Lateral Ionic Conduction in Planar Array Fuel Cells

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Abstract
A performance degradation phenomenon is observed in planar array fuel cells. This effect occurs when multiple cells sharing the same electrolyte membrane are connected in series to build voltage. The open circuit voltage (OCV) and low current behavior of such a series connected planar stack is lower than should be expected. The flow of ionic cross currents between cells in the array, dubbed membrane cross-conduction, is proposed as the likely cause for this loss phenomenon. This hypothesis is confirmed by experimental observations. An equivalent circuit model for a planar double cell is developed which takes into account membrane cross conduction. This model is shown to predict the observed current-voltage behavior of an experimental planar double cell while a simple series model does not. The validated model is used to investigate the impact of various fuel cell parameters on the membrane cross-conduction effect. Design rules are extracted to minimize membrane cross-conduction losses for a linear fuel cell array. It is concluded that the membrane cross-conduction phenomenon primarily affects the OCV and low current density behavior of planar fuel cell arrays. Losses due to membrane cross conduction are minimal for conservative cell spacing, but can be significant for densely packed fuel cell arrays. © 2003 The Electrochemical Society. All rights reserved.