Carbon-Dotted Defective CoO with Oxygen Vacancies: A Synergetic Design of Bifunctional Cathode Catalyst for Li–O2 Batteries

Noble-metal-free bifunctional cathode catalysts, which can promote both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), are quite necessary for lithium–air batteries. In this study, we propose a novel strategy to improve the catalytic performance of CoO through the integration with the dotted carbon species and oxygen vacancies. We have successfully prepared carbon-dotted defective CoO with oxygen vacancies (CoO/C) by sintering the pink precursors obtained from the ethanol-mediated Co(Ac)2·4H2O. In comparison with the commercial or oxygen-vacancies-only CoO, the cycling stability, the initial capacity, and the rate capability of CoO/C-catalyzed cathode have all been greatly enhanced, and the overpotential has also been decreased, which can be attributed to the synergetic effect of the dotted carbon species and oxygen vacancies on both ORR and OER. Oxygen vacancies can enhance the mobility of e– and Li+ and bind to O2 and Li2O2 as active sites. The dotted carbon species not only improve the conductivity of CoO but also stabilize the oxygen vacancies during ORR/OER. In addition, our further investigation on the evolution of the morphology and phase composition of CoO/C and commercial CoO based cathodes under different charge/discharge states confirms that CoO/C can largely accelerate the formation and decomposition of Li2O2 during discharge–charge cycles.