EFFECT OF FRIT CONTENT IN THE SILVER CURRENT COLLECTOR INKS ON THE ELECTROCHEMICAL PERFORMANCE OF SOLID OXIDE FUEL CELL CATHODES

Abstract

Silver (Ag) inks are often used as precursors to form current collector layers on theintermediate-temperature solid oxide fuel cell (SOFC) cathodes. It has been commonpractice to add glassy phase (frit) particles into the Ag inks to achieve good adhesionbetween the current collector and the cathode layers upon firing. However,insufficient attention has been given to the effects of frit content on themicrostructure and the current collecting properties of Ag layers. This studypresents the effect of frit addition on the measured electrochemical performance ofLa0.6Sr0.4FeO3 (LSF) thin film cathodes. Microstructural analyses reveal that fritaddition significantly densifies the Ag current collector layer. The glassy phasereplacing Ag reduces the contact area between the Ag particles and the LSF thin filmcathode, resulting in increased ohmic resistances. The glassy phase also seals theelectrocatalytic surface of the LSF thin film, thus enhancing the cathode polarizationresistances. Electrochemical impedance spectroscopy measurements onsymmetrical half-cells reveal that ohmic resistances matching the resistivity of theyttria stabilized zirconia electrolyte (YSZ) and acceptable cathode polarizationresistances (e.g., 0.5 ?cm2 at 700?in air) can be obtained when frit-free Ag currentcollector inks are used.