Novel High Temperature Proton Conducting Fuel Cells: Production Of La_(0.995)sr_(0.005)nbo_(4-δ) Electrolyte Thin Films And Compatible Cathode Architectures

摘要

For breakthrough development in solid oxide fuel cells, novel cell architectures integrating better performing materials and cost-effective manufacturing processes with potential for mass production must be realised. The present work addresses this on the basis of the recent discovery of acceptor doped rare-earth ortho-niobate proton conductors and the development of a versatile fabrication process. La_(0.995)Sr_(0.005)NbO_(4-δ)/NiO anodes are produced by tape-casting and co-lamination of green layers. Their porosity is finely tuned by using a pyrolyzable pore former. La_(0.995)Sr_(0.005)NbO_(4-δ) electrolytes are spin-coated using ceramic-based suspensions. Fully dense electrolytes with thickness ranging from 9 μm to 26 μm are obtained after sintering in air at 1350 ℃. The cathode layers are then screen-printed. To match thermal expansion and to avoid chemical reaction between the functional layers, special attention is paid to the design of cathode architectures. CaTi_(0.9)Fe_(0.1)O_(3-δ), La_2NiO_(4+δ) and La_4Ni_3O_(10) mixed oxygen ion and electron conducting oxides are investigated as either monophase or La_(0.995)Sr_(0.005)NbO_(4-δ)-based composite electrodes. The latter gives the whole cell an innovative "semi-monolithic" concept, which can take advantage of the chemical and mechanical stability of La_(0.995)Sr_(0.005)NbO_(4-δ), as well as of inherent material integration. Most promising cell architectures are finally selected based on thermo-mechanical and chemical compatibility of all functional layers.