Flexible self-supporting porous carbon electrode and preparation method and application thereof

Abstract

The invention discloses a flexible self-supporting porous carbon electrode and a preparation method and application thereof, and belongs to the technical field of electrode material preparation. The method comprises the following steps: firstly, carrying out amidoximation modification on polyacrylonitrile felt to prepare amidoxime polyacrylonitrile felt; then carrying out dipping treatment through a zinc salt solution to obtain an amidoxime polyacrylonitrile felt precursor chelated with zinc ions; and finally, through high-temperature pyrolysis conversion, the prepared flexible self-supporting porous carbon electrode material not only retains the flexible characteristic and the fiber structure of the precursor, but also forms a rich pore structure on the surface of the fiber, so that the specific surface area is remarkably improved. According to the structure, a continuous electron conduction network is constructed, an efficient ion transmission channel is provided, and meanwhile the charge storage capacity is improved. Experimental results show that when the material is used as a flexible supercapacitor electrode, the material shows excellent specific capacity and cycling stability.

Description

Technical Field

[0001] This invention belongs to the field of electrode material preparation technology, specifically relating to a flexible self-supporting porous carbon electrode, its preparation method, and its application. Background Technology

[0002] Supercapacitors have shown significant advantages in the field of flexible electronic power supply due to their high power density, fast response capability and long cycle life. However, traditional supercapacitors usually rely on rigid components, which fundamentally limits their mechanical flexibility. Therefore, developing intrinsic flexible electrodes is a key frontier for advancing high-performance flexible supercapacitors.

[0003] Carbon-based materials have become the preferred choice for supercapacitor electrodes due to their high porosity, large specific surface area, excellent conductivity, good chemical stability, and cost-effectiveness. A common flexible electrode fabrication strategy involves mixing powdered carbon materials (such as activated carbon, carbon nanotubes, and graphene) with a binder and then coating it onto a flexible current collector. While this method utilizes mature carbon materials, it suffers from problems such as weak interfacial adhesion, increased contact resistance, and binder clogging of pores. Furthermore, high-load carbon layers can hinder charge transport dynamics due to the high tortuosity of their pore structure, thus limiting device performance. In contrast, self-supporting carbon materials integrate the current collector and electrode material, eliminating the need for cumbersome electrode fabrication processes and enabling high electrode material loading. Self-supporting carbon materials possess a hierarchical porous structure, combining abundant mesopores / micropores with low-torsion macropores. This unique structure promotes electrolyte penetration, shortens ion diffusion paths, and maximizes the electrochemical active area, thereby reducing internal resistance and improving rate performance and energy density. Controlled pyrolysis allows for the direct carbonization of intrinsically flexible, monolithic carbon-rich precursors (such as polymer films, cellulose paper, and cotton fabrics) to prepare electrodes with intact structures, no binders, and tunable porosity. This bottom-up approach also allows for the control of carbon matrix doping or the construction of nanocomposite materials. However, ensuring that precursor-derived carbon materials simultaneously possess excellent conductivity, high porosity, high specific surface area, and mechanical flexibility remains a challenge. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a flexible self-supporting porous carbon electrode, its preparation method and application, so as to solve the technical problem that it is difficult to synergistically improve high conductivity, high porosity, low tortuosity and strong mechanical flexibility in carbon-based electrode materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for preparing a flexible self-supporting porous carbon electrode, comprising the following steps: S1. Place polyacrylonitrile felt in solution A, heat in a water bath at 40-80℃ for 5-120 min, then rinse and freeze-dry to obtain amylopime polyacrylonitrile felt; solution A is a hydroxylamine solution with a concentration of 0.2-2 mol / L, or a mixed solution containing hydroxylamine hydrochloride with a concentration of 0.2-2 mol / L and an inorganic base with a concentration of 0.2-2 mol / L; the cyano group can undergo a nucleophilic addition reaction with hydroxylamine hydrochloride to transform into amylopime group, so polyacrylonitrile felt can be obtained by amylopime reaction to obtain amylopime polyacrylonitrile felt grafted with amylopime group; at the same time, the side reactions such as nitrile hydrolysis accompanying the amylopime reaction will cause some cyano groups to be transformed into carboxyl and amide groups.

[0006] S2. Place the cyclohexime polyacrylonitrile felt in a zinc salt solution and soak it at room temperature for 2-72 hours. The cyclohexime polyacrylonitrile felt contains abundant cyclohexime groups, which have a good chelating ability for zinc ions. Therefore, immersing the cyclohexime polyacrylonitrile felt in a salt solution containing zinc ions can chelate and adsorb zinc ions. Then take it out and freeze-dry it to obtain the electrode precursor. S3. Place the electrode precursor in a protective atmosphere and heat-treat it at 200-300℃ for 1-3 hours, then heat it to 800-1200℃ for 1-8 hours to obtain a flexible self-supporting porous carbon electrode.

[0007] During pyrolysis, the amylopectin groups in the felt fibers firmly anchor zinc ions and inhibit their large-scale aggregation. With the carbonization reaction, zinc ions are converted into highly dispersed elemental zinc through carbothermic reduction. Since elemental zinc has a low boiling point, it gradually evaporates with increasing pyrolysis temperature, thus serving as an in-situ template to induce the formation of a porous structure. Simultaneously, oxygen-containing functional groups such as amylopectin, carboxyl, and amide groups can form cross-linked structures through strong bond networks like ether bonds during pyrolysis. This cross-linking reduces the molecular chain packing density, transforming the linear polymer into a thermally stable three-dimensional network; it also significantly inhibits material shrinkage and maintains flexibility. Furthermore, oxygen-containing functional groups can undergo progressive decomposition over a wide temperature range, generating porous structures. These hierarchical pores not only effectively buffer densification shrinkage but also prevent structural collapse by regulating the gas release rate, thereby improving the material's mechanical stability.

[0008] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, the inorganic base is sodium hydroxide or potassium hydroxide.

[0009] Furthermore, the freeze-drying temperature is -20~-40℃, and the time is 12-48h.

[0010] Furthermore, the zinc salt solution is a zinc nitrate, zinc chloride, or zinc sulfate solution.

[0011] Furthermore, the concentration of zinc ions in the zinc salt solution is 0.01-2 mol / L.

[0012] Furthermore, the protective atmosphere is provided by nitrogen, argon, or helium.

[0013] Furthermore, the heating rate after heat treatment is 2-10℃ / min.

[0014] Furthermore, the pyrolysis temperature was 900℃ and the pyrolysis time was 2 hours.

[0015] The present invention also discloses a flexible self-supporting porous carbon electrode prepared by the above preparation method.

[0016] The present invention also discloses the application of the above-mentioned flexible self-supporting porous carbon electrode in the preparation of flexible supercapacitors.

[0017] The beneficial effects of this invention are as follows: 1. This invention utilizes a zinc-chelated amine oxime polyacrylonitrile felt as a precursor to prepare a flexible, self-supporting porous carbon electrode material via pyrolysis. This electrode material exhibits high mechanical strength and flexibility, along with a rich hierarchical porous structure and a large specific surface area, making it suitable for direct application as an electrode in flexible supercapacitors. Electrochemical testing of the flexible, self-supporting porous carbon electrode prepared by this method yielded a result at 1 mA / cm². 2 Achieving 1.47 F / cm at current density 2 The areal capacitance (corresponding to a mass specific capacitance of 85.13 F / g) of the assembled flexible symmetrical supercapacitor at 1 mA / cm² 2 The output can reach 0.28F / cm. 2 The area capacity is 38.8 μWh / cm³, with an energy density of 38.8 μWh / cm³. 2 The device exhibits almost no capacitance decay when bent or folded, and withstands 5000 cycles of 10mA / cm. 2 After charge-discharge cycle testing, the capacitance retention rate remained as high as 90%, fully demonstrating its huge application potential in the field of flexible energy storage.

[0018] 2. The raw materials used in this invention are economical, the process steps are simple, it is suitable for large-scale production, and it has high potential for industrial application. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of the method of the present invention; Figure 2 For FSPCE 0.2 -900, SCE-900, FSCE-900, PCE 0.2 -900 electrode physical photo; Figure 3 For FSPCE0.2 Scanning electron microscope images of -900, FSCE-900, SCE-900 and polyacrylonitrile felt (PAN); Figure 4 For FSPCE 0.2 Thermogravimetric analysis curves of -900, FSCE-900, and SCE-900 electrodes; Figure 5 For FSPCE 0.2 Nitrogen isothermal adsorption-desorption curves for -900 and FSCE-900; Figure 6 For FSPCE 0.2 Cyclic voltammetry (CV) curves of -900 and FSCE-900 at scan rates of 1, 2, 5, 10, and 20 mV / s; Figure 7 For FSPCE 0.2 Current-sweep rate relationship graphs for -900 and FSCE-900; Figure 8 For FSPCE 0.2 -900 at 1, 2, 5, 10, 20 mA / cm 2 Constant current charge-discharge (GCD) curves at current density; Figure 9 For FSCE-900 at 1, 2, 5, 10, 20 mA / cm 2 Constant current charge-discharge (GCD) curves at current density; Figure 10 For FSPCE 0.2 Area ratio capacitance of -900 and FSCE-900; Figure 11 For FSPCE 0.2 -900 and FSCE-900 mass ratio capacitors; Figure 12 For FSPCE 0.2 CV curves of a flexible symmetrical supercapacitor assembled with -900 electrodes at scan rates of 1, 2, 5, 10, and 20 mV / s; Figure 13 For FSPCE 0.2 The flexible symmetrical supercapacitor assembled with -900 electrodes operates at 1, 2, 5, 10, and 20 mA / cm². 2 GCD curves at current density; Figure 14 For FSPCE 0.2 -900 is the CV curve of a flexible symmetrical supercapacitor assembled with electrodes under different bending angles; Figure 15 For FSPCE 0.2GCD curves of a flexible symmetrical supercapacitor assembled with electrodes at different bending angles (-900). Figure 16 For FSPCE 0.2 -900 represents the cyclic stability test results of the flexible symmetrical supercapacitor assembled with electrodes. Detailed Implementation

[0020] The specific embodiments of the present invention are described below to facilitate understanding of the invention by those skilled in the art. Unless otherwise specified, specific conditions are applied according to conventional conditions or the manufacturer's recommendations. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various modifications are obvious as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims. All inventions utilizing the concept of this invention are protected.

[0021] Example 1 A method for fabricating a flexible self-supporting porous carbon electrode, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps: S1. Cut the polyacrylonitrile felt (PAN) into pieces with dimensions of 30×10×2mm. 3 The rectangular block was placed in a mixed solution of 1 mol / L hydroxylamine hydrochloride and 1 mol / L sodium hydroxide, heated in a water bath at 70 °C for 60 min, then rinsed with deionized water, and freeze-dried at -40 °C for 24 h to obtain a terephthalimide polyacrylonitrile felt (APAN). S2. APAN was placed in a 0.2 mol / L zinc nitrate solution and soaked at room temperature for 72 h. Then, it was removed and freeze-dried at -40 °C for 24 h to obtain a zinc-chelated amylopyridine polyacrylonitrile felt (Zn). 0.2 -APAN); S3, Zn 0.2 -APAN was placed in a nitrogen atmosphere and heat-treated at 250℃ for 1 hour, followed by pyrolysis at a heating rate of 5℃ / min to 900℃ for 2 hours to obtain a flexible self-supporting porous carbon electrode (FSPCE). 0.2 -900).

[0022] Example 2 The difference between this embodiment and Embodiment 1 is that the pyrolysis temperature is replaced with 1000℃, while the other implementation conditions are the same as in Embodiment 1, resulting in a flexible self-supporting porous carbon electrode (FSPCE). 0.2 -1000).

[0023] Example 3 The difference between this embodiment and Embodiment 1 is that the concentration of the S2 zinc nitrate solution is replaced with 0.02 mol / L, while the other implementation conditions are the same as in Embodiment 1, resulting in a flexible self-supporting porous carbon electrode (FSPCE). 0.02 -900).

[0024] Example 4 A method for fabricating a flexible self-supporting porous carbon electrode includes the following steps: S1. Cut the polyacrylonitrile felt (PAN) into pieces with dimensions of 30×10×2mm. 3 The rectangular block was placed in a mixed solution of 0.2 mol / L hydroxylamine hydrochloride and 0.2 mol / L sodium hydroxide, heated in a water bath at 40 °C for 100 min, then rinsed with deionized water, and freeze-dried at -20 °C for 48 h to obtain a terephthalimide polyacrylonitrile felt (APAN). S2. Place APAN in a 2 mol / L zinc chloride solution and soak for 2 hours at room temperature. Then remove it and freeze-dry it at -20℃ for 48 hours to obtain a zinc ion-chelated amylonoxime-modified polyacrylonitrile felt (Zn2-APAN). S3. Zn2-APAN was placed in an argon atmosphere and heat-treated at 200℃ for 3 hours. Then, it was heated to 1200℃ at a heating rate of 10℃ / min for 1 hour to obtain a flexible self-supporting porous carbon electrode (FSPCE2-1200).

[0025] Example 5 A method for fabricating a flexible self-supporting porous carbon electrode includes the following steps: S1. Cut the polyacrylonitrile felt (PAN) into pieces with dimensions of 30×10×2mm. 3 The rectangular block was placed in a 2 mol / L hydroxylamine solution, heated in a water bath at 80 °C for 5 min, then rinsed with deionized water, and freeze-dried at -30 °C for 12 h to obtain a terephthalimide polyacrylonitrile felt (APAN). S2. APAN was placed in a 0.01 mol / L zinc sulfate solution and soaked for 50 h at room temperature. Then it was taken out and freeze-dried at -30℃ for 12 h to obtain a zinc-chelated amylopyridine polyacrylonitrile felt (Zn). 0.01 -APAN); S3, Zn 0.01 -APAN was placed in a helium atmosphere and heat-treated at 300℃ for 2 hours, followed by pyrolysis at a heating rate of 2℃ / min to 800℃ for 8 hours to obtain a flexible self-supporting porous carbon electrode (FSPCE). 0.01 -800).

[0026] Comparative Example 1 The difference between this comparative example and Example 1 is that steps S1 and S2 are omitted, and the polyacrylonitrile felt (PAN) is directly subjected to heat treatment and pyrolysis. The remaining implementation conditions are the same as in Example 1, resulting in a self-supporting carbon electrode named SCE-900.

[0027] Comparative Example 2 The difference between this comparative example and Example 1 is that step S2 is omitted, while the remaining implementation conditions are the same as in Example 1, resulting in a flexible self-supporting carbon electrode named FSCE-900.

[0028] Comparative Example 3 The difference between this comparative example and Example 1 is that step S1 is omitted, while the remaining implementation conditions are the same as in Example 1, resulting in a porous carbon electrode named PCE. 0.2 -900.

[0029] The samples used in the following experiments are materials prepared in Example 1 and Comparative Examples 1-3.

[0030] Experimental Example 1: Structural Characterization Example 1 (FSPCE) 0.2 Comparative Example 1 (SCE-900), Comparative Example 2 (FSCE-900), Comparative Example 3 (PCE-900) 0.2 -900) Actual photographs of the electrode fabrication process are shown below. Figure 2 As shown. It can be seen that FSPCE 0.2 The -900, SCE-900, and FSCE-900 electrodes all exhibit a self-supporting structure. 0.2 The -900 electrode failed to maintain its support structure, and parts of its structure had become powdery. Comparing the electrode's external dimensions reveals that, among self-supported carbon-based electrodes prepared by pyrolyzing polymer precursors of the same size, FSPCE... 0.2 The -900 and FSCE-900 electrodes are similar in size, both larger than the SCE-900 electrode. Among the three self-supporting electrodes, FSPCE... 0.2 Both the -900 and FSCE-900 electrodes exhibit flexibility, while the SCE-900 electrode lacks flexibility. These results indicate that the prior amine oxime reaction followed by pyrolysis of the PAN felt is a crucial step in maintaining the electrode's self-supporting properties and reducing shrinkage during pyrolysis. APAN can form chelates with zinc ions, thereby inhibiting the large-scale aggregation of zinc species during pyrolysis, which is essential for maintaining the overall self-supporting structure of the electrode.

[0031] Electrode material FSPCE 0.2 Scanning electron microscope (SEM) images of -900, FSCE-900, SCE-900 and PAN are as follows: Figure 3 As shown. The results indicate that FSPCE 0.2Both -900 and FSCE-900 successfully retained fiber morphology similar to the original PAN, while SCE-900 exhibited obvious fiber melting and agglomeration. This morphological difference confirms that unmodified PAN undergoes partial fiber melting during direct pyrolysis, leading to fiber adhesion and agglomeration, ultimately resulting in a significant decrease in electrode flexibility. Pretreatment of PAN via oximeization effectively maintains the integrity of its fiber morphology during pyrolysis. This phenomenon can be attributed to the introduction of various oxygen-containing functional groups, such as amine oxime, carboxyl, and amide groups, into the PAN precursor during pyrolysis. These functional groups can form a three-dimensional cross-linked network through strong interactions such as ether bonds. This cross-linked structure transforms the linear polymer into a thermally stable three-dimensional network structure, preventing fiber agglomeration during melting and thus enhancing the electrode's flexibility.

[0032] Further comparison with FSPCE 0.2 The SEM images of -900 and FSCE-900 show that FSPCE 0.2 The fiber surface of -900 exhibits a distinctly rough structure, while the fiber surface of FSCE-900 remains relatively smooth. This difference mainly stems from the fact that under high-temperature carbonization conditions, zinc ions can be carbothermally reduced to elemental zinc, which then escapes through evaporation, leaving a rich porous structure on the fiber surface.

[0033] FSPCE by thermogravimetric analysis 0.2 The formation process of -900, FSCE-900, and SCE-900 electrodes. Results are as follows... Figure 4 As shown, APAN pyrolysis forms flexible FSCE-900 and Zn 0.2 - APAN (the zinc-chelated amylopyridine polyacrylonitrile felt prepared in step S2 of Example 1) is pyrolyzed to form flexible FSPCE. 0.2 The processes of forming SCE-900 exhibit a gradual trend of mass loss, while the process of PAN pyrolysis to form SCE-900 shows a rapid trend of mass loss. This difference is mainly attributed to the difference between APAN and Zn. 0.2 -APAN is rich in oxygen-containing functional groups such as amine oxime, carboxyl, and amide groups. These functional groups exhibit staged decomposition characteristics during pyrolysis, which not only slows down the pyrolysis process but also effectively alleviates structural shrinkage and stress accumulation through controlled gas release. Furthermore, the gradual decomposition process avoids fiber melting and structural collapse caused by rapid pyrolysis, thereby significantly improving the material's mechanical stability and structural integrity.

[0034] FSPCE 0.2 The nitrogen adsorption-desorption isotherms of -900 and FSCE-900 are as follows: Figure 5 As shown. FSPCE 0.2-900 exhibits typical Type IV isotherm characteristics, with a noticeable hysteresis loop visible in the relative pressure (P / P0) range of 0.42-0.95, indicating the presence of microporous and mesoporous structures in the material. Its BET specific surface area is measured to be 160 m². 2 / g. In contrast, FSCE-900 did not exhibit significant nitrogen adsorption or desorption behavior across the entire P / P0 range, indicating that the material possesses almost no microporous or mesoporous structure. These results demonstrate that chelating zinc ions with a metallo-oxime group in the precursor can significantly increase the specific surface area of ​​the flexible self-supporting electrode obtained from pyrolysis and promote the formation of microporous and mesoporous structures.

[0035] Experimental Example 2: Electrochemical Performance Testing First, a three-electrode system test was conducted: a 6 mol / L potassium hydroxide solution was selected as the electrolyte, and the flexible self-supporting electrode FSPCE was used. 0.2 The -900 or FSCE-900 is used directly as the working electrode, with a carbon rod as the counter electrode and an Hg / HgO electrode as the reference electrode. Cyclic voltammetry (CV) curves are collected at different scan rates within the potential range of -1.0~0V vs Hg / HgO, and constant current charge-discharge (GCD) tests are performed at different current densities.

[0036] Subsequently, the flexible supercapacitor was assembled and the two-electrode system was tested: a polyvinyl alcohol-potassium hydroxide gel electrolyte was sandwiched between two FSPCE plates. 0.2 Between the -900 electrodes, a flexible symmetrical supercapacitor was constructed after encapsulation. CV curves were collected at different scan rates within the potential range of -1.0~0V vsHg / HgO, and GCD tests were performed at different current densities.

[0037] Figure 6 and Figure 7 FSPCE was demonstrated 0.2 The CV curves and current-sweep rate relationship graphs of -900 and FSCE-900 are shown. From the CV curves ( Figure 6 It can be seen that, at the same scan rate (20mV / s), FSPCE 0.2 -900 exhibits a larger double-layer current density; furthermore, the current-scan rate plot ( Figure 7 ) in FSPCE 0.2 The steeper slope of -900 indicates that it has a higher double-layer capacitance.

[0038] FSPCE 0.2 The GCD curves of -900 and FSCE-900 are as follows: Figure 8 and Figure 9 As shown in the figure. It can be seen that at 1, 2, 5, 10, and 20 mA / cm... 2At the same current density, both exhibit typical triangular GCD curves, indicating good double-layer behavior and reversibility. At the same current density, FSPCE... 0.2 The charge / discharge time of the -900 is significantly longer than that of the FSCE-900, indicating that it has higher capacitance performance.

[0039] FSPCE 0.2 The areal capacitance and mass capacitance of -900 and FSCE-900 at different discharge currents are as follows: Figure 10 and Figure 11 As shown. The results show that FSPCE 0.2 -900 at 1-20 mA / cm 2 It exhibits higher areal specific capacitance and mass specific capacitance than FSCE-900 across the current density range, mainly due to its larger specific surface area and more optimized pore structure, which significantly improves the overall capacitance performance of the electrode material.

[0040] The CV and GCD curves of a flexible symmetrical supercapacitor assembled with FSPCE0.2-900 electrodes are shown below. Figure 12 and Figure 13 As shown in the figure, it can be seen that the device exhibits different scanning rates (1, 2, 5, 10, and 20 mV / s) and current densities (1, 2, 5, 10, and 20 mA / cm²). 2 Under these conditions, both exhibit highly symmetrical and regularly shaped CV and GCD curves, demonstrating excellent reversibility and charge / discharge efficiency.

[0041] With FSPCE 0.2 The CV and GCD curves of the flexible symmetrical supercapacitor assembled with -900 electrodes at different bending angles are shown below. Figure 14 and Figure 15 As shown, even when bent to 90º and 120º, no significant deformation was observed in its CV and GCD curves. These results clearly demonstrate that this supercapacitor possesses excellent mechanical flexibility and structural stability, making it suitable for applications in flexible electronic devices.

[0042] With FSPCE 0.2 The stability test results of the flexible symmetrical supercapacitor assembled with -900 electrodes are as follows: Figure 16 As shown in the figure. It can be seen that this device operates at 10 mA / cm². 2 After undergoing 5000 charge-discharge cycles at high current density, the capacitance retention rate is still as high as 90%, indicating that it has excellent cycle stability.

[0043] In summary, this invention successfully prepared a flexible, self-supporting porous carbon electrode material using a zinc-chelated, amylated polyacrylonitrile felt as a pyrolysis precursor. The oxygen-containing functional groups introduced by the amylated modification effectively promoted the cross-linking reaction of the fibers at low temperatures, constructing a stable three-dimensional network structure and significantly enhancing the mechanical flexibility of the derived carbon material. Simultaneously, zinc species act as an in-situ template agent during pyrolysis, inducing the formation of a hierarchical porous structure with a high specific surface area. The obtained flexible, self-supporting porous carbon electrode not only exhibits excellent flexibility, making it suitable for direct assembly of flexible supercapacitors, but also demonstrates high specific capacitance and good cycling stability.

Claims

1. A method for preparing a flexible self-supporting porous carbon electrode, characterized in that, Includes the following steps: S1. Place polyacrylonitrile felt in solution A, heat in a water bath at 40-80℃ for 5-120 min, then rinse, and freeze-dry to obtain amylopectin polyacrylonitrile felt; the solution A is a hydroxylamine solution with a concentration of 0.2-2 mol / L, or a mixed solution containing hydroxylamine hydrochloride with a concentration of 0.2-2 mol / L and an inorganic base with a concentration of 0.2-2 mol / L. S2. Place the amylopyridine polyacrylonitrile felt in a zinc salt solution and soak it at room temperature for 2-72 hours. Then remove it and freeze-dry it to obtain the electrode precursor. S3. Place the electrode precursor in a protective atmosphere and heat-treat it at 200-300℃ for 1-3 hours, then heat it to 800-1200℃ for 1-8 hours to obtain a flexible self-supporting porous carbon electrode.

2. The method for preparing a flexible self-supporting porous carbon electrode according to claim 1, characterized in that, The inorganic base is sodium hydroxide or potassium hydroxide.

3. The method for preparing a flexible self-supporting porous carbon electrode according to claim 1, characterized in that, The freeze-drying temperature is -20~-40℃, and the time is 12-48h.

4. The method for preparing a flexible self-supporting porous carbon electrode according to claim 1, characterized in that, The zinc salt solution is a zinc nitrate, zinc chloride, or zinc sulfate solution.

5. The method for preparing a flexible self-supporting porous carbon electrode according to claim 1, characterized in that, The concentration of zinc ions in the zinc salt solution is 0.01-2 mol / L.

6. The method for preparing a flexible self-supporting porous carbon electrode according to claim 1, characterized in that, The protective atmosphere is provided by nitrogen, argon, or helium.

7. The method for preparing a flexible self-supporting porous carbon electrode according to claim 1, characterized in that, The heating rate after heat treatment is 2-10℃ / min.

8. The method for preparing a flexible self-supporting porous carbon electrode according to claim 1, characterized in that, The pyrolysis temperature is 900℃ and the pyrolysis time is 2h.

9. A flexible self-supporting porous carbon electrode, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the flexible self-supporting porous carbon electrode according to claim 9 in the preparation of flexible supercapacitors.

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