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 150C. The asdeveloped 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 80C, 130.9 mAh g−1 of batteries assembled with annealed separators at 150C for 5 hours, and 140.3 mAh g−1 of annealed batteries at 150C 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.
Journal Name: International Journal of Energy Research (IF 3.741)