Process for the preparation of high quality lithium sulfide

Abstract

The present application relates to a preparation method of high-quality lithium sulfide, and belongs to the technical field of high-purity lithium sulfide preparation. The present application solves the technical problem of providing a preparation method of high-quality lithium sulfide. The method comprises the following steps: mixing a lithium source, sulfur powder and anhydrous hydrazine uniformly under a protective atmosphere, and then starting a temperature rising reaction to obtain high-quality lithium sulfide; the temperature rising reaction is divided into two stages, the first stage has a temperature of 130-160 DEG C, a pressure of 0.1-0.2 MPa, and a heat preservation time of 2-4 h; the second stage has a temperature of 400-450 DEG C, a pressure of 0.1-0.2 MPa, and a heat preservation time of 2-4 h. The present application first proposes a low-quality lithium sulfide repair technology, after one-step reaction, the low-quality lithium sulfide is purified, and the product purity can reach more than 99%. In addition, the method can also be used to prepare high-quality lithium sulfide from ordinary lithium source, and has the advantages of simple process, strong operability, low energy consumption, scalable production, no secondary pollution, safety operation and commercialization of lithium sulfide.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of high-quality lithium sulfide, in particular to a method for repairing low-quality lithium sulfide to reach high purity, and belongs to the technical field of high-purity lithium sulfide preparation. BACKGROUND

[0002] Lithium sulfide (Li2S) is a key raw material for synthesizing sulfide solid-state electrolyte, and the purity and related impurity content of the lithium sulfide are one of important factors affecting the electrochemical performance of the lithium sulfide. Existing preparation methods of the lithium sulfide can be roughly divided into a ball milling method, a solvent method, a high-temperature and high-pressure method and a direct carbon composite method, and the high-quality lithium sulfide is directly synthesized in a dry and oxygen-free environment.

[0003] The lithium sulfide is chemically active, sensitive to moisture, oxygen and carbon dioxide, and if not properly stored, the lithium sulfide is very easy to hydrolyze and deteriorate, so that the purity of the lithium sulfide is reduced, and the deteriorated lithium sulfide will affect the electrochemical performance when used as a solid-state electrolyte raw material. Therefore, it is very important to repair the deteriorated lithium sulfide in the actual research and production application process.

[0004] An application No. CN201910993397.1 discloses a preparation method of lithium sulfide, in which a sulfur source and a lithium source are mixed and ground, an oxidation-reduction reaction occurs in the presence of a reducing agent hydrazine hydrate, vacuum defoaming treatment is adopted in the reaction process, and then vacuum freeze drying is performed, so that the lithium sulfide product is finally obtained. However, it is difficult to improve the purity of the lithium sulfide product to more than 99% by using the patent. SUMMARY

[0005] In view of the above defects, the technical problem to be solved by the application is to provide a preparation method of high-quality lithium sulfide.

[0006] The preparation method of high-quality lithium sulfide provided by the application comprises the following steps:

[0007] The lithium source, sulfur powder and anhydrous hydrazine are mixed under a protective atmosphere, and then a temperature rising reaction is started to obtain high-quality lithium sulfide; the temperature rising reaction is divided into two stages, the temperature of the first stage is 130-160 DEG C, the pressure is 0.1-0.2 MPa, and the holding time is 2-4 h; the temperature of the second stage is 400-450 DEG C, the pressure is 0.1-0.2 MPa, and the holding time is 2-4 h; and the lithium source is low-quality lithium sulfide, lithium hydroxide, lithium thiosulfate or lithium sulfite.

[0008] In an embodiment of the application, the low-quality lithium sulfide is lithium sulfide containing hydroxyl or carbonate impurities, and preferably the purity of the low-quality lithium sulfide is 80-95%.

[0009] In an embodiment of the application, the purity of the high-quality lithium sulfide is greater than or equal to 99%.

[0010] In one embodiment of the present application, when the lithium source is low-quality lithium sulfide, the mass ratio of low-quality lithium sulfide, sulfur powder and anhydrous hydrazine is 1:0.05-0.2:0.02-0.1; when the lithium source is lithium hydroxide, lithium thiosulfate or lithium sulfite, the molar ratio of Li2O:S:N2H4 is 1:1-2:2-4.

[0011] In one embodiment of the present application, the mixing is performed by stirring, and the stirring speed is 50-150 r / min.

[0012] In some embodiments of the present application, the protective atmosphere is an inert gas atmosphere.

[0013] Compared with the prior art, the present application has the following advantages:

[0014] The present application first proposes a low-quality lithium sulfide repair technology. After one-step reaction, the low-quality lithium sulfide is purified, and the product purity can reach more than 99%. In addition, the present application can also be used to prepare high-quality lithium sulfide from ordinary lithium sources. The process is simple, easy to operate, low in energy consumption, and can be produced on a large scale without secondary pollution. The present application can meet the requirements of safe operation and commercialized lithium sulfide. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 FIG. 1 is an XRD diffraction pattern of the lithium sulfide solid product prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0016] The present application discloses a preparation method of high-quality lithium sulfide, which comprises the following steps:

[0017] Under a protective atmosphere, a lithium source, sulfur powder and anhydrous hydrazine are mixed, and then a temperature rising reaction is started to obtain high-quality lithium sulfide;

[0018] The temperature rising reaction is divided into two stages. The temperature of the first stage is 130-160℃, the pressure is 0.1-0.2 MPa, and the holding time is 2-4 h. The temperature of the second stage is 400-450℃, the pressure is 0.1-0.2 MPa, and the holding time is 2-4 h.

[0019] The lithium source is low-quality lithium sulfide, lithium hydroxide, lithium thiosulfate or lithium sulfite.

[0020] It is found that vacuum freeze drying reduces the hydrolysis activity of lithium sulfide by reducing the drying temperature, but vacuum drying is limited to a certain extent because the negative pressure is helpful to the forward reaction of lithium sulfide hydrolysis. Therefore, the present application improves the raw materials and adopts an inert gas micro-positive pressure segmented repair drying method to solve the defects of the prior art from the principles and processes, and greatly improves the quality of lithium sulfide.

[0021] Various lithium sources can be prepared into high-quality lithium sulfide by the method of the present application. In one embodiment of the present application, the lithium source is low-quality lithium sulfide. The low-quality lithium sulfide is lithium sulfide containing hydroxyl or carbonate impurities, and has a purity of 80-95%. By the method of the present application, the low-quality lithium sulfide can be repaired to improve its purity.

[0022] In one embodiment of the present application, the high-quality lithium sulfide has a purity of ≥99%.

[0023] In theory, excess sulfur powder and anhydrous hydrazine can be added. In one embodiment of the present application, when the lithium source is low-quality lithium sulfide, the mass ratio of low-quality lithium sulfide, sulfur powder and anhydrous hydrazine is 1:0.05-0.2:0.02-0.1; when the lithium source is lithium hydroxide, lithium thiosulfate or lithium sulfite, the molar ratio of Li2O:S:N2H4 is 1:1-2:2-4.

[0024] In one embodiment of the present application, the mixing is performed by stirring, and the stirring speed is 50-150 r / min.

[0025] The protective atmosphere of the present application is an atmosphere that does not participate in the reaction. In some embodiments, the protective atmosphere is an inert gas atmosphere, and commonly used inert gases are suitable for the present application, such as helium, argon, neon, krypton, etc.

[0026] The specific embodiments of the present application are further described below in conjunction with examples, which do not limit the present application to the described embodiments. The low-quality lithium sulfide in the examples is lithium sulfide that has not been used up and has been left for a long time after being exposed to air. The product quality is detected, as shown in Table 1.

[0027] Example 1

[0028] A method for preparing high-quality lithium sulfide, the process steps are as follows:

[0029] (1) The low-quality lithium sulfide 1, sulfur powder and anhydrous hydrazine are weighed according to the mass ratio of Li2S:S:N2H4→1:0.2:0.1, mixed and then added into a reaction device, argon is passed and stirred to obtain a repaired raw material mixture.

[0030] (2) The repaired raw material mixture is dried at a high temperature, the drying temperature is 130°C, the pressure is 0.1 MPa, and the temperature is maintained for 4 h; then the temperature is raised to 400°C, the pressure is maintained at 0.1 MPa, and the temperature is maintained for 4 h, to finally obtain the repaired lithium sulfide solid product 1.

[0031] The composition parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is shown in Figure 1 , in which the upper part is the XRD diffraction pattern of the lithium sulfide prepared in the example.

[0032] Example 2

[0033] A method for preparing high-quality lithium sulfide, the process steps are as follows:

[0034] (1) The deteriorated lithium sulfide, sulfur powder and anhydrous hydrazine are weighed according to the mass ratio Li2S:S:N2H4→1:0.1:0.05, mixed and then added into a reaction device, argon is passed and stirred to obtain a repaired raw material mixture.

[0035] (2) The repaired raw material mixture is dried at high temperature, the drying temperature is 140°C, the pressure is 0.15 MPa, and the temperature is kept for 3.3 h; then the temperature is raised to 420°C, the pressure is 0.15 MPa, and the temperature is kept for 3.8 h, finally the repaired lithium sulfide solid product 2 is obtained.

[0036] The ingredient parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the lithium sulfide product 1. Figure 1

[0037] Example 3

[0038] A method for preparing high-quality lithium sulfide, the process steps are as follows:

[0039] (1) The deteriorated lithium sulfide, sulfur powder and anhydrous hydrazine are weighed according to the mass ratio Li2S:S:N2H4→1:0.05:0.02, mixed and then added into a reaction device, argon is passed and stirred to obtain a repaired raw material mixture.

[0040] (2) The repaired raw material mixture is dried at high temperature, the drying temperature is 150°C, the pressure is 0.2 MPa, and the temperature is kept for 2.5 h; then the temperature is raised to 400°C, the pressure is 0.2 MPa, and the temperature is kept for 3.2 h, finally the repaired lithium sulfide solid product is obtained.

[0041] The ingredient parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the lithium sulfide product 1. Figure 1

[0042] Example 4

[0043] A method for preparing high-quality lithium sulfide, the process steps are as follows:

[0044] (1) The deteriorated lithium sulfide 4, sulfur powder and anhydrous hydrazine are weighed according to the mass ratio Li2S:S:N2H4→1:0.2:0.1, mixed and then added into a reaction device, argon is passed and stirred to obtain a repaired raw material mixture.

[0045] ​​(2) The obtained repair raw material mixture is dried at high temperature, the drying temperature is 150℃, the pressure is 0.17MPa, and the temperature is kept for 3.5h; then the temperature is increased to 420℃, the pressure is kept at 0.17MPa, and the temperature is kept for 2.6h, finally the repaired lithium sulfide solid product 4 is obtained.

[0046] The ingredient parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the lithium sulfide product 1. Figure 1

[0047] Example 5

[0048] A method for preparing high-quality lithium sulfide, the process steps are as follows:

[0049] (1) The metamorphic lithium sulfide 5, sulfur powder and anhydrous hydrazine are weighed according to the mass ratio of Li2S:S:N2H4→1:0.11:0.07, mixed and then added into a reaction device, argon is passed and stirred to obtain a repair raw material mixture.

[0050] (2) The obtained repair raw material mixture is dried at high temperature, the drying temperature is 156℃, the pressure is 0.19MPa, and the temperature is kept for 2.5h; then the temperature is increased to 430℃, the pressure is kept at 0.15MPa, and the temperature is kept for 3.2h, finally the repaired lithium sulfide solid product 5 is obtained.

[0051] The ingredient parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the lithium sulfide product 1. Figure 1

[0052] Example 6

[0053] A method for preparing high-quality lithium sulfide, the process steps are as follows:

[0054] (1) The metamorphic lithium sulfide 6, sulfur powder and anhydrous hydrazine are weighed according to the mass ratio of Li2S:S:N2H4→1:0.06:0.021, mixed and then added into a reaction device, argon is passed and stirred to obtain a repair raw material mixture.

[0055] (2) The obtained repair raw material mixture is dried at high temperature, the drying temperature is 160℃, the pressure is 0.2MPa, and the temperature is kept for 4h; then the temperature is increased to 450℃, the pressure is kept at 0.2MPa, and the temperature is kept for 4h, finally the repaired lithium sulfide solid product 6 is obtained.

[0056] The ingredient parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the lithium sulfide product 1. Figure 1

[0057] Comparative Example 1

[0058] ​​​(1) The deteriorated lithium sulfide 6, sulfur powder and anhydrous hydrazine were weighed according to the mass ratio Li2S:S:N2H4→1:0.06:0.021, mixed and then added into a reaction device, argon was passed and stirred to obtain a repair raw material mixture.

[0059] (2) The obtained repair raw material mixture was dried at high temperature, the drying temperature was 160°C, the pressure was 0.2 MPa, and the holding time was 8 h; finally, the repaired lithium sulfide solid product 6-1 was obtained.

[0060] The composition parameters of the obtained product are shown in Table 1.

[0061] Comparative Example 2

[0062] (1) The deteriorated lithium sulfide 6, sulfur powder and anhydrous hydrazine were weighed according to the mass ratio Li2S:S:N2H4→1:0.06:0.021, mixed and then added into a reaction device, argon was passed and stirred to obtain a repair raw material mixture.

[0063] (2) The obtained repair raw material mixture was dried at high temperature, the drying temperature was 160°C, the pressure was 0.2 MPa, and the holding time was 8 h; finally, the repaired lithium sulfide solid product 6-1 was obtained.

[0064] The composition parameters of the obtained product are shown in Table 1.

[0065] Comparative Example 3

[0066] (1) The deteriorated lithium sulfide 6, sulfur powder and anhydrous hydrazine were weighed according to the mass ratio Li2S:S:N2H4→1:0.06:0.021, mixed and then added into a reaction device, argon was passed and stirred to obtain a repair raw material mixture.

[0067] (2) Vacuum defoaming process: the repair raw material mixture was placed in a vacuum defoaming barrel, vacuum was drawn, and after the bubbles were eliminated, the vacuum state was maintained for 4 h, then the gas pressure was changed to normal pressure, and a lithium sulfide slurry was obtained;

[0068] (3) The obtained lithium sulfide slurry was transferred to a vacuum freeze dryer, vacuum freeze drying was carried out at a low temperature of-60°C and a pressure below 100 Pa for 6 h, the dried material was vacuum capped and then taken out, and finally a lithium sulfide solid product 6-3 was obtained.

[0069] The composition parameters of the obtained product are shown in Table 1.

[0070] Example 7

[0071] A method for preparing high-quality lithium sulfide, the process steps are as follows:

[0072] (1) Lithium hydroxide, sulfur powder and anhydrous hydrazine are weighed according to the molar ratio Li2O:S:N2H4→1:2:4, mixed and then added into a reaction device, argon is passed through and stirring is performed to obtain a repair raw material mixture.

[0073] (2) The obtained repair raw material mixture is dried at a high temperature, the drying temperature is 130℃, the pressure is 0.1MPa, and the temperature is kept for 4h; then the temperature is raised to 400℃, the pressure is kept at 0.1MPa, and the temperature is kept for 4h, finally the lithium sulfide solid product 7 is obtained.

[0074] The component parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the product obtained in Example 1. Figure 1

[0075] Example 8

[0076] A method for preparing high-quality lithium sulfide, the process steps are as follows:

[0077] (1) Lithium sulfite, sulfur powder and anhydrous hydrazine are weighed according to the molar ratio Li2O:S:N2H4→1:2:4, mixed and then added into a reaction device, argon is passed through and stirring is performed to obtain a repair raw material mixture.

[0078] (2) The obtained repair raw material mixture is dried at a high temperature, the drying temperature is 130℃, the pressure is 0.1MPa, and the temperature is kept for 4h; then the temperature is raised to 400℃, the pressure is kept at 0.1MPa, and the temperature is kept for 4h, finally the lithium sulfide solid product 7 is obtained.

[0079] The component parameters of the obtained product are shown in Table 1, and the XRD diffraction pattern thereof is similar to that of the product obtained in Example 1. Figure 1

[0080] Table 1

[0081]

[0082]

[0083] It can be seen that by using the method of the present application, low-quality lithium sulfide can be repaired, and after one-step reaction, the low-quality lithium sulfide is purified, and the purity of the product can reach more than 99%. Lithium hydroxide, lithium sulfite and the like can also be used as a lithium source to directly prepare high-quality lithium sulfide, and the purity of the product can reach more than 99%.​​

Claims

1. A method for preparing high-quality lithium sulfide, characterized in that, Includes the following steps: Under a protective atmosphere, lithium source, sulfur powder and anhydrous hydrazine are mixed and then heated to react, resulting in high-quality lithium sulfide. The heating reaction is divided into two stages. The first stage has a temperature of 130–160°C, a pressure of 0.1–0.2 MPa, and a holding time of 2–4 h. The second stage has a temperature of 400–450°C, a pressure of 0.1–0.2 MPa, and a holding time of 2–4 h. The lithium source is low-quality lithium sulfide, lithium hydroxide, lithium thiosulfate, or lithium sulfite.

2. The method for preparing high-quality lithium sulfide according to claim 1, characterized in that: The low-quality lithium sulfide is lithium sulfide containing hydroxide or carbonate impurities.

3. The method for preparing high-quality lithium sulfide according to claim 2, characterized in that: The purity of the low-quality lithium sulfide is 80-95%.

4. The method for preparing high-quality lithium sulfide according to claim 1, characterized in that: High-quality lithium sulfide has a purity of ≥99%.

5. The method for preparing high-quality lithium sulfide according to claim 1, characterized in that: When the lithium source is low-quality lithium sulfide, the mass ratio of low-quality lithium sulfide, sulfur powder, and anhydrous hydrazine is 1:0.05-0.2:0.02-0.1; when the lithium source is lithium hydroxide, lithium thiosulfate, or lithium sulfite, the molar ratio is Li2O:S:N2H4 = 1:1-2:2-4.

6. The method for preparing high-quality lithium sulfide according to claim 1, characterized in that: During the mixing process, the stirring speed is 50-150 r / min.

7. The method for preparing high-quality lithium sulfide according to claim 1, characterized in that: The protective atmosphere is an inert gas atmosphere.

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