Graphene fiber fabric silicon-carbon negative electrode composite material and preparation method thereof

Abstract

The application discloses a graphene fiber fabric silicon-carbon negative electrode composite material and a preparation method thereof, deposits silicon on the surface of a porous graphene fiber fabric to obtain a porous graphene fiber fabric with nano-silicon deposited in pores; and then carbon is coated to obtain a silicon-carbon negative electrode composite material. At present, from the electrochemical performance, the negative electrode material cannot be considered in the first efficiency and the cycle performance, meanwhile, the preparation process of the material is complex, the production cost is high, and the industrial application is difficult. The application effectively solves the problems in the prior art, the disclosed graphene fiber fabric silicon-carbon negative electrode material has a unique structure design, fully gives play to the advantages of high specific capacity of silicon and excellent conductivity of graphene, simultaneously utilizes the graphene fiber fabric to relieve the volume change of silicon, greatly improves the power characteristics and cycle stability of the electrode; and the whole preparation process is simple and controllable, and is favorable for large-scale production and application.

Description

Technical Field

[0001] This invention pertains to battery anode technology and relates to a silicon-carbon anode material, specifically a graphene fiber fabric silicon-carbon anode composite material and its preparation method. Background Technology

[0002] With the increasing demand for high-energy-density lithium-ion batteries in fields such as electric vehicles and portable electronic devices, the theoretical capacity of traditional graphite anode materials can no longer meet the requirements of next-generation high-energy-density batteries. Silicon-based anode materials have attracted much attention due to their high theoretical specific capacity of up to 4200 mAh / g, and have become one of the important candidate materials to replace graphite anodes.

[0003] However, silicon undergoes a volume change of up to 300% during charge and discharge, leading to unstable electrode structures and making them prone to pulverization and failure. To address this issue, researchers have proposed a method of depositing nano-silicon on a carbon material framework. This method utilizes the mechanical strength and conductivity of carbon materials to mitigate the volume change of silicon, thereby improving the cycle stability of the battery.

[0004] For example, CN105739379B discloses a silicon / carbon nanotube composite anode material, which uses chemical vapor deposition to deposit silicon on the surface of carbon nanotubes and then converts it into nano-silicon particles through heat treatment. This structure can effectively alleviate the volume expansion of silicon. CN104849589B discloses a method for preparing silicon / carbon nanotube composite anode materials, which uses a hydrothermal method to deposit silicon on the surface of carbon nanotubes and then converts it into nano-silicon particles through heat treatment. Carbon nanotubes provide good conductivity and mechanical strength, which helps to improve electrode performance. CN116230911B discloses a high-power silicon-carbon anode composite material and its preparation method, which uses specific preparation processes such as electrospinning and gas atomization to deposit nano-silicon on a carbon fiber skeleton and add organic lithium salts. Organic lithium is deposited on the surface of its nano-silicon-metal carbon fibers using a gas atomization method. The organic lithium on its surface reduces the irreversible capacity during the first charge and discharge process and improves the first efficiency. This scheme is complex and not suitable for industrial production. CN115784233B synthesizes a uniform resin layer on the surface of silicon powder using an electrochemical method. During the synthesis process, lithium is added to the silicon through an electric field, improving the initial efficiency of the silicon-carbon anode material. However, this method is complex and unsuitable for industrial production. To address the volume expansion problem of silicon-carbon anode materials, existing technologies uniformly mix silicon suboxide (SiOx) and graphene slurry in a liquid phase system, using pitch as an additive. Through a series of processes including spray drying, high-temperature heat treatment, and chemical vapor deposition, spherical graphene / pitch-pyrolysis carbon-encapsulated silicon oxide composite anode materials are prepared. Different graphene-modified silicon-carbon composite anodes combined with graphite have a capacity of approximately 850 mAh / g. CN114400310B provides a high-efficiency graphene composite silicon-carbon anode material, which is composed of silicon-carbon particles with a core-shell structure and graphene microplates. The outer layer is an inorganic carbon layer, and the inner layer is silicate-encapsulated nano-silicon particles. The silicon-carbon particles with a core-shell structure and the graphene microplates are combined through the interaction of silicates, but the initial efficiency does not exceed 84%.

[0005] In summary, existing technologies all embody the technical approach of depositing nano-silicon on a carbon material framework, aiming to solve the problem of large volume changes in silicon anode materials during charging and discharging. However, the effect of porous carbon framework on improving the cycle stability and rate performance of batteries still needs to be improved. Summary of the Invention

[0006] In view of the low cycle stability and rate performance of existing silicon-carbon anodes, this invention discloses a graphene fiber fabric silicon-carbon anode composite material and its preparation method. The carbon fiber fabric skeleton can not only effectively alleviate the volume change of silicon, but also provide a good conductive channel, thereby improving the rate characteristics of the electrode.

[0007] The present invention adopts the following technical solution.

[0008] A method for preparing a graphene fiber fabric silicon-carbon anode composite material includes the following steps: depositing silicon on the surface of a porous graphene fiber fabric to obtain a porous graphene fiber fabric with nano-silicon deposited in the pores; and then carbon coating the porous graphene fiber fabric with nano-silicon deposited in the pores to obtain the graphene fiber fabric silicon-carbon anode composite material.

[0009] In this invention, the porous graphene fiber fabric includes porous graphene fiber nonwoven fabric.

[0010] In this invention, porous graphene fiber fabric is obtained by reducing porous graphene oxide fiber fabric, for example, by reducing porous graphene oxide fiber nonwoven fabric to obtain porous graphene fiber nonwoven fabric; as an example, porous graphene oxide fiber nonwoven fabric is heated to obtain porous graphene fiber nonwoven fabric.

[0011] In this invention, the heating temperature is 500–900°C, and the heating time is 0.5–4 hours; preferably, the heating temperature is 600–800°C, and the heating time is 1–3 hours.

[0012] In this invention, heating is carried out in an inert atmosphere.

[0013] In this invention, porous graphene oxide fiber fabrics are prepared using porous graphene oxide fibers, preferably porous graphene oxide fiber nonwoven fabrics are prepared using porous graphene oxide fibers; for example, porous graphene oxide fibers are filtered to obtain porous graphene oxide fiber nonwoven fabrics.

[0014] Preferably, the porous graphene oxide fiber has a length of 0.5–5 cm and a diameter of 100–500 μm; more preferably, the porous graphene oxide fiber has a length of 0.6–3 cm and a diameter of 150–400 μm; further preferably, the porous graphene oxide fiber has a length of 0.7–2 cm and a diameter of 200–350 μm; and even more preferably, the porous graphene oxide fiber has a length of 0.8–1.5 cm and a diameter of 220–320 μm.

[0015] In this invention, porous graphene oxide fibers are prepared using porous graphene oxide. The specific preparation operation is a conventional technique, which can refer to wet spinning or electrospinning.

[0016] In this invention, during silicon deposition, the silicon source gas includes silane, and further includes one or more of silane, disilane, propane, and silicon tetrachloride; the protective atmosphere can be nitrogen, helium, xenon, radon, neon, argon, etc.

[0017] In this invention, when depositing silicon, the temperature is 300℃~1000℃ and the time is 0.5~10 hours; preferably, the temperature is 400℃~800℃ and the time is 1~8 hours; more preferably, the temperature is 450℃~700℃ and the time is 1~5 hours; even more preferably, the temperature is 480℃~600℃ and the time is 1~4 hours; for example, the temperature is 500℃, 520℃, 540℃, 550℃, 560℃, 580℃ or any temperature within the range, and the time is 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or any time within the range.

[0018] In this invention, the flow rate of the silicon source gas is 0–50 ml / min, and the flow rate of the inert gas is 0–50 ml / min, excluding 0; preferably, the flow rate of the silicon source gas is 5–40 ml / min, and the flow rate of the inert gas is 5–40 ml / min; more preferably, the flow rate of the silicon source gas is 10–35 ml / min, and the flow rate of the inert gas is 10–35 ml / min; even more preferably, the flow rate of the silicon source gas is 15–30 ml / min, and the flow rate of the inert gas is 15–30 ml / min; for example, the flow rates of the two gases can be independently selected from 20 ml / min, 21 ml / min, 22 ml / min, 23 ml / min, 24 ml / min, 25 ml / min, 26 ml / min, 27 ml / min, 28 ml / min, 29 ml / min, or any flow rate within the range.

[0019] In this invention, carbon coating includes gas-phase carbon coating, liquid-phase carbon coating, or solid-phase carbon coating, specifically existing technologies. As an example, the gas source used for gas-phase coating is one or more of methane, ethane, propane, acetylene, propyne, butyne, propylene, and ethylene. The deposition time is 0.5–3 hours, and the deposition temperature is 300–700°C. Preferably, the deposition time is 1–2 hours, and the deposition temperature is 400–600°C. The gas-phase carbon deposition heat preservation process can be a single-stage heat preservation or segmented heat preservation.

[0020] This invention discloses the preparation method of the above-mentioned graphene fiber fabric silicon-carbon anode composite material and the graphene fiber fabric silicon-carbon anode composite material prepared therefrom.

[0021] This invention discloses a negative electrode sheet comprising the above-mentioned graphene fiber fabric silicon-carbon negative electrode composite material.

[0022] This invention discloses a lithium-ion battery, comprising the aforementioned negative electrode sheet or graphene fiber fabric silicon-carbon negative electrode composite material.

[0023] The present invention discloses an electrochemical device, including the above-mentioned lithium-ion battery, the above-mentioned negative electrode sheet or graphene fiber fabric silicon-carbon negative electrode composite material.

[0024] This invention discloses the application of the above-mentioned graphene fiber fabric silicon-carbon anode composite material in the preparation of lithium-ion battery anode sheets.

[0025] This invention discloses the application of the above-mentioned graphene fiber fabric silicon-carbon anode composite material or anode sheet in lithium-ion batteries.

[0026] Existing technologies often use porous carbon as a matrix to limit the volume expansion of silicon particles, but this can affect the overall performance of the electrode. This invention employs a carbon fiber skeleton, which not only effectively mitigates the volume change of silicon but also provides excellent conductive channels, thereby improving the rate performance of the electrode. Addressing the shortcomings of existing porous carbon matrices, such as poor conductivity and inability to effectively enhance the strength of the carbon skeleton, this invention provides a high-power and high-conductivity silicon-carbon anode composite material. Specifically, this technical solution utilizes graphene nonwoven fabric to limit the volume expansion of the silicon anode during charging and discharging. This not only effectively mitigates the volume change of silicon but also provides excellent electron transport channels, significantly improving the electrode's conductivity and rate performance. Simultaneously, the graphene nonwoven fabric also effectively enhances the mechanical strength of the carbon-based skeleton, improving the structural stability of the electrode during long-term cycling.

[0027] In summary, the silicon-carbon anode composite material preparation method proposed in this invention can effectively solve the key problems in the existing technology, achieve the goals of high power and high cycle stability, and provide a new technical path for the development of next-generation high-performance lithium-ion batteries. Detailed Implementation

[0028] This invention discloses the preparation of a graphene fiber fabric silicon-carbon anode and its application in lithium-ion batteries. Its structure and composition include: graphene with a porous structure; the fabric is composed of numerous short graphene fibers randomly arranged, facilitating rapid electron and ion transport; silicon particles are deposited within the porous graphene, effectively suppressing their volume expansion during charging and discharging; and the entire fabric is coated with a carbon layer, providing protection and preventing oxidation of the silicon particles in air.

[0029] In this invention, the first stage involves preparing porous graphene fiber fabric from graphene oxide using a wet spinning method, and using this fabric structure as a substrate; the second stage involves the deposition of a mixed gas of silicon source gas and inert gas, which results in the deposition of silicon particles in the graphene, providing good conductivity and effectively suppressing the volume expansion of the silicon particles; finally, carbon coating is performed.

[0030] The method for preparing the graphene fiber fabric silicon-carbon anode of the present invention includes the following steps: (1) Porous graphene oxide fibers were prepared using porous graphene oxide, and porous graphene oxide fiber nonwoven fabric was prepared using porous graphene oxide fibers; porous graphene fiber nonwoven fabric was obtained by reducing porous graphene oxide fiber nonwoven fabric. (2) Silicon is deposited on the surface of porous graphene fiber fabric to obtain porous graphene fiber fabric with nano-silicon deposited in the pores. (3) Then, the porous graphene fiber fabric with nano-silicon deposited in the pores is carbon coated to obtain a graphene fiber fabric silicon-carbon anode composite material.

[0031] In the above technical solution, the length of the porous graphene oxide fiber is 0.5-5 cm and the diameter is 100-500 μm; preferably, the length of the porous graphene oxide fiber is 0.6-3 cm and the diameter is 150-400 μm; more preferably, the length of the porous graphene oxide fiber is 0.7-2 cm and the diameter is 200-350 μm; and even more preferably, the length of the porous graphene oxide fiber is 0.8-1.5 cm and the diameter is 220-320 μm.

[0032] In this invention, the specific preparation operation of porous graphene oxide fibers is a conventional technique, which can refer to wet spinning or electrospinning.

[0033] As an example, porous graphene oxide fibers are prepared by means of a porous graphene oxide solution, wherein the concentration of the porous graphene oxide solution is 8-12 mg / ml, preferably 9-11 mg / ml.

[0034] Furthermore, the preparation method of the graphene fiber fabric silicon-carbon anode of the present invention includes the following steps: (1) The pH of the porous graphene oxide aqueous solution is adjusted to alkaline using ammonia or other alkaline solutions. The adjusted porous graphene oxide aqueous solution is then injected into a setting solution (such as ethanol) using a syringe pump. The shear force is controlled by adjusting the injection flow rate, thereby controlling the fiber length. The prepared fibers are then filtered to obtain porous graphene oxide nonwoven fabric and dried. Subsequently, the porous graphene oxide nonwoven fabric is heated to remove oxygen-containing functional groups, resulting in porous graphene nonwoven fabric. The mass fraction of the ammonia is 25-28%, and the concentration of the porous graphene oxide aqueous solution is 9%. The concentration of the porous graphene oxide aqueous solution is ~11 mg / ml; it can be prepared by conventional modified Hummers method and hydrogen peroxide etching, or it can be purchased commercially, without affecting the understanding of the technical effects of the present invention by those skilled in the art; the pH range is 8-11; the ethanol is anhydrous ethanol; the fiber length is 1 cm-1.5 cm; the injection flow rate is 0.05-0.2 ml / min; the filtration method is vacuum filtration; the heating temperature is 600-800℃; the heating time is 0.5-3 h; (2) The prepared porous graphene fiber fabric is placed in the reaction equipment cavity, and silicon source gas and inert gas are mixed and deposited at a certain temperature to obtain porous graphene nonwoven fabric with nano-silicon deposited in the pores; the certain temperature is 300-1000℃; the flow rate range of silicon source gas and inert gas is 0-50ml / min excluding 0; the reaction equipment cavity includes chemical vapor deposition equipment such as fluidized bed and rotary furnace; the silicon source gas is silane, silane, propane, silicon tetrachloride, etc.; the protective atmosphere can be nitrogen, helium, xenon, radon, neon, argon, etc. (3) Carbon coating is applied to the porous graphene nonwoven fabric in which nano-silicon is deposited in the above pores to prepare a surface carbon layer, thereby obtaining the graphene fiber fabric silicon-carbon anode of the present invention; the carbon coating method is gas phase, liquid phase or solid phase coating, and the gas source used for gas phase coating is one or more of methane, ethane, propane, acetylene, propyne, butyne, propylene and ethylene; the carbon deposition time is 0.5 to 3 hours, and the temperature of the gas phase carbon deposition is 300 to 700°C; the heat preservation process of the gas phase carbon deposition can be a single heat preservation or a segmented heat preservation; liquid phase and solid phase coating are commonly used coating methods in this technical field.

[0035] The following specific experiments illustrate the technological advancements of this invention. The raw materials used are all existing products, and the specific preparation operations and performance tests are all conventional techniques. The porous graphene oxide and porous carbon are conventional commercially available products.

[0036] The test methods for the various indicators involved in the embodiments and comparative examples are described below.

[0037] Specific surface area is determined by nitrogen adsorption method.

[0038] Electronic conductivity: The electronic conductivity of the porous graphene silicon-carbon thin film anode was measured using a four-point probe resistivity meter.

[0039] Mechanical properties: The fabric was cut into rectangles of 0.5×3cm and clamped on a stretching machine for mechanical property testing.

[0040] Using the porous graphene-silicon-carbon thin film composite material prepared in this embodiment and the comparative example as the negative electrode, lithium sheet as the counter electrode, Celgard 2500 separator, and LiPF6 electrolyte with a molar concentration of 1 mol / L (solvent being ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1), a coin cell half-cell was assembled in a glove box and its electrochemical performance was tested. For the comparative example powder composite material, the negative electrode material and binder lithium-modified polyacrylic acid were added to a mortar and ground in a mass ratio of 9.5:0.5, then added to deionized water and pulped in a pulper to form a slurry. This slurry was coated onto a copper foil current collector, dried in a vacuum oven at 80°C for 12 hours, and then the dried electrode was cut into circular pieces to serve as the negative electrode of the coin cell half-cell.

[0041] The testing process for the assembled coin cell was as follows: Constant current charge-discharge mode testing was performed using a charge-discharge apparatus. The discharge cutoff voltage was 0.005V, and the charge cutoff voltage was 2V. Routine charge-discharge tests were conducted at a current density of C / 10. Detailed test data for the first-cycle coulombic efficiency, charge specific capacity, and capacity retention (cycle life) after 300 cycles of the coin cell are shown in Table 1. The above discharge process represents lithium insertion, corresponding to charging in a full cell; charging represents lithium removal, corresponding to discharging in a full cell. The full-charge expansion rate test represents the electrode expansion rate of the coin cell. First, the thickness 1 of the porous graphene silicon-carbon film anode was measured before charging, and then the thickness 2 of the porous graphene silicon-carbon film anode was measured after one cycle of charge-discharge. The electrode expansion rate = (thickness 2 - thickness 1) / thickness 1 × 100%. Electrode expansion rate test data are shown in Table 1.

[0042] First-cycle efficiency: The first-cycle coulombic efficiency of the negative electrode of a coin cell is tested. Example 1

[0043] Preparation of porous graphene nonwoven fabric: The pH of a 10 mg / ml porous graphene oxide aqueous solution was adjusted to 8 using ammonia. The adjusted porous graphene oxide aqueous solution was then injected into anhydrous ethanol at a flow rate of 0.06 ml / min using a syringe pump to obtain fibers approximately 1 cm in length. The prepared fiber solution was then vacuum filtered to obtain porous graphene oxide nonwoven fabric, which was dried at room temperature. Subsequently, the porous graphene oxide nonwoven fabric was placed in a tube furnace under nitrogen atmosphere and heated at 600°C for 2 hours to remove oxygen-containing functional groups and increase conductivity, thus obtaining the porous graphene nonwoven fabric. Silicon deposition: The prepared porous graphene nonwoven fabric was placed in the reaction equipment chamber, and silane and nitrogen were introduced at a certain temperature. The gas flow rates of silane and nitrogen were 23 ml / min and 25 ml / min, respectively. The deposition time was 1 h and the deposition temperature was 540℃. Carbon coating: The deposited sample was coated with carbon using acetylene as the carbon source gas. The coating temperature was 500 °C and the holding time was 1.5 h. Example 2

[0044] Preparation of porous graphene nonwoven fabric: The pH of a 10 mg / ml porous graphene oxide aqueous solution was adjusted to 8 using ammonia. The adjusted porous graphene oxide aqueous solution was then injected into anhydrous ethanol at a flow rate of 0.06 ml / min using a syringe pump to obtain fibers approximately 1 cm in length. The prepared fibers were then vacuum filtered to obtain porous graphene oxide nonwoven fabric, which was dried at room temperature. Subsequently, the porous graphene oxide nonwoven fabric was placed in a tube furnace under nitrogen atmosphere and heated at 700℃ to remove oxygen-containing functional groups and increase conductivity for 2 hours, yielding the porous graphene nonwoven fabric. Silicon deposition: The prepared porous graphene nonwoven fabric was placed in the reaction equipment chamber, and silane and nitrogen were introduced at a certain temperature. The gas flow rates of silane and nitrogen were 23 ml / min and 25 ml / min, respectively. The deposition time was 1 h and the deposition temperature was 540℃. Carbon coating: The deposited sample was coated with carbon using acetylene as the carbon source gas. The coating temperature was 500 °C and the holding time was 1.5 h. Example 3

[0045] Preparation of porous graphene nonwoven fabric: The pH of a porous graphene oxide aqueous solution with a concentration of 10 mg / ml was adjusted to 8 using ammonia water. Then, the adjusted porous graphene oxide aqueous solution was injected into anhydrous ethanol at a flow rate of 0.06 ml / min using a syringe pump to obtain fibers with a length of about 1 cm. The prepared fibers were then filtered under vacuum to obtain porous graphene oxide nonwoven fabric, which was dried at room temperature. Subsequently, the porous graphene oxide nonwoven fabric was placed in a tube furnace under nitrogen and heated at 800℃ to remove oxygen-containing functional groups and increase conductivity. The heating time was 2 h to obtain porous graphene nonwoven fabric. Silicon deposition: The prepared porous graphene nonwoven fabric was placed in the reaction equipment chamber, and silane and nitrogen were introduced at a certain temperature. The gas flow rates of silane and nitrogen were 23 ml / min and 25 ml / min, respectively. The deposition time was 1 h and the deposition temperature was 540℃. Carbon coating: The deposited sample was coated with carbon using acetylene as the carbon source gas. The coating temperature was 500 °C and the holding time was 1.5 h. Example 4

[0046] Preparation of porous graphene nonwoven fabric: The pH of a porous graphene oxide aqueous solution with a concentration of 10 mg / ml was adjusted to 8 using ammonia water. Then, the adjusted porous graphene oxide aqueous solution was injected into anhydrous ethanol at a flow rate of 0.06 ml / min using a syringe pump to obtain fibers with a length of about 1 cm. The prepared fibers were then filtered under vacuum to obtain porous graphene oxide nonwoven fabric, which was dried at room temperature. Subsequently, the porous graphene oxide nonwoven fabric was placed in a tube furnace under nitrogen and heated at 700℃ to remove oxygen-containing functional groups and increase conductivity. The heating time was 2 h to obtain porous graphene nonwoven fabric. Silicon deposition: The prepared porous graphene nonwoven fabric was placed in the reaction equipment chamber, and silane and nitrogen were introduced at a certain temperature. The gas flow rates of silane and nitrogen were 23 ml / min and 25 ml / min, respectively. The deposition time was 1.5 h and the deposition temperature was 540℃. Carbon coating: The deposited sample was coated with carbon using acetylene as the carbon source gas. The coating temperature was 500 °C and the holding time was 1.5 h. Example 5

[0047] Preparation of porous graphene nonwoven fabric: The pH of a porous graphene oxide aqueous solution with a concentration of 10 mg / ml was adjusted to 8 using ammonia water. Then, the adjusted porous graphene oxide aqueous solution was injected into anhydrous ethanol at a flow rate of 0.06 ml / min using a syringe pump to obtain fibers with a length of about 1 cm. The prepared fibers were then filtered under vacuum to obtain porous graphene oxide nonwoven fabric, which was dried at room temperature. Subsequently, the porous graphene oxide nonwoven fabric was placed in a tube furnace under nitrogen and heated at 700℃ to remove oxygen-containing functional groups and increase conductivity. The heating time was 2 h to obtain porous graphene nonwoven fabric. Silicon deposition: The prepared porous graphene nonwoven fabric was placed in the reaction equipment chamber, and silane and nitrogen were introduced at a certain temperature. The gas flow rates of silane and nitrogen were 23 ml / min and 25 ml / min, respectively. The deposition time was 2 h and the deposition temperature was 540℃. Carbon coating: The deposited sample was coated with carbon using acetylene as the carbon source gas. The coating temperature was 500 °C and the holding time was 1.5 h. Example 6

[0048] Preparation of porous graphene nonwoven fabric: The pH of the porous graphene oxide aqueous solution was adjusted to 8 using ammonia water. Then, the adjusted porous graphene oxide aqueous solution was injected into the ethanol solution at a flow rate of 0.06 ml / min using a syringe pump to obtain fibers with a length of about 1 cm. The prepared fibers were filtered to obtain porous graphene oxide nonwoven fabric and dried at room temperature. Subsequently, the porous graphene oxide nonwoven fabric was placed in a tube furnace under nitrogen and heated at 700℃ to remove oxygen-containing functional groups and increase conductivity, thus obtaining porous graphene nonwoven fabric. Silicon deposition: The prepared porous graphene nonwoven fabric was placed in the reaction equipment chamber, and silane and nitrogen were introduced at a certain temperature. The gas flow rates of silane and nitrogen were 23 ml / min and 25 ml / min, respectively. The deposition time was 2.5 h and the deposition temperature was 540℃. Carbon coating: The deposited sample was coated with carbon using acetylene as the carbon source gas. The coating temperature was 500 °C and the holding time was 1.5 h. Example 7

[0049] Preparation of porous graphene nonwoven fabric: The pH of a porous graphene oxide aqueous solution with a concentration of 10 mg / ml was adjusted to 8 using ammonia water. Then, the adjusted porous graphene oxide aqueous solution was injected into anhydrous ethanol at a flow rate of 0.06 ml / min using a syringe pump to obtain fibers with a length of about 1 cm. The prepared fibers were then filtered under vacuum to obtain porous graphene oxide nonwoven fabric, which was dried at room temperature. Subsequently, the porous graphene oxide nonwoven fabric was placed in a tube furnace under nitrogen and heated at 700℃ to remove oxygen-containing functional groups and increase conductivity. The heating time was 2 h to obtain porous graphene nonwoven fabric. Silicon deposition: The prepared porous graphene nonwoven fabric was placed in the reaction equipment chamber, and silane and nitrogen were introduced at a certain temperature. The gas flow rates of silane and nitrogen were 23 ml / min and 25 ml / min, respectively. The deposition time was 3 h and the deposition temperature was 540℃. Carbon coating: The deposited sample was coated with carbon using acetylene as the carbon source gas. The coating temperature was 500 °C and the holding time was 1.5 h.

[0050] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the thermal reduction temperature of the porous graphene oxide fabric is 500°C, while other conditions remain unchanged.

[0051] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that the thermal reduction temperature of the porous graphene oxide fabric is 900°C, while other conditions remain unchanged. The measured conductivity is 2520 S·cm and the capacity is 686.5 mAh / g.

[0052] Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that 12 mg / ml of spinning solution was used to prepare porous graphene oxide fabric, while other conditions remained unchanged. The measured conductivity was 1790 S·cm, and the first-efficiency was 83.95%.

[0053] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that Comparative Example 4 uses a spinning solution of 8 mg / ml to prepare porous graphene oxide fabric, while other conditions remain unchanged.

[0054] Comparative Example 5 The silicon deposition time and carbon coating time in Comparative Example 5 were no different from those in Example 4, except that the substrate was changed from porous graphene fabric to commercially available porous carbon, thereby preparing the anode material; this is the mainstream product currently in production.

[0055] Comparative Example 6 The difference between Comparative Example 6 and Example 6 is that the fiber of about 1 cm was placed in a tube furnace and heated, and then used as a substrate to prepare the negative electrode material. That is, the step of obtaining porous graphene oxide nonwoven fabric by filtration was omitted. The initial efficiency was measured to be 84.7% and the cycle life was 88.4%.

[0056] Comparative Example 7 The difference between Comparative Example 7 and Example 6 is that porous graphene oxide was placed in a tube furnace and heated, and then used as a substrate to prepare a negative electrode material. The measured initial efficiency was 83.1%, the cycle life was 87.1%, and the full charge expansion rate was 75%.

[0057] Table 1 Performance of Examples and Comparative Examples

[0058] As can be seen from Examples 1-3 and Comparative Examples 1-2, the conductivity of the porous graphene oxide fabric silicon-carbon anode gradually increases with different thermal reduction temperatures, while the capacity of the electrode material first increases and then decreases. Examples 2 and 4-7 show that as the deposition time increases, the amount of silicon deposited continuously increases. When the silicon content reaches 60.88%, the mechanical properties of the fabric severely decrease, leading to a decrease in the expansion of the anode material. Furthermore, the fabric exhibits characteristics of being easily broken and fractured, which exposes silicon particles between the layers to the electrolyte, resulting in a decrease in the initial efficiency. Comparative Example 4 shows that a lower spinning solution concentration severely reduces the mechanical properties of the fabric, also leading to a significant decrease in the initial efficiency and expansion of the anode material. Existing technologies disclose the preparation of silicon-carbon anodes using graphene; however, the technical performance of silicon-carbon anodes obtained from graphene fibers and graphene powder is inferior to that of mainstream porous carbon materials currently used in production.

[0059] Currently, researchers have made numerous attempts to design the structure and composition of silicon-carbon anode materials. From an electrochemical performance perspective, anode materials cannot simultaneously achieve both high initial efficiency and good cycle performance, primarily because the breakage of nano-silicon particles cannot be fundamentally suppressed. Furthermore, the material preparation process is complex, production costs are high, and industrial application is difficult. The graphene fiber fabric silicon-carbon anode material disclosed in this invention features a unique structural design. It uses a porous graphene fiber fabric as the matrix, woven from numerous short graphene fibers, which facilitates rapid electron and ion transport. Silicon particles are uniformly dispersed within the graphene fiber fabric, fully utilizing the conductivity and buffering effect of graphene. Simultaneously, a thin carbon layer coats the silicon particles, effectively preventing oxidation and improving material stability. This graphene fiber fabric structural design fully leverages the advantages of silicon's high specific capacity and graphene's excellent conductivity. Furthermore, the graphene fiber fabric mitigates silicon volume changes, significantly improving the electrode's power characteristics and cycle stability. Moreover, the entire preparation process is simple and controllable, facilitating large-scale production and application, and effectively solving the problems of existing technologies.

Claims

1. A method for preparing a graphene fiber fabric silicon-carbon anode composite material, comprising the following steps: depositing silicon on the surface of a porous graphene fiber fabric to obtain a porous graphene fiber fabric with nano-silicon deposited in the pores; and then carbon coating the porous graphene fiber fabric with nano-silicon deposited in the pores to obtain a graphene fiber fabric silicon-carbon anode composite material.

2. The method for preparing the graphene fiber fabric silicon-carbon anode composite material according to claim 1, characterized in that, Porous graphene fiber fabrics include porous graphene fiber nonwoven fabrics; porous graphene fiber fabrics are obtained by reducing porous graphene oxide fiber fabrics.

3. The method for preparing the graphene fiber fabric silicon-carbon anode composite material according to claim 2, characterized in that, Porous graphene oxide fiber fabrics were prepared using porous graphene oxide fibers.

4. The method for preparing the graphene fiber fabric silicon-carbon anode composite material according to claim 1, characterized in that, During silicon deposition, the silicon source gas includes silane, the temperature is 300℃~1000℃, and the time is 0.5~10 hours; the flow rate of the silicon source gas is 0~50ml / min, and the flow rate of the inert gas is 0~50ml / min.

5. The method for preparing the graphene fiber fabric silicon-carbon anode composite material according to claim 1, characterized in that, Carbon coating includes gas phase carbon coating, liquid phase carbon coating, or solid phase carbon coating.

6. The graphene fiber fabric silicon-carbon anode composite material prepared by the preparation method of any one of claims 1 to 5.

7. A negative electrode sheet comprising the graphene fiber fabric silicon-carbon negative electrode composite material of claim 6.

8. A lithium-ion battery comprising the negative electrode sheet of claim 7 or the graphene fiber fabric silicon-carbon negative electrode composite material of claim 6.

9. An electrochemical device comprising the lithium-ion battery of claim 8, the negative electrode of claim 7, or the graphene fiber fabric silicon-carbon negative electrode composite material of claim 6.

10. The application of the graphene fiber fabric silicon-carbon anode composite material of claim 6 in the preparation of lithium-ion battery anode sheets; the application of the graphene fiber fabric silicon-carbon anode composite material of claim 6 or the anode sheet of claim 7 in lithium-ion batteries.

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