Method for regenerating lithium iron phosphate

Abstract

The present invention relates to a method for regenerating lithium iron phosphate and, more specifically, to a method for regenerating lithium iron phosphate, comprising the steps of: (a) adding a basic solution into a dissolution solution containing Fe and P and filtering same; (b) adding a hydrogen peroxide aqueous solution into the filtered dissolution solution containing Fe and P to prepare a hydrogen peroxide mixed solution; (c) heating the hydrogen peroxide mixed solution to synthesize FePO4 and separating same; (d) adding the separated FePO4 into a solution containing lithium to synthesize a mixture of FePO4 and Li3PO4; (e) lowering the temperature of a reaction solution containing the mixture to room temperature to precipitate and separate the mixture of FePO4 and Li3PO4; and (f) adding a carbon source to the separated mixture of FePO4 and Li3PO4 and heat-treating same to prepare lithium iron phosphate.

Description

Lithium iron phosphate regeneration method

[0001] [Cross-reference with application(s)]

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2025-0021514 filed on February 19, 2025, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] The present invention relates to a method for regenerating lithium iron phosphate, and more specifically, to a method for regenerating lithium iron phosphate with significantly improved production efficiency by synthesizing amorphous ferric phosphate (FePO4) from a spent lithium iron phosphate cathode, adding the synthesized amorphous FePO4 to an aqueous lithium salt solution to obtain a mixture of amorphous FePO4 and Li3PO4, adding a carbon source thereto, and heat-treating to produce regenerated lithium iron phosphate.

[0004] The demand for lithium-ion batteries has continuously increased since the 1990s alongside the portable electronic device market, and has recently surged globally due to the rapid expansion of the electric vehicle market. This could lead to instability in the supply and demand of lithium resources in the near future, and the continuously accumulating end-of-life waste batteries could also cause significant environmental problems. To address these issues, the recycling of used lithium-ion batteries is a critical technical challenge.

[0005] A lithium-ion battery is largely composed of a positive electrode in which a positive active material is coated on a metal foil such as aluminum, a negative electrode in which a negative active material is coated on a metal foil such as copper, a separator that prevents the positive and negative electrodes from mixing with each other, and an electrolyte that enables the movement of lithium ions between the positive and negative electrodes.

[0006] The cathode accounts for more than 60% of the cost of a lithium-ion battery, and lithium composite oxides such as lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (LiNiMnCoO2), lithium manganese oxide (LiMnO2), or lithium iron phosphate (LiFePO4) are used as active materials for the cathode. As the cathode contains valuable metals, methods to recover these valuable metals from spent lithium-ion battery cathodes are receiving significant attention.

[0007] Among these, lithium iron phosphate (LiFePO4) has a very stable hexahedral crystal structure. In order to break down this stable structure and recover valuable metals, a high concentration of strong acid or strong base is used on the spent anode to dissolve the valuable metals, and then Li and FePO4 are recovered. A lithium source and a carbon source are added to the recovered FePO4, and ball milling is performed for about 14 hours to ensure that the recovered FePO4, lithium source, and carbon source are uniformly mixed and the particle size is adjusted into a fine particle form, after which heat treatment is performed to regenerate it into lithium iron phosphate. However, this process consumes a lot of time and energy, resulting in a problem of low production efficiency.

[0008] Therefore, there is a need for a method to regenerate lithium iron phosphate from spent lithium iron phosphate cathodes that regenerates lithium iron phosphate more efficiently than conventional methods.

[0009]

[0010] [Prior Art Literature]

[0011] [Patent Literature]

[0012] Chinese Patent Publication No. 115259129

[0013] To solve the problems of the conventional technology described above, the present invention aims to provide a method for regenerating lithium iron phosphate that significantly improves production efficiency by greatly reducing regeneration time and energy consumption, thereby eliminating the ball milling process that conventionally required a long time to perform, by synthesizing amorphous ferric phosphate (FePO4) from a spent lithium iron phosphate cathode, adding the synthesized amorphous FePO4 to an aqueous lithium salt solution to obtain a mixture of amorphous FePO4 and Li3PO4, filtering and drying, adding a carbon source to the obtained powder, and heat-treating it to regenerate the lithium iron phosphate.

[0014]

[0015] The above and other objectives of the present invention can all be achieved by the present invention described below.

[0016] To achieve the above objective, the present invention provides a method for regenerating lithium iron phosphate, characterized by comprising: I) a step of adding a basic solution to a solution containing Fe and P and filtering it; (b) a step of adding an aqueous hydrogen peroxide solution to the filtered solution containing Fe and P to prepare a hydrogen peroxide mixture; (c) a step of heating the hydrogen peroxide mixture to synthesize FePO4 and separating it; (d) a step of adding the separated FePO4 to a solution containing lithium to synthesize a mixture of FePO4 and Li3PO4; (e) a step of lowering the reaction solution containing the mixture to room temperature to precipitate and separate the mixture of FePO4 and Li3PO4; and (f) a step of adding a carbon source to the separated mixture of FePO4 and Li3PO4 and heat-treating it to produce lithium iron phosphate.

[0017] II) In the above I), the solution of step (a) may be a solution in which waste lithium iron phosphate is dissolved in an acidic solution.

[0018] III) In I) or II) above, after the addition of the basic solution in step (a) is completed, the solution may have a pH of 1.0 to 1.4.

[0019] IV) In the above I) to III), the solution containing Fe and P in step (a) can be prepared by including: (i) a step of crushing a waste lithium iron phosphate cathode to obtain cathode material powder; (ii) a step of adding the obtained cathode material powder to an acidic solution with a concentration of 0.5 to 0.7 molar concentration (mol / L) to form a leaching solution containing dissolved lithium and a leaching residue and separating them; and (iii) a step of adding the separated leaching residue to an acidic solution with a concentration of 0.8 to 1.3 molar concentration (mol / L) to obtain a solution containing Fe and P.

[0020] V) In I) to IV) above, in step (b), an aqueous hydrogen peroxide solution may be added in an amount equal to 1 to 5 volume% of the solution based on hydrogen peroxide.

[0021] VI) In the above I) to V), the hydrogen peroxide mixture in step (c) can be heated to 28 to 60 ℃.

[0022] VII) In the above I) to VI), the step of adding a basic solution after heating the hydrogen peroxide mixture in step (c) may be further included.

[0023] VIII) In I) to VII) above, the hydrogen peroxide mixture may have a pH of 1.0 to 1.8 after the addition of the basic solution.

[0024] IX) In the above I) to VIII), the FePO4 separated in step (c) can be washed with an acidic washing solution and then introduced into step (d).

[0025] X) In the above I) to IX), the solution containing lithium in step (d) can be added in an amount such that 1 to 3.5 moles of lithium are added to 1 mole of separated FePO4.

[0026] XI) In I) to X) above, the solution containing lithium in step (d) may be an aqueous solution of a lithium salt or an aqueous leaching solution of a spent cathode active material.

[0027] XII) In the above I) to XI), the synthesis in step (d) can be carried out at a temperature of 50 to 100 ℃.

[0028] XIII) In the above I) to XII), the synthesis in step (d) can be carried out for 30 minutes to 5 hours.

[0029] XIV) In the above I) to XIII), the carbon source in step (f) may be one or more selected from the group consisting of glucose, sucrose, graphite, carbon nanotubes, citric acid, and carbon black.

[0030] XV) In I) to XIV) above, the heat treatment in step (f) can be carried out at 650 to 800 ℃ under a reducing atmosphere for 17 to 25 hours.

[0031] XVI) In I) to XV) above, the FePO4 is amorphous, and the lithium iron phosphate may be crystalline.

[0032] XVII) In the above I) to XVI), the synthesis in step (d) may be performed by heating a lithium-containing solution to a synthesis temperature, adding the separated FePO4, and stirring for a synthesis time.

[0033] XVIII) In I) to XVII) above, the aqueous leaching solution of the waste cathode active material may be a solution obtained by heat-treating a waste cathode containing one or more types of cathode active materials selected from the group consisting of a lithium nickel oxide (LNO)-based cathode active material, a nickel-cobalt-manganese (NCM)-based cathode active material, a nickel-cobalt-aluminum (NCA)-based cathode active material, and a nickel-cobalt-manganese-aluminum (NCMA)-based cathode active material to thermally decompose the binder and conductive material to obtain a cathode active material, and then leaching the cathode active material into water.

[0034] According to the present invention, by synthesizing amorphous ferric phosphate (FePO4) from a spent lithium iron phosphate cathode, adding the synthesized amorphous FePO4 to an aqueous lithium salt solution to obtain a mixture of amorphous FePO4 and Li3PO4, filtering and drying, and then adding a carbon source to the obtained powder and heat-treating it to regenerate lithium iron phosphate, the ball milling process that had to be performed for a long time in the past can be omitted, thereby significantly reducing regeneration time and energy consumption and greatly improving production efficiency, the invention provides a method for regenerating lithium iron phosphate and the effect of greatly improving production efficiency.

[0035] The following drawings attached to this specification illustrate embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention in conjunction with the detailed description provided below; therefore, the present invention should not be interpreted as being limited to the matters described in these drawings.

[0036]

[0037] FIG. 1 is a process diagram for the step of synthesizing FePO4 from a waste lithium iron phosphate cathode as one embodiment according to the present invention.

[0038] FIG. 2 is a process diagram for a method of regenerating lithium iron phosphate from a solution containing FePO4 and lithium synthesized as one embodiment according to the present invention.

[0039] Figure 3 is the result of X-ray diffraction (XRD) pattern analysis of FePO4 synthesized according to Example 1 of the present invention.

[0040] Figure 4 is the result of X-ray diffraction (XRD) analysis of a mixture of FePO4 and Li3PO4 obtained by separating and drying after synthesis according to Example 1 of the present invention.

[0041] Figure 5 is the result of X-ray diffraction (XRD) pattern analysis of the regenerated LiFePO4 finally obtained according to Example 1 of the present invention.

[0042] The inventors synthesized amorphous ferric phosphate (FePO4) by adding a basic solution to a solution containing Fe and P obtained from a cathode material powder from which the current collector was removed by crushing a spent lithium iron phosphate cathode; obtained a mixture of amorphous FePO4 and Li3PO4 by adding the synthesized amorphous FePO4 to a lithium-containing solution and filtering and drying it; and then regenerated lithium iron phosphate by adding a carbon source to the obtained powder and heat-treating it. By doing so, they confirmed that the ball milling process, which conventionally required a long time, could be omitted, thereby significantly reducing regeneration time and energy consumption and greatly improving production efficiency. Based on this, they devoted themselves to further research and completed the present invention.

[0043]

[0044] The method for recovering lithium described herein will be explained in detail below.

[0045] However, terms and words used in this specification and claims cannot be interpreted as being limited to their ordinary or dictionary meanings, and must be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor may appropriately define the concept of the terms to best describe his application. Accordingly, it should be understood that the embodiments described in this specification and the configurations illustrated in the drawings are merely one embodiment of the invention and do not represent all of the technical spirit of the invention, and that there may be various equivalents and modifications that can replace them, and that they may be arranged, replaced, combined, separated, or designed into various other configurations.

[0046] All technical and scientific terms used in this description have the same meaning as commonly understood by those skilled in the art to which the present invention belongs, unless otherwise defined.

[0047]

[0048] Lithium iron phosphate regeneration method

[0049] The method for regenerating lithium iron phosphate according to the present invention comprises: (a) a step of adding a basic solution to a solution containing Fe and P and filtering it; (b) a step of adding an aqueous hydrogen peroxide solution to the filtered solution containing Fe and P to prepare a hydrogen peroxide mixture; (c) a step of heating the hydrogen peroxide mixture to synthesize FePO4 and separating it; (d) a step of adding the separated FePO4 to a solution containing lithium to synthesize a mixture of FePO4 and Li3PO4; (e) a step of lowering the reaction solution containing the mixture to room temperature to precipitate and separate the mixture of FePO4 and Li3PO4; and (f) a step of adding a carbon source to the separated mixture of FePO4 and Li3PO4 and heat-treating it to produce lithium iron phosphate. In this case, the ball milling process, which conventionally required a long time to be performed, can be omitted, thereby significantly reducing regeneration time and energy consumption and greatly improving production efficiency.

[0050]

[0051] The method for regenerating lithium iron phosphate is explained in detail below, divided into steps.

[0052]

[0053] (a) A step of adding a basic solution to a solution containing Fe and P and filtering it.

[0054] The method for regenerating lithium iron phosphate according to the present invention may include the step of (a) introducing a basic solution into a dissolved solution containing Fe and P and filtering it. In this case, there is an advantage in that the purity of FePO4 is greatly improved as impurities derived from waste lithium iron phosphate cathode material, such as aluminum and titanium, which are leached together with Fe and P in the dissolved solution, are precipitated and removed.

[0055]

[0056] The solution of step (a) above may be, for example, a solution in which waste lithium iron phosphate is dissolved in an acidic solution, and in this case, Fe and P are easily leached out, which has the advantage of producing high-purity and high-yield FePO4.

[0057]

[0058] The solution containing Fe and P in step (a) above may, for example, have a pH of 0.1 to 0.5, preferably 0.2 to 0.4, and has the advantage of facilitating the leaching of Fe and P within this range.

[0059] In the present description, the solution containing Fe and P may be a compound or ion containing Fe and a compound or ion containing P, preferably an ion containing Fe and an ion containing P, and specifically, the ion containing Fe is Fe 2+ , Fe 3+ or it may be a mixture of these, and the ion containing P is PO4 3- , PO3 3- , and HPO3 2- It may be one or more types selected from a group consisting of

[0060] In this description, pH measurement can be performed using measurement methods commonly used in the technical field to which this invention belongs, and unless otherwise specified, it can be measured using a general pH measuring device at room temperature, specifically using a METTLER TOLEDO SevenDirect SD30.

[0061] In this description, room temperature may be one point within the range of 20 ± 5 ℃.

[0062]

[0063] The solution containing Fe and P in step (a) above may, for example, contain Fe at a concentration of 23,000 ppm or more, preferably 25,000 ppm or more, more preferably 26,000 ppm or more, even more preferably 27,000 ppm or more, and even more preferably 27,000 to 30,000 ppm, and in this case, there is an advantage of producing high yield and high purity FePO4.

[0064] The solution containing Fe and P in step (a) above may, for example, contain P at a concentration of 10,000 ppm or more, preferably 12,000 ppm or more, more preferably 14,000 ppm or more, even more preferably 15,000 ppm or more, and even more preferably 15,000 to 17,000 ppm, and in this case, there is an advantage of producing high yield and high purity FePO4.

[0065] The solution containing Fe and P in step (a) above may, for example, contain lithium in an amount of 500 ppm or less, preferably 400 ppm or less, more preferably 300 ppm or less, even more preferably 250 ppm or less, and even more preferably 100 to 250 ppm, and in this case, there is an advantage of producing high-purity FePO4.

[0066] In this specification, ppm is based on weight unless otherwise defined.

[0067] In this description, Fe, P, and Li can be measured by ICP analysis of the leachate. Specifically, 0.2 g of the leachate is taken, placed in a conical tube, and its exact weight is measured. Then, 0.1 ml of nitric acid with a concentration of 70 wt% is added to it, followed by the addition of 500 µl of 1000 g / kg internal standard (Sc (Scandium)), and the solution is diluted with ultrapure water to 50 ml for ICP measurement.

[0068]

[0069] In step (a) above, the basic solution may be, for example, an aqueous ammonia solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, or an aqueous calcium hydroxide solution, and preferably an aqueous ammonia solution. In this case, there is an advantage that impurities derived from waste lithium iron phosphate cathode material, such as aluminum and titanium, are easily precipitated in the solution containing Fe and P.

[0070]

[0071] After the addition of the above basic solution is completed, the solution containing Fe and P may have a pH of, for example, 1.0 to 1.4, preferably 1.1 to 1.4, and more preferably 1.1 to 1.3. Within this range, impurities derived from waste lithium iron phosphate cathode material, such as aluminum and titanium, which are leached together with Fe and P in the solution, are precipitated and have the advantage of being easily removed in a subsequent process.

[0072]

[0073] Step (a) above can be performed by adding a basic solution to the solution, for example, while stirring, and in this case, there is an advantage of shortening the impurity precipitation time.

[0074] The above stirring speed may be, for example, 300 to 700 rpm, preferably 350 to 600 rpm, more preferably 400 to 550 rpm, and within this range, there is an advantage that impurities in the solution are precipitated within a short time.

[0075]

[0076] In step (a) above, the basic solution may contain, for example, a basic component at a concentration of 0.8 to 1.3 molar (mol / L), preferably 0.9 to 1.2 molar, and more preferably 0.9 to 1.1 molar, and within this range, there is an advantage that the pH of the solution containing Fe and P is easy to adjust.

[0077]

[0078] In step (a) above, the basic solution may preferably be an aqueous ammonia solution, and the aqueous ammonia solution may be included at a concentration of, for example, 0.8 to 1.3 molar concentration (mol / L), preferably 0.9 to 1.2 molar concentration, more preferably 0.9 to 1.1 molar concentration, and there is an advantage that the pH of the solution containing Fe and P is easy to adjust within this range.

[0079]

[0080] In step (a) above, the basic solution can be continuously introduced, for example, and in this case, there is an advantage that impurities derived from waste lithium iron phosphate cathode material, such as aluminum and titanium, are easily precipitated and easily removed.

[0081] In this description, the term "continuous feeding" means that it is not "batch feeding," and refers to feeding in a drop-by-drop, little-by-little, step-by-step, or continuous flow manner for at least 10 minutes, preferably at least 30 minutes, within the leaching time range.

[0082]

[0083] The solution of step (a) above can be prepared by, for example, (i) crushing a waste lithium iron phosphate cathode to obtain cathode material powder; (ii) introducing the obtained cathode material powder into an acidic solution with a concentration of 0.5 to 0.7 molar (mol / L) to form a leaching solution in which lithium is dissolved and a leaching residue, and separating them; and (iii) introducing the separated leaching residue into an acidic solution with a concentration of 0.8 to 1.3 molar (mol / L) to obtain a solution containing Fe and P; and in this case, there is an advantage of synthesizing FePO4 in a high yield.

[0084]

[0085] In this description, the positive electrode refers to a positive electrode active material layer comprising a positive electrode active material, a binder, and a conductive material coated on a current collector.

[0086] In this description, the anode material powder refers to a powder obtained by crushing and / or sieving waste anodes, and most of the current collectors are removed from the waste anodes, and a small amount of current collectors with a particle size of about a few micrometers may be included.

[0087] In this description, the term "anode material" means that it includes an anode active material or is an anode active material.

[0088]

[0089] The above-mentioned spent lithium iron phosphate cathode may include, for example, a cathode active material having an olivine structure, and in this case, it has the advantages of excellent high-temperature stability and lifespan characteristics and low cost.

[0090] In this description, the olivine structure is a type of cathode active material structure with a hexahedron-shaped lattice structure in a 3D form. Since PO (phosphorus-oxygen) is strongly bonded, it can maintain its structure even if all lithium ions are removed, resulting in minimal performance degradation due to charging and discharging and excellent thermal stability. Additionally, it is economical because it uses inexpensive iron instead of expensive cobalt metal, but it has a lower energy density compared to other cathode materials, and has low electrical conductivity and lithium ion diffusion.

[0091] The above olivine structure can be confirmed through X-ray diffraction analysis (XRD).

[0092]

[0093] The positive active material having the above olivine structure may be, for example, a compound represented by the following chemical formula 1, and in this case, it has the advantages of excellent high-temperature stability and lifespan characteristics and low cost.

[0094] [Chemical Formula 1]

[0095]

[0096] (In the above chemical formula 1, M comprises one or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, X comprises one or more elements selected from the group consisting of F, S, and N, and a, b, and c are each -0.5≤a≤0.5, 0≤b≤0.5, and 0≤c≤0.1.)

[0097]

[0098] The positive electrode active material having the above olivine structure may preferably include lithium iron phosphate (LiFePO4), in which case it has excellent high-temperature stability and lifespan characteristics and has the advantage of being inexpensive.

[0099]

[0100] The positive electrode of the above-mentioned waste lithium-ion battery may be, for example, a discarded lithium-ion battery positive electrode, a defective product generated during the positive electrode coating process, or a positive electrode scrap discarded after cutting the electrode plate; preferably, it may be a discarded lithium-ion battery positive electrode, and in this case, there are eco-friendly and economic advantages in recycling resources by recovering FePO4, etc., along with expensive lithium.

[0101]

[0102] In step (i) above, grinding can be performed using, for example, dry grinding equipment, specifically using a hand mill, pin mill, disc mill, cutting mill, hammer mill, or blender. In this case, the current collector is finely cut into pieces, and the waste anode material is separated from the current collector pieces, which has the advantage of facilitating subsequent processes.

[0103]

[0104] The above-mentioned crushed waste anode can be obtained as anode material powder, for example, through sieving. In this case, the current collector remains on the top of the mesh while the anode material passes through the mesh, thereby separating them and providing the advantage of obtaining a powder of uniform size.

[0105] The above sieving can be performed, for example, with a sieve of 120 to 250 mesh, preferably 140 to 240 mesh, more preferably 170 to 230 mesh, and even more preferably 180 to 210 mesh. In this case, the size of the waste cathode material powder is homogenized, which has the advantage of facilitating leaching in the subsequent leaching step.

[0106] In this description, the sieve is not particularly limited as long as it follows the definition of the present invention and uses a method or device defined in the art to which the present invention belongs.

[0107]

[0108] In step (ii) above, the acidic solution may be a solution containing one or more selected from the group consisting of, for example, sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, carbonic acid, acetic acid, and oxalic acid, preferably a solution containing hydrochloric acid or sulfuric acid, and more preferably a solution containing sulfuric acid, in which case lithium is easily leached and Fe and P remain as leaching residues.

[0109] The above acidic solution may preferably be an acidic aqueous solution, in which case there is an advantage that lithium is easily and selectively leached out while Fe and P remain as leaching residues.

[0110]

[0111] In step (ii) above, the acidic solution may have a concentration of, for example, 0.5 to 0.7 molar (mol / L), preferably 0.55 to 0.65 molar, and within this range, lithium is easily leached and Fe and P remain as leaching residues, which has the advantage.

[0112] In step (ii) above, the acidic solution may preferably be sulfuric acid or an aqueous sulfuric acid solution, and the sulfuric acid may be included with an acid concentration of, for example, 0.5 to 0.7 molar concentration (mol / L), preferably 0.55 to 0.65 molar concentration, and within this range, lithium is easily leached and Fe and P remain as leaching residues, which has the advantage.

[0113]

[0114] In step (ii) above, the solid-liquid ratio of the cathode material powder and the acidic solution may be, for example, 7 to 15 mL / g, preferably 8 to 13 mL / g, more preferably 9 to 12 mL / g, and within this range, lithium is easily and selectively leached out, while Fe and P remain as leaching residues, which has the advantage.

[0115] In this description, the solid-to-liquid ratio refers to the volume of liquid relative to the weight of the solid, that is, the volume of acidic solution (mL) relative to the cathode material powder content (g).

[0116]

[0117] In this description, leaching refers to the selective dissolution of metal elements or compounds contained in a solid material using a solvent such as an inorganic acid, organic acid, or alkali.

[0118]

[0119] In the above step (ii), separation can preferably be achieved using vacuum filtration. In this case, the leachate and leachate residue are easily separated through a simple process, reducing process costs and offering environmentally friendly advantages.

[0120] In this description, vacuum filtration is not particularly limited to conventional vacuum filtration applied in the technical field to which the present invention belongs.

[0121]

[0122] In step (iii) above, the acidic solution may preferably be sulfuric acid or an aqueous sulfuric acid solution, and the sulfuric acid may be included with an acid concentration of, for example, 0.8 to 1.3 molar concentration (mol / L), preferably 0.9 to 1.2 molar concentration, more preferably 0.9 to 1.1 molar concentration, and within this range, Fe and P are sufficiently leached, which has the economic advantage of increasing the yield of FePO4.

[0123] The reason the molar concentrations of the acidic solution in step (ii) and the acidic solution in step (iii) are different is that the molar concentration of the acidic solution in step (ii) is within a range that allows lithium to be easily leached from the cathode powder, and the molar concentration of the acidic solution in step (iii) is within a range that allows Fe and P to be easily leached from the separated leaching residue; since the leaching targets are different in steps (ii) and (iii), the molar concentrations of the acidic solutions are different.

[0124]

[0125] In the step of filtering by adding a basic solution to the above-mentioned solution containing Fe and P, vacuum filtration can be used, for example, and in this case, there is an advantage that the solution and impurities can be easily separated with only a simple process.

[0126] The above vacuum filtration may preferably be vacuum vacuum filtration, specifically vacuum vacuum filtration using a filtration flask, and in this case, there is an advantage that FePO4 is easily separated.

[0127] In this description, vacuum reduced pressure filtration is not particularly limited to conventional vacuum reduced pressure filtration in the technical field to which the present invention belongs, and may include, for example, filtration in a partial vacuum state or a low pressure state.

[0128]

[0129] The filtered solution above may, for example, have a pH of 1.0 to 1.4, preferably 1.1 to 1.4, and more preferably 1.1 to 1.3. In this case, since impurities are removed by adding a basic solution to the solution, the pH may be the same as or similar to the pH of the solution into which the basic solution was added.

[0130]

[0131] The above-mentioned separated impurities may include, for example, Fe and P in addition to Al and Ti, and in this case, Fe and P can be recovered by leaching the separated impurities back into an acidic solution.

[0132]

[0133] (b) a step of preparing a hydrogen peroxide mixture by adding an aqueous hydrogen peroxide solution to a filtered solution containing Fe and P.

[0134] The method for regenerating lithium iron phosphate according to the present invention may include the step of (b) introducing an aqueous hydrogen peroxide solution into a filtered solution containing Fe and P to prepare a hydrogen peroxide mixture, and in this case, there is an advantage that the synthesis of FePO4 is easy.

[0135]

[0136] For example, the above-mentioned aqueous hydrogen peroxide solution can be added in an amount of 1 to 5 volume% of the solution based on hydrogen peroxide, preferably in an amount of 1 to 4 volume% of the solution, more preferably in an amount of 1 to 3 volume% of the solution, and even more preferably in an amount of 1.5 to 2.5 volume% of the solution, and there is an advantage that the synthesis of FePO4 is easy within this range.

[0137]

[0138] The above-mentioned aqueous hydrogen peroxide solution may, for example, have a concentration of 25 to 40 weight%, preferably 27 to 35 weight%, more preferably 29 to 33 weight%, and within this range, there is an advantage that the synthesis of FePO4 is easy without the generation of by-products.

[0139]

[0140] The above hydrogen peroxide mixture may, for example, have a pH of 0.1 to 0.7, preferably 0.2 to 0.6, and more preferably 0.3 to 0.5, and within this range Fe is Fe 3+It has the effect of facilitating the synthesis of FePO4 while suppressing the generation of byproducts by maintaining it.

[0141]

[0142] In step (b) above, the temperature rise resulting from the addition of an aqueous hydrogen peroxide solution to the solution containing Fe and P is minimal; for example, the mixture prepared after the addition of the aqueous hydrogen peroxide solution is less than 28°C, 27°C or lower, or 26°C or lower, and as a specific example, it may be 20°C or higher or room temperature. Therefore, in order for FePO4 synthesis to proceed easily, the temperature of the hydrogen peroxide mixture must be raised.

[0143]

[0144] (c) A step of synthesizing FePO4 by heating a hydrogen peroxide mixture and separating it.

[0145] The method for regenerating lithium iron phosphate according to the present invention may include (c) a step of synthesizing FePO4 by heating a hydrogen peroxide mixture and separating it, and in this case, there is an advantage that FePO4 synthesis is easy.

[0146]

[0147] In step (c) above, the heating can be performed by heating the hydrogen peroxide mixture to, for example, 28 to 60 ℃, preferably 28 to 55 ℃, more preferably 30 to 50 ℃, and even more preferably 30 to 42 ℃, and there is an advantage that FePO4 synthesis is easily carried out within this range.

[0148]

[0149] In step (c) above, the method may further include a step of heating the hydrogen peroxide mixture and then adding, for example, a basic solution to adjust the pH to 1.0 to 1.8. In this case, the pH is maintained constant during the synthesis process, which has the advantage of synthesizing FePO4 in high yield.

[0150] The above basic solution may be, for example, an aqueous ammonia solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, or an aqueous calcium hydroxide solution, and preferably an aqueous ammonia solution, having the advantage of easy pH adjustment.

[0151] The above basic solution may preferably be an aqueous ammonia solution, and the aqueous ammonia solution may be included, for example, at a concentration of 0.8 to 1.3 molar (mol / L), preferably 0.9 to 1.2 molar, more preferably 0.9 to 1.1 molar, and within this range, the pH can be easily adjusted.

[0152] The addition of a basic solution to the above hydrogen peroxide mixture can be carried out, for example, while stirring, and in this case, there is an advantage that FePO4 can be easily synthesized without side reactions.

[0153] The above stirring speed may be, for example, 300 to 700 rpm, preferably 350 to 600 rpm, more preferably 400 to 550 rpm, and there is an advantage that FePO4 is easily synthesized within this range.

[0154] For example, the addition of a basic solution to the above hydrogen peroxide mixture can be continuous, and in this case, there is an advantage that FePO4 is synthesized stably without side reactions.

[0155] After the addition of the above basic solution is completed, the hydrogen peroxide mixture may have a pH of, for example, 1.0 to 1.8, preferably 1.1 to 1.6, more preferably 1.2 to 1.5, and there is an advantage that FePO4 is synthesized in high yield within this range.

[0156] After the addition of the above basic solution is completed, stirring can be performed for, for example, 30 to 60 minutes, preferably 35 to 55 minutes, more preferably 40 to 50 minutes, and in this case, there is an advantage that FePO4 is synthesized stably without side reactions.

[0157] The above-mentioned synthesized FePO4 can be separated using, for example, reduced-pressure filtration, and in this case, there is an advantage that the synthesized FePO4 is easily separated.

[0158] By separating the FePO4 synthesized from the above hydrogen peroxide mixture, there is an advantage of easily removing impurities and saving energy during the subsequent washing step.

[0159] The above vacuum filtration may preferably be vacuum vacuum filtration, specifically vacuum vacuum filtration using a filtration flask, and in this case, there is an advantage that FePO4 is easily separated.

[0160]

[0161] The FePO4 separated in step (c) above can be washed with an acidic washing solution, for example, and then introduced into step (d). In this case, impurities are easily removed, and no byproducts are generated due to the re-leaching of FePO4, which has the advantage of increasing the purity of the synthesized FePO4.

[0162] The above acidic washing solution can be prepared, for example, by adding sulfuric acid, hydrochloric acid, or a mixture thereof to distilled water, and preferably by adding hydrochloric acid. In this case, there is an advantage that the acidic washing solution is easy to prepare and impurities can be easily removed.

[0163] The above acidic washing solution may, for example, have a pH of 1.3 to 1.6, preferably 1.3 to 1.5, and more preferably 1.3 to 1.4. Within this range, impurities are easily removed, and no by-products are generated by the re-leaching of FePO4, which has the advantage of increasing the purity of the synthesized FePO4.

[0164] The solid-liquid ratio of the separated FePO4 and the acidic washing solution may be, for example, 15 to 25 mL / g, preferably 17 to 23 mL / g, and more preferably 19 to 22 mL / g, and within this range, there is an advantage that impurities are reduced and by-products are not generated.

[0165] The above washing can be performed by adding an acidic washing solution to the separated FePO4 and stirring for, for example, 5 to 20 minutes, preferably 5 to 15 minutes, more preferably 10 to 15 minutes, and in this case, there is an advantage that impurities are reduced and by-products are not generated.

[0166] The above washing may include, for example, vacuum filtration, and in this case, there is an advantage of easily separating FePO4 and the acidic washing solution.

[0167] The above-mentioned washed FePO4 can be introduced into step (d) after drying, for example, and in this case, there is an advantage of improved heat treatment efficiency.

[0168] The above drying may preferably be vacuum drying, and as a specific example, it may be carried out under vacuum at 70 to 200°C, more preferably at 75 to 130°C, and even more preferably at 75 to 100°C for 1 to 24 hours until there is no further change in weight, and within this range, it has the effect of efficiently removing moisture contained in the washed FePO4.

[0169]

[0170] Unless otherwise specified in this description, there are no specific restrictions on the temperature, and for example, it may be room temperature.

[0171]

[0172] In this description, vacuum drying is not particularly limited to conventional vacuum drying in the technical field to which the present invention belongs, and may include, for example, drying in a partial vacuum state or a low-pressure state.

[0173]

[0174] (d) A step of synthesizing a mixture of FePO4 and Li3PO4 by adding the separated FePO4 to a lithium-containing solution.

[0175] The method for regenerating lithium iron phosphate according to the present invention may include (d) a step of synthesizing a mixture of FePO4 and Li3PO4 by introducing the separated FePO4 into a lithium-containing solution. In this case, the ball milling process, which conventionally required a long time to be performed, can be omitted, thereby significantly reducing the regeneration time and energy consumption and greatly improving production efficiency. Here, the term 'synthesization' is adopted based on the formation of Li3PO4 and may also be referred to as 'formation' or 'manufacturing'.

[0176]

[0177] In step (d) above, the solution containing lithium may be, for example, an aqueous solution of a lithium salt or an aqueous leaching solution of a spent cathode active material, and in this case, there is an advantage that the yield of lithium iron phosphate is improved because synthesis with FePO4 is facilitated.

[0178] The above-mentioned lithium salt aqueous solution may be, for example, a solution in which lithium carbonate or lithium hydroxide is dissolved in water, and in this case, there is an advantage of synthesizing high-purity lithium iron phosphate without side reactions.

[0179] The aqueous leaching solution of the above-mentioned waste cathode active material may, for example, be a solution obtained by leaching the waste cathode active material into water. Specifically, it may be a solution obtained by heat-treating a waste cathode containing one or more types of cathode active materials selected from the group consisting of lithium nickel oxide (LNO)-based cathode active materials, nickel-cobalt-manganese (NCM)-based cathode active materials, nickel-cobalt-aluminum (NCA)-based cathode active materials, and nickel-cobalt-manganese-aluminum (NCMA)-based cathode active materials to thermally decompose the binder and conductive material to obtain a cathode active material, and then leaching the material into water. In this case, synthesis with FePO4 is easy, and there is an economic advantage of reducing production costs.

[0180]

[0181] In step (d) above, the solution containing lithium can be introduced in an amount such as 1 to 3.5 moles of lithium, for example, with respect to 1 mole of separated FePO4, preferably 1.5 to 3.3 moles of lithium, more preferably 2 to 3.1 moles of lithium, even more preferably 2.3 to 2.9 moles of lithium, and even more preferably 2.5 to 2.9 moles of lithium. In this case, it is regenerated into lithium iron phosphate with a high lithium content, which has the advantage of improving battery performance when applied to a secondary battery.

[0182]

[0183] The solid-liquid ratio of the solution containing FePO4 and lithium separated in step (d) above may be, for example, 40 to 75 mL / g, preferably 45 to 70 mL / g, more preferably 50 to 70 mL / g, and there is an advantage that lithium and FePO4 are synthesized with high efficiency within this range.

[0184]

[0185] In step (d) above, the synthesis can be carried out, for example, at a temperature of 50 to 100°C, preferably 60 to 95°C, more preferably 70 to 90°C, and even more preferably 75 to 85°C. Within this range, the lithium in the lithium-containing solution reacts easily with FePO4, which has the advantage of improving the yield of lithium iron phosphate.

[0186]

[0187] In step (d) above, the synthesis can be carried out for, for example, 30 minutes to 5 hours, preferably 30 minutes to 4 hours, more preferably 1 to 3 hours, and more preferably 1 to 2 hours, and in this case, there is an advantage that lithium and FePO4 in the lithium-containing solution are sufficiently synthesized without side reactions.

[0188]

[0189] In step (d) above, the synthesis can be carried out, for example, at a stirring speed of 300 to 700 rpm, preferably 350 to 600 rpm, more preferably 400 to 550 rpm, and within this range, there is an advantage that lithium and FePO4 in the lithium-containing solution are sufficiently synthesized without side reactions.

[0190]

[0191] In step (d) above, for example, the synthesis can be performed by heating a lithium-containing solution to the synthesis temperature and then adding the separated FePO4, and in this case, the synthesis with FePO4 is facilitated.

[0192]

[0193] (e) lowering the reaction solution containing the above mixture to room temperature to precipitate and separate the mixture of FePO4 and Li3PO4.

[0194] The method for regenerating lithium iron phosphate according to the present invention may include (e) a step of lowering the reaction solution containing the above mixture to room temperature to precipitate and separate the mixture of FePO4 and Li3PO4, and in this case, the ball milling process, which conventionally had to be performed for a long time, can be omitted, thereby significantly reducing the regeneration time and energy consumption and greatly improving production efficiency.

[0195]

[0196] The reaction solution containing the above mixture can be cooled slowly in the atmosphere to room temperature, for example, and in this case, the mixture of FePO4 and Li3PO4 precipitates as a powder and has the advantage of being easily separated.

[0197] In the above mixture of FePO4 and Li3PO4, for example, FePO4 may be amorphous and Li3PO4 may be crystalline.

[0198] In this description, "noncrystalline" or "amorphous" refers to a material lacking regularity in atoms or molecules and can be confirmed by pattern analysis using X-ray diffraction (XRD).

[0199]

[0200] The above separation can preferably be achieved using vacuum filtration. In this case, the mixture of FePO4 and Li3PO4 is easily separated into powder through a simple process, which offers the advantages of reduced process costs and an eco-friendly environment.

[0201] The separated powder above can be introduced into step (f) after drying, for example, and in this case, there is an advantage of improved heat treatment efficiency.

[0202] The above drying can preferably be vacuum drying, and more preferably, can be carried out under vacuum at 70 to 200°C until there is no further change in weight, and as a specific example, can be carried out at 80 to 130°C for 1 to 24 hours, and within this range, it has the effect of efficiently removing moisture contained in the washed powder.

[0203]

[0204] (f) A step of producing lithium iron phosphate by adding a carbon source to a mixture of separated FePO4 and Li3PO4 and heat-treating it.

[0205] The method for regenerating lithium iron phosphate according to the present invention may include the step of (f) introducing a carbon source into a mixture of separated FePO4 and Li3PO4 and heat-treating it to produce lithium iron phosphate. In this case, FePO4 and Li3PO4 are synthesized and crystalline LiFePO4 with a carbon coating on its surface is produced, thereby improving the electrical conductivity of the lithium iron phosphate and providing the advantage of excellent battery characteristics when applied to a secondary battery.

[0206] In step (f) above, the carbon source may be one or more selected from the group consisting of glucose, sucrose, graphite, carbon nanotubes, citric acid, and carbon black, and preferably sucrose. In this case, the electrical conductivity of lithium iron phosphate is improved, which has the effect of providing excellent battery performance when applied to a secondary battery.

[0207] The above carbon source can be added in an amount of, for example, 3 to 10 weight percent of the weight of the separated powder, preferably 4 to 8 weight percent, and more preferably 5 to 7 weight percent, and within this range, it is sufficiently uniformly coated on the lithium iron phosphate, which has the advantage of improving electrical conductivity.

[0208] In step (f) above, the heat treatment can be carried out, for example, under a reducing atmosphere, preferably a nitrogen atmosphere, in which case the synthesis of crystalline LiFePO4 is easily achieved, and Fe 2+ It has the advantage of preventing oxidation and improving the electrical conductivity of the regenerated lithium iron phosphate by coating the surface with carbon.

[0209]

[0210] In step (f) above, the heat treatment can be carried out, for example, at 650 to 800 ℃, preferably at 670 to 770 ℃, more preferably at 700 to 750 ℃, and within this range, FePO4 and Li3PO4 are synthesized and there is an advantage of obtaining crystalline LiFePO4 with carbon coating on the surface.

[0211] The above heat treatment may have a temperature rise rate of, for example, 1 to 20 ℃ / min, preferably 3 to 10 ℃ / min, and has the advantage of being able to be implemented within this range without putting strain on the heat treatment equipment.

[0212] The above heat treatment is performed using various types of furnaces, for example, a box-type furnace, and considering productivity, a rotary kiln capable of continuous processing is used.

[0213] After the above heat treatment, it can be slowly cooled or rapidly cooled in the atmosphere.

[0214]

[0215] In step (f) above, the heat treatment can be carried out for, for example, 17 to 25 hours, preferably 17 to 23 hours, more preferably 20 to 22 hours, and within this range, FePO4 and Li3PO4 are synthesized and there is an advantage of obtaining crystalline LiFePO4 with carbon coated on the surface.

[0216] In this description, the heat treatment time refers to the time spent processing at the corresponding heat treatment temperature, and the time taken to reach the corresponding heat treatment temperature is not calculated.

[0217]

[0218] Figures 1 and 2 below are flowcharts of a method for producing lithium iron phosphate from a spent lithium iron phosphate anode according to one embodiment of the present invention, Figure 1 shows the step of synthesizing FePO4 from a spent lithium iron phosphate anode, and Figure 2 shows the step of producing regenerated lithium iron phosphate from a solution containing the synthesized FePO4 and lithium.

[0219]

[0220] Referring to FIG. 1, first, a spent lithium iron phosphate cathode is prepared (step S10).

[0221] The above waste lithium iron phosphate anode may preferably be a discarded lithium-ion battery anode, a defective product generated during the anode coating process, or an anode scrap discarded after cutting the electrode plate, and preferably, a discarded lithium-ion battery anode may be prepared.

[0222] The above-mentioned anode has a structure in which an anode active material and a conductive material are bonded to an aluminum foil by a binder.

[0223] The above-mentioned anode may include an anode active material having an olivine structure, preferably lithium iron phosphate having an olivine structure, and more preferably LiFePO4 having an olivine structure, in which case there are advantages such as excellent high-temperature stability and lifespan characteristics and low cost.

[0224]

[0225] Next, the waste lithium iron phosphate cathode is crushed to obtain cathode material powder (step S20).

[0226] The above grinding can be performed using dry grinding equipment, specifically using a hand mill, pin mill, disc mill, cutting mill, hammer mill, or blender. As a specific example, grinding is performed using a blender, and in this case, the current collector is cut into small pieces and the anode material separates from the current collector, thus providing the advantage of easily separating the current collector and the anode material.

[0227] The above-mentioned crushed waste anode may preferably further include a sieve step, in which case the current collector is separated from the crushed waste anode and anode material powder of uniform size can be obtained.

[0228] The above sieving can preferably be performed using a sieve with a mesh size of 120 to 250, specifically a sieve with a mesh size of 200, in which case the current collector can be separated and a uniformly sized anode material powder can be obtained.

[0229]

[0230] Next, waste cathode material powder is introduced into an acidic solution with a concentration of 0.5 to 0.7 molar (mol / L) to form a leaching solution in which lithium is dissolved and a leaching residue, and these are separated (step S30).

[0231] The above acidic solution may be a solution containing one or more selected from the group consisting of, for example, sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, carbonic acid, acetic acid, and oxalic acid, and specifically may be an aqueous sulfuric acid solution, in which case lithium is easily and selectively leached and Fe and P remain as leaching residues, which has the advantage.

[0232] The above acidic solution may preferably be an acidic aqueous solution, in which case there is an advantage that lithium is easily and selectively leached out while Fe and P remain as leaching residues.

[0233] The above acidic solution may preferably be sulfuric acid or an aqueous sulfuric acid solution, and the sulfuric acid may have an acid concentration of, for example, 0.5 to 0.7 molar concentration (mol / L), preferably 0.55 to 0.65 molar concentration (mol / L), and as a specific example, 0.6 molar concentration, and in this case, there is an advantage that lithium is easily and selectively leached and Fe and P remain as leaching residues.

[0234] In step S30, the solid-liquid ratio of the waste cathode material powder and the acidic solution can preferably be 7 to 15 mL / g, and as a specific example, 10 mL / g. In this case, lithium is sufficiently leached, but Fe and P are not leached and remain as leaching residue, which has the advantage.

[0235]

[0236] Next, the lithium-dissolved leaching solution and the leaching residue are separated (step S40).

[0237] The above separation can preferably be performed using vacuum filtration, in which case the leachate and leachate residue are easily separated with only a simple process, reducing process costs and offering the advantages of being environmentally friendly.

[0238]

[0239] Next, the separated leaching residue is added to an acidic solution with a concentration of 0.8 to 1.3 molar (mol / L) to obtain a dissolved solution containing Fe and P (step S50).

[0240] The above acidic solution may be a solution containing one or more selected from the group consisting of, for example, sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, carbonic acid, acetic acid, and oxalic acid, and specifically may be an aqueous sulfuric acid solution, in which case it has the advantage of leaching Fe and P.

[0241] The above acidic solution may preferably be an acidic aqueous solution, in which case there is an advantage that Fe and P are easily leached out.

[0242] The above acidic solution may preferably be sulfuric acid or an aqueous sulfuric acid solution, and the sulfuric acid may have a concentration of 0.8 to 1.3 molar, preferably 0.9 to 1.2 molar, and as a specific example, a concentration of 1.0 molar. In this case, Fe and P are sufficiently leached from the leaching residue obtained in step S40, so the yield of FePO4 is increased, which has an economic advantage.

[0243] The above-mentioned solution containing Fe and P may preferably have a pH of 0.1 to 0.5, and as a specific example, may have a pH of 0.2 to 0.4, and there is an advantage that Fe and P exist in a leached state within this range.

[0244]

[0245] Next, a basic solution is added to the dissolved solution containing Fe and P (step S60).

[0246] Step S60 has the advantage of significantly improving the purity of the FePO4 produced by adding a basic solution to a dissolved solution containing Fe and P to precipitate and remove impurities.

[0247] The above basic solution may be, for example, an aqueous ammonia solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, or an aqueous calcium hydroxide solution, and specifically, an aqueous ammonia solution. In this case, there is an advantage that impurities derived from waste lithium iron phosphate cathode material, such as aluminum and titanium, are precipitated and easily removed.

[0248]

[0249] The above-mentioned solution containing Fe and P may contain Fe at a concentration of 23,000 ppm or more, for example, 27,000 ppm, and in this case, there is an advantage in producing high yield and high purity FePO4.

[0250] The above-mentioned solution containing Fe and P may contain P at a concentration of 10,000 ppm or more, for example, 15,000 ppm, and in this case, there is an advantage in producing high yield and high purity FePO4.

[0251] The above-mentioned solution containing Fe and P may contain lithium at a concentration of 500 ppm or less, for example, and 250 ppm as a specific example, and in this case, there is an advantage in producing high-purity FePO4.

[0252]

[0253] The above basic solution may preferably be an aqueous ammonia solution, and the aqueous ammonia solution may contain a basic component at a concentration of 0.8 to 1.3 molar (mol / L), preferably 0.9 to 1.2 molar, more preferably 0.9 to 1.1 molar, and as a specific example, at a concentration of 1 molar. In this case, pH adjustment is easy, and there is an advantage that impurities derived from waste lithium iron phosphate cathode material, such as aluminum and titanium, are precipitated and easily removed.

[0254] After the addition of the above basic solution is completed, the solution may preferably have a pH of 1.0 to 1.4, and as a specific example, a pH of 1.2. In this case, there is an advantage that impurities such as aluminum and titanium are precipitated and easily removed.

[0255] The above basic solution can be continuously added to the solution, and in this case, there is an advantage that impurities such as aluminum and titanium precipitate and are easily removed.

[0256] The above basic solution can be added, for example, under stirring, and in this case, there is an advantage that impurities precipitate within a short time.

[0257]

[0258] Next, the solution to which the basic solution has been added is filtered (step S70).

[0259] By filtering the solution to which the above basic solution has been added, impurities are easily removed, allowing for the production of high-purity FePO4.

[0260] The above filtration can preferably utilize reduced-pressure filtration, which has the advantage of easily separating the dissolved solution and impurities through a simple process.

[0261] The above impurities may be, for example, impurities derived from waste lithium iron phosphate cathode materials such as aluminum and titanium.

[0262]

[0263] Next, an aqueous hydrogen peroxide solution is added to the filtered solution containing Fe and P to prepare a hydrogen peroxide mixture (step S80).

[0264] In step S80, the aqueous hydrogen peroxide solution can preferably be added in an amount of 1 to 5 volume% of the solution based on hydrogen peroxide, and as a specific example, in an amount of 2 volume% of the solution, and in this case, there is an advantage that the synthesis of FePO4 is easy.

[0265] The above aqueous hydrogen peroxide solution may preferably have a concentration of 25 to 40 weight%, and as a specific example, 30 weight%, in this case Fe is Fe 3+ It has the effect of facilitating the synthesis of FePO4 while suppressing the generation of byproducts by maintaining it.

[0266]

[0267] Next, the hydrogen peroxide mixture is heated (step S90).

[0268] The above hydrogen peroxide mixture can preferably be heated to 28 to 60°C, and as a specific example, to 30°C, in which case there is an advantage that FePO4 synthesis is easy.

[0269]

[0270] Next, FePO4 is synthesized by adding a basic solution to a heated hydrogen peroxide mixture (step S100).

[0271] After adding the basic solution to the heated hydrogen peroxide mixture, the pH can preferably be 1 to 1.8, and as a specific example, 1.2. In this case, the pH is maintained at a constant level during synthesis, which has the advantage of stably synthesizing FePO4 in a high yield.

[0272] The above basic solution may preferably be an aqueous ammonia solution, and in this case, the pH is maintained constant during synthesis, which has the advantage of stably synthesizing FePO4 in a high yield.

[0273] In step S100, the basic solution can preferably be introduced while stirring, and more preferably while stirring at 300 to 700 rpm, and as a specific example, while stirring at 500 rpm, in this case there is an advantage that FePO4 is synthesized in a high yield.

[0274] In step S100, the basic solution can preferably be continuously added, and in this case, there is an advantage that FePO4 is synthesized stably without side reactions.

[0275] Preferably, the temperature can be maintained while the above basic solution is introduced, and in this case, there is an advantage that FePO4 is synthesized stably without side reactions.

[0276] After the addition of the basic solution in step S100 is completed, stirring can be further performed for preferably 30 to 60 minutes, specifically for 40 minutes, and in this case, there is an advantage that FePO4 is synthesized stably without side reactions.

[0277] In step S100, a basic solution is added, and after the addition is complete, additional stirring can preferably be performed at a heated temperature. In this case, there is an advantage that the synthesis of FePO4 is carried out stably without side reactions.

[0278]

[0279] Next, the synthesized FePO4 is separated (step S110).

[0280] Separating the FePO4 synthesized in step S100 has the advantage of facilitating the removal of impurities in the subsequent washing step and saving energy.

[0281] The above separation can preferably be achieved using reduced pressure filtration, more preferably vacuum reduced pressure filtration, specifically vacuum reduced pressure filtration using a filtration flask, in which case there is an advantage that FePO4 is easily separated.

[0282]

[0283] Next, the separated FePO4 is washed with an acidic washing solution (step S120).

[0284] Through the above washing step, iron phosphate with an incorrect stoichiometric ratio, i.e., Fe x PO y There is an advantage in that the purity of the synthesized FePO4 is increased as impurities such as (where x is not 1, y is not 4, and x:y is not 1:4) are easily removed and no by-products are generated.

[0285] The above acidic washing solution may preferably have a pH of 1.3 to 1.6, more preferably 1.3 to 1.5, and in this case, impurities are easily removed and by-products are not generated by the re-leaching of FePO4, which has the advantage of increasing the purity of the synthesized FePO4.

[0286] The above acidic cleaning solution may, as a specific example, be a mixture of hydrochloric acid, sulfuric acid, or a mixture thereof with distilled water, and as a specific example, hydrochloric acid may be mixed; in this case, there is an advantage that the acidic cleaning solution is easy to manufacture and impurities can be easily removed.

[0287] In step S120, the solid-liquid ratio of FePO4 to the acidic washing solution may preferably be 15 to 25 mL / g, and as a specific example, 20 mL / g; in this case, the formation of byproducts is suppressed, and iron phosphate with an unstood stoichiometric ratio, i.e., Fe x PO y There is an advantage in that impurities such as [such as] are easily removed and no by-products are generated, thereby increasing the purity of the synthesized FePO4.

[0288] In step S120, washing can be performed by introducing an acidic washing solution and preferably for 5 to 20 minutes, specifically for 10 minutes, under stirring, and in this case, there is the advantage that impurities are reduced and by-products are not generated.

[0289] Washing in step S120 may preferably include vacuum filtration, in which case there is an advantage of easily separating FePO4 and the acidic washing solution.

[0290] Step S120 may further include a step of drying the washed FePO4, in which case the moisture contained in the washed FePO4 is effectively removed.

[0291] The above drying can preferably be vacuum drying, and more preferably, can be carried out under vacuum at 70 to 200°C until there is no further change in weight, and as a specific example, can be carried out at 80 to 130°C for 1 to 24 hours, and within this range, it has the effect of efficiently removing moisture contained in the washed FePO4.

[0292]

[0293] Also, referring to FIG. 2, the FePO4 separated in step S120 is added to a lithium-containing solution to synthesize a mixture of FePO4 and Li3PO4 (step S130).

[0294] The above lithium-containing solution may be, for example, an aqueous solution of a lithium salt or an aqueous leaching solution of spent cathode active material, and in this case, synthesis with FePO4 is facilitated, which has the advantage of improving the yield of lithium iron phosphate.

[0295] The above lithium aqueous solution may be, for example, a solution in which lithium carbonate or lithium hydroxide is dissolved in water, and in this case, there is an advantage of synthesizing high-purity lithium iron phosphate without side reactions.

[0296] The aqueous leaching solution of the above-mentioned waste cathode active material may be a solution obtained by heat-treating a waste cathode containing one or more types of cathode active materials selected from the group consisting of, for example, lithium nickel oxide (LNO)-based cathode active materials, nickel-cobalt-manganese (NCM)-based cathode active materials, nickel-cobalt-aluminum (NCA)-based cathode active materials, and nickel-cobalt-manganese-aluminum (NCMA)-based cathode active materials to thermally decompose the binder and conductive material to obtain a cathode active material, and then leaching the material into water. In this case, synthesis with FePO4 is easy, and there is an economic advantage of reducing production costs.

[0297]

[0298] The above lithium-containing solution can be introduced in an amount of 1 to 3.5 moles of lithium relative to 1 mole of separated FePO4, preferably 1.5 to 3.3 moles of lithium, more preferably 2 to 3.1 moles of lithium, even more preferably 2.3 to 2.9 moles, and even more preferably 2.5 to 2.9 moles. In this case, it is regenerated into lithium iron phosphate with a high lithium content, which has the advantage of improving battery performance when applied to a secondary battery.

[0299] The solid-liquid ratio of the above-described solution containing FePO4 and lithium can be, for example, 40 to 75 mL / g, and specifically, 50 to 70 mL / g, and there is an advantage that lithium and FePO4 are synthesized with high efficiency within this range.

[0300] The above synthesis can be carried out, for example, at a temperature of 50 to 100°C, and specifically at a temperature of 80°C. In this case, the lithium in the lithium-containing solution reacts easily with FePO4, which has the advantage of improving the yield of lithium iron phosphate.

[0301] The above synthesis can be carried out for, for example, 30 minutes to 5 hours, and specifically for 1 hour, and in this case, there is an advantage that lithium and FePO4 in a lithium-containing solution are sufficiently synthesized without side reactions.

[0302] The above synthesis can be carried out, for example, at a stirring speed of 300 to 700 rpm, and specifically at 500 rpm. In this case, there is an advantage that lithium and FePO4 in a lithium-containing solution are sufficiently synthesized without side reactions.

[0303] For example, in the above synthesis, a lithium-containing solution can be heated to the synthesis temperature and then separated FePO4 can be added, in which case the synthesis with FePO4 is facilitated.

[0304]

[0305] Next, the reaction solution containing the above mixture is lowered to room temperature to precipitate the mixture of FePO4 and Li3PO4 (step S140).

[0306] When the reaction solution containing the above mixture is lowered to room temperature, the mixture of FePO4 and Li3PO4 precipitates as a powder, making it easy to separate.

[0307] The reaction solution containing the above mixture can be cooled slowly in the atmosphere to room temperature, for example, and in this case, the mixture of FePO4 and Li3PO4 precipitates as a powder and has the advantage of being easily separated.

[0308] In the above mixture of FePO4 and Li3PO4, FePO4 may be amorphous and Li3PO4 may be crystalline.

[0309]

[0310] Next, the precipitated powder is separated from the reaction solution containing the above mixture (step S150).

[0311] The above separation can preferably be performed using vacuum filtration, in which case the reaction solution and powder are easily separated with only a simple process, reducing process costs and offering the advantages of being environmentally friendly.

[0312] The separated powder can be introduced into step S160 after drying, for example, and in this case, there is an advantage of improved heat treatment efficiency.

[0313]

[0314] Next, a carbon source is added to the mixture of separated FePO4 and Li3PO4 and heat-treated (step S160).

[0315] In step S160, the separated mixture of FePO4 and Li3PO4 is heat-treated to synthesize Li3PO4 and FePO4 into crystalline LiFePO4, and the surface is coated with carbon.

[0316] The above carbon source may be one or more selected from the group consisting of glucose, sucrose, graphite, carbon nanotubes, citric acid, and carbon black, and a specific example may be sucrose. In this case, the electrical conductivity is improved by carbon coating of lithium iron phosphate, and when applied to a secondary battery, the battery performance is excellent.

[0317] The above carbon source can be added in an amount of 3 to 10 weight percent, preferably 4 to 8 weight percent, more preferably 5 to 7 weight percent, of the weight of the mixture of separated FePO4 and Li3PO4, and as a specific example, in an amount of 5 weight percent, and within this range, there is an advantage that the electrical conductivity of the regenerated lithium iron phosphate is excellent.

[0318] In step S160, the heat treatment can be performed, for example, in a reducing atmosphere, and specifically, under a nitrogen atmosphere, in this case Fe 2+ There is an advantage in that the electrical conductivity of the regenerated lithium iron phosphate is improved by preventing oxidation and coating the surface with carbon.

[0319] The above heat treatment can be carried out, for example, at 650 to 800 ℃, preferably at 670 to 770 ℃, more preferably at 700 to 750 ℃, and as a specific example, at 700 ℃, and within this range, FePO4 and Li3PO4 are synthesized into crystalline LiFePO4 and the surface is carbon coated, which has the advantage.

[0320] The above heat treatment can be carried out for, for example, 17 to 25 hours, preferably 17 to 23 hours, more preferably 20 to 22 hours, and as a specific example, for 20 hours, and within this range, FePO4 and Li3PO4 are synthesized and there is an advantage in obtaining crystalline LiFePO4 with carbon coated on the surface.

[0321] The above heat treatment preferably has a temperature rise rate of 1 to 20 ℃ / min, more preferably 3 to 10 ℃ / min, and a specific example is 3 ℃ / min, and has the advantage of being able to be implemented within this range without putting strain on the heat treatment equipment.

[0322] The above heat treatment is performed using various types of furnaces, for example, a box-type furnace, and considering productivity, a rotary kiln capable of continuous processing is used.

[0323] After the above heat treatment, it can be slowly cooled or rapidly cooled in the atmosphere.

[0324]

[0325] Hereinafter, preferred embodiments are presented to aid in understanding the present invention; however, the following embodiments are merely illustrative of the invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the invention, and that such variations and modifications fall within the scope of the appended claims.

[0326]

[0327] [Example]

[0328] Preparation Example: Aqueous extract of waste cathode active material

[0329] After stamping the anode plate, discarded anode scrap (current collector: aluminum foil, anode active material: NCM-based lithium composite transition metal oxide) was crushed, and the scrap was heat-treated in air at 590°C for 30 minutes to remove the binder and conductive material, separate the current collector and the anode active material, and then recover the anode active material. Here, the rate of temperature increase until reaching the heat treatment temperature was 5°C / min, and oxygen (O2) was supplied at 10 L / min.

[0330] The recovered positive electrode active material was immersed in distilled water and stirred simultaneously. At this time, the weight ratio of the recovered positive electrode active material to distilled water was set to 1:30, and the mixture was stirred at 500 rpm for 10 minutes. After stirring, the positive electrode active material (leaching residue) and the leaching solution from which lithium was leached were separated by vacuum filtration using a filter. In the aqueous leaching solution of the separated waste positive electrode active material, lithium existed as lithium carbonate, and the concentration of lithium in the aqueous leaching solution was 2500 ppm.

[0331] Distilled water was mixed with the above aqueous leachate having a lithium concentration of 2500 ppm to prepare aqueous leachates having lithium concentrations of 2200 ppm, 2000 ppm, 1000 ppm, and 500 ppm, respectively.

[0332]

[0333] Example 1

[0334] The spent lithium iron phosphate anode was crushed with a blender to separate the current collector. The anode material from which the current collector was separated was sieved through a 200-mesh sieve to obtain spent anode material powder having an olivine structure. X-ray diffraction (XRD) analysis of the obtained spent anode material powder confirmed that it contained lithium iron phosphate powder with an olivine structure.

[0335] 100 g of the above-prepared waste cathode material powder was added to 1000 ml of an aqueous sulfuric acid solution with a concentration of 0.6 molar (mol / L) at room temperature and leached to form a leaching solution containing dissolved lithium and a leaching residue, and the leaching residue was obtained by separating them by vacuum filtration.

[0336] The leaching residue obtained above was leached in a 1 molar aqueous sulfuric acid solution at room temperature for 20 hours at a solid-to-liquid ratio of 10 mL / g to obtain a solution containing Fe and P. The solution contained 27,000 ppm of Fe, 15,000 ppm of P, and 250 ppm of Li, which was confirmed by ICP analysis. At this time, the pH of the solution was 0.3.

[0337] 50 ml of the above-mentioned solution containing Fe and P was taken, and while stirring at room temperature, an aqueous ammonia solution with a concentration of 1 molar was continuously added at a rate of 1 ml / min to make the pH of the solution 1.2, thereby precipitating impurities such as aluminum and titanium.

[0338] The above-mentioned dissolved solution containing precipitated impurities such as aluminum and titanium was separated by vacuum filtration to remove the impurities.

[0339] A hydrogen peroxide aqueous solution (30 wt% concentration) was added to 50 ml of the above-mentioned filtered solution in an amount equal to 2 volume% of the solution based on hydrogen peroxide, and the temperature was raised to 30 ℃ to prepare a hydrogen peroxide mixture. At this time, the process was carried out under stirring at 500 rpm.

[0340] FePO4 was synthesized by continuously adding a 1 molar aqueous ammonia solution to the heated hydrogen peroxide mixture at a rate of 0.1 ml / min to maintain the pH of the mixture at 1.2. At this time, the mixture was stirred at 500 rpm and the heated temperature was maintained.

[0341] The above-mentioned synthesized FePO4 and mixture were separated using vacuum filtration.

[0342] The above-described separated FePO4 was mixed with an acidic solution (washing solution) with a pH of 1.3 prepared with distilled water and hydrochloric acid at a solid-to-liquid ratio of 20 mL / g and washed for 10 minutes by stirring at 500 rpm.

[0343] After the above washing, FePO4 and the washing solution were separated using vacuum filtration to obtain washed FePO4. The washed FePO4 was vacuum dried at 80°C. The dried FePO4 was confirmed to be amorphous through XRD analysis, and this is shown in Figure 3 below.

[0344] A mixture of FePO4 and Li3PO4 was synthesized by adding 2 g of the dried FePO4 to the aqueous leaching solution obtained in the above preparation example, which has a lithium concentration of 2200 ppm, at a solid-liquid ratio of 60 mL / g. Here, 2 g of FePO4 corresponds to 0.013 mol, and the aqueous leaching solution of the spent cathode active material contains 2200 ppm of lithium, which is an amount corresponding to 2.87 mol of lithium per 1 mol of FePO4.

[0345] The above synthesis was carried out at 80°C for 1 hour under stirring at a stirring speed of 500 rpm.

[0346] The reaction solution containing the above mixture of FePO4 and Li3PO4 was lowered to room temperature in the atmosphere to precipitate the mixture of FePO4 and Li3PO4, separated by vacuum filtration, and dried to obtain a powder. Through X-ray diffraction (XRD) pattern analysis of the dried powder, it was confirmed that crystalline Li3PO4 and amorphous FePO4 were mixed, which is shown in Figure 4 below.

[0347] Sucrose was mixed with the dried powder as a carbon source to a concentration of 5% by weight of the dried powder, and the mixture was heat-treated at 700°C for 20 hours under a nitrogen atmosphere. The heat-treated powder was confirmed to be crystalline LiFePO4 through X-ray diffraction (XRD) pattern analysis, as shown in Figure 5 below. ICP analysis was performed on the heat-treated powder.

[0348]

[0349] Example 2

[0350] A mixture of FePO4 and Li3PO4 was synthesized by adding 2 g of the dried FePO4 from Example 1 to the aqueous leaching solution obtained in the preparation example with a lithium concentration of 2000 ppm at a solid-liquid ratio of 70 mL / g, except that the mixture was carried out in the same manner as Example 1.

[0351]

[0352] Example 3

[0353] A mixture of FePO4 and Li3PO4 was synthesized by adding 2 g of the dried FePO4 from Example 1 to the aqueous leaching solution obtained in the preparation example with a lithium concentration of 2500 ppm at a solid-liquid ratio of 50 mL / g, in the same manner as Example 1.

[0354]

[0355] Example 4

[0356] A mixture of FePO4 and Li3PO4 was synthesized by adding 2 g of the dried FePO4 from Example 1 to the aqueous leaching solution obtained in the preparation example with a lithium concentration of 500 ppm at a solid-liquid ratio of 100 mL / g, in the same manner as Example 1.

[0357]

[0358] Example 5

[0359] A mixture of FePO4 and Li3PO4 was synthesized by adding 2 g of the dried FePO4 from Example 1 to the aqueous leaching solution obtained in the preparation example with a lithium concentration of 1000 ppm at a solid-liquid ratio of 80 mL / g, in the same manner as Example 1.

[0360]

[0361] [Test Example I: ICP Analysis]

[0362] The Li, Fe, and P content of the powders finally prepared in Examples 1 to 5 above was measured through ICP analysis.

[0363]

[0364] * ICP analysis: 0.1 g of powder was aliquoted and placed in a conical tube, and the exact weight was measured. Then, 0.1 ml of nitric acid with a concentration of 70 wt% was added, followed by the addition of 500 µl of 1000 g / kg internal standard (Sc(Scandium)), and the mixture was diluted with ultrapure water to a volume of 50 ml and measured by ICP. The results are shown in Table 1 below.

[0365]

[0366] Classification Li concentration * (ppm) Solid-to-Liquid Ratio (mL / g) Lithium Molar Ratio per Mole of FePO41 Li (wg%) Fe (wg%) P (wg%) Example 1 2 200 60 2.8 7 4.8 3 1.0 5 1 1.68 Example 2 2 200 70 3.0 4 4.2 9 3 2.2 0 1 3.64 Example 3 2 5 200 50 2.7 2 4.6 2 3 0.7 3 1 1.20 Example 4 5 200 100 1.0 9 2.3 6 3 3.2 5 1 4.75 Example 5 1 200 80 1.7 4 3.3 5 3 2.8 4 1 4.01

[0367] * The Li concentration is the Li concentration in the aqueous leachate prepared in the above "Preparation Example: Aqueous Leachate of Waste Anode Active Material".

[0368] As shown in Table 1 above, it was confirmed through Examples 1 to 5 that lithium iron phosphate can be easily regenerated without omitting the conventional ball milling process, which takes a long time. Specifically, in Examples 1 and 3, in which the lithium molar ratio per mole of FePO41 was 2.3 to 2.9 moles, it was found that the lithium content in the regenerated lithium iron phosphate was high even with less lithium input compared to Example 2.

[0369]

[0370] [Test Example II: X-ray Diffraction (XRD) Pattern Analysis]

[0371] The results of X-ray diffraction (XRD) pattern analysis of the FePO4 synthesized in Example 1 above, the mixture of synthesized FePO4 and Li3PO4, and the final powder prepared are shown in Figures 3 to 5 below.

[0372]

[0373] * X-ray Diffraction (XRD) Pattern Analysis: In the XRD pattern analysis, the horizontal axis represents 2θ (Theta) (degrees) and the vertical axis represents counts, indicating the intensity of constructive interference of incident light within the crystal. The XRD patterns were obtained using a standard X-ray diffraction apparatus commonly used in laboratories. Specifically, the analysis was performed using the Rigaku XG-2100 X-ray diffraction analyzer. However, there is no variation depending on the apparatus or method.

[0374]

[0375] As shown in Figure 3 below, it was confirmed that the FePO4 synthesized from waste lithium iron phosphate has an amorphous structure through X-ray diffraction (XRD) pattern analysis.

[0376] In addition, as shown in Figure 4 below, it was found through the XRD pattern that the synthesized mixture of FePO4 and Li3PO4 contained amorphous FePO4 and crystalline Li3PO4.

[0377] In addition, as shown in Fig. 5 below, it was confirmed through the XRD pattern that the powders finally obtained in Examples 1 to 5 had carbon-coated crystalline LiFePO4. From this, it was confirmed that the present invention has the effect of significantly improving production efficiency by greatly reducing regeneration time and energy consumption, even while omitting the ball milling process that had to be carried out for a long time in the past.

Claims

1. (a) A step of adding a basic solution to a dissolved solution containing Fe and P and filtering it; (b) a step of preparing a hydrogen peroxide mixture by adding an aqueous hydrogen peroxide solution to a filtered solution containing Fe and P; (c) a step of synthesizing FePO4 by heating a hydrogen peroxide mixture and separating it; (d) a step of synthesizing a mixture of FePO4 and Li3PO4 by adding the separated FePO4 to a lithium-containing solution; (e) lowering the reaction solution containing the above mixture to room temperature to precipitate and separate the mixture of FePO4 and Li3PO4; and (f) a step of producing lithium iron phosphate by adding a carbon source to a mixture of separated FePO4 and Li3PO4 and heat-treating it; characterized by including Method for regenerating lithium iron phosphate.

2. In Paragraph 1, The solution of step (a) above is characterized as being a solution in which waste lithium iron phosphate is dissolved in an acidic solution. Method for regenerating lithium iron phosphate.

3. In Paragraph 1, The solution is characterized by having a pH of 1.0 to 1.4 after the addition of the basic solution is completed in step (a) above. Method for regenerating lithium iron phosphate.

4. In Paragraph 1, The solution of step (a) above is characterized by being prepared by comprising: (i) a step of crushing a spent lithium iron phosphate cathode to obtain cathode material powder; (ii) a step of adding the obtained cathode material powder to an acidic solution with a concentration of 0.5 to 0.7 molar (mol / L) to form a leaching solution containing dissolved lithium and a leaching residue and separating them; and (iii) a step of adding the separated leaching residue to an acidic solution with a concentration of 0.8 to 1.3 molar (mol / L) to obtain a solution containing Fe and P. Method for regenerating lithium iron phosphate.

5. In Paragraph 1, The above step (b) is characterized by adding an amount of aqueous hydrogen peroxide solution that is 1 to 5 volume percent of the solution based on hydrogen peroxide. Method for regenerating lithium iron phosphate.

6. In Paragraph 1, Characterized by heating the hydrogen peroxide mixture to 28 to 60 ℃ in step (c) above. Method for regenerating lithium iron phosphate.

7. In Paragraph 1, The method is characterized by further including the step of adding a basic solution after heating the hydrogen peroxide mixture in step (c) above. Method for regenerating lithium iron phosphate.

8. In Paragraph 7, The hydrogen peroxide mixture is characterized by having a pH of 1.0 to 1.8 after the addition of the above basic solution. Method for regenerating lithium iron phosphate.

9. In Paragraph 1, The FePO4 separated in step (c) above is washed with an acidic washing solution and then introduced into step (d), characterized by Method for regenerating lithium iron phosphate.

10. In Paragraph 1, The solution containing lithium in step (d) above is characterized by being added in an amount such that it is 1 to 3.5 moles of lithium relative to the separated FePO41 moles. Method for regenerating lithium iron phosphate.

11. In Paragraph 1, The solution containing lithium in step (d) above is characterized as being an aqueous lithium salt solution or an aqueous leaching solution of spent cathode active material. Method for regenerating lithium iron phosphate.

12. In Paragraph 1, In step (d) above, the synthesis is characterized by being carried out at a temperature of 50 to 100 ℃. Method for regenerating lithium iron phosphate.

13. In Paragraph 1, In the above step (d), the synthesis is characterized by being carried out for 30 minutes to 5 hours. Method for regenerating lithium iron phosphate.

14. In Paragraph 1, The carbon source in step (f) above is characterized as being one or more selected from the group consisting of glucose, sucrose, graphite, carbon nanotubes, citric acid, and carbon black. Method for regenerating lithium iron phosphate.

15. In Paragraph 1, The heat treatment in step (f) above is characterized by being carried out at 650 to 800 ℃ for 17 to 25 hours under a reducing atmosphere. Method for regenerating lithium iron phosphate.

16. In Paragraph 1, The above FePO4 is amorphous and the above lithium iron phosphate is crystalline, characterized by being amorphous. Method for regenerating lithium iron phosphate.

17. In Paragraph 1, In step (d) above, the synthesis is characterized by heating a lithium-containing solution to a synthesis temperature, adding the separated FePO4, and stirring for a synthesis time. Method for regenerating lithium iron phosphate.

18. In Paragraph 11, The aqueous leaching solution of the above-mentioned spent cathode active material is characterized by being a solution obtained by heat-treating a spent cathode comprising one or more cathode active materials selected from the group consisting of lithium nickel oxide (LNO)-based cathode active material, nickel-cobalt-manganese (NCM)-based cathode active material, nickel-cobalt-aluminum (NCA)-based cathode active material, and nickel-cobalt-manganese-aluminum (NCMA)-based cathode active material to thermally decompose a binder and a conductive material to obtain a cathode active material, and then leaching the cathode active material into water. Method for regenerating lithium iron phosphate.

Images