Advanced polyimide separator via co-precursor method for lithium-ion batteries with low thermal runaway risks

Separator is an important component in lithium-ion batteries, and it plays a critical role in ensuring the overall thermal safety and electrochemical performance of a battery . To date, the development of safe and robust lithium-ion batteries is still hindered by the commercial polyolefin membrane due to its poor thermal stability and inferior electrolyte wettability . Thus, to address this shortcoming, an advanced polyimide aerogel separator was designed by simple one-pot reaction via co-precursor and cross-linking methods in this work. Based on molecular structure designation and gelation time control, the as-prepared polyimide aerogel separator (C-PI separator) possessed high porosity, good flexibility, excellent thermal stability, and superior electrolyte wettability, which are essential attributes of a high-performing separator. LiFePO 4 |Li metal battery was later assembled with C-PI separator, and the cell demonstrated outstanding long-term cyclic performance (>1000 cycles at 1C with 93.6 % retention). Compared with PE separators, the NCM523-graphite pouch cell assembled with C-PI separators exhibited high thermal stability with a higher thermal runaway temperature (204.9 °C vs. 140.4 °C) and a lower maximum temperature rise (0.06 °C/min vs. 8 °C/min), demonstrating its application potential in scenarios with high requirements for safety. Furtherly, the thermal runaway mechanisms of the full cells were explored and explained in this work.