Determining single Electrode Entropies via a novel indirect Measuring Method

Abstract

The entropy is a fundamental thermodynamic parameter to describe the working principle of a battery. Its value can be determined on a full cell level, describing the entropy differences between anode and cathode. However, its origin is based on individual effects occurring on each half-cell. Here, the entropy of a single electrode towards the used electrolyte can be measured. On this level, the effect describes the heat flux at the charge transfer reaction and the temperature induced potential difference of the electrode–electrolyte interface. In this paper, a new method to determine those entropies is developed and is described in detail. As a main advantage of this method, neither half-cell temperatures differences, nor half-cell heat flows need to be identified. Instead, an unknown but equal temperature gradient is generated between two identical electrodes resulting in a voltage difference. Through the comparison of the voltage progressions of electrodes with different entropies, their individual entropy is determined, by comparing its value towards a reference. The used experimental set-up is based on common experimental cells, making it widely accessible.