Determination of the through-plane thermal conductivity and specific heat capacity of a Li-ion cylindrical cell

Abstract

Despite the high popularity of lithium-ion batteries there is still a lack of simple and easily applicable methods for determining the Li-ion cell thermal parameters. Information about the specific heat capacity and thermal conductivity of Li-ion cells is required to ensure appropriate operation of the thermal control system of the Li-ion battery, which prevents battery operation in an unacceptable temperature range. The method presented in this paper allows to simultaneously determine the specific heat capacity and through-plane thermal conductivity of any Li-ion cylindrical cell in a simple and inexpensive way with the help of temperature and heat flux measurements on the cell surface. Moreover, the method allows to estimate the temperature dependence of the thermal parameters under consideration. The applicability of the method is evaluated on the reference sample, whose thermal parameters are close to the thermal parameters of Li-ion cylindrical cells and well known. The slight deviation of the measured values of specific heat capacity and thermal conductivity from the reference values, being less than 0.5% and 3.2%, respectively, for all cases under study, confirms the applicability of the method for determination of the thermal parameters of cylindrical Li-ion cells. Therefore, the method is applied to measure the thermal parameters of 18650-type and 26650-type cylindrical Li-ion cells at different values of temperature and SoC. The uncertainty analysis of the proposed method allows to give recommendations to achieve a high accuracy of thermal parameter determination.