Enhancing the Performance of CoO as Cathode Catalyst for Li-O2 Batteries through Confinement into Bimodal Mesoporous Carbon

Abstract

Rechargeable Li-O2 batteries show great potential owing to the super high energy density. However, the poor kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) limits their practical application. The exploration of noble metals-free cathode catalysts with high catalytic activity on both ORR and OER is still a big challenge. Herein, CoO has been confined into bimodal mesoporous carbon frameworks (CoO@BMC) via a wet-chemistry impregnation approach and the performance of CoO@BMC as cathode catalyst for Li-O2 batteries has been largely improved. For comparison, CoO@CMK-3 composite has also been prepared. In comparison with bulk CoO, BMC and CoO@CMK-3, CoO@BMC based cathode shows a higher initial capacity (∼4000mAhg−1), much higher cycling stability, higher rate capability and lower overpotential,which can be largely attributed to the synergetic effect of CoO and hierarchical BMC on both ORR and OER. In addition, the formation and decomposition of Li2O2 and side products in the process of ORR and OER have also been analyzed and the results indicate that CoO@BMC nanocomposite can efficiently promote the decomposition of Li2O2 and even some side products of carbonates.