MoS /Celgard Separator as Efficient Polysulfide Barrier for Long-Life Lithium-Sulfur Batteries.

A high lithium conductive MoS /Celgard composite separator is reported as efficient polysulfides barrier in Li-S batteries. Significantly, thanks to the high density of lithium ions on MoS surface, this composite separator shows high lithium conductivity, fast lithium diffusion, and facile lithium transference. When used in Li-S batteries, the separator is proven to be highly efficient for depressing polysulfides shuttle, leading to high and long cycle stability. With 65% of sulfur loading, the device with MoS /Celgard separator delivers an initial capacity of 808 mAh g and a substantial capacity of 401 mAh g after 600 cycles, corresponding to only 0.083% of capacity decay per cycle that is comparable to the best reported result so far. In addition, the Coulombic efficiency remains more than 99.5% during all 600 cycles, disclosing an efficient ionic sieve preventing polysulfides migration to the anode while having negligible influence on Li ions transfer across the separator. The strategy demonstrated in this work will open the door toward developing efficient separators with flexible 2D materials beyond graphene for energy-storage devices.