Fabrication of Co–Ni–Zn ternary Oxide@NiWO₄ core-shell nanowire arrays and Fe₂O₃-CNTs@GF for ultra-high-performance asymmetric supercapacitor

Hererin, we report Co–Ni–Zn ternary oxide@NiWo₄ core-shell nanowire arrays on Ni foam (Co–Ni–Zn–O@NiWO₄) and Fe₂O₃ nanosheets interconnected with carbon nanotubes on 3D graphene Ni foam (Fe₂O₃-CNTs@GF) as the binder-free electrodes for supercapacitor applications. In the optimized conditions, the unique Co–Ni–Zn–O@NiWO₄ electrode exhibits an excellent areal capacitance of 9.31 (2909.9 F g⁻¹) F cm⁻² at a current density of 2.5 mA cm⁻² and an outstanding rate capability of 65.7% up to the current density of 60 mA cm⁻². In addition, Fe₂O₃-CNTs@GF is prepared using chemical vapor deposition (CVD) followed by the hydrothermal method. Under the optimized conditions, Fe₂O₃-CNTs@GF shows a high areal capacitance of 812 (386.7 F g⁻¹) mF cm⁻² at 2 mA cm⁻² and excellent rate performance of 59.1%. Moreover, an asymmetric supercapacitor (ASC) device fabricated with Co–Ni–Zn–O@NiWO₄ as positive electrode and Fe₂O₃-CNTs@GF as negative electrode delivers an excellent specific capacitance of 229.7 F g⁻¹ at 0.5 A g⁻¹ and rate capability of 52.2% up to 16 Ag^-1. The as-fabricated device also exhibits an ultra-high energy density of 81.6 W h kg⁻¹ and outstanding capacitance retention of 93.1% up to 10,000 cycles. Due to these excellent supercapacitive properties, as-fabricated ASC device may be used in energy storage application.