BiOCl@Polypyrrole metal catalysts with a core-shell structure to construct high-safety and stable lithium‑sulfur...

Lithium‑sulfur batteries (LSBs) are promising alternatives to lithium-ion batteries due to their high energy density and low cost. However, issues like the lithium polysulfide (LiPSs) shuttle effect, lithium dendrite growth, and flammable electrolytes hinder commercialization. In this study, we have developed a metal-based catalyst, bismuth oxychloride (BiOCl) nanoflowers coated with conductive polypyrrole (Bi@Ppy), via hydrothermal synthesis. The BiOCl core forms strong BiS bonds with LiPSs, accelerating Li₂S nucleation, suppressing the shuttle effect, and enhancing reaction kinetics. The Ppy shell provides a conductive network for efficient ion/electron transport. As a result, LSBs with modified separators deliver an initial capacity of 1220.1 mAh g^-1 at 0.2C and show a low decay rate of 0.044 % per cycle over 800 cycles at 1C. Additionally, Bi@Ppy promotes uniform Li⁺ deposition, preventing dendrite growth caused by ion concentration gradients. It also improves battery safety through dual-phase flame retardation-trapping radicals in the gas phase and catalyzing carbonization in the condensed phase. This work offers a rational design strategy for high-activity metal-based catalysts and presents a scalable approach to safer, long-cycling LSBs.