A core-shell structured porous carbon and silicon-carbon anode material with an internal conductive network, its preparation method and application

Abstract

This invention discloses a core-shell porous carbon and silicon-carbon anode material with an internal conductive network, its preparation method, and its application, belonging to the field of battery material technology. The silicon-carbon anode material uses a core-shell porous carbon with an internal conductive network as a framework. Nano-silicon is filled into the pores of the framework through chemical vapor deposition, and a dense conductive carbon layer is coated on the outside of the particles. The core-shell porous carbon with an internal conductive network consists of a uniformly dispersed porous carbon core and a resin-based porous carbon shell, with a highly conductive graphitized carbon layer coated on the surface of the porous carbon core as the internal conductive network. The core-shell porous carbon with an internal conductive network of this invention achieves advantages such as high electronic conductivity, high lithium-ion diffusion coefficient, highly controllable specific surface area / pore structure, and high single-particle crush strength by constructing an internal conductive network within the porous carbon and independently controlling the carbon microcrystalline structure of the core and shell, thereby improving the specific capacity, rate performance, and cycle life of the silicon-carbon anode material.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a core-shell structure porous carbon and silicon-carbon anode material with an internal conductive network, its preparation method, and its application. Background Technology

[0002] Silicon anode materials are considered ideal for high-energy-density lithium-ion batteries and solid-state batteries due to their high lithium intercalation capacity (4200 mAh / g) and low lithium intercalation potential (≈0.3 V vs. Li / Li+). However, the poor intrinsic electronic conductivity of pure silicon and the volume expansion of up to 300% during lithium intercalation have made it difficult to use it alone as a lithium battery anode.

[0003] Nanoscale silicon combined with carbon materials has been proven to effectively improve electronic conductivity and suppress silicon volume expansion. G. Yushin et al. [High-performance lithium-ion anodes using a hierarchical bottom-up approach, Nat. Mater., 9, 353-358 (2010)] first deposited silicon particles with a size of approximately 30 nm in dendritic carbon black via chemical vapor deposition, achieving a specific capacity of 1950 mAh / g and an initial coulombic efficiency of 85%. In recent years, many domestic and international companies, led by Group 14, have adopted porous carbons such as coconut shell-based, resin-based, and petroleum coke-based carbons as carbon frameworks, further improving the specific capacity, initial coulombic efficiency, and cycle life of the resulting fumed silicon-carbon materials, driving another industrial upgrade in the anode material field.

[0004] However, in current practical applications, fumed silicon-carbon still suffers from poor rate performance. Fast charge / discharge performance is a crucial indicator of lithium-ion batteries. Modified graphite anode materials can achieve a rate performance of 6C, while hard carbon anode materials can even exceed 10C. Fumed silicon-carbon, limited by factors such as the electronic conductivity of its carbon skeleton and the lithium-ion diffusion rate, can only achieve a rate performance of 1-2C, making it difficult to meet the demands of fields such as 3C digital batteries and automotive power batteries.

[0005] Therefore, it is of great practical significance to develop a gas-phase silicon-carbon anode material and its preparation method that has the advantages of high specific capacity and long cycle life, as well as excellent rate performance. Summary of the Invention

[0006] To enable fumed silicon-carbon anode materials to simultaneously achieve high specific capacity, long cycle life, and excellent rate performance, the present invention aims to provide a core-shell structured porous carbon / silicon-carbon anode material with an internal conductive network, its preparation method, and its application. By constructing an internal conductive network in porous carbon and independently controlling the carbon microcrystalline structure of the core and shell, the porous carbon achieves advantages such as high electronic conductivity, high lithium-ion diffusion rate, highly controllable specific surface area / pore structure, and high single-particle crushing strength, thereby simultaneously satisfying the requirements of high specific capacity, excellent rate performance, and long cycle life of fumed silicon-carbon anode materials.

[0007] The present invention achieves the above objectives through the following technical solutions:

[0008] The present invention provides a core-shell structured porous carbon with an internal conductive network, wherein the porous carbon is composed of a uniformly dispersed porous carbon core and a resin-based porous carbon shell, the surface of the porous carbon core is coated with a highly conductive graphitized carbon layer, and the graphitized carbon layer constitutes an internal conductive network.

[0009] Furthermore, the raw material for the porous carbon core can be one or more of biomass, resin, petroleum coke, and coal coke, with a D100 particle size of <1 micrometer and a highly conductive graphitized carbon layer thickness of 5-100 nanometers.

[0010] Preferably, the raw material for the porous carbon core can be one or both of biomass and resin.

[0011] Furthermore, the resin-based porous carbon shell accounts for no less than 20 wt.% of the total mass of the core-shell structure porous carbon.

[0012] Furthermore, the porous carbon D50 has a particle size range of 6-10 micrometers, a (D90-D10) / D50 ratio range of (0.9-1.1), and a BET multi-point specific surface area range of 1000-2300 m². 2 / g, with a total pore volume at a single point ranging from 0.5 to 1.2 cm³. 3 / g.

[0013] Preferably, the specific surface area of ​​BET multi-point is in the range of 1800-2300m². 2 / g, with a total pore volume at a single point ranging from 0.8 to 1.2 cm³. 3 / g.

[0014] This embodiment also provides a method for preparing core-shell porous carbon with an internal conductive network, including the following steps:

[0015] (1) One or more of biomass, resin, petroleum coke, and coal coke are carbonized at high temperature T1 for a certain time t1 to obtain carbonized material;

[0016] (2) The carbonized material in (1) is crushed to the target particle size to obtain carbonized material particles;

[0017] (3) Place the carbonized material particles in (2) in a rotary kiln, heat it to a high temperature T2 and introduce carbon source gas to maintain it for a period of time t2, and coat the graphitized carbon layer by chemical vapor deposition.

[0018] (4) Disperse the coated carbonized material particles in (3) evenly in thermoplastic phenolic resin powder, heat to high temperature T3 and carbonize for a certain time t3, then crush to 0.2-1 mm;

[0019] (5) Place the particles obtained in (4) in an activation device, heat to a high temperature T4 and activate for a certain time t4, then passivate, acid wash, crush and classify to obtain the core-shell structured porous carbon with an internal conductive network;

[0020] Furthermore, the T1 carbonization temperature is 600-1000℃, and the t1 carbonization time is 0.5-6h; the T2 coating temperature is 700-1000℃, and the t2 coating time is 0.1-2h; the T3 carbonization temperature is 600-1000℃, and the t3 carbonization time is 0.5-6h; the T4 activation temperature is 800-1100℃, and the t4 activation time is 5-20h. By adjusting the T1 and T3 carbonization temperatures and the t1 and t3 carbonization times, the microcrystalline structure of the porous carbon core and porous carbon shell can be controlled respectively.

[0021] Preferably, the T1 carbonization temperature is 800-1000℃, and the t1 carbonization time is 3-6h; the T2 coating temperature is 900-1000℃, and the t2 coating time is 1-2h; the T3 carbonization temperature is 800-1000℃, and the t3 carbonization time is 3-6h; the T1 carbonization temperature is not lower than the T3 carbonization temperature, and the t1 carbonization time is not lower than the t3 carbonization time.

[0022] Furthermore, the coating step (3) can use any one of methane, ethylene, acetylene, and propane as the carbon source gas;

[0023] Preferably, either ethylene or propane can be used as the carbon source gas;

[0024] Furthermore, the activation step (5) can use one or a mixture of two of water vapor and CO2 in any proportion as an activator;

[0025] The present invention also provides a silicon-carbon anode material, wherein the silicon-carbon uses the core-shell structure porous carbon with an internal conductive network as the carbon skeleton, and nano-silicon is filled into the skeleton pores by chemical vapor deposition and coated with a dense conductive carbon layer on the outside of the particles.

[0026] The present invention also provides a lithium-ion battery, wherein the lithium-ion battery uses fumed silicon-carbon as the negative electrode material, which is prepared by using porous carbon with an internal conductive network as the framework.

[0027] The beneficial effects that the core-shell structured porous carbon and silicon-carbon anode material with an internal conductive network, its preparation method, and its application disclosed in this application may bring include, but are not limited to:

[0028] 1. The electronic conductivity of porous carbon is significantly improved, resulting in a significant improvement in the rate performance of fumed silicon-carbon anodes fabricated using this porous carbon as a framework: The porous carbon disclosed in this invention uses nanoscale carbon particles as porous carbon cores, with an sp2 hybridized conductive carbon layer coated on the outer surface of the core. The nanoscale carbon particles are then coated with resin, and after carbonization and activation, they form core-shell structured porous carbon particles. The conductive carbon layer on the surface of the nanoscale carbon particles constitutes the internal conductive network of the porous carbon particles. First, the internal conductive network constructed by the conductive carbon layer on the outer surface of the core can directly improve the electronic conductivity of the porous carbon. Second, by adjusting the carbonization process of the porous carbon core and porous carbon shell, different microcrystalline structures can be obtained, which can optimize the lithium-ion diffusion coefficient of the porous carbon shell while ensuring the strength of the porous carbon core framework. Combining the above-mentioned optimization of electronic channels and lithium-ion channels, the specific capacity, rate performance, and cycle life of the silicon-carbon anode are ultimately significantly improved.

[0029] 2. Full utilization of porous carbon resources: The nano-sized carbon particles used in this invention can be obtained by using the micro powder collected in the air jet milling process of traditional technology as raw material, and further pulverizing it to the target particle size. This can turn waste into treasure, not only reducing the overall cost, but also solving the problem of generating a large amount of hazardous carbon micro powder waste in traditional processes. Attached Figure Description

[0030] Figure 1 SEM image of precursor 1 in Example 1;

[0031] Figure 2 SEM of the core-shell porous carbon with an internal conductive network described in Example 1;

[0032] Figure 3 XRD of the silicon-carbon composite material prepared from porous carbon as described in Example 1;

[0033] Figure 4 Half-cell charge-discharge curves of the silicon-carbon composite material prepared from porous carbon as described in Example 1;

[0034] Figure 5 SEM image of precursor 1 in Example 5;

[0035] Figure 6 SEM of the core-shell porous carbon with an internal conductive network described in Example 5;

[0036] Figure 7 XRD of the silicon-carbon composite material prepared from porous carbon as described in Example 5;

[0037] Figure 8Half-cell charge-discharge curves of silicon-carbon composite materials prepared from porous carbon as described in Example 5.

[0038] Figure 9 Example 1: A schematic diagram of the core-shell porous carbon structure with an internal conductive network. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0040] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0041] Example 1:

[0042] (S1) Place the coconut shell in a rotary kiln and heat it to 800℃ (T1) at a nitrogen-saturated atmosphere at a heating rate of 5℃ / min. After carbonization for 2 hours (t1), obtain the coconut shell carbonized material. Then add the carbonized material to an air jet mill and crush it to D100 < 1 micrometer to obtain precursor 1.

[0043] (S2) Take 2 kg of precursor 1 and put it into a rotary kiln. Under a nitrogen-saturated atmosphere, raise the temperature to 800℃ (T2) at a rate of 5℃ / min. Then introduce a mixture of methane and nitrogen at a rate of 3L / min and react for 0.5 h to obtain precursor 2.

[0044] (S3) Mix 1 kg of precursor 2 with 2 kg of thermoplastic phenolic resin powder evenly, compact and mold it, and put it into a track kiln. Under a nitrogen-saturated atmosphere, heat it to 800℃ (T3) at a heating rate of 0.5℃ / min, carbonize it for 2 hours (t3), and crush it to 0.2-1 mm to obtain precursor 3.

[0045] (S4) 2 kg of precursor 3 was placed in a rotary kiln and heated to 870 °C (T4) at a nitrogen-saturated atmosphere at a heating rate of 5 °C / min. A mixture of water vapor and nitrogen gas at a rate of 5 L / min and a rate of 10 L / min was introduced and reacted for 14 h (t4). The mixture was then passivated, acid-washed, crushed, and graded to the target particle size to obtain porous carbon with a core-shell structure and an internal conductive network.

[0046] The accompanying drawings for this embodiment are shown in [the figures]. Figures 1 to 4 .in: Figure 1 The image shows the SEM image of precursor 1 obtained in step (S1), which has a typical morphology of coconut shell carbonized powder. Figure 2 This is a SEM image of the core-shell porous carbon structure finally obtained in this embodiment; from Figure 2It can be seen that the core-shell structured porous carbon prepared by the technical solution described in Example 1 has a uniform microstructure and no obvious macroporous structure. Its morphology is similar to that of commercially available conventional resin porous carbon. Figure 3 The image shows the XRD pattern of the silicon-carbon composite material prepared with porous carbon as the framework in this embodiment. Its structure is amorphous and there are no crystalline silicon diffraction peaks, indicating that the silicon-carbon composite material was successfully prepared with the core-shell structure porous carbon as the framework. Figure 4 The half-cell charge-discharge curve of this silicon-carbon composite material shows a reversible capacity of up to 1929.2 mAh / g and an initial efficiency of up to 92.5%, with electrochemical performance significantly higher than that of commercially available coconut shell-based silicon-carbon composite materials. Figure 9 This is a schematic diagram of a core-shell porous carbon structure with an internal conductive network. The structure consists of a porous carbon core with a graphitized carbon layer and a resin-based porous carbon shell. The graphitized carbon layer on the surface of the porous carbon core forms an internal conductive network.

[0047] Example 2:

[0048] (S1) Place the coconut shell in a rotary kiln and heat it to 800℃ (T1) at a nitrogen-saturated atmosphere at a heating rate of 5℃ / min. After carbonization for 2 hours (t1), obtain the coconut shell carbonized material. Then add the carbonized material to an air jet mill and crush it to D100 < 1 micrometer to obtain precursor 1.

[0049] (S2) Take 2 kg of precursor 1 and put it into a rotary kiln. Under a nitrogen-saturated atmosphere, raise the temperature to 800℃ (T2) at a rate of 5℃ / min. Then introduce a mixture of methane and nitrogen at a rate of 3L / min and react for 0.5 h to obtain precursor 2.

[0050] (S3) Mix 1 kg of precursor 2 with 4 kg of thermoplastic phenolic resin powder evenly, compact and mold it, and put it into a track kiln. Under a nitrogen-saturated atmosphere, heat it to 800℃ (T3) at a heating rate of 0.5℃ / min, carbonize it for 2 hours (t3), and crush it to 0.2-1 mm to obtain precursor 3.

[0051] (S4) 2 kg of precursor 3 was placed in a rotary kiln and heated to 870 °C (T4) at a nitrogen-saturated atmosphere at a heating rate of 5 °C / min. A mixture of water vapor and nitrogen gas at a rate of 5 L / min and a rate of 10 L / min was introduced and reacted for 14 h (t4). The mixture was then passivated, acid-washed, crushed, and graded to the target particle size to obtain porous carbon with a core-shell structure and an internal conductive network.

[0052] Example 3:

[0053] (S1) Place the coconut shell in a rotary kiln and heat it to 800℃ (T1) at a nitrogen-saturated atmosphere at a heating rate of 5℃ / min. After carbonization for 2 hours (t1), obtain the coconut shell carbonized material. Then add the carbonized material to an air jet mill and crush it to D100 < 1 micrometer to obtain precursor 1.

[0054] (S2) Take 2 kg of precursor 1 and put it into a rotary furnace. Under a nitrogen-saturated atmosphere, raise the temperature to 800℃ (T2) at a heating rate of 5℃ / min. Then, introduce a mixture of methane and nitrogen at a rate of 3 L / min and react for 2 h to obtain precursor 2.

[0055] (S3) Mix 1 kg of precursor 2 with 2 kg of thermoplastic phenolic resin powder evenly, compact and mold it, and put it into a track kiln. Under a nitrogen-saturated atmosphere, heat it to 800℃ (T3) at a heating rate of 0.5℃ / min, carbonize it for 2 hours (t3), and crush it to 0.2-1 mm to obtain precursor 3.

[0056] (S4) 2 kg of precursor 3 was placed in a rotary kiln and heated to 870 °C (T4) at a nitrogen-saturated atmosphere at a heating rate of 5 °C / min. A mixture of water vapor and nitrogen gas at a rate of 5 L / min and a rate of 10 L / min was introduced and reacted for 14 h (t4). The mixture was then passivated, acid-washed, crushed, and graded to the target particle size to obtain porous carbon with a core-shell structure and an internal conductive network.

[0057] Example 4:

[0058] (S1) Place the coconut shell in a rotary kiln and heat it to 800℃ (T1) at a nitrogen-saturated atmosphere at a heating rate of 5℃ / min. After carbonization for 2 hours (t1), obtain the coconut shell carbonized material. Then add the carbonized material to an air jet mill and crush it to D100 < 1 micrometer to obtain precursor 1.

[0059] (S2) Take 2 kg of precursor 1 and put it into a rotary kiln. Under a nitrogen-saturated atmosphere, raise the temperature to 800℃ (T2) at a rate of 5℃ / min. Then introduce a mixture of methane and nitrogen at a rate of 3L / min and react for 0.5 h to obtain precursor 2.

[0060] (S3) Mix 1 kg of precursor 2 with 2 kg of thermoplastic phenolic resin powder evenly, compact and mold it, and put it into a track kiln. Under a nitrogen-saturated atmosphere, heat it to 800℃ (T3) at a heating rate of 0.5℃ / min, carbonize it for 2 hours (t3), and crush it to 0.2-1 mm to obtain precursor 3.

[0061] (S4) 2 kg of precursor 3 was placed in a rotary kiln and heated to 870 °C (T4) at a nitrogen-saturated atmosphere at a heating rate of 5 °C / min. A mixture of water vapor and nitrogen gas at a rate of 5 L / min and a rate of 10 L / min was introduced and reacted for 18 h (t4). The mixture was then passivated, acid-washed, crushed, and graded to the target particle size to obtain porous carbon with a core-shell structure and an internal conductive network.

[0062] Example 5:

[0063] (S1) The resin ball fine powder is placed in the track kiln and heated to 800℃ (T1) at a heating rate of 0.3℃ / min under a nitrogen-saturated atmosphere. After carbonization for 2h (t1), the resin carbonized material is obtained. The carbonized material is then added to an air jet mill and depolymerized to D100 < 1 micrometer to obtain precursor 1.

[0064] (S2) Take 2 kg of precursor 1 and put it into a rotary kiln. Under a nitrogen-saturated atmosphere, raise the temperature to 800℃ (T2) at a rate of 5℃ / min. Then introduce a mixture of methane and nitrogen at a rate of 3L / min and react for 0.5 h to obtain precursor 2.

[0065] (S3) Mix 1 kg of precursor 2 with 2 kg of thermoplastic phenolic resin powder evenly, compact and mold it, and put it into a track kiln. Under a nitrogen-saturated atmosphere, heat it to 800℃ (T3) at a heating rate of 0.5℃ / min, carbonize it for 2 hours (t3), and crush it to 0.2-1 mm to obtain precursor 3.

[0066] (S4) 2 kg of precursor 3 was placed in a rotary kiln and heated to 870 °C (T4) at a nitrogen-saturated atmosphere at a heating rate of 5 °C / min. A mixture of water vapor and nitrogen gas at a rate of 5 L / min and a rate of 10 L / min was introduced and reacted for 16 h (t4). The mixture was then passivated, acid-washed, crushed, and graded to the target particle size to obtain porous carbon with a core-shell structure and an internal conductive network.

[0067] The accompanying drawings for this embodiment are shown in [the figures]. Figures 5 to 8 .in: Figure 5 The image shows the SEM image of precursor 1 obtained in step (S1), which has a morphology of uniform submicron carbon spheres. Figure 6 This is a SEM image of the core-shell porous carbon structure finally obtained in this embodiment. Figure 2 It can be seen that the core-shell structured porous carbon prepared by the technical solution described in Example 1 has a uniform microstructure and its morphology is similar to that of commercially available conventional resin porous carbon. Figure 7 The image shows the XRD pattern of the silicon-carbon composite material prepared with porous carbon as the framework in this embodiment. Its structure is amorphous and there are no crystalline silicon diffraction peaks, indicating that the silicon-carbon composite material was successfully prepared with the core-shell structure porous carbon as the framework. Figure 8The half-cell charge-discharge curve of this silicon-carbon composite material shows a reversible capacity of up to 1941.6 mAh / g and an initial efficiency of up to 93.2%, demonstrating significantly higher electrochemical performance than commercially available resin-based silicon-carbon composite materials.

[0068] Example 6:

[0069] (S1) The resin ball fine powder is placed in the track kiln and heated to 800℃ (T1) at a heating rate of 0.3℃ / min under a nitrogen-saturated atmosphere. After carbonization for 2h (t1), the resin carbonized material is obtained. The carbonized material is then added to an air jet mill and depolymerized to D100 < 1 micrometer to obtain precursor 1.

[0070] (S2) Take 2 kg of precursor 1 and put it into a rotary furnace. Under a nitrogen-saturated atmosphere, raise the temperature to 750℃ (T2) at a heating rate of 5℃ / min. Introduce a mixture of acetylene and nitrogen at a rate of 1 L / min and react for 1 h to obtain precursor 2.

[0071] (S3) Mix 1 kg of precursor 2 with 2 kg of thermoplastic phenolic resin powder evenly, compact and mold it, and put it into a track kiln. Under a nitrogen-saturated atmosphere, heat it to 800℃ (T3) at a heating rate of 0.5℃ / min, carbonize it for 2 hours (t3), and crush it to 0.2-1 mm to obtain precursor 3.

[0072] (S4) 2 kg of precursor 3 was placed in a rotary kiln and heated to 870 °C (T4) at a nitrogen-saturated atmosphere at a heating rate of 5 °C / min. A mixture of water vapor and nitrogen gas at a rate of 5 L / min and a rate of 10 L / min was introduced and reacted for 16 h (t4). The mixture was then passivated, acid-washed, crushed, and graded to the target particle size to obtain porous carbon with a core-shell structure and an internal conductive network.

[0073] Comparative Example 1:

[0074] (S1) Place the coconut shell in a rotary kiln and heat it to 800℃ (T1) at a nitrogen-saturated atmosphere at a heating rate of 5℃ / min. After carbonization for 2 hours (t1), obtain the coconut shell carbonized material. Then add the carbonized material to an air jet mill to break it into 0.2-1 mm particles to obtain precursor 1.

[0075] (S2) 2 kg of precursor 1 was placed in a rotary kiln and heated to 850 °C (T4) at a nitrogen-saturated atmosphere at a heating rate of 5 °C / min. A mixture of 5 L / min water vapor and 10 L / min nitrogen gas was introduced and reacted for 20 h (t4). Then, the mixture was passivated, acid-washed, crushed, and graded to the target particle size to obtain coconut shell-based porous carbon.

[0076] Comparative Example 2:

[0077] (S1) 2 kg of thermoplastic phenolic resin powder was compacted and placed in a track kiln. Under a nitrogen-saturated atmosphere, the temperature was raised to 800℃ (T1) at a rate of 0.5℃ / min, carbonized for 2 hours (t1), and crushed to 0.2-1 mm to obtain precursor 1.

[0078] (S4) 2 kg of precursor 1 was placed in a rotary kiln and heated to 890 °C (T4) at a nitrogen-saturated atmosphere at a heating rate of 5 °C / min. A mixture of water vapor at a rate of 5 L / min and nitrogen at a rate of 10 L / min was introduced and reacted for 18 h (t4). Then, the mixture was passivated, acid-washed, crushed, and graded to the target particle size to obtain resin-based porous carbon.

[0079] Table 1: Physicochemical property analysis of porous carbon in Examples 1-6 and Comparative Examples 1-2

[0080] Example 1 1807.9 0.905 90.2 0.621 8.8 255 Example 2 1642.2 0.775 93.5 0.678 9.6 288 Example 3 1785.6 0.889 90.8 0.628 11.9 262 Example 4 2352.9 1.063 84.2 0.524 7.5 208 Example 5 1782.8 0.867 92.3 0.630 9.8 317 Example 6 1749.7 0.879 92.2 0.619 7.9 301 Comparative Example 1 1796.8 0.833 93.3 0.591 5.6 158 Comparative Example 2 1802.1 0.872 91.8 0.621 7.2 261

[0081] According to GB / T 19587-2017, the gas adsorption BET method was used to conduct low-temperature nitrogen adsorption experiments on the porous carbon prepared in the examples and comparative examples using a Tristar 2460 fully automatic specific surface area and pore size analyzer manufactured by Micromeritics Instrument Corporation, to analyze its specific surface area, pore volume and other physical properties. According to GB / T 40007-2021, the porous carbon prepared in the examples and comparative examples was tested using an ST2742 fully automatic powder analyzer manufactured by Suzhou Jingge, to determine the compaction density and powder conductivity. The porous carbon prepared in the examples and comparative examples was tested using a SPFT series single-particle mechanical property testing system manufactured by Yuaneng Technology, to analyze the single-particle crushing strength.

[0082] As can be seen from Table 1, the specific surface area of ​​the core-shell porous carbon with an internal conductive network prepared by the method of the present invention can reach 1600-2400 m². 2 / g, with a pore volume of 0.7-1.1cm. 3 / g. Comparing Examples 1, 1, 5, and 2, it can be found that, while achieving similar specific surface area and pore volume, the core-shell structure of porous carbon with an internal conductive network has significant advantages in powder conductivity and single-particle crushing strength. Comparing Examples 1 and 2, it can be found that increasing the proportion of porous carbon shell can effectively improve the single-particle crushing strength of porous carbon. Comparing Examples 1 and 3, it can be found that increasing the thickness of the internal conductive layer can significantly improve the powder conductivity of porous carbon. Comparing Examples 1 and 4, it can be found that, with the same component proportion, extending the activation time can expand the specific surface area to 2352 m². 2 / g, and further extending the activation time can further expand the specific surface area; comparing Example 1 and Example 5, it can be found that replacing the porous carbon core with a resin base can still produce a core-shell structure porous carbon with an internal conductive network, and the powder conductivity and single particle crushing strength are both improved; comparing Example 5 and Example 6, it can be found that replacing the methane gas with acetylene gas in step (S2) can also obtain a similar internal conductive network.

[0083] Silicon-carbon composite materials were prepared by vapor deposition of silicon and carbon using the same process as in Examples 1 and 5, and Comparative Examples 1 and 2. Specifically, 1 kg of porous carbon was placed in a fluidized bed, heated to 500°C, and then silane gas was introduced for silicon deposition at a ratio of 3 L / min to 12 L / min. After silicon deposition for 315 minutes, the temperature was increased to 580°C, and acetylene gas was introduced for coating at a ratio of 3 L / min to 12 L / min. After coating for 200 minutes, a semi-finished product was obtained. 1 kg of the semi-finished product was placed in a rotary kiln, heated to 580°C, and then a mixture of acetylene and nitrogen gas was introduced at a ratio of 1 L / min to 3 L / min. After coating for 180 minutes, the silicon-carbon composite material was obtained.

[0084] Table 2: Electrochemical properties of silicon-carbon composite materials prepared from porous carbon in Examples 1, 5 and Comparative Examples 1, 2

[0085] Example 1 1929.2 92.5 98.8 Example 5 1941.6 93.2 99.0 Comparative Example 1 1870.1 91.4 97.5 Comparative Example 2 1918.2 91.6 98.1

[0086] As can be seen from Table 2, the silicon-carbon composite material prepared using the core-shell porous carbon with an internal conductive network as the framework described in this invention exhibits higher initial reversible specific capacity and initial coulombic efficiency. Furthermore, benefiting from higher single-particle crushing strength, the prepared silicon-carbon composite material also demonstrates a longer cycle life.

[0087] Based on the data in Tables 1 and 2, it can be seen that the core-shell porous carbon with an internal conductive network prepared by the method of the present invention has better electrical conductivity and strength, and the silicon-carbon composite material prepared with this as a framework has better electrochemical performance.

[0088] The above embodiments illustrate in detail the specific implementation of the technical solution of the present invention, the logical and connection relationships of each component, and the complete working process. Those skilled in the art will understand that various changes and modifications can be made to the above embodiments without departing from the principles and spirit of the present invention, and all such changes and modifications should fall within the protection scope of the appended claims.

Claims

1. A core-shell structured porous carbon with an internal conductive network, characterized in that, The porous carbon is composed of a uniformly dispersed porous carbon core and a resin-based porous carbon shell. The surface of the porous carbon core is coated with a highly conductive graphitized carbon layer, which forms an internal conductive network.

2. A core-shell porous carbon structure with an internal conductive network according to claim 1, characterized in that, The porous carbon core is made from one or more of biomass, resin, petroleum coke, and coal coke, with a D100 particle size of <1 micrometer and a highly conductive graphitized carbon layer thickness of 5-100 nanometers.

3. A core-shell porous carbon structure with an internal conductive network according to claim 1, characterized in that, The resin-based porous carbon shell accounts for no less than 20 wt.% of the total mass of porous carbon in the core-shell structure.

4. A core-shell porous carbon structure with an internal conductive network according to claim 1, characterized in that, The porous carbon D50 has a particle size range of 6-10 micrometers, a (D90-D10) / D50 ratio range of (0.9-1.1), and a BET multi-point specific surface area range of 1000-2300 m². 2 / g, with a total pore volume at a single point ranging from 0.5 to 1.2 cm³. 3 / g.

5. A method for preparing core-shell structured porous carbon with an internal conductive network as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) One or more of biomass, resin, petroleum coke, and coal coke are carbonized at high temperature T1 for a certain time t1 to obtain carbonized material; (2) The carbonized material in step (1) is crushed to the target particle size to obtain carbonized material particles; (3) Place the carbonized material particles from step (2) in a rotary kiln, heat them to a high temperature T2 and introduce carbon source gas to maintain the temperature for a period of time t2, and coat the graphitized carbon layer by chemical vapor deposition. (4) Disperse the coated carbonized material particles in step (3) evenly in thermoplastic phenolic resin powder, heat to high temperature T3 for a certain time t3, and then crush to 0.2-1 mm; (5) Place the particles obtained in step (4) in an activation device, heat them to a high temperature T4 for a certain time t4, and then passivate, acid wash, crush and grade them to obtain the core-shell structured porous carbon with an internal conductive network.

6. The method for preparing core-shell porous carbon with an internal conductive network according to claim 5, characterized in that, The T1 carbonization temperature is 600-1000℃, and the t1 carbonization time is 0.5-6h; the T2 coating temperature is 700-1000℃, and the t2 coating time is 0.1-2h; the T3 carbonization temperature is 600-1000℃, and the t3 carbonization time is 0.5-6h; the T4 activation temperature is 800-1100℃, and the t4 activation time is 5-20h.

7. The method for preparing core-shell porous carbon with an internal conductive network according to claim 5, characterized in that, (3) The coating step uses any one of methane, ethylene, acetylene, or propane as the carbon source gas.

8. The method for preparing core-shell porous carbon with an internal conductive network according to claim 5, characterized in that, (5) The activation step uses one or two of water vapor and CO2 in any proportion as the activator.

9. A silicon-carbon anode material, characterized in that, The silicon-carbon anode material uses porous carbon with an internal conductive network as described in any one of claims 1-4 as the carbon skeleton, and fills the skeleton pores with nano-silicon by chemical vapor deposition and coats the particles with a dense conductive carbon layer.

10. A lithium-ion battery, characterized in that, The lithium-ion battery uses silicon-carbon as the negative electrode material, which is prepared by using porous carbon with an internal conductive network as the framework, as described in any one of claims 1-4.

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