Active material recovery apparatus and positive active material recycling method

Abstract

Provided are: an apparatus for recycling active materials, which is capable of easily recycling electrode active materials in an original shape from electrode scrap, and a method for recycling positive electrode active materials by using the apparatus. The apparatus for recycling active materials according to the present invention is a rotary type firing apparatus, which includes a heat treatment tank forming a heating zone and a screening wall body forming a cooling zone arranged in a line along an axis, and a waste gas injection and degassing system, wherein, in the heat treatment tank, electrode scrap in which a current collector including an active material layer is heat-treated in air while being rotated around the axis, thereby removing a binder and a conductive material from the active material layer to separate the current collector from the active material layer, the active material in the active material layer passes through the screening wall body and the active material in the form of a powder is recycled, the current collector which is not allowed to pass through the screening wall body is separately recycled, and a jagged irregularity is formed in the inside of the heat treatment tank when viewed in a cross section perpendicular to the axis.

Description

Technical Field

[0001] This disclosure relates to a method for the cyclical reuse of resources in the manufacture of lithium-ion secondary batteries. In particular, this disclosure relates to an apparatus for recovering electrode active materials from electrode waste generated during the lithium-ion secondary battery manufacturing process or from used and discarded lithium-ion secondary batteries, and to a method for reusing the recovered active materials. This application claims priority to Korean Patent Application 10-2020-0106079, filed in Korea on August 24, 2020, the disclosure of which is incorporated herein by reference. Background Technology

[0002] Rechargeable lithium-ion batteries have gained attention as an alternative to fossil fuels. While primarily used in traditional handheld devices such as mobile phones, cameras, and power tools, their applications have recently expanded to electric vehicles (EVs, HEVs, and PHEVs), high-capacity energy storage systems (ESS), and uninterruptible power supply systems (UPS).

[0003] Lithium-ion rechargeable batteries comprise: electrode assemblies, wherein a cell has a structure in which a positive electrode plate coated with an active material on a current collector and a negative electrode plate are arranged with a separator between them; and external material (i.e., the battery casing), which seals and houses the electrode assemblies together with the electrolyte. The positive electrode active material of lithium-ion rechargeable batteries primarily uses lithium-based oxides, while the negative electrode active material uses carbon materials. Lithium-based oxides contain metals such as cobalt, nickel, or manganese. In particular, cobalt, nickel, and manganese are very expensive precious metals. Cobalt, in particular, is a strategic metal, and every country in the world pays close attention to its supply and demand. Due to the limited quantity produced by cobalt-producing countries, it is recognized as a metal whose supply and demand are unstable globally. If the supply and demand of raw materials for strategic metals become unbalanced, the price of those raw materials is highly likely to rise.

[0004] Traditionally, research has primarily focused on the recycling and cyclical reuse of these precious metals from lithium-ion batteries discarded at the end of their lifespan (waste batteries). However, it would be even better if resources could be recovered from waste materials discarded after punching the positive electrode plates, or from positive electrode plates that were defective during the punching process, in addition to waste batteries.

[0005] Currently, when manufacturing lithium secondary batteries, such as Figure 1As shown, a positive electrode sheet 30 is manufactured by forming a positive electrode active material layer 20, wherein a long sheet-type positive electrode current collector 10, such as aluminum (Al) foil, is coated with a positive electrode slurry, which contains a mixture of positive electrode active material, conductive material, binder, solvent, etc.; then, a positive electrode plate 40 is punched out to a certain size. The remaining portion after punching is discarded as positive electrode waste 50. If the positive electrode active material can be recovered from the positive electrode waste 50 and reused, it would be highly desirable from both an industrial economic and environmental perspective.

[0006] Traditionally, the recovery of cathode active materials is mostly carried out by dissolving the cathode in hydrochloric acid, sulfuric acid, nitric acid, etc., and then extracting active material elements such as cobalt, nickel, and manganese. These extracted active material elements are then reused as raw materials for synthesizing cathode active materials. However, the method of extracting active material elements using acids has disadvantages: the pure raw material recovery process is not environmentally friendly and requires neutralization and wastewater treatment processes, which increases process costs. Furthermore, this method may not be able to recover lithium, one of the main elements in cathode active materials. To overcome these disadvantages, a direct reuse method is needed that does not require dissolving the cathode active material and extracting the active material in elemental form. Summary of the Invention

[0007] Technical issues

[0008] This disclosure aims to provide an active material recovery device that can easily recover electrode active materials from electrode waste in their original shape.

[0009] This disclosure also aims to provide a method for reusing positive electrode active materials using the active material recovery device.

[0010] Technical solution

[0011] In one aspect of this disclosure, an active material recovery device is provided, comprising: a heat treatment tank and a screening wall, the heat treatment tank and the screening wall being arranged in a line along an axis, wherein the heat treatment tank constitutes a heating zone and the screening wall constitutes a cooling zone; and a waste gas injection and degassing system, wherein the heat treatment tank removes binders and conductive materials in the active material layer by heat-treating the electrode waste, which includes an active material layer on a current collector, in air while rotating the current collector about the axis, and separates the current collector from the active material layer, wherein the active material in the active material layer passes through the screening wall and is recovered as active material in powder form, and the current collector that does not pass through the screening wall is recovered separately, and serrated irregularities are formed in the interior of the heat treatment tank on a cross section orthogonal to the axis.

[0012] Preferably, a spiral rod is provided at the center of the heat treatment tank and the cooling zone as one axis, and the rod rotates.

[0013] The irregular portion may be continuous or discontinuous along the axis.

[0014] Inside the screening wall, serrated irregularities may be formed on a cross-section orthogonal to the axis. These irregularities may be continuous or discontinuous along the axis.

[0015] Air inlets can preferably be formed at multiple locations in the heat treatment tank.

[0016] The air inlet may be formed in the irregular portion and the rod.

[0017] The heat treatment tank can also rotate around the rod.

[0018] The angle of the entire active material recycling device can be adjusted so that the axis of the rod is tilted relative to the ground.

[0019] The active material recovery equipment may have a vibration function.

[0020] The input of new electrode waste and the recycling of the active material can be carried out continuously.

[0021] Preferably, the heat treatment tank has a tubular shape with open ends, so that the electrode waste can be placed into the heat treatment tank and the separated current collector and active material can be conveyed to the screen wall, and the tube is an open system for air to enter and exit.

[0022] Preferably, the screening wall has a tubular shape with open ends, so that the separated current collector and active material can be placed into the screening wall and the current collector can be discharged.

[0023] The heat treatment tank is preferably an open system, wherein air is added or injected at a rate of 10 ml / min to 100 liters / min per 100 grams of electrode waste.

[0024] In one aspect of this disclosure, a method for reusing positive electrode active material is provided, the method comprising: preparing an active material recycling device according to the present disclosure; placing positive electrode waste into a heat treatment tank, the positive electrode waste comprising a lithium composite transition metal oxide positive electrode active material layer on a current collector; removing binders and conductive materials in the active material layer and separating the current collector from the active material layer by heat-treating the positive electrode waste in air while rotating the positive electrode waste about an axis in the heat treatment tank; recovering active material in powder form that has passed through a screening wall; and annealing the active material in air at 400°C to 1000°C to obtain reusable active material.

[0025] Furthermore, the heat treatment can be performed at temperatures between 300°C and 650°C. The heat treatment can be carried out at 550°C for 30 minutes with a temperature rise rate of 5°C / minute.

[0026] Carbon components generated from the carbonization of binders or conductive materials will not remain on the surface of the recycled active materials.

[0027] The method for reusing the positive electrode active material may further include cleaning the recovered active material with a lithium compound solution that is alkaline in aqueous solution before the annealing step. In this case, it is preferable to add a lithium precursor to the cleaned active material before the annealing step. The lithium compound aqueous solution can be prepared to contain more than 0% and equal to or less than 15% lithium compound, and LiOH is preferred. Cleaning can be carried out within one hour. The cleaning step can be performed by immersing the recovered active material in the lithium compound aqueous solution while agitating the recovered active material.

[0028] As another embodiment, the method for reusing the positive electrode active material may further include, after the cleaning step, mixing the cleaned active material with a lithium precursor solution and spray-drying the active material to obtain an active material with added lithium precursor and adjusted particle size.

[0029] The method for reusing the positive electrode active material may further include a step of surface coating on the annealed active material.

[0030] The lithium precursor used for annealing may include at least one of LiOH, Li2CO3, LiNO3, and Li2O.

[0031] The lithium precursor can be added in an amount equal to the proportion of lithium loss compared to the ratio of lithium to other metals in the raw material active material used in the active material layer. For example, the lithium precursor can be added in a lithium addition amount of 0.001 to 0.4 molar ratio. Alternatively, the lithium precursor can be added in an amount of 0.0001 to 0.1 molar ratio relative to a 1:1 molar ratio of lithium to other metals. The annealing temperature can exceed the melting point of the lithium precursor.

[0032] Performing surface coating may include coating a surface with at least one of a metal, organometallic and carbon component in a solid or liquid manner, followed by heat treatment at 100°C to 1200°C.

[0033] The reusable active material is represented by the following chemical formula 1.

[0034] [Chemical Formula 1]

[0035] Li a Ni x Mn y Co z M w O 2+δ

[0036] (In the above chemical formula 1, M includes at least one selected from the group consisting of B, W, Al, Ti, and Mg, 1) <a≤1.1,0≤x<0.95,0≤y<0.8,0≤z<1.0,0≤w≤0.1,-0.02≤δ≤0.02,x+y+z+w=1。)

[0037] The reusable active material may include fluorine (F) in a content equal to or less than 100 ppm.

[0038] Beneficial effects

[0039] According to this disclosure, an active material recovery device can be provided that can easily separate electrode active materials from the current collector by introducing a rotating heat treatment tank during the heat treatment process to increase the air contact rate, and continuously separate the electrode active materials from the current collector. The heat treatment tank, including a serrated irregular portion, can maximize the uniform contact between a large amount of electrode waste and air, thus enabling the recovery of active materials with a high recovery rate.

[0040] In existing recycling equipment, since most waste electrodes are added to the equipment by shredding, separate cutting equipment is required, which may result in equipment contamination (impurities) due to small aluminum fragments. However, the active material recycling equipment according to this disclosure includes a serrated irregular section, so the electrode waste, including defective electrodes, can be cut even when it is put in as is.

[0041] Using the active material recovery equipment according to this disclosure, positive electrode active materials can be recovered from positive electrode waste. This method can reuse waste positive electrode active materials (such as positive electrode waste generated in the manufacturing process of lithium secondary batteries) without the use of acid, and is therefore eco-friendly. The method according to this disclosure does not require neutralization or wastewater treatment processes, thereby mitigating environmental problems and reducing processing costs.

[0042] According to this disclosure, the positive electrode active material can be recovered without any unrecoverable metal elements. Since the current collector is not dissolved, it can also be recovered. This method allows for the direct reuse of the active material recovered in powder form, rather than extracting the active material elements and using them as raw materials to resynthesize the positive electrode active material; therefore, this method is economical.

[0043] According to this disclosure, toxic and explosive solvents such as NMP, DMC, acetone, and methanol are not used, therefore the method is safe. Simple processes such as heat treatment, cleaning, and annealing are utilized, making these processes easy to manage, and the method is suitable for large-scale production.

[0044] According to this disclosure, the electrochemical performance of the recovered active material will not deteriorate, and excellent resistance and capacity characteristics can be achieved. Attached Figure Description

[0045] The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the foregoing disclosure, help to further understand the technical features of the present disclosure; therefore, the present disclosure is not to be construed as limited to the drawings.

[0046] Figure 1 This is a diagram showing the waste positive electrode material discarded after the positive electrode plate is punched out from the positive electrode sheet.

[0047] Figure 2 This is a schematic diagram of an active material recovery device according to one embodiment of the present disclosure.

[0048] Figure 3 yes Figure 2 A cross-sectional view of the heat treatment tank in the active material recovery equipment.

[0049] Figure 4 This is a schematic diagram of an active material recovery device according to another embodiment of the present disclosure.

[0050] Figure 5 This is a schematic diagram of an active material recovery device according to another embodiment of the present disclosure.

[0051] Figure 6 This is a flowchart of a method for reusing active materials according to another embodiment of the present disclosure.

[0052] Figure 7 This is a flowchart of a method for reusing active materials according to another embodiment of the present disclosure.

[0053] Figure 8 This is an image showing the differences in heat treatment results based on the location of the positive electrode waste in Sample 1.

[0054] Figure 9 This is an image showing the state of sample 2 over time according to the experimental process.

[0055] Figure 10 and Figure 11 The results of battery evaluation using the active materials of Embodiments 1 and 2 and Comparative Examples 1 to 5 are shown.

[0056] Figure 12 and Figure 13 These are scanning electron microscope (SEM) images of the active materials of Embodiment 1 and Comparative Examples 1 to 3 and 5.

[0057] Figure 14 These are particle size distribution charts of the active materials in Embodiments 3 and 4, and Comparative Examples 1 and 2.

[0058] Figure 15 The results of battery evaluation using the active materials of Embodiments 3 and 4 and Comparative Example 1 are shown, and the results are summarized in Table 4.

[0059] Figure 16 The battery evaluation results using the active materials of Embodiment 5 and Comparative Examples 6 to 9 are shown.

[0060] Figure 17 XRD patterns of the active materials of Embodiment 5 and Comparative Examples 6, 7 and 9 are shown.

[0061] Figure 18 These are SEM images of the active materials of Embodiment 5 and Comparative Example 6.

[0062] Figure 19 X-ray photoelectron spectroscopy (XPS) spectra of the active materials of Comparative Examples 6, 7, and 9 are shown.

[0063] Figure 20 These are particle size distribution charts of the active materials in Embodiment 5 and Comparative Examples 6, 7 and 9.

[0064] Figure 21 The results of battery evaluation using the active materials of Embodiment 6 and Comparative Examples 6, 7 and 10 are shown.

[0065] Figure 22 XPS graphs of the active materials of Embodiment 6 and Comparative Examples 6 to 8 are shown. Detailed Implementation

[0066] The preferred embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. Before the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general and dictionary meanings, but should be interpreted according to the meanings and concepts corresponding to the technical aspects of this disclosure, based on the principle that inventors are allowed to appropriately define the terms to obtain the best interpretation. Therefore, the descriptions presented herein are merely preferred embodiments for illustrative purposes and are not intended to limit the scope of this disclosure. It should be understood that other equivalent examples and variations can be made without departing from the scope of this disclosure.

[0067] In the following description, reference is made to the accompanying drawings, which form a part of this document. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments and changes may be made without departing from the spirit and scope of the subject matter set forth herein. It will be readily understood that the various aspects of this disclosure, as generally described herein and illustrated in the figures, can be arranged, substituted, combined, separated, and designed into a variety of different configurations, all of which are expressly contemplated herein.

[0068] Unless otherwise defined, all technical and scientific terms used herein generally have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0069] This disclosure should not be limited to the specific embodiments described herein, which are intended to illustrate various aspects. It will be apparent to those skilled in the art that many variations and modifications can be made without departing from the spirit and scope of this disclosure. In addition to the methods and apparatuses listed herein, functionally equivalent methods and apparatuses within the scope of this disclosure will be apparent to those skilled in the art based on the foregoing description. Such variations and modifications should fall within the scope of the appended claims. This disclosure is limited only by the terms of the appended claims and the scope of all their equivalents. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0070] In the traditional process of reusing active materials, the main purpose is to extract precious metals (nickel, cobalt, manganese, etc.) that are elements in the active materials of lithium secondary batteries. These precious metals deteriorate in performance after use and are then resynthesized into active materials. However, the difference in this disclosure is that the active materials are recovered from the positive electrode waste generated during the manufacturing process of lithium secondary batteries.

[0071] Furthermore, in known processes for the cyclic reuse of active materials, the addition of chemical methods—such as acid / alkali dissolution or melting with reduction / additives to extract precious metals and then manufacturing them into metals (direct reduction method) or resynthesizing them into active materials—further complicates the process and incurs economic costs. However, this disclosure relates to a method for directly reusing positive electrode active materials without dissolving them.

[0072] To directly reuse the positive electrode active material, a method for removing the current collector from the positive electrode is needed. This can be achieved through methods such as high-temperature heat treatment to remove the binder, melting the binder with a solvent, completely melting the current collector, and selecting the active material through dry grinding and sieving.

[0073] Solvent stability is crucial for dissolving binders using solvents. While NMP is the most effective solvent, it suffers from toxicity and high cost. Furthermore, it requires solvent recovery processes, such as reprocessing waste solvents. Melting the current collector is cheaper than using solvents. However, it is difficult to remove foreign matter from the surface of the reused active material, and the removal of the current collector generates hydrogen gas, posing an explosion hazard. Dry grinding and sieving are insufficient to completely separate the current collector from the active material. The particle size distribution of the active material changes during grinding, and the binder is difficult to remove, resulting in performance degradation in the reused battery.

[0074] In this disclosure, the active material and the current collector are separated by high-temperature heat treatment. Specifically, equipment for heat treatment in air is provided, which is advantageous for large-scale production and commercialization. Foreign matter should not remain on the surface of the reusable active material. This disclosure even proposes a step for removing foreign matter from the surface of the reusable active material.

[0075] In the following text, refer to Figures 2 to 5 Describes an active material recovery device according to embodiments of the present disclosure.

[0076] first, Figure 2 The active material recovery device 100 shown is a rotary firing device, which includes a heat treatment tank 120 and a screening wall 130.

[0077] The heat treatment tank 120 and the screening wall 130 are arranged in a line along an axis C. The heat treatment tank 120 and the screening wall 130 may be hollow tubes with a certain space to hold the objects to be treated. In this case, the axis C passes through the center of the heat treatment tank 120 and the screening wall 130, and the heat treatment tank 120 and the screening wall 130 can be arranged coaxially.

[0078] The heat treatment tank 120 constitutes a heating zone, and the screening wall 130 constitutes a cooling zone. The heat treatment tank 120 is installed at the front end of the equipment along the conveying direction of the object to be treated, and the screening wall 130 is installed at the rear end of the equipment. By sequentially installing the heat treatment tank 120 and the screening wall 130, the object to be treated is fully heated in the heat treatment tank 120 to induce thermal decomposition, and then conveyed to the screening wall 130.

[0079] The active material recovery equipment 100 also includes a waste gas injection and degassing system 140. The waste gas injection and degassing system 140 can be used to inject air or oxygen into the heat treatment tank 120. The waste gas after heat treatment can be purified using the waste gas injection and degassing system 140, and then discharged.

[0080] Since the active material recovery equipment 100 is a rotary sintering device, the heat treatment tank 120 rotates along axis C. The object to be treated is electrode waste 160, preferably positive electrode waste. Electrode waste 160 includes an active material layer on the current collector 150. The heat treatment tank 120 removes the binder and conductive material in the active material layer by heat-treating the electrode waste 160 in air while rotating it about axis C. The heat treatment can be carried out at 300°C to 650°C, and therefore can also be called high-temperature heat treatment. At temperatures below 300°C, it is difficult to remove the binder, which may prevent the current collector 150 from being separated. At temperatures equal to or greater than 650°C, the current collector 150 may melt (aluminum melting point: 660°C) and may become impossible to separate. When thermal decomposition occurs sufficiently and the binder is removed, the active material layer can be separated from the current collector 150. The rotation direction of the heat treatment tank 120 can be changed in the opposite direction at appropriate time intervals.

[0081] The rotation of the heat treatment tank 120 causes the electrode waste 160 to rotate. Specifically, as... Figure 3As shown in detail, due to the formation of a serrated irregular portion 122 on a cross-section orthogonal to axis C inside the heat treatment tank 120, the rotational characteristics of the electrode waste 160 may increase when the heat treatment tank 120 rotates. When only the heat treatment tank 120 rotates, the electrode waste 160, including heavy metal components, may not rotate well and may only accumulate in the lower part of the interior of the heat treatment tank 120. As a result, the contact with oxygen or air is reduced. The irregular portion 122 has protruding structures that protrude from the interior of the heat treatment tank 120 toward axis C. When the heat treatment tank 120 rotates, the electrode waste 160 is lifted by being sandwiched between the protruding structures of the irregular portion 122 and then separated from the protruding structures by detachment, so that the electrode waste 160 can move around anywhere in the heat treatment tank 120 without accumulating. Furthermore, even if the electrode waste 160 is not finely crushed before being put in, the electrode waste 160 can be cut upon collision with the irregular portion 122. The slit electrode waste 160 can fully contact oxygen or air during rotation. The structure of the irregular portion 122 allows the electrode waste 160 to rotate and mix to a maximum extent. Therefore, incomplete combustion caused by the overlapping of electrode waste can be eliminated.

[0082] The irregular portion 122 can be continuous or discontinuous along axis C; a continuous embodiment is shown in the figure. In the irregular portion 122, protruding structures can be arranged at equal intervals in the circumferential direction and simultaneously form multiple rows in the axial direction. The protruding structures project towards axis C and simultaneously extend in the longitudinal direction of the heat treatment tank 120. The protruding structures can be arranged in the direction of axis C or in a zigzag pattern.

[0083] The active material layer separated from the current collector 150 by heat treatment in the heat treatment tank 120 can have a structure such as individual particles or sheets, wherein the particles are aggregated. Since the active material is not in a continuous film state, the active material is referred to in this disclosure as being in powder form. Accordingly, in the heat treatment tank 120, the active material in powder form can be obtained from the current collector 150 by simple heat treatment in air, and some electrode waste 160 can be conveyed to the screening wall 130 while the active material layer is attached to the current collector 150 only by van der Waals forces, or some active material layers can be separated to become active material 170 in powder form.

[0084] Preferably, the heat treatment tank 120 is a tube open at both ends to allow electrode waste 160 to be placed inside, and to convey active material 170 and current collector 150, in which binders and conductive materials have been removed, to the screening wall 130. Furthermore, it is preferable that the tube is an open system through which air enters and exits. That is, since the tube does not have a closed structure, oxygen from the outside air can be introduced.

[0085] The heat treatment tank 120 includes: a container for receiving, rotating, and mixing electrode waste 160; and a heating unit capable of heat-treating the electrode waste 160 by heating the container. The container can be made of metal or ceramic material. In particular, if the container is made of ceramic material, corrosion caused by reaction with the active material can be prevented, and contamination of the active material by metal ions generated in the container can also be prevented. Furthermore, a heat source such as a microwave oven can be used as the heating unit, thus allowing for a variety of heat source types to be used.

[0086] For example, the container of the heat treatment tank 120 can be a tube made of a ceramic material (e.g., high-purity alumina). Furthermore, since such a tube further includes flanges connecting both ends longitudinally, a heat treatment tank 120 capable of high-capacity processing can be manufactured by connecting two or more tubes to each other and extending their length. Generally, due to the characteristics of the material, it is very difficult to manufacture tubes made of ceramic material exceeding a certain diameter and length, and the product price of such tubes is quite high. Therefore, multiple tubes made of ceramic material with appropriate diameters and lengths can be connected by flanges to the desired length, and by making the tubes to lengths equal to or exceeding several hundred millimeters or several thousand millimeters, high-capacity processing becomes possible.

[0087] The heating unit can be disposed on the outer circumferential surface of the container. For example, the heating unit is a linear heating element, and the heating element is elongated to connect from one side to the other in the longitudinal direction of the container, and can be arranged on the outer circumferential surface of the container. Thus, heat of uniform temperature can be generated in the longitudinal direction of the container. The heating element may include at least one selected from the group consisting of SiC, graphite, carbon nanotubes, carbon nanofibers, and graphene, and may preferably be formed of SiC material.

[0088] The heat treatment tank 120 is preferably an open system, in which air is added or injected at a rate of 10 ml / min to 100 liters / min for every 100 grams of electrode waste 160 placed in. If the heat treatment tank 120 is a tube open at both ends, air addition is smooth. Furthermore, as by Figure 2 and Figure 3 As indicated by the arrows, when air inlets are installed at multiple locations in the heat treatment tank 120, the air or oxygen injected via the waste gas injection and degassing system 140 is smoothly supplied to the portion of the electrode waste 160 that is mixed, thus ensuring that the heat treatment tank 120 is adequately supplied with the air and oxygen required for thermal decomposition.

[0089] When electrode waste 160 is heat-treated, the PVdF (polyvinylidene fluoride) and conductive material present in the active material layer are decomposed and detached from the current collector. However, if sufficient air and oxygen are not supplied, the active material layer will not separate from the current collector due to incomplete combustion, but will instead be strongly carbonized and adhere to the current collector. In this case, fairness is difficult to guarantee due to the reduced recovery rate of the active material. The heat treatment tank 120 can control the amount of air added and has a structure that ensures good contact between the electrode waste 160 and air during heat treatment. In particular, in order to recover a large amount of active material, an irregular portion 122 is formed inside the heat treatment tank 120 to ensure good contact between the electrode waste 160 and air, and the heat treatment tank 120 is also rotated to allow the electrode waste 160 to move around inside the heat treatment tank 120 so as to be heated evenly and to maximize contact with air. Incomplete combustion of the elements constituting the active material layer can be suppressed, thus improving the recovery rate of the finally detached active material. If less than 10 ml / min of air is injected or added per 100 grams of electrode waste, the binder and conductive material will not burn completely, thus reducing the recovery rate of the active material. If more than 100 liters / min of air is injected or added, the active material may be blown away due to the excessive amount added, and temperature control will also be difficult.

[0090] The screening wall 130 may have a mesh structure. The size of the mesh can be appropriately determined so that the current collector 150 does not pass through the screening wall 130. The active material 170 in powder form that passes through the screening wall 130 can be recovered by means of a first collector 180 installed in the lower part of the screening wall 130. The current collector 150 that does not pass through the screening wall 130 can be recovered by means of a second collector 190 installed at the end of the screening wall 130. As described above, when using the active material recovery device 100, each of the active material 170 and the current collector 150 can be recovered. As described above, according to the active material recovery device 100 of this disclosure, the active material 170 can be recovered in its original shape, and the current collector 150 can also be recovered without melting or being discarded.

[0091] The screening wall 130 preferably has a tubular shape with open ends to allow the separated current collector 150 and active material 170 to be placed inside and the current collector 150 to be discharged. The screening wall 130 can also rotate about axis C. If the current collector 150 is stationary, the active material 170 will not easily detach from the current collector 150 because the screening wall 130 does not rotate. With the rotation of the screening wall 130, the active material 170 detaches smoothly from the current collector 150. The current collector 150 and the screening wall 130 collide with each other through the rotation of the screening wall 130, thereby causing the active material 170 to detach from the current collector 150 by impact.

[0092] The screening wall 130 can rotate in the same or opposite direction as the heat treatment tank 120. When the connection between the heat treatment tank 120 and the screening wall 130 is fixed, the heat treatment tank 120 and the screening wall 130 can rotate together. The heat treatment tank 120 and the screening wall 130 can be configured as an integral type or as prefabricated types that are interconnected.

[0093] For example, by forming a connecting groove along the main surface on one side of the heat treatment tank 120 and a connecting protrusion along the main surface on one side of the screening wall 130, the corresponding ends of the heat treatment tank 120 and the screening wall 130 can be securely connected by means of the connecting groove and the connecting protrusion. The connecting groove and the connecting protrusion can be connected by an interference fit connection method or a screw connection method. The connecting groove and the connecting protrusion can also be connected by a locking protrusion and hook structure.

[0094] As described above, when the heat treatment tank 120 and the screening wall 130 are arranged coaxially in a tubular shape, it is preferable that the active material recovery equipment 100 continuously inputs new electrode waste and recovers active materials.

[0095] The screening wall 130 not only includes a heating unit, so a cooling section can be formed by using a slow cooling method of natural cooling, and a cooling means is further provided on the outside of the screening wall 130, so a rapid cooling method or temperature-controlled cooling can be performed.

[0096] Although not shown, serrated irregularities can be formed inside the screening wall 130 on a section orthogonal to the axis C. These irregularities can be continuous or discontinuous along the axis C, similar to the irregularities 122 formed in the heat treatment tank 120. The irregularities formed on the screening wall 130 can facilitate separation.

[0097] Preferably, the active material recovery device 100 also has a vibration function. Vibration can provide physical force so that the active material in which the binder and conductive material have been removed after heat treatment is removed from the current collector. When vibration is applied, the active material 170 in the screening wall 130 passes through the screening wall 130 and falls into the first collector 180 below the screening wall 130.

[0098] then, Figure 4 The active material recovery device 100' shown is a rotary firing device that includes a helical rod 110.

[0099] The heat treatment tank 120 and the screening wall 130 are arranged in a line along the axis of the rod 110. That is, reference... Figure 2 The described active material recovery device 100 further includes a rod 110 arranged to pass through the center of the heat treatment tank 120 and the screening wall 130.

[0100] The heat treatment tank 120 and the screening wall 130 can be arranged coaxially with respect to the rod 110. The rod 110 can be elongated so that it connects from one side to the other in the longitudinal direction of the heat treatment tank 120 and the screening wall 130.

[0101] The active material recovery equipment 100 also includes a waste gas injection and degassing system 140. The waste gas injection and degassing system 140 can be used to inject air or oxygen into the heat treatment tank 120. The waste gas after heat treatment can be purified using the waste gas injection and degassing system 140, and then discharged.

[0102] Rod 110 rotates along its axis. Heat treatment tank 120 removes binder and conductive material from the active material layer by heat-treating electrode waste 160 in air while rotating it about the axis of rod 110. Heat treatment tank 120 may also rotate about the axis of rod 110. In this case, the rotation direction of heat treatment tank 120 may be the same as or opposite to the rotation direction of rod 110. The rotation direction of heat treatment tank 120 may be changed at appropriate time intervals.

[0103] The rotation of rod 110 and / or heat treatment tank 120 causes the electrode waste 160 to rotate. Specifically, rod 110 agitates and pushes the electrode waste 160, which facilitates good contact between the electrode waste 160 and air by agitation and helps the active material layer to be separated as powdered active material 170 by agitation. When only heat treatment tank 120 rotates, the electrode waste 160, including heavy metal components, is likely to rotate poorly and accumulate only in the lower part of the heat treatment tank 120. Thus, contact with oxygen or air is limited. In this disclosure, the electrode waste 160 can be agitated by rotating rod 110 within the heat treatment tank 120. Even if the electrode waste 160 is not finely shredded before being added, it can be chopped by rod 110. The chopped electrode waste 160 rotates with the aid of rod 110, thereby allowing sufficient contact with oxygen or air. The rod 110 does not simply rotate, but rather rotates in a spiral motion; therefore, the rod 110 has protruding structures such as pins, wings, or bars. These protruding structures allow the electrode waste 160 to rotate and mix to the maximum extent. Thus, incomplete combustion caused by the overlapping of electrode waste can be eliminated.

[0104] The heat treatment tank 120 is preferably an open system, in which air is added or injected at a rate of 10 ml / min to 100 liters / min for every 100 grams of electrode waste 160. Since the heat treatment tank 120 is a tube open at both ends, air addition is smooth. Furthermore, when air inlets are installed at multiple locations within the heat treatment tank 120, the air or oxygen injected via the waste gas injection and degassing system 140 is smoothly supplied to the mixed portion of the electrode waste 160, thus ensuring a sufficient supply of air and oxygen required for thermal decomposition to the heat treatment tank 120. In this case, the air inlets can be installed in the irregular portion 122 and the rod 110.

[0105] The heat treatment tank 120 allows for controlled air supply and is structured such that the electrode waste 160 maintains good contact with air during heat treatment. Specifically, to recover a large amount of active material, the rod 110 rotates to ensure good air contact with the electrode waste 160, and the heat treatment tank 120 also rotates, causing the electrode waste 160 to move throughout the tank for uniform heating and maximum air contact. The air and oxygen required for thermal decomposition can be fully and uniformly injected through air inlets located at multiple positions on the irregular portion 122 and the rod 110. According to this configuration, incomplete combustion of elements constituting the active material layer can be suppressed, thus improving the recovery rate of the ultimately released active material.

[0106] then, Figure 5 The active material recovery device 100" shown is characterized in that the angle θ of the entire active material recovery device 100" is adjusted so that the axis of the rod 110 is inclined relative to the ground. As shown, the active material recovery device 100" can be supported in a slightly inclined state, so that the rear end of the active material recovery device 100" (i.e., the right side in the figure) is the lower part. Supports of different heights can be installed at the lower front and lower rear parts of the active material recovery device 100".

[0107] The adjustment of angle θ determines the inclination relative to the ground, allowing the current collector 150 and active material 170 to move downwards under their own weight. As shown, when the inclination is given, the current collector 150 and active material 170 move slowly from left to right via the heat treatment tank 120 and the screening wall 130. The active material 170 in the screening wall 130 passes through the screening wall 130 and falls into the first collector 180 below the screening wall 130, while the current collector 150 that does not pass through the screening wall 130 falls into the second collector 190 installed at the end of the screening wall 130. The angle θ can be maintained at the pre-set state throughout the process, or it can be adjusted and changed as needed during the process.

[0108] The aforementioned active material recovery devices 100, 100', and 100" can process large quantities of electrode waste, thereby significantly improving work efficiency and reducing working time. In particular, the active material recovery devices 100, 100', and 100" are open systems that do not block oxygen from the outside air and can supply sufficient air or oxygen for the complete combustion of the active material layer. The electrode waste can be rotated, which allows for smoother air contact, thus recovering the active material with uniform quality and a high recovery rate.

[0109] The following text will refer to Figure 6 and Figure 7 A method for reusing active materials according to embodiments of the present disclosure is described. First, Figure 6 This is a flowchart of a method for reusing active materials according to another embodiment of the present disclosure.

[0110] refer to Figure 6 First, waste positive electrode material is prepared (step S10).

[0111] As per the above reference Figure 1 The positive electrode waste can be the residue left after punching the positive electrode sheet, which includes a positive electrode active material layer on the current collector. Alternatively, positive electrode waste can be prepared by collecting positive electrodes that have defects during the processing. Furthermore, positive electrode waste can be prepared by separating the positive electrode from discarded lithium-ion batteries after use.

[0112] For example, a slurry is prepared by adding N-methylpyrrolidone (NMP) to lithium cobalt oxide (LiCoO2(LCO)) or NCM-based active materials (including nickel (Ni), cobalt (Co) and manganese (Mn)), carbon-based carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder, and then coating the slurry onto a sheet current collector made of aluminum foil. The sheet is then dried in a vacuum oven at about 120°C to produce a positive electrode sheet, and positive electrode plates of a predetermined size are punched out. The remaining positive electrode waste can also be prepared.

[0113] Lithium-based composite transition metal oxides are used as positive electrode active materials in lithium-ion secondary batteries, primarily utilizing lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compounds (LiFePO4, etc.), or nickel lithium oxide (LiNiO2, etc.). Furthermore, as a method to improve low thermal stability while maintaining the excellent reversible capacity of LiNiO2, nickel-manganese-based lithium composite metal oxides (in which a portion of the nickel (Ni) is replaced by manganese (Mn) with excellent thermal stability) and NCM-based lithium composite transition metal oxides (in which a portion of the nickel (Ni) is replaced by manganese (Mn) and cobalt (Co)).

[0114] As described above, the positive electrode waste has an active material layer on a current collector made of metal foil (such as aluminum foil). This active material layer is formed by coating a slurry containing active material, conductive material, binder, solvent, etc., and has a structure in which the binder connects the active material and the conductive material after the solvent evaporates. Therefore, if the binder is removed, the active material can be separated from the current collector.

[0115] Next, the positive electrode waste is placed into the heat treatment tank 120 of the active material recycling equipment 100, 100' and 100" according to the present disclosure (step S15).

[0116] The method may further include a step of pulverizing the cathode waste to an appropriate size prior to step S15. Pulverization refers to cutting or shredding the cathode waste into suitable, easily handleable fragments. After pulverization, the cathode waste is cut into small fragments, for example, 1 cm × 1 cm. For pulverization, various dry grinding equipment (such as hand mills, pin mills, disc mills, cutting mills, and hammer mills) can be used, or a high-speed cutter can be used. Pulverization can be carried out with consideration of the characteristics (e.g., flowability) required for the disposal of cathode waste and the active material recovery equipment 100, 100', and 100" used in subsequent processes. Since the active material recovery equipment 100, 100', and 100" includes a rod 110, the cathode waste can be shredded as the rod 110 rotates. Therefore, cathode waste that is not too large may be fed in without pulverization.

[0117] Next, the heat treatment tank 120 heat-treats the positive electrode waste in air while simultaneously rotating the waste around axis C (around rod 110 if it is present) to remove the binder and conductive material in the active material layer and separate the current collector from the active material layer (step S30). The heat treatment can be performed at temperatures between 300°C and 650°C, which can be referred to as high-temperature heat treatment. At temperatures below 300°C, it is difficult to remove the binder, resulting in the current collector not being able to be separated. At temperatures equal to or greater than 650°C, the current collector melts (aluminum melting point: 660°C), leading to the current collector not being able to be separated. Therefore, the desired heat treatment temperature is obtained by adjusting the temperature of the heating unit of the heat treatment tank 120.

[0118] A certain heat treatment time is maintained to allow for sufficient thermal decomposition of the adhesive. For example, this heat treatment time is approximately 30 minutes. Preferably, the heat treatment time is set to be equal to or greater than 30 minutes. The longer the heat treatment time, the longer the time for thermal decomposition of the adhesive, but when the heat treatment time exceeds a certain period, there is no difference in the effect of thermal decomposition. Preferably, the heat treatment time is set to be equal to or greater than 30 minutes up to 5 hours.

[0119] For example, a heat treatment of 30 minutes at 550°C can be performed at a temperature rise rate of 5°C / min. This temperature rise rate can be implemented without difficulty (e.g., by means of the heating unit of the heat treatment tank 120), and heating can be performed without causing thermal shock to the positive electrode waste. 550°C allows for good thermal decomposition of the binder while taking into account the melting point of the aluminum current collector. At this temperature, since thermal decomposition is insufficient to occur in less than 10 minutes of heat treatment, heat treatment should be performed for more than 10 minutes, and if possible, for more than 30 minutes.

[0120] Because the binder and conductive material in the active material layer are thermally decomposed in air through heat treatment, turning into CO2 and H2O and being removed. Since the binder is removed, the active material is separated from the current collector, and the active material to be recycled can be in powder form. Therefore, in step S30 alone, the current collector can be separated from the active material layer, and the active material in the active material layer can be recycled.

[0121] Performing the heat treatment in step S30 in air is important. If heat treatment is performed in a reducing or inert gas atmosphere, the binder and conductive material will not be thermally decomposed, but only carbonized. When the binder and conductive material are only carbonized, the carbon component remains on the surface of the active material, which will reduce the performance of the reusable active material. When heat treatment is performed in air, both the binder and conductive material are almost completely removed, leaving no residue, because the carbon material in the binder or conductive material reacts with oxygen and is burned and removed as CO and CO2 gases. The active material recovery devices 100, 100', and 100" are suitable for performing the heat treatment in step S30 because sufficient air contact is possible.

[0122] The heat treatment time refers to the time spent in the heat treatment tank 120 at the desired heat treatment temperature. If the heat treatment time is 30 minutes, the process is controlled so that the positive electrode waste can be heated in the heat treatment tank 120 for 30 minutes and then conveyed to the screening wall 130.

[0123] Now, the active material in powder form that has passed through the screen wall 130 is recovered (step S35). As an open system, the active material recovery devices 100, 100', and 100" can almost completely remove the binder and conductive material through smooth air contact in the aforementioned heat treatment tank 120, and recover the active material in powder form. Since the positive electrode waste conveyed to the screen wall 130 is in a state where the binder has been removed in the previous step, the current collector and active material can be completely detached by means of the rotation of the rod 110. The carbon components generated by the carbonization of the binder or conductive material may not remain on the surface of the active material obtained by passing through the screen wall 130.

[0124] As described above, the use of the active material recovery devices 100, 100', and 100" is complete. By using the active material recovery devices 100, 100', and 100" for heat treatment, the active material can be recovered at a very high recovery rate, and since the recovered active material does not contain carbon components, no separate treatment for carbon removal is required.

[0125] Reusing recycled active materials without modification may lead to poor electrode performance. In this regard, as a subsequent process, this disclosure proposes a method for reusing active materials, which may further include steps such as cleaning, drying, adding lithium precursors, annealing, and surface coating.

[0126] Next, the recovered active material is cleaned and dried (step S40). During the cleaning process, it is important to clean the recovered active material with an aqueous solution of a lithium compound that is alkaline in its aqueous state. This aqueous solution of the lithium compound is prepared to contain greater than 0% and equal to or less than 15% lithium compound, and preferably uses LiOH. The amount of LiOH is preferably equal to or less than 15%. Using excess LiOH may leave excessive LiOH on the surface of the active material even after cleaning, which may affect the subsequent annealing process. In order to clean the surface of the active material as thoroughly as possible in the pre-annealing step, the amount added is limited to equal to or less than 15% because the addition of excess LiOH is detrimental to the process.

[0127] Cleaning can be performed by immersing the recovered active material in an aqueous lithium compound solution. After immersion, cleaning can be carried out within one week (preferably within one day, more preferably within one hour). If cleaning is performed after one week, there is a risk of capacity reduction due to excessive lithium leaching. Therefore, cleaning is preferably carried out within one hour. Cleaning includes immersing the active material in a cleaning solution (such as an aqueous lithium compound solution that is alkaline in its aqueous state), agitating the active material while it is immersed, etc. It is preferable to perform agitation and immersion together whenever possible. If the active material is only immersed in the aqueous lithium compound solution without agitation, the cleaning process may proceed slowly and may result in lithium leaching. Since the process time can be minimized if agitation and immersion are performed together, it is preferable to agitate while immersing in the aqueous lithium compound solution. After filtration, the material can be dried in air in a convection oven.

[0128] The reason for using an aqueous lithium compound solution, which is alkaline in its aqueous state, for cleaning is to remove LiF and metal fluorides that may be present on the surface of the recycled active material and to perform surface modification. In the heat treatment process of step S30, the binder and conductive material in the active material layer are converted into CO2 and H2O, evaporated, and then removed. In this process, CO2 and H2O react with lithium on the surface of the active material to form Li2CO3 and LiOH, and fluorine (F) present in the binder (such as PVdF) reacts with the metal elements constituting the positive electrode active material to form LiF or metal fluorides. If LiF or metal fluorides remain, the battery performance will deteriorate when the active material is reused. In this disclosure, the reactants that may be generated on the surface of the reused active material in the heat treatment process of step S30 are removed by adding the cleaning in step S40, so that foreign matter does not remain on the surface of the active material.

[0129] Clearly, it is important to clean the active material in step S40 using an aqueous lithium compound solution that is alkaline in its aqueous state. While using an aqueous sulfuric acid or hydrochloric acid solution instead of an aqueous lithium compound solution that is alkaline in its aqueous state can clean the F on the surface of the active material, the performance of the reusable cathode active material will decrease because transition metals (Co and Mg) present in the active material will be eluted. The aqueous lithium compound solution that is alkaline in its aqueous state used in the active material reuse method according to this disclosure is highly desirable because it can remove binders that may still be present in trace amounts even after thermal decomposition in step S30, and can replenish the amount of lithium that may be eluted during the cleaning process without eluting transition metals, etc., present in the active material.

[0130] Through step S40, in this disclosure, the LiF content on the surface of the recycled active material can be adjusted to less than 500 ppm, thereby achieving an increased capacity. Preferably, the F content can be set to be equal to or less than 100 ppm. More preferably, the F content can be set to be equal to or less than 30 ppm.

[0131] Next, the lithium precursor is added to the cleaned active material and annealed (step S50).

[0132] In the preceding steps S30 and S40, lithium loss may occur in the active material. In step S50, this lithium loss is compensated for.

[0133] Furthermore, in step S50, the crystal structure of the active material is restored by annealing, thereby restoring or improving the performance of the reused active material to the level of a fresh active material that has never been used.

[0134] Through the preceding steps S30 and S40, deformed structures may appear on the surface of the active material. For example, in an active material that is an NCM-based lithium composite transition metal oxide, a spinel structure may form in step S40, where nickel becomes hydrated and rock-salted [NiCO3·2Ni(OH)2)H2O]. If the battery is manufactured as is, the battery performance may deteriorate (e.g., capacity decrease). In this disclosure, the crystal structure is restored through step S50. For example, the active material that is an NCM-based lithium composite transition metal oxide is restored to a hexagonal structure again. Therefore, it is possible to restore or improve the initial performance of the active material to a level similar to that of a fresh active material.

[0135] The lithium precursor in step S50 may include at least one of LiOH, Li2CO3, LiNO3, and Li2O.

[0136] The amount of lithium precursor added can be the proportion of lithium lost compared to the ratio of lithium to other metals in the original active material (i.e., fresh active material) used for the active material layer before heat treatment. For example, when the ratio of lithium to other metals in the fresh active material is 1, the amount of lithium precursor added can be 0.001 to 0.4 molar ratios. Adding lithium at a molar ratio of 0.01 to 0.2 is appropriate. Besides the amount of lithium lost through cleaning, adding excessive lithium precursor will result in unreacted lithium precursor remaining in the reused active material, which increases resistance during the reuse of the active material. Therefore, it is necessary to apply an appropriate amount of lithium precursor.

[0137] Furthermore, the preferred amount of lithium precursor added is lithium, with an additional 0.0001 to 0.1 molar ratio relative to a 1:1 molar ratio of lithium to other metals. The reason for adding excess lithium as described above is to form a protective surface layer by surface coating on the active material, which will be further described below. When using this active material to manufacture secondary batteries, lifespan characteristics can be maintained while suppressing side reactions caused by the electrolyte.

[0138] The annealing in step S50 can be performed in air at 400°C to 1000°C. The annealing temperature can be 600°C to 900°C. This temperature should be varied within a limited range depending on the type of lithium precursor. Preferably, the annealing time is set to be equal to or greater than one hour. Preferably, the annealing time is about 5 hours. If the annealing time is long, the crystal structure may be fully recovered, but even with a long annealing time, the performance of the active material will not be significantly affected. For example, the annealing time is within 15 hours.

[0139] For example, when Li₂CO₃ is used as a lithium precursor, the annealing temperature is preferably 700°C to 900°C, more preferably 710°C to 780°C. This is because the melting point of Li₂CO₃ is 723°C. Most preferably, annealing is performed at 750°C. When LiOH is used as a lithium precursor, the annealing temperature is preferably 400°C to 600°C, more preferably 450°C to 480°C. This is because the melting point of LiOH is 462°C.

[0140] The annealing temperature is preferably above the melting point of the lithium precursor. However, at temperatures exceeding 1000°C, the positive electrode active material will undergo thermal decomposition, and the performance of the active material will deteriorate; therefore, the temperature should not exceed 1000°C.

[0141] When the process proceeds to step S50, reusable active material can be obtained. Reuse means that the active material is in a state where it can be directly added to the slurry production process like fresh active material, without any additional additives or additional processing to adjust the composition.

[0142] Next, as an optional step, step S60 can be performed further. In step S60, a surface coating is applied to the active material annealed in step S50.

[0143] The surface coating step can involve coating a surface with at least one of a metal, organometallic material, and carbon component in a solid or liquid manner, followed by heat treatment of the coated material at a temperature between 100°C and 1200°C. When heat treatment is performed at temperatures exceeding 1200°C, performance degradation may occur due to the thermal decomposition of the positive electrode active material. In the surface coating step, the coating process, whether solid or liquid, can utilize methods such as mixing, milling, spray drying, and grinding.

[0144] A surface protective layer is formed by a heterogeneous metal through surface coating. When the molar ratio of lithium to other metals in the positive electrode active material is 1:1, if the lithium in the active material reacts with the surface coating material and the molar ratio of lithium to other metals in the positive electrode active material drops to less than 1:1, 100% capacity performance may not be achieved. Therefore, insufficient lithium is added in the preceding step S50 so that not only is the molar ratio of lithium to other metals in the positive electrode active material 1:1, but an excess of lithium is also added so that more lithium is included in the positive electrode active material at a molar ratio of 0.0001 to 0.1 compared to other metals. Thus, during the surface coating process, the molar ratio of lithium to other metals in the positive electrode active material is 1:1, and a surface protective layer can be formed.

[0145] Specifically, when a metal oxide such as B, W, or B-W is coated on the active material and then heat-treated, a lithium borate layer can be formed on the surface of the active material and serve as a surface protection layer. More lithium added in step S50 at a molar ratio of 0.0001 to 0.1 reacts with the metal oxide such as B, W, or B-W in step S60, and the molar ratio of lithium to other metals in the positive electrode active material does not drop below 1:1, so there is no capacity drop.

[0146] The reusable active material obtained by the above method can be represented by Chemical Formula 1 below.

[0147] [Chemical Formula 1]

[0148] Li a Ni x Mn y Co z M w O 2+δ

[0149] (In Chemical Formula 1 above, M includes at least one selected from the group consisting of B, W, Al, Ti, and Mg, 1 < a ≤ 1.1, 0 ≤ x < 0.95, 0 ≤ y < 0.8, 0 ≤ z < 1.0, 0 ≤ w ≤ 0.1, -0.02 ≤ δ ≤ 0.02, and x + y + z + w = 1.)

[0150] The F content of the reusable active material is equal to or lower than 100 ppm. According to the present disclosure, since an active material with a reduced F content can be recovered, if the active material with a reduced F content is reused as the active material, excellent resistance performance and capacity performance can be achieved.

[0151] As described above, according to the present disclosure, the active material can be recovered by a simple heat treatment (step S30). LiF or metal fluoride is removed in the cleaning process of step S40. The cleaning and drying steps using an aqueous solution of a lithium compound that shows alkalinity in an aqueous solution state have the advantages of being safe and inexpensive, removing LiF or metal fluoride without losing other elements, preventing the elution of transition metals, etc., and supplementing the loss of lithium that occurs during the process. The annealing step S50 also has the advantages of being safe and inexpensive, and restores the battery performance of the reusable active material by restoring the crystal structure (i.e., increasing the crystallinity).

[0152] The reusable active material obtained according to this disclosure can have a particle size distribution similar to that of fresh active material, thus potentially eliminating the need for separate processing to adjust the particle size distribution. In particular, since the carbon components generated by carbonization of the binder or conductive material using the active material recovery equipment 100, 100', and 100" suitable for heat treatment do not remain on the surface, steps such as removing the carbon components are unnecessary. Therefore, through the above... Figure 4 The active material obtained by this method can be reused as is and used to manufacture positive electrodes without additional processing.

[0153] The reused active material can also be used 100% as is without adjusting the composition, or the reused active material can be mixed with new active material, or the reused active material can be mixed with conductive material, binder and solvent to form a slurry for use.

[0154] then, Figure 7 This is a flowchart of a method for reusing active materials according to another embodiment of this disclosure. Figure 7 In the figure, the same reference numerals are assigned to the same figures. Figure 6 The same steps are used, and repeated descriptions are omitted.

[0155] refer to Figure 7 ,refer to Figure 6 Steps S10 to S35, as described, are performed in the same manner. Then, the recovered active material is cleaned (step S40'). The cleaning method, the cleaning solution, etc., are the same as those described. Figure 6 The same as step S40 in the previous step.

[0156] Here, the clean active material is not dried, but is directly mixed with the lithium precursor solution and spray-dried (step S45).

[0157] In the preceding steps S30 and S40', lithium loss from the active material may occur. In step S45, this lithium loss is addressed in a simpler and more explicit manner.

[0158] As the lithium precursor solution, a lithium compound soluble in aqueous solution or organic solvent can be used. In particular, the lithium precursor in step S45 may preferably include at least one of LiOH, Li2CO3, LiNO3, and Li2O.

[0159] The temperature of the spray drying step is preferably equal to or higher than 100°C. When the temperature is equal to or lower than 80°C, the solution may not dry completely. More preferably, the temperature of the spray drying step can be between 100°C and 300°C.

[0160] If the active material is dried immediately in an oven or similar container after surface modification treatment via cleaning in step S40', the active material particles may agglomerate to form lumps. To mix the lithium precursor with these agglomerated particles, it may be necessary to grind the lumps, and to mix the solid lithium precursor, a powder mixing or milling process is required during material mixing. In this case, the process is complex and difficult to perform continuously. Furthermore, in the case of NCM-based cathode active materials, when the cathode active material and lithium precursor are powder mixed or milled in the presence of moisture, the cathode active material absorbs moisture, resulting in severe agglomeration. Therefore, this embodiment proposes that after cleaning in step S40', the active material is mixed and dispersed in a lithium precursor solution without drying, and then spray-dried. This eliminates particle agglomeration caused by drying and removes the inconvenience of mixing solid lithium precursors. That is, it is advantageous to produce the active material in powder form rather than in lumps via spray drying.

[0161] During spray drying, the lithium precursor solution is dried immediately after spraying, coating or contacting the active material surface with the lithium precursor components. Another advantage in this regard is that, during the drying of the lithium precursor solution as a solvent, particles aggregate under capillary forces, and the particle size is adjusted. In the case of positive electrode waste made from electrodes, the particles on the surface may be pressed and cracked or broken during rolling. In particular, compared to LCO, NCM-based active materials exhibit a high degree of particle fragmentation during electrode formation due to rolling. Compared to fresh active materials, recycled active materials contain many small particles, resulting in particle inhomogeneity.

[0162] In particular, NCM-based active materials are utilized, including large particles formed by secondary granulation of primary particles with sizes ranging from tens to hundreds of nanometers. In the process of rolling a cathode made from this active material to adjust the porosity in the electrode, the secondary particles break down into primary granulated particles or smaller particles, which are larger than the secondary particles but smaller than the large particles. Since the specific surface area of ​​the active material increases with the number of particles broken down by rolling, problems may arise affecting slurry properties, electrode adhesion, and electrode performance when reusing active materials obtained from rolled electrodes.

[0163] To achieve reusable levels of active materials, it is desirable that the particle size distribution not differ from that of fresh active materials. Spray drying addresses particle inhomogeneity by recovering large particles from smaller particles that break down during coalescence rolling, and also brings the particle size closer to the initial characteristics of fresh active materials. This is particularly effective with NCM-based active materials, which suffer from severe particle breakage during previous rolling processes. Therefore, it is anticipated that batteries using active materials recovered according to the methods of this disclosure will exhibit characteristics similar to those of batteries using fresh active materials.

[0164] As described above, through the spray drying step (S45), the lithium precursor is coated onto the surface of the active material, and the active material is obtained by adjusting the particle size. Since the addition, granulation, and drying of the lithium precursor are carried out in one step, the process is simplified. Furthermore, the special feature of spray drying is that it is not simply a means of obtaining active material, but a means of re-granulating previously used particles that have been crushed by rolling or other methods.

[0165] Furthermore, since the cleaned active material particles in step S40' are merely mixed and dispersed in a lithium precursor solution of a certain concentration, and step S45 is continued, the advantage is that the cleaning in step S40' and the spray drying in step S45 can be continuous processes. Accordingly, in the active material reuse method according to this embodiment, the process is continuous, which has the advantage that the coating, drying, and granulation (particle readjustment) of the lithium precursor are performed simultaneously in one step.

[0166] Here, the lithium precursor is also referenced. Figure 4 The amount added in step S50 is the proportion of lithium lost compared to the ratio of lithium to other metals in the fresh active material.

[0167] Next, the spray-dried active material is annealed (step S50'). Since the lithium precursor is added to the active material in step S45, annealing can be performed immediately after spray drying in this step without the need to add additional lithium precursor. The annealing effect of step S50' is similar to that of the reference. Figure 4 The effect of step S50 described is the same. Thereafter, if necessary, the surface coating in step S60 can be further performed.

[0168] Meanwhile, another method for reusing positive electrode active materials using active material recovery devices 100, 100', and 100" is also feasible. For example, refer to Figure 3The heat treatment time for step S30 described can be set within one hour, preferably within 30 minutes. The longer the heat treatment time, the longer the time for the binder to undergo thermal decomposition. However, when the heat treatment time exceeds a certain time, there is no difference in the thermal decomposition effect; on the contrary, the effect is poor due to the generation of many reaction products such as LiF, which are detrimental to battery performance. Therefore, by limiting the heat treatment time to one hour (preferably 30 minutes), it is feasible to minimize the generation of undesirable foreign matter that adversely affects battery performance.

[0169] In this case, steps S50 and S60 can be performed... Figure 6 Steps S30 and S35 are performed immediately afterward, without step S40. That is, the cleaning step can be omitted due to the shortened heat treatment time. As described above, according to another embodiment of this disclosure, reusable active material can be obtained using only two steps: heat treatment in air (step S30) and annealing after adding the lithium precursor (step S50). In particular, since the heat treatment time is very short (preferably within 30 minutes), there is an advantage that additional steps such as washing to remove reaction products that adversely affect battery performance are not required by suppressing reaction products.

[0170] Meanwhile, another method for reusing positive electrode active materials using active material recovery devices 100, 100', and 100" is also feasible. For example, refer to Figure 6 The cleaning time for step S40 described is shortened to within one hour, preferably within 10 minutes. Prolonged cleaning poses a risk of capacity reduction due to excessive lithium elution. Therefore, a method that minimizes lithium elution by limiting and shortening the cleaning time is feasible.

[0171] In this case, the aqueous lithium precursor solution used as the cleaning solution in step S40 is sufficient to compensate for the lithium loss. Therefore, annealing can be performed without adding additional lithium precursor to the cleaned active material. That is, if Figure 6 The cleaning time in step S40 is set to be very short, so it can be like... Figure 7 Annealing should be performed immediately, as in step S50'.

[0172] As described above, various methods for obtaining reusable positive electrode active materials are feasible according to this disclosure, and these methods can be carried out more efficiently by optimizing the separation of the current collector and the active material layer using the active material recovery device of this disclosure.

[0173] The experimental examples of this disclosure will be described in detail below.

[0174] <Experimental Example 1>

[0175] Samples 1 and 2 were set up using the following method, and the positive electrode waste was thermally treated using the corresponding method. Then the recovery rate of the active material was evaluated.

[0176] Sample 1:

[0177] The cathode waste is simply piled up in the furnace and then heat-treated. This is a case where the cathode waste is placed in the furnace as a fixed type.

[0178] Figure 8 This is an image showing the differences in heat treatment results based on the location of the positive electrode waste in Sample 1.

[0179] Figure 8 (a) is a picture of the positive electrode waste located on the surface of the stacked positive electrode waste. In this case of positive electrode waste, it was observed that the active material separated from the current collector due to thermal decomposition of the binder and conductive material caused by exposure to the outside and contact with air. However, it was also observed that less thermal decomposition occurred in places where the active material layer did not separate from the current collector due to incomplete combustion without sufficient air and oxygen supply. Instead, it was strongly carbonized and adhered to the current collector.

[0180] Figure 8 (b) is an image of the cathode waste located inside the stacked cathode waste. In this case, the assessment suggests insufficient contact with air because the cathode waste is in contact with different cathode wastes at the top and bottom. Significant thermal decomposition was observed in many areas, with the active material layer carbonizing and adhering to the current collector.

[0181] Therefore, it was confirmed that when cathode waste is piled up and subjected to heat treatment as a fixed process, the recovery rate is very poor because the active material is not separated from the current collector due to incomplete combustion. The result was that approximately 40 grams of cathode waste were not recovered when 100 grams of cathode waste were heat-treated.

[0182] Sample 2:

[0183] The cathode waste was placed upright in the furnace to allow it more air contact than sample 1, and then heat-treated. In this case, the cathode waste was placed in the furnace as a stationary type, but the distance between the cathode waste pieces was ensured to maximize the surface area in contact with air.

[0184] Figure 9 This is an image showing the state of sample 2 over time according to the experimental process.

[0185] Figure 9 (a) is a picture showing shredded cathode waste stacked upright in a crucible. Figure 9(b) is a picture showing the state of the positive electrode waste being placed in the furnace and heat-treated in air at 550°C for 30 minutes. Figure 9 (c) is a picture showing the heat-treated cathode waste being removed from the crucible. Figure 9 (d) is an image showing the state of the active material in powder form recovered from the surface of the cathode waste.

[0186] In Sample 2, unlike Sample 1, most of the active material was removed from the current collector and recovered. The recovery rate was equal to or greater than 95%. This confirms that a considerable amount of active material can be recovered simply by heat treatment in air without the use of acid or NMP. In particular, the active material recovery device of this disclosure was invented based on the possibility of further increasing the contact area with air, because even a portion (5%) of the active material remaining in the current collector can be removed, and the recovery rate of the active material can be further improved. Compared with Comparative Example 2, the active material recovery device of this disclosure is portable, rotates the positive electrode waste, and achieves a recovery rate far exceeding 95% due to smoother contact with air.

[0187] <Experimental Example 2>

[0188] Each positive electrode active material was prepared using the methods described below and comparative examples, and its electrochemical performance was evaluated.

[0189] Implementation method 1:

[0190] Based on the above references Figure 6 The method for reusing active materials disclosed herein involves collecting the reused active materials. Positive electrode waste discarded after punching a positive electrode plate containing NCM-based lithium composite transition metal oxide active material is prepared and subjected to heat treatment at 500°C for 30 minutes in step S30. Cleaning is then performed using LiOH in step S40 for 10 minutes. In step S50, a lithium precursor (Li₂CO₃) is applied relative to the molar ratio of lithium to other metals in the original active material (ICP analysis), with the amount of lithium added at a molar ratio of 0.09 during the process, followed by annealing at 750°C for 15 hours. Theoretically, in the case of fresh active material, the molar ratio of lithium to other metals is 1:1. However, since the average error of the ICP active material recovery equipment, which is used to check the molar ratio, is ±0.05 (preferably about ±0.02), the molar ratio of lithium to other metals in the original active material may be 1 ± 0.05:1 as measured by ICP. In this experiment, the lithium precursor is added relative to the analytical ratio obtained through ICP analysis.

[0191] Implementation Method 2:

[0192] In addition to implementation method 1, the following were also executed: Figure 6 The optional step S60 is the active material surface protective layer recycling process.

[0193] Comparative Example 1:

[0194] Fresh NCM-based lithium composite transition metal oxides were used instead of recycled active materials.

[0195] Comparative Example 2:

[0196] In the active material recycling method of this disclosure as described above, only the heat treatment in step S30 is performed to remove the binder and conductive material, separate the aluminum current collector, and collect the NCM-based lithium composite transition metal oxide active material. Step S30 is performed under the same conditions as in Embodiment 1. In the active material recycling method of this disclosure, the surface modification in step S40, the crystal structure restoration in step S50, and the surface coating process in step S60 are not performed.

[0197] Comparative Example 3:

[0198] Based on Comparative Example 2, in the active material reuse method of this disclosure as described above, the process continues up to step S40, surface modification, to collect the active material. That is, although surface modification is performed, the crystal structure restoration in step S50 and the surface coating process in step S60 are not performed in the active material reuse method of this disclosure as described above. Step S40 is performed under the same conditions as in Embodiment 1.

[0199] Comparative Example 4:

[0200] Based on Comparative Example 2, in the active material reuse method of this disclosure as described above, the surface modification in step S40 is not performed; the process is only continued up to the crystal structure restoration in step S50 to collect the NCM-based lithium composite transition metal oxide active material. Unlike Embodiment 1, an annealing treatment for crystal structure restoration is performed, but no lithium precursor is added.

[0201] Comparative Example 5:

[0202] The process is performed in the same manner as in Embodiment 1, except for steps S30, S40, and S50. However, unlike Embodiment 1, an annealing process for restoring the crystal structure is performed without the addition of a lithium precursor.

[0203] ICP analysis was performed on the positive electrode active materials recovered or prepared from the embodiments and comparative examples, and the residual amount of LiF, the ratio of lithium and other metals in the active materials, and the amount of specific elements (such as B or W) were also analyzed.

[0204] A positive electrode was manufactured by weighing 96.25 wt% of positive electrode active material, 1.5 wt% of carbon black as a conductive material, and 2.25 wt% of PVdF as a binder, which were recovered or prepared from each of Embodiments 1 and 2 and Comparative Examples 1 to 5 above, and mixing them with NMP. A battery (coin half-cell, CHC) was then manufactured and its electrochemical performance was evaluated.

[0205] To determine the amount of LiF remaining in the recovered active materials in Comparative Examples 2 and 3, F was detected and analyzed by ICP. The results are shown in Table 1 below.

[0206] [Table 1]

[0207] Comparative Example 2 Comparative Example 3 F content (mg / kg) 1450 ND

[0208] ND refers to a measured F content equal to or less than 30 ppm. Referring to Table 1 above, it can be seen that the F content in the recovered positive electrode active material in Comparative Example 3 is significantly reduced compared to Comparative Example 2. That is, it can be confirmed that LiF is completely dissolved in the lithium compound aqueous solution and removed by cleaning, to the point that LiF may not be detectable by ICP. Therefore, it can be seen that the removal of LiF through step S40 is excellent.

[0209] To determine whether the lithium composition in the positive electrode active material changed during steps S30 and S40 of this disclosure, the ratio of lithium to other metals in the active material was analyzed by ICP. The results are shown in Table 2 below.

[0210] [Table 2]

[0211]

[0212] Referring to Table 2, it can be seen that, compared to Comparative Example 1, the ratio of lithium to other metals in the active material decreased by approximately 0.2 to 0.5 after heat treatment in S30 in Comparative Example 2, while compared to Comparative Example 2, the ratio of lithium to other metals decreased by approximately 0.2 to 0.5 after cleaning and drying in S40 in Comparative Example 3. The NCM-based lithium composite transition metal oxide appears to have a relatively large particle specific surface area due to its spinel structure, and the ratio of lithium to other metals is significantly reduced. Therefore, it can be seen that sufficient lithium must be added.

[0213] Table 2 shows the values ​​measured by ICP analysis. As mentioned above, the error value of ICP analysis is approximately ±0.02. Therefore, even in Comparative Example 1, which is a fresh active material, the ratio of lithium to other metals may be less than 1. Therefore, the amount of lithium precursor added to compensate for lithium loss is the amount of lithium content reduced relative to the ratio of lithium to other metals (molar ratio by ICP analysis) in the raw active material (i.e., fresh active material) used in the active material layer.

[0214] Figure 10 and Figure 11 The results of battery evaluation using the active materials of Embodiments 1 and 2, and Comparative Examples 1 to 5, are shown. Rate performance was examined by evaluating capacity based on the number of cycle repetitions at different currents. The active material recovery equipment used for evaluation was a common charge / discharge testing apparatus commonly used in a laboratory. There were no biases based on the measuring equipment or methods. Figure 10 and Figure 11 In the chart, the horizontal axis represents the number of cycles, and the vertical axis represents the capacity.

[0215] The voltage is set from 3V to 4.3V, and initial charging / discharging is performed at 0.1C / 0.1C. An electrolyte is used to construct the battery, which is carbonate-based, with an ethylene carbonate (EC) to ethyl carbonate (EMC) ratio of 3:7, and includes some additives.

[0216] First, refer to Figure 10 After the initial heat treatment (550°C / 30 minutes) for detachment, Comparative Example 2 before surface modification and Comparative Example 3 after surface modification were examined. In Comparative Example 3, which underwent surface modification, the electrode capacity decreased rapidly. This is because, as described above, the nickel in the NCM-based lithium composite transition metal oxide becomes rock salt due to moisture, resulting in a decrease in its capacity.

[0217] However, when annealing (750°C / 15 hours) was performed without surface modification, which is equivalent to Comparative Example 4, there was almost no capacity improvement compared to Comparative Example 2. This is because LiF remains on the surface of the active material without surface modification. As shown in Table 1 above, LiF can only be removed to a satisfactory degree during cleaning.

[0218] When surface modification and annealing are performed after the initial heat treatment, the capacity increases as shown in Comparative Example 5. This is because, although the capacity decreases after the surface modification step as in Comparative Example 3, it decreases after removing LiF by surface modification and restoring the structure to a hexagonal crystal, as shown by annealing the nickel rock salt.

[0219] Next, refer to Figure 11In Embodiment 1, compared to Comparative Example 5, an improved capacity was demonstrated. In Embodiment 1, a lithium precursor was added during the annealing process, unlike in Comparative Example 5. By adding the lithium precursor in this way, it can be seen that the capacity was improved by replenishing the lithium lost in the preceding steps. The lithium loss occurring during heat treatment and cleaning has been described with reference to Table 2.

[0220] Based on the results of ICP analysis (Table 2), the amount of lithium compound added was the loss rate compared to the lithium content in existing cathode active materials. Further experiments confirmed that when the molar ratio was between 0.09 and 0.1, a capacity improvement comparable to Comparative Example 1 was achieved.

[0221] As described above, according to this disclosure, active materials can be recovered from cathode waste for direct reuse. It is safe because no toxic and explosive solvents such as NMP, DMC, acetone, and methanol are used, and it is suitable for large-scale production due to the use of simple and safe methods such as heat treatment, cleaning and drying, and annealing.

[0222] Figure 12 and Figure 13 These are scanning electron microscope (SEM) images of the active materials of Embodiment 1, Comparative Examples 1 to 3, and Comparative Example 5. These SEM images were taken using general SEM equipment commonly used in laboratories. For example, SEM images can be taken using a HITACHI S-4200. However, there is no bias based on the measuring device or method.

[0223] Figure 12 (a) is a SEM image of the fresh active material from Comparative Example 1, and Figure 12 (b) is Figure 12 Enlarged image of (a). Figure 12 (c) is an image of the surface of cathode waste made from this fresh active material. Figure 12 (d) is Figure 12 Enlarged image of (c). Fresh active material shows no particle breakage, but positive electrode waste made from electrodes shows that the particles on the surface were pressed and broken by the rolling process.

[0224] Figure 12 (e) is the SEM image of Comparative Example 2, and Figure 12 (f) is Figure 12 A magnified view of (e). (See reference) Figure 12 (e) and Figure 12In (f), no binder or conductive material was observed in the recovered active material. That is, it can be confirmed that the binder or conductive material was removed during the high-temperature heat treatment. Therefore, it can be seen that the active material is separated from the current collector only by heat treatment in air, and almost no binder or conductive material remains on the surface of the active material.

[0225] Figure 13 (a) is the SEM image of Comparative Example 3, and Figure 13 (b) is Figure 13 A magnified image of (a). In comparison with images showing positive electrode waste... Figure 13 (c) and Figure 13 As shown in (d), the particles are released through this process.

[0226] Figure 13 (c) is the SEM image of Comparative Example 5, and Figure 13 (d) is Figure 13 Enlarged image of (c). Figure 13 (e) is the SEM image of implementation method 1, and Figure 13 (f) is Figure 13 A magnified image of (e). It can be seen that the particles released in the previous step agglomerate through annealing. In comparison... Figure 13 (f) and Figure 12 As can be seen from (a), the reusable active material of Embodiment 1 has the same shape as the fresh active material.

[0227] ICP analysis was performed on the positive electrode active materials recovered or prepared from the embodiments and comparative examples, and the content of specific elements was also analyzed. The results are shown in Table 3 below.

[0228] [Table 3]

[0229] B content (mg / kg) W content (mg / kg) Comparative Example 1 500 3100 Comparative Example 2 200 2700 Comparative Example 3 ND 200 Comparative Example 5 ND 200 Implementation Method 1 ND 200

[0230] As shown in Comparative Example 1, the fresh active materials used in this experiment also included B and W. Comparative Example 2 shows that the contents of B and W were reduced by heat treatment, and the remaining results indicate that B was almost completely removed in subsequent processes. In the case of W, as seen in Comparative Example 3, a large amount of W was removed by cleaning during the surface modification process.

[0231] Therefore, depending on the type of active material initially used, specific elements may be lost during the process, especially in the case of surface modification processes involving cleaning, where specific elements may be completely removed or leave only a small amount. There may be situations where simply performing the annealing step in Embodiment 1 is insufficient to fully restore the properties. In such cases, it is preferable to perform the additional surface coating step proposed in this disclosure. In the case of the current experimental example, this surface coating step involves coating B and W. Surface coating can act as a surface protective layer for the positive electrode active material. Surface coating can also be a process to supplement specific deficient elements and simultaneously rebuild the surface protective layer in the fresh active material. In the case of the fresh active material used in this experiment, the surface protective layer is made of B and W, and the meaning of lithium loss during this process is interpreted as the ratio of (lithium in the active material itself + lithium forming the surface protective layer) to other metals, rather than a 1:1 ratio of lithium in the active material itself to other metals. Therefore, the 0.09 molar ratio lost in the above experiments (as in Comparative Example 3) can be explained as the sum of the amount of lithium in the positive electrode active material and the amount of lithium forming the surface protective layer, and in this embodiment, a lithium precursor that can replenish as much lithium as possible is added.

[0232] The surface coating step requires a heat treatment process following the solid or liquid reaction. When the reusable active material is represented by the above chemical formula 1, it can be considered that M in chemical formula 1 is supplemented by this surface coating.

[0233] When the surface coating includes B, BW, B-Ti and BW-Ti, the surface coating heat treatment can be carried out at a temperature of 200°C to 500°C. Other components can also be coated with metallic components, carbon components and organometallic components at a temperature of 100°C to 1200°C.

[0234] As described above, according to this disclosure, cathode waste can be reused using simple, environmentally friendly, and economical methods. Even when lithium secondary batteries are manufactured by reusing the NCM-based lithium composite transition metal oxide cathode active material prepared as described above, the battery performance remains unaffected.

[0235] <Experimental Example 3>

[0236] Each positive electrode active material was prepared using the methods described in the above embodiments and comparative examples, and its electrochemical performance was evaluated.

[0237] Implementation Method 3:

[0238] Implementation method 3 is the same as implementation method 1, except that the annealing time is 5 hours shorter than the 15 hours in implementation method 1.

[0239] Implementation Method 4:

[0240] Implementation method 4 is based on the reference Figure 7 The method described above prepares a reusable active material. After proceeding up to step S30 as in Embodiment 1, steps S40', S45, and S50' are performed. In step S40', after cleaning, drying is not performed; the electrode is mixed with 0.1 mol of LiOH powder in an aqueous solution (mixed at a powder-to-aqueous solution ratio of 1:50), and granulated using a spray dryer to perform step S45. Step S50' is performed at 750°C for 5 hours, as in Embodiment 3.

[0241] During step S45, the mixed aqueous solution of washing electrode and 0.1 moles of LiOH is stirred to prevent electrode precipitation, and the ambient temperature (input temperature) when the spray dryer sprays the material into the heating container using the nozzle is adjusted to 180°C, and the ambient temperature (output temperature) when the material exits the heating container and enters the collection container is adjusted to be maintained at 100°C or above.

[0242] Figure 14 These are particle size distribution charts of the active materials from Embodiments 3 and 4, as well as Comparative Examples 1 and 2. The particle size distribution can be obtained using a common laboratory particle size analyzer. For example, the particle size distribution can be measured using a Horiba LA 950V2 particle size analyzer. However, there is no bias based on the measuring instrument or method. Figure 14 In the figure, the horizontal axis represents particle size (μm), and the vertical axis represents volume (%).

[0243] In Comparative Example 2, the active material of Comparative Example 1 was split into submicron-sized (less than 1 micrometer) particles and micronized by pressure during the electrode process. Consequently, the particle size distribution of Comparative Example 2 was significantly different from that of Comparative Example 1.

[0244] Since annealing was performed in both Embodiments 3 and 4, during which the previously added lithium precursor melts and induces particle aggregation, it can be seen that many of the micronized particles shown in Comparative Example 2 disappeared. Specifically, in Embodiment 4 according to this disclosure, compared to Embodiment 3, small particles decreased and large particles slightly increased, but there was no significant difference in particle size distribution. Compared to Embodiment 3, Embodiment 4 can be considered to have a more similar particle size distribution to Comparative Example 1 because it has fewer small particles.

[0245] Accordingly, it is confirmed that when using the spray drying proposed in another embodiment of this disclosure (Embodiment 4), the particle size distribution is more similar to that of the fresh active material (Comparative Example 1) compared to the case of solid-phase mixed lithium precursor (Embodiment 3), and in particular, it has the advantage of being able to perform a process that is continuous with the cleaning step before spray drying.

[0246] Figure 15 The results of battery evaluation using the active materials of Embodiments 3 and 4 and Comparative Example 1 are shown, and the results are summarized in Table 4.

[0247] [Table 4]

[0248]

[0249] refer to Figure 15 As shown in Table 4, both electrodes used in Embodiments 3 and 4 exhibited results similar to those using the electrode in Comparative Example 1. In Comparative Example 1, the initial formation capacity was higher; in Embodiments 3 and 4, the C-rate capacity was slightly higher, but they were determined to be similar to each other. As described above, according to embodiments of this disclosure, reusable active materials similar to fresh active materials (Comparative Example 1) can be obtained.

[0250] <Experimental Example 4>

[0251] Each positive electrode active material was further prepared using the methods described in the following embodiments and comparative examples, and its electrochemical performance was evaluated.

[0252] Implementation Method 5:

[0253] According to another method for reusing active materials disclosed above, the reusable active materials are collected. LCO cathode waste to be discarded after punching the cathode plate is prepared and subjected to heat treatment step S30 at 600°C for 30 minutes at a temperature rise rate of 5°C / min in air. Step S50 is performed without cleaning in step S40 or S40'. A lithium precursor (Li2CO3) with a lithium content 2 mol% excess relative to the amount of lithium in the reusable LCO is placed in air and annealed at 750°C for 15 hours.

[0254] Comparative Example 6: Using new LCO instead of recycled active materials.

[0255] Comparative Example 7: In the active material reuse method of this disclosure as described above, only the heat treatment in step S30 is performed to remove the binder, conductive material, and Al current collector, and to collect the LCO active material. Step S30 is performed under the same conditions as in Embodiment 5.

[0256] Comparative Example 8: LCO active material was collected in the same manner as in Comparative Example 7, except that the heat treatment time was 1 hour.

[0257] Comparative Example 9: LCO active material was collected in the same manner as in Comparative Example 8, except that the heat treatment time was 5 hours.

[0258] Figure 16The results of battery evaluation using the active materials of Embodiment 5 and Comparative Examples 6 to 9 are shown.

[0259] refer to Figure 16 Comparative Example 9, which had the longest heat treatment time (5 hours), demonstrated the lowest rate performance. This is because, during the prolonged high-temperature heat treatment process, such as step S30, the binder and conductive material were removed as CO2 and H2O, reacting with lithium on the surface of the positive electrode active material to form Li2CO3, and reacting with F present in the binder to form LiF. Furthermore, the low battery performance was determined by the Co3O4 generated on the LCO surface due to thermal decomposition.

[0260] In Comparative Example 8, it can be seen that since the heat treatment time is 1 hour, which is shorter than that of Comparative Example 9, the rate performance is better than that of Comparative Example 9 until about the first 3 cycles, but the rate performance deteriorates as the number of cycles increases.

[0261] In Comparative Example 7, the heat treatment time was 30 minutes, shorter than that of Comparative Examples 8 and 9. In Comparative Example 7, the rate performance was superior to that of Comparative Examples 8 and 9. Therefore, it can be confirmed that, in terms of rate performance, a heat treatment time of less than 30 minutes is preferable because the formation of reaction products such as LiF is minimized.

[0262] In Embodiment 5, compared to Comparative Example 7, the process was continued until annealing by adding a lithium precursor, during which Li₂CO₃ was added to replenish the lithium lost in the active material recovery process and restore crystallinity. According to Embodiment 5, not only can the insufficient amount of lithium occurring during the process be replenished, but the deformed structures and Co₃O₄ that may appear on the surface of the active material during regeneration can also be reduced back to the LCO crystal structure. Therefore, Embodiment 5 demonstrates improved results compared to the initial characteristics of the fresh LCO active material in Comparative Example 6. As described above, according to this disclosure, active materials can be recovered from cathode waste for direct reuse.

[0263] Figure 17 XRD patterns of the active materials of Embodiment 5 and Comparative Examples 6, 7, and 9 are shown. In the XRD patterns, the horizontal axis represents 2θ (theta) (degrees), and the vertical axis represents intensity. The XRD patterns were obtained using general X-ray diffraction equipment commonly used in laboratories. For example, an XRD pattern can be analyzed using a Rigaku XG-2100 X-ray diffractometer. However, there is no bias based on the equipment or method.

[0264] Figure 17 (a) is the XRD pattern of Comparative Example 6, i.e., the XRD pattern of fresh LCO. Figure 17 (b) is the XRD pattern of the active material in Comparative Example 7, and Figure 17 (c) is the XRD pattern of the active material of Comparative Example 9. Figure 17 (b) and (c) of 17 with Figure 17 After comparison (a), the Co3O4 phase can be detected. That is, it can be confirmed that Co3O4 was generated on the surface of LCO during the heat treatment process in step S30.

[0265] Figure 17 (d) is the XRD pattern of the active material in Embodiment 5. Figure 17 (b) and (c) of 17 with Figure 17 After comparing (d), it can be seen that the Co3O4 phase has disappeared, and through annealing in step S50, the crystal structure is restored to LCO. Given the positions of the diffraction peaks in the XRD pattern, Figure 17 The crystal structure of (d) and Figure 17 The crystal structure of (a) is similar. Therefore, it can be confirmed that the embodiments of this disclosure restore the level of fresh active material to that of Comparative Example 6. As described above, according to this disclosure, Co3O4 generated in the heat treatment process can be removed during the annealing process, and the active material can be recovered from the cathode waste for direct reuse.

[0266] Figure 18 These are SEM images of the active materials of Embodiment 5 and Comparative Example 6.

[0267] Figure 18 (a) is a SEM image of fresh LCO from Comparative Example 6, and Figure 18 (b) is a SEM image of the reused active material of Example 5. It can be confirmed that the recovered LCO of Example 5 exhibits the same shape as fresh LCO. Furthermore, since only LCO was observed, it can be confirmed that binders and conductive materials were removed during the high-temperature heat treatment process. Therefore, it can be seen that the active material is separated from the current collector simply by heat treatment in air, and almost no binder or conductive material remains on the surface of the active material. As described above, according to this disclosure, the active material can be separated from the current collector without using complex methods or hazardous substances, thus enabling the recycling of the active material in an eco-friendly manner. The active material can be reused without the use of acid, thus eliminating the need for neutralization or wastewater treatment processes, thereby mitigating environmental problems and reducing process costs.

[0268] Figure 19X-ray photoelectron spectroscopy (XPS) spectra of the active materials of Comparative Examples 6, 7, and 9 are shown. In the XPS spectra, the horizontal axis represents the binding energy (unit: eV). XPS spectra can be obtained using general XPS measurement equipment commonly used in laboratories. For example, XPS spectra can be analyzed using K-Alpha analysis equipment from Thermo Fisher Scientific. As mentioned above, during the heat treatment process, F present in the binder may react with Li in the active material to form LiF.

[0269] exist Figure 19 In Comparative Example 6, a peak value of LiF appeared near 684 eV, and the higher the sample intensity, the greater the amount of LiF present on the surface of the positive electrode active material. Since the XPS plot of Comparative Example 6 was measured using fresh LCO, no LiF was detected. In Comparative Example 9, due to the long heat treatment time of 5 hours, a large amount of LiF was generated on the surface of the active material. Therefore, the LiF peak intensity in the XPS was measured to be significantly higher than that of Comparative Example 6. However, in Comparative Example 7, where the heat treatment time was reduced from 5 hours to 30 minutes, it can be seen that the amount of F formed by binder decomposition was relatively reduced, and the amount of LiF present on the surface of the active material was also relatively reduced. LiF should be as small as possible, as it may lead to electrode performance degradation. The results from Comparative Examples 9 and 7 show that reducing the heat treatment time can reduce the amount of LiF on the surface of the regenerated active material and effectively improve the performance of the regenerated active material. Embodiment 5 will have a similar level of LiF as Comparative Example 7, but as described above... Figure 18 The results show that a higher level of LiF than that of fresh active material can be maintained after annealing, thus demonstrating that the amount of LiF remaining in Embodiment 5 has little impact on battery performance. Therefore, if the heat treatment time is optimized as in another embodiment of this disclosure, a separate process such as washing for LiF removal is not required.

[0270] Figure 20 These are particle size distribution charts of the active materials in Embodiment 5 and Comparative Examples 6, 7 and 9.

[0271] Compared to the fresh LCO in Comparative Example 6, all the active materials recovered in Embodiment 5 and Comparative Examples 6, 7, and 9 had similar particle size distributions. Particle size distributions are defined as similar when the volume percentage of particles with the same size differs by only ±2%. As described above, according to this disclosure, since the particle size distribution of the active materials is not different, the initial characteristics are almost maintained, and the performance of batteries using recycled active materials is expected to be similar to that of batteries using fresh active materials.

[0272] <Experimental Example 5>

[0273] Each positive electrode active material was prepared using the methods described in the following embodiments and comparative examples, and its electrochemical performance was evaluated.

[0274] Implementation method 6: Reusable active materials are collected according to another method of active material recycling disclosed above. The cathode waste material to be discarded after punching the cathode plate is prepared and subjected to heat treatment at 600°C for 30 minutes in step S30. Cleaning is performed using LiOH in step S40 for 10 minutes. Annealing is performed at 750°C for 15 hours, without adding additional lithium precursor as in step S50'.

[0275] Comparative Example 10: Except for Comparative Example 7, in the active material recycling method of this disclosure as described above, the LCO active material is recovered by performing surface modification in step S40. That is, in the active material recycling method of this disclosure, the crystal structure restoration in step S50 or S50' is not performed simultaneously with surface modification. Step S40 is performed under the same conditions as in Embodiment 6.

[0276] To determine the amount of LiF remaining in the active materials recovered in Embodiment 6 and Comparative Example 7, F was detected and analyzed by ICP. The results are shown in Table 5 below.

[0277] [Table 5]

[0278] Comparative Example 7 Implementation Method 6 F content (mg / kg) 1900 ND

[0279] Referring to Table 5 above, it can be seen that the F content in the recovered positive electrode active material in Embodiment 6 is significantly reduced compared to Comparative Example 7. That is, it can be confirmed that LiF is completely dissolved in the lithium compound aqueous solution through cleaning and removed to a degree that LiF may not be detectable by ICP. Therefore, it can be seen that step S40 achieves excellent LiF removal efficiency.

[0280] ICP analysis was performed on the positive electrode active materials recovered or prepared from the embodiments and comparative examples, and the amounts of specific elements were also analyzed. The results are shown in Table 6 below.

[0281] [Table 6]

[0282] Al content (wt%) Comparative Example 6 0.33 Comparative Example 7 0.33 Comparative Example 10 0.33 Implementation Method 6 0.33

[0283] As shown in Comparative Example 6, the fresh active material used in this experiment further included Al. Comparative Example 7 showed that even after heat treatment, the Al content did not change, and it can be seen from the Al content that even in Comparative Example 10 and Embodiment 6, which further included subsequent processes, the Al content remained unchanged. As described above, according to this disclosure, it can be seen that LiF or metal fluorides can be removed without losing other elements such as Al, and the elution of transition metals, etc., can be prevented.

[0284] Figure 21 The results of battery evaluation using the active materials of Embodiment 6 and Comparative Examples 6, 7 and 10 are shown.

[0285] refer to Figure 21 Comparative Example 7 demonstrates the lowest rate performance, where, despite the presence of recycled active material, surface modification and crystal structure restoration according to this disclosure were not performed. This is because, during the high-temperature heat treatment process, such as step S30, not only are the binder and conductive material removed as CO2 and H2O and react with lithium on the surface of the positive electrode active material to form Li2CO3 and LiOH, but they also react with F present in the binder, thereby forming LiF or metal fluorides on the surface of the recycled active material. Furthermore, due to the Co3O4 generated on the LCO surface by thermal decomposition, it is determined to exhibit low battery characteristics.

[0286] In Comparative Example 10, surface modification was performed compared to Comparative Example 7. Evaluation showed that Comparative Example 10 achieved better results than Comparative Example 7 because the reactants generated on the surface were removed through cleaning.

[0287] In Embodiment 6, the process continued until annealing, as in Comparative Example 10. The deformed structures and Co3O4 that might appear on the surface of the active material during regeneration were reduced back to the LCO crystal structure, thus demonstrating that Embodiment 6 exhibited improved results compared to the initial characteristics of the fresh LCO active material in Comparative Example 6. As described above, according to this disclosure, active materials can be recovered from cathode waste for direct reuse.

[0288] Figure 22XPS plots of the active materials of Embodiment 6 and Comparative Examples 6 to 8 are shown. Since the XPS plot of Comparative Example 6 was measured using fresh LCO, the presence of LiF was not measured. However, in Comparative Example 7, the presence of LiF formed on the surface of the active material during the heat treatment process was confirmed. In Comparative Example 8, due to the increased heat treatment time to 5 hours, the generation of F increased compared to Comparative Example 7, and because the amount of LiF generated on the surface of the active material increased, the LiF peak intensity in the XPS was measured to be higher than that in Comparative Example 7. Since the amount of LiF present on the surface of the active material leads to electrode characteristic degradation, it is necessary to remove LiF. In Embodiment 6, compared to Comparative Example 7, LiF was removed by cleaning, and it was confirmed that no LiF peak value appeared even in the XPS results.

[0289] The XPS analysis described above confirms that the results of Embodiment 6 are similar to those of Comparative Example 6. Therefore, it can be confirmed that Embodiment 6 of this disclosure restores the level of fresh active material to that of Comparative Example 6. As described above, according to this disclosure, when the cleaning time is shortened, active material can be recovered from cathode waste for direct reuse without the addition of lithium precursors.

[0290] This disclosure has been described in detail. However, it should be understood that while the detailed description and specific embodiments illustrate preferred embodiments of this disclosure, they are given by way of illustration only, as various changes and modifications within the scope of this disclosure will be apparent to those skilled in the art based on this detailed description.

Claims

1. An active material recycling apparatus, which is a rotary firing apparatus, comprising: a heat treatment tank and a screening wall arranged in a line along an axis, wherein the heat treatment tank constitutes a heating zone and the screening wall constitutes a cooling zone; and an exhaust gas injection and degassing system, wherein the heat treatment tank removes a binder and a conductive material in an active material layer on a current collector of electrode scrap by heat treating the electrode scrap in air while rotating the electrode scrap around the axis, and separates the current collector from the active material layer, active material in the active material layer passes through the screening wall and is recycled as active material in powder form, and the current collector that does not pass through the screening wall is separately recycled, and a jagged irregularity is formed in the interior of the heat treatment tank in a cross section orthogonal to the axis, wherein a rod of a spiral type is provided as the axis in the center of the heat treatment tank and the cooling zone, and the rod rotates, and wherein an air inlet is formed in the rod and the irregularity formed in the interior of the heat treatment tank.

2. The active material recovery apparatus according to claim 1, wherein The irregularity formed in the interior of the heat treatment tank is continuous or discontinuous along the axis.

3. The active material recovery apparatus according to claim 1, wherein A jagged irregularity is formed in the interior of the screening wall in a cross section orthogonal to the axis.

4. The active material recovery apparatus according to claim 3, wherein The irregularity formed in the interior of the screening wall is continuous or discontinuous along the axis.

5. The active material recovery apparatus according to claim 1, wherein An air inlet is formed in a plurality of positions in the heat treatment tank.

6. The active material recovery apparatus according to claim 2, wherein The heat treatment tank also rotates around the rod.

7. The active material recovery apparatus according to claim 1, wherein The angle of the entire active material recycling apparatus is adjusted so that the axis is inclined with respect to the ground.

8. The active material recovery apparatus according to claim 1, wherein The active material recycling apparatus has a vibration function.

9. The active material recovery apparatus according to claim 1, wherein The input of new electrode scrap and the recycling of the active material are continuously performed.

10. The active material recovery apparatus according to claim 1, wherein The heat treatment tank has a tubular shape with both ends open, so as to put the electrode scrap into the heat treatment tank and to deliver the separated current collector and active material to the screening wall, and is a pipe of an open type system for air to enter and exit.

11. The active material recovery apparatus according to claim 10, wherein The screening wall has a tubular shape with both ends open, so as to put the separated current collector and active material into the screening wall and to discharge the current collector.

12. The active material recovery apparatus according to claim 1, wherein The heat treatment tank is an open type system in which 10 ml / min to 100 L / min of air is added or injected per 100 g of the electrode scrap put in.

13. A positive electrode active material recycling method, comprising the steps of: preparing an active material recycling apparatus according to any one of claims 1 to 12; putting positive electrode scrap, which includes a lithium composite transition metal oxide positive electrode active material layer on a current collector, into a heat treatment tank; removing a binder and a conductive material in the active material layer and separating the current collector from the active material layer by heat treating the positive electrode scrap in air while rotating the positive electrode scrap around an axis in the heat treatment tank; recycling active material in powder form that has passed through a screening wall; and and The active material is annealed at 400°C to 1000°C in air to obtain a reusable active material.

14. The positive electrode active material recycling method according to claim 13, wherein The heat treatment is performed at 300°C to 650°C.

15. The positive electrode active material recycling method according to claim 13, further comprising the steps of: The recovered active material is cleaned with a lithium compound solution that shows alkalinity in an aqueous solution state before the annealing step.

16. The positive electrode active material recycling method according to claim 15, wherein A lithium precursor is added to the cleaned active material before the annealing step.

17. The positive electrode active material recycling method according to claim 15, further comprising the steps of: After the cleaning step, an active material to which a lithium precursor is added and whose particles are adjusted is obtained by mixing the cleaned active material with a lithium precursor solution and spray-drying the active material.

18. The positive electrode active material reuse method according to claim 13, further comprising a step of performing surface coating on the active material after annealing.

19. The positive electrode active material recycling method according to claim 13, wherein The heat treatment is performed at 550°C for 30 minutes at a temperature increase rate of 5°C / minute.

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