Research on the Repeatability of Thermal Runaway of Lithium-Ion Batteries Triggered by Heating Wires

Due to limitations in available battery samples and testing costs, lithium-ion battery thermal runaway experiments are not practical to repeat multiple times, and the reliability of experimental results is frequently questioned. To systematically evaluate the repeatability of the heating wire-triggered method in thermal runaway tests, this study investigates two types of commercial 18650 cylindrical batteries with NCM/graphite chemistry under different heating power levels and health conditions. The results indicate that under the same heating power, batteries of the same type exhibit good repeatability in thermal runaway onset time and onset temperature, with the consistency of onset time outperforming that of onset temperature. As the heating power increases, the onset time of thermal runaway decreases significantly, while the variation in onset temperature remains relatively small. Compared to fresh batteries, aged batteries show reduced variability in thermal runaway characteristics, with standard deviations in onset time generally below 7 s, the range is less than 15 s, indicating improved repeatability. The heating wire-triggered method demonstrates stable and reliable repeatability under different power levels and aging states. This study provides critical data and technical references for the standardization of lithium-ion battery thermal runaway testing, offering valuable engineering guidance for battery safety assessment.