Early warning of thermal runaway based on state of safety for lithium-ion batteries

Ensuring the safety of lithium-ion power batteries is the primary prerequisite for developing electric vehicles and energy storage systems. The conventional method relies on temperature parameters and only qualitatively assesses the state of safety (SOS), which reduces the warning time of the battery management system (BMS). Here we present a thermal runaway warning method based on SOS. Specifically, we analyze the strain evolution trend of thermal runaway under different abuse conditions and propose the strain trigger point for thermal runaway. Furthermore, multidimensional parameters such as temperature rise, median voltage, capacity, power, and strain are used to quantify the SOS. The SOS is a battery state parameter, with its value ranging from 0% to 100%. Experimental results demonstrate that the presented approach can warn of thermal runaway around 5 h in advance.