A green purification and restoration method for waste lithium ion battery graphite negative electrode material

Abstract

The present application belongs to the technical field of secondary battery material recycling and regeneration. More specifically, it relates to a green purification and repair method for graphite negative electrode material of waste lithium ion battery. The purification and repair method specifically comprises: disassembling the waste lithium ion battery to obtain negative electrode sheets coated with a graphite coating; separating the graphite coating on the surface of the negative electrode sheet; mixing the graphite coating and an aqueous solution of non-ionic surfactant, continuously introducing fine air bubbles, stirring and reacting, filtering, and collecting the filter cake; mixing the filter cake and a repair agent solution, stirring and reacting under heat preservation, filtering, and obtaining a repaired filter cake; the repair agent solution is mixed and compounded by mixing deionized water and an organic solvent at a volume ratio of 1:8-12; the organic solvent is selected from any one of polyethylene glycol or glycerol; after washing the repaired filter cake, drying, and low-temperature activation, the purification and repair are completed.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery material recycling technology. More specifically, it relates to a green purification and remediation method for graphite anode materials from waste lithium-ion batteries. Background Technology

[0002] With the widespread application of lithium-ion batteries, their waste volume is increasing daily. As a core component of lithium-ion batteries, the efficient recycling and high-value reuse of graphite anodes is crucial for promoting sustainable development throughout the battery's entire lifecycle. Currently, the recycling and processing of waste graphite anodes faces two main challenges: incomplete removal of impurities and irreversible damage to the graphite structure after long-term cycling.

[0003] Most existing recycling technologies focus on impurity removal. For example, while acid leaching can effectively remove metallic impurities, it generates a large amount of waste liquid, easily causing environmental pollution, and the intercalation effect of strong acids may further damage the crystal structure of graphite. High-temperature graphitization (temperatures typically above 2500℃) can repair some structural defects and remove impurities, but it is extremely energy-intensive and economically unfeasible, making large-scale application difficult. Furthermore, none of the above methods effectively solve the problems of persistent solid electrolyte interphase (SEI) film on the graphite surface, abnormally increased specific surface area, and loss of active sites.

[0004] Therefore, developing a low-cost, green recycling process that can achieve both deep purification and structural repair under mild conditions is crucial for promoting the direct reuse of waste graphite anodes. Summary of the Invention

[0005] The technical problem this invention aims to solve is the issue of incomplete impurity removal and difficulty in repairing irreversible damage to graphite structures caused by long-term use during the recycling and regeneration of existing lithium-ion battery anode materials. Based on these challenges, this invention provides a green purification and repair method for waste lithium-ion battery graphite anode materials.

[0006] The purpose of this invention is to provide a green purification and remediation method for graphite anode materials from waste lithium-ion batteries.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A green purification and remediation method for waste lithium-ion battery graphite anode materials, comprising the following steps:

[0009] Disassemble used lithium-ion batteries to obtain negative electrode sheets coated with graphite.

[0010] Separate the graphite coating from the surface of the negative electrode sheet;

[0011] The graphite coating and the aqueous solution of the nonionic surfactant were mixed at a solid-liquid ratio of 1:8-15. Micro air bubbles were continuously introduced at a temperature of 50-70℃ and the mixture was stirred for 90-150 min at a stirring speed of 200-400 r / min. The mixture was then filtered and the filter cake was collected.

[0012] Mix the filter cake and the repair agent solution at a solid-liquid ratio of 1:5-10, and keep the mixture at a temperature of 100-130℃ and a stirring speed of 100-300r / min for 2-5 hours. Then filter to obtain the repair filter cake.

[0013] The repair agent solution is prepared by mixing organic solvent and deionized water in a volume ratio of 1:8-12.

[0014] The organic solvent is selected from either polyethylene glycol or glycerol;

[0015] After cleaning the repaired filter cake, dry it and activate it at low temperature to complete the purification and repair process.

[0016] The beneficial effects of the above technical solution include:

[0017] The above technical solution employs a warm aqueous solution system of nonionic surfactants and continuously introduces microbubbles for treatment. Subsequently, a water-based remediation agent solution with a specific composition is used for further treatment at a higher temperature. In this way, the microbubbles can generate intense gas-liquid-solid three-phase interface interactions in the surfactant solution. During the rise of the bubbles, their huge specific surface area can efficiently adsorb surfactant molecules and hydrophobic organic pollutants detached by the surfactant. At the same time, the local microjets and high pressure generated when the microbubbles burst can further impact and detach metal oxide impurities attached to the graphite surface. The surfactant, through its hydrophilic-hydrophobic amphiphilic structure, wets and penetrates between the graphite and the impurities, lowers the detachment energy barrier, and stably disperses the detached impurities in the solution, preventing re-adsorption.

[0018] Furthermore, water-based repair agents, primarily composed of polyethylene glycol or glycerol, exert a dual effect of "solvent intercalation" and "structural relaxation" under heating and stirring conditions at 100-130℃. Organic solvent molecules penetrate into the interlayer spaces of graphite that have partially collapsed or become distorted due to cyclic damage, gently opening up the interlayer spacing through solvation forces and partially restoring lithium-ion transport channels. Simultaneously, this process helps the defective carbon atoms at the edges of graphite microcrystals to rearrange and anneal some amorphous carbon, thereby repairing the crystal structure.

[0019] Ultimately, it was achieved that waste graphite can be efficiently removed and its structure repaired under mild conditions without the use of strong acids, strong alkalis or strong oxidants, resulting in recycled graphite materials with significantly restored electrochemical properties. The process is green and environmentally friendly.

[0020] Furthermore, in the aqueous solution of the nonionic surfactant, the mass fraction of the nonionic surfactant is 0.05-0.2%;

[0021] The nonionic surfactant is selected from any one of tea saponin, alkyl glycoside, sophorolipid, rhamnolipid, polyglycerol fatty acid ester, and lecithin.

[0022] The aforementioned types and concentrations of natural nonionic surfactants possess strong hydrophilicity due to their polyhydroxy or glycoside units in their molecular structure, while their long-chain alkyl or steroidal structures provide hydrophobicity that matches the graphite surface and organic contaminants. At low concentrations, they operate near the critical concentration for micelle formation, where molecules are primarily adsorbed at the interface in monomolecular form, maximizing the reduction of interfacial tension and achieving efficient wetting and stripping. This also avoids the difficulty of subsequent separation caused by excessive micelle encapsulation of impurities, reducing the burden of subsequent cleaning and the complexity of wastewater treatment.

[0023] Furthermore, the continuous introduction of micro air bubbles includes:

[0024] Air is continuously introduced into the reactor through an aeration disc, wherein the average pore size of the aeration disc is 5-15 μm and the air supply pressure is 0.1-0.15 MPa.

[0025] Furthermore, the low-temperature activation includes:

[0026] In an inert atmosphere, heat-treat at a high temperature of 400-600℃ for 15-30 minutes, cool, and discharge to complete the low-temperature activation;

[0027] The inert atmosphere is selected from either nitrogen or argon atmosphere.

[0028] The above technical solution completely thermally decomposes (carbonizes) any trace amounts of surfactants and repair agents that may remain in the previous steps under an oxygen-free environment, preventing them from decomposing and generating gas during battery cycling. Secondly, this temperature can provide enough energy to promote the recrystallization of amorphous carbon and defective carbon atoms on the surface and edges of graphite particles, transforming them into a more ordered graphite microcrystalline structure, repairing the sp² carbon network, and thus reducing the irreversible capacity of the material.

[0029] Furthermore, the graphite coating on the surface of the separated negative electrode sheet includes:

[0030] The negative electrode sheet is immersed in hot water at a temperature of 80-90℃ for 4-6 hours. Then, it is subjected to ultrasonic treatment at an ultrasonic frequency of 180-200kHz for 2-4 hours to separate the No. 1 slurry and the negative electrode sheet with some residual negative electrode active material.

[0031] The negative electrode sheet containing some residual negative electrode active material was mixed with water at a mass ratio of 1:10 and then transferred to a hydrothermal reactor. After hydrothermal reaction, the mixture was ultrasonically treated for 20-30 minutes at an ultrasonic frequency of 80-100kHz. The No. 2 slurry was then separated. The No. 1 slurry and the No. 2 slurry were combined, filtered, and the water was removed to obtain a graphite coating.

[0032] Furthermore, the hydrothermal reaction includes: a hydrothermal reaction for 2-3 hours at a temperature of 120-140℃ and a pressure of 1.0-1.5MPa.

[0033] The above technical solution employs a hydrothermal reaction for further processing. In a sealed hydrothermal reactor, the water vapor pressure is extremely high, allowing it to penetrate every tiny pore at the interface between the coating and the copper foil, generating strong peeling stress. Upon cooling, the water vapor condenses, further disrupting the interfacial bonding.

[0034] Furthermore, the repair agent solution also includes 0.3-0.6% by mass of a silane coupling agent.

[0035] Furthermore, the silane coupling agent is selected from any one of silane coupling agents KH-540, KH-550, KH-560, KH-570, and KH-580.

[0036] The above technical solution further introduces silane coupling agents for auxiliary repair and regeneration. In this process, the silane coupling agent hydrolyzes to generate silanols. Its silanol groups can undergo dehydration condensation with the oxygen-containing photoenergy groups exposed on the graphite surface after purification, forming a strong chemical bond. Simultaneously, condensation occurs between the silanol groups of multiple silane molecules, crosslinking at the graphite particle surface and near-surface defects to form a thin, continuous, and robust Si-O-Si three-dimensional network structure, thereby further repairing microcracks or structural defects. Detailed Implementation

[0037] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0038] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0039] Example 1

[0040] Disassemble used lithium-ion batteries to obtain negative electrode sheets coated with graphite.

[0041] Specifically, the lithium battery is discharged to a voltage of 2.5V, then disassembled, the outer casing is removed to obtain the internal battery cell, the end tape of the battery cell is removed, and the positive electrode, separator and negative electrode are separated.

[0042] Separate the graphite coating from the surface of the negative electrode sheet;

[0043] Specifically, the negative electrode sheet was immersed in hot water at 80°C for 4 hours, and then subjected to ultrasonic treatment at an ultrasonic frequency of 180kHz for 2 hours to separate the No. 1 slurry and the negative electrode sheet with some residual negative electrode active material.

[0044] The negative electrode sheet containing some residual negative electrode active material was mixed with water at a mass ratio of 1:10 and then transferred to a hydrothermal reactor. The mixture was subjected to a hydrothermal reaction at 120℃ and 1.0MPa for 2 hours, followed by ultrasonic treatment at 80kHz for 20 minutes. Slurry #2 was obtained by separation. Slurries #1 and #2 were combined, filtered, and water was removed to obtain a graphite coating. The alkaline solution was selected from a 6% sodium bicarbonate solution.

[0045] The graphite coating and the aqueous solution of the nonionic surfactant were mixed at a solid-liquid ratio of 1:8. Micro air bubbles were continuously introduced at a temperature of 50°C and the mixture was stirred for 90 minutes at a stirring speed of 200 r / min. The mixture was then filtered and the filter cake was collected.

[0046] In the aqueous solution of the nonionic surfactant, the mass fraction of the nonionic surfactant is 0.05%; the nonionic surfactant is selected from tea saponin.

[0047] The continuous introduction of micro air bubbles includes:

[0048] Air is continuously introduced into the reactor through an aeration disc, wherein the average pore size of the aeration disc is 5μm and the air supply pressure is 0.1MPa.

[0049] The filter cake and the repair agent solution were mixed at a solid-liquid ratio of 1:5. The mixture was kept at 100℃ and stirred at 100r / min for 2 hours. After filtration, the repaired filter cake was obtained.

[0050] The repair agent solution is prepared by mixing organic solvent and deionized water in a volume ratio of 1:8.

[0051] The organic solvent is selected from polyethylene glycol 200;

[0052] In addition, the repair agent solution also includes 0.3% by mass of a silane coupling agent; the silane coupling agent is selected from silane coupling agent KH-540;

[0053] The filter cake is washed until the conductivity of the washing solution is <10μS / cm, then dried and activated at low temperature to complete the purification and repair.

[0054] The low-temperature activation is performed by heat treatment at 400°C for 30 minutes in an inert atmosphere, followed by cooling and discharge, thus completing the low-temperature activation.

[0055] The inert atmosphere is selected from nitrogen atmosphere.

[0056] Example 2

[0057] Disassemble used lithium-ion batteries to obtain negative electrode sheets coated with graphite.

[0058] Specifically, the lithium battery is discharged to a voltage of 2.5V, then disassembled, the outer casing is removed to obtain the internal battery cell, the end tape of the battery cell is removed, and the positive electrode, separator and negative electrode are separated.

[0059] Separate the graphite coating from the surface of the negative electrode sheet;

[0060] Specifically, the negative electrode sheet was immersed in hot water at 85°C for 5 hours, and then subjected to ultrasonic treatment at an ultrasonic frequency of 190kHz for 3 hours to separate the No. 1 slurry and the negative electrode sheet with some residual negative electrode active material.

[0061] The negative electrode sheet containing some residual negative electrode active material was mixed with water at a mass ratio of 1:10 and then transferred to a hydrothermal reactor. The mixture was subjected to a hydrothermal reaction at 130℃ and 1.2MPa for 2.5 hours, followed by ultrasonic treatment at 90kHz for 25 minutes. Slurry #2 was obtained by separation. Slurries #1 and #2 were combined, filtered, and water was removed to obtain a graphite coating. The alkaline solution was selected from a 7% sodium bicarbonate solution.

[0062] The graphite coating and the aqueous solution of the nonionic surfactant were mixed at a solid-liquid ratio of 1:12. Micro air bubbles were continuously introduced at a temperature of 60°C and the mixture was stirred for 120 min at a stirring speed of 300 r / min. The mixture was then filtered and the filter cake was collected.

[0063] Wherein, the aqueous solution of the nonionic surfactant has a mass fraction of 0.09%; the nonionic surfactant is selected from alkyl glycosides;

[0064] The continuous introduction of micro air bubbles includes:

[0065] Air is continuously introduced into the reactor through an aeration disc, wherein the average pore size of the aeration disc is 12μm and the air supply pressure is 0.12MPa.

[0066] The filter cake and the repair agent solution were mixed at a solid-liquid ratio of 1:8. The mixture was kept at 120℃ and stirred at 200r / min for 3 hours. After filtration, the repaired filter cake was obtained.

[0067] The repair agent solution is prepared by mixing organic solvent and deionized water in a volume ratio of 1:10.

[0068] The organic solvent is selected from polyethylene glycol 400;

[0069] In addition, the repair agent solution also includes 0.5% by mass of a silane coupling agent; the silane coupling agent is selected from silane coupling agent KH-550;

[0070] The filter cake is washed until the conductivity of the washing solution is <10μS / cm, then dried and activated at low temperature to complete the purification and repair.

[0071] The low-temperature activation is performed by heat treatment at 500°C for 20 minutes in an inert atmosphere, followed by cooling and discharge, thus completing the low-temperature activation.

[0072] The inert atmosphere is selected from argon atmosphere.

[0073] Example 3

[0074] Disassemble used lithium-ion batteries to obtain negative electrode sheets coated with graphite.

[0075] Specifically, the lithium battery is discharged to a voltage of 2.5V, then disassembled, the outer casing is removed to obtain the internal battery cell, the end tape of the battery cell is removed, and the positive electrode, separator and negative electrode are separated.

[0076] Separate the graphite coating from the surface of the negative electrode sheet;

[0077] Specifically, the negative electrode sheet was immersed in hot water at 90°C for 6 hours, and then subjected to ultrasonic treatment at an ultrasonic frequency of 200kHz for 4 hours to separate the No. 1 slurry and the negative electrode sheet with some residual negative electrode active material.

[0078] The negative electrode sheet containing residual negative electrode active material was mixed with water at a mass ratio of 1:10 and then transferred to a hydrothermal reactor. The mixture was subjected to a hydrothermal reaction at 140℃ and 1.5MPa for 3 hours, followed by ultrasonic treatment at 100kHz for 30 minutes. Slurry #2 was obtained by separation. Slurries #1 and #2 were combined, filtered, and water was removed to obtain a graphite coating. The alkaline solution was selected from an 8% sodium bicarbonate solution.

[0079] The graphite coating and the aqueous solution of the nonionic surfactant were mixed at a solid-liquid ratio of 1:15. Micro air bubbles were continuously introduced at a temperature of 70°C and the mixture was stirred for 150 min at a stirring speed of 400 r / min. The mixture was then filtered and the filter cake was collected.

[0080] In the aqueous solution of the nonionic surfactant, the mass fraction of the nonionic surfactant is 0.2%; the nonionic surfactant is selected from sophorolipids.

[0081] The continuous introduction of micro air bubbles includes:

[0082] Air is continuously introduced into the reactor through an aeration disc, wherein the average pore size of the aeration disc is 15μm and the air supply pressure is 0.15MPa.

[0083] The filter cake and the repair agent solution were mixed at a solid-liquid ratio of 1:10. The mixture was kept at 130℃ and stirred at 300r / min for 5 hours. After filtration, the repaired filter cake was obtained.

[0084] The repair agent solution is prepared by mixing organic solvent and deionized water in a volume ratio of 1:12.

[0085] The organic solvent is selected from glycerol;

[0086] In addition, the repair agent solution also includes 0.6% by mass of a silane coupling agent; the silane coupling agent is selected from silane coupling agent KH-560;

[0087] The filter cake is washed until the conductivity of the washing solution is <10μS / cm, then dried and activated at low temperature to complete the purification and repair.

[0088] The low-temperature activation is as follows: heat treatment at 600°C for 15 minutes in an inert atmosphere, followed by cooling and discharge, thus completing the low-temperature activation.

[0089] The inert atmosphere is selected from nitrogen atmosphere.

[0090] Example 4

[0091] The difference between this embodiment and Example 1 is that no silane coupling agent was added, while all other conditions remained unchanged.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is that an equal volume of anhydrous ethanol is used instead of polyethylene glycol, while all other conditions remain unchanged.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 1 is that no micro air bubbles were introduced, while all other conditions remained unchanged.

[0096] Comparative Example 3

[0097] The difference between this comparative example and Example 1 is that no nonionic surfactant was added, and deionized water was used instead of the aqueous solution containing the nonionic surfactant, while the other conditions remained unchanged.

[0098] The performance testing and evaluation of the products obtained from the above embodiments or comparative examples are as follows:

[0099] Take 10g of graphite samples before and after repair, and microwave digest them with aqua regia (HCl:HNO3=3:1) to completely convert them into a clear solution. Refer to the test method for impurity elements in GB / T 30835-2014 "Carbon Composite Lithium Iron Phosphate Cathode Material for Lithium-ion Batteries". The total content of Fe, Cu, Al, Mn, Co, Ni and Li impurity metal elements in the samples is shown in Table 1.

[0100] First assessment of coulomb efficiency and reversible capacity:

[0101] Repair graphite, conductive agent (acetylene black), and binder (PVDF) are mixed in a mass ratio of 92:3:5 to form a slurry, which is then evenly coated onto copper foil, dried, rolled, and punched to obtain the working electrode.

[0102] In an argon glove box, a CR2032 coin cell was assembled using lithium metal sheets as the counter and reference electrodes, Celgard 2400 as the separator, and 1M LiPF6 in EC / DEC (1:1 vol%) as the electrolyte.

[0103] The Blue Electricity testing system was used to perform charging and discharging in the voltage range of 0.005V-2.0V. First, constant current charging and discharging was performed at 0.1C (based on the theoretical capacity of graphite 372Ah / g), and the first discharge capacity (lithium insertion) and the first charge capacity (lithium removal) were recorded.

[0104] Initial Coulombic Efficiency (ICE) = (Initial Charge Capacity / Initial Discharge Capacity) × 100%

[0105] The capacity of the first charge is used as the reversible capacity.

[0106] Detailed test results are shown in Table 1;

[0107] Cyclic performance test:

[0108] After the first charge and discharge cycle is completed, constant current charge and discharge cycle is performed at 0.5C for 200 cycles. The capacity retention rate after 200 cycles is calculated as: Capacity retention rate = (Charging capacity in week N / Charging capacity in week 2) × 100%.

[0109] Detailed test results are shown in Table 1.

[0110] Table 1: Test Results

[0111] Total metal impurities content / ppm <![CDATA[Reversible capacity / mAh·g -1 > First Coulomb efficiency / % Capacity retention rate / % Example 1 120 362 91.2 97.2 Example 2 113 364 91.4 97.3 Example 3 109 365 91.5 97.5 Example 4 122 354 90.2 96.2 Comparative Example 1 690 320 89.5 92.2 Comparative Example 2 778 311 88.2 90.1 Comparative Example 3 684 316 89.2 91.3

[0112] As can be seen from the test results in Table 1, the negative electrode material obtained by the recycling method of the present invention has a lower impurity content and excellent electrochemical performance.

[0113] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A green purification and remediation method for graphite anode materials from waste lithium-ion batteries, characterized in that, The specific steps include: Disassemble used lithium-ion batteries to obtain negative electrode sheets coated with graphite. Separate the graphite coating from the surface of the negative electrode sheet; The graphite coating and the aqueous solution of the nonionic surfactant were mixed at a solid-liquid ratio of 1:8-15. Micro air bubbles were continuously introduced at a temperature of 50-70℃ and the mixture was stirred for 90-150 min at a stirring speed of 200-400 r / min. The mixture was then filtered and the filter cake was collected. The nonionic surfactant is selected from any one of tea saponin, alkyl glycoside, sophorolipid, and polyglycerol fatty acid ester; The continuous introduction of micro air bubbles includes: Air is continuously introduced into the reactor through an aeration disc, wherein the average pore size of the aeration disc is 5-15 μm and the air supply pressure is 0.1-0.15 MPa. Mix the filter cake and the repair agent solution at a solid-liquid ratio of 1:5-10, and keep the mixture at a temperature of 100-130℃ and a stirring speed of 100-300r / min for 2-5 hours. Then filter to obtain the repair filter cake. The repair agent solution is prepared by mixing organic solvent and deionized water in a volume ratio of 1:8-12. The organic solvent is selected from either polyethylene glycol or glycerol; After cleaning and drying the repaired filter cake, it is activated at a low temperature of 400-600℃ to complete the purification and repair process.

2. The green purification and remediation method for graphite anode material from waste lithium-ion batteries according to claim 1, characterized in that, In the aqueous solution of the nonionic surfactant, the mass fraction of the nonionic surfactant is 0.05-0.2%.

3. The green purification and remediation method for graphite anode material from waste lithium-ion batteries according to claim 1, characterized in that, The low-temperature activation includes: Heat treatment in an inert atmosphere for 15-30 minutes, cool, and discharge to complete low-temperature activation; The inert atmosphere is selected from either nitrogen or argon atmospheres.

4. A green purification and remediation method for graphite anode materials from waste lithium-ion batteries according to claim 1, characterized in that, The graphite coating on the surface of the separated negative electrode sheet includes: The negative electrode sheet is immersed in hot water at a temperature of 80-90℃ for 4-6 hours. Then, it is subjected to ultrasonic treatment at an ultrasonic frequency of 180-200kHz for 2-4 hours to separate the No. 1 slurry and the negative electrode sheet with some residual negative electrode active material. The negative electrode sheet containing some residual negative electrode active material was mixed with water at a mass ratio of 1:10 and then transferred to a hydrothermal reactor. After hydrothermal reaction, the mixture was ultrasonically treated for 20-30 minutes at an ultrasonic frequency of 80-100kHz. The No. 2 slurry was then separated. The No. 1 slurry and the No. 2 slurry were combined, filtered, and the water was removed to obtain a graphite coating.

5. A green purification and remediation method for graphite anode materials from waste lithium-ion batteries according to claim 4, characterized in that, The hydrothermal reaction includes: a hydrothermal reaction for 2-3 hours at a temperature of 120-140℃ and a pressure of 1.0-1.5MPa.

6. A green purification and remediation method for graphite anode materials from waste lithium-ion batteries according to claim 1, characterized in that, The repair agent solution also includes 0.3-0.6% by mass of a silane coupling agent.

7. A green purification and remediation method for graphite anode materials from waste lithium-ion batteries according to claim 6, characterized in that, The silane coupling agent is selected from any one of silane coupling agents KH-540, KH-550, KH-560, KH-570, and KH-580.