Influence of Cell Selfheating on Dependence of Area Specific Resistance from Current Density

The dependence of area specific resistance (ASR) of single cell is often characterized as function of temperature and current density. Whereas the ASR temperature dependence shows the Arrhenius-type behaviour, the current density dependence is expected to underly Butler-Volmer equation. Measurement of ASR dependence from current density is, however, ambiguous as it assumes the constant cell temperature during the measurement, which is not true at least at high current densities. To address this challenge series of measurements on single cells with simultaneous temperature sensing have been performed in ceramic housing. The temperature dependence of ASR has been measured at moderate current density of 300 mA/cm². Afterwards the ASR as a function of current density and corresponding increase of cell operating temperature were determined. The decrease of ASR with increase of current density has been measured in all experiments. The analysis of the ASR dependence on current density taking into account the temperature increase during the measurement leads to conclusion that no current density dependence could be observed for the analysed samples. The observed deviation from Butler-Volmer-type behaviour is discussed in terms of magnitude of overpotential losses in electrodes resulting from corresponding current density increase.