Effect Of Reversible Cell Operation On LSM-YSZ Composite Electrode Durability

Solid oxide cells (SOC) can be operated reversibly for energy storage, in addition to the more common steady-state modes – electrolysis or fuel cell operation. The present study seeks to explore the durability of reversibly operated SOCs, about which little is known. The focus is on lanthanum strontium manganite–yttria stabilized zirconia (LSM–YSZ) composite air electrodes, for which degradation by electrode delamination and electrolyte grain boundary pore formation have been observed in electrolysis mode. Symmetric air-LSMYSZ ⎪ YSZ ⎪ LSM-YSZ-air cells were tested with the constant current direction reversed periodically. This mimics the conditions at a reversible SOC air electrode, which alternately acts as anode and cathode. The advantage of this experiment is that both electrodes should evolve identically, maintaining the symmetry and thereby allowing simple interpretation of the electrical data. Symmetric cells were fabricated by screenprinting an ink, containing A-site deficient LSM and YSZ, on opposite sides of dense YSZ electrolyte pellets. The cells were then fired at 1075oC for 1h before screenprinting on a current collecting LSM layer, and then fired again at 1025oC for 1h. Life tests were done at constant temperature and current density magnitude, measuring voltage while the current direction was periodically switched abruptly. Ohmic (RΩ) and polarization (RP) resistances were measured at intervals by electrochemical impedance spectroscopy (EIS) with a Zahner IM6 workstation.