Preparation method of KB / Mo2C / CNT film and application of KB / Mo2C / CNT film in middle layer of lithium-sulfur battery

Abstract

The invention discloses a preparation method of a KB / Mo2C / CNT thin film and application of the KB / Mo2C / CNT thin film in an intermediate layer of a lithium-sulfur battery, and belongs to the technical field of lithium-sulfur batteries. The preparation method comprises the following steps: plating a metal molybdenum oxide target material on a CNT substrate in the form of nanoparticles, then carrying out KB loading and PVP dispensing, and finally carrying out carbon thermal reduction on MoO3 into Mo2C nanoparticles through Joule heat so as to form the KB / Mo2C / CNT film. The film material can be rapidly heated by Joule heat generated when current passes through the nanotube film, the method is especially suitable for synthesis of some materials needing high-temperature treatment, and the method has the advantages of being simple in equipment, convenient to operate, high in adaptability, high in preparation speed and the like. Compared with a traditional film coating method, the film coating technology is simple, rapid and low in cost, the thickness and size of the film can be accurately controlled, different application scenes are met, use of harmful chemical substances is reduced, and environmental protection is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of lithium-sulfur battery technology, specifically relating to a method for preparing a KB / Mo2C / CNT thin film and its application in the intermediate layer of a lithium-sulfur battery. Background Technology

[0002] In the field of secondary battery energy storage, lithium-sulfur batteries have become a highly promising next-generation energy storage system due to the abundant and inexpensive sulfur as the positive electrode active material, and the fact that the charge-discharge process is based on the multi-electron transfer reaction between sulfur and metallic lithium (S8 + 16Li + 16e- ↔ 8Li2S). However, in practical applications, they face three major problems: first, the severe volume expansion during the reaction process may cause safety risks; second, the final products of the positive and negative electrodes have extremely poor conductivity; and third, the shuttle effect caused by soluble lithium polysulfides (LiPSs) leads to irreversible loss of the positive electrode active material, directly limiting the battery's electrochemical performance.

[0003] To address these issues, researchers explored improvement strategies from multiple dimensions—from the source, middle stage, and end stage—forming four major technical directions: positive electrode host material design, electrolyte modification, interlayer design, and negative electrode protection. Among these, carbon materials (such as graphene, carbon nanotubes, and biomass carbon) are widely used in the preparation of positive electrodes and interlayers due to their high conductivity and high specific surface area. However, pure carbon materials are non-polar, only achieving limited physical adsorption and blocking of LiPSs, making it difficult to effectively solve the shuttle effect. Therefore, introducing polar materials has become crucial; metal oxides (TiO2, CeO2, MnO2, Co3O4, etc.) and metal sulfides (CoS2, etc.) have all been explored. Among molybdenum-based materials, MoO3, although rich in Mo-O bonds, has poor conductivity, which increases battery internal resistance and electrochemical polarization when used as an interlayer, thus affecting performance. Mo2C, on the other hand, possesses both excellent conductivity and abundant active sites, reducing battery internal resistance and efficiently adsorbing and converting LiPSs, making it a preferred interlayer material for lithium-sulfur batteries. However, there is currently no rapid preparation technology that can balance efficiency and performance for the preparation of Mo2C composite materials (such as KB / Mo2C / CNT films), and there is still a lack of mature solutions for their application in the intermediate layer of lithium-sulfur batteries.

[0004] Existing technologies typically include magnetron sputtering, chemical vapor deposition (CVD), and spin coating to prepare the aforementioned thin films. While magnetron sputtering can produce large-area films with uniform composition, easily controls the film's composition, and is suitable for industrial production, it requires expensive equipment and is time-consuming. CVD can prepare large-size, high-purity thin film materials, meeting the high-precision applications required for devices or research; however, it has low deposition efficiency, high toxicity, and is easily corrosive, requiring complex reaction gas delivery systems and precise temperature control systems, resulting in high equipment costs. Spin coating is simple to operate, but has low controllability and poor uniformity. It requires high substrate flatness and cleanliness, and defects and inhomogeneities are easily generated during spin coating. Therefore, synthesizing composite intermediates such as Mo2C using these methods suffers from drawbacks such as complex synthesis methods, high energy consumption, and long synthesis and carbonization times.

[0005] Therefore, developing a rapid method for efficiently preparing high-performance KB / Mo2C / CNT thin films and clarifying their application strategy in the intermediate layer of lithium-sulfur batteries is of great practical significance for breaking through existing technological bottlenecks and promoting the industrialization of lithium-sulfur batteries. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing KB / Mo2C / CNT thin films and their application in the interlayer of lithium-sulfur batteries. This invention utilizes the excellent electrical and thermal conductivity of carbon nanotube films to achieve rapid heating and deposition, depositing MoO3 target material as nanoparticles onto a substrate. A conductive material is then added, and the MoO3 is carbothermally reduced to Mo2C nanoparticles via Joule heating to form the KB / Mo2C / CNT thin film. The Joule heating generated by current passing through the nanotube film allows for rapid heating and quick preparation of thin film materials, making it particularly suitable for the synthesis of materials requiring high-temperature processing. Furthermore, it offers advantages such as simple equipment, convenient operation, strong adaptability, and fast preparation speed, making it suitable for the preparation of composite thin films under specific conditions. Compared to traditional deposition methods, the deposition technology of this invention is simple, fast, low-cost, and allows for precise control of film thickness and dimensions, meeting the precise requirements of different application scenarios for film specifications, reducing the use of harmful chemicals, and contributing to environmental protection.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing KB / Mo2C / CNT thin films is disclosed. This method utilizes the excellent electrical and thermal conductivity of carbon nanotube films to achieve rapid heating and film deposition. Molybdenum oxide target material is deposited on a CNT substrate in the form of nanoparticles, followed by KB loading and PVP drop casting. Finally, MoO3 is carbothermally reduced to Mo2C nanoparticles through Joule heating to form KB / Mo2C / CNT thin films.

[0008] Specifically, it includes the following steps: I. Loading of MoO3 raw material MoO3 powder was dispersed in deionized water to prepare a MoO3 particle dispersion, which was then filtered onto the surface of a carbon nanotube membrane and dried to complete the loading of MoO3.

[0009] II. Preparation of target MoO3 thin films using Joule heating When an electric current is applied to both ends of a carbon nanotube film loaded with MoO3, Joule heating is generated, instantly depositing the MoO3 target material loaded on the surface of the carbon nanotube film onto the substrate in the form of nanoparticles, thus forming a MoO3 thin film on the surface of the carbon nanotube film.

[0010] III. Preparation of KB / Mo2C / CNT Thin Films After filtering KB (Kejtien Black) onto the surface of the MoO3 film, a suitable amount of PVP (polyvinylpyrrolidone)-ethanol mixed solution was drop-coated, dried, and then connected to a copper electrode. After energizing, the surface of the carbon nanotube film quickly reached a certain temperature. After maintaining this temperature for a certain period of time, a highly conductive KB / Mo2C / CNT film was obtained.

[0011] Furthermore, the MoO3 can also be a sheet: placing the MoO3 sheet on the surface of the carbon nanotube film completes the loading of MoO3.

[0012] Furthermore, the MoO3 can also be replaced with a precursor that can carbothermally reduce oxides or metal salt solutions at high temperatures, such as tungsten oxide, molybdenum amine, etc.

[0013] Furthermore, the KB can be replaced with other materials with high specific surface area and excellent conductivity, such as acetylene black.

[0014] Furthermore, the PVP can be replaced with other substances that can decompose at high temperatures and reduce oxides, such as glucose, cellulose, starch, etc.

[0015] Furthermore, the carbon nanotube membrane described in step one is subjected to acid treatment before use, by soaking it in nitric acid solution for 3 hours.

[0016] Furthermore, the thickness of the carbon nanotube film mentioned in step one is 20 μm.

[0017] Further, the specific operation of step two is as follows: A carbon nanotube film loaded with MoO3 is placed between two electrodes in the Joule heating chamber, and the two ends of the carbon nanotube film are connected to the two electrodes respectively using conductive silver paste; another carbon nanotube film is placed on top of the MoO3-loaded carbon nanotube film, and the chamber is evacuated to 10... -1The vacuum is continuously pumped below Pa, and a constant voltage is applied between the two electrodes until the surface of the carbon nanotube film reaches above 600°C and is maintained for 2-3 seconds. After the voltage is removed, a metal film composed of nano MoO3 particles is uniformly deposited on the lower surface of the upper carbon nanotube film, thus obtaining a nano MoO3 film.

[0018] Furthermore, in step three, the surface temperature of the carbon nanotube film reaches above 600℃ after energization, and the holding time is 1-5 seconds.

[0019] Another object of the present invention is to provide the application of the KB / Mo2C / CNT film in the intermediate layer of lithium-sulfur batteries.

[0020] The beneficial effects of this invention are: Advantage 1: Simple and quick The Joule heating method proposed in this invention for rapid film deposition and carbothermal reduction, generated in a short time, is simpler, more efficient, and easier to operate compared to traditional vapor deposition. For vacuum evaporation and chemical vapor deposition, with the same substrate and raw materials, the target KB / Mo2C / CNT interlayer film can be formed within seconds of Joule heating, significantly improving efficiency compared to traditional deposition methods that take tens of minutes or even hours, and the carbonization time required.

[0021] Advantage 2: Low energy consumption By directly carbonizing the composite film through Joule heating, energy is applied directly to the target material, resulting in less heat loss and greater energy efficiency compared to traditional methods.

[0022] Advantage 3: Excellent battery performance The Mo2C film has abundant adsorption sites at its edges, effectively adsorbing LiPSs and suppressing the shuttle effect. The CNT film provides both attachment sites for MoO3 and synthesis sites for its carbonization, while also acting as a physical barrier against LiPSs. The highly conductive porous framework provides a large surface area and abundant pores to capture and provide a physical barrier for intermediate polysulfides. The assembled KB / Mo2C / CNT thin-film conductive composite interlayer battery exhibits excellent electrochemical performance. It can suppress the shuttle effect and accelerate LiPSs degradation. + Transfer, batteries assembled using this membrane as an interlayer in lithium-sulfur batteries still retain 426.5 mAh·g after 1000 cycles at 2C. –1 The discharge specific capacity, after 50 cycles at 0.5C and a 36-hour interruption, retained 95.2% of the capacity, and after 100 cycles, the discharge capacity remained at nearly 622.5mAh, demonstrating excellent electrochemical performance.

[0023] Advantage 4: Controllable film size From the perspective of film morphology, the film prepared by the method proposed in this invention has better particle size uniformity (concentrated size distribution), controllable size (sizes of a few nanometers, tens of nanometers, etc. can be adjusted), and adjustable film thickness (e.g., by controlling voltage or deposition time).

[0024] Advantage 5: Environmentally friendly The coating technology of this invention fully considers environmental factors in its design, and the materials and processes used minimize environmental impact. This technology reduces the use of harmful chemicals, contributing to green production and sustainable development. Attached Figure Description

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] Figure 1 This is a scanning electron microscope (SEM) image of the carbon nanotube film surface of the KB / Mo2C / CNT thin film prepared in Example 2.

[0027] Figure 2 (a) TEM image and (b) high-resolution TEM image of the KB / Mo2C / CNT thin film prepared in Example 2.

[0028] Figure 3 XPS Mo 3d spectra on the carbon nanotube film surface of the KB / Mo2C / CNT thin film prepared in Example 2.

[0029] Figure 4 Impedance diagram of a battery with the KB / Mo2C / CNT thin film prepared in Example 3 as the intermediate layer.

[0030] Figure 5 The image shows the CV curve of a battery with the KB / Mo2C / CNT thin film prepared in Example 3 as the intermediate layer.

[0031] Figure 6 The rate capability diagram shows the battery with the KB / Mo2C / CNT thin film prepared in Example 3 as the intermediate layer.

[0032] Figure 7 The images show the first charge-discharge cycles of the battery at different rates using the KB / Mo2C / CNT thin film prepared in Example 3 as the intermediate layer.

[0033] Figure 8 This is a cycle diagram of a battery with the KB / Mo2C / CNT thin film prepared in Example 3 as the intermediate layer, after 50 cycles and 36 hours of rest.

[0034] Figure 9 This is a long-cycle diagram at 2C for a battery with the KB / Mo2C / CNT thin film prepared in Example 3 as the intermediate layer. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1: A carbon nanotube membrane with dimensions of 1.5 × 3.5 cm and a thickness of 20 μm was immersed in nitric acid for 3 h, then washed three times with deionized water and dried. A MoO3 dispersion was prepared using MoO3 powder and deionized water. The above solution was then filtered onto the nitric acid-washed carbon nanotube membrane for loading. After drying, it was removed and placed between two electrodes in a Joule heating chamber. The two ends of the carbon nanotube membrane were connected to the two electrodes respectively using conductive silver paste. Another carbon nanotube membrane was placed on top of the carbon nanotube membrane loaded with MoO3 powder. Further, the chamber was evacuated to 10 °C. -1 A constant pressure was applied between the two electrodes at a pressure below Pa, maintaining a vacuum continuously. The surface temperature of the carbon nanotube film reached above 600°C and was maintained for 3 seconds. After removing the voltage, a metal film composed of nano-MoO3 particles was uniformly deposited on the lower surface of the upper carbon nanotube film, thus obtaining a nano-MoO3 film. Ketjen Black (KB) powder was weighed and added to anhydrous ethanol, and the mixture was magnetically stirred for 30 min to achieve uniform mixing. The mixture was then filtered onto the prepared MoO3 / CNTF. Polyvinylpyrrolidone (PVP) was added to 20 ml of anhydrous ethanol and sonicated for 2 h to obtain a uniform PVP-ethanol viscous mixture. This mixture was then loaded onto the KB-filtered MoO3 / CNT film. After drying, both ends of the sample were attached to two copper electrodes with conductive silver paste. The cavity was then evacuated to 10°C. -1 A vacuum was continuously maintained below Pa, and a constant voltage was applied between the two electrodes until the surface temperature of the carbon nanotube film reached above 600°C for 5 seconds. After removing the voltage, MoO3 was reduced to obtain Mo2C nanoparticles, ultimately yielding the KB / Mo2C / CNT thin film.

[0037] Example 2: A carbon nanotube membrane with dimensions of 1.5 × 3.5 cm and a thickness of 20 μm was immersed in nitric acid for 3 h, then washed three times with deionized water and dried. A MoO3 dispersion was prepared using MoO3 powder and deionized water. The above solution was then filtered onto the nitric acid-washed carbon nanotube membrane for loading. After drying, it was removed and placed between two electrodes in a Joule heating chamber. The two ends of the carbon nanotube membrane were connected to the two electrodes respectively using conductive silver paste. Another carbon nanotube membrane was placed on top of the carbon nanotube membrane loaded with MoO3 powder. Further, the chamber was evacuated to 10 °C. -1 A constant pressure was applied between the two electrodes at a pressure below Pa, maintaining a vacuum continuously. The surface temperature of the carbon nanotube film reached above 600°C and was maintained for 3 seconds. After removing the voltage, a metal film composed of nano-MoO3 particles was uniformly deposited on the lower surface of the upper carbon nanotube film, thus obtaining a nano-MoO3 film. Ketjen Black (KB) powder was weighed and added to anhydrous ethanol, and the mixture was magnetically stirred for 30 min to achieve uniform mixing. The mixture was then filtered onto the prepared MoO3 / CNT film. Polyvinylpyrrolidone (PVP) was added to 20 ml of anhydrous ethanol and sonicated for 2 h to obtain a uniform PVP-ethanol viscous mixture. This mixture was then loaded onto the KB-filtered MoO3 / CNT film. After drying, both ends of the sample were attached to two copper electrodes with conductive silver paste. The cavity was then evacuated to 10°C. -1 A vacuum was continuously maintained below Pa, and a constant voltage was applied between the two electrodes until the carbon nanotube film surface reached approximately 800°C, which was held for 3 seconds. After removing the voltage, MoO3 was reduced to Mo2C nanoparticles, ultimately yielding the KB / Mo2C / CNT film. Characterization is shown in [reference needed]. Figures 1-3 .

[0038] Example 3: A carbon nanotube membrane with dimensions of 1.5 × 3.5 cm and a thickness of 20 μm was immersed in nitric acid for 3 h, then washed three times with deionized water and dried. A MoO3 dispersion was prepared using MoO3 powder and deionized water. The above solution was then filtered onto the nitric acid-washed carbon nanotube membrane for loading. After drying, it was removed and placed between two electrodes in a Joule heating chamber. The two ends of the carbon nanotube membrane were connected to the two electrodes respectively using conductive silver paste. Another carbon nanotube membrane was placed on top of the carbon nanotube membrane loaded with MoO3 powder. Further, the chamber was evacuated to 10 °C. -1A vacuum was continuously maintained below 10⁻¹ Pa, and a constant pressure was applied between the two electrodes until the surface of the carbon nanotube film reached above 800°C for 2 seconds. After removing the voltage, a metal film composed of nano-MoO₃ particles was uniformly deposited on the lower surface of the upper carbon nanotube film, thus obtaining a nano-MoO₃ film. Ketjen Black (KB) powder was weighed and added to anhydrous ethanol, and the mixture was magnetically stirred for 30 min to mix evenly. The mixed solution was then filtered onto the prepared MoO₃ / CNT film. Polyvinylpyrrolidone (PVP) was added to 20 ml of anhydrous ethanol, and the mixture was sonicated for 2 h to obtain a uniform PVP-ethanol viscous mixture. This mixture was then loaded onto the KB-filtered MoO₃ / CNT film. After drying, both ends of the sample were attached to two copper electrodes with conductive silver paste. The cavity was evacuated to below 10⁻¹ Pa and maintained continuously. A constant pressure was applied between the two electrodes until the surface of the carbon nanotube film reached above 900°C for 2 seconds. After removing the voltage, MoO3 was reduced to obtain Mo2C nanoparticles, and finally KB / Mo2C / CNT thin film was obtained.

[0039] The pre-prepared positive electrode slurry was evenly coated onto aluminum foil and dried. After drying, it was transferred to an oven and dried for 12 hours. After removal, it was cut into positive electrode sheets. A 16mm diameter intermediate layer was cut from the prepared KB / Mo2C / CNT film using a cutting machine. The glove box was then adjusted, and the materials were placed inside. The assembly was performed in the following order from bottom to top: positive electrode shell, positive electrode sheet, electrolyte, intermediate layer, electrolyte, PP separator, electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell. After assembly, the battery was compacted and allowed to stand for one day. The battery prepared using the above method was tested using a battery tester and an electrochemical workstation. The battery electrochemical performance is shown in [link to electrochemical performance test]. Figures 4-9 .

[0040] Example 4: A carbon nanotube membrane with dimensions of 1.5 × 3.5 cm and a thickness of 20 μm was immersed in nitric acid for 3 h, then washed three times with deionized water and dried. A MoO3 dispersion was prepared using MoO3 powder and deionized water. The above solution was then filtered onto the nitric acid-washed carbon nanotube membrane for loading. After drying, it was removed and placed between two electrodes in a Joule heating chamber. The two ends of the carbon nanotube membrane were connected to the two electrodes respectively using conductive silver paste. Another carbon nanotube membrane was placed on top of the carbon nanotube membrane loaded with MoO3 powder. Further, the chamber was evacuated to 10 °C. -1A constant pressure was applied between the two electrodes at a pressure below Pa, maintaining a vacuum continuously. The surface temperature of the carbon nanotube film reached above 800°C and was maintained for 2 seconds. After removing the voltage, a metal film composed of nano-MoO3 particles was uniformly deposited on the lower surface of the upper carbon nanotube film, thus obtaining a nano-MoO3 film. Ketjen Black (KB) powder was weighed and added to anhydrous ethanol, and the mixture was magnetically stirred for 30 min to mix evenly. The mixture was then filtered and transferred to the prepared MoO3 / CNTF. Polyvinylpyrrolidone (PVP) was added to 20 ml of anhydrous ethanol and sonicated for 2 h to obtain a uniform PVP-ethanol viscous mixture. This mixture was then loaded onto the KB-filtered MoO3 / CNTF. After drying, both ends of the sample were attached to two copper electrodes with conductive silver paste. The cavity was then evacuated to 10°C. -1 A vacuum was continuously pumped at a pressure below Pa, and a constant voltage was applied between the two electrodes until the surface temperature of the carbon nanotube film reached approximately 1100°C, which was maintained for 1 second. After removing the voltage, MoO3 was reduced to obtain Mo2C nanoparticles, ultimately yielding the KB / Mo2C / CNT thin film.

[0041] The pre-prepared positive electrode slurry was evenly coated onto aluminum foil and allowed to dry. After drying, it was transferred to an oven and dried for 12 hours. The foil was then cut into positive electrode sheets. A 16mm diameter intermediate layer was cut from the prepared KB / Mo2C / CNT intermediate layer film using a cutting machine. The glove box was then adjusted, and the materials were placed inside. The assembly proceeded in the following order from bottom to top: positive electrode shell, positive electrode sheet, electrolyte, intermediate layer, electrolyte, PP separator, electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell. After assembly, the battery was compacted and allowed to stand for one day.

[0042] Example 5: The pre-prepared positive electrode slurry was evenly coated onto aluminum foil and allowed to dry. After drying, it was transferred to an oven and dried for 12 hours. The dried foil was then cut into positive electrode sheets. The glove box was then adjusted, and the materials were placed inside. The assembly proceeded in the following order from bottom to top: positive electrode shell, positive electrode sheet, electrolyte, PP separator, electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell. After assembly, the battery was compacted and allowed to stand for one day.

[0043] The above detailed embodiments provide a specific description of the analytical methods involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A method for preparing a KB / Mo2C / CNT thin film, characterized in that, Molybdenum oxide target material was deposited on CNT substrate in the form of nanoparticles, followed by KB loading and PVP drop casting. Finally, MoO3 was carbothermally reduced to Mo2C nanoparticles by Joule heating to form KB / Mo2C / CNT thin film.

2. The method for preparing a KB / Mo2C / CNT thin film according to claim 1, characterized in that, Includes the following steps: I. Loading of MoO3 raw material MoO3 powder was dispersed in deionized water to prepare a MoO3 particle dispersion, which was then filtered onto the surface of a carbon nanotube membrane and dried to complete the loading of MoO3. II. Preparation of target MoO3 thin films using Joule heating When an electric current is applied to both ends of a carbon nanotube film loaded with MoO3, Joule heating is generated, and the MoO3 target material loaded on the surface of the carbon nanotube film is instantly deposited onto the substrate in the form of nanoparticles, forming a MoO3 thin film on the surface of the carbon nanotube film. III. Preparation of KB / Mo2C / CNT Thin Films After KB was filtered onto the surface of the MoO3 film, an appropriate amount of PVP-ethanol mixed solution was drop-coated, dried, and then connected to a copper electrode. After energizing, the surface of the carbon nanotube film quickly reached a certain temperature. After maintaining this temperature for a certain period of time, a highly conductive KB / Mo2C / CNT film was obtained.

3. The method for preparing a KB / Mo2C / CNT thin film according to claim 2, characterized in that, The MoO3 is selected as a sheet material. The MoO3 sheet material is first cleaned, dried and then placed on the surface of the carbon nanotube membrane, thus completing the loading of MoO3.

4. The method for preparing a KB / Mo2C / CNT thin film according to claim 2, characterized in that, The MoO3 can be replaced with tungsten oxide or molybdenum amine; The KB can be replaced with acetylene black; The PVP can be replaced with any one of glucose, cellulose, or starch.

5. The method for preparing a KB / Mo2C / CNT thin film according to claim 2, characterized in that, The carbon nanotube membrane described in step one is subjected to acid treatment before use, by soaking it in nitric acid solution for 3 hours.

6. The method for preparing a KB / Mo2C / CNT thin film according to claim 2, characterized in that, The thickness of the carbon nanotube film mentioned in step one is 20 μm.

7. The method for preparing a KB / Mo2C / CNT thin film according to claim 2, characterized in that, Step two involves the following steps: A MoO3-loaded carbon nanotube film is placed between two electrodes in a Joule heating chamber, and conductive silver paste is used to connect both ends of the carbon nanotube film to the two electrodes. Another carbon nanotube film is placed on top of the MoO3-loaded carbon nanotube film, and the chamber is evacuated to 10°C. -1 A constant pressure is applied between the two electrodes at a pressure below Pa, and the surface of the carbon nanotube film reaches a temperature above 600°C for 2-3 seconds. After the voltage is removed, a metal film composed of nano MoO3 particles is uniformly deposited on the lower surface of the upper carbon nanotube film, thus obtaining a nano MoO3 film.

8. The method for preparing a KB / Mo2C / CNT thin film according to claim 2, characterized in that, In step three, the surface temperature of the carbon nanotube film reaches above 600℃ after energizing, and the holding time is 1-5 seconds.

9. The application of the KB / Mo2C / CNT thin film prepared by the preparation method according to any one of claims 1-8 in the intermediate layer of a lithium-sulfur battery.

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