Class of Boehmite/Polyacrylonitrile Membranes with Different Thermal Shutdown Temperatures for High-Performance Lithium-Ion Batteries

Nowadays, lithium-ion batteries are required to have a higher energy density and safety because of their wide applications. Current commercial separators have poor wettability and thermal stability, which significantly impact the performance and safety of batteries. In this study, a class of boehmite particles with different grain sizes was synthesized by adjusting hydrothermal temperatures and used to fabricate boehmite/polyacrylonitrile (BM/PAN) membranes. All of these BM/PAN membranes can not only maintain excellent thermal dimensional stability above 200 °C but also have good electrolyte wettability and high porosity. More interestingly, the BM/PAN membranes' thermal shutdown temperature can be adjusted by changing the grain size of boehmite particles. The lithium-ion batteries assembled with BM/PAN separators exhibit different thermal stability phenomena at 150 °C and have excellent rate performance and cycle stability at room temperature. After 120 cycles at 1C, the LiFePO₄ half-cell assembled by the best BM/PAN separator has almost unchanged discharge capacity, whereas the capacity retention of Celgard 2325 is only about 85%. Meanwhile, the NCM523 half-cell assembled with the best BM/PAN separator shows superb cycle stability after 500 cycles at 8C, with a capacity retention of 79% compared with 56% for Celgard 2325.