A vanadium-based oxide-nitride heterostructure as a multifunctional sulfur host for advanced Li-S batteries

The commercial application of lithium-sulfur (Li-S) batteries is obstructed by the inherent dissolution/shuttling of lithium polysulfides (LiPSs) in a sluggish redox reaction. Here, a heterophase V₂O₃-VN yolk-shell nanosphere encapsulated by a nitrogen-doped carbon layer has been designed to address the problems of the short cycle life and rapid capacity decay of Li-S batteries synchronously. The structural merits comprise efficient polysulfide anchoring (V₂O₃), rapid electron transfer (VN) and a reinforced frame (N-doped carbon). The assembled cathode based on the V₂O₃-VN@NC sulfur host delivered a high initial capacity of 1352 mA h g^-1 at 0.1C with excellent rate performance (797 mA h g^-1 at 2C) and favorable cycle stability with a low capacity-decay rate of only 0.038% per cycle over 800 cycles at 1C. Even with a high sulfur loading of 3.95 mg cm^-2, an initial capacity of 954 mA h g^-1 at 0.2C could be achieved, along with a good capacity retention of 75.1% after 150 cycles. Density functional theory computations demonstrated the crucial role of the V₂O₃-VN@NC heterostructure in the trapping-diffusion-conversion of polysulfides. This multi-functional cathode is very promising in realizing practically usable Li-S batteries owing to the simple process and the prominent rate and cyclic performances.