Metal-doped biomass carbon negative electrode material and preparation method thereof

Abstract

The invention provides a metal-doped biomass carbon negative electrode material and a preparation method thereof.The preparation method comprises the steps that an acid activating agent is added into biomass powder for soaking, then a pore inducer is added for high-temperature activating treatment, and activated porous carbon is obtained; preparing a mixed metal salt solution, adding the activated porous carbon into the mixed metal salt solution, sequentially stirring and standing, and performing suction filtration and drying to obtain an intermediate; and putting the intermediate into a vapor deposition reaction cavity, heating under the protection of nitrogen, introducing a silicon source gas and a germanium source gas for a deposition reaction, and cooling after the deposition reaction is completed to obtain the metal-doped biomass carbon negative electrode material. According to the process, through collaborative integration of structural design and element functions, the comprehensive electrochemical performance of the metal-doped biomass carbon negative electrode material is remarkably improved, and the problem that a traditional doped material is insufficient in stability and capacity utilization rate is solved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a metal-doped biomass carbon anode material and its preparation method. Background Technology

[0002] The anode material in a lithium-ion battery is a crucial component for the insertion and release of lithium ions, directly determining the battery's core performance characteristics such as energy density, rate performance, and cycle life. Common anode materials include graphite-based, amorphous carbon-based, silicon-based, and metal-based materials. Graphite (natural and artificial graphite) is the most widely used commercial anode material, offering advantages such as structural stability, low cost, and good cycle performance; however, its theoretical specific capacity is relatively low (372 mAh / g), limiting further improvements in energy density. Novel carbon materials such as amorphous carbon, biomass carbon, hard carbon, and soft carbon possess higher rate performance and good low-temperature characteristics, making them suitable for fast charging and low-temperature applications; however, their low initial coulombic efficiency and large irreversible capacity still need to be addressed. Silicon-based and metal-based materials have extremely high theoretical specific capacities, reaching 4200 mAh / g and 1000~1600 mAh / g respectively, and relatively good conductivity; however, they generally suffer from significant volume expansion, leading to short cycle life and structural failure. Furthermore, high cost is also a significant factor restricting their large-scale application.

[0003] In the operation of lithium-ion batteries, the core function of anode materials is to absorb lithium ions during charging (lithium insertion) and release lithium ions during discharging (lithium removal). Simultaneously, the materials must possess good structural stability, electronic conductivity, and interfacial stability to ensure efficient electrochemical performance and long cycle life. To improve the performance of carbon-based anode materials, researchers have recently introduced metal doping technology, which involves introducing metal elements into carbon materials. Through atomic-level regulation and interface engineering, multiple improvements in conductivity, capacity, and cycle stability are achieved. Metal-doped carbon anode materials have several advantages: First, metal atoms or metal oxides possess excellent electronic conductivity, which helps to construct an efficient carbon framework conductive network. Some active metals themselves possess lithium storage capacity, providing additional specific capacity.

[0004] However, metal doping presents significant volume expansion issues, easily leading to material pulverization or detachment. This disrupts the electron and lithium-ion transport pathways, significantly reducing the electrode's specific capacity and rate performance. It can also trigger side reactions, clog pores, and increase internal resistance and heat generation risk. Furthermore, due to the high reactivity of metal ions, irreversible side reactions may occur during the first charge-discharge cycle, resulting in a decrease in initial coulombic efficiency. This means that the proportion of reversibly stored lithium ions is lower during the first charge-discharge cycle, leading to permanent loss of some lithium ions and irreversible capacity loss. The initial capacity is lower, significantly reducing the usable battery capacity for users, particularly impacting high-energy-density applications such as consumer and power batteries. Long-term operation further exacerbates capacity decay and performance degradation, resulting in shortened cycle life and reduced battery life. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a metal-doped biomass carbon anode material and its preparation method, aiming to solve the problem that metal doping of anode materials leads to structural instability and irreversible electrochemical reactions, which in turn causes capacity decay and reduced cycle life.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for preparing a metal-doped biomass carbon anode material for manufacturing lithium-ion batteries, comprising the following steps: S1. Add an acidic activator to biomass powder and soak it, then add a pore inducer and perform high-temperature activation treatment to obtain activated porous carbon. S2. Prepare a mixed metal salt solution, add activated porous carbon to the mixed metal salt solution, stir and let stand in sequence, filter and dry to obtain an intermediate; S3. The intermediate is placed in the vapor deposition reaction chamber and heated under nitrogen protection. Silicon source gas and germanium source gas are introduced to carry out the deposition reaction. After the deposition reaction is completed, the material is cooled to obtain the metal-doped biomass carbon anode material.

[0007] In some embodiments, step S1 includes: S1.1. Crush and sieve the biomass material to 100~300 mesh particles to obtain biomass powder. First, vacuum dry it at 60℃. Then, disperse the biomass powder in an acidic activator solution at a mass ratio of 1:10. Stir it magnetically at room temperature for 3 hours and continue to let it stand and soak for 24 hours. S1.2. The powder treated in step S1.1 is mechanically mixed with the pore inducer at a mass ratio of 5:1 for 20 minutes. The temperature is then increased to 400~500℃ at 5℃ / min and held for 2 hours. Subsequently, the temperature is increased to 800~1000℃ at 10℃ / min and held for 1 hour to obtain activated porous carbon.

[0008] In some embodiments, in step S1, the biomass material includes at least one of coconut shell, dried seaweed, and tea residue; the acidic surfactant includes at least one of phosphoric acid, nitric acid, and oxalic acid; and the pore-inducing agent includes at least one of sodium bicarbonate, ammonium carbonate, sodium citrate, magnesium carbonate, and potassium hydroxide.

[0009] In some embodiments, step S2 includes: S2.1. Mix nickel salt and vanadium salt in a molar ratio of 1:1 and stir magnetically for 30 minutes at 60°C to prepare a 0.1 mol / L mixed metal salt solution. S2.2 Add activated porous carbon to the mixed metal salt solution, control the solid-liquid mass ratio at 1:20, and perform magnetic stirring at a constant temperature of 60℃ for 4 hours. Use a vacuum filter to separate the solid and liquid. Wash the obtained filter cake three times with deionized water to obtain a wet filter cake. S2.3. The wet filter cake is dried in a vacuum drying oven at 80℃ for 12 hours, and then pre-calcined at 300℃ for 1 hour under an inert atmosphere, with the heating rate controlled at 2~3℃ / min, to obtain the intermediate.

[0010] In some embodiments, in step S2, the nickel salt includes at least one of nickel nitrate, nickel acetate, and nickel chloride, and the vanadium salt includes at least one of ammonium metavanadate, vanadium pentoxide, and vanadium sulfate.

[0011] In some embodiments, step S3 includes: S3.1 Place the intermediate in the CVD reaction chamber, turn on the nitrogen protective atmosphere, set the flow rate to 200 mL / min, raise the temperature to 500℃ at a rate of 5℃ / min, and hold the temperature at that temperature for 10 minutes. S3.2. Introduce germanium source gas, silicon source gas, and auxiliary gas. The volume ratio of the gases is set to silicon source gas: germanium source gas: auxiliary gas = 40:5:1. The total gas flow rate is controlled at 300~400mL / min, and the reaction time is maintained at 100~200 minutes. S3.3 After the deposition reaction is completed, nitrogen gas is continuously introduced for 10 minutes to flush the residual gas in the reaction chamber. The temperature is then lowered to 400°C. Carbon source gas is introduced under nitrogen protection at a flow rate of 2L / min for 100 minutes. The temperature is then lowered to room temperature to obtain metal-doped biomass carbon anode material.

[0012] In some embodiments, in step S3, the germanium source gas includes at least one of germane, germanium tetrachloride, and ethyl germanium; the silicon source gas includes at least one of silane, dichlorosilane, and trimethylsilane; the carbon source gas includes at least one of acetylene, propyne, and methane; and the auxiliary gas is ammonia.

[0013] This invention proposes a metal-doped biomass carbon anode material, which is prepared by the method described above.

[0014] Compared with existing technologies, the metal-doped biomass carbon anode material and its preparation method disclosed in this invention have the following advantages: S1, through the synergistic effect of acidic activators and porosity inducers, constructs a biomass carbon framework with high specific surface area and hierarchical pore structure under high-temperature pyrolysis conditions, enhancing the material's ion diffusion performance and metal loading capacity, providing structural support for subsequent doping. S2 involves fully contacting activated porous carbon with a mixed metal salt solution, achieving initial anchoring of metal ions within the carbon framework, forming uniformly distributed precursor metal sites. Pre-calcination induces the formation of stable metal oxides or coordination structures, improving interfacial bonding strength and mitigating the agglomeration and shedding of doped metals. S3 introduces germanium and silicon source gases through chemical vapor deposition, enabling in-situ deposition of conductive germanium nanoparticles on the carbon surface. Simultaneously, the silicon source forms a thin coating at high temperature, effectively suppressing the volume expansion of germanium and metal ions, improving structural stability and cycle life. In summary, this process, through structural design and synergistic integration of elemental functions, significantly improves the overall electrochemical performance of metal-doped biomass carbon anode materials, overcoming the problems of insufficient stability and capacity utilization faced by traditional doped materials. Attached Figure Description

[0015] Figure 1 This is a flowchart of a metal-doped biomass carbon anode material in one embodiment of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] This invention proposes a method for preparing metal-doped biomass carbon anode materials for manufacturing lithium-ion batteries, the steps of which include: S1. Add an acidic activator to biomass powder and soak it, then add a pore inducer and perform high-temperature activation treatment to obtain activated porous carbon.

[0018] Step S1 includes: S1.1. Crush and sieve the biomass material to 100-300 mesh particles to obtain biomass powder. First, vacuum dry it at 60℃. Then, disperse the biomass powder in an acidic activator solution at a mass ratio of 1:10 in a solution of 0.1-0.5 mol / L. Stir magnetically at room temperature for 3 hours and continue to soak for 24 hours. The biomass material includes at least one of coconut shell, dried seaweed, and tea residue. The acidic activator includes at least one of phosphoric acid, nitric acid, and oxalic acid.

[0019] Step S1.1, through sieving, drying, and acid activation of the biomass powder, significantly improved the structural uniformity and surface reactivity of the carbon source, constructing a basic framework suitable for subsequent pore size control and metal doping. Sieving the raw material to 100-300 mesh increases its specific surface area exposure, ensuring reaction consistency and pyrolysis uniformity, while also facilitating uniform penetration of the adsorbent and gas. Vacuum drying at 60°C helps remove adsorbed water from the raw material, preventing structural collapse caused by violent moisture evaporation during heat treatment.

[0020] The introduction of acidic activators is a key step in structural regulation. Phosphoric acid can undergo esterification with hydroxyl and phenolic hydroxyl groups in biomass, promoting cross-linking of the carbon skeleton, while the gas released during thermal decomposition induces the formation of microporous structures. Nitric acid, with its strong oxidizing properties, can introduce oxygen-containing functional groups such as carboxyl and hydroxyl groups, providing chemically active sites for the subsequent coordination adsorption of metal ions and inducing the formation of surface defects. Oxalic acid can gently complex natural impurities such as calcium and magnesium, helping to purify the skeleton, while the gas generated during thermal decomposition forms micropores. After this treatment, the surface of the biomass carbon source is rich in functional groups and has fewer impurities, exhibiting higher metal affinity and active site density, laying the foundation for efficient metal ion loading and the formation of a uniform porous structure.

[0021] S1.2 The powder treated in step S1.1 is mechanically mixed with a pore-inducing agent at a mass ratio of 5:1 for 20 minutes. The mixture is then heated to 400-500℃ at a rate of 5℃ / min and held at that temperature for 2 hours. Subsequently, the temperature is increased to 800-1000℃ at a rate of 10℃ / min and held for 1 hour to obtain activated porous carbon. The pore-inducing agent includes at least one of sodium bicarbonate, ammonium carbonate, sodium citrate, magnesium carbonate, and potassium hydroxide.

[0022] Step S1.2 achieves the continuous construction of microporous-mesoporous structures through the synergistic effect of pore-inducing agents and high-temperature programmed heat treatment, resulting in three-dimensional activated porous carbon materials with high specific surface area, high pore volume, and multi-scale channels. Sodium bicarbonate decomposes at 400-500℃ to produce carbon dioxide gas, which can induce implosion-type gas etching in the carbon skeleton and induce micropore formation. Ammonium carbonate decomposes to produce carbon dioxide and ammonia gas, which can not only expand pore channels but also introduce nitrogen doping in situ, improving the polarity and lithiophilicity of the material. The composite inducing agent formed by sodium citrate and magnesium carbonate thermally decomposes in the range of 500-800℃, releasing small molecule gases while leaving inorganic salt residues, which helps to build the supporting structure and form a mesoporous network. Potassium hydroxide reacts with carbon at high temperature to produce potassium carbonate, carbon monoxide gas, etc. These gases and molten substances etch the carbon skeleton, inducing the formation of microporous and mesoporous structures, thereby significantly increasing the specific surface area.

[0023] The programmed heating path was designed as a key thermal control strategy. The first stage involved heating at 5℃ / min to 400-500℃ and holding for 2 hours, which helped to stably pyrolyze the cellulose components, allowing the carbon skeleton to initially take shape and form a primary porous structure. The second stage involved heating at 10℃ / min to 800-1000℃ and holding for 1 hour, allowing the carbon skeleton to rearrange and graphitize, forming a stable conductive network and expanding the three-dimensional interconnected channels. The resulting porous carbon material had a specific surface area exceeding 1600 m². 2 With a pore size distribution concentrated in the range of 0.1~10nm, it possesses high electrolyte wettability and rapid ion diffusion capability, providing a structural platform and interface matching guarantee for subsequent metal doping, vapor deposition and other steps.

[0024] S2. Prepare a mixed metal salt solution, add activated porous carbon to the mixed metal salt solution, stir and let stand in sequence, filter and dry to obtain an intermediate; Step S2 includes: S2.1. Mix nickel salt and vanadium salt in a molar ratio of 1:1 and stir magnetically for 30 minutes at 60°C to prepare a 0.1 mol / L mixed metal salt solution; the nickel salt includes at least one of nickel nitrate, nickel acetate, and nickel chloride, and the vanadium salt includes at least one of ammonium metavanadate, vanadium pentoxide, and vanadium sulfate.

[0025] In step S2.1, nickel salt and vanadium salt are mixed in a molar ratio of 1:1 to prepare a 0.1 mol / L mixed metal salt solution. This ensures charge balance and reactivity balance among the dopant components, providing a chemical basis for subsequent synergistic effects. Nickel nitrate and ammonium metavanadate can completely dissociate in water into divalent nickel ions and metavanadate ions, providing excellent solubility and reactivity. Meanwhile, nickel acetate and vanadium pentoxide can slowly release metal ions under weakly acidic or heating conditions, forming stable complexes that facilitate uniform adsorption of metal ions on porous carbon surfaces. This type of metal salt co-coating system has good complexing and coordination capabilities, and can form mixed metal oxides or metal alloy particles during subsequent heating, improving the sodium storage capacity and rate performance of the anode material.

[0026] S2.2 Add activated porous carbon to the mixed metal salt solution, with the solid-liquid mass ratio controlled at 1:20. Stir magnetically for 4 hours at a constant temperature of 60℃. Separate the solid and liquid using a vacuum filter. Wash the obtained filter cake three times with deionized water to obtain a wet filter cake.

[0027] In step S2.2, the solid-liquid mass ratio of activated porous carbon to the mixed metal salt solution is controlled at 1:20 to ensure sufficient contact and diffusion adsorption between metal ions and the carbon material. At this ratio, metal ions in the solution can enter the pores through capillary action, van der Waals forces, and coordination, and combine with polar functional groups such as carboxyl and hydroxyl groups on the porous carbon surface to form a stable adsorption state. Magnetic stirring at 60°C for 4 hours enhances the uniformity of ion distribution in the pores while avoiding particle sedimentation or agglomeration. The synergistic effect of the porous structure and functional groups allows metal ions to be uniformly anchored on the carbon-based surface and inside the pores, laying the foundation for in-situ reduction and crystal nucleation in subsequent heat treatment. In addition, filtration and three washings with deionized water effectively remove unadsorbed free metal ions and residual salts, improving the purity of the intermediate and suppressing side reactions in subsequent heat treatment.

[0028] S2.3. The wet filter cake is dried in a vacuum drying oven at 80℃ for 12 hours, and then pre-calcined at 300℃ for 1 hour under an inert atmosphere, with the heating rate controlled at 2~3℃ / min, to obtain the intermediate.

[0029] The vacuum drying process in step S2.3 slowly removes free water and some weakly bound water from the wet filter cake at 80°C, preventing structural damage and pore collapse caused by rapid water evaporation during subsequent heat treatment. The pre-calcination of the dried intermediate at 23°C / min to 300°C and holding for 1 hour under an inert atmosphere has the following important technical effects: First, the pyrolysis reaction gradually decomposes the metal salts adsorbed on the carbon-based material into corresponding metal oxides or intermediate complex states, such as nickel oxide and vanadium pentoxide, improving thermal stability and interfacial adhesion. Second, the calcination process promotes the formation of a nanoscale distribution of metal precursors on the pore surface, which helps in the composite uniformity and structural control during subsequent deposition stages. This step provides the necessary precursor morphology and structural support for the formation of stable and uniformly distributed metal doping sites.

[0030] In some embodiments, the preparation steps of the mixed metal salt solution may be as follows: (1) Dissolve two or more metal salts (such as nickel nitrate and ferric chloride) in deionized water, and then add a certain amount of chelating agent, such as ethylenediaminetetraacetic acid (EDTA), sodium citrate or ammonia water, adjust the pH of the solution to 6-8, and under stirring conditions, allow the metal ions to complex with the chelating agent to form a stable complexation system, and obtain a transparent or slightly turbid mixed metal salt solution.

[0031] (2) Dissolve metal salts (such as cobalt nitrate and manganese chloride) in water, and slowly add weak alkaline regulators (such as sodium carbonate, urea, and ammonia) at a constant temperature of 60~80℃ to adjust the pH of the reaction solution to slightly alkaline (about 7.59) and induce the formation of colloidal metal hydroxide coprecipitates to obtain a mixed metal salt solution with structural precursor properties.

[0032] (3) Dissolve organometallic complexes (such as isopropyl titanate and zirconium acetate) and soluble metal salts (such as vanadium sulfate and copper nitrate) in a mixed solvent system composed of ethanol, water and ethanolamine in a certain proportion to form a transparent and homogeneous mixed metal salt solution. Introduce the sol into activated porous carbon, and complete the permeation and filling by means of capillary adsorption, thereby forming a precursor adsorbent.

[0033] S3. The intermediate is placed in the vapor deposition reaction chamber and heated under nitrogen protection. Silicon source gas and germanium source gas are introduced to carry out the deposition reaction. After the deposition reaction is completed, the material is cooled to obtain the metal-doped biomass carbon anode material.

[0034] Step S3 includes: S3.1 Place the intermediate in the CVD reaction chamber, turn on the nitrogen protective atmosphere, set the flow rate to 200 mL / min, raise the temperature to 500℃ at a rate of 5℃ / min, and hold at this temperature for 10 minutes.

[0035] Placing the intermediate in a chemical vapor deposition (CVD) reaction chamber and introducing nitrogen at a rate of 200 mL / min to create a protective inert atmosphere effectively prevents oxidation or incomplete thermal decomposition of the intermediate during the heating process. Controlling the heating rate to 5 °C / min promotes a uniform thermal field distribution within the material, reduces the risk of cracking of metal salt pre-calcination residues, and minimizes surface structural collapse. Holding at 500 °C for 10 minutes promotes decarboxylation and dehydration of the intermediate surface, generating active sites and providing a stable interface for subsequent germanium and carbon source deposition.

[0036] S3.2. Introduce germanium source gas, silicon source gas, and auxiliary gas. The volume ratio of the gases is set as silicon source gas: germanium source gas: auxiliary gas = 40:5:1. The total gas flow rate is controlled at 300~400 mL / min, and the reaction time is maintained at 100~200 minutes. The germanium source gas includes at least one of germanane, germanium tetrachloride, and ethyl germanium. The silicon source gas includes at least one of silane, dichlorosilane, and trimethylsilane. The auxiliary gas is ammonia.

[0037] This step involves introducing germanium and silicon source gases onto the surface of an intermediate, followed by vapor-phase deposition under nitrogen protection and isothermal conditions to achieve in-situ construction of a germanium-silicon co-doped layer on the surface of an activated porous carbon framework. The germanium and silicon sources are introduced in a synergistic volume ratio of 1:5 to 10, effectively controlling the Ge / Si ratio and improving the structural stability and cycle life of the deposit. Germanium sources (such as germanane and germanium tetrachloride) possess high electrical conductivity and form a conductive network after deposition, improving the material's specific capacity and rate performance. Silicon sources (such as silane and dichlorosilane) form a stable Si oxide film or buffer layer after deposition, helping to mitigate the volume changes of germanium during charge and discharge, thereby reducing the risk of active particle detachment and enhancing structural integrity. Furthermore, a higher proportion of silicon source gas helps induce the formation of a germanium-silicon co-deposited phase (such as a Ge–Si alloy), improving the dispersibility of germanium and the reversibility of lithium intercalation. Maintaining a total gas flow rate of 300–400 mL / min ensures a stable deposition rate and guarantees a uniform and dense deposition layer. By precisely controlling the gas composition, flow rate, and reaction time, a Ge–Si hybrid layer with moderate thickness, excellent flexibility, and dual electron / ion conductivity is formed on the porous carbon surface, laying the foundation for the subsequent construction of high-capacity, high-stability metal-doped carbon anode materials.

[0038] S3.3 After the deposition reaction is complete, nitrogen gas is continuously introduced for 10 minutes to flush out residual gas in the reaction chamber. The temperature is then lowered to 400°C. Carbon source gas is introduced under nitrogen protection at a flow rate of 2 L / min for 100 minutes. The temperature is then lowered to room temperature to obtain the metal-doped biomass carbon anode material. The carbon source gas includes at least one of acetylene, propyne, and methane.

[0039] After the deposition reaction, nitrogen gas is continuously introduced and the temperature is maintained for 10 minutes. This helps to remove residual active gases from the reaction chamber and prevents secondary reactions or heterogeneous modifications to the material structure during cooling. The temperature is then lowered to 400℃, and a carbon source gas (such as acetylene or propyne) is introduced at a rate of 2 L / min into a nitrogen atmosphere. This induces the decomposition of acetylene / propyne under intermediate temperature conditions to form a dense carbon film, achieving secondary self-limiting deposition. This dense carbon layer can coat germanium particles and Ni / V doping sites, constructing a flexible conductive protective layer. This layer effectively buffers volume changes, prevents the migration of active components, and improves electronic connectivity and overall electrode structural stability, ultimately yielding a high-performance metal-doped biomass carbon anode material.

[0040] Example 1: S1.1. Crush the coconut shells and sieve them to 100~300 mesh particles. First, vacuum dry them at 60℃, then disperse them in 0.2mol / L phosphoric acid at a mass ratio of 1:10. Stir magnetically for 3 hours at room temperature, and then let them stand and soak for 24 hours. S1.2. Coconut shell powder and potassium hydroxide are mechanically mixed at a mass ratio of 5:1 for 20 minutes. The temperature is increased to 500℃ at 5℃ / min and kept at that temperature for 2 hours. Then the temperature is increased to 800℃ and carbonized rapidly at 10℃ / min for 1 hour to obtain activated porous carbon.

[0041] S2.1. Prepare a 0.1 mol / L mixed metal salt solution by magnetically stirring nickel nitrate and ammonium metavanadate at a molar ratio of 1:1 for 30 minutes at 60°C. S2.2 Add activated porous carbon to the mixed metal salt solution, control the solid-liquid mass ratio at 1:20, and perform magnetic stirring at a constant temperature of 60℃ for 4 hours. Use a vacuum filter to separate the solid and liquid. Wash the obtained filter cake three times with deionized water to obtain a wet filter cake. S2.3. The wet filter cake is dried in a vacuum drying oven at 80℃ for 12 hours, and then pre-calcined at 300℃ for 1 hour under an inert atmosphere, with the heating rate controlled at 2℃ / min, to obtain the intermediate.

[0042] S3.1 Place the intermediate in the CVD reaction chamber, turn on the nitrogen protective atmosphere, set the flow rate to 200 mL / min, raise the temperature to 500℃ at a rate of 5℃ / min, and hold the temperature at that temperature for 10 minutes. S3.2. Introduce germane, silane, and ammonia. The volume ratio of the gases is set to silane:germane:ammonia = 40:5:1. The total gas flow rate is controlled at 300 mL / min, and the reaction time is maintained at 200 minutes. S3.3 After the deposition reaction is completed, nitrogen gas is continuously introduced for 10 minutes to flush the residual gas in the reaction chamber. The temperature is then lowered to 400°C. Acetylene gas is introduced under nitrogen protection at a flow rate of 2L / min for 100 minutes. The temperature is then lowered to room temperature to obtain the metal-doped biomass carbon anode material.

[0043] Example 2: S1.1. Crush the coconut shells and sieve them to 100~300 mesh particles. First, vacuum dry them at 60℃, then disperse them in 0.2mol / L phosphoric acid at a mass ratio of 1:10. Stir magnetically for 3 hours at room temperature, and then let them stand and soak for 24 hours. S1.2. Coconut shell powder and potassium hydroxide are mechanically mixed at a mass ratio of 5:1 for 20 minutes. The mixture is then heated to 500°C at a rate of 5°C / min and held at that temperature for 2 hours. Subsequently, the mixture is rapidly carbonized at a rate of 10°C / min to 800°C for 1 hour to obtain activated porous carbon. S2.1 Dissolve nickel nitrate and ammonium metavanadate in deionized water at a molar ratio of 1:1 and stir magnetically for 30 minutes at 60°C to prepare a 0.1 mol / L mixed metal salt solution. S2.2 Add the activated porous carbon to the mixed metal salt solution, with the solid-liquid mass ratio controlled at 1:20. Stir magnetically for 4 hours at a constant temperature of 60°C. Then, perform solid-liquid separation by vacuum filtration. Wash the obtained filter cake three times with deionized water to obtain a wet filter cake. S2.3. The wet filter cake is dried in a vacuum drying oven at 80℃ for 12 hours, and then heated to 300℃ at a heating rate of 2℃ / min under an inert atmosphere and held for 1 hour to perform pre-calcination treatment to obtain the intermediate. S3.1 Place the intermediate in the chemical vapor deposition reaction chamber, turn on the nitrogen protective atmosphere, set the nitrogen flow rate to 200 mL / min, heat to 500°C at a heating rate of 5°C / min, and hold at this temperature for 10 minutes to stabilize the material structure and remove surface adsorbates. S3.2. Under the condition of maintaining the reaction chamber temperature at 500℃, germane, silane, and ammonia are introduced as reaction gases, wherein the volume ratio of silane, germane, and ammonia is set to 40:5:1, the total gas flow rate is controlled at 300mL / min, and the deposition reaction lasts for 200 minutes to form silicon on the surface of the porous carbon framework. Germanium-co-deposition structure; after step S3.2, keep the reaction chamber temperature constant at 500℃, stop the introduction of germanane and silane, and instead introduce a mixed gas consisting of 5% ammonia and 95% argon by volume, with the total flow rate of the mixed gas controlled at 400 mL / min, and continue to introduce it for 20 minutes, so that the deposited silicon... Germanium structures undergo surface reconstruction reactions under doped atmospheres, inducing the formation of secondary nitrogen doping and activation layers; S3.3 Stop the flow of mixed gas, continue to flow nitrogen and keep warm for 10 minutes to flush out residual active gas in the reaction chamber. Then reduce the reaction temperature to 400℃, and while maintaining nitrogen protection, flow acetylene gas at a flow rate of 2L / min for 100 minutes to form an outer carbon coating structure. Finally, allow it to cool naturally to room temperature to obtain the metal-doped biomass carbon anode material.

[0044] Comparative Example 1: Compared with Example 1, the difference is that in step S3.2 only silane gas is introduced, and germane gas and ammonia gas are not introduced.

[0045] Comparative Example 2: Compared with Example 1, the difference is that in step S3.2, a silane gas: germanane gas with a volume ratio of 2:1 is introduced.

[0046] Comparative Example 3: Compared with Example 1, the difference is that in step S3.2, a silane gas: germanane gas with a volume ratio of 60:1 is introduced.

[0047] Comparative Example 4: The difference compared to Example 1 is that borane gas is used instead of germanane gas.

[0048] Comparative Example 5: The difference from Example 1 is that germane is replaced with arsine.

[0049] Comparative Example 6: Compared with Example 1, the difference is that in step S3.3, acetylene:germanium is introduced in a molar ratio of 30:1 during the acetylene venting stage.

[0050] Comparative Example 7: Compared with Example 1, the difference is that in step S3.3, the acetylene gas introduction stage introduces acetylene:germanium in a molar ratio of 60:1.

[0051] Table 1: Electrical Experiment Data.

[0052] Weigh out the metal-doped biomass carbon anode materials, conductive carbon black, and binder CMC from Examples 1-2 and Comparative Examples 1-7, and add deionized water to prepare a homogeneous slurry. The solid content ratio of the metal-doped silicon-carbon anode material: conductive carbon black: binder CMC is 95:1.5:3.5. A homogenizer is used at 2000 rpm for 20 minutes. After sieving, the slurry is evenly coated onto copper foil and dried in a 90℃ vacuum drying oven. The dried electrode is then rolled and cut into circular electrodes of a specific size, and the electrode mass is recorded. In an argon-atmospheric glove box, using a lithium metal sheet as the counter electrode, a coin cell is assembled with the aforementioned electrodes, separator, gasket, etc. The electrolyte used is a silicon-carbon dedicated electrolyte.

[0053] The experimental data obtained by performing charge-discharge cycles on Examples 1-2 and Comparative Examples 1-7 are shown in Table 1. The comparison between Example 1 and Comparative Example 1 shows that the metal-doped biomass carbon anode material with metal doping has excellent cycle performance. The doping of germanium has a significant effect on electrochemical performance such as first efficiency, cycle performance and rate performance. The addition of germanium to the deposition layer can strengthen the connection between the silicon layer and the inner and outer carbon structure layers, optimize the overall structure of the material, facilitate the expression of electrochemical performance, and effectively improve the charging efficiency and service life of lithium-ion batteries. The comparison between Example 1 and Comparative Examples 2 and 3 shows that both excessively high and low germanium concentrations are detrimental to the improvement of electrochemical performance. In particular, excessively low germanium concentrations result in no improvement in electrochemical performance, while excessively high germanium concentrations result in negative benefits to electrochemical performance. This indicates that the improvement of electrochemical performance requires a suitable range of doping gas concentrations. Comparing Example 1 and Comparative Example 4, it can be seen that the electrochemical performance improvement of non-metallic element doping such as boron is not as good as that of metallic elements. Under the experimental preparation conditions, metallic elements have the best effect on improving electrochemical performance. The comparison between Example 1 and Comparative Example 5 shows that other metals besides germanium, such as arsenic, also have the effect of improving electrochemical performance. A comparison of Example 1 and Comparative Examples 6 and 7 shows that the introduction of high or low concentrations of metal deposition elements during the acetylene stage has an adverse effect on the final material properties, with the cycling performance being particularly affected. This may be because the metal elements affect the formation of the acetylene-coated carbon layer.

[0054] A comparison of Examples 1 and 2 shows that introducing a secondary atmosphere control step after deposition, based on the original preparation process, has a positive impact on the overall electrochemical performance of the metal-doped biomass carbon anode material. In Example 2, after silicon and germanium deposition, a nitrogen-containing atmosphere was introduced at a higher temperature to perform secondary control on the material surface, making the doped structure more uniform and stable, thereby further improving the lithium storage behavior of the material.

[0055] Specifically, this secondary atmosphere treatment helps to form stable nitrogen-doped structures and active defect sites on the carbon framework and its surface, enhancing the continuity of electron transport channels and improving the diffusion efficiency of lithium ions within the material. This structural modulation not only improves the material's reactivity but also mitigates, to some extent, the impact of volume changes in the silicon and germanium deposited phases during cycling on structural integrity.

[0056] This invention proposes a metal-doped biomass carbon anode material, which is prepared by a method for preparing metal-doped biomass carbon anode material.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements 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 a metal-doped biomass carbon negative electrode material for making lithium ion batteries, characterized by the steps of include: S1. Add an acidic activator to biomass powder and soak it, then add a pore inducer and perform high-temperature activation treatment to obtain activated porous carbon. S2. Prepare a mixed metal salt solution, add activated porous carbon to the mixed metal salt solution, stir and let stand in sequence, filter and dry to obtain an intermediate; S3. The intermediate is placed in the vapor deposition reaction chamber and heated under nitrogen protection. Silicon source gas and germanium source gas are introduced to carry out the deposition reaction. After the deposition reaction is completed, the material is cooled to obtain the metal-doped biomass carbon anode material.

2. The preparation method of the metal-doped biomass carbon negative electrode material according to claim 1, characterized in that, Step S1 includes: S1.

1. Crush and sieve the biomass material to 100~300 mesh particles to obtain biomass powder. First, vacuum dry it at 60℃. Then, disperse the biomass powder in an acidic activator solution at a mass ratio of 1:

10. Stir it magnetically at room temperature for 3 hours and continue to let it stand and soak for 24 hours. S1.

2. The biomass powder and the pore inducer are mechanically mixed at a mass ratio of 5:1 for 20 minutes. The temperature is increased to 400~500℃ at 5℃ / min and kept at that temperature for 2 hours. Then the temperature is increased to 800~1000℃ at 10℃ / min and kept at that temperature for 1 hour to obtain activated porous carbon.

3. The preparation method of the metal-doped biomass carbon negative electrode material according to claim 1 or 2, characterized in that, In step S1, the biomass material includes at least one of coconut shell, dried seaweed, and tea residue; the acidic surfactant includes at least one of phosphoric acid, nitric acid, and oxalic acid; and the pore inducing agent includes at least one of sodium bicarbonate, ammonium carbonate, sodium citrate, magnesium carbonate, and potassium hydroxide.

4. The preparation method of the metal-doped biomass carbon negative electrode material according to claim 1, characterized in that, Step S2 includes: S2.

1. Mix nickel salt and vanadium salt in a molar ratio of 1:1 and stir magnetically for 30 minutes at 60°C to prepare a 0.1 mol / L mixed metal salt solution. S2.2 Add activated porous carbon to the mixed metal salt solution, control the solid-liquid mass ratio at 1:20, and perform magnetic stirring at a constant temperature of 60℃ for 4 hours. Use a vacuum filter to separate the solid and liquid. Wash the obtained filter cake three times with deionized water to obtain a wet filter cake. S2.

3. The wet filter cake is dried in a vacuum drying oven at 80℃ for 12 hours, and then pre-calcined at 300℃ for 1 hour under an inert atmosphere, with the heating rate controlled at 2~3℃ / min, to obtain the intermediate.

5. The method for preparing a metal-doped biomass carbon anode material according to claim 4, characterized in that, In step S2, the nickel salt includes at least one of nickel nitrate, nickel acetate, and nickel chloride, and the vanadium salt includes at least one of ammonium metavanadate, vanadium pentoxide, and vanadium sulfate.

6. The method according to claim 1, wherein the metal-doped biomass carbon negative electrode material is prepared by the following steps: 1) mixing biomass and metal salt to obtain a mixture; 2) drying the mixture; 3) heating the mixture to obtain a metal-doped biomass carbon negative electrode material. Step S3 includes: S3.1 Place the intermediate in the CVD reaction chamber, turn on the nitrogen protective atmosphere, set the flow rate to 200 mL / min, raise the temperature to 500℃ at a rate of 5℃ / min, and hold the temperature at that temperature for 10 minutes. S3.

2. Introduce germanium source gas, silicon source gas, and auxiliary gas. The volume ratio of the gases is set to silicon source gas: germanium source gas: auxiliary gas = 40:5:

1. The total gas flow rate is controlled at 300~400mL / min, and the reaction time is maintained at 100~200 minutes. S3.3, after the end of the deposition reaction, continue to pass nitrogen to keep warm for 10 minutes to flush the reaction cavity residual gas, reduce the temperature to 400℃, under the protection of nitrogen, pass in carbon source gas, continue to pass in at a flow rate of 2L / min for 100 minutes, reduce the temperature to room temperature, to obtain a metal-doped biomass carbon negative electrode material.

7. The preparation method of the metal-doped biomass carbon negative electrode material according to claim 1 or 6, characterized in that, In step S3, the germanium source gas includes at least one of germane, germanium tetrachloride, and ethyl germanium; the silicon source gas includes at least one of silane, dichlorosilane, and trimethylsilane; the carbon source gas includes at least one of acetylene, propyne, and methane; and the auxiliary gas is ammonia.

8. A metal-doped biomass carbon negative electrode material, characterized in that, A metal-doped biomass carbon negative electrode material is prepared by the method according to any one of claims 1-7.

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