Bifunctional electrolyte additive MgI2 for improving cycle life in high-efficiency redox-mediated Li–O2 batteries

Here, MgI2 is introduced as a bifunctional self-defense redox mediator into dimethyl sulfoxide-based Li-O-2 batteries. During charging, I- is first oxidized to I-3(-), which facilitates the decomposition of Li2O2, and thus reduces overpotential. In addition, Mg2+ spontaneously reacts with the Li anode to form a very stable SEI layer containing MgO, which can resist the synchronous attack by the soluble I-3(-) and improve the interface stability between the Li anode and the electrolyte. Therefore, a Li-O-2 battery containing MgI2 exhibits an extended cycling life span (400 cycles) and a quite low overpotential (0.6 V).