Enhanced polysulfide redox kinetics by niobium oxynitrides via in-situ adsorptive and catalytic effect in wide temperature range

The development of Li-S batteries (LSBs) is hindered by the low utilization of S species and sluggish redox reaction kinetics. Polar metal oxides always possess high adsorption to polar S species, while conductive metal nitrides show fast electron transport and ensure fast redox reaction of S species. The combination merits of metal oxides and metal nitrides in one provide an effective strategy to improve the electrochemical performance of LSBs. In this work, defect design of niobium oxynitrides highly dispersed on graphene (NbON-G) is evaluated as effective trapper and catalyst for S species. Owning to the effective structural merits including enriched active sites, alleviated volume variation, defect modulated electronic property, and in-situ chemisorption and catalytic conversion of soluble lithium polysulfides (LiPSs), the LSBs with NbON-G modified separator show remarkably enhanced performance compared to NbN-G and Nb2O5-G. Surprisingly, even at low temperature of -40 degrees C, the LSBs with NbON-G can operate for 1,000 cycles with 0.04% capacity decay per cycle (Rate: 2 C).