Development And Performance Optimization Of Solid Oxide Fuel Cell Based On La0.6Sr0.4Co0.2Fe0.8O3+δ Composite Electrode

Solid oxide fuel cells（SOFC）have been used in automobiles,power stations,military due to their advantages such as diversified fuel choices,no pollution,high battery structural strength.However,the operating temperature of SOFC is mostly too high.Using it as the power source of the car will increase the start-up time of the SOFC vehicles,and the high temperature working environment will make the operation and maintenance costs of the SOFC vehicles too high and the safety will be reduced.Therefore,reducing the operating temperature of SOFC is very important.However,as the operating temperature is reduced from high to medium or low temperatures,the performance of SOFC cathodes will deteriorate,so it is extremely important to improve the medium-temperature performance of current SOFC cathodes.La_0.6Sr_0.4Co_0.2Fe_0.8O_3+δ（LSCF）has been widely concerned for its advantages such as mixed ion-electron conductivity and good thermal expansion matching performance,but its oxygen surface exchange performance is poor,which will limits its use.In view of this problem,the impregnation method was used to optimize the LSCF in this study to improve its medium-temperature performance of LSCF,explored the impact of the number of impregnation on its catalytic activity and analyzed the influence mechanism through comparative analysis combined with simulation research.In this study,La₂NiO_4+δ（LNO）with good oxygen surface exchange performance was selected as the impregnation material,and it was impregnated on the surface of the LSCF skeleton to prepare the LNO-LSCF composite electrode.In this study,the reasons for the change in catalytic activity of LNO-LSCF composite electrodes with different impregnation times were analyzed from the aspects of micro structure,oxygen surface exchange performance,electrical conductivity,thermal expansion and surface oxygen vacancy concentration.Analysis shows that immersion of LNO on the surface of LSCF framework can improve the thermal expansion matching performance of the cathode,and the presence of LNO particles on the framework surface will increase the oxygen vacancy concentration on the cathode surface and the adsorption capacity of surface oxygen,thereby accelerating the oxygen exchange rate on the cathode surface.At the same time,when the number of immersion times of LNO is less than two,the increase in the number of immersion will make the LNO-LSCF composite electrodes show higher catalytic activity.At 700℃,the polarization resistance value of the LNO~2-LSCF composite electrode obtained by immersion twice is 0.204Ω·cm~2.When the number of immersion times is three,LNO accumulation will occur on the surface of the LSCF skeleton,which will affect the penetration of O2 and the electron transfer rate on the surface.Although impregnating LNO on the surface of the LSCF framework can increase the oxygen exchange rate on the cathode surface,the electron transport rate on the surface will decrease.Therefore,the double perovskite Pr Ba Co₂O_5+δ（PBCO）material was selected as another impregnation material,and PBCO-LSCF composite electrodes was prepared.The differences between PBCO impregnation and LNO impregnation were explored by testing compatibility,XPS,thermal expansion,ECR,and electrochemical performance on the PBCO-LSCF composite electrodes.Studies have shown that LSCF has good chemical compatibility with PBCO and GDC.Impregnating PBCO on the surface of LSCF framework can increase the surface oxygen vacancy concentration of the electrode,thereby accelerating the surface oxygen ion transmission rate,and the existence of LSCF framework can effectively avoid the poor thermal expansion matching performance of PBCO.In addition,the conductivity of PBCO in the test temperature range（650～850℃）can reach545～471S·cm^-1,which is about 10 times higher than LNO,which will make the PBCO-LSCF composite electrodes have a faster surface electron transport rate than LNO-LSCF composite electrodes and exhibit higher catalytic activity.In addition to experimental research,this study also explored the effect of LNO impregnation on the performance of SOFC single cell based on the experimental data of LNO-LSCF composite electrode through COMSOL single cell simulation.Studies have shown that the presence of LNO particles on the surface of the LSCF framework will make the cathodes show higher catalytic activity,and high catalytic activity will accelerate the electrode’s consumption rate of O₂ and H₂,which will increase the output power of the battery.Among them,the LNO~2-LSCF composite electrode has the highest catalytic activity,and the output power of the single cell is the highest.At the same time,through the study of the parameters of the single cell,it is found that reducing the thickness of the electrolyte and the cathode and increasing the inlet pressure of O₂ can improve the performance of the single cell with LNO~2-LSCF composite electrode as the cathode.This research has certain guiding significance for improving the catalytic activity and output power of SOFC in the medium temperature,and has certain value for reducing the operating cost of SOFC vehicles and increasing the output power of SOFC vehicles,and has a certain role in accelerating the commercialization of SOFC vehicles.