Method for regenerating positive electrode active material and regenerated positive electrode active material manufactured therefrom

Abstract

The present invention relates to a method for regenerating a positive electrode active material and a regenerated positive electrode active material manufactured therefrom and, more specifically, to a method for regenerating a positive electrode active material and a regenerated positive electrode active material manufactured therefrom, the method being characterized by comprising: (a) a step for heat-treating a waste positive electrode composition including a positive electrode active material, a conductive material, a binder, and a solvent to remove the solvent; (b) a step for pulverizing the waste positive electrode composition removed of the solvent; (c) a step for heat-treating the pulverized waste positive electrode composition at 300-650 °C to remove the binder and conductive agent and recover the positive electrode active material; (d) a step for adding a lithium precursor to the recovered positive electrode active material and annealing at 400-1,000 °C; and (e) a step for washing the annealed positive electrode active material with a washing solution. The present invention has the effect of providing a method for regenerating a positive electrode active material and a regenerated positive electrode active material manufactured therefrom, wherein a waste positive electrode composition including a positive electrode active material, a conductive material, a binder, and a solvent is heat-treated at a low temperature to remove the solvent, pulverized, and then heat-treated so that the binder and the conductive material are completely removed and the original structure of a fresh positive electrode active material is restored, and the regenerated positive electrode active material has excellent thermal stability and a reduced residual lithium content, and the initial capacity and lifespan characteristics of a secondary battery are excellent.

Description

Method for regenerating a cathode active material and a regenerated cathode active material manufactured thereby

[0001] 〔Cross-citation with the applicant(s)〕

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0018703, filed February 7, 2024, and Korean Patent Application No. 10-2025-0014491, filed February 5, 2025, which is hereby incorporated by reference in its entirety.

[0003] The present invention relates to a method for regenerating a positive electrode active material and a regenerated positive electrode active material manufactured therefrom, and more particularly, to a method for regenerating a positive electrode active material, wherein a spent positive electrode composition comprising a positive electrode active material, a conductive material, a binder, and a solvent is heat-treated at a low temperature to remove the solvent, is pulverized, and then heat-treated so that the binder and conductive material are cleanly removed and the composition is restored to its original state with a fresh positive electrode active material structure, has excellent thermal stability, reduces residual lithium, has excellent initial capacity and lifespan characteristics of a secondary battery, is environmentally friendly because no acid is used in the recovery and regeneration process, and thus neutralization and wastewater treatment are not required, thereby reducing process costs, and the positive electrode active material is regenerated as it is without being decomposed, so there are no discarded metal elements, and no organic solvent is used, so there is no generation of toxic gases or risk of explosion, and the economic feasibility and productivity are greatly improved.

[0004] A lithium secondary battery is largely composed of a cathode in which a positive active material layer is coated on a metal foil such as aluminum, a negative electrode in which a negative active material layer is coated on a metal foil such as copper, a separator that prevents the positive and negative electrodes from mixing, and an electrolyte that allows lithium ions to move between the positive and negative electrodes.

[0005] The above positive electrode is manufactured by applying a positive electrode composition including a positive electrode active material, a binder, a conductive agent, and a solvent to a metal foil such as aluminum, drying the result, and then pressurizing and molding the result.

[0006] The above positive electrode active material is mainly a lithium-based oxide, and the lithium-based oxide generally contains rare metals such as cobalt, nickel, or manganese.

[0007] The positive electrode active material, binder, conductive agent, and solvent that make up the above positive electrode composition are not easily mixed, so they are added and stirred in a specific order to adjust the solid concentration, composition ratio, viscosity, etc. of the slurry, and a predetermined dispersant is added as needed to manufacture the composition. The positive electrode composition is manufactured in large quantities, but if the manufactured positive electrode composition is defective and does not have the desired physical properties, the physical properties cannot be adjusted by methods such as adding specific components, so the entire amount is discarded.

[0008] In addition, the manufactured anode composition is moved to a pipeline and a coating process is performed to apply and dry the anode composition to a metal foil through a slit die. If the anode composition contains a lot of fine particles or is unevenly distributed, causing the pipeline to become clogged, the manufactured anode composition is completely discarded.

[0009] In addition, if the manufactured positive electrode composition remains after being applied to the metal foil, it is discarded because it gels over time, solids precipitate, and the dispersibility decreases.

[0010] In this way, waste of resources and environmental pollution due to solvent toxicity are becoming a problem due to the anode composition being discarded during the anode composition manufacturing process and coating process.

[0011] Therefore, there is a need to develop a method for safely and environmentally friendly regeneration of positive electrode active materials with improved output performance without discarding metal elements from the waste positive electrode composition, using a low process and cost.

[0012] In order to solve the problems of the prior art as described above, the present invention provides a method for regenerating a positive electrode active material, which comprises a waste positive electrode composition comprising a positive electrode active material, a conductive material, a binder, and a solvent, heat-treating the solvent at a low temperature to remove the solvent, pulverizing the waste positive electrode composition, and then heat-treating the waste positive electrode composition so that the binder and conductive material are cleanly removed and the structure of the fresh positive electrode active material is restored to its original state, has excellent thermal stability, reduces the amount of residual lithium, has excellent initial capacity and lifespan characteristics of a secondary battery, is environmentally friendly because no acid is used in the recovery and regeneration process, and thus neutralization and wastewater treatment are not required, so the process cost is reduced, and the positive electrode active material is regenerated as it is without decomposition, so there are no discarded metal elements, and there is no risk of toxic gases or explosion because no organic solvent is used, and has greatly improved economic efficiency and productivity.

[0013] In addition, the present invention aims to provide a positive electrode active material having excellent thermal stability and reduced lithium residue.

[0014] The above and other objects of the present invention can all be achieved by the present invention described below.

[0015] In order to achieve the above object, I) the present invention provides a method for regenerating a positive electrode active material, characterized by comprising the steps of: (a) heat-treating a waste positive electrode composition including a positive electrode active material, a conductive material, a binder, and a solvent to remove the solvent; (b) pulverizing the waste positive electrode composition from which the solvent has been removed; (c) heat-treating the powdered waste positive electrode composition at 300 to 650°C to remove the binder and the conductive material and recovering the positive electrode active material; (d) adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C; and (e) washing the annealed positive electrode active material with a washing solution.

[0016] II) In the above I), the positive electrode composition may be in the form of a slurry.

[0017] III) In the above I) or II), the heat treatment in step (a) can be performed at 80 to 120°C.

[0018] IV) In the above I) to III), the heat treatment of step (a) can be performed for 30 minutes to 4 hours.

[0019] V) In the above I) to IV), the powderization in step (b) may be by dry grinding.

[0020] VI) In the above I) to V), the dry grinding can be performed using a hand mill, pin mill, disc mill, cutting mill or hammer mill.

[0021] VII) In the above I) to VI), the powdering step (b) may further include a sieving step after powdering.

[0022] VIII) In the above I) to VII), the powder obtained through the step (b) may have an average particle size of 45 μm or less.

[0023] IX) In the above I) to VIII), the positive electrode active material may be at least one selected from the group consisting of a lithium nickel oxide (LNO)-based positive electrode active material, a nickel-cobalt-manganese (NCM)-based positive electrode active material, a nickel-cobalt-aluminum (NCA)-based positive electrode active material, a nickel-cobalt-manganese-aluminum (NCMA)-based positive electrode active material, and a lithium iron phosphate (LFP)-based positive electrode active material.

[0024] X) In the above I) to IX), the solvent may be at least one selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methyl-2-pyrrolidone (NMP), acetone, and water.

[0025] XI) In the above I) to X), the lithium precursor may include at least one of LiOH, Li2CO3, LiNO3, and Li2O.

[0026] XII) In the above I) to XI), the lithium precursor of step (d) can be added in an amount that is at least reduced from the molar ratio of lithium in the positive electrode active material of step (a) based on the amount of lithium in the recovered positive electrode active material.

[0027] XIII) In the above I) to XII), the washing solution may be water or a basic lithium compound aqueous solution.

[0028] XIV) In the above I) to XIII), the method for regenerating the positive electrode active material may further include the step of (f) surface coating the washed positive electrode active material.

[0029] In addition, XV) The present invention is at least one 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, a nickel-cobalt-manganese-aluminum (NCMA)-based cathode active material, and a lithium iron phosphate (LFP)-based cathode active material, and the c-axis length of the crystal structure measured by XRD (X-Ray Diffraction) is 14.200 to 14.210 Å, and the cell volume is 101.65 to 101.75 Å. 3 And a cathode active material is provided, characterized in that the crystal size is 82 to 90 nm and the thermal decomposition temperature measured by TGA (Thermogravimetric analysis) is 700 ℃ or higher.

[0030] XVI) In the above I) to XV), the surface of the positive electrode active material may be coated with a coating agent containing metal or carbon.

[0031] According to the present invention, a waste cathode composition that does not meet the specifications generated in the process of manufacturing the cathode, a waste cathode composition that is clogged in a pipeline during the process of coating the cathode composition on a metal foil, or a waste cathode composition remaining after coating on a current collector is subjected to low-temperature heat treatment to remove the solvent, powdered, and then heat treated, thereby cleanly removing the binder and conductive material in the waste cathode composition through smooth contact with air or oxygen, thereby restoring the structure of a fresh cathode active material to its original state, thereby providing a cathode active material having excellent thermal stability, reduced lithium residue, and excellent capacity characteristics and life characteristics of a secondary battery.

[0032] In addition, it is environmentally friendly because it does not use acid in the recovery and regeneration process of the positive electrode active material, and process costs are reduced because neutralization and wastewater treatment are not required, and there are no discarded metal elements because the positive electrode active material is regenerated as it is without decomposition, and there is no risk of toxic gas generation or explosion because no organic solvent is used, and it has the effect of providing a method for regenerating positive electrode active materials with greatly improved economic feasibility and productivity.

[0033] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description given below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be construed as being limited to the matters described in these drawings.

[0034]

[0035] Figure 1 is a graph showing the initial capacity evaluated using a coin half cell for each of the regenerated positive electrode active materials manufactured in Example 1 and Comparative Example 1.

[0036] Figure 2 is a graph showing the life characteristics evaluated using a coin half cell for each of the regenerated or newly produced positive electrode active materials manufactured in Example 1 and Reference Example.

[0037] Figure 3 is a graph showing the results of TGA (Thermogravimetric analysis) analysis of each of the regenerated positive electrode active materials manufactured in Example 1 and Comparative Example 1.

[0038] FIG. 4 is a flowchart of a process for regenerating a waste cathode composition according to one embodiment of the present invention.

[0039] The present inventors have confirmed that a waste positive electrode composition that does not meet the specifications generated during the positive electrode manufacturing process or a waste positive electrode composition remaining after being applied to a positive electrode current collector is subjected to a low-temperature heat treatment to remove the solvent, powdered, and then heat treated, thereby cleanly removing the binder and conductive agent through smooth contact with air or oxygen, and the positive electrode active material regenerated therefrom is restored to its original state with the structure of a fresh positive electrode active material, has excellent thermal stability, reduces the amount of residual lithium, and further improves the initial capacity and life characteristics of a secondary battery. Based on this, they have devoted themselves to further research and completed the present invention.

[0040]

[0041] Below, the method for regenerating the positive electrode active material of this invention is examined in detail step by step.

[0042] However, the terms or words used in this specification and claims cannot be interpreted as limited to their usual or dictionary meanings, and should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own application in the best way. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only one embodiment of the present invention and do not represent all of the technical idea of ​​the present invention, and it should be understood that there may be various equivalents and modified examples that can replace them, and that they can be arranged, replaced, combined, separated, or designed in various other configurations.

[0043] All technical and scientific terms used in this document, unless otherwise defined, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains.

[0044]

[0045] Method for regenerating positive electrode active material

[0046] The method for regenerating a positive electrode active material of the present invention is characterized by including the steps of (a) heat-treating a waste positive electrode composition comprising a positive electrode active material, a conductive material, a binder, and a solvent to remove the solvent; (b) pulverizing the waste positive electrode composition from which the solvent has been removed; (c) heat-treating the powdered waste positive electrode composition at 300 to 650°C to remove the binder and the conductive material and recovering the positive electrode active material; (d) adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C; and (e) washing the annealed positive electrode active material with a washing solution. In this case, the obtained regenerated positive electrode active material is restored to its original structure of a fresh positive electrode active material, so that it has excellent thermal stability, a reduced lithium residue, excellent initial capacity and life characteristics of a secondary battery, is environmentally friendly, has reduced process costs, does not waste any metal elements, does not generate toxic gases or pose a risk of explosion, and has the effects of greatly improving economic efficiency and productivity.

[0047]

[0048] Below, the method for regenerating the positive electrode active material is explained in detail step by step.

[0049]

[0050] (a) A step of heat treating the anode composition to remove the solvent.

[0051] In the present invention, the method for regenerating a positive electrode active material includes (a) a step of heat-treating a waste positive electrode composition including a positive electrode active material, a conductive material, a binder, and a solvent to remove the solvent, and in this case, there is an advantage in that the subsequent process of powdering the positive electrode composition is easy.

[0052]

[0053] The above-mentioned waste cathode composition may be, for example, a slurry in its form, and specific examples thereof may include a defective slurry whose composition does not meet the specifications, a defective slurry resulting from blockage of a pipeline or the like during a coating process, or a residual slurry remaining after application on a current collector.

[0054]

[0055] The above heat treatment can be performed, for example, in an air or oxygen atmosphere, in which case the solvent can be easily removed, which has the advantage of facilitating the subsequent process of powdering the anode composition.

[0056] The oxygen atmosphere may have a purity of, for example, 59% or more, preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and even more preferably 90 to 99%, and within this range, the solvent can be easily removed, which has the advantage of facilitating the powdering of the positive electrode composition, which is a subsequent process.

[0057] The purity % of the above oxygen may be volume % or mol %.

[0058] The purity of the oxygen of this invention is not particularly limited when measured by a measurement method commonly used in the technical field to which the present invention belongs.

[0059]

[0060] The above heat treatment temperature may be, for example, 80 to 120°C, preferably 85 to 115°C, and more preferably 90 to 110°C, and within this range, the solvent is completely removed, which has the advantage of facilitating powderization of the positive electrode composition, which is a subsequent process.

[0061] The heat treatment time may be, for example, 30 minutes to 4 hours, preferably 1 hour to 3.5 hours, more preferably 1.5 hours to 3 hours, and even more preferably 1.5 hours to 2.5 hours, and within this range, the solvent is completely removed, which has the advantage of facilitating the subsequent process of powdering the positive electrode composition.

[0062]

[0063] The above-described positive electrode active material may be at least one selected from the group consisting of lithium cobalt oxide such as LiCoO2 (hereinafter referred to as 'LCO'); lithium manganese oxide such as LiMnO2 or LiMn2O4; lithium iron phosphate compound such as LiFePO4; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide such as LiNiO2; nickel manganese-based lithium composite metal oxide in which some of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and NCM-based lithium composite transition metal oxide in which some of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co), and more preferably, nickel manganese-based lithium composite metal oxide, NCM-based lithium composite transition metal oxide, or a mixture thereof, in which case, excellent reversible capacity and thermal stability are achieved.

[0064] As another specific example, the positive electrode active material is represented by the following chemical formula 1

[0065] [Chemical Formula 1]

[0066] Li a Ni x Mn y Co z M w O 2+δ

[0067] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물일 수 있다.

[0068]

[0069] The above conductive material may be, for example, a carbon-based conductive material, and preferably, carbon black, CNT, or a mixture thereof.

[0070] The binder may be, for example, a polymer binder, preferably polyvinylidene fluoride (PVdF), acrylonitrile-butadiene rubber (NBR) or a mixture thereof, and more preferably polyvinylidene fluoride.

[0071] The above solvent may be a solvent generally used in the technical field to which the present invention belongs for mixing the positive electrode active material, binder and / or conductive material.

[0072] The solvent may be, for example, at least one selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methyl-2-pyrrolidone (NMP), acetone, and water.

[0073]

[0074] The above-mentioned anode composition may further include, for example, a dispersant.

[0075] The above dispersant is, for example, a cellulose compound, polyalkylene oxide, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetal, polyvinyl ether, polyvinyl sulfonic acid, polyvinyl chloride (PVC), polyvinylidene fluoride, chitosan, starch, amylose, polyacrylamide, poly-N-isopropylacrylamide, poly-N,N-dimethylacrylamide, polyethyleneimine, polyoxyethylene, poly(2-methoxyethoxyethylene), poly(acrylamide-co-diallyldimethylammonium chloride), acrylonitrile-butadiene-styrene (ABS) copolymer, an acrylate-styrene-acrylonitrile (ASA) copolymer, a mixture of an acrylate-styrene-acrylonitrile (ASA) copolymer and propylene carbonate, It may be at least one selected from the group consisting of styrene-acrylonitrile (SAN) copolymers and methyl methacrylate-acrylonitrile-butadiene-styrene (MABS) copolymers.

[0076]

[0077] (b) Step of pulverizing the waste cathode composition from which the solvent has been removed.

[0078] The method for regenerating a positive electrode active material of the present invention includes the step of (b) pulverizing a waste positive electrode composition from which a solvent has been removed, and in this case, in the subsequent heat treatment step, the binder and conductive material in the positive electrode composition are cleanly removed without residue, thereby restoring the positive electrode active material structure to its original state, and has excellent thermal stability and the effect of reducing the amount of residual lithium.

[0079]

[0080] The powderization in the above step (b) literally means making into powder or making it into a powder form, and may be, for example, by dry grinding, in which case there is an advantage of uniform grinding.

[0081] In this description, the dry conditions are not particularly limited as long as they are dry conditions commonly defined in the technical field to which the present invention belongs, and may be, for example, a state in which no solvent is added and / or a dry state and / or a condition in which dry grinding equipment is used.

[0082] The above dry grinding is not particularly limited as long as it is a dry grinding method commonly used in the technical field to which the present invention belongs, and preferably, a hand mill, pin mill, disc mill, cutting mill or hammer mill can be used. In this case, the positive electrode composition from which the solvent has been removed is uniformly ground, and there is an advantage that the powdered positive electrode composition can be directly input to the heat treatment step.

[0083]

[0084] The above (b) powdering step may further include a step of sieving the waste cathode composition after powdering, more preferably a step of sieving through a sieve having a mesh size of 230 to 500, more preferably a sieve having a mesh size of 270 to 450, even more preferably a sieve having a mesh size of 325 to 450, and particularly preferably a sieve having a mesh size of 325. In this case, the particle size of the cathode composition becomes uniform, and large particles are removed, so that there is an advantage of improving the dispersibility when manufacturing a slurry of the regenerated cathode active material.

[0085]

[0086] The powdered waste cathode composition obtained through the above step (b) may have an average particle size of, for example, 45 ㎛ or less, preferably 40 ㎛ or less, more preferably 35 ㎛ or less, and even more preferably 10 to 35 ㎛, and within this range, the particle size of the powdered waste cathode composition becomes uniform, so that there is an advantage in that the binder and conductive material are cleanly removed in a subsequent heat treatment process.

[0087] In the present invention, the average particle size can be measured by a measuring method commonly used in the technical field to which the present invention belongs, and for example, can be measured using a laser diffraction method. Specifically, after dispersing the particles of the positive electrode active material in a dispersion medium, the particles are introduced into a commercially available laser diffraction particle size measuring device such as Microtrac MT 3000, and ultrasonic waves of about 28 kHz are irradiated at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0088]

[0089] (c) a step of recovering a cathode active material from a powdered waste cathode composition;

[0090] The method for regenerating a positive electrode active material of the present invention includes a step of (c) heat-treating a powdered waste positive electrode composition at 300 to 650°C to remove a binder and a conductive agent and recover a positive electrode active material, and preferably includes a step of (c) heat-treating the powdered waste positive electrode composition in an air or oxygen atmosphere at 300 to 650°C to remove a binder and a conductive agent and recover a positive electrode active material. In this case, since the powdered waste positive electrode composition comes into smooth contact with air or oxygen, the binder and the conductive agent are thermally decomposed into CO2 and H2O and are cleanly removed, thereby restoring the structure of a fresh positive electrode active material, and there is an advantage of excellent thermal stability and a reduced lithium residual amount.

[0091]

[0092] The above heat treatment temperature may be preferably 400 to 600°C, more preferably 500 to 600°C, and even more preferably 530 to 580°C, and within this range, the binder and conductive agent are cleanly removed, the structure of the fresh positive electrode active material is restored to its original state, and there is an advantage of excellent thermal stability and a reduced lithium residual amount.

[0093]

[0094] The heat treatment time may be preferably 10 minutes to 5 hours, more preferably 30 minutes to 5 hours, even more preferably 30 minutes to 2 hours, and even more preferably 30 minutes to 1 hour, and within this range, the binder and conductive agent are cleanly removed, the structure of the fresh positive electrode active material is restored to its original state, and there are advantages of excellent thermal stability and reduced lithium residue.

[0095] In this description, the heat treatment time refers to the time spent at the corresponding heat treatment temperature, and the time spent reaching the corresponding heat treatment temperature is not counted.

[0096] The above heat treatment can be performed at a temperature increase rate of, for example, 1 to 20°C / min, preferably 3 to 10°C / min, and more preferably 3 to 7°C / min, and can be performed within this range without causing a strain on the heat treatment equipment, and has the advantage of not causing thermal shock, etc. to the powdered positive electrode composition.

[0097]

[0098] The above-mentioned anode composition may include, for example, a dispersant, and the dispersant is not particularly limited as long as it is a dispersant that is thermally decomposed and removed at the heat treatment temperature.

[0099]

[0100] (d) A step of adding a lithium precursor to the recovered positive electrode active material and annealing it.

[0101] The method for regenerating a positive electrode active material of the present invention includes the step of (d) adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C, in which case a positive electrode active material having excellent initial discharge capacity, output performance, capacity characteristics, and resistance characteristics is provided, and the washing process of the recovered active material is omitted, thereby greatly improving economic efficiency and productivity and minimizing damage to the positive electrode active material.

[0102]

[0103] The above (d) annealing step may preferably be a step of adding a lithium precursor to the recovered positive electrode active material without washing and annealing it at 400 to 1000°C in oxygen (O2) or air. In this case, there is an effect of improving the crystallinity of the positive electrode active material, such as increasing the crystallinity or restoring the crystal structure, thereby improving the battery characteristics of the regenerated positive electrode active material.

[0104]

[0105] The lithium precursor may preferably be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, and Li2O.

[0106] The lithium precursor may be added preferably in an amount that is at least reduced from the molar ratio of lithium in the positive electrode active material of step (a) based on the amount of lithium in the recovered positive electrode active material, and as a specific example, when the recovered positive electrode active material of step (d) is a positive electrode active material represented by the chemical formula 1, the lithium precursor may be added in an amount that provides a molar ratio of lithium of 0.0001 to 0.2 with respect to a molar ratio of lithium of 1 in the positive electrode active material, preferably in an amount that provides a molar ratio of lithium of 0.001 to 0.1, more preferably in an amount that provides a molar ratio of lithium of 0.001 to 0.07, even more preferably in an amount that provides a molar ratio of lithium of 0.001 to 0.03, even more preferably in an amount that provides a molar ratio of lithium of 0.001 to 0.02, particularly preferably in an amount that provides a molar ratio of lithium of 0.005 to 0.17, even more preferably in an amount that provides a molar ratio of lithium of 0.007 to 0.015, and most preferably in an amount that provides a molar ratio of lithium of 0.009 to It can be added in an amount that becomes a molar ratio of 0.013 lithium, and within this range, there is an advantage in that the battery characteristics of the regenerated positive electrode active material are improved by supplementing the lithium that is deficient in the regenerated positive electrode active material and improving the crystallinity, such as increasing crystallinity or restoring the crystal structure.

[0107] As another example, the lithium precursor may be added in an amount corresponding to 1 to 25 mol% when the total lithium contained in the raw material positive electrode active material is 100 mol%, more preferably, may be added in an amount corresponding to 1 to 20 mol%, and even more preferably, may be added in an amount corresponding to 3 to 17 mol%, and within this range, no residual precursor that may increase the resistance of the regenerated positive electrode active material remains, which is very useful for improving battery characteristics, and there is an economic advantage in that the crystal structure can be restored with a smaller amount of lithium precursor than before.

[0108] As another example, when the raw material positive electrode active material is a lithium iron phosphate compound, the lithium precursor may be added in an amount corresponding to 0 to 25 mol%, more preferably 0.1 to 20 mol%, and even more preferably 1 to 17 mol%, when the total lithium contained in the raw material positive electrode active material is 100 mol%, and within this range, no residual precursor that may increase the resistance of the regenerated positive electrode active material remains, which is very useful for improving battery characteristics, and the crystal structure can be restored with a smaller amount of lithium precursor than before, which has an economic advantage.

[0109]

[0110] The above annealing temperature can be controlled within a limited range depending on the melting point of the lithium precursor. For example, in the case of LiCO3, the melting point is 723°C, so annealing can be performed at preferably 700 to 900°C, more preferably 710 to 780°C, and in the case of LiOH, the melting point is 462°C, so annealing can be performed at preferably 400 to 750°C, more preferably 400 to 720°C, even more preferably 450 to 700°C, and even more preferably 550 to 670°C. Within this range, the crystal structure is recovered, so that the output performance of the battery is excellent.

[0111] The above annealing temperature may preferably be a temperature exceeding the melting point of the lithium precursor, but if it exceeds 1000°C, thermal decomposition of the positive electrode active material may occur, resulting in a decrease in battery performance, so it may preferably be 1000°C or lower.

[0112]

[0113] The above annealing temperature can be reached at a heating rate of preferably 1 to 10°C / min, more preferably 1 to 5°C / min, and even more preferably 2 to 4°C / min, in which case the crystallinity of the regenerated positive electrode active material is further increased, thereby having the effect of improving the battery characteristics of the regenerated positive electrode active material.

[0114] The above annealing step includes, for example, a cooling process, and the cooling process may be, for example, natural cooling in a furnace, in which case the crystallinity of the regenerated positive electrode active material is further increased, thereby having the effect of improving the battery characteristics of the regenerated positive electrode active material.

[0115]

[0116] In this description, annealing may follow the definition used in the technical field to which the present invention belongs, and as a specific example, it may be defined as a heat treatment operation to cure deformation or lattice defects and increase crystallinity by heating a positive electrode active material having a deformed structure or lattice defects at a temperature above the recrystallization temperature, at which atoms of the main component can sufficiently diffuse and move, for an appropriate period of time.

[0117]

[0118] The positive electrode active material obtained after the step (d) above may have a LiOH remaining on the surface of, for example, 0.90 wt% or less, preferably 0.85 wt% or less, more preferably 0.001 to 0.85 wt%, and even more preferably 0.01 to 0.85 wt%, and within this range, a positive electrode active material having excellent initial capacity and lifespan characteristics is provided.

[0119] The positive electrode active material obtained after the step (d) above may have Li2CO3 remaining on the surface of, for example, 0.7 wt% or less, preferably 0.6 wt% or less, more preferably 0.001 to 0.6 wt%, and even more preferably 0.01 to 0.6 wt%, and within this range, a positive electrode active material having excellent initial capacity and lifespan characteristics is provided.

[0120] The positive electrode active material obtained after the step (d) above may have a total amount of LiOH and Li2CO3 remaining on the surface of, for example, 1.6 wt% or less, preferably 1.4 wt% or less, more preferably 0.001 to 1.4 wt%, and even more preferably 0.01 to 1.4 wt%, and within this range, a positive electrode active material having excellent initial capacity and lifespan characteristics is provided.

[0121] In the present invention, the contents of LiOH and Li2CO3 remaining on the surface of the positive electrode active material can be measured using a measuring method commonly used in the technical field to which the present invention pertains. For example, 5 g of the positive electrode active material is dispersed in 100 ml of distilled water, mixed at 300 rpm for 5 minutes, filtered to remove the positive electrode active material, and the resulting solution is titrated with a 0.1 M HCl solution while measuring the change in pH value to obtain a pH titration curve. The obtained pH titration curve can be used to calculate the amounts of LiOH remaining and Li2CO3 remaining in the positive electrode active material.

[0122] The positive electrode active material obtained after the above step (d) may have a residual fluorine (F) content of, for example, 4000 to 9000 mg / kg, preferably 5000 to 8000 mg / kg, and more preferably 6000 to 7000 mg / kg, and within this range, the conductive material and binder are sufficiently pyrolyzed and cleanly removed, so that the positive electrode active material has excellent initial capacity and life characteristics.

[0123] In this description, the residual fluorine (F) content can be measured using a measurement method commonly used in the technical field to which the present invention belongs, and specifically, can be measured using an ICP analyzer.

[0124]

[0125] (e) A step of washing the annealed positive electrode active material with a washing solution.

[0126] The method for regenerating a positive electrode active material of the present invention includes (e) a step of washing the annealed positive electrode active material with a washing solution, in which case, there is an advantage in that the battery characteristics are improved by removing lithium compounds that do not participate in the reaction after addition of a lithium precursor and remain on the surface of the positive electrode active material.

[0127]

[0128] The above washing may preferably include a step of mixing the annealed positive electrode active material and the washing solution, followed by a step of filtering, and a step of drying the positive electrode active material in the solid content obtained after the filtering. In this case, there is an effect of effectively removing excess lithium that is likely to remain in the positive electrode active material.

[0129] The above drying may be preferably performed at 100 to 500°C, more preferably at 120 to 400°C, even more preferably at 120 to 300°C, and even more preferably at 120 to 200°C, and has the advantage that residual Li is effectively removed within this range.

[0130] The above drying may preferably be vacuum drying.

[0131] In this description, vacuum drying is not particularly limited to vacuum drying commonly performed in the technical field to which the present invention belongs.

[0132]

[0133] The above washing may preferably include a step of mixing an annealed positive electrode active material and a washing solution in a weight ratio of 1:3 to 1:20, more preferably a weight ratio of 1:5 to 1:15, and even more preferably a weight ratio of 1:7 to 1:12, followed by a step of filtering and a step of drying the positive electrode active material in a solid content obtained after the filtering. In this case, there is an effect of effectively removing lithium precursors such as LiOH, Li2CO3, etc.

[0134]

[0135] The above-mentioned cleaning solution may be, for example, water or an aqueous alkaline lithium compound solution, and preferably may be water. In this case, lithium precursors such as LiOH, Li2CO3, etc., which are likely to remain on the surface of the positive electrode active material, are cleanly removed with a small amount of the cleaning solution, thereby significantly improving the output performance of the battery without requiring wastewater treatment.

[0136] The water is more preferably distilled water or deionized water, and in this case, lithium precursors such as LiOH and Li2CO3, which are likely to remain on the surface of the positive electrode active material, are cleanly removed with a small amount of washing liquid, thereby significantly improving the output performance of the battery without requiring wastewater treatment.

[0137] The above basic lithium compound aqueous solution may preferably contain more than 0 wt% and less than 15 wt% of a lithium compound, more preferably more than 0 wt% and less than 10 wt%, or 0.1 to 10 wt% of a lithium compound, and in this case, lithium precursors such as LiOH and Li2CO3, which are likely to remain on the surface of the positive electrode active material, are cleanly removed with a small amount of a washing solution, thereby significantly improving the output performance of the battery without requiring wastewater treatment.

[0138]

[0139] The mixing of the annealed positive electrode active material and the cleaning solution is preferably performed by stirring, and the stirring is not particularly limited, but may be mechanical stirring or ultrasonic stirring.

[0140] The above stirring can be preferably performed for less than 30 minutes, more preferably less than 20 minutes, even more preferably less than 15 minutes, and even more preferably 5 to 10 minutes, and has the advantage that residual lithium is effectively removed within this range.

[0141] The above stirring can be performed, for example, at 200 to 1000 rpm, preferably 300 to 800 rpm, and more preferably 400 to 700 rpm, and has the advantage that residual lithium is effectively removed within this range.

[0142] The above filtration can be performed, for example, by using a filter under reduced pressure or a filter press.

[0143]

[0144] (f) A step of obtaining a reusable positive electrode active material by surface-coating the washed positive electrode active material.

[0145] The method for regenerating a positive electrode active material of the present invention preferably includes a step (f) of surface-coating a washed positive electrode active material to obtain a reusable positive electrode active material, in which case the properties of the positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0146]

[0147] The surface coating is preferably performed by coating a coating agent containing at least one of a metal, an organic metal, and a carbon component on the surface in a solid or liquid manner and then heat-treating at 100 to 1200°C, more preferably 200 to 1000°C, and even more preferably 250 to 800°C. In this case, the properties of the positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0148]

[0149] The coating agent containing the above metal is preferably a coating agent containing at least one selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V and Y, more preferably a coating agent containing at least one selected from the group consisting of B, W, Al, Ti and Mg, and even more preferably a coating agent containing boron (B), tungsten (W) or a mixture thereof, and even more preferably a coating agent containing tungsten (W) and boron (B), and a specific example is a coating agent containing tungsten boride (WB), in which case there is an effect of improving resistance characteristics and life characteristics.

[0150] The coating agent containing the metal may be, for example, an oxide or acid containing the metal as an element within the molecule.

[0151] The coating agent containing the above-mentioned organic metal is not particularly limited as long as it is a coating agent containing an organic metal compound commonly used in the technical field to which the present invention belongs and containing the above-mentioned metal, and a specific example thereof may be a metal alkoxide, etc.

[0152] The coating agent containing the above carbon component is not particularly limited as long as it is a coating agent containing a carbon component commonly used in the technical field to which the present invention belongs, and a specific example thereof may be a sugar such as sucrose.

[0153]

[0154] The coating agent may be included in an amount of 0.001 to 0.3 mol%, for example, based on the components coated on the surface of the actual positive electrode active material excluding the solvent, relative to 100 mol% of the metal in the positive electrode active material before the coating treatment, preferably 0.01 to 0.3 mol%, more preferably 0.01 to 0.15 mol%, even more preferably 0.01 to 0.1 mol%, and even more preferably 0.01 to 0.05 mol%, and within this range, there is an effect of improving structural stability and electrochemical performance while maintaining the properties of the positive electrode active material itself.

[0155]

[0156] The heat treatment time is preferably 1 to 16 hours, more preferably 3 to 7 hours, and within this range, the properties of the positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0157]

[0158] The above coating method is not particularly limited as long as it is a coating method commonly used in the technical field to which the present invention belongs, and may be, for example, a liquid method in which a liquid coating agent is prepared and mixed with a positive electrode active material, a mechanochemical method using the high mechanical energy of ball milling, a fluidized bed coating method, a spray drying method, a precipitation method in which a coating agent is precipitated onto the surface of a positive electrode active material in an aqueous solution state, a method utilizing a reaction between a gaseous coating agent and a positive electrode active material, or a sputtering method.

[0159]

[0160] The above metal, organic metal, and carbon component may be, for example, spherical, plate-shaped, square, or needle-shaped, and such shapes can be controlled by changing process conditions, etc. during the manufacturing process, and the definition of each shape is not particularly limited as long as it follows the definition commonly recognized in the technical field to which the present invention belongs.

[0161]

[0162] The above coating agent preferably has an average diameter of 1 to 1000 nm and a specific surface area of ​​10 to 100 m 2 / g, and more preferably, the average diameter is 10 to 100 nm, and the specific surface area is 20 to 100 m 2 / g, and within this range, it can be uniformly attached to the surface of the positive electrode active material, thereby imparting structural stability to the positive electrode active material, thereby improving the problems of deterioration of life characteristics and electrochemical performance due to lattice deformation or collapse of crystal structure of the positive electrode active material.

[0163] In the present invention, the average diameter can be measured by a measuring method commonly used in the technical field to which the present invention belongs, and for example, can be measured using a laser diffraction method. Specifically, after dispersing the particles of the positive electrode active material in a dispersion medium, the particles are introduced into a commercially available laser diffraction particle size measuring device such as Microtrac MT 3000, and ultrasonic waves of about 28 kHz are irradiated at an output of 60 W, and the average particle diameter (D50) based on 50% of the particle diameter distribution in the measuring device can be calculated.

[0164] In this description, the specific surface area can be measured by a measurement method commonly used in the technical field to which the present invention belongs, for example, by the BET (Brunauer-Emmett-Teller) method, and specifically, can be calculated from the nitrogen gas adsorption amount under liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan.

[0165]

[0166] The a-axis length of the crystal structure of the regenerated positive electrode active material obtained in the above step (f) as measured by XRD may be, for example, 2.871 to 2.888 Å, preferably 2.872 to 2.878 Å, more preferably 2.874 to 2.876 Å, and there is an effect of improving battery characteristics within this range.

[0167] The c-axis length of the crystal structure of the regenerated positive electrode active material obtained in the above step (f) as measured by XRD may be, for example, 14.200 to 14.210 Å, preferably 14.202 to 14.208 Å, more preferably 14.204 to 14.208 Å, and there is an effect of improving battery characteristics within this range.

[0168] The regenerated positive electrode active material obtained in the above step (f) has a cell volume measured by XRD of, for example, 101.65 to 101.75 Å. 3, preferably 101.67 to 101.72 Å 3 , more preferably 101.68 to 101.71 Å 3 It can be done, and within this range, there is an effect of improving battery characteristics.

[0169] The regenerated positive electrode active material obtained in the above step (f) may have a crystal size measured by XRD of, for example, 82 to 90 nm, preferably 84 to 88 nm, and has the effect of improving battery characteristics within this range.

[0170] In the present invention, the a-axis length and c-axis length, cell volume, and crystal size of the crystal structure measured by XRD can be measured by a measurement method commonly used in the technical field to which the present invention belongs, and for example, the data obtained through X-ray diffraction analysis using CuKα rays as a source for a positive electrode active material can be calculated using the Rietveld refinement method to measure the a-axis length and c-axis length of the crystal structure and the cell volume, and the crystallite size can be estimated using the peak broadening of X-ray diffraction data obtained by X-ray diffraction analysis (XRD) and quantitatively calculated using the Scherrer Equation to obtain the crystal size.

[0171] The regenerated positive electrode active material obtained in the above step (f) may have a thermal decomposition temperature measured by TGA (Thermogravimetric analysis) of, for example, 700°C or higher, preferably 720°C or higher, and more preferably 730 to 800°C, and within this range, has excellent thermal stability, thereby improving battery characteristics.

[0172]

[0173] Regenerated cathode active material

[0174] The regenerated positive electrode active material of the present invention is characterized by being manufactured by the regenerated positive electrode active material method described above, and in this case, the output performance of the battery is improved, and the electrochemical performance, resistance characteristics, and capacity characteristics are excellent.

[0175]

[0176] In addition, the regenerative cathode active material of the present invention is at least one 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, a nickel-cobalt-manganese-aluminum (NCMA)-based cathode active material, and a lithium iron phosphate (LFP)-based cathode active material, and the c-axis length of the crystal structure measured by XRD (X-Ray Diffraction) is 14.200 to 14.210 Å, and the cell volume is 101.65 to 101.75 Å. 3 And the crystallite size is 82 to 90 nm, and the thermal decomposition temperature measured by TGA (Thermogravimetric analysis) is 700 ℃ or higher. In this case, the thermal stability is excellent, the lithium residue is reduced, and the initial capacity and life characteristics of the secondary battery are excellent.

[0177]

[0178] As another specific example, the above regenerative positive electrode active material is represented by the following chemical formula 1

[0179] [Chemical Formula 1]

[0180] Li a Ni x Mn y Co z M w O 2+δ

[0181] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)로 표시되는 화합물일 수 있고, 이 경우 열적 안정성이 우수하고 리튬 잔류량이 감소하며, 이차 전지의 초기 용량 및 수명 특성이 뛰어난 효과가 있다.

[0182]

[0183] The a-axis length of the crystal structure of the above-mentioned regenerated positive electrode active material measured by XRD may be, for example, 2.871 to 2.888 Å, preferably 2.872 to 2.878 Å, more preferably 2.874 to 2.876 Å, and there is an effect of improving battery characteristics within this range.

[0184] The c-axis length of the crystal structure of the above-mentioned regenerated positive electrode active material measured by XRD may be, for example, 14.200 to 14.210 Å, preferably 14.202 to 14.208 Å, more preferably 14.204 to 14.208 Å, and there is an effect of improving battery characteristics within this range.

[0185] The above-mentioned regenerated cathode active material has a cell volume measured by XRD of, for example, 101.65 to 101.75 Å. 3 , preferably 101.67 to 101.72 Å 3 , more preferably 101.68 to 101.71 Å 3 It can be done, and within this range, there is an effect of improving battery characteristics.

[0186] The above-mentioned regenerative positive electrode active material may have a crystal size measured by XRD of, for example, 82 to 90 nm, preferably 84 to 88 nm, and has the effect of improving battery characteristics within this range.

[0187] The above-mentioned regenerated positive electrode active material may have a thermal decomposition temperature measured by TGA (Thermogravimetric analysis) of, for example, 700°C or higher, preferably 720°C or higher, and more preferably 730 to 800°C, and within this range, has excellent thermal stability, thereby improving battery characteristics.

[0188]

[0189] The above-mentioned regenerative positive electrode active material may have a surface coated with, for example, metal or carbon, and is preferably coated with metal. In this case, the structural stability of the positive electrode active material is improved without chemical and physical changes in the positive electrode active material itself, thereby improving electrochemical properties such as output performance, life characteristics, and capacity. In addition, the physicochemical properties are also improved due to the effect of reducing the amount of residual lithium and reducing pH by substituting a different element on the surface of the positive electrode active material.

[0190]

[0191] The metal is preferably at least one selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V and Y, more preferably at least one selected from the group consisting of B, W, Al, Ti and Mg, even more preferably boron (B), tungsten (W) or a mixture thereof, even more preferably tungsten (W) and boron (B), and a specific example is tungsten boride (WB), in which case there is an effect of improving resistance characteristics and life characteristics.

[0192]

[0193] The coating agent may be included, for example, in an amount of 0.001 to 0.3 mol% relative to 1 mol% of metal in the positive electrode active material before coating treatment, preferably 0.01 to 0.3 mol%, more preferably 0.01 to 0.15 mol%, even more preferably 0.01 to 0.1 mol%, and even more preferably 0.01 to 0.05 mol%, and within this range, it has the effect of improving structural stability and electrochemical performance while maintaining the properties of the positive electrode active material itself.

[0194]

[0195] The surface coating is preferably performed by coating a coating agent containing at least one of a metal, an organic metal, and a carbon component on the surface in a solid or liquid manner and then heat-treating at 100 to 1200°C, more preferably 200 to 1000°C, and even more preferably 250 to 800°C. In this case, the properties of the positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0196]

[0197] The following Figure 4 is a flowchart for a regeneration process of a positive electrode active material according to one embodiment of the present invention.

[0198] Referring to Fig. 4, first, a lung anode composition is prepared (step S10).

[0199] The above-mentioned waste anode composition is a defective anode composition slurry that is below the standard in terms of solid content concentration, composition ratio, viscosity, etc. generated during the process of manufacturing the anode composition, a cathode composition slurry that has problems such as filter clogging during the process of applying the composition to the metal foil, or a cathode composition slurry remaining after applying the composition to the metal foil.

[0200] The above-mentioned positive electrode composition may include a positive electrode active material, a conductive material, and a binder, and may be in the form of a slurry.

[0201] The above-mentioned anode composition may further include a dispersant.

[0202]

[0203] Next, the anode composition is heat treated to remove the solvent (step S20).

[0204] Here, heat treatment is performed to facilitate the subsequent process of powderization by drying and removing the solvent in the waste cathode composition.

[0205] The above heat treatment can be carried out in an air or oxygen atmosphere, and as a specific example, it can be carried out in an air atmosphere, in which case there is an advantage in that the subsequent process of powderization is easy by removing the solvent.

[0206] The above heat treatment temperature may be, for example, 80 to 120°C, and as a specific example, 100°C, and within this range, all solvents are removed, so there is an advantage in that the subsequent process of powderization is easy.

[0207] The above heat treatment time may be, for example, 30 minutes to 4 hours, and as a specific example, may be 2 hours, and within this range, the solvent is completely dried and removed, so there is an advantage in that the subsequent process of powderization is easy.

[0208] The above heat treatment is performed using various types of furnaces, for example, a box-type furnace, and considering productivity, it is preferable to perform the heat treatment using a rotary kiln capable of continuous treatment.

[0209]

[0210] Next, the waste cathode composition from which the solvent has been removed is powdered (step S30).

[0211] Here, powderization is performed to ensure smooth contact between the waste cathode composition and air or oxygen during the subsequent heat treatment step.

[0212] The above powderization is by dry grinding, and a hand mill, pin mill, disc mill, cutting mill or hammer mill can be used, and a pin mill is a specific example.

[0213] The above powdered waste cathode composition can be sieved, preferably through a sieve having a mesh size of 230 to 500, and specifically, through a sieve having a mesh size of 325. As described above, through sieving, the particle size of the cathode composition becomes uniform, and large particles are removed, so that the dispersion is improved when the regenerated cathode active material is manufactured into a slurry.

[0214] The above powdered waste cathode composition may preferably have an average particle size of 45 ㎛ or less, specifically 10 to 35 ㎛, and in this case, there is an advantage in that the binder and conductive material are cleanly removed in a subsequent heat treatment process.

[0215]

[0216] Next, the powdered waste cathode composition is heat treated (step S40).

[0217] Here, heat treatment is performed to thermally decompose the binder and conductive material in the powdered waste cathode composition.

[0218] The above powdered waste cathode composition is heat treated at 300 to 650°C to remove the binder and conductive material and recover the cathode active material.

[0219] The heat treatment of step S40 is carried out in an air or oxygen atmosphere, and as a specific example, is carried out in air.

[0220] Through the above-described heat treatment in air, the binder and conductive agent within the positive electrode active material layer are thermally decomposed into CO2 and H2O and removed. Since the conductive agent and binder are removed, a positive electrode active material is obtained from the positive electrode composition.

[0221] It is important to perform the above heat treatment in air or in the presence of oxygen. If heat treatment is performed in a reducing or inert gas atmosphere, the binder and conductive agent will carbonize rather than undergo thermal decomposition. Carbonization will leave carbon components on the surface of the positive electrode active material, degrading the performance of the reusable positive electrode active material. However, if heat treatment is performed in air, the carbon components in the binder and conductive agent react with oxygen and disappear into gases such as CO and CO2, thus removing both the binder and conductive agent.

[0222] The above heat treatment is preferably performed at 300 to 650°C, and as a specific example, at 550°C. Below 300°C, it is difficult to remove the binder, and above 650°C, cation mixing occurs due to a change in the structure of the positive electrode active material.

[0223] In this paper, cation mixing means that lithium, which has a high vapor pressure, evaporates more easily than other elements when heat-treated at high temperatures, and Ni is formed in the empty lithium ion layer. 2+ It refers to an irreversible reaction in which .

[0224] The above heat treatment is preferably performed at a temperature increase rate of 1 to 20°C / min, more preferably at a temperature increase rate of 3 to 10°C / min, and a specific example is 5°C / min. Within this range, the heat treatment can be performed without causing a strain on the heat treatment equipment, and has the advantage of not causing thermal shock to the anode composition.

[0225] The above heat treatment can be performed for a period of time sufficient to allow the binder and the conductive material to be sufficiently thermally decomposed, for example, preferably 30 minutes or more, more preferably 30 minutes to 5 hours, and a specific example is about 30 minutes. Within this period, the binder and the conductive material are sufficiently thermally decomposed, and the thermal decomposition efficiency is excellent.

[0226] 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 treatment.

[0227] After the above heat treatment, it can be cooled slowly or rapidly in the air.

[0228]

[0229] Next, a lithium precursor is added to the recovered positive electrode active material and annealed (step S50).

[0230] Since lithium loss occurs in the positive electrode active material during the preceding steps S30 and S40, such lithium loss is supplemented in step S50. In addition, since a deformation structure (e.g., Co3O4 in the case of LCO active material) may appear on the surface of the positive electrode active material during the preceding steps, in step S50, the crystal structure of the positive electrode active material is restored through annealing to improve the battery characteristics of the regenerated positive electrode active material or restore it to the level of a newly formed positive electrode active material. Here, ‘newly formed’ is a concept opposite to ‘regenerated’, meaning something that is created for the first time, and is the same as the ‘raw material’ used in the examples. In addition, the positive electrode active material contains calcium or a calcium compound, thereby improving the life characteristics and resistance characteristics of the regenerated positive electrode active material.

[0231] The lithium precursor includes at least one of LiOH, Li2CO3, LiNO3, and Li2O, and in one embodiment, LiOH is used.

[0232] It is preferable that the lithium precursor be added in an amount at least equal to the molar ratio of lithium lost compared to the molar ratio of lithium and other metals in the newly formed positive electrode active material used in the positive electrode active material layer. Adding an excessive amount of lithium precursor compared to the amount of lithium lost will leave unreacted lithium precursor in the regenerated positive electrode active material, which will increase resistance, and therefore, an appropriate amount of lithium precursor must be added.

[0233] In one embodiment, when the molar ratio of lithium in the new positive electrode active material is 1 with respect to the other metal (M), the lithium precursor may be added in an amount such that the molar ratio of lithium is 0.001 to 0.4, preferably in an amount such that the molar ratio of lithium is 0.01 to 0.4, and more preferably in an amount such that the molar ratio of lithium is 0.09 to 0.2. As a specific example, when the lithium precursor is added in an amount equivalent to the loss ratio of lithium content in the new positive electrode active material based on the ICP analysis results, the capacity improvement effect is shown to be equivalent to that of the new positive electrode active material. Here, the ICP analysis results have an error value of approximately ±0.02.

[0234]

[0235] In one embodiment, the lithium precursor may be added in an amount corresponding to 1 to 25 mol%, more preferably 1 to 20 mol%, and even more preferably 3 to 17 mol%, when the total amount of lithium contained in the raw material cathode active material is 100 mol%, and within this range, no residual precursor that can increase the resistance of the regenerated cathode active material remains, which is very useful for improving battery characteristics.

[0236] The above annealing is performed in air under conditions of, for example, 400 to 1000°C, preferably 600 to 900°C, and this temperature should be adjusted within a limited range depending on the type of lithium precursor.

[0237] The above annealing temperature is preferably a temperature exceeding the melting point of the lithium precursor. However, at a temperature exceeding 1000°C, thermal decomposition of the positive electrode active material occurs, resulting in a decrease in performance, so the temperature should not exceed 1000°C. Accordingly, when Li2CO3 is used as the lithium precursor, the annealing temperature is preferably 700 to 900°C, more preferably 710 to 780°C, and even more preferably 750 to 780°C. In addition, when LiOH is used as the lithium precursor, the annealing temperature is preferably 400 to 600°C, more preferably 450 to 480°C, and even more preferably 470 to 480°C.

[0238] The above annealing time is preferably 1 hour or longer, preferably 15 hours or shorter, and more preferably 4 to 6 hours. A longer annealing time allows sufficient crystal structure recovery, but even long-term annealing does not significantly affect performance. The annealing equipment used in this process may be identical or similar to that used in the heat treatment step S40.

[0239] The above annealing temperature can preferably be reached at a heating rate of 1 to 10°C / min, and as a specific example, can be reached at a heating rate of 2 to 4°C / min, in which case the crystallinity of the regenerated positive electrode active material is further increased, thereby having the effect of improving the battery characteristics of the regenerated positive electrode active material.

[0240] The annealing of step S50 includes, for example, a cooling process, and the cooling process may be, for example, natural cooling in a furnace, in which case the crystallinity of the regenerated positive electrode active material is further increased, thereby having the effect of improving the battery characteristics of the regenerated positive electrode active material.

[0241]

[0242] Next, as a washing step, the annealed positive electrode active material is washed with a washing solution (step S60).

[0243] The washing step S60 requires a residual lithium removal process to remove the lithium precursor that did not participate in the reaction in the annealing step S50, which exists on the surface of the positive electrode active material in the form of LiOH and Li2CO3. These impurities in the form of LiOH and Li2CO3 must be thoroughly removed, as they can later react with the electrolyte to degrade battery performance and generate gases.

[0244] The above washing is preferably performed by mixing the annealed positive electrode active material and the washing solution in a weight ratio of 1:3 to 1:20, and a specific example is mixing the annealed positive electrode active material and the washing solution in a weight ratio of 1:10. In this case, residual lithium is removed with a small amount of the washing solution, so there is an advantage in that a positive electrode active material having excellent initial discharge capacity and life characteristics can be obtained.

[0245] The above-mentioned cleaning solution may be, for example, water or an aqueous solution of a basic lithium compound, preferably water, and in this case, it has the effect of significantly improving the output performance of the battery by cleanly removing lithium precursors such as LiOH and Li2CO3 that are likely to remain on the surface of the positive electrode active material.

[0246] The above washing is preferably performed by mixing the annealed positive electrode active material and the washing solution, filtering the mixture, and then drying the obtained solid positive electrode active material.

[0247] The mixing of the annealed positive electrode active material and the cleaning solution is preferably performed by stirring, and the stirring is not particularly limited, but may be mechanical stirring or ultrasonic stirring.

[0248] The above mechanical stirring is preferably performed at 100 to 1000 rpm and for 5 to 30 minutes, more preferably at 250 to 350 rpm and for 5 to 10 minutes.

[0249] The above filtration is preferably vacuum filtration using a filter, and the above drying is preferably vacuum drying at 50 to 140°C.

[0250]

[0251] Next, surface coating can be performed on the washed positive electrode active material (step S70).

[0252] The above surface coating is, for example, a method of coating a surface with a coating agent containing a metal, organic metal, or carbon component in a solid or liquid manner and then heat-treating it. If the heat-treatment temperature is too low, a surface protective layer by the desired heterogeneous metal is not formed, and if the heat-treatment temperature is too high, the performance of the battery deteriorates due to thermal decomposition of the positive electrode active material.

[0253] Specifically, when a metal oxide or acid such as B, W, or BW is coated on an annealed cathode active material and then heat-treated, a surface protective layer such as a lithium boron oxide layer is formed on the surface of the cathode active material.

[0254] The solid or liquid method of the above surface coating may be, for example, mixing, milling, spray drying or grinding.

[0255]

[0256] secondary battery

[0257] The secondary battery of the present invention includes a regenerated positive electrode active material manufactured by the method for regenerating the positive electrode active material, and in this case, the thermal stability is excellent, the rate performance of the secondary battery is greatly improved, and the electrochemical performance, resistance characteristics, and capacity characteristics are excellent.

[0258] The secondary battery of the present invention may include all of the contents of the positive electrode active material and the regeneration method thereof described above. Therefore, redundant description thereof is omitted herein.

[0259] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0260]

[0261] [Example]

[0262] Example 1

[0263] An attempt was made to prepare a positive electrode composition slurry having a composition ratio of positive electrode active material:conductive material:binder of 97.5:1.5:1, but the prepared positive electrode composition slurry did not have a composition ratio of positive electrode active material:conductive material:binder of 98.5:1:0.5, so a discarded positive electrode composition was prepared.

[0264] At this time, the spent positive electrode composition contained an NCMA-based lithium composite transition metal oxide as a positive electrode active material (the molar % ratio of Ni:Co:Mn:Al was 88:7:4:1), polyvinylidene fluoride (PVDF) as a binder, Super-C as a conductive material, and N-methyl-2-pyrrolidone as a solvent (positive electrode active material:conductive material:binder = 98.5:1:0.5). The spent positive electrode composition was heat-treated in air at 100°C for 2 hours to dry and remove the solvent.

[0265] The waste cathode composition from which the solvent was removed was dry-ground with a pin mill and then sieved through a sieve with a mesh size of 325 to obtain a waste cathode composition powder having an average particle size of 35 μm or less.

[0266] The above-mentioned waste cathode composition powder was heat-treated in air at 550°C for 30 minutes to remove the binder and conductive agent, thereby recovering the cathode active material. Here, the temperature increase rate until the heat treatment temperature was reached was 5°C / min, and air was supplied at 3 L / min.

[0267] The recovered positive electrode active material was annealed in air at 650°C for 5 hours without a washing process, with LiOH added as a lithium precursor. At this time, the lithium precursor was added in an amount corresponding to 15 mol% when the total lithium in the raw positive electrode active material used in the positive electrode composition is 100 mol%.

[0268] The above annealed positive electrode active material and distilled water were mixed at a weight ratio of 1:10, stirred at 300 rpm for 5 minutes, and then filtered under reduced pressure to obtain a solid. The solid was vacuum-dried at 100 to 130°C for 12 hours to obtain a washed positive electrode active material. Here, air was supplied at a rate of 3 L / min.

[0269] The above-mentioned washed positive electrode active material was coated with boric acid and then heated at 300°C for 5 hours to produce a final regenerated positive electrode active material. Here, the temperature increase rate until reaching the heat treatment temperature was 2°C / min, and air was supplied at 3 L / min.

[0270] In this paper, the molar ratio of lithium to other metals in the positive electrode active material was measured using an ICP analyzer. While this can be measured using a standard ICP analyzer commonly used in laboratories, there is no variation depending on the measuring device or method.

[0271]

[0272] Comparative Example 1

[0273] The same procedure as in Example 1 was followed, except that the solvent-removed waste cathode composition was heat-treated in air at 550°C for 30 minutes without going through the dry grinding and sieving steps to powderize it.

[0274]

[0275] Reference example

[0276] Fresh NCMA-based lithium composite transition metal oxides (mol% ratio of Ni:Co:Mn:Al of 88:7:4:1) rather than recycled active materials were used.

[0277]

[0278] [Test Example I: Residual Lithium Content]

[0279] The residual lithium content of the positive electrode active material annealed in Example 1 and Comparative Example 1 was measured as follows, and the results are shown in Table 1 below.

[0280] * Residual lithium content: 5 g of the annealed positive electrode active material was dispersed in 100 ml of distilled water, mixed at 300 rpm for 5 minutes, filtered to remove the positive electrode active material, and the resulting solution was titrated with 0.1 M HCl solution, and the change in pH value was measured to obtain a pH titration curve. The obtained pH titration curve was used to calculate the residual LiOH and residual Li2CO3 in the positive electrode active material.

[0281]

[0282] Classification LiOH (wt%) Li2CO3 (wt%) Total (wt%) Example 10.8240.5581.382 Comparative Example 10.4514.0214.472

[0283] As can be seen in Table 1 above, Example 1, which powdered the positive electrode composition from which the solvent was removed according to the present invention and then subjected to heat treatment, showed a significantly reduced residual lithium content compared to Comparative Example 1, which was subjected to heat treatment without going through the powdering step.

[0284] [Test Example II: Residual Fluorine (F) Content]

[0285] The fluorine (F) content remaining in the annealed positive electrode active material in Example 1 and Comparative Example 1 was measured using an ICP analyzer, and the results are shown in Table 2 below. At this time, the measurement can be performed using a general ICP analyzer widely used in laboratories, but there is no deviation depending on the measuring device or method.

[0286]

[0287] Classification F (mg / kg) Example 16820 Comparative Example 12330

[0288] As can be seen in Table 2 above, Example 1, which was performed by powdering the solvent-removed cathode composition according to the present invention and then heat-treating, had a higher residual fluorine content than Comparative Example 1. From this, it was found that the conductive agent and binder in Example 1 were sufficiently thermally decomposed and cleanly removed compared to Comparative Example 1. When the conductive agent and binder in the cathode composition are thermally decomposed, they exist on the surface of the cathode active material in the form of LiF. In Example 1, which was powdered and then heat-treated, the cathode composition smoothly came into contact with the air, so that the conductive agent and binder were thermally decomposed without residue, and thus the residual fluorine content was high. In Comparative Example 1, since the powdering step was not performed, the cathode composition did not smoothly come into contact with the air, so the thermal decomposition of the conductive agent and binder did not occur sufficiently, resulting in less residual fluorine.

[0289] [Experimental Example III: XRD Analysis]

[0290] The regenerated positive electrode active material or the new positive electrode active material manufactured in Example 1 and Reference Example were each analyzed by XRD to measure the a-axis length, c-axis length, cell volume, and crystal size of the crystal structure, which are shown in Table 3 below.

[0291]

[0292] Classification a axis (Å)c axis (Å)Cell Volume (Å 3 )Crystallite size (nm)Reference Example 2.87414.205101.6084Example 12.87514.207101.6986

[0293] As shown in Table 3 above, it can be confirmed that Example 1 has a similar level of a-axis length, c-axis length, cell volume, and crystal size to the reference example, and from this, it can be seen that the structure of the regenerated positive electrode active material of Example 1 was restored to the original state at or higher than the level of the raw positive electrode active material.

[0294]

[0295] [Experimental Example IV: Coin Half-Cell Evaluation]

[0296] The characteristics of the regenerated or newly produced positive electrode active materials manufactured in Example 1, Comparative Example 1 and Reference Example were measured through the following coin half cell (hereinafter referred to as 'CHC') electrochemical performance evaluation, and the results are shown in Figures 1 and 2 below.

[0297] * CHC manufacturing: 96 wt% of the regenerated cathode active material, 2 wt% of the conductive material carbon black, and 2 wt% of the binder PVdF were weighed and mixed in N-methyl-2-pyrrolidone (NMP) to make a slurry. This was coated on aluminum foil to manufacture the cathode, and then CHC was manufactured. The electrochemical performance (charge capacity CH, discharge capacity DCH, and efficiency Eff (%)) was evaluated under the conditions of ethylene carbonate (EC): dimethyl methyl carbonate (DMC) = 3:7 (weight ratio) as the electrolyte and other additives included.

[0298] * Evaluation of the initial capacity (CH and DCH) of CHC: At 25 ℃, one charge / discharge cycle was performed on each cell under the following conditions. The results are shown in Figure 1 below.

[0299] Charge(CH): 0.2C, CC / CV, 4.25V, 0.05C cut-off

[0300] Discharge(DCH): 0.2C, CC, 2.5V, cut-off

[0301] * Evaluation of high-temperature life characteristics of CHC: At 45 ℃, 30 cycles of charge and discharge were performed on each cell under the following conditions, and the capacity retention rate for each cycle was calculated using the following mathematical formula 1 and shown in Figure 2 below.

[0302] Charge: 0.33C, CC / CV, 4.5V, 0.05C cut-off

[0303] Discharge: 0.33C, CC, 3.0V, 0.05C cut-off

[0304] [Mathematical Formula 1]

[0305] Capacity retention rate (%) = (discharge capacity after N cycles / discharge capacity after 1 cycle) * 100

[0306]

[0307] The following Figure 1 is a graph showing the initial charge / discharge capacity as a result of CHC evaluation for each of the regenerated positive electrode active materials manufactured in Example 1 and Comparative Example 1.

[0308] As shown in Figure 1 below, the regenerative positive electrode active material according to the present invention (Example 1) had superior initial charge / discharge capacity compared to Comparative Example 1.

[0309]

[0310] In addition, the following Figure 2 is a graph showing the change in capacity retention rate according to the number of cycles (Cycle No.) as a result of CHC evaluation for each of the regenerated or new positive electrode active materials manufactured in Example 1 and Reference Example. Referring to this, it was confirmed that the capacity retention rate of the regenerated positive electrode active material according to the present invention (Example 1) at high temperatures was similar to or higher than that of the new positive electrode active material (Reference Example) up to 20 cycles, and that after 20 cycles, the capacity retention rate of Example 1 was somewhat reduced compared to the Reference Example.

[0311]

[0312] [Experimental Example V: Heat Treatment Temperature Analysis by TGA]

[0313] The weight change rate according to the heat treatment temperature of the regenerated positive electrode active materials manufactured from the above Example 1 and Comparative Example 1 was analyzed using TGA, and the results are shown in Figure 3 below. At this time, the temperature conditions were started at 50°C and ended at 900°C, and the heating rate was 5°C / min.

[0314]

[0315] Referring to Figure 3 below, Example 1 begins thermal decomposition at 740°C or higher, while Comparative Example 1 begins thermal decomposition at 600°C. From this, it can be seen that Example 1 has superior thermal stability than Comparative Example 1.

Claims

1. (a) A step of heat-treating a waste cathode composition including a cathode active material, a conductive material, a binder, and a solvent to remove the solvent; (b) a step of powdering the waste cathode composition from which the solvent has been removed; (c) a step of heat-treating the powdered waste cathode composition at 300 to 650°C to remove the binder and conductive material and recover the cathode active material; (d) a step of adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C; and (e) a step of washing the annealed positive electrode active material with a washing solution; characterized in that it comprises; Method for regenerating positive electrode active material.

2. In paragraph 1, The above-mentioned positive electrode composition is characterized in that it is in the form of a slurry. Method for regenerating positive electrode active material.

3. In paragraph 1, The heat treatment of step (a) is characterized in that it is performed at 80 to 120 ℃. Method for regenerating positive electrode active material.

4. In paragraph 1, The heat treatment of step (a) is characterized in that it is performed for 30 minutes to 4 hours. Method for regenerating positive electrode active material.

5. In paragraph 1, The powderization in the above step (b) is characterized by dry grinding. Method for regenerating positive electrode active material.

6. In paragraph 5, The above dry grinding is characterized by using a hand-mill, pin-mill, disc-mill, cutting-mill or hammer-mill. Method for regenerating positive electrode active material.

7. In paragraph 1, The above (b) powdering step is characterized in that it further includes a sieving step after powdering. Method for regenerating positive electrode active material.

8. In paragraph 1, The powder obtained through the above step (b) is characterized in that the average particle size is 45 ㎛ or less. Method for regenerating positive electrode active material.

9. In paragraph 1, The above cathode active material is characterized in that it is at least one selected from the group consisting of lithium nickel oxide (LNO) cathode active material, nickel-cobalt-manganese (NCM) cathode active material, nickel-cobalt-aluminum (NCA) cathode active material, nickel-cobalt-manganese-aluminum (NCMA) cathode active material, and lithium iron phosphate (LFP) cathode active material. Method for regenerating positive electrode active material.

10. In paragraph 1, The solvent is characterized in that it is at least one selected from the group consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methyl-2-pyrrolidone (NMP), acetone, and water. Method for regenerating positive electrode active material.

11. In paragraph 1, The lithium precursor is characterized in that it comprises at least one of LiOH, Li2CO3, LiNO3 and Li2O. Method for regenerating positive electrode active material.

12. In paragraph 1, The lithium precursor of the above step (d) is characterized in that it is added in an amount that is at least as much as the molar ratio of lithium in the positive electrode active material of the above step (a) based on the amount of lithium in the recovered positive electrode active material. Method for regenerating positive electrode active material.

13. In paragraph 1, The above cleaning solution is characterized in that it is water or a basic lithium compound aqueous solution. Method for regenerating positive electrode active material.

14. In paragraph 1, The method for regenerating the positive electrode active material is characterized in that it further includes the step of (f) surface coating the washed positive electrode active material. Method for regenerating positive electrode active material.

15. At least one 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, nickel-cobalt-manganese-aluminum (NCMA)-based cathode active material, and lithium iron phosphate (LFP)-based cathode active material, The c-axis length of the crystal structure measured by XRD (X-Ray Diffraction) was 14.200 to 14.210 Å, and the cell volume was 101.65 to 101.75 Å. 3 and the crystal size is 82 to 90 nm, Characterized by a thermal decomposition temperature of 700 ℃ or higher as measured by TGA (Thermogravimetric analysis) Positive active material.

16. In paragraph 15, The above positive electrode active material is characterized in that the surface is coated with a coating agent containing metal or carbon. Positive active material.

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