Effect of the online reaction byproducts of LiNi0.8Co0.15Al0.05O2-δ electrodes on the performance of solid oxide fuel cells

Abstract

LiNi0.8Co0.15Al0.05O2-δ (NCAL) has been demonstrated to be an excellent electrode with dual catalytic activities of hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) for solid oxide fuel cells (SOFCs). Reports have indicated that the anode NCAL tends to be reduced during cell operation and produce LiOH and Li2CO3. In this work, the effect of the online reaction byproducts of NCAL electrodes, LiOH and Li2CO3, on the performance of SOFCs is investigated. Different amounts of LiOH and Li2CO3 are separately added to the Ce0.8Sm0.2O2-δ (SDC) electrolyte for fabricating SOFCs with NCAL electrodes. The power output under normal and reverse operation is studied for the cells with lithium salt addition from 5 wt% to 30 wt%. Electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis suggested that the addition of LiOH or Li2CO3 to the SDC reduces HOR and ORR activities of the cells, leading to lower cell performance. The cross-sectional SEM of the cells shows that the added LiOH and Li2CO3 makes the electrolyte porous and densifies the electrode, which is the main reason for the reduction of cell performance. In addition, the porosity of electrolyte is modified during cell fabrication in order to construct flowing pathways for the online reaction byproducts of NCAL electrode to move from electrode to electrolyte, resulting in optimized cell performance. This study provides an insight into facilitating the performance of NCAL electrode-based SOFC.