Test of electrodes based on manganese oxide with and without potassium cations for supercapacitors

Abstract

The demand for more efficient energy storage devices with a sustainable approach has turned supercapacitors into a great alternative in applications where high instantaneous power is required. Above all, those based on manganese oxides are attracting attention for their low cost, durability, and relatively high specific capacitance. However, it is known that MnO2 with a pyrolusite structure (β-MnO2) has a poor performance. This work studies this material electrochemically before and after thermally incorporating potassium cations at 800 °C. For the present work, commercial MnO2 and MnO2 doped with potassium ions (K-MnO2) were used as active material for the electrodes of commercial supercapacitors. It was verified that the commercial material is β-MnO2 and that the thermally doped material is predominantly manganese oxide with a cryptomelane structure (α-KxMnO2). Cyclic voltammetry measurements were performed at different scanning rates, to elucidate the electrochemical response of the materials. The results corresponding to K-MnO2 present a higher current compared to commercial MnO2, this implies that this electrode has a higher specific capacitance, which can be attributed to a greater potassium ion insertion/extraction capacity. However, at high scanning speeds, its behavior shows that it is pseudocapacitive.