A layered accordion structure Bi-MOF and a preparation method and application thereof

Abstract

The application discloses layered accordion structure Bi-MOF and a preparation method and application thereof, and relates to the technical field of electrode materials. The preparation method of the Bi-MOF comprises the following steps: dissolving bismuth nitrate and m-benzenetricarboxylic acid in methanol, and heating to obtain an initial Bi-MOF; and reacting the initial Bi-MOF with a weak base, wherein the weak base comprises at least one of ammonia, hexamethylenetetramine and tetramethylammonium hydroxide, to obtain the Bi-MOF. The Bi-MOF micro-morphology and particle size can be adjusted by adding the weak base, the obtained Bi-MOF sample has variable crystallinity and higher specific surface area, more electrochemical reaction sites can be exposed, the penetration rate of an electrolyte is improved, and the capacitive performance of the Bi-MOF is improved. In the preparation process, no surfactant needs to be added, the consumption of a large amount of water in the washing process is reduced, and the problem of environmental pollution caused by the large emission of the surfactant is solved.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, specifically to a layered accordion-structured Bi-MOF, its preparation method, and its applications. Background Technology

[0002] Supercapacitors, with their high power density, fast charging speed, and long cycle life, have become potential energy storage devices, serving as a bridge between traditional capacitors and lithium-ion batteries. However, their relatively low energy density currently limits the large-scale application of supercapacitors.

[0003] Bi-MOF, a pseudocapacitive material, possesses extremely high specific surface area, tunable pore structure, and environmentally friendly characteristics, making it a promising electrode material for supercapacitors. However, intrinsically Bi-MOF materials struggle to simultaneously maintain their porous crystal structure advantages while addressing their poor electronic conductivity. Alkali etching of Bi-MOF helps selectively reshape the local structure of MOFs through chemical action, offering the following advantages: i) constructing hierarchical channels to improve mass transfer efficiency; ii) optimizing the electronic structure of the material to enhance intrinsic conductivity; and iii) forming ligand-deficient defects or unsaturated metal sites to improve specific capacitance. Current literature on alkaline etching of Bi-MOF indicates that adding alkali during the preparation process is a common method to control the microstructure and morphology of Bi-MOF. However, due to the inherent limitations of Bi-MOF, its microstructure remains relatively stable. 3+ With OH - The rapid reaction rate makes it prone to over-etching, leading to the dissolution of a large amount of Bi-MOF framework, destruction of pore structure, and a sharp drop in specific surface area. Furthermore, the sample is prone to aggregation, making it difficult for the alkaline solution to penetrate into the aggregates, resulting in inconsistent etching levels. Additionally, under alkaline conditions, some of the etched Bi... 3+ Will react with OH - The formation of amorphous impurities such as Bi(OH)3 and Bi2O3 reduces the conductivity of electrode materials. Therefore, how to achieve structural control and conductivity enhancement through alkaline etching of Bi-MOF using a new, environmentally friendly method, thereby increasing capacitance, has become a research hotspot. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a layered accordion-structured Bi-MOF, its preparation method, and its applications. The layered accordion-structured Bi-MOF of this invention is prepared by a solvothermal method to form columnar Bi-MOF, and then different weak bases are introduced to control the microstructure and crystallinity of the Bi-MOF. Compared with the conventional solvothermal method, the addition of weak bases not only achieves controllable microstructure and particle size of Bi-MOF, but also results in Bi-MOF samples with higher crystallinity. This base-etched Bi-MOF material has a higher specific surface area, exposing more electrochemical reaction sites; while high crystallinity helps to improve electron transfer efficiency, ultimately improving the capacitance performance of Bi-MOF.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing layered Bi-MOFs, comprising the following steps: S1. Bismuth nitrate and trimesic acid are dissolved in methanol to obtain a mixed solution; the mixed solution is heated to obtain an initial columnar Bi-MOF. S2. The initial columnar Bi-MOF is reacted with a weak base, wherein the weak base includes at least one of ammonia, hexamethylenetetramine, and tetramethylammonium hydroxide, to obtain Bi-MOF.

[0006] This invention prepares columnar Bi-MOFs via a solvothermal method and then introduces a weak base to regulate the microstructure of the Bi-MOFs. The inventors discovered that introducing a weak base during the experiment accelerates the hydrolysis of the organic precursor, improves electrochemical performance, and thus achieves morphology control. The morphology of the Bi-MOFs prepared by this method changes with the weak base and its content. Electrochemical performance tests show that the capacitance of the Bi-MOFs is significantly improved with the addition of a weak base, mainly due to the exposure of more electrochemical active sites and improved conductivity.

[0007] In a preferred embodiment of the present invention, when the weak base is ammonia, the Bi-MOF is in the shape of a long rod, and its column surface has corrosion pits. When the weak base is hexamethylenetetramine, the Bi-MOF is in the shape of a long column, and the column has transverse grooves along its length. When the weak base is tetramethylammonium hydroxide, the Bi-MOF exhibits a layered accordion structure.

[0008] In a preferred embodiment of the present invention, in S1, The ratio of bismuth nitrate, trimesic acid, and methanol is 0.1~0.2 g: 0.7~0.8 g: 50~70 mL; The heating temperature is 110~130 ℃, and the heating time is 20~28 h.

[0009] In a preferred embodiment of the present invention, S1 includes the following specific steps: 0.15 g of bismuth nitrate and 0.75 g of trimesic acid were added to 60 mL of methanol and sonicated for 2-4 minutes to form a transparent mixed solution. The mixed solution was then transferred to a reaction vessel and heated in an oven at 120 °C for 24 h to obtain Bi-MOF.

[0010] In a preferred embodiment of the present invention, when the weak base is ammonia water in step S2, step S2 includes the following specific steps: Ammonia water is poured into a small-capacity first container, and the initial Bi-MOF is placed in a large-capacity second container; The first container is placed entirely into the second container, and the second container is sealed; the second container is heated at 75~85℃ for 2.5~3.5 h to obtain Bi-MOF; The initial Bi-MOF to ammonia water addition ratio is 0.4~0.6 g: 4~6 mL, and the volume fraction of the ammonia water is 25-28%.

[0011] In a preferred embodiment of the present invention, when the weak base in step S2 is hexamethylenetetramine, step S2 includes the following specific steps: Solvent was added to the reaction vessel, and then the initial Bi-MOF and hexamethylenetetramine were added and mixed evenly to obtain Bi-MOF; The initial Bi-MOF, hexamethylenetetramine, and solvent were added in a ratio of 0.4~0.6 g: 0.4~0.6 g: 5~15 mL. The solvent is water or DMF.

[0012] In a preferred embodiment of the present invention, when the weak base in step S2 is tetramethylammonium hydroxide, step S2 includes the following specific steps: Solvent was added to the reaction vessel, followed by the addition of the initial Bi-MOF and tetramethylammonium hydroxide. The mixture was stirred until homogeneous to obtain a layered accordion-structured Bi-MOF. The initial Bi-MOF, tetramethylammonium hydroxide, and solvent were added in a ratio of 0.4–0.6 g: 0.8–1.2 mL: 5–15 mL. The solvent is water or DMF.

[0013] In a preferred embodiment of the present invention, a method for preparing Bi-MOF includes the following steps: Bi(NO3)3·5H2O and trimesic acid are added to 60 mL of methanol, sonicated for 3 minutes to form a transparent solution, transferred to a 100 mL reaction vessel, and heated at 120 °C for 24 h to obtain a Bi-MOF sample; subsequently, the obtained sample is reacted with ammonia, hexamethylenetetramine and tetramethylammonium hydroxide respectively to obtain alkaline etched Bi-MOF material.

[0014] Secondly, the present invention provides a Bi-MOF obtained by the preparation method described above.

[0015] In a preferred embodiment of the present invention, the Bi-MOF has a length of 25~45 μm and a thickness of 50~80 nm.

[0016] Thirdly, the present invention provides an electrode comprising the aforementioned Bi-MOF, wherein the preparation method of the electrode comprises: The Bi-MOF, carbon black and PVDF are mixed evenly, N-methylpyrrolidone is added, and the mixture is ground evenly to form a uniform slurry. This slurry is then coated onto the surface of carbon cloth and dried to obtain the electrode. The mass ratio of Bi-MOF, carbon black, and PVDF is 8:1:1.

[0017] The Bi-MOF prepared by this invention can be used as a negative electrode material for supercapacitors.

[0018] Fourthly, the present invention provides a supercapacitor, including the aforementioned electrodes.

[0019] This invention has at least one of the following beneficial effects: (1) Compared with the current conventional solvothermal method, the addition of weak base not only achieves the controllability of the microstructure and particle size of Bi-MOF, but also changes the microstructure and crystallinity with the change of the amount of weak base added. The obtained Bi-MOF sample has higher crystallinity. This highly crystalline base-etched Bi-MOF material has a higher specific surface area and can expose more electrochemical reaction sites. High crystallinity helps to improve electron transfer efficiency and ultimately improve the capacitance performance of Bi-MOF.

[0020] (2) This invention solves the problems of poor conductivity and altered morphology in the preparation of alkaline etched Bi-MOF materials by the traditional solvothermal method; at the same time, no surfactant needs to be added during the preparation process, which reduces the consumption of a large amount of water during the washing process and the pollution caused by the large amount of surfactant emissions. Attached Figure Description

[0021] Figure 1The image shown is a scanning electron microscope image of Bi-MOF (Comparative Example 1) prepared without the addition of a weak base; Figure 2 The images shown are scanning electron microscope (SEM) images of Bi-MOFs prepared by adding ammonia; where a represents the addition of 5 mL of ammonia (Example 1); b represents the addition of 2.5 mL of ammonia (Example 2); c represents heating for 1 h (Example 3); and d represents heating for 2 h (Example 4). Figure 3 The image shown is a scanning electron microscope image of Bi-MOF prepared by adding hexamethylenetetramine; where ab represents the addition of 0.5 g of hexamethylenetetramine to water (Example 5) and DMF (Example 6), and c represents the addition of 1 g of hexamethylenetetramine to water (Example 7). Figure 4 The image shown is a scanning electron microscope image of Bi-MOF prepared with added tetramethylammonium hydroxide; where ab represents the addition of 1 mL of tetramethylammonium hydroxide to water (Example 8) and DMF (Example 9), and c represents the addition of 0.5 mL of tetramethylammonium hydroxide to water (Example 10). Figure 5 The X-ray diffraction patterns of Bi-MOF under different amounts of alkali are shown; where Bi-MOF corresponds to Example 1, I corresponds to Example 1, II corresponds to Example 5, and III corresponds to Example 8.

[0022] Figure 6 The figure shows the GCD curves of Bi-MOF under different alkali addition conditions. Detailed Implementation

[0023] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0024] Example 1: This embodiment provides a method for preparing Bi-MOF, specifically a solvothermal method for preparing Bi-MOF materials, including the following steps: (1) Take 60 mL of methanol and put it into a beaker. First, add 0.15 g of bismuth nitrate (Bi(NO3)3·5H2O) and 0.75 g of trimesic acid into the beaker containing 60 mL of methanol and sonicate for 3 minutes to form a transparent mixed solution.

[0025] (2) The mixed solution was transferred to the lining of a 100 mL reactor and heated in an oven at 120 °C for 24 h to obtain the initial Bi-MOF.

[0026] (3) Then, take 5 mL of ammonia water (volume fraction of 25%) and put it into a 5 mL beaker. Spread 0.5 g of Bi-MOF sample powder evenly in a 2000 mL beaker. Then place the beaker containing 5 mL of ammonia water into the bottom of the 2000 mL beaker. Seal the 2000 mL beaker with plastic wrap so that the Bi-MOF sample does not come into direct contact with the ammonia water. After heating, the ammonia water evaporates from the small beaker and comes into contact with the Bi-MOF sample in the large beaker.

[0027] (4) Finally, the material was obtained by alkali etching Bi-MOF material, namely layered accordion structure Bi-MOF, by heating in an oven at 80°C for 3 h.

[0028] Comparative Example 1 Compared with Example 1, the difference is that the amount of ammonia added in step (3) is 0 mL, that is, no ammonia is added, and the rest is the same as Example 1.

[0029] Example 2 Compared with Example 1, the difference is that the amount of ammonia added in step (3) is changed to 2.5 mL, and the rest is the same as Example 1.

[0030] Example 3 Compared with Example 1, the difference is that the heating time in step (4) is changed to "1 h", while the rest is the same as Example 1.

[0031] Example 4 Compared with Example 1, the difference is that the heating time in step (4) is changed to "2 h", while the rest is the same as Example 1.

[0032] Example 5: This embodiment provides a method for preparing Bi-MOF, specifically a solvothermal method for preparing Bi-MOF materials, including the following steps: (1) Take 60 mL of methanol and put it into a beaker. First, add 0.15 g of bismuth nitrate (Bi(NO3)3·5H2O) and 0.75 g of trimesic acid into the beaker containing 60 mL of methanol and sonicate for 3 minutes to form a transparent mixed solution.

[0033] (2) The mixed solution was transferred to the lining of a 100 mL reactor and heated in an oven at 120 °C for 24 h to obtain the initial Bi-MOF.

[0034] (3) Then, 10 mL of deionized water was put into a beaker, and 0.5 g of Bi-MOF sample and 0.5 g of hexamethylenetetramine were added to the beaker containing 10 mL of deionized water. The mixture was sonicated for 30 minutes to obtain the alkaline etched Bi-MOF material, namely the layered accordion structure Bi-MOF.

[0035] Example 6 Compared with Example 5, the difference is that "deionized water" in step (3) is replaced with "DMF", and the specific method is as follows: (3) Then, 10 mL of DMF was placed into a beaker, and 0.5 g of Bi-MOF sample and 0.5 g of hexamethylenetetramine were added to the beaker containing 10 mL of DMF. The mixture was sonicated for 30 minutes to obtain the alkaline etched Bi-MOF material, namely the layered accordion structure Bi-MOF.

[0036] Example 7 Compared with Example 5, the difference is that the amount of hexamethylenetetramine added is changed to "1 g", while the rest is the same as Example 1.

[0037] Example 8 This embodiment provides a method for preparing a layered accordion-structured Bi-MOF, specifically using a solvothermal method to prepare the layered accordion-structured Bi-MOF material, including the following steps: (1) Take 60 mL of methanol and put it into a beaker. First, add 0.15 g of bismuth nitrate (Bi(NO3)3·5H2O) and 0.75 g of trimesic acid into the beaker containing 60 mL of methanol and sonicate for 3 minutes to form a transparent mixed solution.

[0038] (2) The mixed solution was transferred to the lining of a 100 mL reactor and heated in an oven at 120 °C for 24 h to obtain the initial Bi-MOF.

[0039] (3) Then, take 10 mL of deionized water, add 0.5 g of Bi-MOF sample and 1 mL of tetramethylammonium hydroxide to a beaker containing 10 mL of deionized water, sonicate for 30 minutes to obtain alkaline etched Bi-MOF material, namely layered accordion structure Bi-MOF.

[0040] Example 9 Compared with Example 8, the difference is that "deionized water" in step (3) is replaced with "DMF", and the specific method is as follows: (3) Then, 10 mL of DMF was placed in a beaker, and 0.5 g of Bi-MOF sample and 1 mL of tetramethylammonium hydroxide were added to the beaker containing 10 mL of DMF. The mixture was sonicated for 30 minutes to obtain the alkaline etched Bi-MOF material, namely the layered accordion structure Bi-MOF.

[0041] Example 10 Compared with Example 8, the difference is that the amount of tetramethylammonium hydroxide added is changed to "0.5 mL", while everything else is the same as in Example 1.

[0042] Characterization and testing: The Bi-MOFs prepared in Examples 1-10 and Comparative Example 1 were characterized and their electrochemical performance was tested. The specific methods are as follows: (1) Characterization: Figure 1 A scanning electron microscope image of the Bi-MOF material prepared in Comparative Example 1; Figure 2 These are scanning electron microscope (SEM) images of the alkaline-etched Bi-MOF materials prepared in Examples 1-4, where a) 5 mL of ammonia water was added (Example 1); b) 2.5 mL of ammonia water was added (Example 2); c) heating for 1 h (Example 3); and d) heating for 2 h (Example 4). Figure 3 These are scanning electron microscope images of the alkaline etched Bi-MOF materials prepared in Examples 5-7, where ab represents the addition of 0.5 g of hexamethylenetetramine to water (Example 5) and DMF (Example 6), and c represents the addition of 1 g of hexamethylenetetramine to water (Example 7). Figure 4 These are scanning electron microscope images of the alkaline etched Bi-MOF materials prepared in Examples 8-10, where ab represents the addition of 1 mL of tetramethylammonium hydroxide to water (Example 8) and DMF (Example 9), and c represents the addition of 0.5 mL of tetramethylammonium hydroxide to water (Example 10). Depend on Figures 1-4 As can be seen, the Bi-MOF prepared in Comparative Example 1 is rod-shaped with a smooth and flat surface. The Bi-MOF materials prepared in Examples 1-4 are rod-shaped, and their surfaces have corrosion pits or holes; the amount of ammonia added and the alkaline etching time have a certain impact on the etching effect. The Bi-MOF bodies prepared in Examples 5-7 are segmented long columnar materials, with the column being divided into multiple regular square units along its length by uniform transverse grooves. The groove depth is uniform, penetrating the width of the column, forming a distinct segmental structure; and hexamethylenetetramine can achieve good etching effects using deionized water or DMF as solvents, although the amount of hexamethylenetetramine added has a certain impact on the etching effect. The Bi-MOF samples prepared in Examples 8-9 have a layered accordion structure, composed of a large number of parallel, tightly stacked ultrathin sheets arranged in an orderly manner; similarly, tetramethylammonium hydroxide can achieve good etching effects using deionized water or DMF as solvents, although the amount of tetramethylammonium hydroxide added has a certain impact on the etching effect. This demonstrates that, compared to the method without the addition of a weak base, the present invention enables the controllability of the microstructure and particle size of Bi-MOFs by adding a weak base.

[0043] Figure 5The images show the X-ray diffraction patterns of the alkaline-etched Bi-MOF materials prepared in Examples 1, 5, 8, and Comparative Example 1. In the examples, Bi-MOF corresponds to Comparative Example 1, I corresponds to Example 1, II corresponds to Example 5, and III corresponds to Example 8. It can be seen that compared to the original Bi-MOF, the alkaline-etched Bi-MOFs prepared in Examples 1, 5, and 8 first exhibit uniform transverse grooves in their microstructure, with the rod-like structure segmented and grooved. Further structural dissociation transforms them into a layered accordion structure with numerous internal gaps. The crystallinity is also higher, indicating that the amount of weak alkali added affects the microstructure and crystallinity. The resulting Bi-MOF samples have higher crystallinity. Highly crystallinity alkaline-etched Bi-MOF materials have a higher specific surface area, exposing more electrochemical reaction sites. Furthermore, high crystallinity helps improve electron transfer efficiency, ultimately enhancing the capacitance performance of Bi-MOFs.

[0044] (2) Electrochemical performance determination: Preparation of the working electrode: The above-mentioned alkaline etched Bi-MOF was used as the electrode active material. The alkaline etched Bi-MOF, Ketjen black and polyvinylidene fluoride (PVDF) were mixed evenly in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone was added and the mixture was ground evenly in a mortar to form a uniform slurry. The slurry was then evenly coated on the surface of carbon cloth and dried at 60 °C. The mass of the electrode active material was calculated based on the mass difference of the carbon cloth before and after drying.

[0045] Electrochemical performance testing process: A three-electrode system was constructed using carbon cloth coated with alkaline-etched Bi-MOF as the working electrode. Before testing, the electrode was activated by 100 cycles of cyclic voltammetry (CV) within the potential window of -1 V to 0 V, and then... -1 Constant current charge-discharge (GCD) tests were conducted at specific charge-discharge current densities, and the capacitance of the electrode material was calculated based on the discharge time curves. Based on these test results, the influence of different weak bases on electrochemical performance was analyzed.

[0046] The results are as follows Figure 6 As shown, Figure 6 The redox plateau in the GCD curve indicates that a redox reaction occurs in Bi-MOF at this point, further illustrating its pseudocapacitive behavior. The Bi-MOF electrode exhibited the longest charge-discharge time when 1 mL of tetramethylammonium hydroxide (Example 8) was added, at a current density of 1 A g. -1 At that time, the capacitance reached 889 F g -1The charge-discharge times of the Bi-MOF electrode with 5 mL of ammonia (Example 1) and the Bi-MOF electrode with 1 mL of tetramethylammonium hydroxide (Example 8) were not significantly different. However, the Bi-MOF electrode with 0.5 g of hexamethylenetetramine (Example 5) had a shorter charge-discharge time. Therefore, the Bi-MOF electrode with 1 mL of tetramethylammonium hydroxide exhibited the best capacitance performance. This is mainly due to the presence of ultrathin nanosheets in the Bi-MOF electrode with 1 mL of tetramethylammonium hydroxide. This sheet-like structure increases the specific surface area of ​​the Bi-MOF, increases the number of surface active sites, accelerates the mass transfer rate, and thus increases the capacitance.

[0047] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing Bi-MOF, characterized in that, Includes the following steps: S1. Dissolve bismuth nitrate and trimesic acid in methanol to obtain a mixed solution; heat the mixed solution to obtain the initial Bi-MOF; S2. The initial Bi-MOF is reacted with a weak base, wherein the weak base includes at least one of ammonia, hexamethylenetetramine, and tetramethylammonium hydroxide, to obtain Bi-MOF.

2. The preparation method according to claim 1, characterized in that, When the weak base is ammonia, the Bi-MOF is in the shape of a long rod, and its column surface has corrosion pits. When the weak base is hexamethylenetetramine, the Bi-MOF is in the shape of a long column, and the column has transverse grooves along its length. When the weak base is tetramethylammonium hydroxide, the Bi-MOF exhibits a layered accordion structure.

3. The preparation method according to claim 1, characterized in that, In S1, The ratio of bismuth nitrate, trimesic acid, and methanol is 0.1~0.2 g: 0.7~0.8 g: 50~70 mL; The heating temperature is 110~130 ℃, and the heating time is 20~28 h.

4. The preparation method according to claim 1, characterized in that, In step S2, when the weak base is ammonia, step S2 includes the following specific steps: Ammonia water is poured into a small-capacity first container, and the initial Bi-MOF is placed in a large-capacity second container; The first container is placed entirely into the second container, and the second container is sealed; the second container is heated at 75~85℃ for 2.5~3.5 h to obtain Bi-MOF; The initial Bi-MOF to ammonia water addition ratio is 0.4~0.6 g: 4~6 mL, and the volume fraction of the ammonia water is 25-28%.

5. The preparation method according to claim 1, characterized in that, In S2, when the weak base is hexamethylenetetramine, S2 includes the following specific steps: Solvent was added to the reaction vessel, and then the initial Bi-MOF and hexamethylenetetramine were added and mixed evenly to obtain Bi-MOF; The initial Bi-MOF, hexamethylenetetramine, and solvent were added in a ratio of 0.4–0.6 g: 0.4–0.6 g: 5–15 mL. The solvent is water or DMF.

6. The preparation method according to claim 1, characterized in that, In step S2, when the weak base is tetramethylammonium hydroxide, step S2 includes the following specific steps: Solvent was added to the reaction vessel, and then the initial Bi-MOF and tetramethylammonium hydroxide were added and mixed evenly to obtain a layered accordion-structured Bi-MOF. The initial Bi-MOF, tetramethylammonium hydroxide, and solvent were added in a ratio of 0.4~0.6 g: 0.8~1.2 mL: 5~15 mL. The solvent is water or DMF.

7. A Bi-MOF, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 6.

8. The Bi-MOF according to claim 8, characterized in that, The Bi-MOF has a length of 25~45 μm and a thickness of 50~80 nm.

9. An electrode, characterized in that, Including the Bi-MOF according to any one of claims 7 to 8, the method for preparing the electrode includes: The Bi-MOF, carbon black and PVDF are mixed evenly, N-methylpyrrolidone is added, and the mixture is ground evenly to form a uniform slurry. This slurry is then coated onto the surface of carbon cloth and dried to obtain the electrode. The mass ratio of Bi-MOF, carbon black, and PVDF is 8:1:

1.

10. A supercapacitor, characterized in that, Includes the electrode as described in claim 9.

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