Nanofiber-constructed composite polymer electrolytes with dual-pathway Li⁺ transport and catalytic sulfide interfaces for lithium-sulfur batteries

Abstract Composite polymer electrolytes (CPEs) are emerging as a promising materials platform for next-generation electrochemical systems, yet their development is often constrained by insufficient mechanical integrity, limited ion-transport efficiency, and unstable interfacial chemistry in hybrid architectures. Herein, we report a nanofiber-constructed hybrid composite electrolyte formed by integrating poly(ionic liquid)-modified aramid nanofibers (PIL@ANFs) with sulfide-based lithium thiophosphate (Li₃PS₄, LPS) nanoparticles. The PIL coating stabilizes ANFs during deprotonation, preserves their nanofibrillar morphology, and enables the formation of a continuous three-dimensional Li⁺ transport scaffold. Uniformly incorporated LPS nanoparticles simultaneously reinforce the mechanical framework, enhance ionic conductivity, and introduce catalytically active sulfide interfaces. The resulting hybrid composite exhibits high ionic conductivity (~ 10 ^-3 S cm ^-1 ), an elevated Li⁺ transference number (> 0.7), and robust interfacial stability at 60 °C. Advanced spectroscopic analyses (X-ray photoelectron spectroscopy and solid-state ⁶Li nuclear magnetic resonance), combined with density functional theory and all-atom molecular dynamics simulations, reveal a dual-mode ion-transport mechanism: localized Li⁺ hopping at polarized sulfide-rich domains coupled with long-range surface diffusion along the PIL@ANF network. This cooperative transport architecture also enables selective polysulfide anchoring on LPS surfaces, accelerating redox kinetics and suppressing interfacial degradation. As a proof of concept, the hybrid electrolyte enables stable lithium metal cycling and delivers high reversible capacity and rate capability in lithium–sulfur cells at elevated temperature. This work establishes a structure-guided strategy for designing mechanically robust, ionically conductive, and catalytically active hybrid composite electrolytes, highlighting the potential of nanofiber–sulfide architectures for advanced electrochemical materials.