A lithium sulfide material and its preparation method and application

Abstract

The present invention provides a lithium sulfide material and a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing organic lithium with an organic solvent, introducing methyl mercaptan to react, and obtaining a crude intermediate product; (2) reacting the crude intermediate product with sulfur vapor under a protective gas atmosphere, and purifying the obtained material to obtain the lithium sulfide material. The method of the present invention has a wide range of raw material sources, mild reaction conditions, and the solvent can be recycled and reused, and can produce high-purity lithium sulfide without generating pollutants.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries and relates to a lithium sulfide material and a preparation method and application thereof. Background Art

[0002] Lithium sulfide is widely used in the field of battery materials, especially as a potential electrolyte material and cathode material in lithium-ion batteries. In recent years, researchers have found that the energy density of all-solid-state lithium-sulfur batteries using new lithium sulfide cathode materials exceeds 600 watt-hours per kilogram, more than double that of currently commercialized lithium-ion batteries. This new material can effectively solve the "shuttle effect" problem of liquid lithium-sulfur batteries, has the characteristics of high energy density and long cycle life, and has great commercial value and broad application prospects for the development of the electric vehicle industry.

[0003] CN116216652A discloses a method for preparing lithium sulfide, which uses nitrogen to react with metallic lithium to prepare lithium nitride, and mixes the prepared lithium nitride with elemental sulfur in a certain proportion to react to obtain lithium sulfide. The method has a simple production process, but uses active metallic lithium elemental sulfur under high temperature conditions, which poses a great safety hazard and makes it difficult to control the progress of the reaction.

[0004] CN117509686A mixes lithium sulfate and carbon source by ball milling after drying, and the obtained material is carbonized under the protection of inert gas or vacuum environment; the obtained carbonized product is mixed with sulfur powder by ball milling, and then calcined; the obtained material is dissolved in an alcohol solvent, filtered and dried to obtain lithium sulfide. Although this method has low raw material cost, it requires high temperature calcination, increases energy consumption cost and has a relatively low yield.

[0005] CN118289714A stirs and mixes lithium fluoride and chlorosilicon compound, introduces hydrogen sulfide gas, stirs, heats, and reacts to obtain lithium sulfide, fluorosilicon compound gas, and hydrogen chloride gas; after filtering, washes with an organic solvent, and dries under reduced pressure to obtain a finished product. This method does not involve high temperature and high pressure process operations, but the use of hydrogen sulfide in the raw material increases the safety risk of the process.

[0006] The above scheme has problems such as harsh reaction conditions, high safety risks, low yield, complex equipment and high energy consumption. It is very necessary to develop a lithium sulfide preparation method with mild conditions, low energy consumption and high yield. Summary of the invention

[0007] The object of the present invention is to provide a lithium sulfide material and a preparation method and application thereof. The method of the present invention has a wide range of raw material sources, mild reaction conditions, and both the solvent and the reactants can be recycled and reused, so that high-purity lithium sulfide can be obtained without generating pollutants.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a lithium sulfide material, the preparation method comprising the following steps:

[0010] (1) After mixing organic lithium with an organic solvent, methyl mercaptan is introduced into the mixture for reaction to obtain a crude intermediate product.

[0011] (2) reacting the intermediate crude product with sulfur vapor under a protective gas atmosphere, and purifying the obtained material to obtain the lithium sulfide material.

[0012] The present invention uses gaseous methyl mercaptan as a sulfur source, and organic lithium is used to prepare lithium methyl mercaptan, that is, a crude intermediate product and organic matter through a liquid phase synthesis method, and then reacts with sulfur vapor under a protective gas atmosphere to obtain lithium sulfide and dimethyl disulfide. Lithium sulfide is insoluble in dimethyl disulfide, and the two can be separated by filtering and purification. The method uses methyl mercaptan as a sulfur source and organic lithium as a lithium source to react in an organic solvent to prepare lithium sulfide. The reaction conditions are mild and sufficient. The lithium methyl mercaptan is subjected to thermal decomposition to obtain dimethyl disulfide and lithium sulfide. The dimethyl disulfide is treated by ethanol absorption, and no pollutants are generated during the entire reaction process.

[0013] Preferably, the organic lithium in step (1) comprises any one of n-butyl lithium, tert-butyl lithium or phenyl lithium, or a combination of at least two of them. Typical but non-limiting combinations include a combination of n-butyl lithium and tert-butyl lithium, a combination of n-butyl lithium and phenyl lithium, or a combination of tert-butyl lithium and phenyl lithium.

[0014] Preferably, the organic solvent in step (1) comprises any one of tetrahydrofuran, diethyl ether or dimethoxyethane, or a combination of at least two of them. Typical but non-limiting combinations include a combination of tetrahydrofuran and diethyl ether, a combination of tetrahydrofuran and dimethoxyethane, or a combination of diethyl ether and dimethoxyethane.

[0015] Preferably, the molar ratio of the organic lithium to the organic solvent in step (1) is 1:(3-5), for example, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0016] Preferably, the molar ratio of methyl mercaptan to organic lithium in step (1) is 2:(1-1.2), for example, 2:1, 2:1.05, 2:1.1, 2:1.15 or 2:1.2, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0017] Preferably, the reaction temperature in step (1) is 0-5°C, for example, 0°C, 1°C, 2°C, 3°C, 4°C or 5°C, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0018] Preferably, the reaction time of step (1) is 4 to 8 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, etc., which is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, after the reaction in step (1), distillation is performed to recover the organic solvent.

[0020] Preferably, the distillation treatment comprises atmospheric distillation.

[0021] Preferably, the temperature of the distillation treatment is 60-70°C, for example, 60°C, 62°C, 65°C, 68°C or 70°C, etc., and is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the protective gas in step (2) comprises any one of argon, nitrogen or helium, or a combination of at least two of them. Typical but non-limiting combinations include a combination of argon and nitrogen, a combination of nitrogen and helium, or a combination of argon and helium, etc.

[0023] Preferably, in step (2), the volume ratio of the sulfur vapor to the protective gas is 1:(1-5), for example: 1:1, 1:2, 1:3, 1:4 or 1:5.

[0024] Preferably, the reaction temperature in step (2) is 80-100°C, for example, 80°C, 85°C, 90°C, 95°C or 100°C, etc., and is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the reaction time is 2 to 4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the purification process in step (2) comprises dissolving the material in ethanol, and obtaining the lithium sulfide material by filtering and distilling.

[0027] Preferably, the temperature of the distillation treatment is 110-140°C, for example, 110°C, 120°C, 125°C, 130°C or 140°C, etc. Other values ​​not listed within this numerical range are also applicable.

[0028] In a second aspect, the present invention provides a lithium sulfide material, which is prepared by the preparation method described in the first aspect.

[0029] In a third aspect, the present invention provides a solid-state battery, wherein the solid-state battery comprises the lithium sulfide material as described in the second aspect.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention realizes efficient preparation of high-purity lithium sulfide by selecting suitable raw materials and optimizing processes. In the preparation process of the lithium sulfide material, the organic solvent used can be recycled and reused, and the reaction conditions are mild, which effectively reduces the raw material cost and energy consumption.

[0032] (2) The purity of the lithium sulfide material obtained by the method of the present invention can reach more than 93.8%, and the yield can reach more than 85.9%. By adjusting the preparation conditions, the purity of the lithium sulfide material obtained can reach more than 99.9%, and the yield can reach more than 91.1%. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0034] Example 1

[0035] This embodiment provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0036] (1) After diethyl ether is poured into a reaction kettle, n-butyl lithium is slowly added at a molar ratio of 1:4, methyl mercaptan is introduced, and the reaction is carried out at 3°C ​​for 6 hours. The diethyl ether is recovered by distillation at 60°C to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.1.

[0037] (2) The crude intermediate product is heated to 90° C. in an atmosphere with a sulfur vapor and nitrogen volume ratio of 1:2, and then reacted for 3 hours to obtain lithium sulfide and dimethyl disulfide, and the crude lithium sulfide is obtained by filtration. The crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 120° C.

[0038] Example 2

[0039] This embodiment provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0040] (1) After tetrahydrofuran is poured into a reaction kettle, tert-butyl lithium is slowly added at a molar ratio of 1:3, methyl mercaptan is introduced, and the reaction is carried out at 5°C for 4 hours. Ether is recovered by distillation at 70°C to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.2.

[0041] (2) The crude intermediate product is heated to 100° C. in an atmosphere of sulfur vapor and nitrogen in a volume ratio of 1:1, and then reacted for 2 hours to obtain lithium sulfide and dimethyl disulfide, and the crude lithium sulfide is obtained by filtration. The crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 140° C.

[0042] Example 3

[0043] This embodiment provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0044] (1) After diethyl ether is poured into a reaction kettle, n-butyl lithium is slowly added at a molar ratio of 1:5, methyl mercaptan is introduced, and the reaction is carried out at 0°C for 8 hours. The diethyl ether is distilled and recovered at 60°C to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.

[0045] (2) The intermediate crude product is heated to 80° C. in an atmosphere with a sulfur vapor and nitrogen volume ratio of 1:3 and reacted for 4 hours to obtain lithium sulfide and dimethyl disulfide, and crude lithium sulfide is obtained by filtration. The crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 110° C.

[0046] Example 4

[0047] This embodiment provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0048] (1) After diethyl ether is poured into a reaction kettle, n-butyl lithium is slowly added at a molar ratio of 1:4, methyl mercaptan is introduced, and the reaction is carried out at 10° C. for 6 hours. The diethyl ether is recovered by distillation at 60° C. to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.1.

[0049] (2) The crude intermediate product is heated to 90° C. in an atmosphere with a sulfur vapor and nitrogen volume ratio of 1:2, and then reacted for 3 hours to obtain lithium sulfide and dimethyl disulfide, and the crude lithium sulfide is obtained by filtration. The crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 120° C.

[0050] Example 5

[0051] This embodiment provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0052] (1) After diethyl ether is poured into a reaction kettle, n-butyl lithium is slowly added at a molar ratio of 1:4, methyl mercaptan is introduced, and the reaction is carried out at -5°C for 6 hours. The diethyl ether is distilled and recovered at 60°C to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.1.

[0053] (2) The crude intermediate product is heated to 90° C. in an atmosphere with a sulfur vapor and nitrogen volume ratio of 1:2, and then reacted for 3 hours to obtain lithium sulfide and dimethyl disulfide, and the crude lithium sulfide is obtained by filtration. The crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 120° C.

[0054] Example 6

[0055] This embodiment provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0056] (1) After diethyl ether is poured into a reaction kettle, n-butyl lithium is slowly added at a molar ratio of 1:4, methyl mercaptan is introduced, and the reaction is carried out at 3°C ​​for 6 hours. The diethyl ether is recovered by distillation at 60°C to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.1.

[0057] (2) The crude intermediate product is heated to 80° C. in an atmosphere of sulfur vapor and nitrogen in a volume ratio of 1:2, and then reacted for 3 hours to obtain lithium sulfide and dimethyl disulfide, and the crude lithium sulfide is obtained by filtration. The crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 120° C.

[0058] Example 7

[0059] This embodiment provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0060] (1) After diethyl ether is poured into a reaction kettle, n-butyl lithium is slowly added at a molar ratio of 1:4, methyl mercaptan is introduced, and the reaction is carried out at 3°C ​​for 6 hours. The diethyl ether is recovered by distillation at 60°C to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.1.

[0061] (2) The intermediate crude product is heated to 120° C. in an atmosphere with a sulfur vapor and nitrogen volume ratio of 1:2, and then reacted for 3 hours to obtain lithium sulfide and dimethyl disulfide, and the crude lithium sulfide is obtained by filtration. The obtained crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 120° C.

[0062] Example 8

[0063] This embodiment provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0064] (1) After diethyl ether is poured into a reaction kettle, n-butyl lithium is slowly added at a molar ratio of 1:4, methyl mercaptan is introduced, and the reaction is carried out at 3°C ​​for 6 hours. The diethyl ether is recovered by distillation at 60°C to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.1.

[0065] (2) The intermediate crude product is heated to 90° C. in an atmosphere with a sulfur vapor and nitrogen volume ratio of 2:1 and reacted for 3 hours to obtain lithium sulfide and dimethyl disulfide, and the crude lithium sulfide is obtained by filtration. The crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 120° C.

[0066] Comparative Example 1

[0067] This comparative example provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0068] (1) After diethyl ether is poured into a reaction kettle, n-butyl lithium is slowly added at a molar ratio of 1:4, methyl mercaptan is introduced, and the reaction is carried out at 3°C ​​for 6 hours. The diethyl ether is recovered by distillation at 60°C to obtain a crude intermediate product, wherein the molar ratio of methyl mercaptan to n-butyl lithium is 2:1.1.

[0069] (2) The intermediate crude product is heated to 90° C. in a sulfur vapor atmosphere and reacted for 3 hours to obtain lithium sulfide and dimethyl disulfide, and the crude lithium sulfide is obtained by filtration. The crude product is then dissolved in ethanol, and the lithium sulfide material is obtained by distillation and filtration at 120° C.

[0070] Comparative Example 2

[0071] This comparative example provides a lithium sulfide material, and the preparation method of the lithium sulfide material is as follows:

[0072] (1) Weigh an excess amount of sucrose, mix it with lithium sulfate and grind it thoroughly. Then, press the ground powder into tablets and place them in a porcelain crucible.

[0073] (2) Place the porcelain boat in a tube furnace and maintain the argon pressure at 0.1 MPa. Raise the temperature from room temperature to 200°C for 0.5 h, keep it at that temperature for 1 h, then raise the temperature to 250°C for 1 h, and keep it at that temperature for 4 h to perform carbonization and coating reaction. After carbonization, continue to raise the temperature to 675°C and keep it at that temperature for 8 h, and purify to obtain lithium sulfide.

[0074] Performance Test:

[0075] The obtained lithium sulfide was subjected to ICP detection, and the purity of the lithium sulfide was measured by reduction method. The test results are shown in Table 1:

[0076] Table 1

[0077]

[0078] As can be seen from Table 1, from Examples 1-8, the purity of the lithium sulfide material obtained by the method of the present invention can reach more than 93.8%, and the yield can reach more than 85.9%. By adjusting the preparation conditions, the purity of the lithium sulfide material obtained can reach more than 99.9%, and the yield can reach more than 91.1%.

[0079] By comparing Example 1 with Examples 4-5, it can be seen that in the preparation process of the lithium sulfide material of the present invention, the temperature of the reaction in step (1) will affect the preparation effect. Controlling the temperature of the reaction in step (1) at 0-5°C can significantly improve the preparation effect. If the temperature of the reaction in step (1) is too high, the reaction may be too violent, the reaction may be locally overheated, and side reactions may increase, thereby affecting the purity and yield of the product. If the temperature of the reaction in step (1) is too low, the reaction activity may decrease and the reaction rate may be too slow, thereby causing a decrease in purity and yield.

[0080] By comparing Example 1 with Examples 6-7, it can be seen that in the preparation process of the lithium sulfide material of the present invention, the temperature of the reaction in step (2) affects the preparation effect. Controlling the temperature of the reaction at 80-100° C. can significantly improve the preparation effect. If the reaction temperature is too high, more chemical bonds in the reactants may be broken, decomposing to generate other products, resulting in a decrease in purity and yield. If the reaction temperature is too low, the thermal decomposition is not complete, and side reactions may occur, affecting the purity and yield.

[0081] By comparing Example 1 and Example 8, it can be seen that in the preparation process of the lithium sulfide material of the present invention, the atmosphere of the reaction in step (2) will affect the preparation effect. If the proportion of sulfur vapor in the atmosphere is too high, it may lead to the generation of more by-product polysulfides, thereby affecting the purity and yield.

[0082] By comparing Example 1 with Comparative Example 1, it can be seen that if the reaction is carried out only under sulfur vapor, more by-products will be generated, which will cause waste of resources and increase safety hazards.

[0083] From the comparison between Example 1 and Comparative Example 2, it can be seen that the preparation of lithium sulfide by carbon thermal method requires reaction at high temperature, and it is difficult to control the reaction process, resulting in an increase in reduction by-products, which affects the yield and purity of the product.

[0084] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a lithium sulfide material, characterized in that: The preparation method comprises the following steps: (1) mixing an organic lithium with an organic solvent, introducing methyl mercaptan into the mixture for reaction to obtain a crude intermediate product; (2) reacting the intermediate crude product with sulfur vapor under a protective gas atmosphere, and purifying the obtained material to obtain the lithium sulfide material; The organic lithium in step (1) comprises any one of n-butyl lithium, tert-butyl lithium or phenyl lithium or a combination of at least two thereof, the organic solvent comprises any one of tetrahydrofuran, diethyl ether or dimethoxyethane or a combination of at least two thereof, and the molar ratio of the organic lithium to the organic solvent is 1:(3-5); The reaction temperature in step (1) is 0-5°C and the reaction time is 4-8h.

2. The preparation method according to claim 1, characterized in that The molar ratio of methyl mercaptan to organic lithium in step (1) is 2:(1-1.2).

3. The preparation method according to claim 1, characterized in that: After the reaction in step (1), distillation is performed to recover the organic solvent; The distillation treatment includes atmospheric distillation, and the temperature of the distillation treatment is 60-70°C.

4. The preparation method according to claim 1, characterized in that: The protective gas in step (2) includes any one of argon, nitrogen or helium, or a combination of at least two of them; The volume ratio of the sulfur vapor to the protective gas in step (2) is 1:(1-5).

5. The preparation method according to claim 1, characterized in that: The reaction temperature in step (2) is 80-100° C., and the reaction time is 2-4 hours.

6. The preparation method according to claim 1, characterized in that: The purification process in step (2) includes dissolving the obtained solid material in ethanol after solid-liquid separation, and obtaining the lithium sulfide material through filtering and distillation. The temperature of the distillation treatment is 110-140°C.

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