Nano-dimensional iron tungstate for super high energy density symmetric supercapacitor with redox electrolyte

In present work, we have developed 2.0 V symmetric supercapacitor with rationally prepared iron tungstate (FeWO₄) nanoparticles as electrodes and redox-active electrolyte. It is revealed that the electrochemical performances of FeWO₄-system were significantly improved due to the addition of potassium iodide (KI) redox additive in conventional KOH electrolyte in terms of the specific capacitance and energy density. Notably, FeWO₄-based symmetric cell with KI-additive shown two-fold enhancement in specific energy (113 Wh/kg) compared with the cell with pristine KOH electrolyte (41.62 Wh/kg). Such an excellent enhancement is attributed to the improvement in the stability of existing KOH electrolyte by KI which influences the strength of OH bond in aqueous media and prevents the breakdown of electrolyte without adversely affecting the redox behavior and on contrary supporting the interactions at the higher potential to produce better results.