A Synergistic Catalytic Mechanism for Oxygen Evolution Reaction in Aprotic Li–O2 Battery

Abstract

The large polarization of a Li–O2 battery is derived from oxygen evolution reaction (OER) processe. To achieve a long-life Li–O2 battery with high round-trip efficiency, various catalysts have been extensively investigated for oxygen cathodes, especially for OER processes. Here, we designed an in situ growth of α-MnO2/RuO2 composite on a graphene nanosheet with a carbon-embedded structure as the cathode electrode for a Li–O2 battery. The synergistic catalytic effect between the α-MnO2 and RuO2 has significantly improved the OER kinetics. The fabricated Li–O2 battery can deliver a high reversible capacity of 2895 mAh/gcomposite with a low charge overpotential of 0.25 V (0.34 V lower than bare RuO2 cathode). The results revealed that more LiO2 intermediates formed when α-MnO2 was introduced into the RuO2 electrode during the oxidation of Li2O2. The facilitation of the initial Li extraction was confirmed by density functional theory (DFT) calculations, which shows that the α-MnO2 and RuO2 interfaces can stabilize the primary Li ions and Li2–xO2 intermediates, respectively. Subsequently, Li2–xO2 would be easily oxidized to O2 by RuO2 catalyst. With the synergy between α-MnO2 and RuO2, the initial delithiation process and O2 evolution are promoted simultaneously. By combining theoretic and experimental results, we proposed a synergistic catalytic mechanism for the OER processes.