Solid electrolyte and method for producing same

Abstract

The present invention relates to a method for producing a solid electrolyte having an argyrodite crystal structure, the method comprising: a mixing step for mixing raw materials such that lithium (Li), phosphorus (P), sulfur (S), oxygen (O), and halogen (X) satisfy formulae (11)-(14); and a heating step for heating the mixture obtained in the mixing step. 4.8 < = Li / P < = 5.3 (11) 3.8 < = S / P < = 4.4 (12) 0 < O / P < = 0.8 (13) 1.0 < X / P < = 2.0 (14) (formula (11) is the molar ratio of Li to P, formula (12) is the molar ratio of S to P, formula (13) is the molar ratio of O to P, and formula (14) is the molar ratio of halogen (X) to P. )

Description

[0001] This invention application is a divisional application filed with China based on the international application PCT application number PCT / JP2020 / 035418, subject to “Solid electrolyte and method of manufacturing thereof”, which has entered the national phase in China. The application number of the Chinese invention application is 202080056688.9, and the application date is September 18, 2020. Technical Field

[0002] This invention relates to solid electrolytes and methods for manufacturing the same. Background Technology

[0003] It is known that sulfide solid electrolytes deteriorate due to moisture in the air. To address this, for example, Patent Document 1 discloses a solid electrolyte characterized by containing Li₂ with an Argyrodite-type crystal structure. 7- a PS 6-a Ha a (Ha represents halogen, a is 0.2 < a ≤ 1.8) and Li3PS4, in the X-ray diffraction patterns obtained by X-ray diffraction (XRD), the peak intensity appearing at diffraction angles 2θ = 26.0–28.8° originating from Li3PS4 has a ratio of 0.04–0.3 to the peak intensity appearing at diffraction angles 2θ = 24.9–26.3° originating from a sulfide-germanium-type crystal structure. Patent Document 2 discloses a sulfide solid electrolyte in which an alkaline compound is mixed, wherein the molar amount of alkali metal contained in the alkaline compound is more than 1 / 1000 and less than 1 / 25 of the molar amount of Li contained in the solid electrolyte.

[0004] Furthermore, Patent Documents 3 and 4 disclose sulfide solid electrolyte particles containing lithium, phosphorus, sulfur, and halogen and having a cubic crystal system of sulfide-germanium sulfide, and sulfide solid electrolytes for lithium secondary batteries whose surfaces are coated with compounds having a non-sulfide-germanium sulfide crystal structure containing lithium, phosphorus, and sulfur.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2019 / 131725

[0008] Patent Document 2: Japanese Patent Application Publication No. 2017-120728

[0009] Patent Document 3: International Publication No. 2019 / 176895

[0010] Patent Document 4: Japanese Patent No. 6293383 Summary of the Invention

[0011] In the solid electrolytes of Patent Documents 1-4, the generation of hydrogen sulfide and ionic conductivity were not adequately balanced, and further improvements are required.

[0012] The purpose of this invention is to provide a solid electrolyte that suppresses the generation of hydrogen sulfide and has high ionic conductivity, and a method for manufacturing the same.

[0013] According to one embodiment of the present invention, a method for manufacturing a solid electrolyte having a sulfide-germanium ore-type crystal structure is provided, comprising: a mixing step, wherein raw materials are mixed such that lithium (Li), phosphorus (P), sulfur (S), oxygen (O) and halogen (X) satisfy the following formulas (11) to (14); and a heating step, wherein the mixture obtained by the mixing step is heated.

[0014] 4.8≤Li / P≤5.3…(11)

[0015] 3.8≤S / P≤4.4…(12)

[0016] 0<O / P≤0.8…(13)

[0017] 1.0 < X / P ≤ 2.0…(14)

[0018] (Equation (11) is the molar ratio of Li to P, Equation (12) is the molar ratio of S to P, Equation (13) is the molar ratio of O to P, and Equation (14) is the molar ratio of halogen (X) to P.)

[0019] Furthermore, according to one embodiment of the present invention, a solid electrolyte is provided having a sulfosilver germanite-type crystal structure comprising lithium (Li), phosphorus (P), sulfur (S), oxygen (O) and halogen (X), wherein the proportion of the Li3PO4 crystal structure in the total crystal is 0.1% by mass or more and 3.0% by mass or less, and the solid electrolyte satisfies the following formulas (21) to (23).

[0020] 4.8≤Li / P≤5.3…(21)

[0021] 3.8≤S / P≤4.4…(22)

[0022] 1.0 < X / P ≤ 2.0…(23)

[0023] (Equation (21) is the molar ratio of Li to P, Equation (22) is the molar ratio of S to P, and Equation (23) is the molar ratio of halogen (X) to P.)

[0024] According to the present invention, a solid electrolyte that suppresses the generation of hydrogen sulfide and has high ionic conductivity, and a method thereof are provided. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the experimental setup for measuring hydrogen sulfide production.

[0026] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the solid electrolyte obtained in Example 1.

[0027] Figure 3 The image shows the XRD pattern of the solid electrolyte obtained in Example 2.

[0028] Figure 4 The image shows the XRD pattern of the solid electrolyte obtained in Example 3.

[0029] Figure 5 The image shows the XRD pattern of the solid electrolyte obtained in Example 4.

[0030] Figure 6 The image shows the XRD pattern of the solid electrolyte obtained in Comparative Example 1.

[0031] Figure 7 The image shows the XRD pattern of the solid electrolyte obtained in Comparative Example 2.

[0032] Figure 8 The image shows the XRD pattern of the solid electrolyte obtained in Comparative Example 3.

[0033] Figure 9 The image shows the XRD pattern of the solid electrolyte obtained in Comparative Example 4.

[0034] Figure 10 The image shows the XRD pattern of the solid electrolyte obtained in Comparative Example 5.

[0035] Figure 11 The image shows the XRD pattern of the solid electrolyte obtained in Example 5. Detailed Implementation

[0036] [First Implementation Method]

[0037] A method for manufacturing a solid electrolyte according to one embodiment of the present invention includes the following mixing and heating steps to manufacture a solid electrolyte having a sulfosilver germanite-type crystal structure.

[0038] Mixing process: The process of mixing raw materials such that lithium (Li), phosphorus (P), sulfur (S), oxygen (O) and halogen (X) satisfy the following formulas (11) to (14).

[0039] 4.8≤Li / P≤5.3…(11)

[0040] 3.8≤S / P≤4.4…(12)

[0041] 0<O / P≤0.8…(13)

[0042] 1.0 < X / P ≤ 2.0…(14)

[0043] (Equation (11) is the molar ratio of Li to P, Equation (12) is the molar ratio of S to P, Equation (13) is the molar ratio of O to P, and Equation (14) is the molar ratio of halogen (X) to P.)

[0044] Heating process: The process of heating the mixture obtained through the mixing process.

[0045] In this embodiment, it is presumed that by adjusting the composition of the starting materials to formulas (11) to (14), a crystal structure with sulfur ions (S) different from that of conventional silver-germanium sulfide can be formed. 2- The amount of ) decreases while the amount of halide ions (Cl) decreases. - ,Br - (etc.) The increased silver-germanium sulfide crystal structure.

[0046] The sulfide-germanium type crystal structure is a type of PS4 3- The structure is the main unit structure of the skeleton, and the sites located around it are S surrounded by Li. 2- And structures occupied by arbitrary halide ions. The typical argentite-germanium sulfide crystal structure is shown in space group F-43M. Crystallographically, this crystal structure is represented in PS4. 3- The structure has 4a and 4d sites around its periphery. Elements with larger ionic radii tend to occupy 4a sites, while elements with smaller ionic radii tend to occupy 4d sites.

[0047] In a unit lattice of a steric sulfide-germanium mineral-type crystal structure, there are a total of 8 sites, including 4a and 4d sites. The inventors of this application envision S occupying sites in the steric sulfide-germanium mineral-type crystal structure. 2- The cause of hydrogen sulfide production was discovered by adding sulfur to the sulfur-containing crystal structure of the sulfide-germanium ore type. 2- The relatively lower content of [something] can reduce the generation of hydrogen sulfide.

[0048] On the other hand, it was confirmed that if the amount of S in the starting material is simply reduced, some elements will not form a sulforaphite-germanium ore crystal structure during the heating process, but will instead form crystal phases other than sulforaphite-germanium ore such as β-Li3PS4. As a result, the ionic conductivity is greatly reduced.

[0049] After conducting in-depth research to solve this technical problem, the inventors surprisingly discovered that by setting the composition of the above formulas (11) to (14), the starting material contains O, which can suppress the formation of crystalline phases other than β-Li3PS4 and silver-germanium sulfide crystals during the heating process and increase the S content in the crystal. 2-The amount of reduced sulfur-silver-germanium mineral-type crystal structure results in a solid electrolyte with sufficient suppression of hydrogen sulfide production and high ionic conductivity.

[0050] The above formulas (11) to (14) in the mixing process preferably satisfy the following formula.

[0051] 4.85≤Li / P≤5.25

[0052] 3.9 ≤ S / P ≤ 4.3

[0053] 0.01≤O / P≤0.7

[0054] 1.2 ≤ X / P ≤ 1.9

[0055] More preferably, the above formulas (11) to (14) in the mixing process satisfy the following formula.

[0056] 4.9 ≤ Li / P ≤ 5.2

[0057] 4.0 ≤ S / P ≤ 4.2

[0058] 0.05≤O / P≤0.6

[0059] 1.4 ≤ X / P ≤ 1.8

[0060] The raw materials used in this embodiment are two or more compounds and / or elements combined to contain the elements necessary for the solid electrolyte to be manufactured in a specified molar ratio. Specifically, two or more compounds and elements containing Li, P, S, O and halogen (X) as a whole are used in combination.

[0061] Examples of lithium-containing raw materials include lithium compounds such as lithium sulfide (Li₂S), lithium oxide (Li₂O), lithium carbonate (Li₂CO₃), and lithium hydroxide (LiOH), as well as elemental lithium metal. From the viewpoint of ease of processing and reaction of the raw materials, lithium compounds are preferred, and Li₂S is more preferred.

[0062] Examples of phosphorus-containing raw materials include phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), phosphorus compounds such as sodium phosphate (Na3PO4), and elemental phosphorus. Among these, phosphorus sulfides are preferred from the viewpoint of ease of handling and reactivity, and phosphorus pentasulfide (P2S5) is more preferred. Phosphorus compounds such as phosphorus pentasulfide (P2S5) and elemental phosphorus can be used without particular limitation as long as they are industrially manufactured and commercially available.

[0063] As a raw material containing halogen (X), it is preferred to use, for example, a raw material of formula (M l -X m(represented by) at least one of halogen compounds and elemental halogens.

[0064] In the formula, M represents sodium (Na), lithium (Li), boron (B), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), germanium (Ge), arsenic (As), selenium (Se), tin (Sn), antimony (Sb), tellurium (Te), lead (Pb), bismuth (Bi); or a substance obtained by combining oxygen and sulfur with these elements, preferably Li or P, more preferably Li.

[0065] X is a halogen element chosen from F, Cl, Br and I.

[0066] Furthermore, l is an integer of 1 or 2, and m is an integer from 1 to 10. When m is an integer from 2 to 10, that is, when there are multiple X, X can be the same or different. For example, in SiBrCl3 described later, m is 4, and X is composed of different elements such as Br and Cl.

[0067] Specifically, examples of halogen compounds include: sodium halides such as NaI, NaF, NaCl, and NaBr; lithium halides such as LiF, LiCl, LiBr, and LiI; boron halides such as BCl3, BBr3, and BI3; aluminum halides such as AlF3, AlBr3, AlI3, and AlCl3; silicon halides such as SiF4, SiCl4, SiCl3, Si2Cl6, SiBr4, SiBrCl3, SiBr2Cl2, and SiI4; phosphorus halides such as PF3, PF5, PCl3, PCl5, POCl3, PBr3, POBr3, PI3, P2Cl4, and P2I4; and SF2, SF4, SF6, and S2F2. 10 Sulfur halides such as SCl2, S2Cl2, S2Br2; Germanium halides such as GeF4, GeCl4, GeBr4, GeI4, GeF2, GeCl2, GeBr2, GeI2; Arsenic halides such as AsF3, AsCl3, AsBr3, AsI3, AsF5; Selenium halides such as SeF4, SeF6, SeCl2, SeCl4, Se2Br2, SeBr4; Tin halides such as SnF4, SnCl4, SnBr4, SnI4, SnF2, SnCl2, SnBr2, SnI2; Antimony halides such as SbF3, SbCl3, SbBr3, SbI3, SbF5, SbCl5; TeF4, Te2F 10 Tellurium halides such as TeF6, TeCl2, TeCl4, TeBr2, TeBr4, and TeI4; lead halides such as PbF4, PbCl4, PbF2, PbCl2, PbBr2, and PbI2; and bismuth halides such as BiF3, BiCl3, BiBr3, and BiI3.

[0068] Examples of suitable lithium halides include lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), as well as phosphorus halides such as phosphorus pentachloride (PCl5), phosphorus trichloride (PCl3), phosphorus pentabromide (PBr5), and phosphorus tribromide (PBr3). Lithium halides or PBr3 are preferred, with lithium halides being more preferred from the viewpoint of ease of processing. Furthermore, LiCl and LiBr are more preferred from the viewpoint of further improving ionic conductivity.

[0069] Halogen compounds can be used alone, or in combination of two or more.

[0070] In this embodiment, compounds obtained from the above-described reactions of raw materials may also be used. For example, Li3PS4 can be synthesized from Li2S and P2S5, and Li3PS4, Li2O, and LiX can be used as raw materials. Furthermore, Li3PS4 can be crystalline or amorphous, or a mixture of crystalline and amorphous materials.

[0071] In one embodiment, it is preferred to use any one or more of Li₂O and LiOH as raw materials. Further, it is preferred to use Li₂S, Li₂O, P₂S₅, and LiX (where X is a halogen) as raw materials. For example, when using Li₂S, Li₂O, P₂S₅, and LiX as raw materials, the molar ratio of the input raw materials can be set to Li₂S:Li₂O:P₂S₅:LiX = 1.5–1.9:0.01–0.8:0.5:1.0–2.0.

[0072] In the mixing process, the above-mentioned raw materials are mixed.

[0073] There are no particular limitations on the mixing method; any well-known method can be used.

[0074] In this embodiment, mechanical stress can be applied to the above-mentioned raw materials to cause a reaction while mixing. Alternatively, they can be mixed and pulverized. Here, "applying mechanical stress" refers to mechanically applying shear force and impact force, etc. Examples of mechanisms for applying mechanical stress include pulverizers such as planetary mills, vibratory mills, rotary mills, and bead mills, or kneaders such as single-shaft kneaders and multi-shaft kneaders.

[0075] The mixing process can be carried out in the presence of a solvent (wet mixing), or it can be carried out without the use of a solvent (dry mixing).

[0076] In the case of dry mixing, for example, when a planetary ball mill is used as the pulverizer, the pulverizing and mixing conditions can be achieved by setting the rotational speed to tens to hundreds of revolutions per minute and performing the treatment for 0.5 to 100 hours. More specifically, in the case of the planetary ball mill (manufactured by FRITSCH, model P-7) used in the embodiments of this application, the rotational speed of the planetary ball mill is preferably 350 rpm to 400 rpm, more preferably 360 rpm to 380 rpm.

[0077] For example, when using zirconia balls, the diameter of the balls used as the pulverizing medium is preferably 0.2 to 20 mm.

[0078] In one embodiment, wet mixing is preferred because there is a possibility of suppressing the formation of β-Li3PS4.

[0079] Organic solvents can be used, and non-polar solvents, polar solvents, or mixtures thereof are preferred. Non-polar solvents or solvents with non-polar solvents as the main component are preferred, for example, the organic solvent comprising more than 95% by mass of a non-polar solvent.

[0080] Hydrocarbon solvents are preferred as nonpolar solvents. Saturated hydrocarbons, unsaturated hydrocarbons, or aromatic hydrocarbons can be used as hydrocarbon solvents.

[0081] Examples of saturated hydrocarbons include hexane, pentane, 2-ethylhexane, heptane, decane, tridecane, and cyclohexane.

[0082] Examples of unsaturated hydrocarbons include hexene, hepten, and cyclohexene.

[0083] Examples of aromatic hydrocarbons include toluene, xylene, ethylbenzene, decahydronaphthalene, and 1,2,3,4-tetrahydronaphthalene.

[0084] Among these, toluene or xylene is preferred.

[0085] Hydrocarbon solvents are preferably pre-dehydrated. Specifically, the water content is preferably 100 ppm by mass or less, and particularly preferably 30 ppm by mass or less.

[0086] In one embodiment, the organic solvent preferably comprises at least one of a nitrile compound and an ether compound.

[0087] Examples of ether compounds include tetrahydrofuran and diethyl ether.

[0088] As a nitrile compound, R(CN) is preferred. n The formula represents a nitrile compound. In the formula, R is an alkyl group having 1 to 10 carbon atoms, or a group having a cyclic aromatic ring having 6 to 18 carbon atoms. n is 1 or 2.

[0089] Examples of suitable alternatives include acetonitrile, propionitrile, 3-chloropropionitrile, benzonitrile, 4-fluorobenzonitrile, tert-butyronitrile, isobutyronitrile, cyclohexanonitrile, hexanonitrile, isohexanonitrile, malondionitrile, and fumaronitrile. Propionitrile, isohexanonitrile, and isobutyronitrile are preferred.

[0090] For example, since nitrile compounds azeotropically react with toluene, they are easily removed from the processed material along with toluene during drying, and are therefore preferred.

[0091] The amount of nitrile and ether compounds contained in the organic solvent is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass, and particularly preferably 0.3 to 1% by mass.

[0092] In wet mixing, a bead mill is preferred. Since the particle size of each raw material can be reduced by using a bead mill for mixing and pulverizing, it is believed that the diffusion path of each element in the heating process is reduced, and each element becomes easier to use to form a sulfide-germanium ore-type crystal structure. As a result, the formation of heterogeneous phases such as the Li3PS4 crystal structure can be suppressed.

[0093] The mixture of raw materials obtained by removing solvent from the processed material after wet mixing using a bead mill is mainly composed of microcrystalline particles. By mixing and pulverizing the raw materials, microparticles can be advanced, resulting in a mixture consisting of microcrystalline particles of each raw material.

[0094] The mixture of raw materials can also be pre-calcined. In one embodiment, the mixture of raw materials is obtained by removing the solvent as described above, and then pre-calcined to obtain a powdered pre-calcined product. The heating temperature and time for pre-calcination can be appropriately adjusted considering the composition of the pre-calcined product. For example, the heating temperature is preferably 150°C to 300°C, more preferably 160°C to 280°C, and particularly preferably 170°C to 250°C. The heating time is preferably 0.1 to 8 hours, more preferably 0.2 to 6 hours, and particularly preferably 0.25 to 4 hours.

[0095] There are no particular limitations on the heating device used in pre-firing. Examples include shear dryers such as FM mixers and Nauta mixers, stationary furnaces such as hearth kilns, and rotary furnaces such as rotary kilns. Furthermore, drying can be performed before pre-firing, or drying and pre-firing can be performed simultaneously. The atmosphere for pre-firing is not particularly limited, but an inert gas atmosphere such as nitrogen or argon is preferred.

[0096] When pre-calcining a mixture of raw materials in a solvent, the aforementioned non-polar solvent, polar solvent, or a mixture thereof can be used as the solvent for pre-calcination. The slurry in which the mixture is dispersed in the solvent is heated. The same solvent used in mixing the raw materials can be used as the solvent for pre-calcination; alternatively, a different solvent can also be used. It is preferable that a solvent removal process is unnecessary when using the same solvent.

[0097] The heating temperature and time for pre-calcination can be appropriately adjusted considering the composition of the raw materials. For example, the heating temperature is preferably 150°C to 300°C, more preferably 160°C to 280°C, even more preferably 170°C to 270°C, and particularly preferably 180°C to 260°C. By setting the temperature within the above range, a PS4 structure is formed, making it easier to incorporate halogens into the silver-germanium sulfide crystal structure. Since the raw material mixture containing microcrystalline particles is pre-calcined in solution, crystals containing a PS4 structure can be formed at relatively low temperatures.

[0098] The heating time is preferably 10 minutes to 6 hours, more preferably 10 minutes to 3 hours, and particularly preferably 30 minutes to 2 hours.

[0099] There are no particular limitations on the heating device used in the pre-calcination, but an autoclave is preferred when the heating temperature exceeds the boiling point of the solvent used.

[0100] The pre-calcined material is recovered by removing the solvent from the slurry used for pre-calcination. There are no particular limitations on the method of solvent removal; the solvent can be distilled off under normal or reduced pressure. Furthermore, filtration can be used in conjunction with distillation to further improve productivity.

[0101] A solid electrolyte can be obtained by heating the mixture or pre-calcined material obtained in the mixing process using a heating step. The heating temperature and time can be appropriately adjusted taking into account the composition of the mixture and pre-calcined material. For example, the heating temperature is preferably 300°C to 470°C, more preferably above 300°C and below 460°C, even more preferably 320°C to 450°C, further preferably 350°C to 440°C, and particularly preferably 380°C to 430°C.

[0102] The heating time is preferably 1 to 360 minutes, more preferably 5 to 120 minutes, and particularly preferably 10 to 60 minutes.

[0103] The heating atmosphere is not particularly limited, but it is preferable to conduct the heating under an inert gas atmosphere such as nitrogen or argon, rather than under a hydrogen sulfide gas stream. For the heating process, a stationary hearth furnace or a rotary kiln can be used.

[0104] When heating the pre-calcined material, the aforementioned non-polar solvents, polar solvents, or mixtures thereof can be used as the solvent for heating. The slurry in which the pre-calcined material is dispersed in the solvent is heated. The same solvent used in pre-calcination, etc., can be used as the solvent for heating; alternatively, different solvents can also be used. Since using the same solvent eliminates the need for solvent replacement or removal before heating, this is preferable. Furthermore, similar to pre-calcination, when the heating temperature exceeds the boiling point of the solvent used, an autoclave is preferred.

[0105] The solid electrolyte obtained by the method of this embodiment contains a sulfide-germanium ore-type crystal structure, which can be confirmed by the presence of diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg in powder X-ray diffraction measurements using CuKα rays.

[0106] The diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg are derived from the sulfogermanium-type crystal structure.

[0107] Sometimes, diffraction peaks of argillite-germanium-type crystal structures also appear at 2θ = 15.3 ± 0.5 deg, 17.7 ± 0.5 deg, 31.1 ± 0.5 deg, 44.9 ± 0.5 deg, and 47.7 ± 0.5 deg. Solid electrolytes can also exhibit these peaks.

[0108] Furthermore, when the center value is set to A, the position of the diffraction peak in this application is determined by A ± 0.5 degrees or A ± 0.4 degrees, but preferably by A ± 0.3 degrees. For example, in the case of the diffraction peak with 2θ = 25.2 ± 0.5 degrees mentioned above, the center value A is 25.2 degrees, and it is preferred to be within the range of 2θ = 25.2 ± 0.3 degrees. The determination of the position of all other diffraction peaks in this application is also done in the same way.

[0109] If the solid electrolyte has an X-ray diffraction pattern of the argyrogermanium sulfide crystal structure as described above, it may also contain an amorphous component in a portion thereof. In X-ray diffraction measurements, the amorphous component substantially exhibits a hollow pattern in the X-ray diffraction pattern, which does not show peaks other than those originating from the raw material. Furthermore, it may also contain crystal structures and raw materials other than the argyrogermanium sulfide crystal structure.

[0110] [Second Implementation]

[0111] The solid electrolyte of this embodiment has a sulfide-silver germanite-type crystal structure comprising lithium (Li), phosphorus (P), sulfur (S), oxygen (O) and halogen (X) as constituent elements. The proportion of the Li3PO4 crystal structure in the solid electrolyte is more than 0.1% by mass and less than 3.0% by mass. The solid electrolyte satisfies the following formulas (21) to (23).

[0112] 4.8≤Li / P≤5.3…(21)

[0113] 3.8≤S / P≤4.4…(22)

[0114] 1.0 < X / P ≤ 2.0…(23)

[0115] (Equation (21) is the molar ratio of Li to P, Equation (22) is the molar ratio of S to P, and Equation (23) is the molar ratio of halogen (X) to P.)

[0116] The above equations (21) to (23) preferably satisfy the following equation.

[0117] 4.85≤Li / P≤5.25

[0118] 3.9 ≤ S / P ≤ 4.3

[0119] 1.2 ≤ X / P ≤ 1.9

[0120] More preferably, the above equations (21) to (23) satisfy the following equation.

[0121] 4.9 ≤ Li / P ≤ 5.2

[0122] 4.0 ≤ S / P ≤ 4.2

[0123] 1.4 ≤ X / P ≤ 1.8

[0124] In solid electrolytes, the proportion of Li3PO4 crystals in the total crystal structure is between 0.1% and 3.0% by mass. As long as it is within this range, a high ionic conductivity can be maintained while suppressing the generation of hydrogen sulfide.

[0125] The proportion of Li3PO4 crystal structure is preferably 0.3% by mass or more, more preferably 0.5% by mass or more. Furthermore, the proportion of Li3PO4 crystal structure is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and more preferably 1.0% by mass or less.

[0126] In one embodiment, the proportion of argyroclase-germanium sulfide crystals in the solid electrolyte is 90% or more by mass of the total crystals. This results in a high ionic conductivity.

[0127] The proportion of the sulfide-germanium ore-type crystal structure is preferably 93% by mass or more, more preferably 95% by mass or more, more preferably 96% by mass or more, and particularly preferably 97% by mass or more.

[0128] In one embodiment, the proportion of β-Li3PS4 crystal structure in the total crystals of the solid electrolyte is 5.0% by mass or less. Preferably, it is 4.0% by mass or less, and more preferably 3.0% by mass or less.

[0129] The proportions of argyrocyanide-type crystal structure, Li3PO4 crystal structure, and β-Li3PS4 crystal structure in the total crystals of the solid electrolyte were determined by radiometric analysis as in the evaluation example.

[0130] The composition of formulas (21) to (23) in this embodiment can be achieved by adjusting the blending of raw materials. For example, the molar ratio of S can be reduced by decreasing the amount of lithium sulfide (Li2S), and the molar ratio of Li and O can be adjusted by blending lithium oxide (Li2O).

[0131] The solid electrolyte of this embodiment can be obtained, for example, by the manufacturing method of the first embodiment described above.

[0132] In the solid electrolyte of this embodiment, examples of halogens (X) include F, Cl, Br, and I. The solid electrolyte may contain one type of halogen (X), or more than two types, but two types are more preferred.

[0133] Preferably, at least one of X is Cl or Br, and more preferably X contains both Cl and Br.

[0134] In one embodiment of the solid electrolyte, in addition to Li, P, S, O and halogen (X) as described above, one or more elements selected from the group consisting of H, Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi may be contained, without impairing the effect of the invention.

[0135] In one embodiment, the solid electrolyte has a composition represented by the following formula (A).

[0136] Li a P b S c O d X e …(A)

[0137] (In the formula, X is a halogen, and a to e represent the composition ratio of each element, satisfying 4.8≤a≤5.3, b=1, 3.8≤c≤4.4, 0<d≤0.8, 1<e≤2.0).

[0138] In formula (A), X can be one selected from the group consisting of F, Cl, Br, and I, or it can be two or more (x1, ..., x...). n (n is an integer between 2 and 4). X is more preferably composed of two elements (x1 and x2). The molar ratio of each element is not particularly limited.

[0139] In formula (A), X is preferably Cl and Br.

[0140] In this application, the molar ratio and composition of each element in the solid electrolyte can be measured using various methods known to those skilled in the art, except for special reasons such as analytical difficulties, and can be measured using ICP-luminescence analysis. For example, in the case of the solid electrolyte described in this application, the molar ratio and composition of elements other than oxygen can be measured using ICP-luminescence analysis.

[0141] The molar ratio of each element can be controlled by adjusting the content of each element in the raw material.

[0142] In one embodiment of the solid electrolyte, from the viewpoint of further suppressing hydrogen sulfide generation, the lattice constant of the argyroclase-germanium sulfide crystal structure is preferably [missing information]. The following is preferred. The following are further preferred options. The following are particularly preferred The following is a hypothesis: if the lattice constant is within the above range, it indicates that the sulfur element at sites 4a and 4d in the sulfide-germanium type crystal structure is sufficiently reduced and replaced by halogen elements with smaller ionic radii.

[0143] In addition, the lattice constant can be measured by the radiometric analysis described in the examples.

[0144] In one embodiment of the solid electrolyte, from the viewpoint of further improving ionic conductivity, the ratio of the peak intensity of the diffraction peak originating from the Li3PS4 crystal structure to the peak intensity of the diffraction peak originating from the 2θ = 25.2 ± 0.5 deg of the argyrophthalite-type crystal structure is preferably less than 0.04.

[0145] This is because, compared with the sulfide-germanium ore type crystal structure, Li3PS4 has a lower ionic conductivity. Therefore, the lower the content of the Li3PS4 crystal structure in the solid electrolyte, the more it can suppress the decrease in ionic conductivity.

[0146] As described above, if the amount of Li2S in the raw materials of a solid electrolyte is reduced in order to suppress the generation of hydrogen sulfide, the sulfur element required for the formation of the silver sulfide-germanium ore crystal structure is lacking, making it easier to generate other crystal phases such as Li3PS4. However, by mixing the raw materials in a specific ratio, the inventors have successfully suppressed the generation of Li3PS4 and reduced the sulfur content of the silver sulfide-germanium ore crystal structure itself, thus achieving a higher level of balance between suppressing the generation of hydrogen sulfide and ionic conductivity.

[0147] Regarding this point, in the invention described in Patent Document 1, the peak intensity ratio derived from Li3PS4 is increased by reducing Li2S. It can be considered that it is not a reduction of sulfur from the sulfosilver-germanium ore-type crystal structure itself as in one embodiment of the present invention. The part of the element reduction is not the sulfosilver-germanium ore-type crystal structure, but rather the part that changes to other crystal structures such as Li3PS4.

[0148] Furthermore, by reducing the sulfur content to decrease hydrogen sulfide production, and simultaneously ensuring the presence of oxygen during the heating process, the sulforaphite-germanium ore crystal structure is maintained, resulting in high ionic conductivity. In Patent Document 2, Li₂O is added only after the sulforaphite-germanium ore crystal structure is formed by heating; oxygen is not present during the heating process for forming the sulforaphite-germanium ore crystal structure as in the first embodiment. Therefore, it is difficult to reduce hydrogen sulfide production while simultaneously exhibiting high ionic conductivity as in the first embodiment.

[0149] The solid electrolyte of this invention can be used in lithium-ion batteries, etc. Specifically, it can be used as a solid electrolyte layer, positive electrode, negative electrode, etc. in batteries.

[0150] In one embodiment, the electrode for a lithium-ion battery can be mixed with known active materials, conductive additives, etc., in addition to a solid electrolyte. Furthermore, a binder can also be mixed in.

[0151] One embodiment of the lithium-ion battery includes the solid electrolyte of the present invention.

[0152] In one embodiment, the lithium-ion battery is an all-solid-state battery.

[0153] In one embodiment, the all-solid-state battery comprises a stack comprising, in sequence, a positive current collector, a positive electrode, an electrolyte layer, a negative electrode, and a negative current collector. Preferably, the lithium-ion battery comprises one or more solid electrolytes selected from the group consisting of a positive electrode, an electrolyte layer, and a negative electrode, including the solid electrolyte of the present invention.

[0154] Example

[0155] The present invention will now be described in more detail with reference to embodiments.

[0156] In addition, the evaluation method is as follows.

[0157] (1) Hydrogen sulfide (H2S) production of solid electrolytes

[0158] A schematic diagram of the experimental setup is shown below. Figure 1 As shown.

[0159] The main components of experimental apparatus 1 are as follows: flask 10 for humidifying nitrogen gas; static mixer 20 for mixing humidified and undhumidified nitrogen gas; dew point meter 30 (VAISALA M170 / DMT152) for measuring the moisture content of the mixed nitrogen gas; double reaction tube 40 for setting the test sample; dew point meter 50 for measuring the moisture content of the nitrogen gas discharged from the double reaction tube 40; and hydrogen sulfide meter 60 (AMI Model 3000RS) for measuring the concentration of hydrogen sulfide in the discharged nitrogen gas. These components are connected via pipes (not shown). The temperature of flask 10 is set to 10°C via cooling tank 11.

[0160] In addition, the tubes connecting the various components use 6mm diameter Teflon (registered trademark) tubing. The tube markings are omitted in this diagram; instead, arrows indicate the flow of nitrogen.

[0161] The evaluation steps are as follows.

[0162] Inside a nitrogen glove box with a dew point of -80°C, approximately 1 g of powder sample 41 is weighed and sealed inside the reaction tube 40 by clamping it with quartz wool 42. The inside of the reaction tube 40 is maintained at approximately room temperature (25°C).

[0163] Nitrogen gas is supplied to apparatus 1 at 0.02 MPa from a nitrogen source (not shown). The supplied nitrogen is distributed via a bifurcation pipe BP, with a portion supplied to flask 10 for humidification. The remaining portion, as unhumidified nitrogen, is directly supplied to static mixer 20. The nitrogen supply to flask 10 is adjusted by needle valve V.

[0164] The dew point is controlled by adjusting the flow rates of unhumidified and humidified nitrogen using a flow meter FM with a needle valve. Specifically, unhumidified nitrogen is supplied to a static mixer 20 at a flow rate of 800 mL / min and humidified nitrogen is supplied at a flow rate of 10–30 mL / min, and the dew point of the mixed gas (the mixture of unhumidified and humidified nitrogen) is confirmed in a dew point meter 30.

[0165] After adjusting the dew point to -30°C, rotate the three-way stopcock 43 to allow the mixed gas to circulate inside the reaction tube 40 for 2 hours. The amount of hydrogen sulfide contained in the mixed gas that has passed through sample 41 is measured using a hydrogen sulfide meter 60, and the amount of hydrogen sulfide generated per 1g of solid electrolyte (cc / g) is calculated. Additionally, the amount of hydrogen sulfide is recorded at 15-second intervals. Furthermore, for reference, the dew point of the exposed mixed gas is measured using a dew point meter 50. To remove hydrogen sulfide from the measured nitrogen, it is passed through an alkaline trap 70.

[0166] (2) Measurement of ionic conductivity of solid electrolytes

[0167] The sample was filled into a tablet forming machine, and a pressure of 22 MPa was applied to form a molded body. Carbon electrodes were placed on both sides of the molded body, and pressure was applied again through the tablet forming machine to produce a molded body for measurement (approximately 10 mm in diameter and 0.1–0.2 cm in thickness). The ionic conductivity of the molded body was measured using AC impedance spectroscopy. The conductivity values ​​were taken at 25 °C.

[0168] (3) X-ray diffraction (XRD) measurement

[0169] In a 20 mm diameter, 0.2 mm deep trough, powdered silver-germanium sulfide solid electrolytes of various types were uniformly filled into the trough using glass as a sample. XRD measurements were performed on the sample using a Kapton film without contact with air. The 2θ positions of the diffraction peaks were determined using the RIETAAN-FP XRD analysis program via Le Bail analysis.

[0170] Measurements were performed using the D2 PHASER powder X-ray diffraction measurement apparatus from BRUKER Corporation under the following conditions.

[0171] In addition, the powder X-ray diffraction measurement device is set up in a room where the temperature is maintained at 25°C.

[0172] Tube voltage: 30kV

[0173] Tube current: 10mA

[0174] X-ray wavelength: Cu-Kα rays

[0175] Optical system: lumped method

[0176] Slit configuration: 4° cable slit, 1mm diverging slit, using a Kβ filter (Ni plate).

[0177] Detector: Semiconductor detector

[0178] Measurement range: 2θ = 10⁻⁶⁰ degrees

[0179] Step width and scan speed: 0.05deg, 0.05deg / sec

[0180] In the analysis of peak positions used to confirm the existence of crystal structures based on measurement results, the XRD analysis program RIETAN-FP is used to correct the baseline with an 11th-order Legendre orthogonal polynomial, thereby determining the peak positions.

[0181] (4) ICP measurement

[0182] The powdered solid electrolytes prepared in each example were weighed and collected in vials under an argon atmosphere. An alkaline aqueous solution of KOH was added to the vial to dissolve the sample while carefully capturing sulfur components. The solution was then appropriately diluted to prepare the measurement solution. Its composition was determined by measuring the solution using a Paschen-Runge ICP-OES apparatus (SPECTRO ARCOS, Germany).

[0183] The standard curve solutions for Li, P, and S were prepared using a 1000 mg / L standard solution for ICP measurement, while the standard curve solutions for Cl and Br were prepared using a 1000 mg / L standard solution for ion chromatography.

[0184] For each sample, two sets of measurement solutions were prepared, and each solution was measured five times, with the average value calculated. The composition was determined by the average value of the two sets of measurements.

[0185] Manufacturing Example 1

[0186] [Manufacturing of Lithium Sulfide (Li2S)]

[0187] The production and purification of Li2S are carried out as described below.

[0188] Toluene (manufactured by Sumitomo Corporation) was used as a non-water-soluble medium for dehydration. 303.8 kg of toluene, with a water content of 100 ppm as measured by a Karl Fischer moisture meter, was added to a 500 L stainless steel reactor under a nitrogen flow. Then, 33.8 kg of anhydrous lithium hydroxide (manufactured by Honjo Chemical Co., Ltd.) was added. The reactor was stirred at 131 rpm with a twinstir impeller while maintaining a temperature of 95 °C.

[0189] Hydrogen sulfide (manufactured by Sumitomo Seikan Co., Ltd.) is blown into the slurry at a supply rate of 100 L / min while the temperature is raised to 104°C. An azeotropic gas of water and toluene is continuously discharged from the reactor. This azeotropic gas is condensed and dehydrated using an external condenser. During this process, an equal amount of toluene as distilled toluene is continuously supplied to maintain a constant liquid level in the reaction mixture.

[0190] The water content in the condensate gradually decreased, and after 24 hours of introducing hydrogen sulfide, no distilled water could be detected. Furthermore, the reaction was carried out under stirring to disperse the solid in toluene, and no water separated from the toluene was observed.

[0191] Then, switch from hydrogen sulfide to nitrogen and flow it at 100 L / min for 1 hour.

[0192] The obtained solid components were filtered and dried to obtain a white powder, namely Li2S.

[0193] Example 1

[0194] As starting materials, Li₂S, P₂S₅, LiBr (manufactured by Honjo Chemical Co., Ltd.), LiCl (manufactured by Honjo Chemical Co., Ltd.), and Li₂O (manufactured by Fujifilm and Wako Pure Chemical Co., Ltd.) of Manufacturing Example 1 were used. The starting materials, coarsely pulverized by a needle mill, were mixed in a molar ratio (Li₂S:P₂S₅:LiCl:LiBr:Li₂O) of 1.65:0.5:1.0:0.6:0.05. Specifically, 0.402 g of Li₂S, 0.589 g of P₂S₅, 0.225 g of LiCl, 0.276 g of LiBr, and 0.008 g of Li₂O were mixed.

[0195] The mixture and 30g of zirconia balls with a diameter of 10mm were placed in a 45mL zirconia jar of a planetary ball mill (FRITSCH, model P-7) and completely sealed. A nitrogen atmosphere was established inside the jar. The mixture was premixed at 150 rpm for 10 minutes. Then, it was mechanically ground at 370 rpm for 15 hours to obtain a powder of the raw material mixture.

[0196] Approximately 1.5 g of the raw material mixture was filled into a carbon granule heating tube (PT2, manufactured by Tokyo Glass Equipment Co., Ltd.) in a glove box under an Ar atmosphere, and then heated in an electric furnace. Specifically, the temperature was increased from room temperature to 380°C in 1 hour, then increased to 430°C in 30 minutes, and held at 430°C for 2 hours. Afterward, the mixture was removed from the furnace and cooled to obtain a solid electrolyte.

[0197] The molar ratio of raw materials, the molar ratio of each element, the amount of hydrogen sulfide produced by the obtained solid electrolyte, and the ionic conductivity are shown in Table 1.

[0198] XRD patterns of solid electrolytes are as follows Figure 2 As shown, diffraction peaks of the silver-germanium sulfide crystal structure were observed at 2θ = 15.6deg, 18.1deg, 25.6deg, 30.1deg, 31.5deg, and 45.1deg.

[0199] Examples 2-4, Comparative Examples 1-5

[0200] Except for changing the molar ratio of the starting materials as shown in Table 1, the solid electrolyte was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. The XRD patterns of the solid electrolytes obtained in Examples 2-4 and Comparative Examples 1-5 are shown below. Figures 3-10 As shown.

[0201] In Example 2, diffraction peaks of a steric argillacene-type crystal structure were observed at 2θ = 15.6deg, 18.1deg, 25.6deg, 30.1deg, 31.5deg, and 45.1deg. Diffraction peaks originating from Li3PO4 were also observed in the solid electrolyte of Example 2.

[0202] In Example 3, diffraction peaks of the silver-germanium sulfide crystal structure were observed at 2θ = 15.7deg, 18.1deg, 25.6deg, 30.1deg, 31.5deg, and 45.1deg.

[0203] In Example 4, diffraction peaks of the silver-germanium sulfide crystal structure were observed at 2θ = 15.7deg, 18.1deg, 25.7deg, 30.2deg, 31.6deg, and 45.1deg.

[0204] Table 2 shows the results of determining the composition of the solid electrolytes by ICP measurement for Examples 2 and 4 and Comparative Examples 1, 2 and 5.

[0205] [Table 1]

[0206]

[0207] [Table 2]

[0208] ICP: Moleby Example 2 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 5 Li 5.00 5.06 5.51 4.89 5.59 P 1.00 1.00 1.00 1.00 1.00 S 4.00 4.01 4.44 4.17 4.17 Cl 1.04 1.08 1.06 1.05 1.09 Br 0.64 0.63 0.64 0.63 0.64

[0209] Example 5

[0210] The same Li₂S, P₂S₅, LiCl, LiBr, and LiOH (lithium hydroxide obtained by drying lithium hydroxide monohydrate produced by Honjo Chemical Co., Ltd.) as in Example 1 were used as starting materials. The starting materials, coarsely ground by a needle mill, were mixed in a molar ratio (Li₂S:P₂S₅:LiCl:LiBr:LiOH) of 1.6:0.5:1.0:0.6:0.2. Specifically, 0.3884 g of Li₂S, 0.5871 g of P₂S₅, 0.224 g of LiCl, 0.2753 g of LiBr, and 0.0253 g of LiOH were mixed.

[0211] In the following example, similar to Example 1, a mixture of raw materials was prepared by processing with a planetary ball mill, and a solid electrolyte was obtained by heat treatment of the mixture. The evaluation results are shown in Table 3.

[0212] XRD patterns of solid electrolytes are as follows Figure 11 As shown, diffraction peaks of the silver-germanium sulfide crystal structure were observed at 2θ = 15.6deg, 18.0deg, 25.6deg, 30.1deg, 31.5deg, and 45.0deg.

[0213] [Table 3]

[0214]

[0215] In Table 1, the molar ratio of sulfur (S) in the solid electrolyte was varied according to the amount of Li₂S prepared in Comparative Examples 1-3. Comparative Example 1, even among solid electrolytes with a sulfide-germanium ore crystal structure, exhibited a high ionic conductivity. It was observed that although the ionic conductivity was excellent, the amount of hydrogen sulfide produced was relatively high. In Examples 1-4 and Comparative Examples 4 and 5, the amount of Li₂S prepared was reduced, while Li₂O was added. As a result, although the amount of S in the solid electrolyte (molar ratio of 4.1) was the same as in Comparative Example 2, the ionic conductivity in Example 2 was sufficiently high, and the amount of hydrogen sulfide produced was significantly suppressed. The same trend was also confirmed in Examples 4 and Comparative Example 3.

[0216] On the other hand, in Comparative Examples 4 and 5, where Li₂O was further added, the amount of hydrogen sulfide produced increased. Therefore, it can be confirmed that adding a specified amount of Li₂O is effective in reducing the S content in the solid electrolyte by reducing the amount of Li₂S used.

[0217] Furthermore, it was confirmed that in Example 5, where LiOH was added instead of Li2O, the same effect as in Example 2 was obtained, and any raw material could be used.

[0218] Evaluation example

[0219] For Examples 2 and 4 and Comparative Examples 1, 4, and 5, radiometric analysis was performed to analyze the lattice constants of the argyrogermanium sulfide crystal structure and the proportions of the argyrogermanium sulfide crystal structure, Li3PO4 crystal structure, and β-Li3PS4 crystal structure in the total crystals of the solid electrolyte. Specifically, the measurements were performed under the following conditions.

[0220] In the glove box, the powder of the solid electrolytes manufactured in Examples 2, 4, Comparative Examples 1, 4 and 5 was filled into a 0.3 mm Φ capillary tube, and the front end of the capillary tube was sealed with curable resin as a sample for radiometric analysis.

[0221] Measurements were performed using the SPring-8 powder diffraction measurement beamline "BL19B2" under the following conditions. Furthermore, during the measurement, a nitrogen-blowing sample cooling device manufactured by RIGAKU Corporation of Japan was used to blow nitrogen gas at 100K onto the sample for 1 minute, and this state was maintained during the measurement.

[0222] X-ray energy: 25keV

[0223] Optical system: Transmission method

[0224] Detector: One-dimensional solid-state Si detector MYTHEN (12-cell array)

[0225] Detector threshold: 19keV

[0226] Measurement range: 2θ = 4-60 degrees

[0227] Step width: 0.005deg

[0228] Exposure time: 30 seconds x 2 times

[0229] The measurement data were corrected using a script specific to the BL19B2 at 0.005° intervals, and the data was then analyzed.

[0230] In the analysis used to confirm the peak positions of the crystal structure, the peaks were determined using the Rigaku XRD analysis program PDXL2 (Version 2.7.3.0) through automatic profile processing. In the analysis used to determine the lattice constants and proportions of the crystal structure, the lattice constants and proportions of the crystal structure were determined using the following functions through Rietveld analysis, using the Rietveld XRD analysis program PDXL2 (Version 2.7.3.0).

[0231] Peak shape: Segmented pseudo-Voigt function

[0232] Background: β-spline function

[0233] Peak displacement: Device function (Δ2θ=Z+Dcosθ+Tsin2θ)

[0234] Furthermore, the lattice constant was analyzed after correcting the X-ray energy value. Specifically, in the above measurement conditions, the temperature was changed to 300K and the exposure time was changed to 20 seconds to measure CeO2. The measurement result was then subjected to Tevold analysis under the above analytical conditions, and the X-ray energy value was corrected to achieve the correct lattice constant.

[0235] Furthermore, in the analysis of peak shape, the same function used for the profile function of the argyrocerite-type crystal structure is also applied to crystals other than the argyrocerite-type crystal structure for analysis.

[0236] Furthermore, in the Tewald analysis, an Rwp value below 10% is used as the criterion for the validity of the results.

[0237] The results are shown in Table 4.

[0238] [Table 4]

[0239]

[0240] Table 4 confirms that the lattice constants of Examples 2 and 4 are smaller compared to the comparative examples. This can be presumed to be because the crystal structures of these examples, which are of the sulfide-germanium type, lack sulfide ions (S₂O₃) with larger ionic radii. 2- Instead, halide ions with smaller ionic radii occupy one or more of the 4a or 4d sites, thus reducing the lattice constant.

[0241] Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art can readily make numerous modifications to these illustrated embodiments and / or examples without departing substantially from the novelty and effects of the present invention. Therefore, these numerous modifications are also included within the scope of the present invention.

[0242] All references contained in this specification and the entire contents of the application that forms the basis of this application’s priority under the Paris Convention are hereby cited.

Claims

1. A solid electrolyte, characterized in that, Having a composition expressed by equation (A), it exhibits diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg in powder X-ray diffraction measurements using CuKα rays. Li a P b S c Oh d X e …(A) Where X is a halogen, and a to e represent the composition ratio of each element, satisfying 4.8≤a≤5.3, b=1, 3.8≤c≤4.4, 0<d≤0.8, and 1<e≤2.

0.

2. The solid electrolyte as described in claim 1, characterized in that, It has a sulfide-germanium mineral-type crystal structure.

3. The solid electrolyte as described in claim 1 or 2, characterized in that, The d satisfies 0.05≤d≤0.

8.

4. The solid electrolyte as described in claim 2 or 3, characterized in that, The sulfosilver germanite-type crystal structure accounts for more than 90% by mass of the total crystals in the solid electrolyte.

5. The solid electrolyte according to any one of claims 1 to 4, characterized in that, It contains the Li3PO4 crystal structure.

6. The solid electrolyte according to any one of claims 1 to 5, characterized in that, The β-Li3PS4 crystal structure in the solid electrolyte accounts for less than 5.0% by mass of the total crystals.

7. The solid electrolyte according to any one of claims 1 to 6, characterized in that, The halogen X is selected from one or more of the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

8. The solid electrolyte according to any one of claims 1 to 6, characterized in that, The halogen X is selected from one or more of chlorine (Cl) and bromine (Br).

9. The solid electrolyte according to any one of claims 2 to 8, characterized in that, The lattice constant of the sulfarginite-germanium type crystal structure is: the following.

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