Highly Reversible O2 Conversions by Coupling LiO2 Intermediate through a Dual-Site Catalyst in Li-O2 Batteries

The reduction of O 2 to solid Li 2 O 2 on discharge and the reverse oxidation of Li 2 O 2 to O 2 on recharge are the essential processes to determine the performance of Li-O 2 batteries. The discovery of effective catalysts with a favorable Li 2 O 2 formation/decomposition mechanism is vital for the development of high-performance Li-O 2 batteries. Here, a soluble catalyst of iodosylbenzene (PhIO) that can offer a highly reversible O 2 conversion is reported for the first time. Benefiting from its ability to capture and couple the LiO 2 intermediate, which is endowed by its polarized I 3+ O 2− bond where the I atom and O atom can serve as a Lewis acidic site and basic site (dual site) to interact with O 2 − and Li + , respectively, the formation and decomposition of Li 2 O 2 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 LiO 2 intermediate can also be effectively suppressed by forming a series of low-reactive intermediates (LiO 2  3PhIO, (LiO 2 ) 2  4PhIO, and Li 2 O 2  4PhIO) instead. Consequently, the PhIO-catalyzed Li–O 2 batteries exhibit a low overpotential, a large capacity, and a good cyclability.