Redox Stability of Tubular Solid Oxide Cell Using LaGaO3 Electrolyte Film Prepared by Dip-Coating

Abstract

Reversible operation of SOFC is now important subjects from energy storage of renewable electric power from solar or wind power. At present, planer type cell design is widely used for this purpose, however, because of tight gas sealing, tubular type cell design is more suitable. In this study, tubular solid oxide cell using La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) thin electrolyte film was prepared by dip-coating and co-sintering process. NiO-YSZ porous substrate with 10 mm diameter and 30 mm length was used for preparation of the cell. For preventing reaction between LSGM and NiO, TiO2-Ce0.6La0.4O2/Ce0.6Mn0.3Fe0.1O2 was used for buffer layer. The cyclic operation of fuel cell and electrolysis mode was measured for investigating the stability of the prepared tubular cell at an intermediate temperature of 600℃ under the fuel of 20%steam-30%H2 in Ar. After 100 redox cycles under the applied current density of ±100 mA cm-2 , OCV was almost the same with the initial value before measurement. The terminal potential in SOFC operation became slightly lower and unstable with increasing cycle number, however, degradation in power density is not significantly observed. The cell also presents a relative stable performance in the electrolysis mode and it seems to be more active to SOEC than that to SOFC. From measurement of internal resistance, degradation may be related with the increased overpotential of anode. Therefore, aggregation and reoxidation of Ni in Ni-YSZ substrate is expected.In order to further increase performance of the cell, effects of Ce infiltration into NiO-YSZ contributes and it was found that the power density and electrolysis performance was much increased by the decreased internal resistance. The redox stability of NiO-YSZ-CeO2 cell was also measured and it also presents a stable redox performance after 100 times cycles by infiltration of CeO2.