Synergism of carbonaceous additives in engineering of the supercapacitive performance of α-and λ-phases of manganese oxide

Abstract

Owing to the presence of valence shells for charge transfer, a high theoretical specific capacitance, and variable redox properties, MnO₂ appears as a promising agent in the realm of energy storage. Crystallographic structures of manganese oxide (MnO₂), a transition metal oxide, play a crucial role in determining its capacitive behavior by controlling the ion intercalation and double-layer formation. In this work, two different phases of MnO₂ were synthesized using the facile chemical reduction method and biological method, say α-MnO₂ and λ-MnO₂. The phases were incorporated with different carbonaceous additives including GO and CNT while maintaining a constant weight ratio of 8:1:1 between active materials (MnO₂), additive, and PVDF binder. Among different composites formed, the best electrode performance is demonstrated by λ-MnO₂/CNT/PVDF composite with an excellent specific capacitance of 356 F/g at a scan rate of 1 A/g. Moreover, the best-performing electrodes are investigated with a symmetrical two-electrode system yielding a wide potential window of 1.8V with an outstanding power density of 13.5 KW/Kg at 5 A/g and an energy density of 53.78 Wh/Kg at 1A/g having a specific capacitance of 190 F/g.