Study On Two Fabrication Methods Of Electrolyte Films For Solid Oxide Fuel Cells And Their Application

Solid oxide fuel cells (SOFCs), which can convert chemical energy intoelectrical energy directly, is attracting more and more attentions because of theirhigh-energy conversion efficiency, low pollution, and fuel flexibility. From theviewpoint of cost reduction and long-term stability, many researchers have paidtheir attentions to fabrication of anode-supported SOFCs operating at reducedtemperature (600~800℃). Reducing the thickness of YSZ electrolyte is aneffective approach to lower the operation temperature of SOFCs while to retainthe high performance. Development of cost-effective fabrication technology ofthin film electrolyte is a key step for fabrication of anode-supported SOFCs.Screen-printing technology was developed to fabricate YB2BOB3B-stabilized ZrOB2B(YSZ) electrolyte thin films onto NiO-YSZ porous anode substrates. Theimportant technological parameters, which influence significantly thecharacterization of the screen-printed YSZ electrolyte thin films, includingparticle size and particle size distribution of the starting YSZ powder,composition of the screen-printing ink, sintering temperature of the screenprintedYSZ green films and printing times were investigated in detail. Theresults show that the screen-printed YSZ electrolyte thin films are dense andcrack-free in both surface and cross section with a thickness of 2μm~30μm. Thescreen-printed YSZ electrolyte thin films adhere tightly with NiO-YSZ porousanode and LaB0.7BSrB0.3BMnOB3B (LSM)-YSZ cathode, respectively. The tight adhesionbetween YSZ electrolyte and electrode helps to reduce the interfacial resistance.The properties of the starting YSZ powder exert a significant effect on themicrostructure of the screen-printed YSZ films. The films prepared from ballmilling modified powder are dense in both surface and cross section while filmsprepared by unmodified powder are porous. Cells with dense YSZ films provideopen-circuit voltage (OCV) of 1.08V, which is very close to the OCV predictedby Nernst equation. The performance of the cells based on dense films is fourtimes higher than that for the cell fabricated by porous electrolyte films. Printingink composition is another important technological parameter for screen-printingtechnique. The ideal YSZ content in printing ink is about 30~45wt.%. The...