Ten micrometer thick polyethylene separator modified by α-LiAlO₂@γ-Al₂O₃ nanosheets for simultaneous suppression of Li dendrite growth and polysulfide shuttling in Li-S batteries

Lithium-sulfur (Li-S) batteries are of considerable interest for low-cost and high-density energy storage. However, the notorious polysulfide shuttling and the undesired Li dendrite growth impel the development of Li-S batteries. To simultaneously mitigate these problems, a thin (∼10 μm) separator is herein developed by coating α-LiAlO₂@γ-Al₂O₃ (LAO) nanosheets on the dual sides of a commercial polyethylene (PE) separator. Owing to the high anion-anchoring capability and the polysulfide absorbing and catalytic effect of LAO, the LAO modified separator (LAOMS) not only suppresses the polysulfide shuttling, but also homogenizes Li⁺ flux and reduces concentration polarization. As a result, the Li-Li cell with LAOMS demonstrates an unprecedented stability over 2500 h when cycled at a high current density of 5 mA/cm². In addition, the Li-S battery with LAOMS exhibits superior cycling lifespan with an ultra-low capacity decay of 0.037% per cycle over 1000 cycles even at 2 C, excellent rate performance, and superior anti-self-discharge capability. Our studies not only shed light on the rational design of functionalized separators for high-performance Li-S batteries, but also provide a thin separator with promising commercial perspective.