Positive electrode active material and method for recycling same

Abstract

The present invention relates to a positive electrode active material and a method for recycling same and, more specifically, to a positive electrode active material and a method for recycling same, wherein the positive electrode active material is at least one selected from the group consisting of a lithium nickel oxide (LNO)-based positive electrode active material, a nickel cobalt manganese (NCM)-based positive electrode active material, a nickel cobalt aluminum (NCA)-based positive electrode active material, and a nickel cobalt manganese aluminum (NCMA)-based positive electrode active material, includes single particles, has an F content of 5,700 to 6,500 mg / kg, and / or has an a-axis lattice constant of 2.8753 to 2.8772 Å, a c-axis lattice constant of 14.243 to 14.255 Å, a cell volume of 101.968 to 102.168 Å3, and a grain size exceeding 130 nm and up to 136 nm, as measured by XRD analysis.

Description

Positive electrode active material and regeneration method thereof

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

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0029795, filed February 29, 2024, and Korean Patent Application No. 10-2025-0004743, filed January 13, 2025, which is hereby incorporated by reference in its entirety.

[0003] The present invention relates to a cathode active material and a method for regenerating the same, and more particularly, to a cathode active material including single particles recovered after heat treatment of a spent cathode, which is directly added with a lithium precursor without a shear washing process, and then annealed and surface coated, and the cathode active material before and / or after annealing is milled to include fluorine (F) in a predetermined content on the surface of the cathode active material, and the crystal structure and grain size of the cathode active material analyzed by XRD are adjusted to be within a predetermined range, thereby obtaining a cathode active material having excellent charge capacity, resistance characteristics, and capacity characteristics, and a method for regenerating a cathode active material which is environmentally friendly because no acid is used in the recovery and regeneration process, and thus reduces process costs because neutralization and wastewater treatment are not required, and does not decompose the cathode active material and thus regenerates it as is, so there are no discarded metal elements, 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, the economy and productivity are greatly improved.

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

[0005] The 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 being applied to the cathode, 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 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 use them again as raw materials for synthesizing anode 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 regenerating single-particle cathode active materials in an environmentally friendly manner, with a low process cost, and without deteriorating output performance, without discarding metal elements from waste cathodes containing single-particle cathode active materials.

[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 including single particles, which is recovered after heat-treating a waste cathode and then adding a lithium precursor directly without a shear washing process, and then annealing and then performing surface coating, and by milling the cathode active material before and / or after annealing, fluorine (F) is included in the surface of the cathode active material at a predetermined content, and the crystal structure and grain size of the cathode active material analyzed by XRD are adjusted to be within a predetermined range, thereby obtaining a cathode active material having excellent charge capacity, resistance characteristics, and capacity characteristics, and a method for regenerating a cathode active material including single particles, which is environmentally friendly because no acid is used in the recovery and regeneration process, and thus, process costs are reduced because neutralization and wastewater treatment are not required, and the cathode active material is regenerated as it is without decomposition, so there are no discarded metal elements, and there is no generation of toxic gases or risk of explosion because no organic solvent is used, and the shear washing process is omitted, thereby greatly improving economic efficiency and productivity.

[0018] In addition, the present invention aims to provide a secondary battery having excellent initial discharge capacity and capacity characteristics by using a method for regenerating the positive electrode active material.

[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 comprises 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 comprises single particles, and has an F content of 5,700 to 6,500 mg / kg, and / or has an a-axis lattice constant of 2.8753 to 2.8772 Å, a c-axis lattice constant of 14.243 to 14.255 Å, and a cell volume of 101.968 to 102.168 Å as measured by X-ray diffraction analysis (XRD). 3 And a cathode active material characterized by a crystal grain size of more than 130 nm and less than or equal to 136 nm is provided.

[0021] II) In the above I), the positive electrode active material may contain Ni in an amount of 40 mol% or more based on 100 mol% of the total metals excluding Li.

[0022] III) In the above I) or II), the positive electrode active material may have a surface coated with a coating agent containing metal or carbon.

[0023] IV) In the above I) to III), the positive electrode active material may be a regenerated positive electrode active material.

[0024] In addition, V) the present invention comprises the steps of: (a) heat-treating a waste positive electrode having a positive electrode active material layer formed on a current collector at 300 to 650°C to thermally decompose a binder and a conductive agent in the positive electrode active material layer, thereby recovering a 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 it at 400 to 1000°C; (c) washing the annealed positive electrode active material with a washing solution; and (d) surface-coating the washed positive electrode active material; and the step of milling the positive electrode active material recovered in the step (b) before annealing; And / or a step of milling the annealed positive electrode active material in the step (c) before washing; or a method for regenerating a positive electrode active material, characterized in that it comprises: (a) a step of heat-treating a waste positive electrode having a mid-nickel positive electrode active material layer formed on a current collector at 300 to 650°C to thermally decompose a binder and a conductive agent in the positive electrode active material layer, thereby recovering a 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; (c) a step of washing the annealed positive electrode active material with a washing solution; and (d) a step of surface-coating the washed positive electrode active material; and a step of milling the positive electrode active material recovered in the step (b) before annealing; and / or a step of milling the annealed positive electrode active material in the step (c) before washing.

[0025] 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.

[0026] In this description, the step of milling before annealing means milling before adding a lithium precursor to the recovered positive electrode active material after heat treatment of the waste positive electrode.

[0027] VI) In the above I) to V), the positive electrode active material is at least one selected from the group consisting of a lithium nickel oxide (LNO)-based positive electrode active material, a nickel-cobalt-manganese (NCM)-based positive electrode active material, a nickel-cobalt-aluminum (NCA)-based positive electrode active material, and a nickel-cobalt-manganese-aluminum (NCMA)-based positive electrode active material, and may contain 40 mol% or more of Ni based on 100 mol% of the total of the remaining metals excluding Li.

[0028] VII) In the above V) to VI), the milling can be performed using a centrifugal mill, a jet mill, or a pin mill.

[0029] VIII) In the above V) to VII), the milling can be performed at 6,000 to 18,000 rpm.

[0030] IX) In the above V) to VIII), the lithium precursor may include at least one of LiOH, Li2CO3, LiNO3, and Li2O.

[0031] X) In the above V) to IX), 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.

[0032] XI) In the above V) to X), the weight ratio of the annealed positive electrode active material or the milled positive electrode active material and the washing solution in the washing step (c) may be 1:0.5 to 1:5.5.

[0033] XII) In the above V) to XI), the step of mixing the annealed positive electrode active material or the milled positive electrode active material of the above step (c) with the washing solution and then filtering it, and the step of drying the positive electrode active material in the solid content obtained after the filtering may be included.

[0034] XIII) In the above V) to XII), the surface coating of step (d) 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.

[0035] In addition, XIV) The present invention provides a secondary battery characterized by including a positive electrode active material of any one of the above I) to IV).

[0036] According to the present invention, a cathode active material including single particles recovered after heat treatment of a waste cathode is directly added with a lithium precursor without a shear washing process, annealed, and then surface coated, and by milling the cathode active material before and / or after annealing, fluorine (F) is included in a predetermined content on the surface of the cathode active material, and the crystal structure and grain size of the cathode active material analyzed by X-ray diffraction analysis (XRD) are adjusted to be within a predetermined range, thereby providing a cathode active material having excellent charge capacity, resistance characteristics, and capacity characteristics.

[0037] In addition, it is possible to directly regenerate single-particle cathode active materials from waste cathodes without deterioration in battery performance, is environmentally friendly because no acid is used in the recovery and regeneration process of the cathode active materials, and thus neutralization and wastewater treatment are not required, reducing process costs, and since the cathode 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 since the shear washing process is omitted, it provides a method for regenerating cathode active materials that greatly improves economic efficiency and productivity.

[0038] 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.

[0039] Figure 1 is a drawing showing anode scrap that is discarded after cutting an electrode plate from a cathode sheet.

[0040] Figure 2 is a graph measuring the capacity retention rate of the regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5.

[0041] Figure 3 is a flowchart of a regeneration process of a positive electrode active material including single particles according to the present invention.

[0042] The present inventors, while studying a method (direct recycled method) for directly regenerating a cathode active material containing single particles from a waste cathode into a cathode active material having excellent rate performance, etc. without decomposing the cathode active material, have discovered that when the single particle cathode active material recovered by heat-treating a waste cathode is annealed by adding a lithium precursor directly without a washing process, and further, when milling, etc. is performed before and / or after annealing the recovered cathode active material, the regenerated single particle cathode active material contains fluorine in a predetermined content, and the crystal structure and grain size analyzed by XRD are adjusted to be within a predetermined range, so that the charge capacity, resistance characteristics, and capacity characteristics of the manufactured lithium secondary battery are significantly improved, and based on this, they have devoted themselves to further research and completed the present invention.

[0043]

[0044] Hereinafter, the cathode active material of this invention and its regeneration method are described in detail.

[0045] 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.

[0046] 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.

[0047]

[0048] Single particle cathode active material

[0049] 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 has an F content of 5,700 to 6,500 mg / kg, and / or has an a-axis lattice constant of 2.8753 to 2.8772 Å, a c-axis lattice constant of 14.243 to 14.255 Å, and a cell volume of 101.968 to 102.168 Å as measured by X-ray diffraction analysis (XRD). 3 And the crystal grain size is more than 130 nm and less than 136 nm, and the cathode active material of the present invention satisfies these conditions, so when applied to a lithium secondary battery, it has excellent effects in terms of charging capacity, resistance characteristics, and capacity characteristics of the battery.

[0050]

[0051] 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-based lithium composite metal oxide in which some of the nickel (Ni) in the lithium nickel oxide is replaced with manganese (Mn); and NCM-based lithium composite transition metal oxide in which some of the 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.

[0052] The above-mentioned positive electrode active material may include 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.

[0053]

[0054] [Chemical Formula 1]

[0055] Li a Ni x Mn y Co z M w O 2+δ

[0056] (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.)

[0057]

[0058] The above-mentioned positive electrode active material may contain, for example, 40 mol% or more, 40 to 95 mol%, more preferably 40 to 70 mol% (in which case the positive electrode active material may be referred to as a mid-nickel positive electrode active material), and even more preferably 50 to 70 mol% of Ni, based on 100 mol% of the total metals excluding Li, and within this range, there are excellent effects in initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0059] In this description, the Ni 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.

[0060]

[0061] 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.

[0062]

[0063] 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 for example, may be a particle composed of 30 or fewer nodules, preferably a particle composed of 1 to 20 nodules, more preferably a particle composed of 1 to 10 nodules, even more preferably a particle composed of 1 to 5 nodules, and most preferably a particle composed of 1 nodule. In this case, 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 cathode material having excellent life characteristics in a high-voltage environment, high thermal stability, and low gas generation due to charge and discharge.

[0064] 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).

[0065] 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 and the positive electrode active material particles having the smallest particle 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.

[0066]

[0067] 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.

[0068] 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.

[0069]

[0070] The above positive electrode active material may preferably contain fluorine (F) in an amount of 5,700 to 6,500 mg / kg, more preferably 5,800 to 6,300 mg / kg, and even more preferably 5,800 to 6,100 mg / kg, and within this range, excellent charging capacity, resistance characteristics, and capacity characteristics are achieved.

[0071] In this description, the fluorine (F) 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.

[0072]

[0073] The above-mentioned positive electrode active material may have an a-axis lattice constant measured by XRD analysis of, for example, 2.8753 to 2.8772 Å, preferably 2.8760 to 2.8770 Å, more preferably 2.8762 to 2.8768 Å, and even more preferably 2.8764 to 2.8768 Å, and within this range, the a-axis lattice constant is reduced compared to the raw positive electrode active material, so that it has a different lattice structure, and when applied to a lithium secondary battery, the battery has excellent charging capacity, resistance characteristics, and capacity characteristics.

[0074]

[0075] The above-mentioned positive electrode active material may have a c-axis lattice constant measured by XRD analysis of, for example, 14.243 to 14.255 Å, preferably 14.245 to 14.254 Å, more preferably 14.247 to 14.254 Å, and even more preferably 14.249 to 14.254 Å, and within this range, the lithium concentration in the lattice increases in the c-axis, which means the z-axis direction of the layered structure, thereby exhibiting excellent charging capacity, resistance characteristics, and capacity characteristics.

[0076]

[0077] The above positive electrode active material has a cell volume measured by XRD analysis of, for example, 101.968 to 102.168 Å. 3 , preferably 101.980 to 102.163 Å 3, more preferably 102.000 to 102.158 Å 3 , more preferably 102.100 to 102.153 Å 3 It can be, and within this range, it has excellent effects in terms of charging capacity, resistance characteristics and capacity characteristics.

[0078] The above-mentioned positive electrode active material may have a crystallite size measured by XRD analysis of, for example, more than 130 nm and less than or equal to 136 nm, preferably 131 to 135 nm, preferably 131 to 134 nm, and within this range, the crystallite size is larger than that of secondary particles, and ionic conductivity is improved, thereby providing an excellent capacity characteristic.

[0079]

[0080] In this paper, the lattice parameter, cell volume, and crystallite size of the positive electrode active material can be measured by XRD analysis, and specifically, the lattice parameter is calculated by indexing the data measured through XRD (X-Ray Diffraction) analysis using Cu Kα X-rays through Rietveld refinement, the cell volume is calculated by multiplying the a-axis lattice constant and the c-axis lattice constant, and the crystallite size can be calculated using the Scherrer equation for the XRD measurement data.

[0081] In this description, a crystal grain means a single crystal particle unit having a regular atomic arrangement.

[0082]

[0083] The above-mentioned positive electrode active material may have a surface coated with, for example, metal or carbon, and is preferably coated with metal. In this case, the structural stability of the positive electrode active material is improved without chemical and physical changes in the positive electrode active material itself, thereby improving electrochemical 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 the pH by substituting a different element on the surface of the positive electrode active material.

[0084]

[0085] The metal is preferably at least one selected from the group consisting of B, W, Al, Ti, Mg, Ni, Co, Mn, Si, Zr, Ge, Sn, Cr, Fe, V and Y, more preferably at least one selected from the group consisting of B, W, Al, Ti and Mg, even more preferably boron (B), tungsten (W) or a mixture thereof, even more preferably tungsten (W) and boron (B), and a specific example is tungsten boride (WB), in which case there is an effect of improving resistance characteristics and life characteristics.

[0086] 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.

[0087]

[0088] The coating agent may be included, for example, in an amount of 0.001 to 0.3 mol% relative to 1 mol% of metal in the positive electrode active material before coating treatment, preferably 0.01 to 0.3 mol%, more preferably 0.01 to 0.15 mol%, even more preferably 0.01 to 0.1 mol%, and even more preferably 0.01 to 0.05 mol%, and within this range, it has the effect of improving structural stability and electrochemical performance while maintaining the properties of the single-particle positive electrode active material itself.

[0089]

[0090] 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 positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0091]

[0092] 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.

[0093]

[0094] Method for regenerating single-particle cathode active material

[0095] The method for regenerating a positive electrode active material of the present invention comprises the steps of: (a) heat-treating a waste positive electrode having a positive electrode active material layer formed on a current collector at 300 to 650°C to thermally decompose a binder and a conductive agent within the positive electrode active material layer, thereby recovering a positive electrode active material including single particles within the positive electrode active material layer; (b) adding a lithium precursor to the recovered positive electrode active material and annealing it at 400 to 1000°C; (c) washing the annealed positive electrode active material with a washing solution; and (d) surface-coating the washed positive electrode active material; and is characterized by comprising the steps of: milling the positive electrode active material recovered in step (b) before annealing; and / or milling the positive electrode active material annealed in step (c) before washing. In this case, since the surface of the positive electrode active material contains a predetermined amount of fluorine (F), and the crystal structure and grain size of the positive electrode active material analyzed by XRD are within a predetermined range, a regenerated single-particle positive electrode active material having excellent charging capacity, resistance characteristics, and capacity characteristics of the applied lithium secondary battery is provided, and since no acid is used in the recovery and regeneration process, it is environmentally friendly, and since neutralization and wastewater treatment are not required, process costs are reduced, and since the positive electrode active material is regenerated as is without decomposition, there are no discarded metal elements, and since no organic solvent is used, there is no generation of toxic gases or risk of explosion, and in particular, since the single-particle positive electrode active material is easily and directly regenerated from the spent positive electrode without deterioration of battery performance, there is a significant improvement in economic efficiency and productivity.

[0096]

[0097] As another example, the method for regenerating a positive electrode active material of the present invention comprises the steps of: (a) heat-treating a waste positive electrode having a mid-nickel positive electrode active material layer formed on a current collector at 300 to 650°C to thermally decompose a binder and a conductive agent in the positive electrode active material layer, thereby recovering a 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 it at 400 to 1000°C; (c) washing the annealed positive electrode active material with a washing solution; and (d) surface-coating the washed positive electrode active material; and is characterized by comprising the steps of: milling the positive electrode active material recovered in step (b) before annealing; and / or milling the positive electrode active material annealed in step (c) before washing. In this case, since the surface of the positive electrode active material contains a predetermined amount of fluorine (F), and the crystal structure and grain size of the positive electrode active material analyzed by XRD are within a predetermined range, a regenerated single-particle mid-nickel positive electrode active material having excellent charging capacity, resistance characteristics, and capacity characteristics of the applied lithium secondary battery is provided, and since no acid is used in the recovery and regeneration process, it is environmentally friendly, and since neutralization and wastewater treatment are not required, process costs are reduced, and since the positive electrode active material is regenerated as is without decomposition, there are no discarded metal elements, and since no organic solvent is used, there is no generation of toxic gases or risk of explosion, and since the single-particle positive electrode active material is easily and directly regenerated from the spent positive electrode without deterioration of battery performance, there is a significant improvement in economic efficiency and productivity.

[0098]

[0099] In this disclosure, the step of milling before annealing refers to milling before adding a lithium precursor to the recovered cathode active material after heat-treating the spent cathode. However, this is not limited to this, and the step of milling may also be performed after adding a lithium precursor to the recovered cathode active material after heat-treating the spent cathode.

[0100]

[0101] Below, the method for regenerating positive electrode active materials is explained in detail step by step.

[0102]

[0103] (a) A step of recovering a single particle cathode active material from a waste cathode.

[0104] According to the present invention, the step of recovering a single-particle positive electrode active material from a waste positive electrode (a) may preferably include a step of heat-treating a waste positive electrode having a positive electrode active material layer formed on a current collector at 300 to 650°C to thermally decompose a binder and a conductive material within the positive electrode active material layer, thereby recovering a 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.

[0105]

[0106] As another example, the present invention may include a step of heat-treating a waste positive electrode having a single-particle mid-nickel positive electrode active material layer formed on a current collector at 300 to 650°C to thermally decompose the binder and conductive material within the positive electrode active material layer, thereby recovering the single-particle mid-nickel positive electrode active material within the positive electrode active material layer. In the case of the 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.

[0107]

[0108] 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.

[0109] 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.

[0110] 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.

[0111] As another specific example, the positive electrode active material may be a compound represented by the following chemical formula 1.

[0112]

[0113] [Chemical Formula 1]

[0114] Li a Ni x Mn y Co z M w O 2+δ

[0115] (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.)

[0116]

[0117] The above-mentioned positive electrode active material may contain, for example, 40 mol% or more, 40 to 95 mol%, more preferably 40 to 70 mol% (in which case the positive electrode active material may be referred to as a mid-nickel positive electrode active material), and even more preferably 50 to 70 mol% of Ni, 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.

[0118]

[0119] 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.

[0120]

[0121] 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.

[0122] 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.

[0123]

[0124] The above conductive material may be, for example, a carbon-based conductive material, and preferably, carbon black, CNT, or a mixture thereof.

[0125] 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.

[0126]

[0127] In the above step (a), the heat treatment may be, for example, at 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.

[0128] The above heat treatment may 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. Within this range, the heat treatment can be performed without causing any strain on the heat treatment equipment, and has the advantage of not causing thermal shock to the anode scrap.

[0129]

[0130] 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.

[0131] 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 residue.

[0132] The purity % of the above oxygen can be volume % or mol %.

[0133] The purity of the oxygen of this invention is not particularly limited when measured using a measurement method commonly used in the technical field to which the present invention belongs.

[0134]

[0135] 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 is easily separated from the current collector, and the separated positive electrode active material has the advantage of being easily sorted into a powder form.

[0136]

[0137] The heat treatment time is preferably 10 minutes to 5 hours, more preferably 30 minutes to 5 hours, even more preferably 30 minutes to 2 hours, and even more preferably 30 minutes to 1 hour. Within this range, the current collector does not melt, and only the binder, etc. are removed, so that the positive electrode active material can be easily separated from the current collector.

[0138] 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.

[0139] The positive electrode active material recovered in the above step (a) can preferably be subjected to a milling or annealing process directly without shear washing, and in this case, the shear washing process is omitted, which has the advantage of greatly improving economic efficiency and productivity.

[0140] 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.

[0141]

[0142] Referring to the following drawing 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.

[0143] In addition, the above-mentioned positive electrode active material layer (20) is formed by coating a slurry containing a mixture of positive electrode active material, conductive material, binder, and 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, and thus waste positive electrode sheets are generated until conditions for manufacturing a positive electrode sheet (30) of the desired quality are found through a predetermined test.

[0144] For reference, in the examples below, anode scrap was used as the anode.

[0145]

[0146] (b) A step of adding a lithium precursor to the recovered positive electrode active material and annealing it.

[0147] The method for regenerating a positive electrode active material of the present invention may include (b) a step of adding a lithium precursor to the recovered positive electrode active material and annealing at 400 to 1000°C, in which case the crystal structure of the regenerated positive electrode active material is restored, thereby providing a positive electrode active material having excellent efficiency, life characteristics, and resistance characteristics, and the pre-washing process of the recovered positive electrode active material is omitted, thereby greatly improving economic efficiency and productivity.

[0148]

[0149] The above annealing step may preferably include a step of milling the recovered positive electrode active material before annealing, and specifically, may include a step of milling before introducing the lithium precursor. In this case, the particles that have clumped together during the heat treatment are loosened, and in the subsequent annealing step, the lithium precursor is uniformly replenished to the single-particle positive electrode active material and heat-treated, thereby restoring the crystal structure, resulting in excellent efficiency, lifespan characteristics, and resistance characteristics. Unlike the secondary particle positive electrode active material, the single-particle positive electrode active material has fewer pores within the particles, and furthermore, if the particles are clumped together, it is difficult for the lithium precursor to be uniformly replenished to the positive electrode active material and heat-treated, so it is preferable to loosen the clumped particles through the milling. On the other hand, the recovered secondary particle positive electrode active material is in a different state from the single-particle positive electrode active material, and thus does not have the milling effect according to the present invention, and even if milled, it is not transformed into the single-particle positive electrode active material.

[0150] In addition, since the recovered positive electrode active material is milled directly without a shear washing process, no loss of lithium occurs due to washing, resulting in better efficiency, life characteristics, and resistance characteristics.

[0151]

[0152] The above milling can be performed using, for example, a centrifugal mill, a jet mill, or a pin mill, and preferably, the milling process can be performed using a pin mill. In this case, there is an advantage in that the clumped particles are uniformly released and the surface of the positive electrode active material is not damaged.

[0153] The above milling can be performed, for example, at 6,000 to 18,000 rpm, preferably at 8,000 to 16,000 rpm, more preferably at 10,000 to 13,000 rpm, and even more preferably at 11,000 to 13,000 rpm, and within this range, particle agglomeration of the single-particle positive electrode active material is resolved, and uniform heat treatment is performed in the subsequent annealing step, thereby substantially improving the recovery of the crystal structure of the regenerated positive electrode active material, thereby resulting in excellent efficiency, life characteristics, and resistance characteristics.

[0154]

[0155] The annealing step (b) above preferably comprises adding a lithium precursor to the recovered positive electrode active material and annealing under an air or oxygen (O2) atmosphere, preferably under air. In this case, there is an effect of improving the battery characteristics of the regenerated positive electrode active material by improving crystallinity, such as increasing the crystallinity of the positive electrode active material or restoring its crystal structure.

[0156]

[0157] 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.

[0158]

[0159] The lithium precursor may preferably be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, and Li2O.

[0160]

[0161] 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.

[0162] 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.

[0163]

[0164] The above annealing temperature can be controlled within a limited range depending on the melting point of the lithium precursor. For example, in the case of LiCO3, the melting point is 723°C, so annealing can be performed at preferably 700 to 900°C, more preferably 710 to 780°C, and in the case of LiOH, the melting point is 462°C, so annealing can be performed at preferably 400 to 750°C, more preferably 500 to 720°C, and even more preferably 600 to 720°C. Within this range, the crystal structure is recovered, so that the efficiency, life characteristics, and resistance characteristics of the battery are excellent.

[0165] 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.

[0166]

[0167] The above annealing time is, for example, 1 hour or more or 15 hours or less, preferably 1 to 15 hours, more preferably 2 to 10 hours, even more preferably 3 to 8 hours, even more preferably 4 to 6 hours, and as a specific example, around 5 hours is preferable, and within this range, sufficient crystal structure recovery is achieved, the crystal grain size is large compared to secondary particles, and ionic conductivity is improved, thereby providing an excellent effect of capacity characteristics.

[0168]

[0169] 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.

[0170] 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.

[0171]

[0172] 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.

[0173]

[0174] (c) Step of washing the annealed positive electrode active material (post-washing)

[0175] 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.

[0176]

[0177] The above washing step may preferably include a step of milling the annealed positive electrode active material before washing, in which case the agglomerated particles are loosened and uniformly dispersed, so that the lithium precursor and / or fluorine are effectively removed with a small amount of washing solution, thereby reducing wastewater, and there is an advantage in that the charge capacity, resistance characteristics and capacity characteristics are improved when applied to a battery thereafter.

[0178]

[0179] The above milling can be performed using, for example, a centrifugal mill, a jet mill, or a pin mill, and preferably, milling can be performed using a pin mill. In this case, there is an advantage in that the clumped particles are uniformly released and the surface of the positive electrode active material is not damaged.

[0180] The above milling can be performed, for example, at 6,000 to 18,000 rpm, preferably at 8,000 to 16,000 rpm, more preferably at 10,000 to 13,000 rpm, and even more preferably at 11,000 to 13,000 rpm, and within this range, particle agglomeration of the positive electrode active material is resolved, a uniform dispersion is formed, and impurities are easily removed in the subsequent washing process, so that there is an advantage in that the charging capacity, resistance characteristics, and capacity characteristics are improved.

[0181]

[0182] The above washing may preferably include a step of mixing the annealed or milled positive electrode active material and a washing solution, followed by a filtering step, and a step of drying the solid positive electrode active material obtained after the filtering step. In this case, there is an effect of effectively removing excess lithium that is likely to remain on the positive electrode active material. In addition, in this case, lithium precursors such as LiOH, Li2CO3, etc. and / or fluorine that 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.

[0183]

[0184] The annealed positive electrode active material or the milled positive electrode active material and the washing solution may be mixed in a weight ratio of, for example, 1:0.5 to 1:5.5, preferably 1:0.5 to 1:4.5, more preferably 1:0.5 to 1:3.5, and even more preferably 1:0.5 to 1:2.5, and in this case, lithium precursors such as LiOH, Li2CO3, etc. and / or fluorine, which are likely to remain on the surface of the positive electrode active material, are effectively removed with a small amount of the washing solution, thereby having the effect of reducing wastewater.

[0185]

[0186] The above-mentioned washing solution may preferably be water or an aqueous alkaline lithium compound solution, more preferably water, and in this case, in order to suppress the cation mixing phenomenon that is likely to occur in the regenerated positive electrode active material, especially in the regenerated mid-nickel positive electrode active material, lithium precursors such as LiOH, Li2CO3, etc., which are more likely to remain due to the excessive addition of 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.

[0187] 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.

[0188] 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, Li2CO3, etc. and / or fluorine, 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.

[0189]

[0190] 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.

[0191] 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.

[0192]

[0193] (d) A step of obtaining a reusable positive electrode active material by surface-coating the washed positive electrode active material.

[0194] The method for regenerating a positive electrode active material of the present invention includes the step of (d) surface-coating a washed positive electrode active material to obtain a reusable positive electrode active material, and in this case, there is an effect of improving structural stability and electrochemical performance while maintaining the excellent properties of the positive electrode active material itself.

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

[0196]

[0197] The coating agent including the above metal is preferably 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, even more preferably a coating agent containing tungsten (W) and boron (B), and a specific example thereof is a coating agent including tungsten boride (WB), in which case there is an effect of improving resistance characteristics and life characteristics.

[0198] 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 may be used as the boron-containing coating agent, in which case there is an effect of improving resistance characteristics and life characteristics.

[0199] The coating agent containing the above metal may be, for example, an oxide, acid, etc. containing the metal as an element in the molecule.

[0200] 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.

[0201] 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.

[0202]

[0203] 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, there is an effect of improving structural stability and electrochemical performance while maintaining the excellent properties of the positive electrode active material itself.

[0204]

[0205] The above heat treatment temperature may be 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.

[0206] The heat treatment time is preferably 1 to 16 hours, more preferably 3 to 7 hours, and within this range, the properties of the positive electrode active material itself are maintained while improving structural stability and electrochemical performance.

[0207]

[0208] 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.

[0209]

[0210] 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.

[0211] 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.

[0212] In the present invention, the average diameter can be measured by a measuring method commonly used in the technical field to which the present invention belongs, and for example, can be measured using a laser diffraction method. Specifically, after dispersing the particles of the positive electrode active material in a dispersion medium, the particles are introduced into a commercially available laser diffraction particle size measuring device such as Microtrac MT 3000, and ultrasonic waves of about 28 kHz are irradiated at an output of 60 W, and the average particle diameter (D50) based on 50% of the particle diameter distribution in the measuring device can be calculated.

[0213] 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.

[0214]

[0215] The positive electrode active material regenerated according to the above positive electrode active material regeneration method may preferably contain fluorine (F) of 5,700 to 6,500 mg / kg, more preferably 5,800 to 6,300 mg / kg, and even more preferably 5,800 to 6,100 mg / kg, and within this range, the charging capacity, resistance characteristics, and capacity characteristics are excellent.

[0216] In this description, the fluorine (F) content can be measured using an IC analysis device, and at this time, it can be measured using a general IC analysis device widely used in laboratories, but there is no deviation depending on the measurement device or method.

[0217]

[0218] 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, 2.8753 to 2.8772 Å, preferably 2.8760 to 2.8770 Å, more preferably 2.8762 to 2.8768 Å, and even more preferably 2.8764 to 2.8768 Å, and within this range, the positive electrode active material has a different lattice structure due to a decrease in the a-axis lattice constant compared to the raw positive electrode active material, and has excellent effects in terms of charge capacity, resistance characteristics, and capacity characteristics.

[0219]

[0220] 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, 14.243 to 14.255 Å, preferably 14.245 to 14.254 Å, more preferably 14.247 to 14.254 Å, and even more preferably 14.249 to 14.254 Å, and within this range, the lithium concentration in the lattice increases in the c-axis, which means the z-axis direction of the layered structure, so that the charging capacity, resistance characteristics, and capacity characteristics are excellent.

[0221]

[0222] The positive electrode active material regenerated according to the above positive electrode active material regeneration method has a cell volume measured by XRD analysis of, for example, 101.968 to 102.168 Å. 3 , preferably 101.980 to 102.163 Å 3 , more preferably 102.000 to 102.158 Å 3 , more preferably 102.100 to 102.153 Å 3 It can be, and within this range, it has excellent effects in terms of charging capacity, resistance characteristics and capacity characteristics.

[0223]

[0224] 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, more than 130 nm and less than or equal to 136 nm, preferably 131 to 135 nm, preferably 131 to 134 nm, and within this range, the crystallite size is larger than that of the secondary particles, and the ionic conductivity is improved, thereby providing an excellent capacity characteristic.

[0225]

[0226] 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 in this case, it has excellent effects in terms of initial discharge capacity, output performance, capacity characteristics, and resistance characteristics.

[0227]

[0228] The following Figure 3 is a flowchart for a regeneration process of a positive electrode active material according to one embodiment of the present invention.

[0229] Referring to Fig. 3, first, a positive electrode scrap is prepared as a positive electrode (step S10).

[0230] For example, a slurry prepared by mixing a single-particle mid-nickel 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. From this, cathode plates of a certain size are stamped out, and the remaining cathode scrap can be prepared.

[0231] 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.

[0232]

[0233] Next, the prepared positive electrode scrap is crushed into an appropriate size (step S20).

[0234] 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.

[0235] 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.

[0236]

[0237] Next, the positive electrode scrap is heat-treated to recover the positive electrode active material (step S30). Here, the heat treatment is performed to thermally decompose the binder within the active material layer. As described above, through the heat treatment, the binder and conductive material within the active material layer are thermally decomposed into CO2 and H2O and removed. Since the binder is removed, the positive electrode active material is separated from the current collector, and the separated positive electrode active material can be easily sorted into a 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 a powder form.

[0238] 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.

[0239] The above heat treatment can be performed in air or an oxygen atmosphere, specifically 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. Carbonization leaves carbon components 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 components in the binder and conductive agent react with oxygen and disappear into gases such as CO and CO2, thereby removing both the binder and conductive agent.

[0240] 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.

[0241] The above heat treatment can be 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 as a specific example, at a temperature increase rate of 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.

[0242] 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 for 30 minutes or more, more preferably for 30 minutes to 5 hours, and as a specific example, can be performed for about 30 minutes, and within this range, the binder is sufficiently thermally decomposed and also has an excellent thermal decomposition efficiency.

[0243] The above heat treatment can be performed using various types of furnaces, for example, a box-type furnace, or a rotary kiln capable of continuous treatment considering productivity.

[0244] After the above heat treatment, it can be cooled slowly or rapidly in the air.

[0245]

[0246] Next, the recovered positive electrode active material is subjected to primary milling (step S40).

[0247] It is important that the above first milling step directly mills the recovered positive electrode active material without a shear washing process. In this case, the surface of the single-particle positive electrode active material is not damaged, the clumped positive electrode active material is released, and the particles are made uniform. In addition, since the washing process is not performed, no loss of lithium occurs due to washing, and the efficiency, life characteristics, and resistance characteristics are superior.

[0248] The above first milling can be performed using, for example, a centrifugal mill, a jet mill, or a pin mill. As a specific example, the first milling can be performed using a pin mill. In this case, there is an advantage in that the surface of the recovered single-particle positive electrode active material is not damaged, and the particles are uniformized, thereby improving battery characteristics.

[0249] The above first milling can be performed, for example, at 6,000 to 18,000 rpm, specifically 12,000 ppm, and within this range, the surface of the single-particle positive electrode active material is not damaged, and the particles are uniformized, thereby improving battery characteristics.

[0250]

[0251] Next, a lithium precursor is added to the first milled positive electrode active material and annealed (step S50).

[0252] Since the above annealing step causes a loss of lithium in the positive electrode active material during the preceding step S30, step S50 compensates for such lithium loss. 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, step S50 restores the crystal structure of the single-particle positive electrode active material 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', and means something that is created for the first time, and is the same as the 'raw material' used in the detailed description and examples of the invention.

[0253] The lithium precursor may be, for example, one or more of LiOH, Li2CO3, LiNO3, and Li2O, and LiOH may be used as a specific example.

[0254]

[0255] 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.

[0256] 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 a margin of error of approximately ±0.02.

[0257]

[0258] 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 700°C as a specific example.

[0259] 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 is suitably 400 to 750°C, more preferably 500 to 720°C, and most preferably 600 to 720°C.

[0260]

[0261] The above annealing time is preferably set to 1 hour or more, taking into account crystal structure recovery, and can be preferably set to 15 hours or less, and more preferably 4 to 6 hours. A longer annealing time allows sufficient crystal structure recovery, but even long-term annealing does not significantly affect performance. In this case, the annealing equipment can be the same or similar equipment as that used in the heat treatment step S30.

[0262]

[0263] Next, the annealed positive electrode active material is subjected to secondary milling (step S60).

[0264] The above secondary milling step S60 improves battery characteristics by dissolving the particles clumped together during the annealing step S50, thereby reducing the particle size of the regenerated positive electrode active material to be similar to the particle size of the positive electrode active material in the spent positive electrode, and has the advantage of reducing wastewater by effectively removing the lithium precursor and / or fluorine with a small amount of washing liquid in the subsequent washing process.

[0265] The above secondary milling can be performed using, for example, a centrifugal mill, a jet mill, or a pin mill, and as a specific example, the milling process can be performed using a pin mill, in which case there is an advantage in that the particle size of the regenerated positive electrode active material is reduced without damaging the particles.

[0266] The above secondary milling can be performed at, for example, 6,000 to 16,000 rpm, specifically 12,000 rpm, and within this range, there are advantages of excellent milling efficiency, reduction in particle size of the regenerated positive electrode active material, and excellent productivity.

[0267]

[0268] Next, the secondary milled positive electrode active material is washed (step S70).

[0269] In the above washing step S70, lithium precursors that did not participate in the reaction in the above annealing step S50 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.

[0270] In the above washing step S70, the positive electrode active material and the washing solution from the above annealing step S50 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, the particles clumped together through milling in the previous step are loosened, so that residual lithium is cleanly removed with a small amount of washing solution, thereby reducing wastewater, which is advantageous.

[0271]

[0272] 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.

[0273]

[0274] 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.

[0275] 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.

[0276] The above mechanical stirring is preferably performed under conditions of 250 to 350 rpm and 3 to 10 minutes.

[0277] 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.

[0278]

[0279] Next, surface coating is performed on the washed positive electrode active material (step S80).

[0280] 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.

[0281] 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.

[0282] The solid or liquid method of the above surface coating may be, for example, mixing, milling, spray drying or grinding.

[0283]

[0284] If the molar ratio of lithium to other metals in the positive electrode active material is 1:1 in the annealing step S50, 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.

[0285]

[0286] secondary battery

[0287] The secondary battery of the present invention includes the above-described regenerated single-particle positive electrode active material, and in this case, by significantly reducing lithium remaining on the surface of the positive electrode active material, 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 positive electrode active material, it is environmentally friendly, and in particular, since the shear washing process is omitted, it has excellent economic efficiency and productivity.

[0288]

[0289] 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.

[0290]

[0291] 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.

[0292]

[0293] [Example]

[0294] Example 1

[0295] 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) 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.

[0296] The recovered positive electrode active material was confirmed to be a single particle through SEM photography.

[0297] The recovered positive electrode active material was first milled at 12,000 rpm using a pin mill without shear washing.

[0298] LiOH, a lithium precursor, was added to the first milled positive electrode active material in an amount that can provide 10 mol% of lithium when the total lithium in the raw positive electrode active material is 100 mol%, and the mixture was annealed in air at a sintering temperature of 700°C for 5 hours. Here, air was supplied at a rate of 3 L / min.

[0299] The above annealed positive electrode active material was milled a second time using a pin mill at 12,000 rpm.

[0300] The above-mentioned secondary milled 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.

[0301] 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 500 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.

[0302] 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.

[0303] In this document, ppm is based on weight unless otherwise specified.

[0304]

[0305] Example 2

[0306] A regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that the first milling was not performed in Example 1.

[0307]

[0308] Example 3

[0309] A regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that secondary milling was not performed in Example 1.

[0310]

[0311] Comparative Example 1

[0312] A regenerated cathode 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 cathode scrap discarded after the cathode plate was punched out 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).

[0313] The positive electrode active material recovered after heat treatment was confirmed to be a secondary particle through SEM images.

[0314]

[0315] Comparative Example 2

[0316] 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) 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.

[0317] The recovered positive electrode active material was confirmed to be a single particle through SEM photography.

[0318] The recovered positive electrode active material was washed by immersing it in distilled water and stirring it simultaneously. At this time, the recovered positive electrode active material:distilled water was mixed at a weight ratio of 1:10, stirred at 500 rpm for 10 minutes, and then filtered under reduced pressure using a filter to extract only the active material.

[0319] The above-mentioned washed cathode active material was dried overnight at 100°C, and then LiOH, a lithium precursor, was added in an amount that can provide 10 mol% of lithium when the total lithium in the raw cathode active material is 100 mol%, and annealed in air at a sintering temperature of 700°C for 5 hours. Here, air was supplied at 3 L / min.

[0320] 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.

[0321] 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 500 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.

[0322]

[0323] Comparative Example 3

[0324] A regenerated positive electrode active material was manufactured in the same manner as in Example 1, except that in the surface coating step of Example 1, boric acid was not added and the final regenerated positive electrode active material was manufactured by heating at 300°C for 5 hours.

[0325]

[0326] Comparative Example 4

[0327] 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) 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.

[0328] The recovered positive electrode active material was confirmed to be a single particle through SEM photography.

[0329] The recovered positive electrode active material was manufactured by performing only the first milling at 12,000 rpm using a pin mill without washing, and annealing, second milling, post-washing, and coating were not performed.

[0330]

[0331] Comparative Example 5

[0332] 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.

[0333]

[0334] [Test Example I: Fluorine (F) Content]

[0335] The fluorine content of the regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was measured using an ICP analyzer, and the results are shown in Table 1 below. At this time, the measurement can be performed using a general ICP analyzer widely used in laboratories, but there is no deviation depending on the measuring device or method.

[0336]

[0337] Classification F (mg / kg) Example 15815 Example 26300 Example 36000 Comparative Example 16050 Comparative Example 2160 Comparative Example 35540 Comparative Example 47200 Comparative Example 5 < 10

[0338] As shown in Table 1 above, it was confirmed that the fluorine content of the regenerated positive electrode active materials of Examples 1 to 3 according to the present invention was within the range of 5700 to 6500 ppm. On the other hand, the regenerated positive electrode active material of Comparative Example 2 had a reduced fluorine content as it was washed twice, but generated a lot of wastewater and further caused a lot of lithium loss, and the fluorine content of the regenerated positive electrode active material of Comparative Example 3 was at a similar level to Example 1, indicating that the surface coating did not affect the fluorine content.

[0339] In addition, the regenerated positive electrode active material of Comparative Example 4, which was manufactured by performing only the first milling, had a significantly increased fluorine content compared to Example 1.

[0340] In addition, Comparative Example 5, which is a new positive electrode active material, has a low fluorine content, and Comparative Example 1, which is a regenerated positive electrode active material including secondary particles, has a fluorine content at the level of the examples.

[0341]

[0342] [Experimental Example II: CHC Cell Evaluation]

[0343] The electrochemical performance of the regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was measured through the CHC cell evaluation as follows, and the results are shown in Table 2 below.

[0344]

[0345] * CHC cell evaluation: 97.5 wt% of the recycled positive electrode 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 a positive electrode, and then a cell (Coin Half Cell, CHC) was manufactured. The electrochemical performance (charge capacity CH, discharge capacity DCH, and charge / discharge efficiency Eff (%)) was evaluated under the conditions of 3-4.45 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.

[0346] The charge / discharge efficiency is calculated using the following mathematical formula 1 and shown in Table 2.

[0347] [Mathematical Formula 1]

[0348] Charge / discharge efficiency (%) = [Discharge capacity (mAh / g) / Charge capacity (mAh / g)] * 100

[0349]

[0350] CHC CapacityCharge Capacity (mAh / g)Discharge Capacity (mAh / g)Charge / Discharge Efficiency (%)Example 1217.0197.090.8Example 2216.3196.290.7Example 3216.7196.490.6Comparative Example 1222.4201.389.7Comparative Example 2216.9195.390Comparative Example 3213.6189.388.6Comparative Example 4209.7177.884.8Comparative Example 5219.1197.490.1

[0351] As shown in Table 2 above, it was confirmed that the regenerated positive electrode active materials of Examples 1 to 3 according to the present invention had better charge capacity (CH), discharge capacity (DCH), and / or charge / discharge efficiency (Eff) than the regenerated positive electrode active materials or new positive electrode active materials of Comparative Examples 1 to 5. In particular, it was found that Comparative Example 2, which was washed instead of milled, had lower discharge efficiency and charge / discharge efficiency than Examples 1 to 3.

[0352] [Experimental Example III: XRD Analysis]

[0353] The a-axis lattice constant, c-axis lattice constant, cell volume, and crystal grain size of the regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were measured by XRD analysis, and the results are shown in Table 3 below.

[0354]

[0355] * 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 cell volume was calculated as the product of the a-axis lattice constant and the c-axis lattice constant, and the crystallite size was calculated using the Scherrer equation from the XRD measurement data.

[0356]

[0357] XRD a-axis lattice constant (Å) c-axis lattice constant (Å) cell volume (Å 3) Grain size (nm) Example 12.876814.253102.148134 Example 22.876414.254102.134131 Example 32.876514.251102.116133 Comparative Example 12.874114.234101.820140 Comparative Example 22.876614.252102.132129 Comparative Example 32.877614.250102.189162 Comparative Example 42.879614.256102.369122 Comparative Example 52.877614.250102.187165

[0358] As shown in Table 3 above, it can be seen that the regenerated positive electrode active material (Examples 1 to 3) according to the present invention has different a-axis lattice constants, c-axis lattice constants, cell volumes, and grain sizes from those of the newly produced positive electrode active material (Comparative Example 5). Specifically, the a-axis lattice constant and cell volume are small, and the c-axis lattice constant and grain size are large. From this, it can be seen that the regenerated single-particle positive electrode active material according to the present invention has different crystal structures and grain sizes from those of the newly produced positive electrode active material through milling before and / or after annealing. In addition, it can be confirmed that the regenerated positive electrode active materials of Examples 1 to 3 have different a-axis lattice constants, c-axis lattice constants, cell volumes, and grain sizes from those of the regenerated positive electrode active materials of Comparative Examples 1 to 4.

[0359]

[0360] [Test Example IV: Evaluation of High-Temperature Life Characteristics]

[0361] The capacity retention rate of the CHC cell manufactured as described above from the regenerated or newly produced positive electrode active materials manufactured or prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was measured as follows, and the results are shown in Figure 2 below.

[0362]

[0363] * High-temperature life characteristic evaluation: At 45 ℃, 30 cycles of charge and discharge were performed on each cell under the following conditions, and the capacity retention rate for each cycle was calculated using the following mathematical formula 2 and shown in Figure 2 below.

[0364] Charge: 0.33C, CC / CV, 4.5V, 0.05C cut-off

[0365] Discharge: 0.33C, CC, 3.0V, 0.05C cut-off

[0366]

[0367] [Equation 2]

[0368] Capacity retention rate (%) = (discharge capacity after N cycles / discharge capacity after 1 cycle) * 100

[0369]

[0370] The following Figure 2 is a graph showing the capacity retention rate according to the number of cycles (Cycle No.) as a result of evaluating the life characteristics of the regenerated single particle positive electrode active material (Examples 1 to 3) according to the present invention, the regenerated secondary particle positive electrode active material (Comparative Example 1), the regenerated positive electrode active material washed without milling (Comparative Example 2), the regenerated positive electrode active material heat-treated without adding boric acid in the surface coating step (Comparative Example 3), the regenerated positive electrode active material subjected only to the first milling step (Comparative Example 4), and the new positive electrode active material (Comparative Example 5).

[0371] Referring to this, it was confirmed that the regenerated positive electrode active material according to the present invention (Examples 1 to 3) had a superior capacity retention rate compared to the regenerated positive electrode active material of Comparative Examples 1 to 4, and was also superior to the newly produced positive electrode active material (Comparative Example 5).

[0372] In particular, it was confirmed that Comparative Example 1, which includes a secondary particle positive electrode active material, had a very low capacity retention rate despite milling being performed both before and after annealing.

[0373]

[0374] [Explanation of symbols]

[0375] 10: Whole house

[0376] 20: Active material layer

[0377] 30: Bipolar sheet

[0378] 40: Bipolar plate

[0379] 50: Bipolar scrap

Claims

1. 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, The F content comprises 5,700 to 6,500 mg / kg, and / or The a-axis lattice constant measured by X-ray diffraction analysis (XRD) was 2.8753 to 2.8772 Å, the c-axis lattice constant was 14.243 to 14.255 Å, and the cell volume was 101.968 to 102.168 Å. 3 and characterized by a crystal grain size of more than 130 nm and less than or equal to 136 nm. Positive active material.

2. In paragraph 1, The above positive electrode active material is characterized in that it contains Ni in an amount of 40 mol% or more based on 100 mol% of the total metals excluding Li. Positive active material.

3. In paragraph 1, 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.

4. In paragraph 1, The above positive electrode active material is characterized in that it is a regenerative positive electrode active material. Positive active material. 5.(a) A step of heat-treating a waste positive electrode having a positive electrode active material layer formed on a current collector at 300 to 650°C to thermally decompose a binder and a conductive material within the positive electrode active material layer, thereby recovering a positive electrode active material including single particles within 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; (c) a step of washing the annealed positive electrode active material with a washing solution; and (d) a step of surface coating the washed positive electrode active material; A step of milling the positive electrode active material recovered in the above step (b) before annealing; and / or A step of milling the annealed positive electrode active material in the above step (c) before washing; characterized in that it includes; Method for regenerating positive electrode active material. 6.(a) A step of heat-treating a waste positive electrode having a mid-nickel positive electrode active material layer formed on a current collector at 300 to 650°C to thermally decompose a binder and a conductive agent within the positive electrode active material layer, thereby recovering a positive electrode active material including single particles within 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; (c) a step of washing the annealed positive electrode active material with a washing solution; and (d) a step of surface coating the washed positive electrode active material; A step of milling the positive electrode active material recovered in the above step (b) before annealing; and / or A step of milling the annealed positive electrode active material in the above step (c) before washing; characterized in that it includes; Method for regenerating positive electrode active material.

7. In paragraph 5 or 6, The above cathode active material layer 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 is characterized in that it contains 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.

8. In paragraph 5 or 6, The above milling is characterized in that it is performed using a centrifugal mill, a jet mill, or a pin mill. Method for regenerating positive electrode active material.

9. In paragraph 5 or 6, The above milling is characterized in that it is performed at 6,000 to 18,000 rpm. Method for regenerating positive electrode active material.

10. In paragraph 5 or 6, 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.

11. In paragraph 5 or 6, 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.

12. In paragraph 5 or 6, In the above step (c), the washing is characterized in that the weight ratio of the annealed positive electrode active material or the milled positive electrode active material and the washing solution is 1:0.5 to 1:5.

5. Method for regenerating positive electrode active material.

13. In paragraph 5 or 6, The washing of the above step (c) is characterized by including a step of mixing the annealed positive electrode active material or the milled positive electrode active material with the washing solution and 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.

14. In paragraph 5 or 6, The surface coating of the above step (d) 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.

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