Surface-coordinated bimetallic Prussian blue nanocubes on carbon nanotube scaffold for fire-safe and kinetics-enhanced lithium-sulfur separator

A multifunctional P-PBA@PDA@CNTs coating is designed via surface coordination. • This design decouples flame retardancy and electrocatalysis in one interlayer. • Accessible bimetallic Co/Fe sites suppress polysulfide shuttling effectively. • Li S batteries deliver 1598.3 mAh g −1 at 0.2C and stable 400 cycle life. • The separator maintains integrity at 200 °C with 48.6% heat release reduction. Lithium‑sulfur (Li S) batteries are trapped by an intrinsic conflict between incendiary hazards and sluggish polysulfide conversion, as traditional flame retardants typically passivate catalytic sites while electrocatalysts fail to suppress thermal runaway. Here, we bypass this compromise through a coordination-driven functional partitioning strategy, constructing a multifunctional composite consisting of phytic acid-coordinated Prussian blue analogue, polydopamine, and carbon nanotubes (denoted as P-PBA@PDA@CNTs) interlayer that decouples these antagonistic roles at the molecular level. Phytic acid (PA) is grafted onto the surface of pre-crystallized bimetallic Prussian blue analogues (PBA) via multidentate coordination, securing a dense phosphorus-rich shield for robust char formation upon thermal attack, while the underlying bimetallic framework retains its catalytic centers for unimpeded electrocatalysis. This precise spatial decoupling yields exceptional thermomechanical integrity at 200 °C, prompt self-extinguishing, and a 48.6% reduction in peak heat release, alongside significantly accelerated liquid-solid conversion kinetics, driven by synergistic chemisorption and catalytic conversion at the unimpeded bimetallic sites. The resulting Li S batteries deliver a near-theoretical capacity of 1598.3 mAh g −1 at 0.2C with stable cyclability, while Li||Li symmetric cells sustain dendrite-free deposition over 600 h. Our surface coordination paradigm offers a molecular blueprint to synchronously resolve the long-standing safety-kinetics dilemma in high-energy Li S systems, moving beyond single-function modifications toward intrinsically synergistic interface engineering. Download: Download high-res image (267KB) Download: Download full-size image