Experimental investigation on the characteristics of thermal runaway and its propagation of large-format lithium ion batteries under overcharging and overheating conditions

Overcharge and overheating are two common safety issues for the large-scale application of lithium-ion batteries (LIBs), and in-depth understanding of the thermal runaway (TR) and its propagation of LIBs induced by overcharging and overheating are strongly required to guide the safety design of battery system. In this paper, investigation on characteristics and mechanism of TR and its propagation of LIBs induced by overcharging and overheating are conducted experimentally. Besides, critical thermal energy triggering TR and chemical thermal contribution are identified. The normalized critical energy triggered by overcharging and overheating to TR are also determined. The results show compared with TR induced by overheating, TR induced by overcharging exhibits a more severe and catastrophic result due to their higher heat release, more combustible gases and mass loss. In addition, critical thermal energy triggering TR may be constant for fully charged batteries under the overheating of 300 W and 400 W, which is slightly affected by heating power (Ph). Moreover, Critical chemical heat shows a certain upward trend with increasing Ph. Critical electric energy triggering TR and critical self-generated heat slightly decrease with increasing overcharge rate. In open environment, TR induced by overheating propagates faster than that induced by overcharging.