A manganese oxide-carbon composite fiber electrode yarn and a preparation method and application thereof

Abstract

The application relates to the field of electrochemistry, in particular to a manganese oxide-carbon composite fiber electrode yarn and a preparation method and application thereof. The method comprises the following steps: S1, uniformly mixing a carbon source, a manganese source and an organic solvent to form a spinning solution; S2, obtaining carbon fibers, taking the carbon fibers as core yarns, and preparing composite nanofiber yarns coated with the carbon fibers by a conjugate electrospinning method; and S3, after twisting treatment of a plurality of the composite nanofiber yarns, performing pre-oxidation treatment in an air atmosphere, and then performing carbonization treatment in an inert atmosphere to obtain the manganese oxide-carbon composite fiber electrode yarn. By adopting the conjugate electrospinning technology, the active component can be directly coated and integrally formed on the surface of the conductive carbon fiber, the use of a binder is avoided, so that the interface resistance can be significantly reduced, and the utilization rate of the active substance and the stability of the electrode structure are improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to a manganese oxide-carbon composite fiber electrode yarn, its preparation method, and its application. Background Technology

[0002] In the field of energy storage, supercapacitors, with their advantages of high power density, rapid charge and discharge, and long cycle life, have become the development direction of high-performance energy storage devices. Electrode materials, as a core component of supercapacitors, are crucial for improving their performance. In recent years, manganese oxide-based materials have attracted much attention in supercapacitor electrode material research due to their high theoretical capacity. However, these materials suffer from poor conductivity and insufficient cycle stability, limiting their application. In contrast, carbon materials exhibit good conductivity, but their capacity is relatively limited, making it difficult to meet the high energy density requirements of high-performance supercapacitors.

[0003] Traditional techniques typically involve compounding manganese oxide-based materials with carbon materials to form a powder, which is then mixed with a binder to fabricate a rigid electrode sheet. This aims to simultaneously improve the electrode sheet's capacity, conductivity, and cycle stability. However, this method is complex, leading to increased production costs and manufacturing difficulties. Furthermore, the use of binders not only reduces the utilization rate of the active material but also hinders ion and electron transport, thereby increasing internal resistance. Simultaneously, it results in poor electrode flexibility, making it unsuitable for use in flexible electronic devices. Moreover, the poor flexibility of the resulting electrode sheet fails to meet the requirements for electrode flexibility in flexible electronic devices, limiting the further application of supercapacitors in the field of flexible electronics.

[0004] Currently, some research attempts have focused on preparing fibrous electrode materials, such as flexible electrode materials prepared by loading active materials onto the surface of carbon fibers. However, these methods often suffer from problems such as uneven active layer, weak bonding between the active layer and the fiber substrate, and insufficient fiber strength and spinnability. This makes it difficult to directly weave these into practically usable electrode yarns, failing to meet the requirements for mechanical properties and processability in actual production. Therefore, there is an urgent need to develop a novel method for preparing electrode yarns. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing manganese oxide-carbon composite fiber electrode yarn. By using carbon fiber as the core yarn, spinning a spinning solution containing manganese source using a conjugate electrospinning method, and then performing a twisting treatment, manganese oxide-carbon composite fiber electrode yarn is produced, which endows it with high electrochemical performance, good mechanical strength and excellent weavability.

[0006] This application also provides a manganese oxide-carbon composite fiber electrode yarn, which has high specific capacitance and excellent conductivity.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing manganese oxide-carbon composite fiber electrode yarn, comprising the following steps: S1. A carbon source, a manganese source, and an organic solvent are mixed evenly to form a spinning solution; wherein the carbon source is an unsaturated polymer, and the manganese source is any one or more of a manganese salt or a manganese-containing organic compound. S2. Obtain carbon fiber, and use the carbon fiber as the core yarn to prepare a composite nanofiber yarn coated with carbon fiber by using a conjugate electrospinning method. S3. After twisting the multiple strands of the composite nanofiber yarn, pre-oxidize it in an air atmosphere, and then carbonize it in an inert atmosphere to obtain manganese oxide-carbon composite fiber electrode yarn.

[0008] Further, in step S1, the mass fraction of the manganese source in the spinning solution is any value between 25wt% and 35wt%, and the mass fraction of the polymer is any value between 10wt% and 20wt%.

[0009] Furthermore, the average molecular weight of the polymer is any value between 120kDa and 180kDa.

[0010] Further, the polymer is any one of polyacrylonitrile, acrylonitrile-methyl acrylate copolymer, acrylonitrile-methyl acrylate-sodium propylene sulfonate copolymer, and acrylonitrile-vinyl chloride copolymer, and the manganese-containing organic compound is any one of manganese acetate, manganese naphthenate, and manganese formate.

[0011] Furthermore, in step S2, the carbon fiber is a high-modulus carbon fiber bundle with a filament bundle of 3k, 6k, or 12k.

[0012] Furthermore, in step S2, the applied positive voltage is any value between 5kV and 7kV, the negative voltage is any value between 6kV and 8kV, the temperature is limited to any value between 10℃ and 30℃, and the relative humidity is limited to any value between 25% and 35%.

[0013] Further, in step S3, the twisting process involves applying a twist of 150 twists / meter to 200 twists / meter to the multiple strands of the composite nanofiber yarn, causing the multiple strands of the composite nanofiber yarn to intertwine around their axial direction, thereby achieving plying.

[0014] Furthermore, in step S3, during the pre-oxidation treatment, the treatment temperature is increased from room temperature to a range of 250°C to 320°C, and the heating rate is any value between 1°C / min and 5°C / min. During the carbonization process, the temperature is increased from room temperature to any value between 500℃ and 1000℃, and the heating rate is any value between 1℃ / min and 5℃ / min.

[0015] This application also provides a manganese oxide-carbon composite fiber electrode yarn, which is prepared by the above-described preparation method.

[0016] This application also provides the application of the above-mentioned manganese oxide-carbon composite fiber electrode yarn as a positive electrode material in supercapacitors.

[0017] The beneficial effects of this invention are as follows: This application provides a method for preparing manganese oxide-carbon composite fiber electrode yarn. By employing conjugate electrospinning technology, the active components are directly coated and integrally formed on the surface of conductive carbon fibers, avoiding the use of binders. This significantly reduces interfacial resistance and improves the utilization rate of active materials and the stability of the electrode structure. Furthermore, by employing conjugate electrospinning technology, in-situ coating is achieved, ensuring that the active components are uniformly distributed on the surface of the carbon fibers and tightly bonded to them. This facilitates rapid charge transfer and improves the charge-discharge efficiency and cycle stability of the electrode. Simultaneously, the twisting process further enhances the mechanical entanglement and electrical contact of the electrode yarn, improving the overall mechanical strength and structural integrity of the electrode yarn.

[0018] The manganese oxide-carbon composite fiber electrode yarn prepared by the method provided in this application not only possesses high specific capacitance and conductivity but also exhibits flexibility, continuity, and weavability. It is suitable for self-supporting electrodes and can be directly integrated into fabrics, providing broader application possibilities for flexible electronic devices. The interwoven fiber structure and excellent porosity of this electrode yarn facilitate electrolyte wetting and ion diffusion, thereby significantly improving the electrochemical performance of supercapacitors, increasing their energy density and power density, and enhancing their feasibility and longevity in practical applications.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This refers to the conjugate electrospinning method shown in step S2 of Embodiment 1 of the present invention; Figure 2 This is a photograph of a 10cm long manganese oxide-carbon fiber composite electrode yarn obtained in Example 1 of the present invention. Figure 3 This is a scanning electron microscope image of the manganese oxide-carbon composite fiber electrode yarn obtained in Example 1 of the present invention; Figure 4 The graphs are obtained by performing electrolyte cyclic voltammetry (CV) tests on the manganese oxide / carbon composite fiber electrode yarn and core yarn obtained in Example 1 of the present invention in 1M Na2SO4. Figure 5 The graph shows the electrolyte cyclic voltammetry test results obtained by the manganese oxide / carbon composite fiber electrode yarn obtained in Example 1 of the present invention in 1M Na2SO4 at different scan rates. Figure 6 The graph shows the manganese oxide / carbon composite fiber electrode yarn obtained in Example 1 of this invention underwent electrolyte constant current charge-discharge (GCD) testing in 1M Na2SO4. Figure 7 The graph shows the electrolyte impedance spectroscopy (EIS) curve obtained by testing the manganese oxide / carbon composite fiber electrode yarn obtained in Example 1 of this invention in 1M Na2SO4. Figure label: 1. Composite nanofiber yarn; 2. Winder; 3. Positive electrode; 4. Negative electrode; 5. First syringe; 6. Second syringe; 7. Receiving device; 8. First solution jet; 9. Second solution jet. Detailed Implementation

[0021] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] A preferred embodiment of this application illustrates a method for preparing a manganese oxide-carbon composite fiber electrode yarn, comprising the following steps: S1. Mix the carbon source, manganese source and organic solvent evenly to form a spinning solution; wherein, the carbon source is preferably an unsaturated polymer, and the manganese source is any one or more of manganese salts and manganese-containing organic compounds; S2. Obtain carbon fiber, and use carbon fiber as core yarn to prepare composite nanofiber yarn coated with carbon fiber by conjugate electrospinning method. S3. After twisting the multi-strand composite nanofiber yarn, pre-oxidize it in an air atmosphere, and then carbonize it in an inert atmosphere to obtain manganese oxide-carbon composite fiber electrode yarn.

[0023] In step S1, by uniformly mixing the carbon source, manganese source and organic solvent, it helps to ensure that the active components such as the carbon source and manganese source in the spinning solution are uniformly distributed on the conductive matrix (i.e. carbon fiber) in the subsequent processing, so that the active components and the conductive matrix are tightly bonded.

[0024] In step S2, by employing conjugate electrospinning technology, the active components can be directly and uniformly coated onto the conductive carbon fiber surface, achieving an integrated molding effect. Compared to the traditional method of first compounding manganese oxide-based materials with carbon materials into powder, and then mixing them with a binder to form the electrode, this embodiment uses conjugate electrospinning technology, which avoids the use of binders, effectively reduces interfacial resistance, allows for smoother charge transfer within the electrode, and significantly improves the utilization rate of the active material. Simultaneously, the integrated molding structure gives the electrode better structural stability, making it less prone to structural damage during charging and discharging, thus helping to extend the electrode's lifespan.

[0025] In step S3, the twisting process combines two or more composite nanofiber yarns into one, further enhancing the mechanical entanglement between the fibers and making the bond between them tighter. The twisting process also improves the electrical contact between fibers and reduces their contact resistance. This significantly enhances the overall mechanical strength and structural integrity of the final electrode yarn, ensuring that the electrode is not easily broken or deformed under external forces, while maintaining a high performance level after multiple charge-discharge cycles. Subsequent pre-oxidation and carbonization processes convert manganese elements in the manganese source into manganese oxide particles, which are then uniformly dispersed in the carbon nanofibers formed by carbonization. The resulting carbon nanofibers directly and uniformly coat the carbon fiber surface, ultimately yielding the manganese oxide-carbon composite fiber electrode yarn.

[0026] The preparation method provided in this embodiment is simple to operate, has high production efficiency, and can make manganese oxide particles uniformly distributed in carbon nanofibers, directly coating the carbon fiber surface to form a core-shell structure. The carbon nanofibers in the shell help to suppress the structural expansion of manganese oxides during charging and discharging, so that the final electrode yarn has a higher specific capacitance than carbon fiber bundles, and has great application potential in supercapacitors, especially pseudocapacitors.

[0027] In one embodiment, in step S1, the mass fraction of the manganese source in the spinning solution is 25wt% to 35wt%, and the mass fraction of the polymer is 10wt% to 20wt%. By precisely limiting the content of each component in the spinning solution, the content of manganese oxide particles in the final carbon nanofibers can be effectively adjusted, thereby improving the conductivity and cycle stability of the electrode material while increasing its capacity.

[0028] In this embodiment or other embodiments, the average molecular weight of the polymer is 120 kDa to 180 kDa. By limiting the average molecular weight of the polymer, the viscosity and rheological properties of the spinning solution can be optimized, which helps to ensure that the formed carbon nanofibers are uniformly coated on the carbon fiber surface and that the formed manganese oxide particles are uniformly dispersed in the carbon nanofibers during subsequent pre-oxidation and carbonization processes, thereby improving the overall performance of the final manganese oxide-carbon composite fiber electrode yarn.

[0029] In some embodiments, the polymer is preferably any one of polyacrylonitrile, acrylonitrile-methyl acrylate copolymer, acrylonitrile-methyl acrylate-sodium propylene sulfonate copolymer, and acrylonitrile-vinyl chloride copolymer, and the manganese source is preferably a manganese-containing organic compound, such as manganese acetate, manganese naphthenate, and manganese formate. By clearly defining the specific types of polymer and manganese source, it is helpful to precisely control the reaction system, thereby ensuring that the manganese oxide particles are distributed in the carbon nanofibers at the expected content, and further optimizing the capacity and conductivity of the manganese oxide-carbon composite fiber electrode yarn.

[0030] In one embodiment, in step S2, the carbon fiber is a high-modulus carbon fiber bundle with a filament bundle of 3k, 6k, or 12k. A high-modulus carbon fiber bundle refers to a carbon fiber bundle with an elastic modulus of not less than 370 GPa and a carbon content of more than 98%. By clearly defining the type of carbon fiber and the filament bundle, the mechanical properties and conductivity of the composite nanofiber yarn can be ensured, thereby improving the structural strength and stability of the final manganese oxide-carbon composite fiber electrode yarn.

[0031] In this embodiment or other embodiments, in step S2, during the spinning process using the conjugate electrospinning method, the applied positive voltage is any value between 5kV and 7kV, the negative voltage is any value between 6kV and 8kV, the temperature is limited to any value between 10℃ and 30℃, and the relative humidity is limited to any value between 25% and 35%. By adjusting the parameters such as voltage, temperature, and relative humidity of the conjugate electrospinning method, the diameter, morphology, and structure of the composite nanofiber yarn can be precisely controlled, forming nanofibers with high specific surface area and good pore structure, which helps to improve the capacity and overall conductivity of the final electrode yarn.

[0032] In one embodiment, step S3 involves applying a twist of 150 to 250 twists per meter to the multi-strand composite nanofiber yarn, causing the yarn to intertwine around its axial direction, thus achieving multi-strand plying. Specifically, the multi-strand composite nanofiber yarn is preferably introduced into a twister, and the rotating component of the twister is manually or mechanically driven to apply a twist of approximately 200 twists per meter, causing the yarn to intertwine around its axial direction and merge into a single strand, thereby producing a tightly structured, high-strength ply yarn. This operation not only improves the mechanical strength of the final electrode yarn but also enhances its flexibility and weavability, meeting the requirements of flexible electronic devices.

[0033] In this embodiment or other embodiments, in step S3, during the pre-oxidation treatment, the treatment temperature is increased from room temperature to a range of 250℃ to 320℃, and the heating rate is any value between 1℃ / min and 5℃ / min. By controlling the temperature range and heating rate of the pre-oxidation treatment, the components in the twisted composite nanofiber yarn can undergo appropriate oxidation reactions to form a stable carbon skeleton structure and manganese oxides, while avoiding excessive oxidation that could damage the material structure, thus providing a good precursor for subsequent carbonization treatment.

[0034] In some embodiments, during the carbonization process, the temperature is increased from room temperature to any value between 500°C and 1000°C, and the heating rate is any value between 1°C / min and 5°C / min. By adjusting the temperature range and heating rate of the carbonization process, the degree of carbonization can be precisely controlled, ensuring that manganese oxide is uniformly dispersed in the carbon nanofibers, and promoting the uniform and stable coating of the carbon nanofibers on the carbon fiber surface. This increases the bonding force between the carbon nanofibers and the carbon fiber, endowing the final manganese oxide-carbon composite fiber electrode yarn with excellent conductivity, higher capacity, and stable mechanical properties.

[0035] This application provides a manganese oxide-carbon composite fiber electrode yarn, which is prepared using the above-described method. This manganese oxide-carbon composite fiber electrode yarn not only possesses excellent conductivity and large capacity, but also exhibits flexibility, continuity, and weavability, making it suitable for direct fabric integration as a self-supporting electrode.

[0036] This application also provides the application of the above-mentioned manganese oxide-carbon composite fiber electrode yarn as a positive electrode material in supercapacitors, especially in pseudocapacitors, which can effectively improve the energy density and power density of the capacitor and enhance its electrical performance.

[0037] Example 1 S1. Weigh 0.8g of manganese acetate tetrahydrate, 2.4g of polyacrylonitrile with an average relative molecular mass of 150,000, and 17.6g of N,N-dimethylformamide. Mix the weighed manganese acetate tetrahydrate, polyacrylonitrile, and N,N-dimethylformamide evenly to form a spinning solution.

[0038] S2. Obtain carbon fiber as the core yarn. The carbon fiber is a 6K high-modulus carbon fiber bundle. A composite nanofiber yarn coated with carbon fiber is prepared by conjugate electrospinning. Specifically, the spinning solution is transferred to two 10mL syringes, labeled as syringe 5 and syringe 6 respectively. A 20G needle is used as the spinning needle to ensure stable and uniform ejection of the spinning solution. At a relative humidity of approximately 30%, a 5kV positive voltage is applied through the positive electrode 3, and a 6kV negative voltage is applied through the negative electrode 4 to establish a stable electrostatic field. The ejection speed of the spinning solution in syringe 5 and syringe 6 is controlled using an injection pump. Specifically, the flow rates of both the first solution jet 8 and the second solution jet 9 are controlled to 0.75mL / h. Under the action of the electrostatic field, the spinning solution forms a spinning cone composed of nanofibers on the receiving device 7, coating the carbon fiber core yarn. The resulting composite nanofiber yarn 1 coated with carbon fiber is then wound onto the winding device 2.

[0039] S3, such as Figure 1 As shown, two strands of composite nanofiber yarn are joined together in a manual twister, with a twist of 200 twists / meter applied, causing the two strands to intertwine around their axis for twisting treatment, thus combining the two strands into one. Subsequently, the twisted composite nanofiber yarn is placed in a muffle furnace, and under an air atmosphere, the temperature in the muffle furnace is increased from room temperature to 280°C at a heating rate of 3°C / min for pre-oxidation treatment. After 2 hours of pre-oxidation treatment, the pre-oxidized composite nanofiber yarn is transferred to a tube furnace, and under a nitrogen atmosphere, the temperature in the tube furnace is increased from room temperature to 800°C at a heating rate of 2°C / min for carbonization treatment. After 2 hours of carbonization treatment, the temperature in the tube furnace is allowed to cool naturally to room temperature, as... Figure 2 As shown, manganese oxide / carbon composite fiber electrode yarns were collected. The structural characteristics of the manganese oxide-carbon composite fiber electrode yarns prepared in Example 1 were examined, and the results are as follows. Figure 3 As shown.

[0040] Depend on Figure 3 It can be seen that the manganese oxide-carbon composite fiber electrode yarn prepared in Example 1 exhibits a nanofiber network structure, which has a large specific surface area and can provide abundant active sites for electrocatalytic reactions.

[0041] The electrocatalytic performance of the manganese oxide-carbon composite fiber electrode yarn prepared in Example 1 was tested and analyzed. Specifically, the manganese oxide-carbon composite fiber electrode yarn prepared in Example 1 was subjected to cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) tests using a three-electrode system in 1M Na2SO4 solution. The results of each test are as follows: Figures 4 to 7 As shown.

[0042] Depend on Figure 4 It can be seen that the manganese oxide-carbon composite fiber electrode yarn and carbon fiber prepared in Example 1 both exhibited relatively stable electrochemical performance, with smooth and symmetrical current responses. However, the specific capacitance of the carbon fiber was only about 0.78 F / cm. 3 The specific capacitance of the prepared manganese oxide-carbon composite fiber electrode yarn is approximately 4.2 F / cm. 3 The energy storage capacity of the manganese oxide-carbon composite fiber electrode yarn is significantly improved. Furthermore, the manganese oxide-carbon composite fiber electrode yarn prepared in Example 1 also exhibits strong conductivity. This demonstrates that the manganese oxide-carbon composite fiber electrode yarn prepared by the method provided in this application not only possesses a high capacitance value but also excellent electrochemical performance. Figure 5 As shown, the cyclic voltammetry curves obtained at different scan rates are all relatively symmetrical and exhibit high current response, indicating that the charge-discharge process of this manganese oxide-carbon composite fiber electrode yarn is reversible, the charge is uniformly distributed on its surface, and it has high cycle stability and strong pseudocapacitive characteristics, making it suitable for fast charge-discharge applications. Figure 6 It can be seen that the charge-discharge curves of the manganese oxide-carbon composite fiber electrode yarn are relatively symmetrical and the discharge process is stable, which further verifies that the manganese oxide-carbon composite fiber electrode yarn has high cycle stability and good charge-discharge performance. This indicates that the manganese oxide-carbon composite fiber electrode yarn can maintain good performance during multiple charge-discharge cycles and is suitable for long-term use. Figure 7 It is evident that the manganese oxide-carbon composite fiber electrode yarn exhibits low impedance in the low-frequency region, indicating its excellent conductivity and low internal resistance. This further demonstrates the superior electrical conductivity of the manganese oxide-carbon composite fiber electrode yarn, which is beneficial for improving the charge-discharge efficiency of the electrode. Therefore, the manganese oxide-carbon composite fiber electrode yarn prepared by the method provided in this application combines high electrochemical performance, excellent mechanical strength, good flexibility, and weavability, possessing broad application potential in supercapacitors, particularly suitable for pseudocapacitive capacitors, effectively enhancing the electrical performance and practicality of capacitors.

[0043] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0044] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a manganese oxide-carbon composite fiber electrode yarn, characterized in that, Includes the following steps: S1. A carbon source, a manganese source, and an organic solvent are mixed evenly to form a spinning solution; wherein the carbon source is an unsaturated polymer, and the manganese source is any one or more of a manganese salt or a manganese-containing organic compound. S2. Obtain carbon fiber, and use the carbon fiber as the core yarn to prepare a composite nanofiber yarn coated with carbon fiber by using a conjugate electrospinning method. S3. After twisting the multiple strands of the composite nanofiber yarn, pre-oxidize it in an air atmosphere, and then carbonize it in an inert atmosphere to obtain manganese oxide-carbon composite fiber electrode yarn.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass fraction of the manganese source in the spinning solution is any value between 25wt% and 35wt%, and the mass fraction of the polymer is any value between 10wt% and 20wt%.

3. The preparation method according to claim 2, characterized in that, The average molecular weight of the polymer is any value between 120 kDa and 180 kDa.

4. The preparation method according to claim 2, characterized in that, The polymer is any one of polyacrylonitrile, acrylonitrile-methyl acrylate copolymer, acrylonitrile-methyl acrylate-sodium propylene sulfonate copolymer, and acrylonitrile-vinyl chloride copolymer, and the manganese-containing organic compound is any one of manganese acetate, manganese naphthenate, and manganese formate.

5. The preparation method according to claim 1, characterized in that, In step S2, the carbon fiber is a high-modulus carbon fiber bundle with a filament bundle of 3k, 6k, or 12k.

6. The preparation method according to claim 1, characterized in that, In step S2, the applied positive voltage is any value between 5kV and 7kV, the negative voltage is any value between 6kV and 8kV, the temperature is limited to any value between 10℃ and 30℃, and the relative humidity is limited to any value between 25% and 35%.

7. The preparation method according to claim 1, characterized in that, In step S3, the twisting process involves applying a twist of 150 twists / meter to 200 twists / meter to the multiple strands of the composite nanofiber yarn, causing the multiple strands of the composite nanofiber yarn to intertwine around their axial direction, thereby achieving plying.

8. The preparation method according to claim 1, characterized in that, In step S3, during the pre-oxidation treatment, the treatment temperature is increased from room temperature to a range of 250℃ to 320℃, and the heating rate is any value between 1℃ / min and 5℃ / min. During the carbonization process, the temperature is increased from room temperature to any value between 500℃ and 1000℃, and the heating rate is any value between 1℃ / min and 5℃ / min.

9. A manganese oxide-carbon composite fiber electrode yarn, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the manganese oxide-carbon composite fiber electrode yarn as described in claim 9 as a positive electrode material in supercapacitors.

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