In-Situ-Grown Mg(OH)₂-Derived Hybrid α-Ni(OH)₂ for Highly Stable Supercapacitor

As one of the most promising candidates for supercapacitor electrodes, transition metal hydroxides usually suffer from the quick decay in capacity during cycling, mainly caused by the decrease of electroactive surface area resulting from the instability of microstructure/morphology upon fast and repeated charging/discharging. Herein, we fabricated a structure-stable Ni(OH) 2 grown on Ni foam via in situ ion-exchange reaction with Mg(OH) 2 as sacrificial substrate and effective dopant. The obtained hybrid Ni(OH) 2 possesses nanosheet morphology, large surface area (220 m 2 /g) and achieves an unprecedented cycling stability with a 95% retention after 10 000 cycles. The asymmetric supercapacitors with the hybrid Ni(OH) 2 exhibit superior supercapacitive performances with large capacity of 167 F/g and maximum energy density of 57.9 Wh/kg at power density of 1.58 kW/kg. Even at a standard power density of 4.0 kW/kg, a high energy density of 49.6 Wh/kg was achieved, making the hybrid Ni(OH) 2 a promising candidate for practical supercapacitor devices.