Research On Composite Electrolytes For Low Temperature Solid Oxide Fuel Cells

Conventional solid oxide fuel cell（SOFC） used yttria stabilized zirconia（YSZ） as electrolyte and operates at high temperature（800-1000℃） to achieve a sufficient ionic conductivity. However, there are many disadvantages of high temperature operation, such as insufficient long-term stability, high manufacture cost, sealing difficulty, and difficulty in materials selection. Lowering operating temperature（400-600℃） is the main direction of solid oxide fuel cells（SOFC）. In recent years, Carbonate doped composite electrolytes have received much attention due to the excellent performance at low-temperature range. But the addition of carbonate obviously reduces the mechanical strength of the cell, the cell were easily damage when working under the environment of high temperature. In the article focuses on the application feasibility of LSGM-Mg O-（Li/Na）2CO3 composite electrolytes in low-temperature SOFC. La_0.9Sr_0.1Ga_0.8Mg_0.2O_0.285 powders are synthesized by acrylamide polymerization. Novel composite electrolytes are obtained by mixing LSGM powders with MgO and binary carbonates, the material systems with various compositions are prepared, and the structure and electrical properties of these materials are studied. The result shows that LSGM、MgO and carbonate can coexistence stabllly. The bending strength enhanced by increasing MgO contents. The conductivity behavior of LSGM-MgO-（Li/Na）2CO3 composite electrolytes have a transition temperature, above the conductivity transition Temperature,the addition of MgO can enhancement the conductivity of LSGM-MgO-（Li/Na）2CO3 composite electrolytes, reaching 0.17S·cm-1 at 650℃. The maximum power densities reach 590 mW·cm-2 at 600℃ and 380 mW·cm-2 at 550 ℃ for SOFC with LSGM-MgO-（Li/Na）2CO3 composite electrolytes. Longtime composite performance tests show that the sample shows a relatively stable conductivity of 0.08 S·cm-1 during a 200 h measurement in air at 600℃。Another different morphology of MgO（2） powders are synthesized by homogeneous precipitation,the partical size is much smaller than the Mg O（1） provideed by national medicine group, the conductivity of LSGM-MgO（2）-（Li/Na）2CO3 composite electrolytes is much higher than LSGM-MgO（1）-（Li/Na）2CO3 composite electrolytes.