Investigation of the risk of thermal runaway in a pouch-type lithium-ion battery with an internal short based on a multiphysics simulation

Most safety accidents involving lithium-ion batteries (LIBs) are caused by internal short circuits (ISCs). If ISCs occur for various reasons, the temperature in a small region near the short circuit can increase to a critical threshold, leading to accelerated heat generation and resulting in thermal runaway. Therefore, it is crucial to identify the internal phenomena preceding thermal runaway to prevent or mitigate associated risks. In this study, an electrochemical-electrical-thermal model was employed to simulate a 22Ah pouch cell with ISCs. We examined the electrical-thermal behaviors of the LIB cells under different conditions, including various sizes, shapes, and locations of ISCs. Our study revealed several significant findings regarding factors influencing thermal runaways. We found that the size of the ISC was a critical factor determining the initiation of thermal runaway. As the radius of ISC increased from 0.25 mm to 1.25 mm, the amount of generated heat energy dramatically increased from 4.1 kJ to 85.4 kJ. When the radius of ISC was 0.35 mm or greater, the local temperature of the LIB cell exceeded the trigger temperature of thermal runaway (150℃). Additionally, we found that the perimeter of the ISC also affected heat generation, even when the area of ISC remained constant. With a maintained ISC area of 1 mm2, the heat generation increased from 17.2 kJ to 28.3 kJ as the perimeter increased from 4 mm to 32.125 mm. However, the location of the ISC had minor effects on the short current and the amount of heat generated. These crucial findings from our study can serve as safety guidelines for estimating the risk of thermal abuse associated with ISCs.