Suppressed polysulfide shuttling and improved Li⁺ transport in Li S batteries enabled by NbN modified PP separator

The practical application of Lithium-Sulfur battery is limited due to its rapid capacity fading and early battery failure caused by the shuttling of soluble polysulfide. Thus, the key to improve the performance of a Lithium-Sulfur battery is to suppress the shuttling effect. Herein, we report a NbN modified PP separator with high performance for Lithium-Sulfur battery applications. The NbN functionalized layer of the separator can strongly interact with soluble polysulfide species, as demonstrated by both experimental investigation and theoretical verification. As a result of the high polysulfide affinity, the composite separator effectively prevents the shuttling of soluble polysulfide through the separator. Besides, the high electrolyte wettability of NbN modification layer lowers the resistance of Li+ transport through the separator. Due to these favorable features, Lithium-Sulfur battery assembled with the multifunctional NbN modified separator exhibits excellent cycling performance with a reversible capacity of 554.6 mAh g⁻¹ after 200 cycles at 0.2C. The significantly improved rate performance of the battery based on the modified separator is also demonstrated. Our results show that NbN is a promising material for the modification of separators in Lithium-Sulfur battery and the strategy of separator engineering is effective for improving the performance of Lithium-Sulfur battery.