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

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 KMnO4 aqueous solution at room temperature. The effects of deposition conditions, including KMnO4 concentration, initial molar ratio of NH3·H2O and KMnO4, bath temperature, and reaction time, on the electrochemical properties of MnO2 thin films are investigated. Layered birnessite-type MnO2 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 Na2SO4. Compressive and tensile bending tests show that as-prepared MnO2 thin film electrodes possess excellent mechanical flexibility and electrochemical stability.

► Layered birnessite-type MnO2 thin films are fabricated on ITO/PET substrates through a facile chemical bath deposition at room temperature.
► The transmittance of the MnO2 thin films at 550 nm is up to 77.4%.
► MnO2 thin films exhibit a special capacitance of 229.2 F g−1 and 9.2 mF cm−2.
► MnO2 thin films show a capacitance retention ratio of 83% after 1000 CV cycles.
► MnO2 thin film electrodes show great mechanical flexibility and electrochemical stability even after 200 tensile and compressive bending cycles.