Study Of Plasma Sprayed Solid Oxide Fuel Cell YSZ Electrolyte And Performance

Solid oxide fuel cells（SOFC）have received widespread attention because of their high-power generation efficiency and environmental friendliness.Among them,metal-supported SOFC have more potential for development due to their quick response and reliable mechanical stability.At present,the difficulties in the preparation of metal-supported SOFC mainly focus on the functional layer,especially the electrolyte.The traditional wet chemical process requires sintering process（>1200°C）,which is difficult to apply to metal substrates;while the film technology involves high equipment costs or low deposition efficiency.Compared with the above preparation methods,plasma spraying technology is highly efficient,low cost,and limited heat input to the substrate,which can deposit SOFC functional layers on metal substrates.The key to plasma spraying metal-supported SOFC is the enhancement of electrolyte densities.Accordingly,yttria stabilized zirconia（YSZ）,which has been widely used as the electrolyte,was selected in this paper to investigate the mechanism of atmospheric plasma spraying（APS）and low-pressure plasma spraying（LPPS）technologies on the enhancement of electrolyte densification.In the first step,APS was employed to deposit YSZ on a heated substrate to obtain a favorable deposition temperature for densification;in the second step,APS was employed to further investigate the effect of different spraying distances on YSZ densification on a heated substrate;in the third step,LPPS was employed to prepare YSZ,and the effect of different spraying distances on YSZ densification was continued to be investigated by taking advantage of low-pressure ambient insulation and plasma jet expansion.The focus was on exploring the connection of YSZ depositional particle morphology on the electrolyte structure and mechanical properties.On this basis,a single cell with YSZ electrolyte was prepared on a porous stainless-steel support,and the cell performance was examined by testing the output performance and impedance curves.The main findings were as follows:（1）The YSZ depositional particle obtained by APS exhibit a more regular morphology as the substrate temperature increasing.The electrolyte deposited on the substrate at 600°C had a porosity of 7.16%,with significantly better densification than the sample at room temperature,and exhibited good mechanical properties.The highest open circuit voltage of its assembled single cell was 0.97 V,the peak power density at900°C was 850 m W·cm^-2,and the ohmic resistance of cell was 0.23Ω·cm².The various electrochemical properties of the cell indicated that the densification of YSZ need further improvement.（2）The YSZ depositional particle with sufficient spreading rate and minimum microcracks was obtained on a 600°C substrate by APS at 80 mm,which formed the densest coating with a porosity of 3.56%.The coating exhibited the best mechanical properties in APS electrolytes.With the highest open circuit voltage of 0.96 V,peak power of 902 m W·cm^-2 at 900°C,and ohmic resistance of 0.10Ω·cm²,the single cell had good power generation,but the open circuit voltage was still less than 1 V.This indicated that the YSZ prepared by APS with the above two optimizations still did not meet the requirement of air tightness for practical application.（3）The YSZ particles deposited by LPPS showed a completely different morphology from that of APS,with a radial shape and edge splash after spreading at each spray distance.The best structured YSZ particles were deposited at 325 mm,resulting in a highly dense electrolyte coating with a porosity of 1.18%at this spraying distance.The excellent structural densities and homogeneity given the coating excellent hardness and elastic modulus,which was much higher than the densest YSZ coating in APS.The open circuit voltage of the single cell assembled by this YSZ was higher than1 V in the tested temperature range,with the highest open circuit voltage of 1.06 V,peak power of 817 m W·cm^-2 at 900°C,and cell ohmic resistance of 0.13Ω·cm².The comprehensive performance of YSZ prepared by LPPS was better than that of APS and could be used directly in SOFC,showing good potential for development.