Preparation And Properties Of Layered Perovskite-like Cathode Materials

With the environmental pollution and resource consumption,people's demand for green and pollution-free energy is also increasing day by day.Solid oxide fuel cels(SOFC)are a kind of efficient,green and pollution-free power generation devices that can directly convert chemical energy into electric energy.High-performance cathode materials are the key technology for the development of medium temperature solid oxidation fuel cells.The development of new cathode materials with high catalytic activity can effectively reduce the polarization loss and improve the performance of fuel cells.In recent years,the composite oxides with layered perovskite-like structure Ln₂Ni F_4+?system are new candidate materials for SOFC cathode materials.The study and improvement of the catalytic activity of Ln₂Ni F_4+?system for oxygen reduction is of great practical significance for its application in SOFC cathode.In this thesis,four cathode materials Ln_1.2Sr_0.8Ni_0.6Fe_0.4O_4+?(Ln=La,Pr,Nd,Sm)were prepared by liquid phase method.The electrochemical properties of the four materials at 600-800?were studied.The results show that the Ln_1.2Sr_0.8Ni_0.6Fe_0.4O_4+?(Ln=La,Pr,Nd,Sm)under the condition of 1000?sintering 5 hours,present the single-phase K₂Ni F₄structure.The electrochemical performance of SSNF cathode material is the best,and the electrochemical properties of LSNF,NSNF and PSNF cathode materials decreased in turn.The polarization impedance of SSNF symmetric half cell is the smallest when sintered at 1000?for 3 hours,minimum value is0.3666?·cm²,so SSNF cathode materials have excellent electrochemical performance.Using Ln_1.2Sr_0.8Ni_0.6Fe_0.4O_4+?as the cathode,Ni_0.9Cu_0.1O_x-SDC as the anode,Ni_0.9Cu_0.1O_x-SDC/SDC/SSNF single cell supported by SDC electrolyte has a maximum output power density of 353.8 m W/cm²at 800?test temperature,the polarization resistance of the single battery is 0.1568?·cm².Although Ni_0.9Cu_0.1O_x-SDC/SDC/SSNF single battery has the best performance among the four materials,there is still a certain distance between its output power density and commercialization,so it is still necessary to further improve the performance of SSNF cathode materials.In order to further promote the properties of cathode materials,SSNF-SDC composite cathode materials were prepared by mechanical mixing method.The experimental results show that the composite ratio of 90:10 composite cathode SSNF-SDC sintered under 1000?3 hours has minimum polarization impedance value,minimum value of 0.3076?·cm².SSNF-SDC composite oxide material with mass composite ratio of 90:10 was used as the cathode,Ni_0.9Cu_0.1O_x-SDC as the anode,Ni_0.9Cu_0.1O_x-SDC/SDC/SSNF-SDC single cell supported by SDC electrolyte has a maximum output power density of 591.9 m W/cm²at 800?test temperature,compared with the uncombined single battery increased 283.1 m W/cm²,overall increased by 67.31%,The polarization impedance value of 0.0527?·cm²,are far less not the impedance of the composite cathode of SDC(0.1568?·cm²).It shows that the composite SDC electrolyte material can improve the performance of the cathode material,and effectively improve the performance of SOFC cathode material.