Method and apparatus for recycling positive electrode material for polyanion-based lithium secondary battery

Abstract

To provide a method and apparatus for recycling a polyanion-based lithium positive electrode material for a lithium secondary battery, which does not generate toxic by-products such as acid waste and simply and efficiently separates a high-value substance from the positive electrode material for the secondary battery.SOLUTION: A method for recycling a polyanion-based lithium secondary battery positive electrode material includes a step S100 of chlorinating a polyanion-based lithium secondary battery positive electrode material separated from a battery with a chlorine-containing gas to form a first mixture containing a compound containing a polyanion and lithium chloride (LiCl), and a step S200 of contacting the first mixture with a solvent to separate and obtain a second mixture containing the compound containing a polyanion, lithium chloride, and the solvent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for recycling polyanion-based lithium secondary battery positive electrode materials for lithium secondary batteries, and more specifically to a method and apparatus for recycling polyanion-based lithium secondary battery positive electrode materials that does not generate toxic by-products such as acid waste and can simply and efficiently separate high-value substances from the secondary battery positive electrode materials. [Background technology]

[0002] As technological development and demand for mobile devices, electric vehicles, and hybrid vehicles increases, the demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which exhibit high energy density and working potential, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0003] Recently, with growing interest in environmental issues, much research is being conducted on electric vehicles (EVs) and hybrid electric vehicles (HEVs) that can replace vehicles that use fossil fuels such as gasoline and diesel, which are one of the main causes of air pollution. Nickel-metal hydride (Ni-MH) secondary batteries have been used as the power source for such electric vehicles (EVs) and hybrid electric vehicles (HEVs), but currently, active research is being conducted on the use of lithium secondary batteries, which have high energy density, high discharge voltage, and output stability, and some have been commercialized.

[0004] A lithium secondary battery has a structure in which an electrode assembly is formed by interposing a porous separator between a positive electrode and a negative electrode, each of which has an active material coated on a current collector, and is impregnated with a non-aqueous electrolyte containing a lithium salt. As the positive electrode active material for such lithium secondary batteries, lithium cobalt oxides, lithium manganese oxides, lithium nickel oxides, lithium composite oxides, etc. are used, and as the negative electrode active material, carbon materials are mainly used, although the use of silicon compounds, sulfur compounds, etc. is also being considered.

[0005] When manufacturing automotive batteries, which require high output characteristics, there is an increasing need to use cathode materials that can support output at low voltages. Recently, the lithium iron phosphate secondary battery (LiFePO4 SECONDARY BATTERY) has been proposed, which uses lithium iron phosphate (LiFePO4), an active material for polyanion-based lithium cathode materials.

[0006] LFP batteries (LiFePO4 batteries) have a lower operating voltage range than the widely used ternary (Li(Ni, Mn, Co)O2) materials and spinel manganese (LiMn2O4) cathode active materials, but they have the advantage of stable operating characteristics, and their application is expanding in the current situation where safety issues are becoming a concern. As interest in lithium secondary batteries grows and their range of applications expands, so too does interest in recycling the high-value materials contained in the batteries.To date, the recycling process for lithium secondary batteries has focused solely on recovering lithium, nickel, manganese cobalt, and other elements contained in ternary materials (Li(Ni, Mn, Co)O2) and spinel manganese (LiMn2O4), and recycling LFP has yet to receive much attention.

[0007] However, post-consumption, especially of LFP batteries, can mitigate the life cycle impact of electric vehicles by almost 50%. The global warming potential associated with production per kg of LFP active material, calculated using life cycle analysis, is approximately 19-55 MJ. Therefore, recycling all lithium-ion batteries, not just those rich in nickel, cobalt, and manganese, would be a good opportunity to stimulate local economies by applying long-term circular economy principles.

[0008] In addition, when conventionally known recycling methods for NCM-based positive electrode materials are applied to polyanion-based positive electrode materials, there are problems in that the methods cannot be applied or the recycling efficiency is significantly reduced due to the difference in crystal structure between NCM-based positive electrode materials and polyanion-based positive electrode materials. As a result, a recycling process for LFP has been proposed (International Publication No. WO2023 / 050014), but this has the drawback that the recycling process is too complicated, making it uneconomical and unusable. In addition, the use of toxic, highly acidic substances in the recycling process makes it extremely unfavorable from an environmental perspective.

[0009] Therefore, there is an urgent need to develop a recycling method for polyanion-based lithium secondary battery cathode materials that can be applied to polyanion-based lithium cathode materials including LFP, that does not use toxic acidic substances in the process, is advantageous from the standpoints of safety and environmental compatibility, and that allows for selective separation and recovery of cathode material materials in a simple and efficient process. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. WO2023 / 050014 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been devised to solve the above problems, and aims to provide a method and apparatus for recycling polyanion-based lithium secondary battery positive electrode materials, which can safely separate lithium and polyanion-based compounds contained in polyanion-based lithium secondary battery positive electrode materials contained in waste batteries, ultimately reducing the social and economic costs of lithium secondary batteries.

[0012] In addition, in the recycling process, by not using toxic acidic chemical substances, it is excellent from the viewpoints of safety and environmental compatibility, does not require further purification steps, and there is another object of providing a recycling method and apparatus for a lithium positive electrode material that is also excellent from the viewpoints of economy and utilization degree.

Means for Solving the Problems

[0013] In order to solve the above-described problems, the present invention reacting a polyvalent anion-based lithium secondary battery positive electrode material separated from a battery with a chlorine-containing gas to form a first mixture containing a compound containing a polyvalent anion and lithium chloride (LiCl); and (2) separating and obtaining a second mixture containing a compound containing a polyvalent anion, lithium chloride, and a solvent by bringing the first mixture into contact with a solvent. A recycling method for a polyvalent anion-based lithium secondary battery positive electrode material is provided.

[0014] Further, after the step (2), a step of removing the solvent from the second mixture to obtain lithium chloride may be further included.

[0015] Also, the polyvalent anion-based lithium secondary battery positive electrode material in the step (1) is LiA x (PO4) y and may be.

[0016] Here, A is any one or more selected from the group consisting of iron (Fe), cobalt (Co), manganese (Mn), and nickel (Ni), and x and y satisfy 0.5 < x ≦ 3.0 and 0.5 < y ≦ 3.0.

[0017] Also, the chlorination reaction temperature can be 20 to 280°C.

[0018] Also, the chlorination reaction temperature can be 170 to 280°C.

[0019] The chlorine-containing gas may include at least one selected from the group consisting of chlorine gas (Cl2), hydrogen chloride (HCl), phosgene (COCl2), and carbon tetrachloride (CCl4).

[0020] The solvent may include at least one selected from the group consisting of water, ethanol, methanol, butanol, propanol, hydrazine, methyl formaldehyde, acetone, formic acid, pyridine, and benzene.

[0021] The present invention also provides a method for recycling a polyanion-based lithium secondary battery positive electrode material, which includes the steps of: (1) chlorinating a polyanion-based lithium secondary battery positive electrode material separated from a battery with a chlorine-containing gas to form a first mixture containing a compound containing a polyanion and lithium chloride (LiCl); (2) contacting the first mixture with a solvent to separate and obtain a second mixture containing the compound containing a polyanion, lithium chloride, and the solvent; (3) reacting the second mixture with a carbonate to form a third mixture containing lithium carbonate (LiCO); and (4) separating the lithium carbonate from the third mixture.

[0022] The present invention also provides a method for recycling a polyanion-based lithium secondary battery positive electrode material, which includes the steps of: (1) chlorinating a polyanion-based lithium secondary battery positive electrode material separated from a battery with a chlorine-containing gas to form a first mixture containing a compound containing a polyanion and lithium chloride (LiCl); (2) contacting the first mixture with a solvent to separate and obtain a second mixture containing the compound containing a polyanion, lithium chloride, and the solvent; (3) reacting the second mixture with a carbonate to form a third mixture containing lithium carbonate (LiCO); (4) separating the lithium carbonate from the third mixture; (5) reacting the lithium carbonate with calcium hydroxide to obtain a fourth mixture containing lithium hydroxide (LiOH) and calcium carbonate (CaCO); and (6) separating the lithium hydroxide from the fourth mixture.

[0023] After step (2), the method may further include step (7) of adding a lithium compound to the compound containing the polyanion to form a fifth mixture; step (8) of reacting the fifth mixture to reform the phase of a polyanion-based lithium secondary battery positive electrode material; and step (9) of improving the crystallinity of the fifth mixture to resynthesize a polyanion-based lithium secondary battery positive electrode material having excellent electrochemical activity.

[0024] Also, the lithium compound may be lithium carbonate separated from the third mixture in step (4) or lithium hydroxide (LiOH) separated from the fourth mixture in step (6).

[0025] The number of moles of lithium ions in the lithium compound may be 100 to 120% of the number of moles of metal ions in the compound containing the polyvalent anion.

[0026] In addition, the step (8) may involve reacting the fifth mixture at a temperature of 200 to 400° C. for 1 to 24 hours.

[0027] In addition, the step (9) may involve reacting the fifth mixture at a temperature of 500 to 850° C. for 1 to 24 hours.

[0028] The resynthesized polyanion-based lithium secondary battery positive electrode material may have an initial discharge capacity of 100 mAh / g or more.

[0029] The present invention also provides an apparatus for recycling a polyanion-based lithium secondary battery positive electrode material, which includes: a first reaction section that chlorinates a polyanion-based lithium secondary battery positive electrode material separated from a battery with a chlorine-containing gas to form a first mixture containing a compound containing a polyanion and lithium chloride; and a first separation section that is connected to the first reaction section and brings the first mixture into contact with a solvent to separate and obtain a second mixture containing the compound containing a polyanion, lithium chloride, and the solvent.

[0030] The recycling device for a polyanion-based lithium secondary battery positive electrode material according to the present invention may further include a second reaction unit communicating with the first separation unit and reacting the second mixture with a carbonate to form a third mixture containing lithium carbonate; and a second separation unit communicating with the second reaction unit and separating the lithium carbonate from the third mixture.

[0031] The recycling device for polyanion-based lithium secondary battery positive electrode material according to the present invention may further include a third reaction unit communicating with the second separation unit and configured to react the lithium carbonate with calcium hydroxide to form a fourth mixture containing lithium hydroxide (LiOH) and calcium carbonate (CaCO3); and a third separation unit communicating with the third reaction unit and configured to separate the lithium hydroxide from the fourth mixture.

[0032] In addition, the recycling device for polyanion-based lithium secondary battery positive electrode material according to the present invention may further include a synthesis unit that is connected to the first separation unit, the second separation unit, and the third separation unit, and that resynthesizes the polyanion-based lithium secondary battery positive electrode material from the polyanion-containing compound, lithium carbonate, and lithium hydroxide separated in the first separation unit, the second separation unit, and the third separation unit.

[0033] In addition, in the recycling device for polyanion-based lithium secondary battery positive electrode material according to the present invention, the first reaction section may further include a gas injection section for injecting gas into the first reaction section. [Effects of the Invention]

[0034] The present invention provides a method and apparatus for recycling polyanion-based lithium positive electrode materials, which can safely separate lithium and polyanion-based compounds contained in polyanion-based lithium positive electrode materials contained in waste batteries, ultimately reducing the social and economic costs of lithium secondary batteries.

[0035] Furthermore, since the recycling process does not use toxic acidic chemicals, it is excellent in terms of safety and environmental compatibility, and does not require any additional purification process, making it extremely advantageous in terms of economy and usability. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 is a flow chart showing a method for recycling a polyanion-based lithium secondary battery positive electrode material according to one embodiment of the present invention. [Figure 2] FIG. 2 is a flow chart that schematically illustrates a method for recycling a secondary battery positive electrode material according to another embodiment of the present invention. [Figure 3] FIG. 3 is a flow chart schematically illustrating a method for recycling a secondary battery positive electrode material according to still another embodiment of the present invention. [Figure 4] FIG. 4 is a flow chart schematically illustrating a method for recycling a secondary battery positive electrode material according to still another embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing a recycling device for polyanion-based lithium secondary battery positive electrode materials according to one embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing a recycling device for a polyanion-based lithium secondary battery positive electrode material according to another embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing a recycling device for a polyanion-based lithium secondary battery positive electrode material according to still another embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing a recycling device for a polyanion-based lithium secondary battery positive electrode material according to still another embodiment of the present invention. [Figure 9] FIG. 9 is a graph showing the analysis results of an X-ray diffraction experiment for all products after chlorinating LFP according to one embodiment of the present invention. [Figure 10] FIG. 10 is a graph showing the results of an X-ray diffraction experiment on the solid-state material remaining after separating the product from the chlorination reaction of LFP according to one embodiment of the present invention by passing it through water. [Figure 11] FIG. 11 is a photograph showing a recycling process of an electrode including a polyanion-based lithium secondary battery positive electrode material according to one embodiment of the present invention. [Figure 12] FIG. 12 is a graph showing the analysis results of an X-ray diffraction experiment on a solid product obtained by separating it through water after a chlorination reaction of an electrode including a polyanion-based lithium secondary battery positive electrode material according to an embodiment of the present invention. [Figure 13] FIG. 13 is a graph showing the comparison of the analytical results of an X-ray diffraction experiment on a resynthesized product of a polyanion-based lithium secondary battery cathode material according to one embodiment of the present invention with the analytical results of an experiment on a cathode material product resynthesized without the method of the present invention. [Figure 14] FIG. 14 is a graph showing the analysis results of the discharge capacity of a resynthesized product of a polyanion-based lithium secondary battery cathode material according to one embodiment of the present invention, compared with the analysis results of a cathode material product resynthesized without the method of the present invention. [Figure 15] FIG. 15 is a graph showing the analytical results of an X-ray diffraction experiment on a resynthesized product of a polyanion-based lithium secondary battery cathode material according to yet another embodiment of the present invention, compared with the analytical results of an experiment on a cathode material product resynthesized without using the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may be embodied in various different forms and is not limited to the embodiments set forth herein.

[0038] As described above, conventional methods for recycling secondary battery cathode materials have limitations, such as not being applicable to polyanion-based lithium cathode materials such as LFP, or even if they are applicable to polyanion-based lithium cathode materials, using toxic acidic substances in the process, which is disadvantageous in terms of safety and environmental compatibility, or requiring an additional purification process, which is disadvantageous in terms of economy and usability.

[0039] The present invention addresses the aforementioned problems by providing a method for recycling a polyanion-based lithium secondary battery cathode material, which includes (1) chlorinating a polyanion-based lithium secondary battery cathode material with a chlorine-containing gas to form a first mixture containing a polyanion-containing compound and lithium chloride; and (2) contacting the first mixture with a solvent to separate and obtain a second mixture containing a polyanion-containing compound, lithium chloride, and the solvent. This method safely separates lithium and polyanion-based compounds contained in polyanion-based lithium cathode materials from discarded batteries, ultimately reducing the social and economic costs of lithium secondary batteries. Furthermore, the recycling process does not use toxic acidic chemicals, making it safer and more environmentally friendly than conventional recycling methods. It does not require additional purification processes and allows for the simple and efficient separation of valuable materials, making it an economically advantageous method.

[0040] FIG. 1 is a flow chart showing a method for recycling a polyanion-based lithium secondary battery positive electrode material according to one embodiment of the present invention. The present invention will be described in detail below with reference to the drawing.

[0041] First, in step (1), a polyanion-based lithium secondary battery positive electrode material separated from the battery is subjected to a chlorination reaction with a chlorine-containing gas to form a first mixture containing a compound containing polyanions and lithium chloride (S100 in FIG. 1).

[0042] Conventional recycling methods for NCM-based cathode materials have had problems in that when these methods are applied to polyanion-based cathode materials, they are either impossible to apply or the recycling efficiency is significantly reduced due to differences in the chemical properties and crystalline structures of NCM-based cathode materials and polyanion-based cathode materials.

[0043] As a result, a recycling method for polyanion-based lithium secondary battery cathode materials has been reported, in which waste batteries are leached in a strong acid solution to separate lithium, cathode metal materials, and polyanion-based materials, as described above. However, such a separation method using a strong acid not only generates additional acid waste, but also has problems such as the reactivity of lithium causing it to be separated together with other metals during the separation process, requiring an additional purification process to separate the lithium, and significantly reducing separation efficiency due to the similar chemical properties of the metals.

[0044] Therefore, the present invention solves the above-mentioned problems by subjecting a polyanion-based lithium secondary battery cathode material to a chlorination reaction with a chlorine-containing gas. More specifically, waste batteries may contain polyanion-based lithium compounds, which are the cathode material for secondary batteries. In the present invention, the chlorination reaction in step (1) separates the compounds into compounds containing lithium and polyanions. That is, lithium is converted into lithium chloride and can be separated from the compounds containing polyanions.

[0045] As a result, the present invention can simplify the entire process by selectively and easily recovering lithium chloride without generating secondary acid waste, thereby maximizing treatment efficiency and process efficiency.

[0046] Specifically, the compound containing a polyvalent anion may be a compound remaining after lithium is removed from the compound of Chemical Formula 1 contained in the polyvalent anion-based lithium secondary battery cathode material described below. For example, if the compound of Chemical Formula 1 is LiFePO4, the compound containing a polyvalent anion may be FePO4.

[0047] In addition, the compound containing a polyvalent anion may be alone or may further contain some impurities or solvents that are usually contained.

[0048] Here, the polyvalent anion-based compound can be recycled in a manner of being resynthesized into the positive electrode material of the secondary battery through the steps described later.

[0049] Specifically, the polyvalent anion-based lithium secondary battery positive electrode material separated from the battery may contain a compound of the following Chemical Formula 1. <Chemical Formula 1>: LiA x (B) y Here, the A is any one or more selected from the group consisting of iron (Fe), cobalt (Co), manganese (Mn), nickel (Ni), vanadium (V), and titanium (Ti), and the B can be any one or more selected from the group consisting of PO4, PO4F, SO4, SO4F, BO3, SiO4, P2O7, MoO4, and WO4. Preferably, the A is any one or more selected from the group consisting of iron, cobalt, and manganese, and the B can be PO4.

[0050] When the A is any one or more selected from the group consisting of iron, cobalt, and manganese, and the B is PO4, the polyvalent anion-based lithium positive electrode material has an olivine structure. When the positive electrode material has such an olivine structure, it is superior in the efficiency of the chlorination reaction in the low-temperature region compared to when it has other structures such as a layered structure or a spinel structure, and as a result, a compound containing lithium and a polyvalent anion can be separated from the positive electrode material with high efficiency in the low-temperature region.

[0051] In addition, x and y in Chemical Formula 1 can satisfy 0.5 < x ≤ 3.0 and 0.5 < y ≤ 3.0.

[0052] In addition, the polyvalent anion-based lithium positive electrode material can be any one or more selected from the group consisting of a positive electrode active material containing a compound of Chemical Formula 1, a positive electrode material containing the positive electrode active material, and an electrode containing the positive electrode material.

[0053] Specifically, the chlorination reaction in step (1) may be carried out at a temperature of 20 to 280°C, more preferably 80 to 280°C, and most preferably 170 to 280°C. The temperature of the chlorination reaction may be the temperature of the chlorine-containing gas. If the chlorination reaction temperature is below 80°C, the polyanion-based lithium cathode material may not react sufficiently with the chlorine-containing gas, resulting in the remaining unreacted polyanion-based lithium cathode material. If the chlorination reaction temperature is below 170°C, the chlorination reaction efficiency of the lithium contained in the polyanion-based lithium secondary battery cathode material may decrease. If the chlorination reaction temperature is above 280°C, the lithium and polyanion-containing compound may further react to form another compound containing both lithium and the polyanion-based compound, making it impossible to separate the lithium and the polyanion-based compound.

[0054] More specifically, referring to Table 1 below, when the reaction temperature is 80 to 280°C, the reaction rate of the polyanion-based lithium secondary battery positive electrode material is superior compared to temperatures outside this range. If the reaction proceeds at temperatures below 80°C, the polyanion-based lithium secondary battery positive electrode material may remain unreacted, while if the reaction proceeds at temperatures above 280°C, side reactions may occur and separation may not be performed properly. In particular, when the reaction proceeds at 170 to 280°C, the separation efficiency is significantly superior compared to temperatures outside this range.

[0055] However, even if polyanion-based lithium secondary battery cathode materials remain, there is no significant problem in recovering lithium chloride through a subsequent dissolution process. Such low-temperature processes have the advantage of reducing energy consumption and extending the life of the reactor and associated facilities, so they can be applied as needed, even if some loss of efficiency is tolerated. Therefore, even when the chlorination reaction is carried out at a temperature range of 20°C to 280°C, LFP can be separated, and this method is advantageous in terms of economic efficiency, such as reducing energy consumption during the process and extending the life of associated facilities.

[0056] Furthermore, when lithium is separated from an NCM-based cathode material with a layered crystalline structure by a chlorination reaction, the reaction proceeds only at temperatures above approximately 450°C due to the crystalline structure. This results in a significant energy consumption during lithium separation, which is economically and environmentally unfavorable. However, when applied to a polyanion-based lithium cathode material without a layered crystalline structure, lithium can be separated at relatively low temperatures due to the difference in the crystalline structure, demonstrating excellent performance from economic and environmental perspectives.

[0057] The chlorination reaction according to the present invention can be carried out under the above-mentioned temperature conditions for 0.1 to 24 hours, preferably 0.3 to 6 hours, and is more efficient when the chlorination reaction is carried out for 0.3 to 6 hours than when it is not carried out.

[0058] Specifically, the chlorine-containing gas is not limited as long as it can react with the polyanion-based lithium secondary battery positive electrode material to form a compound containing lithium chloride and a polyanion. Preferably, the gas contains one or more selected from the group consisting of chlorine gas (Cl), hydrogen chloride (HCl), phosgene (COCl), and carbon tetrachloride (CCl), and more preferably, the gas contains chlorine gas (Cl).

[0059] More specifically, the chlorine-containing gas can be a mixture of 0.1 to 90% by volume of a chlorine-containing compound based on the total weight, with the remaining amount being Ar, N2, O2, or other gases. The remaining amount of gas may serve as a carrier gas. If the chlorine gas is mixed at less than 0.1% by volume, the efficiency of the chlorination reaction may decrease, and the separation of cathode materials, including lithium, may be insufficient. If the chlorine gas is mixed at more than 90% by volume, excessive unreacted chlorine gas may be generated, which may damage the process facilities and reduce process efficiency. Therefore, the mixing ratio of chlorine gas can be appropriately selected taking into account the type and content of the cathode material in the waste battery.

[0060] The amount of the chlorine-containing gas can be appropriately selected depending on the amount of polyanion-based lithium secondary battery positive electrode material input from the waste battery, and preferably, the chlorine-containing gas can be mixed in a molar ratio of 1 to 50 relative to the molar ratio of lithium ions in the polyanion-based lithium secondary battery positive electrode material. If the chlorine-containing gas is contained in an amount less than 1 times the molar ratio of lithium ions in the polyanion-based lithium secondary battery positive electrode material, the intended chlorination reaction may not proceed sufficiently, resulting in a decrease in the efficiency of separation of lithium and the compound containing a polyanion. If the chlorine-containing gas is contained in an amount more than 50 times the molar ratio of lithium ions in the polyanion-based lithium secondary battery positive electrode material, the use of excessive chlorine may result in an increase in process costs.

[0061] Next, in step (2), the first mixture is contacted with a solvent to separate and obtain a second mixture containing a compound containing polyvalent anions and lithium chloride and the solvent (S200 in FIG. 1).

[0062] Conventional separation methods using strong acids have the problem of reduced separation efficiency due to the similar chemical properties of cathode metal materials, i.e., specific cathode metal materials are not separated, but cathode metal materials with similar properties are also separated, requiring additional metal separation and purification processes, which reduces separation and recycling efficiency.

[0063] Thus, the present invention solves the aforementioned problem through the simple process of contacting the first mixture with a solvent. More specifically, lithium chloride produced in step (1) through the chlorination reaction described above has very high solubility in the solvent described below, and is dissolved in the solvent through this step and converted into a liquid. The polyanion-based compounds that do not react with chlorine have almost no solubility in the solvent described below and remain in a solid state, which can be easily separated by washing with the solvent. In other words, since the polyanion-containing compounds are insoluble in the solvent after the chlorination reaction, the present invention allows the selective separation of the cathode metal material through the simple process of washing and separation with the solvent, eliminating the need for a further purification process.

[0064] Specifically, the solvent is not particularly limited as long as it can dissolve lithium chloride without dissolving the compound containing a polyvalent anion, and can separate the first mixture into the compound containing a polyvalent anion and the second mixture upon contact with the first mixture, but preferably includes at least one selected from the group consisting of water, ethanol, methanol, butanol, propanol, hydrazine, methyl formaldehyde, acetone, formic acid, pyridine, and benzene, and more preferably water. When the solvent is water, it has higher solubility for lithium chloride than other solvents, allowing for operation with a relatively small amount, making it economical, and is advantageous from the standpoint of environmental compatibility because it does not generate other toxic chemicals such as organic waste liquid.

[0065] Furthermore, the second mixture may contain some impurities that may normally be contained.

[0066] The amount of solvent added in step (2) can be appropriately selected taking into consideration the amount of the first mixture transferred from step (1), and preferably, the amount of solvent added can be 000 to 100,000 parts by weight per 100 parts by weight of the first mixture transferred from step (1).

[0067] As described above, the method for recycling a secondary battery cathode material according to the present invention can easily separate lithium and polyvalent anions contained in a polyvalent anion-based lithium cathode material through step (2), and at the same time, can realize an environmentally friendly separation process. Since no additional purification process is required, the method can simultaneously achieve process simplification and cost reduction.

[0068] Furthermore, the present invention may further include a step of obtaining lithium chloride by removing the solvent after step (2). The method for removing the solvent is not limited as long as it is a method for separating the solvent from the lithium chloride dissolved in the solvent, but is preferably a method of drying the solvent.

[0069] In this case, the drying process may be carried out at a temperature of 20 to 200° C., more preferably at a temperature of 50 to 150° C. under vacuum conditions, which may be appropriately selected in consideration of the type and properties of the solvent contained in the second mixture.

[0070] The present invention also provides a method for recycling a polyanion-based lithium secondary battery positive electrode material by separating it into lithium carbonate. Figure 2 is a flowchart illustrating a method for recycling a polyanion-based lithium secondary battery positive electrode material by separating it into lithium carbonate according to one embodiment of the present invention, and the present invention will be described in detail below with reference to this figure. In this regard, parts that overlap with the above-mentioned method for recycling a polyanion-based lithium secondary battery positive electrode material will be omitted.

[0071] First, after carrying out steps (1) and (2) of the method for recycling a polyanion-based lithium secondary battery positive electrode material described above, in step (3), the second mixture is reacted with a carbonate to form a third mixture containing lithium carbonate (Li2CO3) (S300 in FIG. 2).

[0072] Specifically, in step (3), the second mixture reacts with a carbonate to form lithium carbonate (Li2CO3) containing lithium and a salt containing chlorine as products. In this case, the carbonate is not limited as long as it can react with the lithium chloride of the second mixture to form lithium carbonate and a salt containing chlorine, but is preferably either sodium carbonate (Na2CO3) or potassium carbonate (K2CO3), and more preferably sodium carbonate.

[0073] The chlorine-containing salt may be, for example, sodium chloride (NaCl) when the carbonate salt is sodium carbonate.

[0074] The amount of carbonate can be appropriately selected taking into consideration the amount of the second mixture formed in step (2), and is preferably mixed in an amount of 0.5 to 5 times the expected number of moles of lithium in the second mixture formed in step (2). In this case, if the carbonate is contained in an amount less than 0.5 times the expected number of moles of lithium in the second mixture, a sufficient amount of lithium carbonate may not be formed, resulting in a problem of reduced separation efficiency. On the other hand, if the carbonate is contained in an amount more than 5 times the expected number of moles of lithium, the amount of carbonate may be too large, requiring subsequent washing and further purification steps.

[0075] Next, in step (4), lithium carbonate is separated from the third mixture (S400 in FIG. 2).

[0076] The method for separating lithium carbonate is not limited as long as it can separate lithium carbonate from a salt containing chlorine, but is preferably a solid-liquid separation method that separates lithium carbonate and a salt containing chlorine using the difference in solubility between the lithium carbonate and the salt containing chlorine.

[0077] Specifically, lithium carbonate has low solubility in the solvent contained in the third mixture, while salts containing chlorine have high solubility in the solvent contained in the third mixture. Therefore, by performing solid-liquid separation using such a difference in solubility, lithium carbonate can be separated.

[0078] In this case, the solvent contained in the third mixture is completely dried, and a second solvent is further added to separate the lithium carbonate and the chlorine-containing salt, and the lithium carbonate and the chlorine-containing salt can be separated using the difference in solubility in the second solvent. The second solvent can be any solvent that can dissolve the chlorine-containing salt without dissolving the lithium carbonate, but is preferably water, alcohol, ammonia, etc., and most preferably water or methanol. In this case, the large difference in solubility between lithium carbonate and the chlorine-containing salt can be advantageous in that high-purity lithium carbonate can be separated.

[0079] The amount of the second solvent used can be appropriately selected taking into consideration the amounts of lithium carbonate and chlorine-containing salt contained in the third mixture, and more preferably, the second solvent can be further added in an amount of 1,000 to 100,000 parts by weight per 100 parts by weight of the total third mixture.

[0080] In this case, the drying process may be carried out at a temperature of 20 to 200°C, and more preferably at a temperature of 50 to 150°C under vacuum conditions, which may be appropriately selected in consideration of the type and properties of the solvent contained in the third mixture.

[0081] According to a preferred embodiment of the present invention, the separated lithium carbonate may be further dried to remove a small amount of solvent contained therein.

[0082] In addition, the lithium carbonate obtained through the above process can be used as a lithium compound to be added to the fifth mixture in the resynthesis process described below.

[0083] The present invention also provides a method for recycling a polyanion-based lithium cathode material by separating it into lithium hydroxide. Figure 3 is a flow chart showing a method for recycling a polyanion-based lithium cathode material by separating it into lithium hydroxide according to one embodiment of the present invention, and the present invention will be described in detail below with reference to this figure. In this case, parts that overlap with the above-mentioned method for recycling a polyanion-based lithium cathode material will be omitted.

[0084] First, after carrying out steps (1) to (4) of the method for recycling a polyanion-based lithium cathode material, in step (5), the lithium carbonate is reacted with calcium hydroxide to obtain a fourth mixture containing lithium hydroxide (LiOH) and calcium carbonate (CaCO3) (S500 in FIG. 3).

[0085] Specifically, the lithium carbonate can react with calcium hydroxide to form lithium hydroxide and calcium carbonate.

[0086] In this case, calcium hydroxide may be composed solely of calcium hydroxide or may further contain a solvent. In this case, the solvent is not limited as long as it can separate the two compounds due to the difference in solubility in the solvent, since lithium hydroxide has a high solubility and calcium carbonate has a low solubility in the solvent in step (6) described below, but is preferably water.

[0087] Specifically, the calcium hydroxide may contain 1,000 to 100,000 parts by weight of the solvent relative to 100 parts by weight of the calcium hydroxide in total.

[0088] The amount of calcium hydroxide can be appropriately selected taking into consideration the amount of lithium carbonate formed in step (4), and is preferably mixed in an amount of 0.5 to 5 times the number of moles of lithium carbonate formed in step (4). In this case, if calcium hydroxide is contained in an amount of less than 0.5 times the number of moles of lithium carbonate, a sufficient amount of lithium hydroxide may not be formed, resulting in a problem of reduced separation efficiency. If calcium hydroxide is contained in an amount of more than 5 times the number of moles of lithium carbonate, the amount of calcium hydroxide may be too large, requiring subsequent washing and further purification steps.

[0089] Next, in step (6), lithium hydroxide is separated from the fifth mixture (S600 in FIG. 3).

[0090] The method for separating lithium hydroxide is not limited as long as it can separate calcium carbonate from a solution containing lithium hydroxide. Preferably, the method is a solid-liquid separation method that separates lithium hydroxide and calcium carbonate by utilizing the difference in solubility between them.

[0091] Specifically, calcium carbonate has low solubility in the solvent contained in the fourth mixture, while lithium hydroxide has high solubility in the solvent, and thus, by performing solid-liquid separation using this difference in solubility, it is possible to separate a solution containing lithium hydroxide. In this case, since the solubility of lithium hydroxide is high and the solubility of calcium carbonate is low in the solvent, as described above, the solvent is not limited as long as it can separate the two compounds based on the difference in solubility, but is preferably water.

[0092] Furthermore, the present invention may further include a step of removing the solvent to obtain lithium hydroxide after step (6). The method for removing the solvent is not limited as long as it is a method for separating the solvent from the lithium hydroxide dissolved in the solvent, but is preferably a method of drying the solvent.

[0093] In this case, the drying process may be carried out at a temperature of 20 to 200°C, and more preferably at a temperature of 50 to 150°C under vacuum conditions, which may be appropriately selected in consideration of the type and properties of the solvent contained in the fourth mixture.

[0094] In addition, the lithium hydroxide obtained through the above process can be used as a lithium compound to be added to the fifth mixture in the resynthesis process described below.

[0095] The present invention also provides a method for recycling polyanion-based lithium cathode materials by resynthesizing a new polyanion-based lithium cathode material. Figure 4 is a flowchart illustrating a method for recycling polyanion-based lithium cathode materials by resynthesizing a new polyanion-based lithium cathode material according to one embodiment of the present invention. Hereinafter, the present invention will be described in detail with reference to this figure. Hereinafter, parts overlapping with the above-described method for recycling polyanion-based lithium cathode materials will be omitted.

[0096] First, after carrying out steps (1) and (2) of the method for recycling polyanion-based lithium positive electrode material described above, in step (7), a lithium compound is added to a compound containing the polyanion to form a fifth mixture (S700 in FIG. 4).

[0097] The lithium mixture is not limited as long as it can be resynthesized into a polyvalent anion-based lithium positive electrode material by reacting with the polyvalent anion-containing compound contained in the second mixture through a process described below, but preferably includes at least one selected from the group consisting of lithium carbonate, lithium hydroxide, lithium nitrate, lithium sulfate, lithium acetate, and lithium oxalate.

[0098] The lithium compound may also include lithium carbonate or lithium hydroxide obtained by the method for recycling a polyanion-based lithium positive electrode material of the present invention.

[0099] Specifically, the amount of lithium compound can be appropriately selected taking into consideration the amount of the compound containing a polyvalent anion formed in step (2), and preferably can be added so that the molar ratio of lithium ions in the lithium compound is 80 to 200%, more preferably 100 to 120%, relative to the molar ratio of metal ions in the compound containing a polyvalent anion contained in the second mixture formed in step (2). In this case, if the molar ratio of lithium ions in the lithium compound relative to the molar ratio of metal ions in the compound containing a polyvalent anion is less than 100%, a lithium-deficient cathode material may be formed, while if the molar ratio exceeds 120%, impurities may be formed or an excessive amount of lithium compound may precipitate.

[0100] Next, in step (8), the fifth mixture is reacted to reform the phase of the polyanion-based lithium secondary battery positive electrode material (S800 in FIG. 4).

[0101] Specifically, the compound containing the polyvalent anion in the fifth mixture reacts with the lithium compound to reform the phase of the polyvalent anion-based lithium cathode material.

[0102] The phase reformation of the polyanion-based lithium secondary battery positive electrode material refers to inducing decomposition of the lithium compound at the decomposition temperature of the lithium compound to induce synthesis of the positive electrode material, and more specifically, may be a process of maintaining the decomposition temperature of the lithium compound for a sufficient time to uniformly insert lithium into the structure of the compound containing a polyanion.

[0103] The method for reforming the phase of the polyanion-based lithium secondary battery positive electrode material is not limited as long as it is a method that uniformly carries out a process in which a compound containing a polyanion and a lithium compound react to form a polyanion-based lithium positive electrode material, but preferably, the reaction is carried out at a temperature of 200 to 400°C for 1 to 24 hours.

[0104] More specifically, the reforming process is carried out at a lower temperature than the resynthesis process for improving the crystallinity of the cathode material, which will be described later, to prevent the synthesis of non-uniform cathode material due to the reductive decomposition reaction of the cathode material and the resulting generation of impurities. In this case, if the temperature of the reforming process is less than 200°C, there may be a problem that the efficiency of the cathode material synthesis reaction is too low due to insufficient thermal energy, and if the temperature of the reforming process is more than 400°C, there may be a problem that the reaction does not occur uniformly.

[0105] Then, in step (9), the crystallinity of the fifth mixture is improved to resynthesize a polyanion-based lithium secondary battery cathode material having excellent electrochemical activity (S900 in FIG. 4).

[0106] Specifically, the method for resynthesizing a polyanion-based lithium secondary battery cathode material with improved crystallinity and excellent electrochemical activity is not limited as long as it can improve the crystallinity of the reaction product formed in step (8), but preferably involves a reaction at a temperature of 500 to 850°C for 1 to 24 hours. At temperatures below 500°C, the effect of improving crystallinity may be reduced, and at temperatures above 850°C, impurities may be formed.

[0107] More specifically, a polyanion-based lithium positive electrode material can be resynthesized through the above process.

[0108] In addition, the resynthesized polyanion-based lithium positive electrode material can have an initial discharge capacity of 100 mAh / g or more.

[0109] The present invention also provides a polyanion-based lithium cathode material recycling apparatus that embodies the above-described polyanion-based lithium cathode material recycling method. Figure 5 shows an apparatus for recycling polyanion-based lithium cathode materials according to one embodiment of the present invention, and the present invention will be described in detail below with reference to this figure. Hereinafter, parts that overlap with the above-described polyanion-based lithium cathode material recycling method will be omitted.

[0110] The present invention provides a recycling device for polyanion-based lithium secondary battery positive electrode material, comprising: a first reaction unit that chlorinates a polyanion-based lithium positive electrode material separated from a battery with a chlorine-containing gas to form a first mixture containing a compound containing polyanion and lithium chloride; and a first separation unit that communicates with the first reaction unit and contacts the first mixture with a solvent to separate and obtain a second mixture containing the compound containing polyanion, lithium chloride, and the solvent.

[0111] In the first reaction section 110, a chlorination reaction is carried out to separate compounds containing lithium chloride and polyvalent anions.

[0112] More specifically, a first mixture containing a compound containing a polyvalent anion and lithium chloride can be obtained by chlorinating the polyvalent anion-based lithium positive electrode material separated from the battery with a chlorine-containing gas in the first reaction unit 110. That is, the lithium in the polyvalent anion-based lithium positive electrode material can be converted into lithium chloride and obtained, and the remaining compound can be separated in the form of a compound containing a polyvalent anion.

[0113] Accordingly, the first reaction unit 110 may further include a separate gas injector (not shown) for injecting the chlorine-containing gas. Also, since the chlorination reaction in the first reaction unit 110 involves the polyanion-based lithium cathode material reacting with the gas under high-temperature conditions, the first reaction unit 110 may further include a heater (not shown) for maintaining a high-temperature state. The shapes and materials of the injector and heater may be conventional as long as they are consistent with the objectives of the present invention and are not particularly limited.

[0114] Next, the first separation section 120 communicates with the first reaction section 110 and contacts the first mixture with a solvent to form a second mixture containing a compound containing polyvalent anions, lithium chloride, and the solvent.

[0115] More specifically, the first mixture formed in the first reaction unit 110 may be transferred to the first separation unit 120 via a transfer path (not shown). The transferred first mixture comes into contact with a solvent, and lithium chloride is dissolved in the solvent and converted into a liquid. Compounds containing polyvalent anions that do not react with chlorine remain in a solid state and can be easily separated by being washed with the solvent.

[0116] Accordingly, the first separation unit 120 may further include a solvent injection unit (not shown) for injecting a solvent, and the shape and material of the injection unit are not particularly limited as long as they are consistent with the object of the present invention.

[0117] In addition, the recycling apparatus for polyanion-based lithium secondary battery cathode material according to the present invention may further include a second reaction unit communicating with the first separation unit and configured to react the second mixture with a carbonate to form a third mixture containing lithium carbonate, and a second separation unit communicating with the second reaction unit and configured to separate the lithium carbonate from the third mixture. Figure 6 shows an apparatus for recycling polyanion-based lithium cathode material according to one embodiment of the present invention, and the present invention will be described in detail below with reference to this figure. Hereinafter, parts overlapping with those of the method and apparatus for recycling polyanion-based lithium secondary battery cathode material described above will be omitted.

[0118] First, the second reaction unit 130 is connected to the first separation unit 120 and reacts the second mixture with carbonate to form a third mixture containing lithium carbonate.

[0119] More specifically, the second mixture containing lithium chloride dissolved in the solvent in the first separation unit 120 and present in a liquid state may be transferred to the second reaction unit 130 through a transfer path (not shown), and the transferred second mixture may react with the carbonate to obtain a third mixture containing lithium carbonate and a salt containing chlorine as products.

[0120] Accordingly, the second reaction section 130 may be provided with carbonate in advance to react with the second mixture transferred from the first separation section 120, but without being limited thereto, the carbonate may be injected through an additional injection section (not shown).

[0121] Next, the second separation part 140 is connected to the second reaction part 130 and separates the third mixture to obtain lithium carbonate.

[0122] More specifically, the third mixture containing lithium carbonate and the chlorine-containing salt formed by reacting with the carbonate in the second reaction unit 130 may be transferred to the second separation unit 140 through a transfer path (not shown). The chlorine-containing salt of the transferred third mixture is dissolved in a solvent and exists in a liquid state, while the lithium carbonate has low solubility in the solvent and remains in a solid state. Therefore, the lithium carbonate can be easily separated and obtained by washing with the solvent.

[0123] More specifically, the second separation unit 140 can separate lithium carbonate and salts containing chlorine contained in the third mixture to selectively recover lithium. In particular, the third mixture containing a solvent can be dried to remove part or all of the solvent contained therein, and lithium carbonate and salts containing chlorine present in a solution state in the third mixture can be separated based on the difference in solubility in the solvent.

[0124] Accordingly, the second separation unit 140 may further include a solvent injection unit (not shown) for injecting a solvent, and the shape and material of such an injection unit are not particularly limited as long as they are consistent with the object of the present invention.

[0125] The recycling apparatus for polyanion-based lithium secondary battery cathode material according to the present invention may further include a third reaction unit communicating with the second separation unit and configured to react the lithium carbonate with calcium hydroxide to form a fourth mixture containing lithium hydroxide and calcium carbonate, and a third separation unit 160 communicating with the third reaction unit 150 and configured to separate lithium carbonate from the fourth mixture. Figure 7 shows an apparatus for recycling polyanion-based lithium cathode material according to one embodiment of the present invention, and the present invention will be described in detail below with reference to this figure. Hereinafter, portions overlapping with the above-described method and apparatus for recycling polyanion-based lithium secondary battery cathode material will be omitted.

[0126] First, the third reaction unit 150 is connected to the second separation unit 140 and can react lithium carbonate with calcium hydroxide to form a fourth mixture containing lithium hydroxide and calcium carbonate.

[0127] More specifically, the lithium carbonate separated in the second separation unit 140 may be transferred to the third reaction unit 150 through a transfer path (not shown), and the transferred lithium carbonate may react with calcium hydroxide to obtain a fourth mixture containing lithium hydroxide and calcium carbonate as a product.

[0128] Accordingly, the third reaction part 150 may be previously prepared with calcium hydroxide to react with the lithium carbonate transferred from the second separation part 140, but is not limited thereto, and calcium hydroxide may be injected through an additional injection part (not shown).

[0129] In this case, calcium hydroxide may be composed solely of calcium hydroxide or may further contain a solvent. In this case, the solvent is not limited as long as it can separate the two compounds in the third separation part (described later) based on the difference in solubility, since lithium hydroxide has a high solubility in the solvent and calcium carbonate has a low solubility in the solvent. However, water is preferred.

[0130] Accordingly, the third reaction part 150 may further include a solvent injection part (not shown) for injecting a solvent, and the shape and material of such an injection part are not particularly limited as long as they are consistent with the object of the present invention.

[0131] Next, the third separation section 160 is connected to the third reaction section 150 and can separate lithium hydroxide from the fourth mixture.

[0132] More specifically, the fourth mixture containing lithium hydroxide and calcium carbonate formed by the reaction with calcium hydroxide in the third reaction unit 150 may be transferred to the third separation unit 160 through a transfer path (not shown). The lithium hydroxide in the transferred fourth mixture is dissolved in a solvent and exists in a liquid state, while the calcium carbonate has low solubility in the solvent and remains in a solid state, and can be easily separated by being washed with the solvent.

[0133] Accordingly, the third separation unit 160 may further include a solvent injection unit (not shown) for injecting a solvent, and the shape and material of the injection unit are not particularly limited as long as they are consistent with the object of the present invention.

[0134] The recycling apparatus for polyanion-based lithium secondary battery cathode material according to the present invention may further include a synthesis unit 170, which is connected to the first separation unit 120, the second separation unit 140, and the third separation unit 160 and resynthesizes a polyanion-based lithium secondary battery cathode material from the polyanion-containing compound, lithium carbonate, and lithium hydroxide separated in the first separation unit 120, the second separation unit 140, and the third separation unit 160. FIG. 8 illustrates an apparatus for recycling polyanion-based lithium secondary battery cathode material according to one embodiment of the present invention, and the present invention will be described in detail below with reference to this figure. Herein, portions overlapping with those of the above-described method and apparatus for recycling polyanion-based lithium secondary battery cathode material will be omitted.

[0135] More specifically, the compound containing polyvalent anions separated in the first separation unit 120 may be transferred to the synthesis unit 170 through a transfer path (not shown), and the transferred compound containing polyvalent anions may react with a lithium compound to be resynthesized into a polyvalent anion-based lithium secondary battery positive electrode material.

[0136] In this case, the lithium compound is not limited as long as it can be resynthesized into a polyanion-based lithium secondary battery cathode material by reacting with the polyanion-containing compound, but is preferably at least one selected from the group consisting of lithium carbonate and lithium hydroxide. Also, in the synthesis unit 170, a lithium compound to be reacted with the transferred polyanion-containing compound may be prepared in advance, but is not limited thereto, and the lithium compound may be injected through an additional injection unit (not shown).

[0137] The lithium compound may be lithium carbonate separated in the second separation unit 140, lithium hydroxide separated in the third separation unit 160, or a mixture of the two compounds. In this case, the lithium carbonate separated in the second separation unit 140 may be transferred to the synthesis unit 170 via a transfer path (not shown), and the lithium hydroxide separated in the third separation unit 160 may also be transferred to the synthesis unit 170 via a transfer path (not shown).

[0138] In addition, since the reaction may occur at a high temperature in the synthesis unit 170, a heater (not shown) for maintaining the high temperature may be further included. The shape and material of the heater may be any conventional one as long as it is suitable for the purpose of the present invention, and are not particularly limited. [Example]

[0139] The present invention will be described in more detail based on the following examples. However, it should be understood that the following examples do not limit the scope of the present invention, but are merely intended to aid in the understanding of the present invention.

[0140] <Example 1 - LFP powder unit recycling experiment> (1) Lithium reaction rate (%) and impurity detection depending on reaction time and temperature Lithium separation experiments were conducted using LFP powder, a polyanion-based lithium secondary battery cathode material. Commercial LFP powder (1 g) was prepared as a polyanion-based lithium secondary battery cathode material. The prepared sample was then subjected to halogenation reactions under Cl2 (10–30 sccm) and Ar (170–190 sccm) (carrier gas) conditions at different temperatures and times, as shown in Table 1. The masses of the total products, including lithium chloride and polyanion-containing compounds (FP, FePO4), and the lithium conversion ratios are shown in Table 1. The lithium conversion ratio was calculated by dividing the number of moles of reacted chlorine by the number of moles of lithium present in the reactants, assuming that chlorine reacts only with the mass increase. The total products were dissolved in 250 ml of water (HO), and the components of the insoluble solid product were analyzed using X-ray diffraction (XRD). The results are shown in Table 1.

[0141] [Table 1]

[0142] As a result, as is clear from Table 1, it was confirmed that the FP phase exists in the temperature range from room temperature to 250°C. This indicates that the chlorination reaction of LFP proceeds even at room temperature, forming LiCl. However, it was confirmed that the LFP phase remains and the lithium reaction rate decreases in the low temperature range below 80°C. In other words, when the reaction proceeds at temperatures between 80°C and 280°C, LFP reacts completely, no impurities are generated, and the reaction efficiency is high, which is advantageous.

[0143] However, even if the LFP phase remains, there is no significant problem in recovering LiCl through a subsequent dissolution process. Such a low-temperature process has the advantage of reducing energy consumption and extending the life of the reactor and associated facilities, so it can be applied as needed, even if it means accepting some loss of efficiency. Therefore, even when the chlorination reaction is carried out at a temperature range of 20°C to 280°C, LFP can be separated, and it is advantageous in terms of economy, such as reducing energy consumption in the process and extending the life of associated facilities.

[0144] Furthermore, when the reaction was carried out for 4 hours at temperatures exceeding 280°C, impurities such as LiFeP2O7, Li3Fe2(PO4)3, and unknown compounds were generated through side reactions, and remained undissolved in the solvent. These impurities included both lithium and polyanion-based compounds. This confirms that the lithium and polyanion-based compounds contained in the positive electrode material for polyanion-based lithium secondary batteries are not properly separated when the reaction temperature exceeds 280°C.

[0145] In addition, when the reaction was carried out for 4 hours, it was confirmed that when the reaction temperature was 170°C to 280°C, the lithium reaction rate was significantly higher than when the reaction temperature was outside this temperature range.

[0146] Furthermore, when the reaction time was varied at a reaction temperature of 200°C, it was confirmed that the lithium reaction rate was low when the reaction time was less than 0.3 hours. Therefore, when the reaction time was 0.3 hours or more, the recycling efficiency of the polyanion-based lithium secondary battery positive electrode material was very good.

[0147] (2) XRD analysis before and after solid-liquid separation In the case of reacting at 200°C for 4 hours in Table 1, an X-ray diffraction experiment was carried out on all products, and the results are shown in Figure 9. In addition, all products were dissolved in 250 ml of water, and an X-ray diffraction experiment was carried out on the insoluble solid product, and the results are shown in Figure 10.

[0148] As a result, as can be seen from Figure 9, LiCl and FePO4 were produced by the chlorination reaction. Furthermore, as can be seen from Figure 10, the produced LiCl was completely dissolved in water, and only FePO4 remained as a solid product after dissolution. This confirms that lithium and polyanion-based compounds can be separated into lithium chloride and polyanion-based compounds by the chlorination reaction of a polyanion-based lithium secondary battery cathode material. Furthermore, it can be confirmed that the produced lithium chloride and polyanion-based compounds can be easily separated by solid-liquid separation using a solvent after the chlorination reaction.

[0149] (3) Analysis of the lithium content in the recovered solid-state FP In the case of reacting for 4 hours at temperatures of 50°C, 100°C, 150°C, 200°C, and 250°C in Table 1, all of the products were dissolved in water, and the Li / Fe molar ratio of the undissolved solid product was measured using inductively coupled plasma analysis, and the results are shown in Table 2.

[0150] [Table 2]

[0151] As a result, as can be seen from Table 2, the lithium content in the recovered solid product was significantly reduced compared to the initial sample, confirming that the separation of lithium and polyvalent anion compounds was successful.

[0152] (4) Analysis of the lithium, iron, and phosphate contents in the recovered lithium chloride aqueous solution In the case of the reaction for 4 hours at temperatures of 50°C, 100°C, 150°C, 200°C, and 250°C in Table 1, all of the products were dissolved in water, and the amounts of lithium, iron, and phosphorus in the solution excluding the insoluble solid products were measured, along with the resulting lithium purity, and the results are shown in Table 3. The lithium purity is calculated as the percentage of the lithium content relative to the total content of lithium, iron, and phosphorus described below.

[0153] [Table 3]

[0154] As a result, as is clear from Table 3, it can be confirmed that lithium is present in a very high purity in the dissolved solution after the chlorination reaction. This shows that high-purity lithium can be extracted simply by contacting the product with a solution after the chlorination reaction.

[0155] <Example 2 - LFP electrode unit recycling experiment> An electrode containing commercial LFP, a carbon conductor, a polymer binder, and an Al conductive material was prepared. The electrode was prepared by coating the Al conductive material with a uniformly thick slurry of 90 wt% LFP, 5 wt% Super-P carbon black, and 5 wt% PVDF binder in NMP (organic solvent). The NMP was then evaporated through a drying process. The prepared sample was then chlorinated at 200°C for 1 hour under Cl2 (10 sccm) and Ar (190 sccm) carrier gas conditions. After the chlorination reaction, the powder separated from the Al conductive material was dissolved in 250 ml of water. Photographs of the reaction process are shown in Figure 11. After the powder was dissolved in water, X-ray diffraction analysis of the insoluble material was performed, and the results are shown in Figure 12.

[0156] First, as is clear from Figure 11, even in the case of a polyanion-based lithium secondary battery cathode material that exists in the form of an electrode, it can be confirmed that lithium and polyanion-based compounds can be easily separated in powder form from the electrode assembly by a chlorination reaction. Also, as is clear from Figure 12, lithium is not present in the insoluble material remaining after dissolving in water, so lithium and polyanion-based compounds can be easily separated by solid-liquid separation.

[0157] <Example 3 - LFP cathode material resynthesis experiment> To resynthesize the LFP cathode material, FePO4, a residual compound of the LFP cathode material, was prepared by chlorination at 200°C for 10 minutes under the same conditions as in Example 1 of the present invention. Next, 0.5 g of the recycled FePO4 was mixed with LiOH·H2O. The ratio of the number of moles of Li to the number of moles of Fe was 1.03. The mixed sample was then reacted at 350°C for 12 hours under conditions of 96.5 vol% argon (Ar) and 3.5 vol% hydrogen (H2). The resulting product was then reacted at 600°C for 12 hours under Ar conditions. The X-ray diffraction analysis and electrochemical performance evaluation of the resulting product were then performed, and the results are shown in Figures 13 and 14, respectively. As can be seen from Figure 13, even when only the 350°C heat treatment was performed, an LFP phase was formed, but defects existed within the material, resulting in reduced electrochemical activity, as can be seen from Figure 14. Furthermore, as can be seen from FIG. 13, the subsequent heat treatment at 600° C. removed defects in the material and improved the crystallinity, which resulted in an increase in electrochemical activity as can be seen from FIG.

[0158] As can be seen from FIG. 14, when the phase reformation step and the crystallinity improvement step of the cathode material were performed sequentially, a cathode material having an excellent initial discharge capacity of 100 mAh / g or more at a current density of 170 mA / g was resynthesized.

[0159] As can be seen from FIG. 15, it was confirmed that the LFP phase was effectively formed even when the molar ratio of Li to Fe was changed to 1.05.

Claims

1. (1) chlorinating the polyanion-based lithium secondary battery positive electrode material separated from the battery with a chlorine-containing gas to form a first mixture containing a polyanion-containing compound and lithium chloride (LiCl); (2) contacting the first mixture with a solvent to separate and obtain a compound containing a polyvalent anion and a second mixture containing lithium chloride and the solvent.

2. 2. The method of claim 1, further comprising the step of removing the solvent from the second mixture to obtain lithium chloride after step (2).

3. The polyanion-based lithium secondary battery positive electrode material in step (1) is LiA ｘ (P.O. ４ ) ｙ The method for recycling a polyanion-based lithium secondary battery positive electrode material according to claim 1, characterized in that: Here, A is at least one selected from the group consisting of iron (Fe), cobalt (Co), manganese (Mn), and nickel (Ni), and x and y satisfy 0.5<x≦3 and 0.5<y≦3.

4. 2. The method for recycling a polyanion-based lithium secondary battery positive electrode material according to claim 1, wherein the chlorination reaction temperature is 20 to 280°C.

5. 2. The method for recycling a positive electrode material for a polyanion-based lithium secondary battery according to claim 1, wherein the chlorination reaction temperature is 170 to 280°C.

6. The chlorine-containing gas is chlorine gas (Cl ２ ), hydrogen chloride (HCl), phosgene (COCl ２ ), carbon tetrachloride (CCl ４ 2. The method for recycling a positive electrode material for a polyanion-based lithium secondary battery according to claim 1, wherein the positive electrode material comprises at least one selected from the group consisting of:

7. 2. The method for recycling a positive electrode material of a polyanion-based lithium secondary battery according to claim 1, wherein the solvent comprises at least one selected from the group consisting of water, ethanol, methanol, butanol, propanol, hydrazine, methyl formaldehyde, acetone, formic acid, pyridine, and benzene.

8. (1) chlorinating the polyanion-based lithium secondary battery positive electrode material separated from the battery with a chlorine-containing gas to form a first mixture containing a polyanion-containing compound and lithium chloride (LiCl); (2) contacting the first mixture with a solvent to separate and obtain a second mixture containing a compound containing a polyvalent anion and lithium chloride and the solvent; (3) reacting the second mixture with a carbonate to form lithium carbonate (Li ２ CO ３ forming a third mixture comprising: (4) A method for recycling a polyanion-based lithium secondary battery positive electrode material, comprising: separating lithium carbonate from the third mixture.

9. (1) chlorinating the polyanion-based lithium secondary battery positive electrode material separated from the battery with a chlorine-containing gas to form a first mixture containing a polyanion-containing compound and lithium chloride (LiCl); (2) contacting the first mixture with a solvent to separate and obtain a second mixture containing a compound containing a polyvalent anion and lithium chloride and the solvent; (3) reacting the second mixture with a carbonate to form lithium carbonate (Li ２ CO ３ forming a third mixture comprising: (4) separating lithium carbonate from the third mixture; (5) Reacting the lithium carbonate with calcium hydroxide to produce lithium hydroxide (LiOH) and calcium carbonate (CaCO ３ obtaining a fourth mixture comprising: (6) A method for recycling a polyanion-based lithium secondary battery positive electrode material, comprising: separating lithium hydroxide from the fourth mixture.

10. After the step (2), (7) adding a lithium compound to the compound containing the polyvalent anion to form a fifth mixture; (8) reacting the fifth mixture to reform the phase of the polyanion-based lithium secondary battery positive electrode material; and (9) The method for recycling a polyanion-based lithium secondary battery positive electrode material according to claim 9, further comprising: improving the crystallinity of the fifth mixture to resynthesize the fifth mixture into a polyanion-based lithium secondary battery positive electrode material having excellent electrochemical activity.

11. 11. The method of claim 10, wherein the lithium compound is lithium carbonate separated from the third mixture in step (4) or lithium hydroxide (LiOH) separated from the fourth mixture in step (6).

12. The method for recycling a positive electrode material for a polyanion-based lithium secondary battery according to claim 10, characterized in that the number of moles of lithium ions in the lithium compound is 100 to 120% of the number of moles of metal ions in the compound containing the polyanion.

13. 11. The method of claim 10, wherein the fifth mixture is reacted at a temperature of 200 to 400° C. for 1 to 24 hours in step (8).

14. 11. The method of claim 10, wherein the fifth mixture is reacted at a temperature of 500 to 850° C. for 1 to 24 hours in step (9).

15. 11. The method for recycling a positive electrode material for a polyanion-based lithium secondary battery according to claim 10, wherein the resynthesized positive electrode material for a polyanion-based lithium secondary battery has an initial discharge capacity of 100 mAh / g or more.

16. a first reaction section that causes a chlorination reaction between a polyanion-based lithium secondary battery positive electrode material separated from the battery and a chlorine-containing gas to form a first mixture containing a compound containing a polyanion and lithium chloride; a first separation unit communicating with the first reaction unit and contacting the first mixture with a solvent to separate and obtain a compound containing a polyvalent anion and a second mixture containing lithium chloride and the solvent.

17. a second reaction section communicating with the first separation section and configured to react the second mixture with a carbonate to form a third mixture containing lithium carbonate; 17. The recycling apparatus for a polyanion-based lithium secondary battery positive electrode material according to claim 16, further comprising: a second separation unit communicating with the second reaction unit and separating lithium carbonate from the third mixture.

18. A second separation section is connected to the second separation section, and the lithium carbonate is reacted with calcium hydroxide to produce lithium hydroxide (LiOH) and calcium carbonate (CaCO ３ a third reaction zone forming a fourth mixture comprising:

18. The recycling device for polyanion-based lithium secondary battery positive electrode material according to claim 17, further comprising: a third separation unit communicating with the third reaction unit and separating lithium hydroxide from the fourth mixture.

19. 19. The recycling device for polyanion-based lithium secondary battery positive electrode materials according to claim 18, further comprising a synthesis unit communicating with the first separation unit, the second separation unit, and the third separation unit, for resynthesizing a polyanion-based lithium secondary battery positive electrode material from the polyanion-containing compound separated in the first separation unit, the second separation unit, and the third separation unit, lithium carbonate, and lithium hydroxide.

20. 17. The recycling apparatus for a polyanion-based lithium secondary battery positive electrode material according to claim 16, wherein the first reaction unit further comprises a gas injector for injecting a gas into the first reaction unit.

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