Verification and Validation of Thermal Models for Li-ion Pouch Cells

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Temperature has significant impact on the dynamic performance, operating limits as well as aging phenomena of Li-ion battery cells. Due to the complex and often limiting heat transport paths and the uneven heat release within the cell core, the inner temperature distribution can be highly inhomogeneous. At the same time, it is challenging to gain valid experimental access to the temperature distribution within the cell. Considering this fact, numerical simulation models come into focus. Thermal models are used to obtain a deep insight into the thermal behavior, especially the heat transport processes and temperature distribution in battery cells. Moreover, the interaction between the heat transport paths within the cell, externally applied thermal management systems and the combined influence of both of them on the temperature distribution can be systematically examined in this way. However, simplifications and model reduction techniques like homogenization approaches are often used to save computational effort and reduce simulation time.
In this context, the verification and validation of the reliability and accuracy of such simulation models by means of comparisons with those from highly detailed models and appropriately designed experiments are of great importance. This contribution presents an approach for a verification strategy of pouch cells. The 3D thermal model[1] with locally resolved material layers and locally assigned material properties as well as heat sources is used to provide an accurate representation of the temperature distribution inside the cell, serving as reference for verification. The higher numerical costs, which are caused by a lower level of homogenization resulting in mapping a large number of layers, are compensated by the use of efficient numerical methods.[2]
A method for verification of thermal simulation models is introduced based on an appropriate test problem with an explicit solution as well as the application of the method to the battery geometry. This contribution will demonstrate an analysis of thermal simulation results taking different cooling scenarios into account.[2]

Keywords: Li-ion battery, Thermal Modeling, Verification, Numerical methods, Temperature distribution.

[1] O. Queisser, L. Cloos, F. Boehm, D. Oehler, T. Wetzel, Energy Technol. 2021, DOI:10.1002/ente.202000915.
[2] Z. Veszelka, O. Queisser, M. Gontscharow, T. Wetzel, W. Dörfler, Energy Technol. 2020, DOI: 10.1002/ente.202000906.

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