Method for producing lithium sulfide

Abstract

The purpose of the present invention is to provide a method for producing lithium sulfide in which the content of hydrogen sulfide is reduced.　The present invention is a method for producing lithium sulfide, the method comprising: reacting gaseous hydrogen sulfide with a powdered lithium source in a reactor to obtain lithium sulfide; substituting the interior of the reactor with an inert gas at a temperature of 180°C or higher after the reaction; and again substituting the interior of the reactor with an inert gas at a temperature of 60°C or lower after the inert gas substitution.

Description

Lithium sulfide manufacturing method

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

[0002] Solid electrolytes have been attracting attention as electrolytes for lithium-ion secondary batteries. Solid electrolytes are used in all-solid-state batteries and are expected to contribute to improving the safety and performance of secondary batteries. Examples of solid electrolytes include sulfide solid electrolytes (see, for example, Patent Document 1). Lithium sulfide is used as a raw material for sulfide solid electrolytes.

[0003] JP 2010-163356 A

[0004] Although Patent Document 1 discloses a method for producing lithium sulfide, further expansion of production is required as a supply source of lithium sulfide. It has been found that lithium sulfide obtained by this production method contains residual hydrogen sulfide, which was used as a raw material.

[0005] Therefore, an object of the present invention is to provide a production method for obtaining lithium sulfide with a reduced content of hydrogen sulfide.

[0006] One embodiment of the present invention relates to a method for producing lithium sulfide, comprising: reacting gaseous hydrogen sulfide with a powdery lithium source in a reactor to obtain lithium sulfide; after the reaction, replacing the atmosphere inside the reactor with an inert gas at a temperature of 180°C or higher; and after the replacement with the inert gas, further replacing the atmosphere inside the reactor with an inert gas at a temperature of 60°C or lower.

[0007] According to the present invention, it is possible to provide a method for producing lithium sulfide that can obtain lithium sulfide with a reduced content of hydrogen sulfide.

[0008] Hereinafter, an embodiment of the present invention (hereinafter also referred to as the present embodiment) will be described. In this specification, for example, when a numerical range is expressed as "1 to 100," it is assumed that the range includes both the lower limit "1" and the upper limit "100." The same applies to other numerical ranges.

[0009] The present embodiment is a method for producing lithium sulfide, comprising: reacting gaseous hydrogen sulfide with a powdered lithium source in a reactor to obtain lithium sulfide (hereinafter also referred to as the "reaction step"); replacing the atmosphere in the reactor with an inert gas at a temperature of 180°C or higher after the reaction (hereinafter also referred to as the "high-temperature replacement step"); and further replacing the atmosphere in the reactor with an inert gas at a temperature of 60°C or lower after the inert gas replacement (hereinafter also referred to as the "low-temperature replacement step"). According to the production method of the present embodiment described above, lithium sulfide with a reduced hydrogen sulfide content can be obtained. Experiments have revealed that the adsorption and desorption of hydrogen sulfide to and from lithium sulfide are temperature dependent. Taking these characteristics into consideration, the above-described production method was able to reduce the hydrogen sulfide content in lithium sulfide.

[0010] The "lithium source" refers to a lithium raw material that reacts with hydrogen sulfide to produce lithium sulfide. Examples of lithium sources include metallic lithium, lithium sulfate, lithium hydroxide, lithium carbonate, and lithium oxide. Among these, lithium hydroxide and lithium carbonate are preferred, and lithium hydroxide is more preferred.

[0011] "Gaseous hydrogen sulfide" has the chemical formula H ２ The hydrogen sulfide introduced into the reactor may contain other components.

[0012] (Reaction Step) In the reaction step, hydrogen sulfide and a powdery lithium source are reacted in a reactor.

[0013] The hydrogen sulfide introduced into the reactor preferably has a water content of 20 vol% or less relative to the hydrogen sulfide. The water content of hydrogen sulfide is more preferably 15 vol% or less, and even more preferably 11 vol% or less, relative to the hydrogen sulfide. Even if the hydrogen sulfide contains water, the reaction proceeds smoothly in the reaction step described below, and the target lithium sulfide is obtained.

[0014] The temperature of the hydrogen sulfide introduced into the reactor may be 100° C. to 300° C., 150° C. to 250° C., or 180° C. to 220° C. In the production method according to this embodiment, even at such temperatures, hydrogen sulfide can be introduced into the reactor without being cooled.

[0015] In the reactor, hydrogen sulfide reacts with a lithium source. The lithium source is lithium hydroxide (LiOH) and lithium carbonate (Li ２ CO ３ When using 2LiOH + H, the following reaction occurs: ２ S → Li ２ S + 2H ２ O Li ２ CO ３ + H ２ S → Li ２ S + H ２ O + CO ２

[0016] The reactor may be any device capable of contacting gaseous hydrogen sulfide with a powdered lithium source. The reactor may be a fixed-bed, moving-bed, tumbling-bed, or fluidized-bed reactor. Furthermore, since the reactor is capable of contacting gas and solid to cause a reaction, a powder dryer may be used. As the powder dryer, a conductive heat transfer dryer such as a disk dryer is preferably used. Examples of disk dryers include those under the product names "Micron Thermoprocessor" and "Torus Disk" (manufactured by Hosokawa Micron Corporation), "Paddle Dryer" (manufactured by Nara Machinery Manufacturing Co., Ltd.), "Inclined Disk Dryer" (manufactured by Tsukishima Holdings Co., Ltd.), and CD dryer. The reaction between hydrogen sulfide and a lithium source produces lithium sulfide, which also produces water. The reaction between lithium sulfide and water can also produce lithium hydroxide. By using a dryer to carry out the gas-solid reaction of hydrogen sulfide and lithium hydroxide, a larger amount of water produced during the reaction can be released outside the reactor, the equilibrium reaction can proceed in favor of the production of lithium sulfide, and lithium sulfide can be obtained in a higher yield. When a dryer is used as the reactor, the lithium source introduced into the reactor does not need to be in powder form from the beginning, as long as it can be converted into powder in the dryer.

[0017] It is preferable to fluidize the lithium source in the reactor. By fluidizing the lithium source in the reactor, the contact efficiency between the powdered lithium source in the reactor and the gaseous hydrogen sulfide is increased, and further, the drying of the powder is facilitated, allowing more water to be released outside the reactor, thereby improving the reaction yield. A disk can be used as a mechanism for fluidizing the powder.

[0018] The temperature inside the reactor may be 100 to 300°C, 150 to 250°C, or 180 to 220°C.

[0019] It is preferable to release an exhaust gas containing hydrogen sulfide from the reactor during the reaction. With the release of the exhaust gas, moisture generated in the reactor and vapor of moisture contained in the raw materials can be discharged, and the reaction for producing lithium sulfide proceeds advantageously.

[0020] (High-temperature substitution step) In the high-temperature substitution step, after the reaction, the inside of the reactor is substituted with an inert gas at a temperature of 180°C or higher. Examples of inert gases include nitrogen and argon. The temperature inside the reactor in the high-temperature substitution step is 180°C or higher, preferably 185°C or higher, more preferably 190°C or higher, and even more preferably 195°C or higher, from the viewpoint of obtaining lithium sulfide with a reduced hydrogen sulfide content. The maximum temperature of the reactor in the inert gas substitution is preferably 250°C or lower. In the high-temperature substitution step, an inert gas is introduced into and discharged from the reactor, and the inert gas is circulated. This allows hydrogen sulfide remaining in the reactor to be discharged outside the reactor. It is believed that performing the substitution with a high-temperature inert gas has the effect of desorbing hydrogen sulfide molecules adsorbed on lithium sulfide molecules.

[0021] (Low-temperature substitution step) In the low-temperature substitution step, after the high-temperature substitution step, the inside of the reactor is further substituted with an inert gas at a temperature of 60° C. or lower. From the viewpoint of obtaining lithium sulfide with a reduced content of hydrogen sulfide, the temperature inside the reactor in the low-temperature substitution step is 60° C. or lower, preferably 55° C. or lower, more preferably 50° C. or lower, and even more preferably 40° C. or lower. By providing the low-temperature substitution step in this manner and performing inert gas substitution at a lowered temperature, the amount of hydrogen sulfide desorbed from lithium sulfide is reduced.

[0022] In the method for producing lithium sulfide according to this embodiment, after the high-temperature substitution step and the low-temperature substitution step, the temperature may be lowered under an inert gas atmosphere. This prevents re-adsorption of hydrogen sulfide onto lithium sulfide, thereby obtaining lithium sulfide with a reduced amount of hydrogen sulfide. The temperature may be lowered to room temperature.

[0023] The lithium sulfide obtained through the above steps may be stored in an airtight packaging container such as a container and shipped as a product.

[0024] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0025] (Example 1) A SUS tube with an inner diameter of 10 mm and an outer diameter of 12 mm was used as a reactor. 5 g of LiOH was filled into the SUS tube with quartz wool packed at the bottom, and quartz wool was further packed on top of the LiOH, filling the reactor with LiOH. ２ H supplied from S cylinder ２ S was introduced into the reactor and reacted at 200°C for 24 hours.

[0026] After the reaction, nitrogen gas was purged for 5 hours at a temperature of 200°C inside the reactor to replace the interior of the reactor with nitrogen gas. At this time, the hydrogen sulfide concentration in the nitrogen at the reactor outlet was measured to determine the hydrogen sulfide concentration. Similarly, after the reaction, nitrogen gas was purged for 5 hours at a temperature of 40°C inside the reactor to replace the interior of the reactor with nitrogen gas. At this time, the hydrogen sulfide concentration in the nitrogen at the reactor outlet was measured to determine the hydrogen sulfide concentration.

[0027]

[0028]

[0029] As described above, according to Example 1, by performing inert gas substitution at a high temperature of 180°C or higher, Li ２ It can be seen that the cumulative amount of hydrogen sulfide released from 1 g of S can be made high (Table 2). On the other hand, it can be seen that the release of hydrogen sulfide can be prevented by replacing the inside of the reactor with an inert gas at a temperature of 60°C or less (Table 1).

Claims

1. A method for producing lithium sulfide, comprising: reacting gaseous hydrogen sulfide with a powdered lithium source in a reactor to obtain lithium sulfide; after the reaction, replacing the atmosphere inside the reactor with an inert gas at a temperature of 180°C or higher; and after the replacement with the inert gas, further replacing the atmosphere inside the reactor with an inert gas at a temperature of 60°C or lower.

2. The method for producing lithium sulfide according to claim 1, wherein the temperature inside the reactor during the reaction is 100°C to 300°C.

3. The method for producing lithium sulfide according to claim 1 or 2, wherein the powdered lithium source is fluidized in the reactor during the reaction.

4. The method for producing lithium sulfide according to any one of claims 1 to 3, wherein the powdered lithium sulfide is fluidized in the reactor during the inert gas substitution.

5. The method for producing lithium sulfide according to any one of claims 1 to 4, wherein the reactor is a disk dryer.

6. The method for producing lithium sulfide according to any one of claims 1 to 5, wherein the maximum temperature of the reactor during the inert gas substitution is 250°C or less.

7. The method for producing lithium sulfide according to any one of claims 1 to 6, wherein the inert gas substitution comprises introducing and discharging an inert gas into and from the reactor, thereby circulating the inert gas.

8. The method for producing lithium sulfide according to any one of claims 1 to 7, comprising: after the inert gas substitution, lowering the temperature in an inert gas atmosphere.

9. The method for producing lithium sulfide according to any one of claims 1 to 8, comprising, after the inert gas substitution, lowering the temperature to room temperature in an inert gas atmosphere.

10. The method for producing lithium sulfide according to any one of claims 1 to 9, wherein the lithium source is lithium hydroxide.

11. The method for producing lithium sulfide according to any one of claims 1 to 9, wherein the lithium source is lithium carbonate.

Images