Advanced binder-free electrodes based on CoMnO@CoO core/shell nanostructures for high-performance supercapacitors.

Three-dimensional (3D) hierarchical CoMnO@CoO core/shell nanoneedle/nanosheet arrays for high-performance supercapacitors were designed and synthesized on Ni foam by a two-step hydrothermal route. The hybrid nanostructure exhibits much more excellent capacitive behavior compared with either the pristine CoMnO nanoneedle arrays alone or CoO nanosheets alone. The formation of an interconnected pore hybrid system is quite beneficial for the facile electrolyte penetration and fast electron transport. The CoMnO@CoO electrode can achieve a high specific capacitance of 1627 F g at 1 A g and 1376 F g at 10 A g. In addition, an asymmetric supercapacitor (ASC) was assembled by using the CoMnO@CoO core/shell hybrid nanostructure arrays on Ni foam as a positive electrode and activated carbon as a negative electrode in an aqueous 3 M KOH electrolyte. A specific capacitance of 125.8 F g at 1 A g (89.2% retention after 5000 charge/discharge cycles at a current density of 2 A g) and a high energy density of 44.8 W h kg was obtained. The results indicate that the obtained unique integrated CoMnO@CoO nanoarchitecture may show great promise as ASC electrodes for potential applications in energy storage.