A method for preparing lithium sulfide

Abstract

This invention belongs to the field of compound preparation technology, specifically relating to a method for preparing lithium sulfide, comprising at least the following steps: First, in a first organic solvent, lithium fluoride and a chlorosilane compound are stirred and mixed, hydrogen sulfide gas is introduced, and the mixture is stirred and heated to react and obtain lithium sulfide, chlorosilane compound gas, and hydrogen chloride gas; Second, the mixture is filtered, the filter residue is washed with a second organic solvent, and dried under reduced pressure to obtain the finished product. Compared with existing technologies, the raw materials used in this invention are readily available and inexpensive, the production process is simple, there are no hazardous unit operations involving high temperature and high pressure, the product is easy to separate and purify, and the purified product has high purity. Moreover, this invention can produce lithium sulfide on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of compound preparation technology, and specifically relates to a method for preparing lithium sulfide. Background Technology

[0002] Compared to traditional liquid lithium-ion batteries, all-solid-state lithium metal batteries are the most promising alternatives to existing high-energy-density lithium-ion batteries. Their energy density is expected to be 2 to 5 times that of existing lithium-ion batteries, with longer cycle life and service life, higher rate performance, and greater safety. Lithium sulfide, as the most important basic raw material for new high-energy, high-safety solid-state lithium-ion batteries, is receiving increasing attention and importance for its production process development, optimization, and commercial application.

[0003] Currently, methods for synthesizing lithium sulfide can be broadly categorized into ball milling, solvent synthesis, and direct carbon composite methods.

[0004] Among them, the ball milling method involves mechanically ball milling a mixture of elemental sulfur and metallic lithium / lithium hydride in an inert atmosphere to obtain lithium sulfide. The ball milling method suffers from high raw material costs, long reaction times, low conversion rates, and the presence of impurities such as lithium polysulfides in the resulting product, making purification difficult and hindering the selection of suitable equipment for industrial-scale production.

[0005] The solvent method involves reacting lithium / lithium compounds and sulfur / sulfur compounds in a solvent medium to prepare lithium sulfide. Organic solvents or liquid ammonia are used as solvents; organic solvents include ethanol, hexane, toluene, diethyl ether, tetrahydrofuran, etc. This method also suffers from the problem of using metallic lithium, resulting in higher costs.

[0006] The direct carbon-recombination method involves reducing lithium sulfate and a carbon source at high temperature to obtain lithium sulfide, which is then further purified to obtain battery-grade lithium sulfide. This method is incomplete, yielding numerous byproducts and resulting in high impurity content.

[0007] As can be seen from the above, the various methods for preparing lithium sulfide in the existing technology have technical problems such as high separation difficulty, poor product quality, and high cost.

[0008] In view of this, the present invention aims to provide a method for preparing lithium sulfide, which can prepare lithium sulfide on a large scale, and the process is simple, low in cost and high in purity. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing lithium sulfide that addresses the shortcomings of existing technologies. This method can produce lithium sulfide on a large scale and is simple, low-cost, and produces high purity.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for preparing lithium sulfide includes at least the following steps:

[0012] The first step involves mixing lithium fluoride and a chlorosilane compound in a first organic solvent, introducing hydrogen sulfide gas, stirring, and heating to produce lithium sulfide, chlorosilane compound gas, and hydrogen chloride gas.

[0013] The second step is filtration. The filter residue is washed with a second organic solvent and dried under reduced pressure to obtain the finished product.

[0014] As an improvement to the method for preparing lithium sulfide of the present invention, the first organic solvent mentioned in the first step is at least one selected from acetonitrile, acetone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, butyl acetate, diethyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, dichloromethane, dichloroethane, toluene, ethylbenzene, and chlorobenzene.

[0015] As an improvement to the preparation method of lithium sulfide of the present invention, the chlorosilane compound mentioned in the first step is at least one of silicon tetrachloride, trimethylchlorosilane, triethylchlorosilane, tripropylchlorosilane, tributylchlorosilane, dimethyldichlorosilane, diethyldichlorosilane, dipropyldichlorosilane, methyltrichlorosilane, ethyltrichlorosilane, and propyltrichlorosilane.

[0016] As an improvement to the preparation method of lithium sulfide of the present invention, the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:0.4:0.5 to 2:3:2.

[0017] As an improvement to the preparation method of lithium sulfide of the present invention, the reaction temperature of the first step is 25-80°C.

[0018] As an improvement to the method for preparing lithium sulfide of the present invention, the second organic solvent mentioned in the second step is at least one selected from acetonitrile, acetone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, butyl acetate, diethyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, dichloromethane, dichloroethane, toluene, ethylbenzene, and chlorobenzene.

[0019] As an improvement to the preparation method of lithium sulfide of the present invention, the fluorosilicone compound gas and hydrogen chloride gas obtained in the first step are adsorbed with alkaline solution.

[0020] As an improvement to the preparation method of lithium sulfide of the present invention, the alkaline solution is at least one of potassium hydroxide, sodium hydroxide and calcium hydroxide, and the fluorosilicone compound and hydrogen chloride gas obtained by the reaction are adsorbed by the alkaline solution to obtain fluoride, chloride and silicon-based compound.

[0021] Compared to existing technologies, the raw materials used in this invention are readily available and inexpensive, the production process is simple, there are no hazardous unit operations involving high temperature and high pressure, the product is easy to separate and purify, and the purified product has high purity. Moreover, this invention can produce lithium sulfide on a large scale. Detailed Implementation

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below.

[0024] Example 1

[0025] This embodiment provides a method for preparing lithium sulfide, the principle of which is as follows:

[0026] 2H2S+4LiF+SiCl4→2Li2S+SiF4+4HCl

[0027] First, add 1000 mL of dimethyl carbonate, 104 g (4 mol) of lithium fluoride and 170 g (1 mol) of silicon tetrachloride to a 2000 mL reaction flask, stir at 60 °C, and introduce 68 g (2 mol) of hydrogen sulfide. The generated gas is adsorbed by sodium hydroxide solution to obtain sodium fluoride, sodium chloride and sodium silicate; stir the reaction for 12 hours.

[0028] The second step was vacuum filtration. The filter residue was washed with dimethyl carbonate and then dried under reduced pressure at 80°C for 10 hours to obtain 82.8g of white solid lithium sulfide, with a yield of 90%.

[0029] The lithium sulfide prepared in this embodiment has a purity of 99.9%, Cl < 5 ppm, and SO4 content of 100%. 2- <5ppm, Na<5ppm, K<3ppm, Mg<3ppm, Ca<3ppm, Fe<10ppm, Hg ND, Cr<1ppm.

[0030] Example 2

[0031] This embodiment provides a method for preparing lithium sulfide, the principle of which is as follows:

[0032] H2S+2LiF+2(CH3)3SiCl→Li2S+2(CH3)3SiF+2HCl

[0033] It includes the following steps:

[0034] 1000 mL of ethyl acetate, 104 g (4 mol) of lithium fluoride, and 436 g (4 mol) of trimethylchlorosilane were added to a 2000 mL reaction flask. The mixture was stirred at 80 °C, and 68 g (2 mol) of hydrogen sulfide was introduced. The generated gas was adsorbed using calcium hydroxide solution. The reaction was stirred for 12 hours, filtered under reduced pressure, and the residue was washed with ethyl acetate and dried under reduced pressure at 80 °C for 10 hours to obtain 84.6 g of white solid, with a yield of 92%.

[0035] The gas was adsorbed with calcium hydroxide solution, and after centrifugation and filtration, calcium fluoride solid and liquid phase were obtained. After separation of the liquid phase, hexamethyldisiloxane (purity 99.5%) and calcium chloride aqueous solution were obtained.

[0036] The lithium sulfide prepared in this embodiment has a purity of 99.9%, Cl < 5 ppm, and SO4 content of 100%. 2- <5ppm, Na<5ppm, K<3ppm, Mg<3ppm, Ca<3ppm, Fe<10ppm, Hg ND, Cr<1ppm.

[0037] Example 3

[0038] The difference from Example 2 is:

[0039] The organic solvent in the first step is diethyl carbonate; the chlorosilane compound is triethylchlorosilane, and the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:2:1.2.

[0040] The reaction temperature in the first step is 70℃. The organic solvent in the second step is diethyl carbonate.

[0041] The alkali solution used in the first step is potassium hydroxide.

[0042] The rest is the same as in Example 2, and will not be repeated here.

[0043] Example 4

[0044] The difference from Example 2 is:

[0045] The organic solvent in the first step is ethyl methyl carbonate; the chlorosilane compound is tripropylchlorosilane, and the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:2:1.1.

[0046] The reaction temperature in the first step is 75℃. The organic solvent in the second step is ethyl methyl carbonate.

[0047] The alkali solution used in the first step is potassium hydroxide.

[0048] The rest is the same as in Example 2, and will not be repeated here.

[0049] Example 5

[0050] The difference from Example 2 is:

[0051] The organic solvent in the first step is ethylene carbonate; the chlorosilane compound is tributylchlorosilane, and the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:2.1:1.05.

[0052] The reaction temperature in the first step is 65℃. The organic solvent in the second step is ethyl methyl carbonate.

[0053] The alkali solution used in the first step is potassium hydroxide.

[0054] The rest is the same as in Example 2, and will not be repeated here.

[0055] Example 6

[0056] The difference from Example 2 is:

[0057] The organic solvent in the first step is acetonitrile; the chlorosilane compound is dimethyldichlorosilane, and the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:1:1.05.

[0058] The reaction temperature in the first step is 55℃. The organic solvent in the second step is acetone.

[0059] The rest is the same as in Example 2, and will not be repeated here.

[0060] Example 7

[0061] The difference from Example 2 is:

[0062] The organic solvent in the first step is ethylene glycol dimethyl ether; the chlorosilane compound is dipropyl dichlorosilane, and the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:1.1:1.1.

[0063] The reaction temperature in the first step is 50°C. The organic solvent in the second step is toluene.

[0064] The rest is the same as in Example 2, and will not be repeated here.

[0065] Example 8

[0066] The difference from Example 2 is:

[0067] The organic solvent in the first step is propyl acetate; the chlorosilane compound is methyltrichlorosilane, and the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:0.7:1.1.

[0068] The reaction temperature in the first step is 52℃. The organic solvent in the second step is butyl acetate.

[0069] The rest is the same as in Example 2, and will not be repeated here.

[0070] Example 9

[0071] The difference from Example 2 is:

[0072] The organic solvent in the first step is methyl tert-butyl ether; the chlorosilane compound is propyltrichlorosilane, and the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:0.72:1.2.

[0073] The reaction temperature in the first step is 45℃. The organic solvent in the second step is butyl acetate.

[0074] The rest is the same as in Example 2, and will not be repeated here.

[0075] Example 10

[0076] The difference from Example 2 is:

[0077] The organic solvent in the first step is acetone; the chlorosilane compound is ethyltrichlorosilane, and the stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide in the first step is 2:0.75:1.01.

[0078] The reaction temperature in the first step is 62℃. The organic solvent in the second step is acetone.

[0079] The alkaline solution used in the first step is sodium hydroxide.

[0080] The rest is the same as in Example 2, and will not be repeated here.

[0081] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for preparing lithium sulfide, characterized in that, It should include at least the following steps: The first step involves mixing lithium fluoride and a chlorosilane compound in a first organic solvent, introducing hydrogen sulfide gas, stirring, and heating to produce lithium sulfide, chlorosilane compound gas, and hydrogen chloride gas. The second step is filtration. The filter residue is washed with a second organic solvent and dried under reduced pressure to obtain the finished product. The first organic solvent mentioned in the first step is at least one selected from acetonitrile, acetone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, butyl acetate, diethyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, dichloromethane, dichloroethane, toluene, ethylbenzene, and chlorobenzene; The stoichiometric molar ratio of lithium fluoride, chlorosilane compound and hydrogen sulfide mentioned in the first step is 2:0.4:0.5 to 2:3:2; The reaction temperature for the first step is 25–80°C; The second organic solvent mentioned in the second step is at least one selected from acetonitrile, acetone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, ethyl acetate, propyl acetate, butyl acetate, diethyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, dichloromethane, dichloroethane, toluene, ethylbenzene, and chlorobenzene.

2. The method for preparing lithium sulfide according to claim 1, characterized in that: The chlorosilane compound mentioned in the first step is at least one of silicon tetrachloride, trimethylchlorosilane, triethylchlorosilane, tripropylchlorosilane, tributylchlorosilane, dimethyldichlorosilane, diethyldichlorosilane, dipropyldichlorosilane, methyltrichlorosilane, ethyltrichlorosilane, and propyltrichlorosilane.

3. The method for preparing lithium sulfide according to claim 1, characterized in that: The fluorosilicone compound gas and hydrogen chloride gas obtained in the first step are adsorbed with an alkaline solution.

4. The method for preparing lithium sulfide according to claim 3, characterized in that: The alkaline solution is at least one of potassium hydroxide, sodium hydroxide, and calcium hydroxide. The fluorine-silicon compound and hydrogen chloride gas obtained from the reaction are adsorbed by the alkaline solution to obtain fluorides, chlorides, and silicon-based compounds.