Artificial graphite negative electrode material and preparation method thereof

Abstract

This invention provides a lithium-ion battery artificial graphite anode material and its preparation method, relating to the technical field of lithium-ion battery anode materials. The method includes the following steps: Step S1, preparation of an impregnation solution; Step S2, coating artificial graphite micropowder with asphalt; Step S3, surface modification; Step S4, high-temperature treatment and graphitization treatment. The lithium-ion battery artificial graphite anode material disclosed in this invention exhibits excellent electrochemical performance, high graphitization degree and compaction density, high charge / discharge capacity and initial coulombic efficiency, and excellent cycle stability.

Description

Technical Field

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

[0002] In recent years, lithium-ion batteries have been widely used in mobile phones, laptops, digital cameras and portable appliances due to their advantages such as high energy density, high operating voltage, stable discharge voltage, good low-temperature performance, low self-discharge, no memory effect, environmental friendliness and long cycle life. They have become the preferred chemical power source for high-end consumer electronics and have also penetrated into cutting-edge technology fields such as aerospace and military, making them an ideal energy source for the 21st century.

[0003] The negative electrode is one of the most important components of a lithium-ion battery, and its performance directly determines the battery efficiency and cycle life. The negative electrode material is crucial in determining its performance. Artificial graphite, as a common negative electrode material for lithium-ion batteries, features high compaction density, high capacity, and good cycle performance, making it an ideal negative electrode material for lithium-ion batteries, especially lithium-ion power batteries. However, the existing preparation process for artificial graphite negative electrode materials for lithium batteries is complex, costly, inefficient, has low capacity, and short lifespan. Due to the numerous active end faces on its surface, the electrolyte decomposes at these active end faces during battery charging and discharging, leading to a decrease in initial coulombic efficiency. Simultaneously, solvent molecule co-intercalation occurs, damaging the structure of the artificial graphite and reducing its capacity and cycle performance.

[0004] To address the aforementioned issues, Chinese invention patent document CN101087021B discloses a method for preparing artificial graphite anode material for lithium-ion batteries, comprising the following steps: pulverizing coal-based or petroleum-based needle coke, preheating, adding modifiers and catalysts, drying and granulating, and heat-treating at a temperature range of 800℃ to 3000℃ for 1 to 48 hours. Compared with existing technologies, this invention uses pulverized needle coke as the anode material, which, after heat treatment, overcomes the disadvantage that highly crystalline graphite materials cannot stably cycle in a PC solvent electrolyte system. Furthermore, it enables high-rate discharge and can be used in lithium-ion power batteries. The process is simple and easy for industrial production. However, the compatibility of this artificial graphite anode material with the electrolyte, as well as the initial coulombic efficiency and capacity retention of lithium batteries using it as the anode material, still need further improvement.

[0005] Therefore, developing a lithium-ion battery artificial graphite anode material with excellent electrochemical performance, high graphitization degree and compaction density, high charge-discharge capacity and first coulombic efficiency, and excellent cycle stability, as well as its preparation method, meets market demand, has broad market value and application prospects, and is of great significance to promoting the development of the field of artificial graphite anode materials. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a lithium battery artificial graphite anode material and its preparation method with excellent electrochemical performance, high degree of graphitization and compaction density, high charge-discharge capacity and first coulombic efficiency, and excellent cycle stability.

[0007] This invention can be achieved through the following technical solutions:

[0008] The method for preparing an artificial graphite anode material for lithium batteries according to the present invention includes the following steps:

[0009] Step S1, Preparation of impregnation solution: N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid and initiator are added to the solvent and mixed evenly to obtain the impregnation solution.

[0010] Step S2, Asphalt Coating of Artificial Graphite Powder: Place artificial graphite powder and asphalt powder in a cone mixer for coarse mixing for 9-15 minutes, then discharge the material. Place the coarsely mixed material in a mechanical blending machine, then start the mechanical blending machine and blend at a speed of 800 r / min to 1200 r / min for 20 to 40 minutes to coat the surface of the artificial graphite powder with asphalt, thus obtaining asphalt-coated artificial graphite powder.

[0011] Step S3, Surface Modification: The asphalt-coated artificial graphite micro powder prepared in step S2 is immersed in the impregnation liquid prepared in step S1 under an inert gas atmosphere. The impregnation liquid is heated at a heating rate of 3-6℃ / min. When the temperature reaches 60-70℃, it is kept at that temperature for 2-4 hours. Then the solvent is removed by rotary evaporation to obtain modified artificial graphite powder.

[0012] Step S4, High-temperature treatment, graphitization treatment: The modified artificial graphite powder prepared in step S3 is subjected to high-temperature treatment and graphitization treatment in sequence to obtain the artificial graphite anode material for lithium batteries.

[0013] Preferably, the mass ratio of N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid, initiator, and solvent in step S1 is (1-2):1:(0.1-0.3):0.2:0.1:(0.05-0.09):(0.03-0.05):(15-20).

[0014] Preferably, the initiator is azobisisobutyronitrile (AIBN).

[0015] Preferably, the solvent is at least one selected from dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0016] Preferably, the mass ratio of artificial graphite powder to asphalt powder in step S2 is 100:(5-10).

[0017] Preferably, the artificial graphite micropowder in step S2 has a particle size of 10-45 μm and a specific surface area of ​​5-10 m². 2 / g, its source has no special requirements, and can be selected from any ordinary artificial graphite powder that can be used as a negative electrode material in the existing technology, such as graphite electrodes, graphitized petroleum coke and graphitized coal tar pitch and other ordinary artificial powders with irregular morphology.

[0018] Preferably, the asphalt powder in step S2 is mesophase asphalt powder with a softening point of 250-290℃, a coking value of ≥75%, toluene-insoluble matter of ≥60%, and ash content of ≤0.5%.

[0019] Preferably, the inert gas in step S3 is any one of nitrogen, helium, neon, and argon.

[0020] Preferably, the mass ratio of the artificial graphite powder to the impregnation liquid in step S3 is 1:(3-5).

[0021] Preferably, the high-temperature treatment in step S4 is performed at a temperature of 950-1250°C for 8-12 hours.

[0022] Preferably, the graphitization treatment in step S4 is performed at a temperature of 3000-3200℃ for 3-5 hours.

[0023] Another objective of this invention is to provide a lithium battery artificial graphite anode material prepared using the above-described method for preparing lithium battery artificial graphite anode material.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The method for preparing artificial graphite anode material for lithium batteries disclosed in this invention is simple, easy to operate, has low dependence on equipment, requires little capital investment, has high preparation efficiency and high finished product qualification rate, and is easy to scale up for production.

[0026] (2) The lithium battery artificial graphite anode material disclosed in this invention improves the adhesion between artificial graphite powder and surface modification layer by coating artificial graphite powder with asphalt, thereby improving stability; at the same time, in combination with other steps, it can also improve compaction density and enhance product processing performance and capacity.

[0027] (3) The artificial graphite anode material for lithium batteries disclosed in this invention comprises an impregnation solution including N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, and tripolyphosphate. The vinyl monomers undergo a copolymerization reaction under the action of an initiator, forming a copolymer layer on the surface of the artificial graphite anode material. After high-temperature treatment and graphitization, a modified layer is formed, reducing active sites and facilitating the formation of an SEI film. This improves the graphite layer shedding phenomenon and electrochemical performance, thereby enhancing cycle performance and capacity. By simultaneously introducing N / Si / F / B components into the surface layer through the impregnation solution, the electrochemical performance of the anode material can be effectively improved, thereby improving the cycle life and battery efficiency of lithium batteries using this anode material.

[0028] (4) The lithium battery artificial graphite anode material disclosed in this invention involves the acid-catalyzed cationic polycondensation reaction of 1-allyl-3-vinylimidazolium tetrafluoroborate and pitch under the action of tripolyphosphoric acid, which further improves the performance stability and electrochemical performance. The reasonable selection of each step and process parameter, and their mutual cooperation, result in the anode material with good electrochemical performance, high degree of graphitization and compaction density, high charge and discharge capacity and first coulombic efficiency, and excellent cycle stability. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments.

[0030] Example 1

[0031] A method for preparing an artificial graphite anode material for lithium batteries includes the following steps:

[0032] Step S1, Preparation of impregnation solution: N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid and initiator are added to the solvent and mixed evenly to obtain the impregnation solution.

[0033] Step S2, Asphalt Coating of Artificial Graphite Powder: Place artificial graphite powder and asphalt powder in a cone mixer for coarse mixing for 9 minutes, then discharge the material. Place the coarsely mixed material in a mechanical blender, then start the mechanical blender and blend at a speed of 800 r / min for 20 minutes to coat the surface of the artificial graphite powder with asphalt to obtain asphalt coated artificial graphite powder.

[0034] Step S3, Surface Modification: The asphalt-coated artificial graphite micro powder prepared in step S2 is immersed in the impregnation liquid prepared in step S1 under an inert gas atmosphere. The impregnation liquid is heated at a heating rate of 3℃ / min. When the temperature reaches 60℃, it is kept at that temperature for 2 hours. Then the solvent is removed by rotary evaporation to obtain modified artificial graphite powder.

[0035] Step S4, High-temperature treatment, graphitization treatment: The modified artificial graphite powder prepared in step S3 is subjected to high-temperature treatment and graphitization treatment in sequence to obtain the artificial graphite anode material for lithium batteries.

[0036] In step S1, the mass ratio of N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphate, initiator, and solvent is 1:1:0.1:0.2:0.1:0.05:0.03:15; the initiator is azobisisobutyronitrile; and the solvent is dimethyl sulfoxide.

[0037] The mass ratio of artificial graphite powder to asphalt powder in step S2 is 100:5.

[0038] The artificial graphite micropowder mentioned in step S2 has a particle size D50 of 23.8 μm and a specific surface area of ​​7.8 m². 2 / g; The asphalt powder mentioned in step S2 is mesophase asphalt powder with a softening point of 260℃, a coking value of ≥75%, toluene-insoluble matter of ≥60%, and ash content of ≤0.5%.

[0039] The inert gas mentioned in step S3 is nitrogen; the mass ratio of the artificial graphite powder to the impregnation liquid is 1:3.

[0040] The high-temperature treatment in step S4 is performed at 950°C for 8 hours; the graphitization treatment is performed at 3000°C for 3 hours.

[0041] A lithium battery artificial graphite anode material prepared using the above-mentioned method for preparing lithium battery artificial graphite anode material.

[0042] Example 2

[0043] A method for preparing an artificial graphite anode material for lithium batteries includes the following steps:

[0044] Step S1, Preparation of impregnation solution: N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid and initiator are added to the solvent and mixed evenly to obtain the impregnation solution.

[0045] Step S2, Asphalt Coating of Artificial Graphite Powder: Place artificial graphite powder and asphalt powder in a cone mixer for coarse mixing for 11 minutes, then discharge the material. Place the coarsely mixed material in a mechanical blender, then start the mechanical blender and blend at a speed of 900 r / min for 25 minutes to coat the surface of the artificial graphite powder with asphalt, thus obtaining asphalt-coated artificial graphite powder.

[0046] Step S3, Surface Modification: The asphalt-coated artificial graphite micro powder prepared in step S2 is immersed in the impregnation liquid prepared in step S1 under an inert gas atmosphere. The impregnation liquid is heated at a heating rate of 4℃ / min. When the temperature reaches 62℃, it is held for 2.5 hours. Then the solvent is evaporated to obtain modified artificial graphite powder.

[0047] Step S4, High-temperature treatment, graphitization treatment: The modified artificial graphite powder prepared in step S3 is subjected to high-temperature treatment and graphitization treatment in sequence to obtain the artificial graphite anode material for lithium batteries.

[0048] In step S1, the mass ratio of N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid, initiator, and solvent is 1.2:1:0.15:0.2:0.1:0.06:0.035:17; the initiator is azobisisobutyronitrile; and the solvent is N,N-dimethylformamide.

[0049] In step S2, the mass ratio of artificial graphite powder to pitch powder is 100:6; the particle size D50 of the artificial graphite powder in step S2 is 23.8 μm, and the specific surface area is 7.8 m². 2 / g; The asphalt powder mentioned in step S2 is mesophase asphalt powder with a softening point of 260℃, a coking value of ≥75%, toluene-insoluble matter of ≥60%, and ash content of ≤0.5%.

[0050] The inert gas mentioned in step S3 is helium; the mass ratio of the artificial graphite powder to the impregnation liquid is 1:3.5.

[0051] The high-temperature treatment in step S4 is performed at 1050°C for 9 hours; the graphitization treatment is performed at 3050°C for 3.5 hours.

[0052] A lithium battery artificial graphite anode material prepared using the above-mentioned method for preparing lithium battery artificial graphite anode material.

[0053] Example 3

[0054] A method for preparing an artificial graphite anode material for lithium batteries includes the following steps:

[0055] Step S1, Preparation of impregnation solution: N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid and initiator are added to the solvent and mixed evenly to obtain the impregnation solution.

[0056] Step S2, Asphalt Coating of Artificial Graphite Powder: Place artificial graphite powder and asphalt powder in a cone mixer for coarse mixing for 12 minutes, then discharge the material. Place the coarsely mixed material in a mechanical blending machine, then start the mechanical blending machine and blend at a speed of 1000 r / min for 30 minutes to coat the surface of the artificial graphite powder with asphalt to obtain asphalt-coated artificial graphite powder.

[0057] Step S3, Surface Modification: The asphalt-coated artificial graphite micro powder prepared in step S2 is immersed in the impregnation liquid prepared in step S1 under an inert gas atmosphere. The impregnation liquid is heated at a heating rate of 4.5℃ / min. When the temperature reaches 65℃, it is kept at that temperature for 3 hours. Then the solvent is removed by rotary evaporation to obtain modified artificial graphite powder.

[0058] Step S4, High-temperature treatment, graphitization treatment: The modified artificial graphite powder prepared in step S3 is subjected to high-temperature treatment and graphitization treatment in sequence to obtain the artificial graphite anode material for lithium batteries.

[0059] In step S1, the mass ratio of N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid, initiator, and solvent is 1.5:1:0.2:0.2:0.1:0.07:0.04:18; the initiator is azobisisobutyronitrile; and the solvent is N-methylpyrrolidone.

[0060] In step S2, the mass ratio of artificial graphite powder to asphalt powder is 100:7.5; the particle size D50 of the artificial graphite powder in step S2 is 23.8 μm, and the specific surface area is 7.8 m². 2 / g; The asphalt powder mentioned in step S2 is mesophase asphalt powder with a softening point of 260℃, a coking value of ≥75%, toluene-insoluble matter of ≥60%, and ash content of ≤0.5%.

[0061] The inert gas mentioned in step S3 is neon; the mass ratio of the artificial graphite powder to the impregnation liquid is 1:4.

[0062] The high-temperature treatment in step S4 is performed at 110°C for 10 hours; the graphitization treatment is performed at 3100°C for 4 hours.

[0063] A lithium battery artificial graphite anode material prepared using the above-mentioned method for preparing lithium battery artificial graphite anode material.

[0064] Example 4

[0065] A method for preparing an artificial graphite anode material for lithium batteries includes the following steps:

[0066] Step S1, Preparation of impregnation solution: N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid and initiator are added to the solvent and mixed evenly to obtain the impregnation solution.

[0067] Step S2, Asphalt Coating of Artificial Graphite Powder: Place artificial graphite powder and asphalt powder in a cone mixer for coarse mixing for 14 minutes, then discharge the material. Place the coarsely mixed material in a mechanical blender, then start the mechanical blender and blend at a speed of 1100 r / min for 35 minutes to coat the surface of the artificial graphite powder with asphalt, thus obtaining asphalt-coated artificial graphite powder.

[0068] Step S3, Surface Modification: The asphalt-coated artificial graphite micro powder prepared in step S2 is immersed in the impregnation liquid prepared in step S1 under an inert gas atmosphere. The impregnation liquid is heated at a heating rate of 5.5℃ / min. When the temperature reaches 68℃, it is kept at that temperature for 3.5 hours. Then the solvent is evaporated to obtain modified artificial graphite powder.

[0069] Step S4, High-temperature treatment, graphitization treatment: The modified artificial graphite powder prepared in step S3 is subjected to high-temperature treatment and graphitization treatment in sequence to obtain the artificial graphite anode material for lithium batteries.

[0070] In step S1, the mass ratio of N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid, initiator, and solvent is 1.8:1:0.25:0.2:0.1:0.08:0.045:19; the initiator is azobisisobutyronitrile; and the solvent is a mixture of dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone in a mass ratio of 1:2:3.

[0071] In step S2, the mass ratio of artificial graphite powder to asphalt powder is 100:9; the particle size D50 of the artificial graphite powder in step S2 is 23.8 μm, and the specific surface area is 7.8 m². 2 / g; The asphalt powder mentioned in step S2 is mesophase asphalt powder with a softening point of 260℃, a coking value of ≥75%, toluene-insoluble matter of ≥60%, and ash content of ≤0.5%.

[0072] The inert gas mentioned in step S3 is argon; the mass ratio of the artificial graphite powder to the impregnation liquid is 1:4.5.

[0073] The high-temperature treatment in step S4 is performed at 1200°C for 11 hours; the graphitization treatment is performed at 3150°C for 4.5 hours.

[0074] A lithium battery artificial graphite anode material prepared using the above-mentioned method for preparing lithium battery artificial graphite anode material.

[0075] Example 5

[0076] A method for preparing an artificial graphite anode material for lithium batteries includes the following steps:

[0077] Step S1, Preparation of impregnation solution: N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid and initiator are added to the solvent and mixed evenly to obtain the impregnation solution.

[0078] Step S2, Asphalt Coating of Artificial Graphite Powder: Place artificial graphite powder and asphalt powder in a cone mixer for coarse mixing for 15 minutes, then discharge the material. Place the coarsely mixed material in a mechanical blender, then start the mechanical blender and blend at a speed of 1200 r / min for 40 minutes to coat the surface of the artificial graphite powder with asphalt to obtain asphalt coated artificial graphite powder.

[0079] Step S3, Surface modification: The asphalt-coated artificial graphite micro powder prepared in step S2 is immersed in the impregnation liquid prepared in step S1 under an inert gas atmosphere. The impregnation liquid is heated at a heating rate of 6℃ / min. When the temperature reaches 70℃, it is kept at that temperature for 4 hours. Then the solvent is evaporated to obtain modified artificial graphite powder.

[0080] Step S4, High-temperature treatment, graphitization treatment: The modified artificial graphite powder prepared in step S3 is subjected to high-temperature treatment and graphitization treatment in sequence to obtain the artificial graphite anode material for lithium batteries.

[0081] In step S1, the mass ratio of N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid, initiator, and solvent is 2:1:0.3:0.2:0.1:0.09:0.05:20; the initiator is azobisisobutyronitrile; and the solvent is dimethyl sulfoxide.

[0082] In step S2, the mass ratio of artificial graphite powder to asphalt powder is 100:10; the particle size D50 of the artificial graphite powder in step S2 is 23.8 μm, and the specific surface area is 7.8 m². 2 / g; The asphalt powder mentioned in step S2 is mesophase asphalt powder with a softening point of 260℃, a coking value of ≥75%, toluene-insoluble matter of ≥60%, and ash content of ≤0.5%.

[0083] The inert gas mentioned in step S3 is nitrogen; the mass ratio of the artificial graphite powder and the impregnation liquid mentioned in step S3 is 1:5.

[0084] The high-temperature treatment in step S4 is performed at 1250°C for 12 hours; the graphitization treatment is performed at 3200°C for 5 hours.

[0085] A lithium battery artificial graphite anode material prepared using the above-mentioned method for preparing lithium battery artificial graphite anode material.

[0086] Comparative Example 1

[0087] A lithium-ion battery artificial graphite anode material is basically the same as that in Example 1, except that methyl vinylsilylfluorene and 1-allyl-3-vinylimidazolium tetrafluoroborate are not added.

[0088] Comparative Example 2

[0089] A lithium battery artificial graphite anode material is basically the same as that in Example 1, except that in step S3, artificial graphite micropowder is used instead of asphalt to coat the artificial graphite micropowder.

[0090] Meanwhile, in order to evaluate the specific technical effects of the artificial graphite anode material for lithium batteries described in this invention, performance tests were conducted using the artificial graphite anode materials for lithium batteries in the embodiments and comparative examples of this invention. The test results are shown in Table 1, and the test methods are as follows: Artificial graphite anode material by mass ratio: Thickener CMC (CMC2200, Daicel, provided by Shanghai Waide International Trade Co., Ltd.): Carbon black conductive agent SP (Swiss Temi high-conductivity carbon black SUPER P Li lithium battery conductive agent): PVDF (Solvay PVDF from the USA). The negative electrode was made of a mixture of 5130 and 95.8:1.2:1.0:2.0, with lithium as the counter electrode. LiPF6 was dissolved at a concentration of 1 mol / L in a mixed solvent of EC / DEC / EMC = 2:3:1 to form a non-aqueous electrolyte, where EC is ethylene carbonate, EMC is methyl ethyl carbonate, and DEC is diethyl carbonate. The separator was a PE / PP / PE composite membrane, and the cells were assembled into a simulated battery. Electrochemical performance tests were conducted on an Arbin BT2000 battery tester in the United States, with a charge / discharge voltage range of 0.01 to 2.0V and a charge / discharge rate of 0.2C.

[0091] Table 1

[0092] project Initial discharge specific capacity (mAh / g) Initial charge / discharge efficiency (%) 300-cycle capacity retention (%) Example 1 420 95.2 98.7 Example 2 423 95.4 99.0 Example 3 428 95.7 99.2 Example 4 430 95.8 99.3 Example 5 434 96.0 99.6 Comparative Example 1 385 93.8 95.9 Comparative Example 2 402 94.3 96.5

[0093] As can be seen from Table 1, the artificial graphite anode material for lithium batteries disclosed in the embodiments of the present invention has superior electrochemical performance compared with the comparative product. The addition of methyl vinylsilicon fluorene, 1-allyl-3-vinylimidazolium tetrafluoroborate and pitch coating are beneficial to improving the above performance.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Anyone skilled in the art can readily implement the present invention based on the above description. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention using the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing an artificial graphite anode material for lithium batteries, characterized in that, Includes the following steps: Step S1, Preparation of impregnation solution: N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid and initiator are added to the solvent and mixed evenly to obtain the impregnation solution. The mass ratio of N-vinylcarbazole, 2,4-diphenyl-4-methyl-1-pentene, methylvinylsilylfluorene, vinyltriethoxysilane, 1-allyl-3-vinylimidazolium tetrafluoroborate, tripolyphosphoric acid, initiator, and solvent in step S1 is (1-2):1:(0.1-0.3):0.2:0.1:(0.05-0.09):(0.03-0.05):(15-20). Step S2, Asphalt Coating of Artificial Graphite Powder: Place artificial graphite powder and asphalt powder in a cone mixer for coarse mixing for 9-15 minutes, then discharge the material. Place the coarsely mixed material in a mechanical blender, then start the mechanical blender and blend at a speed of 800r / min~1200r / min for 20~40 minutes to coat the surface of the artificial graphite powder with asphalt, thus obtaining asphalt-coated artificial graphite powder. Step S3, Surface Modification: The asphalt-coated artificial graphite micro powder prepared in step S2 is immersed in the impregnation liquid prepared in step S1 under an inert gas atmosphere. The impregnation liquid is heated at a heating rate of 3-6℃ / min. When the temperature reaches 60-70℃, it is kept at that temperature for 2-4 hours. Then the solvent is removed by rotary evaporation to obtain modified artificial graphite powder. Step S4, High-temperature treatment, graphitization treatment: The modified artificial graphite powder prepared in step S3 is subjected to high-temperature treatment and graphitization treatment in sequence to obtain the artificial graphite anode material for lithium batteries.

2. The method for preparing a lithium-ion battery artificial graphite anode material as described in claim 1, characterized in that, The initiator is azobisisobutyronitrile.

3. The method for preparing an artificial graphite anode material for lithium batteries as described in claim 1, characterized in that, The solvent is at least one of dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone.

4. The method for preparing a lithium-ion battery artificial graphite anode material as described in claim 1, characterized in that, The mass ratio of artificial graphite powder to asphalt powder in step S2 is 100:(5-10).

5. The method for preparing a lithium-ion battery artificial graphite anode material as described in claim 1, characterized in that, The artificial graphite powder mentioned in step S2 has a particle size of 10-45 μm and a specific surface area of ​​5-10 m². 2 / g.

6. The method for preparing a lithium-ion battery artificial graphite anode material as described in claim 1, characterized in that, The asphalt powder mentioned in step S2 is mesophase asphalt powder with a softening point of 250~290℃, a coking value of ≥75%, toluene-insoluble matter of ≥60%, and ash content of ≤0.5%.

7. The method for preparing an artificial graphite anode material for lithium batteries as described in claim 1, characterized in that, The inert gas mentioned in step S3 is any one of nitrogen, helium, neon, and argon; the mass ratio of the artificial graphite powder to the impregnation liquid is 1:(3-5).

8. The method for preparing a lithium-ion battery artificial graphite anode material as described in claim 1, characterized in that, The high-temperature treatment in step S4 is performed at a temperature of 950-1250℃ for 8-12 hours; the graphitization treatment is performed at a temperature of 3000-3200℃ for 3-5 hours.

9. A lithium battery artificial graphite anode material prepared by the method for preparing lithium battery artificial graphite anode material according to any one of claims 1-8.