What is the thermal runaway mechanism of power batteries?
The concept of battery thermal runaway and thermal safety
Battery thermal runaway refers to a violent reaction in a battery, triggered by certain external conditions (such as puncture, overheating, short circuit, overcharging, etc.), characterized primarily by rapid and massive heat release, and potentially accompanied by other physical or chemical changes (such as short-circuit discharge, combustion, explosion, etc.).
In a power battery system, when a single cell experiences thermal runaway, its violent reaction generates a large amount of heat and may also produce violent reactions such as combustion or explosion. The resulting high temperatures or mechanical shocks often become triggering conditions for thermal runaway in neighboring cells. This process can easily spread from a single cell throughout the battery system, causing a rapid release of large amounts of energy, with extremely high hazards. Battery thermal safety issues under actual use conditions are characterized by complex mechanisms and numerous influencing factors, mainly manifested in the following aspects:
1) The thermal safety of a single power battery cell is directly related to its internal electrochemical system type, material composition, structural form, packaging form, capacity, structure, shape, size, and manufacturing process.
2) Considering the triggering conditions for battery thermal runaway, overheating, overcharging, external impacts, compression, punctures, and short circuits can all trigger thermal runaway.
3) Regarding the propagation of thermal runaway in the battery system, environmental conditions, the triggering method and loading state, the battery pack connection method, the battery thermal management method, and the location of the battery initiating the thermal runaway within the power battery system directly affect the thermal runaway propagation process.
Due to these characteristics, battery thermal safety management is particularly important, especially for improving the overall safety of electric vehicles. The design of a battery thermal safety management system generally aims to provide early warning before thermal runaway, delay its spread and propagation during thermal runaway, and minimize losses after thermal runaway. This involves developing safety protection and control strategies, and designing high-safety power battery materials, internal structures, packing methods, and battery box structures to promptly detect potential thermal runaway hazards and effectively block or delay its propagation.
