Multi-scale thermal modeling, experimental validation, and thermal characterization of a high-power lithium-ion cell for automobile application

Detailed thermal analysis of individual cell types used to power electric propulsion systems is rarely performed. Nano structured lithium-iron-phosphate or LFP cathodes show great promise in automobile application due to stable discharge profile and excellent safety features. This study is aimed at thermal characterization of a commercially favored lithium-ion cell under variable loads and operating conditions. An innovative reduced order electrochemical-thermal coupled model is developed using multi-scale multi-domain (MSMD) approach. A pseudo 2D (1D + 1D) electrochemical heat generation model is dynamically coupled to a 3D heat transport model. 3D cell domain is discretized using finite element (FE) mesh. Six representative discretization elements are selected for coupling. Electrochemical model is solved using a C-based code for each of the six elements. Model is validated using experimentally measured data and found to be in good agreement. Reduced order coupled model adequately captures temporal as well as spatial variations in cell temperature with sufficiently moderate computational expense. Simulation results show that lower operating temperatures and higher applied currents erode cell capacity. Optimum operating temperature window for the selected cell is found between 10 degrees C and 50 degrees C.