The Influence of Anion-Cation Combinations on the Physicochemical Properties of Advanced Electrolytes for Supercapacitors and the Capacitance of Activated Carbons

This work represents a systematic study of four conductive salts and their influence on the physicochemical properties of propylene-carbonate-based electrolytes for electrochemical double-layer capacitors (EDLCs). State-of-the-art tetraethylammonium tetrafluoroborate is compared with tetraethylammonium bis(trifluoromethanesulfonyl) imide, N-butyl-N-methylpyrrolidinium tetrafluoroborate, and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide. By applying these salts, operating voltages of up to 3.5 V can be achieved while retaining a high performance. Furthermore, the influence of the conductive salts on the carbon-electrolyte interface is studied by comparing the electrochemical performance of five commercial porous carbons in the respective electrolytes. The choice of conductive salt has a great influence on the electrochemical performance and maximum operating voltage of an EDLC system, as well as on the specific capacitance of the chosen carbon material; this makes the choice of both materials crucial for successful EDLC design.