Abstract: Nanoscale α-MnO2 was synthesized with potassium permanganate and manganese sulfate mixture in an autoclave at different hydrothermal times.The structure and properties of the samples were characterized by XRD，SEM，and BET analysis methods.Results showed that when the hydrothermal time was 9 h，SEM test showed that the synthesized powders was nanopowder with the particle size at 50~60 nm；XRD analysis showed that the powder was α-MnO2；and the specific surface area of BET test reached 53.66 m2/g.In the three electrode systems of manganese dioxide as the working electrode，a saturated calomel electrode（SCE） as the reference electrode，a platinum wire electrode as auxiliary electrode and using 1 mol/L Na2SO4 solution as electrolyte，the electrochemical behavior was studied by cyclic voltammetry and chronopotentiometry methods.Experimental results showed that when the potential window within the scale of 0~0.8V（vs.SCE），and the scanning speed was 2 mV/s，its specific capacitance reached 76 F/g，and cyclic voltammetry curve was close to a rectangle.

Key words: supercapacitor, electrode material, manganese dioxide