Study On Preparation And Electrochemical Properties Of Ce-doped LaFeO₃ Cathode Materials

Energy is the basis of human survival.With the increasing prominence of environmental problems,solid oxide fuel cell(SOFC)has been widely concerned because of its advantages such as high energy conversion efficiency,wide fuel range and pollution-free product emission.However,the traditional SOFC operating temperature is800-1000?,the higher operating temperature is easy to lead to electrode material instability and the increase of production costs,so the development can meet the commercial application of the medium temperature SOFC(600-800?)has become an inevitable trend.However,with the decrease of operating temperature,the impedance of traditional electrode materials increases and oxygen catalytic activity decreases.Therefore,it is very important to find cathode materials with both good oxygen catalytic activity and high electrochemical performance at medium temperature.In this paper,LaFe_1-xCe_xO_3-?(x=0,0.01,0.05,0.1)cathode material was prepared by partial substitution of LaFeO₃cathode material with orthogonal perovskite structure as matrix,and the effect of Ce element on the electrochemical performance of LaFeO₃cathode material was analyzed.The LaFe_0.9Ce_0.1O_3-?(LFC_0.1)and La_0.6Sr_0.4Co_0.2Fe_0.8O_3-?(LSCF)with the best electrochemical performance were selected to composite the composite cathode material according to the mass ratio of 1:9,2:8 and 3:7,respectively.The electrochemical performance of LSCF-y LFC_0.1composite cathode material was studied.Further confirm the feasibility of LSCF-y LFC_0.1as cathode material for solid oxide fuel cells:LaFe_1-xCe_xO_3-?(x=0,0.01,0.05,0.1)series cathode materials were synthesized by sol-gel method.The phase structure,thermal expansion coefficient and electrochemical properties of the materials were analyzed.The results show that the orthogonal perovskite structure of LaFe_1-xCe_xO_3-?cathode material is formed after calcined at 800?for 2 h.The thermal expansion coefficient of LaFe_1-xCe_xO_3-?cathode material is 11.55×10^-6K at400-800?,which shows a good thermal expansion matching with SDC.With the increase of the doping amount of Ce⁴⁺,the conductivity firstly increases and then decreases.When x=0.01,the highest conductivity is 0.432 S·cm^-1.Under 800?,LFC_0.1|SDC|LFC_0.1symmetry polarization impedance of the battery is 0.91?·cm².Ni O-SDC as anode support,preparation of Ni O-SDC|SDC|LFC_0.1single cell,the highest power density in 750?order battery of 127 m W·cm^-2.LSCF and LFC_0.1were mixed at different mass ratios to obtain composite cathode materials.The results show that the optimal recombination amount of LSCF and LFC_0.1is10%,and the polarization impedance of LSCF-10%LFC_0.1is 0.04?·cm²and the electrical conductivity is 220 S·cm^-1.Ni O-SDC as anode support,preparation of Ni O-SDC|SDC|LSCF-10%LFC_0.1single cell,the highest power density in 750?order battery of 680 m W·cm^-2.The results indicate that LSCF-LFC_0.1composite cathode shows excellent electrochemical performance and is expected to be developed into IT-SOFC cathode material.