Polar Phosphorus Sites in CNTs Suppress Polysulfide Shuttle and Accelerate Conversion in Li-S Cathodes.

Lithium-sulfur batteries offer high energy density but suffer capacity fade from lithium polysulfide dissolution and sluggish redox kinetics. We fabricate phosphorus-doped carbon nanotubes (P-CNTs) by a simple, low-cost vapor-diffusion route and use them as sulfur-host cathodes. Phosphorus incorporation and increased defect density create abundant sites for chemisorption and catalytic conversion of polysulfides, suppressing the shuttle and accelerating kinetics. The conductive, tubular architecture also preserves electron pathways and buffers volume changes, enabling fast charge transfer and structural integrity during cycling. The P-CNTs cathodes deliver an initial specific capacity of 1153.8 mAh g-1 at 0.2 C and sustain 500 cycles at 1.0 C with an average per-cycle decay of only 0.095%. Under a high sulfur loading of 6.55 mg cm-2, an areal capacity of 7.73 mAh cm-2 at 0.2 C is achieved with 66.1% retention after 100 cycles. Spectroscopic and electrochemical analyses indicate strong adsorption of sulfur species on P-CNTs, effectively anchoring LiPSs intermediates and improving coulombic efficiency. These results establish P-CNTs as effective, scalable cathode hosts for long-life, high-loading Li-S batteries and highlight a practical strategy coupling physical confinement with catalytic regulation of polysulfides.