Interfacial aspects induced by saturated aqueous electrolytes in electrochemical capacitor applications

Abstract

This paper reports on the “water-in-salt” electrolyte concept, applying CsF as an ionic compound in a symmetric electrochemical capacitor. CsF has been selected as a highly soluble inorganic salt that allows the amount of free water in the electrolyte to be significantly reduced. Several activated carbons with various microtextural parameters have been investigated to identify the most suitable electrode material. A wide range of electrolyte concentrations have been investigated in terms of conductivity, pH and viscosity. The electrochemical characteristics have been determined for three electrolyte concentrations and indicate critical changes in the electrolyte physicochemical properties. It seems that ion-solvent interactions, residual water content, electrolyte viscosity and charging/discharging conditions remarkably affect the electrochemical performance of capacitors with elevated concentrations of electrolyte. In addition to the capacitance increase, a positive impact on the self-discharge and charge/discharge efficiency has been observed for higher CsF concentrations.