Thermal modelling of cylindrical Li-ion battery cell

Abstract

This thesis investigates the thermal behaviour of a commercial 21700 NCA lithium-ion cell through combined experimental characterisation and lumped thermal modelling. The work focuses on quantifying heat generation mechanisms and predicting temperature evolution under various operating conditions. Experimental measurements include open-circuit voltage profiling, entropic heat coefficient determination, heat-transfer coefficient estimation, and charge–discharge cycling at 0.5C, 1C, and 2C. Additional calorimetric experiments are conducted to validate the thermal model under controlled thermal boundary conditions. The modelling framework incorporates reversible and irreversible heat generation, temperature-dependent parameters, and a thermal time constant extracted from cooling-curve analysis. Model predictions are evaluated against measured temperature responses, showing reasonable agreement across all tested C-rates. The results highlight the influence of current rate on heat generation, voltage relaxation, and thermal response, while demonstrating the suitability of a calibrated lumped model for representing the thermal dynamics of cylindrical Li-ion cells. The developed methodology provides a practical foundation for future battery thermal management design and for scaling cell-level thermal characteristics to module-level simulations.