Thermal Runaway and Fire Behaviors of Lithium Iron Phosphate Battery Induced by Overheating and Overcharging

Lithium ion batteries (LIBs) have become the dominate power sources for various electronic devices. However, thermal runaway (TR) and fire behaviors in LIBs are significant issues during usage, and the fire risks are increasing owing to the widespread application of large-scale LIBs. In order to investigate the TR and its consequences, two kinds of TR tests were conducted triggered by overheating and overcharging ways. The cells are 228 Ah with LiFePO4 as cathode. The TR and fire behaviors were studied comprehensively from the aspect of experimental photographs, temperature characteristics, heat release rate (HRR), total heat release (THR), voltage and mass loss variation. The effects of different triggers were investigated. Under the two trigger conditions, the LIBs did not self-ignite and instead only release a large amount of gases or aerosols. With external ignition sources, the combustion process can be classified into four stages. The relationship between TR and fire behaviors related to the two conditions are discussed, respectively. Compared with overheating, the batteries burn more violently and have higher fire risks during overcharging tests. The work is supposed to provide valuable fundamental data and theory guidance for early warning technology and fire protection.