Redox-Active Water-in-Salt Electrolyte for High-Energy-Density Supercapacitors br

Abstract

In view of the need for environmental friend-liness and cost effectiveness, the enhancement of the energydensity of the aqueous supercapacitor is in high demand.Recently, concentrated aqueous electrolytes known as water-in-salt electrolytes (WiSEs) have attracted much attention due totheir broad electrochemical stability window (2-3 V) relative tothat of conventional dilute aqueous electrolytes (similar to 1V).Meanwhile, the development of redox-active electrolytes hasprovided a great opportunity to improve the capacitance of thesupercapacitors by providing an additional pseudocapacitivecontribution. Herein, a supercapacitor containing a dual redox-active (RA) WiSE is demonstrated that combines the benefits of the wide voltage window of the WiSE and the highcapacitance arising from the RA species, thus significantly amplifying the energy density of the supercapacitor. Moreover, thevoltage plateau arising from the simultaneous redox reactions can deliver a constant power output, representing a distinctiveand attractive alternative to the conventional aqueous supercapacitors.