Life testing of 10 cm × 10 cm fuel-electrode-supported solid oxide cells in reversible operation

Abstract

Reversible solid oxide cells (ReSOCs) can provide significant value by playing different roles – electrical generation or electricity storage – depending on the prevailing electrical grid requirements. Relatively few studies have focused on the life testing of solid oxide cells in this mode-switching operation, and much of that work has focused on small “button” cells. The present study describes electrochemical characterization and post-test characterization from an ∼2600 h life test of a 10 cm × 10 cm fuel-electrode-supported cell operated with periodically reversing current. The cell performance gradually decreased for the first ∼1000 h and then stabilized with low degradation rate until an abrupt test-ending gas crossover failure that resulted in open circuit voltage drop. Post-test characterization of the (La,Sr)CoO3-δ air-electrode showed evidence of Cr vapor contamination from stainless-steel manifolds and Ag contamination from current collection contacts. Partial delamination of the air-electrode and Gd-doped ceria interlayer was observed, along with fractures in the electrolyte near the fuel inlet that probably caused a drop in open circuit voltage near the end of the test. NiNi connectivity was reduced in both the functional and support layers accompanied by Ni particle coarsening, especially at the fuel outlet.