Fabrication Of Anode Functional Layer And Thin Film Electrolyte For Low-Intermediate Temperature Solid Oxide Fuel Cells

Solid oxide fuel cells(SOFCs)have broad development prospects in the energy field.As a power generation device,SOFCs adopt all-solid structures and can convert various clean energy into electric energy directly.Since SOFCs require a high operating temperature in the working process,generally above 1000°C,solid oxide fuel cells are required to have high thermodynamic and chemical stability.So the manufacturing cost of SOFCs remains high,which is not conducive for SOFCs to further commercial development.At present,solid oxide fuel cells are developing in the direction of low and intermediate temperature.La₁₀Si_5.8Mg_0.2O_26.8is used as a new type of electrolyte material and has high ionic conductivity at lower temperature.So this paper uses La₁₀Si_5.8Mg_0.2O_26.8as the electrolyte material to prepare a thin and dense solid electrolyte by magnetron sputtering.The anode of the solid oxide fuel cell is porous with a porosity of 30%-40%,and the size of pores are greater than 1?m.However,it is impossible to prepare a dense electrolyte film with a thickness of several microns on the porous anode substrate of the micron level.When the film thickness is less than or equal to the pore size of the substrate,the film cannot completely cover the holes on the surface of the substrate to form a dense film.In order to prepare a dense electrolyte membrane with a thickness of several microns,a functional layer,namely the anode functional layer,must be added between the microporous anode substrate and the electrolyte membrane,and the macropore diameter of this functional layer is required to be in the sub-micron range and the surface is flat.In this paper,La₁₀Si_5.8Mg_0.2O_26.8powder was prepared by sol-gel method using lanthanum nitrate,magnesium nitrate,ethyl orthosilicate,citric acid,ethylene glycol.The functional layer slurry was prepared by rotary evaporation method.Then the anode functional layer was prepared by screen printing on the surface of the anode substrate.In order to explore the influence of organic matter on the surface morphology of the anode functional layer,this paper analyzed the changes of terpineol and ethyl cellulose with temperature and optimized the heat treatment process of the anode functional layer.Besides,the effects of different slurry preparation processes,ethyl cellulose content,and the time of rotary evaporation operating on the anode functional layer were studied.The SEM was used to characterize the surface morphology,cross-section morphology and thickness before and after reduction of the samples.The XRD was used to analyze the phase before and after reduction of the samples.The porosity of the anode functional layer was measured by image method,and the resistance of the anode functional layer was measured with the multimeter.The experimental results show that when the ethyl cellulose content is 12.5%,the ultrasonic dispersion is used to prepare the suspension of the functional layer slurry and the functional layer slurry is prepared by rotary evaporation for 30minutes by a rotary evaporator,we can prepare the anode functional layer by the screen printing method that meets the requirements.After the isothermal treatment,an anode functional layer with a smooth surface,no cracks,the maximum pore diameter of less than1?m,and the thickness of 13.5?m is obtained.The porosity of the functional layer before reduction is 13.31%.The porosity of the functional layer is 19.8%after reduction and the resistance value of the sample is 2.4?.In order to prepare a dense electrolyte film,this thesis used magnetron sputtering method,with the anode functional layer as the substrate,sputtering continuously for 24 hours.The morphology and phase of the electrolyte film were characterized by the SEM and the XRD.The experimental results show that the surface of the electrolyte film is flat and basically dense after the electrolyte film is annealed.The electrolyte film contains only apatite phase and no other impurity phases.However,there are small pores of about 0.23?m.