Remarkably improved electrochemical and safety performances of lithium-sulfur batteries via BaSO@Ketjen black double-layer-modified separators.

Ketjen black (KB) could be an ideal building block of the interlayer for modification of separators to greatly reduce the shuttling effect in lithium‑sulfur (Li-S) batteries, but it remains a formidable challenge to conformally and robustly coat them on the polyolefin separators. For the first time, a BaSO@KB double-layer-modified polyethylene (PE) separator has been fabricated by uniformly depositing KB conductive carbon onto the PE separator via an intermediate layer of BaSO nanoparticles. The BaSO layer remarkably improves the mechanical properties of PE separator to effectively inhibit lithium dendrite formation and prevent separator puncture, and meanwhile effectively enhances the thermal stabilities of separator to reduce the risk of thermal runaway, thus greatly boosting the battery safety. The KB carbon layer, owing to KB's ultra-high specific surface area and branched nanochain structure, significantly enhances the binding with polysulfides and accelerates the charge transfer. The BaSO@KB modified separator greatly improves the capacity and cyclability of Li-S batteries. When the sulfur loading of cathode is 3.0 mg cm, the initial discharge specific capacity of the cell with the modified separator reached 907 mAh g at a current density of 0.5C. After 200 charge-discharge cycles, the remaining specific capacity was 772 mAh g, resulting in a capacity retention rate of 85.1 %. This work not only develops a novel high-performance carbon/ceramic double-layer-modified separator for practical Li-S battery applications, but offers scientific insights into the great effect of multifunctional separators on the performance enhancement of Li-S batteries.