Revealing the multilevel thermal safety of lithium batteries

The ever-growing endurance mileage anxiety has been stimulating the continuous energy density raising of Li-ion batteries (LIBs) and the burgeoning of battery chemistries beyond Li-ion. However, if operated under abuse conditions, LIBs are easy to get thermal runaway. Encouragingly, great efforts have been devoting for achieving safer LIBs. However, the pace of thermal safety assessment has obviously lagged behind the energy density improvement of LIBs. Therefore, it is urgently needed to systematically, comprehensively and timely study the thermal safety issue of LIBs by combining different testing methods. In this review, we briefly summarize the varied testing methods for thermal safety evaluation of LIBs. Wherein, the highly-integrated accelerating rate calorimetry (ARC, an adiabatic calorimeter) technology is widely used to study the worst case thermal safety of LIBs at multilevel, ranging from ranging from battery materials to single cells and even battery packs. Combined with examples, the realizable specific functions of ARC in evaluating the thermal safety of LIBs are systematically summarized, and it reveals that the thermal safety of LIBs are rather complicated. Finally, critical perspectives in studying and improving thermal safety of LIBs and battery chemistries beyond Li-ion are provided.