Method for producing sulfide solid electrolyte and method for producing all-solid-state cell

Abstract

Provided is a method for producing a sulfide solid electrolyte having high water resistance.　The method for producing a sulfide solid electrolyte includes a step in which a sulfide solid electrolyte is subjected in a solvent to at least one treatment selected from the group consisting of a mixing treatment and a disaggregation treatment, wherein the solvent includes a solvent which is aprotic and contains an oxygen atom.

Description

Method for producing sulfide solid electrolyte and method for producing all-solid-state battery

[0001] The present invention relates to a method for producing a sulfide solid electrolyte and a method for producing an all-solid-state battery.

[0002] Conventionally, non-aqueous electrolyte secondary batteries have been widely used in applications such as portable information terminals and portable electronic devices. The electrolyte used in non-aqueous electrolyte secondary batteries typically uses a flammable organic solvent as the electrolytic solution. For this reason, non-aqueous electrolyte secondary batteries typically have a strong exterior to prevent the organic solvent from leaking and also have functions to address the risk of the electrolytic solution leaking, which places restrictions on the structure of the device.

[0003] Furthermore, in recent years, the applications of non-aqueous electrolyte secondary batteries have expanded to include mobile objects such as electric vehicles, hybrid electric vehicles, and airplanes, as well as stationary power storage systems, and large-capacity non-aqueous electrolyte secondary batteries are in demand, and high-capacity non-aqueous electrolyte secondary batteries are required to have higher safety.

[0004] Under these circumstances, non-aqueous electrolyte secondary batteries using solid electrolytes, which do not use flammable organic solvents and can achieve high safety, have attracted attention. Non-aqueous electrolyte secondary batteries using solid electrolytes are sometimes called all-solid-state batteries.

[0005] Known solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes, of which sulfide solid electrolytes have attracted particular attention in recent years due to their high ionic conductivity.

[0006] For example, Patent Document 1 discloses a sulfide solid electrolyte containing Li, P, S, and halogen as constituent elements, in which the oxygen / sulfur element ratio on the surface measured by XPS is 0.79 or more and 1.25 or less, and the surface is 30 nm (SiO ２Patent Literature 1 describes an invention relating to sulfide solid electrolyte particles in which the oxygen / sulfur element ratio at the surface and at a position 30 nm from the surface satisfies the specific value, thereby providing sufficient ionic conductivity and suppressing the rate of increase in resistance after charge / discharge cycles when used in an all-solid-state battery.

[0007] It is noted that Patent Document 1 describes that the sulfide solid electrolyte particles can be produced by amorphizing a raw material composition by mechanical milling to obtain a sulfide solid electrolyte glass, and then heating the glass at a temperature equal to or higher than the crystallization temperature of the glass in the presence of an oxidizing agent to oxidize and crystallize the glass.

[0008] Japanese Patent Application Laid-Open No. 2020-115425

[0009] Although sulfide solid electrolytes exhibit high ionic conductivity as described above, they lack sufficient water resistance, and may decompose to generate hydrogen sulfide when reacting with trace amounts of moisture in the air. To avoid this situation, sulfide solid electrolytes and all-solid-state batteries are typically produced in a low-moisture environment, which tends to increase production costs and reduce productivity.

[0010] In response to this, water-resistant treatment of sulfide solid electrolytes has been studied. For example, sulfide solid electrolyte particles described in Patent Document 1 have a certain degree of water resistance because their surfaces are treated by oxidation during the manufacturing process. However, when water-resistant treatment is performed during the manufacturing process, the water resistance is sometimes insufficient.

[0011] Therefore, the present invention provides a method for producing a sulfide solid electrolyte having high water resistance.

[0012] The present invention includes, for example, the following aspects. [1] A method for producing a sulfide solid electrolyte, comprising a step of subjecting a sulfide solid electrolyte to at least one treatment selected from the group consisting of a mixing treatment and a crushing treatment in a solvent, wherein the solvent comprises an aprotic solvent containing an oxygen atom. [2] The production method according to [1] above, wherein the solvent comprises at least one selected from the group consisting of an ester solvent and an ether solvent. [3] The production method according to [2] above, wherein the solvent comprises an ester solvent. [4] The production method according to [3] above, wherein the ester solvent comprises at least one selected from the group consisting of ethyl acetate and ethyl propionate. [5] The production method according to any one of [2] to [4] above, wherein the solvent comprises an ether solvent. [6] The production method according to [5] above, wherein the ether solvent comprises dibutyl ether. [7] The production method according to any one of [1] to [6] above, wherein the treatment comprises a mixing treatment. [8] The production method according to any one of [1] to [7] above, wherein the treatment comprises a crushing treatment. [9] The manufacturing method according to any one of [1] to [8] above, wherein the sulfide solid electrolyte comprises an LGPS-type sulfide solid electrolyte.

[10] The manufacturing method according to any one of [1] to [8] above, wherein the sulfide solid electrolyte comprises an argyrodite-type sulfide solid electrolyte.

[11] The manufacturing method according to any one of [1] to

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

[12] A manufacturing method for an all-solid-state battery, comprising a step of forming an all-solid-state battery containing the sulfide solid electrolyte manufactured by the method according to any one of [1] to

[11] above.

[0013] The present invention provides a method for producing a sulfide solid electrolyte having high water resistance.

[0014] Hereinafter, embodiments of the present invention will be described in detail.

[0015] 1. Method for Producing Sulfide Solid Electrolyte The method for producing a sulfide solid electrolyte according to the present invention includes a step of subjecting a sulfide solid electrolyte to at least one treatment selected from the group consisting of a mixing treatment and a crushing treatment in a solvent (hereinafter also referred to as a "water-resistant treatment step"), wherein the solvent includes an aprotic solvent containing oxygen atoms.

[0016] According to the present invention, the water-resistant treatment is not performed during the production process of a sulfide solid electrolyte, but rather after the production of the sulfide solid electrolyte. In this case, the water-resistant treatment is performed by mixing and / or crushing in a predetermined solvent. This allows the production of a sulfide solid electrolyte with high water resistance. In this specification, "after the production of the sulfide solid electrolyte" refers to the point after a sulfide solid electrolyte having a desired crystal structure and particle size (primary particle size) is obtained. For example, when a sulfide solid electrolyte is produced by mechanically milling a raw material composition to produce an amorphous intermediate, crystallizing the intermediate, and then pulverizing the intermediate, the water-resistant treatment performed on the raw material composition, the intermediate, and the sulfide solid electrolyte before pulverization does not fall under the category of water-resistant treatment "after the production of the sulfide solid electrolyte." On the other hand, the water-resistant treatment performed on the pulverized sulfide solid electrolyte falls under the category of water-resistant treatment "after the production of the sulfide solid electrolyte."

[0017] (1) Water-Resistant Treatment Step As described above, the water-resistant treatment step according to the present invention is a step of subjecting a sulfide solid electrolyte to at least one treatment selected from the group consisting of a mixing treatment and a crushing treatment in a solvent.

[0018] [Sulfide Solid Electrolyte] The sulfide solid electrolyte is not particularly limited, but contains at least one of an alkali metal element and an alkaline earth metal element, and sulfur (S).

[0019] Examples of the alkali metal elements include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

[0020] Examples of the alkaline earth metal elements include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Rd). In this specification, the term "alkaline earth metal elements" includes beryllium (Be) and magnesium (Mg).

[0021] Of the above, 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 included alone or in combination of two or more.

[0022] The sulfide solid electrolyte may further 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). The other elements may be contained alone or in combination of two or more.

[0023] Of 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 contains lithium (Li), sulfur (S), and tin (Sn). The sulfide solid electrolyte preferably contains tin (Sn) from the viewpoints of increasing ionic conductivity, improving water resistance, and further enhancing the effect of improving water resistance by the water-resistant treatment of the present invention.

[0024] The sulfide solid electrolyte may be crystalline or non-crystalline (also called "glass" or "amorphous"), but is preferably crystalline.

[0025] The crystalline form of the sulfide solid electrolyte is not particularly limited, but examples include LGPS type, argyrodite type, and Thio-LISICON type.

[0026] The LGPS-type sulfide solid electrolyte is a solid electrolyte containing lithium (Li), germanium (Ge), phosphorus (P), and sulfur (S), and is LiS ６ Octahedron, GeS ４ Tetrahedron, and PS ４ It has a tetrahedron and PS ４ Tetrahedron and GeS ４ Tetrahedron and LiS ６ It shares edges with the octahedron, and PS ４ Tetrahedron and LiS ６ The octahedron contains a predominantly corner-sharing crystal structure.

[0027] In the LGPS-type sulfide solid electrolyte, germanium (Ge) can be substituted with tin (Sn) or silicon (Si). Furthermore, halogens (fluorine (F), chlorine (Cl), bromine (Br), iodine (I)) and oxygen (O) can be introduced into the LGPS-type sulfide solid electrolyte. For example, by substituting a portion of the sulfur (S) with oxygen (O), the size of the tunnel in the crystal through which Li ions pass can be changed to a size that allows for better conduction, and ionic conductivity can be increased.

[0028] In one embodiment, the LGPS-type sulfide solid electrolyte is represented by the following formula: Li-M １ -M ２ -P-S-X １ At this time, M １ is Ge, Sn, or Si, and M ２ is a single bond, Ge, Sn, or Si, and X １ is absent, fluorine (F), chlorine (Cl), bromine (Br), iodine (I), or oxygen (O).

[0029] M １ is preferably Ge or Sn, and more preferably Sn. ２ is preferably a single bond. １ is preferably absent, chlorine (Cl) or oxygen (O), and more preferably absent.

[0030] The specific composition of the LGPS type sulfide solid electrolyte is Li １０ GeP ２ S１２ , Li １０ SnP ２ S 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 ) P ２ S １２ , Li １０ (Ge ０．５ Sn ０．５ ) P ２ S １２ , Li １０ (Si ０．５ Sn ０．５ ) P ２ S １２ , Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ , Li １０ GeP ２ S 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 S ４ ) etc.

[0031] The argyrodite-type sulfide solid electrolyte has a crystal structure similar to that of cubic Cu-argyrodite compounds and Ag-argyrodite compounds.

[0032] The specific composition of the argyrodite-type sulfide solid electrolyte is Li ６ P.S.５ Cl, Li ５．４ P.S. ４．４ Cl １．６ , Li ５．８ P.S. ４．８ Cl １．２ , Li ６ P.S. ５ Br, Li ５．４ P.S. ４．４ Cl ０．８ Br ０．８ , Li ６ P.S. ５ I,,Li ６．６ Ge ０．６ P ０．４ S ５ I, Li ７ Ge ３ P.S. １２ etc.

[0033] Thio-LISICON type sulfide solid electrolyte is γ-Li ３ P.O. ４ It has a skeletal structure of the type.

[0034] In one embodiment, the Thio-LISICON type sulfide solid electrolyte is represented by the following formula: Li ２ S-P ２ S ５ -X ２ At this time, X ２ is absent, Li-halogen, or M ３ S ２ and M ３ is Sn, Ge, Ga, or Si.

[0035] X ２ is absent or contains LiCl, LiBr, LiI, SnS ２ , GeS ２ , SiS ２ Preferably, it is absent or contains LiCl, GeS ２ , SiS ２ It is more preferable that:

[0036] In one embodiment, the Thio-LISICON type sulfide solid electrolyte is represented by the following formula: Li ２ S-M ４ S ２ At this time, M ４is Sn, Ge, Ga, or Si, preferably Sn, Ge, or Si.

[0037] Specific examples of the Thio-LISICON type sulfide solid electrolyte include Li ２ S-SnS ２ , Li ２ S-P ２ S ５ , Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-GeS ２ , Li ２ S-SiS ２ , Li ２ P ２ S ６ , Li ４ P ２ S ６ , Li ７ P ３ S １１ , α-Li ３ P.S. ４ , β-Li ３ P.S. ４ , γ-Li ３ P.S. ４ , LT-Li ７ P.S. ６ , HT-Li ７ P.S. ６ , Li ４．２７５ Ge ０．６１ Ga ０．２５ S ４ etc.

[0038] The sulfide solid electrolytes described above may be used alone or in combination of two or more.

[0039] In one embodiment, from the viewpoints of increasing ion conductivity, improving water resistance, and further enhancing the effect of improving water resistance by the water-resistant treatment of the present invention, the sulfide solid electrolyte preferably includes an LGPS-type sulfide solid electrolyte.

[0040] In one embodiment, from the viewpoint of high ionic conductivity, the sulfide solid electrolyte preferably includes an argyrodite-type sulfide solid electrolyte.

[0041] The particle size (primary particle size) of the sulfide solid electrolyte is preferably 0.1 to 10 μm, and more preferably 0.1 to 5 μm. In this specification, the term "particle size (primary particle size)" refers to the maximum distance between two points on the contour line of an object, and refers to the average value of particle sizes of 50 arbitrary objects contained in one field of view of a scanning electron microscope (SEM).

[0042] The sulfide solid electrolyte may be produced by a known method, or a commercially available product may be used.

[0043] For example, the sulfide solid electrolyte can be produced by a mechanical milling method, which includes preparing an amorphous precursor by mechanical milling a raw material composition and heating the amorphous precursor, or a liquid phase method, which includes preparing a precursor in a solution, removing the solvent, and heating the precursor. Of these, the sulfide solid electrolyte is preferably produced by the mechanical milling method.

[0044] The raw materials used in the production of the sulfide solid electrolyte are not particularly limited, but include a raw material that serves as a lithium source, a raw material that serves as a phosphorus source, a raw material that serves as a sulfur source, a raw material that serves as a silicon source, a raw material that serves as a germanium source, a raw material that serves as a tin source, a raw material that serves as a chlorine source, a raw material that serves as a bromine source, a raw material that serves as an iodine source, a raw material that serves as an oxygen source, and the like.

[0045] The raw material serving as the lithium source is not particularly limited, but may be metallic lithium (Li), lithium sulfide (Li ２ S), lithium chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), Li ３ P.S. ４ , Li ４ SnS ４ etc.

[0046] The raw materials that serve as phosphorus sources include elemental phosphorus (P), diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５), phosphorus pentachloride (PCl ５ ), phosphorus tribromide (PBr ３ ), phosphorus pentabromide (PBr ５ ), Li ３ P.S. ４ etc.

[0047] The raw materials that serve as sulfur sources include elemental sulfur (S), lithium sulfide (Li ２ S), phosphorus sulfide (P ２ S ５ ), silicon sulfide (SiS ２ ), germanium sulfide (GeS ２ ), tin sulfide (SnS), tin disulfide (SnS ２ ), diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ), aluminum sulfide (Al ２ S ３ ), diboron trisulfide (B ２ S ３ ), Li ３ P.S. ４ , Li ４ SnS ４ etc.

[0048] The silicon source material is silicon sulfide (SiS ２ ), silicon (Si), silicon dioxide (SiO ２ ) etc.

[0049] The germanium source material is germanium sulfide (GeS ２ ), germanium (Ge), germanium dioxide (GeO ２ ) etc.

[0050] The raw materials that serve as tin sources include tin sulfide (SnS), tin disulfide (SnS ２ ), tin(II) oxide (SnO), tin(IV) oxide (SnO ２ ), tin(VI) oxide (SnO ３ ), tin (Sn), Li ４ SnS ４ etc.

[0051] The chlorine source materials include lithium chloride (LiCl), phosphorus pentachloride (PCl ５ ) etc.

[0052] Bromine sources include lithium bromide (LiBr), phosphorus tribromide (PBr ３ ), phosphorus pentabromide (PBr ５ ) etc.

[0053] Examples of raw materials that serve as iodine sources include lithium iodide (LiI).

[0054] The raw material serving as the oxygen source is lithium oxide (Li ２ O), phosphorus pentoxide (P ２ O ５ ), silicon dioxide (SiO ２ ), germanium dioxide (GeO ２ ), tin(II) oxide (SnO), tin(IV) oxide (SnO ２ ), tin (IV) oxide (SnO ３ ) etc.

[0055] Among these, the raw material is lithium sulfide (Li ２ S), diphosphorus pentasulfide (P ２ S ５ ), tin sulfide (SnS), tin disulfide (SnS ２ ), Li ３ P.S. ４ , Li ４ SnS ４ It is preferred that the compound contains:

[0056] These solid electrolyte raw materials may be used alone or in combination of two or more. By changing the composition of these raw materials, a desired sulfide solid electrolyte can be produced.

[0057] [Solvent] The solvent includes an aprotic solvent containing oxygen atoms. When the solvent is aprotic, for example, it is possible to prevent the generation of hydrogen sulfide due to decomposition of the sulfide solid electrolyte. Furthermore, when the solvent contains oxygen atoms, it is possible to perform, for example, a water-resistant treatment of the sulfide solid electrolyte (such as oxidation of the surface of the sulfide solid electrolyte).

[0058] The solvent is not particularly limited, but examples thereof include ester solvents, ether solvents, ketone solvents, and sulfoxide solvents.

[0059] Examples of the ester solvent include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, s-butyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and butyl propionate.

[0060] Examples of the ether solvent include diethyl ether, dibutyl ether, t-butyl methyl ether, tetrahydrofuran, 2-methyltetrahydrofuran (MHF), 4-methyltetrahydropyran (MTHP), 1,4-dioxane, and methoxycyclopentane.

[0061] Examples of the ketone solvent include acetone, methyl ethyl ketone, 4-methyl-2-pentanone, 2-butanone, 3-methyl-2-butanone, 2-pentanone, 3-pentanone, 2-heptanone, isoamyl methyl ketone, cyclopentanone, cyclohexanone, and diisobutyl ketone.

[0062] Examples of sulfoxide solvents include dimethyl sulfoxide (DMSO).

[0063] Among these, the solvent preferably contains at least one selected from the group consisting of ester solvents, ether solvents, and ketone solvents, more preferably contains at least one selected from the group consisting of ester solvents and ether solvents, and further preferably contains at least one selected from ethyl acetate, ethyl propionate, and dibutyl ether. The above-mentioned solvents may be used alone or in combination of two or more.

[0064] In a preferred embodiment, the solvent includes an ester solvent, which preferably includes at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, and butyl propionate, more preferably includes at least one selected from the group consisting of ethyl acetate and ethyl propionate, and even more preferably includes ethyl acetate.

[0065] In a preferred embodiment, the solvent includes an ether solvent, preferably at least one selected from diethyl ether, dibutyl ether, and tetrahydrofuran, and more preferably dibutyl ether.

[0066] The amount of the solvent used is preferably 1 to 50 mL, more preferably 3 to 40 mL, even more preferably 5 to 30 mL, and particularly preferably 5 to 20 mL, per gram of the sulfide solid electrolyte.

[0067] 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 to 50 mass %, more preferably 3 to 40 mass %, even more preferably 5 to 30 mass %, and particularly preferably 5 to 20 mass %, based on the total mass of the solvent and the sulfide solid electrolyte.

[0068] [Treatment (Water-Resistant Treatment)] The sulfide solid electrolyte is treated in a solvent, for example, by oxidizing the surface of the sulfide solid electrolyte, to impart water resistance. In this case, the treatment is selected from the group consisting of a mixing treatment and a crushing treatment.

[0069] In this specification, the term "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. In addition, in this specification, the term "disintegration treatment" refers to dispersing or loosening sulfide solid electrolyte particles (secondary particles, aggregates, etc.) that have bonded or aggregated together by applying a separating force in a solvent. Specific examples of disintegration treatment include Filmix treatment (registered trademark, a technology that uniformly disintegrates treated materials using stirring energy from a high-speed rotating thin film), compression treatment, friction treatment, shear treatment, etc.

[0070] The treatment (water-resistant treatment) according to the present invention is selected from the group consisting of a mixing treatment and a crushing treatment. A sulfide solid electrolyte can be made water-resistant by performing a mixing treatment or a crushing treatment in a solution. Because the particle size (primary particle size) of the sulfide solid electrolyte remains almost unchanged before and after both the mixing treatment and the crushing treatment, the water-resistant treatment can be uniformly performed on the surface of each particle of the sulfide solid electrolyte. In this respect, the treatment (water-resistant treatment) according to the present invention differs from a "pulverization treatment." In this specification, the term "pulverization treatment" refers to the application of physical energy to the sulfide solid electrolyte to thereby break down the sulfide solid electrolyte into smaller particles. In other words, the particle size (primary particle size) of the sulfide solid electrolyte becomes smaller through the crushing treatment. When the "pulverization treatment" is performed, the sulfide solid electrolyte is decomposed by the applied physical energy, and even if the sulfide solid electrolyte can be made water-resistant through the pulverization treatment, the degree of water resistance of the surface of each particle of the sulfide solid electrolyte may vary as the sulfide solid electrolyte is fragmented, and therefore the water resistance of the resulting sulfide solid electrolyte may be relatively low.

[0071] (Mixing Treatment) The mixing treatment is not particularly limited and can be carried out by a known method.

[0072] For example, when the mixing treatment is carried out by stirring, the stirring temperature is not particularly limited, but is preferably 10 to 60° C., and more preferably 15 to 45° C. The stirring time is not particularly limited, but is preferably 1 to 120 minutes, and more preferably 5 to 60 minutes.

[0073] When mixing is performed by vibration, the vibration speed is not particularly limited, but is preferably 1 to 50 kHz, and more preferably 5 to 30 kHz. The vibration time is not particularly limited, but is preferably 1 to 120 minutes, and more preferably 5 to 60 minutes. When mixing is performed by vibration, an ultrasonic homogenizer is preferably used.

[0074] In one embodiment, the treatment (water-resistant treatment) according to the present invention preferably includes a mixing treatment from the viewpoint of increasing ionic conductivity, and more preferably includes a stirring treatment from the viewpoint of enabling particles to be uniformly water-resistant without using special equipment.

[0075] In one embodiment, when the treatment (water-resistant treatment) according to the present invention includes a mixing treatment (preferably a stirring treatment), from the viewpoint of further improving water resistance, the solvent preferably includes an ester solvent, more preferably includes at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, and butyl propionate, even more preferably includes at least one selected from the group consisting of ethyl acetate and ethyl propionate, and even more preferably includes ethyl acetate.

[0076] (Crushing Treatment) The crushing treatment is not particularly limited and can be carried out by a known method.

[0077] For example, when disintegration is performed by the FILMICS treatment, the stirring peripheral speed is preferably 5 to 40 m / s, more preferably 10 to 40 m / s, and the treatment time is preferably 0.5 to 10 minutes, more preferably 1 to 5 minutes.

[0078] When disintegration is carried out by compression treatment, the treatment method is preferably ultra-high pressure homogenizer treatment. The treatment pressure of the compression treatment is preferably 10 to 300 MPa, more preferably 30 to 250 MPa.

[0079] When disintegration is carried out by shearing, the treatment method is preferably wet jet mill treatment, and the shear force is preferably 10 to 300 MPa, more preferably 30 to 250 MPa.

[0080] In one embodiment, the treatment (water-resistant treatment) according to the present invention preferably includes a crushing treatment from the viewpoint of enabling uniform dispersion of aggregated particles, and more preferably includes a Filmix treatment from the viewpoint of preventing excessive energy from being applied to the particles and suppressing a decrease in ionic conductivity.

[0081] In one embodiment, when the treatment (water-resistant treatment) according to the present invention includes a crushing treatment (preferably a FILMICS treatment), from the viewpoint of dispersibility of the sulfide solid electrolyte in the solvent, the solvent preferably includes at least one selected from the group consisting of ester solvents and ether solvents, more preferably includes at least one selected from the group consisting of ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, diethyl ether, dibutyl ether, and tetrahydrofuran, and further preferably includes at least one selected from the group consisting of ethyl acetate, ethyl propionate, and dibutyl ether.

[0082] (2) Drying Step The production method according to the present invention may further include a drying step. The drying step is usually carried out after the water-resistant treatment step. The drying step is a step of removing the solvent from the mixed liquid (preferably a suspension (slurry)) containing the sulfide solid electrolyte and the solvent obtained in the water-resistant treatment step.

[0083] The drying step is preferably carried out in an inert gas atmosphere or a vacuum atmosphere, and more preferably in an atmosphere of nitrogen gas, helium gas, or argon gas.

[0084] The drying temperature is preferably 40 to 250° C., and more preferably 50 to 250° C. A drying temperature of 40° C. or higher is preferred because the solvent can be suitably removed. On the other hand, a drying temperature of 250° C. or lower is preferred because deterioration of the sulfide solid electrolyte can be suppressed.

[0085] The drying time is preferably 0.5 to 24 hours, more preferably 1 to 8 hours.

[0086] The drying step may be carried out in two stages. In one embodiment, the drying step includes a first drying step in which drying is carried out at 40 to 100°C (preferably 50 to 90°C) and a second drying step in which drying is carried out at 110 to 250°C (preferably 140 to 200°C). By carrying out the drying step in two stages, the production cost can be reduced. For example, after removing most of the solvent in the first drying step, the solvent coordinated to the sulfide solid electrolyte (coordinating solvent) can be removed in the second drying step, thereby efficiently removing the solvent.

[0087] 2. Method for Manufacturing an All-Solid-State Battery According to one embodiment of the present invention, there is provided a method for manufacturing an all-solid-state battery. The manufacturing method includes a step of forming an all-solid-state battery including a sulfide solid electrolyte manufactured by the above-described method. In one embodiment, the manufacturing method includes a step of forming an all-solid-state battery by stacking a solid electrolyte layer formed using the sulfide solid electrolyte manufactured by the above-described method, a positive electrode layer, and a negative electrode layer. Note that the term "all-solid-state battery" refers to a battery that uses a solid electrolyte as the electrolyte. An all-solid-state battery typically includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

[0088] The solid electrolyte layer is formed using the sulfide solid electrolyte produced by the above-mentioned method. In this case, the solid electrolyte layer may be produced using only the sulfide solid electrolyte, or may be produced in combination with another solid electrolyte. Examples of the other solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, and complex hydride solid electrolytes produced by other methods. These other solid electrolytes may be used alone or in combination of two or more.

[0089] The sulfide solid electrolyte produced by the above-described method has been subjected to a water-resistant treatment, and therefore the resulting solid electrolyte layer can exhibit high water resistance.

[0090] Furthermore, the positive electrode layer and / or the negative electrode layer may be formed using the sulfide solid electrolyte produced by the above-mentioned method. When the positive electrode layer and the negative electrode layer are produced using the sulfide solid electrolyte, the positive electrode layer and the negative electrode layer are formed by combining a known positive electrode active material or a known negative electrode active material for lithium ion secondary batteries. In this case, the amount ratio of the sulfide solid electrolyte contained in the positive electrode layer or the negative electrode layer is not particularly limited. The positive electrode layer and the negative electrode layer may also contain a known current collector, a conductive additive, a binder, etc.

[0091] The all-solid-state battery is produced by forming and stacking the above-mentioned positive electrode layer, solid electrolyte layer, and negative electrode layer, but the method for forming and stacking each layer is not particularly limited.

[0092] For example, there are methods in which a solid electrolyte and / or an electrode active material is dispersed in a solvent to form a slurry, which is then applied by a doctor blade or spin coating, and then rolled to form a film; gas phase methods in which film formation and lamination are carried out using a vacuum deposition method, ion plating method, sputtering method, laser ablation method, or the like; and pressure molding methods in which powder is molded by hot pressing or cold pressing without applying heat, and then the molded film is laminated.

[0093] Since the sulfide solid electrolyte produced by the above method is relatively soft, it is particularly preferable to produce an all-solid-state battery by molding and laminating each layer by a pressure molding method. Pressure molding methods include hot pressing, which is performed with heating, and cold pressing, which is not performed with heating, but cold pressing can also be used to sufficiently mold the electrolyte.

[0094] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0095] [Example 1] (1) Production of LGPS-type sulfide solid electrolyte (1-1) β-Li ３ P.S. ４ In a glove box under an argon atmosphere, Li ２ S (manufactured by Empower Japan, purity 99.95%) and P ２ S ５ (Sigma-Aldrich, purity 99%)２ S:P ２ S ５ The mixture was weighed out so that the molar ratio was 1.35:1.

[0096] Next, (Li ２ S+P ２ S ５ ) to tetrahydrofuran (Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) so that the concentration of Li ２ S and P ２ S ５ The ingredients were added in this order and mixed at room temperature (25°C) for 48 hours or more. The mixture gradually dissolved to obtain a substantially 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.

[0097] The homogeneous solution contains Li ２ S:P ２ S ５ Li so that the molar ratio was 3:1 ２ S was further added, and the mixture was mixed at room temperature (25°C) for 5 days or more to obtain a suspension. The obtained suspension was filtered under pressure, and the sieve was vacuum dried to obtain β-Li ３ P.S. ４ -3THF was obtained.

[0098] (1-2) β-Li ３ P.S. ４ In a glove box under an argon atmosphere, the obtained β-Li ３ P.S. ４ 3THF was added to acetonitrile (Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) to a concentration of 6 wt %, and the mixture was mixed at room temperature (25°C) for at least 2 days to obtain a slurry.

[0099] The resulting slurry was heated at 50°C under reduced pressure to remove acetonitrile, and the resulting powder was dried at 180°C for 4 hours under vacuum to remove the coordinating solvent. The powder was then cooled to room temperature (25°C) to obtain microparticulated β-Li. ３ P.S. ４ A powder was obtained.

[0100] (1-3) Li ４ SnS４ Manufacturing of Li ２ S (purity: 99.8%, manufactured by Empower Japan) and SnS ２ (purity: 99.99%, manufactured by Career Henan Chemical Co.) was dissolved in Li in a glove box under an argon atmosphere. ４ SnS ４ The components were weighed out so as to achieve the stoichiometric ratio, and mixed for 5 minutes using a lab blender (manufactured by Waring Laboratory Science).

[0101] The resulting mixture was fired at 550°C for 16 hours to obtain Li ４ SnS ４ obtained.

[0102] (1-4) Li ４ SnS ４ In a glove box under an argon atmosphere, 92.5 g of the obtained Li ４ SnS ４ The mixture was added to 475 mL of methanol (ultra-dehydrated grade, manufactured by Wako Pure Chemical Industries, Ltd., boiling point: 64°C) and mixed at room temperature (25°C) for 24 hours or more. ４ SnS ４ The Li contained in the resulting solution was ４ SnS ４ The insoluble matter resulting from the manufacturing process was filtered using a membrane filter (polytetrafluoroethylene (PTFE), pore size: 1.0 μm) to obtain Li ４ SnS ４ A homogeneous solution was obtained in which

[0103] Next, under an argon atmosphere, 2.5 L of ultra-dehydrated acetonitrile was placed in a 5 L flask, and the acetonitrile was brought to a total reflux state using a distillation apparatus. ４ SnS ４ 475 mL of the methanol solution was added dropwise to acetonitrile at a rate of 3.5 mL / min. The added methanol evaporated after addition, and Li was left in the acetonitrile. ４ SnS ４ Particles were precipitated. The distillation rate was controlled by the solenoid valve of the distillation section to be 7 mL / min, which was twice the dropping rate. ４SnS ４ After the dropwise addition of the methanol solution was completed, the point when the temperature at the top of the column reached 80°C (the boiling point of acetonitrile: 82°C) was determined to be the end point of the distillation.

[0104] The resulting slurry was heated at 50°C under reduced pressure to remove acetonitrile, and the resulting powder was then dried at 180°C for 4 hours under vacuum to remove the coordinating solvent. The solvent was removed while stirring the slurry. The slurry was then cooled to room temperature (25°C) to obtain the microparticulated Li. ４ SnS ４ A powder was obtained.

[0105] (1-5) Production of LGPS-type sulfide solid electrolyte In a glove box under an argon atmosphere, the β-Li produced in the above step was ３ P.S. ４ powder and Li ４ SnS ４ The powder was ３ P.S. ４ :Li ４ SnS ４ 26.5 g was weighed out to achieve a molar ratio of 2.7:1. The weighed raw materials were ground and mixed for 4 hours using a wet bead mill (UAM015, manufactured by Hiroshima Metal & Machinery Co., Ltd.). For wet mixing, 0.05 mm diameter zirconia beads "YTZ" (manufactured by Nikkato Corporation) were used, and the bead filling rate in the grinding chamber was 80%. Acetonitrile (ultra-dehydrated grade, manufactured by Wako Pure Chemical Industries, Ltd.) was used as the dispersion medium, and the slurry concentration was 6 wt%, the peripheral speed was 8 m / s, and the circulation rate was 10 L / min.

[0106] The slurry obtained after the above treatment was heated at 50°C under reduced pressure to remove acetonitrile, and the resulting powder was then dried at 180°C for 15 minutes under vacuum to remove the coordinating solvent. The solvent was removed while stirring the slurry. The mixture was then cooled to room temperature (25°C) to obtain β-Li. ３ P.S. ４ +Li ４ SnS ４ A precursor powder of

[0107] The obtained precursor powder was fired at 550°C for 2 hours to obtain the LGPS-type sulfide solid electrolyte, Li ９．８１ Sn ０．８１ P２．１９ S １２ Crystals were obtained.

[0108] (2) Water-resistant treatment step and drying step 0.75 g of LGPS-type sulfide solid electrolyte (Li ９．８１ Sn ０．８１ P ２．１９ S １２ The crystals) was added to 8 mL of ethyl acetate (ultra-dehydrated grade, manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was stirred at room temperature (25° C.) for 30 minutes.

[0109] The slurry obtained after the stirring treatment was heated to 80°C to remove ethyl acetate, and the resulting powder was then dried at 180°C for 1 hour to remove the coordinating solvent. The solvent was removed on a hot plate. The powder was then cooled to room temperature (25°C) to obtain the water-resistant LGPS-type sulfide solid electrolyte (Li ９．８１ Sn ０．８１ P ２．１９ S １２ A series of operations was carried out in a glove box under an argon atmosphere. When the particle size (primary particle size) of the LGPS-type sulfide solid electrolyte before and after the water-resistant treatment step and the drying step was compared using SEM images, no change in particle size (primary particle size) was found.

[0110] [Example 2] (2) An LGPS-type sulfide solid electrolyte (Li) was subjected to a water-resistant treatment in the same manner as in Example 1, except that dibutyl ether (Sigma-Aldrich, purity ≧99%) was used instead of ethyl acetate in the water-resistant treatment step and the drying step. ９．８１ Sn ０．８１ P ２．１９ S １２ The particle size (primary particle size) of the LGPS-type sulfide solid electrolyte before and after the water-resistant treatment process and the drying process was compared using SEM images, and no change in particle size (primary particle size) was found. The dibutyl ether used was dehydrated using molecular sieves (3A 1 / 16 manufactured by Wako Pure Chemical Industries, Ltd.).

[0111] [Example 3] (1) Production of LGPS-type sulfide solid electrolyte An LGPS-type sulfide solid electrolyte (Li ９．８１ Sn ０．８１ P２．１９ S １２ crystals) were produced.

[0112] (2) Water-resistant treatment step and drying step 1 g of LGPS-type sulfide solid electrolyte (Li ９．８１ Sn ０．８１ P ２．１９ S １２ The resulting crystals were subjected to a wet-disintegration treatment using a thin-film swirling high-speed mixer, Filmix Model: 30-L (manufactured by Primix Corporation). Ethyl acetate (ultra-dehydrated grade, manufactured by Wako Pure Chemical Industries, Ltd.) was used as the dispersion medium, the slurry concentration was 11 wt %, the peripheral speed was 29.9 m / s, and the treatment time was 1 minute.

[0113] The slurry obtained after the wet crushing treatment was heated to 80°C to remove ethyl acetate, and the resulting powder was dried at 180°C for 1 hour to remove the coordinating solvent. The solvent was removed on a hot plate. The powder was then cooled to room temperature (25°C) to obtain the water-resistant LGPS-type sulfide solid electrolyte (Li ９．８１ Sn ０．８１ P ２．１９ S １２ A series of operations was carried out in a glove box under an argon atmosphere. When the particle size (primary particle size) of the LGPS-type sulfide solid electrolyte before and after the water-resistant treatment step and the drying step was compared using SEM images, no change in particle size (primary particle size) was found.

[0114] [Example 4] (2) An LGPS-type sulfide solid electrolyte (Li) was subjected to a water-resistant treatment in the same manner as in Example 3, except that dibutyl ether (Sigma-Aldrich, purity ≧99%) was used instead of ethyl acetate in the water-resistant treatment step and the drying step. ９．８１ Sn ０．８１ P ２．１９ S １２ The particle size (primary particle size) of the LGPS-type sulfide solid electrolyte before and after the water-resistant treatment process and the drying process was compared using SEM images, and no change in particle size (primary particle size) was found. The dibutyl ether used was dehydrated using molecular sieves (3A 1 / 16 manufactured by Wako Pure Chemical Industries, Ltd.).

[0115] Comparative Example 1 (1) Production of LGPS-type sulfide solid electrolyte: ３ P.S. ４ powder and Li ４ SnS ４ A powder was produced.

[0116] In a glove box under an argon atmosphere, the β-Li produced by the above process was ３ P.S. ４ and Li ４ SnS ４ β-Li ３ P.S. ４ :Li ４ SnS ４ 5.2 g was weighed out to achieve a molar ratio of 2.7:1. The weighed raw materials were ground and mixed for 1 hour using a wet bead mill (Easy Nano RMBII02 model, manufactured by Imex Co., Ltd.). 0.05 mm diameter zirconia beads "YTZ" (manufactured by Nikkato Corporation) were used for wet mixing. A mixed solvent (heptane / dibutyl ether = 20 / 80 vol%) of dibutyl ether (manufactured by Sigma-Aldrich, purity ≥ 99%) and heptane (ultra-dehydrated grade, manufactured by Wako Pure Chemical Industries, Ltd.) was used as the dispersion medium, with a slurry concentration of 8 wt% and a peripheral speed of 12 m / s.

[0117] The solvent was removed from the slurry obtained after the above treatment at 50°C under reduced pressure, and the resulting powder was dried at 180°C for 15 minutes under vacuum to remove the coordinating solvent. The solvent was removed while stirring the slurry. After that, the slurry was cooled to room temperature (25°C) to obtain β-Li. ３ P.S. ４ +Li ４ SnS ４ A precursor powder was obtained.

[0118] The obtained precursor powder was fired at 550°C for 2 hours to obtain the LGPS-type sulfide solid electrolyte, Li ９．８１ Sn ０．８１ P ２．１９ S １２ Crystals were obtained.

[0119] [Comparative Example 2] (2) An LGPS-type sulfide solid electrolyte (Li) was subjected to a water-resistant treatment in the same manner as in Example 3, except that heptane (ultra-dehydrated grade, manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of ethyl acetate in the water-resistant treatment step and the drying step. ９．８１ Sn ０．８１ P ２．１９ S １２ When the particle size (primary particle size) of the LGPS-type sulfide solid electrolyte before and after the water-resistant treatment step and the drying step was compared using SEM images, no change in the particle size (primary particle size) was found.

[0120] (1) Argyrodite-type sulfide solid electrolyte: A commercially available argyrodite-type sulfide solid electrolyte, Li ６ P.S. ５ Cl ０．９ I ０．１ Crystals (NEI Corporation) were obtained.

[0121] (2) Water-resistant treatment process and drying process LGPS-type sulfide solid electrolyte (Li ９．８１ Sn ０．８１ P ２．１９ S １２ Instead of the argyrodite-type sulfide solid electrolyte (Li ６ P.S. ５ Cl ０．９ I ０．１ An argyrodite-type sulfide solid electrolyte (Li crystal) was used, which was treated for water resistance in the same manner as in Example 1. ６ P.S. ５ Cl ０．９ I ０．１ When the particle size (primary particle size) of the argyrodite-type sulfide solid electrolyte before and after the water-resistant treatment step and the drying step was compared using SEM images, no change in particle size (primary particle size) was found.

[0122] The manufacturing methods of Examples 1 to 4, Comparative Examples 1 and 2, and Example 5 are shown in Table 1 below.

[0123]

[0124] [Evaluation] The water-resistant sulfide solid electrolytes produced by the methods of Examples 1 to 4, Comparative Examples 1 and 2, and Example 5, as well as the non-water-resistant LGPS-type sulfide solid electrolyte produced in (1-5) of Example 1 (Reference Example 1) and the non-water-resistant commercially available argyrodite-type sulfide solid electrolyte used as a raw material in Example 5 (Reference Example 2), were evaluated for hydrogen sulfide generation amount, ionic conductivity, and half-width increase rate. The obtained results are shown in Table 2 below.

[0125] [Amount of Hydrogen Sulfide Generated] 10 mg of sulfide solid electrolyte was weighed out under an argon atmosphere and placed in a sealed container (volume 3000 cc, dew point -30°C, dry air at 25°C). While circulating the air in the sealed container with a fan, the amount of hydrogen sulfide generated was measured using a hydrogen sulfide sensor (ToxiRAE Pro series). The amount of hydrogen sulfide generated within 1 hour after the sulfide solid electrolyte was exposed to dry air was measured. The amount of hydrogen sulfide generated was expressed as a value per unit area of ​​the sulfide solid electrolyte.

[0126] [Ionic Conductivity] The sulfide solid electrolyte was subjected to uniaxial molding (480 MPa) to obtain a disk with a thickness of approximately 1 mm and a diameter of 10 mm. Using an all-solid-state battery evaluation cell (manufactured by Hosen Co., Ltd.), AC impedance measurements were performed by the four-terminal method using an "SI1260 IMPEDANCE / GAIN-PHASE ANALYZER" (manufactured by Solartron) at room temperature (25°C), and the lithium ion conductivity was calculated. Specifically, the disk was placed in a thermostatic chamber set at 25°C and held for 30 minutes, after which the lithium ion conductivity was measured. The measurement frequency range was 0.1 Hz to 1 MHz, and the amplitude was 50 mV.

[0127] [Half-width increase rate] The sulfide solid electrolyte was subjected to X-ray diffraction measurement (CuKα: λ=1.5405 Å) using "X'Pert3 Powder" (manufactured by PANalytical) under an Ar atmosphere at room temperature (25°C). Furthermore, the half-width of the main peak with the highest diffraction intensity was calculated. The calculation method is as follows.

[0128] That is, the diffraction data obtained by the X-ray diffraction measurement was imported into the crystal structure analysis software "SmartLab studio II" and background and peak fitting was performed. A split pseudo-Voigt function was selected for profile fitting, and the half-width of each peak was calculated.

[0129] For Examples 1 to 4 and Comparative Examples 1 and 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.

[0130]

[0131] The results in Table 2 show that the sulfide solid electrolytes treated for water resistance in Examples 1 to 5 had a low amount of hydrogen sulfide generated and high water resistance.

Claims

1. A method for producing a sulfide solid electrolyte, comprising the step of subjecting a sulfide solid electrolyte to at least one treatment selected from the group consisting of a mixing treatment and a crushing treatment in a solvent, wherein the solvent comprises an aprotic solvent containing oxygen atoms.

2. The method according to claim 1, wherein the solvent comprises at least one selected from the group consisting of ester solvents and ether solvents.

3. The process of claim 2, wherein the solvent comprises an ester solvent.

4. The process of claim 3, wherein the ester solvent comprises at least one selected from the group consisting of ethyl acetate and ethyl propionate.

5. The process of claim 2, wherein the solvent comprises an ether solvent.

6. The process of claim 5, wherein the ether solvent comprises dibutyl ether.

7. The method of claim 1, wherein the treatment comprises a mixing treatment.

8. The method of claim 1, wherein the treatment includes a crushing treatment.

9. The method of claim 1, wherein the sulfide solid electrolyte comprises a LGPS-type sulfide solid electrolyte.

10. The method of claim 1, wherein the sulfide solid electrolyte comprises an argyrodite-type sulfide solid electrolyte.

11. The method of claim 1, wherein the sulfide solid electrolyte contains tin (Sn).

12. A method for producing an all-solid-state battery, comprising forming an all-solid-state battery containing a sulfide solid electrolyte produced by the method according to any one of claims 1 to 11.

Images