A multifunctional separator for high-performance lithium-sulfur batteries

Lithium-sulfur (Li–S) batteries attract much more attention over the past decades because of its high theoretical specific capacity (1675 mAh g⁻¹). However, the rapid capacity decay caused by the shuttle effect of polysulfides greatly limits its practical applications. In this work, we prepared an acetylene black/γ-Al₂O₃/polypropylene composite separator in a friendly and simple way to improve the performance of Li–S batteries. The γ-Al₂O₃ layer can block the polysulfides diffusion and simultaneously improve the thermal stability of the separator. The acetylene black layer can reduce interface impedance, improve the utilization of active materials and also further block the shuttle of the polysulfides. The Li–S batteries equipped with this composite separator show better cycling performance with an initial discharge capacity of 1096 mAh g⁻¹ and a capacity decay as low as 0.08% per cycle for 500 cycles at 0.5 C (1 C = 1675 mA g⁻¹) and rate performance with a reversible discharge capacity of 871 mAh g⁻¹ at 3 C. Our work can be used for coming commercialization of Li–S batteries.