Method and device for producing sulfide solid electrolyte

Abstract

The present invention relates to a method for producing a sulfide-based solid electrolyte, in which a first sulfide-based solid electrolyte raw material is heated and melted in a furnace to obtain a first melt, a second sulfide-based solid electrolyte raw material is supplied to the first melt, the second sulfide-based solid electrolyte raw material is heated and melted in a gas atmosphere containing elemental sulfur, and the obtained second melt is cooled.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for producing a sulfide-based solid electrolyte. Background Art

[0002] Lithium ion secondary batteries are widely used in portable electronic devices such as mobile phones and laptop computers. In the past, liquid electrolytes have been used in lithium ion secondary batteries. On the other hand, in recent years, all-solid lithium ion secondary batteries that use solid electrolytes as electrolytes for lithium ion secondary batteries have attracted much attention from the perspectives of improved safety, high-speed charging and discharging, and miniaturization of housings.

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

[0004] When synthesizing a sulfide-based solid electrolyte by a melting method, it is necessary to heat the mixed raw materials at a temperature of 600°C or higher. However, due to the phosphorus pentasulfide (P 2 S 5 ) has a relatively low boiling point of 514°C, so when the mixed raw materials are heated at high temperatures, part of the raw materials will volatilize, resulting in a problem of difficulty in controlling the composition of the obtained solid electrolyte.

[0005] As a method for solving the above-mentioned problem, for example, Patent Document 1 discloses a method of synthesizing a composite compound containing lithium, sulfur, and phosphorus in advance and melting the composite compound in the raw material to prevent volatilization of the raw material components.

[0006] As another solution, Patent Document 2 discloses a method of synthesizing a sulfide-based solid electrolyte by heating and melting a raw material while compressing it to prevent volatilization of components and then cooling and solidifying it.

[0007] Patent Document 3 discloses a method in which raw materials are mixed at a predetermined stoichiometric ratio and the mixture is heated and melted in a state in which sulfur is excessive to prevent volatilization of sulfur.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2012-43654

[0011] Patent Document 2: Japanese Patent No. 5640665

[0012] Patent Document 3: Japanese Patent No. 3284215 Summary of the invention

[0013] However, in the method of Patent Document 1, since a composite compound containing lithium, sulfur, and phosphorus needs to be synthesized in advance, the production process is complicated and requires a long time.

[0014] In addition, in the method of Patent Document 2, since it is necessary to compress the raw materials, the equipment structure becomes very complicated, making it difficult to mass-produce the solid electrolyte.

[0015] In addition, in the method of Patent Document 3, although the volatilization of sulfur can be prevented, the volatilization of phosphorus cannot be suppressed, so that the composition control is difficult.

[0016] In view of the above circumstances, an object of the present invention is to provide a method and a production apparatus for producing a sulfide-based solid electrolyte in a short time while suppressing volatilization of raw materials.

[0017] The present inventors have conducted intensive research and have found that by further supplying a second sulfide-based solid electrolyte raw material to a melt obtained by heating and melting a first sulfide-based solid electrolyte raw material in a furnace body, the temperature of the second sulfide-based solid electrolyte raw material supplied to the melt is rapidly increased, and the melt can be melted instantly while mixing. As a result, volatilization of the raw material can be suppressed, and a large amount of sulfide-based solid electrolyte can be produced in a short time, thereby completing the present invention.

[0018] That is, the present invention relates to the following [1] to

[16] .

[0019] [1] A method for producing a sulfide-based solid electrolyte, comprising heating and melting a first sulfide-based solid electrolyte raw material in a furnace to obtain a first melt, supplying a second sulfide-based solid electrolyte raw material to the first melt, heating and melting the raw material in a gas atmosphere containing sulfur, and cooling the obtained second melt.

[0020] [2] The method for producing a sulfide-based solid electrolyte according to [1] above, wherein the second sulfide-based solid electrolyte raw material is supplied at a rate of 5 mass% / min or less relative to 100 mass% of the first melt.

[0021] [3] The method for producing a sulfide-based solid electrolyte according to [1] or [2] above, wherein the composition of the first sulfide-based solid electrolyte raw material is the same as the composition of the second sulfide-based solid electrolyte raw material.

[0022] [4] The method for producing a sulfide-based solid electrolyte according to [1] or [2] above, wherein the gas atmosphere containing the sulfur element is obtained by supplying a sulfur source to the first melt.

[0023] [5] The method for producing a sulfide-based solid electrolyte according to [1] or [2] above, wherein the gas atmosphere containing the sulfur element is obtained by introducing sulfur vapor into the furnace.

[0024] [6] The method for producing a sulfide-based solid electrolyte according to [5] above, wherein the sulfur vapor is generated by heating sulfur at 200 to 450° C. in the furnace.

[0025] [7] The method for producing a sulfide-based solid electrolyte according to [1] or [2] above, wherein the second sulfide-based solid electrolyte raw material is continuously supplied to the first melt.

[0026] [8] The method for producing a sulfide-based solid electrolyte according to [1] or [2] above, wherein the second molten metal is continuously discharged from the furnace body and cooled.

[0027] [9] The method for producing a sulfide-based solid electrolyte according to [1] or [2] above, wherein the heating temperature of the first sulfide-based solid electrolyte raw material or the second sulfide-based solid electrolyte raw material is 600° C. or higher and lower than 900° C.

[0028]

[10] The method for producing a sulfide-based solid electrolyte according to [1] or [2] above, wherein the second melt is cooled using twin rolls.

[0029]

[11] A device for producing a sulfide-based solid electrolyte, comprising:

[0030] Furnace body,

[0031] A heating unit, used for heating the furnace body,

[0032] a first raw material supplying section for supplying a first sulfide-based solid electrolyte raw material to the furnace body;

[0033] a second raw material supplying section for supplying a second sulfide-based solid electrolyte raw material to a first melt obtained by heating and melting the first sulfide-based solid electrolyte raw material supplied to the furnace body,

[0034] a discharge unit for discharging a second molten liquid obtained by supplying a second sulfide-based solid electrolyte raw material to the first molten liquid in the furnace body, and

[0035] The cooling unit is configured to cool the second molten liquid discharged from the discharge unit.

[0036]

[12] The apparatus for producing a sulfide-based solid electrolyte according to

[11] , further comprising a sulfur supply unit for supplying a sulfur source or sulfur vapor to the furnace body.

[0037]

[13] The apparatus for producing a sulfide-based solid electrolyte according to

[11] or

[12] above, wherein the second raw material supply unit continuously supplies the second sulfide-based solid electrolyte raw material to the first melt.

[0038]

[14] The apparatus for producing a sulfide-based solid electrolyte according to

[11] or

[12] above, wherein the second raw material supply unit supplies a fixed amount of the second sulfide-based solid electrolyte raw material to the first melt.

[0039]

[15] The apparatus for producing a sulfide-based solid electrolyte according to

[11] or

[12] above, wherein the cooling section has twin rolls.

[0040]

[16] The apparatus for producing a sulfide-based solid electrolyte according to

[11] or

[12] , further comprising a reheating section for reheating the sulfide-based solid electrolyte obtained by cooling in the cooling section.

[0041] According to the present invention, by further supplying a second sulfide-based solid electrolyte raw material to a melt obtained by heating and melting a first sulfide-based solid electrolyte raw material in a furnace body, and heating and melting the melt in a gas atmosphere containing sulfur, the temperature of the supplied second sulfide-based solid electrolyte raw material is rapidly increased, and the second sulfide-based solid electrolyte raw material can be melted instantly while being mixed with the melt. Therefore, volatilization of the raw material can be suppressed, and a large amount of sulfide-based solid electrolyte can be produced in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of a method for producing a sulfide-based solid electrolyte according to an embodiment of the present invention.

[0043] Figure 2 (a) is a schematic diagram showing a state in which a first melt 11 having a melt surface 13 is obtained by introducing a first sulfide-based solid electrolyte raw material 12 into a furnace body 10 and heating and melting the first sulfide-based solid electrolyte raw material 12 . Figure 2 (b) is a schematic diagram showing a state in which the first molten metal 11 exists only on a part of the bottom surface of the furnace body 10 and a molten metal surface is not formed in the furnace body 10 .

[0044] Figure 3 This is a schematic diagram showing a state in which a second sulfide-based solid electrolyte raw material 22 is supplied to a first molten liquid formed in a furnace body 20 to heat and melt the raw material, thereby obtaining a second molten liquid 21 .

[0045] Figure 4(a) is a schematic diagram for explaining a method of obtaining a sulfur atmosphere by supplying a sulfur source 33a together with a second sulfide-based solid electrolyte raw material 32 to a first melt formed in a furnace body 30 and heating the sulfur source 33a. Figure 4 (b) is a schematic diagram for explaining a method of obtaining a sulfur atmosphere by introducing sulfur vapor 33 b obtained in advance into the furnace body 30 .

[0046] Figure 5 This is a schematic diagram for explaining the flow of discharging the second molten metal 41 from the discharging portion 44 provided in the furnace body 40 and transferring to the cooling step.

[0047] Figure 6 It is a schematic diagram showing an example of an apparatus for producing a sulfide-based solid electrolyte according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The present invention is described in detail below, but the present invention is not limited to the following embodiments and can be implemented by any deformation without departing from the gist of the present invention. In addition, "~" indicating a numerical range is used to include the numerical values ​​recorded before and after it as the lower limit and upper limit. In addition, in the following drawings, parts and parts that play the same role are sometimes marked with the same symbols and described, and repeated descriptions are sometimes omitted or simplified. In addition, the embodiments described in the drawings are modeled for the purpose of clearly describing the present invention, and do not necessarily accurately represent the dimensions and scales of actual devices, etc.

[0049] [Method for producing sulfide-based solid electrolyte]

[0050] The method for producing a sulfide-based solid electrolyte according to an embodiment of the present invention (hereinafter also referred to as the present production method) is characterized in that a first sulfide-based solid electrolyte raw material is heated and melted in a furnace body to obtain a first melt, a second sulfide-based solid electrolyte raw material is supplied to the first melt, heated and melted in a gas atmosphere containing sulfur element, and the obtained second melt is cooled.

[0051] Figure 1 The flowchart of the present production method is shown. In the present production method, first, a first sulfide-based solid electrolyte raw material is heated and melted in a furnace (step S1) to obtain a first melt (step S2).

[0052] As the furnace body, a separate heating unit is provided, and a known furnace body conventionally used for heating a molten solid electrolyte raw material can be appropriately used, and the material and size of the furnace body can be arbitrarily selected.

[0053] The amount of the first molten metal may be a small amount as long as it is enough to form at least a molten metal surface in the furnace body. Figure 2The liquid surface formed by the molten metal covering the entire bottom surface of the furnace body as shown in (a) does not include, for example, Figure 2 (b) shows a situation where the melt exists only in a part of the bottom surface of the furnace body. If a melt surface is temporarily formed in the furnace body by the obtained melt, the raw material (the second sulfide-based solid electrolyte raw material) is supplied, so that the raw material melts instantly due to a sharp rise in temperature. Therefore, the melt can be continuously synthesized one by one corresponding to the additional raw materials, and the sulfide-based solid electrolyte can be obtained in a short time after the subsequent cooling process. Thus, even when a large amount of sulfide-based solid electrolytes are manufactured, the manufacturing time can be greatly shortened. In addition, since the sulfide-based solid electrolyte can be manufactured in a short time, the volatilization of the raw materials in the manufacturing process can be suppressed.

[0054] In this specification, the "first sulfide-based solid electrolyte raw material" refers to a sulfide-based solid electrolyte raw material that is initially supplied to the furnace body and heated and melted in order to obtain a melt of an amount that can at least form a melt surface in the furnace body, that is, the so-called starting material of the melt synthesis. In addition, the "first melt" refers to a melt obtained by heating and melting the above-mentioned "first sulfide-based solid electrolyte raw material".

[0055] The “second sulfide-based solid electrolyte raw material” refers to a sulfide-based solid electrolyte raw material further supplied to the first melt. It should be noted that the sulfide-based solid electrolyte raw material further supplied to the melt obtained by supplying the sulfide-based solid electrolyte raw material to the “first melt” is also included in the “second sulfide-based solid electrolyte raw material”.

[0056] The "second melt" refers to a melt obtained by supplying the "second sulfide-based solid electrolyte raw material" to the "first melt" and heating and melting the melt. It should be noted that a melt obtained by further supplying the "second sulfide-based solid electrolyte raw material" to the "first melt" and heating and melting the melt is also included in the "second melt".

[0057] (Sulfide-based solid electrolyte raw materials)

[0058] In the present manufacturing method, various raw materials can be used as the first sulfide-based solid electrolyte raw material and the second sulfide-based solid electrolyte raw material, and the sulfide-based solid electrolyte obtained by using them can also be various sulfide-based solid electrolytes. As the first sulfide-based solid electrolyte raw material and the second sulfide-based solid electrolyte raw material, electrolyte raw materials with the same composition can be used, or electrolyte raw materials with different compositions can be used. Among them, it is preferred that the composition of the first sulfide-based solid electrolyte raw material is the same as that of the second sulfide-based solid electrolyte raw material. Hereinafter, the first sulfide-based solid electrolyte raw material and the second sulfide-based solid electrolyte raw material are sometimes collectively referred to as "sulfide-based solid electrolyte raw material" or "this raw material".

[0059] As this raw material, a commercially available sulfide-based solid electrolyte raw material can be used, or a raw material obtained by manufacturing a sulfide-based solid electrolyte raw material from a material can be used. In addition, these sulfide-based solid electrolyte raw materials can also be further subjected to a known pretreatment. That is, this production method can appropriately include a step of manufacturing this raw material and a step of pretreating this raw material.

[0060] The sulfide-based solid electrolyte raw material is described in detail below. The sulfide-based solid electrolyte raw material generally contains an alkali metal element (R) and sulfur element (S).

[0061] Examples of the alkali metal element (R) include lithium element (Li), sodium element (Na), and potassium element (K). Among them, lithium element (Li) is preferred.

[0062] As the alkali metal element (R), a simple substance of an alkali metal element, a compound containing an alkali metal element, or a substance (component) containing an alkali metal element, etc. can be used in combination as appropriate. Among them, as the lithium element, a simple substance of Li, a compound containing Li, or a substance (component) containing Li, etc. can be used in combination as appropriate.

[0063] Examples of materials 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 As the substance containing lithium element (Li), lithium sulfide is preferably used from the viewpoint of obtaining a sulfide material.

[0064] As the sulfur element (S), a simple substance of S, a compound containing S, or other substances (components) containing S may be used in combination as appropriate.

[0065] Examples of substances containing sulfur (S) include phosphorus trisulfide (P 2 S 3 ), phosphorus pentasulfide (P 2 S 5 ) and other phosphorus sulfides, other sulfur compounds containing phosphorus, elemental sulfur, and compounds containing sulfur. Examples of compounds containing sulfur include H 2 S.C.S. 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 From the viewpoint of obtaining a sulfide material, the substance containing sulfur element (S) is preferably phosphorus sulfide, and more preferably phosphorus pentasulfide (P 2 S 5 ). These substances may be used alone or in combination of two or more. It should be noted that phosphorus sulfide is considered to be a compound that serves as both a substance containing S and a substance containing P described later.

[0066] The raw material preferably further contains phosphorus (P) from the viewpoint of improving the ion conductivity of the obtained sulfide-based solid electrolyte. As phosphorus (P), P simple substance, P-containing compound and other P-containing substances (components) can be used in combination as appropriate.

[0067] Examples of substances containing phosphorus (P) include phosphorus trisulfide (P 2 S 3 ), phosphorus pentasulfide (P 2 S 5 ) and other phosphorus sulfide, sodium phosphate (Na 3 PO 4 ) and simple phosphorus. As the substance containing phosphorus element (P), from the viewpoint of further exerting the effect of the present invention, phosphorus sulfide with high volatility is preferred, and phosphorus pentasulfide (P 2 S 5 ). These substances may be used alone or in combination of two or more.

[0068] This raw material can be obtained in the form of a mixed raw material by, for example, appropriately mixing the above-mentioned substances according to the composition of the target sulfide-based solid electrolyte. The mixing ratio is not particularly limited. For example, from the perspective of improving the ionic conductivity of the obtained sulfide-based solid electrolyte, the molar ratio S / R of the sulfur element (S) to the alkali metal element (R) in the raw material is preferably 0.65 / 0.35 or less, and more preferably 0.5 / 0.5 or less. In addition, the mixed raw material is preferably obtained by mixing in a prescribed stoichiometric ratio corresponding to the substances used in the mixing. As the above-mentioned mixing method, for example, mixing using a mortar, mixing using a medium such as a planetary ball mill, a pin mill, a powder mixer, and a medium-free mixing such as air flow mixing can be cited.

[0069] An example of a preferred combination of the alkali metal element and sulfur element contained in the raw material is Li 2 S and P 2 S 5 Combination of. 2 S and P 2 S 5 When the molar ratio of Li to P is Li / P, it is preferably 40 / 60 to 88 / 12, and more preferably 50 / 50 to 88 / 12. 2 S 5 Relative to Li 2 S becomes less, thus easily suppressing the 2 S 5 The boiling point is lower than Li 2 The melting point of S causes the volatilization of sulfur and phosphorus components during heat treatment.

[0070] On the other hand, since lithium sulfide is expensive, lithium compounds other than lithium sulfide, metallic lithium, etc. may also be used from the viewpoint of reducing the manufacturing cost of sulfide-based solid electrolytes. Specifically, in this case, the raw material preferably contains metallic lithium, lithium iodide (LiI), lithium carbonate (LiCO), or the like. 2 CO 3 ), lithium sulfate (Li 2 SO 4 ), lithium oxide (Li 2 As the substance containing Li, one or more of lithium ion (LiO) and lithium hydroxide (LiOH) may be used. These substances may be used alone or in combination of two or more.

[0071] The present raw material may contain substances (compounds, etc.) other than the above substances depending on the composition of the target sulfide-based solid electrolyte or as additives, etc.

[0072] For example, in the case of manufacturing a sulfide-based solid electrolyte containing a halogen element such as F, Cl, Br or I, the raw material preferably contains a halogen element (Ha). In this case, the raw material preferably comprises a compound containing a halogen element. As a compound containing a halogen element, lithium halides such as lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), phosphorus halides, phosphoryl halides, sulfur halides, sodium halides, boron halides, etc. can be cited. As a compound containing a halogen element, from the viewpoint of the reactivity of the raw material, lithium halides are preferred, and LiCl, LiBr, and LiI are more preferred. These compounds can be used alone or in combination with two or more.

[0073] Alkali metal halides such as lithium halide are also compounds containing alkali metal elements such as Li. When the raw material contains an alkali metal halide, part or all of the alkali metal element such as Li in the raw material may be derived from the alkali metal halide such as lithium halide.

[0074] When the raw material contains a halogen element (Ha) and a phosphorus element (P), the molar equivalent of Ha relative to P in the raw material is preferably 0.2 molar equivalent or more, more preferably 0.5 molar equivalent or more, from the viewpoint of improving the ion conductivity of the obtained sulfide-based solid electrolyte, etc. In addition, from the viewpoint of the stability of the obtained sulfide-based solid electrolyte, the molar equivalent of Ha is preferably 4 molar equivalents or less, more preferably 3 molar equivalents or less.

[0075] The obtained sulfide-based solid electrolyte may be an amorphous sulfide-based solid electrolyte depending on the purpose. From the viewpoint of improving the ease of forming an amorphous phase, it is also preferred that the raw material contains SiS 2 , B 2 S 3 ,GeS 2 、Al 2 S 3 Since the amorphous phase is easily formed, when the amorphous phase is obtained by rapid cooling, even if the cooling rate is reduced, an amorphous sulfide-based solid electrolyte can be obtained, and the equipment load can be reduced.

[0076] In addition, from the viewpoint of imparting moisture resistance to the sulfide-based solid electrolyte, it is also preferable to contain SiO 2 , B 2 O 3 ,GeO 2 、Al 2 O 3 , P 2 O 5 These compounds may be used alone or in combination of two or more.

[0077] It should be noted that the above-mentioned sulfide and oxide may be contained in the raw material, or may be added separately when the raw material is heated and melted. In addition, the amount of the above-mentioned sulfide and oxide added is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, relative to the total amount of the raw material. In addition, the amount of the above-mentioned sulfide and oxide added is preferably 50% by weight or less, more preferably 40% by weight or less.

[0078] In addition, the raw material may contain a compound that serves as a crystal nucleus as described later.

[0079] Since the present production method can suppress the volatilization of the raw materials as described above, it is particularly preferably used when the raw materials contain highly volatile compounds. Examples of highly volatile compounds include LiI, B 2 S 3 , S, Se, SB 2 S 3 and P 2 S 5 wait.

[0080] (Heating and melting)

[0081] In the present manufacturing method, Figure 2 As shown in (a), first, the first sulfide-based solid electrolyte raw material 12 introduced into the furnace body 10 is heated and melted to obtain the first melt 11. As described later, the furnace body 10 is heated to a temperature at which the first sulfide-based solid electrolyte raw material 12 melts by another heating unit (not shown).

[0082] The first melt 11 obtained by heating and melting is preferably as follows: Figure 2 (a) shows an amount that is at least sufficient to form a melt surface 13 in the furnace body 10. As described above, if the melt surface 13 is temporarily formed in the furnace body 10 by the first melt 11, the temperature of the supplied additional raw material (second sulfide-based solid electrolyte raw material) rises sharply and melts instantly, so that melts can be synthesized sequentially. On the other hand, if Figure 2 As shown in (b), in the case where the first melt 11 exists only on a portion of the bottom surface of the furnace body 10, if a melt surface is not formed in the furnace body 10, the first melt 11 and the second sulfide-based solid electrolyte raw material described later may not be fully mixed, and the sulfide-based solid electrolyte cannot be efficiently synthesized.

[0083] From the above viewpoints, the ratio (mass ratio) of the raw material (second sulfide-based solid electrolyte raw material) initially added to the first melt to the first melt 11 may be, for example, 2 or more, 5 or more, or 10 or more.

[0084] Then, if Figure 1 ,3 As shown, the second sulfide-based solid electrolyte raw material 22 is supplied to the first melt obtained above (step S3), and heated and melted in a gas atmosphere containing sulfur element (step S4). The first melt is usually heated and melted to 600 to 1000° C. as described later, so by further supplying the second sulfide-based solid electrolyte raw material 22 to the first melt, the temperature of the supplied second sulfide-based solid electrolyte raw material 22 is rapidly increased, and mixed with the first melt, thereby obtaining the second melt 21 (step S5).

[0085] It should be noted that in the present manufacturing method, after the first sulfide-based solid electrolyte raw material 12 is heated and melted to obtain the first melt 11, the second sulfide-based solid electrolyte raw material 22 is directly and continuously supplied, thereby obtaining the second melt 21 without passing through an intermediate. Here, the intermediate refers to a compound that has a different chemical bond from the raw material after the raw material reacts, and is a compound that has a different chemical bonding state from the target electrolyte. For example, Li 22 obtained by heating a raw material containing lithium, sulfur, and phosphorus can be cited. 4 P 2 S 6 , Li 3 PS 4 Compounds containing Li, P and S, etc. According to the present production method, the above-mentioned preparatory step of intermediate production is not required, and the process can be simplified. In addition, since a large amount of sulfide-based solid electrolytes can be produced in a short time, there is no need to control the composition after the intermediate.

[0086] The present manufacturing method is based on the following discovery: As described above, the temperature of the second sulfide-based solid electrolyte raw material supplied to the first melt rises sharply, and melts instantly while mixing with the melt. Therefore, it is preferable to adjust the feeding rate of the second sulfide-based solid electrolyte raw material relative to the amount of the first melt. The speed of supplying the second sulfide-based solid electrolyte raw material 22 to the first melt is preferably adjusted to 5 mass% / min or less relative to 100 mass% of the first melt. The above-mentioned speed is further preferably adjusted to 3.5 mass% / min or less, and can be 0.01 mass% / min or more, or 0.05 mass% / min or more.

[0087] The second sulfide-based solid electrolyte raw material 22 may be supplied to the first melt continuously or intermittently. It is preferred that the second sulfide-based solid electrolyte raw material 22 be supplied continuously to the first melt. When the second sulfide-based solid electrolyte raw material 22 is supplied continuously, the supplied raw material melts instantly, so that the melt can be continuously synthesized in sequence, and then the cooling step can be moved to, so that a large amount of sulfide-based solid electrolyte can be efficiently synthesized in a short time.

[0088] When the second sulfide-based solid electrolyte raw material 22 is continuously supplied to the first melt, it is preferred to quantitatively supply the second sulfide-based solid electrolyte raw material 22. The quantitative supply method is not particularly limited, and examples thereof include methods using a screw feeder, a table feeder, and air flow conveying.

[0089] The second sulfide-based solid electrolyte raw material 22 is preferably mixed and stirred before being supplied to the first melt. As a result, the synthesis reaction of the second sulfide-based solid electrolyte raw material 22 is more effectively performed at the moment of mixing with the melt, so that more efficient melting can be achieved. There is no particular limitation on the method of mixing and stirring the second sulfide-based solid electrolyte raw material 22, and a conventionally known method can be used.

[0090] When the second sulfide-based solid electrolyte raw material is supplied to the first melt and heated and melted, it is carried out in a gas atmosphere containing sulfur. By heating and melting the raw material in a gas atmosphere containing sulfur, sulfur is introduced into the first melt, so that the composition change of sulfur accompanying volatilization can be suppressed. Alternatively, after the second melt is obtained by supplying the second sulfide-based solid electrolyte raw material to the first melt and heating and melting it, the second melt can be further heated and melted in a gas atmosphere containing sulfur. In this way, the part of sulfur that is reduced in volatilization during heating and melting is supplemented, so that the composition change of sulfur in the obtained sulfide-based solid electrolyte can be suppressed.

[0091] Examples of the gas containing sulfur element include sulfur gas, hydrogen sulfide gas, carbon disulfide gas, and the like, and compounds containing sulfur element or sulfur element gas.

[0092] The sulfur-containing gas atmosphere can be Figure 4 As shown in (a) of FIG. 1 , the sulfur source 33a is supplied to the first molten metal and a sulfur-containing gas generated by the sulfur source 33a is heated. In this case, the sulfur source 33a is not particularly limited as long as it is a single sulfur or a sulfur compound that produces a sulfur-containing gas by heating. Examples thereof include single 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, Cu 1－x S, etc.), polysulfides such as lithium polysulfide and sodium polysulfide, polysulfide, rubber subjected to vulcanization treatment, etc. As the sulfur source 33a, sulfur powder can be preferably used.

[0093] Alternatively, as another method, the gas atmosphere containing sulfur element may be formed by Figure 4 As shown in (b) of FIG. 1 , sulfur vapor 33b obtained in advance is introduced into the furnace body 30. For example, sulfur is heated at 200 to 450° C. to generate sulfur vapor 33b, and N 2 Inert gas such as nitrogen, argon, and helium is transported into the furnace as a carrier gas, thereby obtaining a gas atmosphere containing sulfur element.

[0094] In addition, as another method, the gas atmosphere containing sulfur element can be obtained by making at least one of the first sulfide-based solid electrolyte raw material and the second sulfide-based solid electrolyte raw material contain a sulfur source. Thus, when the raw material is heated and melted, the sulfur source is also heated, and the raw material can be heated and melted in the generated gas atmosphere containing sulfur element.

[0095] In the present production method, any one method may be used as the method for obtaining the gas atmosphere containing sulfur element, or a combination of a plurality of methods may be used.

[0096] The temperature of heating and melting is not particularly limited in any of the processes of obtaining the first molten liquid and the process of obtaining the second molten liquid, but is preferably 600°C or higher, more preferably 630°C or higher, and further preferably 650°C or higher from the viewpoint of homogenizing the molten liquid in a short time. In addition, from the viewpoint of suppressing the degradation and decomposition of the components in the molten liquid due to heating, the temperature of heating and melting is preferably 1000°C or lower, more preferably 950°C or lower, further preferably lower than 900°C, and particularly preferably lower than 800°C. In addition, it is preferably 600°C or higher and lower than 900°C.

[0097] It should be noted that, in the stage of obtaining the first molten liquid, the furnace body can be heated to the above-mentioned temperature by a heating unit provided in the furnace body, and thereafter, for example, in the stage of obtaining the second molten liquid, it is sufficient to supplement the heat energy of the temperature lowered by the supply of the additional raw material. For example, the above-mentioned temperature can be maintained by maintaining the internal temperature using a heater or the like.

[0098] The heating and melting time for obtaining the first melt is not particularly limited as long as the above-mentioned melt surface can be obtained, and may be, for example, 0.5 hours or more, 1 hour or more, or 2 hours or more.

[0099] The heating and melting time for obtaining the second molten liquid can be appropriately adjusted to match the furnace size, and is not particularly limited. From the perspective of homogeneity, it is preferably 0.5 hours or more, more preferably 1 hour or more, and further preferably 2 hours or more. In addition, if the degradation and decomposition of the components in the molten liquid caused by heating are within an acceptable range, the heating and melting time can also be longer. As a realistic range, it is preferably 100 hours or less, more preferably 50 hours or less, and further preferably 25 hours or less.

[0100] In either the process of obtaining the first molten liquid or the process of obtaining the second molten liquid, the pressure during heating and melting is not particularly limited, and is preferably, for example, normal pressure or slightly increased pressure, and more preferably normal pressure.

[0101] During heating and melting, the dew point in the furnace is preferably -20°C or lower from the viewpoint of preventing side reactions with water vapor, oxygen, etc. The lower limit is not particularly limited, but is usually -80°C or higher. The oxygen concentration is preferably 1000 ppm by volume or lower.

[0102] When the second sulfide-based solid electrolyte raw material is supplied to the first melt, the first melt is preferably mixed and stirred. As a result, the second sulfide-based solid electrolyte raw material 22 is better mixed with the melt, so that instantaneous melting can be further achieved. The mixing and stirring of the first melt may be performed before or after the second sulfide-based solid electrolyte raw material is supplied. There is no particular limitation on the method of mixing and stirring the first melt, and a conventionally known method can be used.

[0103] (cool down)

[0104] The present production method includes a step of cooling the second melt obtained by heating and melting the above-mentioned raw material (step S6). Thus, a solid sulfide-based solid electrolyte is obtained. For example, Figure 5 As shown, the second molten metal 41 is discharged from the discharge portion 44 provided in the furnace body 40 at any time, and the process proceeds to the cooling step of the second molten metal 41. The cooling of the second molten metal 41 can be performed by a known method, and the method is not particularly limited. In order to increase the cooling rate, it is preferred to use a twin roll which is generally known as the fastest quenching roll.

[0105] From the viewpoint of maintaining the composition obtained by heating and melting, the cooling rate is preferably 0.01°C / sec or more, more preferably 0.05°C / sec or more, and further preferably 0.1°C / sec or more. The upper limit of the cooling rate is not particularly limited, and the cooling rate of the twin rolls is, for example, 1,000,000°C / sec or less.

[0106] In addition, when it is desired to make the obtained solid an amorphous sulfide-based solid electrolyte, it is preferred to quench the second melt obtained by heating and melting. The cooling rate during quenching is preferably 10°C / sec or more, more preferably 100°C / sec or more, further preferably 500°C / sec or more, and particularly preferably 700°C / sec or more. In addition, the upper limit of the cooling rate is not particularly limited, and the cooling rate of the twin rolls is, for example, 1,000,000°C / sec or less.

[0107] On the other hand, slow cooling can also be performed during the cooling process to crystallize at least a portion of the solid, thereby obtaining a sulfide-based solid electrolyte having a specific crystal structure or a sulfide-based solid electrolyte composed of a crystalline phase and an amorphous phase. The cooling rate during slow cooling is preferably 0.01°C / sec or more, more preferably 0.05°C / sec or more. In addition, the cooling rate is preferably 500°C / sec or less, more preferably 450°C / sec or less. The cooling rate can be 10°C / sec or less, or 5°C / sec or less. It should be noted that the cooling rate can be appropriately adjusted according to the conditions of crystallization.

[0108] Here, the crystal of the sulfide-based solid electrolyte is preferably an ion-conducting crystal. Specifically, the ion-conducting crystal refers to a crystal having a lithium ion conductivity of greater than 10 －4 S / cm, more preferably greater than 10 －3 S / cm crystals.

[0109] In addition, when it is desired that the solid obtained after cooling is a sulfide-based solid electrolyte containing a crystalline phase, it is preferred that the melt obtained in the heating and melting step contains a compound that becomes a crystal nucleus. As a result, crystals are easily precipitated in the cooling step. The method of making the melt contain a compound that becomes a crystal nucleus is not particularly limited, and examples thereof include methods such as adding a compound that becomes a crystal nucleus to a raw material or an intermediate, and adding a compound that becomes a crystal nucleus to a melt during heating and melting.

[0110] Examples of the compound that serves as a crystal nucleus include oxides, nitrogen oxides, nitrides, carbides, chalcogenides, halides, etc. The compound that serves as a crystal nucleus is preferably a compound that has a certain degree of compatibility with the melt. It should be noted that a compound that is completely incompatible with the melt cannot serve as a crystal nucleus.

[0111] When it is desired that the solid obtained after cooling is a sulfide-based solid electrolyte containing a crystalline phase, the content of the compound that becomes the crystal nucleus in the melt is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 1% by mass or more. On the other hand, from the viewpoint of suppressing the decrease in lithium ion conductivity, the content of the compound that becomes the crystal nucleus in the melt is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0112] When it is desired that the solid obtained after cooling is an amorphous sulfide-based solid electrolyte, it is preferred that the melt does not contain a compound that serves as a crystal nucleus, or that the content of the compound is less than a predetermined amount. Specifically, the content of the compound that serves as a crystal nucleus in the melt is preferably less than 1% by mass, more preferably less than 0.1% by mass. The content of the compound that serves as a crystal nucleus in the melt may also be less than 0.01% by mass.

[0113] The cooling is preferably performed under normal pressure. Normal pressure means that the pressure is not controlled during cooling. Specifically, it is about 0.8 to 1.2 atm.

[0114] (Reheat)

[0115] In the case where the solid obtained in the cooling step is an amorphous sulfide-based solid electrolyte or a sulfide-based solid electrolyte containing an amorphous phase, the manufacturing method may further include a step of reheating the solid. In addition, by reheating the sulfide-based solid electrolyte containing sulfide-based solid electrolyte crystals, ions in the crystal structure can be rearranged, thereby improving lithium ion conductivity.

[0116] It should be noted that the reheating treatment refers to heating the cooled solid to achieve at least one of crystallization and rearrangement of ions in the crystal structure. Here, the heating treatment of these amorphous sulfide-based solid electrolytes or sulfide-based solid electrolytes containing an amorphous phase is also referred to as the reheating treatment including the crystallization treatment.

[0117] (Continuous process)

[0118] In the present manufacturing method, it is preferred that the heating and melting step and the cooling step are performed as continuous steps. That is, it is preferred that the second sulfide-based solid electrolyte raw material is continuously supplied to the first melt obtained in the furnace body, and the second melt generated over time is continuously discharged and moved to the cooling step to continuously manufacture the sulfide-based solid electrolyte. Thus, a series of steps including the input of raw materials, the discharge and cooling of the melt can be performed continuously, and the sulfide-based solid electrolyte can be manufactured in large quantities in a short time more efficiently. Specifically, it is preferred that a series of steps including the following steps are continuously performed, namely, a step of heating and melting the first sulfide-based solid electrolyte raw material in the furnace body to obtain the first melt, a step of supplying the second sulfide-based solid electrolyte raw material to the first melt and heating and melting it in a gas atmosphere containing sulfur element to obtain the second melt, and a step of discharging the second melt from the furnace body and cooling the second melt.

[0119] (Sulfide-based solid electrolyte)

[0120] Examples of the sulfide-based solid electrolyte obtained by the present production method include sulfide-based solid electrolytes containing lithium elements, for example, Li 10 G 2 S 12 Sulfide-based solid electrolytes with LGPS crystal structure, Li 6 PS 5 Cl, Li 5.4 PS 4.4 Cl 1.6 and Li 5.4 PS4.4 Cl 0.8 Br 0.8 Sulfide-based solid electrolytes having an argyrodite-type crystal structure, Li-P-S-Ha-based (Ha represents at least one element selected from halogen elements) glass-ceramics, and Li 7 P 3 S 11 LPS glass-ceramics, etc.

[0121] The sulfide-based solid electrolyte may be an amorphous sulfide-based solid electrolyte, a sulfide-based solid electrolyte having a specific crystal structure, or a sulfide-based solid electrolyte including a crystalline phase and an amorphous phase, depending on its purpose. From the viewpoint of lithium ion conductivity, the crystalline phase is more preferably an argyrodite-type crystalline phase.

[0122] As a sulfide-based solid electrolyte with excellent lithium ion conductivity, a sulfide-based solid electrolyte having the element Li-P-S-Ha is preferred, and a crystalline phase is more preferred. In addition, the halogen element is preferably a halogen element selected from one or more of lithium chloride, lithium bromide and lithium iodide.

[0123] From the viewpoint of improving battery characteristics when used in lithium ion secondary batteries, the lithium ion conductivity of the sulfide-based solid electrolyte is preferably 1.0×10 －4 S / cm or more, more preferably 5.0×10 －4 S / cm or more, more preferably 1.0×10 －3 S / cm or more, particularly preferably 5.0×10 －3 S / cm or more.

[0124] The lithium ion conductivity is measured using an AC impedance measurement device (eg, a potentiostat / galvanostat VSP manufactured by Bio-Logic Sciences Instruments) at a measurement frequency of 100 Hz to 1 MHz, a measurement voltage of 100 mV, and a measurement temperature of 25°C.

[0125] The obtained sulfide-based solid electrolyte can be identified by analysis of the crystal structure based on X-ray diffraction (XRD) measurement, and analysis of the elemental composition by various methods such as ICP emission spectroscopy, atomic absorption spectrometry, and ion chromatography. For example, P and S can be measured by ICP emission spectroscopy, Li can be measured by atomic absorption spectrometry, and Ha can be measured by ion chromatography.

[0126] In addition, by performing Raman spectroscopy, the homogeneity of the composition of the sulfide-based solid electrolyte can be evaluated. Specifically, Raman spectroscopy is performed on a sample obtained from the obtained sulfide-based solid electrolyte at any two or more points. It should be noted that from the viewpoint of improving the evaluation accuracy, the number of measurement points is preferably 8 or more, and more preferably 10 or more.

[0127] Preferred Raman spectroscopic conditions for evaluating the homogeneity of the composition of the sulfide-based solid electrolyte include, for example, a spot diameter of 3 μm and a number of measurement points of 10. By setting the spot diameter to 3 μm, the analysis region in the Raman spectroscopic measurement is a size suitable for evaluating the homogeneity of the composition of the sulfide-based solid electrolyte at a microscopic level.

[0128] It is believed that the PS in each measurement result 4 3－ The smaller the deviation of the peak wave number (peak position) of the structure derived from the sulfide-based solid electrolyte, the more homogeneous the composition of the sulfide-based solid electrolyte. Alternatively, it is considered that the smaller the deviation of the half-peak width of the peak derived from the structure of the sulfide-based solid electrolyte, the more homogeneous the composition of the sulfide-based solid electrolyte.

[0129] Although it depends on the composition of the obtained sulfide-based solid electrolyte, it is preferable to confirm a peak derived from a P—S bond as a peak derived from the structure of the sulfide-based solid electrolyte.

[0130] The position of the peak derived from the P-S bond varies depending on the composition system, but is typically contained at 350 cm －1 ~500cm －1 Hereinafter, the deviation of the peak position and the deviation of the half-peak width of the peak in this specification refer to the deviation confirmed for the strongest peak among the peaks derived from the P—S bond.

[0131] The deviation of the peak position can be evaluated as follows. That is, when the standard deviation of the peak position of each measurement point obtained by Raman spectroscopy is obtained and recorded as (peak position average value) ± (standard deviation), the value of the standard deviation is preferably 2 cm －1 Within, more preferably 1 cm －1 Within, more preferably 0.5cm －1 It should be noted that the peak position here refers to the position of the peak top.

[0132] For example, when the sulfide-based solid electrolyte obtained by the present production method is subjected to Raman spectroscopy with a spot diameter of 3 μm and 10 measurement points, the 350 cm －1 ~500cm －1 The standard deviation of the peak position derived from the P—S bond within the range is preferably 2 cm －1 Within, more preferably 1 cm－1 Within, more preferably 0.5cm －1 Within.

[0133] The deviation of the half-peak width of the peak can be evaluated as follows. That is, the standard deviation of the half-peak width of the peak at each measurement point obtained by Raman spectroscopy is calculated by the method of finding the half-peak width of each peak and finding the standard deviation of the value. When it is recorded as (peak half-peak width average) ± (standard deviation), the value of the standard deviation is preferably 2 cm －1 Within, more preferably 1.5cm －1 It should be noted that the peak half-width here refers to the width at which a value half the peak intensity of the peak derived from the P—S bond intersects with the peak derived from the P—S bond when the Raman spectrum is plotted.

[0134] For example, when the sulfide-based solid electrolyte obtained by the present production method is subjected to Raman spectroscopy with a spot diameter of 3 μm and 10 measurement points, the 350 cm －1 ~500cm －1 The standard deviation of the half-peak width of the peak derived from the P—S bond in the －1 Within, more preferably 1.5cm －1 Within.

[0135] [Sulfide-based solid electrolyte production device]

[0136] The manufacturing apparatus of the sulfide-based solid electrolyte according to the embodiment of the present invention (hereinafter also referred to as the present manufacturing apparatus) is characterized by comprising a furnace body, a heating unit for heating the furnace body, a first raw material supply unit for supplying a first sulfide-based solid electrolyte raw material to the furnace body, a second raw material supply unit for supplying a second sulfide-based solid electrolyte raw material to a first melt obtained by heating and melting the first sulfide-based solid electrolyte raw material supplied to the furnace body, a discharge unit for discharging a second melt obtained by supplying the second sulfide-based solid electrolyte raw material to the first melt in the furnace body, and a cooling unit for cooling the second melt discharged from the discharge unit.

[0137] The present production apparatus can be used to implement the present production method described above, and the contents described in the section [Production method of sulfide-based solid electrolyte] can be directly cited. Figure 6 This is a schematic diagram showing an example of the present production apparatus.

[0138] The heating unit (not shown) for heating the furnace body 50 in the present production apparatus 500 is provided for the purpose of performing the heating and melting described in the section [Production method of sulfide-based solid electrolyte], and its form is not particularly limited.

[0139] The first raw material supply unit 51 in the present production apparatus 500 is provided for supplying the first sulfide-based solid electrolyte raw material described in the section [Production method of sulfide-based solid electrolyte] to the furnace body 50 , and its form is not particularly limited.

[0140] The second raw material supply unit 52 in the manufacturing apparatus 500 is provided to supply the second sulfide-based solid electrolyte raw material to the first melt obtained by heating and melting the first sulfide-based solid electrolyte raw material supplied to the furnace body 50, and its form is not particularly limited.

[0141] The second raw material supply unit 52 may continuously supply the second sulfide-based solid electrolyte raw material to the first melt, may quantitatively supply the second sulfide-based solid electrolyte raw material to the first melt, or may use both.

[0142] It should be noted that although Figure 6 2 shows an example in which different supply ports are used for the first raw material supply unit 51 and the second raw material supply unit 52, but the present embodiment is not limited thereto, and the same supply port provided in the present manufacturing apparatus 500 may be used.

[0143] The discharge unit 53 in the present manufacturing apparatus 500 is provided to discharge the second melt obtained by supplying the second sulfide-based solid electrolyte raw material to the first melt in the furnace body 50 , and its form is not particularly limited.

[0144] The cooling unit 54 in the present manufacturing apparatus 500 is provided to cool the second melt discharged from the discharge unit 53 , and its form is not particularly limited.

[0145] In addition, the cooling unit 54 may also be Figure 6 The device shown has the twin rolls described in the section [Method for producing sulfide-based solid electrolyte].

[0146] The present production apparatus 500 may include a sulfur supply unit 55 for supplying the sulfur source or sulfur vapor described in the section [Production method of sulfide-based solid electrolyte], but the form thereof is not particularly limited.

[0147] It should be noted that although Figure 6 2 shows an example in which different supply ports are used for the sulfur supply unit 55 and the first raw material supply unit 51 and the second raw material supply unit 52, but the present embodiment is not limited thereto, and the same supply ports provided in the present manufacturing apparatus 500 may be used.

[0148] As described in the section [Method for producing a sulfide-based solid electrolyte], the present production apparatus 500 may include a reheating unit (not shown) for reheating the sulfide-based solid electrolyte cooled by the cooling unit 54, but the form thereof is not particularly limited.

[0149] It should be noted that the present invention is not limited to the above-mentioned 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-mentioned embodiments, and modifications and improvements can be made as appropriate. In addition, the material, shape, size, quantity, and configuration position of each component in the above-mentioned embodiment are arbitrary and not limited as long as the present invention can be realized.

[0150] As described above, the present specification discloses the following matters.

[0151] [1] A method for producing a sulfide-based solid electrolyte, comprising heating and melting a first sulfide-based solid electrolyte raw material in a furnace to obtain a first melt, supplying a second sulfide-based solid electrolyte raw material to the first melt, heating and melting the raw material in a gas atmosphere containing sulfur, and cooling the obtained second melt.

[0152] [2] The method for producing a sulfide-based solid electrolyte according to [1] above, wherein the second sulfide-based solid electrolyte raw material is supplied at a rate of 5 mass% / min or less relative to 100 mass% of the first melt.

[0153] [3] The method for producing a sulfide-based solid electrolyte according to [1] or [2] above, wherein the composition of the first sulfide-based solid electrolyte raw material is the same as the composition of the second sulfide-based solid electrolyte raw material.

[0154] [4] The method for producing a sulfide-based solid electrolyte according to any one of [1] to [3] above, wherein the gas atmosphere containing the sulfur element is obtained by supplying a sulfur source to the first melt.

[0155] [5] The method for producing a sulfide-based solid electrolyte according to any one of [1] to [4] above, wherein the gas atmosphere containing the sulfur element is obtained by introducing sulfur vapor into the furnace body.

[0156] [6] The method for producing a sulfide-based solid electrolyte according to [5] above, wherein the sulfur vapor is generated by heating sulfur at 200 to 450° C. in the furnace.

[0157] [7] The method for producing a sulfide-based solid electrolyte according to any one of [1] to [6] above, wherein the second sulfide-based solid electrolyte raw material is continuously supplied to the first melt.

[0158] [8] The method for producing a sulfide-based solid electrolyte according to any one of [1] to [7] above, wherein the second molten metal is continuously discharged from the furnace body and cooled.

[0159] [9] The method for producing a sulfide-based solid electrolyte according to any one of [1] to [8] above, wherein the heating temperature of the first sulfide-based solid electrolyte raw material or the second sulfide-based solid electrolyte raw material is 600° C. or higher and lower than 900° C.

[0160]

[10] The method for producing a sulfide-based solid electrolyte according to any one of [1] to [9] above, wherein the second molten metal is cooled using twin rolls.

[0161]

[11] A device for producing a sulfide-based solid electrolyte, comprising:

[0162] Furnace body,

[0163] A heating unit, used for heating the furnace body,

[0164] a first raw material supplying section for supplying a first sulfide-based solid electrolyte raw material to the furnace body;

[0165] a second raw material supplying section for supplying a second sulfide-based solid electrolyte raw material to a first melt obtained by heating and melting the first sulfide-based solid electrolyte raw material supplied to the furnace body,

[0166] a discharge unit for discharging a second molten liquid obtained by supplying a second sulfide-based solid electrolyte raw material to the first molten liquid in the furnace body, and

[0167] The cooling unit is configured to cool the second molten liquid discharged from the discharge unit.

[0168]

[12] The apparatus for producing a sulfide-based solid electrolyte according to

[11] , further comprising a sulfur supply unit for supplying a sulfur source or sulfur vapor to the furnace body.

[0169]

[13] The apparatus for producing a sulfide-based solid electrolyte according to

[11] or

[12] above, wherein the second raw material supply unit continuously supplies the second sulfide-based solid electrolyte raw material to the first melt.

[0170]

[14] The apparatus for producing a sulfide-based solid electrolyte according to any one of

[11] to

[13] above, wherein the second raw material supply unit supplies a fixed amount of the second sulfide-based solid electrolyte raw material to the first melt.

[0171]

[15] The apparatus for producing a sulfide-based solid electrolyte according to any one of

[11] to

[14] above, wherein the cooling section has twin rolls.

[0172]

[16] The apparatus for producing a sulfide-based solid electrolyte according to any one of

[11] to

[15] , further comprising a reheating unit for reheating the sulfide-based solid electrolyte obtained by cooling in the cooling unit.

[0173] Example

[0174] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Examples 1 and 2 are examples of the present production method, and Examples 3 and 4 are comparative examples.

[0175] (Lithium ion conductivity evaluation)

[0176] The powder obtained in each example was further crushed in a mortar and sieved at 100 μm to obtain a sulfide-based solid electrolyte powder with a volume-based particle size distribution of D50 of 10 μm. The powder was pressed into a powder body at a pressure of 380 MPa as a measurement sample, and the lithium ion conductivity was measured using an AC impedance measurement device (manufactured by Bio-Logic Sciences Instruments, constant potential meter / constant current meter VSP), and evaluated according to the following criteria.

[0177] The measurement conditions are as follows: measurement frequency: 100 Hz to 1 MHz, measurement voltage: 100 mV, and measurement temperature: 25°C.

[0178] (Battery performance evaluation)

[0179] The powder obtained in each example was further crushed in a mortar and sieved at 100 μm to obtain a sulfide-based solid electrolyte powder with a volume-based particle size distribution of D50 of 10 μm. The battery performance of the powder when used in an all-solid lithium-ion secondary battery was evaluated. First, a positive electrode composite material and an all-solid lithium-ion secondary battery were prepared according to the following method, and a charge and discharge test was performed. The results of the charge and discharge test were evaluated according to the following evaluation criteria.

[0180] [Production of positive electrode composite material]

[0181] As the positive electrode active material, LiNbO 3 Layered rock-salt LiCoO 2 The positive electrode composite material was prepared by mixing 35 parts of the sulfide solid electrolyte powder obtained in each example, 60 parts of the positive electrode active material, and 5 parts of the conductive additive (acetylene black, manufactured by Denka Co., Ltd., HS100). 3 The thickness of the coating layer is 7 nm.

[0182] [Fabrication of all-solid-state lithium-ion secondary batteries]

[0183] 80 mg of the sulfide solid electrolyte powder obtained in each method was put into a plastic cylinder with a diameter of 10 mm and press-formed to form a solid electrolyte layer. Then, 10 mg of the positive electrode composite material prepared above was put into the same cylinder and press-formed again to form a positive electrode layer. In addition, indium foil and lithium foil were put into the negative electrode layer from the opposite side of the positive electrode composite material. A fully solid lithium-ion secondary battery was thus prepared, and a battery performance evaluation test was performed under a constraint pressure of 10 kN.

[0184] [Battery performance evaluation test]

[0185] The prepared all-solid lithium ion secondary battery was charged to 3.7 V at 0.1 C at a constant current and constant potential at 25° C., and then discharged to 1.9 V at a constant current and 3 C to obtain the discharge capacity. The discharge capacity shown below is the discharge capacity (mAh / g) per unit weight (g) of the positive electrode active material.

[0186] (Evaluation Criteria)

[0187] 0: Discharge capacity is greater than 30.

[0188] △: The discharge capacity is greater than 0 and 30 or less.

[0189] ×: The discharge capacity is 0.

[0190] Example 1

[0191] 1. Raw material mixing

[0192] In a glove box with a nitrogen atmosphere adjusted to a dew point of -50°C, Li 2 S, P 2 S 5 , LiCl raw material powders were blended in a ratio of 1.9:0.5:1.6 (mol ratio), and stirred and mixed thoroughly. 300 g of the raw materials after stirring and mixing were put into a carbon container replaced with a nitrogen atmosphere with a dew point of -50°C or less.

[0193] 2. First melt formation

[0194] The carbon container was heated to 300°C at a temperature increase rate of 5°C / min, maintained at that temperature for 0.5 hours, and then heated to 700°C at a temperature increase rate of 5°C / min, maintained at that temperature, to form a melt surface.

[0195] 3. Additional input of raw materials

[0196] In a glove box under a nitrogen atmosphere with a dew point of -50°C, the raw material powders prepared in the same mol ratio as the above raw materials are thoroughly stirred and mixed, placed in a sealed container, and put into a hopper connected to a quantitative feeder (MicronFeeder, manufactured by AishinNano Technologies) without being exposed to the atmosphere. The dew point inside the hopper is also adjusted to below -50°C. Using the quantitative feeder, the mixed raw materials are added at a rate of 6 g / min into the carbon container that has formed the above-mentioned melt surface. It should be noted that the injection rate from the start of the injection of the mixed raw materials to the completion of the injection is maintained at less than 2 mass% relative to 100 mass% of the melt. At the same time as the injection, N is fed in at 2SLM from the same piping. 2 In addition, sulfur powder was fed at a rate of 0.6 g / min simultaneously with the feeding of the raw materials, so that the interior of the carbon container was filled with sulfur gas.

[0197] 4. Discharge and cool down

[0198] The melt was discharged from a discharge port attached to the carbon container at a rate of 6 g / min and rapidly cooled to obtain a solid which is a sulfide-based solid electrolyte containing an amorphous phase and an argyrodite-type crystal phase.

[0199] 5. Reheating process

[0200] The obtained solid was crushed into a coarse powder by a cutter, and then placed in a carbon container and subjected to a crystallization treatment at 400°C for 1 hour in a nitrogen atmosphere. Thus, Li was obtained as a sulfide-based solid electrolyte having an argyrodite-type crystal structure with a crystalline phase ratio of 90 vol% or more. 5.4 PS 4.4 Cl 1.6 .

[0201] It should be noted that the steps "3. Additional input of raw materials" and "4. Discharge and cooling and solidification" in the above steps were performed continuously. That is, while additional input of raw materials was performed, the obtained melt was discharged and cooled and solidified continuously.

[0202] The lithium ion conductivity of the obtained electrolyte was measured and found to be 5 mS / cm. In addition, the battery performance was evaluated as 0 (discharge capacity: 38 mAh / g). The results are shown in Table 1.

[0203] Example 2

[0204] Sulfur was heated at 350°C to generate sulfur vapor instead of the sulfur powder fed in "3. Additional feeding of raw materials" of Example 1, and the sulfur vapor was supplied to the carbon container, thereby supplying a sulfur gas atmosphere into the container. Powder of a sulfide-based solid electrolyte was obtained by the same method as in Example 1, except that sulfur was heated at 350°C to generate sulfur vapor instead of the sulfur powder fed in "3. Additional feeding of raw materials", and the sulfur vapor was supplied to the carbon container.

[0205] The conductivity of the obtained electrolyte was measured and found to be 5 mS / cm. In addition, the battery performance was evaluated as 0 (discharge capacity: 45 mAh / g). The results are shown in Table 1.

[0206] Example 3

[0207] 1. Heating of the container

[0208] The carbon container was heated to 700°C in the same manner as in Example 1.

[0209] 2. Raw material input

[0210] The raw material was charged into the carbon container heated to 700° C. in the same manner as in “3. Additional charging of raw material” of Example 1. However, sulfur powder was not supplied.

[0211] 3. Discharge and cool down

[0212] After the internal raw materials were melted, the melt flowed out from the discharge port attached to the carbon container at a rate of about 6 g / min and was rapidly cooled to obtain a solid which was a sulfide-based solid electrolyte containing an amorphous phase and an argyrodite-type crystal phase.

[0213] 4. Reheating process

[0214] Next, the solid was pulverized into a coarse powder by a cutter, and then placed in a carbon container and subjected to a crystallization treatment at 400° C. for 1 hour in a nitrogen atmosphere to perform crystallization.

[0215] It should be noted that the above steps of "2. Raw material input" and "3. Discharge and cooling and solidification" are not performed in a linked and continuous manner, but are performed naturally. That is, the raw material is input at a rate of 6 g / min without the amount of the first melt, and the raw material is immediately melted and discharged. At this time, discharge and cooling and solidification are performed at a discharge rate of about 0 to 6 g / min. After the input is started and 10 g is discharged, the sample is stopped and evaluated.

[0216] The obtained electrolyte also had a crystalline phase other than the argyrodite-type crystal, and the conductivity thereof was measured to be 0.1 mS / cm. In addition, the battery performance evaluation was × (discharge capacity: 0 mAh / g). The results are shown in Table 1.

[0217] Example 4

[0218] 1. Raw material mixing and first melt formation

[0219] The raw materials were mixed in the same manner as in Example 1 to form a first melt having a melt surface.

[0220] 2. Additional input of raw materials

[0221] The raw materials were additionally charged in the same manner as in Example 1 except that sulfur powder was not supplied.

[0222] 3. Discharge and cool down

[0223] The molten metal was discharged from a discharge port attached to the carbon container and rapidly cooled to obtain a solid which is a sulfide-based solid electrolyte containing an amorphous phase and an argyrodite-type crystal phase.

[0224] 4. Reheating process

[0225] The obtained solid was pulverized into a coarse powder by a cutter, and then placed in a carbon container and subjected to a crystallization treatment at 400° C. for 1 hour in a nitrogen atmosphere to perform crystallization.

[0226] As described above, a powder of a sulfide-based solid electrolyte was obtained by the same method as in Example 1.

[0227] The obtained electrolyte also had a crystalline phase other than the argyrodite-type crystal, and the conductivity thereof was measured to be 1 mS / cm. In addition, the battery performance evaluation was △ (discharge capacity: 5 mAh / g). The results are shown in Table 1.

[0228] [Table 1]

[0229] Table 1

[0230]

[0231] As examples 1 and 2 of the embodiments, both showed excellent results in lithium ion conductivity and battery evaluation. Therefore, it can be seen that according to the present manufacturing method, the volatilization of raw materials in the electrolyte manufacturing process can be suppressed. In addition, in examples 1 and 2, the second melt is continuously obtained by adding raw materials to the first melt having a melt surface, and then the cooling process is transferred. Therefore, it can be seen that a large amount of sulfide-based solid electrolytes can be produced in a short time.

[0232] On the other hand, Example 3 as a comparative example was obtained by directly heating the mixed raw materials without obtaining the first melt, and thus the ion conductivity and battery performance were poor. Also, Example 4 as a comparative example was obtained by not supplying sulfur when the raw materials were additionally added to the first melt, and thus the ion conductivity and battery performance were poor.

[0233] Above, various embodiments have been described with reference to the accompanying drawings, but the present invention is certainly not limited to the above examples. It is understood that for those skilled in the art, various variations or modifications can be thought of within the scope of the scope of the patent claim, and these certainly also belong to the technical scope of the present invention. In addition, the various constituent elements in the above embodiments can also be arbitrarily combined within the scope of the invention without departing from the main purpose.

[0234] It should be noted that the present application is based on Japanese patent application (Japanese Patent Application No. 2022-079716) filed on May 13, 2022, the contents of which are incorporated herein by reference.

[0235] Explanation of symbols

[0236] 10, 20, 30, 40 furnace body

[0237] 111st melt

[0238] 121st sulfide-based solid electrolyte raw materials

[0239] 13 Melt surface

[0240] 21, 31, 41 Second melt

[0241] 22, 32 Second sulfide-based solid electrolyte raw materials

[0242] 33a Sulfur source

[0243] 33B Sulfur vapor

[0244] 44 discharge part

[0245] 500 Sulfide-based solid electrolyte manufacturing device

[0246] 50 Furnace

[0247] 511st raw material supply unit

[0248] 52 2nd raw material supply unit

[0249] 53 discharge part

[0250] 54 Cooling unit

[0251] 55Sulfur supply department

Claims

1. A method for producing a sulfide-based solid electrolyte, comprising heating and melting a first sulfide-based solid electrolyte raw material in a furnace to obtain a first melt, supplying a second sulfide-based solid electrolyte raw material to the first melt, heating and melting the raw material in a gas atmosphere containing sulfur, and cooling the obtained second melt.

2. The method for producing a sulfide-based solid electrolyte according to claim 1, wherein: The second sulfide-based solid electrolyte raw material is supplied at a rate of 5 mass% / min or less relative to 100 mass% of the first melt.

3. The method for producing a sulfide-based solid electrolyte according to claim 1 or 2, wherein: The composition of the first sulfide-based solid electrolyte raw material is the same as the composition of the second sulfide-based solid electrolyte raw material.

4. The method for producing a sulfide-based solid electrolyte according to claim 1 or 2, wherein: The gas atmosphere containing sulfur element is obtained by supplying a sulfur source to the first melt.

5. The method for producing a sulfide-based solid electrolyte according to claim 1 or 2, wherein: The gas atmosphere containing sulfur element is obtained by introducing sulfur vapor into the furnace body.

6. The method for producing a sulfide-based solid electrolyte according to claim 5, wherein: The sulfur vapor is generated by heating sulfur at 200 to 450° C. in the furnace.

7. The method for producing a sulfide-based solid electrolyte according to claim 1 or 2, wherein: The second sulfide-based solid electrolyte raw material is continuously supplied to the first melt.

8. The method for producing a sulfide-based solid electrolyte according to claim 1 or 2, wherein: The second molten metal is continuously discharged from the furnace body and cooled.

9. The method for producing a sulfide-based solid electrolyte according to claim 1 or 2, wherein: The heating temperature of the first sulfide-based solid electrolyte raw material or the second sulfide-based solid electrolyte raw material is 600°C or higher and lower than 900°C.

10. The method for producing a sulfide-based solid electrolyte according to claim 1 or 2, wherein: The second melt was cooled using twin rolls.

11. A device for producing a sulfide-based solid electrolyte, comprising: Furnace body, A heating unit, used for heating the furnace body, a first raw material supplying unit for supplying a first sulfide-based solid electrolyte raw material to the furnace body, a second raw material supplying section for supplying a second sulfide-based solid electrolyte raw material to a first melt obtained by heating and melting the first sulfide-based solid electrolyte raw material supplied to the furnace body; a discharge unit for discharging a second molten liquid obtained by supplying a second sulfide-based solid electrolyte raw material to the first molten liquid in the furnace body, and The cooling unit is configured to cool the second melt discharged from the discharge unit.

12. The manufacturing apparatus of the sulfide-based solid electrolyte according to claim 11, wherein: A sulfur supply unit for supplying a sulfur source or sulfur vapor to the furnace body is provided.

13. The manufacturing apparatus of the sulfide-based solid electrolyte according to claim 11 or 12, wherein: The second raw material supply unit continuously supplies the second sulfide-based solid electrolyte raw material to the first melt.

14. The manufacturing apparatus of the sulfide-based solid electrolyte according to claim 11 or 12, wherein: The second raw material supply unit supplies a fixed amount of the second sulfide-based solid electrolyte raw material to the first melt.

15. The manufacturing apparatus of the sulfide-based solid electrolyte according to claim 11 or 12, wherein: The cooling section has twin rollers.

16. The manufacturing apparatus of the sulfide-based solid electrolyte according to claim 11 or 12, wherein: A reheating unit is provided for reheating the sulfide-based solid electrolyte cooled by the cooling unit.

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