Performance of microtubular SOFCs with infiltrated electrodes under thermal cycling

摘要

In this research, tubes consisting of a co-extruded dense YSZ electrolyte (~10 μm) and porous NiO-YSZ anode (~200 μm) were modified with different cathodes and anode infiltration to investigate the effects on both power and thermal cycling tolerance. Type of cathode (produced by infiltration of LSM into a porous YSZ matrix or by hand-painting of an LSM-YSZ ink), the type of pore former used in the cathode (graphite or poly (methyl methacrylate), PMMA) and the infiltration of the anode (no infiltration, or with infiltration steps using a co-precipitated SDC (Samaria doped ceria) mixture, or Ni-SDC mixture) were investigated as variables. The overall aim of this work is to produce cells that are more tolerant to thermal cycling, without sacrificing power density. Testing at 750 ℃ with 20 mL/min of dry hydrogen shows that anode infiltration has a particularly advantageous effect on performance, raising the peak power and reducing the degradation in peak power seen after aggressive cycling (100 ℃/min heating and cooling rates). Cell power can be improved by LSM infiltration into a porous YSZ layer when the thickness of the YSZ layer is optimised and there is sufficient LSM. Infiltrated cells with cathode thicknesses of 20-40 μm functioned better than those 10-15 μm thick despite having a similar LSM/YSZ weight ratio. This may be due to the additional reaction zone available as a result of the higher LSM mass, suggesting that the reaction zone extends beyond 15 μm from the electrolyte. LSM and SDC infiltrated fine particles (50-100 nm) show good distribution and connectivity in the cathode and anode of the cells respectively. When PMMA is used as the pore former in the porous YSZ matrix, a slightly better cell performance is obtained compared with graphite as the pore former. Monitoring the power variation is found to be a more reliable tool than open circuit voltage (OCV) measurements for studying the effect of thermal cycling on cell stability.