Description:
<jats:title>Abstract</jats:title><jats:p>Herein we report a systematic investigation of the chemical and physical properties of acetonitrile‐based electrolytes that contained the salts tetraethylammonium tetrafluroroborate (Et<jats:sub>4</jats:sub>NBF<jats:sub>4</jats:sub>), tetraethylammonium bis(trifluoromethanesulfonyl)‐ imide (Et<jats:sub>4</jats:sub>NTFSI), 1‐butyl‐1‐methylpyrrolidinium tetrafluoroborate (Pyr<jats:sub>14</jats:sub>BF<jats:sub>4</jats:sub>), or 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr<jats:sub>14</jats:sub>TFSI). The ionic conductivity, viscosity, density, and electrochemical stability windows of these electrolytic solutions have been considered in detail. From these results, the electrolyte Et<jats:sub>4</jats:sub>NTFSI (1 mol dm<jats:sup>−3</jats:sup>) in ACN appeared to display a promising set of properties that allow the realization of ACN‐based electrochemical double‐layer capacitors able to display stable behavior at 3.1 V.</jats:p>