Metal-Organic Framework Templated 3D Hierarchical ZnCo O @Ni(OH) Core-Shell Nanosheet Arrays for High-Performance Supercapacitors.

Designing core-shell electrode materials with desired components and architectures is a promising strategy for boosting electrochemical performance. Here, three-dimensional hierarchical ZnCo O @Ni(OH) core-shell nanosheet arrays have been successfully fabricated on a Ni foam substrate, in which the porous ZnCo O nanosheet "core" as the conductive scaffold was synthesized by a metal-organic framework (MOF)-templated method, and the ultrathin Ni(OH) nanoflakes "shell" with rich active sites were grafted on the ZnCo O nanosheet through a hydrothermal treatment. When directly used as a free-standing electrode for supercapacitor, these hierarchical ZnCo O @Ni(OH) core-shell nanosheet arrays exhibited a high capacitance of 3063.2 mF cm (1021.1 F g ) at the current density of 1 mA cm . This electrode significantly outperformed individual Ni(OH) or ZnCo O nanosheet arrays, benefiting from the robust core-shell arrays on Ni foam with good electrical conductivity and abundant active sites, as well as the synergetic effect between MOF-derived porous ZnCo O "core" and the ultrathin Ni(OH) "shell". Moreover, the assembled ZnCo O @Ni(OH) //activated-carbon asymmetric supercapacitor displayed excellent energy and power densities (maximum of 40.0 Wh kg and 8.02 kW kg ) and superior cycling stability of 98.4 % retention with 91.2 % coulombic efficiency over 5 000 cycles at 10 A g .