Preparation method and device of high-purity lithium metal

Abstract

The application provides a preparation method and device of high-purity metal lithium, the method comprises the following steps: S1, mixing lithium-containing raw materials with extraction medium to obtain a mixture, and performing first temperature rising under a protective atmosphere, and then cooling after keeping warm for a set time; S2, performing second temperature rising under a vacuum environment, and collecting the remaining solid to obtain high-purity metal lithium. The device comprises a reaction unit, a condensation unit and an atmosphere control unit, the reaction unit is provided with an air hole, and the air hole is in sealed connection with the condensation unit and the atmosphere control unit. The crude lithium is purified by melt extraction, the metal raw material lithium can be treated to obtain a high-purity metal lithium product, the process flow is short, the distillation temperature is low, the energy consumption is low, the reaction and distillation device are simple, and the problems of low traditional distillation efficiency, high energy consumption, long process flow and complex equipment are solved.

Description

Technical Field

[0001] This invention relates to the field of metallic materials, and more particularly to a method for purifying lithium. Background Technology

[0002] In recent years, with the development of the solar cell field, the preparation technology and equipment of high-purity lithium have become a key research direction. At present, the most commonly used method for purifying metallic lithium is the low-temperature vacuum distillation furnace. Its main mechanism is to melt crude lithium into liquid lithium in a protective medium, remove the protective medium by vacuum impurity removal method, and then separate volatile impurities from metallic lithium by vacuum distillation.

[0003] High-purity lithium metal is usually extracted first by electrolysis to obtain industrial-grade lithium metal with a purity of 96%-99%. Then, it is further purified to obtain high-purity lithium metal. Traditional lithium metal purification mainly uses distillation to separate impurity elements such as sodium and potassium from lithium metal, purifying industrial-grade crude lithium into high-purity lithium metal with a purity of 99.9% to 99.99% or higher. For example, Chinese patent applications CN104805312A, CN119776677A and Chinese patents CN100584972C and CN100432248C all use distillation to obtain high-purity lithium.

[0004] The existing technologies mentioned above still have the following problems: 1. Low distillation efficiency, long distillation time, and high energy consumption; 2. Complex distillation column equipment and difficulty in selecting column structure materials; 3. High difficulty in separating substances with physical properties very similar to lithium; 4. Complex process operation and high requirements for equipment vacuum degree. Summary of the Invention

[0005] This invention provides a method and apparatus for preparing high-purity metallic lithium, which solves the technical problems of existing methods mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A method for preparing high-purity metallic lithium includes the following steps: S1. A lithium-containing raw material is mixed with an extraction medium to obtain a mixture. The mixture is heated for the first time under a protective atmosphere to convert the extraction medium into a liquid phase. After holding at this temperature for a set time, the mixture is cooled. The extraction medium includes cesium and / or rubidium. S2. The cooled mixture is heated a second time in a vacuum environment, so that the extraction medium is transformed into a gas phase, and the remaining solid is collected to obtain the high-purity lithium metal.

[0008] The inventors discovered that although many metals can eutectic with lithium, only rubidium or cesium can selectively dissolve impurity elements Na and K without dissolving the main element lithium. The impurities Na and K in lithium metal have a certain solubility in rubidium or cesium, while lithium metal has no solubility in either. For example, at 500°C, the mass fractions of impurity elements Na and K in lithium metal in molten cesium are 100 wt.% and 100 wt.%, respectively. Based on this, this invention creatively discovers and utilizes the completely different solubility selectivity of cesium / rubidium for Li and Na / K, proposing a method of metal melt extraction. Molten cesium (Cs), rubidium (Rb), or an alloy of both are used as the extraction medium. Under sealed and rare gas protection conditions, the medium is heated to a specific temperature and held at that temperature to keep the rubidium or cesium in a liquid state. Impurity elements are then fully dissolved in the extraction medium. Meanwhile, lithium has a melting point of 180.5℃ and a boiling point of [missing information]. The melting point of rubidium is 39.5℃, and its boiling point is 688℃. The melting point of cesium is 28.5℃, and its boiling point is 668~705℃. After extracting Na and K impurities, the mixture is cooled to room temperature, allowing the molten lithium metal and the extraction medium-impurity system to solidify. The difference between the boiling point of rubidium or cesium and the melting point of lithium metal can be further utilized to perform secondary heating in a vacuum environment. This allows the metal to be purified to be separated from the vapor of the extraction medium, ultimately obtaining a high-purity product with low impurity element content.

[0009] As a further preferred embodiment of the above technical solution, in S1, the mass ratio of the lithium-containing raw material to the extraction medium is 1:(3~8).

[0010] As a further preferred embodiment of the above technical solution, in S1, the final temperature of the first heating is 50~600℃, and the holding time is 2~8h. Firstly, this ensures that the extraction medium is completely transformed into a low-viscosity, high-flow-rate liquid phase, which is beneficial for its full contact with the lithium-containing raw material and for mass exchange. Secondly, the 2-8 hour holding time provides sufficient kinetic conditions, allowing impurity elements enough time to diffuse from the solid-phase lithium metal to the surface and dissolve in the liquid-phase extraction medium, thereby achieving optimal extraction equilibrium. This synergistic effect of temperature control and time window ensures efficient and selective removal of impurities.

[0011] As a further preferred embodiment of the above technical solution, the purity of the extraction medium is ≥99.99%.

[0012] As a further preferred embodiment of the above technical solution, the protective atmosphere is an argon atmosphere with a purity of ≥99.99%. During the initial heating and melting process, a highly inert, oxygen-free, moisture-free, and low-activity environment is created. High-purity argon effectively isolates air, preventing metallic lithium and molten cesium / rubidium from undergoing oxidation, nitridation, or violent reactions with oxygen, nitrogen, water vapor, etc., at high temperatures. This avoids the generation of byproducts and material loss, ensuring the safety of the operation. Simultaneously, the high-purity atmosphere also eliminates the introduction of external impurities (such as oxygen and nitrogen), ensuring the purity of the extraction process and the quality of the final product.

[0013] As a further preferred embodiment of the above technical solution, in S2, the vacuum degree during the second heating process is ≤1.0×10⁻⁶. -2 The second heating phase reached a final temperature of 50–150 °C, with a holding time of 3–6 hours. Strict control of vacuum and heating parameters ensured perfect separation of the extraction medium from high-purity lithium metal. The technical effect was: within ≤1.0 × 10⁻⁶ Pa. - The high vacuum environment of 2Pa significantly reduces the boiling points of cesium and / or rubidium (e.g., cesium's boiling point at atmospheric pressure is 671℃, and rubidium's is 688℃), enabling efficient vaporization and volatilization within a temperature range as low as 50-150℃. This temperature range (50-150℃) is far below the melting point of metallic lithium (180.5℃), ensuring that metallic lithium remains solid throughout, thus achieving non-contact, high-efficiency separation between solid lithium and the gaseous extraction medium. A holding time of 3-6 hours ensures that the medium is fully and completely removed. This method achieves complete recovery of the extraction medium and purification of the product with extremely low energy consumption, avoiding the high equipment requirements and high energy consumption of high-temperature distillation.

[0014] As a further optimization of the above technical solution, the extraction medium, after being converted into a gaseous phase, is collected, condensed, and recycled. Since cesium and rubidium are both rare and expensive metal resources, this method achieves near 100% reuse of the extraction medium through a simple condensation and recovery step. This not only significantly reduces the production cost of high-purity lithium metal, solving a key economic bottleneck for the industrialization of this process, but also reduces resource consumption and waste emissions, aligning with the green and sustainable chemical metallurgical principles.

[0015] As a further preferred embodiment of the above technical solution, the lithium-containing raw material is crude lithium metal with a purity of ≤99.50%.

[0016] As a further preferred embodiment of the above technical solution, the purity of the high-purity lithium metal is ≥99.80%.

[0017] Based on the same technical concept, the present invention also provides a high-purity lithium metal preparation apparatus for implementing the preparation method described above, including a reaction unit, a condensation unit and an atmosphere control unit, wherein the reaction unit is provided with vents, and the reaction unit is sealed to the condensation unit and the atmosphere control unit through the vents.

[0018] This invention provides a reliable, efficient, and integrated hardware support for realizing the above-mentioned preparation method. The sealed connection of the vent and the atmosphere control unit works synergistically to precisely create the required protective atmosphere for step S1 and meet the stringent high vacuum requirements of step S2. Simultaneously, the direct connection between the reaction unit and the condensation unit enables in-situ, efficient condensation and recovery of the vaporized extraction medium in step S2, avoiding contamination and loss during material transfer. This device is compact, easy to operate, and perfectly suited to the method of this invention, effectively solving the problems of complex equipment and excessively high vacuum requirements in the prior art.

[0019] The present invention has the following beneficial effects: This invention uses crude lithium as raw material and molten cesium (Cs), rubidium (Rb), or an alloy of both as extraction media. It leverages the fact that Na and K have certain solubility in cesium and rubidium, while lithium is insoluble in these metals, effectively reducing the Na / K content of impurities in crude lithium. High-purity lithium is then obtained through vacuum distillation. This invention purifies crude lithium through melt extraction, processing raw lithium to produce high-purity lithium products. The Na purification rate is above 84%, the K purification rate is above 83%, and the resulting high-purity lithium has a purity of over 99.8% and a yield of over 95%. Furthermore, the process is short, with low distillation temperature and low energy consumption, requiring only a common heater for temperature control. The reaction and distillation apparatus are simple; besides using ordinary vacuum equipment, only a simple glass distillation tube is needed in the laboratory. This solves the problems of low efficiency, high energy consumption, long process, and complex equipment associated with traditional distillation.

[0020] The present invention will now be described in further detail with reference to specific embodiments. Attached Figure Description

[0021] Figure 1 The process flow diagrams for the preparation of high-purity metallic lithium in Examples 2-7 are shown. Figure 2 This is a schematic diagram of the apparatus for preparing high-purity metallic lithium in Example 1.

[0022] Legend: 1. Furnace body; 2. Reaction vessel; 3. Mixture; 4. Condenser; 5. Collection device; 6. Atmosphere unit. Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0024] Example 1: like Figure 2 As shown, the apparatus for preparing high-purity metallic lithium in this embodiment includes a reaction unit, a condensation unit, and an atmosphere control unit. The reaction unit is provided with a vent, which is sealed to both the condensation unit and the atmosphere control unit. The reaction unit includes a furnace body 1 and a reaction vessel 2 installed in the furnace body 1. The reaction vessel 2 has a vent at its upper end. The condensation unit is a condenser tube 4, which forms a 25° angle with the horizontal direction. One end of the condenser tube 4 is connected to the vent, and the other end is connected to a collection device 5. The atmosphere unit 6 supplies protective gas or evacuates the reaction vessel 2 via the condenser tube 4.

[0025] Example 2: like Figure 1 As shown, the lithium-containing raw material (crude lithium) processed by the high-purity lithium metal preparation method in this embodiment contains impurity elements such as K and Na, with a Na mass percentage of 871 × 10⁻⁶. -3 The mass percentage of K is 65 × 10⁻⁶. -3 %.

[0026] The method for preparing high-purity lithium metal in this embodiment uses the above-mentioned apparatus for preparing high-purity lithium metal (other apparatus may be used in other embodiments), and the specific steps are as follows: S1. Before use, the reaction vessel 2 is cleaned with 3%~5% hydrochloric acid and deionized water in sequence, rinsed with ethanol and then dried.

[0027] S2. Take 20g of lithium metal raw material (purity 98.72%) and place it in reaction vessel 2 inside the glove box. Transfer a vacuum-sealed vial containing 80g of liquid cesium metal (purity 99.99%) to the glove box protected by argon gas (purity 99.999%). Open the vial cap and transfer the liquid cesium metal to the reaction vessel containing lithium metal. Close the vent valve of reaction vessel 2, start the furnace body 1 to heat up to 500℃, and hold for 6 hours. After the holding time is completed, cool down to room temperature.

[0028] S3. After the heat preservation ends and the temperature drops to room temperature, open the vent valve of reaction vessel 2 and begin vacuuming. Wait until the pressure inside the furnace drops to 1.0 × 10⁻⁶. -2 Below Pa, maintain vacuum, heat to 100℃, hold for 4 hours, stop vacuuming after holding, the purified metallic lithium is collected at the bottom of the reactor tank, and the cesium vapor is condensed in the condenser to form liquid metallic cesium, which is then collected and recycled through a collection container.

[0029] S4. Close the valve of reaction vessel 2, remove the reaction vessel, and re-melt it in the glove box for dispensing and sampling analysis. A total of 19.2g of metal was obtained from the reaction vessel, with an overall yield of 96.0%.

[0030] As shown in Table 1, the purity of the finally collected high-purity metallic lithium was increased to 99.82%.

[0031] Table 1: Test results of impurity content in high-purity lithium metal from Example 2

[0032] Example 3: like Figure 1 As shown, the lithium-containing raw material (crude lithium) processed by the high-purity lithium metal preparation method in this embodiment contains impurity elements such as K and Na, with a Na mass percentage of 638 × 10⁻⁶. -3 The mass percentage of K is 103 × 10⁻⁶. -3 %.

[0033] The method for preparing high-purity lithium metal in this embodiment uses the above-mentioned apparatus for preparing high-purity lithium metal (other apparatus may be used in other embodiments), and the specific steps are as follows: S1. Before use, the reaction vessel 2 is cleaned with 3%~5% hydrochloric acid and deionized water in sequence, rinsed with ethanol and then dried.

[0034] S2. Take 20g of lithium metal raw material (purity 99.13%) and place it in reaction vessel 2 inside the glove box. Transfer a vacuum-sealed vial containing 100g of liquid cesium metal (purity 99.99%) to the glove box protected by argon gas (purity 99.999%). Open the vial cap and transfer the liquid cesium metal to the reaction vessel containing lithium metal. Close the vent valve of reaction vessel 2, start the furnace body 1 to heat up to 400℃, and hold for 6 hours. After the holding time is completed, cool down to room temperature.

[0035] S3. After the heat preservation ends and the temperature drops to room temperature, open the vent valve of reaction vessel 2 and begin vacuuming. Wait until the pressure inside the furnace drops to 1.0 × 10⁻⁶. -2 Below Pa, maintain vacuum, heat to 150℃, hold for 4 hours, stop vacuuming after holding, the purified metallic lithium is collected at the bottom of the reactor tank, and the cesium vapor is condensed in the condenser to form liquid metallic cesium, which is then collected and recycled through a collection container.

[0036] S4. Close the valve of reaction vessel 2, remove the reaction vessel, and re-melt it in the glove box for dispensing and sampling analysis. A total of 19.4g of metal was obtained from the reaction vessel, with an overall yield of 97.0%.

[0037] As shown in Table 2, the purity of the finally collected high-purity metallic lithium was increased to 99.80%.

[0038] Table 2: Test results of impurity content in high-purity lithium metal from Example 3

[0039] Example 4: like Figure 1 As shown, the lithium-containing raw material (crude lithium) processed in this embodiment for preparing high-purity metallic lithium contains impurities such as K and Na, with a Na mass percentage of 853 × 10⁻⁶. -3 The mass percentage of K is 196 × 10⁻⁶. -3 %.

[0040] The method for preparing high-purity lithium metal in this embodiment uses the above-mentioned apparatus for preparing high-purity lithium metal (other apparatus may be used in other embodiments), and the specific steps are as follows: S1. Before use, the reaction vessel 2 is cleaned with 3%~5% hydrochloric acid and deionized water in sequence, rinsed with ethanol and then dried.

[0041] S2. Take 20g of lithium metal raw material (purity 98.51%) and place it in reaction vessel 2 inside the glove box. Transfer a vacuum-sealed vial containing 120g of liquid cesium metal (purity 99.99%) to the glove box protected by argon gas (purity 99.999%). Open the vial cap and transfer the liquid cesium metal to the reaction vessel containing lithium metal. Close the vent valve of reaction vessel 2, start the furnace body 1 to heat up to 500℃, and hold for 5 hours. After the holding time is over, cool down to room temperature.

[0042] S3. After the heat preservation ends and the temperature drops to room temperature, open the vent valve of reaction vessel 2 and begin vacuuming. Wait until the pressure inside the furnace drops to 1.0 × 10⁻⁶. -2 Below Pa, maintain vacuum, heat to 100℃, hold for 6 hours, stop vacuuming after holding, the purified metallic lithium is collected at the bottom of the reactor tank, and the cesium vapor is condensed in the condenser to form liquid metallic cesium, which is then collected and recycled through a collection container.

[0043] S4. Close the valve of reaction vessel 2, remove the reaction vessel, and re-melt it in the glove box for dispensing and sampling analysis. A total of 19.5g of metal was obtained from the reaction vessel, with an overall yield of 97.5%.

[0044] As shown in Table 3, the purity of the finally collected high-purity metallic lithium was increased to 99.81%.

[0045] Table 3: Test results of impurity content in high-purity lithium metal from Example 4

[0046] Example 5: like Figure 1 As shown, the lithium-containing raw material (crude lithium) processed in this embodiment for preparing high-purity metallic lithium contains impurities such as K and Na, with a Na mass percentage of 554 × 10⁻⁶. -3 The mass percentage of K is 185 × 10⁻⁶. -3 %.

[0047] The method for preparing high-purity lithium metal in this embodiment uses the above-mentioned apparatus for preparing high-purity lithium metal (other apparatus may be used in other embodiments), and the specific steps are as follows: S1. Before use, the reaction vessel 2 is cleaned with 3%~5% hydrochloric acid and deionized water in sequence, rinsed with ethanol and then dried.

[0048] S2. Take 20g of lithium metal raw material (purity 99.10%) and place it in reaction vessel 2 inside the glove box. Transfer a vacuum-sealed vial containing 120g of liquid cesium metal (purity 99.99%) to the glove box protected by argon gas (purity 99.999%). Open the vial cap and transfer the liquid cesium metal to the reaction vessel containing lithium metal. Close the vent valve of reaction vessel 2, start the furnace body 1 to heat up to 500℃, and hold for 6 hours. After the holding time is completed, cool down to room temperature.

[0049] S3. After the heat preservation ends and the temperature drops to room temperature, open the vent valve of reaction vessel 2 and begin vacuuming. Wait until the pressure inside the furnace drops to 1.0 × 10⁻⁶. -2 Below Pa, maintain vacuum, heat to 150℃, hold for 4 hours, stop vacuuming after holding, the purified metallic lithium is collected at the bottom of the reactor tank, and the cesium vapor is condensed in the condenser to form liquid metallic cesium, which is then collected and recycled through a collection container.

[0050] S4. Close the valve of reaction vessel 2, remove the reaction vessel, and re-melt it in the glove box for dispensing and sampling analysis. A total of 19.3g of metal was obtained from the reaction vessel, with an overall yield of 96.5%.

[0051] As shown in Table 4, the purity of the finally collected high-purity metallic lithium was increased to 99.90%.

[0052] Table 4: Test results of impurity content in high-purity lithium metal from Example 5

[0053] Example 6: like Figure 1As shown, the lithium-containing raw material (crude lithium) processed by the high-purity lithium metal preparation method in this embodiment contains impurity elements such as K and Na, with a Na mass percentage of 691 × 10⁻⁶. -3 The mass percentage of K is 147 × 10⁻⁶. -3 %.

[0054] The method for preparing high-purity lithium metal in this embodiment uses the above-mentioned apparatus for preparing high-purity lithium metal (other apparatus may be used in other embodiments), and the specific steps are as follows: S1. Before use, the reaction vessel 2 is cleaned with 3%~5% hydrochloric acid and deionized water in sequence, rinsed with ethanol and then dried.

[0055] S2. Take 20g of lithium metal raw material (purity 99.00%) and place it in reaction vessel 2 inside the glove box. Transfer a vacuum-sealed vial containing 100g of liquid cesium metal (purity 99.99%) to the glove box protected by argon gas (purity 99.999%). Open the vial cap and transfer the liquid cesium metal to the reaction vessel containing lithium metal. Close the vent valve of reaction vessel 2, start the furnace body 1 to heat up to 400℃, and hold for 7 hours. After the holding time is completed, cool down to room temperature.

[0056] S3. After the heat preservation ends and the temperature drops to room temperature, open the vent valve of reaction vessel 2 and begin vacuuming. Wait until the pressure inside the furnace drops to 1.0 × 10⁻⁶. -2 Below Pa, maintain vacuum, heat to 100℃, hold for 4 hours, stop vacuuming after holding, the purified metallic lithium is collected at the bottom of the reactor tank, and the cesium vapor is condensed in the condenser to form liquid metallic cesium, which is then collected and recycled through a collection container.

[0057] S4. Close the valve of reaction vessel 2, remove the reaction vessel, and re-melt it in the glove box for dispensing and sampling analysis. A total of 19.4g of metal was obtained from the reaction vessel, with an overall yield of 97.0%.

[0058] As shown in Table 5, the purity of the finally collected high-purity metallic lithium was increased to 99.90%.

[0059] Table 5: Test results of impurity content in high-purity lithium metal from Example 6

[0060] Example 7: like Figure 1 As shown, the lithium-containing raw material (crude lithium) processed in this embodiment for preparing high-purity metallic lithium contains impurities such as K and Na, with a Na mass percentage of 782 × 10⁻⁶. -3 The mass percentage of K is 152 × 10⁻⁶. -3 %.

[0061] The method for preparing high-purity lithium metal in this embodiment uses the above-mentioned apparatus for preparing high-purity lithium metal (other apparatus may be used in other embodiments), and the specific steps are as follows: S1. Before use, the reaction vessel 2 is cleaned with 3%~5% hydrochloric acid and deionized water in sequence, rinsed with ethanol and then dried.

[0062] S2. Take 20g of lithium metal raw material (purity 99.03%) and place it in reaction vessel 2 inside the glove box. Transfer a vacuum-sealed vial containing 130g of liquid cesium metal (purity 99.99%) to the glove box protected by argon gas (purity 99.999%). Open the vial cap and transfer the liquid cesium metal to the reaction vessel containing lithium metal. Close the vent valve of reaction vessel 2, start the furnace body 1 to heat up to 500℃, and hold for 8 hours. After the holding time is over, cool down to room temperature.

[0063] S3. After the heat preservation ends and the temperature drops to room temperature, open the vent valve of reaction vessel 2 and begin vacuuming. Wait until the pressure inside the furnace drops to 1.0 × 10⁻⁶. -2 Below Pa, maintain vacuum, heat to 150℃, hold for 6 hours, stop vacuuming after holding, the purified metallic lithium is collected at the bottom of the reactor tank, and the cesium vapor is condensed in the condenser to form liquid metallic cesium, which is then collected and recycled through a collection container.

[0064] S4. Close the valve of reaction vessel 2, remove the reaction vessel, and re-melt it in the glove box for dispensing and sampling analysis. A total of 19.5g of metal was obtained from the reaction vessel, with an overall yield of 97.5%.

[0065] As shown in Table 6, the purity of the finally collected high-purity metallic lithium was increased to 99.90%.

[0066] Table 6: Test results of impurity content in high-purity lithium metal from Example 7

[0067] The above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the technical concept of the present invention should also be considered within the scope of protection of the present invention. It should be noted that rubidium and cesium have essentially the same solubility for sodium and potassium. As mentioned above, at a temperature of 500℃, the mass fractions of impurity elements Na and K in molten cesium metal are 100 wt.% and 100 wt.%, respectively. Both rubidium and rubidium-cesium alloys have the same solubility for impurities as cesium metal. Therefore, in the embodiments, only cesium metal was used as the extraction medium.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing high-purity metallic lithium, characterized in that, Includes the following steps: S1. A lithium-containing raw material is mixed with an extraction medium to obtain a mixture. The mixture is heated for the first time under a protective atmosphere to convert the extraction medium into a liquid phase. After holding at this temperature for a set time, the mixture is cooled. The extraction medium includes cesium and / or rubidium. The final temperature of the first heating is 400~500℃. S2. The cooled mixture is heated a second time in a vacuum environment to convert the extraction medium into a gas phase, and the remaining solid is collected to obtain the high-purity lithium metal; the endpoint temperature of the second heating is 100~150℃.

2. The method for preparing high-purity metallic lithium according to claim 1, characterized in that, In S1, the mass ratio of the lithium-containing raw material to the extraction medium is 1:(3~8).

3. The method for preparing high-purity metallic lithium according to claim 1, characterized in that, In S1, the heat preservation time is 2~8 hours.

4. The method for preparing high-purity metallic lithium according to claim 1, characterized in that, The purity of the extraction medium is ≥99.99%.

5. The method for preparing high-purity metallic lithium according to claim 1, characterized in that, The protective atmosphere is an argon atmosphere with a purity of ≥99.99%.

6. The method for preparing high-purity metallic lithium according to any one of claims 1-5, characterized in that, In S2, the vacuum degree during the second heating process is ≤1.0×10⁻⁶. -2 Pa, heat preservation time is 3~6h.

7. The method for preparing high-purity metallic lithium according to any one of claims 1-5, characterized in that, The extraction medium that has been converted into a gaseous phase is collected, condensed, and recycled.

8. The method for preparing high-purity metallic lithium according to any one of claims 1-5, characterized in that, The lithium-containing raw material is crude lithium metal with a purity of ≤99.50%.

9. The method for preparing high-purity metallic lithium according to any one of claims 1-5, characterized in that, The purity of the high-purity lithium metal is ≥99.80%.

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