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

ABSTRACT

An exceptionally strong solvation effect of dimethyl sulfoxide (DMSO) on I2 is identified by the largest shift observed so far of the I2 Raman peak with respect to I2 vapor and by elongated I-I bond lengths in first-principles molecular-dynamics simulations. This effect together with strong binding by an RuO2 surface to I2 is found to invert the direction of the reaction I- +I2 ⇌I3 - to the left-hand side. Inspired by this finding, we prepared a Li-O2 battery with the Li/DMSO+LiI/RuO2 structure. The synergic action of DMSO and RuO2 on I2 is found to suppress the shuttle effect of the redox mediator (RM) by anchoring I2 molecules, the oxidation product of the RM. Significantly enhanced stability is demonstrated over 100 cycles at charging voltage below 3.65 V.