Phase Inversion and Electrophoretic Deposition Processes for Fabrication of Micro-Tubular Hollow Fiber SOFCs

Abstract

A novel combination of a phase inversion process followed by electrophoretic deposition was used to fabricate anode supported micro-tubular hollow fiber solid oxide fuel cells (SOFCs). The phase inversion process was used to produce 240 μm thick 60 wt% NiO -40 wt% yttria-stabilized zirconia (YSZ) hollow fiber anode precursors with asymmetric porosity. Subsequently, electrophoretic deposition (EPD) was used to apply 40 μm thick, particulate YSZ electrolyte layers onto the un-sintered NiO-YSZ hollow fibers from a YSZ dispersion in ethanol at an applied electric field of ca. 22 kV m −1 . The YSZ-coated NiO-YSZ fibers were sintered in a hydrogen atmosphere at 1500 • C to produce gastight electrolytes. Two dispersions of YSZ and lanthanum strontium manganite (LSM) particles were then painted consecutively on top of the electrolyte layers, as 'graded' LSM-YSZ | LSM cathode precursors that were sintered at 1200 • C. When fed with H 2 fuel and air, a single such SOFC delivered peak power densities of 0.20, 0.18 and 0.14 W cm −2 during operation at 800, 750 and 700 • C, respectively. A lumped parameter model, incorporating calculations of the contact, ohmic, activation and concentration polarization losses, is presented and the means are proposed by which certain potential losses may be obviated.

High-efficiency, nickel-ceramic composite anode current collector for micro-tubular solid oxide fuel cells

“…It could be concluded that inserting the nickelbased anodic current collector effectively lowers the percentage of contact loss down to around 6e10 %. The contributions from both electrodes (anode and cathode) ohmic loss are all less than 0.01%, thus could be considered as negligible, which is also in good agreement with previous results [18]. In this study, current collector resistance (silver wires) becomes the major component and it could be further reduced by adopting thicker and shorter wires.…”

“…The values of some parameters were obtained from Refs. [18,20,21], including s wire , s 0,electrolyte , E electrolyte , s anode and s cathode .…”

“…In this study, the major objective is to prove the effectiveness of the new anodic current collector design in achieving a more uniform current collection and reducing contact loss. Therefore, a simplified method has been adopted to calculate various ohmic contributions, as described in previous studies [18,34]. It is generally accepted that the total ohmic loss is mainly composed of electrolyte ohmic loss, electrode ohmic loss, contact loss and resistance from current collector.…”

“…In SOFC literatures, contact loss is usually considered as negligible, especially for planar geometric design. However, in terms of MT-SOFC, according to Droushiotis's work [18] on anode-supported design using silver wires/wool as lumen-side current collector, the contact loss composes up to 70% of the total ohmic loss. Therefore, development of a new current collection technique with reduced contact loss could be an effective approach to improve the overall performance.…”

“…However, reproducibility and contact loss need to be considered when evaluating the overall cell performance. Some numerical calculations conducted have suggested that the contact loss, which is resulted from problematic adhesion between anode and wires, is the main contributor towards total ohmic loss (up to 70%) [18]. To sum up, a new current collection technique addressing process economy, reduced contact loss, and negligible mass transfer resistance is still of great interest.…”