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

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 Fe2O3/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.