Positive electrode active material and method for regenerating positive electrode active material

Abstract

The invention relates to a positive electrode active material and a regeneration method thereof. More specifically, in a positive electrode active material and a method for regenerating the same, the positive electrode active material is 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, and a nickel cobalt manganese aluminum (NCMA)-based positive electrode active material, which contains a single particle, has an F content of 5700 mg / kg to 6500 mg / kg, and has a specific surface area of 1-5 [mu] m. And / or an a-axis lattice parameter to a c-axis lattice parameter to a cell volume and a grain size greater than 130 nm and equal to or less than 136 nm as measured by XRD analysis.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2024-0029795, filed with the Korean Intellectual Property Office on February 29, 2024, and Korean Patent Application No. 10-2025-0004743, which was filed with the Korean Intellectual Property Office on January 13, 2025, based on the same application, the disclosure of which is incorporated herein by reference in its entirety.

[0003] This invention relates to a positive electrode active material and its regeneration method. More specifically, since the positive electrode active material containing single particles recovered after heat treatment of waste positive electrodes does not undergo a pre-washing process, but is directly annealed by adding a lithium precursor, followed by surface coating, and the positive electrode active material is ground before and / or after annealing, the surface of the positive electrode active material contains a predetermined amount of fluorine (F), and the crystal structure and grain size of the positive electrode active material, as determined by X-ray diffraction (XRD) analysis, are adjusted to a predetermined range. Therefore, this invention relates to a positive electrode active material with excellent charging capacity, resistance characteristics, and capacity characteristics, and a regeneration method for the positive electrode active material. This method is environmentally friendly because no acid is used in the recycling and regeneration process, thus eliminating the need for neutralization and wastewater treatment, thereby reducing process costs. Since the positive electrode active material is regenerated without decomposition, no waste metal elements are generated, and since no organic solvents are used, there is no risk of toxic gases or explosions. Furthermore, since the pre-washing process is eliminated, both economic efficiency and productivity are significantly improved. Background Technology

[0004] A lithium secondary battery mainly consists of the following components: a positive electrode with a layer of positive active material coated on a metal foil (e.g., aluminum), a negative electrode with a layer of negative active material coated on a metal foil (e.g., copper), a separator to prevent the positive and negative electrodes from mixing with each other, and an electrolyte that allows lithium ions to move between the positive and negative electrodes.

[0005] The positive electrode active material layer primarily uses lithium oxides as active materials, while the negative electrode active material layer primarily uses carbon materials. Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4), or lithium iron phosphate compounds (LiFePO4) are all used as lithium oxides. Among them, lithium cobalt oxide, used as the positive electrode active material in lithium secondary batteries, has the advantages of high operating voltage and excellent capacity characteristics. However, due to the high price and unstable supply of cobalt, the commercial application of lithium cobalt oxide in high-capacity batteries is difficult. Furthermore, lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient lifetime characteristics, while lithium manganese oxide has excellent stability but suffers from poor capacity characteristics. Therefore, to overcome the problems of lithium transition metal oxides, lithium composite transition metal oxides containing two or more types of transition metals have been developed. Among them, lithium nickel cobalt manganese oxide containing nickel, cobalt, and manganese is widely used in the field of electric vehicle batteries.

[0006] Meanwhile, lithium nickel cobalt manganese oxides are prone to particle breakage during the rolling process in cathode manufacturing. During charge and discharge, internal cracks form within the particles, increasing the contact area with the electrolyte. Due to side reactions with the electrolyte, gas generation and active material degradation both increase, leading to a decline in lifespan characteristics.

[0007] To address this issue, lithium nickel cobalt manganese oxide, composed of high-strength single particles, is used in the cathode. However, due to its high strength, this oxide is difficult to recycle after use and disposal. Even if the oxide is recycled, problems such as reduced crystallinity persist. This leads to performance degradation when the recycled oxide is used as the cathode in lithium-ion secondary batteries.

[0008] Meanwhile, lithium-ion battery cathodes contain rare metals such as nickel, cobalt, or manganese. Therefore, research is underway to recover and regenerate rare metals from discarded lithium-ion battery cathodes or cathode waste generated during the manufacturing process of lithium-ion batteries (hereinafter referred to as "waste cathodes").

[0009] Conventional techniques for recovering rare metals such as nickel, cobalt, and manganese from waste cathodes of lithium-ion batteries mostly involve dissolving the waste cathodes with hydrochloric acid, sulfuric acid, or nitric acid, then extracting nickel, cobalt, and manganese using organic solvents, and then reusing them as raw materials for synthesizing cathode active materials.

[0010] However, the acid extraction method for rare metals presents environmental pollution problems, necessitating neutralization and wastewater treatment processes, which significantly increases process costs. Furthermore, this method is also disadvantageous in that it cannot recover lithium, the main metal in the positive electrode active material.

[0011] To address these shortcomings, a direct regeneration method has recently been investigated, in which the positive electrode active material is directly regenerated from waste positive electrodes without undergoing decomposition. There are approximately four representative methods of this type, including calcination, solvent dissolution, aluminum (Al) foil dissolution, and crushing and sieving.

[0012] However, although the calcination method is simple, it has the disadvantage of producing foreign matter on the surface of the regenerated positive electrode active material that reduces the battery's output performance, generating waste gas, and consuming a lot of energy.

[0013] Furthermore, solvent dissolution can yield relatively clean regenerated positive electrode active materials. However, this method has drawbacks, including poor stability and the need for expensive solvent recovery processes, as the solvents used to dissolve the binder (e.g., N-methyl-2-pyrrolidone (NMP)) are toxic gases and pose an explosion risk.

[0014] Furthermore, the aluminum foil dissolution method offers good process stability, low cost, and easy removal of the binder. However, its drawbacks include the formation of difficult-to-remove foreign matter on the surface of the regenerated positive electrode active material, and the generation of hydrogen gas during the aluminum foil removal process, posing an explosion risk.

[0015] Finally, the advantage of the crushing and screening method is that it is based on the simplest process, but the disadvantage is that it is difficult to completely separate the current collector and the positive electrode active material. During the crushing process, the particle size distribution of the positive electrode active material will change and residual binder will remain, which will lead to the deterioration of the battery characteristics of the regenerated positive electrode active material.

[0016] Therefore, there is an urgent need to develop a method for regenerating cathode active materials that can safely regenerate single-particle cathode active materials from waste cathodes containing single-particle cathode active materials in an environmentally friendly, low-process, and low-cost manner, without generating waste metal elements and without degrading output performance. Summary of the Invention

[0017] [Technical Issues]

[0018] Therefore, this invention addresses the aforementioned problems. One object of this invention is to provide a positive electrode active material and a method for regenerating positive electrode active materials containing single particles. Since the positive electrode active material containing single particles recovered after heat treatment of waste positive electrodes does not undergo a pre-washing process, but is directly annealed by adding a lithium precursor, followed by surface coating, and the positive electrode active material is ground before and / or after annealing, the surface of the positive electrode active material contains a predetermined amount of fluorine (F), and the crystal structure and grain size of the positive electrode active material, obtained by X-ray diffraction (XRD) analysis, are adjusted to a predetermined range. The positive electrode active material exhibits excellent charging capacity, resistance characteristics, and capacity characteristics. Furthermore, the method is environmentally friendly because no acid is used in the recycling and regeneration process, thus eliminating the need for neutralization and wastewater treatment, thereby reducing process costs. Since the positive electrode active material is regenerated without decomposition, no waste metal elements are generated, and since no organic solvents are used, there is no risk of toxic gases or explosions. In addition, the elimination of the pre-washing process significantly improves economic efficiency and productivity.

[0019] Furthermore, another objective of the present invention is to provide a secondary battery with excellent initial discharge capacity and capacity characteristics.

[0020] The above and other objectives can be achieved by the following invention.

[0021] [Technical Solution]

[0022] To achieve the above objectives, I) the present invention provides a positive electrode active material comprising at least one selected from lithium nickel oxide (LNO) type positive electrode active materials, nickel cobalt manganese (NCM) type positive electrode active materials, nickel cobalt aluminum (NCA) type positive electrode active materials, and nickel cobalt manganese aluminum (NCMA) type positive electrode active materials, wherein the positive electrode active material contains single particles, has an F content of 5700 mg / kg to 6500 mg / kg, and / or, as measured by XRD analysis, the a-axis lattice parameter of the positive electrode active material is... to The c-axis lattice parameters are to The cell volume of the positive electrode active material is to The grain size of the positive electrode active material is greater than 130 nm and equal to or less than 136 nm.

[0023] II) In I), based on 100 mol% of all other metals except Li, the positive electrode active material may contain more than 40 mol% of Ni.

[0024] III) In I) or II), the surface of the positive electrode active material may be coated with a coating agent containing metal or carbon.

[0025] IV) In I) to III), the positive electrode active material can be a regenerated positive electrode active material.

[0026] Furthermore, V) This invention provides a method for regenerating positive electrode active material, comprising the following steps: (a) heat-treating a waste positive electrode on which a positive electrode active material layer is formed on a current collector at 300°C to 650°C, thereby thermally decomposing the binder and conductive material in the positive electrode active material layer and recovering the positive electrode active material containing single particles in the positive electrode active material layer; (b) adding a lithium precursor to the recovered positive electrode active material and annealing the positive electrode active material at 400°C to 1000°C; (c) washing the annealed positive electrode active material with a washing solution; and (d) surface-coating the washed positive electrode active material, wherein the method for regenerating positive electrode active material includes: a grinding step in step (b) before annealing the recovered positive electrode active material; and / or a grinding step in step (c) before washing the annealed positive electrode active material. The grinding step, or the positive electrode active material regeneration method, includes the following steps: (a) heat-treating a waste positive electrode with a medium-nickel type positive electrode active material layer formed on a current collector at 300°C to 650°C, thereby thermally decomposing the binder and conductive material in the positive electrode active material layer and recovering the positive electrode active material containing single particles in the positive electrode active material layer; (b) adding a lithium precursor to the recovered positive electrode active material and annealing the positive electrode active material at 400°C to 1000°C; (c) washing the annealed positive electrode active material with a washing solution; and (d) surface coating the washed positive electrode active material, wherein the positive electrode active material regeneration method includes: the grinding step in step (b) before annealing the recovered positive electrode active material; and / or the grinding step in step (c) before washing the annealed positive electrode active material.

[0027] In the description of this invention, a medium-nickel type cathode active material can refer to a cathode active material based on 100 mol% of all metals except lithium, i.e., 100 mol% of all transition metals, containing more than 40 mol% of nickel, specifically 40 mol% to 70 mol% of nickel.

[0028] In the description of this invention, the pre-annealing grinding step refers to grinding before adding the lithium precursor to the positive electrode active material recovered after heat treatment of the waste positive electrode.

[0029] VI) In I) to V), the positive electrode active material may be at least one selected from LNO-type positive electrode active materials, NCM-type positive electrode active materials, NCA-type positive electrode active materials and NCMA-type positive electrode active materials, and contains more than 40 mol% Ni based on 100 mol% of all other metals except Li.

[0030] VII) In V) to VI), grinding can be performed using a centrifugal mill, a spray mill, or a pin mill.

[0031] In VIII) through VII), grinding can be performed at 6,000 rpm to 18,000 rpm.

[0032] In IX) of V) to VIII), the lithium precursor may contain at least one of LiOH, Li2CO3, LiNO3 and Li2O.

[0033] In step (b), in step (x) of V) to IX), the amount of lithium precursor added is at least the amount by which the lithium molar ratio in the positive electrode active material is reduced in step (a), based on the amount of lithium in the recovered positive electrode active material.

[0034] XI) In V) to X), during the washing in step (c), the weight ratio of the annealed or ground positive electrode active material to the washing liquid can be from 1:0.5 to 1:5.5.

[0035] XII) In V) to XI), step (c) may include the step of mixing the annealed positive electrode active material or the ground positive electrode active material with the washing liquid and filtering it; and the step of drying the solid positive electrode active material obtained after filtration.

[0036] In steps (d), XIII) In V) to XII), at least one of a metal, organometallic and carbon component may be coated on the surface in a solid or liquid manner, and then heat treatment may be performed at 100°C to 1200°C.

[0037] Furthermore, XIV) This invention provides a secondary battery characterized by comprising the positive electrode active material described in any one of I) to IV).

[0038] [Beneficial Effects]

[0039] According to the present invention, the positive electrode active material containing single particles recovered after heat treatment of waste positive electrodes does not undergo a pre-washing process, but is directly annealed by adding a lithium precursor, followed by surface coating. Because the positive electrode active material is milled before and / or after annealing, the surface of the positive electrode active material contains a predetermined amount of fluorine (F), and the crystal structure and grain size of the positive electrode active material, as determined by XRD analysis, are adjusted within a predetermined range. This results in a positive electrode active material with excellent charging capacity, resistance characteristics, and capacity characteristics.

[0040] Furthermore, single-particle cathode active materials can be easily regenerated directly from waste cathodes without degrading battery performance. This method is environmentally friendly because no acid is used in the recycling and regeneration of cathode active materials, eliminating the need for neutralization and wastewater treatment, thus reducing process costs. Since the cathode active materials are regenerated without decomposition, no waste metal elements are produced, and because no organic solvents are used, there is no risk of generating toxic gases or explosions. In particular, the elimination of the pre-washing process provides a cathode active material regeneration method with significantly improved economic efficiency and productivity. Attached Figure Description

[0041] The accompanying drawings are for illustrative purposes only and, together with the description herein, further aid in understanding the technical concept of the invention. Therefore, the invention should not be construed as limited to the contents shown in the drawings.

[0042] Figure 1 This diagram shows the positive electrode waste that is discarded after the electrode plates are cut from the positive electrode sheet.

[0043] Figure 2 A graph showing the capacity retention of the regenerated or new positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5.

[0044] Figure 3 This is a flowchart of the regeneration process of the positive electrode active material containing single particles according to the present invention. Detailed Implementation

[0045] The inventors have researched a direct regeneration method in which single-particle positive electrode active material is directly regenerated from waste positive electrode, thereby obtaining positive electrode active material with excellent output performance (rate performance) without decomposition. In this study, it was confirmed that when the single-particle positive electrode active material recovered after heat treatment of waste positive electrode is directly mixed with lithium precursor and annealed without a washing process, and when the recovered positive electrode active material is milled before and / or after annealing, the regenerated single-particle positive electrode active material contains a predetermined amount of fluorine. The crystal structure and grain size obtained by X-ray diffraction (XRD) analysis are adjusted to a predetermined range, thereby significantly improving charging capacity, resistance characteristics, and capacity characteristics. Based on these results, the inventors conducted further research to complete this invention.

[0046] The following description of the positive electrode active material and its regeneration method will be explained according to the present invention.

[0047] Furthermore, the terms or words used in this specification and claims should not be construed as having their conventional or dictionary meanings, but rather should be interpreted as meanings and concepts consistent with the technical concept of this invention, based on the principle that the inventor can appropriately define the concepts of the terms to best interpret their application. Therefore, the embodiments described in this specification and the configurations shown in the accompanying drawings are merely examples of the invention and do not represent the entirety of the technical concept. It should be understood that various equivalents and modifications can be substituted for them, and they can be rearranged, replaced, combined, split, or designed in various other configurations.

[0048] Unless otherwise defined, all technical and scientific terms used in the description of this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0049] Single-particle positive electrode active material

[0050] The positive electrode active material of the present invention is at least one selected from lithium nickel oxide (LNO) type positive electrode active materials, nickel cobalt manganese (NCM) type positive electrode active materials, nickel cobalt aluminum (NCA) type positive electrode active materials, and nickel cobalt manganese aluminum (NCMA) type positive electrode active materials. The positive electrode active material comprises single particles; has an F content of 5700 mg / kg to 6500 mg / kg; and / or has an a-axis lattice parameter measured by XRD of... to The c-axis lattice parameters are to The unit cell volume is to The grain size is greater than 130 nm and equal to or less than 136 nm. Under these conditions, it exhibits excellent performance in aspects such as charging capacity, resistance characteristics, and capacity characteristics.

[0051] The positive electrode active material may preferably contain at least one selected from the following: 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 lithium composite metal oxide obtained by replacing a portion of the nickel (Ni) in lithium nickel oxide with manganese (Mn); and NCM lithium composite transition metal oxide obtained by replacing a portion of the nickel (Ni) in lithium nickel oxide with manganese (Mn) and cobalt (Co). In this case, excellent effects are achieved in aspects such as electrochemical performance, resistivity characteristics, and capacity characteristics.

[0052] As a specific example, the positive electrode active material may contain a compound represented by the following Formula 1 and has excellent effects in terms of, for example, electrochemical performance, resistance characteristics, capacity characteristics, and the like.

[0053] [Formula 1]

[0054] Li a Ni x Mn y Co z M w O 2+δ

[0055] (In Formula 1 above, M includes at least one selected from B, W, Al, Ti, and Mg, 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, and x + y + z + w = 1.)

[0056] Based on 100 mol% of all the remaining metals other than Li, the positive electrode active material may contain, for example, 40 mol% or more of Ni, 40 mol% to 95 mol% of Ni, more preferably 40 mol% to 70 mol% of Ni (here, the positive electrode active material may refer to a medium-nickel type positive electrode active material), and still more preferably 50 mol% to 70 mol% of Ni. Within this range, it has excellent effects in terms of, for example, initial discharge capacity, output performance, capacity characteristics, and resistance characteristics, etc.

[0057] In the description of the present invention, when measuring the Ni content by an IC (ion chromatography) method or the like commonly used in the technical field to which the present invention pertains, as a specific example, an IC-ICP (inductively coupled plasma) analyzer, an IC-ICP-MS analyzer, or an IC-ICP-AEC analyzer can be used for measurement without particular limitation.

[0058] The positive electrode active material may preferably comprise single particles and more preferably does not contain secondary particles. In this case, a positive electrode active material can be provided, which does not undergo particle breakage during the electrode manufacturing process, thus preventing a decrease in battery performance due to fine powder, having excellent life characteristics under a high-pressure environment, high thermal stability, and a small amount of gas generated during charging / discharging.

[0059] The single particle can be any single particle commonly used in the technical field to which this invention pertains. Under the conditions defined in this invention, it can be, for example, a particle composed of 30 or fewer nodules, or preferably a particle composed of 1 to 20 nodules, more preferably a particle composed of 1 to 10 nodules, even more preferably a particle composed of 1 to 5 nodules, and most preferably a particle composed of 1 nodule. In this case, a positive electrode material can be provided that does not experience particle breakage during electrode manufacturing, thereby preventing battery performance degradation due to fine powder, exhibiting excellent lifespan characteristics under high voltage conditions, high thermal stability, and low gas generation during charging / discharging.

[0060] In the description of this invention, a nodule refers to a particle unit that constitutes a single particle, and can also refer to a single crystal or polycrystalline material that appears to have no grain boundaries when observed using a scanning electron microscope (SEM) or electron backscatter diffraction (EBSD) spectrometer at a magnification of 5,000 to 20,000 times.

[0061] In the description of this invention, the nodule number refers to the average number of nodules in the positive electrode active material particles. Here, to obtain the nodule number, a positive electrode containing the positive electrode active material is cut using ion milling, and a cross-sectional image of the cut positive electrode in the thickness direction is obtained using SEM. Then, in this cross-sectional image, at least 30 particles are selected for both the largest and smallest diameter positive electrode active material particles. Then, through SEM image analysis, the nodule number of each positive electrode active material particle cross-section can be measured, and their arithmetic mean can be calculated.

[0062] The average particle size (D) of a single particle 50 The micrometer can preferably be 2μm to 10μm, more preferably 2μm to 8μm, and even more preferably 3μm to 6μm.

[0063] In the description of this invention, the average particle size (D) 50 The average particle size (D) can be defined as the particle size corresponding to 50% of the volumetric accumulation in the particle size distribution (PSD). 50 The average particle size (D) of the positive electrode active material can be measured using methods such as laser diffraction. 50 In the measurement method, positive electrode active material particles are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), and irradiated with ultrasound at an output power of 60W and a frequency of approximately 28kHz. The average particle size (D) corresponding to 50% of the volumetric accumulation in the measuring device can then be calculated. 50 ).

[0064] The positive electrode active material may contain fluorine (F) preferably from 5700 mg / kg to 6500 mg / kg, more preferably from 5800 mg / kg to 6300 mg / kg, and even more preferably from 5800 mg / kg to 6100 mg / kg, and within this range, it has excellent effects in terms of charging capacity, resistance characteristics and capacity characteristics.

[0065] In the description of this invention, when measuring the fluorine (F) content using methods commonly used in the technical field to which this invention pertains, as a specific example, an IC-ICP analyzer, an IC-ICP-MS analyzer, or an IC-ICP-AEC analyzer can be used for measurement, without any particular limitation.

[0066] In positive electrode active materials, the a-axis lattice parameters measured by XRD analysis can be, for example... to Preferred to More preferably to Even better to Within this range, the a-axis lattice parameter of the positive electrode active material is lower than that of the raw material positive electrode active material, thus having different lattice structures and exhibiting excellent effects in aspects such as charging capacity, resistance characteristics, and capacity characteristics.

[0067] In positive electrode active materials, the c-axis lattice parameters measured by XRD analysis can be, for example... to Preferred to More preferably to Even better to Within this range, the lithium concentration in the lattice increases along the c-axis (pointing towards the z-axis in the layered structure), resulting in excellent performance in areas such as charge capacity, resistance characteristics, and capacitance characteristics.

[0068] In positive electrode active materials, for example, the cell volume measured by XRD analysis can be, for example... to Preferred to More preferably to Even better to Within this range, it exhibits excellent performance in areas such as charging capacity, resistance characteristics, and capacity characteristics.

[0069] In positive electrode active materials, for example, the grain size measured by XRD analysis can be, for example, greater than 130 nm and less than or equal to 136 nm, preferably 131 nm to 135 nm, and more preferably 131 nm to 134 nm. Within this range, the grain size is larger than that of secondary particles, which improves ionic conductivity and thus provides excellent effects in aspects such as capacity characteristics.

[0070] In the description of this invention, the lattice parameters, cell volume, and grain size of the cathode active material can be measured by XRD analysis. Specifically, the data obtained by XRD analysis using Cu Kα rays are indexed and refined by Rietveld. The lattice parameters can be calculated, the cell volume can be calculated by multiplying the a-axis lattice parameters and the c-axis lattice parameters, and the grain size can be calculated using the Scherrer equation from the XRD measurement data.

[0071] In the description of this invention, a crystallite refers to a single crystal particle unit having a regular arrangement of atoms.

[0072] For example, the surface of the positive electrode active material can be coated with metal or carbon. Preferably, in the case of metal coating, the regenerated positive electrode active material itself does not undergo chemical and physical changes, improving the structural stability of the positive electrode active material. Electrochemical properties such as output performance, lifetime characteristics, and capacity are then improved. Furthermore, this heterogeneous element substitution on the surface of the positive electrode active material also brings effects such as reduced residual lithium and lower pH value, thereby improving the physicochemical properties of the battery.

[0073] The metal is preferably at least one selected from B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V, and Y, more preferably at least one selected from B, W, Al, Ti, and Mg, even more preferably boron (B), tungsten (W), or a mixture thereof, and even more preferably tungsten (W) and boron (B). In one embodiment, the metal is tungsten boride (WB), in which case it has the effect of improving resistance characteristics and lifetime characteristics.

[0074] Boron-containing coating agents are preferably selected from H3BO3, B2O3, C6H5B(OH)2, (C6H5O)3B, [CH3(CH2)3O]3B, C 13 H 19 At least one of BO3, C3H9B3O6, and (C3H7O)3B, more preferably H3BO3. In this case, it has the effect of improving resistance characteristics and lifetime characteristics.

[0075] The content of the coating agent, relative to 1 mol% of metal in the uncoated positive electrode active material, can be, for example, 0.001 mol% to 0.3 mol%, preferably 0.01 mol% to 0.3 mol%, more preferably 0.01 mol% to 0.15 mol%, even more preferably 0.01 mol% to 0.1 mol%, and even more preferably 0.01 mol% to 0.05 mol%. Within this range, while maintaining the inherent properties of the single-particle positive electrode active material, it has the effect of improving structural stability and electrochemical performance.

[0076] When coating the surface, a coating agent containing at least one component preferably selected from metals, organometallics, and carbon is applied to the surface in a solid or liquid manner, followed by heat treatment at 100°C to 1200°C. In this case, while maintaining the inherent properties of the positive electrode active material, it has the effect of improving structural stability and electrochemical performance.

[0077] The positive electrode active material can be, for example, a recycled positive electrode active material. In this case, it has advantages such as economic benefits and excellent productivity.

[0078] Regeneration methods for single-particle positive electrode active materials

[0079] The method for regenerating the positive electrode active material of the present invention includes the following steps: (a) heat-treating a waste positive electrode on which a positive electrode active material layer is formed on a current collector at 300°C to 650°C, thereby thermally decomposing the binder and conductive material in the positive electrode active material layer and recovering the positive electrode active material containing single particles in the positive electrode active material layer; (b) adding a lithium precursor to the recovered positive electrode active material and annealing the positive electrode active material at 400°C to 1000°C; (c) washing the annealed positive electrode active material with a washing solution; and (d) surface coating the washed positive electrode active material. The method includes: a grinding step in step (b) before annealing the recovered positive electrode active material; and / or a grinding step in step (c) before washing the annealed positive electrode active material. In this case, a regenerated single-particle positive electrode active material is provided, wherein the surface of the positive electrode active material contains a predetermined amount of fluorine (F), and the crystal structure and grain size of the positive electrode active material obtained by XRD analysis both fall within a predetermined range. Therefore, the charging capacity, resistance characteristics, and capacity characteristics are all excellent. This method is environmentally friendly because no acid is used in the recycling and regeneration process, thus eliminating the need for neutralization and wastewater treatment, thereby reducing process costs. Since the positive electrode active material is directly regenerated without decomposition, there are no waste metal elements; furthermore, since no organic solvents are used, there is no risk of generating toxic gases or explosions. In particular, because single-particle positive electrode active material can be easily regenerated directly from waste positive electrodes without degrading battery performance, economic efficiency and productivity are significantly improved.

[0080] In another example, the method for regenerating the positive electrode active material of the present invention includes the following steps: (a) heat-treating a waste positive electrode on which a medium-nickel type positive electrode active material layer is formed on a current collector at 300°C to 650°C, thereby thermally decomposing the binder and conductive material in the positive electrode active material layer and recovering the positive electrode active material containing single particles in the positive electrode active material layer; (b) adding a lithium precursor to the recovered positive electrode active material and annealing the positive electrode active material at 400°C to 1000°C; (c) washing the annealed positive electrode active material with a washing solution; and (d) surface coating the washed positive electrode active material. This regeneration method includes: a grinding step in step (b) before annealing the recovered positive electrode active material; and / or a grinding step in step (c) before washing the annealed positive electrode active material. In this case, a regenerated single-particle medium-nickel type positive electrode active material is provided, wherein the surface of the positive electrode active material contains a predetermined amount of fluorine (F), and the crystal structure and grain size of the positive electrode active material obtained by XRD analysis both fall within a predetermined range. Therefore, the charging capacity, resistance characteristics, and capacity characteristics are all excellent. This method is environmentally friendly because no acid is used in the recycling and regeneration process, thus eliminating the need for neutralization and wastewater treatment, thereby reducing process costs. Since the positive electrode active material is regenerated without decomposition, there are no waste metal elements; furthermore, since no organic solvents are used, there is no risk of generating toxic gases or explosions. In particular, because single-particle positive electrode active material can be easily regenerated directly from waste positive electrodes without degrading battery performance, economic efficiency and productivity are significantly improved.

[0081] In the description of this invention, the pre-annealing grinding step refers to grinding before adding the lithium precursor to the positive electrode active material recovered after heat treatment of the waste positive electrode.

[0082] The regeneration method for the positive electrode active material will be described in detail below for each individual step.

[0083] (a) Steps for recovering single-particle positive electrode active material from waste positive electrodes

[0084] The step (a) of recovering single-particle positive electrode active material from waste positive electrode of the present invention may preferably include the following step: heat-treating the waste positive electrode on which a layer of positive electrode active material is formed on a current collector at a temperature of 300°C to 650°C, thereby thermally decomposing the binder and conductive material in the positive electrode active material layer, and recovering the single-particle positive electrode active material in the positive electrode active material layer. Recovering the positive electrode active material in this manner has advantages such as simple process and complete removal of binder, conductive material, and current collector.

[0085] In another example, step (a) of the present invention may include the following steps: heat-treating a waste positive electrode having a single-particle nickel-type positive electrode active material layer formed on a current collector at 300°C to 650°C, so that the binder and the conductive material in the positive electrode active material layer are thermally decomposed, and recovering the single-particle nickel-type positive electrode active material in the positive electrode active material layer. In this case, the medium nickel-type positive electrode active material has effects such as simple process and complete removal of the binder, the conductive material, and the current collector.

[0086] The waste positive electrode may preferably be a positive electrode separated from a lithium secondary battery discarded after use, or a defective positive electrode sheet or positive electrode waste generated during the manufacturing process of a lithium secondary battery, and more preferably a positive electrode waste remaining after punching a positive electrode sheet to obtain a positive electrode plate.

[0087] The positive electrode active material layer in step (a) may preferably contain a positive electrode active material, a binder, and a conductive material.

[0088] The positive electrode active material may preferably be at least one selected from the following: 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 obtained by replacing a part of nickel (Ni) in lithium nickel oxide with manganese (Mn); and NCM-based lithium composite transition metal oxide obtained by replacing a part of nickel (Ni) in lithium nickel oxide with manganese (Mn) and cobalt (Co). More preferably, the positive electrode active material may be a nickel-manganese-based lithium composite metal oxide, an NCM-based lithium composite transition metal oxide, or a mixture thereof, in which case, it has excellent effects in terms of reversible capacity and thermal stability, etc.

[0089] In another specific example, the positive electrode active material may be a compound represented by the following formula 1.

[0090] [Formula 1]

[0091] Li a Ni x Mn y Co z M w O 2+δ

[0092] (In the above formula 1, M includes at least one selected from B, W, Al, Ti, Mg, 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, and x + y + z + w = 1.)

[0093] Based on 100 mol% of all metals except Li, the positive electrode active material may contain, for example, more than 40 mol% Ni, 40 mol% to 95 mol% Ni, more preferably 40 mol% to 70 mol% Ni (here, the positive electrode active material may be referred to as a medium-nickel type positive electrode active material), and more preferably 50 mol% to 70 mol% Ni. Within this range, it exhibits excellent effects in aspects such as initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0094] The positive electrode active material recovered in step (a) can preferably be a single particle, and more preferably does not include secondary particles. In this case, a regenerated positive electrode active material can be provided that does not experience particle breakage during electrode manufacturing, thus avoiding battery performance degradation caused by fine powder, exhibiting excellent lifespan characteristics under high voltage conditions, high thermal stability, and low gas generation during charging / discharging.

[0095] The average particle size (D) of a single particle 50 The micrometer can preferably be 2μm to 10μm, more preferably 2μm to 8μm, and even more preferably 3μm to 6μm.

[0096] In the description of this invention, the average particle size (D) 50 The average particle size (D) can be defined as the particle size corresponding to 50% of the volumetric accumulation in the particle size distribution (PSD). Specifically, the average particle size (D) can be measured using laser diffraction. 50 For example, in the average particle size (D) of the positive electrode active material 50 In the measurement method, positive electrode active material particles are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), and irradiated with ultrasound at an output power of 60W and a frequency of approximately 28kHz. The average particle size (D) corresponding to 50% of the volumetric accumulation in the measuring device can then be calculated. 50 ).

[0097] The conductive material is preferably a carbon-based conductive material, or it can be, for example, carbon black, CNT, or a mixture thereof.

[0098] The adhesive can be, for example, a polymer adhesive, preferably polyvinylidene fluoride (PVdF), acrylonitrile-butadiene rubber (NBR) or a mixture thereof, more preferably polyvinylidene fluoride.

[0099] In step (a), the heat treatment temperature can be, for example, 300°C to 650°C, preferably 400°C to 600°C, more preferably 500°C to 600°C, and even more preferably 530°C to 580°C. Within this range, the advantage is that the positive electrode active material is easily separated from the current collector because the current collector does not melt and only the binder is removed.

[0100] During the heat treatment process, the heating rate can be, for example, from 1°C / min to 20°C / min, preferably from 3°C / min to 10°C / min, and more preferably from 3°C / min to 7°C / min. Within this range, the advantage is that heat treatment can be performed without placing a burden on the heat treatment equipment and without causing thermal shock to the positive electrode waste.

[0101] The heat treatment can be carried out in an atmosphere such as air or oxygen, preferably in air, in which case the carbon components of the binder and conductive materials react with oxygen and disappear in the form of gases such as CO and CO2. Therefore, it has the advantage that both the binder and conductive materials are removed.

[0102] The purity of the oxygen can be, 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%. Within this range, the binder and conductive material are removed without residue. Furthermore, the stability of Ni in the regenerated positive electrode active material increases.

[0103] The purity percentage of oxygen can be expressed as volume percentage or molar percentage.

[0104] In the description of this invention, there are no particular limitations on the purity of oxygen when measured using measurement methods commonly used in the technical field to which this invention pertains.

[0105] The air or oxygen supply rate can be, for example, from 1 L / min to 20 L / min, preferably from 1 L / min to 15 L / min, more preferably from 2 L / min to 10 L / min, and even more preferably from 3 L / min to 7 L / min. Within this range, the advantage is that the positive electrode active material is easily separated from the current collector, and the separated positive electrode active material is easily sorted in powder form.

[0106] The heat treatment time is 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. Within this range, the advantage is that the current collector does not melt and only the binder is removed, thus the positive electrode active material is easily separated from the current collector.

[0107] In the description of this invention, the heat treatment time is the time required to perform the treatment at the corresponding heat treatment temperature, and the time required to reach the corresponding heat treatment temperature is not calculated.

[0108] The positive electrode active material recovered in step (a) can preferably be directly subjected to grinding or annealing processes without pre-washing. In this case, the elimination of the pre-washing process has the advantage of significantly improved economic efficiency and productivity.

[0109] In the description of this invention, pre-washing may refer to washing performed before the addition of the lithium precursor, and post-washing may refer to washing performed after the addition of the lithium precursor and annealing.

[0110] Reference Figure 1 An aluminum foil 10, serving as a long sheet-shaped positive electrode current collector, is coated with a positive electrode active material layer 20 containing positive electrode active material, conductive material, adhesive, etc., thereby producing a positive electrode sheet 30. This positive electrode sheet is then punched to a certain size to form a positive electrode plate 40, resulting in positive electrode waste 50 as the remaining portion. Punching is a method of cutting the positive electrode sheet.

[0111] Furthermore, the positive electrode active material layer 20 is formed by coating an aluminum foil 10 with a slurry composed of a positive electrode active material, a conductive material, a binder, a solvent, etc. Since the slurry is highly sensitive to environmental factors such as temperature, it is difficult to determine the coating conditions. Therefore, waste positive electrode sheets, such as positive electrode waste 50, are generated before the conditions for manufacturing the required quality positive electrode sheet 30 are found through certain tests.

[0112] For reference, in the following embodiments, the positive electrode waste 50 is used as a discarded positive electrode.

[0113] (b) The step of adding the lithium precursor to the recycled positive electrode active material and annealing it.

[0114] The cathode active material regeneration method of the present invention may include step (b) of adding a lithium precursor to the recycled cathode active material and annealing it at 400°C to 1000°C. In this case, the crystal structure of the regenerated cathode active material is restored, thereby providing a cathode active material with excellent efficiency, lifetime characteristics, and resistivity characteristics. Furthermore, it is advantageous that the economic benefits and productivity can be significantly improved by omitting the pre-washing process of the recycled cathode active material.

[0115] The annealing step can preferably include a grinding step before annealing the recovered positive electrode active material, specifically, a grinding step before adding the lithium precursor. In this case, the agglomerated particles during heat treatment are released, and in the subsequent annealing step, the lithium precursor is uniformly added to the single-particle positive electrode active material, and then the crystal structure is restored through heat treatment. Therefore, it has excellent effects in terms of efficiency, lifetime characteristics, and resistance characteristics. Unlike secondary particle positive electrode active materials, single-particle positive electrode active materials have fewer pores. Furthermore, when particles agglomerate, it is difficult to uniformly add the lithium precursor to the positive electrode active material and perform heat treatment. Therefore, it is preferable to release the agglomerated particles by grinding. For reference, the state of the recovered secondary particle positive electrode active material is different from that of the single-particle positive electrode active material. Therefore, the recovered secondary particle positive electrode active material does not have the grinding effect described in this invention, and even if grinding is performed, it will not be transformed into single-particle positive electrode active material.

[0116] Furthermore, since the recovered positive electrode active material is ground directly without a pre-washing process, there is no lithium loss due to washing. This further improves efficiency, lifetime characteristics, and resistance characteristics.

[0117] Grinding can be performed using, for example, a centrifugal mill, a spray mill, or a pin mill, with a pin mill being preferred. In this case, the advantage is that it can uniformly release agglomerated particles without damaging the surface of the positive electrode active material.

[0118] The grinding can be performed at, for example, 6000 rpm to 18000 rpm, preferably 8000 rpm to 16000 rpm, more preferably 10000 rpm to 13000 rpm, and even more preferably 11000 rpm to 13000 rpm. Within this range, the agglomeration of individual positive electrode active materials is released, and the heat treatment is carried out uniformly in the subsequent annealing step. Therefore, the crystal structure recovery of the regenerated positive electrode active material is significantly improved, resulting in excellent effects in aspects such as efficiency, lifetime characteristics, and resistivity.

[0119] In the annealing step (b), a lithium precursor is added to the recycled cathode active material, and the annealing can preferably be carried out in an air or oxygen (O2) atmosphere, more preferably in air. In this case, the annealing improves the crystallinity of the cathode active material, for example, by increasing the crystallinity or restoring the crystal structure. Therefore, it has the effect of improving the battery characteristics of the recycled cathode active material.

[0120] The annealing temperature is preferably 500°C to 900°C, more preferably 600°C to 880°C, and even more preferably 700°C to 800°C. This improves the crystallinity of the positive electrode active material, for example, by increasing crystallinity or restoring the crystal structure. Therefore, it has the effect of improving the battery characteristics of the regenerated positive electrode active material.

[0121] The lithium precursor can preferably be selected from at least one of LiOH, Li2CO3, LiNO3 and Li2O.

[0122] In step (b), based on the amount of lithium in the recovered positive electrode active material, the amount of lithium precursor added can be at least the amount by which the lithium molar ratio in the positive electrode active material decreased in step (a). As a specific example, when the recovered positive electrode active material in step (a) is the positive electrode active material shown in Formula 1 above, when the lithium molar ratio in the positive electrode active material is 1, the amount of lithium precursor added can make the lithium molar ratio 0.0001 to 0.2; or make the lithium molar ratio preferably 0.001 to 0.1, more preferably 0.001 to 0.07, even more preferably 0.001 to 0.03, even more preferably 0.001 to 0.02, particularly preferably 0.005 to 0.017, particularly more preferably 0.007 to 0.015, and most preferably 0.009 to 0.013. Within this range, the lithium deficiency in the regenerated positive electrode active material can be compensated, thereby improving crystallinity, for example, increasing crystallinity or restoring the crystal structure. Therefore, the advantage lies in improving the battery characteristics of recycled positive electrode active materials.

[0123] In another example, when the lithium content in the raw cathode active material is 100 mol%, the amount of lithium precursor added can correspond to 1 mol% to 40 mol%, or preferably 1 mol% to 30 mol%, more preferably 7 mol% to 20 mol%. Within these ranges, the regenerated cathode active material will not contain residual precursors that could increase resistance, which is highly advantageous for improving battery characteristics. Furthermore, there is an economic advantage because a smaller amount of lithium precursor can be used to restore the crystal structure.

[0124] The annealing temperature can be adjusted within a limited range based on the melting point of the lithium precursor. For example, for Li₂CO₃ with a melting point of 723°C, annealing is preferably performed at 700°C to 900°C, more preferably at 710°C to 780°C. For LiOH with a melting point of 462°C, annealing is preferably performed at 400°C to 750°C, more preferably at 500°C to 720°C, and even more preferably at 600°C to 720°C. Within these ranges, the crystal structure is restored, thus resulting in excellent effects on aspects such as battery efficiency, lifespan characteristics, and resistance characteristics.

[0125] The annealing temperature mentioned above can preferably be a temperature exceeding the melting point of the lithium precursor. However, if it exceeds 1000°C, thermal decomposition of the positive electrode active material may occur, leading to battery performance degradation. Therefore, it can preferably be below 1000°C.

[0126] The required annealing time can be, for example, more than 1 hour or less than 15 hours, preferably 1 to 15 hours, more preferably 2 to 10 hours, even more preferably 3 to 8 hours, and even more preferably 4 to 6 hours, with a specific example of 5 hours. Within this range, the crystal structure is fully restored, the grain size is larger than that of the secondary grains, and the ionic conductivity is improved, thereby exhibiting excellent capacity characteristics.

[0127] The heating rate to reach the annealing temperature is preferably from 1°C / min to 10°C / min, more preferably from 1°C / min to 7°C / min, and even more preferably from 2°C / min to 4°C / min. In this case, it has the effect of further increasing the crystallinity of the regenerated positive electrode active material, thereby improving the battery characteristics of the regenerated positive electrode active material.

[0128] As a specific example, the annealing step includes a cooling process, which can be, for example, natural cooling within a furnace. In this case, it has the effect of further increasing the crystallinity of the regenerated positive electrode active material, thereby improving the battery characteristics of the regenerated positive electrode active material.

[0129] In the description of this invention, annealing may follow the definition used in the technical field to which this invention pertains, and as a specific example, may be defined as a heat treatment operation. This heat treatment operation involves heating a positive electrode active material with deformed structures or lattice defects at a recrystallization temperature equal to or higher than the recrystallization temperature at which the main component atoms can sufficiently diffuse and move for an appropriate time, thereby treating the deformation or lattice defects and improving crystallinity.

[0130] (c) Steps for washing the annealed positive electrode active material (post-washing)

[0131] The method for regenerating the positive electrode active material of the present invention includes step (c) of washing the annealed positive electrode active material with a washing solution. In this case, the washing solution removes lithium precursors that may remain on the surface of the positive electrode active material. Furthermore, it has the advantage of preventing the residual lithium precursors from reacting with the electrolyte, thereby suppressing battery performance degradation and gas generation.

[0132] The washing step can preferably include a grinding step before the washing and annealing of the positive electrode active material. In this case, the agglomerated particles are released and uniformly dispersed, allowing for effective removal of lithium precursors and / or fluorine with a small amount of washing liquid, thereby reducing wastewater volume. Therefore, when applied to batteries, the advantages include improved charging capacity, resistance characteristics, and capacity characteristics.

[0133] Grinding can be performed using, for example, a centrifugal mill, a spray mill, or a pin mill, with a pin mill being preferred. In this case, the advantage is that agglomerated particles can be released uniformly without damaging the surface of the positive electrode active material.

[0134] The grinding can be performed at, for example, 6000 rpm to 18000 rpm, preferably 8000 rpm to 16000 rpm, more preferably 10000 rpm to 13000 rpm, and even more preferably 11000 rpm to 13000 rpm. Within this range, agglomerated particles of the positive electrode active material are released, forming a uniformly dispersed shape, and impurities are easily removed in the subsequent washing process. Therefore, the advantages are that the charging capacity, resistance characteristics, and capacity characteristics are all improved.

[0135] Washing may preferably include the steps of mixing the annealed or milled positive electrode active material with a washing solution, followed by a filtration step; and drying the filtered solid positive electrode active material. In this case, the effect is to effectively remove excess lithium that tends to remain in the positive electrode active material. The above washing may preferably include the steps of mixing the annealed or milled positive electrode active material with a washing solution, followed by a filtration step; and drying the filtered solid positive electrode active material. In this case, lithium precursors such as LiOH and Li2CO3 and / or fluorine that tend to remain on the surface of the positive electrode active material are effectively removed with a small amount of washing solution, thereby reducing wastewater.

[0136] The weight ratio of the annealed or ground positive electrode active material to the washing liquid can be, for example, 1:0.5 to 1:5.5, preferably 1:0.5 to 1:4.5, more preferably 1:0.5 to 1:3.5, and even more preferably 1:0.5 to 1:2.5. In this case, a small amount of washing liquid effectively removes lithium precursors such as LiOH and Li2CO3 and / or fluorine that tend to remain on the surface of the positive electrode active material, thereby reducing wastewater.

[0137] The washing solution is preferably water or an aqueous solution of an alkaline lithium compound, more preferably water. In this case, a small amount of washing solution effectively removes lithium precursors such as LiOH and Li₂CO₃. Cation mixing easily occurs in regenerated positive electrode active materials, especially regenerated medium-nickel type positive electrode active materials. Excessive addition of lithium to suppress this phenomenon leads to greater residue of lithium precursors. Thus, the battery output performance is significantly improved without the need for wastewater treatment.

[0138] The water used is preferably distilled or deionized water. In this case, a small amount of washing solution effectively removes lithium precursors such as LiOH and Li2CO3 that are prone to remain on the surface of the regenerated positive electrode active material. This results in reduced wastewater and significantly improved battery output performance.

[0139] The alkaline lithium compound aqueous solution preferably contains more than 0% by weight and less than 15% by weight, more preferably more than 0% by weight and less than 10% by weight of lithium compound. In this case, lithium precursors such as LiOH and Li2CO3 and / or fluorine that are prone to remain on the surface of the regenerated positive electrode active material are effectively removed with a small amount of washing solution. This results in reduced wastewater and significantly improved battery output performance.

[0140] The annealed positive electrode active material is mixed with the washing solution, preferably by stirring. There are no particular restrictions on the stirring method, but mechanical stirring or ultrasonic stirring can be used.

[0141] Stirring can preferably be carried out within 30 minutes, more preferably 20 minutes, even more preferably 15 minutes, and even more preferably 5 to 10 minutes. Within these ranges, residual lithium is effectively removed.

[0142] (d) Step of surface coating the washed positive electrode active material to obtain a reusable positive electrode active material.

[0143] The cathode active material regeneration method of the present invention includes step (d) of surface coating the washed cathode active material to obtain a reusable cathode active material. In this case, the following effects are achieved: while maintaining the original excellent properties of the cathode active material, structural stability and electrochemical performance are improved.

[0144] In surface coating, a coating agent is applied to the surface in a solid or liquid manner. The coating agent preferably contains at least one component selected from metals, organometallic materials, and carbon components, followed by heat treatment at a temperature of 100°C to 1200°C. This process achieves the following effect: while maintaining the original excellent properties of the positive electrode active material, it improves structural stability and electrochemical performance.

[0145] The metal-containing coating agent is preferably a coating agent containing at least one selected from B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V, and Y. More preferably, it is a coating agent containing at least one selected from B, W, Al, Ti, and Mg. Even more preferably, it is a coating agent containing boron (B), tungsten (W), or a mixture thereof. Even more preferably, it is a coating agent containing tungsten (W) and boron (B). As a specific example, a coating agent containing tungsten boride (WB) has the effect of improving resistance characteristics and lifetime characteristics.

[0146] Boron-containing coating agents are preferably selected from H3BO3, B2O3, C6H5B(OH)2, (C6H5O)3B, [CH3(CH2)3O]3B, C 13 H 19 At least one of BO3, C3H9B3O6, and (C3H7O)3B, more preferably H3BO3. In this case, it has the effect of improving resistance characteristics and lifetime characteristics.

[0147] Metal-containing coatings can be, for example, oxides or acids that contain metals as elements in a molecule.

[0148] There are no particular limitations on the coating agent containing organometallic compounds, as long as it contains the aforementioned metal and is a commonly used organometallic compound in the technical field to which this invention pertains. As a specific example, it can be a metal alkoxide.

[0149] There are no particular limitations on the type of coating agent containing carbon components, as long as it contains carbon components and is commonly used in the technical field to which this invention pertains. As a specific example, it can be sugar, such as sucrose.

[0150] Based on the actual components (excluding solvent) coated on the surface of the positive electrode active material, the content of the coating agent relative to 1 mol% of metal in the uncoated positive electrode active material can be, for example, 0.001 mol% to 0.3 mol%, preferably 0.01 mol% to 0.3 mol%, more preferably 0.01 mol% to 0.15 mol%, even more preferably 0.01 mol% to 0.1 mol%, and even more preferably 0.01 mol% to 0.05 mol%. Within these ranges, the following effects are achieved: while maintaining the original excellent properties of the positive electrode active material, structural stability and electrochemical performance are improved.

[0151] The heat treatment temperature is preferably from 100°C to 1000°C, more preferably from 200°C to 1000°C, and even more preferably from 200°C to 500°C. Within these ranges, performance degradation due to thermal decomposition of the regenerated positive electrode active material will not occur. This results in improved structural stability and electrochemical performance.

[0152] The time required for heat treatment is preferably from 1 hour to 16 hours, more preferably from 3 hours to 7 hours. Within these ranges, the following effects are achieved: while maintaining the original properties of the positive electrode active material, structural stability and electrochemical performance are improved.

[0153] There are no particular limitations on the coating method, as long as it is a coating method commonly used in the technical field to which this invention pertains. Examples may include: a liquid method in which a liquid coating agent is prepared and mixed with a positive electrode active material; a mechanochemical method utilizing the high mechanical energy of ball milling; a fluidized bed coating method; a spray drying method; a precipitation method in which the coating agent is deposited on the surface of the positive electrode active material in an aqueous solution state; a method utilizing the reaction between a gaseous coating agent and the positive electrode active material; and a sputtering method.

[0154] The metal, organometallic, and carbon components can be, for example, spherical, plate-like, prismatic, or needle-like, and these shapes can be controlled by changing the process conditions during manufacturing. There are no particular limitations on the definition of each shape, as long as they conform to the generally accepted definitions in the technical field to which this invention pertains.

[0155] For the coating agent, the preferred average particle size is 1 nm to 1000 nm, and the specific surface area is 10 m². 2 / g to 100m 2 / g; more preferably, the average particle size can be from 10nm to 100nm, and the specific surface area can be 20m². 2 / g to 100m 2 / g. Within this range, the coating agent adheres uniformly to the surface of the regenerated positive electrode active material and provides structural stability to the regenerated positive electrode active material. This prevents lattice deformation or crystal structure collapse of the positive electrode active material, thereby improving the degradation of lifetime characteristics and electrochemical performance.

[0156] In the description of this invention, the average particle size can be measured using measurement methods commonly used in the art to which this invention pertains, such as laser diffraction. Specifically, to calculate the average particle size (D) based on a 50% particle size distribution in the measuring device... 50 The positive electrode active material particles are dispersed in a dispersion medium and then placed in a commercially available laser diffraction particle size measurement device (such as Microtrac MT 3000) and irradiated with ultrasound with an output power of 60W and a frequency of about 28kHz.

[0157] In the description of this invention, the specific surface area can be measured using methods commonly used in the technical field to which this invention pertains, such as the Brunauer-Emmett-Teller (BET) method. Specifically, it can be calculated using the BELSORP-mini II from BEL Japan based on the amount of nitrogen adsorbed at liquid nitrogen temperature (77K).

[0158] The fluorine (F) content of the positive electrode active material regenerated by the aforementioned positive electrode active material regeneration method is preferably from 5700 mg / kg to 6500 mg / kg, more preferably from 5800 mg / kg to 6300 mg / kg, and even more preferably from 5800 mg / kg to 6100 mg / kg. Within these ranges, it exhibits excellent effects in aspects such as charging capacity, resistance characteristics, and capacity characteristics.

[0159] In the description of this invention, the fluorine (F) content can be measured using an IC analysis device. Here, a commonly used laboratory IC analysis device can be used for measurement, and there will be no deviation due to differences in the measuring device or method.

[0160] In the positive electrode active material regenerated according to the aforementioned positive electrode active material regeneration method, the a-axis lattice parameters measured by XRD analysis can be, for example... to Preferred to More to Even better to Within these ranges, compared to the raw material cathode active material, the cathode active material has a smaller a-axis lattice parameter, thus exhibiting a different lattice structure. This results in superior performance in areas such as charging capacity, resistance characteristics, and capacity characteristics.

[0161] In the positive electrode active material regenerated by the aforementioned positive electrode active material regeneration method, the c-axis lattice parameters measured by XRD analysis can be, for example... to Preferred to More to Even better to Within these ranges, the lithium concentration in the lattice increases along the c-axis (pointing towards the z-axis in the layered structure). This results in excellent performance in areas such as charge capacity, resistance characteristics, and capacitance characteristics.

[0162] In the positive electrode active material regenerated according to the aforementioned positive electrode active material regeneration method, the unit cell volume, as measured by, for example, XRD analysis, can be, for example... to Preferred to More to Even better to Within these ranges, it exhibits excellent performance in areas such as charging capacity, resistance characteristics, and capacity characteristics.

[0163] In the positive electrode active material regenerated according to the aforementioned positive electrode active material regeneration method, the grain size, as measured by, for example, XRD analysis, can be, for example, greater than 130 nm and less than 136 nm, preferably 131 nm to 135 nm, and more preferably 131 nm to 134 nm. Within these ranges, the grain size is larger than that of the secondary particles, which improves ionic conductivity and thus results in excellent capacity characteristics.

[0164] Furthermore, the present invention can also provide a regenerated positive electrode active material, characterized in that the material is prepared by the aforementioned positive electrode active material regeneration method. In this case, it exhibits excellent effects in aspects such as initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0165] Figure 3 This is a flowchart of the regeneration process of the positive electrode active material according to one embodiment of the present invention.

[0166] refer to Figure 3 First, prepare the positive electrode waste as the discarded positive electrode (step S10).

[0167] For example, NMP (N-methylpyrrolidone) is added to a single-particle nickel-type NCM lithium composite transition metal oxide, carbon black, and polyvinylidene fluoride, and these are mixed to prepare a slurry. This slurry is then coated with aluminum foil and dried in a vacuum oven at approximately 120°C to form a positive electrode sheet. This sheet is then punched to obtain positive electrode plates of specified dimensions, after which the remaining positive electrode waste can be obtained.

[0168] The cathode waste has a layer of positive electrode active material on aluminum foil. After the solvent evaporates, the positive electrode active material layer has a structure in which an adhesive bonds the positive electrode active material and the conductive material together. Therefore, when the adhesive is removed, the positive electrode active material separates from the aluminum foil.

[0169] Then, the prepared positive electrode waste is crushed to the appropriate size (step S20).

[0170] Here, crushing includes cutting or shredding the cathode waste into easily manageable sizes. As a specific example, the crushed cathode waste can be 1cm x 1cm in size. During crushing, various dry grinding equipment can be used, such as hand grinders, pin grinders, disc grinders, cutting grinders, and hammer grinders, or a high-speed cutter can be used to increase productivity.

[0171] Whether to crush the material or the size of the fragments can be determined by considering the method of processing the cathode waste and the characteristics required by the equipment used in subsequent processes. For example, when using equipment capable of continuous processing, the cathode waste must be crushed into smaller fragments to ensure better flowability.

[0172] Then, the positive electrode waste is heat-treated to recover the positive electrode active material (step S30). Here, heat treatment is performed to thermally decompose the binder in the active material layer. As described above, through heat treatment, the binder and conductive material in the active material layer are thermally decomposed into CO2 and H2O and removed. Since the binder is removed, the positive electrode active material is separated from the current collector, and the separated positive electrode active material is easily sorted in powder form. Therefore, the active material layer can be separated from the current collector by step S30 alone, and the positive electrode active material in the active material layer can then be recovered in powder form.

[0173] The recycled positive electrode active material may contain single particles, and, as a specific example, does not contain secondary particles. In this case, a positive electrode active material can be provided that does not experience particle breakage during electrode manufacturing, thus avoiding battery performance degradation due to fine powder, exhibiting excellent lifespan characteristics under high voltage conditions, high thermal stability, and low gas generation during charging / discharging.

[0174] Importantly, the heat treatment can be performed in an air or oxygen atmosphere, specifically in air. When heat treatment is performed in a reducing or inert gas atmosphere, the binder and conductive materials are carbonized rather than thermally decomposed. Due to carbonization, carbon components remain on the surface of the positive electrode active material, thus reducing the performance of the reusable positive electrode active material. However, when heat treatment is performed in an air or oxygen atmosphere, the carbon components in the binder and conductive materials react with oxygen and disappear as gases such as CO and CO2. Therefore, both the binder and conductive materials are removed.

[0175] The heat treatment can preferably be carried out at a temperature between 300°C and 650°C, or, as a specific example, at 550°C. In this case, if the temperature is below 300°C, it is difficult to remove the adhesive, making it impossible to separate the current collector, while if the temperature is above 650°C, the current collector melts, making it impossible to separate the current collector.

[0176] The heating rate for heat treatment is preferably from 1°C / min to 20°C / min, more preferably from 3°C / min to 10°C / min, and specifically, 5°C / min. Within these ranges, the advantage is that heat treatment can be performed without burdening the heat treatment equipment and without causing thermal shock to the positive electrode waste.

[0177] The heat treatment can be carried out for a period of time to allow the adhesive, for example, to fully decompose thermally, preferably for 30 minutes or more, more preferably 30 minutes to 5 hours. As a specific example, the heat treatment can be carried out for 30 minutes. Within this range, the adhesive fully decomposes thermally, resulting in excellent thermal decomposition efficiency.

[0178] Heat treatment can be carried out using various types of furnaces, such as box furnaces. For productivity reasons, heat treatment can also be performed using rotary kilns capable of continuous processing.

[0179] After heat treatment, it can be slowly or rapidly cooled in the atmosphere.

[0180] Then, the recovered positive electrode active material is ground once (step S40).

[0181] In a single grinding step, it is important to directly grind the recovered positive electrode active material without a pre-washing process. In this case, agglomerated positive electrode active material is released without damaging the surface of individual particles, resulting in uniform particle size. Since no washing process is performed, lithium loss due to washing does not occur. This has the effect of further improving efficiency, lifetime characteristics, and resistance characteristics.

[0182] The grinding process can be performed using, for example, a centrifugal mill, a spray mill, or a pin mill; as a specific example, a pin mill is used. The advantage in this case is that it achieves particle uniformity without damaging the surface of the recycled individual positive electrode active material particles, thereby improving battery characteristics.

[0183] A single milling operation can be performed, for example, at 6000 rpm to 18000 rpm, specifically 12000 ppm. Within this range, the advantage is that it achieves particle uniformity without damaging the surface of individual positive electrode active materials, thereby improving battery characteristics.

[0184] Then, the lithium precursor is added to the once-milled positive electrode active material, and then annealing is performed (step S50).

[0185] Since lithium loss occurred in the positive electrode active material in the previous step S30, the annealing step S50 compensates for this lithium loss. Furthermore, since deformed structures (e.g., Co3O4 in the case of LCO active material) may appear on the surface of the single-particle positive electrode active material in the previous step, the crystal structure of the single-particle positive electrode active material is restored by annealing in step S50, thereby improving the battery characteristics of the regenerated single-particle positive electrode active material, or restoring these characteristics to the level of new positive electrode active material. Here, "new" is the opposite of "regenerated," referring to material manufactured for the first time, the same as the "raw materials" used in the detailed description and embodiments of the present invention.

[0186] The lithium precursor can be at least one of, for example, LiOH, Li2CO3, LiNO3 and Li2O, and as a specific example, LiOH can be used.

[0187] Preferably, the amount of lithium precursor added can be at least the amount of lithium molar ratio loss compared to the molar ratio of lithium to other metals in the new cathode active material used for the cathode active material layer. When the amount of lithium precursor added is excessive compared to the amount of lithium loss, unreacted lithium precursor will remain in the regenerated cathode active material. This will increase resistance, so an appropriate amount of lithium precursor needs to be added. For example, when the molar ratio of lithium to other metals in the new cathode active material is 1, the amount of lithium precursor added can make the lithium molar ratio 0.001 to 0.4, preferably 0.01 to 0.2.

[0188] As a specific example, when lithium precursors were added at a molar ratio (based on lithium metal) of 0.09 to 0.1 (based on the proportion of lithium content loss in the new cathode active material), ICP analysis revealed a capacity improvement comparable to that of the new cathode active material. Here, the error value of the ICP analysis results is approximately ±0.02.

[0189] Annealing is carried out in oxygen (O2) or air, for example at 400°C to 1000°C, or, as a specific example, in air at 700°C.

[0190] Preferably, the annealing temperature can exceed the melting point of the lithium precursor. However, the temperature should not exceed 1000°C, because the positive electrode active material will undergo thermal decomposition at temperatures above 1000°C, leading to a decrease in performance. When Li₂CO₃ is used as the lithium precursor, the annealing temperature can suitably be 700°C to 900°C, more preferably 710°C to 780°C, and most preferably 750°C to 780°C. Furthermore, when LiOH is used as the lithium precursor, the annealing temperature can suitably be 400°C to 750°C, more preferably 500°C to 720°C, and most preferably 600°C to 720°C.

[0191] The annealing time can preferably be, for example, more than 1 hour, preferably less than 15 hours, and more preferably 4 to 6 hours. A longer annealing time allows for sufficient recovery of the crystal structure. However, a longer annealing time does not significantly affect performance. In this case, the same or similar equipment as that used in heat treatment step S30 can be used for the annealing equipment.

[0192] Then, the annealed positive electrode active material is subjected to secondary grinding (step S60).

[0193] In the secondary grinding step S60, the particles agglomerated by the annealing step S50 are released, allowing the particle size of the regenerated positive electrode active material to be reduced and become close to that of the positive electrode active material in the waste positive electrode. This improves battery performance. Furthermore, it has the advantage of effectively removing lithium precursors and / or fluorine with a small amount of washing liquid, thereby reducing wastewater.

[0194] Secondary grinding can be performed using, for example, a centrifugal mill, a spray mill, or a pin mill. As a specific example, a pin mill is used for the grinding process. The advantage in this case is that the particle size is reduced without damaging the regenerated positive electrode active material particles.

[0195] Secondary grinding can be performed at, for example, 6000 rpm to 16000 rpm, specifically 12000 rpm. Within this range, the advantages are high grinding efficiency, reduced particle size of the regenerated positive electrode active material, and excellent productivity.

[0196] Then, the positive electrode active material that has been milled twice is washed (step S70).

[0197] Since the lithium precursors that did not participate in the reaction during the annealing step S50 are present on the surface of the positive electrode active material in the form of LiOH and Li2CO3, a residual lithium removal process is required to remove them. Lithium impurities such as lithium carbonate (Li2CO3) remaining on the surface of the regenerated positive electrode active material must be thoroughly removed, as they may subsequently react with the electrolyte, thereby reducing battery performance and generating gas.

[0198] In the washing step S70, the annealed positive electrode active material is preferably mixed with the washing liquid at a weight ratio of 1:0.5 to 1:5.5, specifically a weight ratio of 1:1, and then filtered. The resulting solid positive electrode active material is then dried. In this case, the agglomerated particles from the previous step are released by grinding. Therefore, it is advantageous that residual lithium is thoroughly removed using a small amount of washing liquid, thereby reducing wastewater.

[0199] For the washing solution, distilled water or an aqueous solution of an alkaline lithium compound (with an alkaline lithium compound content greater than 0% by weight and less than 10% by weight) is preferably used. More preferably, distilled water is used as the washing solution. In this case, the washing solution is safe and inexpensive, and also has the advantage that transition metals present in the regenerated positive electrode active material are not eluted.

[0200] The washing process is preferably carried out by mixing the annealed positive electrode active material with a washing solution, filtering the mixture, and then drying the resulting solid positive electrode active material.

[0201] The annealed positive electrode active material is mixed with the washing solution, preferably by stirring. There are no particular restrictions on the stirring method, but mechanical stirring or ultrasonic stirring is preferred.

[0202] Mechanical stirring is preferably carried out at 250 rpm to 350 rpm for 3 to 10 minutes.

[0203] The filtration can preferably be vacuum filtration using a filter, and the drying can preferably be vacuum drying at 120°C to 140°C.

[0204] Then, the washed positive electrode active material is surface coated (step S80).

[0205] In surface coating, a coating agent containing, for example, metals, organometallics, or carbon components is applied to the surface in solid or liquid form, followed by heat treatment. If the heat treatment temperature is too low, the desired dissimilar metal surface protective layer cannot be formed; if the heat treatment temperature is too high, the positive electrode active material will undergo thermal decomposition, leading to a decrease in battery performance.

[0206] Specifically, when the washed positive electrode active material is coated with a metal oxide of B, W or BW or an acid and then subjected to heat treatment, a surface protective layer, such as a lithium boron oxide layer, is formed on the surface of the positive electrode active material.

[0207] Solid or liquid methods for surface coating can include methods such as mixing, grinding, spray drying, or milling.

[0208] When the molar ratio of lithium to other metals in the positive electrode active material is 1:1 in the annealing step S50, the molar ratio of lithium to other metals in the positive electrode active material will be less than 1:1 due to the reaction between lithium in the regenerated positive electrode active material and the coating agent in the surface coating step S60. This regenerated positive electrode active material cannot fully utilize 100% of the battery capacity. However, when an excess of lithium precursor is added in the annealing step S40, making the lithium content 0.0001 to 0.1 higher than the molar ratio of lithium to other metals in the regenerated positive electrode active material, the molar ratio of lithium to other metals in the positive electrode active material naturally becomes 1:1 due to the formation of a surface protective layer in the surface coating step S60. Therefore, the battery capacity does not decrease.

[0209] Secondary batteries

[0210] The secondary battery of the present invention comprises regenerated single-particle positive electrode active material. In this case, due to a significant reduction in residual lithium on the surface of the positive electrode active material, its initial discharge capacity, output performance, capacity characteristics, and resistance characteristics are all excellent. Furthermore, since no acids or organic solvents are used in the recycling and regeneration process of the positive electrode active material, this secondary battery is environmentally friendly. In particular, by eliminating the pre-washing process, it offers excellent advantages in terms of economic efficiency and productivity.

[0211] The secondary battery of the present invention may include the above-described regenerated single-particle positive electrode active material and its regeneration method. Therefore, it will not be described again here.

[0212] Preferred embodiments will be provided below to aid in understanding the invention; however, these embodiments are merely illustrative, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and concept of the invention. Furthermore, these changes and modifications naturally fall within the scope of the appended claims.

[0213] Example

[0214] Example 1

[0215] The waste positive electrode material (current collector: aluminum foil, positive electrode active material: NCM lithium-type composite transition metal oxide (based on 100 mol% of all metals except Li, containing 61 mol% Ni)) discarded after punching the positive electrode plate was crushed and then heat-treated in air at 550°C for 30 minutes to remove binder and conductive material. After separating the current collector and positive electrode active material from each other, the positive electrode active material was recovered. The heat treatment temperature was reached at a heating rate of 5°C / min, and air was supplied at 3L / min.

[0216] SEM images confirmed that the recovered positive electrode active material consisted of single particles.

[0217] The recovered positive electrode active material was directly ground once using a needle mill at 12,000 rpm without pre-washing.

[0218] When the lithium content in the raw cathode active material is 100 mol%, LiOH is added as a lithium precursor to the cathode active material after one grinding process, and the amount added can provide the equivalent of 10 mol% lithium. Then, annealing is performed in air at a calcination temperature of 700°C for 5 hours. Here, air is supplied at a rate of 3 L / min.

[0219] The annealed positive electrode active material was subjected to secondary grinding using a needle mill at 12,000 rpm.

[0220] The twice-ground positive electrode active material was mixed with distilled water at a 1:1 weight ratio and stirred at 300 rpm for 5 minutes. Then, it was filtered under vacuum to obtain a solid. The solid was then vacuum-dried at 130°C for 12 hours to obtain the washed positive electrode active material.

[0221] The washed positive electrode active material was coated with boric acid and then heated at 300°C for 5 hours to produce the final regenerated positive electrode active material. Here, based on the total weight of the positive electrode active material, the amount of boric acid added was 500 ppm, the heat treatment temperature was reached at a heating rate of 2°C / min, and air was supplied at 3L / min.

[0222] Here, ICP analysis equipment is used to measure the molar ratio of lithium to other metals in the positive electrode active material. Commonly used laboratory ICP analysis equipment can be used for this measurement, and there will be no deviation due to differences in the measuring device or method.

[0223] In the description of this invention, unless otherwise defined, ppm is based on weight.

[0224] Example 2

[0225] The regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that the grinding process in Example 1 was not performed.

[0226] Example 3

[0227] The regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that the secondary grinding process in Example 1 was not performed.

[0228] Comparative Example 1

[0229] The recycled positive electrode active material was manufactured in the same manner as in Example 1, except that the NCM lithium-type composite transition metal oxide (based on 100 mol% of all metals except Li, containing 61 mol% of Ni, single particles) in the positive electrode waste discarded after punching the positive electrode plate in Example 1 was replaced with NCM lithium-type composite transition metal oxide (based on 100 mol% of all metals except Li, containing 61 mol% of Ni, secondary particles).

[0230] SEM images confirmed that the positive electrode active material recovered after heat treatment was secondary particles.

[0231] Comparative Example 2

[0232] The waste positive electrode material (current collector: aluminum foil, positive electrode active material: NCM lithium-type composite transition metal oxide (based on 100 mol% of all metals except Li, containing 61 mol% Ni)) discarded after punching the positive electrode plate was crushed and then heat-treated in air at 550°C for 30 minutes to remove binder and conductive material. After separating the current collector and positive electrode active material from each other, the positive electrode active material was recovered. The heat treatment temperature was reached at a heating rate of 5°C / min, and air was supplied at 3L / min.

[0233] SEM images confirmed that the recovered positive electrode active material consisted of single particles.

[0234] The recovered positive electrode active material is washed by immersing it in distilled water with stirring. Here, the recovered positive electrode active material and distilled water are stirred at 500 rpm for 10 minutes at a weight ratio of 1:10, and then vacuum filtered to extract only the active material.

[0235] The washed positive electrode active material was dried overnight at 100°C. Then, when the lithium content in the raw positive electrode active material was 100 mol%, LiOH as a lithium precursor was added in an amount sufficient to provide the equivalent of 10 mol% lithium. The material was then annealed in air at a calcination temperature of 700°C for 5 hours. Air was supplied at a rate of 3 L / min.

[0236] The annealed positive electrode active material was mixed with distilled water at a 1:1 weight ratio and stirred at 300 rpm for 5 minutes. The mixture was then vacuum filtered to obtain a solid. The solid was then vacuum dried at 130°C for 12 hours to obtain the washed positive electrode active material.

[0237] The washed positive electrode active material was coated with boric acid and then heated at 300°C for 5 hours to produce the final regenerated positive electrode active material. Here, based on the total weight of the positive electrode active material, the amount of boric acid added was 500 ppm, the heat treatment temperature was reached at a heating rate of 2°C / min, and air was supplied at 3L / min.

[0238] Comparative Example 3

[0239] The regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that in the surface coating step of Example 1, it was heated at 300°C for 5 hours without the addition of boric acid to produce the final regenerated positive electrode active material.

[0240] Comparative Example 4

[0241] The waste positive electrode material (current collector: aluminum foil, positive electrode active material: NCM lithium-type composite transition metal oxide (based on 100 mol% of all metals except Li, containing 61 mol% Ni)) discarded after punching the positive electrode plate was crushed and then heat-treated in air at 550°C for 30 minutes to remove binder and conductive material. After separating the current collector and positive electrode active material from each other, the positive electrode active material was recovered. The heat treatment temperature was reached at a heating rate of 5°C / min, and air was supplied at 3L / min.

[0242] SEM images confirmed that the recovered positive electrode active material consisted of single particles.

[0243] The recycled positive electrode active material was directly ground once at 12,000 rpm using a needle mill without washing, thus producing regenerated positive electrode active material. Annealing, secondary grinding, post-washing, and coating were not performed.

[0244] Comparative Example 5

[0245] Instead of preparing reusable active materials, novel (fresh) NCM-type lithium composite transition metal oxides were prepared (based on 100 mol% of all metals except lithium, containing 61 mol% nickel, with an average particle size of 3.99 μm). SEM images confirmed that the new cathode active material consisted of single particles.

[0246] [Experimental Example I: Fluorine (F) Content]

[0247] The fluorine content of the regenerated or new positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was measured using an ICP analyzer, and the results are listed in Table 1 below. Here, a common laboratory ICP analyzer can be used for the measurement, and there will be no deviation due to differences in the measuring device or method.

[0248] [Table 1]

[0249] Example F (mg / kg) Example 1 5815 Example 2 6300 Example 3 6000 Comparative Example 1 6050 Comparative Example 2 160 Comparative Example 3 5540 Comparative Example 4 7200 Comparative Example 5 <10

[0250] As can be seen from Table 1 above, the fluorine content of the regenerated positive electrode active materials in Examples 1 to 3 of the present invention is 5700ppm to 6500ppm.

[0251] In contrast, the fluorine content in the regenerated positive electrode active material of Comparative Example 2 was reduced due to the two washing processes, resulting in a large amount of wastewater and significant lithium loss. The fluorine content in the regenerated positive electrode active material of Comparative Example 3 was similar to that of Example 1. This demonstrates that surface coating does not affect the fluorine content.

[0252] Furthermore, compared to Example 1, the fluorine content of the regenerated positive electrode active material of Comparative Example 4, which was manufactured by grinding only once, was significantly increased.

[0253] Furthermore, the novel positive electrode active material in Comparative Example 5 has a lower fluorine content. In the regenerated positive electrode active material containing secondary particles in Comparative Example 1, the fluorine content is similar to that of the examples.

[0254] [Experimental Example II: CHC Cell Evaluation]

[0255] For the regenerated or new positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5, the electrochemical performance was measured by the following CHC cell evaluation, and the results are listed in Table 2 below.

[0256] *CHC Cell Evaluation: 97.5 wt% of regenerated positive electrode active material, 1.15 wt% of carbon black as a conductive material, and 1.35 wt% of PVdF as a binder were weighed and mixed with NMP to obtain a slurry. This slurry was used to coat aluminum foil to prepare the positive electrode, and then the cells (coin-type half-cells, CHC) were fabricated. Electrochemical performance (charge capacity CH, discharge capacity DCH, and charge / discharge efficiency Eff (%)) was then evaluated under conditions containing an electrolyte with a weight ratio of 3:4:3 of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) and other additives, with an initial charge / discharge rate of 3V to 4.45V cutoff and 0.1C / 0.1C.

[0257] The charging / discharging efficiency is calculated using the following mathematical formula 1 and is shown in Table 2.

[0258] [Mathematical Expression 1]

[0259] Charge / discharge efficiency (%) = [Discharge capacity (mAh / g) / Charge capacity (mAh / g)] * 100

[0260] [Table 2]

[0261] CHC capacity Charging capacity (mAh / g) Discharge capacity (mAh / g) Charge / discharge efficiency (%) Example 1 217.0 197.0 90.8 Example 2 216.3 196.2 90.7 Example 3 216.7 196.4 90.6 Comparative Example 1 222.4 201.3 89.7 Comparative Example 2 216.9 195.3 90 Comparative Example 3 213.6 189.3 88.6 Comparative Example 4 209.7 177.8 84.8 Comparative Example 5 219.1 197.4 90.1

[0262] As shown in Table 2 above, it can be found that the regenerated positive electrode active materials of Examples 1 to 3 of the present invention are superior in terms of charge capacity (CH), discharge capacity (DCH), and / or charge-discharge efficiency (Eff) compared with the regenerated positive electrode active materials or new positive electrode active materials of Comparative Examples 1 to 5. In particular, it can be found that the discharge capacity and charge-discharge efficiency are lower in Comparative Example 2, which was washed but not polished, compared with Examples 1 to 3.

[0263] [Experimental Example III: XRD Analysis]

[0264] XRD analysis was performed on various regenerated or new positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5. The a-axis lattice parameters, c-axis lattice parameters, cell volume and grain size were measured and are shown in Table 3 below.

[0265] *Lattice parameters and grain size were determined by XRD analysis (specifically, XRD analysis using Cu Kα X-rays). Lattice parameters were calculated by Rietveld refinement indexing of the XRD data, cell volume was calculated by multiplying the a-axis lattice parameter by the c-axis lattice parameter, and grain size was calculated using the Scherrer equation on the XRD data.

[0266] [Table 3]

[0267]

[0268] As shown in Table 3 above, it can be seen that the a-axis lattice parameters, c-axis lattice parameters, cell volume, and grain size of the recycled cathode active materials of the present invention (Examples 1 to 3) differ from those of the new cathode active material (Comparative Example 5). Specifically, the a-axis lattice parameters and cell volume are smaller, while the c-axis lattice parameters and grain size are larger. This reveals that the crystal structure and grain size of the recycled single-particle cathode active material of the present invention differ from those of the new cathode active material due to the grinding performed before and / or after annealing.

[0269] Furthermore, it can be observed that the a-axis lattice parameters, c-axis lattice parameters, cell volume, and grain size of the regenerated positive electrode active materials of Examples 1 to 3 are different from those of the regenerated positive electrode active materials of Comparative Examples 1 to 4.

[0270] [Experimental Example IV: High-Temperature Lifetime Characteristics Evaluation]

[0271] For the CHC cells manufactured or prepared using the recycled or new positive electrode active materials from Examples 1 to 3 and Comparative Examples 1 to 5, the capacity retention rate was measured as follows, and the results are shown in... Figure 2 .

[0272] High-Temperature Lifetime Characteristic Assessment: At 45°C, each cell underwent 30 charge / discharge cycles under the following conditions. For each cycle, the capacity retention rate was calculated using the following mathematical formula 2, and is shown below. Figure 2 middle.

[0273] Charging: 0.33C, CC / CV, 4.5V, 0.05C cutoff

[0274] Discharge: 0.33C, CC, 3.0V, 0.05C cutoff

[0275] [Mathematical Expression 2]

[0276] Capacity retention (%) = (Discharge capacity after N cycles / Discharge capacity after 1 cycle) * 100

[0277] Figure 2 This is a graph showing the capacity retention rate as a function of the number of cycles. It illustrates the evaluation results of the lifetime characteristics of the regenerated single-particle positive electrode active material of the present invention (Examples 1 to 3), and compares it with regenerated secondary particle positive electrode active material (Comparative Example 1), regenerated positive electrode active material obtained by washing without grinding (Comparative Example 2), regenerated positive electrode active material obtained by heat treatment without adding boric acid in the surface coating step (Comparative Example 3), regenerated positive electrode active material obtained by performing only one grinding step (Comparative Example 4), and new positive electrode active material (Comparative Example 5).

[0278] Therefore, it can be seen that, compared with the regenerated positive electrode active materials of Comparative Examples 1 to 4 and the new positive electrode active material of Comparative Example 5, the regenerated positive electrode active materials of the present invention (Examples 1 to 3) exhibit superior performance in terms of capacity retention.

[0279] In particular, it can be observed that in Comparative Example 1, which contains secondary particle positive electrode active material, the capacity retention rate was significantly reduced despite grinding before and after annealing.

[0280] [Figure Labels]

[0281] 10: Current collector

[0282] 20: Active material layer

[0283] 30: Positive electrode plate

[0284] 40: Positive electrode plate

[0285] 50: Positive electrode waste

Claims

1. A positive electrode active material, comprising at least one selected from lithium nickel oxide (LNO) positive electrode active materials, nickel cobalt manganese (NCM) positive electrode active materials, nickel cobalt aluminum (NCA) positive electrode active materials, and nickel cobalt manganese aluminum (NCMA) positive electrode active materials. in, The positive electrode active material contains single particles. The F content is 5700 mg / kg to 6500 mg / kg, and / or X-ray diffraction (XRD) analysis showed that the a-axis lattice parameter of the positive electrode active material was: to The c-axis lattice parameters of the positive electrode active material are: to The cell volume of the positive electrode active material is to The grain size of the positive electrode active material is greater than 130 nm and equal to or less than 136 nm.

2. The positive electrode active material as described in claim 1, wherein, The positive electrode active material contains more than 40 mol% Ni, based on 100 mol% of all other metals except Li.

3. The positive electrode active material as described in claim 1, wherein, The surface of the positive electrode active material is coated with a coating agent containing metal or carbon.

4. The positive electrode active material as described in claim 1, wherein, The positive electrode active material is a regenerated positive electrode active material.

5. A method for regenerating a positive electrode active material, comprising: (a) The waste positive electrode on which a positive active material layer is formed on the current collector is heat-treated at 300°C to 650°C, thereby thermally decomposing the binder and conductive material in the positive active material layer and recovering the positive active material containing single particles in the positive active material layer. (b) Add lithium precursor to the recovered positive electrode active material and anneal the positive electrode active material at 400°C to 1000°C; (c) Wash the annealed positive electrode active material with a washing solution; and (d) Surface coating of the washed positive electrode active material. The method for regenerating the positive electrode active material includes: In (b), the recovered positive electrode active material is ground before annealing; and / or In (c), grinding is performed before washing the annealed positive electrode active material.

6. A method for regenerating a positive electrode active material, comprising: (a) The waste cathode with a medium-nickel type cathode active material layer formed on the current collector is heat-treated at 300°C to 650°C, thereby thermally decomposing the binder and conductive material in the cathode active material layer and recovering the cathode active material containing single particles in the cathode active material layer. (b) Add lithium precursor to the recovered positive electrode active material and anneal the positive electrode active material at 400°C to 1000°C; (c) Wash the annealed positive electrode active material with a washing solution; and (d) Surface coating of the washed positive electrode active material. The method for regenerating the positive electrode active material includes: In (b), the recovered positive electrode active material is ground before annealing; and / or In (c), grinding is performed before washing the annealed positive electrode active material.

7. The method for regenerating the positive electrode active material as described in claim 5 or 6, wherein, The positive electrode active material layer is selected from at least one of lithium nickel oxide (LNO) positive electrode active materials, nickel cobalt manganese (NCM) positive electrode active materials, nickel cobalt aluminum (NCA) positive electrode active materials, and nickel cobalt manganese aluminum (NCMA) positive electrode active materials, and contains more than 40 mol% Ni based on 100 mol% of all other metals except Li.

8. The method for regenerating the positive electrode active material as described in claim 5 or 6, wherein, The grinding is performed using a centrifugal mill, a spray mill, or a pin mill.

9. The method for regenerating the positive electrode active material as described in claim 5 or 6, wherein, The grinding was performed at 6000 rpm to 18000 rpm.

10. The method for regenerating the positive electrode active material as described in claim 5 or 6, wherein, The lithium precursor contains at least one of LiOH, Li2CO3, LiNO3, and Li2O.

11. The method for regenerating the positive electrode active material as described in claim 5 or 6, wherein, In (b), based on the amount of lithium in the recovered positive electrode active material, the amount of lithium precursor added is at least the amount by which the lithium molar ratio in the positive electrode active material in (a) is reduced.

12. The method for regenerating the positive electrode active material as described in claim 5 or 6, wherein, In the washing process (c), the weight ratio of the annealed or ground positive electrode active material to the washing liquid is 1:0.5 to 1:5.

5.

13. The method for regenerating the positive electrode active material as described in claim 5 or 6, wherein, The washing step (c) includes mixing the annealed or ground positive electrode active material with the washing solution and filtering it; and The solid positive electrode active material obtained after filtration is dried.

14. The method for regenerating the positive electrode active material as described in claim 5 or 6, wherein, In the surface coating of step (d), the surface is coated with at least one of a metal, organometallic and carbon component in a solid or liquid manner, and then heat-treated at 100°C to 1200°C.

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