Silicon-carbon negative electrode material with multi-element structure design and preparation method of silicon-carbon negative electrode material
By preparing a silicon-carbon anode material with a multi-element structure consisting of a metal-doped micron-sized porous silicon core, a lithium borate middle layer, and a carbon outer layer, the problems of volume expansion and insufficient conductivity of silicon-based anode materials were solved, thus improving the performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-07
- Publication Date
- 2026-03-13
AI Technical Summary
Existing silicon-based anode materials in lithium-ion batteries suffer from problems such as large volume expansion, low initial coulombic efficiency, and insufficient conductivity.
The silicon-carbon anode material with a multi-component structure design has a metal-doped micron-sized porous silicon core, a lithium borate middle layer, and a carbon outer layer. The material is prepared by etching, mixing, calcination, and CVD carbon coating.
It effectively alleviates the volume expansion of silicon-based materials, improves the initial coulombic efficiency and cycle stability of the battery, reduces resistance, and maintains the stability of the electrode structure.
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Figure CN121662768A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a silicon-carbon anode material with a multi-element structure and its preparation method. Background Technology
[0002] With the increasing demand for high-energy-density lithium-ion batteries in energy storage, traditional graphite anodes (theoretical specific capacity of only 372 mAh / g) are no longer sufficient to meet the performance requirements of next-generation batteries. Silicon-based materials, due to their extremely high theoretical specific capacity (Li at room temperature...),... 15 Si4 phase (with a capacity of 3579 mAh / g) and suitable operating potential make it the most promising alternative. However, silicon suffers from significant volume expansion (>300%), poor conductivity, and instability of the solid electrolyte interphase (SEI) film during charge and discharge, leading to low initial coulombic efficiency and a sharp decline in cycle life and rate performance.
[0003] To address these issues, chemical vapor deposition (CVD) is commonly used in industry to coat silicon anodes with carbon, which largely mitigates the volume expansion of silicon-based materials. However, thick carbon layers reduce conductivity, while thin carbon layers are insufficient to resist electrolyte corrosion. Therefore, to obtain silicon-carbon anode materials with excellent overall performance, new methods are needed to solve these problems. Summary of the Invention
[0004] The technical problem to be solved by the present invention is that silicon-based anodes in the prior art have large volume expansion, low initial coulombic efficiency and insufficient conductivity. In order to overcome the above defects of the prior art, the present invention provides a silicon-carbon anode material with a multi-element structure design and its preparation method.
[0005] The technical solution of the present invention is: a silicon-carbon anode material with a multi-element structure design, wherein the silicon-carbon anode material is a core-shell structure composed of a core, an intermediate layer and an outer shell, wherein the core is metal-doped micron-sized porous silicon, the intermediate layer is lithium borate, and the outer shell is a carbon layer, wherein the mass ratio of the metal, lithium borate, carbon layer and porous silicon is (0.05~0.5):(1~3):(10~20):100.
[0006] In the above scheme, the silicon-carbon anode material particles consist of a metal-doped micron-sized porous silicon core and a double-layered outer shell composed of lithium borate and carbon. When used as a lithium-ion battery anode, the porosity of the micron-sized porous silicon core provides a buffering space for silicon volume changes, while metal doping enhances the intrinsic conductivity of the electrode and reduces resistance, thereby alleviating anode polarization. The double-layered outer shell structure can buffer silicon volume expansion to the greatest extent, reducing silicon particle pulverization and shedding, maintaining the stability of the electrode structure while preventing direct contact between the active material and the electrolyte. This multi-element structural design effectively suppresses silicon volume expansion, improving the battery's initial coulombic efficiency and cycle stability.
[0007] In one possible implementation, the porous silicon has an average particle size of 1 to 5 mm. m, And / or, the average pore size of the porous silicon is 2~30 nm. And / or, the specific surface area of the porous silicon is 200~500m². 2 / g. The optimized numerical ranges for particle size, pore size, and specific surface area described above represent the optimal selection ranges for the performance of the silicon-carbon anode material of this application.
[0008] In one possible implementation, the metal is one or more of zinc, nickel, and copper. These metals are common and readily available, and can effectively improve the intrinsic conductivity of the electrode and reduce resistance.
[0009] A method for preparing a silicon-carbon anode material with a multi-element structure design includes the following steps: S1. Micron-sized silicon powder is dissolved in a corrosion solution composed of metal nitrate, hydrofluoric acid and hydrogen peroxide, heated for etching and deposition, and then filtered, washed and dried to obtain Si-M composite material. S2. Under inert gas protection, the Si-M composite material is mixed and ground with LiOH and H3BO3, and then the mixture is calcined to obtain LiBO2@Si-M composite material; S3. In a mixed atmosphere of inert gas and carbon source gas, the LiBO2@Si-M composite material is subjected to CVD carbon coating to obtain a silicon-carbon anode material with a multi-element structure design.
[0010] Using the above preparation method, silicon-carbon anode materials that can greatly alleviate the volume expansion of silicon-based materials can be obtained without complex preparation equipment. This process is simple and suitable for widespread application.
[0011] In one possible implementation, the metal nitrate is selected from at least one of zinc nitrate, nickel nitrate, and copper nitrate. Metal nitrates are relatively common and readily available. Nitric acid is itself a corrosive solution, so using a metal nitrate in combination with hydrofluoric acid and hydrogen peroxide can provide a good corrosive effect.
[0012] In one possible implementation, the concentration of metallic nitrate in the etching solution is 0.01~0.03 mol / L, the concentration of hydrofluoric acid is 3~5 mol / L, and the amount of hydrogen peroxide added is 1~3% of the total volume. This concentration ratio allows for better etching of micron-sized silicon powder.
[0013] In one possible implementation, the heating temperature in step S1 is 45~60℃; the heating time is 5~20 minutes. This heating method uses a low temperature and short time, making it easy to operate.
[0014] In one possible implementation, in step S2, the mass ratio of LiOH to Si-M composite material is (0.005~0.02):1; the mass ratio of H3BO3 to Si-M composite material is (0.01~0.04):1. This raw material ratio is suitable for obtaining the final optimal mass ratio of metal, lithium borate, carbon layer, and porous silicon.
[0015] In one possible implementation, the calcination in step S2 is carried out in a tube furnace at a temperature of 600-900°C for 2-6 hours. This calcination temperature decomposes the anions in the corrosion solution into oxide gases, which then evaporate, leaving only metal dopant on the porous silicon material.
[0016] In one possible implementation, the inert gas in steps S2 and S3 is at least one of nitrogen, argon, and an argon-hydrogen mixture, and the carbon source gas in step S3 is at least one of acetylene, ethylene, methane, and propane. Nitrogen, argon, and an argon-hydrogen mixture are commonly used inert gas atmospheres. Acetylene, ethylene, methane, and propane are readily available carbon sources, making the entire preparation condition easy to obtain and the preparation method easy to promote.
[0017] The beneficial effects of this invention are as follows: 1. The silicon-carbon anode material is fabricated using a multi-element structure design, comprising a core of metal-doped micron-sized porous silicon particles, and an outer shell consisting of a lithium borate layer and a carbon layer from the inside out. This structure improves the intrinsic conductivity of the electrode, reduces resistance, and alleviates anode polarization.
[0018] 2. The multi-element structure design of the silicon-carbon anode material with a double-layer outer shell can buffer the volume expansion of silicon to the greatest extent, reduce the pulverization and shedding of silicon particles, maintain the stability of the electrode structure, and prevent the active material from directly contacting the electrolyte.
[0019] 3. The silicon-carbon anode material has high initial coulombic efficiency and long cycle life.
[0020] 4. The preparation method of the silicon-carbon anode material is simple and suitable for widespread application. Attached Figure Description
[0021] Figure 1 A schematic diagram of the silicon-carbon anode material with a multi-component structure designed in Example 1; Figure 2 SEM image of the silicon-carbon anode material with a multi-element structure designed in Example 1; Figure 3 TEM image of the silicon-carbon anode material with a multi-component structure designed for Example 1, and mapping image of a single particle; Figure 4 The image shows the SEM image of the silicon-carbon anode material prepared in Comparative Example 2. Detailed Implementation
[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.
[0023] It should be noted that the endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0024] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.
[0025] This invention provides a silicon-carbon anode material with a multi-element structure and its preparation method, wherein the silicon-carbon anode material is prepared by the following steps: S1, with an average particle size of 1~5 Micron-sized silicon powder is dissolved in an etching solution composed of metal nitrate, hydrofluoric acid, and hydrogen peroxide. The solution is heated for etching and deposition, followed by filtration, washing, and drying to obtain a Si-M composite material. The micron-sized silicon powder is the material to be etched. The metal nitrate is selected from at least one of zinc nitrate, nickel nitrate, magnesium nitrate, and copper nitrate. The concentration of the metal nitrate in the etching solution is 0.01–0.03 mol / L, the concentration of HF is 3–5 mol / L, and the volume percentage of H₂O₂ is 1–3%. The heating temperature is 45–60 °C, and the heating time is 5–20 min.
[0026] S2. Under inert gas protection, the Si-M composite material is mixed and ground with LiOH and H3BO3, and then the mixture is calcined to obtain LiBO2@Si-M composite material; wherein the mass ratio of LiOH to Si-M composite material is (0.005~0.02):1; and the mass ratio of H3BO3 to Si-M composite material is (0.01~0.04):1. The inert gas is selected from at least one of nitrogen, argon, and argon-hydrogen mixture. Calcination is carried out in a tubular furnace at a temperature of 600~900℃ and a calcination time of 2~6h.
[0027] S3. In a mixed atmosphere of inert gas and carbon source gas, the LiBO2@Si-M composite material is subjected to CVD carbon coating to obtain a silicon-carbon anode material with a multi-element structure design. The inert gas is selected from at least one of nitrogen, argon, and argon-hydrogen mixture, and the carbon source gas is selected from at least one of acetylene, ethylene, methane, and propane.
[0028] Etching with an etchant solution can etch micron-sized silicon powder into a porous structure, resulting in metal-doped micron-sized porous silicon. The final silicon-carbon anode material particles have a core-shell structure consisting of a core, an intermediate layer, and a shell. The core is metal-doped micron-sized porous silicon, the intermediate layer is lithium borate, and the shell is a carbon layer. The mass ratio of metal, lithium borate, carbon layer, and porous silicon is (0.05~0.5):(1~3):(10~20):100. The average particle size of the obtained porous silicon is 1~5 μm, the average pore size is 2~30 nm, and the specific surface area is 200~500 m². 2 / g. This multi-element structure design of the silicon-carbon anode material can effectively suppress the volume expansion of silicon, improve the battery's initial efficiency and cycle stability.
[0029] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0030] Example 1 The structure of silicon-carbon anode materials with multi-element structure design is as follows: Figure 1As shown, the outermost layer is a carbon layer, the middle layer is a lithium borate layer, and the core is a metal-doped micron-sized porous silicon particle. The particle size of the silicon-carbon anode material with the multi-element structure design is 2-6 μm.
[0031] The preparation method is as follows: Micron-sized silicon powder was dissolved in an etching solution composed of 0.03 mol / L Ni(NO3)2, 5 mol / L HF and 2% H2O2 (volume concentration). The etching was carried out at 55 °C for 20 min. The etched sample was collected and washed with deionized water until the pH was neutral. Then it was washed five times with ethanol by centrifugation. The washed sample was then placed in a vacuum oven and dried at 60 °C for 12 h to obtain the Si-Ni composite material.
[0032] 500g of Si-Ni composite material, 4.8g of LiOH and 12.4g of H3BO3 were mixed and ground in an agate mortar for 0.5h. The mixture was then transferred to a tube furnace and heated to 750℃ for 3h at a heating rate of 5℃ / min under argon-hydrogen protection. After natural cooling, LiBO2@Si-Ni composite material was obtained.
[0033] The LiBO2@Si-Ni composite material was transferred to a fluidized bed and heated to 550℃ in a N2 atmosphere (heating rate of 5℃ / min). Acetylene was introduced as the carbon source gas (flow rate of 30L / min). After a CVD process at a constant temperature for 5 hours, a silicon-carbon anode material with a multi-element structure design was finally obtained.
[0034] Example 2 The difference between this embodiment and Embodiment 1 is that the amount of LiOH used is 2.4g and the amount of H3BO3 used is 6.2g.
[0035] Example 3 The difference between this embodiment and Embodiment 1 is that the amount of LiOH used is 7.2g and the amount of H3BO3 used is 18.6g.
[0036] Example 4 The difference between this embodiment and Embodiment 1 is that the acetylene gas flow rate is 20 L / min.
[0037] Example 5 The difference between this embodiment and Embodiment 1 is that the acetylene gas flow rate is 50 L / min.
[0038] Example 6 The difference between this embodiment and Embodiment 1 is that the metal nitrate used is zinc nitrate.
[0039] Comparative Example 1 The difference between this embodiment and Embodiment 1 is that it does not cover with a LiBO2 layer.
[0040] Comparative Example 2 The difference between this embodiment and Embodiment 1 is that no carbon layer is applied.
[0041] Comparative Example 3 The difference between this embodiment and Embodiment 1 is that it does not cover LiBO2 and a carbon layer.
[0042] Negative electrode preparation: The negative electrode materials of each embodiment and comparative example are used to prepare negative electrode sheets, including the following steps: Silicon-carbon anode material, PVDF binder, and Super-P conductive carbon black were dissolved in NMP solution at a mass ratio of 8:1:1, and then ball-milled to form a negative electrode slurry. The resulting slurry was uniformly coated onto copper foil, dried, and cut to obtain the negative electrode sheet. The active material loading of the negative electrode sheet was 2 mg / cm³. 2 .
[0043] Half-cell assembly: Half-cells were prepared by separately preparing the above-mentioned negative electrode sheets, including the following steps: The batteries were assembled in an argon-filled Braun glove box. The battery model was 2032. The electrolyte was 1.0M LiPF6 dissolved in a solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1. A lithium metal sheet was used as the counter electrode (i.e., the positive electrode). The prepared half-cells were placed on a Land test system battery tester for discharge capacity and first discharge efficiency testing. The charge-discharge capacity was tested at 0.1C and 3C within a charge-discharge voltage range of 0.005V to 1.5V, and the capacity retention rate was tested after 200 charge-discharge cycles at 0.5C.
[0044] The test results are shown in Table 1.
[0045] Table 1. Electrochemical performance test results of the battery Test Result Analysis: The actual SEM image of the silicon-carbon anode material obtained in Example 1 is shown below. Figure 2 As shown in the figure, the negative electrode material is in the form of particles smaller than 5 micrometers. Figure 3 The corresponding TEM analysis shows that the core of the particle is a Si-Ni composite material (corresponding to...). Figure 1 The white dot in the middle refers to Ni, the middle layer is LiBO2, and the surface layer is an amorphous carbon layer. The distribution of the mapping elements corroborates the above viewpoint. Figure 4 Here are SEM images of the actual anode material with only the middle LiBO2 layer, for comparison. Figure 4 and Figure 2 It can be seen that after the surface is covered with an amorphous carbon layer, the particle surface becomes smoother.
[0046] As shown in Table 1, the electrochemical test results reveal that, thanks to the synergistic effect of the lithium borate and carbon layer dual-coating structure, the silicon-carbon anode in Example 1 exhibits excellent initial coulombic efficiency and rate performance. Furthermore, a comparison between Example 1 and Example 5 shows that, compared to zinc doping, nickel doping provides advantages in capacity, conductivity, and cycle stability for the silicon-carbon anode. Therefore, the silicon-carbon anode prepared based on the above-mentioned multi-element structure design demonstrates excellent overall performance, providing a feasible approach for the design of high-energy-density lithium-ion battery anode materials.
[0047] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A silicon-carbon anode material with a multi-element structure design, characterized in that, The silicon-carbon anode material particles have a core-shell structure consisting of a core, an intermediate layer, and an outer shell. The core is metal-doped micron-sized porous silicon, the intermediate layer is lithium borate, and the outer shell is a carbon layer. The mass ratio of the metal, lithium borate, carbon layer, and porous silicon is (0.05~0.5):(1~3):(10~20):
100.
2. The silicon-carbon anode material with a multi-element structure design according to claim 1, characterized in that, The porous silicon has an average particle size of 1~5 mm. m, And / or, the average pore size of the porous silicon is 2~30 nm. And / or, the specific surface area of the porous silicon is 200~500m². 2 / g.
3. The silicon-carbon anode material with a multi-element structure design according to claim 1, characterized in that, The metal is selected from one or more of zinc, nickel, and copper.
4. A method for preparing a silicon-carbon anode material with a multi-element structure design as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Micron-sized silicon powder is dissolved in a corrosion solution composed of metal nitrate, hydrofluoric acid and hydrogen peroxide, heated for etching and deposition, and then filtered, washed and dried to obtain Si-M composite material. S2. Under inert gas protection, the Si-M composite material is mixed and ground with LiOH and H3BO3, and then the mixture is calcined to obtain LiBO2@Si-M composite material; S3. In a mixed atmosphere of inert gas and carbon source gas, the LiBO2@Si-M composite material is subjected to CVD carbon coating to obtain a silicon-carbon anode material with a multi-element structure design.
5. The preparation method according to claim 4, characterized in that, The metal nitrate is selected from at least one of zinc nitrate, nickel nitrate, and copper nitrate.
6. The preparation method according to claim 4, characterized in that, The concentration of metallic nitrate in the corrosion solution is 0.01~0.03 mol / L, the concentration of hydrofluoric acid is 3~5 mol / L, and the amount of hydrogen peroxide added accounts for 1~3% of the total volume.
7. The preparation method according to claim 4, characterized in that, The heating temperature in step S1 is 45~60℃; the heating time is 5~20min.
8. The preparation method according to claim 4, characterized in that, In step S2, the mass ratio of LiOH to Si-M composite material is (0.005~0.02):1; the mass ratio of H3BO3 to Si-M composite material is (0.01~0.04):
1.
9. The preparation method according to claim 4, characterized in that, In step S2, calcination is carried out in a tubular furnace at a temperature of 600-900℃ and a calcination time of 2-6 hours.
10. The preparation method according to claim 4, characterized in that, The inert gas in steps S2 and S3 is selected from at least one of nitrogen, argon and argon-hydrogen mixture, and the carbon source gas in step S3 is selected from at least one of acetylene, ethylene, methane and propane.