Method for producing sulfide solid electrolyte powder

Abstract

The present invention relates to a method for producing a sulfide solid electrolyte, comprising: mixing raw materials to obtain a raw material mixture; synthesizing a powder of at least one of a sulfide solid electrolyte powder and a precursor of the sulfide solid electrolyte powder from the raw material mixture; and performing a heat treatment on the powder, wherein the heat treatment is performed in an atmosphere in which the SO2 concentration is 1-1000 ppm by volume.

Description

Technical Field

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

[0002] Lithium-ion secondary batteries are widely used in portable electronic devices such as mobile phones and laptop computers.

[0003] In the past, liquid electrolytes were used in lithium-ion secondary batteries. On the other hand, all-solid-state lithium-ion secondary batteries using solid electrolytes as their electrolytes have attracted much attention in recent years due to their potential for improved safety, high-speed charging and discharging, and miniaturization of the housing.

[0004] Examples of solid electrolytes used in all-solid-state lithium-ion secondary batteries include sulfide solid electrolytes.

[0005] Examples of methods for synthesizing a sulfide solid electrolyte include a method of mechanically grinding a raw material mixture and then calcining it (solid phase reaction method), and a method of heating and melting the raw material mixture to prepare a melt, and then cooling and solidifying the melt (melting method).

[0006] As an example of a sulfide solid electrolyte, a sulfide solid electrolyte of the argyrodite type is disclosed in Patent Document 1. This sulfide solid electrolyte has a cubic crystal structure belonging to the space group F-43m and contains the composition formula: Li 7-x PS 6-X Ha X (Ha is Cl or Br) (x = 0.2 to 1.8) and L * a * b * The brightness L value of the color system is 60.0 or higher. The purpose is to improve the charge and discharge efficiency and cycle characteristics by increasing the lithium ion conductivity and reducing the electron conductivity.

[0007] Patent Document 2 discloses a sulfide solid electrolyte comprising lithium, phosphorus, sulfur, and two or more elements X selected from halogen elements, and having an argyrodite-type crystal structure in which the molar ratio b of sulfur to phosphorus (S / P) and the molar ratio c of element X to phosphorus (X / P) satisfy the relationship 0.23 < c / b < 0.57. This electrolyte is intended to achieve higher ionic conductivity and suppress hydrogen sulfide generation.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2015 / 012042

[0011] Patent Document 2: International Publication No. 2018 / 047565 Summary of the Invention

[0012] When such a sulfide solid electrolyte is actually used in lithium-ion secondary batteries, it must be prepared as a fine powder with a particle size of several μm or less. Therefore, after obtaining the powdered sulfide solid electrolyte, i.e., the sulfide solid electrolyte powder, it needs to be further finely ground.

[0013] On the other hand, the resulting sulfide solid electrolyte powder is preferably subjected to a heat treatment for the purpose of homogenizing the crystal structure and stabilizing the quality of the solid electrolyte. However, this heat treatment can cause agglomeration or sintering of the powder. Agglomeration is particularly prone to occur at temperatures lower than the sintering temperature. Therefore, before finely pulverizing to form the fine powder, the agglomerated sulfide solid electrolyte powder must be pulverized again, placing a heavy burden on the pulverization process from heat treatment to fine pulverization.

[0014] Therefore, an object of the present invention is to provide a method for producing a sulfide solid electrolyte powder capable of suppressing aggregation of particles during heat treatment.

[0015] The present inventors speculate that the aggregation of particles during heat treatment is caused by the sulfur released from the particle surface acting as a binder to connect the particles together. Based on this speculation, the inventors conducted research and found that by converting the released sulfur into SO2 or SO x By removing the form of , the above-mentioned problems can be solved, thereby completing the present invention.

[0016] That is, the present invention relates to the following [1] to

[10] .

[0017] [1] A method for producing sulfide solid electrolyte powder, comprising:

[0018] mixing raw materials to obtain a raw material mixture;

[0019] synthesizing a powder of at least one of a sulfide powder and a sulfide precursor powder from the raw material mixture; and

[0020] The powder is subjected to heat treatment.

[0021] The above-mentioned heat treatment is performed in an atmosphere having a SO2 concentration of 1 to 1000 ppm by volume.

[0022] [2] The method for producing a sulfide solid electrolyte powder according to [1] above, wherein the powder is placed in a container during the heat treatment,

[0023] The above container satisfies the relationship 2a>b when the longer side of the bottom is a and the height is b.

[0024] [3] The method for producing a sulfide solid electrolyte powder according to [2] above, wherein the surface roughness Ra of the container is 0.1 to 30 μm.

[0025] [4] The method for producing a sulfide solid electrolyte powder according to [2] or [3] above, wherein the material of the container contains at least one of aluminum and carbon as an element.

[0026] [5] The method for producing a sulfide solid electrolyte powder according to any one of [2] to [4] above, wherein the porosity of the container is 1% to 50%.

[0027] [6] The method for producing a sulfide solid electrolyte powder according to any one of [1] to [5] above, wherein the average particle size of the powder is 1 to 100 μm.

[0028] [7] The method for producing a sulfide solid electrolyte powder according to any one of [1] to [6] above, wherein, in the synthesis, a melt obtained by heating the raw material mixture is cooled to obtain the powder containing the sulfide powder.

[0029] [8] The method for producing a sulfide solid electrolyte powder according to any one of [1] to [7] above, wherein, in the synthesis, the powder comprising the sulfide precursor powder is obtained by mechanically grinding the raw material mixture.

[0030] [9] The method for producing a sulfide solid electrolyte powder according to any one of [1] to [8] above, wherein the raw material contains Li, P, S, and Ha,

[0031] The obtained sulfide solid electrolyte powder has an argyrodite-type crystal structure.

[0032]

[10] The method for producing a sulfide solid electrolyte powder according to [9] above, wherein the heat treatment is performed at a temperature of 200 to 600°C.

[0033] The production method according to the present invention can suppress aggregation of particles during heat treatment. Therefore, when the sulfide solid electrolyte powder is used in a solid electrolyte layer of a lithium-ion secondary battery, etc., the burden of the secondary pulverization step before the fine pulverization step can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1This is a flowchart showing a method for producing a sulfide solid electrolyte according to this embodiment.

[0035] Figure 2 This is a flowchart showing one aspect of the method for producing a sulfide solid electrolyte according to the present embodiment.

[0036] Figure 3 This is a flowchart showing one aspect of the method for producing a sulfide solid electrolyte according to the present embodiment. DETAILED DESCRIPTION

[0037] The present invention is described in detail below, but the present invention is not limited to the following embodiments and can be arbitrarily deformed and implemented without departing from the scope of the present invention. In addition, the " to " indicating a numerical range is used to include the numerical values ​​recorded before and after it as the lower limit and upper limit.

[0038] [Method for producing sulfide solid electrolyte powder]

[0039] like Figure 1 As shown, the method for producing sulfide solid electrolyte powder according to the present embodiment (hereinafter also referred to as "this production method") includes the following steps S1 to S3 in order.

[0040] Step S1 is a step of mixing raw materials to obtain a raw material mixture.

[0041] Step S2 is a step of synthesizing at least one of a sulfide powder and a sulfide precursor powder from the raw material mixture obtained in step S1.

[0042] Step S3 is a step of heating the powder obtained in step S2.

[0043] When the present production method is a melting method, step S2 preferably involves cooling a melt obtained by heating the raw material mixture to obtain a powder containing sulfide powder, and more preferably involves cooling and pulverizing the melt to obtain a powder containing sulfide powder.

[0044] Specifically, if Figure 2 As shown, it is further preferred that step S2 includes steps S2a-1 to S2a-3.

[0045] Step S2a-1 is a step of heating and melting the raw material mixture obtained in step S1 to obtain a melt.

[0046] Step S2a-2 is a step of cooling the melt obtained in step S2a-1 to obtain a solid containing crystals.

[0047] Step S2a-3 is a step of pulverizing the solid obtained in step S2a-2 to obtain sulfide powder.

[0048] In step S2a-2, the powder can be obtained while the melt is cooled. In this case, step S2a-2 also serves as the pulverization step S2a-3, so the sulfide powder can be obtained without the additional pulverization step S2a-3.

[0049] The sulfide powder obtained in step S2a-3 is subjected to a heat treatment in step S3 to homogenize the crystal structure, thereby obtaining a sulfide solid electrolyte powder of stable quality. This homogenization and stabilization improves the lithium ion conductivity of the sulfide solid electrolyte powder, thereby enhancing battery performance when used in lithium-ion secondary batteries.

[0050] When the present production method is a solid phase reaction method, it is preferred that in step S2 , the raw material mixture is mechanically ground to obtain a powder comprising a sulfide precursor powder.

[0051] Specifically, if Figure 3 As shown, step S2 preferably includes step S2b.

[0052] Step S2b is a step of mechanically grinding the raw material mixture obtained in step S1 to obtain a sulfide precursor powder.

[0053] The sulfide precursor powder obtained in step S2b is subjected to the heat treatment in step S3 to form a sintered body by calcining the sulfide precursor, thereby obtaining a sulfide solid electrolyte powder.

[0054] Each step is explained.

[0055] Step S1

[0056] In step S1 , raw materials are mixed to obtain a raw material mixture.

[0057] Although it varies depending on the composition of the sulfide solid electrolyte powder to be obtained, for example, a raw material containing a Li element, a raw material containing a P element, and a raw material containing an S element are mixed to obtain a raw material mixture.

[0058] When a sulfide solid electrolyte powder having an argyrodite-type crystal structure is to be obtained, a raw material containing the Ha element is further included in addition to a raw material containing the Li element, a raw material containing the P element, and a raw material containing the S element. In this specification, the Ha element refers to at least one element selected from F, Cl, Br, and I.

[0059] The raw materials may contain other elements depending on the desired composition of the sulfide solid electrolyte powder. For example, if a portion of the element Li, P, S, etc. is substituted with another element, the raw materials may contain the substituted other elements.

[0060] Examples of other elements include Si element, Al element, Sn element, In element, Cu element, Sb element, Ge element, and O element.

[0061] As the raw material containing the Li element, the raw material containing the P element, the raw material containing the S element, and, if necessary, the raw material containing the Ha element, or the raw material containing other elements, conventionally known raw materials can be used.

[0062] Specifically, Li simple substance or a compound comprising Li, P simple substance or a compound comprising P, and S simple substance or a compound comprising S, any compound comprising Ha, etc. can be appropriately combined and used. When the sulfide solid electrolyte powder contains the O element, an oxide can be used as the above-mentioned compound. In addition, the above-mentioned compound can be a compound comprising two or more of Li, P and S, and any other elements such as Ha. For example, as a compound that serves as both a compound comprising S and a compound comprising P, phosphorus pentasulfide (P2S5) and the like can be cited. In addition, as a compound that serves as both a compound comprising Li and a compound comprising Ha, lithium halide can be cited.

[0063] As raw materials containing the Li element, in addition to metallic lithium, there can be cited lithium compounds such as lithium sulfide (Li2S), lithium carbonate (Li2CO3), lithium sulfate (Li2SO4), lithium oxide (Li2O) and lithium hydroxide (LiOH).

[0064] From the viewpoint of ease of operation and reactivity, the raw material containing the Li element is preferably lithium sulfide. On the other hand, since lithium sulfide is expensive, lithium compounds other than lithium sulfide, metallic lithium, etc. are preferred from the viewpoint of suppressing manufacturing costs. Specifically, it is preferred to use one or more selected from metallic lithium, lithium carbonate (Li2CO3), lithium sulfate (Li2SO4), lithium oxide (Li2O) and lithium hydroxide (LiOH). They can be used alone or in combination of two or more.

[0065] As raw materials containing the element S, in addition to elemental sulfur, compounds containing S include phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), other sulfur compounds containing phosphorus, and compounds containing sulfur. Examples of compounds containing sulfur include H2S, CS2, FeS, Fe2S3, FeS2, Fe 1-x S and other iron sulfides, bismuth sulfide (Bi2S3), CuS, Cu2S, Cu 1-x S and other copper sulfides, etc.

[0066] From the perspective of reactivity and preventing the inclusion of elements other than those constituting the target sulfide solid electrolyte powder, the raw material containing the S element is preferably phosphorus sulfide, more preferably phosphorus pentasulfide (PS). These can be used alone or in combination of two or more. Phosphorus sulfide is a compound that serves as both a substance containing S and a substance containing P.

[0067] As raw materials containing P element, in addition to elemental phosphorus, compounds containing P include phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), sodium phosphate (Na3PO4), lithium thiophosphate (Li3PS 4-x O x ) and other phosphorus compounds.

[0068] From the viewpoint of easiness of reaction during synthesis of the intermediate described later and prevention of inclusion of elements other than those constituting the target sulfide solid electrolyte powder, the raw material containing the element P is preferably phosphorus sulfide, more preferably phosphorus pentasulfide (PS). These may be used alone or in combination of two or more.

[0069] In addition, as the raw material containing the P element, when containing an oxide, for example, P2O5, Li3PO4, Li4P2O7, etc. can be mentioned. Among them, P2O5 is preferred from the viewpoint of ease of production. These compounds can be used alone or in combination of two or more.

[0070] As an arbitrary component, as a raw material containing the Ha element, that is, a compound containing Ha, for example, 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.

[0071] From the viewpoint of preventing the inclusion of elements other than those constituting the target sulfide solid electrolyte powder, the raw material containing the Ha element is preferably a lithium halide, more preferably LiCl, LiBr, or LiI. These compounds may be used alone or in combination of two or more.

[0072] In addition, the lithium halide may be a compound containing Li. When the raw material contains the lithium halide, a part or all of the Li in the raw material may be derived from the lithium halide.

[0073] When elements other than Li, S, P, and Ha are contained as elements constituting the sulfide solid electrolyte powder, raw materials containing the other elements are also mixed to obtain a raw material mixture.

[0074] As an optional component, as a raw material containing Si element, for example, SiO2 and SiS2 can be mentioned. Among them, SiO2 is more preferred from the viewpoint of lithium ion conductivity and water resistance. These compounds can be used alone or in combination of two or more.

[0075] Examples of optional components including raw materials containing the Al element include Al2S3, Al2O3, and AlCl3. Among these, Al2S3 and AlCl3 are preferred from the perspective of lithium ion conductivity, with Al2S3 being more preferred. These compounds may be used alone or in combination of two or more.

[0076] As an optional component, as a raw material containing the Sn element, for example, SnS, SnS2, SnO, SnO2, and SnCl2 can be mentioned. Among them, from the perspective of lithium ion conductivity, SnS2 and SnCl2 are preferred, and SnS2 is more preferred. These compounds can be used alone or in combination of two or more.

[0077] Examples of optional components including raw materials containing the In element include In2O3, In2S3, and InCl3. Among these, In2S3 and InCl3 are preferred from the perspective of lithium ion conductivity, and In2S3 is more preferred. These compounds may be used alone or in combination of two or more.

[0078] As an optional component, as a raw material containing the Cu element, for example, Cu2O, CuO, Cu2S, CuS, and CuCl2 can be mentioned. Among them, from the perspective of lithium ion conductivity, CuS and CuCl2 are preferred, and CuS is more preferred. These compounds can be used alone or in combination of two or more.

[0079] As an optional component, examples of raw materials containing the Sb element include Sb2O3, Sb2S3, and SbCl3. Among them, from the perspective of lithium ion conductivity, Sb2S3 and SbCl3 are preferred, and Sb2S3 is more preferred. These compounds may be used alone or in combination of two or more.

[0080] As an optional component, examples of raw materials containing the Ge element include GeO2, GeS, GeS2, and GeCl2. Among them, GeS2 and GeCl2 are preferred from the perspective of lithium ion conductivity, and GeS2 is more preferred. These compounds may be used alone or in combination of two or more.

[0081] As an optional component, examples of raw materials containing element B include B2S3, B2O3, and BCl3. Among them, B2S3 and BCl3 are preferred from the perspective of lithium ion conductivity, and B2S3 is more preferred. These compounds may be used alone or in combination of two or more.

[0082] The raw materials can be mixed by, for example, mixing with a mortar, mixing using a medium such as a planetary ball mill, or mixing without a medium such as a pin mill, a powder mixer, or air flow mixing.

[0083] When this production method is performed using a solid-phase reaction method, the raw material mixture is mechanically ground in step S2b as the next step S2 to form a more uniform mixture, i.e., a sulfide precursor powder, or to obtain an amorphous sulfide precursor powder. During the mechanical grinding process in step S2b, a chemical reaction occurs, and energy is applied as the bonding state of the elements changes. The mixing in step S1 refers to a state of mixing to the extent that multiple raw materials are placed in a single container, or the materials in the container are mixed using a mortar, a stirring blade, or the like, prior to being supplied to step S2b.

[0084] Step S2

[0085] In step S2 , at least one of a sulfide powder and a sulfide precursor powder is synthesized from the raw material mixture obtained in step S2 .

[0086] When the sulfide solid electrolyte powder is produced by a melting method, a powder containing sulfide powder is obtained.

[0087] When the sulfide solid electrolyte powder is produced by a solid phase reaction method, a powder containing a sulfide precursor powder is obtained.

[0088] In the melting method, steps S2a-1 to S2a-3 are performed as described above.

[0089] In step S2a-1, the raw material mixture obtained in step S1 is heated and melted to obtain a melt.

[0090] The specific method for heating and melting the raw material mixture in step S2a-1 is not particularly limited. The raw materials are placed in a heat-resistant container and heated in a heating furnace. The raw material mixture can be sealed in a heat-resistant container. Alternatively, the melting can be performed in an atmosphere containing elemental sulfur. Examples of such atmospheres include a mixed gas atmosphere of a sulfur-containing gas such as sulfur gas, hydrogen sulfide gas, or sulfur dioxide gas and an inert gas.

[0091] Heat-resistant containers that can be used include heat-resistant containers made of carbon, heat-resistant containers containing oxides such as quartz, quartz glass, borosilicate glass, aluminosilicate glass, alumina, zirconia, and mullite, heat-resistant containers containing nitrides such as silicon nitride and boron nitride, and heat-resistant containers containing carbides such as silicon carbide. Furthermore, these heat-resistant containers may be formed entirely of the above materials, or may be containers formed with a layer of carbon or oxides, nitrides, carbides, etc., such as carbon-coated quartz tubes.

[0092] The heating temperature for melting the raw material mixture varies depending on the raw materials used or the composition of the raw material mixture, but is preferably 550 to 1000°C, more preferably 600 to 950°C, even more preferably 630 to 900°C, and particularly preferably 650 to 850°C. From the perspective of improving the meltability of the raw materials and homogenizing the melt in a short period of time, the heating temperature is preferably 550°C or higher, more preferably 600°C or higher, even more preferably 630°C or higher, and particularly preferably 650°C or higher. Furthermore, from the perspective of suppressing degradation of components due to heating, suppressing compositional inhomogeneities due to volatilization of components, and suppressing decomposition, the heating temperature is preferably 1000°C or lower, more preferably 950°C or lower, even more preferably 900°C or lower, and particularly preferably 850°C or lower.

[0093] The time of heating and melting is different according to scale, and is preferably 10 minutes to 10 hours, more preferably 30 minutes to 9.5 hours, further preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours. Here, from the viewpoint of making the reaction well proceed, the time of heating and melting is preferably more than 10 minutes, more preferably more than 30 minutes, further preferably more than 45 minutes, and particularly preferably more than 1 hour. In addition, from the viewpoint of productivity, the time of heating and melting is preferably less than 10 hours, more preferably less than 9.5 hours, and further preferably less than 9 hours.

[0094] The pressure during heating and melting is not particularly limited, but is preferably normal pressure or slightly increased pressure, and more preferably normal pressure.

[0095] The dew point during heating and melting is preferably -20° C. or lower, and the lower limit is not particularly limited, but is usually around -80° C. The oxygen concentration is preferably 1000 ppm by volume or lower.

[0096] In step S2a-1, complete dissolution of the melt can be confirmed by the absence of a peak derived from crystals in high-temperature X-ray diffraction measurement.

[0097] In the next step S2a-2, the melt obtained in step S2a-1 is cooled to precipitate crystals, yielding a solid containing the crystals. The resulting solid is a sulfide compound containing crystals. This sulfide can function as a solid electrolyte, but since it has not undergone the next step S3, its homogeneity is poor.

[0098] Cooling can be performed by a known method and is not particularly limited. More specific cooling methods include, for example, methods in which the melt is poured onto a plate-like body made of carbon or the like and cooled; methods in which the melt is poured into a narrow gap and thinly formed, such as the twin-roll method; and methods in which the melt is sprayed and cooled in a gas.

[0099] The cooling rate is preferably 0.1 to 10,000°C / second, more preferably 0.5 to 5,000°C / second, and even more preferably 1 to 1,000°C / second. From the perspective of improving compositional homogeneity and suppressing quality variations, the cooling rate is preferably 0.1°C / second or higher, more preferably 0.5°C / second or higher, and even more preferably 1°C / second or higher. The upper limit of the cooling rate is not particularly limited; however, considering the cooling rate of a twin-roller, which is generally considered to have the fastest rapid cooling rate, the upper limit is 1,000,000°C / second or lower. From the perspective of practical production, the cooling rate is more preferably 10,000°C / second or lower, even more preferably 5,000°C / second or lower, and even more preferably 1,000°C / second.

[0100] The atmosphere during cooling is preferably a low-moisture, inert atmosphere, similar to that during heating and melting in step S2a-1.

[0101] In the next step S2a-3, the solid obtained in step S2a-2 is pulverized to obtain sulfide powder.

[0102] The pulverization may be either wet pulverization or dry pulverization. However, unlike the fine pulverization performed when the solid electrolyte is used in a lithium ion secondary battery as described later, the pulverization is preferably performed until the average particle size reaches 1 to 300 μm, for example.

[0103] The average particle size herein refers to the median particle size (D50) at which 50% by volume of particles are equal to or smaller than this value, as determined from a volume-based particle size distribution chart obtained by measuring the particle size distribution using a particle size analyzer using a laser diffraction method.

[0104] When the sulfide obtained in step S2a-2 is a powder having an average particle size of about 1 to 100 μm, step S2a-3 may not be performed.

[0105] In the solid-phase reaction method, as described above, the step of mechanically milling the raw material mixture obtained in step S1 to obtain a sulfide precursor powder as step S2b is called synthesis. Mechanical milling is not particularly limited as long as it is a method that mixes the various raw materials that will become the sulfide solid electrolyte while applying mechanical energy. Examples include ball mills such as planetary ball mills, vibration mills, turbo mills, mechanofusion mills, and disk mills.

[0106] When a planetary ball mill is used, the rotation speed of the rotary disk is preferably, for example, 100 to 500 rpm, and the treatment time is preferably, for example, 1 to 100 hours, more preferably 1 to 50 hours.

[0107] The material and size of the container and grinding balls used in the planetary ball mill are not particularly limited, and conventionally known materials can be used. Examples of materials include alumina, zirconia, glass, and silicon nitride. The diameter of the grinding balls is, for example, 0.3 to 20 mm.

[0108] Mechanical milling may be performed dry or wet. When mechanical milling is performed wet, it is preferred to use a dispersion medium that does not react with the raw materials to generate hydrogen sulfide or the like.

[0109] When mechanical milling is performed in a wet process, the sulfide precursor powder is preferably dried before the next step S3. The drying method is not particularly limited, and examples thereof include methods using an externally heated drying furnace or a hot air circulation drying furnace.

[0110] The sulfide precursor powder is different from the sulfide powder obtained by the melting method, which is a powder containing a crystalline compound that functions as a solid electrolyte. It is a powder of a mixture of multiple raw materials mixed very uniformly, a powder in which the chemical bonding state has changed compared to the starting materials due to a reaction, or a powder of an amorphous compound.

[0111] To be used in the subsequent step S3, the sulfide powder or sulfide precursor powder obtained in step S2 preferably has an average particle size of 1 to 300 μm, more preferably 3 to 150 μm, and even more preferably 5 to 100 μm. To suppress scattering during the heat treatment, the average particle size after pulverization is preferably 1 μm or greater, more preferably 3 μm or greater, and even more preferably 5 μm or greater. Furthermore, to facilitate the effects of the subsequent heat treatment and facilitate subsequent fine pulverization, the average particle size after pulverization is preferably 300 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

[0112] Step S3

[0113] In step S3, the powder obtained in step S2 is subjected to a heat treatment.

[0114] As described above, the sulfide powder obtained by the melting method is subjected to the heat treatment in step S3 , thereby becoming a sulfide solid electrolyte powder having improved homogeneity and stable quality as a solid electrolyte.

[0115] The sulfide precursor powder obtained by the solid phase reaction method is converted into a sintered body powder, ie, a sulfide solid electrolyte powder, by the heat treatment in step S3 .

[0116] Generally speaking, once a compound is synthesized and forms a thermodynamically stable structure, further reactions will not proceed. In particular, when the synthesis reaction is a reaction between powders, the formation of a heterogeneous interface will cause the reaction to stop or proceed very slowly.

[0117] In contrast, in the melting method, after obtaining the sulfide powder from the raw material mixture, it is pulverized as needed and then subjected to thermal energy such as heat treatment again, thereby obtaining a sulfide solid electrolyte powder with more uniform particles and more stable quality.

[0118] The heat treatment is performed in an atmosphere having a SO 2 concentration of 1 to 1000 ppm by volume, thereby suppressing the aggregation of the sulfide powder or the sulfide precursor powder.

[0119] The detailed reason for this is not clear, but as mentioned above, it is believed that the sulfur released from the particle surface acts as a binder, connecting the particles together and causing agglomeration. Furthermore, it is believed that the released sulfur that promotes the agglomeration reacts with oxygen in the gas to form SO2 or SO x etc. are removed as exhaust gas, thereby reducing the amount of sulfur that functions as a binder and suppressing aggregation.

[0120] The above-mentioned effect is effective not only during the heat treatment for homogenization and stabilization in the melting method, but also during the heat treatment for calcination for synthesizing a sulfide solid electrolyte in the solid phase reaction method.

[0121] The SO2 concentration of 1 to 1000 vol ppm in the atmosphere is the result of the reaction between the desorbed sulfur and oxygen. The SO2 concentration is preferably 2 to 500 vol ppm, more preferably 3 to 100 vol ppm. While the SO2 concentration is 1 vol ppm or higher, it is preferably 2 vol ppm or higher, and more preferably 3 vol ppm or higher, to further suppress powder agglomeration. Furthermore, the SO2 concentration is 1000 vol ppm or lower, but it is preferably 500 vol ppm or lower, and more preferably 100 vol ppm or lower, to suppress oxidative decomposition of the electrolyte.

[0122] The SO2 concentration can be adjusted by the amount of oxygen introduced during the heat treatment or the amount of oxygen substituted from the container.

[0123] Oxygen can be introduced by flowing a gas containing oxygen element during heating and calcining, or by supplying oxygen from a container or other carrying source.

[0124] Regarding oxygen from the container, for example, compared with the conventional method of removing adsorbed moisture or oxygen by burning a container, there are methods such as using a container that has not been burned or a container that has not been fully burned, and using a porous container with a large specific surface area.

[0125] As for oxygen carried from other sources, for example, there is a method of utilizing oxygen or water adsorbed on a heating object.

[0126] The present inventors have discovered that the aggregation of powder can be mitigated and avoided by utilizing not only the SO 2 concentration in the atmosphere during the heat treatment but also the shape of the container.

[0127] For example, the larger the amount of sulfide solid electrolyte powder produced, the greater the impact of powder crushing or gas permeation on agglomeration. That is, the larger the production scale, the greater the degree to which the powder is compacted due to its own weight. In addition, the closer the powder is to the bottom of the container, the denser the powder is and the easier it is to agglomerate. In addition, it is also related to the fact that sulfur detached from the bottom of the container where the powder is dense is difficult to diffuse to the surroundings. The sulfur deposited at the bottom wets and spreads along the bottom to the entire bottom, easily forming a sulfur-rich layer, resulting in the powder being easily agglomerated. In addition, it is difficult for the oxygen-containing gas that reacts with the detached sulfur to penetrate into the interior of the above-mentioned dense powder aggregate, making it difficult to synthesize SO2 or SO x .

[0128] For these reasons, it is presumed that aggregation is more likely to be promoted when a large amount of sulfide solid electrolyte powder is produced.

[0129] In contrast, the present inventors have discovered that the above-mentioned aggregation can be appropriately suppressed by forming a container with a low height and a wide bottom.

[0130] That is, the container containing the powder for heat treatment preferably satisfies the relationship 2a>b, where the long side of the bottom is a and the height is b. More preferably, a and b satisfy the relationship 1.5a>b.

[0131] It should be noted that when the bottom shape of the container is a shape other than a rectangle, for example, a circle, including a perfect circle and an ellipse, or a polygon can be mentioned. When the bottom shape is a circle, the long side of the bottom refers to the long side of a square or rectangle in which the circle is inscribed. Furthermore, when the bottom shape is a triangle, the length of the longest side is the long side of the bottom. When the bottom shape is a polygon with a pentagon or larger shape, the length of the longest diagonal is the long side of the bottom.

[0132] Furthermore, it was found that powder aggregation was more likely to occur at the interface between the powder and the side or bottom of the container. This is believed to be due to the adhesion between the container and the powder.

[0133] Therefore, the surface roughness Ra of the container is preferably 0.1 to 30 μm, more preferably 0.4 to 10 μm, and even more preferably 0.8 to 8 μm. From the perspective of reducing wettability between the container and the powder and further suppressing aggregation, the surface roughness Ra is preferably 0.1 μm or greater, more preferably 0.4 μm or greater, and even more preferably 0.8 μm or greater. While the upper limit is not particularly limited, from the perspective of ease of use, the surface roughness Ra is preferably 30 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. Surface roughness is determined according to the method specified in JIS B 0601:2001 and refers to the centerline average roughness.

[0134] In relation to the aforementioned adhesiveness, the container's porosity further refers to the open porosity. Here, open porosity refers to the value measured in accordance with JIS R1634:1998. The container's porosity is preferably 1% or higher, more preferably 1% to 50%. To further suppress agglomeration, the porosity is preferably 1% or higher, preferably 5% or higher, more preferably 10% or higher, and even more preferably 15% or higher. The upper limit of the porosity is not particularly limited, provided the powder does not fall, but is, for example, 50% or lower.

[0135] Furthermore, in light of the aforementioned adhesiveness, the container material preferably contains at least one of aluminum and carbon as an element. For example, when the container is a ceramic, examples of its material include carbon, alumina, mullite, and silicon carbide. Furthermore, when the container is a composite material, examples of its material include composite materials such as ceramics and resins reinforced with alumina fiber or carbon fiber, glass ceramics, and alloys. The container may contain at least one of aluminum and carbon as an element on its surface.

[0136] Among them, ceramics containing at least one of aluminum and carbon as an element are more preferred, and the material thereof is further preferably carbon or aluminum oxide, and particularly preferably carbon.

[0137] The wettability between the container and the powder can be evaluated by placing sulfur powder on the same material as the container, heating the sulfur powder to melt it, and then measuring the contact angle. This is because sulfur is believed to be the compound that affects the wettability.

[0138] When heat-treating the sulfide powder, the heating temperature varies depending on the composition of the sulfide powder, i.e., the desired sulfide solid electrolyte, but is, for example, preferably 200 to 600°C, more preferably 350 to 500°C, even more preferably 380 to 460°C, and particularly preferably 400 to 450°C. From the perspective of homogenizing the particles and stabilizing their quality, the heating temperature is preferably 200°C or higher, more preferably 350°C or higher, even more preferably 380°C or higher, and particularly preferably 400°C or higher. From the perspective of preventing sintering of the particles, the heating temperature is preferably 600°C or lower, more preferably 500°C or lower, even more preferably 460°C or lower, and particularly preferably 450°C or lower.

[0139] When heat-treating the sulfide powder, the heating time varies depending on the composition of the sulfide powder, i.e., the desired sulfide solid electrolyte. For example, it is preferably 10 minutes to 10 hours, more preferably 30 minutes to 9.5 hours, even more preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours. From the perspective of particle homogenization and quality stabilization, the heating time is preferably 10 minutes or longer, more preferably 30 minutes or longer, even more preferably 45 minutes or longer, and particularly preferably 1 hour or longer. From the perspective of production cost, the heating time is preferably 10 hours or shorter, more preferably 9.5 hours or shorter, and even more preferably 9 hours or shorter.

[0140] When the sulfide powder is heat-treated, the atmosphere during the heat treatment is preferably an inert atmosphere except for the SO 2 concentration. Examples of the inert atmosphere include a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.

[0141] The dew point during the heat treatment is preferably -20° C. or lower, and the lower limit is not particularly limited, but is usually around -80° C. The oxygen concentration is preferably 1000 ppm by volume or lower.

[0142] It should be noted that the above heating conditions can be adopted not only when the sulfide solid electrolyte has an Argentite-type crystal structure, but also when it has an LGPS-type crystal structure, a Thio-LISICON-type crystal structure, or the like.

[0143] The heating temperature when heat-treating the sulfide precursor powder to crystallize and obtain the sulfide solid electrolyte powder varies depending on the composition of the desired sulfide solid electrolyte, but is preferably 300 to 600°C, more preferably 350 to 575°C, and even more preferably 400 to 550°C. From the perspective of promoting crystallization, the heating temperature is preferably 300°C or higher, more preferably 350°C or higher, and even more preferably 400°C or higher. From the perspective of suppressing thermal decomposition, the heating temperature is preferably 600°C or lower, more preferably 575°C or lower, and even more preferably 550°C or lower.

[0144] The heat treatment time for crystallizing the sulfide precursor powder to obtain the sulfide solid electrolyte powder varies depending on the composition of the target sulfide solid electrolyte, but is preferably 0.1 to 100 hours, more preferably 0.3 to 50 hours, and even more preferably 0.5 to 24 hours. From the perspective of promoting crystallization, the heat treatment time is preferably 0.1 hours or longer, more preferably 0.3 hours or longer, and even more preferably 0.5 hours or longer. From the perspective of manufacturing cost, the heat treatment time is preferably 100 hours or shorter, more preferably 50 hours or shorter, and even more preferably 24 hours or shorter.

[0145] When the sulfide precursor powder is heat-treated to crystallize and obtain the sulfide solid electrolyte powder, the atmosphere during the heat treatment is preferably an inert atmosphere except for the SO2 concentration. Examples of the inert atmosphere include nitrogen, argon, and helium.

[0146] The dew point during the heat treatment is preferably -20° C. or lower, and the lower limit is not particularly limited, but is usually around -80° C. The oxygen concentration is preferably 1000 ppm by volume or lower.

[0147] It should be noted that the above heating conditions can be adopted not only when the sulfide solid electrolyte has an Argentite-type crystal structure, but also when it has an LGPS-type crystal structure, a Thio-LISICON-type crystal structure, or the like.

[0148] The sulfide solid electrolyte powder obtained in step S3 has a smaller difference in average particle size than the powder provided before step S3. Specifically, while the average particle size of the sulfide powder or sulfide precursor powder is preferably 1 to 300 μm, the average particle size of the sulfide solid electrolyte powder is also preferably 1 to 300 μm. This allows the powder to be directly subjected to the fine pulverization step required for producing a fine powder with an average particle size of several μm or less when the sulfide solid electrolyte is actually used in lithium-ion secondary batteries. This eliminates the need for the aforementioned re-pulverization prior to fine pulverization. Furthermore, even when re-pulverization is performed, it can be performed more simply than before.

[0149] When the desired average particle size is 100 μm or less, the proportion of sulfide solid electrolyte powder with a particle size of 100 μm or less is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and particularly preferably 99% by mass or more. This proportion can be determined by a powder passage test using a 100 μm sieve. The test time for the powder passage test varies depending on the amount of powder and the size of the sieve, but is generally sufficient for 5 minutes or more, preferably 10 minutes or more.

[0150] 〔Sulfide solid electrolyte powder〕

[0151] The present invention also relates to a sulfide solid electrolyte powder obtained by the method described in the above-mentioned [Method for producing a sulfide solid electrolyte].

[0152] Specifically, it can be: Li7P3S 11 Such sulfide solid electrolytes, which are called LPS systems and have a crystal structure containing Li, P, and S elements, are 10 GeP2S 12 These include sulfide solid electrolytes known as LGPS-based electrolytes having a crystal structure containing Li, Ge, P, and S; sulfide solid electrolytes having an argyrodite-type crystal structure containing Li, P, S, and Ha; sulfide solid electrolytes composed of Li-PS-Ha-based glass-ceramics; and sulfide solid electrolytes having a lithium-sulfide fast ion conductor-type crystal structure. Furthermore, sulfide solid electrolytes containing both a crystalline phase and an amorphous phase having the aforementioned crystal structures may also be used.

[0153] The argyrodite-type crystal structure is a crystal structure possessed by a group of mineral-derived compounds represented by the composition formula Ag8GeS6. The sulfide solid electrolyte powder of this embodiment is not limited to the above-described crystal structure, and some elements may be substituted with other elements.

[0154] When the sulfide solid electrolyte powder according to the present embodiment has an argyrodite-type crystal structure, it more preferably contains at least one element selected from Cl, Br, and I as the Ha element, and further preferably contains two or more elements.

[0155] Furthermore, the sulfide solid electrolyte according to the present embodiment further preferably contains at least one of Cl and Br as the Ha element, and further preferably contains Cl and Br.

[0156] The crystal structure of the argyrodite type preferably adopts the above structure, as the composition formula, Li α PS β Ha γ It indicates that it preferably satisfies the relationship of 5≤α≤7, 4≤β≤6, and 1.3≤γ≤2. The element ratio more preferably satisfies the relationship of 5.1<α<6.3, 4<β<5.3, and 1.4≤γ≤1.9, and further preferably satisfies the relationship of 5.2<α<6.2, 4.1<β<5.2, and 1.5≤γ≤1.8.

[0157] That is, α is preferably 5 or greater, more preferably greater than 5.1, and even more preferably greater than 5.2, and is preferably 7 or less, more preferably less than 6.3, and even more preferably less than 6.2. β is preferably 4 or greater, more preferably greater than 4, and even more preferably greater than 4.1, and is preferably 6 or less, more preferably less than 5.3, and even more preferably less than 5.2. γ is preferably 1.3 or greater, more preferably 1.4 or greater, and even more preferably 1.5 or greater, and is preferably 2 or less, more preferably 1.9 or less, and even more preferably 1.8 or less.

[0158] In the argyrodite-type crystal structure, a portion of the S element may be replaced by a Ha element or an O element, and may further be replaced by Se, Te, BH4, CN, etc. In addition, a portion of the P element may be replaced by a Si element, an Al element, a Sn element, an In element, an Cu element, an Sb element, a Ge element, etc.

[0159] The sulfide solid electrolyte powder involved in this embodiment can be made into a fine powder with an average particle size of about 0.1 to 2.0 μm by a fine grinding process using a conventionally known method, and then be made into an electrode mixture by applying pressure together with a positive electrode active material or a negative electrode active material, or be made into a solid electrolyte layer by applying pressure together with additives such as a binder as needed, and is preferably used in all-solid-state lithium secondary batteries.

[0160] Example

[0161] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0162] Examples 1, 2, 5, and 7 to 9 are embodiments, and Examples 3, 4, and 6 are comparative examples.

[0163] [Example 1]

[0164] In a dry nitrogen atmosphere, Li 5.4 PS 4.4 Cl 0.8 Br 0.8 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 lithium bromide powder (manufactured by Sigma, purity 99.995%) were weighed in a manner according to the composition ratio of Sigma, and mixed in a mortar to obtain a raw material mixture.

[0165] The obtained raw material mixture is placed in a heat-resistant container and heated at 750°C for 60 minutes in an atmosphere of a gas containing sulfur element to obtain a melt formed by heating and melting the raw material mixture as a synthetic compound. The gas containing sulfur element is a sulfur gas (S x A mixed gas of sulfur gas (x=2 to 8)) and N2 gas as a carrier gas, wherein the content of sulfur gas in the mixed gas is 10% by volume.

[0166] The obtained melt was then cooled to room temperature at a rate of 5° C. / second, pulverized using a mortar to adjust the average particle size to 10 to 20 μm, and then passed through a 100 μm sieve to obtain a sulfide powder.

[0167] One kilogram of the resulting sulfide powder was placed in a cylindrical container made of carbon with a bottom diameter of 150 mm and a height of 150 mm. The container was then heated in an electric furnace at 400°C for one hour in a dry nitrogen atmosphere. The SO₂ concentration in this atmosphere was evaluated using the method described below.

[0168] The mixture was then cooled again at 1°C / second to room temperature, yielding a sulfide solid electrolyte powder containing argyrodite-type crystals. The obtained sulfide solid electrolyte powder was confirmed to have a composition substantially identical to the target composition based on the diffraction pattern obtained by X-ray diffraction measurement and Rietveld analysis.

[0169] [Example 2]

[0170] The obtained sulfide powder was placed in a cylindrical container with a bottom diameter of 150 mm and a height of 150 mm made of alumina. The atmosphere during the heat treatment was set to introduce 10 volume ppm of oxygen into a dry nitrogen atmosphere. Except for the above two points, the same procedure as in Example 1 was carried out to obtain a sulfide solid electrolyte powder.

[0171] [Example 3]

[0172] A sulfide solid electrolyte powder was obtained in the same manner as in Example 1 except that the obtained sulfide powder was placed in a cylindrical container made of quartz having a bottom with a diameter of 150 mm and a height of 150 mm.

[0173] [Example 4]

[0174] Sulfide solid electrolyte powder was obtained in the same manner as in Example 1 except that the obtained sulfide powder was placed in a cylindrical container made of alumina having a bottom with a diameter of 100 mm and a height of 250 mm.

[0175] [Example 5]

[0176] Sulfide solid electrolyte powder was obtained in the same manner as in Example 1 except that the obtained sulfide powder was placed in a cylindrical container made of carbon with a bottom diameter of 100 mm and a height of 250 mm.

[0177] [Example 6]

[0178] A sulfide solid electrolyte powder was obtained in the same manner as in Example 1 except that the obtained sulfide powder was placed in a cylindrical container made of alumina having a bottom with a diameter of 150 mm and a height of 150 mm.

[0179] [Example 7]

[0180] In a dry nitrogen atmosphere, Li 5.4 PS 4.4 Cl 1.6 Lithium sulfide powder (manufactured by Sigma, purity 99.98%), phosphorus pentasulfide powder (manufactured by Sigma, purity 99%), and lithium chloride powder (manufactured by Sigma, purity 99.99%) were weighed in a manner such that the composition ratio of the raw materials was 99.98%, and the mixture was mixed in a mortar to obtain a raw material mixture. The obtained sulfide powder was placed in a cylindrical container having a bottom made of alumina and a diameter of 150 mm and a height of 150 mm. Except for the above, the same procedure as in Example 1 was carried out to obtain a sulfide solid electrolyte powder.

[0181] [Example 8]

[0182] In a dry nitrogen atmosphere, Li 5.4 PS 4.4 Cl 1.6 Lithium sulfide powder (manufactured by Sigma, purity 99.98%), phosphorus pentasulfide powder (manufactured by Sigma, purity 99%), and lithium chloride powder (manufactured by Sigma, purity 99.99%) were weighed in a manner to obtain a raw material mixture at a composition ratio of 99.98%. The mixture was mixed in a mortar.

[0183] The resulting raw material mixture was further mixed using a planetary ball mill (LP-M2, manufactured by Ito Seisakusho Co., Ltd.) to obtain a sulfide precursor. Mixing in the planetary ball mill was performed at 400 rpm for 20 hours using balls with a particle size of 10 mm. The resulting sulfide precursor was pulverized in a mortar to an average particle size of 10 to 20 μm, and then passed through a 100 μm sieve to obtain a sulfide precursor powder.

[0184] One kilogram of the resulting sulfide precursor powder was placed in a cylindrical container made of carbon with a bottom diameter of 150 mm and a height of 150 mm. The powder was then calcined by heating at 400°C for 5 hours in a dry nitrogen atmosphere in an electric furnace. The powder was then cooled to room temperature at a rate of 1°C / second to obtain a sulfide solid electrolyte powder containing argyrodite-type crystals.

[0185] [Example 9]

[0186] A sulfide solid electrolyte powder was obtained in the same manner as in Example 8, except that the atmosphere during the heat treatment of the obtained sulfide precursor powder was a dry nitrogen atmosphere in which 10 vol ppm of oxygen was introduced.

[0187] (Evaluation: Wettability)

[0188] In Examples 1 to 9, the wettability of the sulfide powder or sulfide precursor powder with the container was evaluated by placing sulfur powder on the same material as the container, melting the sulfur powder, and measuring the contact angle. This is because sulfur is believed to be the compound that influences the wettability.

[0189] Specifically, 30 mg of sulfur powder was placed on a plate made of the same material as each container, melted at 150° C., and the contact angle was measured. The cooled droplet was photographed from the horizontal direction using a camera, and the contact angle with the plate was determined.

[0190] The results are shown in the "Wettability" item of Table 1, and the evaluation criteria are as follows.

[0191] ○: The contact angle is 50° or more, which means that the wettability is very low and very good.

[0192] △: The contact angle is 25° or more and less than 50°, which means that the wettability is low and good (pass).

[0193] ×: The contact angle is less than 25°, which means that the wettability is high and poor.

[0194] (Evaluation; SO2 concentration)

[0195] In Examples 1 to 9, the exhaust gas was measured using a detector tube (sulfur dioxide No. 5La, manufactured by GASTEC) to determine the SO2 concentration in the atmosphere during the heat treatment. The measurement was performed immediately after the temperature in the electric furnace reached the target heat treatment temperature.

[0196] The results are shown in the "SO 2 concentration" item of Table 1.

[0197] (Evaluation; Cohesion)

[0198] Using an automatic vibrating sieving machine (AS200 Basic, electromagnetic vibrating sieving machine, manufactured by Retsch), 100 g of the sulfide solid electrolyte powder obtained in Examples 1 to 9 was passed through a 100 μm sieve. The sieving time was 10 minutes. The proportion of powder remaining on the sieve is indicated as "Residual Powder" under "Agglomeration" in Table 1.

[0199] The aforementioned residual powder content is related to the proportion of sulfide solid electrolyte powder particles with a particle size of 100 μm or less. Specifically, the aforementioned residual powder content refers to the proportion of sulfide solid electrolyte powder particles with a particle size greater than 100 μm. Specifically, a residual powder content of 10% by mass or less is equivalent to a proportion of particles with a particle size of 100 μm or less of 90% by mass or greater. In other words, a residual powder content of 10% by mass or less is considered good, more preferably 5% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less.

[0200] [Table 1]

[0201]

[0202] The above results show that, regardless of whether the solid phase reaction method or the melting method is used, by setting the SO2 concentration during the heat treatment to 1 to 1000 ppm by volume, the aggregation of particles during the heat treatment can be suppressed, and a sulfide solid electrolyte powder with a fine particle size can be obtained.

[0203] It was found that the SO₂ concentration during heat treatment can be achieved by reacting sulfur components released from the sulfide powder or sulfide precursor powder with oxygen. In addition to actively introducing a trace amount of oxygen, oxygen components adsorbed in the container are also effective as a source of oxygen. Furthermore, a comparison of the results of Examples 1 and 5, and 1 and 3, shows that the effect of suppressing aggregation is significantly enhanced by optimizing the container shape or the wettability between the container and the sulfide powder or sulfide precursor powder.

[0204] The present invention is described in detail with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. This application is based on Japanese patent application (Japanese Patent Application No. 2023-011196) filed on January 27, 2023, the contents of which are incorporated herein by reference.

Claims

1. A method for producing a sulfide solid electrolyte powder, comprising: Mixing the raw materials to obtain a raw material mixture, synthesizing at least one of a sulfide powder and a sulfide precursor powder from the raw material mixture, and heating the powder; The heat treatment is performed in an atmosphere having a SO2 concentration of 1 to 1000 ppm by volume.

2. The method for producing a sulfide solid electrolyte powder according to claim 1, wherein: During the heating process, the powder is placed in a container. When the long side of the bottom surface of the container is set to a and the height is set to b, the relationship 2a>b is satisfied.

3. The method for producing a sulfide solid electrolyte powder according to claim 2, wherein: The surface roughness Ra of the container is 0.1 to 30 μm.

4. The method for producing a sulfide solid electrolyte powder according to claim 2, wherein: The material of the container contains at least one of aluminum and carbon as an element.

5. The method for producing a sulfide solid electrolyte powder according to claim 2, wherein: The porosity of the container is 1% to 50%.

6. The method for producing a sulfide solid electrolyte powder according to claim 1 or 2, wherein: The average particle size of the powder is 1 to 100 μm.

7. The method for producing a sulfide solid electrolyte powder according to claim 1 or 2, wherein: In the synthesis, a melt obtained by heating the raw material mixture is cooled to obtain the powder including the sulfide powder.

8. The method for producing a sulfide solid electrolyte powder according to claim 1 or 2, wherein: In the synthesis, the powder including the sulfide precursor powder is obtained by mechanically grinding the raw material mixture.

9. The method for producing a sulfide solid electrolyte powder according to claim 1 or 2, wherein: The raw materials include Li element, P element, S element and Ha element, The obtained sulfide solid electrolyte powder has an argyrodite-type crystal structure.

10. The method for producing sulfide solid electrolyte powder according to claim 9, wherein The heating treatment is performed at a temperature of 200 to 600°C.

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