Core-shell 2D/2D FeCo2O4@Ni(OH)2 nano-on-microsheet array architecture for excellent asymmetric supercapacitor performance

Abstract

Core-shell designed electrode architectures with favorable material components are a promising approach to enhance electrochemical performance. Herein, binder-free 2D/2D FeCo2O4@Ni(OH)2 core–shell architectures were successfully grown on a Ni-foam (NF) substrate, where the FeCo2O4 microsheets were hydrothermally processed following the electro-grafting of Ni(OH)2 nanosheets as a “shell” around a FeCo2O4 “core.” These core–shell array architectures were utilized as a discrete electrode system; they exhibited a high specific capacitance of 1944 F g−1 at a current density of 5 A g−1, which is better than the performance of individual FeCo2O4 and Ni(OH)2. This improved performance was attributed to the synergistic effects of the robust core–shell array architectures developed over the NF substrate as well as the enhanced electrical conductivity through electroactive sites at the interface while maintaining the structural integrity of the Ni(OH)2 shell. In addition, the two-electrode device was assembled constituting a FeCo2O4@Ni(OH)2 ΙΙ activated carbon asymmetric supercapacitor, resulting in a maximum energy density of 136 W h kg−1 and power density of 8500 W kg−1, with 78% capacitance retention and 93% coulombic efficiency over 5000 cycles at a current density of 8 A g−1. These results validate the effectiveness of this approach for improving the performance of energy storage devices.