The in-Plane Thermal Conductivity of Lithium-Ion Cells: Parametric Influences and Simulative Prediction

The in-plane thermal conductivity of lithium-ion cells is a crucial parameter for thermal management design of battery systems. However, only few measurement data and very limited information about parametric effects are available. Therefore, a simple but accurate measurement setup is presented which allows for the modification of parametric influences. Following, the effect of temperature, state of charge and state of health on the in-plane thermal conductivity is analyzed with tailored measurements for the first time. Finally, the commonly utilized approach of parallel thermal resistances is validated with experimental data first-ever. It is found that the in-plane thermal conductivity of pristine cells is nearly constant over all operating ranges. Neither temperature, nor state of charge significantly influence the in-plane thermal conductivity of lithium-ion cells. While aging does not drastically influence the in-plane thermal resistance of the cell, the cell thickness increase due to aging can significantly decrease the resulting in-plane thermal conductivity. As the experimental data matches the analytically calculated value which is obtained through parallel thermal resistances, it can be demonstrated that the prediction of the in-plane thermal conductivity with analytical calculations is accurate when cell layer thicknesses are known. Furthermore, it is proven that the copper and aluminum highly dominate the in-plane thermal conductivity.