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 μW h cm−2) and an impressive power density (86.48 mW cm−2) with remarkable cycling durability (84.7% capacity retention for 10 000 cycles). These features make the free-standing NF@NiO a promising candidate for electrochemical energy storage