Method for recovering lithium from secondary batteries by means of plasma electric arc furnace

Abstract

The present invention relates to a method for recovering lithium from secondary batteries by means of a plasma electric arc furnace, the method enabling lithium to be recovered using plasma arc heat at a very high recovery rate from black mass obtained by crushing secondary batteries. The method for recovering lithium from secondary batteries by means of a plasma electric arc furnace according to the present invention comprises: a black mass generation step (11) of manufacturing black mass through a pretreatment step of crushing waste lithium battery cells to recover lithium from the waste lithium batteries; a step (13) of generating black powder by reducing the black mass manufactured in the black mass generation step in a shaft reduction furnace while injecting oxygen; a flux addition step (15) of mixing the black powder with a CaCl2 flux; a step (17) of melting a raw material of the black powder to which the flux has been added in the plasma electric arc furnace; and a step (19) of recovering lithium compound dust generated in the plasma electric arc furnace through a bag filter.

Description

Method for recovering lithium from a secondary battery by a plasma electric arc

[0001] The present invention relates to a method for recovering lithium from a secondary battery using a plasma electric arc, and more specifically, to a method for recovering lithium from a secondary battery using a plasma electric arc capable of recovering lithium with a very high recovery rate from black mass obtained by crushing a secondary battery using plasma arc heat.

[0002] The demand for lithium-ion batteries (LiBs) has been increasing alongside the portable electronic device market since the 1990s, and has recently surged globally due to the rapid expansion of the electric vehicle market. As a result, the supply and demand of lithium resources could soon become a major issue, as much more lithium will be needed than can be obtained from natural resources. Furthermore, the continuous accumulation of waste batteries can also cause significant environmental problems.

[0003] To address these issues, the recycling of used lithium-ion batteries is crucial. If waste lithium batteries can be recycled, environmental damage can be significantly reduced.

[0004] Hydrometallurgy and pyrometallurgy are methods for recovering valuable metals contained in spent batteries. Hydrometallurgy involves pretreatment to recover cathode materials, followed by additional purification and recovery techniques such as leaching, selective precipitation, ion exchange, and solvent extraction to extract valuable metals. Some hydrometallurgy processes have disadvantages, such as relatively long leaching times and low leaching efficiency, due to the high valence state of the cathode active material and the strong binding forces of organic binders. Furthermore, the extensive use of high-concentration acidic solutions and reducing agents, along with complex process steps, generates significant wastewater, which can cause secondary pollution through the emission of wastewater and harmful gases. In particular, lithium can become dispersed during these separation and purification steps, leading to low lithium recovery rates.

[0005] To overcome these disadvantages and extract lithium, a dry smelting method can be used. The dry smelting recycling process has the advantage of reducing processing and operation costs by enabling large-scale processing through rapid chemical reactions driven by high heat. Additionally, the feed materials are relatively flexible and the process is simple. Mixed waste batteries can be directly charged into the melting furnace without undergoing a sorting process, which can resolve issues such as fire and explosion risks, particularly when processing lithium batteries. Furthermore, it eliminates the need to consider the creation of an inert atmosphere during the crushing process in wet smelting. However, the dry smelting process has the disadvantages of low purity of recovered metals and the need for exhaust gas treatment. In particular, unlike other precious metals, lithium is absorbed into the slag along with low-cost metals; therefore, there is also the issue that an additional process for lithium recovery from the slag is required to effectively recover lithium.

[0006] Korean Patent No. 10-2641852 (Title of Invention: Method for Recovering Lithium from Waste Lithium Batteries) discloses a method for recovering lithium by mixing a flux containing a Ca compound and a sulfur component with crushed or broken waste lithium battery cells, melting the mixture at a high temperature of 1300°C or higher, and obtaining a lithium-sulfur compound (Li2SO4) that volatilizes therefrom.

[0007] However, these conventional technologies have a lithium recovery rate of about 90%, and since raw materials in the form of flakes containing any one of the spent lithium battery cells, cell packs, modules, assemblies, or scraps thereof are fed in, there are limitations on the raw materials. Furthermore, there are limitations on the application of electric furnace methods for mass processing due to demanding operating conditions, such as blocking oxygen during heating to prevent oxidation of sulfur components, introducing inert gases like N2 or Ar, or controlling the oxygen partial pressure.

[0008] Therefore, there is a need for a method to recover lithium more efficiently and recycle resources, and the development of a process capable of recycling spent lithium batteries on a large scale using clean energy is required.

[0009] The present invention was devised to solve the aforementioned conventional problems, and the objective of the present invention is to provide a method for recovering lithium from a secondary battery by a plasma electric arc that can achieve a high lithium recovery rate of 95% or more from black mass.

[0010] Another objective of the present invention is to provide a method for recovering lithium from a secondary battery using a plasma electric arc furnace, which is environmentally friendly and reduces waste generation by using clean energy rather than fossil fuels.

[0011] Another objective of the present invention is to provide a method for recovering lithium from a secondary battery using a plasma electric arc, which can reduce processing steps in the wet post-processing stage and recover high-quality lithium by removing impurities from the black mass through high-temperature melting by a reduction furnace and a plasma electric arc.

[0012] Another objective of the present invention is to provide a method for recovering lithium from secondary batteries using a plasma electric arc that can process waste batteries in large quantities and continuously process black mass of waste batteries of various specifications.

[0013] The method for recovering lithium from a secondary battery by a plasma electric arc furnace according to the present invention comprises: a black mass generation step of producing black mass through a pretreatment step of crushing and grinding spent lithium battery cells to recover lithium from spent lithium batteries; a step of producing black powder by reducing the black mass produced in the black mass generation step in a shaft reduction furnace while introducing oxygen; a flux addition step of mixing a flux of CaCl2 with the black powder; a step of melting the black powder raw material with the added flux in a plasma electric arc furnace; and a step of recovering lithium compound dust generated in the plasma electric arc furnace through a bag filter.

[0014] In the method for recovering lithium from a secondary battery by a plasma electric arc furnace according to the present invention, the step of generating the black powder is characterized by operating the black mass in the shaft reduction furnace at 1400~1500℃ together with the combustion heat of graphite so that the oxide is reduced by the graphite, and when the black mass is burned at 1 ton / h, the graphite is burned at 300~400 kg / h, thereby removing the remaining amount of graphite, binder, and electrolyte and undergoing an oxidation / reduction process to oxidize Fe / Mn to FeO / MnO, so that the weight of the black mass is reduced to 45~55 wt%.

[0015] In the method for recovering lithium from a secondary battery by a plasma electric arc furnace of the present invention, the step of generating the black powder is characterized by raising the temperature to 1500°C in the shaft reduction furnace to detoxify the exhaust gas and causing secondary combustion of the exhaust gas, and producing steam by the heat of combustion to use in a subsequent process.

[0016] In the method for recovering lithium from a secondary battery by a plasma electric arc furnace of the present invention, the flux addition step is characterized by adjusting the mixing amount of the CaCl2 flux so that the Li:Cl molar ratio in LiCl becomes 0.5 to 1.5, so that the black powder can be formed into a LiCl lithium compound in a CaO-Al2O3 slag composition.

[0017] In the method for recovering lithium from a secondary battery by a plasma electric arc of the present invention, the flux addition step is characterized by adding Al powder in a weight ratio of 15-25% of the amount of black powder.

[0018] In the method for recovering lithium from a secondary battery by a plasma electric arc furnace of the present invention, the flux addition step involves adding CaCO3 or CaO while adjusting the molar ratio of Li:Cl to 0.5 to 1.5, thereby making the weight ratio of Al2O3 / CaO 0.5 to 1.5 so that the inflow of Li into the slag in the CaO-Al2O3 slag composition is minimized.

[0019] In the method for recovering lithium from a secondary battery by a plasma electric arc furnace according to the present invention, the step of melting in the plasma electric arc furnace is characterized by melting the black powder in the plasma electric arc furnace with an electric arc of DC 60~250V / 800~1700A to produce lithium compound dust, a molten alloy containing all of Ni, Co, and Cu at 1450℃~1650℃, and Al2O3 / CaO slag.

[0020] In the method for recovering lithium from a secondary battery by a plasma electric arc furnace according to the present invention, the ratio of black powder raw material to [Al powder, catalyst, CaCl2 and CaCO3] input during the melting step in the plasma electric arc furnace is 1:1.5 by weight, and the input is characterized by being in the form of powder.

[0021] The method for recovering lithium from a secondary battery by a plasma electric arc of the present invention further comprises a process for manufacturing alloy powder from the molten alloy.

[0022] According to the method for recovering lithium from a secondary battery by the plasma electric arc of the present invention with the above configuration, it is possible to recover lithium with a high recovery rate of 95% or more.

[0023] In addition, according to the present invention, by using clean energy electricity instead of fossil fuels to recover lithium from lithium secondary batteries, it becomes environmentally friendly and reduces waste generation.

[0024] In addition, according to the present invention, by removing impurities through high-temperature melting by a plasma electric arc furnace, the processing steps in the wet post-processing stage can be reduced, and high-quality lithium can be recovered.

[0025] In addition, according to the present invention, secondary battery waste can be processed in large quantities, and lithium can be recovered by continuously processing waste batteries of various specifications.

[0026] FIG. 1 is a flowchart of a method for recovering lithium from a secondary battery by a plasma electric arc according to the present invention.

[0027] FIG. 2 is a drawing showing a cross-section of a plasma electric arc according to the present invention.

[0028] Figure 3 is a photographic diagram showing the process of Example 2 of the method for recovering lithium from a secondary battery by a plasma electric arc according to the present invention.

[0029] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0030] In this specification, the term "lithium battery" is used to include all primary batteries, secondary batteries, or all-solid-state batteries containing lithium, and lithium batteries that have reached the end of their lifespan or are discarded after use are collectively referred to as "waste lithium batteries."

[0031] Key materials used for the positive electrode of a secondary lithium-ion battery include LCO (LiCoO2), NCM (Li[Ni,Co,Mn]O2), NCA (Li[Ni,Co,Al]O2), LMO (LiMn2O4), and LFP (LiFePO4), depending on the composition of the metal salt, while carbonaceous materials such as graphite or silica are used as the negative electrode material, and copper is used as the current collector.

[0032] FIG. 1 is a flowchart of a method for recovering lithium from a secondary battery by a plasma electric arc according to the present invention, wherein the present invention comprises a black mass generation step (11), a black powder generation step (13), a flux addition step (15), a melting step (17) in a plasma electric arc, and a lithium dust recovery step (19).

[0033] Black mass is manufactured (11) by undergoing a pretreatment step of crushing or breaking the waste lithium battery cells to remove the Al / Cu foil of the positive / negative electrode material in order to recover lithium from the waste lithium battery.

[0034] Waste battery cells contain 45 to 55 wt% black mass as confirmed below, and copper, aluminum, iron, and other components are present.

[0035]

[0036] Waste batteries are crushed / grinded in a nitrogen atmosphere in cell form, rather than in pack or module form, and Al / Cu foil is screened out to produce a graphite-containing black mass to be used as a raw material for subsequent processes.

[0037] Moisture / electrolytes remaining in the black mass can be dried by the steam generated during the subsequent graphite combustion process.

[0038] Table 1 below is a table comparing the components of LFP, NCM, and NCA black masses, and it can be seen that the graphite and F content of LFP black mass is relatively high.

[0039]

[0040] In conventional dry processes, waste batteries are crushed into pack / module forms and plastics are pyrolyzed, recovering about 70% of the lithium, while about 30% is lost as slag.

[0041] In such conventional methods, the cathode material Cu is contained as a Ni-Co-Cu alloy during the melting process, and an alloy with a relatively high Cu grade is produced, and a large amount of wastewater is generated when recovering Cu through subsequent acid leaching, but if the black mass of the present invention is adopted as a raw material, the Cu content in the molten alloy is relatively lowered.

[0042] Next, the black mass produced in the black mass generation step (11) is produced into black powder (13) in a shaft reduction furnace, at which time the graphite, binder, and electrolyte are removed, so the carbon content becomes 3% or less, the oxide of the anode active material is reduced, and Fe / Mn is oxidized to FeO / MnO and removed as slag in an electric arc furnace in a subsequent process.

[0043] The present invention involves an oxidation / reduction process step using black mass as a raw material in an oxygen-powered shaft reduction furnace to maximize lithium recovery. Specifically, in the oxidation process where oxygen is introduced into the shaft reduction furnace to remove graphite, binders, and electrolytes from the black mass through an oxidation reaction, LiMO2 is reduced (LiMO2 + CO → Li2O + M + CO2), and Al / Fe / Mn are each oxidized to form oxides. (Here, M represents Metal.)

[0044] In the shaft reduction furnace, the weight of the black mass is reduced by about 45-55%, and the grade of Li / Ni / Co / Cu is concentrated, so the equipment size of the subsequent melting process by the plasma electric arc furnace can be minimized.

[0045] In the shaft reduction furnace, operation is performed at approximately 1400 to 1500°C along with the heat of graphite combustion, and oxides are reduced by graphite, and some Li2CO3 / LiF is also produced. Compared to a general roasting furnace which operates at a temperature of 900 to 1,100°C, the reduction furnace of the present invention operates at a relatively higher temperature compared to the roasting furnace.

[0046] In a shaft reduction furnace, the temperature is raised to 1500°C to detoxify the exhaust gas and secondary combust the exhaust gas. By producing steam from the combustion heat and utilizing it for subsequent processes, energy efficiency can be increased. This process in the shaft reduction furnace is one of the differences from the reaction in a conventional roasting furnace.

[0047] The black mass of NCM contains about 30-40 wt% of graphite. Assuming that 1 ton of black mass is burned per hour, 300-400 kg / h of graphite is burned while 1 ton of black mass is burned for 1 hour. Including the weight loss of the electrolyte and binder, the total weight loss in the shaft reduction furnace is about 45-55 wt% of the black mass.

[0048] Therefore, since the throughput of black powder for recovering the same amount of lithium dust in a subsequent lithium dust recovery process is reduced to 50% or less compared to black mass, it is desirable to recover lithium by turning black mass into black powder through a reduction process in a reduction furnace.

[0049] The exhaust gas from the shaft reduction furnace, which is subjected to secondary combustion at 1,400~1,500℃, is discharged into the atmosphere after passing through a scrubber following the removal of harmful substances.

[0050] By providing additional oxygen to the furnace to raise the temperature of the shaft reduction furnace, the amount of air introduced can be reduced, and in the present invention, it is designed to supply sufficient oxygen so as not to result in incomplete combustion conditions where CO is generated.

[0051] The black powder production process in the shaft reduction furnace of the present invention differs from a process in which a cathode material, etc., is used as a raw material in the absence of graphite, and sulfur compounds / chloride compounds are mixed and roasted in a roasting furnace without using oxygen.

[0052] Next, flux (15) is added to the black powder reduced in the shaft.

[0053] To form a LiCl lithium compound from graphite-removed black powder based on CaO-Al2O3 slag, it is preferable to mix a CaCl2 flux with the black powder. SiO2 is not used as the flux, and Al powder and CaCO3 are used as reducing agents; the graphite-removed black powder is mixed with the Al powder and CaCl2 flux in powder form rather than as pellets.

[0054] As can be seen in Table 2 below, LiF has a vaporization temperature of 1,676°C and poor solubility in water. Li2CO3 has a decomposition temperature of 1,310°C but poor solubility in water, and Li2O has good solubility in water but a vaporization temperature of 2,600°C.

[0055]

[0056] In contrast, the vaporization temperature of LiCl is relatively low at 1,382°C, and since LiCl has good solubility in water and is suitable for water leaching in subsequent processes, it is desirable to generate lithium compound dust containing LiCl. To this end, CaCl2 is added as a flux to supply Cl to the black mass. Li2O + CaSO4 → Li2SO4 + CaO

[0057] Li2O + CaCl2 → 2LiCl + CaO

[0058] Since the reaction equation is △G (Gibbs free energy) < 0, it is a spontaneous reaction, and as the temperature rises, it reacts with CaCl2 to produce volatile LiCl.

[0059] Here, the amount of flux mixed with CaCl2 is adjusted so that the molar ratio of Li:Cl in LiCl is 0.5 to 1.5, preferably 1 to 1.2, in order to produce a lithium compound LiCl under optimal process conditions.

[0060] In addition, a catalyst is mixed to inhibit the incorporation of Li into the slag, and the amount added is 5-40 wt% of the raw material. The catalyst promotes the binding of LiCl and improves the fluidity of the slag.

[0061] As described above, when 1 ton of black mass is reduced in a shaft reduction furnace, about 0.5 tons of black powder is produced, and a total of about 0.5 to 0.75 tons of [Al + catalyst + CaCl2 + CaCO3] is added to this 0.5 tons of black powder.

[0062] Lithium has high reactivity with Al and Si, so LiAlO6, LiSiO4, LiAl(Si2O6), etc., are easily generated when slag is formed.

[0063] Therefore, in order to minimize the inflow of Li into the slag in the CaO-Al2O3 slag composition, the ratio of Al2O3 / CaO should be basic with a weight ratio of 0.5 to 1.5, preferably 0.85 to 1.1, and the slag temperature should be at least 1,450°C or higher.

[0064] To do this, CaCO3 (limestone) or CaO is added while adjusting the molar ratio of Li:Cl to 1 to 1.2.

[0065] To lower the slag melting temperature, it is desirable to maintain the weight ratio of CaO:Al2O3 at 51%:49% (Al2O3 / CaO = 0.96) at 1371℃, with CaO weight% at 45% to 55%.

[0066] In the case of CaO 45% / Al2O3 55%, the Al2O3 / CaO ratio is approximately 1.22, and in the case of CaO 55% / Al2O3 45%, the Al2O3 / CaO ratio is approximately 0.818. However, to adjust the Al2O3 / CaO ratio to 0.85 to 1.1 to match basic conditions during operation, it is advantageous for lithium recovery.

[0067] The amount of Al used as a reducing agent is determined by considering the amount of LiMO2 after the black mass reduction process, and Al (aluminum scrap powder) is added at a weight ratio of 15-25% of the amount of black powder by considering the amounts of Ni / Co / Mn.

[0068] Looking at the phase diagram below, it can be confirmed that the melting point is low when the weight ratio of Al2O3 / CaO in the CaO-Al2O3 base composition is 0.85 to 1.1. Therefore, the amount of CaCl2 added is adjusted so that the molar ratio of Li : Cl is 1 : 1.2 or less, and lithium can be recovered with a recovery rate of over 95% in continuous operation from the binary slag of CaO - Al2O3, rather than the ternary slag of SiO2 - CaO - Al2O3.

[0069]

[0070] After passing through the black powder generation step (13) and flux addition step (15) above, the black powder raw material mixed with flux is subjected to 300KV of DC 250V / 1700A electricity in a plasma electric arc furnace (EAF) to produce lithium dust, Ni,Co,Cu alloy ingot (25), and Al2O3 / CaO slag (23).

[0071] The plasma electric arc furnace can raise the temperature above 1800℃, and the temperature of the molten alloy is 1550-1650℃.

[0072] Dry molten reduction smelting that recovers more than 95% of lithium dust can be successfully commercialized only when the DC plasma electric arc of the present invention is used and CaO-Al2O3 2-component slag is adopted.

[0073] By adopting a DC plasma electric arc furnace that can easily control the temperature of the slag to over 1500℃, the unreduced metal of LiMO2 is reduced by Al, and the slag is made into a binary Al2O3-CaO base, and Li2O reacts with CaCl2 to facilitate the reaction Li2O + CaCl2 → 2LiCl + CaO, thereby enabling the recovery of more than 95% of lithium as lithium compound (LiCl) dust.

[0074] Generally, in black mass, Ni / Co / Mn are mixed as metal oxides, while Fe and Cu are mixed as metals. Through the dry reduction melting smelting process using the plasma electric arc of the present invention, Ni-Co-Cu becomes a mixed alloy, and a Ni-Co-Cu alloy with a relatively low Cu grade is produced, in which trace amounts (0.3% or less) of Fe / Mn may be present.

[0075] The alloy ingot is melted again in a high-frequency induction furnace to produce alloy powder with a mesh size of 200 or less. At this time, the Cu content of the alloy is much lower than that of alloys produced by the conventional dry process, which reduces the amount of acid used and the amount of wastewater generated.

[0076] Therefore, mass processing of spent lithium batteries is not possible by induction heating or microwave heating rather than the plasma electric arc of the present invention, and temperature control of the slag is not easy.

[0077] FIG. 2 is a drawing showing a cross-section of a plasma electric arc according to the present invention.

[0078] In the plasma electric arc furnace of the present invention, the input ratio of black powder raw materials to [Al powder, catalyst, CaCl2 and CaCO3] is 1:1.5, preferably 1:1.15, and is input in the form of powder rather than pellets. The operating temperature is 1600-1650℃.

[0079] Next, the lithium dust is recovered (19) by passing through a cyclone / bag filter, and then lithium carbonate (21) is produced in a subsequent wet process. The composition of the lithium compounds in the lithium dust is mostly LiCl, but trace amounts of LiF may be present.

[0080] [Example 1]

[0081] In Example 1 of the present invention, black powder, flux, and catalyst were mixed, and then separated into Ni-Co alloy and lithium-containing dust in a small plasma electric arc furnace (DC 100V / 1200A 120KV), and the recovery rates of Ni, Co, and Li were measured.

[0082] The raw material components of Example 1 are as shown in Table 3 below.

[0083]

[0084] Here, the recovery rates of Ni, Co, and Li were evaluated as shown in Table 4 below.

[0085]

[0086] According to the measurement results of Example 1, 12% of the input raw material was left as dust, and the recovery rates of Ni and Co were confirmed to be over 98%, and the recovery rate of Li was over 95%.

[0087] [Example 2]

[0088] 120 kg of NCA-based waste batteries and 125 kg of a blending binder were mixed for 10 minutes using a mixer, then loaded into a plasma arc furnace (300 KV with DC 250 V / 1700 A), nickel and cobalt were reduced to metal alloys, and lithium was converted into lithium compounds and collected as dust. As confirmed in Table 5 below, the lithium recovery rate is 97.19%.

[0089]

[0090] Figure 3 is a photograph illustrating the test process of Example 2 of the method for recovering lithium from a secondary battery by a plasma electric arc according to the present invention. As shown in the figure, Example 2 measured the lithium recovery rate through the steps of measuring the weight of the raw material, measuring the weight of the binder, mixing the raw material and the binder, adding the raw material, reacting with the plasma arc, and measuring the product after the reaction.

[0091] [Example 3]

[0092] In Example 3 of the present invention, 120 kg of raw materials from Table 6 below were operated in a small plasma electric arc furnace with DC electricity of 60V-100V and a current of 800-1200A to separate the alloy ingot, lithium-containing dust, and slag, and the recovery rate of each was measured. The operating time was 3 hours / 3 tapping cycles, and the operating temperature was 1450~1550℃.

[0093]

[0094] Flux and auxiliary materials (CaCl2) are added in the mixing ratios of Table 7, and Al scrap is used as Al foil, Al cans, and Al radiator chips, with an input amount of 5-40% of the raw materials.

[0095]

[0096] The average grades of the alloy ingot and slag of Example 3 yielded the results shown in Table 8. From this, it can be confirmed that the Ni / Co recovery rate is over 98% and the Li recovery rate is 95.06%. (Analysis results from Gumi Electronics & Information Technology Institute)

[0097]

[0098] As a result of the slag analysis, the slag composition is SiO2 1.46%, Al2O3 41.70%, CaO 49.20%, and the CaO / Al2O3 ratio is 1.18. The analysis values ​​of the dust are as shown in Table 9.

[0099]

[0100] As confirmed in Examples 1, 2, and 3 above, according to the method for recovering lithium from a secondary battery by a plasma electric arc furnace of the present invention, lithium can be recovered from the black mass of a spent lithium battery with a high recovery rate of at least 95%.

Claims

1. A black mass generation step (11) for producing black mass by undergoing a pretreatment step of crushing waste lithium battery cells to recover lithium from waste lithium batteries; A step (13) of reducing the black mass produced in the above black mass generation step in a shaft reduction furnace while introducing oxygen to produce black powder; Flux addition step (15) of mixing a flux of CaCl2 into the above black powder; A step (17) of melting the black powder raw material with the above flux added in a plasma electric arc furnace; and A method for recovering lithium from a secondary battery by a plasma electric arc furnace, characterized by including the step (19) of recovering lithium compound dust generated in the above plasma electric arc furnace through a bag filter.

2. In Paragraph 1, A method for recovering lithium from a secondary battery by a plasma electric arc furnace, wherein the step (13) of generating the black powder is characterized by operating the black mass in the shaft reduction furnace at 1400~1500℃ with the heat of graphite combustion, so that the oxide is reduced by the graphite, and when the black mass is burned at 1 ton / h, the graphite is burned at 300~400 Kg / h, thereby removing the remaining amount of graphite, binder, and electrolyte and undergoing an oxidation / reduction process to oxidize Fe / Mn to FeO / MnO, so that the weight of the black mass is reduced to 45~55 wt%.

3. In Paragraph 2, A method for recovering lithium from a secondary battery by a plasma electric arc furnace, characterized in that the step (13) of generating the black powder above raises the temperature to 1500°C in the shaft reduction furnace to detoxify the exhaust gas and secondarily combusts the exhaust gas, and produces steam by the combustion heat and uses it in a subsequent process.

4. In Paragraph 1, A method for recovering lithium from a secondary battery by a plasma electric arc, wherein the flux addition step (15) is characterized by adjusting the amount of CaCl2 flux mixed so that the Li:Cl molar ratio in LiCl becomes 0.5 to 1.5 so that the black powder can be produced as a LiCl lithium compound in the CaO-Al2O3 slag composition.

5. In Paragraph 1, A method for recovering lithium from a secondary battery by a plasma electric arc, characterized in that the flux addition step (15) above involves adding Al powder at a weight ratio of 15-25% of the amount of black powder.

6. In Paragraph 5, A method for recovering lithium from a secondary battery by a plasma electric arc furnace, characterized in that the flux addition step (15) adds CaCO3 or CaO while adjusting the molar ratio of Li:Cl to 0.5 to 1.5, thereby making the weight ratio of Al2O3 / CaO 0.5 to 1.5 so that the inflow of Li into the slag in the CaO-Al2O3 slag composition is minimized.

7. In Paragraph 1, A method for recovering lithium from a secondary battery by a plasma electric arc furnace, characterized in that the step (17) of melting in the above plasma electric arc furnace is a step of melting the black powder with an electric arc of DC 60~250V / 800~1700A in the plasma electric arc furnace to produce lithium compound dust, a molten alloy containing all of Ni, Co, and Cu at 1450℃~1650℃, and Al2O3 / CaO slag.

8. In Paragraph 1, A method for recovering lithium from a secondary battery by a plasma electric arc furnace, characterized in that in the step (17) of melting in the above plasma electric arc furnace, the input ratio of black powder raw material: [Al powder, catalyst, CaCl2 and CaCO3] is 1:1.5 by weight ratio and is input in powder form.

9. In Paragraph 7, A method for recovering lithium from a secondary battery by a plasma electric arc furnace, characterized by further including a process for manufacturing alloy powder from the molten alloy.

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