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

Abstract

The invention discloses a method for preparing high-purity lithium sulfide based on a lithium sulfate solution for extracting lithium from lithium ore and sulfide solid electrolyte. In the granulation process, the average particle size of the particles is controlled to be 0.42-2.39 [mu] m by controlling the rotating speed of the granulation disc, the yield of lithium sulfide can be 95% or above, and the conductivity of the Li2S / P2S5 / Li Cl electrolyte at the temperature of 25 DEG C is higher than 4.5 mS / cm. It needs to be noted that the yield of lithium sulfide powder is reduced due to the fact that the granulation particle size is too small, the conductivity of electrolyte is reduced due to the fact that the granulation particle size is too large, and therefore the granulation particle size needs to be strictly controlled in practice.

Description

Technical Field

[0001] The present invention relates to the field of advanced inorganic non-metallic materials and lithium battery electrolytes, and in particular 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, belonging to alkali metal sulfides. In the prior art, lithium sulfide is widely used in the field of battery positive electrode materials and solid electrolyte synthesis. Among them, when lithium sulfide is used as the positive electrode material of lithium-sulfur batteries, 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 used in new energy batteries is a very meaningful topic. Summary of the invention

[0003] The object 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, wherein the method can obtain lithium sulfide powder with high yield and high electrical 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] Preparation of lithium sulfate: spodumene is ball-milled and added to deionized water, and then concentrated sulfuric acid is slowly added under stirring for acidification for 3.2-4.2 hours, wherein 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, water is added to dilute the solution to 6-8 times the volume and stir for 2-5 hours, then slaked lime is added to adjust the pH value to 7.5-7.8 and then filtered to obtain a crude lithium sulfate solution, then calcium hypochlorite is added as an oxidant, stirred for 15-30 minutes and then filtered, then sodium hydroxide is added to adjust the pH value to 12.2-12.5, and sodium carbonate with a weight of 1.8-2.2wt% of the spodumene is added, stirred for 30-45 minutes, and then the solution volume is concentrated to half, and filtered to obtain a lithium sulfate solution;

[0007] Preparation of lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain particles with a particle size of D50 = 0.42-2.39 μm through spray granulation and drying technology. Adjust the particle size of the particles by controlling the rotation speed of the granulation disk during the granulation process. Calcine the particles at 860-1040°C in a protective atmosphere for 8-10 hours, then wash them with anhydrous ethanol several times, and finally evaporate and crystallize to obtain high-purity lithium sulfide powder.

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

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

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

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

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

[0013] Preferably, the lithium sulfide-configured Li2S / P2S5 / LiC1 electrolyte has a conductivity higher than 4.5 mS / cm at 25°C.

[0014] In the present invention, the average particle size of the particles is controlled to be 0.42 μm-2.39 μm by controlling the rotation speed of the granulation disk during the granulation process, so that the lithium sulfide yield is 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 if the granulation particle size is too low, the yield of the lithium sulfide powder will be reduced, and if the granulation particle size is too high, the conductivity of the electrolyte will be reduced. Therefore, the granulation particle size needs to be strictly controlled in practice. DETAILED DESCRIPTION

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

[0016] Example 1

[0017] Preparation of lithium sulfate: spodumene is ball-milled and added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification for 3.2 hours, wherein 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, and water is added to dilute to 6 times the volume of the solution and stirred for 2 hours, and then slaked lime is added to adjust the pH value to 7.5 and filter to obtain a crude lithium sulfate solution, and then add an oxidant calcium hypochlorite, stir for 15 minutes and filter, and then add sodium hydroxide to adjust the pH value to 12.2, and continue to add sodium carbonate 1.8wt% of the weight of spodumene, stir for 30 minutes, concentrate the solution volume to half, and filter to obtain a lithium sulfate solution.

[0018] Preparation of lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain particles with a particle size of D50 = 0.42 μm by spray granulation and drying technology at 172°C. Adjust the particle size of the particles by controlling the rotation speed of the granulation disk during the granulation process. Calcine the particles at 1040°C in a protective atmosphere for 8 hours, then wash them several times with anhydrous ethanol, and finally evaporate and crystallize to obtain high-purity lithium sulfide powder.

[0019] Example 2

[0020] Preparation of lithium sulfate: spodumene is ball-milled and added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification for 3.2 hours, wherein 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, and water is added to dilute to 6 times the volume of the solution and stirred for 2 hours, and then slaked lime is added to adjust the pH value to 7.5 and filter to obtain a crude lithium sulfate solution, and then add an oxidant calcium hypochlorite, stir for 15 minutes and filter, and then add sodium hydroxide to adjust the pH value to 12.2, and continue to add sodium carbonate 1.8wt% of the weight of spodumene, stir for 30 minutes, concentrate the solution volume to half, and filter to obtain a lithium sulfate solution.

[0021] Preparation of lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain particles with a particle size of D50 = 0.85 μm by spray granulation and drying technology at 172°C. Adjust the particle size of the particles by controlling the rotation speed of the granulation disk during the granulation process. Calcine the particles at 1040°C in a protective atmosphere for 8 hours, then wash them several times with anhydrous ethanol, and finally evaporate and crystallize to obtain high-purity lithium sulfide powder.

[0022] Example 3

[0023] Preparation of lithium sulfate: spodumene is ball-milled and added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification for 3.2 hours, wherein 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, and water is added to dilute to 6 times the volume of the solution and stirred for 2 hours, and then slaked lime is added to adjust the pH value to 7.5 and filter to obtain a crude lithium sulfate solution, and then add an oxidant calcium hypochlorite, stir for 15 minutes and filter, and then add sodium hydroxide to adjust the pH value to 12.2, and continue to add sodium carbonate 1.8wt% of the weight of spodumene, stir for 30 minutes, concentrate the solution volume to half, and filter to obtain a lithium sulfate solution.

[0024] Preparation of lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain particles with a particle size of D50 = 1.27 μm by spray granulation and drying technology at 172°C. Adjust the particle size of the particles by controlling the rotation speed of the granulation disk during the granulation process. Calcine the particles at 1040°C in a protective atmosphere for 8 hours, then wash them several times with anhydrous ethanol, and finally evaporate and crystallize to obtain high-purity lithium sulfide powder.

[0025] Example 4

[0026] Preparation of lithium sulfate: spodumene is ball-milled and added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification for 3.2 hours, wherein 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, and water is added to dilute to 6 times the volume of the solution and stirred for 2 hours, and then slaked lime is added to adjust the pH value to 7.5 and filter to obtain a crude lithium sulfate solution, and then add an oxidant calcium hypochlorite, stir for 15 minutes and filter, and then add sodium hydroxide to adjust the pH value to 12.2, and continue to add sodium carbonate 1.8wt% of the weight of spodumene, stir for 30 minutes, concentrate the solution volume to half, and filter to obtain a lithium sulfate solution.

[0027] Preparation of lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain particles with a particle size of D50 = 1.95 μm by spray granulation and drying technology at 172°C. During the granulation process, the particle size of the particles is adjusted by controlling the rotation speed of the granulation disk. The particles are calcined at 1040°C in a protective atmosphere for 8 hours, then washed several times with anhydrous ethanol, and finally evaporated and crystallized to obtain high-purity lithium sulfide powder.

[0028] Example 5

[0029] Preparation of lithium sulfate: spodumene is ball-milled and added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification for 3.2 hours, wherein 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, and water is added to dilute to 6 times the volume of the solution and stirred for 2 hours, and then slaked lime is added to adjust the pH value to 7.5 and filter to obtain a crude lithium sulfate solution, and then add an oxidant calcium hypochlorite, stir for 15 minutes and filter, and then add sodium hydroxide to adjust the pH value to 12.2, and continue to add sodium carbonate 1.8wt% of the weight of spodumene, stir for 30 minutes, concentrate the solution volume to half, and filter to obtain a lithium sulfate solution.

[0030] Preparation of lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain particles with a particle size of D50 = 2.39 μm by spray granulation and drying technology at 172°C. During the granulation process, the particle size of the particles is adjusted by controlling the rotation speed of the granulation disk. The particles are calcined at 1040°C in a protective atmosphere for 8 hours, then washed several times with anhydrous ethanol, and finally evaporated and crystallized to obtain high-purity lithium sulfide powder.

[0031] Comparative Example 1

[0032] Preparation of lithium sulfate: spodumene is ball-milled and added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification for 3.2 hours, wherein 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, and water is added to dilute to 6 times the volume of the solution and stirred for 2 hours, and then slaked lime is added to adjust the pH value to 7.5 and filter to obtain a crude lithium sulfate solution, and then add an oxidant calcium hypochlorite, stir for 15 minutes and filter, and then add sodium hydroxide to adjust the pH value to 12.2, and continue to add sodium carbonate 1.8wt% of the weight of spodumene, stir for 30 minutes, concentrate the solution volume to half, and filter to obtain a lithium sulfate solution.

[0033] Preparation of lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain microparticles with a particle size of D50 = 0.12 μm by spray granulation and drying technology at 172°C. Adjust the particle size of the microparticles by controlling the rotation speed of the granulation disk during the granulation process. Calcine the microparticles at 1040°C in a protective atmosphere for 8 hours, then wash them several times with anhydrous ethanol, and finally evaporate and crystallize to obtain lithium sulfide powder.

[0034] Comparative Example 2

[0035] Preparation of lithium sulfate: spodumene is ball-milled and added to deionized water, and then 98% concentrated sulfuric acid is slowly added under stirring for acidification for 3.2 hours, wherein 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, and water is added to dilute to 6 times the volume of the solution and stirred for 2 hours, and then slaked lime is added to adjust the pH value to 7.5 and filter to obtain a crude lithium sulfate solution, and then add an oxidant calcium hypochlorite, stir for 15 minutes and filter, and then add sodium hydroxide to adjust the pH value to 12.2, and continue to add sodium carbonate 1.8wt% of the weight of spodumene, stir for 30 minutes, concentrate the solution volume to half, and filter to obtain a lithium sulfate solution.

[0036] Preparation of lithium sulfide: Add tartaric acid as a carbon source to the lithium sulfate solution, and then obtain particles with a particle size of D50 = 5.34 μm by spray granulation and drying technology at 172°C. Adjust the particle size of the particles by controlling the rotation speed of the granulation disk during the granulation process. Calcine the particles at 1040°C in a protective atmosphere for 8 hours, then wash them several times with anhydrous ethanol, and finally evaporate and crystallize to obtain lithium sulfide powder.

[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] serial number Lithium sulfide yield 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, the present invention controls the average particle size of the microparticles to 0.42μm-2.39μm by controlling the rotation speed of the granulation disk during the granulation process, which can make the lithium sulfide yield above 95%, and the conductivity of the Li2S / P2S5 / LiCl electrolyte at 25°C is higher than 4.5mS / cm. It is worth mentioning that the spray granulation drying technology is a very mature technology, and adjusting the particle size of the microparticles by controlling the rotation speed of the granulation disk is also a technical means well known to ordinary technicians in this technical field, and the present invention will not repeat the principle thereof. In addition, in order to ensure the comparability of each group of experiments, only the granulation particle size is different in each embodiment and comparative example of the present invention, and the other process parameters are exactly the same.

[0041] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing high-purity lithium sulfide from a lithium sulfate solution based on lithium extraction from lithium ore, characterized in that: The method comprises the following steps: Preparation of lithium sulfate from lithium ore: spodumene is ball-milled and added to deionized water, and then concentrated sulfuric acid is slowly added under stirring for acidification for 3.2-4.2 hours, wherein 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, water is added to dilute to 6-8 times the volume of the solution and stirred for 2-5 hours, then slaked lime is added to adjust the pH value to 7.5-7.8 and then filtered to obtain a crude lithium sulfate solution, and then calcium hypochlorite is added as an oxidant, stirred for 15-30 minutes and then filtered, and then sodium hydroxide is added to adjust the pH value to 12.2-12.5, and sodium carbonate with a weight of 1.8-2.2wt% of the spodumene is continuously added, and the solution volume is concentrated to half after stirring for 30-45 minutes, and then filtered to obtain a lithium sulfate solution; Preparation of lithium sulfide from lithium sulfate: tartaric acid is added as a carbon source to the lithium sulfate solution, and then the spray granulation and drying technology is used to obtain particles with a particle size of D50 = 0.42-2.39 μm. The particle size of the particles is adjusted by controlling the rotation speed of the granulation disk during the granulation process. The particles are calcined at 860-1040°C in a protective atmosphere for 8-10 hours, then washed several times with anhydrous ethanol, and finally evaporated and crystallized to obtain high-purity lithium sulfide powder.

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

3. A method according to claim 1, characterized in that The calcination temperature is 860°C.

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

5. A method according to claim 1, characterized in that The yield of the lithium sulfide powder is over 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 any one of claims 1-5.

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