Characterization of Ag-Based Filler for Electrolyte/Metallic-Interconnect Joint in Metal-Supported Solid Oxide Fuel Cells Applications

Abstract

Metal-supported solid oxide fuel cells (MS-SOFCs) exhibit better electrochemical performance than conventional ceramic-supported cells at lower temperature due to their exceptional thermal, electrical, and mechanical properties. MS-SOFCs can withstand rapid thermal cycling operation and make it practical for mobile applications. A reliable seal is essential for electrolyte/metallic interconnect joint in MS-SOFC applications. In the present study, we proposed an Ag-Ge alloy filler as a high-temperature brazing sealant for use in MS-SOFCs. Commercial ferritic stainless steel (Crofer22H) and La1-XSrXGa1-yMgyO3- δ (LSGM) substrate were employed as metallic interconnect and electrolyte for this study, respectively. The adhesive and hermetic characterization for the electrolyte/metallic interconnect joint joined by the Ag-Ge alloy filler were examined by using high-temperature leak test at elevated temperatures. Results showed that the leak rate of LSGM/Crofer22H coupon is 5.0 x 10-4 mbar∙l/s/cm after aging at 750°C for 100 hours in He/air. In addition, SEM/EDS analyses also revealed that Ge element in the Ag-Ge filler is prone to diffuse toward Crofer22H and LSGM side, and thus improves the interfacial adhesion of the LSGM/Crofer22H joint.

Microstructural Evolution and Gas-Tight Properties of Yttria-Stabilized Zirconia/Crofer 22H Stainless Steel Brazed Joints with the Ag-Ge-Si Filler for Use in Solid-Oxide Fuel Cells

“…There are several methods developed for sealing SOFC stacks, such as glass bonding [7][8][9], mica-based compressive seals [5,10,11], and brazing [12][13][14]. Metallic bonds usually have better stress accommodation than covalent bonds, so more reliable SOFC sealing can be obtained via brazing.…”