Capacitive behaviour of MnF 2 and CoF 2 submicro/nanoparticles synthesized via a mild ionic liquid assisted route
Abstract Submicro /nano sized MnF 2 rods and hierarchical CoF 2 cuboids are respectively synthesized via a facile precipitation method assisted by ionic liquid under a mild condition. The as prepared MF 2 (M Mn, Co) submicro/nanoparticles exhibit impressive specific capacitance in 1.0 M KOH aqueous solution, especially at relatively high current densities, e.g. 91.2, 68.7 and 56.4 F g 1 for MnF 2 and 81.7, 70.6 and 63.0 F g 1 for CoF 2 at 5, 8 and 10 A g 1 respectively. The mechanism of striking capacitance of MF 2 is clarified on the basis of analysing the cycled electrodes by different characterization techniques. Such remarkable capacitance is ascribed to the redox reactions between MF 2 and MOOH in aqueous alkaline electrolytes, which can not be obtained in aqueous neutral electrolytes. This study for the first time provides direct evidences on the pseudocapacitance mechanism of MF 2 in alkaline electrolytes and paves the way of application of transition metal fluorides as electrodes in supercapacitors.