Promoting Li-O2 Batteries With Redox Mediators.

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.