Self-Reinforced Aramid Composites as Flame-Retardant Separators with Lithium-Ion Conduction

Conventional separators for lithium metal batteries suffer from poor thermal stability, flammability, and limited mechanical strength. In this study, we report a self-reinforced aramid separator integrated with Li7La3Zr2O12 (LLZO) via a sodium–naphthalene-based selective dissolution strategy. Controlled partial disruption of hydrogen bonding in copolymerized aramid enables the formation of a hierarchical structure consisting of intact fibers and nanofibrillar networks, thereby providing intrinsic mechanical reinforcement without binders. The separator maintains structural integrity up to ~400 °C and retains over 70% weight at 600 °C, exhibiting self-extinguishing behavior (LOI > 30). Puncture strength is more than three times higher than Celgard®, while LLZO integration doubles the ionic conductivity along with excellent electrolyte wettability. This synergistic design provides a promising route toward intrinsically safe and high-performance lithium metal battery separators.