Research Of Novel Structure Of Cathode Contact Layer And PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+?-La₂NiO_4+? Core-shell Structure Cathode For SOFC

Cathode contact materials are needed in the surface of cathode to collect current without blocking the gas diffusion and the electricity of them should be well. This article develops a novel contact layer with different sizes contact materials LaCo_0.6Ni_0.4O_3-??LCN?:1) LCN powders are prepared by the polyving akohol?PVA? method in different temperatures. The particle size of LCN calcined in 1100 °C for 2 h is larger than calcined in 800 °C for 2 h and the thermal expansion of coarse particles is bigger than fine particles, but the sintering shrinkage is the opposite.2) A novel structure of LCN cathode contact layer with coarse particles and fine particles?FCFP? is designed by these fundamentals. Compared with coarse particles?CP? and fine particles?FP?, the area specific resistance?ASR? stability of FCFP is better than CP and FP. The initial ASR of FP is the smelliest. But there are fewer pores in CP so that the thermal stress is difficult to be released. ASR increase continuously due to the thermal stress and the micro-crack generated in thermal cycle. The initial ASR of CP is the biggest because of the fewer contact points between particles and interconnects. The oxygen partial pressure in the interface is higher than others and the oxide layer is easy to form so that its thermal cycle stability is bad.3) The thermal cycle stability of SOFC single cell with FCFP contact layer is super-duper. The single solid oxide fuel cell?SOFC? with FCFP cathode contact layer shows good performance with an average degradation 0.4% per thermal cycle.In addition, a novel core-shell structured cathode PrBa_0.5Sr_0.5Co_1.5Fe_0.5O_5+??PBSCF?-La₂NiO_4+??LN? is proposed to meet the rigorous requirements for the cathode material of intermediate temperature SOFCs:1) The core is made of a double perovskite ceramic material PBSCF with high oxygen bulk diffusivity and electrical conductivity, while the shell is composed of a Ruddlesden-Popper ceramic material LN with high oxygen surface exchange rate and CO₂ poisoning resistance. The initial electrochemical property of PBSCF-LN structured cathode is lower than that of PBSCF cathode, but the long-term stability and CO₂ poisoning resistance are the opposite.2) The shell LN can protect core PBSCF from growing up and Sr enrichment, and the porous structure can be maintained to guarantee its long-term stability. The shell LN keeps chemically stable in CO₂ atmosphere which can protect core PBSCF from reacting with CO₂ so that the cathode will not be poisoned.