Boosting intermediate temperature performance of solid oxide fuel cells via a tri‐layer ceria–zirconia–ceria electrolyte

Using cost-effective fabrication methods to manufacture a high-performance solid oxide fuel cell (SOFC) is helpful to enhance the commercial viability. Here, we report an anode-supported SOFC with a three-layer Gd$_{0.1}$Ce$_{0.9}$O$_{1.95}$ (gadolinia-doped-ceria [GDC])/Y$_{0.148}$Zr$_{0.852}$O$_{1.926}$ (8YSZ)/GDC electrolyte system. The first dense GDC electrolyte is fabricated by co-sintering a thin, screen-printed GDC layer with the anode support (NiO–8YSZ substrate and NiO–GDC anode) at 1400°C for 5 h. Subsequently, two electrolyte layers are deposited via physical vapor deposition. The total electrolyte thickness is less than 5 μm in an area of 5 × 5 cm$^2$, enabling an area-specific ohmic resistance as low as 0.125 Ω cm$^{−2}$ at 500°C (under open circuit voltage), and contributing to a power density as high as 1.2 W cm$^{−2}$ at 650°C (at an operating cell voltage of 0.7 V, using humidified [10 vol.% H$_2$O] H$_2$ as fuel and air as oxidant). This work provides an effective strategy and shows the great potential of using GDC as an electrolyte for high-performance SOFC at intermediate temperature

Nature and Functionality of La0.58_{0.58}Sr0.4_{0.4}Co0.2_{0.2}Fe0.8_{0.8}O3−δ_{3-δ} / Gd0.2_{0.2}Ce0.8_{0.8}O2−δ_{2-δ} / Y0.16_{0.16}Zr0.84_{0.84}O2−δ_{2-δ} Interfaces in SOFCs

Interdiffusion phenomena and secondary phase formation at the interface La0.58Sr0.4Co0.2Fe0.8O3-δ (LSCF) / Gd0.2Ce0.8O2-δ (GDC) / Y0.16Zr0.84O2-δ (YSZ) are correlated to linear and non-linear losses in symmetrical and full SOFC cells. FIB/SEM (focussed ion beam / scanning electron microscopy) tomography is applied for determining the local distribution of the primary phases LSCF, GDC, and YSZ and elemental analysis via STEM/EDXS (scanning transmission electron microscopy / energy dispersive X-ray spectroscopy) provides information on the secondary phase SrZrO3 (SZO) and the interdiffusion between GDC and YSZ (ID). This reveals the effect of GDC co-sintering temperature (varied from 1100°C to 1400°C), alongside the sintering of LSCF at 1080°C, on these multi-layered microstructures. Electrochemical impedance spectra on symmetrical cells show that the polarization resistance (ASRcat) of the cathode/electrolyte interface is pronouncedly affected by three orders of magnitude, changing the overall power density of anode supported SOFC single cells at 0.8V by as much as a factor of 20. In conclusion, the chemical composition of the ID has a tremendous impact on the electrochemical efficiency of the investigated LSCF/GDC/YSZ interface, and processing parameters of anode supported cells with LSCF cathode have to be carefully chosen for individual SOFC cell concepts

Performances of Solid Oxide Cells with La0.97_{0.97}Ni0.5_{0.5}Co0.5_{0.5}O3−δ_{3-\delta} as Air-Electrodes

Based on previous studies of perovskites in the quasi-ternary system LaFeO$_{3}$–LaCoO$_{3}$–LaNiO$_{3}$, La$_{0.97}$Ni$_{0.5}$Co$_{0.5}$O$_{3}$ (LNC) is chosen as the most promising air-electrode material in the series for solid oxide cells (SOCs). The properties of the material itself have been investigated in detail. However, the evaluation of LNC97 air electrodes in practical SOCs is still at a very early stage. In the present study, SOCs were prepared based on LNC97 air electrodes. The I-U performance of the SOCs in both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes, i.e. reversible SOCs (r-SOCs), was investigated systematically for different air-electrode designs, temperatures and fuel gases. In general, the performance of the r-SOCs tested in the present study is higher than the published results of other LaFeO$_{3}$–LaCoO$_{3}$–LaNiO$_{3}$-based SOCs and is comparable to or even better than state-of-the-art La$_{1-x}$Sr$_{x}$Fe$_{1-y}$Co$_{y}$O$_{3}$ (LSCF)-based SOCs. Mid-term operation of about 1000 h for SOCs in both SOFC and SOEC modes primarily proved the stability of LNC97-based air electrodes. Impedance spectra were systematically applied to understand the polarization processes of the SOCs

Status of light weight cassette design of SOFC

Lightweight SOFC stacks are currently being developed especially for automotive applications such as APU and for portable devices. Within the EU funded project MMLCR=SOFC the Jülich lightweight so-called CS-design was improved concerning better suitability for glass sealing, reduced manufacturing effort and increased power. Based on modelling in combination with manufacturing experience, test results, and post-test analysis substantial changes of the previous CS-design were made. The manufacturing of single parts, particularly due to the improved design of sheet metal interconnects, as well as the assembling processes are suitable for low-cost mass manufacturing. The novel decal concept of glass-ceramic sealant screen printed on foil in order to produce green tapes is used for joining the stack layers offering an enormous potential for cost savings in industrial assembly process. First stack tests with the new CSV–design showed a comparable electrochemical performance to the previous CSIV design having at the same time a better thermo-mechanical behavior.</jats:p