WO2018191765A1 - Electrode-electrolyte unit - Google Patents

Abstract

The invention relates to an electrode-electrolyte unit (10, 10', 10", 10"') for a metal-assisted electrochemical module (20), particularly for a solid oxide fuel cell (SOFC). The invention comprises a metal carrier substrate (11) having a porous, gas-permeable central region (13) and a gas-tight edge region (12) which is integrally joined, at least on the surface (on the side facing the cell), to said central region along an edge section thereof, wherein the gas-permeable surface of the porous central region is separated from the gas-tight surface of the edge region by a boundary line (19). The invention further comprises at least one porous, gas-permeable first electrode (16, 16') formed on the porous central region of the carrier substrate, and at least one ceramic, gas-tight electrolyte layer (18) which is formed on the first electrode, extends beyond said first electrode towards the edge region, and terminates (with the gas-tight edge region) in a gas-tight manner. At least one porous ceramic connection layer (17, 17') is formed between the carrier substrate (11) and the electrolyte layer (18), at least along a subsection of the whole connecting length of the boundary line, wherein said connection layer extends at least over a section of the edge region adjoining the boundary line.

Description

 ELECTRODE ELECTROLYTE UNIT

The present invention relates to an electrode-electrolyte unit for a metal-based electrochemical module according to claim 1 and an electrochemical module according to claim 21.

The electrode-electrolyte unit according to the invention is used in an electrochemical module which is used inter alia as a high-temperature fuel cell or solid oxide fuel cell (SOFC), as a solid oxide electrolyzer cell (SOEC) and as a reversible catalyst Solid oxide fuel cell (R-SOFC) can be used. In the

 Basic configuration includes an electrochemically active cell of the

 electrochemical module, a gas-tight solid electrolyte, which is arranged between a gas-permeable anode and gas-permeable cathode. The electrochemically active components such as anode, electrolyte and cathode are often formed as comparatively thin layers. A mechanical support function required thereby can be achieved by one of the electrochemically active layers, e.g. through the electrolyte, the anode or the cathode, which are then each made correspondingly thick (in these cases we speak of an electrolyte, anode or cathode-supported cell), or by an electrolyte these functional layers separately formed component, such as an electrically conductive ceramic or metallic carrier substrate. In the latter concept with a separately formed, metallic carrier substrate one speaks of a metal-supported cell (MSC). Since with an MSC the electrolyte, its electrical resistance with decreasing thickness and with increasing

Temperature decreases, can be made relatively thin (e.g., with a thickness in the range of 2 to 10 m), MSCs at a

600 ° C to 800 ° C (while, for example, partially supported electrolyte-supported cells)

Operating temperatures of up to 1,000 ° C are operated). Due to their specific advantages, MSCs are particularly suitable for mobile applications, such as For example, suitable for the electrical supply of passenger cars or commercial vehicles (APU - auxiliary power unit).

Usually, the electrochemically active cell units are formed as flat individual elements, which in conjunction with corresponding

 (Metallic) housing parts (such., Interconnector, frame plate, gas lines, etc.) are stacked on a stack and electrically contacted in series. MSC have a great advantage in this regard, as the connection and sealing of individual modules to a stack

 cost-effective manner can be realized by means of welding or metallic soldering processes.

 For the functioning of the electrochemical module, it is essential that the process gas spaces associated with the two electrodes, ie the

 Anodengasraum and the cathode gas space, reliably separated from each other gas-tight and this gas-tight separation even when occurring during operation thermal or oxidation-related loads

 is maintained. In the case of an SOFC, this means reliable separation of the fuel (for example, hydrogen or conventional hydrocarbons, such as methane, natural gas, biogas, etc.) supplied to the anode from the oxidant supplied to the cathode. These

 Gas separation function is taken over by the gas-tight electrolyte in the region of the electrochemically active layers, whereby a major challenge in the sealing in the transition region from the porous carrier substrate to a subsequent gas-tight surface. In WO2014187534 of the applicant is a powder metallurgically produced metallic

Presented carrier substrate in which a porous central region, over which the electrochemically active layers are arranged, is surrounded by a pressed edge region, the surface of which is additionally melted for the purpose of gas-tightness by a laser treatment and thereby sealed gas-tight. For sealing between anode gas space and cathode gas space, the electrolyte layer becomes over the porous area with the anode layer

pulled out so that it expires on the aftertreated by the laser beam, gas-tight surface of the edge region. In practice, this transition region from the porous central region to the gas-tight Edge area, however, is a weak point and there may be problems with the gas tightness. For example, occur in the transition region repeatedly flaking of the layers, which inter alia on a conditional on the melting by the laser beam irregular, partially meandering, surface structure of the edge region

 is due.

The present invention is based on the object, an electrode-electrolyte unit for a metal-based electrochemical module,

 especially for a SOFC, which ensures reliable separation of the two process gas spaces over a long service life in a simple and cost-effective manner.

This object is achieved by the electrode-electrolyte unit according to claim 1 and an electrochemical module according to claim 21. Advantageous developments are specified in the dependent claims.

The electrode-electrolyte unit according to the invention is in a metal-based electrochemical module, in particular in a high-temperature fuel cell or solid oxide fuel cell (SOFC), a solid oxide electrolyzer cell (SOEC) or in a reversible solid oxide fuel cell (R-SOFC), can be used. It instructs

metallic, in particular plate-shaped carrier substrate having a porous, gas-permeable central region and a materially connected to the central region along an edge portion thereof, at least superficially gas-tight on the cell-facing side

Border area on. The gas-permeable surface of the carrier substrate is separated from the at least superficially gas-tight surface of the edge region by a boundary line. On the porous central area of the

Carrier substrate is at least one porous gas-permeable first electrode, and arranged at least one gas-tight ceramic electrolyte layer which extends beyond the first electrode in the direction of the edge region and gas-tight with the gas-tight edge region of the carrier substrate.

Between the carrier substrate and the electrolyte layer is at least along one Part of the entire connecting length of the boundary line at least one porous, ceramic bonding layer is formed, which extends at least over a bordering to the boundary portion of the edge region.

The central region of the carrier substrate and the edge region may be two originally separate components which are interconnected by a material connection such as a welded or soldered connection. In a preferred

 Embodiment, the central region and the edge region are made in one piece (monolithic), the carrier substrate then consists of two imaginary components, which are in material contact. The edge region is rendered gas-tight at least superficially, for example by pressing the porous carrier substrate on the edge side and / or by superficial superficial melting in the edge region on the side of the carrier substrate facing the electrochemically active layers (as described, for example, in WO2014187534).

 These different embodiments of the carrier substrate have in common that in a central region of the carrier substrate, a gas-permeable surface is present, while at least the surface of the edge region is gas-tight. By the meeting of the gas-permeable surface and the gas-tight surface of the arrangement, a boundary line (joint) is defined, wherein surfaces with gas-tight welds or solder joints are assigned to the gas-tight surface.

The metallic carrier substrate is preferably produced by powder metallurgy. Suitable materials for the carrier substrate are in particular iron (Fe) based (ie at least 50 wt.%, In particular at least 70 wt.% Fe-containing), a high chromium content (chromium: Cr) containing alloys (eg at least 16 wt.% Cr ), to which further additives, such as, for example, yttrium oxide (Y 2 O 3) (for increasing the oxidation resistance), titanium (Ti) and molybdenum (Mo) may be added, the proportion of these additives overall being preferably less than 3% by weight (cf. the material referred to as ITM from Plansee SE containing 71.2% by weight of Fe, 26% by weight of Cr 5 2018/000017 and in total less than 3% by weight of Ti, Y2O3 and Mo). Preferably, a powder fraction with an average particle size smaller than 150 μηπ, in particular in the range of about 50- ΟΟ ΟΟμιτι, used to a good

 Coatability for the functional layers to ensure.

In the central region of the carrier substrate are the electrochemically active layers such as first and second electrode (anode, cathode) and

 Electrolyte layer arranged. The electrodes are gas-permeable and can be constructed both as a single layer and as a layer composite of several layers. The anode is usually the electrochemically active layer next to the carrier substrate (first

 Electrode), while the cathode (second electrode) is formed on the side facing away from the carrier substrate of the electrolyte. Alternatively, however, a reverse arrangement of the two electrodes is possible, in which the first electrode is formed by the cathode. The application of the

 Electrochemically active layers are preferably carried out in a known manner by means of PVD (PVD, physical vapor deposition), e.g. Sputtering, and / or thermal coating processes, e.g. Flame spraying or

 Plasma spraying and / or wet chemical processes, e.g. Screen printing,

 Wet powder coating, etc., being responsible for the realization of the entire

 Layer structure of an electrochemical cell unit and several of these methods can be used in combination.

 The anode is usually made of a composite, a so-called cermet, preferably consisting of nickel and yttria fully stabilized zirconia or nickel and gadolinia-doped ceria, while the cathode is usually made of mixed conducting perovskites such

(La, Sr) (Co, Fe) 03). In particular, the first electrode may be multi-layered and have a graded structure in which the mean sintered grain size decreases with increasing distance from the carrier substrate from layer to layer.

Following the first electrode, between the two electrodes, a gas-tight solid electrolyte of a solid, ceramic material of a metal oxide is formed which is conductive for oxygen ions or in a younger generation of SOFC for protons, but not for electrons. Examples of an oxygen ion-conducting electrolyte layer material are doped zirconium oxide, wherein the doping of at least one oxide of

 Contains doping elements from the group Y, Sc, Al, Sr, Ca, Mg,

 (For example, 8YSZ, a fully stabilized with 8 ol% yttria

 Zirconia) or doped cerium oxide, wherein the doping contains at least one oxide of the doping elements from the group of the rare earth elements such as Gd, Sm and / or from the group Y, Sc, Al, Sr, Ca. Examples of a proton conductive electrolyte material are barium-zirconium oxide, barium-cerium oxide, lanthanum-tungsten oxide or lanthanum-niobium oxide. The electrolyte layer typically has a layer thickness in the range of 3 to 5 pm and will

usually applied by PVD. The electrolyte layer extends beyond the layer (s) of the first electrode and closes gas-tight with the gas-tight edge region of the carrier substrate. In the context of the present invention, "gas-tight" means in particular that the leak rate with sufficient gas-tightness is by default <10 ^-3 hPa ^* dm ³ / cm ² s (hPa: hectopascal, dm ³ : cubic decimeter, cm ² : square centimeter, s: second) (measured under air with pressure rise method with the measuring instrument of Dr. Wiesner, Remscheid, type: Integra DDV at a pressure difference dp = 100 hPa). For gas tightness, the electrolyte layer can be in direct contact with the gas-tight surface of the edge region of the carrier substrate or leak on one or more optional gas-tight intermediate layers, which are applied directly to the carrier substrate. Such an at least in the edge region gas-tight intermediate layer can, for example, by a

Diffusion barrier layer be given, which for the suppression of

metallic interdiffusion between the carrier substrate and the anode is carried out and manufacturing due to a part of the

Can extend edge region. Preferably, the

Diffusion barrier layer differently doped lanthanum strontium manganite (LSM), lanthanum stronitum chromite (LSCr) with different lanthanum and strontium or gadolinium oxide doped ceria (CGO); the

Diffusion barrier layer is usually mitteis PVD directly on the

Carrier substrate applied; the layer thickness is usually up to 2 pm and therefore comparatively thin (in comparison, the average

Pore size of the carrier substrate in the central gas-permeable area in the Order of magnitude of 100 μιη lie, which is why the gas permeability in the porous, central area is still given). The boundary line covering the gas-tight area of the gas-permeable area of the surface of the

 Carrier substrate separates, so it remains unchanged with the coating.

The core idea of the invention is to provide at least one additional porous, ceramic bonding layer in the edge region of the carrier substrate between the electrolyte layer and the carrier substrate (or any gas-tight intermediate layer disposed thereon). This intermediate layer in the

 Edge area serves to compensate for irregularities in the surface of the edge region and can therefore over its course a varying

 Have layer thickness. Preferably, it becomes thinner and thinner towards its edges. Irregularities caused, for example, by the above-mentioned laser guidance in the superficial melting process, or sharp-edged gradations or discontinuities at the transitional area between the first electrode and the surface of the edge area can be compensated or smoothed by the bonding layer. The leveling is for the application of the relatively thin

 Electrolyte layer provided a more uniform surface, whereby the risk of mechanical weaknesses and cracking of the gas-tight, as thin as possible running electrolyte layer is significantly reduced.

 The porous bonding layer also helps to reduce stress due to

different thermal expansion coefficients of the

Compensate or reduce the transition area used materials. The different thermal expansion coefficients for

The carrier substrate, the electrode and the electrolyte layer lead to stresses within the layer structure, in particular during production during the sintering process or later during operation, which can lead to cracking or flaking and subsequently to failure of the electrochemical module.

A further advantage of the bonding layer is an improved adhesion of the layer structure in the critical transition region. The bonding layer is preferably a sintered ceramic layer which is connected via sintered necks with the carrier substrate (or an optional gas-tight intermediate layer). It is preferred via a wet-chemical process (eg wet powder coating, brushing, screen printing, etc.)

 applied before it is subsequently sintered. If a comparative fine starting powder is used for the bonding layer (resulting in a small mean pore size), adhesion of the bonding layer becomes more by forming a larger number of sintered necks

 improved. The risk of chipping, both during sintering during production and during later use, is significantly reduced. In an advantageous embodiment, the mean pore size of the sintered bonding layer is smaller than the middle one

 Pore size of the first electrode (in a multi-layered first electrode with different porosity, the pore size of the lowest, the

 Carrier substrate at the closest layer used for comparison). A preferred average pore size for the attachment layer is in the range of from 0.20 μm to 2.00 μm inclusive, more preferably in the range of 0.31 μm to 1 μm inclusive, more preferably in the range of 0.32 μm to 2 μm

 Range from 0.31 pm to 0.5 pm inclusive. General is given in terms of pore size or other similar parameters

 Ready to use parameters are referred to, i. For sintered layers on the sintered state. To determine the porosity, a cross-section running perpendicular to the layer to be examined is made through the electrode-electrolyte unit and a suitably prepared micrograph in the scanning electron microscope (SEM) is examined on the basis of a BSE image (BSE: back-scattered electrons) , The analysis is carried out by threshold value of the different gray levels from the respective REM-BSE image, wherein the brightness and the contrast of the REM-BSE image is adjusted such that the pores and particles in the image are easily recognizable and distinguishable from each other. With the slider, which differentiates grayscale-dependent between pores and particles, a suitable grayscale value is selected as the threshold value. The porosity is determined by determining the area fraction within a selected

Area lying pores relative to the total area of this selected area determined, and also the area proportions of only partially within T2018 / 000017

 9 of the selected area lying pores are included. To determine the pore size, the area of the respective pore in the micrograph is measured and from this the equivalent diameter, which would result for a circular shape of the same area size, is determined.

With regard to the geometric extent of the attachment layer has been found to be advantageous if the bonding layer extending from the boundary line in the direction of the edge region over a maximum length of up to and including 3 cm, in particular up to and including 2 cm, particularly advantageously including 1 cm. Advantageously, the bonding layer extends in the opposite direction, ie in the direction of the central region of the carrier substrate, starting from the boundary line over a maximum length of up to and including 1 cm, in particular up to and including 0.5 cm, particularly advantageously up to and including 0, 3 cm. For this size data for the bonding layer, a good compromise between good adhesion properties and cost-effective production could be found.

For the bonding agent, it is further advantageous if the bonding layer at least in a subsection of the edge region in the immediate,

 cohesive contact both with the electrolyte layer and with the carrier substrate or - if the carrier substrate is superimposed in the edge region with a gas-tight ceramic intermediate layer - with the gas-tight ceramic intermediate layer.

 As far as in this description and the claims to "immediate"

successive layers / components, the presence of intervening layers / components is excluded. If, on the other hand, the term "immediate" is not used, then others can be used, as far as technically reasonable

Layers / components to be provided in between.

The bonding layer preferably consists of the same base material as the electrolyte layer. As a result, in particular thermally induced stresses can be avoided or reduced in the transition region and the adhesion improve with the Eiek rolytschicht. According to the above-mentioned Eiektrolytmaterialien suitable materials for the attachment layer doped zirconia, wherein the doping at least one oxide of the

 Contains doping elements from the group Y, Sc, Al, Sr, Ca, Mg,

 (in particular 8YSZ) or doped cerium oxide, wherein the doping contains at least one oxide of the doping elements from the group of the rare earth elements such as Gd, Sm and / or from the group Y, Sc, Al, Sr, Ca (in particular CGO). Further suitable materials for the bonding layer are barium zirconium oxide, barium cerium oxide, lanthanum tungsten oxide or lanthanum niobium oxide.

 For variants of the electrode-electrolyte unit, in which the carrier substrate at the edge region with a gas-tight intermediate layer such as

 Diffusion barrier layer is coated, it is also advisable, the material of the bonding layer to the material of the gas-tight intermediate layer

 adapt. If the same basic material as for the gas-tight interlayer is chosen for the bonding layer, the adhesion of the

 Bonding layer to the gas-tight intermediate layer and subsequently intensified to the carrier substrate.

For the preparation of the electrode-electrolyte unit, the various layers (optional diffusion barrier layer, first electrode,

 Bonding layer, electrolyte layer) successively applied to the carrier substrate. In the case of layers to be sintered, such as the porous bonding layer, a layer containing the respective ceramic particles and a corresponding organic binder is applied by a wet-chemical method, subsequently sintered and only then

subsequent layer (possibly in an analogous manner) applied. Due in part to the layered sintering, the individual layers are distinguishable from each other, even if they have the same composition. The layer structure can be seen, for example, when perpendicular to the

Layer profile made a cross section through the electrode-electrolyte unit and a correspondingly prepared micrograph in the scanning electron microscope (SEM) on the basis of a REM-BSE image (BSE: back-scattered electrons;

backscattered electrons) is examined. The connection layer can thereby T T2018 / 000017

 11 or after application of the first electrode, which - as explained in more detail below - may also be implemented as a multilayer composite layer, in a preferred variant, more, in particular two Anbind ungsschichten are provided, a first

 Bonding layer, which is applied before the application of the first electrode, and a second bonding layer, which is applied after the application of the first electrode.

In the first embodiment, in which the bonding layer before the

 Layer (s) of the first electrode is applied, the bonding layer in direct materially bonded contact with the carrier substrate or a gas-tight ceramic intermediate layer with which the carrier substrate has been directly coated. The attachment layer dilutes toward its ends and may infiltrate into the material of the carrier substrate in the transition region to the porous central region of the carrier substrate. The

 Layer thickness can thus vary, in particular in the embodiment of the carrier substrate, which originally two separate from each other

 Components is constructed by a welded or soldered connection

 connected to each other. In this case, the bonding layer in the region of the cohesive connection (weld) is usually thicker. The layer of the first electrode runs on or on the bonding layer; In a multilayered embodiment, the lowermost layer of the layer composite lying closest to the carrier substrate may leak out at the attachment layer, while the subsequent layer (s) extend beyond the layer immediately beneath it and extend on top of the underlying layer

Connection layer can leak. The embodiment in which the

Bonding layer is applied in front of the first electrode, in particular has advantages in electrode-electrolyte units in which a gas-tight

ceramic intermediate layer (diffusion barrier layer) is provided and the first electrode is made of a cermet. The ceramic,

optionally finer porosity bonding layer usually adheres better on the ceramic basis than a layer of cermet. In the further embodiment, in which the bonding layer is applied after the first electrode, the bonding layer is in direct material contact with the subsequent electrolyte layer.

 This variant offers particular advantages if the bonding layer and the electrolyte layer are made of the same material and therefore a good adhesion is mediated between these layers. Again, the

 Layer thickness of the bonding layer varies to the sharp-edged

 leveling transition at the first electrode and providing a uniform basis for the subsequent electrolyte layer. For better adhesion in the transition region, care is taken to ensure that the layer of the first electrode or, in the case of a multilayer embodiment, the lowermost layer of the substrate closest to the carrier substrate

 Layer composite of the first electrode over the entire porous central region of the carrier substrate, but does not extend beyond, i. the layer of the first electrode or the lowermost layer thereof, which is coarser than the subsequent layers, extends (apart from a small gap possibly occurring due to the production) up to the boundary line which separates the gas-permeable region from the gas-tight region of the carrier substrate (or coated carrier substrate) ) separates, towards the edge, but not significantly beyond. Quantitatively, this means that the (lowest) layer of the first electrode in the direction of the edge on the gas-permeable surface of the porous support substrate at least up to a distance of 2 mm, in particular up to a distance of 1 mm, particularly preferably up to a distance of 0.5 mm, extending to the borderline, while in the same direction at most over one

Distance of 5 mm, preferably at most over a distance of 3 mm, more preferably at most over a distance of 1 mm, extending over the boundary line away. In other words, that covers

(Lowermost) layer of the first electrode except for a region with a maximum distance of 2 mm from the boundary line away from the central gas-permeable region of the support substrate, and extends - except from an area with a maximum distance of 5 mm from the boundary line removed - not on the gas-tight surface of the

Arrangement. The (lowest) layer of the first electrode is in direct contact with the carrier substrate or with any intermediate layer (diffusion barrier layer) applied to the carrier substrate. A direct contact of the (bottom) layer of the first electrode with the gas-tight surface of the edge region, which is problematic due to the coarseness and associated lack of adhesion, is largely or completely avoided.

 In this variant, the extent of the attachment layer does not only have to be limited to the transition region, but the attachment layer can be extended over the entire first electrode. By seeping into the pores of the uppermost layer of the first electrode is the

 Reduced surface roughness, which is sufficient for sealing a slightly thinner electrolyte layer. With a suitable combination of materials, for example CGO for an anode made of Ni / 8YSZ, this can be additionally functionalized, in the CGO example, due to the sulfur tolerance of CGO, less sensitive to sulfur impurities in the fuel gas.

 In a preferred embodiment, the two aforementioned variants are combined and provided two Anbind ungsschichten, with which the above advantages can be achieved. A first bonding layer is directly on the carrier substrate or with a gas-tight

 ceramic intermediate layer coated carrier substrate arranged.

 Next, the first electrode is deposited, which terminates at and / or on the first bonding layer. This is followed by a second bonding layer, preferably of the same material as the first bonding layer. This is connected at least partially cohesively with the first connection layer. Towards the central region of the carrier substrate, it extends at least over a part of the first electrode, it can also

completely pulled over the first electrode and completely cover this. In the opposite direction, ie in the direction of the

In the case of the gas-tight edge region, the second bonding layer can also be pulled out completely beyond the first bonding layer so that it runs out on the carrier substrate (or the gastight ceramic intermediate layer arranged directly on the carrier substrate). As already mentioned above, in all these variants, the first electrode can be designed as a layer composite, that is to say in multiple layers, in particular in two layers.

 In this case, the material composition preferably does not change, but the individual layers of the layer composite of the first electrode differ only with regard to the mean sintered grain size or, associated therewith, the porosity. In this case, the layer composite can have a gradation of the sintering size, with the mean sintered grain size decreasing from layer to layer as the distance from the carrier substrate increases.

 Preferably, in the layer composite of the first electrode extends

 next layer, which is usually finer-grained than the immediately underlying layer, beyond the immediately underlying layer, whereby a step-shaped transition with improved adhesion properties is formed in the transition region. The stepped transition is compensated by the underlying and / or subsequent bonding layer.

In an advantageous embodiment, the layer composite of the first electrode is constructed in two layers. In embodiments where the first electrode is deposited in front of the tie layer, care is taken that the lowermost, comparatively coarse-grained layer of the first electrode extends substantially to but not significantly beyond the boundary line, while the subsequent, finer-grained layer the first electrode extends beyond the lowermost layer in the direction of the gas-tight surface of the carrier substrate. The finer-grained layer and not the

more coarse-grained layer thus has direct contact with the gas-tight

Surface of the carrier substrate or any intermediate layer.

Further advantages of the invention will become apparent from the following

Description of embodiments with reference to the

attached figures, in which for purposes of illustrating the present invention, the size ratios are not always given to scale. In the various figures, the same reference numerals are used for matching components. 7

 15

From the figures show:

 Fig. 1; a schematic cross-sectional view of an inventive

 Electrode-electrolyte unit according to a first embodiment of the invention;

 Fig. 2; a schematic cross-sectional view of an inventive

 Electrode-electrolyte unit according to a second embodiment of the invention;

 Fig. 3; a schematic cross-sectional view of an inventive

 Electrode-electrolyte unit according to a third embodiment of the invention;

 4 shows a schematic cross-sectional view of a device according to the invention

 Electrode-electrolyte unit according to a fourth embodiment of the invention;

 5 shows an electrochemical module with an electrode electrolyte

 Unit according to FIG. 1 in an exploded view.

In Fig. 1 is a schematic cross-sectional view of a first

 Embodiment of the electrode-electrolyte unit (10) according to the invention shown. Fig. 5 shows an exploded view of an electrochemical module (20) in the form of an SOFC, in which the electrode-electrolyte unit of Fig. 1 is used. The section plane of the section of the electrode-electrolyte unit shown in FIG. 1 takes place in the carrier substrate in FIG. 5 along the line I-II (it should be noted that in the electrochemical module a second terminating electrode is also applied, which is shown in FIG. 1 not

is shown).

 The support substrate (11) for the electrode-electrolyte unit is according to

WO2014187534 powder metallurgically produced from an iron-chromium alloy, preferably from an Fe-based alloy with Fe> 50 wt.% And 15 to 35 wt.% Cr; 0.01 to 2% by weight of one or more elements of the

Group Ti, Zr, Hf, n, Y, Sc, rare earth metals; 0 to 10 wt.% Mo and / or Al; 0 to 5 wt.% Of one or more metals of the group i,, Nb, Ta; 0.1 to 1% by weight O; Residual Fe and impurities exist, wherein at least one metal of the group Y, Sc, rare earth metals and at least one metal of the group Cr, Ti, Al, Mn form a mixed oxide. It was a powder fraction with a Particle size <50 μπι chosen, whereby the surface roughness kept sufficiently small and good coatability is ensured for the subsequent functional layers. The carrier substrate (1 1) is in the edge region (12), which surrounds a porous and gas-permeable central region (13), compressed. On the porous central region (3), the chemically active layers shown in the cross-sectional view in FIG. 1 are arranged. The compaction of the edge area is advantageous, but not mandatory. The carrier substrate (11) was melted on the cell-facing side in the edge region over a large area by means of a laser beam. Due to the solidified melt is a gas-tight

 superficial barrier (14), which extends from the outer periphery of the central region (13) to the point at which the carrier substrate (11) by means of a weld with the contact plate (interconnector) (21) is connected gas-tight. The gas permeable surface of the central region (13) of the carrier substrate is defined by the gas impermeable surface of the

 Edge region (12) of the carrier substrate separated by the boundary line (9). The peripheral edge region (12) of the carrier substrate is connected to two

 enlarged opposite sides and has there gas passage openings (22), which serve to supply and discharge of the process gas.

As a first layer, a diffusion barrier layer (15) of CGO or LSM with a thickness of up to about 2 m is applied directly to the surface of the metallic carrier substrate in the central area (13) and an adjacent part of the edge area (12) by means of PVD, which interdiffuses metal between the carrier substrate (1 1) and the first electrode (16,16 ') (in the case of an SOFC, the anode) blocked (in the porous central region (13) while the pores are not closed by the diffusion barrier layer (15), so that further gas permeability is given). Next follows the first electrode, which consists of two layers (16, 16 ') with different average sintered grain size and porosity. The mean sintered grain size or

Pore size decreases starting from the coarse-grained metal substrate with each electrode layer. The first electrode is produced in layers by printing a suitable paste for each layer by means of screen printing and then sintering the arrangement in a reducing hydrogen atmosphere at temperatures above 1000 ° C. The graduated Aoifbau can of course be refined by using more than the illustrated two layers. The material used for the electrode layers is a cermet of nickel and yttria fully stabilized zirconia (Ni / 8YSZ). The lowermost layer (16) of the first electrode covers the entire porous central region (13) of the carrier substrate (11) as far as the boundary line (19) (apart from a small gap which possibly occurs due to the production), but does not extend significantly beyond that. Only the subsequent, finer-grained layer (16 '), due to their

 more fine-grained structure has better adhesion than the lowermost layer (16), is pulled out beyond the lowermost layer (16) and the boundary line (9) and is in material contact with the diffusion barrier layer (15). As a subsequent layer, a porous ceramic bonding layer (17) of 8YSZ or CGO wet-chemically by brushing a corresponding powder suspension, for example, with addition of dispersant, solvent (eg BCA [2- (2-butoxyethoxy) ethyl] in the transition region of the gas-tight edge region (12) ] acetate, available from Merck KGaA Darmstadt) and binder, and then sintered at about 1000 ° C to 1300 ° C under a hydrogen atmosphere. It was used a fine-grained powder with a d80 value of about 2 pm (and with a d50 value of about 1 pm) and an average pore size ranging from 0.2 pm to 1 pm inclusive For even better adhesion For this powder an even finer powder can be mixed. The fine-grained bonding layer (17) helps meandering irregularities on the otherwise locally smooth carrier substrate surface, caused by the laser guide during

Smoothing process, and to compensate for sharp-edged transitions in the first electrode and provide a uniform substrate with smoother transitions for the thin electrolyte layer (18). The bonding layer (7) extends beyond the first electrode and runs out in the direction of the edge of the carrier substrate (11). Due to the porosity of the first electrode, it can infiltrate it more or less strongly in the region of the electrode and fill up the pores of the uppermost electrode layer somewhat. This penetration into the pores can additionally facilitate the adhesion and sealing by the electrolyte (18) in the relevant area. The bonding layer (17) has direct contact with the subsequent electrolyte layer (18) on one side, on the other hand, immediately contact with the ceramic

 DifTusionbarriereschicht (15) and in the present example, in which the diffusion barrier layer is applied using coating masks and does not extend over the entire carrier substrate, also in contact with the surface of the metallic carrier substrate. The

 ElectroJyt layer (18) is applied by PVD, has a thickness of less than 5 \ im and consists of 8YSZ. It accomplishes a gas-tight separation of the first electrode from the second electrode. The second electrode (in the case of an SOFC the cathode) is also screen-printed on the electrolyte (18) and faces the first electrode (the second electrode is not shown in Fig. 1).

 The embodiment shown in Fig. 2 differs from the

 Embodiment in Fig. 1 in the order of application of the first electrode and bonding layer. In this variant, a ceramic porous bonding layer (17 ') of 8YSZ or CGO is arranged directly on the diffusion barrier-coated carrier substrate (1), the layers of the first electrode (16, 16') follow and run on or on the

 Connection layer (17 ') off. The bonding layer (17 ') protrudes slightly beyond the edge region (12) into the central region (13) of the carrier substrate (11). Since the carrier substrate (11) has relatively large pores in this non-compressed central region (13), the porous attachment layer (17 ') infiltrates into the pores of the carrier substrate (11).

 Fig. 3 shows a third embodiment with two bonding layers (17, 17 '), a first (17'), analogous to the variant in Fig. 2 directly on the with the

 Diffusion barrier (15) coated carrier substrate (1) is arranged, and a second bonding layer (17), which is applied analogously to the variant in Fig. 1 after the first electrode (16, 16 '). The second bonding layer (17) can be expanded in the direction of the central region and extend over the entire first electrode (16, 16 '). The second bonding layer (17) causes both a smoothing in the transition region and a reduction of the surface roughness of the first electrode, whereby the thickness of the

Electrolyte layer (18) can be reduced.

Fig. 4 shows an embodiment of an electrode-electrolyte unit (10 "'), wherein the carrier substrate (1 1) of two originally separate components 0017

 19, a metallic powder-metallurgically produced porous substrate part (13), which is welded to a circumferential gas-tight frame plate (12). The challenge with the seal lies in this example, especially in the relatively deep and sharp-edged weld. The porous substrate part is analogous to the preceding one

Examples of an iron-chromium alloy. In this case, the

Unmasked with the diffusion barrier layer (15). Analogously to the exemplary embodiment of FIG. 3, two connection layers (7, 17 ') are used. Variants with a connection layer as in FIG. 1 or FIG. 2 are also conceivable. If the first electrode (16, 16 ') is applied in front of a bonding layer, care should be taken that at least the lowermost, comparatively coarse-grained layer of the first electrode does not exist

cohesive contact with the weld notch has, but the locally smooth weld for better adhesion directly with finer-grained layers such as the bonding layer or subsequent fine-grained layers of the first electrode is covered.

Claims

2018/191765  20 PCT / AT2018 / 000017 claims Electrode-electrolyte unit (10, 10 ', 10 ", 10"') for a metal-based electrochemical module (20), in particular for a solid oxide fuel cell (SOFC), comprising:  a metallic carrier substrate (11) having a porous gas-permeable central region (13) and a peripheral region (12) which is bonded to the central region along an edge section of the same, at least superficially on the cell-facing side, wherein the gas-permeable surface of the porous central Region (13) is separated from the gas-tight surface of the edge region (12) by a boundary line (9),  at least one porous, gas-permeable first electrode (16, 16 ') formed on the porous central region of the carrier substrate,  at least one ceramic, on the first electrode (16, 16 ')  formed gas-tight electrolyte layer (18) extending beyond the first electrode in the direction of the edge region and with the  gas-tight edge area gas-tight,  characterized in that between the carrier substrate (1 1) and  Electrolyte layer (18) at least along a portion of the entire connection length of the boundary line at least one porous, ceramic bonding layer (17,17 ') is formed, which extends at least over a bordering on the borderline portion of the edge region / 12). Electrode-electrolyte unit according to claim 1, characterized in that the bonding layer (17,17 ') has a smaller average pore size than the first electrode (16,16'). Electrode-electrolyte unit according to one of the preceding claims, characterized in that the bonding layer (17, 17 ') is a sintered ceramic layer. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the bonding layer (17, 17 ') extending from the boundary line (19) towards the edge region (12) over a maximum length of up to and including 3 cm. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the bonding layer (17, 7 '), starting from the boundary line (19) in the direction of the central region (13) of the carrier substrate (11) over a maximum length of up to including 1 cm extends. Electrode-electrolyte unit according to one of the preceding claims, characterized in that in the edge region (12) of the carrier substrate (1 1) directly on the carrier substrate (11) at least one gas-tight ceramic intermediate layer (5) is arranged and the porous, ceramic bonding layer ( 17,17 ') between the gas-tight ceramic intermediate layer (15) and the electrolyte layer (18) is formed. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the bonding layer (17,17 ') at least in a portion of the edge region direct contact both with the electrolyte layer (18) and with the surface of the carrier substrate (1 1) or with the gastight ceramic intermediate layer (5). Electrode-electrolyte unit according to one of the preceding claims, characterized in that the bonding layer (17 ') directly on the carrier substrate () (or arranged thereon a gas-tight ceramic intermediate layer (15)) is arranged and the first electrode (16,16 ') on and / or on the bonding layer (17') expires. Electrode-electrolyte unit according to one of claims 1 to 7, characterized in that the bonding layer (17) terminates on or at the first electrode (16, 16 "). Electrode-electrolyte unit according to one of the preceding claims, characterized in that the first electrode (16,16 ') is formed in multiple layers and each one immediately following  Electrode layer (16 ') beyond the underlying electrode layer (16) also extends. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the lowest layer of the first electrode (16) in the direction of the edge region on the surface of the central region of the carrier substrate at least up to a distance of 2 mm to the boundary line (19 ) extends. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the lowest layer of the first electrode (16) in the direction of the edge region on the gas-tight  Surface of the edge region at most over a distance of 5 mm beyond the boundary line (19) extends beyond. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the bonding layer (17, 17 ') consists of the same material as the electrolyte layer (18). Electrode-electrolyte unit according to one of the preceding claims, characterized in that the bonding layer (17, 17 ') and / or electrolyte layer (18) consists of doped zirconium oxide, wherein the doping comprises at least one oxide of the doping elements from the group Y, Sc, AI, Sr, Ca, Mg contains. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the bonding layer (17, 17 ') and / or electrolyte layer (18) consists of doped cerium oxide, wherein the doping comprises at least one oxide of the doping elements from the group of the rare earth metals. Earth elements such as Gd, Sm and / or from the group Y, Sc, Al, Sr, Ca contains. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the first electrode (16, 16 ') is constructed of a cermet, in particular of a cermet of Ni and YSZ or of Ni and CGO. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the carrier substrate (1) is made of an iron-chromium alloy. Electrode-electrolyte unit according to one of the preceding claims, characterized in that the edge region (12) of the carrier substrate (11) is formed as a circumferential frame plate and cohesively by means of a welding, soldering or adhesive bond with the central region (13) of the carrier substrate ( 11) is connected. Electrode-electrolyte unit according to one of claims 1 to 17, characterized in that the edge region (12) and the central region (13) are produced by powder metallurgy and formed integrally. 20 electrode-electrolyte unit according to claim 19, characterized in that the edge region (12) on the cell-facing side is made gas-tight by superficial melting. 21. Electrochemical module (20), in particular a SOFC, comprising an electrode-electrolyte unit (10, 10 ', 10 ", 10'") according to one of  preceding claims.