3D Hierarchical Co/CoO‐Graphene‐Carbonized Melamine Foam as a Superior Cathode toward Long‐Life Lithium Oxygen Batteries

Abstract

Carbon based materials as one promising cathode to accommodate the insoluble and insulating discharge products (Li2O2) for lithium oxygen (Li‐O2) batteries have attracted great attention due to their large energy density store ability compared with the other carbon‐free cathodes. However, the side reaction occurring at carbon/Li2O2 interfaces hinders their large‐scale application in Li‐O2 batteries. Herein, a simple and cost‐effective strategy is developed for the growth of core‐shell‐like Co/CoO nanoparticles on 3D graphene‐wrapped carbon foam using 3D melamine foam as the initial backbone. This unique 3D hierarchical carbonized melamine foam‐graphene‐Co/CoO hybrid (CMF‐G‐Co/CoO) with a continuous conductive network and elastic properties is used as binder‐free oxygen electrode for Li‐O2 batteries. Electrochemical and structural measurements show that a synergistic effect is observed between Co/CoO and graphene, where Li2O2 grows on the Co/CoO surfaces instead of the carbon surfaces at the initial discharge state (500 mAh ), indicating the reduced carbon/Li2O2 interfaces and alleviative side reactions during the electrochemical process. Importantly, the CMF‐G‐Co/CoO electrode can achieve greatly improved cycle life over the electrode without aid of the Co/CoO. Furthermore, it delivers a large capacity of ≈7800 mAh and outstanding rate capability, exhibiting the great potential for the application in Li‐O2 batteries.