A High‐Energy‐Density Hybrid Supercapacitor with P‐Ni(OH)₂@Co(OH)₂ Core–Shell Heterostructure and Fe₂O₃ Nanoneedle Arrays as Advanced Integrated Electrodes

Abstract

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 Fe 2 O 3 /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.