Recycling and regeneration method and application of graphite anode of waste lithium-ion battery

Abstract

The present invention provides a method for recycling and regenerating the graphite negative electrode of waste lithium-ion batteries and its application. The recycling and regeneration method includes the following steps: removing impurities from the graphite negative electrode material of waste lithium-ion batteries, mixing and reacting the impurity-removed graphite negative electrode material of waste lithium-ion batteries with a self-healing organic material, and carbonizing to obtain the recycled and regenerated graphite negative electrode material. The recycling and regeneration method provided by the present invention mixes and reacts the impurity-removed graphite negative electrode material of waste lithium-ion batteries with a self-healing organic material and carbonizes, thereby repairing defects at the edges of graphite, improving the electrochemical performance of the regenerated graphite, meeting the requirements of battery negative electrode materials, the repaired graphite can be directly used in battery production, and the recycling and regeneration process has a simple process, high purification efficiency, less consumption of non-renewable resources, and is conducive to sustainable development.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery material recycling, and relates to a method for recycling and regenerating graphite anodes of waste lithium-ion batteries and its application. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in fields such as mobile phones, laptop computers, and new energy electric vehicles, which has led to a sharp increase in the demand and production capacity of lithium-ion batteries. However, the service life of lithium batteries is only 3-5 years. With the development of the battery industry, a large number of waste lithium-ion batteries will inevitably be generated. If they cannot be recycled, it will cause serious environmental pollution and waste of resources. Graphite is currently the most widely used commercial anode material, accounting for up to 12-21 wt% in the battery. Compared with graphite ore, the content of graphite in the waste battery anode is higher, and there are fewer types of impurities. Recycling and reusing it can reduce the purification steps and energy consumption. Therefore, considering the increasing demand for graphite and the quantity of waste graphite, as well as the development of sustainable utilization, it is very necessary to recycle and regenerate the graphite anode in waste batteries.

[0003] In order to remove impurities in waste graphite and restore the structure of graphite, methods such as microwave radiation method, sulfate roasting method, and water treatment method have been used to recycle and repair waste graphite. However, the electrochemical performance of the recycled anode material is still insufficient. CN115332662A discloses an organic acid leaching and high-energy ball milling recycling process. The graphite anode sheet is ultrasonically treated in deionized water for 30-60 min to make the graphite on the copper foil current collector fall off. After the powder is heat-treated at 450-600 °C, it is impregnated with hydrochloric acid-hydrogen peroxide, freeze-dried, and then high-energy ball milled to obtain recycled graphite; this process flow is long and corrosive acids are used. Patent CN107887666A discloses a suspension separation and high-temperature roasting recycling process. The waste anode sheet is mixed with an organic acid separating agent, the copper is peeled off to obtain a suspension containing the anode carbon material, which is separated and dried to obtain a primary carbon powder product. Then it is leached with an organic acid and a reducing agent to obtain a purified carbon powder, and finally high-purity graphitization treatment is carried out at 2600-2800 °C; this process uses organic acids instead of inorganic acids, but still requires the use of chemicals such as sodium bisulfite and sodium thiosulfate, and the energy consumption and equipment investment in the high-temperature graphitization process are high.

[0004] Therefore, how to improve the electrochemical performance of the graphite anode material in recycled waste lithium-ion batteries is a technical problem to be solved urgently. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for recycling and regenerating the graphite anode of waste lithium-ion batteries and its application. The recycling and regenerating method provided by the present invention mixes the impurity-removed graphite anode material of waste lithium-ion batteries with a self-healing organic material and then carbonizes it, thereby repairing the defects at the edges of the graphite, improving the electrochemical performance of the regenerated graphite, meeting the requirements of the battery anode material, being directly applicable to battery production, and having the advantages of simple process, high purification efficiency, less consumption of non-renewable resources, and being conducive to sustainable development.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a method for recycling and regenerating the graphite anode of waste lithium-ion batteries, and the recycling and regenerating method includes the following steps:

[0008] Impurities are removed from the graphite anode material of waste lithium-ion batteries, and the impurity-removed graphite anode material of waste lithium-ion batteries is mixed and reacted with a self-healing organic material, and then carbonized to obtain the recycled and regenerated graphite anode material.

[0009] In the recycling and regenerating method provided by the present invention, the impurity-removed graphite anode material of waste lithium-ion batteries is mixed and reacted with a self-healing organic material. The self-healing organic material undergoes a D-A reaction (Diels-Alder reaction), and the organic material after the D-A reaction is carbonized, thereby repairing the defects of the graphite material in the waste batteries after impurity removal at the edges of the graphite, inhibiting the damage of the solvent to the graphite, promoting the charge transfer of lithium ions on the electrode surface, reducing the impedance of the SEI layer (solid electrolyte interface film) and the consumption of active lithium, improving the electrochemical performance of the regenerated graphite, meeting the requirements of the battery anode material, being directly applicable to battery production, and having the advantages of simple process, high purification efficiency, and less consumption of non-renewable resources, which is conducive to sustainable development and large-scale production.

[0010] In the present invention, if the self-healing organic material is not added, it is impossible to improve the electrochemical performance of waste graphite, reduce the defects of waste graphite and reduce the interlayer spacing of waste graphite, and realize the repair of the graphite structure; if the self-healing organic material does not achieve self-healing through D-A, it is very difficult to accurately repair the defects of waste graphite.

[0011] Preferably, the waste lithium-ion batteries are first discharged, disassembled, crushed and screened to obtain the graphite anode material of waste lithium-ion batteries.

[0012] It should be noted that the method for separating graphite materials from waste lithium-ion batteries in the present invention is a conventional technical means; and for the provided processes such as discharging, disassembling, crushing and screening, the specific processing processes and parameters are also conventional technical choices, and those skilled in the art can make adaptive selections and adjustments according to actual needs; and except for the above-defined separation means, the present invention is applicable to any solutions for obtaining graphite materials from waste lithium-ion batteries that can be known by those skilled in the art within a reasonable range.

[0013] Exemplarily, the discharging process includes: immersing the waste lithium battery in a 1.0 mol / L K2SO4 solution for 8 - 10 h (such as 8 h, 9 h or 10 h, etc.).

[0014] The disassembling obtains the negative electrode; then the copper powder and graphite powder are separated by crushing and screening.

[0015] Preferably, the impurity removal includes:

[0016] Heat-treating, acid-leaching and cleaning the graphite negative electrode material of the waste lithium-ion battery to obtain the impurity-removed graphite negative electrode material of the waste lithium-ion battery.

[0017] In the present invention, through the impurity removal treatment of the graphite negative electrode material of the waste lithium-ion battery, the organic binder is removed by heat treatment, and the metal impurities are removed by acid leaching, so as to achieve the purpose of purifying the waste graphite.

[0018] And except for the above-defined impurity removal process, the present invention is also applicable to other conventional technical means for purifying the graphite material of waste lithium-ion batteries.

[0019] Preferably, the heat treatment is carried out in a protective atmosphere.

[0020] It should be noted that the protective atmosphere in the present invention is a conventional atmosphere that does not cause the material to react, including but not limited to a nitrogen atmosphere or an inert gas atmosphere, etc.

[0021] Preferably, the temperature of the heat treatment is 450 - 600 °C, such as 450 °C, 500 °C, 550 °C or 600 °C, etc., but not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0022] Preferably, the mass ratio of the self-healing organic material to the impurity-removed graphite negative electrode material of the waste lithium-ion battery is (3 - 5):100, such as 3:100, 3.5:100, 4:100, 4.5:100 or 5:100, etc., but not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0023] In the present invention, if the mass ratio of the self-healing organic material to the purified waste graphite anode material of the lithium-ion battery is too small, that is, too little self-healing organic material is added, it will affect the restoration of the graphite structure; while if the mass ratio is too large, that is, too much self-healing organic material is added, although the repair effect is achieved, there will be a problem that too much repair organic material will reduce the electrochemical performance of the graphite.

[0024] Preferably, the self-healing organic material includes maleimide materials.

[0025] In the present invention, maleimide materials are selected as the self-healing organic materials. After the D-A reaction, succinimide is obtained, which can bind to the edge of the graphite to repair defects. At the same time, it can also inhibit the damage of the solvent to the graphite, promote the charge transfer of lithium ions on the electrode surface, reduce the impedance of the SEI layer and the consumption of active lithium; while if other self-healing organic materials are selected, such as carbon-based coatings like asphalt, phenolic resin, polyethylene glycol 400 monooleate, etc., however, there is still a certain layer spacing in the repair of the above carbon-based coatings, and it is impossible to ensure that the defects of the waste graphite are repaired evenly, resulting in relatively stable electrochemical performance.

[0026] Preferably, the maleimide molecular material includes N-(2-hydroxyethyl) maleimide material.

[0027] Preferably, the carbonization temperature is 850-1200 °C, such as 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C or 1200 °C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0028] In the present invention, after the mixing reaction at high temperature and then high-temperature carbonization, the defects of the waste graphite material are repaired more effectively; if the carbonization temperature is too low, it is not conducive to the repair of the cracks on the graphite surface, while if the carbonization temperature is too high, it will cause high-temperature oxidation of the graphite.

[0029] Preferably, the carbonization time is 1-2 h, such as 1 h, 1.5 h or 2 h, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] Preferably, the impurities in the substance after the mixing reaction are removed.

[0031] Preferably, the method for removing impurities includes mixing the substance after the mixing reaction with an impurity remover for impurity removal.

[0032] Preferably, the impurity remover includes isopropyl acetate.

[0033] In the present invention, isopropyl acetate is used for impurity removal after the mixing reaction, removing the impurities and by-products in the reaction process and dissolving the unreacted organic raw materials, thereby obtaining a product with higher purity and more excellent performance.

[0034] Preferably, after the impurity treatment, solid-liquid separation, washing and drying are sequentially carried out to obtain the recycled graphite anode material.

[0035] As a preferred technical solution, the recycling method includes the following steps:

[0036] First, the used lithium-ion battery is discharged, disassembled, crushed and screened to obtain the graphite anode material of the used lithium-ion battery;

[0037] The graphite anode material of the used lithium-ion battery is heat-treated at 450-600 °C in a protective atmosphere, acid-leached and washed to obtain the impurity-removed graphite anode material of the used lithium-ion battery;

[0038] The maleimide material and the impurity-removed graphite anode material of the used lithium-ion battery are mixed and reacted at a mass ratio of (3-5):100, carbonized at 850-1200 °C, and then the carbonized material is mixed with isopropyl acetate for impurity removal, followed by solid-liquid separation, washing and drying to obtain the recycled graphite anode material.

[0039] In the second aspect, the present invention provides a recycled graphite anode material, which is obtained by the recycling method as described in the first aspect.

[0040] In the third aspect, the present invention further provides a lithium-ion battery, which includes the recycled graphite anode material as described in the second aspect.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The recycling method provided by the present invention mixes and reacts the impurity-removed graphite anode material of the used lithium-ion battery with the self-healing organic material. The self-healing organic material undergoes a D-A reaction (Diels-Alder reaction), and the organic material after the D-A reaction is carbonized, thereby repairing the defects of the graphite material in the impurity-removed used battery at the edge of the graphite, inhibiting the damage of the solvent to the graphite, promoting the charge transfer of lithium ions on the electrode surface, reducing the impedance of the SEI layer (solid electrolyte interface film) and the consumption of active lithium, improving the electrochemical performance of the recycled graphite, meeting the requirements of the battery anode material, and can be directly used in battery production. Moreover, the recycling process has the advantages of simple process, high purification efficiency and less consumption of non-renewable resources, which is beneficial to sustainable development and large-scale production. Description of the Drawings

[0043] Figure 1 SEM images of graphite at different stages during the recycling and repair process of Example 1.

[0044] Figure 2 Raman spectra of graphite obtained by the recycling and repair method provided in Example 1.

[0045] Figure 3 SEM images of graphite at different stages during the recycling and repair process of Example 4.

[0046] Figure 4 Raman spectra of graphite obtained by the recycling and repair method provided in Example 4.

[0047] Figure 5 SEM images of graphite at different stages during the recycling and repair of Example 7.

[0048] Figure 6 Raman spectra of graphite obtained by the recycling and repair method provided in Example 7.

[0049] Figure 7 SEM images of graphite obtained by the recycling and repair method provided in Comparative Example 1.

[0050] Figure 8 Raman spectra of graphite obtained by the recycling and repair method provided in Comparative Example 1. Detailed implementation manners

[0051] The technical solutions of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0052] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0053] Example 1

[0054] The waste lithium-ion batteries are soaked in 1.0 mol / L K2SO4 solution for 8 h and then dried. Then they are disassembled to obtain the negative electrode materials. The negative electrode materials are mechanically crushed and screened to separate the copper powder and graphite powder. The separated graphite powder is transferred to a tubular furnace and heated at 600 °C for 1 h under a nitrogen atmosphere. Then the graphite powder is soaked in a mixture of 1 mol / L oxalic acid and 4% hydrogen peroxide solution at 80 °C for 2 h. The acid-leached graphite is washed with deionized water and ethanol until neutral, and then the sample is dried in a blast drying oven at 60 °C for 12 h to obtain the purified graphite negative electrode materials of waste lithium-ion batteries;

[0055] A mixture of the purified graphite negative electrode materials of waste lithium-ion batteries (100 g) and N-(2-hydroxyethyl) maleimide (4 g) is stirred and heated at 1000 °C for 1.5 h (carbonization) under a nitrogen atmosphere. After the reaction mixture is cooled to room temperature, isopropyl acetate (400 mL) is added. The product is filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.45 μm to collect the solid product, washed with NMP, and then dried under vacuum to obtain the recycled and regenerated graphite negative electrode materials.

[0056] Figure 1 The SEM images of graphite at different stages during the recycling and repair process of Example 1 are shown (the upper part of the attached figure is the SEM image of the graphite material of the waste lithium-ion battery after purification, and the lower part of the attached figure is the SEM image of the finally repaired graphite material). From Figure 1 It can be seen that after treatment with the recycling and repair method provided by the present invention, there are no obvious cracks in the waste graphite material, and the surface grooves and fragments are reduced.

[0057] Figure 2 The Raman spectrum of graphite obtained by the recycling and repair method provided by Example 1 is shown. From Figure 2 It can be seen that after adding N-(2-hydroxyethyl) maleimide to repair the waste graphite, the ID / IG value is 0.428 after treatment. The D band corresponds to the disordered carbon and defects in the graphite structure, and the G band shows the integrity of the graphite layer. The smaller the ratio, the more ordered the graphite structure and the higher the degree of carbonization.

[0058] Example 2

[0059] This example provides a method for recycling and regenerating the graphite negative electrode of waste lithium-ion batteries. The recycling and regenerating method is as follows:

[0060] The waste lithium-ion batteries are immersed in 1.0 mol / L K2SO4 solution for 9 h and then dried. Then they are disassembled to obtain the anode materials. The anode materials are mechanically crushed and screened to separate the copper powder and graphite powder. The separated graphite powder is transferred to a tubular furnace and heated at 450 °C for 1 h under a nitrogen atmosphere. Then the graphite powder is immersed in a mixture of 1 mol / L oxalic acid and 4% hydrogen peroxide solution at 80 °C for 2 h. The acid-leached graphite is washed with deionized water and ethanol until neutral, and then the sample is dried in a blast drying oven at 60 °C for 12 h to obtain the purified waste lithium-ion battery graphite anode material;

[0061] A mixture of the purified waste lithium-ion battery graphite anode material (100 g) and N-(2-hydroxyethyl) maleimide (3 g) is stirred and heated at 800 °C for 2 h under a nitrogen atmosphere. After the reaction mixture is cooled to room temperature, isopropyl acetate (400 mL) is added. The product is filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.45 μm to collect the solid product, washed with NMP, and then dried under vacuum to obtain the recycled graphite anode material.

[0062] Example 3

[0063] This example provides a method for recycling and regenerating the graphite anode of waste lithium-ion batteries. The recycling and regeneration method is as follows:

[0064] The waste lithium-ion batteries are immersed in 1.0 mol / L K2SO4 solution for 10 h and then dried. Then they are disassembled to obtain the anode materials. The anode materials are mechanically crushed and screened to separate the copper powder and graphite powder. The separated graphite powder is transferred to a tubular furnace and heated at 650 °C for 1 h under a nitrogen atmosphere. Then the graphite powder is immersed in a mixture of 1 mol / L oxalic acid and 4% hydrogen peroxide solution at 80 °C for 2 h. The acid-leached graphite is washed with deionized water and ethanol until neutral, and then the sample is dried in a blast drying oven at 100 °C for 12 h to obtain the purified waste lithium-ion battery graphite anode material;

[0065] A mixture of the purified waste lithium-ion battery graphite anode material (100 g) and N-(2-hydroxyethyl) maleimide (5 g) is stirred and heated at 1200 °C for 1 h under a nitrogen atmosphere. After the reaction mixture is cooled to room temperature, isopropyl acetate (400 mL) is added. The product is filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.45 μm to collect the solid product, washed with NMP, and then dried under vacuum to obtain the recycled graphite anode material.

[0066] Example 4

[0067] This embodiment provides a method for recycling and regenerating the graphite anode of waste lithium-ion batteries. The recycling and regeneration method is as follows:

[0068] Put the waste lithium-ion battery into a 1.0 mol / L K2SO4 solution and soak it for 8 h, then dry it. Then disassemble it to obtain the anode material. Crush the anode material mechanically and screen it to separate the copper powder and graphite powder. Transfer the separated graphite powder to a tubular furnace and heat it at 650 °C for 1 h in a nitrogen atmosphere. Then soak the graphite powder in a mixture of 1 mol / L oxalic acid and 4% hydrogen peroxide solution at 80 °C for 2 h. Wash the acid-leached graphite with deionized water and ethanol until neutral. Then place the sample in a blast drying oven at 60 °C and dry it for 12 h to obtain the graphite anode material of waste lithium-ion batteries after impurity removal;

[0069] Stir a mixture of the graphite anode material of waste lithium-ion batteries after impurity removal (100 g) and bismaleimide resin (5 g), and heat it at 1200 °C in a nitrogen atmosphere for 1.5 h. After cooling the reaction mixture to room temperature, add isopropyl acetate (400 mL). Filter the product through a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.45 μm to collect the solid product, wash it with NMP, and then dry it under vacuum to obtain the recycled and regenerated graphite anode material.

[0070] Figure 3 The SEM images of graphite at different stages during the recycling and repair process of Example 4 are shown (the upper part of the attached figure is the SEM image of the graphite material of waste lithium-ion batteries after impurity removal, and the lower part of the attached figure is the SEM image of the graphite material obtained after final repair). From Figure 3 it can be seen that using bismaleimide resin also plays a good repair role.

[0071] Figure 4 The Raman spectrum of graphite obtained by the recycling and repair method provided in Example 4 is shown. From Figure 4 it can be obtained that the ID / IG value is 0.433 after treatment, which is close to that of Example 1 (ID / IG = 0.428), indicating a relatively high degree of carbonization.

[0072] Example 5

[0073] The difference between this embodiment and Example 1 is that the addition amount of N-(2-hydroxyethyl) maleimide in this embodiment is 2 g, that is, the mass ratio of the graphite anode material of waste lithium-ion batteries after impurity removal to N-(2-hydroxyethyl) maleimide is 100:2.

[0074] The remaining preparation methods and parameters are the same as those in Example 1.

[0075] Example 6

[0076] The difference between this example and Example 1 is that in this example, the addition amount of N-(2-hydroxyethyl) maleimide is 10 g, that is, the mass ratio of the waste lithium-ion battery graphite anode material after impurity removal to N-(2-hydroxyethyl) maleimide is 100:10.

[0077] The remaining preparation methods and parameters are the same as those in Example 1.

[0078] Example 7

[0079] The difference between this example and Example 1 is that in this example, N-(2-hydroxyethyl) maleimide is replaced by asphalt.

[0080] The remaining preparation methods and parameters are the same as those in Example 1.

[0081] Figure 5 The SEM images of graphite at different stages during the recycling and repair process of Example 7 are shown (the upper part of the attached figure is the SEM image of the waste lithium-ion battery graphite material after impurity removal, and the lower part of the attached figure is the SEM image of the finally repaired graphite material). From Figure 5 It can be seen that when asphalt is used as the repair material, the surface grooves and fragments of the repaired graphite material are more obvious.

[0082] Figure 6 The Raman spectrum of graphite obtained by the recycling and repair method provided in Example 7 is shown. From Figure 6 It can be obtained that the ID / IG value of the waste graphite after asphalt treatment is 0.576, indicating that the repair effect of asphalt on the graphite material is poor.

[0083] Example 8

[0084] The difference between this example and Example 1 is that in this example, the carbonization temperature when adding N-(2-hydroxyethyl) maleimide is 500 °C.

[0085] The remaining preparation methods and parameters are the same as those in Example 1.

[0086] Example 9

[0087] The difference between this example and Example 1 is that in this example, the carbonization temperature when adding N-(2-hydroxyethyl) maleimide is 1500 °C.

[0088] The remaining preparation methods and parameters are the same as those in Example 1.

[0089] Example 10

[0090] The difference between this embodiment and embodiment 1 is that, in this embodiment, after the mixing reaction, the product is directly filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size of 0.45 μm to collect the solid product, washed with NMP, and then dried under vacuum to obtain the recycled graphite negative electrode material, that is, the treatment process of isopropyl acetate is not carried out.

[0091] The rest of the preparation methods and parameters were the same as those in Example 1.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is that in this comparative example, N-(2-hydroxyethyl)maleimide is not added for mixing reaction, and the waste lithium-ion battery graphite negative electrode material after impurity removal is directly used as the recycled material.

[0094] The rest of the preparation methods and parameters were the same as those in Example 1.

[0095] Figure 7 The SEM image of graphite obtained by the recovery and repair method provided in Comparative Example 1 is shown. Figure 7 It can be seen that the graphite material after simple impurity removal treatment has obvious grooves and more fragments on the surface.

[0096] Figure 8 The Raman spectrum of graphite obtained by the recovery and repair method provided in Comparative Example 1 is shown. Figure 8 It can be concluded that the ID / IG value of the waste graphite after high-temperature treatment and impurity removal is 0.845, indicating that the repair effect is extremely poor.

[0097] The repaired or unrepaired (i.e., Examples 1-10 and Comparative Example 1) waste graphite was uniformly mixed with polyvinylidene fluoride (PVDF) and conductive carbon black in a mass ratio of 90:5:5, and an appropriate amount of N-methylpyrrolidone was added as a solvent, and stirred overnight on a magnetic stirrer to form a slurry. Then the slurry was evenly coated on the copper foil with an automatic coating machine, with a coating thickness of 100 μm, and then placed in a vacuum drying oven at 80°C overnight. The dried material was taken out and punched into a circular pole piece with a diameter of 12 mm, and packaged into a CR2025 button battery in a glove box with a battery shell, a gasket, a shrapnel, a lithium sheet, a diaphragm and an electrolyte. During the packaging process, 100 μL of electrolyte was added dropwise, and the electrolyte composition was 1 mol / L LiPF6 (EC: DMC: DEC = 1: 1: 1).

[0098] The performance of the lithium-ion batteries provided in Examples 1-10 and Comparative Example 1 was tested. The present invention used a CT-4008-5V20mA NEWARE battery test system to perform a constant current charge and discharge test on a CR2025 button battery at a rate of 0.1C (1C = 372mAh / g) for 2 weeks. The test results are shown in Table 1.

[0099] Table 1

[0100]

[0101]

[0102] It can be seen from Table 1 that:

[0103] From the data results of Example 1 and Examples 5 and 6, it can be known that if the mass ratio of the self-healing organic material to the waste lithium-ion battery graphite anode material after impurity removal is too small, that is, too little self-healing organic material is added, the performance of the regenerated graphite material cannot be uniformly repaired; if the mass ratio is too large, that is, too much self-healing organic material is added, although the repair effect is also achieved, there will be a problem of too much repair material, resulting in the influence on the conductivity of the regenerated graphite material.

[0104] From the data results of Example 1 and Example 7, it can be known that using maleimide material as the self-healing material can better improve the first-cycle Coulombic efficiency of the battery.

[0105] From the data results of Example 1 and Examples 8 and 9, it can be known that if the temperature of the mixed reaction is too low, the repair effect is not significant; if the temperature is too high, although it has a certain repair performance, it will lead to a decrease in the first-cycle Coulombic efficiency of the repaired graphite.

[0106] From the data results of Example 1 and Example 10, it can be known that if the product after the mixed reaction is not subjected to impurity removal treatment, it will affect the first charge specific capacity of the battery, thereby affecting the first-cycle Coulombic efficiency of the battery.

[0107] From the data results of Example 1 and Comparative Example 1, it can be known that for the graphite material obtained by the recycling and regeneration method provided by the present invention, its defects are repaired, meeting the requirements of the battery anode material and can be directly used for battery production.

[0108] In summary, for the recycling and regeneration method provided by the present invention, the waste lithium-ion battery graphite anode material after impurity removal is mixed with the self-healing organic material for reaction. The self-healing organic material undergoes a D-A reaction (Diels-Alder reaction), and the organic material after the D-A reaction is carbonized, thereby repairing the defects of the graphite material in the waste battery after impurity removal at the edge of the graphite, inhibiting the damage of the solvent to the graphite, promoting the charge transfer of lithium ions on the electrode surface, reducing the impedance of the SEI layer (solid electrolyte interface film) and the consumption of active lithium, improving the electrochemical performance of the regenerated graphite, and meeting the requirements of the battery anode material. The repaired graphite can be directly used for battery production, and the recycling and regeneration process has the advantages of simple process, high purification efficiency, and less consumption of non-renewable resources, which is conducive to sustainable development and large-scale production.

[0109] The applicant declares that the above description is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for recycling and regenerating the graphite negative electrode of waste lithium-ion batteries, characterized in that, The recycling and regeneration method includes the following steps: First, the waste lithium-ion battery is discharged, disassembled, crushed and screened to obtain the graphite anode material of the waste lithium-ion battery; The graphite anode material of the waste lithium-ion battery is heat-treated at 450-600 °C under a protective atmosphere, acid-leached and washed to obtain the graphite anode material of the waste lithium-ion battery after impurity removal; The N-(2-hydroxyethyl) maleimide material and the graphite anode material of the waste lithium-ion battery after impurity removal are mixed and reacted at a mass ratio of (3-5):100, carbonized at 850-1200 °C for 1-2 h, and then the carbonized substance is mixed with isopropyl acetate for impurity removal, solid-liquid separation, washing and drying to obtain the recycled and regenerated graphite anode material.

2. A recycled graphite anode material, characterized in that The recycled and regenerated graphite anode material is obtained by the recycling and regeneration method as described in claim 1.

3. A lithium-ion battery, characterized in that, The lithium-ion battery includes the recycled and regenerated graphite anode material as described in claim 2.

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