A method for producing lithium sulfide

Abstract

The application provides a preparation method of lithium sulfide, and relates to the technical field of lithium sulfide synthesis. The lithium sulfide is prepared by stirring and reacting lithium citrate and barium sulfide in an alcohol aqueous solution, performing solid-liquid separation to obtain an alcohol solution of lithium sulfide, and performing rotary evaporation concentration to obtain the lithium sulfide. The application has the advantages of simple operation, low energy consumption, large-scale industrial production, greatly reduced production cost of lithium sulfide, and facilitation of popularization and application of lithium-sulfur batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium sulfide synthesis, and in particular to a method for preparing lithium sulfide. Background Art

[0002] Sustainable development of energy and the environment is a shared aspiration of human society. New energy vehicles, being greener and more environmentally friendly than traditional fuel vehicles, are increasingly popular in relevant countries. Batteries are crucial to these vehicles. With the continuous advancement of technology, demands for battery energy density and safety are increasing. Therefore, lithium-sulfur batteries, with their high energy density and safety, have emerged as a key development direction in the battery industry.

[0003] Lithium sulfide is the primary active material in the positive electrode of lithium-sulfur batteries. However, existing methods for producing lithium sulfide are costly and primarily involve carbon thermal reduction of lithium sulfate, reaction of lithium-containing compounds with sulfur, and reaction of metallic lithium with sulfur-containing compounds. However, carbon thermal reduction of lithium sulfate requires high reaction temperatures and produces significant waste, significantly increasing production costs. Furthermore, the lithium-containing compound used in the reaction of lithium-containing compounds with sulfur must be air-sensitive and expensive, and metallic lithium is also relatively expensive. Therefore, a solution is urgently needed to address these issues. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing lithium sulfide, which is simple to operate and has low energy consumption. It can not only be produced on a large scale industrially, but also greatly reduce the production cost of lithium sulfide, which is conducive to promoting the popularization and application of lithium-sulfur batteries.

[0005] The present invention provides a method for preparing lithium sulfide, which comprises the following steps: stirring lithium citrate and barium sulfide in an alcohol-water solution for reaction, separating the solid and the liquid to obtain a lithium sulfide alcohol solution, and then concentrating the solution by rotary evaporation to obtain lithium sulfide.

[0006] The preparation method provided by the present invention generates a barium citrate precipitate and a lithium sulfide alcohol solution by reacting lithium citrate with barium sulfide, and purifies and extracts the lithium sulfide alcohol solution to obtain high-purity lithium sulfide. The operation is simple and does not require heating, which is beneficial to reducing the production cost of lithium sulfide. At the same time, no highly toxic hydrogen sulfide gas is generated during the reaction process, and the reaction is green and environmentally friendly.

[0007] Optionally, the method includes the following steps: stirring and dissolving lithium citrate in an alcohol aqueous solution to obtain a lithium citrate solution; adding lithium sulfide to the lithium citrate solution and stirring to react to obtain a reaction system; performing solid-liquid separation on the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate; and concentrating and drying the lithium sulfide alcohol solution to obtain lithium sulfide.

[0008] Optionally, the molar ratio of the lithium citrate to the barium sulfide is 1:(1-2).

[0009] Optionally, the ratio of the mass of lithium citrate to the volume of water in the alcohol aqueous solution is 1.6 g / mL-1.8 g / mL.

[0010] Optionally, the alcohol in the alcohol aqueous solution includes methanol or ethanol.

[0011] Optionally, the volume ratio of alcohol to water in the alcohol-water solution is (23-39):1.

[0012] Optionally, the concentration of the lithium citrate in the alcohol aqueous solution is 0.04 g / mL-0.07 g / mL.

[0013] Alternatively, lithium citrate is stirred and dissolved in an alcohol aqueous solution at 50° C.-80° C. to prepare a lithium citrate solution.

[0014] Optionally, lithium citrate is added to an alcohol aqueous solution and then stirred and dissolved at 50° C.-80° C. to prepare a lithium citrate solution.

[0015] Optionally, lithium citrate is stirred in an alcohol aqueous solution for 10 min-30 min to prepare a lithium citrate solution.

[0016] Optionally, barium sulfide is gradually added into the lithium citrate solution at a rate of 4 g / min-9 g / min and stirred for reaction.

[0017] Optionally, the lithium sulfate alcohol solution is concentrated and dried under a protective atmosphere.

[0018] Optionally, the lithium sulfate alcohol solution is concentrated and dried, and then ground and sieved to obtain lithium sulfide powder with a particle size of less than or equal to 100 nm.

[0019] Optionally, the reaction formula of the reaction between lithium citrate and barium sulfide is:

[0020] . BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flow chart of a method for preparing lithium sulfide provided by the present invention;

[0022] Figure 2 This is the XRD characterization diagram of lithium sulfide prepared in Example 1 of the present invention;

[0023] Figure 3 This is a sintered appearance diagram of the lithium sulfide prepared in Example 1 of the present invention when it is made into a lithium-sulfur active material;

[0024] Figure 4 This is an XRD characterization diagram of the lithium sulfide prepared in Example 1 of the present invention when it is made into a lithium-sulfur active material;

[0025] Figure 5This is a characterization diagram of the ionic conductivity of lithium sulfide prepared in Example 1 of the present invention when it is made into lithium-sulfur active material. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs.

[0027] The present invention provides a method for preparing lithium sulfide, comprising: stirring lithium citrate and barium sulfide in an alcohol-water solution, separating the solid and liquid to obtain a lithium sulfide alcohol solution, and then concentrating by rotary evaporation to obtain lithium sulfide. Specifically, when lithium citrate and barium sulfide react, lithium citrate, barium sulfide, and the product barium citrate are insoluble in alcohol, while the product lithium sulfide is soluble in alcohol, so lithium sulfide can be separated separately. In addition, the system in the lithium sulfide alcohol solution is alkaline, so S 2- It is relatively stable and not prone to deterioration.

[0028] In fact, when lithium citrate and barium sulfide react in an alcohol-water solution, lithium citrate and barium sulfide first dissolve in the water portion of the alcohol-water solution. After the reaction, lithium sulfide enters the alcohol portion of the alcohol-water solution, while unreacted lithium citrate, barium sulfide and barium citrate remain in the water portion, thereby obtaining a lithium sulfide alcohol solution. By separating and purifying the lithium sulfide alcohol solution, the reaction of lithium sulfide with water oxygen to produce hydrogen sulfide gas can be avoided.

[0029] At the same time, when the reaction generates barium citrate and precipitates it, the barium citrate combines with water to form a hydrated precipitate, which in turn removes the water portion of the aqueous alcohol solution, facilitating the dissolution of the resulting lithium sulfide in the alcohol portion. In reality, while lithium sulfide is soluble in both water and alcohol, lithium citrate and barium sulfide are soluble in water but not in alcohol, and lithium sulfide readily hydrolyzes in water, at room temperature, lithium citrate becomes alkaline when dissolved in water, inhibiting the hydrolysis of lithium sulfide. Consequently, lithium sulfide remains stable in the aqueous alcohol solution as an ion.

[0030] Specifically, see Figure 1 The method for preparing lithium sulfide provided by the present invention comprises the following steps:

[0031] S1, stirring and dissolving lithium citrate in an alcohol aqueous solution to prepare a lithium citrate solution;

[0032] S2, adding lithium sulfide to the lithium citrate solution and stirring to obtain a reaction system;

[0033] S3, performing solid-liquid separation on the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate;

[0034] S4. Concentrating and drying the lithium sulfide alcohol solution to obtain lithium sulfide.

[0035] In some embodiments, when lithium citrate is prepared into a lithium citrate solution in step S1, the alcohol in the alcohol-water solution includes methanol or ethanol, and the volume ratio of alcohol to water in the alcohol-water solution is (23-39):1. This facilitates the dissolution of lithium sulfide generated by the reaction in the alcohol and increases the solubility of lithium sulfide.

[0036] In some embodiments, the molar ratio of the lithium citrate used in step S1 to the barium sulfide used in step S2 is 1:(1-2). Specifically, the ratio of the mass of lithium citrate to the volume of water in the alcohol-water solution is 1.6 g / mL-1.8 g / mL. Furthermore, the concentration of lithium citrate in the alcohol-water solution is 0.04 g / mL-0.07 g / mL.

[0037] In some embodiments, the lithium citrate solution is prepared by stirring and dissolving lithium citrate in an aqueous alcohol solution at 50°C-80°C. In other embodiments, the lithium citrate solution can be prepared by adding lithium citrate to an aqueous alcohol solution and then stirring and dissolving the solution at 50°C-80°C. In practice, the lithium citrate solution is prepared by stirring the lithium citrate in the aqueous alcohol solution for 10-30 minutes.

[0038] In some embodiments, barium sulfide is gradually added to the lithium citrate solution at a rate of 4 g / min-9 g / min and stirred for reaction. In addition, the lithium sulfate alcohol solution is concentrated and dried under a protective atmosphere. The lithium sulfate alcohol solution can also be concentrated and dried, and then ground and sieved to obtain lithium sulfide powder with a particle size less than or equal to 100 nm.

[0039] Specifically, the reaction formula of the reaction between lithium citrate and barium sulfide is:

[0040] .

[0041] Example 1

[0042] This embodiment 1 provides a method for preparing lithium sulfide, comprising the following steps:

[0043] S1. Add 210 g of lithium citrate into 3000 mL of ethanol-water solution (ethanol to water volume ratio 2640 mL:360 mL), and stir in a 60°C water bath for 20 min until completely dissolved to prepare a lithium citrate solution;

[0044] S2. Within 30 minutes, 253.9 g of barium sulfide powder was evenly added to a lithium citrate solution stirred in a 60° C. water bath to prepare a reaction system;

[0045] S3, filtering the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate;

[0046] S4. After evaporating and crystallizing the lithium sulfide alcohol solution under an argon atmosphere, the lithium sulfide crystals were ball-milled in a ball mill to obtain 129.4 g of lithium sulfide powder with a calculated yield of 93.7%.

[0047] Example 2

[0048] This embodiment 2 provides a method for preparing lithium sulfide, comprising the following steps:

[0049] S1. Add 210 g of lithium citrate into 4000 mL of ethanol-water solution (ethanol to water volume ratio 3640 mL:360 mL), and stir in a 65°C water bath for 20 min until completely dissolved to prepare a lithium citrate solution;

[0050] S2. Within 45 minutes, 256 g of barium sulfide powder was evenly added to a lithium citrate solution stirred in a 65° C. water bath to prepare a reaction system.

[0051] S3, filtering the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate;

[0052] S4. After evaporating and crystallizing the lithium sulfide alcohol solution under an argon atmosphere, the lithium sulfide crystals were ball-milled in a ball mill to obtain 131 g of lithium sulfide powder with a calculated yield of 94.9%.

[0053] Example 3

[0054] This embodiment 3 provides a method for preparing lithium sulfide, comprising the following steps:

[0055] S1. Add 210 g of lithium citrate into 5000 mL of ethanol-water solution (ethanol to water volume ratio 4640 mL:360 mL), and stir in a 70°C water bath for 20 min until completely dissolved to prepare a lithium citrate solution;

[0056] S2. Within 60 minutes, 258 g of barium sulfide powder was evenly added to a lithium citrate solution stirred in a 70° C. water bath to prepare a reaction system.

[0057] S3, filtering the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate;

[0058] S4. After the lithium sulfide alcohol solution was evaporated and crystallized under an argon atmosphere, the lithium sulfide crystals were ball-milled in a ball mill to obtain 130.5 g of lithium sulfide powder, with a calculated yield of 94.6%.

[0059] Verification

[0060] The lithium sulfide prepared in Example 1 was subjected to XRD characterization and compared with a lithium sulfide standard card. Figure 2 As shown. The lithium sulfide prepared in Example 1 was mixed with P2S5 and LiCl in a stoichiometric ratio of 5.5:4.5:1.5 by ball milling in a nitrogen atmosphere, sintered at 480°C for 16 hours, and crushed and sieved to obtain a lithium-sulfur active material. The sintered product was photographed as shown. Figure 3 As shown, the phase analysis and ionic conductivity analysis of lithium-sulfur active materials are respectively as follows Figure 4 and Figure 5 As shown. Figure 5 It can be seen that the ionic conductivity is 7.32 mS / cm, which shows that the lithium sulfide prepared by the present invention can be used for the preparation of high-performance LPSC.

[0061] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A method for preparing lithium sulfide, characterized in that: The following steps are involved: Lithium citrate is stirred and dissolved in an alcohol aqueous solution to prepare a lithium citrate solution with a concentration of 0.04 g / mL to 0.07 g / mL, wherein the volume ratio of alcohol to water in the alcohol aqueous solution is (23-39):1; barium sulfide is added to the lithium citrate solution and stirred for reaction to obtain a reaction system; the reaction system is subjected to solid-liquid separation to obtain a lithium sulfide alcohol solution and a mixed precipitate; and the lithium sulfide alcohol solution is concentrated and dried to obtain lithium sulfide.

2. The preparation method according to claim 1, characterized in that The molar ratio of the lithium citrate to the barium sulfide is 1:(1-2); and / or the ratio of the mass of the lithium citrate to the volume of water in the alcohol aqueous solution is 1.6 g / mL-1.8 g / mL.

3. The preparation method according to claim 1, characterized in that The alcohol in the alcohol aqueous solution includes methanol or ethanol.

4. The preparation method according to claim 1, characterized in that The lithium citrate solution is prepared by stirring and dissolving lithium citrate in an alcohol aqueous solution at 50° C.-80° C.; or, lithium citrate is added to an alcohol aqueous solution and then stirred and dissolved at 50° C.-80° C. to prepare the lithium citrate solution; and / or, lithium citrate is stirred in the alcohol aqueous solution for 10 min-30 min to prepare the lithium citrate solution.

5. The preparation method according to claim 1, characterized in that Barium sulfide was gradually added into the lithium citrate solution at a rate of 4 g / min-9 g / min and stirred for reaction.

6. The preparation method according to claim 1, characterized in that The lithium sulfide alcohol solution is concentrated and dried under a protective atmosphere; and / or, after the lithium sulfide alcohol solution is concentrated and dried, it is ground and sieved to obtain lithium sulfide powder with a particle size of less than or equal to 100 nm.

7. The preparation method according to any one of claims 1 to 6, characterized in that The reaction formula of the reaction between lithium citrate and barium sulfide is: 。

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