Ultrathin Ni-MOF nanosheet coated NiCo2O4 nanowire arrays as a high-performance binder-free electrode for flexible hybrid supercapacitors

Abstract

Metal–organic frameworks (MOFs) as a kind of novel electrode material for energy storage has attracted increasing attention. However, their poor conductivity and difficulties in directly grown on the current collector largely thwart their maximum performance. Herein, an effective strategy was developed to increase the overall electrical conductivity and active surface area of MOFs by implanting conductive NiCo2O4 nanowires on carbon cloth as the interconnected anchors for in situ growth of MOFs nanosheets. The as-synthesized NiCo2O4@Ni-MOF electrode delivers an ultra-high areal capacitance of 7.23 F cm−2 at a current density of 5 mA cm−2, with an exceptional rate capability (5.04 F cm−2 at a very high current density of 30 mA cm−2). Meanwhile, NiCo2O4 NWAs are used as the strain buffer supports for preparing core−shell NiCo2O4@PPy nanorod arrays as a negative electrode. As a result, an HSC is successfully assembled by using the NiCo2O4@Ni-MOF and NiCo2O4@PPy as electrodes, achieving both high volumetric capacitance and energy density. This study presents a versatile strategy for effectively fabricating MOFs based binder-free energy storage materials for future portable and wearable electronic devices.