A composite porous carbon-based silicon-carbon anode material, its preparation method, secondary battery, and power device thereof.

Abstract

This application discloses a composite porous carbon-based silicon-carbon anode material, its preparation method, a secondary battery, and an electrical device. The composite porous carbon-based silicon-carbon anode material is composed of composite porous carbon, nano-silicon particles, and a carbon coating layer. The composite porous carbon is pyrolytic porous carbon coated with resin-based porous carbon. The pyrolytic porous carbon core in the composite porous carbon material has high graphitization and good pore connectivity, exhibiting excellent electronic and lithium-ion conductivity, ensuring good rate performance of the silicon-carbon material. The resin-based porous carbon shell has excellent mechanical strength, effectively limiting the volume expansion of the pyrolytic porous carbon core caused by the lithiation of nano-silicon particles, thereby ensuring good cycle stability of the battery. The surface-coated carbon layer effectively prevents nano-silicon particles from contacting the electrolyte, reducing electrolyte consumption and improving battery coulombic efficiency. Therefore, the composite porous carbon-based silicon-carbon anode material provided in this application has the advantages of both good rate performance and high cycle stability.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a composite porous carbon-based silicon-carbon anode material and its preparation method, a secondary battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and no memory effect, have been widely used in portable electronic devices, electric vehicles, and energy storage systems. However, currently, commercially available lithium-ion battery anode materials mainly use graphite, which has a relatively low theoretical specific capacity (372 mAh / g), making it difficult to meet the urgent demand for higher energy density batteries in electric vehicles and energy storage systems. Silicon, due to its extremely high theoretical specific capacity (3579 mAh / g), is considered one of the most promising next-generation lithium-ion battery anode materials. However, silicon experiences significant volume expansion (over 300%) during lithium intercalation, severely limiting its industrial application. To address the volume expansion problem of silicon-based anode materials, the industry generally adopts a technology route that combines them with carbon materials. Among these, chemical vapor deposition (CVD) silicon-carbon materials utilize CVD to deposit nanoscale silicon particles within the pores of a porous carbon framework, resulting in a low volume expansion rate and good cycle stability, and have become one of the current mainstream silicon-carbon composite solutions.

[0003] Currently, commercially available chemical vapor deposition (CVD) silicon-carbon materials generally employ biomass-based and resin-based porous carbon as the framework. However, both types of porous carbon materials exhibit poor conductivity and lithium-ion transport capabilities, resulting in unsatisfactory rate performance of the prepared CVD silicon-carbon materials. Petroleum coke-based porous carbon possesses excellent electronic and lithium-ion conductivity, leading to improved rate performance in CVD silicon-carbon materials prepared using it. However, petroleum coke-based porous carbon suffers from insufficient mechanical strength, making it difficult to effectively limit the volume expansion after lithiation, resulting in poor cycle stability of the prepared CVD silicon-carbon materials. Therefore, there is an urgent need to develop a CVD silicon-carbon anode material that combines good rate performance and cycle stability. Summary of the Invention

[0004] The purpose of this application is to overcome the above-mentioned deficiencies of the prior art and provide a composite porous carbon-based silicon-carbon anode material and its preparation method, secondary battery and power device. The aim is to provide a composite porous carbon-based chemical vapor deposition silicon-carbon anode material with both excellent electronic / lithium-ion conductivity and low volume expansion rate, thereby improving the rate performance and cycle stability of lithium-ion batteries using it.

[0005] The technical problem solved by this application is achieved by the following technical solution.

[0006] This application provides a composite porous carbon-based silicon-carbon anode material and its preparation method, including the following steps: Step a: Mix the raw material coke with the resin solution evenly, and prepare the first intermediate, namely the resin-coated raw material coke, by spray drying. Step b: The first intermediate is placed in a tube furnace for carbonization treatment, and after cooling to room temperature, the second intermediate, i.e., composite carbon material, is obtained. Step c: Activate the second intermediate by introducing an activation gas, and then cool it to room temperature to obtain the third intermediate, which is a composite porous carbon material. Step d: The third intermediate is fed into a fluidized bed and subjected to chemical vapor deposition of silicon nanoparticles to obtain the fourth intermediate; Step e: Chemical vapor deposition carbon coating is performed on the fourth intermediate to obtain a composite porous carbon-based silicon-carbon anode material.

[0007] In some embodiments of this application, in step a, raw coke and a resin solution with a concentration of 5wt.% to 20wt.% are mixed evenly at a mass ratio of raw coke to resin of 1:1 to 5:1, and the first intermediate is prepared by spray drying under conditions of an inlet air temperature of 80℃ to 180℃ and a feed rate of 1L / h to 5L / h.

[0008] In some embodiments of this application, the resin in the resin solution includes one or more of phenolic resin, epoxy resin, polyester resin, and acrylic resin, and the solvent includes one or more of ethanol, acetone, xylene, and ethyl acetate. The raw coke is an irregular blocky low-sulfur, medium-sulfur, or high-sulfur raw coke powder with a median particle size of 3μm to 12μm.

[0009] In some embodiments of this application, in step b, the carbonization temperature is 900℃~1200℃ and the time is 2h~5h.

[0010] In some embodiments of this application, in step c, the activation treatment temperature is 900℃~1200℃, the time is 2h~12h, the activation gas is selected from one or more of carbon dioxide, water vapor, and air, and the flow rate of the activation gas is 50mL / min~250mL / min.

[0011] In some embodiments of this application, in step d, the temperature for chemical vapor deposition of silicon nanoparticles is 450°C to 550°C, the time is 5h to 12h, and one or more of silane and disilane are used as the silicon source gas.

[0012] In some embodiments of this application, in step e, the temperature for chemical vapor deposition of the carbon layer is 500°C to 800°C, the time is 2h to 8h, and one or more of methane, acetylene, propane, and propylene are used as the carbon source gas.

[0013] This application also provides a composite porous carbon-based silicon-carbon anode material prepared according to the above-described preparation method.

[0014] This application also provides a secondary battery comprising the aforementioned composite porous carbon-based silicon-carbon anode material.

[0015] This application also provides an electrical device that includes the aforementioned secondary battery.

[0016] This application has the following beneficial effects: The composite porous carbon-based silicon-carbon anode material provided in this application comprises composite porous carbon, nano-silicon particles, and a carbon coating layer. The composite porous carbon is a char-based porous carbon coated with resin-based porous carbon. The char-based porous carbon core has a high degree of graphitization and good pore connectivity, exhibiting excellent electronic and lithium-ion conductivity, ensuring good rate performance of the silicon-carbon material. The resin-based porous carbon shell possesses excellent mechanical strength, effectively limiting the volume expansion of the char-based porous carbon core caused by the lithiation of nano-silicon, thereby ensuring good cycle stability of the battery. The surface carbon coating effectively prevents contact between the nano-silicon particles and the electrolyte, thus reducing electrolyte consumption and improving battery coulombic efficiency. Therefore, the composite porous carbon-based silicon-carbon anode material provided in this application combines the advantages of good rate performance and high cycle stability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the preparation process of the composite porous carbon-based silicon-carbon anode material provided in this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] The following is a detailed description of a composite porous carbon-based silicon-carbon anode material, its preparation method, a secondary battery, and an electrical device provided in the embodiments of this application.

[0021] Firstly, this application provides a method for preparing a composite porous carbon-based silicon-carbon anode material, see [link to relevant documentation]. Figure 1 This includes the following steps: Step a: Mix the raw material coke with the resin solution evenly, and prepare the first intermediate, namely the resin-coated raw material coke, by spray drying. Step b: The first intermediate is placed in a tube furnace for carbonization treatment, and after cooling to room temperature, the second intermediate, i.e., composite carbon material, is obtained. Step c: Activate the second intermediate by introducing an activation gas, and then cool it to room temperature to obtain the third intermediate, which is a composite porous carbon material. Step d: The third intermediate is fed into a fluidized bed and subjected to chemical vapor deposition of silicon nanoparticles to obtain the fourth intermediate; Step e: Chemical vapor deposition carbon coating is performed on the fourth intermediate to obtain a composite porous carbon-based silicon-carbon anode material.

[0022] This application provides a method for preparing a composite porous carbon-based silicon-carbon anode material. It innovatively proposes a novel high-performance composite porous carbon material in which silicon is chemically vapor-deposited within a coke-based porous carbon core and a resin-based porous carbon shell, followed by a carbon coating to obtain the composite porous carbon-based silicon-carbon anode material. The nano-silicon particles deposited within the pores of the composite porous carbon material serve as the main component providing capacity. While providing a portion of the capacity, the composite porous carbon material also buffers the expansion of the nano-silicon particles. The carbon coating layer on the surface of the composite porous carbon matrix effectively prevents the nano-silicon particles from contacting the electrolyte, thereby reducing electrolyte consumption and improving the battery's coulombic efficiency. Among them, the coke-based porous carbon core in the composite porous carbon material has a high degree of graphitization and good pore connectivity, exhibiting excellent electronic and lithium-ion conductivity. Furthermore, the coke-based porous carbon more readily forms mesopores and macropores during the activation and pore-forming process, which can buffer the volume expansion of the anode material caused by lithiation of silicon, ensuring good rate performance of the silicon-carbon material. The resin-based porous carbon shell possesses excellent mechanical strength, effectively limiting the volume expansion of the coke-based porous carbon core caused by nano-lithiation of silicon, thereby ensuring good cycle stability of the battery. Therefore, the composite porous carbon-based silicon-carbon anode material provided in this application combines the advantages of good rate performance and high cycle stability.

[0023] In some optional embodiments, in step a, the raw coke and the resin solution with a concentration of 5wt.%~20wt.% are mixed evenly at a mass ratio of raw coke to resin of 1:1~5:1, and the first intermediate is prepared by spray drying under the conditions of an inlet air temperature of 80℃~180℃ and a feed rate of 1L / h~5L / h. For example, the concentration of the resin solution can be 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.%, 10wt.%, 11wt.%, 12wt.%, 13wt.%, 14wt.%, 15wt.%, 16wt.%, 17wt.%, 18wt.%, 19wt.%, 20wt.%, and any other value between 5wt.% and 20wt.%, the mass ratio of raw coke to resin can be 1:1, 2:1, 3:1, 4:1, 5:1, etc., the inlet air temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, and any other value between 80℃ and 180℃, and the feed rate can be 1L / h, 2L / h, 3L / h, 4L / h, 5L / h, and any other value between 1L / h and 5L / h.

[0024] This application utilizes resin-coated coke to prepare composite porous carbon materials. Experimental results show that a higher proportion of coke-based porous carbon results in better rate performance of the silicon-carbon anode material, but worse cycle performance. Coating the surface of the coke with resin can enhance the material's strength and thus improve cycle stability, but it reduces rate performance. Through multiple experiments, it was verified that mixing coke with a resin solution of 5wt.%~20wt.% at a coke-to-resin mass ratio of 1:1~5:1, followed by spray drying to prepare resin-coated coke, and then further carbonization, activation, and coating treatments, yielded a composite porous carbon-based silicon-carbon anode material that exhibits both good rate performance and cycle stability when applied to lithium-ion batteries. Furthermore, it is worth noting that compared to other drying methods, spray drying of the coke for resin coating not only produces the most uniform resin coating layer but also helps suppress the expansion of the silicon-carbon anode material.

[0025] In some optional embodiments, the resin in the resin solution includes one or more of phenolic resin, epoxy resin, polyester resin, and acrylic resin; the solvent includes one or more of ethanol, acetone, xylene, and ethyl acetate; and the raw material coke is irregularly shaped, blocky, low-sulfur, medium-sulfur, or high-sulfur raw material coke powder with a median particle size of 3 μm to 12 μm. For example, the petroleum coke may have a median particle size of 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any other value between 3 μm and 12 μm.

[0026] In some optional embodiments, in step b, the carbonization temperature is 900°C to 1200°C, and the time is 2 hours to 5 hours. For example, the carbonization temperature can be 900°C, 1000°C, 1100°C, 1200°C, or any other value between 900°C and 1200°C, and the time can be 2 hours, 3 hours, 4 hours, 5 hours, or any other value between 2 hours and 5 hours.

[0027] Experiments have shown that excessively high carbonization temperatures can make the carbon layer brittle, while excessively low carbonization temperatures cannot guarantee complete carbonization. A carbonization temperature of 900℃~1200℃ and a time of 2h~5h are advantageous for preparing composite porous carbon materials with good pore structure, and are conducive to achieving the best balance between conductivity and structural stability.

[0028] In some optional embodiments, in step c, the activation treatment temperature is 900℃~1200℃, the time is 2h~12h, the activation gas is selected from one or more of carbon dioxide, water vapor, and air, and the flow rate of the activation gas is 50mL / min~250 mL / min. Exemplarily, the activation treatment temperature can be 900℃, 1000℃, 1100℃, 1200℃, or any other value between 900℃ and 1200℃, and the time can be 2h, 3h, 4h, 5h, or any other value between 2h and 5h. The flow rate of the activating gas can be 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min, 110 mL / min, 120 mL / min, 130 mL / min, 140 mL / min, 150 mL / min, 160 mL / min, 170 mL / min, 180 mL / min, 190 mL / min, 200 mL / min, 210 mL / min, 220 mL / min, 230 mL / min, 240 mL / min, 250 mL / min, and any other value between 50 mL / min and 250 mL / min.

[0029] Experiments have verified that activation temperature is a key parameter for controlling the pore structure of porous carbon frameworks (such as specific surface area, pore size, and pore volume). Too low an activation temperature results in insufficient pore formation, while too high a temperature damages the carbon framework structure. Controlling the activation temperature to 900℃~1200℃ and the time to 2h~12h ensures sufficient silicon storage space while maintaining structural integrity, effectively buffering volume expansion and improving cycle stability.

[0030] In some optional embodiments, in step d, the temperature for chemical vapor deposition of silicon nanoparticles is 450°C to 550°C, the time is 5h to 12h, and one or more of silane and disilane are used as the silicon source gas. Exemplarily, the temperature for chemical vapor deposition of silicon nanoparticles can be 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, or any other value between 450°C and 550°C, and the time can be 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, or any other value between 5h and 12h.

[0031] In some optional embodiments, in step e, the temperature for chemical vapor deposition of the carbon coating layer is 500°C to 800°C, the time is 2h to 8h, and one or more of methane, acetylene, propane, and propylene are used as the carbon source gas. Exemplarily, the temperature for chemical vapor deposition of the carbon coating layer can be any other value between 500°C, 500°C, 500°C, 500°C, and 500°C to 800°C, and the time can be any other value between 2h, 3h, 4h, 5h, 6h, 7h, 8h, and 2h to 8h.

[0032] This application provides a method for preparing a composite porous carbon-based silicon-carbon anode material. After chemically vapor-depositing nano-silicon particles within the composite porous carbon material, a carbon source gas is used to coat the surface with a carbon layer, which can simultaneously improve electronic conductivity, buffer volume expansion, and stabilize the interface. Furthermore, its flexible physical structure can absorb the enormous volume change stress of silicon during charging and discharging, preventing electrode pulverization and peeling, thereby significantly extending cycle life. In addition, the carbon layer can isolate the electrolyte from direct contact with silicon, reducing irreversible side reactions and improving the initial coulombic efficiency.

[0033] Secondly, this application also provides a composite porous carbon-based silicon-carbon anode material prepared according to the above-described preparation method.

[0034] Thirdly, this application also provides a secondary battery comprising the aforementioned composite porous carbon-based silicon-carbon anode material.

[0035] Fourthly, this application also provides an electrical device that includes the aforementioned secondary battery.

[0036] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0037] This application provides a method for preparing a composite porous carbon-based silicon-carbon anode material. (See also...) Figure 1 This includes the following steps: Step a: Using one or more of the following raw material coke powders with a median particle size of 3μm~12μm (low-sulfur, medium-sulfur, and high-sulfur), the raw material coke is mixed with a resin solution with a concentration of 5wt.%~20wt.% at a raw material coke to resin solute mass ratio of 1:1~5:1. Under the conditions of an inlet air temperature of 80℃~180℃ and a feed rate of 1L / h~5L / h, the first intermediate, namely the resin-coated raw material coke, is prepared by spray drying. The solute of the resin solution is one or more of phenolic resin, epoxy resin, polyester resin, and acrylic resin, and the solvent is one or more of ethanol, acetone, xylene, and ethyl acetate. Step b: Place the first intermediate in a tube furnace and carbonize it at 900℃~1200℃ for 2h~5h. After cooling to room temperature, the second intermediate, i.e., composite carbon material, is obtained. Step c: Activate the second intermediate by introducing one or more of carbon dioxide, water vapor, or air as an activation gas at 900℃~1200℃ for 2h~12h. After cooling to room temperature, obtain the third intermediate, i.e., the composite porous carbon material; wherein the flow rate of the activation gas is 50mL / min~250mL / min. Step d: The third intermediate is fed into a fluidized bed and chemically vapor-deposited into nano-silicon particles using one or more of silane or silane as the silicon source gas at 450℃~550℃ for 5h~12h to obtain the fourth intermediate. Step e: At 500℃~800℃, the fourth intermediate is coated with carbon by chemical vapor deposition for 2h~8h using one or more of methane, acetylene, propane and propylene as carbon source gases to obtain composite porous carbon-based silicon-carbon anode material.

[0038] Example 1 This embodiment provides a method for preparing a composite porous carbon-based silicon-carbon anode material, including the following steps: Step a: Using irregular blocky low-sulfur raw coke powder with a median particle size of 3 μm as raw coke, 100 g of raw coke is mixed evenly with 2000 g of phenolic resin-ethanol solution with a concentration of 5 wt.%, and the first intermediate is prepared by spray drying under the conditions of inlet air temperature of 180℃ and feed rate of 5 L / h. Step b: The first intermediate is placed in a tube furnace and carbonized at 1200°C for 5 hours. After cooling to room temperature, the second intermediate is obtained. Step c: Activate the second intermediate by introducing carbon dioxide at 1200℃ for 12 hours, and then cool to room temperature to obtain the third intermediate; The carbon dioxide flow rate was 250 mL / min. Step d: The third intermediate is fed into a fluidized bed and chemically vapor-deposited into nano-silicon particles using silane as the silicon source gas at 450°C for 5 hours to obtain the fourth intermediate. Step e: At 500℃, the fourth intermediate is coated with carbon by chemical vapor deposition for 2 hours using acetylene as the carbon source gas to obtain a composite porous carbon-based silicon-carbon anode material.

[0039] Example 2 This embodiment provides a method for preparing a composite porous carbon-based silicon-carbon anode material, including the following steps: Step a: Using irregular blocky medium-sulfur raw coke powder with a median particle size of 12 μm as raw coke, 100 g of raw coke is mixed with 200 g of epoxy resin-acetone solution with a concentration of 10 wt.%, and the first intermediate is prepared by spray drying under the conditions of air inlet temperature of 80℃ and feed rate of 1 L / h. Step b: The first intermediate is placed in a tube furnace and carbonized at 1000°C for 2 hours. After cooling to room temperature, the second intermediate is obtained. Step c: Activate the second intermediate by introducing water vapor at 1000℃ for 6 hours, and then cool to room temperature to obtain the third intermediate; The carbon dioxide flow rate was 50 mL / min. Step d: The third intermediate is fed into a fluidized bed and subjected to chemical vapor deposition of nano-silicon particles on the third intermediate at 550°C with silane as the silicon source gas for 8 hours to obtain the fourth intermediate. Step e: At 800℃, the fourth intermediate is coated with carbon by chemical vapor deposition for 8 hours using methane as the carbon source gas to obtain a composite porous carbon-based silicon-carbon anode material.

[0040] Example 3 This embodiment provides a method for preparing a composite porous carbon-based silicon-carbon anode material, including the following steps: Step a: Using irregular blocky high-sulfur raw coke powder with a median particle size of 8 μm as raw coke, 100 g of raw coke is mixed with 250 g of acrylic resin-ethyl acetate solution with a concentration of 20 wt.%, and the first intermediate is prepared by spray drying under the conditions of inlet air temperature of 120 ℃ and feed rate of 2 L / h. Step b: The first intermediate is placed in a tube furnace and carbonized at 900°C for 4 hours. After cooling to room temperature, the second intermediate is obtained. Step c: Activate the second intermediate by introducing air at 1200℃ for 2 hours, and then cool to room temperature to obtain the third intermediate; The air inlet flow rate is 100 mL / min; Step d: The third intermediate is fed into a fluidized bed and chemically vapor-deposited into nano-silicon particles using silane as the silicon source gas at 500°C for 12 hours to obtain the fourth intermediate. Step e: At 700℃, the fourth intermediate is coated with carbon by chemical vapor deposition for 4 hours using propane as the carbon source gas to obtain a composite porous carbon-based silicon-carbon anode material.

[0041] Example 4 This embodiment provides a method for preparing a composite porous carbon-based silicon-carbon anode material, including the following steps: Step a: Using irregular blocky medium-sulfur raw coke powder with a median particle size of 5 μm as raw coke, 150 g of raw coke is mixed with 500 g of polyester resin-xylene solution with a concentration of 10 wt.%, and the first intermediate is prepared by spray drying under the conditions of inlet air temperature of 150℃ and feed rate of 3 L / h. Step b: The first intermediate is placed in a tube furnace and carbonized at 1100°C for 3 hours. After cooling to room temperature, the second intermediate is obtained. Step c: Activate the second intermediate by introducing water vapor at 900℃ for 10 hours, and then cool to room temperature to obtain the third intermediate; The air inlet flow rate is 150 mL / min; Step d: The third intermediate is fed into a fluidized bed and chemically vapor-deposited into nano-silicon particles using silane as the silicon source gas at 530°C for 10 hours to obtain the fourth intermediate. Step e: At 750℃, the fourth intermediate is coated with carbon by chemical vapor deposition for 6 hours using propylene as the carbon source gas to obtain a composite porous carbon-based silicon-carbon anode material.

[0042] Example 5 This embodiment provides a method for preparing a composite porous carbon-based silicon-carbon anode material, including the following steps: Step a: Using irregular blocky low-sulfur raw coke powder with a median particle size of 6 μm as raw coke, 100 g of raw coke is mixed with 250 g of phenolic resin-acetone solution with a concentration of 10 wt.%, and the first intermediate is prepared by spray drying under the conditions of inlet air temperature of 160℃ and feed rate of 4 L / h. Step b: The first intermediate is placed in a tube furnace and carbonized at 1000°C for 4 hours. After cooling to room temperature, the second intermediate is obtained. Step c: Activate the second intermediate by introducing carbon dioxide at 1000℃ for 8 hours, and then cool to room temperature to obtain the third intermediate; The air inlet flow rate is 180 mL / min; Step d: The third intermediate is fed into a fluidized bed and subjected to chemical vapor deposition of nano-silicon particles on the third intermediate at 500°C with silane as the silicon source gas for 9 hours to obtain the fourth intermediate. Step e: At 700℃, the fourth intermediate is coated with carbon by chemical vapor deposition for 3 hours using acetylene as the carbon source gas to obtain a composite porous carbon-based silicon-carbon anode material.

[0043] Comparative Example 1 The only difference from Example 5 is that step a, which constructs the resin-based porous carbon shell, is not performed; instead, steps b, c, d, and e are directly performed on the raw material coke to prepare the silicon-carbon anode material.

[0044] Comparative Example 2 The only difference from Example 5 is that commercially available irregular blocky petroleum coke-based porous carbon is used as raw material, and steps d and e are carried out directly to prepare silicon-carbon anode materials.

[0045] Comparative Example 3 The only difference from Example 5 is that: commercially available irregular blocky resin-based carbon powder with a median particle size of 6 μm is used as raw material, and steps a, b, c, d, and e are performed to prepare silicon-carbon anode material.

[0046] Comparative Example 4 The only difference from Example 5 is that: commercially available irregular blocky biomass-based carbon powder with a median particle size of 6 μm is used as raw material, and steps a, b, c, d, and e are performed to prepare silicon-carbon anode materials.

[0047] The silicon-carbon anode materials described in Examples 1-5 and Comparative Examples 1-4 were assembled into CR2032 type button half-cells for electrochemical performance testing. The specific testing scheme is as follows: Button half-cell assembly: 1. Using deionized water as solvent, prepare an electrode slurry with a solid content of 48% by mixing silicon-carbon anode material, conductive carbon black, carbon nanotubes, and polyacrylic acid in a mass ratio of 80:8:2:10. 2. The prepared slurry was coated onto the surface of a copper foil with a thickness of 9 μm using an automatic coating machine. The coating thickness was set to 80 μm. Then, it was vacuum dried at 60°C for 2 hours to obtain the negative electrode sheet. 3. The dried negative electrode sheet was rolled to a thickness of 60μm using an electric double roller mill. Then, the electrode sheet was punched into a circular sheet with a diameter of 10mm using a punching machine. After vacuum drying at 80℃ for 12h, the negative electrode circular sheet was weighed and the mass of active material was calculated. 4. Using elemental lithium sheets as the counter electrode, Celgard 2250 membrane as the battery separator, and 1.0M LiPF6 EC / DEC solution with a volume ratio of 1:1 (with 5wt.% FEC added) as the electrolyte, CR2032 coin cell half-cells were assembled and their electrochemical performance was tested. Electrochemical performance testing: 1. Reversible specific capacity: After assembling the button half-cell, let it stand for 2 hours, then discharge it to 0.005V at a constant current of 0.1C; after standing for 5 minutes, charge it to 1.5V at a constant current of 0.1C. The resulting charging specific capacity is the reversible specific capacity of the negative electrode material.

[0048] 2. First Coulomb Efficiency: In reversible specific capacity testing, the ratio of the charging specific capacity to the discharging specific capacity of the negative electrode material is its first coulomb efficiency.

[0049] 3. Initial Full Charge Expansion Rate: After assembling the button cell, let it stand for 2 hours, then discharge it at a constant current of 0.1C to 0.005V; disassemble the button cell in a glove box and measure the electrode thickness. The electrode expansion rate is calculated as follows: Electrode Expansion Rate = (Electrode Thickness After Cycles - Original Electrode Thickness) / Original Electrode Thickness × 100%.

[0050] 4. Cyclic performance: After assembling the button half-cell, let it stand for 2 hours, then discharge it to 0.005V at a constant current of 0.1C, let it stand for 5 minutes, and then charge it to 1.5V at a constant current of 0.1C. After letting it stand for 5 minutes, repeat the above steps twice to activate the button half-cell. Then discharge it to 0.005V at a constant current of 1C, and then charge it to 1.5V at a constant current of 1C. Repeat the above steps 100 times and then stop.

[0051] 5. Rate performance: The rate performance of the silicon-carbon material is characterized by the ratio of the specific charge capacity of the first 1C cycle to the specific charge capacity of the third 0.1C cycle.

[0052] The test results are shown in Table 1 below.

[0053] Table 1

[0054] As can be seen from the table above, the composite porous carbon-based silicon-carbon anode materials provided in Examples 1-5 of this application exhibit excellent rate performance and cycle stability when applied to lithium-ion batteries, with Example 5 showing the best results, achieving a 1C / 0.1C capacity retention rate of 78.9% and a 100-cycle capacity retention rate of 95.6%. Furthermore, compared to Example 5, Comparative Example 1, which did not perform step a to construct the resin-based porous carbon shell, produced a silicon-carbon anode material with better rate performance, but its cycle capacity retention rate was significantly lower, indicating that step a to construct the resin-based porous carbon shell helps improve cycle stability. Comparative Example 2, using commercially available irregular blocky petroleum coke-based porous carbon as raw material, produced silicon-carbon anode materials with test results similar to Comparative Example 1 when applied to lithium-ion batteries, further demonstrating the improving effect of step a to construct the resin-based porous carbon shell on cycle stability. Comparative Example 3, using commercially available materials with a median particle size of 6... Using irregular blocky resin-based carbon powder with a median particle size of 6 μm as raw material, the prepared silicon-carbon anode material has a similar cycle capacity retention rate to that of Example 5 when applied to lithium-ion batteries, but the rate performance is significantly reduced, indicating the effect of using a coke-based porous carbon core on improving rate performance. In Comparative Example 4, using commercially available irregular blocky biomass-based carbon powder with a median particle size of 6 μm as raw material, the prepared silicon-carbon anode material has significantly worse rate performance and cycle capacity retention rate when applied to lithium-ion batteries than that of Example 5, further demonstrating that the composite porous carbon-based silicon-carbon anode material provided in this application has significant advantages in terms of rate performance and cycle stability.

[0055] The above are merely preferred embodiments of this application and are not intended to limit 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 spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a composite porous carbon-based silicon-carbon anode material, characterized in that, Includes the following steps: Step a: Mix the raw material coke with the resin solution evenly, and prepare the first intermediate, namely the resin-coated raw material coke, by spray drying. Step b: The first intermediate is placed in a tube furnace for carbonization treatment, and after cooling to room temperature, the second intermediate, i.e., composite carbon material, is obtained. Step c: Activate the second intermediate by introducing an activation gas, and then cool it to room temperature to obtain the third intermediate, which is a composite porous carbon material. Step d: The third intermediate is fed into a fluidized bed and subjected to chemical vapor deposition of silicon nanoparticles to obtain the fourth intermediate; Step e: Chemical vapor deposition carbon coating is performed on the fourth intermediate to obtain a composite porous carbon-based silicon-carbon anode material.

2. The preparation method according to claim 1, characterized in that, In step a, the raw coke and the resin solution with a concentration of 5wt.%~20wt.% are mixed evenly at a mass ratio of raw coke to resin of 1:1~5:

1. The first intermediate is prepared by spray drying under the conditions of inlet air temperature of 80℃~180℃ and feed rate of 1L / h~5L / h.

3. The preparation method according to claim 2, characterized in that, The resin in the resin solution includes one or more of phenolic resin, epoxy resin, polyester resin, and acrylic resin, and the solvent includes one or more of ethanol, acetone, xylene, and ethyl acetate; the raw coke is an irregular blocky low-sulfur, medium-sulfur, or high-sulfur raw coke powder with a median particle size of 3μm to 12μm.

4. The preparation method according to claim 1, characterized in that, In step b, the carbonization temperature is 900℃~1200℃ and the time is 2h~5h.

5. The preparation method according to claim 1, characterized in that, In step c, the activation treatment temperature is 900℃~1200℃, the time is 2h~12h, the activation gas is selected from one or more of carbon dioxide, water vapor, and air, and the flow rate of the activation gas is 50mL / min~250 mL / min.

6. The preparation method according to claim 1, characterized in that, In step d, the temperature for chemical vapor deposition of nano-silicon particles is 450℃~550℃, the time is 5h~12h, and one or more of silane and disilane are used as silicon source gases.

7. The preparation method according to claim 1, characterized in that, In step e, the temperature for chemical vapor deposition of the carbon layer is 500℃~800℃, the time is 2h~8h, and one or more of methane, acetylene, propane, and propylene are used as the carbon source gas.

8. A composite porous carbon-based silicon-carbon anode material prepared by the preparation method according to any one of claims 1-7.

9. A secondary battery, characterized in that, The composite porous carbon-based silicon-carbon anode material prepared by the preparation method of any one of claims 1-7 and / or the composite porous carbon-based silicon-carbon anode material of claim 8.

10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.

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