A redox shuttle to facilitate oxygen reduction in the lithium air battery

Abstract

A novel design of the non-aqueous lithium air cell is presented with a demonstration of a new reaction concept, involving a soluble redox shuttle to catalyse oxygen reduction. In principle, this can relieve the requirement for fast diffusion of molecular oxygen from the air interface to the positive electrode. To demonstrate this concept, ethyl viologen ditriflate was dissolved in BMPTFSI, reduced at a carbon electrode and regenerated by aspiration with oxygen. Useful shuttle behaviour, confirmed by several reduction–oxidation cycles, was observed in the case where the electrolyte contained at least 0.3M lithium salt. The beneficial effect of the salt was attributed to its critical role in converting superoxide, which would otherwise destroy the shuttle, into the more desirable product of oxygen reduction, lithium peroxide.