A separator based on natural illite/smectite clay for highly stable lithium-sulfur batteries.

In spite of high theoretical specific capacity and specific energy of lithium-sulfur (Li-S) batteries, the poor cycle stability caused by polysulfides shuttle severely hinders their real-world applications. Here, a natural clay mineral (illite/smectite, ISC) and carbon black (C) coated Celgard2400 (ISC/C@Celgard) separator is reported. The separator shows super-electrolyte-philicity and good mechanical stability. The low-cost and eco-friendly ISC with abundant -OH groups can quickly trap a lot of polysulfides by Li-O and Li-S bonding with polysulfides. The ISC/C layer with uniform nanopores can also inhibit polysulfides shuttle by physical shield. Moreover, good electrical conductivity of the ISC/C layer can reactivate the adsorbed polysulfides and thus enhance S utilization. So, the separator endows the Li-S battery with very high initial reversible capacity (1322 mA h g) at 0.1 C and excellent cycle stability with low capacity decay rate (0.054% per cycle) during 500 cycles at 1.0 C. Furthermore, a very high areal capacity (5.9 mAh cm) is achieved for the battery composed of the separator and the self-supporting high S loading (8.9 mg cm) CNT/S cathode at 0.32 mA cm. This study opens the possibility of developing advanced separators using natural clay minerals for highly stable Li-S batteries.