Construction of hierarchical and core-shell structured Co3O4@MnO2@NiO nanoarrays as binder-free electrodes for high-performance asymmetric supercapacitors

Abstract

Remarkable specific capacity and excellent cycle stability of the electrode materials are vital prerequisites for their practical applications. Transition metal oxide-based materials have been extensively explored and employed as electrode materials for asymmetric supercapacitors. However, the actual specific capacitances of these materials are still far lower than their theoretically predicted values. Thus, it is essential to design transition metal oxide with novel structures in order to maximize their specific capacity and cycle stability. Herein, we constructs hierarchical and core-shell structured Co3O4@MnO2@NiO arrays on nickel foam (Co3O4@MnO2@NiO/NF) through a three-step hydrothermal-annealing process, and use them as a direct binder-free electrode for pseudocapacitors. The as-prepared layered hierarchical Co3O4@MnO2@NiO/NF electrode exhibits an impressive specific capacitance of 6.42 F cm−2 (2054 F g−1) at 1 mA cm−2 in a three-electrode configuration, which is largely because of the synergistic effect among Co3O4, MnO2 and NiO. Furthermore, the 3D nanoarray structure can provides a larger specific surface area, a rapid diffusion path, and more active sites that allow to achieve improved electrochemical performance. In addition, the assembled Co3O4@MnO2@NiO/NF//AC/NF ASC all-solid-state asymmetric supercapacitor (ASC) displays a remarkable energy density (30.7 Wh kg−1 at 400.4 W kg−1), demonstrating that this all-solid-state ASC owns considerable potential for practical applications in such high-performance energy storage devices.