The electrochemical measurement of salt diffusion coefficient, apparent cation transference number and ionic conductivity for a thin-film electrolyte.

Abstract

Further development of the electrochemical measurement procedure, namely the Symmetric Polarization Procedure (SPP), is described. The SPP allows for an additional verification of measurement assumptions through a quick and simple inspection of a symmetry between the procedure outcomes. It also improves the precision of estimated transport properties. A considerable emphasis was also put on detailed outcomes analysis. In particular, a newly developed approach to the analysis of restricted diffusion data is proposed. This approach is based on a power law which is a common form for the rate equation, therefore it allows for a precise estimation of the salt diffusion coefficient and, innovatively, the diffusion domain. Importantly, as a result of this approach, the subdiffusive-like response is recognized in every electrolyte examined herein. The viscoelastic relaxation of polymer matrix is given as most probable cause of such response. Additionally, four approaches that lead to a quantification of the apparent cation transference number are also extensively discussed. It has been demonstrated, how a knowledge about the salt diffusion coefficient, the apparent cation transference number and the ionic conductivity can be used to evaluate the electrochemical performance of an electrolyte. It is also shown, how these properties can be utilized to approximate the diffusion-limited current and the deviation from Nernst-Einstein equation.