A dual-functional poly(vinyl alcohol)/poly(lithium acrylate) composite nanofiber separator for ionic shielding of polysulfides enables high-rate and ultra-stable Li-S batteries

Despite the high theoretical specific capacity, the main challenges of rechargeable lithium-sulfur (Li-S) batteries, including the unceasing shuttle of soluble lithium polysulfides (LiPSs) and severe Li corrosion, seriously hinder their commercial and practical applications. Herein, a bifunctional polyvinyl alcohol/poly(lithium acrylate) (C-PVA/PAA-Li) composite nanofiber separator is developed to address the main challenges in Li-S batteries by simultaneously allowing rapid lithium ion transport and ionic shielding of polysulfides. The C-PVA/PAA-Li composite nanofiber membrane is prepared via the facile electrospinning strategy, followed by thermal crosslinking and in-situ lithiation processes. Differing from the conventional Celgard-based coating methods accompanied by impaired lithium ion transport efficiency, the C-PVA/PAA-Li composite nanofiber membrane possesses well-developed porous structures and high ionic conductivity, thus synergistically reducing the charge transfer resistance and inhibiting the growth of lithium dendrites. The resulting Li-S batteries exhibit an ultra-low fading rate of 0.08% per cycle after 400 cycles at 0.2 C, and a capacity of 633 mA·h·g^-1 at a high current density of 3 C. This study presents an inspiring and promising strategy to fabricate emerging dual-functional separators, which paves the pathway for the practical implementation of ultra-stable and reliable Li-S battery systems.