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 Pyrj(4)TFSI unfortunately reacts with the superoxide radical (O-2(center dot-)) which is produced during the discharge of Li-O-2 cells. To clarify the reaction mechanism of O-2(center dot-) with Pyri4TFS I, we take advantage of the recently described formation of O-2(center dot-) 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(center dot-) 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 Lb O in contact with O-2 using RRDE voltammetry. (C) The Author(s) 2015. Published by ECS. All rights reserved.