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

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.