Flexible and heat-resistant polyphenylene sulfide ultrafine fiber hybrid separators for high-safety lithium-ion batteries

Separators play a critical role in the safety and electrochemical performance of lithium-ion batteries (LIBs). However, the commercial polyolefin-based separators encounter poor thermal stability and flame retardance, which have aroused severe safety issues. Herein, a flexible and heat-resistant porous separator based on sea-island polyphenylene sulfide (PPS) ultrathin fiber and glass nanofiber (GNF) network is rationally designed and successfully fabricated. This hierarchical network is bound via hot pressing and modification of silane coupling agent (γ-3-glycidoxypropyltrimethoxy silane, γ-GPS), endowing the separator with high flexibility and excellent mechanical performance. Also, this novel composite separator features distinguished thermal stability (without any heat shrink at 250 °C for 30 min) and flame retardant properties, guaranteeing the safety of the battery. Due to the inherent polarity and porous structure, the as-prepared PPS-mGNFs separator achieves a small contact angle (18.2°) of liquid electrolyte (LiPF6) and a high electrolyte uptake (253%), implying much better electrolyte wettability than the commercial polyolefin separator. In addition, the LIB integrated with PPS-mGNFs separator exhibits excellent discharge capacity, C-rate performance and cycling performance. This facile and promising strategy provides a platform for the large-scale fabrication of high-performance and safe LIB separators.