A Numerical Investigation Into the Use of Patterned Electrodes in a Segmented-in-Series Tubular SOFC

A typical segmented-in-series tubular SOFC consists of flattened ceramic support tubes with rows of electrochemical cells fabricated on their outer surfaces and connected in series along their length. In this design, the electrical resistance of the long current flow path is minimised by using high conductivity electrodes. Therefore the resistance of the cathode, which typically has a low electrical conductivity, is reduced by fabricating an additional high conductivity current collector layer. This study is concerned with investigating the design of this additional layer using the newly developed SOHAB multi-physics computer code. Initial simulations identified the optimum thickness of a uniform current collector with respect to cell performance and component cost. However, it was found that this uniform layer causes ionic current to concentrate near the edges of the electrolyte, potentially enhancing cell degradation. Further simulations investigated whether a patterned current collector could be designed to control the current flow within the cell and reduce this detrimental effect. It was found that, for an identical thickness collector layer, a patterned design could reduce spatial variations of ionic current by a factor of over two with a negligible effect on cell performance. Therefore, patterned current collectors represent a means to control the current flow path within a segmented-in-series cell and further improve its performance.