High-capacity super-fast-charging graphite composite negative electrode material, and preparation method and application thereof

Abstract

This invention relates to the field of battery material preparation technology, and particularly to a high-capacity ultra-fast charging graphite composite anode material, its preparation method, and its application. The graphite composite anode material comprises, from the inside out: a graphite core, a hierarchical porous hard carbon layer, and graphene quantum dots; the graphene quantum dots are distributed within the pores and on the surface of the hierarchical porous hard carbon layer. Through a carefully designed gradient structure, this invention significantly improves the reversible capacity and cycle stability of the material while ensuring high initial coulombic efficiency.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation technology, and in particular to a high-capacity ultra-fast charging graphite composite anode material, its preparation method, and its application. Background Technology

[0002] The layered crystal structure of graphite anodes results in high capacity but also a low diffusion coefficient of lithium ions within the crystal lattice, directly affecting the material's charge-discharge performance. Consequently, under fast charging or low-temperature conditions, lithium is easily deposited on the graphite surface, forming lithium dendrites that may puncture the separator. Furthermore, the solid-liquid interface stability between graphite and the electrolyte is poor, leading to low coulombic efficiency during the initial charge-discharge process and room for improvement in long-term cycle life.

[0003] Existing technologies often employ strategies involving surface modification of graphite particles through coating, such as using amorphous carbon, graphene, or carbon nanotubes. However, amorphous carbon itself typically has poor electrical conductivity, and coating it introduces additional resistance, affecting battery performance. Materials like graphene and carbon nanotubes have large specific surface areas, which can exacerbate electrolyte decomposition reactions on the surface, impacting the battery's initial coulombic efficiency. Summary of the Invention

[0004] In view of this, the present invention provides a high-capacity ultrafast-charging graphite composite anode material, its preparation method, and its application. The graphite composite anode material provided by the present invention can provide a continuous three-dimensional channel for electronic conduction and rapid ion diffusion, significantly improving rate performance; through the quantum confinement effect of GQDs and surface functional groups, a stable, high-ionic-conductivity solid electrolyte interface film is induced to form; while ensuring high initial coulombic efficiency, the reversible capacity and cycle stability of the material are greatly improved.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a high-capacity ultra-fast charging graphite composite anode material, wherein the graphite composite anode material comprises, from the inside out: a graphite core, a multi-level porous hard carbon layer, and graphene quantum dots (GQDs). The graphene quantum dots are distributed inside and on the surface of the hierarchical porous hard carbon layer.

[0006] In some embodiments, the graphite is selected from either synthetic graphite or natural graphite.

[0007] In some embodiments, the pore size distribution of the hierarchical hard carbon layer exhibits a gradient characteristic, wherein the pore size transitions from micropores to mesopores and then to macropores from near the graphite core to the outermost layer of the material; preferably, the micropores are <2 nm, the mesopores are 2-50 nm, and the macropores are 50-100 nm.

[0008] In some embodiments, graphene quantum dots (GQDs) are anchored in a gradient distribution within and on the surface of the hierarchical porous hard carbon layer; wherein, in the macroporous region, the mass loading of GQDs is 1-3 wt%; in the mesoporous region, the mass loading of GQDs is 3-5 wt%; and in the microporous region, the mass loading of GQDs is 5-8 wt%.

[0009] In some embodiments, the size of graphene quantum dots is less than 5 nm, and their surface contains carboxyl and hydroxyl functional groups.

[0010] In a second aspect, the present invention provides a method for preparing a high-capacity ultra-fast charging graphite composite anode material as described in the first aspect, comprising the following steps: Graphite, hard carbon precursor and composite template agent are mixed in solvent to obtain a uniform slurry. After drying, carbonization is performed to remove the template agent and obtain a graphite intermediate coated with hierarchical porous hard carbon. The GQDs solution was mixed with a graphite intermediate coated with hierarchical porous hard carbon. After depressurization, heat treatment is performed. Subsequently, plasma activation treatment is performed; Then, in-situ gas-phase polymerization is carried out in an aniline vapor atmosphere to form a polyaniline transition layer, which is then carbonized at low temperature to obtain the graphite composite anode material.

[0011] In some embodiments, the hard carbon precursor is selected from phenolic resin, epoxy resin, or bitumen.

[0012] In some embodiments, the composite template agent is a mixture of MgO and SiO2 nanospheres; preferably, the mass ratio of MgO to SiO2 nanospheres is 1.5-1.8:1.

[0013] In some embodiments, the solvent is N-methylpyrrolidone.

[0014] In some embodiments, the carbonization process is a gradient temperature carbonization process performed under an inert atmosphere; preferably, carbonization is carried out at 400-500 °C for 1-2 hours, then at 800-900 °C for 2-3 hours, and finally at 1100-1200 °C for 1-2 hours. Carbonization at 800-900 °C forms a macroporous structure, and carbonization at 1100-1200 °C completes graphitization and fixes the mesoporous / microporous structure.

[0015] In some embodiments, the carbonization process is carried out under an inert atmosphere; preferably argon or nitrogen.

[0016] In some embodiments, acid etching is used to remove the template agent; preferably, the acid is HF or HCl.

[0017] In some embodiments, the specific operation of mixing the GQDs solution with the hierarchical porous hard carbon-coated graphite intermediate is as follows: the hierarchical porous hard carbon-coated graphite intermediate is placed in a reactor and a vacuum is drawn; then a low concentration of GQDs solution is injected sequentially and pressure is maintained at 0.1-1 MPa; a medium concentration of GQDs solution is injected and pressure is maintained at 2-4 MPa; and a high concentration of GQDs solution is injected and pressure is maintained at 5-8 MPa.

[0018] In some embodiments, the concentrations of GQDs in the low, medium, and high concentration GQDs solutions are 0.1-0.15 mg / mL, 0.4-0.6 mg / mL, and 0.8-1.2 mg / mL, respectively; preferably, the solvent in the GQDs solution is N-methylpyrrolidone.

[0019] In some embodiments, the pressure is maintained at 0.1-1 MPa for 20-40 minutes; at 2-4 MPa for 50-70 minutes; and at 5-8 MPa for 80-100 minutes.

[0020] In some embodiments, the heat treatment temperature is 150-300 °C and the heat treatment time is 1-3 hours.

[0021] In some embodiments, the plasma activation treatment atmosphere is an N2 / H2 mixed gas; preferably, the volume ratio of N2 to H2 in the N2 / H2 mixed gas is 8-10:1; the treatment is carried out at a power of 60-100 W for 8-15 minutes. Surface cleaning and activation: The N2 / H2 mixed plasma effectively removes residual organic pollutants and oxide layers on the graphite / hard carbon surface through high-energy ion and free radical bombardment, significantly reducing the surface contact angle, improving material affinity, and creating a clean, high-energy reaction substrate for the subsequent uniform adsorption of aniline vapor.

[0022] In some embodiments, the in-situ vapor-phase polymerization temperature in an aniline vapor atmosphere is 50-60 °C, and the polymerization time is 1-2 hours. Aniline vapor polymerization, as a key interface engineering step after plasma activation in this high-capacity ultrafast-charging graphite composite anode material system, plays a crucial role in forming a continuous, conductive, and ion-selective polyaniline (PANI) transition layer through in-situ vapor deposition. The electron delocalization characteristics of the PANI transition layer can homogenize the electrode surface potential distribution and reduce local current density concentration. Combined with GQDs-induced ion flux modulation, this bilayer interface synergistically achieves Li + The spatial homogenization transport suppresses non-uniform lithium metal precipitation from the source, significantly improving battery safety under high rate and low temperature conditions.

[0023] In some embodiments, the low-temperature carbonization temperature is 300-400 °C, and the carbonization time is 0.5-1 hour; preferably, the low-temperature carbonization is carried out under an inert atmosphere. Low-temperature carbonization, as the final heat treatment step in the preparation of this high-capacity ultra-fast charging graphite composite anode material, plays a crucial role in selectively carbonizing and structurally stabilizing the polyaniline (PANI) transition layer formed by in-situ polymerization. Partial carbonization of polyaniline and a leap in conductivity: Under an inert atmosphere at 400 °C, the polyaniline molecular chain undergoes dehydrogenation and deamination reactions, and the side chain amino (-NH2) and imine groups break, initiating main chain crosslinking and conjugated system expansion, forming a "graphite-like carbon" structure with partial graphitization characteristics. This process transforms PANI from a semiconductor state (conductivity ~10⁻⁶) to a more stable state. -5 The conductivity (S / cm) transitions to a highly conductive state (conductivity increases to 10). -1 -10 0 The S / cm significantly reduces the charge transfer resistance at the electrode / electrolyte interface, enhancing the electron transport network. The carbonized PANI is further anchored to the surface functional groups of GQDs via CN covalent bonds, while simultaneously forming a continuous "hard carbon-PANI-GQDs" ternary interface with hierarchical porous hard carbon. This structure achieves a dual-channel synergy of "electron-ion" at the microscale: PANI provides a high-speed electron transport path, and GQDs regulate Li... + Flux, hard carbon providing structural support, and the three work together to suppress lithium dendrite nucleation, improving safety at high rates and low temperatures. Unlike high-temperature carbonization (>800 ℃), the 400 ℃ treatment avoids the volume shrinkage and pore collapse caused by excessive PANI carbonization, fully preserving the connectivity of the hierarchical pore structure, ensuring that electrolyte wetting and ion diffusion dynamics are not hindered, and providing a structural basis for ultra-fast charging performance.

[0024] In some embodiments, low-temperature carbonization is preferably carried out under nitrogen or argon gas.

[0025] Thirdly, the present invention provides a battery, wherein the negative electrode of the battery is prepared from the graphite composite negative electrode material described in the first aspect or the graphite composite negative electrode material prepared in the second aspect.

[0026] Compared with the prior art, the present invention has achieved the following beneficial effects: The material spatial structure gradient provided by this invention creates a pore size gradient from micropores to mesopores to macropores, as well as a GQDs concentration gradient from low to high, constructing an advanced system with clearly defined functional zones and synergistic effects. The synergistic cooperation of the graphite core, the multi-level porous hard carbon layer, and the graphene quantum dots improves the material's rate performance and interface stability, achieving a unity of "fast charging, durability, and high energy". Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 This is an SEM image of the graphite composite anode material of Embodiment 1 of the present invention; Figure 2 This is a comparison chart of the rate retention rate of Embodiment 1 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0029] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0031] Example 1 Raw materials: 100 g of artificial graphite (D50 = 13 μm), 4.08 g of phenolic resin, 1.65 g of MgO template agent, 0.98 g of SiO2 nanospheres (particle size ~20 nm), and 200 mL of N-methylpyrrolidone.

[0032] Construction of a hierarchical porous hard carbon layer: The above raw materials were ball-milled and mixed for 6 hours, then spray-dried and granulated, and placed in a tube furnace. Under an Ar atmosphere, the temperature was increased to 450 °C at 5 °C / min and held for 1 hour, then increased to 850 °C at 3 °C / min and held for 2 hours, and finally increased to 1150 °C at 2 °C / min and held for 1 hour. After natural cooling, the mixture was etched with a 5% HF solution for 2 hours, washed, and dried to obtain intermediate A.

[0033] GQDs gradient impregnation: (The solvent is NMP, and the comparative examples in the following cases are all NMP) 10 g of intermediate A was loaded into a high-pressure reactor and a vacuum was drawn.

[0034] 30 mL of 0.12 mg / mL GQDs solution was injected sequentially and pressurized at 0.5 MPa for 30 minutes; then 30 mL of 0.50 mg / mL GQDs solution was injected and pressurized at 3 MPa for 60 minutes; finally, 30 mL of 1 mg / mL GQDs solution was injected and pressurized at 6 MPa for 90 minutes.

[0035] After slowly depressurizing, the material is treated at 200 °C for 2 hours.

[0036] Interface engineering treatment: The material was placed in a plasma device and treated for 10 minutes at 80 W with a N2:H2 mixture of 9:1. It was then exposed to aniline vapor and polymerized at 55 °C for 1.5 hours. Finally, it was heat-treated in a tube furnace at 350 °C for 0.5 hours under an Ar atmosphere to obtain the final product.

[0037] The graphite composite anode material prepared in this embodiment is used to prepare a battery. The specific steps for preparing the battery include: Graphite anode material, conductive agent and binder are mixed and dissolved in solvent at a mass ratio of 96:1:3, with the solid content controlled at 50%, coated on copper foil current collector, and vacuum dried to obtain anode sheet.

[0038] The negative electrode, electrolyte, SK separator, lithium sheet, and casing are assembled using conventional manufacturing processes for a button cell battery. The electrolyte solvent is ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute is LiPF6 with a concentration of 1 mol / L; the battery's electrical performance is tested using a battery testing system.

[0039] The test conditions were: constant current charge and discharge at room temperature (0.1 C), and charge / discharge cutoff voltage of 0.01 V - 2 V.

[0040] Double charge test method: At room temperature, constant current and constant voltage charging is performed at different rates (1 C, 2 C, 3 C, 4 C, 5 C), followed by 0.1C discharging, with a charge / discharge cutoff voltage of 0.01 V - 2 V.

[0041] Low-temperature discharge test method: At -30 ℃, constant current charge and discharge at 0.1 C, with a charge and discharge cutoff voltage of 0.01 V - 2 V.

[0042] Example 2 Raw materials: 100 g of artificial graphite (D50 = 13 μm), 4.08 g of epoxy resin, 1.65 g of MgO template agent, 0.98 g of SiO2 nanospheres (particle size ~20 nm), and 200 mL of N-methylpyrrolidone.

[0043] Construction of a hierarchical porous hard carbon layer: The above raw materials were ball-milled and mixed for 6 hours, then spray-dried and granulated, and placed in a tube furnace. Under an Ar atmosphere, the temperature was increased to 500 °C at 5 °C / min and held for 1 hour, then increased to 900 °C at 3 °C / min and held for 2 hours, and finally increased to 1200 °C at 2 °C / min and held for 1 hour. After natural cooling, the mixture was etched with a 5% HF solution for 2 hours, washed, and dried to obtain intermediate A.

[0044] GQDs gradient impregnation: 10 g of intermediate A was loaded into a high-pressure reactor and a vacuum was drawn.

[0045] 30 mL of 0.12 mg / mL GQDs solution was injected sequentially and pressurized at 0.8 MPa for 30 minutes; then 30 mL of 0.50 mg / mL GQDs solution was injected and pressurized at 4 MPa for 60 minutes; finally, 30 mL of 1 mg / mL GQDs solution was injected and pressurized at 5 MPa for 90 minutes.

[0046] After slowly depressurizing, the material is treated at 150 °C for 3 hours.

[0047] Interface engineering treatment: The material was placed in a plasma device and treated for 10 minutes at 80 W with a N2:H2 mixture of 9:1. It was then exposed to aniline vapor and polymerized at 55 °C for 1.5 hours. Finally, it was heat-treated in a tube furnace at 300 °C for 1 hour under an Ar atmosphere to obtain the final product.

[0048] The graphite composite anode material prepared in this embodiment is used to prepare a battery. The specific steps for preparing the battery include: Graphite anode material, conductive agent and binder are mixed and dissolved in solvent at a mass ratio of 96:1:3, with the solid content controlled at 50%, coated on copper foil current collector, and vacuum dried to obtain anode sheet.

[0049] The negative electrode, electrolyte, SK separator, lithium sheet, and casing are assembled using conventional manufacturing processes for a button cell battery. The electrolyte solvent is ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute is LiPF6 with a concentration of 1 mol / L; the battery's electrical performance is tested using a battery testing system.

[0050] The test conditions were: constant current charge and discharge at room temperature (0.1 C), and charge / discharge cutoff voltage of 0.01 V - 2 V.

[0051] Double charge test method: At room temperature, constant current and constant voltage charging is performed at different rates (1 C, 2 C, 3 C, 4 C, 5 C), followed by 0.1C discharging, with a charge / discharge cutoff voltage of 0.01 V - 2 V.

[0052] Low-temperature discharge test method: At -30 ℃, constant current charge and discharge at 0.1 C, with a charge and discharge cutoff voltage of 0.01 V - 2 V.

[0053] Example 3 Raw materials: 100 g of artificial graphite (D50 = 13 μm), 4.08 g of pitch, 1.65 g of MgO template agent, 0.98 g of SiO2 nanospheres (particle size ~20 nm), and 200 mL of N-methylpyrrolidone.

[0054] Construction of a hierarchical porous hard carbon layer: The above raw materials were ball-milled and mixed for 6 hours, then spray-dried and granulated, and placed in a tube furnace. Under an Ar atmosphere, the temperature was increased to 400 °C at 5 °C / min and held for 1 hour, then increased to 800 °C at 3 °C / min and held for 2 hours, and finally increased to 1100 °C at 2 °C / min and held for 1 hour. After natural cooling, the mixture was etched with a 5% HF solution for 2 hours, washed, and dried to obtain intermediate A.

[0055] GQDs gradient impregnation: 10 g of intermediate A was loaded into a high-pressure reactor and a vacuum was drawn.

[0056] 30 mL of 0.12 mg / mL GQDs solution was injected sequentially and pressurized at 0.3 MPa for 30 minutes; then 30 mL of 0.50 mg / mL GQDs solution was injected and pressurized at 2 MPa for 60 minutes; finally, 30 mL of 1 mg / mL GQDs solution was injected and pressurized at 7 MPa for 90 minutes.

[0057] After slowly depressurizing, the material is treated at 200 °C for 2 hours.

[0058] Interface engineering treatment: The material was placed in a plasma device and treated for 10 minutes at 80 W with a N2:H2 mixture of 9:1. It was then exposed to aniline vapor and polymerized at 55 °C for 1.5 hours. Finally, it was heat-treated in a tube furnace at 350 °C for 0.5 hours under an Ar atmosphere to obtain the final product.

[0059] The graphite composite anode material prepared in this embodiment is used to prepare a battery. The specific steps for preparing the battery include: Graphite anode material, conductive agent and binder are mixed and dissolved in solvent at a mass ratio of 96:1:3, with the solid content controlled at 50%, coated on copper foil current collector, and vacuum dried to obtain anode sheet.

[0060] The negative electrode, electrolyte, SK separator, lithium sheet, and casing are assembled using conventional manufacturing processes for a button cell battery. The electrolyte solvent is ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute is LiPF6 with a concentration of 1 mol / L; the battery's electrical performance is tested using a battery testing system.

[0061] The test conditions were: constant current charge and discharge at room temperature (0.1 C), and charge / discharge cutoff voltage of 0.01 V - 2 V.

[0062] Double charge test method: At room temperature, constant current and constant voltage charging is performed at different rates (1 C, 2 C, 3 C, 4 C, 5 C), followed by 0.1C discharging, with a charge / discharge cutoff voltage of 0.01 V - 2 V.

[0063] Low-temperature discharge test method: At -30 ℃, constant current charge and discharge at 0.1 C, with a charge and discharge cutoff voltage of 0.01 V - 2 V.

[0064] Example 4 Raw materials: 100 g of artificial graphite (D50 = 13 μm), 4.08 g of phenolic resin, 1.65 g of MgO template agent, 0.98 g of SiO2 nanospheres (particle size ~20 nm), and 200 mL of N-methylpyrrolidone.

[0065] Construction of a hierarchical porous hard carbon layer: The above raw materials were ball-milled and mixed for 6 hours, then spray-dried and granulated, and placed in a tube furnace. Under an Ar atmosphere, the temperature was increased to 450 °C at 5 °C / min and held for 1 hour, then increased to 900 °C at 3 °C / min and held for 2 hours, and finally increased to 1200 °C at 2 °C / min and held for 1 hour. After natural cooling, the mixture was etched with a 5% HF solution for 2 hours, washed, and dried to obtain intermediate A.

[0066] GQDs gradient impregnation: 10 g of intermediate A was loaded into a high-pressure reactor and a vacuum was drawn.

[0067] 30 mL of 0.14 mg / mL GQDs solution was injected sequentially and pressurized at 0.5 MPa for 30 minutes; then 30 mL of 0.50 mg / mL GQDs solution was injected and pressurized at 3 MPa for 60 minutes; finally, 30 mL of 1.1 mg / mL GQDs solution was injected and pressurized at 6 MPa for 90 minutes.

[0068] After slowly depressurizing, the material is treated at 150 °C for 3 hours.

[0069] Interface engineering treatment: The material was placed in a plasma device and treated for 10 minutes at 80 W with a N2:H2 mixture of 9:1. It was then exposed to aniline vapor and polymerized at 60 °C for 1 hour. Finally, it was heat-treated in a tube furnace at 300 °C for 1 hour under an Ar atmosphere to obtain the final product.

[0070] The graphite composite anode material prepared in this embodiment is used to prepare a battery. The specific steps for preparing the battery include: Graphite anode material, conductive agent and binder are mixed and dissolved in solvent at a mass ratio of 96:1:3, with the solid content controlled at 50%, coated on copper foil current collector, and vacuum dried to obtain anode sheet.

[0071] The negative electrode, electrolyte, SK separator, lithium sheet, and casing are assembled using conventional manufacturing processes for a button cell battery. The electrolyte solvent is ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute is LiPF6 with a concentration of 1 mol / L; the battery's electrical performance is tested using a battery testing system.

[0072] The test conditions were: constant current charge and discharge at room temperature (0.1 C), and charge / discharge cutoff voltage of 0.01 V - 2 V.

[0073] Double charge test method: At room temperature, constant current and constant voltage charging is performed at different rates (1 C, 2 C, 3 C, 4 C, 5 C), followed by 0.1C discharging, with a charge / discharge cutoff voltage of 0.01 V - 2 V.

[0074] Low-temperature discharge test method: At -30 ℃, constant current charge and discharge at 0.1 C, with a charge and discharge cutoff voltage of 0.01 V - 2 V.

[0075] Comparative Example 1 (Uniform coating without gradient structure) Preparation: The same type and amount of graphite, hard carbon precursor, and template agent as in Example 1 were used, but the gradient pressure impregnation of GQDs was not performed after carbonization. Instead, the intermediate was directly immersed in a 5% (w / w) NMP solution of GQDs, stirred at atmospheric pressure for 6 hours, and then subjected to the same heat treatment and interface treatment. The material obtained in this comparative example has a hierarchical porous hard carbon coating layer, but the GQDs are randomly and uniformly distributed within the pores without a concentration gradient. The specific steps are as follows: Raw materials: 100 g of artificial graphite (D50 = 13 μm), 4.08 g of phenolic resin, 1.65 g of MgO template agent, 0.98 g of SiO2 nanospheres (particle size ~20 nm), and 200 mL of N-methylpyrrolidone.

[0076] Construction of a hierarchical porous hard carbon layer: The above raw materials were ball-milled and mixed for 6 hours, then spray-dried and granulated, and placed in a tube furnace. Under an Ar atmosphere, the temperature was increased to 450 °C at 5 °C / min and held for 1 hour, then increased to 850 °C at 3 °C / min and held for 2 hours, and finally increased to 1150 °C at 2 °C / min and held for 1 hour. After natural cooling, the mixture was etched with a 5% HF solution for 2 hours, washed, and dried to obtain intermediate A.

[0077] Intermediate A was directly immersed in a 5% (w / w) NMP solution containing GQDs and stirred at atmospheric pressure for 6 hours. The material was then treated at 200 °C for 2 hours.

[0078] Interface engineering treatment: The material was placed in a plasma device and treated for 10 minutes at 80 W with a N2:H2 mixture of 9:1. It was then exposed to aniline vapor and polymerized at 55 °C for 1.5 hours. Finally, it was heat-treated in a tube furnace at 350 °C for 0.5 hours under an Ar atmosphere to obtain the final product.

[0079] The graphite composite anode material prepared in this comparative example was used to prepare a battery. The specific steps for preparing the battery included: Graphite anode material, conductive agent and binder are mixed and dissolved in solvent at a mass ratio of 96:1:3, with the solid content controlled at 50%, coated on copper foil current collector, and vacuum dried to obtain anode sheet.

[0080] The negative electrode, electrolyte, SK separator, lithium sheet, and casing are assembled using conventional manufacturing processes for a button cell battery. The electrolyte solvent is ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute is LiPF6 with a concentration of 1 mol / L; the battery's electrical performance is tested using a battery testing system.

[0081] The test conditions were: constant current charge and discharge at room temperature (0.1 C), and charge / discharge cutoff voltage of 0.01 V - 2 V.

[0082] Double charge test method: At room temperature, constant current and constant voltage charging is performed at different rates (1 C, 2 C, 3 C, 4 C, 5 C), followed by 0.1C discharging, with a charge / discharge cutoff voltage of 0.01 V - 2 V.

[0083] Low-temperature discharge test method: At -30 ℃, constant current charge and discharge at 0.1 C, with a charge and discharge cutoff voltage of 0.01 V - 2 V.

[0084] Comparative Example 2 (Hierarchical Porous Hard Carbon Coating Without GQD Modification) Preparation: A graphite intermediate with a hierarchical porous hard carbon coating was prepared using the same method as in Example 1, but the entire "gradient impregnation and anchoring of graphene quantum dots" step was omitted, and subsequent interface engineering was performed directly. The specific preparation steps are as follows: Raw materials: 100 g of artificial graphite (D50 = 13 μm), 4.08 g of phenolic resin, 1.65 g of MgO template agent, 0.98 g of SiO2 nanospheres (particle size ~20 nm), and 200 mL of N-methylpyrrolidone.

[0085] Construction of a hierarchical porous hard carbon layer: The above raw materials were ball-milled and mixed for 6 hours, then spray-dried and granulated, and placed in a tube furnace. Under an Ar atmosphere, the temperature was increased to 450 °C at 5 °C / min and held for 1 hour, then increased to 850 °C at 3 °C / min and held for 2 hours, and finally increased to 1150 °C at 2 °C / min and held for 1 hour. After natural cooling, the mixture was etched with a 5% HF solution for 2 hours, washed, and dried to obtain intermediate A.

[0086] Interface engineering treatment: Intermediate material A was placed in a plasma device and treated for 10 minutes at 80W with a N2:H2 mixture of 9:1. It was then exposed to aniline vapor and polymerized at 55 °C for 1.5 hours. Finally, it was heat-treated in a tube furnace at 350 °C for 0.5 hours under an Ar atmosphere to obtain the final product.

[0087] The graphite composite anode material prepared in this comparative example was used to prepare a battery. The specific steps for preparing the battery included: Graphite anode material, conductive agent and binder are mixed and dissolved in solvent at a mass ratio of 96:1:3, with the solid content controlled at 50%, coated on copper foil current collector, and vacuum dried to obtain anode sheet.

[0088] The negative electrode, electrolyte, SK separator, lithium sheet, and casing are assembled using conventional manufacturing processes for a button cell battery. The electrolyte solvent is ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute is LiPF6 with a concentration of 1 mol / L; the battery's electrical performance is tested using a battery testing system.

[0089] The test conditions were: constant current charge and discharge at room temperature (0.1 C), and charge / discharge cutoff voltage of 0.01 V - 2 V.

[0090] Double charge test method: At room temperature, constant current and constant voltage charging is performed at different rates (1 C, 2 C, 3 C, 4 C, 5 C), followed by 0.1C discharging, with a charge / discharge cutoff voltage of 0.01 V - 2 V.

[0091] Low-temperature discharge test method: At -30 ℃, constant current charge and discharge at 0.1 C, with a charge and discharge cutoff voltage of 0.01 V - 2 V.

[0092] Comparative Example 3 uses conventional hard carbon-coated graphite material (without hierarchical porous structure and GQDs modification).

[0093] Raw materials: 100 g of artificial graphite (D50 = 13 μm), 4.08 g of phenolic resin.

[0094] The above raw materials were ball-milled and mixed for 6 hours, then spray-dried and granulated, and placed in a tube furnace. Under an Ar atmosphere, the temperature was increased to 450 °C at 5 °C / min and held for 1 hour, then increased to 850 °C at 3 °C / min and held for 2 hours, and finally increased to 1150 °C at 2 °C / min and held for 1 hour, followed by natural cooling.

[0095] The graphite composite anode material prepared in this comparative example was used to prepare a battery. The specific steps for preparing the battery included: Graphite anode material, conductive agent and binder are mixed and dissolved in solvent at a mass ratio of 96:1:3, with the solid content controlled at 50%, coated on copper foil current collector, and vacuum dried to obtain anode sheet.

[0096] The negative electrode, electrolyte, SK separator, lithium sheet, and casing are assembled using conventional manufacturing processes for a button cell battery. The electrolyte solvent is ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute is LiPF6 with a concentration of 1 mol / L; the battery's electrical performance is tested using a battery testing system.

[0097] The test conditions were: constant current charge and discharge at room temperature (0.1 C), and charge / discharge cutoff voltage of 0.01 V - 2 V.

[0098] Double charge test method: At room temperature, constant current and constant voltage charging is performed at different rates (1 C, 2 C, 3 C, 4 C, 5 C), followed by 0.1C discharging, with a charge / discharge cutoff voltage of 0.01 V - 2 V.

[0099] Low-temperature discharge test method: At -30 ℃, constant current charge and discharge at 0.1 C, with a charge and discharge cutoff voltage of 0.01 V - 2 V.

[0100] Comparative Example 4 (the carbonization process is different from that in Example 1) Raw materials: 100 g of artificial graphite (D50 = 13 μm), 4.08 g of phenolic resin, 1.65 g of MgO template agent, 0.98 g of SiO2 nanospheres (particle size ~20 nm), and 200 mL of N-methylpyrrolidone.

[0101] Construction of a hierarchical porous hard carbon layer: The above raw materials were ball-milled and mixed for 6 hours, then spray-dried and granulated, and placed in a tube furnace. Under an Ar atmosphere, the temperature was increased to 450 °C at 5 °C / min and held for 1 hour, then increased to 1150 °C at 2 °C / min and held for 1 hour. After natural cooling, the mixture was etched with a 5% HF solution for 2 hours, washed, and dried to obtain intermediate A.

[0102] GQDs gradient impregnation: 10 g of intermediate A was loaded into a high-pressure reactor and a vacuum was drawn.

[0103] 30 mL of 0.12 mg / mL GQDs solution was injected sequentially and pressurized at 0.5 MPa for 30 minutes; then 30 mL of 0.50 mg / mL GQDs solution was injected and pressurized at 3 MPa for 60 minutes; finally, 30 mL of 1 mg / mL GQDs solution was injected and pressurized at 6 MPa for 90 minutes.

[0104] After slowly depressurizing, the material is treated at 200 °C for 2 hours.

[0105] Interface engineering treatment: The material was placed in a plasma device and treated for 10 minutes at 80 W with a N2:H2 mixture of 9:1. It was then exposed to aniline vapor and polymerized at 55 °C for 1.5 hours. Finally, it was heat-treated in a tube furnace at 350 °C for 0.5 hours under an Ar atmosphere to obtain the final product.

[0106] The graphite composite anode material prepared in this embodiment is used to prepare a battery. The specific steps for preparing the battery include: Graphite anode material, conductive agent and binder are mixed and dissolved in solvent at a mass ratio of 96:1:3, with the solid content controlled at 50%, coated on copper foil current collector, and vacuum dried to obtain anode sheet.

[0107] The negative electrode, electrolyte, SK separator, lithium sheet, and casing are assembled using conventional manufacturing processes for a button cell battery. The electrolyte solvent is ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1; the solute is LiPF6 with a concentration of 1 mol / L; the battery's electrical performance is tested using a battery testing system.

[0108] The test conditions were: constant current charge and discharge at room temperature (0.1 C), and charge / discharge cutoff voltage of 0.01 V - 2 V.

[0109] Double charge test method: At room temperature, constant current and constant voltage charging is performed at different rates (1 C, 2 C, 3 C, 4 C, 5 C), followed by 0.1C discharging, with a charge / discharge cutoff voltage of 0.01 V - 2 V.

[0110] Low-temperature discharge test method: At -30 ℃, constant current charge and discharge at 0.1 C, with a charge and discharge cutoff voltage of 0.01 V - 2 V.

[0111] The test results of Examples 1-4 and Comparative Examples 1-4 are shown in Table 1 and 2. Figure 2 As shown.

[0112] Table 1 Performance Comparison of Examples 1-4 and Comparative Examples 1-4

[0113] Electrochemical and phase performance tests show that: The example group significantly outperformed the comparative group in all indicators, especially in high-rate cycling and low-temperature performance, indicating that the synergistic system of hierarchical porous structure + GQDs gradient anchoring + PANI interface engineering has a systematic optimization effect on lithium-ion transport kinetics and interface stability.

[0114] Examples 1 to 4, serving as optimized samples of the synergistic system, exhibited highly consistent high-performance characteristics, with specific capacity remaining stable in the range of 351.4 to 352.1 mAh / g. Example 3 slightly led with 352.1 mAh / g, but the difference among the four examples was less than 0.3%, indicating that within the "hierarchical pore + GQDs + PANI" framework, the contribution of fine-tuning the precursor type and carbonization process to capacity is approaching saturation, and the utilization rate of active materials is nearing its theoretical limit. In terms of first-efficiency, Example 3 ranked first with 92.56%, followed by Example 1 at 92.45%, with the other two closely behind. Both were significantly better than the comparative group, reflecting that the gradient anchoring of GQDs effectively suppressed electrolyte decomposition and irreversible lithium-ion consumption. Regarding cycle stability, after 500 charge-discharge cycles, the capacity retention rates of all example groups were above 92%, with Example 3 reaching 96.20% and Example 1 reaching 96.12%, far exceeding the lowest level of 88.02% in the comparative example group. This indicates that the PANI flexible SEI film and the GQDs conductive network synergistically constructed a stable electrode / electrolyte interface, effectively suppressing structural pulverization and active material loss. In terms of rate performance, Example 1 maintained 80.39% capacity output at 5C, the best among the four, while Example 3 maintained 80.18%, a slight difference, but both significantly higher than the highest 76.03% in the comparative example group. This demonstrates that the lithium-ion transport kinetics at high rates benefit from the synergistic effect of macroporous channels and gradient conductive networks, rather than being dominated by a single component. In an extreme low-temperature environment of -30°C, Example 1 showed the best capacity retention rate at 56.49%, followed by Example 3 at 56.21%. All four examples remained stable above 56.1%, representing an improvement of over 11 percentage points compared to the highest 45.36% in the comparative group. This highlights the systematic reduction effect of the PANI film on the lithium-ion desolvation energy barrier, thus preserving low-temperature electrochemical activity. Overall, the performance within the example groups was highly convergent, with differences stemming from subtle variations in precursor pyrolysis behavior. However, none of the examples exceeded the performance upper limit of the synergistic system. The core advantage lies in the deep coupling of structural integrity and interface engineering, rather than the extreme optimization of a single parameter.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-capacity, ultra-fast charging graphite composite anode material, characterized in that, The graphite composite anode material comprises, from the inside out: a graphite core, a multi-level porous hard carbon layer, and graphene quantum dots. The graphene quantum dots are distributed inside and on the surface of the hierarchical porous hard carbon layer.

2. The graphite composite anode material as described in claim 1, characterized in that, Graphite is selected from either artificial graphite or natural graphite.

3. The graphite composite anode material as described in claim 1, characterized in that, The pore size distribution of the hierarchical hard carbon layer exhibits a gradient characteristic, wherein the pore size transitions from micropores to mesopores and then to macropores from near the graphite core to the outermost layer of the material; preferably, the micropores are <2 nm, the mesopores are 2-50 nm, and the macropores are 50-100 nm.

4. The graphite composite anode material as described in claim 3, characterized in that, Graphene quantum dots (GQDs) are anchored in a gradient distribution within and on the surface of the hierarchical porous hard carbon layer; wherein, in the macroporous region, the mass loading of GQDs is 1-3 wt%; in the mesoporous region, the mass loading of GQDs is 3-5 wt%; and in the microporous region, the mass loading of GQDs is 5-8 wt%; preferably, the size of the graphene quantum dots is less than 5 nm.

5. The method for preparing the graphite composite anode material as described in claim 1, characterized in that, Includes the following steps: Graphite, hard carbon precursor and composite template agent are mixed in solvent to obtain a uniform slurry. After drying, carbonization is performed to remove the template agent and obtain a graphite intermediate coated with hierarchical porous hard carbon. The GQDs solution was mixed with a graphite intermediate coated with hierarchical porous hard carbon. After depressurization, heat treatment is performed. Subsequently, plasma activation treatment is performed; Then, in-situ gas-phase polymerization is carried out in an aniline vapor atmosphere to form a polyaniline transition layer, which is then carbonized at low temperature to obtain the graphite composite anode material.

6. The preparation method according to claim 5, characterized in that, The hard carbon precursor is selected from at least one of phenolic resin, epoxy resin or bitumen; Alternatively, the composite template agent is a mixture of MgO and SiO2 nanospheres; Alternatively, the carbonization process can be carried out under an inert atmosphere with a gradient temperature increase; preferably, carbonization is performed at 400-500 °C for 1-2 hours, then at 800-900 °C for 2-3 hours, and finally at 1100-1200 °C for 1-2 hours. Alternatively, acid etching can be used to remove the template agent; Alternatively, the specific operation of mixing the GQDs solution with the hierarchical porous hard carbon-coated graphite intermediate is as follows: place the hierarchical porous hard carbon-coated graphite intermediate in a reactor and evacuate it; then sequentially inject a low concentration of GQDs solution and maintain the pressure at 0.1-1 MPa; inject a medium concentration of GQDs solution and maintain the pressure at 2-4 MPa; inject a high concentration of GQDs solution and maintain the pressure at 5-8 MPa.

7. The preparation method according to claim 6, characterized in that, The mass ratio of MgO to SiO2 nanospheres is 1.5-1.8:1; Alternatively, the acid solution may be HF or HCl; Alternatively, in low, medium, and high concentration solutions of GQDs, the concentrations of GQDs are 0.1-0.15 mg / mL, 0.4-0.6 mg / mL, and 0.8-1.2 mg / mL, respectively. Alternatively, the solvent in the GQDs solution is N-methylpyrrolidone; Alternatively, maintain pressure at 0.1-1 MPa for 20-40 minutes; at 2-4 MPa for 50-70 minutes; or at 5-8 MPa for 80-100 minutes.

8. The preparation method according to claim 5, characterized in that, The heat treatment temperature is 150-300 ℃, and the heat treatment time is 1-3 hours; Alternatively, the plasma activation treatment atmosphere is an N2 / H2 mixed gas; the treatment is carried out at a power of 60-100 W for 8-15 minutes; preferably, the volume ratio of N2 to H2 in the N2 / H2 mixed gas is 8-10:

1.

9. The preparation method according to claim 5, characterized in that, The in-situ gas-phase polymerization temperature in an aniline vapor atmosphere is 50-60 ℃, and the polymerization time is 1-2 hours; Alternatively, the low-temperature carbonization temperature is 300-400 ℃, and the carbonization time is 0.5-1 hour; preferably, the low-temperature carbonization is carried out under an inert atmosphere.

10. A battery, characterized in that, The battery negative electrode is prepared from the graphite composite negative electrode material according to any one of claims 1-4 or the graphite composite negative electrode material prepared according to any one of claims 5-9.

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