Hydrogen-Bond-Regulated PAN/PTFBZ Nanofibrous Composite Barriers for Flame-Resistant Thermal Runaway Protection

Electrospun polymer barriers are attractive for lightweight thermal protection in compact lithium-ion battery (LIB) devices, but their limited flame resistance and structural stability under thermal abuse restrict their practical use. Herein, a hydrogen-bond-regulated nanofibrous composite barrier was developed by incorporating trifluoromethyl-modified benzoxazine (TFBZ)-derived components into a polyacrylonitrile (PAN) matrix. The benzoxazine-derived phenolic hydroxyl groups could interact with the nitrile groups of PAN through O-H···N≡C hydrogen bonding, contributing to improved interfacial compatibility and fibrous-network stabilization while retaining the processability of PAN. Thermogravimetric analysis showed that PAN/PTFBZ retained 96.1% of its mass at 300 °C, compared with 75.8% for pure PAN. Cone calorimetry showed that the total heat release and total smoke production were reduced by 64.9% and 45.1%, respectively, and the limiting oxygen index (LOI) increased from 18% to 31%. In battery-level thermal abuse tests, the time to complete thermal runaway (TR) increased from 1068.7 ± 14.6 s to 1884.7 ± 44.2 s, corresponding to 76.4% delay. These results suggest that interfacial hydrogen-bonding regulation, together with the ─CF3-modified benzoxazine-derived structure and compact char formation, contributes to improved flame resistance, structural retention, and battery-level thermal-abuse protection.