Method for in-situ growth of carbon nanofiber reinforced lithium battery performance by plasma-induced silicon-carbon negative electrode

Abstract

The application relates to a method for improving the performance of lithium batteries by in-situ growth of carbon nanofibers on a silicon-carbon negative electrode through plasma induction, and belongs to the technical field of new materials and functional materials. The silicon-carbon negative electrode material is subjected to surface activation through plasma pretreatment technology, and then carbon nanofibers are in-situ grown through chemical vapor deposition to construct a three-dimensional conductive network structure. The plasma-assisted chemical vapor deposition technology is adopted, the silicon-carbon surface activated by plasma is used as a substrate, and in-situ growth is carried out to obtain uniformly distributed carbon nanofibers, so that a three-dimensional conductive composite structure closely combined with silicon-carbon particles is formed, and the high-rate cycle stability of the lithium ion battery is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of new materials and functional materials technology, specifically relating to a method for plasma-assisted CVD modification of silicon-carbon anodes. Through the synergistic effect of plasma pretreatment and CVD technology, carbon nanofibers are grown in situ on the surface of silicon-carbon anodes to construct a three-dimensional conductive network structure. Background Technology

[0002] Silicon-carbon anode materials, as a research hotspot for next-generation lithium-ion battery anode materials, are considered one of the key materials for breaking through the current energy density bottleneck of batteries due to their extremely high theoretical specific capacity (4200 mAh / g) and moderate operating potential. Since its inception, silicon-carbon anodes have become a research focus in the field of high-energy-density energy storage. This material, by combining nano-silicon with carbon materials, fully utilizes the high lithium storage capacity of silicon and the good conductivity and volume buffering effect of carbon, exhibiting a significantly superior capacity advantage and rate performance compared to traditional graphite anodes, opening up new research directions for the development of high-energy-density lithium-ion batteries. However, in actual industrial production and applications, silicon-carbon anodes still face many key problems that urgently need to be solved. The huge volume expansion of silicon materials during charging and discharging (exceeding 300%) can lead to pulverization and peeling of electrode materials, resulting in rapid capacity decay; at the same time, the low intrinsic conductivity of silicon limits electron transport efficiency, seriously affecting its rate performance. Small fluctuations in parameters such as silicon particle size distribution, carbon coating uniformity, and electrode structure design can significantly affect the electrochemical performance stability of the composite anode. In addition, existing silicon-carbon composite processes generally suffer from insufficient interfacial bonding and low efficiency in building conductive networks: poor interfacial compatibility between silicon and carbon matrix and uneven dispersion of conductive additives not only reduce the structural stability of the electrode, but also easily cause the active material to lose electrical contact during cycling.

[0003] Currently, the mainstream methods for modifying silicon-carbon anodes include mechanical ball milling, spray drying, sol-gel methods, and chemical vapor deposition (CVD), each with its own characteristics but also significant limitations. While mechanical ball milling and spray drying can achieve physical composites of silicon and carbon, they struggle to form a uniform and dense carbon coating layer, resulting in insufficient interfacial bonding strength. The sol-gel method can prepare nanoscale composite structures, but its complex process and long cycle time make it difficult to meet the demands of large-scale production. Traditional CVD methods can grow carbon nanomaterials on silicon surfaces, but limited by reaction temperature and catalyst activity, the in-situ growth of carbon nanofibers is poorly controllable, making it difficult to achieve uniform coverage on the surface of silicon-carbon particles with complex morphologies.

[0004] In application fields, lithium-ion batteries, as the core energy carrier for new energy vehicles, portable electronic devices, and large-scale energy storage, are facing increasingly higher requirements for energy density, power density, and cycle life. Silicon-carbon anode materials, with their ultra-high capacity advantage, have become a key technological direction for achieving breakthroughs in battery energy density. However, their poor cycle stability and insufficient rate performance severely restrict their commercialization process. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for enhancing lithium-ion battery performance through plasma-induced in-situ growth of carbon nanofibers on a silicon-carbon anode. This invention employs plasma pretreatment technology to activate the surface of the silicon-carbon anode material, followed by in-situ growth of carbon nanofibers via chemical vapor deposition to construct a three-dimensional conductive network structure. Using plasma-assisted chemical vapor deposition (PECVD) technology, with the plasma-activated silicon-carbon surface as a substrate, uniformly distributed carbon nanofibers are grown in situ, forming a tightly bonded three-dimensional conductive composite structure with the silicon-carbon particles, effectively improving the high-rate cycle stability of lithium-ion batteries.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for enhancing lithium battery performance through plasma-induced in-situ growth of carbon nanofibers on a silicon-carbon anode includes the following steps:

[0008] Step 1. Place silicon carbon in the reaction chamber of the plasma treatment equipment, close the chamber and evacuate to below 10 Pa; introduce inert gas as discharge gas, adjust the gas flow rate to 20 ~ 30 mL / min, set the plasma power to 50 ~ 300 W, and perform high-energy ion bombardment treatment on the silicon carbon anode for 10 ~ 60 min.

[0009] Step 2. After plasma treatment, allow the sample to cool naturally to room temperature. Place the removed silicon-carbon sample into the tube furnace of a chemical vapor deposition apparatus. In an inert gas atmosphere, adjust the temperature to 500-600°C, remove air from the chamber, and ensure uniform sample temperature. Then, introduce carbon source gas and reducing gas at a total flow rate of 60-80 mL / min for 30-120 min to grow carbon nanofibers.

[0010] Step 3. Using the silicon-carbon with carbon nanofibers grown in Step 2 as the negative electrode active material, carbon black as the conductive additive, and PVDF as the binder, mix them in a mass ratio of 8:1:1. Then add N-methylpyrrolidone and stir continuously to prepare a conductive slurry. Coat the prepared conductive slurry onto copper foil, dry it, cut it into small pieces, and assemble it into a silicon-carbon lithium-ion half-cell in a glove box.

[0011] Furthermore, in steps 1 and 2, the inert gas is Ar, N2, etc.

[0012] Furthermore, the average particle size of the silicon-carbon particles described in step 1 is 10 to 50 μm.

[0013] Furthermore, in step 2, the heating rate is 5 ~ 10 ℃ / min, and the flow rate of the inert gas introduced during the heating process is 60 ~ 80 mL / min.

[0014] Furthermore, in step 2, the carbon source gas is acetylene, and the volume ratio of the carbon source gas to the reducing gas is 3:5; the reducing gas is a mixture of hydrogen and argon with a volume ratio of 1:4.

[0015] Furthermore, in step 2, the time for growing carbon nanofibers is 30 min to 120 min.

[0016] Furthermore, in step 3, 2.5 to 3.5 mL of N-methylpyrrolidone is added to every 1g of negative electrode active material.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. This invention provides a method for plasma-induced in-situ growth of carbon nanofibers on a silicon-carbon anode to enhance lithium battery performance. The method employs plasma pretreatment technology to treat the silicon-carbon anode material, achieving synergistic activation of the silicon and carbon components: on one hand, high-energy plasma bombards the crystalline silicon surface, effectively activating the silicon and generating numerous dangling bonds and unsaturated silicon active sites, significantly enhancing its surface energy and chemical reactivity; on the other hand, plasma can etch and reconstruct the surface carbon layer, controllably introducing carbon dangling bonds and edge defect structures to form a defect-rich carbon surface. This plasma-activated silicon-carbon surface possesses abundant silicon active sites and carbon defect sites, providing direct nucleation sites for subsequent carbon nanofiber growth without metal catalysts. Furthermore, the plasma-activated carbon layer exhibits stronger gas adsorption and catalytic cracking capabilities, significantly promoting the surface adsorption, dissociation, and cracking of carbon source gases, thereby achieving in-situ uniform growth of carbon nanofibers on the silicon-carbon surface without a catalyst.

[0019] 2. This invention provides a method for plasma-induced in-situ growth of carbon nanofibers in silicon-carbon anodes to enhance lithium-ion battery performance. The method employs plasma pretreatment technology to treat the silicon-carbon anode material, achieving cleaning and activation of the interface between silicon-carbon and carbon fibers. This results in a high-strength chemical bond interface between the in-situ grown carbon nanofibers and the silicon-carbon matrix, with an interfacial bonding strength far superior to traditional mechanical mixing or coating methods. Therefore, the silicon-carbon / carbon nanofiber composite structure constructed by this invention exhibits higher structural stability and superior electrochemical performance compared to the original silicon-carbon material. This method features low reaction temperature, simple process, no metal catalyst residue, and fully leverages the dual regulatory advantages of plasma on silicon and carbon, laying an important foundation for the large-scale, low-cost preparation of silicon-carbon anode materials and the development of high-performance lithium-ion batteries. Attached Figure Description

[0020] Figure 1 The fine C 1s spectra in the XPS spectra of the original silicon-carbon obtained in Examples 1-3 are as follows: (a); (b) Si / C-PE-10min; (c) Si / C-PE-30min; (d) Si / C-PE-60min.

[0021] Figure 2 The fine Si 2p spectra in the XPS spectra of (a) pristine silicon-carbon; (b) Si / C-PE-10min; (c) Si / C-PE-30min; and (d) Si / C-PE-60min obtained in Examples 1-3 are shown.

[0022] Figure 3 Raman spectra of the original silicon-carbon, Si / C-PE-10min, Si / C-PE-30min and Si / C-PE-60min obtained in Examples 1-3;

[0023] Figure 4 The images shown are SEM images of the Si / C-PE-10min-CNFs sample (a, b), the Si / C-PE-30min-CNFs sample (c, d), and the Si / C-PE-60min-CNFs sample (e, f) obtained in Example 4.

[0024] Figure 5 The microstructure of CNFs grown on the Si / C-PE-30min-CNFs sample obtained in Example 4 at different magnifications;

[0025] Figure 6The C 1s fine spectra of (a) Si / C-PE-10min-CNFs; (b) Si / C-PE-30min-CNFs; (c) Si / C-PE-60min-CNFs obtained in Example 4; and the Si 2p fine spectra of (d) Si / C-PE-10min-CNFs; (e) Si / C-PE-30min-CNFs; (f) Si / C-PE-60min-CNFs.

[0026] Figure 7 Raman spectra of Si / C-PE-10min-CNFs, Si / C-PE-30min-CNFs and Si / C-PE-60min-CNFs obtained in Example 4;

[0027] Figure 8 The results of long-cycle performance tests of Si / C-PE-10min-CNFs, Si / C-PE-30min-CNFs and Si / C-PE-60min-CNFs obtained in Examples 5 to 7 as negative electrode materials at a discharge rate of 0.2 C from the first cycle to the 1000th cycle.

[0028] Figure 9 The results of rate testing of different silicon-carbon samples obtained in Examples 5-7 as negative electrode materials are shown; where (a) corresponds to the original silicon-carbon; (b) corresponds to Si / C-PE-10min-CNFs; (c) corresponds to Si / C-PE-30min-CNFs and; and (d) corresponds to Si / C-PE-60min-CNFs.

[0029] Figure 10 The EIS curves of lithium-ion batteries obtained in Examples 5-7 are as follows: original silicon-carbon, Si / C-PE-10min-CNFs, Si / C-PE-30min-CNFs and Si / C-PE-60min-CNFs are used as negative electrode materials. Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

[0031] Example 1

[0032] 10 g of silicon carbide powder was placed in a quartz boat and then placed into the cavity of a plasma generator. The power was set to 300 W and the gas atmosphere was argon. Plasma bombardment was carried out for 10 min. The sample was then taken out and named Si / C-PE-10min.

[0033] Example 2

[0034] 10 g of silicon carbide powder was placed in a quartz boat and then placed into the cavity of a plasma generator. The power was set to 300 W and the gas atmosphere was argon. Plasma bombardment was carried out for 30 min. The sample was then taken out and named Si / C-PE-30min.

[0035] Example 3

[0036] 10 g of silicon carbide powder was placed in a quartz boat and then placed into the cavity of a plasma generator. The power was set to 300 W and the gas atmosphere was argon. Plasma bombardment was carried out for 60 min. The sample was then taken out and named Si / C-PE-60min.

[0037] Example 4

[0038] A method for plasma-induced in-situ growth of carbon nanofibers in a silicon-carbon anode to enhance the performance of lithium batteries, characterized by comprising the following steps:

[0039] Step 1: Weigh 1 g of Si / C-PE powder and place it in the CVD rotary furnace. Introduce argon gas at a rate of 20 mL / min and test the airtightness of the device. If the airtightness is good, introduce argon gas at a rate of 60 mL / min for 10 min and then purge the air from the rotary furnace.

[0040] Step 2: Under the protection of argon gas at a flow rate of 60 mL / min, the reaction apparatus is heated to 600 °C. After the temperature stabilizes for 10 min, argon gas is continuously introduced at a flow rate of 40 mL / min, along with acetylene gas at a flow rate of 30 mL / min and hydrogen gas at a flow rate of 10 mL / min. The reaction time is 120 min. Then, the mixture is cooled to room temperature to obtain silicon-carbon materials with grown carbon nanofibers, which are named Si / C-PE-10min-CNFs, Si / C-PE-30min-CNFs, and Si / C-PE-60min-CNFs, respectively.

[0041] Example 5

[0042] 240 mg Si / C-PE-10min-CNFs, 30 mg Super P and 30 mg PVDF were used as the active material, conductive agent and binder of the negative electrode of the battery, respectively, and mixed together. Lithium sheet was used as the negative electrode. 1 ml of N-methylpyrrolidone was added and stirred with a solder paste mixer for 4 h. The conductive paste was then coated on copper foil with a thickness of 200 µm and dried in a vacuum oven at 80 °C for 12 h. After drying, it was cut into negative electrode sheets with a diameter of 14.5 mm for assembling button batteries.

[0043] Example 6

[0044] 240 mg Si / C-PE-30min-CNFs, 30 mg Super P and 30 mg PVDF were used as the active material, conductive agent and binder of the negative electrode of the battery, respectively, and mixed together. Lithium sheet was used as the negative electrode. 1 ml of N-methylpyrrolidone was added and stirred with a solder paste mixer for 4 h. The conductive paste was then coated on copper foil with a thickness of 200 µm and dried in a vacuum oven at 80 °C for 12 h. After drying, it was cut into negative electrode sheets with a diameter of 14.5 mm for assembling button batteries.

[0045] Example 7

[0046] 240 mg Si / C-PE-60min-CNFs, 30 mg Super P and 30 mg PVDF were used as the active material, conductive agent and binder of the negative electrode of the battery, respectively, and mixed together. Lithium sheet was used as the negative electrode. 1 ml of N-methylpyrrolidone was added and stirred with a solder paste mixer for 4 h. The conductive paste was then coated on copper foil with a thickness of 200 µm and dried in a vacuum oven at 80 °C for 12 h. After drying, it was cut into negative electrode sheets with a diameter of 14.5 mm for assembling button batteries.

[0047] Figure 1-2 XPS spectra of silicon-carbon anodes in Examples 1-3 after plasma modification, used to represent changes in surface chemical bonds; Figure 1 The original silicon-carbon sample contained mainly C-C and CO chemical bonds, with C-Si and C=O bonds appearing in the etched sample. The carbon in the original silicon-carbon sample mainly existed as C-C bonds, with a small amount of CO bonds, accounting for 84.2% and 15.8%, respectively. After plasma etching, the chemical bonding of the sample changed, with the relative content of C-C bonds decreasing significantly, from 84.2% to 20.6%, 24.2%, and 25.7% with varying modification time, indicating that the carbon coating was effectively etched during the etching process. Furthermore, new C=O and C-Si bonds appeared, with C-Si bonds accounting for the highest proportion, indicating that plasma etching promoted interfacial bonding between carbon and silicon. The CO bond content also decreased significantly, reflecting the removal of oxygen-containing functional groups by plasma etching. The appearance of C=O bonds also indicates that plasma etched the carbon, promoting the formation of highly active carbon dangling bonds on the surface, connecting O atoms to form stable C=O bonds, and providing active sites for subsequent in-situ growth. Figure 2The results indicate that silicon in the original silicon-carbon sample mainly exists in the forms of Si-O and Si-Si, with a low Si-C bond content, and no amorphous silicon was detected. Si-O originates from surface silicon suboxides, Si-Si from crystalline silicon formed by silane deposition, and Si-C is generated during carbon coating. After plasma etching, the Si-O bond content remained relatively stable, indicating that the oxide layer on the silicon surface was not significantly damaged during etching. The Si-C bond content significantly increased from 7.7% to 21-22%, consistent with the increasing trend of C-Si bonds in the C 1s spectrum, further confirming that etching promoted bonding at the carbon-silicon interface. The Si-Si bond content decreased significantly, and new amorphous silicon appeared, indicating that plasma etching disrupted the long-range ordered structure of some crystalline silicon, leading to its transformation into an amorphous structure.

[0048] Figure 3 The effects of plasma etching following Examples 1-3 on the structure of silicon-carbon anode materials; Figure 3 The results show that the D and G peaks of the original silicon-carbon sample are weak and broadened, indicating that the surface carbon layer mainly exists in the form of amorphous carbon. After plasma etching, the characteristic peak intensities of silicon in the Si / C-PE sample are significantly reduced and the peak shapes are broadened, indicating that the etching process induces the transformation of crystalline silicon to disordered silicon. Further analysis of the changes in carbon structure shows that as the etching time increases from 10 min to 60 min, the intensity ratio of the D peak to the G peak first increases and then decreases, reaching 1.01, 1.12, and 1.10, respectively. When the etching time is 30 min, the ID / IG value reaches its maximum, indicating that the degree of disorder in the carbon layer is highest at this time.

[0049] Figure 4-5 The morphology of CNFs grown from Si / C-PE-10min-CNFs, Si / C-PE-30min-CNFs and Si / C-PE-60min-CNFs obtained in Example 4 is shown. Figure 4 In the Si / C-PE-60min sample, when the modification time reaches 30 min, a large number of CNFs grow, indicating that there are many carbon defect sites under this modification condition. More defect sites provide a larger CNF growth substrate for the carbon produced by acetylene cracking. Furthermore, the grown CNFs have a relatively large diameter, indicating a large range of defect sites in the growth substrate. When the modification time is further extended, due to the effect of plasma, the carbon defect sites on the Si / C-PE-60min sample disappear due to excessive plasma bombardment, resulting in fewer and smaller CNFs. Figure 5In this study, CNFs exhibited a non-directional growth pattern on silicon-carbon surfaces, with fibers interwoven and randomly distributed without a clear preferred orientation. This growth pattern is related to the substrate surface structure. Further analysis of the fiber size characteristics revealed that the diameters of CNFs were mainly concentrated between 50 and 200 nm, indicating that they possessed a good nanoscale structure.

[0050] Figure 6 XPS spectra of Si / C-PE-10min-CNFs, Si / C-PE-30min-CNFs, and Si / C-PE-60min-CNFs were obtained for Example 4. In the C 1s fine spectrum, C-C bonds and C-Si bonds were mainly detected on the sample surface. After the CVD growth process, the characteristic peaks of CO and C=O bonds present in the original samples completely disappeared, which is attributed to the cleaning and etching effect of the hydrogen atmosphere. The proportion of C-Si bonds in the three samples was as high as 89.3%, 80.1%, and 89.7%, respectively, indicating that during the CVD process, the carbon source gas was efficiently cracked on the material surface and chemically bonded with highly active silicon to form a high-strength silicon carbide structure. From the Si 2p fine spectrum, it can be seen that the proportion of Si-O bonds in the three samples decreased compared with that before CVD treatment, further confirming the effective etching of the inert oxide layer on the silicon surface by hydrogen, thereby exposing more highly active silicon sites. Meanwhile, the proportion of Si-C bonds increased significantly, which is highly consistent with the high proportion of C-Si bonds observed in the C 1s spectrum. Correspondingly, the proportion of Si-Si bonds and a-Si components decreased, which is a direct reflection of the chemical bonding between silicon and carbon, forming a hybrid structure.

[0051] Figure 7 The Raman spectra of Si / C-PE-10min-CNFs, Si / C-PE-30min-CNFs, and Si / C-PE-60min-CNFs obtained in Example 4 are shown. The coexistence of two characteristic peaks indicates that the grown CNFs exhibit typical Raman characteristics of carbon materials. Originally at 520 cm⁻¹... -1 The characteristic peaks of crystalline silicon that should appear completely disappeared in the Raman spectra of all samples. This phenomenon indicates that the CNFs grown after CVD treatment have good coverage uniformity and a certain thickness, and the fiber structure does not contain silicon.

[0052] Figure 8The figures show the long-cycle discharge data of the silicon-carbon lithium-ion half-cells assembled in Examples 5-7. Throughout the cycle, the discharge specific capacity of the original silicon-carbon exhibits a rapid decline with increasing cycle number, indicating that the pure silicon-carbon system is unable to effectively buffer the massive volume expansion during silicon intercalation / deintercalation, leading to electrode structure damage and contact failure, resulting in significantly insufficient capacity maintenance. In contrast, the modified silicon-carbon materials all exhibited significantly improved long-cycle stability, indicating that modification improved structural stability and electrochemical reversibility. The construction of the surface SiC structure and the in-situ growth of CNFs not only effectively alleviated the mechanical stress caused by the volume expansion of silicon particles and suppressed the continuous growth of the SEI film and electrode pulverization, but also ensured the rapid transport of electrons and lithium ions during long cycles, thereby significantly improving the cycle life of the silicon-based anode. Furthermore, the composite of CNFs further optimized the bonding state between the carbon network and silicon particles, strengthening the structural synergistic effect.

[0053] Figure 9 The figures show the rate performance of the silicon-carbon lithium-ion half-cells assembled in Examples 5-7. The original silicon-carbon half-cell had an average discharge specific capacity of 506.6 mAh / g at 0.2 C, which decreased significantly at 0.5 C, with an average discharge specific capacity of 161.8 mAh / g. As the rate increased to 1 C and 2 C, it could barely discharge. When the rate recovered to 0.2 C, the capacity only recovered to 240.7 mAh / g. In contrast, the modified silicon-carbon showed significantly improved rate performance under the same conditions, achieving average discharge specific capacities of 300 mAh / g and 150 mAh / g at 0.5 C and 1 C, respectively. However, as the rate increased to 2 C, due to the poor intrinsic conductivity of silicon-carbon, it still could not discharge at high discharge rates. After rate recovery, the capacity could recover to an average of 600 mAh / g, demonstrating good rate recovery performance. The inherent electronic conductivity of raw silicon-carbon is low. At higher discharge rates of 1 C and 2 C, the electron transport velocity cannot meet the demands of instantaneous high current, leading to severe electrode polarization, rapid voltage drop, and ineffective discharge. Furthermore, the pulverization of silicon-carbon particles causes direct contact failure of the electrode material, resulting in loss of reactivity. Simultaneously, the volume expansion and contraction of silicon-carbon particles disrupts the originally stable SEI film, accelerating the consumption of active lithium ions at high discharge rates. Modified silicon-carbon, facilitated by the conductive network of CNFs, can effectively improve electronic conductivity, and the formation of Si-C hybrid structures on the particle surface can effectively mitigate SEI film rupture and reduce the loss of active lithium ions.

[0054] Figure 10Electrochemical impedance spectroscopy (EIS) diagrams of the silicon-carbon lithium-ion half-cells assembled in Examples 5-7 are shown. It can be observed that the modified silicon-carbon exhibits lower electrochemical transfer impedance, which is lower than that of the original silicon-carbon. CNFs possess excellent intrinsic conductivity, enabling them to construct highly efficient three-dimensional conductive networks between silicon-carbon particles. This network structure significantly increases the pathway for electrons to transport from the current collector to the active material particles, reduces the resistance to electron migration within the electrode, and thus significantly reduces the impedance associated with the charge transfer process.

Claims

1. A method for plasma-induced in-situ growth of carbon nanofibers in a silicon-carbon anode to enhance the performance of lithium batteries, characterized in that, Includes the following steps: Step 1. Place silicon carbon in the reaction chamber of the plasma device and evacuate to below 10 Pa; An inert gas was introduced as the discharge gas, the gas flow rate was adjusted to 20 ~ 30 mL / min, the plasma power was set to 50 ~ 300 W, and the silicon-carbon was subjected to plasma treatment for 10 ~ 60 min. Step 2. After plasma treatment, the silicon-carbon material is allowed to cool naturally to room temperature. The extracted silicon-carbon material is then placed in a tube furnace of a chemical vapor deposition apparatus and heated to 500-600°C in an inert gas atmosphere. Carbon source gas and reducing gas are then introduced, with a total gas flow rate of 60-80 mL / min for 30-120 min, to grow carbon nanofibers. Step 3. Use the silicon-carbon with carbon nanofibers grown in Step 2 as the negative electrode active material to assemble a silicon-carbon lithium-ion half-cell.

2. The method for enhancing lithium battery performance by in-situ growth of carbon nanofibers in a plasma-induced silicon-carbon anode according to claim 1, characterized in that, In steps 1 and 2, the inert gas is Ar or N2.

3. The method for enhancing lithium battery performance by in-situ growth of carbon nanofibers in a plasma-induced silicon-carbon anode according to claim 1, characterized in that, The average particle size of the silicon-carbon in step 1 is 10 ~ 50 μm.

4. The method for enhancing lithium battery performance by in-situ growth of carbon nanofibers in a plasma-induced silicon-carbon anode according to claim 1, characterized in that, In step 2, the heating rate is 5 ~ 10 ℃ / min, and the flow rate of the inert gas introduced during the heating process is 60 ~ 80 mL / min.

5. The method for enhancing lithium battery performance by in-situ growth of carbon nanofibers in a plasma-induced silicon-carbon anode according to claim 1, characterized in that, In step 2, the carbon source gas is acetylene, and the volume ratio of the carbon source gas to the reducing gas is 3:5; the reducing gas is a mixture of hydrogen and argon with a volume ratio of 1:

4.

6. The method for enhancing lithium battery performance by in-situ growth of carbon nanofibers in a plasma-induced silicon-carbon anode according to claim 1, characterized in that, In step 2, the growth time of carbon nanofibers is 30 min to 120 min.

7. The method for enhancing lithium battery performance by in-situ growth of carbon nanofibers in a plasma-induced silicon-carbon anode according to claim 1, characterized in that, In step 3, silicon-carbon with carbon nanofibers grown in step 2 is used as the negative electrode active material, carbon black as the conductive additive, and PVDF as the binder. They are mixed in a mass ratio of 8:1:1 and N-methylpyrrolidone is added and stirred to prepare a conductive slurry. The prepared conductive slurry is coated on copper foil and assembled into a silicon-carbon lithium-ion half-cell.

8. The method for enhancing lithium battery performance by in-situ growth of carbon nanofibers in a plasma-induced silicon-carbon anode according to claim 7, characterized in that, Add 2.5 to 3.5 mL of N-methylpyrrolidone to every 1g of negative electrode active material.

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