Reversible Solid Oxide Cells (RSOCs) are a promising technology for electrical energy storage through hydrogen – a flexible multi-purpose energy carrier. A key component of planar stacks of cells is the sealant joining the cell to the interconnect, which must be chemically and physically stable and ensure gas tightness between oxidizing (air) and reducing atmospheres (H₂).

Novel glass-ceramics compositions for a working temperature of 850 °C were designed and characterized in terms of sintering capability, thermal and thermomechanical properties. Crystalline phases and different amounts of residual glassy phase were tailored in order to assure a good thermomechanical compatibility with a Crofer22APU interconnect. The gas tightness of the glass-ceramic sealant has been tested in a dual atmosphere environment at 800 °C and nearly atmospheric pressure. Samples comprising of two plates of interconnect material (Crofer22APU) have been joined together by the sealant and have been exposed to air on one side and H₂/steam on the other side to investigate the gas leakage rate through the sealant. The leakage rate has been evaluated by measuring the volumetric gas flow rate at the outlet of each chamber. The gas tightness of the sealant has been tested in relevant RSOC conditions at different pressure gradients between the two atmospheres (from 5 mbar to 50 mbar), flow rates and H₂/H₂O ratios.

The compatibility between the glass-ceramic sealants and the Crofer stainless steel (bare and pre-oxidised) is reviewed and discussed by means of SEM and EDS analysis before and after the dual atmosphere tests.