关键词: 锂离子电池, 热失控, 火灾, 爆喷, 高速摄影

Abstract:

Nickel-cobalt-manganese （NCM） lithium-ion batteries were selected for usage in electric passenger vehicles to study the variation in temperature, voltage, and characteristics of explosion venting and fire during thermal runaway. Battery thermal runaway and fire tests were performed during overheating and overcharging by temperature and voltage measurements and high-speed photography. The tests determined the relation between the temperature and voltage variation laws and the explosion venting process. Under overheating conditions, the dominant side reaction involved the positive electrode and electrolyte, resulting in the production of large amounts of oxygen and combustible hydrocarbons, and the time span from battery expansion to explosion venting near the electrode tab was only 0.5 s, during which a jet flame initially appeared. Under overcharging conditions, the dominant side reaction involved the negative electrode and electrolyte; this initially produced a solid-liquid-gas mixture during explosion venting and formed a jet flame after a period of continuous venting. Under the two trigger conditions, the battery burning times were less than 50 s, the highest temperatures were approximately 700 °C, the combustion residue temperatures exceeded 500 °C, and the voltages did not change significantly before explosion venting. When compared with the experimental data obtained by previous scholars, the safety of the NCM battery series is ranked from 333, 622, 811 from high to low. This study provides an experimental basis for the practical application, thermal runaway fire prevention, and early warning technology for high-specific-energy lithium-ion batteries.

Key words: lithium-ion battery, thermal runaway, fire, explosive venting, high-speed photography