Reactivity of the ionic liquid Pyr₁₄TFSI with superoxide radicals generated from KO₂or by contact of O₂with Li₇Ti₅O₁₂

Ionic liquids are attractive candidates as electrolyte solvents for Li-O₂cells, primarily due to their low volatility, high anodic stability, and low flammability. Specifically, the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr₁₄TFSI) has attracted considerable attention thanks to its electrochemical and chemical stability. In this work, we demonstrate via our recently developed UV-Vis screening method that Pyr₁₄TFSI unfortunately reacts with the superoxide radical (O₂^•-) which is produced during the discharge of Li-O₂cells. To clarify the reaction mechanism of O₂^•- with Pyr₁₄TFSI, we take advantage of the recently described formation of O₂^•- upon contact between lithiated lithium titanate (LTO) and O₂to produce a sufficient amount of degradation products from the reaction of Pyr₁₄TFSI with O₂^•- that can be detected by NMR. Furthermore, we validate this new screening method for solvent decomposition by superoxide radicals by investigating the behavior of lithiated LTO in contact with O₂using RRDE voltammetry.