Lithium-sulfur (Li-S) batteries have attracted considerable attention based on their high energy density. Nevertheless, the shuttle effect of lithium polysulfide (LiPS) and the growth of lithium dendrite remain primary issues hindering their commercial application. Herein, a novel functional separator based on polypropylene (PP) matrix was proposed, modified with an ultrathin poly[2,6-diimidazo(4,5-b:4',5'-e)pyridinylene-1,4(2,5-dihydroxy)phenylene] (PIPD) nanofibers layer via a scalable blade-coating process. Compared to unmodified PP, PIPD-coated separator demonstrates significantly enhanced mechanical strength. The PIPD nanofiber coating demonstrates superior lithiophilicity, effectively reducing lithium-ion desolvation energy barrier while enhancing deposition kinetics, thereby promoting the formation of uniform lithium nucleation sites. Additionally, the imidazole groups in PIPD act as Lewis acids, notably adsorbing Lewis-based LiPSs and mitigating the shuttle effect. Consequently, Li||Li cells assembled with modified separators demonstrated stable cycling over 1,800 hours at 1 mA cm-2/1 mAh cm-2. Remarkably, Li-S batteries demonstrated a specific capacity retention of 728.9 mAh g-1 after 450 cycles at 3C, with an ultralow capacity fade rate of only 0.072% per cycle. The proposed innovative strategy enhances the performance and safety of Li-S batteries while paving the way for their commercial viability in advanced energy storage applications.