Method for recovering cathode material from lithium ion battery cathode scraps

Abstract

This invention discloses a method for recovering cathode material from lithium-ion battery cathode scrap, comprising: immersing the lithium-ion battery cathode scrap to be recovered in a bio-based solvent for microwave ultrasonic treatment, filtering, and drying to obtain coarse cathode material powder; placing the coarse cathode material powder in a plasma treatment chamber and subjecting it to weak plasma treatment with an argon-oxygen mixed gas to obtain cathode material. This invention utilizes a bio-based solvent and microwave ultrasonic treatment technology to achieve the peeling of the cathode material coating from the cathode current collector in a mild liquid environment, obtaining coarse cathode material powder; and utilizes weak plasma treatment technology to remove residual impurities from the coarse cathode material powder under low-temperature, low-damage conditions through a synergistic effect of physicochemical processes, recovering cathode material with excellent electrochemical performance. This cathode material exhibits high discharge specific capacity and excellent cycle performance in lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode scrap recycling technology, and in particular to a method for recycling cathode materials from lithium-ion battery cathode scrap. Background Technology

[0002] As a core component of lithium-ion batteries, the consumption and production capacity of cathode materials are increasing, resulting in a growing amount of scrap material during the production of cathode sheets. This scrap material, being unused, is pure and singular in composition (uncontaminated by electrolyte), and its active substances have not undergone electrochemical cycling, maintaining their intact crystal structure and electrochemical activity. Failure to recycle it will inevitably lead to a waste of resources.

[0003] Currently, there are two main methods for recycling lithium-ion battery cathode materials: hydrometallurgy and pyrometallurgy. Both methods involve recovering the main elements from the material one by one, and then using the recovered materials to synthesize new cathode materials. These two methods are primarily used for processing already discarded batteries. However, the active materials in the cathode scraps retain their intact structure and function. Using the above two methods would damage their structure, requiring a complex synthesis process to re-synthesize the cathode material, artificially prolonging the recycling process, increasing the economic cost of recycling, and amplifying environmental pressure.

[0004] In addition, existing methods generally use acid dissolution, alkali dissolution, or other soaking methods to recycle waste cathode materials, which involves the use of corrosive reagents and poses significant safety and environmental risks.

[0005] Therefore, developing a safe and environmentally friendly technology for recycling lithium-ion battery cathode scrap is a technical challenge that urgently needs to be addressed in the current field of lithium-ion battery cathode scrap recycling. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a method for recycling cathode materials from lithium-ion battery cathode scraps. By utilizing bio-based solvents, microwave-assisted ultrasonic treatment technology, and weak plasma treatment technology, cathode materials with excellent electrochemical performance are recovered. This method eliminates the need for corrosive reagents, is safe and environmentally friendly, green and efficient, and has a simple process. It can meet the needs of large-scale recycling and reuse of cathode scraps and has broad industrial application value.

[0007] The first aspect of the present invention provides a method for recycling cathode materials from lithium-ion battery cathode scraps, comprising the following steps: The scraps of positive electrode material from lithium-ion batteries to be recycled are immersed in a bio-based solvent and subjected to microwave ultrasonic treatment, then filtered and dried to obtain coarse powder of positive electrode material. The coarse powder of the cathode material is placed in a plasma treatment chamber and subjected to weak plasma treatment by introducing an argon-oxygen mixed gas to obtain the cathode material.

[0008] In the method for recycling cathode materials from lithium-ion battery cathode scraps as described above, the bio-based solvent is dihydro-L-glucanone or methyl lactate.

[0009] The method for recycling cathode materials from lithium-ion battery cathode scraps as described above includes the following steps: first, microwave treatment with a microwave frequency of 2450MHz and a microwave power of 1-1.2KW is used; the temperature is raised to 50-100℃ within 5-10 minutes and maintained; after the temperature is raised, ultrasonic waves with a frequency of 15-30kHz are applied simultaneously; and the treatment continues for 10-120 minutes at 50-100℃ under the combined effect of microwave and ultrasonic waves.

[0010] The method for recycling cathode materials from lithium-ion battery cathode scraps as described above, wherein the microwave power is 1KW.

[0011] The method for recycling cathode materials from lithium-ion battery cathode scraps as described above includes the filtration step of filtering through a 30-300 mesh sieve.

[0012] In the method for recycling cathode materials from lithium-ion battery cathode scraps as described above, the drying temperature is 50-100℃ and the time is 2-5 hours.

[0013] In the method for recycling cathode materials from lithium-ion battery cathode scraps as described above, the pressure in the plasma treatment chamber is 5-70 Pa, the temperature is 30-50 °C, the power of the plasma generator is 50-100 W, and the processing time is 2-15 min.

[0014] In the method for recycling cathode materials from lithium-ion battery cathode scraps as described above, the volume ratio of argon to oxygen in the argon-oxygen mixed gas is 9:1.

[0015] The method for recycling cathode materials from lithium-ion battery cathode scraps as described above, wherein the cathode material is one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium cobalt oxide, and lithium manganese oxide.

[0016] A second aspect of the present invention provides a positive electrode material recovered using the above-described method for recovering positive electrode material from lithium-ion battery positive electrode scraps.

[0017] The solution of the present invention has at least the following effects: This invention provides a method for recycling cathode materials from lithium-ion battery cathode scraps. The method involves microwave and ultrasonic treatment of the scraps with a bio-based solvent. Under the synergistic effect of the bio-based solvent and microwave / ultrasonic waves, the cathode material coating is peeled off from the cathode current collector in a mild liquid environment, yielding coarse cathode material powder. Residual impurities in the coarse cathode material powder are removed using weak plasma treatment technology under low-temperature, low-damage conditions through a synergistic physicochemical process, resulting in a cathode material with excellent electrochemical performance. This cathode material exhibits high discharge specific capacity (up to 152 mAh / g) and excellent cycle performance in lithium-ion batteries (capacity retention of up to 87.6% after 500 cycles). This method requires no corrosive reagents, is safe and environmentally friendly, green and efficient, has a simple process, does not damage the chemical structure of the cathode material itself, avoids costly secondary synthesis, and can meet the needs of large-scale recycling and reuse of cathode scraps, thus possessing broad industrial application value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 These are scanning electron microscope images of the lithium iron phosphate cathode material (LFP) before treatment and the lithium iron phosphate cathode material (LFP-R) after treatment in Example 1 of the present invention. Figure 1 In the image, a and b are scanning electron microscope images of lithium iron phosphate (LFP) cathode material before treatment at different scales. Figure 1 c and d in the image are scanning electron microscope images of the treated lithium iron phosphate cathode material (LFP-R) at different scales.

[0020] Figure 2 The images show the X-ray diffraction patterns of the lithium iron phosphate cathode material (LFP) before and after treatment (LFP-R) in Example 1 of this invention.

[0021] Figure 3 The graphs show the 1C charge-discharge curves of the lithium iron phosphate cathode material (LFP) before treatment and the lithium iron phosphate cathode material (LFP-R) after treatment in Example 1 of the present invention in the voltage range of 2.5-4.3V.

[0022] Figure 4 The 1C charge-discharge curves of commercial lithium iron phosphate cathode materials in the voltage range of 2.5-4.3V are shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this art or in accordance with the product instructions. Reagents or instruments used without specified manufacturers are all conventional products that can be obtained commercially.

[0024] In the following description, the term "and / or" is used to describe the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural.

[0025] Those skilled in the art should understand that, in the following description of the embodiments of the present invention, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0026] Those skilled in the art will understand that the numerical ranges in the embodiments of the present invention should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, the technical / scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention pertains. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0029] The first aspect of the present invention provides a method for recycling cathode materials from lithium-ion battery cathode scraps, comprising the following steps: (1) The scraps of the positive electrode of the lithium-ion battery to be recycled are immersed in a bio-based solvent for microwave ultrasonic treatment, filtered and dried to obtain coarse powder of positive electrode material; (2) The coarse powder of the positive electrode material is placed in a plasma treatment chamber and subjected to weak plasma treatment by argon-oxygen mixed gas to obtain the positive electrode material.

[0030] In this invention, lithium-ion battery positive electrode scrap refers to positive electrode sheets separated from unfilled lithium-ion battery cells or defective materials or waste generated during the production and processing of positive electrode sheets. This type of lithium-ion battery positive electrode scrap has not come into contact with electrolyte and is not contaminated by electrolyte. Specifically, the positive electrode sheets separated from unfilled lithium-ion battery cells refer to: brand-new lithium-ion battery cells with defects that cannot be sold as qualified products. The defective brand-new lithium-ion battery cells are disassembled to separate the positive electrode sheets, which are then used as lithium-ion battery positive electrode scrap. The defects refer to physical structural flaws or dimensional deviations generated during the manufacturing process of the lithium-ion battery cell, such as burrs on the electrode edge, coating peeling, exposed foil, electrode wrinkles, scratches, and dimensional deviations. The defective materials or waste generated during the production and processing of positive electrode sheets specifically refer to the defective materials or waste generated during the coating, slitting, and cutting processes of lithium-ion battery positive electrode sheets. These defective materials or waste are used as scraps for lithium-ion battery positive electrodes.

[0031] This invention does not impose specific limitations on the amount of bio-based solvent used, as long as the scrap lithium-ion battery cathode material to be recycled is completely submerged in the bio-based solvent, thus providing a foundation for the smooth progress of subsequent processes.

[0032] In step (1), the bio-based solvent has a high dielectric constant and is a strong polar solvent, which can effectively reduce the crystallinity of the binder (such as PVDF), making it easier for the binder molecular chains to separate and disperse in the solvent, thereby weakening the adhesion between the positive electrode material and the positive electrode current collector, and achieving the separation of the two.

[0033] In step (1), the role of microwave ultrasonic treatment is as follows: first, the treatment is carried out under microwave action to increase the solubility of the binder (such as PVDF) in the bio-based solvent and generate thermal stress. Then, the treatment is carried out under the synergistic action of microwave and ultrasonic to make the peeling process between the positive electrode material and the positive electrode current collector more thorough and rapid, and to make the binder (such as PVDF) fully dissolved in the bio-based solvent, thereby realizing the separation of the positive electrode material and the positive electrode current collector.

[0034] In step (1), drying is done to remove residual solvent.

[0035] In step (2), the weak plasma treatment is to etch away the impurities and residual organic matter on the surface of the coarse powder of the cathode material, improve the purity of the recovered cathode material, and thus improve its electrochemical performance.

[0036] This invention provides a method for recycling cathode materials from lithium-ion battery cathode scraps. The method involves microwave and ultrasonic treatment of the scraps with a bio-based solvent. Under the synergistic effect of the bio-based solvent and microwave / ultrasonic waves, the cathode material coating is peeled off from the cathode current collector in a mild liquid environment, yielding coarse cathode material powder. Residual impurities in the coarse cathode material powder are removed using weak plasma treatment technology under low-temperature, low-damage conditions through a synergistic physicochemical process, resulting in a cathode material with excellent electrochemical performance. This cathode material exhibits high discharge specific capacity (up to 152 mAh / g) and excellent cycle performance in lithium-ion batteries (capacity retention of up to 87.6% after 500 cycles). This method requires no corrosive reagents, is safe and environmentally friendly, green and efficient, has a simple process, does not damage the chemical structure of the cathode material itself, avoids costly secondary synthesis, and can meet the needs of large-scale recycling and reuse of cathode scraps, thus possessing broad industrial application value.

[0037] In some embodiments, the bio-based solvent is dihydro-L-glucosamine or methyl lactate, preferably dihydro-L-glucosamine.

[0038] Using dihydro-L-glucanone or methyl lactate as bio-based solvents is safe, environmentally friendly, renewable, and has significant environmental advantages.

[0039] In some embodiments, the microwave ultrasonic treatment steps include: first, using microwaves with a frequency of 2450MHz and a power of 1-1.2KW for treatment; raising the temperature to 50-100℃ within 5-10 minutes and maintaining it (treatment is first performed under microwave conditions); after the temperature rise is completed, simultaneously applying ultrasonic waves with a frequency of 15-30kHz; and continuing treatment for 10-120 minutes under the conditions of 50-100℃ and the synergistic effect of microwaves and ultrasonic waves.

[0040] In this invention, microwaves with a frequency of 2450MHz and a power of 1-1.2KW are first used for treatment. The temperature is raised to 50-100℃ within 5-10 minutes and maintained to increase the solubility of the binder (such as PVDF) in the bio-based solvent. After the temperature is raised, ultrasonic waves with a frequency of 15-30kHz are applied simultaneously. The treatment continues for 10-120 minutes at 50-100℃ under the synergistic effect of microwaves and ultrasonic waves to separate the positive electrode material from the positive electrode current collector and to fully dissolve the binder (such as PVDF) in the bio-based solvent, thereby achieving the separation of the positive electrode material from the positive electrode current collector.

[0041] Furthermore, the microwave ultrasonic treatment steps include: first, using microwaves with a frequency of 2450MHz and a power of 1KW for treatment, raising the temperature to 80℃ within 8 minutes and maintaining it (treatment is first performed under microwave conditions), and then simultaneously applying ultrasonic waves with a frequency of 25kHz after the temperature rise is completed, and continuing treatment for 15 minutes under the conditions of 80℃ and the synergistic effect of microwaves and ultrasonic waves.

[0042] In some embodiments, the filtration step includes filtering through a 30-300 mesh sieve, preferably 150 mesh.

[0043] In some embodiments, the drying temperature is 50-100°C and the drying time is 2-5 hours. More preferably, the drying temperature is 80°C and the drying time is 3 hours.

[0044] In some embodiments, the pressure inside the plasma processing chamber is 5-70 Pa, the temperature is 30-50 °C, the power of the plasma generator is 50-100 W, and the processing time is 2-15 min. Further, the pressure inside the plasma processing chamber is preferably 70 Pa, the temperature is preferably 30 °C, the power of the plasma generator is preferably 80 W, and the processing time is preferably 5 min.

[0045] In some embodiments, the volume ratio of argon to oxygen in the argon-oxygen mixture is 9:1.

[0046] In some embodiments, the positive electrode material is one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium cobalt oxide, and lithium manganese oxide, preferably lithium iron phosphate.

[0047] A second aspect of the present invention provides a method for recovering cathode materials using the aforementioned lithium-ion battery cathode scrap.

[0048] The present invention will be further described below through specific embodiments.

[0049] In the following examples, the unfilled lithium iron phosphate (LFP) cells and the scrapped LFP cells come from the same battery manufacturer. The binder used on the positive electrode sheets of both the unfilled LFP cells (i.e., brand new LFP cells that have never been in contact with electrolyte) and the scrapped LFP cells (i.e., used LFP cells that have completed their service life or are unusable due to performance degradation) is polyvinylidene fluoride (PVDF), and the conductive agent used is conductive carbon black (SP). The microwave and ultrasonic co-processing reactor used includes both microwave and ultrasonic modes (i.e., it combines the functions of a microwave reactor and an ultrasonic reactor), and has individual and co-processing functions for microwave and ultrasonic control. It can be arbitrarily combined and programmed or operate independently, and can simultaneously perform programmable temperature and timing control.

[0050] Example 1 This embodiment provides a method for recycling cathode materials from lithium-ion battery cathode scraps, including the following steps: (1) After disassembling the unfilled lithium iron phosphate cell, separate the positive electrode sheet, cut the positive electrode sheet into strips of 1×4cm, and use the strips as scraps of positive electrode material of lithium-ion battery to be recycled (also known as unprocessed lithium iron phosphate positive electrode material, denoted as LFP). (2) 20 mL of dihydro-L-glucose ketone was injected into the microwave and ultrasonic co-processing reactor. Then the lithium-ion battery positive electrode scrap to be recycled was placed into the microwave and ultrasonic co-processing reactor. The lithium-ion battery positive electrode scrap to be recycled was completely immersed in the dihydro-L-glucose ketone and then subjected to microwave ultrasonic treatment to separate the positive electrode material from the positive electrode current collector and obtain positive electrode slurry. The steps of the microwave ultrasonic treatment are as follows: start the microwave reactor, use microwaves with a frequency of 2450MHz and a power of 1KW for treatment, raise the temperature to 80℃ within 8 minutes and maintain it (this process is carried out under microwave conditions), and simultaneously start the ultrasonic reactor (apply ultrasonic waves with a frequency of 25kHz) when the temperature reaches 80℃, and continue treatment for 15 minutes under the conditions of 80℃, microwave frequency of 2450MHz, microwave power of 1KW and ultrasonic frequency of 25kHz.

[0051] (3) The positive electrode slurry is filtered through a 150-mesh sieve, and the material with a particle size ≤0.106mm is collected and dried at 80℃ for 3h to obtain coarse powder of positive electrode material; (4) Set the pressure in the plasma treatment chamber to 70 Pa, the temperature to 30 °C, and the power of the plasma generator to 80 W. Place the coarse powder of the positive electrode material on the plasma generator in the plasma treatment chamber, introduce argon-oxygen mixed gas (the volume ratio of argon to oxygen is 9:1), turn on the power, and perform weak plasma treatment for 5 min under the above pressure, temperature and power conditions to obtain lithium iron phosphate positive electrode material that can be used directly (also called treated lithium iron phosphate positive electrode material, denoted as LFP-R).

[0052] Example 2 The method for recycling cathode materials from lithium-ion battery cathode scraps provided in this embodiment is basically the same as that in Embodiment 1, except that dihydro-L-glucanone is replaced with methyl lactate.

[0053] Comparative Example 1 The method for recycling cathode materials from lithium-ion battery cathode scraps provided in this comparative example is basically the same as that in Example 1, except that the microwave power of 1KW is replaced with microwave power of 0.5KW.

[0054] Comparative Example 2 The method for recycling cathode materials from lithium-ion battery cathode scraps provided in this comparative example is basically the same as that in Example 1, except that the microwave power of 1KW is replaced with microwave power of 1.5KW.

[0055] Comparative Example 3 The method for recycling cathode materials from lithium-ion battery cathode scraps provided in this comparative example is basically the same as that in Example 1, except that dihydro-L-glucanone is replaced with deionized water.

[0056] Comparative Example 4 (without ultrasonic treatment) The method for recycling positive electrode materials from lithium-ion battery positive electrode scraps provided in this comparative example is basically the same as that in Example 1, except that step (2) is not ultrasonically treated. Specifically, (2) 20 mL of dihydro-L-glucanone is injected into a microwave and ultrasonic co-processing reactor, and then the lithium-ion battery positive electrode scraps to be recycled are placed in the microwave and ultrasonic co-processing reactor. The lithium-ion battery positive electrode scraps to be recycled are completely immersed in the dihydro-L-glucanone and then microwave treated to obtain positive electrode slurry. The microwave treatment steps are as follows: start the microwave reactor, use a microwave with a frequency of 2450 MHz and a power of 1 KW for treatment, raise the temperature to 80°C within 8 min and maintain it, and continue treatment for 15 min under the conditions of 80°C, 2450 MHz, and 1 KW.

[0057] Comparative Example 5 (without microwave treatment) The method for recycling positive electrode materials from lithium-ion battery positive electrode scraps provided in this comparative example is basically the same as that in Example 1, except that step (2) is not microwave treatment. Specifically, (2) 20 mL of dihydro-L-glucanone is injected into a microwave and ultrasonic co-processing reactor, and then the lithium-ion battery positive electrode scraps to be recycled are placed in the microwave and ultrasonic co-processing reactor. The lithium-ion battery positive electrode scraps to be recycled are completely immersed in the dihydro-L-glucanone and then ultrasonically treated to obtain positive electrode slurry. The ultrasonic treatment step is as follows: the temperature is raised to 80°C within 8 min and maintained, and the ultrasonic reactor is started simultaneously when the temperature reaches 80°C. The treatment is continued for 15 min at a temperature of 80°C and an ultrasonic frequency of 25 kHz.

[0058] Comparative Example 6 (contaminated with electrolyte, waste electrode material) The method for recovering cathode materials from scrapped lithium iron phosphate battery cells provided in this comparative example is basically the same as that in Example 1, except that step (1) is used: scrapped lithium iron phosphate battery cells are used. Specifically, the method for recovering cathode materials from scrapped lithium iron phosphate battery cells provided in this comparative example includes the following steps: (1) After dismantling the scrapped lithium iron phosphate battery cell, separate the positive electrode sheet, cut the positive electrode sheet into strips of 1×4cm, and use the strips as scrap lithium-ion battery electrode sheet material to be recycled; (2) 20 mL of dihydro-L-glucose ketone was injected into the microwave and ultrasonic co-processing reactor. Then the scrap lithium-ion battery cathode material to be recycled was placed into the microwave and ultrasonic co-processing reactor. The scrap lithium-ion battery cathode material to be recycled was completely immersed in the dihydro-L-glucose ketone and then subjected to microwave ultrasonic treatment to separate the cathode material from the cathode current collector and obtain cathode slurry. The steps of the microwave ultrasonic treatment are as follows: start the microwave reactor, use microwaves with a frequency of 2450MHz and a power of 1KW for treatment, raise the temperature to 80℃ within 8 minutes and maintain it (this process is carried out under microwave conditions), and simultaneously start the ultrasonic reactor (apply ultrasonic waves with a frequency of 25kHz) when the temperature reaches 80℃, and continue treatment for 15 minutes under the conditions of 80℃, microwave frequency of 2450MHz, microwave power of 1KW and ultrasonic frequency of 25kHz.

[0059] (3) The positive electrode slurry is filtered through a 150-mesh sieve, and the material with a particle size ≤0.106mm is collected and dried at 80℃ for 3h to obtain coarse powder of positive electrode material; (4) Set the pressure in the plasma treatment chamber to 70 Pa, the temperature to 30 °C, and the power of the plasma generator to 80 W. Place the coarse powder of the positive electrode material on the plasma generator in the plasma treatment chamber, introduce argon-oxygen mixed gas (the volume ratio of argon to oxygen is 9:1), turn on the power, and perform weak plasma treatment for 5 min under the above pressure, temperature and power conditions to obtain the recovered lithium iron phosphate positive electrode material.

[0060] Comparative Example 7 The method for recycling cathode materials from lithium-ion battery cathode scraps provided in this comparative example is basically the same as that in Example 1, except that the argon-oxygen mixed gas (the volume ratio of argon to oxygen is 9:1) is replaced with an argon-hydrogen mixed gas (the volume ratio of argon to hydrogen is 9:1).

[0061] Performance testing 1. Scanning electron microscopy was performed on the untreated lithium iron phosphate cathode material (LFP) and the treated lithium iron phosphate cathode material (LFP-R) in Example 1 of the present invention. The results are as follows: Figure 1 As shown. Figure 1 These are scanning electron microscope images of the lithium iron phosphate cathode material (LFP) before treatment and the lithium iron phosphate cathode material (LFP-R) after treatment in Example 1 of the present invention. Figure 1 In the image, a and b are scanning electron microscope images of lithium iron phosphate (LFP) cathode material before treatment at different scales. Figure 1 c and d in the image are scanning electron microscope images of the treated lithium iron phosphate cathode material (LFP-R) at different scales.

[0062] from Figure 1 In images a and b, it is clearly visible that before treatment, the lithium iron phosphate (LFP) cathode material particles contain a large amount of conductive agent SP and binder PVDF (appearing as long strips); while after treatment, the conductive carbon black and binder PVDF added during the preparation of the cathode electrode are no longer visible between the LFP-R cathode material particles, the particle gaps are clear, and there is no gel-like material connecting them. Figure 1 (c and d in the text) indicates that the method of the present invention can effectively remove impurities from the scrap material of lithium-ion battery cathode.

[0063] 2. X-ray diffraction tests were performed on the untreated lithium iron phosphate cathode material (LFP) and the treated lithium iron phosphate cathode material (LFP-R) in Example 1 of the present invention. The results are as follows: Figure 2 As shown. Figure 2 The images show the X-ray diffraction patterns of the lithium iron phosphate cathode material (LFP) before and after treatment (LFP-R) in Example 1 of this invention.

[0064] Depend on Figure 2 It can be seen that the XRD pattern of the lithium iron phosphate cathode material (LFP) before treatment has clear diffraction peaks, maintains the original olivine structure, and does not have other impurity phases. The lithium iron phosphate cathode material (LFP-R) after treatment has the same olivine structure as the lithium iron phosphate cathode material (LFP) before treatment, and does not have other impurity peaks. This shows that the method of the present invention can completely preserve the original structure of the lithium-ion battery cathode scraps without introducing new impurity phases or destroying its structural stability.

[0065] 3. Charge-discharge curve tests were performed on the untreated lithium iron phosphate cathode material (LFP) and the treated lithium iron phosphate cathode material (LFP-R) in Example 1 of this invention. The results are as follows: Figure 3 As shown. Figure 3The graphs show the 1C charge-discharge curves of the lithium iron phosphate cathode material (LFP) before treatment and the lithium iron phosphate cathode material (LFP-R) after treatment in Example 1 of the present invention in the voltage range of 2.5-4.3V.

[0066] Charge-discharge curves of commercial lithium iron phosphate cathode materials were tested, and the results are as follows: Figure 4 As shown. Figure 4 The 1C charge-discharge curves of commercial lithium iron phosphate cathode materials in the voltage range of 2.5-4.3V are shown.

[0067] Depend on Figures 3-4 It can be seen that the treated lithium iron phosphate cathode material (LFP-R) has almost the same electrochemical performance as the commercial lithium iron phosphate cathode material, with a 1C discharge specific capacity of 152 mAh / g; while the untreated lithium iron phosphate cathode material (LFP) has a 1C discharge specific capacity of only 145 mAh / g.

[0068] 4. The untreated lithium iron phosphate (LFP) cathode material in Example 1 of this invention, the lithium iron phosphate cathode materials in Examples 1-2, and the lithium iron phosphate cathode materials in Comparative Examples 1-7 were used as cathode material samples to be tested for electrochemical performance. The specific steps included: The positive electrode material sample to be tested, conductive agent SP, binder PVDF, and N-methylpyrrolidone were mixed evenly in a mass ratio of 80:10:10:100, coated on aluminum foil, and vacuum dried at 100℃ for 12 hours before being cut to obtain a positive electrode sheet with a diameter of 1.58 cm. Lithium metal was used as the negative electrode, and polypropylene microporous membrane was used as the separator. The electrolyte was prepared by dissolving LiPF6 in a mixed solvent of EC (ethylene carbonate) and DEC (diethyl carbonate) in a mass ratio of 1:1 to obtain an electrolyte (LiPF6 concentration of 1 mol / L). The electrolyte was then assembled into a CR2032 coin cell. Cyclic performance tests were conducted under the following conditions: temperature of 25℃, rate of 1C, and test voltage range of 2.5-4.3V. The relevant test results are recorded in Table 1.

[0069] Table 1 Cyclic performance test results In Table 1, the 1C discharge specific capacity refers to the initial discharge specific capacity at a 1C rate.

[0070] As shown in Table 1, the lithium iron phosphate cathode material (LFP-R) in Example 1 achieved a discharge specific capacity of 152 mAh / g at a 1C charge-discharge rate, and retained 87.6% of its capacity after 500 cycles. This indicates that the lithium iron phosphate cathode material obtained by the method of this invention has excellent electrochemical performance and is significantly superior to Comparative Examples 1-7. Comparing Example 1 with Comparative Examples 1-2, it can be seen that the discharge specific capacity and capacity retention of the lithium iron phosphate cathode materials in Comparative Examples 1 and 2 after being fabricated into batteries are lower than those in Example 1. The reason for this is that at low power (e.g., 0.5 kW), the energy is insufficient to fully activate and achieve effective separation; at high power (e.g., 1.5 kW), overheating damage occurs, leading to phase transitions in the active materials of the cathode material and affecting its structure. Comparing Example 1 and Comparative Example 3, it is evident that the electrochemical performance of the lithium iron phosphate cathode material prepared using deionized water is extremely poor. This is because deionized water cannot effectively remove the residual PVDF binder in the cathode material, affecting the cathode material's performance and thus the battery's performance. Comparing Example 1 and Comparative Example 4, it is evident that the lithium iron phosphate cathode material in Example 1 exhibits higher discharge specific capacity and capacity retention rate after being assembled into a battery. This indicates that microwave and ultrasonic synergy can complement each other in the impurity removal mechanism, forming a multi-dimensional synergistic effect of thermal activation, mechanical stripping, and interface disturbance, achieving efficient separation, effectively removing impurities, and improving the electrochemical performance of the cathode material. Comparing Example 1 and Comparative Example 5, it was found that ultrasonic treatment alone cannot achieve a synergistic effect to strip and fully dissolve the PVDF binder. Comparing Example 1 and Comparative Example 6, it was found that the battery assembled using the lithium iron phosphate cathode material in Comparative Example 6 exhibits extremely poor cycle stability (capacity retention rate of only 45% after 500 cycles). This is due to the inherent structural instability and poor electrochemical performance of the lithium iron phosphate cathode material in Comparative Example 6. Comparing Example 1 with Comparative Example 7, it was found that the lithium iron phosphate cathode material in Example 1 had a higher discharge specific capacity and capacity retention rate after being prepared into a battery. This is because the active material density is higher under argon-oxygen mixed gas conditions, which makes it easier to excite active oxygen and can more effectively remove impurities and residual binder PVDF from the surface of the cathode material, thereby improving the purity of the cathode material recovery.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recycling cathode materials from lithium-ion battery cathode scraps, characterized in that, Includes the following steps: The scraps of positive electrode material from lithium-ion batteries to be recycled are immersed in a bio-based solvent and subjected to microwave ultrasonic treatment, then filtered and dried to obtain coarse powder of positive electrode material. The coarse powder of the cathode material is placed in a plasma treatment chamber and subjected to weak plasma treatment by introducing an argon-oxygen mixed gas to obtain the cathode material. The bio-based solvent is dihydro-L-glucosamine or methyl lactate; The steps of the microwave ultrasonic treatment include: first, using microwaves with a frequency of 2450MHz and a power of 1-1.2KW for treatment; raising the temperature to 50-100℃ within 5-10 minutes and maintaining it; after the temperature rise is completed, simultaneously applying ultrasonic waves with a frequency of 15-30kHz; and continuing the treatment for 10-120 minutes under the conditions of 50-100℃ and the synergistic effect of microwaves and ultrasonic waves.

2. The method for recycling cathode materials from lithium-ion battery cathode scraps according to claim 1, characterized in that, The microwave power is 1KW.

3. The method for recycling cathode materials from lithium-ion battery cathode scraps according to claim 1, characterized in that, The filtration step includes filtering through a 30-300 mesh sieve.

4. The method for recycling cathode materials from lithium-ion battery cathode scraps according to claim 1, characterized in that, The drying temperature is 50-100℃, and the time is 2-5 hours.

5. The method for recycling cathode materials from lithium-ion battery cathode scraps according to claim 1, characterized in that, The pressure inside the plasma processing chamber is 5-70 Pa, the temperature is 30-50 °C, the power of the plasma generator is 50-100 W, and the processing time is 2-15 min.

6. The method for recycling cathode materials from lithium-ion battery cathode scraps according to claim 1, characterized in that, In the argon-oxygen mixture, the volume ratio of argon to oxygen is 9:

1.

7. The method for recycling cathode materials from lithium-ion battery cathode scraps according to claim 1, characterized in that, The cathode material is one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium cobalt oxide, and lithium manganese oxide.

8. A method for recovering positive electrode material using lithium-ion battery positive electrode scraps as described in any one of claims 1-7.

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