Multi-length-scale thermal modeling of lithium-ion batteries from sub-cell to pack

Lithium-ion batteries (LIBs) have become the preferred power source for electric vehicles (EVs) due to their superior characteristics compared to other storage technologies. Battery thermal management systems are paramount for optimal performance and reliability, to maintain EV battery packs operating within a tight temperature range (25–40 °C) while keeping spatial temperature uniformity. EV battery packs are advanced engineering systems that exhibit hierarchical thermal transport across multiple length scales and physical domains, ranging from electrodes to sub-cell, cell, module, pack, and vehicle domains. This paper presents a novel cost-effective multi-length-scale methodology designed for modeling thermal transport in EV battery packs hierarchically, following successive incremental sub-domain thermal analyses and transferring effective anisotropic thermophysical properties and distributed heat generation rates across sub-cell, cell, module, and pack domains. Through a detailed industry-relevant case study of a pouch-cell-based EV battery pack, this work demonstrates the implementation of this hierarchical methodology and its ability to evaluate how design modifications at different scales influence the system’s thermal performance. This hierarchical multi-length-scale methodology enables the quantification of how changes in the design of a component at smaller scales impact the overall performance and reliability of the entire system.