Influence of sintering temperature on ceramic fuel cell electrolyte conductivity with lithium-compound electrode

Using lithium compounds as anode in ceramic fuel cells will form LiOH/Li2CO3 at the anode, which diffuse into the Gd-doped CeO2 (GDC) electrolyte significantly improving its ionic conductivity. Here the importance of the density and microstructure of the electrolyte on this conductivity improvement is analyzed. Test cells with Ni0.8Co0.15Al0.05LiO2 (NCAL) electrode and GDC electrolyte are prepared at four sintering temperatures of 900, 1100, 1300, and 1550 degrees C. The amount of LiOH/Li2CO3 that enters into the electrolyte from the NCAL anode decreases with increasing sintering temperature, which led to lower electrolyte ionic conductivity and fuel cell performance. The results of XPS and EPR show that the concentration of oxygen vacancy in GDC containing LiOH/Li2CO3 increased significantly. The effective interface of LiOH/Li2CO3-GDC composite electrolyte results in higher ionic conductivity as compared to the composite electrolytes with larger grains and a smaller amount of LiOH/Li2CO3 due to higher sintering temperatures.