Nanostructured Thin Film Materials for Solid Oxide Fuel Cells by Atomic Layer Deposition

Nickel yttria-stabilized zirconia (Ni-YSZ) is the most commonly used anode material for solid oxide fuel cells (SOFCs). The electrochemical performance of Ni-YSZ anodes can be extensively improved when the size of constituent particles of nickel is reduced. However, under SOFC operating environments, nano-sized Ni particles suffer from sintering. Nanoscale Ni-YSZ anodes can undergo severe structure changes which constrain how small the nickel particle size can be reduced. In this work, a nanostructured Ni-YSZ anode was successfully fabricated by combining atomic layer deposition (ALD) and glancing angle deposition (GLAD) techniques. Electrode characterization shows that the surface area increased to greater than 3 times that of a plane geometry electrode. In addition, the ALD/GLAD coating approach provides an ionic conductive YSZ electrolyte phase combined with an electrical conductive Ni phase, and also allows control of the porosity of the nano-composite electrode through the deposition and post-deposition annealing process. The surface roughness of Ni-YSZ anode also decreases as the ALD YSZ coating layer increases. It was also shown that the atomic composition of YSZ film is precisely controlled by ALD process and is not affected by the post-deposition annealing process. Conductivity measurements of the Ni-YSZ anodes show a resistivity in the order of 10-4 cm·S-1. Furthermore, the ALD YSZ layer on the Ni shows a strong sintering-resistant effect for coating layers as thin as 1.9nm on. In this work, we developed characterization methods to study electronic and electrochemical properties of thin film materials for SOFCs. A new half-cell/full cell characterization system was also designed.