Method for regenerating cathode active material and regenerated cathode active material manufactured therefrom

Abstract

The present invention relates to a method for manufacturing a regenerated cathode active material and a cathode active material manufactured therefrom and, more specifically, to a method for manufacturing a regenerated cathode active material and a cathode active material manufactured therefrom, the method comprising the steps of: (a) heat-treating a spent cathode having a cathode active material layer formed on a current collector to thermally decompose a binder and conductive agent in the active material layer, thereby separating the current collector from the cathode active material layer and recovering the cathode active material within the cathode active material layer; (b) adding a lithium precursor to the recovered cathode active material and annealing same at 400 to 1000 °C for 8 to 12 hours; and (c) washing the annealed cathode active material with a cleaning solution.

Description

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

[0001] The present invention relates to a method for regenerating a positive electrode active material and a regenerated positive electrode active material manufactured therefrom, and more particularly, to a method for regenerating a positive electrode active material including single particles recovered after heat-treating a waste positive electrode and then adding a lithium precursor directly thereto without a shear washing process and annealing the positive electrode active material at a predetermined temperature for a predetermined time, thereby reducing residual lithium on the surface of the positive electrode active material and restoring the crystal structure and grain size of the positive electrode active material to the level of a new positive electrode active material, thereby producing a positive electrode active material having excellent efficiency, lifespan characteristics, and resistance characteristics when applied to a lithium secondary battery, and a method for regenerating a positive electrode active material in which no acid is used in the recovery and regeneration process, which is environmentally friendly, and thus neutralization and wastewater treatment are not required, and thus process costs are reduced, and since the positive electrode active material is regenerated as is without decomposition, no metal elements are discarded, and since no organic solvent is used, there is no generation of toxic gases or risk of explosion, and a shear washing process is omitted, and since a single particle positive electrode active material is directly regenerated from a waste positive electrode, the economy and productivity are greatly improved.

[0002] 〔Cross-citation with the applicant(s)〕

[0003] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0029793, filed February 29, 2024, and Korean Patent Application No. 10-2025-0004744, filed January 13, 2025, which is hereby incorporated by reference in its entirety.

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

[0005] The positive electrode active material layer mainly uses lithium oxide as an active material, and the negative electrode active material layer mainly uses carbon material as an active material. Lithium oxides such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compound (LiFePO4) are used. Among these, lithium cobalt oxide has the advantages of high operating voltage and excellent capacity characteristics, but the price of cobalt as a raw material is high, and the supply is unstable, making it difficult to commercially apply it to large-capacity batteries. In addition, lithium nickel oxide has poor structural stability, making it difficult to implement sufficient life characteristics. On the other hand, lithium manganese oxide has excellent stability but has the problem of poor capacity characteristics. Therefore, in order to complement the problems of the lithium transition metal oxides, lithium composite transition metal oxides containing two or more transition metals have been developed, and among them, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0006] However, lithium nickel cobalt manganese oxide has the problem that particle breakage easily occurs during the rolling process during the manufacture of the positive electrode, and cracks occur inside the particles during the charge / discharge process, which increases the contact area with the electrolyte, increases gas generation and active material degradation due to side reactions with the electrolyte, and thus reduces the life characteristics.

[0007] To improve this, lithium nickel cobalt manganese oxide, which is composed of high-strength single particles, is applied to the positive electrode, but its high strength makes it difficult to recover after use, and even if recovered, there is a problem that battery performance is reduced due to problems such as decreased crystallinity.

[0008] Meanwhile, since the positive electrode contains rare metals such as cobalt, nickel, or manganese, much research is being conducted to recover and recycle rare metals from the positive electrode of a lithium secondary battery that is discarded after use or from positive electrode scrap generated during the lithium secondary battery manufacturing process (hereinafter referred to as “spent positive electrode”).

[0009] Conventional techniques for recovering rare metals such as cobalt, nickel, or manganese from spent anodes mostly involve dissolving the spent anodes in hydrochloric acid, sulfuric acid, or nitric acid, and then extracting cobalt, manganese, nickel, etc. with an organic solvent to then use them as raw materials for synthesizing cathode active materials.

[0010] However, the method of extracting rare metals using acids has the problem of environmental pollution, requires a neutralization process and a wastewater treatment process, which significantly increases the process cost, and has the disadvantage of not being able to recover lithium, the main metal of the positive electrode active material.

[0011] To overcome these shortcomings, a method of directly regenerating the positive electrode active material from the spent positive electrode without decomposing it (direct recycled method) has been recently studied, and four types of this method have been introduced, including calcination, solvent dissolution, aluminum foil dissolution, and crushing and screening.

[0012] However, although the above-mentioned firing method is a simple process, it has the disadvantages of generating foreign substances on the surface of the regenerated positive electrode active material that reduce the output performance of the battery, generating waste gas, and consuming a lot of energy.

[0013] In addition, the above solvent dissolution method can obtain a regenerated positive electrode active material with a relatively clean surface, but has the disadvantage of poor stability due to the solvent such as N-methyl-2-pyrrolidone (NMP) used to dissolve the binder being a toxic gas and having a risk of explosion, and requiring an expensive solvent recovery process.

[0014] In addition, the above aluminum foil melting method has good process stability, low process cost, and easy binder removal, but has the disadvantages of generating foreign substances that are difficult to remove on the surface of the regenerated positive electrode active material, and generating hydrogen gas during the process of removing the aluminum foil, which poses a risk of explosion.

[0015] Lastly, although the above crushing and screening method has the advantage of being the simplest process, it has the disadvantages of being difficult to completely separate the current collector and the positive electrode active material, the particle size distribution of the positive electrode active material changes during the crushing process, and the binder remains, which deteriorates the battery characteristics of the regenerated positive electrode active material.

[0016] Therefore, there is an urgent need to develop a method for safely and environmentally friendly regeneration of single-particle cathode active materials without waste of metal elements from waste cathodes containing single-particle cathode active materials, with a low process cost and without degradation of output performance.

[0017] In order to solve the problems of the prior art as described above, the present invention provides a method for regenerating a cathode active material, wherein a lithium precursor is added directly to a cathode active material containing single particles recovered after heat treatment of a waste cathode without a shear washing process and annealing is performed at a predetermined temperature for a predetermined time, thereby reducing residual lithium on the surface of the cathode active material and restoring the crystal structure and grain size of the cathode active material to the level of a new cathode active material, thereby providing a cathode active material with excellent efficiency, lifespan characteristics, and resistance characteristics when applied to a lithium secondary battery, and further, since no acid is used in the recovery and regeneration process of the cathode active material, it is environmentally friendly, and since neutralization and wastewater treatment are not required, the process cost is reduced, and since the cathode active material is regenerated as it is without decomposition, no metal elements are discarded, and since no organic solvent is used, there is no generation of toxic gases or risk of explosion, and since a shear washing process is omitted and single-particle cathode active material is directly regenerated from a waste cathode, the economy and productivity are greatly improved.

[0018] In addition, the present invention aims to provide a secondary battery having excellent initial discharge capacity and capacity characteristics.

[0019] The above and other objects of the present invention can all be achieved by the present invention described below.

[0020] In order to achieve the above object, I) the present invention provides a method for regenerating a positive electrode active material, characterized by comprising the steps of: (a) heat-treating a waste positive electrode having a positive electrode active material layer including a single-particle positive electrode active material formed on a current collector to thermally decompose a binder and a conductive agent in the positive electrode active material layer, thereby separating the current collector from the positive electrode active material layer and recovering the positive electrode active material including single particles in the active material layer; (b) adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C for 8 to 12 hours; and (c) washing the annealed positive electrode active material with a washing solution; or (a) heat-treating a waste positive electrode having a positive electrode active material layer including a single-particle mid-nickel positive electrode active material formed on a current collector to thermally decompose a binder and a conductive agent in the active material layer, thereby separating the current collector from the positive electrode active material layer and recovering the single-particle mid-nickel positive electrode active material in the active material layer; (b) a step of adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C for 8 to 12 hours; and (c) a step of washing the annealed positive electrode active material with a washing solution. A method for regenerating a single-particle mid-nickel positive electrode active material is provided.

[0021] In this description, the mid-nickel positive electrode active material may mean a positive electrode active material containing nickel in an amount of 40 mol% or more, specifically 40 to 70 mol%, based on 100 mol% of total metals excluding lithium, i.e., 100 mol% of total transition metals.

[0022] II) In the above I), the positive electrode active material includes at least one selected from the group consisting of 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, and may include 40 mol% or more of Ni based on 100 mol% of the total of the remaining metals excluding Li.

[0023] III) In the above I) or II), the heat treatment in step (a) can be performed at 300 to 650°C.

[0024] IV) In the above I) to III), the positive electrode active material recovered in step (a) can be provided for annealing without washing.

[0025] V) In the above I) to IV), in the step (b), the lithium precursor can be added in an amount at least reduced from the molar ratio of lithium in the positive electrode active material in the step (a) based on the amount of lithium in the recovered positive electrode active material.

[0026] VI) In the above I) to V), the lithium precursor may include at least one of LiOH, Li2CO3, LiNO3, and Li2O.

[0027] VII) In the above I) to VI), the washing in step (c) may include a step of mixing the annealed positive electrode active material and the washing solution and then filtering them, and a step of drying the positive electrode active material in the solid content obtained after the filtering.

[0028] VIII) In the above I) to VII), the washing solution may be water or a basic lithium compound aqueous solution.

[0029] IX) In the above I) to VIII), the method for regenerating the positive electrode active material may include a step of surface-coating the washed positive electrode active material to obtain a reusable positive electrode active material.

[0030] X) In the above I) to IX), the surface coating can be performed by coating at least one of a metal, an organic metal, and a carbon component on the surface in a solid or liquid manner and then heat-treating at 100 to 1200°C.

[0031] XI) In the above I) to X), the positive electrode active material regenerated according to the positive electrode active material regeneration method has a D5 value of 1.95 ㎛ or more in the particle size distribution (PSD), or D 95 The value may be greater than 7.11 ㎛.

[0032] In addition, XII) The present invention is at least one selected from the group consisting of a lithium nickel oxide (LNO)-based cathode active material, a nickel-cobalt-manganese (NCM)-based cathode active material, a nickel-cobalt-aluminum (NCA)-based cathode active material, and a nickel-cobalt-manganese-aluminum (NCMA)-based cathode active material, and includes a single particle, and / or has an a-axis lattice constant of 2.8763 to 2.8783 Å, a c-axis lattice constant of 14.200 to 14.250 Å, and a crystal grain size of 148 nm or more, and / or a D5 value of 1.95 ㎛ or more on a particle size distribution (PSD), or D 95 A positive electrode active material is provided, characterized by a value of 7.11 ㎛ or more.

[0033] XIII) In the above XII), the positive electrode active material may have a D50 value of 3.45 to 3.91 ㎛ in particle size distribution (PSD).

[0034] XIV) In the above XII) or XIII), the positive electrode active material may include a total of 1.09 wt% or less of LiOH and Li2CO3.

[0035] XV) In the above XII) to XIV), the positive electrode active material may be more than 70 mol% based on 100 mol% of the total of the remaining metals excluding Li.

[0036] XVI) In the above XII) to XV), the surface of the positive electrode active material may be coated with a coating agent containing metal or carbon.

[0037] XVII) In the above XII) to XVI), the positive electrode active material may be a regenerated positive electrode active material.

[0038] In addition, the present invention provides a secondary battery characterized in that it includes a positive electrode active material of any one of XV) to XVII).

[0039] According to the present invention, by adding a lithium precursor directly to a cathode active material including single particles recovered after heat treatment of a waste cathode and annealing it at a predetermined temperature for a predetermined time without a shear washing process, residual lithium on the surface of the cathode active material is reduced, and the crystal structure and grain size of the cathode active material are restored to the level of a new cathode active material, thereby providing a cathode active material with excellent efficiency, life characteristics, and resistance characteristics.

[0040] In addition, it is possible to directly regenerate single-particle positive electrode active materials from waste positive electrodes without deterioration of battery performance, is environmentally friendly because no acid is used in the recovery and regeneration process of positive electrode active materials, and thus neutralization and wastewater treatment are not required, reducing process costs, and since the positive electrode active materials are regenerated as they are without decomposition, no metal elements are discarded, and since no organic solvent is used, there is no generation of toxic gases or risk of explosion, and in particular, the shear washing process is omitted, and it is possible to directly regenerate single-particle positive electrode active materials from waste positive electrodes, thereby greatly improving economic feasibility and productivity.

[0041] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description given below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be construed as being limited to the matters described in these drawings.

[0042] Figure 1 is a drawing showing anode scrap that is discarded after cutting an electrode plate from a cathode sheet.

[0043] Figure 2 is an SEM photograph of the positive electrode active material regenerated in Example 1.

[0044] Figure 3 is an SEM photograph of the positive electrode active material regenerated in Example 2.

[0045] Figure 4 is an SEM photograph of the positive electrode active material regenerated in Comparative Example 1.

[0046] Figure 5 is an SEM photograph of the positive electrode active material regenerated in Comparative Example 2.

[0047] Figure 6 is an SEM photograph of the positive electrode active material regenerated in Comparative Example 3.

[0048] Figure 7 is an SEM photograph of the positive electrode active material regenerated in Comparative Example 4.

[0049] Figure 8 is an SEM photograph of a new positive electrode active material of a reference example.

[0050] Figure 9 is a flowchart for a regeneration process of a positive electrode active material according to the present invention.

[0051] The present inventors, while studying a method for directly regenerating single-particle positive electrode active materials from waste positive electrodes without decomposing them (direct recycled method) to regenerate positive electrode active materials with excellent rate performance, etc., have confirmed that when single-particle positive electrode active materials recovered by heat treatment of waste positive electrodes are directly added with a lithium precursor without a shear washing process and annealed at a predetermined temperature for a predetermined period of time, residual lithium on the surface of the regenerated single-particle positive electrode active material is reduced, and the crystal structure and grain size of the regenerated single-particle positive electrode active material are restored to the level of a new positive electrode active material, thereby improving the efficiency, life characteristics, and resistance characteristics of the manufactured lithium secondary battery. Based on this, they have devoted themselves to further research and completed the present invention.

[0052]

[0053] Hereinafter, the regenerative positive electrode active material of the present invention, the regeneration method thereof, and the secondary battery including the same are described in detail.

[0054] However, the terms or words used in this specification and claims cannot be interpreted as limited to their usual or dictionary meanings, and should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own application in the best way. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only one embodiment of the present invention and do not represent all of the technical idea of ​​the present invention, and it should be understood that there may be various equivalents and modified examples that can replace them, and that they can be arranged, replaced, combined, separated, or designed in various other configurations.

[0055] All technical and scientific terms used in this document, unless otherwise defined, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains.

[0056]

[0057] Method for regenerating single-particle cathode active material

[0058] The method for regenerating a positive electrode active material of the present invention is characterized by including the steps of: (a) heat-treating a waste positive electrode having a positive electrode active material layer including a single-particle positive electrode active material formed on a current collector to thermally decompose a binder and a conductive agent in the active material layer, thereby separating the current collector from the positive electrode active material layer and recovering the positive electrode active material including single particles in the positive electrode active material layer; (b) adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C for 8 to 12 hours; and (c) washing the annealed positive electrode active material with a washing solution. In this case, residual lithium on the surface of the positive electrode active material is reduced, and the crystal structure and grain size of the positive electrode active material are restored to the level of a new positive electrode active material, thereby providing a regenerated single-particle positive electrode active material having excellent efficiency, cycle life characteristics, and resistance characteristics of a manufactured lithium secondary battery. In addition, it is environmentally friendly because it does not use acid in the process of recovering and regenerating the positive electrode active material, and the process cost is reduced because neutralization and wastewater treatment are not required. In addition, the positive electrode active material is regenerated as it is without being decomposed, so there are no discarded metal elements. In addition, since no organic solvent is used, there is no risk of generating toxic gases or explosion. In particular, it has the advantage of greatly improving economic efficiency and productivity because single-particle positive electrode active material can be easily and directly regenerated from the spent positive electrode without deteriorating battery performance.

[0059]

[0060] In addition, the method for regenerating a positive electrode active material of the present invention is characterized by including the steps of: (a) heat-treating a waste positive electrode having a positive electrode active material layer including a single-particle mid-nickel positive electrode active material formed on a current collector to thermally decompose a binder and a conductive agent in the positive electrode active material layer, thereby separating the current collector from the positive electrode active material layer and recovering the positive electrode active material including single particles in the active material layer; (b) adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C for 8 to 12 hours; and (c) washing the annealed positive electrode active material with a washing solution. In this case, residual lithium on the surface of the positive electrode active material is reduced, and the crystal structure and grain size of the positive electrode active material are restored to the level of a new positive electrode active material, thereby providing a regenerated single-particle mid-nickel positive electrode active material having excellent efficiency, cycle life characteristics, and resistance characteristics of a manufactured lithium secondary battery. In addition, it is environmentally friendly because it does not use acid in the process of recovering and regenerating the positive electrode active material, and the process cost is reduced because neutralization and wastewater treatment are not required. In addition, the positive electrode active material is regenerated as it is without being decomposed, so there are no discarded metal elements. In addition, since no organic solvent is used, there is no risk of generating toxic gases or explosion. In particular, it has the advantage of greatly improving economic efficiency and productivity because single-particle positive electrode active material can be easily and directly regenerated from the spent positive electrode without deteriorating battery performance.

[0061]

[0062] Below, the method for regenerating positive electrode active materials is explained in detail step by step.

[0063]

[0064] (a) A step of recovering a single particle cathode active material from a waste cathode.

[0065] According to the present invention, the step of (a) recovering a single-particle positive electrode active material from a waste positive electrode may preferably include a step of heat-treating a waste positive electrode having a positive electrode active material layer including a single-particle positive electrode active material formed on a current collector to thermally decompose a binder and a conductive material within the active material layer, thereby separating the current collector from the positive electrode active material layer and recovering the positive electrode active material including single particles within the positive electrode active material layer. In the case of positive electrode active material recovered under such conditions, the process is simple and has the effect of cleanly removing the binder, conductive material, and current collector.

[0066]

[0067] As another example, the step of recovering a positive electrode active material from a waste positive electrode according to the present invention (a) may preferably include a step of heat-treating a waste positive electrode having a positive electrode active material layer including a single-particle mid-nickel positive electrode active material formed on a current collector to thermally decompose a binder and a conductive material in the active material layer, thereby separating the current collector from the positive electrode active material layer and recovering the single-particle mid-nickel positive electrode active material in the active material layer. In the case of a mid-nickel positive electrode active material recovered under such conditions, the process is simple and has the effect of cleanly removing the binder, conductive material, and current collector.

[0068]

[0069] The above-mentioned waste positive electrode may preferably be a positive electrode separated from a lithium secondary battery discarded after use, a defective positive electrode sheet or positive electrode scrap generated in a lithium secondary battery manufacturing process, and more preferably, a positive electrode scrap remaining after punching out a positive electrode plate from a positive electrode sheet.

[0070] The positive electrode active material layer of the above step (a) may preferably include a positive electrode active material, a binder, and a conductive material.

[0071] The above-described positive electrode active material may be at least one selected from the group consisting of lithium cobalt oxide such as LiCoO2 (hereinafter referred to as 'LCO'); lithium manganese oxide such as LiMnO2 or LiMn2O4; lithium iron phosphate compound such as LiFePO4; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide such as LiNiO2; nickel manganese-based lithium composite metal oxide in which some of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and NCM-based lithium composite transition metal oxide in which some of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co), and more preferably, nickel manganese-based lithium composite metal oxide, NCM-based lithium composite transition metal oxide, or a mixture thereof, in which case, excellent reversible capacity and thermal stability are achieved.

[0072] As another specific example, the positive electrode active material may be a compound represented by the following chemical formula 1, in which case it has excellent effects of reversible capacity and thermal stability.

[0073] [Chemical Formula 1]

[0074] Li a Ni x Mn y Co z M w O 2+δ

[0075] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ0.02, x+y+z+w=1이다.)

[0076]

[0077] The above-mentioned positive electrode active material may include, for example, 40 mol% or more, 40 to 95 mol%, and more preferably 40 to 70 mol% of Ni (in which case the positive electrode active material may be referred to as a mid-nickel positive electrode active material) based on 100 mol% of the total metals excluding Li, and within this range, the initial discharge capacity, output performance, capacity characteristics, and resistance characteristics of the applied lithium secondary battery are excellent.

[0078] In this description, the nickel content is not particularly limited when measured using a measurement method such as IC (Ion Chromatography) commonly used in the technical field to which the present invention belongs, and specific examples thereof include an IC-ICP (Inductively Coupled Plasma) analysis device, an IC-ICP-MS analysis device, or an IC-ICP-AEC analysis device.

[0079]

[0080] The positive electrode active material recovered in the above step (a) may preferably be a single particle, and more preferably may not include secondary particles. In this case, there is no particle breakage during the electrode manufacturing process, so there is no deterioration in battery performance due to fine particles, and there is an effect of providing a regenerated positive electrode active material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation during charge and discharge.

[0081] The above single particle may be a single particle commonly used in the technical field to which the present invention pertains as long as it follows the definition of the present invention, and may be a particle composed of 30 or fewer nodules, for example, 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, there is no particle breakage during the electrode manufacturing process, so there is no deterioration of battery performance due to fine powder, and there is an effect of providing a regenerative positive electrode active material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge.

[0082] In this description, a nodule refers to a particle unit body that constitutes a single particle, and may refer to a single crystal lacking a crystalline grain boundary, or a polycrystal in which no grain boundary exists in appearance when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope (SEM) or an electron backscatter diffraction pattern analyzer (EBSD).

[0083] In this description, the number of nodules means the average number of nodules of positive electrode active material particles, and a positive electrode including positive electrode active material is cut by an ion milling method, and a cross-sectional image in the thickness direction of the cut positive electrode is obtained using a scanning electron microscope (SEM), and then at least 30 particles are selected for each of the positive electrode active material particles having the largest particle size and the smallest particle size within the cross-sectional image, and then the number of nodules in the cross-section of each positive electrode active material particle is measured through SEM image analysis, and the arithmetic mean is obtained.

[0084]

[0085] The above single particles have an average particle diameter (D 50 ) may be preferably 2 to 10 μm, more preferably 2 to 8 μm, and even more preferably 3 to 6 μm.

[0086] In this paper, the average particle diameter (D 50 ) can be defined as the particle size corresponding to 50% of the volume accumulation in the particle size distribution (PSD). The average particle size (D 50 ) can be measured using, for example, a laser diffraction method. Specifically, the average particle diameter (D) of the positive electrode active material 50 ) is a method of measuring the average particle diameter (D) corresponding to 50% of the volume accumulation amount in the measuring device after dispersing the particles of the positive electrode active material in a dispersion medium and introducing them into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiating them with ultrasonic waves of about 28 kHz at an output of 60 W. 50 ) can be produced.

[0087]

[0088] The above conductive material may be, for example, a carbon-based conductive material, and preferably, carbon black, CNT, or a mixture thereof.

[0089] The binder may be, for example, a polymer binder, preferably polyvinylidene fluoride (PVdF), acrylonitrile-butadiene rubber (NBR) or a mixture thereof, and more preferably polyvinylidene fluoride.

[0090]

[0091] In the above step (a), the heat treatment can be performed at, for example, 300 to 650°C, preferably 400 to 600°C, more preferably 500 to 600°C, and even more preferably 530 to 580°C, and within this range, the current collector does not melt, and only the binder, etc. is removed, so that the positive electrode active material is easily separated from the current collector.

[0092] The above heat treatment can be performed at a temperature increase rate of, for example, 1 to 20°C / min, preferably 3 to 10°C / min, and more preferably 3 to 7°C / min, and can be performed within this range without causing a strain on the heat treatment equipment, and has the advantage of not causing thermal shock to the anode scrap.

[0093]

[0094] The above heat treatment can be carried out, for example, in an air or oxygen atmosphere, and preferably carried out under air. In this case, the carbon component in the binder and conductive material reacts with oxygen and disappears into gases such as CO and CO2, so there is an advantage in that both the binder and conductive material are removed.

[0095] The oxygen may have a purity of, for example, 59% or more, preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and still more preferably 90 to 99%, and within this range, there is an advantage in that the stability of Ni in the regenerated positive electrode active material is increased while the binder and conductive agent are removed without remaining.

[0096] The purity % of the above oxygen may be volume % or mol %.

[0097] The purity of the oxygen of this invention is not particularly limited when measured by a measurement method commonly used in the technical field to which the present invention belongs.

[0098]

[0099] The air or oxygen can be supplied at a rate of, for example, 1 to 20 L / min, preferably 1 to 15 L / min, more preferably 2 to 10 L / min, and even more preferably 3 to 7 L / min, and within this range, the positive electrode active material can be easily separated from the current collector, and the separated positive electrode active material can be easily sorted into a powder form.

[0100]

[0101] The heat treatment time may be preferably 10 minutes to 5 hours, more preferably 30 minutes to 5 hours, even more preferably 30 minutes to 2 hours, and even more preferably 30 minutes to 1 hour, and within this range, the current collector does not melt, and only the binder, etc. is removed, so that the positive electrode active material is easily separated from the current collector.

[0102] In this description, the heat treatment time refers to the time spent at the corresponding heat treatment temperature, and the time spent reaching the corresponding heat treatment temperature is not counted.

[0103] The positive electrode active material recovered in the above step (a) can preferably be provided directly to the annealing step without shear washing, and in this case, the washing process is omitted, thereby preventing lithium loss, so that the crystal structure of the positive electrode active material is easily changed in the subsequent step, thereby improving the charging capacity, resistance characteristics, and capacity characteristics of the battery, and there is an advantage in that the process is simplified without generating wastewater, thereby greatly improving economic efficiency and productivity.

[0104]

[0105] In this description, pre-washing may mean washing performed before introducing a lithium precursor, and post-washing may mean washing performed after introducing a lithium precursor and annealing.

[0106]

[0107] Referring to Fig. 1, a positive electrode sheet (30) is manufactured by coating a positive electrode active material layer (20) including a positive electrode active material, a conductive material, a binder, etc. on a long sheet-shaped positive electrode current collector, aluminum foil (10), and then the positive electrode sheet (30) is punched to a certain size to produce a positive electrode plate (40), and the remaining portion is then used to produce positive electrode scrap (50). The punching is one means of cutting the positive electrode sheet.

[0108] In addition, the positive electrode active material layer (20) is formed by coating a slurry containing a mixture of a positive electrode active material, a conductive material, a binder, and a solvent on aluminum foil (10). Since the slurry is very sensitive to the environment such as temperature, it is difficult to determine the coating conditions. Therefore, waste positive electrode sheets such as positive electrode scrap (50) are generated until conditions for manufacturing a positive electrode sheet (30) of the desired quality are found through a predetermined test.

[0109] For reference, in the following examples, anode scrap (50) was used as the positive electrode.

[0110]

[0111] (b) A step of adding a lithium precursor to the recovered positive electrode active material and annealing it.

[0112] The method for regenerating a positive electrode active material of the present invention includes (b) a step of adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C for 8 to 12 hours, in which case the crystal grain size of the regenerated positive electrode active material increases and the crystal structure is restored to the level of a new positive electrode active material, thereby providing a positive electrode active material having excellent efficiency, life characteristics, and resistance characteristics, and the process of pre-washing the recovered positive electrode active material is omitted, thereby greatly improving economic efficiency and productivity.

[0113]

[0114] The above-mentioned annealing time is, for example, 8 to 12 hours, preferably 9 to 12 hours, more preferably 9 to 11 hours, and as a specific example, around 10 hours. Within this range, the crystal structure of the single-particle positive electrode active material is sufficiently recovered, so that the crystal grain size increases and the crystal structure is recovered to the level of a new positive electrode active material, thereby providing excellent effects in terms of battery efficiency, life characteristics, and resistance characteristics. If the above-mentioned annealing time is exceeded, the residual LiOH amount increases, resulting in deterioration in battery performance.

[0115]

[0116] The above (b) annealing step may preferably be performed by adding a lithium precursor to the recovered positive electrode active material and annealing in an air or oxygen (O2) atmosphere, and preferably by annealing in air. In this case, there is an effect of improving the battery characteristics of the regenerated positive electrode active material by improving the crystallinity, such as increasing the crystallinity of the positive electrode active material or restoring the crystal structure.

[0117]

[0118] The above annealing temperature may be preferably 500 to 900°C, more preferably 600 to 880°C, and even more preferably 700 to 800°C, and in this case, there is an effect of improving the battery characteristics of the regenerated positive electrode active material by improving the crystallinity, such as increasing the crystallinity of the positive electrode active material or restoring the crystal structure.

[0119]

[0120] The above lithium precursor may preferably be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, and Li2O.

[0121]

[0122] In the step (b), the lithium precursor can be added at least in an amount reduced from the molar ratio of lithium in the positive electrode active material of the step (a) based on the amount of lithium in the recovered positive electrode active material, and as a specific example, when the recovered positive electrode active material of the step (a) is a positive electrode active material represented by the chemical formula 1, the amount is an amount that results in a molar ratio of lithium of 0.0001 to 0.2 with respect to a molar ratio of lithium of 1 in the positive electrode active material, preferably an amount that results in a molar ratio of lithium of 0.001 to 0.1, more preferably an amount that results in a molar ratio of lithium of 0.001 to 0.07, even more preferably an amount that results in a molar ratio of lithium of 0.001 to 0.03, even more preferably an amount that results in a molar ratio of lithium of 0.001 to 0.02, particularly preferably an amount that results in a molar ratio of lithium of 0.005 to 0.017, and even more preferably an amount that results in a molar ratio of lithium of 0.007 to 0.015, and as a most preferred example It can be added in an amount that makes the molar ratio of lithium 0.009 to 0.013, and within this range, the lithium that is deficient in the regenerated positive electrode active material is supplemented, thereby improving the crystallinity, such as increasing crystallinity or restoring the crystal structure, thereby improving the battery characteristics of the regenerated positive electrode active material.

[0123] As another example, the lithium precursor may be added in an amount corresponding to 1 to 40 mol% when the total lithium contained in the raw material positive electrode active material is 100 mol%, preferably may be added in an amount corresponding to 1 to 30 mol%, and more preferably may be added in an amount corresponding to 7 to 20 mol%, and within this range, no residual precursor that may increase the resistance of the regenerated positive electrode active material remains, which is very useful for improving battery characteristics, and has an economic advantage because the crystal structure can be restored with a smaller amount of lithium precursor than before.

[0124]

[0125] The above annealing temperature can be controlled within a limited range depending on the melting point of the lithium precursor. For example, in the case of LiCO3, the melting point is 723°C, so annealing can be performed at preferably 700 to 900°C, more preferably 710 to 780°C, and in the case of LiOH, the melting point is 462°C, so annealing can be performed at preferably 400 to 600°C, more preferably 450 to 480°C. Within this range, the crystal structure is recovered, so that the efficiency, life characteristics, and resistance characteristics of the battery are excellent.

[0126] The above annealing temperature may preferably be a temperature exceeding the melting point of the lithium precursor, but if it exceeds 1000°C, thermal decomposition of the positive electrode active material may occur, resulting in a decrease in battery performance, so it may preferably be 1000°C or lower.

[0127] The above annealing temperature can be reached at a heating rate of preferably 1 to 10°C / min, more preferably 1 to 7°C / min, and even more preferably 2 to 4°C / min, in which case the crystallinity of the regenerated positive electrode active material is further increased, thereby having the effect of improving the battery characteristics of the regenerated positive electrode active material.

[0128] The above annealing step includes, for example, a cooling process, and the cooling process may be, for example, natural cooling within a furnace, in which case the crystallinity of the regenerated positive electrode active material is further increased, thereby having the effect of improving the battery characteristics of the regenerated positive electrode active material.

[0129]

[0130] In this description, annealing may follow the definition used in the technical field to which the present invention belongs, and as a specific example, it may be defined as a heat treatment operation to cure deformation or lattice defects and increase crystallinity by heating a positive electrode active material having a deformed structure or lattice defects at a temperature above the recrystallization temperature, at which atoms of the main component can sufficiently diffuse and move, for an appropriate period of time.

[0131]

[0132] (c) Step of washing the annealed positive electrode active material (post-washing)

[0133] The method for regenerating a positive electrode active material of the present invention includes (c) a step of washing the annealed positive electrode active material with a washing solution, in which case, a lithium precursor that is likely to remain on the surface of the positive electrode active material is removed with the washing solution, thereby having the advantage of preventing a decrease in battery performance and gas generation due to a subsequent reaction between the residual lithium precursor and the electrolyte.

[0134] The above washing may preferably include a step of mixing the annealed positive electrode active material and the washing solution, followed by a step of filtering, and a step of drying the positive electrode active material in the solid content obtained after the filtering. In this case, there is an effect of effectively removing excess lithium that is likely to remain in the positive electrode active material.

[0135] The above washing may preferably include a step of mixing the annealed positive electrode active material with a washing solution and then filtering it, and a step of drying the positive electrode active material in a solid content obtained after the filtering. In this case, lithium precursors such as LiOH, Li2CO3, etc., which are likely to remain on the surface of the positive electrode active material, are effectively removed with a small amount of washing solution, thereby reducing wastewater.

[0136]

[0137] The annealed active material and the cleaning solution may be mixed, for example, at a weight ratio of 1:0.5 to 1:5.5, preferably at a weight ratio of 1:0.5 to 1:4.5, more preferably at a weight ratio of 1:0.5 to 1:3.5, and even more preferably at a weight ratio of 1:0.5 to 1:2.5. In this case, lithium precursors such as LiOH and Li2CO3, which are likely to remain on the surface of the positive electrode active material, are effectively removed with a small amount of the cleaning solution, thereby reducing wastewater.

[0138]

[0139] The above-mentioned washing solution may preferably be water or an alkaline lithium compound aqueous solution, and more preferably, water may be used as the washing solution. In this case, in order to suppress the cation mixing phenomenon that is likely to occur in a regenerated positive electrode active material, especially a regenerated mid-nickel positive electrode active material, lithium precursors such as LiOH, Li2CO3, etc., which are more likely to remain due to excessively added lithium, are effectively removed with a small amount of washing solution, and there is an effect of significantly improving the output performance of the battery without requiring wastewater treatment.

[0140] The water is preferably distilled water or deionized water, and in this case, lithium precursors such as LiOH and Li2CO3, which are likely to remain on the surface of the regenerated positive electrode active material, are effectively removed with a small amount of washing liquid, thereby reducing waste water and significantly improving the output performance of the battery.

[0141] The above basic lithium compound aqueous solution may preferably contain more than 0 wt% and less than 15 wt% of a lithium compound, more preferably more than 0 wt% and less than 10 wt% of a lithium compound, and in this case, lithium precursors such as LiOH and Li2CO3, which are likely to remain on the surface of the positive electrode active material, are effectively removed with a small amount of washing solution, thereby reducing wastewater and significantly improving the output performance of the battery.

[0142]

[0143] The mixing of the annealed positive electrode active material and the cleaning solution is preferably performed by stirring, and the stirring is not particularly limited, but mechanical stirring or ultrasonic stirring may be used.

[0144] The above stirring can be preferably performed for less than 30 minutes, more preferably less than 20 minutes, even more preferably less than 15 minutes, and even more preferably 5 to 10 minutes, and within this range, residual lithium is effectively removed.

[0145]

[0146] (d) A step of obtaining a reusable positive electrode active material by surface-coating the washed positive electrode active material.

[0147] The method for regenerating a positive electrode active material of the present invention optionally includes a step of (d) surface-coating a washed positive electrode active material to obtain a reusable positive electrode active material, in which case the excellent properties of the positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0148] The surface coating is preferably performed by coating a coating agent containing at least one of a metal, an organic metal, and a carbon component on the surface in a solid or liquid manner and then heat-treating at 100 to 1200°C. In this case, the properties of the excellent positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0149]

[0150] The coating agent including the above metal may be a coating agent including at least one selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V and Y, more preferably a coating agent including at least one selected from the group consisting of B, W, Al, Ti and Mg, even more preferably a coating agent including boron (B), tungsten (W) or a mixture thereof, and even more preferably a coating agent containing tungsten (W) and boron (B), and a specific example may be a coating agent containing tungsten boride (WB), in which case there is an effect of improving resistance characteristics and life characteristics.

[0151] The above boron-containing coating agent is preferably H3BO3, B2O3, C6H5B(OH)2, (C6H5O)3B, [CH3(CH2)3O]3B, C 13 H 19 It may be at least one selected from the group consisting of BO3, C3H9B3O6 and (C3H7O)3B, and more preferably H3BO3, in which case there is an effect of improving the resistance characteristics and life characteristics of the lithium secondary battery to which it is applied.

[0152] The coating agent containing the above metal may be, for example, an oxide, acid, etc. containing the metal as an element in the molecule.

[0153] The coating agent containing the above-mentioned organic metal is not particularly limited as long as it is a coating agent containing an organic metal compound commonly used in the technical field to which the present invention belongs and containing the above-mentioned metal, and a specific example thereof may be a metal alkoxide, etc.

[0154] The coating agent containing the above carbon component is not particularly limited as long as it is a coating agent containing a carbon component commonly used in the technical field to which the present invention belongs, and a specific example thereof may be a sugar such as sucrose.

[0155]

[0156] The coating agent may be included in an amount of 0.001 to 0.3 mol%, for example, based on the components coated on the surface of the actual positive electrode active material excluding the solvent, relative to 1 mol% of the metal in the positive electrode active material before the coating treatment, preferably 0.01 to 0.3 mol%, more preferably 0.01 to 0.15 mol%, even more preferably 0.01 to 0.1 mol%, and even more preferably 0.01 to 0.05 mol%, and within this range, it has the effect of improving structural stability and electrochemical performance while maintaining the excellent properties of the positive electrode active material itself.

[0157]

[0158] The above heat treatment temperature is preferably 100 to 1000°C, more preferably 200 to 1000°C, and even more preferably 200 to 500°C, and within this range, there is an effect of improving structural stability and electrochemical performance without causing performance degradation due to thermal decomposition of the regenerated positive electrode active material.

[0159] The heat treatment time is preferably 1 to 16 hours, more preferably 3 to 7 hours, and within this range, the properties of the excellent positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0160]

[0161] The above coating method is not particularly limited as long as it is a coating method commonly used in the technical field to which the present invention belongs, and may be, for example, a liquid method in which a liquid coating agent is prepared and mixed with a positive electrode active material, a mechanochemical method using the high mechanical energy of ball milling, a fluidized bed coating method, a spray drying method, a precipitation method in which a coating agent is precipitated onto the surface of a positive electrode active material in an aqueous solution state, a method utilizing a reaction between a gaseous coating agent and a positive electrode active material, or a sputtering method.

[0162]

[0163] The above metal, organic metal, and carbon component may be, for example, spherical, plate-shaped, square, or needle-shaped, and such shapes can be controlled by changing process conditions, etc. during the manufacturing process, and the definition of each shape is not particularly limited as long as it follows the definition commonly recognized in the technical field to which the present invention belongs.

[0164] The coating agent preferably has an average diameter of 1 to 1000 nm and a specific surface area of ​​10 to 100 m2 / g, more preferably has an average diameter of 10 to 100 nm and a specific surface area of ​​20 to 100 m2 / g, and is uniformly attached to the surface of the regenerated positive electrode active material within this range, thereby imparting structural stability to the regenerated positive electrode active material, thereby improving problems of deterioration of life characteristics and electrochemical performance due to lattice deformation or collapse of the crystal structure of the positive electrode active material.

[0165] In this description, the average diameter can be measured by a measurement method commonly used in the technical field to which the present invention belongs, and for example, can be measured using a laser diffraction method. Specifically, after dispersing the particles of the positive electrode active material in a dispersion medium, the particles are introduced into a commercially available laser diffraction particle size measuring device such as Microtrac MT 3000, and ultrasonic waves of about 28 kHz are irradiated with an output of 60 W, and the average particle diameter (D) based on 50% of the particle diameter distribution in the measuring device is measured. 50 ) can be produced.

[0166] In this description, the specific surface area can be measured by a measurement method commonly used in the technical field to which the present invention belongs, for example, by the BET (Brunauer-Emmett-Teller) method, and specifically, can be calculated from the nitrogen gas adsorption amount at liquid nitrogen temperature (77K) using BELSORP-mino II of BEL Japan.

[0167]

[0168] The positive electrode active material regenerated according to the above positive electrode active material regeneration method may have a D5 value of, for example, 1.95 ㎛ or more, preferably 1.96 ㎛ or more, more preferably 1.96 to 2.20 ㎛, and even more preferably 1.98 to 2.1 ㎛ in terms of particle size distribution (PSD), and within this range, it has excellent efficiency, life characteristics, and resistance characteristics.

[0169] The positive electrode active material regenerated according to the above positive electrode active material regeneration method has a particle size distribution (PSD) of D 50 The value may be, for example, 3.45 to 3.91 μm, preferably 3.50 to 3.90 μm, more preferably 3.70 to 3.90 μm, and within this range, excellent effects in efficiency, life characteristics, and resistance characteristics are achieved.

[0170] The positive electrode active material regenerated according to the above positive electrode active material regeneration method has a particle size distribution (PSD) of D 95 The value may be, for example, 7.11 ㎛ or more, preferably 7.15 ㎛ or more, more preferably 7.15 to 7.60 ㎛, and even more preferably 7.15 to 7.55 ㎛, and within this range, there is an excellent effect in efficiency, life characteristics, and resistance characteristics.

[0171]

[0172] In this paper, the particle size distribution can be measured using a laser diffraction particle size measuring device. As a specific example, after the particles of the positive electrode active material are dispersed in a dispersion medium using the laser diffraction method, they are introduced into a laser diffraction particle size measuring device (Microtrac MT 3000) and irradiated with an ultrasonic wave of about 28 kHz at an output of 60 W, and 5% (D5) and 50% (D) of the volume accumulation amount in the measuring device are measured. 50 ) and 95%(D 95 ) was measured. Here, the particle size corresponding to 50% of the volume accumulation was measured as the average particle size (D 50 ) is used.

[0173]

[0174] The positive electrode active material regenerated according to the above positive electrode active material regeneration method may preferably contain LiOH 0.17 wt% or less, more preferably 0.11 wt% or less, even more preferably 0.09 wt% or less, and even more preferably 0.01 to 0.09 wt%, and within this range, it has excellent effects in initial discharge capacity, rate performance, and capacity characteristics.

[0175] The positive electrode active material regenerated according to the above positive electrode active material regeneration method may preferably contain Li2CO3 0.96 wt% or less, more preferably 0.1 to 0.96 wt%, and within this range, the initial discharge capacity and capacity characteristics are excellent.

[0176] The positive electrode active material regenerated according to the above positive electrode active material regeneration method may preferably contain a total of Li2CO3 and LiOH of 1.09 wt% or less, more preferably 1.00 wt% or less, even more preferably 0.98 wt% or less, and even more preferably 0.01 to 0.98 wt%, and within this range, the initial discharge capacity and capacity characteristics are excellent.

[0177] In this paper, the residual Li content can be measured using a pH titrator T5 (Mettler Toledo). Specifically, 5 g of the positive electrode active material is dispersed in 100 ml of distilled water, mixed at 300 rpm for 5 minutes, filtered to remove the active material, and the resulting solution (filtrate) is titrated with a 0.1 M HCl solution, while measuring the change in pH value to obtain a pH titration curve. The obtained pH titration curve is used to calculate the residual LiOH and Li2CO3 amounts in the positive electrode active material.

[0178]

[0179] The positive electrode active material regenerated according to the above positive electrode active material regeneration method may have an a-axis lattice constant measured by XRD analysis of, for example, 2.8763 to 2.8783 Å, preferably 2.8767 to 2.8782 Å, more preferably 2.8770 to 2.8781 Å, and even more preferably 2.8776 to 2.8781 Å, and within this range, there is an effect of recovering a lattice structure similar to that of the raw positive electrode active material.

[0180] The positive electrode active material regenerated according to the above positive electrode active material regeneration method may have a c-axis lattice constant measured by XRD analysis of, for example, 14.200 to 14.250 Å, preferably 14.203 to 14.250 Å, more preferably 14.205 to 14.249 Å, and even more preferably 14.235 to 14.249 Å, and within this range, there is an effect of recovering a lattice structure similar to that of the raw positive electrode active material.

[0181] The cathode active material regenerated according to the above cathode active material regeneration method may have a crystallite size measured by XRD analysis of, for example, 148 nm or more, preferably 149 nm or more, more preferably 149 to 168 nm, even more preferably 149 to 157 nm, and even more preferably 149 to 152 nm. In this case, by annealing at a predetermined temperature for a predetermined time, the crystallite size increases, and the crystal structure of the cathode active material is restored to the level of a new cathode active material, so that there is an advantage of excellent efficiency, life characteristics, and resistance characteristics.

[0182] In this paper, the lattice parameter and crystallite size of the positive electrode active material can be measured by XRD analysis, and specifically, the lattice parameter can be calculated by indexing the data measured through XRD (X-Ray Diffraction) analysis using Cu Kα X-rays through Rietveld refinement, and the crystallite size can be calculated using the XRD measurement data and the Scherrer equation.

[0183] In this description, 'crystalline' means a single crystal particle unit having a regular atomic arrangement.

[0184]

[0185] In addition, the present invention can provide a regenerated positive electrode active material characterized by being manufactured by the above positive electrode active material regeneration method, and when the regenerated positive electrode active material of the present invention is applied, the initial discharge capacity, output performance, capacity characteristics, and resistance characteristics of the battery are excellent.

[0186]

[0187] Single particle cathode active material

[0188] The cathode active material of the present invention is at least one selected from the group consisting of a lithium nickel oxide (LNO) cathode active material, a nickel-cobalt-manganese (NCM) cathode active material, a nickel-cobalt-aluminum (NCA) cathode active material, and a nickel-cobalt-manganese-aluminum (NCMA) cathode active material, and includes single particles, and / or has an a-axis lattice constant of 2.8763 to 2.8783 Å and a c-axis lattice constant of 14.200 to 14.250 Å as measured by XRD analysis, and a crystal grain size of 148 nm or more, and / or a D5 value of 1.95 ㎛ or more on a particle size distribution (PSD), or D 95 It is characterized by a value of 7.11 ㎛ or more. In this case, the residual lithium on the surface of the positive electrode active material is reduced, and the crystal structure of the positive electrode active material is restored to the level of a new positive electrode active material, so when applied to a lithium secondary battery, the efficiency, life characteristics, and resistance characteristics of the battery are excellent.

[0189]

[0190] The above-described positive electrode active material may preferably include at least one selected from the group consisting of lithium cobalt oxide such as LiCoO2 (hereinafter referred to as 'LCO'); lithium manganese oxide such as LiMnO2 or LiMn2O4; lithium iron phosphate compound such as LiFePO4; lithium nickel cobalt aluminum oxide (NCA); lithium nickel oxide such as LiNiO2; nickel manganese lithium composite metal oxide in which some of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and NCM lithium composite transition metal oxide in which some of nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn) and cobalt (Co). In this case, the electrochemical performance, resistance characteristics, and capacity characteristics are excellent.

[0191]

[0192] The above-mentioned positive electrode active material may be a compound represented by the following chemical formula 1 as a specific example, and in this case, it has excellent effects such as electrochemical performance, resistance characteristics, and capacity characteristics.

[0193] [Chemical Formula 1]

[0194] Li a Ni x Mn y Co z M w O 2+δ

[0195] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti and Mg, and 1 <a≤1.1, 0<x<0.95, 0<y<0.8, 0<z<1.0, 0≤w≤0.1, -0.02≤δ≤0.02, x+y+z+w=1이다.)

[0196]

[0197] The above-mentioned positive electrode active material may have a D5 value in terms of particle size distribution (PSD) of, for example, 1.95 ㎛ or more, preferably 1.96 ㎛ or more, more preferably 1.96 to 2.20 ㎛, and even more preferably 1.98 to 2.10 ㎛, and within this range, it has excellent efficiency, life characteristics, and resistance characteristics.

[0198] The above-mentioned positive electrode active material may have a D50 value in terms of particle size distribution (PSD) of, for example, 3.45 to 3.91 ㎛, preferably 3.50 to 3.90 ㎛ or more, more preferably 3.70 to 3.90 ㎛, and within this range, it has excellent efficiency, life characteristics, and resistance characteristics.

[0199] The above-mentioned positive electrode active material may have a D95 value of, for example, 7.11 ㎛ or more, preferably 7.15 ㎛ or more, more preferably 7.15 to 7.60 ㎛, even more preferably 7.15 to 7.55 ㎛, and even more preferably 7.15 to 7.30 ㎛ in terms of particle size distribution (PSD), and within this range, it has excellent effects in terms of efficiency, life characteristics, and resistance characteristics.

[0200]

[0201] The above positive electrode active material may preferably contain a total of Li2CO3 and LiOH of 1.09 wt% or less, more preferably 1.00 wt% or less, even more preferably 0.98 wt% or less, and even more preferably 0.01 to 0.98 wt%, and within this range, excellent initial discharge capacity and capacity characteristics are achieved.

[0202] The above positive electrode active material may preferably contain Li2CO30.96 wt% or less, more preferably 0.1 to 0.96 wt%, and within this range, excellent initial discharge capacity and capacity characteristics are achieved.

[0203] The above positive electrode active material may preferably contain LiOH 0.17 wt% or less, more preferably 0.11 wt% or less, even more preferably 0.09 wt% or less, and even more preferably 0.01 to 0.09 wt%, and within this range, there is an excellent effect in initial discharge capacity, rate performance, and capacity characteristics.

[0204]

[0205] The above-mentioned positive electrode active material may have an a-axis lattice constant measured by XRD analysis of, for example, 2.8763 to 2.8783 Å, preferably 2.8767 to 2.8782 Å, more preferably 2.8770 to 2.8781 Å, and even more preferably 2.8776 to 2.8781 Å, and within this range, there is an effect of recovering a lattice structure similar to that of the raw positive electrode active material.

[0206] The above-mentioned positive electrode active material may have a c-axis lattice constant measured by XRD analysis of, for example, 14.200 to 14.250 Å, preferably 14.203 to 14.250 Å, more preferably 14.205 to 14.249 Å, and even more preferably 14.235 to 14.249 Å, and within this range, there is an effect of recovering a lattice structure similar to that of the raw positive electrode active material.

[0207] The above-mentioned positive electrode active material may have a crystal grain size measured by XRD analysis of, for example, 148 nm or more, preferably 149 nm or more, more preferably 149 to 168 nm, even more preferably 149 to 157 nm, and even more preferably 149 to 152 nm, and within this range, the crystal grain size of the new positive electrode active material is similar to that of the new positive electrode active material, and has the advantage of excellent efficiency, life characteristics, and resistance characteristics, and improved capacity.

[0208]

[0209] The above positive electrode active material preferably contains more than 70 mol% of Ni, more preferably 71 to 95 mol%, and even more preferably 80 to 95 mol%, based on 100 mol% of the total metals other than Li, and has the advantage of excellent battery characteristics within this range.

[0210]

[0211] The above-described positive electrode active material may preferably include single particles, and more preferably does not include secondary particles. In this case, there is no particle breakage during the electrode manufacturing process, so that there is no deterioration in battery performance due to fine particles, and there is an effect of providing a positive electrode active material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation during charge and discharge.

[0212]

[0213] The above-mentioned positive electrode active material may have a surface coated with, for example, a metal or carbon, and preferably may be coated with a metal. In this case, the structural stability of the positive electrode active material is improved without chemical and physical changes in the positive electrode active material itself, thereby improving electrochemical characteristics such as output performance, life characteristics, and capacity. In addition, the physicochemical characteristics of the battery are also improved due to the effect of reducing the amount of residual lithium and reducing pH by substituting a different element on the surface of the positive electrode active material.

[0214]

[0215] The metal may be preferably at least one selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V and Y, more preferably at least one selected from the group consisting of B, W, Al, Ti and Mg, even more preferably boron (B), tungsten (W) or a mixture thereof, even more preferably tungsten (W) and boron (B), and a specific example may be tungsten boride (WB), in which case there is an effect of improving resistance characteristics and life characteristics.

[0216]

[0217] The coating agent may be included, for example, in an amount of 0.001 to 0.3 mol% relative to 1 mol% of metal in the regenerated positive electrode active material before coating treatment, preferably 0.01 to 0.3 mol%, more preferably 0.01 to 0.15 mol%, even more preferably 0.01 to 0.1 mol%, and even more preferably 0.01 to 0.05 mol%, and within this range, there is an effect of improving structural stability and electrochemical performance while maintaining the excellent properties of the positive electrode active material itself.

[0218]

[0219] The above surface coating can be preferably performed by coating a coating agent containing at least one of a metal, an organic metal, and a carbon component on the surface in a solid or liquid manner and then heat-treating at 100 to 1200°C. In this case, the properties of the excellent positive electrode active material itself are maintained as is, while improving structural stability and electrochemical performance.

[0220]

[0221] The above-mentioned positive electrode active material may be, for example, a regenerative positive electrode active material, in which case it has the advantages of excellent economic efficiency and productivity.

[0222]

[0223] The following Figure 9 is a flowchart for a regeneration process of a single-particle positive electrode active material according to one embodiment of the present invention.

[0224]

[0225] Referring to Fig. 9, first, a positive electrode scrap is prepared as a positive electrode (step S10).

[0226] For example, a slurry prepared by mixing a single-particle NCM lithium composite transition metal oxide, carbon black, and polyvinylidene fluoride with NMP (N-methyl pyrrolidone) is coated on aluminum foil and dried in a vacuum oven at approximately 120°C to produce a cathode sheet. After stamping out cathode plates of a certain size, the remaining cathode scrap can be prepared.

[0227] The above-mentioned positive electrode scrap has a positive electrode active material layer on aluminum foil, and the positive electrode active material layer has a structure in which a binder binds the positive electrode active material and the conductive material after the solvent evaporates. Therefore, when the binder is removed, the positive electrode active material is separated from the aluminum foil.

[0228] The NCM-based lithium composite transition metal oxide may be a cathode active material specifically including single-particle mid-nickel.

[0229]

[0230] Next, the prepared positive electrode scrap is crushed into an appropriate size (step S20).

[0231] Here, shredding includes cutting or shredding the positive electrode scrap into a size that is easy to handle. As a specific example, the shredded positive electrode scrap may be 1 cm x 1 cm in size. The shredding may be performed using various dry crushing equipment, such as a hand mill, pin mill, disc mill, cutting mill, or hammer mill, or a high-speed cutter to increase productivity.

[0232] The above crushing can be preferably performed or not, and the size of the pieces, etc. can be determined by considering the characteristics required by the equipment used in the handling of the positive electrode scrap and the subsequent process. For example, if equipment capable of continuous processing is used, the positive electrode scrap must be crushed into smaller pieces because the fluidity must be good.

[0233]

[0234] Next, the positive electrode scrap is heat-treated to recover the positive electrode active material (step S30).

[0235] Here, the heat treatment is performed to thermally decompose the binder within the active material layer. As described above, the binder and conductive material within the active material layer are thermally decomposed into CO2 and H2O and removed through heat treatment. Since the binder is removed, the positive electrode active material is separated from the current collector, and the separated positive electrode active material can be easily sorted into powder form. Therefore, step S30 alone can separate the active material layer from the current collector, and further, the positive electrode active material within the active material layer can be recovered in powder form.

[0236] The above-mentioned recovered positive electrode active material may include single particles, and specifically does not include secondary particles. In this case, there is no particle breakage during the electrode manufacturing process, so there is no deterioration in battery performance due to fine particles, and there is an effect of providing a positive electrode active material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation during charge and discharge.

[0237] The above heat treatment can be performed in air or an oxygen atmosphere, and specifically, it can be performed in air. If the heat treatment is performed in a reducing gas or inert gas atmosphere, the binder and conductive agent are carbonized without thermal decomposition. If carbonized, the carbon component remains on the surface of the positive electrode active material, which reduces the performance of the reusable positive electrode active material. However, if the heat treatment is performed in air or an oxygen atmosphere, the carbon component in the binder and conductive agent reacts with oxygen and disappears as gases such as CO and CO2, so both the binder and conductive agent are removed.

[0238] The above heat treatment is preferably performed at 300 to 650°C, and as a specific example, at 550°C. At temperatures below 300°C, it is difficult to remove the binder, making it impossible to separate the current collector. At temperatures above 650°C, the current collector melts, making it impossible to separate the current collector.

[0239] The above heat treatment is preferably performed at a temperature increase rate of 1 to 20°C / min, more preferably at a temperature increase rate of 3 to 10°C / min, and a specific example is 5°C / min. Within this range, the heat treatment can be performed without causing a strain on the heat treatment equipment, and has the advantage of not causing thermal shock to the anode scrap.

[0240] The above heat treatment can be performed for a period of time sufficient to allow the binder to be sufficiently thermally decomposed, for example, preferably 30 minutes or more, more preferably 30 minutes to 5 hours, and a specific example is about 30 minutes. Within this period, the binder is sufficiently thermally decomposed and also has the effect of excellent thermal decomposition efficiency.

[0241] The above heat treatment can be performed using various types of furnaces, for example, a box-type furnace, and considering productivity, a rotary kiln capable of continuous treatment can be used.

[0242] After the above heat treatment, it can be cooled slowly or rapidly in the air.

[0243]

[0244] Next, a lithium precursor is added to the recovered positive electrode active material and annealed (step S40).

[0245] It is important in the above annealing step to add a lithium precursor and anneal the recovered positive electrode active material directly without a washing process. In this case, the shear washing process is omitted, preventing lithium loss, so that the crystal structure of the positive electrode active material can be easily changed in the subsequent step, thereby improving the charging capacity, resistance characteristics, and capacity characteristics of the battery. In addition, since no wastewater is generated and the process is simplified, the economy and productivity are greatly improved, and the battery performance is enhanced.

[0246]

[0247] In addition, since lithium loss occurs in the positive electrode active material during the preceding step S30, such lithium loss is supplemented in step S40. In addition, since a deformation structure (e.g., Co3O4 in the case of LCO active material) may appear on the surface of the single-particle positive electrode active material during the preceding step, in step S40, the crystal structure of the single-particle positive electrode active material is restored through annealing, thereby improving the battery characteristics of the single-particle regenerated positive electrode active material or restoring it to the level of a newly formed positive electrode active material. Here, 'newly formed' is a concept opposite to 'regenerated', meaning something that is created for the first time, and is the same as the 'raw material' used in the examples.

[0248] As a specific example of the above lithium precursor, Li2CO3 is used.

[0249] It is preferable that the lithium precursor be added in an amount at least equal to the molar ratio of lithium lost compared to the molar ratio of lithium and other metals in the new positive electrode active material used in the positive electrode active material layer. Addition of a lithium precursor in an amount too excessive compared to the amount of lithium lost leaves unreacted lithium precursor in the regenerated positive electrode active material, which acts to increase resistance, and therefore, an appropriate amount of lithium precursor needs to be added. For example, when the molar ratio of lithium and other metals in the new positive electrode active material is 1, the lithium precursor may be added in an amount such that lithium is in a molar ratio of 0.001 to 0.4, and preferably, the lithium precursor may be added in an amount such that lithium is in a molar ratio of 0.01 to 0.2.

[0250] As a specific example, adding a lithium precursor at a molar ratio of 0.09 to 0.1 (based on lithium metal), which corresponds to the loss ratio relative to the lithium content in the new cathode active material based on ICP analysis results, results in a capacity improvement effect comparable to that of the new cathode active material. Here, the ICP analysis results have an error value of approximately ±0.02.

[0251]

[0252] The above annealing time is, for example, performed for 8 to 12 hours, and specifically, for 10 hours, so that the crystal grain size of the single-particle positive electrode active material increases and the crystal structure is sufficiently recovered to the level of a new positive electrode active material, thereby improving the efficiency, life characteristics, and resistance characteristics of the manufactured lithium secondary battery, and the pre-washing process of the recovered positive electrode active material is omitted, thereby preventing lithium loss, so that the crystal structure of the positive electrode active material is easily changed in the subsequent step, thereby improving the charging capacity, resistance characteristics, and capacity characteristics of the battery, and the process is simplified without generating wastewater, so that there is an advantage of greatly improving the economy and productivity.

[0253] At this time, the annealing equipment may be the same or similar equipment as in the heat treatment step S30.

[0254]

[0255] The above annealing is performed in oxygen (O2) or air under conditions of 400 to 1000°C, for example, and is performed in air under conditions of 750°C as a specific example.

[0256] The above annealing temperature is preferably a temperature exceeding the melting point of the lithium precursor. However, since a temperature exceeding 1000°C causes thermal decomposition of the positive electrode active material, resulting in a deterioration in performance, the temperature should not exceed 1000°C. Accordingly, when Li2CO3 is used as the lithium precursor, the annealing temperature is suitably 700 to 900°C, more preferably 710 to 780°C, and most preferably 750 to 780°C. In addition, when LiOH is used as the lithium precursor, the annealing temperature may be suitably 400 to 600°C, more preferably 450 to 480°C, and most preferably 470 to 480°C.

[0257]

[0258] Next, the annealed positive electrode active material is washed (step S50).

[0259] In the above washing step S50, lithium precursors that did not participate in the reaction in the above annealing step S40 and exist on the surface of the positive electrode active material in the form of LiOH and Li2CO3 are removed. Lithium impurities, such as lithium carbonate (Li2CO3), remaining on the surface of the regenerated positive electrode active material must be removed, as they may later react with the electrolyte to degrade battery performance and generate gas.

[0260] In the above washing step S50, the positive electrode active material and the washing solution from the above annealing step S40 are preferably mixed in a weight ratio of 1:0.5 to 1:5.5, specifically, 1:1, and filtered, followed by drying the obtained solid positive electrode active material. In this case, there is an advantage in that residual lithium is removed with a small amount of washing solution, thereby reducing wastewater.

[0261]

[0262] The above-mentioned washing solution may preferably be distilled water or a basic lithium compound aqueous solution containing more than 0 wt% and less than 10 wt% of a basic lithium compound, and more preferably distilled water may be used as the washing solution. In this case, there is an advantage in that it is safe and inexpensive and does not elute transition metals present in the regenerative positive electrode active material.

[0263]

[0264] The above washing is preferably performed by mixing the annealed positive electrode active material and the washing solution, filtering the mixture, and then drying the obtained solid positive electrode active material.

[0265] The mixing of the annealed positive electrode active material and the cleaning solution is preferably performed by stirring, and the stirring is not particularly limited, but mechanical stirring or ultrasonic stirring may be used.

[0266] The above mechanical stirring can preferably be performed under conditions of 250 to 350 rpm and 3 to 10 minutes.

[0267] The above filtration is preferably a vacuum filtration using a filter, and the above drying may be a vacuum drying at 120 to 140°C.

[0268]

[0269] Next, as an optional step, surface coating can be performed on the washed positive electrode active material (step S60).

[0270] Surface coating is, for example, a method of coating a surface with a coating agent containing a metal, organic metal, or carbon component in a solid or liquid form and then heat-treating it. If the heat-treatment temperature is too low, a surface protective layer by the desired heterogeneous metal is not formed, and if the heat-treatment temperature is too high, the performance of the battery deteriorates due to thermal decomposition of the positive electrode active material.

[0271] Specifically, when a metal oxide or acid such as B, W, or BW is coated on a washed cathode active material and then heat-treated, a surface protective layer such as a lithium borooxide layer is formed on the surface of the cathode active material.

[0272] The solid or liquid method of the above surface coating may be, for example, mixing, milling, spray drying or grinding.

[0273]

[0274] If the molar ratio of lithium to other metals in the positive electrode active material is 1:1 in the annealing step S40, the lithium in the regenerated positive electrode active material and the coating agent react in the surface coating step S60, so that the molar ratio of lithium to other metals in the positive electrode active material becomes less than 1:1, and such a regenerated positive electrode active material cannot fully exhibit 100% of the battery capacity. However, if the lithium precursor is added in excess in the annealing step S40 so that it contains 0.0001 to 0.1 molar ratio more than the other metals in the regenerated positive electrode active material, a surface protective layer is formed in the surface coating step S60, so that the molar ratio of lithium to other metals in the positive electrode active material naturally becomes 1:1, and thus the battery capacity reduction does not occur.

[0275]

[0276] secondary battery

[0277] The secondary battery of the present invention includes the above-described regenerated single-particle positive electrode active material, and in this case, the lithium component remaining on the surface of the positive electrode active material is greatly reduced, so that the initial discharge capacity, output performance, capacity characteristics, and resistance characteristics are excellent, and in addition, since no acid or organic solvent is used in the recovery and regeneration process of the single-particle positive electrode active material, it is environmentally friendly, and in particular, since the initial washing process is omitted, it has excellent economic efficiency and productivity.

[0278]

[0279] The secondary battery of the present invention may include all of the contents of the above-described regenerated single-particle positive electrode active material and the regeneration method thereof. Therefore, redundant description thereof is omitted herein.

[0280]

[0281] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0282]

[0283] [Example]

[0284] Example 1

[0285] After the positive electrode plate was pressed, the discarded positive electrode scrap (current collector: aluminum foil, positive electrode active material: NCM-based lithium composite transition metal oxide (containing 61 mol% of Ni based on 100 mol% of the remaining metals excluding Li; single particles) was crushed and heat-treated in air at 550°C for 30 minutes to remove the binder and conductive agent, and the current collector and positive electrode active material were separated, and then the positive electrode active material was recovered. Here, the temperature increase rate until the heat treatment temperature was reached was 5°C / min, and air was supplied at 3 L / min.

[0286] The recovered positive electrode active material was confirmed to be a single particle through SEM photography.

[0287] Li2CO3, a lithium precursor, was added directly to the recovered positive electrode active material without washing, and annealed under air at 750°C for 10 hours. In addition, air was supplied at 3 L / min. At this time, the lithium precursor was added in an amount capable of providing 10 mol% of lithium when the total lithium contained in the positive electrode active material in the raw material is assumed to be 100 mol%.

[0288] The above annealed positive electrode active material and distilled water were mixed in a 1:1 weight ratio, stirred at 300 rpm for 5 minutes, and then filtered under reduced pressure to obtain a solid. The solid was vacuum-dried at 130°C for 12 hours to obtain a washed positive electrode active material.

[0289] The above-mentioned washed positive electrode active material was coated with boric acid and then heated at 300°C for 5 hours to produce a final regenerated positive electrode active material. Here, boric acid was added at 1000 ppm based on the total weight of the positive electrode active material, the temperature increase rate until the heat treatment temperature was reached was 2°C / min, and air was supplied at 3 L / min.

[0290] Here, the molar ratio of lithium and other metals in the positive electrode active material was measured using an ICP analyzer, etc. At this time, the measurement can be made using a general ICP analyzer widely used in laboratories, but there is no deviation depending on the measuring device or method.

[0291] In this document, ppm is based on weight unless otherwise specified.

[0292]

[0293] Example 2

[0294] A regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that the NCM-based lithium composite transition metal oxide (containing 61 mol% of Ni based on 100 mol% of the total metals excluding Li, single particles) in the positive electrode scrap discarded after the positive electrode plate was stamped in Example 1 was changed to an NCM-based lithium composite transition metal oxide (containing 81 mol% or more of Ni based on 100 mol% of the total metals excluding Li). In addition, it was confirmed through SEM images that the recovered positive electrode active material was single particles.

[0295]

[0296] Comparative Example 1

[0297] In the annealing step of Example 1, a regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that annealing was performed at 750°C for 5 hours.

[0298]

[0299] Comparative Example 2

[0300] In the annealing step of Example 1, a regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that annealing was performed at 750°C for 15 hours.

[0301]

[0302] Comparative Example 3

[0303] A regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that the NCM-based lithium composite transition metal oxide (containing 61 mol% of Ni based on 100 mol% of the total metals excluding Li, single particle) in the positive electrode scrap discarded after the positive electrode plate was stamped in Example 1 was changed to an NCM-based lithium composite transition metal oxide (containing 61 mol% of Ni based on 100 mol% of the total metals excluding Li, secondary particle). In addition, it was confirmed through SEM images that the recovered positive electrode active material was a secondary particle.

[0304]

[0305] Comparative Example 4

[0306] A regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that the NCM-based lithium composite transition metal oxide (containing 61 mol% of Ni based on 100 mol% of the total metals excluding Li, single particle) in the positive electrode scrap discarded after the positive electrode plate was stamped in Example 1 was changed to an NCM-based lithium composite transition metal oxide (containing 81 mol% of Ni based on 100 mol% of the total metals excluding Li, secondary particle). The recovered positive electrode active material was confirmed to be a secondary particle through SEM images.

[0307]

[0308] Reference example

[0309] A fresh NCM-based lithium composite transition metal oxide (containing 61 mol% of Ni based on 100 mol% of the remaining metals excluding Li, with an average particle size of 3.99 μm) rather than a recycled active material was prepared. The fresh cathode active material was confirmed to be a single particle through SEM images.

[0310]

[0311] [Test Example I: Particle Size Analysis and Residual Lithium Content]

[0312] The residual lithium content of the regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 and 2, Comparative Examples 1 to 4, and Reference Examples was measured as follows, and the results are shown in Table 1 below.

[0313] * Particle size analysis: After dispersing the particles of the positive electrode active material in a dispersion medium using the laser diffraction method, the particles were introduced into a laser diffraction particle size measuring device (Microtrac MT 3000) and irradiated with an ultrasonic wave of approximately 28 kHz at an output of 60 W. The particle size corresponding to 5% (D5), 50% (D50) and 95% (D95) of the volume accumulation amount in the measuring device, the minimum particle size (Dmix) and the maximum particle size (Dmax) were measured. Here, the particle size corresponding to 50% of the volume accumulation amount was measured as the average particle size (D 50 ) is used.

[0314]

[0315] * Residual lithium content: Measured using a pH titrator T5 (Mettler Toledo). Specifically, 5 g of the positive electrode active material was dispersed in 100 ml of distilled water, mixed at 300 rpm for 5 minutes, filtered to remove the active material, and the resulting solution was titrated with a 0.1 M HCl solution, while measuring the change in pH value to obtain a pH titration curve. The obtained pH titration curve was used to calculate the residual LiOH and Li2CO3 amounts in the positive electrode active material.

[0316]

[0317] Classification Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Reference Example Particle Size D5 (㎛) 1.98 2.12 1.88 1.90 5.69 6.76 2.19 D50 (㎛) 3.85 3.50 3.75 3.74 10.13 10.88 3.99 D95 (㎛) 7.17 7.48 7.04 6.99 19.33 20.67 7.21 Residual Lithium (% by weight) LiOH 0.09 0.17 0.17 0.44 0.17 1.83 0.15 Li2CO 3 0.88 1.05 1.06 0.23 0.68 1.88 0.19 Total 0.97 1.22 1.23 0.67 0.85 3.7 10.34

[0318] As shown in Table 1 above, the single-particle regenerated positive electrode active materials of Examples 1 and 2 according to the present invention had slightly larger D5, D50, and D95 ​​than the single-particle regenerated positive electrode active materials of Comparative Examples 1 and 2, and were at a similar level to the new positive electrode active material of the Reference Example, and in particular, it was confirmed that Example 1 was more similar to the Reference Example. In addition, the single-particle regenerated positive electrode active material of Example 2 had slightly different D50 and D95 ​​from the Reference Example, which was due to the difference according to the nickel content.

[0319] In addition, Comparative Examples 3 and 4 are secondary particles, and their D5, D50, and D95 ​​values ​​are much larger than those of the single-particle regenerated positive electrode active materials of Examples 1 and 2. From this, it was predicted that Examples 1 and 2 have less differentiation compared to Comparative Examples 3 and 4, resulting in less side reactions, and thus have excellent life characteristics.

[0320] In addition, as shown in Table 1 above, it was confirmed that the regenerated positive electrode active materials of Examples 1 and 2 according to the present invention had a similar or similar level of residual LiOH to that of the reference example, which is a new positive electrode active material, and from this, it was expected that the regenerated positive electrode active material of the present invention would have a similar or lower level of battery performance degradation due to residual LiOH than the new positive electrode active material.

[0321] Meanwhile, in Comparative Example 2, the amount of residual LiOH was significantly increased due to excessive annealing.

[0322]

[0323] [Experimental Example II: SEM Analysis]

[0324] The regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 and 2, Comparative Examples 1 to 4, and Reference Examples were photographed using a SEM device and are shown in FIGS. 2 to 8, respectively. The SEM images were taken using a general SEM device commonly used in laboratories. Specifically, the images were taken using HITACHI's s-4200. However, there is no deviation depending on the measuring device or method.

[0325]

[0326] As can be seen in the following Figures 2 and 3, the regenerated positive electrode active materials manufactured in Examples 1 and 2 were single particles, split into small particles, and dispersed, and were confirmed to be similar to the reference example, which is the new positive electrode active material of Figure 8.

[0327] In addition, as can be confirmed in Figures 4 and 5 below, it was confirmed that the regenerated positive electrode active materials manufactured in Comparative Examples 1 and 2, respectively, were single particles and were not split into small particles but rather clumped together.

[0328] On the other hand, as can be seen in FIGS. 6 and 7 below, the regenerated positive electrode active materials manufactured in Comparative Examples 3 and 4 were secondary particles, and were confirmed to be somewhat clumped together rather than split or dispersed as compared to the regenerated positive electrode active material manufactured in Example 1.

[0329]

[0330] [Test Example III: CHC Cell Evaluation]

[0331] The electrochemical performance of the regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 and 2, Comparative Examples 1 to 3, and Reference Examples was measured through the CHC cell evaluation as follows, and the results are shown in Table 2 below.

[0332] * CHC cell evaluation: 97.5 wt% of the regenerated cathode active material, 1.15 wt% of the conductive material carbon black, and 1.35 wt% of the binder PVdF were weighed and mixed in NMP to make a slurry. This was coated on aluminum foil to manufacture the cathode, and then the cell (Coin Half Cell, CHC) was manufactured. The electrochemical performance (charge capacity, discharge capacity, and efficiency) was evaluated under the conditions of 3-4.25 V cut, initial formation charge / discharge 0.1 C / 0.1 C, and electrolyte with a weight ratio of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 3:4:3 and other additives.

[0333]

[0334] Classification Initial charge capacity (CH) (mAh / g) Initial discharge capacity (DCH) (mAh / g) Efficiency (%) Example 1 211.4 186.8 8.4 Example 2 222.4 201.3 8.9 7 Comparative example 1 210 184.5 8.7 9 Comparative example 2 199.6 179.4 8.9 9 Comparative example 3 199.6 180.9 9.0 7 Reference example 2 19.9 197.9 9.

[0335] As shown in Table 2 above, the single-particle regenerated positive electrode active materials of Examples 1 and 2 according to the present invention were confirmed to have better initial charge capacity (CH) and initial discharge capacity (DCH) than the regenerated positive electrode active materials of Comparative Examples 1 to 3, and to be at the level of the new positive electrode active material of the Reference Example. In particular, it was confirmed that the initial discharge capacity, which is the most important characteristic in a secondary battery, was more excellent.

[0336] [Experimental Example IV: XRD Analysis]

[0337] The a-axis lattice constant, c-axis lattice constant, and crystal grain size of the regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 and 2, Comparative Examples 1 to 4, and Reference Examples were measured by XRD analysis, and the results are shown in Table 3 below.

[0338]

[0339] * Lattice parameter and crystallite size: Measured by XRD analysis, specifically, XRD (X-Ray Diffraction) analysis using Cu Kα X-rays. The lattice parameter was calculated by indexing the XRD measurement data through Rietveld refinement, and the crystallite size was calculated using the Scherrer equation from the XRD measurement data.

[0340]

[0341] Classification a-axis lattice constant (Å) c-axis lattice constant (Å) crystal grain size (nm) Example 12.8780 14.248 150 Example 22.8770 14.205 155 Comparative example 12.8786 14.252 144 Comparative example 22.8755 14.208 156 Comparative example 32.8680 14.230 110 Comparative example 42.8752 14.215 106 Reference example 2.8776 14.250 160

[0342] As shown in Table 3 above, it can be confirmed that the single particle regenerated positive electrode active materials (Examples 1 and 2) according to the present invention have crystal structure a-axis lattice constants, c-axis lattice constants, and crystal grain sizes more similar to those of the new positive electrode active materials of the reference examples than the regenerated positive electrode active materials of comparative examples 1 to 4, and it can be expected that the battery characteristics are further improved from this.

[0343] [Explanation of symbols]

[0344] 10: Whole house

[0345] 20: Active material layer

[0346] 30: Bipolar sheet

[0347] 40: Bipolar plate

[0348] 50: Bipolar scrap

Claims

1. (a) A step of heat-treating a waste positive electrode having a positive electrode active material layer including a single particle positive electrode active material formed on a current collector to thermally decompose a binder and a conductive material in the active material layer, thereby separating the current collector from the positive electrode active material layer and recovering the positive electrode active material including single particles in the positive electrode active material layer; (b) a step of adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C for 8 to 12 hours; and (c) a step of washing the annealed positive electrode active material with a washing solution; characterized in that it comprises; Method for regenerating positive electrode active material. 2.(a) A step of heat-treating a waste positive electrode having a positive electrode active material layer including a single-particle mid-nickel positive electrode active material formed on a current collector to thermally decompose a binder and a conductive material in the active material layer, thereby separating the current collector from the positive electrode active material layer and recovering the single-particle mid-nickel positive electrode active material in the active material layer; (b) a step of adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C for 8 to 12 hours; and (c) a step of washing the annealed positive electrode active material with a washing solution; characterized in that it comprises; Method for regenerating single-particle mid-nickel cathode active material.

3. In paragraph 1 or 2, The above-mentioned positive electrode active material layer includes at least one selected from the group consisting of 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, and is characterized in that it includes 40 mol% or more of Ni based on 100 mol% of the total of the remaining metals excluding Li. Method for regenerating positive electrode active material.

4. In paragraph 1 or 2, In the above step (a), the heat treatment is characterized in that it is performed at 300 to 650 ℃. Method for regenerating positive electrode active material.

5. In paragraph 1 or 2, Characterized in that the positive electrode active material recovered in the above step (a) is provided for annealing without washing. Method for regenerating positive electrode active material.

6. In paragraph 1 or 2, In the step (b), the lithium precursor is added in an amount at least as much as the molar ratio of lithium in the positive electrode active material of the step (a) is reduced based on the amount of lithium in the recovered positive electrode active material. Method for regenerating positive electrode active material.

7. In paragraph 1 or 2, The lithium precursor is characterized in that it comprises at least one of LiOH, Li2CO3, LiNO3 and Li2O. Method for regenerating positive electrode active material.

8. In paragraph 1 or 2, The washing of the above step (c) is characterized by including a step of mixing the annealed positive electrode active material and the washing solution, then filtering the mixture, and a step of drying the positive electrode active material in the solid content obtained after the filtering. Method for regenerating positive electrode active material.

9. In paragraph 1 or 2, The above cleaning solution is characterized in that it is water or a basic lithium compound aqueous solution. Method for regenerating positive electrode active material.

10. In paragraph 1 or 2, The method for reusing the positive electrode active material is characterized in that it includes a step of surface coating the washed positive electrode active material to obtain a reusable positive electrode active material. Method for regenerating positive electrode active material.

11. In paragraph 10, The above surface coating is characterized by coating at least one of a metal, an organic metal, and a carbon component on the surface in a solid or liquid manner and then heat-treating at 100 to 1200°C. Method for regenerating positive electrode active material.

12. In paragraph 1, The positive electrode active material regenerated according to the above positive electrode active material regeneration method is characterized in that the D5 value in the particle size distribution (PSD) is 1.95 ㎛ or more, or the D95 value is 7.11 ㎛ or more. Method for regenerating positive electrode active material.

13. At least one selected from the group consisting of lithium nickel oxide (LNO)-based cathode active materials, nickel-cobalt-manganese (NCM)-based cathode active materials, nickel-cobalt-aluminum (NCA)-based cathode active materials, and nickel-cobalt-manganese-aluminum (NCMA)-based cathode active materials, Contains single particles, and / or The a-axis lattice constant measured by XRD analysis is 2.8763 to 2.8783 Å, the c-axis lattice constant is 14.200 to 14.250 Å, and the crystal grain size is 148 nm or more, and / or Characterized by a particle size distribution (PSD) D5 value of 1.95 ㎛ or more, or a D95 value of 7.11 ㎛ or more. Positive active material.

14. In paragraph 13, The above positive electrode active material is characterized in that the D50 value in the particle size distribution (PSD) is 3.45 to 3.91 ㎛. Positive active material.

15. In paragraph 13, The above positive electrode active material is characterized in that it contains a total of 1.09 wt% or less of LiOH and Li2CO3. Positive active material.

16. In paragraph 13, The above positive electrode active material is characterized in that Ni exceeds 70 mol% based on 100 mol% of the total metals excluding Li. Positive active material.

17. In paragraph 13, The above positive electrode active material is characterized in that the surface is coated with a coating agent containing metal or carbon. Positive active material.

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