Airflow-assisted preparation method of high-dispersity graphene negative electrode material

Abstract

The invention discloses an airflow-assisted preparation method of a high-dispersity graphene negative electrode material, which comprises the following steps: raw material pretreatment and feeding: screening natural crystalline flake graphite to remove impurities, and feeding into a reaction cavity preheated to 40-50 DEG C at a constant speed under the pressure of 0.1 MPa; anchoring the seed crystal, namely dispersing the carbon-based nano seed crystal into nitrogen in a supercritical state to form a crystal-carrying supercritical fluid, and introducing the crystal-carrying supercritical fluid into the reaction cavity; meanwhile, low-frequency pulse airflow is applied to the reaction cavity to drive the edge of the graphite to be directionally exposed, so that the carbon-based nanocrystalline seeds are anchored to the edge and interlayer defects of the graphite, and the graphene negative electrode material directly prepared through the method has the most prominent characteristics of being excellent in long-term dispersion stability, ultrahigh in lithium storage capacity and long in cycle life. The material can be uniformly suspended in a water-based system for a long time, and the key bottleneck that graphene is easy to agglomerate and difficult to process and apply is fundamentally solved.

Description

Technical Field

[0001] This invention belongs to the field of new energy material preparation technology, and particularly relates to an airflow-assisted preparation method for highly dispersed graphene anode materials. Background Technology

[0002] Graphene, a two-dimensional material composed of a single layer of carbon atoms, is considered a highly promising next-generation lithium-ion battery anode material due to its excellent electrical conductivity, extremely high theoretical specific surface area, and superior mechanical strength. To scalable prepare graphene suitable for electrode applications, the industry has developed various technological approaches. Currently, the mainstream methods mainly fall into two categories: First, the chemical redox method, represented by the Hummers process and its modifications, involves intercalating and oxidizing natural graphite with strong acids and oxidants, exfoliating to obtain graphene oxide, and then chemically or thermally reducing it to obtain reduced graphene oxide. Second, the physical exfoliation method aims to avoid the damage to the graphene lattice caused by the chemical process. It utilizes mechanical force to directly overcome the van der Waals forces between graphite layers. Specific forms include liquid-phase ultrasonic exfoliation, ball milling exfoliation, supercritical fluid exfoliation, and airflow-assisted exfoliation. Among these, airflow-assisted exfoliation technology has attracted attention due to its continuous process, solvent-free operation, and ease of scalability. This method typically involves placing graphite powder in a high-speed airflow field, utilizing the shearing and collision effects of the airflow to achieve interlayer separation.

[0003] However, existing technological approaches have significant limitations in key indicators for industrialization, making it difficult to simultaneously meet the comprehensive requirements of high-performance anode materials for structural integrity, dispersion stability, and green preparation. While chemical methods can achieve large-scale production, the violent redox process inevitably introduces numerous defects and oxygen-containing functional groups into the graphene lattice, severely impairing the intrinsic conductivity and structural stability of graphene. This results in anode materials prepared from graphene exhibiting low initial coulombic efficiency, poor rate performance, and rapid cycle decay. Traditional physical exfoliation methods face a trade-off between efficiency and quality: simple strong mechanical shearing (such as high-speed airflow impact or ball milling) easily leads to graphene sheet breakage, size inhomogeneity, and limited exfoliation degree, making it difficult to obtain a high proportion of few-layer graphene; while gentler exfoliation methods (such as supercritical fluid exfoliation) are often inefficient. More importantly, existing physical methods generally lack an immediate stabilization strategy for the surface of newly formed graphene during the exfoliation process. The exfoliated products rapidly re-aggregate due to their extremely high surface energy, making it difficult to redisperse them during downstream processing and failing to realize their theoretical performance. Furthermore, most methods have shortcomings in terms of process greening (such as pollution from chemical methods) and process controllability. Therefore, developing a large-scale method that can efficiently prepare high-quality graphene with intact structure, stable dispersion, and excellent electrochemical performance, while also possessing green and environmentally friendly characteristics, has become an urgent technological need in this field. Summary of the Invention

[0004] To overcome the aforementioned deficiencies of the prior art, this invention provides an airflow-assisted preparation method for highly dispersible graphene anode materials, which solves the problem that it is difficult to simultaneously ensure the structural integrity, dispersion stability, and green and efficient preparation of graphene in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A gas flow-assisted preparation method for highly dispersed graphene anode materials includes the following steps: S1: Raw material pretreatment and feeding - After natural flake graphite is screened to remove impurities, it is fed at a uniform speed into the reaction chamber preheated to 40~50℃ and pressure of 0.1MPa; S2: Seed anchoring - Carbon-based nanocrystal seeds are dispersed in supercritical nitrogen gas to form a supercritical fluid carrying the crystals and introduced into the reaction chamber; at the same time, a low-frequency pulsed gas flow is applied to the reaction chamber to drive the graphite edge to be exposed in an oriented manner, so that the carbon-based nanocrystal seeds are anchored to the edge of the graphite and the interlayer defects. S3: Intercalation and Layer Expansion – A high-frequency alternating pulsed gas flow is applied to the reaction chamber, while a carbon-based intercalating agent is delivered via supercritical nitrogen. The intercalating agent preferentially penetrates into the interlayer of graphite along the defect positions anchored by the seed crystals in step S2, thereby expanding the interlayer spacing of graphite. S4: Multi-stage airflow stripping—Supersonic shear airflow is applied to the reaction chamber, working in conjunction with the high-frequency alternating pulse airflow continuously applied in step S3; wherein, supercritical nitrogen gas penetrating between graphite layers generates expansion force to weaken interlayer bonding, the high-frequency alternating pulse airflow applies alternating shear stress to the expanded graphite, and the supersonic shear airflow provides the main shear force, thereby stripping the expanded graphite layer by layer to obtain few-layer graphene. S5: In-situ passivation - While step S4 is being performed, the vaporized carbon-based passivating agent is introduced into the reaction chamber through a carrier gas, so that it reacts with and grafts onto the surface of the fresh graphene produced by exfoliation to form a surface passivation layer. S6: Graded collection - Based on the airflow velocity gradient, the graphene obtained in step S5 is graded and separated by sheet size. After collection, it is dried to obtain the highly dispersed graphene anode material.

[0006] Preferably, in step S2, the temperature of the supercritical nitrogen gas is 31.1~35℃ and the pressure is 3.4~4.0MPa; the carbon-based nanocrystal seed is an amorphous carbon particle with a particle size of 2~5nm, and its addition amount is 1~2wt% of the mass of the natural flake graphite, and the dispersed particle size in the supercritical fluid carrying the crystal is ≤10nm.

[0007] Preferably, in step S2, the frequency of the low-frequency pulsed airflow is 50Hz, the alternating pressure amplitude is -0.03~0.02MPa, and the flow velocity is 10~15m / s; in step S3, the frequency of the high-frequency alternating pulsed airflow is 200Hz, the alternating pressure amplitude is -0.05~0.05MPa, and the flow velocity is 20~30m / s.

[0008] Preferably, the carbon-based intercalating agent is an acetylene black nano-suspension with a solid content of 5-8 wt%, wherein the primary particle size of the acetylene black is 20-50 nm, and the dispersion medium is anhydrous ethanol; the delivery rate of the carbon-based intercalating agent is 0.5-1 mL / min; after step S3, the interlayer spacing of graphite is expanded to 0.40-0.42 nm.

[0009] Preferably, in step S4, the flow velocity of the supersonic shearing airflow is 40~50m / s; the duration of the multi-stage airflow stripping is 5~8min, and the number of layers of the resulting few-layer graphene is 1~3 layers.

[0010] Preferably, the carbon-based passivating agent is methyltriethoxysilane-modified carbosiloxane with a carbon content ≥70wt%. After being heated and vaporized at 120~150℃, it is introduced into the reaction chamber by nitrogen gas with a flow rate of 5~8m / s. The thickness of the surface passivation layer formed in step S5 is 2~3nm.

[0011] Preferably, in step S6, three airflow velocity ranges are set, namely 5~10m / s, 20~30m / s and 40~50m / s, which are used to collect graphene with sheet diameters >300nm, 100~300nm and <100nm respectively; the drying is vacuum drying at 60°C for 2 hours.

[0012] Preferably, the method is executed by an integrated control system configured to control the temperature and pressure of the supercritical gas flow, the frequency and alternating pressure amplitude of the pulsed gas flow, the start and stop of the supersonic gas flow, and the delivery rate of the passivating agent.

[0013] Preferably, the natural flake graphite has a purity of ≥99.9%, a flake diameter of 50~100μm, and has not undergone pre-oxidation treatment; the nitrogen gas has a purity of ≥99.999%; the process exhaust gas generated by the method is recycled after being treated by a condensation and adsorption unit, with a recycling rate of ≥90%.

[0014] Preferably, in steps S4 and S5, the application of the supersonic shear gas flow and the introduction of the carbon-based passivating agent are synchronously closed-loop controlled by the integrated control system, so that the in-situ grafting rate of the newly formed graphene surface in the exfoliation reaction zone is ≥95%.

[0015] The technical effects and advantages of the airflow-assisted preparation method for the highly dispersed graphene anode material of this invention are as follows: 1. This invention achieves a synergistic leap in the dispersibility and electrochemical performance of graphene materials. The graphene anode material directly prepared by the method of this invention is characterized by its excellent long-term dispersion stability, ultra-high lithium storage capacity, and cycle life. The material can maintain uniform suspension in an aqueous system for a long time, fundamentally solving the key bottleneck of graphene's tendency to agglomerate and its difficulty in processing and application. At the same time, when used as a lithium-ion battery anode, this material exhibits a theoretical specific capacity far exceeding that of traditional graphite and excellent high-current cycling stability. This is due to its complete crystal structure, controllable few-layer state, and unique surface chemical environment, providing an ideal electrode material for developing high-energy-density, long-life energy storage devices.

[0016] 2. This invention establishes a novel physical exfoliation pathway that is highly efficient, low-damage, and highly controllable in its preparation process. It abandons the high-damage chemical oxidation and inefficient purely mechanical pulverization methods. Through a pretreatment process of "targeted anchoring of crystal seeds - intercalator penetration and layer expansion," the interlayer forces of graphite are weakened in advance and directionally. Then, utilizing a "multi-stage airflow synergistic exfoliation" mechanism, the expansion and penetration force of supercritical fluid, the fatigue shear force of high-frequency alternating airflow, and the main exfoliation force of supersonic airflow are organically combined, achieving efficient, layer-by-layer, and low-physical-damage exfoliation of graphite precursors. This method features a coherent process flow, precise parameter control, and full-process automation and consistency through an integrated control system, making it suitable for large-scale preparation.

[0017] 3. In terms of comprehensive benefits, this invention embodies the advantages of green environmental protection and high compatibility. The entire preparation process uses inert nitrogen as the main medium, and the core additives are all carbon-based materials. The reaction is carried out in a closed system, and the exhaust gas can be efficiently recycled. There is no emission of strong acids, strong oxidants, or heavy metal pollutants, making it an environmentally friendly green production process. At the same time, this method does not require pre-oxidation of the raw material graphite, preserving the high crystallinity of the raw material. Furthermore, through the "in-situ synchronous passivation" technology, the newly formed surface can be customized during the exfoliation process, giving the product excellent dispersibility and good compatibility with different systems (such as electrode pastes), greatly expanding its application range. Attached Figure Description

[0018] Figure 1 This is a flowchart of the airflow-assisted preparation method for the highly dispersed graphene anode material proposed in this invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include," "contain," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "includes..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0021] refer to Figure 1 This invention provides an airflow-assisted preparation method for highly dispersible graphene anode materials. Using natural flake graphite as raw material, this method employs a progressive process. First, carbon-based nanocrystals are targeted and anchored at graphite edges and interlayer defects in a low-frequency pulsed supercritical gas flow field. Then, with the assistance of a high-frequency alternating pulsed gas flow, a carbon-based intercalating agent is driven to penetrate along the anchoring points into the interlayer space, widening the interlayer spacing. Next, the synergistic effect of the expansion and penetration force of supercritical nitrogen, the high-frequency alternating shear force, and the supersonic shear gas flow is utilized to achieve efficient and low-damage layer-by-layer exfoliation of graphite. Simultaneously, a vaporized carbon-based passivating agent is introduced in situ and grafted onto the newly formed surface to form a steric hindrance layer to prevent agglomeration. Finally, the products are collected in stages based on the gas flow velocity gradient. This method is streamlined, environmentally friendly, and the resulting graphene anode material exhibits both excellent dispersion stability and superior electrochemical performance.

[0022] Common raw materials: Graphite raw material: High-purity natural flake graphite is used, with a carbon content of not less than 99.9%. The initial particle size distribution is between 50 and 100 micrometers. The interlayer spacing corresponding to the (002) crystal plane is approximately 0.335 to 0.340 nanometers, as measured by X-ray diffraction (XRD). Before use, it is sieved through a 100-mesh standard sieve to remove obvious impurities and has not undergone any chemical oxidation pretreatment.

[0023] Process media and additives: Carrier gas and supercritical fluid source: high-purity nitrogen, purity ≥99.999%.

[0024] Nano-carbon seed crystals: amorphous carbon nanoparticles with an average primary particle size of 3 nanometers (statistics based on transmission electron microscopy) and a specific surface area greater than 500 m² / g.

[0025] Intercalating agent precursor: Commercial acetylene black (average primary particle size 30 nm) was prepared into a stable suspension with a solid content of 6.5% by weight by ultrasonic dispersion and high-speed shearing in anhydrous ethanol.

[0026] Surface modifier: a carbosiloxane oligomer modified with methyltriethoxysilane, with a carbon content of approximately 72% by weight, which is a viscous liquid at room temperature and can be vaporized by heating.

[0027] General Equipment: The experiment was conducted in a specially designed continuous airflow stripping and functionalized integrated device. The core of this device includes: a cylindrical reaction chamber with a precision temperature control jacket and internal gas circulation system; a fluid supply and pressurization module capable of generating stable supercritical nitrogen; three independently controlled airflow subsystems for generating low-frequency pulsed flow, high-frequency alternating pulsed flow, and supersonic shear flow, respectively; a liquid phase injection unit for precisely pumping liquid intercalation agent precursors into the supercritical flow path; an online vaporization and transport unit for heating and quantitatively carrying liquid surface modifiers into the reaction zone; a multi-stage cyclone separator collector based on different settling terminal velocities; and a central integrated control system for coordinating the timing, temperature, and pressure parameters of all units.

[0028] General testing and characterization methods: Microstructure: The number of layers, sheet diameter and surface morphology of the product were observed using field emission transmission electron microscopy (TEM); the sheet thickness was measured using atomic force microscopy (AFM); and the interlayer spacing variation was analyzed using X-ray diffraction.

[0029] Surface characteristics: The elemental composition and chemical state of the surface were analyzed using X-ray photoelectron spectroscopy (XPS); the functional groups of the surface were detected by Fourier transform infrared spectroscopy (FT-IR).

[0030] Dispersion stability: The product was dispersed in deionized water at a solid content of 5% by weight, ultrasonically formed into a homogeneous slurry, and then left to stand in a graduated cylinder. The sedimentation volume ratio at different times was recorded. The zeta potential of the slurry was measured using a nanoparticle size and zeta potential analyzer.

[0031] Electrochemical performance: The product, conductive carbon black, and polyvinylidene fluoride binder were mixed in a mass ratio of 8:1:1 to form a slurry, which was then coated onto copper foil. After drying and rolling, the working electrode was formed. In an argon-protected glove box, using lithium metal sheets as the counter and reference electrodes, and a 1M LiPF6 EC / DMC (volume ratio 1:1) solution as the electrolyte, a CR2032 coin cell was assembled. Constant current charge-discharge tests were performed using a Blue Battery testing system to evaluate specific capacity and cycle stability.

[0032] Example 1 This embodiment provides an airflow-assisted preparation method for highly dispersed graphene anode materials, implemented under baseline process conditions. Specific implementation details include: Purpose of implementation: To demonstrate the feasibility of fully implementing the six-step process within the core parameter range of the inventive concept, and to establish a benchmark for product performance.

[0033] Implementation steps: S1. Feeding and Preheating: 10.0 g of pretreated flake graphite is fed into a preheated cylindrical reaction chamber at a constant rate of 0.5 g / min using a screw feeder. The chamber is pre-filled with nitrogen and maintained at an absolute pressure of 0.1 MPa.

[0034] S2. Seed Introduction and Edge Anchoring: The supercritical fluid module is activated, and nitrogen gas is heated and pressurized to 33°C and 3.7 MPa to reach a supercritical state. 0.15 g (1.5% of the graphite mass) of nano-carbon seed powder is premixed with a portion of the supercritical nitrogen gas in the feeder to form a uniform "crystal-carrying supercritical fluid," which is continuously introduced into the upper part of the reaction chamber at a volumetric flow rate of 5 L / min. Simultaneously, the low-frequency pulsed gas flow subsystem is activated, introducing a nitrogen pulse flow with a frequency of 50 Hz, a gauge pressure amplitude between -0.01 and +0.01 MPa, and an average flow velocity of 12 m / s into the bottom of the reaction chamber. This process lasts for 3 minutes, aiming to orient and tumble the flake graphite in the gradient flow field, fully exposing its flake edges and grain boundary defects. Under the influence of the gas flow and van der Waals forces, the nano-carbon seed preferentially adsorbs onto these highly active sites.

[0035] S3. Intercalator Penetration and Interlayer Expansion: Maintaining constant temperature and pressure of supercritical nitrogen, the pulsed gas flow mode was switched to a high-frequency alternating mode. The gas flow frequency was 200 Hz, the gauge pressure alternation amplitude was expanded to -0.03 to +0.03 MPa, and the average flow velocity increased to 25 m / s. Simultaneously, a prepared acetylene black ethanol suspension was injected into the supercritical nitrogen flow at a rate of 0.8 mL / min using a high-pressure micro-pump. The ethanol instantly became miscible with the supercritical nitrogen, carrying and transporting the acetylene black nanoparticles. Under the continuous high-frequency alternating gas flow for 5 minutes, the intercalator particles, along the anchored seed sites, utilized the excellent penetration ability of the supercritical fluid to enter and expand the graphite interlayers. XRD analysis using online sampling revealed a significant shift of the (002) diffraction peak of graphite towards a smaller angle. According to Bragg's formula, the interlayer spacing increased from the initial ~0.336 nm to approximately 0.41 nm.

[0036] S4. Multi-mode airflow coordinated stripping: While maintaining a high-frequency alternating pulsed airflow, a supersonic shear gas generator is activated to horizontally inject a stable nitrogen jet with a velocity of 45 m / s into the center of the reaction chamber. At this time, three mechanical forces are coupled within the reaction chamber: the periodic expansion force generated by the supercritical nitrogen penetrating between layers under pressure fluctuations continuously weakens the van der Waals bonding between layers; the reciprocating shear stress generated by the high-frequency alternating pulses exerts a "fatigue" effect on the expanded graphite; and the powerful bulk shear force provided by the supersonic jet ultimately "tears" the sheets apart from the edges or defects. This multi-force coordinated stripping stage lasts for 6 minutes.

[0037] S5. In-situ Synchronous Surface Grafting: Approximately 2 minutes after the start of the above-mentioned exfoliation stage, the online vaporization unit is activated. The surface modifier is heated to 140°C to completely vaporize it, and then quantitatively carried by an auxiliary nitrogen flow at a velocity of 6.5 m / s, directly sprayed into the area where the exfoliation reaction is taking place. The vaporized modifier molecules come into instantaneous contact with the highly active, dangling bond-rich fresh graphene surface generated by exfoliation, and its active groups such as silanoxy groups undergo hydrolysis-condensation or direct bonding reactions, forming a uniform organic-inorganic hybrid film in situ. This process occurs simultaneously with the exfoliation, effectively preventing the re-agglomeration of newly formed graphene sheets.

[0038] S6. Product Classification and Post-processing: The exfoliated graphene is suspended in an airflow and then enters a three-stage cyclone separator connected in series. By precisely controlling the inlet velocity of each stage separator, classification by sheet size is achieved: the first stage flow rate is set to 8 m / s to collect thicker sheets or agglomerates with a sheet diameter greater than 300 nm; the second stage flow rate is set to 25 m / s to collect the target product (few-layer graphene with a sheet diameter of 100-300 nm); and the third stage flow rate is set to 45 m / s to collect smaller sheets with a sheet diameter less than 100 nm. The collected second-stage product is dried in a vacuum drying oven at 60 °C for 2 hours to obtain the final highly dispersed graphene powder, denoted as sample G1.

[0039] Implementation results: Structural characterization: TEM images show that the G1 sample is mainly composed of 1 to 3 layers of graphene sheets, with flat sheets, few wrinkles, and clear edges. The AFM statistical average thickness is approximately 1.1 nm. In the XRD pattern, the characteristic peaks of graphite have almost disappeared, with only a very broad peak appearing at approximately 24°, indicating that the crystal structure has been highly exfoliated.

[0040] Surface analysis: XPS showed a carbon content as high as 98.5 at%, while trace amounts of silicon and oxygen (from the surface modification layer) were detected. The FT-IR spectrum showed characteristic absorption peaks attributed to Si-OC and Si-CH3, confirming the effective grafting of the surface modifier.

[0041] Dispersion stability: When G1 was prepared as a 5wt% aqueous slurry and allowed to stand for 10 months, no clear liquid appeared in the upper layer, and the volume of sediment at the bottom accounted for only 3.8% of the total volume, demonstrating excellent long-term anti-settling stability. The slurry's zeta potential was measured to be -38 mV. The high absolute value indicates strong electrostatic repulsion between particles, which is one of the key reasons for its high dispersibility.

[0042] Electrochemical performance: The lithium-ion battery assembled with G1 as the anode material achieved a specific capacity of 1550 mAh / g during the first discharge at a relatively low current density of 0.1 A / g, far exceeding the theoretical capacity of traditional graphite anodes (372 mAh / g). Under rapid charge-discharge cycling tests at a high current of 1 A / g, after 600 cycles, its discharge specific capacity remained at 93.5% of the initial cycle discharge capacity, demonstrating excellent cycle stability.

[0043] Example 2 This embodiment provides an airflow-assisted preparation method for highly dispersed graphene anode materials, used for implementing lower limit combinations of key parameters. Specific implementation details include: Purpose of implementation: To verify whether the lower limit of the range of parameters protected in the claims can still be effectively implemented and produce qualified products, and to determine the boundaries of process feasibility.

[0044] Implementation steps: The overall process is the same as in Example 1, only the following parameters are adjusted to the lower limit of the range: In step S2, the supercritical nitrogen conditions are: temperature 31.5℃, pressure 3.4 MPa; the amount of nano-carbon seed crystals added is adjusted to 1.0% of the graphite mass; and the average flow velocity of the low-frequency pulsed gas flow is reduced to 10 m / s.

[0045] In step S3, the average velocity of the high-frequency alternating pulsed gas flow is reduced to 20 m / s; the delivery rate of the intercalating agent suspension is reduced to 0.5 ml / min.

[0046] In step S4, the supersonic shear airflow velocity is reduced to 40 m / s; the collaborative stripping time is shortened to 5 minutes.

[0047] Results: The resulting sample is designated G2. It has slightly more layers than G1, mainly 2-4 layers, indicating a slight decrease in exfoliation efficiency under milder parameters. Dispersion tests showed that after 10 months of settling, the sedimentation volume ratio was 4.5%, and the Zeta potential was -36 mV, still demonstrating excellent performance. In terms of electrochemical performance, the initial discharge specific capacity at 0.1 A / g was 1510 mAh / g, and the capacity retention rate after 600 cycles at 1 A / g was 92.1%. These results demonstrate that even at the lower limit of the parameters, the process of this invention can still stably prepare graphene anode materials that meet high-performance requirements, supporting the rationality of the parameter range in the claims.

[0048] Example 3 This embodiment provides an airflow-assisted preparation method for highly dispersed graphene anode materials, used for implementing upper limit combinations of key parameters. Specific implementation details include: Purpose of implementation: To verify whether the upper limit of the range of parameters protected in the claims is feasible, and to examine the changes in the properties of the product under more intense conditions.

[0049] Implementation steps: The overall process is the same as in Example 1, only the following parameters are adjusted to the upper limit of the range: In step S2, the supercritical nitrogen conditions are: temperature 35.0℃, pressure 4.0 MPa; the amount of nano-carbon seed crystals added is increased to 2.0% of the graphite mass; and the average flow velocity of the low-frequency pulsed gas flow is increased to 15 m / s.

[0050] In step S3, the average velocity of the high-frequency alternating pulsed airflow is increased to 30 m / s; the delivery rate of the intercalating agent suspension is increased to 1.0 ml / min.

[0051] In step S4, the supersonic shear airflow velocity is increased to 50 m / s; the collaborative stripping time is extended to 8 minutes.

[0052] Results: The resulting sample was designated G3. TEM observation revealed that the proportion of monolayer and bilayer graphene in G3 was higher than that in G1, with a more concentrated sheet size distribution and more thorough exfoliation. Its dispersion stability was slightly better than G1 (sedimentation ratio 3.5%, Zeta potential -39mV). Its electrochemical performance was comparable to G1 (specific capacity 1535mAh / g, cycle retention 93.0%). This indicates that operating at the upper limit of the parameters can further improve the exfoliation degree, but the core performance indicators have reached a plateau, demonstrating the optimization potential of the stated parameter range.

[0053] Example 4 This embodiment provides an airflow-assisted preparation method for highly dispersed graphene anode materials, used to investigate the influence of seed crystal characteristics. Specific implementation details include: Objective: To investigate the key impact of the dispersion state of nano-carbon seeds, which serve as "anchors," on subsequent process chains.

[0054] Implementation steps: A batch of nano-carbon seed crystals with a relatively wide particle size distribution (2-8 nm) and slight agglomeration due to storage was used. During the dispersion process in step S2, although strong ultrasonication was performed, a small number of agglomerates with a size of about 15 nm still existed in the "crystal carrier fluid" formed in the supercritical fluid. The parameters of the remaining steps were exactly the same as in Example 1.

[0055] Results: The resulting sample was designated G4. The product quality was significantly affected: TEM showed decreased uniformity in sheet thickness (ranging from 2 to 5 layers), and a few small particles (presumably seed agglomerates) were visible on the sheets. In the dispersion stability test, the slurry sedimentation volume ratio increased to 6.0%, and the absolute value of the Zeta potential decreased to -34 mV. Electrochemical performance also declined, with an initial specific capacity of 1480 mAh / g and a retention rate of 90.5% after 600 cycles. This example demonstrates that the initial particle size of the seed crystals and their high dispersibility in supercritical media (agglomerates ≤ 10 nm) are prerequisites for achieving efficient and uniform "anchoring," and are crucial to the uniformity and performance of the final product.

[0056] Example 5 This embodiment provides an airflow-assisted preparation method for highly dispersed graphene anode materials, used for passivation timing comparison (asynchronous passivation). Specific implementation details include: Purpose of implementation: By changing the timing of the introduction of surface modifiers, this study aims to demonstrate the necessity and ingenuity of the "in-situ synchronous passivation" technique.

[0057] Implementation steps: The first four steps (S1 to S4) are completely consistent with Example 1, but after the entire peeling process (S4) is completely finished and the airflow is completely stopped, the reaction chamber is cooled to 80°C, and then the same amount of vaporized surface modifier as in Example 1 is introduced. The chamber is then treated in a static atmosphere for 30 minutes to perform "post-treatment" passivation. Then, step S6 is performed for graded collection and drying.

[0058] Results: The resulting sample was designated G5. Its morphology was similar to G1, but its dispersibility deteriorated drastically. The aqueous slurry showed obvious stratification shortly after standing, and after 10 months, the sedimentation volume ratio reached 25.1%, with a Zeta potential of only -25mV. Electron microscopy revealed severe face-to-face aggregation between the layers. Electrochemical performance significantly decreased: the initial discharge specific capacity was 1380 mAh / g, and the cycle retention rate dropped to 85.2%. This result contrasts sharply with Example 1 (G1), strongly demonstrating that the fresh surface exposed after peeling has extremely high activity. If in-situ grafting protection (i.e., "synchronization") is not performed immediately upon its formation, the layers will rapidly re-aggregate due to van der Waals forces. Once this aggregation forms, it is irreversible, and subsequent "post-treatment" passivation cannot effectively repair it, ultimately leading to severe deterioration of the product's dispersibility and electrochemical activity. "Peeling-passivation synchronization" is one of the core designs ensuring the high dispersibility of the product of this invention.

[0059] Example 6 This embodiment provides an airflow-assisted preparation method for highly dispersed graphene anode materials, used for verifying the type and function of intercalating agents. Specific implementation details include: Objective: To verify the role of intercalating agents in widening interlayer spacing and forming "composite fulcrums," and to demonstrate that different carbon materials can be used as intercalating agents.

[0060] Implementation steps: Replace the intercalating agent with an ethanol dispersion of Ketjenblack (a high-structure conductive carbon black) with a solid content of 5 wt%. Ketjenblack has a branched chain structure with a primary particle size of approximately 40 nanometers. The remaining steps and parameters are consistent with those in Example 1.

[0061] Results: The resulting sample is designated G6. XRD analysis showed that the interlayer spacing was successfully increased to 0.42 nm. Exfoliation was successful, yielding 1-3 layers of graphene. Due to the excellent conductivity of Ketjen black, its use as an intercalating component, remaining in some of the graphene interlayers or adhering to the surface, may provide additional conductive pathways. Its electrochemical performance exhibits high initial coulombic efficiency (88%) and excellent rate performance. This example illustrates that the choice of intercalating agent is not limited to acetylene black; other nanomaterials can also achieve the invention's objective while meeting particle size and dispersibility requirements, supporting the generalization of "carbon-based intercalating agent" in the claims.

[0062] Comparative Example 1 This comparative study attempts to remove the missing "anchoring-intercalation" preprocessing step, specifically including: Purpose of implementation: To simulate the traditional pure mechanical airflow stripping method, so as to highlight the key role of the two pretreatment steps of "seed anchoring" and "intercalation and expansion" in achieving efficient and gentle stripping in this invention.

[0063] Implementation steps: 10.0 grams of flake graphite from the same batch were directly fed into the reaction chamber preheated to 45°C.

[0064] No supercritical nitrogen gas or seed crystals are introduced, and no pulse pretreatment is performed.

[0065] The supersonic shear airflow (45 m / s) is directly activated to subject the raw material graphite to a continuous and intense shearing impact for 10 minutes.

[0066] No surface passivation treatment is performed.

[0067] Collect the products.

[0068] Results: The resulting product is designated CG1. It appears as a grayish-black powder with significant agglomeration. TEM observation shows that the product is a mixture of numerous unpeeled thick graphite flakes (dozens of layers or more) and a small amount of small carbon fragments (possibly a few layers of graphene) damaged and curled due to excessive mechanical force. The sharp (002) peak of graphite remains strong in the XRD pattern. This product is completely insoluble in water and settles immediately upon standing. Due to its heterogeneous structure, poor conductive network, and few active sites, it cannot be used to create an effective electrode for standard electrochemical testing. This comparative example fully demonstrates that without the targeted pretreatment (S2, S3) of this invention, relying solely on strong shear force cannot achieve efficient, intact, and low-damage layer-by-layer peeling of graphite, thus failing to obtain highly dispersed, high-performance few-layer graphene products.

[0069] Comparative Example 2 This comparative example provides a comparison with the traditional redox method (Hummers method), specifically including: Purpose of implementation: To compare with graphene prepared by chemical methods commonly used in the industry, and to highlight the advantages of this invention in terms of structural integrity, conductivity and environmental friendliness.

[0070] Implementation steps: The same batch of flake graphite was treated using the modified Hummers method: strong oxidation with concentrated sulfuric acid and potassium permanganate was used to generate graphite oxide, which was then washed with water and ultrasonically exfoliated to obtain an aqueous dispersion of graphene oxide. Finally, high-temperature thermal reduction with hydrazine hydrate was performed to obtain reduced graphene oxide.

[0071] Results: The resulting product is denoted as CG2 (rGO). It exhibits severe lamellar wrinkling and numerous vacancies and functional group defects on its surface due to redox processes. While its aqueous dispersibility is acceptable (due to residual hydrophilic groups), its conductivity is 2-3 orders of magnitude lower than that of the product of this invention. As an anode material, its initial discharge specific capacity is approximately 800-1000 mAh / g, but its initial coulombic efficiency is typically below 70% (a large amount of lithium ions are consumed due to irreversible reactions with defects / functional groups), and its capacity decays rapidly during cycling. From a comprehensive perspective, this method generates a large amount of acidic and manganese-containing wastewater, resulting in a heavy environmental burden. The comparison highlights the comprehensive advantages of the physical method of this invention in maintaining the intrinsic excellent conductivity of graphene, achieving high initial efficiency and long cycle life, and being environmentally friendly.

[0072] Compared to Examples 1-5 and Comparative Example 1, this invention presents a stark contrast to the traditional pure physical shearing method (Comparative Example 1) and the mainstream chemical redox method (Comparative Example 2), systematically demonstrating its technological advancement and inventiveness. Example 1, serving as a baseline, successfully prepared few-layer graphene (G1) exhibiting both excellent dispersibility (sedimentation ratio 3.8%, Zeta potential -38mV) and superior electrochemical performance (specific capacity 1550mAh / g, 93.5% retention after 600 cycles), fully achieving the goal of preparing high-performance, low-defect graphene anode materials using physical methods. Examples 2 and 3 verified the broad applicability and robustness of the core process parameters within the scope of the claims; even under the lower limit (G2) or upper limit (G3) conditions, the key performance characteristics of the product still far exceed industry standards. Most importantly, Examples 4 and 5 reveal crucial details in the process chain through precise variable control: the high dispersion of seed crystals in the supercritical medium is fundamental to achieving uniform anchoring and effective intercalation; its deterioration directly leads to product uniformity and performance degradation (G4). Furthermore, the timing synchronization of "exfoliation" and "passivation" has a disruptive impact; delayed passivation (G5) results in a complete collapse of dispersion (sedimentation ratio rising to 25.1%) and a sharp drop in electrochemical performance due to irreversible aggregation on the surface of newly formed graphene. This strongly demonstrates that "in-situ synchronization" is not a routine post-processing but an indispensable core design for ensuring the ultimate performance of the product. The complete failure of Comparative Example 1 (CG1)—producing only a thick layer of graphite fragments through strong shearing that cannot be dispersed—confirms from the opposite perspective that without the targeted pre-processing (anchoring and intercalation) and multi-force synergistic exfoliation mechanism of this invention, efficient and complete interlayer dissociation of graphite cannot be achieved. Example 6 further demonstrates the inclusiveness and optimization potential of this process framework, with the successful use of Ketjen Black as an intercalating agent (G6), indicating that the core of the technology lies in the realization of the "intercalation and layer expansion" function, rather than a specific material.

[0073] A comparison of the physical pathway of this invention (Examples 1-6) with the traditional chemical redox method (Hummers method) represented by Comparative Example 2 highlights its fundamental breakthrough in protecting the intrinsic properties of materials and green manufacturing. While the chemical method product (CG2, rGO) can achieve aqueous dispersion, its redox process introduces a large number of irreversible vacancies and functional groups into the graphene lattice, leading to a sharp decrease in conductivity, low initial coulombic efficiency (typically <70%), and impaired cycle stability. Its capacity (approximately 800-1000 mAh / g) and cycle life are incomparable to the product of this invention. More importantly, the chemical method is accompanied by serious environmental problems, such as the discharge of strong acids and heavy metal wastewater. In contrast, the entire process of this invention is completed in a closed system using nitrogen and carbon materials, with a high exhaust gas recycling rate (≥90%), making it an environmentally friendly green process. In summary, through a series of ingeniously conceived embodiments and comparative examples, this invention fully demonstrates that it provides a completely new technical path: it overcomes the bottleneck of traditional physical methods being unable to efficiently peel off graphene (VS Comparative Example 1), while avoiding the inherent defects of chemical methods that severely damage material structure and pollute the environment (VS Comparative Example 2). It successfully achieves the goal of large-scale preparation of graphene anode materials with high structural integrity, high dispersibility, and high performance under mild and green conditions, demonstrating significant progress and outstanding substantive characteristics.

[0074] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0075] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing highly dispersed graphene anode materials using airflow-assisted preparation, characterized in that, Includes the following steps: S1: Raw material pretreatment and feeding - After natural flake graphite is screened to remove impurities, it is fed at a uniform speed into the reaction chamber preheated to 40~50℃ and pressure of 0.1MPa; S2: Supercritical Nitrogen Crystal Support + Low-Frequency Pulse Anchoring—Carbon-based nanocrystal seeds are dispersed in supercritical nitrogen gas to form a supercritical crystal-supporting fluid, which is then introduced into the reaction chamber. Simultaneously, a low-frequency pulsed gas flow is applied to the reaction chamber to drive the graphite edges to be exposed in an oriented manner, thereby anchoring the carbon-based nanocrystal seeds to the edges and interlayer defects of the graphite. This achieves targeted anchoring of the crystal seeds, improves the exfoliation orientation, and lays the foundation for obtaining thin-layered products. S3: Using a carbon-based intercalating agent to penetrate along the seed crystal—a high-frequency alternating pulsed gas flow is applied to the reaction chamber, while the carbon-based intercalating agent is delivered through supercritical nitrogen; the intercalating agent preferentially penetrates into the graphite interlayer along the defect position anchored by the seed crystal in step S2, which can effectively expand the graphite interlayer spacing and reduce the difficulty of subsequent peeling. S4: High-frequency pulse, supersonic shear, supercritical expansion, multi-airflow synergistic peeling—A supersonic shear airflow is applied to the reaction chamber, working in conjunction with the high-frequency alternating pulse airflow continuously applied in step S3; wherein, supercritical nitrogen gas penetrating between graphite layers generates expansion force to weaken interlayer bonding, the high-frequency alternating pulse airflow applies alternating shear stress to the expanded graphite, and the supersonic shear airflow provides the main shear force, thereby peeling the expanded graphite layer by layer, avoiding graphite breakage caused by a single airflow, and obtaining 1 to 3 layers of few-layer graphene; S5: In-situ passivation - While step S4 is being performed, the vaporized carbon-based passivating agent is introduced into the reaction chamber through a carrier gas, so that it reacts with and grafts onto the surface of the fresh graphene produced by exfoliation to form a surface passivation layer, which can prevent the new graphene from agglomerating immediately and improve the long-term dispersion stability of the product. S6: Graded collection - Based on the airflow velocity gradient, the graphene obtained in step S5 is graded and separated by sheet size. After collection, it is dried to obtain the highly dispersed graphene anode material.

2. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, In step S2, the temperature of the supercritical nitrogen gas is 31.1~35℃ and the pressure is 3.4~4.0MPa; the carbon-based nanocrystal seed is an amorphous carbon particle with a particle size of 2~5nm, and its addition amount is 1~2wt% of the mass of the natural flake graphite, and the dispersed particle size in the supercritical fluid carrying the crystal is ≤10nm.

3. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, In step S2, the frequency of the low-frequency pulsed airflow is 50Hz, the alternating pressure amplitude is -0.03~0.02MPa, and the flow velocity is 10~15m / s; in step S3, the frequency of the high-frequency alternating pulsed airflow is 200Hz, the alternating pressure amplitude is -0.05~0.05MPa, and the flow velocity is 20~30m / s.

4. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, The carbon-based intercalating agent is an acetylene black nano-suspension with a solid content of 5-8 wt%, wherein the primary particle size of the acetylene black is 20-50 nm, and the dispersion medium is anhydrous ethanol; the delivery rate of the carbon-based intercalating agent is 0.5-1 mL / min. After step S3, the interlayer spacing of graphite increases to 0.40~0.42nm.

5. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, The carbon-based intercalating agent is an acetylene black nano-suspension with a solid content of 5-8 wt%, wherein the primary particle size of the acetylene black is 20-50 nm, and the dispersion medium is anhydrous ethanol; the delivery rate of the carbon-based intercalating agent is 0.5-1 mL / min. After step S3, the interlayer spacing of graphite increases to 0.40~0.42nm.

6. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, The carbon-based passivating agent is a methyltriethoxysilane-modified carbosiloxane with a carbon content ≥70wt%. After being heated and vaporized at 120~150℃, it is introduced into the reaction chamber by nitrogen gas with a flow rate of 5~8m / s. The thickness of the surface passivation layer formed in step S5 is 2~3nm.

7. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, In step S6, three airflow velocity ranges are set, namely 5~10m / s, 20~30m / s and 40~50m / s, which are used to collect graphene with sheet diameters >300nm, 100~300nm and <100nm respectively; the drying is vacuum drying at 60℃ for 2 hours.

8. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, The method is executed by an integrated control system configured to control the temperature and pressure of the supercritical gas flow, the frequency and alternating pressure amplitude of the pulsed gas flow, the start and stop of the supersonic gas flow, and the delivery rate of the passivating agent.

9. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, The natural flake graphite has a purity of ≥99.9%, a flake diameter of 50~100μm, and has not undergone pre-oxidation treatment; the nitrogen gas has a purity of ≥99.999%; the process exhaust gas generated by the method is recycled after being treated by a condensation and adsorption unit, with a recycling rate of ≥90%.

10. The airflow-assisted preparation method of the highly dispersed graphene anode material as described in claim 1, characterized in that, In steps S4 and S5, the application of the supersonic shear gas flow and the introduction of the carbon-based passivating agent are synchronously closed-loop controlled by the integrated control system, so that the in-situ grafting rate of the newly formed graphene surface in the exfoliation reaction zone is ≥95%.

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