Silicon-based composite negative electrode material and preparation method thereof, negative electrode plate and lithium ion battery

Abstract

The invention provides a silicon-based composite negative electrode material and a preparation method thereof, a negative electrode plate and a lithium ion battery, in the preparation method of the silicon-based composite negative electrode material provided by the invention, metal selenide nanocrystallines are introduced, and uniform deposition of silicon is induced in a subsequent chemical vapor deposition process by utilizing the induction effect of the metal selenide nanocrystallines; the silicon particles can be uniformly distributed in the carbon skeleton, the capacity of the obtained silicon-based composite negative electrode material is improved, and the diffusion path of lithium ions is improved, so that the novel silicon-based composite negative electrode material with a high-conductivity and high-stability structure is constructed. Besides, the existence of the metal selenide nanocrystalline in the material accelerates the de-intercalation process of lithium ions in the composite negative electrode material, the electrochemical reaction kinetics is optimized, the electrochemical capacity of the obtained composite negative electrode material is remarkably improved, and meanwhile, the composite negative electrode material has good cycle performance and first effect; and a feasible path is provided for the innovation of the lithium ion battery technology.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a silicon-based composite anode material and its preparation method, an anode sheet, and a lithium-ion battery. Background Technology

[0002] With the rise of the "low-altitude economy" and the global pursuit of sustainable energy, the rapid development of electric vehicles and energy storage devices has spurred demand for higher-performance battery systems. Against this backdrop, improving the energy density of lithium-ion batteries (LIBs), currently the most widely used type of rechargeable battery, has become particularly crucial. Traditional graphite anodes, while demonstrating stable performance in commercial applications, have reached their theoretical capacity limit (372 mAh·g). -1 This limits further improvements in the overall energy density of LIBs. In contrast, silicon anode materials, with their ultra-high theoretical capacity (4200 mAh·g), offer significant advantages. -1 ) and lower lithium potential (~0.4V vs. Li) + Li ( / Li) has shown great potential and has become a popular candidate for next-generation LIB anode materials.

[0003] However, silicon materials face significant challenges in practical applications, particularly in terms of conductivity and cycle stability. Silicon anodes undergo significant volume changes (up to 400%) during lithium-ion insertion and extraction, leading to increased mechanical stress between particles and potentially causing particle breakage and electrode cracking. Simultaneously, silicon's low conductivity translates to poor charge transport efficiency, further exacerbating electrode performance degradation during charge and discharge. Furthermore, the continuous formation and degradation of the solid electrolyte interphase (SEI) depletes active lithium, reducing the battery's initial charge-discharge efficiency and long-term cycle performance.

[0004] To overcome these challenges, researchers have begun exploring silicon-based composite materials, especially silicon-carbon composites, aiming to combine the high conductivity and mechanical stability of carbon materials with the high capacity of silicon. Carbon, as a supporting structure for silicon, not only significantly improves the material's electrical conductivity but also utilizes its stable framework structure to buffer the volume expansion of silicon during charging and discharging, reducing the mechanical stress on silicon particles.

[0005] However, although silicon-carbon composites provide an ideal carrier for silicon nanoparticles, existing technologies often struggle to achieve uniform deposition of nano-silicon within the carbon framework during actual preparation, leading to inconsistent performance in the resulting silicon-carbon composites. Furthermore, current silicon-carbon composite material preparation technologies suffer from complex processes and high costs. Therefore, developing a simple and efficient method for preparing silicon-carbon composites, and producing a silicon-carbon composite material with stable cycling and high initial charge-discharge efficiency, has become an urgent need in the current lithium-ion battery research field. Summary of the Invention

[0006] The main objective of this invention is to provide a silicon-based composite anode material and its preparation method, anode sheet, and lithium-ion battery, in order to solve the problems of complex and costly preparation processes of silicon-carbon composite materials in the prior art, as well as the difficulty in uniformly depositing nano-silicon in the carbon skeleton and the resulting inconsistent performance of silicon-carbon composite materials.

[0007] This application provides a method for preparing a silicon-based composite anode material, comprising the following steps: In the presence of a first carbon source, ammonia, a soluble metal salt, and a reducing agent are mixed to carry out a first reaction to obtain a reaction solution; the reaction solution is sequentially acid-washed, separated, and subjected to a first drying to obtain a first solid; wherein the reducing agent is an organic reducing agent containing an aldehyde group; the first solid is mixed with selenane gas to carry out a first chemical vapor deposition to form a first mixture; an activation gas is introduced into the first mixture to activate and create pores, resulting in a second mixture; the second mixture is cooled to obtain a second solid; the second solid is sequentially pulverized, sieved, washed, and subjected to a second drying to obtain a third solid; the third solid is mixed with silane gas to carry out a second chemical vapor deposition to obtain a silicon-based composite anode material precursor; a second carbon source is coated onto the surface of the silicon-based composite anode material precursor to obtain the silicon-based composite anode material.

[0008] Furthermore, the metal ion in the soluble metal salt is selected from one or more of alkali metal ions, alkaline earth metal ions, transition metal ions, and aluminum ions; preferably, the metal ion in the soluble metal salt is selected from Ag. + Al 3+ Na + K + Ca 2+ Pb 2+ and Ce 2+ At least one of the following: preferably, the soluble metal salt is selected from at least one of silver nitrate, aluminum nitrate, sodium nitrate, potassium nitrate, calcium nitrate, lead nitrate, and cerium nitrate; more preferably, the soluble metal salt is selected from silver nitrate; preferably, the temperature of the first reaction is 10–40°C and the time is 0.5–2 h.

[0009] Further, the weight ratio of the first solid to the selenane gas is (1-10):(1-50); preferably, the weight ratio of the activation gas to the first mixture is (1-10):(1-50); preferably, the weight ratio of the third solid to the silane gas is (1-10):(1-50).

[0010] Further, the organic reducing agent containing an aldehyde group is selected from one or more of formaldehyde, acetaldehyde, and glucose; preferably, the concentration of the soluble metal salt is 0.05-0.2 mol / L; preferably, the mass concentration of ammonia is 5-10%; preferably, in the first reaction system, the weight ratio of the first carbon source, the soluble metal salt, ammonia, and the reducing agent is (1-5):(2-10):(1-10):(1-10).

[0011] Further, the temperature of the first chemical vapor deposition is 300–1000°C, and the time is 1–6 h; preferably, the temperature of the second chemical vapor deposition is 500–800°C, and the time is 5–8 h; preferably, the activating gas is at least one of water vapor or carbon dioxide; preferably, the temperature of the activation pore-forming process is 800–1500°C, and the time is 5–12 h.

[0012] Further, the first carbon source is selected from one or more of phenolic resin, petroleum coke, coal-based materials and biomass materials; preferably, the temperature of the first drying is 80-120°C and the time is 12-16 hours; preferably, the temperature of the second drying is 200-500°C and the time is 2-12 hours; preferably, the first drying and the second drying are vacuum drying.

[0013] Further, the step of coating the second carbon source onto the surface of the silicon-based composite anode material precursor includes: mixing the second carbon source with the silicon-based composite anode material precursor in gaseous form, and performing the coating operation by a third chemical vapor deposition; preferably, the weight ratio of the second carbon source to the silicon-based composite anode material precursor is (0.01-0.2):1; preferably, the second carbon source is one or more of acetylene, ethylene, and methane; preferably, the temperature of the third chemical vapor deposition is 500-800°C, and the time is 2-12 hours.

[0014] Furthermore, the pickling solution used in the pickling process is selected from one or more of hydrochloric acid, acetic acid, sulfuric acid and citric acid; preferably, the mass concentration of the pickling solution is 5-10%; preferably, the separation operation is carried out by suction filtration; more preferably, the suction filtration time is 10-20 min.

[0015] Furthermore, before performing the first chemical vapor deposition, the preparation method further includes: introducing a first protective gas to remove air from the reaction system; and / or, before performing the second chemical vapor deposition, the preparation method further includes: introducing a second protective gas to remove air from the reaction system; preferably, the second protective gas and the second protective gas are each independently selected from one or more of helium, argon and nitrogen; preferably, after the second solid is crushed and sieved, the particle size of the fifth solid obtained is 3μm≤D50≤10μm; preferably, washing is performed with water; preferably, the washing time is 1 to 5 hours.

[0016] According to a second aspect of the present invention, a silicon-based composite anode material is also provided, which is prepared by the above-described preparation method; preferably, the specific surface area of ​​the silicon-based composite anode material is ≥1800 m². 2 / g, pore volume ≥0.9cm³ 3 / g, micropore ratio ≥80%.

[0017] According to a third aspect of the present invention, a negative electrode sheet is also provided, which includes a current collector and a negative electrode material layer located on one side surface of the current collector, wherein the material of the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes the aforementioned silicon-based composite negative electrode material.

[0018] According to a fourth aspect of the present invention, a lithium-ion battery is also provided, the lithium-ion battery comprising the above-described negative electrode sheet.

[0019] The method for preparing the silicon-based composite anode material provided in this application involves first reacting ammonia, a soluble metal salt, and a reducing agent in the presence of a first carbon source. Following a series of treatments including acid washing, separation, and drying, the resulting solid and selenane gas undergo a first chemical vapor deposition to form metal selenide nanocrystals. Under the influence of the generated metal selenide nanocrystals, a second chemical vapor deposition is performed with silane gas. Finally, a second carbon source is coated onto the surface of the resulting solid material to obtain the silicon-based anode material. The aldehyde groups (such as formaldehyde and acetaldehyde) in the reducing agent during the first reaction can reduce metal ions in the soluble metal salt to form metal nanocrystals. These nanocrystals can induce uniform silicon deposition during the subsequent chemical vapor deposition process, thereby constructing a silicon-carbon composite material with high conductivity and high stability. The method for preparing silicon-based composite anode materials provided in this application introduces metal selenide nanocrystals, which, through their inductive effect, induce uniform silicon deposition during subsequent chemical vapor deposition. This ensures that silicon particles are uniformly distributed within the carbon framework, improving the capacity of the resulting silicon-based composite anode material and optimizing the lithium-ion diffusion path. This results in a novel silicon-based composite anode material with high conductivity and high stability. Furthermore, the presence of metal selenide nanocrystals accelerates the lithium-ion insertion / extraction process in the composite anode material, optimizing its electrochemical reaction kinetics. The resulting composite anode material not only exhibits a significant improvement in electrochemical capacity but also possesses excellent cycle performance and first-efficiency, providing a feasible path for the innovation of lithium-ion battery technology. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 SEM images of the silicon-based composite anode material prepared according to Example 1 of the present invention are shown.

[0022] Figure 2 SEM images of the silicon-based composite anode material according to Comparative Example 1 of the present invention are shown;

[0023] Figure 3 The first charge-discharge curves of the button cells corresponding to Embodiment 1 and Comparative Example 1 of the present invention are shown.

[0024] Figure 4 The cycle performance curves of the coin cells corresponding to Embodiment 1 and Comparative Example 1 of the present invention are shown.

[0025] Figure 5 The diagrams show the crushing force test results of the silicon-based anode materials corresponding to Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] As described in the background section, the porous carbon framework in silicon-carbon composites provides an ideal carrier for silicon nanoparticles. However, in actual preparation processes, existing technologies often struggle to uniformly deposit nano-silicon materials within the carbon framework, leading to inconsistent electrochemical performance of the resulting silicon-carbon composites and reducing their effectiveness in battery applications. Furthermore, the preparation of silicon-carbon composites is hampered by complex processes and high costs, further limiting their development and application in actual production.

[0028] To address the aforementioned problems, this application provides a method for preparing a silicon-based composite anode material. This method includes the following steps: In the presence of a first carbon source, ammonia, a soluble metal salt, and a reducing agent are mixed to carry out a first reaction, yielding a reaction solution; the reaction solution is sequentially acid-washed, separated, and subjected to a first drying process to obtain a first solid; wherein the reducing agent is an organic reducing agent containing an aldehyde group; the first solid is mixed with selenane gas to carry out a first chemical vapor deposition, forming a first mixture; an activation gas is introduced into the first mixture to activate and create pores, yielding a second mixture; the second mixture is cooled to obtain a second solid; the second solid is sequentially pulverized, sieved, washed, and subjected to a second drying process to obtain a third solid; the third solid is mixed with silane gas to carry out a second chemical vapor deposition, yielding a silicon-based composite anode material precursor; a second carbon source is coated onto the surface of the silicon-based composite anode material precursor, and the resulting fourth solid is sintered to obtain the silicon-based composite anode material.

[0029] Specifically, in the above preparation method, firstly, in the presence of a first carbon source, ammonia, a soluble metal salt, and a reducing agent are mixed to carry out a first reaction, obtaining a reaction solution. The reaction solution is then subjected to acid washing, separation, and a first drying process to obtain a first solid. The ammonia in the above reaction system can react with the metal ions in the soluble metal salt under the action of a reducing agent containing an aldehyde group, undergoing a first reaction similar to a "silver mirror reaction," uniformly generating a substance containing metal ions on and inside the first carbon source, resulting in a first solid comprising the substance containing metal ions and the first carbon source. Then, the first solid is mixed with selenane gas to carry out a first chemical vapor deposition, forming a first mixture. Next, an activation gas is introduced into the first mixture to activate and create pores, obtaining a second mixture. After cooling, the second mixture yields a second solid. As described above, the first solid includes a first carbon source and a substance containing metal ions. The first solid is mixed with selenane gas and subjected to first chemical vapor deposition (CVD). This process allows the metal ions in the first solid to fully react with selenane (SeH2), generating nanoscale metal selenide microcrystals, which are then uniformly mixed with the first carbon source. The activation pore-forming operation further enriches the pore size distribution of the resulting second solid, better forming a porous silicon-based material. Next, the second solid is sequentially pulverized, sieved, washed, and then dried to obtain a third solid. This third solid is mixed with silane gas for second CVD to obtain a silicon-based composite anode material precursor. The resulting second solid undergoes a series of treatments and is then mixed with silane (SiH4) gas for second CVD. The induction effect of the metal selenide microcrystals in the porous carbon material allows for uniform deposition of silicon within the porous carbon material, thereby further enhancing the electrochemical capacity of the formed silicon-based composite anode material. Finally, the second carbon source is coated onto the surface of the silicon-based composite anode material precursor to obtain the silicon-based composite anode material. In the preparation method of the silicon-based composite anode material provided by this invention, a novel silicon-based composite anode material is successfully constructed by introducing metal nanocrystals and utilizing their catalytic and structural effects. This material not only significantly improves capacity but also possesses good cycle performance and first-efficiency. The reasons for the above effects may include the following aspects:

[0030] Firstly, unlike traditional preparation methods, this invention innovatively utilizes metal nanocrystals to guide the uniform deposition of silicon in a porous carbon matrix. The presence of metal nanocrystals promotes uniform silicon deposition because they act as deposition templates, causing subsequently introduced silicon to tend to form around the nanocrystals rather than be randomly distributed. This step not only ensures that silicon particles are uniformly distributed within the carbon framework, reducing agglomeration, but also improves the capacity of the resulting silicon-based composite anode material and enhances the lithium-ion diffusion path. Simultaneously, it leverages the high specific surface area of ​​porous carbon to reduce stress accumulation caused by volume expansion during silicon cycling, maintaining the integrity of the composite material and improving the initial charge-discharge efficiency.

[0031] Secondly, the metal nanocrystals formed in the above process can remain in the silicon-based composite anode material. During charge and discharge, they can interact with lithium ions to form lithium alloys, accelerating the lithium ion insertion / extraction process and optimizing the electrochemical reaction kinetics of the battery, thereby improving the initial coulombic efficiency and cycle life. At the same time, the interaction between the metal nanocrystals and silicon may also produce a certain buffering effect, further limiting the volume change of the material and avoiding structural damage during cycling.

[0032] In summary, the method for preparing the silicon-based composite anode material provided in this application introduces metal selenide nanocrystals, which, through their inductive effect, induce uniform silicon deposition during the subsequent chemical vapor deposition process. This ensures that silicon particles are uniformly distributed within the carbon framework, improving the capacity of the resulting silicon-based composite anode material and optimizing the lithium-ion diffusion path. This results in a novel silicon-based composite anode material with high conductivity and high stability. Furthermore, the presence of metal selenide nanocrystals in the material accelerates the lithium-ion insertion / extraction process in the composite anode material, optimizing its electrochemical reaction kinetics. The resulting composite anode material not only exhibits a significant improvement in electrochemical capacity but also possesses excellent cycle performance and first-efficiency, providing a feasible path for the innovation of lithium-ion battery technology.

[0033] In a preferred embodiment, the metal ions in the soluble metal salt are selected from one or more of alkali metal ions, alkaline earth metal ions, transition metal ions, and aluminum ions. As described above, ammonia in the reaction system can react with the metal ions in the soluble metal salt under the action of a reducing agent containing an aldehyde group, undergoing a first reaction similar to the "silver mirror reaction" to generate a substance containing metal ions. The resulting substance containing metal ions can fully react with selenane (SeH2) to generate nanoscale metal selenide microcrystals. The metal selenide microcrystals generated above will have a positive inducing effect on the subsequent silicon deposition process, thereby making the performance of the prepared silicon-based composite anode material more uniform. In addition, the presence of metal selenide nanocrystals in the material accelerates the lithium ion insertion / extraction process in the composite anode material and optimizes its electrochemical reaction kinetics. When the metal ions in the soluble metal salt are selected from the specific types mentioned above, the above effects are even better, and the performance of the prepared silicon-based composite anode material can be further improved. Preferably, the metal ions in the soluble metal salt are selected from Ag. + Al 3+ Na + K+, Ca 2+ Pb 2+ and Ce 2+ At least one of the following; the metal ions in the soluble metal salt are of the specific types mentioned above, which can improve the performance of the prepared silicon-based composite anode material. For example, but not limitingly, the soluble metal salt is selected from at least one of silver nitrate, aluminum nitrate, sodium nitrate, potassium nitrate, calcium nitrate, lead nitrate, and cerium nitrate; more preferably, the soluble metal salt is selected from silver nitrate. Preferably, the temperature of the first reaction is 10–40°C, and the time is 0.5–2 h. Controlling the temperature and time of the first reaction within the above ranges can improve the performance of the first reaction.

[0034] In a preferred embodiment, the weight ratio of the first solid to the selenane gas is (1-10):(1-50). Controlling the weight ratio of the first solid to the selenane gas within the above range allows for better generation of metal selenide microcrystalline particles, thereby better utilizing the role of the metal selenide microcrystalline particles and improving the electrochemical performance of the prepared silicon-based composite anode material. Preferably, the weight ratio of the activation gas to the first mixture is (1-10):(1-50). Controlling the weight ratio of the activation gas to the first mixture within the above range during the activation and pore-forming operation allows for a richer pore size distribution in the obtained second solid, better forming a porous silicon composite material. Preferably, the weight ratio of the third solid to the silane gas is (1-10):(1-50). Controlling the weight ratio of the third solid to the silane gas within the above range allows for better high conductivity and mechanical stability, and better capacity in the prepared silicon-based composite anode material. More preferably, the weight ratio of the first solid to the selenane gas is (2-10):1; and / or, the weight ratio of the third solid to the silane gas is (1-10):(1-10). By controlling the weight ratio of the first solid to the selenane gas and the weight ratio of the third solid to the silane gas within the above ranges, the overall electrochemical performance of the prepared silicon-based composite anode material can be further improved.

[0035] In a preferred embodiment, the aldehyde-containing organic reducing agent is selected from one or more of formaldehyde, acetaldehyde, and glucose. The aldehyde-containing reducing agent can react with ammonia and metal ions in the soluble metal salt in the first reaction system in a first reaction similar to the "silver mirror reaction," generating a substance containing metal ions. The aforementioned specific types of reducing agents have better reducing properties and are also inexpensive and readily available. Preferably, the concentration of the soluble metal salt is 0.05–0.2 mol / L; preferably, the mass concentration of ammonia is 5–10%; preferably, the weight ratio of the first carbon source, soluble metal salt, ammonia, and reducing agent in the first reaction system is (1–5):(2–10):(1–10):(1–10). Controlling the weight ratio of the first carbon source, soluble metal salt, ammonia, and reducing agent in the first reaction system within the above range allows the first reaction to proceed better.

[0036] In a preferred embodiment, the temperature of the first chemical vapor deposition is 300–1000°C, and the time is 1–6 hours. Controlling the temperature and time of the first chemical vapor deposition within the above range allows the metal ions in the first solid to react more fully with the selenane, thereby facilitating the better formation of nanoscale metal selenide microcrystals and making the microcrystals more uniformly mixed with the first carbon source. Preferably, the temperature of the second chemical vapor deposition is 500–800°C, and the time is 5–8 hours. Controlling the temperature and time of the second chemical vapor deposition within the above range allows the silicon material to be better deposited on the surface of the carbon material, thereby making the various components in the silicon-based composite anode material precursor more uniformly mixed. Preferably, the activation gas is at least one of water vapor or carbon dioxide; preferably, the temperature of the activation pore-forming process is 800–1500°C, and the time is 5–12 hours. When using steam for activation and pore-forming, the steam reacts with the carbon material at high temperatures. The steam erodes surface and internal defects in the carbon material, generating hydrogen and carbon monoxide or carbon dioxide. This process removes blockages such as tar and hydrocarbons, increasing the material's porosity. Simultaneously, the steam reacts with unstable carbon sites, creating new pores and further increasing the material's porosity. When using carbon dioxide for activation and pore-forming, the carbon dioxide reacts with the carbon material at high temperatures to generate carbon monoxide. During gas diffusion, this carbon dioxide creates a porous structure within the material, expanding existing pores. These activation and pore-forming operations result in a richer pore size distribution in the obtained second solid, leading to a better formation of porous silicon composite materials. In particular, controlling the activation process parameters within the aforementioned ranges further enhances the effectiveness of the activation and pore-forming operation.

[0037] In a preferred embodiment, the first carbon source is selected from one or more of phenolic resin, petroleum coke-based materials, and biomass materials. These types of carbon sources not only have high carbon content but also contain unstable groups (such as hydroxyl and carboxyl groups) or polymerizable monomers. Using these specific types as the first carbon source is beneficial for further improving the electrochemical performance of the generated silicon-based composite anode material. Preferably, the first drying temperature is 80–120°C, and the time is 12–16 hours; preferably, the second drying temperature is 200–500°C, and the time is 2–12 hours; preferably, the first and second drying are vacuum drying.

[0038] In a preferred embodiment, the step of coating the second carbon source onto the surface of the silicon-based composite anode material precursor includes: mixing the second carbon source with the silicon-based composite anode material precursor in gaseous form, and performing the coating operation through a third vapor phase deposition. Using the above method to coat the second carbon source onto the surface of the silicon-based composite anode material precursor can further promote the formation of carbon nanotubes on the surface of the precursor, thereby constructing a silicon-carbon composite material with higher conductivity and higher stability. Specifically, the carbon nanotube formation process includes: the second carbon source pyrolyzes on the surface of a metal catalyst to generate carbon atoms, and the pyrolyzed carbon atoms dissolve in the metal particles to form a solid solution. When the carbon atoms in the metal particles are supersaturated, the carbon atoms precipitate from the inertial plane of the metal particles and then connect to form carbon nanotubes through a graphite hexagonal coil structure via tip growth or root growth.

[0039] On the other hand, the metal selenide nanocrystals on the material surface can also promote the growth of carbon nanotubes. These carbon nanotubes fill the pores of the porous carbon framework, increasing the structural stability of the material and forming a continuous conductive network, significantly improving the electronic conductivity. By growing carbon nanotubes on the material surface, a three-dimensional conductive network is formed, greatly enhancing the electronic conductivity of the composite anode material. This not only helps to improve the electrochemical reaction rate but also facilitates the rapid migration of lithium ions, reduces polarization during charge and discharge, and improves the cycle performance of the material. Furthermore, the filling effect of carbon nanotubes reduces the specific surface area of ​​the material, thereby reducing the volume expansion caused by lithium ion insertion and extraction. Compared to the conventional method of carbon coating of silicon-based composite anode material precursors using ball milling, mixing a second carbon source in gaseous form with the silicon-based composite anode material precursor results in a more uniform and homogeneous carbon coating in the formed silicon-based composite anode material.

[0040] Preferably, the weight ratio of the second carbon source to the silicon-based composite anode material precursor is (0.01–0.2):1. Preferably, the second carbon source is one or more of acetylene, ethylene, and methane; using the above carbon sources and controlling the weight ratio of the second carbon source to the silicon-based composite anode material precursor within the above range can further improve the electrochemical performance of the prepared silicon-based composite anode material. Preferably, the temperature of the third chemical vapor deposition is 500–800°C, and the time is 2–12 h. Controlling the temperature and time of the third chemical vapor deposition within the above range allows the second carbon source to better coat the surface of the silicon-based composite anode material precursor, thereby enabling better formation of the carbon nanotube structure on the material surface, and thus improving the performance of the prepared silicon-based composite anode material.

[0041] In a preferred embodiment, the pickling solution used in the pickling process is selected from one or more of hydrochloric acid, acetic acid, sulfuric acid, and citric acid; preferably, the mass concentration of the pickling solution is 5-10%; preferably, the separation operation is carried out by vacuum filtration; more preferably, the vacuum filtration time is 10-20 minutes. Controlling the parameters in the preparation process of silicon-based composite anode material within the above range is beneficial to further improve the electrochemical performance of the prepared silicon-based composite anode material.

[0042] In a preferred embodiment, before performing the second chemical vapor deposition, the preparation method further includes: before performing the first chemical vapor deposition, the preparation method further includes: introducing a first protective gas to remove air from the reaction system; and / or, before performing the second chemical vapor deposition, the preparation method further includes: introducing a second protective gas to remove air from the reaction system; preferably, the second protective gas and the second protective gas are each independently selected from one or more of helium, argon, and nitrogen; preferably, after the second solid is crushed and sieved, the particle size of the fifth solid obtained is 3μm≤D50≤10μm; preferably, a washing operation is performed with water; preferably, the washing time is 1-5 hours. The washing process can remove residual by-products and impurities on the surface of the second solid and further optimize the pore structure of the material, improving the purity and stability of the material. Performing the above washing operation with water yields better results. Controlling the parameters in the preparation process of the silicon-based composite anode material within the above range can improve the electrochemical performance of the prepared silicon-based composite anode material.

[0043] According to a second aspect of the present invention, a silicon-based composite anode material is also provided, which is prepared by the above-described preparation method. In the process of preparing the silicon-based composite anode material, the present invention successfully constructs a novel silicon-based composite anode material by introducing metal nanocrystals and utilizing their catalytic and structural effects. This material not only significantly improves electrochemical capacity and mechanical strength, but also enables lithium-ion batteries to possess good cycle performance and first-efficiency. Preferably, the specific surface area of ​​the silicon-based composite anode material is ≥1800 m². 2 / g, pore volume ≥0.9cm³ 3 / g, micropore ratio ≥80%. Controlling the specific surface area, pore capacity, and micropore ratio of silicon-based composite anode materials within the above range can further improve the performance of the prepared silicon-based composite anode materials.

[0044] It should be further noted that, due to the special nature of the materials field and the limitations of existing testing and characterization methods, it is difficult to fully and quantitatively characterize the complex microstructure of the silicon-based composite anode material obtained above. However, experiments show that using the silicon-based composite anode material prepared in this application as an anode material can effectively improve the overall performance of the battery.

[0045] According to a third aspect of the present invention, a negative electrode sheet is also provided, the negative electrode sheet comprising a current collector and a negative electrode material layer located on one side surface of the current collector, the material of the negative electrode material layer comprising a negative electrode active material, the negative electrode active material comprising the aforementioned silicon-based composite negative electrode material.

[0046] According to a fourth aspect of the present invention, a lithium-ion battery is also provided, comprising the aforementioned negative electrode sheet. Using the silicon-based composite negative electrode material prepared by the method provided in this application as the negative electrode active material in the negative electrode sheet enables the prepared lithium-ion battery to have a higher battery capacity while further improving its cycle stability.

[0047] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0048] Example 1

[0049] (1) Preparation of silicon-based composite anode materials

[0050] One kilogram of a first carbon source (phenolic resin), 0.5 kilograms of a 5% ammonia solution, 5 kilograms of a 0.05 mol / L soluble metal salt solution (silver nitrate solution), and 0.5 kilograms of a 5% acetaldehyde solution (reducing agent) were mixed and stirred at 30°C for 1 hour to carry out the first reaction. After the reaction was completed, a 5% acetic acid solution was added to the resulting reaction solution and stirred for 30 minutes. Then, the mixture was filtered for 10 minutes, and the resulting solid was transferred to a vacuum oven and dried under vacuum at 100°C for 12 hours to obtain the first solid.

[0051] The first solid was transferred to a rotary kiln. Argon gas was first introduced to purge the air from the kiln, followed by the introduction of selenoethane and argon gases. The mixture was then subjected to first chemical vapor deposition at 300°C for 3 hours at a kilometer speed of 1 r / min, yielding a first mixture (wherein, the selenoethane gas flow rate was 5 L / h, the argon gas flow rate was 5 L / h, and the weight ratio of the first solid to the selenoethane gas was 2:1). Water vapor was then introduced into the mixture obtained after vapor deposition at a rate of 5 L / h and activated at 800°C to create pores (the weight ratio of the activation gas to the first mixture was 2:1). After cooling to room temperature, the resulting second mixture yielded the second solid.

[0052] The second solid was ground in a mechanical mill until the D50 was 5 μm. Then, 500 g of the material was placed in a beaker, and 3 kg of deionized water was added for washing for 2 h. This process was repeated 3 times. The material was then transferred to a box furnace and dried under vacuum at 300 °C for 5 h to obtain the third solid. The third solid was then transferred to a rotary furnace. Argon gas was first introduced to purge the air from the rotary furnace, and then silane gas and argon gas were introduced. The furnace was held at 600 °C for 6 h at a furnace rotation speed of 1 r / min to perform the second chemical vapor deposition (during the above process, the flow rate of silane gas was 5 L / h, the flow rate of argon gas was 5 L / h, and the weight ratio of the third solid to silane gas was 1:2) to obtain the silicon-based composite anode material precursor.

[0053] A silicon-based composite anode material precursor was mixed with a second carbon source (acetylene), and carbon coating (third chemical vapor deposition) was performed by chemical vapor deposition at 700℃ for 8 hours at a furnace rotation speed of 1 r / min (the weight ratio of silicon-based composite anode material precursor to second carbon source was 10:1). After cooling, a silicon-based composite anode material was obtained, wherein the weight content of the second carbon source in the silicon-based composite anode material was 3%. The prepared silicon-based composite anode material was characterized by SEM, and the results are as follows. Figure 1 As shown, according to Figure 1 It can be seen that the silicon-based composite anode material prepared by the above preparation method exhibits a spherical morphology with a smooth surface and uniform morphology.

[0054] (2) Battery assembly

[0055] The silicon-based composite negative electrode prepared in the above examples and comparative examples was mixed with conductive carbon black (SP) and polyacrylonitrile (LA133) at a weight ratio of 8:1:1, and then coated with a 12 μm thick layer onto the surface of a 6 μm thick copper current collector to form a negative electrode sheet. The resulting negative electrode sheet was then assembled into a CR2016 coin cell using a stacking method. The preparation method of the positive electrode sheet of the above coin cell includes: using LiNi as the positive electrode active material... 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 8:1:1 to form a slurry. This slurry was then coated with a 12 μm thick layer onto an 8 μm thick aluminum current collector. After drying, the positive electrode was formed. The electrolyte was a 1 mol / L LiPF6 solution of ethylene carbonate (EC) and dimethyl carbonate (DMC), in which EC and DMC were mixed in a volume ratio of 3:7.

[0056] Example 2

[0057] (1) Preparation of silicon-based composite anode materials

[0058] One kilogram of a first carbon source (petroleum coke), 0.5 kilograms of a 5% ammonia solution, 5 kilograms of a 0.05 mol / L soluble metal salt solution (silver nitrate solution), and 0.5 kilograms of a 5% formaldehyde solution (reducing agent) were mixed and stirred at 10°C for 2 hours to carry out the first reaction. After the reaction was completed, a 5% acetic acid solution was added to the resulting reaction solution and stirred for 30 minutes. Then, the mixture was filtered for 10 minutes, and the resulting solid was transferred to a vacuum oven and dried under vacuum at 80°C for 16 hours to obtain the first solid.

[0059] The first solid was transferred to a rotary kiln. Argon gas was first introduced to purge the air from the kiln, followed by the introduction of selenoethane and argon gases. The mixture was then subjected to first chemical vapor deposition at 300°C for 6 hours at a kilometer speed of 1 r / min, yielding a first mixture (wherein, the selenoethane gas flow rate was 5 L / h, the argon gas flow rate was 5 L / h, and the weight ratio of the first solid to the selenoethane gas was 2:1). Water vapor was then introduced into the mixture obtained after vapor deposition at a rate of 5 L / h and activated at 800°C to create pores (the weight ratio of the activation gas to the first mixture was 10:1). The resulting second mixture was cooled to room temperature to obtain the second solid.

[0060] The second solid was ground in a mechanical mill until the D50 was 5 μm. Then, 500 g of the material was placed in a beaker, and 3 kg of deionized water was added for washing for 2 h. This process was repeated 3 times. The material was then transferred to a box furnace and dried under vacuum at 200 °C for 12 h to obtain the third solid. The third solid was then transferred to a rotary furnace. Argon gas was first introduced to purge the air from the rotary furnace, and then silane gas and argon gas were introduced. The furnace was held at 600 °C for 6 h at a furnace speed of 1 r / min to perform the second chemical vapor deposition (during the above process, the flow rate of silane gas was 5 L / h, the flow rate of argon gas was 5 L / h, and the weight ratio of the third solid to silane gas was 1:2) to obtain the silicon-based composite anode material precursor.

[0061] The silicon-based composite anode material precursor was mixed with a second carbon source (ethylene), and carbon coating was carried out by chemical vapor deposition (third chemical vapor deposition) at 500℃ for 12 hours under the condition of furnace rotation speed of 1 r / min (the weight ratio of silicon-based composite anode material precursor to second carbon source is 10:1). After cooling, the silicon-based composite anode material was obtained, wherein the weight content of the second carbon source in the silicon-based composite anode material is 3%.

[0062] (2) Battery assembly

[0063] The silicon-based composite negative electrode prepared in the above examples and comparative examples was mixed with conductive carbon black (SP) and polyacrylonitrile (LA133) at a weight ratio of 8:1:1, and then coated with a 12 μm thick layer onto the surface of a 6 μm thick copper current collector to form a negative electrode sheet. The resulting negative electrode sheet was then assembled into a CR2016 coin cell using a stacking method. The preparation method of the positive electrode sheet of the above coin cell includes: using LiNi as the positive electrode active material... 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 8:1:1 to form a slurry. This slurry was then coated with a 12 μm thick layer onto an 8 μm thick aluminum current collector. After drying, the positive electrode was formed. The electrolyte was a 1 mol / L LiPF6 solution of ethylene carbonate (EC) and dimethyl carbonate (DMC), in which EC and DMC were mixed in a volume ratio of 3:7.

[0064] Example 3

[0065] (1) Preparation of silicon-based composite anode materials

[0066] One kilogram of a first carbon source (phenolic resin), 0.5 kilograms of a 5% ammonia solution, 5 kilograms of a 0.05 mol / L soluble metal salt solution (silver nitrate solution), and 0.5 kilograms of a 5% glucose solution (reducing agent) were mixed and stirred at 40°C for 0.5 h to carry out the first reaction. After the reaction was completed, a 5% acetic acid solution was added to the resulting reaction solution and stirred for 30 min, followed by filtration for 10 min. The resulting solid was transferred to a vacuum oven and dried under vacuum at 120°C for 12 h to obtain the first solid.

[0067] The first solid was transferred to a rotary kiln. Argon gas was first introduced to purge the air from the kiln, followed by the introduction of selenoethane and argon gases. The mixture was then subjected to first chemical vapor deposition at 1000°C for 2 hours at a kilometer speed of 1 r / min, yielding a first mixture (wherein, the selenoethane gas flow rate was 5 L / h, the argon gas flow rate was 5 L / h, and the weight ratio of the first solid to the selenoethane gas was 2:1). Water vapor was then introduced into the mixture obtained after vapor deposition at a rate of 5 L / h and activated at 800°C to create pores (the weight ratio of the activation gas to the first mixture was 1:50). After cooling to room temperature, the resulting second mixture yielded the second solid.

[0068] The second solid was ground in a mechanical mill until the D50 was 5 μm. Then, 500 g of the material was placed in a beaker, and 3 kg of deionized water was added for washing for 2 h. This process was repeated 3 times. The material was then transferred to a box furnace and dried under vacuum at 500 °C for 2 h to obtain the third solid. The third solid was then transferred to a rotary furnace. Argon gas was first introduced to purge the air from the rotary furnace, and then silane gas and argon gas were introduced. The furnace was held at 600 °C for 6 h at a furnace rotation speed of 1 r / min to perform the second chemical vapor deposition (during the above process, the flow rate of silane gas was 5 L / h, the flow rate of argon gas was 5 L / h, and the weight ratio of the third solid to silane gas was 1:2) to obtain the silicon-based composite anode material precursor.

[0069] A silicon-based composite anode material precursor was mixed with a second carbon source (methane), and carbon coating (third chemical vapor deposition) was carried out by holding at 800℃ for 2 hours at a furnace rotation speed of 1 r / min (the weight ratio of silicon-based composite anode material precursor to second carbon source was 10:1). After cooling, a silicon-based composite anode material was obtained, wherein the weight content of the second carbon source in the silicon-based composite anode material was 3%.

[0070] (2) Battery assembly

[0071] The silicon-based composite negative electrode prepared in the above examples and comparative examples was mixed with conductive carbon black (SP) and polyacrylonitrile (LA133) at a weight ratio of 8:1:1, and then coated with a 12 μm thick layer onto the surface of a 6 μm thick copper current collector to form a negative electrode sheet. The resulting negative electrode sheet was then assembled into a CR2016 coin cell using a stacking method. The preparation method of the positive electrode sheet of the above coin cell includes: using LiNi as the positive electrode active material... 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (SP), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 8:1:1 to form a slurry. This slurry was then coated with a 12 μm thick layer onto an 8 μm thick aluminum current collector. After drying, the positive electrode was formed. The electrolyte was a 1 mol / L LiPF6 solution of ethylene carbonate (EC) and dimethyl carbonate (DMC), in which EC and DMC were mixed in a volume ratio of 3:7.

[0072] Example 4

[0073] The difference between Example 4 and Example 1 is that the soluble metal salt solution used in the preparation of the silicon-based composite anode material is aluminum nitrate solution.

[0074] Example 5

[0075] The difference between Example 5 and Example 1 is that the soluble metal salt solution used in the preparation of the silicon-based composite anode material is lead nitrate solution.

[0076] Example 6

[0077] The difference between Example 6 and Example 1 is that the soluble metal salt solution used in the preparation of the silicon-based composite anode material is sodium nitrate solution.

[0078] Example 7

[0079] The difference between Example 7 and Example 1 is that the soluble metal salt solution used in the preparation of the silicon-based composite anode material is calcium nitrate solution.

[0080] Example 8

[0081] The difference between Example 8 and Example 1 is that, in the process of preparing silicon-based composite anode material, the temperature of the first chemical vapor deposition is 300°C and the time is 6 hours.

[0082] Example 9

[0083] The difference between Example 9 and Example 1 is that, in the process of preparing silicon-based composite anode material, the temperature of the first chemical vapor deposition is 1000℃ and the time is 1h.

[0084] Example 10

[0085] The difference between Example 10 and Example 1 is that the temperature of the second chemical vapor deposition in the preparation of silicon-based composite anode material is 500°C and the time is 8 hours.

[0086] Example 11

[0087] The difference between Example 11 and Example 1 is that, in the process of preparing silicon-based composite anode material, the temperature of the second chemical vapor deposition is 800°C and the time is 5 hours.

[0088] Example 12

[0089] The difference between Example 12 and Example 1 is that, in the process of preparing silicon-based composite anode material, the weight ratio of the first solid to selenane gas is 1:50; and the weight ratio of the third solid to silane gas is 1:50.

[0090] Example 13

[0091] The difference between Example 13 and Example 1 is that, in the process of preparing silicon-based composite anode material, the weight ratio of the first solid to selenane gas is 10:1; and the weight ratio of the third solid to silane gas is 10:1.

[0092] Example 14

[0093] The difference between Example 14 and Example 1 is that, in the process of preparing silicon-based composite anode material, the temperature of the first chemical vapor deposition is 500°C and the time is 0.5h, while the temperature of the second chemical vapor deposition is 500°C and the time is 3h.

[0094] Example 15

[0095] The difference between Example 15 and Example 1 is that, in the process of preparing silicon-based composite anode material, the weight ratio of the first solid to selenane gas is 12:1; and the weight ratio of the third solid to silane gas is 12:1.

[0096] Comparative Example 1

[0097] The silicon-based composite anode material used in the fabrication of the coin cells was purchased. This silicon-based composite anode material is a bulk resin-based material with a D50 of 8 μm, a specific capacity of 1600–1800 mAh / g, and an initial efficiency of 84–88%. The silicon-based composite anode material was characterized by SEM, and the results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the silicon-based composite anode material has an irregular morphology.

[0098] Comparative Example 2

[0099] Phenolic resin was mixed with a curing agent (hexamethylenetetramine) and cured at 150-180℃ to form a block resin. In an inert atmosphere (N2), the temperature was increased to 800℃ at 5℃ / min and held for 2 hours to obtain primary carbon. The primary carbon was mixed with KOH at a mass ratio of 1:4 and activated at 700℃ for 2 hours. After washing until neutral, it was dried to obtain block resin porous carbon. The block resin porous carbon was placed in a chemical vapor deposition (CVD) chamber, and a mixture of silane (SiH4) and argon (Ar) gas (volume ratio 1:10) was introduced at a total flow rate of 50 sccm. Deposition was carried out at 650℃ for 2 hours, where silicon atoms were deposited on the porous carbon surface to form silicon nanoparticles. Acetylene (C2H2) was then introduced for carbon coating at 500℃ for 1 hour. After deposition, the sample was allowed to cool naturally to room temperature and removed to obtain a silicon-based composite anode material.

[0100] The electrochemical performance of the above-mentioned coin cells was tested, and the results are shown in Table 1. The initial discharge specific capacity was tested under the following conditions: 25℃, 0.05C discharge to 0.005V; the initial charge specific capacity was tested under the following conditions: 25℃, 0.1C charge to 1.5V; the initial coulombic efficiency was calculated as the ratio of the initial charge specific capacity to the initial discharge specific capacity; and the capacity retention rate was tested under the following conditions: 25℃, 1000 cycles, and a voltage range of 2.75V to 4.25V.

[0101] Table 1

[0102]

[0103] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0104] In Examples 1 to 15, the silicon-based composite anode materials prepared using the preparation method provided in this application were used as anode active materials in the fabrication of coin cells. According to the data in Table 1, the coin cells in the above examples not only possess excellent charge-discharge capacity, but also exhibit good initial efficiency and cycle stability. In particular, controlling the parameters during the preparation of the silicon-based composite anode material within the preferred range results in even better overall electrochemical performance of the corresponding coin cells.

[0105] In Comparative Example 1, the silicon-based composite anode material used was commercially available. In Comparative Example 2, the silicon-based composite anode material was prepared using conventional methods. According to the data in the table, the battery capacity, initial efficiency, and cycle performance of the coin cells corresponding to Examples 1 and 2 are significantly different from those of the coin cells corresponding to the embodiments of this application.

[0106] Furthermore, the initial charge and discharge conditions of the coin cells corresponding to Example 1 and Comparative Example 1 were plotted as curves to obtain... Figure 3 The first charge-discharge curve shown; according to Figure 3 It can be seen that the coin cell corresponding to Example 1 has better initial efficiency performance. The cycle performance of the coin cells corresponding to Example 1 and Comparative Example 1 is plotted as curves, yielding... Figure 4 The cycle performance curve shown; according to Figure 4 It can be seen that the coin cell corresponding to Example 1 exhibits excellent cycle stability. The crushing force test was performed on the silicon-based composite anode materials corresponding to Example 1, Comparative Example 1, and Comparative Example 2, and the results are as follows: Figure 5 As shown, according to Figure 5 It can be seen that the silicon-based composite anode material prepared in Example 1 has better mechanical properties.

[0107] In summary, this application successfully constructed a novel silicon-based composite anode material by introducing metal nanocrystals and utilizing their inductive effect during the preparation of the silicon-based composite anode material. The resulting composite anode material not only significantly improves the electrochemical capacity but also possesses good cycle performance and first-efficiency, providing a feasible path for the innovation of lithium-ion battery technology.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-based composite anode material, characterized in that, The preparation method includes the following steps: In the presence of a first carbon source, ammonia, a soluble metal salt, and a reducing agent are mixed to carry out a first reaction to obtain a reaction solution; the reaction solution is then subjected to acid washing, separation, and a first drying to obtain a first solid; wherein the reducing agent is an organic reducing agent containing an aldehyde group; The first solid is mixed with selenane gas to perform a first chemical vapor deposition to form a first mixture; an activation gas is passed into the first mixture to activate and create pores, resulting in a second mixture; the second mixture is cooled to obtain a second solid. The second solid is successively crushed, sieved, washed, and dried to obtain a third solid; the third solid is mixed with silane gas to perform a second chemical vapor deposition to obtain a silicon-based composite anode material precursor. The silicon-based composite anode material precursor is obtained by coating the surface of the second carbon source onto it.

2. The method for preparing the silicon-based composite anode material according to claim 1, characterized in that, The metal ions in the soluble metal salt are selected from one or more of alkali metal ions, alkaline earth metal ions, transition metal ions, and aluminum ions. And / or, the metal ions in the soluble metal salt are selected from Ag. + Al 3+ Na + K + Ca 2+ Pb 2+ and Ce 2+ At least one of them; And / or, the soluble metal salt is selected from at least one of silver nitrate, aluminum nitrate, sodium nitrate, potassium nitrate, calcium nitrate, lead nitrate, and cerium nitrate; And / or, the soluble metal salt is selected from the silver nitrate; And / or, the temperature of the first reaction is 10–40°C, and the time is 0.5–2 h.

3. The method for preparing the silicon-based composite anode material according to claim 1, characterized in that, The weight ratio of the first solid to the selenane gas is (1-10):(1-50); And / or, the weight ratio of the activating gas to the first mixture is (1-10):(1-50); And / or, the weight ratio of the third solid to the silane gas is (1-10):(1-50).

4. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 3, characterized in that, The aldehyde-containing organic reducing agent is selected from one or more of formaldehyde, acetaldehyde, and glucose; And / or, the concentration of the soluble metal salt is 0.05–0.2 mol / L; And / or, the mass concentration of the ammonia solution is 5-10%; And / or, in the first reaction system, the weight ratio of the first carbon source, the soluble metal salt, the ammonia water and the reducing agent is (1-5):(2-10):(1-10):(1-10).

5. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 3, characterized in that, The temperature of the first chemical vapor deposition is 300–1000℃, and the time is 1–6 hours; And / or, the temperature of the second chemical vapor deposition is 500–800°C, and the time is 5–8 hours; And / or, the temperature of the activation pore-forming process is 800–1500°C, and the time is 5–12 hours; And / or, the activating gas is at least one of water vapor or carbon dioxide.

6. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 3, characterized in that, The first carbon source is selected from one or more of phenolic resin, petroleum coke, coal-based materials, and biomass materials; And / or, the temperature of the first drying is 80-120°C, and the time is 12-16 hours; And / or, the second drying temperature is 200–500°C, and the time is 2–12 hours; And / or, the first drying and the second drying are vacuum drying.

7. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 3, characterized in that, The step of coating the second carbon source onto the surface of the silicon-based composite anode material precursor includes: mixing the second carbon source with the silicon-based composite anode material precursor in the form of a gas, and performing the coating operation by a third vapor deposition.

8. The method for preparing the silicon-based composite anode material according to claim 7, characterized in that, The weight ratio of the second carbon source to the silicon-based composite anode material precursor is (0.01–0.2):1; And / or, the second carbon source is one or more of acetylene, ethylene, and methane; And / or, the temperature of the third chemical vapor deposition is 500–800°C, and the time is 2–12 h.

9. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 3, characterized in that, The pickling solution used in the pickling process is selected from one or more of hydrochloric acid, acetic acid, sulfuric acid, and citric acid; And / or, the mass concentration of the pickling solution is 5-10%; And / or, the separation operation is performed by vacuum filtration; the vacuum filtration time is 10 to 20 minutes.

10. The method for preparing the silicon-based composite anode material according to any one of claims 1 to 3, characterized in that, Before performing the first chemical vapor deposition, the preparation method further includes: introducing a first protective gas to remove air from the reaction system; and / or, before performing the second chemical vapor deposition, the preparation method further includes: introducing a second protective gas to remove air from the reaction system.

11. The method for preparing the silicon-based composite anode material according to claim 10, characterized in that, The second protective gas and the second protective gas are each independently selected from one or more of helium, argon and nitrogen; And / or, after the second solid is crushed and sieved, the particle size of the fifth solid obtained is 3μm≤D50≤10μm; And / or, the washing operation is performed with water; the washing time is 1 to 5 hours.

12. A silicon-based composite anode material, characterized in that, The silicon-based composite anode material is prepared by the preparation method according to any one of claims 1 to 11; And / or, the specific surface area of ​​the silicon-based composite anode material is ≥1800 m². 2 / g, pore volume ≥0.9cm³ 3 / g, micropores account for ≥80%.

13. A negative electrode sheet, comprising a current collector and a negative electrode material layer located on one side surface of the current collector, wherein the material of the negative electrode material layer comprises a negative electrode active material, characterized in that, The negative electrode active material includes the silicon-based composite negative electrode material as described in claim 12.

14. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode sheet as described in claim 13.

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