High capacity supercapacitors based on modified activated carbon aerogel

Abstract

Carbon aerogel derived from a modified resorcinol-formaldehyde (RF) method without supercritical drying step was activated under CO 2 flow and further modified with a surfactant sodium oleate solution. Carbon aerogel, activated carbon aerogel (ACA) and modified activated carbon aerogel (MACA) were characterized by Brunaver, Emmett and Teller(BET) surface measurement, constant-current charge-discharge and cyclic voltammetry(CV). It was found that the specific surface area of the ACA was twice that without activation. At relatively low discharge rates the specific capacitance and energy delivered from the capacitor were improved greatly by the activation of carbon aerogel. To apply the ACA at high discharge rate, a surface modification was introduced. After the surface modification the wettability of the organic electrolyte based on non-polar organic solvent (i.e. propylene carbonate) to the ACA was improved greatly and, as a result, the internal resistance of the capacitor decreased and the specific capacitance and energy delivered increased at all the test discharge rates. The effects from the modification become more marked at higher discharge rates, i.e. at 48 mA cm )2 , the energy delivered increased by ca. 70%, which indicates the MACA more suitable as electrode material in electric double-layer capacitors (EDLCs) for high current applications.

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