Method for producing lithium metal, lithium sulfide and aluminum-silicon-iron alloy through electrolytic reduction of lithium ore

Abstract

According to the method for producing the metal lithium, the lithium sulfide and the aluminum-silicon-iron alloy through electrolytic reduction of the lithium ore, environmental pollution caused by traditional lithium ore roasting and sulfuric acid leaching is reduced, elements such as Li, Al, Si and Fe in the lithium ore are utilized in a high-valued mode, the problem of emission of acidolysis residues in a wet-method lithium extraction process is solved, the production efficiency is high, and the method is suitable for industrial production. According to the method, lithium sulfide is synthesized from lithium ore through a one-step method, a lithium-rich mixture is directly used as a lithium source, the link of producing lithium sulfate and then carrying out carbon reduction is reduced, low-cost manufacturing of lithium sulfide is achieved, commercialization is easy, C is removed through organic solvent leaching, S and O are removed through high-temperature sintering, the crystal form and granularity of lithium sulfide are controlled through ball grinding, the purity of the product is improved, and the method is suitable for industrial production. The direct-current closed submerged arc furnace is more energy-saving and efficient, and meanwhile, a carbon reducing agent is reduced through electrolytic reaction, so that carbon emission is reduced.

Description

Technical Field

[0001] This invention relates to the field of lithium sulfide and aluminum-silicon-iron alloy metallurgical technology, specifically to a method for producing lithium, lithium sulfide and aluminum-silicon-iron alloy by electrolytic synergistic carbothermic reduction of lithium ore under the action of a DC electric field. Background Technology

[0002] Lithium-ion batteries are a crucial component of the current clean energy system, offering an effective way to reduce dependence on traditional fossil fuels, particularly in power supplies and energy storage for automobiles, ships, and aerospace equipment. However, currently commercially available lithium-ion batteries use...

[0003] The electrolyte is mainly an organic liquid or gel electrolyte, which is prone to leakage, flammability, explosion and other safety accidents, posing potential safety hazards to lithium-ion batteries.

[0004] Lithium sulfide possesses a high theoretical specific capacity (1166 mAh / g), making it a crucial component of novel high-energy, high-safety solid-state lithium-ion batteries. It is also a raw material for solid-state sulfide electrolytes (Li6-xPS5-xCl1+x) and a cathode material for high-capacity lithium-sulfur batteries. Sulfide solid-state electrolytes have garnered widespread attention both domestically and internationally due to their extremely high ionic conductivity. However, sulfide solid-state electrolytes also face drawbacks affecting their widespread application, namely cost. The high price of lithium sulfide, a key raw material, keeps the cost of sulfide solid-state electrolytes high. Therefore, developing a low-cost, large-scale method for preparing battery-grade lithium sulfide is crucial for realizing the large-scale application of sulfide electrolytes.

[0005] Currently, methods for synthesizing lithium sulfide can be categorized into ball milling, solvent method, high-temperature and high-pressure method, and carbothermal reduction method.

[0006] Ball milling method: Under an inert atmosphere, elemental sulfur and metallic lithium / lithium hydride are mixed in a certain proportion and then mechanically ball-milled to obtain lithium sulfide. The disadvantages are high raw material cost (lithium hydride), long reaction time, low conversion rate, and the presence of impurities such as lithium polysulfides in the obtained product, making purification difficult and equipment selection challenging for industrial applications.

[0007] Solvent method: Lithium sulfide is prepared by reacting lithium / lithium compounds and sulfur / sulfur compounds in a solvent medium. Disadvantages include the flammability, explosiveness, and volatility of organic solvents, causing severe environmental pollution and making recycling difficult; the operating conditions are also highly hazardous and difficult to control.

[0008] High-temperature and high-pressure method: Under an inert / reducing protective atmosphere, lithium / lithium compounds and sulfur / sulfur compounds are reacted at high temperature and high pressure to prepare lithium sulfide through reduction or gas-phase reactions. The disadvantages are that the high temperature and high pressure make operating conditions difficult to control, require sophisticated equipment selection, and increase the risks associated with the reaction process and post-processing.

[0009] Carbothermic reduction method: This method uses carbon and Li₂SO₄ as raw materials. Utilizing the strong reducing properties of carbon, carbon materials / carbon precursors are directly added to the lithium sulfide preparation reaction, resulting in a one-step synthesis of uniformly dispersed and high-performance lithium sulfide / carbon composite materials. Carbothermic reduction of Li₂SO₄ is one of the mainstream methods for preparing Li₂S in the market and is also the main method for preparing Li₂S@C composite materials in lithium-sulfur battery systems. The disadvantage is that the product may contain Li₂O, Li₂CO₃, S, etc., requiring further purification. Summary of the Invention

[0010] (a) Technical problems to be solved

[0011] To address the aforementioned problems in the prior art, this invention provides a method for producing lithium sulfide and aluminum-silicon-iron alloy by electrolytic synergistic carbothermic reduction of lithium ore under the action of a DC electric field, thereby solving a series of problems in the prior art, such as high energy consumption, high production cost, low purity of lithium sulfide, difficulty in disposing of and utilizing lithium slag, and significant environmental pollution.

[0012] (2) Technical solution

[0013] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0014] A method for producing metallic lithium, lithium sulfide, and aluminum-silicon-iron alloy by electrolytic reduction of lithium ore involves the following steps: Under the action of direct current, lithium ore melts due to Joule heating and electrochemical reaction. Oxides in the lithium ore move towards the cathode and are reduced to metallic alloys, while oxygen ions [O2-] move towards the anode and are oxidized to oxygen. The lithium ore undergoes an electrolytic reaction between the electrodes to generate a primary aluminum-silicon-iron alloy liquid. Simultaneously, the molten liquid undergoes a reduction reaction around the electrodes under the action of a carbon reducing agent to generate the aluminum-silicon-iron alloy. Metallic lithium volatilizes into the flue gas and is enriched through a condensation and dust collection system. The lithium-rich mixture is then mixed with sulfuric acid and carbon powder, and crude lithium sulfide is synthesized at high temperature under an inert atmosphere. The crude lithium sulfide is then leached with an organic solvent, separated, distilled, dried, and crushed to obtain high-purity lithium sulfide.

[0015] S1: The smelting equipment is a DC closed submerged arc furnace, which includes a rectifier system, an electrode control system, a charging system, a water cooling system, and a flue gas purification system; the charging system includes charging zone A and charging zone B.

[0016] S2:A feeding zone is located in the central area of ​​the submerged arc furnace, where lithium ore granules are added through the feeding pipe. During the closing operation, under the action of a large DC current and plasma gas, both the anode and cathode are fully arced, heating the lithium ore into a molten state. Lithium ore granules are then added, and an electrochemical reaction occurs between the electrodes to decompose the lithium ore, producing a primary aluminum-silicon-iron alloy.

[0017] S3:B The feeding zone is located outside the electrode. After the furnace charge is heated to a given temperature, a mixture of lithium ore and coke in a certain proportion is added through the feeding pipe to carry out a carbothermic reduction reaction and prepare a primary aluminum-silicon-iron alloy.

[0018] S4: The primary alloy liquid is periodically discharged through the tap hole, and the aluminum-silicon-iron alloy is sent for refining.

[0019] S5: The smelting flue gas is processed through a condensation and dust collection system to recover a lithium-rich mixture. This mixture is then combined with sulfuric acid and carbon powder, and crude lithium sulfide is synthesized at high temperature under an inert atmosphere. The crude lithium sulfide is then leached with an organic solvent, separated, distilled with a solvent, dried, sintered, and crushed to obtain high-purity lithium sulfide. The solvent leaching residue is returned to the DC submerged arc furnace for smelting.

[0020] Preferably, the lithium ore is one or more of spodumene, lepidolite, and clay-type lithium ore mixed in any proportion, and the lithium ore particle size is 0-30mm, used in feeding zone A.

[0021] Preferably, the particle size of the lithium ore and coke mixture is 20-60 mm, and the mass ratio of lithium ore to coke is 1-4:1, for use in feeding zone B.

[0022] Preferably, the carbothermic reaction temperature of lithium ore is 1500–2200℃, and the reaction time is 1–24h.

[0023] Preferably, the main components of the lithium-rich mixture recovered in the condenser are Li, Li₂O, carbon ash, and aluminosilicate dust. The lithium-rich mixture is mixed with carbon powder and sulfur powder to achieve carbothermic reduction of Li₂O to generate metallic lithium, followed by high-temperature synthesis of Li₂S from Li and S. The molar ratio of Li₂O to C in the lithium-rich mixture is 2:1 to 1.1, and the molar ratio of Li to S is 2:0.95 to 1. The reduction temperature of the lithium-rich mixture with sulfuric acid and carbon powder is 750 to 850°C. The inert gas is either nitrogen or argon.

[0024] Preferably, crude lithium sulfide is leached with an organic solvent, wherein the organic solvent is one or more of anhydrous ethanol, anhydrous methanol, and anhydrous isopropanol; the solid-liquid ratio of the lithium-rich mixture to the organic solvent is 1:5 to 15; the leaching reaction is carried out by mixing and reacting in a closed ball mill for 2 to 4 hours through a feeding system, with nitrogen protection in the system; the slurry after the reaction is transported to a filtration and distillation system through a closed pipeline; the filter residue is returned to the electric arc furnace for smelting; the filtrate is distilled under reduced pressure to obtain the lithium sulfide precursor at a distillation temperature of 80 to 120°C; the evaporated solvent is collected in a storage tank through a condenser for recycling. The lithium sulfide precursor is first dried at 100–300℃ for 4–8 hours, and then sintered in a vacuum furnace at 650–850℃ for 4–8 hours to further remove residual solvent and a small amount of sulfur from the lithium sulfide. The sintered lithium sulfide is then added to a dry ball mill and crushed and ball-milled to obtain the lithium sulfide product with the required particle size. The dry ball mill is placed in a glove box, which is a closed system, and the particle size of the lithium sulfide is 200–300 mesh.

[0025] The main reaction processes involved in the electrolytic synergistic carbothermic reduction of this invention are as follows:

[0026]

[0027] Si 4+ +4e-→Si (4)

[0028] 4Al + 3SiO2 → 2Al2O3 + 3Si (5)

[0029]

[0030] 2[O 2- -4e-→O2 (7)

[0031] SiO2(I)+2C(s)=Si(I)+2CO(g) (8)

[0032] SiO2(I)+C(s)=SiO(g)+CO(g) (9)

[0033] SiO2(I)+3C(s)=SiC(s)+2CO(g) (10)

[0034] SiO2(I)+2SiC(s)=3Si(I)+2CO(g) (11)

[0035] Al2O3(s)+3C(s)=2Al(I)+3CO(g) (12)

[0036] Al2O3(s)+2C(s)=Al2O(g)+2CO(g) (13)

[0037] 2Al2O3(s)+9C(s)=Al4C3(I)+6CO(g) (14)

[0038] Al4C3(I)+Al2O3(s)=6Al(I)+3CO(g) (15)

[0039] 3SiO2(I)+2Al2O3(s)+12C(s)=3Si(I)+4Al(I)+12CO(g) (16)

[0040] 2LiAISi2O6+13C→4SiC+Al2O3+2Li(g)+9CO(g) (17)

[0041] The main reaction process for synthesizing lithium sulfide in this invention is as follows:

[0042]

[0043] In the process of electrolytic and carbothermic reduction of alumina and silicon dioxide, intermediate products such as Al4C3 and SiC carbides react with Al2O3 to form an aluminum-silicon-iron alloy. Since aluminum can be infinitely molten in silicon, the thermodynamic conditions for aluminum reduction are greatly improved in the presence of silicon, making the electrothermal and electrolytic production of aluminum-silicon-iron alloys a reality.

[0044] In the carbothermic reduction of aluminum-silicon alloys, the presence of Fe significantly lowers the onset temperature of the alloy formation reaction. Furthermore, Fe is infinitely miscible with Al and Si in the molten state, and free Fe helps to break down carbides that are easily formed during carbothermic reduction. With sufficient iron present in the reaction, the reduced aluminum and silicon dissolve in the iron, reducing the activity of aluminum and silicon. This allows the reduction reaction of aluminum and silicon oxides to proceed at relatively low temperatures, resulting in an alloy melt that becomes aluminum-silicon-iron.

[0045] The lithium-rich mixture recovered in the condenser of the electric arc furnace needs to be synthesized into crude lithium sulfide using sulfuric acid and carbon at high temperature. The crude product is then dissolved in an organic solvent to separate it from the ash collected by the carbon. The organic solvent is distilled to obtain the lithium sulfide precursor. The precursor is dried at low temperature and then sintered at high temperature to further remove sulfur and oxygen. After ball milling, high-purity lithium sulfide is obtained.

[0046] (III) Beneficial Effects

[0047] The beneficial effects of this invention are as follows:

[0048] This invention provides a method for producing lithium sulfide and aluminum-silicon-iron alloys from lithium ore through electrolytic synergistic carbothermic reduction under a DC electric field. This method reduces the environmental pollution associated with traditional lithium ore roasting and sulfuric acid leaching. Elements such as Li, Al, Si, and Fe in the lithium ore are utilized at high value, solving the problem of acid slag discharge in wet lithium extraction processes. The method boasts high production efficiency. This one-step method synthesizes lithium sulfide from lithium ore, directly using a lithium-rich mixture as the lithium source, eliminating the need for carbon reduction after lithium sulfate production. This achieves low-cost manufacturing of lithium sulfide and facilitates commercialization. Organic solvent leaching removes carbon, high-temperature sintering removes sulfur and oxygen, and ball milling controls the crystal form and particle size of lithium sulfide, improving product purity. The use of a DC closed submerged arc furnace is more energy-efficient and efficient. Furthermore, the electrolytic reaction reduces carbon reducing agents, thus reducing carbon emissions. Attached Figure Description

[0049] Figure 1 This is a process flow diagram of a method for producing lithium sulfide and aluminum-silicon-iron alloy from lithium ore by carbothermic reduction under a DC electric field, according to a specific embodiment of the present invention. Detailed Implementation

[0050] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Example 1

[0052] Please see Figure 1 A method for extracting lithium and aluminum-silicon-iron alloy from lithium ore by electrolytic synergistic carbothermic reduction under a DC electric field, the specific steps of which are as follows:

[0053] S1; The heating power of the DC closed submerged arc furnace control platform is set to 16500KVA and the furnace charge temperature to 2100℃;

[0054] S2: Lithium ore granules are added to the A feeding zone through the feed pipe, and the circuit is closed. Under the action of a high DC current and plasma gas, the anode and cathode are fully arced, and the lithium ore is heated into a melt. An electrochemical reaction occurs between the electrodes to decompose and electrolyze the lithium ore, preparing a primary aluminum-silicon-iron alloy. The lithium ore is spodumene, and its composition is shown in Table 1. The particle size is 0-30 mm.

[0055] S3: After the furnace charge is heated to 2200℃, a certain proportion of lithium ore, iron oxide chips and coke are added to the B charging zone through the feeding pipe. The mixture is dried under high pressure and briquetting to carry out a carbothermic reduction reaction to prepare a primary aluminum-silicon-iron alloy. The mass ratio of spodumene to coke is 3:1, the particle size of the mixture is 20-60mm, and the carbothermic reduction time is 4h.

[0056] S4: The primary alloy liquid is periodically discharged through the tapping port. The aluminum-silicon-iron alloy is then sent for refining. The composition of the aluminum-silicon-iron alloy is shown in Table 2.

[0057] S5: The smelting flue gas is condensed to recover a lithium-rich mixture. The composition of the lithium-rich mixture is shown in Table 3. Carbon powder and sulfuric acid are prepared according to the molar ratio of Li2O to C in the lithium-rich mixture being 2:1.05 and the molar ratio of Li to S in the lithium-rich mixture being 2:0.98. Under argon protection, it is reduced at 800℃ for 4 hours to obtain crude lithium sulfide. The crude lithium sulfide is leached with anhydrous ethanol, and the solid-liquid ratio of crude lithium sulfide to ethanol is 1:10. The mixture is mixed and reacted in a closed ball mill for 2.5 hours through a feeding system. The system is under nitrogen protection. The slurry after the reaction is transported to the filtration and distillation system through a closed pipeline. The filter residue is returned to the electric arc furnace for smelting. The filtrate is distilled under reduced pressure to obtain the lithium sulfide precursor. The distillation temperature is 80℃. The evaporated solvent is collected in a storage tank through a condenser for recycling. The lithium sulfide precursor was first dried at 200℃ for 4 hours, and then sintered in a vacuum furnace at 700℃ for 4 hours to further remove residual solvent and a small amount of sulfur. The sintered lithium sulfide was then fed into a dry ball mill for crushing and ball milling to obtain the desired lithium sulfide product in particle size. The dry ball mill was placed inside a glove box, forming a closed system, and the lithium sulfide particle size was 200–300 mesh. Testing showed that the lithium sulfide content was 99.5%.

[0058] Table 1. Composition of Spodumene

[0059]

[0060] Table 2. Gold Composition Table of Aluminum-Silicon-Iron Alloy

[0061] Element Si Al Mn C P S Fe content% 45.2 30.5 0.2 0.1 0.02 0.02 margin

[0062] Table 3. Composition of Lithium Mixture

[0063] Element Li C O N Al Si Fe content(%) 19.74 16.89 44.48 2.1 3.78 3.56 0.3

[0064] Example 2

[0065] Please see Figure 1 A method for extracting lithium and aluminum-silicon-iron alloy from lithium ore by electrolytic synergistic carbothermic reduction under a DC electric field, the specific steps of which are as follows:

[0066] S1: Set the heating power to 22500KVA and the furnace charge temperature to 2100℃ on the DC submerged arc furnace control platform;

[0067] S2: Lithium ore granules are added to the A feeding zone through the feed pipe, and the circuit is closed. Under the action of a high DC current and plasma gas, both the anode and cathode are fully arced, and the lithium ore is heated into a melt. An electrochemical reaction occurs between the electrodes to decompose the lithium ore and prepare a primary aluminum-silicon-iron alloy. The lithium ore is spodumene, and its composition is shown in Table 4. The particle size is 0-25 mm.

[0068] S3: After the furnace charge is heated to 2100℃, a certain proportion of lithium ore, iron oxide chips and coke, which has been dried by high pressure briquetting, are added to the B charging zone through the feeding pipe to carry out a carbothermic reduction reaction to prepare a primary aluminum-silicon-iron alloy; the mass ratio of spodumene to coke is 3.5:1, the particle size of the mixture is 0-55mm, and the carbothermic reduction time is 3h;

[0069] S4: The primary alloy liquid is periodically discharged through the tapping port. The aluminum-silicon-iron alloy is then sent for refining. The composition of the aluminum-silicon-iron alloy is shown in Table 5.

[0070] S5: The smelting flue gas is condensed to recover a lithium-rich mixture, the composition of which is shown in Table 6. Carbon powder and sulfuric acid are added according to a Li₂O to C molar ratio of 2:1 and a Li to S molar ratio of 2:1 in the lithium-rich mixture. Under argon protection, the mixture is reduced at 780℃ for 5 hours to obtain crude lithium sulfide. The crude lithium sulfide is leached with anhydrous isopropanol at a solid-liquid ratio of 1:9. The mixture is then mixed and reacted for 3 hours in a closed ball mill under nitrogen protection. The resulting slurry is transported through a closed pipeline to a filtration and distillation system. The filter residue is returned to the submerged arc furnace for smelting. The filtrate is distilled under reduced pressure to obtain a lithium sulfide precursor at 110℃. The evaporated solvent is collected in a storage tank via a condenser for recycling. The lithium sulfide precursor is first dried at 250℃ for 4 hours, and then sintered in a vacuum furnace at 750℃ for 4 hours to further remove residual solvent and a small amount of S from the lithium sulfide. The lithium sulfide sintered material is added to a dry ball mill and crushed and ball-milled to obtain lithium sulfide product of the desired particle size. The dry ball mill is placed inside a glove box, making it a closed system. The particle size of the lithium sulfide is 200-300 mesh. Testing shows that the lithium sulfide content is 99.4%.

[0071] Table 4. Composition of Lithium Spodumene

[0072]

[0073] Table 5. Composition of Aluminum-Silicon-Iron Alloy

[0074] Element Si Al Mn C P S Fe content% 40.5 35.2 0.2 0.15 0.02 0.02 margin

[0075] Table 6. Composition of Lithium Mixture

[0076] Element Li C O N Al Si Fe content(%) 18.08 17.28 39.21 1.11 2.75 5.6 0.86

[0077] Example 3

[0078] Please see Figure 1 A method for extracting lithium and aluminum-silicon-iron alloy from lithium ore by electrolytic synergistic carbothermic reduction under a DC electric field, the specific steps of which are as follows:

[0079] S1: Set the heating power to 25000KVA and the charge temperature to 2000℃ on the DC submerged arc furnace control platform;

[0080] S2: Lithium mica granules are added to the A feeding zone through the feed pipe, and the circuit is closed. Under the action of a high DC current and plasma gas, the anode and cathode are fully arced, the lithium ore is heated into a melt, and an electrochemical reaction occurs between the electrodes to decompose and electrolyze the lithium mica, preparing a primary aluminum-silicon-iron alloy; the lithium ore is lithium mica, and the composition is shown in Table 7. The particle size is 0-30mm;

[0081] S3: After the furnace charge is heated to 2000℃, a mixture of lithium mica, iron oxide chips and coke, which has been dried under high pressure and briquetting, is added through the feeding pipe in the B feeding zone to carry out a carbothermic reduction reaction to prepare a primary aluminum-silicon-iron alloy; the mass ratio of lithium mica to coke is 2.5:1, the particle size of the mixture is 20-40mm, and the carbothermic reduction time is 4.5h;

[0082] S4: The primary alloy liquid is periodically discharged through the tapping port. The aluminum-silicon-iron alloy is then sent for refining. The composition of the aluminum-silicon-iron alloy is shown in Table 8.

[0083] S5: The smelting flue gas is condensed to recover a lithium-rich mixture, the composition of which is shown in Table 9. Carbon powder and sulfuric acid are prepared according to the following formula: Li₂O to C molar ratio of 2:1.05 and Li to S molar ratio of 2:0.99. Under argon protection, the mixture is reduced at 790℃ for 4 hours to obtain crude lithium sulfide. The crude lithium sulfide is leached with anhydrous methanol at a solid-liquid ratio of 1:11. The mixture is then mixed and reacted for 3 hours in a closed ball mill under nitrogen protection. The resulting slurry is transported through a closed pipeline to a filtration and distillation system. The filter residue is returned to the submerged arc furnace for smelting. The filtrate is distilled under reduced pressure to obtain the lithium sulfide precursor at 85℃. The evaporated solvent is collected in a storage tank via a condenser for recycling. The lithium sulfide precursor was first dried at 220℃ for 4 hours, and then sintered in a vacuum furnace at 770℃ for 4 hours to further remove residual solvent and a small amount of sulfur. The sintered lithium sulfide was then fed into a dry ball mill for crushing and ball milling to obtain the lithium sulfide product of the desired particle size. The dry ball mill was placed inside a glove box, making it a closed system. The lithium sulfide particle size was 200–300 mesh, and the lithium sulfide content was found to be 99.5%.

[0084] Table 7. Composition of Lithium Mica

[0085]

[0086] Table 8. Gold Composition Table of Aluminum-Silicon-Iron Alloy

[0087] Element Si Al Mn C P S Fe content% 42.4 35.1 0.1 0.3 0.02 0.02 margin

[0088] Table 9. Composition of Lithium Mixture

[0089] Element Li C O Rb Al Si Fe content(%) 12.56 21.34 36.78 3.36 3.86 6.1 0.36

[0090] The simultaneous electrolytic reaction and carbothermic reduction reaction of lithium ore in a DC submerged arc furnace is beneficial for improving metal recovery rate and reducing reducing agent consumption. It also helps to increase the lithium content in flue gas. The one-step high-temperature synthesis of lithium sulfide from lithium-rich mixture with sulfuric acid and carbon powder greatly saves manufacturing costs and is easy to commercialize and scale up production. Crude lithium sulfide is leached with organic solvents to remove carbon, sintered at high temperature to remove sulfur and oxygen, and the crystal form and particle size of lithium sulfide are controlled by ball milling, which improves the purity of the product and ensures product quality.

[0091] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention's specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

[0092] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for producing metallic lithium, lithium sulfide, and aluminum-silicon-iron alloy by electrolytic reduction of lithium ore, characterized in that, Under the influence of direct current, lithium ore melts due to Joule heating and electrochemical reactions. Oxides in the lithium ore move towards the cathode and are reduced to a metallic alloy, while oxygen ions [O2-] move towards the anode and are oxidized to oxygen. The lithium ore undergoes an electrolytic reaction between the electrodes, generating a primary aluminum-silicon-iron alloy liquid. Simultaneously, the molten liquid undergoes a reduction reaction around the electrodes under the action of a carbon reducing agent, generating the aluminum-silicon-iron alloy. Metallic lithium volatilizes into the flue gas and is enriched through a condensation dust collection system. The lithium-rich mixture is then mixed with sulfuric acid and carbon powder, and crude lithium sulfide is synthesized at high temperature under an inert atmosphere. The crude lithium sulfide is then leached with an organic solvent, separated, distilled, dried, and crushed to obtain high-purity lithium sulfide. The specific steps include: S1: The smelting equipment is a DC closed submerged arc furnace, which includes a rectifier system, an electrode control system, a charging system, a water cooling system, and a flue gas purification system; the charging system includes charging zone A and charging zone B. S2:A feeding zone is located in the central area of ​​the submerged arc furnace, where lithium ore granules are added through the feeding pipe. During the closing operation, under the action of a large DC current and plasma gas, both the anode and cathode are fully arced, heating the lithium ore into a molten state. Lithium ore granules are then added, and an electrochemical reaction occurs between the electrodes to decompose the lithium ore, producing a primary aluminum-silicon-iron alloy. S3:B The feeding zone is located outside the electrode. After the furnace charge is heated to a given temperature, a mixture of lithium ore and coke in a certain proportion is added through the feeding pipe to carry out a carbothermic reduction reaction and prepare a primary aluminum-silicon-iron alloy. S4: The primary alloy liquid is periodically discharged through the tap hole, and the aluminum-silicon-iron alloy is sent for refining. S5: The smelting flue gas is processed through a condensation and dust collection system to recover a lithium-rich mixture. This mixture is then combined with sulfuric acid and carbon powder, and crude lithium sulfide is synthesized at high temperature under an inert atmosphere. The crude lithium sulfide is then leached with an organic solvent, separated, distilled with a solvent, dried, sintered, and crushed to obtain high-purity lithium sulfide. The solvent leaching residue is returned to the DC submerged arc furnace for smelting.

2. The method for producing metallic lithium, lithium sulfide, and aluminum-silicon-iron alloy by electrolytic reduction of lithium ore according to claim 1, characterized in that, The lithium ore is a mixture of one or more of spodumene, lepidolite, and clay-type lithium ore in any proportion, with a particle size of 0-30 mm, and is used in feeding zone A.

3. The method for producing metallic lithium, lithium sulfide, and aluminum-silicon-iron alloy by electrolytic reduction of lithium ore according to claim 1, characterized in that, The lithium ore and coke mixture has a particle size of 20-60 mm and a mass ratio of lithium ore to coke of 1-4:1, and is used in the B feeding zone.

4. The method for producing metallic lithium, lithium sulfide, and aluminum-silicon-iron alloy by electrolytic reduction of lithium ore according to claim 1, characterized in that, The carbothermic reaction temperature of lithium ore is 1500–2200℃, and the reaction time is 1–24h.

5. The method for producing metallic lithium, lithium sulfide, and aluminum-silicon-iron alloy by electrolytic reduction of lithium ore according to claim 1, characterized in that, The main components of the lithium-rich mixture recovered in the condenser are Li, Li₂O, carbon ash, and aluminosilicate dust. This lithium-rich mixture is mixed with carbon powder and sulfur powder to achieve a carbothermic reduction of Li₂O to metallic lithium, followed by high-temperature synthesis of Li₂S from Li and S. The molar ratio of Li₂O to C in the lithium-rich mixture is 2:1–1.1, and the molar ratio of Li to S is 2:0.95–1. The reduction temperature of the lithium-rich mixture with sulfuric acid and carbon powder is 750–850°C. The inert gas is either nitrogen or argon.

6. The method for producing metallic lithium, lithium sulfide, and aluminum-silicon-iron alloy by electrolytic reduction of lithium ore according to claim 1, characterized in that, Crude lithium sulfide is leached with an organic solvent, which is one or more of anhydrous ethanol, anhydrous methanol, and anhydrous isopropanol; the solid-liquid ratio of the lithium-rich mixture to the organic solvent is 1:5 to 15; the leaching reaction is carried out by mixing and reacting in a closed ball mill for 2 to 4 hours through a feeding system, with nitrogen protection in the system; the slurry after the reaction is transported to a filtration and distillation system through a closed pipeline; the filter residue is returned to the electric arc furnace for smelting; the filtrate is distilled under reduced pressure to obtain the lithium sulfide precursor at a distillation temperature of 80 to 120°C; the evaporated solvent is collected in a storage tank through a condenser for recycling. The lithium sulfide precursor is first dried at 100–300℃ for 4–8 hours, and then sintered in a vacuum furnace at 650–850℃ for 4–8 hours to further remove residual solvent and a small amount of sulfur from the lithium sulfide. The sintered lithium sulfide is then added to a dry ball mill and crushed and ball-milled to obtain the lithium sulfide product with the required particle size. The dry ball mill is placed in a glove box, which is a closed system, and the particle size of the lithium sulfide is 200–300 mesh.

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