Accelerated ageing of Ni-Yttria Stabilized Zirconia (YSZ) anode functional layers (AFLs) in solid oxide fuel cells (SOFCs) is carried out at 1000-1200°C, the resulting morphological changes are investigated using transmission X-ray microscopy (TXM), and properties are characterized using electrochemical impedance spectroscopy (EIS). Prior to ageing, the as prepared NiO-YSZ AFLs are reduced to Ni-YSZ and then aged at 1100°C for 100 h in order to eliminate early-stage morphological changes. Measured particle size and three phase boundary (TPB) density changes with ageing time and temperature are fit reasonably well using a power-law coarsening model. This model is also used in conjunction with an electrochemical model to predict changes in the anode charge-transfer polarization resistance.

In reversible operation of solid oxide cells for energy storage applications, the current direction switches periodically as the cell alternates between fuel cell and electrolysis modes. Here we report the effect of this alternating current operation on Ni-YSZ fuel electrodes in 1000 h life tests at different current densities. Ni-YSZ/YSZ/Ni-YSZ symmetric cells were used because they allow relatively straightforward interpretation of electrochemical results. At constant cell current density values ≤ 0.4 A/cm 2 , the cell voltage and total resistance values were reasonably stable, with a slight reduction in R P . At current densities ≥ 0.6 A/cm 2 , voltage and total cell resistances were still approximately constant, but there was a steady increase in the R that was almost offset by a decrease in R P . The higher current densities resulted in damage to the electrode/electrolyte interface structure including delamination, explaining the R increase. Increasing the current density also produced more Ni and YSZ nanoparticles in the electrode, yielding the decrease of R P .

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