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-O-2) 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-O-2 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 (CMFG-Co/CoO) with a continuous conductive network and elastic properties is used as binder-free oxygen electrode for Li-O-2 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 g(total)(-1)), 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 approximate to 7800 mAh g(total)(-1) and outstanding rate capability, exhibiting the great potential for the application in Li-O-2 batteries.