Development of robust YSZ thin-film electrolyte by RF sputtering and anode support design for stable IT-SOFC

Abstract

Thin-film solid oxide fuel cells (TF-SOFCs) have attracted attention as a strategy for lowering the operating temperature of SOFCs. However, the porous and rough surface of the SOFC support and the shadowing effect have hindered the construction of pinhole-free thin-film electrolytes during sputtering. In this study, we report the deposition of a gas-tight YSZ thin-film electrolyte (approximately 0.8 μm) by RF sputtering on a Ni-YSZ anode support. To utilize a sputtered thin film as an electrolyte, we examined the relationship between the deposition pressure and thin-film properties and determined the optimal deposition conditions. By designing the anode functional layer (AFL) and annealing, a thin-film electrolyte is successfully deposited on the porous Ni-YSZ support without cracks and pinholes. The resulting thin-film electrolyte cell achieves a high open-circuit voltage (OCV) of approximately 1.09 V and a maximum power density of 0.446 W/cm2 at 600 °C, which implies high ionic conductivity and gas tightness. Moreover, the single cell exhibited exceptional long-term stability (140 h) despite the extremely thin and vacuum-deposited electrolyte components. This study provides guidelines for the practical application of thin films as electrolytes to lower the operating temperature of SOFCs.