The early warning for thermal runaway of lithium-ion batteries based on internal and external temperature model

Currently, external temperature monitoring and early warning are predominantly utilized in lithium-ion batteries (LIBs), but they can't ensure the accuracy of battery safety warnings. Conversely, internal temperature analysis enables precise identification and early warning of thermal runaway events. By placing internal thermocouples into LIBs at various ambient temperatures and charge-discharge rates, the laws of internal temperature evolution were monitored. A general model of internal and external temperature relationship was proposed and applied to the early warning strategy for thermal runaway of LIBs. The experimental results indicate that the temperature difference between the interior and exterior can reach 13.16 °C and 17.17 °C respectively at room temperature. In addition, under different charging and discharging rates and ambient temperatures, a strong linear correlation is observed between the internal and external temperatures of the battery. The slope remains consistent across different charge and discharge rates. With respect to different ambient temperatures, the temperature factor exhibits variability ranging from 1.46 to 1.88. The proposed strategy for thermal runaway early warning moves forward the time window of thermal runaway warning, offering reliable early warning of thermal runaway.