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.