Structural Design of Oxygen Reduction Redox Mediators (ORRMs) Based on Anthraquinone (AQ) for the Li-O₂Battery

A series of oxygen reduction redox mediators (ORRMs) based on anthraquinone (AQ) has been developed for the lithium-oxygen (Li-O2) battery on the basis of a strategy to control the reduction potentials of the AQ moiety. It was found that the discharge capacity of the Li-O2 battery can be significantly improved by introducing electron-withdrawing groups into the AQ moiety, which can positively move the reduction potential of the AQ derivatives. By the introduction of two nitro (NO2) groups to the AQ moieties, an approximate 45-fold increase in the discharge capacity has been realized with a high discharge potential. Furthermore, we found that the water molecule from the oxygen environment exhibits a dramatic synergistic effect with the ORRM on the discharge capacity of the Li-O2 battery.