An Electrochemical-Thermal-Mechanical Model for Large Format Lithium Ion Batteries

Abstract

The intercalation reaction in Lithium-Ion batteries causes significant volume changes in the active material phases during cycling. Due to spatial limitations in common battery applications, this entails mechanical stresses on different length scales and thereby influencing performance and lifetime of the battery[1]. Mechanical effects are closely linked to electrochemical and thermal processes in the cell, giving rise to complex interactions that are difficult to predict. Moreover, large cell dimensions, which become ever so common in today’s battery industry, further increase complexity due to local variations of state variables. Therefore, modeling is essential to enhance understanding of the governing- and limiting processes.In this contribution we present a fully coupled multi-scale-, multi-physics-model that combines an electrochemical model on the particulate electrode level, namely an extended Newman model featuring a particle size distribution, and a homogenized cell material model, displaying anisotropic electrical-, thermal- and mechanical properties. To include mechanical effects into a multi-physics-model[2] a new approach is considered. We apply the poroelastic theory to describe the mechanical behavior governed by the interaction of the porous electrode matrix and the infiltrated electrolyte. The use of homogenization techniques allows to keep the computational effort in check, while still doing justice to the complexity of a three-dimensional-, multi-scale-, and multi physics problem. The model is parametrized in-house by applying different electrochemical-, mechanical-, and microstructural characterization methods. The model, its parameterization and validation as well as selected simulation results will be presented. Acknowledgements This work was funded by the Deutsche Forschungsgemeinschaft (DFG) in the framework of the research training group SiMET (281041241/GRK2218).[1] Y. Zhao, P. Stein, Y. Bai, M. Al-Siraj, Y. Yang, B.-X. Xu, Journal of Power Sources 2019, 413, 259–283.[2] A. Schmidt, D. Oehler, A. Weber, T. Wetzel, E. Ivers-Tiffée, Electrochimica Acta 2021, 393, 1–14.