Interface Resistance Analysis in Solid Oxide Fuel Cells

A sophisticated design of the interface structure between the cathode and the electrolyte is essential to improve the performance of solid oxide fuel cells (SOFCs). It is because the interface is the place where it directly affects both the ohmic resistance and the polarization resistance as interface contact and interface reaction, respectively. To improve interface properties, electrolyte surface treatment or inserting interface functional layer between the cathode and the electrolyte have been applied. They improved cell performance by effectively enhancing the interfacial characteristics such as interface bonding and interface reaction area. However, although both ohmic and polarization resistance greatly contributed to the improved cell performance, a detailed analysis related to ohmic resistance compared to polarization resistance is insufficient. Unlike polarization resistance which can quantify interface reaction related resistance using distribution of relaxation time (DRT) model, there is no proper methodology to quantify interface resistance in the case of ohmic resistance. The interface resistance has been analyzed to the extent that it belongs to the remaining resistance except for the electrolyte resistance from total ohmic resistance in consideration of the ionic conductivity and thickness of the electrolyte, which still not completely separate the interface resistance from the total ohmic resistance. Furthermore, in recent years, the electrolyte thickness has gradually decreased to less than 5 μm for high-performance and the electrolyte resistance has been significantly reduced, increasing proportion of interface resistance in total ohmic resistance. Therefore, we need to reduce the interface resistance for further cell improvement. Also, quantifying the interface resistance and having a deeper understanding of the correlation between interface resistance and interface structure should be supported. Here, to realize the interface resistance from the ohmic resistance, we designed several types of interface structure using electrostatic spray deposition (ESD) which can precisely control the particle size and be used to fabricate a thin functional layer. Using the different interface properties and equivalent circuit models, we separate the interface resistance from the ohmic resistance quantitatively. Our results can suggest a simple and effective interface analysis method for achieving high performance SOFCs. Figure 1