Thermal insulation-flame retardant synergistic polyimide composite aerogel for mitigating thermal runaway in lithium-ion batteries

Lithium-ion batteries (LIBs) serve as a critical energy source in electric vehicles and distributed energy storage systems. However, they face significant safety concerns caused by thermal runaway (TR) and its propagation. These issues severely threaten system stability and operational safety. Aerogels have attracted widespread attention for their exceptional thermal insulation properties. Among them, polyimide (PI) aerogels combine the advantages of low thermal conductivity inherent to aerogels along with the high decomposition temperature and self-extinguishing properties of PI. This unique property makes them ideal thermal-insulating and flame-retardant materials that can mitigate the propagation of TR. However, the relatively poor flame resistance of PI aerogels presents a major obstacle to their wider practical application. To address this challenge, this study developed PI aerogels with excellent flame retardant properties. Specifically, ammonium polyphosphate, an intumescent flame retardant, was incorporated into the aerogel system to fabricate a composite aerogel with synergistic thermal insulation and flame-retardant capabilities. The results showed that when applied to LIBs modules, the 2 mm-thick PI aerogel successfully delayed the TR propagation, extending the TR triggering interval between adjacent batteries from 10 s to 595 s, with an average delay of 585 s. This indicates that the material constructed in this study demonstrates great potential for improving the safety of battery systems.