Methods for manufacturing sulfide solid electrolytes and all-solid-state batteries

Abstract

This invention provides a method for manufacturing a sulfide solid electrolyte with high water resistance. The method includes a step of treating the sulfide solid electrolyte in a solvent selected from mixing and depolymerization processes, wherein the solvent is an aprotic solvent containing oxygen atoms.

Description

Technical Field

[0001] This invention relates to methods for manufacturing sulfide solid electrolytes and methods for manufacturing all-solid-state batteries. Background Technology

[0002] Currently, non-aqueous electrolyte secondary batteries are widely used in portable information terminals, portable electronic devices, and other applications. The electrolyte used in non-aqueous electrolyte secondary batteries typically employs flammable organic solvents. Therefore, non-aqueous electrolyte secondary batteries require robust outer packaging to prevent organic solvent leakage and usually have features to mitigate risks in the event of electrolyte leakage; these factors impose constraints on device construction.

[0003] Furthermore, in recent years, the applications of non-aqueous electrolyte secondary batteries have expanded to electric vehicles, hybrid electric vehicles, aircraft, and other mobile or stationary energy storage systems, requiring large-capacity non-aqueous electrolyte secondary batteries. Higher safety standards are also required for large-capacity non-aqueous electrolyte secondary batteries.

[0004] Given this situation, non-aqueous electrolyte secondary batteries that use solid electrolytes, which can achieve high safety, instead of flammable organic solvents, have attracted attention. Furthermore, non-aqueous electrolyte secondary batteries using solid electrolytes are sometimes referred to as all-solid-state batteries.

[0005] As solid electrolytes, sulfide solid electrolytes and oxide solid electrolytes are known. Among them, sulfide solid electrolytes have received special attention in recent years due to their high ionic conductivity.

[0006] For example, Patent Document 1 discloses an invention concerning sulfide solid electrolyte particles, which contains a sulfide solid electrolyte comprising Li, P, S, and halogens as constituent elements. The oxygen / sulfur ratio at the surface, measured using XPS, is 0.79 to 1.25, and the oxygen / sulfur ratio at a position 30 nm (converted from SiO2 sputtering velocity) at the surface is 0.58 or less. Patent Document 1 describes how surface oxidation, achieved by satisfying the aforementioned specific values ​​for the oxygen / sulfur ratio at the surface and at a position 30 nm from the surface of the sulfide solid electrolyte, provides sufficient ionic conductivity and suppresses the rate of resistance increase after charge-discharge cycles when used in all-solid-state batteries.

[0007] It also describes that the sulfide solid electrolyte particles described in Patent Document 1 can be manufactured as follows: the raw material composition is amorphized by mechanical grinding, and the obtained sulfide solid electrolyte glass is heated in the presence of an oxidant at a temperature above the crystallization temperature of the glass, thereby causing it to oxidize and crystallize.

[0008] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2020-115425 Summary of the Invention

[0009] The technical problem that the invention aims to solve As mentioned above, sulfide solid electrolytes exhibit high ionic conductivity, but their water resistance is insufficient. They can decompose and potentially generate hydrogen sulfide through reaction with trace amounts of moisture in the atmosphere. To avoid this, the manufacturing environment for sulfide solid electrolytes and all-solid-state batteries is typically designed to be low-moisture. However, this often results in increased manufacturing costs and reduced productivity.

[0010] To address this, studies have been conducted on water-resistant treatments for sulfide solid electrolytes. For example, the sulfide solid electrolyte particles described in Patent Document 1 undergo surface treatment via oxidation during manufacturing, thus achieving a certain degree of water resistance. However, even with water-resistant treatment during manufacturing, the water resistance is sometimes insufficient.

[0011] Therefore, the present invention provides a method for manufacturing a sulfide solid electrolyte with high water resistance, etc.

[0012] Technical solutions for solving technical problems The present invention includes, for example, the following methods.

[0013] [1] A method for manufacturing a sulfide solid electrolyte, comprising a step of treating the sulfide solid electrolyte in a solvent with at least one treatment selected from mixing treatment and disaggregation treatment, The solvents mentioned above include those that are aprotic and contain oxygen atoms.

[0014] [2] The manufacturing method as described in [1] above, wherein the solvent comprises at least one selected from ester solvents and ether solvents.

[0015] [3] The manufacturing method as described in [2] above, wherein the solvent comprises an ester solvent.

[0016] [4] The manufacturing method as described in [3] above, wherein the ester solvent comprises at least one selected from ethyl acetate and ethyl propionate.

[0017] [5] The manufacturing method as described in any one of [2] to [4] above, wherein the solvent comprises an ether solvent.

[0018] [6] The manufacturing method as described in [5] above, wherein the ether solvent comprises dibutyl ether.

[0019] [7] The manufacturing method as described in any one of [1] to [6] above, wherein the above treatment includes a mixing treatment.

[0020] [8] The manufacturing method as described in any one of [1] to [7] above, wherein the above treatment includes a depolymerization treatment.

[0021] [9] The manufacturing method as described in any one of [1] to [8] above, wherein the sulfide solid electrolyte comprises an LGPS type sulfide solid electrolyte.

[0022]

[10] The manufacturing method as described in any one of [1] to [8] above, wherein the sulfide solid electrolyte comprises a sulfide solid electrolyte of the silver sulfide type.

[0023]

[11] The manufacturing method as described in any one of [1] to

[10] above, wherein the sulfide solid electrolyte contains tin (Sn).

[0024]

[12] A method for manufacturing an all-solid-state battery, comprising a step of forming an all-solid-state battery, wherein the all-solid-state battery comprises a sulfide solid electrolyte manufactured using any one of the methods described in [1] to

[11] .

[0025] Invention Effects The present invention provides a method for manufacturing a sulfide solid electrolyte with high water resistance. Detailed Implementation

[0026] The specific embodiments of the present invention will be described in detail below.

[0027] 1. Method for manufacturing sulfide solid electrolytes The method for manufacturing the sulfide solid electrolyte of the present invention includes a step of performing at least one treatment selected from mixing treatment and depolymerization treatment on the sulfide solid electrolyte in a solvent (hereinafter also referred to as "water-resistant treatment step"). In this case, the solvent comprises an aprotic solvent containing oxygen atoms.

[0028] Using this invention, a water-resistant treatment is performed after the manufacture of the sulfide solid electrolyte, without performing a water-resistant treatment during the manufacturing process. In this case, the water-resistant treatment is carried out by mixing and / or depolymerizing in a specified solvent. This allows the manufacture of a sulfide solid electrolyte with high water resistance. In this specification, "after the manufacture of the sulfide solid electrolyte" refers to the point in time after obtaining a sulfide solid electrolyte with the desired crystalline structure and particle size (primary particle size). For example, if an amorphous intermediate is manufactured by mechanically grinding a raw material composition, and then crystallized and the sulfide solid electrolyte is manufactured by pulverizing it, the water-resistant treatment performed on the raw material composition, the intermediate, and the sulfide solid electrolyte before pulverization is not considered a water-resistant treatment "after the manufacture of the sulfide solid electrolyte." On the other hand, the water-resistant treatment performed on the pulverized sulfide solid electrolyte is considered a water-resistant treatment "after the manufacture of the sulfide solid electrolyte."

[0029] (1) Water-resistant treatment process The water-resistant treatment process involved in this invention, as described above, is a process of performing at least one treatment selected from mixing treatment and depolymerization treatment on a sulfide solid electrolyte in a solvent.

[0030] [Sulfide solid electrolyte] As a sulfide solid electrolyte, there are no particular restrictions, but it contains at least one of the alkali metal elements and alkaline earth metal elements, as well as sulfur (S).

[0031] Examples of the aforementioned alkali metal elements include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

[0032] Examples of alkaline earth metal elements include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Rd). In this specification, "alkaline earth metal elements" includes beryllium (Be) and magnesium (Mg).

[0033] In the above-mentioned context, the alkali metal element and alkaline earth metal element preferably include at least one of lithium (Li) and sodium (Na), and more preferably lithium (Li). The alkali metal element and alkaline earth metal element may be contained individually or in combination of two or more.

[0034] Sulfide solid electrolytes may also contain other elements. Examples of such other elements include tin (Sn), silicon (Si), germanium (Ge), antimony (Sb), phosphorus (P), halogens (fluorine (F), chlorine (Cl), bromine (Br), iodine (I)), and oxygen (O). These other elements may be contained individually or in combination of two or more.

[0035] Among these, the sulfide solid electrolyte preferably contains tin (Sn). That is, in one embodiment, the sulfide solid electrolyte preferably contains at least one of an alkali metal element and an alkaline earth metal element, sulfur (S) and tin (Sn), and more preferably lithium (Li), sulfur (S) and tin (Sn). From the viewpoint of increasing ionic conductivity, improving water resistance, and further enhancing the water resistance improvement effect of the water-resistant treatment of the present invention, the sulfide solid electrolyte preferably contains tin (Sn).

[0036] Sulfide solid electrolytes can be crystalline or amorphous (also known as "glass" or "amorphous"), but are preferably crystalline.

[0037] There are no particular restrictions on the crystalline form of sulfide solid electrolytes; examples include LGPS type, silver-germanium sulfide type, and Thio-LISICON type.

[0038] LGPS type sulfide solid electrolyte is a solid electrolyte containing lithium (Li), germanium (Ge), phosphorus (P) and sulfur (S), and contains the following crystal structure as the main body. This crystal structure has LiS6 octahedron, GeS4 tetrahedron and PS4 tetrahedron. The PS4 tetrahedron, GeS4 tetrahedron and LiS6 octahedron share edges, and the PS4 tetrahedron and LiS6 octahedron share vertices.

[0039] In LGPS-type sulfide solid electrolytes, germanium (Ge) can be replaced with tin (Sn) or silicon (Si). Additionally, halogens (fluorine (F), chlorine (Cl), bromine (Br), iodine (I)) and oxygen (O) can be introduced into LGPS-type sulfide solid electrolytes. For example, by replacing some sulfur (S) with oxygen (O), the size of the tunnels through which Li ions pass in the crystal becomes more conductive, thus increasing ionic conductivity.

[0040] In one embodiment, the LGPS type sulfide solid electrolyte is represented by the following formula.

[0041] Li-M 1 -M 2 -P-S-X 1 At this time, M 1 For Ge, Sn, or Si, M 2 For single bonds, Ge, Sn or Si, X 1 It does not exist, or it is fluorine (F), chlorine (Cl), bromine (Br), iodine (I), or oxygen (O).

[0042] M 1 Preferably Ge or Sn, more preferably Sn. M 2 A single bond is preferred. X 1Preferably, it is absent, or it is chlorine (Cl) or oxygen (O), and more preferably, it is absent.

[0043] As a specific component of LGPS-type sulfide solid electrolytes, Li can be listed as an example. 10 GeP2S 12 Li 10 SnP2S 12 Li 10.35 Ge 1.35 P 1.65 S 12 Li 10.35 Si 1.35 P 1.65 S 12 Li 9.81 Sn 0.81 P 2.19 S 12 Li 10 (Si) 0.5 Ge 0.5 P2S 12 Li 10 (Ge) 0.5 Sn 0.5 P2S 12 Li 10 (Si) 0.5 Sn 0.5 P2S 12 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Li 10 GeP2S 11.7 O 0.3 Li 9.42 Si 1.02 P 2.1 S 9.96 O 2.04 Li 10.35 [Sn] 0.27 Si 1.08 P 1.65 S 12 (Li) 3.45 [Sn] 0.09 Si 0.36 P 0.55 S4), etc.

[0044] The sulfide solid electrolyte of the sulfide type has the same crystal structure as cubic Cu-sulfide-sulfide and Ag-sulfide compounds.

[0045] As specific components of sulfide solid electrolytes of the silver-germanium sulfide type, Li6PS5Cl and Li can be listed. 5.4PS 4.4 Cl 1.6 Li 5.8 PS 4.8 Cl 1.2 Li6PS5Br, Li 5.4 PS 4.4 Cl 0.8 Br 0.8 Li6PS5I, Li 6.6 Ge 0.6 P 0.4 S5I, Li7Ge3PS 12 wait.

[0046] Thio-LISICON type sulfide solid electrolytes have a γ-Li3PO4 type framework structure.

[0047] In one embodiment, the Thio-LISICON type sulfide solid electrolyte is represented by the following formula.

[0048] Li2S-P2S5-X 2 At this time, X 2 It does not exist, or it is a Li-halogen or M-halogen. 3 S2, M 3 It can be Sn, Ge, Ga, or Si.

[0049] X 2 Preferably, it is absent or is LiCl, LiBr, LiI, SnS2, GeS2, or SiS2; more preferably, it is absent or is LiCl, GeS2, or SiS2.

[0050] In another embodiment, the Thio-LISICON type sulfide solid electrolyte is represented by the following formula.

[0051] Li2S-M 4 S2 At this time, M 4 It is Sn, Ge, Ga or Si, preferably Sn, Ge or Si.

[0052] Specific examples of Thio-LISICON type sulfide solid electrolytes include Li₂S-SnS₂, Li₂S-P₂S₅, Li₂S-P₂S₅-LiI, Li₂S-P₂S₅-LiCl, Li₂S-P₂S₅-LiBr, Li₂S-GeS₂, Li₂S-SiS₂, Li₂P₂S₆, Li₄P₂S₆, and Li₇P₃S₆. 11 , α-Li3PS4, β-Li3PS4, γ-Li3PS4, LT-Li7PS6, HT-Li7PS6, Li 4.275Ge 0.61 Ga 0.25 S4, etc.

[0053] The aforementioned sulfide solid electrolytes can be used alone or in combination of two or more.

[0054] In one embodiment, from the viewpoints of increased ionic conductivity, improved water resistance, and enhanced water resistance resulting from the water-resistant treatment of the present invention, the sulfide solid electrolyte preferably comprises an LGPS type sulfide solid electrolyte.

[0055] In one embodiment, from the viewpoint of high ionic conductivity, the sulfide solid electrolyte preferably comprises a sulfide solid electrolyte of the sulfide type.

[0056] The particle size (primary particle size) of the sulfide solid electrolyte is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm. In this specification, "particle size (primary particle size)" refers to the maximum distance between two points on the outline of the object, and is the average particle size of any 50 objects contained in a field of view of a scanning electron microscope (SEM).

[0057] Sulfide solid electrolytes can be manufactured using known methods or commercially available products.

[0058] For example, sulfide solid electrolytes can be manufactured using methods such as: mechanical milling, which includes preparing an amorphous precursor by mechanically milling a raw material composition and heating the amorphous precursor; and liquid-phase methods, which include preparing the precursor in a solution, removing the solvent, and heating the precursor. Among these, sulfide solid electrolytes are preferably manufactured using mechanical milling.

[0059] There are no particular restrictions on the raw materials used in the manufacture of sulfide solid electrolytes. Raw materials that can be used as lithium sources, phosphorus sources, sulfur sources, silicon sources, germanium sources, tin sources, chlorine sources, bromine sources, iodine sources, oxygen sources, etc.

[0060] There are no particular restrictions on the raw materials used as lithium sources, and examples include lithium metal (Li), lithium sulfide (Li2S), lithium chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), Li3PS4, and Li4SnS4.

[0061] Raw materials that can be used as phosphorus sources include elemental phosphorus (P), phosphorus trisulfide (P2S3), phosphorus pentasulfide (P2S5), phosphorus pentachloride (PCl5), phosphorus tribromide (PBr3), phosphorus pentabromide (PBr5), and Li3PS4.

[0062] Raw materials that can be used as sulfur sources include elemental sulfur (S), lithium sulfide (Li2S), phosphorus sulfide (P2S5), silicon sulfide (SiS2), germanium sulfide (GeS2), tin sulfide (SnS), tin disulfide (SnS2), phosphorus trisulfide (P2S3), phosphorus pentasulfide (P2S5), aluminum sulfide (Al2S3), boron trisulfide (B2S3), Li3PS4, and Li4SnS4.

[0063] Raw materials that can be used as silicon sources include silicon sulfide (SiS2), silicon (Si), and silicon dioxide (SiO2).

[0064] Raw materials that can be used as germanium sources include germanium sulfide (GeS2), germanium (Ge), and germanium dioxide (GeO2).

[0065] Raw materials that can be used as sources of tin include tin sulfide (SnS), tin disulfide (SnS2), tin oxide (II) (SnO), tin oxide (IV) (SnO2), tin oxide (VI) (SnO3), tin (Sn), and Li4SnS4.

[0066] Raw materials that can be used as chlorine sources include lithium chloride (LiCl) and phosphorus pentachloride (PCl5).

[0067] Raw materials that can be used as bromine sources include lithium bromide (LiBr), phosphorus tribromide (PBr3), and phosphorus pentabromide (PBr5).

[0068] Examples of raw materials that can be used as iodine sources include lithium iodide (LiI).

[0069] Raw materials that can be used as oxygen sources include lithium oxide (Li2O), phosphorus pentoxide (P2O5), silicon dioxide (SiO2), germanium dioxide (GeO2), tin oxide (II) (SnO), tin oxide (IV) (SnO2), and tin oxide (IV) (SnO3).

[0070] Among these, the preferred raw materials include lithium sulfide (Li2S), phosphorus pentasulfide (P2S5), tin sulfide (SnS), tin disulfide (SnS2), Li3PS4, and Li4SnS4.

[0071] These solid electrolyte raw materials can be used alone or in combination of two or more. By changing their raw material composition, it is possible to manufacture the desired sulfide solid electrolyte.

[0072] [Solvent] The solvent includes aprotic solvents containing oxygen atoms. The aprotic nature of the solvent helps prevent the formation of hydrogen sulfide due to the decomposition of the sulfide solid electrolyte. Furthermore, the presence of oxygen atoms in the solvent allows for water-resistant treatment of the sulfide solid electrolyte (such as oxidation of the sulfide solid electrolyte surface).

[0073] There are no particular limitations on the solvents mentioned above; examples include ester solvents, ether solvents, ketone solvents, sulfoxide solvents, etc.

[0074] Examples of ester solvents include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and butyl propionate.

[0075] Examples of ether solvents include diethyl ether, dibutyl ether, tert-butyl methyl ether, tetrahydrofuran, 2-methyltetrahydrofuran (MHF), 4-methyltetrahydropyran (MTHP), 1,4-dioxane, and methoxycyclopentane.

[0076] Examples of ketone solvents include acetone, methyl ethyl ketone, 4-methyl-2-pentanone, 2-butanone, 3-methyl-2-butanone, 2-pentanone, 3-pentanone, 2-heptanone, isopentylmethyl ketone, cyclopentanone, cyclohexanone, and diisobutyl ketone.

[0077] Examples of sulfoxide solvents include dimethyl sulfoxide (DMSO).

[0078] Among these, the solvent preferably includes at least one selected from ester solvents, ether solvents, and ketone solvents; more preferably, it includes at least one selected from ester solvents and ether solvents; and even more preferably, it includes at least one selected from ethyl acetate, ethyl propionate, and dibutyl ether. The aforementioned solvents can be used alone or in combination of two or more.

[0079] In a preferred embodiment, the solvent comprises an ester solvent. The ester solvent preferably comprises at least one selected from methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, and butyl propionate; more preferably, it comprises at least one selected from ethyl acetate and ethyl propionate; and even more preferably, it comprises ethyl acetate.

[0080] In a preferred embodiment, the solvent comprises an ether solvent. The ether solvent preferably comprises at least one selected from diethyl ether, dibutyl ether, and tetrahydrofuran, and more preferably dibutyl ether.

[0081] The amount of solvent used relative to 1g of sulfide solid electrolyte is preferably 1-50mL, more preferably 3-40mL, even more preferably 5-30mL, and particularly preferably 5-20mL.

[0082] The sulfide solid electrolyte in the solvent is preferably a suspension (slurry) dispersed in the solvent. The content of the sulfide solid electrolyte in the solvent is preferably 1-50% by mass, more preferably 3-40% by mass, further preferably 5-30% by mass, and particularly preferably 5-20% by mass, relative to the total mass of the solvent and the sulfide solid electrolyte.

[0083] [Treatment (water-resistant treatment)] Sulfide solid electrolytes can be made water-resistant by treating them in a solvent, such as by oxidizing the surface of the sulfide solid electrolyte. In this case, the treatment is selected from mixing treatment and depolymerization treatment.

[0084] In this specification, "mixing treatment" refers to mixing a solvent and a sulfide solid electrolyte in a solvent. Specific examples of mixing treatment include stirring treatment and vibration treatment.

[0085] In addition, in this specification, "depolymerization treatment" refers to the process of applying a separating force to sulfide solid electrolytes (secondary particles, aggregates, etc.) that are bonded or agglomerated together in a solvent to disperse or disintegrate them. Specific examples of depolymerization treatment include FILMIX treatment (a registered trademark, a technique for uniformly depolymerizing materials using the stirring energy generated by a high-speed gyratory film), compression treatment, friction treatment, and shear treatment.

[0086] The treatment (water-resistant treatment) involved in this invention is selected from mixing treatment and depolymerization treatment. Water resistance of sulfide solid electrolytes can be achieved by performing mixing treatment or depolymerization treatment in solution.

[0087] Regarding the mixing and depolymerization treatments, the particle size (primary particle size) of the sulfide solid electrolyte remains almost unchanged before and after the treatment. Therefore, the water resistance treatment can be carried out uniformly on the surface of each particle of the sulfide solid electrolyte. In this respect, the treatment (water resistance treatment) involved in this invention differs from "pulverization treatment." In this specification, "pulverization treatment" refers to the process of subdividing the sulfide solid electrolyte by applying physical energy. That is, through pulverization treatment, the particle size (primary particle size) of the sulfide solid electrolyte becomes smaller. In the case of "pulverization treatment," even if water resistance can be achieved by pulverization treatment through the decomposition of the sulfide solid electrolyte by the applied physical energy, the degree of water resistance on the surface of each particle of the sulfide solid electrolyte may deviate due to the subdivision of the sulfide solid electrolyte, resulting in relatively low water resistance of the obtained sulfide solid electrolyte.

[0088] (Mixed processing) There are no particular restrictions on the mixing process; well-known methods can be used.

[0089] For example, when mixing is performed by stirring, there is no particular limitation on the stirring temperature, but it is preferably 10 to 60°C, and more preferably 15 to 45°C.

[0090] There is no particular limitation on the stirring time, but it is preferably 1 to 120 minutes, and more preferably 5 to 60 minutes.

[0091] Furthermore, when the mixing process is carried out by vibration treatment, there is no particular limitation on the vibration speed, which is preferably 1 to 50 kHz, and more preferably 5 to 30 kHz.

[0092] There is no particular limitation on the vibration time, but it is preferably 1 to 120 minutes, and more preferably 5 to 60 minutes.

[0093] In addition, an ultrasonic homogenizer is suitable for mixing by vibration.

[0094] In one embodiment, regarding the treatment (water-resistant treatment) involved in the present invention, from the viewpoint of increasing ionic conductivity, a mixing treatment is preferred; from the viewpoint of being able to uniformly perform water-resistant treatment on particles without using special equipment, a stirring treatment is more preferred.

[0095] In one embodiment, where the treatment (water-resistant treatment) involved in the present invention includes a mixing treatment (preferably a stirring treatment), from the viewpoint of further improving water resistance, the solvent preferably comprises an ester solvent, more preferably comprises at least one selected from methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate and butyl propionate, further preferably comprises at least one selected from ethyl acetate and ethyl propionate, and even more preferably comprises ethyl acetate.

[0096] (Depolymerization process) There are no particular restrictions on the depolymerization process; it can be carried out using well-known methods.

[0097] For example, when depolymerization is performed by FILMIX treatment, the stirring circumferential speed is preferably 5 to 40 m / s, more preferably 10 to 40 m / s.

[0098] In addition, the processing time is preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes.

[0099] In addition, when depolymerization is performed by compression, the preferred treatment method is ultra-high pressure homogenizer treatment.

[0100] The processing pressure for compression is preferably 10 to 300 MPa, more preferably 30 to 250 MPa.

[0101] In addition, when depolymerization is carried out by shearing, the preferred treatment method is wet jet milling.

[0102] The shear force is preferably 10 to 300 MPa, more preferably 30 to 250 MPa.

[0103] In one embodiment, regarding the treatment (water-resistant treatment) involved in the present invention, from the viewpoint of being able to uniformly disperse the agglomerated particles, it is preferable to include a deagglomeration treatment, and from the viewpoint of being able to suppress the decrease in ionic conductivity without applying excessive energy to the particles, it is more preferably to include a FILMIX treatment.

[0104] In one embodiment, when the treatment (water-resistant treatment) involved in the present invention includes a depolymerization treatment (preferably FILMIX treatment), from the viewpoint of the dispersibility of the sulfide solid electrolyte in the solvent, the solvent preferably contains at least one selected from ester solvents and ether solvents, more preferably contains at least one selected from ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, diethyl ether, dibutyl ether and tetrahydrofuran, and even more preferably contains at least one selected from ethyl acetate, ethyl propionate and dibutyl ether.

[0105] (2) Drying process The manufacturing method of the present invention may further include a drying step. The drying step is usually performed after the water-resistant treatment step. The drying step is a step of removing the solvent from a mixture (preferably a suspension (slurry)) containing the sulfide solid electrolyte and solvent obtained in the water-resistant treatment step.

[0106] The drying process is preferably carried out in an inert gas atmosphere or a vacuum atmosphere, and more preferably in an atmosphere of nitrogen, helium or argon.

[0107] The drying temperature is preferably 40–250°C, more preferably 50–250°C. A drying temperature of 40°C or higher is preferred because it allows for proper removal of the solvent. On the other hand, a drying temperature of 250°C or lower is preferred because it helps to suppress the deterioration of the sulfide solid electrolyte.

[0108] The drying time is preferably 0.5 to 24 hours, more preferably 1 to 8 hours.

[0109] The drying process can be carried out in two stages. In one embodiment, the drying process includes a first drying stage at 40–100°C (preferably 50–90°C) and a second drying stage at 110–250°C (preferably 140–200°C). By carrying out the drying process in two stages, manufacturing costs can be reduced. For example, by removing most of the solvent in the first drying stage and then removing the solvent coordinated with the sulfide solid electrolyte (coordination solvent) in the second drying stage, solvent removal can be effectively achieved.

[0110] 2. Manufacturing method of all-solid-state batteries According to one aspect of the present invention, a method for manufacturing an all-solid-state battery can be provided. The manufacturing method includes a step of forming an all-solid-state battery, the all-solid-state battery comprising a sulfide solid electrolyte manufactured using the above method.

[0111] In one embodiment, the manufacturing method includes a step of stacking a solid electrolyte layer, a positive electrode layer, and a negative electrode layer to form an all-solid-state battery, wherein the solid electrolyte layer is formed using a sulfide solid electrolyte manufactured using the method described above. An "all-solid-state battery" refers to a battery that uses a solid electrolyte as the electrolyte. All-solid-state batteries typically include a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

[0112] The aforementioned solid electrolyte layer is formed using a sulfide solid electrolyte manufactured using the method described above. In this case, the solid electrolyte layer can be manufactured using only the aforementioned sulfide solid electrolyte, or it can be manufactured using other solid electrolytes. Examples of other solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, and coordination hydride solid electrolytes manufactured using other methods. These other solid electrolytes can be used alone, or two or more can be used in combination.

[0113] Because the sulfide solid electrolyte produced by the above method has undergone water-resistant treatment, the resulting solid electrolyte layer exhibits high water resistance.

[0114] Alternatively, the positive and / or negative electrode layers can also be formed using a sulfide solid electrolyte manufactured using the method described above. When using a sulfide solid electrolyte to manufacture the positive and negative electrode layers, a known lithium-ion secondary battery is combined with either a positive or negative active material to form the positive and negative electrode layers. In this case, the proportion of sulfide solid electrolyte contained in the positive or negative electrode layer is not particularly limited. The positive and negative electrode layers may also include known current collectors, conductive additives, binders, etc.

[0115] All-solid-state batteries are manufactured by forming and stacking the above-mentioned positive electrode layer, solid electrolyte layer and negative electrode layer. There are no particular restrictions on the forming method and stacking method of each layer.

[0116] Examples include: methods for dispersing solid electrolytes and / or active electrode materials in a solvent to obtain a slurry-like substance, coating the slurry-like substance using a doctor blade or spin coating, and then calendering it to form a film; vapor phase methods for film formation and lamination using vacuum evaporation, ion plating, sputtering, laser ablation, etc.; and pressure forming methods for forming powders by hot pressing or cold pressing without heating, and then laminating them.

[0117] The sulfide solid electrolyte produced by the above method is relatively soft, therefore, it is particularly preferable to use a pressure molding method to form and stack the layers to produce an all-solid-state battery. As a pressure molding method, there are hot pressing with heating and cold pressing without heating, but even cold pressing can achieve sufficient molding.

[0118] Example The present invention will now be described in more detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0119] [Example 1] (1) Manufacturing of LGPS type sulfide solid electrolyte (1-1) Preparation of β-Li3PS4 Li2S (manufactured by Enpower Japan, purity 99.95%) and P2S5 (manufactured by Sigma-Aldrich, purity 99%) were measured in a glove box under an argon atmosphere at a molar ratio of Li2S:P2S5 = 1.35:1.

[0120] Next, Li₂S and P₂S₅ were added sequentially to tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrating grade) at a concentration of 10 wt%, and mixed at room temperature (25°C) for at least 48 hours. The mixture dissolved slowly, yielding a generally homogeneous solution containing a small amount of insoluble matter. The insoluble matter was filtered using a membrane filter (polytetrafluoroethylene (PTFE), pore size: 1.0 μm) to obtain a homogeneous solution.

[0121] Li₂S was further added to the homogeneous solution to achieve a molar ratio of Li₂S:P₂S₅ = 3:1. The mixture was then stirred at room temperature (25°C) for more than 5 days to obtain a suspension. The resulting suspension was then filtered under pressure, and the filter residue was vacuum dried to obtain β-Li₃PS₄·3THF.

[0122] (1-2) Powdering process of β-Li3PS4 In a glove box under an argon atmosphere, the obtained β-Li3PS4·3THF was added to acetonitrile (manufactured by Wako Pure Chemical Industries, Inc., ultra-dehydrating grade) to a concentration of 6 wt%, and mixed at room temperature (25°C) for more than 2 days to obtain a slurry.

[0123] The obtained slurry was subjected to reduced pressure and acetonitrile removal at 50°C. The resulting powder was then dried under vacuum at 180°C for 4 hours to remove the coordinating solvent. Afterward, it was cooled to room temperature (25°C) to obtain micronized β-Li3PS4 powder.

[0124] (1-3) Manufacturing of Li4SnS4 Li2S (purity: 99.8%, manufactured by Enpower Japan) and SnS2 (purity: 99.99%, manufactured by Career Henan Chemical) were weighed in an argon-atmospheric glove box at a stoichiometric ratio of Li4SnS4 and mixed for 5 minutes using a Lab Blender (manufactured by Waring Laboratory Science).

[0125] Li4SnS4 was obtained by calcining the resulting mixture at 550°C for 16 hours.

[0126] (1-4) Powdering process of Li4SnS4 In a glove box under an argon atmosphere, 92.5 g of the obtained Li4SnS4 was added to 475 mL of methanol (ultra-dehydrating grade, manufactured by Wako Pure Chemical Industries, Ltd., boiling point: 64 °C), and mixed at room temperature (25 °C) for at least 24 hours. The Li4SnS4 dissolved slowly. The solution was filtered using a membrane filter (polytetrafluoroethylene (PTFE), pore size: 1.0 μm) to remove insoluble matter from the Li4SnS4 manufacturing process, thus obtaining a homogeneous solution containing dissolved Li4SnS4.

[0127] Next, under an argon atmosphere, 2.5 L of superhydrated acetonitrile was added to a 5 L flask, and the acetonitrile was brought to total reflux using a distillation apparatus. 475 mL of the previously prepared Li₄SnS₄ methanol solution was added dropwise to the acetonitrile at a rate of 3.5 mL / min. The added methanol evaporated after addition, and Li₄SnS₄ particles precipitated from the acetonitrile. The solenoid valve of the distillation section was used to operate the distillation process, ensuring the distillation rate reached twice the adding rate, i.e., 7 mL / min. After the addition of the Li₄SnS₄ methanol solution was completed, the point at which the temperature at the top of the column reached 80 °C (boiling point of acetonitrile: 82 °C) was taken as the endpoint of the distillation.

[0128] The obtained slurry was subjected to reduced pressure and 50°C to remove acetonitrile. The resulting powder was then dried under vacuum at 180°C for 4 hours to remove the coordinating solvent. Solvent removal was performed while stirring the slurry. Afterward, it was cooled to room temperature (25°C) to obtain micronized Li4SnS4 powder.

[0129] (1-5) Manufacturing of LGPS type sulfide solid electrolytes 26.5 g of the β-Li3PS4 powder and Li4SnS4 powder produced in the above process were measured in a glove box under an argon atmosphere at a molar ratio of β-Li3PS4:Li4SnS4 = 2.7:1. The measured raw materials were pulverized and mixed for 4 hours using a wet bead mill (manufactured by Hiroshima Metal Machinery Co., Ltd., UAM015). During wet mixing, 0.05 mm diameter zirconia beads "YTZ" (manufactured by Nikkato Co., Ltd.) were used, and the bead filling rate of the pulverizing chamber was 80%. Acetonitrile (ultra-dehydrating grade, manufactured by Wako Pure Chemical Industries Co., Ltd.) was used as the dispersion medium, with a slurry concentration of 6 wt%, a circumferential speed of 8 m / s, and a circulation rate of 10 L / min.

[0130] After the above treatment, the acetonitrile in the resulting slurry was removed under reduced pressure at 50°C. Then, the resulting powder was dried under vacuum at 180°C for 15 minutes to remove the coordination solvent. Solvent removal was carried out while stirring the slurry. Afterward, it was cooled to room temperature (25°C) to obtain the precursor powder of β-Li3PS4+Li4SnS4.

[0131] The obtained precursor powder was calcined at 550°C for 2 hours to obtain Li as an LGPS-type sulfide solid electrolyte. 9.81 Sn 0.81 P 2.19 S 12 crystallization.

[0132] (2) Water-resistant treatment process and drying process 0.75g of LGPS type sulfide solid electrolyte (Li 9.81 Sn 0.81 P 2.19 S 12 The crystals were added to 8 mL of ethyl acetate (ultra-dehydrating grade, manufactured by Wako Pure Chemical Industries, Ltd.) and stirred at room temperature (25°C) for 30 minutes.

[0133] After stirring, the resulting slurry was subjected to ethyl acetate removal at 80°C, and then the resulting powder was dried at 180°C for 1 hour to remove the coordinating solvent. Solvent removal was performed on a hot plate. Afterwards, it was cooled to room temperature (25°C) to obtain a water-resistant LGPS-type sulfide solid electrolyte (Li). 9.81 Sn 0.81 P 2.19 S 12 Crystallization). A series of operations were carried out in a glove box under an argon atmosphere. Additionally, SEM images were used to compare the particle size (primary particle size) of the LGPS-type sulfide solid electrolyte before and after the water-resistant treatment and drying processes; the primary particle size remained unchanged.

[0134] [Example 2] In the water-resistant treatment and drying processes (2), dibutyl ether (manufactured by Sigma-Aldrich, purity ≥99%) was used instead of ethyl acetate. Otherwise, the water-resistant LGPS type sulfide solid electrolyte (Li) was manufactured according to the same method as in Example 1. 9.81 Sn 0.81 P 2.19 S 12 (Crystallization). The particle size (primary particle size) of the LGPS type sulfide solid electrolyte before and after the water-resistant treatment and drying processes was compared using SEM images; the primary particle size remained unchanged. The dibutyl ether used was a dibutyl ether that had undergone dehydration treatment using a molecular sieve (Wako Pure Chemical Industries 3A 1 / 16).

[0135] [Example 3] (1) Manufacturing of LGPS type sulfide solid electrolyte LGPS type sulfide solid electrolyte (Li) was manufactured using the same method as in Example 1. 9.81 Sn 0.81 P 2.19 S 12 crystallization).

[0136] (2) Water-resistant treatment process and drying process For 1g of LGPS type sulfide solid electrolyte (Li 9.81 Sn 0.81 P 2.19 S 12 (Crystallization) Wet depolymerization was performed using a FILMIX model 30-L (manufactured by PRIMIX Corporation) as a thin-film gyratory high-speed mixer. The dispersion medium was ethyl acetate (ultra-dehydrating grade, manufactured by Wako Pure Chemical Industries Co., Ltd.), the slurry concentration was 11 wt%, the circumferential speed was 29.9 m / s, and the processing time was 1 minute.

[0137] Following wet depolymerization, the resulting slurry was subjected to ethyl acetate removal at 80°C, and the resulting powder was dried at 180°C for 1 hour to remove the coordinating solvent. Solvent removal was performed on a hot plate. Afterward, the mixture was cooled to room temperature (25°C) to obtain a water-resistant LGPS-type sulfide solid electrolyte (Li). 9.81 Sn 0.81 P 2.19 S 12 Crystallization). A series of operations were carried out in a glove box under an argon atmosphere. Additionally, SEM images were used to compare the particle size (primary particle size) of the LGPS-type sulfide solid electrolyte before and after the water-resistant treatment and drying processes; the primary particle size remained unchanged.

[0138] [Example 4] In the water-resistant treatment and drying processes (2), dibutyl ether (manufactured by Sigma-Aldrich, purity ≥99%) was used instead of ethyl acetate. Otherwise, the water-resistant LGPS type sulfide solid electrolyte (Li) was manufactured according to the same method as in Example 3. 9.81 Sn 0.81 P 2.19 S 12 (Crystallization). The particle size (primary particle size) of the LGPS type sulfide solid electrolyte before and after the water-resistant treatment and drying processes was compared using SEM images; the primary particle size remained unchanged. The dibutyl ether used was a dibutyl ether that had undergone dehydration treatment using a molecular sieve (Wako Pure Chemical Industries 3A 1 / 16).

[0139] [Comparative Example 1] (1) Manufacturing of LGPS type sulfide solid electrolyte β-Li3PS4 powder and Li4SnS4 powder were prepared using the same method as in Example 1.

[0140] 5.2 g of β-Li3PS4 and Li4SnS4 produced in the above process were measured in a glove box under an argon atmosphere at a molar ratio of β-Li3PS4:Li4SnS4 = 2.7:1. The measured raw materials were pulverized and mixed for 1 hour using a wet bead mill (AIMEX Co., Ltd., Eatano RMBII02 model). Zirconia beads "YTZ" (Nikkato Co., Ltd.) with a diameter of 0.05 mm were used for wet mixing. The dispersion medium was a mixed solvent of dibutyl ether (Sigma-Aldrich Co., Ltd., purity ≥99%) and heptane (ultra-dehydrated grade, Wako Pure Chemical Industries Co., Ltd.) (heptane / dibutyl ether = 20 / 80 vol%), with a slurry concentration of 8 wt% and a circumferential speed of 12 m / s.

[0141] After the above treatment, the obtained slurry was subjected to reduced pressure and solvent removal at 50°C. Then, the obtained powder was dried under vacuum at 180°C for 15 minutes to remove the coordination solvent. Solvent removal was carried out while stirring the slurry. Afterward, it was cooled to room temperature (25°C) to obtain β-Li3PS4+Li4SnS4 precursor powder.

[0142] The obtained precursor powder was calcined at 550°C for 2 hours to obtain Li as an LGPS-type sulfide solid electrolyte. 9.81 Sn 0.81 P 2.19 S 12 crystallization.

[0143] [Comparative Example 2] In the (2) water-resistant treatment and drying processes, heptane (ultra-dehydrating grade, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of ethyl acetate. Otherwise, the water-resistant LGPS type sulfide solid electrolyte (Li) was manufactured according to the same method as in Example 3. 9.81 Sn 0.81 P 2.19 S 12 (Crystallization). In addition, SEM images were used to compare the particle size (primary particle size) of LGPS type sulfide solid electrolyte before and after the water-resistant treatment and drying processes, and the particle size (primary particle size) did not change.

[0144] (1) Sulfur-silver-germanium ore type sulfide solid electrolyte Li6PS5Cl, a commercially available solid electrolyte of silver-germanium sulfide type, is obtained. 0.9 I 0.1 Crystallization (NEICorporation).

[0145] (2) Water-resistant treatment process and drying process Using silver sulfide-germanium sulfide solid electrolyte (Li6PS5Cl) 0.9 I 0.1 Crystallization) to replace LGPS type sulfide solid electrolyte (Li 9.81 Sn 0.81 P 2.19 S 12 (crystallization), except that, a water-resistant silver-germanium sulfide solid electrolyte (Li6PS5Cl) was obtained according to the same method as in Example 1. 0.9 I 0.1 (Crystallization). In addition, SEM images were used to compare the particle size (primary particle size) of the sulfide solid electrolyte of silver-germanium sulfide before and after the water-resistant treatment and drying processes, and the particle size (primary particle size) did not change.

[0146] The manufacturing methods of Examples 1-4, Comparative Examples 1-2 and Example 5 are shown in Table 1 below.

[0147] [Table 1] [evaluate] The hydrogen sulfide production, ionic conductivity, and half-width increase rate were evaluated for the sulfide solid electrolytes prepared using the methods of Examples 1-4, Comparative Examples 1-2, and Example 5 that underwent water-resistant treatment, the LGPS-type sulfide solid electrolytes prepared using the methods of Examples 1 (1-5) (Reference Example 1) that did not undergo water-resistant treatment, and the commercially available silver-germanium sulfide solid electrolytes used as raw materials in Example 5 (Reference Example 2). The results are shown in Table 2 below.

[0148] [Hydrogen sulfide production] 10 mg of sulfide solid electrolyte was weighed under an argon atmosphere and placed in a sealed container (3000 cc volume, dew point -30°C, dry air at 25°C). Air was circulated within the sealed container using a fan, while the amount of hydrogen sulfide produced was measured using a hydrogen sulfide sensor (ToxiRAE Pro series). The amount of hydrogen sulfide produced was measured from the time the sulfide solid electrolyte was exposed to dry air until one hour later. The amount of hydrogen sulfide produced is expressed as the value per unit area of ​​the sulfide solid electrolyte.

[0149] [Ionic conductivity] A sulfide solid electrolyte was subjected to uniaxial molding (480 MPa) to obtain a disc-shaped sample with a thickness of approximately 1 mm and a diameter of 10 mm. Using an all-solid-state battery evaluation unit (manufactured by Hosen Co., Ltd.), the lithium-ion conductivity was calculated by measuring AC impedance using a four-terminal method at room temperature (25°C) with a "SI1260IMPEDANCE / GAIN-PHASE ANALYZER" (manufactured by Solartron). Specifically, the disc-shaped sample was placed in a thermostat set to 25°C and maintained for 30 minutes before measuring the lithium-ion conductivity. The measurement frequency range was 0.1 Hz to 1 MHz, and the amplitude was 50 mV.

[0150] [Half-value width increase rate] X-ray diffraction (XRD) of the sulfide solid electrolyte (CuKα: λ = 1.5405 Å) was performed at room temperature (25 °C) under an Ar atmosphere using an X'Pert3 Powder (PANalytical). The half-width at half-maximum (WWHM) of the main peak with the highest diffraction intensity was then calculated. The calculation method is described below.

[0151] That is, the diffraction data obtained by X-ray diffraction is input into the crystal structure analysis software "SmartLabstudio II" for background and peak fitting. The segmented pseudo-Voigt function is selected for graph fitting to calculate the half-width of each peak.

[0152] For Examples 1-4 and Comparative Examples 1-2, the half-width increase rate was calculated based on the half-width of the peak in Reference Example 1. For Example 5, the half-width increase rate was calculated based on the half-width of the peak in Reference Example 2.

[0153] [Table 2] According to the results in Table 2, the sulfide solid electrolytes of Examples 1-5 that underwent water-resistant treatment had low hydrogen sulfide production and high water resistance.

Claims

1. A method for manufacturing a sulfide solid electrolyte, characterized in that: This includes a step of treating a sulfide solid electrolyte in a solvent using at least one treatment selected from mixing and depolymerization. The solvent is a non-proton solvent containing oxygen atoms.

2. The manufacturing method as described in claim 1, characterized in that: The solvent comprises at least one selected from ester solvents and ether solvents.

3. The manufacturing method as described in claim 2, characterized in that: The solvent includes ester solvents.

4. The manufacturing method as described in claim 3, characterized in that: The ester solvent comprises at least one selected from ethyl acetate and ethyl propionate.

5. The manufacturing method as described in claim 2, characterized in that: The solvent includes ether solvents.

6. The manufacturing method as described in claim 5, characterized in that: The ether solvent includes dibutyl ether.

7. The manufacturing method as described in claim 1, characterized in that: The processing includes mixed processing.

8. The manufacturing method as described in claim 1, characterized in that: The process includes depolymerization.

9. The manufacturing method as described in claim 1, characterized in that: The sulfide solid electrolyte includes an LGPS type sulfide solid electrolyte.

10. The manufacturing method as described in claim 1, characterized in that: The sulfide solid electrolyte includes a sulfide solid electrolyte of the sulfide type.

11. The manufacturing method as described in claim 1, characterized in that: The sulfide solid electrolyte contains tin (Sn).

12. A method for manufacturing an all-solid-state battery, characterized in that: The process includes forming an all-solid-state battery, the all-solid-state battery comprising a sulfide solid electrolyte manufactured using any one of claims 1 to 11.

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