Lithiation phase-controllable silicon-carbon-mxene composite negative electrode material, preparation method and application thereof in lithium ion battery

Abstract

The present invention belongs to the technical field of lithium-ion battery preparation, and discloses a silicon-carbon-MXene composite anode material with controllable lithiation phase, a preparation method thereof and application thereof in lithium-ion batteries. The material uses silicon oxide SiO with a specific stoichiometric ratio x (0.6<x<1.4) as the core, and a nano-carbon buffer layer and a two-dimensional MXene conductive confinement layer are coated sequentially to form a "sandwich" structure. Through the SiO x has a synergistic effect with the spatial confinement effect of high-proportion MXene, the material can effectively regulate the phase transition behavior during lithium ion intercalation, and significantly inhibit the destructive crystalline high lithiation phase Li 15 generation of Si₄, prompting silicon to mainly undergo reversible low lithiation / amorphous phase transition. The material is suitable for lithium-ion batteries with high energy density and long cycle life, and has broad prospects in the fields of electric vehicles and large-scale energy storage. The method is also applicable to alloy-type anode materials such as tin and germanium, and has universal applicability.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery preparation technology, specifically relating to a silicon-carbon-MXene composite anode material with controllable lithiation phase, its preparation method, and its application in lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic devices and electric vehicles, and their energy density and cycle life are key indicators for evaluating battery performance. The theoretical specific capacity of traditional commercial graphite anodes is approximately 372 mAh / g, approaching their performance limit and failing to meet the demands for long battery life and lightweight design. Silicon, with its theoretical specific capacity as high as 4200 mAh / g and relatively low lithium intercalation potential, is considered one of the most promising next-generation lithium-ion battery anode materials. However, pure silicon materials suffer from severe volume expansion during charge and discharge: it is generally believed that under deep lithium intercalation conditions, silicon forms a lithium-silicon alloy (Li) upon complete lithium intercalation. 15 The Si4 phase expands in volume by approximately 300-380% compared to before lithium insertion, causing silicon particles to crack and pulverize, and leading to instability at the interface with the current collector and electrolyte, which in turn causes rapid capacity decay of the battery. In addition, silicon has inherently poor conductivity, and during the large-scale lithium insertion / extraction process, it is also prone to forming a thick solid electrolyte interphase (SEI) film, further reducing cycle efficiency.

[0003] To address the aforementioned problems with silicon anodes, researchers have proposed various improvement schemes. For example, embedding nano-silicon into a porous carbon matrix to form secondary silicon-carbon particles is currently a widely accepted main direction. This approach, through nano-sized silicon particles and carbon buffering volume changes, alleviates particle pulverization during cycling to some extent. Chinese battery companies have also disclosed related technical solutions: existing patents demonstrate a silicon-carbon composite gradient layer structure for anode materials, where the silicon content gradually decreases from the inside to the outside of the carbon matrix, forming a gradient transition, and is covered with a carbon coating layer on the outside. This structure reduces overall expansion by dispersing stress and limiting surface silicon content. Other disclosed technologies propose using special network structures or inorganic coatings to stabilize silicon anodes: for example, constructing silicon carbide or carbide networks to confine nano-silicon clusters within them, or coating the surface of a graphite matrix with a layer of transition metal carbides (such as TiC, WC, etc.) to enhance structural stability and conductivity. These methods reduce the volume effect and interfacial side reactions of silicon anodes to some extent. On the other hand, existing technologies disclose the use of silicon nanowire arrays directly as the negative electrode, vertically growing silicon nanowires on the current collector, fundamentally providing space to accommodate silicon expansion, and improving cycle life through special processes. In addition, there are studies on pre-doping silicon materials with lithium (such as pre-lithiated silicon oxide) to improve initial efficiency, or adding a viscoelastic coating between silicon and the current collector to buffer stress. These existing technological approaches each have their own focus: some focus on establishing a stable conductive network, while others alleviate deformation stress or improve initial efficiency, but generally do not address the issue from the perspective of controlling the silicon-lithium alloy phase transition. Therefore, when the battery is deeply charged, crystalline Li may still be generated uncontrollably. 15 Highly lithiated phases such as Si4 cause irreversible damage to the material structure, hindering the improvement of cycle performance.

[0004] In summary, effectively controlling the lithium-intercalation phase composition of silicon-based anodes while maintaining their high capacity advantage and avoiding the formation of destructive highly lithiated phases is a pressing technical challenge in this field. If the degree of complete lithiation of silicon can be limited in the material structure or its phase transition path can be altered, causing it to primarily undergo a reversible low-lithiation / amorphous phase during charge and discharge, while minimizing the formation of Lithium-ionized phases, then this challenge could be addressed. 15 High-lithiation crystalline phases such as Si4 hold promise for significantly reducing the volume expansion and pulverization of silicon anodes, thereby improving battery cycle life and safety. However, to date, no literature or patents have specifically disclosed an effective solution for achieving controllable lithiation phase transitions through composite material design. Summary of the Invention

[0005] The existing silicon-based anode materials mentioned above tend to form Li during the final stage of lithium intercalation. 15Technical problems such as high lithiation phase like Si₄, which leads to volume expansion and degraded cycle performance. Aiming at the above problems, the present invention provides a brand-new silicon carbon-MXene composite anode material, expecting to achieve a breakthrough in inhibiting the formation of high lithiation phase of silicon. The purpose of the present invention is to provide a silicon carbon-MXene composite anode material with controllable lithiation phase and a preparation method thereof. By introducing a coating of two-dimensional transition metal carbide MXene on the surface of the silicon carbon material and utilizing the composite structure of silicon oxide and carbon, the evolution process of the lithiation phase of silicon is effectively regulated, and the occurrence of high lithium-insertion phase is inhibited, thereby significantly improving the volume stability and cycle life of the material.

[0006] To achieve the above purpose, the present invention adopts the following technical solution: A silicon carbon-MXene composite anode material with controllable lithiation phase, comprising: a silicon-based active material serving as a core, a carbon layer coated on the surface of the silicon-based active material, and a MXene two-dimensional conductive coating layer coated on the surface of the carbon layer; The silicon-based active material is silicon oxide with the general chemical formula SiO x , wherein 0.6 < x < 1.4; The carbon layer is a nano carbon buffer layer with a thickness of 5~50 nm, and the mass ratio of the silicon-based active material to the carbon layer is 85:15~99:1; The mass of MXene in the MXene two-dimensional conductive coating layer accounts for 5~40% of the mass of the silicon-based active material.

[0007] Preferably, in SiO x silicon oxide, 0.8 < x < 1.2; the thickness of the nano carbon buffer layer is 8~30 nm, the mass ratio of the silicon-based active material to the carbon layer is 94:6; the mass of the MXene coating layer accounts for 10~30% of the mass of the silicon-based active material core; The MXene is a two-dimensional transition metal carbide / nitride, selected from Ti₃C₂T x , Ti₂C₃T x , V₂C₃T x , Nb₂C₃T x at least one of the foregoing; The composite anode material is in the morphology of micron-level secondary particles, with an average particle size of 5~20 μm; the secondary particles are formed by assembling primary particles composed of the nano-scale silicon-based active material and carbon through aggregation via the MXene layer; The composite anode material has a multi-level structure from inside to outside of SiO x core - carbon intermediate layer - MXene outer shell.

[0008] Preferably, the MXene is Ti₃C₂T x; The composite anode material exhibits a micron-sized secondary particle morphology with an average particle size of 10~15 μm.

[0009] A method for preparing a silicon-carbon-MXene composite anode material with controllable lithium-ion phase includes the following steps: (1) Preparation of silicon-carbon precursor suspension: SiO2 x Powder, carbonizable organic carbon source and dispersing additive are mixed in solvent and then subjected to high-energy ball milling at a ball-to-material ratio of 1:(10~15), a rotation speed of 200~800 rpm and a processing time of 0.5~10h to obtain a uniform silicon-carbon precursor suspension. (2) Preparation of MXene dispersion slurry: MXene powder is dispersed in a solvent and subjected to ultrasonic and / or high-speed shearing treatment to obtain a stable MXene slurry; (3) Composite and drying molding: The suspension / slurry obtained in steps (1) and (2) are mixed evenly in proportion, and then the mixture is molded by spray drying process. The air inlet temperature of spray drying is 120~200℃ to obtain composite intermediate particles. (4) High-temperature heat treatment: The composite intermediate particles are heat-treated at 600~900℃ in an inert atmosphere for 1~5h to obtain the final composite anode material.

[0010] Preferably, in step (1), the organic carbon source is selected from at least one of glucose, polyvinyl alcohol, carboxymethyl cellulose, phenolic resin, and asphalt; the rotation speed is 450~460 rpm, and the treatment time is 2h; the mass of the dispersing additive is SiO2. x 0.5%~1% In step (2), the solvent is water; a surfactant or thickener is used as the dispersant, and the dispersant accounts for 0.1~10% of the mass of MXene; In step (3), the inlet air temperature for spray drying is 180°C; In step (4), high-temperature heat treatment: heat treatment is carried out at 700~800℃, and the holding time is 2~4h.

[0011] Preferably, the organic carbon source is selected from glucose; The dispersant accounts for 1-5% of the mass of MXene.

[0012] A lithium-ion battery anode, wherein the active material comprises the aforementioned silicon-carbon-MXene composite anode material with controllable lithiation phase.

[0013] A lithium-ion battery includes a positive electrode, a separator, an electrolyte, and a negative electrode, wherein the negative electrode is the negative electrode of the lithium-ion battery.

[0014] Preferably, the initial coulombic efficiency of the lithium-ion battery is not less than 85%, and the capacity retention rate is not less than 95% after 50 cycles at a 0.1C rate.

[0015] In the cyclic voltammetry curve, the voltage range of 0.01-0.05V corresponds to Li 15 The reduction / oxidation peaks of Si4 formation / decomposition are significantly weakened or disappear.

[0016] An electric vehicle or large-scale energy storage system includes the lithium-ion battery as its power source or energy storage unit.

[0017] Compared with the prior art, the present invention has at least the following technical effects: The purpose of this invention is to provide a silicon-carbon-MXene composite anode material with controllable lithiation phase and its preparation method. By introducing a two-dimensional transition metal carbide MXene coating on the surface of silicon-carbon material and utilizing the composite structure of silicon oxide and carbon, the lithiation phase evolution process of silicon can be effectively controlled, and the occurrence of high lithiation phase can be suppressed, thereby significantly improving the volume stability and cycle life of the material.

[0018] This silicon-carbon-MXene composite anode material with controllable lithium-ion phase has the following advantages: (1) Significant Lithification Phase Regulation: The composite anode material of this invention can effectively regulate the phase transition behavior of silicon during lithium intercalation and suppress the high lithium content of Li 15 The Si4 phase is formed. Silicon mainly undergoes a reversible transition to the amorphous LixSi phase, which greatly alleviates the abrupt volume change problem caused by complete lithiation. This mechanism effectively reduces the volume expansion rate, thereby improving cycle life.

[0019] (2) Stable Conductive Network: The two-dimensional MXene sheets and carbon layers together construct a conductive network and mechanical support framework that runs through the entire particle. The addition of MXene, which is over 20%, is rare among similar silicon-based composite materials both domestically and internationally. However, it is this high proportion of MXene that endows the material with excellent conductivity and structural stability, ensuring smooth electron transport and maintaining the integrity of the particle morphology during charging and discharging. This synergistic network, composed of a rigid MXene support and a carbon buffer layer, not only suppresses expansion but also ensures high activity utilization.

[0020] (3) Excellent initial efficiency and long-cycle performance: utilizing SiO xAs a substrate material, it effectively improves the initial coulombic efficiency of the material (because some lithium is used to form a stable phase with oxygen, reducing irreversible losses), while mitigating the volume change stress during the initial lithium intercalation process. Combined with MXene coating, the material of this invention exhibits high initial discharge capacity and coulombic efficiency in actual batteries, as well as superior long-cycle stability compared to traditional silicon-carbon materials. It achieves this with high silicon content and high areal capacity (e.g., lithium loading on the negative electrode surface >3 mAh / cm²). 2 Under the conditions described above, the cycle life of the material of the present invention is significantly extended, and the capacity retention rate is much higher than that of the comparative material without lithiation phase control measures.

[0021] (4) Simple and feasible process: The preparation method of this invention adopts a process combining aqueous ball milling and spray drying, which is environmentally friendly and efficient, and suitable for industrial scale-up. Compared with some processes that require complex CVD deposition or high vacuum growth of nanowires, this method has simple equipment, low cost, and easy control of product consistency. At the same time, since MXene has good hydrophilicity and dispersibility, it can achieve uniform coating in the aqueous phase without the need for a large amount of additional organic solvents or surface modifiers. The process route is safe and has a high yield.

[0022] (5) Wide applicability: In addition to silicon-based materials, the concept of this invention is also applicable to other alloy-type anode materials (such as tin, germanium, etc.). Experiments have shown that, with similar structural designs, the high lithium intercalation phase in these materials in lithium-ion batteries is also suppressed, exhibiting better cycle stability. Therefore, this invention has versatility and is of great significance for promoting the practical application of high-energy-density anode materials.

[0023] In summary, this invention provides a lithium-ion battery anode material with a unique structure and excellent performance. While maintaining high capacity, it overcomes the long-standing problems of volume expansion and cycle life of silicon-based materials through phase change regulation, and is expected to be applied in the next generation of high-energy-density batteries. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the microstructure of the lithium-phase controllable silicon-carbon-MXene composite anode material of the present invention; Figure 2 This is a flowchart illustrating the preparation process of the composite anode material of the present invention. Figure 3 A scanning electron microscope (SEM) schematic diagram of the spray-dried composite intermediate and a magnified view of a portion thereof; Figure 4 This is a schematic diagram of XRD testing after high-temperature heat treatment; Figure 5 This is a transmission electron microscope (TEM) schematic diagram of the composite anode material after high-temperature heat treatment. The scale bar is 20 nm. Figure 6This is a schematic diagram of the electrochemical testing of the tin-carbon-MXene composite anode material in Example 3. Detailed Implementation

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0026] Example: Example 1: Preparation of silicon oxide@carbon / MXene composite anode material 1.1 Preparation of raw materials: This embodiment uses SiO 0.95 It is a silicon-based active material, with glucose as the carbon source, Ti3C2T x Using MXene as the coating material, silicon-carbon-MXene composite anode materials with controllable lithiumization phase were prepared.

[0027] like Figure 1 The figure shown is a schematic diagram of the microstructure of the lithium-phase controllable silicon-carbon-MXene composite anode material of the present invention. The figure clearly shows the SiO2 phase... x The core consists of nanoparticle aggregates, covered by a continuous nano-carbon buffer layer (middle layer, black), and the outermost layer is wrapped by Mxene two-dimensional sheets (shell, cyan / blue), forming a complete "sandwich" constraint structure.

[0028] 1.2 Preparation method: like Figure 2 The diagram shown is a flow chart of the fabrication process for composite anode materials, which sequentially displays: SiO2 x The process involves four key steps: ball milling of the carbon source, dispersion of MXene, spray drying of the mixed slurry, and final heat treatment.

[0029] 1.2.1 Preparation of precursor solution: Take SiO2 0.95 10 g of powder (average particle size approximately 100 nm) was added to 50 mL of deionized water, and while stirring, 0.6 g of glucose (carbon source, approximately SiO2 mass) was added. 0.95 6% of SiO₂) and stearic acid 0.05 g (dispersant, accounting for 6% of SiO₂) 0.95(0.5%). The mixture was magnetically stirred at room temperature for 1 hour to achieve initial dispersion. Then, the suspension was poured into a ball mill jar, and stainless steel grinding balls (5 mm, 1 mm, and 0.5 mm in diameter, in a ratio of 2:2:1, with a total ball-to-material ratio of 10:1) were added. The mixture was then ball-milled at 500 rpm for 2 hours. After ball milling, a uniform and fine gray silicon-carbon precursor slurry was obtained.

[0030] 1.2.2 Preparation of MXene dispersion: Ti3C2T was prepared by hydrochloric acid + lithium fluoride etching method. x MXene powder (purity >99%). Take 2 g of the obtained MXene powder and add it to 40 mL of deionized water. Add 0.1 g of polyvinylpyrrolidone (PVP, 5% of MXene by mass) as a dispersant. Treat with an ultrasonic oscillator (200 W) for 30 min, supplemented with mechanical stirring, to fully exfoliate the MXene sheets. A thick, dark green MXene slurry is obtained, with no visible large precipitates or agglomerates.

[0031] 1.2.3 Spray Drying Molding: The MXene slurry obtained in the previous step is mixed with the silicon-carbon precursor slurry in the same container and stirred thoroughly for 30 minutes to form a homogeneous mixture. At this point, the SiO₂ content in the mixed slurry... 0.95 The mass ratio of glucose char and MXene is approximately 94:6:20 (corresponding to MXene accounting for a certain percentage of SiO₂). 0.95 (21% of the total). The mixed slurry was dried using a centrifugal spray dryer with the inlet air temperature set at 180°C, the outlet air temperature at approximately 80°C, and the centrifugal atomizing disc rotation speed at 20,000 rpm. The slurry was atomized into tiny droplets and rapidly dried in hot air, resulting in a grayish-black dried powder (composite intermediate).

[0032] like Figure 3 The image shows a scanning electron microscope (SEM) schematic of the spray-dried composite intermediate and a magnified view of a portion thereof, with scale bars of 2 μm and 1 μm, respectively.

[0033] Results combined Figure 3 Scanning electron microscopy revealed that the intermediate powder particles were nearly spherical with a particle size distribution of 1-5 μm, and some particles exhibited a composite morphology of internal silicon-carbon and surface lamellar material.

[0034] 1.2.4 High-Temperature Heat Treatment: The above intermediate powder was placed in a quartz boat in a tube furnace and subjected to a two-stage heat treatment under argon protection: First, the temperature was increased to 350℃ at a rate of 5℃ / min and held at that temperature for 1 hour to carbonize the glucose carbon source and initially form a carbon coating; then, the temperature was further increased to 750℃ and held at that temperature for 2 hours, followed by natural cooling to room temperature. A blackish-gray powder was obtained after heat treatment, which is the target silicon-carbon-MXene composite anode material. The material yield was approximately 90%.

[0035] like Figure 4 The image shows a schematic diagram of XRD testing after high-temperature heat treatment. like Figure 5 The image shown is a transmission electron microscope (TEM) schematic of the composite anode material after high-temperature heat treatment, with a scale bar of 20 nm.

[0036] Material structure and performance testing: results combined Figure 4 As can be seen from the XRD test, the main diffraction peaks in the product belong to nano-silicon and graphitized carbon, with no obvious Li. x Si alloy phase peaks.

[0037] Results combined Figure 5 TEM observation revealed that the silicon particles (approximately 50 nm in size) were coated with a dense carbon layer with a thickness of ~8 nm, and outside the carbon layer was a transparent MXene sheet that encapsulated the particles.

[0038] Specific surface area (BET method) is 85 m² 2 / g, pore volume 0.15 cm 3 / g.

[0039] 1.2.5 The material was mixed with a conductive agent and a binder to prepare a CR2032 coin cell (negative electrode active material formulation: composite material: Super P: PVDF = 8:1:1). Cyclic testing was conducted at a current density of 0.1C: the specific capacity reached 1350 mAh / g in the first charge cycle, and the initial coulombic efficiency was approximately 86%. After 50 cycles, the capacity retention was above 95%.

[0040] Voltage plateau analysis shows almost no Li around 0.01 V. 15 The Si4 plateau also lacks the strong reduction peak at 0.05 V characteristic of traditional nano-silicon on its cyclic voltammetry curve, indicating that Li... 15 The formation of the Si4 phase was successfully suppressed.

[0041] This contrasts sharply with the control sample (silicon-carbon material without MXene coating): the control sample showed obvious Li+ in the first lap. 15 Si4 deintercalation peaks and capacity decay exceeding 20% ​​after 10 cycles.

[0042] This embodiment demonstrates that the composite material prepared according to the above method exhibits particle morphology and internal structure that can be observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM): it consists of spherical or near-spherical micron-sized secondary particles with a tightly packed internal structure of silicon and carbon, and an external coating of lamellar MXene. BET surface area testing reveals the material's moderate specific surface area and pore volume, indicating that the material ensures sufficient contact with the electrolyte while avoiding side reactions caused by excessively high specific surface area. X-ray diffraction (XRD) patterns primarily show broad diffraction peaks for silicon and a small amount of diffraction peaks for graphitic carbon, with almost no Li. 15 The characteristic diffraction peaks of Si4 confirm that the material remains predominantly amorphous after a complete lithium intercalation cycle. Furthermore, electrochemical testing verifies the material's effectiveness in suppressing highly lithiated phases: the half-cell cyclic voltammogram shows that Li4 remains dominant near 0.01 V. 15 The reduction peak corresponding to Si4 is significantly weakened or absent, and the plateau of the galvanostatic charge-discharge curve near 0 V is shortened, which contrasts sharply with standard nano-silicon materials. Cycle life tests show that the battery using the composite material of this invention exhibits excellent stability under high capacity conditions, with a significantly improved capacity retention.

[0043] The composite material of this invention effectively avoids the degradation caused by high lithiation phase through structural regulation, and achieves excellent cycle stability while improving capacity.

[0044] Example 2: High MXene content silicon-carbon composite material (MXene accounts for 30%) This embodiment verifies the effect of higher MXene addition on material properties. The preparation process is similar to that of Example 1, but the addition of MXene and SiO2... x The quality ratio has been increased to 30%.

[0045] Example 3: Tin-Carbon-MXene Composite Anode Material SiO in Example 1 x The powder was replaced with a pre-prepared tin oxide / carbon black composite powder (containing nano Sn particles), and the remaining process steps were basically the same to obtain a tin-carbon-MXene composite material.

[0046] Comparative example: without MXene, otherwise the same as in Example 3. like Figure 6 The diagram shows an electrochemical test of the tin-carbon-MXene composite anode material in Example 3. Figure A shows a comparison of the 0.1C cycle performance, where the red curve represents the material of this invention, and the blue curve represents a comparative example of ordinary silicon-carbon material without MXene coating. Figure B shows a cyclic voltammetry curve from 0.01 to 2.0V, where the red line represents the material of this invention, and the blue line represents the comparative example.

[0047] Results combined Figure 6 As can be seen from A in the figure, the composite anode material of the present invention retains a capacity of over 95% after 50 cycles at a 0.1C rate, and the curve is stable; the capacity decay of the comparative example is rapid.

[0048] As shown in B, the peaks of the composite anode material of this invention are significantly weakened or even disappear, proving that the formation of the highly lithiated phase is effectively suppressed. The comparative example shows a distinct pair of peaks corresponding to Li around 0.05V and 0.01V. 15 Redox peaks of Si4 formation and decomposition.

[0049] In summary, electrochemical tests show that this material exhibits good performance near 0.01 V in Li 4.4 The formation of the Sn phase is significantly suppressed, and the cycle stability is significantly improved compared with the tin-carbon material without MXene coating, proving that the present invention is also effective for Sn-based anodes.

[0050] The above embodiments demonstrate that the lithium-phase controllable silicon-carbon-MXene composite anode material and its preparation method provided by this invention are feasible and can significantly improve the cycle life and rate performance of high-capacity anode materials. It should be noted that this invention is not limited to the specific embodiments described above. Those skilled in the art can adjust the material composition, process parameters, etc., without departing from the principles of this invention.

[0051] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A silicon-carbon-MXene composite anode material with controllable lithium-ion phase, characterized in that, include: The core is a silicon-based active material, with a carbon layer covering the surface of the silicon-based active material and an MXene two-dimensional conductive coating layer covering the surface of the carbon layer. The silicon-based active material is of the general chemical formula SiO₂. x Silicon oxide, where 0.6 < x < 1.4; The carbon layer is a nano-carbon buffer layer with a thickness of 5~50 nm, and the mass ratio of the silicon-based active material to the carbon layer is 85:15~99:

1. The MXene mass in the MXene two-dimensional conductive coating layer accounts for 5-40% of the mass of the silicon-based active material.

2. The silicon-carbon-MXene composite anode material with controllable lithiation phase according to claim 1, characterized in that, SiO x In the silicon oxide, 0.8 < x < 1.2; the thickness of the nano-carbon buffer layer is 8~30 nm; the mass ratio of the silicon-based active material to the carbon layer is 94:6; the mass of the MXene coating layer accounts for 10~30% of the core mass of the silicon-based active material. The MXene is a two-dimensional transition metal carbide / nitride selected from Ti3C2T. x Ti2C3T x V2C3T x Nb2C3T x At least one of them; The composite anode material exhibits a micron-sized secondary particle morphology with an average particle size of 5~20 μm. The secondary particles are formed by the aggregation of primary particles composed of nanoscale silicon-based active materials and carbon through the MXene layer; The composite negative electrode material is composed of SiO₂ from the inside out. x A multi-level structure consisting of a core, a carbon intermediate layer, and an MXene shell.

3. The silicon-carbon-MXene composite anode material with controllable lithiation phase according to claim 2, characterized in that, The MXene is Ti3C2T x ; The composite anode material exhibits a micron-sized secondary particle morphology with an average particle size of 10~15 μm.

4. A method for preparing a silicon-carbon-MXene composite anode material with controllable lithiation phase as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Preparation of silicon-carbon precursor suspension: SiO2 x Powder, carbonizable organic carbon source and dispersing additive are mixed in solvent and then subjected to high-energy ball milling at a ball-to-material ratio of 1:(10~15), a rotation speed of 200~800 rpm and a processing time of 0.5~10h to obtain a uniform silicon-carbon precursor suspension. (2) Preparation of MXene dispersion slurry: MXene powder is dispersed in a solvent and subjected to ultrasonic and / or high-speed shearing treatment to obtain a stable MXene slurry; (3) Composite and drying molding: The suspension / slurry obtained in steps (1) and (2) are mixed evenly in proportion, and then the mixture is molded by spray drying process. The air inlet temperature of spray drying is 120~200℃ to obtain composite intermediate particles. (4) High-temperature heat treatment: The composite intermediate particles are heat-treated at 600~900℃ in an inert atmosphere for 1~5h to obtain the final composite anode material.

5. The method according to claim 4, characterized in that, In step (1), the organic carbon source is selected from at least one of glucose, polyvinyl alcohol, carboxymethyl cellulose, phenolic resin, and asphalt; the rotation speed is 450~460 rpm, and the treatment time is 2 hours; the mass of the dispersing additive is SiO2. x 0.5% to 1%; In step (2), the solvent is water; a surfactant or thickener is used as the dispersant, and the dispersant accounts for 0.1~10% of the mass of MXene; In step (3), the inlet air temperature for spray drying is 180°C; In step (4), high-temperature heat treatment: heat treatment is carried out at 700~800℃, and the holding time is 2~4h.

6. The method according to claim 5, characterized in that, The organic carbon source is selected from glucose; The dispersant accounts for 1-5% of the mass of MXene.

7. A lithium-ion battery negative electrode, characterized in that, Its active material comprises the silicon-carbon-MXene composite anode material with controllable lithiation phase as described in any one of claims 1 to 3.

8. A lithium-ion battery, comprising a positive electrode, a separator, an electrolyte, and a negative electrode, characterized in that, The negative electrode is the lithium-ion battery negative electrode according to claim 7.

9. A lithium-ion battery according to claim 8, characterized in that, The initial coulombic efficiency of the lithium-ion battery is not less than 85%, and after 50 cycles at a 0.1C rate, the capacity retention rate is not less than 95%.

10. An electric vehicle or a large-scale energy storage system, characterized in that, The lithium-ion battery as described in claim 8 or 9 is included as its power source or energy storage unit.

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