A high-rate graphite negative electrode material for lithium ion batteries and a preparation method thereof

Abstract

The application belongs to the technical field of lithium ion battery negative graphite material, and specifically discloses a lithium ion battery high-rate graphite negative material and a preparation method thereof.A lithium ion battery high-rate graphite negative material comprises the following raw materials in parts by weight: carboxymethyl cellulose 1-2 parts, modified asphalt 8-10 parts, graphite 20-25 parts, boron nitride 1-3 parts, N-methyl pyrrolidone 15-20 parts, deionized water 5-6 parts and modified phenolic resin 4-7 parts.The application adopts core modification, cooperates with surface double protection, improves conductivity, has high rate and long cycle, and has good thermal stability and life extension.

Description

Technical Field

[0001] This application relates to the technical field of graphite anode materials for lithium-ion batteries, and in particular to a high-rate graphite anode material for lithium-ion batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries store and release electrical energy by moving lithium ions back and forth between the positive and negative electrodes. They have many advantages such as high energy density, long cycle life, no memory effect, and environmental friendliness, and have been widely used in consumer electronics, vehicle power batteries, and energy storage.

[0003] Lithium-ion batteries mainly consist of four parts: the positive electrode, the negative electrode, the electrolyte, and the separator. The capacity, rate charge / discharge capability, and lifespan of a lithium-ion battery are closely related to the material of the negative electrode. As a crucial component of lithium-ion batteries, the negative electrode directly affects the performance of the entire battery system. Natural graphite is widely used due to its high charge / discharge capacity, good charge / discharge platform, and low cost. However, the large initial irreversible capacity loss and rapid capacity decay during cycling are fatal drawbacks of natural graphite.

[0004] To improve the rate performance of artificial graphite anode materials, a coating material is typically applied to the surface of the artificial graphite. However, this coating material is prone to breakage during cycling, allowing the electrolyte to gradually penetrate into the graphite anode material. During this process, the electrolyte reacts with the exposed graphite anode material, continuously forming a solid electrolyte interface film on the surface. This consumes a significant amount of active lithium, and the electrolyte further penetrates into the uncoated areas of the graphite anode material, damaging its structure, leading to continuous capacity decay, and ultimately deteriorating rate and cycle performance.

[0005] Therefore, how to simultaneously improve the cycle performance and rate performance of natural graphite anode materials is a problem that still needs to be solved. Summary of the Invention

[0006] To improve the poor cycle performance and rate performance of natural graphite anode materials, this application provides a high-rate graphite anode material for lithium-ion batteries and its preparation method.

[0007] This application provides a high-rate graphite anode material for lithium-ion batteries, employing the following technical solution: A high-rate graphite anode material for lithium-ion batteries, comprising the following raw materials by weight: 1-2 parts carboxymethyl cellulose, 8-10 parts modified pitch, 20-25 parts graphite, 1-3 parts boron nitride, 15-20 parts N-methylpyrrolidone, 5-6 parts deionized water, and 4-7 parts modified phenolic resin.

[0008] By employing the above technical solutions, carboxymethyl cellulose provides a suitable slurry viscosity, preventing the sedimentation of graphite and modified asphalt, ensuring uniform dispersion of raw materials, improving slurry stability, and enhancing the bonding force between the anode material and the current collector. Modified asphalt, as a carbon source, forms an amorphous carbon coating layer after high-temperature carbonization, reducing the anode interface impedance and improving the material's conductivity and structural stability. Graphite, as the main active material of the anode, provides the main framework for lithium-ion intercalation and deintercalation, determining the basic capacity of the anode material.

[0009] Boron nitrides, acting as structural stabilizers, enhance the thermal stability and mechanical strength of materials, mitigate volume expansion during lithium-ion intercalation / deintercalation, and improve high-rate performance. N-methylpyrrolidone, as an organic solvent, assists in the dissolution and dispersion of organic raw materials, ensuring slurry uniformity. Modified phenolic resin, as a secondary carbon coating raw material, further optimizes the surface structure of the negative electrode, enhances the cycle stability of the material, and can repair surface defects without excessively increasing resistance.

[0010] This application employs core modification combined with dual surface protection to enhance conductivity, resulting in high rate capability, long cycle life, good thermal stability, and extended lifespan. The graphite anode material maintains high specific capacity while possessing ultra-fast charging (high rate capability) and excellent durability (long cycle life), making it suitable for the needs of current electric vehicle fast charging technology and high-end consumer electronics products.

[0011] Preferably, the modified asphalt is composed of petroleum asphalt, glucose, nano-nickel, and a metal-organic framework / montmorillonite composite.

[0012] By adopting the above technical solutions, petroleum asphalt serves as the modified substrate, providing a carbon source. After modification, it can form a highly conductive and stable carbon coating layer. Glucose, as a carbon source supplement and modifier, can introduce active groups during the pretreatment stage, optimizing the surface structure of the asphalt, enhancing its thermal stability, and improving the subsequent high-temperature modification effect. Nano-nickel, as a catalyst, can reduce the activation energy of the high-temperature modification reaction, promote the graphitization degree of the asphalt, and improve the conductivity of the modified asphalt.

[0013] Metal-organic framework / montmorillonite composites, as structure modifiers, can improve the pore structure of modified asphalt, increase its specific surface area, and synergistically catalyze with nickel to enhance its compatibility with components such as graphite and boron nitrides, thereby improving the high-rate performance and cycle stability of the final graphite anode material. The hydrocarbon gas generated by asphalt pyrolysis, under the catalysis of nano-nickel and metal particles derived from metal-organic frameworks, will grow carbon nanofibers or graphene sheets in situ between or on the surface of montmorillonite.

[0014] The resulting modified pitch consists of an amorphous carbon skeleton composed of pitch coke and glucose coke, and graphitized carbon fibers, carbon nanotubes, or highly crystalline carbon sheets grown by metal catalysis using nickel and metal-organic framework materials. During the secondary carbonization process, these graphite particles are connected like bridges, significantly reducing the contact resistance between particles and improving high-rate performance. After carbonization, the modified pitch exhibits significantly higher mechanical strength than ordinary pitch carbon, better binding graphite particles together, resisting particle shedding caused by high-current charge-discharge, improving the overall crystallinity of the material, reducing interfacial impedance, and enhancing cycle life under high-rate charge-discharge conditions.

[0015] Preferably, the metal-organic framework / montmorillonite composite is composed of montmorillonite, metal-organic framework, and silicon nanowires.

[0016] By employing the above technical solution, montmorillonite, as a carrier of the composite, possesses a large specific surface area and a good layered structure, enabling it to support metal-organic framework materials. Simultaneously, it exhibits excellent structural stability and dispersibility, improving the pore structure of the modified asphalt. Metal-organic framework materials, characterized by high specific surface area and controllable pore structure, can enhance the adsorption performance and structural tunability of the composite, synergistically working with montmorillonite to optimize the interfacial compatibility and structural stability of the modified asphalt.

[0017] Silicon nanowires, acting as structural reinforcing agents, can improve the mechanical strength and conductivity of the composite, while also enhancing the interaction between the composite and components such as nano-nickel and pitch, further optimizing the performance of modified pitch and indirectly improving the high-rate and cycle performance of graphite anodes. The composite formed by montmorillonite, metal-organic framework materials, and silicon nanowires exhibits a multi-level structure with interwoven nanowires. The metal-organic framework material is embedded in the interlayer of montmorillonite, while the silicon nanowires are entangled and adhered to the surface of the montmorillonite sheets, forming a conductive network. This results in a three-dimensional structure that significantly reduces battery internal resistance, achieves high-rate performance, enhances structural stability, and optimizes lithium-ion transport.

[0018] It is subsequently used in the preparation of modified asphalt, which effectively improves the pore structure and compatibility of modified asphalt, thereby helping to improve the structural stability and high-rate charge and discharge performance of high-rate graphite anode materials for lithium-ion batteries.

[0019] Preferably, the modified phenolic resin is composed of phenolic resin, bamboo charcoal powder, talc powder, and nanocellulose.

[0020] By adopting the above technical solution, phenolic resin serves as the substrate, providing a basis for carbon coating. After modification, it can form a dense and stable carbon layer, enhancing the structural integrity and cycle stability of the graphite anode material. Bamboo charcoal powder, as a carbon source supplement and structural reinforcing agent, possesses high conductivity and a large specific surface area, which can improve the conductivity of the modified phenolic resin. Simultaneously, it improves the pore structure of the carbon layer, facilitating lithium-ion transport, and its fibrous structure can enhance the mechanical strength of the coating layer like a microskeleton.

[0021] Talc powder, as a filler, is embedded in phenolic resin carbon to enhance the mechanical strength and heat resistance of the modified phenolic resin, while optimizing its dispersibility and preventing cracking and peeling of the carbon coating layer. Nanocellulose, with its abundant hydroxyl groups, can improve the dispersibility and compatibility of phenolic resin, enhance its binding force with components such as graphite and modified asphalt, and further optimize the carbon coating effect. Nanocellulose forms a fiber network, which, in synergy with bamboo charcoal powder, enhances the flexibility and integrity of the coating layer.

[0022] The carbon fiber network formed by the carbonization of bamboo charcoal powder and nanocellulose, together with the phenolic resin carbon matrix, constitutes a three-dimensional conductive network covering the surface of graphite particles, significantly reducing interfacial impedance and facilitating high-rate charge and discharge. The rigid particles of talc and the fibrous skeleton of bamboo charcoal powder together enhance the compressive strength and toughness of the coating layer, protecting the graphite particles from crushing during electrode rolling and better resisting the volume expansion stress of graphite during cycling, thereby extending cycle life.

[0023] Preferably, the talc pretreatment includes the following steps: dispersing talc powder in deionized water, adding a silane coupling agent, stirring for 10-13 minutes, adding maleic anhydride grafted polymer and cashew nut shell oil, stirring at 85-90°C for 1-2 hours, and drying to obtain pretreated talc powder.

[0024] By adopting the above technical solution, talc powder, as a pretreated substrate, is modified and used as a filler for modified phenolic resin, thereby improving the mechanical strength and heat resistance of the resin and optimizing the performance of the carbon coating layer. Silane coupling agents, as surface modifiers, can introduce active groups onto the surface of talc powder, reduce the surface polarity of talc powder, and improve its compatibility with organic components (phenolic resin, bamboo charcoal powder, etc.).

[0025] Maleic anhydride-grafted polymers act as compatibilizers, reacting with the exposed organic functional groups of the silane coupling agent to form chemical bonds, further enhancing the bonding force between talc and phenolic resin and preventing component separation and agglomeration during subsequent processing. Cashew nut shell oil improves the flexibility of talc and also helps improve its dispersibility, preventing talc from clumping after pretreatment and ensuring uniform mixing with other materials. Its long-chain structure increases the flexibility of the resin system, making the coating layer less prone to cracking.

[0026] After the pretreated talc powder is prepared, it can be directly used in the preparation of modified phenolic resin. After pretreatment, its compatibility and dispersibility are significantly improved, which can effectively avoid agglomeration in the modified phenolic resin, further optimize the performance of the modified phenolic resin, and indirectly improve the structural stability of high-rate graphite anode materials for lithium-ion batteries.

[0027] Preferably, the graphite has a particle size D50 ≤ 10 μm.

[0028] By adopting the above technical solution, the rate performance of the material is improved by shortening the solid-phase diffusion path, enabling the subsequent modified asphalt to bond uniformly, the phenolic resin to effectively coat, and the alumina film to completely cover. The final product is a micron-sized secondary particle formed by the carbonization and bonding of modified asphalt with ≤10μm graphite as the primary particle, coated with a modified phenolic resin carbon layer containing talc-reinforced nodes and a porous carbon network, and finally covered with an alumina film. This approach leverages the fast-charging advantage while compensating for the disadvantage of numerous side reactions through coating, ultimately achieving excellent performance with high rate and long cycle life.

[0029] Preferably, the thickness of the alumina film is 10-20 nm.

[0030] By adopting the above technical solution, 10-20nm is an optimal range that ensures complete coverage, enables rapid lithium-ion transport, and provides good flexibility. It does not hinder the rapid insertion / extraction of lithium ions, perfectly matches high-rate designs, and can form a continuous, dense protective layer, effectively suppressing side reactions and significantly improving cycle life and initial coulombic efficiency.

[0031] Secondly, this application also provides a method for preparing a high-rate graphite anode material for lithium-ion batteries, comprising the following steps: (1) Mix carboxymethyl cellulose, modified bitumen, graphite, boron nitride, N-methylpyrrolidone and deionized water to obtain a slurry; (2) Carbonize the slurry at 1200-1250℃ for 5-6 hours, grind it, and obtain the preform; (3) Mix the preform with the modified phenolic resin, dry it, then coat it with an alumina film, and sieve it to obtain a high-ratio graphite anode material.

[0032] By employing the above technical solution, fine-grained graphite particles ≤10μm are used as primary particles, and secondary particles are formed through modified pitch carbonization bonding, achieving both high magnification and high compaction density. Boron and nitrogen elements are uniformly doped into the carbon framework to enhance intrinsic conductivity. The surface is coated with a porous carbon layer containing bamboo charcoal powder, nanocellulose carbon network, and talc-reinforced nodes, with uniform and controllable thickness. The outermost layer is a 10-20nm alumina film, effectively suppressing side reactions and improving initial coulombic efficiency and cycle stability.

[0033] Preferably, an alumina film is deposited using atomic layer deposition technology.

[0034] By adopting the above technical solution, using atomic layer deposition (ALD) to coat alumina films is the optimal technical approach to ensure precise control of the alumina film thickness within 10-20 nm and to achieve uniform, pinhole-free coating. This comprehensive protection ensures structural stability of the material during long-term cycling, minimizes side reactions, and significantly improves cycle life. The uniform alumina coating enhances the material's thermal stability and strengthens battery safety.

[0035] Thirdly, this application also provides a lithium-ion battery, the lithium-ion battery comprising the aforementioned high-rate graphite anode material.

[0036] In summary, this application has the following beneficial effects: 1. This application employs core modification combined with double surface protection to improve conductivity, resulting in high rate capability and long cycle life, good thermal stability and extended lifespan. The graphite anode material maintains high specific capacity while also possessing ultra-fast charging and excellent durability.

[0037] 2. In this application, the modified phenolic resin is used as a secondary carbon coating raw material to further optimize the surface structure of the negative electrode and enhance the cycle stability of the material. It can repair surface defects without excessively increasing the resistance.

[0038] 3. In this application, the modified asphalt is used as a carbon source. After high-temperature carbonization, it can form an amorphous carbon coating layer, which reduces the negative electrode interface impedance and improves the conductivity and structural stability of the material. Detailed Implementation

[0039] The present application will be further described in detail below with reference to the embodiments.

[0040] The raw materials used in the examples and comparative examples are all commercially available.

[0041] Preparation Example 1 The preparation of modified asphalt includes the following: Grind 12 kg of petroleum asphalt, pass it through a 200-mesh sieve, disperse it in 80 L of water, add 2 kg of glucose, heat it at 300 °C for 2 h under an argon atmosphere, centrifuge it to obtain the pretreated material; The pretreated material, 4 kg of nano-nickel, and 6 kg of metal-organic framework / montmorillonite composite were mixed and heated at 1000℃ for 3 hours under an argon atmosphere to obtain modified asphalt.

[0042] The preparation of the metal-organic framework / montmorillonite composite includes the following steps: 8 kg of montmorillonite was acid-washed (soaked in 20 L of 5% hydrochloric acid solution for 20 min), washed with water, and heated at 200 °C for 1.5 h to obtain activated montmorillonite. 1.2 kg of metal-organic framework material (MOF-303(Al), purchased from Beijing Bailingwei Technology Co., Ltd.) was dispersed in 40 L of deionized water, and the activated montmorillonite, 0.8 kg of cetyltrimethylammonium bromide, and 1 kg of silicon nanowires (purchased from Guangzhou Hongwu Materials Technology Co., Ltd.) were added. The mixture was ground for 3 h and dried to obtain the metal-organic framework / montmorillonite composite.

[0043] Preparation Example 2 The difference from Preparation Example 1 is that glucose is not added.

[0044] Preparation Example 3 The difference from Preparation Example 1 is that no nano-nickel was added.

[0045] Preparation Example 4 The difference from Preparation Example 1 is that no metal-organic framework material / montmorillonite composite is added.

[0046] Preparation Example 5 The difference from Preparation Example 1 is that no metal-organic framework material is added.

[0047] Preparation Example 6 The difference from Preparation Example 1 is that silicon nanowires are not added.

[0048] Preparation Example 7 The preparation of modified phenolic resin includes the following: Mix 1.2 kg of bamboo charcoal powder, 0.5 kg of paraffin wax, and 1.9 kg of talc powder, then grind them to obtain a mixture. 8 kg of phenolic resin (purchased from Jinan Dahui Chemical Technology Co., Ltd.) was dissolved in 30 L of ethanol, 0.5 kg of nanocellulose was added, and the mixture was stirred at 65 °C for 15 min. The mixture was then added, stirred for 3 h, and dried to obtain modified phenolic resin.

[0049] Talc pretreatment includes the following steps: 3 kg of talc powder is dispersed in 10 L of deionized water, 0.6 kg of silane coupling agent KH550 is added, and the mixture is stirred for 13 min. Then, 1.1 kg of maleic anhydride-grafted polymer (specifically maleic anhydride-grafted polypropylene) and 0.4 kg of cashew nut shell oil are added, and the mixture is stirred at 90 °C for 2 h. After drying, pretreated talc powder is obtained.

[0050] Preparation Example 8 The difference from Preparation Example 7 is that bamboo charcoal powder is not added.

[0051] Preparation Example 9 The difference from Preparation Example 7 is that talc is not added.

[0052] Preparation Example 10 The difference from Preparation Example 7 is that nanocellulose is not added.

[0053] Preparation Example 11 The difference from Preparation Example 7 is that maleic anhydride grafted polymer is not added.

[0054] Preparation Example 12 The difference from Preparation Example 7 is that cashew shell oil is not added.

[0055] Example 1 A high-rate graphite anode material for lithium-ion batteries, comprising the following raw materials by weight: 1 kg carboxymethyl cellulose, 8 kg modified pitch, 20 kg graphite, 1 kg boron nitride (purchased from Suzhou Beike Nanotechnology Co., Ltd.), 15 kg N-methylpyrrolidone, 6 kg deionized water, and 7 kg modified phenolic resin.

[0056] The modified bitumen is composed of petroleum bitumen, glucose, nano-nickel, and metal-organic framework / montmorillonite composite.

[0057] The metal-organic framework / montmorillonite composite is composed of montmorillonite, metal-organic framework, and silicon nanowires.

[0058] The modified phenolic resin is composed of thermoplastic phenolic resin, bamboo charcoal powder, talc powder, and nanocellulose.

[0059] The graphite particle size D50 ≤ 10 μm. The thickness of the alumina film is 10 nm. The alumina film is deposited using atomic layer deposition (ALD), specifically, using trimethylaluminum as the aluminum source and water as the oxygen source, and performing 100 deposition cycles at 100 °C to obtain a uniform and dense alumina film.

[0060] The above-mentioned method for preparing a high-rate graphite anode material for lithium-ion batteries includes the following steps: (1) Mix carboxymethyl cellulose, modified bitumen, graphite, boron nitride, N-methylpyrrolidone and deionized water to obtain a slurry; (2) Carbonize the slurry at 1200℃ for 6 hours, grind it, and obtain the preform; (3) Mix the preform with the modified phenolic resin, dry it, then coat it with an alumina film, and sieve it to obtain a high-ratio graphite anode material.

[0061] The modified asphalt was prepared using Preparation Example 1, and the modified phenolic resin was prepared using Preparation Example 7.

[0062] Example 2: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that, by weight, it includes the following raw materials: 2 kg of carboxymethyl cellulose, 10 kg of modified pitch, 25 kg of graphite, 3 kg of boron nitride, 20 kg of N-methylpyrrolidone, 5 kg of deionized water, and 4 kg of modified phenolic resin; the thickness of the alumina film is 20 nm.

[0063] Example 3: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that the modified asphalt is prepared using Preparation Example 2.

[0064] Example 4: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that the modified asphalt was prepared using Preparation Example 3.

[0065] Example 5: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that the modified asphalt was prepared using Preparation Example 4.

[0066] Example 6: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that the modified asphalt is prepared using Preparation Example 5.

[0067] Example 7: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that the modified asphalt was prepared using Preparation Example 6.

[0068] Example 8: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that the modified phenolic resin is prepared using Example 8.

[0069] Example 9: A high-rate graphite anode material for lithium-ion batteries, differing from Example 1 in that the modified phenolic resin was prepared using Example 9.

[0070] Example 10: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that the modified phenolic resin is prepared using Preparation Example 10.

[0071] Example 11: A high-rate graphite anode material for lithium-ion batteries, differing from Example 1 in that the modified phenolic resin was prepared using Preparation Example 11.

[0072] Example 12: A high-rate graphite anode material for lithium-ion batteries, which differs from Example 1 in that the modified phenolic resin is prepared using Preparation Example 12.

[0073] Comparative Example 1 A high-rate graphite anode material for lithium-ion batteries differs from Example 1 in that it does not contain modified asphalt.

[0074] Comparative Example 2 A high-rate graphite anode material for lithium-ion batteries differs from Example 1 in that it does not contain modified phenolic resin.

[0075] The performance testing experiment was conducted on the high-rate graphite anode material for lithium-ion batteries prepared in Examples 1-12 and Comparative Examples 1-2. Using high-rate graphite anode materials from the examples and comparative examples as the anode, and lithium sheets as the counter electrode, LIR2430 coin cells were fabricated. The anode sheet compaction density was 1.68 g / m³. Charge-discharge tests were conducted according to GB / T24533-2019 "Graphite Anode Materials for Lithium-ion Batteries," and full-cell tests were performed. The test results are shown in Table 1.

[0076] Table 1 Test data for the examples and comparative examples

[0077] As shown in Table 1, the high-rate graphite anode material for lithium-ion batteries prepared in Examples 1-2 of this application exhibits excellent charge-discharge performance and high cycle stability retention at high and low temperatures. Specifically, Example 1 shows an initial discharge capacity of 386.5 mAh / g, an initial discharge efficiency of 97.8%, a capacity retention rate of 93.6% after 3000 cycles at 50℃ and 1C, and a capacity retention rate of 96.5% after 2000 cycles at -20℃ and 1C. Therefore, the high-rate graphite anode material for lithium-ion batteries prepared in this application utilizes core modification combined with dual surface protection to improve conductivity, resulting in high rate capability, long cycle life, good thermal stability, and extended lifespan.

[0078] In addition, the battery prepared in Example 1 retained 96.5% of its capacity after 400 cycles of 5C charge-discharge, indicating that the negative electrode material prepared in this application has a high rate capability.

[0079] Examples 3-5 modified asphalts without the addition of glucose, nano-nickel, or metal-organic framework / montmorillonite composite. Table 1 shows that the initial discharge capacity, initial discharge efficiency, capacity retention at 50°C, 50°C, 3000 cycles at 1C, and capacity retention at -20°C, 2000 cycles at 1C, for Examples 3-5 were significantly worse than those of Examples 1-2. This indicates that glucose, as a carbon source supplement and modifier, can introduce active groups during the pretreatment stage, optimizing the surface structure of the asphalt, enhancing thermal stability, and improving the subsequent high-temperature modification effect. Nano-nickel, as a catalyst, can reduce the activation energy of the high-temperature modification reaction, promote the graphitization of the asphalt, and improve the conductivity of the modified asphalt. The metal-organic framework / montmorillonite composite, as a structure modifier, improves the pore structure of the modified asphalt, increases the specific surface area, and synergistically catalyzes with nickel, enhancing its compatibility with graphite, boron nitrides, and other components, thereby improving the high-rate performance and cycle stability of the final graphite anode material.

[0080] Examples 6-7 involved metal-organic framework (MOF) / montmorillonite composites without the addition of MOF or silicon nanowires. Table 1 shows that the initial discharge capacity, initial discharge efficiency, capacity retention at 50°C, 50°C, 3000 cycles at 1C, and capacity retention at -20°C, 2000 cycles at 1C, for Examples 3-5 were significantly worse than Examples 1-2. However, the performance of all related tests was superior to Example 5. This indicates that MOF possesses high specific surface area and controllable pore structure, enhancing the adsorption performance and structural tunability of the composite. It also synergistically works with montmorillonite to optimize the interfacial compatibility and structural stability of the modified asphalt. Silicon nanowires, as a structural reinforcing agent, improve the mechanical strength and conductivity of the composite, while also improving the interaction between the composite and components such as nano-nickel and asphalt, further optimizing the performance of the modified asphalt and indirectly enhancing the high-rate and cycling performance of the graphite anode.

[0081] Examples 8-10 modified phenolic resins without the addition of bamboo charcoal powder, talc powder, or nanocellulose. Table 1 shows that the initial discharge capacity, initial discharge efficiency, capacity retention at 50℃, 50℃, 3000 cycles at 1C, and capacity retention at -20℃, 2000 cycles at 1C, were significantly worse than those of Examples 1-2. This indicates that bamboo charcoal powder, as a carbon source supplement and structural reinforcing agent, possesses high conductivity and a large specific surface area, improving the conductivity of the modified phenolic resin and simultaneously improving the pore structure of the carbon layer, thus facilitating lithium-ion transport. Talc powder, embedded in the carbon of the phenolic resin, enhances the mechanical strength and heat resistance of the modified phenolic resin, while optimizing its dispersibility and preventing cracking and peeling of the carbon coating layer. Nanocellulose, with its abundant hydroxyl groups, improves the dispersibility and compatibility of the phenolic resin, strengthens its bonding force with components such as graphite and modified asphalt, further optimizing the carbon coating effect. Nanocellulose forms a fiber network, synergistically enhancing the flexibility and integrity of the coating layer with bamboo charcoal powder.

[0082] In Examples 11-12, maleic anhydride-grafted polymer and cashew nut shell oil were not added during the talc pretreatment. Table 1 shows that the initial discharge capacity, initial discharge efficiency, capacity retention at 50°C, 50°C, 3000 cycles at 1C, and capacity retention at -20°C, 2000 cycles at 1C, were significantly worse than in Examples 1-2, but the corresponding performance was better than in Example 9. This indicates that the maleic anhydride-grafted polymer, acting as a compatibilizer, reacts with the exposed organic functional groups of the silane coupling agent to form chemical bonds, enhancing the bonding force between talc and phenolic resin and preventing component separation and agglomeration during subsequent processing. Cashew nut shell oil improves the flexibility of talc and also helps improve its dispersibility, preventing talc agglomeration after pretreatment and ensuring uniform mixing with other materials. The long-chain structure increases the flexibility of the resin system, making the coating layer less prone to cracking.

[0083] Comparative Examples 1 and 2 were performed without modified asphalt and modified phenolic resin, respectively. Table 1 shows that the initial discharge capacity, initial discharge efficiency, capacity retention at 50°C, 50°C, and 3000 cycles at 1C, and capacity retention at -20°C and 2000 cycles at 1C, for Comparative Examples 1 and 2 were significantly worse than those of Examples 1 and 2. This indicates that modified asphalt, as a carbon source, can form an amorphous carbon coating layer after high-temperature carbonization, reducing the negative electrode interface impedance and improving the material's conductivity and structural stability. Modified phenolic resin, as a secondary carbon coating raw material, further optimizes the negative electrode surface structure and enhances the material's cycle stability, repairing surface defects without excessively increasing resistance.

[0084] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-rate graphite anode material for lithium-ion batteries, characterized in that, By weight, it includes the following raw materials: 1-2 parts carboxymethyl cellulose, 8-10 parts modified bitumen, 20-25 parts graphite, 1-3 parts boron nitride, 15-20 parts N-methylpyrrolidone, 5-6 parts deionized water, and 4-7 parts modified phenolic resin.

2. The high-rate graphite anode material for lithium-ion batteries according to claim 1, characterized in that, The modified asphalt is composed of petroleum asphalt, glucose, nano-nickel, and a metal-organic framework / montmorillonite composite.

3. The high-rate graphite anode material for lithium-ion batteries according to claim 2, characterized in that, The metal-organic framework / montmorillonite composite is composed of montmorillonite, metal-organic framework, and silicon nanowires.

4. The high-rate graphite anode material for lithium-ion batteries according to claim 1, characterized in that, The modified phenolic resin is composed of phenolic resin, bamboo charcoal powder, talc powder, and nanocellulose.

5. The high-rate graphite anode material for lithium-ion batteries according to claim 4, characterized in that, The talc pretreatment includes the following steps: dispersing talc powder in deionized water, adding a silane coupling agent, stirring for 10-13 minutes, adding maleic anhydride grafted polymer and cashew nut shell oil, stirring at 85-90℃ for 1-2 hours, and drying to obtain pretreated talc powder.

6. The high-rate graphite anode material for lithium-ion batteries according to claim 1, characterized in that, The graphite has a particle size D50 ≤ 10 μm.

7. The high-rate graphite anode material for lithium-ion batteries according to claim 1, characterized in that, The thickness of the alumina film is 10-20 nm.

8. The method for preparing a high-rate graphite anode material for lithium-ion batteries according to claim 1, characterized in that, Includes the following steps: (1) Mix carboxymethyl cellulose, modified bitumen, graphite, boron nitride, N-methylpyrrolidone and deionized water to obtain a slurry; (2) Carbonize the slurry at 1200-1250℃ for 5-6 hours, grind it, and obtain the preform; (3) Mix the preform with the modified phenolic resin, dry it, then coat it with an alumina film, and sieve it to obtain a high-ratio graphite anode material.

9. The method for preparing a high-rate graphite anode material for lithium-ion batteries according to claim 8, characterized in that, Alumina films were deposited using atomic layer deposition (ALD) technology.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the high-rate graphite anode material according to any one of claims 1-9.

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