A multi-layered Fe₂O₃/graphene composite with mesopores as a catalyst for rechargeable aprotic lithium–oxygen batteries

Aprotic Li–O₂ batteries have attracted a huge amount of interest in the past decade owing to their extremely high energy density. However, identifying a desirable cathodic catalyst for this promising battery system is one of the biggest challenges at present. In this work, a multi-layered Fe₂O₃/graphene nanosheets (Fe₂O₃/GNS) composite with sandwich structure was synthesized using an easy thermal casting method, and served as a cathodic catalyst for aprotic Li–O₂ batteries. The aprotic Li–O₂ cell with the Fe₂O₃/GNS catalyst demonstrated a better reversibility, lower overpotential for oxygen evolution, and a higher Coulombic efficiency (close to 100%) than those of pure GNS. An excellent rate performance and good cycle stability were also confirmed. The results, characterized by ex and in situ methods, revealed that the dominant discharge product Li₂O₂ was decomposed below 4.35 V. This superior electrochemical performance is mainly attributed to the unique sandwich structure of the Fe₂O₃/GNS catalyst with mesopores, which can provide substantially more catalytic sites and prevent direct contact between carbon and Li₂O₂. (paper)