An Amino-Modified ZIF-67/Aramid Nanofiber Coating for High-Performance Lithium Battery Separators

To improve the thermal safety, hydrophilicity and ion transport performance of polypropylene (PP) separators in lithium-ion batteries, a composite coating was developed using amino-modified zeolitic imidazolate framework material (ZIF-67-NH 2 ) and aramid nanofiber (ANF). The coating was applied to the PP separator via a two-step sequential method: (1) ANF dispersion was coated onto the PP substrate to form a support network layer with high mechanical strength and excellent thermal stability; (2) ZIF-67-NH 2 dispersion was uniformly loaded on the ANF layer to construct a functional layer with high specific surface area, regular pore structure and rich active sites. Amino modification of ZIF-67 significantly improved its electrolyte affinity and lithium-ion transport activity. Compared to the pristine PP separator, the modified separator exhibited a thermal shrinkage rate of only 31% at 170°C, indicating superior thermal stability. The water contact angle reached 20°, indicating significantly enhanced wettability. The impedance decreased from 105.6 to 71.2 Ω, and the apparent ionic conductivity increased from 0.0118 to 0.0877 mS/cm. In the cycling test, the battery using the modified separator exhibited an initial discharge capacity of 80 mAh/g, which is approximately 8% higher than that of the battery using the pristine PP separator (73.9 mAh/g), also demonstrating improved capacity retention and stability.