Cross-scale investigation of overcharge-induced thermal runaway propagation mechanism in sodium-ion batteries under multi-module configuration

In electrochemical energy storage systems, the sodium-ion battery is typically integrated in the form of a “cell-module-cluster”, but its cross-scale thermal runaway triggering risk and the propagation mechanism remain unclear. This study reveals the cross-scale thermal runaway triggering and propagation behavior of sodium-ion batteries of “cell-module-cluster” under overcharge conditions, and investigates the effects of key factors, including module spacing, triggering cell location, and heat dissipation condition, on the thermal runaway propagation behavior. Results demonstrate that the thermal runaway propagation in a module containing the overcharged cell follows a sequential triggering mode, while thermal runaway in the downstream module exhibits a simultaneous triggering mode with greater severity. Furthermore, increasing the module spacing or enhancing the heat dissipation capacity can effectively reduce the heat accumulation and prevent the trigger of thermal runaway. On the above basis, the multi-dimensional evaluation strategy is proposed to quantitatively assess the hazard of sodium-ion battery cluster thermal runaway. The findings serve as a foundation for the safe design of sodium-ion batteries in energy storage systems.