A highly efficient composite separator embedded with colloidal lanthanum oxide nanocrystals for high‐temperature lithium‐ion batteries

Summary Highly efficient microporous composite separator based on polyvinylidene fluoride‐hexafluoro propylene (PVDF‐HFP) and colloidal La2O3 (C‐La2O3) is prepared for high‐temperature lithium‐ion batteries (LIBs) through facile slide coating technique. The presence of colloidal La2O3 nanocrystals in PVDF‐HFP significantly enhances the mechano‐thermal stability of separator due to the robust microporous structure. Moreover, the C‐La2O3 nanocrystals also help in improving the conductivity of lithium ions by incorporating additional Li+ conduction pathways due to the Lewis acid‐base interaction between La atom and PVDF‐HFP chain. The PVDF‐HFP/C‐La2O3 separator owns minimal shrinkage of 6.2% after thermal annealing for 1 hour at 150°C. The as‐developed separator exhibits high wettability and electrolyte uptake (238%) due to the robust microporous structure and low crystallinity, which leads towards high ionic conductivity (0.75 × 10−3 S cm−1). The cells developed with PVDF‐HFP/C‐La2O3 separator deliver the discharge capacity of 158.2 mAh g−1 at room temperature, 163 mAh g−1 on direct testing at 80°C, 130.9 mAh g−1 of batteries assembled with annealed separators at 150°C for 5 hours, and 140.3 mAh g−1 of annealed batteries at 150°C for 5 hours at 0.5 C after 100 cycles with a capacity retention of ≈98%. The PVDF‐HFP/C‐La2O3 separator is a promising substitute of commercial separators with remarkable performances for high‐temperature LIBs. A highly efficient polyvinylidene fluoride‐hexafluoro propylene/colloidal‐lanthanum oxide (PVDF‐HFP/C‐La2O3) composite separator is prepared through facile slide coating method for high temperature lithium ion batteries. The as‐developed separator owns interconnected microporous structure, robust thermal and dimensional stabilities, high electrolyte uptake, and mechanically strong to supress the dendrite penetrations. LFP/Li batteries based on PVDF‐HFP/C‐La2O3 separator deliver remarkable cyclic performances at room and elevated temperatures.