A High-Energy-Density Hybrid Supercapacitor with P-Ni(OH)2 @Co(OH)2 Core-Shell Heterostructure and Fe2 O3 Nanoneedle Arrays as Advanced Integrated Electrodes.

Abstract

Transition metal hydro/oxides (TMH/Os) are treated as the most promising alternative supercapacitor electrodes thanks to their high theoretical capacitance due to the various oxidation states and abundant cheap resources of TMH/Os. However, the poor conductivity and logy reaction kinetics of TMH/Os severely restrict their practical application. Herein, hierarchical core-shell P-Ni(OH)2 @Co(OH)2 micro/nanostructures are in situ grown on conductive Ni foam (P-Ni(OH)2 @Co(OH)2 /NF) through a facile stepwise hydrothermal process. The unique heterostructure composed of P-Ni(OH)2 rods and Co(OH)2 nanoflakes boost the charge transportation and provide abundant active sites when used as the intergrated cathode for supercapacitors. It delivers an ultrahigh areal specific capacitance of 4.4 C cm-2 at 1 mA cm-2 and the capacitance can maintain 91% after 10 000 cycles, showing an ultralong cycle life. Additionally, a hybrid supercapacitor composed with P-Ni(OH)2 @Co(OH)2 /NF cathode and Fe2 O3 /CC anode shows a wider voltage window of 1.6 V, a remarkable energy density of 0.21 mWh cm-2 at the power density of 0.8 mW cm-2 , and outstanding cycling stability with about 81% capacitance retention after 5000 cycles. This innovative study not only supplies a newfashioned electronic apparatus with high-energy density and cycling stability but offers a fresh reference and enlightenment for synthesizing advanced integrated electrodes for high-performance hybrid supercapacitors.