Solid electrolyte and method for manufacturing the same

Abstract

The present application relates to a method for manufacturing a solid electrolyte having a kesterite-type crystal structure, comprising: a mixing step of mixing raw materials so that lithium (Li), phosphorus (P), sulfur (S), oxygen (O), and halogen (X) satisfy the following formulas (11) to (14); and a heating step of heating a mixture obtained by 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 a molar ratio of Li to P, formula (12) is a molar ratio of S to P, formula (13) is a molar ratio of O to P, and formula (14) is a molar ratio of halogen (X) to P.)

Description

Technical Field

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

[0002] It is known that sulfide solid electrolytes are degraded by moisture in the air. For example, Patent Document 1 discloses a solid electrolyte characterized by containing Li-ion sulfide having an Argyrodite crystal structure. 7- a PS 6-a Ha a (Ha represents a halogen, a is 0.2 < a ≤ 1.8) and Li3PS4, and in an X-ray diffraction pattern measured by X-ray diffraction (XRD), the ratio of the peak intensity appearing at a diffraction angle 2θ = 26.0 to 28.8° derived from Li3PS4 to the peak intensity appearing at a diffraction angle 2θ = 24.9 to 26.3° derived from an argyrodite-type crystal structure is 0.04 to 0.3. Patent Document 2 discloses a sulfide solid electrolyte, wherein an alkaline compound is mixed in the solid electrolyte, and the ratio of the molar amount of the alkali metal contained in the alkaline compound to the molar amount of Li contained in the solid electrolyte is 1 / 1000 or more and 1 / 25 or less.

[0003] In addition, Patent Documents 3 and 4 disclose sulfide solid electrolyte particles containing lithium, phosphorus, sulfur and halogen and having a cubic argyrodite-type crystal structure, and sulfide solid electrolytes for lithium secondary batteries whose surfaces are coated with a compound having a non-argyrodite-type crystal structure containing lithium, phosphorus and sulfur.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2019 / 131725

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-120728

[0008] Patent Document 3: International Publication No. 2019 / 176895

[0009] Patent Document 4: Japanese Patent No. 6293383 Summary of the Invention

[0010] In the solid electrolytes of Patent Documents 1 to 4, suppression of hydrogen sulfide generation and ion conductivity are not sufficiently achieved at the same time, and further improvement is required.

[0011] An object of the present invention is to provide a solid electrolyte that suppresses the generation of hydrogen sulfide and has high ion conductivity, and a method for producing the same.

[0012] According to one embodiment of the present invention, a method for manufacturing a solid electrolyte having an argyrodite-type crystal structure is provided, comprising: a mixing step of mixing raw materials so that lithium (Li), phosphorus (P), sulfur (S), oxygen (O) and halogen (X) satisfy the following formulas (11) to (14); and a heating step of heating the mixture obtained by the mixing step.

[0013] 4.8≤Li / P≤5.3…(11)

[0014] 3.8≤S / P≤4.4…(12)

[0015] 0<O / P≤0.8…(13)

[0016] 1.0<X / P≤2.0…(14)

[0017] (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.)

[0018] In addition, according to one embodiment of the present invention, a solid electrolyte is provided, having an argyrodite-type crystal structure containing lithium (Li), phosphorus (P), sulfur (S), oxygen (O) and halogen (X), wherein the proportion of the Li3PO4 crystal structure in the solid electrolyte to the total crystal is not less than 0.1 mass % and not more than 3.0 mass %, and the solid electrolyte satisfies the following formulas (21) to (23).

[0019] 4.8≤Li / P≤5.3…(21)

[0020] 3.8≤S / P≤4.4…(22)

[0021] 1.0<X / P≤2.0…(23)

[0022] (Formula (21) is the molar ratio of Li to P, formula (22) is the molar ratio of S to P, and formula (23) is the molar ratio of halogen (X) to P.)

[0023] According to the present invention, it is possible to provide a solid electrolyte that suppresses the generation of hydrogen sulfide and has high ion conductivity, and a method for producing the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the test equipment for measuring the amount of hydrogen sulfide generated.

[0025] Figure 2 This is the X-ray diffraction (XRD) pattern of the solid electrolyte obtained in Example 1.

[0026] Figure 3 This is the XRD pattern of the solid electrolyte obtained in Example 2.

[0027] Figure 4 This is the XRD pattern of the solid electrolyte obtained in Example 3.

[0028] Figure 5 This is the XRD pattern of the solid electrolyte obtained in Example 4.

[0029] Figure 6 This is the XRD pattern of the solid electrolyte obtained in Comparative Example 1.

[0030] Figure 7 This is the XRD pattern of the solid electrolyte obtained in Comparative Example 2.

[0031] Figure 8 This is the XRD pattern of the solid electrolyte obtained in Comparative Example 3.

[0032] Figure 9 This is the XRD pattern of the solid electrolyte obtained in Comparative Example 4.

[0033] Figure 10 This is the XRD pattern of the solid electrolyte obtained in Comparative Example 5.

[0034] Figure 11 This is the XRD pattern of the solid electrolyte obtained in Example 5. DETAILED DESCRIPTION

[0035] [First embodiment]

[0036] A method for producing a solid electrolyte according to one embodiment of the present invention includes the following mixing step and heating step, and produces a solid electrolyte having an argyrodite-type crystal structure.

[0037] Mixing step: A step of mixing raw materials so that lithium (Li), phosphorus (P), sulfur (S), oxygen (O) and halogen (X) satisfy the following formulas (11) to (14).

[0038] 4.8≤Li / P≤5.3…(11)

[0039] 3.8≤S / P≤4.4…(12)

[0040] 0<O / P≤0.8…(13)

[0041] 1.0<X / P≤2.0…(14)

[0042] (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.)

[0043] Heating step: A step of heating the mixture obtained in the mixing step.

[0044] In this embodiment, it is presumed that by adjusting the composition of the starting material to the formulas (11) to (14), a sulfide ion (S) in the crystal, which is different from the conventional argyrodite-type crystal structure, can be formed. 2- ) decreases while the amount of halogen ions (Cl - Br - etc.) increased argyrodite-type crystal structure.

[0045] Argentatite crystal structure is a 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 any halogen ion occupied structure. The general argyrodite crystal structure is a crystal structure represented by the space group F-43M. In crystallography, this crystal structure is in PS4 3- There are 4a sites and 4d sites around the structure. Elements with large ionic radius tend to occupy 4a sites, while elements with small ionic radius tend to occupy 4d sites.

[0046] In the unit cell of the argyrodite crystal structure, there are a total of 8 4a sites and 8 4d sites. The inventors of the present application assume that the S occupies the sites in the argyrodite crystal structure. 2- The reason for the generation of hydrogen sulfide is that it is found that by 2- The content rate is relatively reduced, which can reduce the generation of hydrogen sulfide.

[0047] 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 argyrodite-type crystal structure during the heating process, but will form crystal phases other than argyrodite-type crystals such as β-Li3PS4, resulting in a significant decrease in ion conductivity.

[0048] After intensive research to solve the technical problem, the present inventors surprisingly found that by setting the composition of the above formulas (11) to (14) so ​​that the starting raw materials contain O, the formation of crystal phases other than argyrodite-type crystals such as β-Li3PS4 during the heating process can be suppressed, and the S content in the crystal can be increased. 2- The amount of the argyrodite-type crystal structure is reduced, and as a result, a solid electrolyte can be obtained that sufficiently suppresses the amount of hydrogen sulfide generated and has high ion conductivity.

[0049] The above-mentioned formulas (11) to (14) in the mixing step preferably satisfy the following formula.

[0050] 4.85≤Li / P≤5.25

[0051] 3.9≤S / P≤4.3

[0052] 0.01≤O / P≤0.7

[0053] 1.2≤X / P≤1.9

[0054] More preferably, the above-mentioned formulas (11) to (14) in the mixing step satisfy the following formula.

[0055] 4.9≤Li / P≤5.2

[0056] 4.0≤S / P≤4.2

[0057] 0.05≤O / P≤0.6

[0058] 1.4≤X / P≤1.8

[0059] The raw materials used in this embodiment are a combination of two or more compounds and / or simple substances, so as to contain the elements required for the solid electrolyte to be produced at a predetermined molar ratio. Specifically, a combination of two or more compounds and simple substances containing Li, P, S, O, and a halogen (X) as a whole is used.

[0060] Examples of raw materials containing lithium include lithium compounds such as lithium sulfide (Li2S), lithium oxide (Li2O), lithium carbonate (Li2CO3), and lithium hydroxide (LiOH), as well as lithium metal. Among these, lithium compounds are preferred, and Li2S is more preferred, from the perspective of ease of handling the raw materials and ease of reaction.

[0061] Examples of raw materials containing phosphorus 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 sulfide is preferred from the perspective of ease of handling and reaction, 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 manufacturable and commercially available.

[0062] As the raw material containing halogen (X), for example, a raw material of the formula (M l -X m ) represented by, at least one of a halogen compound and an elemental halogen.

[0063] 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 or sulfur with these elements, preferably Li or P, more preferably Li.

[0064] X is a halogen element selected from F, Cl, Br and I.

[0065] Furthermore, l is an integer of 1 or 2, and m is an integer of 1 to 10. When m is an integer of 2 to 10, that is, when there are multiple Xs, Xs may be the same or different. For example, in SiBrCl3 described below, m is 4, and X is composed of different elements such as Br and Cl.

[0066] Halogen compounds include, specifically, 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 S2F. 10 , SCl2, S2Cl2, S2Br2 and other sulfur halides; GeF4, GeCl4, GeBr4, GeI4, GeF2, GeCl2, GeBr2, GeI2 and other germanium halides; AsF3, AsCl3, AsBr3, AsI3, AsF5 and other arsenic halides; SeF4, SeF6, SeCl2, SeCl4, Se2Br2, SeBr4 and other selenium halides; SnF4, SnCl4, SnBr4, SnI4, SnF2, SnCl2, SnBr2, SnI2 and other tin halides; SbF3, SbCl3, SbBr3, SbI3, SbF5, SbCl5 and other antimony halides; TeF4, Te2F 10 , TeF6, TeCl2, TeCl4, TeBr2, TeBr4, TeI4 and other tellurium halides; PbF4, PbCl4, PbF2, PbCl2, PbBr2, PbI2 and other lead halides; BiF3, BiCl3, BiBr3, BiI3 and other bismuth halides, etc.

[0067] Among them, lithium halides such as lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI) and phosphorus halides such as phosphorus pentachloride (PCl5), phosphorus trichloride (PCl3), phosphorus pentabromide (PBr5), and phosphorus tribromide (PBr3) can be preferably mentioned. Among them, lithium halides or PBr3 are preferred, lithium halides are more preferred from the viewpoint of ease of handling, and LiCl and LiBr are even more preferred from the viewpoint of further improving ion conductivity.

[0068] As the halogen compound, one of the above-mentioned compounds may be used alone, or two or more thereof may be used in combination.

[0069] In this embodiment, compounds obtained by reacting the above raw materials can also be used. For example, Li3PS4 can be synthesized from Li2S and P2S5, and Li3PS4, Li2O, and LiX can be used as raw materials. In addition, Li3PS4 can be crystalline or amorphous, or a mixture of crystalline and amorphous materials.

[0070] In one embodiment, it is preferred to use one or more of Li2O and LiOH as raw materials. Furthermore, it is preferred to use Li2S, Li2O, P2S5, and LiX (X is a halogen) as raw materials. For example, when using Li2S, Li2O, P2S5, and LiX as raw materials, the molar ratio of the raw materials can be set to Li2S:Li2O:P2S5:LiX=1.5-1.9:0.01-0.8:0.5:1.0-2.0.

[0071] In the mixing step, the above-mentioned raw materials are mixed.

[0072] The mixing method is not particularly limited, and a known method can be employed.

[0073] In this embodiment, mechanical stress may be applied to the raw materials to cause a reaction while mixing them, or they may be mixed and then pulverized. Here, "applying mechanical stress" refers to mechanically applying shear force, impact force, etc. Examples of the mechanism for applying mechanical stress include pulverizers such as planetary mills, vibration mills, rotary mills, and bead mills, or kneaders such as single-shaft kneaders and multi-shaft kneaders.

[0074] The mixing step may be performed in the presence of a solvent (wet mixing) or may be performed without using a solvent (dry mixing).

[0075] In the case of dry mixing, for example, when a planetary ball mill is used as a pulverizer, the pulverization and mixing conditions can be set to a rotation speed of several tens to several hundreds of revolutions per minute and a treatment for 0.5 to 100 hours. More specifically, in the case of the planetary ball mill (Fritsch, Model P-7) used in the Examples of the present application, the rotation speed of the planetary ball mill is preferably 350 rpm to 400 rpm, and more preferably 360 rpm to 380 rpm.

[0076] For example, when zirconia balls are used, the diameter of the balls as the pulverizing media is preferably 0.2 to 20 mm.

[0077] In one embodiment, wet mixing is preferred because there is a possibility that the generation of β-Li3PS4 can be suppressed.

[0078] As the solvent, an organic solvent can be used, preferably a non-polar solvent, a polar solvent or a mixed solvent thereof. Preferably, it is a non-polar solvent or a solvent mainly composed of a non-polar solvent, for example, 95% by mass or more of the organic solvent is a non-polar solvent.

[0079] As the nonpolar solvent, a hydrocarbon solvent is preferred. As the hydrocarbon solvent, saturated hydrocarbons, unsaturated hydrocarbons, or aromatic hydrocarbons can be used.

[0080] Examples of the saturated hydrocarbon include hexane, pentane, 2-ethylhexane, heptane, decane, tridecane and cyclohexane.

[0081] Examples of the unsaturated hydrocarbon include hexene, heptene, and cyclohexene.

[0082] Examples of the aromatic hydrocarbon include toluene, xylene, ethylbenzene, decalin, and 1,2,3,4-tetrahydronaphthalene.

[0083] Among these, toluene or xylene is preferred.

[0084] The hydrocarbon solvent is preferably dehydrated in advance. Specifically, the water content is preferably 100 ppm by mass or less, particularly preferably 30 ppm by mass or less.

[0085] In one embodiment, the organic solvent preferably contains at least one of a nitrile compound and an ether compound.

[0086] Examples of the ether compound include tetrahydrofuran and diethyl ether.

[0087] As the nitrile compound, preferably R(CN) n A nitrile compound represented by wherein R is an alkyl group having 1 to 10 carbon atoms, or a group having an aromatic ring having 6 to 18 ring carbon atoms. n is 1 or 2.

[0088] For example, acetonitrile, propionitrile, 3-chloropropionitrile, benzonitrile, 4-fluorobenzonitrile, tert-butyl nitrile, isobutyronitrile, cyclohexanenitrile, hexanenitrile, isocaproonitrile, malononitrile, and fumaronitrile can be mentioned. Preferred are propionitrile, isocaproonitrile, and isobutyronitrile.

[0089] For example, nitrile compounds are preferred because they form an azeotropic form with toluene and are therefore easily removed from the treated product together with toluene during drying.

[0090] The amount of the nitrile compound and the ether compound 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.

[0091] A bead mill is preferably used for wet mixing. Because mixing and pulverizing the raw materials using a bead mill can reduce the particle size of the pulverized particles, it is believed that the diffusion paths of the elements during the heating process are shortened, making it easier for the elements to form an argyrodite-type crystal structure. As a result, the formation of heterogeneous phases such as the Li3PS4 crystal structure can be suppressed.

[0092] The raw material mixture obtained by removing the solvent from the processed product after wet mixing using a bead mill is mainly composed of fine crystals. By mixing and pulverizing the raw materials, the raw materials can be further atomized to obtain a mixture composed of fine crystals of each raw material.

[0093] The mixture of raw materials may also be pre-calcined. In one embodiment, the mixture of raw materials is obtained by removing the solvent as described above and pre-calcining to obtain a powdered pre-calcined product. The heating temperature and time of the pre-calcination can be appropriately adjusted taking into account 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.

[0094] The heating apparatus used for pre-calcining is not particularly limited. Examples include shear-type dryers such as FM mixers and Nauta mixers, stationary furnaces such as hearth kilns, and rotary kilns such as rotary kilns. Drying may be performed before pre-calcining, or drying and pre-calcining may be performed simultaneously. The atmosphere for pre-calcining is not particularly limited, but is preferably an inert gas atmosphere such as nitrogen or argon.

[0095] When the raw material mixture is pre-calcined in a solvent, the aforementioned non-polar solvent, polar solvent, or a mixture thereof can be used as the pre-calcining solvent. A slurry containing the mixture dispersed in the solvent is heated. The pre-calcining solvent can be the same as that used for mixing the raw materials, or a different solvent can be used. Using the same solvent is preferred because it eliminates the need for a solvent removal step.

[0096] The heating temperature and time for pre-calcination can be appropriately adjusted in consideration of 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, further preferably 170°C to 270°C, and particularly preferably 180°C to 260°C. By setting the temperature range to the above, a PS4 structure is formed, making it easier to incorporate halogens into the argyrodite-type crystal structure. Since the raw material mixture of the fine crystals is pre-calcined in a solution, crystals containing a PS4 structure can be formed at a relatively low temperature.

[0097] 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.

[0098] The heating device used for calcination is not particularly limited, but when the heating temperature exceeds the boiling point of the solvent used, an autoclave is preferably used.

[0099] The solvent is removed from the slurry used for pre-calcination to recover the pre-calcined product. The method for removing the solvent is not particularly limited, and the solvent can be distilled off under normal pressure or reduced pressure. In addition, in order to further improve productivity, filtration can also be used.

[0100] The solid electrolyte can be obtained by heating the mixture or calcined product obtained in the mixing step in a heating step. The heating temperature and time can be appropriately adjusted in consideration of the composition of the mixture and calcined product. For example, the heating temperature is preferably 300°C to 470°C, more preferably above 300°C and below 460°C, more preferably 320°C to 450°C, further preferably 350°C to 440°C, and particularly preferably 380°C to 430°C.

[0101] The heating time is preferably 1 to 360 minutes, more preferably 5 to 120 minutes, and particularly preferably 10 to 60 minutes.

[0102] The heating atmosphere is not particularly limited, but is preferably performed in an inert gas atmosphere such as nitrogen or argon, rather than a hydrogen sulfide stream. A firing furnace such as a stationary hearth furnace or a rotary kiln can be used in the heating step.

[0103] As a solvent for heating, the above-mentioned non-polar solvent, polar solvent, or mixed solvent thereof can be used in the case of heating the preform. The slurry in which the preform is dispersed in the solvent is heated. As a solvent for heating, the same solvent as that used in the preform or the like can be used, and in addition, a different solvent can be used. Since in the case of using the same solvent, there is no need to perform a process of replacing or removing the solvent before heating, it is preferable. In addition, as in the preform, in the case where the heating temperature exceeds the boiling point of the solvent used, it is preferable to use an autoclave.

[0104] The solid electrolyte obtained by the production method of the present embodiment contains a argyrodite-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 measurement using CuKα rays.

[0105] The diffraction peaks at 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg are peaks derived from the argyrodite-type crystal structure.

[0106] Sometimes the diffraction peaks of the argyrodite-type crystal structure also appear at, for example, 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. The solid electrolyte can also have these peaks.

[0107] In addition, in the case where the central value is set to A, the position of the diffraction peak is determined as A ± 0.5 deg or A ± 0.4 deg in the present application, but it is preferable to be determined as A ± 0.3 deg. For example, in the case of the above-mentioned diffraction peak at 2θ = 25.2 ± 0.5 deg, the central value A is 25.2 deg, and it is preferable to be present in the range of 2θ = 25.2 ± 0.3 deg. The same applies to the determination of the positions of all other diffraction peaks in the present application.

[0108] If the solid electrolyte has an X-ray diffraction pattern of the argyrodite-type crystal structure as described above, it can also contain an amorphous component in a part thereof. The amorphous component shows a substantially hollow pattern in X-ray diffraction measurement, which does not show peaks other than those derived from the raw material. In addition, it can also contain crystal structures other than the argyrodite-type crystal structure and raw materials.

[0109] [Second Embodiment]

[0110] The solid electrolyte of the present embodiment has a sulfide silver germanium mineral type crystal structure including lithium (Li), phosphorus (P), sulfur (S), oxygen (O), and halogen (X) as constituent elements, the proportion of Li3PO4 crystal structure in the total crystal in the solid electrolyte is 0.1 mass% or more and 3.0 mass% or less, and the solid electrolyte satisfies the following formulas (21) to (23).

[0111] 4.8 ≤ Li / P ≤ 5.3 … (21)

[0112] 3.8 ≤ S / P ≤ 4.4 … (22)

[0113] 1.0 < X / P ≤ 2.0 … (23)

[0114] (Formula (21) is the molar ratio of Li to P, formula (22) is the molar ratio of S to P, and formula (23) is the molar ratio of halogen (X) to P.)

[0115] The above formulas (21) to (23) preferably satisfy the following formulas.

[0116] 4.85 ≤ Li / P ≤ 5.25

[0117] 3.9 ≤ S / P ≤ 4.3

[0118] 1.2 ≤ X / P ≤ 1.9

[0119] More preferably, the above formulas (21) to (23) satisfy the following formulas.

[0120] 4.9 ≤ Li / P ≤ 5.2

[0121] 4.0 ≤ S / P ≤ 4.2

[0122] 1.4 ≤ X / P ≤ 1.8

[0123] The proportion of Li3PO4 crystal structure in the total crystal in the solid electrolyte is 0.1 mass% or more and 3.0 mass% or less. As long as it is within this range, a high ion conductivity can be maintained while suppressing the generation of hydrogen sulfide.

[0124] The proportion of Li3PO4 crystal structure is preferably 0.3 mass% or more, and further preferably 0.5 mass% or more. In addition, the proportion of Li3PO4 crystal structure is preferably 2.0 mass% or less, further preferably 1.5 mass% or less, and more preferably 1.0 mass% or less.

[0125] In one embodiment, the proportion of sulfide silver germanium mineral type crystal structure in the total crystal in the solid electrolyte is 90 mass% or more. Thereby, a high ion conductivity can be exhibited.

[0126] The proportion of the argyrodite-type crystal structure is preferably 93% by mass or more, more preferably 95% by mass or more, further preferably 96% by mass or more, and particularly preferably 97% by mass or more.

[0127] In one embodiment, the proportion of the β-Li3PS4 crystal structure in the total crystal structure in the solid electrolyte is 5.0 mass % or less, preferably 4.0 mass % or less, and more preferably 3.0 mass % or less.

[0128] The ratio of the argyrodite-type crystal structure, the Li3PO4 crystal structure, and the β-Li3PS4 crystal structure to the total crystal in the solid electrolyte is a value obtained by radiometric analysis as in the evaluation example.

[0129] The compositions of formulas (21) to (23) of this embodiment can be achieved by adjusting the blending of raw materials. For example, the molar ratio of S can be reduced by reducing the blending amount of lithium sulfide (Li2S), and the molar ratio of Li and O can be adjusted by blending lithium oxide (Li2O).

[0130] The solid electrolyte of the present embodiment can be obtained, for example, by the production method of the above-mentioned first embodiment.

[0131] In the solid electrolyte of this embodiment, examples of the halogen (X) include F, Cl, Br, and I. The type of halogen (X) contained in the solid electrolyte may be one or two or more, but two types are more preferred.

[0132] It is preferred that at least one of X is Cl or Br, and it is more preferred that X contains Cl and Br.

[0133] In one embodiment, the solid electrolyte may contain, in addition to the above-mentioned Li, P, S, O and halogen (X), one or more elements selected from the group consisting of H, Si, Ge, Sn, Pb, B, Al, Ga, As, Sb and Bi to the extent that the effects of the invention are not impaired.

[0134] In one embodiment, the solid electrolyte has a composition represented by the following formula (A).

[0135] Li a P b S c O d X e …(A)

[0136] (wherein X is a halogen, 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).

[0137] X of formula (A) can be one selected from the group consisting of F, Cl, Br and I, and in addition, two or more (xl,..., x n : n is an integer of 2 or more and 4 or less). X is more preferably constituted of two (xl, x2). The molar ratio of each element is not particularly limited.

[0138] X of formula (A) is preferably Cl and Br.

[0139] In the present application, the molar ratio and composition of each element in the solid electrolyte can be measured by various methods known to those skilled in the art, and can be measured by ICP emission spectrometry except for particular reasons such as difficulty in analysis. For example, in the case of the solid electrolyte described in the present application, the molar ratio and composition of elements other than oxygen can be measured by ICP emission spectrometry.

[0140] The molar ratio of each element can be controlled by adjusting the content of each element in the raw material.

[0141] In the solid electrolyte of one embodiment, the lattice constant of the argyrodite crystal structure is preferably 10.0 A or more and 11.0 A or less from the viewpoint of further inhibiting generation of hydrogen sulfide. More preferably, the lattice constant of the argyrodite crystal structure is 10.0 A or more and 11.0 A or less. Further preferably, the lattice constant of the argyrodite crystal structure is 10.0 A or more and 11.0 A or less. In particular, the lattice constant of the argyrodite crystal structure is 10.0 A or more and 11.0 A or less. The lattice constant of the argyrodite crystal structure is 10.0 A or more and 11.0 A or less. It is speculated that if the lattice constant is within the above range, the sulfur element in the 4a and 4d sites in the argyrodite crystal structure is sufficiently reduced and is replaced with a halogen element having a smaller ionic radius.

[0142] In addition, the lattice constant can be measured by the X-ray analysis described in the examples.

[0143] In the solid electrolyte of one embodiment, the ratio of the peak intensity of the diffraction peak derived from the Li3PS4crystal structure to the peak intensity of the diffraction peak derived from the argyrodite crystal structure at 2Θ = 25.2 ± 0.5 deg is preferably less than 0.04 from the viewpoint of further increasing the ion conductivity.

[0144] This is because the ion conductivity of Li3PS4is lower than that of the argyrodite crystal structure, and thus the lower the content of the Li3PS4crystal structure in the solid electrolyte, the more the decrease in the ion conductivity can be inhibited.

[0145] As described above, generally, if the amount of Li2S in the raw material of the solid electrolyte is reduced in order to suppress the generation of hydrogen sulfide, the amount of sulfur element required for the generation of the argyrodite crystal structure is deficient, and it becomes easy to generate other crystal phases such as Li3PS4, but the present inventors have succeeded in suppressing the amount of generation of Li3PS4 and reducing the sulfur element content of the argyrodite crystal structure itself by mixing the raw materials at a specific ratio, and it is possible to give consideration to the suppression of the generation of hydrogen sulfide and the ion conductivity on a higher level.

[0146] In this regard, in the invention described in Patent Document 1, by reducing Li2S, the peak intensity ratio originating from Li3PS4 is increased, and it can be considered that the sulfur element is not reduced from the argyrodite crystal structure itself as in one embodiment of the present invention, and the portion in which the element is reduced is not the argyrodite crystal structure, but a portion that changes to other crystal structures such as Li3PS4.

[0147] Further, by reducing the generation of hydrogen sulfide by reducing the content of sulfur element, and by making oxygen element exist during the heating process so as to maintain the argyrodite crystal structure, a high ion conductivity is exhibited. In Patent Document 2, Li2O is added only after the argyrodite crystal structure is generated by heating, and oxygen element is not made to exist during the heating process of forming the argyrodite crystal structure as in the first embodiment. Therefore, it is difficult to reduce the amount of generation of hydrogen sulfide while exhibiting a high ion conductivity as in the first embodiment.

[0148] The solid electrolyte of the present invention can be used for a lithium ion battery or the like. Specifically, it can be used for a solid electrolyte layer, a positive electrode, a negative electrode, or the like of a battery.

[0149] In one embodiment, the electrode for a lithium ion battery can be mixed with a known active material, a conductive aid, or the like, in addition to the solid electrolyte. Further, a binder can also be mixed.

[0150] The lithium ion battery of one embodiment includes the solid electrolyte of the present invention.

[0151] In one embodiment, the lithium ion battery is a full solid battery.

[0152] In one embodiment, the full solid battery includes a laminate that includes, in order, a positive electrode current collector, a positive electrode, an electrolyte layer, a negative electrode, and a negative electrode current collector. The lithium ion battery preferably includes the solid electrolyte of the present invention in one or more selected from the group consisting of a positive electrode, an electrolyte layer, and a negative electrode.

[0153] Example

[0154] The present invention will be described in more detail below according to an example.

[0155] In addition, the evaluation method is described below.

[0156] (1) Hydrogen sulfide (H2S) generation from solid electrolytes

[0157] The schematic diagram of the test device is as follows: Figure 1 shown.

[0158] The main components of the test apparatus 1 are as follows: a flask 10 for humidifying nitrogen; a static mixer 20 for mixing humidified and unhumidified nitrogen; a dew point meter 30 (Vaisala M170 / DMT152) for measuring the moisture content of the mixed nitrogen; a double reaction tube 40 for holding the measurement sample; a dew point meter 50 for measuring the moisture content of the nitrogen gas discharged from the double reaction tube 40; and a hydrogen sulfide meter 60 (AMI Model 3000RS) for measuring the hydrogen sulfide concentration in the discharged nitrogen gas. These components are connected by tubes (not shown). The temperature of the flask 10 is set at 10°C by a cooling tank 11.

[0159] In addition, Teflon (registered trademark) tubes with a diameter of 6 mm were used as tubes connecting the components. In this figure, the tubes are not marked, and the flow of nitrogen gas is instead indicated by arrows.

[0160] The evaluation steps are as follows.

[0161] In a nitrogen glove box with a dew point of -80°C, about 1 g of powder sample 41 was weighed and placed inside a reaction tube 40, sandwiched between quartz wool 42 and sealed. The inside of the reaction tube 40 was kept at approximately room temperature (25°C).

[0162] Nitrogen gas was supplied from a nitrogen source (not shown) at 0.02 MPa into the apparatus 1. A portion of the supplied nitrogen gas passed through a bifurcated branch pipe BP and was supplied to the flask 10 for humidification. The remaining portion was directly supplied to the static mixer 20 as unhumidified nitrogen gas. The amount of nitrogen gas supplied to the flask 10 was adjusted by a needle valve V.

[0163] The dew point was controlled by adjusting the flow rates of unhumidified and humidified nitrogen using a flow meter FM with a needle valve. Specifically, unhumidified nitrogen was supplied to a static mixer 20 at a flow rate of 800 mL / min and humidified nitrogen at a flow rate of 10 to 30 mL / min, whereupon the gases were mixed. The dew point of the mixed gas (a mixture of unhumidified and humidified nitrogen) was then measured using a dew point meter 30.

[0164] After the dew point is adjusted to -30°C, the three-way stopcock 43 is rotated to circulate the mixed gas inside the reaction tube 40 for 2 hours. The amount of hydrogen sulfide contained in the mixed gas that has passed through the sample 41 is measured with a hydrogen sulfide meter 60, and the amount of hydrogen sulfide generated per 1g of solid electrolyte (cc / g) is calculated. In addition, the amount of hydrogen sulfide is recorded at intervals of 15 seconds. In addition, for reference, the dew point of the mixed gas after exposure is measured with a dew point meter 50. In order to remove hydrogen sulfide from the nitrogen after measurement, it is passed through an alkali trap 70.

[0165] (2) Measurement of ionic conductivity of solid electrolytes

[0166] The sample was placed in a tablet forming machine and a pressure of 22 MPa was applied to form a compact. Carbon electrodes were placed on both sides of the compact, and pressure was again applied using the tablet forming machine to produce a compact for measurement (approximately 10 mm in diameter and 0.1-0.2 cm thick). The ionic conductivity of this compact was measured using AC impedance spectroscopy. Conductivity values ​​are reported at 25°C.

[0167] (3) X-ray diffraction (XRD) measurement

[0168] A sample was prepared by evenly filling a 20 mm diameter, 0.2 mm deep cell with the argyrodite-type solid electrolyte powder produced in each case with glass. This sample was measured using a Kapton film for XRD, isolated from air. The 2θ position of the diffraction peak was determined using Le Bail analysis using the XRD analysis program RIETAN-FP.

[0169] The measurement was performed using a powder X-ray diffraction measuring apparatus D2 PHASER manufactured by BRUKER CO., LTD. under the following conditions.

[0170] The powder X-ray diffraction measurement apparatus was installed in a room whose temperature was controlled at 25°C.

[0171] Tube voltage: 30kV

[0172] Tube current: 10mA

[0173] X-ray wavelength: Cu-Kα ray

[0174] Optical system: Concentration method

[0175] Slit configuration: Soller slit 4°, divergence slit 1mm, Kβ filter (Ni plate)

[0176] Detector: semiconductor detector

[0177] Measuring range: 2θ = 10-60 degrees

[0178] Step width, scanning speed: 0.05deg, 0.05deg / sec

[0179] In the analysis of the peak position for confirming the presence of the crystal structure based on the measurement results, the peak position was determined by correcting the baseline using an 11th-order Legendre orthogonal polynomial using an XRD analysis program RIETAN-FP.

[0180] (4)ICP measurement

[0181] The solid electrolyte powder produced in each case was weighed and collected into a vial under an argon atmosphere. A KOH alkaline aqueous solution was added to the vial to dissolve the sample while taking care to capture the sulfur component. The sample was then appropriately diluted to prepare a measurement solution. The composition was determined by measuring the sample using a Paschen-Runge ICP-OES instrument (SPECTRO ARCOS, manufactured by SPECTRO GmbH, Germany).

[0182] The standard curve solutions for Li, P, and S were prepared using 1000 mg / L standard solutions for ICP measurement, and the standard curve solutions for Cl and Br were prepared using 1000 mg / L standard solutions for ion chromatography.

[0183] For each sample, two sets of measurement solutions were prepared, and five measurements were performed on each solution to calculate the average value. The composition was determined from the average value of the measured values ​​of the two sets of measurement solutions.

[0184] Production Example 1

[0185] [Manufacturing of lithium sulfide (Li2S)]

[0186] Li2S was produced and purified as follows.

[0187] Toluene (manufactured by Sumitomo Corporation) was used as a non-aqueous medium for dehydration treatment. Under a nitrogen flow, 303.8 kg of toluene having a moisture content of 100 ppm as measured by a Karl Fischer titrator was added to a 500 L stainless steel reactor. Subsequently, 33.8 kg of anhydrous lithium hydroxide (manufactured by Honjo Chemical Co., Ltd.) was added and stirred at 131 rpm using a twinstir stirring blade while maintaining the temperature at 95°C.

[0188] Hydrogen sulfide (manufactured by Sumitomo Seika Co., Ltd.) was blown into the slurry at a feed rate of 100 L / min while the temperature was raised to 104°C. A azeotropic gas of water and toluene was continuously discharged from the reactor. This azeotropic gas was condensed using a condenser outside the system to remove water. During this time, an amount of toluene equal to the distilled toluene was continuously supplied to maintain a constant reaction liquid level.

[0189] The amount of water in the condensate gradually decreased, and no distilled water was observed 24 hours after the introduction of hydrogen sulfide. During the reaction, the solid was dispersed in toluene and stirred, and no water separated from the toluene was present.

[0190] Then, the hydrogen sulfide gas was switched to nitrogen gas, and the gas was circulated at 100 L / min for 1 hour.

[0191] The obtained solid component was filtered and dried to obtain white powder, namely Li2S.

[0192] Example 1

[0193] As starting materials, Li2S, P2S5, LiBr (manufactured by Honjo Chemical Co., Ltd.), LiCl (manufactured by Honjo Chemical Co., Ltd.), and Li2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) from Production Example 1 were used. The starting materials, coarsely ground using a pin mill, were mixed so that the molar ratio (Li2S:P2S5:LiCl:LiBr:Li2O) was 1.65:0.5:1.0:0.6:0.05. Specifically, 0.402g of Li2S, 0.589g of P2S5, 0.225g of LiCl, 0.276g of LiBr, and 0.008g of Li2O were mixed.

[0194] The mixture and 30g of 10mm diameter zirconium oxide balls were placed in a 45mL zirconium oxide jar of a planetary ball mill (Fritsch, model P-7) and completely sealed. The jar was set to a nitrogen atmosphere. The rotating speed was set to 150rpm in the planetary ball mill and the mixture was processed (pre-mixed) for 10 minutes. Afterwards, the mixture was processed (mechanically ground) at 370rpm for 15 hours to obtain a powder of the raw material mixture.

[0195] In an Ar atmosphere glove box, approximately 1.5 g of the raw material mixture was placed in a carbon pellet heating tube (PT2, manufactured by Tokyo Glass Instruments Co., Ltd.) and heated in an electric furnace. Specifically, the temperature was raised from room temperature to 380°C over 1 hour, then to 430°C over 30 minutes, and maintained at 430°C for 2 hours. The mixture was then removed from the furnace and allowed to cool, yielding a solid electrolyte.

[0196] Table 1 shows the molar ratio of the raw materials, the molar ratio of each element, the amount of hydrogen sulfide generated, and the ion conductivity of the obtained solid electrolyte.

[0197] The XRD pattern of the solid electrolyte is as follows Figure 2 Diffraction peaks of the argyrodite type crystal structure were observed at 2θ=15.6deg, 18.1deg, 25.6deg, 30.1deg, 31.5deg, and 45.1deg.

[0198] Examples 2 to 4, Comparative Examples 1 to 5

[0199] The solid electrolyte was prepared and evaluated in the same manner as in Example 1 except that the molar ratio of the starting materials was changed to that shown in Table 1. The results are shown in Table 1. The XRD patterns of the solid electrolytes obtained in Examples 2 to 4 and Comparative Examples 1 to 5 are shown in Table 1. Figures 3 to 10 shown.

[0200] In Example 2, diffraction peaks of an argyrodite-type crystal structure were observed at 2θ=15.6 degrees, 18.1 degrees, 25.6 degrees, 30.1 degrees, 31.5 degrees, and 45.1 degrees. In the solid electrolyte of Example 2, a diffraction peak derived from Li3PO4 was also observed.

[0201] In Example 3, diffraction peaks of the argyrodite-type crystal structure were observed at 2θ=15.7 degrees, 18.1 degrees, 25.6 degrees, 30.1 degrees, 31.5 degrees, and 45.1 degrees.

[0202] In Example 4, diffraction peaks of the argyrodite-type crystal structure were observed at 2θ=15.7 degrees, 18.1 degrees, 25.7 degrees, 30.2 degrees, 31.6 degrees, and 45.1 degrees.

[0203] Table 2 shows the results of determining the composition of the solid electrolytes of Examples 2 and 4 and Comparative Examples 1, 2, and 5 by ICP measurement.

[0204] [Table 1]

[0205]

[0206] [Table 2]

[0207] ICP: molar ratio 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

[0208] Example 5

[0209] The same Li2S, P2S5, LiCl, LiBr, and LiOH (lithium hydroxide obtained by drying lithium hydroxide monohydrate manufactured by Honjo Chemical Co., Ltd.) as in Example 1 were used as starting materials. The starting materials, coarsely ground using a pin mill, were mixed so that the molar ratio (Li2S:P2S5:LiCl:LiBr:LiOH) was 1.6:0.5:1.0:0.6:0.2. Specifically, 0.3884g of Li2S, 0.5871g of P2S5, 0.224g of LiCl, 0.2753g of LiBr, and 0.0253g of LiOH were mixed.

[0210] Subsequently, a planetary ball mill was used to prepare a raw material mixture in the same manner as in Example 1, and the mixture was heat-treated to obtain a solid electrolyte. The evaluation results are shown in Table 3.

[0211] The XRD pattern of the solid electrolyte is as follows Figure 11 Diffraction peaks of the argyrodite-type crystal structure were observed at 2θ=15.6deg, 18.0deg, 25.6deg, 30.1deg, 31.5deg, and 45.0deg.

[0212] [Table 3]

[0213]

[0214] In Table 1, the molar ratio of S in the solid electrolyte is changed according to the preparation amount of Li2S in Comparative Examples 1 to 3. Comparative Example 1 is an example of relatively high ion conductivity even among solid electrolytes having an argyrodite-type crystal structure. It can be seen that although the ion conductivity is excellent, the amount of hydrogen sulfide produced is relatively large. In Examples 1 to 4 and Comparative Examples 4 and 5, the preparation amount of Li2S is reduced, and Li2O is added on the other hand. As a result, although the amount of S in the solid electrolyte (molar ratio of 4.1) is the same as that in Comparative Example 2, the ion conductivity is sufficiently high in Example 2, and the amount of hydrogen sulfide produced is also greatly suppressed. The same tendency can be confirmed from Example 4 and Comparative Example 3.

[0215] On the other hand, the amount of hydrogen sulfide generated increased in Comparative Examples 4 and 5, in which Li2O was further added. Therefore, it was confirmed that adding a predetermined amount of Li2O is effective in reducing the S content in the solid electrolyte by reducing the amount of Li2S used.

[0216] Furthermore, it was confirmed that in Example 5 in which LiOH was added instead of Li 2 O, the same effects as those in Example 2 were obtained, and that any raw material could be used.

[0217] Evaluation Example

[0218] For Examples 2 and 4 and Comparative Examples 1, 4, and 5, radiometric analysis was performed to analyze the lattice constants of the argyrodite-type crystal structure and the proportions of the argyrodite-type crystal structure, Li3PO4 crystal structure, and β-Li3PS4 crystal structure in the total crystal structure in the solid electrolyte. Specifically, measurements were performed under the following conditions.

[0219] In a glove box, the solid electrolyte powders prepared in Examples 2 and 4 and Comparative Examples 1, 4, and 5 were loaded into a 0.3 mmφ capillary tube, and the tip of the capillary tube was sealed with a curable resin to prepare samples for radiometric analysis.

[0220] The measurement was performed using SPring-8's powder diffraction measurement beamline "BL19B2" under the following conditions. Furthermore, a nitrogen purge-type sample cooling device manufactured by Rigaku Corporation was used to purge nitrogen gas at 100K onto the sample for 1 minute, maintaining this state for the measurement.

[0221] X-ray energy: 25keV

[0222] Optical system: transmission method

[0223] Detector: One-dimensional solid Si detector MYTHEN (12-link)

[0224] Detector threshold: 19keV

[0225] Measuring range: 2θ = 4-60 degrees

[0226] Step width: 0.005deg

[0227] Exposure time: 30 seconds x 2 times

[0228] The measurement data was corrected at 0.005° intervals using a script dedicated to BL19B2, and the analysis was performed using this data.

[0229] The peak position analysis for confirming the crystal structure was performed using the XRD analysis program PDXL2 (Version 2.7.3.0) manufactured by Rigaku Corporation, and the peak position was determined by PDXL automatic profile processing. The lattice constants and abundance ratios of the crystal structure were determined using the XRD analysis program PDXL2 (Version 2.7.3.0) manufactured by Rigaku Corporation, and the lattice constants and abundance ratios of the crystal structure were determined by Rietveld analysis using the following function.

[0230] Peak shape: Split-type pseudo-Voigt function

[0231] Background: Beta-Spline Functions

[0232] Peak shift: device function (Δ2θ=Z+Dcosθ+Tsin2θ)

[0233] In addition, the analysis of the lattice constant was performed based on the correction of 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 results were subjected to the Tewold analysis under the above analysis conditions, and the X-ray energy value was corrected so that the lattice constant reached

[0234] Further, in the analysis of the peak shape, the same function as the profile function for the argyrodite crystal structure is applied to crystals other than the argyrodite crystal structure for analysis.

[0235] Further, in the Rietveld analysis, the Rwp value of 10% or less is taken as a criterion for the effectiveness of the results.

[0236] The results are shown in Table 4.

[0237] [Table 4]

[0238]

[0239] From Table 4, it is confirmed that the lattice constants of Examples 2 and 4 are smaller than those of the comparative examples. It is presumed that this is because, in the interior of the argyrodite crystal structure of the examples, the sulfur ions (S 2- ) having a large ionic radius are absent, and instead, one or more of the 4a or 4d sites are occupied by halogen ions having a small ionic radius, so the lattice constants are smaller.

[0240] Although the several embodiments and / or examples of the present application have been described in detail above, various modifications can be made to these examples without departing from the novel teachings and advantages of the present application. Accordingly, the scope of the present application is not intended to be limited to the above examples, but is to be accorded the full scope of the claims attached hereto and equivalents thereof.

[0241] All documents described in this specification are incorporated herein by reference in their entirety.

Claims

1. A method for producing a solid electrolyte having an argyrodite-type crystal structure, characterized by: A mixing step of mixing raw materials so that lithium Li, phosphorus P, sulfur S, oxygen O and halogen X satisfy the following formulas (11) to (14); a heating step of heating the mixture obtained in the mixing step; 4.8≤Li / P≤5.3…(11) 3.8≤S / P≤4.4…(12) 0.01≤O / P≤0.7…(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.

2. The manufacturing method according to claim 1, wherein The formulas (11) to (14) in the mixing step satisfy the following formula: 4.85≤Li / P≤5.25 3.9≤S / P≤4.3 0.01≤O / P≤0.7 1.2≤X / P≤1.

9.

3. The manufacturing method according to claim 1, wherein: The formulas (11) to (14) in the mixing step satisfy the following formula: 4.9≤Li / P≤5.2 4.0≤S / P≤4.2 0.05≤O / P≤0.6 1.4≤X / P≤1.

8.

4. The manufacturing method according to claim 1, wherein: As the raw material, one or more selected from the group consisting of Li2S, Li2O, Li2CO3, LiOH and lithium metal element is used.

5. The manufacturing method according to claim 1, wherein: As the raw material, one or more of Li2O and LiOH are used.

6. The manufacturing method according to claim 1, wherein: Li2S was used as the raw material.

7. The manufacturing method according to claim 1, wherein: As the raw material, one or more selected from the group consisting of phosphorus sulfide, phosphorus compounds, and simple phosphorus are used.

8. The manufacturing method according to claim 7, wherein: As the raw material, one or more selected from the group consisting of P2S3, P2S5, Na3PO4 and phosphorus element is used.

9. The manufacturing method according to claim 8, wherein: P2S5 was used as the raw material.

10. The manufacturing method according to claim 1, wherein At least one of LiX and elemental halogen is used as the raw material, wherein X is a halogen.

11. The manufacturing method according to claim 10, wherein: Li3PS4, Li2O and LiX are used as the raw materials, wherein X is a halogen.

12. The manufacturing method according to claim 11, wherein: The halogen X is one or more selected from the group consisting of fluorine F, chlorine Cl, bromine Br, and iodine I.

13. The manufacturing method according to claim 11, wherein: The halogen X includes chlorine Cl and bromine Br.

14. The manufacturing method according to claim 1, wherein: The mixing process is carried out in a solvent.

15. The manufacturing method according to claim 1, wherein: A bead mill was used in the mixing step.

16. A solid electrolyte having an argyrodite-type crystal structure comprising lithium Li, phosphorus P, sulfur S, oxygen O, and halogen X, characterized in that: The proportion of Li3PO4 crystal structure in the total crystal in the solid electrolyte is 0.1 mass % or more and 3.0 mass % or less, and the solid electrolyte satisfies the following formulas (21) to (23): 4.8≤Li / P≤5.3…(21) 3.8≤S / P≤4.4…(22) 1.0<X / P≤2.0…(23) Formula (21) is the molar ratio of Li to P, formula (22) is the molar ratio of S to P, and formula (23) is the molar ratio of halogen X to P.

17. The solid electrolyte according to claim 16, wherein The formulas (21) to (23) satisfy the following formula: 4.85≤Li / P≤5.25 3.9≤S / P≤4.3 1.2≤X / P≤1.

9.

18. The solid electrolyte according to claim 17, wherein The formulas (21) to (23) satisfy the following formula: 4.9≤Li / P≤5.2 4.0≤S / P≤4.2 1.4≤X / P≤1.

8.

19. The solid electrolyte according to claim 16, wherein The proportion of argyrodite-type crystal structure in the solid electrolyte to the total crystal is greater than 90% by mass.

20. The solid electrolyte according to claim 19, wherein The proportion of argyrodite-type crystal structure in the solid electrolyte to the total crystal is greater than 93% by mass.

21. The solid electrolyte according to claim 20, wherein The proportion of argyrodite-type crystal structure in the solid electrolyte to the total crystal is greater than 97% by mass.

22. The solid electrolyte according to claim 16, wherein The proportion of the β-Li3PS4 crystal structure in the total crystals in the solid electrolyte is less than 5.0% by mass.

23. The solid electrolyte according to claim 22, wherein The proportion of the β-Li3PS4 crystal structure in the total crystals in the solid electrolyte is less than 3.0% by mass.

24. The solid electrolyte according to claim 16, wherein The solid electrolyte has diffraction peaks at 2θ=25.2±0.5 degrees and 29.7±0.5 degrees in powder X-ray diffraction measurement using CuKα rays.

25. The solid electrolyte according to claim 16, wherein The halogen X is one or more selected from the group consisting of fluorine F, chlorine Cl, bromine Br, and iodine I.

26. The solid electrolyte according to claim 25, wherein The halogen X is one or more selected from chlorine Cl and bromine Br.

27. The solid electrolyte according to claim 16, wherein The lattice constant of the argyrodite-type crystal structure is the following.

28. The solid electrolyte according to claim 27, wherein The lattice constant of the argyrodite-type crystal structure is the following.

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