Abstract
Estimating the temperature distribution within Li-ion batteries during operation is critical for safety and control purposes. Although existing control-oriented thermal models - such as thermal equivalent circuits (TEC) - are computationally efficient, they only predict average temperatures, and are unable to predict the spatially resolved temperature distribution throughout the cell. We present a low-order 2D thermal model of a cylindrical battery based on a Chebyshev spectral-Galerkin (SG) method, capable of predicting the full temperature distribution with a similar efficiency to a TEC. The model accounts for transient heat generation, anisotropic heat conduction, and non-homogeneous convection boundary conditions. The accuracy of the model is validated through comparison with finite element simulations, which show that the 2-D temperature field (r, z) of a large format (64 mm diameter) cell can be accurately modelled with as few as 4 states. Furthermore, the performance of the model for a range of Biot numbers is investigated via frequency analysis. For larger cells or highly transient thermal dynamics, the model order can be increased for improved accuracy. The incorporation of this model in a state estimation scheme with experimental validation against thermocouple measurements is presented in the companion contribution (Part II).
Highlights
We present and validate a low-order thermal model of a cylindrical battery cell, capable of capturing 2-D thermal dynamics
To validate the SG model, the results were compared with high fidelity Finite Element Methods (FEM) simulations, implemented using the Matlab Partial Differential Equation Toolbox
To ensure the accuracy of the FEM solution, a fine mesh consisting of 3760 elements was used
Summary
High battery temperatures could trigger thermal runaway resulting in fires, venting and electrolyte leakage. While such incidents are rare [3], consequences include costly recalls and potential endangerment of human life. We present and validate a low-order thermal model of a cylindrical battery cell, capable of capturing 2-D thermal dynamics. The model is based on the spectral-Galerkin method, achieving high accuracy with minimal computational requirements, making it suitable for online applications. Matlab code to simulate the presented model is available online.
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