Separator modified by ternary iron molybdenum nitride and nitrogen-doped carbon composite enabling efficient polysulfide conversion for lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) are appealing energy storage systems by virtue of the high theoretical energy density and abundant resources of sulfur. However, the sluggish redox reaction kinetics and shuttle effect of soluble lithium polysulfides (LiPSs) seriously restrict their practical applications. Searching for highly efficient and low cost electrocatalysts towards LiPSs conversion is one of the most promising approaches to relieve the shuttle effect and enhance the sulfur utilization. In this work, we first demonstrate the application of ternary iron molybdenum nitride hybridized with nitrogen-doped carbon, denoted as (Fe0.81Mo0.19)MoN2/NC composite, as an advanced separator modifier to boost the bidirectional catalytic conversion of LiPSs. Impressively, the as-fabricated LSBs with (Fe0.81Mo0.19)MoN2/NC modified separator display an ultrahigh initial discharge capacity of 1366.1 mAh g−1 at 0.1 C and still remains a high value of 809.1 mAh g−1 at a high rate of 4 C. Furthermore, a remarkable discharge capacity of 569.2 mAh g−1 is retained when cycling at a high rate of 1 C for 700 cycles (corresponding to a low attenuation rate of 0.065 % per cycle), indicating the good long-term cycling stability. The excellent performance could be attributed to the multiple advantages of high electrical conductivity, numerous active sites, strong adsorption ability and excellent catalytic activity, thereby effectively suppressing the shuttle effect of LiPSs. The present work indicates that the ternary transition metal nitrides could be promising separator modifiers for high-performance LSBs.