An experimental analysis on thermal runaway and its propagation in Cell-to-Pack lithium-ion batteries

• A description of the characteristics of TR in Cell-to-Pack batteries is provided. • There is very low variability between jelly roll temperature at different locations. • The specific heat capacity and energy loss of the multiphase vents were calculated. • The time it takes for TR to propagate within the battery is affected by heating power. • The temperature of the jelly roll is 487℃ higher than the surface temperature. Thermal runaway and its propagation are the technological barriers for the large-scale promotion of new energy vehicles and energy storage. This paper investigates the temperature characteristics between jelly rolls, influence of heating power on internal propagation time and energy flow during thermal runaway propagation through experiments and models. Results indicated that the maximum temperature between jelly rolls has a maximum temperature difference up to 487℃ compared to the surface temperature during thermal runaway. The distribution of energy flow showed that approximately 60% of total energy was used to self-heated and approximately 31% was emitted through venting. Experimental results and model calculation shows that the time it takes for thermal runaway to propagate within the Cell-to-Pack battery is affected by heating power. This study provides a reference for creating safe cell designs, developing mitigation strategies for addressing thermal runaway propagation in system, and investigating battery-related accidents in new energy vehicles and energy storage.