High-Safety and Swelling-Tolerant Electrospun Polyacrylonitrile/Poly(ether imide)/Boehmite Separator Enables Durable Lithium-Ion Batteries

Conventional polyolefin separators in lithium-ion batteries (LIBs) suffer from poor electrolyte affinity, limited thermal stability, and insufficient resistance to dendrite penetration, which critically constrain battery safety and durability. Here, we report a multifunctional electrospun electrospun polyacrylonitrile (PAN)/poly­(ether imide) (PEI)/boehmite (BM) composite separator. Uniformly dispersed BM nanoparticles, enriched with surfaceOH groups, establish strong interfacial interactions with polymer chains, thereby reinforcing the fiber matrix, acting as rigid barriers to effectively block dendrite penetration, and simultaneously enhancing electrolyte wettability. The resulting continuous three-dimensional porous network maintains structural integrity upon prolonged electrolyte exposure, providing stable Li+ transport channels, swelling tolerance, and superior thermo-mechanical robustness, as evidenced by a tensile strength of 13.7 MPa (compared to 5.1 MPa for pure PAN). Benefiting from this structural design, Li||Li symmetric cells operate stably for over 600 h at 0.5 mA·cm–2 with suppressed dendrite growth, while Li||Lithium Manganese Oxide (LiMnO2) half-cells deliver excellent rate performance and retain 90.1% of capacity after 400 cycles at 1.0C. This work demonstrates a simple yet effective separator design strategy, offering new insights into the development of swelling-tolerant and dendrite-resistant separators for safe and durable LIBs.