CN109637839B - Preparation method of carbon nano tube/manganese dioxide composite material electrode - Google Patents
Preparation method of carbon nano tube/manganese dioxide composite material electrode Download PDFInfo
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- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
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Abstract
The invention discloses a preparation method of a carbon nano tube/manganese dioxide composite material electrode, which comprises the following steps: 1) ultrasonically cleaning the carbon cloth, ultrasonically treating the carbon cloth in a nitric acid solution, and drying the carbon cloth; 2) placing the carbon nano tube in a nitric acid solution for ultrasonic oscillation, washing and filtering, drying, calcining and grinding; 3) ultrasonically dispersing the carbon nano tube in absolute ethyl alcohol, and spraying the absolute ethyl alcohol on carbon cloth to obtain carbon cloth loaded with the carbon nano tube; 4) and carrying out hydrothermal reaction on the carbon cloth loaded with the carbon nano tube and a mixed solution of potassium permanganate and potassium sulfate manganese sulfate to obtain the carbon nano tube/manganese dioxide composite material electrode. The composite material electrode prepared by the invention has larger specific capacitance and good flexibility, and can be applied to a super capacitor to develop a light-weight and flexible super capacitor, the capacitance of the super capacitor reaches 22.7-76.5 mF, the capacitance after bending is 29.6-106.6 mF, and the capacitance characteristic is still stable when deformation occurs.
Description
Technical Field
The invention relates to the technical field of electrode materials of a super capacitor, in particular to a preparation method of a carbon nano tube/manganese dioxide composite material electrode and a super capacitor comprising the carbon nano tube/manganese dioxide composite material electrode.
Background
In recent years, there has been social attention to environmental problems such as "greenhouse effect" caused by greenhouse gases such as carbon dioxide and the like, and acid rain areas which are expanding due to excessive emission of sulfur dioxide and the like. The key to solve these problems lies in seeking more environmentally friendly energy and more reasonable energy utilization.
Among various forms of energy, electric energy plays an important role in human production and life as the most directly available secondary energy, and almost all primary energy such as new energy of solar energy, wind energy, water energy and the like and traditional energy such as coal and the like must be converted into electric energy to be utilized by human beings. In this conversion process, the efficiency of energy utilization is affected by the operating efficiency of the energy storage element.
As a novel energy storage element, the super capacitor draws extensive attention of industrial scholars by the characteristics of high power density, high charge and discharge efficiency, strong environmental adaptability, environmental friendliness and the like, so that research and development of the super capacitor and electrode materials thereof are of great significance for more reasonably utilizing energy, protecting the earth ecological environment and accelerating the prior scientific and technical change.
The current development situation of the super capacitor has the problems of large volume, heavy weight, no flexibility and the like, and the application of the super capacitor in many fields is influenced, so that the development of the super capacitor which is light in weight, flexible, stable and has large capacitance is urgently needed.
Disclosure of Invention
The invention aims to solve the problems of large volume, heavy weight, no flexibility and the like of a super capacitor, and provides a preparation method of a carbon nanotube/manganese dioxide composite material electrode and the super capacitor comprising the carbon nanotube/manganese dioxide composite material electrode. The super capacitor is environment-friendly, energy-saving, stable, efficient, light in weight and good in flexibility.
In order to achieve the purpose, the invention adopts the following scheme:
the preparation method of the carbon nano tube/manganese dioxide composite material electrode comprises the following steps:
1) cutting carbon cloth, ultrasonically cleaning, adding a nitric acid solution, ultrasonically treating for 2-4h, cleaning the treated carbon cloth, and drying for later use;
2) placing the carbon nano tube in a nitric acid solution for ultrasonic oscillation, standing, washing and filtering until the filtrate is neutral, drying, calcining and grinding the washed and filtered carbon nano tube for later use;
3) adding absolute ethyl alcohol into the carbon nano tube obtained in the step 2), performing ultrasonic oscillation to form a dispersion system, spraying the dispersion system on the carbon cloth obtained in the step 1), and drying to obtain carbon cloth loaded with the carbon nano tube;
4) and carrying out hydrothermal reaction on the carbon cloth loaded with the carbon nano tube and a mixed solution of potassium permanganate and manganese sulfate to prepare the carbon nano tube/manganese dioxide composite material electrode.
Preferably, in the step 1), the carbon cloth is cut by ultrasonic cleaning with deionized water for 15-30 min; the concentration of the added nitric acid solution is 10-25%; the temperature set during drying is 65-85 ℃. More preferably, the carbon cloth is cut for 15min by adopting deionized water ultrasonic cleaning; the concentration of the added nitric acid solution is 20 percent; the temperature set during drying was 70 ℃.
Preferably, in the step 2), the carbon nanotube is placed in a nitric acid solution with the concentration of 10-25% for ultrasonic oscillation for 2-4h, the ultrasonic power is 200-500W, the standing is 3-4.5h, the temperature set during drying is 90-120 ℃, and the calcination is performed for 3-8h at the temperature of 350-500 ℃. More preferably, the carbon nanotubes are placed in 20% nitric acid solution for ultrasonic oscillation for 2h, the ultrasonic power is 300W, the carbon nanotubes are kept standing for 4h, the temperature set during drying is 100 ℃, and the carbon nanotubes are calcined for 6h at the temperature of 400 ℃.
Preferably, in the step 3), the mass-to-volume ratio of the carbon nanotubes is 0.8-1.5mg/ml, the ultrasonic oscillation time is 2-4h, the ultrasonic power is 200-500W, and the temperature set during drying is 60-90 ℃. More preferably, the mass-to-volume ratio of the carbon nanotubes is 1mg/ml, the ultrasonic oscillation time is 2h, the ultrasonic power is 300W, and the temperature set during drying is 70 ℃.
Preferably, in the step 4), the molar ratio of potassium permanganate to manganese sulfate in the mixed solution of potassium permanganate and manganese sulfate is 5-7:1, wherein the hydrothermal reaction is carried out at 150-. More preferably, the molar ratio of potassium permanganate to manganese sulfate is 6: 1.
Preferably, the hydrothermal reaction is carried out at 160 ℃ for 6-12 h. More preferably, the hydrothermal reaction is carried out at 160 ℃ for 6-9 h. More preferably, the hydrothermal reaction is carried out at 160 ℃ for 8-9 h.
The potassium permanganate and the potassium sulfate can be dissolved by adopting water with proper amount according to actual needs by a person skilled in the art to form a mixed solution with proper concentration.
The invention also provides the carbon nano tube/manganese dioxide composite material electrode prepared by the preparation method.
The invention also provides a super capacitor, a carbon nano tube/manganese dioxide composite material electrode of the super capacitor and an alkaline solid electrolyte.
Preferably, the alkaline solid electrolyte is prepared by mixing and compounding polyvinyl alcohol solution with the concentration of 0.08-0.25g/ml and NaOH solution with the concentration of 0.2-1g/ml according to the mass ratio of 1.5-5: 1. More preferably, the alkaline solid electrolyte is prepared by mixing and compounding 1-0.15g/ml polyvinyl alcohol solution and 0.2-0.5g/ml NaOH solution according to the mass ratio of 1: 2-3.
The invention also provides a preparation method of the super capacitor, which comprises the following steps: and (3) placing two carbon nanotube/manganese dioxide composite material electrodes on a heating platform at 85 ℃, coating an alkaline solid electrolyte on one surface of each electrode, aligning and pressing the other electrode together, and obtaining the super capacitor after the alkaline solid electrolyte is bonded and solidified with the electrodes.
Preferably, the length of the two carbon nanotube/manganese dioxide composite material electrodes is 1-3cm, the width of the two carbon nanotube/manganese dioxide composite material electrodes is 0.2-0.8cm, and the thickness of the alkaline solid electrolyte coated on the electrodes is 0.5-2 mm. More preferably, the two carbon nanotube/manganese dioxide composite electrodes have a size of 2cm by 0.5cm, and the thickness of the alkaline solid electrolyte coated on the electrodes is 0.8-2 mm.
More specifically, the method for preparing the supercapacitor by using the carbon nano tube/manganese dioxide composite material electrode and the alkaline solid electrolyte comprises the following steps:
(1) pretreating carbon cloth: cutting the carbon cloth into 4cm by 2cm, ultrasonically cleaning the carbon cloth with deionized water for 15min, diluting nitric acid and deionized water to the concentration of 20%, placing the carbon cloth cleaned with deionized water, ultrasonically treating the carbon cloth for 2h, repeatedly cleaning the treated carbon cloth with deionized water, washing away residual nitric acid, and drying the carbon cloth in a drying oven at 70 ℃ for later use;
(2) pretreating the carbon nano tube: placing the carbon nano tube in 20% nitric acid for ultrasonic oscillation for 2h, standing for 4h, washing and filtering the treated carbon nano tube until the filtrate is neutral, drying the carbon nano tube after filtration and washing at 100 ℃, then placing the carbon nano tube in the air for calcination at 400 ℃ for 6h, and repeatedly grinding for later use;
(3) loading carbon nanotubes on carbon cloth: taking the carbon cloth in the step (1) and the carbon nano tube in the step (2), adding absolute ethyl alcohol into the carbon nano tube according to the proportion of 1mg/ml, ultrasonically oscillating for 2 hours to form a dispersion system, uniformly spraying the obtained dispersion system on the carbon cloth, and drying at 70 ℃ to obtain the carbon cloth loaded with the carbon nano tube;
(4) hydrothermal synthesis of manganese dioxide: preparing a mixed solution of potassium permanganate and manganese sulfate according to a molar ratio (potassium permanganate: manganese sulfate) of 6:1, vertically placing carbon cloth loaded with a carbon nano tube into a 100ml polytetrafluoroethylene reaction kettle, adding 50ml of the mixed solution of potassium permanganate and manganese sulfate, placing the reaction kettle at 160 ℃ for reaction for 5-14h, taking out a sample after the reaction is finished, cleaning a surface paste, and placing at 70 ℃ for drying for 6h to prepare a composite material electrode;
(5) preparing an electrolyte: accurately weighing 4g of polyvinyl alcohol (PVA), pouring 30ml of deionized water, putting the PVA into a magnetic stirrer, stirring for about 1 hour at the temperature of 85 ℃ and the rotating speed of 1400 revolutions per minute, simultaneously weighing 0.1mol of NaOH and adding 10ml of deionized water, magnetically stirring for 10 minutes until the solution is clear, quickly pouring the NaOH solution into the polyvinyl alcohol solution under the condition of magnetic stirring, and continuously stirring for 30 minutes to obtain alkaline colloidal electrolyte;
(6) assembling the super capacitor: cutting two electrodes with the area of 2cm x 0.5cm, placing on a heating platform at 85 ℃, coating the colloidal electrolyte on one surface of the electrode, wherein the coating thickness is about 1mm, aligning and lightly pressing the other electrode together after the colloidal body is uniformly covered on the surface of the electrode, placing for 12h at room temperature, and obtaining the super capacitor after the electrolyte and the electrode are fully bonded and solidified.
The invention has the beneficial effects that: the composite material electrode prepared by the invention has larger specific capacitance, extremely high specific surface area, high surface activity and good flexibility, and when the composite material electrode is applied to a super capacitor, the super capacitor with the characteristics of light weight, flexibility and the like can be developed, the capacitance of the super capacitor reaches 22.7 mF-76.5 mF, the capacitance after bending is 29.6 mF-106.6 mF, and the capacitance characteristic is still stable when deformation occurs; the invention adopts a physical method and a chemical method at the same time, firstly sprays the carbon nano tube on the surface of the carbon cloth, then compounds the nano manganese dioxide on the carbon cloth loaded with the carbon nano tube through hydrothermal reaction, and loads the electrode material on the surface of the carbon cloth in two steps, thereby better controlling the loading capacity of the carbon nano tube on the carbon cloth and simultaneously improving the uniformity degree of the distribution of the carbon nano tube.
Drawings
FIG. 1 is an X-ray diffraction pattern of carbon nanotube/manganese dioxide composite electrodes prepared in examples 1 to 3;
FIG. 2 is a low-magnification SEM photograph of the carbon nanotube/manganese dioxide composite electrode prepared in examples 1-3;
FIG. 3 is a high magnification SEM photograph of the carbon nanotube/manganese dioxide composite electrode prepared in examples 1-3;
FIG. 4 is a graph showing the variation of specific capacitance values of the carbon nanotube/manganese dioxide composite electrodes prepared in examples 1 to 3;
FIG. 5 shows flexibility test conditions of the carbon nanotube/manganese dioxide doped supercapacitor prepared in example 4;
fig. 6 is the capacitance of the carbon nanotube/manganese dioxide doped supercapacitor prepared in example 4 at different scan rates.
Detailed Description
The following examples are presented to assist those skilled in the art in a more complete understanding of the present invention, and are not intended to be limiting.
Example 1
A preparation method of a carbon nano tube/manganese dioxide composite material electrode comprises the following steps:
1) cutting the carbon cloth into 4cm by 2cm, ultrasonically cleaning the carbon cloth with deionized water for 15min, diluting nitric acid and deionized water to the concentration of 20%, placing the carbon cloth cleaned with deionized water, ultrasonically treating the carbon cloth for 2h, repeatedly cleaning the treated carbon cloth with deionized water, washing away residual nitric acid, and drying the carbon cloth in a drying oven at 70 ℃ for later use;
2) placing the carbon nano tube in 20% nitric acid for ultrasonic oscillation for 2h, standing for 4h, washing and filtering the treated carbon nano tube until the filtrate is neutral, drying the carbon nano tube after filtration and washing at 100 ℃, then placing the carbon nano tube in the air for calcination at 400 ℃ for 6h, and repeatedly grinding for later use;
3) adding absolute ethyl alcohol into the carbon nano tube obtained in the step 2) according to the proportion of 1mg/ml, and performing ultrasonic oscillation for 2 hours to form a dispersion system; uniformly spraying the obtained dispersion system on the carbon cloth obtained in the step 1), and drying at 70 ℃ to obtain carbon cloth loaded with carbon nanotubes;
4) the molar ratio (potassium permanganate: manganese sulfate) 6:1, vertically placing carbon cloth loaded with carbon nano tubes into a 100ml polytetrafluoroethylene reaction kettle, adding 50ml of mixed solution, placing the reaction kettle at 160 ℃ for reaction for 6h respectively, marking an obtained sample as a1, taking out after the reaction is finished, cleaning surface paste, and placing at 70 ℃ for drying for 6h to obtain the composite material electrode.
Example 2
A preparation method of a carbon nano tube/manganese dioxide composite material electrode comprises the following steps:
1) cutting the carbon cloth into 4cm by 2cm, and ultrasonically cleaning for 15min by using deionized water; diluting nitric acid with deionized water to 20%, placing into carbon cloth cleaned with deionized water, and performing ultrasonic treatment for 2 h; repeatedly cleaning the treated carbon cloth by using deionized water, washing away residual nitric acid, and drying in a drying oven at 70 ℃ for later use;
2) placing the carbon nano tube in 20% nitric acid for ultrasonic oscillation for 2h, standing for 4h, washing and filtering the treated carbon nano tube until the filtrate is neutral, drying the carbon nano tube after filtration and washing at 100 ℃, then placing the carbon nano tube in the air for calcination at 400 ℃ for 6h, and repeatedly grinding for later use;
3) adding the carbon nano tube obtained in the step 2) into absolute ethyl alcohol according to the proportion of 1mg/ml, and performing ultrasonic oscillation for 2 hours to form a uniform mixing system; uniformly spraying the obtained mixed system on the carbon cloth obtained in the step 1), and drying at 70 ℃ to obtain carbon cloth loaded with carbon nano tubes;
4) the molar ratio (potassium permanganate: manganese sulfate) 6:1, preparing a mixed solution of potassium permanganate and manganese sulfate, vertically placing carbon cloth loaded with carbon nanotubes into a 100ml polytetrafluoroethylene reaction kettle, and adding 50ml of the mixed solution; and (3) respectively reacting the reaction kettle at 160 ℃ for 9h to obtain a sample a2, taking out the surface paste after the reaction is finished, and drying at 70 ℃ for 6h to obtain the composite material electrode.
Example 3
A preparation method of a carbon nano tube/manganese dioxide composite material electrode comprises the following steps:
1) cutting the carbon cloth into 4cm by 2cm, ultrasonically cleaning the carbon cloth with deionized water for 15min, diluting nitric acid and deionized water to the concentration of 20%, placing the carbon cloth cleaned with deionized water, ultrasonically treating the carbon cloth for 2h, repeatedly cleaning the treated carbon cloth with deionized water, washing away residual nitric acid, and drying the carbon cloth in a drying oven at 70 ℃ for later use;
2) placing the carbon nano tube in 20% nitric acid for ultrasonic oscillation for 2h, standing for 4h, washing and filtering the treated carbon nano tube until the filtrate is neutral, drying the carbon nano tube after filtration and washing at 100 ℃, then placing the carbon nano tube in the air for calcination at 400 ℃ for 6h, and repeatedly grinding for later use;
3) adding the carbon nano tube obtained in the step 2) into absolute ethyl alcohol according to the concentration of 1mg/ml, and performing ultrasonic oscillation for 2 hours to form a uniform mixed system; uniformly spraying the obtained mixed system on the carbon cloth obtained in the step 1), and drying at 70 ℃ to obtain carbon cloth loaded with carbon nano tubes;
4) the molar ratio (potassium permanganate: manganese sulfate) 6:1 preparing a mixed solution of potassium permanganate and manganese sulfate; vertically placing the carbon cloth loaded with the carbon nano tubes into a 100ml polytetrafluoroethylene reaction kettle, and adding 50ml of mixed solution; and (3) respectively reacting the reaction kettle at 160 ℃ for 12h to obtain a sample a3, taking out the surface paste after the reaction is finished, and drying at 70 ℃ for 6h to obtain the composite material electrode.
The present invention provides structural characterization of the carbon nanotube/manganese dioxide composite electrode prepared in examples 1-3, and the results of the diffraction pattern measurement using an X' pert PRO type X-ray diffractometer of PANalytical are shown in fig. 1.
From figure 1 it can be seen that all three samples have four distinct and broad peaks. When the reaction time is 6h, the 2 theta values of the peaks are respectively 12.19 degrees, 24.81 degrees, 36.52 degrees and 65.81 degrees; when the reaction time is 9h, the 2 theta values of the peaks are respectively 12.19 degrees, 24.94 degrees, 36.57 degrees and 65.58 degrees; when the reaction time is 12h, the 2 theta values of the peaks are respectively 12.47 degrees, 24.39 degrees, 36.82 degrees and 65.65 degrees. Analysis of the X-ray diffraction peaks for the three samples indicated that the product of the hydrothermal reaction was predominantly delta-MnO2. Meanwhile, we have also found that the characteristic peak of the sample having a reaction time of 12 hours is weak with respect to the samples having reaction times of 6 hours and 9 hours, and two of them appear at 29.87 ° and 30.80 ° in 2 θThe result is a sharp, hetero-peak, which indicates that the product has a low purity and other products are formed when the reaction time is 12 hours, which is caused by excessive reaction.
Fig. 2 shows SEM photographs of the electrode material at low magnification, and the scanning electron acceleration voltages are all 3.0kV, wherein (a) is an electron micrograph of the carbon nanotube/manganese dioxide composite electrode prepared in example 1 at a magnification of 39 times, (b) is an electron micrograph of the carbon nanotube/manganese dioxide composite electrode prepared in example 2 at a magnification of 32 times, and (c) is an electron micrograph of the carbon nanotube/manganese dioxide composite electrode prepared in example 3 at a magnification of 23 times. As can be seen from the figure, the carbon cloth has an ordered network structure, a layer of dense manganese dioxide powder is attached to the carbon cloth current collector carrying the carbon nanotubes through a hydrothermal reaction, and it can be seen under a low-magnification electron microscope that the grown manganese dioxide powder is generally uniform, but the part of the manganese dioxide powder is not covered by manganese dioxide, which is caused by uneven contact between the electrode material and the solution during the hydrothermal reaction or by falling off during washing or after drying due to insufficient adhesive strength between the product and the substrate material after the reaction is finished. As the reaction time length increases, at a reaction time length of 9 hours, the reaction becomes more sufficient due to the longer reaction time, and thus a thicker manganese dioxide layer is formed, and many pores are formed on the surface. When the reaction time reaches 12h, the reaction time is too long, the manganese dioxide falls off and increases, and the manganese dioxide layer covered on the electrode material becomes thinner again, which is almost as dense as the manganese dioxide layer with the reaction time of 6 h. In summary, the nano manganese dioxide electrode material prepared by hydrothermal reaction at the temperature of 160 ℃ for 9 hours has a good growth condition.
Fig. 3 shows SEM photographs of the electrode material at a high magnification, wherein (a) is an electron micrograph of the carbon nanotube/manganese dioxide composite electrode prepared in example 1 at an acceleration voltage of 3.00kV at a magnification of 3 ten thousand times, (b) is an electron micrograph of the carbon nanotube/manganese dioxide composite electrode prepared in example 2 at an acceleration voltage of 3.00kV at a magnification of 3 ten thousand times, and (c) is an electron micrograph of the carbon nanotube/manganese dioxide composite electrode prepared in example 3 at an acceleration voltage of 3.00kV at a magnification of 21290 times.
Under the high-power photograph, the spherical manganese dioxide of sea urchin generated by the hydrothermal reaction is coated with the carbon nano tube, and coral-shaped aggregates are formed by a large number of nano linear structures, so that the fluffy structure greatly increases the specific surface area of the material, provides more active sites for redox reaction and ion adsorption, greatly improves the capacity of pseudo-capacitance of the electrode material, and improves the overall electrochemical performance of the electrode material. According to the legend, the diameter of the nanowire structure forming the sea urchin sphere is about 20nm, the length is about 100-200nm, the size of the formed sea urchin sphere is uniform, the diameter range is 200 nm-1 um, the diameter of the sea urchin sphere tends to decrease along with the increase of the reaction time, the electrode material prepared when the reaction time is 9 hours has an ideal structure, the agglomeration is weakened, and the spheres are dispersed uniformly. However, as the reaction time continues to increase, the nanowire structure with smaller diameter constituting the sea urchin sphere also tends to change to the nanorod structure with larger diameter, and the agglomeration phenomenon is enhanced again, as shown in (c), which reduces the specific surface area of the material and lowers the electrochemical performance of the material. Therefore, by analyzing the morphology, the hydrothermal reaction is carried out for 9 hours at 160 ℃ to generate a perfect nano manganese dioxide material.
TABLE 1 specific capacitance value (mF/cm) of each sample calculated by cyclic voltammetry at different scan rates2)
The data obtained by cyclic voltammetry were calculated by using the equation, and the area-specific capacitances of the three samples at different scanning speeds are shown in table 1, and the data are plotted as a line graph, and the results are shown in fig. 4.
FIG. 4 is a curve showing the variation of specific capacitance values measured at different scanning rates for samples reacted at 160 ℃ for different periods of time, and by comparison, it was found that the area specific capacitance value of the sample reacted for 6 hours at the scanning rate of 100mV/s to 5mV/s reached 5.73mF/cm2-129.4mF/cm2Area ratio capacitance value of sample with reaction time of 9h under sweep speed of 100mV/s-5mV/sReaching 4.3mF/cm2-122.4mF/cm2The area ratio capacitance value of the sample with the reaction time of 12h reaches 2.6mF/cm under the sweep speed of 100mV/s-5mV/s2-42.7mF/cm2In general, the specific capacitance of the sample with the reaction time of 6h at 160 ℃ is not greatly different from that of the sample with the reaction time of 9h, but the specific capacitance of the sample with the reaction time of 12h is relatively small.
Example 4
A preparation method of a carbon nanotube/manganese dioxide doped super capacitor comprises the following steps:
1) cutting the carbon cloth into 4cm by 2cm, ultrasonically cleaning the carbon cloth with deionized water for 15min, diluting nitric acid and deionized water to the concentration of 20%, placing the carbon cloth cleaned with deionized water, ultrasonically treating the carbon cloth for 2h, repeatedly cleaning the treated carbon cloth with deionized water, washing away residual nitric acid, and drying the carbon cloth in a drying oven at 70 ℃ for later use;
2) placing the carbon nano tube in 20% nitric acid for ultrasonic oscillation for 2h, standing for 4h, washing and filtering the treated carbon nano tube until the filtrate is neutral, drying the carbon nano tube after filtration and washing at 100 ℃, then placing the carbon nano tube in the air for calcination at 400 ℃ for 6h, and repeatedly grinding for later use;
3) taking the carbon cloth obtained in the step 1) and the carbon nano tubes obtained in the step 2), adding absolute ethyl alcohol into the carbon nano tubes according to the proportion of 1mg/ml, ultrasonically oscillating for 2 hours to form a dispersion system, uniformly spraying the dispersion system on the carbon cloth, and drying at 70 ℃ to obtain the carbon cloth loaded with the carbon nano tubes;
4) the molar ratio (potassium permanganate: manganese sulfate) 6:1, vertically placing carbon cloth loaded with carbon nano tubes into a 100ml polytetrafluoroethylene reaction kettle, adding 50ml of mixed solution, placing the reaction kettle at 160 ℃ for reaction for 9h respectively, taking out paste on the surface after the reaction is finished, and drying at 70 ℃ for 6h to obtain a composite electrode;
5) accurately weighing 4g of polyvinyl alcohol (PVA), pouring 30ml of deionized water, putting the mixture into a magnetic stirrer, and stirring for about 1 hour at the temperature of 85 ℃ and the rotating speed of 1400 revolutions per minute; meanwhile, 0.1mol of NaOH is weighed and added with 10ml of deionized water, the mixture is magnetically stirred for 10min until the solution is clear, the NaOH solution is quickly poured into the polyvinyl alcohol solution under the condition of magnetic stirring, and the stirring is continued for 30min, so that the alkaline colloidal electrolyte is obtained;
(6) and (3) placing two composite material electrodes prepared in the step (3) on a heating platform at 85 ℃, coating an alkaline colloidal electrolyte on one surface of each electrode, wherein the coating thickness is about 1mm, aligning and lightly pressing the other electrode together after the alkaline colloidal electrolyte is uniformly covered on the surface of each electrode, placing at room temperature for 12 hours, and obtaining the carbon nano tube/manganese dioxide doped supercapacitor after the electrolyte is fully bonded with the electrodes and is solidified.
Analysis of the experimental results was performed for example 4: fig. 5 illustrates the flexibility of the assembled solid state flexible supercapacitor. As can be seen from the photographs of the flexibility test of the assembled solid-state flexible supercapacitor in FIG. 5, the device has good flexibility due to the good ductility of the electrode material and the use of polyvinyl alcohol for preparing the gel electrolyte.
The carbon nanotube/manganese dioxide doped supercapacitor prepared in test example 4 was subjected to cyclic voltammetry at different scan rates under different deformation conditions, the capacitance values of the calculated supercapacitor are shown in table 2, and the data were plotted as a line graph, and the results are shown in fig. 6.
TABLE 2 specific capacitance (mF/cm) of the supercapacitor by cyclic voltammetry measurements at different sweep rates under different deformation conditions2)
As can be seen from Table 2, at sweep rates of 40mV/s, 80mV/s, and 100mV/s, the capacitance of the supercapacitor was between 76.5mF and 22.7mF without bending, and after bending, the capacitance was between 106.6mF and 29.6mF, and in general, the capacitance was stable when the strain occurred. At the same time, however, the capacitance of the supercapacitor increases after the bend occurs as compared to when the bend is not occurring (as shown in fig. 6). This is because the supercapacitor uses a solid electrolyte, when the supercapacitor is not bent, the contact between the electrolyte and the electrode is not tight enough, and after the supercapacitor is bent, the electrolyte is pressed to be in more sufficient contact with the electrode, which has a certain influence on the change of the capacitance.
Claims (9)
1. The preparation method of the carbon nano tube/manganese dioxide composite material electrode is characterized by comprising the following steps of:
1) ultrasonically cleaning the carbon cloth, adding a nitric acid solution, ultrasonically treating for 2-4h, cleaning the carbon cloth, and drying for later use;
2) placing the carbon nano tube in a nitric acid solution for ultrasonic oscillation, standing, washing and filtering, drying, calcining and grinding for later use;
3) adding absolute ethyl alcohol into the carbon nano tube obtained in the step 2), performing ultrasonic oscillation to form a dispersion system, spraying the dispersion system on the carbon cloth obtained in the step 1), and drying to obtain carbon cloth loaded with the carbon nano tube;
4) carrying out hydrothermal reaction on carbon cloth loaded with carbon nano tubes and a mixed solution of potassium permanganate and manganese sulfate to prepare a carbon nano tube/manganese dioxide composite material electrode;
in the step 4), the molar ratio of potassium permanganate to manganese sulfate in the mixed solution of potassium permanganate and manganese sulfate is 5-7:1, wherein the hydrothermal reaction is carried out at the temperature of 150-.
2. The preparation method according to claim 1, wherein in the step 1), the carbon cloth is ultrasonically cleaned by deionized water for 15-30 min; the concentration of the added nitric acid solution is 10-25%; the temperature set during drying is 65-85 ℃.
3. The method as claimed in claim 1, wherein in the step 2), the carbon nanotubes are placed in 10-25% nitric acid solution for ultrasonic oscillation for 2-4h, the ultrasonic power is 200-500W, the carbon nanotubes are left for 3-4.5h, the temperature set during drying is 90-120 ℃, and the carbon nanotubes are calcined for 3-8h at the temperature of 350-500 ℃.
4. The method as claimed in claim 1, wherein in step 3), the volume ratio of the mass of the carbon nanotube to the absolute ethyl alcohol is 0.8-1.5mg/ml, the ultrasonic oscillation time is 2-4h, the ultrasonic power is 200W and 500W, and the temperature set during drying is 60-90 ℃.
5. A carbon nanotube/manganese dioxide composite electrode produced by the production method according to any one of claims 1 to 4.
6. A supercapacitor comprising the carbon nanotube/manganese dioxide composite electrode of claim 5 and an alkaline solid electrolyte.
7. The supercapacitor according to claim 6, wherein the alkaline solid electrolyte is prepared by mixing and compounding 0.08-0.25g/ml polyvinyl alcohol solution and 0.2-1g/ml NaOH solution according to a mass ratio of 1.5-5: 1.
8. The method for preparing the supercapacitor according to any one of claims 6 to 7, comprising the steps of: and (3) heating two carbon nanotube/manganese dioxide composite material electrodes, coating an alkaline solid electrolyte on one surface of each electrode, and aligning and pressing the other electrode together to obtain the super capacitor.
9. The method of claim 8, wherein the length of the two carbon nanotube/manganese dioxide composite electrodes is 1-3cm, the width thereof is 0.2-0.8cm, and the thickness of the alkaline solid electrolyte coated on the electrodes is 0.5-2 mm.
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