Nickel cobalt hydroxide/reduced graphene oxide/carbon nanotubes for high performance aqueous asymmetric supercapacitors

Highlights: • Ni-Co hydroxide/rGO/CNTs hybrids are prepared by the vacuum filtration method. • Asymmetric supercapacitor is prepared with as-prepared materials and active carbon. • The supercapacitor shows high specific capacitance and excellent cycling stability. In this work, the hybrid nanostructures composed of Ni-Co hydroxide, reduced graphene oxide (rGO) and carbon nanotubes (CNTs) are successfully synthesized and used as a self-supported electrode for supercapacitors. It is found that the hybrid shows a big capacity of 1093 F g⁻¹, excellent rate capability, and superior cycle life (100% capacity maintain after 5000 cycles). One asymmetric supercapacitor (ASC) is developed using Ni-Co hydroxide/rGO/CNTs as positive material and active carbon as negative material. This ASC displays a maximum energy density of 34.7 Wh kg⁻¹ at a high power density of 1.55 kW kg⁻¹ and still keeps 20.7 Wh kg⁻¹ at 15.5 kW kg⁻¹. Moreover, it displays remarkable cycle life with 112.8% capacity retention after 10000 cycles. Such asymmetric supercapacitor demonstrates great potential for practical application in energy storage devices.