Silicon carbon nanoparticle-silicon nanowire composite material as well as preparation method and application thereof

Abstract

The invention discloses a silicon carbon nanoparticle-silicon nanowire composite material and a preparation method and application thereof, and belongs to the technical field of energy storage. The silicon-carbon nanoparticle-silicon nanowire composite material is composed of silicon nanowires and silicon-carbon nanoparticles, the silicon nanowires are interwoven to form a three-dimensional network structure, the silicon-carbon nanoparticles are embedded in the three-dimensional network structure interwoven by the silicon nanowires, and the silicon-carbon nanoparticles are uniformly distributed in the three-dimensional network structure. On one hand, the conductivity of the silicon-based material is enhanced through the silicon-carbon material; on the other hand, a silicon nanofiber network is constructed, the double-volume expansion inhibition effect on the silicon nanoparticles and the silicon nanowires is achieved, and unification of electric conduction, stress buffering, interface stability and rapid dynamics is achieved.

Description

Technical Field

[0001] This application relates to a silicon-carbon nanoparticle-silicon nanowire composite material, its preparation method and application, belonging to the field of energy storage technology. Background Technology

[0002] In the industrialization of high-energy-density solid-state batteries, silicon-based anode materials are considered a key pathway to overcome the limitations of traditional graphite anodes due to their ultra-high theoretical specific capacity (approximately 4200 mAh / g). However, the volume expansion of silicon during charging and discharging, reaching up to 300%, leads to severe structural pulverization, interfacial instability, and a sharp drop in cycle life, severely restricting its commercial application. Currently, silicon-carbon anode materials, as a key component of high-energy-density lithium-ion battery systems, have achieved initial commercialization in consumer electronics and high-end power batteries. By embedding nano-silicon particles into graphite or amorphous carbon matrices, they alleviate the volume expansion problem of pure silicon to some extent and improve conductivity and cycle performance. However, existing silicon-carbon composite materials still face severe challenges: silicon particles are prone to agglomeration and breakage during repeated lithium insertion and extraction, leading to continuous reconstruction of the SEI film and an increase in interfacial impedance. Especially in the rigid interface environment of solid-state batteries, microcracks are prone to contact failure, severely restricting cycle life and rate performance. In addition, traditional ball milling or mechanical mixing methods are difficult to achieve uniform dispersion of the silicon phase, further limiting the structural stability of the material.

[0003] Meanwhile, silicon nanowire anode materials, due to their one-dimensional continuous structure which can effectively accommodate axial expansion, exhibit excellent structural integrity and electrochemical reversibility, and are considered highly promising candidates for high-capacity anodes. However, silicon nanowires have poor intrinsic conductivity, large specific surface area, and are prone to side reactions with electrolytes; moreover, their preparation often relies on the VLS method assisted by noble metal catalysts, which is costly, has low yield, and is difficult to scale up. More importantly, in solid-state battery systems, although silicon nanowire arrays can suppress radial expansion, they lack effective three-dimensional conductive network support, resulting in high interfacial contact impedance and limited ion transport paths, leading to insufficient actual capacity utilization.

[0004] Given the aforementioned bottlenecks, integrating the conductive buffering advantages of silicon-carbon materials with the strain tolerance characteristics of silicon nanowires to construct an integrated "silicon-carbon-silicon nanowire" composite structure has become a strategic direction for breaking through the performance ceiling of solid-state battery anodes. This composite architecture can not only provide continuous electron channels and mechanical constraints through the carbon matrix, but also achieve efficient lithium-ion transport and anisotropic expansion management by utilizing the directional alignment of silicon nanowires. As shown in the recent patent US20240387652A1 from Group14, silicon nanowires were grown in situ using CVD in-situ in hierarchical porous carbon microspheres, achieving a reversible capacity of >1500 mAh / g and a 91% retention rate after 800 cycles in a sulfide all-solid-state battery. Anhui Deyi Energy Technology Co., Ltd. recently obtained a patent (202510368593.5) that uses a high-temperature melt electrolysis process to disperse nano-silicon particles in a network of interwoven silicon carbide nanowires. The porous network structure can provide space for volume expansion, which can reduce the damage to the electrode structure caused by volume expansion during the lithium insertion and extraction process of silicon-based anodes. The resulting silicon-based anode material has a volume expansion rate of 86.6% after 200 cycles.

[0005] Despite significant progress in the preparation of silicon-carbon-silicon nanowires, limitations remain, such as the high cost and difficulty in mass production of CVD, and the high energy consumption and low purity of melt electrolysis. Therefore, developing novel silicon-carbon-silicon nanowire synthesis processes remains crucial for reducing costs and increasing efficiency in silicon-based anode materials. With the global window of opportunity for solid-state battery industrialization rapidly opening, my country urgently needs to accelerate original research and development and core patent layout for silicon-carbon-silicon nanowire composite materials to solve the anode challenges of high energy density, long lifespan, and high safety in solid-state batteries, and seize the commanding heights of next-generation electrochemical energy storage technology. Summary of the Invention

[0006] To address the aforementioned issues, this application provides a silicon-carbon nanoparticle-silicon nanowire composite material. This material enhances the conductivity of silicon-based materials through silicon-carbon materials and constructs a silicon nanofiber network, thereby suppressing the dual volume expansion of silicon nanoparticles and silicon nanowires and achieving a balance between conductivity and stress buffering, interface stability and rapid dynamics.

[0007] According to the first aspect of this application, this application provides a silicon-carbon nanoparticle-silicon nanowire composite material, comprising silicon nanowires and silicon-carbon nanoparticles; The silicon nanowires intertwine to form a three-dimensional network structure, and the silicon-carbon nanoparticles are embedded in the three-dimensional network structure formed by the intertwining silicon nanowires, and the silicon-carbon nanoparticles are uniformly distributed in the three-dimensional network structure.

[0008] In this silicon-carbon nanoparticle-silicon nanowire composite material, silicon-carbon nanoparticles are embedded within the three-dimensional network structure of silicon nanowires, forming a porous architecture similar to reinforced concrete. The silicon-carbon nanoparticles provide conductive reinforcement, and the pores between the silicon-carbon nanoparticles and silicon nanowires effectively accommodate the volume expansion of silicon during lithium insertion / extraction. Furthermore, the silicon nanowires, with their axial stress adaptability and continuous one-dimensional electron channels, achieve axially ordered construction of nano-silicon through directional alignment, effectively offsetting the internal friction of expansion stress in the X-axis direction, further suppressing overall volume expansion, thereby significantly improving the specific capacity and cycle stability of the silicon-based anode.

[0009] Optionally, the silicon-carbon nanoparticles account for 8-92% of the weight of the composite material, and the silicon nanowires account for 8-92% of the weight of the composite material.

[0010] Within the specified proportion range of the composite material, the silicon-carbon nanoparticles and silicon nanowires can provide sufficient space for the silicon nanofiber network constructed from silicon nanowires to accommodate the silicon-carbon nanoparticles. Furthermore, the silicon-carbon nanoparticles and silicon nanowires can form a three-dimensional conductive network with effective support, achieving a balance between conductivity and the ability to accommodate silicon volume expansion.

[0011] Preferably, the silicon-carbon nanoparticles account for 30-60% of the weight of the composite material, and the silicon nanowires account for 40-70% of the weight of the composite material.

[0012] Optionally, the particle size of the silicon-carbon nanoparticles is 20-500 nm.

[0013] Optionally, the silicon nanowires have a diameter of 20-500 nm and a length of 0.02-10000 mm, wherein 70% of the silicon nanowires have a length of 0.08-4000 mm.

[0014] The diameter and length of silicon nanowires can be controlled by adjusting the reaction parameters. The diameter and length range of the silicon nanowires in this application covers the minimum and maximum values ​​under various reaction conditions, so the range is relatively large. However, more than 70% of the silicon nanowires grow uniformly and have a concentrated length range of 0.08-4000 mm.

[0015] Optionally, the specific surface area of ​​the silicon-carbon nanoparticle-silicon nanowire composite material is 1-10.0 m². 2 / g.

[0016] The silicon-carbon nanoparticle-silicon nanowire composite material of this application is composed of two forms of material, achieving a balance between electrical conductivity and the ability to accommodate volume expansion in these two forms. The specific surface area can be maintained at 1-10.0 m² at the weight percentage of the silicon-carbon nanoparticles and silicon nanowires in the composite material. 2 / g.

[0017] Preferably, the specific surface area of ​​the silicon-carbon nanoparticle-silicon nanowire composite material is 5.2-8.5 m². 2 / g.

[0018] According to a second aspect of this application, this application provides a method for preparing silicon-carbon nanoparticle-silicon nanowire composite materials, comprising the following steps: (1) A mixture of silicon material, fluorinated organic matter and dispersant in a weight ratio of 1:(0.2-10):(0.01-2) is placed in a solvent and mixed to obtain a mixed slurry. The mixed slurry is then dried to obtain a mixture. (2) Place the mixture in the reactor and inject inert gas into the reactor to make the pressure inside the reactor 0-5 MPa; (3) The mixture was subjected to a high-temperature induced reaction to obtain a silicon-carbon nanoparticle-silicon nanowire composite material.

[0019] This preparation method involves high-temperature induction of silicon-carbon nanoparticle-silicon nanowire composite material under an inert atmosphere. The high-temperature induction treatment under an inert atmosphere causes silicon atoms to evaporate. Under this inert atmosphere, some silicon atoms grow directionally to form silicon nanowires, while others bond with carbon atoms to form silicon-carbon nanoparticles. As the reaction proceeds, a three-dimensional network structure of silicon-based composite material with silicon-carbon nanoparticles uniformly embedded within silicon nanowires is formed. Insufficient inert atmosphere leads to intensified silicon oxidation, generating amorphous silicon dioxide, which hinders the directional migration and growth of silicon atoms, making it difficult to form continuous silicon nanowires. It also affects silicon-carbon bonding, resulting in a decreased yield of silicon-carbon nanoparticles and a wider particle size distribution.

[0020] The weight ratio of silicon, fluorinated organics, and dispersants ensures the formation of silicon-carbon particles and silicon nanowires. The dispersant promotes the dispersion of the formed silicon-carbon nanoparticles within the silicon nanowires, preventing excessively high or low local concentrations. Insufficient fluorinated organics lead to an increase in the number of silicon-carbon nanoparticles and a decrease in the number of silicon nanowires. Excessive fluorinated organics or dispersants result in an overly thick carbon layer, preventing some silicon particles from participating in lithium insertion or delithiation reactions. Furthermore, an excessively thick carbon layer increases the lithium-ion transport path length, significantly reducing the electrochemical performance of the silicon-based composite material.

[0021] Optionally, the fluorinated organic compound in step (1) is at least one of fluorinated starch, fluorinated phenolic resin, fluorinated epoxy resin, and fluorinated plastic, and the molecular weight of the fluorinated organic compound is 50,000 to 10,000,000.

[0022] Optionally, the average particle size of the fluorinated organic compound is 0.1-200 μm.

[0023] Optionally, the fluoroplastic is tetrafluoroethylene or vinylidene fluoride.

[0024] Optionally, the average particle size of the silicon material in step (1) is 2-50 μm.

[0025] Preferably, the average particle size of the silicon material in step (1) is 15 μm.

[0026] Optionally, the dispersant in step (1) is at least one of vinyl alcohol, ethylene glycol, sulfonic acid amine, and triethanolamine.

[0027] Optionally, the solvent in step (1) is at least one of water, ethanol, acetone, n-hexane, cyclohexane, and methylpyrrolidone.

[0028] Optionally, the mixing method in step (1) is at least one of stirring, ultrasonication, and microwave enhancement.

[0029] Preferably, the mixing method in step (1) is ultrasound.

[0030] Optionally, the drying method described in step (1) is at least one of spray drying, vacuum drying, atmospheric pressure drying, infrared drying, and microwave drying.

[0031] Preferably, the drying method described in step (1) is centrifugal spray drying.

[0032] Optionally, the inert gas in step (2) is nitrogen or argon.

[0033] Micron-sized silicon decomposes into individual silicon atoms under the induction of a high-temperature atmosphere. In an inert, oxygen-free atmosphere, the silicon atoms instantly form bonds at high temperatures, some forming silicon nanowires and others forming silicon-carbon nanoparticles.

[0034] Optionally, the high-temperature induced heating method in step (3) is at least one of Joule heating, plasma, flash evaporation technology, and alloy resistance wire heating.

[0035] Preferably, the high-temperature induced heating method in step (3) is Joule heating.

[0036] Optionally, the high-temperature induced heating rate in step (3) is 50-2000℃ / s, the temperature is 600-2200℃, and the time is 0.1-2h.

[0037] The higher the temperature, the more silicon nanowires are generated. Therefore, this temperature range is limited so that some silicon can grow directionally to produce silicon nanowires, while some silicon can bond with carbon atoms to form silicon-carbon nanoparticles. Ultimately, a silicon-based composite material with a three-dimensional network structure in which silicon-carbon nanoparticles are uniformly embedded in silicon nanowires is formed. This avoids the situation where one silicon-carbon nanoparticle or silicon nanowire is too much or too little, which would prevent the formation of a three-dimensional network structure with effective support.

[0038] According to a third aspect of this application, this application provides a solid-state battery anode material, which includes the silicon-carbon nanoparticle-silicon nanowire composite material as described in any one of the preceding claims or the silicon-carbon nanoparticle-silicon nanowire composite material prepared by any one of the preceding claims.

[0039] According to a fourth aspect of this application, this application provides the application of silicon-carbon nanoparticle-silicon nanowire composite materials as described in any of the preceding claims, or silicon-carbon nanoparticle-silicon nanowire composite materials prepared by any of the preceding claims, in energy storage devices.

[0040] The beneficial effects of this application include, but are not limited to: 1. The silicon-carbon nanoparticle-silicon nanowire composite material according to this application has the ability to enhance the conductivity of silicon-carbon nanoparticles. The pore space between silicon-carbon nanoparticles and silicon nanowires and silicon nanowires work together to suppress the volume expansion of the overall material and synergistically enhance the rate performance and cycle stability, which has broad application prospects.

[0041] 2. According to the preparation method of silicon-carbon nanoparticle-silicon nanowire composite material of this application, silicon-carbon nanoparticles synthesized under high temperature atmosphere are embedded in the three-dimensional network structure of silicon nanowires to form a porous structure similar to reinforced concrete. The conductivity of the outer carbon layer of silicon-carbon nanoparticles will enhance the overall conductivity of silicon-carbon nanoparticle-silicon nanowire composite material, and the pores formed can effectively accommodate the volume expansion of silicon during the lithium insertion and extraction process.

[0042] 3. According to the preparation method of silicon-carbon nanoparticle-silicon nanowire composite material of this application, the silicon nanowires synthesized by high temperature in the atmosphere have the advantages of axial stress self-adaptability and continuous one-dimensional electron channels. Through directional arrangement, the nano-silicon is constructed in an orderly manner along the axial direction, which can effectively realize the internal friction cancellation of expansion stress in the X direction and further suppress the overall volume expansion.

[0043] 4. The solid-state battery anode material according to this application has the advantages of high specific capacity and good cycle stability, which can extend the battery's service life and improve its safety.

[0044] 5. The solid-state battery anode material according to this application can achieve directional modulation of conductivity and volume expansion coefficient by adjusting the weight ratio of silicon-carbon nanoparticles and silicon nanowires, thereby achieving a balance between high specific capacity and cycle stability. It can achieve a specific capacity of up to 2178mAh, an initial efficiency of up to 92.42%, and a long cycle life of 300 charge-discharge cycles at 0.5C, and has broad application prospects. Attached Figure Description

[0045] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a SEM image of the silicon-carbon nanoparticle-silicon nanowire composite material involved in Example 3 of this application; Figure 2 This is a SEM image of the silicon-carbon nanoparticle-silicon nanowire composite material involved in Example 4 of this application; Figure 3 This is a SEM image of the silicon-carbon nanoparticle-silicon nanowire composite material involved in Example 5 of this application; Figure 4 This is a solid-state battery performance test diagram of the silicon-carbon nanoparticle-silicon nanowire composite material involved in Example 3 of this application; Figure 5 This is a solid-state battery performance test diagram of the silicon-carbon nanoparticle-silicon nanowire composite material involved in Example 4 of this application; Figure 6 This is a solid-state battery performance test diagram of the silicon-carbon nanoparticle-silicon nanowire composite material involved in Example 5 of this application; Figure 7 This is a performance graph of the solid-state battery cycle performance of the silicon-carbon nanoparticle-silicon nanowire composite material involved in Example 5 of this application. Detailed Implementation

[0046] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0047] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0048] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art. The control agents used in the following embodiments and comparative examples are all commercially available products.

[0049] Example 1 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 2 μm), fluorinated phenolic resin (molecular weight of 50,000 and average particle size of 0.1 μm) and sulfonic acid amine in a weight ratio of 1:0.2:0.01 are placed in acetone. The weight ratio of acetone to silicon material, fluorinated phenolic resin and sulfonic acid amine is 5:1. The mixture is stirred and mixed to obtain a slurry. The slurry is then microwave-dried at 60°C to obtain a mixture.

[0050] (2) Place the mixture in the reactor, use a vacuum pump to evacuate to a pressure of 0.008 MPa, then add inert nitrogen atmosphere until the pressure returns to normal. Repeat this cycle twice to ensure that the reactor is completely protected by an inert atmosphere, and finally make the pressure in the reactor 0 MPa.

[0051] (3) The mixture is subjected to a high-temperature induced reaction in an atmosphere. Plasma heating is selected as the heating method. The temperature is increased to 2200℃ at a heating rate of 2000℃ / s and reacted for 0.1h to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0052] Example 2 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 50 μm), fluorinated starch (molecular weight of 10 million, average particle size of 200 μm) and ethylene glycol in a weight ratio of 1:10:2 are placed in cyclohexane. The weight ratio of cyclohexane to silicon material, fluorinated starch and ethylene glycol is 5:1. The mixture is prepared by microwave-enhanced mixing. The mixture is then dried at 60°C under normal pressure to obtain a mixed material.

[0053] (2) Place the mixture in the reactor, use a vacuum pump to evacuate to a pressure of 0.008 MPa, then add inert argon gas until the pressure returns to normal. Repeat this process twice to ensure that the reactor is completely protected by an inert atmosphere, and finally make the pressure in the reactor 5 MPa.

[0054] (3) The mixture is subjected to a high-temperature induced reaction in an atmosphere. The heating method is selected by heating with alloy resistance wire. The temperature is increased to 600℃ at a heating rate of 50℃ / s and reacted for 2 hours to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0055] Example 3 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 30 μm), fluorinated organic material (a mixture of tetrafluoroethylene and polyvinylidene fluoride with a molecular weight of 1 million and an average particle size of 80 μm) with a weight ratio of 1:1.1:0.05, and vinyl alcohol are placed in a water-ethanol mixed solvent (the weight ratio of water and ethanol is 2:1). The weight ratio of the mixed solvent to the total weight of silicon material, fluorinated organic material and vinyl alcohol is 6:1. The mixture is ultrasonically mixed to obtain a mixed slurry. Then the mixed slurry is centrifuged and spray-dried at 60°C to obtain a mixed material.

[0056] (2) Place the mixture in the reactor and use a vacuum pump to evacuate to a pressure of 0.008 MPa. Then add inert nitrogen atmosphere until the pressure returns to normal. Repeat this cycle twice to ensure that the reactor is completely protected by an inert atmosphere. Finally, the pressure of the inert atmosphere stabilizes at 0.1 MPa.

[0057] (3) The mixture is subjected to a high-temperature induced reaction in the atmosphere. The heating method is selected by Joule heating. The temperature is increased to 1500℃ at a heating rate of 1600℃ / s and reacted for 0.1h to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0058] Example 4 The difference between this embodiment and Example 3 is that the weight ratio of silicon material and mixed fluorinated organic matter is 1:0.9, the inert atmosphere is argon, the heating rate is 1500℃ / s, and the reaction is carried out at 1400℃ for 0.15h.

[0059] Example 5 The difference between this embodiment and Example 3 is that the weight ratio of silicon material and mixed fluorinated organic material is 1:1.5, the inert atmosphere is argon, the heating rate is 1450℃ / s, and the reaction is carried out at 1500℃ for 0.1h.

[0060] Example 6 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 15 μm), fluorinated organic material (a mixture of tetrafluoroethylene and polyvinylidene fluoride with a molecular weight of 800,000 and an average particle size of 30 μm) with a weight ratio of 1:0.6:0.05, and vinyl alcohol are placed in a water-ethanol mixed solvent (the weight ratio of water and ethanol is 1:2). The weight ratio of the mixed solvent to the total weight of silicon material, fluorinated organic material and vinyl alcohol is 6:1. The mixture is ultrasonically mixed to obtain a mixed slurry. Then the mixed slurry is centrifuged and spray-dried at 60°C to obtain a mixed material.

[0061] (2) Place the mixture in the reactor and use a vacuum pump to evacuate to a pressure of 0.008 MPa. Then add inert nitrogen atmosphere until the pressure returns to normal. Repeat this cycle twice to ensure that the reactor is completely protected by an inert atmosphere. Finally, the pressure of the inert atmosphere stabilizes at 0.1 MPa.

[0062] (3) The mixture is subjected to a high-temperature induced reaction in the atmosphere. The heating method is selected by Joule heating. The temperature is increased to 1500℃ at a heating rate of 1300℃ / s and reacted for 0.1h to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0063] Example 7 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 15 μm), fluorinated organic material (a mixture of tetrafluoroethylene and polyvinylidene fluoride with a molecular weight of 800,000 and an average particle size of 50 μm) with a weight ratio of 1:1.3:0.06, and vinyl alcohol are placed in a water-ethanol mixed solvent (water and ethanol weight ratio of 1:1). The weight ratio of the mixed solvent to the total weight of silicon material, fluorinated organic material and vinyl alcohol is 7:1. The mixture is ultrasonically mixed to obtain a mixed slurry. Then the mixed slurry is centrifuged and spray-dried at 50°C to obtain a mixed material.

[0064] (2) Place the mixture in the reactor and use a vacuum pump to evacuate to a pressure of 0.005 MPa. Then add inert nitrogen atmosphere until the pressure returns to normal. Repeat this cycle twice to ensure that the reactor is completely protected by an inert atmosphere. Finally, the pressure of the inert atmosphere stabilizes at 0.1 MPa.

[0065] (3) The mixture is subjected to a high-temperature induced reaction in the atmosphere. The heating method is selected by Joule heating. The temperature is increased to 1500℃ at a heating rate of 1400℃ / s and reacted for 0.3h to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0066] Example 8 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 40 μm), fluorinated organic material (a mixture of tetrafluoroethylene and polyvinylidene fluoride with a molecular weight of 800,000 and an average particle size of 120 μm) with a weight ratio of 1:1.05:0.08, and vinyl alcohol are placed in a water-ethanol mixed solvent (water and ethanol weight ratio of 1:3). The weight ratio of the mixed solvent to the total weight of silicon material, fluorinated organic material and vinyl alcohol is 6:1. The mixture is ultrasonically mixed to obtain a mixed slurry. Then the mixed slurry is centrifuged and spray-dried at 70°C to obtain a mixed material.

[0067] (2) Place the mixture in the reactor and use a vacuum pump to evacuate to a pressure of 0.008 MPa. Then add inert nitrogen atmosphere until the pressure returns to normal. Repeat this cycle twice to ensure that the reactor is completely protected by an inert atmosphere. Finally, the pressure of the inert atmosphere stabilizes at 0.1 MPa.

[0068] (3) The mixture is subjected to a high-temperature induced reaction in the atmosphere. The heating method is selected by Joule heating. The temperature is increased to 1500℃ at a heating rate of 1400℃ / s and reacted for 0.3h to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0069] Example 9 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 35 μm), fluorinated organic material (a mixture of tetrafluoroethylene and polyvinylidene fluoride with a molecular weight of 8 million and an average particle size of 150 μm) with a weight ratio of 1:1.2:0.055, and vinyl alcohol are placed in a water-ethanol mixed solvent (the weight ratio of water and ethanol is 1:3). The weight ratio of the mixed solvent to the total weight of silicon material, fluorinated organic material and vinyl alcohol is 6:1. The mixture is ultrasonically mixed to obtain a mixed slurry. Then the mixed slurry is centrifuged and spray-dried at 50°C to obtain a mixed material.

[0070] (2) Place the mixture in the reactor and use a vacuum pump to evacuate to a pressure of 0.008 MPa. Then add inert nitrogen atmosphere until the pressure returns to normal. Repeat this cycle twice to ensure that the reactor is completely protected by an inert atmosphere. Finally, the pressure of the inert atmosphere stabilizes at 0.1 MPa.

[0071] (3) The mixture is subjected to a high-temperature induced reaction in the atmosphere. The heating method is selected by Joule heating. The temperature is increased to 1300℃ at a heating rate of 1200℃ / s and reacted for 0.1h to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0072] Example 10 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 70 μm), fluorinated organic material (a mixture of tetrafluoroethylene and polyvinylidene fluoride with a molecular weight of 800,000 and an average particle size of 20 μm) with a weight ratio of 1:1.33:0.083, and vinyl alcohol are placed in a water-ethanol mixed solvent (water and ethanol weight ratio of 1:2). The weight ratio of the mixed solvent to the total weight of silicon material, fluorinated organic material and vinyl alcohol is 4:1. The mixture is ultrasonically mixed to obtain a mixed slurry. Then the mixed slurry is centrifuged and spray-dried at 50°C to obtain a mixed material.

[0073] (2) Place the mixture in the reactor and use a vacuum pump to evacuate to a pressure of 0.008 MPa. Then add inert nitrogen atmosphere until the pressure returns to normal. Repeat this cycle twice to ensure that the reactor is completely protected by an inert atmosphere. Finally, the pressure of the inert atmosphere stabilizes at 0.1 MPa.

[0074] (3) The mixture is subjected to a high-temperature induced reaction in the atmosphere. The heating method is selected by Joule heating. The temperature is increased to 1500℃ at a heating rate of 1400℃ / s and reacted for 0.3h to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0075] Example 11 The difference between this embodiment and Example 10 is that the weight ratio of silicon material and mixed fluorinated organic material is 1:0.85, the inert atmosphere is argon, the heating rate is 1500℃ / s, and the reaction is carried out at 1400℃ for 0.1h.

[0076] Example 12 This embodiment relates to a method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, comprising the following steps: (1) Silicon material (average particle size of 180 μm), fluorinated organic material (a mixture of tetrafluoroethylene and polyvinylidene fluoride with a weight ratio of 2:1, molecular weight of 800,000, average particle size of 25 μm) and ethylene alcohol in a water-ethanol mixed solvent (water and ethanol weight ratio of 1:3) with a weight ratio of 6:1 between the mixed solvent and the total weight of silicon material, fluorinated organic material and ethylene alcohol, were ultrasonically mixed to obtain a mixed slurry. The mixed slurry was then centrifuged and spray-dried at 50 °C to obtain a mixed material.

[0077] (2) Place the mixture in the reactor and use a vacuum pump to evacuate to a pressure of 0.005 MPa. Then add inert nitrogen atmosphere until the pressure returns to normal. Repeat this cycle twice to ensure that the reactor is completely protected by an inert atmosphere. Finally, the pressure of the inert atmosphere stabilizes at 0.08 MPa.

[0078] (3) The mixture is subjected to a high-temperature induced reaction in the atmosphere. The heating method is selected by Joule heating. The temperature is increased to 1500℃ at a heating rate of 1400℃ / s and reacted for 0.3h to obtain silicon carbon nanoparticle-silicon nanowire composite material.

[0079] Example 13 The difference between this embodiment and Example 12 is that the weight ratio of silicon material and mixed fluorinated organic material is 1:1.5, the inert atmosphere is argon, the heating rate is 1200℃ / s, and the reaction is carried out at 1400℃ for 0.3h.

[0080] Example 14 The difference between this embodiment and Example 13 is that the weight ratio of silicon material and mixed fluorinated organic matter is 1:1.2, the inert atmosphere is nitrogen, the heating rate is 1300℃ / s, and the reaction is carried out at 1500℃ for 0.2h.

[0081] Example 15 The difference between this embodiment and embodiment 6 is that the heating rate in step (3) is 45℃ / s.

[0082] Example 16 The difference between this embodiment and embodiment 6 is that the heating rate in step (3) is 2100℃ / s.

[0083] Example 17 The difference between this embodiment and embodiment 6 is that the temperature is raised to 2300℃ in step (3).

[0084] Example 18 The difference between this embodiment and embodiment 6 is that the temperature is raised to 550°C in step (3).

[0085] Example 19 The difference between this embodiment and embodiment 6 is that the reaction time in step (3) is 2.1 h.

[0086] Comparative Example 1 The difference between this comparative example and Example 6 is that in step (2), no inert atmosphere replacement is performed and the reactor is at atmospheric pressure, while in step (3), the reaction is carried out at atmospheric pressure.

[0087] Comparative Example 2 The difference between this comparative example and Example 6 is that the weight ratio of silicon material to fluorinated organic material in step (1) is 1:11.

[0088] Comparative Example 3 The difference between this comparative example and Example 6 is that the weight ratio of silicon material to dispersant in step (1) is 1:3.

[0089] Comparative Example 4 The difference between this comparative example and Example 6 is that no dispersant is added in step (1).

[0090] Test Example 1 The silicon-carbon nanoparticle-silicon nanowire composite materials prepared in the above embodiments and comparative examples were subjected to crystal phase, specific surface area, and morphology analysis. The test results are shown in Table 1 and 2. Figure 1 , Figure 2 , Figure 3 The particle size of silicon-carbon nanoparticles and the diameter and length of silicon nanowires were tested, and the test results are shown in Table 2. The specific test methods are as follows: Weight ratio of silicon-carbon nanoparticles to silicon nanofibers: X-ray single-crystal diffraction area normalization method; Morphological analysis: Field emission electron microscopy; Specific surface area: N2 adsorption-desorption method; Silicon-carbon nanoparticle size: Scanning electron microscopy; Diameter and length of silicon nanowires: Scanning electron microscopy.

[0091] Table 1

[0092] Figure 1 , Figure 2 and Figure 3SEM images of the products from Examples 3, 4, and 5, respectively. Figure 1-3 It can be seen that the proportion of silicon carbon nanoparticles and silicon nanowires in silicon carbon nanoparticle-silicon nanowire composites changes with the ratio of silicon powder and fluorinated organic matter and the atmosphere. A relatively suitable silicon-carbon ratio and an inert atmosphere are conducive to the formation of silicon nanofibers.

[0093] Table 2

[0094] Test Example 2 Using the silicon-carbon nanoparticle-silicon nanowire composite material prepared in the above embodiments and comparative examples as the active material, a negative electrode sheet was prepared by mixing the active material, acetylene black, and binder in a weight ratio of 90:5:5. A copper foil was used as the current collector, a sulfide solid electrolyte as the electrolyte, and an indium-plated lithium sheet as the counter electrode to assemble a solid-state battery. The electrochemical performance of the battery was tested, and the test results are shown in Table 3. Figure 4 , Figure 5 , Figure 6 The figures show the test performance of solid-state batteries assembled from silicon-carbon nanoparticle-silicon nanowire composite materials prepared in Examples 3, 4, and 5, respectively. Figure 7 This is a graph showing the stability test performance of a solid-state battery assembled from the silicon-carbon nanoparticle-silicon nanowire composite material prepared in Example 5.

[0095] Table 3

[0096] from Figure 1-6 It can be seen that the proportions of silicon-carbon nanoparticles and silicon nanowires in the silicon-carbon nanoparticle-silicon nanowire composite material change with the ratio of silicon powder and fluorinated organic matter and the atmosphere. A relatively suitable silicon-carbon ratio and inert atmosphere are conducive to the formation of silicon nanofibers, which to some extent contributes to the improvement of the electrical performance of the anode material. Figure 7 It can be seen that the solid-state battery assembled from the silicon-carbon nanoparticle-silicon nanowire composite material prepared in Example 5 still retains a capacity of up to 80% after 322 charge-discharge cycles at 0.5C, indicating that it has a long cycle life.

[0097] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A silicon-carbon nanoparticle-silicon nanowire composite material, characterized in that, Including silicon nanowires and silicon-carbon nanoparticles; The silicon nanowires intertwine to form a three-dimensional network structure, and the silicon-carbon nanoparticles are embedded in the three-dimensional network structure formed by the intertwining silicon nanowires, and the silicon-carbon nanoparticles are uniformly distributed in the three-dimensional network structure.

2. The silicon-carbon nanoparticle-silicon nanowire composite material according to claim 1, characterized in that, The silicon-carbon nanoparticles account for 8-92% of the weight of the composite material, and the silicon nanowires account for 8-92% of the weight of the composite material. The silicon-carbon nanoparticles have a particle size of 20-500 nm; and / or The silicon nanowires have a diameter of 20-500 nm and a length of 0.02-10000 mm, of which 70% of the silicon nanowires have a length of 0.08-4000 mm.

3. The silicon-carbon nanoparticle-silicon nanowire composite material according to claim 1, characterized in that, The specific surface area of ​​silicon-carbon nanoparticle-silicon nanowire composites is 1-10.0 m². 2 / g.

4. A method for preparing a silicon-carbon nanoparticle-silicon nanowire composite material, characterized in that, Includes the following steps: (1) A mixture of silicon material, fluorinated organic matter and dispersant in a weight ratio of 1:(0.2-10):(0.01-2) is placed in a solvent and mixed to obtain a mixed slurry. The mixed slurry is then dried to obtain a mixture. (2) Place the mixture in the reactor and fill the reactor with inert gas to make the pressure inside the reactor 0-5 MPa; (3) The mixture was subjected to a high-temperature induced reaction to obtain a silicon-carbon nanoparticle-silicon nanowire composite material.

5. The method for preparing the silicon-carbon nanoparticle-silicon nanowire composite material according to claim 4, characterized in that, The fluorinated organic compound mentioned in step (1) is at least one of fluorinated starch, fluorinated phenolic resin, fluorinated epoxy resin, and fluorinated plastics; The particle size of the fluorinated organic compound is 0.1-200 μm.

6. The method for preparing silicon-carbon nanoparticle-silicon nanowire composite material according to claim 5, characterized in that, The molecular weight of the fluorinated organic compound is 50,000 to 10,000,000.

7. The method for preparing the silicon-carbon nanoparticle-silicon nanowire composite material according to claim 4, characterized in that, The average particle size of the silicon material in step (1) is 2-50 μm.

8. The method for preparing the silicon-carbon nanoparticle-silicon nanowire composite material according to claim 4, characterized in that, The high-temperature induced heating rate in step (3) is 50-2000℃ / s, the temperature is 600-2200℃, and the time is 0.1-2h.

9. A solid-state battery anode material, characterized in that, It includes silicon-carbon nanoparticle-silicon nanowire composite materials according to any one of claims 1-3 or silicon-carbon nanoparticle-silicon nanowire composite materials prepared by any one of claims 4-8.

10. The application of the silicon-carbon nanoparticle-silicon nanowire composite material according to any one of claims 1-3 or the silicon-carbon nanoparticle-silicon nanowire composite material according to any one of claims 4-8 in energy storage devices.

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