Modeling of patterned mixed-conducting electrodes and the importance of sheet resistance at small feature sizes Rupak Das, David Mebane, Erik Koep, Meilin Liu ⁎ Center for Innovative Fuel Cell and Battery Technologies, School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, GA 30332–0245, USA Received 15 June 2005; received in revised form 2 April 2006; accepted 27 December 2006 Abstract The sheet resistance of patterned electrodes was modeled and corrected using a finite volume technique. Results show that the sheet resistance of patterned electrodes may dramatically reduce the utilization or the performance of the electrodes when the feature size (e.g., thickness or width) is sufficiently small. Further, the utilization of a patterned electrode with a given geometry can be estimated, which may be used for correcting the sheet resistance effect on electrode performance. These results are important not only to fundamental study of electrode reaction mechanisms and kinetics but also to better design of porous mixed-conducting electrodes for solid oxide fuel cells. © 2007 Elsevier B.V. All rights reserved. Keywords: Mixed conductor; Patterned electrode; Simulations; Sheet resistance 1. Introduction Computational approaches to analysis and optimization of fuel cell materials, components, and systems have attracted much attention in recent years [1–8]. While porous/dense mixed ionic-electronic conductors (MIECs) have been widely used as electrodes for SOFCs to reduce the interfacial polarization re- sistance [9–19], many fundamental issues still remain unan- swered regarding geometrical aspects, electrode kinetics and transport mechanisms of dense electrodes. Increasingly popular analytical tools for uncovering answers to these questions are patterned electrodes and thin films of high aspect ratio. In many studies involving these cell structures, the electrical resistance (or sheet resistance) of the electrodes are recognized to exert a significant influence [3,9]. Brichzin et al. [3] made a correction to the interfacial resistance using a technique for calculating the effect of sheet resistance on utilization [11,14,16,18]. In this paper, the effect of sheet resistance on the utilization of patterned electrodes is quantitatively examined as a function of feature size. The geometrical parameters are varied in order to show the dependence of electrode polarization resistance and TPB utilization on the sheet resistance at different electrode thicknesses. While patterned LSM electrodes were used for this model study, our proposed computational approach is applicable to any patterned electrode. In our work we utilized the commercial CFD code Fluent. 2. Model formulation We are not actually interested in modeling the sheet resistance itself, since sheet resistance is easily separated from interfacial resistance in the impedance spectrum. Rather, we are interested in modeling the effect that the sheet resistance has on the electrode polarization resistance through reduced activity along the MIEC at locations far from the current collector. As such, the focus of the model is on electrical transport within the MIEC, i.e., the movement of holes from the reaction sites to the current collector (or electrons from the current collector to the reaction sites). The schematic configuration of the full-scale electrode system used for this calculation appears in Fig. 1. The current collector is placed as the topmost layer and has several stripes. Solid State Ionics 178 (2007) 249 – 252 www.elsevier.com/locate/ssi ⁎ Corresponding author. Tel.: +1 404 894 6114; fax: +1 404 894 9140. E-mail address: meilin.liu@mse.gatech.edu (M. Liu). 0167-2738/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ssi.2006.12.021