Specification
Title of Invention: Active material reuse method using cathode scrap
technical field
[One]
The present invention relates to a method of recycling resources when manufacturing a lithium secondary battery. The present invention particularly relates to a method of recovering and reusing positive electrode scraps generated in a lithium secondary battery manufacturing process or a positive electrode active material of a lithium secondary battery that is discarded after use. This application is a priority claim application for Korean Patent Application No. 10-2020-0065045 filed on May 29, 2020, and all contents disclosed in the specification and drawings of the application are incorporated herein by reference.
background
[2]
Lithium secondary batteries that can be repeatedly charged and discharged are in the spotlight as an alternative means of fossil energy. Lithium secondary batteries have been mainly used in traditional handheld devices such as cell phones, video cameras, and power tools. However, in recent years, electric vehicles (EVs, HEVs, PHEVs), large-capacity power storage devices (ESSs), uninterruptible power supply systems (UPS), etc., the application fields are gradually increasing.
[3]
A lithium secondary battery includes an electrode assembly in which unit cells having a structure in which a positive electrode plate and a negative electrode plate coated with an active material are coated on a current collector with a separator interposed therebetween, and an exterior material for sealing and housing the electrode assembly together with an electrolyte, that is, a battery case to provide The cathode active material of the lithium secondary battery mainly uses a lithium-based oxide, and the anode active material uses a carbon material. The lithium-based oxide contains a metal such as cobalt, nickel, or manganese. In particular, cobalt, nickel, and manganese are very expensive valuable metals. Among them, cobalt is a strategic metal, and each country in the world has a special interest in supply and demand. is known If there is an imbalance in the supply and demand of raw materials for strategic metals, raw material prices are highly likely to rise.
[4]
In the past, research on recovering and recycling these valuable metals from lithium secondary batteries (waste batteries) that are discarded after their lifespan has been completed has been mainly conducted. In addition to the waste battery, it is more preferable if resources can be recovered from the waste discarded after the positive electrode plate is punched or from the positive electrode having a defect in the process.
[5]
Currently, when manufacturing a lithium secondary battery, as shown in FIG. 1 , a cathode active material layer 20 is coated with a cathode active material, a conductive material, a binder, a solvent, etc. ) by forming the positive electrode sheet 30, and then punching out the positive electrode plate 40 to a predetermined size. The part remaining after punching is discarded as anode scrap (scrap, 50). If it is possible to recover the positive electrode active material from the positive electrode scrap 50 and reuse it, it would be very desirable from an industrial-economic point of view and an environmental point of view.
[6]
Conventionally, the method of recovering the positive active material is mostly used as a raw material for the synthesis of the positive active material by dissolving the positive electrode in hydrochloric acid, sulfuric acid, nitric acid, etc., extracting active material elements such as cobalt, nickel, and manganese. However, the method of extracting active material elements using an acid has disadvantages in that the process for recovering pure raw materials is not environmentally friendly and requires a neutralization process and a wastewater treatment process, which increases the process cost. In addition, lithium, which is one of the main elements of the cathode active material, cannot be recovered. In order to solve these disadvantages, a method that can be directly reused without dissolving the cathode active material and extracting the active material in elemental form is required.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[7]
The problem to be solved by the present invention is to provide a method for recovering and reusing an active material from a cathode scrap.
means of solving the problem
[8]
The positive electrode active material reuse method of the present invention in order to solve the above problems, (a) a positive electrode scrap including a lithium composite transition metal oxide positive electrode active material layer on a current collector is heat-treated in air at 300 ~ 650 ℃ within 1 hour, the active material separating the current collector from the active material layer and recovering the active material in the active material layer by thermally decomposing the binder and the conductive material in the layer; and (b) adding a lithium precursor to the recovered active material and annealing to obtain a reusable active material.
[9]
The heat treatment may be performed within 30 minutes.
[10]
The lithium precursor may be any one or more of LiOH, Li 2 CO 3 , LiNO 3 and Li 2 O.
[11]
The lithium precursor may be added in an amount capable of adding as much as the ratio of lithium lost compared to the ratio of lithium and other metals in the raw material active material used for the active material layer.
[12]
For example, the lithium precursor may be added in an amount in which lithium is added in a molar ratio of 0.001 to 0.4.
[13]
The annealing may be performed at 400 to 1000° C. in air.
[14]
The temperature of the annealing step may be a temperature exceeding the melting point of the lithium precursor.
[15]
The active material in the active material layer may be recovered in the form of powder, and carbon components generated by carbonization of the binder or the conductive material may not remain on the surface.
[16]
The reusable active material may have a particle size distribution similar to that of the active material in the active material layer.
[17]
Another positive electrode active material reuse method according to the present invention is (a) a positive electrode scrap remaining after punching a positive electrode plate from a positive electrode comprising a lithium composite transition metal oxide positive electrode active material layer on a current collector in air at 300 to 650 ° C. for 1 hour separating the current collector from the active material layer and recovering the active material in the active material layer by thermally decomposing the binder and the conductive material in the active material layer by heat treatment within; and (b) adding at least one of LiOH, Li 2 CO 3 , LiNO 3 and Li 2 O to the recovered active material and annealing in air at 400 to 1000° C.
Effects of the Invention
[18]
According to the present invention, the waste positive electrode active material such as positive electrode scrap generated during the manufacturing process of a lithium secondary battery can be reused without using an acid, so it is eco-friendly. Since the method according to the present invention does not require a neutralization process or a wastewater treatment process, it is possible to alleviate environmental issues and reduce process costs.
[19]
According to the present invention, it is possible to recover the positive electrode active material without the unrecoverable metal element. Since the current collector is not dissolved, the current collector can also be recovered. It is economical because it is a method that can directly reuse the active material recovered in powder form, rather than extracting the active material element and using it again as a raw material for synthesizing the cathode active material.
[20]
According to the present invention, it is safe because it does not use toxic and explosive solvents such as NMP, DMC, acetone, and methanol, and because simple processes such as heat treatment and annealing are used, process management is easy and suitable for mass production.
[21]
According to the present invention, generation of undesirable reaction products such as LiF can be minimized through heat treatment for a very short time, so that additional treatment such as washing with water for removing such reaction products is unnecessary.
Brief description of the drawing
[22]
The following drawings attached to this specification illustrate embodiments of the present invention, and together with the detailed description to be described later serve to further understand the technical spirit of the present invention, the present invention is limited only to the matters described in those drawings should not be interpreted as
[23]
1 is a view showing positive electrode scrap discarded after the positive electrode plate is punched from the positive electrode sheet.
[24]
2 is a flowchart of an active material reuse method according to the present invention.
[25]
3 is a result of cell evaluation using the active materials of Examples and Comparative Examples.
[26]
4 is an X-ray diffraction (XRD) pattern of the active materials of Examples and Comparative Examples.
[27]
5 is a scanning electron microscope (SEM) photograph of the active materials of Examples and Comparative Examples.
[28]
6 is an X-Ray Photoelectron Spectroscopy (XPS) pattern of the active material of Comparative Examples.
[29]
7 is a TGA (Thermogravimetric Analysis) analysis result of Comparative Example 2.
[30]
8 is a particle size distribution graph of the active materials of Examples and Comparative Examples.
Modes for carrying out the invention
[31]
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his or her application. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention. Accordingly, the embodiments described in the present specification and the configurations shown in the drawings are only one embodiment of the present invention and do not represent all the technical spirit of the present invention, so various equivalents that can be substituted for them at the time of the present invention It should be understood that there may be variations and variations.
[32]
DETAILED DESCRIPTION In the following description, reference is made to the accompanying drawings, which form a part hereof. The implementations, drawings, and claims described in the detailed description are not intended 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 disclosed herein. It is immediately understood that aspects of the invention, as generally described herein and illustrated in the drawings, can be arranged, substituted, combined, separated, and designed in various other configurations, all of which are expressly contemplated herein. will be able
[33]
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 invention belongs.
[34]
The invention is not limited with respect to the specific embodiments described herein. As will be apparent to those skilled in the art, many changes and modifications can be made without departing from the spirit and scope of the present invention. In addition to those enumerated herein, functionally equivalent methods within the scope of this disclosure will be apparent to those skilled in the art from the foregoing description. Such changes and modifications are intended to fall within the scope of the appended claims. The invention shall be limited only by the claims, along with the full scope of equivalents to which such claims are entitled. It should be understood that the present invention is not limited to particular methods, which may, of course, vary. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.
[35]
In the case of the conventional active material recycling process, if the main purpose was to extract valuable metals (nickel, cobalt, manganese, etc.) as elements in the lithium secondary battery active material whose performance has deteriorated after use and resynthesize the active material, the present invention is a lithium secondary battery There is a difference in that the active material is also recovered from the cathode scrap generated during the manufacturing process.
[36]
In addition, in the case of the known active material recycling process, there is a chemical method such as extracting a valuable metal through acid/base dissolution or melting using reduction/additive, and manufacturing it as a metal (direct reduction method) or a resynthesized active material. In addition, the complexity and economic cost of the process are additionally incurred. However, the present invention relates to a method of directly reusing a cathode active material without dissolving it.
[37]
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, it is possible to remove the binder through high-temperature heat treatment, to melt the binder using a solvent, to completely melt the current collector, and to select the active material through dry grinding and sieving. do.
[38]
The stability of the solvent is important in dissolving the binder using the solvent. Although NMP is the most efficient solvent, it has the disadvantages of toxicity and high price. In addition, there is a disadvantage that a solvent recovery process such as reprocessing the waste solvent is required. Melting the current collector will be cheaper than using a solvent. However, there is a risk of explosion because it is difficult to remove foreign substances from the surface of the reusable active material and hydrogen gas is generated during the current collector removal process. It is difficult to completely separate the current collector and the active material by dry grinding and sieving. Since the particle size distribution of the active material is changed during the pulverization process and it is difficult to remove the binder, there is a disadvantage in that the characteristics of the reused battery deteriorate.
[39]
In the present invention, the active material and the current collector are separated by high-temperature heat treatment. In particular, since heat treatment is carried out in air, it is advantageous for mass production and commercialization because it is a relatively simple process that does not require a special device configuration and only needs to be heated. However, foreign substances should not remain on the surface of the reusable active material. The present invention proposes a process condition that minimizes the generation of foreign substances on the surface of the reusable active material.
[40]
Hereinafter, an active material reuse method according to an embodiment of the present invention will be described with reference to FIG. 2 . 2 is a flowchart of an active material reuse method according to the present invention.
[41]
Referring to FIG. 2 , first, discarded anode scrap is prepared (step s10).
[42]
As described above with reference to FIG. 1, the positive electrode scrap may be a portion left after manufacturing a positive electrode sheet including a lithium composite transition metal oxide positive electrode active material layer on a current collector and punching out. In addition, it is possible to prepare anode scrap by collecting anodes having defects during the process. In addition, positive electrode scrap may be prepared by separating the positive electrode from the discarded lithium secondary battery after use.
[43]
For example, a lithium cobalt oxide active material such as LiCoO 2 (LCO) or an NCM-based active material including nickel, cobalt and manganese, carbon-based carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder ) by adding N-methyl pyrrolidone (NMP) to the mixed slurry, which is coated on a sheet-type current collector made of aluminum foil, and then dried in a vacuum oven at about 120 ° C. It may be a case of preparing the anode scrap remaining after punching out.
[44]
As described above, the positive electrode scrap has an active material layer on a current collector of a metal foil such as 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 may be separated from the current collector.
[45]
Next, the anode scrap is crushed to an appropriate size (step s20). Shredding refers to the cutting or shredding of anode scrap into pieces of suitable, easy-to-handle size. After crushing, the anode scrap is cut into small pieces, for example 1 cm x 1 cm. For crushing, various dry crushing equipment such as hand-mill, pin-mill, disk-mill, cutting-mill and hammer-mill may be used, or a high-speed cutter may be used.
[46]
Crushing can be carried out in consideration of the characteristics required in the equipment used in the handling of anode scrap and subsequent processes. For example, in the case of using equipment that requires continuous processing in loading and unloading anode scrap, the fluidity of the anode scrap must be good, so that too large anode scrap must be crushed.
[47]
Now, the anode scrap is heat-treated in air (step s30).
[48]
In the present invention, the heat treatment is performed to thermally decompose the binder in the active material layer. Heat treatment can be performed at 300 ~ 650 °C, so it can be called high temperature heat treatment. At a temperature of less than 300 ℃, it is difficult to remove the binder, so that the current collector cannot be separated. At a temperature of 650 ℃ or higher, the current collector melts (Al melting point: 660 ℃), and the current collector cannot be separated.
[49]
The heat treatment time is maintained so that the binder can be sufficiently thermally decomposed. Heat treatment within 1 hour. Preferably within 30 minutes. The longer the heat treatment time, the longer the time for thermal decomposition of the binder to occur. However, if it exceeds a certain amount of time, there is no difference in the thermal decomposition effect, and rather, a lot of reaction products harmful to the battery performance are generated, which is not good.
[50]
The heat treatment equipment may be various types of furnaces. For example, it may be a box-type furnace or a rotary kiln capable of continuous processing in consideration of productivity.
[51]
After heat treatment, it may be slowly cooled or rapidly cooled in the atmosphere.
[52]
For example, the heat treatment may be performed at a temperature increase rate of 5°C/min at 550°C or 600°C for 30 minutes. The temperature increase rate is, for example, a degree that can be implemented without excessive force in a box-type furnace and can be heated without generating a thermal shock or the like to the anode scrap. 550°C and 600°C are to allow the thermal decomposition of the binder to occur well while considering the melting point of the Al current collector. At this temperature, heat treatment for less than 10 minutes is insufficient for thermal decomposition, so heat treatment should be carried out for more than 10 minutes, and heat treatment should be performed for 30 minutes if possible.
[53]
As the binder and conductive material in the active material layer are thermally decomposed through heat treatment in air, they become CO 2 and H 2 O and are removed. Since the binder is removed, the active material is separated from the current collector, and the active material to be recovered may be selected in powder form. Accordingly, only in step s30, the current collector may be separated from the active material layer and the active material in the active material layer may be recovered.
[54]
It is important that the heat treatment of step s30 be performed in air. If the heat treatment is performed in a reducing gas or inert gas atmosphere, the binder and the conductive material are not thermally decomposed and only carbonized. When carbonization is done, the carbon component remains on the surface of the active material, thereby degrading the performance of the reusable active material. When heat treatment is performed in air, the carbon material in the binder or the conductive material reacts with oxygen and is burned and removed as CO and CO 2 gas, so that almost all of the binder and the conductive material are removed without remaining.
[55]
Therefore, according to the present invention, the active material is recovered in the form of a powder, and the carbon component generated by carbonization of the binder or the conductive material may not remain on the surface.
[56]
However, if the heat treatment time is long, a large amount of undesirable reaction products such as LiF may be induced. Therefore, the heat treatment time is limited to within 1 hour, preferably within 30 minutes, to minimize the generation of unwanted foreign substances that may adversely affect the battery performance.
[57]
Next, a lithium precursor is added to the recovered active material and annealed (step s40). Through step s40, a reusable active material may be obtained.
[58]
Loss of lithium in the active material may occur during the previous step s30. In step s40, such lithium loss is compensated.
[59]
In addition, in step s40, the crystal structure of the active material is restored through annealing to restore or improve the characteristics of the reused active material to the level of a fresh active material that has never been used.
[60]
During the previous step s30, a deformed structure may appear on the surface of the active material. In addition, in the case of the LCO active material, Co 3 O 4 may be generated by thermal decomposition on the surface. If the battery is manufactured while Co 3 O 4 is present as it is, battery characteristics may deteriorate. In the present invention, the initial properties can be restored or improved to a level similar to that of the fresh active material by restoring the crystal structure and removing Co 3 O 4 through step s40.
[61]
The lithium precursor of step s40 may be any one or more of LiOH, Li 2 CO 3 , LiNO 3 and Li 2 O.
[62]
The lithium precursor is added in an amount capable of adding as much as the ratio of lithium lost compared to the ratio of lithium and other metals in the raw material active material (ie, fresh active material) used in the active material layer. For example, when the ratio of lithium to other metals in the fresh active material is 1, a lithium precursor in an amount capable of adding lithium in a molar ratio of 0.001 to 0.4 may be added. Preferably, lithium in a molar ratio of 0.01 to 0.2 is added. The addition of an excess amount of lithium precursor other than the amount of lost lithium leaves unreacted lithium precursors in the reused active material, which serves to increase resistance in the active material reuse process, so that it is necessary to administer an appropriate amount of the lithium precursor.
[63]
Annealing may be performed at 400 to 1000° C. in air. The annealing temperature may be 600-900°C. This temperature should be changed within a limited range depending on the type of the lithium precursor. It is preferable to set the annealing time to 1 hour or more. Preferably, it is about 5 hours. If the annealing time is long, the crystal structure can be sufficiently recovered, but even if it is used for a long time, the performance is not greatly affected. Annealing time is made into 15 hours or less, for example. The annealing equipment may use the same or similar equipment as in the heat treatment step s30.
[64]
For example, when Li 2 CO 3 is used as a lithium precursor, the annealing temperature is preferably 700 to 900° C., more preferably 710 to 780° C. This is because the melting point of Li 2 CO 3 is 723°C. Most preferably, it is carried out at 750°C. In the case of using LiOH as a lithium precursor, the annealing temperature is preferably 400 to 600° C., more preferably 450 to 480° C. This is because the melting point of LiOH is 462°C.
[65]
The annealing temperature is preferably a temperature exceeding the melting point of the lithium precursor. However, at a temperature exceeding 1000°C, thermal decomposition of the positive electrode active material occurs and the performance of the active material is deteriorated, so that the temperature should not exceed 1000°C. Most preferably, the anode active material is annealed at a temperature below the temperature before the start of thermal decomposition, that is, at a temperature at which O 2 in the active material is released by high-temperature treatment and a rapid mass decrease on the TGA starts due to this.
[66]
In both LCO and NCM, when the temperature is too high, O 2 is released, which causes structural collapse and a significant decrease in the mass of the cathode active material. Since TGA measurement can detect the temperature at which the mass begins to rapidly decrease as thermal decomposition begins, it is preferable to allow annealing at or below this temperature.
[67]
As described above, according to the present invention, a reusable active material can be obtained with only two steps: heat treatment in air (step s30) and annealing after addition of the lithium precursor (step s40). In particular, since the heat treatment is carried out for a very short time, preferably within 30 minutes, reaction products that adversely affect battery characteristics are suppressed, and an additional step such as washing with water to remove the reaction products is not required. And in annealing, it is possible to safely, inexpensively and effectively remove components that can be problematic when remaining in the LCO active material such as Co 3 O 4 , and to recover the battery characteristics of the reused active material by improving the crystal structure, that is, crystallinity. There are advantages. As such, it is possible to obtain a recycled active material with only two steps of heat treatment and annealing.
[68]
The reusable active material obtained according to the present invention may have a particle size distribution similar to that of the active material existing in the active material layer in the positive electrode scrap, so that a separate treatment may not be required. Since the carbon component generated by carbonization of the binder or the conductive material does not remain on the surface, a step or the like for removing the carbon component is not required. Accordingly, the active material obtained through the method of FIG. 2 may be reused as it is without additional treatment and used to manufacture the positive electrode.
[69]
100% of the reusable active material can be used as it is without adjusting the composition, or it can be mixed with fresh LCO and mixed with a conductive material, a binder, and a solvent to make a slurry and use it.
[70]
Hereinafter, an experimental example of the present invention will be described in detail.
[71]

[72]
Each positive electrode active material was prepared in the same manner as in Examples and Comparative Examples below, and electrochemical performance was evaluated.
[73]
Example: A reused active material was collected according to the active material reuse method of the present invention as described above. The heat treatment in step s30 was performed at 600°C in air at a temperature of 5°C/min for 30 minutes at a temperature increase rate of 5°C/min by preparing the LCO positive electrode scrap to be discarded after the positive electrode plate was punched. In step s40, a lithium precursor (Li 2 CO 3 ) in an excess amount of 2 mol% lithium relative to the lithium amount in the reused LCO was added and annealed at 750° C. in air for 15 hours.
[74]
Comparative Example 1: Fresh LCO was used instead of a reused active material.
[75]
Comparative Example 2: Only the heat treatment of step s30 of the active material reuse method of the present invention as described above was performed to remove the binder, the conductive material, and the Al current collector, and the LCO active material was collected. Step s30 was performed under the same conditions as in Example. The crystal structure recovery of step s40 in the active material reuse method of the present invention was not performed.
[76]
Comparative Example 3: The LCO active material was collected in the same manner as in Comparative Example 2, except that the heat treatment time was 1 hour.
[77]
Comparative Example 4: The LCO active material was collected in the same manner as in Comparative Example 2, except that the heat treatment time was 5 hours.
[78]
96 wt% of the positive active material recovered or prepared in each of the Examples and Comparative Examples, 2 wt% of carbon black as a conductive material, and 2 wt% of PVdF as binder, mixed with NMP to make a slurry to prepare a positive electrode Half Cell, CHC) was prepared and the electrochemical performance was evaluated.
[79]
3 is a result of cell evaluation using the active materials of Examples and Comparative Examples. At different currents, the rate performance was examined by evaluating the capacity according to the number of cycle repetitions. The equipment used for evaluation is a general charging/discharging test device that is well used in the laboratory. There is no deviation depending on the measuring device or method. In the graph of FIG. 3 , the horizontal axis indicates the number of cycles and the vertical axis indicates capacity.
[80]
The voltage was set to 3~4.5V, and the initial formation charge/discharge was performed at 0.2C/0.2C. The electrolyte constituting the cell was carbonate-based, with Ethylene carbonate (EC):Ethyl methyl carbonate (EMC) = 3:7 and some additives were used.
[81]
Referring to FIG. 3 , the lowest rate performance can be confirmed in Comparative Example 4, in which the heat treatment time is the longest at 5 hours. This is because if the high-temperature heat treatment process as in step s30 is carried out for a long time, the binder and the conductive material are removed as CO 2 and H 2 O, reacting with lithium on the surface of the positive electrode active material to form Li 2 CO 3 , and reacting with F present in the binder to form LiF because it is formed. In addition , it is judged to show low battery characteristics due to Co 3 O 4 generated by thermal decomposition on the LCO surface.
[82]
Comparative Example 3 has a shorter heat treatment time of 1 hour than Comparative Example 4, and the rate performance is better than that of Comparative Example 4 until about the initial cycle 3, but it can be seen that the rate performance deteriorates as the number of cycles increases.
[83]
Comparative Example 2 had a heat treatment time of 30 minutes, which was shorter than Comparative Examples 3 and 4. In the case of Comparative Example 2, the rate performance is superior to those of Comparative Examples 3 and 4. 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.
[84]
In Example 2, compared to Comparative Example 2, annealing was performed by adding a lithium precursor. In order to supplement lithium lost in the process of recovering the active material and recover crystallinity, Li 2 CO 3 was added and annealed. According to the example, it is possible not only to supplement the insufficient amount of lithium generated during the process, but also to reduce the deformed structure and Co 3 O 4 that may appear on the surface of the active material during regeneration to the LCO crystal structure, so that the fresh active material of Comparative Example 1 It is confirmed that the results are improved compared to the initial characteristics. As described above, according to the present invention, the active material can be recovered from the cathode scrap to a level that can be directly reused. It is safe because it does not use toxic and explosive solvents such as NMP, DMC, acetone, and methanol, and it is suitable for mass production because it uses simple and safe methods such as heat treatment and annealing.
[85]
4 is an XRD pattern of the active materials of Examples and Comparative Examples. In the XRD pattern, the horizontal axis is 2θ (Theta) (degrees), and the vertical axis is intensity. The XRD pattern was obtained using a general X-ray diffraction apparatus that is well used in the laboratory. For example, it can be analyzed using an X-ray diffractometer XG-2100 manufactured by Rigaku. However, there is no deviation depending on the device or method.
[86]
4A is an XRD pattern of Comparative Example 1, that is, fresh LCO. (b) is the XRD pattern of the active material of Comparative Example 2, and (c) is the XRD pattern of the active material of Comparative Example 4. Comparing (b) and (c) with (a), the Co 3 O 4 phase is confirmed. That is, it can be confirmed that Co 3 O 4 is generated on the surface of the LCO in the heat treatment of step s30.
[87]
Figure 4 (d) is an XRD pattern of the active material of Example. Comparing (b), (c) and (d), it can be seen that the Co 3 O 4 phase is lost through the annealing of step s40 and the crystal structure is restored to LCO. Looking at the position of the diffraction peak in the XRD pattern, the crystal structure of (d) is similar to the crystal structure of (a). Therefore, it can be confirmed that the Example of the present invention is restored to the level of the fresh active material of Comparative Example 1. As described above, according to the present invention, Co 3 O 4 generated in the heat treatment process can be removed in the annealing process, and the active material can be recovered from the cathode scrap to a level that can be directly reused.

Claims
[Claim 1]
(a) By thermally decomposing the binder and the conductive material in the active material layer by thermally decomposing the positive electrode scrap including the lithium composite transition metal oxide positive electrode active material layer on the current collector at 300 ~ 650 ° C. in air within 1 hour, the current collector is separating from the active material layer and recovering the active material in the active material layer; and (b) adding a lithium precursor to the recovered active material and annealing to obtain a reusable active material.
[Claim 2]
The method of claim 1 , wherein the heat treatment is performed within 30 minutes.
[Claim 3]
The method of claim 1, wherein the lithium precursor is at least one of LiOH, Li 2 CO 3 , LiNO 3 and Li 2 O.
[Claim 4]
The method of claim 1 , wherein the lithium precursor is added in an amount capable of adding as much as the ratio of lithium lost compared to the ratio of lithium and other metals in the raw material active material used for the active material layer.
[Claim 5]
5. The method of claim 4, wherein the lithium precursor is added in an amount to which lithium is added in a molar ratio of 0.001 to 0.4.
[Claim 6]
The method of claim 1 , wherein the annealing is performed at 400 to 1000° C. in air.
[Claim 7]
The method of claim 1 , wherein the temperature of the annealing step exceeds the melting point of the lithium precursor.
[Claim 8]
The method of claim 1 , wherein the active material in the active material layer is recovered in a powder form, and carbon components generated by carbonization of the binder or the conductive material do not remain on the surface.
[Claim 9]
The method of claim 1 , wherein the reusable active material has a particle size distribution similar to that of the active material in the active material layer.
[Claim 10]
(a) The positive electrode scrap remaining after punching out the positive electrode plate from the positive electrode including the lithium composite transition metal oxide positive electrode active material layer on the current collector is heat-treated in the air at 300 ~ 650 ° C for 1 hour, and the binder and the conductive material in the active material layer by thermally decomposing, separating the current collector from the active material layer and recovering the active material in the active material layer; and (b) adding at least one of LiOH, Li 2 CO 3 , LiNO 3 and Li 2 O to the recovered active material and annealing in air at 400 to 1000°C.