Electrochemical Characterization of Intermediate-Temperature Solid Oxide Fuel Cells with PVD-Coated Electrolyte

Abstract

Intermediate temperature solid oxide fuel cells (SOFCs) working in the range of 600–800°C are interesting because they allow the expansion of the choice of materials that can be used, decrease system cost, and reduce the corrosion rate of system components [1]. The thickness of the electrolyte should be reduced, so reducing the area-specific resistance of the fuel cell for working in this temperature range. Physical vapor deposition methods, such as magnetron sputtering are used to produce thin-film electrolytes [2]. This work is an extension of our previous efforts focusing on scaling the technology of magnetron deposition of electrolyte to large-area cells [3]. It is known that area-specific resistance of small button cells is much less than that of industrial-sized planar anode-supported SOFC cells (10 cm×10 cm or greater). Such difference in ASR is due to large ohmic losses in a SOFC stack that are highly dependent on contact resistance at the cathode/bipolar plate interface. For example, the power density of our 10 cm×5 cm cell with magnetron sputtered yttria-stabilized zirconia (YSZ)/gadolinium-doped ceria (GDC) bilayer electrolyte and La0.6Sr0.4Co0.2Fe0.8O3/Gd0.1Ce0.9O1.95 (LSCF/GDC) cathode was 430 mW/cm2 at 0.7 V and at 750°C [4]. This value was about 40% of that of the 2 cm diameter button cell (1025 mW/cm2) with a similar structure and composition. The area-specific resistance of the former cell was 0.54 Ohm·cm2, while it was 0.2 Ohm·cm2 for the latter one. The goal of this work is to increase the performance of the large-area cell with PVD-deposited electrolyte by improving the structure and composition of the cathode active and contact layers. 4-µm-thick YSZ electrolyte and 2-µm-thick GDC barrier layer were deposited on the 5 cm×5 cm commercial NiO/10ScCeSZ anodes (KCERACELL CO., Korea) by means of reactive magnetron sputtering. LSCF/GDC cathode active layer with an active area of 4 cm×4 cm was screen printed onto the electrolyte. Electrochemical investigations were performed in the temperature interval of 600–800 °С. Figure shows the resulting performance – I–V–P curves of the large-area (5 cm×5 cm) cell with PVD-deposited electrolyte. High power densities of 0.29, 0.55, 0.83, 1.16 и 1.4 W/cm2 were achieved at 0.7 V and at 600, 650, 700, 750 and 800°C, respectively. Acknowledgements. This work was funded by the Russian Science Foundation (Grant No. 17-79-30071).[1] D. J. L. Brett et al., Chem. Soc. Rev., 37, 1568 (2008)[2] S. Sønderby et al., Surf. Coat. Technol., 240, 1 (2014)[3] A. Solovyev et al., J. Electrochem. En. Conv. Stor., 15(4), 044501 (2018)[4] A. Solovyev et al., Fuel Cells, 17(3), 378 (2017) Figure 1: I–V–P curves of the large-area (5 cm×5 cm) cell with PVD-deposited electrolyte. Figure 1