Capture of Polysulfides Enabled by a Nitrogen-Doped Carbon-Coated Halloysite Nanotube-Modified Separator to Enhance Performance for Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries stand out as highly promising energy storage systems because of their superior theoretical capacity and the affordability of sulfur as an active material. However, their inherent drawbacks have hindered the commercialization of Li-S batteries. Of these, the polysulfide shuttle effect is one of the most critical issues, leading to the rapid decline in battery capacity. To specifically address this issue, we successfully synthesized nitrogen-doped carbon-coated halloysite nanotubes (HNT@NC) using a one-step sintering method and modified the Celgard 2325 separator on the side facing the sulfur cathode (HNT@NC-Separator). The study found that HNT@NC-Separator exhibits excellent electrolyte wettability and superb mechanical strength. Its surface has abundant polar sites that effectively capture lithium polysulfides, thereby improving the cycling and rate performance of Li-S batteries. At a current density of 0.2 C, the Li-S battery assembled with the HNT@NC-Separator achieved an initial discharge capacity of 840.8 mAh g^-1, maintaining a capacity of 486.1 mAh g^-1 after 100 cycles. At a current density of 1 C, the initial discharge capacity was 770.4 mAh g^-1, maintaining a capacity of 412.9 mAh g^-1 after 100 cycles. In the rate performance test, the capacity retention rate exceeded 75%.