MnO₂@NiO nanosheets@nanowires hierarchical structures with enhanced supercapacitive properties

Transitional metal oxides are demonstrated as promising candidates for pseudocapacitive electrode materials for use in high-performance supercapacitors. Here, we report a rational design of the MnO₂@NiO nanosheets@nanowires hybrid structure. The as-prepared hierarchical structure shows highly uniformity and interconnection between ultrathin MnO₂ nanosheets and NiO nanowires. The well-designed MnO₂@NiO is directly used as binder-free electrode and exhibits a high specific capacitance (374.6 F g⁻¹ at a current density of 0.25 A g⁻¹; areal capacitance of 1.3 F cm⁻²), good rate capability, and excellent cycling stability (92.7% capacitance retention after 5000 charge/discharge cycles). An asymmetric supercapacitor (ASC) is assembled using the MnO₂@NiO as the positive electrode and activated microwave exfoliated graphite oxide as the negative electrode. The assembled ASC shows excellent electrochemical performance with an energy density of 15.4 W kg⁻¹ and a maximum power density of 9360 W kg⁻¹. These analytical and experimental results clearly indicate the advantages of multicomponent hierarchical core–shell structure for engineering high-performance electrochemical capacitors.