Detection of Li-ion battery failure and venting with Carbon Dioxide sensors

Li-ion battery thermal runaway is a critical safety issue for Electric Vehicles. The proposed global technical regulation No. 20 by the United Nations on Electric Vehicle Safety requires an advanced warning 5 minutes prior to the evolution of hazardous conditions caused by thermal runaway. To achieve this 5-min advanced warning, a robust and sensitive detection methodology is required. Gas venting is often a precursor of thermal runaway, and therefore the use of gas-based detection method was evaluated in this paper to explore its response and implementation within a battery pack. The composition of battery vent-gas during a thermal runaway event includes CO2, CO, H2 and volatile organic compounds (VOCs). Among these gas species, there is still some debate about which is most suitable for detection. To resolve this debate, the composition of vent-gas under different testing conditions is summarized from the literature and CO2 is proposed as the target gas species due to its significant presence and early occurrence in all venting events. After evaluating available sensors, the Non-Dispersive Infrared (NDIR) CO2 sensor is considered due to its robustness and cost effectiveness. To further clarify the responsiveness of the NDIR CO2 sensor, an overcharging experiment leading to cell venting was conducted with a prototype gas sensor suite. The measured CO2 concentrations of over 30,000 ppm were detected with the gas sensor. Lastly, we demonstrate how a representative venting experiment of a single cell can be used to guide and set the sensed CO2 threshold that will trigger an alarm in a battery pack volume.