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

摘要

Estimating the temperature distribution within Li-ion batteries duringoperation is critical for safety and control purposes. Although existingcontrol-oriented thermal models - such as thermal equivalent circuits (TEC) -are computationally efficient, they only predict average temperatures, and areunable to predict the spatially resolved temperature distribution throughoutthe cell. We present a low-order 2D thermal model of a cylindrical batterybased on a Chebyshev spectral-Galerkin (SG) method, capable of predicting thefull temperature distribution with a similar efficiency to a TEC. The modelaccounts for transient heat generation, anisotropic heat conduction, andnon-homogeneous convection boundary conditions. The accuracy of the model isvalidated through comparison with finite element simulations, which show thatthe 2-D temperature field (r, z) of a large format (64 mm diameter) cell can beaccurately modelled with as few as 4 states. Furthermore, the performance ofthe model for a range of Biot numbers is investigated via frequency analysis.For larger cells or highly transient thermal dynamics, the model order can beincreased for improved accuracy. The incorporation of this model in a stateestimation scheme with experimental validation against thermocouplemeasurements is presented in the companion contribution (Part II).