Porous carbon material, silicon-carbon negative electrode material, preparation method and secondary battery

Abstract

The application relates to a porous carbon material, a silicon-carbon negative electrode material, a preparation method and a secondary battery, wherein the R value in the X-ray diffraction pattern of the porous carbon material is 1.4-5, the R value is the ratio of the diffraction peak intensity of a (002) crystal face to the background intensity; in the Raman spectrum of the porous carbon material, the ratio I D1 / I G of the D1 peak intensity representing defect-induced graphite structure to the G peak intensity representing a graphite lattice is 0.201-2.859, and the ratio I 3 / I D3 of the D3 peak intensity representing amorphous carbon sp G hybrid carbon atoms to the G peak intensity representing a graphite lattice is 0.336-1.403. By controlling the number of oxygen-containing functional groups, the application optimizes the diffusion channel of lithium ions in the porous carbon material, so that the lithium ions can more quickly reach the surface of silicon particles for reaction, thereby improving the rate performance of the battery.

Description

Technical Field

[0001] This application belongs to the technical field of battery anode materials, and specifically relates to porous carbon materials, silicon-carbon anode materials, preparation methods, and secondary batteries. Background Technology

[0002] With the continuous development of lithium-ion battery technology, silicon-carbon anode materials have become a research hotspot due to their potential for high energy density and long cycle life. However, the performance of silicon-carbon anode materials largely depends on the quality of their porous carbon substrate.

[0003] Porous carbon substrates, as an important component of silicon-carbon anode materials, can be prepared using various methods, mainly including chemical activation, physical activation, and template methods. Chemical activation typically uses strong bases (such as KOH), strong acids (such as H3PO4), or salts (such as ZnCl2) as activators, reacting them with the carbon precursor at high temperatures to form a porous structure through etching. Physical activation mainly utilizes gases (such as CO2 or water vapor) at high temperatures to react with the carbon precursor, forming pores through gas molecule diffusion and etching. Template methods involve introducing a template with a specific structure into the carbon precursor beforehand, followed by carbonization and template removal steps to obtain porous carbon with a regular pore structure.

[0004] Although the methods described above can prepare carbon materials with porous structures, the carbon structure is often damaged to some extent during the activation process. This damage not only leads to a decrease in the strength of the carbon material but also generates a large number of defects, such as vacancies and dangling bonds. These defects severely affect the electronic conductivity of the carbon material, thereby reducing the rate performance of novel silicon-carbon anodes prepared using this material as a substrate. Rate performance is one of the important performance indicators of lithium-ion batteries, reflecting the battery's performance at different charge and discharge rates. Poor rate performance means that the battery's performance will drop significantly during rapid charge and discharge, thus limiting the application of silicon-carbon anode materials in high-performance lithium-ion batteries. Summary of the Invention

[0005] In view of the limitations of the prior art, the present invention aims to provide a porous carbon material and a method for preparing the same, so as to prepare a porous carbon material with lower defect content and higher electronic conductivity. It also provides a silicon-carbon anode material equipped with the porous carbon material of this application, thereby improving the rate performance of novel silicon-carbon anodes prepared using this material as a substrate.

[0006] In one aspect of this application, a porous carbon material is provided, wherein the R-value in the X-ray diffraction pattern of the porous carbon material is 1.4 to 5, and the R-value is the ratio of the diffraction peak intensity of the (002) crystal plane to the background intensity. In the X-ray diffraction pattern, a background line is formed by drawing common tangents between the peaks and valleys on both sides of the (002) crystal plane diffraction peak. A tangent line parallel to the background line is drawn to determine the tangent point, and the intensity of the tangent point is the diffraction peak intensity. The intensity on the background line at the diffraction angle 2θ corresponding to the tangent point is the background intensity. In the Raman spectrum of the porous carbon material, the ratio of the D1 peak intensity, which characterizes the defect-induced graphite structure, to the G peak intensity, which characterizes the graphite lattice, is I. D1 / I G The value ranges from 0.201 to 2.859, representing the sp values ​​of amorphous carbon. 3 The ratio of the D3 peak intensity of hybrid carbon atoms to the G peak intensity characterizing the graphite lattice is I. D3 / I G The range is 0.336 to 1.403.

[0007] In some embodiments, the R value in the X-ray diffraction pattern of the porous carbon material is 2.021 to 2.387.

[0008] In some embodiments, the ratio of the D1 peak intensity, which characterizes the defect-induced graphite structure, to the G peak intensity, which characterizes the graphite lattice, in the Raman spectrum of the porous carbon material is I. D1 / I G The range is 0.773 to 1.638.

[0009] In some embodiments, the porous carbon material is characterized by Raman spectroscopy of amorphous carbon sp. 3 The ratio of the D3 peak intensity of hybrid carbon atoms to the G peak intensity characterizing the graphite lattice is I. D3 / I G The value ranges from 0.691 to 0.899.

[0010] In some embodiments, the particle size of the porous carbon material is 0.337–0.365 nm.

[0011] In some embodiments, the length La of the graphene basal plane in the porous carbon material is 2.98–4.57 nm.

[0012] In some embodiments, the length La of the graphene basal plane in the porous carbon material is 3.59–4.14 nm.

[0013] In some embodiments, the BET specific surface area of ​​the porous carbon material is 978–1324 m². 2 / g.

[0014] In some embodiments, the BET specific surface area of ​​the porous carbon material is 1032–1213 m².2 / g.

[0015] In some embodiments, the average pore size of the porous carbon material is 3.41 to 3.89 nm.

[0016] In some embodiments, the average pore size of the porous carbon material is 3.44 to 3.77 nm.

[0017] In some embodiments, the resistivity of the porous carbon material is 0.007 to 0.079 Ω·cm.

[0018] In another aspect of this application, a method for preparing the porous carbon material is provided, comprising the following steps:

[0019] The porous template is pretreated by immersing it in a metal salt solution;

[0020] The pretreated porous template is placed in a reactor and heated to the carbon deposition temperature;

[0021] Carbon-containing gas is introduced at the carbon deposition temperature for vapor phase deposition;

[0022] The porous carbon material is obtained by removing the porous template.

[0023] In some embodiments, the porous template is cleaned, dried, and / or activated before immersion.

[0024] In some embodiments, the porous template is cleaned with ethanol, vacuum dried, and / or activated at high temperature before immersion.

[0025] In some embodiments, the porous template is selected from zeolite, copper foam, silicon dioxide, magnesium oxide, magnesium hydroxide, or calcium oxide.

[0026] In some embodiments, the porous template is selected from zeolite.

[0027] In some embodiments, the metal salt is selected from one or more of ferric chloride, molybdenum chloride, lanthanum chloride, nickel chloride, cobalt chloride, and calcium chloride.

[0028] In some embodiments, the metal salt is selected from lanthanum chloride.

[0029] In some embodiments, the carbon-containing gas is a mixture of carbon precursor gas and argon.

[0030] In some embodiments, the carbon precursor gas is selected from CO, CH4, C2H2, C2H6, C3H8, and C4H. 10 One or more of C2H4, C3H6, C4H8, C6H6, C7H8, C2H6O, etc.

[0031] In some embodiments, the carbon-containing gas has a volume fraction of 5% C2H2 and 95% Ar.

[0032] In some implementations, the heating rate to the carbon deposition temperature is 1–10 °C / min.

[0033] In some implementations, the heating rate to the carbon deposition temperature is 5°C / min.

[0034] In some embodiments, the carbon deposition temperature is 600–1000°C.

[0035] In some embodiments, the carbon deposition temperature is 900°C.

[0036] In some embodiments, the vapor deposition time is 1 to 3 hours.

[0037] In some implementations, the porous template is removed by chemical etching, high-temperature calcination, or physical methods.

[0038] In some implementations, the porous template is removed by sequentially treating it with 10% hydrofluoric acid and 10% hydrochloric acid.

[0039] In another aspect of this application, a silicon-carbon anode material is provided, the silicon-carbon anode material comprising the porous carbon material and a silicon-based material distributed within the pores of the porous carbon material.

[0040] In some embodiments, the silicon-based material is selected from one or more of nano-silicon particles, silicon oxide, silicon alloy, or porous silicon.

[0041] In some embodiments, the silicon-based material is selected from nano-silicon particles.

[0042] In some embodiments, the silicon-based material is selected from nano-silicon particles, and the mass content of nano-silicon particles in the silicon-carbon anode material is 10% to 95%.

[0043] In some embodiments, the silicon-based material is selected from nano-silicon particles, and the mass content of nano-silicon particles in the silicon-carbon anode material is 85% to 95%.

[0044] In some embodiments, the silicon-based material is selected from nano-silicon particles, and the mass content of nano-silicon particles in the silicon-carbon anode material is 90%.

[0045] In some embodiments, the silicon-carbon anode material further includes a coating layer covering the surface of the porous carbon material.

[0046] In some embodiments, the coating layer comprises a carbon-based material, a conductive polymer, or a metal oxide.

[0047] In some embodiments, the coating layer comprises a carbon-based material, which includes one or more of amorphous carbon, graphitic carbon, carbon nanotubes, and carbon fibers.

[0048] In some embodiments, the coating layer comprises a conductive polymer, which includes one or more of polyaniline (PANI), polypyrrole (PPy), and polythiophene (PTh).

[0049] In some embodiments, the coating layer comprises a metal oxide, which includes one or more of aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2).

[0050] In another aspect of this application, a method for preparing the silicon-carbon anode material is provided, comprising the following steps: placing the porous carbon material in a reactor, heating it to the silicon deposition temperature in an inert gas environment, and introducing a gaseous silicon source for silicon deposition.

[0051] In some embodiments, the reactor includes a rotary kiln or a fluidized bed.

[0052] In some embodiments, the silicon deposition temperature is 450–1000°C.

[0053] In some embodiments, the silicon deposition temperature is 550°C.

[0054] In some embodiments, the temperature is increased to the silicon deposition temperature at a heating rate of 5–10 °C / min.

[0055] In some embodiments, the silicon deposition time is 600 min to 4000 min.

[0056] In some embodiments, the inert gas flow rate is 3 L / min to 16 L / min.

[0057] In some embodiments, the gaseous silicon source is selected from at least one of silane (SiH4), disilane (Si2H6), trichlorosilane (SiHCl3), dichlorosilane (SiH2Cl2), and tetrachlorosilane (SiCl4).

[0058] In some embodiments, the gaseous silicon source is selected from silane (SiH4).

[0059] In some embodiments, the flow rate of the vapor silicon source is 1 L / min to 2 L / min.

[0060] In some embodiments, the method for preparing the silicon-carbon anode material includes the following steps:

[0061] The porous carbon material is placed in a reactor and heated to the silicon deposition temperature in an inert gas environment. A gaseous silicon source is then introduced to perform silicon deposition.

[0062] Maintain the inert gas flow rate and introduce a gaseous carbon source for carbon deposition.

[0063] In some embodiments, the gaseous carbon source is selected from CO, CH4, C2H2, C2H6, C3H8, and C4H. 10 One or more of C2H4, C3H6, C4H8, C6H6, C7H8, C2H6O, etc.

[0064] In some embodiments, the flow rate of the gaseous carbon source is 1 to 3 L / min.

[0065] In some embodiments, the carbon deposition temperature is 550°C.

[0066] In some embodiments, the carbon deposition time is 60 to 120 minutes.

[0067] In another aspect of this application, a secondary battery is provided, the secondary battery comprising the silicon-carbon anode material.

[0068] In some embodiments, the secondary battery is selected from lithium-ion batteries, lithium polymer batteries, or lead-acid batteries.

[0069] In some embodiments, the positive electrode material of the secondary battery is selected from lithium cobalt oxide, lithium nickel manganese cobalt oxide, or lithium iron phosphate.

[0070] The beneficial effects of this application are:

[0071] This application provides a novel porous carbon material. By controlling the R value in the X-ray diffraction pattern of the porous carbon material to be between 1.4 and 5, the porous carbon material maintains a high specific surface area and provides good pore structure and connectivity, which is beneficial for the rapid diffusion and storage of lithium ions. D1 / I G With a ratio in the range of 0.2 to 3, by controlling the degree of defects in porous carbon materials, the active sites of the material can be increased, thereby improving its activity in electrochemical reactions, without compromising the overall structure of the material due to excessive defects. Furthermore, the applicant controls I... D3 / I G The value ranges from 0.336 to 1.403, I D3 / I G The value is positively correlated with the number of oxygen-containing functional groups in porous carbon materials. Low oxygen-containing functional groups help reduce sites that hinder the diffusion of lithium ions, optimize the diffusion channels of lithium ions in porous carbon materials, and enable lithium ions to reach the surface of silicon particles more quickly to react, thereby improving the rate performance of the battery. Attached Figure Description

[0072] Figure 1 This is a schematic diagram illustrating the determination of the R-value of the porous carbon material in this application. Detailed Implementation

[0073] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this application, not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0074] In one embodiment of this application, a porous carbon material is provided. The R-value in the X-ray diffraction pattern of this porous carbon material is 1.4–5, where R is the ratio of the diffraction peak intensity of the (002) crystal plane to the background intensity. In the X-ray diffraction pattern, a background line is formed by drawing common tangents to the peaks and valleys on both sides of the (002) crystal plane diffraction peak. A tangent line parallel to the background line is drawn to determine the tangent point, and the intensity at the tangent point is the diffraction peak intensity. The intensity at the diffraction angle 2θ corresponding to the tangent point on the background line is the background intensity. In the Raman spectrum of the porous carbon material, the ratio of the D1 peak intensity (characterizing the defect-induced graphite structure) to the G peak intensity (characterizing the graphite lattice) is I. D1 / I G The value ranges from 0.201 to 2.859, representing the sp values ​​of amorphous carbon. 3 The ratio of the D3 peak intensity of hybrid carbon atoms to the G peak intensity characterizing the graphite lattice is I. D3 / I G The range is 0.336 to 1.403.

[0075] Porous carbon, as the substrate for silicon-carbon anode materials, significantly influences the rate performance of these materials. A higher degree of graphitization in the porous carbon is more beneficial to the rate performance of the silicon-carbon anode, which is reflected in the Raman spectrum as I. D1 / I G A smaller value is better, indicating that porous carbon has fewer defects. Therefore, the ideal I value for porous carbon materials is... D1 / I G The ratio is typically below 1.1; however, current techniques for preparing porous carbon materials generally involve chemical or physical activation. The activation process can damage the carbon structure to some extent, creating numerous defects and resulting in a relatively high Ig ratio. D1 / I G The ratio of the D1 peak to the G peak intensity in the Raman spectrum (ID / IG ≥ 1.1) indicates poor electronic conductivity, which consequently affects the rate performance of the novel silicon-carbon anode prepared using this substrate.

[0076] The applicant discovered that the number of single carbon layers and oxygen-containing functional groups in the structure of porous carbon also affect the rate performance of silicon-carbon anodes formed from porous carbon. The applicant indirectly reflects the number of stacked carbon layers by characterizing the X-ray diffraction patterns of porous carbon materials with R values ​​ranging from 1.4 to 5, and by controlling I... D3 / I G The value limits the oxygen-containing functional groups, overcoming the I D1 / I G The ratio limits the rate performance of porous carbon structures. Specifically, by controlling the R-value in the X-ray diffraction pattern of the porous carbon material to 1.4–5, the porous carbon forms a unique microstructure. This structure not only maintains a high specific surface area but also provides good porosity and connectivity, which is beneficial for the rapid diffusion and storage of lithium ions. D3 / I G A ratio ranging from 0.691 to 0.893 indicates a low number of oxygen-containing functional groups in porous carbon. Fewer oxygen-containing functional groups reduce defects and active sites in porous carbon materials, which typically hinder lithium-ion diffusion. Therefore, by reducing the number of oxygen-containing functional groups, the diffusion channels of lithium ions in porous carbon materials can be optimized, allowing lithium ions to reach the silicon particle surface more quickly for reaction, thereby improving the rate performance of the battery.

[0077] In this application, the R-values ​​in the X-ray diffraction patterns of porous carbon materials were obtained through X-ray diffraction (XRD) with Cu Kα radiation (λ = 0.15406 nm) (Rigaku SmartLab SE; Rigaku). Specifically, as... Figure 1 As shown, a background line is formed by drawing common tangents to the valleys on both sides of the (002) peak. Then, a tangent is drawn on the (002) peak, which is parallel to the background line. The point of tangency between the tangent and the (002) peak is determined. The intensity corresponding to the point of tangency is denoted as the diffraction peak intensity (B). The diffraction angle corresponding to the point of tangency is determined. The intensity of the background line at the point of diffraction angle is denoted as the background intensity (A). The ratio of B / A is determined as the value of parameter R.

[0078] In this application, peak D1 is located at approximately 1350 cm⁻¹ in the Raman spectrum. -1A characteristic peak near the D1 peak is primarily attributed to the disordered structure or defects in the carbon material. These defects can include vacancies, substitutional impurities, edge effects, etc. The presence and intensity of the D1 peak are generally related to the degree of graphitization of the carbon material and the number and type of lattice defects. The D3 peak is typically located at approximately 1500 cm⁻¹ in Raman spectroscopy. -1 A nearby characteristic peak shows a linear correlation with oxygen-containing functional groups in amorphous carbon. The G peak is located at 1580 cm⁻¹. -1 At this point, the G band is due to the stretching vibration of sp2 carbon atom pairs (E2g symmetry), representing a perfect graphitized carbon structure. Specifically, the D1, D3, and G peaks were detected using a Renishaw inVia micro Raman spectrometer equipped with a 532 nm wavelength laser.

[0079] In some embodiments, the R-value in the X-ray diffraction pattern of the porous carbon material is 2.021 to 2.387. Specifically, the stacking quantity can be 2.021, 2.079, 2.137, 2.195, 2.253, 2.311, 2.329, 2.347, 2.365, or 2.387.

[0080] In some embodiments, the ratio of the D1 peak intensity, which characterizes the defect-induced graphite structure, to the G peak intensity, which characterizes the graphite lattice, in the Raman spectrum of the porous carbon material is I. D1 / I G The range is 0.773 to 1.638. Specifically, I D1 / I G The possible values ​​are 0.773, 0.858, 0.943, 1.028, 1.113, 1.198, 1.283, 1.368, 1.453, and 1.638.

[0081] In some embodiments, the particle size of the porous carbon material is 0.337–0.365 nm. Specifically, the particle size can be 0.337 nm, 0.339 nm, 0.341 nm, 0.343 nm, 0.345 nm, 0.347 nm, 0.349 nm, 0.351 nm, 0.352 nm, 0.354 nm, 0.356 nm, 0.358 nm, 0.360 nm, 0.361 nm, 0.362 nm, 0.363 nm, 0.364 nm, or 0.365 nm.

[0082] In this application, particle size, also known as particle size or diameter, refers to the size of a material particle. When a certain physical property or physical behavior of the particle being measured is most similar to that of a homogeneous sphere of a certain diameter, the diameter of that sphere is taken as the equivalent particle size. For spherical particles, their size is usually directly expressed as diameter. For non-spherical particles, the concept of equivalent particle size is used to describe their size. Since the shape of actual particles is usually non-spherical, it is difficult to directly express their size using diameter. Therefore, in the field of particle size testing, the equivalent particle size is usually used to describe the size of non-spherical particles. Equivalent particle size means that when the physical property or physical behavior of a particle is most similar to that of a homogeneous sphere of a certain diameter, the diameter of that sphere is taken as the equivalent particle size. In this application, particle size can be measured using the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0083] In some embodiments, the length La of the graphene basal surface in the porous carbon material is 2.98–4.57 nm. Preferably, the length La of the graphene basal surface in the porous carbon material is 3.59–4.14 nm. Specifically, the length La can be 2.98 nm, 3.07 nm, 3.16 nm, 3.25 nm, 3.34 nm, 3.43 nm, 3.52 nm, 3.59 nm, 3.61 nm, 3.7 nm, 3.79 nm, 3.88 nm, 3.97 nm, 4.06 nm, 4.14 nm, 4.24 nm, 4.33 nm, 4.42 nm, 4.51 nm, 4.56 nm, or 4.57 nm. Controlling the length of the graphene basal surface in porous carbon materials can form a more continuous conductive network, which is conducive to the rapid transport of electrons in silicon-carbon anode materials and helps lithium ions to diffuse rapidly and uniformly between the graphene basal surface and silicon particles, thereby improving the charge and discharge performance of silicon-carbon anode materials. A graphene basal surface of moderate length can form a stable structure, which helps to alleviate the volume change of silicon particles during charge and discharge.

[0084] In this application, the graphene basal surface refers to a two-dimensional planar structure in porous carbon materials, which is mainly composed of graphene or contains graphene fragments. These structures may consist of single or multiple layers of graphene sheets and may have different edge structures (such as armrest-shaped or serrated). The length of the graphene basal surface refers to the maximum dimension of the planar region along a specific direction (such as the longest axis direction). This length can be measured by techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Specifically, the length La of the graphene basal surface is detected by X-ray diffraction (XRD). (Rigaku SmartLab SE; Rigaku) ​​The profile fitting analysis of the (002) peak located at approximately 2θ to 26° is performed, and La is calculated using the Scherrer equation. k is the Scherrer constant (k = 1.84 for La), λ is the radiation wavelength, β is the half-width at half-maximum of (002) reflection, and θ is the reflection angle of (002).

[0085] In some embodiments, the BET specific surface area of ​​the porous carbon material is 978–1324 m². 2 / g, preferably, the BET specific surface area of ​​the porous carbon material is 1032-1213m² / g. 2 / g. Specifically, the BET specific surface area of ​​the porous carbon material can be 978m². 2 / g、987m 2 / g、996m 2 / g、1005m 2 / g、1014m 2 / g、1023m 2 / g、1032m 2 / g、1041m 2 / g, 1050m 2 / g, 1059m 2 / g, 1068m 2 / g、1077m 2 / g、1086m 2 / g、1095m 2 / g、1104m 2 / g、1113m 2 / g、1122m 2 / g、1131m 2 / g、1140m 2 / g、1213m 2 / g、1324m 2 / g. The BET specific surface area of ​​the porous carbon material is within this range, which significantly enhances the electrochemical activity of the material, improves the transport efficiency of electrolyte ions, and thus optimizes the energy storage performance. The high specific surface area also means more active sites, which is beneficial for further increasing the capacity.

[0086] In this application, BET specific surface area refers to the total surface area of ​​a unit mass of solid material measured by gas adsorption method based on the Brunauer-Emmett-Teller (BET) multilayer adsorption theory, with units of square meters per gram (m²). 2 / g). The measurement is based on the BET equation, which describes the relationship between the amount of gas molecules adsorbed on a solid surface and pressure when multiple adsorption layers are formed. The measurement employs a static volumetric method, where the sample is physically adsorbed with an inert gas (such as nitrogen) by precisely controlling temperature and pressure conditions. The amount of adsorption is measured at different pressures, and the specific surface area is calculated using the BET equation. This application uses Micromeritics ASAP 2020 for the measurement.

[0087] In some embodiments, the average pore size of the porous carbon material is 3.41–3.89 nm, preferably 3.44–3.77 nm. Specifically, the average pore size of the porous carbon material is 3.41 nm, 3.44 nm, 3.49 nm, 3.53 nm, 3.57 nm, 3.61 nm, 3.65 nm, 3.69 nm, 3.73 nm, 3.77 nm, 3.81 nm, 3.82 nm, 3.84 nm, 3.86 nm, 3.88 nm, or 3.89 nm.

[0088] In this application, pore size refers to the diameter of a channel or opening formed in a material (such as metal, plastic, ceramic, composite material, etc.) that allows fluids (such as gas, liquid) or solid particles to pass through. The shape of the pore can be circular, elliptical, square, rectangular, polygonal, or other irregular shapes, depending on the application and processing technology. It is usually considered circular, and its size is expressed by its radius. The size and shape of the pore need to be accurately measured and verified using equipment such as microscopes, scanning electron microscopes (SEM), laser rangefinders, and gas-liquid flow meters. Specifically, the pore size is measured using Micromeritics ASAP 2020. The average pore size of the porous carbon material is within this range, which not only provides sufficient space to alleviate the volume expansion of silicon particles during charging and discharging, effectively extending battery cycle life, but also promotes rapid lithium-ion diffusion, improving the battery's rate performance.

[0089] In some embodiments, the resistivity of the porous carbon material is 0.007–0.079 Ω·cm. Specifically, the resistivity is 0.007 Ω·cm, 0.015 Ω·cm, 0.023 Ω·cm, 0.031 Ω·cm, 0.039 Ω·cm, 0.047 Ω·cm, 0.055 Ω·cm, 0.063 Ω·cm, 0.071 Ω·cm, and 0.079 Ω·cm. In this application, the porous carbon material prepared using a compaction density meter from Yuaneng Technology is pressed into a block structure. The resistivity of the powder is then tested using a complete set of ceramic molds and a four-probe mode, and data is taken at a pressure of 100 MPa.

[0090] In another embodiment of this application, a method for preparing a porous carbon material is provided, comprising the following steps: pre-treating a porous template by immersing it in a metal salt solution; placing the pre-treated porous template in a reactor and heating it to the carbon deposition temperature; introducing a carbon-containing gas at the carbon deposition temperature for vapor deposition; and removing the porous template to obtain the porous carbon material.

[0091] The porous carbon material is prepared by template-based vapor deposition. This involves preheating the porous template to its carbon deposition temperature to prepare it for carbon-containing gas deposition. Controlling the heating rate is crucial for maintaining the integrity and stability of the template structure, avoiding excessively fast or slow rates that could adversely affect the template. At the carbon deposition temperature, carbon-containing gas is introduced for deposition; this process is the core of the porous carbon material preparation. The carbon-containing gas decomposes at high temperature and deposits within the pores of the template to form a carbon layer. By adjusting parameters such as deposition time, type, and concentration of the carbon-containing gas, the thickness of the carbon layer and the retention of the pore structure can be precisely controlled. Finally, the porous template is removed by chemical etching, pyrolysis, or other methods to obtain a porous carbon material with a uniform pore structure and good electrical conductivity.

[0092] In some embodiments, the porous template is cleaned, dried, and / or activated before heating. Preferably, this includes ethanol cleaning, vacuum drying, and / or high-temperature activation. Specifically, the porous template is completely immersed in anhydrous ethanol, gently shaken, or cleaned using an ultrasonic cleaner to fully wet and disperse impurities and residues on the template surface. The cleaning time depends on the degree of contamination and pore structure of the template, generally recommended to be between 5 and 30 minutes. The cleaning is repeated 1-2 times to ensure thorough cleaning. The cleaned porous template is placed in a vacuum drying oven and heated to a temperature below the pyrolysis temperature of the template material, while simultaneously evacuating to a certain level and maintaining this temperature for a period of time until the template is completely dry. The dried porous template is placed in a high-temperature furnace and heated to the activation temperature (usually higher than the pyrolysis temperature of the template material but lower than its structural failure temperature), maintaining this temperature for a period of time to allow physicochemical changes to occur on the template surface and inside, such as removing residual impurities and increasing porosity.

[0093] In some embodiments, the porous template is selected from zeolite, copper foam, silica, magnesium oxide, magnesium hydroxide, or calcium oxide. However, considering the connectivity of the porous carbon framework and the tunability of the pore structure, the porous template is preferably selected from zeolite. Zeolite is a class of microporous crystalline aluminosilicate materials with more than 200 structural types. Each structural type has its unique pore structure, such as pore size, shape, and connectivity. Currently, zeolites include microporous zeolites, mesoporous zeolites, and macroporous zeolites. Therefore, the pore size and wall thickness of deposited porous carbon can be customized according to the pore size and wall thickness of the zeolite. The pore diameter in many zeolites is suitable for accommodating fullerenes and carbon nanotubes, and they are interconnected along smooth curved surfaces to form an open three-dimensional (3D) network. In principle, such nanoporous systems should be ideal templates for synthesizing 3D graphene structures. Another important property of zeolites is their ion exchange capacity. The zeolite framework contains cations to compensate for the negative charge of aluminum in the tetrahedral silicate framework. The synthesized cations are typically sodium or ammonium ions, which can be exchanged with other cations through conventional solution-based ion exchange processes, thus facilitating the adsorption of catalyst ions during subsequent impregnation of other catalyst solutions.

[0094] In some embodiments, the metal salt is selected from one or more of ferric chloride, molybdenum chloride, lanthanum chloride, nickel chloride, calcium chloride, and cobalt chloride; preferably, the metal salt is selected from lanthanum chloride. The metal salt ions can be adsorbed in the pores of the porous template, lowering the temperature required for carbon source decomposition, which is beneficial for carbon source deposition inside the template's pore structure, reducing deposition on the template surface, and forming high-quality porous carbon materials.

[0095] In some embodiments, the carbon-containing gas is a mixture of a carbon precursor gas and argon, wherein the carbon precursor gas is selected from CO, CH4, C2H2, C2H6, C3H8, and C4H. 10 One or more of C2H4, C3H6, C4H8, C6H6, C7H8, C2H6O, etc. Preferably, the carbon-containing gas is selected from C2H2, and specifically, the volume fraction of the carbon-containing gas is: 5% C2H2, 95% Ar.

[0096] In some embodiments, the heating rate to the carbon deposition temperature is 1–10 °C / min. Preferably, the heating rate to the carbon deposition temperature is 5 °C / min. Specifically, the heating rates to the carbon deposition temperature are 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, and 10 °C / min.

[0097] In some embodiments, the carbon deposition temperature is 600–1000°C. Preferably, the carbon deposition temperature is 900°C. Specifically, the carbon deposition temperature is 600°C, 630°C, 660°C, 690°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 805°C, 810°C, 815°C, 820°C, 825°C, 830°C, 835°C, 840°C, 845°C, 850°C, 855°C, 860 ... The deposition temperatures range from 5℃ to 1000℃. Increasing the deposition temperature increases the graphitization degree of the deposited graphite layer, reduces defects, and improves the initial coulombic efficiency. It also decreases the resistivity of the porous carbon powder, increasing the conductivity of the resulting porous carbon-deposited silane and thus improving the rate performance of the silicon-carbon anode. However, excessively high temperatures will cause the carbon source to deposit on the surface before penetrating the template, hindering pore formation and silane deposition.

[0098] In some embodiments, the vapor deposition time is 1–3 hours. Specifically, the vapor deposition time is 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. Increasing the deposition time increases the number of carbon layers, which is beneficial for improving the strength of the carbon skeleton, further offsetting the stress generated by the volume expansion of the lithium battery during charging and discharging, preventing the carbon skeleton from collapsing, and thus improving the service life of the material. However, excessively long deposition times will increase the number of carbon layers and cause the carbon source to be deposited on the template surface.

[0099] In some embodiments, the porous template is removed using chemical etching, high-temperature calcination, or physical methods. Preferably, the porous template is removed by sequential treatment with 10% hydrofluoric acid and 10% hydrochloric acid. Before formally removing the porous template, the sample is cleaned with solvents such as deionized water or ethanol to remove surface impurities and contaminants. Hydrofluoric acid is effective in dissolving silicate materials, such as silicon dioxide. The sample is immersed in the hydrofluoric acid solution, and the reaction time and temperature are controlled to ensure complete dissolution of the template. In some cases, hydrochloric acid can be used to further remove residues or adjust the surface properties of the porous carbon material. After etching, the sample is neutralized with deionized water or an alkaline solution (such as sodium hydroxide solution) to remove residual acid. The sample is then cleaned again with deionized water. For some templates that cannot be effectively removed by chemical etching, high-temperature calcination can be used. The sample is placed in a high-temperature furnace, heated to a high temperature at an appropriate heating rate, and held at that temperature for a period of time to ensure complete combustion or decomposition of the template. After removing the template, post-treatment of the porous carbon material may be required to further optimize its performance. For example, activators (such as water vapor, carbon dioxide, etc.) are used to activate porous carbon materials to increase their specific surface area and porosity.

[0100] In another embodiment of this application, a silicon-carbon anode material is provided, the silicon-carbon anode material comprising the porous carbon material and a silicon-based material distributed within the pores of the porous carbon material.

[0101] In some embodiments, the silicon-based material is selected from one or more of nano-silicon particles, silicon oxides, silicon alloys, or porous silicon. Preferably, the silicon-based material is selected from nano-silicon particles. Silicon has a theoretical specific capacity much higher than graphite (approximately 10 times that of graphite), therefore, using nano-silicon particles can significantly improve the energy density of lithium-ion batteries. Nanoscale silicon particles have a larger specific surface area, which can effectively shorten the diffusion path of lithium ions from the electrolyte to the interior of the active material, thus improving the charge and discharge rate. Although silicon undergoes significant volume expansion (approximately 300%) during lithiation, nano-sizing can alleviate this problem to some extent because smaller particles are more adaptable to volume changes, reducing the risk of cracking and pulverization. Compared to pure silicon, the Li2O formed during the lithiation process of silicon oxides (such as SiO, SiO2, etc.) can act as a buffer matrix, effectively absorbing some of the volume expansion stress and improving the cycle stability of the material. The irreversible Li2O layer formed during the first charge of silicon oxides can reduce lithium loss in the first cycle, thereby improving the first coulombic efficiency. By alloying with other metals (such as magnesium, tin, and copper), silicon alloys with lower volume expansion coefficients and higher conductivity can be formed, thereby significantly improving cycle stability and rate performance while maintaining high capacity. Alloying can also adjust the lithiation / delithiation potential of the material, helping to avoid side reactions with electrolyte components and extending battery life. The porous structure provides additional space for silicon volume expansion, reducing structural damage caused by volume changes, thus improving cycle stability. Using one or more combinations of nano-silicon particles, silicon oxides, silicon alloys, or porous silicon can leverage their respective advantages to achieve high energy density, good cycle stability, and excellent rate performance. For example, the combination of nano-silicon particles and silicon oxides can improve cycle stability through the formation of a Li2O layer while maintaining high capacity; the introduction of silicon alloys can further adjust the operating potential, reduce side reactions, and reduce the volume expansion effect; the addition of porous silicon further optimizes volume expansion management and lithium-ion transport efficiency. This composite strategy provides broad space and possibilities for the development of high-performance silicon-carbon anode materials.

[0102] In some embodiments, the silicon-based material is selected from nano-silicon particles, and the mass content of nano-silicon particles in the silicon-carbon anode material is 10% to 95%. Preferably, the mass content of nano-silicon particles in the silicon-carbon anode material is 85% to 95%. More preferably, the mass content of nano-silicon particles in the silicon-carbon anode material is 90%. Specifically, the mass content of nano-silicon particles in the silicon-carbon anode material is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0103] In another embodiment of this application, a silicon-carbon anode material is provided, the silicon-carbon anode material comprising the porous carbon material and a silicon-based material distributed within the pores of the porous carbon material, and a coating layer covering the surface of the porous carbon material.

[0104] In some embodiments, the silicon-based material is selected from one or more of silicon nanoparticles, silicon oxide, silicon alloys, or porous silicon. Preferably, the silicon-based material is selected from silicon nanoparticles.

[0105] In some embodiments, the silicon-based material is selected from nano-silicon particles, and the mass content of nano-silicon particles in the silicon-carbon anode material is 10% to 95%. Preferably, the mass content of nano-silicon particles in the silicon-carbon anode material is 85% to 95%. More preferably, the mass content of nano-silicon particles in the silicon-carbon anode material is 90%. Specifically, the mass content of nano-silicon particles in the silicon-carbon anode material is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0106] In some embodiments, the coating layer comprises a carbon-based material, preferably one or more of amorphous carbon, graphitic carbon, carbon nanotubes, and carbon fibers. Although amorphous carbon has low crystallinity, its excellent conductivity can significantly improve the overall electron transport performance of the silicon-carbon anode material, which is beneficial for high-rate charge-discharge of the battery. The coating of amorphous carbon can effectively fill the micropores and defects on the surface of porous carbon materials, enhancing the structural integrity of the material and reducing structural damage caused by volume expansion during charge-discharge cycles. Graphitic carbon itself has good lithium storage performance, and as a coating layer, it can increase the overall capacity of the anode material. Carbon nanotubes have excellent conductivity and a one-dimensional structure, which can form a conductive network on the surface of the silicon-carbon anode material, accelerating lithium-ion transport and improving the charge-discharge performance of the battery. At the same time, the high mechanical strength of carbon nanotubes helps to improve the overall mechanical properties of the anode material and resist the stress caused by volume changes during charge-discharge. Carbon fibers have good toughness and strength, and as a coating layer, they can significantly improve the crack resistance and anti-pulverization ability of the anode material, extending the battery's lifespan.

[0107] In some embodiments, the coating layer comprises a conductive polymer, including one or more of polyaniline (PANI), polypyrrole (PPy), and polythiophene (PTh). The introduction of the conductive polymer significantly improves the conductivity of the silicon-carbon anode material. Polyaniline (PANI), polypyrrole (PPy), and polythiophene (PTh) all possess good conductivity; they can form a uniform conductive network on the surface of porous carbon materials, effectively reducing the resistance to electron transport within the material, thereby improving the charge / discharge rate and efficiency of the battery. Furthermore, they can tightly coat the surface of porous carbon materials, forming a protective barrier that effectively prevents the electrolyte from eroding the porous carbon and silicon-based materials, while reducing stress caused by volume expansion and contraction during charge / discharge, thereby improving the cycle stability and lifespan of the material.

[0108] In some embodiments, the coating layer comprises a metal oxide, including one or more of aluminum oxide (Al₂O₃), titanium dioxide (TiO₂), and silicon dioxide (SiO₂). Alumina, titanium dioxide, and silicon dioxide are all high-hardness inorganic materials that can form a robust protective layer on the surface of porous carbon materials, effectively preventing cracking and pulverization of silicon-based materials during charge and discharge due to volume expansion and contraction, thereby extending the cycle life of the anode material. These metal oxides also possess good chemical and thermal stability, resisting the corrosion of organic solvents and lithium salts in the electrolyte, preventing side reactions between the anode material and the electrolyte, reducing the risk of thermal runaway, and improving battery safety. It is worth noting that although silicon dioxide (SiO₂) itself does not possess high lithium-ion conductivity, it can react with lithium under certain conditions to form compounds such as lithium silicate (Li₄SiO₄). These compounds can further alleviate the volume expansion of silicon-based materials and provide a certain capacity contribution. Therefore, under specific conditions, the introduction of silicon dioxide can also have a positive impact on the performance of silicon-carbon anode materials.

[0109] In another embodiment of this application, a method for preparing the silicon-carbon anode material is provided, comprising the following steps: placing the porous carbon material in a reactor, heating it to the silicon deposition temperature under an inert gas environment, and introducing a gaseous silicon source for gaseous silicon deposition. The use of an inert gas aims to prevent oxidation or hydrolysis reactions between the porous carbon material and the subsequent gaseous silicon source at high temperatures, thereby maintaining the purity and structural integrity of the material. The silicon deposition temperature is typically higher than the vaporization temperature of the silicon source but lower than the pyrolysis temperature of the porous carbon material, ensuring that the silicon source can be fully vaporized and uniformly deposited within the pores of the porous carbon material, while avoiding damage to the porous carbon material structure. Once the reactor reaches the set temperature, a gaseous silicon source (such as silane, silicon tetrachloride, etc.) is introduced for gaseous silicon deposition. The gaseous silicon source undergoes decomposition or reduction reactions at high temperatures, and the generated silicon atoms or silicon-based compounds are deposited within the pores of the porous carbon material to form a silicon-based material. This method uses vapor deposition to uniformly distribute silicon-based materials within the pores of porous carbon materials, which can effectively alleviate the stress caused by volume expansion and contraction of silicon-based materials during charging and discharging, thereby improving the structural stability and cycle life of silicon-carbon anode materials.

[0110] In some embodiments, the reactor comprises a rotary kiln or a fluidized bed. In a rotary kiln, the porous carbon material within is continuously and uniformly exposed to the gaseous silicon source through rotation, ensuring uniform deposition of the silicon-based material within the pores of the porous carbon material. This dynamic process helps reduce localized overheating and uneven deposition during the deposition process, thereby improving material uniformity and deposition efficiency. In a fluidized bed, the porous carbon material is fluidized by gas, forming a fluid-like state. This allows the gaseous silicon source to contact the porous carbon material more effectively and undergo a deposition reaction. The high mass transfer efficiency of the fluidized bed contributes to achieving rapid and uniform deposition of silicon-based materials.

[0111] In some embodiments, the temperature is increased to 550°C at a heating rate of 5–10°C / min. Specifically, the heating rates are 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, and 10°C / min.

[0112] In some embodiments, the silicon deposition time is 600–4000 min. Specifically, the silicon deposition time is 600 min, 800 min, 1000 min, 1200 min, 1400 min, 1600 min, 1800 min, 2000 min, 2200 min, 2400 min, 2600 min, 2800 min, 3000 min, 3200 min, 3400 min, 3600 min, 3800 min, 3900 min, 3950 min, or 4000 min. Extending the deposition time is beneficial for increasing the loading of active material, thereby improving the specific capacitance of the electrode. However, excessively long deposition times may also lead to an excessively thick silicon layer, causing severe volume expansion of silicon during lithium intercalation, resulting in pulverization of active material particles, damage to the SEI film formed on the surface, increased electrode internal resistance, and accelerated capacity decay. Within the above deposition time range, it is ensured that the silicon layer can fully load the active material and improve the specific capacitance, without causing volume expansion and active material pulverization due to excessive thickness. This effectively avoids the increase in electrode internal resistance and the aggravation of capacity decay, and significantly improves the cycle stability and service life of the electrode.

[0113] In some embodiments, the inert gas flow rate is 3–16 L / min. Specifically, the inert gas flow rate is 3 L / min, 5 L / min, 7 L / min, 9 L / min, 11 L / min, 13 L / min, 15 L / min, or 16 L / min.

[0114] In some embodiments, the gaseous silicon source is selected from at least one of silane (SiH4), disilane (Si2H6), trichlorosilane (SiHCl3), dichlorosilane (SiH2Cl2), and tetrachlorosilane (SiCl4). Preferably, the gaseous silicon source is selected from silane (SiH4). Silane is a highly reactive gas that can rapidly decompose and deposit silicon at relatively low temperatures. Due to its high reactivity and low molecular weight, silane can more easily penetrate into the pores of porous carbon materials, achieving uniform deposition of silicon-based materials. This helps to improve the specific capacity and cycle stability of silicon-carbon anode materials.

[0115] In some embodiments, the flow rate of the vapor silicon source is 1 L / min to 2 L / min.

[0116] In another embodiment of this application, a method for preparing the silicon-carbon anode material is provided, comprising the following steps: placing the porous carbon material in a reactor, heating it to the silicon deposition temperature under an inert gas environment, and introducing a gaseous silicon source for gaseous silicon deposition; maintaining the inert gas flow rate and introducing a gaseous carbon source for carbon deposition. After gaseous silicon deposition, maintaining the inert gas flow rate and introducing a gaseous carbon source for carbon deposition can form an additional carbon protective layer on the surface and within the pores of the silicon-based material. This carbon protective layer can further alleviate the volume expansion and contraction of the silicon-based material during charge and discharge, enhance the structural stability of the material, and thus improve cycle life. Simultaneously, the deposition of the gaseous carbon source may fill some of the pores of the porous carbon material. More importantly, by precisely controlling the carbon deposition conditions (such as temperature, time, type and concentration of the gaseous carbon source), fine regulation of the pore structure can be achieved, which helps to form a more open and uniform pore structure, improving the specific surface area and lithium-ion transport performance of the material.

[0117] In some embodiments, the gaseous carbon source is selected from CO, CH4, C2H2, C2H6, C3H8, and C4H. 10 One or more of the following carbon sources can be used: C2H4, C3H6, C4H8, C6H6, C7H8, and C2H6O. Small molecule carbon sources such as CO and CH4 typically have high deposition rates, enabling the formation of thicker carbon layers in a shorter time. This is particularly advantageous for applications requiring rapid coverage of silicon-based material surfaces or filling of pores. Large molecule carbon sources such as C2H2, C2H4, and C6H6 may have lower deposition rates but can form more dense and stable carbon structures, which positively impacts the structural stability and cycle life of the material. The carbon layer structures (e.g., amorphous carbon, graphitized carbon) and properties (e.g., conductivity, hardness) formed by different carbon sources vary. By selecting appropriate carbon sources, the overall structure and performance of silicon-carbon anode materials can be controlled to meet different application requirements. For example, amorphous carbon layers typically exhibit better flexibility and buffering properties, mitigating the volume expansion of silicon-based materials; while graphitized carbon layers possess higher conductivity and lower internal resistance, contributing to improved battery charge / discharge rates and energy efficiency. By combining different types of carbon sources, silicon-carbon anode materials with multilayer structures can be constructed. These multilayer structures combine the advantages of different carbon layers, further improving the overall performance and stability of the material. For example, a small-molecule carbon source can be used to quickly coat the surface of the silicon-based material, followed by a large-molecule carbon source to form a denser and more stable carbon layer. Alternatively, different carbon sources can be used at different deposition stages to form multilayer structures with specific structures and functions.

[0118] In some embodiments, the flow rate of the gaseous carbon source is 1–3 L / min. Specifically, the flow rate of the gaseous carbon source is 1 L / min, 2 L / min, or 3 L / min.

[0119] In some embodiments, the carbon deposition time is 60–120 min. Specifically, the carbon deposition time is 60 min, 63 min, 66 min, 69 min, 72 min, 75 min, 78 min, 81 min, 84 min, 87 min, 90 min, 93 min, 96 min, 99 min, 102 min, 105 min, 108 min, 111 min, 114 min, 117 min, or 120 min.

[0120] In another embodiment of this application, a secondary battery is provided, the secondary battery comprising the silicon-carbon anode material.

[0121] In some embodiments, the secondary battery can be any of a lithium-ion battery, a lithium polymer battery, or a lead-acid battery. These types of batteries each have their own advantages and are suitable for different application scenarios. However, from the perspective of energy density, cycle life, and environmental friendliness, lithium-ion batteries are more preferably chosen as the carrier of this technical solution. Lithium-ion batteries, with their high energy density, long cycle life, and low self-discharge rate, have become the mainstream battery technology in fields such as electric vehicles and portable electronic devices.

[0122] In some embodiments, the positive electrode material of the secondary battery can be selected from any one of lithium cobalt oxide, lithium nickel manganese cobalt oxide, or lithium iron phosphate. Lithium cobalt oxide has high energy density and good cycle performance, but its cost is relatively high; lithium nickel manganese cobalt oxide has higher energy density and lower cost, but its cycle stability may be slightly inferior; lithium iron phosphate is known for its excellent cycle stability and safety, but its energy density is relatively low. Depending on specific application requirements and cost considerations, the most suitable positive electrode material can be selected to match the silicon-carbon anode material to achieve optimal battery performance.

[0123] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments.

[0124] Porous carbon materials

[0125] Example 1

[0126] A porous carbon material was prepared by the following method: A zeolite template was immersed in deionized water and ultrasonically cleaned for 30 minutes to remove surface impurities and dust. Then, the zeolite template was immersed in a 1M lanthanum chloride solution to allow lanthanum ions to exchange with the zeolite, resulting in a lanthanum ion-loaded zeolite template. The zeolite template was dried with nitrogen gas to ensure the surface was dry and free of moisture. The pretreated zeolite template was placed in a tubular reactor of a high-temperature furnace, and the tube was purged with purified nitrogen gas at a rate of 50 ml / min for 30 minutes to ensure complete air replacement. The furnace was heated to 800°C at a heating rate of 5°C / min. At 800°C, carbon-containing gas was introduced into the tube at a flow rate of 30 mL / min and maintained for 2 hours to allow carbon deposition in the pores of the zeolite template. The system was then naturally cooled to room temperature under a nitrogen atmosphere, and the sample was collected to obtain a carbon composite material containing the zeolite template. The carbon composite material was immersed in a 10% hydrofluoric acid solution for 24 hours, with periodic stirring, to remove silicon components from the zeolite template. The sample was washed with deionized water until the washing solution was neutral. The sample was then immersed in a 10% hydrochloric acid solution for 12 hours to remove residual metal ions and other impurities. The sample was washed again with deionized water until the washing solution was neutral. The washed sample was placed in a vacuum drying oven and dried at 80°C for 12 hours, or dried using nitrogen gas, ensuring complete drying. The dried porous carbon material sample was then collected.

[0127] The zeolite template is selected from Y-type zeolite, which is a tetrahedral network structure composed of sodalite units, forming a supercage, that is, a large cavity with a diameter of 1.3 nm. Each supercage is connected to four other supercages through an opening with a diameter of 0.74 nm.

[0128] The carbon-containing gas is a mixture of 5% carbon gas and 95% argon gas by volume.

[0129] Example 2

[0130] A porous carbon material was prepared using the same method as in Example 1, except that: a lanthanum-loaded zeolite template was placed in a tubular reactor of a high-temperature furnace, and the tube was purged with purified nitrogen at a rate of 50 ml / min for 30 minutes to ensure complete replacement of the air in the system. The furnace was then heated to 900°C at a heating rate of 5°C / min. At 900°C, carbon-containing gas was introduced into the tube at a flow rate of 30 mL / min and maintained for 2 hours to allow carbon to deposit in the pores of the zeolite template. The system was then naturally cooled to room temperature under a nitrogen atmosphere, and the sample was collected to obtain a carbon composite material containing the zeolite template.

[0131] Example 3

[0132] The preparation method is the same as in Example 1, except that: the lanthanum ion-loaded zeolite template is placed in a tubular reactor of a high-temperature furnace, and the tube is cleaned with purified nitrogen at a rate of 50 ml / min for 30 minutes to ensure that the air in the system is completely replaced. The furnace is heated to 1000°C at a heating rate of 5°C / min. At 1000°C, carbon-containing gas is introduced into the tube at a flow rate of 30 mL / min and maintained for 2 hours to allow carbon to be deposited in the pores of the zeolite template. The system is then naturally cooled to room temperature under a nitrogen atmosphere, and the sample is collected to obtain a carbon composite material containing the zeolite template.

[0133] Example 4

[0134] The preparation method is the same as in Example 2, except that: the lanthanum ion-loaded zeolite template is placed in the tubular reactor of a high-temperature furnace, and the tube is cleaned with purified nitrogen at a rate of 50 ml / min for 30 minutes to ensure that the air in the system is completely replaced. The furnace is heated to 900°C at a heating rate of 5°C / min. At 900°C, carbon-containing gas is introduced into the tube at a flow rate of 30 mL / min and maintained for 1 hour to allow carbon to be deposited in the pores of the zeolite template. The system is then naturally cooled to room temperature under a nitrogen atmosphere, and the sample is collected to obtain a carbon composite material containing the zeolite template.

[0135] Example 5

[0136] The preparation method is the same as in Example 2, except that: the lanthanum ion-loaded zeolite template is placed in the tubular reactor of a high-temperature furnace, and the tube is cleaned with purified nitrogen at a rate of 50 ml / min for 30 minutes to ensure that the air in the system is completely replaced. The furnace is heated to 900°C at a heating rate of 5°C / min. At 900°C, carbon-containing gas is introduced into the tube at a flow rate of 30 mL / min and maintained for 3 hours to allow carbon to be deposited in the pores of the zeolite template. The system is then naturally cooled to room temperature under a nitrogen atmosphere, and the sample is collected to obtain a carbon composite material containing the zeolite template.

[0137] Example 6

[0138] The preparation method is the same as in Example 3, except that: the zeolite template is impregnated with a 3M lanthanum chloride solution, heated to 1000 degrees Celsius, and carbon gas deposition is performed for 5 hours to deposit carbon in the pores of the zeolite template. Under a nitrogen atmosphere, the system is naturally cooled to room temperature, and the sample is collected to obtain a carbon composite material containing the zeolite template. Then, acid washing is performed to obtain porous carbon, and the obtained porous carbon material is graphitized at 1500 degrees Celsius to obtain a porous carbon material with enhanced skeletal strength.

[0139] Example 7

[0140] The preparation method is the same as in Example 1, except that the deposition temperature is 600 degrees and the deposition time is 1 hour.

[0141] Example 8

[0142] The preparation method is the same as in Example 1, except that the zeolite template is impregnated with a 3M metal salt solution, wherein the metal salts are calcium chloride and lanthanum chloride, and the molar ratio of calcium chloride to lanthanum chloride is 1:1.

[0143] Example 9

[0144] The preparation method is the same as in Example 1, except that the 1M lanthanum chloride solution is replaced with a 2M lanthanum chloride solution.

[0145] Comparative Example 1

[0146] A porous carbon material is prepared by the following method: Glucose and KOH are added to an aqueous KOH solution at a 1:1 mass ratio. After stirring at 80°C for 6 hours, the mixture is filtered to separate the solid material, which is then thoroughly washed with deionized water until the pH reaches neutral. The ion-exchanged sample is dried in a vacuum oven at 80°C for 8 hours. The resulting solid powder is heated to 900°C at a rate of 5°C / min and held for 1.5 hours in argon atmosphere. Finally, the sample is immersed in an excess of dilute HCl solution with stirring, then washed with deionized water until the pH is neutral, and dried in a vacuum oven at 80°C for 8 hours to obtain porous carbon.

[0147] Comparative Example 2

[0148] The preparation method is the same as in Example 1, except that: no catalyst is included, and the deposition temperature is 500 degrees and the deposition time is 5 hours.

[0149] Property testing of porous carbon materials

[0150] 1) Number of carbon layers in a single layer

[0151] The results were obtained by X-ray diffraction (XRD) with Cu Kα radiation (λ = 0.15406 nm) (Rigaku SmartLab SE; Rigaku).

[0152] Empirical parameter R, such as Figure 1 As shown, the height of (002) Bragg peak is measured by the ratio of its height to the background. Figure 1 As shown, the common tangent of the convex curves (peak and valley) on both sides of the (002) peak forms the background line 1. Then, the straight line is translated upward until it is tangent to the (002) peak to determine the tangency point 2. The intersection of the perpendicular line drawn downward from the tangency point and the background line 1 is determined as point 3. The height between the tangency point 2 and the X-axis is defined as B, and the height between the intersection point 3 and the X-axis is defined as A. The ratio of B / A is determined as the value of parameter R.

[0153] 2) Graphene basal plane length

[0154] Profile fitting analysis was performed on the (002) peak located at approximately 2θ–26°, and La was calculated using the Scherrer equation:

[0155]

[0156] Where k is the Scherer constant (k = 1.84 for La), λ is the radiation wavelength, β is the half-width at half maximum (FWHM) of the reflection of (002), and θ is the reflection angle of (002).

[0157] 3) Specific surface area, pore volume, and pore diameter.

[0158] The specific surface area, pore volume, and pore size of the samples were characterized by analyzing the nitrogen adsorption and desorption isotherms at 77 K (ASAP 2020, Micromeritics, USA).

[0159] 4)I D1 / I G and I D3 / I G

[0160] Raman spectra were recorded using a Renishaw inVia instrument equipped with a 532nm wavelength laser.

[0161] Peak fitting of the Raman spectrum yielded peaks D1, D2, D3, D4, and G, with peak G located at 1580 cm⁻¹. -1 At this point, the G band is due to the stretching vibration of sp2 carbon atom pairs (E2g symmetry), representing a perfect graphitized carbon structure. It is located at 1350 cm⁻¹. -1 The D1 peak at I represents defect-induced graphite. D1 / I G This can represent the degree of graphitization of the carbon structure, 1500 cm -1 The D3 band at I is the short-range sp3 vibrational response of amorphous carbon. The appearance of the D3 band is caused by some adsorbed molecules, molecular fragments, and oxygen-containing functional groups. D3 / I G The ratio is linearly correlated with the content of oxygen-containing functional groups.

[0162] 5) Powder resistivity

[0163] After the porous carbon material was pressed into a block structure using a Yuaneng Technology compaction density meter, the resistivity of the powder was tested using a complete set of ceramic molds and a four-probe mode, and the data was taken at a pressure of 100MPa.

[0164] 6) Particle size

[0165] Particle size was measured using a laser particle size analyzer, specifically the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0166] The test results are shown in Table 1.

[0167] Table 1 Properties of porous carbon materials

[0168]

[0169] As shown in Table 1, in Examples 1 to 3, with the gradual increase of deposition temperature, the I of the prepared porous carbon materials... D1 / I G Value and I D3 / I G The values ​​all showed a decreasing trend. This phenomenon indicates that increasing the deposition temperature promotes the graphitization degree of the porous carbon material structure and leads to a decrease in the number of oxygen-containing functional groups in the material. In the comparison between Example 2 and Examples 4 to 5, it can be found that with the extension of deposition time, the I... D1 / I G Value and I D3 / I G The values ​​also showed a decreasing trend. This indicates that, within a certain time range, increasing the deposition time helps to improve the graphitization degree of porous carbon materials and correspondingly reduce the oxygen-containing functional groups in the material. In the comparison between Example 1 and Examples 8 to 9, by changing the concentration of the metal salt solution, the I... D1 / I G Value and I D3 / I G The value was significantly affected. Specifically, Example 8 used a mixed solution of calcium chloride and lanthanum chloride to catalyze the porous template, with the same concentration as in Example 1, but the effect on the I value of the porous carbon material was significantly reduced. D1 / I G Value and I D3 / I G The influence of the value is relatively small. However, in Example 9, by increasing the concentration of the metal salt, the graphitization degree of the prepared porous carbon material was improved, while the number of oxygen-containing functional groups was reduced.

[0170] Silicon-carbon anode materials

[0171] Example 10

[0172] A silicon-carbon anode material is prepared by the following method: The reactor interior is cleaned with ethanol or acetone, then dried with nitrogen gas at a flow rate of 6 L / min. The reactor is then evacuated to a certain vacuum level using a vacuum pump to remove residual moisture and air. 1 kg of the porous carbon material from Example 1 is uniformly added to a fluidized bed, ensuring a loose bed without significant accumulation. The nitrogen valve is opened, and the flow rate is adjusted to 3 L / min, continuously introducing nitrogen to displace the air in the reactor. The heating device is started, and the temperature is slowly increased to 550°C at a rate of 5°C / min, with continuous nitrogen protection during this process. Once the temperature reaches 550°C, silane gas is introduced at a flow rate of 2 L / min to initiate the pyrolysis reaction. The temperature and silane flow rate are kept constant, and the reaction is carried out at this constant temperature for 4000 min. During this period, the gas flow rate is checked and adjusted periodically to ensure stable reaction. After the isothermal reaction was completed, the silane gas valve was closed, and the nitrogen flow rate was kept constant. The gas switching device was adjusted to introduce acetylene gas at a flow rate of 1 L / min to carry out the carbon deposition reaction. The isothermal reaction was continued for another 120 min, during which the gas flow rate and reaction temperature were monitored. After the acetylene deposition was completed, the acetylene gas valve was closed, and the nitrogen flow rate was kept constant to slowly cool the reactor. Heating was stopped, and the reactor was allowed to cool naturally to room temperature to prepare a silicon-carbon anode material with a carbon content of 10 wt%.

[0173] Example 11

[0174] A silicon-carbon anode material is prepared by the following method: The reactor interior is cleaned with ethanol or acetone, then dried with nitrogen gas at a flow rate of 6 L / min. The reactor is then evacuated to a certain vacuum level using a vacuum pump to remove residual moisture and air. 1 kg of the porous carbon material from Example 1 is uniformly added to a fluidized bed, ensuring a loose bed without significant accumulation. The nitrogen valve is opened, and the flow rate is adjusted to 16 L / min, continuously introducing nitrogen to displace the air in the reactor. The heating device is started, and the temperature is slowly increased to 550°C at a rate of 10°C / min, with continuous nitrogen protection during this process. Once the temperature reaches 550°C, silane gas is introduced at a flow rate of 1 L / min to initiate a pyrolysis reaction. The temperature and silane flow rate are kept constant, and the reaction is carried out at this constant temperature for 600 min. During this period, the gas flow rate is checked and adjusted periodically to ensure stable reaction. After the isothermal reaction was completed, the silane gas valve was closed, and the nitrogen flow rate was kept constant. The gas switching device was adjusted to introduce acetylene gas at a flow rate of 3 L / min to carry out the carbon deposition reaction. The isothermal reaction was continued for 60 min, during which the gas flow rate and reaction temperature were monitored. After the acetylene deposition was completed, the acetylene gas valve was closed, and the nitrogen flow rate was kept constant to slowly cool the reactor. Heating was stopped, and the reactor was allowed to cool naturally to room temperature to prepare a silicon-carbon anode material with a carbon mass ratio of 95 wt%.

[0175] Example 12

[0176] The preparation method is the same as in Example 10, except that the porous carbon material from Example 2 is used as the substrate.

[0177] Example 13

[0178] The preparation method is the same as in Example 10, except that the porous carbon material from Example 3 is used as the substrate.

[0179] Example 14

[0180] The preparation method is the same as in Example 10, except that the porous carbon material from Example 4 is used as the substrate.

[0181] Example 15

[0182] The preparation method is the same as in Example 10, except that the porous carbon material from Example 5 is used as the substrate.

[0183] Example 16

[0184] The preparation method is the same as in Example 10, except that the porous carbon material from Example 6 is used as the substrate.

[0185] Example 17

[0186] The preparation method is the same as in Example 10, except that the porous carbon material from Example 7 is used as the substrate.

[0187] Example 18

[0188] The preparation method is the same as in Example 10, except that the porous carbon material from Example 8 is used as the substrate.

[0189] Example 19

[0190] The preparation method is the same as in Example 10, except that the porous carbon material from Example 9 is used as the substrate.

[0191] Comparative Example 3

[0192] The preparation method is the same as in Example 10, except that the porous carbon material of Comparative Example 1 is used as the substrate.

[0193] Comparative Example 4

[0194] The preparation method is the same as in Example 10, except that porous carbon material from Comparative Example 2 is used as the substrate.

[0195] Application examples

[0196] Batteries were assembled using the products prepared in Examples 7-12 and Comparative Examples 3-4 as negative electrode materials.

[0197] The obtained silicon-based anode material, used as the anode active material, was weighed together with carbon black (as a conductive additive), sodium carboxymethyl cellulose (as a binder), and styrene-butadiene rubber in a mass ratio of 1:1 (90%:4%:6%). The mixture was then placed in a pulping machine at room temperature to prepare a slurry. The prepared slurry was uniformly coated onto copper foil. After drying in a forced-air drying oven at 60°C for 2 hours, the foil was cut into 8×8mm electrode sheets and then vacuum-dried in a vacuum drying oven at 100°C for 10 hours. The dried electrode sheets were then immediately transferred to a glove box for use in battery assembly.

[0198] The simulated battery was assembled in a glove box containing a high-purity Ar atmosphere, using lithium metal as the counter electrode and a 1-molar solution of LiPF6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) (v:v = 1:1) as the electrolyte.

[0199] During battery assembly, five batteries were prepared for each test group, and a total of five sets of data were tested. The final performance was taken as the average of the five sets of data.

[0200] Performance tests were conducted on the lithium-ion batteries prepared above:

[0201] Constant current charge-discharge tests were conducted using the CT2001A Blue Dot battery testing system from Wuhan Landian Electronics Co., Ltd., at charge-discharge rates of 0.1C and 0.5C, with a voltage range of 0.03–1.50V (vs. Li+ / Li). The initial discharge capacity at 0.1C (mAh / g) and initial efficiency (%) were measured. After activation at 0.1C and 0.2C for two weeks each, a 100-cycle test at 0.5C was performed. The capacity retention rate after 100 cycles at a high rate of 0.5C was calculated by comparing the 0.5C discharge capacity at the 100th cycle with that at the 1st cycle.

[0202] The experimental parameters and effect data of each embodiment and comparative example are listed in Table 2 below.

[0203] Table 2 Properties of silicon-carbon anodes

[0204]

[0205] As shown in Table 2, the silicon-carbon anode material in this embodiment exhibits superior performance compared to Comparative Examples 3 and 4 in terms of resistance characteristics, initial charge-discharge efficiency, and capacity retention under 0.5C / 0.5C conditions. This advantage is mainly attributed to the high degree of graphitization and relatively low number of oxygen-containing functional groups in the porous carbon material matrix used in this application. Specifically, the porous carbon substrates in Comparative Examples 3 and 4 have I D1 / I G Ratio and I D3 / IG The ratios are all higher than those in the embodiments of this application, which directly results in the silicon-carbon anode materials prepared by them having higher resistance, lower first charge-discharge efficiency, and lower capacity retention.

[0206] Of particular note is that, although Comparative Example 4 and Example 17 have I D1 / I G The ratios are similar, but due to their I D3 / I G The ratio is higher than that of the embodiments in this application. This difference significantly affects the initial charge-discharge efficiency and capacity retention of the silicon-carbon anode, resulting in poor performance of Comparative Example 4 in these two performance indicators. Therefore, it can be inferred that the optimized graphitization degree and lower oxygen-containing functional group content of the porous carbon material matrix in this application play a key role in improving the overall electrochemical performance of the silicon-carbon anode material.

[0207] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A porous carbon material, wherein, The R-values ​​in the X-ray diffraction patterns of the porous carbon material are 2.021~2.

387. The R-value is the ratio of the diffraction peak intensity of the (002) crystal plane to the background intensity. In the X-ray diffraction pattern, a background line is formed by drawing common tangents to the peaks and valleys on both sides of the (002) crystal plane diffraction peak. A tangent line parallel to the background line is drawn to determine the tangent point. The intensity at the tangent point is the diffraction peak intensity. The intensity at the diffraction angle 2θ corresponding to the tangent point on the background line is the background intensity. In the Raman spectrum of the porous carbon material, the ratio of the D1 peak intensity (characterizing the defect-induced graphite structure) to the G peak intensity (characterizing the graphite lattice) is I. D1 / I G The values ​​range from 0.773 to 1.638, representing the sp values ​​of amorphous carbon. 3 The ratio of the D3 peak intensity of hybrid carbon atoms to the G peak intensity characterizing the graphite lattice is I. D3 / I G The value ranges from 0.691 to 0.

899. The method for preparing the porous carbon material includes: The porous template is pretreated by immersing it in a metal salt solution; The pretreated porous template is placed in a reactor and heated to the carbon deposition temperature; Carbon-containing gas is introduced at the carbon deposition temperature for vapor phase deposition; The porous carbon material is obtained by removing the porous template. The preparation method includes the following features (c1) to (c5): c1) The metal salt is selected from one or more of ferric chloride, molybdenum chloride, lanthanum chloride, nickel chloride, cobalt chloride, and calcium chloride; c2) The porous template is selected from zeolite, copper foam, silicon dioxide, magnesium oxide, magnesium hydroxide or calcium oxide; c3) The carbon-containing gas is a mixture of carbon precursor gas and argon; c4) The carbon deposition temperature is 600~1000℃; c5) The vapor deposition time is 1~3h.

2. A porous carbon material according to claim 1, wherein the porous carbon material comprises at least one of the following features b1) to b5): b1) The particle size of the porous carbon material is 0.337~0.365 nm; b2) The length La of the graphene basal plane in the porous carbon material is 2.98~4.57 nm; b3) The BET specific surface area of ​​the porous carbon material is 978~1324 m². 2 / g; b4) The average pore size of the porous carbon material is 3.41~3.89 nm; b5) The resistivity of the porous carbon material is 0.007~0.079 Ω·cm.

3. A method for preparing the porous carbon material according to claim 1 or 2, comprising: The porous template is pretreated by immersing it in a metal salt solution; The pretreated porous template is placed in a reactor and heated to the carbon deposition temperature; Carbon-containing gas is introduced at the carbon deposition temperature for vapor phase deposition; The porous carbon material is obtained by removing the porous template. The preparation method includes the following features (c1) to (c5): c1) The metal salt is selected from one or more of ferric chloride, molybdenum chloride, lanthanum chloride, nickel chloride, cobalt chloride, and calcium chloride; c2) The porous template is selected from zeolite, copper foam, silicon dioxide, magnesium oxide, magnesium hydroxide or calcium oxide; c3) The carbon-containing gas is a mixture of carbon precursor gas and argon; c4) The carbon deposition temperature is 600~1000℃; c5) The vapor deposition time is 1~3h.

4. The preparation method according to claim 3, wherein the carbon precursor gas is selected from CO, CH4, C2H2, C2H6, C3H8, C4H 10 One or more of C2H4, C3H6, C4H8, C6H6, C7H8, and C2H6O.

5. A silicon-carbon anode material, comprising the porous carbon material of claim 1 or 2 or the porous carbon material obtained by the preparation method of claim 3 or 4, and a silicon-based material distributed within the pores of the porous carbon material.

6. The silicon-carbon anode material according to claim 5, wherein the silicon-based material is selected from one or more of nano-silicon particles, silicon oxide, silicon alloy, or porous silicon.

7. The silicon-carbon anode material according to claim 5, wherein the silicon-based material is nano-silicon particles, and the mass content of the nano-silicon particles in the silicon-carbon anode material is 10%~95%.

8. The silicon-carbon anode material according to claim 5, wherein the silicon-carbon anode material further comprises a coating layer covering the surface of the porous carbon material.

9. The silicon-carbon anode material according to claim 8, wherein the coating layer comprises a carbon-based material, and the carbon-based material comprises one or more of amorphous carbon, graphite carbon, carbon nanotubes, and carbon fibers; The coating layer includes a conductive polymer, which includes one or more of polyaniline, polypyrrole and polythiophene; The coating layer comprises a metal oxide, which includes one or more of aluminum oxide, titanium dioxide, and silicon dioxide.

10. A secondary battery comprising the silicon-carbon anode material as described in any one of claims 5 to 9.

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