Blocking thermal runaway propagation in large-format sodium-ion battery system through localized energy release

Cascading thermal runaway (TR) propagation poses a critical safety concern for large-format sodium-ion battery (SIB) systems because of the heightened risks of fires or explosions. However, effectively suppressing TR propagation without introducing unintended side effects remains a significant challenge. Herein, we demonstrate a localized energy release method to mitigate TR, by reducing the state of charge (SOC) of cells adjacent to the thermally runaway unit. We discover that as the SOCs decreased from 100% to 25%, the TR trigger temperature decreased significantly, and the maximum temperature decrease from 367 to 229 °C. Meanwhile, the volume of gas decreased to one-third of its original value, while the range of explosion limits significantly narrowed. The analysis of the morphology of the debris further confirms that the structural damage is greater at higher SOC levels. Moreover, an Entropy Weight and Technique for Order Preference by Similarity to an Ideal Solution (EW-TOPSIS) method has been established to assess the safety status of SIBs, showing that the TR possibility is nearly linear with the SOCs, and the TR hazard is exponentially related to the SOCs. Finally, when the SOC of cells adjacent to the TR cell is reduced to 25%, TR can be directly blocked without the need for additional cooling or thermal insulation methods. This study not only advances the understanding of TR behavior in SIBs but also offers a straightforward approach to mitigating the TR risk in SIB systems.