Green regeneration method of bio-based carbon coated waste lithium battery negative electrode material

Abstract

The invention relates to the field, in particular to a green regeneration method of a bio-based carbon coated waste lithium battery negative electrode material. The preparation method comprises the following steps: S1, raw material pretreatment: disassembling and classifying a waste lithium battery negative electrode material to obtain a battery negative electrode material; s2, foreign matter removal: carrying out impurity removal treatment on the battery negative electrode material to obtain an impurity-removed material; s3, coating carbonization: mixing the impurity-removed material with the bio-based carbon source coating material, and performing dispersion grinding, spray drying and carbonization repair to obtain a carbonized material; s4, modifying and doping: sequentially carrying out surface modification, boron source doping, crushing and packaging on the carbonized material to obtain the bio-based carbon-coated regenerated negative electrode material, and regenerating the waste lithium battery negative electrode material by utilizing the bio-based carbon source coating material, so that the method has the advantages of environmental friendliness and low cost. The regenerated lithium battery negative electrode material has relatively good reversible capacity, cycle capacity retention rate, tap density and first coulombic efficiency, and a relatively high repairing effect is obtained.

Description

Technical Field

[0001] This application relates to the field of green recycling of bio-based carbon-coated waste lithium battery anode materials. Background Technology

[0002] In recent years, with the rapid development of the electric vehicle industry and the continuous upgrading of vehicles, a considerable number of retired lithium-ion power batteries are generated in the market every year. These retired batteries contain abundant reusable resources. Their proper recycling not only achieves resource recycling and effectively alleviates resource shortages, but also avoids environmental pollution caused by improper disposal, which is of vital importance to ecological environmental protection. Therefore, the battery recycling industry has emerged and gradually become an important branch of environmental protection and resource utilization. Although the industry has made some progress in the recycling of high-value metal elements, the regeneration of anode materials has not received sufficient attention due to its low added value and high process complexity. However, in the long run, achieving closed-loop recycling of all components, including anode materials, has significant value and positive impact on improving the resource utilization rate of the entire battery industry, reducing carbon emissions, and promoting sustainable development. This not only helps companies reduce production costs and improve market competitiveness, but also aligns with the current global advocacy of green development, and has profound strategic significance for addressing climate change and protecting the Earth's environment.

[0003] Previously, for anode materials containing a large number of impurities recovered from lithium-ion batteries, the industry typically employed two main methods to purify and repair them. One was a chemical method, typically represented by acid washing, which involves reacting specific chemical solutions with impurities to remove them; the other was a physical method, with high-temperature heat treatment being common, using high temperatures to decompose or volatilize the impurities. To further improve the performance of the repaired anode materials, such as increasing rate capability and extending cycle life, existing technologies often involve carbon coating of purified graphite, with the selected coating materials mostly being petroleum-based products such as phenolic resin, asphalt, and epoxy resin. While these materials can improve the performance of anode materials to some extent, they have also revealed many problems in practical applications.

[0004] Most importantly, when using petroleum-based phenolic resin for carbon coating, the preparation and use processes typically rely on organic solvents for dispersion and dilution. These solvents are highly volatile, posing not only air pollution but also safety hazards, potentially leading to fires, explosions, and other accidents. Furthermore, these coating materials are non-renewable petroleum derivatives, and their widespread use contradicts the current trend of "low-carbon and environmentally friendly" industrial upgrading, hindering sustainable development. Finally, during the coating process, uneven dispersion of the organic resin can result in poor continuity and uneven thickness of the coating layer. This severely affects the overall conductive network and structural stability of the anode material, ultimately making it difficult for the repaired anode material to achieve ideal performance and meet the requirements of high-performance batteries. Summary of the Invention

[0005] The purpose of this application is to overcome the above-mentioned technical problems and provide a green recycling method for bio-based carbon-coated waste lithium battery anode materials.

[0006] A green recycling method for bio-based carbon-coated waste lithium battery anode materials, prepared by the following method: S1. Raw material pretreatment: Disassemble and classify the waste lithium battery negative electrode material to obtain the battery negative electrode material; S2. Foreign matter removal: The negative electrode material of the battery is treated to remove impurities, resulting in a cleaned material. S3, Coating and Carbonization: The impurity-removing material is mixed with the bio-based carbon source coating material, and then dispersed, ground, spray-dried, and carbonized to obtain carbonized material; S4. Modification and doping: The carbon material is subjected to surface modification, boron source doping, pulverization and packaging in sequence to obtain boron-doped bio-based carbon-coated regenerated anode material. The bio-based carbon source coating material comprises: a bio-based hydroxyl polymer aqueous pre-dispersion, natural rubber latex, water-soluble rosin resin liquid, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) aqueous dispersion, and emulsifier in a weight ratio of 10:(30-40):(15-23):(1-2):(0.5-2).

[0007] Using bio-based carbon source coating materials for the regeneration of waste lithium battery anode materials is environmentally friendly and enables green regeneration of these materials. It allows the regenerated lithium battery anode materials to possess better reversible capacity, cycle capacity retention, tap density, and initial coulombic efficiency, resulting in higher repair efficiency. Simultaneously, with the assistance of a bio-based hydroxyl polymer aqueous pre-dispersion, the emulsifier promotes the dispersion compatibility between the raw material system of the bio-based carbon source coating material, improving the mixing uniformity between the impurity removal material and the bio-based carbon source coating material. After dispersion, grinding, and spray drying, stable coated particles are formed, facilitating subsequent carbonization repair.

[0008] Specifically, the core solution of this invention uses a bio-based carbon source coating material, which is not a simple superposition of various environmentally friendly components, but rather produces a significant and unexpected synergistic effect through its specific chemical properties and physical states under certain formulation ratios. This synergy is manifested in the following three levels: First level: Synergistic dispersion and film formation to construct a uniform and stable aqueous coating precursor; The "medium-emulsification-thickening" three-phase stable system: The bio-based hydroxyl polymer aqueous pre-dispersion serves as a continuous hydrophilic viscous medium, providing a basic dispersion platform and film-forming framework for the entire system. The emulsifier's activity is effectively activated in this viscous medium, efficiently emulsifying and dispersing the hydrophobic natural rubber latex particles, preventing demulsification and aggregation. Simultaneously, the water-soluble rosin resin liquid, as a natural and highly efficient thickener and interfacial active substance, interweaves between the two, not only enhancing the overall system's adhesive stability but also forming a transition layer at the oil-water interface. This bridges and eliminates the compatibility differences between the hydrophilic polymer medium and the hydrophobic rubber particles, thus achieving highly uniform and stable dispersion of all components at the microscopic level, forming a composite colloid that can be stored for a long time.

[0009] The second level: the synergy between adhesion and structure forms a dense and stable composite coating layer. A three-dimensional bonding network of "rigid-flexible-wetting": During the subsequent drying and carbonization process, each component plays a complementary bonding role, synergistically constructing a stable coating structure. Bio-based hydroxyl polymers (such as sodium hydroxymethyl cellulose) form a rigid carbon skeleton after carbonization, providing structural support; natural rubber latex acts as a flexible bonding phase, its polymer chains shrinking and cross-linking during drying, imparting elasticity to the coating layer and buffering stress; water-soluble rosin resin, as an excellent wetting agent and auxiliary binder, significantly improves the wettability and adhesion between the coating material and the waste graphite surface. The three components work synergistically to form a composite coating precursor on the graphite surface, with a flexible and strongly bonded inner layer and a rigid outer layer resistant to volume changes. This structure is highly stable after spray drying, laying an ideal foundation for subsequent carbonization.

[0010] Third level: Synergy of conductivity and electrochemistry – endowing recycled materials with superior performance An integrated functional interface of "intrinsic conductivity-pyrolytic carbon-structural buffer": A poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) aqueous dispersion exists as a nanofiber network in the coating material, establishing an initial intrinsic conductive pathway before carbonization. During carbonization, the bio-based hydroxyl polymer and rosin resin pyrolyze to generate easily graphitized amorphous carbon, which fuses with the PEDOT:PSS network, strengthening and stabilizing the conductive network. Simultaneously, the soft carbon generated from the pyrolysis of natural rubber latex not only contributes to conductivity but, more importantly, its disordered carbon structure possesses excellent ion transport capabilities and buffering space. These three elements synergistically form a composite interface layer on the surface of recycled graphite that is both rigid and flexible, and exhibits dual ion-electron conductivity. This layer not only significantly reduces interfacial impedance and promotes rapid lithium-ion insertion / extraction (contributing to high first-cycle efficiency and high capacity), but its flexible components also effectively adapt to the volume changes of graphite during cycling, maintaining interfacial integrity (contributing to ultra-high cycle retention).

[0011] Synergistic Effect Summary: Through the above triple synergy, this coating system achieves a 1+1>2 effect: it successfully unifies the contradictory requirements of environmentally friendly water-based materials and high performance, organically integrating multiple independent functions such as dispersion, bonding, conductivity, and buffering into a whole within a single formulation through the physicochemical interactions between raw materials. This ultimately ensures optimization of the entire process from slurry dispersion to finished product performance. The resulting regenerated battery anode material exhibits superior repair performance, such as an initial coulombic efficiency exceeding 93%, a reversible capacity exceeding 345 mAh / g, a capacity retention rate exceeding 98% after 300 cycles, and a tap density exceeding 1.05 g / cm³.

[0012] Preferably, the bio-based hydroxy polymer in the aqueous predispersive solution is one or more of hydroxy chitosan, sodium hydroxymethyl cellulose, and polyhydroxy fatty acid esters.

[0013] This invention utilizes one or more of hydroxy chitosan, sodium hydroxymethyl cellulose, and polyhydroxy fatty acid esters as the aqueous pre-dispersion of a bio-based hydroxy polymer. It combines this with steps such as disassembling and classifying waste lithium-ion battery anode materials, removing impurities, mixing with bio-based carbon source coating materials for dispersion and grinding, spray drying, carbonization repair, surface modification, boron source doping, pulverization, and packaging. By leveraging the environmental friendliness of the bio-based carbon source coating materials, the invention achieves green recycling of waste lithium-ion battery anode materials. This results in recycled lithium-ion battery anode materials exhibiting better reversible capacity, cycle capacity retention, tap density, and initial coulombic efficiency, achieving a higher repair effect.

[0014] Preferably, the bio-based hydroxy polymer is composed of hydroxy chitosan, sodium hydroxymethyl cellulose, and polyhydroxy fatty acid ester.

[0015] First, the waste lithium battery anode materials are disassembled and classified to remove impurities, resulting in impurity-removed materials. Then, a bio-based carbon source coating material (including a bio-based hydroxyl polymer aqueous pre-dispersion solution, etc.) with a specific composition and weight ratio is mixed with the impurity-removed materials. After dispersion grinding, spray drying, and carbonization repair, carbonized materials are obtained. The carbonized materials are then subjected to surface modification and boron source doping treatments. Meanwhile, the bio-based hydroxyl polymer is composed of hydroxy chitosan, sodium hydroxymethyl cellulose, and polyhydroxy fatty acid esters. The whole method is more environmentally friendly and can greenly regenerate waste lithium battery anode materials. The regenerated lithium battery anode materials obtained have a reversible capacity of over 345 mAh / g, a capacity retention rate of over 98% after 300 cycles, a tap density recovery from 0.90 to over 1.05 g / cm³, and an initial coulombic efficiency of over 93%, demonstrating a high repair effect.

[0016] Preferably, the polyhydroxy fatty acid ester is one or a combination of multiple of poly(3-hydroxybutyrate), poly(hydroxyvalerate), and poly(3-hydroxybutyrate-3-hydroxyvalerate copolymer).

[0017] Using one or more of poly(3-hydroxybutyrate), poly(hydroxyvalerate), and poly(3-hydroxybutyrate-3-hydroxyvalerate copolymer) as polyhydroxy fatty acid esters, combined with the dismantling, sorting, impurity removal, mixing and dispersing grinding with a specific proportion of bio-based carbon source coating material, spray drying, carbonization repair, and subsequent surface modification, boron source doping, pulverization and packaging steps, the bio-based carbon source coating material is made environmentally friendly, enabling the green recycling of waste lithium battery anode materials. The resulting recycled lithium battery anode material has better reversible capacity, cycle capacity retention, tap density and first coulombic efficiency, achieving a high repair effect.

[0018] Preferably, the bio-based carbon source coating material is obtained by the following method: 1) Heat the natural rubber latex to 30-35℃ while stirring; slowly add water-soluble rosin resin solution and 1 / 2 emulsifier dropwise, controlling the drop rate to 1-5mL / min. After the dropwise addition is complete, continue stirring for 10-20min to allow the rubber latex and rosin resin to be fully compatible, thus obtaining emulsion A. 2) Slowly pour the bio-based hydroxy polymer aqueous pre-dispersion into emulsion A, increase the stirring speed to 600-700 r / min, and stir for 20-30 min; add the emulsifier and continue stirring to mix thoroughly and evenly to obtain emulsion B; 3) While stirring, slowly add poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) aqueous dispersion. After the addition is complete, stir for 20-30 minutes to ensure that the conductive phase is evenly dispersed in the composite emulsion. Then homogenize, adjust the pH to 7.5-8.5, and mature to obtain the bio-based carbon source coating material.

[0019] By preparing bio-based carbon source coating materials according to specific steps and parameters, rubber latex and rosin resin can be fully compatible, and the conductive phase can be uniformly dispersed in the composite emulsion, resulting in high-performance bio-based carbon source coating materials. Combined with raw material pretreatment, foreign matter removal, coating carbonization, modification and doping, green recycling of waste lithium battery anode materials can be achieved, enabling the recycled lithium battery anode materials to have better reversible capacity, cycle capacity retention, tap density and first coulombic efficiency, and obtain higher repair effect.

[0020] Preferably, the impurity removal process in step S2 is as follows: The primary battery negative electrode material is obtained by sieving through a multi-layer vibrating screen to separate impurities of different particle sizes, followed by air separation. The material is then immersed in a citric acid aqueous solution containing surfactants for acid washing and impurity removal, followed by washing and drying to obtain the impurity-removed material.

[0021] Multi-layer vibrating screens can separate impurities of different particle sizes, airflow separation further assists in impurity removal, and citric acid aqueous solution can remove some impurities. After washing and drying, impurities in the battery negative electrode material can be effectively removed, providing purer raw materials for subsequent processes such as coating and carbonization, which helps to improve the performance of the final boron-doped bio-based carbon-coated regenerated negative electrode material.

[0022] Preferably, the dispersion and grinding parameters in step S3 are as follows: ball-to-material ratio (5-10):1; the revolution speed of the planetary ball mill is 300-600 rpm, the rotation speed of the rotating arm is 600-1200 rpm, and the grinding time is 3-5 hours.

[0023] Dispersing and grinding the mixture of impurity removal material and bio-based carbon source coating material with a specific ball-to-material ratio, revolution speed, rotor speed and grinding time can ensure that the two are fully mixed, which is conducive to the formation of a good coating structure in the subsequent spray drying and carbonization repair process. This improves the green recycling effect of waste lithium battery anode materials and gives the recycled anode materials better electrochemical performance, such as improved reversible capacity, cycle capacity retention, tap density and first coulombic efficiency.

[0024] Preferably, the parameters for spray drying in step S3 are: inlet air temperature 150-180℃, outlet air temperature 85-100℃, and time 10-30 min.

[0025] The process involves dismantling and classifying waste lithium-ion battery anode materials to obtain battery anode materials, followed by impurity removal to obtain impurity-removed materials. These impurity-removed materials are then mixed with a bio-based carbon source coating material composed of a bio-based hydroxyl polymer aqueous pre-dispersion, natural rubber latex, water-soluble rosin resin liquid, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) aqueous dispersion, and emulsifier in a specific weight ratio. After dispersion and grinding under specific parameters, the mixture is spray-dried under conditions of 150-180℃ inlet air temperature, 85-100℃ outlet air temperature, and 10-30 minutes. Following carbonization repair, surface modification, boron source doping, pulverization, and packaging, this method not only enables the green recycling of waste lithium-ion battery anode materials, avoiding the secondary pollution and high energy consumption problems of traditional methods, but also allows the recycled lithium-ion battery anode materials to possess better reversible capacity, cycle capacity retention rate, tap density, and first coulombic efficiency, achieving a higher repair effect.

[0026] Preferably, the parameters for carbonization repair in step S3 are: carbonization temperature 780-820℃, holding time 3-4h, and heating rate 3-5℃ / min.

[0027] Waste lithium-ion battery anode materials are disassembled, sorted, and impurity-removed sequentially. The removed materials are then mixed with a bio-based carbon source coating material, dispersed, ground, and spray-dried. Carbonization repair is then carried out at a carbonization temperature of 780-820℃, held for 3-4 hours, and a heating rate of 3-5℃ / min. Following this, surface modification, boron source doping, pulverization, and packaging are performed. Using a bio-based carbon source coating material reduces the use of organic solvents, enabling green recycling of waste lithium-ion battery anode materials. These carbonization repair parameters ensure repair effectiveness while avoiding damage to the graphite crystal structure from excessively high temperatures. This improves the reversible capacity, cycle capacity retention, tap density, and initial coulombic efficiency of the recycled anode material, resulting in stable and efficient repair performance.

[0028] Preferably, the specific process of step S4 is as follows: The carbon material is immersed in a silane coupling agent hydrolysate and mixed thoroughly until the coupling agent is fully grafted onto the surface of the carbon material. After drying, a surface-modified carbon material is obtained. This material is then mixed thoroughly with a boron source, dried, and then heated at a rate of 2-3℃ / min, a doping temperature of 800-900℃, and a holding time of 3-4h. After cooling to below 150℃, the material is pulverized to obtain a boron-doped bio-based carbon-coated regenerated anode material.

[0029] First, the carbon layer defects are repaired by modifying with a silane coupling agent, and then boron source doping is performed to avoid boron atoms preferentially filling defect sites during the doping process, ensuring that the doped atoms are uniformly distributed in the carbon layer lattice. The doping temperature is slightly higher than the carbonization temperature in step S3, which not only utilizes residual heat to reduce energy consumption, but also avoids the collapse of the carbon layer structure through gradient heating. The porous structure of the bio-based carbon coating provides diffusion channels for boron atoms, and boron doping compensates for the lack of conductivity of bio-based carbon, achieving the effect of "coating protection-doping enhancement".

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. The bio-based carbon source coating material is environmentally friendly, significantly reducing the use of organic solvents and eliminating environmental pollution and safety hazards caused by the volatilization of organic solvents. In addition, the bio-based carbon source is renewable, which is in line with the trend of "low-carbon and environmentally friendly" industrial upgrading. 2. With the assistance of a bio-based hydroxy polymer aqueous pre-dispersion, the emulsifier greatly improves the dispersion compatibility of the bio-based carbon source coating material system, making the impurity removal material and the bio-based carbon source coating material more uniformly mixed. After specific dispersion, grinding and spray drying, stable coated particles are formed, creating favorable conditions for subsequent carbonization repair. This significantly improves the electrochemical performance of the regenerated battery anode material, such as an initial coulombic efficiency of 93-95%, a reversible capacity of over 345 mAh / g, a capacity retention rate of over 98% after 300 cycles, and a tap density that is effectively restored from 0.90 to over 1.05 g / cm³. 3. First, the surface of the carbide is modified using a silane coupling agent to repair defects in the carbon layer. Then, boron source doping is carried out to effectively prevent boron atoms from preferentially filling defect sites during doping, ensuring that the doped atoms are uniformly distributed in the carbon layer lattice. The doping temperature is slightly higher than the carbonization temperature, which can make full use of residual heat to reduce energy consumption and prevent the carbon layer structure from collapsing through gradient heating. The porous structure of the bio-based carbon coating provides diffusion channels for boron atoms. Boron doping compensates for the insufficient conductivity of bio-based carbon, achieving a significant synergistic effect of "coating protection - doping enhancement". Detailed Implementation

[0031] The present application will be further described in detail below with reference to the embodiments.

[0032] The CAS number for hydroxy chitosan is 123938-86-3; Sodium hydroxymethyl cellulose CAS No. 9085-26-1; The number-average molecular weight of polyhydroxy fatty acid esters is 2000-10000; The poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) aqueous dispersion is obtained by dispersing poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) in water. The CAS number of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) is 155090-83-8; the solubility is 1.3-1.7%. Poly(3-hydroxybutyrate) CAS number 26063-00-3, it is in powder form, and after grinding, it is sieved through a 1000-mesh sieve; Natural rubber latex, with a cured content of 30-40%; Water-soluble rosin resin liquid, brand: Shenghe Chemical HH8280EDIBHS.

[0033] Example of preparation of bio-based carbon source coating material Preparation Example 1 A bio-based carbon source coating material is obtained by the following method: 1) Heat the natural rubber latex to 35°C while stirring; slowly add water-soluble rosin resin solution and 1 / 2 emulsifier dropwise, controlling the drop rate at 3 mL / min. After the addition is complete, continue stirring for 25 min to allow the rubber latex and rosin resin to fully mix, thus obtaining emulsion A. 2) Slowly pour the bio-based hydroxy polymer aqueous predispersant into emulsion A, increase the stirring speed to 650 r / min, and stir for 25 min; add the remaining emulsifier, and continue stirring to mix thoroughly to obtain emulsion B; 3) While stirring, slowly add poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) aqueous dispersion. After the addition is complete, stir for 25 minutes to ensure that the conductive phase is evenly dispersed in the composite emulsion. Then homogenize twice at a pressure of 40 MPa, adjust the pH to 8.5, and mature for 4 hours at a temperature of 25°C to obtain the bio-based carbon source coating material.

[0034] The above-mentioned components—bio-based hydroxyl polymer aqueous predispersant, natural rubber latex, water-soluble rosin resin solution, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) aqueous dispersion, and emulsifier (OP-10)—are composed in a weight ratio of 10:38:18:1.5:1.5. The polyhydroxy fatty acid ester is a poly(3-hydroxybutyrate)-3-hydroxyvalerate copolymer.

[0035] Preparation Example 2 The difference between Preparation Example 2 and Preparation Example 1 lies in the amount of raw materials used and the process parameters, as detailed below: The weight ratio of the bio-based hydroxyl polymer aqueous predispersant, natural rubber latex, water-soluble rosin resin liquid, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) aqueous dispersion, and emulsifier is 10:30:15:1:0.5.

[0036] Process parameters: In step 1): Heat to 30℃, control the stirring rate at 5mL / min, and continue stirring for 20min; In step 2): Increase the stirring speed to 700 r / min and stir for 30 min; In step 3): Stir for 30 minutes and adjust the pH to 8.5.

[0037] Preparation Example 3 The difference between Preparation Example 3 and Preparation Example 1 lies in the amount of raw materials used and the process parameters, as detailed below: The weight ratio of the bio-based hydroxyl polymer aqueous predispersant, natural rubber latex, water-soluble rosin resin liquid, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) aqueous dispersion, and emulsifier is 10:40:23:2:2.

[0038] Process parameters: In step 1): Heat to 35°C, control the stirring rate at 1 mL / min, and continue stirring for 10 min; In step 2): Increase the stirring speed to 600 r / min and stir for 30 min; In step 3): Stir for 20 minutes and adjust the pH to 7.5.

[0039] Preparation Example 4 The difference between Preparation Example 4 and Preparation Example 1 is that the bio-based hydroxyl polymer is composed of sodium hydroxymethyl cellulose and polyhydroxy fatty acid ester in a weight ratio of 1.5:0.5.

[0040] Preparation Example 5 The difference between Preparation Example 5 and Preparation Example 1 is that the bio-based hydroxy polymer is composed of hydroxy chitosan, sodium hydroxymethyl cellulose, and polyhydroxy fatty acid ester in a weight ratio of 1:0.5:0.5.

[0041] Preparation of comparative examples Preparation of Comparative Example 1 The difference between Comparative Example 1 and Preparation Example 1 is that the bio-based hydroxy polymer aqueous predispersant was replaced with an equal amount of natural rubber latex.

[0042] Preparation of Comparative Example 2 The difference between Comparative Example 2 and Preparation Example 1 is that the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) aqueous dispersion was replaced with an equal amount of natural rubber latex.

[0043] Preparation of Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that natural rubber latex was replaced in equal amounts with water-soluble rosin resin liquid. Example

[0044] Example 1

[0045] A green recycling method for bio-based carbon-coated waste lithium battery anode materials includes the following steps: S1. Raw material pretreatment: After immersing the waste lithium battery in a 10% sodium chloride solution for 2 hours, discharge it, dry it, disassemble the battery, and then classify it to obtain the corresponding battery negative electrode material.

[0046] S2. Foreign Matter Removal: The battery negative electrode material is sieved through a multi-layer vibrating screen to separate impurities of different particle sizes. Then, airflow separation is used to separate impurities. The vibration frequency is 300Hz, the sieving time is 20min, and the airflow separation wind speed is 2m / s. The material after airflow separation (sieved through 500 mesh) is sent to a high-gradient magnetic separator (magnetic field strength 10000Gs). Magnetic metal impurities are separated by magnetic adsorption, which enhances the separation of light plastic impurities from the battery negative electrode material, resulting in primary battery negative electrode material. This material is then immersed in a 20% citric acid aqueous solution (containing 2wt% OP-10) and stirred at 50℃ for 30min. It is then rinsed and filtered with deionized water, and washed with clean water until the conductivity of the washing liquid is ≤50μS / cm. The resulting solid is dried in an oven at 100℃ for 3h to obtain the impurity-removed material.

[0047] S3, Coating and Carbonization: The impurity-removed material and the bio-based carbon source coating material obtained in Preparation Example 1 are mixed at a weight ratio of 10:3 and a ball-to-material ratio of 8:1. The planetary ball mill has a revolution speed of 300 rpm and a rotor speed of 1200 rpm. The grinding time is usually 4 hours. The mixture is then transferred to a spray drying oven. The spray drying parameters are: inlet air temperature 160℃, outlet air temperature 95℃, and time 20 minutes. Carbonization repair is obtained, and carbonized material is obtained.

[0048] S4. Modification and doping: The carbon material is subjected to surface modification, boron source doping, pulverization and packaging in sequence to obtain boron-doped bio-based carbon-coated regenerated anode material. Specifically, the carbon material is immersed in a silane coupling agent hydrolysate (KH-560 is added to a mixture of anhydrous ethanol and deionized water (volume ratio 1:1), glacial acetic acid is added dropwise to adjust the pH to 4, and the mixture is magnetically stirred for 30 min to obtain the hydrolysate. The mixture is thoroughly mixed until the coupling agent is fully grafted onto the surface of the carbon material. The mixture is then dried (drying at 80℃ for 5 h) to obtain a surface-modified carbon material. This material is then mixed evenly with a boron source (weight ratio 10:0.1), dried, and then heated at a rate of 2℃ / min, with a doping temperature of 880℃ and a holding time of 4 h. The temperature is then lowered to 145℃ and pulverized to obtain a boron-doped bio-based carbon-coated regenerated anode material.

[0049] The bio-based hydroxy polymer aqueous predispersant was obtained by dispersing 100 g / L of bio-based hydroxy polymer in water, and the bio-based hydroxy polymer was hydroxy chitosan.

[0050] Example 2

[0051] The difference between Example 2 and Example 1 lies in the process parameters and the bio-based carbon source coating material, as detailed below: Process parameters: The dispersion and grinding parameters in step S3 are as follows: ball-to-material ratio 5:1; planetary ball mill revolution speed 300 rpm, arm rotation speed 600 rpm, grinding time 5 h.

[0052] The parameters for spray drying in step S3 are: inlet air temperature 150℃, outlet air temperature 85℃, and time 30min.

[0053] The parameters for carbonization repair in step S3 are: carbonization temperature 780℃, holding time 4h, and heating rate 3℃ / min.

[0054] The heating rate was 2℃ / min, the doping temperature was 900℃, and the holding time was 3h.

[0055] The bio-based carbon source coating material was obtained from Preparation Example 2.

[0056] Example 3

[0057] The difference between Example 3 and Example 1 lies in the process parameters and the bio-based carbon source coating material, as detailed below: The dispersion and grinding parameters in step S3 are as follows: ball-to-material ratio 10:1; planetary ball mill revolution speed 600 rpm, arm rotation speed 1200 rpm, grinding time 3 hours.

[0058] The parameters for spray drying in step S3 are: inlet air temperature 180℃, outlet air temperature 100℃, and time 10min.

[0059] The parameters for carbonization repair in step S3 are: carbonization temperature 820℃, holding time 3h, and heating rate 5℃ / min.

[0060] The heating rate was 3℃ / min, the doping temperature was 800℃, and the holding time was 4h.

[0061] The bio-based carbon source coating material was obtained using Preparation Example 3.

[0062] Example 4

[0063] The difference between Example 4 and Example 1 is that the bio-based carbon source coating material obtained in Example 4 is used.

[0064] Example 5

[0065] The difference between Example 5 and Example 1 is that the bio-based carbon source coating material obtained in Example 5 is used.

[0066] Comparative example

[0067] Comparative example 1 The difference between Comparative example 1 and Example 1 is that the bio-based carbon source coating material obtained by preparing Comparative example 1 is used.

[0068] Comparative example 2 The difference between Comparative example 2 and Example 1 is that the bio-based carbon source coating material obtained by preparing Comparative example 1 is used.

[0069] Comparative example 3 The difference between Comparative example 3 and Example 1 is that the bio-based carbon source coating material obtained by preparing Comparative example 1 is used.

[0070] Detection method / Test method The boron-doped bio-based carbon-coated recycled anode materials obtained in Examples 1-5 and Comparative examples 1-3 were used for the following experimental tests.

[0071] Initial Coulomb efficiency: Refer to the test standard GB / T44027.1-2024 "Determination methods for carbon materials - Part 1: Determination of initial discharge specific capacity, initial Coulomb efficiency, and discharge capacity retention rate at different rates". If the initial Coulomb efficiency reaches more than 93%, it is recorded as qualified.

[0072] 2. Reversible capacity: Refer to GB / T44027.1-2024 "Determination methods for carbon materials - Part 1" and GB / T24533-2019 "Graphite-based anode materials for lithium-ion batteries", test conditions: Ambient temperature: 25°C, charge-discharge regime: For the second cycle: same as the initial Coulomb efficiency test, for the third cycle: constant current charge (0.1C) to 2.0V → constant voltage charge until the current < 0.05C → stand for 30 min → constant current discharge (0.1C) to 0.005V (record the discharge capacity).

[0073] Cycle capacity retention rate: The test method is based on: GB / T31484-2015 "Requirements and test methods for cycle life of power batteries for electric vehicles" and GB / T18287-2013 "Lithium-ion batteries and chargers for mobile phones", when repeated 300 times, its cycle capacity retention rate.

[0074] Tap density Refer to the tap density meter: Dandong Baite BT-312 type automatic tap density meter; Tap density test standard (≥1.05 g / cm³), test method basis: GB / T 5162-2021 "Determination of Tap Density of Metal Powders"; sample preparation: Vacuum dry the recycled anode material at 120 °C for 2 h, cool to room temperature, and use a tap density tester (amplitude 3 mm, frequency 250 times / min). If the tap density is above 1.05 g / cm³, it is recorded as qualified.

[0075] The above data is specifically shown in Table 1 as follows; Table 1 Experimental data of Examples 1-5 and Comparative Examples 1-3

[0076] Combining Example 1 and Comparative Examples 1-3 and referring to Table 1, it can be seen that the first Coulomb efficiency and tap density of Comparative Examples 1-3 are unqualified (the first Coulomb efficiency is less than 93%, and the tap density is less than 1.05 g / cm³), and both the reversible capacity and the retention rate of the cycle capacity are higher than those of Example 1. It shows that the bio-based carbon source coating material includes: bio-based hydroxy polymer water predispersion, natural rubber latex, water-soluble rosin resin solution, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) aqueous dispersion, and emulsifier in a weight ratio of 10:(30-40):(15-23):(1-2):(0.5-2). It not only has environmental protection, enables the green regeneration of waste lithium battery anode materials, but also the obtained regenerated lithium battery anode materials have better reversible capacity, retention rate of cycle capacity, tap density, and first Coulomb efficiency, achieving a higher repair effect.

[0077] This specific embodiment is only an interpretation of the present application, and it is not a limitation to the present application. After reading this specification, those skilled in the art can make modifications without creative contributions to this embodiment as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A green recycling method for bio-based carbon-coated waste lithium battery anode materials, characterized in that, It is prepared by the following method: S1. Raw material pretreatment: Disassemble and classify the waste lithium battery negative electrode material to obtain the battery negative electrode material; S2. Foreign matter removal: The negative electrode material of the battery is treated to remove impurities, resulting in a cleaned material. S3, Coating and Carbonization: The impurity-removing material is mixed with the bio-based carbon source coating material, and then dispersed, ground, spray-dried, and carbonized to obtain carbonized material; S4. Modification and doping: The carbon material is subjected to surface modification, boron source doping, pulverization and packaging in sequence to obtain boron-doped bio-based carbon-coated regenerated anode material. The bio-based carbon source coating material comprises: a bio-based hydroxyl polymer aqueous pre-dispersion, natural rubber latex, water-soluble rosin resin liquid, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) aqueous dispersion, and emulsifier in a weight ratio of 10:(30-40):(15-23):(1-2):(0.5-2).

2. The green recycling method for bio-based carbon-coated waste lithium battery anode material according to claim 1, characterized in that: The bio-based hydroxy polymer in the aqueous predispersed solution is one or more of hydroxy chitosan, sodium hydroxymethyl cellulose, and polyhydroxy fatty acid esters.

3. The green recycling method for bio-based carbon-coated waste lithium battery anode material according to claim 2, characterized in that: The bio-based hydroxy polymer is composed of hydroxy chitosan, sodium hydroxymethyl cellulose, and polyhydroxy fatty acid esters.

4. The green recycling method for bio-based carbon-coated waste lithium battery anode material according to claim 3, characterized in that: The polyhydroxy fatty acid ester is one or a combination of multiple of poly(3-hydroxybutyrate), poly(hydroxyvalerate), and poly(3-hydroxybutyrate-3-hydroxyvalerate copolymer).

5. A green recycling method for bio-based carbon-coated waste lithium battery anode material according to any one of claims 1-4, characterized in that, Bio-based carbon source coatings are obtained by the following methods: 1) Heat the natural rubber latex to 30-35℃ while stirring; slowly add water-soluble rosin resin solution and 1 / 2 emulsifier dropwise, controlling the drop rate to 1-5mL / min. After the dropwise addition is complete, continue stirring for 10-20min to allow the rubber latex and rosin resin to be fully compatible, thus obtaining emulsion A. 2) Slowly pour the bio-based hydroxy polymer aqueous pre-dispersion into emulsion A, increase the stirring speed to 600-700 r / min, and stir for 20-30 min; add the emulsifier and continue stirring to mix thoroughly and evenly to obtain emulsion B; 3) While stirring, slowly add poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) aqueous dispersion. After the addition is complete, stir for 20-30 minutes to ensure that the conductive phase is evenly dispersed in the composite emulsion. Then homogenize, adjust the pH to 7.5-8.5, and mature to obtain the bio-based carbon source coating material.

6. A green recycling method for bio-based carbon-coated waste lithium battery anode material according to claim 1, characterized in that, The impurity removal process in step S2 is as follows: The primary battery negative electrode material is obtained by sieving through a multi-layer vibrating screen to separate impurities of different particle sizes, followed by air separation. The material is then immersed in a citric acid aqueous solution containing surfactants for acid washing and impurity removal, followed by washing and drying to obtain the impurity-removed material.

7. A green recycling method for bio-based carbon-coated waste lithium battery anode material according to claim 1, characterized in that: The dispersion and grinding parameters in step S3 are as follows: ball-to-material ratio (5-10):1; the revolution speed of the planetary ball mill is 300-600 rpm, the rotation speed of the rotating arm is 600-1200 rpm, and the grinding time is 3-5 hours.

8. A green recycling method for bio-based carbon-coated waste lithium battery anode material according to claim 1, characterized in that, The parameters for spray drying in step S3 are: inlet air temperature 150-180℃, outlet air temperature 85-100℃, and time 10-30 min.

9. A green recycling method for bio-based carbon-coated waste lithium battery anode material according to claim 1, characterized in that... The parameters for carbonization repair in step S3 are: carbonization temperature 780-820℃, holding time 3-4h, and heating rate 3-5℃ / min.

10. A green recycling method for bio-based carbon-coated waste lithium battery anode material according to claim 1, characterized in that, The specific process of step S4 is as follows: The carbon material is immersed in a silane coupling agent hydrolysate and mixed thoroughly until the coupling agent is fully grafted onto the surface of the carbon material. After drying, a surface-modified carbon material is obtained. This material is then mixed thoroughly with a boron source, dried, and then heated at a rate of 2-3℃ / min, a doping temperature of 800-900℃, and a holding time of 3-4h. After cooling to below 150℃, the material is pulverized to obtain a boron-doped bio-based carbon-coated regenerated anode material.

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