Degradation Mechanism and Ni Migration in Anode of Solid Oxide Cells

Abstract

Solid oxide cells (SOCs) suffer from drawbacks such as performance degradation due to various phenomena. One of the most studied degradation phenomena is due to the Ni migration in the Ni/YSZ fuel electrode. The various driving forces that cause Ni migration have been widely reported due to the high-water vapor concentration and applied current density. The Ni coarsening and separation/detachment of Ni are inseparable phenomena due to the Ni migration. Due to these phenomena, the fuel electrode loses its electronic conduction pathway leading to performance degradation of the cell. There are two different directions of Ni detachment/separation in porous Ni/YSZ electrode based on the operating condition. During fuel cell operating conditions, the Ni tends to gather in the vicinity of the interface of the electrolyte/fuel electrode. On the other hand, Ni separation from the interface is widely reported at electrolysis operating conditions. Those detachments lead to Ni migration and finally cause Ni particles to increase in size but decrease in number. Those degradation mechanisms and the driving force of the Ni migration in fuel cell and electrolysis operating conditions are presented and discussed to shed light on suppressing the performance degradation of SOC.