Stabilizing NiCo2O4 hybrid architectures by reduced graphene oxide interlayers for improved cycling stability of hybrid supercapacitors

Abstract

We demonstrate nickel cobaltite@reduced graphene oxide (NiCo₂O₄@rGO) hybrid architectures directly deposited on nickel-foam (NF). The rGO interlayers restrict the growth of NiCo₂O₄ nanoneedles into smaller and thinner dimensions compared to NiCo₂O₄ without rGO layers, providing kinetic and structural stability for hybrid architectures. Accordingly, the NiCo₂O₄@rGO hybrid on NF achieves a specific capacitance of 1427 F g⁻¹ at 8 A g⁻¹, a coulombic efficiency of 96.2%, and a capacitance retention of 83.8% over 10 000 cycles, which are greater than 1036 F g⁻¹, 89.1%, and 40.8% of NiCo₂O₄ on NF in an aqueous 2 M KOH electrolyte. In order to enlarge the potential window of the aqueous system, hybrid supercapacitors (HSCs) are configured using the NiCo₂O₄@rGO hybrid on NF as a positive electrode and rGO on NF as a negative electrode. The HSCs exhibit a good cycling stability of 81.1% over 10 000 cycles, delivering maximum energy and power densities of 25.24 W h kg⁻¹ and 21.42 kW kg⁻¹.