Flexible carbon nanofiber / porous carbon microsphere composite membrane and preparation method thereof

Abstract

The invention relates to a flexible carbon nanofiber / porous carbon microsphere composite membrane and a preparation method thereof. The flexible carbon nanofiber / porous carbon microsphere composite membrane is prepared from the following materials in parts by weight: 3-10 parts of aramid resin; 20 to 60 parts by weight of N, N-dimethylacetamide; 2-5 parts by weight of polyvinyl alcohol; and 30-72 parts by weight of polytetrafluoroethylene. On the basis of a synchronous electrostatic spinning / electrostatic spraying method, polyisophthaloyl metaphenylene diamine nanofibers and polyvinyl alcohol / polytetrafluoroethylene microspheres are distributed in an overlapping manner, a pretreatment-carbonization process is combined, a PMIA component is converted into carbon nanofibers to form a stable framework, PTFE in a PVA / PTFE component is decomposed to form holes, PVA is converted into carbon microspheres with a honeycomb porous structure, and the composite material is prepared. The flexible carbon nanofiber / porous carbon microsphere composite membrane with a carbon nanofiber supporting and honeycomb porous carbon microsphere distribution structure is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of composite membranes, and particularly to a flexible carbon nanofiber / porous carbon microsphere composite membrane and a preparation method thereof. Background Art

[0002] Due to their adjustable microtopography and hierarchical pore structure characteristics, porous carbon materials exhibit significant application potential in the fields of energy storage, environmental governance, and chemical engineering. Porous carbon materials are divided into zero-dimensional carbon materials (such as carbon spheres), one-dimensional carbon materials (such as carbon nanotubes and carbon fibers), two-dimensional carbon materials (such as graphene nanosheets), and three-dimensional carbon materials (such as three-dimensional graphene, three-dimensional carbon fiber materials, and hierarchical porous carbon). Their performance advantages can be attributed to three key structural characteristics: (1) The interconnected nanoscale pore network (hierarchical distribution of micropores, mesopores, and macropores) can optimize mass transfer kinetics and provide a fast diffusion path for adsorption separation and catalytic reactions; (2) The high specific surface area can increase the density of active sites and significantly improve the interfacial reaction efficiency; (3) The preparation and synthesis routes of porous carbon materials are free and diverse, and through the flexible combination of technologies such as precursor selection, template engineering, and electrospinning, continuous, efficient, and controllable preparation can be achieved. Meeting the requirements of large-scale production and customized applications. Therefore, porous carbon materials show excellent prospects in multiple fields.

[0003] As an efficient technology for preparing nanofibers, the core advantage of electrospinning technology lies in the ability to control the fiber diameter, porosity, and spatial orientation by regulating the spinning process parameters (such as solution concentration, voltage intensity, receiving distance, etc.). By using this technology to prepare carbon precursors, the microstructure of the precursor fibers can be flexibly designed, and these structural features can be effectively retained and further optimized during the subsequent carbonization process, thereby endowing the porous carbon materials with a unique hierarchical pore network. At the same time, its strong compatibility allows for blending with various functional components (such as metal oxides, conductive polymers, or nanoparticles). Compared with traditional methods, electrospinning technology enables the continuous and efficient production of various carbon materials with both continuous conductive networks and adjustable surface characteristics, showing unique advantages in fields such as capacitors, electrodes, and catalysis, providing a feasible path for constructing multifunctional composite porous carbon materials.

[0004] However, compared with traditional carbon nanofiber materials, the mechanical strength of porous carbon nanofibers is significantly reduced due to the presence of a large number of pores, which limits the application of porous carbon nanofibers. If one hopes to increase the strength by reducing the pores, the specific surface area will be limited, and there are limitations in active substance loading and interfacial modification. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies of the prior art. Aiming at the problem of the contradiction between pores and strength in carbon materials (more pores and lower strength, higher strength and fewer pores), based on the synchronous electrospinning / electrospraying technology, combined with the pretreatment and carbonization processes, a flexible carbon nanofiber / porous carbon microsphere composite membrane is provided. Among them, the carbon nanofibers provide a supporting framework, which is beneficial to ensuring the strength of the obtained carbon material; the porous carbon microspheres provide a pore structure, providing space for functional loading, and realizing the demand for carbon materials with high strength and many pores in the fields of adsorption, catalysis, energy, etc.

[0006] The invention object of the present invention also lies in providing a preparation method of the flexible carbon nanofiber / porous carbon microsphere composite membrane.

[0007] The present invention solves its technical problems through the following technical solutions:

[0008] A flexible carbon nanofiber / porous carbon microsphere composite membrane, the materials for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane and their weight fraction ratios are:

[0009] Aramid resin: 3 - 10 parts by weight;

[0010] N,N-dimethylacetamide: 20 - 60 parts by weight;

[0011] Polyvinyl alcohol: 2 - 5 parts by weight;

[0012] Polytetrafluoroethylene: 30 - 72 parts by weight.

[0013] Moreover, the materials for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane and their weight fraction ratios are preferably:

[0014] Aramid resin: 4 - 6 parts by weight;

[0015] N,N-dimethylacetamide: 25 - 30 parts by weight;

[0016] Polyvinyl alcohol: 4 - 5 parts by weight;

[0017] Polytetrafluoroethylene: 60 - 65 parts by weight.

[0018] A preparation method of a flexible carbon nanofiber / porous carbon microsphere composite membrane, which comprises the following steps:

[0019] Step 1, preparing a primary composite nanofiber membrane:

[0020] 1.1. Blend the polyvinyl alcohol solution and the polytetrafluoroethylene solution according to the solute mass in the weight fraction ratio of 2 - 5:30 - 72, add 5 - 20% of the solution mass of water for dilution, and stir to obtain a polyvinyl alcohol / polytetrafluoroethylene electrospray solution;

[0021] 1.2. Dissolve the aramid resin in the N,N-dimethylacetamide solvent, and then stir at 25°C - 30°C for 3 ± 0.5 h to obtain an aramid resin electrospinning solution with a mass fraction of 15 wt%. The weight fraction ratio of the aramid resin to N,N-dimethylacetamide is: 3 - 10:20 - 60;

[0022] 1.3. Use the above-mentioned polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and aramid resin electrospinning solution according to the weight fraction ratio, and prepare a dry and uniform primary composite nanofiber membrane by electrospinning for standby;

[0023] Step 2. Preparation of the flexible carbon nanofiber / porous carbon microsphere composite membrane:

[0024] 2.1. Pretreat the primary composite nanofiber membrane in a muffle furnace in an air atmosphere. The preset temperature range is from room temperature to 260 ± 5°C, the heating rate is 2 ± 0.5 °C / min, and the holding time is 1 ± 0.5 h. After cooling to room temperature, the pretreated fiber membrane is obtained;

[0025] 2.2. Put the pretreated fiber membrane into an open-type - vacuum atmosphere tubular electric furnace and carbonize it in a nitrogen atmosphere. Raise the temperature to the carbonization temperature at a heating rate of 2 ± 0.5 °C / min respectively. The carbonization temperature is 500 °C - 900 °C. After holding for 1 h, cool to room temperature to obtain the carbonized fiber membrane, that is, the finished product of the flexible carbon nanofiber / porous carbon microsphere composite membrane.

[0026] Moreover, the carbonization temperature is preferably 800 °C.

[0027] Moreover, in the above step 1.3, the above-mentioned polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and aramid resin electrospinning solution are used to prepare a dry and uniform primary composite nanofiber membrane by electrospinning for standby. The specific steps are as follows:

[0028] A. Fill the pre-prepared polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and aramid resin electrospinning solution into the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution pipette and aramid resin electrospinning solution pipette respectively. Install an electrostatic spraying solution spray needle with a diameter of 0.8 mm and an electrospinning solution spinning needle at the outlet end of the pipette. Precisely control the extrusion speed of the two solutions through a precision micro - propulsion pump, and both are set to a constant flow rate of 0.8 ml / h. Precisely regulate each component in the composite membrane by adjusting the ratio of the number of polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution pipettes and aramid resin electrospinning solution pipettes;

[0029] B. Apply a voltage of 30 kV. Set the distance between the electrospray needle of the polyvinyl alcohol / polytetrafluoroethylene electrospray solution and the receiving device to 20 cm, and set the distance between the electrospinning needle of the aramid resin electrospinning solution and the receiving device to 18 cm. The temperature is 25 ± 5°C, and the relative humidity is 40% - 60%. Connect the positive pole of the high-voltage power supply to the electrospray needle of the electrospray solution and the electrospinning needle of the electrospinning solution through an insulated wire clamp. The receiving device uses a metal roller wrapped with aluminum foil and is reliably grounded. At the same time, insulate the contact parts between the wire clamp and the electrospray needle of the electrospray solution and the electrospinning needle of the electrospinning solution to ensure experimental safety;

[0030] C. During the electrospinning process, the electrospinning needle of the aramid resin electrospinning solution and the electrospray needle of the polyvinyl alcohol / polytetrafluoroethylene electrospray solution move horizontally in a uniform reciprocating motion. The metal roller of the receiving device rotates at a constant speed. The electrospray needle of the polyvinyl alcohol / polytetrafluoroethylene electrospray solution forms polyvinyl alcohol / polytetrafluoroethylene microdroplets, and the electrospinning needle of the aramid resin electrospinning solution forms aramid resin nanofibers, ensuring that the polyvinyl alcohol / polytetrafluoroethylene microdroplets and the aramid resin nanofibers are uniformly intertwined and deposited under the action of the electric field force. After electrospinning, carefully peel the composite nanofiber membrane from the receiving roller and transfer it to a 60°C vacuum oven for drying for 11 - 12 hours to completely remove the residual solvent and moisture, and finally obtain a dry and uniform primary composite nanofiber membrane for standby.

[0031] Moreover, the weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrospray solution is 1 - 2:1 - 3, and the number ratio of the pipettes loaded with the aramid resin electrospinning solution to the pipettes loaded with the polyvinyl alcohol / polytetrafluoroethylene electrospray solution is 1 - 2:1 - 3.

[0032] Moreover, the weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrospray solution is preferably 1:2.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1. The flexible carbon nanofiber / porous carbon microsphere composite membrane of the present invention, based on the synchronous electrospinning / electrospray method, overlaps and distributes poly(m - phenylenediamine isophthalamide) (PMIA) nanofibers and polyvinyl alcohol (PVA) / polytetrafluoroethylene (PTFE) microspheres. Combining the pretreatment - carbonization process, the PMIA component is converted into carbon nanofibers to form a stable skeleton, while in the PVA / PTFE component, PTFE decomposes to form pores, and PVA is converted into carbon microspheres with a honeycomb - like porous structure, providing abundant loading sites for active substances, and preparing a flexible carbon nanofiber / porous carbon microsphere composite membrane with a structure supported by carbon nanofibers and distributed with honeycomb - like porous carbon microspheres.

[0035] 2. The preparation method of the flexible carbon nanofiber / porous carbon microsphere composite membrane of the present invention can achieve controllable adjustment of each component in the composite membrane material by precisely controlling the electrospinning process parameters and the mixing ratio of the aramid resin electrospinning solution and the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution. The weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution is preferably 1:2; the number of pipettes for loading the aramid resin electrospinning solution and the number of pipettes for loading the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution are 1-2; when the volume ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution is controlled at 1:2 and the carbonization temperature is set at 800 °C, the obtained material exhibits the best hierarchical pore structure, which simultaneously includes micropores, mesopores and macropores, meeting the requirements for carbon materials with high strength and many pores in the fields of adsorption, catalysis, energy, etc.

[0036] 3. The flexible carbon nanofiber / porous carbon microsphere composite membrane of the present invention and its preparation method optimize the composite electrospinning process of the aramid resin electrospinning solution and the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution by the synchronous electrospinning / electrostatic spraying method, and successfully prepare a flexible carbon nanofiber / porous carbon microsphere composite membrane (CNF / HPCNS) with a three-dimensional carbon nanofiber / honeycomb-like porous carbon sphere composite structure.

[0037] 4. The flexible carbon nanofiber / porous carbon microsphere composite membrane of the present invention and its preparation method have the characteristics of simple and controllable preparation process, wide raw material sources, strong structural designability, etc., providing a new direction for the construction of carbon materials. Brief Description of the Drawings

[0038] Figure 1 SEM images of samples prepared by different weight fraction ratios and different processes of the aramid resin electrospinning solution and the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution of the present invention, including:

[0039] Figure 1 a1 is the SEM image of the CNF primary composite nanofiber membrane of Example 1#;

[0040] Figure 1 a2 is the SEM image of the fiber membrane of Example 1# CNF after pretreatment;

[0041] Figure 1 a3 is the SEM image of the fiber membrane of Example 1# CNF after carbonization;

[0042] Figure 1 b1 is the SEM image of the HPCNS primary composite nanofiber membrane of Example 2#;

[0043] Figure 1 b2 is the SEM image of the fiber membrane of Example 2# HPCNS after pretreatment;

[0044] Figure 1 b3 is the SEM image of the fiber membrane after carbonization of Example 2#HPCNS;

[0045] Figure 1 c1 is the SEM image of the as - prepared composite nanofiber membrane of Example 3#CNF / HPCNS(2:1);

[0046] Figure 1 c2 is the SEM image of the fiber membrane after pretreatment of Example 3#CNF / HPCNS(2:1);

[0047] Figure 1 c3 is the SEM image of the fiber membrane after carbonization of Example 3#CNF / HPCNS(2:1);

[0048] Figure 1 d1 is the SEM image of the as - prepared composite nanofiber membrane of Example 4#CNF / HPCNS(1:1);

[0049] Figure 1 d2 is the SEM image of the fiber membrane after pretreatment of Example 4#CNF / HPCNS(1:1);

[0050] Figure 1 d3 is the SEM image of the fiber membrane after carbonization of Example 4#CNF / HPCNS(1:1);

[0051] Figure 1 e1 is the SEM image of the as - prepared composite nanofiber membrane of Example 5#CNF / HPCNS(1:2);

[0052] Figure 1 e2 is the SEM image of the fiber membrane after pretreatment of Example 5#CNF / HPCNS(1:2);

[0053] Figure 1 e3 is the SEM image of the fiber membrane after carbonization of Example 5#CNF / HPCNS(1:2);

[0054] Figure 1 f1 is the SEM image of the as - prepared composite nanofiber membrane of Example 6#CNF / HPCNS(1:3);

[0055] Figure 1 f2 is the SEM image of the fiber membrane after pretreatment of Example 6#CNF / HPCNS(1:3);

[0056] Figure 1 f3 is the SEM image of the fiber membrane after carbonization of Example 6#CNF / HPCNS(1:3);

[0057] Figure 2Schematic diagram of the tensile properties and complete properties of the samples prepared by different weight fraction ratios and different processes of the aramid resin electrospinning solution and the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution of the present invention, including:

[0058] Figure 2 a is the tensile curve of Examples 1, 3, 4, and 5;

[0059] Figure 2 b is the physical object of the flexible carbon nanofiber / porous carbon microsphere composite film of Example 5#CNF / HPCNS(1:2);

[0060] Figure 2 c is the bending picture of the flexible carbon nanofiber / porous carbon microsphere composite film of Example 5#CNF / HPCNS(1:2);

[0061] Figure 3 XRD pattern of the flexible carbon nanofiber / porous carbon microsphere composite film CNF / HPCNS product of Example 5 at different carbonization temperatures;

[0062] Figure 4 Product analysis spectrum of Example 5 of the present invention, including:

[0063] Figure 4 a is the full XPS spectrum of the as-prepared composite nanofiber membrane, the pretreated fiber membrane, and the flexible carbon nanofiber / porous carbon microsphere composite film product of Example 5;

[0064] Figure 4 b is the O1s spectrum of the product of Example 5#CNF / HPCNS(1:2);

[0065] Figure 4 c is the C1s spectrum of the product of Example 5#CNF / HPCNS(1:2);

[0066] Figure 5 Low-temperature nitrogen adsorption curve and pore size distribution diagram of the products of Examples 1 to 6 of the present invention, including:

[0067] Figure 5 a is the low-temperature nitrogen adsorption curve of the products of Examples 1, 2, 3, 4, 5, and 6 of the present invention;

[0068] Figure 5 b is the pore size distribution diagram of the products of Examples 1, 2, 3, 4, 5, and 6 of the present invention. Detailed implementation manners

[0069] The present invention will be further described in detail below through specific examples. The following examples are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0070] Example 1:

[0071] As a comparative example, a pure aramid resin nanofiber membrane (#CNF) was prepared, which included the following steps:

[0072] (1) Preparation of pure aramid resin nanofiber membrane (#CNF): 10 g of PMIA resin with a solution concentration of 25 wt% was dissolved in 6.8 g of DMAC, and then stirred at 30 °C for 3 h until the PMIA was completely dissolved. A pipette was used to load the aramid resin electrospinning solution, and the mass fraction of PMIA in the aramid resin electrospinning solution was 15 wt%.

[0073] (2) The spinning parameters were set as follows: the applied voltage was 30 kV, the constant feeding rate of the spinning solution was set at 0.8 ml / h, the receiving distance between the needle of the aramid resin electrospinning solution and the receiving device was 18 cm, the ambient temperature was controlled at 25 ± 5 °C, the humidity was maintained at 40% - 60%, and the micro-feeding pump was started.

[0074] (3) After spinning, it was peeled off from the receiving roller of the receiving device and transferred to a 60 °C vacuum oven for drying for 11 - 12 hours to obtain a nascent nanofiber membrane.

[0075] (4) The dried nascent nanofiber membrane was pretreated in a muffle furnace in an air atmosphere. The preset temperature range was from room temperature to 260 ± 5 °C, the heating rate was 2 ± 0.5 °C / min, the holding time was 1 ± 0.5 h, and after cooling to room temperature, the pretreated fiber membrane was obtained.

[0076] (5) The pretreated fiber membrane was put into an open - type - vacuum atmosphere tube furnace for carbonization in a nitrogen atmosphere. It was heated to 800 °C at a heating rate of 2 ± 0.5 °C / min, held for 1 h, and then cooled to room temperature to obtain a pure aramid resin nanofiber membrane (#CNF).

[0077] Example 2:

[0078] As a comparative example, a pure polyvinyl alcohol / polytetrafluoroethylene microsphere membrane (#HPCNS) was provided, which included the following steps:

[0079] (1) A pipette was used to load the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution. The components of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution were: 6.25 g of polyvinyl alcohol PVA; 93.75 g of polytetrafluoroethylene PTFE.

[0080] (2)Set the spinning parameters as follows: applied voltage 30 kV, the constant propulsion speed of the spinning solution is set to 0.8 ml / h, the receiving distance between the needle of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and the receiving device is 20 cm, the ambient temperature is controlled at 25 ± 5 °C, the humidity is maintained at 40% - 60%, and start the micro - propulsion pump.

[0081] (3)After spinning, peel it from the receiving roller of the receiving device and transfer it to a 60 °C vacuum oven for drying for 11 - 12 hours to obtain the as - prepared nanofiber membrane.

[0082] (4)Pre - treat the dried as - prepared nanofiber membrane in a muffle furnace in an air atmosphere. The preset temperature range is from room temperature to 260 ± 5 °C, the heating rate is 2 ± 0.5 °C / min, the holding time is 1 ± 0.5 h, and after cooling to room temperature, obtain the pre - treated fiber membrane.

[0083] (5)Put the pre - treated fiber membrane into an open - type - vacuum atmosphere tubular electric furnace and carbonize it in a nitrogen atmosphere. Raise the temperature to 800 °C at a heating rate of 2 ± 0.5 °C / min respectively, hold for 1 h, and then cool to room temperature to obtain the pure polyvinyl alcohol / polytetrafluoroethylene microsphere membrane (#HPCNS).

[0084] Example 3

[0085] For the flexible carbon nanofiber / porous carbon microsphere composite membrane of the present invention, the weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution is 2:1, and the materials and their weight fraction ratios for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane are as follows:

[0086] Aramid resin (PMIA) 10 g;

[0087] N, N - dimethylacetamide (DMAC) 56.67 g;

[0088] Polyvinyl alcohol (PVA) 2.08 g;

[0089] Polytetrafluoroethylene (PTFE) 31.25 g.

[0090] The preparation method of the above - mentioned flexible carbon nanofiber / porous carbon microsphere composite membrane:

[0091] Step 1: Prepare the as - prepared composite nanofiber membrane:

[0092] 1.1. The polyvinyl alcohol solution and the polytetrafluoroethylene solution are blended according to the mass of the solute at the weight fraction ratio of 2 - 5:30 - 72, and 5 - 20% of the mass of the solution is added with water for dilution. After stirring, a polyvinyl alcohol / polytetrafluoroethylene electrospray solution is obtained. In this embodiment, a 10 wt% polyvinyl alcohol solution and a 60 wt% polytetrafluoroethylene solution are blended according to the above weight fraction, and 10% of the mass of the solution is added with water for dilution. After magnetic stirring at room temperature for 2 h, a polyvinyl alcohol / polytetrafluoroethylene electrospray solution is obtained.

[0093] 1.2. The aramid resin is dissolved in the N,N - dimethylacetamide solvent, and stirred to obtain an aramid resin electrospinning solution with a mass fraction of 12 - 17 wt%. The weight fraction ratio of the aramid resin to N,N - dimethylacetamide is: 3 - 10:20 - 60. In this embodiment, the aramid resin is dissolved in the N,N - dimethylacetamide solvent according to the above weight, and then stirred at 25°C - 30°C for 3 h to obtain an aramid resin electrospinning solution with a mass fraction of 15 wt%.

[0094] 1.3. Using the above polyvinyl alcohol / polytetrafluoroethylene electrospray solution and aramid resin electrospinning solution, a dry and uniform primary composite nanofiber membrane is prepared by electrospinning for standby. The specific steps are as follows;

[0095] A. The pre - prepared polyvinyl alcohol / polytetrafluoroethylene electrospray solution and aramid resin electrospinning solution are respectively filled into a polyvinyl alcohol / polytetrafluoroethylene electrospray solution pipette and an aramid resin electrospinning solution pipette. At the outlet end of the pipette, a flat - headed polyvinyl alcohol / polytetrafluoroethylene electrospray solution spray needle with a diameter of 0.4 - 1.2 mm and an aramid resin electrospinning solution spinning needle are installed. The needle diameter is preferably 0.8 mm. The extrusion speed of the two solutions is precisely controlled by a precision micro - propulsion pump, and both are set to a constant flow rate of 0.4 - 2.0 ml / h. In this embodiment, a constant flow rate of 0.8 ml / h is set. The precise regulation of each component in the composite membrane is achieved by adjusting the ratio of the number of polyvinyl alcohol / polytetrafluoroethylene electrospray solution pipettes and aramid resin electrospinning solution pipettes.

[0096] The volume ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrospray solution is controlled at 2:1. 2 pipettes are used to load the aramid resin electrospinning solution, and 1 pipette is used to load the polyvinyl alcohol / polytetrafluoroethylene electrospray solution. When the carbonization temperature is set at 800°C, the obtained material exhibits the best hierarchical pore structure containing micropores, mesopores and macropores, with a specific surface area reaching 256.2 m² / g and a total pore volume of 0.4921 cm³ / g.

[0097] B. Apply a voltage of 25 - 35 kV, preferably 30 kV in this embodiment. Set the distance between the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid spray needle and the receiving device to 16 - 22 cm, preferably 20 cm in this embodiment. Set the distance between the aramid resin electrospinning liquid spinning needle and the receiving device to 15 - 20 cm, preferably 18 cm. The temperature is 15 - 35, preferably 25 °C, and the relative humidity is 40% - 60%. Connect the positive pole of the high-voltage power supply to the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid spray needle and the aramid resin electrospinning liquid spinning needle through an insulated wire clamp. The receiving device uses a metal receiving roller wrapped with aluminum foil and is reliably grounded. At the same time, insulate the contact part between the wire clamp and the needle to ensure experimental safety.

[0098] C. During the spinning process, the aramid resin electrospinning liquid spinning needle and the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid spray needle move horizontally in a uniform reciprocating motion. The metal roller of the receiving device rotates at a constant speed. The polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid spray needle forms polyvinyl alcohol / polytetrafluoroethylene microdroplets, and the aramid resin electrospinning liquid spinning needle forms aramid resin nanofibers, ensuring that the polyvinyl alcohol / polytetrafluoroethylene microdroplets and the aramid resin nanofibers are uniformly intertwined and deposited under the action of the electric field force. After spinning, carefully peel the composite nanofiber membrane from the receiving roller and transfer it to a 60 °C vacuum oven for drying for 11 - 12 hours to thoroughly remove residual solvents and moisture, and finally obtain a dry and uniform primary composite nanofiber membrane for standby.

[0099] Step 2. Preparation of the flexible carbon nanofiber / honeycomb porous carbon microsphere composite membrane:

[0100] 2.1. Pretreat the dried primary composite nanofiber membrane in a muffle furnace in an air atmosphere. The preset temperature range is from room temperature to 250 - 270 °C, preferably raise the temperature to 260 °C, the heating rate is 0.5 - 3.0 °C / min, preferably 2 °C / min, and the holding time is 0.5 - 3.0, preferably hold for 1 h. After cooling to room temperature, obtain the pretreated fiber membrane;

[0101] 2.2. Put the pretreated fiber membrane into an open-type - vacuum atmosphere tube furnace and carbonize it in a nitrogen atmosphere. Raise the temperature to the carbonization temperature of 800 °C at a heating rate of 0.5 - 3.0 °C / min, preferably 2 °C / min, hold for 0.5 - 2.0 h, preferably hold for 1 h in this embodiment, and then cool to room temperature to obtain the flexible carbon nanofiber / honeycomb porous carbon microsphere composite membrane product (Carbon Nanofiber / Honeycomb Porous Carbon Nanospheres, CNF / HPCNS), labeled as #CNF / HPCNS(2:1).

[0102] Example 4

[0103] A flexible carbon nanofiber / porous carbon microsphere composite membrane, with the weight fraction ratio of aramid resin electrospinning solution to polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution being 1:1. The materials for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane and their weight fraction ratios are as follows:

[0104] Aramid resin (PMIA) 7.5 g;

[0105] N,N-dimethylacetamide (DMAC) 42.5 g;

[0106] Polyvinyl alcohol (PVA) 3.125 g;

[0107] Polytetrafluoroethylene (PTFE) 46.875 g.

[0108] The preparation method of the above flexible carbon nanofiber / porous carbon microsphere composite membrane:

[0109] (1) Use 1 pipette to load the aramid resin electrospinning solution and 1 pipette to load the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution.

[0110] (2) Set the electrospinning parameters as follows: applied voltage 30 kV, the constant feeding rate of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and the aramid resin electrospinning solution is set to 0.8 ml / h, the receiving distance between the needle of the aramid resin electrospinning solution and the collecting device is 18 cm, the receiving distance between the needle of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and the receiving device is 20 cm, control the ambient temperature at 25±5°C, maintain the humidity at 40%-60%, and start the micro-feeding pump.

[0111] (3) After electrospinning, peel it off on the receiving roller and transfer it to a 60°C vacuum oven for drying for 11-12 hours to obtain a primary composite nanofiber membrane.

[0112] (4) Pretreat the dried primary composite fiber membrane in a muffle furnace in an air atmosphere. The preset temperature range is from room temperature to 260±5°C, the heating rate is 2±0.5°C / min, and the holding time is 1±0.5 h. After cooling to room temperature, obtain the pretreated fiber membrane.

[0113] (5) Put the pretreated fiber membrane into an open-type-vacuum atmosphere tube furnace and carbonize it in a nitrogen atmosphere. Raise the temperature to 800°C at a heating rate of 2±0.5°C / min respectively, hold for 1 h and then cool to room temperature to obtain the flexible carbon nanofiber / porous carbon microsphere composite membrane product, labeled as #CNF / HPCNS(1:1).

[0114] Others are the same as in Example 3.

[0115] Example 5

[0116] A flexible carbon nanofiber / porous carbon microsphere composite membrane, the weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution is 1:2, and the materials for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane and their weight fraction ratios are as follows:

[0117] Aramid resin (PMIA) 5 g;

[0118] N,N-dimethylacetamide (DMAC) 28.3 g;

[0119] Polyvinyl alcohol (PVA) 4.167 g;

[0120] Polytetrafluoroethylene (PTFE) 62.5 g.

[0121] The preparation method of the above flexible carbon nanofiber / porous carbon microsphere composite membrane:

[0122] (1) Use 1 pipette to load the aramid resin electrospinning solution, and 2 pipettes to load the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution.

[0123] (2) Set the electrospinning parameters as follows: the applied voltage is 30 kV, the constant feeding rate of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and the aramid resin electrospinning solution is set to 0.8 ml / h, the receiving distance between the needle of the aramid resin electrospinning solution and the collecting device is 18 cm, the receiving distance between the needle of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and the receiving device is 20 cm, the environmental temperature is controlled at 25±5 °C, the humidity is maintained at 40%-60%, and start the micro-feeding pump.

[0124] (3) After electrospinning, peel it off from the receiving roller and transfer it to a 60 °C vacuum oven for drying for 11-12 hours to obtain a primary composite nanofiber membrane.

[0125] (4) Pretreat the dried primary composite nanofiber membrane in a muffle furnace in an air atmosphere. The preset temperature range is from room temperature to 260±5 °C, the heating rate is 2±0.5 °C / min, the holding time is 1±0.5 h, and after cooling to room temperature, obtain the pretreated fiber membrane.

[0126] (5) Put the pretreated fiber membrane into an open-type-vacuum atmosphere tubular electric furnace and carbonize it in a nitrogen atmosphere. Raise the temperature to 800 °C at a heating rate of 2±0.5 °C / min respectively, hold for 1 h and then cool to room temperature to obtain the flexible carbon nanofiber / porous carbon microsphere composite membrane, labeled as #CNF / HPCNS(1:2).

[0127] Others are the same as in Example 3.

[0128] For comparison, products at carbonization temperatures of 500 °C, 600 °C, 700 °C, and 900 °C in this example were prepared simultaneously.

[0129] Example 6

[0130] A flexible carbon nanofiber / porous carbon microsphere composite membrane, with the weight fraction ratio of aramid resin electrospinning solution to polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution being 1:3. The materials for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane and their weight fraction ratios are as follows:

[0131] Aramid resin (PMIA) 3.75 g;

[0132] N,N-dimethylacetamide (DMAC) 21.25 g;

[0133] Polyvinyl alcohol (PVA) 4.6875 g;

[0134] Polytetrafluoroethylene (PTFE) 70.3125 g;

[0135] The preparation method of the above flexible carbon nanofiber / porous carbon microsphere composite membrane:

[0136] (1) Use 1 pipette to load the aramid resin electrospinning solution and 3 pipettes to load the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution.

[0137] (2) Set the electrospinning parameters as follows: applied voltage 30 kV, the constant propulsion speed of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and the aramid resin electrospinning solution is set to 0.8 ml / h, the receiving distance between the needle of the aramid resin electrospinning solution and the collecting device is 18 cm, the receiving distance between the needle of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution and the receiving device is 20 cm, the ambient temperature is controlled at 25 ± 5 °C, and the humidity is maintained at 40% - 60%. Start the micro-propulsion pump.

[0138] (3) After electrospinning, peel the as-spun nanofiber membrane from the receiving roller and transfer it to a 60 °C vacuum oven for drying for 11 - 12 hours.

[0139] (4) Pretreat the dried as-spun composite fiber in a muffle furnace in an air atmosphere. The preset temperature range is from room temperature to 260 ± 5 °C, the heating rate is 2 ± 0.5 °C / min, and the holding time is 1 ± 0.5 h. After cooling to room temperature, the pretreated fiber is obtained.

[0140] (5) Place the pretreated fiber membrane into an open-type vacuum atmosphere tube furnace and carbonize it under a nitrogen atmosphere. Raise the temperature to 800 °C at a heating rate of 2 ± 0.5 °C / min, hold for 1 h, and then cool to room temperature to obtain a flexible carbon nanofiber / porous carbon microsphere composite membrane, labeled as #CNF / HPCNS(1:3).

[0141] Figure 1 SEM images of different Examples 1-6.

[0142] Figure 1 a1 is the SEM image of the #CNF primary composite nanofiber membrane of Example 1; Figure 1 a2 is the SEM image of the pretreated fiber membrane of #CNF in Example 1; Figure 1 a3 is the SEM image of the carbonized fiber membrane of #CNF in Example 1. It can be seen that the pure aramid resin nanofiber membrane (#CNF) of Example 1 presents a uniform nanofibrous morphology, and obvious adhesion phenomena are observed in the carbonized carbon nanofibers, which is due to the micro-melting phenomenon of aramid resin during the pre-oxidation / carbonization process.

[0143] Figure 1 b1 is the SEM image of the #HPCNS primary composite nanofiber membrane of Example 2; Figure 1 b2 is the SEM image of the pretreated fiber membrane of #HPCNS in Example 2; Figure 1 b3 is the SEM image of the carbonized fiber membrane of #HPCNS in Example 2. Example 2 is a pure polyvinyl alcohol / polytetrafluoroethylene microsphere membrane (#HPCNS), which presents an electrostatic spraying state due to the use of a low-concentration solution during the preparation process and forms spherical shapes on the receiving roller. After carbonization, due to the thermal decomposition of polytetrafluoroethylene, the spherical shapes turn to form a honeycomb porous structure.

[0144] Figure 1 c1 is the SEM image of the #CNF / HPCNS(2:1) primary composite nanofiber membrane of Example 3; Figure 1 c2 is the SEM image of the pretreated fiber membrane of #CNF / HPCNS(2:1) in Example 3; Figure 1 c3 is the SEM image of the carbonized fiber membrane of #CNF / HPCNS(2:1) in Example 3. Figure 1 d1 is the SEM image of the #CNF / HPCNS(1:1) primary composite nanofiber membrane of Example 4; Figure 1 d2 is the SEM image of the pretreated fiber membrane of #CNF / HPCNS(1:1) in Example 4; Figure 1 d3 is the SEM image of the carbonized fiber membrane of #CNF / HPCNS(1:1) in Example 4; Figure 1e1 is the SEM image of the as - prepared CNF / HPCNS (1:2) composite nanofiber membrane in Example 5; Figure 1 e2 is the SEM image of the pretreated fiber membrane of CNF / HPCNS (1:2) in Example 5; Figure 1 e3 is the SEM image of the carbonized fiber membrane of CNF / HPCNS (1:2) in Example 5; Figure 1 f1 is the SEM image of the as - prepared CNF / HPCNS (1:3) composite nanofiber membrane in Example 6; Figure 1 f2 is the SEM image of the pretreated fiber membrane of CNF / HPCNS (1:3) in Example 6; Figure 1 f3 is the SEM image of the carbonized fiber membrane of CNF / HPCNS (1:3) in Example 6.

[0145] The flexible carbon nanofiber / porous carbon microsphere composite membranes of Examples 3 - 6 have both fibrous and spherical shapes, forming a three - dimensional structure, and after carbonization, an intertwined state of carbon nanofibers and honeycomb microspheres is formed. When the polyvinyl alcohol / polytetrafluoroethylene component is less, after pretreatment and carbonization, the fiber component still shows a micro - molten state similar to that of a pure aramid resin nanofiber membrane (#CNF). As the polyvinyl alcohol / polytetrafluoroethylene component increases, heat - insulating protection is formed during pretreatment and carbonization, the fiber component no longer melts, and at the same time, the number of spherical shapes in the image increases. When the weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrospray solution reaches 1:2, the two components of nanofibers and microspheres are evenly intertwined and distributed. However, when the polyvinyl alcohol / polytetrafluoroethylene electrospray solution continues to increase, reaching a weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrospray solution of 1:3, although more microsphere components are obtained and a higher specific surface area may be achieved, due to the lack of nanofiber components, it may not provide sufficient support during application.

[0146] Therefore, the optimal weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrospray solution is selected to reach 1:2. The three - dimensional carbon nanofiber / honeycomb porous carbon sphere structure formed after carbonization can provide a large number of attachment sites while providing good support, and provides good conditions for subsequent loading or modification.

[0147] Figure 2 This is a schematic diagram of the tensile properties and comprehensive properties of samples prepared by different weight fraction ratios and different processes of the aramid resin electrospinning solution and the polyvinyl alcohol / polytetrafluoroethylene electrospray solution of the present invention, where Figure 2 a is the tensile curve of Examples 1, 3, 4, and 5.

[0148] It can be seen that the pure aramid resin nanofiber membrane (#CNF) of Example 1 has the highest strength, with a strength of 0.43 MPa and an elongation at break that can reach 9.8%. As the component of the pure aramid resin electrospinning solution in the membrane body decreases and the component of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution increases, the strength of the flexible carbon nanofiber / porous carbon microsphere composite membrane shows a downward trend, and the elongation at break also decreases. When the weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrostatic spraying solution is 1:3, after carbonization, due to the low component of the aramid resin electrospinning solution and insufficient support, the membrane cannot complete the test. This proves that the aramid resin electrospinning solution in the flexible carbon nanofiber / porous carbon microsphere composite membrane plays an effective supporting role.

[0149] Figure 2 b is the flexible carbon nanofiber / porous carbon microsphere composite membrane of Example 5, and the physical object of the flexible carbon nanofiber / porous carbon microsphere composite membrane labeled #CNF / HPCNS(1:2); Figure 2 c is the flexible carbon nanofiber / porous carbon microsphere composite membrane of Example 5. The picture of the sample bending of the flexible carbon nanofiber / porous carbon microsphere composite membrane labeled #CNF / HPCNS(1:2) can be seen. It can be seen that the carbon membrane can be restored well after being bent by more than 90 degrees. It can be seen that the flexible carbon nanofiber / porous carbon microsphere composite membrane of Example 5 labeled #CNF / HPCNS(1:2) has good flexibility, which can provide good conditions for subsequent applications.

[0150] Figure 3 It is the XRD pattern of the flexible carbon nanofiber / porous carbon microsphere composite membrane products at different carbonization temperatures in Example 5. It can be seen from the figure that when the carbonization temperature is 500 °C, CNF / HPCNS has a main diffraction peak at 2θ = 18.2 °, which corresponds to the crystal plane of polytetrafluoroethylene PTFE. This is due to the incomplete decomposition of polytetrafluoroethylene PTFE at a lower carbonization temperature. As the temperature continues to rise, the sample has a broad diffraction peak in the range of 2θ = 20° - 30°, corresponding to the (002) crystal plane of amorphous carbon and having low crystallinity characteristics, indicating the porous morphology of the sample.

[0151] Figure 4 It is the product analysis spectrum diagram of Example 5 of the present invention, where Figure 4 a is the full XPS spectrum diagram of the as - prepared composite nanofiber membrane, the pre - treated fiber membrane, and the flexible carbon nanofiber / porous carbon microsphere composite membrane products of Example 5; Figure 4 b is the O1s spectrum diagram of the #CNF / HPCNS(1:2) product of Example 5; Figure 4c is the C1s spectrum of the product of Example 5 #CNF / HPCNS(1:2). XPS tests were carried out on the as - prepared composite nanofiber membrane, the pre - treated fiber membrane, and the flexible carbon nanofiber / porous carbon microsphere composite membrane of Example 5, labeled as the #CNF / HPCNS(1:2) product, to explore the elemental composition and elemental form of the materials. Four elements appear in the figure, namely the peaks of C, O, N, and F.

[0152] It can be seen that the F1s peak in the as - prepared composite nanofiber membrane and the pre - treated fiber membrane disappears in the flexible carbon nanofiber / porous carbon microsphere composite membrane of Example 5, labeled as the #CNF / HPCNS(1:2) sample, while the remaining C1s, O1s, and N1s peaks are retained, indicating that the F element decomposes during the carbonization process, and the C1s peak value increases significantly, proving the success of carbonization. The O1s spectrum of the flexible carbon nanofiber / porous carbon microsphere composite membrane of Example 5, labeled as #CNF / HPCNS(1:2), can be fitted into two characteristic peaks: the - O - H bond at 533.5 eV and the C = O bond at 530.2 eV, indicating that there are abundant oxygen - containing functional groups on the material surface. Figure 4 The spectrum in b is decomposed into three characteristic peaks: the main peak of C - C / C - H bond at 284.8 eV shows the formation of carbon materials, and the weaker O - C = O peak at 288.6 eV further confirms the existence of oxygen - containing functional groups. The existence of these oxygen - containing groups significantly enhances the surface polarity of the material, not only optimizing the interfacial wettability through hydrogen - bonding interactions, but also providing abundant chemically active sites for the anchoring of heterogeneous components, making the flexible carbon nanofiber / porous carbon microsphere composite membrane of Example 5, labeled as #CNF / HPCNS(1:2), exhibit good interfacial binding ability and functional controllability in the composite construction, laying a foundation for porous design and modification improvement.

[0153] Table 1 Structural parameters and electrical conductivity analysis of CNF, HPCNS, and CNF / HPCNS

[0154]

[0155] Figure 5 This is the low - temperature nitrogen adsorption curve and pore size distribution diagram of the products of Examples 1 to 6 of the present invention, including Figure 5 a is the low - temperature nitrogen adsorption curve of the products of Examples 1, 2, 3, 4, 5, and 6 of the present invention; Figure 5 b is the pore size distribution diagram of the products of Examples 1, 2, 3, 4, 5, and 6 of the present invention.

[0156] As Figure 5As shown in Figure a, the low-temperature nitrogen adsorption isotherm types of the pure polyvinyl alcohol / polytetrafluoroethylene microsphere membrane (#HPCNS) in Example 2 and the carbon nanofiber / porous carbon microsphere composite membrane samples in Examples 3-6 are a combination of Type I and Type IV isotherms, indicating that the carbon nanofiber / porous carbon microsphere composite membrane is a material integrating micropores, mesopores, and macropores. The low-temperature nitrogen adsorption isotherm type of the pure aramid resin nanofiber membrane (#CNF) in Example 1 is Type I, meaning that there are a large number of macropores or slit-shaped mesopores larger than in the pure aramid resin nanofiber membrane (#CNF) among carbon materials, and relatively fewer micropores. Figure 5 As shown in Figure b, the pure polyvinyl alcohol / polytetrafluoroethylene microsphere membrane (#HPCNS) sample has a large number of micropores and mesopores, while the pure aramid resin nanofiber membrane (#CNF) sample has fewer pores. The flexible carbon nanofiber / porous carbon microsphere sample presents a hierarchical pore structure and contains a large number of micropores around 2-3 nm and macropores > 35 nm, which may be due to the coexistence of polyvinyl alcohol / polytetrafluoroethylene microspheres and aramid resin nanofiber membranes.

[0157] A similar trend of change is also presented in the electrical conductivity of the materials. With the increase in the components of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray solution, the electrical conductivity increases from 18.42 S / cm of the pure aramid resin nanofiber membrane (#CNF) in Example 1 to 65.36 S / cm of the pure polyvinyl alcohol / polytetrafluoroethylene microsphere membrane (#HPCNF) in Example 2. For the flexible carbon nanofiber / porous carbon microsphere composite membrane in Example 5, the electrical conductivity of the sample labeled #CNF / HPCNS(1:2) is 59.82 S / cm. This improvement in conductivity can be attributed to two aspects: on the one hand, compared with the pure aramid resin nanofiber membrane (#CNF) in Example 1, the appropriate porous structure provides more channels for electron transport, and the relatively large number of micropore structures is conducive to the rapid transfer of interfacial charges. On the other hand, the higher the degree of graphitization, the better the electrical conductivity. The introduction of polytetrafluoroethylene in polyvinyl alcohol / polytetrafluoroethylene makes the structural matrix of the honeycomb porous carbon spheres thinner. The thin fibers are more conducive to the removal of heteroatoms during the carbonization process and are more likely to achieve a higher degree of graphitization. This synergistic optimization of structural parameters and electrical conductivity makes the flexible carbon nanofiber / porous carbon microsphere composite membrane an ideal carrier for electrode materials, providing a good foundation for subsequent loading of active substances.

[0158] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art can understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the content disclosed in the embodiments and drawings.

Claims

1. A flexible carbon nanofiber / porous carbon microsphere composite membrane, characterized in that: The materials and their weight fraction ratios for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane are as follows: 3-10 parts by weight of aramid resin; N, N-dimethylacetamide 20-60 parts by weight; 2-5 parts by weight of polyvinyl alcohol; Polytetrafluoroethylene 30-72 parts by weight.

2. The flexible carbon nanofiber / porous carbon microsphere composite membrane according to claim 1, characterized in that: The materials and their weight fraction ratios for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane are as follows: 4-6 parts by weight of aramid resin; 25-30 parts by weight of N,N-dimethylacetamide; Polyvinyl alcohol 4-5 parts by weight; 60-65 parts by weight of polytetrafluoroethylene.

3. A method for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane according to claim 1 or 2, characterized in that: The steps include: Step 1: Preparation of primary composite nanofiber membrane: 1.

1. Blend the polyvinyl alcohol solution and the polytetrafluoroethylene solution in a solute mass ratio of 2-5:30-72, add 5-20% water by mass of the solution to dilute, and stir to obtain a polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid; 1.

2. Dissolve the aramid resin in N, N-dimethylacetamide solvent, and stir to obtain an aramid resin electrospinning solution with a mass fraction of 12-17 wt%, wherein the weight fraction ratio of the aramid resin to the N, N-dimethylacetamide is 3-10:20-60; 1.3, using the above polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid and aramid resin electrostatic spinning liquid according to the above weight fraction ratio, through synchronous electrospinning / electrostatic spraying method to prepare a primary composite nanofiber membrane for use; Step 2: Preparation of flexible carbon nanofiber / porous carbon microsphere composite membrane: 2.

1. Pre-treat the nascent composite nanofiber membrane in an air atmosphere in a muffle furnace, with a preset temperature range of from room temperature to 250-270 °C, a heating rate of 0.5-3.0 °C / min, and a holding time of 0.5-3.0 h, and obtain the pre-treated fiber membrane after cooling to room temperature; 2.

2. The pretreated fiber membrane is placed in an open-vacuum atmosphere tubular electric furnace for carbonization under a nitrogen atmosphere, and the temperature is raised to the carbonization temperature at a rate of 0.5-3.0℃ / min, and the carbonization temperature is 500℃-900℃. After keeping warm for 0.5-2.0h, it is cooled to room temperature to obtain the carbonized fiber membrane, i.e., the finished flexible carbon nanofiber / porous carbon microsphere composite membrane.

4. The method for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane according to claim 3, characterized in that: The carbonization temperature is 800°C.

5. The method for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane according to claim 3, characterized in that: In the step 1.3, the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid and the aramid resin electrostatic spinning liquid are used to prepare a primary composite nanofiber membrane by a synchronous electrospinning / electrostatic spraying method, and the specific steps are as follows: A. The pre-configured polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid and aramid resin electrostatic spinning liquid are respectively loaded into the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid pipette and the aramid resin electrostatic spinning liquid pipette. The outlet ends of the pipettes are respectively equipped with a 0.4-1.2 mm diameter electrostatic spray liquid spray needle and an electrostatic spinning liquid spinning needle. The extrusion speed of the two solutions is accurately controlled by a precision micro-propulsion pump and set to a constant flow rate of 0.4-2.0 ml / h. The precise regulation of each component in the composite membrane is achieved by adjusting the ratio of the number of polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid pipettes and the number of aramid resin electrostatic spinning liquid pipettes; B. Apply a voltage of 25-35 kV, set the distance between the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid spray needle and the receiving device to 16-22 cm, set the distance between the aramid resin electrostatic spinning liquid spinning needle and the receiving device to 15-20 cm, set the temperature to 15-35°C, and the relative humidity to 40%-60%. Connect the positive electrode of the high-voltage power supply to the electrostatic spray liquid spray needle and the electrostatic spinning liquid spinning needle through an insulated wire clamp, and ground the receiving device. At the same time, insulate the contact parts between the wire clamp and the electrostatic spray liquid spray needle and the electrostatic spinning liquid spinning needle to ensure experimental safety. C. During the spinning process, the spinning needle of the aramid resin electrospinning liquid and the spray needle of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid make uniform reciprocating motion in the horizontal direction, the metal roller of the receiving device keeps rotating at a constant speed, the spray needle of the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray liquid forms polyvinyl alcohol / polytetrafluoroethylene droplets, and the spinning needle of the aramid resin electrospinning liquid forms aramid resin nanofibers, ensuring that the polyvinyl alcohol / polytetrafluoroethylene droplets and the aramid resin nanofibers are uniformly interwoven and deposited under the action of the electric field force. After the spinning is completed, the composite nanofiber membrane is peeled off from the receiving roller, and the primary composite nanofiber membrane is obtained after drying for use.

6. The method for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane according to claim 5, characterized in that: The weight fraction ratio of the aramid resin electrospinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray solution is 1-2:1-3, and the number of pipettes loaded with the aramid resin electrospinning solution and the number of pipettes loaded with the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray solution are 1-2:1-3.

7. The method for preparing the flexible carbon nanofiber / porous carbon microsphere composite membrane according to claim 6, characterized in that: The weight fraction ratio of the aramid resin electrostatic spinning solution to the polyvinyl alcohol / polytetrafluoroethylene electrostatic spray solution is 1:2.

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