Dependence of open-circuit potential and power density on electrolyte thickness in solid oxide fuel cells with mixed conducting electrolytes

A continuum-level electrochemical model previously developed by the authors [1] is used to investigate the dependence of open-circuit voltage (OCV), and maximum power density on electrolyte thickness for solid oxide fuel cells (SOFCs) with mixed conducting electrolytes. Experimental results confirm the models predictions that OCV decreases monotonically with decreasing electrolyte thickness due to increased permeation flux [1]. The model was further extended to show that there exists an optimal electrolyte thickness at which maximum power density occurs for mixed conducting electrolytes. As expected, for electrolyte thickness greater than optimal losses from ohmic overpotential reduce cell output. However, when the electrolyte thickness is lower than optimal losses from an increasing electronic “leakage” current reduce cell output.