MoS₂/Celgard Separator as Efficient Polysulfide Barrier for Long‐Life Lithium–Sulfur Batteries

TLDR

The MoS₂ surface’s high lithium‑ion density confers the composite separator with high lithium conductivity, rapid diffusion, and facile transference. The study demonstrates that a MoS₂/Celgard composite separator can serve as an efficient polysulfide barrier, opening avenues for flexible 2D‑material separators in energy‑storage devices. The MoS₂/Celgard separator delivers high lithium conductivity and fast diffusion, suppresses polysulfide shuttling, and achieves an initial capacity of 808 mAh g⁻¹ with 401 mAh g⁻¹ after 600 cycles (0.083 % decay per cycle) while maintaining >99.5 % Coulombic efficiency.

Abstract

A high lithium conductive MoS2 /Celgard composite separator is reported as efficient polysulfides barrier in Li-S batteries. Significantly, thanks to the high density of lithium ions on MoS2 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 MoS2 /Celgard separator delivers an initial capacity of 808 mAh g-1 and a substantial capacity of 401 mAh g-1 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.