NiCo-MOF / Co(OH)2 / NF composite electrode material and preparation method thereof

Abstract

The application relates to the field of electrochemical energy storage technology, in particular to a NiCo-MOF / Co(OH)2 / NF composite electrode material and a preparation method thereof. As an active material of a supercapacitor positive electrode, NiCo-MOF has poor conductivity, and the electrochemical performance needs to be further improved. In view of the above problems, the application provides a NiCo-MOF / Co(OH)2 / NF composite electrode material. Co(OH)2 in the electrode material contributes to the pseudo-capacitance response, and NiCo-MOF provides rich pore structures and stable frame support. NiCo-MOF takes the form of nanosheets as a conductive support, and Co(OH)2 nanoneedles grow through the surface of the NiCo-MOF sheet layer, and the two form a nanoneedle-penetrating-sheet-layer structure, which helps to improve the charge transfer efficiency and ion diffusion capacity of the electrode interior, relieve the structural strain of the active material in the charging and discharging cycle process, enhance the structural reversibility of the electrode material in the repeated charging and discharging process, so that the specific capacitance can be improved, the cycle life can be effectively prolonged, and the energy density of the supercapacitor can be improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a NiCo-MOF / Co(OH)2 / NF composite electrode material and its preparation method. Background Technology

[0002] Supercapacitors, as electrochemical energy storage devices situated between traditional capacitors and secondary batteries, have shown broad application prospects in electric vehicles, smart grids, portable electronic devices, and wearable devices due to their significant advantages such as high power density, long cycle life, fast charge / discharge speed, and environmental friendliness. However, compared to batteries, supercapacitors have relatively low energy density, a limitation that restricts their large-scale application in many scenarios. Among the various strategies for improving the energy density of supercapacitors, developing high-performance electrode materials is considered one of the most crucial approaches.

[0003] Metal-organic frameworks (MOFs) are a novel class of porous crystalline materials formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination bonds. These materials have attracted widespread attention in fields such as gas adsorption and separation, catalysis, and energy storage due to their high specific surface area, large porosity, tunable pore structure, and abundant coordination unsaturated sites. In recent years, researchers have attempted to use MOFs directly as electrode materials for supercapacitors, achieving some progress. Among them, cobalt-based MOFs (Co-MOFs), with their high theoretical specific capacitance and designable pore and layered structures, are considered a promising electrode material. However, most original MOFs exhibit poor intrinsic conductivity and limited electron transport capabilities, while their electrochemical stability and cycle durability are insufficient for practical applications. These problems severely restrict the direct application of MOFs in the field of supercapacitors.

[0004] To overcome these limitations, researchers have explored various modification strategies, mainly including two aspects: first, constructing MOF-based composites by introducing highly conductive materials into MOFs to improve charge transport efficiency; second, using MOFs as precursors to derive materials such as metal oxides, metal sulfides, metal hydroxides, or porous carbon through heat treatment or chemical transformation. In the field of bimetallic MOFs, nickel-cobalt bimetallic MOFs (NiCo-MOFs) have attracted attention due to the synergistic effect between the two metal ions. Studies have shown that NiCo-MOFs exhibit superior electrochemical performance compared to monometallic Co-MOFs; the specific capacitance of core-shell NiCo-MOFs can reach 10¹⁶ F / g, far exceeding the 557 F / g of Co-MOFs. However, NiCo-MOFs still face the challenge of insufficient conductivity.

[0005] On the other hand, cobalt hydroxide (Co(OH)2), as a typical pseudocapacitive electrode material, possesses high theoretical specific capacitance and good electrochemical reversibility. Furthermore, Co(OH)2 nanomaterials are easily combined with highly conductive materials and can be directly grown on conductive substrates such as nickel foam to form self-supporting electrode structures. However, Co(OH)2 itself has poor conductivity, and its use alone is insufficient to achieve ideal rate performance and cycle stability.

[0006] Based on the aforementioned research background, this invention uses nickel foam as a conductive substrate. First, a NiCo-MOF / NF electrode material is obtained by in-situ growth of a nickel-cobalt bimetallic MOF (NiCo-MOF) on the surface of the nickel foam. Then, using this electrode as a carrier, Co(OH)₂ nanosheets are introduced onto its surface via a hydrothermal reaction to construct a NiCo-MOF / Co(OH)₂ / NF composite electrode material with a hierarchical array structure. This composite electrode material aims to fully leverage the synergistic advantages of NiCo-MOF's high specific surface area and abundant active sites, Co(OH)₂'s high theoretical specific capacitance, and nickel foam's high conductivity, thereby effectively improving the electrode material's specific capacitance and cycle stability. Summary of the Invention

[0007] The existing technology has the problem that NiCo-MOF, as an active material for the positive electrode of supercapacitors, has poor conductivity, and its electrochemical performance needs further improvement. To address these issues, this invention provides a NiCo-MOF / Co(OH)2 / NF composite electrode material, the preparation method of which includes the following steps: (1) Add cobalt nitrate, urea and ammonium fluoride to deionized water, stir well to obtain a mixed solution; (2) The NiCo-MOF / NF electrode material was added to the above mixed solution and hydrothermally reacted at 120°C for at least 8 hours. After the reaction was completed, the obtained electrode material was washed with water and dried to obtain the NiCo-MOF / Co(OH)2 / NF composite electrode material. NiCo-MOF / NF electrode materials use terephthalic acid as the organic ligand and water-soluble inorganic Ni salt and water-soluble inorganic Co salt as the Ni ligands, respectively. 2+ Source, Co 2+ The source is a nickel-cobalt bimetallic MOF material obtained by in-situ growth on the surface of nickel foam through solvothermal reaction, with a molar ratio of water-soluble inorganic Ni salt and water-soluble inorganic Co salt of 3:2 or 1:4.

[0008] Preferably, in step (1), the molar ratio of cobalt nitrate, urea, and ammonium fluoride is 2:6:5, and the molar ratio of cobalt nitrate to terephthalic acid, the organic ligand used in the preparation of NiCo-MOF / NF electrode material, is 2:1.

[0009] Preferably, the water-soluble inorganic Ni salt used in the preparation of the NiCo-MOF / NF electrode material is nickel nitrate.

[0010] Preferably, the water-soluble inorganic Co salt used in the preparation of NiCo-MOF / NF electrode material is cobalt nitrate.

[0011] Preferably, the preparation method of NiCo-MOF / NF electrode material includes the following steps: (1) Cut NF to the required size, and then place NF in acetone and 3M hydrochloric acid aqueous solution in sequence and sonicate for at least 20 min respectively. After taking it out, wash it with water, wash it with alcohol and dry it in sequence to obtain pretreated NF. (2) Dissolve terephthalic acid, cobalt nitrate hexahydrate and nickel nitrate hexahydrate in DMF at a molar ratio of 1:0.4:0.6 and stir until homogeneous to obtain a pink mixed solution; (3) Mix deionized water and anhydrous ethanol at a volume ratio of 1:1 to obtain an alcohol solution; (4) Add the alcohol solution to the pink mixed solution, with a volume ratio of alcohol solution to pink mixed solution of (30-40): (5-15). After stirring evenly, the electrode impregnation solution is obtained. (5) The pretreated NF is completely immersed in the electrode impregnation solution and subjected to hydrothermal reaction at 120-130℃ for at least 12h. After the reaction is completed, the NF is removed, sonicated in anhydrous ethanol for at least 2min, and finally dried under vacuum to obtain NiCo-MOF / NF electrode material.

[0012] Preferably, the temperature of the hydrothermal reaction in step (5) is 125°C.

[0013] Beneficial effects: (1) In the NiCo-MOF / Co(OH)2 / NF composite electrode material obtained in this invention, NiCo-MOF serves as a conductive support in the form of nanosheets, while Co(OH)2 nanoneedles are grown through the NiCo-MOF sheets to form a hierarchical array structure. In this structure, the NiCo-MOF nanosheets can effectively support and disperse the Co(OH)2 nanoneedles, preventing the NiCo-MOF nanosheets from agglomerating, thereby maintaining more active sites exposed in the electrolyte. At the same time, this nanoneedle-penetrating structure increases the contact area between the electrode material and the electrolyte, providing a more unobstructed channel for ion diffusion and electron transport, which helps to improve the charge transfer efficiency and ion diffusion capability inside the electrode.

[0014] (2) The composite electrode material constructed in this invention combines the high redox activity of Co(OH)2 with the large specific surface area of ​​NiCo-MOF. Co(OH)2 contributes to the high pseudocapacitive response, while NiCo-MOF provides abundant pore structure and stable framework support. More importantly, there is a good synergistic effect between cobalt ions in Co(OH)2 and cobalt ions in NiCo-MOF. This synergistic effect helps to regulate the electronic structure of the electrode material and improve its intrinsic conductivity. Simultaneously, this synergistic effect can also alleviate the structural strain of the active material during charge-discharge cycles, enhance the structural reversibility of the electrode material during repeated charge-discharge processes, thereby effectively extending the cycle life while improving the specific capacitance, ultimately increasing the energy density of the supercapacitor.

[0015] (3) In this invention, both the NiCo-MOF / NF electrode material and the final NiCo-MOF / Co(OH)2 / NF composite electrode material are obtained by in-situ growth on a nickel foam substrate. This in-situ growth method avoids the problem of introducing inactive components due to the addition of binders and conductive agents in traditional coating processes, and also avoids the damage to the nickel foam skeleton structure caused by mechanical coating. If conventional coating methods are used, the three-dimensional network structure of nickel foam is prone to collapse or pore blockage during coating pressure, which leads to the obstruction of ion and charge transport, a decrease in effective specific surface area, and deterioration of electrode performance. However, the in-situ growth route used in this invention is mild and controllable, and the macroscopic skeleton and microscopic pores of nickel foam are completely preserved, with a strong bond between the active material and the substrate and low contact resistance. In addition, the preparation process is simple to operate, requires low raw material costs, and has good scalability, which is conducive to the practical promotion and application of this composite electrode material in supercapacitor energy storage devices. Attached Figure Description

[0016] Figure 1 : SEM comparison images of NiCo-MOF / Co(OH)2 / NF-1 and NiCo-MOF / NF; where a and b are NiCo-MOF / NF; c and d are NiCo-MOF / Co(OH)2 / NF.

[0017] Figure 2 XRD patterns of NiCo-MOF / Co(OH)2 / NF, Co(OH)2 / NF, and NiCo-MOF / NF.

[0018] Figure 3 The CV curves of the three-electrode system corresponding to NiCo-MOF / Co(OH)2 / NF-1 at different scan rates are shown.

[0019] Figure 4The GCD curves of the three-electrode system corresponding to NiCo-MOF / Co(OH)2 / NF-1 under different current densities are shown.

[0020] Figure 5 The GCD comparison curves for the three-electrode systems corresponding to Example 1 and Comparisons 1-5 are shown at a current density of 1 A g⁻¹.

[0021] Figure 6 The impedance diagram is shown for the NiCo-MOF / Co(OH)2 / NF-1 cathode material obtained in Example 1. Detailed Implementation

[0022] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0023] The nickel foam used in the following embodiments of the present invention is from Suzhou Kesheng New Materials Co., Ltd., and the nickel purity reaches 99.5% or higher.

[0024] Example 1 A NiCo-MOF / Co(OH)2 / NF composite electrode material is prepared by the following method: (1) Cut the nickel foam (NF) (10cm×10cm×0.1cm) into pieces of 1cm×3cm. Then, place the NF in acetone and 3M hydrochloric acid aqueous solution for ultrasonic pretreatment for 20 min respectively. The ultrasonic frequency is 30kHz. After taking it out, wash it three times with deionized water and anhydrous ethanol respectively. Then, place it in a vacuum dryer at 60℃ for 12h to obtain pretreated NF. (2) Terephthalic acid (1 mmol, 166 mg), cobalt nitrate hexahydrate (0.4 mmol, 116.4 mg), and nickel nitrate hexahydrate (0.6 mmol, 174 mg) were dissolved in 35 mL of deionized water DMF and stirred until a pink mixed solution was obtained. (3) Mix 5 mL of deionized water with 5 mL of ethanol and stir for 20 min to obtain an alcohol solution; (4) Add the alcohol solution obtained in step (3) to the pink mixed solution obtained in step (2), stir evenly, and then obtain the electrode impregnation solution; (5) The pretreated NF was completely immersed in the electrode impregnation solution and hydrothermally reacted at 125℃ for 12h. After the reaction was completed, the NF was taken out, sonicated in anhydrous ethanol for 2min, and finally vacuum dried (60℃, 12h) to obtain NiCo-MOF / NF electrode material. (6) Dissolve cobalt nitrate hexahydrate (2 mmol, 582.1 mg), urea (6 mmol, 360 mg), and ammonium fluoride (5 mmol, 185 mg) in 30 mL of deionized water and stir until homogeneous to obtain a mixed solution; (7) The NiCo-MOF / NF electrode material obtained in step (5) is completely immersed in the mixed solution obtained in step (6), and hydrothermally reacted at 120°C for 8 hours. After washing with water 3 times and vacuum drying (80°C, 10 hours), NiCo-MOF / Co(OH)2 / NF-1 electrode material is obtained.

[0025] Comparative Example 1 is the same as Example 1, except that in step (2) of Comparative Example 1, the amount of cobalt nitrate hexahydrate added is 0.6 mmol, and the amount of nickel nitrate hexahydrate added is 0.4 mmol. The obtained electrode material is denoted as NiCo-MOF / Co(OH)2 / NF-2.

[0026] Comparative Example 2 is the same as Example 1, except that in step (2) of Comparative Example 2, the amount of cobalt nitrate hexahydrate added is 0.2 mmol, and the amount of nickel nitrate hexahydrate added is 0.8 mmol. The obtained electrode material is denoted as NiCo-MOF / Co(OH)2 / NF-3.

[0027] Example 2 is the same as Example 1, except that in step (2) of Comparative Example 3, the amount of cobalt nitrate hexahydrate added is 0.8 mmol, and the amount of nickel nitrate hexahydrate added is 0.2 mmol. The obtained electrode material is denoted as NiCo-MOF / Co(OH)2 / NF-4.

[0028] Comparative Example 3 is the NiCo-MOF / NF electrode material obtained in Example 1.

[0029] Comparative Example 4 uses the electrode material Co(OH)2 / NF, and its preparation method is as follows: (1) Cut the nickel foam (NF) (10cm×10cm×0.1cm) into pieces of 1cm×3cm. Then, place the NF in acetone and 3M hydrochloric acid aqueous solution for ultrasonic pretreatment for 20 min respectively. The ultrasonic frequency is 30kHz. After taking it out, wash it three times with deionized water and anhydrous ethanol respectively. Then, place it in a vacuum dryer at 60℃ for 12h to obtain pretreated NF. (2) Cobalt nitrate hexahydrate (2 mmol, 582.1 mg), urea (6 mmol, 360 mg), and ammonium fluoride (5 mmol, 185 mg) were dissolved in 30 mL of deionized water and stirred until homogeneous to obtain a mixed solution. The pretreated NF was completely immersed in the obtained mixed solution and hydrothermally reacted at 120 °C for 8 h. The electrode material was taken out, washed with water 3 times, and then vacuum dried (60 °C, 12 h) to obtain Co(OH)2 / NF. The Co(OH)2 obtained by in-situ growth on the NF surface was in the form of nanoneedles.

[0030] Comparative Example 5 is NiCo-MOF / Co(OH)2 / NF-5, and its preparation method is as follows: (1) Cut the nickel foam (NF) (10cm×10cm×0.1cm) into pieces of 1cm×3cm. Then, place the NF in acetone and 3M hydrochloric acid aqueous solution for ultrasonic pretreatment for 20 min respectively. The ultrasonic frequency is 30kHz. After taking it out, wash it three times with deionized water and anhydrous ethanol respectively. Then, place it in a vacuum dryer at 60℃ for 12h to obtain pretreated NF. (2) Terephthalic acid (1 mmol, 166 mg), cobalt nitrate hexahydrate (0.4 mmol, 116.4 mg), and nickel nitrate hexahydrate (0.6 mmol, 174 mg) were dissolved in 35 mL of deionized water DMF and stirred until a pink mixed solution was obtained. (3) Mix 5 mL of deionized water with 5 mL of ethanol and stir for 20 min to obtain an alcohol solution; (4) Add the alcohol solution obtained in step (3) to the pink mixed solution obtained in step (2), stir evenly, and then obtain the electrode impregnation solution; (5) The pretreated NF was completely immersed in the electrode impregnation solution and hydrothermally reacted at 125℃ for 12h. After the reaction was completed, the NF was taken out, sonicated in anhydrous ethanol for 2min, and finally vacuum dried (60℃, 12h) to obtain NiCo-MOF / NF electrode material. (6) Dissolve 100 mg of cobalt nitrate hexahydrate and 0.1 g of hexamethylenetetramine in 30 mL of deionized water, stir well, and obtain a mixed solution; (7) The NiCo-MOF / NF electrode material obtained in step (5) is completely immersed in the mixed solution obtained in step (6), and hydrothermally reacted at 120°C for 8 hours. After washing with water 3 times and vacuum drying (80°C, 10 hours), the electrode material NiCo-MOF / Co(OH)2 / NF-5 is obtained. The Co(OH)2 formed in situ on the NF surface is in the form of microspheres.

[0031] Instruction manual attached Figure 1SEM comparison images of NiCo-MOF / Co(OH)2 / NF-1, NiCo-MOF / NF, and Co(OH)2 / NF are shown; where a and b are NiCo-MOF / NF, and c and d are NiCo-MOF / Co(OH)2 / NF-1. Figure 1 In (a) and (b), NiCo-MOF / NF are clearly arranged in a relatively regular nanosheet pattern, forming a structure similar to a nanosheet array. Figure 1 In (c) and (d), the Co(OH)2 nanorods penetrate the nanosheets and are densely distributed, forming a composite three-dimensional structure that ensures sufficient active sites and improves charge storage capacity.

[0032] Instruction manual attached Figure 2 The XRD patterns are shown for NiCo-MOF / Co(OH)2 / NF-1, Co(OH)2 / NF, and NiCo-MOF / NF. Figure 2 It can be seen that the diffraction peaks of Co(OH)2 match the crystal planes of the standard card (PDF#01-073-2134), indicating the successful synthesis of Co(OH)2. NiCo-MOF has X-ray diffraction peaks similar to those of the original Ni-MOF, indicating the basic lattice characteristics. Simultaneously, diffraction peaks appear at 8.97° and 20.7° after compositing with NiCo-MOF. Due to the addition of terephthalic acid, lattice strain occurs at these points, representing the (100) and (102) crystal planes of NiCo-MOF, respectively. Furthermore, the peaks of Co(OH)2 do not disappear, indicating that the prepared NiCo-MOF / Co(OH)2 / NF composite was successfully synthesized. This is consistent with... Figure 1 The SEM results were consistent.

[0033] Performance testing The electrodes obtained in Example 1 and Comparative Example 1 of this invention were subjected to relevant performance tests using a three-electrode system. The electrodes obtained in Example 1 and Comparative Example 1 were used as the working electrodes of the three-electrode system, with a platinum mesh as the counter electrode, an Hg / HgO electrode as the reference electrode, a 3M potassium hydroxide aqueous solution as the electrolyte, and a Metrohm (PGSTAT-302N) electrochemical workstation.

[0034] Example 1: Scan rates of 5, 10, 20, 30, and 50 mV·s were measured in the voltage range of 0-0.6V. 1 The CV curve at that time is shown in the instruction manual. Figure 3As shown in the figure, the test results show that with the increase of the scan rate, the oxidation peak and reduction peak shift towards the positive and negative potentials, respectively, the anodic peak current gradually increases, and the cathode peak current gradually decreases. However, at higher scan rates, electrolyte ions cannot effectively diffuse into the interior of the electrode material in a short time, and the reaction only occurs on the electrode surface. The interior of the material becomes an ineffective region, leading to an increase in overpotential, limiting the redox reaction, and weakening or disappearing the oxidation peak.

[0035] Example 1: 1, 2, 3, 5, and 10 A g were measured within the operating voltage range of 0-0.5V. -1 The GCD curve at that time is shown in the attached instruction manual. Figure 4 As shown. Within a potential window of 0-0.5 V, the NiCo-MOF / Co(OH)2 / NF was measured at current densities of 1, 2, 3, 5, and 10 A g. -1 The GCD curves at different times were obtained, and the results showed that the GCD curves were nearly symmetrical and exhibited a certain voltage plateau, indicating good coulombic efficiency.

[0036] Examples 1-2 and Comparative Examples 1-5 of the present invention were performed at a current density of 1 A g. -1 The GCD curves obtained from the tests are shown in the attached instruction manual. Figure 5 As shown in the figure, NiCo-MOF / Co(OH)2 / NF-1 exhibits a longer charge-discharge duration, superior performance, and a larger capacitance at 1 A g. -1 The specific capacitance of NiCo-MOF / Co(OH)2 / NF-1 is 3782 Fg. -1 .

[0037] Instruction manual attached Figure 6 The impedance diagram of NiCo-MOF / Co(OH)2 / NF-1 obtained in Example 1 shows that the diameter of the semicircle is relatively small, indicating that the resistance is also relatively small.

[0038] The examples and comparative examples were measured at 1 A g. -1 The specific test results of the capacitance at that time are shown in Table 1.

[0039] Table 1

[0040] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A NiCo-MOF / Co(OH)2 / NF composite electrode material, characterized in that, The preparation method includes the following steps: (1) Add cobalt nitrate, urea and ammonium fluoride to deionized water, stir well to obtain a mixed solution; (2) The NiCo-MOF / NF electrode material was added to the above mixed solution and hydrothermally reacted at 120°C for at least 8 hours. After the reaction was completed, the obtained electrode material was washed with water and dried to obtain the NiCo-MOF / Co(OH)2 / NF composite electrode material. NiCo-MOF / NF electrode materials use terephthalic acid as the organic ligand and water-soluble inorganic Ni salt and water-soluble inorganic Co salt as the Ni ligands, respectively. 2+ Source, Co 2+ The source is a nickel-cobalt bimetallic MOF material obtained by in-situ growth on the surface of nickel foam through solvothermal reaction, with a molar ratio of water-soluble inorganic Ni salt and water-soluble inorganic Co salt of 3:2 or 1:

4.

2. The NiCo-MOF / Co(OH)2 / NF composite electrode material according to claim 1, characterized in that, In step (1), the molar ratio of cobalt nitrate, urea, and ammonium fluoride is 2:6:5, and the molar ratio of cobalt nitrate to terephthalic acid, the organic ligand used in the preparation of NiCo-MOF / NF electrode material, is 2:

1.

3. The NiCo-MOF / Co(OH)2 / NF composite electrode material according to claim 1, characterized in that, The water-soluble inorganic Ni salt used in the preparation of NiCo-MOF / NF electrode materials is nickel nitrate.

4. The NiCo-MOF / Co(OH)2 / NF composite electrode material according to claim 1, characterized in that, The water-soluble inorganic Co salt used in the preparation of NiCo-MOF / NF electrode materials is cobalt nitrate.

5. The NiCo-MOF / Co(OH)2 / NF composite electrode material according to claim 1, characterized in that, The preparation method of NiCo-MOF / NF electrode material includes the following steps: (1) Cut NF to the required size, and then place NF in acetone and 3M hydrochloric acid aqueous solution in sequence and sonicate for at least 20 min respectively. After taking it out, wash it with water, wash it with alcohol and dry it in sequence to obtain pretreated NF. (2) Dissolve terephthalic acid, cobalt nitrate hexahydrate and nickel nitrate hexahydrate in DMF at a molar ratio of 1:0.4:0.6 and stir until homogeneous to obtain a pink mixed solution; (3) Mix deionized water and anhydrous ethanol at a volume ratio of 1:1 to obtain an alcohol solution; (4) Add the alcohol solution to the pink mixed solution, with a volume ratio of alcohol solution to pink mixed solution of (30-40): (5-15). After stirring evenly, the electrode impregnation solution is obtained. (5) The pretreated NF is completely immersed in the electrode impregnation solution and subjected to hydrothermal reaction at 120-130℃ for at least 12h. After the reaction is completed, the NF is removed, sonicated in anhydrous ethanol for at least 2min, and finally dried under vacuum to obtain NiCo-MOF / NF electrode material.

6. The NiCo-MOF / Co(OH)2 / NF composite electrode material according to claim 1, characterized in that, The temperature of the hydrothermal reaction in step (5) is 125℃.

7. A supercapacitor, characterized in that, The positive electrode is the NiCo-MOF / Co(OH)2 / NF composite electrode material according to any one of claims 1-6.

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