Benign-to-malignant transition in external short circuiting of lithium-ion batteries

External short circuiting (ESC) is a main source of battery faults. However, the ESC damage mechanism and its evolution process are unclear, resulting in difficulties in safety management. Here, we report the impact of different ESC durations on battery performance and divide the ESC process into four stages. The analysis reveals that there is a benign regime in which the ESC effect is comparable to nominal charge-discharge cycling. When ESC duration is close to a critical time, there is a benign-to-malignant transition. The critical time corresponds to the inflection point at the end of battery current curve, which reflects heating-induced membrane melting and contraction that distorts the jellyroll. The critical time surface under various conditions is established and the center temperatures of the critical time and battery completely failure are disclosed, paving the way for fault diagnosis and using “benign ESC” in a controlled fashion.