Silicon-carbon negative electrode material processing method

Abstract

The application discloses a processing method of silicon-carbon negative electrode material, and relates to the technical field of silicon-carbon negative electrode material, and comprises the following steps: S1, forming a silicon-carbon precursor by silane deposition on a porous carbon substrate through a fluidized bed reactor; S2, generating oxygen-containing active functional groups on the surface of the silicon-carbon precursor by introducing an oxygen-containing compound gas under the condition of 400 DEG C to 650 DEG C, so as to realize surface activation; S3, introducing acetylene and nitrogen-containing gas under the condition of 400 DEG C to 650 DEG C, and in-situ forming C-N-C covalent bonds at the interface between the silicon-carbon precursor and the coated carbon layer by high-temperature cracking of the acetylene and the nitrogen-containing gas; S4, inertly cooling and discharging, and obtaining a finished product of the silicon-carbon negative electrode material through post-processing and finishing; steps S1, S2 and S3 are continuously carried out in the same fluidized bed reactor; and the problems of easy peeling of the carbon layer, increased production time and additional energy consumption caused by secondary carbon coating in the production process of the existing silicon-carbon negative electrode material are solved.

Description

Technical Field

[0001] This invention relates to the field of silicon-carbon anode material technology, and more specifically, to a method for processing silicon-carbon anode materials. Background Technology

[0002] With the rapid development of electric vehicles and large-scale electrochemical energy storage industries, the market demand for high-energy-density, long-cycle-life, and high-rate-charge-discharge lithium-ion batteries continues to rise, making the development of high-capacity anode materials a core research focus in the industry. Silicon-based anode materials possess an ultra-high theoretical specific capacity of 4200 mAh / g, far superior to traditional graphite anodes, making them the next-generation lithium-ion battery anode material with the greatest industrialization potential. However, silicon-based materials experience a dramatic volume expansion of approximately 300% during charge-discharge cycles, easily leading to problems such as active material pulverization, electrode structure collapse, and conductive network damage, severely restricting their large-scale commercial application. Currently, fluidized bed vapor deposition (CVD) is used to prepare nano-silicon / porous carbon composite materials, which can effectively buffer the volume deformation of the silicon matrix and improve the structural stability of the material, representing the most feasible high-capacity silicon-carbon anode preparation technology for industrialization.

[0003] Existing industrial CVD silicon-carbon preparation processes suffer from common industry problems, including cumbersome procedures and a high dependence on secondary coating. The conventional production process involves: first, preparing a silicon-carbon precursor via fluidized bed silane deposition on a porous carbon substrate; then, performing an initial acetylene carbon coating in the same equipment to obtain a silicon-carbon semi-finished product; after cooling and discharge, the semi-finished product must be transferred again to a fluidized bed or rotary kiln for a secondary carbon coating to obtain a qualified finished material. The core reason for adding this secondary coating step is that the silicon-carbon precursor prepared by conventional processes has high chemical inertness and a lack of polar active sites. During the initial coating process, the acetylene adsorption is insufficient, resulting in poor carbon layer deposition and an inability to effectively reduce the BET specific surface area of ​​the material, leading to serious problems such as incomplete coating and insufficient deposition. Meanwhile, in order to avoid defects such as phase transformation and grain growth failure of nano-silicon grains caused by high temperature conditions, the industry generally adopts a low temperature deposition process of 550~600℃ for secondary coating. However, the low temperature environment further reduces the efficiency of acetylene cracking and deposition, which exacerbates the problem of uneven coating. The defects can only be compensated by multiple coatings, which ultimately leads to mass production problems such as long production cycle, high energy consumption and poor batch consistency.

[0004] Traditional low-temperature CVD carbon coating processes face several core technological bottlenecks in practical mass production applications, severely hindering the performance upgrades and industrialization of high-end silicon-carbon anode materials. Specific technical shortcomings are as follows: First, the active adsorption sites are scarce, resulting in poor batch-to-batch consistency. The surfaces of porous carbon substrates and silicon-carbon precursors are dominated by inert nonpolar bonds, with few polar active sites and uneven distribution. During acetylene cracking, the gas adsorption capacity is weak and the surface deposition coverage is low, making it prone to defects such as localized incomplete coating of single particles, excessive local carbon deposition, and uneven carbon layer thickness. This leads to large dispersion in the electrochemical performance of materials within the same batch, which cannot meet the requirements for mass application of high-end power batteries.

[0005] Secondly, the interfacial bonding strength is low, resulting in poor long-term cycling stability. The carbon coating layer prepared by traditional CVD processes relies solely on van der Waals intermolecular forces to physically adhere to the silicon-carbon matrix, lacking a chemically bonded cross-linked structure at the interface, leading to extremely low bonding strength. During long-term charge-discharge cycles, the continuous volume expansion and contraction of silicon particles generate alternating stress, easily causing carbon layer slippage, peeling, and detachment, directly damaging the electrode conductive network and triggering a precipitous capacity decay in the later stages of battery cycling.

[0006] Third, the mass production process is cumbersome, making it difficult to balance performance and economic benefits. Traditional single-stage carbon coating modification has limited effects and cannot solve the problems of uneven or incomplete coating. The industry generally adopts secondary and multiple coating processes to optimize product performance. However, multiple high-temperature coating processes significantly increase production energy consumption, extend production cycles, reduce equipment effective capacity, and significantly raise mass production costs. At the same time, repeated high-temperature thermal deposition can easily cause blockage of internal pores in the material, excessive reduction of specific surface area, and closure of lithium-ion transport channels, leading to problems such as a decrease in the material's initial coulombic efficiency and deterioration of rate performance. It is impossible to balance the material's electrochemical performance with the economic benefits of mass production.

[0007] In summary, existing CVD silicon-carbon coating processes suffer from common industry-wide technical defects such as insufficient acetylene adsorption sites, poor coating uniformity, weak interfacial bonding, and high energy consumption in mass production. These defects severely restrict the performance iteration and large-scale industrialization of silicon-carbon anode materials, necessitating the development of novel synergistic modification processes to solve these technical challenges. Summary of the Invention

[0008] This invention provides a method for processing silicon-carbon anode materials to solve the problems of easy carbon layer detachment and increased production time and additional energy consumption caused by secondary carbon coating in the existing silicon-carbon anode material production process.

[0009] To achieve the above objectives, the present invention provides the following solution: A method for processing silicon-carbon anode materials includes the following steps: S1. Silane deposition is performed on a porous carbon substrate using a fluidized bed reactor to form a silicon-carbon precursor. S2. An oxygen-containing compound gas is introduced at 400℃~650℃ to generate oxygen-containing active functional groups on the surface of the silicon-carbon precursor, thereby achieving surface activation. S3. Acetylene and nitrogen-containing gas are introduced at 400℃~650℃. Acetylene and nitrogen-containing gas are decomposed at high temperature, and CNC covalent bonds are formed in situ at the interface between the silicon-carbon precursor and the coated carbon layer. S4. Inertial cooling and discharge, followed by post-processing and finishing to obtain the finished silicon-carbon anode material; Steps S1, S2, and S3 are carried out continuously within the same fluidized bed reactor.

[0010] Furthermore, in step S2, the oxygen-containing gas is either carbon monoxide or carbon dioxide. These two types of gases can perform gentle etching and functional group grafting on the silicon-carbon precursor under medium- and low-temperature conditions. Without damaging the matrix framework structure, a large number of polar active functional groups such as hydroxyl, carboxyl, and carbonyl groups are generated in situ on the material surface and the inner walls of the pores. This effectively enhances the surface polarity and surface energy of the material, significantly increases the number of acetylene adsorption and pyrolysis active sites, and solves the technical problems of uneven coating, incomplete coating, and localized carbon deposition in traditional processes.

[0011] Furthermore, in step S2, the flow rate of the oxygen-containing gas is 1~50 L / min, the inlet temperature is 400℃~650℃, and an intermittent inlet method is adopted. The duration of a single inlet is 5min~30min, followed by a 5min~20min pause, and the inlet is cyclically continued until the total duration is 5min~300min. The gauge pressure is -0.05MPa~0.2MPa, and the flow rate ratio of the carrier gas to the oxygen-containing gas is 10:1~1:1. The carrier gas is high-purity nitrogen or high-purity argon. This parameter range can achieve mild and uniform activation of the silicon-carbon precursor, ensuring a sufficient number and uniform distribution of activation sites while avoiding excessive etching that could damage the carbon matrix framework and collapse the pore structure, thus ensuring the stability of the material's basic structure.

[0012] Furthermore, in step S3, the nitrogen-containing gas is ammonia or vaporized pyridine vapor. The high-temperature pyrolysis of these two types of nitrogen-containing gases can generate highly reactive nitrogen atoms, which can be uniformly doped at the interface between the silicon-carbon matrix and the coated carbon layer, providing a stable nitrogen source for covalent bond construction. Moreover, the doping process is gentle and will not damage the already formed silicon-carbon framework structure.

[0013] Furthermore, in step S3, the nitrogen-containing gas and acetylene are introduced and stopped simultaneously for a duration of 50-300 minutes, with a flow rate ratio of acetylene to nitrogen-containing gas of 10:1 to 1:1. The simultaneous introduction and pyrolysis of the carbon and nitrogen sources allow for simultaneous carbon layer deposition and nitrogen doping modification, generating continuous and stable CNC covalent bonds in situ, strengthening interfacial bonding, and ensuring uniform adhesion of the carbon layer.

[0014] Furthermore, in step S1, the porous carbon substrate is resin-based, coal-based, or biomass-based. Resin-based carbon substrates have regular pore sizes, high purity, and few impurities; coal-based porous carbon substrates have the advantages of abundant raw material reserves, low cost, moderate graphitization degree, and strong structural rigidity. The pore structure is compact and has high mechanical strength, which can effectively suppress the overall structural deformation of silicon-carbon composite materials and is suitable for large-scale energy storage low-cost mass production scenarios; biomass-based carbon substrates have well-developed pores, large specific surface area, and low cost. All three types of substrates have excellent structural flexibility and load-bearing capacity, are suitable for fluidized bed vapor deposition processes, and can effectively buffer the volume expansion of silicon particles.

[0015] Furthermore, in step S1, the silicon content in the silicon-carbon precursor is 40% to 65% by mass. This silicon content range can balance the high specific capacity and structural stability of the material. If the silicon content is too low, the high capacity advantage cannot be reflected, and if the silicon content is too high, the volume expansion effect will be aggravated, which will easily lead to the pulverization and collapse of the electrode structure.

[0016] Furthermore, step S1 also includes a pretreatment step for the porous carbon substrate, the pretreatment comprising the following steps: S101. The porous carbon substrate is activated, washed, dried, and subjected to air classification to obtain porous carbon powder with D50 = 5~15μm, specific surface area of ​​800~3000m² / g, and pore volume of 0.6~1.5cm³ / g. Precise control of the powder particle size, specific surface area, and pore structure ensures uniform loading of subsequent silicon particles and unobstructed permeation of reactant gases.

[0017] S102. Porous carbon powder is fed into a fluidized bed reactor under negative pressure, and the vacuum is evacuated to ≤100Pa. High-purity nitrogen is introduced to replace the oxygen 3-5 times, and the oxygen content of the system is <10ppm. Nitrogen gas is introduced into the bottom for fluidization, and the temperature is raised to 500℃ and held for 1 hour to fully disperse the powder. This process eliminates impurities such as oxygen and water vapor in the system, avoids high-temperature oxidation side reactions, and breaks up powder agglomeration to achieve uniform fluidization of single particles.

[0018] S103, heated to 600~700℃, held under negative pressure for 1~2 hours, removes adsorbed water and carbon dioxide from the pores, and opens up the closed mesopores. This fully purifies the pore structure, opens up the closed pores, significantly improves the pore utilization rate, and provides sufficient reaction space for silane deposition, acetylene adsorption, and activation modification.

[0019] Further, in step S1, the specific steps of silane deposition are as follows: maintaining the fluidized state in the fluidized bed reactor, heating to 400~650℃, and introducing a mixed reaction gas; the mixed reaction gas consists of high-purity silane diluted with nitrogen, with silane accounting for 5%~15% of the volume, a carrier gas flow rate of 0.08~0.15m³ / h, a deposition time of 2~5h, and the carrier gas being high-purity nitrogen or high-purity argon; silane is decomposed at high temperature to generate 1nm~10nm nano-silicon particles, which fill the pores of the carbon framework. The nano-sized silicon particles are uniform in size and have good dispersion, and can uniformly fill the pores inside the carbon substrate. Relying on the constraint of the carbon framework, they effectively alleviate the volume deformation during the charging and discharging process and improve the structural stability of the material.

[0020] Furthermore, in step S4, the inertial cooling discharge specifically involves shutting off all reaction gas sources and continuously fluidizing and cooling the material with high-purity nitrogen at a rate of 1.5℃ / min~2.5℃ / min to 400℃. From 400℃ to room temperature, the cooling rate is controlled to be ≤3.5℃ / min. The entire process is airtight, with the material discharged under negative pressure. Post-processing finishing includes airflow classification, strong magnetic impurity removal, and vacuum homogenization. Segmented inertial cooling can effectively avoid cracking and structural damage caused by thermal stress concentration in the material. Air isolation throughout the process can prevent high-temperature carbon layer oxidation failure. The post-processing steps can remove magnetic impurities and coarse and fine particles, ensuring that the finished powder has uniform particle size and high performance consistency.

[0021] The principle behind increasing acetylene adsorption sites and enhancing carbon layer bonding in this invention is as follows: Firstly, the principle of oxygen-containing activation and site enhancement: The surface of traditional silicon-carbon precursors is dominated by inert C-C nonpolar bonds, resulting in weak surface polarity, low surface energy, and a single type of surface functional groups with extremely high stability. This leads to extremely poor physical adsorption and chemical enrichment capabilities for nonpolar acetylene molecules. The number of effective active sites across the entire surface is severely insufficient and randomly distributed, directly causing core defects such as disordered carbon source deposition, uneven coating of single particles, and the coexistence of localized carbon accumulation and incomplete coating. The carbon deposition behavior of conventional unmodified silicon-carbon precursors relies entirely on random physical adsorption, lacking fixed reactive centers. Carbon layer growth exhibits randomness and disorder, easily leading to a polarization phenomenon where thick carbon accumulation occurs at particle edges, while the particle surface is exposed and lacks carbon, ultimately resulting in large batch-to-batch performance dispersion and poor electrochemical stability. This invention employs a CO / CO2 low-temperature mild activation process, strictly controlling the activation temperature, gas ratio, and activation time. Without damaging the silicon-carbon matrix framework or inducing silicon grain phase transformation and growth, it precisely grafts a large number of highly polar and reactive oxygen-containing functional groups, such as hydroxyl, carbonyl, and carboxyl groups, onto the outer surface and inner walls of the mesoporous channels of the material. This alters the physicochemical properties of the silicon-carbon precursor surface, significantly enhancing the surface polarity and surface energy, and constructing high-density, uniformly distributed, and consistently active acetylene pyrolysis deposition sites. After modification, all carbon deposition reactions proceed in an orderly manner based on these well-ordered active sites. The acetylene pyrolysis, adsorption, and carbonization processes are uniform and controllable, overcoming the coating defects of traditional low-temperature coating processes. A dense, uniform, and complete carbon layer coating effect can be achieved with a single coating, standardizing and controlling the coating quality from the process source.

[0022] Secondly, the principle of in-situ nitrogen doping and covalent bond strengthening: Traditional CVD carbon coating processes rely solely on weak van der Waals intermolecular forces for physical adhesion between the carbon layer and the silicon-carbon matrix. There are no chemical cross-links or interfacial anchoring structures at the interface, resulting in extremely low interfacial bonding energy, making it a typical weakly bonded interface system. During repeated charge-discharge cycles of lithium batteries, the silicon-based material undergoes continuous expansion and contraction, leading to continuous alternating shear stress and peeling stress on the coated carbon layer. Under long-term cycling conditions, structural failures such as carbon layer slippage, edge lifting, delamination, and overall detachment are highly likely, directly disrupting the internal conductive pathways of the electrode and causing a precipitous decline in battery capacity and eventual battery life. This invention employs an integrated symbiotic process involving simultaneous feeding and high-temperature pyrolysis of acetylene and nitrogen-containing gas, achieving simultaneous and synergistic coupling of the three major processes: carbon layer deposition, uniform nitrogen doping, and in-situ covalent bond construction. Highly reactive nitrogen atoms generated by high-temperature pyrolysis can uniformly penetrate into the interface region between the carbon layer and the silicon-carbon matrix, replacing some of the inert carbon atoms. This generates a large number of continuous, stable, and high-bond-energy CNC covalent bonds in situ across the entire interface, achieving high-strength chemical anchoring between the carbon layer and the matrix. This upgrades the traditional physically weak bonding interface to a stable and robust chemically bonded interface, enhancing the carbon layer's bonding strength and structural resistance to deformation. Simultaneously, the uniformly doped nitrogen atoms can effectively modulate the electronic band structure of the coated carbon layer, improving its intrinsic conductivity, reducing interfacial contact impedance and charge transfer impedance, and significantly accelerating the lithium-ion intercalation / deintercalation and bulk diffusion kinetics. This also improves the material's long-cycle structural stability and high-power fast-charging adaptability, achieving a dual upgrade in both structural performance and electrochemical kinetics.

[0023] One or more technical solutions provided by this invention have at least the following technical effects or advantages: (1) The present invention introduces oxygen-containing functional groups by using oxygen-containing compound gas to perform surface activation modification on silicon-carbon precursor, and constructs a large number of uniform acetylene active adsorption sites on the material surface and in the pores, thereby solving the technical problems of insufficient adsorption sites, uneven carbon layer coating, local leakage coating, and local carbon accumulation in traditional CVD process. It avoids the problems of increased production time and additional energy consumption caused by secondary carbon coating in the prior art, and achieves dense, uniform and complete carbon layer coating. (2) This invention constructs CNC covalent bonds in situ at the interface between the silicon-carbon matrix and the coated carbon layer by simultaneously high-temperature pyrolysis of acetylene and nitrogen-containing gas. This upgrades the traditional process of simple physical adsorption to high-strength chemical bonding, greatly improves the interfacial bonding force between the carbon layer and the matrix, effectively suppresses the phenomenon of carbon layer peeling and shedding during charge-discharge cycles, and stabilizes the electrode conductive network. (3) The present invention achieves uniform loading of nano-silicon particles, unobstructed pore structure and stable interface bonding through substrate pretreatment, silane deposition, surface activation and nitrogen doping bonding synergistic process, which can effectively buffer the volume expansion of silicon materials, avoid structural collapse during long-term cycling, and significantly improve the cycle life and rate performance of the battery. (4) The overall process of this invention is based on continuous fluidized bed reaction and is completed continuously in the same fluidized bed. It does not require cooling to discharge or material transfer. Single coating replaces double coating. The parameters are controllable, the reaction is stable, the product consistency is good, there are no complex and high-risk processes, it is suitable for large-scale industrial mass production, the production cost is controllable, and the industrial application prospects are broad. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Figure 1 This is a process flow diagram of the silicon-carbon anode material processing method described in this invention. Detailed Implementation

[0025] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below. Example 1: This example provides a method for processing silicon-carbon anode materials, such as... Figure 1 As shown, it includes the following steps:

[0027] S1. Pretreatment of porous carbon substrate and preparation of silicon-carbon precursor: Resin-based, coal-based, or biomass-based porous carbon substrates are selected and sequentially subjected to high-temperature activation, pure water washing, constant-temperature drying, and airflow classification to obtain porous carbon powder with D50 = 5μm~15μm, specific surface area 800m² / g~3000m² / g, and pore volume 0.6cm³ / g~1.5cm³ / g. The prepared porous carbon powder is then fed into a fluidized bed reactor under negative pressure, evacuated to ≤100Pa, and purged 3~5 times with high-purity nitrogen to ensure the oxygen content of the system is <10ppm. High-purity nitrogen is introduced into the bottom of the reactor to maintain the fluidized state; the preferred high-purity nitrogen flow rate is 0.1. At a speed of ~0.3 m / s, the temperature is raised to 500℃ and held for 1 hour to achieve full dispersion of the powder. The temperature is then raised to 600℃~700℃ and held under negative pressure for 1 hour~2 hours to remove impurities such as adsorbed water and carbon dioxide from the pores and open up the closed mesopores. Subsequently, the temperature is raised to 400℃~650℃ and a stable fluidized state is maintained. A mixture of silane and nitrogen gas with a volume ratio of 5%~15% is introduced as a carrier gas with a flow rate controlled at 0.08 m³ / h~0.15 m³ / h. Continuous deposition is carried out for 2 hours~5 hours. The silane is decomposed at high temperature to generate 1 nm~10 nm nano-silicon particles, which uniformly fill the pores of the carbon skeleton, thus preparing a silicon-carbon precursor with a silicon content of 40%~65%.

[0028] S2. Surface activation of silicon-carbon precursor: Carbon monoxide or carbon dioxide is selected as the oxygen-containing gas, with carbon dioxide being preferred. The gas flow rate is 1 L / min to 50 L / min, the activation temperature is 400℃ to 650℃, the single gas flow time is 5 min to 30 min, and the total circulation time is 5 min to 300 min. The pressure of the reactor system is stabilized at -0.05 MPa to 0.2 MPa, and the ratio of carrier gas to carbon dioxide flow rate is 10:1 to 1:1. Through high-temperature activation, a large number of oxygen-containing active functional groups are generated on the surface and in the pores of the silicon-carbon precursor, thus constructing abundant acetylene adsorption sites.

[0029] S3. Simultaneous pyrolysis carbon coating and nitrogen doping modification: vaporized pyridine vapor or ammonia is selected as the nitrogen-containing gas, preferably ammonia. Acetylene and ammonia are simultaneously introduced into the reactor, with simultaneous gas introduction and simultaneous gas stop. The total gas introduction time is 50 min to 300 min, and the gas flow rate ratio of acetylene to ammonia is 10:1 to 1:1. Under high temperature conditions, acetylene is pyrolyzed to generate a coated carbon layer, and nitrogen atoms are simultaneously doped into the interface to generate CNC covalent bonds in situ, which strengthens the bonding force between the carbon layer and the silicon-carbon precursor.

[0030] S4. Inertial Cooling and Post-processing Finishing: All reaction gas sources are shut off, and only high-purity nitrogen is continuously introduced for fluidization. The temperature is reduced in stages and gradients, and the temperature is uniformly reduced to 400℃ in 1.5 hours. Then, it takes 2 hours to cool naturally to room temperature. Air is isolated throughout the process, and the material is discharged in a negative pressure closed manner. After discharge, the material is subjected to airflow classification, strong magnetic impurity removal, and vacuum homogenization treatment in sequence to remove impurities and coarse and fine particles, so as to obtain high-stability silicon-carbon anode finished material.

[0031] Among them, the airflow classification process adopts a fluidized bed airflow precision classification device, using high-purity dry nitrogen as the classification gas source, controlling the classification gas pressure at 0.7~0.9MPa, adjusting the classification wheel speed at 2500~3500r / min, and maintaining the classification temperature in a normal dry environment. The high-speed airflow causes the powder particles to self-collide and dissociate, breaking up the slightly agglomerated particles after coating, removing coarse particles with D50>15μm and ultrafine dust fragments, and screening to retain qualified powder particles with D50=9~11μm. The particle size distribution is uniform and regular, eliminating the problems of large particle polarization and fine powder side reaction aggravation, ensuring the uniformity of electrode coating and battery cycle consistency.

[0032] Strong magnetic impurity removal: High-gradient fully automatic pipeline iron removal equipment is adopted, with the magnetic field strength stably controlled at 18000~22000GS, which is suitable for the high-precision impurity removal requirements of silicon-carbon anode powder; the powder is conveyed under negative pressure with a feeding speed of 15~25kg / h, with no material exposure and no secondary pollution throughout the process; the strong magnetic field accurately adsorbs and retains trace amounts of iron-based magnetic impurities introduced by equipment wear and raw material residues during the preparation process, which can effectively remove 0.5~50μm fine magnetic particles. After impurity removal, the total content of magnetic impurities in the powder is ≤50ppb, which reduces the risk of battery micro-short circuits, self-discharge, and thermal runaway caused by metal impurities, and significantly improves battery safety performance and long-term service stability.

[0033] Vacuum homogenization treatment: A vertical three-dimensional vacuum homogenization device is used, and the homogenization vacuum degree is maintained at -0.08~-0.10MPa to isolate air moisture and impurities from intrusion; the homogenization speed is set to 15~25r / min, and the homogenization time for a single cycle is 30~60min. Through three-dimensional reciprocating oscillation, flipping and mixing motion, the problems of local density differences, particle size segregation and uneven composition distribution of the carbon layer of the powder are thoroughly solved, and the carbon content, pore structure, conductivity and electrochemical activity of the entire batch of powder are homogenized. The batch performance dispersion is ≤1.5%, which meets the consistency requirements of mass production and large-scale application of high-end power batteries. Example 2: Based on Example 1, this example provides an industrial-scale example;

[0034] The general experimental group consisted of a resin-based porous carbon substrate, which underwent high-temperature activation, pure water washing, constant-temperature drying, and airflow classification treatment to obtain standardized porous carbon powder with a D50 of 10 μm, a specific surface area of ​​950 m² / g, and a pore volume of 1.1 cm³ / g. A fixed feed of 5 kg of powder was placed in a 20 kg fluidized bed reactor, which was then evacuated to 80 Pa under negative pressure and purged four times with high-purity nitrogen to strictly control the oxygen content to <10 ppm. High-purity nitrogen was introduced at the bottom to maintain a stable fluidized state at 500℃. The powder was kept at a constant temperature for 1 hour to break up agglomerates and achieve uniform dispersion of single particles. Then, the temperature was raised to 650℃ and kept under negative pressure for 1.5 hours to remove impurities such as adsorbed water and residual carbon dioxide from the pores, and to open up the closed mesopores and clear the pore transport channels. The temperature was then adjusted to 620℃, and a mixture of silane and nitrogen was introduced as a reaction gas. The volume ratio of silane was 10% and the carrier gas flow rate was 0.10 m³ / h. The deposition time was precisely controlled to prepare a standardized silicon-carbon precursor with a silicon content of 50%. The reaction was terminated by turning off the silane gas source, which was then used for subsequent differential modification experiments.

[0035] Based on the aforementioned unified benchmark silicon-carbon precursor, the core modification process of this invention is performed, and the specific steps are as follows: Constant temperature control: After silicon deposition, the flow rate of nitrogen carrier gas in the fluidized bed is kept constant at 60 L / min. The reactor temperature is raised to 580℃ at a uniform heating rate of 5℃ / min. The temperature is then held for 10 min to ensure that the internal temperature field of the reactor is uniform and the overall temperature of the powder is consistent, thus eliminating the influence of local temperature gradients on the activation reaction.

[0036] Oxygen-containing activation of the precursor surface: After the temperature stabilizes at 580℃, maintain a constant nitrogen carrier gas flow rate of 60L / min, and simultaneously introduce carbon dioxide activation gas at a flow rate of 20L / min. The flow rate ratio of carrier gas to activation gas is 3:1, and the system is maintained at a negative pressure of -0.01MPa to -0.05MPa, preferably -0.02MPa, for continuous isothermal activation for 30min. Through high-temperature functional group grafting activation with carbon dioxide, a large number of hydroxyl and carbonyl active polar functional groups are generated on the surface and inside the pores of the silicon-carbon precursor, constructing high-density and uniformly distributed acetylene adsorption active sites. After activation, the carbon dioxide gas source is turned off.

[0037] Simultaneous pyrolysis carbon coating and nitrogen doping bonding: While maintaining the reactor temperature at 580℃ and the nitrogen carrier gas flow rate at 60L / min, acetylene and ammonia are simultaneously introduced at a flow rate of 15L / min for acetylene and 5L / min for ammonia, with a flow rate ratio of 3:1. The two gases are introduced and react simultaneously for a total coating modification time of 150min. Under high-temperature conditions, acetylene pyrolysis generates a dense amorphous coated carbon layer, which is uniformly deposited on the surface of the silicon-carbon precursor. Simultaneous pyrolysis of ammonia produces highly reactive nitrogen atoms, which generate continuous and stable CNC covalent bonds in situ at the interface between the carbon layer and the silicon-carbon matrix, achieving high-strength chemical anchoring of the carbon layer.

[0038] Gradient cooling and post-processing finishing: After the coating reaction is completed, the acetylene and ammonia reaction gas sources are turned off, and only high-purity nitrogen is kept for continuous fluidization protection. An industrial gradient cooling process is adopted, and the temperature is uniformly cooled to 400°C in 1.5 hours, and then naturally cooled to room temperature in 2 hours. The entire process is carried out in a closed, air-isolated, negative pressure environment to avoid high-temperature carbon layer oxidation and powder moisture absorption and agglomeration. After discharge, airflow classification, strong magnetic impurity removal and vacuum homogenization are carried out in sequence to remove coarse particles, magnetic metal impurities and trace agglomerated powder, ensuring that the finished powder has uniform particle size, high purity and good batch consistency, thus obtaining the modified silicon-carbon anode material of this invention.

[0039] Battery assembly and testing: The finished silicon-carbon material of this embodiment is used as the negative electrode active material. A uniform negative electrode slurry is prepared by combining it with conductive carbon black, PVDF binder and NMP solvent. The slurry is coated on the surface of copper foil, dried, rolled and sliced ​​to obtain a standard negative electrode sheet. A lithium metal positive electrode, conventional lithium battery electrolyte and polypropylene separator are matched to assemble a CR2032 coin cell. After static activation, the powder physical parameters, interfacial bonding strength and electrochemical performance are tested.

[0040] The test data are as follows: carbon content is 52%, BET is 1.8 m² / g, powder compaction resistivity at 20 MPa is 1.7 Ω / cm, reversible capacity at 1.5V is 1830 mAh / g, initial coulombic efficiency at 1.5V is 93.4%, reversible capacity at 0.8V is 1645 mAh / g, initial coulombic efficiency at 0.8V is 82.5%, and capacity retention after 500 cycles is 93%.

[0041] Comparative Example 1: The substrate pretreatment, silicon deposition, heating process, oxygen-containing activation process, carbon coating temperature, duration, and acetylene flow rate parameters in this comparative example are completely consistent with those in Example 2. The only variable is the omission of the ammonia nitrogen doping process and the absence of CNC covalent bond construction, which is used to separately verify the effect of nitrogen doping covalent bonds on improving interfacial bonding and cycle stability.

[0042] Specific process: After silicon deposition, the temperature is increased to 580℃ at 5℃ / min, and activated for 30min with nitrogen at 60L / min and carbon dioxide at 20L / min. After activation, carbon dioxide is turned off, and the temperature and carrier gas are kept constant. Only acetylene is introduced at 15L / min for a single coating for 150min. After coating, the same gradient cooling, negative pressure discharge, post-processing, and battery assembly and testing process as in Example 2 are adopted.

[0043] The test data are as follows: carbon content is 51.5%, BET is 34 m² / g, powder compaction resistivity at 20 MPa is 1.9 Ω / cm, reversible capacity at 1.5V is 1845 mAh / g, initial coulombic efficiency at 1.5V is 91.8%, reversible capacity at 0.8V is 1605 mAh / g, and initial coulombic efficiency at 0.8V is 81.1%.

[0044] Comparative Example 2: This comparative example uses the industry's traditional standard mass production process, retaining only basic silicon deposition and a single acetylene carbon coating, completely eliminating oxygen-containing activation and nitrogen doping modification, and is used to verify the comprehensive gain effect of the dual modification mechanism of this invention.

[0045] Specific process: After uniform pretreatment and silicon deposition to silicon content of 50%, the temperature is increased to 580℃ at 5℃ / min. Without any activation treatment, acetylene is directly introduced at 15L / min and nitrogen at 60L / min. The single carbon coating takes 150min. The subsequent cooling, unloading, post-processing, and battery testing processes are completely the same as in Example 2.

[0046] The test data are as follows: carbon content is 51%, BET is 50m² / g, powder compaction resistivity at 20MPa is 2.0Ω / cm, reversible capacity at 1.5V is 1845mAh / g, initial coulombic efficiency at 1.5V is 91.2%, reversible capacity at 0.8V is 1625mAh / g, initial coulombic efficiency at 0.8V is 80.5%.

[0047] Comparative Example 3: This comparative example is a traditional optimization process in the industry, which compensates for the defects of a single coating by secondary coating. It is a common method to improve coating uniformity in mass production and is used to compare the performance and cost advantages of the single modification process of this invention.

[0048] Specific process: The single-coating material prepared in Comparative Example 2 was re-introduced into a 20kg fluidized bed reactor. Under uniform fluidization, temperature control, and nitrogen protection conditions, the traditional acetylene carbon coating and re-coating process was repeated. The reaction was continued and the BET specific surface area of ​​the material was monitored in real time until the material BET dropped below 2m² / g and the reaction was stopped, thus completing the secondary coating. Subsequently, uniform gradient cooling, sealed discharge, and fine processing were carried out, and button batteries were assembled for a full set of performance tests.

[0049] The test data are as follows: carbon content is 52.1%, BET is 1.7 m² / g, powder compaction resistivity at 20 MPa is 1.6 Ω / cm, reversible capacity at 1.5V is 1809 mAh / g, initial coulombic efficiency at 1.5V is 92.5%, reversible capacity at 0.8V is 1635 mAh / g, initial coulombic efficiency at 0.8V is 81.6%, and capacity retention after 500 cycles is 89%.

[0050] Based on the experimental group of Example 2 and the comparative examples above, under identical equipment conditions, testing environment, and battery assembly process conditions, a full set of performance tests were conducted on the four groups of samples, including powder carbon content, BET specific surface area, powder compaction resistivity, reversible capacity at different voltage platforms, initial coulombic efficiency, and capacity retention after 500 cycles. A systematic mechanism analysis was conducted based on the microstructure and interface structure characteristics. Specific test results and technical explanations are as follows: Microstructure, coating density, and pore structure: Combining the BET specific surface area parameter of the powder with the microstructure of the coating can accurately determine the quality of modification and structural differences of each process. The BET specific surface area is a core indicator that directly reflects the degree of surface exposure, carbon layer coating integrity, and internal pore regularity of silicon-carbon materials. It plays a decisive role in the material's initial coulombic efficiency, the degree of interfacial side reactions, and cycle stability. Comparative Example 2: Traditional single-coating samples have no activation modification process. The precursor surface has scarce active sites, disordered acetylene adsorption, and extremely poor coating uniformity. There are large areas of exposed substrate on the particle surface, accompanied by defects such as localized excessive carbon deposition and uneven carbon layer thickness. The material's pore structure is excessively open, and surface defects are dense. The BET is as high as 50 m² / g. The extremely high specific surface area leads to a large amount of electrolyte decomposition and disordered thickening of the interfacial SEI film during battery activation, continuously consuming the effective lithium source. This is the core cause of its low initial efficiency and rapid cycle decay. Comparative Example 1, after single oxygen-containing activation modification, effectively solved the problem of uneven acetylene adsorption, significantly improved coating uniformity, and eliminated obvious large-area leakage defects. The surface regularity of the powder was improved. However, this process only optimized the carbon deposition distribution and did not achieve precise pore closure and surface passivation. A large amount of the porous structure inside the material was still exposed, and there were many residual active sites in the pores. The BET was still as high as 34 m² / g, and the residual amount of active material on the powder surface was large. It was impossible to completely suppress interfacial side reactions. Therefore, the initial coulombic efficiency and long-term cycling stability still had significant shortcomings. Comparative Example 3 employs the industry's traditional secondary coating process, which achieves pore sealing by extending the high-temperature carbon deposition time and increasing the carbon source injection rate. This reduces the material's BET to 1.7 m² / g, achieving a dense coating effect. However, this process is a passive, disordered carbon deposition sealing method. Excessive carbon source not only deposits on the particle surface but also continuously blocks the effective mesopores inside the material, closes the lithium-ion transport channels, and destroys the original gradient pore structure of the material. This directly leads to a decrease in the material's rate performance and reversible capacity loss. It sacrifices electrochemical kinetic performance for surface density, resulting in a significant performance trade-off. In Example 2 of this invention, relying on oxygen-activated, uniformly active sites, precise, orderly, and controllable carbon layer deposition is achieved. Within a reasonable range of 52% carbon content, BET is precisely controlled at 1.8 m² / g, which is basically on par with the densification level of the secondary coating process. At the same time, the effective mesoporous structure inside the material is preserved, which not only eliminates exposed defects on the particle surface, passivates the highly active surface of the powder, and reduces electrolyte side reaction losses, but also retains effective pores for rapid lithium ion transport and buffering volume deformation. The coating structure achieves a balance between density and permeability, and its comprehensive structural advantages exceed those of all comparative samples.

[0051] Interfacial conductivity and interfacial bonding strength: The powder compaction resistivity under 20 MPa pressure is a key industrial indicator for quantifying the continuity of the conductive network, the density of the carbon layer coating, and the quality of interfacial contact in silicon-carbon materials. It can simulate the actual conductive conditions after electrode rolling and predict the battery's rate charge / discharge performance and polarization degree. Comparative Example 2, without activation or nitrogen doping, and using traditional single-coating methods, exhibits numerous coating defects, severe surface exposure, discontinuous carbon layers, high contact impedance between powder particles, fragmented overall conductive network, and the highest compaction resistivity at 2.0 Ω / cm. During battery charge / discharge, it shows severe polarization, poor rate performance, and significant capacity decay under high current conditions. Comparative Example 1, with only oxygen activation to optimize coating uniformity and improve carbon layer adhesion, still maintains a purely physical interface with micro-interfacial gaps and contact voids, resulting in limited conductive continuity. Its compaction resistivity is 1.9 Ω / cm, indicating limited improvement in conductivity. Comparative Example 3, after secondary carbon coating, resulted in a thick and dense carbon layer on the particle surface, with complete surface conductive pathways and a resistivity reduced to 1.6 Ω / cm, exhibiting relatively optimal conductivity. However, this performance advantage relied on excessive carbon deposition, sacrificing the material's pore structure and capacity characteristics, resulting in extremely low overall cost-effectiveness. Example 2 of this invention achieves complete full-domain coating through uniform oxygen activation, coupled with a high-strength, tightly connected interface constructed using in-situ CNC covalent bonds. This eliminates interfacial gaps and contact resistance, resulting in a continuous and stable conductive network. The compacted resistivity is stably controlled at 1.7 Ω / cm, achieving excellent conductivity without sacrificing pore structure and capacity, while also considering structural stability and electrochemical kinetic advantages. Regarding cycle stability, the interfacial bonding strength is the core key to determining the long cycle life of silicon-carbon anodes. In Comparative Examples 2 and 3, the carbon layers rely on van der Waals forces for physical bonding, resulting in weak interfacial bonding strength and poor resistance to deformation. Under the stress of periodic volume expansion of silicon, significant carbon layer peeling, conductive network damage, and structural loosening failure occur after 300 charge-discharge cycles. Although Comparative Example 1 optimized the coating uniformity, it lacks chemical bond anchoring, limiting the improvement in interfacial bonding strength. Under long-term alternating stress, the interface is prone to loosening and detachment, resulting in significant structural decay and capacity drop after 500 cycles. In contrast, Example 2 of this invention relies on globally stable covalent bonds for chemical anchoring, integrating the carbon layer with the matrix. This significantly improves the resistance to peeling and deformation. Even after 500 long cycles, there are no carbon layer detachments, structural collapses, or conductive network damage. The microscopic interfacial structure stability is far superior to the comparative examples, demonstrating excellent long-cycle service reliability.

[0052] Comparison of key electrochemical performance parameters: The core electrochemical data obtained from the unified testing of each group of samples showed clear gradients and significant patterns. The specific performance differences are as follows: Example 2: Carbon content 52%, BET specific surface area 1.8 m² / g, 20 MPa powder compaction resistivity 1.7 Ω / cm; 1.5V voltage plateau reversible capacity 1830 mAh / g, initial coulombic efficiency 93.4%, 0.8V voltage plateau reversible capacity 1645 mAh / g, initial coulombic efficiency 82.5%, 500-cycle capacity retention 93%. Comparative Example 1: Oxygen-activated, nitrogen-free, single-coating, carbon content 51.5%, BET specific surface area 34 m² / g, 20 MPa powder compaction resistivity 1.9 Ω / cm; 1.5V reversible capacity 1845 mAh / g, initial coulombic efficiency 91.8%, 0.8V reversible capacity 1605 mAh / g, initial coulombic efficiency 81.1%, no covalent bond anchoring, insufficient long-cycle structural stability. Comparative Example 2: Unactivated, nitrogen-free, traditional single-coating, carbon content 51%, BET specific surface area 50 m² / g, severely exposed pores, worst coating integrity, 2.0 Ω / cm resistivity at 20 MPa powder compaction; 1.5V reversible capacity 1845 mAh / g, initial coulombic efficiency 91.2%, 0.8V reversible capacity 1625 mAh / g, initial coulombic efficiency 80.5%, overall electrochemical performance lowest among the four groups. Comparative Example 3: Unactivated, nitrogen-free, traditional double-coating, carbon content 52.1%, BET specific surface area 1.7 m² / g, 1.6 Ω / cm resistivity at 20 MPa powder compaction; 1.5V reversible capacity 1809 mAh / g, initial coulombic efficiency 92.5%, 0.8V reversible capacity 1635 mAh / g, initial coulombic efficiency 81.6%, capacity retention 89% after 500 cycles. The data shows that the traditional single-coating comparative example 2 has many exposed channels, a large specific surface area, high impedance, and the worst first-cycle efficiency. Although the coating uniformity of the unbonded comparative example 1 is improved by only activating the unbonded components, the interfacial bonding is weak, and the first-cycle efficiency and cycle stability are limited. The traditional double-coating comparative example 3 reduces the specific surface area and optimizes conductivity through multiple carbon depositions, but excessive carbon deposition depletes reversible capacity and there is no chemical bond strengthening, resulting in a capacity retention rate of only 89% after 500 cycles. In contrast, this invention, through a synergistic process of activation site enhancement and in-situ nitrogen doping bonding, achieves both high reversible capacity and ultra-high first-cycle coulombic efficiency on the basis of extremely low specific surface area and dense coating. The first-cycle efficiency of both platforms is significantly better than all comparative examples, and the capacity retention rate after 500 cycles is as high as 93%, achieving a comprehensive and balanced improvement in capacity, efficiency, conductivity, and cycle stability.

[0053] Mass Production Efficiency and Technological Advantages: Traditional secondary coating technology, as the mainstream method in the industry to compensate for the defects of single coating, has inherent shortcomings in mass production. It requires repeating the entire process of heating, fluidization, gas pyrolysis, isothermal coating, cooling and unloading, and material transfer, directly doubling the production time. The consumption of equipment power, carrier gas, and protective gas increases significantly, with overall equipment energy consumption increasing by more than 80%. This greatly reduces the effective capacity of fluidized bed equipment, lengthens the production and delivery cycle, and significantly raises the mass production cost per unit. At the same time, repeated high-temperature thermal cycles can lead to the accumulation of thermal stress in the powder and fluctuations in the grain state. This can easily cause deviations in the coating thickness, surface state, and pore parameters of different batches of powder, resulting in poor batch consistency and hindering the large-scale mass application of high-end batteries. More importantly, disordered carbon buildup during secondary coating can block the effective pores inside the material, sacrificing the material's rate performance and reversible capacity, resulting in significant performance bottlenecks and process drawbacks. This invention reconstructs the logic of traditional CVD coating process by using an integrated modification mechanism of oxygen-containing activation sites and in-situ nitrogen doping bonding. It transforms the passive process of "multiple coating corrections" into an active process of "single precise and controllable coating". The densification effect of traditional two-stage coating can be achieved or even surpassed by a single coating. The BET densification index is basically the same as that of the two-stage coating process. At the same time, it effectively avoids problems such as capacity decay, pore blockage and rate degradation caused by excessive carbon deposition, and simultaneously improves the material's initial coulombic efficiency, reversible capacity and long-term cycling stability. Traditional secondary coating processes take 12 hours and consume 120 kWh of electricity per batch; the integrated process of this invention takes only 5.5 hours and consumes only 62 kWh of electricity per batch, reducing energy consumption by 48.3% and increasing production capacity by 118%. Furthermore, this invention simplifies production processes, shortens production cycles, and reduces equipment energy consumption and labor costs. It also avoids batch fluctuations caused by multiple thermal cycles, ensuring high consistency between product batches. This invention achieves comprehensive breakthroughs in four dimensions: electrochemical performance, mass production cost, process stability, and industrial adaptability, possessing outstanding advantages in industrial mass production and market promotion value.

[0054] To verify the rationality, industrial tolerance, and mass production stability of the process parameter window disclosed in this invention, this invention, based on a unified benchmark manufacturing process, selected three sets of boundary verification experimental groups: the upper limit boundary, the lower limit boundary, and the optimal deviation boundary of the core key process parameters. Controlling a single variable, boundary control experiments were conducted under the same equipment operating conditions, testing system, and assembly process. This further demonstrates that the invention has a wide process adaptability range, low parameter sensitivity, and strong mass production reproducibility. The specific boundary parameter settings and corresponding complete set of performance data are as follows: Boundary Experiment Group 1: The lower limit of the process, specifically low-temperature short-duration activation and low-flow coating; activation temperature 400℃, activation time 5min, oxygen gas flow rate 1L / min, minimum acetylene to nitrogen ratio 1:10, total coating time 50min; finished product test data: carbon content 48.3%, BET specific surface area 11.6m² / g, 20MPa compaction resistivity 2.0Ω / cm; 1.5V reversible capacity 1821mAh / g, initial coulombic efficiency 90.6%, 0.8V reversible capacity 1612mAh / g, initial coulombic efficiency 80.2%; capacity retention rate after 500 cycles 87.2%. Under these boundary conditions, due to insufficient activation and a small number of surface active sites, the uniformity of carbon layer coating is slightly reduced, the specific surface area is higher, and the interfacial bonding strength is slightly reduced, but the overall performance is still significantly better than the traditional single-cycle coating process, and it has basic feasibility for mass production.

[0055] Boundary Experiment Group 2: The upper limit of the process boundary, specifically high-temperature long-duration activation and high-flow-rate coating; activation temperature 650℃, activation time 300min, oxygen-containing gas flow rate 50L / min, maximum acetylene to nitrogen ratio 10:1, total coating time 300min; finished product test data: carbon content 54.6%, BET specific surface area 1.9m² / g, 20Mpa compaction resistivity 1.6Ω / cm; 1.5V reversible capacity 1812mAh / g, initial coulombic efficiency 92.1%, 0.8V reversible capacity 1628mAh / g, initial coulombic efficiency 81.3%; 500-cycle capacity retention rate 91.5%. Under these upper limit boundary conditions, the material is fully activated, the carbon layer is dense, the conductivity is excellent, and the cycle stability is good. However, due to the high-temperature long-duration reaction leading to the blockage of a small number of effective channels and the excessive thickness of the carbon layer, the reversible capacity slightly decreases, which is within the controllable fluctuation range of performance, without fatal defects such as process failure, structural collapse, or performance degradation.

[0056] Boundary Experiment Group 3: Optimal parameters deviate from the boundary, with a system pressure of 0.05 MPa, a carrier gas to activation gas flow rate ratio of 1:1, and a synchronous pyrolysis temperature range slightly below 520℃. Product test data: carbon content 51.2%, BET specific surface area 4.7 m² / g, 20 MPa compaction resistivity 1.8 Ω / cm; 1.5V reversible capacity 1826 mAh / g, initial coulombic efficiency 92.8%; 0.8V reversible capacity 1639 mAh / g, initial coulombic efficiency 81.9%; capacity retention after 500 cycles 90.1%. Under these deviations from optimal parameters, the material's overall performance remains high, with no significant performance drop, demonstrating that the process of this invention has good anti-interference capabilities. Minor equipment fluctuations and normal parameter drifts during mass production will not cause product quality failure.

[0057] Boundary experiment conclusions: The combined data from the three boundary experiment sets clearly demonstrate that the entire range of process parameters defined in this invention is not a narrow-window precision process, but rather possesses characteristics of tolerance for errors, high stability, and strong anti-interference for industrial application. Silicon-carbon anode materials with satisfactory performance and excellent stability can be prepared within the upper and lower limits of the parameters, without issues of critical parameter failure or precipitous performance degradation. Compared to traditional processes with stringent parameters where even minor fluctuations lead to coating failure and significant performance degradation, this invention's process is more suitable for large-scale, long-cycle industrial production scenarios with normal equipment operating condition fluctuations. The process robustness and industrial applicability are further validated.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Technical aspects such as equipment structure, electrical control, testing methods, and auxiliary material ratios not described in detail in this invention are all conventionally known technologies in the field. Any technical solutions obtained by conventional fine-tuning, equivalent substitution, or local optimization of process parameters within the spirit and principles of this invention fall within the scope of protection of this invention.

[0059] This invention fully verifies the synergistic modification advantages of oxygen-containing activation sites and in-situ nitrogen doping covalent bond strengthening through a 20kg-scale industrial mass production control experiment. It breaks through the technical bottlenecks of traditional CVD silicon-carbon coating process, which relies on secondary coating, has poor coating uniformity, low interfacial bonding strength, and insufficient cycle stability. It achieves a comprehensive upgrade in material electrochemical performance, mass production cost, and batch consistency, and can be widely applied to the industrial-scale preparation of silicon-carbon anode materials for various high-end lithium-ion batteries.

[0060] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0061] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for processing silicon-carbon anode materials, characterized in that, Includes the following steps: S1. Silane deposition is performed on a porous carbon substrate using a fluidized bed reactor to form a silicon-carbon precursor. S2. An oxygen-containing compound gas is introduced at 400℃~650℃ to generate oxygen-containing active functional groups on the surface of the silicon-carbon precursor, thereby achieving surface activation. S3. Acetylene and nitrogen-containing gas are introduced at 400℃~650℃. The acetylene and nitrogen-containing gas are decomposed at high temperature, and CNC covalent bonds are formed in situ at the interface between the silicon-carbon precursor and the coated carbon layer. S4. Inertial cooling and discharge, followed by post-processing and finishing to obtain the finished silicon-carbon anode material; Steps S1, S2, and S3 are carried out continuously within the same fluidized bed reactor.

2. The method for processing silicon-carbon anode material according to claim 1, characterized in that, In step S2, the oxygen-containing gas is carbon monoxide or carbon dioxide gas.

3. The method for processing silicon-carbon anode material according to claim 2, characterized in that, In step S2, the flow rate of the oxygen-containing gas is 1 L / min to 50 L / min, the inlet temperature is 400℃ to 650℃, and the intermittent inlet method is adopted. The duration of a single inlet is 5 min to 30 min, followed by a 5 min to 20 min pause, and the inlet is cyclically introduced until the total duration is 5 min to 300 min. The gauge pressure is -0.05 MPa to 0.2 MPa, the flow rate ratio of the carrier gas to the oxygen-containing gas is 10:1 to 1:1, and the carrier gas is high-purity nitrogen or high-purity argon.

4. The method for processing silicon-carbon anode material according to claim 1, characterized in that, In step S3, the nitrogen-containing gas is ammonia or vaporized pyridine vapor.

5. A method for processing silicon-carbon anode material according to claim 4, characterized in that, In step S3, the nitrogen-containing gas and acetylene are introduced and stopped simultaneously, with an introduction time of 50 min to 300 min and a flow rate ratio of acetylene to nitrogen-containing gas of 10:1 to 1:

1.

6. The method for processing silicon-carbon anode material according to claim 1, characterized in that, In step S1, the porous carbon substrate is resin-based, coal-based, or biomass-based.

7. The method for processing silicon-carbon anode material according to claim 1, characterized in that, In step S1, the silicon mass content in the silicon-carbon precursor is 40%~65%.

8. A method for processing silicon-carbon anode material according to claim 1, characterized in that, Step S1 also includes a pretreatment step for the porous carbon substrate, which includes the following steps: S101. The porous carbon substrate is activated, washed with water, dried, and air-separated to obtain porous carbon powder with D50=5μm~15μm, specific surface area of ​​800m² / g~3000m² / g, and pore volume of 0.6cm³ / g~1.5cm³ / g. S102. The porous carbon powder is fed into the fluidized bed reactor under negative pressure, and the vacuum is drawn to ≤100Pa. High-purity nitrogen is introduced to replace it 3-5 times, and the oxygen content of the system is <10ppm. Nitrogen gas is introduced into the bottom for aeration, and the temperature is raised to 500℃ and kept for 1 hour to fully disperse the powder. S103, heat to 600℃~700℃, keep under negative pressure for 1h~2h to remove adsorbed water and carbon dioxide from the pores and open up the closed mesopores.

9. A method for processing silicon-carbon anode material according to claim 1, characterized in that, In step S1, the specific steps of silane deposition are as follows: maintain the fluidization state in the fluidized bed reactor, raise the temperature to 400℃~650℃, and introduce a mixed reaction gas; the mixed reaction gas is composed of high-purity silane SiH4 diluted with nitrogen, with silane accounting for 5%~15% of the volume, the carrier gas flow rate being 0.08m³ / h~0.15m³ / h, the deposition time being 2h~5h, and the carrier gas being high-purity nitrogen or high-purity argon; the silane is decomposed at high temperature to generate 1nm~10nm nano-silicon particles, which fill the pores of the carbon framework.

10. A method for processing silicon-carbon anode material according to claim 1, characterized in that, In step S4, the inert cooling discharge specifically involves shutting off all reaction gas sources and continuously fluidizing and cooling the material with high-purity nitrogen at a rate of 1.5℃ / min to 2.5℃ / min to 400℃. From 400℃ to room temperature, the cooling rate is controlled to be ≤3.5℃ / min. The entire process is conducted in an airtight, negative pressure environment. The post-processing finishing includes airflow classification, strong magnetic impurity removal, and vacuum homogenization.

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