Effect of low-pressure environment on thermal runaway behavior of NCM523/graphite pouch cells with different overcharge cycles

Abstract

In the aviation field, the development and application of electric aircraft powered by lithium-ion batteries (LIBs) have received extensive attention. However, abuse due to overcharge poses a significant obstacle to its safe application. In this work, to investigate the thermal runaway (TR) behavior of overcharged LIBs in low-pressure flight environment, the TR characteristics of NCM523/graphite pouch cells with different overcharge cycles at 30 kPa are studied. The results suggest that the increase of overcharge cycles leads to a decrease of thermal stability, and an increase of TR intensity and heat release of the LIBs. In addition, the TR jet intensity at 30 kPa is significantly stronger than that of 95 kPa due to the larger differential pressure for the release of combustibles. The TR intensity and heat release at 30 kPa are significantly weaker than that of 95 kPa due to the lower oxygen content for burning. The electrochemical analysis and the disassembly photos confirm the destruction of electrode structure and the deposition of lithium. The X-ray computed tomography images and X-ray diffraction patterns suggest that the side reactions in the inner layer of the cell are more obvious than the outer layer, and the internal deformation expands from the inside out.