Silicon-carbon negative electrode material and preparation method thereof

Abstract

The invention provides a silicon-carbon negative electrode material and a preparation method thereof, and relates to the technical field of battery manufacturing. The silicon-carbon negative electrode material comprises porous carbon, nano silicon and a nano carbon layer, at least part of the nano silicon is distributed in pores of the porous carbon; at least part of the surface of the porous carbon is covered by the nanocarbon layer; and the half-peak width FWHM of the diffraction peak of the porous carbon at 16-26 degrees in an X-ray diffraction pattern is less than 12. The high-crystallinity porous carbon carrier with the FWHM smaller than 12 is utilized, the mechanical strength of a framework is remarkably enhanced, the volume expansion of nano silicon can be effectively bound, the structural integrity is maintained, and the expansion rate of the pole piece is reduced by matching with carbon layer coating, so that the cycle life of the battery is greatly prolonged.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and more specifically, to a silicon-carbon anode material and its preparation method. Background Technology

[0002] Lithium-ion batteries, with their significant advantages such as high energy density, long cycle life, and no memory effect, have become one of the most widely used energy storage devices. With the continuous expansion and upgrading of applications such as mobile communication terminals, electric vehicles, and large-scale energy storage power stations, the market is placing increasingly stringent demands on the energy density of lithium-ion batteries. To overcome the energy bottlenecks of existing battery systems, developing electrode materials with higher specific capacity has become a research hotspot and an industry consensus in the field of electrochemical energy storage.

[0003] Among numerous anode materials, silicon-based anodes are considered one of the key materials for improving the energy density of lithium-ion batteries due to their extremely high theoretical specific capacity (far exceeding that of traditional graphite anodes). However, silicon materials undergo significant volume expansion and contraction during lithium insertion / extraction. This drastic volume change can easily lead to the pulverization and shedding of active particles, thereby damaging the conductive network of the electrode. To alleviate this problem, existing technologies typically use porous carbon as a carrier, filling the pore structure of porous carbon with nano-silicon through methods such as vapor deposition. The binding effect and reserved space of the carbon skeleton buffer the volume expansion of silicon, thus preparing silicon-carbon composite anode materials.

[0004] However, existing silicon-carbon anode supports, i.e., porous carbon materials, are typically fabricated using activation processes. The activation process is essentially an etching reaction, designed to create abundant pores within the carbon material through physical or chemical means. While this method effectively increases pore volume to load more silicon, the etching reaction severely disrupts the crystal structure of the carbon material, leading to a significant reduction in its graphitization or crystallinity. This low crystallinity directly results in a substantial decrease in the mechanical strength of the porous carbon matrix, making its framework structure more fragile.

[0005] In summary, existing porous carbon supports suffer from insufficient matrix strength due to activation-induced pore formation. When faced with the high expansion stress generated by silicon charging and discharging, the fragile carbon framework often fails to provide effective mechanical restraint and support, making it highly susceptible to structural collapse or breakage during cycling. This not only fails to effectively suppress the volume effect of silicon but also leads to overall instability of the negative electrode structure, ultimately resulting in a cycle life that cannot meet the requirements for long-term use of lithium-ion batteries.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a silicon-carbon anode material and its preparation method. The silicon-carbon anode material significantly reduces the electrode expansion rate and greatly improves the battery cycle life by using a highly crystalline, high-strength porous carbon support to bind the expansion of nano-silicon.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a silicon-carbon anode material, the silicon-carbon anode material comprising porous carbon, nano-silicon and a nano-carbon layer; In this embodiment, at least a portion of the nano-silicon is distributed within the pores of the porous carbon; at least a portion of the surface of the porous carbon is covered by the nano-carbon layer. The porous carbon exhibits a full width at half maximum (FWHM) of less than 12 for the diffraction peaks at 16°–26° in the X-ray diffraction pattern.

[0009] In an optional embodiment, the porous carbon has a full width at half maximum (FWHM) of 6 to 9 for the diffraction peaks at 16°–26° in the X-ray diffraction pattern; and / or, The average pore size of the porous carbon is 2 nm to 15 nm; and / or, The porous carbon has a pore volume of 0.30 cm³. 3 / g~0.9cm 3 / g; and / or, The silicon-carbon anode material is in bulk form with an average particle size of 3 μm to 12 μm; and / or, The nano-silicon accounts for 30% to 60% of the weight of the silicon-carbon anode material; and / or, The specific surface area of ​​the silicon-carbon anode material is <5m². 2 / g; and / or, The compacted density of the silicon-carbon anode material under 10 tons of pressure is 1.70 g / cm³. 3 ~1.80g / cm 3 .

[0010] In an optional implementation, the specific surface area of ​​the silicon-carbon anode material is <3m². 2 / g.

[0011] Secondly, the present invention provides a method for preparing a silicon-carbon anode material as described in any of the foregoing embodiments, comprising: Phenolic raw materials, aldehyde raw materials and pore-forming agents are mixed in a liquid phase system and subjected to polymerization reaction to obtain precursor materials; The precursor material is carbonized to obtain a porous carbon material; the carbonization process does not involve strong corrosive activation to create pores that would damage the carbon crystal structure. Silicon is vapor-deposited within the pores of the porous carbon material, and a carbon layer is vapor-deposited on the surface of the material after silicon deposition to obtain the silicon-carbon anode material.

[0012] In an optional embodiment, the phenolic raw material includes at least one selected from phenol, hydroquinone, and resorcinol; and / or, The aldehyde raw materials include at least one of formaldehyde, acetaldehyde, and furfural; and / or, The pore-forming agent comprises an amphiphilic block copolymer; and / or, The carbonization treatment temperature is 900℃~1400℃; and / or, The step of mixing and polymerizing includes: prepolymerizing the phenolic raw material and the aldehyde raw material under conditions of pH 4-8, then adding the pore-forming agent to continue the reaction; and / or, The temperature for silicon vapor deposition is 400℃~550℃, the gas source includes a mixture of silane and inert gas, the volume ratio of silane to inert gas is 1:(0.5~10), and the deposition duration is 5h~50h; and / or, The temperature of the vapor-phase deposited carbon layer is 500℃~650℃, the gas source includes a mixture of acetylene and inert gas, the volume ratio of acetylene to inert gas is 1:(1~5), and the deposition duration is 2h~20h.

[0013] Thirdly, the present invention provides a porous carbon material, wherein the full width at half maximum (FWHM) of the diffraction peaks at 16° to 26° in the X-ray diffraction pattern is less than 12.

[0014] In an optional embodiment, the porous carbon material has a full width at half maximum (FWHM) of 6 to 9 for the diffraction peaks at 16°–26° in the X-ray diffraction pattern; and / or, The average pore size of the porous carbon material is 2 nm to 15 nm; and / or, The porous carbon material has a pore volume of 0.30 cm³. 3 / g~0.9cm 3 / g.

[0015] Fourthly, the present invention provides a negative electrode sheet comprising a silicon-carbon negative electrode material as described in any of the foregoing embodiments, or a silicon-carbon negative electrode material prepared by the preparation method described in the foregoing embodiments.

[0016] Fifthly, the present invention provides a battery comprising a negative electrode as described in the foregoing embodiments.

[0017] In a sixth aspect, the present invention provides an electrical device including a battery as described in the foregoing embodiments.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The silicon-carbon anode material provided by this invention utilizes highly crystalline porous carbon as a carrier, effectively solving the problem of short cycle life caused by volume expansion during charge and discharge of silicon-based anode materials. The porous carbon exhibits a full width at half maximum (FWHM) of less than 12 for the diffraction peaks at 16°–26° in its X-ray diffraction pattern, indicating that it retains strong carbon crystallinity and framework structure. Compared to traditional porous carbon materials that suffer from decreased crystallinity and weakened strength due to activation-induced pore formation, the carbon framework of this material possesses significantly higher mechanical strength.

[0019] This high-strength carbon skeleton provides excellent mechanical support. During battery charging and discharging, when the nano-silicon within the pores expands in volume, the robust carbon matrix effectively binds and withstands this expansion stress, preventing the internal structure of the particles from collapsing and pulverizing. Simultaneously, the surface-covering nano-carbon layer further enhances the overall structural stability and conductivity of the material. Therefore, this silicon-carbon anode material can significantly reduce the expansion rate of the electrode during cycling, maintaining the integrity of the electrode structure and good electrical conductivity, thereby greatly improving the cycle stability and lifespan of lithium-ion batteries. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 The image shows the XRD pattern of the porous carbon material prepared in Example 1. Figure 2 The image shows the XRD pattern of the porous carbon material prepared in Comparative Example 1. Detailed Implementation

[0022] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0023] In this embodiment of the application, a silicon-carbon anode material is provided, the silicon-carbon anode material comprising porous carbon, nano-silicon, and a nano-carbon layer; wherein at least a portion of the nano-silicon is distributed within the pores of the porous carbon; at least a portion of the surface of the porous carbon is covered by the nano-carbon layer; and the full width at half maximum (FWHM) of the diffraction peaks at 16° to 26° in the X-ray diffraction pattern of the porous carbon is <12.

[0024] The aforementioned silicon-carbon anode material mainly consists of three core components: porous carbon, nano-silicon, and nano-carbon layer.

[0025] The porous carbon serves as the matrix or carrier of the entire composite material. It possesses an internal pore structure, providing physical space for loading active substances. In this embodiment, the porous carbon exhibits specific crystal structure characteristics.

[0026] The nano-silicon is a high-capacity active material. Compared to carbon materials, silicon has an extremely high theoretical specific capacity and is a key component for improving battery energy density.

[0027] The nano-carbon layer is a coating structure located on the outermost layer of the material, which serves to protect and conduct electricity.

[0028] The statement that "at least a portion of the nano-silicon is distributed within the pores of the porous carbon" clarifies the spatial relationship between the nano-silicon and the porous carbon. The nano-silicon is not simply attached to the carbon surface, but rather enters the internal pores of the porous carbon. This "pore-filling" structure utilizes the pore space of the porous carbon to accommodate the silicon, reserving expansion space on the one hand, and using the carbon framework to physically isolate and confine the silicon on the other.

[0029] The phrase "at least a portion of the surface of the porous carbon is covered by the nano-carbon layer" indicates the outermost coating state. The nano-carbon layer acts like a skin covering the surface of the silicon-loaded porous carbon particles. This coating not only repairs surface defects but also prevents the internal silicon from being directly exposed to the electrolyte, reducing side reactions and enhancing the conductive connections between particles.

[0030] The statement that "the full width at half maximum (FWHM) of the diffraction peaks at 16°–26° in the X-ray diffraction pattern of the porous carbon is less than 12" is a key limitation on the essential properties of the porous carbon support.

[0031] It should be noted that in XRD patterns, the diffraction peaks between 16° and 26° typically correspond to the (002) crystal plane of carbon materials. The full width at half maximum (FWHM) is an important parameter reflecting the degree of crystallinity. A smaller FWHM value generally indicates larger grain size, fewer defects, and a relatively higher degree of graphitization or order. Here, an FWHM value less than 12 is specified to indicate that this porous carbon has high crystallinity and structural order, distinguishing it from amorphous carbon or activated carbon materials whose crystalline structure has been severely damaged by intense etching.

[0032] It is important to note that while reducing FWHM implies improved carbon crystallinity and strength, this invention does not pursue an infinitely low FWHM (e.g., less than 5 or close to graphite values). This is because achieving extremely low FWHM (e.g., through high-temperature graphitization treatment above 2000°C) would lead to a complete rearrangement of the amorphous regions within the carbon material, often accompanied by severe collapse and closure of the mesoporous structure and a sharp loss of pore volume. Once the pore structure disappears, nano-silicon cannot effectively fill the interior of the particles and can only adhere to the surface, resulting in low battery capacity and poor cycle life. Therefore, in the embodiments of this application, controlling FWHM within the range of 6 to 12 (or even more preferably 6 to 9) is a key balance point found between a "high-strength framework" and an "effective pore structure," avoiding both the fragile framework problem of traditional activated carbon (FWHM>15) and the lack of pores in graphitized carbon (FWHM<5).

[0033] The core mechanism of this material design lies in using a high-strength carbon framework to solve the problem of silicon volume expansion and achieving performance improvement through the synergistic effect of the three components.

[0034] Based on its structural characteristic of FWHM less than 12, this porous carbon retains a relatively complete carbon microcrystalline structure, thus possessing high mechanical strength and rigidity. When the nano-silicon within the pores undergoes significant volume expansion during lithium intercalation, this high-strength carbon framework acts like a robust cage, exerting a strong mechanical binding force on the internal silicon, resisting expansion stress, and preventing the particles from fragmenting or pulverizing.

[0035] Highly crystalline porous carbon itself has good electrical conductivity, forming the internal conductive framework; the outer nano-carbon layer constructs the external conductive network. The combination of the two ensures that even after silicon undergoes a certain degree of deformation, the active material can still maintain a good electronic pathway with the current collector, reducing polarization.

[0036] The coating of the nano-carbon layer effectively reduces the direct contact area between the electrolyte and the internal active silicon and porous carbon, which is conducive to the formation of a stable solid electrolyte interphase (SEI) membrane, thereby improving the first-cycle coulombic efficiency and cycle stability.

[0037] Based on the above structure and mechanism, this silicon-carbon anode material maintains high crystallinity and high mechanical strength because the porous carbon support has not undergone a destructive activation process. It can significantly suppress the volume effect of silicon during charge and discharge, resulting in a significant reduction in the electrode expansion rate and maintaining the integrity of the electrode structure. The robust framework prevents the pulverization and shedding of active materials, and together with the stable interface film, the battery maintains a high capacity retention rate during long-term cycling. Furthermore, it combines the high capacity of silicon and the stability of carbon, while also taking into account good conductivity and low side reactions.

[0038] Furthermore, although FWHM less than 12 is usually obtained through specific preparation processes (such as activation-free), any carbon material that meets the requirements of the half-width parameter and porous structure, regardless of whether its precursor is a phenolic resin or other polymer, falls within the scope of the materials provided in this application.

[0039] Furthermore, the nano-silicon distributed within the pores can be in the form of particles, thin films, or filled states, as long as it is located inside the pores.

[0040] The nano-carbon layer on the aforementioned covering surface can be amorphous carbon, graphite-like carbon, etc., as long as it can play a covering role and has electrical conductivity.

[0041] Furthermore, provided that the value is less than 12, the FWHM value can be even lower (e.g., 6 to 9) to represent higher crystallinity and strength, thereby meeting the requirements of higher silicon content or more stringent cycling conditions.

[0042] In some embodiments, the porous carbon has a full width at half maximum (FWHM) of 6 to 9 for the diffraction peaks at 16° to 26° in the X-ray diffraction pattern. For example, the FWHM can be 6, 6.5, 7, 7.5, 8, 8.5, 9, etc.

[0043] This embodiment further provides a range for the crystallinity of porous carbon. A full width at half maximum (FWHM) between 6 and 9 indicates that the carbon material has a higher degree of crystallinity and a more ordered microcrystalline structure than those described in the previous embodiments.

[0044] This optimized crystallinity endows the carbon skeleton with higher mechanical strength and rigidity, enabling it to more effectively resist the enormous expansion stress brought about by high silicon content, thereby further reducing the electrode expansion rate and improving the long-cycle stability of the battery. At the same time, higher crystallinity also helps to improve the conductivity of the carbon material itself.

[0045] In some embodiments, the average pore size of the porous carbon is 2 nm to 15 nm. For example, the average pore size can be 2 nm, 3 nm, 4 nm, 5 nm, 8 nm, 10 nm, 12 nm, 13 nm, 14 nm, 15 nm, etc.

[0046] The average pore size mentioned above refers to the average size of the pores inside porous carbon. 2nm to 15nm falls within the mesoporous range. This pore size range is ideal for loading nano-silicon. Pores that are too small (such as micropores) cannot effectively fill silicon through vapor deposition, limiting capacity; pores that are too large may lead to a decrease in volumetric energy density. Mesopores of 2–15nm ensure the smooth entry and decomposition deposition of silane gas while also providing adequate buffer space for silicon volume expansion, achieving a balance between high capacity and structural stability.

[0047] Furthermore, the average pore size of the porous carbon described in this invention can be precisely controlled within the range of 2 nm to 15 nm. The pore size mainly depends on the molecular weight of the pore-forming agent (amphiphilic block copolymer) and its micelle size in the system, as well as the ratio of the phenolic precursor to the pore-forming agent.

[0048] For example, when it is necessary to prepare porous carbon with a smaller pore size (e.g., 2-4 nm), the amount of pore-forming agent can be appropriately reduced or a surfactant with a smaller molecular weight can be selected; when it is necessary to prepare porous carbon with a larger pore size (e.g., 10-15 nm) to accommodate higher loading of nano-silicon, the proportion of pore-forming agent can be increased (e.g., the molar ratio of phenol to pore-forming agent can be adjusted to 1:0.015), or a pore expander (e.g., mesitylene) can be introduced during the polymerization process to expand the micelle core.

[0049] Examples 1-5 below show a pore size of about 4.5 nm, which is a typical preferred value for balancing specific surface area and loading. However, based on the universality of the soft template mechanism described above, other pore sizes in the range of 2-15 nm can be achieved.

[0050] In some embodiments, the porous carbon has a pore volume of 0.30 cm³. 3 / g~0.9cm 3 / g. For example, the pore volume can be 0.30 cm³. 3 / g, 0.35cm 3 / g, 0.40cm 3 / g, 0.50cm 3 / g, 0.60cm 3 / g, 0.70cm 3 / g, 0.80cm 3 / g, 0.85cm 3 / g, 0.90cm 3 / g etc.

[0051] The pore volume mentioned above represents the total volume of pores in a unit mass of porous carbon. This pore volume range directly determines the loading potential and volume buffering capacity of silicon. A pore volume of 0.30~0.9 cm³ / g can accommodate sufficient nano-silicon, thereby ensuring that the composite material has a high specific capacity (e.g., above 1800 mAh / g), while still having a margin to buffer expansion and prevent particle breakage.

[0052] In some embodiments, the silicon-carbon anode material is in bulk form and has an average particle size of 3 μm to 12 μm. For example, the average particle size can be 3 μm, 4 μm, 5 μm, 6 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc.

[0053] This embodiment provides macroscopic morphology and size distribution. Block morphology generally refers to particles with irregular three-dimensional shapes, while particle size is the statistical average diameter of the particles.

[0054] The particle size range of 3μm to 12μm is moderate, avoiding both the increased side reactions and agglomeration problems caused by excessively large specific surface areas of nano-sized particles, and the excessively long lithium-ion diffusion paths and rate performance degradation caused by excessively large particles. This particle size distribution is beneficial for slurry dispersion, coating, and electrode compaction, thereby improving the electrode's processing performance and electrochemical performance.

[0055] In some embodiments, the nano-silicon accounts for 30% to 60% of the weight of the silicon-carbon anode material. For example, this weight percentage can be 30%, 35%, 40%, 45%, 50%, 55%, 58%, 60%, etc.

[0056] This embodiment provides the proportion of silicon, the active material, in the total weight of the composite material. This proportion range is crucial for balancing high capacity and cycle stability. A silicon content below 30% may not fully realize the high energy density advantage of silicon anodes; while a content above 60% will lead to excessive volume expansion, exceeding the tolerance of the porous carbon framework and causing a sharp decline in cycle life. A content of 30% to 60% ensures that the material has a specific capacity far exceeding that of graphite, while maintaining good structural stability.

[0057] In the embodiments described below, the loading of nano-silicon can be effectively controlled by adjusting the vapor deposition time, gas flow rate, and temperature. For example, under the conditions of Examples 1-5, the final weight percentage of nano-silicon in the prepared silicon-carbon anode materials was tested to be between 40% and 55%, falling within the preferred range of 30% to 60%. Simultaneously, through particle size control of the precursor materials and subsequent processing, the average particle size (D50) of the final silicon-carbon anode materials was tested to be between 5 μm and 10 μm, also falling within the range of 3 μm to 12 μm defined in the claims.

[0058] In some embodiments, the specific surface area of ​​the silicon-carbon anode material is <5m². 2 / g. For example, the specific surface area can be 0.5 m². 2 / g, 1.0 m 2 / g, 1.5 m 2 / g, 2.0 m 2 / g, 2.5 m 2 / g, 3.0 m 2 / g, 3.5 m 2 / g, 4.0 m 2 / g, 4.5m 2 / g、4.9 m 2 / g etc.

[0059] In some implementations, the specific surface area of ​​the silicon-carbon anode material is <3m². 2 / g.

[0060] The specific surface area (BET) mentioned above reflects the effective contact area between the material and the electrolyte. A lower specific surface area (<5m²) indicates a lower contact area with the electrolyte. 2 / g, preferably <3 m 2 / g) means that the material surface is denser and smoother, with better pore sealing. This can significantly reduce the contact area between the material and the electrolyte, thereby reducing irreversible lithium loss caused by the formation of the SEI film during the first charge and discharge (i.e., improving the first efficiency), and reducing electrolyte consumption during cycling, thus improving the battery's long cycle life.

[0061] In some embodiments, the silicon-carbon anode material has a powder compaction density of 1.70 g / cm³ under 10 tons of pressure. 3 ~1.80g / cm 3 For example, the compacted density of this powder can be 1.70 g / cm³. 3 1.71 g / cm 3 1.72 g / cm 3 1.73 g / cm 3 1.75 g / cm 3 1.76 g / cm 3 1.78 g / cm 3 1.79 g / cm 3 1.80 g / cm 3 etc.

[0062] These are parameters characterizing the packing density and particle mechanical strength of powder materials after being subjected to high pressure (10 tons). Higher compaction density (1.70~1.80 g / cm³) is achieved through compaction. 3This directly reflects the material's excellent pressure resistance and particle strength, indicating that the porous carbon skeleton is not easily broken or collapsed under pressure. This not only helps to improve the volumetric energy density of the electrode, but also directly reflects the material's high strength and resistance to expansion, ensuring the integrity of the electrode structure during assembly and cycling.

[0063] This application also provides a method for preparing the silicon-carbon anode material as described in any of the foregoing embodiments, including: Step S1: Phenolic raw materials, aldehyde raw materials and pore-forming agents are mixed in a liquid phase system and subjected to polymerization reaction to obtain precursor materials.

[0064] This embodiment provides a complete process method for preparing high-strength silicon-carbon anode materials, which mainly includes three core stages: precursor synthesis, activation-free carbonization, and vapor deposition of silicon and carbon coating.

[0065] This step is the liquid-phase polymerization stage, which is the process of constructing a porous carbon framework. Based on the soft template mechanism, phenolic and aldehyde raw materials serve as carbon source monomers, undergoing condensation reactions in the liquid phase to generate a phenolic resin polymer network. Simultaneously, the pore-forming agent acts as a template molecule, utilizing its amphiphilic or other physicochemical properties to self-assemble and uniformly disperse within the polymer matrix during the polymerization process.

[0066] In this process, the in-situ composite of the pore-forming agent and the polymer precursor ensures the uniform distribution of the subsequently formed pores at the microscale, avoiding the problem of uneven distribution caused by physical mixing.

[0067] For example, phenol or resorcinol (phenol source) and formaldehyde (aldehyde source) can be dissolved in water or alcohol-water solvent, acid or alkali can be added to adjust the pH value to initiate polymerization, and an amphiphilic block copolymer (such as F127) can be added as a pore-forming agent. The reaction is stirred at a certain temperature and then cured and dried to finally obtain a resin precursor (material A) containing the pore-forming agent.

[0068] In some preferred embodiments, the feeding ratio of the aldehyde raw material, phenolic raw material, and pore-forming agent needs to be controlled to ensure the formation of a dense and uniform polymer skeleton. Specifically, the molar ratio of the phenolic raw material, aldehyde raw material, and pore-forming agent can be 1:(3~4):(0.005~0.015).

[0069] It is worth noting that the formation of precursor materials is not limited to the in-situ polymerization of monomers (phenols and aldehydes). In some embodiments, pre-prepared methyl phenolic resin (Resol) can also be used directly as a raw material. After mixing it with a pore-forming agent in a solvent, it can be cured and subsequently carbonized to obtain the highly crystalline porous carbon material described in this invention.

[0070] Step S2 involves carbonizing the precursor material to obtain a porous carbon material; the carbonization process does not involve strong corrosive activation to create pores that would damage the carbon crystal structure.

[0071] This step, the activation-free carbonization stage, is crucial in determining the properties of carbon materials. The precursor is subjected to high-temperature heat treatment (pyrolysis) under an inert atmosphere. During this process, the polymer undergoes carbonization, transforming into an inorganic carbon framework, while the pore-forming agent undergoes thermal decomposition or volatilization, leaving pores in situ and forming a porous structure.

[0072] It should be noted that traditional processes typically use CO2, steam, or KOH for "activation" after carbonization to expand pores. This essentially involves etching carbon atoms, creating numerous defects and damaging the graphite microcrystalline structure, resulting in low crystallinity, large peak width at half maximum (HWHM), and low intensity. This step, "avoiding highly corrosive activation for pore formation that damages the carbon crystal structure," explicitly excludes such drastic and corrosive activation treatments.

[0073] It is important to emphasize that the "non-destructive etching activation for pore formation" referred to in this invention is intended to exclude traditional strong etching processes that aim to significantly increase pore volume but severely damage the crystallinity of carbon materials, such as prolonged high-temperature (e.g., >850°C) steam / CO2 activation or chemical activation such as KOH / NaOH. However, this does not absolutely exclude any form of post-processing. For example, in some embodiments, mild, non-etching treatments can be performed, such as low-temperature short-time surface cleaning or light treatments aimed at unclogging some pores, as long as such treatments do not cause a significant increase in the FWHM value of porous carbon beyond the "less than 12" range defined in this invention, they should all fall within the scope of protection of this invention. As shown in Example 4 below, a light treatment using low-flow steam at 880°C, aimed at surface cleaning rather than etching for pore formation, resulted in the material maintaining an FWHM value of 9.22 after treatment, fully meeting the requirements of this application.

[0074] Since it is not chemically etched, the resulting carbon framework retains high crystal integrity and order (corresponding to the characteristic of FWHM < 12 in the aforementioned embodiments), thereby endowing the porous carbon with extremely high mechanical strength and rigidity, enabling it to withstand the subsequent expansion of silicon.

[0075] Specifically, the precursor can be placed in a tube furnace or rotary furnace, protected with nitrogen, heated to a high temperature (e.g., 900~1400℃) and kept at a constant temperature to completely carbonize the organic matter, and then cooled. No activating gas is introduced during the process, and no chemical reagent impregnation is performed.

[0076] Step S3: Silicon is vapor-deposited in the pores of the porous carbon material, and a carbon layer is vapor-deposited on the surface of the material after silicon deposition to obtain the silicon-carbon anode material.

[0077] This step is the vapor deposition of silicon and carbon coating, a functional assembly step, which uses chemical vapor deposition (CVD) technology.

[0078] The aforementioned deposited silicon refers to the use of the small size and high permeability of silicon source gas (such as silane) molecules to diffuse into the nanopores of porous carbon, where it decomposes upon heating to generate elemental silicon, which is then deposited on the pore walls.

[0079] The aforementioned carbon deposition is achieved by switching the carbon source gas (such as acetylene) after silicon deposition and performing a secondary CVD on the outer surface of the particles to form a dense carbon protective layer.

[0080] The synergistic effect can be divided into two aspects: firstly, internal filling, which utilizes the pore space of porous carbon to accommodate silicon, thus realizing the structure of "nano-silicon distributed in the pores"; secondly, external wrapping, which involves the outer carbon layer sealing off some of the pores, not only enhancing the overall conductivity but also repairing surface defects and limiting the contact between the internal silicon and the electrolyte.

[0081] For example, silicon deposition can place the activated porous carbon in a fluidized bed or rotary furnace and introduce a mixture of silane and nitrogen at a certain temperature (e.g., 400~550℃); and carbon coating can be carried out by raising the temperature (e.g., 500~650℃) after the above steps are completed and introducing carbon source gases such as acetylene or methane for short-term treatment.

[0082] In addition, phenolic raw materials are not limited to phenol, but can also be hydroquinone, resorcinol, etc.; aldehydes are not limited to formaldehyde, but can also be acetaldehyde, furfural, etc.

[0083] The polymerization of the aforementioned precursors can be solution polymerization, emulsion polymerization, or sol-gel method; the carbonization equipment can be industrial furnaces such as roller kilns and pusher kilns.

[0084] Regarding pore-forming agents, any substance that can occupy space before carbonization or decompose during carbonization can be used as a potential pore-forming agent, such as various types of surfactants.

[0085] In some embodiments, the phenolic raw material includes at least one of phenol, hydroquinone, and resorcinol.

[0086] In some embodiments, the aldehyde raw material includes at least one of formaldehyde, acetaldehyde, and furfural.

[0087] This embodiment provides specific chemical precursors for synthesizing porous carbon frameworks. These raw materials form a three-dimensional cross-linked phenolic resin network through a polycondensation reaction.

[0088] Phenolic compounds provide aromatic ring structures and are the main source of carbon skeletons, determining the carbon yield and basic structural units of the final carbon materials.

[0089] Aldehydes act as cross-linking agents (or bridging agents), connecting phenolic molecules through methylene bridging bonds.

[0090] Phenol, resorcinol, and other raw materials have moderate reactivity, making it easy to control the polymerization rate; formaldehyde and other small-molecule aldehydes have high cross-linking efficiency. The resin generated by these specific raw material combinations can form a dense and high-strength glassy carbon or hard carbon skeleton after carbonization, which is the material basis for achieving the "high strength" property.

[0091] In addition, a single component (such as phenol + formaldehyde) or a mixed component (such as a phenol / resorcinol mixture) can be used to adjust the polymerization rate and the final pore structure.

[0092] In some embodiments, the pore-forming agent comprises an amphiphilic block copolymer.

[0093] This embodiment involves a specific type of pore-forming agent, based on a "soft template method" pore-forming strategy. The amphiphilic block copolymer molecular chain contains both hydrophilic segments (such as polyethylene oxide (PEO) and hydrophobic segments (such as polypropylene oxide (PPO)). In an aqueous system, these molecules self-assemble to form micelles with specific shapes (such as spherical or columnar). Examples include, but are not limited to, F127 and P123.

[0094] It should be noted that although amphiphilic block copolymers are preferred, in some embodiments of the present invention, other types of soft template agents, such as cationic surfactants (e.g., hexadecyltrimethylammonium bromide CTAB), can also be used as pore-forming agents, as long as they can form micelle structures during precursor polymerization and decompose to form pores during carbonization, are all within the scope of protection of this application.

[0095] Guided by the hydrophilic segments, the phenolic resin precursor polymerizes and crosslinks around these micelles. During subsequent high-temperature processing, the block copolymer decomposes and vaporizes, leaving behind spaces that form a regular mesoporous structure. Compared to hard templates or physical pore creation, amphiphilic block copolymers can induce the formation of uniform mesopores with extremely narrow pore sizes and good channel connectivity, without introducing difficult-to-remove inorganic impurities.

[0096] Because a specific amphiphilic block copolymer is used as a pore-forming agent, it can be fully pyrolyzed and released during high-temperature carbonization. Testing showed that the prepared porous carbon material has extremely low ash residue (e.g., only about 1% or less). This trace residue does not negatively affect the initial coulombic efficiency and electrochemical performance of the silicon-carbon anode material, thus eliminating the need for additional acid washing and impurity removal processes, further simplifying the process.

[0097] In some embodiments, the carbonization temperature is 900°C to 1400°C. For example, it can be 900°C, 950°C, 1000°C, 1100°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, etc.

[0098] The parameters mentioned above are key conditions for the heat treatment process of the precursor's transformation into inorganic carbon. Within this temperature range, the organic polymer chains break, non-carbon elements (H, O, N, etc.) escape in gaseous form, and carbon atoms rearrange to form a disordered layered graphite microcrystalline structure.

[0099] This temperature range is key to achieving "high crystallinity / high strength". Below 900℃, carbonization is incomplete and the carbon skeleton is not strong enough; between 900~1400℃, carbon microcrystals gradually grow, which allows the material to maintain its porous structure without collapsing while significantly improving the rigidity and conductivity of the skeleton (corresponding to FWHM<12).

[0100] In some embodiments, the step of mixing and polymerizing includes: prepolymerizing the phenolic raw material and the aldehyde raw material under conditions of pH 4 to 8, and then adding the pore-forming agent to continue the reaction. For example, the pH value can be pH 4.0, pH 4.5, pH 5.0, pH 5.5, pH 6.0, pH 6.5, pH 7.0, pH 7.5, pH 8.0, etc.

[0101] This step involves a two-step synthesis process. The pH value mentioned above, that is, under weakly acidic to weakly alkaline conditions, controls the reaction rate of phenolic resin, first causing it to generate a low molecular weight prepolymer (such as methyl phenolic resin or oligomer).

[0102] The aforementioned post-addition of pore-forming agent refers to adding the pore-forming agent after a certain degree of oligomerization has been formed.

[0103] In this method, the prepolymerization step avoids the possibility of excessively rapid phase separation or unstable micelle structure that might result from directly mixing monomers with pore-forming agents. Through prepolymerization, oligomers can better synergistically assemble with amphiphilic pore-forming agents through forces such as hydrogen bonds, thereby ensuring that the final porous carbon has uniform pore size and avoiding the formation of macroporous or non-porous regions.

[0104] In some embodiments, the temperature for vapor deposition of silicon is 400°C to 550°C, and the gas source includes a mixture of silane and an inert gas (such as nitrogen or argon). To precisely control the deposition rate and amount of silicon within the pores, the volume ratio of silane to inert gas is preferably 1:(0.5~10), and the deposition duration is 5h to 50h. Temperatures can be, for example, 400°C, 420°C, 440°C, 450°C, 480°C, 500°C, 520°C, 530°C, 550°C, etc.

[0105] The above describes the process of growing nano-silicon within carbon pores using the thermal decomposition reaction of silane (SiH4) in this method. The temperature range of 400–550°C is the kinetic control zone for silane decomposition. At this temperature and the aforementioned gas flow ratio, the inert gas dilutes the silane and acts as a carrier gas, ensuring a moderate reaction rate and allowing sufficient time for slow deposition within the pores. This avoids excessively high temperatures or concentrations of silane, which could lead to rapid decomposition and pore blockage at the pore openings, thus achieving uniform silicon filling within the pores (i.e., "distributed within the pores").

[0106] In some embodiments, the temperature for vapor-phase deposition of the carbon layer is 500°C to 650°C, and the gas source includes a mixture of acetylene and an inert gas (such as nitrogen or argon). The volume ratio of acetylene to the inert gas is preferably 1:(1~5), and the deposition duration is 2h to 20h. The temperature can be, for example, 500°C, 520°C, 540°C, 550°C, 580°C, 600°C, 620°C, 640°C, 650°C, etc.

[0107] The above describes the process of generating amorphous carbon through the cracking of hydrocarbon gases (such as acetylene C2H2). The decomposition temperature of acetylene is typically slightly higher than that of silanes. At 500–650°C and the aforementioned time and gas flow ratio, acetylene can form a dense and uniform carbon coating layer on the surface of deposited silicon particles. Controlling the ratio of acetylene to inert gas at 1:1–5 effectively controls the thickness of the carbon layer, preventing it from being too thick to hinder lithium-ion conduction or too thin to provide adequate protection.

[0108] This process not only repairs potential surface defects but also constructs an excellent electronically conductive layer. Furthermore, the moderate temperature prevents excessive grain growth of the internal nano-silicon or the formation of silicon carbide (SiC) impurities through reaction with carbon.

[0109] In this embodiment of the application, a porous carbon material is also provided, wherein the full width at half maximum (FWHM) of the diffraction peaks at 16° to 26° in the X-ray diffraction pattern of the porous carbon material is less than 12.

[0110] This embodiment provides a porous carbon material with a special microstructure. The porous carbon material serves as a precursor, intermediate, or necessary raw material for preparing the silicon-carbon anode material described in the preceding embodiments. Its core characteristic is that "the full width at half maximum (FWHM) of the diffraction peaks at 16° and 26° in the X-ray diffraction pattern is <12". The broad peaks at 16° and 26° in the XRD pattern are usually attributed to the (002) crystal plane diffraction of the carbon material, reflecting the stacking of the disordered graphite structure. The smaller the FWHM value, the larger the size (Lc) of the carbon crystallites, the fewer the lattice defects, and the relatively higher the degree of crystallization order.

[0111] It should be noted that the mechanical strength of carbon materials is closely related to their crystallinity. Compared with amorphous activated carbon prepared by vigorous activation etching, which typically has a large FWHM (e.g., >15), the porous carbon with an FWHM <12 specified in this application has a more complete carbon framework and fewer structural defects.

[0112] This high crystallinity directly endows the material with extremely high mechanical strength and rigidity. When used as a functional carrier (e.g., for loading active substances), its robust framework can withstand enormous internal stresses without easily collapsing or pulverizing, thus significantly improving the structural stability and service life of the composite material. Simultaneously, the good crystallinity also endows the material with excellent electronic conductivity.

[0113] In some embodiments, the full width at half maximum (FWHM) of the diffraction peaks at 16°–26° in the X-ray diffraction pattern of the porous carbon material is 6–9. For example, the FWHM can be 6, 6.5, 7, 7.2, 7.5, 8, 8.3, 8.5, 8.8, 9, etc.

[0114] The aforementioned half-peak width (FWHM) limit is a specific state between highly graphitized carbon (very small FWHM) and ordinary amorphous carbon (large FWHM).

[0115] Porous carbon within this range achieves a balance between strength and lithium storage / loading capacity. Too small a FWHM (e.g., excessive graphitization) is usually accompanied by the closure or disappearance of the pore structure (high-temperature graphitization leads to pore collapse); too large an FWHM results in insufficient strength.

[0116] A half-peak width of 6 to 9 indicates that the material retains a rich, open pore structure and has a robust framework that can resist external pressure or internal expansion forces, making it an ideal material for high-performance anode carriers.

[0117] In some embodiments, the average pore size of the porous carbon material is 2 nm to 15 nm. For example, the average pore size can be 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 13.5 nm, 15 nm, etc.

[0118] This embodiment provides that the average size of the internal pores of porous carbon falls into the mesoporous category.

[0119] The aforementioned mesoporous channels of 2nm to 15nm facilitate the rapid transport and diffusion of guest molecules (such as electrolyte ions and gas precursors). When used as a carrier, this pore size can effectively confine the filler, preventing particle aggregation and growth. Furthermore, compared to micropores (<2nm), mesopores provide greater free space to buffer volume changes in the filler.

[0120] In some embodiments, the pore volume of the porous carbon material is 0.30 cm³. 3 / g~0.9cm 3 / g. For example, the pore volume can be 0.30 cm³. 3 / g, 0.35 cm 3 / g, 0.40 cm 3 / g, 0.50 cm 3 / g, 0.60 cm 3 / g, 0.70 cm 3 / g, 0.75cm 3 / g, 0.80 cm 3 / g, 0.90 cm 3 / g etc.

[0121] This embodiment provides the pore volume per unit mass of porous carbon: 0.30 cm³ 3 / g~0.9cm 3 The pore volume of / g ensures that the material has sufficient internal space to load functional materials (such as nano-silicon), thereby significantly improving the overall capacity or functional density of the composite material. This pore volume range avoids the problem of a fragile skeleton caused by excessively high porosity (thin pore walls) and the problem of insufficient loading caused by excessively low porosity, ensuring that the material still has excellent volume stability and mechanical integrity under high loads.

[0122] Furthermore, although the aforementioned embodiments primarily focus on its application as a negative electrode support, based on its characteristics of "high strength + mesoporous + high conductivity," this porous carbon material can also be extended to fields such as supercapacitor electrode materials (utilizing its high specific surface area and conductivity), catalyst supports (utilizing its mesoporous confinement effect and stability), or adsorption and separation materials.

[0123] Furthermore, while maintaining FWHM < 12, the pore size distribution can be further precisely controlled within the above range by adjusting the preparation process (such as changing the type or ratio of template agent) (e.g., preparing monodisperse mesoporous carbon).

[0124] This application also provides a negative electrode sheet, comprising a silicon-carbon negative electrode material as described in any of the foregoing embodiments, or a silicon-carbon negative electrode material prepared by the preparation method described in the foregoing embodiments.

[0125] This application also provides a battery, including the negative electrode sheet as described in the foregoing embodiments.

[0126] This battery mainly comprises core components such as a negative electrode, a positive electrode, an electrolyte, and a separator. The negative electrode uses the aforementioned silicon-carbon anode material with high structural stability, while the positive electrode can be made from conventional positive electrode active materials such as lithium cobalt oxide, lithium iron phosphate, or ternary materials, depending on the requirements. The electrolyte can be a liquid electrolyte, a solid electrolyte, or a gel polymer electrolyte, and the separator is typically a porous polymer film such as polyethylene or polypropylene. Based on the excellent electrochemical performance of this anode material, this type of battery encompasses various lithium-based secondary battery systems, including but not limited to lithium-ion batteries, lithium metal batteries (as a hybrid anode), lithium-sulfur batteries (as a sulfur carrier or anode protective layer), and solid-state lithium batteries, characterized by high energy density and long cycle life.

[0127] This application also provides an electrical device, including a battery as described in the foregoing embodiments.

[0128] The term "electrical equipment" refers to any device that incorporates the aforementioned high-performance batteries as a power source or energy storage component. Due to the use of batteries with long cycle life and low volume expansion, such devices achieve longer battery life and higher safety and reliability. The scope is extremely broad, including but not limited to: mobile communication terminals (such as smartphones, tablets, and smartwatches), portable electronic products (such as laptops, digital cameras, and Bluetooth headsets), electric vehicles (such as electric cars, electric bicycles, hoverboards, and drones), energy storage systems (such as home energy storage power supplies, portable outdoor power supplies, and large-scale grid energy storage power stations), as well as various power tools (such as electric drills and chainsaws) and medical electronic devices.

[0129] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0130] Example 1 This embodiment provides a silicon-carbon anode material and its preparation method.

[0131] Experimental methods: (1) Preparation of precursor material A: 1 kg of phenol (phenolic raw material) was dissolved completely in water, and formaldehyde (aldehyde raw material) was added, with a molar ratio of phenol to formaldehyde of 1:4. Sodium hydroxide was then added as a pH adjuster to adjust the pH of the system to 5.5, and the solid content of the entire system was controlled at 15% (in addition, the concentration of the liquid phase system has a certain influence on the morphology of the polymerization product. In some embodiments, the solid content of the polymerization reaction system is controlled between 10% and 30% to facilitate the diffusion of reaction heat and the stable assembly of micelles). The solution was stirred and heated to 65°C and maintained for 40 minutes for prepolymerization. Afterwards, a solution containing pore-forming agent F127 (amphiphilic block copolymer) was added, with a molar ratio of phenol to F127 of 1:0.0075. The reaction was continued at 75°C for 96 hours. After the reaction was completed, the solution was cooled, filtered, and dried to obtain material A.

[0132] It should be noted that the pore-forming agent can be pre-dissolved in a solvent to form a solution before being added. In some embodiments, the solvent for dissolving the pore-forming agent can be water, ethanol, or a mixture of both to ensure sufficient extension and dispersion of the pore-forming agent molecules.

[0133] (2) Preparation of porous carbon materials: Material A is placed in a rotary kiln and heated to 1000℃ under nitrogen protection. It is then carbonized at a constant temperature for 3 hours (no activation or pore formation is performed during this process). After cooling to room temperature, it is sieved to obtain porous carbon materials.

[0134] (3) Preparation of silicon-carbon anode material: The obtained porous carbon material was placed in a rotary kiln and heated to 450°C under nitrogen protection. Silane and nitrogen gas were introduced at a flow rate of 0.5 L / min, and deposition continued for 12 hours before stopping the introduction of silane. Then, the temperature was raised to 550°C, and acetylene and nitrogen gas were introduced at a flow rate of 1 L / min. Deposition continued for 6 hours before stopping the introduction of acetylene. After natural cooling to room temperature, the silicon-carbon anode material of Example 1 was obtained after sieving and demagnetization.

[0135] Example 2 This embodiment provides a silicon-carbon anode material and its preparation method.

[0136] Experimental methods: (1) Preparation of precursor material A: 1 kg of resorcinol was dissolved in water, and formaldehyde was added, with a molar ratio of resorcinol to formaldehyde of 1:3. Sodium hydroxide was added to adjust the pH of the system to 6.0, and the solid content was controlled at 15%. The solution was stirred and heated to 50°C and held for 30 minutes for prepolymerization. Then, a solution containing pore-forming agent F127 was added, with a molar ratio of resorcinol to F127 of 1:0.01. The reaction was continued at 70°C for 72 hours, then cooled, filtered, and dried to obtain material A.

[0137] (2) Preparation of porous carbon materials: Material A is placed in a rotary kiln and heated to 1100℃ under nitrogen protection. It is carbonized at a constant temperature for 3 hours, cooled to room temperature, and then sieved to obtain porous carbon materials.

[0138] (3) Preparation of silicon-carbon anode material: The obtained porous carbon material was placed in a rotary kiln and heated to 460°C under nitrogen protection. Silane and nitrogen gas were introduced at a flow rate of 0.5 L / min, and deposition continued for 15 hours. Then, the temperature was raised to 570°C, and acetylene and nitrogen gas were introduced at a flow rate of 1 L / min, and deposition continued for 8 hours. The material was then cooled, sieved, and demagnetized to obtain the silicon-carbon anode material of Example 2.

[0139] Example 3 This embodiment provides a silicon-carbon anode material and its preparation method.

[0140] Experimental methods: (1) Preparation of precursor material A: Dissolve 1 kg of phenol in water, add formaldehyde (phenol to formaldehyde molar ratio 1:3), add sodium hydroxide to adjust pH to 4.5, and control solid content to 15%. Heat to 60℃ and maintain for 30 minutes for prepolymerization. Add a solution containing pore-forming agent P123 (phenol to P123 molar ratio 1:0.0005). Continue reaction at 78℃ for 72 hours, cool, filter, and dry to obtain material A.

[0141] (2) Preparation of porous carbon materials: Material A is placed in an atmosphere furnace (which can be a roller kiln, pusher kiln or rotary kiln), heated to 1200℃ under nitrogen protection, carbonized at a constant temperature for 3 hours, cooled to room temperature and then screened to obtain porous carbon materials.

[0142] (3) Preparation of silicon-carbon anode material: The obtained porous carbon material was placed in a fluidized bed and heated to 500°C under nitrogen flow at 10 L / min. Silane and nitrogen were introduced at 1 L / min and the deposition continued for 6 hours. Then, the temperature was increased to 600°C, and acetylene and nitrogen were introduced at 2 L / min and 10 L / min, and the deposition continued for 4 hours. The material was then cooled, sieved, and demagnetized to obtain the silicon-carbon anode material of Example 3.

[0143] Example 4 This embodiment provides a silicon-carbon anode material and its preparation method.

[0144] Experimental methods: (1) Preparation of precursor material A: Dissolve 1 kg of resorcinol in water, add formaldehyde, and the molar ratio of resorcinol to formaldehyde is 1:3. Add sodium hydroxide to adjust the pH to 4.5 and control the solid content to 15%. Heat to 60℃ and maintain for 30 minutes for prepolymerization. Add a solution containing pore-forming agent P123, and the molar ratio of resorcinol to P123 is 1:0.0015. Continue the reaction at 78℃ for 72 hours, cool, filter, and dry to obtain material A.

[0145] (2) Preparation of porous carbon materials: Material A was first placed in an atmosphere furnace and heated to 1200°C under nitrogen protection for 3 hours. After cooling, the material was sieved to obtain material B. Material B was then placed in a fluidized bed and heated to 880°C. 1 L / min of water vapor and 10 L / min of nitrogen were introduced for 8 hours. The purpose of introducing water vapor here is not for traditional etching to create pores (traditional activation usually leads to a significant increase in FWHM to over 15), but rather to perform slight surface cleaning and pore unblocking of the carbon material. Due to the low processing temperature (880°C) and low water vapor flow rate, this process did not destroy the highly crystalline framework already formed in material B (after treatment, the FWHM was only 9.22, still less than 12). It was only used to fine-tune the pore size distribution and remove trace residues in the pores. Therefore, this step does not belong to the "activation pore-creating" process that leads to a significant decrease in crystallinity, which is excluded by this invention.

[0146] (3) Preparation of silicon-carbon anode material: Spherical porous carbon material was placed in a fluidized bed and deposited at 450°C with 1 L / min silane and 10 L / min nitrogen for 10 hours. Then, it was deposited at the same temperature of 450°C with 1 L / min acetylene and 10 L / min nitrogen for 6 hours. After cooling, sieving, and demagnetizing, the silicon-carbon anode material of Example 4 was obtained.

[0147] Example 5 This embodiment provides a silicon-carbon anode material with higher crystallinity.

[0148] Experimental methods: (1) Preparation of precursor material A: exactly the same as step (1) in Example 1.

[0149] (2) Preparation of porous carbon materials: Material A was placed in a rotary kiln and heated to 1350 degrees Celsius under nitrogen protection. The temperature was maintained for 3 hours, then cooled to room temperature and sieved to obtain porous carbon materials. (Note: Increasing the temperature helps to improve crystallinity and reduce FWHM).

[0150] (3) Preparation of silicon-carbon anode material: The process parameters are the same as those in step (3) of Example 1.

[0151] Testing showed that the porous carbon material prepared in Example 5 had a full width at half maximum (FWHM) of 7.85 at 16-26 degrees in its XRD pattern, and a pore volume of 0.58 cm³. 3 / g, with an average pore size of 4.32 nm. Although the high temperature caused a slight shrinkage in pore volume, the FWHM decreased significantly, indicating a further increase in the crystallinity of the carbon framework.

[0152] The specific surface area of ​​the prepared silicon-carbon anode material increased from 2.15 m² under 10 tons of pressure. 2 The particle size distribution changed from 3.25 m² / g to 3.25 m² / g, with a change rate of only 51.2%, demonstrating extremely high particle strength; battery testing showed that the capacity retention rate was 94.2% after 50 cycles.

[0153] Example 6 This embodiment provides a silicon-carbon anode material with large pore size and high silicon content.

[0154] Experimental methods: (1) Preparation of precursor material A: 1 kg of phenol was dissolved completely in water, and formaldehyde was added at a molar ratio of phenol to formaldehyde of 1:4. Sodium hydroxide was added to adjust the pH of the system to 5.5, and the solid content was controlled at 15%. The solution was stirred and heated to 65°C and maintained for 40 minutes for prepolymerization. To obtain a larger pore size, the amount of pore-forming agent was increased by adding a solution containing pore-forming agent F127, and the molar ratio of phenol to F127 was adjusted to 1:0.015. The reaction was continued at 75°C for 96 hours, then cooled, filtered, and dried to obtain material A.

[0155] (2) Preparation of porous carbon materials: Same as in Example 1 (carbonization at 1000°C for 3 hours).

[0156] (3) Preparation of silicon-carbon anode material: The obtained porous carbon material was placed in a rotary kiln and heated to 450°C under nitrogen protection. To achieve a higher silicon loading, silane and nitrogen were introduced at a flow rate of 1 L / min, and the deposition time was extended to 25 hours. Then, the silane was stopped. The temperature was then raised to 550°C, and acetylene and nitrogen were introduced at a flow rate of 1 L / min. The deposition time was 6 hours. The material was then cooled, sieved, and demagnetized to obtain the silicon-carbon anode material of Example 6.

[0157] Example 7 This embodiment provides a silicon-carbon anode material with small pore size and low silicon content.

[0158] Experimental methods: (1) Preparation of precursor material A: It is basically the same as in Example 1, but in order to obtain a smaller pore size and reduce the amount of pore-forming agent, the molar ratio of phenol to F127 is adjusted to 1:0.005.

[0159] (2) Preparation of porous carbon materials: Same as in Example 1.

[0160] (3) Preparation of silicon-carbon anode material: The obtained porous carbon material was placed in a rotary kiln and heated to 450°C under nitrogen protection. To control a low silicon loading, silane and nitrogen were introduced at a flow rate of 0.2 L / min and 1 L / min, respectively, shortening the deposition time to 6 hours. Then, the temperature was raised to 550°C, and acetylene and nitrogen were introduced at a flow rate of 1 L / min for 6 hours of deposition. After cooling, sieving, and demagnetization, the silicon-carbon anode material of Example 7 was obtained.

[0161] Comparative Example 1 This comparative example provides a silicon-carbon anode material prepared using a traditional activation process.

[0162] Experimental methods: (1) Preparation of material A: Same as step (1) in Example 1.

[0163] (2) Preparation of porous carbon materials (activation method): Material A was placed in a rotary kiln and heated to 1000℃ under nitrogen protection for 3 hours. After cooling, the material was pulverized to obtain carbon material. The carbon material was then placed in a fluidized bed, heated to 880℃, and charged with 100 mg / min water vapor and 10 L / min nitrogen. The activation reaction was carried out for 8 hours. After cooling, the material was sieved and demagnetized to obtain the porous carbon material for comparison.

[0164] (3) Preparation of silicon-carbon anode material: Same as step (3) in Example 1.

[0165] Comparative Example 2 This comparative example provides a silicon-carbon anode material that has undergone ultra-high temperature graphitization treatment, resulting in an extremely low half-maximum width (FWHM) and closed pores.

[0166] Experimental methods: (1) Preparation of material A: Same as in Example 1.

[0167] (2) Preparation of porous carbon materials: Material A was placed in an ultra-high temperature graphitization furnace and heated to 2500℃ under argon protection, and kept at a constant temperature for 3 hours. The extremely high temperature caused carbon atoms to rearrange and become highly graphitized. After cooling to room temperature, the material was sieved to obtain highly graphitized carbon materials.

[0168] (3) Preparation of silicon-carbon anode material: The carbon material was placed in a rotary furnace, and the process conditions (temperature, airflow, time) for silicon deposition and carbon coating were exactly the same as in step (3) of Example 1. Due to the large number of closed pores in the matrix, silicon was mainly deposited on the particle surface. After cooling, sieving, and demagnetizing, the anode material of Comparative Example 2 was obtained.

[0169] Test Experiment To verify the effectiveness of the technical solution of the present invention, the materials prepared in Examples 1-4 and Comparative Example 1 were subjected to the following performance tests: 1. Structural and physical property testing: (1) XRD test: The crystal structure of porous carbon material was tested using an X-ray diffractometer, and the full width at half maximum (FWHM) of the diffraction peaks at 16-26 degrees was recorded.

[0170] (2) Pore structure test: The pore volume and average pore size of porous carbon materials were tested using a nitrogen adsorption-desorption apparatus.

[0171] (3) Specific surface area (BET) and pressure resistance test: The specific surface area of ​​silicon-carbon anode material powder in the initial state and after being treated with 10 tons of pressure is tested. The pressure resistance of the particles is characterized by the rate of change of specific surface area (particle breakage will lead to the formation of new interfaces, thereby increasing BET).

[0172] (4) Compacted density test: Measure the bulk density of the powder after it has been subjected to 10 tons of pressure.

[0173] Test results: Table 1. Structural parameters of porous carbon materials

[0174] Analysis: From Table 1 and Figure 1 , Figure 2 It can be seen that the porous carbon prepared by the activation-free process in Examples 1-7 all had XRD full width at half maximum (FWHM) between 7.85 and 10.92 (less than 12). By adjusting the proportion of pore-forming agent, Examples 6 and 7 successfully achieved a wide range of pore size control from 2.65 nm to 13.80 nm while maintaining excellent pore structure. In contrast, the FWHM of Comparative Example 1 increased sharply to 18.32 after activation, and its crystallinity decreased significantly; conversely, although Comparative Example 2 had an extremely low FWHM (4.25, highly graphitized) after ultra-high temperature treatment at 2500℃, its pore volume decreased drastically to 0.04 cm³. 3 / g, the pore structure almost completely collapsed and closed, losing the space to load nano-silicon, which, from the opposite perspective, confirms the necessity of controlling FWHM within a moderate range (such as <12 and having a porous structure).

[0175] Table 2. Physical properties and voltage withstand performance of silicon-carbon anode materials

[0176] Analysis: As shown in Table 2, the silicon-carbon anode materials prepared in Examples 1-7 of this invention have a silicon content between 2.5% and 58.4% and an average particle size (D50) between 6.8 μm and 8.9 μm, which are all within the preferred range defined by the methods and products provided in the embodiments of this application.

[0177] More importantly, after being subjected to 10 tons of pressure, the specific surface area (BET) growth rate of the materials in the examples was significantly lower than that of the comparative examples. Among them, Example 5, with the highest crystallinity, performed the best, with a BET growth rate of only 51.16%, the lowest among all samples. This strongly demonstrates that, with similar silicon content and particle size, the highly crystalline carbon framework (low FWHM) obtained by the activation-free process of this invention does indeed bring stronger particle compressive strength. In contrast, although the silicon content (47.5%) and particle size (8.5 μm) of the material in Comparative Example 1 are comparable to those of the examples, its poor matrix carbon crystallinity leads to extremely low particle strength, resulting in severe fragmentation under pressure and a BET growth rate as high as 294.4%.

[0178] 2. Electrochemical performance testing: (1) Battery preparation: The prepared silicon-carbon anode material, binder PAA, conductive agent Super-P, and conductive agent HCNT2 were mixed in a weight ratio of 84.9:5:10:0.1, and deionized water was added to make a slurry. The slurry was coated onto copper foil, dried, and rolled (the electrode compaction density was 0.8 g / cm³). 3 Electrodes were fabricated by lamination. A CR2016 coin cell was assembled using a lithium metal sheet as the counter electrode and 1.0 mol / L LiPF6 (EC:DMC:FEC=4:5.5:0.5, containing 10% FEC) as the electrolyte.

[0179] (2) Test conditions: Charge and discharge voltage range 0.005V-1.5V. First, discharge with a constant current of 150mA / g, then discharge with a constant current of 30mA / g to 0.005V, and finally charge with a constant current of 150mA / g.

[0180] (3) Test indicators: Record the reversible capacity in the first week, the coulombic efficiency in the first week, the capacity retention rate after 50 cycles, and test the electrode expansion rate when the first lithium insertion is at 100% SOC.

[0181] Table 3. Electrochemical performance test results

[0182] analyze: As can be seen from the data in Table 3, the silicon-carbon anode materials prepared in Examples 1-7 of this invention exhibit excellent electrochemical performance: The electrode expansion rates during the initial lithium-ionization fully charged state (100% SOC) were all controlled within a good range (91.5%-99.2%), significantly lower than the 106.3% of Comparative Example 1. Although Example 6 had a silicon loading as high as 58.4% and a capacity exceeding 2300 mAh / g, the electrode expansion rate was still controlled below 100%. Example 7, due to its lower silicon content, exhibited extremely low expansion (91.5%) and extremely high cycle retention (96.8%). This directly demonstrates that the high-strength porous carbon matrix of this invention can more effectively confine the volume expansion of silicon and has a universal protective effect on products with different silicon contents.

[0183] In contrast, in Comparative Example 2, the carbon framework underwent ultra-high temperature treatment, leading to pore collapse (FWHM < 5). The vapor-deposited nano-silicon could not penetrate the pores and could only adhere to the outer surface of the particles. During charge and discharge, the surface silicon completely lost the mechanical constraint of the carbon framework, resulting in an abnormally high electrode expansion rate (125.4%). The silicon particles rapidly pulverized and detached, with an initial coulombic efficiency of only 87.5%, and a capacity retention rate plummeting to 62.3% after 50 cycles. This not only demonstrates the importance of distributing silicon within the pores but also perfectly supports the technical logic of this application regarding "maintaining an effective pore structure and avoiding excessive pursuit of extremely low half-widths when FWHM is less than 12."

[0184] These data clearly demonstrate that preserving the high crystallinity and strength of the carbon skeleton through activation-free processes plays a decisive role in reducing electrode expansion and improving battery cycle life, and this effect is further enhanced as crystallinity increases (FWHM decreases).

[0185] In summary, this invention obtains a high-strength porous carbon support with specific crystallization characteristics (FWHM<12) through an activation-free preparation process, successfully solving the technical problems of low strength, large expansion, and poor cycle life of traditional activated porous carbon-based silicon-carbon anode materials.

[0186] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention 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 the present invention.

Claims

1. A silicon-carbon anode material, characterized in that, The silicon-carbon anode material comprises porous carbon, nano-silicon, and a nano-carbon layer; In this embodiment, at least a portion of the nano-silicon is distributed within the pores of the porous carbon; at least a portion of the surface of the porous carbon is covered by the nano-carbon layer. The porous carbon exhibits a full width at half maximum (FWHM) of less than 12 for the diffraction peaks at 16°–26° in the X-ray diffraction pattern.

2. The silicon-carbon anode material as described in claim 1, characterized in that, The porous carbon exhibits a full width at half maximum (FWHM) of 6–9 for the diffraction peaks at 16–26 degrees in the X-ray diffraction pattern; and / or, The average pore size of the porous carbon is 2 nm to 15 nm; and / or, The porous carbon has a pore volume of 0.30 cm³. 3 / g~0.9cm 3 / g; and / or, The silicon-carbon anode material is in bulk form with an average particle size of 3 μm to 12 μm; and / or, The nano-silicon accounts for 30% to 60% of the weight of the silicon-carbon anode material; and / or, The specific surface area of ​​the silicon-carbon anode material is <5m². 2 / g; and / or, The compacted density of the silicon-carbon anode material under 10 tons of pressure is 1.70 g / cm³. 3 ~1.80g / cm 3 .

3. The silicon-carbon anode material as described in claim 2, characterized in that, The specific surface area of ​​silicon-carbon anode materials is <3m². 2 / g.

4. A method for preparing the silicon-carbon anode material as described in any one of claims 1-3, characterized in that, include: Phenolic raw materials, aldehyde raw materials and pore-forming agents are mixed in a liquid phase system and subjected to polymerization reaction to obtain precursor materials; The precursor material is carbonized to obtain a porous carbon material. The carbonization process does not involve highly corrosive activation pore-forming that would damage the carbon crystal structure. Silicon is vapor-deposited within the pores of the porous carbon material, and a carbon layer is vapor-deposited on the surface of the material after silicon deposition to obtain the silicon-carbon anode material.

5. The method for preparing the silicon-carbon anode material as described in claim 4, characterized in that, The phenolic raw materials include at least one of phenol, hydroquinone, and resorcinol; and / or The aldehyde raw materials include at least one of formaldehyde, acetaldehyde, and furfural; and / or, The pore-forming agent comprises an amphiphilic block copolymer; and / or, The carbonization treatment temperature is 900℃~1400℃; and / or, The step of mixing and polymerizing includes: prepolymerizing the phenolic raw material and the aldehyde raw material under conditions of pH 4-8, then adding the pore-forming agent to continue the reaction; and / or, The temperature for silicon vapor deposition is 400℃~550℃, the gas source includes a mixture of silane and inert gas, the volume ratio of silane to inert gas is 1:(0.5~10), and the deposition duration is 5h~50h; and / or, The temperature of the vapor-phase deposited carbon layer is 500℃~650℃, the gas source includes a mixture of acetylene and inert gas, the volume ratio of acetylene to inert gas is 1:(1~5), and the deposition duration is 2h~20h.

6. A porous carbon material, characterized in that, The porous carbon material has a full width at half maximum (FWHM) of less than 12 for the diffraction peaks at 16°–26° in the X-ray diffraction pattern.

7. The porous carbon material as described in claim 6, characterized in that, The porous carbon material exhibits a full width at half maximum (FWHM) of 6–9 for the diffraction peaks at 16–26 degrees in the X-ray diffraction pattern; and / or, The average pore size of the porous carbon material is 2 nm to 15 nm; and / or, The porous carbon material has a pore volume of 0.30 cm³. 3 / g~0.9cm 3 / g.

8. A negative electrode sheet, characterized in that, Includes the silicon-carbon anode material as described in any one of claims 1-3, or the silicon-carbon anode material prepared by the preparation method described in claim 4 or 5.

9. A battery, characterized in that, Includes the negative electrode as described in claim 8.

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

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