Dynamic ejection phenomenon and modeling of velocity driven by internal pressure in thermal runaway of high-capacity NCM523 lithium-ion batteries: Advancing safety design and fire accident investigation

• Investigation of jet behavior during thermal runaway of 50Ah Li(Ni₀.₅Mn₀.₂Co₀.₃) batteries, with the jet process specifically divided into four distinct stages. • Capture of characteristic points in the jet process using high-speed imaging technology, and calculation of jet velocity based on dynamic visualization. • Systematic analysis of temperature and internal pressure during the jet process, to reveal the evolution law of thermal runaway jets. • Proposal of a predictive model for the dynamic coupling relationship between internal pressure and jet velocity based on internal pressure characteristics, considering the influence of radiative heat loss during the jet process. With the wide application of new energy vehicles, thermal runaway and combustion behavior of lithium-ion batteries have become key safety issues. The dynamic characteristics of thermal runaway jet fire eruption,such as eruption behavior and Particle Ejection Velocit,directly determine the fire diffusion risk and prevention and control efficiency. In this paper, by studying the jet behavior of 50Ah Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 batteries, combined with high-speed imaging, temperature measurement and pressure monitoring technology, the evolution law of jet is systematically analyzed, and the specific process, temperature and velocity of jet are analyzed. The jet process is divided into four processes, and a prediction model for estimating the Particle Ejection Velocit by internal pressure is established. This study reveals the key physical characteristics of the battery thermal runaway jet, which provides technical support and data reference for the safety design of ternary lithium-ion batteries and the traceability and cause analysis of lithium-ion battery accidents based on the jet behavior.