Ev grade lithium sulfide and method of preparing the sane

Abstract

To provide a novel method of preparing EV grade lithium sulfide, and EV grade lithium sulfide.SOLUTION: The method of preparing EV grade lithium sulfide according to the present invention comprises the steps of: mixing and reacting sulfur powder, metallic lithium, and a lithium-containing additive to obtain a crude product of lithium sulfide; crushing / calcining the crude lithium product; and removing residual sulfur powder therefrom to obtain EV grade lithium sulfide. The lithium-containing additive is at least one of lithium hydride, lithium nitride, and lithium carbide, and the mole ratio of the sulfur powder, the metallic lithium, and the lithium-containing additive is 1:2:0.1 to 0.3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to EV grade lithium sulfide and its preparation method, which belongs to the technical field of lithium ion battery materials. [Background technology]

[0002] Lithium-ion batteries, as an important renewable energy storage device, are crucial for the reliable operation of EV vehicles and energy storage systems. All-solid-state lithium-ion batteries are widely used in fields such as EV vehicles, energy storage systems, and mobile devices due to their advantages such as high safety, high energy density, long cycle life, excellent anti-polarization ability and environmental friendliness. All-solid-state lithium-ion batteries are safer because they use solid electrolytes instead of traditional liquid electrolytes. As the lithium source material for solid electrolytes, lithium sulfide has a significant impact on the performance of lithium-ion batteries. However, the conventional synthesis methods for lithium sulfide have problems such as high impurity content, low whiteness of the product, and high cost, which greatly restrict the development of all-solid-state lithium-ion batteries.

[0003] Conventional methods for preparing high-purity lithium sulfide mainly include the following methods. (1) In Patent Document 1, lithium sulfide is prepared by a high-temperature carbon reduction method. The lithium sulfide product obtained by this preparation method is gray and has low whiteness. (2) In Patent Documents 2 and 3, lithium sulfide is prepared by the reaction of a lithium source with hydrogen sulfide. This preparation method requires the use of highly toxic hydrogen sulfide gas, so the requirements for process safety are relatively strict. (3) In Patent Document 4, lithium sulfide is prepared by mixing a lithium source with a sulfur source and adding hydrazine hydrate. The whiteness of the product is high, but the purity is low at 95%. (4) In Patent Document 5, lithium sulfide is prepared by the reaction of battery-grade metallic lithium with sulfur powder, but the requirements for the purity of the raw materials are strict because it is necessary to use battery-grade metallic lithium. (5) Patent Document 6 discloses a green method for preparing lithium sulfide, which comprises homogeneously mixing lithium-containing material and sulfur elemental substance under an inert atmosphere, transferring the mixture to a reactor, evacuating the reactor with a vacuum pump, introducing a certain amount of hydrogen, heating the mixture to a set temperature at a certain rate, and then keeping the mixture warm for a certain period of time. When the temperature of the reactor drops, the gas in the reactor is collected and evacuated, and the reactor is opened under an inert atmosphere to obtain lithium sulfide powder. The lithium-containing material is either lithium amide, lithium imide, or lithium nitride, or a mixture thereof. However, Patent Document 6 requires the use of flammable gas H2, and the reaction is an exothermic reaction, so that the requirements for the experimental equipment are strict and there is a high safety risk. (6) Patent Document 7 discloses a method for preparing lithium sulfide, which comprises reacting inexpensive nitrogen with metallic lithium in the presence of an inert atmosphere or under vacuum to prepare lithium nitride, setting the remaining amount of metallic lithium in the lithium nitride within a preset safety threshold range, and mixing and reacting the prepared lithium nitride with sulfur elemental substance at a certain ratio to obtain lithium sulfide. However, the preparation process of this method has strict requirements on raw material parameters, and the reaction process is difficult to control, making it difficult to mass-produce. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] China Patent Application Publication No. 112678780 [Patent Document 2] China Patent Application Publication No. 113415812 [Patent Document 3] Patent No. I366554 [Patent Document 4] China Patent Application Publication No. 112678781 [Patent Document 5] China Patent Publication No. 116040587 [Patent Document 6] China Patent Application Publication No. 112520703 [Patent Document 7] China Patent Application Publication No. 116216652 Summary of the Invention [Problem to be solved by the invention]

[0005] The first object of the present invention is to provide a new method for preparing EV grade lithium sulfide. The second object of the present invention is to provide a new EV grade lithium sulfide. [Means for solving the problem]

[0006] In order to achieve the first object of the present invention, the above-mentioned method for preparing EV grade lithium sulfide includes: The process involves mixing and reacting sulfur powder, metallic lithium, and lithium-containing additives to obtain a crude lithium sulfide product, which is then crushed and fired to remove residual sulfur powder, and then EV-grade lithium sulfide is obtained. The present invention has low requirements for raw materials, and the raw material lithium metal may be industrial grade lithium metal with a purity of 99% or more. In one embodiment, the molar ratio of the sulfur powder, metallic lithium, and the lithium-containing additive is 1:2:0.1-0.3. In one embodiment, the sulfur powder has a particle size range of 70 microns to 80 microns and the lithium-containing additive has a particle size range of 80 microns to 90 microns. In one embodiment, the reaction temperature is from 100°C to 180°C. In one embodiment, the lithium-containing additive is at least one of lithium hydride, lithium nitride, and lithium carbide. In one embodiment, the reaction also includes stirring, the stirring time is 4 to 8 hours, and the stirring speed is 20 to 40 rpm, and preferably, the reaction temperature is 140°C, the stirring time is 6 hours, and the stirring speed is 20 rpm. In one embodiment, the method further comprises the steps of sieving the lithium sulfide crude product, grinding the lithium sulfide crude product having a particle size of less than 20 mesh after the sieving, and returning the lithium sulfide crude product having a particle size of 20 mesh or greater to the reaction as a feedstock. In one embodiment, the pulverization is performed at a rotation speed of 20,000 to 25,000 rpm for a pulverization time of 1 to 3 minutes. In one embodiment, the particle size range of the lithium sulfide crude product before the calcination is 20 microns to 50 microns. In one embodiment, the firing is carried out at 400 to 600° C. for 3 to 5 hours, and preferably, the firing temperature is 600° C. and the firing time is 4 hours. In one embodiment, the method further includes wet ball milling, i.e., the method includes a step of wet ball milling the calcined lithium sulfide crude product, wherein the solvent for the wet ball milling is at least one of isopropyl alcohol and normal propyl alcohol, and the ball milling parameters are a ball milling rotation speed of 300 to 500 rpm, a ball milling time of 8 to 12 hours, and a mass ratio of the ball milling balls to the lithium sulfide crude product to the solvent of 4 to 1:1:1 to 0.1. In one embodiment, the wet ball milling is performed with the solvent being isopropyl alcohol, the ball milling speed being 400 rpm, and the ball milling time being 8 hours. In one embodiment, the mass ratio of the ball milling balls to the lithium sulfide crude product to the solvent is 1:1:0.8. In one embodiment, the method further includes washing and drying, i.e., washing the ball-milled lithium sulfide with at least one of n-hexane, n-pentane, and cyclohexane, and stirring, heating, and drying to obtain high-purity EV grade lithium sulfide. Preferably, the washing is performed by stirring and washing with n-hexane 2 to 3 times. In one embodiment, the reaction and the washing and drying are carried out under a protective atmosphere, which is preferably at least one of nitrogen, argon, and helium. In one embodiment, the drying temperature is 80 to 100° C., the stirring speed is 30 to 60 rpm, and the drying time is 4 to 8 hours. In one embodiment, the reaction is carried out in a titanium apparatus and the drying is carried out in a titanium TA2 apparatus.

[0007] In order to achieve the second object of the present invention, the EV grade lithium sulfide is prepared by the above-mentioned method for preparing EV grade lithium sulfide, and the purity of the EV grade lithium sulfide is 99.9% or more, and the whiteness is 80 or more, and preferably the purity of the EV grade lithium sulfide is 99.95% or more, the whiteness is 80 or more, and the D50 particle size is 15 microns or less. Effect of the Invention

[0008] Compared with the prior art, the present invention has the following beneficial effects: The product according to the present invention can reach a whiteness of 80 or more. In the reaction of metallic lithium and sulfur powder to prepare lithium sulfide, a certain proportion of additives is added. The presence of a certain proportion of lithium-containing additives greatly improves the phenomenon of insufficient reaction due to agglomeration in the reaction of metallic lithium, and the purity of the product exceeds 99.9%. In addition, the addition of additives causes the solidified lithium sulfide crude product to form a loose skeletal structure, making the product easier to grind, reducing the risk of violent reaction again in the grinding process, and eliminating the need for a vacuum environment during the preparation process.

[0009] The preparation of lithium sulfide by this method has the advantages of simple process, high operational feasibility, large-scale production, no toxic gas or secondary pollution, safe handling and meeting the requirements for EV-grade lithium sulfide. The present invention also allows the preparation of high purity lithium sulfide at low cost using industrial grade lithium. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of a process flow of the present invention. [Diagram 2] FIG. 2 is an XRD diagram of Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In order to achieve the first object of the present invention, the above-mentioned method for preparing EV grade lithium sulfide comprises the steps of mixing and reacting sulfur powder, metallic lithium and a lithium-containing additive to obtain a crude lithium sulfide product, which is then pulverized and calcined to remove residual sulfur powder, and then obtaining EV grade lithium sulfide.

[0012] The present invention has low requirements for raw materials, and the raw material lithium metal may be industrial grade lithium metal with a purity of 99% or more. EV grade lithium sulfide is battery grade lithium sulfide.

[0013] As shown in Figure 1, in one embodiment, after reaction, the lithium sulfide crude product can be sieved according to particle size, i.e., the larger and harder ones are returned to the reaction process, and the smaller lithium sulfide particle size is crushed. The sieving tool is a 20 mesh screen (830 microns).

[0014] The reaction of the present invention can be carried out in a dry room and does not have strict environmental requirements, but the gas in the reaction apparatus must be an inert gas atmosphere. The inert gas is a gas that does not react with the raw materials of the present invention.

[0015] In one embodiment, the molar ratio of the sulfur powder, metallic lithium, and the lithium-containing additive is 1:2:0.1-0.3. In one embodiment, the sulfur powder has a particle size range of 70 microns to 80 microns and the lithium-containing additive has a particle size range of 80 microns to 90 microns.

[0016] In one embodiment, the baking temperature of the reaction is 100°C to 180°C. In one embodiment, the lithium-containing additive is at least one of lithium hydride, lithium nitride, and lithium carbide.

[0017] In one embodiment, the reaction also includes stirring, the stirring time is 4 to 8 hours, and the stirring speed is 20 to 40 rpm, and preferably, the reaction temperature is 140° C., the stirring time is 6 hours, and the stirring speed is 20 rpm.

[0018] In one embodiment, the method further comprises the steps of sieving the lithium sulfide crude product, grinding the lithium sulfide crude product having a particle size of less than 20 mesh after the sieving, and returning the lithium sulfide crude product having a particle size of 20 mesh or greater to the reaction as a feedstock.

[0019] In one embodiment, the pulverization is performed at a rotation speed of 20,000 to 25,000 rpm for a pulverization time of 1 to 3 minutes. In one embodiment, the particle size range of the lithium sulfide crude product before calcination is 20 microns to 50 microns. In one embodiment, the firing is carried out at 400 to 600° C. for 3 to 5 hours, and preferably, the firing temperature is 600° C. and the firing time is 4 hours. In one embodiment, the method further includes wet ball milling, i.e., the method includes a step of wet ball milling the calcined lithium sulfide crude product, the solvent of the wet ball milling is at least one of isopropyl alcohol and normal propyl alcohol, and the ball milling parameters are a ball milling rotation speed of 300 to 500 rpm, a ball milling time of 8 to 12 hours, and a mass ratio of the ball milling balls to the lithium sulfide crude product to the solvent of 4 to 1:1:1 to 0.1. In one embodiment, the wet ball milling is performed using isopropyl alcohol as a solvent, at a ball milling speed of 400 rpm, and for a ball milling time of 8 hours. In one embodiment, the mass ratio of the ball milling balls to the lithium sulfide crude product and the solvent is 1:1:0.8.

[0020] In one embodiment, the method further includes washing and drying, i.e., washing the ball-milled lithium sulfide with at least one of n-hexane, n-pentane, and cyclohexane, and stirring, heating, and drying to obtain high-purity EV grade lithium sulfide. Preferably, the washing is performed by stirring and washing with n-hexane 2 to 3 times.

[0021] In one embodiment, the reaction and the washing and drying are carried out under a protective atmosphere, preferably at least one of nitrogen, argon, and helium.

[0022] In one embodiment, the drying temperature is 80 to 100° C., the stirring speed is 30 to 60 rpm, and the drying time is 4 to 8 hours.

[0023] In one embodiment, the reaction is carried out in a titanium apparatus and the drying is carried out in a titanium TA2 apparatus.

[0024] A second object of the present invention is to provide a new EV grade lithium sulfide.

[0025] In order to achieve the second object of the present invention, the EV grade lithium sulfide is prepared by the above-mentioned method for preparing EV grade lithium sulfide, and the purity of the EV grade lithium sulfide is 99.9% or more, and the whiteness is 80 or more, and preferably the purity of the EV grade lithium sulfide is 99.95% or more, the whiteness is 80 or more, and the D50 particle size is 15 microns or less. EXAMPLES

[0026] Hereinafter, specific embodiments of the present invention will be further described in conjunction with examples, but the present invention is not limited to the scope of the described examples.

[0027] Example 1 (1) A 300 micron thick industrial grade metallic lithium sheet, sulfur powder with a particle size range of 70 microns to 75 microns, and lithium hydride with a particle size range of 80 microns to 85 microns were weighed out so that the molar ratio of Li:S:LiH was 1:2:0.2, and the raw materials for the reaction were stirred and reacted under a nitrogen atmosphere to obtain a crude lithium sulfide product. The stirring time was 6 hours, the reaction temperature was 140°C, and the stirring speed was 20 rpm. The reaction formula is as follows. 2Li+S=Li2S 2LiH+S=Li2S+H2↑

[0028] (2) After the reaction, the lithium sulfide crude product was sieved, and the lithium sulfide crude product having a particle size of 20 mesh or more was used as the raw material for the next reaction, and the lithium sulfide crude product having a particle size of less than 20 mesh was pulverized. The pulverization time was 2 minutes, and the rotation speed of the pulverizer was 25,000 rpm. After pulverization, the lithium sulfide crude product having a particle size range of 20 microns to 40 microns was calcined at a high temperature in order to remove the residual sulfur powder. The calcination temperature was 600°C, and the calcination time was 5 hours.

[0029] (3) The calcined lithium sulfide crude product was subjected to wet ball milling. The solvent was isopropyl alcohol, and the ball milling parameters were a ball milling speed of 400 rpm, a ball milling time of 8 h, and a ratio of the grinding balls, the lithium sulfide crude product, and the solvent of 1:1:0.8.

[0030] (4) The wet ball milled lithium sulfide was washed with n-hexane, and then stirred, heated and dried under inert gas protection with protective gas flow at a rotation speed of 30 rpm. The stirring was carried out for 30 minutes, the heating and drying temperature was 100°C, and the drying time was 6 hours. This resulted in a lithium sulfide product. This product was numbered YP-1. The composition parameters of the obtained product are shown in Table 1. The purity of the obtained product was 99.97%, and its XRD diffraction pattern is shown in Figure 2.

[0031] Example 2 (1) Industrial grade metallic lithium with a thickness of 300 microns, sulfur powder with a particle size range of 70 microns to 75 microns, and lithium nitride with a particle size range of 80 microns to 85 microns were weighed out so that the molar ratio of Li:S:Li3N was 1:2:0.2, and the raw materials for the reaction were stirred and reacted under a nitrogen atmosphere to obtain a crude lithium sulfide product. The stirring time was 6 hours, the reaction temperature was 140°C, and the stirring speed was 20 rpm. The reaction formula is as follows. 2Li+S=Li2S 2Li3N+3S=3Li2S+N2↑

[0032] (2) After the reaction, the lithium sulfide crude product was sieved, and the lithium sulfide crude product having a particle size of 20 mesh or more was used as the raw material for the next reaction, and the lithium sulfide crude product having a particle size of less than 20 mesh was pulverized. The pulverization time was 2 minutes, and the rotation speed of the pulverizer was 25,000 rpm. After pulverization, the lithium sulfide crude product having a particle size range of 20 microns to 40 microns was calcined at a high temperature in order to remove the residual sulfur powder. The calcination temperature was 600°C, and the calcination time was 5 hours.

[0033] (3) The calcined lithium sulfide crude product was subjected to wet ball milling. The solvent was isopropyl alcohol, the ball milling parameters were ball milling speed 400 rpm, wet ball milling time 8 h, and the ratio of the grinding balls to the lithium sulfide crude product and the solvent was 1:1:0.8.

[0034] (4) The wet ball milled lithium sulfide was washed with n-hexane, and then stirred, heated and dried under inert gas protection with protective gas flow at a rotation speed of 30 rpm. The stirring was carried out for 30 minutes, the heating and drying temperature was 100°C, and the drying time was 6 hours. This resulted in a lithium sulfide product. This product was numbered YP-2. The composition parameters of the obtained product are shown in Table 1. The purity of the obtained product is 99.98%.

[0035] Example 3 (1) Industrial grade metallic lithium with a thickness of 300 microns, sulfur powder with a particle size range of 70 microns to 75 microns, and lithium carbide with a particle size range of 80 microns to 85 microns were weighed out so that the molar ratio of Li:S:Li2C2 was 1:2:0.2, and the raw materials for the reaction were stirred and reacted under a nitrogen atmosphere to obtain a crude lithium sulfide product. The stirring time was 6 hours, the reaction temperature was 140°C, and the stirring speed was 20 rpm. The reaction formula is as follows. 2Li+S=Li2S Li2C2+5S=Li2S+2CS2(g)

[0036] (2) After the reaction, the lithium sulfide crude product was sieved, and the lithium sulfide crude product having a particle size of 20 mesh or more was used as the raw material for the next reaction, and the lithium sulfide crude product having a particle size of less than 20 mesh was pulverized. The pulverization time was 2 minutes, and the rotation speed of the pulverizer was 25,000 rpm. After pulverization, the lithium sulfide crude product having a particle size range of 20 microns to 40 microns was calcined at a high temperature in order to remove the residual sulfur powder. The calcination temperature was 600°C, and the calcination time was 5 hours.

[0037] (3) The calcined lithium sulfide crude product was subjected to wet ball milling. The solvent was isopropyl alcohol, and the ball milling parameters were a ball milling speed of 400 rpm, a ball milling time of 8 h, and a ratio of the grinding balls, the lithium sulfide crude product, and the solvent of 1:1:0.8.

[0038] (4) The wet ball milled lithium sulfide was washed with n-hexane, and then stirred, heated and dried under inert gas protection with protective gas flow at a rotation speed of 30 rpm. The stirring was carried out for 30 minutes, the heating and drying temperature was 100°C, and the drying time was 6 hours. This resulted in a lithium sulfide product. This product was numbered YP-3. The composition parameters of the obtained product are shown in Table 1. The purity of the obtained product is 99.96%.

[0039] Example 4 (1) Weigh out an industrial grade metallic lithium sheet having a thickness of 300 microns, sulfur powder having a particle size range of 70 microns to 75 microns, and lithium hydride having a particle size range of 80 microns to 85 microns so that the molar ratio of Li:S:LiH=1:2:0.2, and stir and react the raw materials for the reaction under a nitrogen atmosphere to obtain a stirred lithium sulfide crude product. The stirring time was 6 hours, the reaction temperature was 140°C, and the stirring speed was 20 rpm. The reaction formula is as follows. 2Li+S=Li2S 2LiH+S=Li2S+H2↑

[0040] (2) The obtained lithium sulfide crude product was pulverized. The pulverization time was 2 minutes, and the rotation speed of the pulverizer was 25,000 rpm. After pulverization, the lithium sulfide crude product having a particle size range of 20 microns to 40 microns was calcined at a high temperature in order to remove the residual sulfur powder. The calcination temperature was 600°C, and the calcination time was 5 hours.

[0041] (3) The calcined lithium sulfide crude product was subjected to wet ball milling. The solvent was isopropyl alcohol, and the ball milling parameters were a ball milling speed of 400 rpm, a ball milling time of 8 h, and a ratio of the grinding balls, the lithium sulfide crude product, and the solvent of 1:1:0.8.

[0042] (4) The wet ball milled lithium sulfide was washed with n-hexane, and then stirred, heated, and dried under inert gas protection with protective gas flow at a rotation speed of 30 rpm. Stirring was carried out for 30 minutes, and the heating and drying temperature was set to 100°C and the drying time was set to 6 hours. This resulted in the lithium sulfide product. The product number is YP-4. The composition parameters of the obtained product are shown in Table 1. The purity of the obtained product is 99.97%.

[0043] Comparative Example 1 (1) Industrial grade metallic lithium with a thickness of 300 microns and sulfur powder with a particle size range of 70 to 75 microns were weighed so that the molar ratio of Li:S was 1:2, and the raw materials for the reaction were stirred and reacted under a nitrogen atmosphere to obtain a crude lithium sulfide product. The stirring time was 6 hours, the reaction temperature was 140°C, and the stirring speed was 20 rpm. The reaction formula is as follows. 2Li+S=Li2S 2LiH+S=Li2S+H2↑

[0044] (2) After the reaction, the lithium sulfide crude product was sieved, and the lithium sulfide crude product having a particle size of 20 mesh or more was used as the raw material for the next reaction, and the lithium sulfide crude product having a particle size of less than 20 mesh was pulverized. The pulverization time was 2 minutes, and the rotation speed of the pulverizer was 25,000 rpm. After pulverization, the lithium sulfide crude product having a particle size range of 20 microns to 40 microns was calcined at a high temperature in order to remove the residual sulfur powder. The calcination temperature was 600°C, and the calcination time was 5 hours.

[0045] (3) The calcined lithium sulfide crude product was subjected to wet ball milling. The solvent was isopropyl alcohol, and the ball milling parameters were a ball milling speed of 400 rpm, a ball milling time of 8 h, and a ratio of the grinding balls, the lithium sulfide crude product, and the solvent of 1:1:0.8.

[0046] (4) The wet ball milled lithium sulfide was washed with n-hexane, and then stirred, heated and dried at 30 rpm under inert gas protection. The stirring was carried out for 30 min, the heating and drying temperature was 100°C and the drying time was 6 h. The product was numbered DB-1. The composition parameters of the obtained product are shown in Table 1. The purity of the obtained product is 99.73%.

[0047] Comparative Example 2 (1) Industrial grade metallic lithium with a thickness of 300 microns, sulfur powder with a particle size range of 70 microns to 75 microns, and lithium hydride with a particle size range of 80 microns to 85 microns were weighed out so that the molar ratio of Li:S:LiH=1:2:0.2, and the raw materials for the reaction were stirred and reacted under a nitrogen atmosphere to obtain a crude lithium sulfide product. The stirring time was 6 hours, the reaction temperature was 140°C, and the stirring speed was 20 rpm. The reaction formula is as follows. 2Li+S=Li2S 2LiH+S=Li2S+H2↑

[0048] (2) After the reaction, the lithium sulfide crude product was sieved. The lithium sulfide crude product having a particle size of 20 mesh or more was used as the raw material for the next reaction, and the lithium sulfide crude product having a particle size of less than 20 mesh was pulverized. The pulverization time was 2 minutes, and the rotation speed of the pulverizer was 25,000 rpm. After pulverization, the lithium sulfide crude product having a particle size range of 20 microns to 40 microns was calcined at a high temperature in order to remove the residual sulfur powder. The calcination temperature was 600°C, and the calcination time was 5 hours.

[0049] (3) The calcined lithium sulfide crude product was subjected to dry ball milling. The ball milling parameters were: ball milling speed 400 rpm, ball milling time 8 h, and the ratio of grinding balls to lithium sulfide crude product was 1:1.

[0050] (4) The dry ball milled lithium sulfide was washed with n-hexane, and then stirred, heated and dried at a rotation speed of 30 rpm under inert gas protection with protective gas flow to obtain a lithium sulfide product. The stirring was carried out for 30 min, the heating and drying temperature was 100°C, and the drying time was 6 h. The product number was DB-2. The composition parameters of the obtained product are shown in Table 1. The purity of the obtained product is 99.85%.

[0051] Comparative Example 3 (1) Industrial grade metallic lithium with a thickness of 300 microns and sulfur powder with a particle size range of 70 microns to 75 microns were weighed so that the molar ratio of Li:S was 1:2, and the raw materials for the reaction were stirred and reacted under a nitrogen atmosphere to obtain a crude lithium sulfide product. The stirring time was 6 hours, the reaction temperature was 140°C, and the stirring speed was 20 rpm. The reaction formula is as follows. 2Li+S=Li2S

[0052] (2) After the reaction, the lithium sulfide crude product was sieved, and the lithium sulfide crude product having a particle size of 20 mesh or more was used as the raw material for the next reaction, and the lithium sulfide crude product having a particle size of less than 20 mesh was pulverized. The pulverization time was 2 minutes, and the rotation speed of the pulverizer was 25,000 rpm. After pulverization, the lithium sulfide crude product having a particle size range of 20 microns to 40 microns was calcined at a high temperature in order to remove the residual sulfur powder. The calcination temperature was 600°C, and the calcination time was 5 hours.

[0053] (3) The calcined lithium sulfide crude product was subjected to dry ball milling. The ball milling parameters were: ball milling speed 400 rpm, ball milling time 8 h, and grinding ball to raw material ratio 1:1.

[0054] (4) The dry ball milled lithium sulfide was washed with n-hexane, and then stirred, heated and dried at a rotation speed of 30 rpm under inert gas protection with protective gas flow to obtain a lithium sulfide product. The stirring was carried out for 30 minutes, the heating and drying temperature was 100°C, and the drying time was 6 hours. The product number is DB-3. The composition parameters of the obtained product are shown in Table 1. The purity of the obtained product is 99.5%.

[0055] Comparative Example 4 (1) Industrial grade metallic lithium with a thickness of 300 microns, sulfur powder with a particle size range of 70 microns to 75 microns, and lithium hydride with a particle size range of 80 microns to 85 microns were weighed out so that the molar ratio of Li:S:LiH was 1:2:1, and the raw materials for the reaction were stirred and reacted under a nitrogen atmosphere to obtain a crude lithium sulfide product. The stirring time was 6 hours, the reaction temperature was 140°C, and the stirring speed was 20 rpm. The reaction formula is as follows. 2Li+S=Li2S 2LiH+S=Li2S+H2↑

[0056] (2) After the reaction, the lithium sulfide crude product was sieved, and the lithium sulfide crude product having a particle size of 20 mesh or more was used as the raw material for the next reaction, and the lithium sulfide crude product having a particle size of less than 20 mesh was pulverized. The pulverization time was 2 minutes, and the rotation speed of the pulverizer was 25,000 rpm. After pulverization, the lithium sulfide crude product having a particle size range of 20 microns to 40 microns was calcined at a high temperature to remove the residual sulfur powder. The calcination temperature was 600°C, and the calcination time was 5 hours.

[0057] (3) The calcined lithium sulfide crude product was subjected to wet ball milling. The solvent was isopropyl alcohol, and the ball milling parameters were a ball milling speed of 400 rpm, a ball milling time of 8 h, and a ratio of the grinding balls, the lithium sulfide crude product, and the solvent of 1:1:0.8.

[0058] (4) The wet ball milled lithium sulfide was washed with n-hexane, and stirred, heated and dried under protection of inert gas with protective gas flow. The stirring time was 30 min, the stirring speed was 30 rpm, the heating and drying temperature was 100°C, and the drying time was 6 h. This resulted in a lithium sulfide product. This product was numbered DB-4. The composition parameters of the obtained product are shown in Table 1. The purity of the obtained product is 98.36%. [Table 1]

[0059] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of and priority to Chinese patent application CN 2023112166149, filed on September 20, 2023, which is incorporated in its entirety by reference and for all other purposes.

Claims

1. The process includes a step of mixing and reacting sulfur powder, metallic lithium, and a lithium-containing additive to obtain a lithium sulfide crude product, and then pulverizing and calcining the lithium sulfide crude product to remove residual sulfur powder, and then obtaining EV grade lithium sulfide, the lithium-containing additive is at least one of lithium hydride, lithium nitride, and lithium carbide; The method for preparing EV grade lithium sulfide, wherein the molar ratio of the sulfur powder, metallic lithium, and lithium-containing additive is 1:2:0.1-0.

3.

2. 2. The method for preparing EV grade lithium sulfide according to claim 1, wherein the particle size range of the sulfur powder is 70 microns to 80 microns, and the particle size range of the lithium-containing additive is 80 microns to 90 microns.

3. The method for preparing EV grade lithium sulfide according to claim 1, wherein the reaction temperature is 100°C to 180°C.

4. The method for preparing EV grade lithium sulfide according to claim 1, characterized in that the reaction also includes stirring, the stirring time is 4 to 8 hours, and the stirring speed is 20 to 40 rpm.

5. 2. The method for preparing EV grade lithium sulfide according to claim 1, wherein the reaction also includes stirring, the reaction temperature is 140° C., the stirring time is 6 h, and the stirring speed is 20 rpm.

6. 2. The method for preparing EV grade lithium sulfide according to claim 1, further comprising the steps of sieving the lithium sulfide crude product, pulverizing the lithium sulfide crude product having a particle size of less than 20 mesh after the sieving, and returning the lithium sulfide crude product having a particle size of 20 mesh or more to the reaction as a raw material.

7. The method for preparing EV grade lithium sulfide according to claim 1, characterized in that the pulverization is performed at a rotation speed of 20,000 to 25,000 rpm for a pulverization time of 1 to 3 minutes.

8. 2. The method for preparing EV grade lithium sulfide according to claim 1, wherein the particle size range of the lithium sulfide crude product before calcination is 20 microns to 50 microns.

9. The method for preparing EV grade lithium sulfide according to claim 1, characterized in that the calcination is carried out at 400 to 600 ° C. for 3 to 5 h.

10. The method for preparing EV grade lithium sulfide according to claim 9, characterized in that the calcination is performed at a calcination temperature of 600° C. for a calcination time of 4 hours.

11. The method further comprises wet ball milling, i.e., wet ball milling the calcined lithium sulfide crude product; The method for preparing EV grade lithium sulfide according to claim 1, characterized in that the solvent for the wet ball milling is at least one of isopropyl alcohol and normal propyl alcohol, and the ball milling parameters are a ball milling rotation speed of 300 to 500 rpm, a ball milling time of 8 to 12 hours, and a mass ratio of the ball milling balls to the lithium sulfide crude product to the solvent of 4 to 1:1:1 to 0.

1.

12. 12. The method for preparing EV grade lithium sulfide according to claim 11, wherein the wet ball milling is performed using isopropyl alcohol as the solvent, at a ball milling speed of 400 rpm, and for a ball milling time of 8 hours.

13. 12. The method for preparing EV grade lithium sulfide as claimed in claim 11, wherein the mass ratio of the ball milling balls, the lithium sulfide crude product and the solvent is 1:1:0.

8.

14. The method for preparing EV grade lithium sulfide as claimed in claim 11, characterized in that the method further comprises washing and drying, i.e. washing the ball milled lithium sulfide with at least one of n-hexane, n-pentane, and cyclohexane, stirring, heating and drying to obtain high purity EV grade lithium sulfide.

15. The method for preparing EV grade lithium sulfide according to claim 14, characterized in that the washing is carried out by stirring and washing with n-hexane 2 to 3 times.

16. 15. The method for preparing EV grade lithium sulfide according to claim 14, wherein the reacting and the washing and drying are carried out under a protective atmosphere.

17. 17. The method for preparing EV grade lithium sulfide according to claim 16, wherein the protective atmosphere is at least one of nitrogen, argon, and helium.

18. The method for preparing EV grade lithium sulfide according to claim 14, characterized in that the drying temperature is 80 to 100 ° C., the stirring speed is 30 to 60 rpm, and the drying time is 4 to 8 h.

19. 15. The method for preparing EV grade lithium sulfide according to claim 14, characterized in that the reaction is carried out in a titanium apparatus and the drying is carried out in a titanium TA2 apparatus.

20. EV grade lithium sulfide prepared by the method for preparing EV grade lithium sulfide according to any one of claims 1 to 19, and having a purity of 99.9% or more and a whiteness of 80 or more.

21. 21. The EV grade lithium sulfide of claim 20, having a purity of 99.95% or more, a whiteness of 80 or more, and a D50 particle size of 15 microns or less.

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