Redox-active electrolyte-based MnWO4//AC asymmetric supercapacitors

Abstract

Finding supercapacitive materials with high energy and power densities has attracted signi cant interest in recent years. Herein, we are reporting layered MnWO 4 nanostructure for supercapacitor applications. MnWO 4 //AC asymmetric cell was fabricated by using hydrothermally synthesized MnWO 4 nanostructure as a cathode and activated carbon as an anode. Prior to device fabrication, the structural and electrochemical properties of MnWO 4 were thoroughly studied. MnWO 4 //AC asymmetric cell with KOH electrolyte showed speci c capacitance and energy density of 90 F/g (at 1 mA/cm 2) and 51 Wh/kg, respectively. Upon addition of redox-active KI into KOH, both the speci c capacitance and energy density were signi cantly enhanced (144 F/g and 90 Wh/Kg, respectively). The enhanced electrochemical properties of MnWO 4 //AC asymmetric cell can be attributed to the high-speed solution-phase Faradic reactions contributed by KI redox species in the KOH electrolyte.

Perspectives on Working Voltage of Aqueous Supercapacitors

“…When redox active couple dissolved in the electrolyte, faradaic reaction can be introduced into electrode materials to provide additional pseudocapacitance, enhancing supercapacitors charge storage capacity. [ 84–86 ] Furthermore, redox potentials of redox active couple approaching the water decomposition voltages is considered more promising additives. [ 87 ] Thanks to the additive takes precedence over water molecules oxidation and/or reduction, protecting solvent water from decomposition, appropriately broadening the safe working voltage window.…”