Preparation method of graphite negative electrode material compounded by regenerated graphite and catalytic biochar and graphite negative electrode material thereof

Abstract

The application relates to the technical field of lithium ion battery negative electrode materials, and discloses a preparation method of a regenerated graphite and catalytic biochar composite graphite negative electrode material and the graphite negative electrode material. The preparation method of the regenerated graphite and catalytic biochar composite graphite negative electrode material takes waste lithium ion battery graphite and biomass powder as raw materials, prepares regenerated graphite through discharge disassembly, thermal repair and carbon coating, prepares catalytic biochar through catalytic electrolysis, and then carries out shearing and compounding, thermal treatment and repair and other steps on the regenerated graphite and the catalytic biochar, so that the total content of metal impurities in the prepared regenerated graphite and catalytic biochar composite graphite negative electrode material is small, the tap density is 1.01-1.07 g / cm 3 , the first coulombic efficiency is 91.3%-93.9%, the 1C rate capacity retention rate reaches 92.2%-95.4%, and the 100-week cycle capacity attenuation rate is only 0.029%-0.046% / week.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery anode material technology, and in particular to a method for preparing a graphite anode material composed of recycled graphite and catalytic biochar, and the graphite anode material thereof. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and no memory effect, are widely used in consumer electronics, new energy vehicles, energy storage systems, and other fields. Graphite materials are the most important anode materials for lithium-ion batteries. With the rapid development of the power battery industry, the output of waste lithium-ion batteries has increased significantly. Recycling graphite resources from waste batteries can not only reduce the manufacturing cost of anode materials but also reduce resource waste and environmental pollution.

[0003] In existing technologies, the regeneration and repair of graphite from waste batteries mostly employs single methods such as heat treatment and ball milling. Although the repaired graphite can restore some electrochemical performance, its rate performance still has significant shortcomings and cannot meet the high-rate charge and discharge requirements of high-end power batteries. Meanwhile, biomass-based carbon materials have become a research hotspot due to their wide availability, environmental friendliness, and excellent conductivity. Electrochemical graphitized biochar can provide excellent conductivity, but it has structural defects. Its porous structure and low packing density dilute the overall tap density of the material when combined with recycled graphite, resulting in a reduction in active material per unit volume. This leads to a decrease in the overall volumetric energy density and initial coulombic efficiency of the composite material, which to some extent restricts the combined application of recycled graphite and biomass carbon materials in high-end lithium-ion batteries. Summary of the Invention

[0004] To at least overcome one of the problems existing in the prior art, one objective of this application is to provide a method for preparing a graphite anode material composed of recycled graphite and catalytic biochar. This method involves thermally treating and combining recycled graphite obtained through thermal repair and carbon coating with catalytic biochar obtained through catalytic electrolysis. This results in a graphite anode material with low metal impurity content, a tap density in the range of 1.01~1.07 g / cm³, an initial coulombic efficiency exceeding 91.3%, a 1C rate capacity retention exceeding 92%, and a 100-cycle capacity decay rate of less than 0.05% / week. The overall preparation method is simple, requires no complex or special equipment, meets the needs of industrial production, and fully utilizes waste lithium-ion battery graphite and biomass waste, achieving resource recycling, reducing the manufacturing cost of the anode material, and meeting the development needs of a green and low-carbon industry. A second objective of this application is to provide the aforementioned graphite anode material.

[0005] Therefore, this application adopts the following technical solution: The first aspect of this application provides a method for preparing a graphite anode material composed of recycled graphite and catalytic biochar, comprising the following steps: S1. Mixed recycled graphite and catalytic biochar, sheared and dispersed to obtain composite precursor powder; S2. The composite precursor powder is subjected to heat treatment, cooling, pulverization and sieving to obtain the graphite anode material composed of recycled graphite and catalytic biochar. The method for preparing the recycled graphite is as follows: waste lithium-ion batteries are discharged, crushed, screened, and impurities are removed. After being thermally repaired at 600~1000℃, they are mixed with carbon source precursors and carbon coating is performed to obtain recycled graphite. The method for preparing the catalytic biochar is as follows: mixing biomass powder, nickel catalyst, and molten salt, and then performing catalytic electrolysis at a temperature of 700~900℃ and a voltage of 2.2~3.0V to obtain catalytic biochar.

[0006] In the preparation method of the graphite anode material composed of recycled graphite and catalytic biochar in this application, recycled graphite obtained through thermal repair and carbon coating is combined with catalytic biochar obtained through nickel-catalyzed molten salt electrolysis. The two waste resources are then subjected to shear dispersion and heat treatment in sequence to ensure thorough microscopic mixing. Specifically, the recycled graphite obtained from waste lithium-ion batteries, after removing impurities, effectively repairs the crystal defects in the graphite, fills the surface pores, improves its structural stability, and solves the problem of electrochemical performance degradation after graphite regeneration, providing a foundation for high capacity and tap density in the composite material. Meanwhile, the catalytic biochar, under the synergistic effect of the nickel catalyst and molten salt electrolysis, lowers the activation energy of biomass graphitization and provides a stable ion conduction environment. Specific temperature and voltage ranges facilitate the full catalytic graphitization of biomass, resulting in catalytic biochar with uniform structure and good conductivity.

[0007] Preferably, in step S1, the mass ratio of the regenerated graphite to the catalytic biochar is (3~7):(2~5). More preferably, in step S1, the mass ratio of the regenerated graphite to the catalytic biochar is (4~7):(2~5). Even more preferably, in step S1, the mass ratio of the regenerated graphite to the catalytic biochar is (4.5~7):(3~5).

[0008] Within the aforementioned mass ratio range of recycled graphite to catalytic biochar, the problem of reduced tap density and insufficient volumetric energy density of graphite anode material caused by excessive addition of catalytic biochar is effectively avoided. At the same time, the problem of insufficient conductive network construction and limited rate performance improvement caused by excessive addition of recycled graphite is also avoided.

[0009] Preferably, in step S1, the rotational speed of the shear dispersion is 8000~15000 r / min, and the time is 10~60 min. More preferably, in step S1, the rotational speed of the shear dispersion is 9500~15000 r / min, and the time is 20~60 min. Even more preferably, in step S1, the rotational speed of the shear dispersion is 11000~15000 r / min, and the time is 20~60 min.

[0010] The shearing dispersion at a speed of 8000~15000 r / min generates sufficient shearing and impact forces, enabling the recycled graphite and catalytic biochar to be uniformly dispersed at the microscopic level to form a composite precursor powder with uniform phase distribution. This avoids agglomeration and the formation of large particles, laying the foundation for the formation of a continuous conductive network in subsequent heat treatment. The dispersion time of 10~60 min balances dispersion effect and production efficiency, avoiding uneven dispersion caused by too short a time and preventing production efficiency from being affected by too long a time.

[0011] Preferably, in step S2, the heat treatment temperature is 800~1200℃, the time is 1~5h, and the heat treatment is carried out in an inert atmosphere. More preferably, in step S2, the heat treatment temperature is 850~1200℃, the time is 2~5h, and the heat treatment is carried out in an inert atmosphere.

[0012] The heat treatment temperature of 800~1200℃ in step S2 helps the interface between the regenerated graphite and the catalytic biochar to fully fuse, enhance the interfacial bonding force between the two phases, and allow the conductive channels of the catalytic biochar and the matrix of the regenerated graphite to intertwine to form a stable three-dimensional conductive network, thereby improving the structural stability and charge transport efficiency of the composite graphite anode material. Meanwhile, the inert atmosphere effectively isolates the air, avoids the oxidation reaction of the composite precursor powder at high temperature, prevents the graphite structure from being damaged or the conductivity of the catalytic biochar from decaying, and ensures the electrochemical performance and structural integrity of the final graphite anode material.

[0013] Preferably, in the method for preparing recycled graphite, the heat treatment holding time is 1.5~5 hours, and the heat treatment is carried out in an inert atmosphere. More preferably, in the method for preparing recycled graphite, the heat treatment holding time is 2~5 hours, and the heat treatment is carried out in an inert atmosphere.

[0014] Preferably, the inert atmosphere gas is selected from one or more of nitrogen and argon. More preferably, the inert atmosphere gas is selected from nitrogen.

[0015] Preferably, in the method for preparing recycled graphite, the carbon source precursor is selected from at least one of acetylene, methane, ethylene, and sucrose. More preferably, in the method for preparing recycled graphite, the carbon source precursor is selected from at least one of acetylene, methane, and ethylene. Even more preferably, in the method for preparing recycled graphite, the carbon source precursor is selected from acetylene.

[0016] Preferably, in the method for preparing recycled graphite, the carbon coating treatment is carried out at a temperature of 600-800°C for 1-3 hours. More preferably, in the method for preparing recycled graphite, the carbon coating treatment is carried out at a temperature of 650-800°C for 2-3 hours.

[0017] At temperatures of 600-800℃, the carbon source precursor is fully carbonized to form a dense carbon coating layer. This avoids the problem of excessive graphitization and brittleness of the carbon coating layer caused by excessively high temperatures, which would result in the loss of lithium-ion transport advantages. It also prevents problems such as incomplete carbonization of the carbon source and loose coating layer that are easy to fall off due to excessively low temperatures. The carbon coating treatment time of 1-3 hours ensures that the carbon source is fully deposited and uniformly coated on the surface of the recycled graphite, forming a carbon coating layer of moderate thickness. This avoids the problem of discontinuous coating layer and inability to effectively repair graphite defects due to too short a time, and the problem of excessively thick coating layer and increased lithium-ion transport resistance due to too long a time. This ensures the ion transport efficiency and structural stability of the recycled graphite.

[0018] Preferably, in the method for preparing catalytic biochar, the biomass powder is selected from at least one of straw powder and fruit shell powder. More preferably, the fruit shell powder is selected from at least one of coconut shell powder, walnut shell powder, and apricot shell powder. Even more preferably, the fruit shell powder is selected from coconut shell powder.

[0019] Preferably, in the method for preparing catalytic biochar, the nickel catalyst is selected from at least one of nickel nitrate, nickel sulfate, and nickel chloride. More preferably, in the method for preparing catalytic biochar, the nickel catalyst is selected from at least one of nickel nitrate and nickel sulfate.

[0020] Preferably, the mass of the nickel catalyst is 3% to 9% of the mass of the biomass powder. More preferably, the mass of the nickel catalyst is 4% to 9% of the mass of the biomass powder. More preferably, the mass of the nickel catalyst is 6% to 9% of the mass of the biomass powder.

[0021] Straw powder and nutshell powder are agricultural wastes that are not only widely available and inexpensive, but their natural fibrous structure also facilitates the formation of a porous conductive network during electrolysis. Nickel nitrate, nickel sulfate, or nickel chloride, used as nickel catalysts, are reduced to metallic nickel at high temperatures, effectively catalyzing the transformation of carbon in the biomass powder into a graphitized structure. The mass of the nickel catalyst is within the range of 3% to 9% of the biomass powder mass, ensuring sufficient distribution of catalytic active centers while avoiding the problems of insufficient catalysis due to too low a dosage or nickel particle agglomeration due to too high a dosage, which would reduce catalytic efficiency.

[0022] Preferably, in the method for preparing catalytic biochar, the molten salt is selected from at least one of lithium chloride-potassium chloride, sodium carbonate-potassium chloride, and lithium fluoride-sodium chloride. More preferably, in the method for preparing catalytic biochar, the molten salt is selected from at least one of lithium chloride-potassium chloride and lithium fluoride-sodium chloride.

[0023] Preferably, the mass of the molten salt is 1.3 to 8 times the mass of the biomass powder. More preferably, the mass of the molten salt is 2 to 8 times the mass of the biomass powder. Even more preferably, the mass of the molten salt is 5 to 8 times the mass of the biomass powder.

[0024] Preferably, the method for preparing the catalytic biochar further includes: after electrolysis, washing the product with deionized water until neutral, and drying it at 80~120℃ to obtain catalytic biochar.

[0025] Lithium chloride-potassium chloride, sodium carbonate-potassium chloride, and lithium fluoride-sodium chloride are eutectic point molten salt systems. As electrolytic media, they can form a uniform molten state at 700–900℃, providing excellent ionic conductivity and heat transfer environment for the electrochemical reaction, ensuring its smooth progress. Furthermore, these molten salts are chemically stable and do not undergo side reactions with biomass or nickel catalysts, avoiding the generation of impurities. The molten salt mass being 1.3–8 times the mass of the biomass powder ensures complete immersion of the biomass powder in the molten salt, allowing for sufficient contact between the biomass, molten salt, and catalyst, thereby improving the uniformity and completeness of the electrolytic reaction. Simultaneously, the selected molten salts are all readily soluble in water, allowing for rapid removal by washing after the electrolytic reaction, preventing residual molten salt from affecting the conductivity and lithium-ion transport properties of the biochar.

[0026] Preferably, the method for preparing the recycled graphite specifically includes the following steps: Lithium-ion batteries were immersed in a 10wt% sodium chloride aqueous solution and discharged for 40-56 hours. After discharge, the batteries were removed, washed with water, and dried in an oven at 65-75℃ for 3-5 hours. The resulting powder was then transferred to a shear crusher and crushed at 1000-1500 rpm for 20-30 minutes. The powder was passed through a 150-200 mesh vibrating sieve, and the waste graphite powder was collected. This powder was added to 1-2 mol / L dilute hydrochloric acid, maintaining a solid-liquid ratio of 1:(5-8) (g / mL), and stirred at room temperature for 2-3 hours for acid washing to remove impurities. After filtration, the powder was washed with water until neutral and then vacuum dried at 100℃ for 10-12 hours to obtain pretreated graphite powder. The pretreated graphite powder was then... Graphite powder is placed in a corundum boat and pushed into a tube furnace. Nitrogen gas is introduced and the flow rate is controlled at 90-120 mL / min. After purging the air for 30 min, the temperature is increased to 600-1000℃ at a rate of 5-10℃ / min and held for 1.5-5 h for heat repair treatment. The temperature is then adjusted to 600-800℃, and nitrogen gas is continued to be introduced and the flow rate is controlled at 180-200 mL / min. A carbon source precursor is introduced and the flow rate is controlled at 20-35 mL / min for carbon coating treatment for 1-3 h. The carbon source precursor is then turned off, and nitrogen gas is continued to be introduced to cool to room temperature, thus obtaining regenerated graphite.

[0027] Preferably, the method for preparing the catalytic biochar specifically includes the following steps: Take biomass powder, nickel catalyst, and molten salt, and premix for 5-10 min; transfer to a ball mill for ball milling to ensure uniform dispersion of each component; transfer to a mold with a diameter of 15 mm, and press under a pressure of 10-20 MPa for 1-2 min to form a disc with a thickness of 2-3 mm; wrap the disc with a nickel mesh, fix it with molybdenum wire as the cathode, use a graphite rod as the anode, assemble it in a tubular electrolytic furnace, introduce argon gas and control the argon gas flow rate at 80-110 mL / min, remove the air and continue to maintain the argon gas flow rate, heat to 700-900 °C at a heating rate of 5-10 °C / min, apply a constant voltage of 2.2-3.0 V DC voltage for 8-10 h, cool, wash until neutral, and vacuum dry to obtain catalytic biochar.

[0028] The second aspect of this application provides a graphite anode material composed of recycled graphite and catalytic biochar, which is prepared by the method for preparing the graphite anode material composed of recycled graphite and catalytic biochar described in the first aspect of this application.

[0029] Compared with the prior art, this application has at least the following beneficial effects: 1) The method for preparing a graphite anode material composed of recycled graphite and catalytic biochar in this application involves thermally repairing and carbonizing waste lithium-ion battery graphite to obtain recycled graphite, effectively repairing the lattice defects generated during long-term cycling of waste graphite and filling surface pores, providing a high-capacity main framework for the composite graphite anode material. Simultaneously, catalytic biochar is prepared by nickel-catalyzed molten salt electrolysis of biomass powder, achieving efficient graphitization conversion of biomass. The composite of recycled graphite and catalytic biochar retains the high capacity and tap density advantages of recycled graphite while introducing a three-dimensional conductive network constructed by catalytic biochar, achieving a synergistic improvement in high volumetric energy density and high rate performance.

[0030] 2) In the preparation method of the graphite anode material composed of recycled graphite and catalytic biochar in this application, the recycled graphite and catalytic biochar are compounded at a specific mass ratio of (3~7):(2~5), and high-speed shear dispersion and heat treatment are carried out in sequence to make the two phase materials uniformly distributed at the microscopic level and achieve full fusion of the interface to form a stable three-dimensional conductive network. The tap density of the graphite anode material prepared in this application is in the range of 1.01~1.07 g / cm3, the initial coulombic efficiency can reach more than 91.3%, and the 1C rate capacity retention rate exceeds 92%.

[0031] 3) The graphite anode material composed of recycled graphite and catalytic biochar in this application has excellent cycle stability. The heat treatment allows the two-phase interface to be fully fused, effectively buffering the volume expansion of the graphite anode material during charge and discharge, and suppressing capacity decay. The capacity decay rate after 100 cycles is less than 0.05% / week.

[0032] 4) The preparation method of this application uses waste lithium-ion battery graphite and biomass powder waste as raw materials, realizing the synergistic utilization of the two waste carbon materials. Compared with the use of pure natural graphite or artificial graphite, it greatly reduces the manufacturing cost. At the same time, the method has simple steps, does not require complex special equipment, and meets the requirements of industrial-scale production. Detailed Implementation

[0033] The following detailed description of the contents of this application is provided through specific embodiments, comparative examples, and tables, but is not limited to all the arguments and data.

[0034] Preparation example: Example of recycled graphite preparation: Preparation Example 1: A method for preparing recycled graphite specifically includes the following steps: Take 100 kg of waste 18650 lithium-ion batteries, immerse them in a 10 wt% sodium chloride aqueous solution, and after 48 hours of full discharge, remove them, rinse the surface with clean water, and dry them in a 70℃ oven for 3 hours. Transfer them to a shear crusher and crush them at 1200 r / min for 30 minutes. Pass them through a 150-mesh vibrating screen and collect the waste graphite powder that passes through the screen. Add the powder to 1 mol / L dilute hydrochloric acid, maintaining a solid-liquid ratio of 1:5 (g / mL), and stir at room temperature for 2 hours to remove impurities by acid washing. After filtration, wash the filter cake with deionized water until the filtrate is neutral, and vacuum dry it at 100℃ for 12 hours to obtain pretreated graphite powder. Place the pretreated graphite powder in a corundum boat, push it into a tube furnace, and introduce nitrogen gas with a flow rate controlled at 100 m³ / h. After purging the air for 30 minutes, the temperature was increased to 800℃ at a rate of 5℃ / min, and held at that temperature for 2 hours for heat repair treatment. The temperature was then reduced to 700℃, and nitrogen gas was continuously introduced at a flow rate of 200 mL / min. Acetylene gas was introduced at a flow rate of 20 mL / min for carbon coating treatment for 2 hours. After that, the acetylene gas was turned off, and nitrogen gas was continuously introduced to cool the carbon to room temperature, thus obtaining regenerated graphite.

[0035] Preparation Example 2: A method for preparing recycled graphite is the same as in Preparation Example 1, except that the thermal repair temperature in Preparation Example 2 is 950°C.

[0036] Preparation Example 3: A method for preparing recycled graphite is the same as in Preparation Example 1, except that the acetylene gas flow rate in Preparation Example 3 is 30 mL / min.

[0037] Example of catalytic biochar preparation: Preparation Example 4: A method for preparing catalytic biochar specifically includes the following steps: Take 100g coconut shell powder, 6g nickel nitrate, and 500g lithium chloride-potassium chloride molten salt (molten salt molar ratio of 59:41), add them to a polytetrafluoroethylene beaker, and stir with a glass rod for 5-10 minutes to premix. Transfer to an alumina ball mill jar, add zirconia grinding balls (controlling the ball-to-material mass ratio to 3.5:1), place in a planetary ball mill, and ball mill at 200 rpm for 40 minutes to ensure uniform dispersion of the components. Transfer to a 15mm diameter mold, press under 15MPa pressure for 1 minute to form a 2-3mm thick disc. Wrap the disc with a nickel mesh, fix it with molybdenum wire as the cathode, use a high-purity graphite rod as the anode, assemble in a tubular electrolytic furnace, introduce argon gas and control the argon gas flow rate to 100... After removing air at a flow rate of mL / min for 30 min, the argon flow rate was maintained, and the temperature was increased to the electrolysis temperature of 850℃ at a heating rate of 8℃ / min. A constant voltage of 2.5V DC was applied for electrolysis for 8 h. The mixture was then cooled to room temperature under argon protection, removed, washed three times with 0.5mol / L dilute hydrochloric acid, washed with deionized water until neutral, and then vacuum dried at 100℃ for 12 h to obtain catalytic biochar.

[0038] High-purity graphite rods refer to graphite materials with a carbon content ≥ 99.99% and an ash content ≤ 100ppm.

[0039] Preparation Example 5: A method for preparing catalytic biochar is the same as in Preparation Example 4, except that the catalytic electrolysis temperature in Preparation Example 5 is 750°C.

[0040] Preparation Example 6: A method for preparing catalytic biochar is the same as in Preparation Example 4, except that the catalytic electrolysis voltage in Preparation Example 6 is 3.0V.

[0041] Preparation of comparative examples: Comparative example of recycled graphite preparation: Preparation of Comparative Example 1: A method for preparing recycled graphite is the same as in Preparation Example 1, except that the thermal repair temperature in Preparation Comparative Example 1 is 1100℃.

[0042] Preparation of Comparative Example 2: A method for preparing recycled graphite is the same as in Preparation Example 1, except that in Preparation Comparative Example 2, after heat repair treatment, it is directly cooled to room temperature without carbon coating treatment.

[0043] Preparation of Comparative Example 3: A method for preparing recycled graphite specifically includes the following steps: Take 100 kg of waste 18650 lithium-ion batteries, immerse them in a 10 wt% sodium chloride aqueous solution, and after 48 hours of full discharge, remove them, rinse the surface with clean water, and dry them in a 70℃ oven for 3 hours. Transfer them to a shear crusher and crush them at 1200 r / min for 30 minutes. Pass them through a 150-mesh vibrating screen and collect the waste graphite powder that passes through the screen. Add the powder to 1 mol / L dilute hydrochloric acid, maintaining a solid-liquid ratio of 1:5 (g / mL), and stir at room temperature for 2 hours to remove impurities by acid washing. After filtration, wash the filter cake with deionized water until the filtrate is neutral, and vacuum dry it at 100℃ for 12 hours to obtain pretreated graphite powder. Place the pretreated graphite powder in a corundum boat, push it into a tube furnace, and introduce nitrogen gas with a flow rate controlled at 100 m³ / h. After purging the air for 30 minutes, the temperature was increased to 700℃ at a rate of 5℃ / min. Nitrogen gas was continuously introduced and the flow rate was controlled at 200 mL / min. Acetylene gas was introduced and the flow rate was controlled at 20 mL / min. After carbon coating treatment for 2 hours, the acetylene was turned off, and nitrogen gas was continuously introduced to cool to room temperature, thus obtaining regenerated graphite.

[0044] Comparative example of catalytic biochar preparation: Preparation of Comparative Example 4: A method for preparing catalytic biochar is the same as that for preparation example 4, except that the catalytic electrolysis temperature in preparation example 4 is 650℃.

[0045] Preparation of Comparative Example 5: A method for preparing catalytic biochar is the same as in Preparation Example 4, except that the catalytic electrolysis voltage in Preparation Comparative Example 5 is 3.5V.

[0046] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices used in this application can be obtained from conventional commercial sources.

[0047] Examples of methods for preparing graphite anode materials composed of recycled graphite and catalytic biochar: The preparation method of the graphite anode material composed of recycled graphite and catalytic biochar of this application specifically includes the following steps: S1. The recycled graphite and catalytic biochar in a mass ratio of (3~7):(2~5) are put into a high-speed shearing machine and sheared and dispersed at a speed of 8000~15000 r / min for 10~60 min to obtain composite precursor powder. S2. The composite precursor powder is loaded into an alumina boat and placed in a tube furnace. Under an inert atmosphere, the temperature is raised to 800-1200℃ at a heating rate of 3-10℃ / min and held for 1-5 hours for heat treatment. After cooling to room temperature, the material is pulverized with a pulverizer and passed through a 200-300 mesh sieve to obtain a graphite anode material composed of recycled graphite and catalytic biochar.

[0048] The preparation method of recycled graphite is as follows: Lithium-ion batteries are immersed in a 10wt% sodium chloride aqueous solution, discharged for 40-56 hours, then removed, washed with water, and dried in an oven at 65-75℃ for 3-5 hours; transferred to a shear crusher and crushed at 1000-1500 r / min for 20-30 minutes; passed through a 150-200 mesh vibrating sieve, and the waste graphite powder collected is added; added to 1-2 mol / L dilute hydrochloric acid, maintaining a solid-liquid ratio of 1:(5-8) (g / mL), stirred at room temperature for 2-3 hours for acid washing to remove impurities; filtered, washed with water until neutral, and vacuum dried at 100℃ for 10-12 hours to obtain pretreated graphite. Pretreated graphite powder was placed in a corundum boat and pushed into a tube furnace. Nitrogen gas was introduced and the flow rate was controlled at 90-120 mL / min. After purging the air for 30 min, the temperature was increased to 600-1000℃ at a rate of 5-10℃ / min and held for 1.5-5 h for heat repair treatment. The temperature was adjusted to 600-800℃, and nitrogen gas was introduced and the flow rate was controlled at 180-200 mL / min. A carbon source precursor was introduced and the flow rate was controlled at 20-35 mL / min. After carbon coating treatment for 1.5-2 h, the carbon source precursor was turned off, and nitrogen gas was introduced to cool to room temperature to obtain regenerated graphite. The preparation method of catalytic biochar is as follows: Take biomass powder, nickel catalyst, and molten salt, and premix for 5-10 min; transfer to a ball mill for ball milling to ensure uniform dispersion of each component; transfer to a mold with a diameter of 15 mm, and press under a pressure of 10-20 MPa for 1-2 min to form a disc with a thickness of 2-3 mm; wrap the disc with a nickel mesh, fix it with molybdenum wire as the cathode, use a graphite rod as the anode, assemble it in a tubular electrolytic furnace, introduce argon gas and control the argon gas flow rate at 80-110 mL / min, remove the air and continue to maintain the argon gas flow rate, heat to 700-900 °C at a heating rate of 5-10 °C / min, apply a constant voltage of 2.2-3.0 V DC voltage for 8-10 h, cool, wash until neutral, and vacuum dry to obtain catalytic biochar.

[0049] Regarding step S1, in some specific implementations, the mass ratio of regenerated graphite to catalytic biochar can be 3:2, 5:2, 4:2, 7:4, or 7:5, the rotation speed of shear dispersion can be 8000 r / min, 9000 r / min, 11000 r / min, 13000 r / min, or 15000 r / min, and the time can be 10 min, 30 min, 40 min, or 60 min.

[0050] Regarding step S2, in some specific embodiments, the heating rate can be 3℃ / min, 5℃ / min, 8℃ / min, or 10℃ / min; the heat treatment temperature can be 800℃, 850℃, 950℃, or 1200℃; and the time can be 1h, 2h, 4h, or 5h. The inert atmosphere gas can be selected from one or more of nitrogen and argon.

[0051] Regarding the preparation method of recycled graphite, in some specific embodiments, the crushing rotation speed can be 1000 r / min, 1200 r / min, 1400 r / min, or 1500 r / min, and the crushing time can be 20 min, 25 min, or 30 min; the nitrogen flow rate for thermal remediation can be 90 mL / min, 100 mL / min, or 120 mL / min, the heating rate can be 5 °C / min, 6 °C / min, 8 °C / min, or 10 °C / min, and the thermal remediation temperature can be 600 °C, 750 °C, or 800 °C. The temperature can be 900℃ or 1000℃, and the holding time can be 1.5h, 2h, 3h, 4h or 5h; the carbon coating temperature can be 600℃, 700℃ or 800℃, the carbon coating nitrogen flow rate can be 180mL / min, 190mL / min or 200mL / min, the carbon source precursor gas flow rate can be 20mL / min, 25mL / min, 30mL / min or 35mL / min, and the carbon coating treatment time can be 1h, 2h or 3h; the carbon source precursor can be selected from at least one of acetylene, methane, ethylene and sucrose.

[0052] In some specific embodiments of the method for preparing catalytic biochar, the argon flow rate can be 80 mL / min, 90 mL / min, or 110 mL / min; the heating rate can be 5℃ / min, 8℃ / min, or 10℃ / min; the catalytic electrolysis temperature can be 700℃, 750℃, 850℃, or 900℃; the catalytic electrolysis voltage can be 2.2V, 2.5V, or 3.0V; and the time can be 8h, 9h, or 10h. The biomass powder can be selected from at least one of straw powder and fruit shell powder, wherein the fruit shell powder can be selected from at least one of coconut shell powder, walnut shell powder, or apricot shell powder. The nickel catalyst can be selected from at least one of nickel nitrate, nickel sulfate, or nickel chloride. The mass of the nickel catalyst is 3%, 4%, 6%, 7%, or 9% of the mass of the biomass powder. The molten salt can be selected from at least one of lithium chloride-potassium chloride, sodium carbonate-potassium chloride, or lithium fluoride-sodium chloride. The mass of the molten salt is 1.3 times, 3 times, 5 times, 7 times, or 8 times the mass of the biomass powder.

[0053] Based on the preparation method of the graphite anode material composed of recycled graphite and catalytic biochar according to this application, the following examples and comparative examples are provided: Example 1

[0054] A method for preparing a graphite anode material composed of recycled graphite and catalytic biochar, specifically including the following steps: S1. 500g of recycled graphite from Preparation Example 1 and 200g of catalytic biochar from Preparation Example 4 were put into a high-speed shear mill and sheared and dispersed at 9000 r / min for 40 min to obtain composite precursor powder. S2. The composite precursor powder is loaded into an alumina boat and placed in a tube furnace. Nitrogen gas is introduced and the flow rate is controlled at 100 mL / min. The air is removed for 30 min, and the flow rate is maintained. The temperature is increased to 900℃ at a rate of 5℃ / min and held for 3 h for heat treatment. After cooling to room temperature, the material is pulverized with a pulverizer and passed through a 200-mesh sieve to obtain a graphite anode material composed of recycled graphite and catalytic biochar. Example 2

[0055] The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as that in Example 1, except that in step S1 of Example 2, the recycled graphite in Preparation Example 1 is replaced by the recycled graphite in Preparation Example 2, and the catalytic biochar in Preparation Example 4 is replaced by the catalytic biochar in Preparation Example 5. Example 3

[0056] The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as that in Example 1, except that in step S1 of Example 3, the recycled graphite in Preparation Example 1 is replaced by the recycled graphite in Preparation Example 3, and the catalytic biochar in Preparation Example 4 is replaced by the catalytic biochar in Preparation Example 6. Example 4

[0057] The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as that in Example 1, except that the catalytic biochar in step S1 of Example 4 is replaced by the catalytic biochar in Example 5. Example 5

[0058] The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as in Example 1, except that the shearing speed in step S1 of Example 5 is 11000℃. Example 6

[0059] The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as in Example 1, except that the heat treatment temperature of step S2 in Example 6 is 1200℃.

[0060] Comparative Example 1: The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as that in Example 1, except that the recycled graphite in step S1 of Comparative Example 1 is replaced by an equal amount of recycled graphite from Comparative Example 1.

[0061] Comparative Example 2: The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as that in Example 1, except that the recycled graphite in step S1 of Comparative Example 2 is replaced by recycled graphite in Comparative Example 2.

[0062] Comparative Example 3: The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as that in Example 1, except that the recycled graphite in Comparative Example 3 is replaced by recycled graphite in Comparative Example 3.

[0063] Comparative Example 4: The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as that in Example 1, except that in Comparative Example 4, step S1 is replaced with an equal amount of catalytic biochar prepared in Comparative Example 4.

[0064] Comparative Example 5: The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as that in Example 1, except that in Comparative Example 5, the catalytic biochar in step S1 of the preparation example 4 is replaced with the catalytic biochar prepared in Comparative Example 5.

[0065] Comparative Example 6: The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as in Example 1, except that the shearing speed in step S1 of Comparative Example 6 is 7000℃. Comparative Example 7: The preparation method of a graphite anode material composed of recycled graphite and catalytic biochar is the same as in Example 1, except that the heat treatment temperature in step S2 of Comparative Example 7 is 1250℃. Material performance testing: The graphite anode materials obtained in Examples 1-6 and Comparative Examples 1-7 were subjected to various performance tests, and the test methods are as follows: 1. Total content of iron, nickel and copper: The content of metallic impurities iron, nickel and copper in the graphite anode material was detected by ICP-OES inductively coupled plasma spectroscopy, and the total content of iron, nickel and copper was calculated by adding them together.

[0066] 2. Tap density: Tested using an automatic tap density meter.

[0067] 3. Electrical Performance Testing: Graphite anode material, Super P, CMC, and SBR were mixed in a mass ratio of 95:1.5:1.5:2 to form a slurry, which was then uniformly coated onto copper foil. After drying, the slurry was cut into circular electrode sheets with a diameter of 12 mm. Using lithium metal sheets as the counter electrode, CR2032 coin cell half-cells were assembled in an argon-protected glove box. Under a voltage window of 0.005~2.0V and a temperature of 25℃, the initial discharge capacity, initial charge capacity, and initial coulombic efficiency were tested using a Blue Electric testing system. The initial coulombic efficiency was calculated as: (Initial charge capacity / Initial discharge capacity) × 100%. Further testing was conducted at the same 0.1C rate. The battery was subjected to charge-discharge cycles at 0.1C, 0.5C, and 1C rates, with 10 cycles at each rate. The charging capacity of the last cycle at each rate was recorded, and the capacity retention rate at that rate was calculated: Capacity retention rate at a certain rate = Charging capacity at that rate / Initial charging capacity at 0.1C rate × 100%. Constant current charge-discharge cycles were performed at 1C rate, and the discharge capacity of the first and 100th cycles was recorded. The 100-cycle capacity decay rate at that rate was calculated: 100-cycle capacity decay rate at a certain rate = [1 - (Discharge capacity of the 100th cycle / Discharge capacity of the 1st cycle)] / 100 × 100%.

[0068] The test results are shown in Table 1: The test performance of the graphite anode materials of Examples 1-6 and Comparative Examples 1-7 is shown in Table 1 below:

[0069] The preparation methods of the graphite anode materials composed of recycled graphite and catalytic biochar in Examples 1-6 use waste lithium-ion battery graphite and biomass powder as raw materials. Recycled graphite is prepared through discharge dismantling, thermal repair, and carbon coating. Catalytic biochar is prepared through catalytic electrolysis. Then, the recycled graphite and catalytic biochar are subjected to shearing composite and thermal treatment repair steps. This results in a graphite anode material composed of recycled graphite and catalytic biochar with low total content of metal impurities (iron, nickel, and copper), a tap density of 1.01-1.07 g / cm3, an initial coulombic efficiency of 91.3%-93.9%, a 1C rate capacity retention of 92.2%-95.4%, and a 100-cycle capacity decay rate of only 0.029%-0.046% / week. This indicates that the graphite anode material prepared by the method of this application has significantly improved and optimized electrochemical performance.

[0070] Comparative Examples 1-3 are all methods for preparing recycled graphite, and some parameters or steps are outside the scope of this application. Compared with Example 1, the graphite anode materials of Comparative Examples 1-3 show varying degrees of decline in various properties. The total content of iron, nickel, and copper is all higher than 35 ppm, the tap density is generally low, and the highest 1C capacity retention rate is only 90.1%. This may be because the heat repair temperature of Comparative Example 1 is too high, resulting in excessive sintering of the graphite lattice and an increase in structural defects; Comparative Example 2 did not undergo carbon coating treatment, resulting in many surface defects and high porosity of graphite, which in turn leads to poor interfacial bonding between recycled graphite and catalytic biochar; and the recycled graphite preparation process of Comparative Example 3 does not sufficiently repair the lattice of waste graphite and has limited impurity removal effect. All three factors lead to insufficient structural stability of the recycled graphite itself, resulting in increased metal impurity content, low tap density, and a downward trend in electrical properties such as first coulombic efficiency of the obtained graphite anode material.

[0071] In Comparative Examples 4 and 5, the electrolysis parameters of the catalytic biochar were outside the scope of this application. Compared with Example 1, the impurity content of the graphite anode materials in Comparative Examples 4 and 5 was higher, the 1C capacity retention rate decreased, and the 100-cycle capacity decay rate increased. This may be because the electrolysis temperature of Comparative Example 4 was too low, resulting in insufficient graphitization of the biomass and an imperfect conductive structure of the generated catalytic biochar, leading to poor fluidity and ion conduction of the molten salt system. In Comparative Example 5, the electrolysis voltage was too high, causing local over-reaction of the biomass, defects in the structure of the catalytic biochar, and easy introduction of impurities. The removal and conversion of metal impurities were insufficient, ultimately resulting in a decrease in the rate performance and cycle stability of the graphite anode material.

[0072] Comparative Examples 6 and 7 represent cases where the shear speed and heat treatment temperature during the composite process of recycled graphite and catalytic biochar are outside the range of this application. Compared with Example 1, the tap density of both is no higher than 0.96 g / cm3, and the electrochemical performance is significantly reduced. This may be because the shear dispersion speed of Comparative Example 6 is insufficient, resulting in uneven dispersion of recycled graphite and catalytic biochar, easy agglomeration, and insufficient interfacial bonding between the two phases, making it difficult to form a continuous and stable conductive network. On the other hand, the heat treatment temperature of Comparative Example 7 is too high, which may cause local ablation of the graphite structure, excessive reaction at the interface between the two phases, and damage to the integrity of the final graphite anode material structure, thereby leading to a decrease in tap density and related electrochemical performance.

[0073] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application. For those skilled in the art, other variations or modifications can be made based on the above description. Any obvious variations or modifications derived from the technical solutions of this application are still within the protection scope of this application.

Claims

1. A method for preparing a graphite anode material composed of recycled graphite and catalytic biochar, characterized in that, Includes the following steps: S1. Mixed recycled graphite and catalytic biochar, sheared and dispersed to obtain composite precursor powder; S2. The composite precursor powder is subjected to heat treatment, cooling, pulverization and sieving to obtain the graphite anode material composed of recycled graphite and catalytic biochar. The method for preparing the recycled graphite is as follows: waste lithium-ion batteries are discharged, crushed, screened, and impurities are removed. After being thermally repaired at 600~1000℃, they are mixed with carbon source precursors and carbon coating is performed to obtain recycled graphite. The method for preparing the catalytic biochar is as follows: mixing biomass powder, nickel catalyst, and molten salt, and then performing catalytic electrolysis at a temperature of 700~900℃ and a voltage of 2.2~3.0V to obtain catalytic biochar.

2. The method for preparing the graphite anode material composed of recycled graphite and catalytic biochar according to claim 1, characterized in that, In step S1, the mass ratio of the regenerated graphite to the catalytic biochar is (3~7):(2~5).

3. The method for preparing the graphite anode material composed of recycled graphite and catalytic biochar according to claim 1, characterized in that, In step S1, the rotation speed of the shearing dispersion is 8000~15000 r / min, and the time is 10~60 min.

4. The method for preparing the graphite anode material composed of recycled graphite and catalytic biochar according to claim 1, characterized in that, In step S2, the heat treatment temperature is 800~1200℃, the time is 1~5h, and the heat treatment is carried out in an inert atmosphere.

5. The method for preparing the graphite anode material composed of recycled graphite and catalytic biochar according to claim 1, characterized in that, In the method for preparing the recycled graphite, the heat treatment holding time is 1.5 to 5 hours, and the heat treatment is carried out in an inert atmosphere.

6. The method for preparing the graphite anode material composed of recycled graphite and catalytic biochar according to claim 1, characterized in that, In the method for preparing recycled graphite, the carbon source precursor is selected from at least one of acetylene, methane, ethylene, and sucrose.

7. The method for preparing the graphite anode material composed of recycled graphite and catalytic biochar according to claim 1, characterized in that, In the method for preparing the recycled graphite, the carbon coating treatment is carried out at a temperature of 600~800℃ for 1~3h.

8. The method for preparing the graphite anode material composed of recycled graphite and catalytic biochar according to claim 1, characterized in that, In the method for preparing catalytic biochar, the biomass powder is selected from at least one of straw powder and fruit shell powder; the nickel catalyst is selected from at least one of nickel nitrate, nickel sulfate, and nickel chloride; and the mass of the nickel catalyst is 3% to 9% of the mass of the biomass powder.

9. The method for preparing the graphite anode material composed of recycled graphite and catalytic biochar according to claim 1, characterized in that, In the method for preparing catalytic biochar, the molten salt is selected from at least one of lithium chloride-potassium chloride, sodium carbonate-potassium chloride, and lithium fluoride-sodium chloride, and the mass of the molten salt is 1.3 to 8 times the mass of the biomass powder.

10. A graphite anode material composed of recycled graphite and catalytic biochar, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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