In-situ measurement of the thermophysical properties of cylindrical batteries under calibrated iso-flux condition

Abstract

The thermophysical properties of lithium-ion batteries are significant in the thermal management and thermal safety for electric vehicles (EV). In this paper, an in-situ measurement method of the thermophysical properties focusing on the cylindrical batteries are proposed, in which the thermal protection setup is developed to enable radial thermal conductivity measurements under a calibrated iso-flux condition, with a minimal heat leakage by no more than 3 % during the test period. Based on the theoretical analysis, the radial thermal conductivity of the cylindrical battery is obtained during the transient temperature rise stage, whereas the specific heat is obtained by double exponential fitting during the stage close to the quasi-steady state. The radial thermal conductivity is calculated through matching the one-dimensional thermal simulation results with experimental data. It is indicated that the experimentally obtained specific heat ranges from 987.2 to 1076 J kg⁻¹ °C⁻¹, increasing proportionally as the radial thermal conductivity rises from 1.147 to 1.250 W m⁻¹ °C⁻¹ with the temperature ranging from −15 °C to 45 °C. This method possesses the advantages of simultaneous determination of specific heat and normal thermal conductivity with reduced test time and augmented accuracy, which would have profound impact in the analysis and design of battery thermal management.