Silicon-based / graphene / carbon nanotube thick electrode material and preparation method and application thereof

Abstract

The invention discloses a silicon-based / graphene / carbon nanotube thick electrode material and a preparation method and application thereof, and relates to the technical field of lithium ion batteries, the preparation method comprises the following steps: (1) mixing a silicon-based material, a polymer, a metal catalyst and a solvent to obtain uniform slurry; (2) uniformly coating a current collector with the slurry, and heating and curing to form a thin film; (3) performing laser irradiation on the thin film to obtain a silicon-based / graphene composite material; and (4) vertically growing a carbon nanotube on the silicon-based / graphene composite material by using a chemical vapor deposition method to obtain the silicon-based / graphene / carbon nanotube thick electrode material. When the thick electrode material is used as a lithium ion battery negative electrode material, a lithium ion battery can have high initial coulombic efficiency, high area capacity, excellent rate capability and long cycle stability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a silicon-based / graphene / carbon nanotube thick electrode material, its preparation method, and its application. Background Technology

[0002] In recent years, with the increasing demand for longer driving ranges in electric vehicles and the rapid development of portable electronic devices towards thinner, lighter, and more multifunctional designs, the market's urgent need for high-energy-density, long-cycle-life lithium-ion batteries has continued to grow. Among numerous candidate anode materials, silicon-based materials are widely considered one of the key materials for improving the performance of existing graphite anodes and realizing next-generation high-energy-density lithium-ion batteries due to their extremely high theoretical specific capacity (approximately 4200 mAh / g), abundant crustal reserves, and environmental friendliness. However, the large-scale application of silicon-based anodes still faces a series of technical challenges, severely restricting their commercialization process.

[0003] First, silicon-based materials have low intrinsic conductivity, which restricts electron migration during charging and discharging, resulting in poor rate performance. Second, silicon-based materials undergo dramatic volume expansion during lithium intercalation, with a theoretical expansion rate exceeding 280%. Repeated expansion and contraction can easily lead to particle breakage, electrode structure collapse, and detachment of the active material from the current collector, resulting in rapid capacity decay. Furthermore, the surface of silicon-based materials is prone to irreversible side reactions with the electrolyte during the first and subsequent cycles, forming an unstable and continuously thickening porous solid electrolyte interphase (SEI) film. This not only consumes a large amount of active lithium but also significantly increases interfacial impedance, further deteriorating cycle stability and coulombic efficiency.

[0004] To alleviate these problems, traditional strategies include nanostructuring silicon-based materials (such as nanoparticles, nanowires, and thin films) or combining them with carbon materials to improve conductivity and buffer volume changes. However, these methods often have limitations: nanostructuring processes are complex, have low yields, and are prone to agglomeration; while some carbon composite structures can improve conductivity, they struggle to simultaneously achieve ion transport and mechanical stability. For example, graphene possesses excellent conductivity and mechanical strength, but its two-dimensional sheets tend to stack during the composite process, forming dense barriers that restrict the effective diffusion of lithium ions in thick electrodes; carbon nanotubes can construct three-dimensional conductive networks and provide vertical ion channels, but they tend to be randomly distributed in electrode slurries and have insufficient interfacial adhesion with silicon-based materials or graphene, resulting in poor network connectivity and ineffective stress dispersion.

[0005] Meanwhile, the pursuit of higher battery energy density in electric vehicles and energy storage systems is driving electrode design towards higher load capacity and thicker electrodes, aiming to accommodate more active material per unit area. However, thick electrodes extend the transport paths of electrons and ions, easily forming significant transport barriers within the material, leading to increased polarization and decreased rate performance. While traditional thin electrodes can reduce transport resistance, they cannot meet the practical demands of high energy density. Therefore, existing solutions still have shortcomings in addressing the three major challenges of silicon's massive volume expansion, low conductivity, and unstable SEI, especially lacking an integrated strategy that can simultaneously optimize at multiple scales: macroscopic structure (such as the three-dimensional conductive network of thick electrodes), mesoscopic interfaces (such as stable inorganic-rich SEI), and microscopic composition (such as silicon / carbon synergy).

[0006] In summary, developing a silicon-based composite anode material with controllable fabrication process, stable structure, and friendly interface can simultaneously solve the mechanical failure caused by volume expansion, the rate limitation caused by insufficient conductive network, and the cycle degradation caused by SEI instability. This has become a crucial direction for breakthroughs in the current lithium-ion battery field. This will not only help improve the overall electrochemical performance of silicon-based anodes but also provide key material foundations and technological support for realizing next-generation lithium-ion batteries with high energy density and long lifespan. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing silicon-based / graphene / carbon nanotube thick electrode materials, and to apply the obtained silicon-based / graphene / carbon nanotube thick electrode materials to lithium-ion batteries, so that lithium-ion batteries can take into account high energy density, long cycle life and high rate performance.

[0008] The technical problem to be solved by this invention is achieved by the following technical solution: One objective of this invention is to provide a method for preparing silicon-based / graphene / carbon nanotube thick electrode materials, the method comprising the following steps: (1) A homogeneous slurry is obtained by mixing silicon-based materials, polymers, metal catalysts and solvents; (2) The slurry is evenly coated onto the current collector and heated to cure, forming a thin film; (3) The thin film was irradiated with laser to obtain a silicon-based / graphene composite material; (4) Carbon nanotubes were vertically grown on silicon-based / graphene composite material by chemical vapor deposition to obtain silicon-based / graphene / carbon nanotube thick electrode material.

[0009] Furthermore, the preparation method further includes repeating steps (1) to (3) multiple times after obtaining the silicon-based / graphene composite material in step (3), so that the silicon-based / graphene composite material is stacked layer by layer to obtain a thick electrode material. The types and amounts of silicon-based materials and polymers used in each layer can be the same or different.

[0010] Furthermore, the silicon-based material includes, but is not limited to, one or more of silicon suboxide, elemental silicon, silicon carbide, silicon nitride, silicon-oxygen-carbon, silicon alloy, and lithium silicate. Even further, the size of the silicon-based material is 0.1 nm to 50 μm.

[0011] Furthermore, the polymer includes, but is not limited to, one or more of polyethylene, polypropylene, polystyrene, polysulfide rubber, polyvinyl chloride, polyetheretherketone, polyphenylene sulfide, polyethersulfone, polyaryletherketone, polyimide, polyester, polyamide, and polyurethane.

[0012] Furthermore, the metal catalyst includes, but is not limited to, one or more of the following: elemental metals (transition metals such as iron, cobalt, and nickel; refractory elemental metals such as molybdenum and tungsten; rare earth elemental metals such as yttrium and lanthanum); metal alloys (bimetallic alloys, high-entropy alloys); metal oxides (single oxides such as ferric oxide, magnetite, molybdenum dioxide, and tungsten oxide; spinel-type oxides such as cobalt tetroxide and nickel ferrite; perovskite-type oxides such as lanthanum cobaltate); and metal salts (inorganic acid salts such as ferric chloride, ferric nitrate, and ferrous sulfate; organic acid salts such as ferric acetate and cobalt acetylacetonate; and co-catalyst salts such as sodium molybdate and ammonium tungstate). Even further, the size of the metal catalyst is 0.1 nm to 50 μm.

[0013] Furthermore, the mass ratio of the silicon-based material, polymer, and metal catalyst is 1 : (0.1~5000) : (0.001~1000).

[0014] Furthermore, the current collector includes, but is not limited to, one or more of the following: continuous copper foil, copper wire braided copper mesh, foamed copper, three-dimensional nanoporous copper foil, continuous carbon-coated copper foil, three-dimensional nanoporous carbon-coated copper foil, nickel foil, foamed nickel, carbon cloth, stainless steel sheet, alloy current collector, metal-polymer composite current collector, and titanium foil.

[0015] Furthermore, the laser is one or more of solid-state lasers, liquid lasers, gas lasers, semiconductor lasers, and fiber lasers.

[0016] Furthermore, the laser irradiation has a wavelength of 0.05~200 μm, a power of 0.05~5000 W, a scanning rate of 0.01~2000 mm / s, a scanning spacing of 0.001~1000 mm, a pulse frequency of 0.001~1000 kHz, a duty cycle of 0.1~100%, a focal length of 0.1~2000 cm, and a voltage of 0.1~10000 kV, and is carried out in an air, inert gas, or vacuum environment.

[0017] Furthermore, the thickness of the silicon-based / graphene composite material is 0.1~1000 μm.

[0018] Furthermore, the chemical vapor deposition temperature is 10~2000℃, the time is 0.01~200 h, the heating rate is 0.01~25℃ / min, the pressure is 0.001~50000 kPa, and the gas flow rate is 0.01~10000 mL / min.

[0019] Furthermore, the carbon source gas for the chemical vapor deposition is one or more of methane, ethylene, propylene, and acetylene, and the auxiliary gas is one or more of hydrogen, argon, nitrogen, carbon monoxide, oxygen, propylene, and ammonia. Even further, the volume ratio of the carbon source gas to the auxiliary gas is 1:(0.01~99.9).

[0020] Furthermore, the carbon nanotubes are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. Even further, the carbon nanotubes have a diameter of 0.01~1000 nm and a length of 0.001~2000 μm.

[0021] Furthermore, the thickness of the silicon-based / graphene / carbon nanotube thick electrode material is 0.1~1000 μm.

[0022] The second objective of this invention is to provide a silicon-based / graphene / carbon nanotube thick electrode material obtained by the aforementioned preparation method.

[0023] The third objective of this invention is to provide the application of the aforementioned silicon-based / graphene / carbon nanotube thick electrode materials in lithium-ion batteries.

[0024] The beneficial effects of this invention are: 1. The raw materials selected for this invention are broad and inexpensive. Metallurgical-grade silicon powder, silicon alloy microparticles, and recycled silicon waste can be flexibly used as silicon-based raw materials. The metal catalyst can be selected from transition metals with catalytic activity, such as iron, nickel, and copper. The polymers are widely available, and the carbon source gases (such as methane, ethylene, and acetylene) are also bulk industrial products. These raw material systems do not rely on high-purity nano-silicon or expensive single-walled carbon nanotubes, reducing raw material costs from the source, improving resource recycling rates, and allowing for customization of different particle sizes, morphologies, and conductivity properties through raw material ratio control, providing an economically feasible basis for large-scale production.

[0025] 2. The preparation method provided by this invention integrates three processes: coating-heat curing, laser irradiation, and chemical vapor deposition, forming complementary advantages. The first step, coating-curing, is simple and controllable, and can be completed at room temperature and pressure, making it suitable for large-area current collector loading. The second step, laser irradiation, utilizes the photothermal effect to generate high-energy-density thermal shock in a very short time, embedding silicon-based particles and metal catalysts into the graphene framework, shortening the reaction time, avoiding excessive growth and agglomeration of silicon grains, and simultaneously removing oxygen functional groups from graphene, improving conductivity and crystal quality. The third step, chemical vapor deposition, grows vertically oriented carbon nanotubes in situ, constructing a continuous three-dimensional conductive network on the graphene surface. The entire process requires no solvent, uses few types of reaction gases, and is recyclable, making it a green, low-energy-consumption, and short-cycle process. Furthermore, the parameters of each step can be precisely adjusted, ensuring the controllability and repeatability of the material structure.

[0026] 3. The silicon-based / graphene / carbon nanotube thick electrode material of this invention achieves multi-scale synergistic optimization in structure: vertically oriented carbon nanotubes and graphene intertwine to form a continuous three-dimensional conductive network, significantly reducing the resistance to electron and ion transport inside the thick electrode and improving the areal capacity of high-load electrodes; the directional ion channels formed by carbon nanotubes and the homogenized electric field induced by space charge can reduce the ion transport barrier under fast charging conditions, alleviate concentration polarization and electrochemical polarization, and form a stable SEI layer rich in fast ion conductors (such as lithium oxide and lithium carbonate), suppressing the excessive generation of high-barrier lithium fluoride; the high aspect ratio and mechanical flexibility of carbon nanotubes, combined with the continuous conductive substrate of graphene, form an adaptive flexible coating network, which can dynamically match the huge volume expansion of silicon during charging and discharging (up to 280%), effectively buffering stress, suppressing particle pulverization and interlayer delamination, and maintaining the integrity of the electrode structure.

[0027] 4. The silicon-based / graphene / carbon nanotube thick electrode material of the present invention has excellent electrochemical characteristics: thanks to the synergistic effect of the vertical conductive network and flexible coating, the electrode obtains high initial discharge capacity and first coulombic efficiency, exhibiting excellent rate performance and long cycle stability; at the same time, the areal capacity of the thick electrode is significantly improved, which can meet the requirements of high energy density lithium-ion batteries for high load and low polarization.

[0028] 5. The preparation method provided by this invention also has advantages in terms of environmental protection and economy: the laser irradiation process does not require a high-temperature furnace and a large amount of inert gas protection, the chemical vapor deposition reaction gas can be recycled, the overall process has low energy consumption, low pollution, and high safety; the raw materials are widely available, the process flow is short, the equipment investment is relatively controllable, and it can be scaled up by modifying existing lithium battery electrode production lines, which has good scalability and commercialization prospects, and is expected to accelerate the practical application of silicon-based anodes in electric vehicle power batteries and large-scale energy storage systems.

[0029] 6. This invention overcomes the mutual constraints between electron / ion transport, interface stability, and mechanical integrity in traditional silicon-based thick electrodes by simultaneously optimizing at multiple scales, including macroscopic (thick electrode three-dimensional conductive network) and microscopic (fast kinetic SEI). It achieves a balance between high energy density, high power density, and long cycle life, meeting the stringent requirements of electric vehicles and portable electronic devices for next-generation lithium-ion batteries in terms of range, fast charging, and durability. This invention has significant scientific value and market promotion potential. Attached Figure Description

[0030] Figure 1 The image shows a scanning electron microscope (SEM) image of the silicon suboxide / graphene / carbon nanotube thick electrode material prepared in Example 1. Figure 2 Transmission electron microscope (TEM) image of the silicon suboxide / graphene / carbon nanotube thick electrode material prepared in Example 1; Figure 3 SEM image of the silicon suboxide / graphene thick electrode material prepared in Comparative Example 1; Figure 4 The cycling curves and coulombic efficiency of lithium-ion batteries using the silicon suboxide / graphene / carbon nanotube thick electrode material prepared in Example 1 and the silicon suboxide / graphene thick electrode material prepared in Comparative Example 1 as negative electrode materials are shown. Figure 5 The rate performance curves of lithium-ion batteries using the silicon suboxide / graphene / carbon nanotube thick electrode material prepared in Example 1 and the silicon suboxide / graphene thick electrode material prepared in Comparative Example 1 as negative electrode materials are shown. Figure 6 The electrochemical impedance spectroscopy (EIS) spectra of lithium-ion batteries using the silicon suboxide / graphene / carbon nanotube thick electrode material prepared in Example 1 and the silicon suboxide / graphene thick electrode material prepared in Comparative Example 1 as negative electrode materials are shown before and after cycling at a current density of 0.1 A / g. Detailed Implementation

[0031] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments and illustrations.

[0032] Example 1 (1) Weigh 2 g of silica nanoparticles (SiOx, D 50 =500 nm) and 0.2 g of metallic iron powder (D 50 =20 nm) was added to 50 mL of N-methylpyrrolidone and ultrasonically dispersed evenly at room temperature. Then, 50 g of N-methylpyrrolidone solution of polyimide (solid content of 30%) was added and stirred thoroughly to obtain a uniform silica / iron powder / polyimide composite slurry.

[0033] (2) The above slurry was uniformly coated onto the carbon-coated copper foil current collector (10 μm thick) using a four-sided coating apparatus, and the wet film coating thickness was controlled to be 20 μm. Then, it was placed in a vacuum oven for segmented heating, drying and curing. The heating program was as follows: 60℃ / 12h, 80℃ / 2h, 100℃ / 1h, 140℃ / 1h, 180℃ / 1h, 240℃ / 1h, 300℃ / 0.5h. After natural cooling to room temperature, a silicon suboxide / iron powder / polyimide composite film deposited on the carbon-coated copper foil was obtained.

[0034] (3) The above-mentioned thin film was irradiated in an air atmosphere using a carbon dioxide infrared laser. The laser process parameters included: wavelength of 10.6 μm, power of 10 W, scanning rate of 200 mm / s, scanning spacing of 0.1 mm, pulse frequency of 10 kHz, duty cycle of 50%, focal length of 10 cm, and voltage of 20 kV. During the laser irradiation process, the polyimide underwent rapid graphitization and in-situ graphene generation, constructing a silicon suboxide / graphene composite material on the carbon-coated copper foil.

[0035] (4) Repeat steps (2) to (3) four times to accumulate the silicon suboxide / graphene composite material layer by layer on the carbon-coated copper foil, finally obtaining a thickness of 75 μm and an area loading of 5.5 mg / cm². 2 A silica-suboxide / graphene composite material. Multiple cycles can increase the loading of active materials while maintaining the uniformity of graphene coating and the interfacial bonding strength.

[0036] (5) The silica-suboxide / graphene composite material prepared in step (4) was placed in a tube furnace, and a vertically oriented single-walled carbon nanotube network was grown in situ on its surface using chemical vapor deposition (CVD). The CVD conditions included: methane as the carbon source gas, hydrogen as the auxiliary gas, a methane to hydrogen volume ratio of 9:1, a deposition temperature of 600℃, a heating rate of 3℃ / min, a deposition time of 1 h, a deposition chamber pressure of 100 kPa, and a gas flow rate of 100 mL / min, resulting in a silica-suboxide / graphene / carbon nanotube thick electrode material (abbreviated as SiOx / LIG / CNT). During the CVD process, metallic iron catalyzed the cracking of methane and vertically grew carbon nanotubes (approximately 50 nm in diameter and approximately 20 μm in length) on the graphene surface.

[0037] Figure 1 This is a SEM image of the silicon suboxide / graphene / carbon nanotube thick electrode material prepared in Example 1. From... Figure 1 It can be clearly observed that laser-induced graphene (LIG) successfully constructed an interconnected and highly ordered three-dimensional porous network architecture. These pore structures not only endow the material with a rich specific surface area but also provide ample channels for subsequent loading of active materials and ion transport. Notably, during laser-induced graphitization, the SiOx component can be uniformly embedded into the three-dimensional framework, achieving excellent composite and fusion. Simultaneously, a large number of carbon nanotubes grow vertically on the surface of the graphene sheets, forming an extremely dense arrangement.

[0038] Figure 2 This is a TEM image of the silicon suboxide / graphene / carbon nanotube thick electrode material prepared in Example 1. From... Figure 2 It can be clearly observed that the graphene sheets are uniformly coated with SiOx particles, and a large number of carbon nanotubes grow on the surface of the graphene sheets. Their tubular structure and arrangement are clearly visible under high resolution, forming an extremely dense and orderly distribution.

[0039] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, except that: carbon nanotubes were not deposited by chemical vapor deposition, that is, the silicon suboxide / graphene thick electrode material (SiOx / LIG) was directly obtained through step (4), with an areal loading of 5.2 mg / cm². 2 .

[0040] Figure 3 This is a SEM image of the silicon suboxide / graphene thick electrode material prepared in Comparative Example 1. (From...) Figure 3 It can be seen that LIG exhibits a three-dimensional hierarchical porous structure, with SiOx nanoparticles uniformly embedded in the graphene network; and Figure 1The comparison revealed that the SiOx / LIG composite material did not exhibit the characteristic morphology of carbon nanotubes.

[0041] Example 2 (1) Weigh 3 g of elemental silicon nanoparticles (Si, D) 50 =200 nm) and 0.05 g cobalt tetroxide (D 50 =50 nm) was added to 60 mL of N,N-dimethylformamide and ultrasonically dispersed at room temperature. Then, 60 g of polystyrene toluene solution (solid content 60%) was added and stirred thoroughly to obtain a homogeneous silicon / cobalt tetroxide / polystyrene composite slurry.

[0042] (2) The above slurry was uniformly coated onto carbon cloth (12 μm thick) using a four-sided coating apparatus, and the wet film coating thickness was controlled to be 25 μm. Then, it was placed in a vacuum oven for segmented heating, drying and curing. The heating program was as follows: 60℃ / 6h, 80℃ / 2h, 100℃ / 2h, 140℃ / 1h, 200℃ / 1h, 280℃ / 1h, 300℃ / 1h. After natural cooling to room temperature, a silicon / cobalt tetroxide / polystyrene composite film was obtained deposited on the carbon cloth.

[0043] (3) The above-mentioned thin film was irradiated in an air atmosphere using a carbon dioxide infrared laser. The laser process parameters included: wavelength of 1064 nm, power of 8.5 W, scanning rate of 150 mm / s, scanning spacing of 0.08 mm, pulse frequency of 15 kHz, duty cycle of 20%, focal length of 12 cm, and voltage of 30 kV. During the laser irradiation process, polystyrene underwent rapid graphitization and in-situ graphene generation, constructing a silicon / graphene composite material on the carbon cloth.

[0044] (4) Repeat steps (2) to (3) five times to accumulate the silicon / graphene composite material layer by layer on the carbon cloth, finally obtaining a thickness of 90 μm and an area loading of 7.7 mg / cm². 2 A silicon / graphene composite material. Multiple cycles can increase the loading of active materials while maintaining the uniformity of graphene coating and the strength of interfacial bonding.

[0045] (5) The silicon / graphene composite material prepared in step (4) was placed in a tube furnace, and a vertically oriented single-walled carbon nanotube network was grown in situ on its surface using chemical vapor deposition (CVD). The CVD conditions included: acetylene as the carbon source gas, ammonia as the auxiliary gas, an acetylene to ammonia volume ratio of 8:2, a deposition temperature of 650℃, a heating rate of 4℃ / min, a deposition time of 1.5h, a deposition chamber pressure of 150 kPa, and a total gas flow rate of 150 mL / min, resulting in a silicon / graphene / carbon nanotube thick electrode material (abbreviated as Si / LIG / CNT). During the CVD process, cobalt tetroxide catalyzed the cracking of acetylene and vertically grew carbon nanotubes (approximately 20 nm in diameter and approximately 2 μm in length) on the graphene surface.

[0046] Example 3 (1) Weigh 3 g of silicon carbide nanoparticles (SiC, D) 50 =300 nm) and 1g nickel nitrate (D 50 =800 nm) was added to 100 mL of N,N-dimethylacetamide and ultrasonically dispersed at room temperature. Then, 60 g of N,N-dimethylacetamide solution of polyether ether ketone (solid content 60%) was added and stirred thoroughly to obtain a uniform silicon carbide / nickel nitrate / polyether ether ketone composite slurry.

[0047] (2) The above slurry was uniformly coated onto a single-sided smooth copper foil (15 μm thick) using a four-sided coating apparatus, and the wet film coating thickness was controlled to be 18 μm. Then, it was placed in a vacuum oven for segmented heating, drying and curing. The heating program was as follows: 60℃ / 6h, 80℃ / 1h, 100℃ / 1h, 120℃ / 1h, 140℃ / 1h, 180℃ / 1h, 260℃ / 1h, 300℃ / 0.5h. After natural cooling to room temperature, a silicon carbide / nickel nitrate / polyetheretherketone composite film was obtained deposited on the copper foil.

[0048] (3) The above-mentioned thin film was irradiated in an air atmosphere using a carbon dioxide infrared laser. The laser process parameters included: wavelength of 355 nm, power of 6.0 W, scanning rate of 80 mm / s, scanning spacing of 0.05 mm, pulse frequency of 25 kHz, duty cycle of 40%, focal length of 24 cm, and voltage of 22 kV. During the laser irradiation process, polyetheretherketone (PEEK) underwent rapid graphitization and in-situ graphene generation, constructing a silicon carbide / graphene composite material on the copper foil.

[0049] (4) Repeat steps (2) to (3) six times to accumulate silicon carbide / graphene composite material layer by layer on carbon cloth, finally obtaining a thickness of 110 μm and an area loading of 14.0 mg / cm². 2A silicon carbide / graphene composite material. Multiple cycles can increase the loading of active materials while maintaining the uniformity of graphene coating and the interfacial bonding strength.

[0050] (5) The silicon carbide / graphene composite material prepared in step (4) was placed in a tube furnace, and a vertically oriented single-walled carbon nanotube network was grown in situ on its surface using chemical vapor deposition (CVD). The CVD conditions included: ethylene as the carbon source gas, carbon monoxide as the auxiliary gas, a volume ratio of ethylene to carbon monoxide of 7:3, a deposition temperature of 700℃, a heating rate of 5℃ / min, a deposition time of 0.5h, a deposition chamber pressure of 200 kPa, and a total gas flow rate of 200 mL / min, resulting in a silicon silicide / graphene / carbon nanotube thick electrode material (referred to as Si / LIG / CNT). During the CVD process, nickel nitrate catalyzed the cracking of ethylene and the vertical growth of carbon nanotubes (approximately 25 nm in diameter and 5 μm in length) on the graphene surface.

[0051] Example 4 The preparation method of this embodiment is the same as that of Example 1, except that the polymer is replaced with polyethersulfone.

[0052] Example 5 The preparation method of this embodiment is the same as that of Embodiment 2, except that the carbon source gas is methane.

[0053] Example 6 The preparation method in this embodiment is the same as in Example 3, except that the metal catalyst is elemental nickel (D). 50 =50 nm).

[0054] The silicon suboxide / graphene / carbon nanotube thick electrode material prepared in Example 1 and the silicon suboxide / graphene thick electrode material prepared in Comparative Example 1 were used as negative electrode materials to assemble CR2025 coin cells, and their lithium storage performance was tested. The results are as follows: Figure 4 , Figure 5 , Figure 6 As shown.

[0055] The fabrication and assembly process of the CR2025 coin cell is as follows: The silicon suboxide / graphene / carbon nanotube thick electrode material prepared on carbon-coated copper foil in Example 1 and the silicon suboxide / graphene thick electrode material prepared on carbon-coated copper foil in Comparative Example 1 were cut into 12 mm diameter discs using a die-cutting machine. The mass of the active material in each electrode disc was weighed using a precision electronic balance, and the mass data was recorded for subsequent specific capacity calculation. Celgard 2400 was selected as the microporous membrane and cut into 19 mm diameter discs; the counter electrode was a lithium metal sheet (15.6 mm in diameter and 0.5 mm in thickness), used as both the reference and counter electrode. A 1 M electrolyte was prepared by dissolving lithium hexafluorophosphate in a 1:1 volume ratio mixture of ethylene carbonate and dimethyl carbonate. The entire battery assembly process was carried out in an argon-filled glove box (H2O≤0.1 ppm, O2≤0.1 ppm) to prevent moisture and oxygen from affecting the electrodes and electrolyte. After assembly, the coin cells were left to stand at room temperature for 12 hours to allow the electrolyte to fully penetrate the electrodes and separator, forming a stable interface.

[0056] Electrochemical performance testing methods: A battery testing system (Wuhan Landian, LAND CT2001A) was used to conduct constant current charge-discharge cycle tests in a constant temperature environment of 25±1℃. Cyclic voltammetry (CV) tests (scan rate of 0.1 mV / s, voltage range of 0.01~3.0 V) and electrochemical impedance spectroscopy (EIS) tests (frequency range of 100 kHz~0.01 Hz, AC amplitude of 5 mV) were both performed on an electrochemical workstation (Shanghai Chenhua, CHI 660e).

[0057] Figure 4 The cycling curves and coulombic efficiencies of lithium-ion batteries using SiOx / LIG / CNT prepared in Example 1 and SiOx / LIG prepared in Comparative Example 1 as anode materials at a current density of 0.1 A / g are shown. Figure 4 It can be seen that during the first charge and discharge process, the lithium-ion battery using SiOx / LIG / CNT as the negative electrode material exhibits a high initial discharge capacity, reaching 1873.9 mAh / g (10.3 mAh / cm²), and the initial coulombic efficiency is as high as 87.7%, significantly better than SiOx / LIG (82.4%). The improvement in initial efficiency is mainly due to the synergistic effect between LIG and CNT: firstly, the vertically and three-dimensionally distributed CNTs and LIG form a continuous and multi-channel conductive network, shortening the Li-CNT gap. +The diffusion path inside the electrode improves ion transport efficiency and reduces polarization resistance. Secondly, the composite structure of CNT and LIG can more uniformly disperse local current density, effectively suppressing the uneven deposition of local lithium during charging and discharging and the resulting continuous decomposition of electrolyte, thereby reducing the irreversible consumption of active lithium and forming a more stable and uniform SEI film, improving interfacial compatibility and electrochemical stability.

[0058] In terms of cycle performance, Figure 4 Further analysis shows that lithium-ion batteries using SiOx / LIG / CNT as the anode material maintain excellent cycle stability after multiple charge-discharge cycles, with a reversible capacity of 1653.1 mAh / g (9.1 mAh / cm²) and a capacity retention rate as high as 88.2%. In contrast, lithium-ion batteries using SiOx / LIG as the anode material exhibit significant capacity decay, with the reversible capacity dropping to 1184.7 mAh / g (6.2 mAh / cm²) after cycling, and a capacity retention rate of only 64.9%. This indicates that the introduction of CNTs not only improves rate performance by constructing efficient conductive and ion transport channels, but also stabilizes the electrode structure and mitigates interface degradation caused by volume expansion during long cycles, thereby delaying capacity decay. In summary, the composite structure of LIG and CNTs plays a crucial role in improving the initial efficiency, cycle life, and capacity retention rate of silicon-based anodes, providing an effective structural optimization approach for the design of high-capacity, long-life lithium-ion battery anodes.

[0059] Figure 5 The rate performance curves of lithium-ion batteries using SiOx / LIG / CNT prepared in Example 1 and SiOx / LIG prepared in Comparative Example 1 as anode materials are shown. Figure 5 It is evident that lithium-ion batteries using SiOx / LIG / CNT as the anode material exhibit superior rate capacity and reversibility, maintaining a high discharge capacity at various current densities (6.1 mAh / cm² at 4.0 A / g). However, under the same current density, the reversible capacity of lithium-ion batteries using SiOx / LIG as the anode material remains consistently low, especially at the ultra-high current density of 4.0 A / g, where its capacity decays to only 762.7 mAh / g (4.0 mAh / cm²), demonstrating a significant kinetic disadvantage. This performance gap stems from the three-dimensional hierarchical conductive structure constructed by SiOx / LIG / CNT, which not only shortens the electron transport path and enables rapid charge transfer but also provides an efficient diffusion channel for lithium ions. This effectively alleviates the kinetic limitations of ion transport and charge transfer at high current densities, ensuring that high reversible capacity and structural stability are maintained even during rapid charge and discharge processes.

[0060] Figure 6The images show the electrochemical impedance spectroscopy spectra of lithium-ion batteries using SiOx / LIG / CNT prepared in Example 1 and SiOx / LIG prepared in Comparative Example 1 as negative electrode materials before and after cycling at a current density of 0.1 A / g. Figure 6 The Nyquist plot typically comprises three characteristic sections: a semicircle in the high-frequency region corresponding to the solid electrolyte interfacial resistance (RSEI), a semicircle in the mid-frequency region reflecting the charge transfer resistance (Rct), and a diagonal line in the low-frequency region originating from the Warburg impedance (Zw) related to lithium-ion diffusion. Cyclic testing results show that the Rct and RSEI of lithium-ion batteries using SiOx / LIG / CNT as the anode material are both lower than those of SiOx / LIG. This highlights the crucial role of the three-dimensional LIG / CNT conductive network. This network optimizes the charge transfer path by constructing continuous and multi-channel conductive pathways and stabilizes the SEI layer structure during charge and discharge, thereby effectively reducing interfacial impedance and accelerating lithium-ion diffusion kinetics, enabling the electrode to maintain good electrochemical performance under high-rate and long-cycle conditions.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a silicon-based / graphene / carbon nanotube thick electrode material, characterized in that: The preparation method includes the following steps: (1) A homogeneous slurry is obtained by mixing silicon-based materials, polymers, metal catalysts and solvents; (2) The slurry is evenly coated onto the current collector and heated to cure, forming a thin film; (3) The thin film was irradiated with laser to obtain a silicon-based / graphene composite material; (4) Carbon nanotubes were vertically grown on silicon-based / graphene composite material by chemical vapor deposition to obtain silicon-based / graphene / carbon nanotube thick electrode material.

2. The preparation method according to claim 1, characterized in that: The preparation method further includes repeating steps (1) to (3) multiple times after obtaining the silicon-based / graphene composite material in step (3) to stack the silicon-based / graphene composite material layer by layer to obtain a thick electrode material.

3. The preparation method according to claim 1, characterized in that: The silicon-based material is one or more of silicon suboxide, elemental silicon, silicon carbide, silicon nitride, silicon-oxygen-carbon, silicon alloy, and lithium silicate. Preferably, the silicon-based material has a size of 0.1 nm to 50 μm; Preferably, the polymer is one or more of polyethylene, polypropylene, polystyrene, polysulfide rubber, polyvinyl chloride, polyetheretherketone, polyphenylene sulfide, polyethersulfone, polyaryletherketone, polyimide, polyester, polyamide, and polyurethane. Preferably, the current collector is one or more of the following: continuous copper foil, copper wire braided copper mesh, foamed copper, three-dimensional nanoporous copper foil, continuous carbon-coated copper foil, three-dimensional nanoporous carbon-coated copper foil, nickel foil, foamed nickel, carbon cloth, stainless steel sheet, alloy current collector, metal-polymer composite current collector, and titanium foil.

4. The preparation method according to claim 1, characterized in that: The metal catalyst is one or more of the following: elemental metal, metal alloy, metal oxide, and metal salt. Preferably, the size of the metal catalyst is 0.1 nm to 50 μm; Preferably, the mass ratio of the silicon-based material, polymer, and metal catalyst is 1 : (0.1~5000) : (0.001~1000).

5. The preparation method according to claim 1, characterized in that: The laser is one or more of the following: solid-state laser, liquid laser, gas laser, semiconductor laser, and fiber laser; Preferably, the wavelength of the laser irradiation is 0.05~200 μm, the power is 0.05~5000 W, the scanning rate is 0.01~2000 mm / s, the scanning spacing is 0.001~1000 mm, the pulse frequency is 0.001~1000 kHz, the duty cycle is 0.1~100%, the focal length is 0.1~2000 cm, and the voltage is 0.1~10000 kV; Preferably, the laser irradiation is performed in an air, inert gas, or vacuum environment.

6. The preparation method according to claim 1, characterized in that: The chemical vapor deposition temperature is 10~2000℃, the time is 0.01~200 h, the heating rate is 0.01~25℃ / min, the pressure is 0.001~50000 kPa, and the gas flow rate is 0.01~10000 mL / min; Preferably, the carbon source gas for chemical vapor deposition is one or more of methane, ethylene, propylene, and acetylene, and the auxiliary gas is one or more of hydrogen, argon, nitrogen, carbon monoxide, oxygen, propylene, and ammonia; more preferably, the volume ratio of the carbon source gas to the auxiliary gas is 1:(0.01~99.9).

7. The preparation method according to claim 1, characterized in that: The carbon nanotubes are one or more of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. Preferably, the carbon nanotubes have a diameter of 0.01~1000 nm and a length of 0.001~2000 μm.

8. The preparation method according to claim 1, characterized in that: The thickness of the silicon-based / graphene composite material is 0.1~1000 μm; Preferably, the thickness of the silicon-based / graphene / carbon nanotube thick electrode material is 0.1~1000 μm.

9. A silicon-based / graphene / carbon nanotube thick electrode material obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the silicon-based / graphene / carbon nanotube thick electrode material according to claim 9 in lithium-ion batteries.

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