Study On Preparation And Electrochemical Performance Of Sc-doped La_0.6Sr_0.4Co_0.2Fe_0.8O_3-? Cathode Materials

Energy is the foundation of social development.Due to frequent energy crisis and environmental protection issues,Solid Oxide Fuel Cells?SOFC?as a new type of high-efficiency,clean and pollution-free and sustainable new power generation devices has become the focus of domestic and foreign research in recent years.The main factor hindering the commercial development of SOFC is that the operating temperature is too high to seal the material.Long-term operation will also cause problems such as extreme performance degradation.Therefore,reducing the working temperature to low and medium temperatures?600-800??is the focus of widespread research.This can reduce production costs and improve materials stability.However,lowering the operating temperature of SOFC will cause the cathodic polarization resistance to increase greatly.Therefore,research on high performance and stable new cathode materials is the key to SOFC.In this paper,La_0.6Sr_0.4Co_0.2Fe_0.8O_3-??LSCF?is used as the matrix,and part of Fe³⁺is replaced with Sc³⁺at the B position to obtain La_0.6Sr_0.4Co_0.2Fe_0.8-xSc_xO_3-??LSCFSc_x,x=0.02,0.04,0.06,0.08,0.1?cathode material.The influence of Sc³⁺doping on its electrochemical performance was studied and compared with the performance of traditional cathode material LSCF.The sol-gel method was used to synthesize LSCFSc_x?x=0,0.02,0.04,0.06,0.08,0.1?cathode materials,the phase structure and micro-morphology were observed,and the thermal expansion and electrochemical properties were tested.The results show that the introduction of a certain amount of Sc³⁺replacing part of Fe³⁺in the B position of LSCF can form a stable cubic phase perovskite structure.The maximum thermal expansion coefficient of LSCFSc_x cathode material is 12.6×10^-66 k^-1,which has good chemical compatibility with electrolyte SDC.XRD analysis showed that no diffraction peaks of other heterophases appeared in the range of Sc³⁺doping amount x=0.02-0.1,and as Sc³⁺doping amount increased,the XRD diffraction peak gradually shifted to a small angle.At the same temperature,the conductivity gradually decreases with the increase of Sc³⁺doping amount.When the doping amount x=0.1,the conductivity of LSCFSc_0.1.1 at 800?is 162 S·cm^-1,meeting requirements for conductivity of SOFC cathode materials.At800?,the ASR value of the symmetric cell LSCFSc_x|SDC|LSCFSc_x decreases first and then increases with the increase of Sc³⁺doping amount.The lowest ASR value is 0.0259?·cm² when the doping amount x=0.08,compared with the traditional LSCF decreased by about 82%,indicating that x=0.08 is the optimal doping amount.The maximum power density of single cell La_0.6Sr_0.4Co_0.2Fe_0.72Sc_0.08O_3-?|SDC|NiO-SDC using La_0.6Sr_0.4Co_0.2Fe_0.72Sc_0.08O_3-?as cathode material,SDC as electrolyte and NiO-SDC as anode at 800?reaches 806 mW·cm^-2.The experimental results show that doping a certain amount of Sc³⁺in the B site of the SOFC cathode material LSCF can improve the catalytic activity of the cathode for oxygen reduction reaction and improve the output performance of the battery,which is a promising future SOFC cathode material.