(783b) Capacitance Behaviour of Supercapacitors Based-On Carbon Nanotube and Ionic Liquids

As a novel class of energy storage devices, electrical double layer (EDL) capacitors, also called supercapacitors, have attracted great attention, owing to their advantageous properties, such as high power density, high capacitance, and excellent durability. With high specific surface area and electrical conductivity, recently, carbon-based materials are the most widely used electrodes for supercapacitors, including activated carbons, templated and carbide-derived carbons (CDC), carbon nanotubes (CNTs),and onion-like carbons (OLCs), among others. Based upon our previous work on the ionic liquids near OLCs, supercapacitors composed of CNTs with diameters ranging in size from 0.67 nm to 2.02 nm in an ionic liquid were studied to investigate the dependence of capacitance on the pore size using molecular dynamics simulations. We find that the surface charge density increases almost linearly with the potential applied on EDLs near CNTs. This leads to a nearly flat shape of the differential capacitance versus the potential, which is similar with that near the OLCs rather than planar electrodes. Furthermore, our simulations reveal that the capacitance of EDLs on CNTs increases with the curvature of CNT surface increasing, which is in agreement with theoretical prediction. Both interesting capacitive behaviours of CNT-based supercapacitors invite experimental exploration to take advantage of these phenomena.