Novel Core–Shell FeOF/Ni(OH)2 Hierarchical Nanostructure for All‐Solid‐State Flexible Supercapacitors with Enhanced Performance

Abstract

Well‐controlled core–shell hierarchical nanostructures based on oxyfluoride and hydroxide are for the first time rationally designed and synthesized via a simple solvothermal and chemical precipitation route, in which FeOF nanorod acts as core and porous Ni(OH)2 nanosheets as shell. When evaluated as electrodes for supercapacitors, a high specific capacitance of 1452 F g−1 can be obtained at a current density of 1 A g−1. Even as the current density increases to 10 A g−1, the core–shell hybrid still reserves a noticeable capacitance of 1060 F g−1, showing an excellent rate capacity. Furthermore, all‐solid‐state flexible asymmetric supercapacitor based on the FeOF/Ni(OH)2 hybrid as a positive electrode and activated carbon as a negative electrode shows high power density, high energy density, and long cycling lifespan. The excellent electrochemical performance of the FeOF/Ni(OH)2 core–shell hybrid is ascribed to the unique microstructure and synergistic effects. FeOF nanorod from FeF3 by partial substitution of fluorine with oxygen behaves as a low intrinsic resistance, thus facilitating charge transfer processes. While the hierarchical Ni(OH)2 nanosheets with large surface area provide enough active sites for redox chemical reactions, leading to greatly enhanced electrochemical activity. The well‐controllable oxyfluoride/hydroxide hybrid is inspiring, opening up a new way to design new electrodes for next‐generation all‐solid‐state supercapacitors.