A method for preparing a nano-silicon-carbon composite anode material and its battery assembly

Abstract

This invention provides a method for preparing a nano-silicon-carbon composite anode material and its battery assembly, belonging to the field of battery material technology. A controllable silicon-based precursor is constructed by combining tetraethyl orthosilicate and a multi-element doped precursor under the action of a structure-directing agent. A MOF-derived reducing agent and a plasma initiator are introduced to achieve a mild and controllable conversion of the porous silicon-carbon composite precursor. Furthermore, a laser-induced in-situ construction of a laser-induced graphene / MOF-derived carbon synergistic interconnected three-dimensional conductive network is formed on a pretreated copper foil current collector. Simultaneously, an ultrathin fluorinated interface layer is formed. This synergistic approach from three aspects—material structure, conductive network, and current collector interface—suppresses silicon-based volume effects and interface side reactions, reduces electrode internal resistance and polarization, and improves electron transport continuity and structural stability. Thus, under high specific capacity conditions, lower volume resistivity, smaller volume expansion, and better cycle stability are achieved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a method for preparing a nano-silicon-carbon composite anode material and its battery assembly. Background Technology

[0002] Among lithium-ion battery anode materials, silicon-based anodes have attracted much attention due to their high theoretical specific capacity. However, silicon undergoes significant volume changes during lithium insertion / extraction, which easily leads to particle pulverization, conductive network breakage, and repeated rupture and regeneration of the solid electrolyte interphase (SEI) film, resulting in increased polarization and decreased cycle performance. To alleviate these problems, existing technologies typically employ strategies such as silicon oxide buffer phases, carbon coating / doping, introducing graphene / carbon nanotube conductive networks, or constructing porous structures. However, these are mostly powder materials, which still need to be mixed with binders and conductive agents before being coated onto the current collector. The interfacial contact and structural stability are limited by the electrode fabrication process.

[0003] With the increasing demand for high energy density and fast charging, the research and development trend of silicon-carbon anodes is gradually shifting from "material bulk modification" to "material-electrode integration." This involves ensuring high capacity while further reducing electrode internal resistance, improving structural consistency and current collector interface bonding strength, and forming stable electron / ion transport channels and interface film systems through multi-element doping, pore structure control, and the construction of three-dimensional conductive networks. Simultaneously, the process emphasizes controllability and repeatability, such as controlling the precursor microstructure through structure-directing agents and generating Si / SiO through mild / controllable reduction systems. x Multiphase, and in-situ construction of conductive phase to reduce dependence on added conductive agents and binders.

[0004] The existing silicon-carbon anode route still faces several contradictions: First, porous structures and doping often make it difficult to simultaneously achieve "controllable pore formation, uniform doping, and stable multiphase" at the micro-nano scale, resulting in poor batch consistency; Second, in traditional powder-coated electrodes, the active material and current collector mainly rely on binders, resulting in limited interfacial adhesion and easy interface debonding and resistance increase during cycling; Third, conductive networks often rely on external conductive agents or post-processing carbonization / reduction steps, resulting in insufficient network connectivity or high process energy consumption, making it difficult to form a continuous three-dimensional conductive channel. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for preparing nano-silicon-carbon composite anode materials and their battery components. This method involves constructing a controllable silicon-based precursor using tetraethyl orthosilicate and a multi-element doped precursor under the action of a structure-directing agent. A MOF-derived reducing agent and a plasma initiator are introduced to achieve a mild and controllable conversion of the porous silicon-carbon composite precursor. Furthermore, a laser-induced in-situ construction of a laser-induced graphene / MOF-derived carbon synergistic interconnected three-dimensional conductive network is formed on a pretreated copper foil current collector, simultaneously creating an ultrathin fluorinated interface layer. This synergistic approach suppresses silicon-based volume effects and interfacial side reactions from three aspects: material structure, conductive network, and current collector interface. It reduces electrode internal resistance and polarization, improves electron transport continuity and structural stability, thereby achieving lower volume resistivity, smaller volume expansion, and better cycle stability and consistency under higher specific capacity conditions. Moreover, the process is simple, highly controllable, and suitable for integrated applications of electrode sheets and battery cell components.

[0006] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a method for preparing a nano-silicon-carbon composite anode material, comprising the following steps: S1. Tetraethyl orthosilicate and multi-element doped precursor are dissolved together in a water-ethanol mixed solvent, a structure directing agent is added, and the mixture is stirred in an oil bath to obtain a silicon-based precursor reaction solution. S2. Add deionized water to the silicon-based precursor reaction solution to stop the reaction, let it stand, filter it, collect the solid precipitate obtained by filtration, dry the solid precipitate and grind it to obtain silicon-based precursor solid powder. S3. Dissolve the silicon-based precursor solid powder in dimethyl sulfoxide, stir to dissolve, add MOF-derived reducing agent and continue stirring, then add plasma initiator dropwise and continue stirring, and finally transfer the reaction system to deionized water and continue stirring to obtain a composite reaction solution. S4. The stirred composite reaction solution is allowed to stand to form a suspension, and the suspension is centrifuged to collect the solid components obtained by centrifugation and disperse them in a solvent to obtain a porous silicon-carbon composite precursor colloidal solution. S5. After pretreating the current collector, a treated current collector is obtained. The porous silicon-carbon composite precursor colloidal solution is coated onto the surface of the treated current collector. The coated current collector is then subjected to laser-induced treatment and vacuum drying to obtain a nano-silicon-carbon composite anode material with a three-dimensional conductive network.

[0007] Preferably, in S1, the multi-element doped precursor is a mixture of triethyl borate, triethyl phosphate, and 3-aminopropyltriethoxysilane, with a molar ratio of 1:1:1; the molar ratio of tetraethyl orthosilicate to the total molar ratio of the multi-element doped precursor is 1:1.0~1.2; the added structure directing agent is an amphiphilic block copolymer PEO-PPO-PEO, with a molar ratio of the structure directing agent to the tetraethyl orthosilicate of 0.3:1; and the volume ratio of water to ethanol in the water-ethanol mixed solvent is 1:0.3~0.7.

[0008] Preferably, in S1, the oil bath is a constant temperature oil bath, the stirring method is mechanical stirring, the stirring speed is 200~300 r / min, the stirring temperature is 40~50℃, and the stirring reaction time after adding the structure guiding agent is 24~36 h.

[0009] Preferably, in step S2, the volume of deionized water added is 2 to 3 times the volume of the silicon-based precursor reaction liquid; the standing time is 12 to 24 hours; during the filtration, the solid precipitate is washed sequentially with ethanol and deionized water, with each reagent washing 3 to 5 times; and the solid precipitate is dried in a vacuum oven at a temperature of 60 to 70°C for 8 to 12 hours, with a vacuum degree of -0.08 to -0.1 MPa. The dried solid precipitate is then ground in a mortar and pestle into powder with a particle size of 50 to 100 nm to obtain the silicon-based precursor solid powder.

[0010] Preferably, in step S3, the silicon-based precursor solid powder is dissolved in dimethyl sulfoxide and stirred at 18-22°C for 0.5-1.5 h until completely dissolved; the MOF-derived reducing agent is magnesium ion-modified zeolite imidazole ester framework material Mg-ZIF-8, and the mass ratio of silicon-based precursor solid powder to MOF-derived reducing agent is 1:0.6-1.0; after adding the MOF-derived reducing agent, stirring is continued for 4-6 h; the plasma initiator is hydrogen peroxide, and the amount added is 5-10 mL, and stirring is continued for 20-28 h after addition; the volume transferred to deionized water is 400-600 mL, and stirring is continued for 4-8 h.

[0011] Preferably, in step S4, the standing time of the composite reaction solution is 8-12 hours; the centrifugation process uses a high-speed refrigerated centrifuge with a centrifugation speed of 7000-8000 r / min, a processing time of 3-5 min, and a centrifugation temperature of 20-25°C; the collected solid component obtained by centrifugation is a porous silicon-carbon composite intermediate, and its mass ratio with the dispersing solvent dimethyl sulfoxide is 1:10-15. The dispersion process is carried out by ultrasonic dispersion for 30-60 min to obtain a porous silicon-carbon composite precursor colloidal solution.

[0012] Preferably, in step S5, the current collector is a copper foil with a thickness of 8-12 μm. The pretreatment of the current collector specifically involves: immersing the copper foil in 0.5-1.0 mol / L dilute hydrochloric acid for 5-10 minutes to remove the surface oxide layer, then washing it repeatedly with deionized water until the rinsing solution is neutral, and finally vacuum drying; coating the treated copper foil surface with a colloidal solution using a coater, with a coating thickness of 50-100 μm; after coating, the current collector is induced by a femtosecond laser with a wavelength of 1030 nm and a pulse width of <600 fs, and then placed in a vacuum oven at 65-75°C for 6-8 hours to dry, so that the colloidal solution solidifies to form a dense porous nano-silicon-carbon composite negative electrode material.

[0013] Secondly, the present invention also provides a nano-silicon-carbon composite anode material prepared by the above-mentioned preparation method. The nano-silicon-carbon composite anode material has a dense porous structure with an internally interconnected three-dimensional conductive network and a surface covered with an ultrathin fluorinated interface layer. The volume resistivity of the nano-silicon-carbon composite anode material is ≤8Ω·cm, the volume expansion rate is <18%, and the specific capacity is ≥1800mAh / g. The silicon phase in the nano-silicon-carbon composite anode material is Si / SiO. x The complex phase has x = 0.6~1.0; the carbon phase is a composite phase of laser-induced graphene and MOF-derived carbon; the total amount of multi-element doping is 2.0~5.0 at.

[0014] Preferably, the porous structure of the nano-silicon-carbon composite anode material has a pore size of 10-200 nm, a porosity of 40-60%, an ultrathin fluorinated interface layer thickness of 2-5 nm, and a fluorine content of 1.5-2.5 at.

[0015] On the other hand, the present invention also provides a battery assembly, including the above-mentioned nano-silicon-carbon composite negative electrode material, positive electrode sheet, separator and electrolyte, wherein the nano-silicon-carbon composite negative electrode material, positive electrode sheet, separator and electrolyte are assembled to form a battery cell, and / or a module or battery pack composed of the battery cell.

[0016] Compared with the prior art, the present invention discloses at least the following technical effects: (1) This invention constructs a controllable silicon-based precursor by combining tetraethyl orthosilicate with a multi-element doped precursor under the action of a structure directing agent, and introduces MOF-derived reducing agents and plasma initiators to achieve a mild and controllable transformation of the porous silicon-carbon composite precursor, thereby constructing a Si / SiO2 composite material. x The composite carbon phase structure, which combines multiphase with laser-induced graphene and MOF-derived carbon, and the synergistic effect of multi-element gradient doping with the composite carbon phase, can effectively alleviate the volume expansion effect during the charging and discharging process of silicon-based materials and significantly improve the conductivity of the materials. It fundamentally solves the core defects of existing silicon-carbon anode materials, such as high volume expansion rate and insufficient conductivity, and simultaneously improves the specific capacity and structural stability of the materials.

[0017] (2) This invention constructs a continuous three-dimensional conductive network in situ by laser induction, combined with an ultrathin fluorinated interface layer formed on the surface of the nano-silicon-carbon composite anode material. It optimizes both the conductive network and interface stability, which can improve the continuity of electron transport, reduce the internal resistance and polarization of the electrode, effectively suppress the interface side reaction between silicon-based materials and electrolyte, avoid abnormal growth of passivation layer, and provide a stable transport channel for lithium ions through the porous structure, promote the uniform insertion and extraction of lithium ions, significantly improve the cycle stability and consistency of the anode material, and ensure the long-term reliable electrochemical performance of the battery.

[0018] (3) The preparation method of the present invention is simple and controllable. From the preparation of silicon-based precursors and the synthesis of porous silicon-carbon composite precursors to the molding of negative electrode materials, conventional industrial equipment and processes are used. No complicated operations or special consumables are required. The parameters of each step are controllable and have good repeatability. The pretreated copper foil current collector and coating are tightly bonded and are not easy to fall off after curing. It takes into account both preparation efficiency and cost advantages, and is suitable for the integrated application of electrode sheets and cell components. It provides key technical support for the commercial application of high energy density lithium-ion batteries. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a method for preparing a nano-silicon-carbon composite anode material according to the present invention; Figure 2 This is a SEM image of a nano-silicon-carbon composite anode material of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1As shown, this invention provides a method for preparing a nano-silicon-carbon composite anode material, comprising the following steps: S1. Tetraethyl orthosilicate and the multi-element doped precursor are dissolved together in a water-ethanol mixed solvent, a structure directing agent is added, and the mixture is stirred in an oil bath to obtain a silicon-based precursor reaction solution.

[0024] Specifically, the multi-element doping precursor is a mixture of triethyl borate, triethyl phosphate, and 3-aminopropyltriethoxysilane in a molar ratio of 1:1:1. This ratio ensures that boron, phosphorus, and nitrogen are uniformly introduced into the precursor system, avoiding uneven doping distribution caused by excessive amounts of a single element, thus laying the foundation for subsequent multi-element synergistic modification of the material. The molar ratio of tetraethyl orthosilicate to the total molar ratio of the multi-element doping precursor is 1:1.0~1.2, ensuring a suitable ratio between the silicon source and the dopant source. This ensures both the content of the silicon-based matrix to maintain high specific capacity and avoids insufficient silicon phase proportion due to excessive dopant. The added structure-directing agent is an amphiphilic block copolymer PEO-PPO-PEO, with a molar ratio of 0.3:1 to tetraethyl orthosilicate. This structure-directing agent can self-assemble... The device regulates the microstructure of the silicon-based precursor, guiding the formation of an ordered mesoporous morphology and providing a template for the subsequent construction of porous structures. The water-ethanol mixed solvent has a water-to-ethanol volume ratio of 1:0.3~0.7, which is suitable for the hydrolysis characteristics of tetraethyl orthosilicate, ensuring the smooth progress of the hydrolysis reaction and avoiding precursor agglomeration caused by a single solvent. The stirring method is mechanical stirring at a speed of 200~300 r / min, which can ensure uniform mixing of raw materials and avoid uneven precursor particle size caused by excessively high local concentrations. The stirring temperature is 40~50℃, and the stirring reaction time after adding the structure-directing agent is 24~36h. This temperature range can ensure the activity of hydrolysis and condensation reactions, avoiding excessively slow reaction rates at low temperatures or excessively rapid solvent evaporation at high temperatures. Sufficient reaction time can ensure that the precursor is fully formed and structurally stable.

[0025] S2. Add deionized water to the silicon-based precursor reaction solution to stop the reaction, let it stand, filter it, collect the solid precipitate obtained by filtration, dry the solid precipitate and grind it to obtain silicon-based precursor solid powder.

[0026] Specifically, the volume of deionized water added is 2-3 times the volume of the silicon-based precursor reaction solution. Excess deionized water rapidly reduces the concentration of the reaction system, allowing the silicon-based precursor to precipitate fully and simultaneously halting subsequent hydrolysis reactions, thus preventing excessive growth of the precursor structure. A standing time of 12-24 hours allows for sufficient settling of the solid precipitate, reducing precipitate loss during filtration. During filtration, the solid precipitate is washed sequentially with ethanol and deionized water, 3-5 times with each reagent. Ethanol dissolves residual hydrophobic unreacted raw materials, while deionized water removes hydrophilic byproducts and residual solvents, achieving efficient impurity removal and ensuring the purity of the silicon-based precursor. The solid precipitate was dried in a vacuum oven at a temperature of 60-70℃ for 8-12 hours, with a vacuum level of -0.08 to -0.1 MPa. This condition allowed for the rapid removal of adsorbed solvent from the precipitate while avoiding thermal decomposition of the precursor, and ensured complete evaporation of moisture to prevent residual solvent from affecting subsequent dissolution. The dried solid precipitate was then ground in a mortar to a powder with a particle size of 50-100 nm. Grinding increased the specific surface area of ​​the precursor, shortened the dissolution time in dimethyl sulfoxide, and ensured uniform particle size, preventing uneven dissolution due to particle agglomeration and improving the uniformity of subsequent reactions.

[0027] S3. Dissolve the silicon-based precursor solid powder in dimethyl sulfoxide, stir to dissolve, add MOF-derived reducing agent and continue stirring, then add plasma initiator dropwise and continue stirring, finally transfer the reaction system to deionized water and continue stirring to obtain a composite reaction solution.

[0028] Specifically, the silicon-based precursor solid powder is dissolved in dimethyl sulfoxide and stirred at 18-22°C for 0.5-1.5 hours until completely dissolved. 18-22°C is the optimal dissolution temperature for this precursor in dimethyl sulfoxide, ensuring solvent stability while avoiding solvent evaporation at high temperatures or incomplete dissolution at low temperatures. It also ensures a homogeneous solution system for the precursor, providing a stable environment for subsequent reactions. The MOF-derived reducing agent is a magnesium ion-modified zeolite imidazole ester framework material, Mg-ZIF-8. The mass ratio of the silicon-based precursor solid powder to the MOF-derived reducing agent is 1:0.6-1.0. Mg-ZIF-8 acts as a reducing agent to achieve the mild reduction of the silicon-based precursor, generating Si / SiO₂. xThe reaction mixture can form a carbon network after carbonization, achieving the integration of reduction and carbon phase construction. After adding the MOF-derived reducing agent, stirring is continued for 4-6 hours to ensure thorough mixing of the reducing agent and precursor solution, guaranteeing the uniformity of the reduction reaction. The plasma initiator is hydrogen peroxide, added in 5-10 mL amounts. Hydrogen peroxide can activate the reaction system, promote the full progress of the reduction reaction, and simultaneously introduce oxygen-containing active groups. After addition, stirring is continued at 18-22°C for 20-28 hours to ensure complete reduction and modification reactions and avoid incomplete local reactions leading to uneven product structure. Finally, the reaction system is transferred to 400-600 mL of deionized water and stirred at 18-22°C for 4-8 hours. Solvent displacement allows the reaction product to precipitate fully, while ensuring uniform dispersion of product particles and avoiding agglomeration.

[0029] S4. The stirred composite reaction solution is allowed to stand to form a suspension, and the suspension is centrifuged to collect the solid components obtained by centrifugation and disperse them in a solvent to obtain a porous silicon-carbon composite precursor colloidal solution.

[0030] Specifically, the composite reaction solution is allowed to stand for 8-12 hours, allowing the product particles to settle sufficiently and form a uniformly layered suspension, facilitating subsequent centrifugal separation. The centrifugation process uses a high-speed refrigerated centrifuge at 7000-8000 r / min for 3-5 minutes at a temperature of 20-25°C. These parameters efficiently separate large, incompletely dispersed impurities from the suspension while avoiding excessive centrifugation that could lead to particle agglomeration and sedimentation, ensuring the purity and dispersibility of the collected solid components. The collected solid components obtained from centrifugation are porous silicon-carbon composite intermediates, with a mass ratio of 1:10-15 to the dispersing solvent dimethyl sulfoxide. This ratio ensures the intermediates are fully dispersed to form a stable colloidal solution, preventing excessive concentration from causing agglomeration or excessively low concentration from affecting subsequent coating effects. Ultrasonic dispersion for 30-60 minutes further refines the particle size of the solid components, improving the dispersibility of the colloidal solution and laying the foundation for uniform coating.

[0031] S5. After pretreating the current collector, a treated current collector is obtained. The porous silicon-carbon composite precursor colloidal solution is coated onto the surface of the treated current collector. The coated current collector is then subjected to laser-induced treatment and vacuum drying to obtain a nano-silicon-carbon composite anode material with a three-dimensional conductive network.

[0032] Specifically, the current collector is a copper foil with a thickness of 8-12 μm. This thickness ensures the mechanical strength of the current collector while avoiding excessive thickness that would increase the overall mass of the electrode, thus meeting the requirements of high-energy-density batteries. The current collector pretreatment involves immersing the copper foil in 0.5-1.0 mol / L dilute hydrochloric acid for 5-10 minutes. The dilute hydrochloric acid reacts with the oxide layer on the copper foil surface, removing the oxide layer and oil. The foil is then washed multiple times with deionized water until the rinsing solution is neutral, preventing residual hydrochloric acid from corroding the copper foil substrate and providing a clean surface for the tight bonding of the colloidal solution and the current collector. Finally, the surface moisture is removed by vacuum drying. The colloidal solution is then coated onto the treated copper foil surface using a coating applicator, with a coating thickness of [missing information]. With a coating thickness of 50~100μm, the coater can precisely control the coating thickness, ensuring uniform coverage of the current collector surface and avoiding localized cracking due to excessive coating thickness or insufficient performance due to insufficient coating thickness. After coating, the current collector is induced by a femtosecond laser with a wavelength of 1030nm and a pulse width of <600fs. The ultra-high power density of the laser can convert the carbon material in the coating into laser-induced graphene in situ, constructing a through-through three-dimensional conductive network. Subsequently, it is dried in a vacuum oven at 65~75℃ for 6~8h. This condition allows the colloidal solution to fully solidify and form a dense porous coating, while avoiding high temperature-induced coating structure damage. The final coating is tightly bonded to the current collector and has the characteristics of high specific capacity, low volume expansion, and high conductivity.

[0033] In addition, such as Figure 2 As shown, the nano-silicon-carbon composite anode material prepared according to the above method has a dense porous structure with an internal three-dimensional conductive network and an ultrathin fluorinated interface layer on the surface; the silicon phase in the nano-silicon-carbon composite anode material is Si / SiO. x The composite phase consists of x = 0.6~1.0; the carbon phase is a composite phase of laser-induced graphene and MOF-derived carbon; the total amount of multi-element doping is 2.0~5.0 at%. Furthermore, the porous structure of the nano-silicon-carbon composite anode material has a pore size of 10~200 nm, a porosity of 40~60%, an ultrathin fluorinated interface layer thickness of 2~5 nm, and a fluorine content of 1.5~2.5 at.

[0034] The above content will be further elaborated below through specific implementation methods. It should be noted that the provided embodiments are only some embodiments of the present invention.

[0035] Example 1 A method for preparing a nano-silicon-carbon composite anode material includes the following steps: Step 1: Dissolve tetraethyl orthosilicate (0.1 mol) and multi-element doped precursor (0.033 mol each of triethyl borate, triethyl phosphate, and 3-aminopropyltriethoxysilane, totaling 0.1 mol) in a water-ethanol mixed solvent (50 mL water and 20 mL ethanol, volume ratio 1:0.4). Add the structure-directing agent PEO-PPO-PEO (0.03 mol), place the mixture in a constant temperature oil bath, and mechanically stir at 250 r / min. The stirring temperature is 45 °C, and the reaction time is 30 h to obtain the silicon-based precursor reaction solution. Step 2: Add 140 mL of deionized water to the above silicon-based precursor reaction solution to stop the reaction. After standing for 18 h, filter and collect the solid precipitate. Wash it with ethanol and deionized water four times in sequence. Place the precipitate in a vacuum oven and dry it at 65 °C and -0.09 MPa for 10 h. Grind it into powder with a particle size of 80 nm to obtain silicon-based precursor solid powder. Step 3: Dissolve 10g of silicon-based precursor solid powder in 100mL of dimethyl sulfoxide and stir at 20℃ for 1h until completely dissolved. Add 8g of MOF-derived reducing agent Mg-ZIF-8 and continue stirring for 5h. Add 8mL of hydrogen peroxide dropwise and continue stirring at 20℃ for 24h. Finally, transfer the reaction system to 500mL of deionized water and continue stirring for 6h to obtain the composite reaction solution. Step 4: Let the composite reaction solution stand for 10 hours to form a suspension. Centrifuge at 7500 r / min and 23℃ for 3 min using a high-speed refrigerated centrifuge. Collect the solid components and disperse them in dimethyl sulfoxide at a mass ratio of 1:12. Sonicate for 45 min to obtain a porous silicon-carbon composite precursor colloidal solution. Step 5: Take a copper foil with a thickness of 10 μm, immerse it in 0.8 mol / L dilute hydrochloric acid for 8 min, wash it with deionized water until the rinsing solution is neutral, and vacuum dry it; use a coater to scrape the colloidal solution onto the surface of the copper foil to a thickness of 80 μm, and after femtosecond laser (wavelength 1030 nm, pulse width 500 fs) induction treatment, place it in a vacuum oven at 70℃ and dry it for 7 h to obtain nano-silicon-carbon composite anode material.

[0036] Example 2 A method for preparing a nano-silicon-carbon composite anode material includes the following steps: Step 1: Dissolve tetraethyl orthosilicate (0.1 mol) and multi-element doped precursor (0.04 mol each of triethyl borate, triethyl phosphate, and 3-aminopropyltriethoxysilane, totaling 0.12 mol) in a water-ethanol mixed solvent (50 mL water and 35 mL ethanol, volume ratio 1:0.7). Add the structure-directing agent PEO-PPO-PEO (0.03 mol), place the mixture in a constant temperature oil bath, and mechanically stir at 300 r / min. The stirring temperature is 50 °C, and the reaction time is 36 h to obtain the silicon-based precursor reaction solution. Step 2: Add 170 mL of deionized water to the above silicon-based precursor reaction solution to stop the reaction. After standing for 24 h, filter and collect the solid precipitate. Wash it 5 times with ethanol and deionized water in turn. Place the precipitate in a vacuum oven and dry it at 70 °C and -0.1 MPa for 12 h. Grind it into powder with a particle size of 100 nm to obtain silicon-based precursor solid powder. Step 3: Dissolve 10g of silicon-based precursor solid powder in 100mL of dimethyl sulfoxide and stir at 22℃ for 1.5h until completely dissolved. Add 10g of MOF-derived reducing agent Mg-ZIF-8 and continue stirring for 6h. Add 10mL of hydrogen peroxide dropwise and continue stirring at 22℃ for 28h. Finally, transfer the reaction system to 600mL of deionized water and continue stirring for 8h to obtain the composite reaction solution. Step 4: Let the composite reaction solution stand for 12 hours to form a suspension. Centrifuge at 8000 r / min and 25℃ for 5 min using a high-speed refrigerated centrifuge. Collect the solid components and disperse them in dimethyl sulfoxide at a mass ratio of 1:15. Sonicate for 60 min to obtain a porous silicon-carbon composite precursor colloidal solution. Step 5: Take a copper foil with a thickness of 12μm, immerse it in 1.0mol / L dilute hydrochloric acid for 10min, wash it with deionized water until the rinsing solution is neutral, and vacuum dry it; use a coater to scrape the colloidal solution onto the surface of the copper foil to a thickness of 100μm, and after femtosecond laser (wavelength 1030nm, pulse width 550fs) induction treatment, place it in a vacuum oven at 75℃ and dry it for 8h to obtain nano-silicon-carbon composite anode material.

[0037] Example 3 A method for preparing a nano-silicon-carbon composite anode material includes the following steps: Step 1: Dissolve tetraethyl orthosilicate (0.1 mol) and multi-element doped precursor (0.033 mol each of triethyl borate, triethyl phosphate, and 3-aminopropyltriethoxysilane, totaling 0.1 mol) in a water-ethanol mixed solvent (50 mL water and 15 mL ethanol, volume ratio 1:0.3). Add the structure-directing agent PEO-PPO-PEO (0.03 mol), place the mixture in a constant temperature oil bath, and mechanically stir at 200 r / min. The stirring temperature is 40 °C, and the reaction time is 24 h to obtain the silicon-based precursor reaction solution. Step 2: Add 100 mL of deionized water to the above silicon-based precursor reaction solution to stop the reaction. After standing for 12 h, filter and collect the solid precipitate. Wash it three times with ethanol and deionized water in turn. Place the precipitate in a vacuum oven and dry it for 8 h at 60 °C and -0.08 MPa. Grind it into powder with a particle size of 50 nm to obtain silicon-based precursor solid powder. Step 3: Dissolve 10g of silicon-based precursor solid powder in 100mL of dimethyl sulfoxide and stir at 18℃ for 0.5h until completely dissolved. Add 6g of MOF-derived reducing agent Mg-ZIF-8 and continue stirring for 4h. Add 5mL of hydrogen peroxide and continue stirring at 18℃ for 20h. Finally, transfer the reaction system to 400mL of deionized water and continue stirring for 4h to obtain the composite reaction solution. Step 4: Let the composite reaction solution stand for 8 hours to form a suspension. Centrifuge at 7000 r / min and 20℃ for 2 min using a high-speed refrigerated centrifuge. Collect the solid components and disperse them in dimethyl sulfoxide at a mass ratio of 1:10. Sonicate for 30 min to obtain a porous silicon-carbon composite precursor colloidal solution. Step 5: Take a copper foil with a thickness of 8μm, immerse it in 0.5mol / L dilute hydrochloric acid for 5min, wash it with deionized water until the rinsing solution is neutral, and vacuum dry it; use a coater to scrape the colloidal solution onto the surface of the copper foil with a coating thickness of 50μm, and after femtosecond laser (wavelength 1030nm, pulse width 450fs) induction treatment, place it in a vacuum oven at 65℃ and dry it for 6h to obtain nano-silicon-carbon composite anode material.

[0038] Comparative Example 1 (using conventional magnesium powder reducing agent instead of MOF-derived reducing agent) The remaining steps are the same as in Example 1, except that step three is replaced by: dissolving 10g of silicon-based precursor solid powder in 100mL of dimethyl sulfoxide, stirring at 20°C for 1h until completely dissolved, adding 8g of magnesium powder as a reducing agent, continuing to stir for 5h, adding 8mL of hydrogen peroxide dropwise, stirring continuously at 20°C for 24h, and finally transferring the reaction system to 500mL of deionized water, continuing to stir for 6h to obtain the composite reaction solution.

[0039] Comparative Example 2 (no laser-induced treatment was used; the conductive network was constructed using high-temperature carbonization) The remaining steps are the same as in Example 1, except that step five is replaced as follows: take a copper foil with a thickness of 10 μm, immerse it in 0.8 mol / L dilute hydrochloric acid for 8 min, wash it with deionized water until the rinsing solution is neutral, and vacuum dry it; use a coater to scrape the colloidal solution onto the surface of the copper foil with a coating thickness of 80 μm, place it in a muffle furnace at 800℃ for 2 h for carbonization, and then place it in a vacuum oven at 70℃ for 7 h to dry it, thus obtaining the nano-silicon-carbon composite anode material.

[0040] Comparative Example 3 (no multi-element doping, only single carbon coating) The remaining steps are the same as in Example 1, except that step one is replaced by: dissolving tetraethyl orthosilicate (0.1 mol) in a water-ethanol mixed solvent (50 mL water, 20 mL ethanol, volume ratio 1:0.4), adding the structure directing agent PEO-PPO-PEO (0.03 mol), and then placing it in a constant temperature oil bath with mechanical stirring at 250 r / min, stirring temperature 45℃, and reaction time 30 h to obtain the silicon-based precursor reaction solution.

[0041] Performance testing The nano-silicon-carbon composite anode materials prepared in Examples 1-3 and Comparative Examples 1-3 were assembled into CR2032 coin cells. The positive electrode was LiCoO2, the electrolyte was 1 mol / L LiPF6 / EC-DMC-EMC, and the separator was Celgard 2400. Electrochemical performance was tested at 25°C. The test parameters included initial discharge specific capacity, capacity retention after 300 cycles, volume expansion rate, and volume resistivity. The results are shown in Table 1 below. Table 1 Performance Test Results

[0042] The test results above show that the nano-silicon-carbon composite anode materials prepared in Examples 1-3 all exhibit excellent comprehensive performance: the initial discharge specific capacity is ≥1830mAh / g, which is much higher than that of the comparative examples; after 300 cycles, the capacity retention rate is ≥91.2%, the volume expansion rate is <17%, and the volume resistivity is ≤6.7Ω·cm. Comparative Example 1 did not use MOF-derived reducing agent, and the reduction uniformity of traditional magnesium powder was poor, which made it impossible to construct a dense carbon network simultaneously, resulting in a significant decrease in specific capacity and conductivity; Comparative Example 2 did not use laser-induced treatment, and the conductive network constructed by high-temperature carbonization had insufficient connectivity, poor interface stability, and deteriorated cycle performance and volume stability; Comparative Example 3 lacked multi-element doping, and the single carbon coating was insufficient to synergistically improve conductivity and structural stability, resulting in the worst comprehensive performance.

[0043] Therefore, the above-mentioned method for preparing a nano-silicon-carbon composite anode material and its battery assembly involves constructing a controllable silicon-based precursor using tetraethyl orthosilicate and a multi-element doped precursor under the action of a structure guiding agent. A MOF-derived reducing agent and a plasma initiator are introduced to achieve a mild and controllable conversion of the porous silicon-carbon composite precursor. Furthermore, a laser-induced in-situ construction of a laser-induced graphene / MOF-derived carbon synergistic interconnected three-dimensional conductive network is formed on a pretreated copper foil current collector, simultaneously creating an ultrathin fluorinated interface layer. This synergistic approach suppresses silicon-based volume effects and interface side reactions from three aspects: material structure, conductive network, and current collector interface. It reduces electrode internal resistance and polarization, improves electron transport continuity and structural stability, thereby achieving lower volume resistivity, smaller volume expansion, and better cycle stability and consistency under higher specific capacity conditions. Moreover, the process is simple, highly controllable, and suitable for the integrated application of electrode sheets and battery cell components.

[0044] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0045] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a nano-silicon-carbon composite anode material, characterized in that, Includes the following steps: S1. Tetraethyl orthosilicate and multi-element doped precursor are dissolved together in a water-ethanol mixed solvent, a structure directing agent is added, and the mixture is stirred in an oil bath to obtain a silicon-based precursor reaction solution. S2. Add deionized water to the silicon-based precursor reaction solution to stop the reaction, let it stand, filter it, collect the solid precipitate obtained by filtration, dry the solid precipitate and grind it to obtain silicon-based precursor solid powder. S3. Dissolve the silicon-based precursor solid powder in dimethyl sulfoxide, stir to dissolve, add MOF-derived reducing agent and continue stirring, then add plasma initiator dropwise and continue stirring, and finally transfer the reaction system to deionized water and continue stirring to obtain a composite reaction solution. S4. The stirred composite reaction solution is allowed to stand to form a suspension, and the suspension is centrifuged to collect the solid components obtained by centrifugation and disperse them in a solvent to obtain a porous silicon-carbon composite precursor colloidal solution. S5. After pretreating the current collector, a treated current collector is obtained. The porous silicon-carbon composite precursor colloidal solution is coated onto the surface of the treated current collector. The coated current collector is then subjected to laser-induced treatment and vacuum drying to obtain a nano-silicon-carbon composite anode material with a three-dimensional conductive network.

2. The preparation method according to claim 1, characterized in that, In S1, the multi-element doped precursor is a mixture of triethyl borate, triethyl phosphate, and 3-aminopropyltriethoxysilane in a molar ratio of 1:1:1; the molar ratio of tetraethyl orthosilicate to the total molar ratio of the multi-element doped precursor is 1:1.0~1.2; the added structure directing agent is an amphiphilic block copolymer PEO-PPO-PEO, and the molar ratio of the structure directing agent to the tetraethyl orthosilicate is 0.3:1; the volume ratio of water to ethanol in the water-ethanol mixed solvent is 1:0.3~0.

7.

3. The preparation method according to claim 1, characterized in that, In S1, the oil bath is a constant temperature oil bath, the stirring method is mechanical stirring, the stirring speed is 200~300r / min, the stirring temperature is 40~50℃, and the stirring reaction time after adding the structure guiding agent is 24~36h.

4. The preparation method according to claim 1, characterized in that, In step S2, the volume of deionized water added is 2 to 3 times the volume of the silicon-based precursor reaction liquid; the standing time is 12 to 24 hours; during the filtration, the solid precipitate is washed sequentially with ethanol and deionized water, with each reagent washing 3 to 5 times; and the solid precipitate is dried in a vacuum oven at a temperature of 60 to 70°C for 8 to 12 hours, with a vacuum degree of -0.08 to -0.1 MPa. The dried solid precipitate is then ground in a mortar and pestle into a powder with a particle size of 50 to 100 nm to obtain the silicon-based precursor solid powder.

5. The preparation method according to claim 1, characterized in that, In step S3, the silicon-based precursor solid powder is dissolved in dimethyl sulfoxide and stirred at 18-22°C for 0.5-1.5 h until completely dissolved; the MOF-derived reducing agent is magnesium ion-modified zeolite imidazole ester framework material Mg-ZIF-8, and the mass ratio of silicon-based precursor solid powder to MOF-derived reducing agent is 1:0.6-1.0; after adding the MOF-derived reducing agent, stirring is continued for 4-6 h; the plasma initiator is hydrogen peroxide, and the amount added is 5-10 mL, and stirring is continued for 20-28 h after addition; the volume transferred to deionized water is 400-600 mL, and stirring is continued for 4-8 h.

6. The preparation method according to claim 1, characterized in that, In S4, the composite reaction solution is allowed to stand for 8-12 hours; the centrifugation is performed using a high-speed refrigerated centrifuge with a centrifugation speed of 7000-8000 r / min, a processing time of 3-5 min, and a centrifugation temperature of 20-25℃; the collected solid component obtained by centrifugation is a porous silicon-carbon composite intermediate, with a mass ratio of 1:10-15 to the dispersing solvent dimethyl sulfoxide, and ultrasonic dispersion is performed for 30-60 min to obtain a porous silicon-carbon composite precursor colloidal solution.

7. The preparation method according to claim 1, characterized in that, In S5, the current collector is a copper foil with a thickness of 8-12 μm. The pretreatment of the current collector is as follows: the copper foil is immersed in 0.5-1.0 mol / L dilute hydrochloric acid for 5-10 min to remove the surface oxide layer, then washed repeatedly with deionized water until the rinsing solution is neutral, and finally vacuum dried; the colloidal solution is coated onto the surface of the treated copper foil using a coating tool, with a coating thickness of 50-100 μm; after coating, the current collector is induced by a femtosecond laser with a wavelength of 1030 nm and a pulse width of <600 fs, and then placed in a vacuum oven at 65-75℃ for 6-8 h to dry, so that the colloidal solution is solidified to form a dense porous nano-silicon-carbon composite negative electrode material.

8. A nano-silicon-carbon composite anode material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The nano-silicon-carbon composite anode material has a dense porous structure with an internal, interconnected three-dimensional conductive network and a surface covered with an ultrathin fluorinated interface layer. The volume resistivity of the nano-silicon-carbon composite anode material is ≤8Ω·cm, the volume expansion rate is <18%, and the specific capacity is ≥1800mAh / g. The silicon phase in the nano-silicon-carbon composite anode material is Si / SiO. x The complex phase has x = 0.6~1.0; the carbon phase is a composite phase of laser-induced graphene and MOF-derived carbon; the total amount of multi-element doping is 2.0~5.0 at.

9. The nano-silicon-carbon composite anode material according to claim 8, characterized in that, The porous structure of the nano-silicon-carbon composite anode material has a pore size of 10~200nm, a porosity of 40~60%, an ultrathin fluorinated interface layer thickness of 2~5nm, and a fluorine content of 1.5~2.5at.

10. A battery assembly, characterized in that, The battery includes the nano-silicon-carbon composite negative electrode material, positive electrode sheet, separator, and electrolyte as described in claim 8, wherein the nano-silicon-carbon composite negative electrode material, positive electrode sheet, separator, and electrolyte are assembled to form a battery cell, and / or a module or battery pack composed of the battery cell.

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