A Highly‐Efficient Composite Separator with Strong Ligand Interaction for High‐Temperature Lithium‐Ion Batteries

Abstract A PVDF‐HFP/colloidal‐TiO 2 composite separator is synthesized for high‐temperature lithium‐ion batteries. Incorporation of colloidal TiO 2 in the PVDF‐HFP matrix forms a highly‐uniform composite micro‐structure with strong adsorption interactions between TiO 2 and PVDF‐HFP due to the presence of citric acid. The strong interactions are giving rise to advantageous mechanical robustness, separator/electrode interface and electrolyte uptake. The separator shows remarkable stability upon thermal treatment at 150 °C. With a high ionic conductivity up to 1.57×10 −3 S cm −1 , the LFP/Li cell with PVDF‐HFP/colloidal‐TiO 2 composite separator delivers charge‐discharge capacities of 156.95 mAh g −1 (0.1 C) at room temperature and 120.8 mAh g −1 (0.5 C) after annealing cells at 140 °C for 3 hours with a 99 % capacity retention after 100 cycles. The PVDF‐HFP/colloidal‐TiO 2 separator demonstrates promising potentials for practical applications in high‐temperature environments.