Silicon-carbon composite negative electrode material and preparation method and application thereof

Abstract

The invention discloses a silicon-carbon composite negative electrode material as well as a preparation method and application thereof. The silicon-carbon composite negative electrode material comprises a silicon-carbon material and a carbon layer coated on the surface of the silicon-carbon material, the silicon-carbon material is prepared through a CVD deposition method, the silicon-carbon material comprises a porous carbon skeleton and nanometer silicon deposited in the porous carbon skeleton, and the nanometer silicon is formed by silane; the carbon layer comprises metal ions and is formed by pyrolyzing a carbon source and a metal source in a calcining process. The surface of the commercial CVD deposition silicon-carbon composite negative electrode material is coated with the fluorine-containing carbon layer, the fluorine-containing carbon layer uses polyvinylidene fluoride as a carbon source, the fluorine-containing carbon layer with certain graphitization is formed through calcination, metal ions provide conductivity, the silicon-carbon composite negative electrode material can have both conductivity and toughness, and the service life of the silicon-carbon composite negative electrode material is prolonged. And the volume expansion of the silicon-carbon material is relieved to the greatest extent, and the interface stability is improved, so that the cycling stability of the lithium ion battery is improved.

Description

Technical Field

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

[0002] Lithium-ion batteries, with their low cost and reliable safety, hold immense potential for next-generation energy storage devices. In recent years, a variety of anode materials have emerged, with silicon-based anode materials considered key for next-generation high-energy-density lithium-ion batteries. However, silicon-based anode materials face a severe challenge in practical applications: the insertion and extraction of lithium ions into and out of silicon triggers a volume expansion and contraction of up to 300%. This dramatic "breathing effect" causes silicon particles to break down and pulverize, lose electrical contact with the current collector, and continuously damage the solid electrolyte interphase (SEI) film on the surface of the regenerated electrode. This continuously consumes active lithium and electrolyte, ultimately leading to rapid capacity decay.

[0003] To overcome this bottleneck, current technological approaches mainly revolve around "nano-sizing" and "composite processing." Among these, silicon-carbon composite technology, which can balance the high capacity of silicon with the structural stability of carbon, has become the most mature and commercially viable approach. However, there are numerous methods for preparing silicon-carbon composites: mechanical ball milling, while simple, results in silicon particles that easily agglomerate and have a loose interface with carbon, failing to effectively buffer volume expansion and exhibiting poor cycle stability; the sol-gel method can achieve uniform mixing of silicon and carbon, but it has a long reaction cycle, high cost, and difficulty in precisely controlling the pore size of the product, making large-scale production challenging; while electrospinning produces silicon-carbon fibers with unique structures, the silicon content is generally below 20%, failing to fully leverage the high capacity advantage of silicon and resulting in limited improvement in energy density.

[0004] In contrast, CVD deposition is considered the most promising technology route for preparing silicon-carbon composite anode materials. This method involves depositing silane in the form of nano-silicon into a porous carbon framework. During the preparation process, parameters such as reaction temperature, silane concentration, gas flow rate, and reaction time are adjusted to achieve uniform silicon deposition within the porous carbon framework. This ensures that the nano-silicon is tightly bonded to the carbon framework in thin layers or granular form, preventing silicon particle agglomeration. The silicon deposition amount is generally no more than 50%. The resulting silicon-carbon composite anode material exhibits excellent performance: the high theoretical specific capacity of silicon (4200 mAh / g) is fully utilized, significantly improving the battery energy density; the stable structure and special composite morphology of the carbon material effectively buffer the volume expansion of silicon during charge and discharge. Although the porous carbon framework has a significant confinement and buffering effect on the deposited nano-silicon, the nano-silicon in the porous framework reacts with the electrolyte penetrating into the pores after volume expansion / shrinkage and pulverization, forming a new SEI film. Therefore, its cycle stability cannot yet meet the requirements of practical applications. Coating the surface of silicon-carbon composite anode materials with a uniform and dense carbon layer is an effective strategy to shield electrolyte penetration and stabilize the SEI film. However, existing technologies have not yet developed a suitable carbon layer for coating the surface of silicon-carbon composite anode materials prepared by CVD deposition. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a silicon-carbon composite anode material.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned silicon-carbon composite anode material.

[0007] Another object of the present invention is to provide a lithium-ion battery.

[0008] Another object of the present invention is to provide the application of the above-mentioned silicon-carbon composite anode material in lithium-ion batteries.

[0009] The objective of this invention is achieved through the following technical solution.

[0010] A silicon-carbon composite anode material includes: a silicon-carbon material and a carbon layer coated on the surface of the silicon-carbon material; Silicon-carbon materials are prepared by CVD deposition. The silicon-carbon materials include: a porous carbon framework and nano-silicon deposited in the porous carbon framework, wherein the nano-silicon is formed from silane. The carbon layer includes: metal ions (the metal ions are introduced by a metal source), the metal ions are at least one of iron ions and copper ions, the carbon layer is formed by the pyrolysis of the carbon source and the metal source during calcination, the carbon source is polyvinylidene fluoride (PVDF) (the carbon layer is a fluorinated carbon layer). The ratio of silicon-carbon material, carbon source, and metal source by mass fraction is 700:(35~70):14.

[0011] In the above technical solution, the particle size of silicon-carbon material is 5-10 micrometers.

[0012] In the above technical solution, the metal ion is preferably an iron ion.

[0013] A method for preparing a silicon-carbon composite anode material includes: mixing silicon-carbon material and a composite system until homogeneous, stirring at 80-120°C until dry, calcining at 600-800°C under a nitrogen or inert gas atmosphere, and cooling to room temperature to obtain the silicon-carbon composite anode material. Silicon-carbon materials are prepared by CVD deposition. The silicon-carbon materials include: a porous carbon framework and nano-silicon deposited in the porous carbon framework, wherein the nano-silicon is formed from silane. The composite system includes a carbon source, a solvent, and a metal source. The carbon source is polyvinylidene fluoride (PVDF), and the metal source is used to provide metal ions, which are at least one of iron ions and copper ions. The ratio of the mass fraction of the carbon source, the volume fraction of the solvent, and the mass fraction of the metal source is (175~350):10:70. The unit of mass fraction is mg, and the unit of volume fraction is mL. By mass fraction, the ratio of carbon source in silicon-carbon materials and composite systems is 700:(35~70).

[0014] In the above technical solution, the method for obtaining the composite system includes: mixing a carbon source and a solvent until homogeneous, adding a metal source, mixing until homogeneous, and obtaining the composite system.

[0015] In the above technical solution, the solvent is N-methylpyrrolidone (NMP).

[0016] In the above technical solution, the metal source is at least one of iron acetylacetone and copper acetylacetone.

[0017] In the above technical solution, the preferred metal source is iron acetylacetone.

[0018] In the above technical solutions, preferably, calcination is carried out at 650~750℃.

[0019] A lithium-ion battery, comprising: the silicon-carbon composite anode material.

[0020] In the above technical solution, in 1 Ag -1 At the given current density, the initial discharge specific capacity of the lithium-ion battery is 1701.67 mAh g. -1 The discharge specific capacity after 50 cycles is 809.06 mAh g. -1 The capacity retention rate was 47.54%.

[0021] Application of silicon-carbon composite anode materials in improving the specific capacity of lithium-ion batteries during charging, discharging and / or capacity retention.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention involves coating a commercially available CVD-deposited silicon-carbon composite anode material with a fluorinated carbon layer. The fluorinated carbon layer uses polyvinylidene fluoride (PVDF) as the carbon source and is formed through calcination to achieve a certain degree of graphitization. Metal ions provide conductivity. This allows the silicon-carbon composite anode material to simultaneously maintain conductivity and toughness, minimizing volume expansion of the silicon-carbon material and improving interfacial stability, thereby enhancing the cycle stability of the lithium-ion battery. Lithium-ion batteries prepared from this silicon-carbon composite anode material exhibit cycle stability at 1 A g. -1 At the current density, the initial discharge specific capacity is 1701.67 mAh g. -1 The discharge specific capacity after 50 cycles is 809.06 mAh g. -1 The capacity retention rate is 47.54%, while the capacity retention rate of lithium-ion batteries made of silicon-carbon materials (without a carbon layer) is only 6.09%. The lithium-ion battery of the present invention has potential application prospects in high-performance ion batteries. Attached Figure Description

[0023] Figure 1 SEM images of silicon-carbon materials; Figure 2 Elemental analysis diagram of silicon-carbon materials; Figure 3 The XRD patterns of the silicon-carbon composite anode materials prepared in Examples 1-7 are shown below. Figure 4 The XRD patterns of the silicon-carbon composite anode material prepared in Comparative Example 1, the anode material prepared in Comparative Example 2, and the silicon-carbon composite anode material prepared in Comparative Example 3 are shown. Figure 5 SEM images are shown, where (a) to (g) are SEM images of the silicon-carbon composite anode materials prepared in Examples 1 to 7, respectively. Figure 6 SEM images are shown, where (a) and (b) are SEM images of the silicon-carbon composite anode material prepared in Comparative Example 1 and the anode material prepared in Comparative Example 2, respectively. Figure 7 Here are charge-discharge curves, where (a) is the charge-discharge curve of the lithium-ion batteries prepared in Examples 8-10, and (b) is the charge-discharge curve of the lithium-ion batteries prepared in Examples 11-14. Figure 8 The lithium-ion batteries prepared for comparative examples 4-6 were tested at 0.2 A g. -1 The following is a charge / discharge curve diagram; Figure 9The graph shows the cycle performance, where (a) represents the lithium-ion batteries prepared in Examples 8-10 at 1 A g. -1 The following are the cycle performance graphs: (b) shows the lithium-ion batteries prepared in Examples 11-14 at 1 A g. -1 The following is a graph showing the cyclic performance. Figure 10 The lithium-ion batteries prepared for comparative examples 4-6 were tested at 1 A g. -1 The following is a graph showing the cyclic performance. Figure 11 The elemental analysis diagram is shown for the silicon-carbon composite anode material prepared in Example 2. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0025] The raw material information involved in the following examples is as follows:

[0026] All performance indicators in the following examples and comparative examples were rigorously measured using precise instruments or standard testing methods: XRD patterns were determined using an X-ray diffractometer (ARL EQUINOX 3000, Thermo Fisher Scientific) at 40 kV and 40 mA, with 2θ ranging from 10 to 100°.

[0027] The microstructure of the material surface was characterized using a Quanta FEG 250 field emission scanning electron microscope and a Verios 460 L ultra-high resolution field emission scanning electron microscope from FEI Corporation, USA.

[0028] On the LAND system (LAND CT2001A, China), the voltage is between 0.01 and 1.5 V (vs. Li / Li). + Constant current charge-discharge measurements and cycle performance tests are performed within the potential window.

[0029] 1 A g -1 =0.25C.

[0030] Examples 1-7

[0031] A method for preparing a silicon-carbon composite anode material includes: mixing silicon-carbon material and a composite system at 20°C, stirring at 400 rpm for 4 h until homogeneous, and then stirring at 100°C at 600 rpm for 12 h until dry to obtain a silicon-carbon composite anode material precursor; transferring the silicon-carbon composite anode material precursor to a tube furnace under an argon atmosphere, heating it to X°C at a rate of 5°C / min and calcining it at X°C for 2 h, and cooling it to room temperature (with furnace cooling) to obtain the silicon-carbon composite anode material. The silicon-carbon material is prepared by CVD deposition. The silicon-carbon material includes a porous carbon framework and nano-silicon deposited in the porous carbon framework. The nano-silicon is formed by silane. Specifically, the silicon-carbon material used in this invention was purchased from the Shandong Provincial Laboratory of Advanced Materials and Green Manufacturing in Yantai (i.e., commercial CVD deposited silicon-carbon composite anode material), batch number BJW-SiC-20240428-YYC, with a silicon-to-carbon ratio of 3:7 and a particle size of 5~10 micrometers. At 20°C, the carbon source and solvent were mixed and stirred at 400 rpm for 24 h until homogeneous. Then, the metal source was added and stirred at 400 rpm for 24 h until homogeneous to obtain a composite system. The solvent was N-methylpyrrolidone (NMP), the carbon source was polyvinylidene fluoride (PVDF), the metal source was Y, and the metal source was used to provide metal ions, which were Z. The ratio of the mass fraction of the carbon source, the volume fraction of the solvent, and the mass fraction of the metal source was A. The unit of mass fraction was mg, and the unit of volume fraction was mL. The carbon source ratio in silicon-carbon materials and composite systems is B, based on mass fractions.

[0032] X, Y, Z, A, and B are shown in Table 1.

[0033]

[0034] Comparative Example 1 A method for preparing a silicon-carbon composite anode material is basically the same as that in Example 2, except that no metal source is added.

[0035] Comparative Example 2

[0036] A negative electrode material, which is a silicon-carbon material (the same as the commercial CVD-deposited silicon-carbon composite negative electrode material in Example 1).

[0037] Comparative Example 3

[0038] A method for preparing a silicon-carbon composite anode material is basically the same as that in Example 2, except that "the carbon source is polyvinylidene fluoride (PVDF)" is replaced with "the carbon source is polytetrafluoroethylene (PTFE)".

[0039] Examples 8-14 and Comparative Examples 4-6

[0040] A method for preparing a lithium-ion battery includes: assembling a positive electrode shell, an electrode sheet, a separator, a lithium sheet, a gasket, and a negative electrode shell in a glove box to obtain a lithium-ion battery. The electrolyte used is LiPF6 (electrolyte concentration of 1M, electrolyte type LB-048), and the separator is a Celgard 2325 membrane. The method for obtaining the electrode sheet includes: mixing a negative electrode material, a conductive agent (acetylene black), and a binder solution (the binder solution is a mixture of sodium carboxymethyl cellulose and deionized water, with a sodium carboxymethyl cellulose concentration of 15 mg / mL). -1 The sodium carboxymethyl cellulose solution in the negative electrode material, conductive agent, and binder solution was in a ratio of 8:1:1 by mass. The mixture was ground thoroughly in an agate mortar for 30 minutes until homogeneous, yielding a slurry. The slurry was then evenly coated onto a copper foil used as a current collector using a scraper. The slurry was dried in a vacuum oven at 80 °C for 12 hours to allow the deionized water to evaporate completely. Once cooled to room temperature, the slurry was removed and cut into 12 mm diameter circular electrode sheets using a cutting machine. These circular electrode sheets were then pressed at 10 MPa for 30 seconds using a pressing machine to obtain electrode sheets with a diameter of 12 mm. The negative electrode material was one of the silicon-carbon composite negative electrode materials prepared in Examples 1-7, Comparative Examples 1 and 3, and the negative electrode material in Comparative Example 2.

[0041] Table 2

[0042] Figure 1 SEM images of silicon-carbon materials (commercially CVD-deposited silicon-carbon composite anode materials). Figure 2 This is an elemental analysis diagram of a silicon-carbon material (a commercially available CVD-deposited silicon-carbon composite anode material). (Source: [Insert Source Here]) Figure 2 It can be seen that the C content of the silicon-carbon material is 69.23 wt%, and the Si content is 30.77 wt%.

[0043] Figure 3 The images show the XRD patterns of the silicon-carbon composite anode materials prepared in Examples 1-7. Figure 4 The images show the XRD patterns of the silicon-carbon composite anode materials prepared in Comparative Examples 1 and 3, and the anode material in Comparative Example 2. Figure 3 and Figure 4 In the diagram, "PDF#75-1621" is the standard card for graphite, and "PDF#77-2110" is the standard card for elemental silicon. It can be seen that the XRD patterns of the silicon-carbon composite anode materials prepared in Examples 1-7, Comparative Examples 1 and 3 show obvious broadened and diffused peaks around 25°, indicating that a carbon layer with a certain degree of graphitization was formed on the surface of the silicon-carbon material after high-temperature sintering.

[0044] Figure 5 of (a), Figure 5 (b) Figure 5 (c) Figure 5 (d) Figure 5 of (e) Figure 5 (f) and Figure 5 (g) are SEM images of the silicon-carbon composite anode materials prepared in Examples 1-7, respectively. Figure 5 It can be seen that the silicon-carbon composite anode materials prepared in Examples 1-7 have a typical bulk structure and are relatively uniformly distributed.

[0045] Figure 6 (a) and Figure 6 (b) shows the SEM images of the silicon-carbon composite anode material prepared in Comparative Example 1 and the anode material prepared in Comparative Example 2, respectively.

[0046] Figure 11 The elemental analysis diagram of the silicon-carbon composite anode material prepared in Example 2 is shown below. Figure 11 It can be seen that metal ions have been successfully introduced into silicon-carbon composite anode materials.

[0047] At 0.01 ~ 1.5 V and 0.2 A g -1 Below, the lithium-ion batteries prepared in Examples 8-10 were subjected to charge-discharge tests, and the resulting charge-discharge curves are shown in the figure. Figure 7 As shown in (a), the specific charge capacity of the lithium-ion battery prepared in Example 8 is 1305.65 mAh g. -1 The lithium-ion battery prepared in Example 9 has a specific charge capacity of 1344.94 mAh g⁻¹. -1 The lithium-ion battery prepared in Example 10 has a specific charge capacity of 1475.24 mAh g⁻¹. -1 .

[0048] At 0.01 ~ 1.5 V and 0.2 A g -1 Below, charge-discharge tests were performed on the lithium-ion batteries prepared in Examples 11-14, and the resulting charge-discharge curves are shown in the figure. Figure 7 As shown in (b), the specific charge capacity of the lithium-ion battery prepared in Example 11 is 1322.05 mAh g. -1 The lithium-ion battery prepared in Example 12 has a specific charge capacity of 1449.07 mAh g⁻¹. -1 The lithium-ion battery prepared in Example 13 has a specific charge capacity of 996.22 mAh g⁻¹. -1 The lithium-ion battery prepared in Example 14 has a specific charge capacity of 1304.05 mAh g⁻¹. -1 .

[0049] At 0.01 ~ 1.5 V and 0.2 A g -1 Below, compared to Example 4 ( Figure 8 Comparative Example 1 and Comparative Example 5 Figure 8 Comparative Example 2 and Comparative Example 6 Figure 8 The lithium-ion battery prepared in "Comparative Example 3" was subjected to charge-discharge tests, and the resulting charge-discharge curves are shown in the figure below. Figure 8 As shown, the specific charge capacity of the lithium-ion battery prepared in Comparative Example 4 is 1408.91 mAh g. -1 The lithium-ion battery prepared in Comparative Example 5 had a specific charge capacity of 1512.32 mAh g⁻¹. -1 The lithium-ion battery prepared in Comparative Example 6 had a specific charge capacity of 1436.89 mAh g. -1 .

[0050] At 0.01~1.5 V, 1 A g -1 The lithium-ion batteries prepared in Examples 8-10 were subjected to cycle tests at different current densities, and the cycle performance graphs are shown below. Figure 9 As shown in (a), by Figure 9 As shown in (a), the initial discharge specific capacity of the lithium-ion battery prepared in Example 8 is 1598.79 mAh g. -1 The discharge specific capacity after 50 cycles is 681.03 mAh g. -1 The capacity retention rate was 42.59%; the initial discharge specific capacity of the lithium-ion battery prepared in Example 9 was 1701.67 mAh g. -1 The discharge specific capacity after 50 cycles is 809.06 mAh g. -1 The capacity retention rate was 47.54%; the initial discharge specific capacity of the lithium-ion battery prepared in Example 10 was 1703.64 mAh g⁻¹. -1 The discharge specific capacity after 50 cycles is 680.07 mAh g. -1 The capacity retention rate was 39.91%.

[0051] At 0.01~1.5 V, 1 A g -1 The lithium-ion batteries prepared in Examples 11-14 were subjected to cycle tests at current densities, and the cycle performance graphs are shown below. Figure 9 As shown in (b), the initial discharge specific capacity of the lithium-ion battery prepared in Example 11 is 1680.78 mAh g. -1 The discharge specific capacity after 50 cycles is 670.07 mAh g. -1 The capacity retention rate was 39.87%; the initial discharge specific capacity of the lithium-ion battery prepared in Example 12 was 1777.84 mAh g⁻¹.-1 The discharge specific capacity after 50 cycles is 765.93 mAh g. -1 The capacity retention rate was 43.08%; the initial discharge specific capacity of the lithium-ion battery prepared in Example 13 was 1291.17 mAh g. -1 The discharge specific capacity after 50 cycles is 568.52 mAh g. -1 The capacity retention rate was 44.03%; the initial discharge specific capacity of the lithium-ion battery prepared in Example 14 was 1608.84 mAh g. -1 The discharge specific capacity after 50 cycles is 573.13 mAh g. -1 The capacity retention rate was 35.62%.

[0052] At 0.01 ~ 1.5 V, 1 A g -1 Under current density, compared with Comparative Example 4 ( Figure 10 Comparative Example 1 and Comparative Example 5 Figure 10 Comparative Example 2 and Comparative Example 6 Figure 10 The lithium-ion battery prepared in "Comparative Example 3" was subjected to cycle testing, and the cycle performance graph is shown in the figure below. Figure 10 As shown, the initial discharge specific capacity of the lithium-ion battery prepared in Comparative Example 4 is 1698.70 mAhg. -1 The discharge specific capacity after 50 cycles is 590.79 mAh g. -1 The capacity retention rate was 34.77%; the initial discharge specific capacity of the lithium-ion battery prepared in Comparative Example 5 was 1758.35 mAh g⁻¹. -1 The discharge specific capacity after 50 cycles is 107.11 mAh g. -1 The capacity retention rate was 6.09%; the initial discharge specific capacity of the lithium-ion battery prepared in Comparative Example 6 was 1746.86 mAh g⁻¹. -1 The discharge specific capacity after 50 cycles is 468.27 mAh g. -1 The capacity retention rate was 26.80%.

[0053] The lithium-ion batteries prepared in Examples 8-14 and Comparative Examples 4-6 were used at 0.2 A g. -1 The first-cycle charging specific capacity is 0.2 A g. -1 The first-cycle discharge specific capacity at 1 A g -1 The first charge specific capacity at 1 A g -1 First-cycle discharge specific capacity and capacity retention after 50 cycles (based on 1 A g) -1 The specific capacity calculated from the discharge is shown in Table 3.

[0054] Table 3

[0055] The lithium-ion battery prepared in Example 9 exhibits significantly superior charging specific capacity, discharging specific capacity, and capacity retention compared to Comparative Example 4. This is because metal ions can form coordination bonds with oxygen-containing functional groups (-OH, -COOH) on the surface of silicon-carbon materials, constructing a "flexible-rigid" metal coordination interface layer. This interface layer acts like an "elastic mesh," buffering the stress generated by silicon expansion and preventing carbon from cracking due to expansion, thus maintaining the integrity of the silicon-carbon material. In contrast, the negative electrode material used in Comparative Example 4 did not incorporate metal ions, failing to form this metal coordination interface layer, resulting in the destruction of the structural integrity of the silicon-carbon material.

[0056] The lithium-ion battery prepared in Comparative Example 5 was tested at 0.2 A g. -1 The charge specific capacity and discharge specific capacity of the battery prepared in Comparative Example 5 were basically the same as those in the previous example, but the lithium-ion battery prepared in Comparative Example 5 had a lower charge specific capacity than the previous example. -1 The charge and discharge specific capacities of the samples were significantly lower than those in Examples 8-14, indicating that coating the surface of the commercially available CVD-deposited silicon-carbon composite anode material with a fluorinated carbon layer can greatly improve its battery performance. Among Examples 8-10, Example 9 is the optimal embodiment overall; among Examples 11-13, Example 12 is the optimal embodiment, i.e., the optimal calcination temperature is 700°C. Among Examples 8-14, Example 9 is the optimal embodiment overall, especially showing significant advantages in charge specific capacity, discharge specific capacity, and capacity retention rate at high current densities, demonstrating that using iron acetylacetone as a metal source further improves the cycle stability of the lithium-ion battery.

[0057] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A silicon-carbon composite anode material, characterized in that, include: Silicon-carbon materials and the carbon layer coating the surface of the silicon-carbon materials; Silicon-carbon materials are prepared by CVD deposition. The silicon-carbon materials include: a porous carbon framework and nano-silicon deposited in the porous carbon framework, wherein the nano-silicon is formed from silane. The carbon layer includes: metal ions, wherein the metal ions are at least one of iron ions and copper ions, and the carbon layer is formed by the pyrolysis of a carbon source and a metal source during calcination, wherein the carbon source is polyvinylidene fluoride. The ratio of silicon-carbon material, carbon source, and metal source by mass fraction is 700:(35~70):

14.

2. A method for preparing a silicon-carbon composite anode material, characterized in that, include: The silicon-carbon material and the composite system are mixed until homogeneous, stirred until dry, calcined at 600~800℃ in a nitrogen or inert gas atmosphere, and cooled to room temperature to obtain the silicon-carbon composite anode material. Silicon-carbon materials are prepared by CVD deposition. The silicon-carbon materials include: a porous carbon framework and nano-silicon deposited in the porous carbon framework, wherein the nano-silicon is formed from silane. The composite system includes a carbon source, a solvent, and a metal source. The carbon source is polyvinylidene fluoride, and the metal source is used to provide metal ions, which are at least one of iron ions and copper ions. The ratio of the mass fraction of the carbon source, the volume fraction of the solvent, and the mass fraction of the metal source is (175~350):10:

70. The mass fraction is in mg, and the volume fraction is in mL. By mass fraction, the ratio of carbon source in silicon-carbon materials and composite systems is 700:(35~70).

3. The preparation method according to claim 2, characterized in that, The method for obtaining the composite system includes: mixing the carbon source and solvent until homogeneous, adding the metal source, mixing until homogeneous, and obtaining the composite system.

4. The preparation method according to claim 3, characterized in that, The solvent is N-methylpyrrolidone.

5. The preparation method according to claim 2, characterized in that, The metal source is at least one of iron acetylacetone and copper acetylacetone.

6. A lithium-ion battery, characterized in that, include: The silicon-carbon composite anode material according to claim 1.

7. The lithium-ion battery according to claim 6, characterized in that, In 1 A g -1 At the specified current density, the initial discharge specific capacity of the lithium-ion battery is 1701.67 mAh g. -1 The discharge specific capacity after 50 cycles is 809.06 mAh g. -1 The capacity retention rate was 47.54%.

8. The application of the silicon-carbon composite anode material as described in claim 1 in improving the specific capacity of lithium-ion batteries.

9. The application of the silicon-carbon composite anode material as described in claim 1 in improving the discharge specific capacity of lithium-ion batteries.

10. The application of the silicon-carbon composite anode material as described in claim 1 in improving the capacity retention of lithium-ion batteries.

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