Li-ion batteries are the most promising candidates as the power source for the (hybrid) electric vehicles and stationary energy storage systems. However, potential risks involved with the batteries are not yet fully understood. With rising the temperature, a chain of exothermic reactions can occur between the cell components, which can lead to thermal runaway. During the thermal runaway, the battery can release a significant amount of flammable and toxic gases.

In this work, the gases evolved during three groups of abuse tests, namely, overheating, overcharge and short-circuit tests, were analyzed using an accelerating rate calorimeter (ARC, EV+, Thermal Hazard Technology) and the gas chromatography – mass spectrometry (GC-MS, Clarus 690 Arnel 4019, Perkin-Elmer) method. The batteries studied in this work were mainly NMC-based cylindrical, prismatic, and pouch (LiPo) cells. Conducting the overheating abuse tests in the ARC inside a pressure-tight canister, venting of the cylindrical 21700 and the pouch cells occurred at 152 °C and 97 °C, respectively. The temperature of 152 °C is comparable to the highest values among the venting temperatures reported in the literature ( 100 °C – 170 °C), which indicates that the NMC 21700 cylindrical cell type is one of the most promising candidates with respect to the safety issues. Also, using the GC-MS method, we could identify EMC, DMC, CO2, CO, CH4 and C2H6 gas components for the cells that underwent the short-circuit abuse tests, whereas for the cells that experienced overheating, no CO, CH4, and C2H6 could be recognized. The result implies that the CO, CH4 and C2H6 were evolved mainly due to the electrochemical reactions occurring in the battery cells under the short circuit abuse condition. Furthermore, we could determine the possible sources and formation pathways of all the evolved gas components in the studied cells.