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

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 FeF 3 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.