Towards a Simplified Electrochemical Method of Assessing Cations Transference Numbers of Electrolytes

A simplified method is presented to extract the transport parameters of a liquid electrolyte solution from an experiment in a four-electrode cell. By observing that both polarisation and relaxation tend exponentially to a finite value with the same time constant, it becomes possible to precisely evaluate the limiting voltage attained upon polarisation though no steady state can be reached in practice, and use this input to evaluate the cation transference number as a function of the thermodynamic factor. This procedure simplifies the data analysis by avoiding complete fitting of the polarisation with a complicated numerical model. Such approach can favour the deployment of the four-electrode method to evaluate electrolyte transport parameters, which are crucial for the development of better performing batteries.