Study On The Preparation And Properties Of Anode Supported SOFC Electrolyte Films And Electrode Materials

Solid oxide fuel cell?SOFC?is a new type of green power generation technology,which can translate the chemical energy into electricity directly with the ionic conductor as the diaphragm.It has a promising future for high energy conversion efficiency and environmental protection.However,the high working temperature can cause many problems,reducing the service life and efficiency of SOFC.The most common way to realize the low working temperature is to use the anode to support SOFC,preparing the electrolyte material into thin film.As the important part of SOFC,the properties of anode and electrolyte film are very important.Firstly,porous NiO/YSZ anode material was prepared by using graphite as pore forming agent,and the effect of the pore forming agent on the microstructure and properties of anode materials was discussed.The results showed that with the increase of pore forming agent content,the porosity and shrinkage of the anode materials increased,the thermal shock resistance improved,and the bending strength and conductivity of the anode decreased.The bending strength of the anode materials with 10wt%graphite was about 50MPa,the porosity was 38%,and the conductivity was 720s/cm,which could meet the basic requirements of SOFC.Secondly,the gradient anode material was prepared by dry pressing method,making the content of NiO and pore forming agent decreased from the support layer to the functional layer,refining the size of the powder and decreasing the porosity,so as to increase the catalytic activity,solve the aging problem and improve the performance.For the anode functional layer,the longer the ball milling time,the finer the powder particles,the more uniform the mixing,thus ensuring a higher reaction three phase boundaries.Then,the electrolyte film was prepared on the anode support by slurry spin coating method,and the influence of the spin coating parameters on the thickness and density of the electrolyte film was studied.It was found that when the content of ethyl cellulose was 3wt%,the solid content was 40wt%,and the pre-sintering temperature was 800?,the film was dense.When the spin coating time was 20s,the speed was 4000r/min,and spin coated 4 times,the electrolyte film with thickness of about 15um could be obtained,which was even and smooth,and connected with the anode support closely.The addition of Bi₂O₃ into the YSZ slurry as sintering aids could reduce the sintering temperature,improve the densification,make the grain grow well,and reduce the grain boundary resistance of the electrolyte.However,too much Bi₂O₃ would lead to partial c-ZrO2 translate into m-ZrO2 with lower oxygen ion conductivity,while reducing the thermal shock resistance of the electrolyte.The relative density of YSZ electrolyte sintered at 1250C0 with 3wt%Bi₂O₃ was about 97.5%,which could reach the density of pure YSZ electrolyte sintered at 1450?,avoiding the generation of m-ZrO2,which was more fit.Finally,the perovskite type LSM cathode powder with high specific surface area and high reactivity was prepared by sol-gel method.Mixing LSM powder with YSZ powder,the longer the ball milling time,the more uniform the powder mixture,and the smaller the particle size.A SOFC single cell could be obtained by spin coating composite cathode film on the anode supported electrolyte.The ethyl cellulose in the slurry played the roles of binder and pore forming agent.When its content was 6wt%and the sintering temperature was 1100?,the skeleton structure of the composite cathode was refined,the pore was uniform,the surface film was smooth,and the cathode contacted with the electrolyte closely,making the cathode has more three phase boundaries,thereby increasing the electrochemical activity of the cathode.