Micron-sized CuO spheres anchored on three-dimensional nickel foams for high-performance aqueous asymmetric capacitor

Despite its high theoretical specific capacitance and low cost, copper oxide still suffers from insufficient utilization of active sites and poor cyclic stability when applied in asymmetric capacitors. In this work, micron-sized CuO electrode has been successfully obtained using nickel foam as substrate through an electrodeposition method. By optimizing the electrodeposition potential and designing structure, the CuO microsphere electrode delivers a high specific capacitance of 985 F g −1 at 1 A g −1 . Furthermore, the asymmetric capacitor assembled with CuO electrode and activated carbon electrode exhibits a maximum energy density of 44.5 Wh kg −1 at 1600 W kg −1 and a long lifespan of 93.4% capacitance retention after 10000 cycles at 5 A g −1 . These results demonstrate that the microsphere structure contributes to maintaining excellent structural stability during long cycles and then facilitate their electrochemical kinetics and capacitive performances. This work presents a novel strategy for designing and enhancing micron-sized positive electrodes for high-performance asymmetric capacitors.