Active material recovery equipment and positive electrode active material recycling method

Abstract

Provided are: an apparatus for recovering active materials, and a method for reusing positive active materials by using the apparatus, the apparatus being capable of easily recovering electrode active materials in their original shape from electrode waste. The apparatus for recovering active materials according to the present invention is a rotary firing apparatus having a spiral-type rod inside thereof, the apparatus comprising: a heat treatment tank and a screening wall body arranged on a line along the axis of the rod, wherein the heat treatment tank forms a heating zone, and the screening wall body forms a cooling zone; and an exhaust gas injection and degassing system, wherein, in the heat treatment tank, the electrode waste including an active material layer on a current collector is heat-treated in air while being rotated around the axis of the rod, thereby removing a binder and a conductive material from the active material layer to separate the active material layer from the current collector, the active material in the active material layer passes through the screening wall body and the active material in the form of powder is recovered, and the current collector that has not passed through the screening wall body is recovered separately.

Description

Technical Field

[0001] The present disclosure relates to a method for recycling resource cycles when manufacturing lithium secondary batteries. In particular, the present disclosure relates to an apparatus for recovering electrode active materials from electrode waste generated in a lithium secondary battery manufacturing process or from lithium secondary batteries discarded after use, and to a method for recycling the recovered active materials. This application claims priority to Korean Patent Application No. 10-2020-0101962 filed in Korea on August 13, 2020, the disclosure of which is incorporated herein by reference. Background Art

[0002] Lithium secondary batteries that can be repeatedly charged and discharged have attracted attention as an alternative to fossil energy. Lithium secondary batteries are mainly used in traditional handheld devices (such as mobile phones, cameras, and power tools). However, recently, the application fields of lithium secondary batteries have gradually expanded to electric vehicles (EV, HEV, and PHEV), large-capacity energy storage systems (ESS), uninterruptible power supply systems (UPS), etc.

[0003] A lithium secondary battery includes: an electrode assembly, in which a unit cell has a structure in which a positive plate and a negative plate coated with an active material on a current collector are arranged with a separator sandwiched therebetween; and an external material (i.e., a battery case) that seals and contains the electrode assembly together with an electrolyte. The positive electrode active material of a lithium secondary battery mainly uses lithium-based oxides, and 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. Among them, cobalt is a strategic metal, and every country in the world pays special attention to the supply and demand of cobalt. Due to the limited number of cobalt producing countries, it is recognized as a metal whose supply and demand are unstable worldwide. If there is an imbalance in the supply and demand of raw materials for strategic metals, the price of raw materials is very likely to rise.

[0004] Conventionally, research has been mainly conducted on recovering and recycling these precious metals from lithium secondary batteries (waste batteries) that are discarded at the end of their life after use. In addition to waste batteries, it would be more preferable if resources could be recovered from waste discarded after punching positive plates or positive plates that have defects during the punching process.

[0005] Currently, when manufacturing lithium secondary batteries, such as Figure 1As shown in , 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 an aluminum (Al) foil is coated with a positive electrode slurry in which a positive electrode active material, a conductive material, a binder, a solvent, etc. are mixed; and then a positive electrode plate 40 is punched out in a certain size. The remaining portion after punching is discarded as a positive electrode waste 50. If the positive electrode active material can be recovered from the positive electrode waste 50 and reused, it will be very desirable from the perspective of industrial economy and the perspective of the environment.

[0006] Traditionally, in most cases, the method for recovering positive electrode active materials is carried out by the following operation: dissolving the positive electrode in hydrochloric acid, sulfuric acid, nitric acid, etc., and then extracting active material elements such as cobalt, nickel, manganese, and the extracted active material elements are reused as raw materials for synthesizing positive electrode active materials. However, the method of using acid to extract active material elements has the disadvantage that the pure raw material recovery process is not environmentally friendly, and a neutralization process and a wastewater treatment process are required, which increases the process cost. In addition, the disadvantage of this method is that lithium, one of the main elements of the positive electrode active material, may not be recovered. In order to solve these shortcomings, a direct reuse method is needed that does not require dissolving the positive electrode active material and extracting the active material in elemental form. Summary of the invention

[0007] Technical issues

[0008] The present disclosure aims to provide an active material recovery apparatus capable of easily recovering an electrode active material in its original shape from electrode scrap.

[0009] The present disclosure also aims to provide a positive electrode active material recycling method using the active material recycling device.

[0010] Technical Solution

[0011] In one aspect of the present disclosure, an active material recovery device is provided, which includes: a heat treatment tank and a screening wall, wherein the heat treatment tank and the screening wall are arranged on a line along the axis of the rod, 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 a binder and a conductive material in the active material layer by heat-treating the electrode waste including an active material layer on the current collector in the air while rotating the electrode waste around the axis of the rod, and separates the current collector from the active material layer, and the active material in the active material layer passes through the screening wall and is recovered as an active material in powder form, and the current collector that does not pass through the screening wall is recovered separately.

[0012] The heat treatment tank may also be rotatable about the axis of the rod.

[0013] The angle of the entire active material recovery apparatus may be adjusted so that the axis of the rod is inclined relative to the ground.

[0014] The active material recovery device may have a vibration function.

[0015] The input of new electrode waste and the recovery of the active material can be carried out continuously.

[0016] Preferably, the heat treatment tank has a tubular shape with both ends open so that the electrode waste is placed in the heat treatment tank and the separated current collector and active material are transferred to the screening wall, and the tube is an open system for air to enter and leave.

[0017] Preferably, the screening wall has a tubular shape with both ends open, so that the separated current collector and active material can be placed into the screening wall and the current collector can be discharged.

[0018] The heat treatment tank is preferably an open system, in which 10 ml / min to 100 liters / min of air is added or injected per 100 grams of the electrode waste placed therein.

[0019] Some may have air inlets formed at multiple locations in the heat treatment tank.

[0020] In one aspect of the present disclosure, a method for recycling positive electrode active materials is provided, the method comprising: preparing an active material recovery device according to the present disclosure; placing positive electrode waste material into a heat treatment tank, the positive electrode waste material comprising a lithium composite transition metal oxide positive electrode active material layer on a current collector; 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 waste material in air while rotating the positive electrode waste material around an axis of a rod in the heat treatment tank; recovering the active material in powder form that has passed through a screening wall; and annealing the active material at 400°C to 1000°C in air to obtain an active material that can be recycled.

[0021] In addition, the heat treatment may be performed at 300° C. to 650° C. The heat treatment may be performed at 550° C. for 30 minutes at a temperature increase rate of 5° C. / min.

[0022] The carbon component generated by carbonization of the binder or the conductive material does not remain on the surface of the recovered active material.

[0023] The method for recycling positive electrode active materials may further include, before the annealing step, cleaning the recovered active material with a lithium compound solution that exhibits alkalinity in an aqueous solution state. In this case, before the annealing step, a lithium precursor is preferably added to the cleaned active material. The lithium compound aqueous solution may be prepared to contain more than 0% and equal to or less than 15% of a lithium compound, and LiOH is preferably used. Cleaning may be performed within one hour. The cleaning step may be performed by immersing the recovered active material in the lithium compound aqueous solution while stirring the recovered active material.

[0024] As another embodiment, the positive electrode active material recycling method 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 to which a lithium precursor is added and whose particles are adjusted.

[0025] The method for recycling positive electrode active materials may further include the step of performing surface coating on the annealed active material.

[0026] The lithium precursor used for annealing may include at least one of LiOH, Li2CO3, LiNO3, and Li2O.

[0027] The lithium precursor may be added in an amount proportional to the loss of lithium 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 may be added in an amount of lithium addition of 0.001 to 0.4 in a molar ratio. In addition, the lithium precursor may be added in an amount of lithium added in a molar ratio of 0.0001 to 0.1 relative to a molar ratio of 1:1 of lithium to other metals. The annealing temperature may exceed the melting point of the lithium precursor.

[0028] Performing the surface coating may include coating at least one of a metal, an organic metal, and a carbon component on the surface in a solid or liquid manner, and then performing a heat treatment at 100° C. to 1200° C.

[0029] The recyclable active material is represented by Chemical Formula 1 below.

[0030] [Chemical formula 1]

[0031] Li a Ni x Mn y Co z M w O 2+δ

[0032] (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。)

[0033] The reusable active material may include fluorine (F) in an amount equal to or less than 100 ppm.

[0034] Beneficial Effects

[0035] According to the present disclosure, it is possible to provide an active material recovery apparatus capable of easily detaching an electrode active material from a current collector by increasing an air contact rate by introducing a rotating heat treatment tank during a heat treatment process, and continuously separating the electrode active material from the current collector.

[0036] Using the active material recovery equipment according to the present disclosure, it is possible to recover positive active materials from positive electrode waste. The method can reuse discarded positive active materials (such as positive electrode waste generated in the manufacturing process of lithium secondary batteries) without using acid, so the method is eco-friendly. The method according to the present disclosure does not require a neutralization process or a wastewater treatment process, thereby alleviating environmental problems and reducing processing costs.

[0037] According to the present disclosure, the positive electrode active material can be recycled without non-recyclable metal elements. Since the current collector is not dissolved, the current collector can also be recycled. The method can directly reuse the active material recovered in the form of powder, rather than extracting the active material elements and synthesizing the positive electrode active material again as a raw material, so the method is economical.

[0038] According to the present disclosure, no toxic and explosive solvents such as NMP, DMC, acetone, methanol are used, so the method is safe. Simple processes such as heat treatment, cleaning, annealing are used, so it is easy to manage these processes and the method is suitable for large-scale production.

[0039] According to the present disclosure, the electrochemical performance of the recovered active material will not be deteriorated, and excellent resistance and capacity characteristics can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] 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 understood as being limited to the drawings.

[0041] Figure 1 The figure shows the positive electrode waste material which is discarded after the positive electrode plate is punched out from the positive electrode sheet.

[0042] Figure 2 is a schematic diagram of an active material recovery apparatus according to one embodiment of the present disclosure.

[0043] Figure 3 is a schematic diagram of an active material recovery apparatus according to another embodiment of the present disclosure.

[0044] Figure 4 is a flow chart of an active material recycling method according to another embodiment of the present disclosure.

[0045] Figure 5 is a flow chart of an active material recycling method according to another embodiment of the present disclosure.

[0046] Figure 6 is a graph showing the difference in heat treatment results according to the position of the positive electrode scrap in Sample 1.

[0047] Figure 7 are pictures showing the state of Sample 2 according to time according to the experimental process.

[0048] Figure 8 and Fig. 9 Results of battery evaluation using the active materials of Embodiments 1 and 2 and Comparative Examples 1 to 5 are shown.

[0049] Fig.10 and Fig.11 1 and 2 are scanning electron microscope (SEM) images of the active materials of Embodiment 1 and Comparative Examples 1 to 3 and 5.

[0050] Fig.12 1 is a graph showing particle size distribution of active materials of Embodiments 3 and 4 and Comparative Examples 1 and 2.

[0051] Fig.13 The results of battery evaluation using the active materials of Embodiments 3 and 4 and Comparative Example 1 are shown, and the result values ​​are summarized in Table 4.

[0052] Fig.14 The evaluation results of batteries using the active materials of Embodiment 5 and Comparative Examples 6 to 9 are shown.

[0053] Fig.15 XRD patterns of active materials of Embodiment 5 and Comparative Examples 6, 7, and 9 are shown.

[0054] Fig.16 1 and 2 are SEM images of the active materials of Embodiment 5 and Comparative Example 6.

[0055] Fig.17 X-ray photoelectron spectroscopy (XPS) graphs of the active materials of Comparative Examples 6, 7, and 9 are shown.

[0056] Fig.181 is a graph showing particle size distribution of active materials of Embodiment 5 and Comparative Examples 6, 7 and 9.

[0057] Fig.19 The results of battery evaluation using the active materials of Embodiment 6 and Comparative Examples 6, 7, and 10 are shown.

[0058] Fig. 20 XPS charts of the active materials of Embodiment 6 and Comparative Examples 6 to 8 are shown. DETAILED DESCRIPTION

[0059] Hereinafter, the preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in this specification and the appended claims should not be interpreted as being limited to the general and dictionary meanings, but should be interpreted according to the meanings and concepts corresponding to the technical aspects of the present disclosure based on the principle that the inventor is allowed to appropriately define the terms to obtain the best interpretation. Therefore, the descriptions presented herein are only preferred embodiments for illustrative purposes and are not intended to limit the scope of the present disclosure, so it should be understood that other equivalent examples and variations may be made without departing from the scope of the present disclosure.

[0060] In the following description, reference is made to the accompanying drawings which form a part hereof. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit and scope of the subject matter presented herein. It is readily understood that the various aspects of the present disclosure as generally described herein and illustrated in the drawings may be arranged, substituted, combined, separated, and designed into a variety of different configurations, all of which are expressly contemplated herein.

[0061] Unless defined otherwise, 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 belongs.

[0062] The present disclosure should not be limited by the specific embodiments described in this application, which are intended to illustrate various aspects. It is obvious to those of ordinary skill in the art that many modifications and changes can be made without departing from the spirit and scope of the present disclosure. In addition to the methods and devices listed herein, functionally equivalent methods and devices within the scope of the present disclosure will be obvious to those of ordinary skill in the art based on the foregoing description. Such modifications and changes should fall within the scope of the appended claims. The present disclosure is limited only by the terms of the appended claims and the scope of all equivalents of these claims. It should also be understood that the terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting.

[0063] In the case of the conventional active material cycle recycling process, the main purpose is to extract precious metals (nickel, cobalt, manganese, etc.) as elements in the active materials of lithium secondary batteries, which deteriorate in performance after utilization and re-synthesize the active materials. However, the difference of the present disclosure is that active materials are recovered from positive electrode waste generated in the lithium secondary battery manufacturing process.

[0064] In addition, in the case of known active material cycle recycling processes, a chemical method of extracting precious metals by acid / alkali dissolution or melting with reduction / additives and making precious metals into metals (direct reduction method) or re-synthesized active materials is added, which additionally complicates the process and generates economic costs. However, the present disclosure relates to a method for directly recycling positive electrode active materials without dissolving the positive electrode active materials.

[0065] In order to directly reuse the positive electrode active material, a method for removing the current collector from the positive electrode is required. To remove the current collector from the positive electrode, the binder can be removed by high temperature heat treatment, the binder can be melted by solvent, the current collector can be completely melted, the active material can be selected by dry grinding and screening, etc.

[0066] The stability of the solvent is very important for using the solvent to dissolve the binder. Although NMP is the most effective solvent, NMP has the disadvantages of toxicity and high price. In addition, there is a disadvantage that a solvent recovery process is required, such as reprocessing the waste solvent. Melting the current collector would be cheaper than using a solvent. However, since it is difficult to remove foreign matter from the surface of the reused active material and hydrogen is produced during the removal of the current collector, there is a risk of explosion. It is difficult to completely separate the current collector from the active material by dry grinding and screening. Since the particle size distribution of the active material changes during the grinding process and it is difficult to remove the binder, there is a disadvantage that the performance of the reused battery will deteriorate.

[0067] In the present disclosure, the active material and the current collector are separated by high temperature heat treatment. In particular, an apparatus is provided that performs heat treatment in air and is advantageous for large-scale production and commercialization. Foreign matter should not remain on the surface of the recycled active material. In the present disclosure, even a step of removing foreign matter from the surface of the recycled active material is proposed.

[0068] In the following question, please refer to Figure 2 and Figure 3 An active material recovery apparatus according to an embodiment of the present disclosure is described.

[0069] first, Figure 2 The active material recovery apparatus 100 shown in FIG. 1 is a rotary firing apparatus including a spiral-type rod 110 therein.

[0070] The heat treatment tank 120 and the screening wall 130 are arranged in a line along the axis of the rod 110. The heat treatment tank 120 and the screening wall 130 may have a hollow tubular shape with a certain space in which the object to be treated may be contained. At this time, the rod 110 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 may be coaxially arranged. The rod 110 may have an elongated shape so as to be connected from one side to the other side in the longitudinal direction of the heat treatment tank 120 and the screening wall 130.

[0071] 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 device along the conveying direction of the object to be treated, and the screening wall 130 is installed at the rear end of the device. By sequentially installing the heat treatment tank 120 and the screening wall 130, the object to be treated is sufficiently heated in the heat treatment tank 120 to cause thermal decomposition, and then conveyed to the screening wall 130.

[0072] The active material recovery apparatus 100 further includes an exhaust gas injection and degassing system 140. The exhaust gas injection and degassing system 140 may be used to inject air or oxygen into the heat treatment tank 120. The exhaust gas injection and degassing system 140 may be used to purify exhaust gas after heat treatment and then be discharged.

[0073] The rod 110 rotates along its axis. The object to be processed is the electrode waste 160, preferably the positive electrode waste. The electrode waste 160 includes an active material layer on the current collector 150. The heat treatment tank 120 heat treats the electrode waste 160 in the air while rotating the electrode waste 160 around the axis of the rod 110, thereby removing the binder and the conductive material in the active material layer. The heat treatment can be performed at 300°C to 650°C, so it can also be called high-temperature heat treatment. At a temperature below 300°C, there is a problem that it is difficult to remove the binder and the current collector 150 may not be separated. At a temperature equal to or greater than 650°C, the current collector 150 melts (aluminum melting point: 660°C) and may not be separated. When the thermal decomposition occurs sufficiently and the binder is removed, the active material layer can be separated from the current collector 150. The heat treatment tank 120 can also rotate around the axis of the rod 110. At this time, the rotation direction of the heat treatment tank 120 can be the same as or opposite to the rotation direction of the rod 110. The rotation direction of the heat treatment bath 120 may be changed at appropriate time intervals.

[0074] The rotation of the rod 110 and / or the heat treatment tank 120 causes the rotation of the electrode waste 160. In particular, the rod 110 pushes the electrode waste 160 while stirring the electrode waste 160, which helps the electrode waste 160 to contact the air well by means of the stirring force, and helps the active material layer to be separated as the active material 170 in the form of powder by means of the stirring force. When only the 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 inside the heat treatment tank 120. Thus, there is less contact with oxygen or air. In the present disclosure, the electrode waste 160 can be stirred by rotating the rod 110 in the heat treatment tank 120. Even if the electrode waste 160 is not put in after being finely crushed, the electrode waste 160 can also be split by the rod 110. The split electrode waste 160 is rotated by the rod 110, so that the split electrode waste 160 can fully contact oxygen or air. The rod 110 does not simply rotate but spirally rotates, so the rod 110 has a protruding structure such as a pin, a wing or a rod. Such a protruding structure allows the electrode scraps 160 to be rotated and mixed to the maximum extent. Therefore, incomplete combustion caused by the overlap phenomenon between the electrode scraps can be eliminated.

[0075] The active material layer separated from the current collector 150 by heat treatment in the heat treatment tank 120 may have a structure such as a single particle or a sheet, in which the particles are agglomerated, and since the active material is not in a continuous film state, in the present disclosure, the active material is referred to as having a powder form. As such, in the heat treatment tank 120, the active material in powder form may be obtained from the current collector 150 by simple heat treatment in air, and some of the electrode waste 160 may be transferred to the screening wall 130 in a state where the active material layer is attached to the current collector 150 only by van der Waals force, or some of the active material layer is separated to become an active material 170 in powder form.

[0076] It is preferred that the heat treatment tank 120 has a tubular shape with both ends open so that the electrode waste 160 is placed therein and the active material 170 and the current collector 150 from which the binder and the conductive material are removed are transferred to the screening wall 130. In addition, it is preferred that the tube is an open system through which air enters and leaves. That is, since the tube does not have a closed structure, oxygen in the external air can be introduced.

[0077] The heat treatment tank 120 includes: a container for receiving, rotating and mixing the 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 active materials can be prevented, and active materials can be prevented from being contaminated by metal ions generated in the container. In addition, a heat source such as a microwave oven can also be used as the heating unit, so the types of heat sources available are diverse.

[0078] For example, the container of the heat treatment tank 120 can be a tube made of a ceramic material (e.g., high-purity alumina). In addition, since such a tube further includes a flange connected in the longitudinal direction at both ends of the tube, the heat treatment tank 120 capable of large-capacity processing can be manufactured by connecting two or more tubes to each other and extending the length. In general, due to the characteristics of the material, it is very difficult to manufacture a tube made of a ceramic material exceeding a certain diameter and a certain length, and the product price of the tube is quite high. Therefore, a plurality of tubes made of ceramic materials and having an appropriate diameter and length can be connected to the desired length by means of a flange, and by making the tube into a length such as equal to or exceeding hundreds of millimeters or thousands of millimeters, large-capacity processing can be performed.

[0079] The heating unit may be disposed on the outer circumferential surface of the container. For example, the heating unit is a linear heating element, and the heating element has a long strip shape so as to be connected from one side in the longitudinal direction of the container to the other side, and may be arranged on the outer circumferential surface of the container. Thus, heat of uniform temperature may 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 a SiC material.

[0080] The heat treatment tank 120 is preferably an open system, wherein 10 ml / min to 100 liters / min of air is added or injected for every 100 grams of electrode waste 160 put in. If the heat treatment tank 120 has a tubular shape with both ends open, adding air is smooth. Figure 2 As shown by arrows in FIG. 1 , when air inlets are installed at a plurality of locations in the heat treatment tank 120, since air or oxygen injected via the exhaust gas injection and degassing system 140 is smoothly supplied to the portion where the electrode waste 160 is mixed, air and oxygen required for thermal decomposition can be sufficiently supplied to the heat treatment tank 120. The air inlet may be installed even in the rod 110.

[0081] When the electrode waste 160 is heat treated, the PVdF (polyvinylidene fluoride) and the conductive material present in the active material layer are decomposed and separated from the current collector. However, if sufficient air and oxygen are not supplied, the active material layer will not be separated from the current collector due to incomplete combustion, but will be strongly carbonized and attached to the current collector. In this case, since the recovery rate of the active material is reduced, it is difficult to ensure fairness. The heat treatment tank 120 can control the amount of air added and has a structure in which the electrode waste 160 is in good contact with the air during heat treatment. In particular, in order to recover a large amount of active materials, the rod 110 rotates so that the electrode waste 160 is in good contact with the air, and the heat treatment tank 120 also rotates so that the electrode waste 160 moves back and forth inside the heat treatment tank 120 so that it is evenly heated and can be in contact with the air to the maximum extent. The incomplete combustion of the elements constituting the active material layer can be suppressed, so the recovery rate of the active material finally separated can be improved. If less than 10 ml / min of air is injected or added per 100 g of electrode waste 160, the binder and conductive material will not be completely burned, so the recovery rate of active material is reduced. If more than 100 liters / min of air is injected or added, the active material may be blown away due to the excessive amount of air added, and temperature control may be difficult.

[0082] The screening wall 130 may have a mesh structure. The size of the mesh may be appropriately determined so that the current collector 150 does not pass through the screening wall 130. The active material 170 in the form of powder that passes through the screening wall 130 may be recovered by means of a first collector 180 installed in the lower portion of the screening wall 130. The current collector 150 that does not pass through the screening wall 130 may be recovered by means of a second collector 190 installed at the end of the screening wall 130. As described above, when the active material recovery apparatus 100 is used, each of the active material 170 and the current collector 150 may be recovered. As described above, according to the active material recovery apparatus 100 of the present disclosure, the active material 170 may be recovered in its original shape, and the current collector 150 may also be recovered without being melted or thrown away.

[0083] The screening wall 130 preferably has a tubular shape with both ends open so that the separated current collector 150 and active material 170 can be placed therein and the current collector 150 can be discharged. The active material 170 is smoothly separated from the current collector 150 by the rotation of the rod 110. The rod 110 rotates and stirs the current collector 150, so that the active material 170 is separated from the current collector 150, and the current collector 150 and the screening wall 130 collide with each other, so that the active material 170 falls off from the current collector 150 by impact. The screening wall 130 can also rotate around the axis of the rod 110. If the current collector 150 is in a stopped state, the active material 170 is not easily fallen off from the current collector 150 because there is no rotating rod 110 or the screening wall 130 does not rotate.

[0084] The rotation direction of the screening wall 130 may be the same as or opposite to the rotation direction of the rod 110. The rotation direction of the screening wall 130 may be changed at appropriate time intervals. The screening wall 130 may also be in the same direction as the rotation direction of the heat treatment tank 120. When the connection portion between the heat treatment tank 120 and the screening wall 130 is fixed, the heat treatment tank 120 and the screening wall 130 may rotate together. The heat treatment tank 120 and the screening wall 130 may be configured as an integral type or a prefabricated type connected to each other.

[0085] For example, by forming a coupling groove along the main surface on one side of the heat treatment groove 120 and forming a coupling protrusion along the main surface on one side of the screening wall 130, the ends of the heat treatment groove 120 and the screening wall 130 corresponding to each other can be firmly connected by means of the coupling groove and the coupling protrusion. The coupling groove and the coupling protrusion can be connected by means of an interference fit connection method or a screw connection method. The coupling groove and the coupling protrusion can be connected in a locking protrusion and hook structure.

[0086] As described above, when the heat treatment tank 120 and the screening wall 130 are coaxially arranged in a tubular shape, it is preferred that the active material recovery apparatus 100 continuously performs input of new electrode scraps and recovery of active materials.

[0087] The screening wall 130 not only includes a heating unit, so that a cooling portion can be formed by a slow cooling method using natural cooling, and cooling means is further provided outside the screening wall 130, so that a rapid cooling method or temperature-controlled cooling can be performed.

[0088] Preferably, the active material recovery device 100 also has a vibration function. Vibration can give physical force so that the active material from which the binder and the conductive material are removed after the heat treatment is separated 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 to the first collector 180 below the screening wall 130.

[0089] then, Figure 3 The active material recovery device 100' shown in the figure is characterized in that the angle θ of the entire active material recovery device 100' is adjusted to make the axis of the rod 110 tilt relative to the ground. As shown, the active material recovery device 100' can be supported in a slightly tilted state so that the rear end (i.e., the right side in the figure) of the active material recovery device 100' is the lower part. Brackets with different heights can be installed at the front lower part and the rear lower part of the active material recovery device 100', respectively.

[0090] Adjustment of the angle θ gives an inclination to the ground, and the inclination enables the current collector 150 and the active material 170 to move downward under the weight of the current collector 150 and the active material 170. As shown, when the inclination is given, the current collector 150 and the active material 170 slowly move from the left side to the right side of the figure by means of 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 to the first collector 180 below the screening wall 130, and the current collector 150 that does not pass through the screening wall 130 falls to the second collector 190 installed at the end of the screening wall 130. The angle θ may be maintained in a state set before the process throughout the process, or may be adjusted and changed as needed during the process.

[0091] The above-mentioned active material recovery equipment 100 and 100' can process a large amount of electrode waste, thereby greatly improving work efficiency and reducing work time. In particular, the active material recovery equipment 100 and 100' is an open system that does not block oxygen in the outdoor air and can supply sufficient air or oxygen for complete combustion of the active material layer. The electrode waste can be rotated, which makes air contact smoother, thereby recovering the active material with uniform quality and high recovery rate.

[0092] In the following, reference will be made to Figure 4 and Figure 5 The active material recycling method according to the embodiment of the present disclosure is described. First, Figure 4 is a flow chart of an active material recycling method according to another embodiment of the present disclosure.

[0093] refer to Figure 4 , first, discarded positive electrode waste is prepared (step S10).

[0094] As above reference Figure 1 The positive electrode waste can be the part remaining after manufacturing a positive electrode sheet including a positive electrode active material layer on a current collector and punching the positive electrode sheet. In addition, the positive electrode waste can be prepared by collecting positive electrodes that have defects in the processing process. In addition, the positive electrode waste can be prepared by separating the positive electrode from a lithium secondary battery discarded after use.

[0095] For example, a slurry is prepared by adding N-methylpyrrolidone (NMP) to lithium cobalt oxide (LiCoO2 (LCO)) as an active material or an NCM-based active material (including nickel (Ni), cobalt (Co) and manganese (Mn)), carbon-based carbon black as a conductive material and polyvinylidene fluoride (PVdF) as a binder, and mixing them. The slurry is coated on a sheet-type current collector made of aluminum foil and then dried in a vacuum oven at about 120°C to prepare a positive electrode sheet, and a positive electrode plate of a predetermined size is punched out, and the remaining positive electrode waste can be prepared.

[0096] Lithium composite transition metal oxides are used as positive electrode active materials for lithium secondary batteries, among which lithium cobalt oxide (LiCoO2), lithium manganate (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compounds (LiFePO4, etc.) or nickel lithium oxide (LiNiO2, etc.) are mainly used. In addition, as a method for improving low thermal stability while maintaining the excellent reversible capacity of LiNiO2, nickel-manganese-based lithium composite metal oxides (in which a part of nickel (Ni) is replaced by manganese (Mn) having excellent thermal stability) and NCM-based lithium composite transition metal oxides (in which a part of nickel (Ni) is replaced by manganese (Mn) and cobalt (Co)) are used.

[0097] As described above, the positive electrode waste has an active material layer on a current collector of a metal foil such as an aluminum foil. The active material layer is formed by coating a slurry in which an active material, a conductive material, a binder, a solvent, etc. are mixed, and has a structure in which the binder connects the active material and the conductive material after the solvent is volatilized. Therefore, if the binder is removed, the active material can be separated from the current collector.

[0098] Next, the cathode waste is placed in the heat treatment tank 120 of the active material recovery apparatus 100 and 100 ′ according to the present disclosure (step S15 ).

[0099] The method may further include a step in which the positive electrode waste is crushed to an appropriate size before step S15. Crushing refers to cutting or chopping the positive electrode waste into pieces of a suitable, easily handled size. After crushing, the positive electrode waste is cut into small pieces, for example, 1 cm × 1 cm. For crushing, various dry grinding equipment (such as hand grinders, pin grinders, disc grinders, cutting mills and hammer mills) can be used, or a high-speed cutter can be used. Crushing can be performed in consideration of the characteristics (such as fluidity) required for the active material recovery equipment 100 and 100' used in the disposal of the positive electrode waste and subsequent processes. Since the active material recovery equipment 100 and 100' include a rod 110, the positive electrode waste can be split when the rod 110 rotates. Therefore, if the positive electrode waste is not too large, it can be put in without being crushed.

[0100] Next, the heat treatment tank 120 heat treats the positive electrode waste in the air while rotating the positive electrode waste around the rod 10 to remove the binder and the 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 300°C to 650°C, which can be called high-temperature heat treatment. At a temperature below 300°C, it is difficult to remove the binder, which causes the problem that the current collector cannot be separated. At a temperature equal to or greater than 650°C, the current collector melts (aluminum melting point: 660°C), which results in the phenomenon that the current collector cannot be separated. Therefore, the desired heat treatment temperature is obtained by adjusting the temperature of the heating unit of the heat treatment tank 120.

[0101] A certain heat treatment time is maintained so that the binder can be fully thermally decomposed. For example, the heat treatment time is about 30 minutes. Preferably, the heat treatment time is set to be equal to or greater than 30 minutes. The longer the heat treatment time is, the longer the time for the binder to thermally decompose is, but when the heat treatment time exceeds a certain time, the effect of thermal decomposition is no different. Preferably, the heat treatment time is set to be equal to or greater than 30 minutes to 5 hours.

[0102] For example, heat treatment may be performed at 550°C for 30 minutes at a temperature rise rate of 5°C / minute. This temperature rise rate can be implemented without difficulty (for example, by means of a heating unit of the heat treatment tank 120), and heating can be performed without causing thermal shock to the positive electrode waste, etc. 550°C allows good thermal decomposition of the binder while taking into account the melting point of the aluminum current collector. At this temperature, since heat treatment for less than 10 minutes is insufficient for thermal decomposition to occur, heat treatment for more than 10 minutes should be performed, and if possible, heat treatment for more than 30 minutes should be performed.

[0103] Since the binder and the conductive material in the active material layer are thermally decomposed by heat treatment in the air, they become CO2 and H2O and are removed. Since the binder is removed, the active material is separated from the current collector, and the active material to be recovered in the form of powder can be selected. Therefore, only in step S30, the current collector can be separated from the active material layer, and the active material in the active material layer can be recovered.

[0104] It is important to perform the heat treatment of step S30 in the air. If the heat treatment is performed in a reducing gas or inert gas atmosphere, the binder and the conductive material will not be thermally decomposed but only carbonized. When the binder and the conductive material are only carbonized, the carbon component remains on the surface of the active material, which will reduce the performance of the recycled active material. When the heat treatment is performed in the air, since the carbon material in the binder or the conductive material reacts with oxygen and is burned and removed as CO and CO2 gases, both the binder and the conductive material are almost removed without remaining. The active material recovery equipment 100 and 100' are suitable for performing the heat treatment of step S30 because there can be sufficient air contact.

[0105] The heat treatment time refers to the time spent at a desired heat treatment temperature in the heat treatment tank 120. If the heat treatment time is 30 minutes, the process is controlled so that the cathode waste can be heated in the heat treatment tank 120 for 30 minutes and then transferred to the screening wall 130.

[0106] Now, the active material in the form of powder that has passed through the screening wall 130 is recovered (step S35). The active material recovery apparatus 100 and 100' as an open system can almost completely remove the binder and the conductive material through smooth air contact in the above-mentioned heat treatment tank 120, and recover the active material in the form of powder. Since the positive electrode waste transferred to the screening wall 130 is in a state where the binder has been removed in the previous step, the current collector and the active material can be completely separated by the rotation of the rod 110. The carbon component generated by the carbonization of the binder or the conductive material may not remain on the surface of the active material obtained by passing through the screening wall 130.

[0107] As described above, the use of the active material recovery apparatus 100 and 100' is completed. By using the active material recovery apparatus 100 and 100' for heat treatment, the active material can be recovered at a very high recovery rate, and since the recovered active material has no carbon component, a separate process for removing the carbon component is not required.

[0108] If the recovered active material is reused intact, poor electrode performance may result. In this regard, as a subsequent process, the present disclosure proposes a method for recycling active materials, which may further include steps such as cleaning, drying, adding lithium precursors, annealing, and surface coating.

[0109] 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 lithium compound solution that shows alkalinity in an aqueous solution state. This aqueous lithium compound solution is prepared to contain greater than 0% and equal to or less than 15% of a lithium compound, and preferably utilizes LiOH. The amount of LiOH is preferably equal to or less than 15%. Using excessive LiOH may leave excessive LiOH on the surface of the active material even after cleaning, which may affect future annealing processes. In order to clean the surface of the active material as much as possible in the pre-annealing step, since the addition of excessive LiOH is not conducive to the process, the addition amount is limited to equal to or less than 15%.

[0110] Cleaning can be carried out by soaking the recovered active material in such an aqueous solution of a lithium compound. After soaking, cleaning can be carried out within a week (preferably within a day, more preferably within an hour). If cleaning is carried out more than a week later, there is a capacity drop due to excessive elution of lithium. Therefore, it is preferably cleaned within an hour. Cleaning includes soaking the active material in a cleaning solution (such as an aqueous solution of a lithium compound that shows alkalinity in an aqueous solution state), stirring the active material in an immersed state, etc. It is better to stir and soak together as much as possible. If the active material is only soaked in an aqueous solution of a lithium compound without stirring, the cleaning process may proceed slowly and may cause lithium leaching. Since the process time can be minimized if stirring and soaking are carried out together, it is preferably stirred while soaking in an aqueous solution of a lithium compound. It can be dried in air in a convection oven after filtering.

[0111] The reason for cleaning with an aqueous lithium compound solution that shows alkalinity in an aqueous solution state is to remove LiF and metal fluorides that may be present on the surface of the recovered 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 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 the present disclosure, the reactants that may be produced on the surface of the reused active material in the heat treatment process of step S30 are removed by adding the cleaning of step S40, so that foreign matter does not remain on the surface of the active material.

[0112] Obviously, it is important to clean the active material with an aqueous solution of a lithium compound that exhibits alkalinity in an aqueous solution state in step S40. If an aqueous solution of sulfuric acid or hydrochloric acid is used instead of an aqueous solution of a lithium compound that exhibits alkalinity in an aqueous solution state, F on the surface of the active material can be cleaned, but since the transition metals (Co and Mg) present in the active material are eluted, the performance of the recycled positive electrode active material will decrease. The aqueous solution of a lithium compound that exhibits alkalinity in an aqueous solution state used in the active material recycling method according to the present disclosure is very desirable because the aqueous solution of a lithium compound can remove a binder that may be present in trace amounts even after the thermal decomposition of step S30, and can replenish the amount of lithium that may be eluted in the cleaning process without eluting the transition metals, etc. present in the active material.

[0113] Through step S40, in the present disclosure, the LiF content on the surface of the recovered active material can be adjusted to less than 500 ppm, which can achieve the effect of increasing the capacity. Preferably, the F content can be set to be equal to or lower than 100 ppm. More preferably, the F content can be set to be equal to or lower than 30 ppm.

[0114] Next, a lithium precursor is added to the cleaned active material and annealing is performed (step S50 ).

[0115] In the previous steps S30 and S40, lithium loss in the active material may occur. In step S50, this lithium loss is compensated.

[0116] Furthermore, in step S50 , the crystal structure of the active material is restored by annealing, and the performance of the reused active material is restored or improved to the level of fresh active material that has never been used.

[0117] Through the previous steps S30 and S40, a deformed structure may appear on the surface of the active material. For example, in the active material that is an NCM-based lithium composite transition metal oxide, in step S40, a spinel structure may be formed in which nickel is rock-salted by moisture [NiCO3·2Ni(OH)2)H2O]. If the battery is manufactured as it is, the battery performance may deteriorate (such as a decrease in capacity). In the present disclosure, the crystal structure is restored by 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, the initial performance of the active material can be restored or improved to a level similar to that of the fresh active material.

[0118] The lithium precursor of step S50 may include at least one of LiOH, Li 2 CO 3 , LiNO 3 , and Li 2 O.

[0119] The amount of lithium precursor added can be the ratio 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 added in a molar ratio of 0.001 to 0.4. It is appropriate to add lithium in a molar ratio of 0.01 to 0.2. In addition to the amount of lithium lost by cleaning, etc., adding an excess of lithium precursor will cause unreacted lithium precursor to remain in the reused active material, which plays a role in increasing resistance during the reuse of the active material. Therefore, it is necessary to apply an appropriate amount of lithium precursor.

[0120] In addition, the amount of lithium precursor added is preferably relative to the molar ratio of lithium to other metals being 1:1, and lithium can be added in an additional molar ratio of 0.0001 to 0.1. The reason for adding excess lithium as described above is to form a surface protective layer by surface coating on the active material, which will be further described below. In the case of manufacturing a secondary battery using such an active material, the life characteristics can be maintained while suppressing the side reactions caused by the electrolyte.

[0121] The annealing of step S50 may be performed at 400°C to 1000°C in air. The annealing temperature may be 600°C to 900°C. The temperature should be changed within a limited range according to 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 restored, but even if the annealing time is long, the performance of the active material will not be significantly affected. For example, the annealing time is within 15 hours.

[0122] 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, the annealing is performed at 750°C. In the case of using LiOH 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.

[0123] The annealing temperature is preferably a temperature exceeding the melting point of the lithium precursor. However, at a temperature exceeding 1000°C, the positive electrode active material may be thermally decomposed and the performance of the active material may be degraded, so the temperature should not exceed 1000°C.

[0124] When the process proceeds to step S50, a reusable active material can be obtained. Reusability means that the active material is in such a state that the active material can be directly put into slurry production like a fresh active material without any additional additives or additional treatments for adjusting the composition.

[0125] Next, as an optional step, step S60 may be further performed. In step S60, surface coating is applied to the active material annealed in step S50.

[0126] The surface coating step may involve coating at least one of a metal, an organometal, and a carbon component on the surface in a solid or liquid manner, and then heat-treating the coated material at 100°C to 1200°C. When heat-treatment is carried out at a temperature 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 performed on the surface in a solid or liquid manner can utilize methods such as mixing, milling, spray drying, and grinding.

[0127] Through surface coating, a surface protective layer is formed by a heterogeneous metal. 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, in the previous step S50, insufficient lithium is added so that not only the molar ratio of lithium to other metals in the positive electrode active material is 1:1, but also an excessive amount of lithium is added such that, compared with other metals in the positive electrode active material, more lithium is included in a molar ratio of 0.0001 to 0.1. 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.

[0128] 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 protective layer. The additional lithium added in step S50 in a molar ratio of 0.0001 to 0.1 reacts with metal oxides 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 to less than 1:1, so capacity degradation does not occur.

[0129] The reusable active material obtained by the above method can be represented by the following Chemical Formula 1.

[0130] [Chemical Formula 1]

[0131] Li a Ni x Mn y Co z M w O 2+δ

[0132] (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, and x + y + z + w = 1.)

[0133] The F content of the recyclable active material is equal to or lower than 100 ppm. According to the present disclosure, since the active material with reduced F content can be recovered, if the active material with reduced F content is reused as an active material, excellent resistance performance and capacity performance can be implemented.

[0134] As described above, according to the present disclosure, active materials can be recovered by 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 lithium compound solution that shows alkalinity in an aqueous solution state have the advantages of being safe and cheap, removing LiF or metal fluoride without losing other elements, preventing the elution of transition metals, etc., and replenishing the loss of lithium that occurs during the process. The annealing step S50 also has the advantages of being safe and cheap, and recovering the battery performance of the reused active material by restoring the crystal structure (i.e., improving the crystallinity).

[0135] The reusable active material obtained according to the present disclosure may have a particle size distribution similar to that of the fresh active material, and thus may not require a separate treatment for adjusting the particle size distribution. In particular, since the carbon component generated by carbonization of the binder or the conductive material by means of the active material recovery apparatus 100 and 100' suitable for heat treatment does not remain on the surface, a step of removing the carbon component or the like is not required. Figure 4 The active material obtained by the method can be reused as it is and used to manufacture the positive electrode without additional treatment.

[0136] The recycled active material may be used 100% as it is without adjusting the composition, or may be mixed with new active material, or may be mixed with a conductive material, a binder, and a solvent to prepare a slurry and used.

[0137] then, Figure 5 is a flow chart of an active material recycling method according to another embodiment of the present disclosure. Figure 5 In the Figure 4 The same steps are performed and repeated descriptions are omitted.

[0138] refer to Figure 5 ,refer to Figure 4 Steps S10 to S35 described above are performed in the same manner. Then, the recovered active material is cleaned (step S40'). The cleaning method, the solution used for cleaning, etc. are the same as those described above. Figure 4 The same as step S40 in.

[0139] Here, the cleaned active material is not dried but directly mixed with the lithium precursor solution and spray-dried (step S45).

[0140] In the previous steps S30 and S40', a loss of lithium in the active material may occur. In step S45, this loss of lithium is supplemented more simply and clearly.

[0141] As the lithium precursor solution, a lithium compound soluble in an aqueous solution or an organic solvent may be used. In particular, the lithium precursor of step S45 may preferably include at least one of LiOH, Li2CO3, LiNO3 and Li2O.

[0142] The temperature of the spray drying step may preferably be equal to or higher than 100° C. When the temperature is equal to or lower than 80° C., there may be a problem that the solution is not completely dried. More preferably, the temperature of the spray drying step may be 100° C. to 300° C.

[0143] If the active material is dried in an oven or the like immediately after the surface modification treatment by cleaning in step S40', the active material particles may aggregate to form a mass. In order to mix the lithium precursor with these agglomerated particles, the mass may need to be ground, and in order to mix the solid lithium precursor, a powder mixing or milling process is required when mixing the materials. In this case, the process is complicated and it is difficult to carry out a continuous process. In addition, in the case of NCM-based positive active materials, when the positive active material and the lithium precursor are powder mixed, milled, etc. in the presence of moisture, the positive active material will eat moisture, thereby seriously agglomerating. Therefore, the present embodiment proposes that after cleaning in step S40', the active material is mixed and dispersed in the lithium precursor solution without drying, and the active material is spray-dried. Thus, the agglomeration of particles caused by drying can be eliminated, and the inconvenience of mixing solid lithium precursors can be eliminated. That is, it is advantageous to produce the active material in powder form rather than in mass by spray drying.

[0144] In the spray drying process, since the lithium precursor solution is dried immediately after spraying, the lithium precursor component is coated or contacted on the surface of the active material. In this regard, there is also an advantage that when the lithium precursor solution as a solvent is dried, the particles are agglomerated under the action of capillary force and the particles are adjusted. In the case of positive electrode waste made of electrodes, the particles on the surface may be pressed and cracked or broken during rolling. In particular, compared with LCO, NCM-based active materials have a high degree of particle splitting due to rolling during the process of forming the electrode. Compared with fresh active materials, since the recovered active materials include many small particles, there is a problem of uneven particles.

[0145] In particular, NCM-based active materials including large particles that are secondary granulated by aggregating primary particles having a size of tens to hundreds of nanometers are used. In the process of rolling a positive electrode made of such an active material to adjust the porosity in the electrode, the secondary particles are split into primary granulated particles or smaller particles that are larger in size than the secondary particles but smaller than the large particles. Since the specific surface area of ​​the active material increases as the number of particles crushed by rolling increases, in the case of a reused active material obtained from the rolled electrode, problems that affect slurry properties, electrode adhesion, and electrode performance may occur when reused.

[0146] In order to make the active material reach a reusable level, it is expected that the particle size distribution should not be different from that of the fresh active material. Since spray drying can recover large particles by agglomerating small particles that are split during the rolling process, spray drying can solve the unevenness of the particles and can also make the particle size close to the initial characteristics of the fresh active material. In particular, the effect is very good in NCM-based active materials, because NCM-based active materials have serious particle breakage in the previous rolling process. Therefore, it is expected that the characteristics of the battery recycling the active material recovered by the method according to the present disclosure will be similar to the characteristics of the battery using fresh active materials.

[0147] As described above, through the spray drying step (S45), the lithium precursor is coated on the surface of the active material, and the active material is obtained by adjusting the particles. Since the addition, granulation and drying of the lithium precursor are performed in one step, there is an effect of simplifying the process. In addition, the special feature of spray drying is that it is not a means of simply obtaining an active material, but a means of re-granulating the previously used particles crushed by rolling or the like.

[0148] In addition, in the case where the cleaned active material particles in step S40' are only mixed and dispersed in a lithium precursor solution of a certain concentration, step S45 is continued, so there is an advantage in that the cleaning in step S40' and the spray drying in step S45 can be a continuous process. As such, in the active material recycling method according to the present embodiment, the process is continuous, which has the advantage that coating, drying and granulation (particle readjustment) of the lithium precursor are simultaneously performed in one step.

[0149] Here, the lithium precursor is also prepared according to reference Figure 4 The amount of addition in step S50 described above may be the ratio of lithium lost compared to the ratio of lithium to other metals in the fresh active material.

[0150] Next, the spray-dried active material is annealed (step S50'). Since the lithium precursor is added to the active material in step S45, in this step, annealing can be performed immediately after spray drying without adding additional lithium precursor. The annealing effect of step S50' is similar to that of reference Figure 4 The effect of step S50 described above is the same. Thereafter, if necessary, surface coating of step S60 may be further performed.

[0151] Meanwhile, another positive electrode active material recycling method using the active material recycling apparatus 100 and 100' is also feasible. Figure 3 The heat treatment time of 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, but when the heat treatment time exceeds a certain time, the thermal decomposition effect does not differ. On the contrary, the effect is poor due to the generation of many reaction products such as LiF that are harmful to battery performance. Therefore, by limiting the heat treatment time to within one hour (preferably 30 minutes), a method that can minimize the generation of undesirable foreign matter that can adversely affect battery performance is feasible.

[0152] In this case, steps S50 and S60 may be performed in Figure 4 The heat treatment is performed immediately after step S30 and step S35 without step S40. That is, since the time of the heat treatment is shortened, the cleaning step can be omitted. As described above, according to another embodiment of the present disclosure, a reusable active material can be obtained by only using the two steps of heat treatment in air (step S30) and annealing after adding a lithium precursor (step S40). In particular, since the heat treatment is performed for a short time (preferably within 30 minutes), there is an advantage in that, by suppressing the reaction products, there is no need for additional steps such as washing for removing reaction products that have an adverse effect on battery performance.

[0153] Meanwhile, another positive electrode active material recycling method using the active material recycling apparatus 100 and 100' is also feasible. Figure 4 The cleaning time of step S40 described is shortened to within one hour, preferably within 10 minutes. If cleaning is performed for a long time, there is a risk of capacity reduction due to excessive elution of lithium. Therefore, a method that can minimize the elution of lithium by limiting the cleaning time and shortening the cleaning time is feasible.

[0154] In this case, the lithium precursor aqueous solution used as the cleaning solution in step S40 alone is sufficient to replenish the loss of lithium. Therefore, annealing can be performed without adding additional lithium precursor to the cleaned active material. That is, if Figure 4If the cleaning time of step S40 is set to be very short, then Figure 5 Annealing is performed immediately as in step S50' in FIG.

[0155] As described above, according to the present disclosure, various methods of obtaining reusable positive active materials are possible, and these methods can be more efficiently performed by optimizing the separation of the current collector and the active material layer using the active material recovery apparatus of the present disclosure.

[0156] Hereinafter, experimental examples of the present disclosure will be described in detail.

[0157] <Experimental Example 1>

[0158] Samples 1 and 2 were set up in the following manner, the positive electrode waste was heat-treated by the corresponding method, and then the active material recovery rate was evaluated.

[0159] Sample 1:

[0160] The cathode scrap is simply piled in the furnace and then heat treated. This is a case where the cathode scrap is placed in the furnace as a fixed type.

[0161] Figure 6 is a graph showing the difference in heat treatment results according to the position of the cathode scrap in Sample 1.

[0162] Figure 6 (a) is a picture of the positive electrode waste located on the surface of the piled positive electrode waste. In the case of this positive electrode waste, it was observed that the active material was separated from the current collector due to thermal decomposition of the binder and the conductive material due to exposure to the outside and contact with the air, but it was also observed that the place where thermal decomposition was less occurred, that is, the active material layer was not separated from the current collector due to incomplete combustion without sufficient air and oxygen supply, but was strongly carbonized and attached to the current collector.

[0163] Figure 6 (b) is a picture of the positive electrode waste located inside the piled positive electrode waste. In the case of this positive electrode waste, it was evaluated that the contact with the air was insufficient because the positive electrode waste was in contact with different positive electrode wastes at the top and bottom. It was observed that less thermal decomposition occurred in quite a few places, and the active material layer was carbonized and attached to the current collector.

[0164] Therefore, it was confirmed that when the positive electrode waste was piled in a pile form and heat-treated as a fixed type, the recovery rate was very poor because the active material was not separated from the current collector due to incomplete combustion. The result obtained was that when 100 grams of positive electrode waste was heat-treated, about 40 grams of positive electrode waste was not recovered.

[0165] Sample 2:

[0166] The positive electrode scrap was placed upright in the furnace so that it had more air contact than Sample 1, and then heat treated. In this case, the positive electrode scrap was placed in the furnace as a fixed type, but the distance between the positive electrode scraps was ensured to maximize the surface in contact with the air.

[0167] Figure 7 are pictures showing the state of Sample 2 according to time according to the experimental process.

[0168] Figure 7 (a) is a picture showing a state where shredded cathode scraps are stacked upright in a crucible. Figure 7 (b) is a picture showing a state where the cathode scrap is put into a furnace and heat-treated at 550° C. for 30 minutes in air. Figure 7 (c) is a picture showing the positive electrode waste after heat treatment taken out of the crucible. Figure 7 (d) is a picture showing the state of the active material in powder form recovered from the surface of the positive electrode scrap.

[0169] In Sample 2, unlike Sample 1, the result was obtained that most of the active materials were separated from the current collector and recovered. The recovery rate was equal to or greater than 95%. Through this, it was confirmed that a considerable amount of active materials can be recovered by simply performing heat treatment in air without using acid or NMP. In particular, the active material recovery equipment disclosed in the present invention was invented based on whether the contact area with the air can be further increased, because even a portion (5%) of the active material remaining in the current collector can be separated, and the recovery rate of the active material can be further improved. Compared with Comparative Example 2, the active material recovery equipment disclosed in the present invention is portable, which rotates the positive electrode waste, and because the contact with the air is smoother, the recovery rate is much higher than 95%.

[0170] <Experimental Example 2>

[0171] Each positive electrode active material was prepared by the following methods of the embodiment and comparative example, and its electrochemical performance was evaluated.

[0172] Implementation 1:

[0173] According to the above reference Figure 4The active material recycling method disclosed in the present invention collects the recycled active material. The positive electrode waste discarded after punching the positive electrode plate with NCM-based lithium composite transition metal oxide active material is prepared, and the heat treatment of step S30 is performed at 500°C for 30 minutes. The cleaning of step S40 is performed for 10 minutes using LiOH. In step S50, a lithium precursor (Li2CO3) is applied in an amount that can further add lithium at a molar ratio of 0.09 during the process relative to the molar ratio of lithium to other metals in the original active material (ICP analysis), and annealed at 750°C for 15 hours. Theoretically, in the case of fresh active materials, the molar ratio of lithium to other metals is 1:1, but since the average error of the ICP active material recovery equipment as an active material recovery equipment for checking 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 was added relative to the analytical ratio analyzed by ICP.

[0174] Implementation 2:

[0175] In addition to implementation 1, the Figure 4 The optional step S60 is a process for recovering the active material surface protection layer.

[0176] Comparative Example 1:

[0177] Fresh NCM-based lithium complex transition metal oxides were used instead of recycled active materials.

[0178] Comparative Example 2:

[0179] In the active material recycling method of the present disclosure as described above, only the heat treatment of step S30 is performed to remove the binder and the 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 the present disclosure, the surface modification of step S40, the crystal structure recovery of step S50, and the surface coating process of step S60 are not performed.

[0180] Comparative Example 3:

[0181] On the basis of Comparative Example 2, in the active material recycling method of the present disclosure as described above, the surface modification up to step S40 is performed to collect the active material. That is, although the surface modification is performed, in the active material recycling method of the present disclosure as described above, the crystal structure recovery of step S50 and the surface coating process of step S60 are not performed. Step S40 is performed under the same conditions as in Embodiment 1.

[0182] Comparative Example 4:

[0183] On the basis of Comparative Example 2, in the active material recycling method disclosed above, the surface modification of step S40 is not performed, and only the crystal structure recovery of step S50 is performed to collect the NCM-based lithium composite transition metal oxide active material. Unlike Embodiment 1, the annealing treatment for crystal structure recovery is performed without adding a lithium precursor.

[0184] Comparative Example 5:

[0185] Only steps S30 , S40 , and S50 are performed in the same manner as in Embodiment 1. However, unlike Embodiment 1, annealing treatment for restoring the crystal structure is performed without adding a lithium precursor.

[0186] ICP analysis was performed on the positive electrode active materials recovered or prepared from the embodiments and comparative examples, and the remaining 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.

[0187] A positive electrode was manufactured from a slurry prepared by weighing 96.25 wt % of a positive electrode active material recovered or prepared from each of the above Embodiments 1 and 2 and Comparative Examples 1 to 5, 1.5 wt % of carbon black as a conductive material, and 2.25 wt % of PVdF as a binder and mixing them with NMP, and then a battery (coin half cell, CHC) was manufactured and its electrochemical performance was evaluated.

[0188] In order to understand the amount of LiF remaining in the active materials recovered in Comparative Examples 2 and 3, F was detected and analyzed using ICP. The results are shown in Table 1 below.

[0189] [Table 1]

[0190] Comparative Example 2 Comparative Example 3 F content (mg / kg) 1450 ND

[0191] ND means that the measured F content is equal to or less than 30ppm. Referring to Table 1 above, it can be seen that the F content in the positive electrode active material recovered in Comparative Example 3 is significantly reduced compared with Comparative Example 2. That is, it can be confirmed that LiF is completely dissolved in the lithium compound aqueous solution by cleaning and is removed, so that LiF may not be detected by ICP. Therefore, it can be seen that the removal of LiF is very excellent through step S40.

[0192] In order to understand whether the lithium content in the positive electrode active material changes during steps S30 and S40 of the present disclosure, the ratio of lithium to other metals in the active material was analyzed by ICP. The results are shown in Table 2 below.

[0193] [Table 2]

[0194]

[0195] Referring to Table 2, it can be seen that, compared with Comparative Example 1, the ratio of lithium to other metals in the active material decreased by about 0.2 to 0.5 through the heat treatment of S30 in Comparative Example 2, and the ratio of lithium to other metals decreased by about 0.2 to 0.5 through the cleaning and drying of S40 in Comparative Example 3 compared with Comparative Example 2. The NCM-based lithium composite transition metal oxide seems to have a relatively large particle specific surface area due to the change to the spinel structure, and the ratio of lithium to other metals is greatly reduced. Therefore, it can be seen that sufficient lithium must be supplemented.

[0196] Table 2 shows the values ​​measured by ICP analysis, and as described above, the error value of ICP analysis is about ±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 supplement the loss of lithium is the content of lithium reduced relative to the ratio of lithium to other metals in the raw material active material (i.e., fresh active material) used in the active material layer (i.e., the molar ratio by ICP analysis).

[0197] Figure 8 and Fig. 9 Results of battery evaluation using active materials of Embodiment 1 and Embodiment 2 and Comparative Examples 1 to 5 are shown. Rate performance was examined by evaluating capacity according to the number of cycle repetitions at different currents. The active material recovery equipment used for evaluation is a general charge / discharge test equipment commonly used in laboratories. There is no deviation according to the measuring equipment or method. Figure 8 and Fig. 9 In the graph of , the horizontal axis represents the number of cycles, and the vertical axis represents the capacity.

[0198] The voltage was set to 3 V to 4.3 V, and the initial formation charge / discharge was performed at 0.1 C / 0.1 C. The electrolyte of the battery was formed using a carbonate-based battery having a ratio of ethylene carbonate (EC) to ethyl carbonate (EMC) of 3:7 and partially including additives.

[0199] First, refer to Figure 8 After the initial heat treatment (550°C / 30 minutes) for release, the electrode capacity of Comparative Example 2 before surface modification and Comparative Example 3 after surface modification was rapidly decreased in Comparative Example 3 after surface modification. This is because, as described above, the nickel in the NCM-based lithium composite transition metal oxide is rock-salted by moisture, and its capacity decreases.

[0200] However, when annealing (750°C / 15 hours) was performed without performing surface modification, which corresponds to Comparative Example 4, there was almost no effect of capacity improvement compared with Comparative Example 2. This is because LiF remains on the surface of the active material when surface modification is not performed. It has been shown in Table 1 above that LiF can be removed to a satisfactory extent only when cleaning is performed.

[0201] When surface modification and annealing treatment were performed after the primary heat treatment, the capacity increased as shown in Comparative Example 5. This is because, although the capacity decreased as in Comparative Example 3 after the surface modification step, the capacity of the nickel rock salt decreased by annealing after LiF was removed by surface modification and the structure was restored to hexagonal crystals.

[0202] Next, refer to Fig. 9 , Embodiment 1 is compared with Comparative Example 5, and it is confirmed that the capacity is improved. In Embodiment 1, a lithium precursor is added during the annealing process compared with Comparative Example 5. By adding the lithium precursor in this way, it can be seen that the capacity is improved by replenishing the lithium lost in the previous step. The lithium loss occurring by heat treatment and cleaning has been described with reference to Table 2.

[0203] Based on the results of ICP analysis (Table 2), the amount of lithium compound added is the loss rate compared to the lithium content in the existing positive electrode active material. As a result, it was confirmed by additional experiments that when the addition molar ratio was 0.09 to 0.1, a capacity improvement effect comparable to that of Comparative Example 1 was obtained.

[0204] As described above, according to the present 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 because simple and safe methods such as heat treatment, cleaning and drying, and annealing are used.

[0205] Fig.10 and Fig.11 1 is a scanning electron microscope (SEM) image of the active material of Embodiment 1 and Comparative Examples 1 to 3 and Comparative Example 5. These SEM images were taken with a general SEM device commonly used in a laboratory. For example, the SEM image can be taken with HITACHI's s-4200. However, there is no deviation according to the measuring device or method.

[0206] Fig.10 (a) is a SEM image of the fresh active material of Comparative Example 1, and Fig.10 (b) is Fig.10 An enlarged image of (a). Fig.10 (c) is a picture of the surface of the cathode waste made with this fresh active material. Fig.10 (d) is Fig.10 (c) is an enlarged image of the fresh active material. There is no particle breakage in the fresh active material, but the positive electrode scrap made from the electrode shows that the particles on the surface are pressed and broken by the rolling process.

[0207] Fig.10 (e) is a SEM image of Comparative Example 2, and Fig.10 (f) is Fig.10 (e) is an enlarged view of. Fig.10 (e) and Fig.10 (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 the heat treatment in air, and the binder or conductive material is almost not left on the surface of the active material.

[0208] Fig.11 (a) is a SEM image of Comparative Example 3, and Fig.11 (b) is Fig.11 The enlarged image of (a) is shown in Figure 2. Fig.11 (c) and Fig.11 In (d), it can be seen that particles are released through the process.

[0209] Fig.11 (c) is a SEM image of Comparative Example 5, and Fig.11 (d) is Fig.11 An enlarged image of (c). Fig.11 (e) is a SEM image of embodiment 1, and Fig.11 (f) is Fig.11 The enlarged image of (e) shows that the particles released in the previous step are aggregated by annealing. Fig.11 (f) and Fig.10 As shown in (a), it can be seen that the shape of the recycled active material of Embodiment 1 is the same as that of the fresh active material.

[0210] ICP analysis was performed on the positive electrode active materials recovered or prepared from the embodiments and comparative examples, and the contents of specific elements were also analyzed. The results are shown in Table 3 below.

[0211] [Table 3]

[0212] 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

[0213] As shown in Comparative Example 1, the fresh active material utilized in this experiment additionally includes B and W. Comparative Example 2 shows that the contents of B and W are reduced by heat treatment, and from the remaining results, it can be seen that B is almost removed in the subsequent process. In the case of W, as shown in Comparative Example 3, it can be seen that a large amount of W is removed by cleaning in the surface modification process.

[0214] Therefore, since specific elements may be lost during the process depending on the type of active material initially utilized, in particular, in the surface modification process by cleaning, specific elements may be completely removed or a small amount of the element may remain, there may be a situation where it is difficult to fully restore the characteristics by only performing the annealing step in Implementation 1. In this case, it is preferred to perform the additional surface coating step proposed in the present disclosure. In the case of the current experimental example, the surface coating step is to coat 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 for supplementing specific deficient elements and at the same time rebuilding the surface protective layer in the fresh active material. In the case of the fresh active material utilized in this experiment, the surface protective layer is made of BW, and the meaning of lithium loss during the process is interpreted as the ratio of (lithium in the active material itself + lithium forming the surface protective layer) to other metals, rather than the 1:1 ratio of lithium in the active material itself to other metals. Therefore, the molar ratio of 0.09 lost in the above experiment (as in Comparative Example 3) can be explained as the sum of the lithium in the positive electrode active material and the lithium forming the surface protection layer, and in this embodiment, a lithium precursor is added in an amount that can replenish as much lithium as possible.

[0215] The surface coating step requires a heat treatment process to be performed after 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 the surface coating.

[0216] When the surface coating layer 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, and other components can also be coated with metal components, carbon components and organic metal components at a temperature within 100°C to 1200°C.

[0217] As described above, according to the present disclosure, cathode waste can be reused using a simple, environmentally friendly, and economical method, and even if a lithium secondary battery is manufactured by reusing the NCM-based lithium composite transition metal oxide cathode active material prepared as described above, there is no problem with the performance of the battery.

[0218] <Experimental Example 3>

[0219] Various positive electrode active materials were prepared using the methods in the above embodiments and comparative examples, and their electrochemical properties were evaluated.

[0220] Implementation 3:

[0221] Embodiment 3 is the same as Embodiment 1, except that the annealing time is 5 hours, which is shorter than 15 hours in Embodiment 1.

[0222] Implementation 4:

[0223] Implementation method 4 is based on reference Figure 5 The recycled active material prepared by the method described above. After performing step S30 as in embodiment 1, steps S40', S45 and S50' were performed. After cleaning in step S40', drying was not performed, (washing the electrode) was mixed with 0.1 mol of LiOH powder in an aqueous solution (mixed at a ratio of 1:50 between powder and aqueous solution), and granulated with a spray drying device to perform step S45. As in embodiment 3, step S50' was performed at 750°C for 5 hours.

[0224] When executing step S45, the mixed aqueous solution of the washed electrode and 0.1 mol of LiOH is stirred to prevent electrode precipitation, and the atmospheric temperature (input temperature) when the spray drying equipment uses a nozzle to spray toward the heating container is adjusted to 180°C, and the atmospheric temperature (output temperature) when coming out of the heating container to the collecting container is adjusted to maintain 100°C or above.

[0225] Fig.12 : is a particle size distribution chart of the active materials of Embodiment 3 and Embodiment 4 and Comparative Examples 1 and Comparative Examples 2. The particle size distribution can be obtained by a general particle size analyzer commonly used in laboratories. For example, the particle size distribution can be measured with a Horiba LA 950V2 particle size analyzer. However, there is no deviation according to the measuring instrument or method. Fig.12 In FIG. 1 , the horizontal axis represents the particle size (μm), and the vertical axis represents volume %.

[0226] In the case of Comparative Example 2, the active material of Comparative Example 1 was split into submicron-sized (less than 1 micron) particles and micronized by pressure in the electrode process. As such, the particle size distribution of Comparative Example 2 is greatly different from that of Comparative Example 1.

[0227] Since annealing is performed until the annealing process, during which the previously added lithium precursor melts and induces the agglomeration of particles, it can be seen that many micronized particles shown in Comparative Example 2 disappear. In particular, in the case of Embodiment 4 according to the present disclosure, small particles decrease and large particles slightly increase compared to Embodiment 3, but there is no significant difference in particle size distribution. Compared to Embodiment 3, Embodiment 4 can be regarded as more similar to the particle size distribution of Comparative Example 1 because there are fewer small-sized particles.

[0228] As such, it was confirmed that when using the spray drying proposed in another embodiment of the present disclosure (Embodiment 4), the particle size distribution was more similar to that of the fresh active material (Comparative Example 1) compared to the case of mixing the lithium precursor in a solid phase (Embodiment 3), and in particular had the advantage of being able to perform a process continuous with the cleaning step before spray drying.

[0229] Fig.13 Results of battery evaluation using active materials of Embodiment 3 and Embodiment 4 and Comparative Example 1 are shown, and the result values ​​are summarized in Table 4.

[0230] [Table 4]

[0231]

[0232] refer to Fig.13 As shown in Table 4, both electrodes using Embodiment 3 and Embodiment 4 show similar results to the electrode using Comparative Example 1. In Comparative Example 1, the initial formation capacity is high, and in Embodiment 3 and Embodiment 4, the C rate capacity is slightly high, but it can be determined that they are similar to each other. As described above, according to the embodiments of the present disclosure, a recycled active material similar to the fresh active material (Comparative Example 1) can be obtained.

[0233] <Experimental Example 4>

[0234] Each positive electrode active material was further prepared using the methods in the following embodiments and comparative examples, and its electrochemical performance was evaluated.

[0235] Implementation 5:

[0236] According to another active material recycling method of the present disclosure as described above, the recycled active material is collected. The LCO positive electrode waste to be discarded after punching the positive electrode plate is prepared, and the heat treatment of step S30 is performed at 600°C for 30 minutes at a temperature rise rate of 5°C / min in air. Step S50 is performed without the cleaning of step S40 or S40'. A lithium precursor (Li2CO3) with an excess of 2 mol% of lithium relative to the lithium amount of the recycled LCO is placed and annealed at 750°C in air for 15 hours.

[0237] Comparative Example 6: New LCO was used instead of recycled active material.

[0238] Comparative Example 7: In the active material recycling method of the present disclosure as described above, only the heat treatment of step S30 is performed to remove the binder, the conductive material and the Al current collector, and collect the LCO active material. Step S30 is performed under the same conditions as in Embodiment 5.

[0239] 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.

[0240] 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.

[0241] Fig.14 Results of battery evaluation using active materials of Embodiment 5 and Comparative Examples 6 to 9 are shown.

[0242] refer to Fig.14 , in Comparative Example 9 in which the heat treatment time is the longest (5 hours), the lowest rate performance can be confirmed. This is because, when a high-temperature heat treatment process such as step S30 is performed for a long time, the binder and the conductive material are removed as CO2 and H2O, react with lithium on the surface of the positive electrode active material to form Li2CO3, and react with F present in the binder to form LiF. In addition, due to the thermal decomposition of Co3O4 generated on the surface of LCO, it is determined that it exhibits low battery performance.

[0243] 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 cycle 3, but the rate performance deteriorates as the number of cycles increases.

[0244] In Comparative Example 7, the heat treatment time was 30 minutes, which was shorter than Comparative Examples 8 and 9. In the case of Comparative Example 7, the rate performance was better than Comparative Examples 8 and 9. Therefore, it can be confirmed that the heat treatment time is preferably within 30 minutes in terms of rate performance because the generation of reaction products such as LiF is minimized.

[0245] In Embodiment 5, compared with Comparative Example 7, the annealing is performed by adding a lithium precursor, during which Li2CO3 is added to supplement the lithium lost in the process of recovering the active material and restore the crystallinity. According to Embodiment 5, not only can the insufficient amount of lithium occurring during the process be supplemented, but also the deformed structure and Co3O4 that may appear on the surface of the active material during the regeneration process can be restored to the LCO crystal structure again, thus confirming that Embodiment 5 shows improved results compared with the initial characteristics of the fresh LCO active material of Comparative Example 6. As described above, according to the present disclosure, the active material can be recovered from the positive electrode waste for direct reuse.

[0246] Fig.15The XRD patterns of the active materials of Embodiment 5 and Comparative Examples 6, 7, and 9 are shown. In the XRD pattern, the horizontal axis represents 2θ (Theta) (degrees), and the vertical axis represents intensity. The XRD pattern is obtained using a general X-ray diffraction device commonly used in laboratories. For example, the XRD pattern can be analyzed using an X-ray diffractometer XG-2100 manufactured by Rigaku. However, there is no deviation according to the device or method.

[0247] Fig.15 (a) is the XRD pattern of Comparative Example 6, ie, the XRD pattern of fresh LCO. Fig.15 (b) is an XRD pattern of the active material of Comparative Example 7, and Fig.15 (c) is the XRD pattern of the active material of Comparative Example 9. Fig.15 (b) and (c) of 15 and Fig.15 After comparison with (a), Co3O4 phase can be detected. That is, it can be confirmed that Co3O4 is generated on the surface of LCO during the heat treatment process in step S30.

[0248] Fig.15 (d) is an XRD pattern of the active material of Embodiment 5. Fig.15 (b) and (c) of 15 and Fig.15 After comparing with (d), it can be seen that the Co3O4 phase disappears, and the crystal structure is restored to LCO through annealing in step S50. Fig.15 The crystal structure of (d) Fig.15 The crystal structure of (a) is similar. Therefore, it can be confirmed that the embodiment of the present disclosure recovers to the level of the fresh active material of Comparative Example 6. As described above, according to the present disclosure, Co3O4 generated in the heat treatment process can be removed during the annealing process, and active materials can be recovered from positive electrode waste for direct reuse.

[0249] Fig.16 1 and 2 are SEM images of the active materials of Embodiment 5 and Comparative Example 6.

[0250] Fig.16 (a) is a SEM image of fresh LCO of Comparative Example 6, and Fig.16(b) is an SEM picture of the recycled active material of Example 5. It can be confirmed that the recycled LCO of Embodiment 5 also exhibits the same shape as the fresh LCO. In addition, since only LCO was observed, it can be confirmed that the binder and the conductive material were removed during the high-temperature heat treatment process. Therefore, it can be seen that the active material is separated from the current collector only by heat treatment in the air, and almost no binder or conductive material remains on the surface of the active material. As described above, according to the present disclosure, the active material can be separated from the current collector without using complicated methods or harmful substances, so the active material can be recycled in an eco-friendly manner. The active material can be reused without using acid, so there is no need for a neutralization process or a wastewater treatment process, thereby alleviating environmental problems and reducing process costs.

[0251] Fig.17 X-ray photoelectron spectroscopy (XPS) graphs of the active materials of Comparative Examples 6, 7 and 9 are shown. In the XPS graph, the horizontal axis represents the binding energy (unit: eV). The XPS graph can be obtained using a general XPS measurement device commonly used in a laboratory. For example, the K-Alpha of Thermo Fisher Scientific can be used to analyze the XPS graph. As described above, during the heat treatment process, F present in the binder may react with Li in the active material to form LiF.

[0252] exist Fig.17 In the comparative example 6, a peak of LiF appeared near 684 eV, and according to the sample, the higher the intensity, the more LiF existed on the surface of the positive electrode active material. Since the XPS graph of Comparative Example 6 was measured with fresh LCO, the presence of LiF was not measured. In Comparative Example 9, due to the heat treatment time of up to 5 hours, a large amount of LiF was produced on the surface of the active material. Therefore, the LiF peak intensity of XPS was measured to be significantly higher than that of Comparative Example 6. However, in the case of Comparative Example 7 in which the heat treatment time was reduced from 5 hours to 30 minutes, it can be seen that the F formed due to the decomposition of the binder is relatively reduced, and the amount of LiF present on the surface of the active material is also relatively reduced. LiF should be as small as possible because it may cause degradation of electrode performance. It can be seen from the results of Comparative Examples 9 and 7 that reducing the heat treatment time can reduce the amount of LiF on the surface of the regenerated active material and can effectively improve the performance of the regenerated active material. Implementation Example 5 will have a similar level of LiF as Comparative Example 7, but as mentioned above Fig.14 As shown in the results of , LiF at a level higher than that of fresh active materials can be secured after annealing, so it can be seen that the amount of LiF remaining in Embodiment 5 has little effect on battery performance. Therefore, if the heat treatment time is optimized like another embodiment of the present disclosure, a separate process such as washing for removing LiF is not required.

[0253] Fig.18 1 is a graph showing particle size distribution of active materials of Embodiment 5 and Comparative Examples 6, 7 and 9.

[0254] All active materials recovered in Embodiment 5 and Comparative Examples 6, 7, and 9 have similar particle size distributions compared to the fresh LCO of Comparative Example 6. When the volume % of particles having the same particle size differs only within the range of ±2%, the particle size distribution is defined as being similar. As described above, according to the present disclosure, since there is no difference in the particle size distribution of the active material, the initial characteristics are almost maintained, and it is expected that the performance of the battery using the reused active material will be similar to that of the battery using the fresh active material.

[0255] <Experimental Example 5>

[0256] Each positive electrode active material was prepared by the following methods of the embodiment and comparative example, and its electrochemical performance was evaluated.

[0257] Implementation 6: According to another active material recycling method of the present disclosure as described above, active materials are collected for recycling. Positive waste to be discarded after punching positive plates is prepared and heat treatment is performed at 600°C for 30 minutes in step S30. Cleaning is performed using LiOH for 10 minutes in step S40. Annealing is performed at 750°C for 15 hours without adding additional lithium precursor as in step S50'.

[0258] Comparative Example 10: In the active material recycling method of the present disclosure as described above, except for Comparative Example 7, the LCO active material is recovered by performing the surface modification of step S40. That is, in the active material recycling method of the present disclosure, the crystal structure recovery of step S50 or S50' is not performed while performing the surface modification. Step S40 is performed under the same conditions as in Embodiment 6.

[0259] In order to understand the amount of LiF remaining in the active materials recovered in Embodiment 6 and Comparative Example 7, F was detected and analyzed by means of ICP. The results are shown in Table 5 below.

[0260] [Table 5]

[0261] Comparative Example 7 Implementation 6 F content (mg / kg) 1900 ND

[0262] Referring to Table 5 above, it can be seen that the content of F in the positive electrode active material recovered 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 by cleaning and is removed to the extent that LiF may not be detected by ICP. Therefore, it can be seen that the removal effect of LiF is excellent through step S40.

[0263] 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.

[0264] [Table 6]

[0265] Al content (wt%) Comparative Example 6 0.33 Comparative Example 7 0.33 Comparative Example 10 0.33 Implementation 6 0.33

[0266] As shown in Comparative Example 6, the fresh active material used in this experiment further includes Al. Comparative Example 7 shows that the Al content does not change even through heat treatment, and from the Al content, it can be seen that the Al content remains unchanged even in Comparative Example 10 and Embodiment 6 that further include subsequent processes. As described above, according to the present disclosure, it can be seen that LiF or metal fluoride can be removed without losing other elements such as Al, and the elution of transition metals and the like can be prevented.

[0267] Fig.19 Results of battery evaluation using active materials of Embodiment 6 and Comparative Examples 6, 7, and 10 are shown.

[0268] refer to Fig.19 , the lowest rate performance can be confirmed in Comparative Example 7, in which the surface modification and crystal structure recovery according to the present disclosure are not performed despite the presence of the recycled active material. This is because, during the high-temperature heat treatment process such as step S30, not only the binder and the conductive material are removed as CO2 and H2O and react with the lithium on the surface of the positive active material to form Li2CO3 and LiOH, but also react with F present in the binder to form LiF or metal fluoride on the surface of the recycled active material. In addition, due to the thermal decomposition of Co3O4 generated on the surface of LCO, it is determined that it exhibits low battery characteristics.

[0269] In Comparative Example 10, surface modification was performed as compared with Comparative Example 7. It was evaluated that Comparative Example 10 was able to obtain better results than Comparative Example 7 because the reactants generated on the surface were removed by cleaning.

[0270] In Embodiment 6, annealing was performed until compared with Comparative Example 10. The deformed structure and Co3O4 that may appear on the surface of the active material during the regeneration process are reduced to the LCO crystal structure again, thus confirming that Embodiment 6 shows improved results compared with the initial characteristics of the fresh LCO active material of Comparative Example 6. As described above, according to the present disclosure, active materials can be recovered from positive electrode waste for direct reuse.

[0271] Fig. 20XPS graphs of the active materials of Embodiment 6 and Comparative Examples 6 to 8 are shown. Since the XPS graph of Comparative Example 6 was measured with 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 can be confirmed. In Comparative Example 8, since the heat treatment time was increased to 5 hours, the generation of F increased compared to Comparative Example 7, and since the amount of LiF generated on the surface of the active material increased, the LiF peak intensity of XPS was measured to be higher than the LiF peak intensity of Comparative Example 7. Since the amount of LiF present on the surface of the active material can cause the electrode characteristics to deteriorate, it is necessary to remove LiF. In Embodiment 6, LiF was removed by cleaning compared to Comparative Example 7, and it can be confirmed that no peak of LiF appears even in the XPS results.

[0272] Through the above-mentioned XPS analysis, it can be confirmed that the results of Embodiment 6 are similar to those of Comparative Example 6. Therefore, it can be confirmed that Embodiment 6 of the present disclosure recovers to the level of the fresh active material of Comparative Example 6. As described above, according to the present disclosure, when the cleaning time is shortened, the active material can be recovered from the cathode waste to be directly reused without adding a lithium precursor.

[0273] The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present disclosure, are given by way of illustration only, as various changes and modifications within the scope of the present disclosure will be apparent to those skilled in the art based on this detailed description.

Claims

1. An active material recovery device, the active material recovery device is a rotary firing device including a spiral rod therein, the active material recovery device comprising: a heat treatment tank and a screening wall, the heat treatment tank and the screening wall being arranged on a line along the axis of the rod, wherein the heat treatment tank constitutes a heating zone and the screening wall constitutes a cooling zone; and Exhaust gas injection and degassing systems, wherein the heat treatment tank removes a binder and a conductive material in the active material layer and separates the current collector from the active material layer by heat-treating the electrode waste in air while rotating the electrode waste including the active material layer on the current collector around the axis of the rod, The active material in the active material layer passes through the screening wall and is recovered as the active material in powder form, and the current collector that does not pass through the screening wall is recovered separately, and The rod pushes the electrode waste while stirring the electrode waste.

2. The active material recovery device according to claim 1, wherein: The heat treatment tank also rotates about the axis of the rod.

3. The active material recovery device according to claim 1, wherein: The angle of the entire active material recovery apparatus is adjusted so that the axis of the rod is inclined relative to the ground.

4. The active material recovery device according to claim 1, wherein: The active material recovery device has a vibration function.

5. The active material recovery device according to claim 1, wherein: The input of new electrode waste and the recovery of the active material are carried out continuously.

6. The active material recovery device according to claim 1, wherein: The heat treatment tank has a tubular shape with both ends open so that the electrode scrap is put into the heat treatment tank and the separated current collector and active material are transferred to the screening wall, and the heat treatment tank is a tube as an open system for air to enter and leave.

7. The active material recovery device according to claim 6, wherein: The screening wall has a tubular shape with both ends open so that the separated current collector and active material can be placed in the screening wall and the current collector can be discharged.

8. The active material recovery device according to claim 1, wherein: The heat treatment tank is an open system, in which 10 ml / min to 100 liters / min of air is added or injected into every 100 grams of the electrode waste.

9. The active material recovery device according to claim 1, wherein: Air inlets are formed at a plurality of locations in the heat treatment tank.

10. A method for recycling positive electrode active materials, the method comprising the following steps: Preparation of an active material recovery device according to any one of claims 1 to 9; placing a cathode waste material including a lithium composite transition metal oxide cathode active material layer on a current collector into a heat treatment tank to perform heat treatment; 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 waste in air while rotating the positive electrode waste about an axis of a rod in the heat treatment tank; recovering the active material in powder form that has passed through the screening wall; as well as The active material is annealed at 400° C. to 1000° C. in air to obtain a reusable active material.

11. The method for recycling positive electrode active materials according to claim 10, wherein: The heat treatment is performed at 300°C to 650°C. 12 . The method for recycling a positive electrode active material according to claim 10 , further comprising, before the annealing step, cleaning the recovered active material with a lithium compound solution showing alkalinity in an aqueous solution state.

13. The method for recycling positive electrode active materials according to claim 12, wherein: Prior to the annealing step, a lithium precursor is added to the cleaned active material.

14. The method for recycling positive electrode active materials according to claim 12, further comprising, after the cleaning step, obtaining an active material to which a lithium precursor is added and whose particles are adjusted by mixing the cleaned active material with a lithium precursor solution and spray-drying the active material. 15 . The method for recycling a cathode active material according to claim 10 , further comprising the step of performing surface coating on the annealed active material.

16. The method for recycling positive electrode active materials according to claim 10, wherein: The heat treatment was performed at 550° C. for 30 minutes at a temperature rise rate of 5° C. / min.

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