Identifying Key Aspects of Thermal Runaway Modelling for Lithium-ion Battery Cells 2022-01-0718

Electrification and hybridization of powerplants in the transportation sector is one of the most important changes in the last few decades. Lithium-ion batteries are the main energy storage systems, but despite the maturity of this technology, it has certain constrains compared to traditional internal combustion engines in the day-to-day usage. As the operating conditions of the batteries are pushed to the limits to overcome certain disadvantages relative to other conventional systems like charge and discharge times or vehicle driving range, new concerns and safety limitations must be considered. High power rates and cooling deficiencies can produce excessive operating temperatures within the cells, leading to problems with degradation or even unchain chemical reactions that can end in thermal runaway, one of the most worrying failure modes attaining electric platforms nowadays. One of the main challenges in the ordeal of designing the system considering these effects is the crossed interaction between the different thermochemical and electrochemical phenomena present during the usage of the battery cell. The objective of the present work is to study the effect of different factors and their interdependence by means of a virtual environment developed using GT-Power that is experimentally validated to include electrochemical phenomena with the package GT-AutoLion. This package allows for the consideration of internal heat generation and aging of the battery cell together with thermal runaway mechanisms to include the possibility of failure modes under extreme operating conditions. With this tool, different parameters like the cell state of charge, heat transfer or grade of aging are considered to study the interdependence of these factors and how they can affect the cell performance. The results show that while temperature dependencies are well captured by the independent models, secondary effects such as state of charge and battery aging are not well captured by the formulation of current state-of-the-art thermal runaway mechanisms.