Electrolytic Transport, Electric Fields, and the Propensity for Charge Density in Electrolytes

Abstract

This research presents a universal characterization of the electric field coupled with a non-isotropic electrolyte conducting an electric current. Also presented is a reorganization of Maxwell’s fundamental equations for the case where multiple forms of charge density may be created, such as in an electrolyte. This thesis suggests that the electric field does not balance charge density, but that it balances the strength of the phenomena causing charge density, and names this strength: the propensity for charge density.

Also presented in this thesis are models and research that corroborate each other and this reorganization of Maxwell’s equations. A one-dimensional transport model was used to model crevice corrosion. It couples the two schools of crevice corrosion theory: the critical crevice solution theory and the IR drop crevice corrosion theory. Simulations showed the correct scaling law for the corroding crevices examined should be: L2/G. Also, a tendency for cathodic reactions occurring towards the tip of the crevices was numerically observed. This one-dimensional transport model incorporates a simplified one-dimensional version of the universal characterization of the electric field and supports the theory of the propensity for charge density.

A universal multi-dimensional electrolyte model was developed incorporating the universal characterization of the electric field. It was shown how this model simulates different systems incorporating complex and different phenomena using the same governing equations and the same boundary conditions; the only parameters changed between multi-dimensional simulations were the initial concentrations and diffusion coefficients, system geometry, and the positions and rates of spatially distinct anodic and cathodic reactions. It was demonstrated that this model could predict current distributions for multi-dimensional liquid-junctions, a system containing a moving liquid-boundary, and a charging plasticized lithium-ion cell. For the lithium-ion cell, it was shown how this model predicts a phenomenon that was not reported by numerical simulations based on classical dilute solution theory, but was experimentally observed.

The numerical results presented in this thesis are important because they support the theory of the propensity for charge density. The theory of the propensity for charge density clarifies theory pertaining to an electric field coupled to an electrochemical system.