Oxygen-vacancy-decorated ZnO/NiO@N-doped carbon core-shell microspheres with high electrochemical performance for supercapacitor applications

Abstract

In this study, ZnO/NiO@NC was prepared using polyvinylpyrrolidone (PVP) as a structural guide and carbon source, and an oxygen-vacancy-rich ZnO/NiO@N-doped carbon shell (ZnO/NiO@NC) electrode material was obtained by annealing under an N2 atmosphere. When the current density of the galvanostatic charge–discharge (GCD) was set to 0.5 A/g, the ZnO/NiO@NC electrode exhibited maximum specific capacitance (860.00 F/g), longer charge/discharge time, and a lower impedance compared with other materials. Its specific capacity was maintained above 80%, indicating that the active material had superior stability owing to encapsulation by the carbon shell. The excellent electrochemical performance is attributed to the formation of an effective p-n heterostructure between ZnO and NiO as the basic skeleton, surface oxygen vacancies, and the rich mesoporous structure after high-temperature reduction calcination. Furthermore, the excellent electrical conductivity of the N-doped carbon shell further improves the electrochemical performance of the material.