Method for manufacturing lithium metal using lithium compound

Abstract

The method for producing lithium metal using a lithium compound according to the present invention may include a) a step of preparing a mixture of a lithium compound and a metal reducing agent, b) a step of preparing a reaction product by compressing the mixture and burning it in an argon gas atmosphere, and c) a step of separating lithium by immersing the reaction product in a high-boiling point fluid having a boiling point greater than or equal to the melting point of metallic lithium (Li).

Description

Technology Field

[0001] The present invention relates to a method for manufacturing lithium metal, and more specifically, to a method for manufacturing lithium metal using a lithium compound capable of separating lithium using a high-boiling point fluid after burning a lithium compound and a metal reducing agent. Background Technology

[0002] Generally, the industrial method for producing high-purity lithium metal is to electrolyze the lithium chloride (LiCl) component in a LiCl-KCl mixture at a temperature range of 400 to 450°C. The related electrochemical reactions are as follows.

[0003] Cathode reaction: Li + + e - → Li (1)

[0004] Anode reaction: Cl - - e → 1 / 2Cl2(2)

[0005] Net reaction: LiCl → Li + 1 / 2Cl2(3)

[0006] This is because lithium (Li) is in liquid form at the cathode. + It refers to what is obtained through the electrolytic reduction of ions. Chlorine gas (1 / 2Cl2) generated at the anode is undesirable and should be avoided if possible. It is based on the electrolysis of lithium hydroxide (LiOH) as follows.

[0007] 2LiOH → 2Li + 1 / 2O2 + H2O; E Ф = 2.87 V (4)

[0008] The voltage is much lower than that of lithium chloride (LiCl). However, as can be seen from Equation (4), the anode process of electrolysis for lithium hydroxide (LiOH) involves multiple electrons and releases two somewhat complex byproducts. Furthermore, since any lithium (Li) generated by electrolysis readily reacts with lithium hydroxide (LiOH) to form lithium oxide (Li2O), it is expected that lithium metal cannot be directly electrolytically extracted from lithium hydroxide (LiOH)-containing salts.

[0009] Li + LiOH → Li2O + 1 / 2 H2; ΔG=-96.9 kJmol -1 (5)

[0010] As shown in Fig. 1, the decomposition voltage of lithium carbonate (Li2CO3) is lower than that of lithium chloride (LiCl), and it is desirable if lithium carbonate (Li2CO3) can be used as a raw material for the production of metallic lithium (Li).

[0011] Li2CO3→ 2Li + 1 / 2O2+ CO2; E Ф = 3.14 V

[0012] However, lithium carbonate (Li2CO3) also faces a problem similar to that of lithium hydroxide (LiOH). That is, CO3 2- The area around the cathode is Li + It can react with lithium (Li) at nearly the same potential as reduction, but does not occur when sodium (Na) and potassium (K) are electrolytically extracted from their respective carbonates. These results are consistent with what is observed in Li-CO2 batteries when the battery is severely discharged.

[0013] CO3 2- + 6Li + 4e → C + 3Li2O (6)

[0014] High-temperature pyrolysis of lithium compounds is another approach to producing lithium (Li) metal. Although the production of lithium (Li) metal from lithium chloride (LiCl) via plasma pyrolysis has been reported, the production yield of lithium (Li) in a single pass was approximately 60%. Current processes face challenges in scaling up due to high temperature, high vacuum, low energy efficiency, and toxic byproducts such as chlorine (Cl2).

[0015] The thermochemical reduction approach for lithium compounds involves using cheaper elements to exchange lithium (Li) in the compounds and utilizing high temperatures to overcome thermodynamic disadvantages.

[0016] Various elements and chemicals, including carbon, magnesium, aluminum, silicon, hydrogen, iron, or calcium carbide, have been used as reducing agents, and the lithium compounds used are lithium oxide and lithium hydroxide.

[0017] Li2O + xM → 2Li + MxO; (M = C, Mg, Al, Si, FeSi, H2) (7)

[0018] 2Li2O + MC2→ Li + 2CO + M; (M = Ca or Fe) (8)

[0019] 6LiOH + C → 2Li + 2Li2CO3+ 3H2(9)

[0020] 2LiOH + 2Mg → 2Li + 2MgO + H2(10)

[0021] 2LiOH + Al → Li + LiAlO2(11)

[0022] All of the above reactions require a low vacuum of less than 0.01 Torr and high temperatures of 900 to 1600°C. In addition, each of these methods has its own disadvantages. In carbon-thermal reactions, carbon monoxide (CO), a byproduct, can cause side reactions and contaminate the product. When magnesium (Mg) is used as a reducing agent, it was difficult to obtain high-purity lithium (Li) due to the tendency to form Li-Mg alloys. Furthermore, when hydrogen is used as a reducing agent, lithium hydride (LiH) impurities were present. When silicon and aluminum are used, the production yield is low due to byproducts of lithium silicate and lithium aluminate.

[0023] Currently, existing battery recycling processes recover lithium in the form of lithium compounds such as lithium hydroxide (LiOH) and lithium carbonate (Li2CO3). However, as the demand for lithium metal is expected to increase significantly when next-generation rechargeable batteries using lithium metal as electrodes are commercialized, it is necessary to develop technologies for recovering lithium metal from lithium compounds, which are the final products of the battery recycling process.

[0024] Therefore, research is needed to produce high-purity lithium metal to solve the aforementioned problem. Prior art literature

[0025] 1. Korean Registered Patent No. 10-1792753 2. Korean Registered Patent No. 10-1438272 The problem to be solved

[0026] The objective of the present invention is to provide a method for manufacturing lithium metal using a lithium compound, which can separate lithium using a high-boiling point fluid after burning the lithium compound and a metal reducing agent. means of solving the problem

[0027] A method for producing lithium metal using a lithium compound according to one experimental example of the present invention may include a) a step of preparing a mixture of a lithium compound and a metal reducing agent, b) a step of preparing a reaction product by compressing the mixture and burning it in an argon gas atmosphere, and c) a step of separating the lithium and metal reducing agent compounds contained in the reaction product using a high-boiling point fluid having a boiling point greater than or equal to the melting point of metallic lithium (Li).

[0028] According to one experimental example of the present invention, the high-boiling point fluid may have a boiling point of 200°C or higher and be a fluid inert to lithium.

[0029] According to one experimental example of the present invention, the high-boiling point fluid may be at least one selected from mineral oil, silicone oil, and mixtures thereof.

[0030] According to one experimental example of the present invention, step c) can be performed in an argon gas atmosphere at a temperature range of 250 to 300°C.

[0031] According to one experimental example of the present invention, step c) can be performed in an autoclave sealed to prevent evaporation of the high-boiling point fluid.

[0032] In step b) according to one experimental example of the present invention, one end of the mixture can be ignited and reacted by self-combustion synthesis to produce a reaction product.

[0033] According to one experimental example of the present invention, the argon pressure in step b) may be 0.1 to 5.0 MPa.

[0034] After step b) according to one experimental example of the present invention, a step of crushing the reaction product in pellet form may be further included.

[0035] The lithium compound according to one experimental example of the present invention may be at least one selected from lithium hydroxide (LiOH), lithium carbonate (Li2CO3), lithium chloride (LiCl), and lithium fluoride (LiF).

[0036] According to one experimental example of the present invention, the metal reducing agent may be an alkaline earth metal or an alloy powder thereof.

[0037] The alkaline earth metal or its alloy powder according to one experimental example of the present invention may be at least one selected from magnesium (Mg), calcium (Ca), and calcium-magnesium alloy (CaMg2).

[0038] According to one experimental example of the present invention, the molar ratio of the lithium hydroxide (LiOH) and the alkaline earth metal or alloy powder thereof may be 1:0.5 to 1:1.

[0039] According to one experimental example of the present invention, the average particle size of the lithium compound may be 10 to 100 μm.

[0040] According to one experimental example of the present invention, the average particle size of the metal reducing agent may be 50 to 250 μm. Effects of the invention

[0041] The lithium metal manufacturing method of the present invention relates to a method for manufacturing lithium metal using a lithium compound capable of separating lithium using a high-boiling point fluid after burning a lithium compound and a metal reducing agent.

[0042] In particular, lithium can be separated at temperatures below 300°C at atmospheric pressure, and there is an advantage in that lithium metal can be efficiently manufactured in a simple manner without high temperature and vacuum conditions and complex equipment. Brief explanation of the drawing

[0043] FIG. 1 is a schematic diagram of a combustion-reduction process according to one experimental example of the present invention. FIG. 2 shows (a) a temperature-time profile of a LiOH-Mg system, (b) an XRD pattern of the reaction product, and (c, d) SEM micrographs of the reaction product according to one experimental example of the present invention. Figure 3 shows (a) a lithium (Li) droplet on the surface of a high-boiling point fluid and (b) an XRD pattern of lithium (Li) metal according to one experimental example of the present invention. Specific details for implementing the invention

[0044] Specific experimental examples of the present invention will be described in detail below with reference to the drawings. However, the concept of the present invention is not limited to the experimental examples presented. Those skilled in the art who understand the concept of the present invention may easily propose other inventions that are regressive or other experimental examples included within the scope of the concept of the present invention by adding, changing, or deleting other components within the same scope of the concept, and such are also to be considered to be included within the scope of the concept of the present invention.

[0045] Additionally, functional components within the same scope of the same concept appearing in the drawings of each experimental example are described using the same reference numeral.

[0046] A method for manufacturing lithium metal using a lithium compound according to the present invention may include a) a step of preparing a mixture, b) a step of preparing a reaction product, and c) a step of separating the reaction product.

[0047] The above step a) of preparing the mixture is a step of preparing a mixture of a lithium compound and a metal reducing agent. The lithium compound may be at least one selected from lithium hydroxide (LiOH), lithium carbonate (Li2CO3), lithium chloride (LiCl), and lithium fluoride (LiF), and the metal reducing agent may be an alkaline earth metal or an alloy powder thereof. The alkaline earth metal or an alloy powder thereof may be at least one selected from magnesium (Mg), calcium (Ca), and a calcium-magnesium alloy (CaMg2).

[0048] The molar ratio of the lithium hydroxide (LiOH) and the alkaline earth metal or alloy powder thereof may be 1:0.5 to 1:1. In particular, the molar ratio of the lithium hydroxide (LiOH) and magnesium (Mg) may be 1:1, the molar ratio of the lithium hydroxide (LiOH) and calcium (Ca) may be 1:1, and the molar ratio of the lithium hydroxide (LiOH) and calcium magnesium alloy (CaMg2) may be 1:0.67. The lithium compound may have a size in the range of 0.5 to 300 μm and an average particle size of 10 to 100 μm, and the metal reducing agent may have a size in the range of 50 to 500 μm and an average particle size of 50 to 250 μm.

[0049] The main source of lithium (Li) is lithium hydroxide (LiOH) powder derived from used lithium-ion batteries (LiB). Lithium hydroxide (LiOH) powder is mixed with alkaline earth metal (EAM-Ca, Mg) or alloy (CaMg2) powder.

[0050] Step b) above, which is the step of preparing the reaction product, involves compressing the mixture and combusting it in an argon gas atmosphere to produce the reaction product. Alternatively, the reaction product can be prepared by igniting one end of the mixture and reacting it using the self-combustion synthesis method.

[0051] Additionally, the argon pressure may be 0.1 to 5.0 MPa. If the argon pressure is less than 0.1 MPa, the reduced lithium (Li) may vaporize or react with magnesium oxide (MgO) to produce lithium oxide (Li2O) or lithium-magnesium oxide. As the argon pressure increases, the vaporization temperature of lithium (Li) increases, but the concentration of lithium hydride (LiH) in the reactants also increases, resulting in a process yield of less than 10% in the range exceeding 5 MPa.

[0052] In particular, as the above argon pressure decreases, the formation of lithium hydride (LiH) is suppressed and the recovery rate increases, but due to the vaporization of lithium (Li), a pressure range of 1 MPa to 2 MPa is preferred.

[0053] The resulting mixture is compressed into a metal cup and placed inside a combustion chamber. In an argon gas atmosphere, the compressed molded body of the mixture is combusted to produce reaction products containing lithium (Li) and metal oxides (MgO, CaO).

[0054] The self-generating combustion synthesis method has the significant economic advantage over other manufacturing processes because it does not require a high-temperature reactor or an additional heat source, and the equipment is simple, resulting in low equipment costs and a simple manufacturing process. After step b) above, a step of crushing the reaction product in pellet form may be further included. The sponge-shaped combusted pellets obtained during the combustion process can be crushed into millimeter-sized pieces.

[0055] The above c) reaction product separation step is a step of separating lithium by immersing the reaction product in a high-boiling point fluid.

[0056] The high-boiling point fluid may be a fluid having a boiling point higher than the melting point of metallic lithium (Li) and being inert to lithium. In the present invention, the high-boiling point fluid has a boiling point of 200°C or higher. In particular, the high-boiling point fluid may be at least one selected from mineral oil, silicone oil, and mixtures thereof. Preferably, the high-boiling point fluid may have a boiling point of 300°C or higher.

[0057] Even for high-boiling point fluids with a boiling point of 300°C or lower, heating to 300°C or higher is possible by using a condensation tube in which the fluid itself is pressurized and the boiling point rises during the heating process.

[0058] In addition, when the separation step is heated to a temperature above the melting point of lithium (Li) and below 250°C, the process yield is lower than when performed at a temperature of 250 to 300°C, but lithium (Li) can be recovered.

[0059] Preferably, the separation step can be carried out in a high temperature range of 250 to 300°C to achieve a high process yield.

[0060] In particular, the above silicone oil may be a methylphenyl-based silicone oil in which some of the methyl groups of dimethyl silicone oil are substituted with phenyl groups. The high content of phenyl groups can improve heat resistance, and since it has a boiling point exceeding 300°C, the separation process can be carried out by minimizing evaporation even in a temperature range of 250 to 300°C during the separation process.

[0061] In addition, the density of the high-boiling point fluid may be greater than the density of magnesium oxide (MgO) and less than the density of lithium (Li). Liquid lithium (Li) and magnesium oxide (MgO) may be separated due to the density difference. If the density of the high-boiling point fluid is greater or less than the densities of lithium (Li) and magnesium oxide (MgO), both lithium (Li) and magnesium oxide (MgO) may float or sink in the high-boiling point fluid, and liquid lithium (Li) and magnesium oxide (MgO) cannot be separated. If liquid lithium (Li) and magnesium oxide (MgO) exist in the same layer without being separated, they may form lithium oxide (Li2O) or lithium-magnesium oxide.

[0062] In addition, the viscosity of the high-boiling point fluid may be 400 cSt or less at 25°C. If the viscosity is high, bubbles may be generated when the reaction product is immersed in the high-boiling point fluid, and lithium may be oxidized due to the bubbles.

[0063] The above high-boiling point fluid may be an oil that does not react with lithium (Li) having a boiling point exceeding 300°C. The above c) reaction product separation step may be performed in an argon gas atmosphere at a temperature range of 250 to 300°C and may be performed in an autoclave sealed to prevent evaporation of the high-boiling point fluid.

[0064] If the above high-boiling point fluid has a boiling point of 300°C or lower, the above c) reaction product separation step can be performed in a heating device including a condensation tube. When using a condensation tube, the fluid itself is pressurized during the heating process, and the boiling point rises, making it possible to heat to 300°C or higher.

[0065] Lithium (Li) is separated from the combustion reaction products in a heating device including a condensation tube or a stainless steel autoclave using high boiling point oil and argon pressure at a temperature in the range of 250 to 300°C. Liquid lithium (Li) can be effectively separated from the metal oxide phase.

[0066] In particular, the lithium separation method using a high-boiling point fluid has the advantage of being able to separate lithium at a temperature of 300°C or lower under atmospheric pressure, and to efficiently produce lithium metal in a simple manner without high temperature and vacuum conditions or complex equipment.

[0067] The following describes manufacturing examples and experimental examples of the present invention. However, it is specified that these manufacturing examples and experimental examples are intended to explain the composition and effects of the present invention more specifically, and that the scope of the present invention is not limited thereto.

[0068] Experimental method

[0069] FIG. 1 is a schematic diagram of a combustion-reduction process according to one experimental example of the present invention. As shown in FIG. 1(a), lithium hydroxide (LiOH) powder obtained from a discarded lithium-ion battery is combined with magnesium (Mg), calcium (Ca), or calcium-magnesium alloy (CaMg2) powder in a molar ratio of 1:1 to 0.67. This mixture is manually compressed into a stainless steel cup. As shown in FIG. 1(b), the cup containing the reaction mixture is placed in a combustion chamber and locally ignited using an electric heating filament. This process is carried out in an argon gas atmosphere in the range of 0.5 to 2.0 MPa.

[0070] As shown in Fig. 1(c), combustion proceeds from top to bottom via self-ignition synthesis after local ignition at the top of a mixture of lithium hydroxide (LiOH) and an alkaline earth metal (EAM). Fig. 1(d) shows the combusted pellet. Even after the combustion reaction, the weight of the sample remains unchanged, which indicates that all the lithium (Li) metal is retained within the sample.

[0071] FIG. 2 shows (a) a temperature-time profile of a LiOH-Mg system, (b) an XRD pattern of the reaction product, and (c, d) SEM micrographs of the reaction product according to one experimental example of the present invention.

[0072] As shown in Fig. 2(a), the temperature of the combustion wave monitored by the thermocouple of the LiOH-Mg system reaches 1200 to 1250°C. As shown in Fig. 2(b), the entire combustion process lasts for less than 10 seconds, and the combustion wave propagation speed is 0.4 cm / s. In XRD analysis, only the presence of the magnesium oxide (MgO) peak is observed because the lithium (Li) peak is difficult to detect by XRD analysis.

[0073] As shown in Fig. 2(c), an SEM micrograph of the reaction sample shows that the product consists of large molten aggregates. As shown in Fig. 2(d), these aggregates generally consist of two types of components: molten lithium (Li) and magnesium oxide (MgO) particles.

[0074] FIG. 3 shows (a) a lithium (Li) droplet on a high-boiling point fluid surface and (b) an XRD pattern of lithium (Li) metal according to one experimental example of the present invention. For the purpose of separating lithium (Li) metal from magnesium oxide (MgO), a reaction sample is first ground into small pieces under an argon atmosphere.

[0075] Next, these pieces are placed in a stainless steel autoclave and immersed in oil, a high-boiling point fluid. The autoclave is then tightly sealed and placed in a laboratory oven set to 300°C. As the heating process proceeds, lithium (Li) droplets separate and accumulate on the surface of the oil.

[0076] As shown in Fig. 3(a), in this process, the oil containing the reaction components is transferred to a glass beaker for observation. XRD analysis performed on this droplet confirms that lithium (Li) metal was successfully formed, as shown in Fig. 3(b).

[0077] Experimental Example 1

[0078] 24 g of lithium hydroxide (LiOH) powder is mixed with 24 g of magnesium (Mg) (1:1) and compressed into a stainless steel cup with a diameter of 4.0 cm and a height of 6 cm. The mixture is burned in an argon gas atmosphere of 2.0 MPa. The combustion temperature was 1200°C.

[0079] The reaction product is crushed into millimeter-sized pieces and heat-treated at 300°C in mineral oil under an argon atmosphere. The process yield of lithium (Li) is 95%.

[0080] Experimental Example 2

[0081] 24 g of lithium hydroxide (LiOH) powder is mixed with 24 g of magnesium (Mg) (1:1) and compressed into a stainless steel cup with a diameter of 4.0 cm and a height of 6 cm. The mixture is burned in an argon gas atmosphere of 2.0 MPa. The combustion temperature was 1200°C.

[0082] The reaction product is crushed into millimeter-sized pieces and heat-treated at 250°C in mineral oil under an argon atmosphere. The process yield of lithium (Li) is 75%.

[0083] Experimental Example 3

[0084] 24 g of lithium hydroxide (LiOH) powder is mixed with 24 g of magnesium (Mg) (1:1) and compressed into a stainless steel cup with a diameter of 4.0 cm and a height of 6 cm. The mixture is burned in an argon gas atmosphere of 2.0 MPa. The combustion temperature was 1200°C.

[0085] The reaction product is crushed into millimeter-sized pieces and heat-treated at 200°C in mineral oil under an argon atmosphere. The process yield of lithium (Li) is 60%.

[0086] Experimental Example 4

[0087] 24 g of lithium hydroxide (LiOH) powder is mixed with 24 g of magnesium (Mg) (1:1) and compressed into a stainless steel cup with a diameter of 4.0 cm and a height of 6 cm. The mixture is burned in an argon gas atmosphere of 5.5 MPa. The combustion temperature was 1300°C.

[0088] The reaction product is crushed into millimeter-sized pieces and heat-treated at 300°C in mineral oil under an argon atmosphere. The process yield of lithium (Li) is 9%.

[0089] Experimental Example 5

[0090] 24 g of lithium hydroxide (LiOH) powder is mixed with 24 g of magnesium (Mg) (1:1) and compressed into a stainless steel cup with a diameter of 4.0 cm and a height of 6 cm. The mixture is burned in an argon gas atmosphere of 2.0 MPa. The combustion temperature was 1200°C.

[0091] The reaction product is broken into millimeter-sized pieces and heat-treated at 300°C in silicone oil under argon. The process yield of lithium (Li) is 95%.

[0092] Experimental Example 6

[0093] 24 g of lithium hydroxide (LiOH) powder was mixed with 24 g of magnesium (Mg) (1:1) and compressed into a stainless steel cup with a diameter of 4.0 cm and a height of 6 cm. The mixture was burned in an argon gas atmosphere of 1.0 MPa. The combustion temperature was 1150°C.

[0094] The reaction product is crushed into millimeter-sized pieces and heat-treated at 300°C in mineral oil under an argon atmosphere. The process yield of lithium (Li) is 90%.

[0095] Experimental Example 7

[0096] 24 g of lithium hydroxide (LiOH) powder is mixed with 24 g of magnesium (Mg) (1:1) and compressed into a stainless steel cup with a diameter of 4.0 cm and a height of 6 cm. The mixture is burned in an argon gas atmosphere of 0.5 MPa. The combustion temperature was 1000°C.

[0097] The reaction product is crushed into millimeter-sized pieces and heat-treated at 300°C in mineral oil under an argon atmosphere. The process yield of lithium (Li) is 80%.

[0098] Experimental Example 8

[0099] 24 g of lithium hydroxide (LiOH) powder was mixed with 40 g of small calcium (Ca) granules in a 1:1 molar ratio, and the mixture was compressed into a stainless steel cup with a diameter of 4.0 cm and a height of 6 cm. The mixture was burned in an argon gas atmosphere of 2.0 MPa. The combustion temperature was 1350°C.

[0100] The reaction product is crushed into millimeter-sized pieces and heat-treated at 300°C in mineral oil under an argon atmosphere. The process yield of lithium (Li) is 90%.

[0101] Experimental Example 9

[0102] 24g of lithium hydroxide (LiOH) powder is mixed with 40 pieces of calcium magnesium alloy (CaMg2) powder (1:0.67), and the mixture is compressed into a stainless steel cup with a diameter of 4.0cm and a height of 6cm. The mixture is burned in an argon gas atmosphere of 2.0 MPa.

[0103] The reaction product is crushed into millimeter-sized pieces and heat-treated at 300°C in mineral oil under an argon atmosphere. The process yield of lithium (Li) is 90%.

[0104] Table 1 below shows the process yield of lithium (Li) according to the process conditions of Experimental Examples 1 to 9.

[0105] lithium compounds metal reducing agent SHS pressure Separation process oil Separation process temperature Process yield Experimental Example 1 LiOH Mg 2.0 MPa minerals 300℃ 95% Experimental Example 2 LiOH Mg 2.0 MPa minerals 250℃ 75% Experimental Example 3 LiOH Mg 2.0 MPa minerals 200℃ 60% Experimental Example 4 LiOH Mg 5.5 MPa minerals 300℃ 9% Experimental Example 5 LiOH Mg 2.0 MPa silicone 300℃ 95% Experimental Example 6 LiOH Mg 1.0 MPa minerals 300℃ 90% Experimental Example 7 LiOH Mg 0.5 MPa minerals 300℃ 80% Experimental Example 8 LiOH Ca 2.0 MPa minerals 300℃ 90% Experimental Example 9 LiOH CaMg2 2.0 MPa minerals 300℃ 90%

[0106] As shown in Experimental Examples 1, 8, and 9 of Table 1, when magnesium (Mg) was used as the metal reducing agent, the process yield was 95% or higher, showing a higher process yield of lithium (Li) than when calcium (Ca) and calcium-magnesium alloy (CaMg2) were used, and as shown in Experimental Examples 1 and 5, when mineral oil and silicon oil were used, there was no significant change in the process yield of lithium (Li).

[0107] In Experimental Example 4, where the argon pressure is 5.5 MPa in the lithium (Li) separation step, the process yield is 9%. As the argon pressure increases, the vaporization temperature of lithium (Li) increases, but the concentration of lithium hydride (LiH) of the reactant also increases, so the process yield is less than 10% in the range exceeding 5 MPa. Therefore, the argon pressure may be 0.1 to 5.0 MPa, and in particular, 1 to 2 MPa is preferred to exhibit a process yield of 90% or more of lithium (Li).

[0108] In addition, the lithium (Li) separation step has a process yield of 75% or more in a temperature range of 250 to 300°C and a process yield of 80% or more in a temperature range exceeding 250°C.

[0109] The lithium metal manufacturing method of the present invention relates to a method for manufacturing lithium metal using a lithium compound capable of separating lithium using a high-boiling point fluid after burning a lithium compound and a metal reducing agent.

[0110] After preparing a reaction product using the self-ignition synthesis method, which is very economical compared to other manufacturing processes because it does not require a high-temperature reactor or an additional heat source, has a simple apparatus resulting in low equipment costs, and has a simple manufacturing process, lithium can be separated by immersing the reaction product in a high-boiling point fluid.

[0111] In particular, the lithium separation method using a high-boiling point fluid has the advantage of being able to separate lithium at a temperature of 300°C or lower under atmospheric pressure, and to efficiently produce lithium metal in a simple manner without high temperature and vacuum conditions or complex equipment.

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