A graphite anode material, its preparation method, and a lithium battery

Abstract

This invention relates to the field of battery materials technology, specifically disclosing a graphite anode material, its preparation method, and a lithium battery. The graphite anode material comprises a graphite matrix, a soft carbon intermediate layer coating the graphite matrix, and a nitrogen-doped carbon functional layer coating the soft carbon intermediate layer and chemically bonded to it. This invention constructs a core-shell-shell three-layer composite structure: the graphite matrix provides the bulk lithium storage capacity; the soft carbon intermediate layer effectively buffers the anisotropic volume changes of graphite during charge and discharge, preventing particle cracking and providing a stable substrate for the outer functional layer; the in-situ polymerized-carbonized nitrogen-doped carbon functional layer is the key innovation, as its nitrogen active sites preferentially adsorb lithium salt anions from the electrolyte, inducing the formation of a thin, dense, and stable SEI film rich in excellent lithium-ion conductors such as LiF / Li3N in the early stages of charge and discharge. The nitrogen-doped carbon functional layer optimizes the interfacial ion transport kinetics, significantly inhibiting the continuous growth of the SEI film and electrolyte decomposition in subsequent cycles.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a graphite anode material, its preparation method, and a lithium battery. Background Technology

[0002] Graphite anodes dominate the lithium-ion battery market, holding over 95% market share due to their moderate theoretical capacity (372 mAh / g), stable cycle performance, and low cost. However, their inherent drawbacks are becoming increasingly apparent: First, the slow diffusion kinetics of lithium ions between graphite layers lead to lithium deposition on the surface during fast charging, causing safety hazards and capacity decay. Second, during long-term cycling, the electrolyte continuously decomposes at the active sites on the graphite edges, resulting in excessive growth and thickening of the solid electrolyte interphase (SEI) film. This continuously consumes active lithium ions and electrolyte, causing irreversible capacity loss, increased impedance, and reduced cycle life. Furthermore, traditional artificial graphite production relies on intermittent Atchison furnaces for high-temperature (3000℃) graphitization. This process accounts for 40%-50% of the total cost of anode materials, with an energy efficiency of less than 30%, becoming a major bottleneck for cost reduction, efficiency improvement, and achieving dual-carbon goals in the industry.

[0003] To improve the performance of graphite anodes, the industry mainly adopts surface coating and structural modification strategies. For example, coating soft carbon layers with pitch can alleviate volume expansion and improve conductivity, but the uniformity of coating and the bonding force with the substrate are difficult to control precisely. While preparing carbon or oxide coatings using physical or chemical vapor deposition (CVD) can effectively improve interfacial stability, the process is complex, the equipment is expensive, and it is difficult to scale up. Recent research, such as succinimidyl modification, grafts nitrogen-containing functional groups onto the graphite surface via the Diels-Alder reaction (DA reaction), which can optimize the SEI film composition at the molecular level and improve cycle stability. However, this type of chemical modification is usually treated as a separate post-processing step, requiring additional reaction, washing, and heat treatment processes, which are disconnected from the core graphitization production process, increasing process complexity and overall energy consumption.

[0004] In summary, current technologies lack a solution that can synergistically complete the intrinsic crystallinity enhancement (graphitization) of graphite materials and the precise engineering of micro-interfaces (surface modification) within the same efficient and continuous production process. While existing continuous graphitization technologies can significantly reduce energy consumption, they primarily focus on the transformation of physical structures and do not integrate the chemical functionalization design of the material surface. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a composite graphite anode material and its preparation method that have both excellent electrochemical performance and efficient, low-carbon preparation process, overcoming the shortcomings of existing graphite anode materials such as poor fast-charging performance, severe long-cycle degradation, and lengthy and energy-intensive modification processes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a graphite anode material comprising a graphite matrix, a soft carbon intermediate layer coated on the graphite matrix, and a nitrogen-doped carbon functional layer coated on and chemically bonded to the soft carbon intermediate layer.

[0007] This invention constructs a core-shell-shell three-layer composite structure: a graphite matrix (core) provides the main body for lithium storage capacity; a soft carbon intermediate layer (inner shell) effectively buffers the anisotropic volume changes of graphite during charging and discharging, preventing particle cracking and providing a stable substrate for the outer functional layer; the in-situ polymerized-carbonized nitrogen-doped carbon functional layer (outer shell) is the key innovation, as its nitrogen active sites can preferentially adsorb lithium salt anions (such as PF6) in the electrolyte. - In the early stages of charging and discharging, a thin and dense stable SEI film rich in excellent lithium-ion conductors such as LiF / Li3N is induced to form. The nitrogen-doped carbon functional layer not only optimizes the interfacial ion transport dynamics, but also significantly inhibits the continuous growth of the SEI film and electrolyte decomposition in subsequent cycles.

[0008] The graphite anode material provided by this invention has excellent electrochemical performance. The synergistic effect of the soft carbon intermediate layer and the nitrogen-doped carbon functional layer gives the material high ionic and electronic conductivity. The stable SEI film induced by the nitrogen-doped carbon functional layer greatly reduces the irreversible consumption of active lithium and inhibits the formation of lithium dendrites under fast charging.

[0009] As a further improvement to the above-mentioned solution of the present invention, the graphite matrix comprises natural flake graphite or artificial graphite, and its particle size D50 is 10~25μm.

[0010] As a further improvement to the above-mentioned solution of the present invention, the coating amount of the soft carbon intermediate layer is 3% to 8% of the mass of the graphite matrix.

[0011] As a further improvement to the above-mentioned scheme of the present invention, the nitrogen-doped carbon functional layer is formed by in-situ Diels-Alder polymerization of nitrogen-containing heterocyclic monomers on the surface of the soft carbon intermediate layer to form a polymer precursor, which is then carbonized.

[0012] As a further improvement of the above-mentioned solution of the present invention, the coating amount of the nitrogen-doped carbon functional layer is 1% to 5% of the mass of the graphite matrix, the thickness is 5-30 nm, and the molar doping content of nitrogen element in the nitrogen-doped carbon functional layer is 2 at% to 6 at.

[0013] The graphite anode material of this invention maintains a high capacity (≥360 mAh / g) while achieving a coulombic efficiency of over 94% for the first time. After 1000 cycles at 3C rate, the capacity retention rate exceeds 90%, effectively solving the technical bottlenecks of traditional graphite anodes, such as poor fast charging performance, rapid cycle life decay, complex modification process, and high energy consumption.

[0014] The present invention also provides a method for preparing the graphite anode material as described above, which includes the following steps: S1. Mix the graphite matrix with the soft carbon precursor solution, dry, and pre-carbonize to obtain primary coated graphite; S2. The primary coated graphite is mixed with nitrogen-containing heterocyclic monomers, initiators and solvents, and then subjected to in-situ Diels-Alder polymerization to obtain a polymer precursor. S3. The polymer precursor is fed into a continuous graphitization furnace and preheated, carbonized, graphitized, and cooled in sequence to obtain a graphite anode material.

[0015] The traditional route is: graphitization → cooling → surface modification → secondary heat treatment. The route of this invention is: surface polymer coating → entering a continuous graphitization furnace → medium-temperature zone: polymer carbonization / nitrogen doping → high-temperature zone: matrix graphitization → cooling. This invention cleverly embeds the surface chemical modification step into the continuous graphitization production process, organically combining the energy-intensive graphitization process with precise surface chemical modification on a continuous production line. This achieves both crystallinity enhancement and surface functionalization of the graphite matrix in a single step, fully utilizing the multi-temperature zones and continuous material movement characteristics of the continuous graphitization furnace. The polymer precursor undergoes carbonization and forms the target nitrogen-doped structure. This carbonization temperature range is much lower than the graphitization temperature, but it is precisely the efficient window for the polymer carbonization and nitrogen doping reaction. Subsequently, the material does not require cooling and directly enters the high-temperature zone to complete the final crystallization of the graphite matrix. This integrated process eliminates the separate modification heat treatment step, significantly reducing energy consumption and production cycle time, achieving a balance between cost reduction and efficiency improvement with performance enhancement. While achieving green manufacturing, it fundamentally improves the fast-charging and long-cycle performance of the graphite anode.

[0016] This invention utilizes a nitrogen-containing polymer precursor generated through in-situ polymerization via Diels-Alder polymerization. This precursor exhibits a strong chemical affinity for graphite and soft carbon layers. During subsequent carbonization, the nitrogen-containing polymer precursor transforms into a doped carbon layer rich in pyridine nitrogen and graphitic nitrogen. These nitrogen-active sites preferentially adsorb lithium salt anions (such as PF6) from the electrolyte. - In the early stages of charging and discharging, a thin and dense stable SEI film rich in excellent lithium-ion conductors such as LiF / Li3N is induced to form. The nitrogen-doped carbon functional layer not only optimizes the interfacial ion transport dynamics, but also significantly inhibits the continuous growth of the SEI film and electrolyte decomposition in subsequent cycles.

[0017] As a further improvement to the above-mentioned scheme of the present invention, in step S1, the soft carbon precursor is mesophase pitch, coal tar or phenolic resin; the pre-carbonization is carried out at 700~900℃ for 1~3h.

[0018] As a further improvement to the above-mentioned scheme of the present invention, in step S2, the nitrogen-containing heterocyclic monomer is selected from at least one of N-phenylmaleimide, succinimide acrylate or its derivatives; after mixing the primary coated graphite with the nitrogen-containing heterocyclic monomer, initiator and solvent, the pH of the solution is adjusted to 8-9, and then an in-situ Diels-Alder polymerization reaction is carried out at 60-90°C for 2-6 hours.

[0019] As a further improvement to the above-described scheme of the present invention, in step S3, an argon-hydrogen mixture (wherein the hydrogen volume percentage is 1%~5%) is introduced into the continuous graphitization furnace. The continuous graphitization furnace has a first temperature zone of 400~600℃, a second temperature zone of 800~1200℃, and a third temperature zone of 2600~3000℃. The residence time of the polymer precursor in the second temperature zone is 30~90 min, and the residence time in the third temperature zone is 20~40 min. The carbonization of the polymer precursor in the second temperature zone completes the formation of a nitrogen-doped carbon functional layer, and the full graphitization of the graphite matrix is ​​simultaneously completed in the third temperature zone.

[0020] This invention offers significant technological and cost advantages. Compared to the traditional two-step method of graphitization followed by independent modification, the integrated continuous process of this invention can shorten the total production time by approximately 35% and reduce the overall energy consumption related to heat treatment by more than 25%. This is mainly due to the high thermal efficiency (>70%) of the continuous graphitization furnace and the elimination of intermediate cooling and reheating processes.

[0021] This invention exhibits excellent process compatibility and versatility. The preparation method can be seamlessly integrated with existing anode material production lines, including mixing, coating, and sintering processes. The DA reaction conditions employed are mild and easily implemented on a large scale in a liquid-phase system. This technological principle can also be extended to the surface functionalization of other carbon-based anode materials (such as hard carbon and composite silicon-carbon materials).

[0022] The present invention also provides a lithium battery comprising the graphite anode material as described above. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a graphite anode material provided by the present invention.

[0024] 1. Graphite matrix; 2. Soft carbon intermediate layer; 3. Nitrogen-doped functional layer. Detailed Implementation

[0025] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0027] like Figure 1 As shown, this invention provides a graphite anode material, comprising a graphite matrix 1, a soft carbon interlayer 2 coated on the graphite matrix, and a nitrogen-doped carbon functional layer 3 coated on and chemically bonded to the soft carbon interlayer 2. The graphite matrix is ​​natural flake graphite or artificial graphite with a particle size D50 of 10-25 μm. The coating amount of the soft carbon interlayer is 3%-8% of the mass of the graphite matrix. The nitrogen-doped carbon functional layer is formed by in-situ Diels-Alder polymerization of nitrogen-containing heterocyclic monomers on the surface of the soft carbon interlayer to form a polymer precursor, followed by carbonization. The coating amount of the nitrogen-doped carbon functional layer is 1%-5% of the mass of the graphite matrix, with a thickness of 5-30 nm, and the nitrogen doping content in the nitrogen-doped carbon functional layer is 2%-6%. The graphite anode material of this invention maintains a high capacity (≥360 mAh / g) while achieving a coulombic efficiency of over 94% for the first time. After 1000 cycles at 3C rate, the capacity retention rate exceeds 90%, effectively solving the technical bottlenecks of traditional graphite anodes, such as poor fast-charging performance, rapid cycle life decay, complex modification processes, and high energy consumption. The method for preparing the graphite anode material of the present invention includes the following steps: S1. Mix the graphite matrix with the soft carbon precursor solution, dry, and pre-carbonize to obtain primary coated graphite; the soft carbon precursor is mesophase pitch, coal tar, or phenolic resin; the pre-carbonization is carried out at 700~900℃ for 1~3h. S2. The primary coated graphite is mixed with a nitrogen-containing heterocyclic monomer, an initiator, and a solvent, and then subjected to an in-situ Diels-Alder polymerization reaction to obtain a polymer precursor; the nitrogen-containing heterocyclic monomer is selected from at least one of N-phenylmaleimide, succinimide acrylate, or its derivatives; after mixing the primary coated graphite with the nitrogen-containing heterocyclic monomer, an initiator, and a solvent, the pH of the solution is adjusted to 8-9, and then an in-situ Diels-Alder polymerization reaction is carried out at 60-90°C for 2-6 hours; S3. The polymer precursor is fed into a continuous graphitization furnace and subjected to preheating, carbonization, graphitization, and cooling to obtain a graphite anode material. An argon-hydrogen mixture (with hydrogen comprising 1%–5% by volume) is introduced into the continuous graphitization furnace. The furnace has a first temperature zone of 400–600°C, a second temperature zone of 800–1200°C, and a third temperature zone of 2600–3000°C. The polymer precursor is held in the second temperature zone for 30–90 minutes and in the third temperature zone for 20–40 minutes. Carbonization of the polymer precursor in the second temperature zone forms a nitrogen-doped carbon functional layer, while simultaneous graphitization of the graphite matrix is ​​completed in the third temperature zone.

[0028] The present invention will now be described in detail with reference to specific embodiments.

[0029] Example 1 This embodiment proposes a graphite anode material with a continuous graphitization-in-situ chemical modification dual-functional coating layer, and its preparation method is as follows: S1. Dissolve 80g of mesophase pitch (softening point 240℃) in tetrahydrofuran, then add 1000g of natural flake graphite (purity 99.9%) with a particle size D50 of 18μm to the solution, mix thoroughly and stir for 4h; then dry at 120℃ for 12h, then pre-carbonize at 800℃ at 5℃ / min under nitrogen protection and hold for 2h, and after natural cooling, obtain primary coated graphite with a soft carbon mesolayer on the surface.

[0030] S2. The primary coated graphite obtained in S1 was dispersed in 2000 mL of deionized water, 20 g of N-phenylmaleimide (monomer) and 1 g of potassium persulfate (initiator) were added, the pH was adjusted to 8.5 with ammonia, and the mixture was stirred continuously in a 75°C constant temperature water bath for 4 h. After the reaction was completed, the mixture was filtered, washed three times with deionized water and ethanol, and dried in a vacuum drying oven at 80°C for 10 h to obtain an intermediate with a polymer precursor coated on its surface.

[0031] S3. The dried intermediate obtained in S2 is continuously fed into a tubular continuous graphitization furnace via an automatic feeding system. An argon-hydrogen mixture (Ar:H2=97:3) is introduced into the furnace. The material first passes through a preheating zone (500℃, residence time 10 min), and then enters the critical medium-temperature reaction zone. The temperature of the medium-temperature reaction zone is set at 1000℃, and the material residence time is 60 min. In this zone, the polymer precursor completes carbonization and forms a nitrogen-doped carbon functional layer. Finally, the material enters the high-temperature graphitization zone, where the temperature is set at 2850℃ and the residence time is 30 min, so that the graphite matrix completes high-level graphitization. After being cooled to room temperature in the cooling section, the material is discharged, crushed, and sieved (300 mesh) to obtain the final composite graphite material.

[0032] Example 2 The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the amount of N-phenylmaleimide used is 10g.

[0033] Example 3 The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, the amount of N-phenylmaleimide used is 30g.

[0034] Example 4 The difference between this embodiment and embodiment 1 is that in step S2 of this embodiment, succinimide acrylate is used instead of N-phenylmaleimide, and the amount of succinimide acrylate used is 10g.

[0035] Example 5 The difference between this embodiment and embodiment 4 is that in step S2 of this embodiment, the amount of succinimide acrylate used is 20g.

[0036] Example 6 The difference between this embodiment and embodiment 4 is that in step S2 of this embodiment, the amount of succinimide acrylate used is 30g.

[0037] Example 7 The difference between this embodiment and embodiment 1 is that in step S3 of this embodiment, the temperature of the medium-temperature reaction zone of the continuous graphitization furnace is adjusted to 800℃.

[0038] Example 8 The difference between this embodiment and embodiment 1 is that in step S3 of this embodiment, the residence time of the material in the medium-temperature reaction zone of the continuous graphitization furnace is 90 min.

[0039] Comparative Example 1 This comparative example presents a graphite anode material, the preparation method of which is as follows: 1000g of natural flake graphite (99.9% purity) with a particle size D50 of 18μm is continuously fed into a tubular continuous graphitization furnace via an automatic feeding system. An argon-hydrogen mixture (Ar:H2=97:3) is introduced into the furnace. The material first passes through a preheating zone (500℃, residence time 10min), then enters a medium-temperature zone with a set temperature of 1000℃ and a residence time of 60min. Finally, the material enters a high-temperature graphitization zone with a set temperature of 2850℃ and a residence time of 30min, allowing the graphite matrix to achieve high-level graphitization. After cooling to room temperature in a cooling section, the material is discharged, crushed, and sieved (300 mesh) to obtain the final graphite anode material.

[0040] Comparative Example 2 This comparative example presents a graphite anode material, the preparation method of which is as follows: 80g of mesophase pitch (softening point 240℃) was dissolved in tetrahydrofuran, and then 1000g of natural flake graphite (purity 99.9%) with a particle size D50 of 18μm was added to the solution and stirred thoroughly for 4h. Subsequently, it was dried at 120℃ for 12h, and then pre-carbonized at 800℃ at 5℃ / min under nitrogen protection and held for 2h. After natural cooling, the obtained primary coated graphite was graphitized in a conventional intermittent Atchison furnace at 2850℃ for 30min under an argon-hydrogen mixed atmosphere (Ar:H2 volume ratio of 97:3) to obtain the final graphite anode material.

[0041] Comparative Example 3 This comparative example presents a graphite anode material, the preparation method of which is as follows: S1. Dissolve 80g of mesophase pitch (softening point 240℃) in tetrahydrofuran, then add 1000g of natural flake graphite (purity 99.9%) with a particle size D50 of 18μm to the solution, mix thoroughly and stir for 4h; then dry at 120℃ for 12h, then pre-carbonize at 800℃ at 5℃ / min under nitrogen protection and hold for 2h, and after natural cooling, obtain primary coated graphite with a soft carbon mesolayer on the surface.

[0042] S2. The primary coated graphite obtained in S1 was dispersed in 2000 mL of deionized water, 20 g of N-phenylmaleimide (monomer) and 1 g of potassium persulfate (initiator) were added, the pH was adjusted to 8.5 with ammonia, and the mixture was stirred continuously in a 75°C constant temperature water bath for 4 h. After the reaction was completed, the mixture was filtered, washed three times with deionized water and ethanol, and dried in a vacuum drying oven at 80°C for 10 h to obtain an intermediate with a polymer precursor coated on its surface.

[0043] S3. The dried intermediate obtained in S2 is carbonized in a tube furnace at 1000℃ for 2 hours in an argon-hydrogen mixed atmosphere (Ar:H2 volume ratio of 97:3) to obtain the graphite anode material.

[0044] Test case The graphite anode materials prepared in Examples 1-8 and Comparative Examples 1-3 were mixed with conductive carbon black and polyvinylidene fluoride (PVDF) at a weight ratio of 95:2:3 to form a slurry. This slurry was then uniformly coated onto copper foil to form a thin layer, dried, and cut into circular pieces as anode sheets. Using a lithium metal sheet as the counter electrode, and a 1M LiPF6 EC / DEC / EMC (1:1:1 vol%) solution with 2wt% FEC additive as the electrolyte, CR2032 button cells were assembled in an argon glove box. The CR2032 button cells were subjected to constant current charge-discharge tests within a voltage range of 0.01-2V. The specific capacity of the first discharge cycle at 0.1C, the first charge-discharge efficiency, and the capacity retention rate after 1000 cycles at 3C were tested. The test results are shown in Table 1.

[0045] Table 1 Test Results

[0046] The results in Table 1 show that: The graphite anode materials prepared in Examples 1-6 of this invention comprehensively outperform the three comparative examples in terms of initial coulombic efficiency, high rate performance, and long cycle life. In particular, Examples 1 and 5 have an initial efficiency of >97%, and their capacity can still be maintained above 91.5% after 1000 cycles at a harsh 3C rate, which is significantly better than that of Comparative Example 1 (79.6%), Comparative Example 2 (82.6%) using the traditional process, and Comparative Example 3 (85.4%) modified by the two-step method.

[0047] Compared to Comparative Example 3, although both underwent similar surface chemical modifications, Example 1 of the present invention exhibits superior performance. This confirms the effectiveness of the integrated continuous process: within a continuous graphitization furnace, the carbonization process of the polymer precursor is more closely integrated with the high-temperature treatment of the graphite matrix, potentially promoting stronger chemical bonding between the functional layer and the matrix, resulting in a more desirable interface structure.

[0048] The process of this invention eliminates the need for a separate carbonization furnace and secondary heating / cooling process required for carbonizing the functional layer. According to calculations, the overall energy consumption for producing one ton of anode material can be reduced by about 28%.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A graphite anode material, characterized in that, It includes a graphite matrix, a soft carbon intermediate layer covering the graphite matrix, and a nitrogen-doped carbon functional layer covering the soft carbon intermediate layer and chemically bonded to it.

2. The graphite anode material according to claim 1, characterized in that, The graphite matrix comprises natural flake graphite or artificial graphite, with a particle size D50 of 10~25μm.

3. The graphite anode material according to claim 1, characterized in that, The coating amount of the soft carbon intermediate layer is 3% to 8% of the mass of the graphite matrix.

4. The graphite anode material according to claim 1, characterized in that, The nitrogen-doped carbon functional layer is formed by in-situ Diels-Alder polymerization of nitrogen-containing heterocyclic monomers on the surface of the soft carbon intermediate layer to form a polymer precursor, which is then carbonized.

5. The graphite anode material according to claim 1, characterized in that, The coating amount of the nitrogen-doped carbon functional layer is 1% to 5% of the mass of the graphite matrix, and the nitrogen doping content in the nitrogen-doped carbon functional layer is 2 at% to 6 at%.

6. A method for preparing a graphite anode material as described in any one of claims 1-5, characterized in that, It includes the following steps: S1. Mix the graphite matrix with the soft carbon precursor solution, dry, and pre-carbonize to obtain primary coated graphite; S2. The primary coated graphite is mixed with nitrogen-containing heterocyclic monomers, initiators and solvents, and then subjected to in-situ Diels-Alder polymerization to obtain a polymer precursor. S3. The polymer precursor is fed into a continuous graphitization furnace and preheated, carbonized, graphitized, and cooled in sequence to obtain a graphite anode material.

7. The method for preparing the graphite anode material according to claim 6, characterized in that, In step S1, the soft carbon precursor is mesophase pitch, coal tar, or phenolic resin; the pre-carbonization is carried out at 700~900℃ for 1~3 hours.

8. The method for preparing the graphite anode material according to claim 6, characterized in that, In step S2, the nitrogen-containing heterocyclic monomer is selected from at least one of N-phenylmaleimide, succinimide acrylate or its derivatives; after mixing the primary coated graphite with the nitrogen-containing heterocyclic monomer, initiator and solvent, the pH of the solution is adjusted to 8-9, and then in-situ Diels-Alder polymerization is carried out at 60-90℃ for 2-6 hours.

9. The method for preparing the graphite anode material according to claim 6, characterized in that, In step S3, an argon-hydrogen mixture is introduced into the continuous graphitization furnace. The continuous graphitization furnace has a first temperature zone of 400~600℃, a second temperature zone of 800~1200℃, and a third temperature zone of 2600~3000℃. The residence time of the polymer precursor in the second temperature zone is 30~90min, and the residence time in the third temperature zone is 20~40min.

10. A lithium battery, characterized in that, It includes the graphite anode material as described in any one of claims 1-5.

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