Fast-charging graphite negative electrode material, preparation method thereof and lithium ion battery

Abstract

The invention discloses a fast-charging graphite negative electrode material, a preparation method thereof and a lithium ion battery, and belongs to the technical field of lithium ion batteries. The preparation method provided by the invention comprises the following steps: carrying out pore-forming treatment on graphite by adopting laser etching to obtain porous graphite; preparing a catalyst metal layer on the surface of the porous graphite through a vapor deposition method, and annealing to obtain metal nanoparticles; growing a carbon nanotube in situ through a vapor deposition method; and removing the metal nanoparticles, and then carrying out fast ion layer coating to obtain the fast-charging graphite negative electrode material. According to the invention, a multi-stage structure with an efficient ion / electron transmission channel and an interface lithium compensation function is constructed, and the fast charging performance, the first efficiency and the cycling stability of a battery assembled by the material are remarkably improved.

Description

Technical Field

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

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] As one of the most important electrochemical energy storage systems today, the rapid charging capability and energy efficiency of lithium-ion batteries have become key factors restricting their further development in fields such as electric vehicles and portable electronic devices. Graphite anode materials still dominate the market due to their cost and overall performance advantages. However, their inherent layered crystal structure leads to slow lithium-ion insertion / extraction kinetics, which, under high-current charging, not only causes severe electrode polarization and capacity decay but also poses safety hazards such as lithium plating.

[0004] To improve fast-charging performance, constructing porous structures to expand ion transport channels is an effective approach. However, while introducing porous structures enhances ion transport capabilities, it also places higher demands on the conductivity network and interfacial stability of the material. Currently, conductive agents such as carbon nanotubes are often introduced to construct three-dimensional conductive networks to compensate for electron transport. However, traditional physical mixing or solution impregnation catalytic growth methods struggle to achieve robust and uniform ohmic contacts in graphite matrices, especially within complex pores. The introduced carbon nanotubes are prone to aggregation or uneven distribution, resulting in limited conductivity enhancement. More seriously, such methods may introduce harmful impurities, such as residual halogen elements from certain catalyst precursors, which can significantly exacerbate electrolyte decomposition and damage electrode interfaces. This not only increases the battery's internal resistance but also poses a hidden danger of accelerated performance degradation during long-term cycling.

[0005] Furthermore, low initial coulombic efficiency is another core bottleneck restricting graphite anodes, especially when matched with high-capacity cathode systems. Irreversible consumption of active lithium during the formation of the solid electrolyte interface film directly reduces the energy density of the full cell. Although pre-lithiation technology has been extensively studied, achieving precise, uniform lithium compensation compatible with existing electrode processes while avoiding the introduction of negative effects remains a significant challenge for current technology.

[0006] Therefore, existing modification strategies often only focus on solving single problems such as ion transport, electronic conductivity, or lithium compensation, making it difficult to systematically overcome multiple challenges such as high internal resistance, insufficient fast-charging performance, and low initial efficiency. This results in graphite materials that are difficult to balance in terms of overall performance and long-term reliability. Developing a graphite anode material and its preparation method that can synergistically optimize ion / electron transport and achieve efficient interfacial lithium compensation has become a key bottleneck in the current development of fast-charging battery technology. Summary of the Invention

[0007] In view of this, the present invention provides a fast-charging graphite anode material and its preparation method, as well as a lithium-ion battery. The present invention constructs a multi-level structure with both efficient ion / electron transport channels and interface lithium compensation function through the synergistic application of laser etching and vapor deposition technology, which significantly improves the fast-charging performance, first-cycle efficiency and cycle stability of the battery assembled from the material.

[0008] In a first aspect, the present invention provides a method for preparing a fast-charging graphite anode material, comprising the following steps: Porous graphite was obtained by laser etching to create pores in the graphite. A catalyst metal layer was prepared on the surface of porous graphite by vapor deposition, followed by annealing to obtain metal nanoparticles. In-situ growth of carbon nanotubes via vapor deposition; After removing the metal nanoparticles, a fast-ion layer is applied to coat the material, thus obtaining the fast-charging graphite anode material.

[0009] Preferably, the graphite has a particle size D50 of 5~20μm, the porous graphite has a porosity of 5~30%, and a pore size of 2~100nm.

[0010] Preferably, in the step of preparing the catalyst metal layer by vapor deposition, the thickness of the catalyst metal layer is 0.5~20 nm, and the metal is one or more of nickel, cobalt, and iron.

[0011] Furthermore, in the step of preparing the catalyst metal layer by vapor deposition, atomic layer deposition is used for vapor deposition.

[0012] Preferably, the annealing temperature is 350~500℃ and the annealing time is 2~5h.

[0013] Preferably, in the step of in-situ growth of carbon nanotubes by vapor deposition, chemical vapor deposition is used, and the mass of the grown carbon nanotubes is 0.4 to 2% of the mass of porous graphite.

[0014] Preferably, metal nanoparticles are removed by physical grinding or chemical etching.

[0015] Preferably, the coating amount of the fast ion layer is 0.1-3% of the mass of porous graphite, the fast ion layer is prepared by atomic layer deposition, and the material of the fast ion layer is one or more of LiF, Li2O or Li3P.

[0016] Secondly, the present invention provides a fast-charging graphite anode material, which is prepared by the above-described preparation method.

[0017] Thirdly, the present invention provides a lithium-ion battery comprising the above-mentioned fast-charging graphite anode material.

[0018] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) This invention achieves synergistic effects among the various steps by combining laser etching for pore formation, vapor deposition catalysis, in-situ growth of carbon nanotubes, and fast ion layer coating. Among them, the regular channels formed by laser etching provide an ideal substrate for subsequent uniform deposition, while the vapor deposition process ensures the uniform distribution of metal catalysts and fast ion conductors in the complex channels. This multi-level structure construction enables the material to have both excellent ion / electron transport channels and interface stability.

[0019] (2) The present invention adopts the full vapor deposition route and constructs the catalyst layer and fast ion layer through atomic layer deposition technology. This not only achieves precise control at the nanoscale, but more importantly, it fundamentally avoids harmful impurities such as halogens that may be introduced by traditional solution methods, significantly improving the intrinsic purity and chemical stability of the material, and laying a solid foundation for the long cycle life and high temperature storage performance of the battery.

[0020] (3) The graphite anode material prepared by the present invention exhibits significantly improved comprehensive performance: the in-situ grown carbon nanotubes and the fast ion conductor layer work together to effectively reduce the interface impedance and enhance the high current charging capability of the material, enabling it to achieve a higher constant current charging SOC at a high rate of 5C; at the same time, the active lithium component in the fast ion layer effectively compensates for the lithium loss in the first cycle, increasing the first efficiency of the full battery to about 90%, solving the technical problem of the difficulty in achieving both fast charging and high first efficiency. Attached Figure Description

[0021] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0022] Figure 1 This is a schematic diagram of the structure of the fast-charging graphite anode material prepared in Example 1 of the present invention; In the figure, 1 is porous graphite; 2 is carbon nanotubes; and 3 is a fast ion conductor layer. Detailed Implementation

[0023] 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.

[0024] This invention provides a method for preparing a fast-charging graphite anode material, comprising the following steps: Porous graphite was obtained by laser etching to create pores in the graphite. A catalyst metal layer was prepared on the surface of porous graphite by vapor deposition, followed by annealing to obtain metal nanoparticles. In-situ growth of carbon nanotubes via vapor deposition; After removing the metal nanoparticles, a fast-ion layer is applied to coat the material, thus obtaining the fast-charging graphite anode material.

[0025] The present invention provides a graphite anode material with excellent fast-charging characteristics through multi-level structural collaborative design. First, laser etching technology is used to precisely create pores on the surface and inside of graphite particles. This process selectively removes carbon atoms using a high-energy laser beam, forming micro / nano structures with controllable pore size and regular channels along the graphite crystal substrate. This directional pore-forming method not only significantly increases the lithium-ion transport channels and shortens the diffusion path of ions between graphite layers, but more importantly, it creates an ideal substrate for subsequent functionalization modifications.

[0026] Based on the obtained well-organized porous structure, an ultrathin catalyst metal layer was prepared on the graphite surface using vapor deposition. This metal layer was then transformed into uniformly distributed metal nanoparticles during subsequent annealing. These nanoparticles serve as catalytically active sites, providing the necessary conditions for the in-situ growth of carbon nanotubes.

[0027] Subsequently, in-situ growth of carbon nanotubes was achieved via vapor deposition in a carbon source atmosphere. During growth, the carbon source catalytically decomposes on the surface of the metal nanoparticles, and carbon atoms precipitate from the other side of the metal particles through a dissolution-diffusion mechanism, forming carbon nanotubes that are firmly bonded to the graphite matrix. This in-situ growth method ensures the formation of a stable electronic conduction channel between the carbon nanotubes and porous graphite, constructing a three-dimensional conductive network that runs through the entire material.

[0028] Finally, after removing the residual metal catalyst, a fast ion conductor layer was coated onto the material surface using a vapor deposition process. This coating layer, in synergy with the previously constructed porous structure and carbon nanotube network, provides both a rapid lithium-ion transport channel and a reversible lithium source in the early stages of electrochemical cycling, while effectively controlling the composition and structure of the solid electrolyte interface film at the electrode-electrolyte interface.

[0029] There is a close synergistic relationship among the various process steps described above. The regular channels created by laser etching provide an ideal template for the uniform distribution of the catalyst; the uniformly distributed catalyst ensures the controllable growth of carbon nanotubes in three-dimensional space; and the in-situ grown carbon nanotube network creates favorable conditions for the uniform coating of the subsequent fast ion layer. This precise construction of a multi-level structure enables the material to simultaneously possess optimized ion transport paths, efficient electron conduction networks, and stable electrode-electrolyte interfaces, thereby achieving a significant improvement in fast-charging performance.

[0030] In an optional embodiment of the present invention, the particle size D50 of the graphite is 5~20 μm, more preferably 8~15 μm; too small a particle size will lead to a decrease in tap density and an increase in side reactions, while too large a particle size will prolong the ion diffusion path. The porosity of the porous graphite is 5~30%, and the pore size of the porous graphite is 2~100 nm, providing sufficient ion transport channels while maintaining structural strength. The above porosity values ​​are values ​​measured using the mercury porosimetry method.

[0031] This invention does not impose special restrictions on the specific process and parameters of laser etching, as long as porous graphite with specific parameters can be obtained. Preferably, this invention uses a nanosecond pulsed laser with a wavelength of 350 nm and a power density of 10~100 MW / cm². 2 The scanning speed is 0.1~10mm / s.

[0032] In an optional embodiment of the present invention, in the step of preparing the catalyst metal layer by vapor deposition, the thickness of the catalyst metal layer is 0.5~20 nm, and the metal is one or more of nickel, cobalt, and iron, which can effectively catalyze the growth of carbon nanotubes during the vapor deposition process. Further, atomic layer deposition is used for the vapor deposition. Specifically, the precursor can be selected from organometallic compounds such as Ni(Cp)2, Ni(acac)2, CoCp(CO)2, and Co(acac)2, and the deposition temperature is preferably 150~300℃.

[0033] In an optional embodiment of the present invention, the annealing temperature is 350~500℃, more preferably 380~420℃; and the annealing time is 2~5h, more preferably 2.5~4h.

[0034] In an optional embodiment of the present invention, in the step of in-situ growth of carbon nanotubes by vapor deposition, chemical vapor deposition is used, and the mass of the grown carbon nanotubes is 0.4-2% of the mass of porous graphite, more preferably 0.5-1%. The present invention does not impose special limitations on the specific process of chemical vapor deposition. Preferably, methane is used as the carbon source, and the structural parameters and mass fraction of the carbon nanotubes are controlled by adjusting the volume ratio of methane to hydrogen, the growth temperature, and the growth time. Preferably, the volume ratio of methane to hydrogen is 1:(1-4), the growth temperature is 700-900℃, and the growth time is 2-30 min.

[0035] In optional embodiments of the present invention, metal nanoparticles are removed by physical grinding or chemical etching, more preferably by chemical etching. Chemical etching can be performed using a 3-30 wt% H₂O₂ aqueous solution, at a temperature of 40-60°C, for a time of 3-5 hours. After chemical etching, the nanoparticles must be washed with water and dried.

[0036] In an optional embodiment of the present invention, the coating amount of the fast ion layer is 0.1-3% of the mass of porous graphite, more preferably 0.5-1%. The fast ion layer is prepared by atomic layer deposition, and the material of the fast ion layer is one or more of LiF, Li2O, or Li3P. The present invention does not impose any special limitation on the specific method of atomic layer deposition; any atomic layer deposition method commonly used in the art can be used. For example, when depositing a LiF layer, Li(thd) (lithium 2,2,6,6-tetramethylheptanedione) and TiF4 can be used as precursors, and the deposition temperature is 200-300°C. When depositing a Li3P layer, LiOtBu (lithium tert-butoxide) and P(TMS)3 (tris(trimethylsilyl)phosphine) can be used as precursors, and the deposition temperature is 200-300°C.

[0037] This invention also provides a fast-charging graphite anode material, prepared by the above-described method. The fast-charging graphite anode material provided by this invention features a multi-level structure that combines efficient ion / electron transport channels with interface lithium compensation functionality.

[0038] The present invention also provides a lithium-ion battery comprising the above-mentioned fast-charging graphite anode material.

[0039] The lithium-ion battery of the present invention has the advantages of the fast-charging graphite anode material, and has excellent fast-charging performance, initial efficiency and cycle stability.

[0040] This invention does not impose any special limitations on the specific preparation method of the above-mentioned lithium-ion battery; any commonly used lithium-ion battery preparation method in the field can be used.

[0041] The technical solution of the present invention will be further described below with reference to specific embodiments. The present invention does not impose any special restrictions on the source of reagents used in the following embodiments; commercially available products well known to those skilled in the art can be used.

[0042] Example 1 This embodiment provides a fast-charging graphite anode material and its preparation method.

[0043] (1) Take 1 kg of artificial graphite raw material with a particle size D50 of 10 μm. Use a nanosecond pulsed laser etching system (wavelength 1064 nm, power density 50 MW / cm²). 2 A porous graphite matrix with a porosity of 20% and a pore size distribution of 2~100nm was obtained by directional pore formation of graphite at a scanning speed of 2mm / s.

[0044] (2) Using an atomic layer deposition apparatus, a nickel metal layer with a thickness of 5 nm was deposited on the surface of porous graphite at 200 °C with bis(cyclopentadiene) nickel (Ni(Cp)2) as a precursor. Subsequently, the nickel layer was annealed at 400 °C for 3 hours in an argon / hydrogen mixed atmosphere (volume ratio 95:5) to transform the nickel layer into uniformly distributed nickel nanoparticles.

[0045] (3) Place the material obtained in step (2) in a chemical vapor deposition furnace, introduce a methane / hydrogen mixed gas (volume ratio 1:2), and react at 800°C for about 15 minutes to grow carbon nanotubes in situ. The mass of the carbon nanotubes is 0.5% of the mass of the porous graphite matrix.

[0046] (4) The material was chemically etched with 10wt% hydrogen peroxide solution at 50℃ for 4h to remove nickel catalyst particles. Then it was washed with deionized water until neutral and vacuum dried at 80℃ for 6h.

[0047] (5) Using an atomic layer deposition apparatus, Li(thd) and TiF4 were used as precursors to deposit a LiF fast ion conductor layer at 250°C. The mass of the coating was controlled to be 0.5% of the mass of the porous graphite matrix, and finally fast-charging graphite anode material was prepared.

[0048] Figure 1 This is a schematic diagram of the structure of the fast-charging graphite anode material prepared in this embodiment. Carbon nanotubes 2 are grown inside the pores of porous graphite 1 and on the surface of porous graphite 1. The LiF fast ion conductor layer 3 covers the inside and surface of the pores of porous graphite 1.

[0049] Example 2 This embodiment provides a fast-charging graphite anode material and its preparation method.

[0050] (1) Take 1 kg of artificial graphite raw material with a particle size D50 of 10 μm. Use a nanosecond pulsed laser etching system (wavelength 1064 nm, power density 50 MW / cm²). 2 A porous graphite matrix with a porosity of 20% and a pore size distribution of 2~100nm was obtained by directional pore formation of graphite at a scanning speed of 2mm / s.

[0051] (2) Using an atomic layer deposition apparatus, a nickel metal layer with a thickness of 5 nm was deposited on the surface of porous graphite at 200 °C with bis(cyclopentadiene) nickel as a precursor. Subsequently, the nickel layer was annealed at 400 °C for 3 hours in an argon / hydrogen mixed atmosphere (volume ratio 95:5) to transform the nickel layer into uniformly distributed nickel nanoparticles.

[0052] (3) Place the material obtained in step (2) in a chemical vapor deposition furnace, introduce a methane / hydrogen mixed gas (volume ratio 1:2), and react at 800°C for about 15 minutes to grow carbon nanotubes in situ. The mass of the carbon nanotubes is 0.5% of the mass of the porous graphite matrix.

[0053] (4) The material was chemically etched with 10wt% hydrogen peroxide solution at 50℃ for 4h to remove nickel catalyst particles. Then it was washed with deionized water until neutral and vacuum dried at 80℃ for 6h.

[0054] (5) Using an atomic layer deposition device, Li(thd) and TiF4 are used as precursors to deposit a LiF fast ion conductor layer at 250°C. The mass of the coating is controlled to be 1% of the mass of the porous graphite matrix, and finally fast-charging graphite anode material is prepared.

[0055] Example 3 This embodiment provides a fast-charging graphite anode material and its preparation method.

[0056] (1) Take 1 kg of artificial graphite raw material with a particle size D50 of 10 μm. Use a nanosecond pulsed laser etching system (wavelength 1064 nm, power density 30 MW / cm²). 2 A porous graphite matrix with a porosity of 10% and a pore size distribution of 2~100nm was obtained by directional pore formation of graphite at a scanning speed of 5mm / s.

[0057] (2) Using an atomic layer deposition apparatus, a nickel metal layer with a thickness of 10 nm was deposited on the surface of porous graphite at 200 °C with bis(cyclopentadiene) nickel as a precursor. Subsequently, the nickel layer was annealed at 400 °C for 3 hours in an argon / hydrogen mixed atmosphere (volume ratio 95:5) to transform the nickel layer into uniformly distributed nickel nanoparticles.

[0058] (3) Place the material obtained in step (2) in a chemical vapor deposition furnace, introduce a methane / hydrogen mixed gas (volume ratio 1:3), react at 850°C for about 20 minutes, and grow carbon nanotubes in situ. The mass of the carbon nanotubes is 1% of the mass of the porous graphite matrix.

[0059] (4) The material was chemically etched with 10wt% hydrogen peroxide solution at 50℃ for 4h to remove nickel catalyst particles. Then it was washed with deionized water until neutral and vacuum dried at 80℃ for 6h.

[0060] (5) Using an atomic layer deposition apparatus, Li3P fast ion conductor layer was deposited at 200℃ with LiOtBu and P(TMS)3 as precursors. The mass of the coating was controlled to be 1% of the mass of the porous graphite matrix, and finally fast-charging graphite anode material was prepared.

[0061] Comparative Example 1 The difference between this comparative example and Example 1 is that step (1) of this comparative example uses an oxidation etching method to create the hole. Step (1) of this comparative example is as follows: Take 1 kg of the same artificial graphite raw material as in Example 1 (D50 is 10 μm). Use concentrated nitric acid to oxidize and etch at 80°C for 12 hours to create pores. Then wash with deionized water until neutral and dry. The final porous graphite has a porosity of about 20% and a pore size distribution of 2~100 nm.

[0062] Comparative Example 2 The difference between this comparative example and Example 1 is that this comparative example physically mixes a porous graphite matrix and carbon nanotubes. The specific steps of this comparative example are as follows: (1) Take 1 kg of artificial graphite raw material with a particle size D50 of 10 μm. Use a nanosecond pulsed laser etching system (wavelength 1064 nm, power density 50 MW / cm²). 2 A porous graphite matrix with a porosity of 20% and a pore size distribution of 2~100nm was obtained by directional pore formation of graphite at a scanning speed of 2mm / s.

[0063] (2) Porous graphite and multi-walled carbon nanotubes (2 μm in length and 20 nm in diameter) were placed in a mechanical fusion machine with a rotation speed of 800 rpm, a blade gap width of 0.3 cm, and a fusion time of 1 h to achieve physical mixing. The amount of multi-walled carbon nanotubes added was controlled to be 5% of the mass of porous graphite.

[0064] (3) Using an atomic layer deposition apparatus, Li(thd) and TiF4 were used as precursors to deposit a LiF fast ion conductor layer at 250°C. The mass of the coating was controlled to be 0.5% of the mass of the porous graphite matrix, and the graphite anode material was finally prepared.

[0065] Comparative Example 3 The difference between this comparative example and Example 1 lies in step (2). In this comparative example, the nickel catalyst is prepared by liquid-phase impregnation + thermal reduction. Step (2) of this comparative example is as follows: Porous graphite was immersed in a 0.1 mol / L NiCl2 aqueous solution for 2 hours, dried at 100 °C, and then reduced at 400 °C in a hydrogen / argon atmosphere for 1 hour to support a nickel catalyst.

[0066] Comparative Example 4 The difference between this comparative example and Example 1 is that, in step (5) of this comparative example, amorphous carbon coating is used instead of fast ion conductor coating. Step (5) of this comparative example is as follows: The material from step (4) was placed in a chemical vapor deposition furnace, acetylene gas was introduced, and vapor deposition was carried out at 700°C. The amount of amorphous carbon coating was controlled to be 0.5% of the graphite mass, and finally the graphite anode material was prepared.

[0067] Comparative Example 5 This comparative example provides a graphite anode material and its preparation method.

[0068] (1) Take 1 kg of artificial graphite raw material (D50 is 10 μm) that is the same as that in Example 1 without any pore-forming treatment.

[0069] (2) The above-mentioned original graphite material was placed directly in a chemical vapor deposition furnace, and acetylene gas was introduced as a carbon source. Amorphous carbon coating was carried out at 700°C. By controlling the gas flow rate and reaction time, the coating amount of amorphous carbon was 2% of the graphite mass, and finally the graphite anode material was obtained.

[0070] Test case 1. Battery assembly: (1) Button cell assembly: The graphite anode materials prepared in Examples 1-3 and Comparative Examples 1-5 were mixed with CMC, SBR, and SP in water at a mass ratio of 96:1:2:1 to form a slurry. The slurry was then uniformly coated onto a copper foil current collector. After drying and rolling, the slurry was cut to obtain anode sheets of the corresponding size. In an argon-protected glove box (water and oxygen content <0.1ppm), a CR2032 type button cell was assembled using a lithium metal sheet as the counter electrode, a Celgard 2400 polypropylene separator, and a 1M LiPF6 EC / DEC (volume ratio 1:1) solution as the electrolyte.

[0071] (2) Assembly of soft-pack batteries: The graphite negative electrode materials prepared in each embodiment and comparative example were mixed with CMC, SBR and SP in water at a mass ratio of 96:1:2:1 to form a slurry, which was then uniformly coated on an 8μm thick copper foil. After drying and rolling, the negative electrode sheets were cut to the corresponding sizes. Commercial lithium iron phosphate was used as the positive electrode material. It was mixed with conductive carbon black and PVDF in NMP at a mass ratio of 94:3:3 to form a slurry, which was then coated on an aluminum foil. After drying and rolling, the slurry was cut. The positive electrode sheets, PP / PE / PP three-layer composite separator (14μm thick) and the above-mentioned negative electrode sheets were stacked in sequence, and an electrolyte (1mol / L LiPF6 / EC+PC+DEC+EMC, volume ratio 1:0.3:1:1) was injected. After vacuum sealing, standing, formation and secondary sealing, a soft-pack battery with a rated capacity of 3Ah was made.

[0072] 2. Performance Testing: (1) Initial charge and discharge efficiency test The assembled coin cells (half-cells) were charged at a constant current of 0.1C (based on the theoretical graphite capacity of 372mAh / g) to 0.005V at 25℃, then switched to constant voltage charging until the current dropped to 0.05C. After resting for 5 minutes, they were discharged at a constant current of 0.1C to the cutoff voltage of 1.5V. The initial charge and discharge capacities were recorded. The coulombic efficiency for the first week was calculated using the following formula: First-week coulomb efficiency = (Initial discharge capacity / Initial charge capacity) × 100% The pouch battery (full cell) was charged to 3.65V at a constant current of 0.33C under the same conditions, then switched to constant voltage charging until the current dropped to 0.05C. After resting for 5 minutes, it was discharged to 2.5V at a constant current of 0.33C. The capacity was recorded and the first efficiency of the full cell was calculated using the same formula as above.

[0073] (2) Fast charging performance test The pouch cell was discharged to 2.5V at a constant current of 0.33C at 25℃, and then charged to 3.65V at constant currents of 1C, 2C, 3C, and 5C. The capacity charged during the constant current phase at each current was recorded, and the percentage of the battery's rated capacity was calculated to obtain the constant current charging state of charge (SOC). This SOC is used to evaluate the material's rate charging performance at different fast charging rates.

[0074] (3) DC and AC internal resistance test Adjust the SOC of the pouch battery to 50%, discharge it with a 2C current for 30 seconds, record the voltage change before and after the pulse, and calculate the DC internal resistance using the formula DCR = ΔV / I. The AC internal resistance is directly read using an AC internal resistance meter at a frequency of 1000 Hz and recorded as ACR.

[0075] (4) High-rate cycling performance test The pouch battery was charged at 3C constant current to 3.65V at 25℃, then switched to constant voltage until the current ≤0.05C, followed by constant current discharge to 2.5V at 1C. This charge-discharge cycle was repeated. The discharge capacity of the first and 500th cycles was recorded, and the capacity retention rate was calculated using the following formula: Capacity retention rate = (500th cycle discharge capacity / 1st cycle discharge capacity) × 100%.

[0076] (5) High-temperature storage performance test The pouch cell charged to 100% SOC was stored in a constant temperature environment of 60℃ for 7 days. After storage, the cell was cooled to 25℃: the cell thickness change was measured and the thickness expansion rate was calculated; the cell was discharged at a constant current of 1C to 2.5V, the remaining capacity was recorded, and the capacity recovery rate was calculated; the DC internal resistance (DCR) of the cell at 50% SOC after storage was tested, and the DCR change rate was analyzed.

[0077] The test results are summarized in Tables 1, 2 and 3.

[0078] Table 1. Results of basic electrochemical performance tests

[0079] As shown in Table 1, the initial efficiency of all examples in both coin cells and pouch cells remained stable at around 90%, significantly higher than that of Comparative Example 4. This demonstrates the effectiveness of the LiF fast ion layer as a pre-lithiation agent, successfully compensating for the loss of active lithium during the first charge and discharge cycle. Examples 1-3 exhibited lower ACR and DCR, demonstrating the synergistic effect of the three-dimensional conductive network constructed by in-situ grown carbon nanotubes and the optimized interfacial ion transport of the LiF fast ion layer, which significantly reduced the ohmic and polarization resistance of the battery. After 500 cycles under harsh 3C fast charging conditions, the batteries in Examples 1-3 still retained over 95% of their capacity, demonstrating the durability of this material system in long-term fast charging applications. This is attributed to the stable SEI film and robust conductive network.

[0080] Table 2 Fast charging performance test results

[0081] As shown in Table 2, at all charging rates, the constant current charging SOC of Examples 1-3 is higher than that of the comparative example, especially at the highest 5C rate, where the advantage is most significant. This indicates that the material of this invention can withstand extremely high charging currents, allowing more charge to be delivered before the voltage reaches its upper limit. The excellent fast charging performance is a direct result of the synergistic effect of laser-etched porous structure (shortening ion paths), in-situ CNT growth (providing electron channels), and LiF layer (enhancing interfacial ion conduction). Comparative Example 5 (without pores) exhibits the worst performance, demonstrating that the porous structure is the physical basis for achieving fast charging.

[0082] Table 3. High-Temperature Storage Stability Test Results

[0083] As shown in Table 3, the batteries assembled from the materials in Examples 1-3 exhibited lower thickness expansion, higher capacity recovery rate, and lower DCR change rate after high-temperature storage, reflecting the high purity and interfacial stability of the material system. Comparative Example 3 showed the highest values ​​for thickness expansion rate and DCR change rate, fully exposing how chlorine impurities can violently catalyze electrolyte decomposition at high temperatures, generating a large amount of gas and damaging the SEI film, leading to severe battery swelling and a surge in interfacial impedance. The high expansion rate of Comparative Example 1 indicates that impurities or defects on its pore walls became the source of instability at high temperatures. Although Comparative Example 5 had a low expansion rate (dense structure), its low capacity recovery rate indicated that without a porous structure to provide buffering and fast ion channels, the byproducts generated by high-temperature side reactions made it more difficult for lithium ions to insert / extract from the dense graphite, resulting in greater irreversible / reversible capacity loss.

[0084] 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 method for preparing a fast-charging graphite anode material, characterized in that, Includes the following steps: Porous graphite was obtained by laser etching to create pores in the graphite. A catalyst metal layer was prepared on the surface of porous graphite by vapor deposition, followed by annealing to obtain metal nanoparticles. In-situ growth of carbon nanotubes via vapor deposition; After removing the metal nanoparticles, a fast-ion layer is applied to coat the material, thus obtaining the fast-charging graphite anode material.

2. The preparation method according to claim 1, characterized in that, The graphite has a particle size D50 of 5~20μm, and the porous graphite has a porosity of 5~30% and a pore size of 2~100nm.

3. The preparation method according to claim 1, characterized in that, In the step of preparing the catalyst metal layer by vapor deposition, the thickness of the catalyst metal layer is 0.5~20nm, and the metal is one or more of nickel, cobalt, and iron.

4. The preparation method according to claim 3, characterized in that, In the step of preparing the catalyst metal layer by vapor deposition, atomic layer deposition is used for vapor deposition.

5. The preparation method according to claim 1, characterized in that, The annealing temperature is 350~500℃, and the annealing time is 2~5h.

6. The preparation method according to claim 1, characterized in that, In the step of in-situ growth of carbon nanotubes by vapor deposition, chemical vapor deposition is used, and the mass of the grown carbon nanotubes is 0.4 to 2% of the mass of porous graphite.

7. The preparation method according to claim 1, characterized in that, Metal nanoparticles are removed by physical grinding or chemical etching.

8. The preparation method according to claim 1, characterized in that, The fast ion layer has a coating amount of 0.1-3% of the porous graphite mass. The fast ion layer is prepared by atomic layer deposition and is made of one or more of LiF, Li2O or Li3P.

9. A fast-charging graphite anode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. A lithium-ion battery, characterized in that, Including the fast-charging graphite anode material as described in claim 9.

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