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CN-122010104-A - Airflow auxiliary preparation method of high-dispersity graphene anode material

CN122010104ACN 122010104 ACN122010104 ACN 122010104ACN-122010104-A

Abstract

The invention discloses an airflow auxiliary preparation method of a high-dispersity graphene anode material, which comprises the following steps of raw material pretreatment and feeding, namely screening natural crystalline flake graphite to remove impurities, conveying the natural crystalline flake graphite into a reaction cavity preheated to 40-50 ℃ and with the pressure of 0.1MPa at a constant speed, anchoring seed crystals, namely dispersing carbon-based nano seed crystals in supercritical nitrogen to form a crystal-carrying supercritical fluid and introducing the supercritical fluid into the reaction cavity, and simultaneously applying low-frequency pulse airflow to the reaction cavity to drive the edges of the graphite to be exposed directionally, so that the carbon-based nano seed crystals are anchored to the edges and interlayer defects of the graphite. The material can keep uniform suspension 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.

Inventors

  • ZHU HUAISHUI
  • YU LIJUN
  • DENG LIMIN
  • ZHU XIANGSHUI
  • PENG GUANGYU
  • DONG XINJIAN

Assignees

  • 江西双亿新能源科技有限公司

Dates

Publication Date
20260512
Application Date
20260120

Claims (10)

  1. 1. The airflow-assisted preparation method of the high-dispersity graphene anode material is characterized by comprising the following steps of: S1, raw material pretreatment and feeding, namely screening natural crystalline flake graphite to remove impurities, and then conveying the natural crystalline flake graphite into a reaction cavity preheated to 40-50 ℃ and under the pressure of 0.1MPa at a constant speed; S2, supercritical nitrogen crystal loading and low-frequency pulse anchoring, namely dispersing carbon-based nano crystal seeds in supercritical nitrogen to form crystal loading supercritical fluid and introducing the supercritical fluid into the reaction cavity, and simultaneously, applying low-frequency pulse airflow to the reaction cavity to drive graphite edges to be exposed in a directional manner, so that the carbon-based nano crystal seeds are anchored to the edges and interlayer defects of the graphite to realize crystal seed targeting anchoring and improve stripping orientation, and laying a foundation for obtaining a lamellar product; S3, applying high-frequency alternating pulse air flow to the reaction cavity along the permeation of the seed crystal by adopting the carbon-based intercalation agent, and simultaneously conveying the carbon-based intercalation agent through supercritical nitrogen, wherein the intercalation agent preferentially permeates into the graphite layers along the defect position anchored by the seed crystal in the step S2, so that the interlayer spacing of the graphite layers can be effectively enlarged, and the subsequent stripping difficulty is reduced; S4, high-frequency pulse, supersonic shearing and supercritical expansion, wherein the supersonic shearing airflow is applied to the reaction cavity to act together with the high-frequency alternating pulse airflow continuously acting in the step S3, wherein supercritical nitrogen permeated between graphite layers generates expansion force to weaken interlayer bonding, the high-frequency alternating pulse airflow applies alternating shearing stress to expanded graphite, the supersonic shearing airflow provides main shearing force, so that the expanded graphite is peeled layer by layer, graphite breakage caused by single airflow is avoided, and 1-3 layers of few-layer graphene is obtained; S5, in-situ passivation, namely introducing the vaporized carbon-based passivating agent into the reaction cavity through carrier gas while the step S4 is carried out, so that the vaporized carbon-based passivating agent reacts with the surface of the fresh graphene generated by stripping and is grafted to form a surface passivation layer, the instant agglomeration of the new graphene can be prevented, and the long-term dispersion stability of the product is improved; And S6, carrying out grading collection, namely carrying out sheet diameter grading separation on the graphene obtained in the step S5 based on the airflow speed gradient, and drying after collection to obtain the high-dispersity graphene anode material.
  2. 2. The airflow-assisted preparation method of the high-dispersibility graphene anode material according to claim 1, wherein in the step S2, the temperature of supercritical nitrogen is 31.1-35 ℃, the pressure is 3.4-4.0 MPa, the carbon-based nano seed crystal is amorphous carbon particles with the particle size of 2-5 nm, the addition amount of the carbon-based nano seed crystal is 1-2 wt% of the mass of the natural crystalline flake graphite, and the dispersion particle size in the crystal-carrying supercritical fluid is less than or equal to 10nm.
  3. 3. The airflow-assisted preparation method of the high-dispersity graphene anode material according to claim 1, wherein in the step S2, the frequency of the low-frequency pulse airflow is 50Hz, the alternating pressure amplitude is-0.03-0.02 MPa, the flow rate is 10-15 m/S, and in the step S3, the frequency of the high-frequency alternating pulse airflow is 200Hz, the alternating pressure amplitude is-0.05 MPa, and the flow rate is 20-30 m/S.
  4. 4. The airflow-assisted preparation method of the high-dispersibility graphene anode material according to claim 1, wherein the carbon-based intercalating agent is acetylene black nano suspension with a solid content of 5-8wt%, wherein the primary particle size of acetylene black is 20-50 nm, the dispersion medium is absolute ethyl alcohol, the conveying rate of the carbon-based intercalating agent is 0.5-1 mL/min, and the interlayer spacing of graphite is enlarged to 0.40-0.42 nm after the step S3.
  5. 5. The airflow-assisted preparation method of the high-dispersibility graphene anode material according to claim 1, wherein the carbon-based intercalating agent is acetylene black nano suspension with a solid content of 5-8wt%, wherein the primary particle size of acetylene black is 20-50 nm, the dispersion medium is absolute ethyl alcohol, the conveying rate of the carbon-based intercalating agent is 0.5-1 mL/min, and the interlayer spacing of graphite is enlarged to 0.40-0.42 nm after the step S3.
  6. 6. The airflow-assisted preparation method of the high-dispersibility graphene anode material according to claim 1, wherein the carbon-based passivating agent is methyltriethoxysilane modified carbosiloxane, the carbon content of the carboxirane modified carboxirane is more than or equal to 70wt%, the carboxirane modified carboxirane is heated and gasified at 120-150 ℃, nitrogen with the flow rate of 5-8 m/S is carried and introduced into a reaction cavity, and the thickness of the surface passivation layer formed in the step S5 is 2-3 nm.
  7. 7. The airflow-assisted preparation method of the high-dispersibility graphene anode material according to claim 1, wherein in the step S6, three-level airflow speed intervals of 5-10 m/S, 20-30 m/S and 40-50 m/S are set and are sequentially used for collecting graphene with a sheet diameter of >300nm, 100-300 nm and <100nm, and the drying is vacuum drying at 60 ℃ for 2 hours.
  8. 8. The method of airflow-assisted preparation of a highly dispersible graphene anode material of claim 1, wherein the method is performed by an integrated control system configured to linkage regulate temperature and pressure of supercritical airflow, frequency and alternating pressure amplitude of pulsed airflow, start-stop of supersonic airflow, and delivery rate of passivating agent.
  9. 9. The airflow-assisted preparation method of the high-dispersibility graphene anode material according to claim 1, wherein the purity of the natural crystalline flake graphite is greater than or equal to 99.9%, the sheet diameter is 50-100 μm, the purity of the nitrogen is greater than or equal to 99.999%, and the recycling rate of the process tail gas generated by the method is greater than or equal to 90% after being treated by a condensation and adsorption unit.
  10. 10. The airflow-assisted preparation method of the high-dispersity graphene anode material according to claim 1, wherein in the steps S4 and S5, the application of the supersonic shearing airflow and the introduction of the carbon-based passivating agent are synchronously controlled in a closed loop manner through the integrated control system, so that the in-situ grafting rate of the surface of the nascent graphene in the stripping reaction zone is more than or equal to 95%.

Description

Airflow auxiliary preparation method of high-dispersity graphene anode material Technical Field The invention belongs to the technical field of preparation of new energy materials, and particularly relates to an airflow auxiliary preparation method of a high-dispersity graphene anode material. Background Graphene, which is a two-dimensional material composed of a single layer of carbon atoms, is considered as a potential negative electrode material for a next-generation lithium ion battery because of its excellent electrical conductivity, extremely high theoretical specific surface area, and excellent mechanical strength. In order to prepare graphene suitable for electrode applications on a large scale, a variety of technical paths have been developed in the industry. The main current methods mainly comprise two main types, namely a chemical oxidation-reduction method, which is represented by a Hummers method and an improved method thereof, wherein natural graphite is subjected to intercalation oxidation by strong acid and an oxidant, and is stripped to obtain graphene oxide, and then the graphene oxide is subjected to chemical or thermal reduction to obtain reduced graphene oxide. And secondly, a physical stripping method aims at avoiding damage to graphene lattices in a chemical process, and utilizes mechanical force to directly overcome Van der Waals force between graphite layers, wherein specific forms comprise liquid phase ultrasonic stripping, ball milling stripping, supercritical fluid stripping, airflow auxiliary stripping and the like. Among them, the air-assisted exfoliation technique is attracting attention because of its continuous process, no need of solvent, and easy scale-up, and generally, the method employs shearing and collision of air flow to achieve interlayer separation by placing graphite powder in a high-speed air flow field. However, the prior art paths have significant limitations on key indexes of industrialization, and are difficult to simultaneously meet the comprehensive requirements of structural integrity, dispersion stability and green preparation of the high-performance anode material. Although the chemical method can be produced on a large scale, a great amount of defects and oxygen-containing functional groups are inevitably introduced into the crystal lattice in a severe oxidation-reduction process, so that the intrinsic conductivity and structural stability of graphene are seriously damaged, and the anode material prepared from the graphene is low in initial coulomb efficiency, poor in rate capability and quick in cycle attenuation. The traditional physical stripping method faces the contradiction between efficiency and quality, namely, the purely strong mechanical shearing (such as high-speed air flow impact or ball milling) is easy to cause the breakage of graphene sheets, the uneven size and the limited stripping degree, the high-proportion few-layer graphene is difficult to obtain, and the milder stripping mode (such as supercritical fluid stripping) is often low in efficiency. More importantly, the existing physical method generally lacks an immediate stabilization strategy for the surface of the newly generated graphene in the peeling process, and peeled products are rapidly agglomerated again due to extremely high surface energy, so that the peeled products are difficult to redisperse in downstream processing and cannot exert theoretical performance. In addition, most methods have short plates in terms of process greenization (e.g., chemical contamination) and process controllability. Therefore, developing a large-scale method capable of efficiently preparing high-quality graphene with complete structure, stable dispersion and excellent electrochemical performance and simultaneously having the characteristics of green and environment protection has become an urgent technical requirement in the field. Disclosure of Invention In order to overcome the defects in the prior art, the invention provides an airflow auxiliary preparation method of a high-dispersity graphene anode material, which solves the problem that the structural integrity, dispersion stability and green efficient preparation of graphene are difficult to be considered in the prior art. In order to achieve the above purpose, the present invention provides the following technical solutions: the airflow-assisted preparation method of the high-dispersity graphene anode material comprises the following steps of: S1, raw material pretreatment and feeding, namely screening natural crystalline flake graphite to remove impurities, and then conveying the natural crystalline flake graphite into a reaction cavity preheated to 40-50 ℃ and under the pressure of 0.1MPa at a constant speed; S2, anchoring the seed crystal, namely dispersing the carbon-based nano seed crystal in nitrogen in a supercritical state to form a crystal-carrying supercritical fluid and introducing the supercritical fluid into the reaction cavi