A polysulfide-trapping interface for electrochemically stable sulfur cathode development.

Lithium-sulfur (Li-S) cells have a strong edge to become as an inexpensive, high-capacity rechargeable battery system. However, currently several prohibitive challenges occur within the sulfur core, especially the polysulfide-diffusion problem. To address these scientific issues, we present here a boron-doped multiwall carbon nanotube coated separator (B-CNT-coated separator). The B-CNT-coated separator creates a polysulfide trap between the pure sulfur cathode and the polymeric separator as a "polysulfide-trapping interface," stabilizing the active material and allowing the dissolved polysulfides to activate the bulk sulfur cores. Therefore, the dissolved polysulfides change from causing fast capacity fade to assisting with the activation of bulk sulfur clusters in pure sulfur cathodes. Moreover, the hetero-atom-doped polysulfide-trapping interface is currently one of the missing pieces of carbon-coated separators, which might inspire further studies in its effect and battery chemistry. Li-S cells employing B-CNT-coated separators (i) exhibit improved cyclability at various cycling rates from 0.2C to 1.0C rate and (ii) attain a high capacity retention rate of 60% with a low capacity fade rate of 0.04% cycle-1 after 500 cycles. We believe that our B-CNT-coated separator could light up a new research area for integrating hetero-atom-doped carbon into the flexible, light-weight, carbon-coated separator.