Characteristics of Temperature and Gas Concentrations within Battery Module During Overheating- and Overcharging-Induced LiFePO4 Battery Failure

This paper studies the evolution of temperature of gases and concentrations of O2, CO2, and CO gases, and battery's temperature during overheating- and overcharging-induced LiFePO 4 battery failure within a full-scale module box. Under the both abusive conditions, the battery experienced two times of safety venting. The CO and CO2 concentrations sharply rose at different locations simultaneously at both safety venting under overheating and overcharging, indicating that the released gases filled the module box instantly. Peak concentrations of 4269 ppm CO and 1.3% CO2 were measured during the first safety venting under overheating, whereas higher peaks of 7100 ppm CO and 6.52% CO2 under overcharging were measured. The lower peak CO and CO2 concentrations under overheating was attributed to the more amount of released vaporized electrolyte and smoke. During the safety venting in the overheating experiment, the area where the temperatures rose over 5 ℃ accounted for 92% of the battery module's horizontal area. However, under overcharging, the area under the corresponding condition accounted for only 36%. The main release time of smoke and gases under overheating was about three times of the time under overcharging, leading to the more widespread rise of the temperature of the released gases. The venting of more vaporized electrolyte was another reason of the widespread rise under overheating. The distinct characteristics under each abusive condition should be given attention to in the study of battery failure mechanism, as well as in the development of early warning systems.