Interlayer Gap Widened 2D α-Co(OH)2 Nanoplates with Decavanadate Anion for High Potential Aqueous Supercapacitor

Abstract Two dimensional (2D) layered metal hydroxides possess unique structure and electrochemical properties. However, it is mandatory to go beyond outer surface to exploit their full potential and make the inner surface available for charge storage. Here, we demonstrate a decavanadate (DV) anion incorporation strategy to widen the gap of α-Co(OH)2 nanoplates (ACH). DV is a redox active polyoxometalate so it not only work as a spacer but offers additional charge storage through pseudocapacitance. DV intercalation provides ion-buffering reservoirs to boost deep faradic redox reactions with good ionic diffusion and enhanced electrochemically active surface area. Consequently, DV-ACH nanoplates exhibits specific capacitance of 257.55 F g−1@ 1 A g−1 and work well from -0.5 to 0.9 V in ecofriendly electrolyte with good reversibility coefficient. This performance is relatively much superior even in neural electrolyte than ACH electrode studied in alkaline electrolyte, pointing towards a safer way for high performance energy storage devices. Asymmetric cell based on DV-ACH can operate up to 1.8 V and delivers a maximum energy density of 27.67 Wh kg−1 @ 544.9 W kg−1 with excellent cycling stability (96% after 5000 cycles). These results suggest the high efficiency of polyoxometalate modulated metal hydroxides for next generation supercapacitors.