Nitrogen-Coordinated CoS@NC Yolk-Shell Polyhedrons Catalysts Derived from a Metal-Organic Framework for a Highly Reversible Li-O Battery.

Transition-metal sulfides (TMS) are one of the most promising cathode catalysts for Li-O batteries (LOBs) owing to their excellent stabilities and inherent metallicity. In this work, a highly efficient mode has been used to synthesize Co@CNTs [pyrolysis products of metal-organic frameworks (MOFs)]-derived CoS(CoS)@NC. Benefiting from the special yolk-shell hierarchical porous morphology, the existence of Co-N bonds, and dual-function catalytic activity (ORR/OER) of the open metal sites contributed by MOFs, the CoS@NC-400/AB electrode illustrated excellent charge-discharge cycling for up to nearly 100 times at a current density of 0.1 mA cm under a limited capacity of 500 mA h g (based on the total weight of CoS@NC and AB) with a high discharge voltage plateau and a low charge cut-off voltage. Meanwhile, the average transferred electron number () is around 3.7 per O molecule for CoS@NC-400, which is the chief approach for a four-electron pathway of the ORR under alkaline media. Therefore, we believe that the novel CoS@NC-400/AB electrode could serve as an excellent catalyst in the LOBs.