Silicon-based negative electrode material, preparation method thereof and application thereof in lithium ion battery
By preparing silicon-based anode materials with layered stacked silicon nanosheet structures through molten salt electrolysis, the problems of volume expansion and reaction kinetics of silicon-based anode materials were solved, and the performance of lithium-ion batteries was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 江西省自然资源权益与储备保障中心
- Filing Date
- 2025-11-03
- Publication Date
- 2026-07-03
Smart Images
Figure CN121405095B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery anode material technology, and particularly relates to a silicon-based anode material, its preparation method, and its application in lithium-ion batteries. Background Technology
[0002] Lithium-ion batteries (LIBs), as a type of rechargeable battery, have gradually taken a dominant position in the development of portable electronic devices and the new energy industry due to their advantages such as high specific energy, good cycle capability, and environmental friendliness.
[0003] Among numerous lithium-ion battery anode materials, silicon-based anode materials stand out due to their specific capacity, which is nearly ten times higher than that of currently mainstream commercial graphite anodes (3579 mAh g⁻¹). -1 Li 15 Si4) has a low lithium insertion / extraction voltage plateau (< 0.5 V vs. Li / Li). + Silicon-based anodes, with their abundant resources and other advantages, are widely recognized as the most promising anode material for next-generation high-energy-density lithium-ion batteries. However, the high specific capacity of silicon-based anodes is accompanied by massive volume expansion (>300%) during lithium insertion / extraction, leading to continuous pulverization during cycling. This reduces the effective electrical contact between the active material and the current collector (copper foil), and the SEI film continues to grow, resulting in low coulombic efficiency, poor cycle stability, and a sharp decline in overall battery performance. Furthermore, silicon, as a semiconductor material, has relatively low intrinsic electronic conductivity (10⁻⁶ ppm). -5 ~10 -3 S cm -1 Furthermore, its lithium-ion diffusion coefficient is relatively low (10). -14 ~10 -12 cm 2 s -1 Therefore, silicon-based materials have an inherent problem of low reaction kinetics, which leads to problems such as lithium capture, resulting in poor rate performance, low coulombic efficiency, and low capacity retention of lithium-ion batteries.
[0004] Currently, to address the aforementioned issues of volume expansion and low reaction kinetics, researchers have conducted extensive studies focusing on improving the volume expansion of silicon-based materials, forming a stable SEI film, and enhancing the material's conductivity. On one hand, elemental silicon in lithium-ion batteries experiences significant volume expansion (greater than 300%) during charge and discharge, making it impossible to form a stable SEI film on its surface. As the SEI film is continuously renewed, lithium ions cease to participate in the battery's charge-discharge cycle, resulting in a decrease in overall battery capacity. Carbon materials, as anodes in lithium-ion batteries, possess advantages such as abundant micropores, high strength, and strong conductivity. Furthermore, precursors for preparing carbon materials are widely available and easily modified according to requirements. Conformally coated silicon-carbon composites obtained after silicon-based carbonization can alleviate the volume expansion of silicon-based materials, stabilize the SEI film on the material surface, and enhance the conductivity of the anode. On the other hand, lithium-ion intercalation during silicon charging leads to enormous volume expansion, which can cause cracks after multiple charge-discharge cycles, ultimately leading to electrode breakage or even pulverization, limiting its commercial application. Nanostructuring of silicon materials is one of the effective methods to improve the performance of silicon-based anode materials. Silicon nanomaterials (such as silicon nanoclusters, one-dimensional silicon nanowires, and two-dimensional silicon thin films) exhibit significant surface and size effects, reducing the diffusion distance between lithium ions and thus mitigating the stress caused by uneven lithium ion diffusion. These advantages of nanomaterials can address the issue of gradually decreasing cycle capacity during lithium insertion / extraction in silicon-based anode materials.
[0005] The key to improving the electrochemical performance of silicon-based anode materials lies in mitigating the volume effect, maintaining structural stability during cycling, and ensuring effective electrical contact between active materials. Nanostructuring is one of the most direct and effective methods to enhance the electrochemical performance of silicon-based materials. Reducing particle size not only alleviates internal mechanical stress, maintains electrode structural integrity, and improves cycling stability, but also effectively shortens the lithium-ion transport path, increases transport sites, and reduces lithium capture, thereby improving the material's rate performance, coulombic efficiency, and capacity retention. However, excessive nanostructuring leads to a sharp increase in the specific surface area of silicon-based materials, resulting in more side reactions, the formation of a large amount of SEI film, a lower initial coulombic efficiency (ICE), and lower tap density, thus reducing the volumetric specific capacity and hindering its commercial development. Therefore, nanostructuring has evolved from single nanoparticles, nanowires, and nanofilms to micro / nano hierarchical structures, where primary nanoparticles are used to construct secondary particles at the micrometer scale. These micro / nano hierarchical structures not only effectively overcome volume changes but also significantly reduce specific surface area compared to single nanostructure materials, minimizing side reactions and SEI film formation. However, as micro / nano structures become increasingly complex, they place higher demands on reaction equipment, reaction conditions, and raw materials, inevitably leading to higher costs in the fabrication of silicon-based anode materials. Therefore, finding a simple and economical method to construct silicon-based anode materials with micro / nano hierarchical structures is a recent research focus for researchers.
[0006] When the roots of higher plants absorb groundwater, they simultaneously absorb soluble silica. This silica is then transported through the vascular tissue to the stems, leaves, flowers, and fruits, where it precipitates as amorphous silica particles containing organic matter between or within cells—this is phytoliths. The chemical composition (mass fraction) of the raw phytolith silica ore is: SiO2 77.01~80.54%, Al2O3 3.03~5.35%, Fe2O3 1.08~3.73%, CaO 0.07~0.69%, LOI (loss on ignition) 11.96~16.13%, and TiO2 approximately 0.69%. The mineral composition (mass fraction) is: gangue 8%, clay 3%, pyrite 0.5%, goethite 0.5%, humic matter 10%, and SiO2 78%. Phytoliths are widely available and inexpensive, and are naturally rich in silica and plant-derived carbon. Their derived carbon can be used as an electron conduction medium, and silica can be used as a silicon source. They have potential application value in the preparation of silicon-based anode materials. However, there are currently no reports on the preparation of high-performance silicon-based anode materials using phytoliths via molten salt electrolysis. Summary of the Invention
[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing silicon-based anode materials, their application, and their use in lithium-ion batteries. The method for preparing the silicon-based anode material utilizes economical phytoliths rich in silica and plant-derived carbon as raw materials, employing a simple and scalable molten salt electrolysis method to prepare micro / nano-hierarchical structured silicon-based anode materials with excellent lithium storage performance.
[0008] The present invention adopts the following technical solution:
[0009] In a first aspect, the present invention provides a method for preparing a silicon-based anode material, comprising the following steps:
[0010] The phytoliths were placed in hydrochloric acid and subjected to a hydrothermal reaction. After filtration, purified phytoliths were obtained.
[0011] The purified silicone was encapsulated in foamed metal and used as the working electrode;
[0012] Add molten salt electrolyte to the electrolytic cell, place the working electrode in the electrolytic cell, and place the anode in the electrolytic cell at the same time;
[0013] Under an inert atmosphere, molten salt electrolyte is heated to melt it, and the working electrode is connected as the cathode to the negative terminal of the power supply and the anode is connected to the positive terminal of the power supply to carry out electrolysis, thereby obtaining silicon-based anode material.
[0014] Preferably, the phytoliths are placed in hydrochloric acid and subjected to a hydrothermal reaction at a temperature of 150~160℃ for 4~5 hours, followed by filtration to obtain purified phytoliths.
[0015] Preferably, the molten salt electrolyte includes NaCl, KCl, and MgCl2; or, the molten salt electrolyte includes NaCl, MgCl2, and CaCl2.
[0016] Preferably, the molten salt electrolyte is heated to 750-760°C under an inert atmosphere to melt it.
[0017] Preferably, in the step of placing the phytolith in hydrochloric acid for hydrothermal reaction, the mass-to-volume ratio of the phytolith to the hydrochloric acid is (7~8) g:(60~70) mL, and the concentration of the hydrochloric acid is 0.5~1 mol / L;
[0018] The foam metal is foamed nickel.
[0019] Preferably, if the molten salt electrolyte includes NaCl, KCl, and MgCl2, then the mass ratio of the purified phytolith, NaCl, KCl, and MgCl2 is (0.7~0.8):(14.63~15.63):(41.75~42.75):(43.7~44.7).
[0020] If the molten salt electrolyte includes NaCl, MgCl2, and CaCl2, then the mass ratio of the purified phytolith, NaCl, MgCl2, and CaCl2 is (0.35~0.45):(13.34~14.34):(30.675~31.675):(47.52~48.52).
[0021] The control voltage during electrolysis is 2.2~2.6V, and the electrolysis time is 6~12h.
[0022] Preferably, in the step of placing the phytolith in hydrochloric acid for a hydrothermal reaction, the mass-to-volume ratio of the phytolith to the hydrochloric acid is 7 g:70 mL, and the concentration of the hydrochloric acid is 0.1~2 mol / L, preferably 0.5 mol / L;
[0023] The foam metal is foamed nickel.
[0024] Preferably, after electrolysis, the electrolysis product is obtained. The electrolysis product is then soaked in water for 8 hours, in 1 mol / L hydrochloric acid for 8 hours, and in 1 mol / L hydrofluoric acid for 6 hours in sequence. After washing again until neutral, it is dried to obtain a silicon-based anode material.
[0025] Secondly, the present invention also provides a silicon-based anode material, which is prepared by the aforementioned preparation method.
[0026] Thirdly, the present invention also provides an application of the silicon-based anode material prepared by the above-described preparation method in the preparation of lithium-ion batteries.
[0027] Fourthly, the present invention provides a lithium-ion battery, comprising a silicon-based anode material or a silicon-based anode material prepared by the aforementioned preparation method.
[0028] The preparation method of the silicon-based anode material of the present invention, as well as its application, have the following advantages compared with the prior art:
[0029] The present invention discloses a method for preparing silicon-based anode materials, using phytoliths rich in silicon dioxide and plant-derived carbon as raw materials, and employing a molten salt electrolysis method to prepare layered stacked silicon nanosheet structure silicon-based anode materials. The present invention uses economical silicon oxide phytoliths as raw materials and employs a simple and scalable molten salt electrolysis method to prepare layered stacked silicon nanosheet structure silicon-based anode materials with excellent lithium storage performance, thereby solving the volume expansion problem of silicon-based materials and the cycle stability of their lithium-ion batteries. Specifically, hydrochloric acid was used as an etchant to etch the phytolith under hydrothermal conditions to dissolve impurities. The etched phytolith was then centrifuged, washed, and filtered to obtain purified phytolith, whose main components were silicon dioxide and plant-derived carbon. Subsequently, the purified phytolith was used as the cathode, and an electrolytic system consisting of molten salt electrolyte and anode was formed. Electrolysis was performed to reduce the silicon dioxide in the phytolith to silicon, thereby preparing a silicon-based anode material with a layered stacked silicon nanosheet structure. As the conductive phase in the current collector / oxide / electrolyte three-phase line, the presence of plant-derived carbon in the phytolith can significantly improve the electrolysis efficiency. At the same time, it can also be dispersed in the stacked silicon nanosheet layers, improving the electrochemical performance of the product. The prepared silicon-based anode material with a layered stacked silicon nanosheet structure helps to alleviate the volume expansion of silicon and has continuous lithium-ion and electron transport channels. These characteristics endow the silicon-based anode material with a layered stacked silicon nanosheet structure with good lithium storage cycle stability. Electrochemical performance tests show that the prepared silicon-based anode material with layered stacked silicon nanosheet structure has high specific capacity and first coulombic efficiency, and also exhibits excellent rate performance and cycle stability. Attached Figure Description
[0030] 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.
[0031] Figure 1 X-ray diffraction (XRD) patterns of the silicon-based anode materials prepared in Example 1 and Comparative Example 1, and the purified implanted silicon particles.
[0032] Figure 2 The Raman spectrum of the silicon-based anode material prepared in Example 1;
[0033] Figure 3 This is a SEM image of the purified phytolith obtained in step S1 of Example 1;
[0034] Figure 4 This is a SEM image of the silicon-based anode material prepared in Example 1.
[0035] Figure 5 The current-time curves during the molten salt electrolysis process in Example 1 are shown.
[0036] Figure 6 The first charge-discharge curves of the batteries assembled in Example 1 and Comparative Examples 1-2 at a current density of 0.2 A / g are shown.
[0037] Figure 7 Cycle stability curves of the button batteries assembled in Example 1 and Comparative Examples 1-2;
[0038] Figure 8 The results show the rate performance of the batteries assembled in Example 1 and Comparative Examples 1-2 in the current density range of 0.2-4 A / g.
[0039] Figure 9 The image shows the cycle performance curve of the battery assembled from the silicon-based anode material prepared in Example 2. Detailed Implementation
[0040] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.
[0041] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.
[0042] This invention provides a method for preparing a silicon-based anode material, comprising the following steps:
[0043] S1. Place the phytoliths in hydrochloric acid and carry out a hydrothermal reaction. Filter the solution to obtain purified phytoliths.
[0044] S2. The purified silicone body is wrapped with foam metal and used as the working electrode;
[0045] S3. Add molten salt electrolyte to the electrolytic cell, place the working electrode in the electrolytic cell, and place the anode in the electrolytic cell at the same time.
[0046] S4. Under an inert atmosphere, the molten salt electrolyte is heated to melt it, and the working electrode is connected as the cathode to the negative terminal of the power supply and the anode is connected to the positive terminal of the power supply to carry out electrolysis to obtain a silicon-based negative electrode material.
[0047] The present invention discloses a method for preparing silicon-based anode materials, using silicide implants as raw materials and employing molten salt electrolysis to prepare layered stacked silicon nanosheet structured silicon-based anode materials. The present invention uses economical silicon oxide silicide implants as raw materials and employs a simple and scalable molten salt electrolysis method to prepare micro / nano-hierarchical structured silicon-based anode materials with excellent lithium storage performance, thereby solving the volume expansion problem of silicon-based materials and the cycle stability of their lithium-ion batteries. Specifically, hydrochloric acid was used as an etchant to etch the phytolith under hydrothermal conditions to dissolve impurities. The etched phytolith was then centrifuged, washed, and filtered to obtain purified phytolith, whose main components were silicon dioxide and plant-derived carbon. Subsequently, the purified phytolith was used as the cathode, and an electrolytic system consisting of molten salt electrolyte and anode was formed to perform electrolysis, reducing the silicon dioxide in the phytolith to silicon, thereby preparing a silicon-based anode material with a layered stacked silicon nanosheet structure. As an important component of the conductive phase and current collector in the current collector / oxide / electrolyte three-phase line, the presence of plant-derived carbon in the phytolith can significantly improve the electrolysis efficiency. At the same time, it can also be dispersed in the stacked silicon nanosheet layers, improving the electrochemical performance of the product. The prepared silicon-based anode material with a layered stacked silicon nanosheet structure helps to alleviate the volume expansion of silicon and has continuous lithium-ion and electron transport channels. These characteristics endow the silicon-based anode material with a layered stacked silicon nanosheet structure with good lithium storage cycle stability. Electrochemical performance tests show that the prepared silicon-based anode material with layered stacked silicon nanosheet structure has high specific capacity and first coulombic efficiency, and also exhibits excellent rate performance and cycle stability.
[0048] In some embodiments, the phytoliths are placed in hydrochloric acid and subjected to a hydrothermal reaction at a temperature of 150-160°C for 4-5 hours, followed by filtration to obtain purified phytoliths.
[0049] In some embodiments, the molten salt electrolyte includes NaCl, KCl, and MgCl2; or, the molten salt electrolyte includes NaCl, MgCl2, and CaCl2.
[0050] In some embodiments, the molar ratio of NaCl, KCl, and MgCl2 is (0.2~0.3):(0.2~0.3):(0.5~0.6), preferably, the molar ratio of NaCl, KCl, and MgCl2 is 0.271:0.221:0.508; specifically, before electrolysis, a mixed salt of NaCl, KCl, and MgCl2 is taken, ground, poured into a graphite crucible, and stored in an oven to dry in order to remove any possible moisture. The drying temperature is 200 °C, and the drying time is 12 h.
[0051] In some embodiments, the molten salt electrolyte is heated to 750-760°C under an inert atmosphere to melt it; specifically, the inert atmosphere includes at least one of nitrogen, helium, neon, and argon.
[0052] In some embodiments, the purified biofilm is wrapped with foam metal, and then the foam metal is fixed to a conductive molybdenum wire with molybdenum wire to serve as a working electrode.
[0053] In some embodiments, the anode is graphite.
[0054] In some embodiments, molten salt electrolyte is placed in a graphite crucible, and the working electrode is also placed in the graphite crucible. The graphite crucible is placed in a tube with one end closed, and heated under an inert protective environment to bring the molten salt electrolyte to a molten state. During electrolysis, a dual-electrode configuration is used, where the graphite crucible acts as the anode and the working electrode acts as the cathode. The working electrode, as the cathode, is connected to the negative terminal of the power supply, and the anode is connected to the positive terminal of the power supply for electrolysis. In the molten state, the mixed molten salt acts as the electrolyte. Specifically, electrolysis is performed at a constant potential. After constant voltage electrolysis, the working electrode is quickly removed from the molten salt state and allowed to cool freely to room temperature in a nitrogen atmosphere. The electrolysis product is collected, and the molybdenum wire and nickel foam are removed. The product is then continuously soaked in deionized water, dilute hydrochloric acid, and dilute hydrofluoric acid to thoroughly remove residual molten salt and residual silica. Finally, the product is soaked in deionized water and centrifuged until the solution is neutral. After filtration and drying, a blackish-gray powder is obtained. The obtained product is the silicon-based anode material with a nanosheet layered stacked structure.
[0055] In some embodiments, in the step of placing the phytolith in hydrochloric acid for a hydrothermal reaction, the mass-to-volume ratio of the phytolith to the hydrochloric acid is (7~8) g:(60~70) mL, and the concentration of the hydrochloric acid is 0.5~1 mol / L; preferably, the mass-to-volume ratio of the phytolith to the hydrochloric acid is 7 g:70 mL, and the concentration of the hydrochloric acid is 0.5~1 mol / L.
[0056] In some embodiments, the foam metal is foamed nickel.
[0057] Specifically, the phytoliths are placed in hydrochloric acid and then placed in a reaction vessel for hydrothermal reaction. After the hydrothermal reaction is completed, the hydrothermal product is washed and dried to obtain black powder particles, which are the purified phytoliths. The drying temperature is 60 ℃ and the drying time is 12 h.
[0058] In some embodiments, if the molten salt electrolyte includes NaCl, KCl, and MgCl2, then the mass ratio of the purified phytolith, NaCl, KCl, and MgCl2 is (0.7~0.8):(14.63~15.63):(41.75~42.75):(43.7~44.7).
[0059] If the molten salt electrolyte includes NaCl, MgCl2, and CaCl2, then the mass ratio of the purified phytolith, NaCl, MgCl2, and CaCl2 is (0.35~0.45):(13.34~14.34):(30.675~31.675):(47.52~48.52).
[0060] The control voltage during electrolysis is 2.2~2.6V, and the electrolysis time is 6~12h.
[0061] In some embodiments, after electrolysis, an electrolysis product is obtained. This product is then sequentially soaked in water for 8-9 hours, in 0.1-2 mol / L hydrochloric acid for 8-9 hours, and in 1-2 mol / L hydrofluoric acid for 6-7 hours. After washing again until neutral, the product is dried to obtain a silicon-based anode material. Preferably, after electrolysis, the product is sequentially soaked in water for 8 hours, in 1 mol / L hydrochloric acid for 8 hours, and in 1 mol / L hydrofluoric acid for 8 hours to thoroughly remove residual molten salt and residual silica. Finally, the product is soaked in deionized water and centrifuged until the solution is neutral. After filtration and drying, a blackish-gray powder is obtained. The resulting product is the silicon-based anode material with a nanosheet layered stacked structure.
[0062] In some embodiments, the graphite crucible has the following specifications: a height of 80 mm, an inner circumference of 65 mm, and a sidewall width of 5 mm.
[0063] In some embodiments, the reactor material is a stainless steel reactor lined with polytetrafluoroethylene.
[0064] In some embodiments, the foam metal is nickel foam, which has the following dimensional characteristics: a length of 4 cm, a width of 4 cm, a thickness of 1.7 mm, and a pore size of 110 PPI (PPI represents the number of pores per inch).
[0065] In some embodiments, before encapsulating the purified phytolith with foam metal, the foam metal is further immersed in 0.5 mol / L hydrochloric acid for 1 min.
[0066] In some embodiments, in the step of fixing the foam metal to the conductive molybdenum wire as a working electrode using a molybdenum wire, the diameter of the molybdenum wire is 0.1 mm and the cross-sectional diameter of the conductive molybdenum wire is 1 mm.
[0067] In some embodiments, the quartz tube has a total length of 500 mm, an internal diameter of 94 mm, and a wall thickness of 3 mm.
[0068] The present invention discloses a method for preparing silicon-based anode materials, using phytoliths as raw materials and a mixture of NaCl, MgCl2, KCl, or CaCl2 as electrolytes. A layered stacked silicon nanosheet structure silicon-based anode material is prepared using molten salt electrolysis. The silicon dioxide in the phytoliths is electrolytically reduced to silicon, while the plant-derived carbon in the phytoliths acts as an electron conduction medium to improve electrolysis efficiency. The prepared layered stacked silicon nanosheet structure silicon-based material, when applied to lithium-ion battery manufacturing, not only alleviates internal mechanical stress, maintains electrode structural integrity, and improves cycle stability, but also effectively shortens the lithium-ion transport path, increases transport sites, and reduces lithium capture. This improves the material's rate performance, coulombic efficiency, and capacity retention, thereby enhancing its cycle performance as a lithium-ion battery anode material. During electrochemical performance evaluation, this anode material at 0.2 A g… -1 At a current density of 0.5 Ag, it exhibits an initial charge-discharge efficiency of 75.46%. -1 After 120 charge-discharge cycles at a current density, the discharge capacity of this material remained at 1077.80 mAh g⁻¹. -1 The capacity retention rate is as high as 83.27%. This result is significantly better than that of nano-silicon and silicon-carbon materials on the market.
[0069] Based on the same inventive concept, the present invention also provides a silicon-based anode material, which is prepared by the above-described preparation method.
[0070] Based on the same inventive concept, the present invention also provides a silicon-based anode material prepared by the above-described preparation method or the application of the above-described silicon-based anode material in the preparation of lithium-ion batteries.
[0071] Based on the same inventive concept, the present invention also provides a lithium-ion battery, comprising a silicon-based anode material prepared by the above-described preparation method or the above-described silicon-based anode material.
[0072] The following specific embodiments further illustrate the silicon-based anode material of the present invention, its preparation method, and its application in lithium-ion batteries. This section further illustrates the content of the present invention with reference to specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.
[0073] In the following embodiments of the present invention, the purified silica particles have a particle size of 5 μm. The listed specifications are merely to demonstrate the feasibility of a method for preparing silicon-based materials with a layered stacked silicon nanosheet structure. Silicon-based materials with binary layered stacked silicon nanosheet structures prepared using starting materials of different particle sizes are all within the scope of patent protection of this invention.
[0074] Example 1
[0075] This embodiment provides a method for preparing a silicon-based anode material, including the following steps:
[0076] S1. Place 7g of phytoliths in 60mL of 0.5 mol / L... -1 The product was hydrothermally reacted in hydrochloric acid at 150°C for 4 hours. After hydrothermal reaction, the product was washed and dried at 60°C for 12 hours to obtain black powder particles, which were the purified phytoliths (average particle size of 5 μm).
[0077] S2. Immerse the nickel foam in 1 mol / L hydrochloric acid for 1 min. The nickel foam has a length of 4 cm, a width of 4 cm, a thickness of 1.7 mm, and a pore size of 110 PPI.
[0078] 0.7 g of purified biomass was wrapped with soaked nickel foam, and the nickel foam was fixed to a 1 mm diameter conductive Mo wire with a diameter of 0.1 mm using a 0.1 mm diameter Mo wire as the working electrode.
[0079] S3. 14.63 g of sodium chloride (NaCl), 41.75 g of potassium chloride (KCl) and 43.7 g of magnesium chloride (MgCl2) were mixed and ground to obtain a molten salt electrolyte. The electrolyte was then placed in a graphite crucible with a height of 80 mm, an inner diameter of 65 mm and a wall thickness of 5 mm. The graphite crucible was then placed in an oven at 200 ℃ and dried for 12 h to remove moisture from the molten salt electrolyte.
[0080] S4. The working electrode is placed in a graphite crucible, which is then placed inside a quartz tube with a length of 500 mm, an inner diameter of 94 mm, a wall thickness of 3 mm, and a single-end seal. The crucible is heated in a nitrogen atmosphere. The electrolysis operation uses a dual-electrode configuration, with the graphite crucible as the anode and the working electrode as the cathode. Molten mixed salt is used as the electrolyte, and constant voltage electrolysis is performed at 750 °C and 2.5 V for 10 h. After electrolysis, the working electrode is quickly removed from the molten salt and cooled to ambient temperature in a nitrogen atmosphere. The electrolysis products are collected, and molybdenum wire and nickel foam are removed. Then, the product is successively soaked in deionized water for 8 h, in 1 mol / L hydrochloric acid for 8 h, and in 1 mol / L hydrofluoric acid for 6 h. It is then washed again until neutral and dried to obtain a gray powdery layered stacked silicon nanosheet structure silicon-based anode material.
[0081] This embodiment also provides a lithium-ion battery, including a negative electrode sheet, a Celgard 2400 polypropylene separator, lithium metal (as a counter electrode), and an electrolyte;
[0082] The electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF6) in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, DMC, and DEC was 1:1:1. FEC (fluoroethylene carbonate) was also added to the mixed solvent at a volume fraction of 10% of the mixed solvent volume. The concentration of lithium hexafluorophosphate (LiPF6) was 1 mol / L. -1 ;
[0083] The method for preparing the negative electrode sheet is as follows: the silicon-based negative electrode material with layered stacked silicon nanosheet structure (as active material) prepared in Example 1 is mixed with SP conductive agent and sodium alginate binder in a mass ratio of 8:1:1 to obtain a negative electrode slurry;
[0084] The negative electrode slurry was coated onto copper foil and then dried at 60 °C for 12 h to obtain the negative electrode sheet.
[0085] The CR2032 button cell was assembled by combining the negative electrode, Celgard 2400 polypropylene separator, lithium metal (as counter electrode), and electrolyte.
[0086] Comparative Example 1
[0087] This comparative example provides a method for preparing a silicon-based anode material, similar to Example 1, except that calcium chloride molten salt is used instead of magnesium chloride molten salt for the comparative experiment. Specifically, sodium chloride, potassium chloride, and calcium chloride are used as the molten salt medium, without magnesium chloride, and the electrolysis time is 5 hours, as detailed below:
[0088] S1. Take 13.34 g of sodium chloride (NaCl), 39.14 g of potassium chloride (KCl), and 47.52 g of calcium chloride (CaCl2), mix them, and grind them to obtain a molten salt electrolyte. Then, place it in a graphite crucible with a height of 80 mm, an inner diameter of 65 mm, and a wall thickness of 5 mm. Next, place the graphite crucible in an oven at a temperature of 200 ℃ and dry it for 12 h to remove the moisture from the molten salt electrolyte.
[0089] S2. Immerse the nickel foam in 1 mol / L hydrochloric acid for 1 min. The nickel foam has a length of 4 cm, a width of 4 cm, a thickness of 1.7 mm, and a pore size of 110 PPI.
[0090] 0.7 g of purified implanted silica was wrapped with soaked nickel foam (the purified implanted silica was obtained according to the method in Example 1), and the nickel foam was fixed on a conductive Mo wire with a diameter of 1 mm using a 0.1 mm diameter Mo wire as a working electrode.
[0091] S3. The molten salt electrolyte from S1 was loaded into a graphite crucible, which was then placed inside a single-ended sealed quartz tube and heated under a nitrogen atmosphere. Electrolysis was performed using a dual-electrode configuration, with the graphite crucible acting as the anode and the working electrode as the cathode. Molten mixed salt was used as the electrolyte, and constant voltage electrolysis was conducted at 2.5 V at 750 °C for 5 h. After electrolysis, the working electrode was quickly removed from the molten salt and cooled to ambient temperature under a nitrogen atmosphere. The reaction product was then removed from the quartz tube, and the Mo filaments and nickel foam were removed. Next, deionized water and 1 mol L⁻¹ were used sequentially. -1 dilute hydrochloric acid and 1 mol L -1 The product was soaked in dilute hydrofluoric acid to remove residual molten salt and silica for 8 h, 8 h, and 6 h at each step. After treatment, it was centrifuged and washed with deionized water until the washing solution was neutral, then filtered and dried to obtain a blackish-gray powdered silicon-based material, which is the silicon-based anode material.
[0092] This comparative example also provides a lithium-ion battery, including a negative electrode, a Celgard 2400 polypropylene separator, lithium metal (as a counter electrode), and an electrolyte.
[0093] The electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF6) in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, DMC, and DEC was 1:1:1. FEC (fluoroethylene carbonate) was also added to the mixed solvent at a volume fraction of 10% of the mixed solvent volume. The concentration of lithium hexafluorophosphate (LiPF6) was 1 mol / L. -1 ;
[0094] The method for preparing the negative electrode sheet is as follows: the silicon-based negative electrode material (as the active material) prepared in Comparative Example 1 is mixed with SP conductive agent and sodium alginate binder in a mass ratio of 8:1:1 to obtain the negative electrode slurry;
[0095] The negative electrode slurry was coated onto copper foil and then dried at 60 °C for 12 h to obtain the negative electrode sheet.
[0096] The CR2032 button cell was assembled by combining the negative electrode, Celgard 2400 polypropylene separator, lithium metal (as counter electrode), and electrolyte.
[0097] Comparative Example 2
[0098] This comparative example provides a lithium-ion battery, including a negative electrode, a Celgard 2400 polypropylene separator, lithium metal (as a counter electrode), and an electrolyte.
[0099] The electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF6) in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, DMC, and DEC was 1:1:1. FEC (fluoroethylene carbonate) was also added to the mixed solvent at a volume fraction of 10% of the mixed solvent volume. The concentration of lithium hexafluorophosphate (LiPF6) was 1 mol / L. -1 ;
[0100] The method for preparing the negative electrode sheet is as follows: purified phytosilica (as an active material, the purified phytosilica body is obtained according to the method in Example 1) is mixed with SP conductive agent and sodium alginate binder in a mass ratio of 8:1:1 to obtain negative electrode slurry;
[0101] The negative electrode slurry was coated onto copper foil and then dried at 60 °C for 12 h to obtain the negative electrode sheet.
[0102] The CR2032 button cell was assembled by combining the negative electrode, Celgard 2400 polypropylene separator, lithium metal (as counter electrode), and electrolyte.
[0103] Example 2
[0104] This embodiment provides a method for preparing a silicon-based anode material. Compared with Example 1, calcium chloride is added to the molten salt used in this embodiment, the amount of implant material is smaller, the electrolysis voltage is lower (2.4 V), and the electrolysis time is shorter (6 h). Specifically:
[0105] S1. Take 13.34 g of sodium chloride (NaCl), 30.675 g of magnesium chloride (MgCl2) and 47.52 g of calcium chloride (CaCl2), mix them and grind them to obtain molten salt electrolyte, and then place it in a graphite crucible with a height of 45 mm, an inner diameter of 40 mm and a wall thickness of 5 mm; then, place the graphite crucible in an oven at a temperature of 200 ℃ and dry it for 12 h to remove the moisture from the molten salt electrolyte;
[0106] S2. Immerse the nickel foam in 1 mol / L hydrochloric acid for 1 min. The nickel foam has a length of 4 cm, a width of 4 cm, a thickness of 1.7 mm, and a pore size of 110 PPI.
[0107] 0.35g of purified implant (the purified implant was obtained according to the method in Example 1) was wrapped with soaked nickel foam, and the nickel foam was fixed on a conductive Mo wire with a diameter of 1 mm using a 0.1 mm diameter Mo wire as a working electrode.
[0108] S3. The molten salt electrolyte from S1 was loaded into a graphite crucible, which was then placed inside a single-ended sealed quartz tube and heated under a nitrogen atmosphere. Electrolysis was performed using a dual-electrode configuration, with the graphite crucible acting as the anode and the working electrode as the cathode. Molten mixed salt was used as the electrolyte, and constant voltage electrolysis at 2.4V was conducted at 750 °C for 6 h. After electrolysis, the working electrode was quickly removed from the molten salt and cooled to ambient temperature under a nitrogen atmosphere. The reaction product was then removed from the quartz tube, and the Mo wire and nickel foam were removed. Next, the product was sequentially treated with deionized water for 8 h and 1 mol L⁻¹. -1 Soaking in dilute hydrochloric acid for 8 h and 1 mol L -1 The silicon-based anode material was obtained by soaking in dilute hydrofluoric acid for 6 hours; after treatment, it was washed by centrifugation with deionized water until the washing solution was neutral, and then filtered and dried.
[0109] This embodiment also provides a lithium-ion battery, including a negative electrode sheet, a Celgard 2400 polypropylene separator, lithium metal (as a counter electrode), and an electrolyte;
[0110] The electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF6) in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), wherein the volume ratio of EC, DMC, and DEC was 1:1:1. FEC (fluoroethylene carbonate) was also added to the mixed solvent at a volume fraction of 10% of the mixed solvent volume. The concentration of lithium hexafluorophosphate (LiPF6) was 1 mol / L. -1 ;
[0111] The method for preparing the negative electrode sheet is as follows: the silicon-based negative electrode material (as the active material) prepared in Example 2 is mixed with SP conductive agent and sodium alginate binder in a mass ratio of 8:1:1 to obtain a negative electrode slurry;
[0112] The negative electrode slurry was coated onto copper foil and then dried at 60 °C for 12 h to obtain the negative electrode sheet.
[0113] The CR2032 button cell was assembled by combining the negative electrode, Celgard 2400 polypropylene separator, lithium metal (as counter electrode), and electrolyte.
[0114] Performance Characterization
[0115] Figure 1 The images show the X-ray diffraction (XRD) patterns of the silicon-based anode materials prepared in Example 1 and Comparative Example 1, as well as the purified silicide particles; specifically, Figure 1 In the middle section, A-layered stacked silicon nanosheets represent the silicon-based anode material prepared in Example 1, B-blackish-gray silicon-based material represents the silicon-based anode material prepared in Comparative Example 1, C-purified silicide particles, PDF#46-1045-SiO2 represents the diffraction peak of the silicon dioxide standard card, and PDF#27-1402-Si represents the diffraction peak of the silicon standard card.
[0116] from Figure 1 As can be seen from curve A, the silicon-based anode material prepared in Example 1 only shows the characteristic diffraction peaks of pure Si, with no SiO2 diffraction peaks, indicating that the SiO2 in the silicide has been completely reduced to cubic Si through molten salt electrolysis.
[0117] from Figure 1 As can be seen from curve B, in addition to the diffraction peak of Si, the silicon-based anode material prepared in Comparative Example 1 still clearly has the characteristic peak of SiO2. This indicates that under the process conditions of replacing MgCl2 molten salt with NaCl-KCl-CaCl2 molten salt and electrolysis for 5 hours in Comparative Example 1, only part of SiO2 is converted into Si, and the reduction is incomplete.
[0118] from Figure 1 As can be seen from curve C, the XRD pattern of the purified phytolith is dominated by SiO2 diffraction peaks with no obvious Si peaks, indicating that its main component is unreduced SiO2.
[0119] Figure 2 The image shows the Raman spectrum of the silicon-based anode material prepared in Example 1. From... Figure 2As can be seen from the spectrum, only the characteristic Raman peaks of cubic phase Si appear (no SiO2 related peaks). Combined with the XRD results in Figure 1, this confirms that after molten salt electrolysis (NaCl-KCl-MgCl2, 10h electrolysis), the SiO2 in the phytolith has been completely converted into pure cubic structure Si, with no impurity phase residue.
[0120] Figure 3 This is a SEM image of the purified biofilm obtained in step S1 of Example 1. From... Figure 3 As can be seen, the original phytolith particles have an average size of about 5 μm, are in block or agglomerated form, have no nanoscale sheet structure, and are dense with no obvious pores between particles.
[0121] Figure 4 This is a SEM image of the silicon-based anode material prepared in Example 1. From... Figure 4 As can be seen from the example, the product after electrolysis in Example 1 is completely transformed into a "layered stacked silicon nanosheet" structure, the original bulk particle size is significantly reduced, and gaps and pores are formed between the layers. The advantages of this structure are: to alleviate the mechanical stress during the silicon lithium insertion and extraction process and avoid electrode breakage; to shorten the lithium ion transport path, increase the transport sites, and reduce lithium capture; to provide buffer space for volume expansion and lay the structural foundation for subsequent excellent electrochemical performance.
[0122] Figure 5 The current-time curves in the molten salt electrolysis process of Example 1 reflect the dynamic process of the electrolysis reaction.
[0123] from Figure 5 As can be seen, the initial current value is relatively large, indicating that the electrolysis reaction is fast and efficient in the early stage. As the electrolysis time increases, the current decreases rapidly and gradually stabilizes. The reason for this phenomenon is that the SiO2 content in the phytolith is high in the early stage, and the reduction reaction is vigorous; as the reaction proceeds, the SiO2 concentration decreases, the reaction rate slows down, and eventually a dynamic equilibrium is reached.
[0124] Figure 6 The first charge-discharge curves of the CR2032 button cells assembled in Example 1 and Comparative Examples 1-2 at a current density of 0.2 A / g are shown. Figure 6 In the middle section, A-layered stacked silicon nanosheets represent the CR2032 coin cell assembled from the silicon-based anode material prepared in Example 1; B-blackish-gray silicon-based material represents the CR2032 coin cell assembled from the silicon-based anode material prepared in Comparative Example 1; and C-purified implanted silicon particles represent the CR2032 coin cell assembled from the purified implanted silicon particles in Comparative Example 2.
[0125] from Figure 6As can be seen from curve A (Example 1), the CR2032 button battery assembled from the silicon-based anode material prepared in Example 1 has a lithium intercalation capacity (discharge capacity) of 2268.75 mAh / g, a lithium deintercalation capacity (charge capacity) of 1712 mAh / g, and an initial coulombic efficiency of 75.46%, with optimal initial lithium storage capacity and efficiency.
[0126] from Figure 6 As can be seen from curve B (Comparative Example 1), the CR2032 button battery assembled from the silicon-based anode material prepared in Comparative Example 1 has a lithium insertion capacity (discharge capacity) of 1750 mAh / g, a lithium removal capacity (charge capacity) of 1096 mAh / g, and an initial coulombic efficiency of 62.6%. The efficiency decreases because some SiO2 is not reduced and the ineffective reaction occurs.
[0127] from Figure 6 As can be seen from curve C (Comparative Example 2), the CR2032 button battery assembled from purified silicide in Comparative Example 2 has a lithium intercalation capacity (discharge capacity) of 1209 mAh / g, a lithium deintercalation capacity (charge capacity) of 709 mAh / g, and an initial coulombic efficiency of 58.6%, which is lower than that in Example 1. This is because SiO2 itself has low lithium storage activity and lacks nanosheet structure to assist ion transport.
[0128] Figure 7 The cycle stability curves of the CR2032 button batteries assembled in Example 1 and Comparative Examples 1-2 are shown. The test conditions are uniform: first, charge and discharge 3 times at a current density of 0.2 A / g to activate the material, and then cycle continuously 120 times at a current density of 0.5 A / g. Figure 7 In the diagram, A - layered stacked silicon nanosheets represent the cycle stability of the CR2032 coin cell assembled from the silicon-based anode material prepared in Example 1; B - blackish-gray silicon-based material represents the cycle stability of the CR2032 coin cell assembled from the silicon-based anode material prepared in Comparative Example 1; and C - purified implanted silicon particles represent the cycle stability of the CR2032 coin cell assembled from purified implanted silicon particles in Comparative Example 2.
[0129] from Figure 7 Curve A (Example 1) shows that the CR2032 coin cell assembled from the silicon-based anode material prepared in Example 1 retains a discharge specific capacity of 1077.80 mAh / g after 120 cycles, with a capacity retention rate as high as 83.27%. This excellent stability stems from the microstructure of "layered stacked silicon nanosheets"—the numerous pores between the layers effectively alleviate the volume expansion during the silicon lithium insertion / extraction process, maintain the integrity of the electrode structure, and reduce repeated rupture and continuous growth of the SEI film.
[0130] from Figure 7 Curve B (Comparative Example 1) shows that the CR2032 coin cell assembled from the silicon-based anode material prepared in Comparative Example 1 has a discharge specific capacity that drops to 397.5 mAh / g after 120 cycles. ， The capacity retention rate was only 56.12%. Due to incomplete electrolysis (some SiO2 residue) and the lack of a stable layered structure, the active material was easily pulverized during cycling, leading to electrical contact failure.
[0131] from Figure 7 Curve C (Comparative Example 2) shows that the CR2032 button battery assembled from purified phytoliths in Comparative Example 2 has a discharge specific capacity of only 381.5 mAh / g and a capacity retention of 33.38% after 120 cycles. The purified phytoliths are mainly composed of SiO2, which has low lithium storage activity, low initial coulombic efficiency, and no nanostructure to buffer volume change, resulting in the worst cycle performance.
[0132] Figure 8 The CR2032 button cells assembled in Examples 1 and Comparative Examples 1 and 2 were tested in the current density range of 0.2 to 4 A / g.
[0133] Results of the rate performance test within the range; Figure 8 In the middle section, A-layered stacked silicon nanosheets represent the rate performance of the CR2032 coin cell assembled from the silicon-based anode material prepared in Example 1 at different current densities; B-blackish-gray silicon-based material represents the rate performance of the CR2032 coin cell assembled from the silicon-based anode material prepared in Comparative Example 1 at different current densities; and C-purified implanted silica particles represent the rate performance of the CR2032 coin cell assembled from purified implanted silica particles in Comparative Example 2 at different current densities.
[0134] from Figure 8 As shown in curve A (Example 1), the CR2032 coin cell assembled from the silicon-based anode material prepared in Example 1 exhibits excellent rate performance. At current densities of 0.2 A / g, 0.5 A / g, 1 A / g, 2 A / g, and 4 A / g, the discharge specific capacities are 1553.2 mAh / g, 1116.2 mAh / g, 796.2 mAh / g, 525.4 mAh / g, and 262.4 mAh / g, respectively. When the current density recovers from 4 A / g to 1 A / g, the reversible discharge capacity rebounds to 754.5 mAh / g, indicating strong electrode structure stability and good tolerance to high current densities. The advantage lies in the two-dimensional layered structure, which provides ample ion contact areas and active centers, while the interlayer gaps form continuous lithium-ion transport channels, reducing transport resistance.
[0135] and Figure 8As can be seen from curves B (Comparative Example 1) and C (Comparative Example 2), the CR2032 button batteries assembled in Comparative Examples 1 and 2 have poor rate performance, especially at high current densities (≥1 A / g), where the specific capacity drops sharply. In Comparative Example 1, the silicon-based anode material has increased ion transport resistance due to SiO2 residue, and in Comparative Example 2, the purified silicon implant has no nano-active structure, so neither can meet the requirements of high-rate charge and discharge.
[0136] Figure 9 The cycling performance curve of the CR2032 button cell assembled from the silicon-based anode material prepared in Example 2 is shown. The test conditions are: first, charge and discharge 3 times at a current density of 0.2 A / g (to activate the material), and then cycle 120 times continuously at a current density of 0.5 A / g.
[0137] from Figure 9 As can be seen, the CR2032 button battery assembled from the silicon-based anode material prepared in Example 2 still maintains a discharge specific capacity of 1080.8 mAh / g after 120 cycles, with a capacity retention rate as high as 82.94%, which is close to the performance of Example 1 (83.27%). This indicates that the preparation process of the present invention is flexible—that is, by adding magnesium chloride to the molten salt and reducing the amount of silicon implant, it is still possible to prepare silicon-based anode materials with excellent cycle stability by appropriately reducing the voltage and shortening the electrolysis time, thus providing feasibility for large-scale production.
[0138] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0139] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.
Claims
1. A method for preparing a silicon-based anode material, characterized in that, Includes the following steps: The phytoliths were placed in hydrochloric acid and subjected to hydrothermal reaction at 150-160℃ for 4-5 hours. After filtration, purified phytoliths were obtained. The purified silicone was encapsulated in foamed metal and used as the working electrode; Add molten salt electrolyte to the electrolytic cell, place the working electrode in the electrolytic cell, and place the anode in the electrolytic cell at the same time; Under an inert atmosphere, molten salt electrolyte is heated to melt it, and the working electrode is connected as the cathode to the negative terminal of the power supply and the anode is connected to the positive terminal of the power supply to carry out electrolysis, thereby obtaining silicon-based anode material; The molten salt electrolyte includes NaCl, KCl, and MgCl2; or, the molten salt electrolyte includes NaCl, MgCl2, and CaCl2; In the step of placing the phytolith in hydrochloric acid for hydrothermal reaction, the mass-to-volume ratio of the phytolith to the hydrochloric acid is (7~8)g:(60~70)mL, and the concentration of the hydrochloric acid is 0.5~1mol / L. The control voltage during electrolysis is 2.2~2.6V, and the electrolysis time is 6~12h; The molten salt electrolyte is heated to 750-760°C under an inert atmosphere until it melts.
2. The method for preparing the silicon-based anode material as described in claim 1, characterized in that, If the molten salt electrolyte includes NaCl, KCl, and MgCl2, then the mass ratio of the purified phytolith, NaCl, KCl, and MgCl2 is (0.7~0.8):(14.63~15.63):(41.75~42.75):(43.7~44.7). If the molten salt electrolyte includes NaCl, MgCl2, and CaCl2, then the mass ratio of the purified phytolith, NaCl, MgCl2, and CaCl2 is (0.35~0.45):(13.34~14.34):(30.675~31.675):(47.52~48.52).
3. The method for preparing the silicon-based anode material as described in claim 1, characterized in that, After electrolysis, the electrolysis products are obtained. The electrolysis products are then soaked in water for 8-9 hours, in 0.1-2 mol / L hydrochloric acid for 8-9 hours, and in 1-2 mol / L hydrofluoric acid for 6-7 hours. After washing again until neutral, the products are dried to obtain silicon-based anode materials.
4. The method for preparing the silicon-based anode material as described in claim 1, characterized in that, The foam metal is foamed nickel.
5. A silicon-based anode material, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 4.
6. The application of a silicon-based anode material prepared by any one of the preparation methods described in claims 1 to 4, or the silicon-based anode material described in claim 5, in the preparation of lithium-ion batteries.
7. A lithium-ion battery, characterized in that, This includes silicon-based anode materials prepared by any of the preparation methods described in claims 1 to 4, or silicon-based anode materials as described in claim 5.