Preparation of Zirconia Thin Film Cells with Metal Supports for a Planar Fuel Cell Stack

Abstract

Planar thin-film solid electrolyte cells were investigated to develop a small size portable power supply. Problems caused by the reduction of electrolyte thickness are analyzed to find effective counter measures. Thin-film cells are damaged by the thermal stresses generated from the mismatch of thermal expansions between electrolyte film and substrate. The stresses decreased (1) by the use of low thermal expansion coefficient materials for the electrolyte support and (2) by inserting a porous nickel layer between the electrolyte and the support. The solid phase reaction between cathode and electrolyte must also be described in the development of thin-film solid electrolyte cells. The cell performance was lowered by the electron conduction induced by the reduction of electrolyte film by the fuel gas at elevated temperatures. The grain boundaries enhance the solid-phase reaction and the expansion of the reduced area toward the cathode. Therefore, it is preferable to suppress the grain growth in the electrolyte film. A stack design of the planar thin film cell and a conceptual flow diagram for a power generation system are presented.