CN113066951B - Preparation method and application of flexible self-supporting silicon/carbon nanotube film composite electrode - Google Patents

Preparation method and application of flexible self-supporting silicon/carbon nanotube film composite electrode Download PDF

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CN113066951B
CN113066951B CN202110269894.4A CN202110269894A CN113066951B CN 113066951 B CN113066951 B CN 113066951B CN 202110269894 A CN202110269894 A CN 202110269894A CN 113066951 B CN113066951 B CN 113066951B
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吴昊
李亚利
宋远强
耿浩
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Changzhou University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
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    • H01M4/0435—Rolling or calendering
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
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    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
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    • Y02E60/10—Energy storage using batteries

Abstract

The invention belongs to the technical field of lithium ion batteries, and discloses a preparation method and application of a flexible self-supporting silicon/carbon nanotube film composite electrode. Compared with the prior art, the method has high silicon load, and the silicon is more uniformly distributed in the carbon tube film, thereby being beneficial to improving the specific capacity and the cycle performance of the assembled lithium-silicon battery.

Description

Preparation method and application of flexible self-supporting silicon/carbon nanotube film composite electrode
Technical Field
The invention relates to a silicon-carbon cathode material, mainly relates to a silicon-carbon nanotube composite material and application thereof as a lithium ion battery cathode material, and belongs to the technical field of lithium ion batteries.
Background
In the existing secondary battery system, the lithium ion battery is the most competitive secondary battery at present, both from the viewpoint of development space and from the viewpoint of technical indexes such as service life, specific energy, operating voltage and self-discharge rate. With the continuous development of electronic technology, higher requirements are also put forward on lithium ion batteries, and higher energy density, better cycle life, better high and low temperature charge and discharge performance, better safety performance and the like are required, so that the positive electrode and negative electrode materials for the lithium ion batteries are required to be further developed and perfected.
At present, most of lithium ion battery negative electrode materials in practical application are carbon materials, such as natural graphite, graphitized mesocarbon microbeads and the like. In the non-carbon negative electrode material, silicon has extremely high theoretical specific capacity and a lower lithium storage reaction voltage platform, and the silicon is widely distributed in nature, and the content of the silicon in the crust is second to that of oxygen, so the silicon-based negative electrode material is a novel high-energy material with great development prospect. However, the electronic conductivity and ionic conductivity of silicon are low, resulting in poor kinetics of electrochemical reactions; the cycle stability of ordinary pure silicon is poor. And the phase change and volume expansion of silicon in the lithiation process can generate larger stress, so that the electrode is broken and pulverized, the resistance is increased, and the cycle performance is suddenly reduced.
In recent years, new concepts such as flexible mobile phones, electronic garments, wearable electronic products and medical equipment are continuously emerging, the research and development process of flexible electronic equipment is accelerated, and accordingly, the flexible battery technology becomes a new research hotspot. The most important point of the flexible battery is the composition of a flexible current collector and an active material with high specific volume, so that a truly flexible electrode material is prepared.
At present, silicon powder and a carbon source material are subjected to pyrolysis, ball milling and mixing to prepare a silicon-carbon composite material, so that the volume expansion phenomenon in the charging and discharging processes of a battery is relieved, and the cycle performance of the silicon-based material is improved. However, the existing silicon-carbon composite electrode and lithium-silicon battery have some disadvantages, such as the limitation of using the traditional copper foil as a current collector, the combination of the active substance and the copper foil is not tight enough, the active substance is easy to fall off, and the flexibility cannot be realized; the active substance can be combined with the current collector only by preparing slurry, and the steps are complicated. In the existing silicon-carbon nanotube composite technology, one type is to compound carbon nanotube powder and silicon powder and then pump-filter, roll and form a film by composite powder, and the flexible film obtained by the method has loose structure and poor bending resistance, and is difficult to realize the preparation of a large-area composite film; the other type is that the ready-made carbon nanotube film is compounded with silicon, a soaking method and a coating method are mostly adopted, the composite film obtained by the method has low silicon loading capacity, the silicon is not uniformly dispersed in the carbon nanotube film, and most of the silicon is only loaded on the surface layer of the carbon nanotube film. These problems affect the performance of the silicon-carbon nanotube composite film as an electrode material, and further solution is needed.
Therefore, how to prepare the flexible self-supporting silicon/carbon nanotube film composite electrode which is more favorable for improving the electrode performance is the focus of research of the invention.
Disclosure of Invention
The invention provides a preparation method of a flexible self-supporting silicon-carbon nanotube composite electrode and application of the flexible self-supporting silicon-carbon nanotube composite electrode as a negative electrode in a lithium silicon battery, aiming at the problems in the background art and the development requirements of flexible batteries and flexible electronic equipment. The continuous flexible carbon nanotube film is compounded with silicon in the preparation process, the unique three-dimensional network conductive structure of the carbon nanotube film is utilized, the silicon layer is coated in the carbon nanotube film, the silicon is uniformly distributed in the carbon nanotube network by combining compaction, and the loading capacity of the silicon is obviously higher than that of the prior art.
The technical scheme is as follows:
the invention relates to a preparation method of a flexible self-supporting silicon-carbon nanotube composite electrode and a flexible lithium-silicon battery, and the specific scheme is as follows:
(1) and (3) preparing a flexible carbon nanotube film. Ethanol, ferrocene and thiophene are mixed according to the mass ratio of 80: 1-2: 1, mixing and ultrasonically mixing for standby. Heating a vertical tube furnace to 1100-1200 ℃ in an argon atmosphere and keeping the temperature, introducing 400-1000 sccm hydrogen and argon in a volume ratio of 9:1 and keeping the temperature for 5min, injecting the ultrasonic solution into the tube furnace at an air inlet end by using a micro-injection pump at an injection speed of 10-20 ml/h under the condition, floating in a quartz furnace tube cavity in a top growth mode to generate multi-walled carbon nanotubes, crosslinking the multi-walled carbon nanotubes to form a semi-transparent cylindrical carbon nanotube continuous body (extremely thin and light), allowing the continuous body to float out of a tube opening under the drive of airflow, collecting the continuous body for 2-3 h by using an electric roller shaft to obtain a complete flexible carbon nanotube film (CNTf), wherein the flexible carbon nanotube film is formed by laminating thousands of continuous layers.
(2) And (3) modifying the silicon powder. Mixing commercial silicon powder (with the particle size of 1-2 microns) and expanded graphite, and then ball-milling for 2-4 hours to obtain modified commercial silicon powder which can float on water surface and does not settle; wherein the expanded graphite accounts for 3-7% of the total mass. Dispersing nano silicon powder (with the particle size of 50-100 nm) in ethanol, adding a surfactant (CTAB, DLS and the like) accounting for 1-5% of the mass of the silicon powder, magnetically stirring for 1-3 hours, drying and grinding to obtain modified nano silicon powder which can float on the water surface and does not settle.
The silicon powder is required to float on the water surface and not settle because the carbon tube continuum is required to contact and attach the silicon powder and then contract when meeting water, so that the silicon powder can be wrapped in the carbon tube continuum when the carbon tube continuum contracts, and if the carbon tube continuum is changed into silicon powder dispersion liquid, the adverse effects are two: firstly, the volume of the water collecting tank is large, and a large amount of silicon powder is wasted when dispersion liquid is prepared; secondly, the carbon tube continuum shrinks immediately when contacting the dispersion liquid, and then the effect of contacting the silicon in the coating dispersion liquid is greatly reduced, so that the loading capacity and uniformity of the silicon are affected. And if water is replaced by other oily solvent, the electrochemical performance of the silicon-carbon nanotube composite electrode, such as the reduction of conductivity, can be greatly influenced by the presence of oil.
(3) Preparing a flexible composite electrode: preparing a continuous cylindrical carbon nanotube continuous body by adopting the method in the step (1), enabling the continuous body to downwards float out of a pipe opening under the drive of airflow and collecting the continuous body by using an electric roller, enabling the lower part of the roller to be in contact with the water surface, enabling the modified silicon powder in the step (2) to float on the water surface, enabling the cylindrical carbon nanotube continuous body (extremely thin and semitransparent cylindrical) floating out of a furnace body under the drive of the airflow to adsorb the silicon powder floating on the water surface when the cylindrical continuous body contacts with the water surface when a continuous film starts to be collected, enabling the cylindrical continuous body to rapidly shrink into a film when meeting the water volume, wrapping the silicon powder, winding and laminating the carbon nanotube continuous body on the roller after loading the silicon powder through the continuous collection of the roller, and obtaining the silicon-carbon nanotube composite film with the thickness of 40-60 mu m after continuously collecting for 2-4 h. And (3) pressing the film for 3-5 times by using a roller press after drying to obtain the flexible composite electrode with the thickness of 20-25 mu m, wherein the load mass of the silicon powder is 40-60% of the total mass of the composite electrode. And cutting the flexible composite electrode into the required size of the pole piece for later use by using a cutting machine.
According to the invention, silicon powder is attached to each layer of carbon tube continuum in the process of winding and laminating thousands of extremely thin and light carbon tube continuum into a carbon nanotube film with a certain thickness, the ultra-large surface area of the semitransparent cylindrical structure of the carbon tube continuum just after the carbon tube continuum leaves a tube furnace is utilized to contact with the silicon powder floating on the water surface, the silicon powder is tightly wrapped in the silicon powder after the carbon tube continuum shrinks with water, and thousands of layers are wound and laminated on a roll shaft, so that a silicon-carbon nanotube composite film with an operable thickness (45-65 mu m) is finally directly obtained. The carbon tube continuum has the largest surface area when just drifted out of the tubular furnace mouth, which is most beneficial to the attachment of silicon powder, therefore, before the carbon tube film is laminated, the silicon powder is attached to the single-layer carbon tube continuum, which has higher silicon content, and the silicon is more evenly distributed and more tightly combined in the carbon tube network, which is beneficial to the improvement of the performance of the electrode material.
(4) Preparing a flexible lithium silicon battery: transferring the flexible composite electrode obtained in the step (3) to a glove box (H)2O<1ppm，O2<1ppm), the battery is packaged according to the sequence of an electrode shell, a flexible composite electrode, a diaphragm, a lithium sheet, a gasket and the electrode shell, and the electrolyte used is 1mol/L LiPF6And the volume ratio of the/EC + EMC + DMC is 1: 1, the diaphragm is a Polyethylene (PE)/polypropylene (PP) composite membrane diaphragm (Celgard2325), the flexible lithium-silicon battery is obtained after packaging, and the flexible lithium-silicon battery is stood for 24 hours to be tested.
And (5) testing the performance. The new Weir battery test system is used for testing the constant-current charge-discharge performance and the multiplying power performance of the battery, the voltage range is 0.01V-2V, the activation current density of the first two circles is 100mA/g, and the subsequent circulation current density is 200 mA/g.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a technical basis for preparing a continuous carbon nanotube film by using a Floating Catalytic Chemical Vapor Deposition (FCCVD) method, modified silicon powder floats on the water surface, a cylindrical carbon nanotube continuum (ultra-thin and semi-transparent cylindrical) is collected by rotating a roller to pass through water, the silicon powder floating on the water surface is uniformly and tightly wrapped in the cylindrical carbon nanotube continuum by using the ultra-large surface area and the self-adsorbability of the carbon nanotube continuum and the characteristic that the cylindrical carbon nanotube continuum shrinks sharply when meeting water, thousands of layers of carbon nanotube continuum attached with silicon are wound and laminated into a composite film with certain practical thickness after being continuously collected for hours, and finally the composite film material is rolled to obtain the flexible silicon-carbon nanotube composite electrode film material. According to the requirements, different silicon powders and different carbon sources can be adopted to prepare the flexible composite electrode. The method directly loads silicon in the continuous carbon tube film preparation and collection process, the process is stable, and continuous preparation can be realized. Compared with the traditional Si/Cu electrode, the method omits the slurry grinding and coating processes, has good flexibility and bending resistance, and obviously improves the specific capacity and the cycle performance. Compared with the existing silicon-carbon nanotube composite technology, the method has the advantages of higher silicon loading capacity (up to more than 50 percent), more uniform silicon distribution in the carbon tube film, and easier realization of the prepared large-area composite film, and has wider application range as the electrode of the flexible battery.
The electrode manufactured by the method can realize self-support without a current collector, so that the process of grinding and coating slurry in the traditional Cu/Si electrode is omitted, and the production efficiency of the battery is improved; the continuous flexible composite electrode film produced by the method has good flexibility, small quality, large film area, stable process, wide application range and easy realization of industrialization; the specific capacity and the cycle performance of the lithium silicon battery assembled by the composite electrode prepared by the method are superior to those of the lithium silicon battery of the traditional copper foil current collector; the method has the advantages of simple preparation process, low production cost and convenient popularization and application, and the prepared flexible lithium silicon battery has stable performance.
Drawings
FIG. 1 is a diagram of a flexible silicon/carbon nanotube composite film;
FIG. 2 is a diagram showing modified silica powder floating on water surface by adsorption of a carbon nanotube continuum;
FIG. 3 is a graph showing floatability of modified silicon powder in example 1;
FIG. 4 is SEM and EDS images of the flexible silicon/carbon nanotube composite electrode of example 1;
fig. 5 is a cyclic charge-discharge curve of the flexible silicon/carbon nanotube composite electrode in the lithium silicon battery of example 1.
Detailed Description
Example 1
(1) And (3) preparing modified silicon powder 1. Weighing 4.85g of commercial silicon powder and 0.15g of expanded graphite, pouring the mixture into a ball milling tank, and adding a proper amount of ethanol. And putting the mixture into a ball mill for ball milling for 2-4 h. And pouring the suspension into a beaker after the ball milling is finished, transferring the suspension into an oven at 80 ℃ for drying for 12 hours, and grinding the suspension into powder to obtain the modified silicon powder.
(2) And (3) preparing the flexible silicon/carbon nanotube composite membrane. 0.987g of ferrocene and 0.49g of thiophene are weighed and poured into 50ml of ethanol for 30min of ultrasound. The mixed solution is sucked into a syringe for standby. Heating the vertical tubular furnace to 1150-1190 ℃ in the argon atmosphere, introducing hydrogen at the speed of 900sccm, introducing argon at the speed of 100sccm, keeping the speed for more than 5min, injecting the ultrasonic solution into the tubular furnace at the gas inlet end by using a micro injection pump at the injection speed of 15ml/h under the condition of keeping the condition, generating a continuous tubular carbon nanotube continuum in the quartz furnace tube after a moment, and drifting out of the tube opening along with gas flow to collect the continuous tubular carbon nanotube continuum by using an electric roller shaft. Meanwhile, pouring the modified silicon powder obtained in the step (1) into a water tank below the roller shaft, enabling the silicon powder to float on the water surface, collecting the carbon nanotube continuous body adhered with the silicon powder by the roller shaft, and continuously collecting for 2 hours to obtain the flexible silicon/carbon nanotube composite film with the thickness of 45-55 microns.
(3) And (4) preparing a flexible electrode. And (3) flatly paving the flexible silicon/carbon nanotube composite membrane obtained in the step (2) on a glass plate, transferring the flexible silicon/carbon nanotube composite membrane to an oven with the temperature of 80-90 ℃ for drying for 12h, then transferring the flexible silicon/carbon nanotube composite membrane to a vacuum drying oven with the temperature of 60-70 ℃ for drying for 12h, pressing the membrane for 3-5 times by using a roller press after drying to obtain the flexible silicon/carbon nanotube composite electrode with the thickness of 23-25 mu m, and weighing and comparing the flexible silicon/carbon nanotube composite electrode with the silicon loading mass of 53%. Cutting the flexible composite electrode into pieces by using a cutting machine
Figure BDA0002973856530000051
The round flexible pole piece is reserved.
(4) And (5) packaging the battery. Transferring the pole piece obtained in the step (3) to a glove box (H)2O<1ppm，O2<1ppm) in the electrode shell, softThe battery is packaged by sequentially arranging a composite electrode, a diaphragm, a lithium sheet, a gasket and an electrode shell, and the electrolyte used is 1mol/L LiPF6The volume ratio of the/EC + EMC + DMC (1: 1), the diaphragm is a Polyethylene (PE)/polypropylene (PP) composite membrane diaphragm (Celgard2325), the electrode shell is a CR2025 battery shell, the lithium silicon battery with the flexible electrode is obtained after packaging, and the lithium silicon battery is tested after standing for 24 hours.
(5) And (5) testing the performance. And (4) carrying out constant-current charge and discharge performance test on the battery obtained in the step (4) by using a new Wille battery test system, wherein the voltage range is 0.01V-2V, the activation current density of the first two circles is 100mA/g, and the subsequent circulation current density is 200 mA/g. Test results show that the first discharge capacity can reach 3002mAh/g, the second circle specific capacity is reduced to 1233mAh/g, after circulating for 150 circles, the specific capacity is kept at 740mAh/g, and the coulomb efficiency is stabilized at 99.8%. The cycling stability is superior to other silicon carbon nanotube composite cathode batteries. Fig. 4 is a SEM image and an EDS image of the flexible silicon/carbon nanotube composite electrode. As can be seen from fig. 4, the silicon particles are attached to the pores of the carbon tube film, the carbon tubes are also inserted into the surface of the carbon tube film, the silicon particles are tightly bonded to the nano-silicon, and the silicon particles are distributed in the carbon tube network more uniformly.
Example 2
(1) And (3) preparing modified silicon powder 2. Adding 80ml of ethanol into a beaker, heating to 40 ℃ and keeping, starting magnetic stirring, slowly adding 0.25g of CTAB (cetyl trimethyl ammonium bromide) powder, after completely dissolving, adding 5g of nano silicon powder, magnetically stirring for 2 hours, drying and grinding to obtain the modified silicon powder which can float on the water surface and does not settle.
(2) And (3) preparing the flexible silicon/carbon nanotube composite membrane. This step is the same as step (2) in example 1.
(3) And (3) preparing a flexible electrode. This procedure was the same as in the step (3) of example 1, and the amount of silicon supported was 45% after weighing comparison.
(4) And (5) packaging the battery. This step is the same as step (4) in example 1.
(5) And (5) testing the performance. The test conditions were the same as in example 1. Test results show that the first discharge capacity can reach 2530mAh/g, the second circle specific capacity is reduced to 1076mAh/g, after the battery is circulated for 150 circles, the specific capacity is kept at 820mAh/g, and the coulomb efficiency is stabilized at 99.8%. The cycling stability is superior to other silicon carbon nanotube composite cathode batteries.
Comparative example 1
(1) And (3) preparing a flexible carbon nanotube film. Mixing ethanol, ferrocene and thiophene according to the mass ratio, and ultrasonically mixing for later use. Heating a vertical tube furnace to 1150 ℃ in an argon atmosphere, introducing 900sccm hydrogen and 100sccm argon according to a volume flow ratio of 9:1, keeping the mixture for 5min, injecting an ultrasonic solution into the tube furnace at an air inlet end by using a micro-injection pump at an injection speed of 10-20 ml/h, floating in a quartz furnace tube cavity in a top growth mode to generate multi-walled carbon nanotubes, crosslinking the multi-walled carbon nanotubes to form a semi-transparent cylindrical carbon nanotube continuum (extremely thin and light), allowing the continuum to float out of a tube opening under the drive of airflow, and collecting the solution for 2-3 h by using an electric roller to obtain a complete flexible carbon nanotube film (CNTf). The obtained flexible carbon nanotube film was formed by laminating several thousands of continuous bodies.
(2) 3g of commercial silicon powder is dispersed in 50ml of aqueous solution, the aqueous solution is coated on the CNTf prepared in the step (1), after drying at 70 ℃ for 12h, the flexible composite electrode is cut into pieces by using a cutting machine
Figure BDA0002973856530000071
The round flexible pole piece is ready for use. The silicon carrying amount after weighing and comparison is only 18%, and the silicon powder is mainly concentrated on the surface of the carbon tube film and is easy to crack and fall off in the cutting process.
(3) And (7) packaging the battery. This step is the same as step (4) in example 1.
(4) And (5) testing the performance. The test conditions were the same as in example 1. The test result shows that after the battery is cycled to 30 circles, the specific capacity of the battery is reduced to 310mAh/g, and after the battery is cycled for 50 circles, the specific capacity is reduced to 105 mA/g. The cycle stability is poor.

Claims (3)

1. The application of the flexible self-supporting silicon-carbon nanotube film composite electrode as a negative electrode in a lithium silicon battery is characterized in that the preparation method of the flexible self-supporting silicon-carbon nanotube film composite electrode comprises the following steps:
(1) firstly, modifying silicon powder to obtain modified silicon powder which floats on the surface of a liquid and does not settle;
the modification method comprises the following steps: mixing silicon powder with the particle size of 1-2 microns with expanded graphite, and then ball-milling for 2-4 hours to obtain modified silicon powder which floats on the water surface and does not settle;
or dispersing 50-100 nm nano silicon powder in ethanol, adding a surfactant, magnetically stirring for 1-3 h, drying, and grinding to obtain modified silicon powder floating on the water surface and not settling;
(2) weighing ferrocene and thiophene, ultrasonically mixing in ethanol to obtain a mixed solution, and sucking the mixed solution into an injector for later use;
(3) heating the tubular furnace to 1150-1190 ℃ in an argon atmosphere, keeping for more than 5min through hydrogen and argon mixed gas, injecting the mixed liquid into the tubular furnace at an injection speed of 10-20 ml/h by using a micro-injection pump at an air inlet end, enabling a continuous cylindrical carbon nano tube continuous body to appear in the quartz furnace tube, enabling the continuous cylindrical carbon nano tube continuous body to float out of a tube opening along with air flow, collecting the continuous cylindrical carbon nano tube continuous body by using an electric roller, pouring the modified silicon powder obtained in the step (1) into a water tank below the roller before collection, enabling the silicon powder to float on the water surface, collecting the carbon nano tube continuous body adhered with the silicon powder by the roller during collection, obtaining a flexible self-supporting silicon-carbon nano tube composite membrane after continuously collecting for a period of time, and pressing the membrane by using a roller press after drying to obtain a flexible composite electrode, wherein the load mass fraction of the silicon powder is 40% -60%.
2. The application of the flexible self-supporting silicon-carbon nanotube film composite electrode as a negative electrode in a lithium silicon battery according to claim 1 is characterized in that the mass ratio of ferrocene, thiophene and ethanol in the step (2) is 1-2: 1: 80.
3. The use of the flexible self-supporting silicon-carbon nanotube film composite electrode as a negative electrode in a lithium silicon battery according to claim 1, wherein the volume ratio of hydrogen to argon in the mixed gas in the step (3) is 9: 1.
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