Li₇La₃Zr₂O₁₂ Nanofiber-Modified Polypropylene Composite Separator for High-Performance Lithium-Ion Batteries

Separators dominate lithium-ion battery (LIB) safety by isolating electrodes, guiding Li⁺ transport and avoiding short circuits. However, commercial polypropylene (PP) separators suffer from inferior electrolyte wettability, severe thermal shrinkage, and insufficient suppression of lithium dendrite growth. Herein, garnet-type Li₇La₃Zr₂O₁₂ (LLZO) nanofibers were synthesized via spherical section free surface electrospinning (SSFSE) followed by calcination. LLZO nanofiber-modified PP separators (LLZO@PP) were fabricated by coating a single side of PP separators with the as-synthesized LLZO nanofibers. Systematic morphological, structural and electrochemical characterizations reveal that the modified LLZO@PP separators exhibit improved thermal stability and electrolyte wettability compared with the pristine PP separator. The optimized LLZO@PP separator delivers a high ionic conductivity of 0.571 mS cm^-1 and a wide electrochemical window of 4.8 V at 25 °C. Furthermore, the Li//LiFePO₄ half-cell assembled with the optimal LLZO@PP separator achieves a capacity retention of 90.21% after 100 cycles at 0.5 C. This work offers a facile and scalable route to construct LLZO nanofiber-modified composite separators, which can effectively improve the safety and superior electrochemical performance of high-performance LIBs.