A preparation method for an asymmetric supercapacitor electrode

Abstract

A preparation method of an asymmetric supercapacitor electrode. The ZIF-8 / CNT composite material is prepared by an in-situ growth method, and cobalt-doped ZIF-8 / CNT is optimized and synthesized by an ion exchange method. Finally, the ZnCoS / CNT composite material is prepared using this as a template and used as the positive electrode material of the electrode. This positive electrode material combines the advantages of bimetallic sulfide and CNT, has a large specific surface area and a special conductive network structure. Using 1,3,5-benzenetricarboxylic acid as a ligand and Fe as a metal ion, the Fe-MOF / CNT composite material is synthesized, and Fe2O3 / CNT prepared by high-temperature carbonization of it in a nitrogen atmosphere is used as the negative electrode material of the electrode. This negative electrode material has adjustable pore size and good thermal stability. Finally, the asymmetric supercapacitor assembled with ZnCoS / CNT as the positive electrode and Fe2O3 / CNT as the negative electrode has both outstanding specific capacitance and excellent conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of the electronics industry, and in particular, to a method for preparing an asymmetric supercapacitor electrode. Background Art

[0002] With the development and utilization of renewable energy, there is an urgent need for efficient energy storage devices. Among various electrochemical energy conversion and storage technologies, electrochemical supercapacitors (SCs) have been widely used in electrical energy storage technologies due to their fast charge and discharge capabilities, excellent cycle stability, and high power density. SCs are classified into electric double-layer capacitors and pseudocapacitors according to the energy storage mechanism. Pseudocapacitors are an important type of electrochemical capacitor for electrical energy storage devices, which store energy through surface Faraday reactions. In addition, pseudocapacitors have a higher specific capacitance than traditional electric double-layer capacitors (EDLCs), and the mechanism of traditional electric double-layer capacitors is based on double-layer ion adsorption. However, rationally designing unique electrode materials with high performance remains a huge challenge.

[0003] Transition metal oxides are considered to be one of the most promising candidates for pseudocapacitor electrode materials because they have ideal high specific capacitance and potential redox sites. However, low electrochemical stability and electronic conductivity are two major obstacles to these materials, which result in lower rate capabilities. Recently, many efforts have been devoted to meeting the challenges of the stability and conductivity problems of pseudocapacitor electrode materials, and the results obtained show that transition metal sulfides (TMS) have higher electrochemical performance and excellent conductivity than the corresponding oxides. In addition, the synergistic effect of hetero-metal ions in TMS enhances the charge transfer of the electrode material, thereby improving the intrinsic conductivity of the electrode material, which helps to improve the rate performance. All in all, the electrochemical contribution of bimetallic sulfides can provide a richer redox reaction, resulting in a more prominent specific capacitance than single-component sulfides. Advanced carbon-based materials are beneficial to improving the conductivity of electrode materials due to their large surface area, high conductivity, and inherent stability. Therefore, how to combine the excellent characteristics of the above two to develop an electrode material with a prominent specific capacitance and excellent conductivity is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a preparation method for an asymmetric supercapacitor electrode. A ZIF-8 / CNT composite material is prepared by an in-situ growth method, and cobalt-doped ZIF-8 / CNT is synthesized and optimized by an ion exchange method. Finally, a ZnCoS / CNT composite material is prepared using this as a template and used as the positive electrode material of the electrode. This positive electrode material combines the advantages of bimetallic sulfide and CNT, has a large specific surface area and a special conductive network structure; using 1,3,5-benzenetricarboxylic acid as a ligand and Fe as a metal ion, an Fe-MOF / CNT composite material is synthesized, and Fe 2 O 3 / CNT prepared by high-temperature carbonization of it in a nitrogen atmosphere is used as the negative electrode material of the electrode. This negative electrode material has adjustable pore size and good thermal stability. Finally, an asymmetric supercapacitor assembled with ZnCoS / CNT as the positive electrode and Fe 2 O 3 / CNT as the negative electrode has both outstanding specific capacitance and excellent conductivity.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] A preparation method for an asymmetric supercapacitor electrode, characterized by including the following steps:

[0007] Step 1, preparation of the positive electrode material: A ZIF-8 / CNT composite material is prepared by an in-situ growth method, and cobalt-doped ZIF-8 / CNT is synthesized and optimized by an ion exchange method. Finally, a ZnCoS / CNT composite material is prepared using this as a template;

[0008] Step 2, preparation of the negative electrode material: Using 1,3,5-benzenetricarboxylic acid as a ligand and Fe as a metal ion, an Fe-MOF / CNT composite material is synthesized, and Fe 2 O 3 / CNT prepared by high-temperature carbonization of it in a nitrogen atmosphere;

[0009] Step 3, preparation of the supercapacitor electrode: First, the positive electrode material in Step 1 or the negative electrode material in Step 2 is mixed with activated carbon, and a binder is added to bond it to a nickel foam current collector. After drying, a single supercapacitor electrode is obtained.

[0010] As a preferred embodiment of the present invention, a preparation method for an asymmetric supercapacitor electrode provided by an embodiment of the present invention further includes some or all of the following technical features:

[0011] Preferably, the preparation of the positive electrode material in Step 1 specifically includes the following steps:

[0012] Step 1.1 Preparation of ZIF-8-CNT: Dissolve 0.1 g of Zn(NO 3 ) 2 in 50 mL of methanol solution, denoted as solution A; separately take 0.1 g of 2-methylimidazole and 20 mg of CNT in 50 mL of anhydrous methanol, denoted as solution B; pour solution A into solution B, mix evenly, leave at room temperature for 24 h, centrifuge, and dry to obtain ZIF-8-CNT powder;

[0013] Step 1.2 Preparation of ZIF-8-Co-CNT: Take 0.05 g of ZIF-8-CNT and dissolve it in a solution of Co(NO 3 ) 2 , ultrasonic for 20 mins, leave at room temperature for 6 h for ion exchange, finally centrifuge, wash three times with water, and dry to obtain ZIF-8-Co-CNT;

[0014] Step 1.3 Preparation of ZnCoS-CNT composite material: Take the ZIF-8-Co / CNT prepared in Step 1.2 in 50 mL of 0.5 M thioacetamide solution, ultrasonic for 0.5 h, then place it in a reaction kettle and react at 150 °C for 2 h. After the reaction is completed and cooled to room temperature, centrifuge, wash three times with water, and dry to obtain ZnCoS-CNT.

[0015] Preferably, in the preparation process of ZIF-8-Co-CNT in Step 1.2, separately take 0.05 g of ZIF-8-CNT and dissolve it in Co(NO 3 ) 2 solutions with concentrations of 0.5 M and 1 M, and the obtained ZIF-8-Co-CNT are respectively denoted as ZIF-8-Co-1 / CNT with a Co(NO 3 ) 2 concentration of 0.5 M and ZIF-8-Co-2 / CNT with a concentration of 1 M.

[0016] Among them, when the Co(NO 3 ) 2 solution in Step 1.2 is 0.5 M, the specific operation in Step 1.3 is as follows: Take 0.02 g of ZIF-8-Co-1 / CNT obtained in Step 1.2 in 50 mL of 0.5 M thioacetamide solution, ultrasonic for 0.5 h, then place it in a reaction kettle and react at 150 °C for 2 h. After the reaction is completed and cooled to room temperature, centrifuge, wash three times with water, and dry to obtain ZnCoS-CNT-1.

[0017] And when the Co(NO 3 ) 2When the solution is 1 M, the specific operation of Step 1.3 is as follows: Take 0.02 g of ZIF-8-Co-2 / CNT obtained in Step 1.2 and place it in 50 mL of 0.5 M thioacetamide solution. After ultrasonic treatment for 0.5 h, place it in a reaction kettle and react at 150 °C for 2 h. After the reaction is completed and cooled to room temperature, centrifuge and wash three times with water, and dry to obtain ZnCoS-CNT-2.

[0018] Preferably, the preparation of the negative electrode material in Step 2 specifically includes the following steps:

[0019] Step 2.1, Preparation of Fe-MOF-CNT composite material: Take 1.6 g of FeCl 3 , 0.991 g of trimesic acid, and 50 mg of CNT and dissolve them in 100 ml of DMF solution; after mixing evenly, carry out microwave reaction in a microwave reactor at a power of 500 W for 10 min, and then carry out solvent thermal reaction in a reaction kettle at 150 °C for 2 h; finally, centrifuge, wash three times with DMF water, and dry to obtain yellow powder of Fe-MOF-CNT;

[0020] Step 2.2, Preparation of Fe 2 O 3 -CNT composite material: Take 0.1 g of Fe-MOF-CNT and place it in a tube furnace, heat it to 500 °C at a rate of 5 °C / min and calcine for 2 h; after the tube furnace is cooled to room temperature, collect to obtain black powder of Fe 2 O 3 -CNT.

[0021] Among them, in Step 3, the positive electrode material in Step 1, or the negative electrode material in Step 2 and activated carbon are mixed at a mass ratio of 4:1.

[0022] Preferably, the preparation of the supercapacitor electrode in Step 3 specifically includes the following steps:

[0023] First, weigh the positive electrode material in Step 1 above, or the negative electrode material in Step 2 and activated carbon at a mass ratio of 4:1, and put them into a 10 mL small glass bottle;

[0024] Then mix the above materials with a binder, and finally add 0.8 mL of absolute ethanol as a dispersant;

[0025] Then place the mixture in an ultrasonic machine and ultrasonic for half an hour to form a uniformly mixed suspension;

[0026] Finally, drop the suspension in 10 steps onto a 1×1 cm 2 foam nickel current collector, and place the current collector in an electrothermal constant temperature blast drying oven and dry it at 80 °C, controlling the mass of the active material of a single electrode to be about 1 mg.

[0027] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0028] The preparation method of the asymmetric supercapacitor electrode disclosed in the present invention prepares a ZIF-8 / CNT composite material by an in-situ growth method, optimizes and synthesizes cobalt-doped ZIF-8 / CNT by an ion exchange method, and finally prepares a ZnCoS / CNT composite material using this as a template and uses it as the positive electrode material of the electrode. This positive electrode material combines the advantages of bimetallic sulfide and CNT, has a large specific surface area and a special conductive network structure; uses 1,3,5-benzenetricarboxylic acid as a ligand and Fe as a metal ion to synthesize an Fe-MOF / CNT composite material, and prepares Fe 2 O 3 / CNT by high-temperature carbonization in a nitrogen atmosphere and uses it as the negative electrode material of the electrode. This negative electrode material has adjustable pore size and good thermal stability. Finally, using ZnCoS / CNT as the positive electrode and Fe 2 O 3 / CNT as the negative electrode to assemble an asymmetric supercapacitor has both outstanding specific capacitance and excellent conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 XRD patterns of the synthesized ZIF-8 / CNT, ZIF-8-Co-1 / CNT, ZIF-8-Co-2 / CNT (a) and ZnS-CNT, ZnCoS-CNT-1, ZnCoS-CNT-2 (b).

[0030] Figure 2 Scanning electron microscope images of MOFs precursors and sulfided samples are shown. Among them, ZIF-8 / CNT (a), ZIF-8-Co-1 / CNT (c), ZIF-8-Co-2 / CNT (e) and ZnS-CNT (b), ZnCoS-CNT-1 (d), ZnCoS-CNT-2 (f).

[0031] Figure 3 Electrochemical performance of the supercapacitor sample. (a) CV curves of ZnCoS-CNT-2 measured at different scanning rates; (b) galvanostatic charge-discharge curves of ZnCoS-CNT-2 at different constant current densities; (c) CV curves of ZnS-CNT, ZnCoS-CNT-1 and ZnCoS-CNT-2 at a scanning rate of 100 mV s -1 when the comparison diagram; (d) GCD curves at 1 Ag -1 ; (e) specific capacitance at different current densities. (f) Nyquist plot (the insert is an enlarged view of the curve in the high-frequency region).

[0032] Figure 4 For Fe-MOF-CNT (a, b), Fe 2 O 3 -CNT (d, e) SEM images and XRD patterns (c, f).

[0033] Figure 5 For Fe 2 O 3 -CNT electrode material CV curves at different scan rates (a); CD curves at different current densities (b) and specific mass capacitance (c).

[0034] Figure 6 For ZnCoS-CNT / / Fe 2 O 3 -CNT asymmetric supercapacitor (ACS) electrochemical characterization is as follows: (a) CV curves in different voltage ranges; (b) CV images at different scan rates; (c, d) CD curves and specific capacitance at different current densities; (e) energy-power distribution diagram. (f) Cycling stability diagram for 5000 cycles at a current density of 10 A g -1 Current density.

[0035] Figure 7 For ZnCoS-CNT / / Fe2O3-CNT asymmetric supercapacitor EIS spectra before and after cycling tests. Detailed implementation methods

[0036] The present invention will be described in detail below in conjunction with examples and drawings. As part of this specification, the principles of the present invention are illustrated through examples, and other aspects, features, and advantages of the present invention will become apparent through this detailed description. In the accompanying drawings referred to, the same or similar components in different figures are denoted by the same reference numerals.

[0037] Example 1 Preparation of positive electrode material

[0038] 1.1. Preparation of ZIF-8-CNT: Dissolve 0.1 g of Zn(NO 3 ) 2 in 50 mL of methanol solution, denoted as solution A. Separately, take 0.1 g of 2-methylimidazole and 20 mg of CNT in 50 mL of anhydrous methanol, denoted as solution B. Pour solution A into solution B, mix well, leave at room temperature for 24 h, centrifuge, and dry to obtain ZIF-8-CNT powder.

[0039] 1.2. Preparation of ZIF-8-Co-CNT: Take 0.05 g of ZIF-8-CNT each in Co(NO 3 ) 2In the solution, ultrasonic for 20 mins, place at room temperature for 6 h for ion exchange, finally centrifuge, wash three times with water, and dry. Respectively, when the concentration of Co(NO 3 ) 2 is 0.5 M, it is denoted as ZIF-8-Co-1 / CNT, and when it is 1 M, it is denoted as ZIF-8-Co-2 / CNT.

[0040] 1.3 Preparation of ZnS-CNT, ZnCoS-CNT-1, and ZnCoS-CNT-2 composites:

[0041] Take 0.02 g of ZIF-8-CNT from step 1.1, put it in 50 mL of 0.5 M thioacetamide solution, ultrasonic for 0.5 h, then place it in a reaction kettle and react at 150 °C for 2 h. After the reaction is over and cooled to room temperature, centrifuge, wash three times with water, and dry to obtain ZnS-CNT.

[0042] Take 0.02 g of ZIF-8-Co-1 / CNT from 1.1 and put it in 50 mL of 0.5 M thioacetamide solution, ultrasonic for 0.5 h, then place it in a reaction kettle and react at 150 °C for 2 h. After the reaction is over and cooled to room temperature, centrifuge, wash three times with water, and dry to obtain ZnS-CNT and ZnCoS-CNT-1.

[0043] Take 0.02 g of ZIF-8-Co-2 / CNT from step 1.1 and put it in 50 mL of 0.5 M thioacetamide solution, ultrasonic for 0.5 h, then place it in a reaction kettle and react at 150 °C for 2 h. After the reaction is over and cooled to room temperature, centrifuge, wash three times with water, and dry to obtain ZnCoS-CNT-2.

[0044] Combined with the attached drawings, Figure 1 are the XRD patterns of the synthesized ZIF-8 / CNT, ZIF-8-Co-1 / CNT, ZIF-8-Co-2 / CNT (a) and ZnS-CNT, ZnCoS-CNT-1, ZnCoS-CNT-2 (b). It can be observed from Figure 1 a that the synthesized ZIF-8-Co-1 / CNT and ZIF-8-Co-2 / CNT coincide with the simulated ZIF-8 diffraction peaks, and there are obvious sharp peaks between 2θ of 5 to 50 degrees, indicating that with the increase of Co ion concentration, the crystallinity of ZIF-8-Co-1 / CNT and ZIF-8-Co-2 / CNT decreases. The spectrum shown in Figure b is consistent with the standard spectra of ZnS (PDF 05-0566) and ZnCoS (PDF 47-1656), indicating that the successfully synthesized materials are ZnS and ZnCoS.

[0045] Figure 2 Shows the scanning electron microscope images of the MOFs precursor and the sulfided samples. Figure 2The SEM image of ZIF-8 is shown in a. As can be seen from the figure, ZIF-8 has a dodecahedral structure and grows around the carbon nanotubes. Figure 2 The SEM images of ZIF-8-Co-1 / CNT and ZIF-8-Co-2 / CNT are shown in c and f. Obviously, after ion exchange, the dodecahedral structure of ZIF-8 is destroyed and forms flakes stacked irregularly. Figure 2 The SEM images of ZnS-CNT, ZnCoS-CNT-1, and ZnCoS-CNT-2 after sulfidation are shown in b, d, and f. It can be seen from the figure that the dodecahedron of ZnS-CNT becomes smoother, and the presence of carbon nanotubes can be clearly seen. The morphologies of ZnCoS-CNT-1 and ZnCoS-CNT-2 become rougher, and the carbon nanotubes are exposed.

[0046] As Figure 3 shown, Figure 3 a-b are the CV curves and CD curves of the ZnCoS-CNT-2 electrode at different scan rates and different current densities. As Figure 3 shown in a, the voltage window range of the CV curve is 0 - 0.6V, and there is an obvious pair of redox peaks, indicating that its main capacitance contribution is pseudocapacitance. As Figure 3 shown in b, a pair of charge-discharge platforms appear in the CD curve, indicating its typical pseudocapacitance behavior, which is consistent with the results of the CV curve. At the same time, the charging and discharging processes of the CD curve are basically symmetric, indicating that the electrode material has a good Coulomb effect. Figure 3 c is the CV curve of the separate ZnS-CNT, ZnCoS-CNT-1, and ZnCoS-CNT-2 composite electrodes, and the scan rate is 100mV s -1 . As shown in the figure, there is an obvious pair of redox peaks in the CV curves of the three electrode materials, indicating that the composite electrodes are all pseudocapacitors. In addition, the integral area of the CV curve of the ZnCoS-CNT-2 composite electrode is larger than that of the ZnS-CNT and ZnCoS-CNT-1 composite electrodes, indicating that the ZnCoS-CNT-2 composite electrode has a higher capacitance value. Figure 3 d is the CD curve of the three composite electrodes at a current density of 1A g -1 . It can be seen that the charge-discharge time of the ZnCoS-CNT-2 composite electrode is the longest, indicating that the composite electrode has a stronger charge storage ability, which is consistent with the comparison results of the CV curve. According to the calculation formula of specific capacitance, the specific capacitances of the three composite electrodes are obtained, as Figure 3 shown in d. The specific capacitance of the ZnS-CNT composite electrode is 239F g -1 , ZnCoS-CNT-1 is 757F g -1 and ZnCoS-CNT-2 is 948F g -1Obviously, the ZnCoS-CNT-2 composite electrode has a higher capacitance value, indicating that it has more electrochemically reactive sites. This is mainly attributed to the synergistic effect of the bimetals, which is beneficial to improving the conductivity of the electrode material and has more redox reaction kinetics. Finally, the three electrode materials were further tested for AC impedance, as Figure 3 shown in e. In the low-frequency region, the composite electrode ZnCoS-CNT-2 has a steeper slope and is closer to the y-axis compared to the ZnS-CNT and ZnCoS-CNT-1 electrodes, indicating that ZnCoS-CNT-2 has a faster charge diffusion rate. In the high-frequency region, due to the presence of carbon nanotubes, there is no obvious difference in the intrinsic resistance of the three composite electrodes.

[0047] Preparation of the negative electrode material in Example 2

[0048] 2.1 Preparation of the Fe-MOF-CNT composite material: Take 1.6 g of FeCl 3 , 0.991 g of trimesic acid (H 2 (BDC)), and 50 mg of CNT and dissolve them in 100 ml of DMF solution. After mixing evenly, carry out microwave reaction in a microwave reactor at a power of 500 W for 10 min, and then carry out solvothermal reaction in a reaction kettle at 150 °C for 2 h. Finally, centrifuge, wash three times with DMF water, and dry to obtain yellow powder of Fe-MOF-CNT.

[0049] 2.2 Preparation of the Fe 2 O 3 -CNT composite material: Take 0.1 g of Fe-MOF-CNT and place it in a tube furnace. Heat it to 500 °C at a rate of 5 °C / min and calcine for 2 h. After the tube furnace cools to room temperature, collect the Fe 2 O 3 -CNT black powder.

[0050] As Figure 4 shown, Figure 4 a is Fe-MOF-CNT prepared by the direct hydrothermal method of 1,3,5-benzenetricarboxylic acid. It can be seen in the figure that the Fe-MOF has a regular octahedron structure, and the CNT is clearly visible around the Fe-MOF, which can effectively prevent the accumulation of Fe-MOF. Through XRD testing and comparison with the simulated spectrum of MOFs ( Figure 4 c), the main peaks can all match the simulated spectrum, indicating that the MOFs material was successfully synthesized. Through annealing treatment in a nitrogen atmosphere, Fe 2 O 3 -CNT was successfully synthesized, as Figure 4 shown in b. Obviously, after calcination, the organic components volatilize, and the surface of the Fe-MOF octahedron structure becomes rough, which is beneficial for the electrolyte to enter the interior of the octahedron structure and increase the reactive sites. The synthesized Fe 2O 3 -CNT coincides with the standard card (PDF 89-0599) of Fe 2 O 3 , and the Fe 2 O 3 -CNT composite material has good crystallinity.

[0051] Example 3 Preparation of Supercapacitor Electrodes

[0052] First, weigh the positive electrode material in Step 1 above, or the negative electrode material in Step 2, and activated carbon in a mass ratio of 4:1, and put them into a 10 mL small glass bottle;

[0053] Then use a pipette to transfer 10 μL of Nafion as a binder and mix it with other substances, and finally add 0.8 mL of absolute ethanol as a dispersant;

[0054] Then place the mixture in an ultrasonic machine and ultrasonicate for half an hour to form a uniformly mixed suspension;

[0055] Finally, gradually drop the suspension 10 times onto a 1×1 cm 2 nickel foam current collector, and place the current collector in an electrothermal constant temperature blast drying oven at 80 °C for drying, controlling the mass of the active material of a single electrode to be about 1 mg.

[0056] As Figure 5 shown, electrochemical tests were carried out on the synthesized Fe 2 O 3 -CNT composite electrode. Figure 5 a is the CV image of the Fe 2 O 3 -CNT composite electrode at different scanning speeds. It can be seen from the figure that the Fe 2 O 3 -CNT composite electrode has relatively obvious oxidation-reduction peaks, indicating its typical pseudocapacitance behavior. Its main oxidation-reduction is a reversible oxidation-reduction reaction process from trivalent to divalent. Figure 5 b is the CD curve of the electrode material at different current densities. As can be seen from the figure, the discharge time is longer than the charging time, mainly because after charging is completed, there is always some energy remaining in the active material during the discharge process. After specific capacitance conversion, the specific capacitance at different current densities is as Figure 5 c shown. When the current density is 1 A g -1 , the specific capacitance is 269 F g -1 . And when the current density is 10 A g -1 , the specific capacitance is still 88.2 F g -1 .

[0057] The selection of the electrochemical voltage window plays a crucial role in improving the electrochemical properties of asymmetric supercapacitors. As Figure 5-6 shown in a, the CV curves of the ZnCoS-CNT / / Fe 2 O 3 -CNT asymmetric supercapacitor (ACS) were tested at a scanning rate of 100 mV s -1 in the voltage window value range of 1.0 - 2.0 V. As shown in the figure, when the operating potential window of the ZnCoS-CNT / / Fe 2 O 3 -CNT ACS increased from 1.4 to 1.5 V, the CV curves showed a completely regular geometry, indicating that the electrode materials could maintain the maximum reversible reaction. Figure 6 Figure b shows the CV curves of the ZnCoS-CNT / / Fe 2 O 3 -CNT ACS at a scanning rate of 5 - 100 mV s -1 at the optimized voltage window of 1.5 V. Obviously, the CV curves indicate that the capacitance of this capacitor is mainly the double-layer capacitance. The CD curves of the ZnCoS-CNT / / Fe 2 O 3 -CNT ACS are as Figure 6 shown in c. At different current densities, the CD curves show good charge-discharge balance, indicating that the ZnCoS-CNT / / Fe 2 O 3 -CNT ACS has good Coulombic efficiency. Through the calculation formula of specific capacitance, at a current density of 1 A g -1 , the specific capacitance reaches 148.3 F g -1 . Even when the current density is 10 A g -1 , the capacitance still retains 51.7%, showing good rate performance. As expected, for the ZnCoS-CNT / / Fe 2 O 3 -CNT ACS we fabricated, the device reaches a high energy density of 46.3 Wh kg -1 at a power density of 749.1 W kg -1 . Even at a higher power density of 6001 W kg -1 , the ASC device still maintains an energy density of 25 Wh kg -1 . It is worth noting that the energy density and power density we obtained are mostly better than those of other reported similar ternary metal sulfides. At the same time, the charge-discharge test was cycled 5000 times at a current density of 10 A g -1 . As Figure 6 shown in f, the ZnCoS-CNT / / Fe 2 O3 - The CNT ACS still maintained 83.3% of its capacity, indicating that the ACS has good conductivity and electrochemical cycling stability, which is mainly attributed to the addition of carbon nanotubes effectively improving the electrochemical performance of the capacitor. The first five cycles and the last five cycles of the GC curve are also shown in Figure 5-6 the inset of Figure f, indicating that ZnCoS-CNT / / Fe 2 O 3 - CNT ACS has excellent reversibility and Coulomb efficiency. To further verify the excellent electrochemical performance of ZnCoS-CNT / / Fe 2 O 3 - CNT ACS, we tested the AC impedance of the device before and after cycling. As Figure 7 shown, before and after cycling, the ion diffusion resistance of ZnCoS-CNT / / Fe 2 O 3 - CNT ACS did not increase significantly, further confirming its good conductivity.

[0058] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A preparation method of an asymmetric supercapacitor electrode, characterized in that, it includes the following steps: Step 1, preparation of the positive electrode material: Prepare the ZIF-8 / CNT composite material by the in-situ growth method, synthesize cobalt-doped ZIF-8 / CNT by the ion exchange method, and finally prepare the ZnCoS / CNT composite material using this as a template; The specific steps for preparing the positive electrode material in Step 1 are as follows: Step 1.1 Preparation of ZIF-8-CNT: Dissolve 0.1 g of Zn(NO 3 ) 2 in 50 mL of methanol solution, denoted as solution A; separately take 0.1 g of 2-methylimidazole and 20 mg of CNT in 50 mL of anhydrous methanol, denoted as solution B; pour solution A into solution B, mix evenly, leave it at room temperature for 24 h, centrifuge, and dry to obtain ZIF-8-CNT powder; Step 1.2 Preparation of ZIF-8-Co-CNT: Dissolve 0.05 g of ZIF-8-CNT in a solution of Co(NO 3 ) 2 , sonicate for 20 mins, leave at room temperature for 6 h for ion exchange, finally centrifuge, wash three times with water, and dry to obtain ZIF-8-Co-CNT; Step 1.3, preparation of the ZnCoS-CNT composite material: Take the prepared ZIF-8-Co / CNT in Step 1.2 and place it in 50 mL of 0.5 M thioacetamide solution. After ultrasonic treatment for 0.5 h, place it in a reaction kettle and react at 150 °C for 2 h; After the reaction is completed and cooled to room temperature, centrifuge and wash three times with water, and dry to obtain ZnCoS-CNT; Step 2. Preparation of the negative electrode material: Using 1,3,5-benzenetricarboxylic acid as a ligand and Fe as a metal ion, an Fe-MOF / CNT composite material was synthesized, and Fe 2 O 3 / CNT was prepared by high-temperature carbonization of the composite material in a nitrogen atmosphere; The preparation of the negative electrode material in step 2 specifically includes the following steps: Step 2.1: Preparation of Fe-MOF-CNT composite material: Take 1.6 g of FeCl 3 , 0.991 g of trimesic acid, and 50 mg of CNT and dissolve them in 100 ml of DMF solution; after mixing evenly, carry out microwave reaction in a microwave reactor at a power of 500 W for 10 min, then carry out solvothermal reaction in a reaction kettle at 150 °C for 2 h; finally, centrifuge, wash three times with DMF water, and dry to obtain yellow powder of Fe-MOF-CNT; Step 2.2, Preparation of Fe 2 O 3 -CNT composite material: Take 0.1 g of Fe-MOF-CNT and place it in a tubular furnace. Heat it to 500 °C at a rate of 5 °C / min and calcine for 2 h. After the tubular furnace cools down to room temperature, collect the Fe 2 O 3 -CNT black powder; Step 3, preparation of the supercapacitor electrode: First, mix the positive electrode material in Step 1 above or the negative electrode material in Step 2 with activated carbon, add a binder to bond it to the nickel foam current collector, and dry to obtain a single supercapacitor electrode.

2. The preparation method of the asymmetric supercapacitor electrode according to claim 1, characterized in that: In Step 1.2, during the preparation of ZIF-8-Co-CNT, 0.05 g of ZIF-8-CNT was separately dissolved in solutions with concentrations of 0.5 M and 1 M of Co(NO 3 ) 2 . The obtained ZIF-8-Co-CNT was denoted as ZIF-8-Co-1 / CNT for the 0.5 M Co(NO 3 ) 2 solution and ZIF-8-Co-2 / CNT for the 1 M solution.

3. The preparation method of the asymmetric supercapacitor electrode according to claim 1, characterized in that, for Step 1.3, the specific operation is: Take 0.02 g of ZIF-8-Co-1 / CNT obtained in Step 1.2 and place it in 50 mL of 0.5 M thioacetamide solution. After ultrasonic treatment for 0.5 h, place it in a reaction kettle and react at 150 °C for 2 h. After the reaction is completed and cooled to room temperature, centrifuge and wash three times with water, and dry to obtain ZnCoS-CNT-1.

4. The preparation method of the asymmetric supercapacitor electrode according to claim 1, characterized in that, for Step 1.3, the specific operation is: Take 0.02 g of ZIF-8-Co-2 / CNT obtained in Step 1.2 and place it in 50 mL of 0.5 M thioacetamide solution. After ultrasonic treatment for 0.5 h, place it in a reaction kettle and react at 150 °C for 2 h. After the reaction is completed and cooled to room temperature, centrifuge and wash three times with water, and dry to obtain ZnCoS-CNT-2.

5. The preparation method of the asymmetric supercapacitor electrode according to claim 1, characterized in that: in Step 3, the positive electrode material in Step 1, or the negative electrode material in Step 2 and activated carbon are mixed in a mass ratio of 4:

1.

6. The preparation method of the asymmetric supercapacitor electrode according to claim 1, characterized in that: the specific steps for preparing the supercapacitor electrode in Step 3 are as follows: First, weigh the positive electrode material in Step 1 above, or the negative electrode material in Step 2 and activated carbon in a mass ratio of 4:1, and put them into a 10 mL small glass bottle; Then mix the above materials with the binder, and finally add 0.8 mL of absolute ethanol as a dispersant; Then place the mixture in an ultrasonic machine and ultrasonic for half an hour to form a uniformly mixed suspension; Finally, the suspension was gradually dropped onto the nickel foam current collector in 10 portions, and the current collector was placed in an electrothermal constant temperature forced air drying oven and dried at 80 °C. The mass of the active material of a single electrode was controlled to be about 1 mg. 2 on a nickel foam current collector, and the current collector was placed in an electrothermal constant temperature forced air drying oven and dried at 80 °C. The mass of the active material of a single electrode was controlled to be about 1 mg.

7. The preparation method of the asymmetric supercapacitor electrode according to claim 6, characterized in that: The mixing of the above materials with the binder specifically involves using a pipette to transfer 10 μL of Nafion as the binder and mixing it with the above materials.

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