EQCM study of Room Temperature Ionic Liquids Based on Perfluoroethyltrifluoroborate with and without Li[BF₄]

Abstract

The electrochemical behavior of room temperature ionic liquids (RTILs) based on perfluoroethyltrifluoroborate ([C₂F₅BF₃]⁻) was investigated with and without Li[BF₄]. The plating-stripping corresponding to the peak of lithium could be observed on a nickel electrode in the RTIL based on a quaternary ammonium cation. However, the addition of ca. 0.4 mol dm⁻³ of Li[BF₄] had almost no effect on the cathodic limit potential of EMI[C₂F₅BF₃]. The results of electrochemical quartz crystal microbalance (EQCM) measurements in propylene carbonate solution containing ca. 2.0 mol dm⁻³ of RTILs and 20 mmol dm⁻³ of LiBF₄ indicate that a solid-electrolyte interface formation, which inhibits the reductive decomposition of the EMI cation, was not significant in EMI[C₂F₅BF₃] with the addition of Li[BF₄].