. Among these, it is preferred to appropriately select and use solvents having a solubility parameter in the above range.

[0186] More specifically, examples include aliphatic hydrocarbon solvents such as hexane (7.3), pentane (7.0), 2-ethylhexane, heptane (7.4), octane (7.5), decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane (8.2) and methylcyclohexane (7.8); aromatic hydrocarbon solvents such as benzene, toluene (8.8), xylene (8.8), mesitylene, ethylbenzene (8.8), tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene (9.5), chlorotoluene (8.8), and bromobenzene; ethanol (12.7), butanol (11.4 ) and other alcohol solvents; ester solvents such as ethyl acetate (9.1) and butyl acetate (8.5); aldehyde solvents such as formaldehyde, acetaldehyde (10.3), and dimethylformamide (12.1); ketone solvents such as acetone (9.9) and methyl ethyl ketone; ether solvents such as diethyl ether (7.4), diisopropyl ether (6.9), dibutyl ether, tetrahydrofuran (9.1), dimethoxyethane (7.3), cyclopentyl methyl ether (8.4), tert-butyl methyl ether, and anisole; and solvents containing carbon atoms and heteroatoms such as acetonitrile (11.9), dimethyl sulfoxide, and carbon disulfide. The values in parentheses in the above examples are SP values.

[0187] Among these solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether solvents are preferred. From the perspective of more stably obtaining high ion conductivity, heptane, cyclohexane, methylcyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole are more preferred. Methylcyclohexane, diethyl ether, diisopropyl ether, and dibutyl ether are further preferred. Methylcyclohexane, diisopropyl ether, and dibutyl ether are further preferred. Methylcyclohexane, diisopropyl ether, and dibutyl ether are particularly preferred. The solvent used in this embodiment is preferably the organic solvent exemplified above and is an organic solvent different from the complexing agent. In this embodiment, these solvents can be used alone or in combination.

[0188] When a solvent is used, the content of the raw material in the raw material content may be set to a content per 1 L of the total amount of the complexing agent and the solvent.

[0189] The complex slurry can be dried in embodiments C and D at a temperature corresponding to the type of residual complexing agent (complexing agent not introduced into the complex) and solvent. For example, it can be carried out at a temperature above the boiling point of the complexing agent or solvent, and can be dried under reduced pressure (vacuum drying) using a vacuum pump or the like at a temperature of typically 5 to 100°C, preferably 10 to 85°C, more preferably 15 to 70°C, and even more preferably around room temperature (23°C) (e.g., room temperature ±5°C) to volatilize the complexing agent and solvent. In addition, during the heating in embodiments C and D, if a solvent remains in the electrolyte precursor, the solvent is also removed.

[0190] The solvent is different from the complexing agent forming the complex and is difficult to form a complex. Therefore, the solvent that can remain in the complex is usually 3% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less.

[0191] In embodiment C, except for the aspects related to the above-mentioned solvent, for example, the complexing agent, mixing, cooling and storage, drying, heating, amorphous solid electrolyte, crystalline solid electrolyte, etc. are the same as those described in the above-mentioned embodiment A. In addition, in embodiment D, except for the aspects related to the above-mentioned solvent, it is also the same as the above-mentioned embodiment B.

[0192] In Embodiments C and D, the preferred method of pulverizing the complex, the pulverizer used for pulverization, the pulverization being performed after mixing or after drying, and various conditions related to pulverization are the same as those in Embodiment A.

[0193] The sulfide solid electrolyte obtained by the production method of this embodiment has high ionic conductivity and excellent battery performance, making it preferably used in batteries. It is particularly preferred when lithium is used as the conductive seed. The sulfide solid electrolyte obtained by the production method of this embodiment can be used in the positive electrode layer, the negative electrode layer, or the electrolyte layer. In addition, each layer can be produced using known methods.

[0194] [Positive electrode composite materials, negative electrode composite materials]

[0195] For example, when used in a positive electrode layer or a negative electrode layer, the positive electrode active material and the negative electrode active material are dispersed in a complex slurry, mixed, and dried to adhere the complex to the surface of the active material. Similarly to the above embodiment, the complex is heated to form an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte. In this case, by heating the complex together with the active material, a positive electrode composite material or a negative electrode composite material having a sulfide solid electrolyte adhered to the surface of the active material can be obtained.

[0196] As the positive electrode active material, any material can be used without particular limitation as long as it can promote the battery chemical reaction associated with the movement of lithium ions caused by the lithium element, which is preferably used as the element exhibiting ionic conductivity in this embodiment, through its relationship with the negative electrode active material. Examples of positive electrode active materials capable of such intercalation and deintercalation of lithium ions include oxide-based positive electrode active materials and sulfide-based positive electrode active materials.

[0197] As oxide-based positive electrode active materials, preferred examples include lithium-containing transition metal composite oxides such as LMO (lithium manganate), LCO (lithium cobaltate), NMC (lithium nickel cobalt manganate), NCA (lithium nickel cobalt aluminum oxide), LNCO (lithium nickel cobalt oxide), and olivine-type compounds (LiMeNPO4, Me = Fe, Co, Ni, Mn).

[0198] Examples of the sulfide-based positive electrode active material include titanium sulfide (TiS 2 ), molybdenum sulfide (MoS 2 ), iron sulfide (FeS, FeS 2 ), copper sulfide (CuS), and nickel sulfide (Ni 3 S 2 ).

[0199] In addition to the above-mentioned positive electrode active materials, niobium selenide (NbSe 3 ) or the like can also be used.

[0200] In this embodiment, the positive electrode active material may be used alone or in combination of two or more.

[0201] As the negative electrode active material, any substance that can promote the battery chemical reaction associated with the movement of lithium ions, preferably lithium, can be used without particular limitation. The lithium element is preferably an element exhibiting ionic conductivity in this embodiment, preferably a metal that can form an alloy with lithium, an oxide thereof, or an alloy of the metal and lithium. As the negative electrode active material capable of such lithium ion insertion and extraction, any substance known as a negative electrode active material in the battery field can be used without limitation.

[0202] Examples of such negative electrode active materials include metallic lithium, metallic indium, metallic aluminum, metallic silicon, metallic tin, and other metals that can form alloys with metallic lithium, oxides of these metals, and alloys of these metals with metallic lithium.

[0203] The electrode active material used in this embodiment may have a coating layer coated on its surface.

[0204] As a material for forming the coating layer, an element exhibiting ionic conductivity in the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment, preferably a nitride, oxide, or ion conductor such as a composite of lithium, can be cited. Specifically, lithium nitride (Li3N), a Li4GeO4-based structure such as Li 4-2x Zn x Conductors with a crystalline lithium superion conductor (LISICON) structure such as GeO4, and conductors with a Li3PO4 skeleton structure such as Li 4-x Ge 1-x P x S4 and other conductors with thio-LISICON crystal structure, La 2 / 3-x Li 3x Conductors with a perovskite crystal structure such as TiO3, conductors with a sodium fast ion conductor (NASICON) crystal structure such as LiTi2(PO4)3, etc.

[0205] In addition, Li y Ti 3-y O4(0<y<3), Li4Ti5O 12 Conductors such as lithium titanate (LTO), lithium metal oxides of metals belonging to Group 5 of the periodic table such as LiNbO3, LiTaO3, or oxides such as Li2O-B2O3-P2O5, Li2O-B2O3-ZnO, and Li2O-Al2O3-SiO2-P2O5-TiO2.

[0206] The electrode active material having the coating layer is obtained, for example, by allowing a solution containing various elements constituting a material forming the coating layer to adhere to the surface of the electrode active material and then calcining the adhered electrode active material preferably at 200° C. to 400° C.

[0207] Here, as the solution containing various elements, solutions containing various metal alkoxides such as lithium ethoxide, titanium isopropoxide, niobium isopropoxide, and tantalum isopropoxide can be used. In this case, as the solvent, alcohol solvents such as ethanol and butanol; aliphatic hydrocarbon solvents such as hexane, heptane, and octane; and aromatic hydrocarbon solvents such as benzene, toluene, and xylene can be used.

[0208] In addition, the above-mentioned attachment may be performed by dipping, spraying, or the like.

[0209] From the perspective of improving manufacturing efficiency and battery performance, the firing temperature is preferably 200°C to 400°C, more preferably 250°C to 390°C. The firing time is usually about 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0210] The coating ratio of the coating layer is preferably 90% or more, more preferably 95% or more, and further preferably 100% based on the surface area of the electrode active material, i.e., preferably the entire surface is coated. In addition, the thickness of the coating layer is preferably 1 nm or more, more preferably 2 nm or more, and the upper limit is preferably 30 nm or less, more preferably 25 nm or less.

[0211] The thickness of the coating layer can be measured by cross-sectional observation using a transmission electron microscope (TEM), and the coverage can be calculated from the thickness of the coating layer, elemental analysis values, and BET surface area.

[0212] In addition, the battery preferably uses a current collector in addition to the positive electrode layer, the electrolyte layer and the negative electrode layer. The current collector can use a known current collector. For example, a layer obtained by coating a substance that reacts with the solid electrolyte such as Au, Pt, Al, Ti or Cu can be used.

[0213] Example

[0214] Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[0215] (Reference Example 1)

[0216] In a 1L reaction tank equipped with a stirring blade, 13.19g of lithium sulfide, 21.26g of phosphorus pentasulfide, 4.15g of lithium bromide, and 6.40g of lithium iodide were introduced under a nitrogen atmosphere. 100mL of tetramethylethylenediamine (TMEDA) as a complexing agent and 800mL of methylcyclohexane as a solvent were added, and the stirring blade was activated to stir and mix. A circulating bead mill ("star mill LMZ015 (model)", manufactured by Ashizawa Finetech Co., Ltd.) was loaded with 456g of zirconia balls (diameter: 0.5mm) (bead filling rate relative to the grinding chamber: 80%). The mixture was pulverized for 60 minutes while circulating between the reaction tank and the grinding chamber at a pump flow rate of 550mL / min, a peripheral speed of 8m / s, and a mill jacket temperature of 20°C to obtain a complex slurry.

[0217] The resulting complex slurry was then immediately dried at room temperature (23°C) under vacuum to obtain a powdered complex. The powdered complex was then heated at 120°C under vacuum for 2 hours to obtain an amorphous solid electrolyte. Furthermore, the amorphous solid electrolyte was heated at 200°C under vacuum for 2 hours to obtain a crystalline solid electrolyte.

[0218] The crystalline sulfide solid electrolyte obtained in Reference Example 1 was subjected to powder X-ray diffraction (XRD) measurement using an X-ray diffraction (XRD) apparatus ("D2 Phaser (trade name)", manufactured by Bruker Japan Co., Ltd.). The X-ray diffraction spectrum is shown in FIG. Figure 4 In addition, the complex and amorphous sulfide solid electrolyte obtained in Reference Example 1 were also subjected to powder X-ray diffraction (XRD) measurement in the same manner, and their X-ray diffraction spectra are shown together with the X-ray diffraction spectrum of the crystalline sulfide solid electrolyte. Figure 6 .according to Figure 4 as well as Figure 6 The crystalline sulfide solid electrolyte obtained in Reference Example 1 exhibited crystallization peaks primarily at 2θ = 20.2° and 23.6°, similar to Example 1 described below, indicating a type II crystal structure in the sulfide crystalline lithium superion conductor region. Furthermore, the ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured to be 4.1 (mS / cm).

[0219] In this example, the measurement of ion conductivity was performed as follows.

[0220] The obtained crystalline sulfide solid electrolyte was formed into a 10 mm diameter (cross-sectional area S: 0.785 cm 2), round particles with a height (L) of 0.1 to 0.3 cm were used to make the sample. Electrode terminals were obtained from the top and bottom of the sample, and the AC impedance method was used for measurement at 25°C (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. Near the right end of the arc observed in the high-frequency side area, the real part Z'(Ω) at the point where -Z"(Ω) is the minimum is used as the bulk resistance R(Ω) of the electrolyte, and the ionic conductivity σ(S / cm) is calculated according to the following formula.

[0221] R=ρ(L / S)

[0222] σ=1 / ρ

[0223] (Reference Example 2)

[0224] In a 1L reaction tank with a stirring blade, 15.3g of lithium sulfide and 24.7g of phosphorus pentasulfide were added under a nitrogen atmosphere. After the stirring blade was operated, 400mL of tetrahydrofuran pre-cooled to -20°C was introduced into the container. After naturally warming to room temperature (23°C), stirring was continued for 72 hours, and the obtained reaction solution slurry was put into a glass filter (pore size: 40-100μm) to obtain a solid component, and the solid component was dried at 90°C to obtain 38g of Li3PS4 (purity: 90% by mass) as a white powder. For the obtained powder, the result of powder X-ray diffraction (XRD) measurement using an X-ray diffraction (XRD) device (SmartLab device, (Strain) Rigaku) was that a halo pattern was shown, confirming that it was amorphous Li3PS4.

[0225] (Reference Example 3)

[0226] The white powder Li3PS4 obtained in Reference Example 2 was vacuum dried at 180°C for 2 hours to obtain β-Li3PS4 (crystalline).

[0227] Powder X-ray diffraction (XRD) measurements were performed on amorphous Li3PS4, lithium sulfide, phosphorus pentasulfide, lithium bromide, and lithium iodide of Reference Example 2, as solid electrolyte raw materials, and β-Li3PS4 (crystalline) of Reference Example 3. The X-ray diffraction spectra are shown in Figure 5 .

[0228] (Example 1)

[0229] A crystalline sulfide solid electrolyte was obtained in the same manner as in Reference Example 1, except that the pulverized complex slurry was stored in a refrigerator (set temperature: -5°C) for 1 day. Powder X-ray diffraction (XRD) measurement was performed on the obtained crystalline sulfide solid electrolyte in the same manner as in Reference Example 1. The X-ray diffraction spectrum is shown in FIG. Figure 4 Furthermore, the ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured. The measurement results are shown in Table 1.

[0230] (Example 2)

[0231] A crystalline sulfide solid electrolyte was obtained in the same manner as in Reference Example 1, except that the pulverized complex slurry was stored in a refrigerator (set temperature: -5°C) for 2 days. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured. The measurement results are shown in Table 1.

[0232] (Example 3)

[0233] A crystalline sulfide solid electrolyte was obtained in the same manner as in Reference Example 1, except that the pulverized complex slurry was cooled and stored for one day while circulating a refrigerant through the jacket of the reaction vessel to maintain the temperature in the reaction vessel at 10°C. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured. The measurement results are shown in Table 1.

[0234] (Example 4)

[0235] A crystalline sulfide solid electrolyte was obtained in the same manner as in Reference Example 1, except that the pulverized complex slurry was cooled and stored for 2 days while circulating a refrigerant through the jacket of the reaction vessel to maintain the temperature in the reaction vessel at 10°C. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured. The measurement results are shown in Table 1.

[0236] (Comparative Example 1)

[0237] A crystalline sulfide solid electrolyte was obtained in the same manner as in Reference Example 1, except that the pulverized complex slurry was stored at room temperature (23°C) for 1 day. Powder X-ray diffraction (XRD) measurement was performed on the obtained crystalline sulfide solid electrolyte in the same manner as in Reference Example 1. The X-ray diffraction spectrum is shown in FIG. Figure 4 Furthermore, the ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured. The measurement results are shown in Table 1.

[0238] (Comparative Example 2)

[0239] A crystalline sulfide solid electrolyte was obtained in the same manner as in Reference Example 1, except that the pulverized complex slurry was stored at room temperature (23° C.) for 2 days. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured. The measurement results are shown in Table 1.

[0240] [Table 1]

[0241] Table 1

[0242]

[0243] As shown in Table 1, it was confirmed that according to the production method of this embodiment, even when the complex slurry was kept for a long time, a sulfide solid electrolyte having high ionic conductivity was obtained, similar to the sulfide solid electrolyte obtained in the reference example in which the complex slurry was dried, heated, etc. immediately after preparation. On the other hand, in Comparative Examples 1 and 2, in which the complex slurry was kept for a long time without cooling, the ionic conductivity was significantly reduced.

[0244] according to Figure 4 It was confirmed that the X-ray diffraction spectra of the sulfide solid electrolytes obtained in Reference Example 1, Example 1, and Comparative Example 1 showed that crystallization peaks were detected mainly at 2θ = 20.2° and 23.6° in all of the sulfide solid electrolytes, indicating that they had a type II crystal structure in the sulfide crystallized lithium superion conductor region.

[0245] Furthermore, in the X-ray diffraction spectrum of the sulfide solid electrolyte obtained in Comparative Example 1, a crystallization peak derived from lithium bromide was detected at 2θ = 28.1°. This is believed to be because the complex slurry was stored for a long time without cooling, causing lithium bromide to separate from the complex and not be incorporated into the sulfide solid electrolyte. Therefore, although the obtained sulfide solid electrolyte has a type II crystal structure of a sulfide crystallized lithium superion conductor region, the ionic conductivity is lower than that of Reference Example 1 and the Examples.

[0246] Industrial Applicability

[0247] The method for producing a sulfide solid electrolyte according to this embodiment enables the production of a sulfide solid electrolyte having high ionic conductivity and excellent battery performance. The sulfide solid electrolyte obtained by the production method according to this embodiment is preferably used in batteries, particularly batteries used in information-related devices and communication equipment such as personal computers, video cameras, and mobile phones.

Claims

1. A method for producing a sulfide solid electrolyte, comprising the step of subjecting a slurry to at least one treatment selected from drying and heating, wherein: include: A solid electrolyte raw material containing lithium, sulfur, phosphorus and halogen elements and a complexing agent are mixed in a reaction tank to obtain a complex slurry containing a complex formed by the solid electrolyte raw material and the complexing agent; the complex slurry is transferred to an intermediate tank equipped with a cooling device for cooling, The cooling is performed by maintaining the complex slurry for 0.1 hour or more.

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The method further includes pulverizing the complex, wherein the complex slurry contains the pulverized complex.

3. The method for producing a sulfide solid electrolyte according to claim 2, wherein: In pulverizing the complex, a pulverizer is used to pulverize the complex slurry.

4. The method for producing a sulfide solid electrolyte according to claim 3, wherein: The pulverizer is a flow-through pulverizer.

5. The method for producing a sulfide solid electrolyte according to any one of claims 2 to 4, wherein: The pulverization is performed for a period of time of 0.1 hours to 100 hours.

6. The method for producing a sulfide solid electrolyte according to claim 5, wherein: The pulverization is performed for a period of time of 0.8 hours to 24 hours.

7. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The step of subjecting the slurry to at least one treatment selected from drying and heating includes the drying.

8. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The step of performing at least one treatment selected from drying and heating on the slurry includes the heating.

9. The method for producing a sulfide solid electrolyte according to claim 1, wherein: In the step of subjecting the slurry to at least one treatment selected from drying and heating, the drying and heating are performed.

10. The method for producing a sulfide solid electrolyte according to claim 9, wherein: The heating is performed after the drying is performed.

11. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The drying is to dry the complex slurry.

12. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The heating is heating the complex slurry.

13. The method for producing a sulfide solid electrolyte according to claim 2, wherein: The cooling is performed after the pulverization and before the complex slurry is dried or heated.

14. The method for producing a sulfide solid electrolyte according to claim 2, wherein: The cooling is performed after the pulverization and before the complex slurry is dried.

15. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The cooling is performed by maintaining the complex slurry at less than 23°C.

16. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The cooling is performed by maintaining the complex slurry at 15°C or below.

17. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The cooling is performed by maintaining the complex slurry at 10°C or lower.

18. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The cooling is performed by maintaining the complex slurry for 1 hour or more.

19. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The cooling is performed by maintaining the complex slurry for more than 12 hours.

20. The method for producing a sulfide solid electrolyte according to claim 1, wherein The mixing is to mix the solid electrolyte raw material, the complexing agent and a solvent that does not dissolve the complex.

21. The method for producing a sulfide solid electrolyte according to claim 20, wherein: The solubility parameter of the solvent is 10 or less.

22. The method for producing a sulfide solid electrolyte according to claim 20 or 21, wherein: The solvent is at least one solvent selected from aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents and ether solvents.

23. The method for producing a sulfide solid electrolyte according to claim 22, wherein: The solvent is at least one selected from heptane, cyclohexane, methylcyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole.

24. The method for producing a sulfide solid electrolyte according to claim 22, wherein: The solvent is an alicyclic hydrocarbon solvent.

25. The method for producing a sulfide solid electrolyte according to claim 24, wherein: The alicyclic hydrocarbon solvent is methylcyclohexane.

26. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The complexing agent includes a compound containing at least one heteroelement selected from nitrogen, oxygen, and chlorine.

27. The method for producing a sulfide solid electrolyte according to claim 26, wherein: The heteroelement is nitrogen.

28. The method for producing a sulfide solid electrolyte according to claim 26, wherein: The complexing agent includes a compound having a group containing a nitrogen element.

29. The method for producing a sulfide solid electrolyte according to claim 28, wherein: The nitrogen-containing group is an amino group.

30. The method for producing a sulfide solid electrolyte according to claim 29, wherein: The complexing agent includes a compound having a tertiary amino group.

31. The method for producing a sulfide solid electrolyte according to claim 30, wherein: The complexing agent comprises an aliphatic tertiary diamine having two tertiary amino groups.

32. The method for producing a sulfide solid electrolyte according to claim 31, wherein: The aliphatic tertiary diamine is at least one selected from tetramethylethylenediamine and tetramethyldiaminopropane.

33. The method for producing a sulfide solid electrolyte according to claim 31 or 32, wherein: The aliphatic tertiary diamine is tetramethylethylenediamine.

34. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The solid electrolyte raw material includes lithium sulfide and phosphorus sulfide.

35. The method for producing a sulfide solid electrolyte according to claim 34, wherein: The solid electrolyte raw material includes lithium sulfide and phosphorus pentasulfide.

36. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The solid electrolyte raw material includes amorphous Li3PS4 or crystalline Li3PS4.

37. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The solid electrolyte raw material includes at least one selected from lithium halide and a halogen monomer as a solid electrolyte raw material containing a halogen element.

38. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The halogen element is at least one element selected from chlorine, bromine and iodine.

39. The method for producing a sulfide solid electrolyte according to claim 38, wherein: The halogen element is at least one element selected from bromine and iodine.

40. The method for producing a sulfide solid electrolyte according to claim 39, wherein: The halogen elements are bromine and iodine.

41. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The solid electrolyte raw material includes lithium bromide.

42. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The solid electrolyte raw material includes lithium iodide.

43. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The reaction tank is provided with a stirrer, and the mixing is performed by the stirrer.

44. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The mixing was performed without using a pulverizer.

45. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The content of the solid electrolyte raw material relative to 1 L of the complexing agent is 5 g or more and 500 g or less.

46. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The content of the solid electrolyte raw material relative to 1 L of the complexing agent is 45 g or more and 250 g or less.

47. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The drying temperature is 5-100°C.

48. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The drying temperature is 15-70°C.

49. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The drying is performed under reduced pressure.

50. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The drying is vacuum drying.

51. The method for producing a sulfide solid electrolyte according to claim 1, wherein: An amorphous sulfide solid electrolyte is obtained by the heating.

52. The method for producing a sulfide solid electrolyte according to claim 51, wherein: The heating temperature is below 130°C.

53. The method for producing a sulfide solid electrolyte according to claim 51 or 52, wherein: The heating temperature is below 125°C.

54. The method for producing a sulfide solid electrolyte according to claim 51 or 52, wherein: The heating is performed under a reduced pressure atmosphere.

55. The method for producing a sulfide solid electrolyte according to claim 51 or 52, wherein: The heating is performed in vacuum.

56. The method for producing a sulfide solid electrolyte according to claim 51 or 52, wherein: After the above heating, further heating is performed to obtain a crystalline sulfide solid electrolyte.

57. The method for producing a sulfide solid electrolyte according to claim 56, wherein: The heating temperature for obtaining the crystalline sulfide solid electrolyte is 130° C. or higher.

58. The method for producing a sulfide solid electrolyte according to claim 56, wherein: The heating temperature for obtaining the crystalline sulfide solid electrolyte is 140° C. or higher.

59. The method for producing a sulfide solid electrolyte according to claim 56, wherein: The heating for obtaining the crystalline sulfide solid electrolyte is performed under a reduced pressure atmosphere.

60. The method for producing a sulfide solid electrolyte according to claim 56, wherein: The heating for obtaining the crystalline sulfide solid electrolyte is performed in a vacuum.

61. The method for producing a sulfide solid electrolyte according to claim 1, wherein: The sulfide solid electrolyte comprises a sulfide crystalline lithium superion conductor region with a type II crystal structure.

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