Influence of Particle Size Distribution on the Performance of Ionic Liquid-based Electrochemical Double Layer Capacitors.

Electrochemical double layer capacitors (EDLCs) employing ionic liquid electrolytes are the subject of much research as they promise increased operating potentials, and hence energy densities, when compared with currently available devices. Herein we report on the influence of the particle size distribution of activated carbon material on the performance of ionic liquid based EDLCs. Mesoporous activated carbon was ball-milled for increasing durations and the resultant powders characterized physically (using laser diffraction, nitrogen sorption and SEM) and investigated electrochemically in the form of composite EDLC electrodes. A bi-modal particle size distribution was found for all materials demonstrating an increasing fraction of smaller particles with increased milling duration. In general, cell capacitance decreased with increased milling duration over a wide range of rates using CV and galvanostatic cycling. Reduced coulombic efficiency is observed at low rates (