Self-assembled BNNSs/rGO heterostructure as a synergistic adsorption and catalysis mediator boosts the electrochemical kinetics of lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) battery with high theoretical specific capacity (1675 mAh/g), has been deemed as one of the most potential candidates of secondary energy storage system. However, the large-scale applications of Li-S batteries have been obstructed by internally sluggish multi-step redox reaction and terrible shuttle effect of lithium polysulfides (LiPSs). Herein, boron nitride nanosheets/reduced graphene oxide (BNNSs/rGO) heterostructure prepared by self-assembly crosslinking method has been designed to modify commercial separator for Li-S batteries. The hierarchical pores, physical and chemical cross-links within heterostructure can significantly enhance the adsorption capacity for LiPSs, uniquely physical and electronic interaction between BNNSs and rGO can effectively catalyze the conversion of sulfurated species. Benefiting from the synergistic adsorption-catalysis effect, BNNSs/rGO not only greatly inhibits the shuttle behaviors, but also considerably accelerates the electrochemical reaction kinetics for LiPSs and Li2S. Attributed to these merits, Li-S battery with BNNSs/rGO heterostructure mediator delivers superiorly reversible capacity as high as 915.0 mAh/g at 1 C. Even at high sulfur loading of 3.9 mg cm−2, the cell delivers ultra-stable specific capacity of 629.1 mAh/g at 1 C, and still maintains 605.5 mAh/g over 500 cycles corresponding to a capacity fade of merely 0.0075% per cycle.