Abstract :
In solid oxide fuel cells, the measured cell resistance is usually higher than the calculated value based on the electrolyte thickness. Such a phenomenon is called a constriction resistance and can be represented by a cell:electrolyte resistivity ratio, λ = ρcell:ρelectrolyte, where ρcell = Rcell/δ (δ is the electrolyte thickness). As ρelectrolyte is a property of the electrolyte and is not affected by the electrolyte thickness, the change in λ with electrolyte thickness is an indication of the dependence of the constriction effect on the electrolyte thickness. In this study, the relationship between cell resistivity and the thickness of a yttria-stabilized zirconia Y2O3–ZrO2 (YSZ) electrolyte is investigated. The ρcell increases with decrease in electrolyte thickness and can be expressed as follows ρ_cell=A_0exp(E_a/RT)-B_0 δexp(E_b/RT)
This empirical relationship is valid when 0 ≤ δ ≤ δ* where δ* is the electrolyte thickness when ρcell = ρelectrolyte (i.e., λ = 1). The constriction effect depends significantly on the electrolyte thickness and the electrocatalytic activities of the electrodes, as well as on the operating temperature. The validity of the relationship is discussed.
