Method for producing sulfide solid electrolyte

Abstract

To provide a method for producing a sulfide solid electrolyte having high ionic conductivity.SOLUTION: A method for producing a sulfide solid electrolyte comprises mixing a raw material-containing component containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms in a solvent, and heating the mixture. The solvent contains a complexing agent including a monoamine compound with a six-membered ring structure containing one hetero atom.SELECTED DRAWING: None

Description

[Technical field]

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

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

[0003] The manufacturing methods of the solid electrolyte used in the solid electrolyte layer are roughly divided into a solid phase method and a liquid phase method, and the liquid phase method is further divided into a homogeneous method in which the solid electrolyte material is completely dissolved in a solvent, and a heterogeneous method in which the solid electrolyte material is not completely dissolved and a solid-liquid coexisting suspension is formed. For example, as a homogeneous method among the liquid phase methods, a method in which the solid electrolyte is dissolved in a solvent and reprecipitated is known (see, for example, Patent Document 1), and as a heterogeneous method, a method in which a solid electrolyte raw material such as lithium sulfide is reacted in a solvent containing a polar aprotic solvent (see, for example, Patent Documents 2 and 3), and a manufacturing method of a solid electrolyte using a specific compound as a complexing agent (see, for example, Patent Documents 4 and 5) are known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-191899 A [Patent Document 2] International Publication No. 2014 / 192309 Brochure [Patent Document 3] International Publication No. 2018 / 054709 Brochure [Patent Document 4] International Publication No. 2020 / 105737 Brochure [Patent Document 5] International Publication No. 2021 / 132173 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for producing a sulfide solid electrolyte having high ionic conductivity. [Means for solving the problem]

[0006] As a result of intensive research into solving the above problems, the present inventors have found that the problems can be solved by the following invention. [1] mixing a raw material containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms in a solvent; and heating, The method for producing a sulfide solid electrolyte, wherein the solvent contains a complexing agent including a monoamine compound having a six-membered ring structure containing one heteroatom. [2] An electrolyte precursor comprising lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and a complexing agent including a monoamine compound having a six-membered ring structure containing one heteroatom. [3] A sulfide solid electrolyte containing a monoamine compound that is composed of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms and has a six-membered ring structure containing one heteroatom. Effect of the Invention

[0007] According to the present invention, a method for producing a sulfide solid electrolyte having high ionic conductivity can be provided. [Brief description of the drawings]

[0008] [Figure 1] 1 is an X-ray diffraction pattern of the solid electrolyte obtained in Example 1. [Diagram 2] 1 is an X-ray diffraction pattern of the solid electrolyte obtained in Example 2. [Diagram 3] 1 is an X-ray diffraction pattern of the solid electrolyte obtained in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0010] (Findings Obtained by the Inventor to Achieve the Invention) As a result of intensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention.

[0011] In a method for producing a solid electrolyte using a complexing agent, the complexing agent has a significant effect on the ionic conductivity and other properties of the resulting solid electrolyte. Therefore, in search of a better complexing agent, various compounds have been investigated as complexing agents. Specifically, amine compounds containing a ring structure are known as complexing agents (see Patent Document 5). In Patent Document 5, N-methylmorpholine, N,N'-dimethylpiperazine, etc. are used, and a solid electrolyte having an ionic conductivity of approximately 1.90 mS / cm is obtained by a method for producing a solid electrolyte using these complexing agents. However, in recent years, there has been an increasing demand for improved performance of batteries using solid electrolytes, and there is a need to search for complexing agents that can produce solid electrolytes with higher ionic conductivity.

[0012] As another complexing agent, a diamine compound such as tetramethylethylenediamine (TMEDA) is known, and a solid electrolyte having an ionic conductivity of 1.1 to 4.3 mS / cm is obtained by a method for producing a solid electrolyte using such a complexing agent (see Patent Document 4). However, as the mass production of solid electrolytes progresses, the demand for complexing agents is increasing, and a more stable supply system for complexing agents is required. Therefore, there is a need to find alternative complexing agents other than diamine compounds that can provide solid electrolytes with the same ionic conductivity as those obtained when diamine compounds such as TMEDA are used, and to secure alternatives.

[0013] The present inventors have used amine compounds of various structures and have examined their suitability as complexing agents. In the course of the examination, they have found that a solid electrolyte with high ionic conductivity can be produced by using a monoamine compound having a six-membered ring structure containing one heteroatom as a complexing agent. The reason why the complexing agent contributes to improving the ionic conductivity of the solid electrolyte is unclear, but the following is presumed. That is, the complexing agent has at least one heteroatom, and thus suppresses excessive interaction with lithium atoms compared to the complexing agent described in Patent Document 5, which contains two or more heteroatoms. Furthermore, the complexing agent is easily detached when heated due to steric hindrance caused by the six-membered ring structure. Due to the above two effects, when the complexing agent is used, it is considered that the complexing agent can be easily removed when heated, and a solid electrolyte with higher purity and higher ionic conductivity can be obtained.

[0014] TMEDA described in the above-mentioned Patent Document 4 is a compound having two nitrogen atoms as heteroatoms, and N-methylmorpholine and N,N'-dimethylpiperazine described in Patent Document 5 are compounds having two heteroatoms in a ring structure. As described above, compounds containing two heteroatoms in one molecule are known as compounds conventionally used as complexing agents. It has been believed that by adopting a compound having two heteroatoms as a complexing agent, raw materials containing lithium atoms can be bonded together via the two heteroatoms, thereby obtaining a solid electrolyte with high ionic conductivity (see Patent Document 1

[0031] , Patent Document 2

[0032] , etc.). In response to this, the present inventors have found that a sulfide solid electrolyte having high ionic conductivity can be obtained using a compound having a six-membered ring structure containing one heteroatom, particularly a monoamine compound, which is a compound having at least one heteroatom. It is a surprising phenomenon that a compound having at least one heteroatom can also exhibit the performance as a complexing agent.

[0015] (Various aspects of the present embodiment) A method for producing a sulfide solid electrolyte according to a first embodiment of the present invention includes the steps of: mixing a raw material containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms in a solvent; and heating, a method for producing a sulfide solid electrolyte, wherein the solvent contains a complexing agent containing a monoamine compound having a six-membered ring structure containing one heteroatom; It is.

[0016] In the method for producing the sulfide solid electrolyte of the present embodiment, a monoamine compound having a six-membered ring structure containing one heteroatom is used as a complexing agent, so that, as described above, it is possible to ensure a certain degree of interaction with lithium atoms while suppressing excessive interaction. This allows the raw materials to be efficiently incorporated into the structure of the solid electrolyte during heating while the complexing agent can be easily removed, making it possible to obtain a sulfide solid electrolyte with higher purity and higher ion conductivity.

[0017] A method for producing a sulfide solid electrolyte according to a second embodiment of the present invention includes the steps of: In the first embodiment, the six-membered ring structure is a piperidine skeleton. That is it.

[0018] Further, a method for producing a sulfide solid electrolyte according to a third embodiment of the present invention includes the steps of: In the first or second embodiment, the monoamine compound is an alkylpiperidine. That is it.

[0019] Further, a method for producing a sulfide solid electrolyte according to a fourth embodiment of the present invention includes the steps of: In the third embodiment, the alkylpiperidine is 1-methylpiperidine. That is it.

[0020] As the complexing agent used in the production method of the present embodiment, as described above, a monoamine compound having a six-membered ring structure containing one heteroatom can be used. From the viewpoint of easily exerting the effects of the present invention, however, it is preferable to use a monoamine compound in which the six-membered ring structure is a piperidine skeleton, it is more preferable to use an alkylpiperidine, and it is even more preferable to use 1-methylpiperidine.

[0021] A method for producing a sulfide solid electrolyte according to a fifth embodiment of the present invention includes the steps of: In any one of the first to fourth embodiments, the solvent comprises a hydrocarbon solvent. That is it.

[0022] Since the solubility of the complex in the hydrocarbon solvent is low, the addition of the hydrocarbon solvent can suppress the dissolution of halogen atoms that tend to dissolve from the complex. As a result, the halogen atoms are well dispersed in the obtained electrolyte precursor and further in the sulfide solid electrolyte, and it becomes easier to obtain a sulfide solid electrolyte having high ionic conductivity.

[0023] Further, a method for producing a sulfide solid electrolyte according to a sixth embodiment of the present invention includes the steps of: In the fifth embodiment, the hydrocarbon solvent is cyclohexane. That is it.

[0024] As the hydrocarbon solvent, it is preferable to use cyclohexane from the viewpoint of easily exerting the effect of preventing the elution of halogen atoms described above.

[0025] A method for producing a sulfide solid electrolyte according to a seventh aspect of the present embodiment includes the steps of: In any one of the first to sixth embodiments, by the mixing, an electrolyte precursor containing the lithium atom, the sulfur atom, the phosphorus atom, the halogen atom, and the complexing agent is obtained. That is it.

[0026] In addition, a method for producing a sulfide solid electrolyte according to an eighth embodiment of the present invention includes the steps of: In any one of the first to seventh embodiments, the solvent includes a solvent A including a solvent containing an oxygen atom and a solvent B including the complexing agent, the raw material contains a substance group C including the lithium atom, the sulfur atom, and the phosphorus atom, and a substance group D including the halogen atom; The mixing is carried out by the following (i) and (ii): That is it. (i) Mixing the substance C in the solvent A to obtain amorphous Li 3 P.S. 4 To obtain. (ii) In the solvent B, the amorphous Li 3 P.S. 4 and said substance D to obtain an electrolyte precursor.

[0027] In addition, a ninth aspect of the present embodiment provides a method for producing a sulfide solid electrolyte in the eighth aspect, The oxygen-containing solvent is tetrahydrofuran. That is it.

[0028] In this embodiment, amorphous Li 3 P.S. 4 is formed once, but by using tetrahydrofuran as the solvent, Li 3 P.S. 4 It can promote the formation of Li 3 P.S. 4 By forming the above, the basic structure of the resulting solid electrolyte can be secured, so that a solid electrolyte having high purity and high ionic conductivity can be easily obtained.

[0029] The electrolyte precursor according to a tenth aspect of the present embodiment is composed of a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom, and a complexing agent including a monoamine compound having a six-membered ring structure including one heteroatom. That is it.

[0030] The electrolyte precursor according to the present embodiment contains a complexing agent including a monoamine compound having a six-membered ring structure including one heteroatom, and as described above, the complexing agent can be easily removed during heating. As a result, by using the electrolyte precursor, a sulfide solid electrolyte having higher purity and higher ion conductivity can be obtained.

[0031] The sulfide solid electrolyte according to the eleventh aspect of the present embodiment includes a monoamine compound having a six-membered ring structure including one heteroatom and including a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom. That is it.

[0032] [Sulfide solid electrolyte] In this specification, the term "sulfide solid electrolyte" refers to an electrolyte that maintains a solid state under a nitrogen atmosphere at 25° C. The sulfide solid electrolyte in this embodiment is a sulfide solid electrolyte that contains lithium element, sulfur element, phosphorus element, and halogen element and has ionic conductivity due to lithium element.

[0033] The term "sulfide solid electrolyte" includes both crystalline sulfide solid electrolytes having a crystal structure and amorphous sulfide solid electrolytes. In this specification, the crystalline sulfide solid electrolyte is a solid electrolyte in which a peak derived from a solid electrolyte is observed in the X-ray diffraction pattern in a powder X-ray diffraction (XRD) measurement, and it does not matter whether or not there is a peak derived from the raw material of the solid electrolyte. That is, the crystalline sulfide solid electrolyte includes a crystal structure derived from a solid electrolyte, and a part of the crystal structure may be derived from the solid electrolyte, or the whole of the crystal structure may be derived from the solid electrolyte. And, as long as the crystalline sulfide solid electrolyte has the X-ray diffraction pattern as described above, a part of the crystalline sulfide solid electrolyte (also called "glass component") may be included. Therefore, the crystalline sulfide solid electrolyte includes so-called glass ceramics obtained by heating the amorphous solid electrolyte (glass component) to a crystallization temperature or higher.

[0034] In this specification, the amorphous sulfide solid electrolyte (glass component) refers to one in which the X-ray diffraction pattern in a powder X-ray diffraction (XRD) measurement is a halo pattern in which no peaks other than those derived from the material are observed, and it does not matter whether or not there are peaks derived from the raw materials of the solid electrolyte.

[0035] [Method for producing sulfide solid electrolyte] The method for producing the sulfide solid electrolyte of the present embodiment includes mixing raw material components including lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms in a solvent; and heating, The solvent is characterized in that it contains a complexing agent containing a monoamine compound having a six-membered ring structure containing one heteroatom.

[0036] (Raw material content) The raw material content used in this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. More specifically, the raw material content is a content containing a substance containing these atoms (hereinafter also referred to as "solid electrolyte raw material"), and preferably contains two or more solid electrolyte raw materials.

[0037] Examples of the solid electrolyte raw material include lithium sulfide; lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; diphosphorus trisulfide (P 2 S 3 ), diphosphorus pentasulfide (P 2 S 5 ) and other phosphorus sulfides; and raw materials containing at least two kinds of atoms selected from the above-mentioned atoms, as well as fluorine (F 2 ), Chlorine (Cl 2 ), Bromine (Br 2 ), iodine (I 2 Representative examples of the raw material include a halogen element such as halogen, phosphorus, and sulfur.

[0038] Among the above, examples of the solid electrolyte raw material containing lithium atoms, sulfur atoms, and phosphorus atoms include lithium sulfide; diphosphorus trisulfide (P 2 S 3 ), diphosphorus pentasulfide (P 2 S 5 Among the phosphorus sulfides, diphosphorus pentasulfide is preferred.

[0039] Among the above, as the solid electrolyte raw material containing a halogen atom, either a simple halogen or a lithium halide can be preferably used. The halogen atoms contained in the raw material are preferably fluorine, chlorine, bromine, and iodine atoms, more preferably chlorine, bromine, and iodine atoms, and even more preferably bromine and iodine atoms. The solid electrolyte raw material is preferably one containing these halogen atoms. Therefore, the halogen element is preferably chlorine (Cl 2 ), Bromine (Br 2 ), iodine (I 2) is more preferred, and bromine (Br 2 ) and iodine (I 2 As the lithium halide, lithium chloride, lithium bromide, and lithium iodide are more preferred, and lithium bromide and lithium iodide are even more preferred. These may be used alone or in combination.

[0040] As the combination of the solid electrolyte raw materials contained in the raw material inclusion, for example, a combination of lithium sulfide, phosphorus sulfide and lithium halide, a combination of lithium sulfide, phosphorus sulfide and a halogen element, a combination of lithium sulfide, phosphorus sulfide, lithium halide and a halogen element are preferably mentioned, and a combination of lithium sulfide, diphosphorus pentasulfide and lithium halide, and a combination of lithium sulfide, diphosphorus pentasulfide and a halogen element are more preferably mentioned. In addition, in the above combination, lithium bromide and lithium iodide are preferable as the lithium halide, and bromine and iodine are preferable as the halogen element. As described above, the solid electrolyte raw material containing halogen atoms can be selected according to the type of sulfide solid electrolyte to be obtained.

[0041] The raw material contains at least two kinds of atoms selected from the above-mentioned elements. The other solid electrolyte raw materials include various phosphorus fluorides (PF 3 , P.F. 5 ), various phosphorus chlorides (PCl 3 , PCl 5 , P 2 Cl 4 ), various phosphorus bromides (PBr 3 , PBr 5 ), various phosphorus iodides (PI 3 , P 2 I 4 Phosphorus halides such as thiophosphoryl fluoride (PSF 3 ), thiophosphoryl chloride (PSCl 3 ), thiophosphoryl bromide (PSBr 3 ), thiophosphoryl iodide (PSI 3 ), thiophosphoryl dichloride fluoride (PSCl 2F), thiophosphoryl dibromide fluoride (PSBr 2 F) and the like.

[0042] Examples of solid electrolyte raw materials other than those mentioned above that are contained in the raw material inclusion include solid electrolyte raw materials that contain at least one atom selected from the above-mentioned atoms and also contain atoms other than the above-mentioned atoms, more specifically, lithium compounds such as lithium oxide, lithium hydroxide, and lithium carbonate; alkali metal sulfides such as sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide; silicon sulfide, germanium sulfide, boron sulfide, gallium sulfide, and tin sulfide (SnS, SnS 2 ), metal sulfides such as aluminum sulfide and zinc sulfide; phosphate compounds such as sodium phosphate and lithium phosphate; halides of alkali metals other than lithium, such as sodium halides such as sodium iodide, sodium fluoride, sodium chloride and sodium bromide; metal halides such as aluminum halides, silicon halides, germanium halides, arsenic halides, selenium halides, tin halides, antimony halides, tellurium halides and bismuth halides; phosphorus oxychloride (POCl 3 ), phosphorus oxybromide (POBr 3 ) and the like phosphorus oxyhalides; When oxygen atoms are introduced into the solid electrolyte, lithium oxide, lithium hydroxide, and phosphate compounds such as lithium phosphate are preferred.

[0043] In this embodiment, PS 4 Structure containing Li 3 P.S. 4 can also be used as a solid electrolyte raw material. 3 P.S. 4 In this case, the combination of solid electrolyte raw materials contained in the raw material is Li 3 P.S. 4 and the lithium halide, Li 3 P.S. 4 and the above-mentioned elemental halogens, Li 3P.S. 4 and the lithium halide and an elemental halogen.

[0044] The solid electrolyte raw material such as lithium sulfide used in this embodiment is preferably in the form of particles. The average particle size of the solid electrolyte raw material (D 50 ) is preferably 0.1 to 1000 μm, more preferably 0.5 to 100 μm, and further preferably 1 to 20 μm. 50 ) is the particle size at which the particle size distribution cumulative curve is accumulated from the smallest particle size to 50% (volume basis) of the total, and the volume distribution is the average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device. In addition, among the examples of the raw materials, the solid raw materials preferably have an average particle size approximately the same as that of the lithium sulfide particles, that is, preferably within the same range as the average particle size of the lithium sulfide particles.

[0045] When the raw material contains lithium sulfide, diphosphorus pentasulfide, and lithium halide, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, and even more preferably 74 mol% or more, and the upper limit is preferably 85 mol% or less, more preferably 83 mol% or less, and even more preferably 80 mol% or less, from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. The range is typically preferably 60 to 85 mol%, more preferably 65 to 83 mol%, even more preferably 70 to 80 mol%, and even more preferably 74 to 80 mol%. Furthermore, when a sulfide solid electrolyte having a thiolithium region II crystal structure is to be obtained, in addition to the above range, 74 to 78.5 mol%, 74 to 78 mol%, and 74 to 76 mol% are particularly preferred. When a sulfide solid electrolyte having an argyrodite crystal structure is to be obtained, in addition to the above range, 76 to 83 mol%, 77 to 80 mol%, and 78 to 80 mol% are particularly preferred.

[0046] When the raw material content includes lithium sulfide, diphosphorus pentasulfide, lithium halide, and other raw materials used as necessary, the content of lithium sulfide and diphosphorus pentasulfide relative to the total is preferably 50 mol% or more, more preferably 55 mol% or more, and even more preferably 60 mol% or more, and the upper limit is preferably 100 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less, and even more preferably 80 mol% or less. The range is typically preferably 50 to 100 mol%, more preferably 55 to 90 mol%, even more preferably 60 to 85 mol%, and even more preferably 60 to 80 mol%. Furthermore, when a sulfide solid electrolyte having a thiolicon region II type crystal structure is to be obtained, in addition to the above range, particularly preferably 65 to 90 mol%, 70 to 85 mol%, or 75 to 83 mol%, and when a sulfide solid electrolyte having an argyrodite type crystal structure is to be obtained, in addition to the above range, particularly preferably 50 to 78 mol%, 55 to 70 mol%, or 55 to 65 mol%.

[0047] When the raw material contains lithium bromide and lithium iodide in combination as lithium halides, from the viewpoint of improving ion conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 mol% or more, more preferably 20 mol% or more, even more preferably 35 mol% or more, and even more preferably 45 mol% or more, and the upper limit is preferably 99 mol% or less, more preferably 90 mol% or less, even more preferably 75 mol% or less, and even more preferably 60 mol% or less. The range is typically preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 35 to 75 mol%, and even more preferably 45 to 60 mol%. When it is desired to obtain a sulfide solid electrolyte having a thiolicon region II type crystal structure, the content is preferably 40 to 75 mol %, 40 to 65 mol %, or 45 to 55 mol %, in addition to the above range.

[0048] In addition, when the raw material contains lithium bromide and lithium chloride in combination as lithium halides, from the viewpoint of improving ion conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium chloride is preferably 1 mol% or more, more preferably 15 mol% or more, even more preferably 25 mol% or more, and even more preferably 35 mol% or more, and the upper limit is preferably 99 mol% or less, more preferably 75 mol% or less, even more preferably 60 mol% or less, and even more preferably 45 mol% or less. The range is typically preferably 1 to 99 mol%, more preferably 15 to 75 mol%, even more preferably 25 to 60 mol%, and even more preferably 35 to 45 mol%. When it is desired to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure, the content is preferably 25 to 45 mol %, or 35 to 40 mol %, in addition to the above range.

[0049] In the case where the raw material contains a halogen element as a raw material, and contains lithium sulfide and diphosphorus pentasulfide, the ratio of the number of moles of lithium sulfide excluding the same number of moles of lithium sulfide as the halogen element to the total number of moles of lithium sulfide and diphosphorus pentasulfide excluding the same number of moles of lithium sulfide as the halogen element is preferably within the range of 60 to 90%, more preferably within the range of 65 to 85%, even more preferably within the range of 68 to 82%, even more preferably within the range of 72 to 78%, and particularly preferably within the range of 73 to 77%. This is because higher ion conductivity can be obtained at these ratios.

[0050] From the same viewpoint, when the raw material contains lithium sulfide, diphosphorus pentasulfide, and an elemental halogen, the content of the elemental halogen relative to the total amount of lithium sulfide, diphosphorus pentasulfide, and the elemental halogen is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, even more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%.

[0051] When the raw material contents include lithium sulfide, diphosphorus pentasulfide, an elemental halogen, and a lithium halide, the content of the elemental halogen (α mol %) and the content of the lithium halide (β mol %) relative to the total amount of lithium sulfide, diphosphorus pentasulfide, the elemental halogen, and the lithium halide preferably satisfy the following formula (1), more preferably satisfy the following formula (2), even more preferably satisfy the following formula (3), and even more preferably satisfy the following formula (4). 2≦2α+β≦100…(1) 4≦2α+β≦80 …(2) 6≦2α+β≦50 …(3) 6≦2α+β≦30 …(4)

[0052] When the raw material contains two types of halogens as simple substances, the molar number of one halogen atom in the substance is A1 and the molar number of the other halogen atom in the substance is A2, and A1:A2 is preferably 1 to 99:99 to 1, more preferably 10:90 to 90:10, even more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

[0053] When the raw material contains two types of halogen elements, the two types of halogen elements being bromine and iodine, the moles of bromine are A1 and the moles of iodine are A2, and A1:A2 is preferably 1:99 to 99:1, more preferably 20:80 to 80:20, even more preferably 35:65 to 80:20, and even more preferably 45:55 to 70:30. Furthermore, when the two types of halogen elements are bromine and chlorine, the molar number of bromine is B1 and the molar number of chlorine is B2, then B1:B2 is preferably 1:99 to 99:1, more preferably 15:85 to 75:25, even more preferably 25:75 to 60:40, and even more preferably 35:45 to 65:55.

[0054] In addition, the raw material contains Li 3 P.S. 4 If raw materials are included, Li 3 P.S. 4 The content is preferably from 60 to 100 mol %, more preferably from 60 to 90 mol %, and further preferably from 65 to 80 mol %. As mentioned above, Li 3 P.S. 4 The solid electrolyte raw material may be prepared by manufacturing. In this case, it is obtained by reacting lithium sulfide with diphosphorus pentasulfide in a molar ratio of 3:1. 3 P.S. 4 When using lithium sulfide, the compounding ratio with other raw materials such as lithium halide and elemental halogen may be similar to that of the above-mentioned lithium sulfide and diphosphorus pentasulfide. For example, when lithium sulfide and diphosphorus pentasulfide are reacted in a molar ratio of 3:1, 2 moles of Li 3 P.S. 4Therefore, 2 moles of Li 3 P.S. 4 corresponds to a total of 4 moles of lithium sulfide and diphosphorus pentasulfide. Therefore, in the blending ratio when the above lithium sulfide and diphosphorus pentasulfide are used, the number of moles of lithium sulfide and diphosphorus pentasulfide is 3 P.S. 4 It is sufficient to apply it as twice the value of Li 3 P.S. 4 When using a halogen atom, Li 3 P.S. 4 The amount of the halogen element used is preferably from 1 to 50 mol %, more preferably from 10 to 40 mol %, further preferably from 20 to 30 mol %, and even more preferably from 22 to 28 mol %.

[0055] (solvent) The solvent used in the method for producing a sulfide solid electrolyte of this embodiment contains a complexing agent. The complexing agent is a compound capable of forming a complex by coordinating (bonding) with the solid electrolyte raw material contained in the raw material content, particularly with the lithium atom contained in the raw material content. The complexing agent used in this embodiment contains a monoamine compound having a six-membered ring structure containing one heteroatom.

[0056] As the solvent used in this embodiment, it is possible to widely adopt solvents that have been conventionally used in the production of solid electrolytes, for example, hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and compounds containing heteroatoms such as nitrogen atom, oxygen atom, halogen atom such as chlorine atom, and sulfur atom. Here, compounds containing heteroatoms tend to function as compounds capable of forming complexes, and are preferably used as complexing agents. Therefore, a monoamine compound having a six-membered ring structure containing one heteroatom is a solvent containing a heteroatom, but corresponds to a complexing agent as described below.

[0057] (Complexing Agent) In the method for producing a sulfide solid electrolyte of the present embodiment, a complexing agent is used as described above. In this embodiment, a complexing agent containing a monoamine compound having a six-membered ring structure containing one heteroatom (sometimes simply referred to as a "monoamine compound" in this specification) is used. In addition, in this embodiment, examples of complexing agents other than the monoamine compound include compounds containing heteroatoms such as the nitrogen atom, oxygen atom, halogen atom such as chlorine atom, and sulfur atom. The complexing agent used in this embodiment may be one type or two or more types. That is, the complexing agent used in this embodiment may be not only the monoamine compound but also other complexing agents other than the monoamine compound. The complexing agent is usually Li 3 P.S. 4 As mentioned above, a complexing agent is a compound that can form a complex by coordinating (bonding) with a lithium atom. 3 P.S. 4 In addition, since a compound containing a hetero atom such as a halogen atom is preferably used, a complex containing a halogen atom can also be easily formed.

[0058] The complexing agent can be used without any particular limitation as long as it has the above-mentioned properties and contains a monoamine compound having a six-membered ring structure containing one heteroatom. The heteroatoms present in the molecules of the complexing agent, such as nitrogen, oxygen, and chlorine, have a high affinity with lithium atoms, and are considered to have a property of easily forming a complex (hereinafter also simply referred to as a "complex") by bonding with the solid electrolyte raw material contained in the raw material content. Therefore, it is considered that a complex is formed by mixing the solid electrolyte raw material with the complexing agent, and the dispersion state of the solid electrolyte raw material, especially the dispersion state of the halogen atoms, is easily maintained uniformly. Furthermore, since the complexing agent has a six-membered ring structure in the molecule, the effect of easily removing the complexing agent during heating is obtained, and as a result, it is considered that a sulfide solid electrolyte with high ionic conductivity is obtained.

[0059] From the viewpoint of easily obtaining the effects of the present application, the heteroatom in the six-membered ring structure may be an oxygen atom, a nitrogen atom, a chlorine atom, a phosphorus atom, a sulfur atom, etc., and an oxygen atom or a nitrogen atom is preferable, and a nitrogen atom is more preferable. That is, the monoamine compound preferably has a six-membered ring structure containing one nitrogen atom. Such a monoamine compound can also be said to be a compound in which the one nitrogen atom forms an amino group.

[0060] In this embodiment, the number of heteroatoms contained in the molecule of the complexing agent is 1 or more. The upper limit is preferably 4 or less, more preferably 2 or less, and particularly preferably 1. That is, it is particularly preferable that the complexing agent contains only one heteroatom in the molecule.

[0061] Specifically, the six-membered ring structure containing one nitrogen atom preferably has a piperidine skeleton or a pyridine skeleton, and more preferably has a piperidine skeleton. That is, the monoamine compound preferably has a piperidine skeleton.

[0062] Examples of the monoamine compound having a piperidine skeleton include unsubstituted or substituted piperidines, and from the viewpoint of easily achieving the effects of the present invention, substituted piperidines are preferred. As the piperidine having a substituent, it is possible to adopt piperidines to which an aliphatic hydrocarbon group such as an alkyl group or an alkenyl group, an alicyclic hydrocarbon group such as a cycloalkyl group, an aromatic hydrocarbon group such as a phenyl group, the above-mentioned heteroatom, or a heteroatom-containing group containing the above-mentioned heteroatom such as a hydroxyl group, etc. is added. Among them, piperidines to which an aliphatic hydrocarbon group is added are preferred, and piperidines to which an alkyl group is added are more preferred. These groups may be added to a carbon atom or a nitrogen atom in the piperidine molecule, but from the viewpoint of easily obtaining the effect of the present invention, it is preferred that they are added to a nitrogen atom. The number of carbon atoms in the aliphatic hydrocarbon group is preferably 1 or more. Also, it is preferably 12 or less, more preferably 8 or less, even more preferably 4 or less, and still more preferably 2 or less. Also, it is particularly preferably 1. Also, the hydrocarbon group may be linear or branched. In view of the above, the monoamine compound having a six-membered ring structure containing one heteroatom is particularly preferably 1-methylpiperidine.

[0063] The amount of the complexing agent used per 1 g of the total mass of the raw materials is preferably 0.1 to 30 mL, more preferably 0.5 to 20 mL, and even more preferably 1.5 to 15 mL, from the viewpoint of efficiently obtaining the effect of using the complexing agent, that is, forming a complex in which the halogen atoms are more dispersed and fixed, and obtaining a glass ceramic solid electrolyte with high ionic conductivity.

[0064] (Other complexing agents) In this embodiment, the monoamine compound may be used by adding other complexing agents. As the complexing agent other than the monoamine compound, for example, a compound having a group containing a hetero element such as an oxygen element or a halogen element such as a chlorine element has a high affinity with lithium element, and can be cited as the complexing agent other than the monoamine compound. Among them, specific examples of the compound containing an oxygen element include 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; and the like. In addition, a compound having a nitrogen element as a hetero element and a group other than an amino group, such as a nitro group, an amide group, etc., can also provide the same effect. In this embodiment, the content of the monoamine compound in the complexing agent is preferably as high as possible, specifically, 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass, that is, it is particularly preferable that the entire amount of the complexing agent is the monoamine compound.

[0065] (Other solvents) In this embodiment, a solvent other than the complexing agent (hereinafter also referred to as "other solvent") may be used as the solvent, and can be used when mixing the raw material ingredients and the complexing agent. When a solid complex is formed in a liquid complexing agent, if the complex is easily dissolved in the complexing agent, separation of the components may occur. Therefore, by using a solvent in which the complex is not dissolved, it is possible to suppress the dissolution of the components in the resulting sulfide solid electrolyte. In addition, by mixing the raw materials and the complexing agent using a solvent, the complex formation is promoted, each main component can be more evenly present, and a complex in which the halogen element is more dispersed and fixed can be obtained, which makes it easier to achieve the effect of obtaining high ionic conductivity.

[0066] The method for producing a solid electrolyte according to the present embodiment is a so-called heterogeneous method, and it is preferable that the complex does not completely dissolve in the liquid complexing agent but precipitates. The solubility of the complex can be adjusted by adding a solvent. In particular, since halogen elements are easily eluted from the complex, the elution of the halogen elements can be suppressed by adding a solvent to obtain a desired complex. As a result, a crystalline solid electrolyte having high ionic conductivity can be obtained through a complex in which components such as halogens are dispersed.

[0067] Preferred examples of solvents having such properties include solvents having a solubility parameter of 10 or less. In this specification, the solubility parameter is a value δ ((cal / cm) calculated by the following formula (1) as described in various documents, such as "Chemical Handbook" (published in 2004, revised 5th edition, Maruzen Co., Ltd.). 3 ) 1 / 2 ) and is also called the Hildebrand parameter or SP value.

[0068]

number

[0069] By using a solvent with a solubility parameter of 10 or less, it is possible to make it difficult to dissolve the halogen element, the raw material containing the halogen element such as lithium halide, and further the component containing the halogen element constituting the cocrystal contained in the complex (for example, an aggregate in which lithium halide and the complexing agent are bonded), etc., compared to the complexing agent, and it becomes easy to fix the halogen element in the complex, and the halogen element is present in a well-dispersed state in the obtained complex and further in the solid electrolyte, and it becomes easy to obtain a solid electrolyte having high ionic conductivity. That is, it is preferable that the solvent used in this embodiment has a property in which the complex does not dissolve. 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.

[0070] More specifically, the solvent used in this embodiment can be a wide variety of solvents that have been used conventionally in the production of solid electrolytes, such as hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; alcohol solvents, ester solvents, aldehyde solvents, ketone solvents, ether solvents with 4 or more carbon atoms on one side, and solvents containing carbon atoms and heteroatoms; and the like. Among these, preferably, those with a solubility parameter in the above range may be appropriately selected and used. Note that, although alcohol solvents and the like are compounds containing heteroatoms, those with a solubility parameter in the above range may function as a simple solvent because they are less likely to function as a complexing agent in relation to the monoamine compound used as a complexing agent.

[0071] More specifically, aliphatic hydrocarbon solvents such as hexane (7.3), pentane (7.0), 2-ethylhexane, heptane (7.4), octane (7.5), decane, undecane, dodecane, tridecane, etc.; alicyclic hydrocarbon solvents such as cyclohexane (8.2) and methylcyclohexane, etc.; benzene, toluene (8.8), xylene (8.8), mesitylene, ethylbenzene (8.8), tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene (9.5), chlorotoluene (8.8), bromobenzene, etc. Examples of aromatic hydrocarbon solvents include: alcohol solvents such as ethanol (12.7) and butanol (11.4); aldehyde solvents such as formaldehyde, acetaldehyde (10.3), and dimethylformamide (12.1); ketone solvents such as acetone (9.9) and methyl ethyl ketone; ether solvents such as dibutyl ether, cyclopentyl methyl ether (8.4), tert-butyl methyl ether, and anisole; and solvents containing carbon atoms and heteroatoms such as acetonitrile (11.9), dimethyl sulfoxide, and carbon disulfide. The numbers in parentheses in the above examples are SP values.

[0072] Among these solvents, aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and ether-based solvents are preferred, and from the viewpoint of obtaining a more stable and high ion conductivity, heptane, cyclohexane, toluene, ethylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, dimethoxyethane, cyclopentyl methyl ether, tert-butyl methyl ether, and anisole are more preferred, diethyl ether, diisopropyl ether, and dibutyl ether are even more preferred, and diisopropyl ether and dibutyl ether are even more preferred. In addition, it is preferable to use a hydrocarbon solvent, and it is particularly preferable to use cyclohexane. 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 may be used alone or in combination.

[0073] (mixture) The manufacturing method of this embodiment includes mixing the raw material ingredients in a solvent containing the complexing agent.

[0074] In this embodiment, the raw material content and the complexing agent may be mixed in either a solid or liquid form, but since the solid electrolyte raw material contained in the raw material content contains a solid, and the complexing agent is liquid, they are usually mixed in a form (slurry form) in which the solid electrolyte raw material exists in the liquid complexing agent. In addition, when mixing the raw material and the complexing agent, a solvent may be further mixed as necessary. Hereinafter, in the section explaining the mixing of the raw material and the complexing agent, unless otherwise specified, the complexing agent also includes the solvent used as necessary.

[0075] There is no particular limitation on the method for mixing the solid electrolyte raw material and the complexing agent, and the solid electrolyte raw material and the complexing agent may be mixed in a device capable of mixing the solid electrolyte raw material and the complexing agent. For example, it is preferable to supply the complexing agent into a tank, operate the stirring blade, and then gradually add the solid electrolyte raw material, since this provides a good mixed state of the solid electrolyte raw material and improves the dispersibility of the raw material. However, when a halogen element is used as the solid electrolyte raw material, the solid electrolyte raw material may not be solid, specifically, fluorine and chlorine are gaseous, and bromine is liquid, at room temperature and normal pressure. In such a case, for example, when the solid electrolyte raw material is liquid, it may be supplied into the tank together with a complexing agent separately from other solid solid electrolyte raw materials, and when the solid electrolyte raw material is gas, it may be supplied by blowing into the mixture of the solid solid electrolyte raw material and the complexing agent.

[0076] The manufacturing method of this embodiment is characterized by including mixing the solid electrolyte raw material and the complexing agent. That is, since it is sufficient to mix the solid electrolyte raw material and the complexing agent, and grinding is not required, the solid electrolyte raw material can be manufactured by a method that does not use equipment generally called a grinder, such as a media-type grinder such as a ball mill or a bead mill, which is used for the purpose of grinding the solid electrolyte raw material. In the manufacturing method of this embodiment, the solid electrolyte raw material and the complexing agent contained in the raw material content are mixed by simply mixing the solid electrolyte raw material and the complexing agent, and a complex, i.e., an electrolyte precursor, can be formed. In addition, in order to shorten the mixing time to obtain the complex or to pulverize it, the mixture of the raw material and the complexing agent may be ground by a grinder, but as already described, it is preferable not to use a grinder.

[0077] An example of an apparatus for mixing the solid electrolyte raw material and the complexing agent is a mechanical stirring mixer equipped with stirring blades in a tank. Examples of mechanical stirring mixers include high-speed stirring mixers and double-arm mixers, and the high-speed stirring mixer is preferably used from the viewpoint of increasing the uniformity of the solid electrolyte raw material in the mixture of the solid electrolyte raw material and the complexing agent and obtaining higher ion conductivity. Examples of the high-speed stirring mixer include a vertical shaft rotary mixer and a horizontal shaft rotary mixer, and either type of mixer may be used.

[0078] Examples of the shape of the stirring blade used in the mechanical stirring mixer include a blade type, an arm type, an anchor type, a paddle type, a full zone type, a ribbon type, a multi-stage blade type, a double arm type, a shovel type, a biaxial blade type, a flat blade type, a C-shaped blade type, and the like. From the viewpoint of improving the uniformity of the solid electrolyte raw material and obtaining higher ion conductivity, the shovel type, the flat blade type, the C-shaped blade type, and the like are preferred.

[0079] In addition, in a mechanical stirring mixer, it is preferable to install a circulation line that discharges the material to be stirred outside the mixer and then returns it to the inside of the mixer. This allows raw materials with a high specific gravity, such as lithium halide, to be stirred without settling or remaining in the mixer, making it possible to mix more uniformly. The location of the circulation line is not particularly limited, but it is preferable to install it at a location where it can be discharged from the bottom of the mixer and returned to the top of the mixer. This makes it easier to uniformly mix the solid electrolyte raw material, which tends to settle, by carrying it on the convection caused by the circulation. Furthermore, it is preferable that the return port is located below the liquid surface of the object to be mixed. This can prevent the object to be mixed from splashing and adhering to the wall surface inside the mixer.

[0080] The temperature conditions when mixing the solid electrolyte raw material and the complexing agent are not particularly limited, and are, for example, −30 to 100° C., preferably −10 to 50° C., and more preferably about room temperature (23° C.) (for example, about room temperature ±5° C.) The mixing time is about 0.1 to 150 hours, and from the viewpoint of more uniform mixing and obtaining higher ionic conductivity, is preferably 1 to 120 hours, more preferably 4 to 100 hours, and even more preferably 8 to 80 hours.

[0081] By mixing the solid electrolyte raw material and the complexing agent, a complex is formed by the solid electrolyte raw material and the complexing agent. The complex corresponds to the electrolyte precursor as described above, and more specifically, it is considered that the lithium atom, the sulfur atom, the phosphorus atom, and the halogen atom contained in the solid electrolyte raw material are directly bonded to each other with and / or without the complexing agent due to the action of the complexing agent and the lithium atom, the sulfur atom, the phosphorus atom, and the halogen atom contained in the solid electrolyte raw material. That is, in the manufacturing method of this embodiment, the complex obtained by mixing the solid electrolyte raw material and the complexing agent, that is, the electrolyte precursor, can be said to be composed of the complexing agent, the lithium atom, the sulfur atom, the phosphorus atom, and the halogen atom. When a monoamine compound having a six-membered ring structure containing one heteroatom is used as the complexing agent, the electrolyte precursor obtained in the manufacturing method of this embodiment is an electrolyte precursor composed of a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom, and a complexing agent containing a monoamine compound having a six-membered ring structure containing one heteroatom. The complex obtained in this embodiment is not completely dissolved in the complexing agent, which is a liquid, and is usually a solid, so that a suspension (containing an electrolyte precursor) in which the complex is suspended in the complexing agent and a solvent used as necessary is obtained. Therefore, the method for producing a solid electrolyte in this embodiment corresponds to a heterogeneous system in a so-called liquid phase method.

[0082] By selecting the size and material of the medium (beads, balls) used, the rotor rotation speed, time, etc., it is possible to perform mixing, stirring, crushing, or any combination of these processes, and it is possible to adjust the particle size, etc. of the resulting crystalline sulfide solid electrolyte.

[0083] (Obtaining the electrolyte precursor) In the method for producing the sulfide solid electrolyte of the present embodiment, it is preferable that the mixing produces an electrolyte precursor containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and a complexing agent containing the monoamine compound. More specifically, it is preferred that the solvent comprises solvent A including a solvent containing an oxygen atom and solvent B including a complexing agent including the monoamine compound, the raw material contents comprise substance group C including lithium atoms, sulfur atoms, and phosphorus atoms, and substance group D including halogen atoms, and that the mixing is carried out by the following (i) and (ii). (i) Mixing the substance group C in the solvent A to obtain amorphous Li 3 P.S. 4 To obtain. (ii) In the solvent B, the amorphous Li 3 P.S. 4 and the substance group D to obtain an electrolyte precursor.

[0084] The oxygen atom-containing solvent functions as a complexing agent in (i) above. Specific examples of the oxygen atom-containing solvent include ester solvents, aldehyde solvents, ketone solvents, ether solvents, etc., as described above. Among these, the oxygen atom-containing solvent is preferably an ether solvent, more preferably diethyl ether, diisopropyl ether, dibutyl ether, or tetrahydrofuran, and even more preferably tetrahydrofuran.

[0085] As the solvent A, in addition to the above-mentioned solvents, various solvents can be used, such as aliphatic hydrocarbon solvents such as hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane; alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, mesitylene, ethylbenzene, and tert-butylbenzene; and paraffin-based solvents such as an oligomer obtained by polymerizing at least one kind of normal paraffin, such as normal butene and normal propylene, with a polymerization degree of about 3 to 10 and its hydrogenated derivative, and an isoparaffin-based solvent which is an oligomer obtained by polymerizing at least one kind of paraffin, such as isobutene, normal butene, normal propylene, and isopropylene, containing at least isoparaffin, with a polymerization degree of about 3 to 10 and its hydrogenated derivative.

[0086] In the above (i), the substance group C containing lithium atoms, sulfur atoms, and phosphorus atoms includes, as described above, lithium sulfide; diphosphorus trisulfide (P 2 S 3 ), diphosphorus pentasulfide (P 2 S 5 Among the phosphorus sulfides, diphosphorus pentasulfide is preferred.

[0087] The preferred embodiment of the mixing in (i) above is as described above. In the above (i), by the mixing, a substance containing a complex formed by the substance group C and the solvent containing an oxygen atom as a complexing agent is obtained. The step (i) includes removing the complexing agent from the complex obtained by the mixing to obtain amorphous Li 3 P.S. 4 A preferred embodiment of the drying step is as described below.

[0088] In the above (ii), as described above, either a halogen atom or a lithium halide can be preferably used as the halogen atom-containing substance group D. In addition, the preferred embodiment of the solvent B containing the complexing agent containing the monoamine compound and the preferred embodiment of mixing are as described above.

[0089] (Dry) The manufacturing method of this embodiment may include drying the electrolyte precursor-containing material after obtaining the electrolyte precursor-containing material. In removing the complexing agent, by heating the electrolyte precursor obtained by drying the electrolyte precursor-containing material, the electrolyte precursor can be heated more directly, and therefore the complexing agent can be separated and removed more efficiently from the electrolyte precursor.

[0090] Examples of the drying method include filtration using a glass filter or the like, solid-liquid separation by decantation, and solid-liquid separation using a centrifuge, etc. Specifically, solid-liquid separation can be easily performed by decantation, in which the suspension is transferred to a container, a solid is precipitated, and then the complexing agent and a solvent used as necessary are removed as a supernatant, or by filtration using a glass filter having a pore size of about 10 to 200 μm, preferably 20 to 150 μm.

[0091] Alternatively, drying can be carried out by heating using a dryer or the like. The electrolyte precursor-containing material may be dried under any pressure condition, such as under pressure, normal pressure, or reduced pressure, and is preferably dried under normal pressure or reduced pressure. In particular, when drying is performed at a lower temperature, it is preferable to dry the material under reduced pressure, or even under vacuum, using a vacuum pump or the like.

[0092] The temperature conditions for drying may be a temperature equal to or higher than the boiling point of the remaining complexing agent or the solvent used as necessary. Since the temperature conditions may vary depending on the type of complexing agent and solvent used, the specific temperature conditions cannot be generally stated, but the temperature is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, and the upper limit is preferably 110°C or lower, more preferably 85°C or lower, and even more preferably 70°C or lower.

[0093] As for the pressure conditions, as described above, normal pressure or reduced pressure is preferable. In the case of reduced pressure, specifically, the pressure is preferably 85 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less. The lower limit may be a vacuum (0 KPa). Considering the ease of adjusting the pressure, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more.

[0094] In the production method of this embodiment, when drying is performed, drying may be performed while heating after the solid-liquid separation. In the manufacturing method of the present embodiment, drying may or may not be performed. That is, in the manufacturing method of the present embodiment, the object to be heated may be the electrolyte precursor-containing material or the electrolyte precursor obtained by drying.

[0095] (heating) The method for producing the sulfide solid electrolyte of the present embodiment includes heating. The heating includes, for example, heating the electrolyte precursor-containing material obtained by the mixing or the electrolyte precursor obtained by the drying to remove the complexing agent from the electrolyte precursor; heating the electrolyte precursor-containing material or the electrolyte precursor from which the complexing agent has been removed to obtain a crystalline sulfide solid electrolyte; when an amorphous sulfide solid electrolyte is obtained by removing the complexing agent from the electrolyte precursor, heating the amorphous sulfide solid electrolyte to obtain a crystalline sulfide solid electrolyte; and heating the electrolyte precursor to obtain a crystalline sulfide solid electrolyte.

[0096] By heating, the complexing agent in the electrolyte precursor is removed, and a sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms is obtained. Here, the removal of the complexing agent in the electrolyte precursor is supported by the fact that it can be confirmed from the results of X-ray diffraction patterns, gas chromatography analysis, etc. that the complexing agent constitutes the electrolyte precursor (complex), and in addition, the X-ray diffraction pattern of the sulfide solid electrolyte obtained by removing the complexing agent from the electrolyte precursor is the same as that of the sulfide solid electrolyte obtained by a conventional method without using a complexing agent.

[0097] In the manufacturing method of this embodiment, a crystalline sulfide solid electrolyte may be obtained by heating an electrolyte precursor-containing material or an electrolyte precursor, or a sulfide solid electrolyte that can become an amorphous sulfide solid electrolyte may be obtained by first heating an electrolyte precursor-containing material or an electrolyte precursor to obtain an amorphous sulfide solid electrolyte, and then heating the amorphous sulfide solid electrolyte. That is, according to the manufacturing method of this embodiment, an amorphous sulfide solid electrolyte can also be produced.

[0098] In the manufacturing method of this embodiment, whether to obtain an amorphous sulfide solid electrolyte, a crystalline sulfide solid electrolyte, or even to obtain a crystalline sulfide solid electrolyte after obtaining an amorphous sulfide solid electrolyte, or to obtain a crystalline sulfide solid electrolyte directly from an electrolyte precursor-containing material or an electrolyte precursor is appropriately selected according to desire, and can be adjusted by the heating temperature, heating time, etc.

[0099] The heating temperature may be determined according to the structure of the crystalline sulfide solid electrolyte obtained by heating the amorphous sulfide solid electrolyte, for example, when obtaining an amorphous sulfide solid electrolyte (including the case of removing a complexing agent from an electrolyte precursor). Specifically, the amorphous sulfide solid electrolyte is subjected to differential thermal analysis (DTA) at a temperature rise rate of 10°C / min using a differential thermal analyzer (DTA device), and the heating temperature is preferably set to 5°C or less, more preferably 10°C or less, and even more preferably 20°C or less, starting from the temperature of the top of the exothermic peak observed on the lowest temperature side. There is no particular limit to the lower limit, but it may be set to about -40°C or more, which is the temperature of the top of the exothermic peak observed on the lowest temperature side. By setting the temperature range, an amorphous sulfide solid electrolyte (one in which the complexing agent has been removed from the electrolyte precursor) can be obtained more efficiently and reliably.

[0100] The heating temperature for obtaining an amorphous sulfide solid electrolyte (including the heating temperature for removing the complexing agent from the electrolyte precursor) cannot be generally specified because it varies depending on the structure of the crystalline sulfide solid electrolyte to be obtained. However, it is usually preferably 135° C. or lower, more preferably 130° C. or lower, and even more preferably 125° C. or lower. There is no particular lower limit, but it is preferably 90° C. or higher, more preferably 100° C. or higher, and even more preferably 105° C. or higher.

[0101] When obtaining a crystalline sulfide solid electrolyte, the heating temperature may be determined according to the structure of the crystalline sulfide solid electrolyte, and is preferably higher than the heating temperature for obtaining an amorphous sulfide solid electrolyte. Specifically, the amorphous sulfide solid electrolyte is subjected to differential thermal analysis (DTA) at a temperature rise rate of 10°C / min using a differential thermal analyzer (DTA device), and the temperature is preferably set to 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, starting from the peak top temperature of the exothermic peak observed on the lowest temperature side. There is no particular limit to the upper limit, but it may be about 40°C or lower. By setting the temperature range, a crystalline sulfide solid electrolyte can be obtained more efficiently and reliably.

[0102] The heating temperature for obtaining a crystalline sulfide solid electrolyte cannot be generally defined because it varies depending on the composition and structure of the crystalline sulfide solid electrolyte to be obtained. Generally, however, the heating temperature is preferably 130° C. or higher, more preferably 135° C. or higher, and even more preferably 140° C. or higher. There is no particular upper limit, but the heating temperature is preferably 600° C. or lower, more preferably 550° C. or lower, and even more preferably 500° C. or lower.

[0103] The heating time is not particularly limited as long as the desired amorphous sulfide solid electrolyte or crystalline sulfide solid electrolyte can be obtained, but is preferably, for example, 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.

[0104] The heating is preferably performed in an inert gas atmosphere (e.g., nitrogen atmosphere, argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum). For example, an inert gas atmosphere containing a certain concentration of hydrogen may be used. This is because deterioration (e.g., oxidation) of the crystalline sulfide solid electrolyte can be prevented. The heating method is not particularly limited, and examples thereof include a method using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, a baking furnace, etc. Also, for industrial purposes, a horizontal dryer having a heating means and a feeding mechanism, a horizontal vibration fluidized dryer, etc. may be used, and may be selected according to the amount of processing to be heated.

[0105] (Amorphous sulfide solid electrolyte) The sulfide solid electrolyte obtained by the manufacturing method of this embodiment is either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte.

[0106] The amorphous sulfide solid electrolyte produced by the manufacturing method of this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. Representative examples include Li 2 SP 2 S 5 - LiI, Li 2 SP 2 S 5 -LiCl, Li 2 SP 2 S 5 -LiBr, Li 2 SP 2 S 5 -LiI-LiBr, etc., which are solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide; and solid electrolytes containing other atoms such as oxygen and silicon atoms, e.g., Li 2 SP 2 S 5 -Li 2 O-LiI, Li 2 S-SiS 2 -P 2 S 5 In order to obtain a higher ionic conductivity, a solid electrolyte such as Li-LiI is preferable. 2 SP2 S 5 - LiI, Li 2 SP 2 S 5 -LiCl, Li 2 SP 2 S 5 -LiBr, Li 2 SP 2 S 5 A solid electrolyte composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li-LiI-LiBr, is preferred. 2 SP 2 S 5 A solid electrolyte composed of lithium sulfide, phosphorus sulfide, and two kinds of lithium halides, such as --LiI-LiBr, is more preferable. The types of atoms constituting the sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectroscopic analyzer.

[0107] In the solid electrolyte (amorphous solid electrolyte and crystalline solid electrolyte) obtained by the method for producing a solid electrolyte of the present embodiment, the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms is preferably 1.0-1.8:0.1-0.8:1.0-2.0:0.01-0.6, more preferably 1.1-1.7:0.2-0.6:1.2-1.8:0.05-0.5, and still more preferably 1.2-1.6:0.25-0.5:1.3-1.7:0.08-0.4. Furthermore, when bromine and iodine, or bromine and chlorine are used in combination as halogen atoms, the composition ratio (molar ratio) of lithium atoms, phosphorus atoms, sulfur atoms, bromine, and iodine (or chlorine) is preferably 1.0-1.8:0.1-0.8:1.0-2.0:0.01-0.3:0.01-0.3, more preferably 1.1-1.7:0.2-0.6:1.2-1.8:0.02-0.25:0.02-0.25, even more preferably 1.2-1.6:0.25-0.5:1.3-1.7:0.03-0.2:0.03-0.2, and still more preferably 1.35-1.45:0.3-0.45:1.4-1.7:0.04-0.18:0.04-0.18. By setting the composition ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above range, it becomes easier to obtain a solid electrolyte having a higher ionic conductivity and a crystal structure described later, particularly a thiolicon region II type crystal structure or an argyrodite type crystal structure.

[0108] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, a particulate shape. The average particle size (D 50 ) is, for example, 0.01 μm or more, further 0.03 μm or more, 0.05 μm or more, or 0.1 μm or more, and the upper limit is 200.0 μm or less, further 100.0 μm or less, 10.0 μm or less, 1.0 μm or less, or 0.5 μm or less. (Crystalline sulfide solid electrolyte)

[0109] The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may be a so-called glass ceramic obtained by heating an amorphous sulfide solid electrolyte to a crystallization temperature or higher, and the crystal structure thereof may be Li 3 P.S. 4 Crystal structure, Li 4 P 2 S 6 Crystal structure, Li 7 P.S. 6 Crystal structure, Li 7 P 3 S 11 Examples of such structures include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0110] Li 4-x Ge 1-x P x S 4 Thio-LISICON Region II crystal structure (Kanno et al., Journal of The Electrochemical Society, 148(7)A742-746(2001)), Li 4-x Ge 1-x Px S 4 Also included are crystal structures similar to the thio-LISICON Region II type (see SoLid State Ionics, 177 (2006), 2721-2725). The crystal structure of the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is preferably the thio-LISICON Region II type crystal structure among the above, since it can provide higher ionic conductivity. Here, the "thio-LISICON Region II type crystal structure" refers to a Li 4-x Ge 1-x P x S 4 Thio-LISICON Region II crystal structure, Li 4-x Ge 1-x P x S 4 This indicates that the crystal structure is similar to that of the thio-LISICON Region II type. 4-x Ge 1-x P x S 4 The expression "thio-LISICON Region II type crystal structure" means that the crystal structure was composed of the atoms at the time of discovery in the document. The sulfide solid electrolyte obtained by the manufacturing method of the present embodiment has a thio-LISICON Region II type crystal structure, which means that a crystal structure exhibiting the same diffraction peak as that of the thio-LISICON Region II type crystal structure is formed by each atom (Li / P / S / halogen) contained in the raw material contents. The same applies to the argyrodite type crystal structure described later.

[0111] The crystalline sulfide solid electrolyte obtained by the heating may contain the thiolicon region II type crystal structure or may contain it as the main crystal, but from the viewpoint of obtaining higher ionic conductivity, it is preferable that it contains it as the main crystal. In this specification, "containing it as the main crystal" means that the ratio of the target crystal structure among the crystal structures is 80% or more, preferably 90% or more, and more preferably 95% or more. In addition, from the viewpoint of obtaining higher ionic conductivity, the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains crystalline Li 3 P.S. 4 (β-Li 3 P.S. 4 ) is preferably not included.

[0112] In X-ray diffraction measurements using CuKα radiation, Li 3 P.S. 4 Diffraction peaks of the crystal structure appear, for example, at 2θ = 17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, and Li 4 P 2 S 6 Diffraction peaks of the crystal structure appear, for example, at 2θ = 16.9°, 27.1°, and 32.5°, and Li 7 P.S. 6 Diffraction peaks of the crystal structure appear, for example, at 2θ = 15.3°, 25.2°, 29.6°, and 31.0°. 7 P 3 S 11 Diffraction peaks of the crystal structure appear, for example, at 2θ = 17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°. 4-x Ge 1-x P x S 4 The diffraction peaks of the thio-LISICON Region II crystal structure appear, for example, at 2θ = 20.1°, 23.9°, and 29.5°. 4-x Ge 1-x P x S 4Diffraction peaks with a crystal structure similar to that of the thio-LISICON Region II type appear, for example, around 2θ = 20.2° and 23.6°. Note that the peak positions may shift within a range of ±0.5°.

[0113] The above-mentioned Li 7 PS 6 Crystalline sulfide solid electrolytes having a crystal structure of the argyrodite type having the structural framework of and having a part of P substituted with Si are also preferably mentioned. As the composition formula of the argyrodite type crystal structure, for example, the composition formula Li 7-x P 1-y Si y S 6 And Li 7+x P 1-y Si y S 6 (where x is -0.6 to 0.6 and y is 0.1 to 0.6). The argyrodite type crystal structure represented by this composition formula is cubic or orthorhombic, preferably cubic, and in 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°.

[0114] As the composition formula of the argyrodite type crystal structure, the composition formula Li 7-x-2y PS 6-x-y Cl x (0.8 ≤ x ≤ 1.7, 0 < y ≤ -0.25x + 0.5) is also mentioned. The argyrodite type crystal structure represented by this composition formula is preferably cubic, and in 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°. Also, as the composition formula of the argyrodite type crystal structure, the composition formula Li 7-x PS 6-x Ha x(Ha is Cl or Br, and x is preferably 0.2 to 1.8). The argyrodite-type crystal structure represented by this composition formula is preferably a cubic crystal, and has peaks that appear mainly 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. The positions of these peaks may vary within a range of ±0.5°.

[0115] In addition, the composition ratio of the atoms contained in the crystalline sulfide solid electrolyte is preferably a composition ratio according to a composition formula corresponding to the various crystal structures, and is within the range of the composition ratio of each atom contained in the amorphous sulfide solid electrolyte. If the composition ratio of each atom is within the range, it is easy to form a thiosilicon region II type crystal structure or an argyrodite type crystal structure among the crystal structures.

[0116] The content of the complexing agent contained in the crystalline sulfide solid electrolyte obtained by the heating is less than the content of the complexing agent contained in the amorphous sulfide solid electrolyte. The content of the complexing agent in the crystalline sulfide solid electrolyte is preferably 0% by mass, i.e., no complexing agent is contained at all. From the viewpoint of efficiently obtaining a sulfide solid electrolyte with high ionic conductivity, however, the content is usually 10% by mass or less, further 8% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, with the lower limit being approximately 0.01% by mass or more.

[0117] Similarly to the complexing agent, when a solvent is used, the solvent may remain. In this case, the content of the solvent is also in the same range as the content of the complexing agent.

[0118] The shape of the crystalline sulfide solid electrolyte is not particularly limited, but may be, for example, a particulate shape. The average particle size (D 50) is, for example, 0.01 μm or more, further 0.03 μm or more, 0.05 μm or more, or 0.1 μm or more, and the upper limit is 15 μm or less, further 12 μm or less, or 10 μm or less.

[0119] Furthermore, the sulfide solid electrolyte of this embodiment preferably has an ion conductivity of 2.0 mS / cm or more, and more preferably 2.5 mS / cm or more. A specific method for measuring the ionic conductivity may be the method used in the examples.

[0120] (electrolyte precursor) The electrolyte precursor of the present embodiment is an electrolyte precursor composed of lithium atoms, sulfur atoms, phosphorus atoms, halogen atoms, and a complexing agent containing a monoamine compound having a six-membered ring structure containing one heteroatom. The electrolyte precursor of the present embodiment can be easily produced by the production method of the present embodiment. As described above, the electrolyte precursor is a complex, and is a solid electrolyte raw material coordinated (bonded) via a complexing agent. The atoms constituting the electrolyte precursor, their compounding ratios, and the complexing agent are the same as those described in the manufacturing method of this embodiment.

[0121] (Sulfide solid electrolyte) The sulfide solid electrolyte of the present embodiment is a sulfide solid electrolyte containing a monoamine compound having a six-membered ring structure containing one heteroatom and composed of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms. The sulfide solid electrolyte of the present embodiment can be easily produced by the production method of the present embodiment described above. The atoms constituting the sulfide solid electrolyte, their compounding ratios, and the complexing agent are the same as those described in the manufacturing method of this embodiment. In the sulfide solid electrolyte of this embodiment, the "complexing agent" is used in the manufacturing process and remains in the sulfide solid electrolyte. In other words, the complexing agent contained in the sulfide solid electrolyte of this embodiment makes it possible to know what solvent was used in the manufacturing process.

[0122] (Application) The sulfide solid electrolyte obtained by the manufacturing method of the present embodiment has excellent coating suitability and can be used in the manufacture of batteries without using a solvent, etc., and can efficiently exhibit excellent battery performance. In addition, since it has high ionic conductivity and excellent battery performance, it is suitable for use in batteries. The sulfide solid electrolyte obtained by the manufacturing method of the present embodiment may be used in the positive electrode layer, the negative electrode layer, or the electrolyte layer. Each of these layers can be manufactured by a known method.

[0123] In addition, the battery preferably uses a current collector in addition to the positive electrode layer, the electrolyte layer, and the negative electrode layer, and a known current collector can be used. For example, a layer of a material that reacts with the solid electrolyte, such as Au, Pt, Al, Ti, or Cu, coated with Au or the like can be used. EXAMPLES

[0124] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0125] (Measurement of ionic conductivity) The ionic conductivity was measured as follows. From the crystalline sulfide solid electrolytes obtained in the examples and comparative examples, a 10 mm diameter (cross-sectional area S: 0.785 cm 2 ) and a height (L) of 0.1-0.3 cm were molded into a circular pellet to prepare a sample. Electrode terminals were attached to the top and bottom of the sample, and measurements were made at 25°C using an AC impedance method (frequency range: 5 MHz-0.5 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S / cm) was calculated according to the following formula: R=ρ(L / S) σ=1 / ρ

[0126] (Powder X-ray diffraction (XRD) measurement) Powder X-ray diffraction (XRD) measurements were carried out as follows. The sulfide solid electrolyte powder obtained in the examples and comparative examples was filled into a groove with a diameter of 20 mm and a depth of 0.2 mm, and smoothed with glass to prepare a sample. This sample was sealed with Kapton film for XRD and measured under the following conditions without exposing it to air. Measurement equipment: D2 PHASER, manufactured by Bruker Corporation Tube voltage: 30kV Tube current: 10mA X-ray wavelength: Cu-Kα ray (1.5418Å) Optical system: Concentration method Slit configuration: Solar slit 4°, divergence slit 1mm, Kβ filter (Ni plate) Detector: Semiconductor detector Measurement range: 2θ=10-60deg Step width, scan speed: 0.05deg, 0.05deg / sec

[0127] (Production Example 1) In a 1 L reactor equipped with an agitator, 15.3 g of lithium sulfide and 24.7 g of diphosphorus pentasulfide were added under a nitrogen atmosphere. After the agitator was turned on, 400 mL of tetrahydrofuran, which had been cooled to -20°C in advance, was introduced into the vessel. After allowing the vessel to naturally warm to room temperature (23°C), stirring was continued for 72 hours. The resulting reaction liquid slurry was poured into a glass filter (pore size: 40-100 μm) to obtain a solid content, which was then dried at 90°C to obtain Li as a white powder. 3 P.S. 4 (purity: 90% by mass) was obtained. The obtained powder was subjected to powder X-ray diffraction (XRD) measurement using an X-ray diffraction (XRD) device (SmartLab device, manufactured by Rigaku Corporation). A halo pattern was observed, indicating the presence of amorphous Li 3 P.S. 4 It was confirmed that this is the case.

[0128] Example 1 In a Schlenk flask (volume: 100 mL) equipped with a stirrer, 1.70 g (Li3 P.S. 4 0.185g of lithium bromide and 0.285g of lithium iodide were introduced. After rotating the stirrer, 20mL of 1-methylpiperidine was added and stirring was continued for 72 hours. The obtained electrolyte precursor-containing material was dried under vacuum (room temperature: 23°C) to obtain a powdered electrolyte precursor. Next, the powdered electrolyte precursor was heated under vacuum at 120°C for 2 hours to obtain an amorphous solid electrolyte. Furthermore, the electrolyte precursor was heated under vacuum at 180°C for 2 hours to obtain a crystalline sulfide solid electrolyte (the heating temperature (180°C in this example) for obtaining a crystalline sulfide solid electrolyte may be referred to as the "crystallization temperature").

[0129] The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 2.9 mS / cm. In addition, in the X-ray diffraction spectrum of the crystalline sulfide solid electrolyte (Figure 1), crystallization peaks were detected mainly at 2θ = 20.4°, 23.6°, and 29.3°, and the crystalline sulfide solid electrolyte had a thiolithicomregion II crystal structure.

[0130] Example 2 A crystalline sulfide solid electrolyte of Example 2 was produced in the same manner as in Example 1, except that the 20 mL of 1-methylpiperidine in Example 1 was changed to 7.2 mL of 1-methylpiperidine and 12.8 mL of cyclohexane. The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 3.3 mS / cm. In addition, in the X-ray diffraction spectrum of the crystalline sulfide solid electrolyte (Figure 2), crystallization peaks were detected mainly at 2θ = 20.4°, 23.6°, and 29.3°, and the crystalline sulfide solid electrolyte had a thiolithicomregion II crystal structure.

[0131] Comparative Example 1 In a Schlenk flask (capacity: 100 mL) containing a stirring bar, 0.586 g of lithium sulfide, 0.945 g of diphosphorus pentasulfide, 0.185 g of lithium bromide, and 0.285 g of lithium iodide were introduced under a nitrogen atmosphere. The Schlenk flask was cooled in an ice bath, the stirring bar was rotated, and 20 mL of tetrahydrofuran was added. Stirring was continued for 72 hours, and the obtained electrolyte precursor-containing material was dried under vacuum (room temperature: 23°C) to obtain a powdered electrolyte precursor. Next, the powdered electrolyte precursor was heated under vacuum at 120°C for 2 hours to obtain an amorphous sulfide solid electrolyte. Furthermore, the amorphous sulfide solid electrolyte was heated under vacuum at 180°C for 2 hours to obtain a crystalline sulfide solid electrolyte.

[0132] The ionic conductivity of the obtained crystalline sulfide solid electrolyte was measured and found to be 1.7 mS / cm. In addition, in the X-ray diffraction spectrum of the crystalline sulfide solid electrolyte (FIG. 3), crystallization peaks were detected at 2θ=20.4°, 23.6°, and 29.3°, but compared with Examples 1 and 2, the peak at 2θ=29.3° was particularly low, and the content of the thiolicon region II type crystal structure was low.

[0133] (Comparative Examples 2 to 4) The compounds of Comparative Examples 2 to 4 were prepared in the same manner as in Comparative Example 1, except that 20 mL of the solvent shown below was used instead of 20 mL of tetrahydrofuran in Comparative Example 1. According to the X-ray diffraction spectra (not shown) of the compounds obtained in Comparative Examples 2 to 4, they had a slight amount of thiolicon region II type crystal structure or no thiolicon region II type crystal structure at all, and no crystalline sulfide solid electrolyte was obtained in Comparative Examples 2 to 4.

[0134] The solvents used in Comparative Examples 2 to 4 are as follows. Comparative Example 2: 1-Ethylpyrrolidine Comparative Example 3: 4-Dimethylaminopyridine Comparative Example 4: N,N-Dimethylcyclohexylamine

[0135] As is clear from the comparison of Examples 1 and 2 with Comparative Examples 1 to 4, it was found that in Examples 1 and 2, in which a monoamine compound having a six-membered ring structure containing one heteroatom was used as a complexing agent, a sulfide solid electrolyte having high ionic conductivity was obtained. Furthermore, it was found that in Example 2, in which cyclohexane was used as the solvent, a sulfide solid electrolyte having higher ionic conductivity was obtained. [Industrial Applicability]

[0136] The crystalline sulfide solid electrolyte of the present embodiment has high ionic conductivity and excellent battery performance, and is therefore suitable for use in, for example, an electrode mixture in combination with an electrode active material, or in a lithium ion battery, which is suitable for use in, for example, information-related devices and communication devices such as personal computers, video cameras, and mobile phones.

Claims

1. mixing a raw material containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms in a solvent; and heating, The method for producing a sulfide solid electrolyte, wherein the solvent contains a complexing agent including a monoamine compound having a six-membered ring structure including one heteroatom.

2. The method for producing a sulfide solid electrolyte according to claim 1 , wherein the six-membered ring structure is a piperidine skeleton.

3. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the monoamine compound is an alkylpiperidine.

4. The method for producing a sulfide solid electrolyte according to claim 3, wherein the alkylpiperidine is 1-methylpiperidine.

5. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 4, wherein the solvent comprises a hydrocarbon solvent.

6. The method for producing a sulfide solid electrolyte according to claim 5 , wherein the hydrocarbon solvent is cyclohexane.

7. The method for producing a sulfide solid electrolyte according to any one of claims 1 to 6, wherein the mixing provides an electrolyte precursor containing the lithium atom, the sulfur atom, the phosphorus atom, the halogen atom, and the complexing agent.

8. the solvent includes a solvent A including a solvent containing an oxygen atom and a solvent B including the complexing agent, the raw material contains a substance group C including the lithium atom, the sulfur atom, and the phosphorus atom, and a substance group D including the halogen atom; The method for producing a sulfide solid electrolyte according to any one of claims 1 to 7, wherein the mixing is carried out by the following (i) and (ii): (i) Mixing the substance group C in the solvent A to obtain amorphous Li ３ P.S. ４ To obtain. (ii) In the solvent B, the amorphous Li ３ P.S. ４ and said substance group D to obtain an electrolyte precursor.

9. The method for producing a sulfide solid electrolyte according to claim 8, wherein the solvent containing oxygen atoms is tetrahydrofuran.

10. An electrolyte precursor comprising lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, and a complexing agent including a monoamine compound having a six-membered ring structure containing one heteroatom.

11. A sulfide solid electrolyte comprising a monoamine compound having a six-membered ring structure containing one heteroatom and composed of a lithium atom, a sulfur atom, a phosphorus atom, and a halogen atom.

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