Highly Reversible O<inf>2</inf> Conversions by Coupling LiO<inf>2</inf> Intermediate through a Dual-Site Catalyst in Li-O<inf>2</inf> Batteries

Abstract

The reduction of O2 to solid Li2O2 on discharge and the reverse oxidation of Li2O2 to O2 on recharge are the essential processes to determine the performance of Li-O2 batteries. The discovery of effective catalysts with a favorable Li2O2 formation/decomposition mechanism is vital for the development of high-performance Li-O2 batteries. Here, a soluble catalyst of iodosylbenzene (PhIO) that can offer a highly reversible O2 conversion is reported for the first time. Benefiting from its ability to capture and couple the LiO2 intermediate, which is endowed by its polarized I3+=O2− bond where the I atom and O atom can serve as a Lewis acidic site and basic site (dual site) to interact with O2− and Li+, respectively, the formation and decomposition of Li2O2 by a one-electron pathway can be effectively promoted, thus greatly improving the electrode surface passivation issue and the reaction kinetics. In addition, the side reactions caused by the traditional high-reactive LiO2 intermediate can also be effectively suppressed by forming a series of low-reactive intermediates (LiO2-3PhIO, (LiO2)2-4PhIO, and Li2O2-4PhIO) instead. Consequently, the PhIO-catalyzed Li–O2 batteries exhibit a low overpotential, a large capacity, and a good cyclability.