Mechanical Characterization of Thin SOFC Electrolytes With Honeycomb Support

Abstract

Planar solid oxide fuel cells are made up of repeating sequences of electrolytes, electrodes, seals, and current collectors. The electrolyte should be as thin as possible for optimal electrochemical efficiency; however, for electrolyte-supported cells, the thin electrolytes are susceptible to damage during production, assembly, and operation. To produce cells that are sufficiently mechanically robust, electrolytes can be made having a cosintered honeycomb structure that supports thin, electrochemically efficient electrolyte membranes. Use of finite element analysis is desirable to mechanically characterize such electrolytes. To maintain reasonable numbers of elements and element aspect ratios, it is not possible to simultaneously model the small-scale details together with the overall membrane response. A two-scale approach is devised: the smaller mesoscale analyzes a representative area of the electrolyte, while the larger macroscale examines the electrolyte as a whole. Elastic properties for the mesoscale model are measured over a range of temperatures using a sonic resonance technique. Effective properties for the macroscale are obtained over a range of mesoscale geometries and can be obtained without needing to rerun the mesoscale simulations. The effective properties are experimentally validated using four-point bend experiments on representative samples. The bulk properties and the effective properties can then be used as material inputs for the macroscale model in order to design cells that are more sufficiently mechanically robust without sacrificing electrochemical performance.