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 2 is identified by the largest shift observed so far of the I 2 Raman peak with respect to I 2 vapor and by elongated I−I bond lengths in first‐principles molecular‐dynamics simulations. This effect together with strong binding by an RuO 2 surface to I 2 is found to invert the direction of the reaction I − +I 2 ⇌I 3 − to the left‐hand side. Inspired by this finding, we prepared a Li–O 2 battery with the Li/DMSO+LiI/RuO 2 structure. The synergic action of DMSO and RuO 2 on I 2 is found to suppress the shuttle effect of the redox mediator (RM) by anchoring I 2 molecules, the oxidation product of the RM. Significantly enhanced stability is demonstrated over 100 cycles at charging voltage below 3.65 V.