Probing physicochemical properties of a mixed-anion protic ionic liquid based on [TFSI] and [NO3]

Journal article, 2025

Mixtures comprising two protic ionic liquids, both having the same cation but different anions, 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide and 1-ethylimidazolium nitrate, were systematically investigated as a function of composition, here defined by the molar fraction of bis(trifluoromethylsulfonyl)imide anion present in the mixture. To assess their potential as electrolytes for lithium-ion batteries, samples containing lithium bis(trifluoromethanesulfonyl)imide salt (0.2 M) were also studied. In order to provide a thorough characterization, phase behavior, density, viscosity, ionic conductivity, and intermolecular interactions were all analyzed. This work provides insights into the structure–property correlation in these mixed ionic liquid systems and their suitability for energy storage applications.