Nitrogen-doped resin carbon-coated negative electrode material and preparation method and application thereof

Abstract

According to the preparation method of the nitrogen-doped resin carbon-coated graphite, the surface of the graphite is uniformly coated with the resin by introducing the surfactant, so that a nitrogen-doped resin carbon layer with a specific rod-shaped structure is formed. The method solves the problem that the surface of the graphite is difficult to uniformly coat the resin, is suitable for preparing a resin graphite composite material of a lithium ion battery negative electrode and a chemical vapor deposition silicon negative electrode, can improve the conductivity and volume expansion of the silicon negative electrode, and improves the coulombic efficiency and the cycle life.

Description

Technical Field

[0001] The present invention belongs to the field of new energy materials, and particularly relates to a nitrogen-doped resin carbon-coated anode material, a preparation method thereof, and an application thereof. Background Art

[0002] Graphite has a very wide application in anode materials for lithium-ion batteries. However, with the gradual development of electric vehicles, lithium-ion batteries with graphite as the anode are gradually difficult to meet the market's demand for high-capacity density. The cost of graphite anode materials is relatively low and the industrial chain is mature. Direct modification of graphite anode materials is one of the current methods to alleviate capacity anxiety. However, due to the high temperature resistance and difficulty in oxidation of graphite, it is difficult to form oxygen-containing groups on the surface of graphite, and it is difficult to uniformly coat resin on the surface of graphite and form a specific structure by a simple solution method.

[0003] Patent document CN201810416134.X discloses a lithium-ion battery anode material suitable for low temperature and a preparation method thereof; the preparation method includes: (1) performing modification treatment on graphite powder; (2) dispersing the modified graphite powder into an organic solvent and slowly adding it to molten caprolactam; (3) coating the modified graphite powder adsorbed with caprolactam with a soft carbon layer material, and then immersing it in an ethanol solution for soaking; (4) coating the modified graphite powder coated with porous soft carbon with a hard carbon layer material; (5) performing high-temperature curing and carbonization treatment to obtain the lithium-ion battery anode material; however, the preparation process of this method is complex, and the influence of the content of the amorphous material coated on the surface on the final material morphology is not considered; Patent document CN202210959769.0 discloses a silicon-carbon anode material and a preparation method thereof; the microstructure of the silicon-carbon anode material is a microsphere with a core-shell structure having a core part and a shell part, the core part is a mixture of nano-silicon and graphite, and the shell part is an amorphous carbon layer coating the core part; the nano-silicon is loaded on the surface of the graphite and / or the nano-silicon is embedded in the pores of the graphite. In this prior art, a silicon-carbon material precursor is prepared by a liquid phase method, and high-temperature calcination under an inert gas condition can ensure that the metal reducing agent fully reduces nano-silicon dioxide to nano-silicon, and a graphite catalyst is used to promote the graphitization process of the porous inorganic carbon material, and at the same time, high-temperature pyrolysis carbonization of the organic carbon source is ensured to form an amorphous carbon layer, but this method also has a complex preparation process.

[0004] Patent document CN201810445606.4 discloses a preparation method and application of a silicon-carbon composite material, which includes the following steps: (1) Mix nano-silicon powder, surfactant and organic solvent, and then perform ultrasonic treatment to obtain a suspension; (2) Mix the above suspension with a polymer precursor solution, perform ultrasonic treatment, and then evaporate the solvent to obtain nano-silicon powder with a polymer coating on the surface; (3) Mix the nano-silicon powder with a polymer coating obtained in step (2) and graphite, and then perform high-energy ball milling; (4) Perform high-temperature carbonization treatment on the material obtained in step (3); (5) Perform chemical vapor deposition on the material obtained in step (4) to obtain the silicon-carbon composite material. In the present invention, the nano-silicon powder is treated with a surfactant and a polymer and then compounded with graphite by high-energy ball milling, so that the nano-silicon powder is evenly distributed in the graphite; the silicon powder can fully exert its advantages of nano-size and alleviate the capacity attenuation caused by the huge volume change during charge and discharge. However, the preparation process of this method is complex, and the influence of the content of materials and process steps in the surface coating on the final material morphology is not considered.

[0005] Patent document CN202110628472.1 discloses a preparation method of a silicon-carbon anode material. The implementation method includes the following steps: S1, preparation of nano-graphite powder; S2, preparation of modified hydroxylated graphite powder; S3, preparation of modified graphite powder; S4, preparation of raw particles of the silicon-carbon composite material. S5, preparation of the silicon-carbon anode material. In the present invention, the surface of the nano-graphite powder is hydroxylated, which can be well dispersed in solvents such as ethanol and water, and then nano-silicon oxide particles are grafted onto the surface of the nano-graphite powder through a silicon-oxygen coupling agent, and then a uniformly mixed silicon-carbon anode material is obtained through spray granulation and roasting. The preparation process of this material is simple and has little pollution. At the same time, the nano-graphite can be evenly coated on the surface of the nano-silicon oxide particles, enhancing the conductivity of the silicon-carbon anode material, reducing the volume expansion during the silicon cycle, solving the problem of uneven dispersion in the preparation process of the silicon-carbon anode material, and having the characteristics of high cycle capacity and long cycle life. However, this method also has a complex process. Summary of the Invention

[0006] Graphite is heat-resistant and difficult to oxidize. It is difficult to form oxygen-containing groups on the surface of graphite, and it is difficult to coat resin on the surface of graphite and form a specific structure by a simple solution method. To solve the above problems, this patent proposes a preparation method of nitrogen-doped resin carbon-coated graphite, adding a surfactant to form rod-shaped micelles with graphite and uniformly coating them on the surface of graphite.

[0007] To achieve the above effects, on the one hand, the present invention provides a preparation method of a nitrogen-doped resin carbon-coated anode material, which includes the following steps: S1, disperse graphite powder in a mixed solvent, and then add a certain amount of surfactant to obtain a mixed solution of the surfactant-modified anode material; S2. Add ammonia water, phenol, and formaldehyde solution to the mixed solution in step S1 in sequence. After stirring and reacting for a period of time, separate the resin-coated graphite gel, and dry and grind it into powder; S3. Calcinate the powder obtained in step S2 under a protective atmosphere to obtain a nitrogen-doped resin carbon-coated anode material.

[0008] Further, in step S1, the particle size of the graphite is 5 - 20 μm.

[0009] Further, in step S1, the surfactant is an alkyl group cationic surfactant or a polyether nonionic surfactant. Preferably, the surfactant is cetyltrimethylammonium bromide.

[0010] Further, in step S1, the mixed solvent is one or more of methanol, ethanol, isopropanol, and water.

[0011] Further, the phenol is one or more of catechol, resorcinol, hydroquinone, phenol, o-aminophenol, m-aminophenol, and p-aminophenol.

[0012] Further, in step S2, the mass-volume ratio of phenol to formaldehyde is less than 1 g : 0.9 mL.

[0013] Further, in step S2, the temperature of the reaction is 20 - 100 °C, and the reaction time is 0.5 - 24 h.

[0014] Further, in step S3, the protective atmosphere is at least one of nitrogen, helium, neon, argon, krypton, and xenon. Preferably, the protective atmosphere is argon; for the calcination, it is controlled at a heating rate of 1 - 10 °C / min, and carbonize at 500 - 1600 °C for 1 - 5 hours. Preferably, the heating rate is 2 °C / min for the calcination. -1 The heating rate, and perform the calcination at a heating rate of 2 °C / min. -1 The heating rate of the heating rate.

[0015] On the other hand, the present invention also provides an anode material prepared by the above preparation method. The anode material includes a graphite core and resin carbon. The resin carbon is uniformly coated on the surface of the anode active material. The resin carbon has a rod-like structure, and the particle size of the graphite core is 5 - 20 μm.

[0016] The present invention also discloses the application of an anode material prepared by the above method in a lithium-ion battery.

[0017] Compared with the prior art, the beneficial effects of the present invention are: The preparation method proposed by the present invention adds a surfactant to uniformly coat the nitrogen-doped resin on the graphite surface to form a resin carbon layer with a specific rod-like structure. The process is relatively simple, does not require complex steps and special equipment, and is easy to industrialize. By adjusting the reaction conditions and the ratio of raw materials, the structure and performance of the nitrogen-doped resin carbon layer can be accurately controlled, thereby improving the flexibility and operability of the preparation method.

[0018] Nitrogen-doped resin carbon-coated graphite has a specific rod-like structure and a large specific surface area, which is conducive to the formation of a rich conductive network. At the same time, the nitrogen element provides active sites. The structural design of this material enables it to isolate oxygen. When used in the negative electrode of lithium-ion batteries, it improves the conductivity and volume expansion of the silicon negative electrode. It reduces the volume change of the silicon negative electrode during the charge and discharge process, improves the stability of the battery structure, and thus increases the cycle life of the battery. It improves the coulomb efficiency of the battery, reduces the energy loss of the battery during the charge and discharge process, and improves the energy utilization rate of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work. In the drawings: Figure 1 The following are scanning electron microscope images (SEM images) and X-ray diffraction patterns of the graphite particles used in the present invention.

[0020] Figure 2 It is the SEM image of the nitrogen-doped rod-shaped resin-coated graphite precursor of Examples 1-4 of the present invention.

[0021] Figure 3 These are SEM images of nitrogen-doped resin carbon-coated graphite obtained by calcining under different conditions in Examples 1-4 of the present invention.

[0022] Figure 4 The nitrogen-doped rod-shaped resin-coated graphite of Example 1 of the present invention was heated at 2 °C min in an argon atmosphere. -1 TG curve of graphite when the heating rate is increased to 800℃ and kept for 3 h.

[0023] Figure 5 The nitrogen-doped rod-shaped resin-coated graphite of Example 1 of the present invention was heated at 2 °C min in an argon atmosphere. -1 Transmission electron microscopy image (TEM image) of the sample heated at 800 °C for 3 h.

[0024] Figure 6is the bright and dark field image contrast and the distribution of carbon and nitrogen elements of the nitrogen-doped rod-shaped resin-coated graphite in Example 1 of the present invention under an argon atmosphere at a heating rate of 2 °C min -1 and heating to 800 °C and holding for 3 h.

[0025] Figure 7 is the first charge-discharge curve of the nitrogen-doped rod-shaped resin-coated graphite and graphite in Example 1 of the present invention.

[0026] Figure 8 is the rate performance graph of the nitrogen-doped rod-shaped resin-coated graphite in Example 1 of the present invention.

[0027] Figure 9 is the SEM image and rate performance graph of the graphite / resin carbon material in Comparative Example 1 of the present invention. Detailed implementation manners

[0028] The following combines the drawings and examples to further describe in detail the specific implementation manners of the present invention. The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0029] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or collections.

[0030] To make the drawings concise, only the parts related to the present invention are schematically shown in each drawing, and they do not represent the actual structure of the product. In addition, to make the drawings concise and easy to understand, in some drawings, components with the same structure or function are only schematically shown one of them, or only one of them is marked. In this article, "one" not only means "only this one", but also can mean "more than one" situation.

[0031] It should also be further understood that the term "and / or" used in the description of this application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0032] In the embodiments shown in the drawings, the indication of directions (such as up, down, left, right, front and back) is used to explain that the structures and movements of various components of the present invention are not absolute but relative. When these components are in the positions shown in the drawings, these descriptions are appropriate. If the descriptions of the positions of these components change, then the indication of these directions also changes accordingly.

[0033] In addition, in the description of this application, the terms "first", "second", etc. are only used for distinguishing descriptions, and cannot be understood as indicating or implying relative importance.

[0034] Example 1 A preparation method of resin carbon-coated graphite, comprising the following steps: Add 10 g of graphite powder with a particle size of 10 μm to a mixed solution of 100 mL of ethanol and water (the volume ratio of ethanol to water is 1:1), ultrasonically treat for 30 minutes to ensure uniform dispersion of the graphite, and then add 0.5 g of cetyltrimethylammonium bromide to the dispersion and stir until completely dissolved to obtain a cetyltrimethylammonium bromide-modified graphite mixed solution; Sequentially add 5 mL of ammonia water, 2 g of catechol, and 1.8 mL of formaldehyde solution (AR, containing 10-15% methanol stabilizer) to the above mixed solution, continue to stir for 30 minutes to ensure full mixing of the reactants, place the mixed solution in a constant temperature water bath, react at 60 °C for 12 hours to form a resin-coated graphite gel. After the reaction is completed, let the mixture stand for 2 hours until the gel and the solution are separated, use centrifugal separation (3000 rpm, 10 minutes) to separate the resin-coated graphite gel, dry the separated gel at 80 °C for 12 hours to obtain a dry resin-coated graphite bulk material, grind the dried bulk material into a powder and set aside. Place the obtained resin carbon-coated graphite powder in a tubular furnace and introduce argon as a protective atmosphere. Increase the temperature to 800 °C at a heating rate of 2 °C min -1 and hold at this temperature for 3 hours for carbonization treatment. After the calcination is completed, naturally cool to room temperature to obtain the carbonized resin carbon-coated graphite material.

[0035] Example 2 A preparation method of resin carbon-coated graphite, comprising the following steps: Add 10 g of graphite powder with a particle size of 10 μm to a mixed solution of 100 mL of ethanol and water (the volume ratio of ethanol to water is 1:1), ultrasonically treat for 30 minutes to ensure uniform dispersion of the graphite, and then add 0.5 g of cetyltrimethylammonium bromide to the dispersion and stir until completely dissolved to obtain a cetyltrimethylammonium bromide-modified graphite mixed solution; Add 5 mL of ammonia water, 2 g of catechol, and 1.8 mL of formaldehyde solution (AR, containing 10 - 15% methanol stabilizer) to the above mixed solution in sequence, and continue stirring for 30 minutes to ensure the full mixing of reactants. Place the mixed solution in a constant temperature water bath and react at 60 °C for 12 hours to form resin-coated graphite gel. After the reaction, let the mixture stand for 2 hours until the gel and the solution are layered. Use centrifugal separation (3000 rpm, 10 minutes) to separate the resin-coated graphite gel. Dry the separated gel at 80 °C for 12 hours to obtain a dry resin-coated graphite bulk material. Grind the dried bulk material into powder for standby. Place the obtained resin-coated graphite powder in a tubular furnace and introduce argon as a protective atmosphere. Increase the temperature to 800 °C at a heating rate of 5 °C min -1 and hold at this temperature for 3 hours for carbonization treatment. After the calcination, cool naturally to room temperature to obtain the carbonized resin-carbon-coated graphite material.

[0036] Example 3 A preparation method of resin-carbon-coated graphite, comprising the following steps: Add 10 g of graphite powder with a particle size of 10 μm to a mixed solution of 100 mL of ethanol and water (the volume ratio of ethanol to water is 1:1), and perform ultrasonic treatment for 30 minutes to ensure the uniform dispersion of graphite. Then add 0.5 g of cetyltrimethylammonium bromide to the dispersion and stir until completely dissolved to obtain a cetyltrimethylammonium bromide-modified graphite mixed solution; Add 5 mL of ammonia water, 2 g of catechol, and 1.8 mL of formaldehyde solution (AR, containing 10 - 15% methanol stabilizer) to the above mixed solution in sequence, and continue stirring for 30 minutes to ensure the full mixing of reactants. Place the mixed solution in a constant temperature water bath and react at 60 °C for 12 hours to form resin-coated graphite gel. After the reaction, let the mixture stand for 2 hours until the gel and the solution are layered. Use centrifugal separation (3000 rpm, 10 minutes) to separate the resin-coated graphite gel. Dry the separated gel at 80 °C for 12 hours to obtain a dry resin-coated graphite bulk material. Grind the dried bulk material into powder for standby. Place the obtained resin-coated graphite powder in a tubular furnace and introduce argon as a protective atmosphere. Increase the temperature to 800 °C at a heating rate of 10 °C min -1 and hold at this temperature for 3 hours for carbonization treatment. After the calcination, cool naturally to room temperature to obtain the carbonized resin-carbon-coated graphite material.

[0037] Example 4 A preparation method of resin-carbon-coated graphite, comprising the following steps: 10 g of graphite powder with a graphite particle size of 10 μm was added to 100 mL of a mixed solution of ethanol and water (the volume ratio of ethanol to water was 1:1), and ultrasonic treatment was performed for 30 minutes to ensure that the graphite was evenly dispersed, and then 0.5 g of hexadecyltrimethylammonium bromide was added to the dispersion and stirred until it was completely dissolved to obtain a hexadecyltrimethylammonium bromide-modified graphite mixed solution; Add 5 mL of ammonia water, 2 g of catechol, and 1.8 mL of formaldehyde solution (AR, containing 10-15% methanol stabilizer) to the above mixed solution in sequence, continue stirring for 30 minutes to ensure that the reactants are fully mixed, place the mixed solution in a constant temperature water bath, and react at 60°C for 12 hours to form a resin-coated graphite gel. After the reaction is completed, let the mixture stand for 2 hours, wait for the gel and the solution to separate, and use centrifugal separation (3000 rpm, 10 minutes) to separate the resin-coated graphite gel. Dry the separated gel at 80°C for 12 hours to obtain a dry resin-coated graphite block material. Grind the dried block material into powder for later use. Place the obtained resin-coated graphite powder in a tubular furnace and introduce nitrogen as a protective atmosphere. Heat at 2°C min -1 The temperature was raised to 800°C at a heating rate of , and maintained at this temperature for 3 hours for carbonization treatment. After the calcination was completed, it was naturally cooled to room temperature to obtain a carbonized resin carbon-coated graphite material.

[0038] Comparative Example 1 The preparation method of resin carbon coated graphite comprises the following steps: 10 g of graphite powder with a particle size of 10 μm was added to 100 mL of a mixed solution of ethanol and water (the volume ratio of ethanol to water was 1:1), and ultrasonic treatment was performed for 30 minutes to ensure that the graphite was evenly dispersed to obtain a mixed solution; Add 5 mL of ammonia water, 2 g of catechol, and 1.8 mL of formaldehyde solution (AR, containing 10-15% methanol stabilizer) to the mixed solution in sequence, continue stirring for 30 minutes to ensure that the reactants are fully mixed, place the mixed solution in a constant temperature water bath, and react at 60 °C for 12 hours to form a resin-coated graphite gel. After the reaction is completed, let the mixture stand for 2 hours, wait for the gel and the solution to separate, and use centrifugal separation (3000 rpm, 10 minutes) to separate the resin-coated graphite gel. Dry the separated gel at 80 °C for 12 hours to obtain a dry resin-coated graphite block material. Grind the dried block material into powder for later use. The obtained resin-coated graphite powder is placed in a tubular furnace and argon is introduced as a protective atmosphere. At 2 °C min -1 The temperature was raised to 800°C at a heating rate of , and maintained at this temperature for 3 hours for carbonization treatment. After the calcination was completed, it was naturally cooled to room temperature to obtain a carbonized resin carbon-coated graphite material.

[0039] Figure 1 They are the scanning electron microscope image (SEM image) and X-ray diffraction pattern of the graphite particles used in the present invention. The graphite has a massive structure and obvious graphite characteristic peaks, with high purity and no obvious impurities.

[0040] Figure 2 They are the SEM images of the nitrogen-doped resin-coated graphite precursors in Examples 1-4 of the present invention. The catechol-formaldehyde resin synthesized by the method adding a surfactant in this example uniformly coats on the surface of the graphite and has a special rod-like micelle structure.

[0041] Figure 3 They are the SEM images of the nitrogen-doped resin carbon-coated graphite obtained from the nitrogen-doped resin-coated graphite in Examples 1-4 of the present invention under different calcination conditions respectively. In Examples 1 and 4, the heating rate is 2 ℃ / min -1 and the temperature is raised to 800 ℃ and held for 3 h. Under the sintering condition of a protective atmosphere, the resin can well coat on the outer surface of the graphite, and finally the material becomes a rod-like structure. While calcined at other heating rates, the finally obtained material presents an irregular shape.

[0042] Figure 4 It is the thermogravimetric curve of the nitrogen-doped resin carbon-coated graphite in Example 1 of the present invention. It can be seen from the curve that the graphite can be well stabilized in the air until the temperature reaches 750℃, and then the graphite begins to react with oxygen to generate carbon dioxide. The thermogravimetric curve of the nitrogen-doped rod-like resin carbon-coated graphite has two weight loss steps starting at 450℃ corresponding to the oxidation of the resin carbon and 750℃ corresponding to the oxidation of the graphite. The resin carbon accounts for about 44% of the total mass of the material.

[0043] Figure 5 It is the TEM image of the nitrogen-doped resin carbon-coated graphite in Example 1 of the present invention. The resin carbon uniformly coats on the surface of the graphite and has a rod-like structure.

[0044] Figure 6 They are the bright and dark field images and the N, C element distribution maps of the nitrogen-doped resin carbon-coated graphite prepared in Example 1 of the present invention. By comparing the bright field image with the dark field image, it can be more intuitively seen that there is a uniformly coated rod-like structure resin carbon on each surface of the graphite. In the element distribution, it can be observed that the C element and the N element are uniformly distributed. Among them, the nitrogen element comes from the cationic surfactant cetyltrimethylammonium bromide and ammonia water.

[0045] Figure 7The first charge-discharge curves of the materials prepared in Example 1 and Comparative Example 1 of the present invention are shown. As can be seen from the figure, the first-cycle Coulombic efficiency of the nitrogen-doped resin carbon-coated graphite prepared in Example 1 is much higher than that of the nitrogen-doped resin carbon / graphite in Comparative Example 1. This is because the nitrogen-doped resin carbon-coated graphite has a specific rod-like structure and a large specific surface area, which is conducive to forming a rich conductive network, providing more ion and electron channels, and improving the Coulombic efficiency of the material.

[0046] Figure 8 It is the rate performance graph of the nitrogen-doped resin carbon-coated graphite prepared in Example 1 of the present invention and the nitrogen-doped resin carbon / graphite prepared in Comparative Example 1. It can be observed that the resin carbon-coated graphite material with a surfactant added in Example 1 has more excellent rate performance compared with the nitrogen-doped resin carbon / graphite negative electrode, with better carrier transport rate and higher specific capacity.

[0047] Figure 9 It is the SEM image of the graphite / resin carbon material without surfactant added in Comparative Example 1 of the present invention. Since no surfactant is added, a rod-like structure resin carbon cannot be formed, and there is no good conductive contact between the resin carbon and the graphite.

[0048] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. A method for preparing a nitrogen-doped resin carbon-coated negative electrode material, characterized in that: The steps include: S1, dispersing graphite powder in a mixed solvent, and then adding a certain amount of surfactant to obtain a surfactant-modified negative electrode material mixed solution; S2, adding ammonia water, phenol and formaldehyde solution to the mixed solution in step S1 in sequence, stirring and reacting for a period of time to separate the resin-coated graphite gel, drying and grinding into powder; S3, calcining the powder obtained in step S2 under a protective atmosphere to obtain a nitrogen-doped resin carbon-coated negative electrode material.

2. The method for preparing the nitrogen-doped resin carbon-coated negative electrode material according to claim 1, characterized in that: In step S1, the graphite particle size is 5-20 μm.

3. The method for preparing a nitrogen-doped resin carbon-coated negative electrode according to claim 1, characterized in that: In step S1, the surfactant is an alkyl group cationic surfactant or a polyether nonionic surfactant, and preferably the surfactant is hexadecyltrimethylammonium bromide.

4. The method for preparing the nitrogen-doped resin carbon-coated negative electrode material according to claim 1, characterized in that: In step S1, the mixed solvent is one or more of methanol, ethanol, isopropanol and water.

5. The method for preparing the nitrogen-doped resin carbon-coated negative electrode material according to claim 1, characterized in that: The phenol is one or more of catechol, resorcinol, hydroquinone, phenol, o-aminophenol, m-aminophenol and p-aminophenol.

6. The method for preparing the nitrogen-doped resin carbon coated negative electrode material according to claim 1, characterized in that: In step S2, the mass volume ratio of phenol to formaldehyde is less than 1 g:0.9 mL.

7. The method for preparing the nitrogen-doped resin carbon coated negative electrode material according to claim 1, characterized in that: In step S2, the reaction temperature is 20-100°C, and the reaction time is 0.5-24 h.

8. The method for preparing the nitrogen-doped resin carbon coated negative electrode material according to claim 1, characterized in that: In step S3, the protective atmosphere is at least one of nitrogen, helium, neon, argon, krypton, and xenon, preferably argon; the calcination is controlled at 1-10 °C min -1 Heating rate: carbonize at 500~1600℃ for 1~5 hours, preferably at 2℃min -1 Calcination is carried out at a heating rate of .

9. A negative electrode material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The negative electrode material comprises a graphite core and resin carbon, wherein the resin carbon is uniformly coated on the surface of the negative electrode active material, the resin carbon has a rod-like structure, and the particle size of the graphite core is 5-20 μm.

10. Use of the negative electrode material according to claim 9 in a lithium ion battery.

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