Nanoribbon-like NiCo2O4/reduced graphene oxide nanocomposite for high-performance hybrid supercapacitor

Nanoribbon-like NiCo2O4/reduced graphene oxide (RGO) nanocomposites were in situ prepared by an oxalate-assisted hydrothermal method. The various RGO contents (10, 20, and 30 wt%) were added during oxalate precipitation. The plate-like shape of oxalate precipitates was thermally decomposed into the nanoribbon-like morphology in which the NiCo2O4 nanoparticles were aligned in one direction. A network of pores between nanoparticles (∼21–14 nm) is caused by exhausting a large volume of gases during calcination at 450 °C. The specific capacity increases from 418 to 758 C g−1 at 1 A g−1 with the amounts of RGO up to 30 wt%. Furthermore, the NiCo2O4/RGO nanocomposites exhibit higher rate capability than the pristine NiCo2O4 nanoparticles. The NiCo2O4-30 wt% RGO//active carbon hybrid capacitor has a high energy density of 61 Wh kg−1 at the current density of 1 A g−1 and excellent cycling stability of 92% at 3 A g−1 after 5000 cycles.