ZnO/MnO_<i>x</i>Nanoflowers for High-Performance Supercapacitor Electrodes

Abstract

A crystalline ZnO/MnOx nanoflower (NF) nanocomposite was deposited on Ni nanocones via an economical synthesis method in which the ZnO NFs were first synthesized, and MnOx was then deposited on the ZnO petals to form a heterostructured composite. The effect of the MnOx coating on the performance of the nanocomposite was analyzed by comparing the performance of supercapacitors employing ZnO and the ZnO/MnOx nanocomposites. The ZnO/MnOx nanocomposites exhibited excellent current rate capability and an excellent capacitance of 556 F·g–1 at a current density of 1 A·g–1. The optimized ZnO/MnOx NF electrode presented a remarkable long-term cycling stability, with a capacitance retention of 96% after 10,000 cycles. In a coin cell assembly, at an operating voltage of 0.9 V, the energy density of the optimized supercapacitor cell was 16 Wh·kg,–1 at a power density of 225 W·kg–1. Becasue of its excellent electrochemical performance, the optimized ZnO/MnOx NF composite electrode is promising for high-energy-density supercapacitor applications.