Effect of Fabrication Processes on Electrochemical Performance of Metal-Supported Solid Oxide Fuel Cells

Abstract

Metal supported solid oxide fuel cells (MSCs) which have the robust porous metal substrate are expected for the use in some mobilities. MSCs are prepared by various fabrication processes such as sputtering and screen printing. When the electrolyte layer is fabricated by the wet processes, the electrolyte must be sintered with metal substrate at a high temperature. However, it is difficult to obtain the dense electrolyte on porous metal substrate because sintering temperatures of an electrolyte ceramic and a metal material used in substrates are different. In this study, MSCs were fabricated on the sintered porous metal substrates by screen printing and spin coating with high-temperature sintering in reduced atmosphere. The electrochemical performance of MSCs strongly depended on the process conditions. MSCs were prepared by the process which is similar to the process for anode supported cell fabrication. Anode paste including nickel oxide and scandia stabilized zirconia with a weight ratio of 60/40 was coated on the green compact of substrate by screen printing. After drying, the electrolyte layer is coated on it by same procedure. Samples were heat-treated around 400 ºC for 1 h to degrease the organic compounds included in cells. These are finally sintered at 1100 – 1250 ºC in reduced atmosphere. The relationship between the electrochemical performance and the structural property were investigated.In order to obtain dense electrolyte, the shrinkage behavior of porous metal substrates is quite important. Large shrink of substrate can assist the densification of electrolyte in the sintering process. It was found that the degrease temperature affected the shrinkage behavior in sintering process. It was considered that the oxidation of metal particles in substrate affected on the shrinkage. When the sintering temperature were high to obtain the dense electrolyte, Fe and Cr diffused from the substrate to the anode layer. This metal elements diffusion strongly deteriorated the performance of the anode. Additionally, gas atmosphere also affected the metal elements diffusion. When the MSCs are prepared by wet process with high temperature sintering, controlling the sintering behavior of all components by adjusting the process parameter was quite important to low polarization resistance.