Venting composition and rate of large-format LiNi0.8Co0.1Mn0.1O2 pouch power battery during thermal runaway

Lithium-ion batteries have been widely used as a power supply and energy storage device, but safety issues such as thermal runaway still make the application not very optimistic. Venting is one of the thermal runaway characteristics of lithium-ion batteries. The gas composition and venting rate is of far-reaching significance for evaluating the impact of batteries on the environment and people, predicting and simulating the development of thermal safety events. Therefore, in this study, a large-format pouch power battery (LiNi0.8Co0.1Mn0.1O2) was investigated for venting during thermal runaway, including composition and rate. The thermal runaway processes of 0%, 50%, and 100% SOC cells were analyzed according to the temperature, pressure, and video recordings. The gas chromatograph-mass spectrometer (GC-MS) was used to comprehensively identify the venting gas composition of cells. Results show that with the increase of SOC, the gas production composition of the battery became more complex, and the marked gas concentration was higher. The gas and heat production of the cells also increased accordingly. The gas production mechanism of the thermal runaway cells is revealed, and it is believed that the increase in the amount of lithium intercalation in the negative electrode enables more gas production reactions to occur more thoroughly. Besides, three methods for predicting the cell's venting rate based on mass loss, temperature and pressure changes, and gas concentration are compared.