Investigation on Long-Term Stability of Vermiculite Seals for Reversible Solid Oxide Cell

Abstract

A reversible solid oxide cell (RSOC) integrating solid oxide fuel (SOFC) and a solid oxide electrolysis cell (SOEC) usually utilizes compressive seals. In this work, the vermiculite seals of various thickness and compressive load during thermal cycles and long-term operation were investigated. The leakage rates of seals were gradually increased with increasing thickness and input gas pressure. The thinner seals had good sealing performance. The compressive load was carried out at thinner seals, the possible holes were squeezed, and finally the leakage rates were lower. With a fixed input gas pressure of 1 psi, 2 psi, and 3 psi, the leakage rates of 0.50 mm vermiculite remained at around 0.009 sccm/cm, 0.017 sccm/cm and 0.028 sccm/cm during twenty thermal cycles, while the leakage rates remained at around 0.011 sccm/cm for about 240 h. Simultaneously, elemental diffusions between seals and components were limited, implying good compatibility. Furthermore, the open circuit voltage (OCV) remained at around 1.04 V during 17 thermal cycles, which is close to Nernst potentials. The stack performance confirmed that the vermiculite seals can meet the structural support and sealing requirements. Therefore, the vermiculite shows good promise for application in stacks during thermal cycles and long-term operation.

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

“…Therefore, medium-temperature SOFCs (IT-SOFCs, 600-800 • C), which use high-catalyticactivity materials, have become popular in recent years [2,3]. For IT-SOFC stack assembly, robust interfacial sealing is usually required for long-term stable operation [4][5][6].…”

“…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.…”