Quantification the expansion behavior and deformation dynamic variation of lithium-ion batteries during thermal runaway

Thermal runaway in lithium-ion batteries results in significant expansion deformation, which can potentially trigger electrical arcing and secondary hazards. However, research on the dynamic deformation behavior during thermal runaway and its mechanical impact on surrounding components remains limited. The expansion dynamics of a prismatic battery during thermal runaway were investigated. A novel sliding device was developed wherein aluminum blocks were used to simulate adjacent batteries. Real-time displacement measurements were employed to capture the free-expansion of the battery, and the pushing effect on the adjacent blocks was quantified. The sequence correlation between the temperature and the load displacement was established. A theoretical analysis of the thermo-gas-mechanical coupling mechanisms governing the load movement was performed. The results showed that expansion force during thermal runaway could substantially displace adjacent blocks, and the displacement was positively correlated with the peak temperature. Based on the time-temperature-displacement sequence, the expansion process was divided into four distinct stages. Notably, configurations with three or four aluminum blocks exhibited significantly reduced displacement. This is attributed to the increased friction, which affected the onset temperature of thermal runaway, altered internal gas generation, and consequently influenced the expansion force. Furthermore, a logical relationship was established among the internal material loss, the post-incident deformation morphology, and the position of the failing battery within a module. This study quantified the relationship between external mechanical load and thermal runaway expansion, thereby providing critical insights for mitigating arc risks and informing the design of safer battery system, particularly regarding structural layout and electrical insulation strategies.