Silicon-carbon composite material and preparation method thereof

Abstract

The invention provides a silicon-carbon composite material and a preparation method thereof. The preparation method comprises the following steps: S1, mixing raw materials including a magnesium source, a lithium source, a silicon source, a carbon source and a solvent to obtain a spinning solution; s2, carrying out spinning treatment on the spinning solution by utilizing an electrostatic spinning technology to obtain a fiber film; and S3, carrying out pre-oxidation treatment on the fiber film, and then sequentially carrying out sintering treatment and cooling treatment to obtain the silicon-carbon composite material. By adopting the scheme provided by the invention, the problem of high technological conditions required for preparing the silicon-carbon composite material with excellent rate capability in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the field of composite materials, and in particular to a silicon-carbon composite material and a preparation method thereof. Background Art

[0002] Nano silicon has the advantages of high theoretical capacity, low lithium deintercalation voltage platform, abundant reserves, environmental friendliness, and low cost, and has great development potential. However, it has the disadvantages of large volume change, poor cycle, and low initial efficiency during the charge and discharge process, which limits its commercial application. At present, the industry mostly uses solid-phase high-temperature coating or chemical deposition methods to carbon-coat nano silicon or silicon oxide to improve the electrochemical properties of silicon materials. Among them, there are problems of poor dispersion of nano silicon and uneven coating thickness in solid-phase high-temperature coating, and the chemical deposition method has strict requirements on process conditions and equipment, and its standardized use is limited, which is not conducive to industrial production.

[0003] In the prior art, electrospinning is a new processing method for preparing ultra-fine nanofibers. It can obtain fiber bodies of different structural states by mixing spinning precursors, adjusting spinning processes, changing spinning systems, etc. Compared with other methods, it is simple to operate, mild in conditions, and low in cost. CN111074382A successfully prepared silicon-carbon composite fiber materials using electrospinning technology. CN 113422009A uses a lithium source as a lithium supplement and uses electrospinning technology to prepare a silicon-carbon composite material with high first efficiency. The above methods can alleviate the volume expansion of the silicon negative electrode to a certain extent and improve the first coulomb efficiency of the material. However, it cannot effectively improve the problems of low conductivity and rate cycle difference of nano-silicon materials. CN110311121A uses atomic vapor deposition and vapor deposition to obtain magnesium-doped pre-lithiated silicon-carbon composite materials, which reduces irreversible capacity, improves first efficiency, and improves conductivity and rate performance. However, the process conditions for using this method are high and the standardized use is limited.

[0004] There is no effective solution to the above problems yet. Summary of the invention

[0005] The main purpose of the present invention is to provide a silicon-carbon composite material and a preparation method thereof, so as to solve the problem of high process conditions required for preparing silicon-carbon composite materials with good rate performance in the prior art.

[0006] In order to achieve the above objective, according to one aspect of the present invention, a method for preparing a silicon-carbon composite material is provided.

[0007] Specifically, the preparation method comprises:

[0008] Step S1, mixing raw materials including a magnesium source, a lithium source, a silicon source, a carbon source and a solvent to obtain a spinning solution; Step S2, spinning the spinning solution using an electrospinning technology to obtain a fiber film; Step S3, pre-oxidizing the fiber film and then sintering and cooling it in sequence to obtain a silicon-carbon composite material.

[0009] Specifically, in step S1, the weight ratio of the magnesium source in the spinning solution is 1% to 15%, and / or the weight ratio of the lithium source in the spinning solution is 5% to 25%, and / or the weight ratio of the silicon source in the spinning solution is 10% to 35%, and / or the weight ratio of the carbon source in the spinning solution is 5% to 35%;

[0010] And / or the lithium source is an inorganic lithium source and / or an organic lithium source, preferably the inorganic lithium source is selected from at least one of lithium carbonate, lithium sulfide, lithium nitrate, metallic lithium powder and lithium hydroxide, and preferably the organic lithium source is selected from at least one of lithium carboxymethyl cellulose, butyl lithium and phenyl lithium.

[0011] Specifically, the magnesium source is an inorganic magnesium source and / or an organic magnesium source, preferably the inorganic magnesium source is magnesium acetate and / or magnesium nitrate, and preferably the organic magnesium source is biscyclopentenyl magnesium and / or bismethylcyclopentadienyl magnesium.

[0012] Specifically, the solvent is selected from at least one of toluene, xylene, tetrahydrofuran and chloroform.

[0013] Specifically, the carbon source is selected from at least one of polyvinyl pyrrolidone, polystyrene, polycaprolactone and polyacrylonitrile.

[0014] Specifically, step S2 includes: sucking the spinning solution into a syringe; adjusting the distance between the spinneret of the syringe and the receiving plate; and performing a spinning process using the spinneret at room temperature to obtain a fiber film.

[0015] Specifically, the spacing is 10 cm to 25 cm, and / or the flow rate of the spinning solution is 0.3 to 1.5 mL / h, and / or the voltage condition of the spinning process is 15 to 35 kV.

[0016] Specifically, step S3 includes: after removing the fiber film from the surface of the receiving plate, pre-oxidizing the fiber film in an air atmosphere to obtain a pre-oxidized fiber sample; sintering the pre-oxidized fiber sample in an inert atmosphere to obtain a sintered fiber sample; naturally cooling the sintered fiber sample to room temperature to obtain a silicon-carbon composite material; wherein the preferred inert atmosphere is argon and / or a hydrogen-argon mixture.

[0017] Specifically, in the preparation method, the pre-oxidation treatment temperature is 180-250° C., and / or the pre-oxidation treatment time is 1.5-2.5 h, and / or the sintering treatment temperature is 1000-2500° C., and / or the sintering treatment time is 2-10 h.

[0018] According to another aspect of the present invention, a silicon-carbon composite material is provided. The silicon-carbon composite material is prepared by the above-mentioned preparation method.

[0019] By applying the technical solution of the present invention, firstly, the raw materials of magnesium source, lithium source, silicon source, carbon source and solvent are mixed to obtain a spinning solution, and the lithium source and magnesium source are added to obtain a spinning solution to reduce resistance and improve conductivity; secondly, the spinning solution is spun by electrostatic spinning technology to obtain a fiber film, which is simple to operate and the prepared silicon carbide fiber has a large specific surface area and porosity; finally, the fiber film is pre-oxidized and then sintered and cooled in sequence to obtain a silicon-carbon composite material. The technical solution of the present application solves the problem of high process conditions required for preparing silicon-carbon composite materials with good rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 A flow chart of an embodiment of a method for preparing a silicon-carbon composite material according to the present invention is shown. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art. In the accompanying drawings, for the sake of clarity, the thickness of the layers and regions may be enlarged, and the same reference numerals are used to represent the same devices, and thus their descriptions will be omitted.

[0026] according to Figure 1 As shown, a specific embodiment of the present application provides a method for preparing a silicon-carbon composite material.

[0027] Furthermore, the preparation method comprises:

[0028] Step S1, mixing raw materials including a magnesium source, a lithium source, a silicon source, a carbon source and a solvent to obtain a spinning solution;

[0029] Step S2, spinning the spinning solution using electrospinning technology to obtain a fiber film;

[0030] Step S3, pre-oxidizing the fiber film and then sintering and cooling it in sequence to obtain a silicon-carbon composite material.

[0031] Applying the technical solution of the present invention, first, the raw materials of magnesium source, lithium source, silicon source, carbon source and solvent are mixed to obtain a spinning solution, and the lithium source and magnesium source are added to obtain a spinning solution to reduce resistance and improve conductivity; secondly, the spinning solution is spun by electrostatic spinning technology to obtain a fiber film. This method is simple to operate, and the prepared silicon carbide fiber has a large specific surface area and porosity; finally, the fiber film is pre-oxidized and then sintered and cooled in sequence to obtain a silicon-carbon composite material. The technical solution of the present application is adopted to solve the problem of high process conditions required for preparing silicon-carbon composite materials with good rate performance.

[0032] Further, in step S1, the weight ratio of the magnesium source in the spinning solution is 1% to 15%, and / or the weight ratio of the lithium source in the spinning solution is 5% to 25%, and / or the weight ratio of the silicon source in the spinning solution is 10% to 35%, and / or the weight ratio of the carbon source in the spinning solution is 5% to 35%. The lithium source is an inorganic lithium source and / or an organic lithium source, preferably the inorganic lithium source is selected from at least one of lithium carbonate, lithium sulfide, lithium nitrate, metal lithium powder and lithium hydroxide, and preferably the organic lithium source is selected from at least one of lithium carboxymethyl cellulose, butyl lithium and phenyl lithium.

[0033] Preferably, lithium carbonate, lithium sulfide, lithium nitrate, metallic lithium powder and lithium hydroxide are all common inorganic lithium compounds, and they all contain high-purity lithium elements. When preparing lithium-ion batteries, it is necessary to select a high-purity inorganic lithium source to ensure the performance and stability of the battery. Therefore, at least one of lithium carbonate, lithium sulfide, lithium nitrate, metallic lithium powder and lithium hydroxide is preferably used as the inorganic lithium source raw material.

[0034] Optionally, the reason why the organic lithium source is selected from lithium carboxymethyl cellulose, butyl lithium and phenyl lithium is that: these three organic lithium sources have high reactivity and can undergo carbon-lithium bond reactions under milder conditions, thereby achieving the formation of carbon-carbon bonds; the reactivity of these three organic lithium sources can be regulated by different reaction conditions, making the reaction process more controllable, which is beneficial to the selectivity and purity of the product; these three organic lithium sources have different structural characteristics and can be used for different types of organic synthesis reactions, increasing the diversity and flexibility of the reaction; these three organic lithium sources have good solubility in common organic solvents, which is beneficial to their use in organic synthesis reactions.

[0035] Furthermore, the magnesium source is an inorganic magnesium source and / or an organic magnesium source, preferably the inorganic magnesium source is magnesium acetate and / or magnesium nitrate, and preferably the organic magnesium source is biscyclopentenyl magnesium and / or bismethylcyclopentadienyl magnesium.

[0036] Optionally, magnesium acetate and magnesium nitrate are easily soluble in water, easy to prepare solutions and suspensions, and convenient for production operation and use; compared with other magnesium sources, magnesium acetate and magnesium nitrate are relatively low in price, which can reduce production costs; magnesium acetate and magnesium nitrate both have high purity and stable chemical properties, so magnesium acetate and / or magnesium nitrate are selected as inorganic magnesium source raw materials in this embodiment.

[0037] Optionally, biscyclopentene magnesium and bismethylcyclopentadienyl magnesium are commonly used organomagnesium reagents, have high reactivity and selectivity, can effectively participate in various organic synthesis reactions; These two organomagnesium reagents are easy to prepare and store, easy to use, and suitable for various reaction conditions. Biscyclopentene magnesium and bismethylcyclopentadienyl magnesium are excellent in carbon-carbon bond formation reaction, nucleophilic reaction, reduction reaction, etc., and are helpful to prepare carbon silicon composite materials, so biscyclopentene magnesium and bismethylcyclopentadienyl magnesium are selected as organomagnesium source raw materials in the present embodiment.

[0038] Furthermore, the solvent is selected from at least one of toluene, xylene, tetrahydrofuran and chloroform. Toluene, xylene, tetrahydrofuran and chloroform all have good solubility and dissolubility, can effectively dissolve carbon source and silicon source, and are conducive to the preparation of carbon-silicon composite materials.

[0039] Furthermore, the carbon source is selected from at least one of polyvinyl pyrrolidone, polystyrene, polycaprolactone and polyacrylonitrile. Polyvinyl pyrrolidone, polystyrene, polycaprolactone and polyacrylonitrile are all common polymer materials, which are not easy to decompose at high temperatures, have high strength and rigidity, and are not easily corroded by chemical substances. Therefore, selecting these carbon sources as materials can ensure the stability and durability of the carbon-silicon composite material.

[0040] Furthermore, step S2 includes: sucking the spinning solution into a syringe; adjusting the distance between the spinneret of the syringe and the receiving plate; and performing a spinning process using the spinneret at room temperature to obtain a fiber film.

[0041] It should be noted that electrospinning is a method of spraying a polymer solution into fibers through a high-voltage electrostatic field. In this process, the receiving plate and the collector are two components that play different roles. The receiving plate and the collector work together to help achieve uniform spraying and formation of the fibers.

[0042] The receiving plate is located below the nozzle, receives the ejected fibers, supports the fibers and helps form a fiber web. The receiving plate is usually a plane with an insulating material, and the formation and arrangement of the fibers can be controlled by adjusting its height and angle. In this embodiment, the receiving plate can be made of polytetrafluoroethylene (PTFE) or silicone. These two materials have good high temperature resistance and smooth surface, can effectively receive the fibers generated in the electrospinning process, and ensure the uniformity and quality of the fibers. In addition, these two materials also have good corrosion resistance, which can ensure the long-term stability and durability of the receiving plate.

[0043] The collector is located below the receiving plate and is used to collect and fix the ejected fibers. The collector can be a flat plate collector, a drum collector, and a high-speed flywheel collector, wherein the flat plate collector can be horizontal or vertical.

[0044] Furthermore, the spacing is 10 cm to 25 cm, and / or the flow rate of the spinning solution is 0.3 to 1.5 mL / h, and / or the voltage condition of the spinning process is 15 to 35 kV.

[0045] The spacing refers to the distance between the spinneret and the receiving plate. Generally speaking, the larger the spacing, the longer the fiber stretching and solidification time, and the larger the fiber diameter; the smaller the spacing, the shorter the fiber stretching and solidification time, and the smaller the fiber diameter. Therefore, the spacing setting needs to be adjusted according to actual needs. In this embodiment, the spacing is set to 10cm to 25cm, which is the range obtained by the experimenters after multiple experiments. In this range, a fiber film is formed with a larger specific surface area and porosity.

[0046] The flow rate of the spinning solution refers to the speed at which the solution is ejected from the spinneret, and the size of the flow rate will directly affect the diameter and shape of the fiber. Generally speaking, the greater the flow rate, the smaller the diameter of the fiber will be, and the smaller the flow rate, the larger the diameter of the fiber will be. In this embodiment, the syringe is a plastic syringe with a stainless steel needle with an inner diameter of 0.3 to 1 mm, and the syringe is placed on a syringe pump to control the flow rate. The control flow rate is 0.3 to 1.5 mL / h, which has the best effect.

[0047] Voltage is a very important parameter in electrospinning, which affects the strength of the electrostatic field and the degree of fiber stretching. Generally speaking, the higher the voltage, the greater the degree of fiber stretching and the smaller the fiber diameter; the lower the voltage, the smaller the degree of fiber stretching and the larger the fiber diameter. According to the experimenters' repeated experiments, the voltage was set to 15-35kV, and the fiber film obtained had better performance.

[0048] Furthermore, step S3 includes: after removing the fiber film from the surface of the receiving plate, pre-oxidizing the fiber film in an air atmosphere to obtain a pre-oxidized fiber sample; sintering the pre-oxidized fiber sample in an inert atmosphere to obtain a sintered fiber sample; naturally cooling the sintered fiber sample to room temperature to obtain a silicon-carbon composite material; wherein the preferred inert atmosphere is argon and / or a hydrogen-argon mixture.

[0049] Optionally, argon and hydrogen-argon mixed gas have lower costs than other inert gases such as helium, krypton, etc., and argon and hydrogen-argon mixed gas are relatively easy to obtain. In this embodiment, argon and hydrogen-argon mixed gas are used as inert gases to reduce preparation costs.

[0050] Further, the pre-oxidation temperature is 180-250° C., the pre-oxidation time is 1.5-2.5 hours, the sintering temperature is 1000-2500° C., and / or the sintering time is 2-10 hours. The heating rate during this process is 2-5° C. / min.

[0051] Optionally, the temperature of the pre-oxidation treatment is set to 180-250°C. Within this temperature range, the rate of the oxidation reaction is high, and the pre-oxidation treatment can be completed in a shorter time, thereby improving production efficiency. The temperature of the oxidation reaction can also be effectively controlled to avoid deformation or burning of the material due to excessively high temperature.

[0052] Optionally, the pre-oxidation treatment time is set to 1.5 to 2.5 hours to ensure that the pre-oxidant in the composite material can fully react and decompose, effectively enhancing the material performance. If the treatment time is too short, the pre-oxidant may not be fully decomposed, affecting the performance of the subsequent composite material; while a long treatment time may cause over-oxidation, resulting in a decrease in material performance. Therefore, setting the pre-oxidation treatment time within the range of 1.5 to 2.5 hours is the range obtained by the experimenters after multiple experiments.

[0053] Optionally, sintering is a process of heating and cooling a material to form a solid structure. In this embodiment, sintering can make the material particles more firmly bonded, improve the hardness, strength and wear resistance of the material; through sintering, the gaps between the material particles can be reduced, thereby improving the density and uniformity of the material; sintering can form a dense oxide layer or protective layer on the surface of the material, improving the material's antioxidant and corrosion resistance; sintering can change the material's grain structure and arrangement, and improve the material's thermal conductivity and electrical conductivity. In this embodiment, the sintering temperature is set to 1000-2500°C, and the sintering time is 2-10h, which is the range obtained by the experimenters after multiple experiments.

[0054] According to another embodiment of the present application, a method for preparing a silicon-carbon composite material is provided, and the steps are as follows:

[0055] Step 1: Preparation of spinning precursor solution:

[0056] Each component is calculated according to the weight ratio of the solution concentration, wherein the weight ratio of Mg(NO3)2.4H2O is 15% in the solution, the weight ratio of CH3OOHLi is 15% in the solution, the weight ratio of polycarbosilane (PCS) is 35% in the solution, the weight ratio of polyacrylonitrile is 35% in the solution, and the organic solvent is chloroform. The mixed solution is continuously stirred at room temperature for 15 hours to form a uniform and stable spinning solution.

[0057] Step 2: Electrospinning:

[0058] The mixed solution was sucked into a plastic syringe with a stainless steel needle with an inner diameter of 0.6 mm, and the syringe was placed on a syringe pump to control the flow rate. The distance between the spinneret and the receiving plate was 20 cm, the solution flow rate was 0.8 mL / h, the voltage between the plates was 20 kV, and spinning was performed at room temperature to obtain a fiber film.

[0059] Step 3: Heat Treatment:

[0060] The polymer-containing fiber was removed from the receiving plate surface and placed in air atmosphere at 200°C for 2.5 hours, and pre-oxidized in air to make it cross-linked. Then the pre-oxidized fiber sample was treated at high temperature for 3 hours in an inert atmosphere, with the treatment temperature being 1500°C and the heating rate being 3°C / min, and then naturally cooled to room temperature, and finally Mg / Li / C / SiC composite nanofibers were obtained.

[0061] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0062] 1. The preparation method of this embodiment is simple. The raw materials of magnesium source, lithium source, silicon source, carbon source and solvent are mixed evenly, and the raw materials are obtained by electrospinning technology. The lithium-magnesium co-doped silicon-carbon composite material can be obtained by calcining. The method is simple, low-cost, and can be widely used.

[0063] 2. The lithium doped in the raw material is used as a lithium supplement. The lithium ions released by the lithium supplement during the charge and discharge process form lithium silicate, which reduces the irreversible capacity of the material and improves the initial efficiency. At the same time, the excess lithium ions are released to improve the material's cycle performance and power performance. The doped magnesium reduces impedance, improves conductivity or increases the lithium ion insertion and extraction rate of the material. The obtained carbon nanofiber has a large specific surface area, which can effectively shorten the transmission distance of lithium ions and improve the electrochemical performance of the material.

[0064] 3. Electrospinning is a new processing method for preparing ultrafine nanofibers. Compared with other methods, it is simple to operate, mild in conditions, and low in cost. Silicon carbide fibers prepared based on electrospinning technology have a large specific surface area and porosity, and can take advantage of the corrosion resistance and high temperature oxidation resistance of silicon carbide. It can also be designed and achieve better performance by adjusting the spinning process and changing the spinning system.

[0065] 4. The silicon-carbon composite material prepared by the present invention can not only effectively alleviate the volume expansion of silicon-based negative electrode materials, but also effectively block the direct contact between silicon nanowires and electrolyte, thereby greatly improving the cycle performance of lithium-ion batteries.

[0066] According to another aspect of the present invention, a silicon-carbon composite material is provided. The silicon-carbon composite material is prepared by the above-mentioned preparation method.

[0067] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0068] In addition to the above, it should be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this specification refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of the present invention.

[0069] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a silicon-carbon composite material, characterized in that: The preparation method comprises: Step S1, mixing raw materials including a magnesium source, a lithium source, a silicon source, a carbon source and a solvent to obtain a spinning solution; Step S2, spinning the spinning solution using electrospinning technology to obtain a fiber film; Step S3, performing a pre-oxidation treatment on the fiber film, followed by a sintering treatment and a cooling treatment, to obtain a silicon-carbon composite material.

2. The preparation method according to claim 1, characterized in that: In the step S1, the weight ratio of the magnesium source in the spinning solution is 1% to 15%, and / or the weight ratio of the lithium source in the spinning solution is 5% to 25%, and / or the weight ratio of the silicon source in the spinning solution is 10% to 35%, and / or the weight ratio of the carbon source in the spinning solution is 5% to 35%; And / or the lithium source is an inorganic lithium source and / or an organic lithium source, preferably the inorganic lithium source is selected from at least one of lithium carbonate, lithium sulfide, lithium nitrate, metallic lithium powder and lithium hydroxide, and preferably the organic lithium source is selected from at least one of lithium carboxymethyl cellulose, butyl lithium and phenyl lithium.

3. The preparation method according to claim 1 or 2, characterized in that: The magnesium source is an inorganic magnesium source and / or an organic magnesium source. Preferably, the inorganic magnesium source is magnesium acetate and / or magnesium nitrate. Preferably, the organic magnesium source is dicyclopentenyl magnesium and / or dimethylcyclopentadienyl magnesium.

4. The preparation method according to any one of claims 1 to 3, characterized in that The solvent is selected from at least one of toluene, xylene, tetrahydrofuran and chloroform.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The carbon source is selected from at least one of polyvinyl pyrrolidone, polystyrene, polycaprolactone and polyacrylonitrile.

6. The preparation method according to any one of claims 1 to 5, characterized in that The step S2 comprises: aspirating the spinning solution into a syringe; adjusting the distance between the spinneret of the syringe and the receiving plate; The spinning process is carried out using the spinneret at room temperature to obtain the fiber film.

7. The preparation method according to claim 6, characterized in that: The spacing is 10 cm to 25 cm, and / or the flow rate of the spinning solution is 0.3 to 1.5 mL / h, and / or the voltage condition of the spinning process is 15 to 35 kV.

8. The preparation method according to claim 6, characterized in that: The step S3 comprises: After removing the fiber film from the surface of the receiving plate, the fiber film is subjected to the pre-oxidation treatment in an air atmosphere to obtain a pre-oxidized fiber sample; Under an inert atmosphere, sequentially performing the sintering treatment on the pre-oxidized fiber sample to obtain a sintered fiber sample; The sintered fiber sample is naturally cooled to room temperature to obtain the silicon-carbon composite material; Among them, the inert atmosphere is preferably argon and / or a hydrogen-argon mixed gas.

9. The preparation method according to claim 8, characterized in that: The pre-oxidation treatment temperature is 180-250° C., and / or the pre-oxidation treatment time is 1.5-2.5 hours, and / or the sintering treatment temperature is 1000-2500° C., and / or The sintering time is 2 to 10 hours.

10. A silicon-carbon composite material, characterized in that: The silicon-carbon composite material is prepared by the preparation method according to any one of claims 1 to 9.

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