Metal-doped silicon-based material and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion battery electrode materials, and discloses a metal-doped silicon-based material and a preparation method and application thereof. The method comprises the following steps: uniformly mixing a silicon source with metal fluoride; the method comprises the following steps: carrying out chemical etching at 200-450 DEG C under the conditions of inert atmosphere and pressurization, and constructing a nano-scale defect channel on the silicon surface by using fluorine ions; raising the temperature to 500-900 DEG C for thermal diffusion, and driving the metal atoms to diffuse into the silicon substrate through the defect channel to form a gradient doping structure of which the concentration is gradually reduced from the surface to the bulk phase; and pickling, washing and drying to obtain the product. Through an etching-diffusion synergistic mechanism, gradient doping of metal in micron silicon is realized, and bulk phase structure stability and interface charge transfer dynamics of the material are effectively enhanced. The prepared metal-doped silicon-based material has high specific capacity, excellent rate capability and long cycle stability when being applied to a lithium ion battery negative electrode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrode material technology, and particularly relates to a method for preparing metal-doped silicon-based materials. Background Technology

[0002] New energy vehicles, large-scale energy storage devices, and other fields have placed higher demands on the energy density, cycle stability, and fast-charging performance of lithium-ion batteries. The theoretical specific capacity of traditional graphite anode materials is only 372 mA hg. -1 The current technology is no longer sufficient to meet the development needs of the next generation of high-performance lithium-ion batteries, making the development of new high-capacity anode materials a core focus of industry research.

[0003] Silicon-based materials (including elemental silicon, silicon suboxide, porous silicon, etc.) have extremely high theoretical specific capacity (elemental silicon approximately 3579 mA hg). -1 silicon suboxide approximately 2600 mA hg -1 With its suitable lithium insertion / extraction potential and abundant reserves, silicon-based materials are considered the most promising next-generation anode material to replace graphite. However, silicon-based materials face two major bottlenecks in practical applications: First, the lithiation process generates a volume expansion of up to 200%-300%, leading to cracking and pulverization of electrode particles, damaging the stability of the solid electrolyte interface layer, and causing rapid capacity decay. Second, silicon itself is a semiconductor with low electronic conductivity and ion diffusion coefficient. Especially for micron-sized silicon-based materials, the problems of unstable bulk structure and slow interfacial charge transport are more prominent, which seriously restricts their long-cycle stability and high-rate charge-discharge performance.

[0004] To address these issues, researchers have developed various modification strategies. Surface engineering strategies (such as carbon coating, electrolyte modulation, and binder modification) alleviate stress caused by volume expansion by constructing an external buffer layer, but they only act on the surface of silicon particles and cannot solve the fundamental problem of bulk structural instability. Furthermore, the modification effect significantly diminishes as particle size and cycle number increase. While nano-sizing strategies can improve the fracture toughness and rate performance of materials, the high specific surface area leads to intensified interfacial side reactions, poor chemical stability, and high production costs, making it difficult to meet the needs of industrial applications. Publication number CN116544397A discloses a carbon-coated metal fluoride modified silicon anode material, its preparation method, and its application. The core of this technology lies in a concept of "physical encapsulation" and "synergistic effect": it constructs a "silicon-metal fluoride-carbon" core-shell structure by pre-coating a layer of metal fluoride (such as BiF3, SnF2) particles onto the surface of nano-silicon particles and then coating the outermost layer with a carbon layer. In this structure, the outer carbon layer and the middle metal fluoride layer primarily serve as physical buffer layers to accommodate the volume expansion of silicon during cycling. Simultaneously, the metal fluoride acts as an active material, reacting with lithium to provide additional capacity. The key to this technical approach lies in the fact that the heat treatment during its preparation is carried out under relatively mild conditions, aiming to convert carbon sources such as polydopamine into conductive carbon layers. The metal elements in the final product mainly exist as independent metal fluoride particles between the silicon particle surface and the carbon layer, without achieving metal atom doping into the silicon lattice, thus failing to fundamentally alter the bulk electronic conductivity and structural stability of the silicon substrate.

[0005] Metal doping has attracted widespread attention as an effective means to improve the bulk structure and transport properties of materials. In existing technologies, metal doping often employs in-situ doping (such as ball milling, hydrothermal reaction followed by calcination), which suffers from problems such as uneven distribution of the doped metal, difficulty in penetrating the material interior, and difficulty in controlling the content. Furthermore, it easily forms alloy phases, leading to metal particle precipitation during cycling and affecting lithium storage reversibility. Currently, some patents disclose metal doping technologies. For example, CN113506861A discloses a method for preparing metal-doped silicon suboxide composite anode materials via evaporation deposition, achieving uniform metal distribution in the silicon substrate and improving initial coulombic efficiency and cycle stability. However, this method is complex, involving high-temperature vacuum deposition and subsequent sintering, resulting in high costs, and the control over the metal doping concentration and spatial distribution remains insufficient. Another example is CN119461384A, which proposes achieving metal doping of SiO through dry mixing and heat treatment. x This method is simple to operate, but the uniformity of metal distribution and the bonding strength with the silicon matrix still need to be improved.

[0006] Therefore, developing a simple, controllable, and environmentally friendly method for preparing metal-doped silicon-based materials, and simultaneously addressing the issues of bulk structural instability and slow interfacial transport in silicon-based materials by precisely controlling the type, concentration, and distribution of metal doping, is of great significance for promoting the industrial application of high-energy-density lithium-ion batteries. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a metal-doped silicon-based material, its preparation method, and its applications.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A method for preparing a metal-doped silicon-based material, comprising the following steps: (1) The silicon source and the metal fluoride are mixed uniformly to obtain a mixture; wherein, the metal fluoride is selected from the Elingham diagram as a metal fluoride (MF). n The formation free energy of silicon tetrafluoride (SiF4) is higher than that of tin fluoride, antimony fluoride, bismuth fluoride, silver fluoride, copper fluoride, and nickel fluoride can be selected. According to the Allingham diagram in metallurgical thermodynamics, the standard formation free energy of these metal fluorides is higher than that of silicon tetrafluoride (SiF4). This allows them to be reduced by elemental silicon in subsequent high-temperature steps (the general reaction formula is: 4 / n MF). n + Si → 4 / n M + SiF4↑). The spontaneous thermodynamic driving force of this reaction originates from the generation and escape of gaseous SiF4 and the formation of more stable Si-F bonds. Through the above reaction, highly reactive elemental metals are generated in situ. These metal atoms will then diffuse into the silicon matrix, achieving atomic-level gradient doping.

[0009] (2) The mixture obtained in step (1) is heated to 200-450℃ under an inert atmosphere, pressurized to 0.1-1 MPa, and kept at a constant temperature for 0.5-12 h; then, under an inert atmosphere, the temperature is further increased to 500-900℃ and kept at a constant temperature for 5-30 h, and finally cooled to room temperature to obtain a solid product. First, chemical etching is performed at 200-450℃ to construct nanoscale defect channels on the silicon surface using fluorine ions; then, the temperature is increased to a high temperature of 500-900℃ for thermal diffusion, driving metal atoms to diffuse into the silicon substrate through the defect channels, forming a gradient doped structure with decreasing concentration from the surface to the bulk phase.

[0010] (3) The solid product obtained in step (2) is etched with 5-20% acid by mass for 1-12 h, and then repeatedly washed with deionized water until pH=6-7, in order to remove unreacted metal fluorides. The washed material is placed in a vacuum oven and dried at 50-100℃ for 12-24 h to obtain metal-doped silicon-based material. The doped atoms entering the silicon lattice can effectively pin grain boundaries and dislocations, significantly inhibiting their slip and proliferation during lithium (ion) insertion / extraction, thereby enhancing the structural stability of silicon-based materials from a bulk perspective, resisting volume expansion stress during cycling, and preventing particle pulverization.

[0011] More preferably, the metal fluoride in step (1) above is at least one of stannous fluoride (SnF2), bismuth fluoride (BiF3), antimony fluoride (SbF3), and copper fluoride (CuF2).

[0012] Furthermore, in step (1) above, the mass ratio of the metal in the metal fluoride to the silicon source is 0.01-0.5:1. More preferably, the mass ratio of the metal in the metal fluoride to the silicon source is 0.05-0.3:1.

[0013] In step (1) above, the silicon source is at least one of photovoltaic waste silicon powder, commercial micron silicon, silicon suboxide and porous silicon, and the silicon source particle size is 0.1-10μm.

[0014] The heating rate in step (2) above is 1-5℃ / min; the inert atmosphere gas is one or a mixture of nitrogen and argon.

[0015] Furthermore, the acid used for acid etching in step (3) above is at least one of hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid.

[0016] Metal-doped silicon-based materials are prepared using the above-described preparation method; wherein the metal elements are distributed in the silicon matrix lattice in the form of gradient doping.

[0017] The above-mentioned metal-doped silicon-based materials are used in lithium-ion batteries.

[0018] For example, a method for preparing a lithium-ion battery includes the following steps: (S1) Electrode Preparation: The prepared metal-doped silicon-based material is used as the negative electrode active material, sodium alginate (SA) as the binder, and Super P as the conductive agent. The negative electrode active material, conductive agent, and binder are mixed evenly at a mass ratio of 8:1:1, and an appropriate amount of deionized water is added for grinding. Then, a coating tool is used to control the coating thickness of the slurry, and the slurry is evenly coated onto the copper foil current collector. The slurry surface is allowed to dry at room temperature, and then transferred to a vacuum drying oven at 70℃ for 12 h. Finally, electrode sheets with a diameter of 16 mm are cut out using a manual slicer, and the electrode sheets are accurately weighed and the mass of the active material is calculated.

[0019] (S2) Battery Assembly: The battery assembly environment must be maintained at a water oxygen content below 0.01 ppm. The entire assembly process is completed in a glove box under a high-purity argon atmosphere. The battery assembly components used are the electrode sheets from the previous step, CR2032 button cell casing, Celgard 2400 polypropylene membrane, lithium metal sheet, NCM811 positive electrode sheet, LFP positive electrode sheet, stainless steel spring sheet, stainless steel gasket, and lithium-ion battery electrolyte. The electrolyte used is LiPF6 (1.0 M), dissolved in a mixture of ethylene carbonate (EC), methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1, containing 5 wt% fluoroethylene carbonate (FEC). The counter electrode for the half-cell is a lithium metal sheet, and the counter electrode for the full cell is an LFP. The battery assembly process begins with adding a small amount of electrolyte to the negative electrode casing, followed by the electrode plates. Sufficient electrolyte is then added to wet the plates, and next, the separator, lithium foil, stainless steel gasket, and stainless steel spring are placed in. Finally, the positive electrode casing is covered. The assembled battery is then placed on a button cell packaging machine using insulating clamps for hydraulic sealing. The packaged button cells are left to stand for 12 hours before subsequent electrochemical testing.

[0020] The beneficial effects of this invention are: (1) Wide range of silicon sources: For the first time, micron-sized silicon, silicon suboxide and porous silicon are incorporated into the same metal doping system. The silicon source can be flexibly selected according to actual needs (such as volumetric energy density and cost control), breaking through the limitation of the single silicon source in the existing technology and adapting to the needs of different energy storage scenarios.

[0021] (2) Strong controllability of doping: This invention achieves metal doping based on the unique "fluoride ion etching-thermal reduction diffusion" principle. First, in the medium and low temperature stage, the fluoride ions (F ions) released by the decomposition of metal fluorides... -This method selectively etches crystal planes on the silicon source surface to construct nanoscale defect channels. Subsequently, at high temperatures, thermodynamically unstable metal fluorides are reduced by silicon (based on the Ellingham diagram screening), generating highly active metal elemental atoms in situ. These atoms, through the defect channels, diffuse directionally into the silicon matrix under the influence of concentration gradient and thermal drive, ultimately forming a gradient doped structure with decreasing concentration from the surface to the bulk phase. This synergistic strategy enables precise control over doping concentration, gradient depth, and defect types (mainly including substitutional atomic defects formed by doped atoms replacing silicon lattice positions, and elastic lattice distortion caused by atomic size mismatch), fundamentally solving the problems of uneven distribution and insufficient bulk phase modification in traditional non-in-situ doping, and achieving directional design of material structures.

[0022] (3) Synergistic optimization of structure and performance: Metal gradient doping introduces a high concentration of point defects (such as substitutional atoms and interstitial atoms) into the silicon matrix. These defects have a strong "pinning effect" on grain boundaries and dislocations. Specifically, during lithiation, when the silicon lattice expands and generates lattice mismatch stress, the doped atoms, as pinning points, can effectively hinder the slip, multiplication, and migration of dislocations and grain boundaries, thereby delaying the initiation and propagation of microcracks and significantly improving the plasticity and fracture toughness of the material. At the same time, these point defects (especially substitutional atoms) can reduce the diffusion activation energy of lithium ions in the silicon lattice as local active sites, providing more low-barrier paths for lithium ion migration, thereby simultaneously optimizing the structural stability and electrochemical kinetic performance of the material.

[0023] (4) The process is green and easy to scale up: the preparation process does not require toxic chemical reagents, the heat treatment, pickling and other processes are mature and can be achieved with conventional tube furnaces and other equipment. Furthermore, low-cost silicon sources such as photovoltaic waste silicon can be used, which reduces production costs and has the potential for industrial promotion. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are 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.

[0025] Figure 1 This is a schematic diagram of the metal-doped silicon material of the present invention.

[0026] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the metal-doped silicon material prepared in Example 1 of this invention.

[0027] Figure 3This is a transmission electron microscope (TEM) image of the metal-doped silicon material prepared in Example 2 of the present invention.

[0028] Figure 4 The high-resolution XPS spectra (a) of Sn element in the metal-doped silicon material prepared in Example 3 of the present invention at different etching depths and the corresponding Sn content (b).

[0029] Figure 5 This is a scanning electron microscope (SEM) image of the metal-doped silicon material prepared in Example 4 of the present invention.

[0030] Figure 6 The first charge-discharge cycle curves are shown for batteries assembled from metal-doped silicon materials prepared in Example 3 and Comparative Example 1.

[0031] Figure 7 Cycling curves of batteries assembled from metal-doped silicon materials prepared in Example 3 and Comparative Example 1 (current density of 0.1 A g for the first 3 cycles). -1 ).

[0032] Figure 8 The cycling curve is shown for the battery assembled from the metal-doped silicon material prepared in Example 5 of this invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods or product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0036] In one embodiment of the present invention, a method for preparing a metal-doped silicon-based material includes the following steps: (1) The silicon source and the metal fluoride are mixed uniformly, and the mass ratio of the silicon source to the metal in the metal fluoride is 1:0.05-0.3 to obtain a mixture; (2) The mixture obtained in step (1) is heated to 200-450℃ under an inert atmosphere, pressurized to 0.1-1 MPa, and kept at a constant temperature for 0.5-12 h; then heated to 500-900℃ under an inert atmosphere and kept at a constant temperature for 5-30 h, and finally cooled to room temperature to obtain a solid product.

[0037] (3) The solid product obtained in step (1) is treated with dilute acid, then washed repeatedly with deionized water, and then dried to obtain the metal-doped silicon-based material.

[0038] In one embodiment of the present invention, by adjusting the amount of metal fluoride doping in step (1), the proportion of the product can be adjusted, thereby controlling the concentration and depth of metal doping.

[0039] In one embodiment of the present invention, by adjusting the temperature of the chemical etching process in step (2) to 200-450°C and the thermal diffusion temperature to 500-900°C, the etching rate of the silicon crystal plane by the metal fluoride and the thermally driven metal doping kinetics after reduction can be controlled. Preferably, the etching temperature is 300°C and the thermal diffusion temperature is 500°C.

[0040] In one embodiment of the present invention, the reaction kinetics and doping depth of the metal fluoride with silicon can be controlled by adjusting the reaction pressure in step (2) to 0.1-1 MPa. Low pressure restricts atomic diffusion, easily leading to a lower doping depth; high pressure significantly promotes the full fusion of the metal and the silicon substrate, forming a gradient doped structure. Preferably, the reaction pressure is 1 MPa. By adjusting the amount of metal fluoride, the chemical etching process in step (2), and the diffusion process, a metal-doped silicon-based material with a gradient doped structure is obtained, such as... Figure 1 As shown (M is a metallic element).

[0041] Example 1 The preparation method of a metal-doped silicon-based material according to this embodiment includes the following steps: (1) The washed and dried photovoltaic waste silicon powder (particle diameter of 1-2 μm) is uniformly mixed with tin fluoride (SnF2) to obtain a mixture; wherein the mass ratio of photovoltaic waste silicon powder to Sn in the mixture is 1:0.3.

[0042] (2) The mixture obtained in step (1) is heated to 300°C (heating rate of 5°C / min) under an inert atmosphere, pressurized to 1 MPa, and kept at a constant temperature for 5 h; then, the temperature is increased to 500°C at a heating rate of 5°C / min and kept at a constant temperature for 5 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) is treated with 20% dilute hydrochloric acid for 12 h, and then washed repeatedly with deionized water until pH=6-7; the washed material is placed in a vacuum oven and dried at 50℃ for 12 h to obtain the metal-doped silicon-based material.

[0043] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the Sn-doped micron-sized Si particles obtained in Example 1 of this invention. The XRD results show that the Sn-doped micron-sized Si particles contain a crystal structure of Si and Sn, indicating that Sn is successfully doped into the micron-sized Si lattice structure by reacting with Si and SnF2.

[0044] Example 2 The preparation method of a metal-doped silicon-based material according to this embodiment includes the following steps: (1) The washed and dried photovoltaic waste silicon powder (particle diameter of 1-2 μm) is uniformly mixed with tin fluoride (SnF2) to obtain a mixture; wherein the mass ratio of photovoltaic waste silicon powder to Sn in the mixture is 1:0.05.

[0045] (2) The mixture obtained in step (1) is heated to 300℃ (heating rate of 5℃ / min) under an inert atmosphere, pressurized to 1 MPa, and kept at a constant temperature for 5 h; then, the temperature is increased to 500℃ at a heating rate of 5℃ / min and kept at a constant temperature for 10 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) is treated with 20% dilute hydrochloric acid for 12 h, and then washed repeatedly with deionized water until pH=6-7; the washed material is placed in a vacuum oven and dried at 50℃ for 12 h to obtain the metal-doped silicon-based material.

[0046] Figure 3 This is a transmission electron microscope (TEM) image of the Sn-doped micron-sized Si particles obtained in Example 2 of this invention. TEM analysis was used to observe the morphology and structure of the material. The TEM results show that the morphology of the Sn-doped micron-sized Si particles is similar to that of micron-sized Si particles, and there are no obvious Sn particles, indicating successful Sn doping.

[0047] Example 3 The preparation method of a metal-doped silicon-based material according to this embodiment includes the following steps: (1) The washed and dried photovoltaic waste silicon powder (particle diameter of 1-2 μm) is uniformly mixed with tin fluoride (SnF2) to obtain a mixture; wherein the mass ratio of photovoltaic waste silicon powder to Sn in the mixture is 1:0.1.

[0048] (2) The mixture obtained in step (1) is heated to 300℃ (heating rate of 5℃ / min) under an inert atmosphere, pressurized to 1 MPa, and kept at a constant temperature for 5 h; then, the temperature is increased to 500℃ at a heating rate of 5℃ / min and kept at a constant temperature for 10 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) is treated with 20% dilute hydrochloric acid for 12 h, and then washed repeatedly with deionized water until pH=6-7; the washed material is placed in a vacuum oven and dried at 50℃ for 12 h to obtain the metal-doped silicon-based material.

[0049] Figure 4 This image shows the high-resolution XPS spectra of Sn at different etching depths in this embodiment, along with the corresponding Sn content. It was found that the intensity of tin gradually decreases from the surface to the interior, indicating that it is doped into the silicon lattice in a gradient distribution.

[0050] Example 4 The preparation method of a metal-doped silicon-based material according to this embodiment includes the following steps: (1) Commercial silicon suboxide (particle diameter 1-2 μm) was selected as the silicon source. First, the silicon suboxide was etched with 20% hydrofluoric acid to remove the silicon dioxide layer on its surface. Then, under inert gas, it was placed in a tube furnace and disproportionated at 900°C for 4 hours. The disproportionation treatment of silicon suboxide was to allow more elemental silicon nanoparticles to precipitate within its structure, which would be beneficial for subsequent doping reactions. The disproportionated silicon suboxide powder was uniformly mixed with bismuth fluoride (BiF3) to obtain a mixture; wherein the mass ratio of silicon suboxide powder to bismuth in the mixture was 1:0.05.

[0051] (2) The mixture obtained in step (1) is heated to 300℃ (heating rate of 5℃ / min) under an inert atmosphere, pressurized to 1 MPa, and kept at a constant temperature for 5 h; then, the temperature is increased to 500℃ at a heating rate of 5℃ / min and kept at a constant temperature for 10 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) is treated with 20% dilute nitric acid for 12 h and then washed repeatedly with deionized water until pH=6-7. The washed material is placed in a vacuum oven and dried at 50℃ for 12 h to obtain the metal-doped silicon-based material.

[0052] Figure 5This is a scanning electron microscope (SEM) image of the Bi-doped micron-sized silicon suboxide particles obtained in this embodiment. SEM analysis was used to observe the material morphology and structure. The SEM results show that the morphology of the Bi-doped micron-sized silicon suboxide particles is similar to that of micron-sized silicon suboxide, and there are no obvious Bi particles, indicating successful Bi doping.

[0053] Example 5 The preparation method of a metal-doped silicon-based material according to this embodiment includes the following steps: (1) Commercial silicon suboxide (particle diameter 1-2 μm) was selected as the silicon source. First, the silicon suboxide was etched with 20% hydrofluoric acid to remove the silicon dioxide layer on its surface. Then, under inert gas, it was placed in a tube furnace and disproportionated at 900 degrees Celsius for 4 hours. The disproportionation treatment of silicon suboxide was to allow more elemental silicon nanoparticles to precipitate within its structure, which would be beneficial for subsequent doping reactions. The disproportionated silicon suboxide powder was uniformly mixed with bismuth fluoride (BiF3) to obtain a mixture; wherein the mass ratio of silicon suboxide powder to bismuth in the mixture was 1:0.1.

[0054] (2) The mixture obtained in step (1) is heated to 300℃ (heating rate of 5℃ / min) under an inert atmosphere, pressurized to 1 MPa, and kept at a constant temperature for 5 h; then, the temperature is increased to 500℃ at a heating rate of 5℃ / min and kept at a constant temperature for 10 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) is treated with 20% dilute nitric acid for 12 h and then washed repeatedly with deionized water until pH=6-7. The washed material is placed in a vacuum oven and dried at 50℃ for 12 h to obtain the metal-doped silicon-based material.

[0055] Example 6 The preparation method of a metal-doped silicon-based material according to this embodiment includes the following steps: (1) The washed and dried photovoltaic waste silicon powder (particle diameter of 3-5μm) is uniformly mixed with antimony fluoride (SbF3) to obtain a mixture; wherein the mass ratio of photovoltaic waste silicon powder to Sb in the mixture is 1:0.2.

[0056] (2) The mixture obtained in step (1) was heated to 450℃ (heating rate of 3℃ / min) under an inert atmosphere, pressurized to 0.6 MPa, and kept at a constant temperature for 0.5 h; then, the temperature was increased to 600℃ at a heating rate of 1℃ / min and kept at a constant temperature for 7 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) is treated with 5% nitric acid for 6 h and then washed repeatedly with deionized water until pH=6-7. The washed material is placed in a vacuum oven and dried at 100℃ for 16 h to obtain the metal-doped silicon-based material.

[0057] Example 7 The preparation method of a metal-doped silicon-based material according to this embodiment includes the following steps: (1) Wash and dry porous silicon (D 50 The porous silicon (with a particle size of 2 μm) was uniformly mixed with antimony fluoride (SbF3) to obtain a mixture; wherein the mass ratio of porous silicon to Sb in the mixture was 1:0.1.

[0058] (2) The mixture obtained in step (1) is heated to 200℃ (heating rate of 1℃ / min) under an inert atmosphere, pressurized to 1 MPa, and kept at a constant temperature for 12 h; then, the temperature is increased to 600℃ at a heating rate of 1℃ / min and kept at a constant temperature for 30 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) is treated with 5% nitric acid for 1 h and then washed repeatedly with deionized water until pH=6-7. The washed material is placed in a vacuum oven and dried at 80℃ for 24 h to obtain the metal-doped silicon-based material.

[0059] Example 8 The preparation method of a metal-doped silicon-based material according to this embodiment includes the following steps: (1) The washed and dried photovoltaic waste silicon powder (particle diameter of 0.1-2μm) is uniformly mixed with tin fluoride (SnF2) and copper fluoride (CuF2) to obtain a mixture; wherein the mass ratio of photovoltaic waste silicon powder to Sn and Cu in the mixture is 1:0.1:0.1.

[0060] (2) The mixture obtained in step (1) is heated to 300℃ (heating rate of 5℃ / min) under an inert atmosphere, pressurized to 0.1 MPa, and kept at a constant temperature for 12 h; then, the temperature is increased to 900℃ at a heating rate of 1℃ / min and kept at a constant temperature for 10 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) was treated with 10% hydrochloric acid for 6 h and then washed repeatedly with deionized water until pH=6-7. The washed material was placed in a vacuum oven and dried at 100℃ for 16 h to obtain the metal-doped silicon-based material.

[0061] Comparative Example 1 The preparation method of the silicon-based material in this comparative example includes the following steps: The washed and dried photovoltaic waste silicon powder (particle diameter of 1-2 μm) was heated to 300℃ (heating rate of 5℃ / min) under an inert atmosphere, pressurized to 1 MPa, and kept at a constant temperature for 5 h; then, the temperature was further increased to 500℃ at a heating rate of 5℃ / min and kept at a constant temperature for 10 h, and finally cooled to room temperature to obtain silicon-based materials.

[0062] Application examples The materials prepared in the above embodiments and comparative examples were applied to lithium-ion batteries. The battery preparation steps are as follows: (S1) Electrode Preparation: The materials prepared in the above examples and comparative examples are negative electrode active materials, sodium alginate (SA) is a binder, and Super P is a conductive agent. The negative electrode active material, conductive agent, and binder are mixed evenly at a mass ratio of 8:1:1, and an appropriate amount of deionized water is added and the mixture is ground evenly. Then, a coating tool is used to control the coating thickness of the slurry, and the slurry is evenly coated onto the copper foil current collector. The slurry surface is allowed to dry at room temperature, and then it is transferred to a vacuum drying oven at 70°C for 12 h. Finally, electrode sheets with a diameter of 16 mm are cut out using a manual slicer.

[0063] (S2) Battery Assembly: The battery assembly environment must be maintained at a water oxygen content below 0.01 ppm. The entire assembly process is completed in a glove box under a high-purity argon atmosphere. The battery assembly components used are the electrode sheets from the previous step, CR2032 button cell casing, Celgard 2400 polypropylene membrane, lithium metal sheet, NCM811 positive electrode sheet, LFP positive electrode sheet, stainless steel spring sheet, stainless steel gasket, and lithium-ion battery electrolyte. The electrolyte used is LiPF6 (1.0 M), dissolved in a mixture of ethylene carbonate (EC), methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1, containing 5 wt% fluoroethylene carbonate (FEC). The counter electrode for the half-cell is a lithium metal sheet, and the counter electrode for the full cell is an LFP. The battery assembly process begins with adding a small amount of electrolyte to the negative electrode casing, followed by the electrode plates. Sufficient electrolyte is then added to wet the plates, and next, the separator, lithium foil, stainless steel gasket, and stainless steel spring are placed in. Finally, the positive electrode casing is covered. The assembled battery is then placed on a button cell packaging machine using insulating clamps for hydraulic sealing. The packaged button cells are left to stand for 12 hours before subsequent electrochemical testing.

[0064] Figure 6 The figures show the initial charge-discharge curves of the batteries assembled using the materials prepared in Example 3 and Comparative Example 1. As can be seen from the figures, the electrode of Example 3 exhibits a higher initial coulombic efficiency than that of Comparative Example 1, reaching 88.6%, indicating that Sn doping significantly improves the reversibility of lithium ions. Furthermore, the lithium intercalation / deintercalation plateau of the electrode in Example 3 differs slightly from that of the electrode in Comparative Example 1, possibly corresponding to differences in the microscopic lithium intercalation / deintercalation mechanism.

[0065] Figure 7 To assemble batteries using materials prepared in Example 3 and Comparative Example 1 at 2 A g -1 Cycling performance at current density. The electrode of Example 3 was found to have significantly enhanced cycling stability, maintaining 1472.4 mA hg after 200 cycles. -1 The specific capacity corresponds to a 70% capacity retention. Comparative Example 1 electrode exhibits a rapid capacity decay trend in the first 10 cycles, reaching only 569.7 mA hg after 200 cycles. -1 Specific capacity.

[0066] Figure 8 The battery assembled using the metal-doped silicon material prepared in Example 5 was tested at 0.2 A g. -1 Cyclic performance at current density shows that it maintains 1000 mA hg after 200 cycles. -1 The above capacity.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a metal-doped silicon-based material, characterized in that, The steps are as follows: (1) The silicon source and the metal fluoride are mixed uniformly to obtain a mixture; wherein the standard Gibbs free energy of formation of the metal fluoride is higher than that of SiF4. (2) The mixture obtained in step (1) is heated to 200-450℃ and pressurized to 0.1-1 MPa under an inert atmosphere and kept at a constant temperature for 0.5-12 h; then the temperature is further increased to 500-900℃ and kept at a constant temperature for 5-30 h, and finally cooled to room temperature to obtain a solid product. (3) The solid product obtained in step (2) is subjected to acid etching, cleaning and drying to obtain metal-doped silicon-based material.

2. The method for preparing metal-doped silicon-based materials according to claim 1, characterized in that, In step (1), the metal fluoride is at least one of tin fluoride, bismuth fluoride, antimony fluoride, silver fluoride, copper fluoride, and nickel fluoride.

3. The method for preparing metal-doped silicon-based materials according to claim 1, characterized in that, In step (1), the mass ratio of the metal in the metal fluoride to the silicon source is 0.01-0.5:

1.

4. The method for preparing metal-doped silicon-based materials according to any one of claims 1-3, characterized in that, In step (1), the silicon source particle size is 0.1-10 μm.

5. The method for preparing metal-doped silicon-based materials according to claim 4, characterized in that, In step (1), the silicon source is at least one of photovoltaic waste silicon powder, commercial micron silicon, silicon suboxide, and porous silicon.

6. The method for preparing metal-doped silicon-based materials according to claim 5, characterized in that, The heating rate in step (2) is 1-5℃ / min.

7. The method for preparing metal-doped silicon-based materials according to claim 6, characterized in that, The acid used for acid etching in step (3) is at least one of hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid.

8. The method for preparing metal-doped silicon-based materials according to claim 7, characterized in that, The concentration of the acid is 5-20 wt%; the acid etching time is 1-12 h.

9. Metal-doped silicon-based materials prepared by the preparation method according to any one of claims 1-3 or 5-8.

10. The application of the metal-doped silicon-based material according to claim 9 in lithium-ion batteries.

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