A porous graphene silicon carbon thin film negative electrode and a preparation method and application thereof

Abstract

The present application relates to a kind of porous graphene silicon carbon film negative electrode and its preparation method and application, comprising: the closely stacked porous graphene oxide sheet, and the silicon carbon composite particles uniformly dispersed between porous graphene oxide sheet;The sheet quantity of porous graphene oxide sheet is greater than or equal to 2;Silicon carbon composite particles include: porous carbon matrix, nano silicon particles deposited and grown in the pore of porous carbon matrix, and carbon coating layer coated on the outer surface of porous carbon matrix;The sheet diameter of porous graphene oxide sheet is 10 μm~20 μm, and the thickness is 1 nm~3 nm;The pore size range of the pore of porous graphene oxide sheet is 3 nm~5 nm;The specific surface area of porous graphene silicon carbon film negative electrode is 1 m 2 / g~5 m 2 / g;The porous graphene silicon carbon film negative electrode is applied to lithium ion battery, and the conductivity, rate performance and cycle performance of battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a porous graphene silicon-carbon thin film anode, its preparation method, and its application. 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 widespread attention due to their high theoretical specific capacity of up to 4200 mAh / g, becoming one of the important candidate materials to replace graphite anodes. 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.

[0003] To address this issue, researchers have proposed a method for depositing nano-silicon on a carbon framework. This method utilizes the mechanical strength and conductivity of carbon materials to mitigate the volume changes of silicon, thereby improving the cycle stability of the battery. Specifically, the carbon framework can provide sufficient space for the nano-silicon to accommodate volume changes, while also providing good electron transport channels to improve the rate performance of the battery. However, porous carbon suffers from poor conductivity and cannot effectively enhance the strength of the carbon framework.

[0004] For example, Chinese invention patent CN111146430A (published on May 12, 2020) discloses a porous core-shell silicon-carbon anode material for lithium-ion batteries and its preparation method. This patent involves encapsulating nano-silicon with a particle size D50 of less than 100 nm within porous carbon, followed by carbon coating, to form a porous core-shell structure, thereby mitigating the volume change of silicon during charging and discharging. However, the porous carbon used in this invention has drawbacks, including poor conductivity, limited carbon skeleton strength, and limited ability to suppress silicon volume expansion.

[0005] Chinese invention patent CN112582615A (published March 30, 2021) discloses a one-dimensional porous silicon-carbon composite anode material, its preparation method, and its application. This patent involves oxidizing and non-melting SiO2 / polymer composite fibers obtained by electrospinning, followed by metallothermic reduction to obtain Si / SiO2 / carbon composite fiber material. After acid washing, water washing, and drying, the Si / SiO2 / carbon composite fiber material is further processed by hydrofluoric acid washing, water washing, and drying to remove excess SiO2, forming a porous silicon nanoparticle-embedded structure within the carbon fibers. Finally, high-temperature heat treatment yields the one-dimensional porous silicon / carbon composite anode material. This patent describes a process where carbon fiber is obtained through electrospinning of a polymer matrix. Porous silicon is then induced in situ through metallothermic reduction and etching, forming a structure containing porous silicon nanoparticles within the carbon fibers. While the carbon fibers do offer some protection against the volume expansion of silicon, their impact on the material's conductivity, specific capacity, and the initial coulombic efficiency and cycle capacity retention in batteries is limited. Furthermore, the preparation method of this patented material is complex and inefficient.

[0006] In summary, these patents explore novel technical pathways for depositing nano-silicon on a carbon material framework, aiming to overcome the defect of significant volume changes in silicon anode materials during charging and discharging, thereby improving the cycle life and power characteristics of the battery. Summary of the Invention

[0007] The purpose of this invention is to address the problems of poor conductivity, limited carbon skeleton strength, and limited suppression of silicon volume expansion in existing porous carbon substrates, and to provide a porous graphene silicon-carbon thin film anode, its preparation method, and its application.

[0008] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a porous graphene silicon-carbon thin film anode, the porous graphene silicon-carbon thin film anode comprising: tightly stacked porous graphene oxide sheets, and silicon-carbon composite particles uniformly dispersed between the porous graphene oxide sheets;

[0009] The porous graphene oxide sheet has a number of layers greater than or equal to 2;

[0010] The silicon-carbon composite particles include: a porous carbon matrix, nano-silicon particles deposited and grown in the pores of the porous carbon matrix, and a carbon coating layer covering the outer surface of the porous carbon matrix.

[0011] The porous graphene oxide sheet has a diameter of 10μm to 20μm and a thickness of 1nm to 3nm; the pore size of the porous graphene oxide sheet ranges from 3nm to 5nm.

[0012] The specific surface area of ​​the porous graphene-silicon-carbon thin film anode is 1 m². 2 / g~5m 2 / g.

[0013] Preferably, the mass of the porous graphene oxide sheet accounts for 9% to 37.5% of the total mass of the porous graphene silicon-carbon thin film anode.

[0014] The thickness of the porous graphene silicon-carbon thin film anode is between 70 μm and 100 μm.

[0015] Preferably, the porous carbon matrix has a porosity of 60% to 75% and an average pore size between 1.0 nm and 2.0 nm; the mass of the nano-silicon particles accounts for 48% to 52% of the silicon-carbon composite particles.

[0016] The thickness of the carbon coating layer is 1 nm to 5 nm;

[0017] The carbon coating layer accounts for 1% to 10% of the mass of the silicon-carbon composite particles.

[0018] Secondly, embodiments of the present invention provide a method for preparing the porous graphene-silicon-carbon thin film anode described in the first aspect above, the method comprising:

[0019] Step S1: Weigh silicon-carbon composite particles, or prepare silicon-carbon composite particles. The preparation of silicon-carbon composite particles includes: placing a porous carbon matrix in the cavity of a reaction device, heating it under a protective gas environment, then introducing a mixture of silicon source gas and protective gas, maintaining the temperature, so that the silicon element decomposed by the silicon source gas is deposited in the pores of the porous carbon matrix and grows into nano-silicon particles, thereby obtaining a silicon-carbon precursor material; and performing carbon coating treatment on the silicon-carbon particle precursor to obtain silicon-carbon composite particles.

[0020] Step S2: Place the silicon-carbon composite particles in a container and add a porous graphene oxide solution to the container, then stir at room temperature to obtain a mixed solution;

[0021] Step S3: The mixed solution is filtered, and the filtered product is dried at room temperature to obtain a thin film material.

[0022] Step S4: The thin film material is placed in a tube furnace and heat-treated in a protective gas environment. After cooling to room temperature and being discharged, a porous graphene silicon-carbon thin film anode is obtained.

[0023] Preferably, the reaction equipment includes any one of a fluidized bed reactor, a rotary kiln, and a chemical vapor deposition furnace;

[0024] The heating temperature is 300℃~600℃; the heat preservation time is 2~4 hours;

[0025] The silicon source gas includes one or more of the following: silane, silane, propane, and silicon tetrachloride; the flow rate range of both the silicon source gas and the protective gas is 0 to 5 L / min, but not including 0.

[0026] The protective gas in the preparation method includes one or more of the following: nitrogen, helium, xenon, radon, neon, and argon.

[0027] Preferably, the carbon coating treatment method includes any one of gas phase coating, liquid phase coating, or solid phase coating;

[0028] The gas source used for the gas phase coating includes one or more of methane, ethane, propane, acetylene, propyne, butyne, propylene, and ethylene; the gas phase coating time is 1 hour to 8 hours; and the gas phase coating temperature is 300℃ to 1000℃.

[0029] Preferably, the solvent of the porous graphene oxide solution is N,N-dimethylformamide (DMF);

[0030] The concentration of the porous graphene oxide solution is 1 mg / ml to 5 mg / ml;

[0031] The mass ratio of the silicon-carbon composite particles to the solute in the porous graphene oxide solution is 10:6 to 10:2.

[0032] The stirring speed is 50 rpm to 100 rpm, and the stirring time is 30 min to 60 min.

[0033] Preferably, the filtration conditions are as follows: filtration is performed using a circulating water vacuum pump at normal temperature and pressure.

[0034] The drying time is 3 to 8 hours.

[0035] Preferably, the heat treatment temperature is 1000℃~1500℃, and the heat treatment time is 2 hours~4 hours.

[0036] Thirdly, embodiments of the present invention provide a lithium-ion battery, the lithium-ion battery comprising the porous graphene silicon-carbon thin film negative electrode described in the first aspect above.

[0037] This invention provides a method for preparing a porous graphene silicon-carbon thin film anode. The method involves filtering and drying a mixed solution of silicon-carbon composite particles and porous graphene oxide solution to form a thin film material, followed by heat treatment to obtain the porous graphene silicon-carbon thin film anode. The preparation method provided by this invention is simple to operate and low in cost.

[0038] The porous graphene-silicon-carbon thin-film anode prepared by the above-described preparation method provided in this invention exhibits high conductivity, high ion conductivity, low expansion rate, and high stability. When applied to lithium-ion batteries, the porous graphene oxide sheets possess a layer-by-layer structure. The van der Waals forces between the graphene sheets enhance the adhesion between electrode materials, maintain a good conductive network, reduce contact resistance, and improve the overall conductivity of the battery. The porous structure of the graphene oxide sheets provides excellent ion transport channels, thereby improving the rate performance of the battery. The silicon-carbon particles are dispersed between the graphene sheets, and the high silicon content effectively suppresses volume changes in silicon during charge and discharge, enhancing the structural integrity of the electrode and improving the cycle stability of the battery. Compared to existing technologies, the porous graphene-silicon-carbon thin-film anode provided in this invention improves material capacity while maintaining good cycle stability, fully leveraging the synergistic effect of carbon and silicon materials to enhance the conductivity, rate performance, and cycle performance of lithium-ion batteries. Attached Figure Description

[0039] Figure 1 A flowchart illustrating the preparation method of the porous graphene silicon-carbon thin film anode provided in this embodiment of the invention.

[0040] Figure 2 Scanning electron microscope (SEM) image of the porous graphene silicon-carbon thin film anode prepared in Example 3 of this invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0043] This invention provides a porous graphene silicon-carbon thin film anode, comprising: tightly stacked porous graphene oxide sheets, and silicon-carbon composite particles uniformly dispersed between the porous graphene oxide sheets; the thickness of the porous graphene silicon-carbon thin film anode is between 70 μm and 100 μm.

[0044] The number of layers in a porous graphene oxide sheet is a positive integer greater than or equal to 2.

[0045] The silicon-carbon composite particles include: a porous carbon matrix, nano-silicon particles deposited and grown in the pores of the porous carbon matrix, and a carbon coating layer covering the outer surface of the porous carbon matrix.

[0046] The porous graphene oxide sheets have a diameter of 10μm to 20μm and a thickness of 1nm to 3nm; the pore size of the porous graphene oxide sheets ranges from 3nm to 5nm.

[0047] The specific surface area of ​​the porous graphene-silicon-carbon thin film anode is 1 m². 2 / g~5m 2 / g can be any value within the above range, for example: 1m 2 / g、2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g, etc., but not limited to the listed values; other unlisted values ​​within this range also apply. The specific surface area of ​​the porous graphene-silicon-carbon thin film anode of this invention is within the above-mentioned range, which can avoid direct contact between the electrolyte and the anode material, thereby improving the first-cycle coulombic efficiency of the battery.

[0048] The mass percentage of porous graphene oxide sheets in the total mass of porous graphene silicon-carbon thin film anodes ranges from 9% to 37.5%.

[0049] The porous carbon matrix has a porosity of 60%–75% and an average pore size between 1.0 nm and 2.0 nm; the mass percentage of nano-silicon particles in the silicon-carbon composite particles is 48%–52%.

[0050] The thickness of the carbon coating is 1 nm to 5 nm;

[0051] The carbon coating accounts for 1% to 10% of the mass of the silicon-carbon composite particles.

[0052] This invention provides a method for preparing the above-mentioned porous graphene-silicon-carbon thin film anode, such as... Figure 1 As shown, the specific steps include:

[0053] Step S1: Weigh silicon-carbon composite particles, or prepare silicon-carbon composite particles. The preparation of silicon-carbon composite particles includes: placing a porous carbon matrix in the chamber of a reaction device, heating it under a protective gas environment, then introducing a mixture of silicon source gas and protective gas, maintaining the temperature, so that the silicon element decomposed by the silicon source gas is deposited in the pores of the porous carbon matrix and grows into nano-silicon particles, thus obtaining a silicon-carbon precursor material; and then performing carbon coating treatment on the silicon-carbon particle precursor to obtain silicon-carbon composite particles.

[0054] This invention can directly use commercially available silicon-carbon composite particles, or it can prepare silicon-carbon composite particles.

[0055] The porous carbon matrix used to prepare the silicon-carbon composite particles has a porosity of 60% to 75% and an average pore size between 1.0 nm and 2.0 nm; the mass percentage of nano-silicon particles in the silicon-carbon composite particles is 48% to 52%.

[0056] The silicon source gas includes one or more of the following: silane, silane, propane, and silicon tetrachloride; the flow rate range of both the silicon source gas and the protective gas is 0 to 5 L / min, but excluding 0.

[0057] The heating temperature is 300℃~600℃; the holding time is 2~4 hours.

[0058] The protective gas used in the preparation method includes one or more of the following: nitrogen, helium, xenon, radon, neon, and argon.

[0059] Carbon coating methods include any one of gas phase coating, liquid phase coating, or solid phase coating; gas phase coating is preferred because the carbon source gas deposited in the gas phase can more effectively protect silicon particles from oxidation and further improve the chemical stability of the material.

[0060] The gas source used for gas phase coating includes one or more of the following: methane, ethane, propane, acetylene, propyne, butyne, propylene, and ethylene; the gas phase coating time is 1 hour to 8 hours; and the gas phase coating temperature is 300℃ to 1000℃.

[0061] The reaction equipment includes any one of the following: fluidized bed, rotary furnace, and chemical vapor deposition furnace.

[0062] Step S2: Place the silicon-carbon composite particles in a container and add a porous graphene oxide solution to the container. Then stir at room temperature to obtain a mixed solution.

[0063] The solvent for the porous graphene oxide solution is N,N-dimethylformamide (DMF).

[0064] The concentration of the porous graphene oxide solution is 1 mg / ml to 5 mg / ml.

[0065] The mass ratio of silicon-carbon composite particles to solute in porous graphene oxide solution is 10:6 to 10:2.

[0066] The stirring was carried out using conventional and known methods, with a stirring speed of 50 rpm to 100 rpm and a stirring time of 30 min to 60 min.

[0067] Step S3: The mixed solution is filtered by vacuum filtration, and then the filtered product is dried at room temperature to obtain the thin film material.

[0068] The specific conditions for vacuum filtration are as follows: filtration is performed using a circulating water vacuum pump at normal temperature and pressure. The drying time is 3 to 8 hours.

[0069] Step S4: The thin film material is placed in a tube furnace and heat-treated in a protective gas environment. After cooling to room temperature and being discharged, a porous graphene silicon carbon thin film anode is obtained.

[0070] The heat treatment temperature is 1000℃~1500℃, and the heat treatment time is 2 hours~4 hours.

[0071] The porous graphene-silicon-carbon thin film anode provided in this invention can be directly used as an anode in the assembly of lithium-ion batteries. Because the van der Waals forces between the porous graphene oxide sheets of the porous graphene-silicon-carbon thin film anode can enhance the adhesion between electrode materials, maintain a good conductive network, reduce the contact resistance of the electrode materials, and improve the overall conductivity of the battery; the porous structure of the porous graphene oxide sheets can provide good ion transport channels, thereby improving the rate performance of the battery; the silicon-carbon particles are dispersed between the graphene sheets, and the silicon content is high, the graphene sheets can effectively suppress the volume change of silicon during charging and discharging, enhance the structural integrity of the electrode, and improve the cycle stability of the battery.

[0072] To better understand the technical solution provided by the present invention, the following uses several specific examples to illustrate the preparation process and characteristics of the porous graphene silicon-carbon thin film anode of the present invention.

[0073] Example 1

[0074] This embodiment provides a process for preparing a porous graphene silicon-carbon thin film anode, the specific process of which is as follows.

[0075] (1) Preparation of silicon-carbon composite particles: 500g of porous carbon matrix is ​​placed in the cavity of a chemical vapor deposition furnace and heated to 480℃ in a nitrogen atmosphere. Then, a mixture of silane and nitrogen gas with a flow rate of 2.3L / min and a flow rate of 2.5L / min is introduced and kept at the temperature for 3 hours. The silicon element decomposed by silane is deposited in the pores of the porous carbon matrix and grows into nano-silicon particles. The introduction of silane is stopped to obtain silicon-carbon precursor material. Then, the temperature of the chemical vapor deposition furnace is raised to 540℃ and acetylene gas with a flow rate of 0.5L / min is introduced to carbon-coat the silicon-carbon particle precursor to obtain silicon-carbon composite particles.

[0076] (2) Take 50 mg of silicon-carbon composite particles and place them in a beaker. Add 10 ml of porous graphene oxide solution with a concentration of 1 mg / ml to the beaker. Then stir at 65 rpm for 40 min at room temperature to obtain a mixed solution. The solvent of the porous graphene oxide solution is DMF. The average diameter of the porous graphene oxide sheets is 15 μm, the average thickness is 2 nm, and the average pore size is 4 nm.

[0077] (3) The mixed solution was filtered by a circulating water vacuum pump at room temperature and pressure, and the filtered product was dried at room temperature for 5 hours to obtain the thin film material.

[0078] (4) The thin film material was placed in a tube furnace and heat-treated at 1200℃ for 3 hours in an argon atmosphere. After cooling to room temperature, the porous graphene silicon-carbon thin film anode was obtained. The carbon content in the porous graphene silicon-carbon thin film anode was 54.85 wt%.

[0079] The specific surface area of ​​the porous graphene-silicon-carbon thin film anode prepared in this embodiment was tested by nitrogen adsorption method. The test results are detailed in Table 1.

[0080] The electronic conductivity of the porous graphene silicon-carbon thin film anode prepared in this embodiment was tested: The electronic conductivity of the porous graphene silicon-carbon thin film anode was measured using a four-point probe resistivity meter, and the test results are detailed in Table 1.

[0081] The porous graphene silicon-carbon thin film anode prepared in this embodiment was subjected to bending conductivity testing: the electrode was bent 500 times and then the resistance of the electrode was tested using conventional methods to measure the ratio of the resistance of the electrode to that of the electrode before bending.

[0082] The porous graphene-silicon-carbon thin film anode prepared in this embodiment will be used as the anode, the lithium sheet as the counter electrode, the Ce L gard 2500 separator, and the electrolyte with a molar concentration of 1 mol / L Li PF6 (the solvent is ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) will be used to assemble a coin half cell in a glove box and test its electrochemical performance.

[0083] 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, specific charge capacity, and capacity retention after 300 cycles of the coin cell are shown in Table 1.

[0084] The full-charge expansion rate test is the electrode expansion rate of the coin cell. First, the thickness 1 of the porous graphene silicon-carbon film negative electrode before charging is measured, and then the thickness 2 of the porous graphene silicon-carbon film negative electrode after one week of charging and discharging is measured. The electrode expansion rate = (thickness 2 - thickness 1) / thickness 1 × 100%. The electrode expansion rate test data are shown in Table 1.

[0085] The discharge of the coin cell is a lithium insertion process, which corresponds to the charging process in a full cell. The charging of the coin cell is a lithium removal process, which corresponds to the discharge process in a full cell.

[0086] The withstand voltage test was evaluated by detecting the electrochemical performance of the sample before and after pressure. The withstand voltage test conditions were as follows: the porous graphene silicon carbon film negative electrode was pressurized by a pressure device to 50 MPa for 5 min. After pressure, the same assembly and testing methods as the above-mentioned coin half cell were used to test the first-cycle coulombic efficiency (hereinafter referred to as the first-cycle efficiency after pressure) of the negative electrode of the coin half cell. The test data are detailed in Table 1.

[0087] Example 2

[0088] This embodiment provides a process for preparing a porous graphene silicon-carbon thin film anode, the specific process of which is as follows.

[0089] (1) Preparation of silicon-carbon composite particles: 500g of porous carbon matrix is ​​placed in the cavity of a chemical vapor deposition furnace and heated to 480℃ in a nitrogen atmosphere. Then, a mixture of silane and nitrogen gas with a flow rate of 2.3L / min and a flow rate of 2.5L / min is introduced and kept at the temperature for 3 hours. The silicon element decomposed by silane is deposited in the pores of the porous carbon matrix and grows into nano-silicon particles. The introduction of silane is stopped to obtain silicon-carbon precursor material. Then, the temperature of the chemical vapor deposition furnace is raised to 540℃ and acetylene gas with a flow rate of 0.5L / min is introduced to carbon-coat the silicon-carbon particle precursor to obtain silicon-carbon composite particles.

[0090] (2) Take 50 mg of silicon-carbon composite particles and place them in a beaker. Add 15 ml of porous graphene oxide solution with a concentration of 1 mg / ml to the beaker. Then stir at 65 rpm for 40 min at room temperature to obtain a mixed solution. The solvent of the porous graphene oxide solution is DMF. The average diameter of the porous graphene oxide sheets is 15 μm, the average thickness is 2 nm, and the average pore size is 4 nm.

[0091] (3) The mixed solution was filtered by a circulating water vacuum pump at room temperature and pressure, and the filtered product was dried at room temperature for 5 hours to obtain the thin film material.

[0092] (4) The thin film material was placed in a tube furnace and heat-treated at 1200℃ for 3 hours in an argon atmosphere. After cooling to room temperature, the porous graphene silicon-carbon thin film anode was obtained. The carbon content in the porous graphene silicon-carbon thin film anode was 56.12 wt%.

[0093] The specific surface area, electronic conductivity, and bending conductivity of the porous graphene silicon-carbon thin film anode prepared in this embodiment were tested. The testing process was the same as in Example 1, and the test results are detailed in Table 1.

[0094] The porous graphene-silicon-carbon thin film anode prepared in this embodiment will be used as the anode to assemble a coin cell and test its electrochemical performance. The assembly and testing process is the same as in Example 1. The test results are detailed in Table 1.

[0095] Example 3

[0096] This embodiment provides a process for preparing a porous graphene silicon-carbon thin film anode, the specific process of which is as follows.

[0097] (1) Preparation of silicon-carbon composite particles: 500g of porous carbon matrix is ​​placed in the cavity of a chemical vapor deposition furnace and heated to 480℃ in a nitrogen atmosphere. Then, a mixture of silane and nitrogen gas with a flow rate of 2.3L / min and a flow rate of 2.5L / min is introduced and kept at the temperature for 3 hours. The silicon element decomposed by silane is deposited in the pores of the porous carbon matrix and grows into nano-silicon particles. The introduction of silane is stopped to obtain silicon-carbon precursor material. Then, the temperature of the chemical vapor deposition furnace is raised to 540℃ and acetylene gas with a flow rate of 0.5L / min is introduced to carbon-coat the silicon-carbon particle precursor to obtain silicon-carbon composite particles.

[0098] (2) Take 50 mg of silicon-carbon composite particles and place them in a beaker. Add 30 ml of porous graphene oxide solution with a concentration of 1 mg / ml to the beaker. Then stir at 65 rpm for 40 min at room temperature to obtain a mixed solution. The solvent of the porous graphene oxide solution is DMF. The average diameter of the porous graphene oxide sheets is 15 μm, the average thickness is 2 nm, and the average pore size is 4 nm.

[0099] (3) The mixed solution was filtered by a circulating water vacuum pump at room temperature and pressure, and the filtered product was dried at room temperature for 5 hours to obtain the thin film material.

[0100] (4) The thin film material was placed in a tube furnace and heat-treated at 1200°C for 3 hours in an argon atmosphere. After cooling to room temperature, the porous graphene silicon-carbon thin film anode was obtained. The carbon content in the porous graphene silicon-carbon thin film anode was 60.54 wt%.

[0101] SEM image of the porous graphene-silicon-carbon thin film anode prepared in Example 3, as shown below. Figure 2 As shown, the porous graphene silicon-carbon thin film anode is composed of porous graphene oxide sheets and silicon-carbon composite particles dispersed between the porous graphene oxide sheets.

[0102] The specific surface area, electronic conductivity, and bending conductivity of the porous graphene silicon-carbon thin film anode prepared in this embodiment were tested. The testing process was the same as in Example 1, and the test results are detailed in Table 1.

[0103] The porous graphene-silicon-carbon thin film anode prepared in this embodiment will be used as the anode to assemble a coin cell and test its electrochemical performance. The assembly and testing process is the same as in Example 1. The test results are detailed in Table 1.

[0104] To better illustrate the effects of the embodiments of the present invention, comparative examples 1-3 are compared with the above embodiments.

[0105] Comparative Example 1

[0106] This comparative example provides a preparation process for a porous graphene silicon-carbon thin film anode. The difference from Example 1 is that in step (2), the amount of porous graphene oxide solution with a concentration of 1 mg / ml is 5 ml. The other preparation processes are the same as in Example 1. The final porous graphene silicon-carbon thin film anode does not show the shape of a thin film anode, but is fragmented.

[0107] The specific surface area and electronic conductivity of the porous graphene silicon-carbon thin film anode prepared in this comparative example were measured. The testing process was the same as in Example 1, and the test results are detailed in Table 1.

[0108] The porous graphene-silicon-carbon thin film anode prepared using the comparative method will be used as the anode to assemble a coin cell and test its electrochemical performance.

[0109] Anode preparation process: The fragmented porous graphene silicon-carbon film anode prepared in this embodiment was mixed with Super P conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 16:2:1:1 (5 mg total) to prepare an aqueous anode slurry. The solid content of the slurry was controlled at approximately 45 wt%. The slurry was homogenized using a homogenizer. The slurry was coated onto copper foil to a thickness of 70 μm. After drying at 80°C, rolling, cutting, and vacuum drying at 110°C for 12 hours, the electrode sheet was obtained.

[0110] The prepared electrode sheets were used to assemble coin cells and tested, following the same procedure as in Example 1. The test results are detailed in Table 1.

[0111] Comparative Example 2

[0112] This comparative example uses silicon-carbon composite particles prepared in step (1) of Example 1 to directly prepare the negative electrode, wherein the carbon content of the silicon-carbon composite particles is 50.28 wt%.

[0113] The specific surface area and electronic conductivity of the silicon-carbon composite particles prepared in this comparative example were tested. The testing process was the same as in Example 1, and the test results are detailed in Table 1.

[0114] A negative electrode was prepared using silicon-carbon composite particles prepared in a comparative manner and assembled into a coin cell for testing.

[0115] Anode preparation process: A water-based anode slurry was prepared by mixing silicon-carbon composite particles with Super P conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber at a mass ratio of 16:2:1:1 (5 mg total). The solid content of the slurry was controlled at approximately 45 wt%. The slurry was homogenized using a homogenizer. The slurry was then coated onto copper foil to a thickness of 70 μm. After drying at 80℃, rolling, cutting, and vacuum drying at 110℃ for 12 hours, the electrode sheet was obtained.

[0116] The assembly of the coin cells and the testing of their electrochemical performance were performed in the same manner as in Example 1. The test results are detailed in Table 1.

[0117] Comparative Example 3

[0118] This comparative example provides a preparation process for a graphene oxide silicon carbon thin film anode. The difference from Example 2 is that the material mixed with the silicon carbon composite particles in step (2) is graphene oxide, not porous graphene oxide. The specific process is as follows.

[0119] (1) Same as in Example 2, silicon-carbon composite particles were obtained.

[0120] (2) Take 50 mg of silicon-carbon composite particles and place them in a beaker. Add 15 ml of graphene oxide solution with a concentration of 1 mg / ml to the beaker. Then stir at 65 rpm for 40 min at room temperature to obtain a mixed solution. The solvent of the graphene oxide solution is DMF, the average diameter of the graphene oxide sheets is 15 μm, and the average thickness is 2 nm.

[0121] (3) The mixed solution was filtered by a circulating water vacuum pump at room temperature and pressure, and the filtered product was dried at room temperature for 5 hours to obtain the thin film material.

[0122] (4) The thin film material was placed in a tube furnace and heat-treated at 1200℃ for 3 hours in an argon atmosphere. After cooling to room temperature, the graphene silicon-carbon thin film anode was obtained. The carbon content in the graphene silicon-carbon thin film anode was 54.85 wt%.

[0123] The specific surface area, electronic conductivity, and bending conductivity of the graphene oxide silicon carbon thin film anode prepared in this comparative example were tested. The testing process was the same as in Example 1, and the test results are detailed in Table 1.

[0124] The graphene oxide silicon carbon thin film anode prepared in the comparative example was used as the anode to assemble a coin cell and test its electrochemical performance. The assembly and testing process was the same as in Example 1, and the test results are detailed in Table 1.

[0125] Table 1 summarizes the test data for Examples 1-3 and Comparative Examples 1-3:

[0126]

[0127]

[0128] Table 1

[0129] Analyze the test data in Table 1:

[0130] A comparison of the test data from Comparative Example 1 and Examples 1-3 shows that the capacity of the thin-film electrode initially increases and then decreases with the continuous increase of porous graphene oxide content. This is mainly because: less porous graphene oxide (Comparative Example 1) is insufficient to form a good layered structure, leading to easy breakage of the film and thus reducing conductivity and capacity; while with the increase of porous graphene oxide content (Examples 1-3), the performance of the electrode material gradually improves, the conductivity increases, and the cycle life and mechanical stability are also significantly improved. This is because porous graphene helps to form a dense layered structure, improving conductivity and structural stability. At the same time, appropriate addition can also provide more active sites and electron transport channels, increasing lithium storage capacity and suppressing volume change. However, excessive addition will reduce silicon content and also affect battery capacity. Therefore, an appropriate amount of porous graphene oxide can improve battery performance, increasing conductivity, pressure resistance, and cycle life.

[0131] A comparison of the data from Comparative Example 3 and Example 2 shows that, compared to Comparative Example 3 which uses a conventional graphene film structure, the porous graphene film in Example 2 exhibits higher first-cycle coulombic efficiency, higher reversible capacity, and superior cycle stability, while the conductivity of Example 2 is similar to that of Comparative Example 3. This is because the porous structure increases the electrode / electrolyte contact area, which is beneficial for charge transfer and ion diffusion, thereby improving the first-cycle coulombic efficiency. Furthermore, the porous structure provides more buffer space for the silicon particles, effectively suppressing volume changes during charge and discharge, enhancing the structural stability of the electrode, and improving the reversible capacity.

[0132] Comparative Examples 2 and 3, and Example 2, demonstrate that the thin film structure, which sandwiches silicon carbon particles between porous graphene oxide sheets, exhibits superior electrochemical performance compared to conventional silicon carbon particles. This thin film structure forms dense conductive channels, significantly reducing contact resistance and improving overall conductivity, thereby substantially enhancing the first-cycle coulombic efficiency, charge specific capacity, and cycle stability. Simultaneously, the graphene sheets provide a buffer space for the silicon particles, effectively suppressing volume changes during charge and discharge and enhancing the structural integrity of the electrode.

[0133] Table 1 shows the first-cycle coulombic efficiency after pressure testing, which is achieved by assembling the negative electrodes of Examples 1-3 and 1-3 into coin cells after pressure testing. The first-cycle coulombic efficiency of Examples 1-3 is higher than that of Comparative Examples 1-3. This is because the carbon skeleton in the porous graphene silicon-carbon film negative electrode of Examples 1-3 has better strength than the carbon skeleton in the material of Comparative Examples 1-3, and has a better effect on suppressing silicon volume expansion.

[0134] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. 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 porous graphene-silicon-carbon thin film anode, characterized in that, The porous graphene silicon-carbon thin film anode comprises: tightly stacked porous graphene oxide sheets, and silicon-carbon composite particles uniformly dispersed between the porous graphene oxide sheets. The porous graphene oxide sheet has a number of layers greater than or equal to 2; The silicon-carbon composite particles include: a porous carbon matrix, nano-silicon particles deposited and grown in the pores of the porous carbon matrix, and a carbon coating layer covering the outer surface of the porous carbon matrix. The porous graphene oxide sheet has a diameter of 10μm to 20μm and a thickness of 1nm to 3nm; the pore size of the porous graphene oxide sheet ranges from 3nm to 5nm. The specific surface area of ​​the porous graphene-silicon-carbon thin film anode is 1 m². 2 / g~5m 2 / g.

2. The porous graphene-silicon-carbon thin film anode according to claim 1, characterized in that, The percentage of the mass of the porous graphene oxide sheet to the total mass of the porous graphene silicon-carbon thin film anode is 9% to 37.5%. The thickness of the porous graphene silicon-carbon thin film anode is between 70 μm and 100 μm.

3. The porous graphene-silicon-carbon thin film anode according to claim 1, characterized in that, The porous carbon matrix has a porosity of 60% to 75% and an average pore size between 1.0 nm and 2.0 nm; the mass of the nano-silicon particles accounts for 48% to 52% of the silicon-carbon composite particles. The thickness of the carbon coating layer is 1 nm to 5 nm; The carbon coating layer accounts for 1% to 10% of the mass of the silicon-carbon composite particles.

4. A method for preparing a porous graphene-silicon-carbon thin film anode according to any one of claims 1-3, characterized in that, The preparation method includes: Step S1: Weigh silicon-carbon composite particles, or prepare silicon-carbon composite particles. The preparation of silicon-carbon composite particles includes: placing a porous carbon matrix in the cavity of a reaction device, heating it under a protective gas environment, then introducing a mixture of silicon source gas and protective gas, maintaining the temperature, so that the silicon element decomposed by the silicon source gas is deposited in the pores of the porous carbon matrix and grows into nano-silicon particles, thereby obtaining a silicon-carbon precursor material; and performing carbon coating treatment on the silicon-carbon particle precursor to obtain silicon-carbon composite particles. Step S2: Place the silicon-carbon composite particles in a container and add a porous graphene oxide solution to the container, then stir at room temperature to obtain a mixed solution; Step S3: The mixed solution is filtered, and the filtered product is dried at room temperature to obtain a thin film material. Step S4: The thin film material is placed in a tube furnace and heat-treated in a protective gas environment. After cooling to room temperature and being discharged, a porous graphene silicon-carbon thin film anode is obtained.

5. The preparation method according to claim 4, characterized in that, The reaction equipment includes any one of the following: fluidized bed, rotary furnace, and chemical vapor deposition furnace; The heating temperature is 300℃~600℃; the heat preservation time is 2~4 hours; The silicon source gas includes one or more of the following: silane, silane, propane, and silicon tetrachloride; the flow rate range of both the silicon source gas and the protective gas is 0 to 5 L / min, but not including 0. The protective gas in the preparation method includes one or more of the following: nitrogen, helium, xenon, radon, neon, and argon.

6. The preparation method according to claim 4, characterized in that, The carbon coating treatment method includes any one of gas phase coating, liquid phase coating or solid phase coating; The gas source used for the gas phase coating includes one or more of methane, ethane, propane, acetylene, propyne, butyne, propylene, and ethylene; the gas phase coating time is 1 hour to 8 hours; and the gas phase coating temperature is 300℃ to 1000℃.

7. The preparation method according to claim 4, characterized in that, The solvent for the porous graphene oxide solution is N,N-dimethylformamide (DMF); The concentration of the porous graphene oxide solution is 1 mg / ml to 5 mg / ml; The mass ratio of the silicon-carbon composite particles to the solute in the porous graphene oxide solution is 10:6 to 10:

2. The stirring speed is 50 rpm to 100 rpm, and the stirring time is 30 min to 60 min.

8. The preparation method according to claim 4, characterized in that, The specific conditions for the filtration are: filtration is performed using a circulating water vacuum pump at normal temperature and pressure. The drying time is 3 to 8 hours.

9. The preparation method according to claim 4, characterized in that, The heat treatment temperature is 1000℃~1500℃, and the heat treatment time is 2 hours~4 hours.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the porous graphene silicon-carbon thin film negative electrode as described in any one of claims 1-3.

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