NICKEL FOAM -SUPPORTED DEFECTIVE TRICOBALT TETROXIDE NANOMATERIAL, LOW TEMPERATURE RESISTANT SUPERCAPACITOR AND PREPARATION METHOD THEREOF

Abstract

The present invention relates to the field of electrode material of a low temperature resistant supercapacitor, and in particular to a nickel foam-supported defective tricobalt tetroxide nanomaterial, a low temperature resistant supercapacitor and a preparation method thereof. The method includes the following steps: dissolving cobalt acetate in an ethylene glycol solution and stirring uniformly to obtain a pink transparent solution; adding hexadecyl trimethyl ammonium bromide to the pink transparent solution, and stirring until the hexadecyl trimethyl ammonium bromide dissolves to obtain a mixed solution; putting the mixed solution into a teflon-lined reactor, adding pretreated nickel foam for hydrothermal reaction, taking out the nickel foam after the reaction is completed, and ultrasonic cleaning the nickel foam repeatedly before drying; and heat-treating the nickel foam obtained after drying. The defective tricobalt tetroxide (D-Co.sub.3O.sub.4) grown on the nickel foam prepared by the present invention still has a high specific capacity at a low temperature, and the assembled supercapacitor can withstand low temperature, and thus has great application prospects.

Claims

1. A method for preparing a nickel foam-supported defective tricobalt tetroxide nanomaterial, comprising the following steps: dissolving cobalt acetate in an ethylene glycol solution and stirring uniformly to obtain a pink transparent solution; adding hexadecyl trimethyl ammonium bromide to the pink transparent solution, and stirring until the hexadecyl trimethyl ammonium bromide dissolves to obtain a mixed solution; putting the mixed solution into a teflon-lined reactor, and adding pretreated nickel foam to the reactor for reaction, wherein a purple-pink substance is grown on the surface of the nickel foam after reaction, and the nickel foam is washed repeatedly before being dried; heat-treating the nickel foam composite material obtained after drying.

2. The method for preparing a nickel foam-supported defective tricobalt tetroxide nanomaterial according to claim 1, wherein the step of pretreating the nickel foam comprises: cutting the foam nickel into pieces, ultrasonic cleaning the pieces in hydrochloric acid, ethanol and an aqueous solution in sequence, and then drying them.

3. The method for preparing a nickel foam-supported defective tricobalt tetroxide nanomaterial according to claim 2, wherein a drying temperature in the step of pretreating the nickel foam is 60-80° C.

4. The method for preparing a nickel foam-supported defective tricobalt tetroxide nanomaterial according to claim 3, wherein a duration of the ultrasonic clean is 10-15 minutes.

5. The method for preparing a nickel foam-supported defective tricobalt tetroxide nanomaterial according to claim 1, wherein process conditions of the heat-treating are as follows: the temperature is 500-700° C., a heating rate is controlled at 2-5 min.sup.−1, and a treatment time is 2-5 hours.

6. The method for preparing a nickel foam-supported defective tricobalt tetroxide nanomaterial according to claim 1, wherein a reaction temperature in the teflon-lined reactor is 200-300° C., and a reaction time is 8-10 hours.

7. A nickel foam-supported defective tricobalt tetroxide nanomaterial prepared by the method for preparing a nickel foam-supported defective tricobalt tetroxide nanomaterial according to claim 1.

8. A low temperature resistant supercapacitor, containing the nickel foam-supported defective tricobalt tetroxide nanomaterial according to claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Upon reading the detailed description of preferred embodiments below, various other advantages and benefits will become clear to those skilled in the art. The drawings are only used for the purpose of illustrating the preferred embodiments, and should not be considered as a limitation to the present invention. Moreover, throughout the drawings, identical components are denoted by identical reference signs. In the drawings:

[0026] FIG. 1 is a scanning electron microscopy image of a nickel foam-supported tricobalt tetroxide nanomaterial prepared in Example 1 of the present invention;

[0027] FIG. 2 is a scanning electron microscopy image of a nickel foam-supported tricobalt tetroxide nanomaterial prepared in Example 3 of the present invention;

[0028] FIG. 3 is a surface scanning image of scanning electron microscopy of the nickel foam-supported tricobalt tetroxide nanomaterials obtained in Example 1 and 3 of the present invention after calcination;

[0029] FIG. 4 is a transmission electron microscopy image of the nickel foam-supported tricobalt tetroxide nanomaterial obtained in Example 1 of the present invention after calcination;

[0030] FIG. 5 is a high resolution transmission electron microscopy image of the nickel foam-supported tricobalt tetroxide nanomaterial obtained in Example 1 of the present invention after calcination;

[0031] FIG. 6 is a partially enlarged image of A in FIG. 5;

[0032] FIG. 7 is a XRD pattern of the nickel foam-supported tricobalt tetroxide nanomaterials obtained in Examples 1 and 3 of the present invention;

[0033] FIG. 8 is a partially enlarged image of FIG. 7;

[0034] FIG. 9 is a cyclic voltammetry curve of the nickel foam-supported tricobalt tetroxide nanomaterials obtained in Examples 1 and 3 of the present invention at a scan rate of 5 mV s.sup.1;

[0035] FIG. 10 is a galvanostatic charge and discharge curve of the nickel foam-supported tricobalt tetroxide nanomaterials obtained in Examples 1 and 3 of the present invention when the current density is 1 A g.sup.−1;

[0036] FIG. 11 is a specific capacity of the nickel foam-supported tricobalt tetroxide nanomaterials obtained in Examples 1 and 3 of the present invention under different current densities;

[0037] FIG. 12 is a 1000 cycles stability test curve of the nickel foam-supported tricobalt tetroxide nanomaterials obtained in Examples 1 and 3 of the present invention.

DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present invention, not to limit the present invention.

[0039] The defective tricobalt tetroxide nanomaterial in the present invention means that the crystal lattice of tricobalt tetroxide is distorted.

Example 1

[0040] This example relates to a method for preparing a low temperature resistant nickel foam-supported defective tricobalt tetroxide nanomaterial, which includes the following steps.

[0041] 1. The nickel foam was cut into pieces with an area of 1×2 cm.sup.2, ultrasonic cleaned in 3M hydrochloric acid, ethanol and an aqueous solution in sequence, the cleaning time was 10 minutes, respectively; and then the treated nickel foam was placed into a 60° C. oven for drying, so that a clean nickel foam-based material was finally obtained;

[0042] 2. A certain amount of cobalt acetate was dissolved in 30 mL of ethylene glycol solution and was stirred uniformly to obtain a pink transparent solution;

[0043] 3. Hexadecyl trimethyl ammonium bromide (abbreviated as CTAB) was added to the solution prepared in step 2, and was stirred until it was completely dissolved;

[0044] 4. The mixed solution in step 2 was transferred to a teflon-lined reactor, and the nickel foam obtained in step 1 was added to the reactor to react at 200° C. for 8 hours. After the reactor was cooled to room temperature, a purple-pink substance was grown on the surface of the nickel foam after reaction, and the nickel foam was ultrasonic cleaned with absolute ethanol and distilled water repeatedly before being dried;

[0045] 5. The nickel foam composite material was heat-treated at a temperature of 500° C. for 2 hours with a heating rate being controlled at 2° C. min.sup.−1, so as to finally obtain the nickel foam-supported defective tricobalt tetroxide nanomaterial (D-Co.sub.3O.sub.4).

Example 2

[0046] 1. The nickel foam was cut into pieces with an area of 1×2 cm.sup.2, ultrasonic cleaned in 3M hydrochloric acid, ethanol and an aqueous solution in sequence, the cleaning time was 10 minutes, respectively; and then the treated nickel foam was placed in a 80° C. oven for drying, so that a clean nickel foam-based material was finally obtained;

[0047] 2. A certain amount of cobalt acetate was dissolved in 30 mL of ethylene glycol solution and was stirred uniformly to obtain a pink transparent solution;

[0048] 3. Hexadecyl trimethyl ammonium bromide (abbreviated as CTAB) was added to the solution prepared in step 2, and was stirred until it was completely dissolved;

[0049] 4. The mixed solution in step 2 was transferred to a teflon-lined reactor, and the nickel foam obtained in step 1 was added to the reactor to react at 300° C. for 10 hours;

[0050] 5. After the reactor was cooled to room temperature, a purple-pink substance was grown on the surface of the nickel foam after reaction to obtain purple-pink nickel foam, and the nickel foam was ultrasonic cleaned with absolute ethanol and distilled water repeatedly before being dried;

[0051] 6. heat-treating the nickel foam composite material at a temperature of 700° C. for 5 hours with a heating rate being controlled at 5° C. min.sup.−1, so as to finally obtain the nickel foam-supported defective tricobalt tetroxide nanomaterial (D-Co.sub.3O.sub.4).

Example 3

[0052] As compared with Example 1, the difference was that no CTAB was added in step 3 of Example 3, and other steps and process conditions were the same as those in Example 1, so as to obtain nickel foam-supported non-defective tricobalt tetroxide (Co.sub.3O.sub.4).

[0053] Comparative Experiments

[0054] 1. Collecting Scanning Electron Microscopy Images and Transmission Electron Microscopy Images of the Materials

[0055] Scanning electron microscopy images and transmission electron microscopy images of the nickel foam-supported tricobalt tetroxide nanomaterials prepared in Examples 1 and 3 were taken respectively, as specifically shown in FIGS. 1-2, from which it can be seen that the nickel foam-supported tricobalt tetroxide nanomaterials prepared in Examples 1 and 3 have similar morphologies, each being a petal-like morphology assembled from unique nanosheets.

[0056] 2. Collecting Scanning Electron Microscopy Images and Transmission Electron Microscopy Images of the Materials after Calcination

[0057] The nickel foam-supported tricobalt tetroxide nanomaterials prepared in Examples 1 and 3 were calcinated respectively, and scanning electron microscopy images, transmission electron microscopy images and surface scanning images of scanning electron microscopy of the nickel foam-supported tricobalt tetroxide nanomaterials after calcination were taken, as specifically shown in FIGS. 3-6. The element distribution in FIG. 3 shows that the distribution of C, Co, and O in the material is uniform. It can be seen from FIGS. 4-6 that the surface of the D-Co.sub.3O.sub.4 material becomes rougher than that of Co.sub.3O.sub.4 synthesized without CTAB added; at the same time, a large number of nanoparticles appears, which is caused by the removal of CO.sub.2 and H.sub.2O during the annealing process. In addition, it can be clearly seen from FIG. 6 that there are ordered detachment faults in D-Co.sub.3O.sub.4, and these detachment faults are parallel to each other, which is advantageous for improving electrochemical properties.

[0058] 3. Collecting XRD Patterns

[0059] XRD patterns of the tricobalt tetroxide nanomaterials prepared in Examples 1 and 3 were obtained respectively, as specifically shown in FIGS. 7-8, it can be seen that the D-Co.sub.3O.sub.4 and Co.sub.3O.sub.4 nanostructures are characterized by X-ray diffraction (XRD). Diffraction peaks of the two nanomaterials both well match with Co.sub.3O.sub.4 (PDF #62-3103). The peaks are located at 18.9, 31.1, 36.8, 44.8, 59.2 and 65.2 respectively, which correspond to planes (111), (220), (311), (222), (511) and (440) of Co.sub.3O.sub.4 respectively. FIG. 8 is an enlarged XRD spectrum of FIG. 7. As compared with Co.sub.3O.sub.4, the (311) diffraction peak of D-Co.sub.3O.sub.4 is obviously moved to a lower angle, which is mainly due to the increase of d-spacing caused by lattice distortion. At the same time, the (311) characteristic peak of D-Co.sub.3O.sub.4 is obviously broadened, indicating that the lower the nanometer value of the material prepared in Example 1 is, the smaller crystal grains, the larger lattice distortion.

[0060] 4. Determining Electrochemical Performance

[0061] The Shanghai Chenhua CHI 660C electrochemical comprehensive tester was used to test the electrochemical performance. At the same time, the Xinwei charge-discharge tester was used to test the cycle performance of the supercapacitor. In a three-electrode system, a platinum sheet with an area of 2×2 cm.sup.2, a double-salt bridge saturated calomel electrode and a KOH aqueous solution with a concentration of 3M were selected as a counter electrode, a reference electrode and an electrolytic solution in the test, respectively. The active material was prepared into an electrode sheet which served as a working electrode to test its electrochemical performance. The test of electrochemical performance mainly includes cyclic voltammetry (CV) curve test, galvanostatic charge and discharge (GCD) test, AC impedance (with an EIS amplitude of 5 mV, and a frequency of 0.01 Hz-100 kHz) test and cycle stability test, etc.

[0062] In a two-electrode system, first, the nickel foam-supported tricobalt tetroxide nanomaterials prepared in Examples 1 and 3 were used as the electrode material for charge-matching with the negative electrode material, and then an appropriate electrolytic solution or electrolyte and packaging materials were selected to assemble them into a device. (supercapacitor), so as to test its electrochemical performance under low temperature conditions. The specific capacity of electrode material at different current densities can be calculated according to the discharge time of galvanostatic charge and discharge, and the calculation formula is shown as follows, where C.sub.s is an area specific capacity, with a unit of mF cm.sup.−2:

[00001]$\begin{array}{cc}{C}_S=\frac{I\times \Delta t}{s\times \Delta V}& \left(1\right)\end{array}$

[0063] I: current density, with a unit of mA cm.sup.−2;

[0064] Δt: galvanostatic discharge time, with a unit of s;

[0065] ΔV: the window of working potential, with a unit of V;

[0066] s: the area of the active material participating in the electrochemical reaction, with a unit of cm.sup.−2.

[0067] The test results are shown in FIGS. 9-12. As shown in FIGS. 9-12, the D-Co.sub.3O.sub.4 electrode material prepared in Example 1 also exhibits excellent electrochemical performance at low temperatures (ice-water mixture). FIG. 9 is a comparison image of cyclic voltammetry curves of D-Co.sub.3O.sub.4 and Co.sub.3O.sub.4 electrodes at 5 mV s.sup.−1. Obviously, the closed area of the integral curve of D-Co.sub.3O.sub.4 is larger than that of Co.sub.3O.sub.4, indicating that it can store more capacitance. The GCD image at 1 mA cm.sup.−2 in FIG. 10 also obtains similar results, wherein the discharge time of the D-Co.sub.3O.sub.4 electrode is longer. FIG. 11 shows the specific capacitances of D-Co.sub.3O.sub.4 and Co.sub.3O.sub.4 at different current densities. The results show that when the current density is 1 mA cm.sup.−2, the specific capacitance of D-Co.sub.3O.sub.4 is 1052 mF cm.sup.−2, and the specific capacitance of Co.sub.3O.sub.4 is 338 mF cm.sup.−2. When the current density is increased to 10 mA cm.sup.2, the specific capacitance of D-Co.sub.3O.sub.4 is always superior to that of Co.sub.3O.sub.4. Stability is one of the important indicators to measure the practicality of electrodes. After 1000 cycles under the condition of 10 A g.sup.−1 (FIG. 12), the prepared D-Co.sub.3O.sub.4 still retains 86% of the initial specific capacitance, whereas Co.sub.3O.sub.4 only retains 74% after 1000 cycles, indicating that D-Co.sub.3O.sub.4 has good cycle stability.

[0068] Described above are only preferred specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any change or replacement that can be easily conceived by those skilled in the art within the technical scope disclosed in the present application shall be covered within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the scope of protection of the claims.