The Research Of Medium Temperature Solid Oxide Fuel Cell Based On Perovskite Composite Cathode Material

Solid oxide fuel cell（SOFC）is an energy-conversion system of great industrial interest because of its high-energy efficiency,adaptability to fuel and environmental advantages.As a solid-state device,it can mitigate problems of liquid electrolyte leakage and electrode corrosion.However,the necessity for high operating temperatures has resulted in challenges concerning poor material matching,short life and high cost et al.Therefore,it is very important to reduce the operating temperature of the solid oxide fuel cells to 500-800°C.Reducing the operating temperature can decrease the cost of the cell and accelerate the process of its business.In recent years,some cobalt base cathode materials cause the extensive concern of the researchers,but the thermal expansion coefficient（TEC）of these cathodes is too high to match with the electrolyte.Therefore,this thesis aims to deeply investigate the new-type cathodes with low thermal expansion coefficient and high performance.YBaCo_1.4Cu_0.6O_5+δ（YBCC）oxide is investigated as cathode by sol-gel method for intermediate-temperature solid oxide fuel cell.The Ce0.8Sm0.2O1.9（SDC）and La0.9Sr0.1Ga0.8Mg0.2O₃-δ（LSGM）electrolyte materials are prepared with glycine-nitrate combustion method.In order to lower TEC values of YBCC cathode,we prepared the YBCC-xSDC（x=20,30,40,50 wt%）composite cathode.XRD results show that YBCC cathode is formed the pure phase with calcining at 1000°C for 10 h.The YBCC cathode is chemically compatible with the electrolyte SDC and LSGM.The TEC values of YBCC–xSDC is decreasing from 15.22×10-6 K-1 to 12.45×10-6 K-1 with the increasing of the content of SDC.The electrochemical performance of composite cathode YBCC–xSDC on LSGM electrolyte is evaluated using ac impedance spectroscopy.The optimal compound proportion of SDC is 30%.LSGM electrolyte supported-single cell NiO-SDC/SDC/LSGM/YBCC–30SDC is prepared by screen printing progress.The power density of YBCC–30SDC cathode on LSGM electrolyte is 662 mW cm-2 at 850 oC.We prepared Pr_0.5Sr_0.5Co_0.8Cu_0.2O_3-δ（PSCC）cathode with the sol-gel method,and synthesised the Ce0.8Sm0.2O1.9（SDC）electrolyte with glycine-nitrate combustion method.In order to reduce the thermal expansion coefficient of PSCC cathode materials,we preparedPSCC–xSDC（x= 20,30,40,50,60,wt%）composite cathode materials.And we prepared the solid oxide fuel cell with PSCC–xSDC cathode and evaluated the performance.The XRD results show that the PSCC is good chemical compatibility with the SDC electrolyte material.The maximum electric conductivity of PSCC cathode can achieve 900 S cm-1.The coefficient of thermal expansion of PSCC cathode decreased significantly with the increasing of SDC.The optimal compound proportion of SDC is 50%.The polarization resistance（Rp）and power density of PSCC-50 SDC cathode on SDC electrolyte is 0.029 Ω cm2 and 428.18 m W cm-2 at 800 oC,respectively.The above results show that the perovskite cathode YBCC-xSDC and PSCC-xSDC has good electrochemical properties and thermodynamic temperature and can become candidate materials for intermediate-temperature solid oxide fuel cell.