Inverting the Triiodide Formation Reaction by the Synergy between Strong Electrolyte Solvation and Cathode Adsorption for Lithium-Oxygen Batteries.

An exceptionally strong solvation effect of dimethyl sulfoxide (DMSO) on I is identified by the largest shift observed so far of the I Raman peak with respect to I vapor and by elongated I-I bond lengths in first-principles molecular-dynamics simulations. This effect together with strong binding by an RuO surface to I is found to invert the direction of the reaction I +I ⇌I to the left-hand side. Inspired by this finding, we prepared a Li-O battery with the Li/DMSO+LiI/RuO structure. The synergic action of DMSO and RuO on I is found to suppress the shuttle effect of the redox mediator (RM) by anchoring I molecules, the oxidation product of the RM. Significantly enhanced stability is demonstrated over 100 cycles at charging voltage below 3.65 V.