Facile synthesis of carbon nanotube-supported NiO//Fe₂O₃ for all-solid-state supercapacitors

We have successfully prepared iron oxide and nickel oxide on carbon nanotubes on carbon cloth for the use in supercapacitors via a simple aqueous reduction method. The obtained carbon cloth–carbon nanotube@metal oxide (CC-CNT@MO) three-dimensional structures combine the high specific capacitance and rich redox sites of metal oxides with the large specific area and high electrical conductivity of carbon nanotubes. The prepared CC-CNT@Fe₂O₃ anode reaches a high capacity of 226 mAh·g⁻¹ at 2 A·g⁻¹ with a capacitance retention of 40% at 40 A·g⁻¹. The obtained CC-CNT@NiO cathode exhibits a high capacity of 527 mAh·g⁻¹ at 2 A·g⁻¹ and an excellent rate capability with a capacitance retention of 78% even at 40 A·g⁻¹. The all-solid-state asymmetric supercapacitor fabricated with these two electrodes delivers a high energy density of 63.3 Wh·kg⁻¹ at 1.6 kW·kg⁻¹ and retains 83% of its initial capacitance after 5000 cycles. These results demonstrate that our simple aqueous reduction method to combine CNT and metal oxides reveals an exciting future in constructing high-performance supercapacitors.