Long-Term Stability of Anode-Supported Solid Oxide Fuel Cells with a Co-Sintered Cathode Backbone and Infiltrated La_0.95Co_0.4Ni_0.6O₃ (LCN) Electro-Catalyst

Infiltration is a fabrication method that is offering potentially significant improvements in cell performance at reduced materials and fabrication costs, especially when combined with co-sintering. However, important questions regarding the long-term performance and microstructural stability of infiltrated electrodes, as well as the mechanical properties of such electrodes have remained unanswered.

Here, we present the results of a three-year project, where large footprint (12 × 12 cm2) anode-supported solid oxide fuel cells with a co-sintered cathode backbone and infiltrated La0.95Co0.4Ni0.6O3 (LCN) cathode active phase were developed and thoroughly characterized. We report the initial and long-term (1500+ hours) performance of infiltrated cathode backbone cells hours running with 40% H2O/H2 as fuel and ambient air as oxidant, coupled with a scanning transmission electron microscopy - energy dispersive X-ray spectroscopy (STEM-EDS) investigation of microstructural changes in the infiltrated electrodes (Fig. 1). Some electrodes were further aged at elevated temperatures (750- 900°C) for periods reaching up to 5000 hours, while following changes in the electrode properties with scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, and van der Pauw in-plane conductivity measurements. Finally, the mechanical properties of co-sintered cathode backbone cells were determined in four-point bending tests carried out both at room temperature and at 800°C in air. To our knowledge, this is the first time infiltrated cells have been characterized in such detail.

The results of the study suggest that significant coarsening of the infiltrated phase takes place upon long-term testing and aging, resulting in decreased active surface area, reduced in-plane electronic conductivity, increased electrode impedance, as well as re-arrangement of the electro-catalyst in the porous backbone. The Weibull strength of the cells at room temperature was 400 MPa with a Weibull modulus of 12. Both the strength and the modulus were found to be lower at elevated temperature.

This study was funded by EUDP (Danish Energy Agency) project 64012-0225 “SOFC Accelerated – Development to Accelerate Field Demonstrations”.