Challenges and Opportunities in Hierarchical Multi-Length-Scale Thermal Modeling of Electric Vehicle Battery Systems

This expert view article reviews the latest developments, challenges, and opportunities in hierarchical modeling of electric vehicle (EV) battery systems across multiple length scales from battery electrodes to cells, modules, and packs. Special emphasis has been placed on thermal modeling developments over the past six years. The article starts with an overview of lithium-ion battery-powered EVs, adoption barriers, and the fundamentals of battery heat generation, temperature effects, and battery thermal management systems (BTMS). This article provides a comprehensive insight into the latest electrode-to-pack modeling methodologies and the complex multiphysics phenomena impacting BTMS across hierarchical length scales. At the electrode level, this article reviews atomistic modeling methods with density functional theory, molecular dynamics, and machine learning algorithms, as well as how these methods have revealed novel two-dimensional materials and heterostructures as promising nanostructured electrode materials for next-generation batteries. At the cell level, the article focuses on form-factor dependent cell performance, characterization of anisotropic thermophysical properties and distributed heat generation, and high-fidelity battery cell thermal models coupled with electrochemical and equivalent circuit models. At the module and pack (system) levels, the article highlights the challenges of scaling up high-fidelity electrochemical-thermal coupled models to the system level, the advantages of reduced-order lumped-parameter thermal and electrical network models, and the opportunities presented by surrogate modeling methodologies, including data-driven and physics-informed machine learning approaches. This expert view concludes with a perspective on the role of digital twins for battery systems.