Preparation method of high-entropy oxide supercapacitor electrode material

Abstract

The invention is mainly applied to the field of supercapacitors, and discloses a preparation method for a high-entropy oxide electrode material. The method specifically comprises the following steps: dissolving zinc nitrate hexahydrate, ferric nitrate nonahydrate, cobalt nitrate hexahydrate and nickel nitrate hexahydrate in an equal molar ratio in absolute ethyl alcohol, and then adding a 50% manganese nitrate aqueous solution and a proper amount of urea; after stirring and dissolving, transferring the mixed solution into a reaction kettle, and adding a piece of foamed nickel; and then carrying out hydrothermal reaction on the reaction kettle. And taking out the foamed nickel after full reaction, cleaning redundant impurities, drying, and calcining the foamed nickel attached with the high-entropy oxide precursor in the air to obtain the electrode material attached with the (FeCoNiMnZn) 3O4 high-entropy oxide.

Description

Technical Field

[0001] The present invention is mainly used in the field of supercapacitors and relates to a high entropy oxide supercapacitor electrode material and a preparation method thereof. Background Art

[0002] Supercapacitors have excellent rate performance, cycle stability, and power density. In addition, they can make up for the energy gap between high-power output traditional dielectric capacitors and high-energy storage batteries, making them widely used in the field of new energy. Supercapacitors are divided into double-layer capacitors and pseudocapacitors, and many studies are more inclined to pseudocapacitors with better energy storage performance. In recent years, research on supercapacitor electrode materials has mostly been on transition metal oxides, sulfides, nitrides, and carbon-based materials, but it is difficult to adjust the physical and chemical properties of these materials without sacrificing electrochemical performance.

[0003] As a new type of material, high entropy oxide has many advantages in the application of supercapacitor electrode materials, and its biggest advantage lies in diversification and the composition of multiple elements. The present invention takes (FeCoNiMnZn)3O4 electrode material as an example, and the high entropy oxide elements are selected as Fe, Co, Ni, Mn and Zn. Fe, Co, and Mn are selected as elements of high entropy oxide mainly because of their advantages such as non-toxicity, rich elements, low cost, and high safety. Co and Zn elements have higher storage capacity. At present, most methods for preparing high entropy oxide electrode materials are to prepare high entropy oxide powder by wet chemical method, solid phase reaction method, solution gel method, etc., and then mix the powder with conductive agent and binder and apply it to the current collector. This film making method is simple in process and low in cost, but the attachment of active materials will not be particularly strong, resulting in a weaker contact surface and a higher contact resistance, which will affect the electron transmission of this electrode. To solve the above method, the present invention provides a preparation method of in-situ growth high entropy oxide electrode material. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a high entropy oxide supercapacitor electrode material to solve the problems mentioned in the above technical background.

[0005] Step 1: A method for preparing a high entropy oxide supercapacitor electrode material comprises the following steps: weighing zinc nitrate hexahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate and 50% manganese nitrate aqueous solution in a molar ratio of 1:1:1:1:2.

[0006] Step 2: Add the medicine weighed in step 1 into anhydrous ethanol, add an appropriate amount of urea and stir thoroughly.

[0007] Step 3: Transfer the mixed solution in step 2 to a reactor, add a weighed piece of clean nickel foam, tighten the reactor and transfer it to a temperature of 140°C for sufficient reaction, so that the high entropy oxide precursor is attached to the nickel foam.

[0008] Step 4: Take out the nickel foam to which the high entropy oxide precursor is attached after the reaction, clean the excess impurities on the surface with deionized water, and dry the nickel foam at 60°C for 12 hours.

[0009] Step 5: Calcine the nickel foam on which the high entropy oxide is grown in step 4 in an air atmosphere at 400°C for 3 hours to obtain an electrode material with a spinel structure (FeCoNiMnZn)3O4 high entropy oxide attached.

[0010] The present invention uses a method of directly growing high entropy oxide on nickel foam, so that the electrode material has better electrical contact and electron transmission, and the active material can better utilize the three-dimensional structure of nickel foam, thereby improving the overall surface area and electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 : XRD pattern of high entropy oxide (FeCoNiMnZn)3O4 powder.

[0012] Figure 2 : Scanning electron microscope image of high entropy oxide (FeCoNiMnZn)3O4 powder.

[0013] Figure 3 : Cyclic voltammetry curves of (FeCoNiMnZn)3O4 electrode measured at different voltage scan rates.

[0014] Figure 4 : Constant current charge and discharge curves of (FeCoNiMnZn)3O4 electrode measured at different current densities.

[0015] Figure 5 : Cyclic stability and coulombic efficiency of the (FeCoNiMnZn)3O4 electrode measured after 3000 cycles at a current density of 10 A / g. DETAILED DESCRIPTION

[0016] In order to clearly illustrate the purpose, preparation scheme and advantages of the present invention, the following section will use (FeCoNiMnZn)3O4 as an example with reference to the accompanying drawings to explain in detail the implementation method of electrode material preparation.

[0017] The present invention in situ grows high entropy oxide on the current collector by a hydrothermal method, and the active material grows directly on the current collector, which can avoid the problem of high resistance of the electrode material caused by smearing, and the in situ growth of the active material allows the electrode material to have a larger specific surface area.

[0018] Implementation Example 1: The specific preparation method of this invention will be described in detail below with reference to specific examples.

[0019] Step 1, preparation of mixed solution: Zinc nitrate hexahydrate (0.287 g), iron nitrate nonahydrate (0.405 g), cobalt nitrate hexahydrate (0.291 g), nickel nitrate hexahydrate (0.290 g) and 50% manganese nitrate aqueous solution (0.358 g) in a molar ratio of 1:1:1:1:2 were added to 10 mL of anhydrous ethanol, and 1.6 mmol of urea was added and stirred until dissolved.

[0020] Step 2, preparing nickel foam with high entropy oxide precursor attached: The mixed solution prepared in step 1 was transferred to a 25 ml reactor, a cleaned nickel foam was added, and the reactor was tightened. The reactor was placed in a blast drying oven and reacted at 140 ° C for 12 hours. The nickel foam with high entropy oxide precursor attached was taken out, and the excess impurities on the surface of the nickel foam were washed with deionized water, and then dried at 60 ° C for 12 hours. The excess high entropy oxide precursor powder in the reactor was collected, and obtained by centrifugation twice with deionized water and anhydrous ethanol, and then the high entropy oxide precursor was transferred to 60 ° C and dried for 12 hours to obtain a brown powder.

[0021] Step 3, calcination: The nickel foam and high entropy oxide precursor powder dried in step 2 were transferred to a tube furnace and calcined at 400°C for 3 hours at a heating rate of 5°C per minute to obtain black high entropy oxide powder and nickel foam with high entropy oxide attached.

[0022] Implementation Example 2 The black high entropy oxide powder obtained in Example 1 was characterized to obtain an XRD pattern of spinel high entropy oxide (FeCoNiMnZn)3O4.

[0023] Implementation Example 3 The black high entropy oxide powder obtained in Example 1 was characterized to obtain a SEM image of the spinel high entropy oxide (FeCoNiMnZn)3O4.

[0024] Implementation Example 4 The energy storage performance of high entropy oxide (FeCoNiMnZn)3O4 electrode material was tested.

[0025] The electrode material was used as the working electrode in a three-electrode configuration assembled in 1 M KOH electrolyte, with Ag / AgCl as the reference electrode and platinum foil as the counter electrode. The electrode material was subjected to cyclic voltammetry scanning test, constant current charge-discharge test and cycle stability test.

[0026] like Figure 3 The voltammetric curves of the (FeCoNiMnZn)3O4 electrode at different scan rates are shown. Obvious redox peaks appear in the curves, indicating that high entropy oxides mainly store energy through reversible redox reactions of metal ions, indicating that the material has obvious pseudocapacitive properties.

[0027] like Figure 4 Shown is the constant current charge and discharge curve of the (FeCoNiMnZn)3O4 electrode. When the current density is 1 A / g, the specific capacitance of the electrode material can reach 747.5 F / g.

[0028] like Figure 5 The figure shows the cycle stability test of the (FeCoNiMnZn)3O4 electrode. The test was carried out at a high current density of 10 A / g. It was found that after 3000 cycles of charge and discharge, the retention rate of the specific capacitance could reach 90.91%, and the coulombic efficiency could be stabilized at around 100%.

Claims

1. A method for preparing a high entropy oxide supercapacitor electrode material, characterized in that: The steps described are as follows: (1): Add zinc nitrate hexahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate and 50% manganese nitrate aqueous solution in a molar ratio of 1:1:1:1:2 to an appropriate amount of anhydrous ethanol, then add an appropriate amount of urea and stir until dissolved; (2): The mixed solution obtained in step (1) was transferred to a 25 mL reactor, a cleaned and weighed piece of nickel foam was placed in it, and the reactor was tightened to carry out a hydrothermal reaction; (3): Take out the nickel foam after the reaction in step (2), wash it with deionized water, and then dry it at 60° C. for 12 hours; (4): The dried nickel foam is calcined at 400°C in an air atmosphere to obtain an electrode material with a spinel structure (FeCoNiMnZn)3O4 high entropy oxide.

2. The preparation method according to claim 1, characterized in that: The calcination temperature was 400°C in air atmosphere.

3. The preparation method according to claim 1, characterized in that: The method can also be used to prepare electrode materials attached with high entropy oxides such as (FeCoNiMnMo)3O4, (FeCoNiCrZn)3O4 or (FeCoNiCrMg)3O4, and use them in supercapacitors.

4. The preparation method according to claim 1, characterized in that: Five elements, zinc, iron, cobalt, manganese and nickel, were selected to synthesize high entropy oxides and used to prepare electrode materials for supercapacitors.

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