Multi-functional thermal barrier suppresses battery thermal runaway propagation and degradation

Thermal runaway propagation is the utmost safety issue for electric vehicles, especially with the wide application of large-format high-energy batteries. Mitigating thermal runaway propagation is one of the most significant challenges. This study proposes a multi-functional ultrathin, robust, and elastic thermal barrier to suppress the catastrophic thermal runaway propagation in large-format battery modules. The composite thermal barrier exhibits superior thermal-mechanical properties, maintaining the temperature rise within 35 °C and 120 °C under 1000 °C fire strikes and severe durability-heating tests, respectively. Besides, the thermal barriers provide desirable damage tolerance under severe suppression, lessening the “Breathing Effect” of the batteries and maintaining higher remaining capacity after 1000 cycles. Moreover, the thermal barrier effectively suppresses the thermal runaway propagation. The thermal runaway propagation interval between the first two triggered battery cells is extended to 762.8 s for escape, rescue, and fire extinguishing; the following cells are safe. Microscopic characterization proves that the thermal barrier contains more silica after burning. The overall shape remains complete, providing an enhanced thermal resistance effect. A novel dynamic thermal runaway propagation mitigation model is proposed, which is consistent with the experiments. Furthermore, the “No thermal runaway propagation” boundary thermal conductivity (λ = 0.04 (W/(m·K)) is determined based on dynamic modeling and the Bisection method. Thermal runaway propagation can be eliminated with lower thermal conductivity. This study guides the safety-durability design of high-energy-density electric vehicles and other hazardous applications.