COMPOSITION GRADIENTS INDUCED BY CURRENT FLOW IN Li2CO3-K2CO3 MIXTURES

摘要

In a molten carbonate fuel cell current flow can cause gradients in the Li/K ratio of a LLKCO3 electrolyte if the cation mobilities are, as in most binary molten salt mixtures, unequal. A one dimensional model predicts 10-20 percent composition gradients from estimated values of mobility, activity and diffusivity, none of which is well known. Predictions from a similar model for a system of known properties have been confirmed experimentally by electrolysis-relaxation experiments. The model calculations for carbonates appear consistent with electrolysis-relaxation measurements on fuel cell tiles, but clearly indicate the need for additional specific physical property data, especially the transference number.