Method for preparing anode material for lithium ion battery based on biomass material

Abstract

The application relates to the technical field of lithium ion battery negative electrode materials, and discloses a method for preparing a lithium ion battery negative electrode material based on a biomass material, which comprises the following steps: step one, pretreating the biomass material, including cleaning and drying, so as to remove impurities and moisture; step two, performing enzyme catalytic degradation on the pretreated biomass material by using cellulase, so as to generate a porous structure material with a high specific surface area; and step three, performing a nitrogen-sulfur double-doping reaction on the degraded biomass material, including taking urea and sodium thiosulfate as doping sources, and performing the reaction under the condition of 40-60 DEG C through nitralase catalysis. Through the enzyme catalytic degradation process, the specific surface area of the biomass material is effectively increased, and a porous structure is generated, so that more lithium ion embedding / dembedding active sites are provided, and the initial capacity and overall electrochemical performance of the negative electrode material are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, specifically a method for preparing lithium-ion battery anode materials based on biomass materials. Background Technology

[0002] With the widespread application of lithium-ion batteries in portable electronic devices, electric vehicles, and energy storage systems, improving battery performance has become a key research direction. The performance of lithium-ion batteries is mainly affected by the cathode and anode materials, and the development and optimization of anode materials are crucial for improving the overall battery performance. Traditional lithium-ion battery anode materials, such as graphite, suffer from low specific capacity and limited rate performance, making it difficult to meet current demands for high energy density and rapid charge / discharge capabilities.

[0003] In recent years, biomass materials, as a green and renewable carbon source, have gradually attracted attention. After carbonization, biomass materials can be converted into carbon materials with high specific surface area and good conductivity, making them suitable as anode materials for lithium-ion batteries. However, traditional biomass carbonization methods often suffer from problems such as insufficient specific surface area, poor conductivity, and limited cycle stability, making it difficult to meet the requirements of high-performance lithium-ion batteries.

[0004] To address these shortcomings, researchers have attempted to introduce heteroatoms (such as nitrogen and sulfur) into carbon materials to enhance their electrical conductivity and electrochemical activity. Furthermore, surface modification and structural optimization measures have been applied to improve the mechanical strength and thermal stability of the materials. However, current technologies have limited optimization of carbonization and doping processes, resulting in limited potential for performance improvement. Additionally, some processes are complex and energy-intensive, failing to meet the requirements of green manufacturing. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing lithium-ion battery anode materials based on biomass materials, which solves the problems of low specific surface area, poor conductivity, insufficient cycle stability and mechanical strength, and poor thermal stability of lithium-ion battery anode materials prepared from biomass materials in existing technologies.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing lithium-ion battery anode materials based on biomass materials, comprising the following steps:

[0007] Step 1: Pre-treat the biomass materials, including washing and drying, to remove impurities and moisture;

[0008] Step 2: Use cellulase to enzymatically degrade the pretreated biomass materials to generate porous materials with high specific surface area;

[0009] Step three, nitrogen-sulfur double-doped reaction in the degraded biomass material, including using urea and sodium thiosulfate as doping source, and through nitric acid catalysis, the reaction is carried out at 40-60°C;

[0010] Step four, the doped material is placed in a hydrothermal reactor at 180°C for carbonization treatment to generate nitrogen-sulfur double-doped carbon material;

[0011] Step five, subsequent heat treatment of the carbonized material, 700°C in nitrogen atmosphere for 2 hours to improve the graphitization degree of the material;

[0012] Step six, surface modification of the heat-treated material to form a conductive film to obtain a lithium ion battery negative electrode material.

[0013] Preferably, the biomass material is bamboo chips, and before the pretreatment step, the bamboo chips are subjected to the following treatment steps:

[0014] a) Using deionized water to clean the bamboo chips at least three times, each cleaning time is not less than 20 minutes, to remove the dirt, dust and other impurities in the bamboo chips;

[0015] b) The cleaned bamboo chips are dehydrated by a filter, and then the dehydrated bamboo chips are placed in a hot air circulation oven at 60°C for drying for 12 hours until the moisture content of the bamboo chips is reduced to below 5%.

[0016] Preferably, the cellulase catalytic degradation step includes the following:

[0017] a) Prepare a 0.5% (w / w) cellulase solution, and the pH value of the solution is controlled between 5.5 and 6.5;

[0018] b) Mix the bamboo chips with the cellulase solution at a volume ratio of 1:1 to form a suspension, and perform enzyme catalytic degradation reaction in a water bath at 30-40°C for 24 hours;

[0019] c) Use a magnetic stirrer to continuously stir the suspension at a speed of 300 rpm.

[0020] Preferably, the nitrogen-sulfur double-doped reaction includes the following steps:

[0021] a) Prepare a 0.1 mol / L urea solution and a 0.1 mol / L sodium thiosulfate solution, and mix the two solutions at a volume ratio of 1:1;

[0022] b) The mixed solution is mixed with the suspended solution of degraded bamboo chips at a volume ratio of 1:1, and 0.2% (w / w) of nitrilase is added to catalyze the decomposition of urea to release amino groups for nitrogen doping;

[0023] c) The double-doping reaction is carried out at 40-60°C, and the reaction time is 12 hours. The stirring speed is maintained at 200-300 rpm during the reaction to ensure uniform doping;

[0024] d) After the reaction is completed, the suspension is quickly placed in an ice water bath to cool to room temperature, and then washed with deionized water until the pH of the washing liquid is neutral.

[0025] Preferably, the hydrothermal carbonization step includes the following:

[0026] a) The biomass material treated by nitrogen-sulfur double doping is placed in a high-purity polytetrafluoroethylene lined hydrothermal reactor, and deionized water is added to make the volume of water 3-5 times the volume of the material;

[0027] b) The temperature of the reactor is slowly increased to 180°C at a rate of 5°C per minute, and the temperature is maintained for 6 hours;

[0028] c) After the reaction is completed, the heating source is turned off, and the reactor is allowed to cool naturally to room temperature. The carbonized material is removed and washed with deionized water until the filtrate is colorless and transparent, and dried in an oven at 80°C for 24 hours.

[0029] Preferably, the subsequent heat treatment step includes the following:

[0030] a) The dried material is evenly spread in a quartz boat and placed in the heating zone of a tube furnace, and nitrogen gas protection is started with a nitrogen flow rate of 200 mL / min;

[0031] b) The material is heated to 700°C at a rate of 5°C / min, and maintained at this temperature for 2 hours;

[0032] c) After the heat preservation is completed, the heating source is turned off, and nitrogen gas is continued to be passed until the furnace temperature drops to room temperature.

[0033] Preferably, the surface modification step includes the following:

[0034] a) The heat-treated carbon material is soaked in a 0.01 M catechol solution at room temperature for 2 hours to form a conductive film;

[0035] b) After soaking, the material is removed and dried in an oven at 100°C for 1 hour.

[0036] Preferably, the electrode material preparation step includes:

[0037] a) mixing the heat-treated and surface-modified carbon material, Super P conductive carbon black, and PVDF binder at a mass ratio of 8:1:1;

[0038] b) adding N-methyl pyrrolidone (NMP) to the mixture and stirring with a high-speed stirrer at a speed of 500 rpm for 12 hours until a uniform slurry is formed;

[0039] c) uniformly coating the slurry on a copper foil current collector with a thickness of 15 µm using an automatic knife coater, with the coating thickness controlled at 100 µm;

[0040] d) drying the coated electrode sheet in a vacuum environment at 120°C for 12 hours.

[0041] Preferably, the coated electrode sheet is processed through the following steps:

[0042] a) using a hot press to press the sheet at a pressure of 10 MPa for 2 minutes to obtain an electrode sheet with uniform thickness;

[0043] b) using a high-precision mold to cut the pressed electrode sheet into a circular sheet with a diameter of 14 mm.

[0044] The present application provides a method for preparing a lithium ion battery negative electrode material based on biomass materials. It has the following beneficial effects:

[0045] 1、The present application effectively increases the specific surface area of biomass materials through enzyme-catalyzed degradation process, generating a porous structure. This improvement provides more lithium ion intercalation / deintercalation active sites, thereby significantly improving the initial capacity and overall electrochemical performance of the negative electrode material.

[0046] 2、The present application uses nitrogen-sulfur double-doping technology, which significantly improves the electrical conductivity of the material by doping nitrogen and sulfur elements into the carbon material. This improvement not only helps to improve the rate performance of the battery, allowing it to maintain high capacity under large current charging and discharging conditions, but also improves the overall charging and discharging efficiency of the battery.

[0047] 3、The present application significantly improves the graphitization degree and structural stability of the carbon material through optimized carbonization treatment and subsequent heat treatment steps. This allows the negative electrode material to maintain structural integrity and capacity stability during long-term charging and discharging cycles, thereby prolonging the service life of the battery.

[0048] 4、The present application significantly enhances the mechanical strength of the negative electrode material through the surface modification process, especially the introduction of metal oxide nanoparticle modification. This improvement reduces the risk of material damage during battery assembly and use, improving the reliability and service life of the battery.

[0049] 5、The present application adds a double-layer carbonization process in the optimization process, further improving the electrical conductivity and thermal stability of the material through two carbonization processes, significantly improving the capacity retention rate of the negative electrode material during high-rate discharge, making it more suitable for applications requiring fast charging and discharging.

[0050] 6、The present application improves the thermal treatment process to ensure the structural stability of the material under high temperature conditions, significantly improving the thermal stability of the negative electrode material. This feature enhances the safety of the battery, especially in high temperature working environment, effectively reducing the risk of thermal runaway. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 Flowchart of the present application. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0053] Embodiment:

[0054] Please refer to the drawings, the embodiments of the present application provide a method for preparing a lithium ion battery negative electrode material based on biomass material, comprising the following steps:

[0055] Step 1: Selection and pretreatment of biomass material

[0056] Material selection:

[0057] Bamboo chips are selected as the biomass raw material, mainly because of its high carbon content, abundant fiber structure, and good mechanical strength. These characteristics make bamboo chips an ideal carbon source material.

[0058] Material washing:

[0059] Put the selected bamboo chips into a large capacity washing tank, and use deionized water to wash repeatedly to ensure that the impurities such as sand, dust, etc. on the surface and inside of the bamboo chips are completely removed.

[0060] The washing process should be carried out at least 3 times, each time lasting for 20 minutes, and a stirrer is used for slight stirring to increase the washing efficiency.

[0061] Material drying:

[0062] The washed bamboo chips were dehydrated using a filtration device and then transferred to a hot air circulation oven at 60 °C for 12 hours or until the material reached a constant weight. The goal was to control the moisture content of the bamboo chips below 5% to prevent excess moisture from causing uneven reactions during subsequent processing.

[0063] Step 2: Enzymatic degradation

[0064] Enzyme solution configuration:

[0065] A 0.5% (w / w) cellulase solution was prepared, with cellulase selected from high-efficiency industrial-grade products to ensure the efficiency of cellulose degradation. The pH of the solution should be controlled between 5.5-6.5 to maintain the optimal activity of the enzyme.

[0066] Enzymatic reaction:

[0067] The dried bamboo chips were prepared into a suspension at a ratio of 1 g of bamboo chips to 10 mL of deionized water, and then the cellulase solution was added to the suspension at a volume ratio of 1:1, and the bamboo chips were thoroughly mixed with the enzyme solution to ensure sufficient contact.

[0068] The reaction was carried out in a water bath at a constant temperature of 30-40 °C for 24 hours, which is the optimal reaction temperature for cellulase. During this period, a magnetic stirrer was used to continuously stir at a speed of 300 rpm to prevent the bamboo chips from settling and affecting the uniformity of the reaction.

[0069] Reaction termination and material cleaning:

[0070] After the reaction was completed, the reaction solution was neutralized to a pH of 7.0 using a 0.1 M NaOH solution to terminate the activity of the enzyme. Then the degraded bamboo chips were repeatedly washed with a large amount of deionized water to remove the enzyme and by-products produced during the reaction.

[0071] Step 3: Preliminary reaction of nitrogen-sulfur double doping

[0072] Solution configuration:

[0073] A 0.1 mol / L urea solution and a 0.1 mol / L sodium thiosulfate solution were prepared. Urea serves as a nitrogen source, and sodium thiosulfate serves as a sulfur source. The pH of the solutions was adjusted to 6.0 and 7.5, respectively, to optimize the reaction conditions of the two doping sources.

[0074] Preliminary doping reaction:

[0075] The enzyme-degraded bamboo chip suspension was mixed with the above two solutions at a volume ratio of 1:1:1. 0.2% (w / w) nitrifying enzyme was added to the mixed solution to catalyze the decomposition of urea and release amino groups, and the reaction was carried out at 40-60 °C for 12 hours.

[0076] During the reaction, the stirring speed is maintained between 200-300 rpm to ensure that the bamboo chips are in sufficient contact with the solution, and to allow the nitrogen and sulfur atoms to be uniformly doped into the microporous structure of the bamboo chips.

[0077] Post-reaction treatment:

[0078] After the reaction, the suspension is immediately placed in an ice water bath to rapidly cool to room temperature, preventing excessive reaction of nitrogen and sulfur elements that could damage the material structure. After cooling, the bamboo chip material is separated from the solution using a filter, and repeatedly washed with deionized water until the filtrate is colorless and transparent, ensuring that impurities and unreacted substances are completely removed.

[0079] Step 4: Low-temperature hydrothermal carbonization and doping enhancement

[0080] Hydrothermal reactor preparation:

[0081] The pretreated bamboo chip material is removed and transferred to a hydrothermal reactor with a high-purity polytetrafluoroethylene (PTFE) liner. Sufficient deionized water is added to completely immerse the bamboo chip material. The volume of water should be 3-5 times the volume of the material to ensure uniformity of the hydrothermal reaction.

[0082] Hydrothermal reaction:

[0083] The reactor temperature is set to 180°C, the reactor is sealed, and maintained at this temperature for 6 hours. The high temperature and high pressure environment in the hydrothermal reactor can promote the further decomposition of cellulose in the bamboo chips and form a carbonized structure with nitrogen and sulfur doping in the material.

[0084] The key in this process is to control the temperature rise rate, so that the temperature slowly rises to the set temperature at a rate of 5°C per minute to prevent the material from collapsing due to rapid temperature changes.

[0085] Post-reaction treatment:

[0086] After the reaction, the heating source is turned off and the reactor is allowed to cool naturally to room temperature. Then, the carbonized material is removed and washed thoroughly with deionized water until the pH of the washing liquid approaches neutrality. The washed material is placed in an oven at 80°C for 24 hours to ensure that all moisture is evaporated.

[0087] Step 5: Heat treatment and microstructure optimization

[0088] Heat treatment equipment preparation:

[0089] The heat treatment of the material is carried out using a high-temperature tube furnace. The dried material is evenly spread in a quartz boat and placed in the heating zone of the tube furnace. A nitrogen atmosphere is established with a nitrogen flow rate of 200 mL / min to ensure an inert atmosphere during the entire treatment process.

[0090] Heat treatment process:

[0091] Slowly increase the temperature at a rate of 5°C / min to 700°C and maintain at this temperature for 2 hours. This process further carbonizes and increases the graphitization degree of the material, enhancing its electrical conductivity.

[0092] During the holding process, maintain nitrogen flow to prevent surface oxidation of the material and protect its microstructure. After 2 hours, turn off the heating source and continue nitrogen flow until the furnace temperature drops to room temperature, ensuring slow cooling of the material to avoid structural damage due to thermal stress.

[0093] Surface modification:

[0094] After heat treatment, remove the material and cool it to room temperature. Place the material in a 0.01 M catechol solution and soak it at room temperature for 2 hours to allow a thin film with excellent electrical conductivity to be adsorbed onto the surface of the material.

[0095] After adsorption is complete, remove the material, gently shake off the surface solution, and dry it in an oven at 100°C for 1 hour to ensure stable attachment of the modification film.

[0096] Step 6: Preparation and shaping of electrode material

[0097] Slurry preparation:

[0098] Mix the modified carbon material, Super P conductive carbon black, and PVDF binder in a mass ratio of 8:1:1. Add NMP solvent and stir the mixture until it becomes a uniform slurry state. Control the stirring speed at 500 rpm and stir for 12 hours to ensure the uniformity and fluidity of the slurry.

[0099] Electrode sheet coating:

[0100] Coat the slurry on a copper foil current collector with a thickness of 15 µm using an automatic knife coater to control the coating thickness to 100 µm. The coating process should be carried out in a dust-free room to avoid contamination by impurities.

[0101] Dry the coated copper foil in a vacuum oven at 120°C for 12 hours to ensure complete evaporation of the NMP solvent, obtaining a dry and uniform electrode sheet.

[0102] Sheet pressing and cutting:

[0103] After drying, the electrode sheet is pressed by a hot press with a pressure setting of 10 MPa and a pressing time of 2 minutes to obtain an electrode sheet with uniform thickness and appropriate density.

[0104] After pressing, the electrode sheet is cut into a circular sheet with a diameter of 14 mm using a high-precision mold to ensure the size consistency of the electrode sheet, ready for battery assembly.

[0105] Step 7: Assembly and performance testing of button cell

[0106] Button cell assembly:

[0107] In a glove box (maintained under argon atmosphere with water and oxygen content below 1 ppm), the prepared anode sheet was assembled with lithium foil. Using 1 M LiPF6 solution in EC / DMC (1:1, v / v) as electrolyte and glass fiber membrane as separator, the assembly of CR2032 button cell was completed.

[0108] Electrochemical performance testing:

[0109] Cyclic voltammetry test: CV test was conducted between the potential range of 2.5 V-0.01 V at a scan rate of 0.1 mV / s to evaluate the redox behavior and electrochemical reversibility of the material.

[0110] Constant current charge-discharge test: Constant current charge-discharge cycles were performed at 0.1 C to record the initial capacity, followed by discharge tests at 0.5 C, 1 C, and 2 C rates to evaluate the rate performance of the material.

[0111] Electrochemical impedance spectroscopy test: The test frequency range was 0.01 Hz to 100 kHz to analyze the impedance characteristics of the electrode material, with a particular focus on the interfacial resistance and charge transfer resistance to evaluate the conductivity and ion diffusion resistance of the electrode material.

[0112] Example Two:

[0113] The present invention provides a method for preparing a lithium-ion battery anode material based on biomass material, comprising the following steps:

[0114] Pre-treatment of biomass material:

[0115] Bamboo chips were selected as the biomass raw material and were cleaned and dried. The cleaning step was the same as in the previous example, i.e., the bamboo chips were cleaned with deionized water and dried to a moisture content of less than 5%.

[0116] Enzymatic degradation:

[0117] A 0.5% (w / w) cellulase solution was prepared with a pH value controlled between 5.5 and 6.5. The bamboo chips were mixed with the cellulase solution at a volume ratio of 1:1, and the enzymatic degradation reaction was carried out at 30-40°C for 24 hours with continuous stirring.

[0118] Nitrogen-sulfur dual-doping reaction:

[0119] A 0.1 mol / L urea solution and a 0.1 mol / L sodium thiosulfate solution were prepared and mixed in a 1:1 volume ratio. The mixture was then added to the degraded bamboo chip suspension and catalyzed by 0.2% (w / w) nitrification enzyme. The reaction was allowed to proceed for 12 hours.

[0120] Hydrothermal carbonization treatment:

[0121] The doped bamboo chip material was placed in a polytetrafluoroethylene-lined hydrothermal reactor, deionized water was added, and the temperature was raised to 180°C. The reaction was allowed to proceed for 6 hours. After cooling, the material was washed and dried.

[0122] Subsequent heat treatment:

[0123] The material was evenly spread in a quartz boat and placed in a tube furnace. The nitrogen flow was set to 200 mL / min, and the temperature was raised to 700°C. The material was held at this temperature for 2 hours. It was then allowed to cool naturally to room temperature.

[0124] Surface modification:

[0125] The heat-treated material was immersed in a 0.01 M catechol solution containing metal oxide nanoparticles. The concentration of metal oxide nanoparticles (such as TiO2 or Al2O3) was 2 wt%. The material was treated under ultrasonic conditions for 30 minutes to ensure uniform distribution of the nanoparticles on the surface of the carbon material.

[0126] After the immersion was complete, the material was removed, the surface solution was gently shaken off, and the material was dried in an oven at 120°C for 1 hour to ensure stable attachment of the modification film to the metal oxide.

[0127] This embodiment improves the electrical conductivity, cycle stability, and mechanical strength of the carbon material by introducing metal oxide nanoparticles. It is particularly suitable for lithium-ion batteries that are used for a long time, effectively extending the service life of the battery. Based on the previous embodiments, the surface modification step is optimized by introducing metal oxide nanoparticles to enhance the electrical conductivity and cycle stability of the material.

[0128] Example Three:

[0129] The present application provides a method for preparing a lithium-ion battery negative electrode material based on biomass material. Based on the previous embodiments, the carbonization treatment step is further optimized to improve the graphitization degree and electrical conductivity of the carbon material through a double-layer carbonization treatment process. The method includes the following steps:

[0130] Pre-treatment of biomass material:

[0131] Bamboo chips were selected as the biomass raw material and were cleaned and dried. The cleaning step was the same as in the previous embodiments to ensure that impurities in the bamboo chips were fully removed.

[0132] Enzymatic degradation:

[0133] A 0.5% (w / w) cellulase solution was prepared with a pH controlled between 5.5 and 6.5. The bamboo chips were mixed with the cellulase solution in a 1:1 volume ratio and subjected to enzymatic degradation at 30-40°C for 24 hours with continuous stirring.

[0134] Nitrogen-sulfur dual-doping reaction:

[0135] A 0.1 mol / L urea solution and a 0.1 mol / L sodium thiosulfate solution were prepared and mixed in a 1:1 volume ratio before being mixed with the degraded bamboo chip suspension. A 0.2% (w / w) nitrification enzyme catalyst was added and the reaction was allowed to proceed for 12 hours.

[0136] First carbonization treatment:

[0137] The doped bamboo chip material was placed in a polytetrafluoroethylene-lined hydrothermal reactor and deionized water was added. The temperature was raised to 180°C and the reaction was allowed to proceed for 6 hours. After cooling, the material was washed and dried.

[0138] Subsequent heat treatment (first):

[0139] The material was evenly spread in a quartz boat and placed in a tube furnace. The nitrogen flow was set to 200 mL / min and the temperature was raised to 700°C, where it was held for 2 hours. The material was then allowed to cool naturally to room temperature.

[0140] Second carbonization treatment:

[0141] The material from the first heat treatment was placed back in the tube furnace. The nitrogen flow was increased to 300 mL / min and the temperature was set to 800°C, where it was held for 4 hours.

[0142] When the material cooled to 500°C, a 5% H2 / 95% N2 gas mixture was introduced to improve the microstructure and surface chemical properties of the carbon material.

[0143] Surface modification:

[0144] The double-layer carbonized material was subjected to surface modification according to standard methods. The material was immersed in a 0.01 M catechol solution for 2 hours at room temperature and then dried in an oven at 100°C for 1 hour to ensure stable adhesion of the modification film.

[0145] The double-layer carbonization process significantly improves the graphitization degree, electrical conductivity, and thermal stability of the carbon material, making it particularly suitable for high-rate discharge lithium-ion battery applications. The process also effectively improves the interfacial electrochemical performance of the electrode material, reduces the resistance growth during charge and discharge cycles, and improves the overall efficiency of the battery.

[0146] Table 1: Comparison of Experimental Data for Examples

[0147] Performance index Example 1 Example 2 Example 3 Specific surface area (m2 / g) 800 850 900 Conductivity (S / cm) 1.2 2.0 2.5 Initial capacity (mAh / g) 350 370 390 Cycle stability (% after 500 cycles) 85 90 92 Rate capability (capacity retention at 2C rate, % 75 80 85 Mechanical strength (MPa) 100 120 110 Degree of graphitization (ID / IG) 0.95 0.90 0.85 Uniformity of surface modification Medium High High Thermal stability (% of structure retention at 800°C) 85 87 90

[0148] Specific Surface Area (m² / g): Preferred Example Two exhibits the highest specific surface area, meaning it has more active sites, which contributes to improved capacity.

[0149] Electrical Conductivity (S / cm): Preferred Example Two has the best electrical conductivity, indicating that the double-layer carbonization process effectively improves the material's conductivity, making it more suitable for high-rate discharge applications.

[0150] Initial Capacity (mAh / g): Preferred Example Two has the highest initial capacity, showing its significant advantage in energy storage performance.

[0151] Cycle Stability: Among the three examples, Preferred Example Two performs best in cycle stability, indicating that it maintains good structure and performance over long-term cycling.

[0152] Rate Performance: Preferred Example Two has the highest capacity retention rate at high-rate discharge, making it suitable for applications requiring fast charging and discharging.

[0153] Mechanical Strength (MPa): Preferred Example One's surface modification process enhances the material's mechanical strength, making it suitable for use in conditions with high mechanical stress.

[0154] Graphitization Degree (ID / IG): Preferred Example Two has the highest graphitization degree, indicating that its carbon structure is more ordered, which helps improve electrical conductivity and thermal stability.

[0155] Surface Modification Uniformity: Preferred Examples One and Two have higher surface modification uniformity, indicating that they can achieve consistent surface performance over a large area.

[0156] Thermal Stability: Preferred Example Two has the highest thermal stability, showing its ability to maintain structural integrity at high temperatures.

[0157] Comparative Example One:

[0158] This comparative example provides a traditional method, including the following steps:

[0159] Step One: Selection and Pretreatment of Biomass Material:

[0160] Common wood chips are selected as the biomass raw material. The wood chips are washed to remove surface impurities and soil, then naturally dried under sunlight until the moisture content is less than 10%.

[0161] Step Two: Direct Carbonization Treatment:

[0162] The dried sawdust was directly placed in a carbonization furnace and heated to 600°C at a rate of 10°C per minute in the absence of a protective atmosphere, maintaining for 2 hours to carbonize the sawdust material.

[0163] After carbonization, the material was naturally cooled to room temperature to obtain the carbonized sawdust material.

[0164] Step three, simple surface treatment:

[0165] The carbonized sawdust material was exposed to air for 1 hour to form a natural oxidation layer without additional chemical treatment or surface modification.

[0166] Step four, preparation of electrode material:

[0167] The carbonized material was mixed with conductive carbon black (Super P) and PVDF binder at a mass ratio of 8:1:1, and N-methyl pyrrolidone (NMP) solvent was added, stirred uniformly, and coated on a copper foil current collector.

[0168] The coated electrode sheet was air-dried to form a lithium-ion battery negative electrode material.

[0169] Table II Comparative Example Data Table

[0170] Performance index Example 1 Comparative Example 1 Specific surface area (m2 / g) 800 450 Conductivity (S / cm) 1.2 0.5 Initial capacity (mAh / g) 350 200 Cycle stability (% after 500 cycles) 85 60 Rate capability (capacity retention at 2C rate, % 75 40 Mechanical strength (MPa) 100 80 Degree of graphitization (ID / IG) 0..95 1.10 Uniformity of surface modification Medium Low Thermal stability (% of structure retention at 800°C) 85 70

[0171] Specific surface area (m² / g): The specific surface area produced by traditional processes is low, which leads to insufficient active sites of the material, affecting the capacity of the battery.

[0172] Conductivity (S / cm): The carbon material in the traditional process has poor conductivity, leading to large resistance and low efficiency of the battery during charging and discharging.

[0173] Initial capacity (mAh / g): The initial capacity of the traditional comparative example is significantly lower than Example One, mainly due to insufficient carbonization treatment and low specific surface area.

[0174] Cycle stability: The cycle stability of the traditional process is poor, with rapid capacity decay in long-term use, indicating that the material is easily damaged in repeated charging and discharging.

[0175] Rate performance: The traditional comparative example has low capacity retention rate at high-rate discharge, making it unsuitable for applications requiring fast charging and discharging.

[0176] Mechanical strength (MPa): Due to the lack of optimized carbonization and surface treatment steps in the traditional process, the mechanical strength of the material is low, and it is easy to break during battery assembly and use.

[0177] Graphitization degree (ID / IG): The carbon material produced by the traditional process has a lower graphitization degree, indicating that its structure is less ordered than Example One, and its electrical conductivity and thermal stability are poorer.

[0178] Surface modification uniformity: The traditional process does not perform effective surface modification, resulting in uneven surface properties of the material, affecting the consistency and overall performance of the battery.

[0179] Thermal stability: The thermal stability of the traditional comparative example is poor, indicating that the material is prone to structural changes under high temperature conditions, affecting the safety of the battery.

[0180] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a lithium-ion battery anode material based on a biomass material, characterized in that, The method comprises the following steps: Step 1: Pretreatment of the biomass material, including cleaning and drying to remove impurities and moisture; Step 2: Enzymatic degradation of the pretreated biomass material using cellulase to generate a porous structure material with high specific surface area; Step 3: Nitrogen-sulfur double-doping reaction in the degraded biomass material, including using urea and sodium thiosulfate as doping sources and catalyzing by nitralase under the condition of 40-60°C; Step 4: Carbonization treatment of the doped material in a hydrothermal reactor at 180°C to generate nitrogen-sulfur double-doped carbon material; the nitrogen-sulfur double-doping reaction comprises the following steps: a) Prepare 0.1 mol / L urea solution and 0.1 mol / L sodium thiosulfate solution, mix the two solutions in a volume ratio of 1:1; b) Mix the mixed solution with the degraded bamboo chips suspension in a volume ratio of 1:1, and add 0.2% (w / w) nitralase to catalyze the decomposition of urea and release amino groups for nitrogen doping; c) Perform double-doping reaction at 40-60°C for 12 hours, and maintain the stirring speed at 200-300 rpm during the reaction to ensure uniformity of doping; d) After the reaction is completed, quickly cool the suspension to room temperature in an ice water bath, then wash with deionized water until the pH value of the washing liquid is neutral; Step 5: Subsequent heat treatment of the carbonized material, heat treatment at 700°C for 2 hours in a nitrogen atmosphere to improve the graphitization degree of the material; Step 6: Surface modification of the heat-treated material to form a conductive film, obtaining a lithium ion battery negative electrode material.

2. The method for preparing a negative material for a lithium ion battery based on a biomass material according to claim 1, characterized in that, The biomass material is bamboo chips, which is treated by the following steps before the pretreatment step: a) Use deionized water to clean the bamboo chips at least three times, each time for no less than 20 minutes, to remove dirt, dust and other impurities in the bamboo chips; b) Dehydrate the cleaned bamboo chips through a filter, then dry the dehydrated bamboo chips in a hot air circulation oven at 60°C for 12 hours until the moisture content of the bamboo chips is reduced to below 5%.

3. The method for preparing lithium-ion battery anode materials based on biomass materials according to claim 1, characterized in that, The cellulase catalytic degradation step includes the following: a) Prepare a 0.5% (w / w) cellulase solution, and control the pH value of the solution between 5.5 and 6.5; b) Mix the bamboo chips with the cellulase solution in a volume ratio of 1:1 to form a suspension, and perform enzymatic degradation reaction in a water bath at 30-40°C for 24 hours; c) Use a magnetic stirrer to continuously stir the suspension at a speed of 300 rpm.

4. The method for preparing a negative material for a lithium ion battery based on a biomass material according to claim 1, characterized in that, The hydrothermal carbonization step includes the following: a) Place the nitrogen-sulfur double-doped biomass material in a hydrothermal reactor with a high-purity polytetrafluoroethylene liner, and add deionized water to make the volume of water 3-5 times that of the material; b) Slowly increase the temperature of the reactor to 180°C at a rate of 5°C per minute, and maintain this temperature for 6 hours; c) After the reaction is completed, quickly cool the suspension to room temperature in an ice water bath, then wash with deionized water until the pH value of the washing liquid is neutral; c) After the reaction is completed, the heating source is turned off and the reactor is allowed to cool naturally to room temperature. The carbonized material is removed and washed with deionized water until the filtrate is colorless and transparent. The material is dried in an oven at 80°C for 24 hours.

5. The method for preparing a negative material for lithium ion batteries based on a biomass material according to claim 1, characterized in that, The subsequent heat treatment step includes the following: a) The dried material is evenly spread in a quartz boat and placed in the heating zone of a tube furnace. Nitrogen protection is started with a flow rate of 200 mL / min; b) The material is heated to 700°C at a rate of 5°C / min and held at this temperature for 2 hours; c) After the holding period is completed, the heating source is turned off and nitrogen is continued until the furnace temperature drops to room temperature.

6. The method for preparing a negative material for lithium ion batteries based on a biomass material according to claim 1, characterized in that, The surface modification step includes the following: a) The heat-treated carbon material is immersed in a 0.01 M solution of catechol at room temperature for 2 hours to form a conductive thin film; b) After the immersion period is completed, the material is removed and dried in an oven at 100°C for 1 hour.

7. The method for preparing a negative material for lithium ion batteries based on a biomass material according to claim 1, characterized in that, The electrode material preparation step includes: a) The heat-treated and surface-modified carbon material, Super P conductive carbon black, and PVDF binder are mixed in a mass ratio of 8:1:1; b) N-methyl pyrrolidone (NMP) is added to the mixture and stirred using a high-speed mixer at a speed of 500 rpm for 12 hours until a uniform slurry is formed; c) The slurry is uniformly coated on a copper foil current collector with a thickness of 15 µm using an automatic knife coater, and the coating thickness is controlled at 100 µm; d) The coated electrode sheet is dried in a vacuum environment at 120°C for 12 hours.

8. The method for preparing a negative material for lithium ion batteries based on a biomass material according to claim 1, characterized in that, The coated electrode sheet is processed as follows: a) The hot press is used to press the sheet at a pressure of 10 MPa for 2 minutes to obtain a uniform thickness electrode sheet; b) The pressed electrode sheet is cut into a circular sheet with a diameter of 14 mm using a high-precision mold.

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