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-O 2 cells, primarily due to their low volatility, high anodic stability, and low flammability. Specifically, the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr 14 TFSI) 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 Pyr 14 TFSI unfortunately reacts with the superoxide radical (O • − 2 ) which is produced during the discharge of Li-O 2 cells. To clarify the reaction mechanism of O • − 2 with Pyr 14 TFSI, we take advantage of the recently described formation of O • − 2 upon contact between lithiated lithium titanate (LTO) and O 2 to produce a sufficient amount of degradation products from the reaction of Pyr 14 TFSI with O • − 2 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 O 2 using RRDE voltammetry.