Production of Micro-Tubular Solid Oxide Fuel Cells

An innovative current collection architecture for micro-tubular solid oxide fuel cells (SOFC) has been developed. A nickel wire is coiled around a thin carbon composite rod in order to fabricate cell supports. Different carbon composites such as pencil leads and carbon fibres were investigated. The cell support was then coated with ceramic slurries based NiO/YSZ and YSZ for anode and electrolyte, respectively, by successive dip coatings. Effect of thermal behaviour, porosity, amount of binder and dip coating parameters were conjunctly analysed to produce anode and electrolyte crack-free layers with the thickness desired. Pyrolisable materials were then eliminated under air atmosphere at 800ºC followed by co-sintering of half-cells at 1380ºC for 2 h in argon to avoid the oxidation of the nickel wire. In order to complete the cells, sintered half-cells were dipped into cathode inks consisted of LSM-YSZ composite for a functional layer and LSM pure to increase the electrical conductivity of the cathode. The cathode was also sintered at 1150ºC for 2 h under argon atmosphere. Complete cells with an outer diameter below 1.2 mm and length of 30 mm with an effective cathode length of 20 mm and whose active cathode area is 0.75 cm2 were produced. The efficiency of the current collector method developed is evaluated by comparison with the performance of a micro-tubular cell produced and tested under similar conditions, but with a common current collection method. The results of I-V curves shown that the innovative current collection method enhances the performance of a typical micro-tubular cell in the order of 3-4 times. The improvement in performance is attributed to the reduction of current paths of the micro-tubular cells. Suggestions for the production and characterization of current collector-supported micro-tubular cells are also given