A supercapacitor electrode material CNT@M-Ni-OH and a preparation method and application thereof

Abstract

The application relates to a supercapacitor electrode material CNT@M-Ni-OH and a preparation method and application thereof, which comprises the following steps: (1) modifying carbon nanotubes by using a modifier to obtain modified carbon nanotubes; (2) growing microporous MOFs on the modified carbon nanotubes by using a solvothermal or hydrothermal method to obtain a carbon nanotube@MOF composite material; and (3) preparing an electrode material CNT@M-Ni-OH by mixing a dispersion liquid of the carbon nanotube@MOF composite material with a nickel salt solution and performing a hydrothermal reaction, wherein M is a metal ion in the MOFs. The material is a core-shell structure formed by a large number of nanosheet-shaped hydroxides coated around CNTs, can provide more contact areas with electrolytes, promotes ion diffusion, and meanwhile, the CNTs can effectively improve the conductivity of the electrode material and improve electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrode materials, and particularly relates to a supercapacitor electrode material CNT@M-Ni-OH, its preparation method, and its application. Background Technology

[0002] With the rapid depletion of natural fossil resources and the drastic deterioration of the ecological environment, the demand for clean, efficient, and sustainable energy storage devices is becoming increasingly urgent. Therefore, the research and development of energy storage devices is of great significance. Among various energy storage devices, supercapacitors are considered a very promising option due to their rapid energy storage and high power output. Generally speaking, the core component of a supercapacitor is the electrode material, and research on supercapacitors mainly focuses on the synthesis and development of novel electrode materials with high capacitance.

[0003] Nickel-based hydroxides have attracted researchers' attention due to their high theoretical capacity and low cost. However, pure nickel-based hydroxides typically limit their practical applications due to drawbacks such as easy aggregation, low conductivity, and poor cycling stability. Introducing other metal ions (such as Zn, Al, Cr, Mn, and Co) onto Ni(OH)₂ can effectively improve the stability and electrochemical activity of the electrode. Simultaneously, combining highly conductive carbon materials with Ni(OH)₂ can enhance the conductivity of the electrode material, thereby improving electrochemical activity. For example, Chang (Chang,Y.;Yang,J.;Zhao,C;et al.Nanohybrids from NiCoAl-LDH coupled with carbon for pseudocapacitors:understanding the role of nano-structured carbon[J].Nanoscale.2014,6(6),3097~3104.) synthesized NiCoAl-LDH by co-precipitation and then combined it with carbon nanotubes. This ternary composite material combines the advantages of the three materials, with higher specific capacitance, larger specific surface area, and more significant electrochemical effects in terms of cycle stability and conductivity compared to binary composite materials.

[0004] Metal-organic frameworks (MOFs) possess high porosity, high specific surface area, and tunable structure, making them highly applicable in sensing, gas adsorption, separation, and catalysis. Furthermore, the high porosity, excellent specific surface area, and low density of MOFs make them ideal templates for fabricating functional shell or hollow structure materials with large surface areas and porosity. When using MOFs as templates to prepare micro / nanomaterials with internal cavities or functional shells, MOFs can act as both sacrificial templates and donor metal ions, making them bifunctional materials. Moreover, materials prepared using MOFs as templates inherit some of the characteristics of MOFs, exhibiting high specific surface area and high morphological tunability. Therefore, MOFs can be used to prepare supercapacitor materials with excellent electrochemical performance. For example, Jiang et al. (Jiang, Z.; Li, Z.; Qin, Z.; et al. LDH nanocages synthesized with MOF templates and their high performance as supercapacitors[J]. Nanoscale. 2013, 5(23), 11770~11775.) prepared hollow layered double hydroxide (LDH) polyhedra based on ZIF-67. Yilmaz et al. (Yilmaz, G.; Yam, KM; Zhang, C.; et al. In situ transformation of MOFs into layered double hydroxide embedded metal sulfides for improved electrocatalytic and supercapacitive performance[J]. Advanced Materials. 2017, 29(26), 1606814.) reported that NiCo-LDH / Co9S8 derived from MOFs has a high specific capacitance. However, these technologies suffer from drawbacks such as the difficulty in uniformly dispersing and the tendency for nano-M-Ni-OH to agglomerate, which are detrimental to improving the electrochemical activity of M-Ni-OH electrode materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a supercapacitor electrode material CNT@M-Ni-OH, its preparation method and application, thereby solving the technical problems of low electrochemical activity caused by the difficulty in uniformly dispersing and easy agglomeration of M-Ni-OH in the prior art.

[0006] To achieve the above-mentioned technical objectives, the technical solution of the preparation method of the present invention is as follows:

[0007] Includes the following steps:

[0008] (1) Carbon nanotubes were modified with a modifier to obtain modified carbon nanotubes;

[0009] (2) Microporous MOFs are grown on modified carbon nanotubes by solvothermal or hydrothermal methods to obtain carbon nanotube@MOFs composite materials.

[0010] (3) The carbon nanotube@MOFs composite material was prepared into a dispersion and mixed with a nickel salt solution for hydrothermal reaction to prepare the electrode material CNT@M-Ni-OH, wherein the mass ratio of the carbon nanotube@MOFs composite material to the nickel salt was 1:(2~5), and M was the metal ion in MOFs.

[0011] Further, in step (1), the modifier is dopamine or silane coupling agent, and the modification is carried out in an acidic solution with a pH of 8 to 9; the mass ratio between the modifier and carbon nanotubes is 1:(1 to 2), and the modification time is 2 to 24 hours.

[0012] Furthermore, the acidic solution is a hydrochloric acid solution, acetic acid solution, sulfuric acid solution, or TRIS solution; the silane coupling agent is of type KH-540, KH-550, or KH-560.

[0013] Furthermore, in step (2), the raw materials for the microporous MOFs include coordination metals and ligands. The mass molar ratio of modified carbon nanotubes to coordination metals is 40 mg: (0.5–2) mmol; the molar ratio of coordination metals to ligands is 1: (5–20); the coordination metal is one or both of Co(NO3)2·6H2O and Zn(NO3)2·6H2O; and the ligands include imidazole ligands and vinylamide ligands.

[0014] Furthermore, in step (2), the reaction temperature for both solvothermal and hydrothermal methods is 80–140°C, and the reaction time is 12–36 h.

[0015] Further, in step (3), the concentration of the carbon nanotube@MOFs composite material dispersion is 2 to 5 mg / mL, and the solvent of the carbon nanotube@MOFs composite material dispersion is one or more of water, ethanol, methanol and DMF.

[0016] Furthermore, in step (3), the nickel salt used is Ni(NO3)2·6H2O, the concentration of the Ni(NO3)2·6H2O solution is 16-25 mg / mL, and the solvent of the Ni(NO3)2·6H2O solution is water.

[0017] Furthermore, in step (3), the hydrothermal reaction conditions are: heating at 90-120℃ for 12-36 hours.

[0018] The supercapacitor electrode material CNT@M-Ni-OH was prepared by the above method.

[0019] The above describes the application of the supercapacitor electrode material CNT@M-Ni-OH in supercapacitors.

[0020] Compared with the prior art, the beneficial effects of the present invention include:

[0021] This invention provides a method for preparing CNT@M-Ni-OH, an electrode material for supercapacitors, using MOFs as a template. The method involves first surface modification of carbon nanotubes, then uniformly growing microporous MOFs on the carbon nanotubes to prepare a CNT@MOFs composite material. Finally, the CNT@MOFs undergo a hydrolysis reaction with nickel salts to generate the CNT@M-Ni-OH composite electrode material. The structure of the CNT@M-Ni-OH prepared by this method consists of a core-shell structure formed by a large number of nanosheet-like hydroxides surrounding the CNTs. This structure provides a larger contact area with the electrolyte, promoting ion diffusion. Simultaneously, the CNTs effectively improve the conductivity of the electrode material, thereby further enhancing electrochemical performance. The material of this invention achieves a specific capacitance of 1664.70–2039.63 F / g at a current density of 1 A / g, and retains a capacitance of 85.4%–99.0% after 1000 cycles. Attached Figure Description

[0022] Figure 1 This is a flowchart of the preparation method of the present invention;

[0023] Figure 2(a) is a SEM image of CNT@NiCoZn-OH in this invention;

[0024] Figure 2(b) is a SEM image of CNT@NiCo-OH in this invention;

[0025] Figure 2(c) is a SEM image of CNT@NiZn-OH in this invention;

[0026] Figure 3(a) is the CV diagram of CNT@NiCoZn-OH in this invention;

[0027] Figure 3(b) is the CV diagram of CNT@NiCo-OH in this invention;

[0028] Figure 3(c) is the CV diagram of CNT@NiZn-OH in this invention;

[0029] Figure 4(a) is the GCD diagram of CNT@NiCoZn-OH in this invention;

[0030] Figure 4(b) is the GCD diagram of CNT@NiCo-OH in this invention;

[0031] Figure 4(c) is the GCD diagram of CNT@NiZn-OH in this invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages 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 and not intended to limit the invention.

[0033] This invention provides a method for preparing CNT@M-Ni-OH electrode material for supercapacitors using MOFs as templates. The aim is to solve the defects of nano-M-Ni-OH being difficult to uniformly disperse in CNTs and being prone to agglomeration. This is beneficial to improving the electrochemical activity of M-Ni-OH electrode material. At the same time, the introduction of carbon nanotubes can enhance the conductivity of the composite material, thereby increasing the electron migration rate of the electrode material and thus improving the capacitance and stability of the electrode material.

[0034] See Figure 1 The method of the present invention includes the following steps:

[0035] A. Modify carbon nanotubes with dopamine or silane coupling agent in acidic solution so that microporous MOFs can grow on carbon nanotubes. The ratio of dopamine or silane coupling agent, carbon nanotubes and acidic solution is 1g:(1~2)g:(100~500)mL, and the modification time is 2~24h.

[0036] B. Carbon nanotube@MOFs composite materials were prepared by growing microporous MOFs on the outer surface of carbon nanotubes using a solvothermal or hydrothermal reaction method: the ratio of modified carbon nanotubes to total solvent was 40 mg: (30-60) mL; the growth time was 12-36 h; and the growth temperature was 80-140 °C.

[0037] C. CNT@M-Ni-OH was prepared by reacting carbon nanotubes@MOFs composite material with nickel nitrate via a hydrothermal method. The concentration of the carbon nanotubes@MOFs composite material dispersion was 2–5 mg / mL; the concentration of the Ni(NO3)2·6H2O aqueous solution was 16–25 mg / mL; and the mass ratio of carbon nanotubes@MOFs composite material to Ni(NO3)2·6H2O was 1:(2–5) mg. The hydrothermal reaction conditions were: heating at 90–120℃ for 12–36 h.

[0038] Preferably, the acidic solution is a dilute hydrochloric acid solution, a dilute acetic acid solution, a dilute sulfuric acid solution, or a TRIS solution, with a pH value of 8.5.

[0039] Preferably, the MOFs are ZIF-5, ZIF-7, ZIF-8, ZIF-11, ZIF-20, ZIF-67, ZIF-68 and various ZIF mixtures.

[0040] In step B) of this invention, the raw materials of MOFs include coordination metals and ligands, wherein the coordination metal is one or both of Co(NO3)2·6H2O and Zn(NO3)2·6H2O, and the ligands include imidazole ligands and vinylamide ligands. The imidazole ligand is preferably 2-methylimidazolium, and the vinylamide ligand is preferably polyvinylpyrrolidone.

[0041] The ratio between modified carbon nanotubes and coordination metal is 40 mg: (0.5–2) mmol; the molar ratio of Co(NO3)2·6H2O and Zn(NO3)2·6H2O in the coordination metal is (0–1): (0–1), and the two are not simultaneously zero, and the preferred molar ratio is 1:1.

[0042] The theoretical molar ratio of metal source to ligand is 1:1. To ensure the full reaction of the metal source, an excess of ligand is used, preferably 5 to 20 times the molar amount of ligand as the metal source. Since both the metal source and ligand used are soluble in solvents such as water, and the product is insoluble, high-purity MOFs materials can be obtained. This invention can select the metal source and the corresponding ligand according to the specific type of MOFs.

[0043] The preferred molar ratio of 2-methylimidazolium to polyvinylpyrrolidone in the ligand is (3-4):(1-2).

[0044] Preferably, the organosilane coupling agent is KH-540, KH-550, or KH-560.

[0045] Preferably, the solvent in solvothermal treatment is one or a mixture of water, ethanol, methanol and DMF.

[0046] The present invention will be further described in detail below through specific embodiments.

[0047] Example 1

[0048] (1) Dissolve 0.3 g of trihydroxyaminomethane in 250 mL of water, adjust the pH to 8.5 with hydrochloric acid, and prepare a 0.5 mmol / L Tris buffer solution; place 0.5 g of carbon nanotubes in 195 mL of Tris buffer solution and stir for 15 min, then sonicate for 15 min to ensure uniform dispersion of carbon nanotubes in Tris buffer solution; dissolve 0.5 g of dopamine in 10 mL of Tris buffer solution and pour it into the above solution, and stir magnetically for 2 h. Finally, wash twice with acetone and deionized water by suction filtration, and dry in an oven at 60 °C for 24 h to obtain the product CNT@PDA.

[0049] (2) 40 mg CNT@PDA was dispersed in 20 mL of methanol under ultrasonic conditions for 10 min to ensure uniform dispersion. 0.25 mmol Co(NO3)2·6H2O and 0.25 mmol Zn(NO3)2·6H2O were dissolved in 10 mL of methanol and added to the above solution, followed by magnetic stirring. Then, a 10 mL methanol solution containing 328 mg (4 mmol) 2-methylimidazole and 187.5 mg (1.7 mmol) polyvinylpyrrolidone was added dropwise to the above solution. After continuous stirring for 12 h, the mixture was filtered to obtain CNT@CoZn-ZIFs (ZIFs are a type of MOF). The molar ratio of modified carbon nanotubes to coordinating metal was 40 mg:0.5 mmol; the molar ratio of coordinating metal to ligand was 1:10.4.

[0050] (3) 80 mg CNT@CoZn-ZIFs were ultrasonically dispersed in a mixed solvent of 40 mL ethanol and dimethylformamide (DMF) (volume ratio 1:1). Then, 10 mL of water containing 160 mg Ni(NO3)2·6H2O was added to the above solution. After thorough mixing, the solution was heated at 90 °C for 12 h, filtered, washed with water, and dried to obtain the product CNT@NiCoZn-OH.

[0051] Example 2

[0052] 40 mg of the same CNT@PDA as in Example 1 was dispersed in 20 mL of methanol under ultrasonic conditions for 10 min to ensure uniform dispersion. 0.5 mmol of Co(NO3)2·6H2O was dissolved in 10 mL of methanol and then added to the above solution, followed by magnetic stirring. Then, a 10 mL methanol solution containing 328 mg of 2-methylimidazole and 187.5 mg of polyvinylpyrrolidone was added dropwise to the above solution. After continuous stirring for 12 h, the mixture was filtered to obtain CNT@Co-ZIFs.

[0053] 80 mg of CNT@Co-ZIFs were ultrasonically dispersed in 40 mL of a mixed solvent of ethanol and dimethylformamide (DMF) (volume ratio 1:1). Then, 10 mL of water containing 160 mg of Ni(NO3)2·6H2O was added to the above solution. After thorough mixing, the solution was heated at 90 °C for 12 h, filtered, washed with water, and dried to obtain the product CNT@NiCo-OH.

[0054] Example 3

[0055] 40 mg of the same CNT@PDA as in Example 1 was dispersed in 20 mL of methanol under ultrasonic conditions for 10 min to ensure uniform dispersion. 0.5 mmol of Zn(NO3)2·6H2O was dissolved in 10 mL of methanol and added to the above solution, followed by magnetic stirring. Then, a 10 mL methanol solution containing 328 mg of 2-methylimidazole and 187.5 mg of polyvinylpyrrolidone was added dropwise to the above solution. After continuous stirring for 12 h, the mixture was filtered to obtain CNT@Zn-ZIFs.

[0056] 80 mg of CNT@Zn-ZIFs were ultrasonically dispersed in 40 mL of a mixed solvent of ethanol and dimethylformamide (DMF) (volume ratio 1:1). Then, 10 mL of water containing 160 mg of Ni(NO3)2·6H2O was added to the above solution. After thorough mixing, the solution was heated at 90 °C for 12 h, filtered, washed with water, and dried to obtain the product CNT@NiZn-OH.

[0057] Electrochemical performance was tested using a Koster electrochemical workstation. Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and cycle stability tests were performed on the prepared material. The electrolyte was 3 mol / L KOH, and the tests were conducted using a three-electrode system at room temperature. The electrode sheet made of composite material was used as the working electrode, platinum wire as the counter electrode, and a silver electrode as the reference electrode.

[0058] In GCD, we can obtain the discharge time of the composite material at different current densities, according to the formula:

[0059] Cs=(I*Δt) / (m*ΔV) (1)

[0060] The specific capacitance can be calculated. Here, Cs represents the specific capacitance of the electrode material (F / g); I represents the discharge current (A); Δt represents the discharge time (s); m represents the mass of the active material in the electrode (g); and ΔV represents the voltage range of the test system.

[0061] Figures 2(a) to 2(c) The images show SEM images of CNT@NiCoZn-OH, CNT@NiZn-OH, and CNT@NiCo-OH, respectively. It can be clearly seen from the images that all three materials have the structural feature of CNTs connecting to the outer layer of interlaced nanosheets to form a whole. The CNTs and the outer layer of interlaced nanosheets provide more electrolyte contact area, thereby enabling rapid ion diffusion.

[0062] Figures 3(a) to 3(c)The figure shows the CV curves of CNT@NiCoZn-OH, CNT@NiZn-OH, and CNT@NiCo-OH. As can be seen from the figure, the CV curves of the three materials exhibit obvious redox peaks, rather than an approximately rectangular shape. This indicates that the electrodes of the three materials are mainly composed of Faraday pseudocapacitors, and that Faraday reactions inevitably occurred in the electrode materials during the electrochemical reaction. These peaks are caused by the redox reactions of metal ions on the electrode surface during the electrochemical process.

[0063] Figures 4(a) to 4(c) The graphs show the GCD curves of the three materials. The graphs demonstrate the high symmetry of the constant current charge-discharge curves, indicating that the CNT@NiCoZn-OH composite material possesses excellent conductivity and coulombic efficiency. The specific capacity and cycle performance of the CNT@NiCoZn-OH, CNT@NiZn-OH, and CNT@NiCo-OH electrodes at a current density of 1 A / g were calculated using formula (1), as shown in Table 1 below.

[0064] Table 1. Electrochemical performance of the three products obtained in Examples 1 to 3 as electrode materials.

[0065]

[0066] As shown in Table 1, the specific capacitances of the three materials prepared in this invention at a current density of 1 A / g are 2039.63 F / g, 1930.01 F / g, and 1664.70 F / g, respectively. After 1000 cycles, the capacitance retention rates of the three materials reached 97.7%, 99.0%, and 85.4%, respectively. Therefore, the CNT@NiCoZn-OH composite material exhibits the best overall performance.

[0067] Example 4

[0068] (1) Take a hydrochloric acid solution with a pH of 8.5; place 1g of carbon nanotubes in 170mL of hydrochloric acid solution and stir for 15min, then sonicate for 15min to disperse the carbon nanotubes evenly in the hydrochloric acid solution; dissolve 0.5g of KH-540 silane coupling agent in 10mL of hydrochloric acid solution and pour it into the above solution, and stir magnetically for 3h. Finally, wash twice with acetone and deionized water by suction filtration, and dry in an oven at 60℃ for 24h to obtain the product modified carbon nanotubes.

[0069] (2) 40 mg of modified carbon nanotubes were dispersed in 20 mL of methanol under ultrasonic conditions for 10 min to ensure uniform dispersion. 0.3 mmol Co(NO3)2·6H2O and 0.3 mmol Zn(NO3)2·6H2O were dissolved in 10 mL of methanol and added to the above solution, followed by magnetic stirring. Then, a 10 mL methanol solution containing 3.6 mmol of 2-methylimidazole and 1.2 mmol of polyvinylpyrrolidone was added dropwise to the above solution. After continuous stirring for 24 h, the mixture was filtered to obtain CNT@CoZn-ZIFs.

[0070] (3) 80 mg of CNT@CoZn-ZIFs were ultrasonically dispersed in 20 mL of a mixed solvent of ethanol and dimethylformamide (DMF) (volume ratio 1:1). Then, 10 mL of water containing 240 mg of Ni(NO3)2·6H2O was added to the above solution. After thorough mixing, the solution was heated at 100 °C for 12 h. After filtration, washing with water, and drying, the product CNT@NiCoZn-OH was obtained. The specific capacitance of this product CNT@NiCoZn-OH was 1997.32 F / g at a current density of 1 A / g, and the capacitance retention rate was 97.2% after 1000 cycles.

[0071] Example 5

[0072] (1) Take a sulfuric acid solution with a pH of 8.5; place 0.75g of carbon nanotubes in 210mL of sulfuric acid solution and stir for 15min, then sonicate for 15min to disperse the carbon nanotubes evenly in the sulfuric acid solution; dissolve 0.5g of KH-560 silane coupling agent in 10mL of sulfuric acid solution and pour it into the above solution, and stir magnetically for 5h. Finally, wash twice with acetone and deionized water by vacuum filtration, and dry in an oven at 60℃ for 24h to obtain the product modified carbon nanotubes.

[0073] (2) 40 mg of modified carbon nanotubes were dispersed in 20 mL of methanol under ultrasonic conditions for 10 min to ensure uniform dispersion. 0.4 mmol Co(NO3)2·6H2O and 0.4 mmol Zn(NO3)2·6H2O were dissolved in 10 mL of methanol and added to the above solution, followed by magnetic stirring. Then, a 10 mL methanol solution containing 4 mmol of 2-methylimidazole and 1.6 mmol of polyvinylpyrrolidone was added dropwise to the above solution. After continuous stirring for 36 h, the mixture was filtered to obtain CNT@CoZn-ZIFs.

[0074] (3) 80 mg CNT@CoZn-ZIFs were ultrasonically dispersed in 30 mL of water. Subsequently, 20 mL of water containing 400 mg Ni(NO3)2·6H2O was added to the above solution. After thorough mixing, the solution was heated at 120 °C for 12 h, filtered, washed with water, and dried to obtain the product CNT@NiCoZn-OH. The specific capacitance of the product CNT@NiCoZn-OH was 2013.58 F / g at a current density of 1 A / g, and the capacitance retention rate was 97.5% after 1000 cycles.

[0075] Comparative Example 1

[0076] The modification process in step (1) is removed, and carbon nanotubes are used to replace the modified carbon nanotubes in step (2). The other steps are the same as in Example 4.

[0077] The specific capacitance of the obtained product is 1102 F / g at a current density of 1 A / g, and the capacitance retention rate is 70.5% after 1000 cycles. This is because the unmodified carbon nanotubes are not conducive to the growth of MOFs, resulting in a decrease in active sites and a decline in the electrochemical performance of the obtained material.

[0078] This invention provides a method for preparing CNT@M-Ni-OH, an electrode material for supercapacitors, using MOFs as templates. The method first modifies the surface of carbon nanotubes (CNTs) with dopamine or silane coupling agents to grow MOFs on the CNTs. Then, using nitrate as a metal source, CNT@MOFs material is synthesized together with organic ligands and the modified carbon nanotubes. Finally, CNT@M-Ni-OH is prepared by reacting it with nickel nitrate via a hydrothermal method. In this composite material, layered hydroxides are dispersed around the carbon nanotubes to form a uniform core-shell structure. This structure provides a specific surface area, which is beneficial for promoting ion diffusion, thereby effectively improving electrochemical performance.

[0079] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing CNT@M-Ni-OH, a supercapacitor electrode material, characterized in that, Includes the following steps: (1) Modified carbon nanotubes are obtained by modifying carbon nanotubes with a modifier; the modifier is dopamine or silane coupling agent; (2) Microporous MOFs were grown on modified carbon nanotubes by a solvothermal method to obtain carbon nanotube@MOFs composite material; (3) The carbon nanotube@MOFs composite material was prepared into a dispersion and mixed with a nickel salt solution for hydrothermal reaction to prepare the electrode material CNT@M-Ni-OH, wherein the mass ratio of the carbon nanotube@MOFs composite material to the nickel salt was 1:(2~5), and M was the metal ion in MOFs.

2. The method for preparing the supercapacitor electrode material CNT@M-Ni-OH according to claim 1, characterized in that, In step (1), the modification is carried out in an acidic solution with a pH of 8 to 9; the mass ratio between the modifier and carbon nanotubes is 1:(1 to 2), and the modification time is 2 to 24 h.

3. The method for preparing the supercapacitor electrode material CNT@M-Ni-OH according to claim 2, characterized in that, The acidic solution is hydrochloric acid, acetic acid, sulfuric acid, or TRIS solution; the silane coupling agent is KH-540, KH-550, or KH-560.

4. The method for preparing the supercapacitor electrode material CNT@M-Ni-OH according to claim 1, characterized in that, In step (2), the raw materials for microporous MOFs include coordination metals and ligands. The molar ratio of modified carbon nanotubes to coordination metals is 40 mg: (0.5-2) mmol; the molar ratio of coordination metals to ligands is 1: (5-20); the coordination metal is one or both of Co(NO3)2·6H2O and Zn(NO3)2·6H2O, and the ligands include imidazole ligands and vinylamide ligands.

5. The method for preparing the supercapacitor electrode material CNT@M-Ni-OH according to claim 1, characterized in that, In step (2), the reaction temperature of the solvothermal method is 80-140℃ and the time is 12-36 h.

6. The method for preparing the supercapacitor electrode material CNT@M-Ni-OH according to claim 1, characterized in that, In step (3), the concentration of the carbon nanotube@MOFs composite material dispersion is 2 to 5 mg / mL, and the solvent of the carbon nanotube@MOFs composite material dispersion is one or more of water, ethanol, methanol and DMF.

7. The method for preparing the supercapacitor electrode material CNT@M-Ni-OH according to claim 1, characterized in that, In step (3), the nickel salt used is Ni(NO3)2·6H2O, the concentration of the Ni(NO3)2·6H2O solution is 16-25 mg / mL, and the solvent of the Ni(NO3)2·6H2O solution is water.

8. The method for preparing the supercapacitor electrode material CNT@M-Ni-OH according to claim 1, characterized in that, In step (3), the hydrothermal reaction conditions are: heating at 90-120 °C for 12-36 h.

9. The supercapacitor electrode material CNT@M-Ni-OH prepared by the preparation method according to any one of claims 1-8.

10. The application of the supercapacitor electrode material CNT@M-Ni-OH as described in claim 9 in supercapacitors.

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