Thermally Stable Al₂O₃/PTFE Composite Separator for High-Safety Lithium-Ion Batteries

In response to the growing demand for carbon neutrality and safer energy storage, advanced separator technology is essential for ensuring the stability of lithium-ion batteries (LIBs). Conventional separators, typically made from polyolefin-based polymers, suffer from low thermal stability and poor wettability, leading to safety and performance concerns. In this study, we fabricated a nonwoven polytetrafluoroethylene (PTFE) nanofiber (NF) separator using emulsion electrospinning incorporating aluminum oxide (Al₂O₃) particles without polymeric binders. The resulting nonwoven PTFE NF separator demonstrated superior porosity, thermal stability, and electrolyte wettability compared to conventional polyolefin-based separators. Its excellent thermal stability and elongation properties make it more durable for practical battery applications. Furthermore, plasma surface modification of the Al₂O₃-PTFE NF enhanced electrolyte wettability, improving ionic conductivity (2.79 mS cm^-1) and boosting the overall electrochemical performance of LIB cells. These advancements highlight the PTFE NF separator as a promising candidate for safer, more efficient energy storage components, addressing critical challenges in LIB safety and performance.