Determination of transport parameters in liquid binary electrolytes: Part II. Transference number

In the literature, various numerical methods for the simulation of ion-transport in concentrated binary electrolytes for lithium ion batteries can be found, whereas the corresponding transport parameters are rarely discussed. In this contribution, a novel method for the determination of the transference number in non-aqueous electrolytes is proposed. The method is based on data from a concentration cell and on the value of the thermodynamic factor obtained from independent measurements based on quantifying the redox potential of ferrocene. The concentration dependent transference numbers obtained by this new method are compared to values obtained by the classical approach, which is based on experiments in a polarization cell and a concentration cell. For the latter, a set of commonly used and some newly proposed analysis methods as well as their theoretical justification are discussed. Using an exemplary electrolyte (lithium perchlorate in a mixture of ethylene carbonate and diethyl carbonate), we will demonstrate that our newly proposed method based on concentration cell experiments and a thermodynamic factor derived from independent measurements is a more accurate approach for obtaining concentration dependent transference numbers. At the end, the experimentally determined concentration dependent transference numbers are compared to data available in the literature.