Effect of the electrolyte particularities on manganese dioxide in the neutral electrolytes containing alkaline (Li(+), Na(+), or K(+)) and alkaline-earth (Mg(2+), Ca(2+), or Ba(2+)) metal cations for electrochemical capacitor is investigated by cyclic voltammetry and electrochemical impedance spectroscopy. A very high capacitance of 357.9 F g(-1) is measured when Ca(2+) ion is used as electrolyte cation. The results show that cations of the electrolyte instead of proton or anions are responsible for the pseudo-capacitive behavior of manganese dioxide. The capacitance of manganese dioxide is found to depend strongly on the electrolyte particularities, for example, pH value, cation and anion species, and salt concentrations. A logarithmic dependence of capacitance of MnO(2) on cation activity is obtained for all alkaline and alkaline-earth metal cations. The capacitance of MnO(2) can be doubled by replacing univalent cation with bivalent cation at a close cation activity. (C) 2011 Elsevier B.V. All rights reserved.