Performance and stability of La2NiO4-infiltrated La0.9Sr0.1Ga0.8Mg0.2O3 oxygen electrodes during current switched life testing

Solid oxide cells operated reversibly or in electrolysis mode are promising for energy storage, but oxygen electrode degradation is an issue. Prior stability studies have focused on the widely-used powder-processed perovskite oxide electrodes in devices operating at ≥ 700 °C. Here we provide initial results on a different type of electrode designed for lower temperature - the Ruddlesden-Popper material La2NiO4 with a nano-scale structure produced by infiltration into a La0.9Sr0.1Ga0.8Mg0.2O3 scaffold. Life tests were performed in air at 650 °C on symmetric cells with La0.9Sr0.1Ga0.8Mg0.2O3 electrolytes with the current direction reversed every 6 h over 1000 h. The voltage degradation rate increased from ∼3%/kh at a current density of 1.0 A/cm2 to ∼15%/kh at 2.0 A/cm2. EIS measurements revealed that both the ohmic and polarization resistances increased more rapidly at the higher current density. Post-test observations showed no electrode delamination, but increased current density caused a change in the La2NiO4 nano-structure, along with evidence of electrolyte fracture.