Step potential electrochemical spectroscopy (SPECS) has been applied to a range of different electrolytic manganese dioxide (EMD) samples to examine the effects that material composition, structure and morphology have on the performance of these materials as electrochemical capacitor electrodes. The applications of SPECS enabled deconvolution of the electrode behaviour into double layer and diffusional or pseudo-capacitive effects. The technique was even sensitive enough to resolve double layer charge storage associated with either the geometric or porous surface area. The relationships between each of the contributions to total capacitance and the EMD material properties have been described and discussed. (C) 2016 Elsevier Ltd. All rights reserved.