Decorating nanoporous ZIF-67-derived NiCo2O4 shells on a Co3O4 nanowire array core for battery-type electrodes with enhanced energy storage performance

Abstract

Particle-shaped metal–organic framework-derived metal oxides almost dominate the applications for energy storage. However, they always suffer from agglomeration and terrible internal resistance, which reduce the surface area of active materials, ion diffusion and charge transfer efficiency during the charge–discharge process. Constructing metal–organic framework-derived core–shell nanostructures is a promising route to overcome this obstacle. In this work, a layer of ZIF-67-derived nanoporous NiCo₂O₄ nanoflakes was perfectly decorated on a Co₃O₄ nanowire array to build up a core–shell nanowire array architecture. Due to the unique structure that facilitates ion diffusion and charge transfer but without losing the high surface area, the resulting ZIF-67-derived core–shell nanostructure exhibits 3.37 C cm⁻² of area capacity at a current density of 4 mA cm⁻² as well as good rate capability and durability. In addition, the assembled asymmetric supercapacitor delivers a high specific energy density of 50.6 W h kg⁻¹ at a specific power density of 856 W kg⁻¹. Even at a high power density of 11.1 kW kg⁻¹, the device still has an energy density of 30.2 W h kg⁻¹. The strategy proposed here provides a good way to synthesize metal–organic framework-derived metal oxide nanostructures, and the as-prepared electrodes will be excellent materials for energy storage and other applications.