Preparation device and method of biomass-based hard carbon negative electrode material and application thereof

Abstract

The application discloses a kind of preparation device of biomass-based hard carbon negative material, comprising: surface distortion system, high-energy surface modification system and high-temperature carbonization system.The application also provides a kind of preparation device of biomass-based hard carbon negative material for preparing biomass-based hard carbon negative material using the above preparation method and the application of biomass-based hard carbon negative material prepared by the above preparation method.The preparation device and preparation method of biomass-based hard carbon negative material of the application are based on the principle of biomass heteroatomic doping modification-high temperature pyrolysis carbonization, based on the crystal structure characteristics of hard carbon material, combined with material surface distortion-high-energy surface modification-high-temperature carbonization, which can improve production efficiency and reduce production cost while realizing the efficient preparation of biomass-based amorphous hard carbon negative material.

Description

Technical Field

[0001] This invention belongs to the field of battery materials, and particularly relates to an apparatus, preparation method and application of a negative electrode material. Background Technology

[0002] Due to the limited global lithium resources that cannot meet the demand for power and energy storage lithium batteries, sodium-ion batteries are gradually gaining favor in the energy storage battery market. Currently, sodium-ion battery anode materials include carbon-based materials, titanium-based materials, alloy materials, and organic materials. Among them, amorphous hard carbon materials have become the preferred material for commercial sodium-ion battery anode materials due to their advantages such as wide availability of raw materials, low cost, environmental friendliness, and relatively excellent sodium storage performance.

[0003] Hard carbon is a difficult-to-graphitize carbon material, and it cannot be completely graphitized even at high temperatures (2800℃). The interlayer spacing of hard carbon is greater than 0.36 nm. This larger interlayer spacing facilitates the insertion and extraction of sodium ions. Simultaneously, the numerous defects and pores in hard carbon provide a large number of active sodium storage sites, giving it a high sodium storage capacity. Biomass feedstocks are widely distributed in nature, making biomass feedstocks a good choice for producing bio-based hard carbon materials.

[0004] Currently, most publicly disclosed methods for preparing biomass-based hard carbon anode materials involve modifying biomass precursors followed by high-temperature pyrolysis. This method suffers from low production efficiency, difficulty in large-scale production, and unsatisfactory electrochemical performance of the hard carbon materials, particularly low initial coulombic efficiency and low specific capacity. There are few reports on methods and apparatus for preparing biomass-based hard carbon materials that address the crystal structure characteristics of these materials. Therefore, developing new methods and apparatus based on the crystal structure characteristics of biomass-based hard carbon materials to achieve efficient and stable production of biomass-based hard carbon anode materials with high specific capacity and high initial coulombic efficiency is of practical significance. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a preparation device, preparation method, and application of a high-efficiency, high-electrochemical-performance biomass-based hard carbon anode material. To solve the above technical problem, the technical solution proposed by this invention is as follows:

[0006] An apparatus for preparing biomass-based hard carbon anode materials includes:

[0007] Surface distortion system: used to break up biomass raw material airflow and enhance the surface lattice distortion of the broken biomass raw material to obtain a first modified material; the surface distortion system includes an airflow breaking chamber;

[0008] High-energy surface modification system: used to achieve surface modification of the first modified material, increasing the crystal disorder to obtain a second modified material; the high-energy surface modification system includes a high-energy modification chamber and a plasma emission component for ionizing the modification atmosphere in the high-energy modification chamber to obtain anions to modify the first modified material; the surface distortion system is connected to the high-energy surface modification system through a gas flow pipe;

[0009] High-temperature carbonization system: used to heat the second modified material under an inert atmosphere to carbonize and decompose the second modified material to obtain biomass-based hard carbon anode material.

[0010] In the above-mentioned preparation apparatus, preferably, the airflow crushing chamber is provided with a feed pipe and multiple compressed air pipes, and the inner wall of the airflow crushing chamber is provided with a high-hardness wear-resistant lining; one end of the feed pipe is provided with a compressed air inlet, and the other end is connected to the airflow crushing chamber; the feed pipe is provided with a feed port on the side near the compressed air inlet; and the feed pipe is provided with a Laval nozzle on the side near the airflow crushing chamber.

[0011] In the above-mentioned preparation apparatus, preferably, the high-energy modification chamber is provided with a modifier injection port, and the bottom of the high-energy modification chamber is provided with a storage tank with an observation window; the plasma emission assembly includes a radio frequency transmitter and a plasma emission electrode.

[0012] In the above-mentioned preparation apparatus, preferably, the high-temperature carbonization system includes a movable ceramic boat and a heating furnace tube, and the heating furnace tube is connected to a vacuum pumping component, a heat preservation component, a gas filling component for filling inert gas during high-temperature carbonization, and a cooling component for cooling the material.

[0013] This invention introduces mechanically crushed and sieved biomass-based pre-pyrolytic carbon particles through the feed inlet. Driven by high-speed compressed air at the feed inlet, the sieved biomass-based pre-pyrolytic carbon particles are further accelerated through a Laval nozzle, reaching supersonic speeds, and then enter the gas-liquid crushing chamber. Multiple compressed air pipes (i.e., high-energy compressed air inlets) are arranged around the chamber walls of the gas-liquid crushing chamber. Driven by the rotating airflow, the materials collide, rub, and shear against each other, achieving thorough crushing. During the crushing process, coarse particles move towards the chamber walls under greater centrifugal force and collide back at the walls, resulting in a cyclic crushing effect; fine particles concentrate in the center of the gas-liquid crushing chamber under less centrifugal force and flow out along the airflow conveying pipe. The lining of the gas-liquid crushing chamber is made of a high-hardness and high-wear-resistant material; in this invention, corundum material coated with nano-tungsten carbide can be used. Meanwhile, the high-frequency, ultra-high-energy collisions, impacts, and frictions of the biomass-based prepyrolysis particles caused by high-energy compressed air can cause lattice distortion of the grains on the surface of the biomass-based prepyrolysis particles, thereby enhancing the reactivity and defects of the particle lattice surface.

[0014] The high-energy modification chamber of this invention can be equipped with a vertical air outlet at the top, and the modifier injection port can be made of 316 stainless steel for injecting modifiers required for the high-energy surface modification reaction process, such as O2, NH3, CF4, H2S, N2, etc. The modifier, along with the first modified material flowing out at high speed from the surface distortion system, undergoes a spiral motion within the high-energy modification chamber. By adjusting the frequency and power of the radio frequency generator, a plasma beam is generated by the plasma emission electrode, ionizing molecules in the atmosphere to obtain anions, which react with the highly surface-reactive first modified material, achieving further high-energy surface modification of the first modified material. The second modified material, after further high-energy surface modification, continues its spiral motion until it falls into the storage tank. A material observation window is provided on the left side of the storage tank for observing the material storage status. When the material height approaches the upper edge of the observation window, the valve at the bottom of the storage tank can be opened to release the material.

[0015] The high-temperature carbonization system of this invention includes a movable ceramic boat and a heating furnace tube. Specifically, the movable ceramic boat includes a high-temperature ceramic boat and a movable boat plate. The heating furnace tube includes a high-temperature furnace tube and electric heating units distributed on its surface. The gas filling assembly includes an inlet pipe and a horizontal outlet pipe located on the high-temperature furnace tube. A feed furnace door cover is provided at one end of the high-temperature furnace tube, and a fixed furnace door cover is provided at the other end. A heat insulation assembly is provided on the surface of the high-temperature furnace tube. A vacuum assembly is connected to the high-temperature furnace tube. Cooling assemblies are connected in the feed furnace door cover and the fixed furnace door cover. The high-temperature furnace tube can be made of corundum, the electric heating units are preferably made of silicon molybdenum rods, the heat insulation assembly can be made of mullite, and the inlet pipe and the horizontal outlet pipe are made of 316 stainless steel. The heat insulation assembly is provided outside the electric heating units and the high-temperature furnace tube to reduce heat loss and effectively save energy. The contact interfaces between the feed furnace door cover, the fixed furnace door cover and the high-temperature furnace tube are equipped with sealing rings for sealing treatment to prevent oxidation of high-temperature samples. The feed furnace door and the fixed furnace door are equipped with cooling components (cooling water inlet and outlet) for cooling during high-temperature processes, preventing the sealing rings from melting and ensuring operator safety. The vacuum assembly can be a mechanical pump, used for vacuuming the high-temperature furnace tubes before heating, further ensuring the sample undergoes crystal transformation in an oxygen-deficient environment. To protect equipment and personnel safety during material preparation, the mechanical pump must not be operated at temperatures above 1000℃.

[0016] As a general technical concept, the present invention also provides a method for preparing biomass-based hard carbon anode materials using the above-mentioned apparatus for preparing biomass-based hard carbon anode materials, comprising the following steps:

[0017] S1: The biomass raw material is pre-pyrolyzed, then crushed and screened to obtain pre-treated raw material;

[0018] S2: The pretreated raw material is fed into the airflow crushing chamber of the surface distortion system to further crush the pretreated raw material with airflow, and the surface lattice distortion degree of the further crushed raw material is enhanced to obtain the first modified material.

[0019] S3: The first modified material is sent into the high-energy modification chamber of the high-energy surface modification system through the gas delivery pipe, and a modifier is added to the high-energy modification chamber. Then, the plasma emission component is activated to ionize the modifier in the high-energy modification chamber to obtain anions to modify the first modified material, thereby increasing the crystal disorder of the first modified material to obtain the second modified material.

[0020] S4: The second modified material is fed into the high-temperature carbonization system and heated in an inert atmosphere to carbonize and decompose the second modified material to obtain a biomass-based hard carbon anode material.

[0021] In the above preparation method, preferably, the degree of surface lattice distortion of the first modified material is measured by the full width at half maximum (FWHM) of the peak in the particle XRD pattern. Specifically, FWHM = K·D·sinθ, where K is an empirical coefficient, D is the grain size, and θ is the X-ray emission angle, and FWHM is controlled to be 0.11-0.15.

[0022] In the above preparation method, preferably, the crystal disorder DD of the second modified material is (I D1 +I D2 +I D3 +I D4 ) / I G , among which, I D1 Sp, the second modified material 3 Hybridization intensity, I D2 I represents the bonding strength between the graphite lattice and polyenes and impurity ions in the second modified material. D3 I represents the amorphous graphite lattice strength of the second modified material. D4 I represents the surface defect intensity of the graphite lattice in the second modified material. G Sp, the second modified material 2 Hybridization intensity, and DD is controlled to be 1.5-2.2.

[0023] In the above preparation method, preferably, the pressure of the compressed air is controlled to be 0.6-1.0 MPa during airflow atomization; the modifier includes O2, NH3, CF4, H2S or N2; and the radio frequency of the plasma emission component is controlled to be 20-60 MHz, and the power is 200-1000 W.

[0024] In the above preparation method, preferably, the pre-pyrolysis temperature is 300-600℃, the pre-pyrolysis time is 1-5h, and the sieve size is controlled at 200-300 mesh when sieving; when heating under an inert atmosphere, the inert atmosphere is nitrogen or argon, the heating rate is controlled at 1-10℃ / min, the holding temperature is 1000-1600℃, and the holding time is 1-5h.

[0025] As a general technical concept, the present invention also provides an application of the biomass-based hard carbon anode material prepared by the above-mentioned preparation method, wherein the preparation method of the biomass-based hard carbon anode material is used as the anode of a sodium-ion battery, and the interlayer spacing d of the biomass-based hard carbon anode material is [not specified]. 002 >0.360nm, with a particle size of 1-10μm.

[0026] The biomass raw materials of this invention can be derived from commonly used biomass raw materials such as coconut shells, reeds, asphalt, bamboo, sugarcane bagasse, corn stalks, and reed.

[0027] To better understand this invention, the preparation method of hard carbon anode material is described in detail, including the following steps:

[0028] S1: The biomass raw material is preheated in a muffle furnace filled with an inert protective atmosphere at a low temperature. After being kept at this temperature for a certain period of time, it is cooled to room temperature and then mechanically crushed and sieved to obtain the pretreated raw material.

[0029] S2: The pre-treated raw material (i.e., biomass-based prepyrolysis carbon particles) after sieving is added through the feed inlet. The air pressure at the compressed air inlet and in the compressed air pipe is adjusted. Driven by compressed air, the biomass-based prepyrolysis carbon particles are accelerated to supersonic speed through the Laval nozzle and enter the airflow crushing chamber. In the airflow crushing chamber, the biomass-based prepyrolysis carbon particles undergo intense collisions and impacts under the influence of high-energy compressed air, increasing the degree of lattice distortion on the particle surface. Simultaneously, under intense collisions and impacts, the biomass-based prepyrolysis carbon particles break down. During the crushing process, coarse biomass-based prepyrolysis carbon particles move towards the chamber wall under centrifugal force, collide with the chamber wall, and then return to the center of the chamber, thus undergoing cyclic crushing. Biomass-based prepyrolysis carbon particles with surface distortion treatment below a certain particle size flow out along the airflow input pipe, obtaining the first modified material.

[0030] S3: The first modified material (i.e., surface-distorted biomass-based prepyrolytic carbon particles) flows into the high-energy modification chamber through the gas inlet pipe. Simultaneously, depending on the actual situation, additional modifier is introduced through the modifier injection port, and the particles undergo spiral motion within the chamber. The RF generator is powered on, and the frequency and power are adjusted. The surface activity of the surface-distorted biomass-based prepyrolytic carbon particles is enhanced, and the plasma beam generated by the plasma emission electrode ionizes the atmosphere to produce anions. These anions modify the surface-distorted biomass-based prepyrolytic carbon particles, increasing the number of heteroatoms and resulting in biomass-based hard carbon precursor particles with a higher degree of disorder—this is the second modified material.

[0031] S4: During the high-temperature crystal transformation stage, the bottom valve of the storage tank is opened, and the biomass-based hard carbon precursor particles naturally fall into the high-temperature ceramic boat under gravity. After the material in the high-temperature ceramic boat is filled to 2 / 3 of its volume, the furnace door is opened, and the material is pushed into the center of the constant temperature zone of the high-temperature furnace tube along with the movable boat plate. Then, the furnace door, air inlet pipe, and horizontal air outlet pipe are closed, and a vacuum is created using a mechanical pump. The electric heating unit is controlled to heat the material to a certain temperature at a certain heating rate. During the high-temperature process, an inert protective atmosphere is introduced through the air inlet pipe. After holding the material at this temperature for a certain period of time, cooling water is introduced into the cooling water pipe to cool the material down to room temperature, thus obtaining the biomass-based hard carbon anode material.

[0032] More specifically, the preparation method includes the following steps:

[0033] S1: The biomass raw material is pre-pyrolyzed in a muffle furnace filled with an inert protective atmosphere at a relatively low temperature. After being held at this temperature for a certain period of time, it is cooled to room temperature, and then mechanically crushed and sieved. The preferred pre-pyrolysis temperature is 300-600℃, the pre-pyrolysis time is 1-5 hours, and the sieve size is 200-300 mesh.

[0034] S2: The particle size of the material has a significant impact on the pyrolysis process and efficiency. The cooled prepyrolysis material is mechanically crushed and sieved, then precisely crushed using an air mill to obtain biomass-based prepyrolysis carbon particles with controllable particle size, narrow particle size distribution, smooth particle surface, and regular shape after surface distortion treatment. The work W required for particle impact damage is shown in the following formula:

[0035]

[0036] Where σ is the ultimate tensile strength of the material, E is the elastic modulus of the material, m is the mass of the material particles, and ρ is the density of the material. To achieve precise crushing, the airflow or material velocity in air jet milling must be very high, generating significant energy during high-speed collisions to break the particles. Combining high-energy compressed air and a Laval nozzle, the gas enters the contraction section of the Laval nozzle with a certain initial velocity. The gas velocity increases continuously as the cross-section decreases, reaching the throat. After entering the expansion section of the Laval nozzle, the transonic airflow velocity increases continuously as the cross-section increases. Therefore, after passing through the Laval nozzle, the airflow and material particles possess extremely high kinetic energy and impact force, enabling efficient and precise crushing of the material particles. Simultaneously, the energy from high-speed collisions and impacts causes lattice distortion of the particle surface grains, enhancing the reactivity of the particle lattice surface. The degree of distortion on the surface of a grain lattice can be measured by the full width at half maximum (FWHM) of the (002) peak in the grain XRD pattern. Specifically, FWHM = K·D·sinθ, where K is an empirical coefficient, D is the grain size, and θ is the X-ray emission angle. The narrower the FWHM, the larger the grain size, the fewer the grain defects, and the smaller the degree of grain distortion.

[0037] Screened biomass-based prepyrolytic carbon particles are added through the feed inlet. The compressed air and air pressure in the compressed air pipe are adjusted, and the particles are accelerated to supersonic speeds via a Laval nozzle before entering the airflow crushing chamber. In the chamber, the particles undergo intense collisions and impacts under the influence of high-energy compressed air, increasing the degree of lattice distortion on the particle surface. Simultaneously, the particles break down under these intense collisions and impacts. During the airflow crushing process, coarse particles experience greater centrifugal force and move towards the chamber wall, while fine particles experience less centrifugal force and move towards the center. Therefore, only fine particles meeting the particle size requirements flow out along the airflow conveyor pipe. Thus, during crushing, coarse biomass-based prepyrolytic carbon particles move towards the chamber wall under centrifugal force, collide with the wall, and then return towards the center, resulting in cyclic crushing. Biomass-based prepyrolytic carbon particles with surface distortion treatment below a certain particle size flow out along the airflow conveyor pipe. Considering the energy consumption of the actual preparation process, the compressed air pressure for fine air crushing is 0.6-1.0 MPa. Under this condition, the collection of biomass-based prepyrolysis carbon particles with fine particle size and surface distortion treatment can be achieved more efficiently, and the full width at half maximum (FWHM) of the biomass-based prepyrolysis carbon particles with surface distortion treatment can be controlled to be 0.11-0.15.

[0038] S3: The degree of defects in biomass-based hard carbon precursor particles affects the electrochemical performance of the final hard carbon anode material. Driven by a high-speed airflow, surface-distorted biomass-based prepyrolytic carbon particles and the modifier introduced through the modifier injection port move in a spiral motion within the high-energy modification chamber. (The surface-distorted biomass-based prepyrolytic carbon particles move under the influence of the high-speed airflow and flow into the high-energy modification chamber from one side of the top. Since the cross-sectional shape of the high-energy modification chamber is circular, the airflow moves in a spiral motion along the curved surface after flowing in, thus driving the material to move in a spiral motion). The surface-distorted biomass-based prepyrolytic carbon particles possess high surface reactivity; therefore, the anions obtained from the plasma beam ionization atmosphere can be rapidly embedded into the honeycomb lattice of graphite domains in the surface-distorted biomass-based prepyrolytic carbon particles, thereby achieving efficient and high-energy further surface modification of the surface-distorted biomass-based prepyrolytic carbon particles. The disorder degree (DD) of high-energy surface-modified biomass-based hard carbon precursor particles is an important parameter for measuring the degree of order (or disorder) in the crystal structure of a material. Specifically, the crystal disorder degree DD = (I D1 +I D2 +I D3 +I D4 ) / I G , among which, I D1 Sp, a high-energy surface-modified biomass-based hard carbon precursor 3 Hybridization (edge ​​defect intensity of graphite lattice), I D2 To determine the binding strength between the graphite lattice and polyenes and impurity ions in high-energy surface-modified biomass-based hard carbon precursors, I D3 I represents the amorphous graphite lattice strength of biomass-based hard carbon precursors modified with high-energy surfaces. D4 I represents the surface defect intensity of the graphite lattice in high-energy surface-modified biomass-based hard carbon precursors. G Sp, a high-energy surface-modified biomass-based hard carbon precursor 2 Hybridization (graphitization) intensity. The greater the disorder of biomass-based hard carbon precursor particles modified with high-energy surfaces, the higher the degree of disorder of the precursor material crystals. This means that amorphous hard carbon anode materials are more easily generated during high-temperature pyrolysis, and there are more sodium storage active sites, resulting in higher specific capacity.

[0039] Surface-distorted biomass-based prepyrolytic carbon particles flow into the high-energy modification chamber through an airflow pipe, where they undergo spiral motion. The RF generator is powered on, and the RF frequency and power are adjusted. Due to the enhanced surface activity of the surface-distorted biomass-based prepyrolytic carbon particles, and the plasma beam generated by the plasma emission electrode, the atmosphere is ionized to produce anions. These anions modify the surface-distorted biomass-based prepyrolytic carbon particles, increasing the number of heteroatoms within them. Considering the energy consumption of the actual preparation process, the RF frequency is set to 20-60MHz and the power to 200-1000W during the high-energy surface modification process, controlling the disorder of the biomass-based hard carbon precursor particles to be 1.5-2.2.

[0040] S4: In the high-temperature crystal transformation stage, the amorphous hard carbon anode material is prepared by combining the principle of high-temperature pyrolysis of biomass materials. Biomass-based hard carbon precursor particles obtained through surface distortion treatment and high-energy surface modification are used as precursors for hard carbon materials. During high-temperature processing, the precursors undergo dehydrogenation, degassing, and condensation reactions, retaining the carbon atom framework structure; the residual carbon material is the hard carbon material. The biomass-based hard carbon precursor particle powder is placed in a high-temperature tube furnace, an inert protective atmosphere is introduced, and the temperature is raised to a certain level and held for a certain time to obtain the hard carbon material. In the actual hard carbon preparation process, the inert protective atmosphere is nitrogen or argon, the heating rate is 1-10℃ / min, the holding temperature is 1000-1600℃, and the holding time is 1-5h. Excessive holding temperature may degrade the performance of the hard carbon material. Considering the energy consumption of the actual production process, it is preferable that the holding temperature does not exceed 1600℃.

[0041] Compared with the prior art, the advantages of the present invention are as follows:

[0042] The apparatus and method for preparing biomass-based hard carbon anode materials of this invention are based on the principle of biomass heteroatomic doping modification-high-temperature pyrolysis carbonization. Based on the crystal structure characteristics of hard carbon materials, and combining material surface distortion-high-energy surface modification-high-temperature carbonization, the method utilizes the ultra-high energy of high-speed collision, friction, and shearing driven by high-speed airflow during precise crushing and pretreatment of raw materials to increase the degree of grain distortion in the pre-pyrolysis particles of biomass, thereby enhancing the reactivity of the pre-pyrolysis particles and making it easier to react with heteroatoms to complete doping. High-energy surface modification utilizes high-energy plasma to obtain high-energy charged heteroelement ions, which can complete the heteroatomic doping of the first modified material in a short time, increasing the disorder of the surface-distorted biomass particles and obtaining a second modified material with uniform size. Through the above apparatus and method, production efficiency can be improved and production costs reduced while achieving efficient preparation of biomass-based amorphous hard carbon anode materials. This hard carbon anode achieves a first-charge specific capacity of 348.22 mAh·g at a 0.1C rate. -1It has an initial efficacy of up to 89.88% and excellent overall electrochemical performance.

[0043] The apparatus and method for preparing biomass-based hard carbon anode materials of this invention are developed based on thermodynamic theory, kinetic enhancement theory, and plasma physics theory in the field of hard carbon anode materials, combined with mechanical design and manufacturing fundamentals. The apparatus adopts a vertical construction structure, with rationally designed individual components, resulting in a scientifically sound overall system. This complete set of equipment boasts advantages such as small footprint, high integration, and easy maintenance. It can be used for high-energy modification of various biomass-based hard carbon precursors and efficient preparation of hard carbon anode materials, effectively solving many problems in the electrochemical performance of current hard carbon materials, such as low initial coulombic efficiency and low specific capacity. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the apparatus for preparing the biomass-based hard carbon anode material of the present invention.

[0046] Figure 2 The image shows the Raman spectrum of the hard carbon precursor material in Example 1.

[0047] Figure 3 This is a charge-discharge curve of the hard carbon anode material in Example 1.

[0048] Legend:

[0049] 1. Feed inlet; 2. Feed pipe; 3. Laval nozzle; 4. Compressed air pipe; 5. High-hardness wear-resistant liner; 6. Airflow crushing chamber; 7. Airflow conveying pipe; 8. Vertical air outlet; 9. Modifier injection port; 10. High-energy modification chamber; 11. Radio frequency transmitter; 12. Plasma emission electrode; 13. Storage tank; 14. Observation window; 15. High-temperature ceramic boat; 16. Movable boat plate; 17. Feed furnace door cover; 18. High-temperature furnace tube; 19. Air inlet pipe; 20. Electric heating unit; 21. Insulation component; 22. Cooling water pipe; 23. Fixed furnace door cover; 24. Horizontal air outlet pipe; 25. Vacuum assembly. Detailed Implementation

[0050] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0051] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0052] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0053] Example 1:

[0054] like Figure 1 As shown, the apparatus for preparing biomass-based hard carbon anode material in this embodiment includes:

[0055] Surface distortion system: used to break up biomass feedstock by airflow and enhance the degree of surface lattice distortion of the broken biomass feedstock to obtain a first modified material; the surface distortion system includes an airflow breaking chamber 6;

[0056] High-energy surface modification system: used to achieve surface modification of the first modified material, increasing the crystal disorder to obtain the second modified material; the high-energy surface modification system includes a high-energy modification chamber 10 and a plasma emission component for ionizing the modifying atmosphere in the high-energy modification chamber 10 to obtain anions to modify the first modified material; the surface distortion system is connected to the high-energy surface modification system through a gas flow pipe 7;

[0057] High-temperature carbonization system: used to heat the second modified material under an inert atmosphere to carbonize and decompose the second modified material to obtain biomass-based hard carbon anode material.

[0058] In this embodiment, the airflow crushing chamber 6 is provided with a feed pipe 2 (the feed angle can be 45 degrees) and multiple compressed air pipes 4 (specifically, there can be 4 pipes in this embodiment, and the 4 compressed air pipes 4 can be evenly and horizontally arranged along the outer wall of the airflow crushing chamber 6). The inner wall of the airflow crushing chamber 6 is provided with a high-hardness wear-resistant liner 5. One end of the feed pipe 2 is provided with a compressed air inlet, and the other end is connected to the airflow crushing chamber 6. The feed pipe 2 is provided with a feed inlet 1 on the side near the compressed air inlet, and the feed pipe 2 is provided with a Laval nozzle 3 on the side near the airflow crushing chamber 6.

[0059] In this embodiment, the high-energy modification chamber 10 is provided with a modifier injection port 9, the top of the high-energy modification chamber 10 is provided with a vertical air outlet 8, and the bottom of the high-energy modification chamber 10 is provided with a storage tank 13 with an observation window 14; the plasma emission assembly includes a radio frequency transmitter 11 and a plasma emission electrode 12.

[0060] In this embodiment, the high-temperature carbonization system includes a movable ceramic boat and a heating furnace tube. The heating furnace tube is connected to a vacuum pumping assembly 25, a heat insulation assembly 21, a gas filling assembly for introducing inert gas during high-temperature carbonization, and a cooling assembly for material cooling. Specifically, the movable ceramic boat includes a high-temperature ceramic boat 15 and a movable boat plate 16. The heating furnace tube includes a high-temperature furnace tube 18 and electric heating units 20 distributed on its surface. The gas filling assembly includes an inlet pipe 19 and a horizontal outlet pipe 24 located on the high-temperature furnace tube 18. A feed furnace door cover 17 is provided at one end of the high-temperature furnace tube 18, and a fixed furnace door cover 23 is provided at the other end. A heat insulation assembly 21 is provided on the surface of the high-temperature furnace tube 18. The vacuum pumping assembly 25 is connected to the high-temperature furnace tube 18. Cooling assemblies are connected to the feed furnace door cover 17 and the fixed furnace door cover 23. Sealing rings are provided at the contact interfaces between the feed furnace door cover 17, the fixed furnace door cover 23, and the high-temperature furnace tube 18 for sealing to prevent oxidation of the high-temperature sample. The feed furnace door cover 17 and the fixed furnace door cover 23 are equipped with cooling components (cooling water pipes 22) for cooling during high-temperature processes. The vacuum assembly 25 can be a mechanical pump.

[0061] This embodiment utilizes the aforementioned apparatus for preparing biomass-based hard carbon anode materials to prepare a method for preparing biomass-based hard carbon anode materials, including the following steps:

[0062] S1: The biomass raw material is pre-pyrolyzed, then crushed and screened to obtain pre-treated raw material;

[0063] S2: The pretreated raw material is fed into the airflow crushing chamber 6 of the surface distortion system to further crush the pretreated raw material with airflow, and the surface lattice distortion degree of the further crushed raw material is enhanced to obtain the first modified material.

[0064] S3: The first modified material is sent into the high-energy modification chamber 10 of the high-energy surface modification system through the gas delivery pipe 7, and a modifier is added to the high-energy modification chamber 10. Then, the plasma emission component is activated to ionize the modifier in the high-energy modification chamber 10 to obtain anions to modify the first modified material, thereby increasing the crystal disorder of the first modified material to obtain the second modified material.

[0065] S4: The second modified material is fed into a high-temperature carbonization system and heated in an inert atmosphere to carbonize and decompose the second modified material to obtain a biomass-based hard carbon anode material.

[0066] In this embodiment, the degree of surface lattice distortion of the first modified material is measured by the full width at half maximum (FWHM) of the 002 peak in the particle XRD pattern. Specifically, FWHM = K·D·sinθ, where K is an empirical coefficient, D is the grain size, and θ is the X-ray emission angle, and FWHM is controlled to be 0.11-0.15.

[0067] In this embodiment, the crystal disorder DD of the second modified material is (I D1 +I D2 +I D3 +I D4 ) / I G , among which, I D1 Sp, the second modified material 3 Hybridization intensity, I D2 I represents the bonding strength between the graphite lattice and polyenes and impurity ions in the second modified material. D3 I represents the amorphous graphite lattice strength of the second modified material. D4 I represents the surface defect intensity of the graphite lattice in the second modified material. G Sp, the second modified material 2 Hybridization intensity, and DD is controlled to be 1.5-2.2.

[0068] In this embodiment, the pressure of the compressed air is controlled to be 0.6-1.0 MPa when the airflow is broken; the modifier includes O2, NH3, CF4, H2S or N2, and the radio frequency of the plasma emission component is controlled to be 20-60 MHz, and the power is 200-1000 W.

[0069] In this embodiment, the preheating temperature is 300-600℃, the preheating time is 1-5h, and the sieve size is controlled at 200-300 mesh during sieving; when heating under an inert atmosphere, the inert atmosphere is nitrogen or argon, the heating rate is controlled at 1-10℃ / min, the holding temperature is 1000-1600℃, and the holding time is 1-5h.

[0070] The application of the biomass-based hard carbon anode material prepared by the above-described preparation method in this embodiment is to use the preparation method of the biomass-based hard carbon anode material as the anode of a sodium-ion battery, and the interlayer spacing d of the biomass-based hard carbon anode material is... 002 >0.360nm, with a particle size of 1-10μm.

[0071] This embodiment uses coconut shell biomass as an example to illustrate the preparation method of biomass-based hard carbon anode material, which includes the following steps:

[0072] S1: 200g of coconut shell biomass raw material is preheated at 400℃ for 2 hours and then mechanically crushed. After passing through a 200-mesh sieve, the preheated carbon is added through the feed inlet 1. The compressed air pressure on the feed pipe 2 and the compressed air pipe 4 is adjusted to 0.75MPa. The preheated carbon is accelerated to supersonic speed by the Laval nozzle 3 under the push of the compressed air and enters the airflow crushing chamber 6. In the airflow crushing chamber 6, the preheated carbon particles of coconut shell undergo strong collisions and impacts under the drive of high-energy compressed air, which enhances the degree of lattice distortion on the particle surface. The full width at half maximum (FWHM) of the (002) crystal face peak of the obtained surface-distorted preheated carbon particles is 0.13. At the same time, under strong collisions and impacts, the preheated carbon particles of coconut shell will break. During the crushing process, the coarse preheated carbon particles of coconut shell will move towards the cavity wall of the airflow crushing chamber 6 due to centrifugal force, collide with the high-hardness wear-resistant inner lining 5 of the cavity wall, and then return to the center of the cavity, thus undergoing cyclic crushing. Coconut shell preheating carbonization particles with surface distortion treatment below 3μm will flow out along the airflow delivery pipe 7.

[0073] S2: Surface-distorted coconut shell pre-pyrolytic carbon particles flow into the high-energy modification chamber 10 through the gas delivery pipe 7, while O2 is simultaneously introduced through the modifier injection port 9 at a flow rate of 40 mL / min, causing the particles to undergo spiral motion. The RF transmitter 11 is powered on, with the frequency adjusted to 30 MHz and the power to 300 W. The surface reactivity of the surface-distorted coconut shell pre-pyrolytic carbon particles is enhanced, and the plasma beam generated by the plasma emission electrode 12 ionizes the oxygen in the atmosphere to produce oxygen anions. These oxygen anions modify the surface-distorted coconut shell pre-pyrolytic carbon particles, increasing the C=O and CO bonds in the pre-pyrolytic carbon, resulting in coconut shell-based hard carbon precursor particles with a disorder degree (DD) of 1.61. Their Raman spectra are shown below. Figure 2 As shown. Excess gas flows out from the vertical outlet 8.

[0074] S3: During the high-temperature crystal transformation stage, the material surface height is observed in real time through the material observation window 14. When the material surface height approaches the upper edge of the material observation window 14, the bottom valve of the storage tank 13 is opened, and the coconut shell-based hard carbon precursor particles naturally fall into the high-temperature ceramic boat 15 under gravity. After the material in the high-temperature ceramic boat 15 is filled to 2 / 3 of the boat's volume, the feeding furnace door cover 17 and the movable boat plate 16 are opened and pushed together into the center of the constant temperature zone of the high-temperature furnace tube 18. Then, the feeding furnace door cover 17, the air inlet pipe 19 on the insulation component 21, and the horizontal air outlet pipe 24 on the fixed furnace door cover 23 are closed, and a vacuum is drawn by a mechanical pump. The electric heating unit 20 is controlled to heat up to 1400℃ at a heating rate of 5℃ / min. During the high-temperature process, a N2 protective atmosphere is introduced through the air inlet pipe 19 at a flow rate of 0.3L / min. After holding for 2 hours, cooling water is introduced into the cooling water pipe 22 to cool down to room temperature to obtain the hard carbon anode material.

[0075] The hard carbon anode material of this embodiment, weighed in a mass ratio of 90:5:5, was mixed and ground with conductive carbon black Super-P and binder PVDF (polyvinylidene fluoride). The mixture was dissolved in NMP (N-methylpyrrolidone) as a solvent, and after thorough mixing, it was coated onto aluminum foil to form a negative electrode sheet. In a vacuum glove box, a sodium metal sheet was used as the positive electrode, a Whatman GF / D glass fiber membrane was used as the battery separator, and 1 mol / L NaPF6 (DME = 100 vol%) was used as the electrolyte to assemble a CR2032 coin cell. Electrochemical performance tests were conducted at 0.1C in the 0-2V range, and the charge-discharge curves are shown below. Figure 3 As shown, by Figure 3 It can be seen that the initial charge specific capacity of this hard carbon anode material is 348.22 mAh·g. -1 The first-efficacy rate was 89.88%.

[0076] Example 2:

[0077] The apparatus for preparing the biomass-based hard carbon anode material in this embodiment is the same as that in Embodiment 1.

[0078] This embodiment uses coconut shell biomass as an example to illustrate the preparation method of biomass-based hard carbon anode material, which includes the following steps:

[0079] S1: 200g of coconut shell biomass raw material is preheated at 400℃ for 2 hours and then mechanically crushed. After passing through a 200-mesh sieve, the preheated carbon is added through the feed inlet 1. The compressed air pressure on the feed pipe 2 and the compressed air pipe 4 is adjusted to 0.75MPa. The preheated carbon is accelerated to supersonic speed by the Laval nozzle 3 under the push of the compressed air and enters the airflow crushing chamber 6. In the airflow crushing chamber 6, the preheated carbon particles of coconut shell undergo strong collisions and impacts under the drive of high-energy compressed air, which enhances the degree of lattice distortion on the particle surface. The full width at half maximum (FWHM) of the (002) crystal face peak of the obtained surface-distorted preheated carbon particles is 0.13. At the same time, under strong collisions and impacts, the preheated carbon particles of coconut shell will break. During the crushing process, the coarse preheated carbon particles of coconut shell will move towards the cavity wall of the airflow crushing chamber 6 due to centrifugal force, collide with the high-hardness wear-resistant inner lining 5 of the cavity wall, and then return to the center of the cavity, thus undergoing cyclic crushing. Coconut shell preheating carbonization particles with surface distortion treatment below 3μm will flow out along the airflow delivery pipe 7.

[0080] S2: Surface-distorted coconut shell pre-pyrolytic carbon particles flow into the high-energy modification chamber 10 through the gas delivery pipe 7, while O2 is simultaneously introduced through the modifier injection port 9 at a flow rate of 40 mL / min, causing the particles to undergo spiral motion. The power of the radio frequency transmitter 11 is turned on, and the frequency and power are adjusted to 30 MHz and 300 W. The surface reactivity of the surface-distorted coconut shell pre-pyrolytic carbon particles is enhanced, and the plasma beam generated by the plasma emission electrode 12 ionizes the oxygen in the atmosphere to produce oxygen anions. The oxygen anions can modify the surface-distorted coconut shell pre-pyrolytic carbon particles, increasing the C=O and CO bonds in the coconut shell pre-pyrolytic carbon, resulting in coconut shell-based hard carbon precursor particles with a disorder degree DD of 1.61, while excess gas flows out from the vertical gas outlet 8.

[0081] S3: During the high-temperature crystal transformation stage, the material surface height is observed in real time through the material observation window 14. When the material surface height approaches the upper edge of the material observation window 14, the bottom valve of the storage tank 13 is opened, and the coconut shell-based hard carbon precursor particles naturally fall into the high-temperature ceramic boat 15 under gravity. After the material in the high-temperature ceramic boat 15 is filled to 2 / 3 of the boat's volume, the feeding furnace door cover 17 and the movable boat plate 16 are opened and pushed into the center of the constant temperature zone of the high-temperature furnace tube 18. Then, the feeding furnace door cover 17, the air inlet pipe 19 on the insulation component 21, and the horizontal air outlet pipe 24 on the fixed furnace door cover 23 are closed, and a vacuum is drawn by a mechanical pump. The electric heating unit 20 is controlled to heat up to 1200℃ at a heating rate of 5℃ / min. During the high-temperature process, a N2 protective atmosphere is introduced through the air inlet pipe 19 at a flow rate of 0.3L / min. After holding for 2 hours, cooling water is introduced into the cooling water pipe 22 to cool down to room temperature to obtain the hard carbon anode material.

[0082] The hard carbon anode material of this embodiment, weighed in a mass ratio of 90:5:5, was mixed and ground with conductive carbon black Super-P and binder PVDF (polyvinylidene fluoride). The mixture was dissolved in NMP (N-methylpyrrolidone) as a solvent, and after thorough mixing, it was coated onto aluminum foil to form a negative electrode sheet. Using a sodium metal sheet as the positive electrode, a Whatman GF / D glass fiber separator, and a 1 mol / L NaPF6 electrolyte (DME = 100 vol%), a CR2032 coin cell was assembled in a vacuum glove box. Electrochemical performance tests were conducted at 0.1C in the 0-2V range, and the initial charge specific capacity was 322.28 mAh·g. -1 The first-efficacy rate was 85.94%.

[0083] Example 3:

[0084] The apparatus for preparing the biomass-based hard carbon anode material in this embodiment is the same as that in Embodiment 1.

[0085] This embodiment uses coconut shell biomass as an example to illustrate the preparation method of biomass-based hard carbon anode material, which includes the following steps:

[0086] S1: 200g of coconut shell biomass raw material is preheated at 400℃ for 2 hours and then mechanically crushed. After passing through a 200-mesh sieve, the preheated carbon is added through the feed inlet 1. The compressed air pressure on the feed pipe 2 and the compressed air pipe 4 is adjusted to 0.75MPa. The preheated carbon is accelerated to supersonic speed by the Laval nozzle 3 under the push of the compressed air and enters the airflow crushing chamber 6. In the airflow crushing chamber 6, the preheated carbon particles of coconut shell undergo strong collisions and impacts under the drive of high-energy compressed air, which enhances the degree of lattice distortion on the particle surface. The full width at half maximum (FWHM) of the (002) crystal face peak of the obtained surface-distorted preheated carbon particles is 0.13. At the same time, under strong collisions and impacts, the preheated carbon particles of coconut shell will break. During the crushing process, the coarse preheated carbon particles of coconut shell will move towards the cavity wall of the airflow crushing chamber 6 due to centrifugal force, collide with the high-hardness wear-resistant inner lining 5 of the cavity wall, and then return to the center of the cavity, thus undergoing cyclic crushing. Coconut shell preheating carbonization particles with surface distortion treatment below 3μm will flow out along the airflow delivery pipe 7.

[0087] S2: Surface-distorted coconut shell pre-pyrolytic carbon particles flow into the high-energy modification chamber 10 through the gas delivery pipe 7, while O2 is simultaneously introduced through the modifier injection port 9 at a flow rate of 40 mL / min, causing the particles to undergo spiral motion. The power of the radio frequency transmitter 11 is turned on, and the frequency and power are adjusted to 30 MHz and 300 W. The surface reactivity of the surface-distorted coconut shell pre-pyrolytic carbon particles is enhanced, and the plasma beam generated by the plasma emission electrode 12 ionizes the oxygen in the atmosphere to produce oxygen anions. The oxygen anions can modify the surface-distorted coconut shell pre-pyrolytic carbon particles, increasing the C=O and CO bonds in the coconut shell pre-pyrolytic carbon, resulting in coconut shell-based hard carbon precursor particles with a disorder degree DD of 1.61, while excess gas flows out from the vertical gas outlet 8.

[0088] S3: During the high-temperature crystal transformation stage, the material surface height is observed in real time through the material observation window 14. When the material surface height approaches the upper edge of the material observation window 14, the bottom valve of the storage tank 13 is opened, and the coconut shell-based hard carbon precursor particles naturally fall into the high-temperature ceramic boat 15 under gravity. After the material in the high-temperature ceramic boat 15 is filled to 2 / 3 of the boat's volume, the feeding furnace door cover 17 and the movable boat plate 16 are opened and pushed together into the center of the constant temperature zone of the high-temperature furnace tube 18. Then, the feeding furnace door cover 17, the air inlet pipe 19 on the insulation component 21, and the horizontal air outlet pipe 24 on the fixed furnace door cover 23 are closed, and a vacuum is drawn by a mechanical pump. The electric heating unit 20 is controlled to heat up to 1000℃ at a heating rate of 5℃ / min. During the high-temperature process, a N2 protective atmosphere is introduced through the air inlet pipe 19 at a flow rate of 0.3L / min. After holding for 2 hours, cooling water is introduced into the cooling water pipe 22 to cool down to room temperature to obtain the hard carbon anode material.

[0089] The hard carbon anode material of this embodiment, weighed in a mass ratio of 90:5:5, was mixed and ground with conductive carbon black Super-P and binder PVDF (polyvinylidene fluoride). The mixture was dissolved in NMP (N-methylpyrrolidone) as a solvent, and after thorough mixing, it was coated onto aluminum foil to form a negative electrode sheet. Using a sodium metal sheet as the positive electrode, a Whatman GF / D glass fiber separator, and a 1 mol / L NaPF6 electrolyte (DME = 100 vol%), a CR2032 coin cell was assembled in a vacuum glove box. Electrochemical performance tests were conducted at 0.1C in the 0-2V range, and the initial charge specific capacity was 296.95 mAh·g. -1 The first-efficacy rate was 82.97%.

[0090] Example 4:

[0091] The apparatus for preparing the biomass-based hard carbon anode material in this embodiment is the same as that in Embodiment 1.

[0092] This embodiment uses coconut shell biomass as an example to illustrate the preparation method of biomass-based hard carbon anode material, which includes the following steps:

[0093] S1: 200g of coconut shell biomass raw material is preheated at 400℃ for 2 hours and then mechanically crushed. After passing through a 200-mesh sieve, the preheated carbon is added through the feed inlet 1. The compressed air pressure on the feed pipe 2 and the compressed air pipe 4 is adjusted to 0.75MPa. The preheated carbon is accelerated to supersonic speed by the Laval nozzle 3 under the push of the compressed air and enters the airflow crushing chamber 6. In the airflow crushing chamber 6, the preheated carbon particles of coconut shell undergo strong collisions and impacts under the drive of high-energy compressed air, which enhances the degree of lattice distortion on the particle surface. The full width at half maximum (FWHM) of the (002) crystal face peak of the obtained surface-distorted preheated carbon particles is 0.13. At the same time, under strong collisions and impacts, the preheated carbon particles of coconut shell will break. During the crushing process, the coarse preheated carbon particles of coconut shell will move towards the cavity wall of the airflow crushing chamber 6 due to centrifugal force, collide with the high-hardness wear-resistant inner lining 5 of the cavity wall, and then return to the center of the cavity, thus undergoing cyclic crushing. Coconut shell preheating carbonization particles with surface distortion treatment below 3μm will flow out along the airflow delivery pipe 7.

[0094] S2: Surface-distorted coconut shell preheated carbon particles flow into the high-energy modification chamber 10 through the gas delivery pipe 7, while NH3 is simultaneously introduced through the modifier injection port 9 at a flow rate of 40 mL / min, causing the particles to undergo spiral motion. The power of the radio frequency transmitter 11 is turned on, and the frequency and power are adjusted to 30 MHz and 300 W. The surface reactivity of the surface-distorted coconut shell preheated carbon particles is enhanced, and the plasma beam generated by the plasma emission electrode 12 ionizes the atmosphere to produce anions. The anions modify the surface-distorted coconut shell preheated carbon particles, increasing the number of heteroatoms and yielding coconut shell-based hard carbon precursor particles with a disorder degree DD of 1.76. Excess gas flows out from the vertical outlet 8.

[0095] S3: During the high-temperature crystal transformation stage, the material surface height is observed in real time through the material observation window 14. When the material surface height approaches the upper edge of the material observation window 14, the bottom valve of the storage tank 13 is opened, and the coconut shell-based hard carbon precursor particles naturally fall into the high-temperature ceramic boat 15 under gravity. After the material in the high-temperature ceramic boat 15 is filled to 2 / 3 of the boat's volume, the feeding furnace door cover 17 and the movable boat plate 16 are opened and pushed together into the center of the constant temperature zone of the high-temperature furnace tube 18. Then, the feeding furnace door cover 17, the air inlet pipe 19 on the insulation component 21, and the horizontal air outlet pipe 24 on the fixed furnace door cover 23 are closed, and a vacuum is drawn by a mechanical pump. The electric heating unit 20 is controlled to heat up to 1400℃ at a heating rate of 5℃ / min. During the high-temperature process, a N2 protective atmosphere is introduced through the air inlet pipe 19 at a flow rate of 0.3L / min. After holding for 2 hours, cooling water is introduced into the cooling water pipe 22 to cool down to room temperature to obtain the hard carbon anode material.

[0096] The hard carbon anode material of this embodiment, weighed in a mass ratio of 90:5:5, was mixed and ground with conductive carbon black Super-P and binder PVDF (polyvinylidene fluoride). The mixture was dissolved in NMP (N-methylpyrrolidone) as a solvent, and after thorough mixing, it was coated onto aluminum foil to form a negative electrode sheet. Using a sodium metal sheet as the positive electrode, a Whatman GF / D glass fiber separator, and a 1 mol / L NaPF6 electrolyte (DME = 100 vol%), a CR2032 coin cell was assembled in a vacuum glove box. Electrochemical performance tests were conducted at 0.1C in the 0-2V range, and the initial charge specific capacity was 371.06 mAh·g. -1 The first-efficacy rate was 86.23%.

[0097] Comparative Example 1:

[0098] Compared with Example 3, this comparative example does not perform the high-energy surface modification in S2 after S1, and obtains coconut shell-based hard carbon precursor particles with a disorder degree DD of 1.33. Then, it directly performs the high-temperature crystal transformation in S3 to obtain hard carbon anode material.

[0099] The hard carbon anode material of this example, weighed in a mass ratio of 90:5:5, was mixed and ground with conductive carbon black Super-P and binder PVDF (polyvinylidene fluoride). The mixture was dissolved in NMP (N-methylpyrrolidone) as a solvent, and after thorough mixing, it was coated onto aluminum foil to form a negative electrode sheet. Using a sodium metal sheet as the positive electrode, a Whatman GF / D glass fiber separator, and a 1 mol / L NaPF6 electrolyte (DME = 100 vol%), a CR2032 coin cell was assembled in a vacuum glove box. Electrochemical performance tests were conducted at 0.1C in the 0-2V range, and the initial charge specific capacity was 267.40 mAh·g. -1 The first-efficacy rate was 80.46%.

[0100] Comparative Example 2:

[0101] Compared with Example 3, in this comparative example, pretreated pre-pyrolytic carbon with a disorder degree DD of 1.18 is directly used as a hard carbon precursor, and then the high-temperature crystal transformation in S3 is directly carried out to obtain a hard carbon anode material, including the following steps:

[0102] 200g of coconut shell biomass raw material was preheated at 400℃ for 2 hours and then mechanically crushed. After passing through a 200-mesh sieve, it was directly subjected to high-temperature crystal transformation. The preheated coconut shell granules, after mechanical crushing and sieving, were loaded into a high-temperature ceramic boat 15 to 2 / 3 of its volume. The furnace door 17 and the movable boat plate 16 were then opened and pushed into the center of the constant temperature zone of the high-temperature furnace tube 18. The furnace door 17, the air inlet pipe 19 on the insulation component 21, and the horizontal air outlet pipe 24 on the fixed furnace door 23 were then closed, and a vacuum was created using a mechanical pump. The electric heating unit 20 was controlled to heat the material to 1000℃ at a heating rate of 5℃ / min. During the high-temperature process, a protective atmosphere of N2 was introduced through the air inlet pipe 19 at a flow rate of 0.3L / min. After holding at this temperature for 2 hours, cooling water was introduced into the cooling water pipe 22 to cool the material to room temperature, thus obtaining the hard carbon anode material.

[0103] The hard carbon anode material of this comparative example, weighed in a mass ratio of 90:5:5, was mixed and ground with conductive carbon black Super-P and binder PVDF (polyvinylidene fluoride). The mixture was dissolved in NMP (N-methylpyrrolidone) as a solvent, and after thorough mixing, it was coated onto aluminum foil to form a negative electrode sheet. Using a sodium metal sheet as the positive electrode, a Whatman GF / D glass fiber separator, and a 1 mol / L NaPF6 electrolyte (DME = 100 vol%), a CR2032 coin cell was assembled in a vacuum glove box. Electrochemical performance tests were conducted at 0.1C in the 0-2V range, and the initial charge specific capacity was 250.67 mAh·g. -1 The first-efficacy rate was 75.34%.

Claims

1. A device for preparing biomass-based hard carbon anode material, characterized in that, include: Surface distortion system: used to break up the biomass raw material airflow and enhance the surface lattice distortion degree of the broken biomass raw material to obtain a first modified material; The surface distortion system includes an airflow disruption chamber (6); High-energy surface modification system: used to achieve surface modification of the first modified material, thereby increasing the crystal disorder to obtain a second modified material; the high-energy surface modification system includes a high-energy modification chamber (10) and a plasma emission component for ionizing the modifier in the high-energy modification chamber (10) to obtain anions to modify the first modified material; the surface distortion system is connected to the high-energy surface modification system through a gas flow pipe (7); the modifier includes O2, NH3, CF4, H2S or N2; High-temperature carbonization system: used to heat the second modified material under an inert atmosphere to carbonize and decompose the second modified material to obtain biomass-based hard carbon anode material; The airflow crushing chamber (6) is provided with a feed pipe (2) and multiple compressed air pipes (4). The inner wall of the airflow crushing chamber (6) is provided with a high-hardness wear-resistant lining (5). One end of the feed pipe (2) is provided with a compressed air inlet, and the other end is connected to the airflow crushing chamber (6). The feed pipe (2) is provided with a feed inlet (1) on the side near the compressed air inlet. The feed pipe (2) is provided with a Laval nozzle (3) on the side near the airflow crushing chamber (6). The high-energy modification chamber (10) is provided with a modifier injection port (9), and the bottom of the high-energy modification chamber (10) is provided with a storage tank (13) with an observation window (14); the plasma emission assembly includes a radio frequency transmitter (11) and a plasma emission electrode (12).

2. The preparation apparatus according to claim 1, characterized in that, The high-temperature carbonization system includes a movable ceramic boat and a heating furnace tube. The heating furnace tube is connected to a vacuum pumping component (25), a heat preservation component (21), a gas filling component for filling inert gas during high-temperature carbonization, and a cooling component for cooling the material.

3. A method for preparing biomass-based hard carbon anode materials using the preparation apparatus according to claim 1 or 2, characterized in that, Includes the following steps: S1: The biomass raw material is pre-pyrolyzed, then crushed and screened to obtain pre-treated raw material; S2: The pretreated raw material is fed into the airflow crushing chamber (6) of the surface distortion system to further crush the pretreated raw material by airflow, and the surface lattice distortion degree of the further crushed raw material is enhanced to obtain the first modified material. S3: The first modified material is sent into the high-energy modification chamber (10) of the high-energy surface modification system through the gas delivery pipe (7), and a modifier is added to the high-energy modification chamber (10). Then, the plasma emission component is activated to ionize the modifier in the high-energy modification chamber (10) to obtain anions to modify the first modified material, thereby increasing the crystal disorder of the first modified material to obtain the second modified material. S4: The second modified material is fed into the high-temperature carbonization system and heated in an inert atmosphere to carbonize and decompose the second modified material to obtain a biomass-based hard carbon anode material.

4. The method according to claim 3, characterized in that, The degree of surface lattice distortion of the first modified material is measured by the full width at half maximum (FWHM) of the (002) peak in the particle XRD pattern. Specifically, FWHM =K·D·sinθ ,in, K This is an empirical coefficient. D Grain size, θ The X-ray emission angle is set, and the FWHM is controlled to be 0.11-0.

15.

5. The method according to claim 3, characterized in that, The degree of crystal disorder DD of the second modified material = ( I D1 + I D2 + I D3 + I D4 ) / I G ,in, I D1 Sp, the second modified material 3 Hybridization intensity I D2 The binding strength between the graphite lattice and polyenes and impurity ions in the second modified material. I D3 The amorphous graphite lattice strength of the second modified material, I D4 The surface defect strength of the graphite lattice in the second modified material. I G Sp, the second modified material 2 Hybridization intensity, and DD is controlled to be 1.5-2.

2.

6. The method according to any one of claims 3-5, characterized in that, When the airflow is broken up, the pressure of the compressed air is controlled to be 0.6-1.0MPa; the radio frequency of the plasma emission component is controlled to be 20-60MHz and the power is 200-1000W.

7. The method according to any one of claims 3-5, characterized in that, The preheating temperature is 300-600℃, the preheating time is 1-5h, and the sieve size is controlled at 200-300 mesh when sieving; when heating in an inert atmosphere, the inert atmosphere is nitrogen or argon, the heating rate is controlled at 1-10℃ / min, the holding temperature is 1000-1600℃, and the holding time is 1-5h.

8. The application of a biomass-based hard carbon anode material prepared by the method described in any one of claims 3-7, characterized in that, The biomass-based hard carbon anode material is used as the anode in a sodium-ion battery, and the interlayer spacing d of the biomass-based hard carbon anode material is... 002 >0.360nm, with a particle size of 1-10μm.

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