Strongly Coupled Carbon Nanosheets/Molybdenum Carbide Nanocluster Hollow Nanospheres for High-Performance Aprotic Li–O₂ Battery

A highly efficient oxygen electrode is indispensable for achieving high-performance aprotic lithium–O₂ batteries. Herein, it is demonstrated that strongly coupled carbon nanosheets/molybdenum carbide (α-MoC_{1− x}) nanocluster hierarchical hybrid hollow spheres (denoted as MoC_{1− x}/HSC) can work well as cathode for boosting the performance of lithium–O₂ batteries. The important feature of MoC_{1− x}/HSC is that the α-MoC_{1− x} nanoclusters, uniformly incorporated into carbon nanosheets, can not only effectively prevent the nanoclusters from agglomeration, but also help enhance the interaction between the nanoclusters and the conductive substrate during the charge and discharge process. As a consequence, the MoC_{1− x}/HSC shows significantly improved electrocatalytic performance in an aprotic Li–O₂ battery with greatly reduced charge and discharge overpotentials and long cycle stability. The ex situ scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy studies reveal that the mechanism for the high-performance Li–O₂ battery using MoC_{1− x}/HSC as cathode is that the incorporated molybdenum carbide nanoclusters can make oxygen reduction on their surfaces easy, and finally form amorphous film-like Li-deficient Li₂O₂ with the ability to decompose at a low potential. To the best of knowledge, the MoC_{1− x}/HSC of this paper is among the best cathode materials for lithium–O₂ batteries reported to date.