Bifunctional electrolyte additive MgI 2 for improving cycle life in high-efficiency redox-mediated Li-O 2 batteries.

Here, MgI 2 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 Li 2 O 2 , and thus reduces overpotential. In addition, Mg 2+ 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 MgI 2 exhibits an extended cycling life span (400 cycles) and a quite low overpotential (0.6 V).