Redox Mediator with the Function of Intramolecularly Disproportionating Superoxide Intermediate Enabled High-Performance Li–O2 Batteries

The large charge overpotential and poor cycling stability triggered by sluggish Li 2 O 2 oxidation kinetics and severe superoxide-related side reactions greatly restrict the development and application of lithium–oxygen batteries. Finding out high-efficiency catalysts that can effectively facilitate a highly reversible formation/decomposition of lithium peroxide is still a crucial challenge in the field of Li–O 2 batteries. Herein, a soluble catalyst of 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) that can promote highly reversible formation and decomposition of Li 2 O 2 during discharge and charge processes is reported for the first time. During discharge, it can capture and couple two LiO 2 intermediates via its sulfonate and ammonium ions, and induce the intramolecular disproportionation reaction to produce Li 2 O 2 through ionic microenvironment, which not only prompts the solution-phase growth of Li 2 O 2 , but also restricts the reactivity of LiO 2 intermediate, thus significantly alleviating the electrode surface passivation issue and suppressing the superoxide-related side reactions. During charge, it can quickly transport electrons between the electrode and Li 2 O 2 by serving as a new kind of redox mediator (RM), thus greatly facilitating the Li 2 O 2 oxidation kinetics. As a result, the Li–O 2 batteries that incorporate ABTS exhibit outstanding electrochemical performance, low charge overpotential, high discharge capacity, and high cycling stability.