Ultra-lightweight Ion-Sieving Membranes for High-Rate Lithium Sulfur Batteries

Abstract The practical application of lithium-sulfur (Li-S) batteries is impeded by the shuttle effect of intermediate polysulfides and the inherent sluggish kinetics. Herein, Mo2C nanocatalysts anchoring on holey graphene scaffold (Mo2C@HGr) is explored as a lightweight and ultrathin modified separator to conquer the above issues. The artificially customized holes on holey graphene sheets facilitate ionic transfer and electrolyte penetration, and further enhance the sulfur utilization under lean electrolyte conditions. The experimental results together with theoretic calculation demonstrate the favourable chemical adsorption ability of Mo2C sites that blocking the diffusion of LiPSs. Abundant triple-phase interfaces among Mo2C nanomediators, holey graphene and electrolyte boost the conversion kinetics of the intercepted LiPSs. As a result, the cell with Mo2C@HGr modified separator shows superior rate capability (836 mAh g−1) even at 5 C current with a negligible Mo2C@HGr loading of 0.08 mg cm-2. Furthermore, ultrahigh areal capacity of 5.9 mAh cm-2 is still attained with high sulfur loading of 6 mg cm-2 under lean electrolyte operation (E/S = 5.6 µL mg−1). This design concept can be extended to other graphene based multifunctional nanocomposite toward the development of more practical Li-S batteries.