Design and characterization of apatite La9.8Si5.7Mg0.3O26±δ-based micro-tubular solid oxide fuel cells

Abstract

In this study, electrolyte-supported (Cell A) and anode-supported (Cell B) micro-tubular solid oxide fuel cells (SOFCs) based on the La9.8Si5.7Mg0.3O26±δ (LSMO) electrolyte is built through an extrusion and dip-coating processes. The formulations and process conditions for these cells are established and optimized. Both cell configurations show no visible delamination or cracking, and reaction zones and inter-diffusion of any species are absent at the interfaces of the multilayer structures. The micro-tubes LSMO and LSMO-NiO have a high flexural strength of ~70 MPa. Cell B with a 3.33 mm outer diameter, a 12 μm LSMO electrolyte layer, a ~300 μm LSMO-NiO functional anode layer, a 9 μm NiO current-collector layer, and a 44 μm La0.6Sr0.4Co0.2Fe0.8O3-δ cathode layer has superior electrochemical performances than does Cell A. The polarization resistance (Rp) value for Cell B accounts for 67.6% and 50.5% of the total resistance (Rt) value at 700 °C and 895 °C, respectively, suggesting that Rp dominates at low temperatures and ohmic resistance (Ro) and Rp values are equally important at high temperatures. Cell B's open-circuit voltages (OCVs) are slightly below the theoretical value due to poor sealing of cells. The maximum power densities (MPDs) of Cell B, increase with increasing operating temperature and are 0.12, 0.24, and 0.27 W cm−2 at 750 °C, 850 °C, and 895 °C, respectively. Compared to Cell A, Cell B displays lower OCV values but higher MPD (0.27 W cm−2 vs. 0.06 W cm−2 at 895 °C) due to its significantly lower Ro value, mainly due to the thin layer of LSMO electrolytes.