A pH dependent high voltage aqueous supercapacitor with dual electrolytes

Abstract

Improving the energy density without compromising the power capability is a classical challenge for electrochemical capacitors. Since energy is quadratically related to voltage by 1/2(Capacitance)(Voltage)2 the most beneficial strategy to boost the energy density is to target the working voltage window. However, expanding the voltage window beyond 1.23 V in aqueous system is thermodynamically challenged due to parasitic water splitting reactions. We show that the parasitic chemistry can be arrested by decoupling the direct acid-alkali chemistry, and the voltage window in aqueous supercapacitors can be expanded with energy boosting up to ∼230%.