Thermally Stable, Ion‐Regulating Aramid Nanofiber‐Polyacrylamide Modified Separator Enabling Safe and High‐Performance Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) face critical challenges such as unstable solid electrolyte interphase (SEI), dendritic lithium growth, and transition metal dissolution from high‐nickel cathodes, which compromise cycling stability and safety. To address these issues, a multifunctional composite separator is developed by constructing an aramid nanofiber (ANF)‐polyacrylamide (PAM) hybrid layers on PP separators. The ANF‐PAM@PP separator exhibits exceptional thermal stability, mechanical robustness, and uniform pore structure, enabling homogeneous Li‐ion flux distribution and suppressed dendrite initiation. The PAM is rich in amide groups and effectively chelates dissolved transition metal ions via coordination bonding, reducing SEI degradation and electrolyte decomposition. Density functional theory (DFT) calculations confirm strong metal ion adsorption on ANF‐PAM due to high binding energies. Li||Li symmetric cells with the modified separator achieve stable cycling for >1000 h at 2 mA cm −2 , while Li||NCM811 cells retain 81.8% capacity after 150 cycles at 3C. This work provides a scalable strategy for designing high‐performance separators to enable durable and safe LMBs.