Silicon-carbon composite negative electrode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking as well as preparation method and application of silicon-carbon composite negative electrode material

Abstract

The invention discloses a silicon-carbon composite negative electrode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking and a preparation method and application thereof.The preparation method comprises the following steps that S1, phenyl polyhedral oligomeric silsesquioxane is added into a 1, 2-dichloroethane solution, heating is conducted under stirring, AlCl3 and a crosslinking agent are added, heating is conducted under stirring, and a silicon-carbon composite negative electrode material is obtained; after the reaction, filtering and washing to obtain a cross-linked polymer; s2, putting the cross-linked polymer into high-temperature equipment, and heating and carbonizing in an inert atmosphere to obtain SiOx (at) C microspheres; s3, adding anhydrous AlCl3 into molten 1-butyl-3-methylimidazole chloride, adding magnesium powder and SiOx-C microspheres while stirring, reacting in an inert atmosphere, washing a product with dichloromethane and diluted hydrochloric acid, and drying to obtain a primary silicon-carbon material; and S4, placing the primary silicon-carbon material in a reactor, and introducing a carbon source gas in an inert atmosphere for carbon coating to obtain the silicon-carbon composite negative electrode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material technology, and more specifically, to a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking, its preparation method, and its application. Background Technology

[0002] Silicon-based materials are considered ideal for next-generation high-energy-density lithium-ion battery anodes due to their advantages such as high theoretical specific capacity, low delithiation potential, and abundant crustal reserves. However, two inherent defects in silicon materials severely hinder their commercialization. First, their poor intrinsic electronic conductivity leads to poor rate performance and significant irreversible capacity loss during charge and discharge. Second, they undergo enormous volume changes during lithium-ion insertion / extraction, with an expansion rate as high as 300%. This repeated and drastic expansion and contraction causes silicon particles to pulverize and active materials to detach from the current collector. Simultaneously, the SEI film on the electrode surface continuously ruptures and regenerates, continuously consuming electrolyte and active lithium, ultimately leading to rapid capacity decay and a sharp decline in cycle life.

[0003] To overcome these challenges, researchers generally employ nano-sizing and composite strategies. Among these, composite with carbon materials is one of the most mainstream and effective methods. Carbon materials possess excellent electrical conductivity and a certain degree of mechanical flexibility, enabling them to both construct conductive networks to improve overall conductivity and act as a buffer matrix to mitigate the volume expansion of silicon. In common silicon-carbon composite materials, carbon coating is a widely used technique. By coating a layer of carbon onto the surface of silicon particles, direct contact between silicon and the electrolyte can be suppressed, forming a stable SEI film.

[0004] Cage-like silsesquioxanes are a class of organic-inorganic hybrid materials with regular nanocage-like structures. Their unique Si-O-Si inorganic framework forms a stable cage-like structure after high-temperature carbonization, providing channels for lithium-ion transport and reserving buffer space for volume expansion. Among numerous polyhedral oligomeric silsesquioxane derivatives, phenyl polyhedral oligomeric silsesquioxanes have attracted considerable attention due to the introduction of benzene rings into their molecular structure. The presence of benzene rings implies a higher carbon content, which, upon pyrolysis, generates a carbon matrix with higher conductivity. This is crucial for improving the overall electrochemical performance of electrode materials, demonstrating significant application potential. However, the application of phenyl polyhedral oligomeric silsesquioxanes in silicon-carbon anode materials has not yet been reported. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that existing silicon-based anode materials have poor electronic conductivity and high expansion rate. In order to overcome the above defects of the prior art, the present invention provides a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking, its preparation method and application.

[0006] The first objective of this invention is to provide a method for preparing a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking, comprising the following steps: S1. Add phenyl polyhedral oligomeric silsesquioxane to a 1,2-dichloroethane solution, heat to 70-75℃ under stirring, then add AlCl3 and a crosslinking agent, react for 12-24 hours, filter and wash to obtain the crosslinked polymer; S2. Place the crosslinked polymer in a high-temperature furnace and heat it to 800-1000℃ under an inert atmosphere for 2-5 hours to obtain SiO. x @C Microsphere; S3. Add anhydrous AlCl3 to molten 1-butyl-3-methylimidazolium chloride, and while stirring, add magnesium powder and the aforementioned SiO2. x @C microspheres were then reacted at 150-250℃ for 3-10 days under an inert atmosphere. The product was washed with dichloromethane and dilute hydrochloric acid and then vacuum dried to obtain primary silicon-carbon material. S4. The primary silicon-carbon material is placed in a reactor, and carbon source gas is introduced under an inert atmosphere to form a continuous carbon coating layer, thereby obtaining a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking.

[0007] In the above scheme, phenyl polyhedral oligomeric silsesquioxanes are used as raw materials for the first time. Utilizing the reactivity of their benzene rings, efficient crosslinking is achieved through Friedel-Crafts alkylation to obtain crosslinked polymers. The crosslinked polymers are then carbonized to obtain SiO₂. x @C microspheres were then combined with molten 1-butyl-3-methylimidazolium chloride in the low-temperature ionic liquid anhydrous AlCl3, followed by magnesium powder catalytic reduction. The resulting primary silicon-carbon material was then carbon-coated via gas-phase pyrolysis, achieving confined growth and interface optimization of silicon nanoparticles under mild conditions. The resulting silicon-carbon composite material is uniform and dense, possessing strong mechanical strength, effectively preventing structural damage caused by volume expansion. The silicon-carbon material formed by phenyl polyhedral oligomeric silsesquioxanes has high carbon content and good conductivity, and the cross-linking between benzene rings forms a rigid cross-linked network, further improving conductivity.

[0008] In one possible implementation, the phenyl polyhedral oligomeric silsesquioxane mentioned in step S1 is selected from one or more of T8-Ph, T10-Ph, and T12-Ph. And / or, the crosslinking agent is selected from carbon tetrachloride and / or dimethoxymethane.

[0009] In one possible implementation, in step S1, the molar ratio of phenyl polyhedral oligomeric silsesquioxane to 1,2-dichloroethane solution is 1:(1~4), the molar ratio of AlCl3 to crosslinking agent is (0.5~2.5):(1~2), and the molar ratio of phenyl polyhedral oligomeric silsesquioxane to AlCl3 is 1:2.5.

[0010] In one possible implementation, the heating rate of step S2 is 5~10℃ / min.

[0011] In one possible implementation, the molar ratio of anhydrous AlCl3 to butyl-3-methylimidazolium chloride in step S3 is (1~2):(1~3), and the magnesium powder and SiO2... x The mass ratio of the C microspheres is (2.5~3):1, and the molar ratio of magnesium powder to anhydrous AlCl3 is (2~3):1.

[0012] In one possible implementation, the carbon source gas in step S4 is selected from at least one of acetylene, ethylene, and methane, and the flow ratio of the carbon source gas to the inert gas is 1:(2~3).

[0013] In one possible implementation, the carbon coating temperature in step S4 is 560-580°C, and the time is 2-5 hours.

[0014] The second objective of this invention is to provide a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking, which is prepared by the preparation method described above.

[0015] In one possible implementation, a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking includes a crosslinked mesh cage-like carbon skeleton with a particle size of 5-20 μm, silicon particles with a particle size of 2-10 nm, and a continuous carbon coating layer with a thickness of 2-20 nm. The silicon particles are confined within the crosslinked mesh cage-like carbon skeleton, and the continuous carbon coating layer covers the surface of the crosslinked mesh cage-like carbon skeleton.

[0016] The third objective of this invention is to provide an application of a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking in lithium-ion battery anode materials.

[0017] The beneficial effects of this invention are as follows: 1. A three-dimensional cross-linked network is formed by the benzene ring of phenyl polyhedral oligomeric silsesquioxane through Friedel-Crafts alkylation reaction. After carbonization, a highly graphitized and mechanically strong three-dimensional cross-linked network cage-like carbon skeleton is formed. SiOx nanoparticles are uniformly distributed in the skeleton structure, which can effectively suppress the volume expansion of silicon and prevent structural damage.

[0018] 2. The inherent nanocage structure of polyhedral oligomeric silsesquioxane materials provides abundant ion transport channels in composite materials and provides buffer space for volume changes.

[0019] 3. The low-temperature reduction process precisely converts SiOx into 2nm-scale silicon nanocrystals, avoiding excessive grain growth. The final vapor-phase carbon coating constructs a continuous conductive interface, effectively suppressing excessive growth of the SEI film, thereby significantly improving the material's conductivity, structural stability, and first-pass coulombic efficiency.

[0020] 4. The obtained silicon-carbon composite anode material has high initial coulombic efficiency, excellent cycle stability and good rate performance. The preparation process is simple and the cost is low, making it suitable for high-performance lithium-ion batteries. Attached Figure Description

[0021] Figure 1 Example 1: Schematic diagram of sample structure; Figure 2 Example 1: SEM image of the sample; Figure 3 Example 1: TEM image of the sample; Figure 4 Charge-discharge characteristics of the sample in Example 1; Figure 5 Cyclic performance graph of sample in Example 1; Figure 6 Rate performance graph of the sample in Example 1. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0023] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0025] like Figure 1 As shown, a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking includes a crosslinked network cage-like carbon skeleton with a particle size of 5-20 μm, silicon particles with a particle size of 2-10 nm, and a continuous carbon coating layer with a thickness of 2-20 nm. The silicon particles are confined within the crosslinked network cage-like carbon skeleton, and the continuous carbon coating layer covers the surface of the crosslinked network cage-like carbon skeleton. Its preparation method includes the following steps: S1. To facilitate the description of the amount of each component added, the following explanation is based on 1 mol of phenyl polyhedral oligomeric silsesquioxane. In actual operation, the values ​​can be expanded or reduced accordingly: Add 1 mol of phenyl polyhedral oligomeric silsesquioxane to 1-4 mol of 1,2-dichloroethane solution. Under a certain stirring rate, heat to 70-75℃, then add 0.5-2.5 mol of AlCl3 and a crosslinking agent. After reacting for 12-24 hours, filter and wash to obtain the crosslinked polymer. The phenyl polyhedral oligomeric silsesquioxane is selected from one or more of T8-Ph, T10-Ph, and T12-Ph, and the crosslinking agent is selected from carbon tetrachloride and / or dimethoxymethane.

[0026] S2. Place the crosslinked polymer in a high-temperature carbonization furnace, heat it to 800-1000℃ under an inert atmosphere, and hold it for 2-5 hours to obtain SiO. x @C microspheres; the heating rate is 5~10℃ / min.

[0027] S3. Add 1-2 mol of anhydrous AlCl3 to 1-3 mol of molten 1-butyl-3-methylimidazolium chloride, and then add magnesium powder and the SiO2 while stirring. x @C microspheres were then reacted at 150-250℃ under an inert atmosphere for 3-10 days. The product was washed with dichloromethane and 5% HCl and vacuum dried to obtain primary silicon-carbon material; magnesium powder and SiO2. x The mass ratio of the C microspheres is (2.5~3):1, and the molar ratio of magnesium powder to anhydrous AlCl3 is (2~3):1.

[0028] S4. Place the primary silicon carbide material in a tube furnace, introduce a carbon source gas under an inert atmosphere for carbon coating to form a continuous carbon coating layer, and obtain a silicon-carbon composite anode material crosslinked based on phenyl polyhedral oligomeric silsesquioxane. The carbon source gas is selected from at least one of acetylene, ethylene, and methane, and the flow rate ratio of the carbon source gas to the inert gas is 1:(2 - 3). The temperature of carbon coating is 560 - 580 °C, and the time is 1 - 3 h.

[0029] The obtained silicon-carbon composite anode material crosslinked based on phenyl polyhedral oligomeric silsesquioxane can be applied in the anode material of lithium-ion batteries.

[0030] The following further illustrates the present invention with specific embodiments.

[0031] Example 1 Step (1): Weigh 0.5 g of T12-Ph and add it to 100 ml of 1,2-dichloroethane solution. Under a certain stirring rate, heat up to 75 °C; then add 2 g of AlCl3 and 20 ml of dimethoxymethane solution; after reacting for 12 h, filter, wash, and dry the product to obtain a crosslinked polymer.

[0032] Step (2): Put the crosslinked polymer obtained in step (1) into a tube furnace, and perform heat treatment at 900 °C for 2 h under a nitrogen atmosphere to obtain SiO x @C microspheres.

[0033] Step (3): Add 6.8 g of anhydrous aluminum chloride to 3.0 g of molten 1-butyl-3-methylimidazolium chloride, and stir for 3 minutes; then add 0.5 g of magnesium powder and 0.2 g of the SiO x @C microspheres obtained in step (2), and stir for 5 minutes; react at 200 °C for 5 days in a tube furnace under a nitrogen atmosphere. The product is first washed with dichloromethane and then with 5% HCl, and vacuum dried at 50 °C for 12 h to obtain the primary silicon carbide material.

[0034] Step (4): Place the primary silicon carbide material obtained in step (3) in a tube furnace. Using acetylene gas as the carbon source, the flow rate ratio of acetylene to nitrogen is 1:3, the coating temperature is 570 °C, and the coating time is 2 h to form a continuous carbon coating layer to obtain the final product of silicon-carbon composite anode material. The SEM and TEM diagrams of the obtained material are as shown in Figure 2 and Figure 3 It can be seen from the figure that the granular product has a cage-shaped carbon skeleton, silicon particles are loaded on the carbon skeleton, and the outer layer of the carbon skeleton is coated with amorphous carbon.

[0035] Perform electrochemical performance tests on the obtained silicon-carbon composite anode material. The results are as shown in Figure 3-5 It is shown that the initial charge specific capacity measured in the first charge-discharge curve at a 0.1C rate is 1903.58 mAh·g−1 , the initial discharge specific capacity is 2051.04 mAh·g −1 , the initial Coulombic efficiency is 92.81%; after 200 cycles, the capacity retention rate is 86.77%; at the current densities of 0.1, 0.2, 0.5, 1, 2, 5 and 10 A·g -1 , the specific capacities of the silicon-carbon composite anode material are 1911.4, 1814.3, 1652.5, 1470.3, 1328.9, 1155.1 and 892.6 mAh·g respectively -1 .

[0036] Example 2 Step (1): Weigh 0.5 g of T12-Ph and add it to 100 ml of 1,2-dichloroethane solution. Under a certain stirring rate, heat it up to 75 °C; then add 2 g of AlCl3 and 20 ml of dimethoxymethane solution; after reacting for 12 h, filter and wash the product to obtain a cross-linked polymer.

[0037] Step (2): Put the cross-linked polymer obtained in step (1) into a tube furnace and heat-treat it at 900 °C for 2 h under a nitrogen atmosphere to obtain SiO x @C microspheres.

[0038] Step (3): Add 6.8 g of anhydrous aluminum chloride to 3.0 g of molten 1-butyl-3-methylimidazolium chloride and stir for 3 minutes; then add 0.5 g of magnesium powder and 0.2 g of the SiO x @C microspheres obtained in step (2), and stir for 5 minutes; react in a tube furnace at 200 °C for 3 days under a nitrogen atmosphere. The product is first washed with dichloromethane and then washed with 5% HCl, and dried in vacuum at 50 °C for 12 h to obtain the primary silicon-carbon material.

[0039] Step (4): Place the primary silicon-carbon material obtained in step (3) in a tube furnace. Using acetylene gas as the carbon source, the flow ratio of acetylene to nitrogen is 1:3, the coating temperature is 570 °C, and the coating time is 2 h to form a continuous carbon coating layer to obtain the final product of the silicon-carbon anode material.

[0040] The test results of the electrochemical performance show that in the first charge-discharge curve at a 0.1C rate, the measured initial charge specific capacity is 1201.63 mAh·g −1 , the initial discharge specific capacity is 1664.31 mAh·g −1 , the initial Coulombic efficiency is 72.2%; after 200 cycles, the capacity retention rate is 74.63%; at the current densities of 0.1, 0.2, 0.5, 1, 2, 5 and 10 A·g -1At current densities of, the specific capacities are 1682.2, 1533.7, 1472.5, 1280.3, 1158.6, 935.1, and 742.4 mAh·g respectively -1 .

[0041] Example 3 Step (1): Weigh 0.5 g of T12-Ph and add it to 100 ml of 1,2-dichloroethane solution. While stirring at a certain rate, heat up to 75 °C; then add 2 g of AlCl3 and 20 ml of dimethoxymethane solution; after reacting for 12 h, filter and wash the product to obtain a cross-linked polymer

[0042] Step (2): Put the cross-linked polymer obtained in step (1) into a tube furnace and heat-treat it at 900 °C for 2 h under a nitrogen atmosphere to obtain SiO x @C microspheres

[0043] Step (3): Add 6.8 g of anhydrous aluminum chloride to 3.0 g of molten 1-butyl-3-methylimidazolium chloride and stir for 3 minutes; then add 0.5 g of magnesium powder and 0.2 g of SiO x @C microspheres, stir for 5 minutes; react at 200 °C for 10 days in a tube furnace under a nitrogen atmosphere. The product is first washed with dichloromethane and then with 5% HCl, and vacuum-dried at 50 °C for 12 h to obtain a primary silicon-carbon material

[0044] Step (4): Place the primary silicon-carbon material obtained in step (3) in a tube furnace. Using acetylene gas as the carbon source, the flow ratio of acetylene to nitrogen is 1:3, the coating temperature is 570 °C, and the coating time is 2 h to form a continuous carbon coating layer to obtain the final product, the silicon-carbon anode material

[0045] The results of electrochemical performance tests show that in the first charge-discharge curve at a 0.1C rate, the initial charge specific capacity is measured to be 1466.95 mAh·g −1 , the initial discharge specific capacity is 1892.84 mAh·g −1 , and the initial Coulomb efficiency is 77.5%; after 200 cycles, the capacity retention rate is 81.88%; at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A·g -1 , the specific capacities of the silicon-carbon anode material are 1883.1, 1724.3, 1602.9, 1352.3, 1197.9, 1003.2, and 832.​​​​​​Step (1): Weigh 0.5 g of T8-Ph and add it to 100 ml of 1,2-dichloroethane solution. While stirring at a certain rate, heat and raise the temperature to 75 °C; then add 2 g of AlCl3 and 20 ml of dimethoxymethane solution; after reacting for 12 h, filter and wash the product to obtain a cross-linked polymer.

[0047] Step (2): Put the cross-linked polymer obtained in step (1) into a tubular furnace and heat-treat it at 900 °C for 2 h under a nitrogen atmosphere to obtain SiO x @C microspheres.

[0048] Step (3): Add 6.8 g of anhydrous aluminum chloride to 3.0 g of molten 1-butyl-3-methylimidazolium chloride and stir for 3 minutes; then add 0.5 g of magnesium powder and 0.2 g of SiO x @C microspheres, stir for 5 minutes; react in a tubular furnace under a nitrogen atmosphere at 200 °C for 5 days. The product is first washed with dichloromethane and then washed with 5% HCl, and dried in vacuo at 50 °C for 12 h to obtain a primary silicon-carbon material.

[0049] Step (4): Place the primary silicon-carbon material obtained in step (3) in a tubular furnace. Using acetylene gas as the carbon source, the flow ratio of acetylene to nitrogen is 1:3, the coating temperature is 570 °C, and the coating time is 2 h to form a continuous carbon coating layer to obtain the final product, the silicon-carbon anode material.

[0050] The results of the electrochemical performance test show that in the first charge-discharge curve at a rate of 0.1C, the initial charge specific capacity measured is 1434.99 mAh·g −1 , the initial discharge specific capacity is 1789.04 mAh·g −1 , the initial Coulomb efficiency is 80.21%; after 200 cycles, the capacity retention rate is 81.64%; at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A·g -1 , the specific capacities of the silicon-carbon anode material are 1779.3, 1651.2, 1532.4, 1324.7, 1221.5, 1019.9, and 738.1 mAh·g -1 .

[0051] Example 5 Step (1): Weigh 0.5 g of T10-Ph and add it to 100 ml of 1,2-dichloroethane solution. While stirring at a certain rate, heat and raise the temperature to 75 °C; then add 2 g of AlCl3 and 20 ml of dimethoxymethane solution; after reacting for 12 h, filter and wash the product to obtain a cross-linked polymer.

[0052] Step (2): Put the cross-linked polymer obtained in step (1) into a tubular furnace and heat-treat it at 900 °C for 2 h under a nitrogen atmosphere to obtain SiO x @C microspheres.

[0053] Step (3): Add 6.8 g of anhydrous aluminum chloride to 3.0 g of molten 1-butyl-3-methylimidazolium chloride and stir for 3 minutes; then add 0.5 g of magnesium powder and 0.2 g of the SiO x @C microspheres obtained in step (2), stir for 5 minutes; react in a tubular furnace under a nitrogen atmosphere at 200 °C for 5 days, wash the product first with dichloromethane and then with 5% HCl, and vacuum dry at 50 °C for 12 h to obtain the primary silicon-carbon material.

[0054] Step (4): Place the primary silicon-carbon material obtained in step (3) in a tubular furnace, use acetylene gas as the carbon source, the flow ratio of acetylene to nitrogen is 1:3, the coating temperature is 570 °C, and the coating time is 2 h to form a continuous carbon coating layer to obtain the final product of silicon-carbon anode material.

[0055] The test results of the electrochemical performance show that in the first charge-discharge curve at a 0.1C rate, the initial charge specific capacity is measured to be 1715.41 mAh·g −1 , the initial discharge specific capacity is 1935.04 mAh·g −1 , and the initial Coulomb efficiency is 88.65%; after 200 cycles, the capacity retention rate is 82.38%; at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A·g -1 , the specific capacities of the silicon-carbon anode are 1901.9, 1826.1, 1633.3, 1420.1, 1298.9, 1075.7, and 802.4 mAh·g[[ID=2), respectively.0]] -1 .

[0056] Comparative Example 1 Step (1): Weigh 0.5 g of T10-Ph and add it to 100 ml of 1,2-dichloroethane solution. Heat it up to 75 °C at a certain stirring rate; then add 2 g of AlCl3 and 20 ml of dimethoxymethane solution; after reacting for 12 h, filter and wash the product to obtain the cross-linked polymer.

[0057] Step (2): Put the cross-linked polymer obtained in step (1) into a tubular furnace and heat-treat it at 900 °C for 2 h under a nitrogen atmosphere to obtain SiO x @C microspheres.

[0058] Step (3): The SiO xThe @C microspheres were placed in a tubular furnace. Using acetylene gas as the carbon source, with a flow rate ratio of acetylene to nitrogen of 1:3, a coating temperature of 570 °C, and a coating time of 2 h, a continuous carbon coating layer was formed to obtain the final product, the silicon-carbon anode material.

[0059] The results of the electrochemical performance test showed that in the first charge-discharge curve at a 0.1C rate, the initial charge specific capacity was measured to be 1279.47 mAh·g −1 , and the initial discharge specific capacity was 1791.61 mAh·g −1 , and the initial Coulombic efficiency was 71.41%; after 200 cycles, the capacity retention rate was 78.98%; at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A·g -1 , the specific capacities of the silicon-carbon anode material were 1501.3, 1426.7, 1293.5, 980.7, 838.2, 625.4, and 482.7 mAh·g -1 .

[0060] Comparative Example 2 Step (1): Weigh 0.5 g of T10-Ph and add it to 100 ml of 1,2-dichloroethane solution. While stirring at a certain rate, heat it up to 75 °C; then add 2 g of AlCl3 and 20 ml of dimethoxymethane solution; after reacting for 12 h, filter and wash the product to obtain a crosslinked polymer.

[0061] Step (2): Put the crosslinked polymer obtained in step (1) into a tubular furnace and heat-treat it at 900 °C for 2 h under a nitrogen atmosphere to obtain SiO x @C microspheres.

[0062] Step (3): Add 6.8 g of anhydrous aluminum chloride to 3.0 g of molten 1-butyl-3-methylimidazolium chloride and stir for 3 minutes; then add 0.5 g of magnesium powder and 0.2 g of the SiO x @C microspheres obtained in step (2), and stir for 5 minutes; react at 200 °C for 5 d in a tubular furnace under a nitrogen atmosphere. The product is first washed with dichloromethane and then with 5% HCl, and vacuum-dried at z0 °C for 12 h to obtain the primary silicon-carbon material.

[0063] The results of the electrochemical performance test showed that in the first charge-discharge curve at a 0.1C rate, the initial charge specific capacity was measured to be 1246.37 mAh·g −1 , and the initial discharge specific capacity was 1768.21 mAh·g −1 , and the initial Coulombic efficiency was 70.45%; after 200 cycles, the capacity retention rate was 79.73%; at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A·g -1At the specified current densities, the specific capacities of the silicon-carbon anode were 1701.42, 1557.9, 1404.2, 1371.1, 1108.9, 977.3, and 739.5 mAh·g, respectively. -1 .

[0064] The performance test results of the silicon-carbon composite anode materials for lithium-ion batteries obtained in each embodiment and comparative example are shown in Table 1 below.

[0065] Table 1. Performance test results of silicon-carbon composite anode materials for lithium-ion batteries obtained from each embodiment and comparative example. Based on the above embodiments and comparative examples, it can be seen that Examples 1 to 3 are silicon-carbon composite anode materials obtained with different reduction times, and Examples 4 and 5 are silicon-carbon composite anode materials obtained with different phenyl polyhedral oligomeric silsesquioxanes; Comparative Example 1 is a comparative material prepared without reduction; Comparative Example 2 is a comparative material prepared without gas-phase carbon coating; the remaining conditions for Comparative Examples 1 and 2 are the same as those for Example 1. By comparing the initial charge specific capacity and initial discharge specific capacity, initial coulombic efficiency, capacity retention after 200 cycles, and rate performance at current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 10 A·g⁻¹ measured in the first charge-discharge curves of the silicon-carbon composite anode materials prepared in each embodiment and comparative example, it can be seen that: First, the benzene ring of the phenyl polyhedral oligomeric silsesquioxane forms a three-dimensional cross-linked network through Friedel-Crafts alkylation reaction, and then after high-temperature carbonization, a highly graphitized, high-mechanical-strength cage-like carbon skeleton with uniformly distributed SiO₂ is formed. x The structure of nanoparticles effectively suppresses the volume expansion of silicon while preventing structural damage. However, the performance of silicon-carbon composite anode materials obtained using different phenyl polyhedral oligomeric silsesquioxanes varies. This is because T10-Ph, due to its excellent solubility, can form a more continuous, uniform, and robust carbon network. This carbon network effectively limits the coarsening of silicon grains during subsequent reduction and provides a buffer space for their volume expansion. T8-Ph, due to its poor solubility, forms a carbon network with poor uniformity, greater brittleness, and insufficient buffering capacity. T12-Ph falls between the two. Secondly, SiO2 is reduced at a lower temperature using an ionic liquid reduction method. x This results in a structure where nano-silicon is uniformly distributed within a carbon framework. However, different reduction times lead to variations in their properties; the shorter reduction time (3d) results in SiO₂... x It cannot be fully reduced, leaving residual SiO xA higher reduction time (10 days) results in poorer material performance; this leads to a higher specific surface area, increasing the contact area between the active material and the electrolyte, resulting in the formation of more SEI films and causing more lateral reactions, leading to significant irreversible capacity loss. A 5-day reduction time can reduce SiO₂... x Achieving thorough and uniform reduction in an ionic liquid medium results in nano-silicon with a suitable size that does not damage the carbon framework. This leads to high initial coulombic efficiency, excellent cycling stability, and good rate performance. Finally, to enhance the electrical properties of the silicon-carbon composite, a carbon layer structure is coated onto the material surface using vapor-phase coating technology. This structure possesses excellent protective and buffering capabilities, maintaining the stability of the silicon-carbon composite structure while forming a stable SEI film, preventing continuous SEI growth during cycling, thereby improving initial coulombic efficiency and long-term cycle life. In summary, this invention utilizes the benzene rings of phenyl polyhedral oligomeric silsesquioxanes to form a three-dimensional cross-linked network through Friedel-Crafts alkylation. After carbonization, a highly graphitized, high-mechanical-strength cage-like carbon framework is formed, providing abundant ion transport channels and buffering space for volume changes. The low-temperature reduction process precisely reduces SiO₂... x The silicon nanocrystals are transformed into 2 nm-scale silicon nanocrystals, and the final gas-phase carbon coating constructs a continuous conductive interface that can effectively buffer volume changes and form a multi-level composite structure with good conductivity.

[0066] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking, characterized in that, Includes the following steps: S1. Add phenyl polyhedral oligomeric silsesquioxane to a 1,2-dichloroethane solution, heat to 70-75℃ under stirring, then add AlCl3 and a crosslinking agent, react for 12-24 hours, filter and wash to obtain the crosslinked polymer; S2. Place the crosslinked polymer in a high-temperature furnace and heat it to 800-1000℃ under an inert atmosphere for 2-5 hours to obtain SiO. x @C Microsphere; S3. Add anhydrous AlCl3 to molten 1-butyl-3-methylimidazolium chloride, and while stirring, add magnesium powder and the aforementioned SiO2. x @C microspheres were then reacted at 150-250℃ for 3-10 days under an inert atmosphere. The product was washed with dichloromethane and dilute hydrochloric acid and then vacuum dried to obtain primary silicon-carbon material. S4. The primary silicon-carbon material is placed in a reactor, and carbon source gas is introduced under an inert atmosphere to form a continuous carbon coating layer, thereby obtaining a silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking.

2. The preparation method according to claim 1, characterized in that, The phenyl polyhedral oligomeric silsesquioxane mentioned in step S1 is selected from one or more of T8-Ph, T10-Ph, and T12-Ph. And / or, the crosslinking agent is selected from carbon tetrachloride and / or dimethoxymethane.

3. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of phenyl polyhedral oligomeric silsesquioxane to 1,2-dichloroethane solution is 1:(1~4), the molar ratio of AlCl3 to crosslinking agent is (0.5~2.5):(1~2), and the molar ratio of phenyl polyhedral oligomeric silsesquioxane to AlCl3 is 1:2.

5.

4. The preparation method according to claim 1, characterized in that, The heating rate in step S2 is 5~10℃ / min.

5. The preparation method according to claim 1, characterized in that, In step S3, the molar ratio of anhydrous AlCl3 to butyl-3-methylimidazol chloride is (1~2):(1~3), and magnesium powder and SiO2 are used. x The mass ratio of the C microspheres is (2.5~3):1, and the molar ratio of magnesium powder to anhydrous AlCl3 is (2~3):

1.

6. The preparation method according to claim 1, characterized in that, In step S4, the carbon source gas is selected from at least one of acetylene, ethylene, and methane, and the flow ratio of the carbon source gas to the inert gas is 1:(2~3).

7. The preparation method according to claim 1, characterized in that, In step S4, the carbon coating temperature is 560-580℃ and the time is 2-5 hours.

8. A silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking according to claim 8, characterized in that, It includes a cross-linked mesh cage-like carbon skeleton with a particle size of 5-20 μm, silicon particles with a particle size of 2-10 nm, and a continuous carbon coating layer with a thickness of 2-20 nm. The silicon particles are confined within the cross-linked mesh cage-like carbon skeleton, and the continuous carbon coating layer covers the surface of the cross-linked mesh cage-like carbon skeleton.

10. The application of the silicon-carbon composite anode material based on phenyl polyhedral oligomeric silsesquioxane crosslinking as described in claim 8 or 9 in lithium-ion battery anode materials.

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