On-board monitoring of 2-D spatially-resolved temperatures in cylindrical lithium-ion batteries: Part I. Low-order thermal modelling

TL;DR

This paper introduces a low-order 2D thermal model for cylindrical Li-ion batteries using a spectral-Galerkin method, capable of accurately predicting detailed temperature distributions efficiently, aiding safety and control.

Contribution

It presents a novel spectral-Galerkin based 2D thermal model that predicts full temperature fields with minimal computational complexity, surpassing traditional average-temperature models.

Findings

Model accurately predicts 2D temperature distribution with as few as 4 states.

Validated against finite element simulations showing high accuracy.

Performance analyzed across different Biot numbers and transient conditions.

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).