Sulfide solid electrolyte and sulfide solid electrolyte production method

Abstract

Provided are: a sulfide solid electrolyte production method which provides, at a high production efficiency, a sulfide solid electrolyte that contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and that has high water resistance, the method including mixing a raw-material-containing substance and a protonic organic solvent containing oxygen atoms to thereby prepare a solution; and a sulfide solid electrolyte that contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and that has a prescribed diffraction peak in an X-ray diffraction measurement using a CuKα ray.

Description

Sulfide solid electrolyte and method for producing sulfide solid electrolyte

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

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

[0003] Methods for producing solid electrolytes used in solid electrolyte layers are broadly divided into solid-phase methods and liquid-phase methods. Liquid-phase methods include homogeneous methods in which the solid electrolyte material is completely dissolved in a solvent, and heterogeneous methods in which the solid electrolyte material is not completely dissolved and a solid-liquid coexistence suspension is formed. For example, a solid-phase method is known in which raw materials such as lithium sulfide and diphosphorus pentasulfide are mechanically milled using a device such as a ball mill or a bead mill, and then heated as necessary to produce an amorphous or crystalline solid electrolyte (see, for example, Patent Document 1). Among liquid-phase methods, a homogeneous method is known in which the solid electrolyte is dissolved in a solvent and then reprecipitated (see, for example, Patent Document 2), and a heterogeneous method is known in which raw materials such as lithium sulfide are reacted in a solvent containing a polar aprotic solvent (see, for example, Patent Documents 3 and 4, and Non-Patent Document 1).

[0004] One promising solid electrolyte material is a sulfide solid electrolyte having an LGPS crystal structure. For example, as a method for producing a sulfide solid electrolyte having an LGPS crystal structure composed of lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, a so-called melt quenching method (see, for example, Patent Documents 5 and 6) is adopted, in which solid raw materials such as lithium sulfide, diphosphorus pentasulfide, and diphosphorus pentoxide are fired at 700 to 950 ° C., melted, and then rapidly cooled. In addition, as a method for producing a sulfide solid electrolyte having an LGPS crystal structure composed of lithium atoms, germanium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, a solid-phase method is adopted in which a solid raw material is pulverized using a vibrating mill to produce an amorphous sulfide solid electrolyte, which is then heated and crystallized (see, for example, Patent Document 7).

[0005] International Publication No. 2017 / 159667 Pamphlet Japanese Patent Application Laid-Open No. 2014-191899 International Publication No. 2014 / 192309 Pamphlet International Publication No. 2018 / 054709 Pamphlet Japanese Patent Application Laid-Open No. 2019-192490 Japanese Patent Application Laid-Open No. 2013-30440 Japanese Patent Application Laid-Open No. 2013-149599

[0006] “CHEMISTRY OF MATERIALS”, 2017, No. 29, pp. 1830-1835

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms and having high water resistance with high production efficiency.

[0008] A method for producing a sulfide solid electrolyte according to the present invention is a method for producing a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, comprising: preparing a solution by mixing a raw material containing lithium atoms, phosphorus atoms, and sulfur atoms with a protic organic solvent containing oxygen atoms. The sulfide solid electrolyte according to the present invention is a solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and having an LGPS-type crystal structure having diffraction peaks at least at 2θ=25.5±0.4° and 31.0±0.4° in X-ray diffraction measurement using CuKα radiation, and having a diffraction peak at 2θ=26.4±0.5° in X-ray diffraction measurement using CuKα radiation.

[0009] According to the present invention, a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms and having high water resistance can be provided with high production efficiency.

[0010] 1 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 1. FIG. 2 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 2. FIG. 3 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 3. FIG. 4 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 5. FIG. 5 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 6. FIG. 6 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 7. FIG. 7 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 8. FIG. 8 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 9. FIG. 10 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 11. FIG. 12 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 12. 1 is an X-ray diffraction pattern of the crystalline sulfide solid electrolyte obtained in Example 13; FIG. 2 is an X-ray diffraction pattern of the powder obtained after drying in Comparative Example 1; FIG. 3 is an X-ray diffraction pattern of the powder obtained after heating in Comparative Example 1; FIG. 4 is an explanatory drawing for determining the half width of the diffraction peak; FIG. 5 is an explanatory drawing for determining the half width of the diffraction peak; FIG. 6 is an explanatory drawing for determining the half width of the diffraction peak; ３１ 11 is a P-NMR spectrum; 12 is a CV curve measured by the method of CV measurement 1 of the crystalline sulfide solid electrolyte obtained in Example 11; and 13 is a CV curve measured by the method of CV measurement 2 of the crystalline sulfide solid electrolyte obtained in Example 11.

[0011] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. In this specification, the upper and lower limit values ​​of a numerical range expressed as "greater than or equal to," "less than or equal to," and "to" can be arbitrarily combined, and the numerical values ​​of the examples can also be used as the upper and lower limit values. Furthermore, preferred specifications can be arbitrarily adopted. In other words, one preferred specification can be adopted in combination with one or more other preferred specifications. It can be said that a combination of preferred items is more preferable.

[0012] (Findings Obtained by the Inventors to Achieve the Present Invention) The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found the following, which has led to the completion of the present invention.

[0013] The manufacturing method employed varies depending on the type of sulfide solid electrolyte to be obtained. For example, methods for manufacturing sulfide solid electrolytes containing lithium, phosphorus, sulfur, and oxygen atoms, such as the sulfide solid electrolytes having an LGPS-type crystal structure described in Patent Documents 4 to 7, have primarily employed solid-phase methods, such as calcining solid raw materials or using a pulverizer. However, calcining solid raw materials requires high temperatures of 700 to 950°C, which results in significant energy consumption, a high equipment load, and reduced production efficiency. The use of a pulverizer also results in significant energy consumption and reduced production efficiency. Furthermore, calcining at high temperatures causes particles to aggregate and solidify, necessitating the need to pulverize the solid electrolyte with strong force during battery production, which increases energy consumption and further reduces production efficiency. Furthermore, as demand for solid electrolytes increases, more efficient mass production is required, but this is difficult to achieve, especially when using a pulverizer.

[0014] Therefore, the present inventors focused on the conventional liquid-phase methods for producing sulfide solid electrolytes disclosed in Patent Documents 2 to 4, Non-Patent Document 1, etc., and investigated whether the liquid-phase method could be applied to the production of sulfide solid electrolytes containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms. After investigating various raw materials and organic solvents as the solvent used in the liquid-phase method, it was found that by using a raw material containing lithium atoms, phosphorus atoms, and sulfur atoms as the raw material and a protic organic solvent containing oxygen atoms, a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms can be obtained without employing high-temperature firing or grinding with a grinder, as in the manufacturing methods disclosed in Patent Documents 5 to 7. Eliminating the use of high-temperature firing and grinding with a grinder reduces energy consumption and equipment load, and is extremely effective in improving production efficiency. Furthermore, employing a liquid-phase method makes it easier to adapt to scale-based production and facilitates mass production.

[0015] The sulfide solid electrolytes having an LGPS-type crystal structure composed of lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms described in Patent Documents 5 and 6 are made from lithium sulfide, diphosphorus pentasulfide, and diphosphorus pentoxide as starting materials. The sulfide solid electrolyte having an LGPS-type crystal structure composed of lithium atoms, germanium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms described in Patent Document 7 are made from lithium sulfide, lithium oxide, diphosphorus pentasulfide, and germanium sulfide as starting materials. That is, the sulfide solid electrolytes having an LGPS-type crystal structure described in Patent Documents 5 to 7 are made from atoms supplied from the solid raw materials that serve as starting materials. In contrast, the present inventors have discovered that when a raw material containing lithium atoms, phosphorus atoms, and sulfur atoms is used in combination with a protic organic solvent containing oxygen atoms, the oxygen atoms contained in the protic organic solvent contribute to the formation of the crystal structure of the sulfide solid electrolyte. Thus, the fact that atoms contained in the organic solvent used in the reaction of the raw materials constitute the crystal structure of the sulfide solid electrolyte is a surprising phenomenon that is not recognized in the conventional liquid phase methods disclosed not only in Patent Documents 5 to 7 but also in Patent Documents 2 to 4 and Non-Patent Document 1. It is also a surprising phenomenon that a sulfide solid electrolyte containing thium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms can be obtained without employing high-temperature firing or pulverization with a pulverizer.

[0016] Based on the above findings, it has been discovered that in a method for producing a sulfide solid electrolyte by a liquid phase method in which raw material ingredients are reacted in an organic solvent, by using a combination of raw material ingredients containing lithium atoms, phosphorus atoms, and sulfur atoms and a protic organic solvent containing oxygen atoms, a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms can be produced with high production efficiency while employing a liquid phase method, and mass production can be easily achieved.

[0017] (Regarding various aspects of the present embodiment) A method for producing a sulfide solid electrolyte according to a first aspect of the present embodiment is a method for producing a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, the method comprising: preparing a solution by mixing a raw material containing lithium atoms, phosphorus atoms, and sulfur atoms with a protic organic solvent containing oxygen atoms.

[0018] The method for producing a sulfide solid electrolyte of this embodiment includes mixing a raw material containing lithium atoms, phosphorus atoms, and sulfur atoms with a protic organic solvent containing oxygen atoms. By using a protic organic solvent containing oxygen atoms, the raw material containing materials dissolves in the protic organic solvent, producing a solution. Then, in the solution, the oxygen atoms contained in the protic organic solvent react with each atom contained in the raw material containing materials, and the oxygen atoms are incorporated as atoms constituting the sulfide solid electrolyte, accelerating the reaction of the raw materials, resulting in the production of a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms.

[0019] According to the production method of this embodiment, a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms can be obtained by simply mixing the components, without employing high-temperature calcination or pulverization using a pulverizer, in a very simple manner. Therefore, according to the production method of this embodiment, the sulfide solid electrolyte can be produced with high production efficiency, and the use of a liquid-phase process facilitates mass production. The resulting sulfide solid electrolyte has excellent water resistance, such as suppressing hydrogen sulfide generation and battery performance degradation even when in contact with moisture (e.g., atmospheric moisture) during battery fabrication and use. It also has excellent electrochemical stability when used in a battery.

[0020] A second aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the first aspect, wherein the raw material content containing lithium atoms, phosphorus atoms, and sulfur atoms contains lithium sulfide and phosphorus sulfide.

[0021] The raw material components used in the production method of this embodiment preferably contain lithium sulfide and phosphorus sulfide. By using these raw materials, oxygen atoms contained in the protic organic solvent are incorporated and the reaction of the raw materials is promoted, making it possible to produce a sulfide solid electrolyte with high production efficiency.

[0022] A third aspect of the present embodiment is directed to the second aspect of the method for producing a sulfide solid electrolyte, wherein the amount of lithium sulfide mixed is 45.0 mol % or more and 78.0 mol % or less with respect to the total amount of the lithium sulfide and the phosphorus sulfide.

[0023] Regarding lithium sulfide and phosphorus sulfide, which are preferably used as raw material components in the production method of this embodiment, by using these raw materials in a specific range, oxygen atoms contained in the protic organic solvent are incorporated and the reaction of the raw materials is promoted, making it possible to produce a sulfide solid electrolyte with high production efficiency. ４ ３－ In the manufacturing method of this embodiment, a protic organic solvent is used, and oxygen atoms contained therein are converted into the PS ４ ３－ By reacting with phosphorus sulfide, which contributes to the formation of the structure, PS ４ ３－ At least some of the sulfur atoms in the structure are incorporated with oxygen atoms, ４－α O α － It is believed that the compound forms a structure (where α is an integer of 1 or more and 4 or less).

[0024] A fourth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to third aspects, wherein the raw material inclusions do not contain a raw material containing an oxygen atom.

[0025] As described above, according to the production method of this embodiment, the reaction of the raw materials proceeds while incorporating oxygen atoms contained in the protic organic solvent, thereby obtaining a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms. Therefore, even if the raw material contents do not contain raw materials containing oxygen atoms, a sulfide solid electrolyte containing oxygen atoms can be obtained. The fourth aspect of this embodiment clarifies this point.

[0026] A fifth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the first aspect, wherein preparing the solution comprises mixing a raw material-containing material containing lithium atoms and sulfur atoms with the protic organic solvent containing oxygen atoms, and then adding and mixing a raw material-containing material containing phosphorus atoms and sulfur atoms. A sixth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the first aspect, wherein preparing the solution comprises mixing a raw material-containing material containing lithium atoms and sulfur atoms with the protic organic solvent containing oxygen atoms.

[0027] In either case, the order in which the raw material ingredients and the protic organic solvent are mixed is specified, and mixing in this order promotes the reaction of the raw materials while efficiently incorporating oxygen atoms contained in the protic organic solvent, thereby enabling the production of a sulfide solid electrolyte with high production efficiency. From these forms, it can be said that in the production method of this embodiment, it is preferable to first mix the protic organic solvent containing oxygen atoms with the raw material ingredients containing lithium atoms and sulfur atoms.

[0028] A seventh aspect of the present embodiment is directed to the method for producing a sulfide solid electrolyte of the fifth or sixth aspect, wherein the raw material inclusion containing lithium atoms and sulfur atoms contains lithium sulfide, and the raw material inclusion containing phosphorus atoms and sulfur atoms contains phosphorus sulfide.

[0029] In the fifth and sixth embodiments, lithium sulfide and phosphorus sulfide are added as raw materials in a predetermined order and mixed with a protic organic solvent, whereby oxygen atoms contained in the protic organic solvent are efficiently incorporated and the reaction of the raw materials is promoted, making it possible to produce a sulfide solid electrolyte with high production efficiency.

[0030] The method for producing a sulfide solid electrolyte according to an eighth aspect of the present embodiment is the method for producing a sulfide solid electrolyte according to any one of the first to seventh aspects, wherein the protic organic solvent containing an oxygen atom is at least one solvent selected from an alcohol solvent, a nitro group-containing solvent, and a carboxylic acid solvent.

[0031] By using at least one solvent selected from alcohol solvents, nitro group-containing solvents, and carboxylic acid solvents as the protic organic solvent containing oxygen atoms, the reaction of the raw materials is promoted while the oxygen atoms contained in the protic organic solvent are efficiently incorporated, making it possible to produce a sulfide solid electrolyte with high production efficiency.

[0032] A ninth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to any one of the first to eighth aspects, wherein the method further comprises heating the solution after preparing the solution. A tenth aspect of the present embodiment is a method for producing a sulfide solid electrolyte according to the ninth aspect, wherein the heating temperature in the heating is 200° C. or higher and 450° C. or lower.

[0033] Further heating can produce a crystalline sulfide solid electrolyte. That is, further heating is heating for crystallization. If a crystalline sulfide solid electrolyte is desired, further heating can be performed. In this case, a sulfide solid electrolyte having a better crystal structure can be efficiently produced by setting the temperature to 200°C or higher and 450°C or lower.

[0034] The method for producing a sulfide solid electrolyte according to an eleventh aspect of the present embodiment is any one of the first to tenth aspects, wherein the sulfide solid electrolyte has an LGPS-type crystal structure.

[0035] In the manufacturing method of this embodiment, it is possible to manufacture a desired sulfide solid electrolyte by changing the types and compounding ratios of the raw materials contained in the raw material inclusions. A sulfide solid electrolyte having an LGPS crystal structure is known to have extremely high ionic conductivity among sulfide solid electrolytes containing oxygen atoms, and is therefore preferable as the sulfide solid electrolyte to be obtained by the manufacturing method of this embodiment.

[0036] A sulfide solid electrolyte according to a twelfth aspect of the present embodiment includes lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and has an LGPS-type crystal structure having diffraction peaks at least at 2θ=25.5±0.4° and 31.0±0.4° in X-ray diffraction measurement using CuKα rays, and has a diffraction peak at 2θ=26.4±0.5° in X-ray diffraction measurement using CuKα rays.

[0037] The sulfide solid electrolyte of this embodiment has an LGPS crystal structure, i.e., in X-ray diffraction measurement using CuKα radiation, it has a diffraction peak due to the LGPS crystal structure and also has a diffraction peak at 2θ = 26.4 ± 0.5 °. The diffraction peak at 2θ = 26.4 ± 0.5 ° possessed by the sulfide solid electrolyte of this embodiment is not a diffraction peak due to the LGPS crystal structure. Therefore, the sulfide solid electrolyte of this embodiment is considered to have a crystal structure other than the LGPS crystal structure (hereinafter also referred to as "other crystal structure"). Furthermore, it is considered that having other crystal structures in addition to the LGPS crystal structure results in high water resistance and electrochemical stability.

[0038] Although there are no particular limitations on the method for producing the sulfide solid electrolyte of this embodiment, it is preferable to produce it by the above-mentioned method for producing the sulfide solid electrolyte of this embodiment, because the sulfide solid electrolyte of this embodiment, which has an LGPS crystal structure and further has a diffraction peak at 2θ=26.4±0.5°, can be produced with high production efficiency.

[0039] In the sulfide solid electrolyte of this embodiment, it is not clear what kind of crystal structure causes the peak to appear, but it is thought that other crystal structures other than the LGPS crystal structure exist depending on the presence of oxygen atoms. For example, when the sulfide solid electrolyte of this embodiment is produced by the sulfide solid electrolyte production method described above, it is thought that when the reaction of the raw materials progresses while incorporating oxygen atoms contained in the protic organic solvent, other crystal structures are generated by the oxygen atoms and raw materials that did not contribute to the formation of the LGPS crystal structure. In other words, it is thought that the other crystal structure is a crystal structure formed by the oxygen atoms and raw materials contained in the protic organic solvent that did not result in the formation of the LGPS crystal structure. It is thought that this other crystal structure causes the diffraction peak at 2θ = 26.4 ± 0.5 ° that is not expressed in the LGPS crystal structure.

[0040] A sulfide solid electrolyte according to a thirteenth aspect of the present embodiment is the sulfide solid electrolyte of the twelfth aspect, further having a diffraction peak at 2θ=30.0±0.5° in X-ray diffraction measurement using CuKα radiation; a sulfide solid electrolyte according to a fourteenth aspect is the sulfide solid electrolyte of the twelfth or thirteenth aspect, further having a diffraction peak at 2θ=16.7±0.5° in X-ray diffraction measurement using CuKα radiation; and a sulfide solid electrolyte according to any one of the twelfth to fourteenth aspects, further having a diffraction peak at 2θ=33.9±0.5° in X-ray diffraction measurement using CuKα radiation, and the intensity (I ３３．９ ) and the intensity of the diffraction peak at 2θ=31.0±0.4° (I ３１．０ ) and the intensity ratio (I ３３．９ / I ３１．０ ) is 0.065 or more and 1.0 or less.

[0041] The diffraction peaks at 2θ=16.7±0.5°, 2θ=30.0±0.5°, and 2θ=33.9±0.5° are not peaks that appear due to the LGPS-type crystal structure, but are peaks that appear due to other crystal structures. The other crystal structures are characterized by the intensity ratio (I ３３．９ / I ３１．０) within the above range, water resistance and electrochemical stability are improved.

[0042] The reason why the intensity ratio falls within the above range is thought to be as follows. It is known that sulfide solid electrolytes having an LGPS crystal structure exhibit a peak at 2θ = 34.0°. However, the sulfide solid electrolyte of this embodiment has a higher diffraction peak intensity at 2θ = 34.0° compared to one having only the LGPS crystal structure. This is thought to be because the other crystal structure has a diffraction peak at 2θ = 33.9°, and the intensity is increased due to a synergistic effect with the diffraction peak at 2θ = 34.0° due to the LGPS crystal structure. This tendency in peak intensity is particularly pronounced in sulfide solid electrolytes obtained by the above-mentioned method for producing a sulfide solid electrolyte. This is thought to be because, when the production method of this embodiment is adopted, oxygen atoms contained in the protic organic solvent are more easily incorporated into the crystal structure than when an oxide containing oxygen atoms is used as a raw material.

[0043] A sulfide solid electrolyte according to a sixteenth aspect of the present embodiment is any one of the twelfth to fifteenth aspects, further having a diffraction peak at 2θ=21.1±0.4° in X-ray diffraction measurement using CuKα rays.

[0044] The LGPS crystal structure of the sulfide solid electrolyte of this embodiment has diffraction peaks at least at 2θ = 25.5 ± 0.4° and 31.0 ± 0.4° as described above, and also has a diffraction peak at 2θ = 21.1 ± 0.4°.

[0045] A sulfide solid electrolyte according to a seventeenth aspect of the present embodiment is any one of the twelfth to sixteenth aspects, wherein the half width of the diffraction peak at 2θ=31.0±0.4° is 0.4° or more and 1.5° or less.

[0046] When the half-width of the diffraction peak at 2θ = 31.0 ± 0.4° is small, such as 1.5° or less, the crystallite diameter becomes large, resulting in a more excellent crystal structure. As a result, the ionic conductivity is improved, and water resistance and electrochemical stability are also improved. Furthermore, when the half-width is 0.4° or more, the ease of handling of the particles, such as moldability when manufacturing a battery, is improved. In the sulfide solid electrolyte of this embodiment, when the half-width of the diffraction peak at 2θ = 31.0 ± 0.4° is within the above range, it becomes easier to obtain the effects of other crystal structures, resulting in improved ionic conductivity, water resistance, and electrochemical stability.

[0047] The sulfide solid electrolyte according to an eighteenth aspect of the present embodiment is any one of the twelfth to seventeenth aspects, further comprising: ３１ P-NMR measurement revealed that PSO was 34.0±5.0 ppm. ３ ３－ A sulfide solid electrolyte according to a nineteenth aspect is any one of the twelfth to eighteenth aspects, wherein a peak due to ３１ P-NMR measurement revealed that PO was present at 6.0±5.0 ppm. ４ ３－ A sulfide solid electrolyte according to a twentieth aspect is any one of the twelfth to nineteenth aspects, wherein a peak due to ３１ P-NMR measurement revealed that PS was present at 67.0±5.0 ppm. ２ O ２ ３－ A peak due to this is observed.

[0048] The sulfide solid electrolyte of the present embodiment has an LGPS-type crystal structure containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms. The peaks in the sixteenth and seventeenth embodiments are both peaks that appear due to the LGPS-type crystal structure.

[0049] A sulfide solid electrolyte according to a twenty-first aspect of the present embodiment is any one of the twelfth to twentieth aspects, wherein the number of moles of the sulfur atoms (M Ｓ ) and the number of moles of phosphorus atoms (M Ｐ ) and the ratio (M Ｓ / M Ｐ ) is 0.5 or more and 4.0 or less, and the sulfide solid electrolyte according to a twenty-second aspect is the sulfide solid electrolyte according to any one of the twelfth to twenty-first aspects, wherein the number of moles of the lithium atoms (M Ｌ ) and the number of moles of phosphorus atoms (M Ｐ ) and the ratio (M Ｌ / M Ｐ ) is greater than or equal to 2.3 and less than or equal to 3.9.

[0050] The sulfide solid electrolyte of this embodiment has a mole number of lithium atoms (M Ｌ ), the number of moles of sulfur atoms (M Ｓ ) and the number of moles of phosphorus atoms (M Ｐ ) is the ratio (M Ｓ / M Ｐ ) and ratio (M Ｌ / M Ｐ ) relationship, an LGPS-type crystal structure and other crystal structures are likely to be formed, and as a result, excellent ionic conductivity, water resistance, and electrochemical stability are likely to be obtained.

[0051] A sulfide solid electrolyte according to a twenty-third aspect of the present embodiment is any one of the twelfth to twenty-second aspects, further comprising carbon atoms.

[0052] As described above, the sulfide solid electrolyte of this embodiment is preferably obtained by the manufacturing method of this embodiment. In the manufacturing method of this embodiment, a protic organic solvent containing oxygen atoms is used, and therefore carbon atoms contained in the protic organic solvent may remain. In the case where the sulfide solid electrolyte of this embodiment contains carbon atoms but no raw materials containing carbon atoms are used as raw materials, it can be said that the sulfide solid electrolyte of this embodiment is obtained by the manufacturing method of this embodiment.

[0053] (Solid Electrolyte) In this specification, the term "solid electrolyte" refers to an electrolyte that maintains a solid state at 25°C under a nitrogen atmosphere. The sulfide solid electrolyte in this embodiment is a solid electrolyte that contains lithium atoms, sulfur atoms, phosphorus atoms, and oxygen atoms and has ionic conductivity due to the lithium atoms. In addition, since it contains sulfur atoms, it is called a sulfide solid electrolyte.

[0054] The term "solid electrolyte" includes both amorphous solid electrolytes and crystalline solid electrolytes. In this specification, a crystalline solid electrolyte is a solid electrolyte in which peaks derived from the solid electrolyte are observed in an X-ray diffraction pattern in X-ray diffraction measurement, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present. That is, a crystalline solid electrolyte includes a crystalline structure derived from the solid electrolyte, and a portion of the crystalline structure may be derived from the solid electrolyte, or the entire crystalline structure may be derived from the solid electrolyte. Furthermore, as long as a crystalline solid electrolyte has the X-ray diffraction pattern described above, it may also contain an amorphous solid electrolyte in part. Therefore, crystalline solid electrolytes include so-called glass ceramics obtained by heating an amorphous solid electrolyte to a temperature equal to or higher than its crystallization temperature. Furthermore, in this specification, an amorphous solid electrolyte is one in which a halo pattern in an X-ray diffraction pattern in X-ray diffraction measurement is observed in which substantially no peaks other than those derived from the material are present, regardless of whether or not peaks derived from the raw materials of the solid electrolyte are present.

[0055] [Method for producing sulfide solid electrolyte] A method for producing a sulfide solid electrolyte according to the present embodiment is a method for producing a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, the method comprising: preparing a solution by mixing a raw material containing lithium atoms, phosphorus atoms, and sulfur atoms with a protic organic solvent containing oxygen atoms.

[0056] [Preparing a Solution] The manufacturing method of this embodiment includes preparing a solution by mixing a raw material containing lithium atoms, phosphorus atoms, and sulfur atoms with a protic organic solvent containing oxygen atoms (hereinafter, may be simply referred to as a "protic organic solvent"). The manufacturing method of this embodiment will first be described, starting with the raw material containing materials.

[0057] (Raw material inclusions) The raw material inclusions used in this embodiment contain lithium atoms, sulfur atoms, and phosphorus atoms. More specifically, they are inclusions containing a substance (hereinafter also referred to as "raw material") containing one or more types selected from the group consisting of these atoms, and preferably contain two or more types of raw material.

[0058] The raw materials include, for example, lithium sulfide; diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ Representative examples of the raw material include raw materials containing at least two kinds of atoms selected from the above-mentioned atoms, such as phosphorus sulfide, sulfur element, and the like; and raw materials consisting of one kind of atom selected from the above-mentioned atoms, such as elemental phosphorus and elemental sulfur.

[0059] In the manufacturing method of this embodiment, among the above, lithium sulfide and diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ Among phosphorus sulfides, phosphorus pentasulfide (P ２ S ５ ) is preferred.

[0060] The raw material may also include a substance containing a halogen atom. For example, lithium halides such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide; fluorine (F ２ ), chlorine (Cl ２ ), bromine (Br ２ ), iodine (I ２ Representative examples include simple halogen atoms such as

[0061] The raw material is a substance containing at least one atom selected from lithium atoms, phosphorus atoms, and sulfur atoms, such as various phosphorus fluorides (PF３ , P.F. ５ ), various phosphorus chlorides (PCl ３ , PCl ５ , P ２ Cl ４ ), various phosphorus bromides (PBr ３ , PBr ５ ), various phosphorus iodides (PI ３ , P ２ I ４ ) and the like; phosphorus halides such as thiophosphoryl fluoride (PSF ３ ), thiophosphoryl chloride (PSCl ３ ), thiophosphoryl bromide (PSBr ３ ), thiophosphoryl iodide (PSI ３ ), thiophosphoryl fluoride dichloride (PSCl ２ F), thiophosphoryl fluoride dibromide (PSBr ２ Thiophosphoryl halides such as lithium oxide, lithium hydroxide, lithium carbonate, and the like; 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.

[0062] In the manufacturing method of this embodiment, PS ４ Li containing structure ３ P.S. ４ , Li ７ P ３ S １１ It is also possible to use as a raw material substances that act as solid electrolytes, such as Li３ P.S. ４ When using as a raw material, Li ３ P.S. ４ This can be prepared by manufacturing or the like and used as a raw material.

[0063] The raw material used in the manufacturing method of this embodiment includes P containing oxygen atoms. ２ O ５ and Li ２ Although raw materials such as O and LiOH can be used, they do not necessarily have to be used. In the production method of this embodiment, it is preferable that raw materials containing oxygen atoms are not contained. Unlike conventional production methods, the production method of this embodiment employs a protic organic solvent containing oxygen atoms, so that the reaction of the raw materials proceeds while the oxygen atoms contained in the protic organic solvent are efficiently incorporated, thereby obtaining a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms. Therefore, even without using raw materials containing oxygen atoms, a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms can be obtained.

[0064] The raw material such as lithium sulfide used in this embodiment is preferably in the form of particles. By mixing with a protic organic solvent, a solution can be easily obtained. The average particle size (D ５０ In consideration of the reaction of the raw materials, handling, etc., the average particle size (D) is preferably, for example, 0.1 μm or more and 1000 μm or less, 0.5 μm or more and 100 μm or less, or 1 μm or more and 20 μm or less. ５０ ) is the particle size at which 50% (volume basis) of the total particle size is reached when the particle sizes are sequentially added together starting from the smallest particle size when an integrated particle size distribution curve is drawn, and the volume distribution refers to an average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device.

[0065] When lithium sulfide and diphosphorus pentasulfide are used as raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 45.0 mol% or more, more preferably 55.0 mol% or more, even more preferably 65.0 mol% or more, still more preferably 67.0 mol% or more, particularly preferably 70.0 mol% or more, from the viewpoint of obtaining higher water resistance, electrochemical stability, and higher ionic conductivity, and the upper limit is preferably 80.0 mol% or less, more preferably 78.0 mol% or less, and even more preferably 76.0 mol% or less. Representative numerical ranges are preferably 45.0 to 80.0 mol%, 55.0 to 78.0 mol%, 65.0 to 78.0 mol%, 67.0 to 78.0 mol%, 70.0 to 78.0 mol%, and 70.0 to 76.0 mol%.

[0066] (Protic Organic Solvent Containing Oxygen Atoms) In the production method of this embodiment, a protic organic solvent containing oxygen atoms is used. By using a protic organic solvent containing oxygen atoms, the raw material ingredients are dissolved to form a solution, and the oxygen atoms contained in the protic organic solvent react with the atoms contained in the raw material ingredients in the solution, whereby the oxygen atoms are incorporated as atoms constituting the sulfide solid electrolyte while the raw material reaction progresses, producing a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms.

[0067] The oxygen atom-containing protic organic solvent can be any organic solvent that contains an oxygen atom and has protic properties (i.e., the ability to donate hydrogen ions (protons)). Preferred examples of the oxygen atom-containing protic organic solvent include alcohol solvents, nitro group-containing solvents, and carboxylic acid solvents.

[0068] Preferred examples of alcohol solvents include aliphatic alcohol solvents such as methanol, ethanol, various propanols such as propanol and isopropanol (hereinafter, this may be abbreviated as "various types", including linear, branched, and isomers thereof, and compounds having a specified number of carbon atoms), various butanols, and various decanols; monohydric alcohols such as alicyclic alcohol solvents such as cyclopentanol and cyclohexanol; and polyhydric alcohols such as ethylene glycol. As the alcohol solvent, for example, the above-exemplified solvents can be used alone or in combination. Among the above alcohol solvents, monohydric alcohols are preferred, and monohydric aliphatic alcohol solvents are more preferred.

[0069] As for the alcohol, for example, the various butanols mentioned above may include primary alcohol such as 1-butanol, secondary alcohol such as 2-butanol, and tertiary alcohol such as 2-methyl-2-propanol, but primary alcohol is preferred among them.

[0070] The number of carbon atoms in the alcohol solvent is preferably 1 or more, more preferably 2 or more, and the upper limit is preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and still more preferably 3 or less. An alcohol solvent with 2 carbon atoms, i.e., ethanol, is particularly preferred. The numerical range of the carbon number is typically preferably 1 to 8, 1 to 6, 1 to 4, 2 to 4, or 2 to 3.

[0071] Preferred examples of the nitro group-containing solvent include nitroalkanes such as nitromethane and nitroethane, and preferred examples of the carboxylic acid solvent include formic acid, acetic acid, and propionic acid. These nitro group-containing solvents and carboxylic acid solvents can be used alone or in combination with the solvents listed above. The carbon number of the nitro group-containing solvent and the carboxylic acid solvent is preferably 1 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, even more preferably 3 or less, and even more preferably 2 or less.

[0072] In the production method of this embodiment, the protic organic solvent is preferably at least one solvent selected from alcohol solvents, nitro group-containing solvents, and carboxylic acid solvents, and more preferably an alcohol solvent.

[0073] (Solvent) In the production method of this embodiment, a solvent other than the above-described oxygen atom-containing protic organic solvent can also be used. Examples of such a solvent include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents.

[0074] Representative examples of aliphatic hydrocarbon solvents include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane; representative examples of alicyclic hydrocarbon solvents include cyclohexane and methylcyclohexane; and representative examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, trifluoromethylbenzene, nitrobenzene, chlorobenzene, chlorotoluene, and bromobenzene. These solvents can be used alone or in combination. Note that the above examples are merely examples, and for example, solvents that have isomers may include all isomers. Furthermore, solvents substituted with halogen atoms, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents may also include those substituted with aliphatic groups such as alkyl groups.

[0075] (Mixing) In the manufacturing method of this embodiment, the raw material content is mixed with a protic organic solvent to prepare a solution. There are no particular limitations on the method for mixing the raw material content and the protic organic solvent, and the raw material content and the protic organic solvent can be mixed by adding them to a device capable of mixing them. For example, it is preferable to supply a protic organic solvent to a tank, operate the stirring blade, and then gradually add the raw material content, which results in a good mixing state of the raw material content and promotes dissolution by improving the dispersibility of the raw material content.

[0076] The order in which the raw material ingredients are added is not particularly limited, but from the viewpoint of efficiently incorporating oxygen atoms contained in the protic organic solvent, accelerating the reaction of the raw materials, and producing a sulfide solid electrolyte with high production efficiency, the following mixing methods (1) and (2) are preferred. Mixing method (1): Mixing a raw material ingredient containing lithium atoms and sulfur atoms with the protic organic solvent containing oxygen atoms, and then adding a raw material ingredient containing phosphorus atoms and sulfur atoms and mixing. Mixing method (2): Mixing a raw material ingredient containing lithium atoms and sulfur atoms with the protic organic solvent containing oxygen atoms.

[0077] In the method (1), two types of raw material containing materials, namely, a raw material containing lithium atoms and sulfur atoms and a raw material containing phosphorus atoms and sulfur atoms, are added separately and mixed with a protic organic solvent. In this case, the raw material containing lithium atoms and sulfur atoms is mixed with the protic organic solvent first. In the method (2), two types of raw material containing materials, namely, a raw material containing lithium atoms and sulfur atoms and a raw material containing phosphorus atoms and sulfur atoms, are mixed with a protic organic solvent simultaneously.

[0078] From any of these methods, it can be said that in the production method of this embodiment, it is preferable to first mix the protic organic solvent containing oxygen atoms with the raw material containing lithium atoms and sulfur atoms.

[0079] In the above (1) and (2), the raw material containing lithium atoms and sulfur atoms can be selected from the raw materials contained in the raw material containing materials, and lithium sulfide is preferred, and lithium sulfide is preferable. Furthermore, the raw material containing phosphorus atoms and sulfur atoms can be selected from the raw materials contained in the raw material containing materials, and phosphorus sulfide is preferred, and diphosphorus pentasulfide is more preferred, and diphosphorus pentasulfide is even more preferable.

[0080] In the above (1) and (2), when raw materials other than the raw material containing lithium atoms and sulfur atoms and the raw material containing phosphorus atoms and sulfur atoms are used, the other raw materials may be added at any time. Furthermore, in the above (1) and (2), the amounts of lithium sulfide and phosphorus sulfide (diphosphorus pentasulfide) used are as described above for the raw material containing materials. In the above (1) and (2), when two or more raw materials are added simultaneously to the protic organic solvent, it is preferable to premix the two or more raw materials. By premixing in this way, the raw materials are more uniformly dispersed in the protic organic solvent, facilitating the reaction of the raw materials. Therefore, when the aforementioned lithium sulfide is used as a raw material, the amount of remaining lithium sulfide is particularly reduced.

[0081] In the above steps (1) and (2), the amount of oxygen atoms in the sulfide solid electrolyte can be controlled by adjusting the amount of the protic organic solvent containing oxygen atoms. For example, by reducing the total amount of the protic organic solvent relative to the raw materials in the above steps, the amount of oxygen that enters the structure can be reduced while promoting the reaction of the raw materials.

[0082] An example of an apparatus for mixing the raw material ingredients with the protic organic solvent is a mechanical agitation mixer equipped with an agitator blade in a tank. Examples of mechanical agitation mixers include high-speed agitation mixers and double-arm mixers. High-speed agitation mixers are preferred because they increase the uniformity of the raw material ingredients in the mixture of the raw material ingredients and the protic organic solvent, thereby promoting dissolution, and efficiently incorporating oxygen atoms contained in the protic organic solvent to promote the reaction of the raw materials, thereby producing a sulfide solid electrolyte with high production efficiency. Examples of high-speed agitation mixers include vertical-axis rotary mixers and horizontal-axis rotary mixers. Either type of mixer may be used.

[0083] Examples of the shape of the stirring blade used in the mechanical stirring mixer include anchor type, blade type, arm type, ribbon type, multi-stage blade type, double arm type, shovel type, two-shaft blade type, flat blade type, C-shaped blade type, etc. From the viewpoint of increasing the uniformity of the raw material contents in the mixture of the raw material contents and the protic organic solvent to promote dissolution, and promoting the reaction of the raw materials while efficiently incorporating oxygen atoms contained in the protic organic solvent, and producing a sulfide solid electrolyte with high production efficiency, the shovel type, flat blade type, C-shaped blade type, etc. are preferred.

[0084] Furthermore, 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 mixer. This enables the production of a sulfide solid electrolyte with even higher production efficiency. The location of the circulation line is not particularly limited, but it is preferable to install it at a location where the material is discharged from the bottom of the mixer and returned to the top of the mixer. This makes it easier to stir the raw materials that tend to settle uniformly by causing convection due to circulation, thereby promoting the dissolution of the raw material contents. Furthermore, it is preferable that the return port is located below the liquid surface of the material to be stirred. This makes it possible to prevent the material to be stirred from splashing and adhering to the wall surfaces inside the mixer.

[0085] The temperature conditions when mixing the raw material ingredients with the protic organic solvent are not particularly limited, and are typically -30 to 80 ° C. From the viewpoint of promoting dissolution by increasing the uniformity of the raw material ingredients, and efficiently incorporating oxygen atoms contained in the protic organic solvent to promote the reaction of the raw materials and produce a sulfide solid electrolyte with high production efficiency, the temperature is preferably -10 to 60 ° C., more preferably 0 to 50 ° C., and even more preferably about room temperature (23 ° C.) (for example, about room temperature ± 5 ° C.). The mixing time is typically 30 seconds to 10 hours, and from the same viewpoint as the temperature conditions, it is preferably 1 minute to 1 hour, more preferably 2 to 30 minutes, and even more preferably 3 to 15 minutes. When mixing is performed in multiple batches as in (2) above, the total time of the multiple mixing batches may be within the above mixing time range.

[0086] The manufacturing method of this embodiment involves mixing the raw material content with a protic organic solvent. That is, mixing the raw material content with the protic organic solvent is sufficient; pulverization is not required. Therefore, the method does not require the use of equipment commonly referred to as a pulverizer, such as a media-type pulverizer such as a ball mill or a bead mill, which is typically used for pulverizing raw material content. In this manufacturing method, the raw material content and the protic organic solvent are simply mixed to prepare a solution, and oxygen atoms contained in the protic organic solvent react with the atoms contained in the raw material content in the solution. The oxygen atoms are then efficiently incorporated as atoms constituting the sulfide solid electrolyte, accelerating the reaction of the raw materials, resulting in a sulfide solid electrolyte containing lithium, phosphorus, sulfur, and oxygen atoms. Furthermore, as described above, the mixing time is significantly shorter than that of conventional methods, enabling the production of a sulfide solid electrolyte with high production efficiency. While a pulverizer may be used to atomize the raw materials contained in the raw material content and the resulting sulfide solid electrolyte, it is preferable not to use a pulverizer when mixing the raw material content with the protic organic solvent.

[0087] [Further Heating] The production method of this embodiment preferably includes further heating if a crystalline sulfide solid electrolyte is desired. Heating improves the crystallinity, resulting in a high-quality crystalline sulfide solid electrolyte. In the further heating, the solution obtained by preparing the above solution may be heated, or the solution may be heated after precipitating the solute dissolved in the solution, i.e., the sulfide solid electrolyte, by drying as described below. When the solute is simply precipitated by drying, the resulting sulfide solid electrolyte is amorphous, and by heating this for crystallization, a crystalline sulfide solid electrolyte is obtained.

[0088] The heating temperature is not particularly limited as long as it is a temperature at which a crystalline sulfide solid electrolyte can be obtained, and cannot be generally determined because it can vary depending on the crystalline structure of the resulting crystalline sulfide solid electrolyte. However, it is preferably 130 ° C. or higher, more preferably 150 ° C. or higher, even more preferably 200 ° C. or higher, and even more preferably 250 ° C. or higher, and the upper limit is preferably 600 ° C. or lower, more preferably 500 ° C. or lower, even more preferably 425 ° C. or lower, still more preferably 375 ° C. or lower, particularly preferably 325 ° C. or lower. Typical numerical ranges are preferably 130 to 600 ° C., 150 to 600 ° C., 150 to 550 ° C., 200 to 500 ° C., 200 to 425 ° C., 200 to 375 ° C., 200 to 325 ° C., 250 to 375 ° C., and 250 to 325 ° C.

[0089] The heating time is not particularly limited as long as it is a time that allows a desired crystalline solid electrolyte to be obtained, but is, for example, preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or less, more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.

[0090] Heating can be carried out at normal pressure, but in order to reduce the heating temperature, it can also be carried out under a reduced pressure atmosphere or even a vacuum atmosphere. When heating is carried out under a reduced pressure atmosphere, the pressure condition is preferably 85 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less, and the lower limit may be vacuum (0 kPa). In consideration of ease of pressure adjustment, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more. When the pressure condition is within the above range, the heating condition can be made mild, and the size of the apparatus can be suppressed.

[0091] Furthermore, heating is preferably carried out in an inert gas atmosphere (e.g., a nitrogen atmosphere or an argon atmosphere), because this can prevent deterioration (e.g., oxidation) of the crystalline solid electrolyte. The heating method is not particularly limited, and examples thereof include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, and a baking furnace. Furthermore, industrially, a horizontal dryer or a horizontal vibration fluidized dryer having a heating means and a feeding mechanism can also be used, and the method may be selected depending on the amount of heat to be processed.

[0092] [Drying] The manufacturing method of this embodiment may include drying the solution after preparing the solution. By drying the solution, the solvent in the solution can be volatilized and removed, and a powdered solute, i.e., an amorphous sulfide solid electrolyte, can be obtained. By further heating the powdered solute obtained by drying the solution as described above, the solute (i.e., the sulfide solid electrolyte) can be heated more directly, and a crystalline sulfide solid electrolyte can be obtained more efficiently.

[0093] Examples of drying methods include a method of drying by heating using a dryer or the like. In the method of drying by heating, the solvent contained in the solution is volatilized, making it easy to obtain a solute. Drying by heating may be carried out under any pressure condition, including increased pressure, normal pressure, and reduced pressure, and is preferably carried out under normal pressure or reduced pressure. In particular, when considering drying at a lower temperature, drying under reduced pressure, or even under vacuum, using a vacuum pump or the like is preferred.

[0094] The temperature conditions for drying may be a temperature equal to or higher than the boiling point of the protic organic solvent used and the solvent used as needed. The specific temperature conditions cannot be generalized because they may vary depending on the type of protic organic solvent and solvent used, but the temperature is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, with the upper limit being preferably less than 130°C, more preferably 125°C or lower, and even more preferably 120°C or lower.

[0095] As for the pressure conditions, as described above, normal pressure or reduced pressure is preferable. When reduced pressure is used, specifically, the pressure is preferably 85 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less. The lower limit may be a vacuum (0 kPa). In consideration of ease of pressure adjustment, the pressure is preferably 1 kPa or more, more preferably 2 kPa or more, and even more preferably 3 kPa or more.

[0096] (Amorphous sulfide solid electrolyte) The sulfide solid electrolyte obtained by the production method of this embodiment can be either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte, as desired. That is, if the above-mentioned further heating is not performed, an amorphous sulfide solid electrolyte is obtained, and if heating is performed, a crystalline sulfide solid electrolyte is obtained.

[0097] The amorphous sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and oxygen atoms, and representative examples thereof include Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -P ２ O ５ The types of atoms constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by the types and amounts of raw materials used, or by an ICP emission spectrometer or the like.

[0098] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. 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.

[0099] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains lithium atoms, sulfur atoms, phosphorus atoms, and oxygen atoms, and may be a so-called glass ceramic obtained by heating an amorphous sulfide solid electrolyte (glass) to a temperature equal to or higher than the crystallization temperature.

[0100] The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment is not particularly limited as long as it has a crystal structure composed of lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms. Among them, Li ３＋ｘ P.S. ４－ｙ O ｙ (x satisfies −1≦x≦1, and y satisfies 0<y<4.) A preferred example is a crystalline sulfide solid electrolyte (also referred to as “Li-P—S—O-based sulfide solid electrolyte”) having an LGPS-type crystal structure.

[0101] Here, x is preferably −0.7 or more, more preferably −0.3 or more, even more preferably −0.1 or more, still more preferably 0.0 or more, and particularly preferably 0.2 or more, and the upper limit is preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. Also, y is preferably 0.5 or more, more preferably 0.8 or more, even more preferably 1.0 or more, and even more preferably 1.3 or more, and the upper limit is preferably 3.5 or less, more preferably 3.0 or less, even more preferably 2.5 or less, and even more preferably 2.0 or less.

[0102] The crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment may contain the above-mentioned LGPS-type crystal structure or may contain it as the main crystal, but from the viewpoint of obtaining higher ionic conductivity, it is preferable that it contains it as the main crystal. In this specification, "containing it as the main crystal" means that the proportion of the target crystal structure among the crystal structures is 80% or more, preferably 90% or more, and more preferably 95% or more. Furthermore, from the viewpoint of obtaining higher ionic conductivity, the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment contains crystalline Li ３ P.S. ４(β-Li ３ P.S. ４ ) is preferably not included.

[0103] The number of moles M of lithium atoms, phosphorus atoms, and sulfur atoms contained in the crystalline sulfide solid electrolyte obtained by the production method of this embodiment is Ｌ , L Ｐ and M Ｓ Preferably, the following relationship holds:

[0104] Mole of sulfur atoms (M Ｓ ) and the number of moles of phosphorus atoms (M Ｐ ) and the ratio (M Ｓ / M Ｐ ) is preferably 0.5 or more, more preferably 1.0 or more, even more preferably 1.5 or more, and still more preferably 2.0 or more, and the upper limit is preferably 4.0 or less, more preferably 3.5 or less, even more preferably 3.2 or less, and still more preferably 2.7 or less.

[0105] The number of moles of lithium atoms (M Ｌ ) and the number of moles of phosphorus atoms (M Ｐ ) and the ratio (M Ｌ / M Ｐ ) is preferably 2.3 or more, more preferably 2.7 or more, even more preferably 2.9 or more, still more preferably 3.0 or more, and particularly preferably 3.2 or more, and the upper limit is preferably 3.9 or less, more preferably 3.8 or less, even more preferably 3.7 or less, and still more preferably 3.6 or less. Ｓ / M Ｐ ) and ratio (M Ｌ / M Ｐ ) is within the above range, the LGPS-type crystal structure and other crystal structures are likely to be formed, and as a result, excellent ionic conductivity, water resistance, and electrochemical stability are likely to be obtained.

[0106] The sulfide solid electrolyte obtained by the manufacturing method of this embodiment may further contain carbon atoms in addition to lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. When a raw material containing carbon atoms is not used as a raw material, the carbon atoms are mainly derived from carbon atoms contained in the protic organic solvent containing oxygen atoms. When carbon atoms are contained, the content of carbon atoms in the sulfide solid electrolyte is approximately 0.1 mass% or more and 10 mass% or less.

[0107] In X-ray diffraction measurement using CuKα radiation, the LGPS crystal structure has diffraction peaks at least near 2θ = 25.5 ° and 31.0 °. It may also have a diffraction peak at 2θ = 21.1 °. The LGPS crystal structure of the sulfide solid electrolyte obtained by the manufacturing method of this embodiment may further have diffraction peaks near 2θ = 13.0 °, 15.3 °, 18.1 °, 21.8 °, 24.3 °, 28.5 °, and 34.0 °. Here, the numerical value of 2θ in the diffraction peak of the LGPS crystal structure may fluctuate within a range of ±0.4 °, and may further fluctuate within a range of ±0.3 °, ±0.1 °. In this specification, the numerical value of 2θ related to the LGPS crystal structure is assumed to fluctuate within a range of ±0.4 °, further ±0.3 °, ±0.1 °, unless otherwise specified.

[0108] When the crystalline sulfide solid electrolyte obtained by the manufacturing method of this embodiment has the LGPS-type crystal structure, it also has other crystal structures. In X-ray diffraction measurement using CuKα rays, the diffraction peaks of other crystal structures appear at least near 26.4°. They may also appear near 16.7°, 30.0°, and 33.9°. Here, for diffraction peaks of crystal structures other than the LGPS-type crystal structure, the 2θ value may fluctuate within a range of ±0.5°, and may further fluctuate within a range of ±0.3° or ±0.1°. In this specification, the 2θ value for crystal structures other than the LGPS-type crystal structure is assumed to fluctuate within a range of ±0.5°, or even ±0.3° or ±0.1°, unless otherwise specified.

[0109] Regarding the diffraction peaks of the other crystal structures, the intensity of the diffraction peak at 2θ=33.9° (I ３３．９ ) and the intensity of the diffraction peak at 2θ = 31.0° (I ３１．０ ) and the intensity ratio (I ３３．９ / I ３１．０ ) is preferably 0.065 or more, more preferably 0.075 or more, even more preferably 0.080 or more, and still more preferably 0.085 or more. There is no particular upper limit, and the larger the upper limit, the better, and it is usually 1.0 or less, preferably 0.5 or less. When the intensity ratio is within the above range, the effects of the other crystal structure in the sulfide solid electrolyte of this embodiment, i.e., water resistance and electrochemical stability, are improved.

[0110] Furthermore, the half-value width of the diffraction peak at 2θ=31.0° due to the LGPS crystal structure is preferably 1.5° or less, more preferably 1.4° or less, and even more preferably 1.3° or less, and the lower limit is preferably as small as possible, and although there is no particular limitation, it is usually 0.4° or more. When the half-value width is small within the above range, the crystallite diameter becomes large and the crystal structure becomes more excellent, thereby improving ionic conductivity, water resistance, and electrochemical stability.

[0111] The sulfide solid electrolyte obtained by the manufacturing method of this embodiment is a solid ３１ P-NMR measurement revealed that PSO ３ ３－ It is preferable that a peak due to PO is observed at 6.0±5.0 ppm. ４ ３－ Furthermore, a peak due to PS at 67.0 ± 5.0 ppm ２ O ２ ３－ It is preferable that a peak due to the above is observed.

[0112] PSO ３ ３－ The peak due to PO ４ ３－ Peaks due to and PS ２ O ２ ３－The peak due to indicates that the sulfide solid electrolyte obtained by the production method of this embodiment has oxygen at least in its structure.

[0113] The shape of the crystalline sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. 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, 8.0 μm or less, 6.0 μm or less, 5.0 μm or less, 3.0 μm or less, 1.0 μm or less, or 0.5 μm or less.

[0114] [Sulfide Solid Electrolyte] The sulfide solid electrolyte of the present embodiment contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and has an LGPS-type crystal structure having diffraction peaks at least at 2θ=25.5±0.4° and 31.0±0.4° in X-ray diffraction measurement using CuKα rays, and has a diffraction peak at 2θ=26.4±0.5° in X-ray diffraction measurement using CuKα rays.

[0115] Although there are no particular limitations on the method for producing the sulfide solid electrolyte of this embodiment, it is preferable to produce it by the method for producing a sulfide solid electrolyte of this embodiment, as described above. Therefore, the properties of the sulfide solid electrolyte of this embodiment are the same as those described above as the properties of the sulfide solid electrolyte obtained by the production method of this embodiment.

[0116] The sulfide solid electrolyte of this embodiment (including the sulfide solid electrolyte obtained by the manufacturing method of this embodiment) has excellent water resistance. Specifically, the amount of hydrogen sulfide generated, as measured by the method described in the examples, is 1.5 cm ３ / g-sample or less, even 1.3 cm ３ / g-sample or less, 1.0 cm ３ / g-below the sample, 0.8cm ３ / g-below the sample, 0.7cm ３ / g-sample or less. Thus, the sulfide solid electrolyte of the present embodiment can suppress the amount of hydrogen sulfide generated even when it comes into contact with moisture (e.g., moisture in the air) during, for example, battery production, and has excellent water resistance.

[0117] (Applications) The sulfide solid electrolyte obtained by the manufacturing method of this embodiment has high ionic conductivity and excellent battery performance, and is therefore suitable for use in batteries, particularly lithium ion batteries, and particularly all-solid-state batteries. The sulfide solid electrolyte of this embodiment may be used in a positive electrode layer, a negative electrode layer, or an electrolyte layer. Each layer can be manufactured by a known method.

[0118] The battery preferably includes 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.

[0119] 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.

[0120] (Powder XRD Diffraction Measurement) Powder X-ray diffraction (XRD) measurement was performed as follows. The sulfide solid electrolyte powder obtained in the Examples and Comparative Examples was filled into a groove (diameter: 18 mm, depth: 0.5 mm) on a sample holder, leveled with glass, and a small amount of standard silicon (X-ray diffraction standard sample, manufactured by NIST) was sprinkled on the surface to prepare a sample. This sample was sealed in a general-purpose atmosphere separator (manufactured by Rigaku Corporation) and measured under the following conditions without exposing it to air. Measurement equipment: Miniflex 600, manufactured by Rigaku Corporation Tube voltage: 40 kV Tube current: 15 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: focusing method Slit configuration: incident solar slit 2.5°, receiving solar slit 2.5°, IHS: 10.0 mm, DS: 1.25 deg, SS: 13 mm (open), RS: 13.0 mm, Kβ filter (Ni plate) used Detector: one-dimensional semiconductor detector (D / teX Ultra) Measurement range: 2θ = 10-60 deg step width, scan speed: 0.02 deg, 10 deg / min

[0121] (Method 1 for calculating peak half width and peak intensity) The half width of the peak obtained by the powder XRD diffraction measurement was calculated as follows. That is, a linear baseline was set for the peak shape obtained by the XRD measurement, and the difference between the intensity at each point and the baseline was calculated to obtain an XRD curve (see FIG. 16). The XRD curve was set as an equation (f(x)=(1-α)×L(x)+α×G(x)) consisting of a Lorentzian function L(x) and a Gaussian function G(x), and the intensity A, half width w, and position x were calculated by curve fitting. ０ The ratio α of the functions was determined. ３１．０ ) and the peak intensity at 33.9° (I ３３．９ ) and determine the peak intensity ratio (I ３３．９ / I ３１．０ ) was calculated.

[0122]

[0123] (Method 2 for calculating peak half width and peak intensity) For Comparative Examples 2 and 3, the half width and intensity of the XRD peak described in JP 2019-192490 A were determined as follows. The diagram in JP 2019-192490 A was compared with Example 4 described later in the same display range, a straight line baseline was set for each peak, and the peak intensity was determined from the straight line extended from the midpoint to the peak top. In addition, the peak width at the midpoint of the intensity was determined, and the half width of the peak described in JP 2019-192490 A was calculated from the values ​​of the peak width and half width in Example 4 (see FIG. 17). In addition, the peak intensity at 2θ = 30.9° (I ３１．０ ) and the peak intensity at 33.9° (I ３３．９ ) and determine the peak intensity ratio (I ３３．９ / I ３１．０ ) was calculated.

[0124] (Measurement of Ion Conductivity) In the present example, the measurement of ion conductivity was carried out as follows. A 10 mm diameter (cross-sectional area S: 0.785 cm ) sample was taken from the crystalline solid electrolyte obtained in the examples and comparative examples. ２ ) and a height (L) of 0.1 to 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: 7 MHz to 0.1 Hz, amplitude: 100 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

[0125] (solid ３１ P-NMR measurement) Measurement was performed using the following equipment under the following conditions: Equipment: ECZ400R (manufactured by JEOL Ltd.) Observation nuclei: ３１P Observation frequency: 161.994 MHz Measurement temperature: room temperature Pulse sequence: single pulse 90° pulse width: 3.2 μs Waiting time after FID measurement until next pulse application: 60 s MAS (magic angle spinning) rotation speed: 11 kHz Number of accumulations: 64 Measurement range: 250 ppm to -150 ppm Sample amount: 100 mg External standard: NH ４ H ２ P.O. ４ (chemical shift 1.00 ppm)

[0126] Peak separation: When peak separation is required, the obtained solid ３１ The P-NMR spectrum is analyzed using the software "FT-NMR" (software included in "FT-NMR Data Processing by Personal Computer," Revised Edition (Second Edition) (Sankyo Publishing)) to determine the separated peaks. The software calculates the separated peaks, calculated NMR signal values, and the residual sum of squares R2 from the NMR signals (experimental values) using the nonlinear least squares method. Peak separation is considered complete when the residual sum of squares R2 within the analysis range between the experimental and calculated values, assuming the maximum peak height to be 1, is 0.007 or less and the number of separated peaks is the smallest.

[0127] (CV Measurement 1) To evaluate the electrochemical stability during oxidation-reduction, CV measurement was performed using the following CV measurement cell. In a glove box under an Ar atmosphere, 120 mg of the solid electrolyte obtained in Example 11 was weighed and placed in a battery cell with a diameter of 10 mm. The cell was then pressed and molded at 360 MPa using a stainless steel mold. One side of the mold was removed, and an In / Li alloy foil made by bonding an In foil (10 mmφ, thickness: 0.3 mm) and a Li foil (8 mmφ, thickness: 0.25 mm) was placed inside. After the mold was replaced, the cell was pressed again at 120 MPa and secured with four screws sandwiching an insulator to obtain a measurement cell.

[0128] The measurement cell obtained by the above method was connected to a measuring instrument (SI-1287, manufactured by Solartron), and a CV curve was obtained under the following conditions: Measurement temperature: 25°C, Sweep rate: 1.0 mV / s, Potential measurement range: Open circuit voltage -> -1.12 V -> +5.00 V -> -1.12 V

[0129] Example 1: 20 mL of ethanol (EtOH), a protic organic solvent containing oxygen atoms, was added to a 100 mL Schlenk tube equipped with a stirrer under a nitrogen atmosphere. After rotating the stirrer, 0.552 g of lithium sulfide was introduced and stirring was continued for 5 minutes. Then, 0.890 g of diphosphorus pentasulfide was introduced and stirring was continued for 5 minutes to prepare a solution. The resulting solution was dried under vacuum at 120°C to obtain a powder solute (amorphous sulfide solid electrolyte). The resulting powder solute was heated in an electric furnace at 400°C for 2 hours to obtain a crystalline sulfide solid electrolyte powder. The ratio of lithium sulfide to diphosphorus pentasulfide was 3:1 (molar ratio). Powder XRD diffraction measurement was performed on the resulting crystalline sulfide solid electrolyte. The X-ray diffraction pattern is shown in Figure 1. The ionic conductivity was measured and found to be 2.8 x 10 －５ (S / cm).

[0130] Example 2: 0.552 g of lithium sulfide and 0.890 g of diphosphorus pentasulfide were mixed in a mortar for 5 minutes. The resulting mixture was introduced into a 100 mL Schlenk flask equipped with a stirrer under a nitrogen atmosphere. After rotating the stirrer, 20 mL of ethanol (EtOH), a protic organic solvent containing oxygen atoms, was added and stirred for 5 minutes to prepare a solution. The resulting solution was dried under vacuum at 120°C to obtain a powder solute (amorphous sulfide solid electrolyte). The resulting powder solute was heated in an electric furnace at 400°C for 2 hours to obtain a crystalline sulfide solid electrolyte powder. The ratio of lithium sulfide to diphosphorus pentasulfide was 3:1 (molar ratio). Powder XRD diffraction analysis was performed on the resulting crystalline sulfide solid electrolyte. The X-ray diffraction pattern is shown in Figure 2. The ionic conductivity was measured and found to be 2.8 x 10 －５ (S / cm).

[0131] (Examples 3, 6, 8, and 10) A crystalline sulfide solid electrolyte powder was obtained in the same manner as in Example 1, except that lithium sulfide and diphosphorus pentasulfide were used in amounts corresponding to the ratios shown in Table 1, and the protic organic solvent was changed to a solvent shown in Table 1. Powder XRD diffraction measurements were performed on the obtained crystalline sulfide solid electrolyte. The X-ray diffraction patterns are shown in Figures 3, 6, 8, and 10, respectively. The results of measuring ionic conductivity are also shown in Table 1.

[0132] Examples 4, 5, 7, 9, and 11-13: A crystalline sulfide solid electrolyte powder was obtained in the same manner as in Example 2, except that lithium sulfide and diphosphorus pentasulfide were used in amounts corresponding to the ratios shown in Table 1, and the protic organic solvent and heating conditions (heating temperature and heating time) were changed to those shown in Table 1. Powder XRD diffraction measurements were performed on the obtained crystalline sulfide solid electrolyte. X-ray diffraction patterns are shown in Figures 4, 5, 7, 9, and 11-13, respectively. The results of ionic conductivity measurements are also shown in Table 1. For Example 11, CV measurements were performed based on the above method, and the results are shown in Figure 19.

[0133] Comparative Example 1: The same procedure as in Example 1 was carried out except that ethanol was replaced with toluene, an aprotic solvent. Instead of a solution, a slurry-like fluid was obtained. The slurry-like fluid was dried at 120°C under vacuum to obtain a powder. The X-ray diffraction pattern is shown in Figure 14. In the aprotic solvent, the reaction of the raw materials did not proceed, and Li ２ S, P ２ S ５ The resulting powder was then heated at 400°C for 2 hours in an electric furnace to obtain a powder. The resulting powder was subjected to powder XRD diffraction measurement. The X-ray diffraction pattern is shown in Figure 15. The results of measuring the ionic conductivity are shown in Table 2. The heating resulted in the formation of Li ４ P ２ S ６ Crystals and a small amount of β-Li ３ P.S. ４ It was found that crystals had appeared and the conductivity was low.

[0134] (Comparative Examples 2 and 3) Example 1 and Comparative Example 1 described in JP 2019-192490 A are referred to as Comparative Examples 2 and 3 in this specification. The results of determining the half-width and intensity of the XRD peak along with the composition and manufacturing conditions described in the publication are shown in Table 2.

[0135] For the powders obtained in Examples 1 to 13, the half-width of the diffraction peak at 2θ=31.0° was determined by the above-mentioned method (calculation method 1), and the intensity (I ３３．９ ), the intensity of the diffraction peak at 2θ=31.0±0.4° (I ３１．０ ) and determine the intensity ratio (I ３３．９ / I ３１．０ The results are shown in Table 1. For Comparative Examples 2 and 3, the half-width of the diffraction peak at 2θ=30.9° was determined by the above-mentioned method (calculation method 2) using the diagrams described in JP-A-2019-192490, and the intensity (I ３３．９ ), the intensity of the diffraction peak at 2θ = 30.9° (I ３１．０ ) and determine the intensity ratio (I ３３．９ / I ３１．０ ) was calculated. The results are shown in Table 2. Here, the peak at 2θ = 30.9° in Comparative Examples 2 and 3 corresponds to the peak at 2θ = 31.0° in the Examples, so the intensity ratios in Comparative Examples 2 and 3 can be directly compared with those in the Examples. Note that for Comparative Example 3, no clear peak was observed at 2θ = 33.9°, and the peak intensity ratio could not be calculated.

[0136] For the powders of Examples 4 and 9, solid ３１ P-NMR measurement was carried out. ３１ The P-NMR spectrum is shown in Figure 18. ３１ Based on the data obtained by P-NMR measurement, the phosphorus ratio (mol%) contained in each structure was calculated based on the peak area attributable to each structure. Specifically, the phosphorus ratio (mol%) contained in each structure was calculated from the ratio of the peak area of ​​each structure to the total area of ​​the peaks attributable to each structure shown in Table 3. The calculated phosphorus ratio (mol%) of each structure is shown in Table 3.

[0137] Note: In Tables 1 and 2, "(1)" in the mixing method indicates that lithium sulfide is mixed with an organic solvent, and then phosphorus sulfide is added and mixed (the above-mentioned mixing method (1)). "(2)" indicates that all raw material ingredients are mixed with an organic solvent (the above-mentioned mixing method (2)). "Quenching" indicates a melt-quenching method.

[0138]

[0139]

[0140] From the results of Figures 1 to 13, the sulfide solid electrolyte obtained in the examples had crystallization peaks detected at 2θ = 13.0°, 15.3°, 18.1°, 21.1°, 21.8°, 24.3°, 25.5°, 28.5°, 31.0°, and 34.0°, and therefore could be said to have an LGPS-type crystal structure. Furthermore, crystallization peaks were also detected at 2θ = 16.7°, 26.4°, 30.0°, and 33.9°, and therefore could be said to have other crystal structures as well. In addition, the ionic conductivity was 2.7 x 10 －５ ~1.6 x 10 －４ (S / cm), and had excellent ionic conductivity.

[0141] Also, solid ３１ From the results of P-NMR measurement, the crystalline sulfide solid electrolytes of Examples 4 and 9 were ３ ３－ The peak due to PO (34.0±5.0 ppm) and PO ４ ３－ The peak due to PS (6.0 ± 5.0 ppm) ２ O ２ ３－ A peak (67.0±5.0 ppm) due to oxygen atoms was observed, and it was confirmed that the crystal structure contained oxygen atoms.

[0142] CV measurement results of Example 11 in FIG. 19 (potential is "vs Li / Li ＋ As shown in the table, the sulfide solid electrolyte of the present embodiment does not exhibit any deterioration behavior over a wide potential range of −1.12 to 5.0 V, and it has been confirmed that the sulfide solid electrolyte is an electrochemically stable material.

[0143] From the results of the above examples, it was confirmed that the powder obtained by preparing a solution by mixing a raw material ingredient and a protic organic solvent was a sulfide solid electrolyte having an LGPS-type crystal structure containing oxygen atoms, even though no raw material containing oxygen atoms was used as the raw material ingredient. In other words, it was confirmed that the oxygen atoms of the protic organic solvent containing oxygen atoms were incorporated into the sulfide solid electrolyte and incorporated as atoms constituting the crystal structure. Furthermore, it was also confirmed that a sulfide solid electrolyte having an LGPS-type crystal structure could be obtained at a low temperature of 300 to 400 °C, whereas a high temperature of 700 to 950 °C was previously required.

[0144] Example 14 Using the sample obtained in Example 11, the following CV measurement and hydrogen sulfide generation test were carried out.

[0145] (CV Measurement 2) In a glove box under an Ar atmosphere, 120 mg of the sample was weighed, placed in a 10 mm diameter battery cell, and pressed at 360 MPa using a stainless steel mold to form a pellet (φ10 mm, thickness: 0.3 mm). This was sandwiched between a working electrode (stainless steel current collector) and a counter electrode / reference electrode (a stainless steel current collector with a φ8 mm metallic lithium foil (thickness: 0.25 mm) attached) to prepare a measurement cell. The measurement cell was sealed in a sealed container using a separable flask, and CV measurement (3 cycles) was performed under the following conditions. The measurement instrument used was the same as that used in CV Measurement 1 above (Solartron, SI-1287). Measurement temperature: 25°C, Sweep rate: 1.0 mV / s, Potential measurement range: Open circuit voltage ⇒ -0.5 V ⇒ +5.00 V

[0146] (Hydrogen Sulfide Generation Test) In a glove box under an argon atmosphere, 10 mg of a sample was weighed out, and the sample and a hydrogen sulfide sensor ("ToxiRAE Pro PGM-1860 (HS) (model number)," manufactured by RAE Systems) were placed in a separable flask (volume: 1 L). Next, nitrogen gas adjusted to a dew point of -40°C was introduced into the separable flask, and the hydrogen sulfide concentration in the separable flask 3 hours after the sample had been exposed was measured with the hydrogen sulfide sensor.

[0147] The results of CV measurement performed by the above-mentioned CV measurement 2 method are shown in Figure 20. CV measurement 2 uses metallic Li foil, and is therefore performed under harsher conditions that make reduction more likely than CV measurement 1. The results in Figure 20 confirm that even under such harsh conditions, degradation behavior is suppressed, and that the material is electrochemically stable.

[0148] Furthermore, from the hydrogen sulfide concentration measured by the above method, the amount of hydrogen sulfide generated in 3 hours was 0.5 cm ３ In contrast, in the hydrogen sulfide generation test, the sample was ３ P.S. ４ (β-Li ３ P.S. ４ ), the amount of hydrogen sulfide generated was 1.6 cm ３ From this result, it was confirmed that the method for producing a sulfide solid electrolyte of the present embodiment can provide a sulfide solid electrolyte that suppresses the amount of hydrogen sulfide generated and has excellent water resistance.

[0149] According to the method for producing a sulfide solid electrolyte of this embodiment, a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms can be produced with high production efficiency. Furthermore, since a liquid phase method is used in which raw material components are mixed with a protic organic solvent to prepare a solution, it is easy to adapt to changes in scale and to mass production. The sulfide solid electrolyte of this embodiment obtained by the production method of this embodiment is suitable for use in batteries, particularly lithium ion batteries, and particularly as all-solid-state batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones.

Claims

1. A solution is prepared by mixing a raw material containing lithium atoms, phosphorus atoms, and sulfur atoms with a protic organic solvent containing oxygen atoms. including, A method for producing a sulfide solid electrolyte containing lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms.

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein the raw material containing the lithium atom, phosphorus atom, and sulfur atom contains lithium sulfide and phosphorus sulfide.

3. The method for producing a sulfide solid electrolyte according to claim 2, wherein the amount of lithium sulfide blended with respect to the total amount of lithium sulfide and phosphorus sulfide is 45.0 mol% or more and 78.0 mol% or less.

4. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, wherein the raw material content does not contain a raw material containing oxygen atoms.

5. A method for producing a sulfide solid electrolyte according to claim 1, comprising preparing the solution by mixing a raw material containing lithium atoms and sulfur atoms with a protic organic solvent containing oxygen atoms, and then adding and mixing a raw material containing phosphorus atoms and sulfur atoms.

6. The method for producing a sulfide solid electrolyte according to claim 1, comprising preparing the solution by mixing a raw material containing lithium atoms and sulfur atoms, a raw material containing phosphorus atoms and sulfur atoms, and a protic organic solvent containing oxygen atoms.

7. A method for producing a sulfide solid electrolyte according to claim 5 or 6, wherein the raw material containing lithium atoms and sulfur atoms contains lithium sulfide, and the raw material containing phosphorus atoms and sulfur atoms contains phosphorus sulfide.

8. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, wherein the protic organic solvent containing the oxygen atom is at least one solvent selected from alcohol solvents, nitro group-containing solvents, and carboxylic acid solvents.

9. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, further comprising heating the solution after preparing the solution.

10. The method for producing a sulfide solid electrolyte according to claim 9, wherein the heating temperature in the heating process is 150°C or more and 600°C or less.

11. A method for producing a sulfide solid electrolyte according to any one of claims 1 to 3, wherein the sulfide solid electrolyte has an LGPS-type crystal structure.

12. It contains lithium atoms, phosphorus atoms, sulfur atoms, and oxygen atoms, and has an LGPS-type crystal structure having diffraction peaks at least at 2θ = 25.5 ± 0.4° and 31.0 ± 0.4° in X-ray diffraction measurements using CuKα rays. A sulfide solid electrolyte exhibiting a diffraction peak at 2θ = 26.4 ± 0.5° in X-ray diffraction measurements using CuKα rays.

13. The sulfide solid electrolyte according to claim 12, further having a diffraction peak at 2θ = 30.0 ± 0.5° in X-ray diffraction measurements using CuKα rays.

14. The sulfide solid electrolyte according to claim 12 or 13, further having a diffraction peak at 2θ = 16.7 ± 0.5° in X-ray diffraction measurements using CuKα rays.

15. In X-ray diffraction measurements using CuKα rays, a diffraction peak is further found at 2θ = 33.9 ± 0.5°, and the intensity of the diffraction peak at 2θ = 33.9 ± 0.5° (I ３３．９ ) and the intensity of the diffraction peak at 2θ = 31.0 ± 0.4° (I ３１．０ ) and the intensity ratio (I ３３．９ / I ３１．０ The sulfide solid electrolyte according to claim 12 or 13, wherein the value of ) is 0.065 or more and 1.0 or less.

16. The sulfide solid electrolyte according to claim 12 or 13, further having a diffraction peak at 2θ = 21.1 ± 0.4° in X-ray diffraction measurements using CuKα rays.

17. The sulfide solid electrolyte according to claim 12 or 13, wherein the full width at half maximum of the diffraction peak at 2θ = 31.0 ± 0.4° is 0.4° or more and 1.5° or less.

18. solid ３１ P-NMR measurement revealed a concentration of 34.0 ± 5.0 ppm of PSO4. ３ ３－ The sulfide solid electrolyte according to claim 12 or 13, wherein a peak due to is observed.

19. Solid ３１ By P-NMR measurement, a peak attributed to PO is observed at 6.0 ± 5.0 ppm ４ ３－ The sulfide solid electrolyte according to claim 12 or 13, in which a peak attributed to PO is observed

20. solid ３１ P-NMR measurement revealed a PS level of 67.0 ± 5.0 ppm. ２ O ２ ３－ The sulfide solid electrolyte according to claim 12 or 13, wherein a peak due to is observed.

21. The number of moles of sulfur atoms (M Ｓ ) and the number of moles of phosphorus atoms (M Ｐ ) ratio (M Ｓ / M Ｐ The sulfide solid electrolyte according to claim 12 or 13, wherein the value of is 0.5 or more and 4.0 or less.

22. The number of moles of lithium atoms (M Ｌ ) and the number of moles of phosphorus atoms (M Ｐ ) ratio (M Ｌ / M Ｐ The sulfide solid electrolyte according to claim 12 or 13, wherein the ratio is 2.3 or more and 3.9 or less.

23. Furthermore, the sulfide solid electrolyte according to claim 12 or 13, further comprising carbon atoms.