TEMPO-Ionic Liquids as Redox Mediators and Solvents for Li–O₂ Batteries

Effective Li–O₂ batteries require additives to suppress the side reactions and the increase in charge potential at the oxygen cathode, which leads to an inevitable battery failure. In this study, two families of new 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-substituted imidazolium ionic liquids (TEMPOImILs) were synthesized, and their properties were examined to determine the optimal structures that function as both solvents and redox mediators in Li–O₂ batteries. Comparison of the characteristics revealed that batteries with TEMPOImILs bearing a hydrogen rather than a methyl substituent in the 2-position of the imidazole moiety had a longer cycle life, whereas the length of the alkyl chain connecting the imidazole ring and 4-hydroxy-TEMPO did not have any substantial effect on the battery performance.