A comparison of FEM results from the use of different governing equations in a galvanic cell part II: Impact of low supporting electrolyte concentration

Abstract

Finite Element Method modeling has been widely used to simulate the distributions of potential, current density, and dissolved species for a wide range of electrochemical systems. The use of the Nernst–Planck–Poisson equations as governing equations is the most rigorous approach, but it brings with it a substantial computational time cost. Reduced-order models offer options in which different assumptions allow more rapid computational solutions. In Part I of this work, it was shown that the loss in accuracy of the reduced-order models is small in high supporting electrolyte concentrations, and there were substantial savings in computational time. The analysis is extended to lower supporting electrolyte concentrations. The most reduced-order modeling approach performs poorly in low supporting electrolyte to electrochemically reactive species (SER) ratios. A modified Laplace approach, in which the conductivity is recalculated at each position at each time step, improves the solution by updating the electrolyte conductivity at each time step, but the errors can still be significant in low SER ratios due to the absence of the diffusion potential term in the calculations.