Safety concerns are the main obstacle preventing the large-scale application of lithium-ion batteries in electric vehicles.

With the continuous improvement of the energy density of lithium-ion batteries, improving their safety is more and more urgent for the development of electric vehicles.

Thermal runaway is a key scientific issue in battery safety research.

Therefore, a comprehensive review of the thermal runaway mechanism of commercial lithium-ion batteries for electric vehicles is presented.

Drawing on typical accidents, a summary of abuse situations that can lead to thermal runaway is presented. Abuse conditions include mechanical abuse, electrical abuse, and thermal abuse.

Internal short circuits are the most common characteristic of all abusive conditions.

Thermal runaway follows the mechanism of a chain reaction in which decomposition reactions of battery component materials occur one after the other.

A new energy release map is proposed to quantify the reaction kinetics of all battery component materials to explain the chain reaction mechanism during thermal runaway.

The relationship between internal short circuits and thermal runaway is further clarified using energy release diagrams for both cases. Finally, a three-level protection concept is proposed to help reduce the risk of thermal runaway.

By providing passive defense and early warning before thermal runaway occurs, the inherent thermal stability of the material is enhanced, secondary hazards such as thermal runaway propagation are reduced, and three-level protection is achieved.