Micro Scale Lithium Ion Battery Modeling with the Finite Element Method

Novel research is currently being performed on commercialization of higher capacity anode materials. Additionally, optimized battery technology for electric vehicles puts increasing demand on faster charging protocols. Both of these demands are theoretically very achievable today, but they inevitably have shortcomings of a decreased battery cycle life and a reduction in battery performance. The shortcomings can be attributed to large mechanical stresses and the rapid growth of corrosive aging mechanisms occurring at electrode-electrolyte interfaces. This dissertation will focus on the study of these unwanted phenomena at the battery's microstructural length scale to aid current research in lithium ion battery optimization. This dissertation combines various existing works to formulate the foundation for a complete multiphysics battery model with the incorporation of corrosive reactions hindering the life cycle and performance of the battery. The reactions that are considered include the formation and growth of the solid electrolyte interphase and plated lithium metal. We will illustrate the implications and limitations of common battery modeling methods with our more detailed microstructural model of a battery cell. We use the finite element method to solve the general governing equations and implement surface reaction kinetics via appropriate Butler-Volmer expressions. We use our model to illustrate the limitations of common experimental techniques, such as the Galvanostatic Intermittent Titration Technique and the Potentiostatic Intermittent Titration Technique, which are used to determine important material transport properties. We then demonstrate how small changes in electrode particle geometry can result in large changes on the mechanical stress and the reaction rates of unwanted chemical reactions. Lastly, we will calculate sensitivity measures through a global sensitivity analysis of the finite element material parameters. These results indicate which material parameters should be experimentally verified and used cautiously in battery modeling.