Synthesis And Supercapacitance Performance Of Composite Electrode Materials

Supercapacitor is a new type energy storage device. With rapid charge-discharge energy storage, long cycle life, free of maintenance and environmental benign, supercapacitor has attracted considerable attention.The performance of supercapacitors largely depends on the specific capacitance and the cycle life of electrode materials. This dissertation focused on the exploration of new electrode materials with high supercapacitance performance. Three composite materials were prepared through electrochemical and chemical methods, Mesoporous carbon nanofibers/Polyaniline(MCFs/ PANI ) , Mesoporous carbon/Polyaniline ( MC/PANI ) and Graphene/Polyaniline(GNS/PANI), and made a research of their surface morphology and structure through SEM, TEM and XRD, and electrochemical performance through cyclic voltammetry (CV), galvanostatic charge–discharge and Nyquist impedance test with a three-electrode system. The main works are as follows:(1) Mesoporous carbon nanofibers (MCFs) was prepared using AAO as hard template, the solution of F127 and phenolic resin`s ethanol solution was dipped into the mesoporous of AAO, and then aged in oven, calcinated in N2 to carbonization and then got rid of AAO template through HCl solution. The surface morphology and structure of MCFs were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The paper also made a research of the influence of time in dissolving AAO template, and observed the result at different time through SEM.(2)Polyaniline (PANI) was prepared within the mesopores and on the surface of mesoporous carbon nanofibers (MCFs) by an electrochemical polymerization method, leading to the formation of a composite material PANI/MCFs. The surface morphology and structure of the composite material were characterized by scanning electron microscope (SEM) , transmission electron microscope (TEM) and thermogravimetric analysis (TGA). The supercapacitance performance of PANI/MCFs was investigated by cyclic voltammetry (CV), galvanostatic charge–discharge and Nyquist impedance test with a three-electrode system in 1.0 mol/L H<sub>2</sub>SO<sub>4</sub> solution. The specific capacitance of the composite material was as high as 391 F/g at a current density of 50 mA/g. The cycling stability was much better than that of pure polyaniline.(3)Mesoporous carbon was prepared through chemical method, and aniline was initiated polymerization in the acid solution which contained mesoporous carbon that was already made. A composite of mesoporous carbon/polyaniline (MC/PANI) was prepared, and its structure was characterized by XRD. The supercapacitance performance of MC, pure PANI and MC/PANI composite were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge and Nyquist impedance test with a three-electrode system in 1.0 mol/L H<sub>2</sub>SO<sub>4</sub> solution. Results show that the cycle stability of MC was the best but the specific capacity was the lowest, 98.5 F/g. With the increase of cycle number, the capacity decay of PANI electrode material was the most serious. There was only 44.5 percent specific capacity left, however, the specific capacitance of the composite material MC/PANI was as high as 593 F/g at a current density of 10 mA/g. And the cycle stability was much better than that of pure PANI, the specific capacity was 81.3 percent left after one thousand cycle numbers.(4) Graphene(GNS) was prepared through optimized Hummers method. Then aniline was initiated polymerization in acid solution which contained graphene that was already well-distributed ahead of time. A composite of GNS/PANI was obtained, and the structure and components were characterized by XRD and Raman spectra. The supercapacitance performance of GNS and GNS/PANI composite were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge and Nyquist impedance test with a three-electrode system in 1.0 mol/L H<sub>2</sub>SO<sub>4</sub> solution. Results show that the specific capacity of GNS/PANI was much higher then that of pure graphene at the same current density. It revealed that the existence of PANI in the composite improved the electrote material`s specific capacity greatly, and the existence of graphene made the cycle stability of the composite much better than that of pure PANI.