Experimental study of thermal runaway propagation along horizontal and vertical directions for LiFePO4 electrical energy storage modules

With the growing installation of electrochemical energy storage systems, the safety issues of lithium-ion batteries have attracted extensive attention. To identify the development of thermal failure in energy storage systems, horizontal and vertical thermal runaway (TR) propagation characteristics of lithium-iron-phosphate battery modules with different connections are systematically investigated herein. Once TR occurs in the initial battery, it initially propagates to subsequent batteries along the horizontal direction, followed by vertical propagation to the upper batteries. Particularly, the almost simultaneous occurrences of TRs in the upper batteries accompanied by extreme combustion are observed during vertical propagation, exhibiting huge thermal hazards. The maximum temperature and heat release of upper batteries are 548.3 °C and 490.7 kJ, much higher than that of lower batteries with values of 423.2 °C and 217.7 kJ, demonstrating upper batteries experience severer TR. Moreover, the heat generated by the combustion of the individual battery can increase temperatures of upper batteries by 30 °C–40 °C, which is insufficient to cause vertical TR propagation, while TRs of upper batteries will eventually be triggered with the proceeding of horizontal TR propagation. The results provide valuable information for TR propagation between battery modules and benefit the safety application of energy storage systems.