Laser crystallized sandwich-like MXene/Fe3O4/MXene thin film electrodes for flexible supercapacitors

Abstract For applications in portable electronics and miniaturized energy storage devices, MXene films derived from MXene inks can be provided as promising electrodes for thin film supercapacitors. Hence, to improve the areal capacitance of MXene films is necessary for pursuing high energy density. Introduction of transitional metal oxides (TMOs) layers into MXene electrodes obviously enhances the areal capacitance since of the extra pseudocapacitance induced by the surface/near surface redox reactions. The severe oxidation of MXene in combination with TMOs, however, hinders the effective improvements in capacitance. Laser crystallization process can effectively alleviate the oxidation of MXene when TMOs is prepared due to the high temperature localization and ultrafast reaction speed. Here, a sandwich-like MXene/Fe3O4/MXene film with a porous Fe3O4 layer is successfully prepared on a flexible Ni tape, showing an excellent electrochemical performance. In 1 M Li2SO4 aqueous electrolyte, the sandwich-like electrode demonstrates 46.4 mF cm−2 at the current density of 0.5 mA cm−2. The as-constructed symmetric all-solid-state device displays an energy density of 0.970 μWh cm−2 at a power density of 0.176 mW cm−2 along with a good cycling stability. This work opens up a new opportunity for modifying MXene films as electrodes for high-performance thin film supercapacitors.