Method for producing lithium hydroxide, method for producing lithium-containing sulfide solid electrolyte starting material, and method for producing sulfide solid electrolyte

Abstract

The present invention provides a method for producing lithium hydroxide, comprising the steps of reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide, and performing solid-liquid separation on the solution into a liquid component containing lithium hydroxide and a solid component containing lithium derived from the lithium carbonate, and recovering lithium hydroxide from the liquid component.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for producing lithium hydroxide, a method for producing a lithium-containing sulfide solid electrolyte material, and a method for producing a sulfide solid electrolyte, and in detail, to a method for producing lithium hydroxide, a method for producing lithium sulfide, a method for producing a lithium-containing sulfide solid electrolyte material, a method for producing lithium hydroxide and a lithium-containing sulfide solid electrolyte material, and a method for producing a sulfide solid electrolyte, and a lithium hydroxide-containing composition for synthesis of a sulfide solid electrolyte, a lithium sulfide-containing composition for synthesis of a sulfide solid electrolyte, and a lithium halide-containing composition for synthesis of a sulfide solid electrolyte. BACKGROUND

[0002] Lithium ion secondary batteries are widely used for portable electronic devices such as mobile phones and notebook computers. In the past, a liquid electrolyte has been used in lithium ion secondary batteries. On the other hand, in recent years, all-solid type lithium ion secondary batteries in which a solid electrolyte is used as an electrolyte for lithium ion secondary batteries have attracted attention from the viewpoints of improvement in safety, high-speed charge and discharge, and miniaturization of a case.

[0003] As a solid electrolyte used in all-solid type lithium ion secondary batteries, for example, a sulfide solid electrolyte can be cited. Lithium sulfide, which is one of raw materials for the sulfide solid electrolyte, is obtained, for example, by reacting lithium hydroxide with hydrogen sulfide. In addition, lithium halide, which is one of raw materials for the sulfide solid electrolyte, is also obtained, for example, by reacting lithium hydroxide with hydrogen halide. In this way, lithium hydroxide is used in the synthesis of lithium sulfide and lithium halide, which are raw materials for the sulfide solid electrolyte. In the synthesis of the above-described lithium hydroxide, a method in which lithium carbonate is reacted with calcium hydroxide is known (for example, Patent Literature 1).

[0004] PRIOR ART DOCUMENT

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2021-172537 SUMMARY

[0007] In the method in which lithium carbonate is reacted with calcium hydroxide to synthesize lithium hydroxide, after lithium carbonate and calcium hydroxide are put into water and stirred to synthesize lithium hydroxide, the lithium hydroxide is recovered by dissolving in water. However, in the recovery of the aqueous solution, the solid component removed by solid-liquid separation contains unreacted lithium carbonate, or lithium hydroxide aqueous solution that is synthesized by reaction but is attached to the solid component. Therefore, in the solid-liquid separation, the lithium component is also removed together with the solid component, and there is a problem that the recovery rate of the lithium component as lithium hydroxide is low.

[0008] Further, in order to improve the recovery rate of lithium component as lithium hydroxide, by recovering the above-mentioned solid component removed by solid-liquid separation and adding water again, unreacted lithium carbonate can be reacted to generate lithium hydroxide, or lithium hydroxide adhering to the solid component can be dissolved in water and recovered. However, in this case, in order to improve the recovery rate of lithium component, several identical processes need to be combined, and there is a problem of causing the manufacturing equipment to be large.

[0009] Further, in order to reduce unreacted lithium, it is effective to increase the amount of calcium hydroxide to be input, but there is a problem of an increase in purchase cost due to an increase in the amount of lithium hydroxide to be used.

[0010] Further, it is also possible to improve the recovery rate of lithium hydroxide by increasing the amount of water, but there is a problem of an increase in energy cost required for removing water in the subsequent drying process due to the use of a large amount of water.

[0011] Further, in the conventional method, only lithium hydroxide can be obtained as a sulfide solid electrolyte raw material, and thus other desired sulfide solid electrolyte raw materials cannot be obtained, and there is a problem of poor manufacturing efficiency of the sulfide solid electrolyte raw material.

[0012] Therefore, an object of the present application is to provide a method capable of efficiently manufacturing lithium hydroxide at low cost, and further efficiently manufacturing a sulfide solid electrolyte raw material and a sulfide solid electrolyte.

[0013] The present inventors have conducted intensive studies, and as a result, have found a method in which, when lithium carbonate is reacted with calcium hydroxide in a liquid to synthesize lithium hydroxide, the amount of lithium component dissolved in water is suppressed, and thus the lithium component remains not only on the liquid component side but also on the solid component side in the subsequent solid-liquid separation, and lithium hydroxide is recovered from the liquid component side and a lithium-containing sulfide solid electrolyte raw material is recovered from the solid component side. According to this method, lithium hydroxide can be efficiently obtained from the liquid component side, and a lithium-containing sulfide solid electrolyte raw material can also be obtained from the solid component side. Therefore, it has been found that, within the same manufacturing process, lithium hydroxide can be efficiently obtained from the liquid component side at low cost, and a lithium-containing sulfide solid electrolyte raw material can also be obtained from the solid component side, and a sulfide solid electrolyte raw material and a sulfide solid electrolyte can be efficiently manufactured, and thus the present application has been completed.

[0014] That is, the present application relates to the following [1] to

[21] .

[0015] [1] A manufacturing method of lithium hydroxide, comprising the steps of:

[0016] reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide,

[0017] solid-liquid separation of the above solution into a liquid component containing the above lithium hydroxide and a solid component containing lithium from the above lithium carbonate, and

[0018] recovering lithium hydroxide from the above liquid component.

[0019] [2] The method for producing lithium hydroxide according to the above [1], wherein the amount of water is 70 to 96 mass% relative to the total amount of liquid in which lithium carbonate is reacted with calcium hydroxide.

[0020] [3] The method for producing lithium hydroxide according to the above [1], wherein the mixing ratio of calcium hydroxide to lithium carbonate (calcium hydroxide / lithium carbonate) is 0.2 to 1.1 on a molar basis.

[0021] [4] The method for producing lithium hydroxide according to the above [1], wherein the temperature of the liquid in which lithium carbonate is reacted with calcium hydroxide is 10 to 95°C.

[0022] [5] A method for producing lithium sulfide, in which lithium hydroxide obtained by the method for producing lithium hydroxide according to any one of the above [1] to [4] is reacted with hydrogen sulfide to produce lithium sulfide.

[0023] [6] A method for producing a sulfide solid electrolyte, in which lithium sulfide obtained by the method for producing lithium sulfide according to the above [5] is used as a raw material.

[0024] [7] A method for producing a lithium-containing sulfide solid electrolyte raw material, comprising the steps of:

[0025] reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide,

[0026] solid-liquid separation of the above solution into a liquid component containing the above lithium hydroxide and a solid component containing lithium from the above lithium carbonate, and

[0027] removing calcium from the above solid component to obtain a lithium-containing sulfide solid electrolyte raw material from the above solid component.

[0028] [8] The method for producing a lithium-containing sulfide solid electrolyte raw material according to the above [7], wherein calcium is removed from the above solid component by adding sulfate ions to the above solid component.

[0029] [9] The method for producing a lithium-containing sulfide solid electrolyte raw material according to the above [7], wherein the lithium-containing sulfide solid electrolyte raw material is lithium halide or lithium sulfate.

[0030]

[10] A method for producing a sulfide solid electrolyte, in which a lithium-containing sulfide solid electrolyte raw material obtained by the method for producing a lithium-containing sulfide solid electrolyte raw material according to any one of the above [7] to [9] is used.

[0031]

[11] A method for producing lithium hydroxide and a lithium-containing sulfide solid electrolyte raw material, comprising the steps of:

[0032] reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide,

[0033] solid-liquid separating the above solution into a liquid component containing the above lithium hydroxide and a solid component containing lithium from the above lithium carbonate,

[0034] recovering lithium hydroxide from the above liquid component, and

[0035] removing calcium from the above solid component to obtain a lithium-containing sulfide solid electrolyte raw material from the above solid component.

[0036]

[12] A method for producing a sulfide solid electrolyte, using lithium sulfide obtained by reacting lithium hydroxide obtained by the above

[11] with hydrogen sulfide and the lithium-containing sulfide solid electrolyte raw material obtained by the above

[11] as raw materials.

[0037]

[13] A lithium hydroxide-containing composition for sulfide solid electrolyte synthesis, containing lithium hydroxide and zinc.

[0038]

[14] The lithium hydroxide-containing composition for sulfide solid electrolyte synthesis according to the above

[13] , further containing aluminum.

[0039]

[15] The lithium hydroxide-containing composition for sulfide solid electrolyte synthesis according to the above

[14] , wherein the sum of the zinc concentration and the aluminum concentration is 10 mass ppm or more.

[0040]

[16] The lithium hydroxide-containing composition for sulfide solid electrolyte synthesis according to any one of the above

[13] to

[15] , further containing 10 mass ppm or more of calcium.

[0041]

[17] A lithium sulfide-containing composition for sulfide solid electrolyte synthesis, containing lithium sulfide and zinc.

[0042]

[18] The lithium sulfide-containing composition for sulfide solid electrolyte synthesis according to the above

[17] , further containing aluminum.

[0043]

[19] The lithium sulfide-containing composition for sulfide solid electrolyte synthesis according to the above

[18] , wherein the sum of the zinc concentration and the aluminum concentration is 10 mass ppm or more.

[0044]

[20] The lithium sulfide-containing composition for synthesis of a sulfide solid electrolyte according to any one of the above

[17] to

[19] , further containing 10 mass ppm or more of calcium.

[0045]

[21] A lithium halide-containing composition for synthesis of a sulfide solid electrolyte, containing: lithium halide; and at least any one of sulfate ions, phosphate ions, and fluoride ions, the concentration of the above ions being 10 mass% or less.

[0046] According to the present application, lithium hydroxide can be efficiently obtained from a liquid component within the same manufacturing process at low cost, and a lithium-containing sulfide solid electrolyte material can also be obtained from a solid component, and a sulfide solid electrolyte material and a sulfide solid electrolyte can be efficiently manufactured. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 (a) of FIG. 1 shows a flowchart of a method for manufacturing lithium hydroxide according to one embodiment of the present application. Figure 1 (b) of FIG. 1 shows a flowchart of a method for manufacturing lithium sulfide according to one embodiment of the present application. Figure 1 (c) of FIG. 1 shows a flowchart of a first method for manufacturing a sulfide solid electrolyte according to one embodiment of the present application.

[0048] Figure 2 (a) of FIG. 2 shows a flowchart of a method for manufacturing a lithium- containing sulfide solid electrolyte material according to one embodiment of the present application. Figure 2 (b) of FIG. 2 shows a flowchart of a method for manufacturing lithium halide as a lithium-containing sulfide solid electrolyte material according to one embodiment of the present application. Figure 2 (c) of FIG. 2 shows a flowchart of a method for manufacturing lithium sulfate as a lithium-containing sulfide solid electrolyte material according to one embodiment of the present application.

[0049] Figure 3 (a) of FIG. 3 shows a flowchart of a method for manufacturing lithium hydroxide and a lithium-containing sulfide solid electrolyte material according to one embodiment of the present application. Figure 3 (b) of FIG. 3 shows a flowchart of a third method for manufacturing a sulfide solid electrolyte according to one embodiment of the present application. DETAILED DESCRIPTION

[0050] Hereinafter, the present application will be described in detail, but the present application is not limited to the following embodiments, and can be implemented with any modifications within the scope of the gist of the present application. In addition, "to" indicating a numerical range is used as a meaning that the numerals written before and after it are included as lower limit values and upper limit values.

[0051] Method for manufacturing lithium hydroxide

[0052] The production method of lithium hydroxide of one embodiment of the present application (hereinafter, also referred to as a production method of lithium hydroxide) is characterized by including the steps of reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide, separating the solution into a liquid component containing the lithium hydroxide and a solid component containing lithium from the lithium carbonate, and recovering lithium hydroxide from the liquid component.

[0053] Figure 1 (a) in FIG. 1 illustrates one example of a flowchart of the production method of lithium hydroxide. In the production method of lithium hydroxide, first, lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide (step Sll). Next, the obtained solution is separated into a liquid component containing the lithium hydroxide and a solid component containing lithium from the lithium carbonate (step S12). Then, lithium hydroxide is recovered from the liquid component among the obtained liquid component and the solid component (step S13). Steps Sll to S13 are preferably performed continuously, and the effect of the present application is further improved when the continuous production method is employed.

[0054] Hereinafter, each of the steps of the production method of lithium hydroxide is described in detail.

[0055] Preparation of lithium hydroxide solution

[0056] In the production method of lithium hydroxide, first, lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide (step Sll). The process of reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide is represented by the following chemical reaction formula.

[0057]

[0058] The lithium carbonate used in the production of lithium hydroxide is not particularly limited, and for example, commercially available lithium carbonate can be used, a solution containing lithium ions and carbonate ions can be electrolytically deposited to produce lithium carbonate, or lithium carbonate obtained by extraction from lithium-ion secondary battery waste or the like can be used.

[0059] Note that, as described later, the produced lithium hydroxide contains zinc and aluminum, and the lithium ion conductivity can be improved; from the viewpoint of obtaining an effect of suppressing the generation of H2S, the lithium carbonate preferably contains zinc and / or aluminum. In that case, the content of zinc with respect to the lithium carbonate can be, for example, 1 to 20 mass ppm, or 1 to 10 mass ppm. In addition, the content of aluminum with respect to the lithium carbonate can be, for example, 1 to 20 mass ppm, or 1 to 10 mass ppm.

[0060] The calcium hydroxide used in the production of lithium hydroxide is not particularly limited, and for example, commercially available calcium hydroxide or calcium oxide reacted with water to obtain calcium hydroxide can be used.

[0061] As a method of reacting lithium carbonate with calcium hydroxide in a liquid, for example, lithium carbonate can be put into a solvent to form a slurry or a solution of lithium carbonate, and calcium hydroxide can be added to the slurry or the solution or the like. Here, the solvent refers to water or the like, and distilled water, ion-exchange water, industrial water or the like can be used. Among them, from the viewpoint of reducing impurities contained in water, distilled water is preferable. Note that the "liquid" in the above "in a liquid" includes a slurry.

[0062] When water is used as the above solvent, the amount of water used is preferably 70 to 96 mass% relative to the total amount of the liquid in which lithium carbonate and calcium hydroxide are reacted. By making the amount of water 70 mass% or more, a slurry or a solution of lithium carbonate and calcium hydroxide is sufficiently formed, and lithium carbonate and calcium hydroxide can be sufficiently reacted in the liquid. In addition, by making the amount of water 96 mass% or less, when the obtained solution containing lithium hydroxide is subjected to solid-liquid separation as described later, lithium from lithium carbonate as a raw material can be sufficiently left on the solid component side. The amount of water is preferably 70 mass% or more, more preferably 75 mass% or more, and further preferably 80 mass% or more, and on the other hand, it is preferably 96 mass% or less, more preferably 95 mass% or less, and further preferably 94 mass% or less.

[0063] In addition, for the same reason as described above, the amount of water used is preferably 250 to 2400 g relative to 50 g of lithium carbonate. The amount of water is more preferably 300 g or more, further preferably 450 g or more, and still further preferably 600 g or more, and on the other hand, it is preferably 2400 g or less, more preferably 2000 g or less, and further preferably 1600 g or less.

[0064] When lithium carbonate and calcium hydroxide are reacted, the mixing ratio of calcium hydroxide to lithium carbonate (calcium hydroxide / lithium carbonate) is preferably 0.2 to 1.1 on a molar basis. By making the above mixing ratio 0.2 or more, lithium carbonate and calcium hydroxide can be sufficiently reacted, and lithium from lithium carbonate as a raw material can be sufficiently left on the solid component side. In addition, by making the above mixing ratio 1.1 or less, the cost of making the amount of calcium hydroxide added excessive can be reduced, and in addition, when a sulfide solid electrolyte material is produced as described later, the amount of sulfate ions used for removal can be reduced.

[0065] The above mixing ratio is preferably 0.2 or more, more preferably 0.3 or more, and further preferably 0.5 or more, and on the other hand, it is preferably 1.1 or less, more preferably 1.05 or less, and further preferably 1.00 or less.

[0066] The temperature of the liquid (reaction temperature) when the lithium carbonate is reacted with the calcium hydroxide is preferably 10 to 95°C. By making the temperature of the liquid 10°C or higher, the reaction from the lithium carbonate to the lithium hydroxide is sufficiently performed. Also, by making the temperature of the liquid 95°C or lower, the energy cost required for heating can be reduced. The temperature of the liquid is preferably 10°C or higher, more preferably 20°C or higher, and further preferably 30°C or higher, and is also preferably 95°C or lower, more preferably 90°C or lower, and further preferably 85°C or lower.

[0067] The pH of the liquid when the lithium carbonate is reacted with the calcium hydroxide in the liquid is preferably 10.1 to 11.1. By making the pH of the liquid 10.1 or higher, the reaction of the lithium carbonate with the calcium hydroxide is sufficiently performed. Also, by making the pH of the liquid 11.1 or lower, the calcium hydroxide does not become excessive, and the cost of the medicine and the cost for removal can be suppressed. The pH of the liquid is preferably 10.1 or higher, more preferably 10.3 or higher, and is also preferably 11.1 or lower, more preferably 10.9 or lower.

[0068] <solid-liquid separation>

[0069] In the method for producing lithium hydroxide, next, the solution containing lithium hydroxide obtained in the above step Sll is subjected to solid-liquid separation into a liquid component containing lithium hydroxide and a solid component containing lithium from the lithium carbonate (step S12).

[0070] The method for the solid-liquid separation is not particularly limited, and a method known in the art can be used. For example, a filtration method, a centrifugal separation method, and the like can be given. The filtration method is preferable in terms of energy cost, and the pressurized filtration method is more preferable. The pressure when the pressurized filtration method is used is not particularly limited, and is preferably 10 kPa or higher, and more preferably 50 kPa or higher, in terms of the effect of easily obtaining an accelerated filtration speed. The upper limit of the pressure is preferably the pressure resistance of the filter, and is preferably 500 kPa or lower, and more preferably 400 kPa or lower.

[0071] The solution containing lithium hydroxide is separated into a liquid component containing lithium hydroxide and a solid component containing lithium from the lithium carbonate by the solid-liquid separation. In the present application, when lithium hydroxide is synthesized by reacting lithium carbonate with calcium hydroxide, by adjusting the amount of water, the reaction temperature, and the mixing ratio, and the like, lithium from the raw material lithium carbonate can be made to remain not only in the liquid component side but also in the solid component side by the solid-liquid separation. Thus, lithium hydroxide can be recovered from the liquid component, and a sulfide solid electrolyte raw material containing lithium can be recovered from the solid component. Therefore, lithium hydroxide can be efficiently produced at low cost, and further, a sulfide solid electrolyte raw material and a sulfide solid electrolyte can be efficiently produced.

[0072] <Recovery of lithium hydroxide>

[0073] In the production method of lithium hydroxide, next, lithium hydroxide is recovered from the liquid component obtained in the above step S12 (step S13).

[0074] The method of recovering lithium hydroxide from the liquid component is not particularly limited, and a conventionally known method can be used. For example, in order to remove the solvent from the liquid component, a method of using a reduced pressure drying furnace to slowly raise the temperature at a pressure of 1 to 50 kPa, and heating to a maximum temperature of 50 to 90°C can be mentioned. The heating time is, for example, 10 to 100 hours.

[0075] The recovery rate of lithium as lithium hydroxide, in other words, the proportion of lithium contained in the liquid component after solid-liquid separation to the total amount of lithium from lithium carbonate as a raw material is preferably 25 to 90% on a mass basis. By making the above recovery rate 25% or more, a sufficient amount of lithium hydroxide can be obtained, and by being 90% or less, the cost required for recovering as lithium hydroxide on the solid component side is suppressed to be low, and lithium from lithium carbonate as a raw material can be sufficiently left over.

[0076] The above recovery rate is more preferably 30% or more, further preferably 35% or more, and in addition, more preferably 85% or less, further preferably 80% or less.

[0077] For the recovered lithium hydroxide, the calcium concentration in the lithium hydroxide is preferably 150 mass ppm or less. In order to make the calcium concentration in the lithium hydroxide 150 mass ppm or less, the amount of water at the time of the reaction of lithium carbonate with calcium hydroxide in the above step Sll, the mixing ratio of calcium hydroxide to lithium carbonate, the temperature of the liquid, and the like can be adjusted, contact with an ion exchange resin can be made, or the recovered liquid described later is subjected to a solid-liquid separation process in a concentrated state, and the like.

[0078] The calcium concentration in the lithium hydroxide is preferably 150 mass ppm or less, more preferably 120 mass ppm or less, and further preferably 100 mass ppm or less. In addition, the calcium concentration in the lithium hydroxide is, for example, usually 10 mass ppm or more.

[0079] In reducing the calcium concentration in the recovered lithium hydroxide, by performing solid-liquid separation in a state where the lithium concentration is concentrated by losing water in a reduced pressure drying furnace, the calcium component can be removed. The solid-liquid separation at the time of calcium removal is preferably performed at a lithium hydroxide component concentration of 6 to 12 mass%. By performing at a lithium hydroxide component concentration of 6 mass% or more, the amount of calcium contained can be sufficiently reduced. By making the lithium hydroxide component concentration 12 mass% or less, not only can calcium be prevented from being removed, but also lithium can be prevented from being removed.

[0080] The concentration of the lithium hydroxide component is preferably 6% by mass or more, more preferably 7% by mass or more, and is preferably 12% by mass or less, more preferably 10% by mass or less.

[0081] The lithium hydroxide obtained by the above production method preferably contains zinc. That is, as one embodiment of the lithium hydroxide obtained by the above production method, there is a lithium hydroxide-containing composition for synthesis of a sulfide solid electrolyte, which contains lithium hydroxide and zinc. By containing zinc in the composition, the lithium ion conductivity of the sulfide solid electrolyte obtained using the composition can be improved, and the effect of suppressing the generation of H2S can be obtained.

[0082] As described above, in order to contain zinc in the above composition, zinc can be contained in the lithium carbonate used as a raw material, or zinc can be added at any stage of the production process of lithium hydroxide.

[0083] In the above composition, the concentration of zinc is preferably 5 ppm by mass or more, more preferably 10 ppm by mass or more, and further preferably 15 ppm by mass or more, and is preferably 200 ppm by mass or less, more preferably 100 ppm by mass or less, and further preferably 50 ppm by mass or less.

[0084] In addition, the above composition preferably further contains aluminum. By containing aluminum in the above composition, the lithium ion conductivity of the sulfide solid electrolyte obtained using the composition can be improved, and the effect of suppressing the generation of H2S can be obtained.

[0085] As described above, in order to contain aluminum in the above composition, aluminum can be contained in the lithium carbonate used as a raw material, or aluminum can be added at any stage of the production process of lithium hydroxide.

[0086] In the above composition, the concentration of aluminum is preferably 1 ppm by mass or more, more preferably 2 ppm by mass or more, and further preferably 3 ppm by mass or more, and is preferably 200 ppm by mass or less, more preferably 100 ppm by mass or less, and further preferably 50 ppm by mass or less.

[0087] In addition, in the above composition, the sum of the concentration of aluminum and the concentration of zinc is preferably 10 ppm by mass or more, more preferably 15 ppm by mass or more, and further preferably 20 ppm by mass or more, and is preferably 400 ppm by mass or less, more preferably 200 ppm by mass or less, and further preferably 100 ppm by mass or less.

[0088] The above composition can further contain calcium. The above composition can have a calcium concentration of 10 ppm by mass or more, 25 ppm by mass or more, 50 ppm by mass or more, and in addition, 150 ppm by mass or less, 120 ppm by mass or less, or 100 ppm by mass or less.

[0089] Method for producing lithium sulfide

[0090] The method for producing lithium sulfide according to one embodiment of the present application (hereinafter, also referred to simply as the method for producing lithium sulfide) is characterized by reacting lithium hydroxide obtained in the method for producing lithium hydroxide according to one embodiment of the present application described above with hydrogen sulfide to produce lithium sulfide.

[0091] Figure 1 (b) in FIG. 1 shows a flowchart of the method for producing lithium sulfide. In the method for producing lithium sulfide, lithium hydroxide obtained via the steps S11 to S13 described above is reacted with hydrogen sulfide to produce lithium sulfide (step S14). The steps S11 to S14 are preferably performed continuously, and the effect of the present application is further improved when this continuous production method is employed.

[0092] The method for reacting lithium hydroxide with hydrogen sulfide is not particularly limited, and for example, hydrogen sulfide can be reacted with the powder of lithium hydroxide in the form of a gas, or lithium hydroxide can be dissolved in a solvent to form a lithium hydroxide solution and hydrogen sulfide gas can be bubbled therein to perform the reaction. Among these, bubbling of hydrogen sulfide gas is preferable.

[0093] As the conditions for reacting the powder of lithium hydroxide with hydrogen sulfide gas, in order to effectively react the powder with hydrogen sulfide, a method in which hydrogen sulfide gas is introduced while the powder is stirred is preferable. The temperature range is preferably 160 to 220°C to effectively perform the reaction.

[0094] As the conditions for bubbling hydrogen sulfide gas into the lithium hydroxide solution, for example, a nozzle is inserted into the lithium hydroxide solution, and bubbling is generally performed at a temperature range of 5 to 40°C for 5 to 180 minutes. The temperature range is preferably 10 to 35°C, and more preferably 15 to 30°C. The time for bubbling is preferably 10 to 90 minutes, and more preferably 15 to 75 minutes.

[0095] The lithium sulfide obtained in the above production method preferably contains zinc. That is, as one embodiment of the lithium sulfide obtained in the above production method, a lithium sulfide-containing composition for synthesizing a sulfide solid electrolyte containing lithium sulfide and zinc can be given. By containing zinc in the composition, the lithium ion conductivity of the sulfide solid electrolyte obtained using the composition can be improved, and an effect of suppressing the generation of H2S can be obtained.

[0096] As described above, in order to cause the above composition to contain zinc, the lithium carbonate serving as a raw material can be caused to contain zinc, or zinc can also be added at any stage of the manufacturing process of lithium sulfide.

[0097] The concentration of zinc in the above composition is preferably 5 ppm by mass or more, more preferably 10 ppm by mass or more, and further preferably 15 ppm by mass or more, and is preferably 200 ppm by mass or less, more preferably 100 ppm by mass or less, and further preferably 50 ppm by mass or less.

[0098] Further, the above composition preferably further contains aluminum. By causing the above composition to contain aluminum, the lithium ion conductivity of the sulfide solid electrolyte obtained using the composition can be provided, and an effect of suppressing the generation of H2S can be obtained.

[0099] As described above, in order to cause the above composition to contain aluminum, the lithium carbonate serving as a raw material can be caused to contain aluminum, or aluminum can also be added at any stage of the manufacturing process of lithium sulfide.

[0100] The concentration of aluminum in the above composition is preferably 1 ppm by mass or more, more preferably 2 ppm by mass or more, and further preferably 3 ppm by mass or more, and is preferably 200 ppm by mass or less, more preferably 100 ppm by mass or less, and further preferably 50 ppm by mass or less.

[0101] Further, in the above composition, the sum of the concentration of aluminum and the concentration of zinc is preferably 10 ppm by mass or more, more preferably 15 ppm by mass or more, and further preferably 20 ppm by mass or more, and is preferably 400 ppm by mass or less, more preferably 200 ppm by mass or less, and further preferably 100 ppm by mass or less.

[0102] The above composition can further contain calcium. In the above composition, the concentration of calcium can be 10 ppm by mass or more, can be 25 ppm by mass or more, can be 50 ppm by mass or more, and can be 150 ppm by mass or less, can be 120 ppm by mass or less, and can be 100 ppm by mass or less.

[0103] First manufacturing method of sulfide solid electrolyte

[0104] The manufacturing method of the sulfide solid electrolyte of one embodiment of the present application (hereinafter, also referred to as the first manufacturing method of the sulfide solid electrolyte) is characterized by generating a sulfide solid electrolyte using lithium sulfide obtained in the above manufacturing method of lithium sulfide of one embodiment of the present application as a raw material.

[0105] Figure 1(c) in FIG. 1 shows a flowchart of the first production method of the sulfide solid electrolyte. In the first production method of the sulfide solid electrolyte, the lithium sulfide obtained through the above-described steps Sll to S14 is used as a raw material to produce the sulfide solid electrolyte (step S15). Steps Sll to S15 are preferably performed continuously, and the effect of the present application is further improved when this continuous production method is employed.

[0106] (Sulfide solid electrolyte raw material)

[0107] In the first production method of the sulfide solid electrolyte, a raw material of the sulfide solid electrolyte other than the lithium sulfide obtained in the production method of the lithium sulfide of one embodiment of the present application (hereinafter, also referred to simply as another sulfide solid electrolyte raw material) can be used. As the raw material of the sulfide solid electrolyte, a commercially available sulfide solid electrolyte raw material can be used, or a material obtained by manufacturing a sulfide solid electrolyte raw material can be used. Further, the known pretreatment can be further performed on these sulfide solid electrolyte raw materials. That is, the present production method can appropriately include a step of manufacturing another sulfide solid electrolyte raw material, or a step of performing pretreatment on another sulfide solid electrolyte raw material.

[0108] Hereinafter, another sulfide solid electrolyte raw material will be described in detail. Note that, hereinafter, as one of the sulfide solid electrolyte raw materials, lithium sulfide is exemplified, but the meaning is that lithium sulfide can be used as a sulfide solid electrolyte raw material separately from the lithium sulfide obtained in the production method of the lithium sulfide of one embodiment of the present application.

[0109] As the sulfide solid electrolyte raw material, an alkali metal element (R) and a sulfur element (S) are typically included.

[0110] As the alkali metal element (R), lithium element (Li), sodium element (Na), and potassium element (K), and the like can be given, and lithium element (Li) is preferable. As the alkali metal element (R), an alkali metal element single substance, a compound containing an alkali metal element, or the like containing an alkali metal element (component), and the like can be appropriately combined and used. As the lithium element, Li single substance, a compound containing Li, or the like containing Li (component), and the like can be appropriately combined and used.

[0111] As the substance containing lithium element (Li), for example, lithium sulfide (Li2S), lithium iodide (LiI), lithium carbonate (Li2CO3), lithium sulfate (Li2SO4), lithium oxide (Li2O), lithium hydroxide (LiOH), and the like lithium compound, metallic lithium, and the like can be given. As the substance containing lithium element (Li), from the viewpoint of obtaining a sulfide material, it is preferable to use lithium sulfide.

[0112] As the element S (sulfur), S single substance, a substance (component) containing S such as a compound containing S, and the like can be appropriately combined and used.

[0113] As the substance containing the element S (sulfur), for example, phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), other sulfur compounds containing phosphorus, elemental sulfur, compounds containing sulfur, and the like can be given. As the compound containing sulfur, H2S, CS2, iron sulfides (FeS, Fe2S3, FeS2, Fe3S8, and the like), bismuth sulfides (Bi2S3), copper sulfides (CuS, Cu2S, Cu5S6, and the like), and the like can be given. From the viewpoint of obtaining a sulfide material, the substance containing the element S (sulfur) is preferably a phosphorus sulfide, and more preferably phosphorus pentasulfide (P2S5). One of them can be used alone, or two or more of them can be used in combination. Note that the phosphorus sulfide is regarded as a compound serving as both the substance containing S and the substance containing P described later. 1－x S, and the like). From the viewpoint of obtaining a sulfide material, the substance containing the element S (sulfur) is preferably a phosphorus sulfide, and more preferably phosphorus pentasulfide (P2S5). One of them can be used alone, or two or more of them can be used in combination. Note that the phosphorus sulfide is regarded as a compound serving as both the substance containing S and the substance containing P described later. 1－x S, and the like). From the viewpoint of obtaining a sulfide material, the substance containing the element S (sulfur) is preferably a phosphorus sulfide, and more preferably phosphorus pentasulfide (P2S5). One of them can be used alone, or two or more of them can be used in combination. Note that the phosphorus sulfide is regarded as a compound serving as both the substance containing S and the substance containing P described later.

[0114] From the viewpoint of improving the ion conductivity of the obtained sulfide solid electrolyte and the like, the sulfide solid electrolyte raw material preferably further contains the element P (phosphorus). As the element P (phosphorus), P single substance, a substance (component) containing P such as a compound containing P, and the like can be appropriately combined and used.

[0115] As the substance containing the element P (phosphorus), for example, phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), phosphorus compounds such as sodium phosphate (Na3PO4), and elemental phosphorus, and the like can be given. As the substance containing the element P (phosphorus), from the viewpoint of further exerting the effects of the present application, a phosphorus sulfide having high volatility is preferred, and phosphorus pentasulfide (P2S5) is more preferred. One of them can be used alone, or two or more of them can be used in combination.

[0116] The sulfide solid electrolyte raw material can be obtained, for example, in the form of a mixed raw material by appropriately mixing the above-described substances in accordance with the composition of the target sulfide solid electrolyte. The mixing ratio is not particularly limited, and for example, from the viewpoint of improving the ion conductivity of the obtained sulfide solid electrolyte and the like, the molar ratio S / R of the element S (sulfur) to the alkali metal element (R) in the sulfide solid electrolyte 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 method of the above-described mixing, for example, mixing using a mortar, mixing using a medium such as a planetary ball mill, mediumless mixing such as a pin mill or a powder stirrer, air flow mixing, and the like can be given.

[0117] As one example of a preferred combination of alkali metal elements and sulfur elements contained in the sulfide solid electrolyte raw material, a combination of Li2S and P2S5 can be given. When Li2S and P2S5 are combined, the molar ratio Li / P of Li to P is preferably 40 / 60 or more, and more preferably 50 / 50 or more. In addition, the molar ratio Li / P of Li to P is preferably 88 / 12 or less. In addition, the molar ratio Li / P of Li to P is preferably 40 / 60 to 88 / 12, and more preferably 50 / 50 to 88 / 12. By adjusting the mixing ratio in such a manner that P2S5 is less than Li2S, the volatilization of sulfur components and phosphorus components at the time of heat treatment due to the fact that the boiling point of P2S5 is lower than the melting point of Li2S is easily suppressed.

[0118] On the other hand, lithium compounds other than lithium sulfide, metallic lithium, and the like can also be used. Specifically, in this case, the sulfide solid electrolyte raw material preferably contains one or more selected from the group consisting of metallic lithium, lithium iodide (LiI), lithium carbonate (Li2CO3), lithium sulfate (Li2SO4), lithium oxide (Li2O), and lithium hydroxide (LiOH) as a substance containing Li. One of them can be used alone, or two or more of them can be used in combination.

[0119] The sulfide solid electrolyte raw material can contain other substances (compounds, etc.) other than the above-described substances in the form of an additive or the like, depending on the composition of the target sulfide solid electrolyte.

[0120] For example, when a sulfide solid electrolyte containing a halogen element such as F, Cl, Br, or I is manufactured, the sulfide solid electrolyte raw material preferably contains a halogen element (Ha). In this case, the sulfide solid electrolyte raw material preferably contains a compound containing a halogen element. As the compound containing a halogen element, lithium halides such as lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), halogenated phosphorus, phosphorus oxyhalide, halogenated sulfur, halogenated sodium, and halogenated boron can be given. As the 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. One of them can be used alone, or two or more of them can be used in combination.

[0121] Note that the halogenated alkali metal such as lithium halide is also a compound containing an alkali metal element such as Li. When the sulfide solid electrolyte raw material contains a halogenated alkali metal, part or all of the alkali metal element such as Li in the sulfide solid electrolyte raw material can come from the halogenated alkali metal such as lithium halide.

[0122] When the sulfide solid electrolyte raw material contains a halogen element (Ha) and a phosphorus element (P), from the viewpoint of improving the ion conductivity of the obtained sulfide solid electrolyte, the molar equivalent of Ha with respect to P in the sulfide solid electrolyte raw material is preferably 0.2 mol equivalent or more, and more preferably 0.5 mol equivalent or more. In addition, from the viewpoint of the stability of the obtained sulfide solid electrolyte, the molar equivalent of Ha is preferably 4 mol equivalent or less, and more preferably 3 mol equivalent or less.

[0123] The obtained sulfide solid electrolyte can be an amorphous sulfide solid electrolyte depending on the purpose, and from the viewpoint of improving the ease of generation of an amorphous phase, it is also preferable that the sulfide solid electrolyte raw material contain a sulfide such as SiS2, B2S3, GeS2, Al2S3. By easily forming an amorphous phase, in the case of obtaining an amorphous phase by quenching, even if the cooling rate is reduced, an amorphous sulfide solid electrolyte can be obtained, and the load on the equipment can be reduced.

[0124] In addition, from the viewpoint of imparting moisture resistance to the sulfide solid electrolyte, it is also preferable to contain an oxide such as SiO2, B2O3, GeO2, Al2O3, P2O5. One of them can be used alone, or two or more of them can be used in combination.

[0125] (Solid phase method, melting method)

[0126] As a method of manufacturing a sulfide solid electrolyte using the lithium sulfide obtained by the method of manufacturing lithium sulfide of one embodiment of the present application and other above-described sulfide solid electrolyte raw materials as necessary, for example, a method based on a solid phase method and a method based on a melting method can be given. Hereinafter, the method based on a solid phase method and the method based on a melting method will be described separately.

[0127] (Solid phase method)

[0128] In the solid phase method, first, the lithium sulfide obtained by the method of manufacturing lithium sulfide is mixed with other above-described sulfide solid electrolyte raw materials as necessary.

[0129] Mixing can be performed by a publicly known method, and it is preferable to mix by mechanical grinding. In the case of mechanical grinding using a ball mill, for example, a rotary ball mill in which a container is made to perform a rotational motion, a vibration ball mill in which a container is made to perform a vibration motion, a planetary ball mill in which a container is made to perform a rotational and a rotational motion, a bead mill, an Attritor (registered trademark), and the like can be given. Among them, a planetary ball mill or a bead mill in which the mixing force and the pulverizing force are higher is preferable.

[0130] The ball mill can be a dry-type mixer or a wet-type mixer using a dispersion medium, and from the viewpoint of efficiently transferring energy, a dry-type mixer is preferable.

[0131] The raw materials are mixed by the above mixing to form a raw material mixture. The raw material mixture becomes a precursor of the sulfide solid electrolyte. The precursor can be a homogeneous amorphous intermediate compound that is amorphized by employing a mixing condition that is much stricter than in the past. The amorphous intermediate compound means that no XRD peaks from the raw materials are observed.

[0132] In addition, as needed, a pulverization process, a heat treatment process can be further included.

[0133] The pulverization process can use either wet pulverization or dry pulverization.

[0134] The average particle diameter of the sulfide solid electrolyte is preferably made 1 to 100 μm by the pulverization process. Here, the average particle diameter means a median particle diameter (D50) that represents the particle diameter of which 50% by volume of the particles is the value or less, which is determined using a particle size distribution meter that utilizes a laser diffraction method, and is calculated from a volume-based particle size distribution chart obtained.

[0135] The purpose of the heat treatment process is to improve the homogeneity and stabilize the quality as the sulfide solid electrolyte.

[0136] When the obtained sulfide solid electrolyte is subjected to heat treatment, the heating temperature is different depending on the composition of the sulfide solid electrolyte, but is preferably, for example, 200 to 600°C, more preferably 350 to 500°C, further preferably 380 to 460°C, and particularly preferably 400 to 450°C. Here, from the viewpoint of the homogenization and stabilization of the quality of the sulfide solid electrolyte, the heating temperature is preferably 200°C or higher, more preferably 350°C or higher, further preferably 380°C or higher, and particularly preferably 400°C or higher. In addition, from the viewpoint of preventing sintering of the particles to each other, the heating temperature is preferably 600°C or lower, more preferably 500°C or lower, further preferably 460°C or lower, and particularly preferably 450°C or lower.

[0137] When the sulfide solid electrolyte is subjected to heat treatment, the heating time is different depending on the composition of the sulfide solid electrolyte, but is preferably, for example, 10 minutes to 10 hours, more preferably 30 minutes to 9.5 hours, further preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours. Here, from the viewpoint of the homogenization and stabilization of the quality of the sulfide solid electrolyte, the time of the heat treatment is preferably 10 minutes or more, more preferably 30 minutes or more, further preferably 45 minutes or more, and particularly preferably 1 hour or more. In addition, from the viewpoint of the manufacturing cost, the time of the heat treatment is preferably 10 hours or less, more preferably 9.5 hours or less, and further preferably 9 hours or less.

[0138] The atmosphere other than the SO2 concentration at the time of the heat treatment is preferably an inactive atmosphere when the sulfide solid electrolyte is subjected to the heat treatment. As the inactive atmosphere, for example, a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, and the like can be given.

[0139] The dew point at the time of the heat treatment is preferably -20°C or lower, and the lower limit is not particularly limited, and is usually about -80°C. The oxygen concentration is preferably 1000 ppm by volume or lower.

[0140] (Melt method)

[0141] In the melt method, first, a raw material mixture is obtained by adding and mixing the above-described sulfide solid electrolyte raw material as needed in the lithium sulfide obtained by the method for producing lithium sulfide. The mixing can be performed, for example, by mixing using a mortar, mixing using a medium such as a planetary ball mill, mixing without a medium such as a pin mill or a powder stirrer, air flow mixing, and the like.

[0142] Next, the above-described obtained raw material mixture is heated to obtain a melt.

[0143] The specific method of heating and melting the raw material mixture is not particularly limited, and, for example, the raw material mixture is put into a heat-resistant container, and heated using a heating furnace. The raw material mixture can also be enclosed in a heat-resistant container. In addition, the melting can be performed in an atmosphere containing a sulfur element. As the atmosphere containing a sulfur element, a mixed gas atmosphere of a gas containing a sulfur element such as sulfur gas, hydrogen sulfide gas, sulfur dioxide gas, and the like and an inactive gas, and the like can be given.

[0144] The heat-resistant container can use a carbon heat-resistant container, quartz, quartz glass, borosilicate glass, aluminosilicate glass, alumina, zirconia, mullite, and the like containing an oxide, a silicon nitride, boron nitride, and the like containing a nitride, silicon carbide, and the like containing a carbide, and the like. In addition, these heat-resistant containers can be formed of the above-described materials as the main body, or can be a carbon-coated quartz tube, a container in which a layer of carbon, an oxide, a nitride, a carbide, and the like is formed.

[0145] The heating temperature at the time of heating and melting of the raw material mixture is not particularly limited, but is preferably, for example, 550 to 1000°C, more preferably 600 to 950°C, further preferably 630 to 900°C, and particularly preferably 650 to 800°C, depending on the raw materials used and the composition of the raw material mixture. Here, the heating temperature is preferably 550°C or higher, more preferably 600°C or higher, further preferably 630°C or higher, and particularly preferably 650°C or higher, from the viewpoint of improving the meltability of the raw materials and homogenizing the melt in a short time. In addition, the heating temperature is preferably 1000°C or lower, more preferably 950°C or lower, further preferably 900°C or lower, and particularly preferably 800°C or lower, from the viewpoint of suppressing deterioration due to heating of the components, suppressing composition unevenness due to volatilization of the components, and suppressing decomposition.

[0146] The time of heating and melting is not particularly limited, but is preferably 10 minutes to 10 hours, more preferably 30 minutes to 9.5 hours, further preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours, depending on the scale. Here, the time of heating and melting is preferably 10 minutes or longer, more preferably 30 minutes or longer, further preferably 45 minutes or longer, and particularly preferably 1 hour or longer, from the viewpoint of allowing the reaction to proceed well. In addition, the time of heating and melting is preferably 10 hours or shorter, more preferably 9.5 hours or shorter, and further preferably 9 hours or shorter, from the viewpoint of productivity.

[0147] The pressure at the time of heating and melting is not particularly limited, but is preferably normal pressure or slightly pressurized, and more preferably normal pressure.

[0148] The dew point at the time of heating and melting is preferably -20°C or lower, and the lower limit is not particularly limited, but is usually about -80°C. The oxygen concentration is preferably 1000 ppm by volume or lower.

[0149] The complete melting of the melt can be confirmed by the absence of peaks from crystals in high-temperature X-ray diffraction measurement.

[0150] Next, the obtained melt is cooled to precipitate crystals. The crystals obtained by the precipitation become the sulfide solid electrolyte.

[0151] The cooling can be performed according to a known method, and the method is not particularly limited. As a more specific method of cooling, for example, a method in which the melt is cast onto a plate-like body made of carbon or the like and cooled; a method in which a thin sheet is formed by flowing into a narrow gap, represented by a twin roll method; a gas atomization method, and the like can be given.

[0152] The cooling rate is preferably 0.1 to 10,000°C / second, more preferably 0.5 to 5,000°C / second, and even more preferably 1 to 1,000°C / second. From the perspective of improving composition homogeneity and suppressing quality variations, the cooling rate is preferably 0.1°C / second or more, more preferably 0.5°C / second or more, and even more preferably 1°C / second or more. The upper limit of the cooling rate is not particularly limited, but considering the cooling rate of the twin rolls, which are generally considered to have the fastest rapid cooling rate, the upper limit is 10 7 From the viewpoint of actual production, the cooling rate is more preferably 10,000°C / second or less, further preferably 5,000°C / second or less, and even more preferably 1,000°C / second or less.

[0153] The atmosphere during cooling is preferably a low-moisture, inert atmosphere, similar to that during heating and melting.

[0154] If necessary, a pulverization step and a heat treatment step may be further included.

[0155] In this case, the pulverization step and the heat treatment step are the same as those in the solid phase method, and the preferred embodiments are also the same. It should be noted that when an atomization method that can simultaneously cool and pulverize is used as the cooling method, it also serves as the pulverization step.

[0156] (Sulfide solid electrolyte)

[0157] The crystal structure of the sulfide solid electrolyte (hereinafter also referred to as sulfide solid electrolyte) obtained by the method for producing a sulfide solid electrolyte according to one embodiment of the present invention is not particularly limited. For example, a crystal structure having Li7P3S 11 Sulfide solid electrolytes containing Li, P, and S elements in a crystal structure called LPS system, etc. 10 GeP2S 12 Powders of sulfide solid electrolytes such as those having a crystal structure containing Li, Ge, P, and S elements called LGPS series, sulfide solid electrolytes having an argyrodite-type crystal structure containing Li, P, S, and Ha elements, sulfide solid electrolytes composed of Li-P-S-Ha series crystallized glass, and sulfide solid electrolytes having other crystal structures.

[0158] The above may be a sulfide solid electrolyte including a crystalline phase and an amorphous phase.

[0159] In the above description, the argyrodite-type crystal structure refers to a crystal structure possessed by a compound group derived from a mineral represented by the composition formula Ag8GeS6. Furthermore, the sulfide solid electrolyte is not limited to the above crystal structure, and some elements may be replaced by other elements.

[0160] When the sulfide solid electrolyte has a crystal structure of argyrodite type, as the Ha element, it is more preferable to contain at least one element selected from the group consisting of Cl, Br, and I, and it is further preferable to contain two or more elements.

[0161] In addition, as the Ha element, it is further preferable for the sulfide solid electrolyte to contain at least one of Cl and Br, and it is also further preferable to contain Cl and Br.

[0162] The crystal structure of argyrodite type preferably takes the above structure, and as the composition formula, it is preferable to be represented by Li α PS β Ha γ and satisfies the relationships of 5 ≤ α ≤ 7, 4 ≤ β ≤ 6, and 1.3 ≤ γ ≤ 2. The above element ratio is more preferably satisfies the relationships of 5.1 < α < 6.3, 4 < β < 5.3, and 1.4 ≤ γ ≤ 1.9, and further preferably satisfies the relationships of 5.2 < α < 6.2, 4.1 < β < 5.2, and 1.5 ≤ γ ≤ 1.8.

[0163] That is, α is preferably 5 or more, more preferably greater than 5.1, and further preferably greater than 5.2, and is preferably 7 or less, more preferably less than 6.3, and further preferably less than 6.2. β is preferably 4 or more, more preferably greater than 4, and further preferably greater than 4.1, and is preferably 6 or less, more preferably less than 5.3, and further preferably less than 5.2. γ is preferably 1.3 or more, more preferably 1.4 or more, and further preferably 1.5 or more, and is preferably 2 or less, more preferably 1.9 or less, and further preferably 1.8 or less.

[0164] In the crystal structure of argyrodite type, a part of S elements can be substituted with Ha elements, O elements, and can be further substituted with Se, Te, BH4, CN, and the like. In addition, a part of P elements can be substituted with Si elements, Al elements, Sn elements, In elements, Cu elements, Sb elements, Ge elements, and the like.

[0165] Method for manufacturing lithium-containing sulfide solid electrolyte raw material

[0166] The method for manufacturing a lithium-containing sulfide solid electrolyte raw material according to one embodiment of the present application (hereinafter, also simply referred to as the method for manufacturing a lithium-containing sulfide solid electrolyte raw material) is characterized by including the steps of: reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide, subjecting the above solution to solid-liquid separation into a liquid component containing the above lithium hydroxide and a solid component containing lithium from the above lithium carbonate, and removing calcium from the above solid component to obtain a lithium-containing sulfide solid electrolyte raw material from the above solid component.

[0167] Figure 2An example of a flowchart of the manufacturing method of the lithium-containing sulfide solid electrolyte raw material is shown in (a). In the manufacturing method of the lithium-containing sulfide solid electrolyte raw material, first, lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide (step S21). Next, the obtained solution is solid-liquid separated into a liquid component containing lithium hydroxide and a solid component containing lithium from the lithium carbonate (step S22). Then, calcium in the obtained solid component is removed (step S23). Thereby, the lithium-containing sulfide solid electrolyte raw material is obtained from the solid component (step S24). Steps S21 to S24 are preferably performed continuously, and the effect of the present application is further improved when this continuous manufacturing method is employed.

[0168] The above steps will be described in detail below with respect to the manufacturing method of the lithium-containing sulfide solid electrolyte raw material.

[0169] Steps S21 and S22 are the same as steps S11 and S12, respectively, in the manufacturing method of lithium hydroxide of one embodiment of the present application described above.

[0170] It should be noted that the recovery rate of lithium as the lithium-containing sulfide solid electrolyte, in other words, the proportion of lithium contained in the solid component after the solid-liquid separation with respect to the total amount of lithium from the lithium carbonate as the raw material is preferably 10 to 80% on a mass basis. By making the above proportion of lithium 10% or more, lithium from the lithium carbonate as the raw material can be sufficiently left on the solid component side, and by making it 80% or less, an adequate amount of lithium hydroxide can be obtained on the liquid component side. The above proportion of lithium is more preferably 15% or more, further preferably 20% or more, and still more preferably 70% or less, further preferably 60% or less.

[0171] In step S23, first, calcium in the solid component obtained via steps S21 and S22 is converted into a hardly soluble calcium compound. As the calcium in the solid component, calcium carbonate, calcium hydroxide, and the like can be given. The method of converting the calcium in the solid component into a hardly soluble calcium compound is not particularly limited, and for example, a method of adding sulfate ions, a method of adding phosphate ions, a method of adding fluoride ions, and the like can be given. Among them, from the viewpoint that the concentration of calcium can be removed to a lower concentration, the method of adding sulfate ions in the solid component is preferable. By adding sulfate ions in the solid component, calcium in the solid component is converted into calcium sulfate, which is removed in the form of calcium sulfate by solid-liquid separation and the like performed later.

[0172] As the method of adding sulfate ions in the solid component, for example, a method of adding water or the like to slurry the solid component and then adding sulfuric acid in the slurry, and the like can be given. The chemical reaction formula in this case is as follows.

[0173] CaCO3+ H2SO4+ H2O → CaSO4-2H2O + CO2

[0174] Ca(OH)2+ H2SO4→ CaSO4-2H2O

[0175] The amount of sulfuric acid added is preferably 1.00 times or more, more preferably 1.01 times or more, further preferably 1.02 times or more, and also preferably 1.30 times or less, more preferably 1.20 times or less, and further preferably 1.10 times or less, with respect to the amount of calcium contained in the solid, on a molar basis.

[0176] By adding more sulfuric acid than calcium content on a molar basis, the solubility of CaSO4-2H2O can be reduced, and the amount of calcium contained in the slurry can be further reduced.

[0177] Next, in step S24, a lithium-containing sulfide solid electrolyte material is obtained from the solid component to which the sulfate ion is added in step S23.

[0178] The obtained lithium-containing sulfide solid electrolyte material is preferably lithium halide or lithium sulfate. Specifically, for example, there are a method of reacting the solid component with hydrogen halide as shown in step S24a of (b) in Figure 2 , a method of reacting the solid component with sulfuric acid as shown in step S24b of (c) in Figure 2 , to obtain lithium sulfate as a sulfide solid electrolyte material.

[0179] As the method of reacting the solid component with hydrogen halide in step S24a of (b) in Figure 2 , for example, there is a method of adding a hydrogen halide acid to the solid component or a solution containing the solid component. In the solid component, since raw material lithium carbonate (Li2CO3), lithium hydroxide (LiOH) are contained, for example, when hydrobromic acid is used as the hydrogen halide acid, the chemical reaction formula is as follows.

[0180] Li2CO3+ 2HBr → 2LiBr + H2O + CO2

[0181] LiOH + HBr → LiBr + H2O

[0182] The amount of hydrogen halide added is preferably 0.9 times or more, more preferably 1.0 times or more, and also preferably 2.0 times or less, more preferably 1.5 times or less, with respect to the amount of lithium contained in the solid, on a molar basis.

[0183] When the amount of the hydrogen halide acid added is more than the amount required for the reaction with lithium, the speed of the reaction can be accelerated, but on the other hand, the final excess hydrogen halide acid can remain. Therefore, it is preferable to adjust the excess halogenated hydrogen to be lost by drying by heating later, or to add lithium carbonate, lithium hydroxide so as to become a lithium halide composition before drying.

[0184] In addition, by adding the hydrogen halide acid while stirring, the reaction of lithium carbonate with the hydrogen halide acid can be accelerated, and in addition, the reaction of unreacted sulfate ions with calcium can also be accelerated.

[0185] In the above step S23, when the calcium in the solid component is removed by a method of adding at least any one of sulfate ions, phosphate ions, and fluoride ions to the solid component, the lithium halide obtained via the subsequent processes has the following characteristic: it contains at least any one of sulfate ions, phosphate ions, and fluoride ions. That is, as one embodiment of the lithium halide obtained by the above production method, a lithium halide-containing composition for sulfide solid electrolyte synthesis can be given, which contains lithium halide; and at least any one of sulfate ions, phosphate ions, and fluoride ions. By having the composition contain at least any one of sulfate ions, phosphate ions, and fluoride ions, the lithium ion conductivity of the sulfide solid electrolyte obtained using the composition can be improved, and an effect of suppressing the generation of H2S can be obtained.

[0186] In the above composition, the concentration of at least any one of sulfate ions, phosphate ions, and fluoride ions is preferably 10% by mass or less. When the concentration of the above ions is 10% by mass or less, the influence on the content of other components can be made extremely small. The concentration of the above ions is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less. In addition, it is generally 0.1% by mass or more.

[0187] On the other hand, as the method of reacting the solid component with sulfate ions in step S24b of (c) to obtain lithium sulfate as a raw material of a sulfide solid electrolyte, for example, a method of adding sulfuric acid to the solid component or a solution containing the solid component can be given. The chemical reaction formula in this case is as follows. Figure 2 Li2CO3+ H2SO4+ H2O → Li2SO4·2H2O + CO2

[0188] 2LiOH + H2SO4→ Li2SO4+ 2H2O

[0189] 2LiOH + H2SO4→ Li2SO4+ 2H2O

[0190] The amount of sulfuric acid added is preferably 0.50 times or more, more preferably 0.60 times or more, and further preferably 0.70 times or more, relative to the amount of lithium contained in the solid, on a molar basis, and is preferably 2.0 times or less, more preferably 1.50 times or less, and further preferably 1.00 times or less.

[0191] When sulfuric acid is added in an amount greater than that required for the reaction with lithium, the reaction rate can be accelerated, but on the other hand, excess sulfuric acid can remain. Therefore, it is preferable to adjust the composition by subsequently adding lithium carbonate and lithium hydroxide to adjust to a lithium sulfate composition.

[0192] Further, by adding sulfuric acid while stirring, the reaction of lithium carbonate with sulfuric acid can be accelerated, and further, the reaction of unreacted sulfate ions with calcium can be accelerated.

[0193] The lithium-containing sulfide solid electrolyte material obtained by the above operation. As the lithium-containing sulfide solid electrolyte material obtained, examples identical to the "substance containing lithium element (Li)" described in the item of the first production method of the sulfide solid electrolyte described above can be given.

[0194]

[0195] The production method of the sulfide solid electrolyte of one embodiment of the present application (hereinafter, also referred to as the second production method of the sulfide solid electrolyte) is characterized by producing a sulfide solid electrolyte using the lithium-containing sulfide solid electrolyte material obtained by the production method of the lithium-containing sulfide solid electrolyte material of one embodiment of the present application.

[0196] Note that, in addition to the above-described lithium-containing sulfide solid electrolyte material, another sulfide solid electrolyte material can be used to produce a sulfide solid electrolyte. The kind of the other sulfide solid electrolyte material, the solid phase method, and the melting method are the same as those described in the item of the first production method of the sulfide solid electrolyte.

[0197]

[0198] ​​The manufacturing method of lithium hydroxide and lithium-containing sulfide solid electrolyte raw material of one embodiment of the present application (hereinafter, also referred to as a manufacturing method of lithium hydroxide and lithium-containing sulfide solid electrolyte raw material) is characterized by including the steps of reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide, solid-liquid separating the solution into a liquid component containing the lithium hydroxide and a solid component containing lithium from the lithium carbonate, recovering lithium hydroxide from the liquid component, and removing calcium from the solid component to obtain a lithium-containing sulfide solid electrolyte raw material from the solid component.

[0199] That is, the manufacturing method of lithium hydroxide and lithium-containing sulfide solid electrolyte raw material of one embodiment of the present application is an embodiment in which the above-described manufacturing method of lithium hydroxide of one embodiment of the present application is combined with the lithium-containing sulfide solid electrolyte raw material of one embodiment of the present application. In other words, it is an embodiment in which lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide, the solution is solid-liquid separated into a liquid component containing the lithium hydroxide and a solid component containing lithium from the lithium carbonate, lithium hydroxide is recovered from the liquid component side, and a lithium-containing sulfide solid electrolyte raw material is obtained from the solid component side.

[0200] The manufacturing method of lithium hydroxide and lithium-containing sulfide solid electrolyte raw material according to one embodiment of the present application can efficiently obtain a variety of sulfide solid electrolyte raw materials because lithium hydroxide is obtained from the liquid component side and a lithium-containing sulfide solid electrolyte raw material is obtained from the solid component side.

[0201] Figure 3 (a) of FIG. 31 shows one example of a flowchart of the manufacturing method of lithium hydroxide and lithium-containing sulfide solid electrolyte raw material. In the manufacturing method of lithium hydroxide and lithium-containing sulfide solid electrolyte raw material, first, lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide (Step S31). Next, the obtained solution is solid-liquid separated into a liquid component containing the lithium hydroxide and a solid component containing lithium from the lithium carbonate (Step S32). Lithium hydroxide is recovered from the liquid component (Step S33a), and calcium in the solid component is removed from the solid component to obtain a lithium-containing sulfide solid electrolyte raw material from the solid component (Step S33b). Steps S31 to S33a and / or Steps S31 to S33b are preferably continuously performed, and the effects of the present application are further improved when the continuous manufacturing method is used.

[0202] Note that the step S31, the step S32, and the step S33a are the same as the step S11, the step S12, and the step S13, respectively, of the above-described manufacturing method of lithium hydroxide of one embodiment of the present application. In addition, the step S33b is the same as the step combining the step S23 and the step S24 of the above-described manufacturing method of lithium-containing sulfide solid electrolyte material of one embodiment of the present application.

[0203] The total of the lithium recovery ratio, in other words, the proportion of lithium contained in the liquid component and the solid component after the solid-liquid separation with respect to the total amount of lithium from lithium carbonate as a raw material is preferably 90 to 99 % on a mass basis. By making the above-described total lithium recovery ratio 90 % or more, lithium from lithium carbonate as a raw material can be effectively recovered, and by being 99 % or less, it is not necessary to spend the cost of recovering lithium contained on the calcium sulfate side when calcium sulfate is removed by solid-liquid separation. The above-described total lithium recovery ratio is more preferably 92 % or more, further preferably 94 % or more, and more preferably 98 % or less, further preferably 97 % or less.

[0204] Manufacturing method of sulfide solid electrolyte (3)

[0205] The manufacturing method of a sulfide solid electrolyte of one embodiment of the present application (hereinafter, also referred to as a manufacturing method of a sulfide solid electrolyte (3)) is characterized by using lithium sulfide obtained by reacting lithium hydroxide and hydrogen sulfide and lithium-containing sulfide solid electrolyte material obtained by the manufacturing method of lithium hydroxide and lithium-containing sulfide solid electrolyte material of one embodiment of the present application as raw materials to produce a sulfide solid electrolyte.

[0206] Figure 3 (b) of FIG. 34 shows a flowchart of the manufacturing method of a sulfide solid electrolyte (3). In the manufacturing method of a sulfide solid electrolyte (3), a sulfide solid electrolyte is produced using lithium hydroxide obtained through the above-described steps S31 to S33a and lithium-containing sulfide solid electrolyte material obtained through the above-described steps S31 to S33b (step S34). The steps S31 to S34 are preferably performed continuously, and the effect of the present application is further improved when the continuous manufacturing method is employed.

[0207] The method of reacting lithium hydroxide and hydrogen sulfide to obtain lithium sulfide is the same as that described in the item of the manufacturing method of lithium sulfide of one embodiment of the present application.

[0208] In addition to the lithium sulfide and lithium-containing sulfide solid electrolyte raw materials described above, other sulfide solid electrolyte raw materials can also be used to produce the sulfide solid electrolyte. The types of other sulfide solid electrolyte raw materials, solid-phase methods, and melt methods are the same as those described in the first method for producing the sulfide solid electrolyte.

[0209] According to the third method for producing a sulfide solid electrolyte, lithium sulfide is obtained using lithium hydroxide obtained from the liquid component side as a raw material, and a sulfide solid electrolyte raw material containing lithium is obtained from the solid component side. Furthermore, these multiple sulfide solid electrolyte raw materials can be used to produce a sulfide solid electrolyte, so the sulfide solid electrolyte can be produced efficiently.

[0210] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications may be adopted within the scope of the present invention. For example, the present invention is not limited to the above-described embodiments, and appropriate modifications and improvements may be made. Furthermore, the materials, shapes, sizes, quantities, and placement of the components in the above-described embodiments are arbitrary and not limited, as long as they can achieve the present invention.

[0211] As described above, this specification discloses the following matters.

[0212] [1] A method for producing lithium hydroxide, comprising the following steps:

[0213] Lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide,

[0214] The solution is separated into a liquid component containing the lithium hydroxide and a solid component containing lithium from the lithium carbonate, and

[0215] Lithium hydroxide is recovered from the liquid component.

[0216] [2] The method for producing lithium hydroxide according to [1] above, wherein the amount of water relative to the total amount of the liquid in which lithium carbonate and calcium hydroxide are reacted is 70 to 96% by mass.

[0217] [3] The method for producing lithium hydroxide according to [1] or [2] above, wherein the mixing ratio of calcium hydroxide to lithium carbonate (calcium hydroxide / lithium carbonate) is 0.2 to 1.1 on a molar basis.

[0218] [4] The method for producing lithium hydroxide according to any one of [1] to [3] above, wherein the temperature of the liquid during the reaction of lithium carbonate and calcium hydroxide is 10 to 95°C.

[0219] [5] A method for producing lithium sulfide, wherein lithium hydroxide obtained by the production method described in any one of the above [1] to [4] is reacted with hydrogen sulfide to produce lithium sulfide.

[0220] [6] A method for producing a sulfide solid electrolyte, wherein lithium sulfide obtained by the production method described in the above [5] is used as a raw material.

[0221] [7] A method for producing a lithium-containing sulfide solid electrolyte raw material, comprising the steps of:

[0222] reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide,

[0223] solid-liquid separating the above solution into a liquid component containing the above lithium hydroxide and a solid component containing lithium from the above lithium carbonate, and

[0224] removing calcium from the above solid component to obtain a lithium-containing sulfide solid electrolyte raw material from the above solid component.

[0225] [8] The method for producing a lithium-containing sulfide solid electrolyte raw material described in the above [7], wherein calcium is removed from the above solid component by adding sulfate ions to the above solid component.

[0226] [9] The method for producing a lithium-containing sulfide solid electrolyte raw material described in the above [7] or [8], wherein the lithium-containing sulfide solid electrolyte raw material is lithium halide or lithium sulfate.

[0227]

[10] A method for producing a sulfide solid electrolyte, using a lithium-containing sulfide solid electrolyte raw material obtained by the production method described in any one of the above [7] to [9].

[0228]

[11] A method for producing lithium hydroxide and a lithium-containing sulfide solid electrolyte raw material, comprising the steps of:

[0229] reacting lithium carbonate and calcium hydroxide in a liquid to obtain a solution containing lithium hydroxide,

[0230] solid-liquid separating the above solution into a liquid component containing the above lithium hydroxide and a solid component containing lithium from the above lithium carbonate,

[0231] recovering lithium hydroxide from the above liquid component, and

[0232] removing calcium from the above solid component to obtain a lithium-containing sulfide solid electrolyte raw material from the above solid component.

[0233]

[12] A method for producing a sulfide solid electrolyte, using as raw materials lithium sulfide obtained by reacting the lithium hydroxide obtained in the production method described in

[11] with hydrogen sulfide and a lithium-containing sulfide solid electrolyte raw material obtained in the production method described in

[11] .

[0234]

[13] A lithium hydroxide-containing composition for synthesizing a sulfide solid electrolyte, comprising lithium hydroxide and zinc.

[0235]

[14] The lithium hydroxide-containing composition for synthesizing a sulfide solid electrolyte according to

[13] above, further comprising aluminum.

[0236]

[15] The lithium hydroxide-containing composition for synthesizing a sulfide solid electrolyte according to

[14] above, wherein the sum of the zinc concentration and the aluminum concentration is 10 ppm by mass or more.

[0237]

[16] The lithium hydroxide-containing composition for synthesizing a sulfide solid electrolyte according to any one of

[13] to

[15] , further comprising 10 ppm by mass or more of calcium.

[0238]

[17] A lithium sulfide composition for synthesizing a sulfide solid electrolyte, comprising lithium sulfide and zinc.

[0239]

[18] The lithium sulfide-containing composition for synthesizing a sulfide solid electrolyte according to

[17] above, further comprising aluminum.

[0240]

[19] The lithium sulfide-containing composition for synthesizing a sulfide solid electrolyte according to

[18] above, wherein the sum of the zinc concentration and the aluminum concentration is 10 ppm by mass or more.

[0241]

[20] The lithium sulfide-containing composition for synthesizing a sulfide solid electrolyte according to any one of

[17] to

[19] above, further comprising 10 ppm by mass or more of calcium.

[0242]

[21] A lithium halide composition for synthesizing a sulfide solid electrolyte, comprising: a lithium halide; and at least one ion selected from the group consisting of a sulfate ion, a phosphate ion, and a fluoride ion, wherein the concentration of the ion is 10% by mass or less.

[0243] Example

[0244] The present invention will be described in detail below with reference to Examples, but the present invention is not limited thereto. Examples 1 to 8 are Examples, and Example 9 is a Comparative Example.

[0245] (Example 1)

[0246] Production of lithium hydroxide

[0247] First, lithium carbonate (manufactured by Kanto Chemical Co., Inc.) 50.0 g was put into distilled water 300 g to make a lithium carbonate slurry. Next, calcium hydroxide (manufactured by Kanto Chemical Co., Inc.) 50.1 g was added to the lithium carbonate slurry, and the mixture was stirred at 85°C for 8 hours using a magnetic stirrer to react lithium carbonate with calcium hydroxide in the liquid. Note that the mixing ratio of calcium hydroxide to lithium carbonate (calcium hydroxide / lithium carbonate) was 1.0. In addition, the amount of water with respect to the total amount of the liquid in which lithium carbonate and calcium hydroxide were reacted was 75.0 mass%, and the amount of water with respect to Li2CO3 was 6.0 mass%.

[0248] Then, solid-liquid separation was performed by a method of filtration under reduced pressure to separate into a liquid component in which lithium hydroxide was dissolved and a solid component. Next, the liquid component in which lithium hydroxide was dissolved was dried under reduced pressure using a reduced-pressure drying furnace at 2 kPa while slowly increasing the temperature to a maximum temperature of 85°C, whereby concentration of the liquid in which lithium hydroxide was dissolved was performed (there is a step of removing water: "O" in Table 2). The solid-liquid separation was performed in a state in which lithium hydroxide was concentrated to 7.6 mass%, and removal of calcium was performed. The recovered liquid was subsequently dried under reduced pressure to obtain lithium hydroxide powder.

[0249] <Production of lithium sulfide>

[0250] The obtained lithium hydroxide powder was put into a vibration drying furnace (product name VH, manufactured by Chuo Kagaku Machine Co., Ltd.) and, under conditions of a temperature of 200 degrees and a pressure of 2 kPa, hydrogen sulfide gas was introduced while stirring to react lithium hydroxide with hydrogen sulfide, thereby obtaining lithium sulfide powder.

[0251] <Production of lithium halide>

[0252] After the solid component recovered at the time of production of lithium hydroxide was made into a slurry by adding distilled water 300 g, 3 mol / L sulfuric acid (manufactured by Junsei Chemical Co., Ltd.) 260 g was added to change the calcium component into calcium sulfate. Next, hydrobromic acid 48 wt% (manufactured by Kanto Chemical Co., Inc.) as a hydrogen halide acid was added to make a lithium bromide aqueous solution containing calcium sulfate. The obtained lithium bromide aqueous solution containing calcium sulfate was subjected to solid-liquid separation by a method of filtration under reduced pressure to remove calcium sulfate, thereby obtaining a lithium bromide solution. The obtained lithium bromide solution was dried and solidified using a vibration drying device (product name VH, manufactured by Chuo Kagaku Machine Co., Ltd.) under conditions of a temperature of 160°C and a pressure of 2 kPa to make lithium bromide powder.

[0253] <Production of sulfide solid electrolyte>

[0254] The obtained lithium sulfide powder and lithium bromide powder were used as raw materials for a sulfide solid electrolyte to produce a sulfide solid electrolyte. First, under a dry nitrogen atmosphere, lithium sulfide was made to have a particle diameter of 0.5 to 1.0 μm by a method of pulverization and classification. 5.3 PS 4.2 Cl 0.8Br 0.8 The above-obtained lithium sulfide powder and lithium bromide powder, and phosphorus pentasulfide powder (manufactured by Sigma, purity 99%) and lithium chloride powder (manufactured by Sigma, purity 99.99%) were weighed in a composition ratio to obtain a raw material mixture.

[0255] Next, the obtained raw material mixture was put in a heat-resistant container, and heated and melted at a pressure of 1 atm and a temperature of 750°C for 0.5 hours. At this time, sulfur gas obtained by heating elemental sulfur at a temperature of 350°C was supplied in a manner that the partial pressure of the sulfur gas was 0.1 atm with N2 as a carrier gas, to obtain a gas atmosphere containing sulfur element, and the heating and melting was performed in the gas atmosphere, thereby introducing sulfur into the melt. The content of the sulfur gas in the gas atmosphere containing sulfur element was 0.1 vol%.

[0256] Then, the solid was cooled at a cooling rate of 1 to 1000°C / sec to obtain a solid of a sulfide solid electrolyte containing an amorphous phase and a argyrodite-type crystalline phase. Next, the solid was subjected to a crystallization treatment at 450°C for 1 hour in a nitrogen atmosphere to obtain a sulfide solid electrolyte composite containing a sulfide solid electrolyte containing an argyrodite-type crystal. Thus, a sulfide solid electrolyte was obtained.

[0257] (Example 2)

[0258] In the production of lithium hydroxide in Example 1, the amount of distilled water into which lithium carbonate was put was changed from 300 g to 600 g, and otherwise, the lithium hydroxide, lithium bromide, and sulfide solid electrolyte in Example 2 were produced in the same manner as in Example 1. Note that the amount of water with respect to the total amount of the liquid in which lithium carbonate was reacted with calcium hydroxide was 85.7 mass%, and the amount of water with respect to Li2CO3 was 12.0 mass%.

[0259] (Example 3)

[0260] In the production of lithium hydroxide in Example 1, the amount of distilled water into which lithium carbonate was put was changed from 300 g to 900 g, and otherwise, the lithium hydroxide, lithium bromide, and sulfide solid electrolyte in Example 3 were produced in the same manner as in Example 1. Note that the amount of water with respect to the total amount of the liquid in which lithium carbonate was reacted with calcium hydroxide was 90.0 mass%, and the amount of water with respect to Li2CO3 was 18.0 mass%.

[0261] (Example 4)

[0262] In the production of lithium hydroxide of Example 1, the amount of distilled water put into lithium carbonate was changed from 300 g to 1200 g, and otherwise, the lithium hydroxide, lithium bromide, sulfide solid electrolyte in Example 4 was produced in the same manner as Example 1. Note that the amount of water with respect to the total amount of the liquid in which lithium carbonate and calcium hydroxide were reacted was 92.3 mass%, and the amount of water with respect to Li2CO3 was 24.0 mass%.

[0263] (Example 5)

[0264] In the production of lithium hydroxide of Example 1, the amount of distilled water put into lithium carbonate was changed from 300 g to 1200 g, and otherwise, the lithium hydroxide, lithium bromide, sulfide solid electrolyte in Example 5 was produced in the same manner as Example 1. Note that the amount of water with respect to the total amount of the liquid in which lithium carbonate and calcium hydroxide were reacted was 92.3 mass%, and the amount of water with respect to Li2CO3 was 24.0 mass%.

[0265] (Example 6)

[0266] In the production of lithium hydroxide of Example 1, the amount of distilled water put into lithium carbonate was changed from 300 g to 600 g, and otherwise, the lithium hydroxide, lithium bromide, sulfide solid electrolyte in Example 6 was produced in the same manner as Example 1. Note that the temperature (reaction temperature) at the time of stirring the slurry of lithium carbonate and calcium hydroxide was changed to 25°C.

[0267] (Example 7)

[0268] In the production of lithium hydroxide of Example 1, the amount of distilled water put into lithium carbonate was changed from 300 g to 600 g, and otherwise, the lithium hydroxide, lithium bromide, sulfide solid electrolyte in Example 7 was produced in the same manner as Example 1. Note that the ratio of calcium hydroxide to lithium carbonate (calcium hydroxide / lithium carbonate) was changed to 0.6, and the amount of sulfuric acid and hydrobromic acid put in at the time of lithium bromide synthesis was changed to 0.6 times the amount put in Example 1.

[0269] (Example 8)

[0270] In the production of lithium hydroxide of Example 1, the amount of distilled water put into lithium carbonate was changed from 300 g to 600 g, and otherwise, the lithium hydroxide, lithium bromide, sulfide solid electrolyte in Example 8 was produced in the same manner as Example 1. Note that the ratio of calcium hydroxide to lithium carbonate (calcium hydroxide / lithium carbonate) was changed to 0.3, and the amount of sulfuric acid and hydrobromic acid put in at the time of lithium bromide synthesis was changed to 0.3 times the amount put in Example 1.

[0271] (Example 9)

[0272] In the production of lithium hydroxide in Example 1, the amount of distilled water into which lithium carbonate was put was changed from 300 g to 3600 g, and otherwise, the production of lithium hydroxide, lithium bromide in Example 9 was attempted in the same manner as in Example 1. However, although the process of removing water from the liquid component in which lithium hydroxide was dissolved was attempted, water could not be removed even if 100 hours were spent, and lithium hydroxide could not be recovered from the liquid component (the process of removing water: indicated as "X" in Table 2). In addition, the solid component did not contain lithium from lithium carbonate as a raw material, and lithium bromide could not be obtained from the solid component. It should be noted that the amount of water with respect to the total amount of the liquid in which lithium carbonate was reacted with calcium hydroxide was 97.3 mass%, and the amount of water with respect to Li2CO3 was 72.0 mass%.

[0273]

[0274] First, 0.1 g of each of the powders of lithium hydroxide obtained above was taken, dissolved in dilute nitric acid, and the lithium concentration in the powder was determined using an atomic absorption spectrometer from the sample solution obtained above. The amount of lithium element was calculated from the lithium concentration in the powder obtained and the weight of the powder, and the proportion (%) of the amount of lithium contained in the lithium hydroxide powder with respect to the amount of lithium from the lithium carbonate used was taken as the Li recovery rate in the form of lithium hydroxide. The results are shown in Table 1.

[0275]

[0276] First, 0.1 g of each of the powders of lithium halide obtained above was taken, dissolved in dilute nitric acid, and the lithium concentration in the powder was determined using an atomic absorption spectrometer from the sample solution obtained above. The amount of lithium element was calculated from the lithium concentration in the powder obtained and the weight of the powder, and the proportion (%) of the amount of lithium contained in the lithium halide powder with respect to the amount of lithium from the lithium carbonate used was taken as the Li recovery rate in the form of lithium halide. The results are shown in Table 1.

[0277] <Overall Li recovery rate>

[0278] The overall Li recovery rate = (Li recovery rate in the form of lithium hydroxide) + (Li recovery rate in the form of lithium halide). The results are shown in Table 1.

[0279] <Concentration of Ca, Al, Zn in lithium hydroxide>

[0280] 0.1 g of the obtained lithium hydroxide powder was taken, dissolved in dilute nitric acid, and the concentration was calculated using ICP (inductively coupled plasma) emission spectroscopy from the sample solution obtained above. The results are shown in Table 2.

[0281] <SO4 concentration in lithium halide>

[0282] The obtained lithium halide powder of 0.1 g was dissolved in ultrapure water, and was measured by ion chromatography. The results are shown in Table 2.

[0283] < Lithium ion conductivity >

[0284] The sulfide solid electrolyte obtained in each example was further pulverized using a mortar, passed through a 100 μm mesh, and a sulfide solid electrolyte powder having a volume-based particle size distribution D50 of 10 μm was obtained. The powder was pressed at a pressure of 380 MPa to form a pressed powder, which was used as a measurement sample, and an AC impedance measurement device (Bio-Logic Sciences Instruments Co., Ltd., potentiostat / galvanostat VSP) was used to measure the lithium ion conductivity. Samples having a value of 5 mS / cm or more were evaluated as "O".

[0285] The measurement conditions were a measurement frequency of 100 Hz to 1 MHz, a measurement voltage of 100 mV, and a measurement temperature of 25°C.

[0286] [Table 1]

[0287]

[0288] [Table 2]

[0289]

[0290] According to the results of Examples 1 to 4, as the amount of distilled water increased, the recovery rate of Li as lithium hydroxide increased, and conversely, the recovery rate of Li as lithium halide decreased. It is considered that as the amount of distilled water increased, a large amount of lithium hydroxide dissolved into the liquid component side at the time of solid-liquid separation, and on the other hand, the residual amount of lithium in the solid component side decreased.

[0291] In addition, according to the results of Example 5, by extending the reaction time of lithium carbonate and calcium hydroxide, the recovery rate of Li as lithium hydroxide increased, and conversely, the recovery rate of Li as lithium halide decreased.

[0292] In addition, according to the results of Example 6, by lowering the reaction temperature of lithium carbonate and calcium hydroxide, the recovery rate of Li as lithium hydroxide decreased, and conversely, the recovery rate of Li as lithium halide increased. It is considered that as the reaction temperature of lithium carbonate and calcium hydroxide decreased, the reaction of lithium carbonate and calcium hydroxide was inhibited, the amount of generated lithium hydroxide decreased, and as a result, the amount of dissolved lithium hydroxide in the liquid component side at the time of solid-liquid separation decreased, and on the other hand, the residual amount of lithium in the solid component side increased.

[0293] In addition, according to the results of Example 7 and Example 8, as the mixing ratio of calcium hydroxide to lithium carbonate (calcium hydroxide / lithium carbonate) decreases, the recovery rate of Li as lithium hydroxide decreases, and, on the contrary, the recovery rate of Li as lithium halide increases.

[0294] In Examples 1 to 8, the recovery rate of Li as lithium hydroxide can be suppressed to be low, and, accordingly, Li can be recovered as lithium halide. That is, lithium hydroxide can be efficiently obtained from the liquid component side, and a lithium-containing sulfide solid electrolyte material can also be obtained from the solid component side. Therefore, within the same manufacturing process, lithium hydroxide can be efficiently obtained from the liquid component at low cost, and a lithium-containing sulfide solid electrolyte material can also be obtained from the solid component.

[0295] In addition, the obtained lithium hydroxide (lithium hydroxide-containing composition) contains aluminum, zinc, and sulfate ions, and has good lithium ion conductivity.

[0296] Furthermore, a sulfide solid electrolyte can be efficiently manufactured using the obtained lithium hydroxide, lithium bromide within the same manufacturing process. In addition, the lithium ion conductivity of the sulfide solid electrolyte is also good.

[0297] On the other hand, according to the results of Example 9, it was found that when the amount of distilled water into which lithium carbonate is put is increased excessively, Li cannot be recovered as lithium hydroxide, and Li cannot be recovered as lithium halide. Therefore, lithium bromide cannot be manufactured, and a sulfide solid electrolyte cannot be manufactured using lithium hydroxide, lithium bromide.

[0298] The above describes various embodiments with reference to the drawings, but the present application is not limited to the above examples. It is obvious for those skilled in the art that various modifications or corrections can be conceived within the scope described in the patent claim, and it is understood that these are naturally included in the technical scope of the present application. In addition, each of the components in the above embodiments can be arbitrarily combined without departing from the gist of the present application.

[0299] Note that this application is based on Japanese Patent Application (Japanese Patent Application No. 2023-031335) filed on March 1, 2023, and the content thereof is incorporated herein by reference.

Claims

1. A method for producing lithium hydroxide, comprising the following steps: Lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide, The solution is separated into a liquid component containing the lithium hydroxide and a solid component containing lithium derived from the lithium carbonate, and Lithium hydroxide is recovered from the liquid component.

2. The method for producing lithium hydroxide according to claim 1, wherein The amount of water is 70 to 96% by mass relative to the total amount of the liquid in which lithium carbonate and calcium hydroxide are reacted.

3. The method for producing lithium hydroxide according to claim 1, wherein The mixing ratio of calcium hydroxide to lithium carbonate, that is, calcium hydroxide / lithium carbonate, is 0.2 to 1.1 on a molar basis.

4. The method for producing lithium hydroxide according to claim 1, wherein The temperature of the liquid when lithium carbonate and calcium hydroxide are reacted is 10 to 95°C. 5 . A method for producing lithium sulfide, comprising reacting lithium hydroxide obtained by the method according to claim 1 with hydrogen sulfide to produce lithium sulfide.

6. A method for producing a sulfide solid electrolyte, comprising using the lithium sulfide obtained by the production method according to claim 5 as a raw material.

7. A method for producing a lithium-containing sulfide solid electrolyte raw material, comprising the following steps: Lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide, The solution is separated into a liquid component containing the lithium hydroxide and a solid component containing lithium derived from the lithium carbonate, and Calcium in the solid component is removed to obtain a lithium-containing sulfide solid electrolyte raw material from the solid component.

8. The method for producing a lithium-containing sulfide solid electrolyte raw material according to claim 7, wherein: Sulfate ions are added to the solid component to remove calcium from the solid component.

9. The method for producing a lithium-containing sulfide solid electrolyte raw material according to claim 7, wherein: The raw material of the lithium-containing sulfide solid electrolyte is lithium halide or lithium sulfate. 10 . A method for producing a sulfide solid electrolyte, comprising using a lithium-containing sulfide solid electrolyte raw material obtained by the production method according to claim 7 .

11. A method for producing lithium hydroxide and lithium-containing sulfide solid electrolyte raw materials, comprising the following steps: Lithium carbonate and calcium hydroxide are reacted in a liquid to obtain a solution containing lithium hydroxide, The solution is separated into a liquid component containing the lithium hydroxide and a solid component containing lithium derived from the lithium carbonate. recovering lithium hydroxide from the liquid component, and Calcium in the solid component is removed to obtain a lithium-containing sulfide solid electrolyte raw material from the solid component.

12. A method for producing a sulfide solid electrolyte, comprising using as raw materials lithium sulfide obtained by reacting lithium hydroxide obtained by the production method according to claim 11 with hydrogen sulfide, and a lithium-containing sulfide solid electrolyte raw material obtained by the production method according to claim 11.

13. A lithium hydroxide-containing composition for synthesizing a sulfide solid electrolyte, comprising lithium hydroxide and zinc.

14. The lithium hydroxide-containing composition for synthesizing a sulfide solid electrolyte according to claim 13, wherein It further contains aluminum.

15. The lithium hydroxide-containing composition for synthesizing a sulfide solid electrolyte according to claim 14, wherein The sum of the zinc concentration and the aluminum concentration is 10 mass ppm or more.

16. The lithium hydroxide-containing composition for synthesizing a sulfide solid electrolyte according to any one of claims 13 to 15, wherein Furthermore, it contains 10 mass ppm or more of calcium.

17. A lithium sulfide-containing composition for synthesizing a sulfide solid electrolyte, comprising lithium sulfide and zinc.

18. The lithium sulfide-containing composition for synthesizing a sulfide solid electrolyte according to claim 17, wherein It further contains aluminum.

19. The lithium sulfide-containing composition for synthesizing a sulfide solid electrolyte according to claim 18, wherein The sum of the zinc concentration and the aluminum concentration is 10 mass ppm or more.

20. The lithium sulfide-containing composition for synthesizing a sulfide solid electrolyte according to any one of claims 17 to 19, wherein Furthermore, it contains 10 mass ppm or more of calcium.

21. A lithium halide composition for synthesizing a sulfide solid electrolyte, comprising: lithium halide; and At least any one of sulfate ions, phosphate ions, and fluoride ions, wherein the concentration of the ion is 10% by mass or less.

Images