Low-temperature sulfurization stabilizes polymerization-programmed La–N4S2 single-atom sites for accelerated solid–solid conversion in SPAN

Polymerization-programmed La–N 4 S 2 single-atom sites accelerate solid–solid conversion in SPAN. • Low-temperature sulfurization stabilizes isolated La sites within a nanoflower-derived framework. • La–N 4 S 2 motifs enhance local polarity and electronic coupling to strengthen Li 2 S x interactions. • La 2.5 –FSPAN retains 1328 mAh g −1 after 100 cycles at 4.5 mg cm −2 and E/S = 10 μL mg −1 . • La w –FSPAN delivers low polarization, strong rate capability, and long-term cycling durability. Sulfurized polyacrylonitrile (SPAN) cathodes suppress polysulfide shuttling yet remain limited by sluggish solid–solid conversion under practical conditions. Here, a polymerization-programmed strategy is developed to embed trace La into a nanoflower polyacrylonitrile scaffold (FPAN), where La is pre-organized through interactions with N-containing functionalities during polymerization, followed by low-temperature sulfurization to afford sulfurized FPAN (FSPAN) with isolated La sites of predominant La–N 4 S 2 six-coordination. The La–N 4 S 2 motif intensifies local polarity and induces pronounced p – d hybridization, driving site-centered charge redistribution that enhances Li + affinity and interfacial electronic coupling for the Li 2 S x ( x  = 4, 2, 1) conversion sequence and facilitates Li 2 S reactivation during charge. Benefiting from the synergy between the La–N 4 S 2 single atoms and the interconnected nanoflower-derived framework, La 2.5 –FSPAN retains 1262 mAh g −1 after 150 cycles at a sulfur loading of 4.5 mg cm −2 with E/S = 10 μL mg −1 , and delivers 769 mAh g −1 at 10C under a sulfur loading of 1.5 mg cm −2 . This work establishes polymerization-guided atomic engineering as a low-temperature route to accelerate solid–solid conversion in SPAN cathodes under practically relevant constraints. Download: Download high-res image (129KB) Download: Download full-size image