Synthesis of layered birnessite-type manganese oxide thin films on plastic substrates by chemical bath deposition for flexible transparent supercapacitors

Abstract

Layered birnessite-type manganese oxide thin films are successfully fabricated on indium tin oxide coated polyethylene terephthalate substrates for flexible transparent supercapacitors by a facile, effective and inexpensive chemical bath deposition technology from an alkaline KMnO 4 aqueous solution at room temperature. The effects of deposition conditions, including KMnO 4 concentration, initial molar ratio of NH 3·H 2O and KMnO 4, bath temperature, and reaction time, on the electrochemical properties of MnO 2 thin films are investigated. Layered birnessite-type MnO 2 thin films deposited under optimum conditions display three-dimensional porous morphology, high hydrophilicity, and a transmittance of 77.4% at 550 nm. A special capacitance of 229.2 F g −1 and a capacitance retention ratio of 83% are obtained from the films after 1000 cycles at 10 mV s −1 in 1 M Na 2SO 4. Compressive and tensile bending tests show that as-prepared MnO 2 thin film electrodes possess excellent mechanical flexibility and electrochemical stability.