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The elaboration of the last generation of metal supported IT-SOFCs by physical surface deposition processes is really challenging. Atmospheric Plasma Spraying (APS) process appears to be well adapted to build the porous anode layer [1] whereas Reactive Magnetron Sputtering (RMS) technique is suitable to deposit thin and dense layer. In the present work, we have deposited a Ni-YSZ anode by APS on porous metallic supports (ITM) produced by PLANSEE SE. Then, a thin YSZ electrolyte film was applied by RMS. Details about the elaboration of the half cell could be found in a previous work [2]. Various strategies have been followed to deposit the cathode layer on top of the previously deposited anode and electrolyte coatings. The Mixed Ionic and Electronic Conductor K2NiF4 structured material presents interesting electrocatalytic properties [3] allowing its utilization as cathode layer. Recent studies deal with the use of thin layers as cathodes in IT-SOFCs [4]. Therefore, RMS process was also evaluated to deposit a thin La2NiO4 layer (LNO) according to already optimized operating conditions [5]. In order to compare the efficiency of this dense layer as an individual cathode or a bonding cathode layer, the complete IT-SOFC building was elaborated by replacing and/or adding a screen-printed La2NiO4 coating (SP LNO). This layer was developed and optimized in ICMCB laboratory and has shown interesting performances in LNO/GDC/LNO half cells [6]. GDC diffusion barrier layers were deposited by RMS in order to limit the deleterious interaction between active layers in use. Different cells with RMS LNO, SP LNO, and RMS LNO + SP LNO were produced and tested in a complete cell bench at 973 K. Impedance Spectroscopy and Voltametry measurements were performed on these samples to assess their electrochemical characteristics and performances. The electrochemical resistances of these cells are too high and their performances are still lower than the literature ones. Analyses of the samples after the electrochemical tests permit to identify the density of the RMS LNO layer as the limiting factor lowering the cathodic electrochemical reaction. The sintering step performed on complete cells with SP LNO deteriorates the layers deposited by RMS as well as the metallic support explaining these performances. Nevertheless, using LNO bonding layer manufactured by RMS seems to be an interesting way to improve the polarization resistance of the cell. References [1] D. Stöver, D. Hatiramani, R. Vaβen, R. Damani, Surface and Coatings Technology 201 (2006) 2002-2005. [2] J. Fondard, P. Bertrand, A. Billard, S. Skrabs, Th. Franco, G. Bertrand, P. Briois, Electrochemical Society Transactions 57 (2013) 673-682. [3] E. Boehm, J.-M.Bassat, P.Dordor, F. Mauvy, J-C.Grenier, Ph. Stevens, Solid State Ionics 176 (2005) 2717 – 2725. [4] I. Garbayo, V; Esposito, S. Sanna, A. Morata, D. Pla, L. Fonseca, N. Sabaté, A. Taracon, Journal of Power Sources 248 (2014) 1042-1049. [5] J. Fondard, A. Billard, G. Bertrand, P. Briois, Solid State Ionics 265 (2014) 73-79. [6] B. Philippeau, F. Mauvy, C. Mazataud, S. Fourcade, J-C. Grenier, Solid State Ionics 249-250 (2013) 17-25.

In the thin-film solid oxide fuel cell (SOFC) concept of the German Aerospace Center (DLR) in Stuttgart, the entire membrane electrode assembly (MEA) is deposited onto a porous metallic substrate by an integrated multistep vacuum plasma spray (VPS) process. This concept enables the production of very thin and stable electrodes and electrolyte layers with a total cell thickness of only 100-120 μm. In this concept, the porous ferrite substrate material predominantly acts as mechanical cell support and as fuel gas distributor. In general, ferrite substrate alloys with high chromium and low manganese content show both excellent corrosion stability and adequate thermal expansion behavior. Nevertheless, at the high process temperature in the SOFC of∼800°C, atomic transport processes can show a detrimental effect on cell performance, at least at the required long-term operation. Problems arise, in particular, through diffusion processes of Fe-, Cr-, and Ni-species between the Ni/8YSZ anode and the ferrite steel-based substrate material. This can induce significant structure changes both in the anode and the substrate. As a reliable solution of this key problem, a plasma sprayed thin diffusion barrier layer is seen at the interface between anode and substrate, which consists of an electrically conductive and chemically stable ceramic component. For this purpose, some doped perovskite-type LaCrO 3 , such as La 1-x Sr x CrO 3-δ La 1-x Ca x CrO 3-δ or La 1-x Sr x Cr 1-y CO y O 3-δ were investigated and tested carefully at DLR. These types of perovskites show a high potential to fulfill all the required properties that are needed for the applicability as an anode-side diffusion barrier layer. The paper focuses on basic investigations of differently doped LaCrΟ 3 compounds under SOFC-relevant conditions concerning thermal expansion, electrical conductivity, chemical stability, etc. Furthermore, first results of electrically and electrochemically characterized half cells carried out with some qualified doped LaCrΟ 3 are shown. Finally, the diffusion barrier layer is demonstrated as a new SOFC component that is effective at cell operating conditions.

A key to the development of metal-supported solid oxide fuel cells (MSCs) is the manufacturing of gas-tight thin-film electrolytes, which separate the cathode from the anode. This paper focuses the electrolyte manufacturing on the basis of 8YSZ (8 mol.-% Y2O3 stabilized ZrO2). The electrolyte layers are applied by a physical vapor deposition (PVD) gas flow sputtering (GFS) process. The gas-tightness of the electrolyte is significantly improved when sequential oxidic and metallic thin-film multi-layers are deposited, which interrupt the columnar grain structure of single-layer electrolytes. Such electrolytes with two or eight oxide/metal layers and a total thickness of about 4 μm obtain leakage rates of less than 3 × 10−4 hPa dm3 s−1 cm−2 (Δp: 100 hPa) at room temperature and therefore fulfill the gas tightness requirements. They are also highly tolerant with respect to surface flaws and particulate impurities which can be present on the graded anode underground. MSC cell tests with double-layer and multilayer electrolytes feature high power densities more than 1.4 W cm−2 at 850 °C and underline the high potential of MSC cells.

International audience; A new cell design with metallic porous support was selected in order to face with the reduction of IT-SOFC's operation temperature. Nevertheless, the excessive roughness of the porous metallic interconnect induce additional problems when a thin electrolyte layer is required. In this work, an anode material (NiO-TSZ) by Atmospheric Plasma Spraying was deposited on metallic supports (ITM) produced by PLANSEE able to cover the roughness of the support. Then, a second thin and dense electrolyte layer (YSZ) by reactive magnetron sputtering was produced on the anode material. In this study, for both processing routes, the optimal process parameters regarding the structural, morphological and electrical characterizations were investigated.

High-temperature fuel cells of the solid oxide fuel cell (SOFC) type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced lightweight planar cells for electricity supply units in cars and other mobile systems. Such cells, in one new design, consist mainly of metallic parts, for example, of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of chromium species from the interconnect or the cell containment into the electrolyte/cathode interface forming insulating phases and by the mutual diffusion of substrate and anode material, for example, iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite, which in both cases reduces performance and system lifetime. Additional intermediate layers of perovskite-type material, (e.g., doped LaCrO3) applied with high-velocity direct-current vacuum plasma spraying (DC-VPS) can reduce such effects considerably if they are stable and of high electronic conductivity.

Metal-supported fuel cells (MSC) are one of the most focused SOFC technologies world-wide for so-called APUs (auxiliary power units) in heavy duty vehicles. In the scope of the present work MSC cells were developed on the basis of a porous support made from a ferritic oxide dispersion strengthened Fe-Cr alloy (ITM). A sintered anode of nickel and 8 mol% yttria stabilized zirconia (8YSZ) and an adaptation layer (8YSZ) were applied to provide a smooth surface with a defined residual porosity which allowed the deposition a very thin, gas-tight electrolyte layer (approx. 1.5 µm) of gadolinium doped ceria (GDC) by reactive sputtering. First cell and stack-tests with a lanthanum strontium cobalt ferrite (LSCF) cathode are presented. In the stack a current density of 1.2 A/cm² was reached at 800 °C and 0.7 V. This was the same power output as conventional anode-supported cells (ASC) under the same testing conditions. Therefore, it is shown that metal-supported cells can deliver the same electrochemical performance as anode-supported cells in a stack.

DLR is one of the pioneer groups to introduce metal supported solid oxide fuel cells (MS-SOFC) in mid 90s and it is continuing the development of the concept towards a reliable light weight 1 kW stack for APU in a funded consortium with ElringKlinger, Plansee and Sulzer Metco. The joint work is an integrated approach incorporating improved materials for functional layers, advanced industrial scale manufacturing and an evolved stack design to define a pilot production set-up for large volume manufacturing. At laboratory scale, the latest generation button cells (12 to 15 cm² effective area) exhibited more than 750 and 520 mW/cm² respectively with hydrogen and simulated reformate gas as fuel at 800{degree sign}C. 2000 hours tests were performed with degradation rate of less than 1.5%/kh. Redox stability of these cells was demonstrated for 20 cycles during which the anodes were fully oxidized. Up-scaling to 85 cm² and 100 cm² effective area cells was accomplished and the cells showed 400 mW/cm² power density using simulated reformate gas at a fuel utilisation of 32%. Further improvements consisting of developing large scale industrial processes for the fabrication of functional layers including low pressure plasma spraying (LPPS) and atmospheric plasma spraying (APS) with TriplexPro are in progress. The aim is to get higher productivity and reproducibility. In addition, a new alloy for interconnects and substrates will be incorporated to further enhance the durability of cells.