Thermal runaway of lithium (Li)-ion batteries is a serious concern for engineers
developing battery packs for electric vehicles, energy storage, and various
other applications due to the serious consequences associated with such an
event. Understanding the causes of the onset and subsequent propagation of the
thermal runaway phenomenon is an area of active research. It is well known that
the thermal runaway phenomenon is triggered when the heat generation rate by
chemical reactions within a cell exceeds the heat dissipation rate. Thermal
runaway is usually initiated in one or a group of cells due to thermal,
mechanical, and electrical abuse such as elevated temperature, crushing, nail
penetration, or overcharging. The rate of propagation of thermal runaway to
other cells in the battery pack depends on the pack design and thermal
management system. Estimating the thermal runaway propagation rate is crucial
for engineering safe battery packs and for developing safety testing protocols.
Since experimentally evaluating different pack designs and thermal management
strategies is both expensive and time consuming, physics-based models play a
vital role in the engineering of safe battery packs. In this article, we present
all the necessary background information needed for developing accurate thermal
runaway models based on predictive chemistry. A framework that accommodates
different types of chemical reactions that need to be modeled, such as solid
electrolyte interphase (SEI) layer formation and decomposition, anode-solvent
and cathode-solvent interactions, electrolyte decomposition, and separator
melting, is developed. Additionally, the combustion of vent gas is also modeled.
A validated chemistry model is used to develop a module-level model consisting
of networks of pouch cells, flow, thermal, and control components, which is then
used to study the thermal runaway propagation at different coolant flow
rates.
