Preparation method of lithium sulfide

Abstract

The invention provides a preparation method of lithium sulfide, and relates to the technical field of lithium sulfide synthesis. The method comprises the following steps: stirring lithium citrate and barium sulfide in an alcohol-water solution to react, performing solid-liquid separation to obtain a lithium sulfide alcohol solution, and performing rotary evaporation and concentration to obtain lithium sulfide. The method is easy to operate and low in energy consumption, large-scale industrial production can be achieved, the production cost of lithium sulfide can be greatly reduced, and popularization and application of the lithium-sulfur battery are promoted.

Description

Technical Field

[0001] The 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 environment is the common aspiration of human society. Compared with traditional fuel vehicles, new energy vehicles are more environmentally friendly and are increasingly welcomed by relevant countries. Batteries are the key to new energy vehicles. With the continuous development of technology, people's requirements for battery energy density and safety are constantly increasing. Therefore, lithium-sulfur batteries with higher energy density and safety have emerged and become an important development direction in the future battery field.

[0003] The main active material of the positive electrode in lithium-sulfur batteries is lithium sulfide. However, the existing production methods of lithium sulfide are relatively expensive, mainly including carbon thermal reduction of lithium sulfate, reaction of lithium-containing compounds with sulfur, and reaction of metallic lithium with sulfur-containing compounds. However, the reaction temperature required for carbon thermal reduction of lithium sulfate is relatively high and the waste discharge is too large, which greatly increases the production cost. When reacting lithium-containing compounds with sulfur, the lithium-containing compounds used need to be air-sensitive compounds, which are relatively expensive. In addition, the price of metallic lithium is also relatively expensive. Therefore, it is urgent to provide a solution to improve the above problems. 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 can greatly reduce the production cost of lithium sulfide, which is conducive to promoting the popularization and application of lithium-sulfur batteries.

[0005] The invention provides a method for preparing lithium sulfide, which comprises the steps of stirring lithium citrate and barium sulfide in an alcohol aqueous solution for reaction, separating the solid from 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 barium citrate precipitate and 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, and the reaction is green and environmentally friendly.

[0007] Optionally, the method comprises 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 for reaction 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] Optionally, 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, after the lithium sulfate alcohol solution is concentrated and dried, it is ground and sieved to obtain lithium sulfide powder with a particle size less than or equal to 100 nm.

[0019] Optionally, the reaction formula of the reaction of lithium citrate and barium sulfide is: . BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of a method for preparing lithium sulfide provided by the present invention; Figure 2 This is the XRD characterization diagram of lithium sulfide prepared in Example 1 of the present invention; Figure 3 This is a sintering appearance diagram of the lithium sulfide prepared in Example 1 of the present invention when it is made into a lithium-sulfur active material; 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; Figure 5 This 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

[0021] 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 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 general skills in the field to which the present invention belongs.

[0022] The present invention provides a method for preparing lithium sulfide, comprising: stirring lithium citrate and barium sulfide in an alcohol aqueous 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.

[0023] In fact, when lithium citrate and barium sulfide react in an alcohol-water solution, lithium citrate and barium sulfide are first dissolved in the water part of the alcohol-water solution. After the reaction, lithium sulfide enters the alcohol part of the alcohol-water solution, while unreacted lithium citrate, barium sulfide and barium citrate remain in the water part, thereby obtaining a lithium sulfide alcohol solution. By separating and purifying the lithium sulfide alcohol solution, it is possible to avoid the deterioration of lithium sulfide and water oxygen to produce hydrogen sulfide gas.

[0024] At the same time, when the reaction generates barium citrate and precipitates, the barium citrate combines with water to form a hydrated precipitate, which can remove the water part in the alcohol aqueous solution, which is conducive to the dissolution of the generated lithium sulfide in the alcohol part. In fact, since lithium sulfide is soluble in both water and alcohol, while lithium citrate and barium sulfide are soluble in water but not in alcohol, and lithium sulfide is easily hydrolyzed in water, but at room temperature, when lithium citrate is dissolved in water, it is alkaline, which can inhibit the hydrolysis of lithium sulfide, so lithium sulfide can remain stable in the alcohol aqueous solution in the form of ions.

[0025] Specifically, see Figure 1 The method for preparing lithium sulfide provided by the present invention comprises the following steps: S1, stirring and dissolving lithium citrate in an alcohol aqueous solution to prepare a lithium citrate solution; S2, adding lithium sulfide into the lithium citrate solution and stirring to react to obtain a reaction system; S3, performing solid-liquid separation on the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate; S4. Concentrating and drying the lithium sulfide alcohol solution to obtain lithium sulfide.

[0026] In some embodiments, when lithium citrate is made into lithium citrate solution in step S1, the alcohol in the alcohol aqueous solution includes methanol or ethanol, and the volume ratio of alcohol to water in the alcohol aqueous solution is (23-39): 1. This is conducive to the dissolution of lithium sulfide in alcohol after the reaction, and increases the solubility of lithium sulfide.

[0027] 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 aqueous solution is 1.6 g / mL-1.8 g / mL. In addition, the concentration of lithium citrate in the alcohol aqueous solution is 0.04 g / mL-0.07 g / mL.

[0028] In some embodiments, lithium citrate is stirred and dissolved in an alcohol aqueous solution at 50° C.-80° C. to obtain a lithium citrate solution. In other embodiments, lithium citrate can be added to an alcohol aqueous solution and then stirred and dissolved at 50° C.-80° C. to obtain a lithium citrate solution. In practice, lithium citrate is stirred in an alcohol aqueous solution for 10 min-30 min to obtain a lithium citrate solution.

[0029] 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. At the same time, 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.

[0030] Specifically, the reaction formula of the reaction between lithium citrate and barium sulfide is: .

[0031] Example 1 This embodiment 1 provides a method for preparing lithium sulfide, comprising the following steps: S1. Add 210 g of lithium citrate into 3000 mL of alcohol aqueous solution (volume ratio of ethanol to water: 2640 mL: 360 mL), stir in a 60°C water bath for 20 min until completely dissolved to obtain a lithium citrate solution; S2. Within 30 minutes, 253.9 g of barium sulfide powder was uniformly added into a lithium citrate solution which was stirred in a 60° C. water bath environment to prepare a reaction system; S3, filtering the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate; 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 129.4 g of lithium sulfide powder, with a calculated yield of 93.7%.

[0032] Example 2 This embodiment 2 provides a method for preparing lithium sulfide, comprising the following steps: S1. Add 210 g of lithium citrate into 4000 mL of alcohol aqueous solution (volume ratio of ethanol to water: 3640 mL: 360 mL), stir in a 65°C water bath for 20 min until completely dissolved to obtain a lithium citrate solution; S2. Within 45 minutes, 256 g of barium sulfide powder was uniformly added into a lithium citrate solution which was stirred in a water bath at 65° C. to prepare a reaction system; S3, filtering the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate; 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 131 g of lithium sulfide powder, with a calculated yield of 94.9%.

[0033] Example 3 This embodiment 3 provides a method for preparing lithium sulfide, comprising the following steps: S1. Add 210 g of lithium citrate into 5000 mL of alcohol aqueous solution (volume ratio of ethanol to water: 4640 mL: 360 mL), stir in a 70°C water bath for 20 min until completely dissolved to obtain a lithium citrate solution; S2. Within 60 minutes, 258 g of barium sulfide powder was uniformly added into a lithium citrate solution which was stirred in a 70° C. water bath environment to prepare a reaction system; S3, filtering the reaction system to obtain a lithium sulfide alcohol solution and a mixed precipitate; 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%.

[0034] Verification The lithium sulfide prepared in Example 1 was characterized by XRD and compared with a lithium sulfide standard card. Figure 2 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 in FIG. 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 indicates that the lithium sulfide prepared by the present invention can be used for the preparation of high-performance LPSC.

[0035] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A method for preparing lithium sulfide, characterized in that: include: Lithium citrate and barium sulfide are stirred and reacted in an alcohol-water solution, and then the solid-liquid is separated to obtain a lithium sulfide alcohol solution, which is then concentrated by rotary evaporation to obtain lithium sulfide.

2. The preparation method according to claim 1, characterized in that: The following steps are involved: The lithium citrate is stirred and dissolved in an alcohol aqueous solution to obtain a lithium citrate solution; lithium sulfide is added into 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.

3. The preparation method according to claim 2, 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.

4. The preparation method according to claim 2, characterized in that: The alcohol in the alcohol aqueous solution includes methanol or ethanol; and / or the volume ratio of alcohol to water in the alcohol aqueous solution is (23-39):1; and / or the concentration of lithium citrate in the alcohol aqueous solution is 0.04g / mL-0.07g / mL.

5. The preparation method according to claim 2, 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 a lithium citrate solution; and / or, lithium citrate is stirred in an alcohol aqueous solution for 10min-30min to prepare a lithium citrate solution.

6. The preparation method according to claim 2, characterized in that: Barium sulfide is gradually added into the lithium citrate solution at a rate of 4 g / min-9 g / min and stirred for reaction.

7. The preparation method according to claim 2, characterized in that: The lithium sulfate alcohol solution is concentrated and dried under a protective atmosphere; and / or, after the lithium sulfate alcohol solution is concentrated and dried, it is ground and sieved to obtain lithium sulfide powder with a particle size less than or equal to 100 nm.

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

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