Silicon-carbon composite fiber negative electrode material based on pre-lithiation and in-situ lithium fluoride interface modification as well as preparation method and application of silicon-carbon composite fiber negative electrode material

Abstract

The invention belongs to the technical field of lithium ion battery negative electrode materials, and particularly discloses a silicon-carbon composite fiber negative electrode material based on pre-lithiation and in-situ lithium fluoride interface modification as well as a preparation method and application of the silicon-carbon composite fiber negative electrode material. The preparation method comprises the following steps: carrying out mechanical ball milling on nano silicon powder and a lithium source in an inert atmosphere to obtain pre-lithiated composite powder of silicon and the lithium source; dissolving a polymer carbon source in an organic solvent, adding the composite powder and a fluorine source, and uniformly mixing to obtain a spinning solution; performing electrostatic spinning on the spinning solution to obtain a composite fiber precursor film; and carrying out pre-oxidation stabilization treatment on the composite fiber precursor film, and then carrying out carbonization treatment in an inert atmosphere to obtain the silicon-carbon composite fiber negative electrode material. According to the preparation method disclosed by the invention, the dual synergistic effect of lithium consumption compensation by pre-lithiation and side reaction inhibition by LiF-based artificial SEI is realized, and the silicon-carbon negative electrode material with excellent comprehensive performance is finally obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery negative electrode materials, and particularly relates to a silicon-carbon composite fiber negative electrode material based on pre-lithiation and in-situ lithium fluoride interface modification and a preparation method and application thereof. BACKGROUND

[0002] Silicon-based materials are considered to be the most potential negative electrode materials for the next generation of high-energy-density lithium ion batteries due to their extremely high theoretical specific capacity (4200 mAh·g -1 However, silicon negative electrodes have a volume change of about 300% during the charging and discharging process, which leads to the destruction of the electrode structure and the continuous rupture and regeneration of the solid electrolyte interface (SEI) film, thereby continuously consuming electrolyte and active lithium, resulting in rapid capacity decay and poor cycle life. In addition, a thick SEI film is formed during the first lithium intercalation process of the silicon negative electrode, which consumes a large amount of lithium ions, resulting in a generally low initial coulombic efficiency (ICE) of the silicon negative electrode, which seriously limits the practical application of the silicon negative electrode in full batteries.

[0003] To address the above problems, the existing technology mainly improves in two aspects: (1) pre-lithiation technology: by pre-introducing an additional lithium source during electrode preparation or material synthesis to compensate for the irreversible lithium loss caused by SEI formation during the first charging and discharging process, thereby improving the initial efficiency. Common pre-lithiation methods include lithium metal foil contact, stabilized lithium metal powder (SLMP), and chemical reaction with lithium-containing compounds. However, these methods have problems such as complex process, air sensitivity, or uncontrollable reaction. (2) Constructing a stable SEI film: by pre-constructing an artificial SEI film on the material surface to inhibit side reactions during the cycle process. Among them, lithium fluoride is an ideal artificial SEI component due to its high interfacial energy, mechanical strength, and excellent lithium ion conductivity. Current methods of introducing LiF rely on electrolyte additives (such as fluoroethylene carbonate (FEC)) or fluorination treatment after synthesis. The uniformity and stability of the LiF layer generated by these methods are insufficient, and the additives will continue to be consumed during the cycle.

[0004] Therefore, it is of great significance to develop a silicon-carbon composite material preparation method that can combine pre-lithiation with the construction of a uniform and stable LiF-based artificial SEI, and has a simple and controllable process. SUMMARY

[0005] In view of the above problems, the present application provides a kind of silicon-carbon composite fiber negative material based on prelithiation and in-situ fluorinated lithium interface modification and its preparation method and application.The present application realizes the preliminary prelithiation of nanosilicon by mechanical ball milling, and ingeniously introduces lithium source and fluorine source in electrostatic spinning precursor solution, realizes deep prelithiation and reaction with fluorine source in subsequent heat treatment process, in-situ generates uniform LiF nanocrystals in silicon-carbon fiber interior and surface, and constructs stable artificial SEI.The preparation method of the present application realizes the double synergistic effect of prelithiation compensation lithium consumption and LiF-based artificial SEI inhibition of side reaction, and finally obtains silicon-carbon negative material with excellent comprehensive performance.

[0006] To solve the above problems, the present application provides a kind of preparation method of silicon-carbon composite fiber negative material based on prelithiation and in-situ fluorinated lithium interface modification, comprising the following steps: S1.prelithiation of silicon and lithium source composite powder is obtained by mechanical ball milling of nanosilicon powder and lithium source in inert atmosphere;Wherein, the mass ratio of nanosilicon powder and lithium source is 5:1-20:1; S2.dissolve polymer carbon source in organic solvent, then add the composite powder and fluorine source to it and mix evenly to obtain spinning solution; S3.electrostatic spinning of the spinning solution to obtain composite fiber precursor film; S4.stabilization treatment of the composite fiber precursor film by pre-oxidation, and then carbonization treatment in inert atmosphere to obtain silicon-carbon composite fiber negative material;Wherein, in-situ solid-phase reaction of lithium source and fluorine source generates LiF nanocrystals during carbonization treatment.

[0007] In the present application, during the carbonization treatment of step S4, the polymer carbon source is carbonized to form a conductive carbon skeleton, the unreacted lithium source (such as Li2CO3) after ball milling reacts with the fluorine source (such as HF produced by PVDF pyrolysis or fluorine-containing free radicals) to generate lithium fluoride (its chemical reaction formula is Li2CO3+2HF→2LiF+H2O+CO2);The unreacted lithium source after ball milling further reacts with silicon at high temperature (Li2CO3+2C+Si→2Li+SiO2+3CO), and the generated active lithium immediately alloys with silicon to achieve deep prelithiation.The generated LiF nanocrystals are uniformly embedded in the carbon fiber matrix and enriched on the surface and around the nanosilicon particles, forming a firm and LiF-rich artificial SEI layer.

[0008] Preferably, in step S1, the lithium source includes at least one of lithium carbonate, lithium hydroxide and lithium acetate;The ball milling time is 2-8h.

[0009] Preferably, in step S2, the polymer carbon source includes at least one of polyacrylonitrile, polyvinyl alcohol, polyacrylic acid, and polyvinylpyrrolidone; the organic solvent includes at least one of N,N-dimethylformamide and N-methylpyrrolidone; and the concentration of the polymer carbon source in the organic solvent is 5-15 wt%.

[0010] Preferably, in step S2, the fluorine source includes at least one of polyvinylidene fluoride, fluoroethylene carbonate, and polytetrafluoroethylene, and the concentration of the fluorine source in the spinning solution is 0.1-10 wt%.

[0011] Preferably, in step S2, the concentration of the composite powder in the spinning solution is 3-7 wt%.

[0012] Preferably, in step S4, the pre-oxidation stabilization treatment specifically involves heating the temperature to 200-280°C at a rate of 1-5°C / min in an oxygen-containing atmosphere and holding it at that temperature for 1-5 hours.

[0013] Preferably, in step S4, the carbonization process specifically involves: first heating to 500°C at a heating rate of 2-10°C / min and holding for 1-2 hours, then heating to 700°C and holding for 1-2 hours.

[0014] Preferably, in steps S1 and S4, the inert atmosphere includes at least one of nitrogen and argon.

[0015] Based on the same inventive concept, the present invention also provides a silicon-carbon composite fiber anode material, which is prepared by any of the preparation methods described above. The silicon-carbon composite fiber anode material is composed of a three-dimensional conductive network formed by interwoven carbon fibers, and nano-silicon particles and lithium fluoride nanocrystals are uniformly dispersed and encapsulated inside the carbon fibers.

[0016] Preferably, the silicon content in the silicon-carbon composite fiber anode material is 10-50 wt%, and the LiF content in the silicon-carbon composite fiber anode material is 2-15 wt%.

[0017] Based on the same inventive concept, the present invention also provides a lithium-ion battery, wherein the negative electrode active material of the lithium-ion battery is prepared by any of the preparation methods described above.

[0018] Preferably, the preparation method of the above-mentioned lithium-ion battery includes: using the silicon-carbon composite fiber negative electrode material prepared in this invention as the negative electrode active material, mixing the active material with conductive carbon black (Super P) and sodium alginate (SA) at a mass ratio of 7:2:1, 7:1.5:1.5 or 8:1:1, grinding in a mortar for 10 min to obtain a uniformly mixed powder, transferring the ground powder to a glass bottle and adding an appropriate amount of deionized water, stirring magnetically for 12 h to obtain an electrode slurry, coating the slurry on a copper foil with a thickness of 10-50 μm, vacuum drying at 70°C, and cutting to obtain an electrode sheet.

[0019] Preferably, the active material: Super P: SA = 7:2:1 by mass, and the slurry coating thickness is 10μm.

[0020] Preferably, the above-mentioned method for preparing lithium-ion batteries further includes: assembling the battery in an argon-filled glove box in the order of negative electrode shell, spring sheet, gasket, lithium sheet, separator, electrode sheet, and positive electrode shell, injecting electrolyte on both sides of the separator, and sealing it on a button cell packaging machine to complete the battery assembly.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Dual pre-lithiation mechanism for efficient lithium consumption compensation: This invention employs a combination of mechanical ball milling for initial pre-lithiation and carbonization for deep pre-lithiation; that is, the mechanical ball milling process achieves mild and uniform pre-lithiation of the nano-silicon surface; and in the subsequent carbonization stage, the unconsumed lithium source is further reacted with silicon. This distributed pre-lithiation ensures the sufficiency and uniformity of the compensation effect, significantly improving the first coulombic efficiency of the material; (2) In-situ construction of LiF-based artificial SEI to improve interfacial stability: This invention creatively introduces a fluorine source into the spinning system, and induces an in-situ solid-phase reaction between the lithium source and the fluorine source during the carbonization process, uniformly generating LiF nanocrystals inside the silicon-carbon composite material and on the surface of nano-silicon. This in-situ generation method allows LiF to be precisely modified at the electrochemically active interface to form a dense, stable, and highly ionicly conductive artificial SEI layer. This SEI layer can effectively suppress the continuous decomposition of the electrolyte and the volume expansion effect of silicon, greatly improving the cycling stability of the material; (3) Synergistic effect of pre-lithiation-LiF artificial SEI: The pre-lithiation and the construction of LiF artificial SEI in this invention are not isolated steps, but rather produce a synergistic enhancement effect. Pre-lithiation reduces the lithium consumption for forming the initial SEI, while the artificial SEI provides a stable LiF protective layer for the pre-lithiated active material, preventing new irreversible capacity loss in subsequent cycles, and together ensuring the high efficiency and stability of the electrode throughout its entire life cycle; (4) Process integration and structural advantages: The method of this invention integrates material synthesis, pre-lithiation, interface modification and one-dimensional nanostructure construction into one, and the process flow is simple and controllable. The resulting three-dimensional continuous fiber network not only provides excellent electron / ion conduction pathways, but its internal carbon matrix and uniformly distributed LiF together constitute an effective stress buffer system, further enhancing the structural integrity of the electrode. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the preparation method of the silicon-carbon composite fiber anode material of the present invention; Figure 2 SEM images of the silicon-carbon composite fiber anode material prepared in Example 1 of this invention are shown below; (a) Sample A before carbonization treatment with a scale bar of 5 μm; (b) Sample A before carbonization treatment with a scale bar of 2 μm; (c) Sample A. Figure 3 The images shown are TEM images and corresponding elemental distribution mapping diagrams of the silicon-carbon composite fiber anode material prepared in Example 1 of this invention; wherein, (a) is a TEM image; (b) is an overlay of elemental distribution mapping diagrams; (c) is a C elemental distribution mapping diagram; (d) is an O elemental distribution mapping diagram; (e) is an F elemental distribution mapping diagram; and (f) is a Si elemental distribution mapping diagram. Figure 4 This is a graph showing the electrochemical performance of sample A after it was assembled into a battery according to Example 1 of the present invention. Figure 5 This is a graph showing the electrochemical performance of sample B after it was assembled into a battery in Example 2 of the present invention. Figure 6 This is a graph showing the electrochemical performance of sample C (Comparative Example 1) assembled into a battery according to the present invention. Figure 7 This is a graph showing the electrochemical performance of sample D (Comparative Example 2) assembled into a battery according to the present invention. Figure 8 This is a graph showing the electrochemical performance of sample E (Comparative Example 3) assembled into a battery according to the present invention. Detailed Implementation

[0023] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved herein can be purchased commercially or prepared by known methods.

[0024] To address the technical problems mentioned in the background section, this invention provides a silicon-carbon composite fiber anode material based on pre-lithiation and in-situ lithium fluoride interface modification, its preparation method, and its applications. This invention achieves preliminary pre-lithiation of nano-silicon through mechanical ball milling and cleverly introduces lithium and fluorine sources into the electrospinning precursor solution. During subsequent heat treatment, deep pre-lithiation is achieved, and the material reacts with the fluorine source, generating uniform LiF nanocrystals in situ within and on the surface of the silicon-carbon fibers, thus constructing a stable artificial SEI. The preparation method of this invention achieves a dual synergistic effect of pre-lithiation compensating for lithium consumption and suppressing side reactions with the LiF-based artificial SEI, ultimately yielding a silicon-carbon anode material with excellent overall performance.

[0025] The following examples and comparative models further illustrate this point.

[0026] Example 1 A method for preparing silicon-carbon composite fiber anode materials based on pre-lithiation and in-situ lithium fluoride interface modification, such as... Figure 1 As shown, it includes the following steps: (1) Place 2.0g of nano-silicon powder and 0.2g of Li2CO3 powder in a ball mill jar and ball mill for 4h under argon protection to obtain a composite powder of pre-lithiated silicon and lithium source; (2) Dissolve 1g of polyacrylonitrile (PAN) in 9g of N,N-dimethylformamide (DMF) and stir for 10h. Then add 0.5g of the composite powder obtained in step (1) and 0.05g of fluoroethylene carbonate (FEC) to the solution. Continue stirring for 12h to obtain a uniform and viscous spinning solution; (3) The spinning solution was transferred to a 10mL syringe for electrospinning, and the composite fiber precursor membrane was collected on the roller receiver. The parameters of electrospinning were: feed rate 0.02mL / min, receiving distance 15cm, and voltage 19kV. (4) The composite fiber precursor membrane is placed in a tube furnace and pre-oxidized by heating it to 250°C at 5°C / min in air atmosphere and holding it at that temperature for 2 hours. Then, under argon protection, the temperature is first raised to 500°C at 5°C / min and held for 1.5 hours, and then raised to 700°C and held for 1 hour for carbonization. After natural cooling, it is lightly ground to obtain the final product, which is denoted as "A".

[0027] Example 2 A method for preparing silicon-carbon composite fiber anode materials based on pre-lithiation and in-situ lithium fluoride interface modification, such as... Figure 1 As shown, it includes the following steps: (1) Place 2.0g of nano-silicon powder and 0.2g of Li2CO3 powder in a ball mill jar and ball mill for 4h under argon protection to obtain a composite powder of pre-lithiated silicon and lithium source; (2) Dissolve 1g of polyacrylonitrile (PAN) in 9g of N,N-dimethylformamide (DMF) and stir for 10h. Then add 0.5g of the composite powder obtained in step (1) and 0.05g of polyvinylidene fluoride (PVDF) to the solution. Continue stirring for 12h to obtain a uniform and viscous spinning solution; (3) The spinning solution was transferred to a 10mL syringe for electrospinning, and the composite fiber precursor membrane was collected on the roller receiver. The parameters of electrospinning were: feed rate 0.02mL / min, receiving distance 15cm, and voltage 19kV. (4) The composite fiber precursor membrane is placed in a tube furnace and pre-oxidized by heating it to 250°C at 5°C / min in air atmosphere and holding it at that temperature for 2 hours. Then, under argon protection, the temperature is first raised to 500°C at 5°C / min and held for 1.5 hours, and then raised to 700°C and held for 1 hour for carbonization. After natural cooling, it is lightly ground to obtain the final product, which is denoted as "B".

[0028] Comparative Example 1 The difference between this comparative example and Example 1 is that Li2CO3 powder is not added in step (1), and fluoroethylene carbonate (FEC) is not added in step (2). Other steps and parameters are the same as in Example 1. The specific steps are as follows: (1) 2.0g of nano-silicon powder was ball-milled for 4h under argon protection to obtain a composite powder of pre-lithiated silicon and lithium source; (2) Dissolve 1g of polyacrylonitrile (PAN) in 9g of N,N-dimethylformamide (DMF) and stir for 10h. Then add 0.5g of the powder obtained in step (1) to the solution. Continue stirring for 12h to obtain a uniform and viscous spinning solution; (3) The spinning solution was transferred to a 10mL syringe for electrospinning, and the composite fiber precursor membrane was collected on the roller receiver. The parameters of electrospinning were: feed rate 0.02mL / min, receiving distance 15cm, and voltage 19kV. (4) The composite fiber precursor membrane is placed in a tube furnace and pre-oxidized by heating it to 250°C at 5°C / min in air atmosphere and holding it at that temperature for 2 hours. Then, under argon protection, the temperature is first raised to 500°C at 5°C / min and held for 1.5 hours, and then raised to 700°C and held for 1 hour for carbonization. After natural cooling, it is lightly ground to obtain the final product, which is denoted as "C".

[0029] Comparative Example 2 The difference between this comparative example and Example 1 is that the amount of Li2CO3 powder added in step (1) is 0.3g, and fluoroethylene carbonate (FEC) is not added in step (2). Other steps and parameters are the same as in Example 1. The specific steps are as follows: (1) Place 2.0g of nano-silicon powder and 0.3g of Li2CO3 powder in a ball mill jar and ball mill for 4h under argon protection to obtain a composite powder of pre-lithiated silicon and lithium source; (2) Dissolve 1g of polyacrylonitrile (PAN) in 9g of N,N-dimethylformamide (DMF) and stir for 10h. Then add 0.5g of the composite powder obtained in step (1) to the solution. Continue stirring for 12h to obtain a uniform and viscous spinning solution; (3) The spinning solution was transferred to a 10mL syringe for electrospinning, and the composite fiber precursor membrane was collected on the roller receiver. The parameters of electrospinning were: feed rate 0.02mL / min, receiving distance 15cm, and voltage 19kV. (4) The composite fiber precursor membrane is placed in a tube furnace and pre-oxidized by heating it to 250°C at 5°C / min in air atmosphere and holding it at that temperature for 2 hours. Then, under argon protection, the temperature is first raised to 500°C at 5°C / min and held for 1.5 hours, and then raised to 700°C and held for 1 hour for carbonization. After natural cooling, it is lightly ground to obtain the final product, which is denoted as "D".

[0030] Comparative Example 3 The difference between this comparative example and Example 1 is that Li2CO3 powder is not added in step (1). Other steps and parameters are the same as in Example 1. The specific steps are as follows: (1) 2.0g of nano-silicon powder was ball-milled for 4h under argon protection to obtain a composite powder of pre-lithiated silicon and lithium source; (2) Dissolve 1g of polyacrylonitrile (PAN) in 9g of N,N-dimethylformamide (DMF) and stir for 10h. Then add 0.5g of the powder obtained in step (1) and 0.05g of fluoroethylene carbonate (FEC) to the solution. Continue stirring for 12h to obtain a uniform and viscous spinning solution; (3) The spinning solution was transferred to a 10mL syringe for electrospinning, and the composite fiber precursor membrane was collected on the roller receiver. The parameters of electrospinning were: feed rate 0.02mL / min, receiving distance 15cm, and voltage 19kV. (4) The composite fiber precursor membrane is placed in a tube furnace and pre-oxidized by heating it to 250°C at 5°C / min in air atmosphere and holding it at that temperature for 2 hours. Then, under argon protection, the temperature is first raised to 500°C at 5°C / min and held for 1.5 hours, and then raised to 700°C and held for 1 hour for carbonization. After natural cooling, it is lightly ground to obtain the final product, denoted as "E".

[0031] Performance testing and results analysis: The samples A before and after carbonization treatment in Example 1 were analyzed by scanning electron microscopy (SEM), and the results are as follows: Figure 2 As shown. By Figure 2It can be seen that sample A obtained after carbonization treatment has a continuous, interwoven fiber network structure, and the fibers contain particles.

[0032] The samples A obtained before and after carbonization treatment in Example 1 were subjected to transmission electron microscopy (TEM) and elemental distribution mapping analysis, and the results are as follows: Figure 3 As shown. By Figure 3 The distribution of Si, C, O, and F elements in the fiber and the presence of F element confirm the successful in-situ construction of LiF-based artificial SEI; indicating that nano-silicon particles and lithium fluoride nanocrystals are uniformly dispersed and encapsulated inside the carbon fiber.

[0033] Samples (A, B, C, D, E) from Examples 1-2 and Comparative Examples 1-3 were used as active materials and mixed with conductive carbon black and sodium alginate binder at a mass ratio of 7:2:1 to form a slurry. This slurry was coated onto copper foil (10 μm coating thickness), vacuum dried at 70°C, and cut to obtain circular electrode sheets with a diameter of 12 mm. Using a lithium metal sheet as the counter electrode, the battery was assembled in an argon-atmospheric glove box in the following order: negative electrode shell, spring, gasket, lithium sheet, separator, electrode sheet, and positive electrode shell. Electrolyte (1M lithium hexafluorophosphate (LiPF6)) was injected into both sides of the separator, with the solvent being a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC / DEC, volume ratio 1:1), and the additive being 20 wt% fluoroethylene carbonate (FEC). The battery was then sealed on a coin cell packaging machine to complete the assembly. The assembled battery underwent electrochemical performance testing, and the results are as follows: Figures 4-8 As shown. By Figures 4-8 It can be seen that at 500mA·g -1 At the specified current density, sample A achieved an initial efficiency of 91.2%, sample B 88.48%, while sample C achieved only 54.76%, sample D 72.68%, and sample E 68.54%. This indicates that pre-lithiation plays a dominant role in improving initial efficiency, while the introduction of a fluorine source also contributes slightly. Figures 4-8 It can be seen that at 500mA·g -1 After 200 cycles at the specified current density, sample A exhibited a capacity retention of 56.56%, sample B 37.77%, sample C 18.4%, sample D 17.4%, and sample E 23.01%. This fully demonstrates the crucial role of in-situ generated LiF artificial SEI in improving cycling stability.

[0034] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing silicon-carbon composite fiber anode material based on pre-lithiation and in-situ lithium fluoride interface modification, characterized in that, Includes the following steps: S1. The nano-silicon powder and the lithium source are mechanically ball-milled under an inert atmosphere to obtain a composite powder of pre-lithiated silicon and lithium source; wherein the mass ratio of the nano-silicon powder to the lithium source is 5:1-20:

1. S2. Dissolve the polymer carbon source in an organic solvent, then add the composite powder and fluorine source to it and mix well to obtain a spinning solution; S3. The spinning solution is electrospun to obtain a composite fiber precursor membrane; S4. The composite fiber precursor film is subjected to pre-oxidation stabilization treatment, and then carbonized under an inert atmosphere to obtain silicon-carbon composite fiber anode material; wherein, during the carbonization process, the lithium source and the fluorine source undergo an in-situ solid-phase reaction to generate LiF nanocrystals.

2. The method for preparing silicon-carbon composite fiber anode material based on pre-lithiation and in-situ lithium fluoride interface modification according to claim 1, characterized in that, In step S1, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium acetate; the ball milling time is 2-8 hours.

3. The method for preparing silicon-carbon composite fiber anode material based on pre-lithiation and in-situ lithium fluoride interface modification according to claim 1, characterized in that, In step S2, the polymer carbon source includes at least one of polyacrylonitrile, polyvinyl alcohol, polyacrylic acid, and polyvinylpyrrolidone; the organic solvent includes at least one of N,N-dimethylformamide and N-methylpyrrolidone; and the concentration of the polymer carbon source in the organic solvent is 5-15 wt%.

4. The method for preparing silicon-carbon composite fiber anode material based on pre-lithiation and in-situ lithium fluoride interface modification according to claim 1, characterized in that, In step S2, the fluorine source includes at least one of polyvinylidene fluoride, fluoroethylene carbonate, and polytetrafluoroethylene, and the concentration of the fluorine source in the spinning solution is 0.1-10 wt%.

5. The method for preparing silicon-carbon composite fiber anode material based on pre-lithiation and in-situ lithium fluoride interface modification according to claim 1, characterized in that, In step S2, the concentration of the composite powder in the spinning solution is 3-7 wt%.

6. The method for preparing silicon-carbon composite fiber anode material based on pre-lithiation and in-situ lithium fluoride interface modification according to claim 1, characterized in that, In step S4, the pre-oxidation stabilization treatment specifically involves heating the temperature to 200-280°C at a rate of 1-5°C / min in an oxygen-containing atmosphere and holding it at that temperature for 1-5 hours.

7. The method for preparing silicon-carbon composite fiber anode material based on pre-lithiation and in-situ lithium fluoride interface modification according to claim 1, characterized in that, In step S4, the carbonization process specifically involves: first heating the temperature to 500℃ at a rate of 2-10℃ / min and holding it at that temperature for 1-2 hours, then heating it to 700℃ and holding it at that temperature for 1-2 hours.

8. A silicon-carbon composite fiber anode material, characterized in that, The silicon-carbon composite fiber anode material is prepared by any one of the preparation methods described in claims 1-7. The silicon-carbon composite fiber anode material is composed of a three-dimensional conductive network formed by interwoven carbon fibers, and nano-silicon particles and lithium fluoride nanocrystals are uniformly dispersed and encapsulated inside the carbon fibers.

9. The silicon-carbon composite fiber anode material according to claim 8, characterized in that, The silicon content in the silicon-carbon composite fiber anode material is 10-50 wt%, and the LiF content in the silicon-carbon composite fiber anode material is 2-15 wt%.

10. A lithium-ion battery, characterized in that, The negative electrode active material of the lithium-ion battery is prepared by any one of the preparation methods described in claims 1-7.

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