| In this paper, we used the simple and efficient electrostatic spinning method to prepare our materials. The coal/PAN interconnected carbon fibers were prepared as the cathode material by using coal as carbon source, and the positive electrode materials with good performance were prepared by using the Polyacrylonitrile carbon fibers(PAN) as the substrate to support the Bimetallic Oxides. Finally, a kind of button type asymmetric super capacitor with good performance was successfully assembled. Then on the base of it, after careful analysis, we had found that the carbon diffusion effect could be used to prepare hollow carbon fibers and then used as electrode material for super capacitor with good performance.In this paper, we mainly did the following researches:Firstly, by using the concentrated sulfuric acid and Potassium Permanganate to oxidize the raw coal which was produced in Xinjiang Kuche, we had obtained the oxidized coal which could be dissolved in organic solvent. Then we prepared the coal/PAN interconnected carbon fibers by electrospinning method. By further study, we found that the more the content of oxidized coal in fibers, the greater the degree of connection between the fibers, which improved the conductivity of carbon fibers to a certain extent. The analysis results showed that when adding 15wt% oxidized coal,the conductivity of coal/PAN interconnected carbon fibers got the highest value. In addition, when the amount of oxidized coal was 50wt%, the specific capacitance value was up to 259.7 F·g-1 at an current density of 1 A·g-1. After 7000 cycles, the specific capacitance was 135.5% of the first charge discharge, which still showed an excellent cycle stability.Secondly, the Ni(Ac)2/PAN composite as-spun fibers were successfully prepared by electrospinning method. The aqueous solution of Na2WO4·2H2O was evenly sprayed on the prepared Ni(Ac)2/PAN composite as-spun fibers by the pneumatic spray gun and in the meantime the water in the solution was kept not been fullyevaporated so as to keep the Ni(Ac)2 in the fiber unchanged when the Na2WO4 and Ni(Ac)2 on the fiber surface were reacted and NiWO4 had been generated. After heat treatment, NiWO4/Ni/carbon composite fibers were successfully prepared. The results of electrochemical measurement showed that the specific capacitance of the composite fibers was up to 792.2 F·g-1 at an current density of 5 A·g-1 after the activation process. In addition, the specific capacitance value could still maintain97.3% of the initial value after 5000 cycles of charge and discharge. We used the prepared NiWO4/Ni/carbon composite fibers and the coal /PAN composite fibers as positive and negative electrode materials for the asymmetric super capacitor respectively and tested its performance. The results showed that after ten thousand cycles of charge and discharge, its energy density increased from 32.5 Wh·kg-1 to41.3 Wh·kg-1 at the power density of 193.8 W·kg-1, which showed a good cycle life.Finally, again we prepared the Ni(Ac)2/PAN composite as-spun fibers by electrospinning method and the aqueous solution of Na2WO4·2H2O was evenly sprayed on the prepared Ni(Ac)2/PAN composite as-spun fibers by the pneumatic spray gun. By controlling the conditions to ensure that the water in the spray process was fully evaporated so that the deposition of Na2WO4 on the fiber kept unchanged.In the process of heat treatment at 600 o C, the carbon formed by PAN in the fibers would be diffused from the side of the Ni element to the side of W element, and finally the Na2WO4/Ni/ carbon composite fibers with hollow structure was prepared.By using hot nitric acid and distilled water to remove the Na2WO4 and Ni metal particles, the hollow carbon fibers were successfully obtained. The obtained hollow carbon fibers had been used as the electrode materials for the super capacitor, and an specific capacitance of 243.7 F·g-1 was obtained at current density of 1A·g-1. |
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