Research Of Composite Cathode Contact Material For Solid Oxide Fuel Cell

The interface between the cathodes and interconnects significantly influence the output performance and long-term stability of solid oxide fuel cell?SOFC?.It?s usually necessary to add a high-temperature conductive ceramic layer between the cathodes and interconnects which aims at improving the interface contact,collecting the electrons on the surface of cathode and inhibiting the high-temperature oxidation of metallic interconnects.The LaCo_0.6Ni_0.4O_3-??LCN?powders were prepared by the polymeric steric entrapment method with polyvinyl alcohol?PVA?as entrapment agent and calcined at800 ^oC for 3 h.The physical properties of LCN including the particle size distribution and thermal expansion coefficient?TEC?were characterized.The electrochemical performance of button-cell was tested with LCN as cathode contact material?CCM?.In order to further improve the conductivity of the cathode contact material,Ag-LCN composites were prepared through mechanical mixing method.The composites were screen printed on the surface of interconnects to test its conductivity.The results indicated that Ag particles were well-distributed in the three-dimensional network structure of LCN matrix when the content of Ag phase is relatively low.Its function as fast conductive pathways could remarkably improve the electrical conductivity of the composites.With the increase of Ag content,its tendency to agglomerate and react with Cr from interconnects would destroy the three-dimensional network of LCN and decrease the conductivity of composites.Among all the samples,10 wt%Ag-LCN composites showed the best performance.The average degradation rate of button-cell with 10 wt%Ag-LCN as CCM was about 0.64%per thermal cycle and its output performance is obviously higher than the cell with pure LCN as CCM which indicated that Ag-LCN composites could be a good choice for CCM.In addition,a novel of YSZ-LCN composite cathode contact material was studied as cathode extension layer.YSZ is an excellent ionic conductor and oxygen reduction reaction could occur at the three-phase boundary which is consisting of YSZ,LCN and air.The results indicated that with the increase of YSZ content,the ohmic resistance of button-cell was not changed greatly and the polarization resistance decreased first and then increased.With a small amount of YSZ,the increase of electrochemical active sites could reduce the polarization resistance without the change of electrical conductivity.Higher YSZ content result in the decrease of electrical conductivity of the composites..The button-cell with 10 wt%YSZ-LCN as CCM showed the best performance in which the polarization resistance is significantly reduced and the output performance is improved obviously.