Study Of Inorganic Electrolyte With High Conductivity For IT-SOFCs

Solid oxide fuel cells (SOFCs) have lots of advantage such as high energy efficiency, modularity and excellent fuel varieties. The intermediate temperature solid oxide fuel cells (IT-SOFCs), which operate at 500-700℃, is the developmental direction of SOFCs, it can widen the selectivity of component materials and improve the reliability of SOFCs system.Ce1-xGdxO2-x/2 (x=0.05-0.3, mole fraction) powders were synthesized by citrate method. Ce0.8Gd0.2O1.9 called GDC for short, which was used as electrolyte powder for subsequent tape casting. Influence of Gd content on conductivity and lattice constant was studied, and the activiation energy for conduction was calculated. Results showed that all powders were cubic fluorite structure. The electrical conductivity of Ce1-xGdxO2-x/2 increased systematically with increasing Gd content and reached a maximum, then decreased.NiO-GDC-C (C as pore former) anode green tapes (called A green tapes for short) were prepared by tape casting, NiO-GDC-C/GDC anode/electrolyte multilayer green tapes (called AE green tapes for short) and NiO-GDC-C/NiO-GDC/GDC gradient anode/electrolyte (called GAE green tapes for short) multilayer green tapes were prepared by co-tape casting. After drying, the thickness was 120μm. These green tapes with smooth face, good microstructure and high strength were obtained. The maximum stress of A green tapes, AE green tapes and GAE green tapes reached 3.83,3.51,3.14 MPa, and the strain to failure was 40%,57%,65%, respectively.Two kinds of half cell were prepared:(1) Half cell AE:which was prepared by laminating and co-sintring 20 sheets of A green tapes and 1 sheet of AE green tapes.(2) Half cell GAE:which was prepared by laminating and co-sintring 20 sheets of A green tapes and 1 sheet of GAE green tapes.Two kinds of single cell were prepared:(Ⅰ) Single AE (half cell AE‖LSCF-GDC):which was prepared by coating LSCF-GDC on half cell AE and sintered subsequently.(Ⅱ) Single GAE (half cell GAE‖LSCF-GDC):which was prepared by coating LSCF-GDC on half cell GAE and sintered subsequently. The performance of single cell was tested. Results showed the maximum power density of single cell AE reached 0.51 W/cm2,0.55 W/cm2,0.49 W/cm2 and 0.37 W/cm2, single cell GAE reached 0.55 W/cm2,0.58 W/cm2,0.52 W/cm2 and 0.39 W/cm2, at 500℃,600℃,700℃and 800℃respectively. The performance of single cell AE closed to single cell GAE. Power density of single cell approximated 0.55 W/cm2 at 500℃,which meaned 10 piles(100 sheets per pile) will generate 12.5 kW power with the size of 5×5 cm. Now, our group are designing the model of single pile, which have the advantage of small, flexible, durable and non pollution, it can meet the needs of variety of special environment. Meanwhile it is expected to extend to more field after improving cost performance.