Electro-thermal-aging framework for immersion cooling battery modules with 3D to 1D model reduction and vehicle level integration

Efficient thermal management of electric vehicle battery modules requires modeling approaches that capture spatial thermal gradients while remaining computationally efficient for system level evaluation under realistic driving conditions. This study presents a multi-scale electro-thermal-aging framework based on systematic three-dimensional (3D) to one-dimensional (1D) model reduction for a 360 cell immersion-cooled lithium-ion battery module integrated into a complete electric vehicle model. Convective heat transfer coefficients and pressure losses extracted from CFD simulations are implemented in a reduced 24-node thermal model representing coolant flow direction effects. Heat generation is obtained from an experimentally validated electrochemical model, and a temperature-dependent degradation model capturing solid-electrolyte interphase growth, cathode film formation, and active material isolation is coupled to each node to enable spatially resolved aging prediction. The reduced model reproduces 3D temperature distributions within 2 °C while decreasing computational time. Vehicle level simulations under NEDC and US06 driving cycles demonstrate that immersion cooling maintains high thermal uniformity, resulting in less than 0.5 % state of health variation across module nodes. The proposed framework provides a computationally efficient tool for evaluating immersion cooling architectures and quantifying their impact on thermal performance, degradation, and vehicle range under realistic driving scenarios.