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Internal short circuit (ISCr) is one of the major reasons for lithium-ion battery thermal runaway. A new phenomenon, named as the Fusing Phenomenon, is observed during the ISCr experiments. During the Fusing Phenomenon, the ISCr current path will melt down due to the Joule heat of the short current and the ISCr process will be interrupted. The Fusing Phenomenon raises the re-ISCr problem, which means that the battery may have an ISCr again after the end of the former ISCr process. The Fusing Phenomenon's life cycle is given by the hypothesis, which includes the heating-melting period, the ion discharging period and the implosion period. The heating-melting period is analyzed using an axisymmetric local ISCr model. When the ISCr area radius increases, the ISCr current path melting position will change from the ISCr area to the ISCr area edge of the aluminum current collector. If the ISCr area radius is large enough, the battery will run into the thermal runaway instead of the Fusing Phenomenon. The influence factors of the Fusing Phenomenon, including the ISCr area radius and the ISCr material, are analyzed. This research provides new insights on the battery ISCr and enriches our understanding of the ISCr process.

Internal short circuit (ISCr) is one of the major safety issues of lithium batteries and would lead to thermal runaway of batteries. Repeating ISCr in laboratory requires to create small-scale short circuit inside integrated batteries, which is very hard for existed safety test methods. In this paper, a novel ISCr trigger method based on shape memory effect of shape memory alloy (SMA) is proposed, which is easy to be implanted into batteries while has minor influences on batteries normal performance. The proposed SMA ISCr trigger method is employed to conduct ISCr experiments, including the severest type of ISCr, the Aluminum-Anode ISCr, and the most common type of ISCr, the Cathode-Anode ISCr. The experiments results show that the Aluminum-Anode ISCr leads to explosion while the Cathode-Anode ISCr only leads to mild self-discharging. Compared with the nail penetration test, the proposed SMA ISCr trigger method in the Aluminum-Anode ISCr experiment has 1) better consistency, given that all of the 4 tested batteries have their maximum temperature in the range of 383∼393 • C; 2) better reliability in evaluating battery safety properties, given that all of the 4 tested batteries have the repeatable explosion behavior. The relative ease of inserting this controllable SMA ISCr and the repeatability of the produced data can lead to better modeling and detection techniques of battery internal shorts such as plating and dendrite formation. The lithium battery becomes more and more popular among electronic devices and electric vehicles, due to its high energy density, good power density and long cycle life.

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