Method for preparing high-purity lithium sulfide from lithium sulfate solution based on lithium ore lithium extraction and sulfide solid electrolyte

Abstract

A method for preparing high-purity lithium sulfide from a lithium sulfate solution based on lithium ore extraction and a sulfide solid electrolyte. In the granulation process of the present invention, the average particle size of the microparticles is controlled within 0.42 μm - 2.39 μm by controlling the rotation speed of the granulation disk, which can make the lithium sulfide yield above 95%, and the conductivity of the Li2S / P2S5 / LiCl electrolyte is higher than 4.5 mS / cm at 25°C. It should be noted that too low granulation particle size will reduce the yield of lithium sulfide powder, and too high granulation particle size will reduce the conductivity of the electrolyte. Therefore, in practice, the granulation particle size needs to be strictly controlled.

Description

Technical Field

[0001] The present invention relates to the fields of advanced inorganic non-metallic materials and lithium battery electrolytes, and particularly relates to a method for preparing high-purity lithium sulfide from a lithium sulfate solution based on lithium extraction from lithium ore and a sulfide solid electrolyte. Background Art

[0002] Lithium sulfide is an advanced inorganic compound composed of lithium and sulfur and belongs to alkali metal sulfides. In the prior art, lithium sulfide is widely used in the fields of synthesis of battery cathode materials and solid electrolytes. Among them, when lithium sulfide is used as the cathode material of a lithium-sulfur battery, it has the characteristics of high energy density. At the same time, the preparation of lithium sulfide from lithium ore has been widely used. Therefore, how to improve the yield of lithium sulfide prepared from lithium ore and the conductivity of the electrolyte configured for new energy batteries is a very meaningful topic. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing high-purity lithium sulfide from a lithium sulfate solution based on lithium extraction from lithium ore, and this method can obtain lithium sulfide powder with high yield and high conductivity.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing lithium sulfide from a lithium sulfate solution based on lithium extraction from lithium ore, the method comprising the following steps:

[0006] Preparing lithium sulfate: After ball-milling spodumene, adding it to deionized water, and then slowly adding concentrated sulfuric acid for acidification treatment for 3.2 - 4.2 h under stirring. Here, the lithium in the lithium ore is calculated as lithium carbonate, and the molar ratio of sulfuric acid to lithium carbonate is 1.25 - 1.30∶1. Dilute with water to 6 - 8 times the volume of the solution and stir for 2 - 5 h. Then add slaked lime to adjust the pH value to 7.5 - 7.8 and filter to obtain a crude lithium sulfate solution. Then add calcium hypochlorite as an oxidant, stir for 15 - 30 min and filter. Then add sodium hydroxide to adjust the pH value to 12.2 - 12.5, continue to add sodium carbonate accounting for 1.8 - 2.2 wt% of the weight of spodumene, stir for 30 - 45 min and then concentrate the volume of the solution to half, and filter to obtain a lithium sulfate solution;

[0007] Preparing lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain fine particles with a particle size D50 = 0.42 - 2.39 μm through spray granulation drying technology. During the granulation process, adjust the particle size of the fine particles by controlling the rotation speed of the granulation disk. Calcinate the fine particles in a protective atmosphere at 860 - 1040 °C for 8 - 10 h, then wash with absolute ethanol for several times, and finally obtain high-purity lithium sulfide powder by evaporation crystallization.

[0008] Preferably, the particle size D50 of the fine particles is 0.85 μm.

[0009] Preferably, the calcination temperature is 860 °C.

[0010] Preferably, the calcination time is 8 h.

[0011] Preferably, the yield of the lithium sulfide powder exceeds 95%.

[0012] Furthermore, the present invention also provides a sulfide solid electrolyte, and the molar composition of the electrolyte is Li2S∶P2S5∶LiCl = 5∶1∶2, and the lithium sulfide is prepared by the above method.

[0013] Preferably, the conductivity of the Li2S / P2S5 / LiCl electrolyte prepared with the lithium sulfide is higher than 4.5 mS / cm at 25 °C.

[0014] In the granulation process of the present invention, by controlling the rotation speed of the granulation disk, the average particle size of the microparticles is controlled within 0.42 μm - 2.39 μm, the yield of lithium sulfide can be more than 95%, and the conductivity of the Li2S / P2S5 / LiCl electrolyte is higher than 4.5 mS / cm at 25 °C. It should be noted that too low granulation particle size will reduce the yield of lithium sulfide powder, and too high granulation particle size will reduce the conductivity of the electrolyte. Therefore, in practice, the granulation particle size needs to be strictly controlled. Detailed Embodiments

[0015] The technical effects of the present invention are verified through specific embodiments below, but the implementation manners of the present invention are not limited thereto.

[0016] Example 1

[0017] Preparation of lithium sulfate: After ball-milling spodumene, it is added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification treatment for 3.2 h. The lithium in the lithium ore is calculated as lithium carbonate, the molar ratio of sulfuric acid to lithium carbonate is 1.25∶1, the solution is diluted with water to 6 times its volume and stirred for 2 h, then slaked lime is added to adjust the pH value to 7.5 and then filtered to obtain a crude lithium sulfate solution. Then, calcium hypochlorite as an oxidant is added, stirred for 15 min and then filtered, and then sodium hydroxide is added to adjust the pH value to 12.2. Sodium carbonate with a weight of 1.8 wt% of the spodumene is further added, stirred for 30 min and then the solution volume is concentrated to half, and after filtration, a lithium sulfate solution is obtained.

[0018] Preparation of lithium sulfide: Tartaric acid is added to the lithium sulfate solution as a carbon source, and then microparticles with a particle size D50 = 0.42 μm are obtained by spray granulation drying technology at 172 °C. During the granulation process, the particle size of the microparticles is adjusted by controlling the rotation speed of the granulation disk. The microparticles are calcined at 1040 °C in a protective atmosphere for 8 h, then washed with absolute ethanol several times, and finally evaporated and crystallized to obtain high-purity lithium sulfide powder.

[0019] Example 2

[0020] Preparation of lithium sulfate: After ball-milling spodumene, it was added to deionized water, and then 98% concentrated sulfuric acid was slowly added under stirring for acidification treatment for 3.2 h. The lithium in the lithium ore was calculated as lithium carbonate, and the molar ratio of sulfuric acid to lithium carbonate was 1.25:1. It was diluted with water to 6 times the volume of the solution and stirred for 2 h. Then, slaked lime was added to adjust the pH value to 7.5, and after filtration, a crude lithium sulfate solution was obtained. Then, calcium hypochlorite as an oxidant was added, stirred for 15 min and then filtered. Then, sodium hydroxide was added to adjust the pH value to 12.2, and 1.8 wt% of sodium carbonate based on the weight of spodumene was continuously added. After stirring for 30 min, the volume of the solution was concentrated to half, and after filtration, a lithium sulfate solution was obtained.

[0021] Preparation of lithium sulfide: Tartaric acid was added to the lithium sulfate solution as a carbon source, and then microparticles with a particle size D50 = 0.85 μm were obtained by spray granulation drying technology at 172 °C. During the granulation process, the particle size of the microparticles was adjusted by controlling the rotation speed of the granulation disk. The microparticles were calcined in a protective atmosphere at 1040 °C for 8 h, then washed several times with absolute ethanol, and finally high-purity lithium sulfide powder was obtained by evaporation crystallization.

[0022] Example 3

[0023] Preparation of lithium sulfate: After ball-milling spodumene, it was added to deionized water, and then 98% concentrated sulfuric acid was slowly added under stirring for acidification treatment for 3.2 h. The lithium in the lithium ore was calculated as lithium carbonate, and the molar ratio of sulfuric acid to lithium carbonate was 1.25:1. It was diluted with water to 6 times the volume of the solution and stirred for 2 h. Then, slaked lime was added to adjust the pH value to 7.5, and after filtration, a crude lithium sulfate solution was obtained. Then, calcium hypochlorite as an oxidant was added, stirred for 15 min and then filtered. Then, sodium hydroxide was added to adjust the pH value to 12.2, and 1.8 wt% of sodium carbonate based on the weight of spodumene was continuously added. After stirring for 30 min, the volume of the solution was concentrated to half, and after filtration, a lithium sulfate solution was obtained.

[0024] Preparation of lithium sulfide: Tartaric acid was added to the lithium sulfate solution as a carbon source, and then microparticles with a particle size D50 = 1.27 μm were obtained by spray granulation drying technology at 172 °C. During the granulation process, the particle size of the microparticles was adjusted by controlling the rotation speed of the granulation disk. The microparticles were calcined in a protective atmosphere at 1040 °C for 8 h, then washed several times with absolute ethanol, and finally high-purity lithium sulfide powder was obtained by evaporation crystallization.

[0025] Example 4

[0026] Preparation of lithium sulfate: After ball-milling spodumene, it is added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification treatment for 3.2 h. Here, the lithium in the lithium ore is calculated as lithium carbonate, and the molar ratio of sulfuric acid to lithium carbonate is 1.25:1. It is diluted with water to 6 times the volume of the solution and stirred for 2 h. Then, slaked lime is added to adjust the pH value to 7.5, and after filtration, a crude lithium sulfate solution is obtained. Then, calcium hypochlorite as an oxidant is added, stirred for 15 min and then filtered. Then, sodium hydroxide is added to adjust the pH value to 12.2, and 1.8 wt% of sodium carbonate based on the weight of spodumene is continuously added. After stirring for 30 min, the volume of the solution is concentrated to half, and after filtration, a lithium sulfate solution is obtained.

[0027] Preparation of lithium sulfide: Tartaric acid is added to the lithium sulfate solution as a carbon source, and then microparticles with a particle size D50 = 1.95 μm are obtained by spray granulation drying technology at 172 °C. During the granulation process, the particle size of the microparticles is adjusted by controlling the rotation speed of the granulation disk. The microparticles are calcined in a protective atmosphere at 1040 °C for 8 h, then washed several times with absolute ethanol, and finally high-purity lithium sulfide powder is obtained by evaporation crystallization.

[0028] Example 5

[0029] Preparation of lithium sulfate: After ball-milling spodumene, it is added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification treatment for 3.2 h. Here, the lithium in the lithium ore is calculated as lithium carbonate, and the molar ratio of sulfuric acid to lithium carbonate is 1.25:1. It is diluted with water to 6 times the volume of the solution and stirred for 2 h. Then, slaked lime is added to adjust the pH value to 7.5, and after filtration, a crude lithium sulfate solution is obtained. Then, calcium hypochlorite as an oxidant is added, stirred for 15 min and then filtered. Then, sodium hydroxide is added to adjust the pH value to 12.2, and 1.8 wt% of sodium carbonate based on the weight of spodumene is continuously added. After stirring for 30 min, the volume of the solution is concentrated to half, and after filtration, a lithium sulfate solution is obtained.

[0030] Preparation of lithium sulfide: Tartaric acid is added to the lithium sulfate solution as a carbon source, and then microparticles with a particle size D50 = 2.39 μm are obtained by spray granulation drying technology at 172 °C. During the granulation process, the particle size of the microparticles is adjusted by controlling the rotation speed of the granulation disk. The microparticles are calcined in a protective atmosphere at 1040 °C for 8 h, then washed several times with absolute ethanol, and finally high-purity lithium sulfide powder is obtained by evaporation crystallization.

[0031] Comparative Example 1

[0032] Preparation of lithium sulfate: After ball-milling spodumene, it is added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification treatment for 3.2 h. The lithium in the lithium ore is calculated as lithium carbonate, and the molar ratio of sulfuric acid to lithium carbonate is 1.25:1. It is diluted with water to 6 times the volume of the solution and stirred for 2 h. Then, slaked lime is added to adjust the pH value to 7.5, and after filtration, a crude lithium sulfate solution is obtained. Then, calcium hypochlorite as an oxidant is added, stirred for 15 min and then filtered. Sodium hydroxide is added again to adjust the pH value to 12.2, and sodium carbonate accounting for 1.8 wt% of the weight of spodumene is continuously added. After stirring for 30 min, the volume of the solution is concentrated to half, and after filtration, a lithium sulfate solution is obtained.

[0033] Preparation of lithium sulfide: Tartaric acid is added to the lithium sulfate solution as a carbon source, and then microparticles with a particle size D50 = 0.12 μm are obtained by spray granulation drying technology at 172 °C. During the granulation process, the particle size of the microparticles is adjusted by controlling the rotation speed of the granulation disk. The microparticles are calcined in a protective atmosphere at 1040 °C for 8 h, then washed several times with absolute ethanol, and finally lithium sulfide powder is obtained by evaporation crystallization.

[0034] Comparative Example 2

[0035] Preparation of lithium sulfate: After ball-milling spodumene, it is added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification treatment for 3.2 h. The lithium in the lithium ore is calculated as lithium carbonate, and the molar ratio of sulfuric acid to lithium carbonate is 1.25:1. It is diluted with water to 6 times the volume of the solution and stirred for 2 h. Then, slaked lime is added to adjust the pH value to 7.5, and after filtration, a crude lithium sulfate solution is obtained. Then, calcium hypochlorite as an oxidant is added, stirred for 15 min and then filtered. Sodium hydroxide is added again to adjust the pH value to 12.2, and sodium carbonate accounting for 1.8 wt% of the weight of spodumene is continuously added. After stirring for 30 min, the volume of the solution is concentrated to half, and after filtration, a lithium sulfate solution is obtained.

[0036] Preparation of lithium sulfide: Tartaric acid is added to the lithium sulfate solution as a carbon source, and then microparticles with a particle size D50 = 5.34 μm are obtained by spray granulation drying technology at 172 °C. During the granulation process, the particle size of the microparticles is adjusted by controlling the rotation speed of the granulation disk. The microparticles are calcined in a protective atmosphere at 1040 °C for 8 h, then washed several times with absolute ethanol, and finally lithium sulfide powder is obtained by evaporation crystallization.

[0037] Next, we evaluated the lithium sulfide yield of the experimental samples in Examples 1-5 and Comparative Examples 1-2, and configured the electrolyte according to the molar ratio of Li2S:P2S5:LiCl = 5:1:2 to evaluate its conductivity at 25 °C. The test results are shown in Table 1.

[0038] Table 1 Test data of each sample

[0039] Number Yield of lithium sulfide Conductivity mS / cm Example 1 95.6 4.62 Example 2 97.2 4.81 Example 3 96.9 4.75 Example 4 95.6 4.70 Example 5 95.3 4.60 Comparative Example 1 90.7 4.51 Comparative Example 2 95.0 4.25

[0040] As can be seen from Table 1, in the granulation process of the present invention, the average particle size of the microparticles is controlled within 0.42 μm - 2.39 μm by controlling the rotation speed of the granulation disk, the lithium sulfide yield can be above 95%, and the conductivity of the Li2S / P2S5 / LiCl electrolyte at 25°C is higher than 4.5 mS / cm. It is worth mentioning that the spray granulation drying technology is a very mature technology, and adjusting the particle size by controlling the rotation speed of the granulation disk is also a technical means well-known to those skilled in the art. The principle thereof will not be elaborated in the present invention. In addition, to ensure the comparability of each group of experiments, only the granulation particle size is different in each example and comparative example of the present invention, and the remaining process parameters are exactly the same.

[0041] The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing high-purity lithium sulfide from a lithium sulfate solution obtained by extracting lithium from lithium ore, characterized in that, The method includes the following steps: Preparation of lithium sulfate from lithium ore: After ball-milling spodumene, add it to deionized water, and then slowly add concentrated sulfuric acid under stirring for acidification treatment for 3.2 - 4.2 h. Here, the lithium in the lithium ore is calculated as lithium carbonate, and the molar ratio of sulfuric acid to lithium carbonate is 1.25 - 1.30∶1. Dilute with water to 6 - 8 times the volume of the solution and stir for 2 - 5 h. Then add slaked lime to adjust the pH value to 7.5 - 7.8 and filter to obtain a crude lithium sulfate solution. Then add calcium hypochlorite as an oxidant, stir for 15 - 30 min and filter. Then add sodium hydroxide to adjust the pH value to 12.2 - 12.5, continue to add sodium carbonate accounting for 1.8 - 2.2 wt% of the weight of spodumene, stir for 30 - 45 min and then concentrate the solution volume to half, and filter to obtain a lithium sulfate solution; Preparation of lithium sulfide from lithium sulfate: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain microparticles with a particle size D50 = 0.42 - 2.39 μm through spray granulation drying technology. During the granulation process, adjust the particle size of the microparticles by controlling the rotation speed of the granulation disk. Calcinate the microparticles in a protective atmosphere at 860 - 1040 °C for 8 - 10 h, then wash with absolute ethanol several times, and finally obtain high-purity lithium sulfide powder by evaporation crystallization.

2. A method according to claim 1, characterized in that, The particle size D50 of the microparticles is 0.85 μm.

3. A method as claimed in claim 1, wherein, The calcination temperature is 860 °C.

4. A method according to claim 1, characterized in that, The calcination time is 8 h.

5. A method according to claim 1, characterized in that, The yield of the lithium sulfide powder exceeds 95%.

6. A sulfide solid electrolyte, characterized in that, The molar composition of the electrolyte is Li2S∶P2S5∶LiCl = 5∶1∶2, and the lithium sulfide is prepared by the method according to any one of claims 1 - 5.

7. A sulfide solid electrolyte as described in claim 6, characterized in that, The Li2S / P2S5 / LiCl electrolyte configured with the lithium sulfide has a conductivity higher than 4.5 mS / cm at 25 °C.