Performance enhancement of asymmetric supercapacitors with bud-like Cu-doped MnO hollow and porous structures on nickel foam as positive electrodes.

Cu-doped MnO hollow nanostructures supported on Ni foams as high-performance electrode materials for supercapacitors were successfully synthesized through a facile hydrothermal method and subsequent calcination. The morphology, structure, and electrochemical performance of the as-prepared MnO nanostructures can be tuned just by varying the Cu doping content. Benefiting from the unique bud-like hollow structure, the 1.5 at% Cu-doped MnO sample has a high specific capacitance of 257.6 F g at 1 A g and remarkable stability (about 90.6% retention of its initial capacitance after 6000 electrochemical cycles). Besides, an asymmetric supercapacitor (ASC) cell based on the 1.5 at% Cu-doped MnO exhibits a high specific capacitance of 305.6 F g at 1 A g and an energy density of 108.6 W h kg at a power density of 799.9 W kg. More importantly, the ASC shows good long-term stability with 86.9% capacity retention after charging/discharging for 6000 cycles at a high current density of 5 A g.