Nickel-Cobalt Layered Double Hydroxide Nanowires on Three Dimensional Graphene Nickel Foam for High Performance Asymmetric Supercapacitors

In this paper, three dimensional reduced graphene oxide skeleton onto nickel foam (3D RGO NF) was fabricated by a facile dip-coating method combined with alkaline reduction. The as-prepared skeleton was used as a substrate to immobilize Ni-Co layered double hydroxide (Ni-Co LDH) with special morphology of nanowires to effectively prevent the agglomeration of material. The Ni-Co LDH/3D RGO NF electrode exhibited an enhanced specific capacitance of 1054 F g−1 compared with Ni-Co LDH/NF, excellent rate capability (60% capacitance retention with a ten-fold increase in current density) as well as long cyclic life (95% capacity retention after 2000 cycles). In addition, an aqueous asymmetric supercapacitor was composed of Ni-Co LDH/3D RGO NF as positive electrode and activated carbon as negative electrode, which exhibited a specific capacitance of 108.7 F g−1 at 2 mA cm−2 in a potential range from 0 to 1.6 V; it showed maximum energy density of 38.6 Wh kg−1 at 69.5 W kg−1. Moreover, the Ni-Co LDH/3D RGO NF//AC has an outstanding cycling stability (about 70% capacitance retention after 4000 cycles), which makes it a potential candidate for electrochemical energy storage devices.

The Ni-Co LDH nanowires, directly grown on three-dimensional graphene nickel foam as binder free electrode with enhanced electrochemical performance, have been successfully fabricated through a three-step method. Meanwhile, an asymmetric supercapacitor device based on Ni-Co/3D ROG NF and active carbon as positive electrode and negative electrode respectively, exhibits a maximum energy density of 38.6 W h kg−1 and a maximum power density of 7231.6 W kg−1, demonstrating its potential utilization for energy storage-conversion applications.220