Characteristics and generation mechanism of ejecta-induced arc for lithium-ion battery during thermal runaway

As the widespread adoption of lithium-ion battery, the incidence of electrical faults is on the rise. While arc faults are commonly associated with loose connectors or damaged insulation, their potential initiation during battery ejection represents a significant and unaddressed research gap in the field of battery safety. In this study, the battery was heated to venting to investigate the characteristics and mechanism of ejecta-induced arc. The results show that the arc can be induced at voltage of 50 V and above under 3 mm and 5 mm electrode spacing, while the critical voltage ranges from 200 V to 400 V at 7 mm spacing. The number of arc events increase if the ejected pieces stuck on the electrode surface since it is equivalent to reduce the electrode spacing. Through the analysis of the electrical characteristics of each arc, three distinct arcing modes are identified: particles dominant, pieces dominant, and combination. Based on the measured resistivity of battery ejecta and resistance estimation of particles dominant arc, the pieces play a more important role than particles in the initiation of ejecta-induced arc. Furthermore, the safety boundary against ejecta-induced arc is proposed based on the critical electric field strength, and the safe electrode spacings for typical voltage of 400 V, 800 V, and 1500 V are 9.9 mm, 14.0 mm, and 19.2 mm, respectively. The results are expected to provide valuable guidance in safety design of lithium-ion battery systems.