Flexible paper-based supercapacitor and preparation method thereof

Abstract

The invention relates to a flexible paper-based supercapacitor, and the supercapacitor sequentially comprises the following structures from bottom to top: a positive electrode, an electrolyte layer, and a negative electrode. Wherein the positive electrode sequentially comprises a carbon nanotube paper layer and a poly (benzodifuran diketone)-activated carbon composite layer from bottom to top; the negative electrode sequentially comprises a poly (benzodifuran diketone)-activated carbon composite layer and a carbon nanotube paper layer from bottom to top; the electrolyte layer comprises a water-based diaphragm; and the electrolyte layer is completely divided into an upper part and a lower part by the water-based diaphragm. The carbon nanotubes are introduced into the cellulose paper, so that the cellulose paper has relatively high conductivity and excellent mechanical flexibility, and can be used as a substrate of a self-supporting electrode to load an active substance; the PBFDO and the active carbon (AC) are compounded to form a double-electrode layer-pseudocapacitance synergistic energy storage system, so that the electrochemical performance of the device is remarkably improved. The strategy breaks through the bottleneck of electrochemical performance and mechanical flexibility of the flexible supercapacitor, and has a wide prospect.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, and in particular to a flexible paper-based supercapacitor and its preparation method. Background Technology

[0002] With the rapid rise of emerging fields such as wearable electronics, flexible robots, and smart medical devices, the application scenarios of energy storage devices are shifting from traditional fixed types to flexible, portable, and wearable devices. The market's performance requirements for energy storage devices are no longer limited to a single electrochemical indicator, but are evolving towards the dual goals of "high electrochemical performance + excellent mechanical flexibility." Flexible supercapacitors, as a type of energy storage device that combines the high power density of traditional capacitors with the high energy density of secondary batteries, offer advantages such as fast charging and discharging speeds (completed within seconds) and long cycle life (up to 1000 cycles). 4 -10 6 With its outstanding advantages such as high efficiency and strong mechanical compatibility, it has become the core energy storage component of flexible electronic devices. Its performance directly depends on the structural design and material selection of the electrode material. Therefore, the development of high-performance flexible electrode materials has become the key to promoting the application of flexible supercapacitors.

[0003] As the core of flexible supercapacitors, flexible electrodes must meet dual performance requirements. In terms of electrochemistry, they need to have high specific surface area, excellent electronic conductivity and ion transport efficiency, as well as abundant charge storage sites; in terms of mechanical properties, they need to meet the requirements of lightweight, repeated bending, self-supporting and other flexible characteristics. The traditional preparation of flexible electrodes often adopts a ternary composite system of "active material-conductive agent-binder", which is loaded onto the surface of metal foil current collector through processes such as coating, scraping or printing. However, this technical route has many inherent defects: (1) the binder is easy to block the pore structure of the active material, reduce the utilization rate of active sites, and also increase the charge transport resistance inside the electrode; (2) the addition of conductive agent increases the load and cost of the process, and some conductive agents have poor compatibility with active materials and binders, which can easily cause interface separation problems; (3) although the metal current collector has excellent conductivity, its rigidity and high mass ratio seriously affect the flexibility improvement and energy density optimization of the device. In addition, the interlayer bonding force of traditional electrodes is generally weak. During repeated mechanical deformation, the active material is prone to detach from the current collector, causing the device performance to degrade rapidly. This makes it difficult to meet the long-term service stability requirements of energy storage devices in application scenarios such as wearable electronic devices.

[0004] Cellulose paper, as a natural polymer material that is abundant, inexpensive, biodegradable, and exhibits excellent mechanical flexibility, offers new insights into the structural innovation of flexible electrodes due to its porous structure formed by interwoven fibers. However, the insulating properties of pure cellulose paper severely limit its direct application as an electrode material, necessitating conductive modification to meet electrochemical performance requirements. Existing conductive modification strategies mainly include carbon material (graphene, carbon nanotubes, activated carbon, etc.) composites, metal nanoparticle deposition, and in-situ polymerization of conductive polymers. Among these, carbon material composite modification is the most commonly used method due to its low cost and significant conductivity improvement. However, traditional composite processes such as solution immersion, chemical vapor deposition, and in-situ reduction have several drawbacks: solution immersion easily leads to localized agglomeration of carbon materials, resulting in uneven conductive network construction; chemical vapor deposition requires harsh reaction conditions such as high temperature and vacuum, and the preparation process is complex; in-situ reduction may introduce impurity ions, affecting the electrochemical stability of the electrode. Furthermore, traditional carbon-modified paper-based electrodes rely on a single double-layer capacitance energy storage mechanism, resulting in relatively low energy density, which is insufficient to meet the high energy density requirements of flexible electronic devices.

[0005] Regarding the selection of active materials, conductive polymers, as typical pseudocapacitive materials, achieve charge storage through rapid and reversible redox reactions. They possess advantages such as high specific capacitance, significant potential for energy density improvement, and solution processability. Combining them with high specific surface area carbon materials can construct a synergistic energy storage system of "electric double-layer capacitor-pseudocapacitor," significantly improving the overall electrochemical performance of the device. Furthermore, the flexibility of conductive polymers ensures good compatibility with paper-based substrates, and their solution processability facilitates integration with papermaking processes, enabling uniform loading and structural control of the active material. However, traditional conductive polymers such as polypyrrole (PPY) and polyaniline (PANI) suffer from insufficient conductivity and poor cycle stability, easily undergoing volume expansion and contraction during charge and discharge, leading to active material detachment.

[0006] In summary, existing flexible supercapacitor electrodes suffer from technical bottlenecks such as complex fabrication processes, high costs, difficulty in simultaneously improving electrochemical performance and mechanical flexibility, easy shedding of active materials, and insufficient cycle stability. These bottlenecks severely restrict the large-scale application of flexible supercapacitors in emerging fields such as wearable electronics and flexible robots.

[0007] Therefore, developing a flexible electrode and supercapacitor that is simple to prepare, low in cost, environmentally friendly, and can achieve a synergistic improvement in high electrochemical performance and excellent mechanical flexibility is key to promoting the practical application of flexible energy storage devices. Summary of the Invention

[0008] To address the shortcomings of existing technologies, such as insufficient conductivity of flexible electrodes, weak interfacial bonding between active materials and substrates leading to easy detachment, complex and costly fabrication processes, and the difficulty in simultaneously achieving electrochemical performance and mechanical flexibility, this invention provides a flexible paper-based supercapacitor and its fabrication method. Specifically, multi-walled carbon nanotubes are incorporated into cellulose paper using a papermaking process, and activated carbon (AC) is additionally added to a novel n-type conductive polymer, poly(benzodifurandione) (PBFDO). The carbon nanotube-based paper (CNTP) formed by the introduction of carbon nanotubes exhibits high conductivity and excellent mechanical flexibility, serving as a substrate for self-supporting electrodes to load active materials. The composite of PBFDO and AC forms a double-layer pseudocapacitive synergistic energy storage system, significantly improving the electrochemical performance of the device. Experimental results show that the obtained flexible paper-based supercapacitor has a specific capacitance of 181.6 F / g, and retains more than 92% of its capacitance after 10,000 cycles at different bending angles. This strategy breaks through the traditional bottlenecks in the electrochemical performance and mechanical flexibility of flexible supercapacitors, demonstrating the broad prospects for realizing high-performance flexible energy storage devices through the synergistic design of substrate materials and active materials.

[0009] One object of the present invention is to provide a flexible paper-based supercapacitor, which comprises, from bottom to top, the following structure: a positive electrode, an electrolyte layer, and a negative electrode; in, The positive electrode comprises, from bottom to top: a carbon nanotube paper layer and a poly(benzodifurandione)-activated carbon composite layer; The negative electrode comprises, from bottom to top: a poly(benzodifurandione)-activated carbon composite layer and a carbon nanotube paper layer; The electrolyte layer includes an aqueous membrane; The aqueous membrane divides the electrolyte layer into upper and lower parts.

[0010] The aqueous separator must be larger than both the positive and negative electrodes to ensure that it can always completely separate the electrolyte layer into two independent parts. The aqueous separator can be parallel to the horizontal planes of the positive and negative electrodes, or it can be at a certain angle to the horizontal planes of the positive and negative electrodes.

[0011] Furthermore, the electrolyte material is selected from one or more of polyvinyl alcohol and neutral salts.

[0012] Furthermore, the neutral salt is selected from one or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

[0013] Furthermore, the material of the aqueous diaphragm is selected from one or more of cellulose paper, polypropylene, and PAN / PVDF-HFP (polyacrylonitrile-polyvinylidene fluoride-hexafluoropropylene copolymer).

[0014] Another object of the present invention is to provide a method for preparing the flexible paper-based supercapacitor, the method comprising the following steps: S1-1. Carbon nanotube paper is obtained by blending carbon nanotubes and cellulose pulp, beating, papermaking, filtration and drying. S1-2. Under an inert atmosphere, 2,3,5,6-tetramethyl-1,4-benzoquinone and 3,7-dihydrobenzo[1,2-b:4,5-b]difuran-2,6-dione are mixed and heated and stirred to obtain a poly(benzodifuran-dione) solution. S1-3. Add the activated carbon dispersion to the poly(benzodifurandione) solution and disperse it by ultrasonication to obtain poly(benzodifurandione)-activated carbon slurry; S1-4. The poly(benzodifurandione)-activated carbon slurry is drop-coated onto the carbon nanotube paper to obtain the positive electrode and the negative electrode. S2. Immerse the positive and negative electrodes in an electrolyte solution; S3. Place an aqueous membrane on the positive electrode, coat it with an electrolyte solution, and wait for the electrolyte to completely wet the aqueous membrane to obtain an electrolyte layer. S4. Place the negative electrode on the side of the electrolyte layer away from the positive electrode to obtain a flexible paper-based supercapacitor.

[0015] Further, in step S1-1, the mass ratio of the carbon nanotubes to the cellulose pulp is (1-3):(1-3).

[0016] Further, in steps S1-2, the concentration of the poly(benzodifurandione) solution is 8-12 mg / ml.

[0017] Further, in step S3, the concentration of polyvinyl alcohol in the electrolyte solution is 0.1-1 g / L.

[0018] Furthermore, in step S3, the concentration of the neutral salt in the electrolyte solution is 1-5 mol / L.

[0019] The present invention has the following beneficial effects: This invention applies paper-based materials, carbon materials, and n-type conductive polymer materials to the construction of electrode materials for flexible paper-based supercapacitors. The resulting electrodes exhibit excellent electrochemical performance in flexible paper-based supercapacitors. After testing, the electrodes of this invention have excellent energy storage performance and structural stability.

[0020] Furthermore, by using a strategy of loading active materials (i.e., poly(benzodifurandione)-activated carbon composite layer) onto carbon nanotube paper to prepare electrodes, the present invention can achieve excellent mechanical flexibility and cycle stability. The flexible paper-based supercapacitor device retains more than 92% of its capacity after 10,000 cycles under bending conditions of 0°, 45°, 90°, and 180°. This is because the carbon nanotube paper adheres well to the solution-processable active material and there is no obvious peeling phenomenon.

[0021] Furthermore, the synergistic effect of the double-layer capacitance and pseudocapacitance of activated carbon and poly(benzodifurandione) can significantly improve the specific capacitance. Experimental results show that by adjusting the ratio of activated carbon to poly(benzodifurandione) to achieve double-layer capacitance-pseudocapacitance synergy, the specific capacitance of flexible paper-based supercapacitor devices can be increased to 181.6 F / g. This strategy breaks through the traditional bottlenecks in the electrochemical performance and mechanical flexibility of flexible supercapacitors, demonstrating the broad prospect of realizing high-performance flexible energy storage devices through the synergistic design of substrate and active materials. Attached Figure Description

[0022] Figure 1 This is a partial structural schematic diagram of the flexible paper-based supercapacitor described in this invention.

[0023] Figure 2 The cyclic voltammetry (CV) curves of the flexible paper-based supercapacitors in Examples 1, 2, 3, and 4 of this invention are shown at a scan rate of 10 mV / s.

[0024] Figure 3 The cyclic voltammetry (CV) curves of the flexible paper-based supercapacitor in Embodiment 2 of the present invention at a scan rate of 10-100 mV / s are shown.

[0025] Figure 4 The galvanostatic charge-discharge curves (GCDs) of the flexible paper-based supercapacitors in Examples 1, 2, 3, 4, Comparative Example 1, and Comparative Example 2 of this invention are shown.

[0026] Figure 5 The image shows the galvanostatic charge-discharge curve (GCD) of the flexible paper-based supercapacitor in Embodiment 2 of the present invention at a current density of 1-10 A / g.

[0027] Figure 6 Images of the flexible paper-based supercapacitor in Embodiment 2 of the present invention at different bending angles.

[0028] Figure 7 The results of GCD cycle stability tests of the flexible paper-based supercapacitor in Embodiment 2 of the present invention under different bending angles are shown. Detailed Implementation

[0029] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0030] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0031] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0032] The preparation examples and embodiments of the present invention use the following raw materials: Cellulose pulp: purchased from Shandong Sun Paper Industry Co., Ltd.

[0033] Carbon nanotubes: grade HQNANO-CNTs-013, purchased from Shenzhen Youyan Technology Co., Ltd.

[0034] Activated carbon: YP-50F, purchased from Shenzhen Youyan Technology Co., Ltd.

[0035] Electrolyte solution: 2 M sodium chloride aqueous solution containing 1 g / L polyvinyl alcohol.

[0036] Hydrophilic separator: Celgard3501NKK cellulose separator from the hydrophilic separator series, purchased from Oulage (Chongqing) New Material Technology Co., Ltd.

[0037] Preparation Example 1 A method for preparing a flexible paper-based electrode includes the following steps: S1-1, Preparation of carbon nanotube paper: Cellulose pulp (1.0 g) and carbon nanotubes (1.0 g) were dispersed in 500 mL of deionized water and mechanically stirred for 2 h until uniformly dispersed to obtain pulp. The pulp was poured into a paper forming machine for vacuum filtration and then transferred to a paper drying machine for drying at 100 °C for 20 min to obtain carbon nanotube paper. S1-2, Preparation of poly(benzodifurandione) solution: The oxidant 2,3,5,6-tetramethyl-1,4-benzoquinone (2.7 g) and 3,7-dihydrobenzo[1,2-b:4,5-b]difuran-2,6-dione (1.9 g) were dissolved in 127 mL of ultra-dry dimethyl sulfoxide and reacted at 90 °C for 3 h under a nitrogen atmosphere. Then, 40 mL of ultra-dry dimethyl sulfoxide was added under nitrogen protection and the reaction was stirred for another 3 h. After the reaction was completed, the product was transferred to a 10 kDa dialysis bag and dialyzed with dimethyl sulfoxide to remove small molecular weight impurities from the reaction solution. After dialysis, an n-type conductive polymer solution (i.e., poly(benzodifuran-dione) solution) was obtained. The solution concentration was adjusted to 10 mg / mL, and the solvent was dimethyl sulfoxide. S1-3. Disperse 100 mg of activated carbon in 10 mL of dimethyl sulfoxide and sonicate until uniformly dispersed to obtain an activated carbon dispersion of 10 mg / mL. Add 0.1 mL of the activated carbon dispersion to 0.9 mL of the poly(benzodifurandione) solution of 10 mg / mL and sonicate until uniformly dispersed to obtain 1.0 mL of poly(benzodifurandione)-activated carbon slurry of 10 mg / mL (mass ratio of activated carbon to poly(benzodifurandione) = 1:9). S1-4. 1.0 mL of the poly(benzodifurandione)-activated carbon slurry was drop-coated onto the carbon nanotube paper and dried at 60 °C for 6 h in a vacuum environment to obtain the positive electrode and the negative electrode, respectively.

[0038] Preparation Example 2 A method for preparing a flexible paper-based electrode includes the following steps: S1-1 and S1-2 are the same as those in Preparation Example 1; S1-3. Disperse 100 mg of activated carbon in 10 mL of dimethyl sulfoxide and sonicate until uniformly dispersed to obtain an activated carbon dispersion of 10 mg / mL. Add 0.3 mL of the activated carbon dispersion to 0.7 mL of the poly(benzodifurandione) solution of 10 mg / mL and sonicate until uniformly dispersed to obtain 1.0 mL of poly(benzodifurandione)-activated carbon slurry of 10 mg / mL (mass ratio of activated carbon to poly(benzodifurandione) = 3:7). S1-4. 1.0 mL of the poly(benzodifurandione)-activated carbon slurry was drop-coated onto the carbon nanotube paper and dried at 60 °C for 6 h in a vacuum environment to obtain the positive electrode and the negative electrode, respectively.

[0039] Preparation Example 3 A method for preparing a flexible paper-based electrode includes the following steps: S1-1 and S1-2 are the same as those in Preparation Example 1; S1-3. Disperse 100 mg of activated carbon in 10 mL of dimethyl sulfoxide and sonicate until uniformly dispersed to obtain an activated carbon dispersion of 10 mg / mL. Add 0.5 mL of the activated carbon dispersion to 0.5 mL of the poly(benzodifurandione) solution of 10 mg / mL and sonicate until uniformly dispersed to obtain 1.0 mL of poly(benzodifurandione)-activated carbon slurry of 10 mg / mL (mass ratio of activated carbon to poly(benzodifurandione) = 5:5). S1-4. 1.0 mL of the poly(benzodifurandione)-activated carbon slurry was drop-coated onto the carbon nanotube paper and dried at 60 °C for 6 h in a vacuum environment to obtain the positive electrode and the negative electrode, respectively.

[0040] Preparation Example 4 A method for preparing a flexible paper-based electrode includes the following steps: S1-1 and S1-2 are the same as those in Preparation Example 1; S1-3. Disperse 100 mg of activated carbon in 10 mL of dimethyl sulfoxide and sonicate until uniformly dispersed to obtain an activated carbon dispersion of 10 mg / mL. Add 0.7 mL of the activated carbon dispersion to 0.3 mL of the poly(benzodifurandione) solution of 10 mg / mL and sonicate until uniformly dispersed to obtain 1.0 mL of poly(benzodifurandione)-activated carbon slurry of 10 mg / mL (mass ratio of activated carbon to poly(benzodifurandione) = 7:3). S1-4. 1.0 mL of the poly(benzodifurandione)-activated carbon slurry was drop-coated onto the carbon nanotube paper and dried at 60 °C for 6 h in a vacuum environment to obtain the positive electrode and the negative electrode, respectively.

[0041] Example 1 A flexible paper-based supercapacitor, comprising, from bottom to top, the following structure: a positive electrode (163 μm), an electrolyte layer (200 μm), and a negative electrode (163 μm). in, The positive electrode comprises, from bottom to top: a carbon nanotube paper layer (160 μm) and a poly(benzodifuran dione)-activated carbon composite layer (3 μm). The negative electrode comprises, from bottom to top: a poly(benzodifurandione)-activated carbon composite layer (3 μm) and a carbon nanotube paper layer (160 μm). The electrolyte layer includes an aqueous membrane; The aqueous membrane completely separates the electrolyte layer into upper and lower parts; The positive and negative electrodes were prepared according to Preparation Example 1; The method for preparing the flexible paper-based supercapacitor includes the following steps: S2. Soak the positive and negative electrodes in the electrolyte solution for 6 hours before use; S3. Place an aqueous separator on the poly(benzodifurandione)-activated carbon composite layer of the positive electrode, allowing the aqueous separator and the poly(benzodifurandione)-activated carbon composite layer to adhere naturally. Then, apply 200 μL of electrolyte solution, allowing the electrolyte to completely wet the aqueous separator and naturally penetrate to a certain thickness above and below the aqueous separator layer, thus obtaining the electrolyte layer. It is worth mentioning that the size of the aqueous separator must be larger than the size of both the positive and negative electrodes to ensure that the aqueous separator can always completely separate the electrolyte layer into two independent parts.

[0042] S4. Place the negative electrode on the electrolyte layer, so that the poly(benzodifurandione)-activated carbon composite layer of the negative electrode is in contact with the electrolyte layer, press it tightly, and dry it in a vacuum environment at 60 °C for 3 h to obtain the flexible paper-based supercapacitor.

[0043] Figure 1 This is a partial structural schematic diagram of the flexible paper-based supercapacitor described in this invention.

[0044] Example 2 A flexible paper-based supercapacitor differs from Example 1 in that the positive and negative electrodes are prepared by Preparation Example 2, while the remaining components, structure, and preparation method are the same as in Example 1.

[0045] Example 3 A flexible paper-based supercapacitor differs from Example 1 in that the positive and negative electrodes are prepared by Preparation Example 3, while the remaining components, structure, and preparation method are the same as in Example 1.

[0046] Example 4 A flexible paper-based supercapacitor differs from Example 1 in that the positive and negative electrodes are prepared by Preparation Example 4, while the remaining components, structure, and preparation method are the same as in Example 1.

[0047] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that S1-3 and S1-4 are modified as follows: S1-3. Disperse 100 mg of activated carbon in 10 mL of dimethyl sulfoxide and sonicate until the dispersion is uniform to obtain an activated carbon dispersion of 10 mg / mL. S1-4. 1.0 mL of the activated carbon dispersion was drop-coated onto the carbon nanotube paper and dried at 60°C in a vacuum environment for 6 h to obtain the positive electrode and the negative electrode, respectively.

[0048] The remaining components, structure, and preparation method are the same as in Example 1.

[0049] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that S1-2 is deleted, and the 10 mg / mL poly(benzodifurandione) solution in S1-3 is replaced with a 10 mg / mL solution of p-type conductive polymer poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) (Clevios PH1000 model). The product of S1-3 is named slurry, and the poly(benzodifurandione)-activated carbon slurry in S1-4 is replaced with slurry.

[0050] Test Example 1 The flexible paper-based supercapacitors prepared in Examples 1-4 were subjected to cyclic voltammetry (CV) electrochemical analysis.

[0051] Test method: The flexible paper-based supercapacitors of Examples 1-4 were used in a two-electrode system and cyclic voltammetry (CV) electrochemical analysis was performed using a CHI660E electrochemical analyzer. The two-electrode cell measurement was performed by connecting the conductive copper wire from the flexible paper-based supercapacitors of Examples 1-4 to the electrochemical analyzer, with a scan rate of 10 mV / s.

[0052] Test results are as follows Figure 2 As shown.

[0053] Figure 2 The cyclic voltammetry (CV) curves of the flexible paper-based supercapacitors in Examples 1, 2, 3, and 4 of this invention are shown at a scan rate of 10 mV / s.

[0054] As can be seen from the figure, the device operates stably within a voltage window of 0 V to 1 V, and the CV curve is close to a rectangle, showing good capacitive behavior and suitable for stable charge and discharge operation.

[0055] Test Example 2 The flexible paper-based supercapacitor prepared in Example 2 was subjected to cyclic voltammetry (CV) electrochemical analysis.

[0056] Test method: The flexible paper-based supercapacitor of Example 2 was used in a two-electrode system and cyclic voltammetry (CV) electrochemical analysis was performed using a CHI660E electrochemical analyzer. The two-electrode cell measurement was performed by connecting the conductive copper wire from the flexible paper-based supercapacitor of Example 2 to the electrochemical analyzer, with scan rates of 10 mV / s, 20 mV / s, 50 mV / s, and 100 mV / s.

[0057] Test results are as follows Figure 3As shown.

[0058] Figure 3 The cyclic voltammetry (CV) curves of the flexible paper-based supercapacitor in Embodiment 2 of the present invention at a scan rate of 10-100 mV / s are shown.

[0059] As can be seen from the figure, the CV curve of the device remains close to a rectangle even at high scan rates, indicating good capacitive behavior and good electrochemical stability.

[0060] Test Example 3 Constant current charge-discharge (GCD) analysis was performed on the flexible paper-based supercapacitors prepared in Examples 1-4 and Comparative Examples 1-2.

[0061] Test method: The flexible paper-based supercapacitors prepared in Examples 1-4 and Comparative Examples 1-2 were analyzed using a two-electrode system with a CHI660E electrochemical analyzer via constant current charge-discharge (GCD) analysis. The two-electrode cell measurements were performed using the method described in Examples 1-4 and Comparative Examples 1-2, where a conductive copper wire was led out from the flexible paper-based supercapacitor and connected to the electrochemical analyzer. The GCD method was used for testing, with a constant charging / discharging current density of 1 A / g applied and a potential window set from 0 V to 1.0 V. The specific capacitance (Cs) can be calculated from the GCD curve using the following equation: Cs = IΔt / mΔV I is the constant discharge current; Δt is the discharge time; m is the mass of the active material; ΔV is the discharge voltage drop.

[0062] Test results are as follows Figure 4 As shown.

[0063] Figure 4 The galvanostatic charge-discharge curves (GCDs) of the flexible paper-based supercapacitors in Examples 1, 2, 3, 4, Comparative Example 1, and Comparative Example 2 of this invention are shown.

[0064] It can be seen that the flexible paper-based supercapacitors of Examples 1, 2, and 3 all exhibit longer charge-discharge times than Comparative Examples 1 and 2, i.e., higher specific capacitance. Among them, Example 2 reaches 181.6 F / g, indicating that the electrode material of Example 2 has an advantage in specific capacitance.

[0065] Test Example 4 The flexible paper-based supercapacitor prepared in Example 2 was subjected to constant current charge-discharge (GCD) analysis.

[0066] Test method: The flexible paper-based supercapacitor from Example 2 was analyzed using a CHI660E electrochemical analyzer via a two-electrode system and constant current charge-discharge (GCD) method. The two-electrode cell measurement was performed by connecting a conductive copper wire from the flexible paper-based supercapacitor in Example 2 to the electrochemical analyzer. A constant charge / discharge current density of 1 A / g–10 A / g was applied, with the potential window set to 0 V–1.0 V. The specific capacitance (Cs) can be calculated from the GCD curve using the following equation: Cs = IΔt / mΔV I is the constant discharge current; Δt is the discharge time; m is the mass of the active material; ΔV is the discharge voltage drop.

[0067] Test results are as follows Figure 5 As shown.

[0068] Figure 5 The image shows the galvanostatic charge-discharge curve (GCD) of the flexible paper-based supercapacitor in Embodiment 2 of the present invention at a current density of 1-10 A / g.

[0069] The figure shows the charging and discharging process of the flexible paper-based supercapacitor of Example 2 at different current densities, demonstrating its good charging and discharging stability and high specific capacitance. It can be seen that at a current density of 1 A / g, the device exhibits a specific capacitance of 181.6 F / g; at a current density of 2 A / g, it still maintains a specific capacitance of 179.7 F / g; even at a current density of 10 A / g, the specific capacitance is maintained at 172.0 F / g, showing that the electrode material of Example 2 has excellent specific capacitance retention at different current densities.

[0070] Test Example 5 The flexible paper-based supercapacitor of Example 2 was subjected to constant current charge-discharge (GCD) analysis using a CHI660E electrochemical analyzer at different bending angles with a two-electrode system.

[0071] Figure 6 Images of the flexible paper-based supercapacitor in Embodiment 2 of the present invention at different bending angles.

[0072] As can be seen, the device maintains its basic shape and has good mechanical flexibility and bendability.

[0073] Figure 7 The results of GCD cycle stability tests of the flexible paper-based supercapacitor in Embodiment 2 of the present invention under different bending angles are shown.

[0074] The figure shows that after 10,000 charge-discharge cycles at 1 A / g and 0-1.0 V, devices with different bending angles have a capacitance retention rate of over 92%, demonstrating the versatility of the paper-based loading and active material composite strategy proposed in this invention in balancing the electrochemical performance and mechanical flexibility of flexible paper-based supercapacitors.

[0075] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0076] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A flexible paper-based supercapacitor, characterized in that, The flexible paper-based supercapacitor comprises, from bottom to top, the following structure: positive electrode, electrolyte layer, and negative electrode; in, The positive electrode comprises, from bottom to top: a carbon nanotube paper layer and a poly(benzodifurandione)-activated carbon composite layer; The negative electrode comprises, from bottom to top: a poly(benzodifurandione)-activated carbon composite layer and a carbon nanotube paper layer; The electrolyte layer includes an aqueous membrane that divides the electrolyte layer into upper and lower parts.

2. The flexible paper-based supercapacitor according to claim 1, characterized in that, The electrolyte material is selected from one or more of polyvinyl alcohol and neutral salts.

3. The flexible paper-based supercapacitor according to claim 2, characterized in that, The neutral salt is selected from one or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

4. The flexible paper-based supercapacitor according to claim 1, characterized in that, The material of the water-based diaphragm is selected from one or more of cellulose paper, polypropylene, and PAN / PVDF-HFP.

5. The method for preparing the flexible paper-based supercapacitor according to any one of claims 1-4, characterized in that, The method for preparing the flexible paper-based supercapacitor includes the following steps: S1-1. Carbon nanotube paper is obtained by blending carbon nanotubes and cellulose pulp, beating, papermaking, filtration and drying. S1-2. Under an inert atmosphere, 2,3,5,6-tetramethyl-1,4-benzoquinone and 3,7-dihydrobenzo[1,2-b:4,5-b]difuran-2,6-dione are mixed and heated and stirred to obtain a poly(benzodifuran-dione) solution. S1-3. Add the activated carbon dispersion to the poly(benzodifurandione) solution and disperse it by ultrasonication to obtain poly(benzodifurandione)-activated carbon slurry; S1-4. The poly(benzodifurandione)-activated carbon slurry is drop-coated onto the carbon nanotube paper to obtain the positive electrode and the negative electrode. S2. Immerse the positive and negative electrodes in an electrolyte solution; S3. Place an aqueous membrane on the positive electrode, coat it with an electrolyte solution, and wait for the electrolyte to completely wet the aqueous membrane to obtain an electrolyte layer. S4. Place the negative electrode on the side of the electrolyte layer away from the positive electrode to obtain a flexible paper-based supercapacitor.

6. The method for preparing the flexible paper-based supercapacitor according to claim 5, characterized in that, In step S1-1, the mass ratio of carbon nanotubes to cellulose pulp is (1-3):(1-3).

7. The method for preparing the flexible paper-based supercapacitor according to claim 5, characterized in that, In steps S1-2, the concentration of the poly(benzodifurandione) solution is 8-12 mg / ml.

8. The method for preparing the flexible paper-based supercapacitor according to claim 5, characterized in that, In step S3, the concentration of polyvinyl alcohol in the electrolyte solution is 0.1-1 g / L.

9. The method for preparing the flexible paper-based supercapacitor according to claim 5, characterized in that, In step S3, the concentration of the neutral salt in the electrolyte solution is 1-5 mol / L.

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