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.