Thermal runaway behavior of large-format sodium-ion and lithium-iron phosphate batteries under different trigger sources: A comparative study

Sodium-ion batteries (SIBs) have emerged as a promising complementary technology to lithium-ion batteries (LIBs), primarily due to their potential for cost-effectiveness and resource sustainability. However, the thermal safety of SIBs still needs to be evaluated, as it is crucial for their potential application in electric vehicles and energy storage fields. In this study, we systematically examine and compare the thermal runaway (TR) and gas venting behaviors of 185 Ah Cu-Fe-Mn-based sodium-ion (CFM) and 314 Ah LiFePO₄ (LFP) batteries under overcharging and overheating conditions-factors. Experimental results indicate that the TR process in CFM batteries exhibits distinct characteristics when compared to LFP batteries. Under overcharging conditions, CFM batteries experience more severe temperature fluctuations than those observed during overheating-maximum TR temperatures reach 620.9 °C and 587.3 °C, respectively-significantly higher than those recorded in LFP batteries. The activation time of the safety valve is similar to the onset of TR in both scenarios. Gas analysis reveals that the primary gaseous compositions generated during TR in CFM batteries are comparable to those produced by LFP batteries, with total gas volumes measuring 397.6 L during overheating and 699.3 L during overcharging. Although CFM batteries demonstrate superior resistance to overcharging relative to LFP counterparts, their elevated TR temperatures coupled with substantial emissions of combustible gases-including hydrogen, carbon monoxide, and methane considerably heighten combustion and explosion risks. These results may contribute to safer integration of CFM batteries in future applications, such as in electric vehicles, charging station and energy storage systems.