Carbon aerogel, carbon black and graphite were used to analyze the influence of conductive filler on the impedance behaviors of activated carbon based electric double layer capacitors (EDLCs). According to the electrochemical impedance spectrum (EIS) data, a new equivalent circuit model was proposed involving the kinetic characteristics of ion diffusion, furthermore, Marquardt fit procedure was applied to the EIS data to obtain the model parameter values. The results indicated that carbon aerogel could significantly decrease the resistance of EDLCs by increasing the diffusion coefficient of ions within electrodes and decreasing the interface resistance because of its suitable particle size, mesoporous structures and finely-branched particle performance. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.