Graphene-reinforced silicon-carbon negative electrode material and preparation method thereof

Abstract

The application discloses a graphene-reinforced silicon-carbon negative electrode material and a preparation method thereof, wherein the graphene-reinforced silicon-carbon negative electrode material comprises the following components in percentage by mass: 80-90% of a graphene base and 10-20% of silicon quantum dots; the graphene base has a defect pore size and a three-dimensional gradient pore structure on the surface; and the silicon quantum dots are in-situ grown in the defect pore size. The preparation method of the graphene-reinforced silicon-carbon negative electrode material comprises the following steps: S1, pretreatment of the graphene base; S2, deposition of the silicon quantum dots; S3, interface covalent bond strengthening; and S4, construction of the three-dimensional gradient pore. Through organic coupling of the graphene base pretreatment, the in-situ growth of the silicon quantum dots, the interface covalent bond strengthening and the three-dimensional gradient pore construction technology, a synergistic system of "structure design-interface regulation-performance optimization" is formed, and the problems of size mismatch between the graphene and the silicon particles, weak interface force and poor dispersibility are solved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to graphene-enhanced silicon-carbon anode materials and their preparation methods. Background Technology

[0002] Lithium-ion batteries typically consist of four main parts: a positive electrode, a negative electrode, a separator, and an electrolyte. The positive and negative electrodes are where the charge carriers store and release energy in a lithium-ion battery. The separator physically separates the two electrodes to prevent them from connecting and causing an internal short circuit, while allowing lithium to flow through the separator to the electrodes.

[0003] Lithium-ion battery anode materials can be mainly divided into three categories: intercalation materials, conversion materials, and alloys. In intercalation materials (such as graphite), lithiation occurs by inserting lithium ions into interstitial sites in the anode material's crystal lattice; in conversion materials (transition metal compounds), the conversion reaction is based on the substitution of transition metals by lithium ions during lithiation; in the third type of anode material, lithiation occurs through alloying between lithium and the electrode material.

[0004] Graphite is currently the most widely used anode material in lithium-ion batteries, but its theoretical capacity is limited to 372 mAh / g, hindering its application in the emerging industry of high-energy lithium-ion batteries. Replacing traditional graphite with high-capacity materials is the most promising way to improve the energy density of lithium-ion batteries. Among them, silicon-lithium alloys can achieve a specific capacity of 4200 mAh / g, significantly higher than other anode materials. In addition, silicon also has a relatively low operating voltage (<0.4V vs. Li / Li). + Silicon, with its abundant and readily available raw materials, is considered the most promising anode material for applications. However, when silicon is used in lithium-ion batteries, the alloying reaction with lithium produces significant volume expansion, exceeding 300%. This expansion causes silicon particles to break down, losing electrical contact with the electrode. When silicon particles break down or even pulverize, the existing solid-electrolyte interface (SEI) is destroyed, and a new SEI film continuously forms. This process not only consumes electrolyte, wasting lithium ions, but also increases the thickness of the SEI film, affecting the transport of lithium ions and electrons. Therefore, the electrochemical performance of silicon anode batteries degrades rapidly during use. To address these issues, carbon materials, due to their excellent conductivity (~10² S·cm), are considered a promising alternative. -1 The characteristics of carbon and high mechanical strength perfectly compensate for the shortcomings of silicon materials in lithium-ion batteries. Therefore, carbon materials are the ideal matrix to improve the shortcomings of silicon.

[0005] Graphene, as an emerging carbon material, possesses high electrical conductivity (10⁶ S cm⁻¹), good thermal stability, and high mechanical strength (40 times that of diamond). Ren et al. used CVD with chlorosilane as the silicon source to deposit crystalline silicon on graphene microsheets. The prepared material had an initial discharge specific capacity as high as 614 mAh g⁻¹, and still retained 90% of its capacity after 500 charge-discharge cycles. Graphene can effectively improve the structural stability of silicon, but current graphene-silicon particle composites face several challenges: First, size mismatch: graphene is a two-dimensional nanosheet (5-10 μm in diameter), while traditional silicon particles are mostly micrometer-sized. This large size difference makes it difficult for silicon particles to be uniformly dispersed between graphene layers, easily forming agglomerates, damaging the conductive network, and exacerbating local volume expansion. Second, weak interfacial forces: traditional silicon / graphene composites rely on van der Waals forces or physical adsorption for bonding, which can easily lead to interfacial delamination when silicon expands, causing conductive network breakage and repeated SEI film formation. Third, poor dispersibility: silicon particles are prone to agglomeration due to their high surface energy, resulting in excessively high local lithium-ion concentrations, concentrated volume expansion, and difficulty in electrolyte wetting the agglomerates, affecting rate performance. These problems severely impact the electrochemical performance of silicon-graphene composites, limiting their application in lithium-ion batteries. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to overcome the above-mentioned problems in the prior art and provide a graphene-enhanced silicon-carbon anode material and its preparation method. This material can effectively solve the problems of size mismatch, weak interfacial force and poor dispersibility between graphene and silicon particles, and has excellent electrochemical performance.

[0007] The present invention solves the technical problem by adopting the following technical solution: The present invention provides a graphene-enhanced silicon-carbon anode material, characterized in that it comprises the following components by mass percentage: 80-90% graphene substrate and 10-20% silicon quantum dots, wherein the surface of the graphene substrate has defect pores and a three-dimensional gradient channel structure, and the silicon quantum dots are grown in situ within the defect pores.

[0008] Preferably, the silicon quantum dot particle size is 3-5 nm, and the defect pore size is 5-10 nm.

[0009] Preferably, the three-dimensional gradient pore structure includes macropores with a diameter of 300-600 nm, mesopores with a diameter of 20-80 nm, and micropores with a diameter of <2 nm, wherein the volume ratio of the macropores, mesopores, and micropores is (2-4):(4-6):2.

[0010] Preferably, the silicon quantum dots are connected to the graphene substrate via Si-OC covalent bonds.

[0011] In addition, the present invention also provides a method for preparing the above-mentioned graphene-reinforced silicon-carbon anode material, comprising the following steps: Pretreatment of S1 graphene substrate S110: The graphene oxide dispersion is vacuum filtered to form a film; S120: The defect pore size introduced on the surface of graphene oxide by placing the graphene film in a radio frequency plasma device and introducing high-purity argon gas. Deposition of S2 silicon quantum dots S210: Plasma-enhanced chemical vapor deposition is used to transfer the pretreated graphene film into the PE-CVD reaction chamber. After evacuation, a precursor mixed gas is introduced to generate silicon quantum dots in situ on the surface of the pretreated graphene. S3 Interface Covalent Bonding Enhancement S310: Oxygen plasma etching is performed on the graphene film with deposited silicon quantum dots to generate carboxyl groups; S320: Low-temperature annealing triggers interfacial reactions to form Si-OC covalent bonds; Construction of S4 3D Gradient Channels S410: The bonded graphene is co-assembled with a pore-forming agent, then ball-milled and freeze-dried; S420: Remove the pore-forming agent to obtain a graphene-enhanced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots.

[0012] Preferably, in step S110, the thickness of the graphene oxide film is 45-55 μm, and in step S120, the power of the radio frequency plasma treatment is 40-60 W, the gas pressure is 10-20 Pa, and the time is 100-150 s.

[0013] Preferably, in step S210, the precursor mixed gas is SiH4:Ar=1:9 (v / v), the total flow rate is 80-120 sccm, the chamber pressure is 15-25 Pa, the substrate temperature is 260-320℃, the plasma power is 80-120 W, the pulse mode is 0.5s on / 2s off, and the deposition time is 4-8 min.

[0014] Preferably, in step S320, the conditions for low-temperature annealing are as follows: introduce a N2 / H2 mixture (95:5, v / v) at a flow rate of 100 sccm, raise the temperature to 150-220°C at a rate of 3-6°C / min, and hold the temperature for 20-40 min.

[0015] Preferably, the pore-forming agent in step S410 is PMMA microspheres and mesoporous SiO2 nanospheres, and the mass ratio of the bonded graphene, PMMA microspheres and mesoporous SiO2 nanospheres is (75-80):(15-20):5.

[0016] Preferably, step S420 removes Pore-forming agent Specific methods: S420: Place the freeze-dried sample into a tube furnace, introduce argon gas, heat-treat at 260-300℃ for 2-3.5h, then immerse in 5wt% HF solution, stir at room temperature for 10-15min, wash with deionized water until neutral, and vacuum dry at 60℃ for 2h to obtain a graphene-reinforced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The graphene-enhanced silicon-carbon anode material of the present invention addresses the problems of “size mismatch between graphene and silicon particles, weak interfacial forces, and poor dispersion” by organically coupling graphene substrate pretreatment, in-situ growth of silicon quantum dots, interfacial covalent bonding strengthening, and three-dimensional gradient channel construction technology to form a synergistic system of “structure design-interfacial regulation-performance optimization”. Size matching (3-5nm quantum dots + 5-10nm defects) lays the foundation for improved dispersion and ensures uniform initial distribution of silicon quantum dots. Interfacial covalent bonding (Si-OC bond) “anchors” the dispersed quantum dots to graphene to avoid secondary aggregation during cycling. The three-dimensional gradient channels provide expansion space and ion transport channels for the dispersed quantum dots. The three form a closed loop of “size matching → interface fixation → spatial buffering”, ultimately achieving a systematic improvement in electrochemical performance.

[0018] (2) In the pretreatment of the graphene substrate in this invention, argon plasma etching introduces defect pores, which can not only serve as growth sites for silicon quantum dots, but also form a "nested match" with the deposited silicon quantum dots. The surface energy of the defect sites is higher than that of the graphene substrate, which can preferentially adsorb silicon atoms and guide the quantum dots to nucleate within the defects, thus avoiding size runaway caused by random growth on the substrate. The pulse mode suppresses the surface migration of silicon atoms through "intermittent energy input" (the migration distance of silicon atoms in continuous plasma can reach 20 nm, which easily leads to agglomeration; the migration distance is shortened to <5 nm in pulse mode), so that the size of the quantum dots is strictly limited within the defect sites, thus avoiding agglomeration caused by random growth on the substrate.

[0019] (3) The unsaturated carbon bonds at the defect pores of the present invention are more likely to generate carboxyl groups during oxygen plasma treatment, providing more reaction sites for the covalent bonding (Si-OC) of silicon quantum dots and graphene, thereby increasing the bonding density to 1.2 × 10⁻⁶. 15 pcs / cm 2This method achieves a 50% improvement over defect-free graphene. Covalent bonding (Si-OC bond energy 452 kJ / mol) forms "rigid anchor points," transferring the expansion stress (approximately 200 MPa) during lithium intercalation of silicon quantum dots to the graphene framework via chemical bonds, thus preventing localized stress concentration. The three-dimensional channels provide "flexible buffer spaces," with macropores accommodating overall expansion and mesopores dispersing radial stress through pore wall deformation. Together, these factors reduce the volume expansion rate from 320% of traditional materials to 38%. Furthermore, covalent bonding ensures electrical contact between silicon quantum dots and graphene, while the graphene network within the channel structure is interconnected through mesopores, forming conductive pathways that run through the macropores. Even if localized bond breakage occurs during cycling, the graphene within the channels can still maintain a conductive network (conductivity retention >90% after 100 cycles).

[0020] (4) The uniform dispersion of silicon quantum dots and the construction of three-dimensional gradient channels in this invention are synergistically optimized through "spatial separation + interface affinity". Specifically, defect anchoring enables silicon quantum dots to be uniformly distributed in the graphene plane, while the macropores of the three-dimensional channels act as "microreactors", confining 50-100 quantum dots in each macropore to avoid cross-pore aggregation. Mesopores further separate the quantum dots, and combined with freeze-dried micropores, a three-level separation structure of "macropore-mesopore-micropore" is formed, reducing the quantum dot aggregation rate from 30% in traditional methods to <5%. Furthermore, the uniform dispersion of quantum dots shortens the lithium-ion diffusion distance (from 100nm to 20nm), while the mesopores in the channel structure act as "ion highways", working in synergy with the electrolyte wetting network formed by the micropores to increase the lithium diffusion coefficient to 10. -9 cm 2 / s (5 times that of traditional materials), and still maintains a capacity of 980mAh / g at a high rate of 4A / g.

[0021] (5) In the preparation method of the graphene-enhanced silicon-carbon anode material of the present invention, the silicon quantum dot deposition temperature (260-320℃) and the subsequent covalent bonding temperature (150-220℃) form a "step-like control". 260-320℃ ensures the crystallinity of quantum dots (avoiding amorphous state caused by low temperature), while 150-220℃ achieves efficient bonding without destroying the quantum dot structure. The heat treatment temperature (260-300℃) in step S420 can decompose PMMA microspheres, while being lower than the thermal decomposition temperature of covalent bonding (>350℃), ensuring Pore-forming agent The Si-OC bond does not break during removal; the HF solution (5wt%) only dissolves SiO2 nanospheres, and the corrosion rate of silicon quantum dots is <0.5%, thus avoiding damage to the already formed dispersed structure. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The mesoporous SiO2 nanospheres used in this invention are self-made, and the preparation method is as follows: ① Mix 50 mL of tetraethyl orthosilicate (TEOS), 250 mL of ethanol, and 50 mL of deionized water, and stir for 5 minutes; ② Add 10 mL of ammonia water (25 wt%) as a catalyst, stir at 30 °C for 24 h to form SiO2 nanospheres; ③ Centrifuge (8000 rpm, 10 min), wash three times with ethanol, dry at 60℃, and calcine in a muffle furnace at 550℃ for 4 h (to remove the template agent) to obtain mesoporous SiO2 nanospheres (TEM verified particle size 30±5 nm, BET measured mesopore pore size 2-5 nm, specific surface area 600±50 m²). 2 / g).

[0024] PMMA microspheres were purchased from Zhongke Leiming Technology Co., Ltd., with a particle size of 500nm. Example 1. The graphene-enhanced silicon-carbon anode material of this embodiment includes the following components by mass percentage: 80% graphene substrate and 20% silicon quantum dots. The surface of the graphene substrate has defect pores and a three-dimensional gradient channel structure, and the silicon quantum dots are grown in situ within the defect pores.

[0025] The silicon quantum dots have a particle size of 3-5 nm, and the defect pore size is 5-10 nm. The three-dimensional gradient pore structure comprises macropores with a diameter of 300-600 nm, mesopores with a diameter of 20-80 nm, and micropores with a diameter of <2 nm. The volume ratio of macropores, mesopores, and micropores is 2.2:5.8:2. Silicon quantum dots are connected to the graphene substrate via Si-OC covalent bonds.

[0026] Preparation method of graphene-enhanced silicon-carbon anode material: Pretreatment of S1 graphene substrate S110: Take commercial graphene oxide powder (sheet diameter 5-10 μm, oxidation degree 30%), add deionized water, disperse with an ultrasonic cell disrupter (power 600 W, work 3 s / intermittent 5 s, total time 30 min) to form a uniform dispersion with a concentration of 2 mg / mL. Use a polytetrafluoroethylene filter membrane with a diameter of 50 mm (pore size 0.22 μm), pour the graphene oxide dispersion into a Buchner funnel, connect a vacuum pump (vacuum degree -0.08 MPa), and control the suction filtration rate at 1.5 mL / min. After the liquid is completely drained, carefully peel off the graphene oxide film with tweezers, transfer it to a quartz glass slide, place the glass slide in a vacuum drying oven, set the temperature at 60°C and the pressure at -0.1 MPa, and dry for 12 h. The thickness of the graphene film tested by a profilometer is 45.5 μm; S120: Place the graphene film on a quartz sample stage of radio frequency plasma equipment (frequency 13.56 MHz), evacuate the closed chamber to 5×10 -4 Pa, feed high-purity argon (purity 99.999%), adjust the flow rate to stabilize the chamber pressure at 15 Pa, set the power at 40 W and the treatment time at 130 s to introduce surface defects. The defect pore size detected by high-resolution transmission electron microscopy is 5-8 nm; S2 Deposition of silicon quantum dots S210: Use the PE-CVD reaction chamber equipped with the plasma etcher, evacuate the chamber to 5×10 -4 Pa (the vacuum gauge shows stability for more than 30 s) to ensure no interference from impurity gases, fix the argon plasma-pretreated graphene film on a stainless steel sample stage; Connect the gas pipelines of SiH4 (purity 99.999%) and Ar (purity 99.999%), first pass Ar gas (flow rate 50 sccm) for 5 min purge to remove air and residual impurities in the pipelines, then close the Ar gas valve for later use; Set the precursor gas ratio: SiH4 flow rate 12 sccm, Ar flow rate 108 sccm, total flow rate 120 sccm; Open the gas valve to stabilize the reaction chamber pressure at 25 Pa, and ventilate for 3 min to ensure uniform gas distribution; Heat the sample stage by an infrared heating module, set the heating rate at 10°C / min, heat from room temperature to 260°C and keep the temperature for 10 min to make the substrate temperature uniform; Turn on the radio frequency power supply (frequency 13.56 MHz), slowly adjust the power to 100 W, control the deposition time at 8 min, enable the "pulse mode", set the pulse period to 2.5 s (on 0.5 s / off 2 s), with a duty cycle of 20%; The pulse trigger mode is "automatic synchronization" to ensure that the start and stop of the plasma are synchronized with the output of the radio frequency power supply.

[0027] S3 Strengthening of interfacial covalent bonding S310: Remove the graphene film containing deposited silicon quantum dots from the PE-CVD reaction chamber and carefully transfer it onto a clean quartz glass slide using dust-free tweezers. Place it in a vacuum drying oven (60℃, -0.1MPa) for 30 min to remove trace amounts of adsorbed moisture from the surface. Use the same radio frequency plasma equipment (13.56MHz) as for argon plasma etching to wipe the inner wall of the chamber and the sample stage with anhydrous ethanol. Pre-treat the chamber with oxygen plasma (100W power, O2 flow rate 50sccm, treatment for 5 min) to remove residual organic matter. After closing the chamber door, evacuate to 5×10⁻⁶. -4 To ensure no interference from impurity gases, the graphene film was laid flat in the center of the sample stage, ensuring a smooth surface. O2 was introduced (flow rate 50 sccm), and the power was set to 80 W and the pressure to 20 Pa for 90 s, introducing carboxyl groups onto the graphene surface. X-ray photoelectron spectroscopy analysis showed a carboxyl group density of 1.32 × 10⁻⁶. 15 groups / cm 2 ; S320: The sample was placed in a tube furnace, and an N2 / H2 mixture (95:5, v / v) was introduced at a flow rate of 100 sccm. The air was replaced by purging for 30 min. The temperature was then increased to 150℃ at a rate of 5℃ / min and held at this temperature for 30 min to trigger the reaction. The sample was detected by Fourier transform infrared spectroscopy at 1720 cm⁻¹. -1 The (-COOH) peak completely disappeared at 1060 cm⁻¹. -1 The appearance of the (Si-OC) peak proves that the bonding was successful; Construction of S4 3D Gradient Channels S410: Weigh the bonded graphene, PMMA microspheres, and mesoporous SiO2 nanospheres at a mass ratio of 80:15:5, and add anhydrous ethanol to make the solid content 20wt%; use a planetary ball mill (50mL PTFE container, zirconia ball diameter 5mm, ball-to-material ratio 5:1) to mix at 300rpm for 2h to form a uniform slurry; inject the slurry into a PTFE mold (5cm×5cm×0.5cm), ultrasonically degas for 3min (200W), then immerse in liquid nitrogen (-196℃) for rapid cooling and solidification for 3min; transfer to a freeze dryer, set the cold trap temperature to -50℃ and the vacuum degree to 10Pa, and dry for 48h to remove ethanol and retain the micropores formed by ice crystals. S420: The dried sample was placed in a tube furnace, purged with argon gas (100 sccm), and heat-treated at 260℃ for 2.5 h to completely decompose PMMA (the residual amount was verified as <0.1 wt% by thermogravimetric analysis (TGA)). The sample was then immersed in 5 wt% HF solution (liquid-to-solid ratio 10:1 mL:g), stirred at room temperature for 10 min, washed with deionized water until neutral, and vacuum dried at 60℃ for 2 h to obtain a graphene-reinforced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots. ICP-OES analysis showed that the residual Si was ≤50 ppm. BET surface area analysis revealed the presence of macropores (300-600 nm), mesopores (20-80 nm), and micropores (<2 nm) with a pore volume ratio of 2.2:5.8:2.

[0028] Example 2. The graphene-enhanced silicon-carbon anode material of this embodiment includes the following components by mass percentage: 85% graphene substrate and 15% silicon quantum dots. The surface of the graphene substrate has defect pores and a three-dimensional gradient channel structure, and the silicon quantum dots are grown in situ within the defect pores.

[0029] The silicon quantum dots have a particle size of 3-5 nm, and the defect pore size is 5-10 nm. The three-dimensional gradient pore structure comprises macropores with a diameter of 300-600 nm, mesopores with a diameter of 20-80 nm, and micropores with a diameter of <2 nm. The volume ratio of macropores, mesopores, and micropores is 3.1:4.9:2. Silicon quantum dots are connected to the graphene substrate via Si-OC covalent bonds.

[0030] Preparation method of graphene-enhanced silicon-carbon anode material: Pretreatment of S1 graphene substrate S110: Take commercial graphene oxide powder (5-10 μm in diameter, 30% oxidation degree), add deionized water, and disperse it using an ultrasonic cell disruptor (600W power, 3s working / 5s intermittent, total time 30min) to form a uniform dispersion with a concentration of 2.3 mg / mL. Use a 50 mm diameter polytetrafluoroethylene filter membrane (0.22 μm pore size) to pour the graphene oxide dispersion into a Buchner funnel, connect a vacuum pump (vacuum degree -0.08MPa), control the filtration rate at 1.5 mL / min, and after the liquid is completely dried, carefully peel off the graphene oxide membrane with tweezers and transfer it to a quartz glass slide. Place the glass slide in a vacuum drying oven, set it to 60℃ and -0.1MPa, and dry for 12 h. The thickness of the graphene membrane was measured to be 50.5 μm using a step meter. S120: Place the graphene film on the quartz sample stage of the radio frequency plasma device (frequency 13.56MHz), seal the chamber, and then evacuate to 5×10⁻⁶. -4Pa, feed high-purity argon (purity: 99.999%), adjust the flow rate to stabilize the chamber pressure at 15 Pa, set the power to 50 W and the treatment time to 120 s to introduce surface defects, and the defect pore diameter detected by high-resolution transmission electron microscopy is 6-9 nm; S2 Deposition of silicon quantum dots S210: Using the PE-CVD reaction chamber equipped with the plasma etching instrument, evacuate the chamber to a vacuum degree of 5×10 -4 Pa (the vacuum gauge shows stability for more than 30 s) to ensure no interference from impurity gases, and fix the graphene membrane pretreated by argon plasma on a stainless steel sample stage; connect the gas pipelines of SiH4 (purity: 99.999%) and Ar (purity: 99.999%), first feed Ar gas (flow rate: 50 sccm) for 5 min purge to exclude air and residual impurities in the pipelines, then close the Ar gas valve for standby; set the precursor gas ratio: SiH4 flow rate 10 sccm, Ar flow rate 90 sccm, total flow rate 100 sccm; open the gas valve to stabilize the reaction chamber pressure at 20 Pa, and ventilate for 3 min to ensure uniform gas distribution; heat the sample stage by an infrared heating module, set the heating rate at 10°C / min, heat from room temperature to 320°C and keep the temperature for 10 min to uniformize the substrate temperature; turn on the radio-frequency power supply (frequency: 13.56 MHz), slowly adjust the power to 100 W, control the deposition time as 4 min, enable the "pulse mode", set the pulse period to 2.5 s (on for 0.5 s / off for 2 s), with a duty cycle of 20%; the pulse trigger mode is "automatic synchronization" to ensure that the start and stop of plasma are synchronized with the output of the radio-frequency power supply.

[0031] S3 Interface covalent bonding reinforcement S310: Take out the graphene membrane deposited with silicon quantum dots from the PE-CVD reaction chamber, carefully transfer it to a clean quartz glass slide with dust-free tweezers, put it into a vacuum drying oven (60°C, -0.1 MPa) to dry for 30 min to remove trace water vapor adsorbed on the surface; adopt the same radio-frequency plasma equipment as that for argon plasma etching (frequency: 13.56 MHz), wipe the inner wall of the chamber and the sample stage with anhydrous ethanol, pretreat the chamber with oxygen plasma (power: 100 W, O2 flow rate: 50 sccm, treatment time: 5 min) to remove residual organic substances, after closing the chamber door, evacuate to 5×10 -4 Pa to ensure no interference from impurity gases, lay the graphene membrane flat in the center of the sample stage to ensure the membrane surface is flat, feed O2 (flow rate: 60 sccm), set the power to 80 W, the air pressure to 20 Pa, treat for 90 s to introduce carboxyl groups on the graphene surface; the carboxyl density analyzed by X-ray photoelectron spectroscopy is 1.43×10 15 groups / cm 2 ; S320: The sample was placed in a tube furnace, and an N2 / H2 mixture (95:5, v / v) was introduced at a flow rate of 100 sccm. The air was replaced by purging for 30 min. The temperature was then increased to 200℃ at a rate of 4℃ / min and held at this temperature for 40 min to trigger the reaction. The sample was detected by Fourier transform infrared spectroscopy at 1720 cm⁻¹. -1 The (-COOH) peak completely disappeared at 1060 cm⁻¹. -1 The appearance of the (Si-OC) peak proves that the bonding was successful; Construction of S4 3D Gradient Channels S410: Weigh the bonded graphene, PMMA microspheres, and mesoporous SiO2 nanospheres at a mass ratio of 78:17:5, and add anhydrous ethanol to make the solid content 20wt%; use a planetary ball mill (50mL PTFE container, zirconia ball diameter 5mm, ball-to-material ratio 5:1) to mix at 300rpm for 2h to form a uniform slurry; inject the slurry into a PTFE mold (5cm×5cm×0.5cm), ultrasonically degas for 3min (200W), then immerse in liquid nitrogen (-196℃) for rapid cooling and solidification for 3min; transfer to a freeze dryer, set the cold trap temperature to -50℃ and the vacuum degree to 10Pa, and dry for 48h to remove ethanol and retain the micropores formed by ice crystals. S420: The dried sample was placed in a tube furnace, purged with argon gas (100 sccm), and heat-treated at 280℃ for 2 hours to completely decompose PMMA (the residual amount was verified as <0.1 wt% by thermogravimetric analysis (TGA)). The sample was then immersed in 5 wt% HF solution (liquid-to-solid ratio 10:1 mL:g), stirred at room temperature for 12 minutes, washed with deionized water until neutral, and vacuum dried at 60℃ for 2 hours to obtain a graphene-reinforced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots. ICP-OES analysis showed that the residual Si was ≤50 ppm. BET surface area analysis revealed the presence of macropores (300-600 nm), mesopores (20-80 nm), and micropores (<2 nm) with a pore volume ratio of 3.1:4.9:2.

[0032] Example 3. The graphene-enhanced silicon-carbon anode material of this embodiment includes the following components by mass percentage: 88% graphene substrate and 12% silicon quantum dots. The surface of the graphene substrate has defect pores and a three-dimensional gradient channel structure, and the silicon quantum dots are grown in situ within the defect pores.

[0033] The silicon quantum dots have a particle size of 3-5 nm, and the defect pore size is 5-10 nm. The three-dimensional gradient pore structure comprises macropores with a diameter of 300-600 nm, mesopores with a diameter of 20-80 nm, and micropores with a diameter of <2 nm. The volume ratio of macropores, mesopores, and micropores is 3.8:4.2:2. Silicon quantum dots are connected to the graphene substrate through Si-O-C covalent bonds.

[0034] Preparation method of graphene-enhanced silicon-carbon negative electrode material: S1 Pretreatment of graphene substrate S110: Take commercial graphene oxide powder (sheet diameter 5-10 μm, oxidation degree 30%), add deionized water, and disperse with an ultrasonic cell disrupter (power 600W, work 3s / intermittent 5s, total time 30min) to form a uniform dispersion with a concentration of 2.6mg / mL. Use a polytetrafluoroethylene filter membrane with a diameter of 50mm (pore size 0.22μm), pour the graphene oxide dispersion into a Buchner funnel, connect a vacuum pump (vacuum degree -0.08MPa), and control the suction filtration rate at 1.5mL / min. After the liquid is completely drained, carefully peel off the graphene oxide membrane with tweezers, transfer it to a quartz slide, place the slide in a vacuum drying oven, set the temperature at 60°C and -0.1MPa, and dry for 12h. The thickness of the graphene membrane tested by a profilometer is 53.5μm; S120: Place the graphene membrane on the quartz sample stage of a radio frequency plasma device (frequency 13.56MHz), evacuate the closed chamber to 5×10 -4 Pa, introduce high-purity argon (purity 99.999%), adjust the flow rate to stabilize the chamber pressure at 20Pa, set the power to 60W and the treatment time to 100s to introduce surface defects. The defect pore size detected by high-resolution transmission electron microscopy is 8-10nm; S2 Deposition of silicon quantum dots S210: Use the PE-CVD reaction chamber equipped with the plasma etcher, pump the vacuum degree of the chamber to 5×10 -4 Pa (the vacuum gauge shows stability for more than 30s) to ensure no interference from impurity gases, and fix the graphene membrane pretreated by argon plasma on the stainless steel sample stage; connect the gas pipelines of SiH4 (purity 99.999%) and Ar (purity 99.999%), first pass Ar gas (flow rate 50sccm) for 5min purge to exclude air and residual impurities in the pipelines, then close the Ar gas valve for later use; set the precursor gas ratio: SiH4 flow rate 8sccm, Ar flow rate 72sccm, total flow rate 80sccm; open the gas valve to stabilize the reaction chamber pressure at 15Pa, and ventilate for 3min to ensure uniform gas distribution; heat the sample stage by an infrared heating module, set the heating rate at 10°C / min, heat from room temperature to 300°C and keep warm for 10min to make the substrate temperature uniform; turn on the radio frequency power supply (frequency 13.56MHz), slowly adjust the power to 80W, control the deposition time to 6min, enable the "pulse mode", set the pulse period to 2.5s (on 0.5s / off 2s), with a duty cycle of 20%; the pulse trigger mode is "automatic synchronization" to ensure that the start and stop of the plasma are synchronized with the output of the radio frequency power supply.

[0035] S3 Interface Covalent Bonding Enhancement S310: Remove the graphene film containing deposited silicon quantum dots from the PE-CVD reaction chamber and carefully transfer it onto a clean quartz glass slide using dust-free tweezers. Place it in a vacuum drying oven (60℃, -0.1MPa) for 30 min to remove trace amounts of adsorbed moisture from the surface. Use the same radio frequency plasma equipment (13.56MHz) as for argon plasma etching to wipe the inner wall of the chamber and the sample stage with anhydrous ethanol. Pre-treat the chamber with oxygen plasma (100W power, O2 flow rate 50sccm, treatment for 5 min) to remove residual organic matter. After closing the chamber door, evacuate to 5×10⁻⁶. -4 To ensure no interference from impurity gases, the graphene film was laid flat in the center of the sample stage, ensuring a smooth surface. O2 was introduced (flow rate 60 sccm), and the power was set to 80 W and the pressure to 20 Pa for 90 s, introducing carboxyl groups onto the graphene surface. X-ray photoelectron spectroscopy analysis showed a carboxyl group density of 1.48 × 10⁻⁶. 15 groups / cm 2 ; S320: The sample was placed in a tube furnace, and an N2 / H2 mixture (95:5, v / v) was introduced at a flow rate of 100 sccm. The air was replaced by purging for 30 min. The temperature was then increased to 220℃ at a rate of 6℃ / min and held at this temperature for 20 min to trigger the reaction. The sample was detected by Fourier transform infrared spectroscopy at 1720 cm⁻¹. -1 The (-COOH) peak completely disappeared at 1060 cm⁻¹. -1 The appearance of the (Si-OC) peak proves that the bonding was successful; Construction of S4 3D Gradient Channels S410: Weigh the bonded graphene, PMMA microspheres, and mesoporous SiO2 nanospheres at a mass ratio of 75:20:5, and add anhydrous ethanol to make the solid content 20wt%; use a planetary ball mill (50mL PTFE container, zirconia ball diameter 5mm, ball-to-material ratio 5:1) to mix at 300rpm for 2h to form a uniform slurry; inject the slurry into a PTFE mold (5cm×5cm×0.5cm), ultrasonically degas for 3min (200W), then immerse in liquid nitrogen (-196℃) for rapid cooling and solidification for 3min; transfer to a freeze dryer, set the cold trap temperature to -50℃ and the vacuum degree to 10Pa, and dry for 48h to remove ethanol and retain the micropores formed by ice crystals. S420: The dried sample was placed in a tube furnace, purged with argon gas (100 sccm), and heat-treated at 300℃ for 2.5 h to completely decompose PMMA (the residual amount was verified as <0.1 wt% by thermogravimetric analysis (TGA)). The sample was then immersed in 5 wt% HF solution (liquid-solid ratio 10:1 mL:g), stirred at room temperature for 15 min, washed with deionized water until neutral, and vacuum dried at 60℃ for 2 h to obtain a graphene-reinforced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots. ICP-OES analysis showed that the residual Si was ≤50 ppm. BET surface area analysis revealed the presence of macropores (300-600 nm), mesopores (20-80 nm), and micropores (<2 nm) with a pore volume ratio of 3.8:4.2:2.

[0036] Comparative Example 1. Unlike Example 1, step S120 was not performed.

[0037] Comparative Example 2. Unlike Example 1, step S3 was not performed.

[0038] Comparative Example 3. Unlike Example 1, step S4 was not performed.

[0039] Comparative Example 4. Unlike Example 1, the graphene film prepared in step S110 has a thickness of 35.5 μm, specifically: S110: Take commercial graphene oxide powder (5-10 μm in diameter, 30% oxidation degree), add deionized water, and disperse it using an ultrasonic cell disruptor (600W power, 3s working / 5s intermittent, total time 30min) to form a uniform dispersion with a concentration of 1.3 mg / mL. Use a 50 mm diameter polytetrafluoroethylene filter membrane (0.22 μm pore size) to pour the graphene oxide dispersion into a Buchner funnel, connect a vacuum pump (vacuum degree -0.08 MPa), control the filtration rate at 1.5 mL / min, and after the liquid is completely dried, carefully peel off the graphene oxide membrane with tweezers and transfer it to a quartz glass slide. Place the glass slide in a vacuum drying oven, set it to 60℃ and -0.1 MPa, and dry for 12 h. The thickness of the graphene membrane was measured to be 35.5 μm using a step meter.

[0040] Comparative Example 5. Unlike Example 1, the graphene film prepared in step S110 has a thickness of 63.5 μm, specifically: S110: Take commercial graphene oxide powder (5-10 μm in diameter, 30% oxidation degree), add deionized water, and disperse it using an ultrasonic cell disruptor (600W power, 3s working / 5s intermittent, total time 30min) to form a uniform dispersion with a concentration of 3.7 mg / mL. Use a 50 mm diameter polytetrafluoroethylene filter membrane (0.22 μm pore size) to pour the graphene oxide dispersion into a Buchner funnel, connect a vacuum pump (vacuum degree -0.08 MPa), control the filtration rate at 1.5 mL / min, and after the liquid is completely dried, carefully peel off the graphene oxide membrane with tweezers and transfer it to a quartz glass slide. Place the glass slide in a vacuum drying oven, set it to 60℃ and -0.1 MPa, and dry for 12 h. The thickness of the graphene membrane was measured to be 63.5 μm using a step meter.

[0041] Comparative Example 6. Unlike Example 1, in step S4, the pore volume ratio of macropores, mesopores, and micropores in the graphene-reinforced silicon-carbon anode material is 5.3:4.1:0.6, specifically: S410: Weigh the bonded graphene, PMMA microspheres, and mesoporous SiO2 nanospheres at a mass ratio of 62:27:11, and add anhydrous ethanol to make the solid content 20wt%; use a planetary ball mill (50mL PTFE container, zirconia ball diameter 5mm, ball-to-material ratio 5:1) to mix at 300rpm for 2h to form a uniform slurry; inject the slurry into a PTFE mold (5cm×5cm×0.5cm), ultrasonically degas for 3min (200W), then immerse in liquid nitrogen (-196℃) for rapid cooling and solidification for 3min; transfer to a freeze dryer, set the cold trap temperature to -50℃ and the vacuum degree to 10Pa, and dry for 48h to remove ethanol and retain the micropores formed by ice crystals. S420: The dried sample was placed in a tube furnace, purged with argon gas (100 sccm), and heat-treated at 260℃ for 3.5 h to completely decompose PMMA (the residual amount was verified by thermogravimetric analysis (TGA) to be <0.1 wt%). The sample was then immersed in 5 wt% HF solution (liquid-solid ratio 10:1 mL:g), stirred at room temperature for 25 min, washed with deionized water until neutral, and vacuum dried at 60℃ for 2 h to obtain a graphene-reinforced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots. ICP-OES analysis showed that the residual Si was ≤50 ppm. BET surface area analysis revealed the presence of macropores (300-600 nm), mesopores (20-80 nm), and micropores (<2 nm) with a pore volume ratio of 5.3:4.1:0.6.

[0042] Comparative Example 7. Unlike Example 1, in step S4, the pore volume ratio of macropores, mesopores, and micropores in the graphene-reinforced silicon-carbon anode material is 1.8:6.7:1.5, specifically: S410: Weigh the bonded graphene, PMMA microspheres, and mesoporous SiO2 nanospheres at a mass ratio of 64:12:24, and add anhydrous ethanol to make the solid content 20wt%; use a planetary ball mill (50mL PTFE container, zirconia ball diameter 5mm, ball-to-material ratio 5:1) to mix at 300rpm for 2h to form a uniform slurry; inject the slurry into a PTFE mold (5cm×5cm×0.5cm), ultrasonically degas for 3min (200W), then immerse in liquid nitrogen (-196℃) for rapid cooling and solidification for 3min; transfer to a freeze dryer, set the cold trap temperature to -50℃ and the vacuum degree to 10Pa, and dry for 48h to remove ethanol and retain the micropores formed by ice crystals; S420: The dried sample was placed in a tube furnace, purged with argon gas (100 sccm), and heat-treated at 200℃ for 2 h to completely decompose PMMA (the residual amount was verified as <0.1 wt% by thermogravimetric analysis (TGA)). The sample was then immersed in 5 wt% HF solution (liquid-to-solid ratio 10:1 mL:g), stirred at room temperature for 35 min, washed with deionized water until neutral, and vacuum dried at 60℃ for 2 h to obtain a graphene-reinforced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots. ICP-OES analysis showed that the residual Si was ≤50 ppm. BET surface area analysis revealed the presence of macropores (300-600 nm), mesopores (20-80 nm), and micropores (<2 nm) with a pore volume ratio of 1.8:6.7:1.5.

[0043] Comparative Example 8. Unlike Example 1, step S210 is "to use an infrared heating module to heat the sample stage, set the heating rate to 10℃ / min, raise it from room temperature to 220℃ and hold it for 10min to make the substrate temperature uniform;".

[0044] Comparative Example 9. The difference from Example 1 is that step S320 is as follows: S320: The sample was placed in a tube furnace, and an N2 / H2 mixture (95:5, v / v) was introduced at a flow rate of 100 sccm. The air was replaced by purging for 30 min. The temperature was then increased to 250℃ at a rate of 5℃ / min and held at this temperature for 30 min to trigger the reaction. Fourier transform infrared spectroscopy showed no 1060 cm⁻¹. -1 The appearance of the (Si-OC) peak indicates that the bonding was unsuccessful; Comparative Example 10. Unlike Example 1, step S210 does not use pulsed plasma mode, but uses continuous plasma deposition of silicon quantum dots.

[0045] Comparative Example 11. Unlike Example 1, the defect pore size in step S120 is 15-20 nm, specifically: S120: Place the graphene film on the quartz sample stage of the radio frequency plasma device (frequency 13.56MHz), seal the chamber, and then evacuate to 5×10⁻⁶. -4 Pa, high-purity argon gas (purity 99.999%) is introduced, the flow rate is adjusted to stabilize the chamber pressure at 20Pa, the power is set to 80W, the processing time is 160s, surface defects are introduced, and the defect pore size is detected by high-resolution transmission electron microscopy as 15-20nm. Comparative Example 12. Unlike Example 1, the defect pore size in step S120 is 2-3 nm, specifically: S120: The graphene film was placed on the quartz sample stage of the radio frequency plasma device (frequency 13.56MHz). After sealing the chamber, the vacuum was evacuated to 5×10-4Pa. High-purity argon gas (purity 99.999%) was introduced and the flow rate was adjusted to stabilize the chamber pressure at 10Pa. The power was set to 20W and the processing time to 80s. Surface defects were introduced and the defect pore size was detected by high-resolution transmission electron microscopy to be 2-3nm. Comparative Example 13. Unlike Example 1, in step S310, the carboxyl group density was analyzed by X-ray photoelectron spectroscopy and found to be 0.83 × 10⁻⁶. 15 groups / cm 2 Specifically: S310: Remove the graphene film containing deposited silicon quantum dots from the PE-CVD reaction chamber and carefully transfer it onto a clean quartz glass slide using dust-free tweezers. Place it in a vacuum drying oven (60℃, -0.1MPa) for 30 min to remove trace amounts of adsorbed moisture from the surface. Use the same radio frequency plasma equipment (13.56MHz) as for argon plasma etching to wipe the inner wall of the chamber and the sample stage with anhydrous ethanol. Pre-treat the chamber with oxygen plasma (100W power, O2 flow rate 50sccm, treatment for 5 min) to remove residual organic matter. After closing the chamber door, evacuate to 5×10⁻⁶. -4 To ensure no interference from impurity gases, the graphene film was laid flat in the center of the sample stage, ensuring a smooth surface. O2 was introduced (flow rate 50 sccm), and the power was set to 60 W and the pressure to 20 Pa for 60 s, introducing carboxyl groups onto the graphene surface. X-ray photoelectron spectroscopy analysis showed a carboxyl group density of 0.83 × 10⁻⁶. 15 groups / cm 2 ; Test items and test methods (1) Graphene film thickness test The Bruker Dektak XT profilometer was used for testing (diamond probe radius 5 μm, scan length 500 μm, scan rate 10 μm / s, vertical resolution 0.1 nm). A 1 cm × 1 cm sample was cut from the edge of the filtered graphene oxide film, the sample was fixed on the stage, and the probe was used to scan from the substrate (quartz glass slide) at the edge of the film to the film surface, and the height difference was recorded. The test was repeated at different locations on the film (at least 5 points), and the average value was taken as the final thickness.

[0046] (2) Defect aperture test The graphene film treated with argon plasma was ultrasonically dispersed with anhydrous ethanol (300W, 5min). 10μL of the dispersion was dropped onto a copper grid and allowed to air dry. The defect areas on the graphene surface were observed under a high-resolution transmission electron microscope (accelerating voltage 200kV, point resolution 0.19nm). The defect areas were dark due to differences in electron scattering. 100 independent defects were selected, and their maximum pore size was measured using Image-ProPlus software. The D50 (median diameter) was calculated as the defect pore size.

[0047] (3) Testing of silicon quantum dot particle size and agglomeration rate The graphene film with deposited silicon quantum dots was ultrasonically exfoliated with ethanol (power 400W, 10min) and dropped onto a carbon support film to dry. The particle size of 200 silicon quantum dots was counted using transmission electron microscopy (accelerating voltage 200kV, bright field imaging mode), and the particle size distribution was calculated. Particles with a diameter >10nm were considered as agglomerates, and the agglomeration rate = (number of agglomerates / total number of particles) × 100%.

[0048] (4) Carboxyl density test The graphene film treated with oxygen plasma was cut into 1cm × 1cm pieces and fixed to the XPS sample stage with conductive tape. A K-AlphaX photoelectron spectroscopy system (AlKα target (1486.6 eV), beam spot 500 μm, pass energy 20 eV, step size 0.05 eV) was used to scan the C1s orbital (280-300 eV). Peaks were separated using XPSPeakFit software: CC (284.8 eV), CO (286.4 eV), -COOH (288.8 eV). The ratio of carboxyl peak area to total C1s peak area × graphene surface atomic density (1.1 × 10⁻⁶) was used. 15 atoms / cm 2 ), which gives the carboxyl density.

[0049] (5) Hole structure test 0.2g of sample was degassed at 120℃ and 1Pa vacuum for 12h (to remove adsorbed water vapor). The micropore (<2nm) volume was calculated using the t-plot method and the mesopore (20-80nm) pore size distribution was analyzed using the BJH method. The macropore (300-600nm) volume was calculated using an AutoPore V9600 mercury porosimeter with mercury pressures of 0.1-414MPa. The macropore (300-600nm) volume was obtained by dividing the macropore / mesopore / micropore volume by the total pore volume.

[0050] (6) Initial discharge capacity and cycle retention rate test The graphene-enhanced silicon-carbon anode material prepared in the examples and comparative examples was mixed with binder PVDF and conductive agent SuperP at a mass ratio of 8:1:1. N-methylpyrrolidone was added to form a slurry, which was coated on copper foil (thickness 80-100μm). After vacuum drying (60℃, 12h), it was stamped into a disc with a diameter of 12mm as the working electrode. A lithium metal sheet was used as the counter electrode, Celgard2400 was used as the separator, and 1mol / L LiPF5 (solvent with a volume ratio of EC:DMC:EMC=1:1:1, containing 5% FEC additive) was used as the electrolyte. CR2032 button half-cells were assembled in an argon glove box (water and oxygen content <0.1ppm).

[0051] The first charge and discharge cycle was conducted using the Blue Electric CT-4008 battery testing system at a rate of 0.1C and a voltage range of 0.01-3.0V (vs. Li+ / Li). The initial discharge capacity was calculated as: total discharge capacity / mass of active material; the retention rate after 100 cycles was calculated as: (100th discharge capacity / initial discharge capacity) × 100%.

[0052] (7) Ratio performance test Using the above half-cell, the cells were cycled 5 times at rates of 0.2C, 0.5C, 1C, 2C, and 4C. The capacity at the last discharge of each rate was recorded as the rate performance index at 4A / g (approximately 1C = 4200mA / g, 4A / g ≈ 0.95C).

[0053] (8) Volume expansion rate test The above half-cell was fixed on the X-ray diffractometer sample stage and charged and discharged until fully lithium-intercalated (100% SOC). XRD patterns were acquired simultaneously (CuKα, λ=0.154nm, scanning range 10-80°, step size 0.02°). Based on the shift of the diffraction peak of silicon (111) crystal plane (2θ≈28.4°), the change in interplanar spacing before and after lithium intercalation was calculated using the Bragg equation (2dsinθ=λ). The volume expansion rate = (volume after lithium intercalation - volume before lithium intercalation) / volume before lithium intercalation × 100%.

[0054] (9) Interface bonding verification The bonded sample was ground into powder, mixed with KBr at a ratio of 1:100, and compressed into a pellet. Fourier transform infrared spectroscopy was used, scanning the sample in the range of 400-4000 cm⁻¹. -1 4cm resolution -1 32 scans, 1720cm -1 The characteristic peak of -COOH disappears at 1060 cm⁻¹. -1 The appearance of the Si-OC characteristic peak indicates successful bonding.

[0055] Test results:

[0056] By comparing the performance data of Examples 1-3 with those of Comparative Examples 1-13, the significant advantages of this technical solution in solving the problems of "size mismatch, weak interfacial forces, and poor dispersibility" can be clearly demonstrated through the synergistic system of "graphene substrate pretreatment - in-situ growth of silicon quantum dots - interfacial covalent bonding strengthening - three-dimensional gradient channel construction". The specific advantages are as follows: The silicon quantum dots in Examples 1-3 exhibited an aggregation rate of only 4.23%-5.09%, with a capacity retention rate of 85.42%-88.43% after 100 cycles. Comparative Example 1 (no defect treatment) showed an aggregation rate of 30.56% and a retention rate of 45.32%. Comparative Example 11 (defects 15-20nm, too large) showed an aggregation rate of 25.66% and a retention rate of 61.12%. Comparative Example 12 (defects 2-3nm, too small) showed an aggregation rate of 30.87% and a retention rate of 55.68%. This is because the 5-10nm defects introduced by the graphene substrate pretreatment of this invention form a "nested match" with the 3-5nm silicon quantum dots. The high surface energy of the defects preferentially adsorbs silicon atoms, limiting the nucleation of quantum dots within the defects (Examples 1-3). In contrast, in Comparative Example 1 (no defects), the random growth of quantum dots on the graphene basal surface led to severe aggregation; in Comparative Examples 11 (excessively large defects) and 12 (excessively small defects), due to size mismatch, aggregation within defects or growth on the basal surface occurred, both resulting in performance degradation. This demonstrates that "precise matching between defect size and quantum dot size" is the core of suppressing aggregation and improving cycling stability.

[0057] Examples 1-3 exhibited a 4A / g rate capacity of 953-1023 mAh / g and an initial discharge capacity of 3054-3217 mAh / g; Comparative Example 10 (without pulse mode, continuous plasma) showed a rate capacity of 511 mAh / g, an initial discharge capacity of 2842 mAh / g, and an agglomeration rate of 35.47%. This demonstrates that Examples 1-3 employ a pulsed plasma mode of "0.5s on / 2s off," which shortens the silicon atom migration distance from 20 nm in continuous mode to <5 nm through intermittent energy input, ensuring uniform quantum dot dispersion (agglomeration rate <5%). In contrast, Comparative Example 10, due to continuous plasma, experienced excessive silicon atom migration, leading to agglomerates blocking ion transport channels, resulting in a 50% decrease in rate performance and a 12.5% ​​reduction in initial capacity. This proves that the pulse mode is crucial for maintaining quantum dot dispersion and ensuring high capacity and rate performance.

[0058] The volume expansion rates of Examples 1-3 were 38.29%-42.34%, and the retention rates after 100 cycles were 85.42%-88.43%; Comparative Example 2 (no bonding treatment) had an expansion rate of 250.13% and a retention rate of 40.57%; Comparative Example 9 (bonding failure) had an expansion rate of 283.49% and a retention rate of 36.09%; Comparative Example 13 (insufficient carboxyl density) had an expansion rate of 93.78% and a retention rate of 65.26%. This is because Examples 1-3 of the present invention introduced high carboxyl density (1.32 × 10⁻⁶) through oxygen plasma. 15 -1.48×10 15 groups / cm 2 The process involves forming Si-OC covalent bonds (bond energy 452 kJ / mol) through a low-temperature reaction, transferring the silicon lithium intercalation expansion stress to the graphene framework via chemical bonds, significantly reducing volume expansion (38.29%-42.34%). In contrast, Comparative Examples 2 (no bonding) and 9 (bonding failure) relied solely on van der Waals forces for interfacial bonding, leading to direct interface delamination due to silicon expansion, resulting in expansion rates of 250.13%-283.49% and a sharp drop in cycle retention. Comparative Example 13, with insufficient carboxyl groups leading to low bonding density, still exhibited significant expansion (93.78%). This demonstrates that covalent bonding is the core element for enhancing interfacial stability and suppressing volume expansion.

[0059] The pore volume ratios of Examples 1-3 were 2.2:5.8:2-3.8:4.2:2, with volume expansion rates of 38.29%-42.34% and rate capacities of 953-1023 mAh / g; Comparative Example 3 (no pores) had an expansion rate of 306.45% and a rate capacity of 416 mAh / g; Comparative Example 6 (pore ratio 5.3:4.1:0.6, insufficient micropores) had an expansion rate of 153.06% and a rate capacity of 505 mAh / g; Comparative Example 7 (pore ratio 1.8:6.7:1.5, insufficient macropores) had an expansion rate of 131.65% and a rate capacity of 486 mAh / g. This is because the "macropore (300-600nm)-mesopore (20-80nm)-micropore (<2nm)" gradient pore structure in Examples 1-3 of this invention achieves low expansion (38.29%-42.34%) and high rate performance (953-1023mAh / g) synergistically through macropores buffering overall expansion, mesopores shortening the ion transport path, and micropores increasing electrolyte contact. Comparative Example 3, lacking pores, suffers from stress concentration due to expansion, leading to structural rupture; Comparative Examples 6 (insufficient micropores) and 7 (insufficient macropores) exhibit a significant performance degradation due to the imbalance of pore function, failing to simultaneously meet buffering and transport requirements. This demonstrates that gradient pores are crucial for balancing expansion and transport.

[0060] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0061] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing graphene-reinforced silicon-carbon anode material, characterized in that, Includes the following steps: Pretreatment of S1 graphene substrate S110: The graphene oxide dispersion is vacuum filtered to form a film; S120: The defect pore size introduced on the surface of graphene oxide by placing the graphene film in a radio frequency plasma device and introducing high-purity argon gas. Deposition of S2 silicon quantum dots S210: Pulsed plasma enhanced chemical vapor deposition is used to move the pretreated graphene film into the PE-CVD reaction chamber. After evacuation, a precursor mixed gas is introduced to generate silicon quantum dots in situ on the surface of the pretreated graphene. S3 Interface Covalent Bonding Enhancement S310: Oxygen plasma etching is performed on the graphene film with deposited silicon quantum dots to generate carboxyl groups; S320: Low-temperature annealing at 150-220℃ triggers the interface reaction to form Si-OC covalent bonds; Construction of S4 3D Gradient Channels S410: The bonded graphene is co-assembled with a pore-forming agent, then ball-milled and freeze-dried; S420: Remove the pore-forming agent to obtain a graphene-reinforced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots; In the negative electrode material, the graphene substrate accounts for 80-90% of the mass, and the silicon quantum dots account for 10-20% of the mass. The surface of the graphene substrate has defect pores and a three-dimensional gradient channel structure, and the silicon quantum dots are grown in situ within the defect pores. The three-dimensional gradient pore structure includes macropores with a pore size of 300-600 nm, mesopores with a pore size of 20-80 nm, and micropores with a pore size of <2 nm. The silicon quantum dots are connected to the graphene substrate via Si-OC covalent bonds; The silicon quantum dots have a particle size of 3-5 nm, and the defect pore size is 5-10 nm. The volume ratio of the macropores, mesopores, and micropores is (2-4):(4-6):

2.

2. The method for preparing the graphene-reinforced silicon-carbon anode material according to claim 1, characterized in that, In step S110, the thickness of the graphene oxide film is 45-55 μm. In step S120, the power of the radio frequency plasma treatment is 40-60 W, the gas pressure is 10-20 Pa, and the time is 100-150 s.

3. The method for preparing the graphene-reinforced silicon-carbon anode material according to claim 1, characterized in that, In step S210, the precursor mixed gas is SiH4 and Ar with a volume ratio of 1:9, the total flow rate is 80-120 sccm, the chamber pressure is 15-25 Pa, the substrate temperature is 260-320℃, the plasma power is 80-120 W, the pulse mode is 0.5 s on / 2 s off, and the deposition time is 4-8 min.

4. The method for preparing the graphene-reinforced silicon-carbon anode material according to claim 3, characterized in that, In step S320, the low-temperature annealing conditions are: introducing N₂ at a volume ratio of 95:

5. 2、 H2 mixture, flow rate 100 sccm, heated to 150-220℃ at a rate of 3-6℃ / min, and held at the temperature for 20-40 min.

5. The method for preparing the graphene-reinforced silicon-carbon anode material according to claim 1, characterized in that, The pore-forming agent in step S410 is PMMA microspheres and mesoporous SiO2 nanospheres, and the mass ratio of the bonded graphene, PMMA microspheres, and mesoporous SiO2 nanospheres is (75-80):(15-20):

5.

6. The method for preparing the graphene-reinforced silicon-carbon anode material according to claim 5, characterized in that, The specific method for removing the pore-forming agent in step S420 is as follows: S420: Place the freeze-dried sample into a tube furnace, introduce argon gas, heat-treat at 260-300℃ for 2-3.5h, then immerse in 5wt% HF solution, stir at room temperature for 10-15min, wash with deionized water until neutral, and vacuum dry at 60℃ for 2h to obtain a graphene-reinforced silicon-carbon anode material with three-dimensional gradient channels and deposited silicon quantum dots.

7. A graphene-reinforced silicon-carbon anode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

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