The Capacitive Behaviors of Manganese Dioxide Thin‐Film Electrochemical Capacitor Prototypes

We have documented the fabrication of manganese dioxide (MnO 2 ) thin‐film electrochemical capacitor (EC) prototypes with dual‐planar electrode configuration. These EC prototypes exhibited good capacitive behaviors in mild Na 2 SO 4 aqueous electrolyte. Enhanced capacitive behaviors of EC prototypes were observed upon prolonged voltammetric cycling which could be associated with microstructural transformation of MnO 2 thin‐film electrodes from densely packed plate‐like to irregular petal‐like surface morphology. Effects of voltammetric scan rates, prolonged voltammetric cycling, electrolyte composition, and electrolyte concentration on the surface morphology of MnO 2 thin‐film electrodes, and associated capacitive behaviors of MnO 2 thin‐film EC prototypes were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) techniques. Results of both CV and EIS indicated that thin‐film MnO 2 EC prototypes exhibited the highest specific capacitance of 327 F/g in 0.2 M Na 2 SO 4 aqueous electrolyte. Being environmentally benign and cheap, MnO 2 thin‐film electrochemical capacitors have high potential utility as pulsed power sources, as well as load‐leveling functions in various consumer electronic devices.