Promoting Li-O2 Batteries With Redox Mediators

Abstract

Li-O₂ batteries have a high theoretical specific energy, 3500 Wh kg^-1 ; however, its practical capacity is far below this value and limited by the passivation with the insulating discharge product Li₂ O₂ . The nonconductive nature of Li₂ O₂ also impedes the charging process, leading to a low coulombic efficiency and high overpotential on charge even at a moderate rate. To address these challenges, redox mediators could be used both during discharge and charge to transfer electrons between O₂ /electrode surface or Li₂ O₂ /electrode surface to overcome the passivation of Li₂ O₂ , which would facilitate the discharge and charge process. The capacity and current density were significantly improved using the redox mediators, thus representing a promising strategy to achieve a high energy density for Li-O₂ batteries.

Keywords: Li-O2; batteries; energy storage; redox mediators.