Mesoporous Co-CoO@NC Micro-Disk Derived from ZIF-9 as Bifunctional Catalyst for Lithium-Oxygen Batteries

Metal and metal oxides are considered as effective catalysts owing to their excellent oxygen reduction and oxygen evolution reaction activity. However, their low electrical conductivity, the collapse of the structure during the cycles and agglomeration in thermal treatment, which can degrade the electrochemical properties, are still puzzles for researchers. Herein, we present a facile method to synthesize mesoporous N-doped carbon matrix modified with cobalt and cobalt oxide (Co-CoO@NC) micro-disk derived from zeolitic imidazolate frameworks, alleviating the agglomeration of the cobalt nanoparticles to form CoO with abundant oxygen vacancies and introducing nitrogen in the carbon matrix with strong metal-N-doped carbon bridging bonds. The porous structure shows numerous mesoporous with diameters of 4-7nm and an excellent specific surface area as high as 739.4m(2) g(-1). The lithium-oxygen batteries based on Co-CoO@NC electrode show improved electrochemical performance, with a high initial discharge capacity up to 5582 mAh g(-1) at 0.05mA cm(-2) and preferable cycling stability with a cut-off specific capacity of 500 mAh g(-1) at 0.1 mA cm(-2). The improved performance is mainly ascribed to the synergic effect of the porous structure, CoO and strong metal-N-doped carbon bridging bonds, leading to the excellent OER and ORR activities.