A negative electrode material, a preparation method thereof, and a battery

Abstract

The application relates to the technical field of negative electrode materials, in particular to a negative electrode material, a preparation method thereof and a battery. The negative electrode material comprises a silicon base, a first coating layer, the first coating layer comprising graphene and carbon nanotubes, the graphene being coated on at least part of the surface of the silicon base, and the carbon nanotubes being compounded in the sheet layer of the graphene; and a second coating layer, the second coating layer being coated on at least part of the surface of the first coating layer, and the second coating layer comprising MXene. The application constructs a negative electrode material (silicon base@G@CNTs / MXene) with a multilayer conductive framework structure, the first coating layer of the graphene and the carbon nanotubes inhibits the volume expansion of the silicon-based material, the outer layer of the MXene optimizes the conductive performance of the composite material, and the comprehensive performance of the negative electrode sheet and the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of negative electrode materials technology, and in particular to a negative electrode material, its preparation method, and a battery. Background Technology

[0002] Silicon-carbon anode materials have a theoretical specific capacity that is significantly higher than that of traditional graphite anodes, and have great potential to improve the energy density of lithium-ion batteries. They have become the ideal anode choice for the next generation of high-energy-density lithium-ion batteries, showing broad application prospects in the power and consumer lithium-ion battery markets.

[0003] Currently, silicon-based anodes still suffer from numerous technical drawbacks in practical applications. Silicon-based materials are prone to volume expansion during charge and discharge, which can not only compress the battery separator causing deformation but also potentially trigger micro-short circuits. Simultaneously, the growth of lithium dendrites reduces battery capacity, increases internal resistance, and may even puncture the separator, leading to battery failure and safety hazards. Furthermore, traditional silicon-carbon anodes suffer from poor interfacial contact between the conductive network and the active material, resulting in low electron transport efficiency. Volume expansion can also cause the active material to detach from the conductive network, and the insufficient stability of the binder further affects the battery's cycle performance. Against this backdrop, there is an urgent need for a technical solution that can effectively suppress the volume expansion of silicon materials and improve the overall performance of silicon-carbon anodes. Summary of the Invention

[0004] To address the core issues of inherent volume expansion, lithium dendrite growth, and poor conductivity in silicon-based anode materials during charge and discharge, this invention provides a silicon-based @G@CNTs / MXene anode material with a multilayer conductive framework structure. This material effectively buffers the volume changes of silicon through graphene encapsulation, enhances its mechanical integrity with covalently grafted carbon nanotubes, and constructs a three-dimensional macroscopic scaffold with both high conductivity and flexibility, forming a multidimensional conductive network with "point-line-surface" synergy. This allows the composite material to achieve high specific capacity while exhibiting excellent rate performance and cycle stability.

[0005] The first aspect of this invention provides a negative electrode material, the negative electrode material comprising: Silicon substrate; A first coating layer comprising graphene and carbon nanotubes, wherein the graphene is coated on at least a portion of the surface of the silicon substrate, and the carbon nanotubes are incorporated into the sheets of graphene. A second coating layer covers at least a portion of the surface of the first coating layer; the second coating layer includes MXene.

[0006] Optionally, the silicon substrate satisfies at least one of the following conditions: (1) The silicon matrix includes at least one of silicon, silicon oxide, silicon carbide, and silicon oxynitride; (2) The silicon substrate comprises SiO with a porous structure. x , 1 < x < 1.5; (3) The porosity of the silicon substrate is 40-80%.

[0007] Optionally, the first covering layer satisfies at least one of the following conditions: (1) The number of graphene sheets is 2-6; (2) The graphene content is 3-6 wt% of the mass of the negative electrode material; (3) The carbon nanotubes include multi-walled carbon nanotubes; (4) The content of the carbon nanotubes is 5-16 wt% of the mass of the negative electrode material; (5) The composite method is that the carbon nanotubes are grafted into the graphene sheets; (6) The composite method is that the carbon nanotubes are amidated and grafted into the graphene sheets.

[0008] Optionally, the MXene satisfies at least one of the following conditions: (1) The general formula of the MXene is M m+1 X m T y Where m is any integer from 1 to 3, y > 0; M is at least one of the transition metal elements Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W, Ni, Fe, Mn, Zn; X is C and / or N; and T is a surface-capping group, wherein the capping group includes at least one of -O, -Cl, -OH, and -F. (2) The MXene includes Ta4C3T y Nb4C3T y V4C3T y Ti3C2T y V2CT y Mo2CT y At least one of them; (3) The content of MXene is 3-12 wt% of the mass of the negative electrode material.

[0009] A second aspect of the present invention provides a method for preparing the negative electrode material as described above, the method comprising: Sol-gel method for preparing silicon substrates; Graphene is chemically vapor-deposited on at least a portion of the surface of the silicon substrate to form a silicon substrate @G; Carbon nanotubes are grafted into the graphene sheets to form a silicon matrix @G@CNTs, and the carbon nanotubes and the graphene form a first coating layer. The silicon substrate @G@CNTs and the MXene electrostatically self-assemble, and a second coating layer is coated on at least a portion of the surface of the first coating layer to form silicon substrate @G@CNTs / MXene, thereby obtaining the negative electrode material.

[0010] Optionally, the silicon substrate comprises SiO₂ with a porous structure. x The porous SiO x The preparation steps include: A silicon source is added to an alkaline solution, and a pore-forming agent is added while stirring. The reaction yields a precursor sol. The precursor sol was subjected to high-temperature reduction and pore formation under an inert gas atmosphere to form SiO with a porous structure. x ; Optionally, the high-temperature reduction pore-forming process includes a first stage and a second stage, wherein, In the first stage, the precursor sol is heated to 400-600°C and kept at that temperature to remove the pore-forming agent and form a porous SiO2 structure. In the second stage, the SiO2 is further heated to 700-850℃ and held at that temperature, causing the SiO2 to be reduced to form a porous SiO2 structure. X ; Optionally, the porous SiO x The preparation steps also satisfy at least one of the following conditions: (1) The heating rate in the first stage is 1-2℃ / min; (2) The heating rate in the second stage is 3-5℃ / min; (3) The pore-forming agent includes PS microspheres; (4) The ratio of the pore-forming agent to the silicon source is (0.5-1) g: (50-80) mL; (5) The reaction time in the precursor sol is 6-8 hours.

[0011] Optionally, the preparation steps for forming the silicon substrate @G include: Nickel is deposited on the surface of the silicon substrate to form a nickel-loaded precursor; The nickel-loaded precursor is placed in an inert gas atmosphere and subjected to cyclic carbon source pulses, and then cooled at a cooling rate of 25-50℃ / min to form a nickel-loaded silicon substrate @G containing the desired graphene sheets. The nickel-loaded silicon substrate @G is subjected to a nickel removal process to form a silicon substrate @G; One cycle of the cyclic carbon source pulse includes a first pulse and a second pulse, wherein, The first pulse is to heat the nickel-loaded precursor to 800-1000°C and introduce a mixed gas of CH4, H2 and Ar for 1-5 minutes. The second pulse is to stop the flow of CH4 and perform the second pulse for 1-3 minutes under a mixed gas of H2 and Ar; The preparation step of forming the silicon substrate @G also satisfies at least one of the following conditions: (1) The number of graphene layers in the nickel-supported silicon substrate @G is 3-6; (2) The number of cycles of the circulating carbon source pulse is 1-3 times; (3) The volume ratio of CH4, H2 and Ar during the first pulse is (1-3):(4-8):(10-30); (4) The volume ratio of H2 to Ar during the second pulse is 1:(3-6).

[0012] Optionally, the fabrication steps for forming the silicon substrate @G@CNTs include: The silicon substrate @G is contacted with a nitrogen-containing reactive gas and subjected to plasma treatment to obtain a silicon substrate @G with amino groups on its surface; The carbon nanotubes are subjected to acyl chloride treatment to obtain acyl chloride carbon nanotubes, which are then dispersed to form a first dispersion. The silicon matrix @G with amino groups on its surface is added to the first dispersion to immobilize and graft the carbon nanotubes onto the graphene sheets, forming silicon matrix @G@CNTs. The preparation step of forming silicon substrate @G@CNTs also satisfies at least one of the following conditions: (1) The radio frequency power of the plasma treatment is 100-300W, and the treatment time is 1-3min; (2) The mass ratio of the amino-containing silicon matrix @G on the surface to the first dispersion is (5-15):(1-10).

[0013] Optionally, the step of forming the silicon substrate @G@CNTs / MXene includes: Preparation of MXene colloids with negative potential; A second dispersion containing the silicon matrix @G@CNTs with a positive potential was prepared; The second dispersion and the MXene colloid are mixed to allow the silicon substrate @G@CNTs and the MXene to electrostatically self-assemble, thereby coating at least a portion of the surface of the first coating layer with the second coating layer to form silicon substrate @G@CNTs / MXene; Optionally, the step of forming the silicon substrate @G@CNTs / MXene also satisfies at least one of the following conditions: (1) The step of preparing a second dispersion containing the silicon matrix @G@CNTs with a positive potential includes: dispersing the silicon matrix @G@CNTs in a solvent, adding a cationic surfactant, and mixing until the potential of the dispersion is positive to obtain a second dispersion; (2) The cationic surfactant includes at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and polydiallyldimethylammonium chloride; (3) The mass ratio of the second dispersion to the MXene colloid is (5-10):1.

[0014] A third aspect of the present invention provides a battery in which the negative electrode sheet contains the negative electrode material as described above.

[0015] Beneficial effects: This invention provides a negative electrode material, its preparation method, and a battery, which have the following advantages: (1) This invention successfully constructs a silicon substrate @G@CNTs / MXene multilayer conductive framework structure as a negative electrode material, which solves the core problems of volume expansion and lithium dendrite growth of silicon-based negative electrodes from the root, while enhancing conductivity, constructing a stable multidimensional conductive network, and improving the overall performance of the electrode. (2) The present invention preferably uses porous SiO2 with a porosity of 40-80% and a particle size of 1 < x < 1.5. x As the core of the silicon substrate, the porous structure provides a buffer space for the volume expansion of silicon, which greatly reduces the electrode expansion rate during charging and discharging, avoids damage to the active material structure, and further improves electrochemical performance. (3) The present invention uses a cyclic pulse method in SiO x Two to six layers of graphene are grown on the surface to form a dense coating layer, which not only isolates the electrolyte from direct contact with the silicon substrate, but also improves the electron conduction efficiency through two-dimensional surface contact, and effectively restricts the local volume deformation of silicon. (4) In this invention, CNTs are preferably covalently grafted onto graphene sheets via amide bonds after acyl chlorination to construct a three-dimensional conductive network, which enhances the mechanical integrity of the electrode, achieves long-range efficient electron conduction, and avoids the conductive network from detaching from the active material during cycling. (5) The outer layer of the negative electrode material of the present invention is coated with MXene material by electrostatic self-assembly. Its high conductivity and flexibility form a macroscopic conductive support, which works in synergy with silicon matrix, graphene and carbon nanotubes to construct a “point-line-surface” conductive system, further improving the rate performance and cycle stability of the battery; (6) The negative electrode material prepared by the present invention significantly improves the energy density and capacity retention of the battery, and significantly reduces the internal resistance. It solves the key pain point of silicon-based negative electrode industrialization, is suitable for power and consumer lithium-ion batteries, and has broad application prospects. Attached Figure Description

[0016] Figure 1 Example 1: Preparation of SiO x Scanning electron microscope (SEM) morphology of @G@CNTs material; Figure 1 (a) is the SEM image of the carbon nanotubes used, (b) is the SEM image of the graphene grown by high-temperature CVD, and (c) and (d) are the SEM images of SiO₂. x SEM topography of @G@CNTs (different observation angles and positions of the same sample); Figure 2 Example 1: Carbon nanotubes, SiO x @G and SiO x Infrared spectrum of the @G@CNTs sample; Figure 3 Example 1 SiO x @G@CNTs / Ti3C2T y Infrared spectrum of the sample. Detailed Implementation

[0017] The first aspect of this invention provides a negative electrode material, the negative electrode material comprising: Silicon substrate; A first coating layer comprising graphene (G) and carbon nanotubes (CNTs), wherein the graphene is coated on at least a portion of the surface of the silicon substrate and the carbon nanotubes are incorporated into the sheets of graphene. A second coating layer covers at least a portion of the surface of the first coating layer; the second coating layer includes MXene.

[0018] Currently, silicon-based anodes still face numerous technical challenges in practical applications. On one hand, silicon-based materials are prone to volume expansion during charging and discharging, which can compress and deform the battery separator, potentially leading to micro-short circuits. On the other hand, the growth of lithium dendrites in lithium-ion battery anodes significantly reduces battery capacity and increases internal resistance; in severe cases, it can even puncture the separator, causing short circuits, battery failure, and potential safety hazards. Furthermore, traditional silicon-carbon anodes exhibit significant structural and performance defects, and the mechanically mixed conductive agents (such as CNTs / graphene) and SiO₂... xPoor interfacial contact between silicon-based materials leads to low electron transport efficiency, and the volume expansion of silicon-based materials can cause the active material to detach from the conductive network, affecting conductivity stability. This invention designs a specific anode material structure, using graphene and carbon nanotubes as the first coating layer to coat the silicon substrate, and MXene as the second coating layer to coat at least a portion of the surface of the first coating layer. This effectively limits the volume expansion of the silicon-based material during charge-discharge cycles and solves the technical problem that lithium dendrite growth in lithium-ion battery anodes reduces battery capacity, effectively improving the conductivity and overall performance of the anode material.

[0019] Optionally, the silicon substrate satisfies at least one of the following conditions: (1) The silicon matrix includes at least one of silicon, silicon oxide, silicon carbide, and silicon oxynitride; (2) The silicon substrate comprises SiO with a porous structure. x , 1 < x < 1.5; (3) The porosity of the silicon substrate is 40-80%.

[0020] Further optionally, the silicon substrate comprises SiO₂ with a porous structure. x x can be listed as 1.1, 1.2, 1.3, 1.4, etc.

[0021] Optionally, the porosity of the silicon substrate is 40-80%, such as 40%, 50%, 60%, 70%, 80%, etc.

[0022] The preferred material of this invention is porous SiO₂ with a porosity of 40-80% and a density of 1 < x < 1.5. x As the core of the silicon substrate, this porous structure provides ample buffer space for the inevitable volume expansion during the charge-discharge cycle of silicon-based materials. It can effectively offset the internal stress caused by volume deformation, significantly reduce the expansion rate of the electrode, and avoid structural damage and pulverization of the active material due to drastic volume changes. At the same time, the porous structure can also increase the contact area between the material and the electrolyte, promote the insertion and extraction of lithium ions, reduce ion transport resistance, and further improve the specific capacity, cycle stability and other electrochemical performance of the material on the basis of suppressing volume expansion. It provides a core structural basis for the stable operation of silicon-based anodes.

[0023] The porosity of the silicon substrate in this invention is determined by a gas displacement method. During implementation, the true density (skeletal density) of the sample is measured using a helium hydrometer, and its apparent density is determined using a geometric method. The porosity is calculated according to the following formula. Simultaneously, referring to the national standard GB / T 19587-2017, the BET specific surface area and BJH pore size distribution of the sample are measured using the nitrogen adsorption method. The porosity test results are cross-validated to ensure the accuracy and reliability of the results.

[0024] Porosity (%) = (1 - apparent density / true density) × 100% Optionally, the graphene satisfies at least one of the following conditions: (1) The number of graphene sheets is 2-6; (2) The graphene content is 3-6 wt% of the mass of the negative electrode material; (3) The carbon nanotubes include multi-walled carbon nanotubes; (4) The content of the carbon nanotubes is 5-16 wt% of the mass of the negative electrode material; (5) The composite method is that the carbon nanotubes are grafted into the graphene sheets; (6) The composite method is that the carbon nanotubes are amidated and grafted into the graphene sheets.

[0025] Further optionally, the number of graphene sheets is 2-6, such as 2, 3, 4, 5, or 6 layers; the content of graphene is 3-6 wt% of the mass of the negative electrode material, such as 3 wt%, 4 wt%, 5 wt%, or 6 wt%.

[0026] Optionally, the carbon nanotubes include multi-walled carbon nanotubes; the content of the carbon nanotubes is 5-16 wt% of the mass of the negative electrode material, such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, etc. The preferred content of carbon nanotubes in this invention is 5-16 wt% of the mass of the negative electrode material; when the carbon nanotube content is less than 5 wt%, it cannot form a continuous conductive network in the electrode system and cannot effectively connect the graphene-coated SiO₂. x The interaction between the carbon nanotubes and the MXene conductive framework results in a single electron transport path, relying solely on point contacts between graphene sheets for conduction. This significantly increases contact resistance, negating the one-dimensional conductive "line bridge" advantage of carbon nanotubes and ultimately reducing the electrode's rate performance and cycle stability. Furthermore, excessively high concentrations of carbon nanotubes readily aggregate in solvents like NMP, hindering uniform dispersion and disrupting the electrode's microstructure. Simultaneously, the over-diluting of the active material leads to a significant decrease in the electrode's volumetric energy density.

[0027] In some embodiments, the composite is achieved by grafting the carbon nanotubes onto the graphene sheets via amidation.

[0028] This invention leverages the high conductivity and two-dimensional ultrathin structure of graphene to effectively enhance the electronic conductivity of the electrode by forming a "surface-to-point" contact mode with the active material, requiring only a small amount of addition. Coating graphene onto the silicon substrate surface creates a two-dimensional electronic conduction channel, ensuring efficient lateral electron transport. Furthermore, selecting carbon nanotubes with a one-dimensional long-chain structure and utilizing their long-range electronic conduction properties, grafting carbon nanotubes into the graphene sheets enables efficient longitudinal electron conduction to the current collector, synergizing with the two-dimensional lateral conduction of graphene to further optimize the overall conductivity of the electrode.

[0029] Specifically, this invention employs a cyclic pulse method to grow 2-6 layers of graphene on the surface of a silicon substrate, forming a dense and suitable coating layer. This effectively isolates the electrolyte from direct contact with the silicon substrate, preventing corrosion of the silicon material. The two-dimensional surface contact characteristics of graphene enhance electron conduction efficiency, while effectively confining local volume deformation of silicon, providing basic expansion buffer and structural protection for the silicon material. Furthermore, multi-walled carbon nanotubes, after acidification and acyl chloride modification, are covalently grafted onto graphene sheets via amide bonds. This covalent connection is strong and stable, bridging the graphene sheets to construct a continuous three-dimensional conductive network. This strengthens the overall mechanical integrity of the electrode and enables long-range, efficient electron conduction, effectively preventing the problem of the conductive network detaching from the active material due to volume deformation of the silicon material during charge-discharge cycles, thus ensuring continuous and stable conductivity.

[0030] Optionally, the MXene satisfies at least one of the following conditions: (1) The general formula of the MXene is M m+1 X m T y Where m is any integer from 1 to 3, y > 0; M is at least one of the transition metal elements Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W, Ni, Fe, Mn, Zn; X is C and / or N; and T is a surface-capping group, wherein the capping group includes at least one of -O, -Cl, -OH, and -F. (2) The MXene includes Ta4C3T y Nb4C3T y V4C3T y Ti3C2T y V2CT y Mo2CT y At least one of them; (3) The content of MXene is 3-12 wt% of the mass of the negative electrode material.

[0031] Wherein, general formula M m+1 X m Ty In this context, y represents the number of surface-capped groups T. This value is not stoichiometric and varies from 1 to 2 due to the variable coverage of functional groups.

[0032] Further optionally, the MXene includes Ti3C2T y T includes -O, -OH and -F, and y is approximately 1.8.

[0033] This invention uses X-ray photoelectron spectroscopy (XPS) to analyze the surface chemical composition of MXene materials to determine T, and uses XPS quantitative analysis combined with thermogravimetric-mass spectrometry (TGA-MS) to determine y.

[0034] With Ti3C2T y For example, by peak fitting analysis of the high-resolution spectra of Ti 2p, O 1s and F 1s, it was determined that the surface functional group T mainly contains oxygen (-O), hydroxyl (-OH) and fluorine (-F).

[0035] Combining XPS quantitative analysis results and TGA-MS characterization results, based on the ratio of the total concentration of O and F atoms to the concentration of Ti atoms measured by XPS, and combined with the Ti3C2 crystal structure model (each Ti3C2 structural unit contains two layers of surface Ti atoms), and simultaneously using TGA-MS to quantitatively analyze the thermal decomposition behavior of surface functional groups, the average number of surface functional groups y was corrected and calculated to be approximately 1.8, proving that the material surface has high-density functional group modification.

[0036] The MXene of this invention is a type of transition metal carbide, nitride, or carbonitride material with a two-dimensional layered structure. It is usually obtained by etching a ternary layered MAX phase (M is a transition metal, A is a main group element, and X is carbon or nitrogen). It has abundant functional groups (such as -OH, -O, -F, etc.) between its layers, and combines metallic-grade electrical conductivity with good mechanical flexibility, showing broad application potential in energy storage, catalysis, electromagnetic shielding and other fields.

[0037] This invention encapsulates MXene material on the outer layer of the negative electrode material through electrostatic self-assembly, leveraging its metallic-grade high conductivity and good flexibility to form a highly adaptable macroscopic conductive scaffold. This outer structure, in synergy with the porous silicon substrate, graphene coating layer, and grafted carbon nanotubes, constructs a highly efficient "point-line-surface" multidimensional conductive system, significantly reducing ion and electron transport resistance, further improving the battery's fast-charging rate performance and long-cycle stability, while also helping to buffer volume expansion stress.

[0038] A second aspect of the present invention provides a method for preparing the negative electrode material as described above, the method comprising: Sol-gel method for preparing silicon substrates; Graphene is chemically vapor-deposited on at least a portion of the surface of the silicon substrate to form a silicon substrate @G; Carbon nanotubes (CNTs) are grafted into the graphene sheets to form a silicon matrix @G@CNTs, and the carbon nanotubes and the graphene form a first coating layer. The silicon substrate @G@CNTs and the MXene electrostatically self-assemble, and a second coating layer is coated on at least a portion of the surface of the first coating layer to form silicon substrate @G@CNTs / MXene, thereby obtaining the negative electrode material.

[0039] Optionally, the silicon substrate comprises SiO₂ with a porous structure. x The porous SiO x The preparation steps include: A silicon source is added to an alkaline solution, and a pore-forming agent is added while stirring. The reaction yields a precursor sol. The precursor sol was subjected to high-temperature reduction and pore formation under an inert gas atmosphere to form SiO with a porous structure. x ; Optionally, the high-temperature reduction pore-forming process includes a first stage and a second stage, wherein, In the first stage, the precursor sol is heated to 400-600°C and kept at that temperature to remove the pore-forming agent and form a porous SiO2 structure. In the second stage, the SiO2 is further heated to 700-850℃ and held at that temperature, causing the SiO2 to be reduced to form a porous SiO2 structure. X ; Optionally, the porous SiO x The preparation steps also satisfy at least one of the following conditions: (1) The heating rate in the first stage is 1-2℃ / min; (2) The heating rate in the second stage is 3-5℃ / min; (3) The pore-forming agent includes PS microspheres; (4) The ratio of the pore-forming agent to the silicon source is (0.5-1) g: (50-80) mL; (5) The reaction time in the precursor sol is 6-8 hours.

[0040] Optionally, the silicon source is added at a rate of 2-3 mL / min.

[0041] Optionally, the silicon source includes tetraethoxysilane (TEOS) or methyl orthosilicate (TMOS).

[0042] In some embodiments, the pore-forming agent may include PS (polystyrene) microspheres, PMMA (polymethyl methacrylate) microspheres, etc.

[0043] Furthermore, in this invention, the amount of pore-forming agent added is positively correlated with the degree of SiO2 reduction. The higher the amount of pore-forming agent added, the higher the degree of SiO2 reduction, and correspondingly, the smaller the x value.

[0044] In some embodiments, the inert gas may include N2, Ar, etc.

[0045] In some embodiments, the alkaline solution comprises a mixture of ethanol, water, and ammonia; the mass ratio of the ethanol, water, and ammonia is (20-25):(5-10):1.

[0046] In some embodiments, the porous SiO x The preparation steps include: Sol-gel pore formation: Under normal temperature conditions, an alkaline solution is added dropwise to 50-80 mL of silicon source at a rate of 2-3 mL / min, and stirred at a rate of 300-400 rpm. During the stirring process, 0.5-1 g of pore-forming agent is added simultaneously. The reaction is carried out for 6-8 h to obtain SiO2 / PS composite gel (i.e. precursor sol). High-temperature reduction pore formation: The SiO2 / PS composite gel is placed in a N2 atmosphere and heated from 25°C to 500°C at a rate of 1-2°C / min, and held at this temperature for 1-2 hours to remove the PS microspheres. The temperature is then increased from 500°C to 800°C at a rate of 3-5°C / min and held for 2-4 hours, causing the SiO2 to be reduced to form a porous SiO2 structure. X， The obtained SiO X Its porosity is 40-80%.

[0047] Optionally, the preparation steps for forming the silicon substrate @G include: Nickel is deposited on the surface of the silicon substrate to form a nickel-loaded precursor; The nickel-loaded precursor is placed in an inert gas atmosphere and subjected to cyclic carbon source pulses, and then cooled at a cooling rate of 25-50℃ / min to form a nickel-loaded silicon substrate @G containing the desired graphene sheets. The nickel-loaded silicon substrate @G is subjected to a nickel removal process to form a silicon substrate @G.

[0048] Optionally, one cycle of the cyclic carbon source pulse includes a first pulse and a second pulse, wherein, The first pulse is to heat the nickel-loaded precursor to 800-1000°C and introduce a mixed gas of CH4, H2 and Ar for 1-5 minutes. The second pulse involves stopping the flow of CH4 and introducing a mixture of H2 and Ar gas for 1-3 minutes. The preparation step of forming the silicon substrate @G also satisfies at least one of the following conditions: (1) The number of graphene layers in the nickel-silicon substrate @G is 3-6 layers, which can be listed as 3 layers, 4 layers, 5 layers, and 6 layers; (2) The number of cycles of the circulating carbon source pulse is 1-3 times, which can be listed as 1 time, 2 times, 3 times; (3) The volume ratio of CH4, H2 and Ar during the first pulse is (1-3):(4-8):(10-30); (4) The volume ratio of H2 to Ar during the second pulse is 1:(3-6).

[0049] A cycle is defined as one round of the first pulse and the second pulse. In some embodiments, when the number of cycles of the carbon source pulse is 1, the number of graphene sheets deposited on the silicon substrate surface is 3; when the number of cycles of the carbon source pulse is 2, the number of graphene sheets generated on the silicon substrate@G is 4; and when the number of cycles of the carbon source pulse is 3, the number of graphene sheets generated on the silicon substrate@G is 6.

[0050] This invention employs a pulse method to prepare sheet-like graphene on the surface of a silicon substrate via chemical vapor deposition (CVD), which can effectively suppress carbon source supersaturation and ensure the generation of the target number of graphene layers.

[0051] In some embodiments, the nickel removal process includes: immersing the nickel-loaded silicon substrate @G in an acidic solution, heating and stirring to completely dissolve the nickel; washing the product, collecting the solid product and drying it to obtain the silicon substrate @G.

[0052] In some embodiments, the step of forming the silicon substrate @G includes: Preparation of nickel-loaded precursor: SiO X Placed in a fluidized bed at 60-80℃, SiO₂ was treated with nickel salt solution at a rate of 0.5-1 mL / min. X Spray treatment is performed, with N2 continuously introduced during the spraying process to maintain the fluidized state of the system and ensure Ni 2+ (Converted to NiO) Selectively deposited only on SiO x The outer surface of the powder; after spraying, Ar is first introduced into the system for 10-15 min, then the system temperature is raised to 450-500℃ at a heating rate of 3-6℃ / min, and H2 / Ar mixed gas is introduced for 30-50 min to deposit the powder on the SiO2 surface. x The NiO on the surface is reduced to metallic Ni nanoparticles, resulting in a nickel-loaded precursor with Ni nanoparticles loaded on the surface.

[0053] High-temperature CVD growth of graphene: A nickel-loaded precursor is laid flat in a quartz boat and pushed into the isothermal zone of a tube furnace; high-flow-rate Ar gas is introduced into the quartz tube for 5-10 min to remove air. Under the Ar atmosphere, the temperature is increased to 900℃ at a rate of 5-10℃ / min, stabilized for 5-10 min, and then a circulating carbon source pulse is performed; specifically including: 1) First pulse: a mixed gas of CH4, H2, and Ar is introduced for 1-5 min; 2) Second pulse: the introduction of CH4 is stopped, and a second pulse is performed for 1-3 min under a mixed gas of H2 and Ar; heating is stopped, and the temperature is lowered at a cooling rate of 25-50℃ / min; the introduction of H2 is stopped when the temperature drops below 200℃, and the powder is collected under the Ar atmosphere to obtain the nickel-loaded silicon substrate @G.

[0054] Post-treatment to remove nickel: Immerse the nickel-loaded silicon substrate @G in an acidic solution of 1-3 mol / L and stir at 60-80℃ for 6-12 h to completely dissolve the nickel; wash the product, collect the solid product and dry it to obtain the silicon substrate @G.

[0055] In some embodiments, the nickel salt solution comprises nickel salt, citric acid and ethylene glycol in a mass ratio of (1-2):(1-2):(5-10).

[0056] Optionally, the nickel salt includes at least one of nickel nitrate, nickel chloride, nickel acetate, and nickel sulfate; more preferably, it is nickel nitrate.

[0057] Optionally, the volume ratio of H2 to Ar in the H2 / Ar mixed gas is (2-6):(94-98).

[0058] Optionally, the H2 / Ar mixed gas is introduced at a rate of 200-400 sccm; more preferably, at 250 sccm.

[0059] In some implementations, the thickness of the Ni nanoparticles is 5-8 nm; examples include 5 nm, 6 nm, 7 nm, 8 nm, etc.

[0060] Optionally, the volume ratio of CH4, H2 and Ar in the first pulse is (1-3):(4-8):(15-30).

[0061] Optionally, the volume ratio of H2 to Ar in the second pulse is 1:(3-6).

[0062] Optionally, after heating is stopped, the time for cooling from 900℃ to 500℃ should be controlled within 10 minutes to effectively suppress multi-layer accumulation.

[0063] In some embodiments, the acidic solution may include dilute hydrochloric acid, dilute nitric acid, etc.

[0064] In some implementations, the method of washing the product is not particularly limited, as long as the washing purpose can be achieved; for example, centrifugation or vacuum filtration.

[0065] Optionally, the drying temperature during the preparation of silicon substrate @G is 60-80℃; examples include 60℃, 65℃, 70℃, 75℃, and 80℃.

[0066] In some embodiments, the present invention uses a combination of full-field Raman scanning and precise electron microscopy verification to determine the number of layers in the generated graphene.

[0067] Taking graphene with 3 layers as an example: First, full-field Raman spectroscopy is used to rapidly image and characterize large-area CVD graphene samples, based on I... 2D / I G Intensity ratio, 2D peak half-width, and fitted peak shape characteristics were used to screen target regions that conformed to the structural characteristics of three-layer graphene. Subsequently, transmission electron microscopy (TEM) samples were prepared for the target regions selected by Raman spectroscopy. High-resolution transmission electron microscopy (HRTEM) was used to image the sample edges, directly visualizing and counting the number of graphene layers (observing three dark lattice lines). Selected area electron diffraction (SAED) characterization was combined to confirm its stacking mode and crystal quality. Only when the sample region simultaneously met the criteria of Raman spectroscopy and HRTEM (Raman spectroscopy exhibiting typical three-layer graphene characteristics, and HRTEM clearly observing three lattice fringes), could the successful preparation of high-quality three-layer graphene be confirmed.

[0068] Optionally, the fabrication steps for forming the silicon substrate @G@CNTs include: The silicon substrate @G is contacted with a nitrogen-containing reactive gas and subjected to plasma treatment to obtain a silicon substrate @G with amino groups on its surface; The carbon nanotubes are subjected to acyl chloride treatment to obtain acyl chloride carbon nanotubes, which are then dispersed to form a first dispersion. The silicon matrix @G with amino groups on its surface is added to the first dispersion to immobilize and graft the carbon nanotubes onto the graphene sheets, forming silicon matrix @G@CNTs. The preparation step of forming silicon substrate @G@CNTs also satisfies at least one of the following conditions: (1) The radio frequency power of the plasma treatment is 100-300W, and the treatment time is 1-3min; (2) The mass ratio of the amino-containing silicon matrix @G on the surface to the first dispersion is (5-15):(1-10).

[0069] In some embodiments, the step of forming the silicon substrate @G@CNTs includes: Acidification of CNTs: Place CNTs in an acid solution and reflux at 60-70℃ for 3-5 hours; cool to room temperature, dilute and centrifuge until the supernatant is neutral to obtain acidified CNTs; Acyl chloride treatment of CNTs: The obtained acidified CNTs were vacuum dried at 60-80℃ for 20-24h, then dispersed in acyl chloride reagent, 1-3 drops of organic solvent were added, and the mixture was refluxed at 70-80℃ for 12h. After the reaction was completed, the excess acyl chloride reagent was removed by rotary evaporation to obtain acyl chloride CNTs (CNT-COCl). Aminated silicon substrate @G: Powdered silicon substrate @G is placed in a quartz boat and spread into a uniform thin layer. It is then transferred to the reaction chamber of a plasma processor. The chamber is evacuated to a high vacuum to completely remove water vapor and oxygen from the air. A nitrogen-containing reactive gas is introduced into the chamber, and radio frequency (RF) is turned on. The power is set to 100W-350W for amination treatment, and the treatment time is 1-3 minutes to obtain aminated silicon substrate @G.

[0070] Amidation grafting: Powdered CNT-COCl was dispersed in anhydrous DMF (N,N-dimethylformamide) and sonicated for 10-20 min to form a CNT-COCl dispersion; powdered aminated silicon matrix @G was added to the CNT-COCl dispersion and sonicated for 10-30 min to ensure SiO2 grafting. x @G powder was fully contacted with CNT-COCl; TEA (triethylamine) was added to catalyze the amidation grafting reaction. After adding TEA, the reaction system was transferred from the ice bath to room temperature and magnetically stirred for 4-6 hours to complete the amidation grafting reaction.

[0071] Examples of acyl chloride reagents include thionyl chloride (SOCl2), oxalyl chloride, phosphorus pentachloride, phosphorus trichloride, etc.; SOCl2 can be selected as an example.

[0072] Examples of organic solvents include DMF (N,N-dimethylformamide), N,N-dimethylacetamide, pyridine, etc.; DMF is an option.

[0073] Optionally, the acid solution is a mixture of concentrated HNO3 and concentrated H2SO4, with a volume ratio of concentrated HNO3 to concentrated H2SO4 of 1:(2-4).

[0074] Optionally, the concentration of the concentrated HNO3 is 65-68 wt%.

[0075] Optionally, the concentration of the concentrated H2SO4 is 95-98 wt%.

[0076] In some embodiments, the thickness of the thin layer is 0.5-3 mm to ensure that the powdered silicon substrate@G can be directly exposed to the plasma atmosphere.

[0077] The nitrogen-containing reactive gas may include ammonia, methylamine, dimethylamine, trimethylamine, hydrazine, etc.; it may also be selected as high-purity ammonia.

[0078] In some implementations, after the amination treatment is completed, the plasma power supply is turned off, and nitrogen-containing reactive gas is continued to be introduced for a period of time to allow the sample to cool in the reactive gas atmosphere, ensuring that the newly generated free radical sites are fully functionalized; the nitrogen-containing reactive gas is stopped, the chamber is evacuated to a high vacuum again, and an inert gas (such as Ar) is introduced to atmospheric pressure. The quartz boat is then removed. At this point, the silicon substrate @G surface should have been successfully introduced with amino groups. The sample is then sealed and stored in a dry environment for subsequent use.

[0079] Optionally, the CNT-COCl is dispersed in DMF under 0°C ice bath conditions to suppress side reactions between CNT-COCl and trace amounts of moisture in the air.

[0080] Optionally, the aminated SiO x The mass ratio of @G and CNT-COCl dispersion is (5-15):(1-10).

[0081] The principle of the amidation grafting reaction in this invention is to react the acyl chloride group (-COCl) of CNT-COCl with the amino group (-NH2) on the plasma-activated silicon substrate @G surface to form an amide bond (-CONH-). The reaction formula for this process is as follows: CNT-COCl+H2N-silicon matrix@G→CNT-CONH-silicon matrix@G+HCl In some embodiments, after the amidation grafting reaction, the product is washed 2-5 times by centrifugation with DMF to dissolve and remove most of the organic byproducts and unreacted raw materials; it is then washed 2-5 times by centrifugation with ethanol to replace the high-boiling-point DMF in the system, facilitating subsequent drying; the washed product is then dried at 60-80°C to obtain SiO2. x @G@CNTs composite powder; SEM / TEM characterization showed that CNTs were successfully grafted into graphene sheets.

[0082] To improve the grafting rate, the amount of TEA added to the reaction system can optionally be 5-10 wt%.

[0083] Optionally, the step of forming the silicon substrate @G@CNTs / MXene includes: Preparation of MXene colloids with negative potential; A second dispersion containing the silicon matrix @G@CNTs with a positive potential was prepared; The second dispersion and the MXene colloid are mixed to allow the silicon substrate @G@CNTs and the MXene to electrostatically self-assemble, thereby coating at least a portion of the surface of the first coating layer with the second coating layer to form silicon substrate @G@CNTs / MXene; Optionally, the step of forming the silicon substrate @G@CNTs / MXene also satisfies at least one of the following conditions: (1) The step of preparing a second dispersion containing the silicon matrix @G@CNTs with a positive potential includes: dispersing the silicon matrix @G@CNTs in a solvent, adding a cationic surfactant, and mixing until the potential of the dispersion is positive to obtain a second dispersion; (2) The cationic surfactant includes at least one of hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride, and polydiallyldimethylammonium chloride; (3) The mass ratio of the second dispersion to the MXene colloid is (5-10):1.

[0084] Optionally, the general formula M of the MXene m+1 X m T y M in m+1 X m It is obtained by selectively etching the A layer of its precursor material MAX; for example, Ti3C2 is obtained by selectively etching the Al layer of Ti3AlC2.

[0085] In some embodiments, the selective etching method is acid etching, that is, an acidic reagent can be selected to selectively etch the A layer; the acidic reagent may include LiF, HF, etc.

[0086] As an example of M3X2 type MXene, when the MXene is Ti3C2T y The preparation steps of the negatively charged MXene colloid include: In a well-ventilated environment, LiF was dissolved in an aqueous HCl solution and stirred until homogeneous. Powdered Ti3AlC2 was added under ice-water bath cooling conditions, and the mixture was magnetically stirred at low speed at 35-40°C for 24-26 hours to selectively etch the Al layer. The mixture was transferred to centrifuge tubes and centrifuged and washed multiple times under Ar protection until the supernatant pH > 6 (near neutral). The mixture was then centrifuged at high speed, and the upper layer rich in Ti3C2 was collected. y The colloidal dispersion is denoted as the first dispersion.

[0087] Optionally, the mass ratio of Ti3AlC2 to LiF is 1:(1-2).

[0088] As an example of M4X3 type MXene, when the MXene is V4AlC3, the preparation steps of the negatively charged MXene colloid include: In a well-ventilated environment, LiF is dissolved in an aqueous HCl solution and stirred until homogeneous. Powdered V4AlC3 is added under ice-water bath cooling conditions, and the mixture is magnetically stirred at low speed at 40-55℃ for 30-50 hours to selectively etch the Al layer. The mixture is then transferred to a centrifuge tube and centrifuged and washed multiple times under Ar protection until the pH of the supernatant is >6 (close to neutral). After high-speed centrifugation, the upper colloidal dispersion rich in V4AlC3 (usually dark green or black) is collected and recorded as the first dispersion.

[0089] Optionally, the mass ratio of V4AlC3 to LiF is 1:(1-4).

[0090] As an example of M2X-type MXene, when the MXene is V2AlC, the preparation steps of the negatively charged MXene colloid include: In a well-ventilated environment, LiF is dissolved in an aqueous HCl solution and stirred until homogeneous. Powdered V2AlC is added under ice-water bath cooling conditions, and after mixing, it is allowed to stand at 30-40℃ for 20-35 hours to selectively etch the Al layer. After etching, deionized water is added to the mixture (the mass ratio of deionized water to the mixture is (60-100):1), shaken, and centrifuged at high speed. The mixture is then centrifuged and washed under Ar protection until the pH of the supernatant is >6 (usually dark black). The wet precipitate is transferred to a beaker, and deionized water is added at a mass ratio of precipitate to water of 1:(150-300). The mixture is ultrasonicated in an ice-water bath under Ar atmosphere to remove Al. The removed suspension is centrifuged at 1000-2000 rpm for 0.5-2 hours, and the upper dark black colloid is collected. This is the colloidal dispersion rich in V4AlC, which is referred to as the first dispersion. The dark precipitate in the lower layer is V2AlC that has not been completely removed and can be recycled and removed again.

[0091] Optionally, the mass ratio of V2AlC to LiF is 1:(1-3).

[0092] Optionally, the concentration of HCl in the HCl aqueous solution is 6-10 mol / L.

[0093] Optionally, the mass ratio of the LiF and HCl aqueous solution is 1:(10-25).

[0094] Optionally, the high-speed centrifugation conditions are centrifugation at 3000-12000 rpm for 5-20 min.

[0095] In some embodiments, the concentration of MXene colloid in the first dispersion is 8-10 mg / mL.

[0096] In some implementations, the resulting MXene colloid should always be stored sealed in a glove box, and its preparation and storage should strictly avoid contact with air to prevent oxidative degradation.

[0097] In some embodiments, the step of forming the silicon substrate @G@CNTs / MXene includes: Powdered silicon matrix @G@CNTs were dispersed in a solvent, and 0.1 wt% of surfactant CTAB was added. The mixture was then sonicated until the system potential turned positive to obtain a second dispersion. The first dispersion and the second dispersion were mixed evenly at a mass ratio of (5-10):1. The mixed slurry was flash-frozen using liquid nitrogen and then freeze-dried to obtain the silicon matrix @G@CNTs / MXene.

[0098] Optionally, the product obtained after freeze-drying has a block structure. The product is further lightly pressed, ground, and sieved to obtain a powdered silicon matrix @G@CNTs / MXene.

[0099] The solvent may include N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), cyclohexanone, etc., and NMP may be selected; in some embodiments, the amount of NMP added is 5-20 mg / mL.

[0100] Optionally, the potential of the first dispersion is 28-38mV.

[0101] Optionally, the mixing process of the first and second dispersions needs to be controlled by slow mixing and gentle stirring until homogeneous. Since the prepared MXene colloid itself is negatively charged, while the second dispersion containing silicon matrix @G@CNTs is positively charged, the two can achieve spontaneous and uniform self-assembly by relying on the electrostatic attraction between the positive and negative charges to obtain the target anode material silicon matrix @G@CNTs / MXene.

[0102] Optionally, the freeze-drying conditions are: freeze-drying at -50~-60℃ for 48-56 hours; the freeze-drying process can effectively and completely preserve the three-dimensional porous structure of the material, avoid structural collapse and shrinkage that are prone to occur during the drying process, and thus maintain its high specific surface area and open pore characteristics.

[0103] This invention prepares a SiOx@G@CNTs / MXene anode material, which effectively limits the volume expansion of silicon-based materials through a double-layer coating structure. Specifically, graphene is first tightly wrapped around SiOx. x On the surface, carbon nanotubes are then grafted between graphene sheets to form the first coating layer, constructing a three-dimensional multi-level conductive network that effectively confines SiO₂. xThe volume expansion during charging and discharging can also isolate SiO. x Direct contact with the electrolyte avoids side reactions, promotes efficient lithium-ion transport, and improves the conductivity of silicon-based materials while ensuring electrode stability. Furthermore, this invention employs MXene (e.g., Ti3C2T). y As the second coating layer, MXene's metallic conductivity is fully utilized, and the resulting layered structure endows the anode material with suitable flexibility and mechanical strength. This helps buffer the stress caused by the volume expansion of the silicon-based material, synergistically improving the overall performance of the electrode. Based on the above structural design, this invention eliminates the need to add a separate conductive agent to the anode slurry, further increasing the proportion of active materials and effectively improving the battery's energy density, thus synergistically addressing many technical shortcomings of traditional silicon-carbon anodes.

[0104] A third aspect of the present invention provides a battery in which the negative electrode sheet contains the negative electrode material as described above.

[0105] In some embodiments, the battery assembly method includes: placing the positive electrode sheet at the bottom of the positive electrode shell in an inert gas atmosphere, and dripping an appropriate amount of electrolyte to wet the electrode surface; then laying a separator to cover the positive electrode sheet, and then placing the negative electrode sheet on top of the separator; after sequentially stacking elastic gaskets and insulating washers, snapping the negative electrode shell together and hydraulically sealing it to form a button cell.

[0106] In some embodiments, the preparation steps of the negative electrode sheet include: mixing the negative electrode material, conductive agent and negative electrode binder as described above to obtain a mixture one; adding the mixture one to water and stirring evenly to obtain a negative electrode slurry; coating the negative electrode slurry onto the surface of the negative electrode current collector, and drying and rolling to obtain a negative electrode sheet.

[0107] Optionally, the mass ratio of the negative electrode material, conductive agent, and binder is (94-98):(1-3):(1-3); most preferably, it is 96:2:2.

[0108] Examples of conductive agents include conductive carbon black and carbon fiber. The role of conductive agents is to improve the conductivity of the negative electrode material, reduce the internal resistance of the electrode, and ensure that electrons can be transported efficiently inside the electrode, thereby achieving the purpose of improving the overall electrical performance of the battery. This invention does not impose any particular limitation on the selection of conductive agents.

[0109] Examples of negative electrode binders include CMC (carboxymethyl cellulose), SBR (styrene-butadiene rubber), PAA (polyacrylic acid) and its derivatives, PAI (polyamide-imide), etc. The function of the negative electrode binder is to firmly bond the negative electrode material to the current collector, while maintaining the structural stability of the negative electrode sheet, preventing the active material from falling off, and achieving the purpose of ensuring the integrity and performance stability of the electrode sheet during the charging and discharging process of the battery. This invention does not impose any particular limitation on the selection of binders.

[0110] In some embodiments, the preparation steps of the positive electrode sheet include: mixing a positive active material, a conductive agent and a positive binder to obtain a second mixture; adding the second mixture to NMP and stirring evenly to obtain a positive slurry; coating the positive slurry onto the surface of the positive current collector, and drying and rolling to obtain a positive electrode sheet.

[0111] Optionally, the mass ratio of the positive electrode active material, conductive agent and positive electrode binder is (93-97):(2-4):(1-3); most preferably it is 95:3:2.

[0112] Examples of positive electrode active materials include, but are not limited to, lithium iron phosphate, ternary nickel cobalt manganese (NCM), ternary nickel cobalt aluminum (NCA), lithium cobalt oxide, lithium manganese oxide, lithium vanadium oxide, and lithium vanadium phosphate; in some embodiments, the positive electrode active material is lithium iron phosphate.

[0113] Examples of positive electrode binders include PVDF (polyvinylidene fluoride), PEO (polyethylene oxide), PI (polyimide), PAI, etc. The function of the positive electrode binder is to uniformly bond the positive electrode active material to the current collector, ensure the mechanical strength and structural stability of the electrode, inhibit the shedding of active material, and ensure the stability of the electrochemical performance of the battery during long-term cycling. This invention does not specifically limit the type of positive electrode binder.

[0114] In some embodiments, the preparation steps of the separator include: coating a PVDF adhesive layer on both sides of a PE base film with a thickness of 5-10 μm, and then coating a ceramic layer on one side facing the positive electrode to prevent the risk of high voltage breakdown.

[0115] Optionally, the electrolyte includes a lithium salt and a mixed solvent; the concentration of the lithium salt in the electrolyte is 0.2-2 mol / L.

[0116] Examples of lithium salts include, but are not limited to, LiPF6, LiBF4, and LiClO4.

[0117] Optionally, the mixed solvent includes at least two of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); further optionally, the mixed solvent includes EC and DMC, with a volume ratio of EC to DMC of 1:(0.5-3); even more preferably, it is 1:1.

[0118] The silicon-based @G@CNTs / MXene anode material prepared by this invention can endow batteries with excellent energy density and capacity retention, and significantly reduce battery internal resistance, fundamentally solving the key industrialization pain points of silicon-based anodes such as volume expansion and poor conductivity. This material has excellent adaptability and can be flexibly combined with various conductive agents and binders, all of which exhibit good performance. It meets the application requirements of power and consumer lithium-ion batteries, possessing extremely high industrialization value in the field of new energy batteries and showing very broad application prospects.

[0119] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0120] Unless otherwise specified, all concentrations involved in this invention are mass concentrations, and all ratios are mass ratios; the room temperature is 25°C.

[0121] Example 1 This embodiment provides a negative electrode material, its preparation method, and a battery; the negative electrode material includes: (1) Silicon substrate: porous SiO x The x-value is 1.3, and the porosity is 80%. (2) First coating layer: The first coating layer includes graphene with 3 layers and multi-walled carbon nanotubes. The graphene is coated on part of the surface of the silicon substrate, and the carbon nanotubes are amidated and grafted into the graphene layers to achieve composite. (3) A second coating layer MXene, specifically Ti3C2T, is coated on at least a portion of the surface of the first coating layer. y T includes -O, -OH, and -F, and y is 1.8; T is determined by X-ray photoelectron spectroscopy (XPS), and y is determined by XPS quantitative analysis combined with thermogravimetric-mass spectrometry (TGA-MS).

[0122] The graphene content is 3 wt% of the anode material mass, the carbon nanotube content is 10 wt% of the anode material mass, and the Ti3C2T content is... y The content is 10 wt% of the mass of the negative electrode material.

[0123] The negative electrode material is denoted as SiO. x @G@CNTs / Ti3C2T y Its preparation steps include: S1. Preparation of silicon-based SiO2 by sol-gel methodx S1.1 Sol-gel pore formation: At 25℃, 50 mL of alkaline solution (a mixture of ethanol, deionized water, and ammonia in a mass ratio of 20:5:1, with an ammonia concentration of 28 wt%) was added dropwise to 50 mL of silicon source (TEOS) at a rate of 2 mL / min. The mixture was stirred at 350 rpm, and 1 g of pore-forming agent (PS microspheres, sourced from Beijing Nanomicro Standards Technology Co., Ltd., model CUP-PS-80nm) was added simultaneously during the stirring process. The reaction was carried out for 8 h to obtain SiO2 / PS composite gel (i.e., precursor sol). S1.2 High-Temperature Reduction Pore Formation: The SiO2 / PS composite gel was placed in a N2 atmosphere and heated from 25°C to 500°C at a rate of 2°C / min, and held at this temperature for 2 hours to remove the PS microspheres. Then, the temperature was increased from 500°C to 800°C at a rate of 4°C / min and held for 2 hours, causing the SiO2 to be reduced to form a porous SiO2 structure. X， The obtained SiO X The x-value is 1.3, and the porosity is 80%; the porosity was determined by the gas displacement method.

[0124] S2. Preparation of SiO x @G S2.1 Preparation of nickel-loaded precursor: SiO X The solution was placed in a fluidized bed at 60°C, and a nickel salt solution (a mixture of nickel nitrate, citric acid, and ethylene glycol in a mass ratio of 1:1:5) was applied to SiO2 through a micro-nozzle at a rate of 0.5 mL / min. X Spraying was performed, with N2 continuously introduced during the spraying process to maintain the fluidized state of the system. After spraying, Ar was introduced into the system for 15 min, and then the system temperature was raised to 450℃ at a heating rate of 5℃ / min. A mixed gas of H2 / Ar (volume ratio of H2 to Ar of 5:95) was introduced at a total flow rate of 250 sccm for 30 min to obtain a nickel-loaded precursor with Ni nanoparticles (thickness of 5 nm) on its surface.

[0125] S2.2 High-Temperature CVD Growth of Graphene: A nickel-loaded precursor was laid flat in a quartz boat and pushed into the isothermal zone of a tube furnace. Ar gas was introduced into the quartz tube at a flow rate of 500 sccm for 5 min to purge air. Under the Ar atmosphere, the temperature was increased to 900℃ at a rate of 5℃ / min, stabilized for 5 min, and then subjected to a circulating carbon source pulse. Specifically, this included: 1) First pulse: A mixed gas of CH4, H2, and Ar (volume ratio 2:5:20, total flow rate 200 sccm) was introduced for a first pulse of 3 min; 2) Second pulse: CH4 was stopped, and a mixed gas of H2 and Ar (volume ratio maintained at 5:20, total flow rate 200 sccm) was introduced for a second pulse of 2 min; heating was stopped, and the temperature was lowered at a cooling rate of 50℃ / min until below 200℃. H2 introduction was stopped, and the temperature was lowered to 25℃. The powder was collected under an Ar atmosphere to obtain nickel-loaded SiO2. x @G.

[0126] S2.3 Post-treatment nickel removal: The nickel-loaded SiO₂ in the quartz boat is removed... x @G was immersed in a 1 mol / L hydrochloric acid aqueous solution and stirred at 60°C for 6 hours to completely dissolve Ni; the product was washed with deionized water until the supernatant was neutral, then washed with ethanol to dehydrate, the solid product was collected by vacuum filtration and dried in a vacuum oven at 60°C to obtain SiO. x @G; The number of graphene sheets generated was determined to be 3 using a combination of full-field Raman scanning and precise electron microscopy verification.

[0127] S3. Preparation of SiO x @G@CNTs S3.1 Acidification treatment of CNTs: 1.2 g of CNTs (multi-walled carbon nanotubes, sourced from XFNANO, model XFM22) were placed in 120 mL of acid solution (a mixture of concentrated HNO3 and concentrated H2SO4 in a volume ratio of 1:3, with concentrated HNO3 concentration of 65 wt% and concentrated H2SO4 concentration of 98 wt%), and refluxed at 60 °C for 5 h; after cooling to room temperature, the mixture was diluted with deionized water and centrifuged until the supernatant was neutral (pH=7) to obtain acidified CNTs; S3.2 Acyl chloride treatment of CNTs: The obtained acidified CNTs were dried under vacuum at 80°C for 24 h, then dispersed in acyl chloride reagent (SOCl2), 2 drops of organic solvent (DMF) were added, and the mixture was refluxed at 75°C for 12 h. After the reaction was completed, excess SOCl2 was removed by rotary evaporator in a fume hood to obtain acyl chloride CNTs (CNT-COCl). S3.3 Preparation of Aminated SiO x @G: Powdered SiO xThe sample was placed in a quartz boat and laid as a uniform thin layer. It was then transferred to the reaction chamber of the plasma processor. The mechanical and molecular pumps were activated, and the chamber was evacuated to a high vacuum to completely remove moisture and oxygen from the air. High-purity ammonia (purity > 99%) was introduced into the chamber, and the RF was turned on and set to 300W for amination treatment for 3 minutes. The plasma power was then turned off, and ammonia was continued to be introduced for 10 minutes to allow the sample to cool in the ammonia atmosphere. When the sample cooled to 25°C, the ammonia introduction was stopped, and the chamber was evacuated to a high vacuum again. Ar was then introduced to atmospheric pressure, and the quartz boat was removed. At this point, SiO₂... x @G surface should have successfully introduced amino groups, resulting in aminated SiO2. x @G, Store in a sealed container in a dry environment for later use.

[0128] S3.4 Amidation Grafting: Powdered CNT-COCl was dispersed in anhydrous DMF (concentration 62.5 wt%) under 0℃ ice bath conditions and sonicated for 15 min to form a CNT-COCl dispersion; powdered aminated SiO2 was then grafted onto anhydrous DMF. x @G is added to the CNT-COCl dispersion (aminated SiO₂) x The mass ratio of @G and CNT-COCl dispersion is 5:1, and aminated SiO₂ x (The solid ratio of G and CNT-COCl was 8:1), and the mixture was sonicated for 15 min to ensure uniform dispersion. 1 wt% TEA was added to the reaction system for amidation grafting. After adding TEA, the reaction system was transferred from an ice bath to room temperature and magnetically stirred for 5 h to complete the amidation grafting reaction. After the reaction, the product was washed three times with DMF and three times with ethanol. The washed product was then dried in a vacuum oven at 80 °C to obtain SiO₂. x @G@CNTs composite powder; Figure 1 As shown, SEM / TEM characterization revealed that CNTs were successfully grafted into the graphene sheets.

[0129] S4. Preparation of SiO x @G@CNTs / Ti3C2T y S4.1 Preparation of Ti3C2T by LiF-HCl Method y In a fume hood, LiF was dissolved in a 6M HCl aqueous solution (LiF to HCl aqueous solution mass ratio 1:15) and stirred until homogeneous. Powdered Ti3AlC2 (LiF to Ti3AlC2 mass ratio 1:2) was added under ice-water bath cooling, and the mixture was magnetically stirred at low speed at 40°C for 24 hours to selectively etch the Al layer. After etching, the mixture was transferred to centrifuge tubes and centrifuged and washed multiple times under Ar protection until the supernatant pH > 6. The mixture was then centrifuged at high speed (10000 rpm for 10 min), and the upper layer rich in Ti3C2 was collected.y The colloidal dispersion of Ti3C2T is denoted as the first dispersion; the first dispersion contains Ti3C2T y The concentration of the colloid was 8.89 mg / mL.

[0130] S4.2 SiO x @G@CNTs positive electrolysis: Powdered SiO x @G@CNTs were dispersed in a solvent (NMP) at an addition rate of 10 mg / mL, and 1 vol% of a 0.1 wt% aqueous solution of a cationic surfactant (CTAB) was added. The mixture was then sonicated until the system potential turned positive (30 mV) to obtain a second dispersion. S4.3 Electrostatic Self-Assembly: The first dispersion was added dropwise to the second dispersion (the first and second dispersions were in a mass ratio of 8:1) at a rate of 1.5 ± 0.5 mL / min and mixed thoroughly. The mixture was then gently stirred (400 rpm) for 50 min. The resulting slurry was transferred to a PTFE (polytetrafluoroethylene) mold and flash-frozen with liquid nitrogen. It was then freeze-dried at -50°C for 50 h. The product was then lightly ground and sieved to obtain powdered SiO₂. x @G@CNTs / Ti3C2T y .

[0131] The battery assembly method includes: in a glove box filled with Ar, using a 2032 coin cell battery as the assembly carrier, placing the positive electrode plate at the bottom of the positive electrode shell, and adding 100mL of electrolyte to wet the electrode surface; then laying a separator to cover the positive electrode plate, and then placing the negative electrode plate on top of the separator; after stacking elastic gaskets and insulating washers in sequence, snapping the negative electrode shell together and hydraulically sealing it to form a coin cell battery.

[0132] The preparation steps of the negative electrode sheet include: preparing the negative electrode material (SiO2) as described above. x @G@CNTs / Ti3C2T y The conductive agent (conductive carbon black) and the negative electrode binder CMC (carboxymethyl cellulose) are mixed at a mass ratio of 96:2:2 to obtain mixture one; mixture one is added to deionized water with a solid content of 42wt%, and stirred evenly to obtain the negative electrode slurry; the negative electrode slurry is then mixed at a concentration of 10mg / cm³. 2 The coating amount is applied to the surface of the copper foil of the negative electrode current collector, and then dried and rolled to obtain the negative electrode sheet.

[0133] The preparation steps of the positive electrode sheet include: mixing the positive electrode active material (lithium iron phosphate), conductive agent (conductive carbon black), and positive electrode binder PVDF (polyvinylidene fluoride, from Solvay, model Solvay 5130) at a mass ratio of 95:3:2 to obtain mixture two; adding mixture two to NMP with a solid content of 68wt% and stirring evenly to obtain a positive electrode slurry; and then adding the positive electrode slurry at a concentration of 22mg / cm³. 2 The coating amount is applied to the surface of the positive current collector aluminum foil, and then dried and rolled to obtain the positive electrode sheet.

[0134] The preparation steps of the separator include: selecting a PE base film with a thickness of 7μm (from Xingyuan Material Co., Ltd., model ND9T602), coating a PVDF adhesive layer with a thickness of 3μm (from Arkema, model Arkema HSV900) on both sides of the PE base film, and then coating a 3μm ceramic layer on one side facing the positive electrode sheet.

[0135] The preparation steps of the electrolyte include: mixing EC and DMC at a volume ratio of 1:1 to obtain a mixed solvent, then dissolving fully dried lithium salt LiPF6 in the mixed solvent at an addition amount of 1 mol / L, and mixing evenly to prepare the electrolyte.

[0136] Example 2 This embodiment provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Embodiment 1; the difference is that the amount of pore-forming agent PS microspheres added in step S1.1 is 0.5g, and the resulting SiO X The x-value is 1.4, and the porosity is 45%.

[0137] Example 3 This embodiment provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Embodiment 1; the difference is that the amount of pore-forming agent PS microspheres added in step S1.1 is 0.8g, and the resulting SiO X The x-value is 1.35, and the porosity is 65%.

[0138] Example 4 This embodiment provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Embodiment 1; the difference is that the graphene has 6 layers. This number of layers is achieved by adjusting S2.2 as follows.

[0139] S2.2 High-Temperature CVD Growth of Graphene: A nickel-loaded precursor was laid flat in a quartz boat and pushed into the isothermal zone of a tube furnace. Ar gas was introduced into the quartz tube at a flow rate of 500 sccm for 5 min to purge air. Under the Ar atmosphere, the temperature was increased to 900℃ at a rate of 5℃ / min, stabilized for 5 min, and then subjected to a cyclic carbon source pulse. Specifically, this included: 1) First pulse: A mixed gas of CH4, H2, and Ar (volume ratio 2:5:20) was introduced for 3 min; 2) Second pulse: CH4 introduction was stopped, and a mixed gas of H2 and Ar (volume ratio maintained at 5:20) was introduced for 2 min. One cycle of the first and second pulses was counted as one set of cycles, and a total of three sets of cycles were performed. Heating was stopped, and the temperature was lowered at a rate of 45℃ / min until below 200℃. H2 introduction was stopped, and the temperature was lowered to room temperature. The powder was collected under an Ar atmosphere to obtain nickel-loaded SiO2. x @G.

[0140] Example 5 This embodiment provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Embodiment 1; the difference is that the graphene has 4 layers. This number of layers is achieved by adjusting S2.2 as follows.

[0141] S2.2 High-temperature CVD growth of graphene: A nickel-loaded precursor is laid flat in a quartz boat and pushed into the isothermal zone of the quartz tube in a tube furnace; Ar is introduced into the quartz tube at a flow rate of 500 sccm. Air was removed for 5 minutes; under an Ar atmosphere, the temperature was increased to 900℃ at a rate of 5℃ / min, stabilized for 5 minutes, and then subjected to a circulating carbon source pulse; specifically including: 1) First pulse: a mixed gas of CH4, H2, and Ar (volume ratio 2:5:20) was introduced at a total flow rate of 200 sccm for 3 minutes; 2) Second pulse: the CH4 was stopped, and a mixed gas of H2 and Ar (volume ratio maintained at 5:20) was introduced at a total flow rate of 200 sccm for 2 minutes; one cycle of the first and second pulses was counted as one cycle, and two cycles were performed in total; heating was stopped, and the temperature was lowered at a cooling rate of 45℃ / min until it dropped below 200℃, at which point the H2 was stopped, and the powder was collected under an Ar atmosphere after cooling to room temperature to obtain nickel-loaded SiO. x @G.

[0142] Example 6 This embodiment provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Embodiment 1; the difference is that in step S3.4, the aminated SiO2... x The ratio of @G to CNT-COCl solids is 5:1.

[0143] Example 7 This embodiment provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Embodiment 1; the difference is that in step S3.4, the aminated SiO2... x The solid ratio of @G to CNT-COCl is 12:1.

[0144] Example 8 This embodiment provides an anode material, its preparation method, and a battery, with the specific implementation method being the same as in Embodiment 1; the difference being that MXene is replaced with V4AlC3, and the resulting anode material is SiO2. x @G@CNTs / V4C3T y .

[0145] Step S4.1 is adjusted as follows: In a fume hood, dissolve LiF in a 10M HCl aqueous solution (LiF to HCl aqueous solution mass ratio of 1:15) and stir until homogeneous; add powdered V4AlC3 (LiF to V4AlC3 mass ratio of 1:3) under ice-water bath cooling, transfer to a 50℃ oil bath, and stir magnetically at low speed for 40 hours to selectively etch the Al layer; after etching, transfer the mixture to a centrifuge tube, and centrifuge and wash multiple times under Ar protection until the pH of the supernatant is >6; centrifuge at 10000 rpm for 10 min, and collect the upper layer rich in V4C3T. y The colloidal dispersion is denoted as the first dispersion; V4C3T in the first dispersion y The concentration of the colloid was 9 mg / mL.

[0146] Example 9 This embodiment provides an anode material, its preparation method, and a battery, with the specific implementation method being the same as in Embodiment 1; the difference being that MXene is replaced with V2AlC, and the resulting anode material is SiO. x @G@CNTs / V2CT y .

[0147] Step S4.1 is adjusted as follows: In a fume hood, dissolve LiF in a 10M HCl aqueous solution (LiF to HCl aqueous solution mass ratio of 1:25) and stir until homogeneous; add powdered V2AlC (LiF to V2AlC mass ratio of 1.6:1) under ice-water bath cooling, mix and stir until homogeneous, and let stand at 35℃ for 30h to selectively etch the Al layer; after etching, add deionized water to the mixture (deionized water to mixture mass ratio of 80:1), shake and centrifuge at 3500rpm for 5min, centrifuge and wash under Ar protection until the supernatant pH>6 and is dark black; transfer the wet precipitate to a beaker, add deionized water at a precipitate to water mass ratio of 1:200, sonicate in an ice-water bath (0℃) under Ar atmosphere for 20min to remove Al; centrifuge the removed suspension at 1500rpm for 1h, collect the upper dark black colloid, which is the colloidal dispersion rich in V4AlC, and is recorded as the first dispersion; V2CT in the first dispersion y The concentration of the colloid was 9 mg / mL.

[0148] Comparative Example 1 This comparative example provides a negative electrode material, its preparation method, and a battery, with the specific implementation method being the same as in Example 1; the difference being that the negative electrode material is SiO2. x For @G@CNTs, step S4 is omitted in the preparation process.

[0149] Comparative Example 2 This comparative example provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Example 1; the difference is that step S1.2 is omitted, that is, the silicon substrate is a SiO2 / PS composite gel without a porous structure.

[0150] Comparative Example 3 This comparative example provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Example 1; the difference is that in step S3, carbon nanotubes are grown on the surface of SiOx@G by in-situ chemical vapor deposition to obtain SiOx@G@CNTs.

[0151] Step S3 specifically includes: dispersing 0.5g of powdered SiOx@G in 20mL of ethanol, adding 5mL of 0.05M ferric nitrate ethanol solution (catalyst), stirring for 12h, drying at 60℃, and annealing at 400℃ for 2h under Ar atmosphere to obtain catalyst-supported SiOx@G; transferring it to a tube furnace, heating to 700℃ under Ar / H2 mixed gas atmosphere (volume ratio 9:1, total flow rate 200sccm), and then introducing C2H2 / Ar mixed gas (volume ratio 1:9, total flow rate 200sccm) for 30min to grow carbon nanotubes; after the reaction is completed, cooling to room temperature under Ar atmosphere to obtain the product SiOx@G@CNTs composite powder.

[0152] Comparative Example 4 This comparative example provides a negative electrode material, its preparation method, and a battery. The specific implementation method is the same as in Example 1; the difference is that multi-walled carbon nanotubes are replaced with single-walled carbon nanotubes, which are from XFNANO and are model XFS17.

[0153] Performance testing 1. Characterization of the structure of the negative electrode material 1.1 SEM morphological observation The SiO prepared in Example 1 x @G@CNTs were characterized by SEM; SEM morphology images are shown below. Figure 1 .

[0154] Figure 1 (a) is the SEM image of the carbon nanotubes used, (b) is the SEM image of the graphene grown by high-temperature CVD, and (c) and (d) are the SEM images of SiO₂. x SEM morphology images of @G@CNTs (different observation angles and positions of the same sample). Figure 1 Figure (a) shows that multi-walled carbon nanotubes have a one-dimensional fibrous structure with uniform diameter and interwoven to form a network framework; Figure (b) shows that graphene grown by high-temperature CVD exhibits a regular layered structure with a smooth surface and smooth edges; Figure (c) shows that CNTs and SiO2... x The surface morphology of the material after @G composite changes significantly. The originally smooth graphene surface shows a large number of uneven undulations, and a large number of carbon nanotube-like structures can be seen at the edge of the sheet, indicating that the graphene and carbon nanotubes have been tightly bonded by amide bonds. In Figure (d), it can be further observed that the carbon nanotubes effectively connect the graphene sheets into one, proving that the graphene and carbon nanotubes have achieved a stable bridging through amide bonds.

[0155] 1.2 Infrared Characterization For carbon nanotubes and SiO in Example 1 x @G、SiO x @G@CNTs and SiO x @G@CNTs / Ti3C2T y The sample was characterized by infrared radiation, and the test results are shown below. Figure 2 and Figure 3 . Figure 2 (a) Showing untreated carbon nanotubes due to their highly symmetrical sp 2 Due to the carbon structure and electron delocalization effect, its infrared absorption is usually weak, making it difficult to observe obvious bulk characteristic absorption peaks; at 3436 cm⁻¹ 1The absorption peaks that appear are usually attributed to the OH stretching vibration of adsorbed water or the hydroxyl groups (-OH) at the tube end defects, and are not characteristic peaks of the CNT bulk structure. Figure 2 (b) is SiO x The infrared spectrum of the @G composite material is as follows: at 3452 cm⁻¹ -1 The broad peak at 1724 cm⁻¹ corresponds to the OH stretching vibration of adsorbed water or hydroxyl groups (-OH) on the material surface; -1 The absorption peak at that location is attributed to graphene or SiO2. x C=O stretching vibration of surface carboxyl groups (-COOH); 1639 cm⁻¹ -1 The characteristic peak at 1535 cm⁻¹ is the amide I band (C=O stretching vibration). -1 The peak at that point corresponds to the in-plane bending vibration of the N–H plane. These two peaks together prove that SiO x Successfully grafted with graphene via amide bonds; 1199cm -1 The absorption peak at this point can be attributed to the stretching vibrations of Si-O-Si or Si-OC, further confirming that SiO x Chemical bonding with graphene. Figure 2 (c) is SiO x Infrared spectrum of @G@CNTs composite material. (Compared with SiO2) x Compared to the spectra of @G and pure carbon nanotubes, its spectral characteristics changed significantly, which can be attributed to the formation of amide bonds (-CO-NH-), which mediate the SiO2... x The bridging effect between @G and CNT causes some of the original vibration modes to weaken or disappear. A comparison shows that in SiO... x In the infrared spectrum of the @G composite material, 1535 cm⁻¹ -1 In-plane bending vibration peaks can be observed at NH, while in SiO x In the spectrum of @G@CNTs, at 1530 cm⁻¹ -1 No obvious absorption peaks were observed nearby, indicating that SiO x The number of NH bonds in @G@CNTs compared to SiO x The significant decrease in @G indicates an increased proportion of amide bonds involved in bridging and a substantial reduction in unreacted amino groups. Amide bonds (-CO-NH-) exhibit characteristic vibrational modes in infrared spectroscopy, with the amide I band being one of its most representative absorption peaks, typically located between 1670 and 1630 cm⁻¹. -1 Within the range; Figure 2 (c) shows 1365cm -1 The left and right sides show the CN stretching vibration peaks, at 1631 cm⁻¹. -1The corresponding peak of the amide C=O stretching vibration (i.e., the amide I band) reflects the stable existence and effective bridging effect of the amide bond in the ternary composite material. Figure 3 The display shows that SiO x @G@CNTs / Ti3C2T y The sample was at 1385 cm. -1 and 1101cm -1 The presence of CF characteristic peaks for MXene confirms that Ti3C2T y The existence of.

[0156] 2. Electrochemical performance The batteries prepared in the examples and comparative examples were tested for the following electrochemical properties, and the test results are shown in Table 1.

[0157] 2.1 Resistance The internal resistance of the batteries was obtained by testing the internal resistance of the examples and comparative examples using a battery internal resistance meter.

[0158] 2.2 Battery Energy Density The energy density of the battery was obtained by testing the example and comparative examples. The test steps included: weighing the battery mass and recording it as m; then charging it to 3.65V at a constant current of 0.33C at 25°C, and then charging it to 3.65V at a constant voltage of 3.65V until the current is ≤0.05C. After standing for 5 minutes, discharging it to 2.0V at a constant current of 0.33C, and recording the discharge energy Q; the battery energy density (E) was calculated according to the formula E=Q / m.

[0159] 2.3 Expansion of the negative electrode sheet The expansion of the negative electrode sheets prepared in the embodiments and comparative examples is characterized by the change in thickness of the negative electrode sheet in the initial (after rolling) and fully charged states. The full charge test steps include: according to the battery scheme in Embodiment 1, connecting the positive and negative electrodes of the battery to form a button half-cell, ensuring a firm connection, setting the charging voltage range to 3.6V-3.65V / cell and the charging current to 0.5C-1C, and monitoring the voltage, current and temperature in real time after starting the charger (avoiding exceeding 45℃). When the voltage of a single cell reaches 3.65V / cell and the current drops to 0.05C, it is determined to be fully charged and charging is stopped; after full charge, the battery is disassembled, and the thickness of the negative electrode sheets in each embodiment and comparative example in the initial and fully charged states is measured, and the electrode sheet expansion rate is calculated.

[0160] 2.4 Capacity retention rate The capacity retention rate of the battery was obtained through test examples and comparative examples. The test steps included: conducting charge-discharge cycle tests on the battery within a voltage range of 2.2V to 3.65V at 25°C: first, charging at a constant current of 1C to 3.65V, then charging at a constant voltage of 3.65V until the current drops to 0.05C; then discharging at a constant current of 0.5C to 2.2V, completing one charge-discharge cycle, which is recorded as one cycle; repeating this charge-discharge cycle, and calculating the capacity retention rate at the 200th cycle (the ratio of the discharge capacity of the 200th cycle to the discharge capacity of the first cycle).

[0161] 2.5x performance The rate capability of the batteries prepared in the test examples and comparative examples includes the following test steps: (1) Calibration of the initial capacity (rated capacity C0) of the battery: The battery is placed in a 25°C environment until the temperature stabilizes; it is charged at a constant current of 1C to the upper limit cutoff voltage of 3.65V, and then switched to constant voltage charging until the current drops to 0.05C; after the charging is completed, it is placed in a 30-minute resting state, and then discharged at a constant current of 1C to the lower limit cutoff voltage of 2.2V. The total discharge capacity is recorded, which is the initial rated capacity C0 of the battery.

[0162] (2) 4C discharge capacity retention test: The battery was fully charged using the same constant current and constant voltage charging regime as in step (1), and after resting for 30 minutes, it was discharged at 4C constant current to the lower limit cutoff voltage of 2.2V. The initial 4C discharge capacity at this time was recorded (denoted as C4C,initial). The battery was then subjected to continuous charge and discharge cycles. The cycle regime was as follows: fully charged at 1C constant current and constant voltage, and rested for 5 minutes; then discharged at 4C constant current to the lower limit cutoff voltage of 2.2V, and rested for 5-10 minutes, which was recorded as one cycle; after 500 cycles, the 4C discharge capacity C4C at this time was recorded.

[0163] (3) Calculate the 4C discharge capacity retention rate according to the following formula: 4C discharge capacity retention (%) = (C4C / C0) × 100% Table 1. Electrochemical performance test results of the examples and comparative examples.

[0164] Table 1 shows that Examples 1-9 used porous SiO XWith a core, a first coating layer consisting of graphene and carbon nanotubes, and a second coating layer consisting of MXene, are sequentially coated to construct an anode material with optimized structure and conductive network. The electrochemical performance of Example 1 is particularly outstanding: the capacity retention rate reaches 97% after 200 cycles at 25°C, and the capacity retention rate is as high as 92% after 500 cycles at 4C rate. At the same time, the battery energy density reaches 310Wh / kg, and the electrode expansion rate is only 12%, achieving a synergistic improvement in cycle stability, rate performance and structural stability.

[0165] Examples 2 and 3 show that by reducing the amount of pore-forming agent PS microspheres, SiO2... x The reduced porosity (45% and 65% respectively) weakens the buffering and restraining effect on the volume expansion of silicon-based materials, and the corresponding increase in electrode expansion rate to 19% and 17%, which in turn leads to electrode structure damage and interface contact deterioration. As a result, the battery's capacity retention rate after 200 cycles drops to 87% and 89% respectively, and the capacity retention rate after 500 cycles of 4C drops to 82% and 84%, resulting in a certain degree of performance degradation.

[0166] Examples 4 and 5 in SiO x In the @G preparation stage, by increasing the number of cycle pulses, carbon atoms dissolved in nickel are continuously precipitated, forming more graphene layers (6 layers and 4 layers, respectively). Excessive graphene deposition increases interfacial impedance and hinders the rapid transport of lithium ions. Therefore, the capacity retention rates after 200 cycles (92% and 91%) and after 500 cycles of 4C (85% and 87%) are lower than those in Example 1, demonstrating the key influence of the number of graphene layers on the performance of the negative electrode and the battery.

[0167] Data from Examples 1, 7, 8 and Comparative Examples 1, 2, 3 show that grafting CNTs onto graphene sheets via an amidation reaction (rather than conventional coating) is key to constructing a highly efficient conductive network; conventional coating (Comparative Example 3) fails to form a continuous three-dimensional conductive network, resulting in interrupted electron transport paths and a significant decrease in rate performance; while SiO2 without MXene coating (Comparative Example 1) or without a porous structure... x All of these factors disrupt the multidimensional conductive framework of "point-line-surface-volume," hindering electron and ion transport, significantly increasing electrode expansion, and consequently reducing battery capacity retention. These results demonstrate that MXene, along with graphene and carbon nanotubes, enhances the performance of porous SiO₂ structures. x The synergistic coating effect effectively improves the electronic conductivity and structural stability of the composite material, thereby significantly improving fast charging performance and cycle life.

[0168] Examples 8 and 9 compare the performance differences of different types of MXene materials; among them, M3X2T y Type (e.g., Ti3C2T) yCompared to the M2X and M4X3 models, the process is more mature and convenient, producing the best conductivity of the negative electrode and battery, and can more effectively construct a multi-dimensional conductive network, resulting in the best overall performance.

[0169] Comparative Example 4 uses single-walled carbon nanotubes instead of multi-walled carbon nanotubes. However, due to the flexibility and poor support of single-walled nanotubes, they cannot provide an effective three-dimensional mechanical framework to confine SiO. x The volume expansion caused the electrode expansion rate to increase to 14%, which is inferior to that of multi-walled carbon nanotubes.

[0170] The above provides a detailed description of the negative electrode material, its preparation method, and the battery provided by the present invention. It should be noted that the above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. The series of detailed descriptions listed in the present invention are only specific descriptions of feasible implementation methods of the present technology. They are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the present application should be included within the scope of protection of this application.

Claims

1. A negative electrode material, characterized in that, The negative electrode material includes: Silicon substrate; A first coating layer comprising graphene and carbon nanotubes, wherein the graphene is coated on at least a portion of the surface of the silicon substrate, and the carbon nanotubes are incorporated into the sheets of graphene. A second coating layer covers at least a portion of the surface of the first coating layer; the second coating layer includes MXene.

2. The negative electrode material according to claim 1, characterized in that, The silicon substrate satisfies at least one of the following conditions: (1) The silicon substrate includes at least one of silicon, silicon oxide, silicon carbide, and silicon oxynitride; (2) The silicon substrate comprises SiO with a porous structure. x , 1 < x < 1.5; (3) The porosity of the silicon substrate is 40-80%.

3. The negative electrode material according to claim 1, characterized in that, The first coating layer satisfies at least one of the following conditions: (1) The number of graphene sheets is 2-6; (2) The graphene content is 3-6 wt% of the mass of the negative electrode material; (3) The carbon nanotubes include multi-walled carbon nanotubes; (4) The content of the carbon nanotubes is 5-16 wt% of the mass of the negative electrode material; (5) The composite method is that the carbon nanotubes are grafted into the graphene sheets; (6) The composite method is that the carbon nanotubes are amidated and grafted into the graphene sheets.

4. The negative electrode material according to claim 1, characterized in that, The MXene satisfies at least one of the following conditions: (1) The general formula of the MXene is M m+1 X m T y Where m is any integer from 1 to 3, y > 0; M is at least one of the transition metal elements Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W, Ni, Fe, Mn, Zn; X is C and / or N; and T is a surface-capping group, wherein the capping group includes at least one of -O, -Cl, -OH, and -F. (2) The MXene includes Ta4C3T y Nb4C3T y V4C3T y Ti3C2T y V2CT y Mo2CT y At least one of them; (3) The content of MXene is 3-12 wt% of the mass of the negative electrode material.

5. A method for preparing the negative electrode material according to any one of claims 1-4, characterized in that, The preparation method includes: Sol-gel method for preparing silicon substrates; Graphene is chemically vapor-deposited on at least a portion of the surface of the silicon substrate to form a silicon substrate @G; Carbon nanotubes are grafted into the graphene sheets to form a silicon matrix @G@CNTs, and the carbon nanotubes and the graphene form a first coating layer. The silicon substrate @G@CNTs and the MXene electrostatically self-assemble, and a second coating layer is coated on at least a portion of the surface of the first coating layer to form silicon substrate @G@CNTs / MXene, thereby obtaining the negative electrode material.

6. The preparation method according to claim 5, characterized in that, The silicon substrate includes SiO₂ with a porous structure. x The porous SiO x The preparation steps include: A silicon source is added to an alkaline solution, and a pore-forming agent is added while stirring. The reaction yields a precursor sol. The precursor sol was subjected to high-temperature reduction and pore formation under an inert gas atmosphere to form SiO with a porous structure. x ; Preferably, the high-temperature reduction pore-forming process includes a first stage and a second stage, wherein, In the first stage, the precursor sol is heated to 400-600°C and kept at that temperature to remove the pore-forming agent and form a porous SiO2 structure. In the second stage, the SiO2 is further heated to 700-850℃ and held at that temperature, causing the SiO2 to be reduced to form a porous SiO2 structure. X ; The porous SiO x The preparation steps also satisfy at least one of the following conditions: (1) The heating rate in the first stage is 1-2℃ / min; (2) The heating rate in the second stage is 3-5℃ / min; (3) The pore-forming agent includes PS microspheres; (4) The ratio of the pore-forming agent to the silicon source is (0.5-1) g: (50-80) mL; (5) The reaction time in the precursor sol is 6-8 hours.

7. The preparation method according to claim 5, characterized in that, The preparation steps for forming the silicon substrate @G include: Nickel is deposited on the surface of the silicon substrate to form a nickel-loaded precursor; The nickel-loaded precursor is placed in an inert gas atmosphere and subjected to cyclic carbon source pulses, and then cooled at a cooling rate of 25-50℃ / min to form a nickel-loaded silicon substrate @G containing the desired graphene sheets. The nickel-loaded silicon substrate @G is subjected to a nickel removal process to form a silicon substrate @G; One cycle of the cyclic carbon source pulse includes a first pulse and a second pulse, wherein, The first pulse is to heat the nickel-loaded precursor to 800-1000°C and introduce a mixed gas of CH4, H2 and Ar for 1-5 minutes. The second pulse is to stop the flow of CH4 and perform the second pulse for 1-3 minutes under a mixed gas of H2 and Ar; The preparation step of forming the silicon substrate @G also satisfies at least one of the following conditions: (1) The number of graphene layers in the nickel-supported silicon substrate @G is 3-6; (2) The number of cycles of the circulating carbon source pulse is 1-3 times; (3) The volume ratio of CH4, H2 and Ar during the first pulse is (1-3):(4-8):(10-30); (4) The volume ratio of H2 to Ar during the second pulse is 1:(3-6).

8. The preparation method according to claim 5, characterized in that, The preparation steps for forming silicon substrate @G@CNTs include: The silicon substrate @G is contacted with a nitrogen-containing reactive gas and subjected to plasma treatment to obtain a silicon substrate @G with amino groups on its surface; The carbon nanotubes are subjected to acyl chloride treatment to obtain acyl chloride carbon nanotubes, which are then dispersed to form a first dispersion. The silicon matrix @G with amino groups on its surface is added to the first dispersion to immobilize and graft the carbon nanotubes onto the graphene sheets, forming silicon matrix @G@CNTs. The preparation step of forming silicon substrate @G@CNTs also satisfies at least one of the following conditions: (1) The radio frequency power of the plasma treatment is 100-300W, and the treatment time is 1-3min; (2) The mass ratio of the amino-containing silicon matrix @G on the surface to the first dispersion is (5-15):(1-10).

9. The preparation method according to claim 5, characterized in that, The step of forming the silicon substrate @G@CNTs / MXene includes: Preparation of MXene colloids with negative potential; A second dispersion containing the silicon matrix @G@CNTs with a positive potential was prepared; The second dispersion and the MXene colloid are mixed to allow the silicon substrate @G@CNTs and the MXene to electrostatically self-assemble, thereby coating at least a portion of the surface of the first coating layer with the second coating layer to form silicon substrate @G@CNTs / MXene; The step of forming the silicon substrate @G@CNTs / MXene also satisfies at least one of the following conditions: (1) The step of preparing a second dispersion containing the silicon matrix @G@CNTs with a positive potential includes: dispersing the silicon matrix @G@CNTs in a solvent, adding a cationic surfactant, and mixing until the potential of the dispersion is positive to obtain a second dispersion; (2) The cationic surfactant includes at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and polydiallyldimethylammonium chloride; (3) The mass ratio of the second dispersion to the MXene colloid is (5-10):

1.

10. A battery, characterized in that, The negative electrode sheet of the battery contains the negative electrode material according to any one of claims 1-4 or the negative electrode material prepared by the preparation method according to claims 5-9.

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