Cathode performance: Influence of MOD-intermediate layer and electrolyte surface enlargement

An electrolyte supported planar single cell with screen printed electrodes displays a considerable polarisation resistance at both electrode/electrolyte interfaces. The development of electrode/electrolyte interfaces with low overpotential and improved long term stability is important for low and high temperature applications of SOFCs. For a conventional strontium doped lanthanummanganite cathode (LSM: La0.8Sr0.2MnO3) on an 8YSZ electrolyte substrate (8YSZ: 8 mol% Y2O3 doped ZrO2) the cathodic reaction is generally assumed to be restricted to the three phase boundary (tpb) LSM/8YSZ/air. In this work, the electrochemical active area was increased by a thin (80-100nm) microporous interface layer using the MOD technique (MOD: Metal organic deposition). A three dimensional cathode/electrolyte interface was realized by first screen printing a porous monolayer of individual YSZ particles (~17mm) onto the electrolyte substrate (8YSZ). Second a thin intermediate layer of substoichiometric LSM (ULSM: La0.75Sr0.2MnO3) or LSC (La0.5Sr0.5MnO3) was applied by MOD technique. Finally, a screen printed ULSM layer (approx. 30mm in thickness) was applied as a current collector and gas distribution layer. Single cells with this modified cathode/electrolyte interface showed a considerable increase in power output, long term stability and thermomechanical stability.