Study On Polythionphene/Polyaniline/Active Carbon Composites As Electrode Materials In Supercapacitors

The supercapacitor called double-layer capacitor is a new type environement friendly energy storage device. The supercapacitor have many good characteristics as high energy density, high power density, long cycle life and less pollution. According to lately research, electrode material mainly includes carbon material, metal oxide, conducting polymer and various kinds of composite materials. Among these conducting polymers, Polythionphene(PTH) is one kind of important structural conducting polymer and have extensive research because of its good properties.In this study, Polythionphene/active carbon(PTH/AC) composites as electrode materials in supercapacitors were synthesized by in-situ polymerization of thionphene on activated carbon. The surface performance and the molecular structure of the composites were investigated by scanning electron microscopy and Fourier transform infrared spectroscopy; and the electrochemical performance were tested by cyclic voltammetry, galvanostatic charge-discharge and electrochemi- cal impedance spectrometry in 6mol/L KOH solution using Hg/HgO as reference electrode. Results show that the composites with uniform distribution have a puff net-like structure with large caverns; When n(AC):n(thionphene)=10:1, the absorbtion of the PTH/AC composites at 790 cm-1 and 1627 cm-1 reached the max at IR spectroscopy. That is because the conjugate action of the activated carbon and thionphene enhanced and the thionphene links mostly connected byα-αduring the polymerization. At the same time, the composites have good electrochemical performance. When n(AC):n(thionphene)=10:1 the capacitance value of PTH/AC composites increased from 144.6F/g(pure PTH) to 401.7F/g. When the charge-discharge current density increased form 100mA/g to 900mA/g, the capacitance of the PTH/AC composites decay from 401.7F/g to 267.8F/g with the sustained percentage of 66.7%, but the capacitance of the pure Polythionphene decay from 144.6F/g to 28.6F/g with the sustained percentage of 19.8%.In the second step, PANI/AC and PTH/PANI/AC composites as electrode materials in supercapacitors were synthesized by in-situ polymerization. The effect of the addition of PANI on the electrochemical and structure performance was investigated. The surface performance and the molecular structure of the composites were investigated by scanning electron microscopy and Fourier transform infrared spectroscopy. The electrochemical performances were tested by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectro-metry. The IR results show that the absorbtion of the PTH/PANI/AC composites at 790 cm-1 and 1632 cm-1 reached the max. That is because the thionphene links mostly connected byα-αduring the polymerization. The electrochemical test results show that the capacitance value of PTH/PANI/AC composites comes up to 597.4 F/g, and the composites have good performance on big charge-discharge current density. When the charge-discharge current density increase from 100mA/g to 900mA/g, the capacitance of the composites decay from 597.4F/g to 345.0F/g with the sustained percentage of 57.8%. The PTH/PANI/AC composites also have good stability, the capacitance value of which decay from 366.0F/g to 293.4F/g with a high sustained percentage of 80.2% after 3000 times charge-discharge at 400mA/g.