Direct Electrochemical Determination of Thermodynamic Factors in Aprotic Binary Electrolytes

We propose a novel method to determine the thermodynamic factor of binary salts dissolved in aprotic solvents as a function of salt concentration. The method is based on cyclic voltammetry experiments conducted in a three-electrode cell with the ferrocene/ferrocenium redox couple being used as an internal standard. The main advantage of this experimental setup is the direct electrochemical determination of the thermodynamic factor from a single type of experiment without the necessity of additional assumptions on other transport parameters. The theoretical derivation of the used relationship between peak/half-wave potentials and the thermodynamic factor as well as non-ideal effects which distort the experimental results, such as uncompensated resistances or concentration overpotentials are discussed in detail. Different strategies are suggested to avoid these non-ideal effects using the peak separation of the cyclic voltammograms as an inherent quality measure for the experimental data. Applicability of the experimental procedure is demonstrated for LiClO4 in EC:DEC (1:1, w:w) in the range from 5 mM to 2 M and repeated for typical LiPF6 containing electrolytes. At the end, the obtained results are compared to thermodynamic factors of similar electrolyte solutions published in literature. (C) The Author(s) 2016. Published by ECS. All rights reserved.