Efficient polysulfide blocker from conductive niobium nitride@graphene for Li-S batteries

Lithium sulfur batteries are one of the most promising alternative electrochemical systems, but their practical applications are largely hindered by the serious shuttling problems and sluggish redox kinetics. Here, the conductive and polar niobium nitride (NbN) is in-situ introduced onto graphene with ultra-small size and high dispersion, and their composite is used to construct an efficient lithium polysulfide blocking layer. The graphene helps to construct highly conductive pathways, and niobium nitride serves as the sulfiphilic sites to chemically adsorb the migrating lithium polysulfides and catalyze their redox conversion. Hence, the cells with the NbN/G interlayers exhibit a long cycle life with a lower capacity decay of 0.096%/cycle at 1 C for 300 cycles and high rate capability of 937 mAh g−1 at 2 C. Further coupling with a sulfur/carbon nanofiber electrode, the cell with an ultra-high sulfur loading of 10.8 mg cm−2 delivers an areal capacity of 12.5 mAh cm−2 at 0.1 C.