Development of equivalent circuit model for thermal runaway in lithium-ion batteries

An integrated equivalent circuit model was developed to analyze thermal runaway in lithium-ion batteries under different conditions. The thermal runaway model was developed by adding various circuit components to a second-order resistor–capacitor circuit, whose values were obtained based on previous experimental studies. First, the characteristics of thermal runaway by electrical abuse were analyzed. When the charge rate was high, the maximum temperature during thermal runaway was high, and the thermal runaway ended fast. At charge rate of 3C, the maximum temperature was 209.4 °C, since a high current generates large heat, and the thermal runaway duration was 1200 s. Next, thermal runaway by mechanical abuse was analyzed by examining the state of charge effect on the maximum temperature. When the state of charge increased from 0.5 to 1, the temperature increased to 470 °C during thermal runaway because a high potential difference arises when the state of charge is high. Lastly, an integrated equivalent circuit model was developed by adding a series of resistors and capacitors in parallel to the conventional battery model. The model showed an accuracy of 87 % compared to previous experimental results. The proposed model can enable the analysis of thermal runaway during fast charge caused by combined abuse factors.