Hae Weon Lee

Low Temperature Performance Improvement of SOFC with Thin Film Electrolyte and Electrodes Fabricated by Pulsed Laser Deposition

The performance of solid oxide fuel cells (SOFCs) with thin film electrolytes and electrodes was investigated at a lower operating temperature regime (T ≤600°C). 2 X 2 cm anode-supported unit cells with thin film components of a Ni-yttria-stabilized zirconia (YSZ) composite anode interlayer, a thin (≤1 μm)YSZ electrolyte, and a lanthanum strontium cobalt oxide cathode were fabricated by using pulsed laser deposition, and the performance of the cells was characterized at the temperature range of 350°C ≤T ≤600°C. Stable open-circuit voltage values above 1 V were successfully obtained with thin film electrolyte cells, which implied that the 1 μm thick electrolyte was fairly dense and gastight. The thin film electrolyte cells exhibited a much more improved cell performance than a thick film (~8 μm)YSZ electrolyte cell at the low operating temperature regime (350-550°C) and, in some cases, showed better power outputs than other thin film membrane micro-SOFCs.

Thin Film (La 0.7 Sr 0.3 ) 0.95 MnO 3-δ Fabricated by Pulsed Laser Deposition and Its Application as a Solid Oxide Fuel Cell Cathode forLow-Temperature Operation

The feasibility of using the thin film technology in utilizing lanthanum strontium manganite (LSM) for a solid oxide fuel cell (SOFC) cathode in a low-temperature regime is investigated in this study. Thin film LSM cathodes were fabricated using pulsed laser deposition (PLD) on anode-supported SOFCs with yttria-stabilized zirconia (YSZ) electrolytes. Although cells with a 1 ㎛ thick LSM cathode showed poor low-temperature cell performance compared to that of a cell with a bulk-processed cathode due to the lack of a triple-phase boundary length, the cell with 200 ㎚-thick gadolinia-doped ceria (GDC) inserted between the LSM and YSZ showed enhanced performance and more stable operation characteristics in a comparison of a cell without a GDC layer. We postulate that the GDC layer likely improved the cathode adhesion, therefore contributing to the improvement of the cell performance instead of serving as an interfacial reaction buffer.

Microstructure refinement of pulsed laser deposited La0.6Sr0.4CoO3−δ thin-film cathodes for solid oxide fuel cell

In this study, the microstructural modification of pulsed laser deposited La0.6Sr0.4CoO3−δ (LSC64) thin-film cathodes for solid oxide fuel cells (SOFCs) to improve the lateral conduction and to reduce the surface composition degradation is investigated. A high-temperature deposited 100 nm-thick denser LSC64 layer is added over 2.4 μm-thick porous cathode to cover and bridge the cathode domains. According to the cell performance analyses using current-voltage-power measurements, the performance of the cell modified with an additional denser layer is increased compared with the cell without the denser layer in all operating temperature range. The degree of improvement of peak power density is bigger than 10% at 650–550 °C and is about 6% at 500 °C. This performance enhancement can be attributed to the electrochemical property improvement, especially oxygen surface exchange property, rather than to the conduction improvement, based on the electrochemical impedance analysis. Improved crystallinity and composition integrity of the denser LSC64 layer is considered to enhance the surface exchange property of the cathode.