Process for the preparation of high purity lithium sulfide

Abstract

The present application relates to a preparation method of high-purity lithium sulfide, and belongs to the technical field of lithium sulfide preparation. The present application solves the technical problem of providing a preparation method of high-purity lithium sulfide. The method comprises the following steps: a, mixing and grinding a sulfur source and a lithium source, mixing the ground material with hydrazine hydrate to obtain a reaction material; b, mixing and reacting to obtain lithium sulfide slurry; c, heating the lithium sulfide slurry to 100-120 DEG C, drying for 1-2 hours, then adding sulfur powder and anhydrous hydrazine, heating to 400-410 DEG C, drying for 1-2 hours to obtain high-purity lithium sulfide powder. The present application is prepared by a simple reaction operation, one-pot method, after stage heating and drying and feeding, the lithium sulfide is reacted twice, the product purity can reach more than 99.9%, and the hydroxyl ion content is less than 0.01%. The method for preparing lithium sulfide is simple in process, strong in operability, low in energy consumption, can be produced on a large scale, has no secondary pollution, can meet the requirements of safe operation and commercialization of high-purity lithium sulfide, and can meet the requirements of safe operation and commercialization of high-purity lithium sulfide.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of high-purity lithium sulfide, and belongs to the technical field of lithium sulfide preparation. BACKGROUND

[0002] Lithium ion batteries have been widely used in the fields of automobiles, aerospace, consumer electronics, etc. The traditional lithium ion battery usually uses liquid electrolyte, which is prone to safety hazards in integrated applications. At the same time, the research on energy density, power density and cycle life of lithium ion batteries has entered a bottleneck period, which is difficult to meet the needs of the new generation of power batteries. In view of the problem of safety, a full solid-state battery using solid-state electrolyte has been developed. Lithium-sulfur batteries have attracted widespread attention in recent years due to their high theoretical specific energy. Among them, as the core raw material for synthesizing sulfide solid-state electrolyte and the preferred positive electrode material of lithium-sulfur batteries, lithium sulfide (Li2S) has become a research hotspot in recent years.

[0003] In the current existing preparation method of lithium sulfide, the following methods are mainly used: (1) liquid phase method, such as patent CN108190845A, which uses a liquid phase method to prepare lithium sulfide. This method has good ability to adjust the particle size of Li2S product, which is beneficial to the activation of the initial charging process. However, this method usually requires high-activity organic lithium compounds as reactants, which are expensive; (2) high-temperature carbon reduction method, such as patent CN108400327A, which uses a high-temperature carbon reduction method to prepare lithium sulfide. The selected lithium source is lithium sulfate, lithium carbonate, lithium hydroxide, etc., which saves production cost. However, there is no corresponding standard and requirement for the product quality and index control of lithium sulfide; (3) patent CN105016310A prepares lithium sulfide by reacting lithium hydroxide with hydrogen sulfide. This preparation method requires the use of toxic hydrogen sulfide gas, which has high safety requirements for the process; (4) in addition, patent CN112678781A uses sulfur powder, lithium hydroxide, and hydrazine hydrate as raw materials. The lithium sulfide obtained by this preparation method contains many impurities, has a high content of hydroxyl ions, and the highest purity is only 95%, which affects the battery performance. Therefore, the existing technology needs to be improved and developed. SUMMARY

[0004] In view of the above defects, the technical problem solved by the present application is to provide a preparation method of high-purity lithium sulfide with a purity of up to 99.9%.

[0005] The preparation method of high-purity lithium sulfide of the present application comprises the following steps:

[0006] a. Grinding and mixing: mix and grind the sulfur source and lithium source, then mix with hydrazine hydrate to obtain the reactant; wherein the sulfur source is sulfur powder, lithium thiosulfate or lithium sulfite; the lithium source is lithium hydroxide, lithium thiosulfate or lithium sulfite;

[0007] b. Mixing reaction: Put the reaction material into a reaction device, pass a protective gas, and stir for 1-4 h, wherein the protective gas is argon, and finally obtain a lithium sulfide slurry;

[0008] c. Drying: heat the lithium sulfide slurry to 100-120 DEG C, dry for 1-2 h, then add sulfur powder and anhydrous hydrazine, heat to 400-410 DEG C, dry for 1-2 h, and obtain high-purity lithium sulfide powder.

[0009] In one embodiment of the present application, in the step a, the sulfur source is sulfur powder; and the lithium source is lithium hydroxide monohydrate.

[0010] In one embodiment of the present application, in the step a, the sulfur source, the lithium source and the hydrazine hydrate are taken in a molar ratio of Li2O:S:N2H4·H2O = 1:1-2:2-4.

[0011] In one embodiment of the present application, in the step b, the stirring speed is 100-150 r / min.

[0012] In one embodiment of the present application, in the step b, the protective gas is an inert gas; preferably, the protective gas is argon.

[0013] In one embodiment of the present application, in the step c, the drying pressure is 0.1-0.2 MPa.

[0014] In one embodiment of the present application, in the step c, the ratio of the amount of sulfur powder and anhydrous hydrazine to the mass of Li2O in the lithium source in the step a is Li2O:S:N2H4 = 1:0.1:0.1-0.2.

[0015] In one embodiment of the present application, in the step c, the molar ratio of sulfur powder to anhydrous hydrazine is 1:1.

[0016] In one embodiment of the present application, the purity of the high-purity lithium sulfide is ≥99.9%.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] The present application can purify lithium sulfide through simple reaction operation, one-pot preparation, stage heating and drying and feeding, and the product purity can reach more than 99.9%, and the hydroxyl ion content is less than 0.01%. The method for preparing lithium sulfide has the advantages of simple process, strong operability, low energy consumption, scaleable production, no secondary pollution, and can meet the requirements of safe operation and commercial high-purity lithium sulfide. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The XRD diffraction pattern of the lithium sulfide prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0020] The preparation method of the high-purity lithium sulfide comprises the following steps:

[0021] a. Grinding and mixing: the sulfur source and the lithium source are mixed and ground, and then mixed with hydrazine hydrate to obtain a reaction material; wherein the sulfur source is sulfur powder, lithium thiosulfate or lithium sulfite; the lithium source is lithium hydroxide, lithium thiosulfate or lithium sulfite;

[0022] b. Mixing reaction: the reaction material is placed in a reaction device, and a protective gas is passed and stirred for 1-4 hours; the protective gas is argon; finally, lithium sulfide slurry is obtained;

[0023] c. Drying: the lithium sulfide slurry is heated to 100-120°C and dried for 1-2 hours, then sulfur powder and hydrazine are added, and heated to 400-410°C and dried for 1-2 hours to obtain high-purity lithium sulfide powder.

[0024] In an embodiment of the present application, in step a, the sulfur source is sulfur powder; and the lithium source is lithium hydroxide monohydrate.

[0025] In an embodiment of the present application, in step a, the sulfur source, the lithium source and hydrazine hydrate are taken in a molar ratio of Li2O:S:N2H4·H2O = 1:1-2:2-4.

[0026] Step b is a normal temperature reaction process, and the following reaction occurs:

[0027] 2S+2LiOH·H2O+N2H4·H2O = Li2S+H2S↑+N2↑+5H2O(g)

[0028] In an embodiment of the present application, in step b, the stirring speed is 100-150 r / min.

[0029] Common protective gases are suitable for the present application; in an embodiment, the protective gas in step b is an inert gas. In a preferred embodiment, the protective gas is argon.

[0030] In an embodiment of the present application, in step c, the drying pressure is 0.1-0.2 MPa.

[0031] In an embodiment of the present application, in step c, the ratio of the amount of sulfur powder and anhydrous hydrazine added to the mass of Li2O in the lithium source in step a is: Li2O:S:N2H4 = 1:0.1:0.1-0.2.

[0032] In the present application, Li2O does not mean that there is lithium oxide in the lithium source, but in order to facilitate material balance, the lithium in the lithium source is calculated as lithium oxide.

[0033] In one embodiment of the present application, in the step c, the molar ratio of sulfur powder to anhydrous hydrazine is 1:1.

[0034] In one embodiment of the present application, the high-purity lithium sulfide has a purity of ≥99.9%.

[0035] The specific embodiments of the present application are further described below with reference to the examples, which do not limit the present application in the scope of the described examples.

[0036] Example 1

[0037] (1) Lithium hydroxide monohydrate, sulfur powder and hydrazine hydrate were weighed according to the molar ratio Li2O:S:N2H4·H2O→1:2:4; the lithium hydroxide monohydrate and sulfur powder were mixed and ground, and then added to the reaction device containing hydrazine hydrate to obtain a reaction raw material mixture.

[0038] (2) Mixing reaction: the reaction materials were placed in the reaction device, a protective gas was passed and stirred for 2 h at a stirring speed of 120 r / min, and the protective gas was argon, and finally a lithium sulfide slurry was obtained.

[0039] (3) The obtained lithium sulfide slurry was subjected to high-temperature drying at a drying temperature of 120℃ and a pressure of 0.1 MPa, after 1 h, a mixture of sulfur powder and hydrazine with a molar ratio of 1:1 was added to the reaction device, and the mass ratio of Li2O:S:N2H4 in the lithium source to the added amount of sulfur powder and anhydrous hydrazine during the drying process was Li2O:S:N2H4=1:0.1:0.1, and then the temperature was raised to 400℃, the pressure was 0.1 MPa, and the temperature was maintained for 2 h, and finally a lithium sulfide solid was obtained.

[0040] The composition parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is shown in Figure 1 .

[0041] Comparative Example 1

[0042] (1) Lithium hydroxide monohydrate, sulfur powder and hydrazine hydrate were weighed according to the molar ratio Li2O:S:N2H4·H2O→1:2:4; the lithium hydroxide monohydrate and sulfur powder were mixed and ground, and then added to the reaction device containing hydrazine hydrate to obtain a reaction raw material mixture.

[0043] (2) Mixing reaction: the reaction materials were placed in the reaction device, a protective gas was passed and stirred for 2 h at a stirring speed of 120 r / min, and the protective gas was argon, and finally a lithium sulfide slurry was obtained.

[0044] (3) The obtained lithium sulfide slurry was subjected to high-temperature drying at a drying temperature of 120℃ and a pressure of 0.1 MPa, after 1 h, the temperature was raised to 400℃, the pressure was 0.1 MPa, and the temperature was maintained for 2 h, and finally a lithium sulfide solid was obtained.

[0045] The ingredient parameters of the product obtained are shown in Table 1, and the XRD diffraction pattern thereof is similar to Figure 1 .

[0046] Comparative Example 2

[0047] (1) Lithium hydroxide monohydrate, sulfur powder and hydrazine hydrate were weighed according to the molar ratio Li2O:S:N2H4·H2O→1:2:4, and then the lithium hydroxide monohydrate and sulfur powder were mixed and ground, and then added to a reaction device containing hydrazine hydrate to obtain a reaction raw material mixture.

[0048] (2) The reaction raw material mixture was subjected to high-temperature drying at a drying temperature of 120°C and a pressure of 0.1 MPa, and after 1 h, a mixture of sulfur powder and hydrazine with a molar ratio of 1:1 was added to the reaction device, and the mass ratio of sulfur powder to anhydrous hydrazine to Li2O in the lithium source was Li2O:S:N2H4=1:0.1:0.1, and then the temperature was raised to 400°C, the pressure was 0.1 MPa, and the temperature was maintained for 2 h, to finally obtain lithium sulfide solid.

[0049] The ingredient parameters of the product obtained are shown in Table 1, and the XRD diffraction pattern thereof is similar to Figure 1 .

[0050] Comparative Example 3

[0051] (1) Lithium hydroxide monohydrate, sulfur powder and hydrazine hydrate were weighed according to the molar ratio Li2O:S:N2H4·H2O→1:2:4, and then the lithium hydroxide monohydrate and sulfur powder were mixed and ground, and then added to a reaction device containing hydrazine hydrate to obtain a reaction raw material mixture.

[0052] (2) The reaction raw material mixture was subjected to high-temperature drying at a drying temperature of 120°C and a pressure of 0.1 MPa, and after 1 h, a mixture of sulfur powder and hydrazine with a molar ratio of 1:1 was added to the reaction device, and the mass ratio of sulfur powder to anhydrous hydrazine to Li2O in the lithium source was Li2O:S:N2H4=1:0.1:0.1, and then the temperature was raised to 400°C, the pressure was 0.1 MPa, and the temperature was maintained for 2 h, to finally obtain lithium sulfide solid.

[0053] (3) The lithium sulfide slurry obtained was subjected to high-temperature drying at a drying temperature of 400°C and a pressure of 0.1 MPa for 4 h, to finally obtain lithium sulfide solid.

[0054] The ingredient parameters of the product obtained are shown in Table 1, and the XRD diffraction pattern thereof is similar to Figure 1 .

[0055] Comparative Example 4

[0056] (1) Lithium hydroxide, sulfur powder and anhydrous hydrazine were weighed according to the mass ratio Li2O:S:N2H4→1:2:4, and then mixed and added to a reaction device, and argon gas was passed and stirred to obtain a repair raw material mixture.

[0057] (2) Vacuum defoaming process: Put the mixed solution of repair raw materials into the vacuum defoaming barrel, vacuumize to below 0.1 MPa, continue to react until no bubbles are generated, then keep the vacuum state for 1 h, open the valve of the vacuum defoaming barrel to reach the normal pressure state, and obtain the lithium sulfide slurry.

[0058] (3) After defoaming, the mixed solution is transferred into the vacuum freeze dryer, vacuum freeze drying is carried out at a low temperature of -50℃ and a pressure of below 100 Pa for 4 h, the dried material is taken out after vacuum pressing, and the lithium sulfide product is obtained. The composition parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the product of Example 1. Figure 1

[0059] Example 2

[0060] (1) Lithium hydroxide monohydrate, sulfur powder and hydrazine hydrate are weighed according to the molar ratio Li2O:S:N2H4·H2O→1:1:4, the lithium hydroxide monohydrate and sulfur powder are mixed and ground, and then added into the reaction device containing hydrazine hydrate to obtain a mixed solution of reaction raw materials.

[0061] (2) Mixing reaction: the reaction material is put into the reaction device, protective gas is passed and stirred for 1 h, the stirring speed is 150 r / min, the protective gas is argon, and finally the lithium sulfide slurry is obtained.

[0062] (3) The obtained lithium sulfide slurry is dried at a high temperature, the drying temperature is 120℃, the pressure is 0.1 MPa, after 1 h, a mixture of sulfur powder and hydrazine with a molar ratio of 1:1 is added into the reaction device, and the mass ratio of Li2O:S:N2H4 in the lithium source is Li2O:S:N2H4=1:0.1:0.1, then the temperature is raised to 400℃, the pressure is 0.1 MPa, and the temperature is kept for 2 h, and finally the lithium sulfide solid is obtained.

[0063] The composition parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the product of Example 1. Figure 1

[0064] Example 3

[0065] (1) Lithium thiosulfate and hydrazine hydrate are weighed according to the molar ratio lithium thiosulfate:hydrazine hydrate=1:2, the lithium thiosulfate is ground and then added into the reaction device containing hydrazine hydrate to obtain a mixed solution of reaction raw materials.

[0066] (2) Mixing reaction: the reaction material is put into the reaction device, protective gas is passed and stirred for 4 h, the stirring speed is 100 r / min, the protective gas is argon, and finally the lithium sulfide slurry is obtained.

[0067] ​​(3) the obtained lithium sulfide slurry is dried at a high temperature, the drying temperature is 120℃, the pressure is 0.2MPa, after 1h, the mixture of sulfur powder and anhydrous hydrazine with a molar ratio of 1:1 is added into the reaction device, the mass ratio of the added sulfur powder and anhydrous hydrazine to Li2O in the lithium source is Li2O:S:N2H4=1:0.1:0.1, then the temperature is increased to 410℃, the pressure is 0.2MPa, and the temperature is kept for 2h, finally the lithium sulfide solid is obtained.

[0068] The ingredient parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to Figure 1

[0069] Example 4

[0070] (1) lithium sulfite and hydrazine hydrate are weighed according to the molar ratio of lithium sulfite:hydrazine hydrate=1:2, the ground lithium sulfite is added into the reaction device containing hydrazine hydrate, and the reaction raw material mixture is obtained.

[0071] (2) mixing and reaction: the reaction material is put into the reaction device, the protective gas is passed and stirred for 3h, the stirring speed is 100r / min, the protective gas is argon, and finally the lithium sulfide slurry is obtained.

[0072] (3) the obtained lithium sulfide slurry is dried at a high temperature, the drying temperature is 100℃, the pressure is 0.2MPa, after 1h, the mixture of sulfur powder and anhydrous hydrazine with a molar ratio of 1:1 is added into the reaction device, the mass ratio of the added sulfur powder and anhydrous hydrazine to Li2O in the lithium source is Li2O:S:N2H4=1:0.1:0.1, then the temperature is increased to 400℃, the pressure is 0.2MPa, and the temperature is kept for 2h, finally the lithium sulfide solid is obtained.

[0073] The ingredient parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to Figure 1

[0074] Table 1

[0075]

[0076]

[0077] It can be seen that by using the method, the purity of the product can reach more than 99.9%, and the hydroxyl radical content is less than 0.01%.​​

Claims

1. A method for preparing high-purity lithium sulfide, characterized in that, Includes the following steps: a. Grinding and mixing: The sulfur source and lithium source are mixed and ground, and then mixed with hydrazine hydrate to obtain the reaction material; wherein, the sulfur source is sulfur powder, lithium thiosulfate or lithium sulfite; and the lithium source is lithium hydroxide, lithium thiosulfate or lithium sulfite. b. Mixing reaction: The reactants are placed in the reaction apparatus, a protective gas is introduced and the mixture is stirred for 1 to 4 hours. The protective gas is argon. Finally, lithium sulfide slurry is obtained. c. Drying: Heat the lithium sulfide slurry to 100℃~120℃ and dry for 1~2 h. Then add sulfur powder and anhydrous hydrazine, heat to 400℃~410℃ and dry for 1~2 h to obtain high-purity lithium sulfide powder.

2. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In step a, the sulfur source is sulfur powder; the lithium source is lithium hydroxide monohydrate.

3. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In step a, sulfur source, lithium source and hydrazine hydrate are taken in a molar ratio of Li2O : S : N2H4·H2O = 1 : 1~2 : 2~4.

4. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In step b, the stirring speed is 100-150 r / min.

5. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In step b, the protective gas is an inert gas.

6. The method for preparing high-purity lithium sulfide according to claim 5, characterized in that: The protective gas is argon.

7. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In step c, the drying pressure is 0.1–0.2 MPa.

8. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In step c, the ratio of the amount of sulfur powder and anhydrous hydrazine added to the mass of Li2O in the lithium source in step a is: Li2O : S : N2H4 = 1 : 0.1 : 0.1~0.

2.

9. The method for preparing high-purity lithium sulfide according to claim 8, characterized in that: In step c, the molar ratio of sulfur powder to anhydrous hydrazine is 1:

1.

10. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: The purity of the high-purity lithium sulfide is ≥99.9%.

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