Post-processing method of porous carbon material, modified porous carbon material and application

Abstract

The present application relates to a kind of post-processing method of porous carbon material, modified porous carbon material and application, post-processing method includes: porous carbon material is mixed with chopped carbon fiber, then three-stage temperature control heat treatment is carried out under inert atmosphere, low temperature activates carbon fiber surface defect, at medium temperature, carbon-containing small molecules released by porous carbon material pyrolysis preferentially deposit in carbon fiber surface and macropore inner wall Form secondary carbon coating layer, high temperature solidifies coating layer, finally obtains the chopped carbon fiber bridging carbon coating porous carbon material, i.e. modified porous carbon material;The present application uses chopped carbon fiber as preferential nucleation site to guide carbon source directional deposition, realize macropore selective plugging while retaining micropore and mesopore structure completely;The macropore ratio of modified porous carbon material provided by the present application is ≤2%, the specific surface area retention rate is ≥88%, prepare silicon-carbon negative electrode material and be used in lithium ion battery, can improve cycle performance and rate capability.

Description

Technical Field

[0001] This invention relates to the field of porous carbon materials technology, and in particular to a post-processing method for porous carbon materials, modified porous carbon materials, and their applications. Background Technology

[0002] Porous carbon materials are widely used in energy storage fields such as lithium-ion batteries and supercapacitors due to their high specific surface area, tunable pore structure, excellent conductivity and chemical stability. Especially when used as a negative electrode material, their pore structure, defect degree and graphite crystallite size directly affect the overall performance of energy storage devices.

[0003] According to the International Union of Pure and Applied Chemistry (IUPAC), pore size can be classified into three categories: micropores, mesopores, and macropores. Micropores have a pore size < 2 nm, mesopores have a pore size greater than or equal to 2 nm and less than or equal to 50 nm, and macropores have a pore size greater than 50 nm. Studies have shown that microporous structures facilitate the uniform deposition of silicon within the pores of a carbon matrix, providing more active sites and diffusion channels. Furthermore, graphitized porous carbon exhibits excellent electrical conductivity. In recent years, an increasing number of patents and publications have focused on synergistically controlling the pore size distribution of porous carbon through activation processes to balance the high specific surface area of ​​micropores for energy storage with the expansion buffering function of mesopores.

[0004] Currently, the mainstream preparation process for porous carbon is a two-step method of "precursor carbonization - high temperature activation". The porous structure is formed by etching with an activator. However, the activated porous carbon generally suffers from problems such as uneven pore structure distribution, high defect rate, and insufficient control of graphite crystallite size. This results in low initial efficiency, rapid capacity decay during cycling, and poor rate performance when used as a negative electrode material, making it difficult to meet the application requirements of high-end energy storage devices.

[0005] Existing technologies for controlling porous carbon structures mainly focus on optimizing the front-end carbonization and activation processes, and some also employ high-temperature annealing or chemical surface modification. However, these traditional post-processing techniques have the following drawbacks: (1) The control dimension is singular, and it is impossible to achieve coordinated control of pore size distribution, defect degree and graphite crystal size.

[0006] (2) The process control is contradictory. High temperature treatment is prone to causing the collapse of micropores and mesopores and a significant loss of specific surface area, while low temperature treatment is difficult to effectively control the growth of graphite microcrystals.

[0007] (3) Poor applicability and scalability, high sensitivity to process parameters, poor batch consistency of products, and difficulty in industrial scale-up.

[0008] In addition, in pore modification methods such as chemical vapor deposition, carbon deposition is prone to occur inside micropores, leading to pore blockage and making it impossible to achieve selective sealing of macropores and narrowing of pore size distribution.

[0009] Therefore, developing a post-processing method for porous carbon that can selectively close macropores while fully preserving micropores / mesopores has become a pressing technical challenge in this field. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing technologies by providing a post-processing method for porous carbon materials, modified porous carbon materials, and their applications. This addresses the problems of wide pore size distribution, high proportion of macropores, inability of traditional post-processing processes to selectively close macropores, easy collapse of micropores and mesopores, significant loss of specific surface area, and difficulty in synergistically controlling pore size distribution, defect degree, and graphite crystallite size, resulting in low initial coulombic efficiency, poor cycle stability, and poor rate performance when used as a negative electrode material.

[0011] This invention achieves selective macropore sealing, complete preservation of micropores and mesopores, narrowing of pore size distribution, and synergistic improvement of mechanical and electrical properties by using chopped carbon fibers as selective nucleation sites and combining them with a three-stage temperature-controlled heat treatment post-processing method. Specifically, the post-processing method provided by this invention uniformly mixes chopped carbon fibers with porous carbon materials and sequentially performs three-stage heat treatment under an inert atmosphere: low-temperature activation, medium-temperature selective deposition, and high-temperature graphitization curing. In the low-temperature stage, surface defects of the carbon fibers are activated. In the medium-temperature stage, high-energy defects and functional groups on the carbon fiber surface are used as preferential nucleation sites to guide the carbon-containing small molecules released by the thermal decomposition of the porous carbon material to preferentially deposit on the carbon fiber surface and the inner wall of the macropores to form a secondary carbon coating layer. At the same time, the fast gas diffusion rate and sufficient carbon source supply in the macropores are utilized to achieve selective macropore sealing, while the diffusion in the micropores is limited and the deposition is minimal, thus ensuring complete preservation. The high-temperature stage cures the coating layer, improving the graphitization degree and structural stability of the coating layer, and finally forming a carbon bridge network between particles, thereby enhancing the overall electrical conductivity and mechanical strength of the porous carbon material.

[0012] To achieve the above objectives, in a first aspect, the present invention provides a post-processing method for porous carbon materials, the post-processing method comprising:

[0013] Porous carbon materials are mixed with chopped carbon fibers, so that the chopped carbon fibers are uniformly dispersed in the gaps and on the surface of the porous carbon materials to obtain a mixture.

[0014] Under an inert atmosphere, the mixture is subjected to a three-stage temperature-controlled heat treatment to obtain a precursor material; the three-stage temperature-controlled heat treatment includes...

[0015] The mixture is placed in a heat treatment device and heated to 200℃ to 500℃ at a heating rate of 0.5℃ / min to 5℃ / min, and held at that temperature for 0.5 hours to 2 hours to remove moisture and impurities from the surface of the chopped carbon fibers and activate the defective active sites on the surface of the chopped carbon fibers.

[0016] The temperature is then increased to 600℃ to 900℃ at a rate of 1℃ / min to 5℃ / min, and held for 1 hour to 3 hours to allow partial pyrolysis of the porous carbon material, generating carbon-containing small molecules. These small carbon molecules are deposited on the surface of the chopped carbon fibers and on the inner walls of the pores of the porous carbon material, forming a carbon coating layer. The defective active sites on the surface of the chopped carbon fibers serve as preferential nucleation and deposition sites for the carbon-containing small molecules, inducing their deposition. A carbon bridge network is formed between the chopped carbon fibers and the porous carbon material through the carbon coating layer. The deposition of the carbon-containing small molecules on the inner walls of the pores of the porous carbon material regulates its pore size distribution.

[0017] Then, the temperature is increased to 900℃ to 1300℃ at a heating rate of 1℃ / min to 5℃ / min, and held for 0.5 hours to 2 hours to solidify the carbon coating layer.

[0018] The heat treatment equipment is cooled to room temperature at a rate of less than or equal to 5°C / min, so that the precursor material is cooled with the furnace to obtain short-cut carbon fiber bridged carbon-coated porous carbon material.

[0019] Preferably, the porous carbon material includes one or more of the following: biomass-based porous carbon, resin-based porous carbon, pitch-based porous carbon, or starch-based porous carbon.

[0020] The porous carbon material can be in any of the following forms: granular, spherical, sheet-like, or felt-like.

[0021] The pore size distribution of the porous carbon material is as follows: micropores account for 80% to 90%, mesopores account for 7% to 15%, and macropores account for greater than 2% and less than or equal to 8%; the pore size of the micropores is less than 2 nm, the pore size of the mesopores is 2 nm to 50 nm, and the pore size of the macropores is greater than 50 nm.

[0022] The porous carbon material has a specific surface area of ​​400 m². 2 / g~1900m 2 / g.

[0023] The porosity of the porous carbon material is 50% to 80%.

[0024] The porous carbon material has a pore volume of 0.5 cm³. 3 / g~1.2cm 3 / g.

[0025] Preferably, the chopped carbon fiber has a length of 10μm to 200μm and a diameter of 5μm to 15μm.

[0026] In the mixture, the mass of the chopped carbon fibers is 1% to 20% of the mass of the porous carbon material.

[0027] Preferably, the carbon-containing small molecules include one or more of CH4, CO, or C2H2.

[0028] Preferably, the mixing includes liquid-phase ultrasonic dispersion mixing or solid-phase mixing.

[0029] The liquid-phase ultrasonic dispersion mixing includes: placing the porous carbon material, the chopped carbon fibers and the solvent in an ultrasonic disperser for ultrasonic dispersion, and then removing the solvent by rotary evaporation or vacuum drying; wherein the solvent includes one or more of ethanol, isopropanol or deionized water; the ultrasonic dispersion time is 10 minutes to 60 minutes, and the ultrasonic dispersion power is 100W to 500W.

[0030] The solid-phase mixing includes: placing the porous carbon material and the chopped carbon fiber in a solid-phase mixing device and mixing them at a speed of 50 rpm to 300 rpm for 0.5 hours to 2 hours.

[0031] Preferably, the inert atmosphere gas includes one or more of nitrogen, argon, or helium.

[0032] Preferably, the heat treatment equipment includes any one of a tube furnace, a box-type atmosphere furnace, a rotary kiln, or a roller kiln.

[0033] In a second aspect, the present invention provides a short-cut carbon fiber bridged carbon-coated porous carbon material prepared by the post-processing method described in the first aspect, wherein the short-cut carbon fiber bridged carbon-coated porous carbon material is in any one of the following forms: granular, spherical, sheet-like or felt-like. In the pore size distribution of the short-cut carbon fiber bridged carbon-coated porous carbon material, the proportion of macropores is less than or equal to 2%, the proportion of mesopores is 7% to 15%, and the proportion of micropores is 85% to 92%.

[0034] The specific surface area of ​​the short-cut carbon fiber bridged carbon-coated porous carbon material is 400 m². 2 / g~1800m 2 / g; the specific surface area of ​​the short-cut carbon fiber-bridged carbon-coated porous carbon material is maintained at a rate of 88% or greater than the specific surface area of ​​the porous carbon material.

[0035] Thirdly, the present invention provides a silicon-carbon anode material, wherein the silicon-carbon anode material comprises the short-cut carbon fiber-bridged carbon-coated porous carbon material described in the second aspect.

[0036] Fourthly, the present invention provides a lithium-ion battery comprising the silicon-carbon anode material described in the third aspect.

[0037] The present invention provides a post-processing method for porous carbon materials, a method for bridging porous carbon materials with short-cut carbon fibers and their application, which has the following technical effects.

[0038] (1) The post-processing method for porous carbon materials provided by the present invention utilizes short-cut carbon fibers as preferential nucleation sites, combined with three-stage temperature-controlled heat treatment, to guide the self-generated carbon-containing small molecules of porous carbon materials to preferentially deposit on the carbon fiber surface and the inner wall of macropores, thereby achieving selective macropore closure. The macropore ratio of the obtained short-cut carbon fiber-bridged carbon-coated porous carbon material is reduced from 2% to 8% before treatment to less than or equal to 2%, and the macropore ratio is reduced by more than 70%; at the same time, the micropore and mesopore structures are completely preserved, the micropore ratio is increased to 85% to 92%, and the specific surface area retention rate is ≥88%, which effectively overcomes the technical defect of carbon deposition easily clogging micropores in the prior art, and the selective pore size control effect is significant.

[0039] (2) After being processed by the method provided by the present invention, the pore size distribution width of the short-cut carbon fiber bridged carbon-coated porous carbon material is significantly narrowed, and the pore size uniformity is significantly improved, which is beneficial to the uniform transport of ions and electrons during energy storage.

[0040] (3) The short-cut carbon fiber bridged carbon-coated porous carbon material obtained by the post-processing method of porous carbon material provided by the present invention forms a continuous carbon bridge network between porous carbon particles by the carbon coating layer on the surface of the short-cut carbon fiber. On the one hand, it improves the mechanical strength of the composite material, and on the other hand, it constructs an efficient conductive path, significantly improving the electrical conductivity and realizing the synergistic enhancement of mechanical and electrical properties.

[0041] (4) The silicon-carbon anode material prepared by the short-cut carbon fiber bridging carbon-coated porous carbon material provided by the present invention has a comprehensive improvement in electrochemical performance. This is due to the optimization of pore size distribution and the improvement of structural stability. When the silicon-carbon anode material prepared by the short-cut carbon fiber bridging carbon-coated porous carbon material is applied to lithium-ion batteries, the initial coulombic efficiency and long-term cycle stability are significantly improved.

[0042] (5) The post-processing method for porous carbon materials provided by the present invention has wide process adaptability and can be mass-produced. The post-processing method of the present invention is applicable to porous carbon from various precursor sources such as biomass-based, resin-based, pitch-based, and starch-based. As a back-end post-processing process, it does not require modification of the front-end carbonization-activation production line. The process parameter window is wide, the operation is simple, and the batch consistency of the obtained materials is good. Attached Figure Description

[0043] Figure 1 A flowchart illustrating the post-processing method for porous carbon materials provided in this embodiment of the invention.

[0044] Figure 2This is a comparison chart showing the effects of different amounts of short-cut carbon fiber added on the macropore ratio and specific surface area retention rate of phenolic resin-based porous carbon particles in Examples 1, 4, 5, 6 and Comparative Example 1 of the present invention.

[0045] Figure 3 This is a comparison curve of the compressive strength improvement rate of porous carbon materials obtained under different amounts of short-cut carbon fibers in Examples 1, 4, 5, 6 and Comparative Example 1 of the present invention.

[0046] Figure 4 This is a comparison of the NLDFT full-pore size distribution curves of the short-cut carbon fiber bridged carbon-coated porous carbon material provided in Example 1 of the present invention, and the porous carbon materials provided in Comparative Example 1 and Comparative Example 2. Detailed Implementation

[0047] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0049] This invention provides a post-processing method for porous carbon materials, such as... Figure 1 As shown, the post-processing method includes the following steps.

[0050] Step 110: Mix the porous carbon material with chopped carbon fibers so that the chopped carbon fibers are evenly dispersed in the gaps and surface of the porous carbon material to obtain a mixture.

[0051] Among them, porous carbon materials include one or more of the following: biomass-based porous carbon, resin-based porous carbon, pitch-based porous carbon, or starch-based porous carbon.

[0052] Porous carbon materials can be in any of the following forms: granular, spherical, sheet-like, or felt-like.

[0053] The pore size distribution of porous carbon materials is as follows: micropores account for 80% to 90%, mesopores account for 7% to 15%, and macropores account for greater than 2% and less than or equal to 8%; among them, the pore size of micropores is less than 2 nm, the pore size of mesopores is 2 nm to 50 nm, and the pore size of macropores is greater than 50 nm.

[0054] The specific surface area of ​​the porous carbon material is 400 m². 2 / g~1900m 2 / g can be any value within this range, for example: 400m 2 / g、500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g, 1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g, 1400m 2 / g, 1500m 2 / g, 1600m 2 / g, 1700m 2 / g、1800m 2 / g、1900m 2 / g, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0055] The porosity of porous carbon materials is 50% to 80%, and can be any value within this range, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] The pore volume of the porous carbon material is 0.5 cm³. 3 / g~1.2cm 3 / g can be any value within this range, for example: 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0057] The short-cut carbon fibers used in this invention specifically refer to discrete carbon fiber monofilaments with a diameter between 5 and 15 μm and a length between 10 and 200 μm, obtained through a mechanical cutting process. Unlike the millimeter-scale short-cut carbon fiber bundles commonly used for composite material reinforcement, this invention utilizes the micron-scale size of these short-cut carbon fibers to match the particle size of porous carbon particles and to exert a heterogeneous nucleation effect.

[0058] The length of the short-cut carbon fiber is 10μm to 200μm, and can be any value within this range, such as: 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] The diameter of the short-cut carbon fiber is 5μm to 15μm, and can be any value within this range, such as 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] Mixing includes liquid-phase ultrasonic dispersion mixing or solid-phase mixing.

[0061] The liquid-phase ultrasonic dispersion mixing process includes: placing porous carbon material, chopped carbon fibers, and solvent in an ultrasonic disperser for ultrasonic dispersion, followed by solvent removal by rotary evaporation or vacuum drying. The solvent includes one or more of ethanol, isopropanol, or deionized water; the ultrasonic dispersion time is 10 to 60 minutes, and the ultrasonic dispersion power is 100 W to 500 W.

[0062] Solid-phase mixing includes: placing porous carbon materials and chopped carbon fibers in a solid-phase mixing device and mixing them at a speed of 50 rpm to 300 rpm for 0.5 hours to 2 hours.

[0063] In the mixture, the mass of chopped carbon fibers is 1% to 20% of the mass of the porous carbon material, and can be any value within this range, such as: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable. In this invention, the preferred range for the amount of chopped carbon fibers added is 5% to 15%, and the optimal range is 10% to 15%.

[0064] Step 120: Under an inert atmosphere, the mixture is subjected to a three-stage temperature-controlled heat treatment to obtain the precursor material.

[0065] The inert atmosphere includes one or more of nitrogen, argon, or helium. The three-stage temperature-controlled heat treatment specifically includes the following steps: 120-1, 120-2, and 120-3.

[0066] Step 120-1: Place the mixture in a heat treatment device and heat it to 200℃~500℃ at a heating rate of 0.5℃ / min~5℃ / min, and hold it at that temperature for 0.5 hours~2 hours to remove moisture and impurities from the surface of the chopped carbon fibers and activate the defective active sites on the surface of the chopped carbon fibers.

[0067] The heat treatment equipment includes any one of the following: tube furnace, box-type atmosphere furnace, rotary furnace or roller kiln.

[0068] Step 120-2: Increase the temperature to 600℃ to 900℃ at a heating rate of 1℃ / min to 5℃ / min, and hold for 1 hour to 3 hours to allow partial pyrolysis of the porous carbon material to produce carbon-containing small molecules. These carbon-containing small molecules are deposited on the surface of the short-cut carbon fibers and on the inner walls of the pores of the porous carbon material to form a carbon coating layer.

[0069] In this process, the defective active sites on the surface of chopped carbon fibers serve as preferential nucleation and deposition sites for carbon-containing small molecules, inducing their deposition. Furthermore, a carbon bridge network is formed between the chopped carbon fibers and the porous carbon material through a carbon coating layer. Carbon-containing small molecules are deposited on the inner walls of the pores of the porous carbon material to regulate the pore size distribution of the porous carbon material.

[0070] Carbon-containing small molecules include one or more of CH4, CO, or C2H2.

[0071] Step 120-3, then heat to 900℃~1300℃ at a heating rate of 1℃ / min~5℃ / min, hold for 0.5 hours~2 hours to solidify the carbon coating layer.

[0072] Step 130: The heat treatment equipment is cooled to room temperature at a rate of less than or equal to 5°C / min, so that the precursor material is cooled with the furnace to obtain short-cut carbon fiber bridged carbon-coated porous carbon material.

[0073] The short-cut carbon fiber bridged carbon-coated porous carbon material obtained by the post-processing method provided in the embodiments of the present invention can be in any of the following forms: granular, spherical, sheet-like, or felt-like.

[0074] In the pore size distribution of the short-cut carbon fiber bridged carbon-coated porous carbon material, the proportion of macropores is less than or equal to 2%, the proportion of mesopores is 7% to 15%, and the proportion of micropores is 85% to 92%.

[0075] The specific surface area of ​​the short-cut carbon fiber bridged carbon-coated porous carbon material is 400 m². 2 / g~1800m 2 / g, with a specific surface area retention rate of greater than or equal to 88% relative to porous carbon materials.

[0076] In this invention, the volume median particle size (Dv50) refers to the volume median particle size of a material, representing the particle size corresponding to 50% of the material's volume distribution, a meaning known in the art. The Dv50 is tested using conventional methods, such as laser diffraction. According to the standard ISO 13320:2020 Particle size analysis—Laser diffraction method, the Dv50 is determined using a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0077] The method for detecting pore size distribution, average pore size, pore volume, specific surface area, and porosity of the present invention is as follows: using a low-temperature nitrogen adsorption method, a fully automated surface area and porosity analyzer (ASAP 2460) is first used for high-precision full-pore screening, and then a precision high-precision surface area and porosity analyzer (BET) is used for focused analysis on a specific pore size range to obtain data such as pore distribution and specific surface area.

[0078] The short-cut carbon fiber bridged carbon-coated porous carbon material provided in the embodiments of the present invention can be used as a carbon matrix to prepare silicon-carbon anode materials.

[0079] The preparation method of silicon-carbon anode material adopts conventional methods, such as: short-cut carbon fiber bridging carbon-coated porous carbon material is combined with silicon source by chemical vapor deposition, melt impregnation or wet spray drying, so that nano-silicon is loaded in the pores and surface of the short-cut carbon fiber bridging carbon-coated porous carbon material.

[0080] The preferred method for preparing silicon-carbon anode materials is chemical vapor deposition (CVD). Specifically, short-cut carbon fiber-bridged porous carbon material is placed in a deposition apparatus. Under a protective gas atmosphere, the temperature is raised to 500℃–1000℃. Argon is used as the carrier gas to introduce the silicon source gas into the deposition apparatus, and the temperature is maintained for 1–4 hours. After silicon deposition, the temperature of the deposition apparatus is adjusted to 600℃–800℃, and carbon source gases such as acetylene or methane are introduced for surface carbon coating. The coating time is 0.5–2 hours, forming the outermost carbon coating layer, thus obtaining the silicon-carbon anode material. The deposition apparatus includes a box furnace or a tube furnace; the silicon source gas includes one or more of silane (SiH4), dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), silicon tetrachloride (SiCl4), or chloromethylsilane. The flow rates of the carrier gas and silicon source gas are 50 sccm–200 sccm. The carrier gas and protective gas include one or more of nitrogen, argon, and helium.

[0081] The silicon-carbon anode material prepared by the present invention using short-cut carbon fiber-bridged carbon-coated porous carbon material as a matrix can be used to prepare anode sheets, which are used to assemble lithium-ion batteries.

[0082] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate a post-processing method for porous carbon materials provided by the present invention, and the characteristics of short-cut carbon fiber-bridged carbon-coated porous carbon materials obtained by the post-processing method.

[0083] Example 1 This embodiment provides a preparation process for short-cut carbon fiber-bridged carbon-coated porous carbon materials, as detailed below.

[0084] Step 1: Mix porous carbon material and chopped carbon fiber at a mass ratio of 9:1, so that the chopped carbon fiber is evenly dispersed in the gaps and surface of the porous carbon material to obtain a mixture.

[0085] Among them, the porous carbon material uses phenolic resin-based porous carbon spheres with a particle size Dv50 of 12 μm and an initial specific surface area of ​​1860 m². 2 / g, micropores account for 88%, mesopores account for 10%, macropores account for 2%, and the most probable pore size is 1.8nm.

[0086] The short-cut carbon fibers are polyacrylonitrile-based carbon fibers with a length of 50μm to 150μm and a diameter of 7μm.

[0087] Step 2: Under a nitrogen atmosphere, the mixture is subjected to a three-stage temperature-controlled heat treatment to obtain the precursor material.

[0088] The three-stage temperature-controlled heat treatment specifically includes the following steps.

[0089] (1) Place the mixture in a tube furnace and heat it to 400°C at a heating rate of 2°C / min. Hold it at that temperature for 1 hour to remove moisture and impurities from the surface of the short-cut carbon fibers and activate the defective active sites on the surface of the short-cut carbon fibers.

[0090] (2) The temperature is then increased to 800℃ at a rate of 2℃ / min and held for 2 hours to partially pyrolyze the porous carbon material to generate carbon-containing small molecules. These small carbon molecules are deposited on the surface of the chopped carbon fibers and on the inner walls of the pores of the porous carbon material to form a carbon coating layer. The defective active sites on the surface of the chopped carbon fibers serve as preferential nucleation and deposition sites for the carbon-containing small molecules, inducing their deposition. A carbon bridge network is formed between the chopped carbon fibers and the porous carbon material through the carbon coating layer. The deposition of carbon-containing small molecules on the inner walls of the pores of the porous carbon material is used to regulate the pore size distribution of the porous carbon material.

[0091] (3) Then, the temperature is increased to 1100℃ at a rate of 2℃ / min and kept at that temperature for 1 hour to solidify the carbon coating layer and make the carbon coating layer structure more stable.

[0092] Step 3: Cool the tube furnace to room temperature at a rate of 5℃ / min to allow the precursor material to cool with the furnace, thereby obtaining short-cut carbon fiber bridged carbon-coated porous carbon material.

[0093] The short-cut carbon fiber bridged carbon-coated porous carbon material prepared in this embodiment was tested, as follows.

[0094] (1) Specific surface area test: The gas adsorption BET method is used to determine the amount of nitrogen adsorbed by the material at liquid nitrogen temperature, and the specific surface area of ​​the material is obtained by calculation using the BET multilayer adsorption theory model.

[0095] Specific surface area test results: The specific surface area of ​​the short-cut carbon fiber bridged carbon-coated porous carbon material provided in this embodiment is 1767 m². 2 / g, the specific surface area retention rate is 95% relative to the specific surface area of ​​the untreated porous carbon material.

[0096] (2) Pore size distribution, most probable pore size and pore size distribution width test: The pore size distribution is based on the adsorption-desorption isotherm obtained by nitrogen adsorption method and is calculated using the nonlocal density functional theory (NLDFT) model; the most probable pore size is directly determined by the peak value of the pore size distribution curve; the pore size distribution width Dv90-Dv10 is quantitatively characterized by the difference between the corresponding pore sizes when the cumulative pore size distribution reaches 10% and 90%.

[0097] Pore ​​size distribution, most probable pore size, and pore size distribution width test results: The pore size distribution of the short-cut carbon fiber bridged carbon-coated porous carbon material prepared in this embodiment is as follows: the micropore ratio is 91%, indicating that the micropores are completely preserved, and the macropore ratio decreased from 2% to 0.4%, a reduction of 80%; the most probable pore size refers to the pore size value that appears most frequently in the pore size distribution curve of the porous material, that is, the pore size corresponding to the peak value on the distribution curve of pore volume or pore area as a function of pore size. The most probable pore size of the short-cut carbon fiber bridged carbon-coated porous carbon material was still 1.8. The pore size remained unchanged compared to the original porous carbon material, indicating that small carbon molecules did not deposit and block the micropores. This is because if the micropores were partially blocked, the most probable pore size would shift to a smaller pore size. The pore size distribution width Dv90-Dv10 test showed that the difference between Dv90 and Dv10 decreased from 3.5 nm to 2.2 nm, a narrowing rate of 37%. This indicates that the pore size distribution of the porous carbon material obtained by the post-processing method of this invention becomes narrower and more uniform. After the macropores are blocked, the pore size of the porous carbon material becomes more concentrated.

[0098] (3) Powder conductivity test: The four-probe method was used for measurement. Specifically, the powder sample was filled into an insulating mold and compacted. Four probes were used to make close contact with the upper surface of the sample. The resistivity was calculated based on the measured resistance and sample size. The formulas are as follows: Resistivity calculation formula: ρ = R × A / L, where R is the measured powder resistance, A is the cross-sectional area of ​​the cylindrical mold, and L is the height of the compacted powder column. Conductivity calculation formula: σ = 1 / ρ = L / (R × A).

[0099] Powder conductivity test results: The powder conductivity of the original porous carbon material is 2.5 S / m, while the powder conductivity of the short-cut carbon fiber bridged carbon-coated porous carbon material provided in this embodiment is 10.5 S / m, which is 3.2 times higher than that of the original porous carbon material.

[0100] (4) Compressive strength test: A single porous carbon particle is pressurized using a powder crushing test system until it breaks. The maximum pressure when the particle breaks is recorded as the compressive strength of the porous carbon particle, i.e., the single particle crushing strength.

[0101] Compressive strength test results: The compressive strength of the short-cut carbon fiber bridged carbon-coated porous carbon material provided in this embodiment is increased by 40% compared with the original porous carbon material.

[0102] A silicon-carbon anode material was prepared by using the short-cut carbon fiber bridged carbon-coated porous carbon material provided in this embodiment, followed by silicon deposition and carbon coating treatment. The specific preparation process is as follows: The short-cut carbon fiber bridged carbon-coated porous carbon material was placed in a tube furnace and heated to 700°C under an argon atmosphere. Silane was introduced into the tube furnace using argon as a carrier gas and held at this temperature for 2 hours, allowing silicon elements from the decomposition of silane to deposit on the pore walls and surface of the short-cut carbon fiber bridged carbon-coated porous carbon material. After silicon deposition, argon gas was switched to purge for 20 minutes, and the temperature of the tube furnace was adjusted to 800°C. A mixed gas of acetylene and argon was then introduced for surface carbon coating treatment for 1 hour, forming the outermost carbon coating layer, thus obtaining the silicon-carbon anode material. The volume ratio of the carrier gas to silane was 1:5, and the total flow rate was 150 sccm; the volume ratio of acetylene to argon was 1:1, and the total flow rate of the mixed gas was 110 sccm.

[0103] The process of assembling a half-cell (CR2032 coin cell) using the silicon-carbon anode material prepared in this embodiment is as follows.

[0104] The electrode preparation process is as follows: The silicon-carbon anode material, conductive additive carbon black, and binder prepared in this embodiment are weighed at a mass ratio of 95:2:3. At room temperature, an appropriate amount of deionized water is added, and the mixture is placed in a pulping machine to prepare a slurry with a solid content of 45 wt%. The prepared slurry is uniformly coated onto copper foil and dried in a forced-air drying oven at 50°C for 2 hours. The slurry is then cut into 8×8 mm electrode sheets and placed in a vacuum drying oven at 100°C for 10 hours. The dried electrode sheets are then transferred to a glove box for later use in battery assembly. The binder is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber at a mass ratio of 1:1.

[0105] Assemble the button cell as follows: In a glove box containing high-purity argon, use a lithium metal sheet as the counter electrode, and use a ethylene carbonate (EC) / dimethyl carbonate (DMC) solution containing 1 mol / L LiPF6 as the electrolyte. The volume ratio of EC to DMC is 1:1. Use a polyethylene (PE) membrane as the separator, and assemble it together with the electrode prepared above to form a half cell.

[0106] The assembled button cells were tested using a Blue Electric Tester in constant current charge-discharge mode. The discharge cutoff voltage was 0.005V, and the charge cutoff voltage was 1.5V. Charge-discharge tests were performed at a 0.1C rate for two cycles, followed by a cycle test at a 0.5C rate. The coulombic efficiency in the first week and the cycle capacity retention after 100 cycles were recorded. See section 1 for detailed test data.

[0107] Example 2 This embodiment provides a preparation process for short-cut carbon fiber-bridged carbon-coated porous carbon material. The difference from Embodiment 1 is that a different porous carbon material is used, but the other preparation processes are the same as in Embodiment 1, as detailed below.

[0108] The porous carbon material used in this embodiment is coconut shell-based porous carbon material with a particle size Dv50 of 12 μm and an initial specific surface area of ​​1650 m². 2 / g, micropores account for 82%, mesopores account for 11%, macropores account for 7%, and the most probable pore size is 1.5nm.

[0109] The short-cut carbon fiber bridged carbon-coated porous carbon material prepared in this embodiment was tested using the same testing method as in Example 1.

[0110] The specific surface area of ​​the short-cut carbon fiber bridged carbon-coated porous carbon material prepared by testing was 1535 m². 2 / g, the specific surface area retained 93% relative to the specific surface area of ​​the untreated porous carbon material; the micropore ratio increased from 82% to 87%; the most probable pore size remained at 1.5nm; the macropore ratio decreased from 7% to 1.2%, a reduction of 83%; and the compressive strength increased by 45%. See Table 1 for a summary of the test data.

[0111] The silicon-carbon anode material was prepared using the short-cut carbon fiber bridged carbon-coated porous carbon material prepared in this embodiment, and the preparation method was the same as in Example 1.

[0112] The silicon-carbon anode material prepared in this embodiment was used to prepare electrode sheets and assemble them into CR2032 coin cells. The cells were then tested, and the specific process was the same as in Example 1. The test data are detailed in Table 1.

[0113] Example 3 This embodiment provides a preparation process for short-cut carbon fiber-bridged carbon-coated porous carbon material. The difference from Embodiment 1 lies in the use of a different porous carbon material and the use of a different temperature-controlled step (2) with a holding time of 1.5 hours to prevent the starch-based porous carbon material from becoming too soft and causing excessive deposition. Other preparation processes are the same as in Embodiment 1, as detailed below.

[0114] The porous carbon material used in this embodiment is a starch-based porous carbon material with a particle size Dv50 of 12 μm and an initial specific surface area of ​​450 m². 2 / g, with a macropore ratio of 15% and a most probable pore size of 6.5nm.

[0115] The short-cut carbon fiber bridged carbon-coated porous carbon material prepared in this embodiment was tested using the same testing method as in Example 1.

[0116] The specific surface area of ​​the short-cut carbon fiber bridged carbon-coated porous carbon material prepared by testing was 415 m². 2 / g, the specific surface area retained 92% relative to the specific surface area of ​​the untreated porous carbon material, the micropore ratio increased from 82% to 86%; the most probable pore size remained at 1.5nm; the macropore ratio decreased from 7% to 1.2%, a reduction of 83%; and the compressive strength increased by 45%. See Table 1 for a summary of the test data.

[0117] This embodiment uses short-cut carbon fiber-bridged carbon-coated porous carbon materials to prepare silicon-carbon anode materials. The preparation method is the same as in Example 1. The silicon-carbon anode material prepared in this embodiment was used to prepare electrode sheets and assemble them into CR2032 coin cells. The cells were then tested, and the specific process was the same as in Example 1. The test data are detailed in Table 1.

[0118] Example 4 This embodiment provides a preparation process for short-cut carbon fiber-bridged carbon-coated porous carbon material. The difference from Embodiment 1 is that the amount of short-cut carbon fiber added is different. The porous carbon material and short-cut carbon fiber are mixed at a mass ratio of 9.5:0.5, that is, the amount of short-cut carbon fiber added is 5wt%. The other preparation processes are the same as those in Embodiment 1, as follows.

[0119] The short-cut carbon fiber-bridged carbon-coated porous carbon material prepared in this embodiment was tested using the same method as in Example 1. Detailed test data are shown in Table 1.

[0120] This embodiment uses short-cut carbon fiber-bridged carbon-coated porous carbon materials to prepare silicon-carbon anode materials. The preparation method is the same as in Example 1. The silicon-carbon anode material prepared in this embodiment was used to prepare electrode sheets and assemble them into CR2032 coin cells. The cells were then tested, and the specific process was the same as in Example 1. The test data are detailed in Table 1.

[0121] Example 5 This embodiment provides a preparation process for short-cut carbon fiber-bridged carbon-coated porous carbon material. The difference from Embodiment 1 is that the amount of short-cut carbon fiber added is different. The porous carbon material and short-cut carbon fiber are mixed at a mass ratio of 8.5:1.5, that is, the amount of short-cut carbon fiber added is 15wt%. The other preparation processes are the same as those in Embodiment 1, as detailed below.

[0122] The short-cut carbon fiber-bridged carbon-coated porous carbon material prepared in this embodiment was tested using the same method as in Example 1. Detailed test data are shown in Table 1.

[0123] This embodiment uses short-cut carbon fiber-bridged carbon-coated porous carbon materials to prepare silicon-carbon anode materials. The preparation method is the same as in Example 1. The silicon-carbon anode material prepared in this embodiment was used to prepare electrode sheets and assemble them into CR2032 coin cells. The cells were then tested, and the specific process was the same as in Example 1. The test data are detailed in Table 1.

[0124] Example 6 This embodiment provides a preparation process for short-cut carbon fiber-bridged carbon-coated porous carbon material. The difference from Embodiment 1 is that the amount of short-cut carbon fiber added is different. The porous carbon material and short-cut carbon fiber are mixed at a mass ratio of 8:2, that is, the amount of short-cut carbon fiber added is 20wt%. The other preparation processes are the same as those in Embodiment 1, as detailed below.

[0125] The short-cut carbon fiber-bridged carbon-coated porous carbon material prepared in this embodiment was tested using the same method as in Example 1. Detailed test data are shown in Table 1.

[0126] This embodiment uses short-cut carbon fiber-bridged carbon-coated porous carbon materials to prepare silicon-carbon anode materials. The preparation method is the same as in Example 1. The silicon-carbon anode material prepared in this embodiment was used to prepare electrode sheets and assemble them into CR2032 coin cells. The cells were then tested, and the specific process was the same as in Example 1. The test data are detailed in Table 1.

[0127] To better illustrate the effects of the embodiments of the present invention, a comparative example is provided to be made with the embodiments described above.

[0128] Comparative Example 1 This comparative example uses the original porous carbon material used in Example 1 as a control group, and directly uses the phenolic resin-based porous carbon spheres from Example 1 as a matrix to perform silicon deposition and carbon coating to prepare silicon-carbon anode materials, with the same preparation process as in Example 1.

[0129] The silicon-carbon anode material prepared in this comparative example was used to prepare electrode sheets and assemble them into CR2032 coin cells. The cells were then tested, and the specific process was the same as in Example 1. The test data are detailed in Table 1.

[0130] A comparison chart of the effects of different amounts of short-cut carbon fibers added in Examples 1, 4, 5, 6 and Comparative Example 1 on the macropore ratio and specific surface area retention of phenolic resin-based porous carbon particles is shown below. Figure 2 The horizontal axis represents the amount of short-cut carbon fiber added (wt%), the left vertical axis represents the proportion of macropores (%), and the right vertical axis represents the specific surface area retention rate (%).

[0131] pass Figure 2 The performance trends of different carbon fiber addition amounts can be observed. Specifically, Comparative Example 1 had a carbon fiber addition of 0 wt%, Example 4 had 5 wt%, Example 1 had 10 wt%, Example 5 had 15 wt%, and Example 6 had 20 wt%. The proportion of macropores continuously decreased with increasing carbon fiber addition: at 5 wt%, it decreased to 0.8%, a decrease of 60%; at 10 wt%, it decreased to 0.4%, a decrease of 80%; and at 15 wt%, it decreased to 0.2%, a decrease of 90%. This indicates that the higher the carbon fiber addition, the more significant the selective macropore blocking effect. The specific surface area retention rate showed a trend of first increasing and then decreasing with increasing carbon fiber addition: the highest specific surface area retention rate was 97% at 5 wt%, 95% at 10 wt%, 92% at 15 wt%, and decreased to 88% at 20 wt%.

[0132] A comparison of the compressive strength improvement curves of porous carbon materials obtained under different amounts of chopped carbon fibers in Examples 1, 4, 5, 6, and Comparative Example 1 of this invention is shown in the figure. Figure 3As shown in the figure, the horizontal axis represents the amount of chopped carbon fiber added (wt%), and the vertical axis represents the increase in compressive strength (%). The figure illustrates the trend of the increase in compressive strength when the carbon fiber addition amounts are 0 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt%. The increase in compressive strength continuously rises with the increase in carbon fiber addition, indicating that the higher the carbon fiber addition amount, the denser the carbon bridge network constructed between porous carbon particles, and the more significant the enhancement effect on the mechanical strength of the material.

[0133] Comparative Example 2 This comparative example provides a post-processing method for porous carbon materials. Unlike Example 1, no short-cut carbon fibers were added, i.e., the amount of short-cut carbon fibers added was 0. However, the same three-stage temperature-controlled heat treatment process as in Example 1 was used, and the other preparation steps were the same as in Example 1.

[0134] Silicon-carbon anode materials were prepared using the post-treated porous carbon materials of this comparative example, and the preparation method was the same as in Example 1. The silicon-carbon anode material prepared in this comparative example was used to prepare electrode sheets and assemble them into CR2032 coin cells. The cells were then tested, and the specific process was the same as in Example 1. The test data are detailed in Table 1.

[0135] The short-cut carbon fiber bridged carbon-coated porous carbon material provided in Example 1 of this invention is compared with the nonlocal density functional theory (NLDFT) full-pore size distribution curves of the porous carbon materials provided in Comparative Example 1 and Comparative Example 2, as shown in the figure. Figure 4 As shown, the horizontal axis represents the pore size (nm), and the vertical axis represents the differential pore volume (dV / dD, cm). 3 / g·nm).

[0136] NLDFT is currently recognized as the most accurate method for analyzing the pore size distribution across the entire pore size range of porous carbon materials. Figure 4 As can be seen, the original porous carbon material in Comparative Example 1 has a distinct micropore peak at 1.8 nm, corresponding to a most probable pore size of 1.8 nm; there is a certain peak area in the macropore region, corresponding to a macropore proportion of 2.0%; the material in Comparative Example 2, which underwent three-stage heat treatment but without the addition of short-cut carbon fibers, showed that the most probable pore size shifted to the left from 1.8 nm to 1.6 nm, indicating that some micropores were blocked by non-selectively deposited carbon layers; the peak area in the macropore region only decreased slightly, and the macropore proportion dropped to 1.6%, indicating that the selective blocking effect of Comparative Example 2 was poor; the porous carbon material in Example 1, after adding 10 wt% short-cut carbon fibers and undergoing three-stage heat treatment, still had a most probable pore size of 1.8 nm, the same as the original porous carbon material, with no change, indicating that no deposition blockage occurred inside the micropores; the peak area in the macropore region decreased significantly, and the macropore proportion dropped to 0.4%, indicating that the macropores were selectively blocked; the peak shape in the mesopore region remained basically unchanged, indicating that the mesopore structure was completely preserved.

[0137] Table 1 summarizes the test data for Examples 1-6 and Comparative Examples 1-2.

[0138] As can be seen from the comparison of the test data in Table 1, the proportion of macropores in each embodiment was significantly reduced after processing by the post-processing method of the present invention. In Example 1, the proportion decreased from the original 2.0% to 0.4%, a reduction of 80%; in Example 2, it decreased from 7% to 1.2%, a reduction of 83%; in Example 3, it decreased from 15% to 2.0%, a reduction of 87%; and in Examples 5 and 6, the proportion of macropores decreased to 0.2% and 0.1%, respectively. This indicates that the post-processing method of this embodiment, which uses chopped carbon fibers as preferred nucleation sites, can achieve selective sealing of macropores and is applicable to porous carbon materials from different precursor sources.

[0139] The micropore ratio in each embodiment did not decrease, but rather increased. For example, in Example 1, it increased from 88% to 91%, and in Examples 5 and 6, it increased from 88% to 92%. This is because the macropores were blocked, forming new micropores and thus increasing the micropore ratio. The most probable pore size remained unchanged in Examples 1, 2, and 4, indicating that carbon-containing small molecules did not deposit and block the micropores. In Comparative Example 2, no carbon fiber was added. Although a three-stage heat treatment was also used, the most probable pore size shifted to the left from 1.8 nm to 1.6 nm, indicating that some micropore openings were blocked. This proves that chopped carbon fiber, as a heterogeneous nucleation site, can effectively guide the preferential deposition of carbon sources on its surface, thereby protecting the microporous structure.

[0140] In Examples 5 and 6, the compressive strength was increased by 65% ​​and 88%, respectively, and the electrical conductivity was increased by 4.4 times and 5.4 times, respectively. In contrast, the original porous carbon in Comparative Example 1 without post-treatment and the porous carbon material in Comparative Example 2 without added carbon fibers showed no significant mechanical strengthening effect. This indicates that after the carbon coating layer was deposited on the carbon fiber surface in Examples 5 and 6, a continuous carbon bridge network was formed between the porous carbon particles. This carbon bridge network not only improved the mechanical strength of the material through the bridging effect of carbon fibers, but also constructed an efficient conductive path, achieving synergistic enhancement of mechanical and electrical properties.

[0141] Coin cells assembled using silicon-carbon anode materials prepared with short-cut carbon fiber bridged carbon-coated porous carbon materials as provided in Examples 1-6 achieved a first-cycle coulombic efficiency of 90.2%–92.5% and a capacity retention of 89.0%–93.0% after 100 cycles, significantly better than Comparative Examples 1 and 2. Among these, Examples 5 and 6 exhibited the most superior electrochemical performance, thanks to their optimal pore size distribution (macrosometry ≤0.2%, micropores ≥92%) and optimal carbon bridge network structure. This is because the macropore sealing of the short-cut carbon fiber bridged carbon-coated porous carbon materials in these embodiments reduces side reaction sites between the electrolyte and electrode materials, thereby improving the first-cycle coulombic efficiency. Furthermore, the improved pore size uniformity and the reinforcing effect of the carbon bridge network on the material structure enhance the cycle stability of the battery.

[0142] In summary, this invention introduces short-cut carbon fibers as heterogeneous nucleation deposit nuclei into porous carbon materials and combines this with three-stage temperature-controlled heat treatment. This allows small carbon molecules released by the thermal decomposition of porous carbon to preferentially deposit on the surface of the carbon fibers and the inner walls of the macropores, achieving selective sealing of macropores while completely preserving the micropore and mesopore structures. Furthermore, a continuous carbon bridge network is constructed between the carbon fibers and porous carbon particles, thereby synergistically improving the material's pore size uniformity, mechanical strength, and electrical conductivity. When silicon-carbon anode materials prepared using this substrate are applied to lithium-ion batteries, the initial coulombic efficiency, cycle stability, and rate performance are all significantly improved.

[0143] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A post-processing method for porous carbon materials, characterized in that, The post-processing method includes: Porous carbon materials are mixed with chopped carbon fibers, so that the chopped carbon fibers are uniformly dispersed in the gaps and on the surface of the porous carbon materials to obtain a mixture. Under an inert atmosphere, the mixture is subjected to a three-stage temperature-controlled heat treatment to obtain a precursor material; the three-stage temperature-controlled heat treatment includes: The mixture is placed in a heat treatment device and heated to 200℃ to 500℃ at a heating rate of 0.5℃ / min to 5℃ / min, and held at that temperature for 0.5 hours to 2 hours to remove moisture and impurities from the surface of the chopped carbon fibers and activate the defective active sites on the surface of the chopped carbon fibers. The temperature is then increased to 600℃ to 900℃ at a rate of 1℃ / min to 5℃ / min, and held for 1 hour to 3 hours to allow partial pyrolysis of the porous carbon material, generating carbon-containing small molecules. These small carbon molecules are deposited on the surface of the chopped carbon fibers and on the inner walls of the pores of the porous carbon material, forming a carbon coating layer. The defective active sites on the surface of the chopped carbon fibers serve as preferential nucleation and deposition sites for the carbon-containing small molecules, inducing their deposition. Furthermore, a carbon bridge network is formed between the chopped carbon fibers and the porous carbon material through the carbon coating layer. The deposition of the carbon-containing small molecules on the inner walls of the pores of the porous carbon material regulates its pore size distribution. Then, the temperature is increased to 900℃ to 1300℃ at a rate of 1℃ / min to 5℃ / min, and held for 0.5 hours to 2 hours to solidify the carbon coating layer. The heat treatment equipment is cooled to room temperature at a rate of less than or equal to 5°C / min, so that the precursor material is cooled with the furnace to obtain short-cut carbon fiber bridged carbon-coated porous carbon material.

2. The post-processing method according to claim 1, characterized in that, The porous carbon material includes one or more of the following: biomass-based porous carbon, resin-based porous carbon, pitch-based porous carbon, or starch-based porous carbon. The porous carbon material may be in any of the following forms: granular, spherical, sheet-like, or felt-like. The pore size distribution of the porous carbon material is as follows: micropores account for 80% to 90%, mesopores account for 7% to 15%, and macropores account for greater than 2% and less than or equal to 8%; the pore size of the micropores is less than 2 nm, the pore size of the mesopores is 2 nm to 50 nm, and the pore size of the macropores is greater than 50 nm. The porous carbon material has a specific surface area of ​​400 m². 2 / g~1900m 2 / g; The porosity of the porous carbon material is 50%–80%; The porous carbon material has a pore volume of 0.5 cm³. 3 / g~1.2cm 3 / g.

3. The post-processing method according to claim 1, characterized in that, The chopped carbon fibers have a length of 10μm to 200μm and a diameter of 5μm to 15μm; In the mixture, the mass of the chopped carbon fibers is 1% to 20% of the mass of the porous carbon material.

4. The post-processing method according to claim 1, characterized in that, The carbon-containing small molecules include one or more of CH4, CO, or C2H2.

5. The post-processing method according to claim 1, characterized in that, The mixing includes liquid-phase ultrasonic dispersion mixing or solid-phase mixing; The liquid-phase ultrasonic dispersion mixing includes: placing the porous carbon material, the chopped carbon fibers and the solvent in an ultrasonic disperser for ultrasonic dispersion, and then removing the solvent by rotary evaporation or vacuum drying; wherein the solvent includes one or more of ethanol, isopropanol or deionized water; the ultrasonic dispersion time is 10 minutes to 60 minutes, and the ultrasonic dispersion power is 100W to 500W. The solid-phase mixing includes: placing the porous carbon material and the chopped carbon fiber in a solid-phase mixing device and mixing them at a speed of 50 rpm to 300 rpm for 0.5 hours to 2 hours.

6. The post-processing method according to claim 1, characterized in that, The inert atmosphere includes one or more of nitrogen, argon, or helium.

7. The post-processing method according to claim 1, characterized in that, The heat treatment equipment includes any one of the following: tube furnace, box-type atmosphere furnace, rotary furnace or roller kiln.

8. A short-cut carbon fiber bridged carbon-coated porous carbon material prepared by the post-processing method according to any one of claims 1-7, characterized in that, The morphology of the short-cut carbon fiber bridged carbon-coated porous carbon material is any one of granular, spherical, sheet-like or felt-like. In the pore size distribution of the short-cut carbon fiber bridged carbon-coated porous carbon material, the proportion of macropores is less than or equal to 2%, the proportion of mesopores is 7% to 15%, and the proportion of micropores is 85% to 92%. The specific surface area of ​​the short-cut carbon fiber bridged carbon-coated porous carbon material is 400 m². 2 / g~1800m 2 / g; the specific surface area of ​​the short-cut carbon fiber-bridged carbon-coated porous carbon material is maintained at a rate of 88% or greater than the specific surface area of ​​the porous carbon material.

9. A silicon-carbon anode material, characterized in that, The silicon-carbon anode material includes the short-cut carbon fiber bridged carbon-coated porous carbon material as described in claim 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the silicon-carbon anode material of claim 9.

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