Methods for selectively recovering lithium from lithium iron phosphate

Abstract

This invention relates to a method for selectively recovering lithium from lithium iron phosphate using a sulfuric acid solution, comprising the step of reacting lithium iron phosphate (LiFePO4, LFP) powder with a sulfuric acid solution for at least 60 minutes, wherein the concentration of the sulfuric acid solution is greater than 1M and less than 3M, and the weight ratio of the lithium iron phosphate (LiFePO4, LFP) powder to the sulfuric acid solution is greater than 1:3 and less than 7.

Description

Technical Field

[0001] This invention relates to a method for selectively recovering lithium from lithium iron phosphate using a sulfuric acid solution. Background Technology

[0002] With the development of battery performance, positive electrode active materials for lithium secondary batteries have evolved in various ways. Initially used LiCoO2, through doping or surface modification techniques, has seen continuous improvement in its early performance, and recently it can even be used at charging voltages close to 4.3V.

[0003] On the other hand, as applications become more complex, the characteristics required for lithium-ion batteries are becoming increasingly demanding. Research and development of new materials requiring high operating voltage and high capacity has begun. In recent years, with the strengthening of carbon regulations both domestically and internationally, efforts are underway to develop secondary batteries for electric vehicles, requiring new materials with high output and high safety. In light of these requirements, materials with excellent safety profiles, such as LiMn₂O₄ and LiFePO₄, have been developed.

[0004] Lithium iron phosphate (LiFePO4, LFP) is widely recognized as one of the most promising cathode materials for lithium-ion batteries due to its advantages such as high output, low cost, low toxicity, excellent thermal stability, and high reversibility. In particular, LiFePO4 (LFP) is considered a very safe cathode material because of its low electrochemical potential. Therefore, lithium-ion batteries using LFP as the cathode material have recently been widely used in electric vehicles (EVs) and hybrid electric vehicles (HEVs), especially electric buses. From 2015 to 2020, 401 GWh of secondary batteries (lithium-ion + LFP) were used. In China, a major producer and consumer of LFP, the demand for LFP batteries in the electric vehicle market increased significantly from 2.59 GWh in 2019 to 20 GWh in 2021.

[0005] The amount of discarded secondary batteries for electric vehicles (EVs) that have reached the end of their service life (5 to 10 years) has entered a phase of substantial increase. Frost & Sullivan predicts that the global post-use battery market will grow at an average annual rate of 99.8%, reaching US$7.8 billion by 2025. Due to the rapid growth in demand for LFP batteries, the disposal of post-use LFP batteries is expected to become a problem.

[0006] In particular, the toxic LiPF6 and metal-ion-containing organic electrolytes in LFP batteries can migrate into soil and groundwater when disposed of in landfills, causing environmental pollution. Therefore, post-processing such as recycling and reuse is crucial. Furthermore, with the development of electric vehicles (EVs) and hybrid electric vehicles (HEVs), the demand for lithium, the main raw material for LFP batteries, has surged. Since South Korea's domestic lithium supply and demand are entirely dependent on imports, the stability of the lithium supply and demand is expected to increase in the future. Therefore, recycling used LFP batteries not only benefits the environment but also contributes to the stability of South Korea's domestic lithium supply and demand.

[0007] Traditional methods for recycling used LFP batteries include hydrometallurgical processes and direct regeneration. Hydrometallurgical processes, primarily used in recycling used lithium-ion batteries, involve leaching the positive electrode active material obtained in the pretreatment step, selectively separating metals from the leaching solution, and then refining. Currently, the hydrometallurgical method for recycling used LFP batteries involves using inorganic acids such as H₂SO₄, HCl, and H₃PO₄ to leach all elements of the positive electrode active material during the leaching process, followed by a complex chemical precipitation separation process using NaOH or NH₃ and H₂O. In this process, excessive and high-concentration acid is added to leach all metals into the solution, thus requiring a large amount of alkali during separation.

[0008] Direct recycling involves recovering used battery cathode materials, immersing them in organic solvents, and reusing them as raw materials for battery cathodes. One method for direct recycling of used LFP batteries involves separating LFP powder directly from the cathode and then heating it at high temperatures or immersing it in organic solvents for recovery. However, the recovered cathode material often contains a large number of impurities, and its structure is generally damaged after multiple charge-discharge cycles, resulting in poor electrochemical performance during reuse. Therefore, to develop an industrially feasible recycling process for used LFP batteries, it is necessary to make the process simpler, more efficient, and more environmentally friendly. Summary of the Invention

[0009] The purpose of this invention is to provide a method for selectively recovering lithium from lithium iron phosphate by controlling the reaction conditions of lithium iron phosphate with sulfuric acid solution.

[0010] A method for selectively recovering lithium from lithium iron phosphate according to an embodiment of the present invention includes the step of reacting lithium iron phosphate (LiFePO4, LFP) powder with sulfuric acid solution for at least 60 minutes, wherein the concentration of the sulfuric acid solution is greater than 1M and less than 3M, and the weight ratio of the lithium iron phosphate (LiFePO4, LFP) powder to the sulfuric acid solution is greater than 1:3 and less than 7.

[0011] In one embodiment, the reaction step can be carried out at room temperature.

[0012] In one embodiment, the reaction step may include stirring the mixture of lithium iron phosphate (LiFePO4, LFP) powder and sulfuric acid solution at a speed of 250 to 350 rpm.

[0013] In one embodiment, during the reaction step, lithium ions can be selectively leached from the lithium iron phosphate powder.

[0014] In one embodiment, the present invention may further include a solid-liquid separation step of the reaction solution after the reaction step.

[0015] In one embodiment, the solution filtered through the solid-liquid separation step includes lithium sulfate, ferrous sulfate (FeSO4) free of impurities, lithium iron pyrophosphate (LiFe(P2O7)) and lithium dihydrogen phosphate (LiH2PO4).

[0016] In one embodiment, the solid-liquid separation can be performed by vacuum filtration.

[0017] In one embodiment, the present invention may further include a step of drying the solution filtered after solid-liquid separation.

[0018] In one embodiment, the drying step may be carried out at a temperature of 350 to 500°C for more than 22 hours and less than 26 hours.

[0019] In one embodiment, lithium sulfate powder free of impurities can be prepared during the drying step.

[0020] In one embodiment, the invention may further include a step of heat-treating a mixture of the lithium sulfate powder and carbon in a carbon dioxide or carbon monoxide atmosphere.

[0021] In one embodiment, the material made from said carbon includes at least one of carbon powder, graphene, graphite, activated carbon, and carbon black.

[0022] In one embodiment, the heat treatment can be performed at a temperature of 700 to 900°C.

[0023] In one embodiment, lithium carbonate (Li2CO3) can be prepared in the heat treatment step.

[0024] In one embodiment, the lithium iron phosphate (LiFePO4, LFP) powder may be a powder recovered from waste lithium-ion batteries.

[0025] Invention Effects

[0026] Unlike previous processes that used excessive and high-concentration inorganic acids to leach all elements contained in lithium iron phosphate into a solution for separation, this invention selectively leaches and recovers lithium, excluding impurities, by controlling the reaction conditions between lithium iron phosphate (LiFePO4, LFP) and sulfuric acid solution. Therefore, compared with existing processes, this is simpler, more efficient, and achieves a lithium recovery rate of over 99%, resulting in a high recovery rate.

[0027] Furthermore, according to the present invention, lithium sulfate powder free of impurities can be easily prepared, and the lithium sulfate powder can be used to prepare lithium carbonate through a simple dry heat treatment process, thus having the advantage of convenient process. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a method for selectively recovering lithium from lithium iron phosphate according to an embodiment of the present invention.

[0029] Figure 2 The XRD (X-ray Diffraction) and ICP-OES (Inductively Coupled Plasma) analysis results of the LFP powder used in the embodiments of the present invention are shown.

[0030] Figure 3 The XRD analysis results of dried powder prepared by varying the concentration of sulfuric acid solution according to an embodiment of the present invention are shown.

[0031] Figure 4 The XRD analysis results of a dried powder prepared by varying the stirring time during the reaction process according to an embodiment of the present invention are shown.

[0032] Figure 5 The XRD analysis results of dried powder prepared by changing the solid-liquid ratio of sulfuric acid solution and LFP powder according to an embodiment of the present invention are shown. Detailed Implementation

[0033] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Various modifications and forms can be made to the present invention; specific embodiments are illustrated in the drawings and described in detail herein. However, it should be understood that the present invention is not intended to be limited to the specific disclosed forms, and all modifications, equivalents, and substitutions included within the spirit and scope of the present invention are permitted.

[0034] The terminology used in this specification is for illustrative purposes and does not limit the invention. Unless otherwise specified in the text, the singular includes the plural. It should be understood that the terms "comprising" or "having," etc., as used herein, are used to designate the presence of features, steps, actions, constituent elements, parts, or combinations thereof described in the specification, without excluding the presence or additional possibilities of one or more other features or steps, actions, constituent elements, parts, or combinations thereof.

[0035] Unless otherwise defined, all terms used in this specification, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and shall not be interpreted in an ideal or overly formulaic sense unless expressly defined in this specification.

[0036] To selectively leach lithium from lithium iron phosphate (LiFePO4, LFP), this invention allows for control of the reaction conditions between LiFePO4, LFP, and sulfuric acid solution. In this case, a 98.08% sulfuric acid (H2SO4) solution can be used as the acid solvent for leaching lithium from LiFePO4, LFP, and the LiFePO4, LFP can be powder recovered from spent lithium-ion batteries.

[0037] Figure 1 A schematic diagram illustrating a method for selectively recovering lithium from lithium iron phosphate according to an embodiment of the present invention.

[0038] Reference Figure 1 The method for selectively recovering lithium from lithium iron phosphate according to the present invention may include a step (S100) of reacting lithium iron phosphate (LiFePO4, LFP) powder with sulfuric acid solution for at least 60 minutes, wherein the concentration of the sulfuric acid solution may be greater than 1M and less than 3M, and the weight ratio of lithium iron phosphate (LiFePO4, LFP) powder to sulfuric acid solution may be greater than 1:3 and less than 7.

[0039] The step (S100) is a process of leaching only lithium ions from lithium iron phosphate, in which a reaction occurs according to the following reaction formula.

[0040] [Reaction Formula]

[0041] 2LiFePO4(s)+H2SO4(aq)=Li2SO4(aq)+2FePO4(s)+H2

[0042] Specifically, in order to leach only lithium ions from lithium iron phosphate (LiFePO4, LFP) powder, the concentration of the sulfuric acid solution reacting with the lithium iron phosphate (LiFePO4, LFP) powder in step (S100) is preferably greater than 1M and less than 3M, most preferably 2M. When the concentration of the sulfuric acid solution is less than 1M, Fe leaching occurs, resulting in impurities such as FeSO4 in the solution. When the concentration of the sulfuric acid solution is greater than 3M, Fe and P leaching occur, resulting in impurities such as FeSO4 and LiFe(P2O7) in the solution.

[0043] Furthermore, in order to leach only lithium ions from lithium iron phosphate (LiFePO4, LFP) powder, in step (S100), the reaction time between the lithium iron phosphate (LiFePO4, LFP) powder and the sulfuric acid solution is preferably 60 minutes or more, and most preferably 60 minutes. When the reaction time is less than 60 minutes, the reaction is incomplete, resulting in a low lithium recovery rate. Due to the leaching of Fe and P, impurities such as FeSO4 and LiH2PO4 may be generated in the solution.

[0044] On the other hand, in order to leach only lithium ions from lithium iron phosphate (LiFePO4, LFP) powder, in step (S100), the weight ratio of lithium iron phosphate (LiFePO4, LFP) powder to sulfuric acid solution is preferably greater than 1:3 and less than 7, and most preferably 1:5. When the weight ratio of LFP powder to sulfuric acid solution is less than 1:3, Fe leaching occurs, resulting in impurities such as FeSO4 in the solution. When the ratio is greater than 1:7, Fe and P leaching occurs, resulting in impurities such as FeSO4 and LiFe(P2O7) in the solution.

[0045] As described above, in this invention, a sulfuric acid solution with a concentration greater than 1M and less than 3M is reacted with lithium iron phosphate powder and lithium iron phosphate (LiFePO4, LFP) powder in a weight ratio greater than 1:3 and less than 7 with the sulfuric acid solution for at least 60 minutes. This allows for the selective leaching of lithium ions from the lithium iron phosphate powder. In this case, step (S100) is preferably performed at room temperature because when the temperature exceeds room temperature, Fe and P leaching occurs, leading to the formation of impurities such as FeSO4 and LiH2PO4 in the solution.

[0046] Additionally, step (S100) may include stirring the mixture of lithium iron phosphate (LiFePO4, LFP) powder and sulfuric acid solution at a speed of 250 to 350 rpm. Therefore, the reaction can be carried out by stirring the mixture.

[0047] Additionally, the present invention may further include a solid-liquid separation step (S200) of the reaction solution after step (S100). In one embodiment, the solid-liquid separation is not particularly limited and can be carried out by known methods, preferably by vacuum filtration.

[0048] The solution filtered through step (S200) contains lithium sulfate (Li2SO4) and free of impurities such as ferrous sulfate (FeSO4), lithium iron pyrophosphate (LiFe(P2O7)), and lithium dihydrogen phosphate (LiH2PO4). This is because only lithium ions are leached out in step (S200) to generate lithium sulfate (Li2SO4).

[0049] On the other hand, the present invention may also include a step (S300) of drying the filtered solution after solid-liquid separation. In one embodiment, step (S300) is preferably carried out at a temperature of 350 to 500°C for more than 22 hours and less than 26 hours, because since the boiling point of sulfuric acid is 337°C, it should be carried out at a temperature of 350 to 500°C to prepare lithium sulfate powder by complete drying. Most preferably, step (S300) may be carried out at a temperature of 400°C for 24 hours.

[0050] In one embodiment, lithium sulfate powder free of impurities can be prepared in step (S300).

[0051] On the other hand, the present invention may also include a step (S400) of heat treating the mixture of the material composed of lithium sulfate powder and carbon prepared in step (S300) in a carbon dioxide or carbon monoxide atmosphere.

[0052] The step (S400) is the process of preparing lithium carbonate from lithium sulfate powder. Lithium sulfate powder is mixed with carbon materials and then heat-treated by injecting carbon dioxide or carbon monoxide to prepare lithium carbonate (Li2CO3).

[0053] In one embodiment, the heat treatment can be carried out under dry conditions. These dry conditions can mean a state free of moisture. Therefore, no intermediate products or byproducts containing water are generated in step (S400).

[0054] In one embodiment, the carbon dioxide or carbon monoxide can be continuously injected into the reaction vessel during the reaction of lithium sulfate powder and carbon materials, and a predetermined concentration of carbon dioxide or carbon monoxide can be maintained to sustain the atmosphere.

[0055] In one embodiment, the carbon material and the injected carbon dioxide or carbon monoxide can be reacted with the lithium sulfate powder by heat treatment to generate lithium carbonate. The carbon material can be a carbon-containing material; for example, carbon-containing materials such as carbon powder, graphene, graphite, activated carbon, carbon black, etc., can be used without limitation. The carbon material can be mixed in a molar ratio of more than 1 mole of the lithium sulfate.

[0056] In one embodiment, in the carbon dioxide atmosphere, the carbon dioxide can react with the carbon material and the lithium sulfate powder to generate lithium carbonate.

[0057] In one embodiment, in the carbon dioxide atmosphere, the carbon dioxide can also react with lithium sulfate powder to produce lithium carbonate in the absence of carbon materials. When the carbon dioxide reacts with lithium sulfate powder together with the carbon materials, the lithium sulfate can be converted into lithium carbonate, therefore, there may be no other byproducts.

[0058] In one embodiment, the heat treatment can be carried out in a furnace at about 700 to 900°C.

[0059] Unlike previous processes that used excessive and high-concentration inorganic acids to leach all elements contained in lithium iron phosphate into a solution for separation, this invention selectively leaches and recovers lithium, excluding impurities, by controlling the reaction conditions between lithium iron phosphate (LiFePO4, LFP) and sulfuric acid solution. Therefore, compared with existing processes, this is simpler, more efficient, and achieves a lithium recovery rate of over 99%, resulting in a high recovery rate.

[0060] Furthermore, according to the present invention, since lithium sulfate powder free of impurities can be easily prepared, and lithium carbonate can be prepared from the lithium sulfate powder by a simple dry heat treatment process, it has the advantage of convenient process.

[0061] [Example]

[0062] This embodiment uses LFP (LiFePO4) powder, a positive electrode active material recovered from a used lithium-ion battery. XRD (X-ray diffraction) and ICP-OES (inductively coupled plasma) analyses were performed on the LFP powder used in this embodiment, and the results are presented below. Figure 2 .

[0063] pass Figure 2 XRD analysis confirmed that the LFP powder used in this embodiment is a LiFePO4 phase, and ICP-OES analysis confirmed that the contents of the main elements are 4.04 wt% Li, 32.7 wt% Fe and 18.7 wt% P.

[0064] On the other hand, in order to confirm the optimal conditions for selectively leaching lithium (Li) from the LFP powder using a 98.08% H2SO4 solution, experiments were conducted by varying the concentration of the sulfuric acid solution, the stirring time, and the solid-liquid ratio of the sulfuric acid solution to the LFP powder.

[0065] 1) Metal leaching results based on sulfuric acid solution concentration

[0066] 10 g of LFP powder was added to beakers containing 50 ml of sulfuric acid solutions with concentrations of 0.5 M, 1 M, 2 M, and 3 M, respectively, and stirred at 300 rpm for 60 minutes. The solid and liquid phases were then separated by vacuum filtration. The filtered solutions were analyzed by ICP-OES to determine the lithium (Li) content and calculate the recovery rate.

[0067] Next, the filtered solution was dried at 400°C for 24 hours to prepare lithium sulfate powder. The dried powder was analyzed by XRD to determine the presence of residual impurities and to perform phase analysis.

[0068] Refer to the display of XRD analysis results Figure 3 The results show that only the Li2SO4 phase was detected in lithium sulfate powder prepared with 2M sulfuric acid solution, while lithium sulfate powder prepared with 0.5M, 1M, and 3M sulfuric acid solutions was detected along with impurities FeSO4 and LiFe(P2O7).

[0069] These results confirm that when using a 2M sulfuric acid solution, lithium impurities are selectively leached out.

[0070] Table 1 shows the measurement results of Li content in the solution after vacuum filtration by ICP-OES analysis and the Li recovery rate calculated by the following formula.

[0071] [Mode]

[0072]

[0073] Table 1

[0074]

[0075] Referring to Table 1, the Li recovery rate was calculated to be 99.79% when the sulfuric acid solution concentration was 2M and 99.87% when the sulfuric acid solution concentration was 3M. ​​However, as... Figure 3 The XRD analysis results showed that impurities were detected in the powder prepared using 3M sulfuric acid solution, while only the Li2SO4 phase was detected in the powder prepared using 2M sulfuric acid solution, thus confirming that 2M sulfuric acid solution is the optimal condition.

[0076] 2) Metal leaching results based on stirring time

[0077] 10 g of LFP powder was added to a beaker containing 50 ml of 2 M sulfuric acid solution, and then stirred at 300 rpm for 5 min, 10 min, 30 min, and 60 min, respectively. The solid and liquid phases were then separated by vacuum filtration. The filtrate was analyzed by ICP-OES to determine the Li content and calculate the recovery rate.

[0078] Next, the filtered solution was dried at 400°C for 24 hours to prepare lithium sulfate powder. The dried powder was analyzed by XRD to determine the presence of residual impurities and for phase analysis.

[0079] Refer to the XRD analysis results shown Figure 4 The results show that in lithium sulfate powder prepared by reaction with a stirring time of 60 minutes, only the Li2SO4 phase was detected, while in lithium sulfate powder prepared by reaction with a reaction time of less than 60 minutes, impurities FeSO4 and LiFe(P2O7) were detected together.

[0080] These results confirm that when the stirring time is set to 60 minutes for the reaction, lithium that has been impurities removed is selectively leached out.

[0081] In addition, Table 2 below shows the Li content measurement results of the solution after vacuum filtration by ICP-OES analysis and the Li recovery rate calculated by the above formula.

[0082] Table 2

[0083]

[0084] Referring to Table 2, the lithium recovery rate was highest at 99.61% when the stirring time was 60 minutes. Therefore, the stirring time of 60 minutes is confirmed to be the optimal condition.

[0085] 3) Metal leaching results based on the solid-liquid ratio of sulfuric acid solution and LFP powder.

[0086] 10 g of LFP powder was added to beakers containing 30 ml, 50 ml, and 70 ml of 2M sulfuric acid solution, respectively, and stirred at 300 rpm for 60 minutes. The solid and liquid phases were then separated by vacuum filtration. The filtrate was analyzed by ICP-OES to determine the lithium content and calculate the recovery rate.

[0087] Next, the filtered solution was dried at 400°C for 24 hours to prepare lithium sulfate powder. The dried powder was analyzed by XRD to determine the presence of residual impurities and to perform phase analysis.

[0088] Refer to the XRD analysis results shown Figure 5 The results show that only the Li2SO4 phase was detected in lithium sulfate powder prepared with a solid-liquid ratio of LFP powder to sulfuric acid solution of 1:5, but impurities FeSO4 and LiFe (P2O7) were detected together in lithium sulfate powder prepared with solid-liquid ratios of 1:3 and 1:7.

[0089] These results confirm that when the solid-liquid ratio of LFP powder to sulfuric acid solution is 1:5, lithium impurities are selectively leached out.

[0090] In addition, Table 3 below shows the measurement results of Li content in the solution after vacuum filtration by ICP-OES analysis and the Li recovery rate calculated by the above formula.

[0091] Table 3

[0092]

[0093] Referring to Table 3, when the solid-liquid ratio of LFP powder to sulfuric acid solution is 1:5, the calculated lithium recovery rate is 99.74%, and when the solid-liquid ratio is 1:7, the calculated lithium recovery rate is 99.80%. However, as... Figure 5 The XRD analysis results showed that impurities were detected in the powder prepared by setting the solid-liquid ratio of LFP powder to sulfuric acid solution to 1:7, while only the Li2SO4 phase was detected in the prepared powder, confirming that a solid-liquid ratio of 1:5 was the optimal condition.

[0094] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention as set forth in the claims.

Claims

1. A method for selectively recovering lithium from lithium-iron-phosphate, characterized in that, The method comprises: a step of reacting lithium iron phosphate (LiFePO4, LFP) powder with a sulfuric acid solution for 60 minutes, wherein the concentration of the sulfuric acid solution is 2M; the weight ratio of the lithium iron phosphate (LiFePO4, LFP) powder to the sulfuric acid solution is 1:5; the lithium iron phosphate (LiFePO4, LFP) powder is recovered from a waste lithium ion battery; the reaction step is performed at room temperature; in the reaction step, only lithium ions are selectively leached from the lithium iron phosphate powder; after the reaction step, a step of performing solid-liquid separation on the reaction solution is further included; the solution filtered through the solid-liquid separation step includes lithium sulfate (Li2SO4); and the filtered solution does not contain ferrous sulfate (FeSO4), lithium iron pyrophosphate (LiFe(P2O7)), and lithium dihydrogen phosphate (LiH2PO4).

2. The method of selectively recovering lithium from lithium-iron-phosphate according to claim 1, characterized in that, The reaction step includes a step of stirring the mixture of the lithium iron phosphate (LiFePO4, LFP) powder and the sulfuric acid solution at a speed of 250 to 350 rpm.

3. The method of selectively recovering lithium from lithium-iron-phosphate salts according to claim 1, characterized in that, The solid-liquid separation is performed by a reduced pressure filtration method.

4. The method of selectively recovering lithium from lithium-iron-phosphate salts according to claim 1, characterized in that, A step of drying the filtered solution after the solid-liquid separation is further included.

5. The method of selectively recovering lithium from lithium-iron-phosphate salts according to claim 4, characterized in that, The drying step is performed at a temperature of 350 to 500°C for 22 hours or more and 26 hours or less.

6. The method of selectively recovering lithium from lithium-iron-phosphate salts according to claim 4, characterized in that, A lithium sulfate powder is prepared in the drying step.

7. The method of selectively recovering lithium from lithium-iron-phosphate salts according to claim 6, characterized in that, A step of heat-treating a mixture of a material composed of the lithium sulfate powder and carbon in a carbon dioxide or carbon monoxide atmosphere is further included.

8. The method of selectively recovering lithium from lithium-iron-phosphate salts according to claim 7, characterized in that, The material composed of the carbon includes at least one of carbon powder, graphene, graphite, activated carbon, and carbon black.

9. The method of selectively recovering lithium from lithium-iron-phosphate salts according to claim 7, characterized in that, The heat treatment is performed at a temperature of 700 to 900°C.

10. The method of selectively recovering lithium from lithium-iron-phosphate salts according to claim 7, characterized in that, A lithium carbonate (Li2CO3) is prepared in the heat treatment step.

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