Method for producing sulfide solid electrolyte composite, sulfide solid electrolyte composite, and method for producing composite powder

Abstract

The present invention provides a method for producing a sulfide solid electrolyte composite, the method comprising: a step for adding fine particles having a BET specific surface area of 5 m2 / g or more to a solution containing at least one sulfide solid electrolyte raw material, and dispersing the fine particles to obtain a fine particle dispersion liquid; a step for obtaining a composite powder of the fine particles and the sulfide solid electrolyte raw material by removing the solvent from the fine particle dispersion liquid; and a step for obtaining a sulfide solid electrolyte composite using the composite powder.

Description

Technical Field

[0001] The present invention relates to a method for producing a sulfide solid electrolyte composite, a method for producing a sulfide solid electrolyte composite, and a method for producing composite powder. Background Art

[0002] Lithium-ion secondary batteries are widely used in portable electronic devices such as mobile phones and laptops. Traditionally, liquid electrolytes have been used in lithium-ion secondary batteries. Meanwhile, all-solid-state lithium-ion secondary batteries, which use solid electrolytes as their electrolytes, have recently attracted attention due to their potential for improved safety, high-speed charging and discharging, and miniaturization of the housing.

[0003] As a solid electrolyte used in all-solid-state lithium-ion secondary batteries, for example, sulfide solid electrolytes can be cited. In the past, when manufacturing sulfide solid electrolytes, it is known to mix aluminum oxide, nitride, etc. into the sulfide solid electrolyte raw material in order to improve lithium ion conductivity. For example, the following patent document 1 discloses a solid electrolyte containing aluminum oxide and having lithium ion conductivity. In addition, the following non-patent document 1 discloses a method using Li 1.5 Al 0.5 A method for producing solid electrolytes using N(LAN) as nitride.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2020 / 105604

[0007] Non-patent literature

[0008] Non-patent document 1: H. Yamane et al., “Lithium aluminum nitride, Li3AlN2 as alithium solid electrolyte”, Solid State Ionics Volume 15, Issue 1, February 1985, Pages 51-54 Summary of the Invention

[0009] However, the above-mentioned alumina and nitrides have poor reactivity with other sulfide solid electrolyte raw materials, and the synthesis of sulfide solid electrolytes takes time. Therefore, the present inventors conducted in-depth research on components with good reactivity with sulfide solid electrolyte raw materials and capable of improving lithium ion conductivity, and found that fine particles with a smaller particle size are used. However, since the fine particles are lightweight and easily scattered, they fly in the air when the fine particles are put into and mixed in the container of the mixing device, or when the raw materials are transported by an air flow, etc., or adsorption to the container wall surface, etc. caused by static electricity occurs. As a result, there is a problem of composition deviation in the obtained sulfide solid electrolyte composite. Therefore, when using fine particles, humidity adjustment using moisture is required, but since the sulfide solid electrolyte raw materials need to be operated in an environment where moisture cannot be used for humidity adjustment, it is difficult to effectively use the fine particles as sulfide solid electrolyte raw materials.

[0010] Therefore, an object of the present invention is to provide a method for manufacturing a sulfide solid electrolyte composite with excellent operability during manufacturing and less deviation of fine particles, and the sulfide solid electrolyte composite.

[0011] The present inventors conducted further in-depth research and found that, according to the following method, a sulfide solid electrolyte composite with excellent operability during manufacturing and less deviation of fine particles can be obtained, and thus the present invention was completed. That is, first, fine particles with a specified BET specific surface area are added to a solution containing at least one sulfide solid electrolyte raw material to obtain a dispersion of the fine particles, and then a composite powder obtained by removing the solvent is used to manufacture a sulfide solid electrolyte composite.

[0012] That is, the present invention relates to the following [1] to

[16] .

[0013] [1] A method for manufacturing a sulfide solid electrolyte composite, comprising:

[0014] Adding fine particles with a BET specific surface area of 5 m 2 / g or more to a solution containing at least one sulfide solid electrolyte raw material, and dispersing the fine particles to obtain a fine particle dispersion step,

[0015] Removing the solvent of the fine particle dispersion to obtain a composite powder of the fine particles and the sulfide solid electrolyte raw material, and

[0016] Using the composite powder to obtain a sulfide solid electrolyte composite step.

[0017] [2] The method for manufacturing a sulfide solid electrolyte composite according to the above [1], wherein the sulfide solid electrolyte composite is obtained by using the composite powder and a solid phase method.

[0018] [3]The manufacturing method of the sulfide solid electrolyte complex according to [1] above, wherein the sulfide solid electrolyte complex is obtained by using the above complex powder and the melting method.

[0019] [4]The manufacturing method of the sulfide solid electrolyte complex according to [1] above, wherein the above fine particles are oxides.

[0020] [5]The manufacturing method of the sulfide solid electrolyte complex according to [4] above, wherein the above oxide is at least one of SiO2, Al2O3, and TiO2.

[0021] [6]The manufacturing method of the sulfide solid electrolyte complex according to [1] above, wherein the above fine particles are nitrides.

[0022] [7]The manufacturing method of the sulfide solid electrolyte complex according to [6] above, wherein the above nitride is at least one of AlN, Si3N4, and BN.

[0023] [8]The manufacturing method of the sulfide solid electrolyte complex according to [1] above, wherein the above sulfide solid electrolyte raw material is lithium halide.

[0024] [9]The manufacturing method of the sulfide solid electrolyte complex according to [8] above, wherein the above lithium halide is lithium bromide.

[0025]

[10] The manufacturing method of the sulfide solid electrolyte complex according to [1] above, wherein the above sulfide solid electrolyte raw material is lithium hydroxide.

[0026]

[11] The manufacturing method of the sulfide solid electrolyte complex according to [1] above, wherein an alkali metal sulfide is added to the above fine particle dispersion liquid and then the solvent is removed.

[0027]

[12] The manufacturing method of the sulfide solid electrolyte complex according to

[11] above, wherein the above alkali metal sulfide is lithium sulfide.

[0028]

[13] The manufacturing method of the sulfide solid electrolyte complex according to [1] above, wherein hydrogen sulfide is introduced into the above fine particle dispersion liquid and then the solvent is removed.

[0029]

[14] The manufacturing method of the sulfide solid electrolyte complex according to [1] above, wherein the sulfide solid electrolyte complex is obtained by using the above complex powder after reacting with hydrogen sulfide.

[0030]

[15] A sulfide solid electrolyte complex, which comprises a BET specific surface area of 5m 2Particles of 5 m² / g or more, with a dispersion degree of the particles relative to the sulfide solid electrolyte composite of 15% or less.

[0031]

[16] A method for manufacturing a composite powder, comprising:

[0032] Adding particles with a BET specific surface area of 5 m² / g or more to a solution containing at least one sulfide solid electrolyte raw material, and dispersing the particles to obtain a particle dispersion liquid, and 2 Removing the solvent of the particle dispersion liquid to obtain a composite powder of the particles and the sulfide solid electrolyte raw material.

[0033] According to the manufacturing method of the present invention, a sulfide solid electrolyte composite with excellent operability during manufacturing and less deviation of particles can be obtained.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A flowchart showing a method for manufacturing a sulfide solid electrolyte composite according to an embodiment of the present invention.

[0036] Figure 2 An example of a flowchart showing a case where, in the method for manufacturing a sulfide solid electrolyte composite according to an embodiment of the present invention, a sulfide solid electrolyte composite is manufactured by a solid phase method using a composite powder.

[0037] Figure 3 An example of a flowchart showing a case where, in the method for manufacturing a sulfide solid electrolyte composite according to an embodiment of the present invention, a sulfide solid electrolyte composite is manufactured by a melting method using a composite powder. DETAILED DESCRIPTION OF THE INVENTION

[0038] Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and any deformation can be implemented without departing from the gist of the present invention. In addition, "~" indicating a numerical range is used in the sense of including the values described before and after as the lower limit value and the upper limit value.

[0039] <Method for Manufacturing Sulfide Solid Electrolyte Composite>

[0040] The method for manufacturing a sulfide solid electrolyte composite according to an embodiment of the present invention (hereinafter, also referred to as this manufacturing method) is characterized in that it includes: adding particles with a BET specific surface area of 5 m² / g or more 2The invention also provides a step of adding fine particles having a weight of 100 g or more to a solution containing at least one sulfide solid electrolyte raw material, dispersing the fine particles to obtain a fine particle dispersion; removing the solvent from the fine particle dispersion to obtain a composite powder of the fine particles and the sulfide solid electrolyte raw material; and obtaining a sulfide solid electrolyte composite using the composite powder.

[0041] Figure 1 An example of a flow chart showing the present production method is shown below. In the present production method, first, a BET specific surface area of 5 m 2 / g or more of fine particles are added to a solution containing at least one sulfide solid electrolyte raw material, and the fine particles are dispersed to obtain a fine particle dispersion (step S1). Next, the solvent in the obtained fine particle dispersion is removed to obtain a composite powder of the fine particles and the sulfide solid electrolyte raw material (step S2). The obtained composite powder is then used to obtain a sulfide solid electrolyte composite (step S3).

[0042] and then, Figure 2 An example of a flow chart for producing a sulfide solid electrolyte composite by a solid phase method using composite powder is shown. Figure 3 An example of a flow chart for producing a sulfide solid electrolyte composite by a melting method using composite powder is shown.

[0043] In solid phase methods, Figure 2 As shown, Figure 1 Step S3 is replaced by step S3a, and a sulfide solid electrolyte composite is obtained by a solid phase method using the composite powder (step S3a).

[0044] On the other hand, in the melting method, e.g. Figure 3 As shown, Figure 1 The above-mentioned step S3 is replaced by step S3b, and a sulfide solid electrolyte composite is obtained by a melting method using the composite powder (step S3b).

[0045] The above-mentioned steps S1 to S3 are preferably performed continuously. When such a continuous production method is adopted, the effects of the present invention are further enhanced.

[0046] The sulfide solid electrolyte composite obtained by this production method is a sulfide solid electrolyte with a BET specific surface area of 5m 2A composite of particles of 5 m² / g or more (hereinafter also simply referred to as particles), where the particles are present in a state of being dispersed in a sulfide solid electrolyte. In other words, the particles are present with a relatively high degree of homogeneity in the sulfide solid electrolyte. The above-mentioned particles can be, for example, silicon oxide (SiO₂) as described later, and have the effect of improving the lithium-ion conductivity of the sulfide solid electrolyte. In addition, since the particles are present with a relatively high degree of homogeneity in the sulfide solid electrolyte, deterioration of battery performance caused by compositional deviation can be suppressed.

[0047] It should be noted that the "state where particles are dispersed in a sulfide solid electrolyte" includes a state where the particles are introduced into the framework structure and homogeneously solid-solved, a state where the particles do not enter the framework structure of the sulfide solid electrolyte and are dispersed as particles or components derived from the particles, and the like.

[0048] Hereinafter, each step of this manufacturing method will be described in detail.

[0049] <Preparation of particle dispersion liquid>

[0050] In this manufacturing method, first, particles with a BET specific surface area of 5 m² / g or more are added to a solution containing at least one sulfide solid electrolyte raw material, and the above-mentioned particles are dispersed to obtain a particle dispersion liquid (step S1). 2 / g or more are added to a solution containing at least one sulfide solid electrolyte raw material, and the above-mentioned particles are dispersed to obtain a particle dispersion liquid (step S1).

[0051] (Particles)

[0052] As the particles with a BET specific surface area of 5 m² / g or more used in this manufacturing method, for example, oxides, nitrides, carbides, borides, etc. with a BET specific surface area of 5 m² / g or more can be cited. Among them, from the viewpoint of improving conductivity, oxides and nitrides are preferred. 2 / g or more, for example, oxides, nitrides, carbides, borides, etc. with a BET specific surface area of 5 m² / g or more can be cited. Among them, from the viewpoint of improving conductivity, oxides and nitrides are preferred. 2 / g or more, for example, oxides, nitrides, carbides, borides, etc. with a BET specific surface area of 5 m² / g or more can be cited. Among them, from the viewpoint of improving conductivity, oxides and nitrides are preferred.

[0053] As oxides, for example, silicon oxide (SiO₂), aluminum oxide (Al₂O₃), titanium oxide (TiO₂), zirconium oxide (ZrO₂), etc. can be cited.

[0054] As nitrides, for example, aluminum nitride (AlN), silicon nitride (Si₃N₄), boron nitride (BN), aluminum carbonitride, chromium nitride, magnesium nitride, etc. can be cited.

[0055] As carbides, for example, boron carbide, aluminum carbide, chromium carbide, hafnium carbide, molybdenum carbide, niobium carbide, silicon carbide, etc. can be cited.

[0056] In addition, lanthanum hexaboride, lanthanum boride, lanthanum trifluoride, molybdenum disulfide, molybdenum silicide, etc. can be cited.

[0057] These can be used alone or in combination of two or more.

[0058] Among them, from the viewpoint of improving the conductivity, oxides and nitrides are preferred.

[0059] The BET specific surface area of the fine particles is 5 m 2 / g or more. With the BET specific surface area being 5 m 2 / g or more, the reactivity with other sulfide solid electrolyte raw materials is good. In addition, the synthesis time of the sulfide solid electrolyte can be shortened. The BET specific surface area of the fine particles is more preferably 5 to 500 m 2 / g. The BET specific surface area of the fine particles is further preferably 10 m 2 / g or more, particularly preferably 20 m 2 / g or more. In addition, it is further preferably 300 m 2 / g or less, particularly preferably 200 m 2 / g or less.

[0060] The BET specific surface area refers to the nitrogen adsorption specific surface area measured by the BET method. For the measurement of the BET specific surface area, for example, a specific surface area measuring device "TristarII 3020" manufactured by Shimadzu Corporation is used. As a pretreatment, it is dried at 230 °C until it becomes 50 mTorr, and then measured by the multi-point method using liquid nitrogen.

[0061] From the viewpoints of good reactivity with other sulfide solid electrolyte raw materials, shortening the synthesis time of the sulfide solid electrolyte, and dispersibility in the solution described below, etc., the primary particle size of the fine particles is preferably 5 to 3000 nm, for example. The primary particle size of the fine particles is further preferably 5 nm or more, particularly preferably 10 nm or more. And it is further preferably 2000 nm or less, particularly preferably 1000 nm or less.

[0062] Here, the primary particle size of the fine particles refers to the particle size observed and measured by SEM. In the case of aggregation, it refers to the particles constituting the aggregate. It is the average value of the average particle sizes of 20 randomly selected particles.

[0063] From the viewpoints of good reactivity with other sulfide solid electrolyte raw materials, shortening the synthesis time of the sulfide solid electrolyte, and dispersibility in the solution described below, etc., the average particle size of the fine particles is preferably 5 to 3000 nm, for example. The average particle size of the fine particles is further preferably 5 nm or more, particularly preferably 10 nm or more. In addition, it is further preferably 2000 nm or less, particularly preferably 1000 nm or less.

[0064] Here, the average particle size refers to the median diameter (D50) of the particle size at which 50% by volume of the particles is below this value, which is obtained by measuring the particle size distribution using a particle size distribution meter using the laser diffraction method and based on the volume-based particle size distribution diagram obtained.

[0065] The amount of the fine particles added to the solution described below is preferably 0.1 to 30% by mass relative to the solution. When the amount of the fine particles is 0.1% by mass or more, an effect of improving the performance of the electrolyte can be expected, and when it is 30% by mass or less, the dispersion state when the fine particles are added can be maintained in a good state. The amount of the fine particles is more preferably 0.5% by mass or more, further preferably 1.0% by mass or more, and more preferably 20% by mass or less, further preferably 10% by mass or less.

[0066] (Sulfide solid electrolyte raw material)

[0067] The solution to which the above-mentioned fine particles are added contains at least one kind of sulfide solid electrolyte raw material. It should be noted that the solution may or may not contain all the sulfide solid electrolyte raw materials for constituting the sulfide solid electrolyte composite finally obtained by this manufacturing method. In the former case, in step S3 described below, when using the composite powder and obtaining the sulfide solid electrolyte composite by a solid-phase method or a melting method, etc., there is no need to additionally add a sulfide solid electrolyte raw material. On the contrary, in the latter case, when using the composite powder and obtaining the sulfide solid electrolyte composite by a solid-phase method or a melting method, etc., a sulfide solid electrolyte raw material not contained in the above solution is additionally added.

[0068] At least one kind of sulfide solid electrolyte raw material contained in the above solution preferably has the property of being soluble in the solution.

[0069] As the sulfide solid electrolyte raw material, a commercially available sulfide solid electrolyte raw material can be used, or a sulfide solid electrolyte raw material manufactured from materials can be used. In addition, these sulfide solid electrolyte raw materials can be further subjected to known pretreatment. That is, this manufacturing method can appropriately include a process of manufacturing a sulfide solid electrolyte raw material and a process of subjecting the sulfide solid electrolyte raw material to pretreatment.

[0070] Hereinafter, the sulfide solid electrolyte raw material will be specifically described. As the sulfide solid electrolyte raw material, it usually contains an alkali metal element (R) and a sulfur element (S).

[0071] As the alkali metal element (R), lithium element (Li), sodium element (Na), potassium element (K), etc. can be cited, and among them, lithium element (Li) is preferred. As the alkali metal element (R), substances (components) containing an alkali metal element such as an alkali metal element simple substance and a compound containing an alkali metal element can be appropriately combined and used. Among them, as the lithium element, substances (components) containing Li such as Li simple substance and a compound containing Li can be appropriately combined and used.

[0072] Examples of substances containing lithium element (Li) include lithium compounds such as lithium sulfide (Li2S), lithium iodide (LiI), lithium carbonate (Li2CO3), lithium sulfate (Li2SO4), lithium oxide (Li2O), and lithium hydroxide (LiOH), as well as metallic lithium. As the substance containing lithium element (Li), lithium sulfide is preferably used from the viewpoint of obtaining a sulfide material.

[0073] As the sulfur element (S), a simple substance of S, a compound containing S, or other substances (components) containing S can be used in combination as appropriate.

[0074] Examples of substances containing elemental sulfur (S) include phosphorus sulfide such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), other sulfur compounds containing phosphorus, elemental sulfur, and compounds containing sulfur. Examples of compounds containing sulfur include H2S, CS2, iron sulfide (FeS, Fe2S3, FeS2, Fe 1－x S, etc.), bismuth sulfide (Bi2S3), copper sulfide (CuS, Cu2S, Cu 1－ x S, etc.). From the perspective of obtaining a sulfide material, the substance containing elemental sulfur (S) is preferably phosphorus sulfide, and more preferably phosphorus pentasulfide (PS). These may be used alone or in combination of two or more. It should be noted that phosphorus sulfide is considered to be a compound that serves as both a substance containing S and a substance containing P, which will be described later.

[0075] From the perspective of improving the ionic conductivity of the resulting sulfide solid electrolyte, the sulfide solid electrolyte raw material preferably further contains phosphorus (P). As phosphorus (P), P alone, P-containing compounds, and other P-containing substances (components) can be used in combination as appropriate.

[0076] Examples of substances containing elemental phosphorus (P) include phosphorus sulfides such as phosphorus trisulfide (PS) and phosphorus pentasulfide (PS), phosphorus compounds such as sodium phosphate (NaPO), and elemental phosphorus. From the perspective of further demonstrating the effects of the present invention, substances containing elemental phosphorus (P) are preferably phosphorus sulfides due to their high volatility, and more preferably phosphorus pentasulfide (PS). These substances may be used alone or in combination of two or more.

[0077] The raw material for the sulfide solid electrolyte can be obtained as a mixed raw material, for example, by appropriately mixing the above substances according to the composition of the target sulfide solid electrolyte. The mixing ratio is not particularly limited. For example, from the viewpoint of improving the ionic conductivity of the obtained sulfide solid electrolyte, etc., the molar ratio S / R of sulfur element (S) to alkali metal element (R) in the raw material for the sulfide solid electrolyte is preferably 0.65 / 0.35 or less, more preferably 0.5 / 0.5 or less. In addition, the mixed raw material is preferably obtained by mixing in a prescribed stoichiometric ratio corresponding to the substances used for mixing. As the method for the above mixing, for example, mixing using a mortar, mixing using a medium such as a planetary ball mill, a rod mill, a powder mixer, and medium-free mixing such as pneumatic mixing can be cited.

[0078] As an example of a preferred combination of the alkali metal element and the sulfur element contained in the raw material for the sulfide solid electrolyte, the combination of Li2S and P2S5 can be cited. In the case of combining Li2S and P2S5, the molar ratio Li / P of Li to P is preferably 40 / 60 or more, more preferably 50 / 50 or more. In addition, the molar ratio Li / P of Li to P is preferably 88 / 12 or less. Further, the molar ratio Li / P of Li to P is preferably 40 / 60 to 88 / 12, more preferably 50 / 50 to 88 / 12. By adjusting the mixing ratio so that P2S5 is less than Li2S, it is easier to suppress the volatilization of the sulfur component and the phosphorus component during the heat treatment due to the lower boiling point of P2S5 compared to the melting point of Li2S.

[0079] On the other hand, since lithium sulfide is expensive, from the viewpoint of suppressing the manufacturing cost of the sulfide solid electrolyte, a lithium compound other than lithium sulfide or metallic lithium, etc. can be used. Specifically, in this case, as the substance containing Li, the raw material for the sulfide solid electrolyte preferably contains one or more selected from metallic lithium, lithium iodide (LiI), lithium carbonate (Li2CO3), lithium sulfate (Li2SO4), lithium oxide (Li2O), and lithium hydroxide (LiOH). These can be used alone or in combination of two or more.

[0080] For the raw material for the sulfide solid electrolyte, according to the composition of the target sulfide solid electrolyte, or as an additive, etc., in addition to the above substances, other substances (compounds, etc.) can be contained.

[0081] For example, in the case of manufacturing a sulfide solid electrolyte containing halogen elements such as F, Cl, Br, or I, the raw material of the sulfide solid electrolyte preferably contains a halogen element (Ha). In this case, the raw material of the sulfide solid electrolyte preferably contains a compound containing a halogen element. Examples of the compound containing a halogen element include lithium halides such as lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), phosphorus halides, phosphoryl halides, sulfur halides, sodium halides, boron halides, etc. From the perspective of the reactivity of the raw material, lithium halides are preferred as the compound containing a halogen element, and LiCl, LiBr, and LiI are more preferred. These can be used alone or in combination of two or more.

[0082] It should be noted that alkali metal halides such as lithium halide can also be compounds containing alkali metal elements such as Li. When the raw material of the sulfide solid electrolyte contains an alkali metal halide, part or all of the alkali metal elements such as Li in the raw material of the sulfide solid electrolyte can be alkali metal elements derived from the alkali metal halide such as lithium halide.

[0083] When the raw material of the sulfide solid electrolyte contains a halogen element (Ha) and a phosphorus element (P), from the perspective of improving the ionic conductivity of the obtained sulfide solid electrolyte, etc., the molar equivalent of Ha relative to P in the raw material of the sulfide solid electrolyte is preferably 0.2 molar equivalent or more, more preferably 0.5 molar equivalent or more. In addition, from the perspective of the stability of the obtained sulfide solid electrolyte, the molar equivalent of Ha is preferably 4 molar equivalents or less, more preferably 3 molar equivalents or less.

[0084] The obtained sulfide solid electrolyte can be an amorphous sulfide solid electrolyte according to its purpose. From the perspective of improving the ease of formation of the amorphous phase, the raw material of the sulfide solid electrolyte preferably further contains sulfides such as SiS2, B2S3, GeS2, and Al2S3. By making the amorphous phase easy to form, when obtaining an amorphous product by rapid cooling, even if the cooling rate is reduced, an amorphous sulfide solid electrolyte can be obtained, and the equipment load can be reduced.

[0085] In addition, from the perspective of imparting moisture resistance, etc., to the sulfide solid electrolyte, it is also preferred to contain oxides such as SiO2, B2O3, GeO2, Al2O3, and P2O5. These can be used alone or in combination of two or more.

[0086] In the above-mentioned raw material of the sulfide solid electrolyte, as the raw material of the sulfide solid electrolyte contained in the above solution, from the aspect of having a relatively high solubility in water which is easy to operate as a solvent, lithium halides, lithium hydroxide, lithium sulfate, etc. are preferred. In addition, lithium bromide is preferred as the lithium halide.

[0087] From the viewpoint of being easy to handle as a powder, the average particle diameter of the sulfide solid electrolyte raw material contained in the above solution is preferably 100 to 1000 μm, for example. Here, the average particle diameter refers to the median diameter (D50) of the particle diameter at which 50% by volume of the particles is below this value, obtained by measuring the particle size distribution using a particle size distribution meter based on the laser diffraction method and according to the obtained volume-based particle size distribution diagram.

[0088] The amount of the sulfide solid electrolyte raw material contained in the above solution is preferably 10 to 40% by mass relative to the solution. By the amount of the sulfide solid electrolyte raw material being 10% by mass or more, it is advantageous in terms of being able to suppress the cost of removing the solvent in the subsequent process of removing the solvent. By being 40% by mass or less, the dissolution residue of the sulfide solid electrolyte raw material can be reduced. The amount of the sulfide solid electrolyte raw material is more preferably 15% by mass or more, further preferably 20% by mass or more. In addition, it is more preferably 35% by mass or less, further preferably 30% by mass or less.

[0089] In addition to the sulfide solid electrolyte raw material, the above solution may contain arbitrary components, such as a solvent, a dispersant, etc.

[0090] Examples of the solvent include water, ethanol, etc. The solvent is preferably water, and in this case, the above solution refers to an aqueous solution.

[0091] Examples of the dispersant include sodium polyacrylate, sulfonic acid-based copolymers, carboxylic acid-based copolymers, etc.

[0092] (Fine particle dispersion liquid)

[0093] The method for dispersing fine particles in the above solution is not particularly limited, but examples include methods such as stirring, pulverization, and addition of a dispersant.

[0094] As the stirring method, a conventionally well-known method can be used. For example, emulsifying devices such as a homogenizer, a homogenizing mixer, a colloid mill, an ultrasonic emulsifier, and a homogenizing disperser can be used.

[0095] As the pulverization method, a conventionally well-known method can be used. For example, a wet jet grinding device can be used.

[0096] As the method for adding a dispersant, a conventionally well-known method can be used. As the dispersant, for example, sodium polyacrylate, sulfonic acid-based copolymers, carboxylic acid-based copolymers, etc. can be used.

[0097] When it is desired to precipitate fine particles not from the sulfide solid electrolyte raw material dissolved in the dispersion liquid itself, but from the raw material obtained by sulfiding the sulfide solid electrolyte raw material dissolved in the dispersion liquid, before moving to the step S2 of removing the solvent, a step of sulfiding the above-mentioned fine particle dispersion liquid may be passed through. Thereby, fine particles can be dispersed in the sulfided sulfide solid electrolyte raw material.

[0098] As the method of the above sulfidation, there is no particular limitation, and for example, a method of introducing hydrogen sulfide into the above-mentioned fine particle dispersion liquid can be cited.

[0099] In the method of introducing hydrogen sulfide into the fine particle dispersion liquid, hydrogen sulfide can be introduced into the fine particle dispersion liquid as a gas.

[0100] As the conditions when introducing hydrogen sulfide as a gas into the fine particle dispersion liquid, a nozzle is inserted into the fine particle dispersion liquid, and usually bubbling is carried out at a temperature range of 5 to 95 °C for 60 to 360 minutes. The temperature during bubbling is preferably carried out at 15 to 85 °C, more preferably at 25 to 75 °C. The bubbling time is preferably 90 to 240 minutes, more preferably 120 to 180 minutes.

[0101] The fine particle dispersion liquid is prepared in the above manner.

[0102] <Preparation of composite powder>

[0103] In this manufacturing method, then, the solvent of the fine particle dispersion liquid is removed to obtain a composite powder of fine particles and a sulfide solid electrolyte raw material (step S2).

[0104] (Removal of solvent)

[0105] In order to remove the solvent of the fine particle dispersion liquid, for example, a method of carrying out reduced-pressure heating drying can be cited by using a reduced-pressure drying device with a vibration mechanism, reducing the pressure to 2 kPa, gradually raising the temperature to 160 °C, and maintaining 160 °C.

[0106] In addition, when drying the fine particle dispersion liquid sulfided by bubbling hydrogen sulfide, a method of heating and drying while introducing dry hydrogen sulfide gas can be cited in such a way that the sulfided sulfide solid electrolyte raw material is not decomposed again by the generated water.

[0107] (Composite powder)

[0108] By removing the solvent from the particulate dispersion, a composite powder of the particulates and the sulfide solid electrolyte raw material (hereinafter, also simply referred to as the composite powder) can be obtained. Here, the composite powder does not mean merely a mixture of the particulates and the sulfide solid electrolyte raw material, but means a composite powder in a state where the particulates are dispersed in the sulfide solid electrolyte raw material. For example, when silica particulates are used as the particulates and lithium bromide is used as the sulfide solid electrolyte raw material, a composite powder in which the silica particulates are dispersed in lithium bromide is obtained.

[0109] It should be noted that the "state where the particulates are dispersed in the sulfide solid electrolyte raw material" includes a state where the particulates enter the framework structure and are uniformly solid-dissolved, a state where the particulates do not enter the framework structure of the sulfide solid electrolyte and are dispersed as particulates or components derived from the particulates, and the like.

[0110] (Sulfurization of the composite powder)

[0111] In step S1, in a case where a reaction caused by hydrogen sulfide gas is not carried out, a case where a reaction is carried out but the reaction is insufficient, or a case where dry hydrogen sulfide gas is not introduced in the solvent removal step and drying is performed and the reaction is insufficient due to a reverse reaction, the above composite powder can be sulfurized before moving to step S3 of obtaining the sulfide solid electrolyte composite. Thereby, a fully sulfurized composite powder can be obtained from an unsulfurized or insufficiently sulfurized composite powder.

[0112] As a method for sulfurizing the above composite powder, there is no particular limitation, and for example, a method of introducing hydrogen sulfide into the above composite powder can be cited. That is, according to this method, in step S3 described later, a sulfide solid electrolyte composite can be obtained using the composite powder after reacting with hydrogen sulfide.

[0113] In the method of introducing hydrogen sulfide into the composite powder, there is a method of introducing hydrogen sulfide as a gas into the composite powder.

[0114] As conditions for introducing hydrogen sulfide as a gas into the composite powder, in order to make the powder react with hydrogen sulfide efficiently, a method of introducing hydrogen sulfide gas while stirring the powder is preferred. For efficient reaction, the temperature is preferably 160 to 220 °C.

[0115] It should be noted that before sulfurizing the composite powder, a step of previously pulverizing the composite powder can be passed through. By passing through the pulverizing step, it is possible to suppress the generation of unreacted portions in the sulfurization reaction. The pulverizing method can adopt any conventionally known method.

[0116] In addition, before the sulfidation of the composite powder, the step of previously pulverizing the composite powder may not be required. In this case, the same apparatus can be used to continuously carry out the sulfidation reaction after removing the solvent.

[0117] (Dispersion degree of the composite powder)

[0118] In order to obtain a sulfide solid electrolyte composite with less deviation and higher homogeneity of the fine particles in the sulfide solid electrolyte, it is preferable that the homogeneity of the fine particles in the composite powder is also high.

[0119] The homogeneity of the fine particles in the composite powder can be evaluated by the dispersion degree of the fine particles relative to the composite powder. The above dispersion degree is preferably 25% or less, more preferably 20% or less, and further preferably 15% or less. The lower limit of the dispersion degree is not particularly limited and is usually 3% or more.

[0120] The dispersion degree of the fine particles relative to the composite powder is the dispersion degree obtained by the following method. That is, first, 0.1 g of the composite powder is collected at 5 points, decomposed and dissolved by heating with nitric acid, sulfuric acid, and hydrofluoric acid (nitric acid + sulfuric acid + hydrofluoric acid), and the metal elements of the fine particles in the obtained liquid are quantified relative to the composite powder by ICP (inductively coupled plasma) optical emission spectroscopy. When there is residue in the dissolved liquid, the amount, ratio, dissolution time, and temperature of the acid are adjusted so that no residue remains in the dissolved liquid for measurement. And for the residue, it can be dissolved, quantified, and totaled separately with caustic soda, etc.

[0121] Let the contents (mass %) of the metal elements of the fine particles at 5 points obtained under the above conditions relative to the composite powder be A1 to A5. Then, the arithmetic mean Aave1 of A1 to A5 shown in the following formula is obtained.

[0122] Aave1 = (A1 + A2 + A3 + A4 + A5) / 5

[0123] Using A1 to A5 and Aave1 obtained from the above formula, the dispersion degree (%) is obtained by the following formula.

[0124]

[0125] The above dispersion degree can be reduced by using fine particles with a smaller particle size of the dispersed fine particles, pulverizing to reduce the particle size, using a dispersant, etc. in the step of preparing the fine particle dispersion liquid to improve the dispersibility.

[0126] As described above, the present invention also provides a method for manufacturing a composite powder. That is, a method for manufacturing a composite powder is also provided, including: having a BET specific surface area of 5 m 2A step of adding particles of 1 g or more to a solution containing at least one raw material of a sulfide solid electrolyte to disperse the particles to obtain a particle dispersion; and a step of removing the solvent of the particle dispersion to obtain a composite powder of the particles and the raw material of the sulfide solid electrolyte.

[0127] <Manufacture of Sulfide Solid Electrolyte Composite>

[0128] In this manufacturing method, then, a sulfide solid electrolyte composite is obtained using the above composite powder (Step S3). As described above, the sulfide solid electrolyte composite refers to a composite of a sulfide solid electrolyte and particles, and the particles exist in a state of being dispersed in the sulfide solid electrolyte. In other words, the particles exist with a relatively high degree of homogeneity in the sulfide solid electrolyte.

[0129] In the above Step S1, when the solution to which particles are added does not contain all the raw materials of the sulfide solid electrolyte that constitutes the sulfide solid electrolyte composite finally obtained by this manufacturing method, in Step S3, in addition to using the above composite powder, a raw material of the sulfide solid electrolyte that is not contained in the above solution can also be used to manufacture the sulfide solid electrolyte composite. As the raw material of the sulfide solid electrolyte used in this case, the same raw materials as those described in the item of Step S1 can be used, but among them, from the viewpoints of easily adjusting the composition of the sulfide solid electrolyte and easily producing a sulfide solid electrolyte with good quality, substances containing a phosphorus element (P) such as phosphorus sulfide, lithium compounds such as lithium sulfide, and lithium halides such as lithium chloride are preferred.

[0130] As a method of obtaining a sulfide solid electrolyte composite using the above composite powder, methods using a solid-phase method as shown in Figure 2 and methods using a melting method as shown in Figure 3 can be cited. Hereinafter, the method using the solid-phase method and the method using the melting method will be described separately.

[0131] (Solid-phase method)

[0132] In the solid-phase method, first, a raw material of a sulfide solid electrolyte is added to the above composite powder and mixed as needed.

[0133] The mixing can be carried out by a conventionally known method, but mechanical grinding for mixing is preferred. In the case of using a mechanical grinding method using a ball mill, a rotating ball mill that imparts a rotational motion to the container, a vibration ball mill that imparts a vibration motion, a planetary ball mill that imparts a revolution and a rotational motion, a bead mill, a grinder (registered trademark), etc. can be cited. Among them, a planetary ball mill and a bead mill with higher mixing force and crushing force are preferred.

[0134] The ball mill can be used for dry mixing or wet mixing with a dispersion medium. However, from the perspective of efficiently transferring energy, dry mixing is preferred.

[0135] Through the above mixing, the raw materials are mixed to form a raw material mixture. This raw material mixture becomes the precursor of the sulfide solid electrolyte. The above precursor can be a homogeneous amorphous intermediate compound that has been amorphized by adopting mixing conditions much stricter than in the past. An amorphous intermediate compound means that no XRD peaks from the raw materials are observed.

[0136] In addition, according to requirements, a pulverizing process and a heat treatment process can be further included.

[0137] Either wet pulverization or dry pulverization can be used in the pulverizing process.

[0138] Preferably, through the pulverizing process, the average particle size of the sulfide solid electrolyte composite is 1 to 100 μm. Here, the average particle size refers to the median particle size (D50) of the particle size at which 50% by volume of the particles is below this value, which is obtained by measuring the particle size distribution using a particle size distribution meter based on the laser diffraction method and according to the obtained volume-based particle size distribution diagram.

[0139] The purpose of the heat treatment process is to improve the homogeneity and stabilize the quality of the sulfide solid electrolyte composite.

[0140] When heat-treating the obtained sulfide solid electrolyte composite, although the heat treatment temperature varies depending on the composition of the sulfide solid electrolyte composite, for example, it is preferably 200 to 600 °C, more preferably 350 to 500 °C, further preferably 380 to 460 °C, and particularly preferably 400 to 450 °C. Here, from the perspective of homogenization and quality stabilization of the sulfide solid electrolyte, the heat treatment temperature is preferably 200 °C or higher, more preferably 350 °C or higher, further preferably 380 °C or higher, and particularly preferably 400 °C or higher. In addition, from the perspective of preventing sintering between particles, it is preferably 600 °C or lower, more preferably 500 °C or lower, further preferably 460 °C or lower, and particularly preferably 450 °C or lower.

[0141] When heat-treating a sulfide solid electrolyte composite, although the heating time varies depending on the composition of the sulfide solid electrolyte composite, for example, it is preferably 10 minutes to 10 hours, more preferably 30 minutes to 9.5 hours, still more preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours. Here, from the viewpoints of homogenization and quality stabilization of the sulfide solid electrolyte composite, the heating time is preferably 10 minutes or more, more preferably 30 minutes or more, still more preferably 45 minutes or more, and particularly preferably 1 hour or more. In addition, from the viewpoint of manufacturing cost, the heating time is preferably 10 hours or less, more preferably 9.5 hours or less, still more preferably 9 hours or less.

[0142] When heat-treating a sulfide solid electrolyte composite, the atmosphere other than the SO2 concentration during the heat treatment is preferably an inert atmosphere. Examples of the inert atmosphere include a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, etc.

[0143] The dew point during the above heat treatment is preferably -20°C or lower. The lower limit is not particularly limited, but is usually around -80°C. The oxygen concentration is preferably 1000 volume ppm or lower.

[0144] (Melt method)

[0145] In the melt method, first, a sulfide solid electrolyte raw material is added to the above composite powder and mixed as needed to obtain a raw material mixture. The mixing can be carried out, for example, by mixing using a mortar, mixing using a medium such as a planetary ball mill, a rod mill, a powder blender, or a non-medium mixing such as pneumatic mixing.

[0146] Next, the raw material mixture obtained above is heated to obtain a melt.

[0147] There is no particular limitation on the specific method of heating and melting the raw material mixture. For example, the raw material mixture is placed in a heat-resistant container and heated in a heating furnace. The raw material mixture can also be sealed in a heat-resistant container. In addition, melting can also be carried out in an atmosphere containing a sulfur element. Examples of the atmosphere containing a sulfur element include a mixed gas atmosphere of a sulfur-containing gas such as sulfur gas, hydrogen sulfide gas, sulfur dioxide gas, etc. and an inert gas.

[0148] As the heat-resistant container, a heat-resistant container made of carbon, a heat-resistant container containing oxides such as quartz, quartz glass, borosilicate glass, aluminosilicate glass, alumina, zirconia, mullite, etc., a heat-resistant container containing nitrides such as silicon nitride, boron nitride, etc., a heat-resistant container containing carbides such as silicon carbide, etc. can be used. In addition, these heat-resistant containers can be formed with the above materials as the main body, or can be containers formed with layers of carbon, oxides, nitrides, carbides, etc. such as a quartz tube coated with carbon.

[0149] When heating and melting the raw material mixture, the heating temperature will vary depending on the raw materials used and the composition of the raw material mixture. However, for example, it is preferably 550 to 1000 °C, more preferably 600 to 950 °C, still more preferably 630 to 900 °C, and particularly preferably 650 to 800 °C. Here, from the viewpoints of improving the meltability of the raw materials and homogenizing the melt in a short time, the heating temperature is preferably 550 °C or higher, more preferably 600 °C or higher, still more preferably 630 °C or higher, and particularly preferably 650 °C or higher. In addition, from the viewpoints of suppressing deterioration caused by heating of the components, suppressing compositional deviation caused by volatilization of the components, and suppressing decomposition, the heating temperature is preferably 1000 °C or lower, more preferably 950 °C or lower, still more preferably 900 °C or lower, and particularly preferably 800 °C or lower.

[0150] Although the heating and melting time also varies depending on the scale, it is preferably 10 minutes to 10 hours, more preferably 30 minutes to 9.5 hours, still more preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours. Here, from the viewpoint of enabling the reaction to proceed well, the heating and melting time is preferably 10 minutes or longer, more preferably 30 minutes or longer, still more preferably 45 minutes or longer, and particularly preferably 1 hour or longer. In addition, from the viewpoint of productivity, the heating and melting time is preferably 10 hours or shorter, more preferably 9.5 hours or shorter, still more preferably 9 hours or shorter.

[0151] The pressure during heating and melting is not particularly limited. For example, it is preferably normal pressure or slightly increased pressure, and more preferably normal pressure.

[0152] The dew point during heating and melting is preferably -20 °C or lower. The lower limit is not particularly limited, but is usually around -80 °C. The oxygen concentration is preferably 1000 volume ppm or lower.

[0153] It can be confirmed that the melt is completely dissolved by the absence of peaks from crystals in high-temperature X-ray diffraction measurement.

[0154] Next, the obtained melt is cooled to precipitate crystals. The crystals obtained by precipitation become a sulfide solid electrolyte complex.

[0155] The cooling can be carried out by a known method, and this method is not particularly limited. As a more specific method of cooling, for example, there can be mentioned a method of flowing the melt onto a plate-like body such as made of carbon and cooling it; a method of flowing into a narrow gap and thinly forming it, represented by the twin-roll method; a gas atomization method, etc.

[0156] The cooling rate is preferably 0.1 to 10000 °C / second, more preferably 0.5 to 5000 °C / second, and still more preferably 1 to 1000 °C / second. Here, from the viewpoints of improving compositional homogeneity and suppressing quality dispersion, the cooling rate is preferably 0.1 °C / second or more, more preferably 0.5 °C / second or more, and still more preferably 1 °C / second or more. In addition, the upper limit value of the cooling rate is not particularly limited, but considering the cooling rate of the twin roll, which is generally regarded as the fastest quenching rate, the upper limit value is 10 7 °C / second or less. From the viewpoint of actual production, the cooling rate is more preferably 10000 °C / second or less, still more preferably 5000 °C / second or less, and even more preferably 1000 °C / second.

[0157] The atmosphere during cooling is the same as that during heating and melting, and a low moisture content and non-reactive atmosphere are preferred.

[0158] According to requirements, a pulverization step and a heat treatment step may be further included.

[0159] In this case, the pulverization step and the heat treatment step are the same as the pulverization step and the heat treatment step in the solid phase method, and the preferred methods are also the same. It should be noted that in the case of using an atomization method that can simultaneously perform cooling and powdering as the cooling method, it also serves as the pulverization step.

[0160] <Sulfide solid electrolyte composite>

[0161] The sulfide solid electrolyte composite obtained by this manufacturing method is a composite in which fine particles are dispersed in the sulfide solid electrolyte. In other words, it is a composite in which fine particles are present with high homogeneity in the sulfide solid electrolyte. The crystal structure of the sulfide solid electrolyte in the sulfide solid electrolyte composite (hereinafter, also simply referred to as the sulfide solid electrolyte) is not particularly limited. For example, sulfide solid electrolytes such as Li7P3S 11 etc., called LPS series, having a crystal structure containing Li element, P element and S element, Li 10 GeP2S 12 etc., called LGPS series, having a crystal structure containing Li element, Ge element, P element and S element, sulfide solid electrolytes having a thiogermanate-type crystal structure containing Li element, P element, S element and Ha element, powders of sulfide solid electrolytes composed of Li-P-S-Ha-based crystallized glass, etc.

[0162] The above may be a sulfide solid electrolyte including a crystalline phase and an amorphous phase.

[0163] Among the above, the argyrodite-type crystal structure refers to the crystal structure possessed by a compound group from a mineral represented by the compositional formula Ag8GeS6. In addition, the sulfide solid electrolyte is not limited to the above crystal structure, and furthermore, some elements can be replaced with other elements.

[0164] When the sulfide solid electrolyte has an argyrodite-type crystal structure, as the Ha element, an element containing at least one selected from Cl, Br, and I is more preferably included, and an element containing two or more kinds is further preferably included.

[0165] In addition, the sulfide solid electrolyte further preferably includes at least one of Cl and Br as the Ha element, and further preferably includes both Cl and Br.

[0166] The argyrodite-type crystal structure is preferably selected as the above structure. As the compositional formula, in terms of Li α PS β Ha γ it is represented, and preferably satisfies the relationships of 5 ≤ α ≤ 7, 4 ≤ β ≤ 6, and 1.3 ≤ γ ≤ 2. The above element ratios more preferably satisfy the relationships of 5.1 < α < 6.3, 4 < β < 5.3, and 1.4 ≤ γ ≤ 1.9, and further preferably satisfy the relationships of 5.2 < α < 6.2, 4.1 < β < 5.2, and 1.5 ≤ γ ≤ 1.8.

[0167] That is, α is preferably 5 or more, more preferably more than 5.1, further preferably more than 5.2, and preferably 7 or less, more preferably less than 6.3, further preferably less than 6.2. β is preferably 4 or more, more preferably more than 4, further preferably more than 4.1, and preferably 6 or less, more preferably less than 5.3, further preferably less than 5.2. γ is preferably 1.3 or more, more preferably 1.4 or more, further preferably 1.5 or more, and preferably 2 or less, more preferably 1.9 or less, further preferably 1.8 or less.

[0168] In the argyrodite-type crystal structure, a part of the S element can be replaced with the Ha element, the O element, and furthermore, can be replaced with Se, Te, BH4, CN, etc. In addition, a part of the P element can be replaced with the Si element, the Al element, the Sn element, the In element, the Cu element, the Sb element, the Ge element, etc.

[0169] As described above, the sulfide solid electrolyte composite is a composite in which fine particles are dispersed in the sulfide solid electrolyte. That is, for the sulfide solid electrolyte composite, the fine particles exist with relatively high homogeneity in the sulfide solid electrolyte.

[0170] The homogeneity of the sulfide solid electrolyte composite can be evaluated by the dispersion degree of the fine particles relative to the sulfide solid electrolyte composite. The above-mentioned dispersion degree is preferably 15% or less, more preferably 12% or less, and further preferably 10% or less. There is no particular limitation on the lower limit of the dispersion degree, but it is usually 3% or more.

[0171] The dispersion degree of the fine particles relative to the sulfide solid electrolyte composite refers to the dispersion degree obtained by the following method. That is, from 5 samples of the sulfide solid electrolyte composite made from the composite powder in which the fine particles are dispersed and produced in the same batch, first, 0.1 g of each sulfide solid electrolyte composite is collected, and it is heated and decomposed and dissolved using nitric acid, sulfuric acid, and hydrofluoric acid (nitric acid + sulfuric acid + hydrofluoric acid). The metal elements of the fine particles in the obtained liquid are quantified relative to the sulfide solid electrolyte composite using ICP (inductively coupled plasma) optical emission spectroscopy. When there is a residue in the dissolved liquid, by adjusting the amount, ratio, dissolution time, and temperature of the acid, the measurement is carried out in a state where no residue remains in the dissolved liquid. And for the residue, it can be dissolved, quantified, and totaled separately using caustic soda, etc.

[0172] Let the content (mass %) of the metal elements of the fine particles in the 5 samples obtained under the above conditions relative to the sulfide solid electrolyte composite be A6 to A10. Then, the arithmetic average value Aave2 of A6 to A10 shown in the following formula is obtained.

[0173] Aave2 = (A6 + A7 + A8 + A9 + A10) / 5

[0174] Using A6 to A10 and Aave2 obtained in the above formula, the dispersion degree (%) is obtained using the following formula.

[0175] [Mathematical formula 4]

[0176]

[0177] The above-mentioned dispersion degree can be reduced by using fine particles with a smaller particle size of the dispersed fine particles, reducing the particle size by pulverization, using a dispersant, etc. to improve the dispersibility in the process of preparing the fine particle dispersion liquid.

[0178] It should be noted that the present invention is not limited to the above-mentioned respective embodiments, and various modification examples can be adopted within the scope of the present invention. For example, the present invention is not limited to the above-mentioned embodiments, and appropriate deformation and improvement can be carried out. In addition, the material, shape, size, quantity, and arrangement position, etc. of each constituent element in the above-mentioned embodiments can be arbitrary as long as the present invention can be realized, and they are not limited.

[0179] As described above, the following matters are disclosed in this specification.

[0180] [1] A method for manufacturing a sulfide solid electrolyte composite, comprising:

[0181] adding fine particles with a BET specific surface area of 5 m 2 / g or more to a solution containing at least one sulfide solid electrolyte raw material, and dispersing the fine particles to obtain a fine particle dispersion liquid;

[0182] removing the solvent of the fine particle dispersion liquid to obtain a composite powder of the fine particles and the sulfide solid electrolyte raw material; and

[0183] using the composite powder to obtain a sulfide solid electrolyte composite.

[0184] [2] The method for manufacturing a sulfide solid electrolyte composite according to [1] above, wherein the sulfide solid electrolyte composite is obtained by using the composite powder and through a solid-phase method.

[0185] [3] The method for manufacturing a sulfide solid electrolyte composite according to [1] above, wherein the sulfide solid electrolyte composite is obtained by using the composite powder and through a melting method.

[0186] [4] The method for manufacturing a sulfide solid electrolyte composite according to any one of [1] to [3] above, wherein the fine particles are oxides.

[0187] [5] The method for manufacturing a sulfide solid electrolyte composite according to [4] above, wherein the oxide is at least one of SiO2, Al2O3, and TiO2 oxides.

[0188] [6] The method for manufacturing a sulfide solid electrolyte composite according to any one of [1] to [3] above, wherein the fine particles are nitrides.

[0189] [7] The method for manufacturing a sulfide solid electrolyte composite according to [6] above, wherein the nitride is at least one of AlN, Si3N4, and BN nitrides.

[0190] [8] The method for manufacturing a sulfide solid electrolyte composite according to any one of [1] to [7] above, wherein the sulfide solid electrolyte raw material is lithium halide.

[0191] [9] The method for manufacturing a sulfide solid electrolyte composite according to [8] above, wherein the lithium halide is lithium bromide.

[0192]

[10] The method for manufacturing a sulfide solid electrolyte composite according to any one of [1] to [7] above, wherein the sulfide solid electrolyte raw material is lithium hydroxide.

[0193]

[11] The method for manufacturing a sulfide solid electrolyte composite according to any one of [1] to

[10] above, wherein an alkali metal sulfide is added to the fine particle dispersion liquid and then the solvent is removed.

[12] The method for manufacturing a sulfide solid electrolyte composite according to

[11] above, wherein the alkali metal sulfide is lithium sulfide.

[0194]

[13] The method for manufacturing a sulfide solid electrolyte composite according to any one of [1] to

[10] above, wherein hydrogen sulfide is introduced into the fine particle dispersion liquid and then the solvent is removed.

[0195]

[14] The method for manufacturing a sulfide solid electrolyte composite according to any one of [1] to

[10] above, wherein the composite powder after reacting with hydrogen sulfide is used to obtain the sulfide solid electrolyte composite.

[0196]

[15] A sulfide solid electrolyte composite comprising fine particles having a BET specific surface area of 5 m 2 / g or more, and the dispersion degree of the fine particles with respect to the sulfide solid electrolyte composite is 15% or less.

[0197]

[16] A method for manufacturing a composite powder, comprising:

[0198] adding fine particles having a BET specific surface area of 5 m 2 / g or more to a solution containing at least one sulfide solid electrolyte raw material, and dispersing the fine particles to obtain a fine particle dispersion liquid; and <U+

[0199] removing the solvent of the fine particle dispersion liquid to obtain a composite powder of the fine particles and the sulfide solid electrolyte raw material.

[0200] Examples

[0201] Examples are given below to specifically illustrate the present invention, but the present invention is not limited to these examples. Examples 1 to 8, 10 to 17 are examples, and Examples 9, 18 are comparative examples.

[0202] <Manufacture of Sulfide Solid Electrolyte Composite>

[0203] (Example 1)

[0204] First, 117.5 g of lithium bromide, which is a raw material for the sulfide solid electrolyte, was put into 330.8 g of water to prepare an aqueous lithium bromide solution. Next, 10.1 g of silicon dioxide (SiO2) nanoparticles (product name: AEROSIL (registered trademark) OX50, manufactured by Nippon AEROSIL Co., Ltd., BET specific surface area: 50 m 2 / g, primary particle size: 40 nm), as fine particles, were put into the aqueous lithium bromide solution, and ultrasonic dispersion was carried out for 1 minute using an ultrasonic homogenizer. Thus, an aqueous lithium bromide solution (fine particle dispersion) in which silicon dioxide nanoparticles were dispersed was obtained.

[0205] Next, using a vibration drying device (product name VH type, manufactured by Chuo Kakoki Co., Ltd.), the aqueous lithium bromide solution in which silicon dioxide nanoparticles were dispersed was dried under reduced pressure and heated at a temperature of 160 °C and a pressure of 2 kPa to obtain lithium bromide in which silicon dioxide nanoparticles were dispersed. Further, it was pulverized using an agate mortar, and thus a lithium bromide powder (composite powder) in which silicon dioxide nanoparticles were dispersed was obtained.

[0206] Next, in a dry nitrogen atmosphere, according to the theoretical composition ratio in which Li 5.3 PS 4.2 Cl 0.8 Br 0.8 was 98 wt%, and SiO2 was 2 wt%, lithium sulfide powder (manufactured by Sigma, purity 99.98%), phosphorus pentasulfide powder (manufactured by Sigma, purity 99%), lithium chloride powder (manufactured by Sigma, purity 99.99%), and the lithium bromide powder in which silicon dioxide nanoparticles were dispersed prepared above were weighed. After mixing these in the same atmosphere using a mixer, a raw material mixture was obtained by further mixing using a planetary ball mill (manufactured by Ito Seisakusho Co., Ltd., LP-M2). The mixing using the planetary ball mill was carried out at 400 rpm for 20 hours using balls with a diameter of 10 mm. The obtained raw material mixture was put into a quartz sealed tube and heated and fired at 450 °C for 5 hours, and thus the sulfide solid electrolyte composite of Example 1 was obtained.

[0207] For the sulfide solid electrolyte composite of Example 1, lithium bromide powder (composite powder) in which silicon dioxide nanoparticles were dispersed, prepared from the same batch as above, was used to prepare a total of 5 samples.

[0208] (Example 2)

[0209] First, 50.0 g of lithium hydroxide monohydrate, which is a raw material for the sulfide solid electrolyte, was put into 330.8 g of water to prepare an aqueous lithium hydroxide solution. Next, 1.9 g of silica (SiO2) nanoparticles (product name: AEROSIL (registered trademark) OX50, manufactured by Nippon AEROSIL Co., Ltd., BET specific surface area: 50 m 2 / g, primary particle size: 40 nm), as fine particles, were put into the aqueous lithium hydroxide solution, and ultrasonic dispersion was carried out for 1 minute using an ultrasonic homogenizer. Thus, an aqueous lithium hydroxide solution in which silica nanoparticles were dispersed was obtained.

[0210] Next, a nozzle was inserted into the lithium hydroxide dispersion in which silica nanoparticles were dispersed, and hydrogen sulfide was passed through at 0.1 SLM while heating. While raising the temperature from 25 °C to 90 °C, hydrogen sulfide was reacted with lithium hydroxide to obtain an aqueous lithium sulfide solution (fine particle dispersion) in which silica nanoparticles were dispersed. And while passing hydrogen sulfide, the temperature was raised to discharge water, and finally the temperature was raised to 200 °C to obtain lithium sulfide (composite) in which silica nanoparticles were dispersed. Furthermore, it was pulverized using an agate mortar, and thus a lithium sulfide powder (composite powder) in which silica nanoparticles were dispersed was obtained.

[0211] Next, a raw material mixture was prepared in the same manner as in Example 1 and heated and fired, and thus a sulfide solid electrolyte composite of Example 2 was obtained.

[0212] A total of 5 samples of the sulfide solid electrolyte composite of Example 2 were also prepared.

[0213] (Example 3)

[0214] First, 50.0 g of lithium hydroxide monohydrate, which is a raw material for the sulfide solid electrolyte, was put into 330.8 g of water to prepare an aqueous lithium hydroxide solution. Next, 1.9 g of silica (SiO2) nanoparticles (product name: AEROSIL (registered trademark) OX50, manufactured by Nippon AEROSIL Co., Ltd., BET specific surface area: 50 m 2 / g, primary particle size: 40 nm), as fine particles, were put into the aqueous lithium hydroxide solution, and an ultrasonic homogenizer was used to carry out ultrasonic dispersion for 1 minute. Thus, an aqueous lithium hydroxide solution in which silica nanoparticles were dispersed was obtained.

[0215] Next, using a vibration drying device (product name VH type, manufactured by Chuo Kakoki Co., Ltd.), the aqueous lithium hydroxide solution in which silica nanoparticles were dispersed was dried under reduced pressure and heated at a temperature of 85 °C and a pressure of 2 kPa to obtain lithium hydroxide in which silica nanoparticles were dispersed, and then it was pulverized using an agate mortar, and thus a lithium hydroxide powder in which silica nanoparticles were dispersed was obtained.

[0216] Next, using a vibration drying device (product name: VH type, manufactured by Chuo Kakoki Co., Ltd.), while stirring lithium hydroxide powder in which silicon oxide nanoparticles are dispersed at a temperature of 200 °C and a pressure of 2 kPa, hydrogen sulfide gas was introduced to react lithium hydroxide with hydrogen sulfide to obtain lithium sulfide powder (composite powder) in which silicon oxide nanoparticles are dispersed. The obtained lithium sulfide powder in which silicon oxide nanoparticles are dispersed was pulverized using an agate mortar.

[0217] Next, a raw material mixture was prepared in the same manner as in Example 1 and heated and fired to obtain the sulfide solid electrolyte composite of Example 3.

[0218] A total of 5 samples of the sulfide solid electrolyte composite of Example 3 were also prepared.

[0219] (Example 4)

[0220] In Example 1, except that 10.1 g of alumina (Al2O3) nanoparticles (product name: AEROSIL (registered trademark) Alu C, manufactured by Nippon AEROSIL Co., Ltd., BET specific surface area: 100 m 2 / g, primary particle size: 13 nm) was used instead of 10.1 g of silicon oxide nanoparticles as the fine particles, the sulfide solid electrolyte composite of Example 4 was produced in the same manner as in Example 1.

[0221] A total of 5 samples of the sulfide solid electrolyte composite of Example 4 were also prepared.

[0222] (Example 5)

[0223] In Example 1, except that 10.1 g of titanium oxide (TiO2) nanoparticles (product name: AEROSIL (registered trademark) TiO2P25, manufactured by Nippon AEROSIL Co., Ltd., BET specific surface area: 50 m 2 / g, primary particle size: 21 nm) was used instead of 10.1 g of silicon oxide nanoparticles as the fine particles, the sulfide solid electrolyte composite of Example 5 was produced in the same manner as in Example 1.

[0224] A total of 5 samples of the sulfide solid electrolyte composite of Example 5 were also prepared.

[0225] (Example 6)

[0226] In Example 1, except that 10.1 g of aluminum nitride (AlN) particles (product name: NP-ALN-3, manufactured by EM Japan Co., Ltd., BET specific surface area: 5 m 2 / g, average particle size: 0.5 μm) was used instead of 10.1 g of silicon oxide nanoparticles as the fine particles, the sulfide solid electrolyte composite of Example 6 was produced in the same manner as in Example 1.

[0227] A total of five samples of the sulfide solid electrolyte composite of Example 6 were also prepared.

[0228] (Example 7)

[0229] In Example 7, except for using 10.1 g of silicon nitride (Si3N4) particles (product name: α-Si3N4, manufactured by Bae Industry Co., BET specific surface area: 13 m 2 / g, average particle size: 0.8 μm) instead of 10.1 g of silicon oxide nanoparticles as the fine particles, the sulfide solid electrolyte composite of Example 7 was prepared in the same manner as in Example 1.

[0230] A total of five samples of the sulfide solid electrolyte composite of Example 7 were also prepared.

[0231] (Example 8)

[0232] In Example 8, except for using 10.1 g of boron nitride (BN) particles (product name: NP-BN-3, manufactured by EM Japan Co., BET specific surface area: 6 m 2 / g, average particle size: 0.5 μm) instead of 10.1 g of silicon oxide nanoparticles as the fine particles, the sulfide solid electrolyte composite of Example 8 was prepared in the same manner as in Example 1.

[0233] A total of five samples of the sulfide solid electrolyte composite of Example 8 were also prepared.

[0234] (Example 9)

[0235] Weigh 117.5 g of lithium bromide (manufactured by Sigma) and 10.1 g of silicon oxide (SiO2) nanoparticles (product name: AEROSIL (registered trademark) OX50, manufactured by Nippon AEROSIL Co., BET specific surface area: 50 m 2 / g, primary particle size: 40 nm), put them into a 1000 mL sealed container, and mix them by shaking thoroughly for 30 minutes to obtain a mixed powder. Then, a raw material mixture was prepared in the same manner as in Example 1 and heated and fired to prepare the sulfide solid electrolyte composite of Example 9.

[0236] A total of five samples of the sulfide solid electrolyte composite of Example 9 were also prepared.

[0237] (Examples 10 to 17)

[0238] In Examples 1 to 9, except for preparing the sulfide solid electrolyte composite by the melting method instead of the solid-phase method, the sulfide solid electrolyte composites of Examples 10 to 17 were prepared in the same manner as in Examples 1 to 9.

[0239] That is, as the melting method, first, in a dry nitrogen atmosphere, according to Li 5.3 PS 4.2 Cl 0.8 Br 0.8 to a theoretical composition ratio of 98 wt% and SiO2 to 2 wt%, weigh lithium sulfide powder (manufactured by Sigma, purity 99.98%), phosphorus pentasulfide powder (manufactured by Sigma, purity 99%), lithium chloride powder (manufactured by Sigma, purity 99.99%) as raw materials for the sulfide solid electrolyte, and the lithium bromide powder dispersed with silica nanoparticles prepared above. After mixing these in the same atmosphere using a mixer (mixing device), a raw material mixture is obtained.

[0240] Next, put the obtained raw material mixture into a heat-resistant container and heat-melt it for 0.5 hours under the conditions of a pressure of 1 atm and a temperature of 750 °C. At this time, elemental sulfur is heated at a temperature of 350 °C to obtain sulfur gas, and the sulfur gas is supplied in such a way that while using N2 as a carrier gas to accompany it, the partial pressure of the sulfur gas becomes 0.1 atm, obtaining a gas atmosphere containing sulfur element, and heat-melting is carried out in this gas atmosphere, thereby introducing sulfur into the melt. The content of sulfur gas in the gas atmosphere containing sulfur element is 0.1 vol%.

[0241] Then, cool at a cooling rate of 1 - 1000 °C / sec to obtain a solid as a sulfide solid electrolyte containing an amorphous phase and a thiogermanate-type crystal phase. Next, crystallize this solid in a nitrogen atmosphere at 450 °C for 1 hour to obtain a sulfide solid electrolyte composite containing a sulfide solid electrolyte with crystals containing the thiogermanate type.

[0242] A total of 5 samples of the sulfide solid electrolyte composites of Examples 10 - 17 were also prepared.

[0243] (Example 18)

[0244] Weigh 117.5 g of lithium sulfide (manufactured by Sigma) and 10.1 g of silica (SiO2) nanoparticle microparticles (product name: AEROSIL (registered trademark) OX50, manufactured by Nippon AEROSIL Co., Ltd., BET specific surface area: 50 m 2 / g, primary particle size: 40 nm), put them into a 1000 mL closed container, and mix them by shaking thoroughly for 30 minutes to obtain a mixed powder. Next, use the same melting method as in Examples 10 - 17 to prepare the sulfide solid electrolyte composite of Example 18.

[0245] A total of 5 samples of the sulfide solid electrolyte composite of Example 18 were also prepared.

[0246] <Evaluation of homogeneity>

[0247] (Dispersion of Particles in Composite Powder)

[0248] The dispersion of particles relative to the composite powder is determined by the following method.

[0249] First, collect 0.1 g of the composite powder obtained in each case at 5 points, decompose and dissolve it by heating with nitric acid, sulfuric acid, and hydrofluoric acid (nitric acid + sulfuric acid + hydrofluoric acid), and use the obtained liquid with an ICP (inductively coupled plasma) optical emission spectrometer (Agilent 5800 manufactured by Agilent Technologies) to quantify the metal elements of the particles relative to the sulfide solid electrolyte composite. That is, when the particles are SiO2 or Si3N4, Si is quantified; when they are AlN, Al is quantified; when they are TiO2, Ti is quantified; when they are BN, B is quantified. In addition, when the particles are Al2O3 or AlN, there are residues in the dissolved liquid, so caustic soda is additionally used for dissolution, quantification, and summation to obtain the total amount.

[0250] Let the contents (mass %) of the metal elements of the particles at the 5 points obtained under the above conditions relative to the composite powder be A1 to A5. Then, calculate the arithmetic mean Aave1 of A1 to A5 shown in the following formula.

[0251] Aave1 = (A1 + A2 + A3 + A4 + A5) / 5

[0252] Using A1 to A5 and Aave1 obtained from the above formula, calculate the dispersion (%) of the particles in the composite powder using the following formula.

[0253]

[0254] The results are shown in Table 1 and Table 2.

[0255] (Dispersion of Particles in Sulfide Solid Electrolyte Composite)

[0256] The dispersion of particles in the sulfide solid electrolyte composite is determined by the following method.

[0257] First, 0.1 g was collected from each of the 5 samples of the sulfide solid electrolyte complex obtained in each case, and heated and decomposed and dissolved using nitric acid, sulfuric acid, and hydrofluoric acid (nitric acid + sulfuric acid + hydrofluoric acid). The resulting liquid was used to quantify the metal elements of the fine particles relative to the sulfide solid electrolyte complex using an ICP (inductively coupled plasma) optical emission spectrometer (Agilent 5800 manufactured by Agilent Technologies). That is, Si was quantified when the fine particles were SiO2 or Si3N4, Al was quantified when they were AlN, Ti was quantified when they were TiO2, and B was quantified when they were BN. In addition, when the fine particles were Al2O3 or AlN, there were residues in the dissolved liquid, so caustic soda was used for dissolution, quantification, and summation to obtain the total amount.

[0258] Let the contents (mass %) of the metal elements of the fine particles at the 5 points obtained under the above conditions relative to the sulfide solid electrolyte complex be A6 to A10. Then, the arithmetic mean Aave2 of A6 to A10 shown in the following formula was calculated.

[0259] Aave2 = (A6 + A7 + A8 + A9 + A10) / 5

[0260] Using A6 to A10 and Aave2 obtained from the above formula, the dispersion (%) of the sulfide solid electrolyte complex was calculated using the following formula.

[0261]

[0262] The dispersion of the sulfide solid electrolyte complex was evaluated according to the following criteria.

[0263] 〇: The dispersion is 15% or less

[0264] ×: The dispersion exceeds 15%

[0265] The results are shown in Table 1 and Table 2.

[0266] (Operability)

[0267] In the manufacture of the sulfide solid electrolyte complex, the operability was evaluated according to the following criteria.

[0268] ○: Does not meet all of the following items.

[0269] ×: Meets at least one of the following items.

[0270] <Items>

[0271] · When weighing and charging into the container of the mixing device, the fine particles fly due to the air flow and generate dust

[0272] · Adsorption of fine particles caused by static electricity onto the container wall surface of the mixing device, etc.

[0273] · When mixing using the mixing device, the fine particles fly in the upper part.

[0274] The results are shown in Table 1 and Table 2.

[0275] Table 1

[0276]

[0277] Table 2

[0278]

[0279] In Examples 1 to 8 and Examples 10 to 17, since fine particles with a BET specific surface area of 5 m 2 / g or more were dispersed in an aqueous solution, the dispersion degree of the fine particles in the finally obtained sulfide solid electrolyte composite was small and the homogeneity was excellent. In addition, since the fine particles were dispersed in an aqueous solution for production, the fine particles did not scatter and the operability during production was excellent.

[0280] On the other hand, in Example 9 and Example 18, deviations occurred during mixing when producing the composite powder, and also during mixing for manufacturing the sulfide electrolyte composite due to scattering, adsorption onto the wall surface, etc., so the dispersion degree of the fine particles in the finally obtained sulfide solid electrolyte composite was large and the homogeneity was poor. In addition, the operability during production was also poor.

[0281] As described above, various embodiments have been described with reference to the attached Figure 1 drawings. Needless to say, the present invention is not limited to the above examples. It is clear that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and they naturally also belong to the technical scope of the present invention. In addition, within the scope not departing from the gist of the invention, the constituent elements of the above embodiments can be arbitrarily combined.

[0282] It should be noted that this application is based on a Japanese patent application (Japanese Patent Application No. 2022-212573) filed on December 28, 2022, the content of which is incorporated herein by reference.

Claims

1. A method for manufacturing a sulfide solid electrolyte composite, comprising: Adding fine particles with a BET specific surface area of 5 m 2 / g or more to a solution containing at least one sulfide solid electrolyte raw material to disperse the fine particles, thereby obtaining a fine particle dispersion liquid; a step of removing the solvent from the fine particle dispersion liquid to obtain a composite powder of the fine particles and the sulfide solid electrolyte raw material; and a step of obtaining a sulfide solid electrolyte composite using the composite powder.

2. The manufacturing method of the sulfide solid electrolyte composite according to claim 1, wherein, The sulfide solid electrolyte composite is obtained by a solid phase method using the composite powder.

3. The method for manufacturing a sulfide solid electrolyte composite according to claim 1, wherein, The sulfide solid electrolyte composite is obtained by a melting method using the composite powder.

4. The method for manufacturing a sulfide solid electrolyte composite according to claim 1, wherein, The fine particles are oxides.

5. The manufacturing method of the sulfide solid electrolyte composite according to claim 4, wherein, The oxide is at least one of SiO2, Al2O3, and TiO2.

6. The manufacturing method of the sulfide solid electrolyte composite according to claim 1, wherein, The fine particles are nitrides.

7. The manufacturing method of the sulfide solid electrolyte composite according to claim 6, wherein, The nitride is at least one of AlN, Si3N4, and BN.

8. The manufacturing method of the sulfide solid electrolyte composite according to claim 1, wherein, The sulfide solid electrolyte raw material is lithium halide.

9. The method for manufacturing a sulfide solid electrolyte composite according to claim 8, wherein, The lithium halide is lithium bromide.

10. The manufacturing method of the sulfide solid electrolyte composite according to claim 1, wherein, The sulfide solid electrolyte raw material is lithium hydroxide.

11. The method for manufacturing a sulfide solid electrolyte composite according to claim 1, wherein, An alkali metal sulfide is added to the fine particle dispersion liquid, and then the solvent is removed.

12. The method for manufacturing a sulfide solid electrolyte composite according to claim 11, wherein, The alkali metal sulfide is lithium sulfide.

13. The manufacturing method of the sulfide solid electrolyte composite according to claim 1, wherein, Hydrogen sulfide is introduced into the fine particle dispersion liquid, and then the solvent is removed.

14. The method for manufacturing a sulfide solid electrolyte composite according to claim 1, wherein, A sulfide solid electrolyte composite is obtained using the composite powder after reaction with hydrogen sulfide.

15. A sulfide solid electrolyte composite, which contains fine particles with a BET specific surface area of 5 m 2 / g or more, and the dispersion degree of the fine particles relative to the sulfide solid electrolyte composite is 15% or less.

16. A method for manufacturing a composite powder, comprising: Adding particles with a BET specific surface area of 5 m 2 / g or more to a solution containing at least one sulfide solid electrolyte raw material to disperse the particles to obtain a particle dispersion; and a step of removing the solvent from the fine particle dispersion liquid to obtain a composite powder of the fine particles and the sulfide solid electrolyte raw material.

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