Enhanced cycle stability of aprotic Li-O2 batteries based on a self-defensed redox mediator

LiBr as a promising redox mediator (RM) has been applied in Li-O2 batteries to improve oxygen evolution reaction kinetics and reduce overpotentials. However, the redox shuttle of Br3 - can induce the unexpected reactions and thus cause the degradation of LiBr and the corrosion of Li anode, resulting in the poor cyclability and the low round-trip efficiency. Herein, MgBr2 is firstly employed with dual functions for Li-O2 batteries, which can serve as a RM and a SEI film-forming agent. The Br- is beneficial to facilitating the decomposition of Li2O2 and thus decreasing the overpotential. Additionally, a uniform SEI film containing Mg and MgO generates on Li anode surface by the in-situ spontaneous reactions of Mg2 + and Li anode in an O2 environment, which can suppress the redox shuttle of Br3 - and improve the inter-face stability of Li anode and electrolyte. Benefiting from these advantages, the cycle life of Li-O2 battery with MgBr2 electrolyte is significantly extended.(c) 2024 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.