Single-Crystal NCM-Enabled Multifunctional Separator Design for High-Performance Lithium-SPAN Batteries

High-energy and sustainable batteries are key to a low-carbon future, and lithium-sulfur (Li-S) systems stand out for their high energy density, abundance, and low cost. Organo-polymer cathodes such as sulfurized polyacrylonitrile (SPAN) cathodes offer solid-state conversion and suppress polysulfide shuttling, yet their sluggish redox kinetics and limited active material utilization hinder practical performance. Herein, we introduce a multifunctional trilayer mixed-conduction separator that synergistically integrates ionic selectivity, kinetic facilitation, and interfacial stabilization. The separator, composed of single-crystal NCM811 (SC-NCM), BP2000 carbon, and Li-Nafion binder sandwiched between two polypropylene separators (PP|SC-NCM|PP), forms Li⁺-ion transport channels, interfacial charge redistribution, and promotes stable solid-state redox reactions (S to Li₂S) within the SPAN cathode. This architecture enhances Li⁺ transference number (0.60), ionic conductivity (1.82 × 10^-3 S·cm^-1), and electrolyte uptake (68%), while suppressing thermal shrinkage and self-discharge. As a result, the cells deliver an initial discharge capacity of 1779 mAh·g^-1 at 0.1C, retains 80% capacity after 500 cycles (1C), and sustain 771 mAh·g^-1 at 10C (high-rate capability). This scalable, recyclable, and multifunctional separator offers a sustainable route to high-performance Li-S batteries and sets a precedent for mixed-conduction membrane designs in next-generation energy-storage technologies.