Hybrid Metal/Electrolyte Monolithic Low Temperature SOFCs

摘要

The program objective is to develop SOFCs, operating in the 500-700 degrees C range, based on Metal/Electrolyte square cell honeycomb formed by simultaneous powder extrusion of electrolyte and metal interconnects on alternate layers. The alloy interconnect is being formed as an oxide powder mixture which will be reduced to the metal and then co-sintered with the electrolyte during hydrogen thermal treatment. Goals include power density of 5 KW/liter, alternative fuels, designed thermal management, and low fabrication cost. The project is divided into electrolyte/electrode development, fabrication of hybrid and electrolyte monoliths, and thermo-mechanical stress modeling and heat transfer. Honeycomb fuel cells offer a great potential for high-power density and low-cost manufacturing. Also, producing multiple layers simultaneously forms a gas-tight high temperature seal in a single step, minimizing or eliminating difficulties encountered in other designs (planar or tubular) of SOFCs. The unique honeycomb cell geometry, however, poses some challenges in application of electrodes with desired microstructures to the honeycomb channels. However, near the end of the program, success was obtained in reduction and co-sintering of crack free, hermetic SOFC platform with alternating layers of metal interconnect and YSZ electrolyte. The structures were electroded and operated as fuel cells at modest powder levels. In, monolithic, all YSZ, honeycomb fuel cells, power levels of 0.09 W/sq cm of electrolyte area, 0.30 W/cu cm of call volume, and 0.15 W/g was achieved in the program.