High performance flexible asymmetric CNO-ZnO//ZnO supercapacitor with an operating voltage of 1.8 V in aqueous medium

Abstract Using the hybrid nanostructure and asymmetric configuration as strategies to enhance the capacitance of ZnO is demonstrated. A novel CNO-ZnO nanocomposite with unique nanoporous microstructure is used to achieve superior electrochemical performance in an asymmetric configuration. The nanoporous morphology with well dispersed ZnO surface sites results in enhanced electrochemical activity through better electron transport and improved electrolyte accessibility in the nanocomposite. A binder-free, flexible asymmetric supercapacitor with nanoporous CNO-ZnO as negative and ZnO as positive is demonstrated to achieve high electrochemical performance. For the first time, an optimized CNO-ZnO//ZnO flexible asymmetric supercapacitor (ASC) is demonstrated in a stable operation voltage window of 1.8 V with a high energy and power density of 10 Wh/kg and 8100 W/kg, respectively. Furthermore, the CNO-ZnO//ZnO ASC device exhibits excellent long cycle life with retention of 92% specific capacitance after 2000 cycles. The overall device performance is attributed to their unique nanoporous microstructure, stable interface formation and interactive effect of constituent phases in the nanocomposite. From the overall findings, ZnO composites with carbon nano onions (CNO) can be a viable and potential choice for supercapacitor applications.