Ni foam supported NiO nanosheets as high-performance free-standing electrodes for hybrid supercapacitors and Ni–Zn batteries

Herein, Ni foam (NF) supported NiO nanosheets with a NF@NiO core@shell structure have been synthesized by a facile etching-reoxidation method. The obtained NF@NiO can function as high-performance free-standing electrodes for both hybrid supercapacitors and Ni-Zn batteries. When employed as the cathode for hybrid supercapacitors, the NF@NiO exhibits a high areal capacitance of 2.01 F cm(-2) at 8 mA cm(-2). By coupling with an FeOOH anode, the assembled NF@NiO//FeOOH asymmetric supercapacitor delivers a peak energy density of 2.15 mW h cm(-3) and a peak power density of 2.75 W cm(-3). A rechargeable Ni-Zn battery is also assembled using NF@NiO as the cathode. The NF@NiO//Zn battery demonstrates a high maximum energy density (25.6 W h cm(-2)) and an impressive power density (86.48 mW cm(-2)) with remarkable cycling durability (84.7% capacity retention for 10000 cycles). These features make the free-standing NF@NiO a promising candidate for electrochemical energy storage.