Method for producing sulfide solid electrolyte

Abstract

The present invention relates to a method for continuously producing a sulfide solid electrolyte, the method comprising: heating and melting a first powder starting material that includes P2S5 so as to form a melt; and additionally feeding a second powder starting material that includes P2S5 into the melt and melting the second powder starting material therein. In this method for producing a sulfide solid electrolyte, an inert gas is caused to flow into the melt when the second powder starting material that includes P2S5 is additionally fed thereinto.

Description

Method for producing sulfide solid electrolyte

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

[0002] Lithium-ion secondary batteries are widely used in portable electronic devices such as mobile phones and laptop computers. Conventionally, liquid electrolytes have been used in lithium-ion secondary batteries. However, in recent years, all-solid-state lithium-ion secondary batteries, which use solid electrolytes as the electrolyte, have been attracting attention due to their potential for improved safety, high-speed charging and discharging, and compact housings.

[0003] Examples of solid electrolytes used in all-solid-state lithium ion secondary batteries include sulfide solid electrolytes.

[0004] Examples of methods for producing sulfide solid electrolytes include a melting method and a solid-phase method. When producing a sulfide solid electrolyte by a melting method, it is necessary to heat a mixture of raw materials at a temperature of, for example, 600°C or higher. However, diphosphorus pentasulfide (P), which is often used as a raw material, ２ S ５ Since the boiling point of sulfide is as low as 514°C, it is prone to volatilization when heated at high temperatures, making it difficult to control the composition of the resulting sulfide solid electrolyte.

[0005] In contrast to this, for example, in Patent Document 1, a composite compound containing lithium, phosphorus, and sulfur is melted and vitrified, and then the molten glass is rapidly cooled, thereby reducing P during melting. ２ S ５ Patent Document 2 discloses a method for preventing only the components from volatilizing. Patent Document 2 discloses a method for suppressing volatilization of raw materials and suppressing compositional deviation by heating and compressing solid raw materials to form a melt. Patent Document 3 discloses a method for achieving a target chemical composition without reducing the sulfur in the constituent compounds by mixing each constituent compound in a predetermined stoichiometric ratio and then heating and melting the mixture under a sulfur excess condition.

[0006] Japanese Patent No. 2012-043654 Japanese Patent No. 5640665 Japanese Patent No. 3284215

[0007] However, in the method disclosed in Patent Document 1, the composite compound needs to be synthesized in advance, which complicates the manufacturing process. Furthermore, it is not possible to suppress volatilization during melting. In addition, in the method disclosed in Patent Document 2, the raw material needs to be compressed, which makes the equipment structure very complicated, making it difficult to mass-produce solid electrolytes. Furthermore, in the method disclosed in Patent Document 3, although volatilization of sulfur can be prevented, P ２ S ５ The volatilization of phosphorus cannot be suppressed, and it remains difficult to control the composition of sulfide solid electrolytes.

[0008] Here, when continuously producing a sulfide solid electrolyte using a melting method, it is necessary to additionally supply powder raw materials to the heated and melted melt. ２ S ５ As mentioned above, P has a low boiling point and a low melting point. ２ S ５ Since P liquefies at a relatively low temperature, ２ S ５ When attempting to supply additional powdered raw material containing the above, the powdered raw material adhering to the walls of the apparatus is likely to liquefy and then solidify to form agglomerates. In particular, if the powdered raw material adheres to the vicinity of the supply port of the powdered raw material, the agglomerates formed through liquefaction will clog the vicinity of the supply port, making it difficult to continue feeding the powdered raw material. Similarly, if the powdered raw material liquefies and forms agglomerates in the supply path through which the powdered raw material is supplied, the supply path will be clogged, making it difficult to continue feeding the powdered raw material.

[0009] One possible solution is to lower the heating and melting temperature, but this makes heating more difficult. Furthermore, the volatile gases generated from the melt are more likely to liquefy and solidify, making it more likely that blockages will occur near the supply port in the device.

[0010] In view of the above, an object of the present invention is to provide a method for continuously producing a sulfide solid electrolyte by a melting method, which can stably produce a sulfide solid electrolyte by suppressing aggregation of volatile components contained in a melt near a supply port of an apparatus or within a supply path.

[0011] As a result of extensive research, the present inventors have found that２ S ５ The present inventors have found that the above-mentioned problems can be solved by introducing an inert gas when adding powder raw material containing the above-mentioned compound, and have completed the present invention.

[0012] That is, the present invention relates to the following [1] to [6]. [1] A method for continuously producing a sulfide solid electrolyte, comprising: ２ S ５ a powder raw material containing the compound P is heated and melted to form a melt; and a second P is added to the melt. ２ S ５ and melting the powder raw material containing the second P ２ S ５ [2] The method for producing a sulfide solid electrolyte according to the above [1], wherein an inert gas is introduced into the melt at the same time as the additional introduction of a powder raw material containing the second P. [3] The method for producing a sulfide solid electrolyte according to the above [1] or [2], wherein the temperature of the heat melting is 600°C or higher. [4] The additional introduction of the powder raw material contains the second P. ２ S ５ and a second flow path through which the inert gas flows, the second flow path being disposed around the first flow path. [5] The method for producing a sulfide solid electrolyte according to any one of [1] to [3], wherein a flow rate of the inert gas passing through the second flow path is greater than a flow rate of the inert gas passing through the first flow path. [6] The method for producing a sulfide solid electrolyte according to any one of [1] to [5], wherein a dew point of the inert gas is less than -50°C.

[0013] According to the present invention, when a sulfide solid electrolyte is continuously produced by a melting method, aggregation of volatile components contained in the melt near the supply port of the apparatus or within the supply path can be suppressed, and therefore, the sulfide solid electrolyte can be stably produced.

[0014] Fig. 1 is a flow diagram showing a method for producing a sulfide solid electrolyte according to this embodiment. Fig. 2 is a schematic diagram showing one embodiment of an apparatus used in the production method according to this embodiment. Fig. 3 is a schematic diagram showing one embodiment of an apparatus used in the production method according to this embodiment.

[0015] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified as desired without departing from the spirit of the present invention. The use of "to" to indicate a range of values ​​means that the values ​​before and after the range are included as the lower and upper limits. In the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. The embodiments shown in the drawings are schematic to clearly explain the present invention and do not necessarily accurately represent the size or scale of actual devices, etc.

[0016] <<Method for Producing Sulfide Solid Electrolyte>> The production method according to this embodiment is a method for continuously producing a sulfide solid electrolyte, and as shown in FIG. 1, includes the following steps: (Step S1) Producing a first P ２ S ５ (Step S2) A step of heating and melting a powder raw material containing the above to form a melt. ２ S ５ A step of further adding and melting a powder raw material containing the second P in the step 2. ２ S ５ When the powder raw material containing the above is additionally charged, an inert gas is simultaneously introduced into the melt.

[0017] Furthermore, the manufacturing method according to this embodiment preferably further includes the following step after step S2: (Step S3) Step of cooling and solidifying the melt

[0018] Each step will be explained below.

[0019] Step S1: First P ２ S ５ A step of heating and melting a powder raw material containing the first P ２ S ５ The powder raw material containing the first P ２ S５ The powder raw materials containing the above may be charged into the device as a mixture of the raw materials, or each raw material may be charged into the device separately without being mixed. In particular, from the viewpoint of improving the homogeneity of the obtained sulfide solid electrolyte, it is preferable to charge the raw materials into the device in the form of a mixture of the raw materials.

[0020] The first P in this embodiment ２ S ５ Various raw materials can be used as each of the raw materials constituting the powder raw material including the above, and the sulfide solid electrolyte obtained using these raw materials may also be various sulfide solid electrolytes.

[0021] Each raw material may be synthesized or commercially available, or may be subjected to known pretreatment. That is, the production method according to this embodiment may include a step S0 of preparing each raw material before step S1. Specifically, step S0 may include at least one of a step of producing each raw material and a step of pretreating at least some of the raw materials, as appropriate.

[0022] First P ２ S ５ The raw materials constituting the powder raw material containing the above may be appropriately determined depending on the composition of the sulfide solid electrolyte to be obtained. ２ S ５ is.

[0023] Each raw material contains, for example, an alkali metal element (R) and a sulfur element (S). ２ S ５ can be a source of elemental sulfur and also a source of elemental phosphorus (P).

[0024] Examples of the alkali metal element (R) include lithium element (Li), sodium element (Na), and potassium element (K). When the sulfide solid electrolyte is applied to a lithium ion secondary battery, the alkali metal element (R) is preferably lithium element (Li).

[0025] As the alkali metal element (R) source, an appropriate combination of an alkali metal element, a substance (component) containing an alkali metal element, such as a compound containing an alkali metal element, etc. can be used. When the alkali metal element (R) is lithium element (Li), an appropriate combination of Li-containing substances (components), such as Li element, a compound containing Li, etc. can be used as the lithium element source.

[0026] Examples of substances containing lithium element (Li) include lithium sulfide (Li ２ S), lithium iodide (LiI), lithium carbonate (Li ２ CO ３ ), lithium sulfate (Li ２ SO ４ ), lithium oxide (Li ２ Examples of the substance containing lithium element (Li) include lithium compounds such as lithium hydroxide (LiOH), lithium ion (LiO), and metallic lithium. The substance containing lithium element (Li) may be used alone or in combination of two or more.

[0027] From the viewpoint of obtaining a sulfide material, it is preferable to use lithium sulfide as the substance containing lithium element (Li). Furthermore, when the obtained sulfide solid electrolyte contains a halogen element, lithium halide (LiHa, where Ha is a halogen element) is also preferable as the substance containing lithium element (Li). Lithium halide will be described later.

[0028] As the sulfur element (S) source, a suitable combination of substances (components) containing S, such as simple S or compounds containing S, can be used. The sulfur element (S) containing substance may be used alone or in combination of two or more. Here, the production method according to this embodiment is ２ S ５ Since the object is to suppress the aggregation in the device due to the liquefaction of P at low temperatures, the powder raw material in this embodiment is at least P ２ S ５ which can be a source of elemental sulfur (S). ２ S ５ Phosphorus sulfide containing the above is a compound that serves as both a substance containing sulfur element (S) and a substance containing phosphorus element (P) described below.

[0029] Substances containing sulfur (S) include phosphorus pentasulfide (P ２ S ５ ), for example, diphosphorus trisulfide (P ２ S ３ ), other sulfur compounds containing phosphorus, elemental sulfur, and compounds containing sulfur.

[0030] Sulfur-containing compounds include H ２ S, CS ２ , iron sulfide (FeS, Fe ２ S ３ , FeS ２ , Fe １－ｘ S, etc.), bismuth sulfide (Bi ２ S ３ ), copper sulfide (CuS, Cu ２ S, Cu １－ｘ S, etc.

[0031] From the viewpoint of improving the ionic conductivity of the resulting sulfide solid electrolyte, it is preferable that each raw material further contains phosphorus (P). As a source of phosphorus (P), a substance (component) containing P, such as simple P or a compound containing P, can be used in appropriate combination. One type of substance containing phosphorus (P) may be used, or two or more types may be used in combination. Here, as described above, the powder raw material in this embodiment contains at least P. ２ S ５ which can be a source of elemental phosphorus (P).

[0032] Substances containing phosphorus (P) include diphosphorus pentasulfide (P ２ S ５ ), for example, diphosphorus trisulfide (P ２ S ３ ) and other phosphorus sulfides, sodium phosphate (Na ３ P.O. ４ As a substance containing phosphorus element (P), phosphorus sulfide, which has high volatility, is preferred from the viewpoint of further exerting the effects of the present invention. From this viewpoint, diphosphorus pentasulfide (P ２ S ５ ) is preferred.

[0033] The first P in this embodiment ２ S５ When a mixture of the raw materials is introduced into the device as a powder raw material containing the above, for example, the mixing ratio of the above substances is determined appropriately depending on the composition of the target sulfide solid electrolyte. ２ S ５ When the powder raw materials containing the above are charged into the device individually without being mixed, for example, the charging ratio of the above substances is determined appropriately depending on the composition of the desired sulfide solid electrolyte.

[0034] The mixing ratio or input ratio of each raw material is not particularly limited. ２ S ５ The molar ratio S / R of sulfur element (S) to alkali metal element (R) in the entire powder raw material including the above is preferably 0.65 / 0.35 or less, and more preferably 0.5 / 0.5 or less, from the viewpoint of improving the ionic conductivity of the resulting sulfide solid electrolyte.

[0035] First P ２ S ５ When a mixture of the raw materials is introduced into the apparatus as a powder raw material containing the above, it is preferable to mix the raw materials in a predetermined stoichiometric ratio according to the substance to obtain a mixture.

[0036] The mixing method for obtaining the mixture is not particularly limited, but examples thereof include mixing in a mortar, mixing using a media such as a planetary ball mill, and medialess mixing such as a pin mill, a powder mixer, and airflow mixing.

[0037] An example of a preferred combination of a substance containing an alkali metal element and a substance containing a sulfur element when mixing or charging the raw materials is Li ２ S and P ２ S ５ In addition, when the obtained sulfide solid electrolyte contains a halogen element as a constituent element, Li ２ S and P ２ S ５ and LiHa.

[0038] Li ２ S and P ２ S ５When these elements are combined, the molar ratio of Li to P, Li / P, is preferably 40 / 60 to 88 / 12, and more preferably 50 / 50 to 88 / 12. ２ S ５ Li ２ By adjusting the mixing ratio or the input ratio so that the amount of Li is relatively small compared to S, ２ Melting point of S is ２ S ５ Since the boiling point of the sulfur component is low, it is easy to suppress the volatilization of the sulfur component and the phosphorus component during the heat treatment.

[0039] On the other hand, since lithium sulfide is expensive, lithium compounds other than lithium sulfide, metallic lithium, etc. may be used from the viewpoint of reducing the manufacturing cost of the sulfide solid electrolyte. Specifically, in this case, the raw material may be a substance containing Li, such as metallic lithium, lithium halide (LiHa), or lithium carbonate (Li ２ CO ３ ), lithium sulfate (Li ２ SO ４ ), lithium oxide (Li ２ These may be used alone or in combination of two or more.

[0040] Each raw material in this embodiment may contain further substances (compounds, etc.) in addition to the above substances depending on the composition of the target sulfide solid electrolyte or as an additive, etc.

[0041] For example, when producing a sulfide solid electrolyte containing a halogen element such as F, Cl, Br, or I, the raw materials preferably contain a halogen element (Ha). In this case, each of the raw materials preferably contains a compound containing a halogen element.

[0042] Examples of compounds 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, and boron halides. Among these, from the viewpoint of reactivity, lithium halides are preferred, LiCl, LiBr, and LiI are more preferred, and LiCl and LiBr are even more preferred. These compounds may be used alone or in combination of two or more.

[0043] In addition, since an alkali metal halide such as lithium halide is also a compound containing an alkali metal element such as Li, it can also serve as a source of the alkali metal element (R) in each raw material.

[0044] The first P in this embodiment ２ S ５ When the powder raw material containing the halogen element (Ha) and the phosphorus element (P), the first P ２ S ５ In the powder raw material containing the first P, the molar equivalent of the halogen element (Ha) relative to the phosphorus element (P) is preferably 0.2 to 4 molar equivalents, more preferably 0.5 to 3 molar equivalents. Here, from the viewpoint of improving the ionic conductivity of the resulting sulfide solid electrolyte, the molar equivalent of the halogen element is preferably 0.2 molar equivalents or more, more preferably 0.5 molar equivalents or more. Furthermore, from the viewpoint of the stability of the resulting sulfide solid electrolyte, the molar equivalent of the halogen element is preferably 4 molar equivalents or less, more preferably 3 molar equivalents or less. ２ S ５ When the powder raw material containing the above-mentioned formula (I) contains two or more halogen elements, it is preferable that the total content thereof satisfies the above-mentioned range of molar equivalents.

[0045] The sulfide solid electrolyte obtained by the production method according to this embodiment may be amorphous depending on the purpose. When the sulfide solid electrolyte contains an amorphous phase, the amorphous phase is easily formed even if the quenching rate is reduced during quenching, and from the viewpoint of reducing the equipment load, SiS is used as each raw material. ２ , B ２ S ３ , GeS ２ , Al２ S ３ These may be used alone or in combination of two or more.

[0046] From the viewpoint of imparting moisture resistance to the resulting sulfide solid electrolyte, SiO ２ , B ２ O ３ , GeO ２ , Al ２ O ３ , P ２ O ５ These may be used alone or in combination of two or more.

[0047] In addition, the first P ２ S ５ When a mixture of the raw materials is introduced into the apparatus as a powder raw material containing the above, the sulfide and oxide may both be contained in the mixture, or may be added separately during heating.

[0048] The amount of oxide added to the sulfide is preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass. Here, the amount is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less.

[0049] The first P in this embodiment ２ S ５ Each of the raw materials constituting the powder raw material including the above may further contain a compound that will become a crystal nucleus, which will be described later.

[0050] In addition, the manufacturing method according to this embodiment is ２ S ５ The problem is to prevent agglomeration inside the equipment due to the liquefaction of P at low temperatures. ２ S ５ It is also effective in suppressing aggregation caused by highly volatile compounds other than P. ２ S ５ Examples of highly volatile compounds other than those mentioned above include LiI, B ２ S ３ , S, Se, Sb ２ S ３ , and P ２S ５ Therefore, P ２ S ５ Together with or P ２ S ５ Alternatively, the production method including steps S1 and S2 is effective when continuously producing a sulfide solid electrolyte using a powder raw material containing the highly volatile compound.

[0051] Heat Melting In step S1 of this embodiment, the first P ２ S ５ After the powder raw material containing the above is charged into the apparatus, the powder raw material is heated to melt and obtain a melt.

[0052] For the heating and melting, a furnace body, which is an apparatus, can be suitably used that is conventionally known and has a heating section, and the material and size of the furnace body can also be selected arbitrarily.

[0053] The first P ２ S ５ The initial amount of powder raw material containing the above may be an amount sufficient to form a melt in the furnace body by heating and melting the material, where the melt surface means a liquid surface formed by the melt covering the entire bottom surface of the furnace body.

[0054] When the melt surface is formed in the furnace body, the second P ２ S ５ When the powdered raw material containing the second P is further added, the temperature of the added powdered raw material rises rapidly and melts instantaneously. ２ S ５ As the powder raw material containing the sulfide is added, a melt is continuously obtained, and the sulfide solid electrolyte is obtained in a short time through a subsequent cooling and solidification process. By continuously producing the sulfide solid electrolyte in this manner, a large amount of the sulfide solid electrolyte can be produced in a short time. Furthermore, as the production process is shortened, volatilization of the raw materials during the production process can also be suppressed.

[0055] The temperature of the heat melting is the first P ２ S ５The temperature for heat melting is not particularly limited as long as the powder raw material containing the above is melted, but is preferably 600 to 1000°C, more preferably 630 to 950°C, even more preferably 650°C or higher but lower than 900°C, and even more preferably 650°C or higher but lower than 800°C. From the viewpoint of homogenizing the melt in a short time, the heat melting temperature is preferably 600°C or higher, more preferably 630°C or higher, and even more preferably 650°C or higher. Furthermore, from the viewpoint of suppressing deterioration or decomposition of the components in the melt, the heat melting temperature is preferably 1000°C or lower, more preferably 950°C or lower, and even more preferably lower than 900°C. The heat melting temperature is the temperature of the molten powder raw material present in the furnace body, and can be adjusted by a heating unit provided in the furnace body.

[0056] The heating and melting time is not particularly limited as long as the above-mentioned melt surface is obtained, but may be, for example, 0.5 hours or more, 1 hour or more, or 2 hours or more.

[0057] The pressure during heating and melting is not particularly limited, but for example, normal pressure or slight pressure is preferred, and normal pressure is more preferred.

[0058] From the viewpoint of preventing side reactions with water vapor, oxygen, etc. during heat melting, the dew point inside the furnace is preferably −20° C. or lower, and although there is no particular lower limit, it is usually −80° C. or higher. In addition, the oxygen concentration inside the furnace is preferably 1000 ppm by volume or lower.

[0059] <Step S2: A second P ２ S ５ Step S2: Adding and Melting a Powder Raw Material Containing a Second P to the Melt Obtained in Step S1 ２ S ５ The powder raw material containing the compound is further charged and melted. When this additional charging is performed, an inert gas is simultaneously introduced into the melt.

[0060] 2 shows an example of an apparatus 10 used in the manufacturing method according to this embodiment. In step S2, a second P is supplied to the melt 11 in the furnace body 1 obtained in step S1 through the supply port 2 as shown by the white arrow. ２ S ５The powder raw material 12 containing the above is additionally charged, and the inert gas 13 is introduced as shown by the black arrow.

[0061] Second P ２ S ５ By adding the powder raw material 12 containing P and injecting the inert gas 13, the P contained in the melt 11 can be reduced. ２ S ５ The volatile components such as volatile compounds are liquefied near the supply port 2, and the second P ２ S ５ This can suppress liquefaction due to the intrusion of the volatile components into the supply passage through which the powder raw material 12 containing the volatile components and the inert gas 13 are supplied. As a result, aggregation of the volatile components in the supply passage and near the supply port 2 is suppressed, and clogging of the supply passage and the supply port 2 can be prevented.

[0062] In addition, thermal convection occurs due to the temperature difference between the vicinity of the supply port and the melt, so the second P ２ S ５ If only the powder raw material 12 containing P is added, the raw material will scatter around. On the other hand, by adding the inert gas 13, the second P ２ S ５ The powder raw material 12 containing P is introduced into the melt. Meanwhile, only the inert gas 13 then flows out from the exhaust port 15, and the second P ２ S ５ While suppressing the scattering of the powder raw material 12 containing the second P ２ S ５ The adhesion of the powder raw material 12 containing the above can also be suppressed.

[0063] Furthermore, if cooling water or the like is used to lower the temperature of the supply path other than the part where the melt 11 exists in the furnace body 1, the volatile components of the melt 11 will be cooled due to the low temperature, and P ２ S ５ In contrast, by introducing the inert gas 13, the components with low melting points such as P ２ S ５ Since the evaporation of volatile components such as ammonium nitrate can be suppressed, it is possible to suppress clogging due to the formation of agglomerates while lowering the temperature of the supply route.

[0064] When the inert gas 13 is introduced, the flow rate of the inert gas 13 is preferably 0.01 to 1.0 m / sec, more preferably 0.05 to 0.5 m / sec. ２ S ５ From the viewpoint of suppressing the volatilization of volatile components such as argon, the gas flow velocity is preferably 0.01 m / s or more, more preferably 0.05 m / s or more. From the viewpoint of preventing scattering, the gas flow velocity is preferably 1.0 m / s or less, more preferably 0.5 m / s or less. In this specification, the gas flow velocity of the inert gas 13 refers to the flow velocity within the supply path of the inert gas 13 until it flows into the furnace body 1.

[0065] The dew point of the inert gas 13 is preferably less than −50° C., more preferably −55° C. or less, and even more preferably −60° C. or less, from the viewpoint of preventing side reactions with the powder raw material or the melt. The lower limit of the dew point of the inert gas 13 is not particularly limited, but is usually −20° C. or more.

[0066] In step S2, the second P is introduced through two or more flow paths. ２ S ５ The introduction of the powder raw material containing the second P into the furnace body and the introduction of the inert gas into the furnace body may be carried out separately. ２ S ５ The powder raw material containing the inert gas and the inert gas are introduced into the furnace body and then mixed together on the way to being added to the melt. Specifically, as shown in FIG. 3, the additional addition is referred to as the second P ２ S ５ It is preferable that the inert gas 13 is introduced through a first flow path 16 through which the powder raw material 12 containing the inert gas is introduced, and a second flow path 17 through which the inert gas 13 is introduced. It is more preferable that the second flow path 17 is arranged around the first flow path 16. The arrangement of the second flow path 17 around the first flow path 16 may be a double-pipe structure, or a plurality of second flow paths 17 may be present and arranged around the first flow path 16. This allows the additionally introduced second P ２ S ５ A temporary wall like a curtain of inert gas 13 is formed around the powder raw material 12 containing the second P２ S ５ The adhesion of the powder raw material 12 containing the above can be further suppressed.

[0067] The second P ２ S ５ Even if only the powder raw material 12 containing the second P is added, ２ S ５ In addition to the introduction of the powder raw material 12 containing the inert gas 13, the inert gas 13 may be introduced, but the flow rate of the inert gas 13 passing through the second flow path 17 is preferably greater than the flow rate of the inert gas 13 passing through the first flow path 16. When a plurality of second flow paths 17 are present, it is preferable that at least one of the flow rates of the inert gas 13 passing through the plurality of second flow paths 17 is greater than the flow rate of the inert gas 13 passing through the first flow path 16, and it is more preferable that all of the flow rates are greater than the flow rate of the inert gas 13 passing through the first flow path 16. Note that the flow rate of the inert gas 13 passing through the first flow path 16 is 0 L / sec, i.e., the flow rate of the inert gas 13 passing through the first flow path 16 is 0 L / sec. ２ S ５ Alternatively, only the powder raw material 12 containing the above may be added.

[0068] The difference between the flow rate of the inert gas 13 passing through the second flow path 17 and the flow rate of the inert gas 13 passing through the first flow path 16 is preferably, for example, 0.5 L / sec or more, more preferably 1 L / sec or more.

[0069] The second P to be added to the melt 11 ２ S ５ The powder raw material 12 containing ２ S ５ The composition of the powder raw material containing the first P may be the same as or different from that of the powder raw material containing the first P. However, from the viewpoint of obtaining a homogeneous sulfide solid electrolyte, a powder raw material having the same composition is preferred. ２ S ５ In the case where priority is given to the ease of forming a melt in the heating and melting of a powder raw material containing ２ S ５ A powder raw material containing a second P ２ S ５ The powder raw material containing the second P may have a different composition. ２ S ５ The composition of the powder raw material containing the first P２ S ５ The composition of the powder raw material containing the above is the same as that of the powder raw material containing the above, and the preferred embodiments are also the same.

[0070] The second P for the melt 11 obtained in step S1 ２ S ５ The additional addition of the powder raw material 12 containing the second P may be continuous or intermittent. ２ S ５ The powder raw material 12 containing the sulfide is instantaneously melted, and the melt is continuously synthesized one after another and transferred to the subsequent cooling and solidification step. From the viewpoint of efficiently producing a large amount of sulfide solid electrolyte in a short time, continuous additional charging is preferred.

[0071] The second P for the melt 11 ２ S ５ When the powder raw material 12 containing the second P is continuously added, ２ S ５ The method for the above-mentioned quantitative supply is not particularly limited, but examples thereof include methods using a screw feeder, a table feeder, air current conveyance, etc.

[0072] The second P to be added to the melt 11 ２ S ５ The rate at which the powder raw material 12 containing P is added is preferably 0.01 to 250 g / sec, more preferably 0.025 to 200 g / sec, and even more preferably 0.05 to 150 g / sec. From the viewpoint of efficiently producing a sulfide solid electrolyte, the rate at which the powder raw material 12 is added is preferably 0.01 g / sec or more, more preferably 0.025 g / sec or more, and even more preferably 0.05 g / sec or more. In addition, the melt 11 and the additionally added second P ２ S ５ From the viewpoint of thoroughly mixing the powder raw material 12 containing the above, the feeding speed is preferably 250 g / sec or less, more preferably 200 g / sec or less, and even more preferably 150 g / sec or less.

[0073] Second P ２ S ５ The inert gas 13 introduced together with the powder raw material 12 containing the second P ２ S ５ There is no particular limitation as long as it does not react with the powder raw material 12 containing nitrogen (N２ Examples of the inert gas 13 include nitrogen (N) gas, argon (Ar) gas, and helium (He) gas. The inert gas 13 may be used alone or in combination of two or more kinds.

[0074] The second P ２ S ５ When the powder raw material 12 containing sulfur is additionally charged and the inert gas 13 is introduced, it is preferable to carry out the process in a sulfur-containing gas atmosphere from the viewpoint of replenishing the amount of sulfur that has been volatilized and lost during heating and melting, and suppressing changes in composition due to volatilization.

[0075] The sulfur-containing gas atmosphere can be realized by generating a gas containing elemental sulfur in the furnace body or by feeding a gas containing elemental sulfur into the furnace body. These methods may be used alone or in combination.

[0076] Examples of gases containing elemental sulfur include sulfur gas, hydrogen sulfide gas, carbon disulfide gas, and other compounds containing elemental sulfur or gases containing elemental sulfur.

[0077] When generating a gas containing elemental sulfur in the furnace body, for example, a sulfur source is heated in the furnace body to generate a gas containing elemental sulfur. ２ S ５ In the powder raw material containing ２ S ５ The first or second P may be supplied into the powder raw material containing ２ S ５ When the powder raw material containing the first or second P is supplied ２ S ５ When the powder raw material containing the sulfur source is heated and melted, the sulfur source is also heated, and a gas containing elemental sulfur is generated, thereby forming a sulfur-containing gas atmosphere.

[0078] The sulfur source may be, for example, elemental sulfur, hydrogen sulfide, organic sulfur compounds such as carbon disulfide, iron sulfide (FeS, Fe ２ S ３ , FeS ２ , Fe １－ｘ S, etc.), bismuth sulfide (Bi ２ S ３ ), copper sulfide (CuS, Cu ２ S, Cu１－ｘ Examples of suitable sulfur vulcanizing agents include sulfur dioxide, sulfur dioxide powder, sulfur dioxide vulcanizing agents, sulfur dioxide vulcanizing agents, sulfur dioxide vulcanizing agents, sulfur dioxide powder ...

[0079] When a gas containing sulfur element is fed into the furnace body, for example, sulfur is heated at 200 to 450°C to generate sulfur vapor, and N ２ An inert gas such as argon gas or helium gas may be used as a carrier gas to transport the gas into the furnace body.

[0080] In step S2, the second P ２ S ５ The temperature of the melt obtained by adding and melting the powder raw material containing the above is preferably approximately the same as that of the melt in step S1.

[0081] In step S2, the temperature is adjusted by a heating unit (not shown) provided in the furnace body 1 so as to be approximately the same as the above temperature. ２ S ５ Since it is sufficient to compensate for the thermal energy equivalent to the temperature drop caused by the additional addition of the powder raw material containing the above, the temperature inside the apparatus may be maintained by a heater or the like instead of the heating section, so that the temperature of the melt is maintained at approximately the same level.

[0082] The pressure during melting in step S2 is not particularly limited, similar to the pressure during heating and melting in step S1, but is preferably, for example, atmospheric pressure or slight pressure, and more preferably atmospheric pressure.

[0083] The dew point inside the furnace during melting in step S2 is preferably −20° C. or lower in order to prevent side reactions with water vapor, oxygen, etc., and although there is no particular lower limit, it is usually −80° C. or higher. In addition, the oxygen concentration inside the furnace is preferably 1000 ppm by volume or lower.

[0084] <Step S3: Step of Cooling and Solidifying the Melt> The production method according to this embodiment preferably includes a step of cooling and solidifying the melt obtained in step S2. By cooling the melt, a solid sulfide solid electrolyte is obtained.

[0085] In step S3, the melt obtained in step S2 is discharged at any time from the discharge port 14 provided in the furnace body 1, and the process proceeds to a cooling and solidification step. A known method can be used to cool the melt, and there is no particular limitation. For example, from the viewpoint of increasing the cooling rate, cooling using twin rollers, which is generally considered to have the fastest quenching rate, is preferred.

[0086] From the viewpoint of maintaining the composition of the melt obtained in step S2, the cooling rate is preferably 0.01° C. / sec or more, more preferably 0.05° C. / sec or more, and even more preferably 0.1° C. / sec or more. There is no particular upper limit to the cooling rate, but the cooling rate of the twin rollers is, for example, 1,000,000° C. / sec or less.

[0087] When an amorphous sulfide solid electrolyte is desired, it is preferable to perform quenching at a higher cooling rate. The cooling rate during quenching is preferably 10°C / sec or higher, more preferably 100°C / sec or higher, even more preferably 500°C / sec or higher, and particularly preferably 700°C / sec or higher. The upper limit of the cooling rate during quenching is not particularly limited, but the cooling rate of the twin rollers is, for example, 1,000,000°C / sec or lower.

[0088] On the other hand, a sulfide solid electrolyte having a crystalline phase may be obtained by slow cooling during the cooling and solidification step. Alternatively, a sulfide solid electrolyte having both a crystalline phase and an amorphous phase may be obtained. The cooling rate during slow cooling is preferably 0.01 to 500°C / sec, more preferably 0.05 to 450°C / sec. It may also be 0.01 to 10°C / sec, or 0.05 to 5°C / sec. Here, the cooling rate is preferably 0.01°C / sec or more, more preferably 0.05°C / sec or more, and is preferably 500°C / sec or less, more preferably 450°C / sec or less. The cooling rate may also be 10°C / sec or less, or 5°C / sec or less. The cooling rate may be adjusted appropriately depending on the crystallization conditions.

[0089] The crystal of the sulfide solid electrolyte is preferably an ion-conductive crystal. Specifically, when the carrier is lithium ions, the ion-conductive crystal has a lithium ion conductivity of 10 －４ The lithium ion conductivity is preferably 10 S / cm or more. －３ More preferably, it is more than 5 S / cm.

[0090] When it is desired to obtain a sulfide solid electrolyte containing a crystalline phase, it is preferable to add a compound that will become a crystal nucleus to the melt obtained in step S2 in order to facilitate crystal precipitation. The method for adding the compound that will become a crystal nucleus to the melt is not particularly limited, but for example, the first P ２ S ５ and the second P added in step S2. ２ S ５ and a method of adding a compound that will become a crystal nucleus directly to a melt that has been heated and melted.

[0091] Examples of compounds that can become crystal nuclei include oxides, oxynitrides, nitrides, carbides, other chalcogen compounds, and halides. Compounds that can become crystal nuclei are preferably compounds that have a certain degree of compatibility with the melt. Note that compounds that are completely incompatible with the melt cannot become crystal nuclei.

[0092] The amount of the compound that becomes the crystal nuclei added to the melt is preferably 0.01 to 20 mass%, more preferably 0.1 to 20 mass%, and even more preferably 1 to 10 mass%. From the viewpoint of favorably forming a crystalline phase in the resulting sulfide solid electrolyte, the amount added is preferably 0.01 mass% or more, more preferably 0.1 mass% or more, and even more preferably 1 mass% or more. Furthermore, from the viewpoint of suppressing a decrease in lithium ion conductivity, the amount added is preferably 20 mass% or less, and more preferably 10 mass% or less.

[0093] When a sulfide solid electrolyte having a large amorphous phase is desired, a compound serving as a crystal nucleus is not added to the melt, or if added, the amount of the compound added is preferably 1% by mass or less, more preferably 0.1% by mass or less. The amount may also be 0.01% by mass or less.

[0094] The cooling and solidification is preferably carried out under normal pressure. "Under normal pressure" means that the pressure is not controlled during cooling. Specifically, the pressure is about 0.8 to 1.2 atm.

[0095] The solid sulfide solid electrolyte obtained in step S3 may be reheated for heat treatment. This heat treatment may be particularly effective when the sulfide solid electrolyte is amorphous or contains an amorphous phase. The heat treatment may also rearrange ions within the crystal structure to increase lithium ion conductivity.

[0096] The heat treatment refers to at least one of a heat treatment for crystallizing the obtained solid and a heat treatment for rearranging ions in the crystal structure. That is, the heat treatment also includes a crystallization treatment by heating of an amorphous sulfide solid electrolyte or a sulfide solid electrolyte containing an amorphous phase.

[0097] In the manufacturing method according to this embodiment, it is preferable to carry out the above steps S2 and S3 as a continuous process. That is, in step S2, the melt obtained in step S1 is subjected to a second P ２ S ５ In step S3, a powder raw material containing the sulfide solid electrolyte is continuously or intermittently added, and the melt produced over time by melting is continuously discharged and cooled to solidify. In this manner, it is preferable to continuously produce the sulfide solid electrolyte.

[0098] By continuously producing sulfide solid electrolyte, the second P ２ S ５ The series of steps including the introduction of the powder raw material containing the sulfide, and the discharge and cooling of the melt are continuously performed, thereby enabling the sulfide solid electrolyte to be produced in large quantities more efficiently in a short period of time. Specifically, it is preferable to continuously perform the series of steps including the above steps S1, S2, and S3.

[0099] <Sulfide Solid Electrolyte> When the sulfide solid electrolyte obtained by the production method according to the present embodiment is used in a lithium ion secondary battery, it may be a sulfide solid electrolyte containing lithium element. For example, Li １０ GeP ２ S １２ sulfide solid electrolytes having an LGPS type crystal structure, such as Li ６ P.S. ５ Cl, Li ５．４ P.S. ４．４ Cl１．６ and Li ５．４ P.S. ４．４ Cl ０．８ Br ０．８ sulfide solid electrolytes having an argyrodite-type crystal structure, such as those described above, Li-P-S-Ha-based crystallized glasses (wherein Ha represents at least one element selected from halogen elements), and Li ７ P ３ S １１ Examples of suitable LPS crystallized glasses include those mentioned above.

[0100] The sulfide solid electrolyte may be an amorphous sulfide solid electrolyte, a sulfide solid electrolyte having a specific crystal structure, or a sulfide solid electrolyte containing a crystalline phase and an amorphous phase, depending on the purpose. From the viewpoint of lithium ion conductivity, the crystalline phase is preferably an argyrodite-type crystalline phase.

[0101] From the viewpoint of lithium ion conductivity, a sulfide solid electrolyte containing elements Li, P, S, and Ha is preferred, and it is more preferred that the solid electrolyte has a crystalline phase. The Ha element is preferably derived from one or more selected from the group consisting of lithium chloride, lithium bromide, and lithium iodide, which are the respective raw materials.

[0102] The lithium ion conductivity of the sulfide solid electrolyte is 1.0 × 10 in terms of the battery characteristics when used in a lithium ion secondary battery. －４ S / cm or more is preferable, and 5.0 × 10 －４ S / cm or more is more preferable, and 1.0 × 10 －３ S / cm or more is more preferable, and 5.0×10 －３ The lithium ion conductivity in this specification is a value measured using an AC impedance measuring device (for example, Potentiostat / Galvanostat VSP manufactured by Bio-Logic Sciences Instruments) under the conditions of a measurement frequency of 100 Hz to 1 MHz, a measurement voltage of 100 mV, and a measurement temperature of 25°C.

[0103] The obtained sulfide solid electrolyte can be identified by analyzing the crystal structure by X-ray diffraction (XRD) measurement, or by analyzing the elemental composition using various methods such as ICP emission spectrometry, atomic absorption spectrometry, and ion chromatography. For example, P and S can be measured by ICP emission spectrometry, Li can be measured by atomic absorption spectrometry, and Ha can be measured by ion chromatography.

[0104] The compositional homogeneity of the sulfide solid electrolyte can be evaluated by Raman spectroscopy. Specifically, Raman spectroscopy is performed at any two or more points on a sample obtained from the obtained sulfide solid electrolyte. Note that, from the viewpoint of improving the accuracy of the evaluation, the number of measurement points is preferably eight or more, and more preferably ten or more.

[0105] Preferable conditions for Raman spectroscopy when evaluating the compositional homogeneity of a sulfide solid electrolyte are, for example, a spot diameter of 3 μm and the number of measurement points of 10. By setting the spot diameter to 3 μm, the analysis area in Raman spectroscopy becomes a size suitable for evaluating the compositional homogeneity of a sulfide solid electrolyte at a microscopic level.

[0106] PS for each measurement result ４ ３－ The smaller the variation in peak wavenumbers (peak positions) resulting from the structure of the sulfide solid electrolyte, the more homogeneous the composition of the sulfide solid electrolyte. Alternatively, the smaller the variation in full width at half maximum of the peak resulting from the structure of the sulfide solid electrolyte, the more homogeneous the composition of the sulfide solid electrolyte.

[0107] Although it depends on the composition of the obtained sulfide solid electrolyte, it is preferable to confirm the peak derived from the P—S bond as a peak derived from the structure of the sulfide solid electrolyte. The position of the peak derived from the P—S bond varies depending on the composition system, but typically, it is found to be around 350 cm －１ ~500cm －１ In this specification, the variations in peak position and full width at half maximum of the peak refer to those confirmed for the most intense peak among the peaks derived from P—S bonds.

[0108] The variation in peak position can be evaluated as follows. That is, when the standard deviation of the peak position for each measurement point obtained by Raman spectrum measurement is calculated and expressed as (average peak position) ± (standard deviation), the value of the standard deviation is 2 cm －１ Preferably within 1 cm －１ Within 0.5 cm, more preferably －１ Here, the peak position refers to the position of the peak top.

[0109] For example, when Raman spectroscopy was performed on the sulfide solid electrolyte obtained by the manufacturing method according to this embodiment with a spot diameter of 3 μm and 10 measurement points, the Raman spectroscopy was performed on the sulfide solid electrolyte obtained by the manufacturing method according to this embodiment with a spot diameter of 3 μm and 10 measurement points. －１ ~500cm －１ The standard deviation of the peak positions of the peaks due to P—S bonds is 2 cm －１ Preferably within 1 cm －１ Within 0.5 cm, more preferably －１ Within.

[0110] The variation in the full width at half maximum of the peak can be evaluated as follows. That is, the standard deviation of the full width at half maximum of the peak at each measurement point obtained by Raman spectrum measurement is calculated by determining the full width at half maximum of each peak and then calculating the standard deviation of that value. When this is expressed as (average full width at half maximum of the peak) ± (standard deviation), the value of the standard deviation is 2 cm －１ Preferably within 1.5 cm －１ In this specification, the full width at half maximum of a peak means the width at which the peak derived from the P—S bond intersects with the value at which the peak intensity becomes half when a Raman spectrum is drawn.

[0111] When Raman spectroscopy was performed on the sulfide solid electrolyte obtained by the manufacturing method according to this embodiment with a spot diameter of 3 μm and the number of measurement points set to 10, the Raman spectroscopy was performed on the sulfide solid electrolyte obtained by the manufacturing method according to this embodiment with a spot diameter of 3 μm and the number of measurement points set to 10. －１ ~500cm －１ The standard deviation of the full width at half maximum of the peak due to the P-S bond is 2 cm －１ Preferably within 1.5 cm－１ Within.

[0112] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the above-described embodiments, and modifications and improvements can be made as appropriate. In addition, the material, shape, dimensions, number, and location of each component in the above-described embodiments are arbitrary and not limited as long as the present invention can be achieved.

[0113] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. Examples 1 and 2 are working examples, and Example 3 is a comparative example.

[0114] <Test Examples> <Example 1> In a glove box adjusted to a nitrogen atmosphere with a dew point of -50°C, Li ２ S, P ２ S ５ The raw material powders of LiCl were mixed in the molar ratio of 1.9:0.5:1.6, and the mixture was thoroughly stirred to obtain the first P ２ S ５ A mixture containing the powder raw material was obtained. 300 g of the obtained mixture was placed in a carbon container purged with a nitrogen atmosphere with a dew point of -50°C or lower. The weighed mixture was placed in a sealed container and placed in a hopper connected to a constant-rate feeder (Micron Feeder, manufactured by Aisin Nanotechnologies) without being exposed to the atmosphere. The dew point inside the hopper was also set to -50°C or lower. The constant-rate feeder and the furnace body were connected by a pipe that served as a flow path, and nitrogen was flowed through the pipe at 10 SLM, i.e., a flow rate of 0.45 m / sec, to place 150 g of the mixture in a carbon container purged with a nitrogen atmosphere with a dew point of -50°C or lower. Next, the introduction of the mixture was stopped, and with the nitrogen gas still flowing, the carbon container was heated to 300°C at a temperature increase rate of 5°C / min, and held for 0.5 hours, and then heated to 700°C at a temperature increase rate of 5°C / min and held there. This resulted in the formation of the mixture, i.e., the first P ２ S ５ The powder raw material containing the above was heated and melted to form a melt, and a melt surface was formed in the furnace body (step S1).

[0115] Next, in a glove box adjusted to a nitrogen atmosphere with a dew point of −50° C., the raw materials prepared in the same molar ratio as the above mixture were thoroughly stirred and mixed to prepare a second P ２ S ５ The mixture containing the powder raw material was placed in a sealed container and poured into a hopper connected to a constant-rate feeder (Micron Feeder, manufactured by Aisin Nano Technologies) without being exposed to the atmosphere. The dew point inside the hopper was also set to -50°C or lower. Nitrogen gas was introduced at 10 SLM, i.e., a flow rate of 0.45 m / sec, and simultaneously the mixture, i.e., the second P ２ S ５ The powder raw material containing the second P was continuously added at a rate of 0.1 g / sec and melted. ２ S ５ At the same time as the powder raw material containing sulfur was added and nitrogen gas was introduced, sulfur vapor was sent into the furnace body by heating the sulfur at 350°C, and a sulfur-containing gas atmosphere was created (step S2).

[0116] The melt was poured out from a discharge port attached to the carbon container and rapidly cooled, thereby obtaining a solid sulfide solid electrolyte containing an amorphous phase and an argyrodite-type crystalline phase (step S3).

[0117] The second P in step S2 ２ S ５ Step S3 was also performed while continuing to add the powder raw material containing the above for two hours, but no blockage occurred and the sulfide solid electrolyte could be continuously and stably produced.

[0118] After that, the temperature inside the furnace was lowered while nitrogen gas was being flowed in, and the second P ２ S ５ The area around the supply port and the piping where the powder raw material containing the second P was introduced was observed with an endoscope. ２ S ５ Although deposits thought to be powder raw materials containing volatile components were observed, the amount of deposition was slight, and it was confirmed that aggregation of volatile components contained in the melt was suitably suppressed.

[0119] Example 2: In step S2, the second P ２ S ５A sulfide solid electrolyte was produced in the same manner as in Example 1, except that a second pipe serving as a second flow path through which only nitrogen gas flows was disposed around a first pipe serving as a first flow path through which the powder raw material containing the sulfide solid electrolyte and the nitrogen gas were introduced. The flow rate of the nitrogen gas in the second pipe was 1 SLM, and the flow rate of the nitrogen gas in the first pipe disposed around the second pipe was 9 SLM, i.e., a flow velocity of 0.45 m / sec.

[0120] The second P in step S2 ２ S ５ Step S3 was also performed while continuing to add the powder raw material containing the above for two hours, but no blockage occurred and the sulfide solid electrolyte could be continuously and stably produced.

[0121] After that, the temperature inside the furnace was lowered while nitrogen gas was being flowed in, and the second P ２ S ５ The area around the supply port and the piping where the powder raw material containing the second P was introduced was observed with an endoscope. ２ S ５ The results showed that the aggregation of volatile components contained in the melt was effectively suppressed. As a result, it was found that sulfide solid electrolytes could be stably produced.

[0122] Example 3: Second P in step S2 ２ S ５ A sulfide solid electrolyte was produced in the same manner as in Example 1, except that nitrogen gas was not introduced when the powder raw material containing

[0123] The second P in step S2 ２ S ５ The addition of powder raw materials containing P was continued to be attempted to obtain a sulfide solid electrolyte continuously, but a blockage occurred midway through the process, and a second P ２ S ５ Since it became impossible to add powder raw materials containing ２ S ５ The additional addition of powdered raw materials containing

[0124] The temperature inside the furnace is lowered as it is, and the second P ２ S ５The vicinity of the supply port into which the powder raw material containing the second P was introduced and the piping were observed with an endoscope. As a result, deposits were found to be attached to the wall surfaces of the piping and the vicinity of the supply port. ２ S ５ It was confirmed that the supply port through which the powder raw material containing

[0125] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-119360) filed on July 21, 2023, the contents of which are incorporated herein by reference.

[0126] 1 Furnace body 2 Supply port 10 Apparatus 11 Melt 12 Second P ２ S ５ Powder raw material containing 13 inert gas 14 outlet 15 exhaust outlet 16 first flow path 17 second flow path

Claims

1. A method for continuously producing a sulfide solid electrolyte, comprising: ２ S ５ A powder raw material containing the above-mentioned is heated and melted to obtain a melt, and a second P is added to the melt. ２ S ５ and melting the powder raw material containing the second P. ２ S ５ When a powder raw material containing the above is additionally charged, an inert gas is simultaneously flowed into the melt.

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein the inert gas is introduced at a gas flow rate of 0.05 m / sec or more.

3. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heating and melting temperature is 600° C. or higher.

4. The additional input is the second P ２ S ５ 3. The method for producing a sulfide solid electrolyte according to claim 1, wherein the inert gas is introduced through a first flow path through which a powder raw material containing the inert gas is introduced and through a second flow path through which the inert gas is introduced, the second flow path being disposed around the first flow path.

5. A method for producing a sulfide solid electrolyte as described in claim 4, wherein a flow rate of the inert gas passing through the second flow path is greater than a flow rate of the inert gas passing through the first flow path.

6. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the dew point of the inert gas is less than -50°C.

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