In-situandex-situmeasurements of thermal conductivity of supercapacitors

Thermal signature of supercapacitors are investigatedin-situandex-situusing commercial supercapacitors. Regarding thein-situmethod, four supercapacitors were connected in series, with thermocouples embedded between the supercapacitors. As the applied current was increased, the temperature measured at the intrinsic positions also increased. When cycling at a current density of 0.11 A cm−2the centre temperature increased by 14 K compared to the stack surface temperature. This is an important figure as literature states that an increase of 10 K leads to a corresponding decrease in the lifetime by a factor of 2. Using the obtained temperature profiles, the effective thermal conductivity of the stack was found to vary between 0.5 W K−1 m−1and 1.0 W K−1 m−1, depending on the compaction of the stack. For the ex-situ measurements, the thermal conductivity and the thicknesses of the supercapacitor material layers were measured individually in order to determine the corresponding thermal conductivity of the stack. When using this method an effective thermal conductivity of the stack of 0.53 ± 0.06 W K−1 m−1was obtained. The analysis also demonstrated that the main contributor to the thermal resistivity and conductivity of the supercapacitor construction is the electrodes. This demonstrates that when managing heat from supercapacitors it is important to focus on the thermal conductivity of the components materials.