Functional Modification and Structural Design of Aramid Nanofiber Separators for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have garnered significant interest for their high energy density and cost-effectiveness. However, the challenges of the polysulfide shuttle effect and rapid capacity decay hinder practical applications and further advancement of Li–S batteries. Herein, we propose that functional modification and structural design involve incorporating a Nafion surface and designing a poly(diallyldimethylammonium chloride) (PDDA)/poly(sodium styrenesulfonate) (PSS) additional self-assembly layer structure based on carboxylated aramid nanofiber separators (C-ANFS). This strategy is conducive to mitigating the synergistic suppression of polysulfide shuttling while simultaneously reinforcing mechanical resistance against lithium dendrite penetration. The chemisorbed polysulfides are realized by introducing carboxyl and amine functional groups and electrostatic attraction layers into the ANF separators. Thus, the as-resulted functional ANF separators possess an exceptional cycle stability and high discharge capacity. Specially, the ANF separators maintained dimensional stability up to 200 °C, showcasing their excellent reliability in extreme conditions. Finally, the Li||S battery exhibited an outstanding cycling stability (860 mAh/g after 200 cycles at 0.5 C) with a low-capacity attenuation rate (0.1% per cycle). Therefore, this study may enrich current research for high-safety energy storage systems in Li–S battery separators.