A preparation process of a silicon-carbon negative electrode composite material with in-situ grown nano-silicon particles
The in-situ growth process of silicon-carbon anode composite materials using nano-silicon particles solves the cycle performance and cost issues of silicon-carbon anode materials, achieving silicon-carbon anode materials with high specific capacity and long cycle life, suitable for industrial applications in high-energy-density lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WEIHAI HENGSHENG NEW MATERIALS TECHNOLOGY CO LTD
- Filing Date
- 2025-06-09
- Publication Date
- 2026-07-24
AI Technical Summary
Existing technologies for preparing silicon-carbon anode materials suffer from problems such as silicon particle volume expansion leading to structural pulverization, SEI film instability, and particle agglomeration, resulting in low cycle performance and initial efficiency, as well as complex processes and high costs.
The process for preparing silicon-carbon anode composite materials by in-situ growth of silicon nanoparticles involves pretreating the carbon matrix material, preparing a precursor solution, and growing silicon nanoparticles under preset conditions. By controlling the reaction parameters and introducing pore-forming agents and conductive additives, a porous structure and conductive network are constructed to enhance interfacial bonding.
This method achieves uniform bonding between nano-silicon particles and a carbon matrix, improves cycle stability and first-time coulombic efficiency, optimizes ion transport pathways, reduces production costs, and meets green manufacturing requirements.
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Figure CN120607238B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of silicon-carbon anode composite preparation technology, specifically to a silicon-carbon anode composite material preparation process for in-situ growth of nano-silicon particles. Background Technology
[0002] Improving the energy density of lithium-ion batteries is crucial for the development of new energy vehicles and portable electronic devices. Currently, the theoretical specific capacity of commercially available graphite anodes (372 mAh / g) is nearing its limit, while silicon-based anodes (theoretical specific capacity approximately 4200 mAh / g) have become a research hotspot for next-generation electrode materials due to their high lithium storage capacity. However, silicon anodes face three major challenges in practical applications: (1) During charge-discharge cycles, the volume of silicon particles expands by more than 300%, leading to the pulverization and failure of the electrode structure; (2) Silicon reacts with liquid electrolyte to form an unstable solid electrolyte interphase (SEI) film, causing the first irreversible capacity loss and degradation of cycle performance; (3) Particles are prone to agglomeration, resulting in low electron / ion transport efficiency.
[0003] Existing technologies primarily improve performance through silicon nanofibers, the construction of carbon composite materials, and coating techniques. For example, while carbon-coated silicon nanofibers prepared by chemical vapor deposition significantly improve cycle life, they are costly. Silicon-carbon composite materials prepared by mechanical ball milling suffer from uneven particle size distribution (CV value > 20%) and weak interfacial bonding (initial efficiency approximately 80%). Furthermore, existing technologies propose high-temperature sintering of silicon particles with a carbon matrix, but this process is complex and energy-intensive.
[0004] Therefore, existing technologies still need further development. Summary of the Invention
[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a process for preparing silicon-carbon anode composite materials with in-situ grown nano-silicon particles, so as to solve the problems existing in the prior art.
[0006] To achieve the above-mentioned technical objectives, according to a first aspect of the present invention, the present invention provides a process for preparing silicon-carbon anode composite material with in-situ grown silicon nanoparticles, the process comprising: S100. The carbon matrix material is pretreated according to a preset method to remove surface impurities and increase surface active sites; a precursor solution containing a silicon source, a reducing agent and a solvent is prepared, wherein the silicon source is at least one of silicate and organosilicon compound, the reducing agent is at least one of sodium borohydride and lithium aluminum hydride, and the solvent is at least one of ethanol, isopropanol and deionized water. S200. The pretreated carbon matrix material is immersed in a precursor solution and reacted under preset temperature and pressure conditions to allow the silicon source to grow nano-silicon particles in situ on the surface of the carbon matrix. After the reaction, the product is washed and dried to remove unreacted impurities. The dried product is then heat-treated to enhance the interfacial bonding between the nano-silicon particles and the carbon matrix. S300: The size of nano-silicon particles is uniformly controlled by adjusting the stirring speed and temperature gradient of the reaction system; the morphology of nano-silicon particles is controlled by using template method and surfactant-assisted method; a pore-forming agent is introduced into the reaction system, and the pore-forming agent decomposes to form a porous structure during heat treatment, thus optimizing the pore structure of the composite material; a conductive additive is added to the composite material, and a conductive network is constructed by mechanical stirring and ultrasonic dispersion, finally obtaining a silicon-carbon anode composite material with in-situ grown nano-silicon particles.
[0007] Specifically, the preset method is at least one of acid washing, alkaline washing, and plasma treatment.
[0008] Specifically, the preset temperature is 60℃-200℃, and the preset pressure is 0.1MPa-3MPa.
[0009] Specifically, the pH and temperature of the reaction system are monitored in real time during the reaction process to maintain the stability of the reaction system.
[0010] Specifically, the template used in the template method is at least one of silica template and polystyrene template, and the surfactant is at least one of sodium dodecylbenzenesulfonate and polyethylene glycol.
[0011] Specifically, the pore-forming agent is at least one of ammonium bicarbonate and ammonium carbonate, and the decomposition temperature of the pore-forming agent during the heat treatment process is lower than the maximum temperature of the heat treatment.
[0012] Specifically, the conductive additive is at least one of carbon black, carbon nanotubes, and graphene.
[0013] Specifically, the mechanical stirring speed is 200-1000 r / min, the stirring time is 1-5 hours, the ultrasonic dispersion power is 100-500 W, and the ultrasonic time is 0.5-2 hours.
[0014] Specifically, the temperature for heat treatment of the dried product is 400℃-800℃, and the heat treatment time is 1-5 hours.
[0015] Specifically, the heat treatment is carried out under the protection of an inert gas, which is at least one of nitrogen and argon.
[0016] Beneficial effects: 1. In-situ growth of uniform nano-silicon: By controlling temperature, pressure and chemical reaction parameters, uniform silicon particle size (50±5nm) and tight bonding with carbon matrix are achieved, with a capacity retention rate of ≥90% after 500 cycles.
[0017] 2. Enhanced stability through strong interfacial bonding: In-situ polymerization and interfacial modification technology enhances the stability of the SEI film, achieving an initial coulombic efficiency of ≥88% and significantly reducing side reactions.
[0018] 3. Optimized ion transport through porous structure: The introduction of pore-forming agents forms a hierarchical porous structure, which greatly shortens the ion diffusion path at the electrode.
[0019] 4. Simple, economical and efficient process: No complicated equipment is required. The one-step reduction method combined with heat treatment reduces the production cost by more than 50% compared with chemical vapor deposition.
[0020] 5. Environmentally friendly and green production: The process produces no toxic byproducts, and the solvents can be recycled, meeting the requirements for green manufacturing of new energy materials.
[0021] In summary, this process breaks through the technical bottleneck of traditional silicon-carbon anodes, achieving a synergistic improvement in high specific capacity and long cycle life, and is expected to promote the industrial application of high-energy-density lithium-ion batteries. Attached Figure Description
[0022] Figure 1 This is a schematic flowchart of the in-situ growth process for silicon-carbon anode composite materials of nano-silicon particles provided in a specific embodiment of the present invention. Detailed Implementation
[0023] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application. Furthermore, the directional terms mentioned in the following embodiments, such as "up," "down," "left," and "right," are only for reference to the directions in the accompanying drawings; therefore, the directional terms used are for illustrative purposes and not for limiting the invention.
[0024] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments.
[0025] Please see Figure 1 This invention provides a process for preparing silicon-carbon anode composite materials with in-situ grown silicon nanoparticles, comprising: S100. The carbon matrix material is pretreated according to a preset method to remove surface impurities and increase surface active sites; a precursor solution containing a silicon source, a reducing agent and a solvent is prepared, wherein the silicon source is at least one of silicate and organosilicon compound, the reducing agent is at least one of sodium borohydride and lithium aluminum hydride, and the solvent is at least one of ethanol, isopropanol and deionized water.
[0026] Specifically, the preset method is at least one of acid washing, alkaline washing, and plasma treatment.
[0027] It is understood that the pretreatment method can be selected from at least one of acid washing, alkaline washing, or plasma treatment to pretreat the carbon matrix material, depending on the actual situation. In a preferred embodiment of the present invention, when acid washing is selected, the carbon matrix material can be immersed in a nitric acid solution of a certain concentration, the concentration of the nitric acid solution being 1-5 mol / L, for 1-3 hours, to remove surface metallic impurities; if plasma treatment is used, an appropriate power (including 300-800W in a preferred embodiment of the present invention) and treatment time (including 10-30 minutes in a preferred embodiment of the present invention) can be set in the plasma treatment equipment to increase the surface active sites of the carbon matrix material.
[0028] It should be further noted that, regarding the pretreatment of carbon-based materials, in a preferred embodiment of the present invention, the following steps are included: Equipment selection: Pickling equipment: Corrosion-resistant plastic reactor (50L capacity, polypropylene material), equipped with a magnetic stirrer (speed adjustable from 0-1000rpm); Plasma equipment: Radio frequency ion cleaner (power adjustable from 0-1000W, vacuum degree adjustable from 1-100Pa).
[0029] Specific parameters: Nitric acid solution concentration: 1.5 mol / L (error ±0.1 mol / L); Soaking time: 2 hours ± 5 minutes; Plasma treatment parameters: power 600W, oxygen flow rate 20L / min, treatment time 25 minutes; Water washing standard: conductivity <5μS / cm (tested after three washes with pure water).
[0030] Quality control: Surface roughness was observed using SEM (Ra value should reach 50-100 nm), and surface functional groups were analyzed using XPS (hydroxyl / carboxyl content > 3 atoms%).
[0031] It is understood that, regarding the preparation of the precursor solution, the silicon source is selected from at least one of silicates (including sodium silicate in a preferred embodiment of the present invention) and organosilicon compounds (including tetraethyl orthosilicate in a preferred embodiment of the present invention); the reducing agent is selected from at least one of sodium borohydride and lithium aluminum hydride; and the solvent is selected from at least one of ethanol, isopropanol, and deionized water. In a preferred embodiment of the present invention, the ratio of the silicon source, reducing agent, and solvent can be adjusted according to actual needs when preparing the precursor solution.
[0032] Specifically, in a preferred embodiment of the present invention, the raw material selection scheme for preparing the precursor solution includes: The raw material specifications in the preferred embodiments of the present invention are shown in Table 1: Table 1 Raw Material Specifications Preparation process: Primary solution: TEOS and anhydrous ethanol are mixed at a volume ratio of 1:3 and magnetically stirred for 1 hour (300 rpm). Reducing agent solution: Sodium borohydride is prepared into a 5 wt% ethanol solution (prepare fresh and store away from light); Final mixing: Mix the primary solution and the reducing agent solution at a volume ratio of 5:1 and stir continuously for 45 minutes; Additives: 0.1 wt% sodium dodecylbenzenesulfonate was added as a dispersant.
[0033] Stability control: Temperature control: The entire preparation process is carried out at an environment of 15±2℃; Vacuum degassing: Degas for 20 minutes using a rotary vane vacuum pump (ultimate vacuum 5 Pa).
[0034] S200. The pretreated carbon matrix material is immersed in a precursor solution and reacted under preset temperature and pressure conditions to allow the silicon source to grow nano-silicon particles in situ on the carbon matrix surface. After the reaction, the product is washed and dried to remove unreacted impurities. The dried product is then heat-treated to enhance the interfacial bonding between the nano-silicon particles and the carbon matrix.
[0035] It should be noted that, regarding the in-situ growth of silicon nanoparticles, the preferred embodiment of this invention includes the following: Impregnation and reaction condition control: The pretreated carbon matrix material was impregnated in the precursor solution, and then the reaction was carried out under the conditions of 60℃-200℃ and atmospheric pressure-5MPa.
[0036] Uniform control of nano-silicon particle size: The uniformity of nano-silicon particle size is achieved by adjusting the stirring speed and temperature gradient of the reaction system. Specifically, the stirring speed can be controlled between 200-1000 r / min, which can be achieved by installing a stirrer and setting an appropriate rotation speed; the temperature gradient can be controlled by setting a partitioned heating or cooling device in the reaction vessel to create a certain temperature difference at different locations in the reaction system. In a preferred embodiment of the present invention, the temperature difference is controlled between 5-20℃.
[0037] Real-time monitoring and stability maintenance: The stability of the reaction system is maintained by real-time monitoring of the pH and temperature during the reaction process. A pH meter and temperature sensor can be installed. When the pH value deviates from the set range (including 3-7 in the preferred embodiment of the invention), it is adjusted by adding an appropriate amount of acid or alkali. When the temperature fluctuates by more than ±5°C, the heating or cooling system is adjusted to ensure uniform size of the nano-silicon particles.
[0038] It should be noted that, regarding product processing, the preferred embodiment of the present invention includes the following: Washing and drying: After the reaction is complete, the product is washed with deionized water multiple times to remove unreacted impurities. Then it is dried. The drying temperature can be set at 60-100℃ and the drying time is 6-12 hours.
[0039] Specifically, the preset temperature is 60℃-200℃, and the preset pressure is 0.1MPa-3MPa.
[0040] Specifically, the pH and temperature of the reaction system are monitored in real time during the reaction process to maintain the stability of the reaction system.
[0041] Specifically, the temperature for heat treatment of the dried product is 400℃-800℃, and the heat treatment time is 1-5 hours.
[0042] Specifically, the heat treatment is carried out under the protection of an inert gas, which is at least one of nitrogen and argon.
[0043] It should be noted that, regarding the heat treatment-enhanced interface bonding, the design scheme of this invention includes the following in a preferred embodiment: Heat treatment conditions: The dried product is subjected to heat treatment at a temperature of 400℃-800℃ for 1-5 hours. The heat treatment is carried out under the protection of an inert gas (in a preferred embodiment of the present invention, at least one of nitrogen and argon) and the flow rate of the inert gas can be controlled at 10-50 ml / min.
[0044] Morphology Control Using Template and Surfactant-Assisted Methods: The morphology of silicon nanoparticles is precisely controlled using template and surfactant-assisted methods. In the template method, the template used can be at least one of silica templates or polystyrene templates. In a preferred embodiment of the invention, when using a silica template, the template is first immersed in a precursor solution containing a silicon source and a reducing agent, and then the above-mentioned reaction and heat treatment steps are performed. Finally, the template is removed by chemical etching to obtain silicon nanoparticles with a specific morphology. The surfactant can be at least one of sodium dodecylbenzenesulfonate or polyethylene glycol. Adding an appropriate amount of surfactant to the reaction system adjusts the growth environment of the silicon nanoparticles, achieving precise morphology control.
[0045] It should be further noted that, regarding the in-situ growth reaction system, the design scheme of the present invention includes the following in the preferred embodiment: The reaction device is designed as a multi-layer reactor structure: Inner layer: Corrosion-resistant Hastelloy alloy reactor (2L capacity); Middle layer: Oil bath heating layer (temperature control accuracy ±0.5℃); Outer layer: Inert gas protective layer (nitrogen flow rate adjustable from 0-50 ml / min); Mixing system: Anchor-type mixing paddle + ultrasonic disperser (dual-mode drive).
[0046] The reaction parameters in the preferred embodiments of the present invention are shown in Table 2: Table 2 Reaction parameters Online monitoring system; pH online monitoring: glass electrode sensor (accuracy ±0.02pH); Viscosity monitoring: Digital viscometer (range 0.1-1000 mPa·s); Pressure monitoring: Piezoresistive sensor (accuracy ±0.1%FS).
[0047] It should be further noted that, regarding the interface strengthening heat treatment, the heat treatment process designed in the preferred embodiment of the present invention includes the following: Heat treatment process: Heating program: Heat to 200℃ at a rate of 10℃ / min (hold for 30min); Heat to 400℃ at a rate of 5℃ / min (hold for 60min); Increase the temperature by 2℃ / min to the final temperature (600-800℃).
[0048] Insulation time: 2-4 hours; Cooling method: Inert gas protection and furnace cooling (≤50℃ / min); Equipment requirements: Tubular furnace: Maximum operating temperature 1200℃, furnace chamber size Φ60×200mm; Temperature control: PID four-channel temperature controller (temperature control accuracy ±2℃); Atmosphere system: Nitrogen purity ≥ 99.999%, flow rate adjustable from 0-500 ml / min.
[0049] S300: The size of nano-silicon particles is uniformly controlled by adjusting the stirring speed, temperature gradient, and solvent evaporation rate of the reaction system; the morphology of nano-silicon particles is controlled by template method and surfactant-assisted method; a pore-forming agent is introduced into the reaction system, and the pore-forming agent decomposes to form a porous structure during heat treatment, thereby optimizing the pore structure of the composite material; a conductive additive is added to the composite material, and a conductive network is constructed by mechanical stirring and ultrasonic dispersion, finally obtaining a silicon-carbon anode composite material with in-situ grown nano-silicon particles.
[0050] It should be noted here that the design scheme of this invention regarding hole formation and conductive network construction includes: Pore-forming agent introduction and pore structure optimization: A pore-forming agent is introduced into the reaction system. The pore-forming agent can be at least one of ammonium bicarbonate or ammonium carbonate. During heat treatment, the pore-forming agent decomposes to form a porous structure. In a preferred embodiment of the invention, a certain amount (5-20 wt%) of ammonium bicarbonate is added to the reaction system. During heat treatment, the ammonium bicarbonate decomposes to produce carbon dioxide gas, thereby forming a porous structure in the composite material. By controlling the amount of pore-forming agent and the heat treatment conditions, the pore structure of the composite material can be optimized, resulting in a porosity of 10-30% and a pore size distribution within the range of 10-100 nm.
[0051] Addition of conductive additives and construction of conductive networks: Conductive additives are added to the composite material, and the conductive additives are at least one of carbon black, carbon nanotubes, and graphene. In a preferred embodiment of the present invention, carbon black is selected as the conductive additive, and the addition amount is 1-5% of the total mass of the composite material. Then, a complete conductive network is constructed by mechanical stirring and ultrasonic dispersion. The mechanical stirring speed is 200-1000 r / min, the stirring time is 1-5 hours, and the ultrasonic dispersion power is 100-500 W, the ultrasonic time is 0.5-2 hours, so that the conductive additives are uniformly dispersed in the composite material, thereby enhancing its conductivity.
[0052] Specifically, the mechanical stirring speed is 200-1000 r / min, the stirring time is 1-5 hours, the ultrasonic dispersion power is 100-500 W, and the ultrasonic time is 0.5-2 hours.
[0053] Specifically, the template used in the template method is at least one of silica template and polystyrene template, and the surfactant is at least one of sodium dodecylbenzenesulfonate and polyethylene glycol.
[0054] Specifically, the pore-forming agent is at least one of ammonium bicarbonate and ammonium carbonate, and the decomposition temperature of the pore-forming agent during the heat treatment process is lower than the maximum temperature of the heat treatment.
[0055] Specifically, the conductive additive is at least one of carbon black, carbon nanotubes, and graphene.
[0056] It should be further noted that, regarding the control of the composite structure, the design scheme of the present invention includes the following in the preferred embodiment: Topography control technology: Template method: Template selection: mesoporous silica (pore size 20-50nm); Loading: 20-30 wt% (relative to carbon matrix); Etching process: Immerse in 1M NaOH solution at 60℃ for 4 hours.
[0057] The surfactant formulation schemes in the preferred embodiments of the present invention include those shown in Table 3: Table 3 Surfactant Compounding Schemes Pore structure optimization: Pore-forming agent selection: Ammonium bicarbonate (particle size 2-5μm); Gradient addition experiment: 5-15wt% (optimized at 1wt% intervals); Decomposition control: CO2 escape rate 1.5 ml / (g·min) (determined by TGA).
[0058] It should be further noted that, regarding the construction of the conductive network, the design scheme of the present invention includes the following in the preferred embodiment: The preferred embodiment of the present invention includes the following additive formulation schemes as shown in Table 4: Table 4. Compound formulation scheme for adjuvants Distributed equipment parameters: Ball mill: 316L stainless steel tank, media is zirconia balls (Φ1-3mm); Ultrasonic equipment: 300W power, 40kHz operating frequency, pulse mode operation (5s on, 2s off).
[0059] It should be further noted that, regarding the process scale-up technology, the design scheme of this invention includes the following in the preferred embodiment: Pilot-scale equipment parameters: Equipment size: 50L reactor (400mm diameter × 800mm height); Mass transfer system: dual-layer mechanical stirring (main stirring 500 rpm + auxiliary stirring 200 rpm); Heating system: Jacketed oil bath (temperature control accuracy ±1℃); Product collection: continuous centrifugation + three-stage washing.
[0060] Process monitoring: Online viscometer: Brookfield RVDV-II+Pro (measuring range 0.1-10) 5 cP); Particle size analyzer: Malvern Nano-ZS (dynamic light scattering, particle size range 1-1000nm); Online XRD: Bruker D8 Advance (real-time monitoring of crystal growth).
[0061] The following case study illustrates the process of preparing silicon-carbon anodes (laboratory grade): Material proportions: Nano-silicon content: 8 wt% (relative to composite materials); Carbon matrix: graphite (specific capacity ≥350mAh / g); Interface modifier: PVDF content 3wt%.
[0062] The performance test results are shown in Table 5: Table 5 Performance Test Results The following case study illustrates the process of scaling up (pilot production line): Equipment parameters: Reactor volume: 30L; Production efficiency: 2kg / batch; Product consistency: Standard deviation <5% (based on d50 particle size).
[0063] The cost analysis results are shown in Table 6: Table 6 Cost Analysis Results The following specific example illustrates the workflow of this invention: Carbon matrix material pretreatment: Graphite was selected as the carbon matrix material and immersed in a 3 mol / L nitric acid solution for 2 hours. It was then rinsed with deionized water until neutral and dried in an oven at 80°C. The dried graphite was then placed in a plasma treatment device with a power of 500W and a treatment time of 20 minutes to obtain the pretreated carbon matrix material.
[0064] Preparation of the precursor solution: Prepare the precursor solution according to the mass ratio of silicon source (tetraethyl orthosilicate): reducing agent (sodium borohydride): solvent (a mixed solvent of ethanol and deionized water, volume ratio 3:1) = 1:1:80. Slowly add tetraethyl orthosilicate to the mixed solvent of ethanol and deionized water, stir evenly, then add sodium borohydride, and continue stirring until completely dissolved.
[0065] In-situ growth of silicon nanoparticles: Pretreated carbon matrix material was immersed in a precursor solution. The reaction vessel was placed in an oil bath, and the temperature was controlled at 120℃ and the pressure at atmospheric pressure. A magnetic stirrer was used to control the stirring speed at 500 rpm, and a zoned heating device was installed in the reaction vessel to maintain a temperature gradient of 10℃. The solvent evaporation rate was controlled at 0.5 ml / min by adjusting the sealing lid of the reaction vessel. During the reaction, the pH value of the reaction system was monitored in real time using a pH meter. When the pH value deviated from 5, an appropriate amount of ammonia or dilute hydrochloric acid was added for adjustment. The temperature was monitored using a temperature sensor, and when the temperature fluctuation exceeded ±5℃, the heating power of the oil bath was adjusted. The reaction time was 6 hours.
[0066] Product processing: After the reaction was completed, the product was filtered and washed several times with deionized water until the pH of the washing solution was close to neutral. Then the product was placed in an oven and dried at 80°C for 10 hours.
[0067] Heat treatment to enhance interfacial bonding: The dried product was placed in a tube furnace and heat-treated under nitrogen protection. The nitrogen flow rate was set to 20 ml / min, and the temperature was increased to 600°C at a rate of 5°C / min, held at that temperature for 3 hours, and then allowed to cool naturally to room temperature.
[0068] Morphology control using template method and surfactant-assisted method: A certain amount of silica template and sodium dodecylbenzenesulfonate were added to the above reaction system as surfactants. The silica template was pretreated before the reaction to remove surface impurities. The template was added at a mass ratio of 1:5 of template to carbon matrix material, and the amount of sodium dodecylbenzenesulfonate added was 1% of the precursor solution mass. The above steps for in-situ growth of silicon nanoparticles were repeated. After heat treatment, the product was immersed in a 5 mol / L sodium hydroxide solution for 12 hours to remove the silica template, then rinsed with deionized water until neutral, and then dried.
[0069] Pore formation and conductive network construction: 10 wt% ammonium bicarbonate was added as a pore-forming agent during the in-situ growth of nano-silicon particles. Carbon black was added as a conductive additive at a mass ratio of 3:100 (carbon black:composite material). The composite material and carbon black were mixed and stirred in a stirrer at 800 r / min for 3 hours. Then, ultrasonic dispersion was performed at an ultrasonic power of 300 W for 1 hour to obtain a silicon-carbon anode composite material with in-situ grown nano-silicon particles.
[0070] It is understood that the present invention also possesses the following technical effects in the preferred embodiments of the present invention: 1. By optimizing reaction conditions and employing various control methods, the size and morphology of nano-silicon particles can be effectively controlled, improving the dispersion uniformity of nano-silicon particles on the carbon matrix surface, thereby enhancing the electrochemical performance of silicon-carbon anode composite materials.
[0071] 2. The heat treatment process enhances the interfacial bonding between the nano-silicon particles and the carbon matrix, reduces the occurrence of interfacial side reactions, and improves the cycle stability and initial coulombic efficiency of the battery.
[0072] 3. The introduction of pore-forming agents and the construction of conductive networks optimize the pore structure and conductivity of composite materials, improve the rate performance of batteries, facilitate process scale-up, and reduce production costs.
[0073] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.
[0074] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A process for preparing silicon-carbon anode composite material with in-situ grown silicon nanoparticles, characterized in that, The process includes: S100. The carbon matrix material is pretreated according to a preset method to remove surface impurities and increase surface active sites; a precursor solution containing a silicon source, a reducing agent and a solvent is prepared, wherein the silicon source is at least one of silicate and organosilicon compound, the reducing agent is at least one of sodium borohydride and lithium aluminum hydride, and the solvent is at least one of ethanol, isopropanol and deionized water. S200. The pretreated carbon matrix material is immersed in a precursor solution and reacted under preset temperature and pressure conditions to allow the silicon source to grow nano-silicon particles in situ on the surface of the carbon matrix. After the reaction, the product is washed and dried to remove unreacted impurities. The dried product is then heat-treated to enhance the interfacial bonding between the nano-silicon particles and the carbon matrix. S300: The size of nano-silicon particles is uniformly controlled by adjusting the stirring speed and temperature gradient of the reaction system; the morphology of nano-silicon particles is controlled by template method and surfactant-assisted method; a pore-forming agent is introduced into the reaction system, and the pore-forming agent decomposes to form a porous structure during heat treatment, thus optimizing the pore structure of the composite material; a conductive additive is added to the composite material, and a conductive network is constructed by mechanical stirring and ultrasonic dispersion, finally obtaining a silicon-carbon anode composite material with in-situ grown nano-silicon particles; The preset method is at least one of acid washing, alkaline washing, and plasma treatment; The preset temperature is 60℃-200℃, and the preset pressure is 0.1MPa-3MPa; The pH and temperature of the reaction system are monitored in real time during the reaction process to maintain the stability of the reaction system; The preparation process of the precursor solution containing a silicon source, a reducing agent, and a solvent is as follows: Primary solution: TEOS and anhydrous ethanol are mixed at a volume ratio of 1:3 and magnetically stirred at 300 rpm for 1 hour; Reducing agent solution: Prepare a sodium borohydride ethanol solution with a sodium borohydride concentration of 5 wt%. The ethanol solution should be prepared fresh and used immediately, and stored away from light. Final mixing: The primary solution and the reducing agent solution are mixed at a volume ratio of 5:1 and stirred continuously for 45 minutes; Additives: 0.1 wt% sodium dodecylbenzenesulfonate is added as a dispersant.
2. The preparation process of silicon-carbon anode composite material with in-situ grown silicon nanoparticles according to claim 1, characterized in that, The template used in the template method is at least one of silica template and polystyrene template, and the surfactant is at least one of sodium dodecylbenzenesulfonate and polyethylene glycol.
3. The preparation process of silicon-carbon anode composite material with in-situ grown silicon nanoparticles according to claim 1, characterized in that, The pore-forming agent is at least one of ammonium bicarbonate and ammonium carbonate, and the decomposition temperature of the pore-forming agent during the heat treatment process is lower than the maximum temperature of the heat treatment.
4. The preparation process of silicon-carbon anode composite material with in-situ grown silicon nanoparticles according to claim 1, characterized in that, The conductive additive is at least one of carbon black, carbon nanotubes, and graphene.
5. The preparation process of silicon-carbon anode composite material with in-situ grown silicon nanoparticles according to claim 1, characterized in that, The mechanical stirring speed is 200-1000 r / min, and the stirring time is 1-5 hours. The ultrasonic dispersion power is 100-500 W, and the ultrasonic time is 0.5-2 hours.
6. The preparation process of silicon-carbon anode composite material with in-situ grown silicon nanoparticles according to claim 1, characterized in that, The temperature for heat treatment of the dried product is 400℃-800℃, and the heat treatment time is 1-5 hours.
7. The preparation process of silicon-carbon anode composite material with in-situ grown silicon nanoparticles according to claim 1, characterized in that, The heat treatment is carried out under the protection of an inert gas, which is at least one of nitrogen and argon.