Towards a Fully REDOX Stable SOFC: Cell Development at Ceres Power

Abstract

Low-temperature SOFCs with thick-film anodes such as those developed by Ceres Power for its metal supported SOFC are inherently more resistant to REDOX cycling as a result of loss of fuel supply at temperature than traditional SOFC designs. This is due to the slow kinetics of nickel oxidation at low temperature and the anode not being the main structural support for the cell layers. High REDOX stability is essential for widespread commercial adoption of SOFC technology as the requirement to supply a protective atmosphere over the anode during uncontrolled shutdowns otherwise adds substantial cost and complexity to the system. The latest generation of Ceres Power metal supported cells show exceptional resistance to REDOX and thermal cycling, even in very aggressive accelerated tests. This has been achieved through development of the anode to achieve very robust microstructures at low processing temperatures. This paper will illustrate the current anode microstructure and the latest accelerated testing results.

SOFC stacks for mobile applications with excellent robustness towards thermal stresses

“…Furthermore, contact of interfaces and sealing seem critical points when exposing stacks with anode supported SOFC to thermal cycles [7]. On the other hand, good stability towards thermal cycling of stacks with metal supported cells was demonstrated in a furnace test environment [8]. More experimental knowledge is needed when aiming at a use of SOFC stacks in the mobile sector, such as dedicated fast thermal cycling experiments in realistic environment outside a furnace and the determination of allowable accompanying thermal gradients at stack level.…”

Influence of Microstructure on the Sulfur Tolerance of Ceria-Based Anodes in Low Temperature SOFC

“…The trend of operating the SOFC-system with ceria-based solid oxide cells at a much lower operation temperature even below 600 °C (12,13) raises the question to which extend the sulfur tolerance is maintained. For this, four different fuel electrodes varying in their microstructure are investigated by electrochemical impedance spectroscopy (EIS) before, during and after sulfur poisoning at 600 °C.…”

Electrochemical Performance of Plasma Sprayed Metal Supported Planar Solid Oxide Fuel Cells

“…Even though a few ways of reducing or avoiding this instability in ASCs have been proposed, these ways add cost and complexity to the SOFC system and cannot necessarily be considered reliable and robust, especially taking the risk into account that a complete failure of system could occur. 4,5 Hence, redox stability in ASCs is still a key concern. Due to mechanical strength provided by the steel substrate and a thinner anode in MSCs, these cells are highly robust and much more reliable in case of fuel supply interruption than ASCs.…”

“…During recent years, the redox instability of ASCs in case of fuel supply interruption at high temperature has been identified as a major issue for long term reliability of SOFC stacks in operation. 4,5 The instability occurs due to reoxidation of nickel in the anode to nickel oxide, which results in at least 40% volume increase leading to catastrophic cell/stack failure. Even though a few ways of reducing or avoiding this instability in ASCs have been proposed, these ways add cost and complexity to the SOFC system and cannot necessarily be considered reliable and robust, especially taking the risk into account that a complete failure of system could occur.…”