Preparation method and application of coating material easy to graphitize

Abstract

The invention belongs to the technical field of lithium ion battery negative electrode materials and coated asphalt, and discloses a preparation method and application of a coating material easy to graphitize. The preparation method comprises the following steps: by taking one or more than two of petroleum residual oil, ethylene tar, medium and low temperature coal tar, coal pitch, petroleum pitch and maltha as raw materials, adding a blending solvent and a catalyst to obtain a blending raw material; the easily-graphitized coating material with relatively low interlayer spacing after carbonization is obtained by sequentially carrying out blending solvent compounding, boron doping and pressurized polymerization or sequentially carrying out blending solvent compounding, boron doping, pressurized polymerization, oxidation crosslinking and reduced pressure distillation / molecular distillation processes. The graphitization performance of the asphalt material is remarkably improved through boron doping, so that the asphalt material can form an ordered carbon layer structure at 1200 DEG C, carbonization shrinkage and microcrack generation are inhibited, and the compactness and uniformity of a coating layer are improved. The obtained coating material is suitable for the negative electrode of the lithium ion battery, and the first charge reversible capacity, the cycle stability and the rate capability of the battery can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery negative electrode materials and coated asphalt, and relates to a preparation method of an easily graphitizable coating material and application thereof. Background Art

[0002] As today's most promising energy storage device, the performance of lithium-ion batteries directly determines the technological advancements in key sectors such as new energy vehicles, consumer electronics, and energy storage systems. Among the four core components of lithium-ion batteries, the performance of the anode material itself directly impacts the entire battery system. Due to inherent structural imperfections in anode materials, coating the anode particles is often necessary to improve their rate and cycling performance.

[0003] In the coating process, the graphite negative electrode material is coated with asphalt, and a "protective cover" with a shell structure is formed on the surface of the material. This not only avoids the co-embedding and mixing of lithium ions and solvents and inhibits the decomposition of the electrolyte, but also effectively improves the first-charge reversible capacity, cycle stability and battery rate performance of the negative electrode material, helps to shape the negative electrode material, and makes the lithium battery have a larger gram capacity, longer service life and faster charging speed.

[0004] Negative electrode material coating technology has been widely used in industry, but existing methods still face technical bottlenecks. Traditional coated asphalt has a low degree of graphitization at conventional heat treatment temperatures (usually below 1200°C), which affects the uniform insertion / extraction of lithium ions, especially during high-rate charge and discharge, which easily induces local polarization. During asphalt carbonization, the volume shrinkage rate is as high as 60-70%, and microcracks are generated at the particle interface. The cracks become electrolyte permeation channels, accelerating the abnormal growth of the SEI film. New coating materials need to be developed to simultaneously solve the problems of insufficient graphitization and high defects during low-temperature carbonization. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for preparing a readily graphitizable coating material and its application. The preparation method provided by the present invention significantly improves the graphitization performance of the asphalt material through boron doping, enabling the formation of an ordered carbon layer structure at 1200°C. It also inhibits carbonization shrinkage and microcracks, improving the density and uniformity of the coating layer. The resulting coating material is suitable for lithium-ion battery negative electrodes and can improve the battery's first-charge reversible capacity, cycle stability, and rate performance. The present invention has a simple process, low cost, and is suitable for industrial production.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0007] A method for preparing an easily graphitizable coating material comprises the following steps: using one or more of petroleum residue, ethylene tar, medium- and low-temperature coal tar, coal tar, petroleum asphalt, and soft asphalt as raw materials, adding a blending solvent and a catalyst to obtain a blended raw material; and sequentially subjecting the material to a blending solvent compounding, boron doping, and pressurized polymerization, or sequentially subjecting the material to a blending solvent compounding, boron doping, pressurized polymerization, oxidative crosslinking, and reduced pressure distillation / molecular distillation to obtain an easily graphitizable coating material having a relatively low interlayer spacing (interlayer spacing less than 0.348 nm at 1200° C.) after carbonization.

[0008] The easily graphitizable solid coating material having a relatively low interlayer spacing (interlayer spacing less than 0.348 nm at 1200° C.) after carbonization is obtained by sequentially undergoing the processes of co-blending solvent compounding, boron doping, pressurized polymerization, oxidative crosslinking, and reduced pressure distillation or molecular distillation.

[0009] The easily graphitizable liquid coating material with a low interlayer spacing (interlayer spacing less than 0.348 nm at 1200°C) after carbonization is obtained through the steps of co-blending solvent, boron doping, and pressurized polymerization.

[0010] The raw materials account for 50 wt% to 100 wt% of the blended raw materials, the blending solvent accounts for 0 wt% to 50 wt% of the blended raw materials, and the catalyst accounts for 0 wt% to 1 wt% of the blended raw materials.

[0011] The catalyst is a Lewis acid catalyst, preferably any one or more of aluminum chloride, boron trifluoride, trimethylaluminum, and zinc chloride.

[0012] The blended solvent comprises one or more of cracked naphthalene fraction or wash oil and borate homologues. In the blended solvent, the cracked naphthalene fraction accounts for 80wt% to 99wt% of the blended solvent, and the borate homologues account for 1wt% to 20wt% of the blended solvent.

[0013] The borate homologue is preferably any one or two or more of phenylboronic acid, naphthaleneboronic acid and polyboronic acid.

[0014] The softening point of the solid easily graphitizable coating material is 100°C to 280°C.

[0015] Furthermore, the blending solvent compounding step specifically includes: adding one or more borate homologues to the cracked naphthalene fraction or the wash oil, stirring at 10-200° C. for 0.5-2 hours to obtain the blending solvent;

[0016] Furthermore, the boron doping step specifically includes: using one or more of petroleum residue, ethylene tar, medium-low temperature coal tar, coal pitch, petroleum pitch, and soft pitch as raw materials, adding a blending solvent and a catalyst to obtain a blended raw material; mixing at 50° C. to 200° C. for 0.5 to 24 hours to obtain a doped modified raw material;

[0017] Furthermore, the pressure polymerization step specifically includes: placing the doped modified raw material obtained in the boron doping step into a reactor, heating it to 50°C to 200°C at a heating rate of 1°C / min to 10°C / min, reacting at this temperature for 0.5h to 5h, heating it again to 50°C to 350°C, introducing nitrogen and pressurizing it to 0.1 to 3.0 MPa, and conducting a polymerization reaction at this temperature for 1h to 24h to obtain a graphitizable liquid coating material;

[0018] Furthermore, the oxidative crosslinking step specifically includes: oxidative crosslinking the graphitizable liquid coating material obtained in the pressure polymerization step, blowing air into the liquid coating material at 100° C. to 380° C., with an air flow rate of 1 L / min to 300 L / min and an oxidation time of 1 hour to 10 hours, to obtain an oxidized asphalt with a softening point greater than 100° C.;

[0019] Furthermore, the oxidized asphalt obtained after oxidative cross-linking is subjected to vacuum distillation or molecular distillation to separate the light fraction and enrich the heavy aromatic components (polycyclic aromatic hydrocarbon condensed ring structure) to prepare an easily graphitizable fixed coating material.

[0020] Furthermore, the parameters of the reduced pressure distillation are: reduced pressure -0.05 to -0.1 MPa, distillation temperature 200° C. to 400° C., stirring speed 0 rpm to 300 rpm, and time 1 h to 10 h.

[0021] Furthermore, the parameters of molecular distillation are: distillation temperature 200° C. to 330° C., vacuum pressure 10 Pa to 200 Pa, and rotation speed 100 rpm to 400 rpm.

[0022] Furthermore, the stirring speed in the steps of compounding the blending solvent and doping with boron is 0 rpm to 700 rpm.

[0023] The present invention also seeks to protect the use of the easily graphitized liquid coating material or the easily graphitized fixed coating material prepared by the above preparation method in the preparation of lithium-ion batteries, wherein the easily graphitized fixed coating material coats the negative electrode material of the lithium-ion battery.

[0024] The beneficial effects of the present invention compared with the prior art are:

[0025] 1) The present invention significantly improves the graphitization performance and electrochemical properties of asphalt materials through boron doping modification. Boron atoms are embedded in the asphalt carbon layer as electron acceptors, catalyzing the orderly arrangement of carbon hexagonal rings, so that the material can obtain a relatively orderly carbon layer structure at 1200°C. At the same time, the electrical conductivity of the material is improved, and the diffusion kinetics of lithium ions are improved. The cross-linking effect of boron can also inhibit structural shrinkage and microcracks during the carbonization process, making the coating layer dense and uniform, and improving the cycle life. This method is simple and suitable for the low-cost preparation of high-performance negative electrode coating materials.

[0026] 2) The present invention significantly optimizes the doping effect through the synergistic effect of borate homologues with asphalt ester solvents such as cracked naphthalene fractions and wash oils. As an excellent solvent, the cracked naphthalene fraction can fully dissolve the asphalt raw material. At the same time, its rich aromatic structure provides a uniformly dispersed medium for borate, ensuring the uniform doping of boron elements in the asphalt molecules. During the blending process, borate undergoes an ester exchange reaction with the active sites of asphalt to form a stable BOC bond, which not only improves the doping efficiency of boron, but also strengthens the cross-linked network of asphalt molecules. This process can achieve the dispersion of boron elements under mild conditions, avoids component segregation caused by high-temperature treatment, and provides a uniform precursor structure for subsequent carbonization.

[0027] 3) The catalyst used in the present invention is a Lewis acid catalyst, which can activate the boron atoms in the borate ester, making it easier to react with the aromatic rings or fatty side chains in the asphalt. The boron atoms can be effectively embedded in the carbon skeleton of the asphalt, significantly improving the material properties.

[0028] 4) This invention allows for the flexible preparation of liquid or solid coating materials through the same process. Liquid materials are suitable for dipping or spraying processes, achieving uniform coating of complex substrates; solid materials are convenient for solid-phase coating after pulverization, meeting the needs of different application scenarios. Both forms of products maintain easy graphitization, significantly reducing production costs and improving process adaptability. DETAILED DESCRIPTION

[0029] The present invention is further illustrated below by way of examples, but the present invention is not limited to the scope of the examples. Based on the examples of the present invention, any simple modifications, equivalent changes, or modifications made by ordinary technicians in this field without making creative work are still within the scope of protection of the present invention.

[0030] A method for preparing an easily graphitized coating material, which uses one or more of petroleum residue, ethylene tar, medium- and low-temperature coal tar, and coal tar as raw materials, adds a blending solvent and a catalyst, and sequentially undergoes blending solvent compounding, boron doping, pressurized polymerization, oxidative crosslinking, and reduced pressure distillation or molecular distillation processes to obtain an easily graphitized coating material having a relatively low interlayer spacing (interlayer spacing less than 0.348 nm at 1200° C.) after carbonization; the method comprises the following steps:

[0031] 1) Compounding of co-blending solvents

[0032] Add one or more borate homologues to the cracked naphthalene fraction or wash oil, place in a reaction kettle and stir at 10-200° C. for 0.5-2 hours to obtain a blended solvent;

[0033] 2) Boron doping

[0034] Using one or more of petroleum residue, ethylene tar, petroleum asphalt, medium and low temperature coal tar, coal tar, and soft asphalt as raw materials, adding a blending solvent and a catalyst to mix, the mixing temperature is 50° C. to 200° C., and the mixing time is 0.5 to 24 hours to obtain a doping modified raw material;

[0035] 3) Pressurized polymerization

[0036] The doped modified raw material is placed in a reactor, heated to 50°C to 200°C at a heating rate of 1°C / min to 10°C / min, reacted at constant temperature for 0.5h to 5h, and then heated to 50°C to 350°C again. Nitrogen is introduced and pressurized to 0.1 to 3.0 MPa, and the polymerization reaction is kept at constant temperature for 1h to 24h to obtain an easily graphitized liquid coating material.

[0037] 4) Oxidative cross-linking

[0038] The graphitizable liquid coating material is further oxidized and cross-linked at a temperature of 100°C to 380°C, air is blown in at a flow rate of 1 L / min to 300 L / min, and the oxidation time is 1 hour to 10 hours to obtain an oxidized asphalt with a softening point greater than 100°C;

[0039] 5) Reprocessing (decompression distillation or molecular distillation)

[0040] The oxidized asphalt is separated into light and heavy components by vacuum distillation or molecular distillation. The parameters used for vacuum distillation are as follows:

[0041] Decompression pressure: -0.05~-0.1Mpa;

[0042] Distillation temperature: 2000℃~400℃;

[0043] Stirring speed: 0rpm~300rpm;

[0044] Time: 1h~10h;

[0045] Oxidized asphalt is obtained by molecular distillation under rotational conditions. The parameters used are as follows:

[0046] Distillation temperature: 200℃~330℃;

[0047] Vacuum pressure: 10Pa~200Pa;

[0048] Speed: 100rpm~400rpm;

[0049] The graphitizable coating material is prepared by a method of reduced pressure distillation or molecular distillation.

[0050] In the blended solvent, the cracked naphthalene fraction accounts for 80 wt% to 99 wt% of the blended solvent, and the borate homologues account for 1 wt% to 20 wt% of the blended raw materials.

[0051] In the doping and modification step, the raw materials petroleum residue, ethylene tar, petroleum asphalt, medium and low temperature coal tar, coal tar, and soft asphalt account for 50wt% to 100wt% of the blended raw materials, the blending solvent accounts for 0wt% to 50wt% of the blended raw materials, and the catalyst accounts for 0wt% to 1wt% of the blended raw materials.

[0052] The catalyst is a Lewis acid catalyst, preferably any one of zinc chloride, aluminum chloride, boron trifluoride, and trimethylaluminum.

[0053] The stirring speed in the steps of compounding the blending solvent and doping with boron is 0 rpm to 700 rpm.

[0054] The softening point of the graphitizable coating material obtained by the reduced pressure distillation or molecular distillation method is 100° C. to 280° C.

[0055] Example 1

[0056] Aryl borate is added to the cracked naphthalene fraction in a mass ratio of 90 wt% to 10 wt% of the cracked naphthalene fraction. The mixture is then stirred in a reactor at 120°C for 2 hours to ensure thorough mixing of the two raw materials, resulting in a blended solvent. Ethylene tar (70 wt% of the blended raw material) and the blended solvent (30 wt% of the blended raw material) are then mixed and placed in a reactor, stirred at 150°C for 1 hour to ensure thorough mixing of the ethylene tar and the blended solvent, resulting in a doped and modified raw material. The doped and modified raw material is placed in a reactor and heated to 200°C at a rate of 5°C / min. The reaction is then maintained at this temperature for 1 hour, then heated again to 330°C. Nitrogen is introduced and pressurized to 0.5 MPa. The polymerization reaction is then maintained at this temperature for 4 hours to produce a graphitizable liquid coating material. The graphitizable liquid coating material is then oxidatively crosslinked at 330°C for 3 hours to produce oxidized asphalt. Oxidized asphalt was added to a short-path molecular distiller at a temperature of 280°C, a vacuum pressure of 100 Pa, a rotation speed of 200 rpm, and a distillation time of 3 hours to produce a readily graphitizable coated asphalt material. Performance indicators are shown in Table 1, and performance indicators after carbonization at 1200°C are shown in Table 2. This readily graphitizable coated asphalt material was solid-phase coated with a negative electrode material, and after carbonization, button-type lithium-ion batteries were assembled for electrochemical testing. The battery test results are shown in Table 3.

[0057] Example 2:

[0058] An aryl borate ester is added to the cracked naphthalene fraction in a mass ratio of 90 wt% to 10 wt%; the mixture is then stirred in a reactor at 120°C for 2 hours to ensure thorough mixing of the two raw materials, thereby obtaining a blended solvent. Ethylene tar (70 wt% of the blended raw material) and the blended solvent (30 wt% of the blended raw material) are then mixed uniformly in a reactor and stirred at 150°C for 1 hour to ensure thorough mixing of the ethylene tar and the blended solvent, thereby obtaining a doped and modified raw material. The doped and modified raw material is then placed in a reactor and heated to 200°C at a rate of 5°C / min. The reaction is then maintained at this temperature for 1 hour, then heated again to 330°C. Nitrogen is introduced and pressurized to 0.5 MPa. The polymerization reaction is then maintained at this temperature for 4 hours, thereby obtaining a graphitizable liquid coating material. The performance indicators are shown in Table 1, and the performance indicators after carbonization at 1200°C are shown in Table 2. The graphitizable coated asphalt material and the negative electrode material were liquid-phase coated and carbonized, and then assembled into a button-type lithium-ion battery for electrochemical testing. The battery test results are shown in Table 3.

[0059] Example 3:

[0060] Polyborate is added to the cracked naphthalene fraction in a mass ratio of 95wt% to 5wt%; the mixture is then stirred in a reactor at 150°C for 2 hours to ensure thorough mixing of the two raw materials, resulting in a blended solvent. Ethylene tar, representing 70wt% of the blended raw material, and the blended solvent, representing 30wt%, are then mixed and placed in a reactor, stirred at 150°C for 1 hour to ensure thorough mixing of the ethylene tar and the blended solvent, resulting in a doped and modified raw material. The doped and modified raw material is placed in a reactor and heated to 200°C at a rate of 5°C / min. The reaction is then maintained at this temperature for 1 hour, then raised to 350°C, nitrogen is introduced, and the reaction is maintained at this temperature for 2 hours to produce a graphitizable liquid coating material. The graphitizable liquid coating material is then oxidatively crosslinked at 330°C for 3 hours to produce oxidized asphalt. Oxidized asphalt was added to a short-path molecular distiller at a temperature of 300°C, a vacuum pressure of 100 Pa, a rotation speed of 200 rpm, and a distillation time of 3 hours to produce a readily graphitizable coated asphalt material. Performance indicators are shown in Table 1, and performance indicators after carbonization at 1200°C are shown in Table 2. This readily graphitizable coated asphalt material was solid-phase coated with a negative electrode material, and after carbonization, button-type lithium-ion batteries were assembled for electrochemical testing. The battery test results are shown in Table 3.

[0061] Example 4:

[0062] An aryl borate ester is added to the cracked naphthalene fraction in a mass ratio of 85 wt% to 15 wt% of the cracked naphthalene fraction. The mixture is then stirred in a reactor at 120°C for 2 hours to ensure thorough mixing of the two raw materials, thereby obtaining a blended solvent. Ethylene tar (70 wt% of the blended raw material), a blended solvent (29 wt% of the blended raw material), and zinc chloride (1 wt% of the blended raw material) are then mixed uniformly in a reactor at 100°C for 1 hour to ensure thorough mixing of the ethylene tar and the blended solvent, thereby obtaining a doped and modified raw material. The doped and modified raw material is then placed in a reactor and heated to 200°C at a rate of 5°C / min. The reaction is then maintained at this temperature for 1 hour, then heated again to 330°C. Nitrogen is introduced and pressurized to 0.5 MPa. The polymerization reaction is then maintained at this temperature for 4 hours, thereby obtaining a readily graphitizable liquid coating material. The readily graphitizable liquid coating material is then subjected to oxidative crosslinking at 300°C for 3 hours to obtain oxidized asphalt. Oxidized asphalt was added to a short-path molecular distiller at a temperature of 300°C, a vacuum pressure of 100 Pa, a rotation speed of 200 rpm, and a distillation time of 3 hours to produce a readily graphitizable coated asphalt material. Performance indicators are shown in Table 1, and performance indicators after carbonization at 1200°C are shown in Table 2. This readily graphitizable coated asphalt material was solid-phase coated with a negative electrode material, and after carbonization, button-type lithium-ion batteries were assembled for electrochemical testing. The battery test results are shown in Table 3.

[0063] Comparative Example 1

[0064] Ethylene tar was placed in a reactor and heated to 350°C at a rate of 5°C / min. The polymerization reaction was maintained at this temperature for 4 hours. The mixture was then added to a short-path molecular distiller set at 250°C, with a vacuum pressure of 100 Pa and a rotation speed of 200 rpm for 1 hour to produce a readily graphitizable low-softening-point coated asphalt material. Performance indicators are shown in Table 1, and those after carbonization at 1200°C are shown in Table 2. This readily graphitizable coated asphalt material was solid-phase coated with a negative electrode material, and after carbonization, button-type lithium-ion batteries were assembled for electrochemical testing. The battery test results are shown in Table 3.

[0065] Comparative Example 2

[0066] Ethylene tar was placed in a reactor and heated to 380°C at a rate of 5°C / min. The polymerization reaction was then maintained at this temperature for 2 hours. The mixture was then added to a short-path molecular distiller set at 280°C, with a vacuum pressure of 100 Pa and a rotation speed of 200 rpm for 3 hours to produce a readily graphitizable low-softening-point coated asphalt material. Performance indicators are shown in Table 1, and those after carbonization at 1200°C are shown in Table 2. This readily graphitizable coated asphalt material was solid-phase coated with a negative electrode material, and after carbonization, button-type lithium-ion batteries were assembled for electrochemical testing. The battery test results are shown in Table 3.

[0067] Table 1 Performance indicators of the embodiments

[0068] Serial number Softening point / ℃ QI / % CV / % Example 1 226.7 0.07 69.6 Example 2 none 0.03 10.2 Example 3 276.3 0.11 74.3 Example 4 280.8 0.86 76.1 Comparative Example 1 151.7 0.02 61.2 Comparative Example 2 247.1 0.01 73.6

[0069] Table 21 Performance indexes after carbonization at 200℃

[0070]

[0071] Table 3 Battery test results

[0072] Serial number D50(μm) Specific surface area (m2 / g) Reversible specific capacity (mAh / g) First coulombic efficiency (%) Anode material standard 12.1 3.88 354.1 92.6 Example 1 14.6 2.17 353.7 94.7 Example 2 13.8 2.03 355.2 95.5 Example 3 14.1 2.26 352.9 94.1 Example 4 15.1 3.11 356.2 95.9 Comparative Example 1 14.7 2.62 353.2 94.1 Comparative Example 2 14.1 2.41 355.0 94.8

[0073] As shown in Table 2, the interlayer spacing (d002) of Examples 1-4 after carbonization at 1200°C is lower than that of Comparative Examples 1 and 2, especially the interlayer spacing of Example 4 is only Far superior to the control and This indicates that boron doping effectively promotes the orderly arrangement of carbon hexacyclic rings, forming a denser graphitized structure. D / I G The ratios are generally lower than those of the comparative examples, further demonstrating the improvement of their graphitization degree.

[0074] In terms of electrochemical performance, as shown in Table 3, the first coulombic efficiency of the coated negative electrode materials of Examples 1-4 is superior to that of the uncoated negative electrode material standard sample, among which Example 4 even reaches 95.9%, significantly higher than the 92.6% of the comparative example. At the same time, the reversible specific capacity of the examples is comparable to or even slightly improved than that of the standard sample, indicating that the coating material of the present invention improves battery performance without sacrificing its capacity. In contrast, although the comparative example also shows certain performance, it is inferior to the examples of the present invention in terms of graphitization degree and electrochemical performance.

[0075] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. For those skilled in the art, any obvious modifications made thereto without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a graphitizable coating material, characterized in that: Method: One or more of petroleum residue, ethylene tar, medium-low temperature coal tar, coal tar, petroleum asphalt, and soft asphalt are used as raw materials, and a blending solvent and a catalyst are added to obtain a blending raw material; and the blending solvent is compounded, boron is doped, and pressurized polymerization is performed in sequence, or the blending solvent is compounded, boron is doped, pressurized polymerization is performed in sequence, oxidative crosslinking, and vacuum distillation / molecular distillation is performed in sequence to obtain a graphitizable coating material with a relatively low interlayer spacing after carbonization; wherein the relatively low interlayer spacing is an interlayer spacing of less than 0.348 nm at 1200°C.

2. The method for preparing a graphitizable coating material according to claim 1, wherein: The raw materials account for 50 wt% to 100 wt% of the blended raw materials, the blending solvent accounts for 0 wt% to 50 wt% of the blended raw materials, and the catalyst accounts for 0 wt% to 1 wt% of the blended raw materials.

3. The method for preparing a graphitizable coating material according to claim 1, wherein: The catalyst is a Lewis acid catalyst.

4. The method for preparing a graphitizable coating material according to claim 1, wherein: The blended solvent includes one or more than two of cracked naphthalene fraction or wash oil and borate homologues.

5. The method for preparing a graphitizable coating material according to claim 1, wherein: The blending solvent compounding step specifically comprises: adding one or more borate homologues to the cracked naphthalene fraction or the wash oil, stirring at 10-200° C. for 0.5-2 hours to obtain the blending solvent; The boron doping step specifically includes: using one or more of petroleum residue, ethylene tar, medium-low temperature coal tar, coal pitch, petroleum pitch, and soft pitch as raw materials, adding a blending solvent and a catalyst to obtain a blended raw material; mixing at 50° C. to 200° C. for 0.5 to 24 hours to obtain a doped modified raw material; The pressure polymerization step specifically includes: placing the doped modified raw material obtained in the boron doping step into a reactor, heating it to 50°C to 200°C at a heating rate of 1°C / min to 10°C / min, reacting at this temperature for 0.5h to 5h, heating it again to 50°C to 350°C, introducing nitrogen and pressurizing it to 0.1 to 3.0 MPa, and conducting a polymerization reaction at this temperature for 1h to 24h to obtain a graphitizable liquid coating material; The oxidative crosslinking step specifically includes: oxidative crosslinking of the easily graphitized liquid coating material obtained in the pressurized polymerization step, blowing air into the liquid coating material at 100°C to 380°C, with an air flow rate of 1L / min to 300L / min and an oxidation time of 1h to 10h, to obtain oxidized asphalt with a softening point greater than 100°C.

6. The method for preparing a graphitizable coating material according to claim 1, wherein: The oxidized asphalt obtained after oxidative cross-linking is subjected to vacuum distillation or molecular distillation to separate the light fraction and enrich the heavy aromatic component to prepare the easily graphitized fixed coating material.

7. The method for preparing a graphitizable coating material according to claim 1, wherein: The parameters of the reduced pressure distillation are: reduced pressure -0.05 to -0.1 MPa, distillation temperature 200° C. to 400° C., stirring speed 0 rpm to 300 rpm, and time 1 h to 10 h.

8. The method for preparing a graphitizable coating material according to claim 1, wherein: The parameters for molecular distillation are: The distillation temperature is 200℃~330℃, the vacuum pressure is 10Pa~200Pa, and the rotation speed is 100rpm~400rpm.

9. The method for preparing a graphitizable coating material according to claim 4, wherein: The cracked naphthalene fraction in the blended solvent accounts for 80 wt% to 99 wt% of the blended solvent, and the borate homologues account for 1 wt% to 20 wt% of the blended raw materials.

10. Use of the easily graphitizable coating material prepared by the method for preparing an easily graphitizable coating material according to any one of claims 1 to 9 in preparing lithium-ion batteries.

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