Method for preparing silicon-carbon negative electrode sheet based on fungal solvolytic-polymeric carbon skeleton

Abstract

This invention relates to the field of silicon-carbon anode battery technology, specifically a method for preparing silicon-carbon anode sheets based on fungal dissolution-polymerization of a carbon framework. The method comprises six steps: fungal pretreatment, controlled fungal dissolution, silicon powder surface modification, in-situ polymerization to prepare a composite precursor, high-temperature sintering and carbonization, and electrode sheet preparation. This invention precisely controls the fungal dissolution conditions, enabling the fungal biomolecules to form a transparent / semi-transparent viscous solution. The hierarchical pores of the fungal-derived carbon framework buffer the volume expansion of silicon, while micropores store silicon particles and mesopores provide ion transport channels, laying the foundation for subsequent in-situ polymerization and silicon-carbon molecular-level composite formation.

Description

Technical Field

[0001] This invention relates to the field of silicon-carbon anode battery technology, specifically to a method for preparing a silicon-carbon anode sheet based on fungal dissolution-polymerization of a carbon skeleton. Background Technology

[0002] Lithium-ion batteries are widely used in power batteries, consumer electronics, and energy storage devices due to their high energy density, long cycle life, and environmental friendliness. Silicon, as a negative electrode material for lithium-ion batteries, has a theoretical specific capacity of up to 4200 mAh / g, far exceeding that of currently commercialized graphite negative electrodes (372 mAh / g), making it one of the core candidate materials for improving the energy density of lithium-ion batteries.

[0003] Silicon materials experience volume expansion of up to 300% during charge and discharge, leading to electrode structure collapse and active material shedding. Simultaneously, an unstable solid electrolyte interphase (SEI) film easily forms between silicon and the electrolyte, causing irreversible lithium-ion loss and significantly reducing battery cycle life and initial coulombic efficiency. Furthermore, silicon's inherently poor conductivity limits its rate performance. To address these issues, the industry widely employs "silicon-carbon composite" technology, using carbon materials as a framework to coat silicon particles, buffer volume expansion, and improve conductivity.

[0004] Currently, the carbon framework of silicon-carbon anodes mainly comes from two types of raw materials: one is artificially synthesized polymers (such as phenolic resin, epoxy resin, polypyrrole, etc.), which have the advantages of controllable structure and strong interfacial bonding with silicon particles, but have problems such as high raw material cost, use of toxic and harmful chemical monomers in the synthesis process, difficulty in environmental treatment, and the need to add additional pore-forming agents and heteroatom dopants in the sintering process. Moreover, they have poor compatibility with existing production lines in the industrialization process, which is not conducive to large-scale green production. The other type is natural biomass (such as straw, wood chips, fungal powder, etc.), which have the advantages of cheap raw materials, environmental friendliness, and natural N / O / S heteroatoms. However, the structure of natural biomass is uncontrollable, and it is mostly physically mixed with silicon particles, resulting in weak interfacial bonding strength. In addition, the batch stability of biomass itself is poor and the impurity content is high, which leads to large performance fluctuations in the prepared silicon-carbon anode sheets, which cannot meet the high performance requirements of power batteries.

[0005] While existing technologies have attempted to prepare silicon-carbon anodes using fungi as a biomass carbon source, these methods all involve directly mixing fungal powder with silicon powder and then sintering, thus retaining the inherent defects of the natural biomass carbon skeleton. Furthermore, as a natural biomaterial, the degree of solubility and polymerization control of fungi, along with their composite method with silicon powder, lacks a clear process solution. This prevents precise control of the carbon skeleton structure and molecular-level bonding at the silicon-carbon interface, hindering the performance improvement and industrial application of fungal-based silicon-carbon anode sheets. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a method for preparing a silicon-carbon negative electrode based on a fungal dissolution-polymerization carbon framework, comprising the following steps: 1) Fungal pretreatment: Select filamentous fungi with a growth cycle of 3-7 days, remove impurities, place them in a vacuum drying oven at 60-80℃ for 12-24 hours to dry them until the moisture content is ≤5%, pulverize them and pass them through a 200-300 mesh sieve to obtain fungal dry powder; 2) Controlled dissolution of fungi: The fungal powder obtained in step 1) is added to dilute acid and dissolved to obtain a fungal dissolution solution; 3) Surface modification of silicon powder: Add nano silicon powder to a silane coupling agent solution, disperse ultrasonically, heat and stir, centrifuge and filter, wash and dry to obtain modified nano silicon powder; 4) Preparation of composite precursor by in-situ polymerization: The modified nano-silica powder obtained in step 3) is added to the fungal solution in step 2), ultrasonically dispersed, and then an initiator is added. The reaction is stirred under nitrogen protection, the reaction solution is filtered and dried to obtain nano-silica powder-fungal precursor particles. 5) High-temperature sintering and carbonization: The nano-silicon powder-fungus precursor particles obtained in step 4) are placed in a tube furnace and heated to 300℃~400℃ at a heating rate of 5~10℃ / min under argon atmosphere protection. They are held at this temperature for 2 hours for pre-carbonization. The temperature is then increased to 700℃~850℃ at a heating rate of 5~10℃ / min and held for 3 hours for main sintering and carbonization. After cooling to room temperature, the particles are pulverized through a 200~300 mesh sieve to obtain silicon-carbon composite active material. 6) Electrode preparation: Mix the silicon-carbon composite active material obtained in step 5) with binder, conductive agent and deionized water, stir at high speed to obtain negative electrode slurry, coat the negative electrode slurry evenly on copper foil current collector with a coating thickness of 80~120μm, dry in a vacuum drying oven at 80℃~100℃ for 12~24h, and then roll and cut at 5~8MPa to obtain the electrode.

[0007] Further, in step 1), the filamentous fungi are selected from one or more combinations of Aspergillus niger, Aspergillus oryzae, and Rhizopus. Filamentous fungi with a growth cycle of 3-7 days are selected. These fungi can synthesize abundant biomacromolecules such as chitin and dextran during their growth. Their natural fibrous structure can form a carbon skeleton precursor with multi-level pores during subsequent dissolution and polymerization, providing a natural advantage for the dispersion and volume expansion buffering of silicon particles. Among them, Aspergillus niger has a finer mycelium diameter (2-5 μm) and well-branched structure, which can form a finer colloidal system after dissolution; Aspergillus oryzae has a higher protein content, which can introduce more nitrogen doping sites after carbonization, improving the conductivity of the carbon skeleton; Rhizopus is rich in dextran, which helps to enhance the flexibility of the carbon skeleton and further alleviate the volume expansion stress of silicon. By selecting single or combined fungal species, the microstructure and surface chemical properties of the carbon skeleton can be initially controlled, laying the foundation for subsequent molecular-level composite with silicon powder.

[0008] Further, in step 2), the dilute acid is either dilute hydrochloric acid or dilute sulfuric acid, with a solid-liquid ratio of fungal powder to dilute acid of 1 g:(10~20 mL). The dissolution temperature is 60℃~80℃, the stirring rate is 300~500 r / min, and the dissolution time is 2~4 h. The dilute acid can break the glycosidic and peptide bonds in the fungal cell wall, causing biomacromolecules such as chitin and dextran to gradually degrade into oligomers, forming a transparent or semi-transparent viscous solution. By controlling the solid-liquid ratio, it is ensured that the fungal powder is fully dispersed and in contact with the dilute acid, avoiding incomplete dissolution or the formation of gel-like precipitates due to excessive concentration. The dissolution temperature is set at 60℃~80℃. Within this temperature range, the catalytic effect of the acid is relatively active, which can effectively accelerate the hydrolysis reaction of biomacromolecules, while avoiding further decomposition or carbonization of oligomers due to excessive temperature. The stirring rate is controlled at 300~500 r / min, which can ensure uniform mixing of the solution, promote the mass transfer process, and prevent excessive shearing of the oligomer molecular chains caused by high-speed stirring. The 2-4 hour dissolution time is set to ensure that the fungal biomolecules reach an appropriate degree of degradation. This ensures the formation of a sufficient number of active functional groups (such as hydroxyl, carboxyl, and amino groups) to facilitate subsequent chemical reactions with the functional groups on the modified silica powder surface, achieving molecular-level composites. However, it also avoids over-dissolution, which could lead to excessively low oligomer molecular weights, affecting subsequent in-situ polymerization and the structural strength of the carbon skeleton. Through the synergistic control of these parameters, the viscosity, solid content, and density of active functional groups in the fungal solution can be precisely controlled, providing a crucial guarantee for the preparation of structurally controllable composite precursors.

[0009] Further, in step 3), the particle size of the nano-silicon powder is 50~200nm; the silane coupling agent is selected from KH550 or KH570, the weight fraction of the silane coupling agent in the silane coupling agent solution is 1~3%, the solvent is a mixture of ethanol and water with a volume ratio of 1:1, the heating and stirring temperature is 50℃~60℃, and the stirring time is 1~2h. Silane modification of the nano-silicon powder can introduce organic functional groups onto the surface of the silicon powder, enabling it to form chemical bonds with the biomacromolecule oligomers in the fungal lysate. Specifically, the amino group (-NH2) in the KH550 molecule can undergo amidation with the carboxyl group (-COOH) of the fungal oligomer, while the double bond (-C=C-) in the KH570 molecule can undergo free radical copolymerization with the active sites of the fungal oligomer under the action of an initiator, thereby achieving molecular-level interfacial bonding between the silicon powder and the fungal precursor. The particle size of the nano-silicon powder is controlled within the range of 50-200 nm, which ensures high specific capacity while reducing absolute volume expansion and shortening the diffusion path of lithium ions. A 1-3% weight fraction of the silane coupling agent in the solution ensures sufficient coating of the coupling agent molecules on the silicon powder surface, preventing incomplete modification due to insufficient dosage, while also preventing silicon powder agglomeration due to excessive dosage. A mixed solvent of ethanol and water (1:1 volume ratio) adjusts the solution polarity, promoting the hydrolysis of the silane coupling agent and the condensation reaction with the hydroxyl groups (-OH) on the silicon powder surface. A heating and stirring temperature of 50-60°C and a stirring time of 1-2 hours provide suitable kinetic conditions for the hydrolysis, condensation, and grafting reaction of the silane coupling agent on the silicon powder surface, ensuring stable and uniform modification. The modified nano-silicon powder surface changes from hydrophilic to lipophilic (or its compatibility with fungal oligomers improves), effectively improving its dispersibility in the fungal solution and laying the foundation for uniform distribution of silicon powder during subsequent in-situ polymerization.

[0010] Further, in step 4), the initiator is either ammonium persulfate or AIBN, the stirring reaction temperature is 60℃~80℃, the stirring rate is 300~500 r / min, and the stirring time is 3~5 h. The role of the initiator is to initiate the polymerization reaction of biomacromolecule oligomers (such as chitin oligomers, dextran oligomers, etc.) in the fungal lysate and the active functional groups (such as the double bonds introduced by KH570) on the surface of the modified nano-silica powder. When ammonium persulfate or AIBN decomposes at a stirring reaction temperature of 60℃~80℃ to generate free radicals, these radicals attack the unsaturated bonds or active sites on the oligomer molecular chains, initiating chain growth reactions. This causes the originally linear or short-chain oligomers to cross-link with each other, forming a three-dimensional network structure, thereby firmly encapsulating or embedding the modified nano-silica powder within it, forming structurally stable nano-silica powder-fungus precursor particles. The stirring rate is controlled at 300-500 r / min to ensure uniform dispersion of the modified nano-silica powder in the fungal solution, guaranteeing that the polymerization reaction occurs evenly on and around the silica powder surface and preventing silica powder agglomeration. A stirring reaction time of 3-5 hours ensures the polymerization reaction proceeds fully, guaranteeing the formation of a precursor network with sufficient strength and cross-linking degree. This allows for the maintenance of a stable framework structure during subsequent carbonization, effectively buffering the volume expansion of silica particles. Simultaneously, the nitrogen-protected atmosphere prevents the oxidation of oligomers during the reaction, ensuring the smooth progress of the polymerization reaction and the chemical stability of the precursor composition.

[0011] In the method of this invention, the silicon-carbon composite active material obtained in step 5) is spherical or near-spherical with a particle size of 100-500 nm, and the silicon powder accounts for 40-60% of the total mass of the composite particles. Two heating and heat-holding carbonization treatments are crucial for obtaining a stable silicon-carbon composite active material. First, the pre-carbonization stage at 300℃-400℃ mainly removes moisture, residual solvents, and some volatile small-molecule organic compounds from the precursor, and causes preliminary cross-linking and pyrolysis of fungal oligomers, forming a preliminary carbon skeleton with a certain mechanical strength, laying the structural foundation for subsequent main sintering carbonization. If the temperature is too low or the holding time is insufficient during this stage, incomplete pyrolysis of the precursor can easily occur, generating a large amount of gas during subsequent high-temperature sintering, damaging the carbon skeleton structure. If the temperature is too high, excessive decomposition of the oligomers may occur, resulting in excessively high porosity and decreased strength of the carbon skeleton. Next, during the main sintering and carbonization stage at 700℃~800℃, under an inert atmosphere, the fungal oligomers undergo further carbonization, forming a highly conductive graphitized or graphitized carbon structure. Simultaneously, a stable chemical bond forms between the silicon powder and the carbon skeleton through interfacial diffusion. The temperature and holding time in this stage directly affect the degree of graphitization, pore structure, and silicon-carbon interfacial bonding strength of the carbon skeleton. Excessive temperature leads to silicon particle agglomeration and grain growth, reducing the specific capacity of the material; insufficient temperature results in insufficient conductivity of the carbon skeleton, affecting the rate performance of the electrode. After two sintering processes, the silicon-carbon composite active material possesses both a well-developed porous structure to buffer the volume expansion of silicon and good conductivity and a stable silicon-carbon interface, thereby effectively improving the overall electrochemical performance of the silicon-carbon anode electrode.

[0012] Further, in step 6), the mass ratio of the silicon-carbon composite active material, binder, conductive agent, and deionized water is (80~85):(5~8):(5~7):(5~8), wherein the binder is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber, and the conductive agent is selected from graphite and / or carbon nanotubes. The selection and proportioning of these materials are key to achieving a balance between the mechanical and electrochemical properties of the electrode. The silicon-carbon composite active material accounts for 80-85%, ensuring a high specific capacity foundation for the electrode. A mixture of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) is selected as the binder. CMC acts as a thickener and dispersant, effectively improving the rheological properties of the slurry and ensuring uniform dispersion of the active material and conductive agent. Simultaneously, the carboxyl groups and other functional groups on its molecular chain can form strong hydrogen bonds with the functional groups on the surface of the silicon-carbon composite particles and the copper foil current collector. SBR acts as an elastic binder; its excellent flexibility and elasticity buffer the volume expansion stress of silicon particles during charging and discharging, inhibiting the shedding of active material. The synergistic effect of both significantly improves the bonding strength and cycle stability of the electrode. Graphite and / or carbon nanotubes are selected as the conductive agent. Graphite can construct a continuous conductive network, reducing the internal resistance of the electrode, while carbon nanotubes, due to their one-dimensional nanostructure, can form "point-line" contacts between active material particles, further improving electron conduction efficiency. Especially when the volume expansion of silicon particles causes damage to the conductive network, carbon nanotubes can act as a bridge, maintaining the conductive path. Deionized water, used as a solvent, is not only environmentally friendly and safe, but also avoids the potential impact of organic solvents on electrode performance. Its addition amount (5-8%) needs precise control to ensure the slurry has suitable viscosity and solid content, meeting the coating process requirements. It should not be too thin, leading to uneven coating and exposed copper foil, nor too thick, causing coating difficulties and a rough electrode surface. Through the scientific proportioning and synergistic effect of the above materials, the final prepared electrode exhibits good flexibility, uniform thickness, moderate compaction density, and excellent electrochemical performance.

[0013] The technical effects of this invention are as follows: 1. Controllable solubility of fungi By precisely controlling the dissolution conditions of fungi (a mixed dissolution system of dilute acid and protease, a solid-liquid ratio of 1:10 to 1:20, and dissolution at 60-80℃ for 2-4 hours), the fungal biomolecules are partially depolymerized into oligomers with a degree of polymerization of 20-50, forming a transparent / semi-transparent viscous solution. This avoids both complete depolymerization into monomers (which would result in a dense and non-porous carbon skeleton after polymerization) and slight swelling without depolymerization (which would prevent polymerization modification). The multi-level pores of the fungal-derived carbon skeleton can buffer the volume expansion of silicon, the micropores store silicon particles, and the mesopores provide ion transport channels, laying the foundation for subsequent in-situ polymerization and silicon-carbon molecular-level composites.

[0014] 2. In-situ polymerization-composite process of fungal oligomers and silicon powder Modified silicon powder is dispersed in a fungal oligomer solution, and an initiator is added to achieve in-situ polymerization. This allows the fungal polymerization product to form a molecular-level coating layer on the silicon powder surface, achieving a dual bond of covalent bonds and hydrogen bonds at the silicon-carbon interface. The functional groups on the carbon skeleton surface enhance the adhesion of silicon, and the carbon coating layer improves conductivity and inhibits SEI film rupture, thus fundamentally solving the problems of weak silicon-carbon interface bonding and silicon powder agglomeration.

[0015] 3. Segmented sintering process adapted to fungal polymerization precursors To address the carbonization characteristics of fungal dissolution-polymerization precursors, a segmented sintering process of "350℃ pre-carbonization + 700~850℃ main sintering" was designed. Pre-carbonization removes impurities and volatile components, while main sintering achieves carbon skeleton formation and stable silicon-carbon interface bonding. At the same time, it avoids silicon powder agglomeration or the formation of SiC without lithium storage activity caused by high temperature. It balances the conductivity of the carbon skeleton and the lithium storage performance of silicon particles, which is significantly different from the existing sintering processes of simple fungal or simple polymer carbon skeletons. Detailed Implementation

[0016] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0017] Example 1 A method for preparing a silicon-carbon negative electrode sheet based on fungal dissolution-polymerization of a carbon framework, the operation of which is as follows: 1. Fungal pretreatment: Select Aspergillus niger (growth cycle 5 days), vacuum dry at 80℃ for 24 hours, pulverize and pass through a 300-mesh sieve to obtain fungal dry powder (moisture content 4%). 2. Fungal dissolution: Solid-liquid ratio 1:15 (g:mL), the dissolution solution is 8% hydrochloric acid + 0.8% protease (based on the mass of dried fungal powder), stirred at 70℃ and 400r / min for 3h to obtain a semi-transparent viscous solution (viscosity 1200mPa·s at 25℃). 3. Silicon powder modification: Nano-silicon powder with a particle size of 100nm is ultrasonically dispersed in a silane coupling agent KH550 solution (mass fraction 2%, ethanol:water = 1:1) for 40min, reacted at 55℃ for 1.5h, and dried to obtain modified silicon powder; 4. In-situ polymerization-composite: Modified silica powder is added to fungal solution and ultrasonically dispersed for 25 min. Ammonium persulfate initiator is added (addition amount 1.5%, based on oligomer mass). The mixture is reacted at 70℃ and 400 r / min for 4 h under nitrogen protection to obtain composite particles (silica powder mass percentage 50%). 5. Sintering: Argon atmosphere, heating rate 8℃ / min, pre-carbonization at 350℃ for 2h, main sintering at 800℃ for 3h, cooling and pulverizing through a 300-mesh sieve to obtain silicon-carbon composite active material. 6. Electrode preparation: Silicon-carbon composite active material: CMC:SBR:graphite = 82:6:6:6 (mass ratio), coating thickness 100μm, vacuum drying at 90℃ for 20h, rolling pressure 6MPa, and cutting to obtain electrode sheets.

[0018] Example 2 A method for preparing a silicon-carbon negative electrode sheet based on fungal dissolution-polymerization of a carbon framework, the operation of which is as follows: 1. Fungal pretreatment: Select yeast (growth cycle 3 days), vacuum dry at 75℃ for 18 hours, pulverize and pass through a 400-mesh sieve to obtain fungal dry powder (moisture content 3%). 2. Fungal dissolution: Solid-liquid ratio 1:12 (g:mL), the dissolution solution is 6% sulfuric acid + 0.5% protease (based on the mass of dried fungal powder), stirred at 65℃ and 350r / min for 2.5h to obtain a transparent viscous solution (viscosity 1000mPa·s at 25℃). 3. Silicon powder modification: Nano silicon powder with a particle size of 80nm is ultrasonically dispersed in a silane coupling agent KH570 solution (mass fraction 1.5%, ethanol:water = 1:1) for 30min, reacted at 50℃ for 1h, and dried to obtain modified silicon powder; 4. In-situ polymerization-composite: Modified silica powder is added to fungal solution and ultrasonically dispersed for 20 min. Initiator AIBN (addition amount 1.2%, based on oligomer mass) is added and reacted at 65℃ and 350 r / min for 3.5 h under nitrogen protection to obtain composite particles (silica powder mass percentage 45%). 5. Sintering: Nitrogen atmosphere, heating rate 5℃ / min, pre-carbonization at 320℃ for 2.5h, main sintering at 750℃ for 4h, cooling and pulverizing through a 400-mesh sieve to obtain silicon-carbon composite active material; 6. Electrode preparation: Silicon-carbon composite active material: CMC:SBR:carbon nanotubes = 80:5:7:8 (mass ratio), coating thickness 90μm, vacuum drying at 85℃ for 24h, rolling pressure 5MPa, and cutting to obtain electrode sheets.

[0019] Example 3 A method for preparing a silicon-carbon negative electrode sheet based on fungal dissolution-polymerization of a carbon framework, the operation of which is as follows: 1. Fungal pretreatment: Select oyster mushroom mycelium (7-day growth cycle), vacuum dry at 85℃ for 30 hours, pulverize and pass through a 200-mesh sieve to obtain fungal powder (5% moisture content); 2. Fungal dissolution: Solid-liquid ratio 1:18 (g:mL), the dissolution solution is 10% phosphate + 1.0% protease (based on the mass of dried fungal powder), stirred at 75℃ and 450r / min for 3.5h to obtain a semi-transparent viscous solution (viscosity 1400mPa·s at 25℃). 3. Silicon powder modification: Nano-silicon powder with a particle size of 150nm is ultrasonically dispersed in a silane coupling agent KH550 solution (mass fraction 2.5%, ethanol:water = 1:1) for 50min, reacted at 60℃ for 2h, and dried to obtain modified silicon powder; 4. In-situ polymerization-composite: Modified silica powder is added to fungal solution and ultrasonically dispersed for 30 min. Ammonium persulfate initiator is added (addition amount 1.8%, based on oligomer mass). The reaction is carried out at 75℃ and 450 r / min for 4.5 h under nitrogen protection to obtain composite particles (silica powder mass percentage 55%). 5. Sintering: Helium atmosphere, heating rate 10℃ / min, pre-carbonization at 380℃ for 1.5h, main sintering at 850℃ for 2.5h, cooling and pulverizing through a 200-mesh sieve to obtain silicon-carbon composite active material; 6. Electrode preparation: Silicon-carbon composite active material: CMC:SBR:graphite:carbon nanotubes = 85:7:5:3 (mass ratio), coating thickness 110μm, vacuum drying at 95℃ for 18h, rolling pressure 7MPa, and cutting to obtain electrode sheets.

[0020] Comparative Example 1 The existing fungal raw powder composite scheme does not perform fungal dissolution and polymerization steps. Instead, it directly mixes the dried Aspergillus niger powder (undissolved) from Example 1 with modified silicon powder (same as Example 1) mechanically, with the silicon powder accounting for 50% by mass. The remaining sintering and electrode preparation steps are completely consistent with Example 1 to prepare silicon-carbon negative electrode sheets.

[0021] Comparative Example 2 The simple polymer carbon skeleton scheme uses phenolic resin as a carbon skeleton precursor to replace the fungal dissolution-polymerization product of the present invention. The remaining steps are completely consistent with those in Example 1. The amount of phenolic resin added is the same as the mass of fungal oligomer in Example 1, and the mass ratio of silica powder is 50%.

[0022] The silicon-carbon anode sheets prepared in the examples and comparative examples were assembled into CR2032 coin-type lithium-ion batteries, and their electrochemical performance was tested (electrolyte: 1 mol / L LiPF6-EC:DMC:EMC = 1:1:1; separator: Celgard 2400). The test results are shown in Table 1 below. The data in the table show that the lithium battery prepared using the silicon-carbon anode sheets obtained in the examples outperforms the comparative example in all aspects, further demonstrating the synergistic effect of the fungal-derived hierarchical porous carbon framework, stable silicon-carbon interface, and highly efficient conductive network constructed in this invention on improving the overall electrochemical performance of the silicon-carbon anode.

[0023] Table 1. Lithium-ion Battery Performance Test Table The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing silicon-carbon anode sheets based on fungal dissolution-polymerization of carbon frameworks, characterized in that, Includes the following steps: 1) Fungal pretreatment Select filamentous fungi with a growth cycle of 3 to 7 days, remove impurities, and dry them in a vacuum drying oven at 60 to 80°C for 12 to 24 hours until the moisture content is ≤5%. After pulverizing, pass the powder through a 200 to 300 mesh sieve to obtain fungal dry powder. 2) Controlled dissolution of fungi The fungal powder obtained in step 1) is dissolved in dilute acid to obtain a fungal solution; 3) Surface modification of silicon powder Nano-silicon powder was added to a silane coupling agent solution, ultrasonically dispersed, heated and stirred, centrifuged, filtered, washed and dried to obtain modified nano-silicon powder. 4) Preparation of composite precursors by in-situ polymerization The modified nano-silicon powder obtained in step 3) was added to the fungal solution in step 2), ultrasonically dispersed, and then an initiator was added. The reaction was stirred under nitrogen protection, the reaction solution was filtered, and dried to obtain nano-silicon powder-fungal precursor particles. 5) High-temperature sintering and carbonization The nano-silicon powder-fungus precursor particles obtained in step 4) are placed in a tube furnace and heated to 300℃~400℃ at a heating rate of 5~10℃ / min under argon atmosphere protection. They are held at this temperature for 2 hours for pre-carbonization. The temperature is then increased to 700℃~850℃ at a heating rate of 5~10℃ / min and held at this temperature for 3 hours for main sintering carbonization. After cooling to room temperature, the particles are pulverized through a 200~300 mesh sieve to obtain silicon-carbon composite active material. 6) Electrode preparation The silicon-carbon composite active material obtained in step 5) is mixed with binder, conductive agent and deionized water. After high-speed stirring, a negative electrode slurry is prepared. The negative electrode slurry is uniformly coated on a copper foil current collector with a coating thickness of 80~120μm. It is then dried in a vacuum drying oven at 80℃~100℃ for 12~24h. After being rolled and cut at 5~8MPa, the final product is obtained.

2. The method according to claim 1, characterized in that, In step 1), the filamentous fungus is selected from one or more combinations of Aspergillus niger, Aspergillus oryzae, and Rhizopus.

3. The method according to claim 1, characterized in that, In step 2), the dilute acid is dilute hydrochloric acid or dilute sulfuric acid, the solid-liquid ratio of fungal powder to dilute acid is 1g:(10~20mL), the dissolution temperature is 60℃~80℃, the dissolution stirring rate is 300~500r / min, and the dissolution time is 2~4h.

4. The method according to claim 1, characterized in that, In step 3), the particle size of the nano-silicon powder is 50~200nm; the silane coupling agent is selected from KH550 or KH570, the weight fraction of the silane coupling agent in the silane coupling agent solution is 1~3%, the solvent is a mixture of ethanol and water with a volume ratio of 1:1; the heating and stirring temperature is 50℃~60℃, and the stirring time is 1~2h.

5. The method according to claim 1, characterized in that, In step 4), the initiator is either ammonium persulfate or AIBN; the stirring reaction temperature is 60℃~80℃, the stirring rate is 300~500r / min, and the stirring time is 3~5h.

6. The method according to claim 1, characterized in that, In step 6), the mass ratio of silicon-carbon composite active material, binder, conductive agent and deionized water is (80~85):(5~8):(5~7):(5~8); the binder is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber, and the conductive agent is selected from graphite and / or carbon nanotubes.

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