Quantitative preparation method of high-capacity self-supporting pseudocapacitance composite membrane electrode

Abstract

The invention provides a quantitative preparation method of a high-capacity self-supporting pseudocapacitance composite membrane electrode, and belongs to the technical field of supercapacitor electrode materials, and the method comprises the following steps: mixing a prepared high-performance pseudocapacitance material alpha-Fe2O3 and a carbon nanotube (CNT) in N-methyl pyrrolidone according to a certain mass ratio, and stirring to form uniformly dispersed slurry; depositing the dispersed slurry on a filter membrane in a vacuum filtration manner to form a wet membrane with a certain thickness; and further drying the wet membrane, and stripping the wet membrane from the filter membrane to obtain the self-supported composite membrane electrode. According to the invention, the mass ratio of the pseudocapacitance material to the CNT conductive skeleton is precisely defined, the key mass ratio window suitable for preparing the high-performance self-supporting composite membrane electrode by the vacuum filtration method is clearly provided for the first time, and the spanning of the membrane forming process from experience exploration to quantitative controllability is realized. And the prepared alpha-Fe2O3 / CNT composite membrane has excellent electrochemical performance and also shows good flexibility at the same time.

Description

Technical Field

[0001] This invention relates to the field of energy storage materials and flexible electronic devices, specifically to a quantitative preparation method for self-supporting composite thin film electrodes for energy storage devices such as supercapacitors and lithium-ion batteries. In particular, it is a controllable preparation method that achieves high active material loading, excellent mechanical properties and complete film formation by precisely limiting the mass ratio range of pseudocapacitive material to CNT. Background Technology

[0002] With the rapid development of emerging technologies such as wearable electronic devices, flexible displays, and implantable medical devices, there is an urgent need for energy storage devices that are lightweight, thin, highly flexible, and have high energy density. Self-supporting membrane electrodes, because they do not require the use of traditional current collectors (such as nickel foam and carbon cloth), can be used directly as active electrodes in energy storage devices, and have the potential to simplify device structure, improve energy density, and achieve good flexibility, making them a current research hotspot.

[0003] Currently, the mainstream approach to fabricating high-performance self-supporting film electrodes relies on constructing a three-dimensional conductive network using one-dimensional (e.g., CNTs) or two-dimensional (e.g., graphene) carbon nanomaterials through vacuum filtration. However, the energy storage mechanism of such pure carbon-based electrodes primarily depends on the electric double-layer capacitance, resulting in generally low areal capacitance (typically < 1 F cm⁻¹). -2 This limits its application in high-energy-output scenarios. To improve capacity, introducing pseudocapacitive materials with Faraday pseudocapacitive behavior (such as Fe2O3, NiO, etc.) is an effective approach. These materials store charge through rapid, reversible redox reactions on or near the surface, and their theoretical specific capacity is much higher than that of carbon materials.

[0004] However, the fabrication of self-supporting thin films by compositing high-capacity rigid pseudocapacitive metal particles with flexible CNTs faces significant challenges. If the CNT content is too high, while film formation is easy, the increase in electrode capacity is limited. Conversely, blindly increasing the proportion of pseudocapacitive materials to pursue high capacity easily leads to discontinuous carbon networks, preventing the composite slurry from forming a complete, dense, and sufficiently strong film during the film-forming process. This results in cracking after drying, brittleness, inability to peel off from the substrate, or extremely poor mechanical strength. In existing technologies, for specific systems (such as α-Fe₂O₃ / CNT), there is a lack of clear guiding principles and theoretical basis for determining a quantitative ratio range that ensures reliable film formation while maximizing the loading of active materials. This restricts the reliable and efficient fabrication of high-performance flexible electrodes. Summary of the Invention

[0005] The purpose of this invention is to provide a universally applicable quantitative preparation method to address the problems of difficulty in film formation and difficulty in balancing performance and mechanical strength of pseudocapacitive materials in the prior art.

[0006] The present invention provides a quantitative preparation method for a high-capacity self-supporting pseudocapacitive composite film electrode. By precisely defining the mass ratio of the pseudocapacitive material to the CNT conductive framework, it for the first time clearly proposes a key mass ratio window suitable for preparing high-performance self-supporting composite film electrodes by vacuum filtration, realizing a leap from "experience-based exploration" to "quantitatively controllable" film formation process. The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0007] A quantitative fabrication method for a high-capacitance self-supporting pseudocapacitive composite thin-film electrode, comprising the following steps:

[0008] S1. A pseudocapacitive active material and carbon nanotubes are mixed at a mass ratio of (0.5~2):1 and dispersed in N-methylpyrrolidone to form a uniform dispersion slurry; the total mass of the pseudocapacitive active material and carbon nanotubes is 150~450 mg; the pseudocapacitive active material is one of α-Fe2O3, Co3O4, and NiO nanoparticles, preferably α-Fe2O3 nanoparticles;

[0009] S2. The dispersion slurry is deposited onto a filter membrane to form a wet film by vacuum filtration;

[0010] S3. Dry the wet membrane and peel it off from the filter membrane to obtain a self-supporting composite thin film electrode.

[0011] The preferred method for preparing α-Fe2O3 nanoparticles includes the following steps:

[0012] (1) Weigh 5.2 mmol of ferric chloride hexahydrate (FeCl3·6H2O) and 5.2 mmol of terephthalic acid and place them in a reaction vessel;

[0013] (2) Add 100 mL of N,N-dimethylformamide (DMF) solvent to the container and stir continuously at room temperature until the solid is completely dissolved to obtain a clear solution;

[0014] (3) Transfer the solution obtained in step (2) to a high-pressure reactor lined with polytetrafluoroethylene, seal it and place it in an oven for a solvothermal reaction at 150°C for 18 hours.

[0015] (4) After the reaction was completed, the mixture was naturally cooled to room temperature. The orange precipitate was collected by centrifugation and washed several times with DMF and ethanol alternately. Finally, it was vacuum dried at 60°C to obtain the MIL-101(Fe) precursor.

[0016] (5) The MIL-101(Fe) precursor obtained in step (4) is placed in a muffle furnace and heated to 350°C at a heating rate of 5°C / min in air atmosphere, and calcined at this temperature for 6 hours.

[0017] (6) After calcination, the furnace is naturally cooled to room temperature to obtain brownish-red α-Fe2O3 nanoparticle powder.

[0018] Preferably, the CNTs in step S1 are carboxylated to enhance their dispersibility and interfacial bonding with the active material.

[0019] Preferably, the composite film electrode obtained in step S3 has a thickness of 50-150 μm, and more preferably 100 μm.

[0020] Preferably, the mass ratio of pseudocapacitive active material to CNT in step S1 is 2:1.

[0021] Another object of the present invention is to provide a high-performance self-supporting pseudocapacitive composite film electrode, which combines high areal capacitance, excellent flexibility, and structural integrity. This electrode is an α-Fe₂O₃ / CNT composite film electrode prepared by the method described in any of the preceding claims, with a capacitance of 1 mA cm⁻¹. -2 At current density, the areal capacitance can reach 5 F cm⁻¹ -2 The above results show that after 5000 cycles at a high current density of 10 mA cm⁻², the capacity retention is as high as 85.2% or more.

[0022] The beneficial effects of this invention are:

[0023] 1. Quantitative and Controllable Breakthrough in Film Formation: This invention, for the first time through systematic experimental research, clarifies that for a system using CNTs as a flexible framework to prepare self-supporting composite films via vacuum filtration, there exists a key "window" for the active material / CNT mass ratio. Within this window, CNTs can construct a continuous and stable three-dimensional conductive and mechanical support network, effectively encapsulating and bridging the active material particles of high-performance pseudocapacitors, ensuring the smooth progress of the film formation process and the integrity of the finished film. This provides a clear and operable quantitative standard for addressing the difficulty of forming pseudocapacitor films.

[0024] 2. Optimal balance between performance and mechanical properties: Within the optimal ratio range (especially 2:1), this invention achieves an optimal balance between maximizing the proportion of pseudocapacitive material and the mechanical reliability of the thin film. The resulting electrode retains excellent flexibility while achieving significantly improved electrochemical performance.

[0025] 3. Strong process universality: This quantitative principle is not only applicable to the α-Fe2O3 / CNT system in the embodiments of this invention, but also has important guiding significance for other nanoscale pseudocapacitive materials (Co3O4, NiO, etc.) that need to be composited with CNTs to form films, providing a general process design guideline for the development of a series of high-performance flexible electrodes.

[0026] 4. Simplified process and high repeatability: Compared with the trial-and-error method that relies on experience, this method provides clear formulation guidance, which greatly reduces process development time and material waste, and ensures the repeatability of the preparation process and the consistency of product performance.

[0027] 5. The α-Fe2O3 / CNT composite thin film electrode prepared by the quantitative preparation method provided in this invention has the advantages of high areal specific capacity, excellent flexibility and structural integrity;

[0028] High electrochemical performance: By optimizing the mass ratio of α-Fe₂O₃ to CNTs, the proportion of active material was greatly increased while ensuring film formation. The resulting thin-film electrode exhibits excellent electrochemical performance at 1 mA cm⁻¹. -2 At current density, the areal capacitance can reach 5 F cm⁻¹ -2 The above figures are significantly higher than those of traditional carbon-based thin-film electrodes.

[0029] Excellent flexibility and mechanical stability: The CNT network provides an excellent mechanical framework, giving the film good flexibility. It can be bent, folded, or even cut into any shape without breaking, and the electrochemical performance of each part is uniform after cutting.

[0030] The electrode exhibits tight interfacial contact and long cycle life: α-Fe₂O₃ nanoparticles are uniformly anchored on the CNT network, resulting in tight contact and low charge transfer resistance. The electrode operates at 10 mA cm⁻¹. -2 After 5000 cycles at high current density, the capacity retention rate is as high as 85.2% or more. Attached Figure Description

[0031] Figure 1 This is a schematic flowchart illustrating the preparation method of the high-capacity self-supporting pseudocapacitive composite film provided in an embodiment of the present invention.

[0032] Figure 2 An objective photograph of the pseudocapacitive composite film prepared in the preferred embodiment of the present invention under bending conditions.

[0033] Figure 3 Scanning electron microscope image of the pseudocapacitive composite film prepared in the preferred embodiment of the present invention.

[0034] Figure 4 The composite film electrode prepared in the preferred embodiment of the present invention is at 1 mA cm⁻¹ -2 Constant current charge-discharge curves at current density.

[0035] Figure 5 The composite film electrode prepared in the preferred embodiment of the present invention operates at 20 mA cm⁻¹. -2 Cyclic stability curves at current density.

[0036] Figure 6The composite film electrode prepared in Example 1 of this invention is at 1 mA cm⁻¹ -2 Constant current charge-discharge curves at current density.

[0037] Figure 7 The composite film electrode prepared in Example 2 of this invention is at 1 mA cm⁻¹ -2 Constant current charge-discharge curves at current density.

[0038] Figure 8 The composite film electrode prepared in Example 3 of this invention is at 1 mA cm⁻¹ -2 Constant current charge-discharge curves at current density.

[0039] Figure 9 The composite film electrode prepared in Example 4 of this invention is at 1 mA cm⁻¹ -2 Constant current charge-discharge curves at current density.

[0040] Figure 10 The composite film electrode prepared in Example 5 of this invention is at 1 mA cm⁻¹ -2 Constant current charge-discharge curves at current density.

[0041] Figure 11 The membrane electrode prepared in Comparative Example 1 of this invention is at 1 mA cm⁻¹ -2 Constant current charge-discharge curves at current density.

[0042] Figure 12 This is an objective photograph showing sheet-like peeling at the center of the membrane electrode prepared in Comparative Example 2 of the present invention. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0044] Preferred embodiment: A 100 μm thick composite film electrode with an α-Fe₂O₃ to CNT mass ratio of 2:1.

[0045] Step 1: Preparation of pseudocapacitive material α-Fe2O3

[0046] Weigh 5.2 mmol of ferric chloride hexahydrate and 5.2 mmol of terephthalic acid, dissolve them in 100 mL of N,N-dimethylformamide (DMF), and stir until completely dissolved. Transfer the solution to a polytetrafluoroethylene-lined high-pressure reactor and solvothermal react at 150 °C for 18 hours. After the reaction, collect the orange precipitate by centrifugation, wash several times with DMF and ethanol, and dry under vacuum at 60 °C to obtain the MIL-101(Fe) precursor. Place the precursor in a muffle furnace, heat it to 350 °C at 5 °C / min under air atmosphere, and calcine for 6 hours. After cooling with the furnace, grind it to obtain brownish-red α-Fe₂O₃ nanoparticle powder.

[0047] Step 2: Quantitative Proportioning of Slurry and Film Formation

[0048] 1. Accurate weighing: Accurately weigh 200 mg of α-Fe2O3 powder and 100 mg of carboxylated multi-walled CNTs prepared in step one, so that the mass ratio of the two is 2:1 (total mass of active material 300 mg). Separately weigh appropriate amounts of acetylene black and polyvinylidene fluoride as conductive agent and binder, respectively.

[0049] 2. Mixing and Dispersion: Place all the above solid materials in a mortar and mix initially, then transfer to a beaker and add an appropriate amount of N-methylpyrrolidone solvent. Stir continuously on a magnetic stirrer at 800 rpm for 24 hours until a uniform, stable, viscous slurry without visible particle agglomeration is formed.

[0050] 3. Vacuum Filtration Membrane Formation: A 50 mm diameter mixed cellulose ester microporous membrane (0.22 μm pore size) is mounted on a sand core filtration flask. Using a dropper, the slurry is slowly and evenly added drop by drop to the center of the membrane while maintaining a constant negative pressure with the vacuum pump. The feeding rate is controlled to ensure uniform deposition of solids on the membrane surface. After all the slurry has been added and the vacuum pump has been used, a uniform wet membrane covering the membrane is obtained.

[0051] 4. Drying and Peeling: The wet filter membrane was transferred to a vacuum drying oven and dried at 80 °C for at least 12 hours to completely remove residual solvent. After drying, a complete, metallic-lustered, brownish-red self-supporting film could be easily peeled off from the filter membrane edge using tweezers. The thickness of the obtained membrane electrode was measured to be 100 μm using vernier calipers.

[0052] Step 3: Electrochemical Performance Testing

[0053] The successfully prepared membrane electrode was cut into 1 cm × 2 cm samples and used directly as the working electrode. A platinum sheet was used as the counter electrode and Hg / HgO was used as the reference electrode. A three-electrode system was constructed in 6 M KOH electrolyte for electrochemical testing.

[0054] Figure 1 The diagram shows a schematic representation of the fabrication process of a high-capacity self-supporting pseudocapacitive composite film electrode according to an embodiment of the present invention. Figure 2 As shown, the prepared composite film electrode has a certain degree of flexibility; it can be folded in half with tweezers and still maintain its shape without breaking. Figure 3 This is a scanning electron microscope diagram of the composite film, which shows that the pseudocapacitive material we synthesized is tightly bonded and overlapped with CNTs. Figure 4 It can be seen that the α-Fe2O3 / CNT composite film at 1 mA cm⁻¹ -2 At current density, the areal capacitance can reach 5039 mF cm⁻¹ -2 Above. At 10 mA cm -2 After 5000 cycles at high current density, the capacity retention rate is as high as 85.2% or more. Figure 5 ).

[0055] Example 1: A 100 μm thick composite film electrode with a mass ratio of α-Fe2O3 to CNT (uncarboxylated) of 2:1.

[0056] The preparation method was exactly the same as in the preferred embodiment, except that the carboxylated CNTs in step two were replaced with untreated CNTs. The resulting composite membrane exhibited some cracking. This is because untreated CNTs, due to their strong van der Waals forces and hydrophobicity, easily agglomerate, forming tangled clumps in the slurry. This not only leads to uneven deposition during vacuum filtration but also causes stress concentration points during drying due to localized sparse CNT networks. In contrast, the negative charge on the surface of carboxylated CNTs enhances electrostatic repulsion, and their hydrophilic groups improve compatibility with the solvent, resulting in a uniform and stable dispersion. This allows CNTs to more uniformly interweave into a continuous, dense, three-dimensional flexible framework during vacuum filtration, effectively coating and bridging a high proportion of rigid pseudocapacitive α-Fe₂O₃ particles, ultimately obtaining a complete and flexible self-supporting film. The resulting composite membrane electrode exhibited performance at 10 mA cm⁻¹. -2 After 5000 cycles at high current density, the capacity retention decreased to 42.3%. At 1 mA cm⁻¹ -2 At current density, the areal capacitance is only 1990 mF cm⁻¹ -2 (like Figure 6As shown in the figure, the membrane electrode formed with carboxylated CNTs exhibited a significant performance degradation. This is because carboxylation can bring multiple benefits to electrochemical performance. First, carboxylated CNTs are easier to disperse, resulting in more contact points and a more complete conductive pathway in the composite film, thus reducing the overall internal resistance of the electrode. Second, the carboxyl functional groups can form hydrogen bonds or weak chemical interactions with hydroxyl groups or metal ions on the surface of the pseudocapacitive material, which enhances the interfacial bonding strength between CNTs and the active material. This close contact not only benefits mechanical stability but, more importantly, provides an efficient path for the rapid transfer of electrons between the two during the Faraday reaction, directly increasing the pseudocapacitive capacity of the material. Third, it improves electrode wettability: the hydrophilic surface provided by carboxylated CNTs makes the composite thin-film electrode easier to wet with electrolyte, shortening the ion diffusion path and resulting in higher utilization of the active material.

[0057] Example 2: A 100 μm thick composite film electrode with an α-Fe₂O₃ to CNT mass ratio of 0.5:1.

[0058] The preparation method was exactly the same as in the preferred embodiment, except that the weighing mass of α-Fe2O3 and CNT in step two was changed to strictly meet the mass ratio of 0.5:1 (i.e., 100 mg of α-Fe2O3, 200 mg of CNT, and a total mass of 300 mg of active material). A complete self-supporting film was successfully obtained. Figure 7 The constant current charge-discharge curves show that the composite film operates at 1 mA cm⁻¹. -2 At current density, the areal capacitance can reach 1321 mF cm⁻¹ -2 At 10 mA cm -2 After 5000 cycles at high current density, the capacity retention rate is as high as 89.7%.

[0059] Example 3: A 100 μm thick composite film electrode with an α-Fe₂O₃ to CNT mass ratio of 1:1.

[0060] The preparation method was exactly the same as in the preferred embodiment, except that the weighing mass of α-Fe₂O₃ and CNT in step two was changed to strictly meet a 1:1 mass ratio (i.e., 150 mg of α-Fe₂O₃, 150 mg of CNT, and a total mass of 300 mg of active material). A complete self-supporting film was successfully obtained. This composite film exhibited performance at 1 mA cm⁻¹. -2 At current density, the areal capacitance is 2607 F cm⁻¹ -2 (like Figure 8 (As shown). At 10 mA cm -2 After 5000 cycles at high current density, the capacity retention rate is 87.6%.

[0061] Comparative data shows that the areal specific capacity of Examples 2 and 3 is significantly lower than that of the optimal example. This is because α-Fe2O3, as the only pseudocapacitive active material, is the fundamental source of electrode capacity. Its reduced proportion directly means a decrease in the number of active sites capable of Faraday reactions per unit electrode, leading to a decrease in specific capacity. However, the cycle stability of Examples 2 and 3 does not decrease compared to the optimal example; in fact, it slightly increases. This is because the active material undergoes volume changes during charge and discharge, which can easily lead to structural damage over time. The high proportion of CNT network can better encapsulate and support the active particles, effectively buffering stress and preventing pulverization and detachment, thereby maintaining the integrity of the electrode structure.

[0062] Example 4: A 50 μm thick composite film electrode with an α-Fe2O3 to CNT mass ratio of 2:1.

[0063] The preparation method was exactly the same as the preferred embodiment, except that the total mass of the active material in step two was changed to 150 mg. However, the mass ratio of α-Fe₂O₃ to CNT remained strictly 2:1 (i.e., 100 mg of α-Fe₂O₃ and 50 mg of CNT), ultimately successfully obtaining a complete self-supporting film with a thickness of 50 μm. This composite film exhibited excellent performance at 1 mA cm⁻¹. -2 At current density, the areal capacitance is 2586 mF / cm. -2 (like Figure 9 (As shown). At 10 mA cm -2 After 5000 cycles at high current density, the capacity retention was 88.1%. Comparative data showed a significant decrease in specific capacity compared to the optimal embodiment. This is because the reduced membrane electrode thickness leads to a decrease in the mass of active material per unit area, directly resulting in a decrease in areal specific capacity. However, the cycle stability slightly improved. This is because the reduced membrane electrode thickness shortens the distance for electron transport and ion migration, accelerating electrolyte wetting and thus enhancing cycle stability.

[0064] Example 5: A 150 μm thick composite film electrode with an α-Fe2O3 to CNT mass ratio of 2:1.

[0065] The preparation method was exactly the same as the preferred embodiment, except that the total mass of the active material in step two was changed to 450 mg. However, the mass ratio of α-Fe₂O₃ to CNT remained strictly 2:1 (i.e., 300 mg of α-Fe₂O₃ and 150 mg of CNT), ultimately successfully obtaining a complete self-supporting film with a thickness of 150 μm. This composite film exhibited excellent performance at 1 mA cm⁻¹. -2 At current density, the areal capacitance is 4690 Fcm. -2 (like Figure 10 (As shown). At 10 mA cm -2After 5000 cycles at high current density, the capacity retention was 58.7%. Comparative data showed a slight decrease in specific capacity compared to the preferred embodiment, while cycle stability significantly declined. This is because the excessive thickness of the membrane electrode hinders ion transport and electron transfer, making electrolyte wetting difficult. Consequently, the increased thickness compared to the preferred embodiment fails to provide capacity. Furthermore, with increased thickness, impedance also increases significantly, thereby reducing cycle stability.

[0066] Comparative Example 1: Pure CNT film

[0067] Only 300 mg of carboxylated multi-walled CNTs were weighed out, without adding any α-Fe₂O₃. The film was processed using the same dispersion, filtration, and drying process as in the preferred embodiment. A pure black, highly flexible CNT film was obtained. Figure 11 It can be seen that the CNT film at 1 mA cm -2 At current density, the areal capacitance can reach 586 F cm⁻¹. -2 At 10 mA cm -2 After 5000 cycles at high current density, the capacitance retention rate is over 90%. This is because CNTs, as a high-quality one-dimensional carbon-based material, inherently possess excellent cycle stability. However, pure CNT films cannot provide pseudocapacitance, resulting in a lower areal capacitance.

[0068] Comparative Example 2: Composite thin film electrode with a mass ratio of α-Fe2O3 to CNT of 3:1

[0069] The preparation method was the same as in Example 1, except that the mass ratio of α-Fe2O3 to CNT in step two was adjusted to 3:1 (i.e., 225 mg of α-Fe2O3, 75 mg of CNT, and a total mass of 300 mg of active material). During vacuum filtration, it was observed that the solid material was deposited unevenly on the filter membrane, forming a cracked pattern. Figure 12 After drying, when attempting to peel it off, the film could not remain intact, with flaky peeling occurring in the central part, making it impossible to obtain a complete self-supporting electrode suitable for testing. This is because when the CNT content is below a certain critical value (corresponding to an upper limit of 2:1 mass ratio), it cannot form an effective continuous network, resulting in weak interparticle bonding, increased internal stress in the film, cracking and pulverizing during the drying process, and loss of film-forming ability.

[0070] In the above embodiments and comparative examples, different synthesis conditions significantly affected the areal capacitance and capacity retention of the pseudocapacitive composite film electrode, as shown in Table 1 below:

[0071] Group <![CDATA[m (α-Fe2O3):m (CNT)]]> Has CNT undergone carboxylation treatment? Membrane electrode thickness (μm) <![CDATA[Areal specific capacitance (mF cm -1 ).]]> Capacity retention rate (%) Best Practice 2：1 yes 100 5039 85.2 Example 1 2：1 no 100 1990 42.3 Example 2 0.5：1 yes 100 1321 89.7 Example 3 1：1 yes 100 2607 87.6 Example 4 2：1 yes 50 2586 88.1 Example 5 2：1 yes 150 4690 58.7 Comparative Example 1 Pure CNT yes 100 586 90 Comparative Example 2 3：1 yes No film formation Unable to measure Unable to measure

[0072] Overall, the thickness of the membrane electrode has a significant impact on its performance, while whether or not to carboxylate CNTs and control the mass ratio of pseudocapacitive material to CNTs are key factors in achieving high-performance composite membrane electrodes.

[0073] This invention, through systematic comparative experiments, not only successfully prepared high-performance α-Fe₂O₃ / CNT composite thin-film electrodes, but more importantly, it revealed and quantified for the first time the key mass ratio window (0.5:1 to 2:1) for achieving reliable film formation through vacuum filtration in this system. In particular, the 2:1 ratio was proven to be the optimal balance point that balances extremely high pseudocapacitive material content (thus obtaining high capacity) with reliable film formation (thus ensuring electrode mechanical integrity). This discovery provides those skilled in the art with a clear, quantifiable, and repeatable general guideline for preparing high-load flexible electrodes, and has significant industrial application value.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A quantitative fabrication method for a high-capacitance self-supporting pseudocapacitive composite thin-film electrode, characterized in that, The method includes the following steps: S1. A pseudocapacitive active material and carbon nanotubes are mixed at a mass ratio of (0.5~2):1 and dispersed in N-methylpyrrolidone to form a uniform dispersion slurry; the total mass of the pseudocapacitive active material and carbon nanotubes is 150~450 mg; the pseudocapacitive active material is one of α-Fe2O3, Co3O4, and NiO nanoparticles; S2. The dispersion slurry is deposited onto a filter membrane to form a wet film by vacuum filtration; S3. Dry the wet membrane and peel it off from the filter membrane to obtain a self-supporting composite thin film electrode.

2. The method for quantitatively preparing a high-capacity self-supporting pseudocapacitive composite thin-film electrode according to claim 1, characterized in that, The pseudocapacitive active material is α-Fe2O3 nanoparticles.

3. The method for quantitatively preparing a high-capacity self-supporting pseudocapacitive composite thin-film electrode according to claim 2, characterized in that, The preparation steps of α-Fe2O3 nanoparticles are as follows: (1) Weigh 5.2 mmol of ferric chloride and 5.2 mmol of terephthalic acid and place them in a reaction vessel; (2) Add 100 mL of N,N-dimethylformamide solvent to the container and stir continuously at room temperature until the solid is completely dissolved to obtain a clear solution; (3) Transfer the solution obtained in step (2) to a high-pressure reactor lined with polytetrafluoroethylene, seal it and place it in an oven for a solvothermal reaction at 150°C for 18 hours. (4) After the reaction was completed, the mixture was naturally cooled to room temperature. The orange precipitate was collected by centrifugation and washed several times with N,N-dimethylformamide and ethanol. Finally, it was vacuum dried at 60°C to obtain the MIL-101(Fe) precursor. (5) The MIL-101(Fe) precursor obtained in step (4) is placed in a muffle furnace and heated to 350°C at a heating rate of 5°C / min in air atmosphere, and calcined at this temperature for 6 hours. (6) After calcination, the furnace is naturally cooled to room temperature to obtain brownish-red α-Fe2O3 nanoparticle powder.

4. The method for quantitatively preparing a high-capacity self-supporting pseudocapacitive composite thin-film electrode according to claim 1, characterized in that, The carbon nanotubes in step S1 have been carboxylated.

5. The method for quantitatively preparing a high-capacity self-supporting pseudocapacitive composite thin-film electrode according to claim 1, characterized in that, The thickness of the composite film electrode obtained in step S3 is 50-150 μm.

6. The method for quantitatively preparing a high-capacity self-supporting pseudocapacitive composite thin-film electrode according to claim 5, characterized in that, The composite film electrode obtained in step S3 has a thickness of 100 μm.

7. The method for quantitatively preparing a high-capacity self-supporting pseudocapacitive composite thin-film electrode according to claim 1, characterized in that, The mass ratio of pseudocapacitive active material to carbon nanotubes in step S1 is 2:

1.

8. A high-performance self-supporting pseudocapacitive composite film electrode prepared by the method according to any one of claims 1 to 7.

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