Polyvinylimidazolium/polyacrylonitrile nanofiber separator with enhanced polysulfide adsorption toward durable lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered potential energy storage solutions for electric vehicles because of their high energy density and cost-effectiveness. Nevertheless, their practical use is hindered by the notorious polysulfide shuttle and safety concerns with polypropylene (PP) separators. Herein, a functional polyvinylimidazolium/polyacrylonitrile (FPVIMPAN) nanofiber separator was fabricated via electrospinning to block polysulfides and enhance stability. The strong affinity of poly(N-vinyl imidazolium) for the electrolyte ensures the separator's excellent wettability in organic electrolytes, reducing internal battery resistance. The FPVIMPAN separator maintained its integrity at 150 degrees C, demonstrating superior thermal stability compared to the traditional PP separator. Density function calculation and lithium polysulfide diffusion experiments confirmed that polyvinylimidazolium strongly adsorbs lithium polysulfides due to the Coulombic attraction between imidazolium cations and polysulfide anions, effectively mitigating the "shuttle effect" and improving cycling stability. Li-S batteries with the FPVIMPAN separator achieved an initial capacity of 948.3 mAh g- 1 at 1.0 C, maintaining 782.2 mAh g- 1 after 300 cycles, outperforming the polyacrylonitrile separator. This work could provide valuable insights for designing suitable and durable separators for metal-sulfur batteries.