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

Abstract 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.