Rapid synthesis of high-areal-capacitance ultrathin hexagon Fe2O3 nanoplates on carbon cloth via a versatile molten salt method

Earth abundant and environmentally benign iron oxides are ideal candidates for electrochemical energy storage. We report herein a rapid (within 1 min), facile one-step molten salt method to homogeneously coat various metal oxides of Fe2O3, Mn3O4, Co3O4, NiO, CuO, ZnO,etc.on carbon cloth (CC) for supercapacitor applications. In particular, ultra-thin Fe(2)O(3)nanoplates coated on CC (Fe2O3@CC) connected in series to form a porous structure. Nanoplates have a larger specific surface area and hence more active sites for electrochemical reactions and the porous architecture effectively relieves the volume expansion of Fe(2)O(3)during charging/discharging, which avoids the structural collapse and benefits the cycling stability. As a result, the Fe2O3@CC exhibits a large areal capacitance of 4175.7 mF cm(-2)at a scan rate of 2 mV s(-1)in -1.0-0 Vvs.Hg/HgO, thanks also to the carbon cloth substrate activated simultaneously by the molten salt. The Fe2O3@CC electrode is especially appropriate for high current density (over 10 mA cm(-2)) charging/discharging. A Mn3O4@CC positive electrode is also synthesisedviathe molten salt method, and then coupled with the Fe2O3@CC negative electrode to assemble a 2 V high-voltage asymmetric supercapacitor (ASC) in 6 M KOH aqueous electrolyte. The Mn3O4@CC//Fe2O3@CC ASC delivers a high energy density of 2.91 mW h cm(-3)at a power density of 25 mW cm(-3)and a high power density of 278 mW cm(-3)with a corresponding energy density of 1.25 mW h cm(-3). An excellent cycling performance of 96% capacitance retention after 10 000 cycles at a high current density of 10 mA cm(-2)is also recorded. The facile, versatile synthetic method and resultant high-performance electrodes are promising for practical applications in flexible electrochemical energy storage.