Study on fabrication process and electrochemical properties of metal-supported solid oxide fuel cells

Abstract

Metal-supported solid oxide fuel cells have been considered as a solution to overcome sealing and strength problems of conventional ceramic-supported solid oxide fuel cells. A metal-supported solid oxide fuel cell with a particular structure compared with the other metal-supported cells was fabricated and characterized by analyzing material properties, electrochemical properties and numerical simulation results in this study: (1) The oxidation-resistant layer was coated by a sputtering method to reduce the oxidation rate of the metal support and increase the electrical conductivity of the oxide layer. LSCr-coated STS430 can reduce the electrical resistance to 1/3 level, compared with the uncoated STS430. Long-term durability test results at $700^\circ C$ for 1000 hours indicate that the LSCr thin layer performs an important role to prohibit serious degradations. (2) Cathode properties on YSZ electrolyte was optimized materially and geometrically with respect to the area specific resistance, thermal expansion coefficient and chemical reactivity as a function of temperature and oxygen partial pressure. LSM/YSZ double layer cathode on YSZ and LSCM-8246 cathode on CGO-layered YSZ were the best combination having sufficiently low impedance to apply them to intermediate temperature-operating solid oxide fuel cells. Area specific resistance of LSCM-8246 cathode was measured as $0.14 \Omegacm^2$ at $700^\circ C$. Oxygen reduction reaction mechanism on LSCM-8246 was investigated because the reaction order is an important factor when predicting fuel cell performances for various operating conditions. The reaction order of LSCM-8246 on CGO-layered YSZ was found to be 3/8. (3) A metal-supported solid oxide fuel cell was newly designed in order to reduce fabrication step by using the commercial stainless steel plate, STS430, as a supporting body of fuel cell. Thin ceramic layer composed of NiO/YSZ and YSZ was joined with the metal support by using a cermet adhesive. ...