ZnO/MnO_x Nanoflowers for High-Performance Supercapacitor Electrodes

A crystalline ZnO/MnO_x nanoflower (NF) nanocomposite was deposited on Ni nanocones via an economical synthesis method in which the ZnO NFs were first synthesized, and MnO_x was then deposited on the ZnO petals to form a heterostructured composite. The effect of the MnO_x coating on the performance of the nanocomposite was analyzed by comparing the performance of supercapacitors employing ZnO and the ZnO/MnO_x nanocomposites. The ZnO/MnO_x 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/MnO_x 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/MnO_x NF composite electrode is promising for high-energy-density supercapacitor applications.