Thermal characterization of Li-ion cell electrodes by photothermal deflection spectroscopy

Abstract

Contactless and temperature-dependent evaluation of thermal diffusivities of Li-ion cell electrodes based on photothermal deflection spectroscopy (PDS) measurements is introduced and applied to electrodes from three prismatic hardcase Li-ion cells. The accuracy of the method is validated using reference materials, which cover a wide range of thermal diffusivity. The effective thermal diffusivities of the three anode and cathode coatings and of the current collectors are determined in the temperature range of 5–45 °C.Furthermore, the temperature-dependent specific heat capacity of the electrodes is evaluated by differential scanning calorimetry (DSC) measurements in the same temperature range. Based on the experimental results the through-plane and in-plane thermal conductivity of the electrodes is calculated and compared to previously reported values. The results indicate significant influence of the porosity and manufacturing process on the effective thermal conductivity of the electrodes. The three mayor impact factors on thermal conductivity of electrodes are (i) composition, (ii) morphology of the coating and (iii) the thickness ratio of coating to current collector.