Electrochemical Performance Of Novel Carbon Materials With High Specific Surface Area

Electrochemical supercapacitor is a new type of energy storage device betweentraditional capacitors and rechargeable batteries. It has the advantages such as quickcharge-discharge ability and high charge-discharge efficiency. Meanwhile its defectssuch as low capacitor performance can not be ignored. Therefore it is urgent to studythe way for improving the electrochemical performance of supercapacitors. Theresearches of this thesis focused on the optimization of pore structure,improve theutilization of surface area, so improve the electrochemical performance of carbonmaterials. The main studies are as follows:In this study, rice husks were converted into rice husks derived carbon (RDC), bycarbonization and chemical activation, and used as supercapacitor electrodes. Themicropore sizes of these modified activated carbon were determined with nitrogenadsorption experiment. Electrochemical characterization was carried out withgalvanostatic cycling, cyclic voltammetry, and impedance spectroscopy. Theelectrochemical characterization showed that the RDC still retained almost90%of itslow rate capacitance at a scan rate of100mVs-1in aqueous electrolyte. The highestgravimetric capacitance reaching155Fg-1in aqueous and135Fg-1in organicelectrolytes. PAN-ACF were produced by treatment with carbonization and activation. Themicropore sizes of these modified fibers were determined with SAXS and nitrogenadsorption experiments. And the details of pore structure of ACF were analyzed bythe independently developed software. Laser Raman spectroscopy XRD and SEMwere employed to characterize the microstructure changes of PAN-based fibers. Thehighest capacitance was reaching147Fg-1in aqueous and125Fg-1in organicelectrolytes (carbonized at850°C).Flexible electrospun titanium carbide (TiC) nano-felts were converted intocarbide-derived carbon (CDC) by dry chlorination and used as binder-freesupercapacitor electrodes. Electrochemical characterization was carried out withgalvanostatic cycling, cyclic voltammetry, and impedance spectroscopy. The highestgravimetric capacitance was identified for the highest synthesis temperature of1000°C, reaching135Fg-1in aqueous and120Fg-1in organic electrolytes. Thenano-felts still retained more than90%of their low rate capacitance at a scan rate of100mVs-1in aqueous electrolyte and the nano-felts synthesized at temperature(400-800°C) lost less than50%of capacitance at scan rates as high as5Vs-1.