Solid oxide cell stacks fabricated in a single repeating unit, each comprising a ceramic cell with a corrugated membrane and a flat metal interconnect

Abstract

The present invention relates to a solid oxide cell (SOC) stack made from single repeating units (SRUs), each of which comprises a ceramic cell with a corrugated membrane and a sealing frame with gas distribution holes and channels, and flat metal interconnects.

Description

[Technical Field]

[0001] The present invention relates to electrochemical devices, and in particular to solid oxide cell (SOC) stacks fabricated from single repeating units (SRUs), each of which comprises a ceramic cell with a corrugated membrane, a sealing frame with gas distribution holes and channels, and flat metal interconnects. [Background technology]

[0002] Hydrogen and electricity generators based on solid oxide cells (SOCs) have been recognized as one of the most promising options for the development of a clean energy-based sustainable economy. Significant efforts have been made towards their optimization, traditionally involving a large amount of materials research, but more recently focusing on structural and manufacturing optimization.

[0003] Among the many SOC architectures proposed over the past decade, tubular and especially flat designs have been the most popular (Bora Timurkutluk, Cigdem Timurkutluk, Mahmut D. Mat, Yuksel Kaplan, A review on cell / stack designs for high performance solid oxide fuel cells, Renewable and Sustainable Energy Reviews, 56 (2016) 1101-1121). Fabrication of flat cells is particularly simple and cost-effective, and they are easily interconnected to form devices with high power and power density (Solid Oxide Fuels Cells: Facts and Figures. Past, Present and Future Perspectives for SOFC Technologies, edited by John T.S. Irvine and Paul Connor, Springer-Verlag London 2013; Stephen J. McPhail, Jari Kiviaho, Bruno Conti, The Yellow Pages of SOFC Technology, published by ENEA & VTT, ISBN: 978-951-38-8602-8 (print); 978-951-38-8603-5 (online) (2017)).

[0004] The basic structure of an SOC device is based on a selected number of so-called single repeating units (SRUs), usually connected in series and positioned between two metal plates called end plates. Each SRU typically includes an interconnect and a solid oxide cell consisting of a fuel electrode, an electrolyte, and an oxygen electrode. The SRU also has channels for distributing and collecting reactant gases to and from both electrodes. There are also typically gas manifolds for directing reactant gases to the distribution channels and collecting exhaust from them. These manifolds are usually formed during stacking of the cells by holes formed in the cells for this purpose. In some designs, one of the gases, usually air, is fed directly into the interconnecting channels from the environment surrounding the stack without using such manifolds.

[0005] Currently, the preferred technique for fabricating flat cells is tape casting. This involves applying a properly formulated, low-viscosity slurry through a thin opening in a doctor blade onto a flexible substrate to obtain a thin layer. After drying, the resulting layer is essentially an organic-inorganic composite in which inorganic particles are bound together with a mixture of thermoplastic polymer and plasticizer. This composite tape is flexible and plastic, and can be easily cut, punched, and stacked.

[0006] In practice, all structural layers of a flat-cell SRU can be fabricated by tape casting, with green tapes of different materials being bonded together by isostatic hot pressing. Upon appropriate heat treatment, the organic components are decomposed and the remaining inorganic particles are sintered, producing a dense, multilayer ceramic structure. However, while co-firing the layers is desirable from a cost-saving perspective, it is often difficult to find materials with compatible sintering and thermal expansion properties.

[0007] Typically, either the electrolyte or one of the electrodes is made relatively thick (on the order of hundreds of microns) to provide mechanical support for the cell, while the other layer is made much thinner to reduce ohmic losses. These thinner layers can also be made by screen printing or plasma spraying, especially if very thin thicknesses are required.

[0008] The interconnect typically includes two sets of channels (one for each electrode) in a cross-flow or parallel-flow configuration. The channels must be large enough to ensure a low pressure drop within the SRU and efficient operation of the system.

[0009] The prior art discloses several processing, performance, or cost improvements for such stacks by introducing a step of corrugating or patterning some of the elements of the SRU without significantly modifying the described tape-casting-based technology. At the same time, significant efforts have also been made to obtain monolithic structures in a single firing step.

[0010] The development of such technology can be traced back to the 1980s. A 1991 report from Argonne National Lab (ANL) (Kevin M. Myles, Samit K. Bhattacharyya, Application of the Monolithic Solid-Oxide Fuel Cell to Space Power Systems, Argonne National Laboratory, for the Eighth Symposium on Space Nuclear Power Systems, Albuquerque, New Mexico, January 6–10, 1991) describes an experimental technique for fabricating monolithic SOFC stacks with corrugated electrodes, which has been under development since 1983. Green electrolyte, electrode, and interconnect tapes were fabricated by tape casting or hot-roll calendering of a polymer-binder mixture. The electrode sheets were then corrugated by folding them over a warm mold and then stacked in a cross-flow configuration with the electrolyte and interconnect sheets. The stack was then heated slightly above the glass transition temperature of the binder to promote bonding between the layers and finally sintered to form a monolithic structure. The main reported advantage of the as-obtained stacks was high power density, but the practical application of this technology was hampered by multiple cracks and an electrode processing yield of only about 60%, despite attempts to promote crack pinning by introducing additional phases.

[0011] U.S. Patent No. 4,476,196 (1984) discloses a monolithic all-ceramic structure with square channels in the fuel or oxygen electrodes arranged in a cross-flow configuration. The layers were fabricated by extrusion and tape casting, then stacked and co-sintered. However, U.S. Patent No. 4,857,420 (1989) pointed out that such co-sintering cannot avoid the formation of multiple microcracks and proposed separating each SRU component into two layers and sintering them separately before stacking.

[0012] US Patent No. 5,273,837 (1993, Corning) claimed a stack structure with at least the electrolyte in the form of very thin (45 μm), flexible, strong corrugated sheets, allowing for improved fracture toughness and thermal shock resistance through a compliant mechanism.

[0013] Similarly, improved mechanical and thermal shock resistance was sought by the method disclosed in Patent No. 5010773 (1999, Corning), but in this case a variety of different textures were proposed.

[0014] To imprint a pattern on a tape-cast sheet, several possible techniques have been proposed, such as vacuum forming, press forming, roll pressing, and granulation. In particular, granulation (or peening) of the green sheet was also proposed by Murata (Publication No. H09-199143, 1996).

[0015] U.S. Patent No. 7,410,716 (2003, Corning) and U.S. Patent No. 7,947,213 (2003, Corning) introduced a method for fabricating textured electrolyte sheets with grooves 5-50 μm deep by embossing. The stated goal in this case was to reduce electrolyte resistance.

[0016] Mitsubishi Heavy Industries has patented a dimple-reinforced three-layer structure of oxygen electrode-electrolyte-fuel electrode layers (European Patent No. 0670606, 1994). After co-sintering, these corrugated layers are stacked with flat ceramic or metal interconnects. Mitsubishi's reports (Akihiro Nakanishi, Masatoshi Hatton, Yoshinori Sakaki, Hitoshi Miyamoto, Hidetoshi Aiki, Koichi Takenobu, and Masanori Nishiura, "Development of MOLB Type SOFC," Proceedings of the Electrochemical Society, PV 2003-7, 53-59 (2003); Yukio Yoshida, Nagao Hisatome, and Koichi Takenobu, "Development of SOFC for Products," Mitsubishi Heavy Industries, Ltd., Technical Review Vol. 40 No. 4 (Aug. 2003)) provide measurements on experimental systems up to 15 kW fabricated using this technology. Increased power density was announced as the main advantage of the technology, with a reported 0.24 W / cm 2 The maximum power density of this cell is comparable to that of a conventional flat cell. To the best of our knowledge, there have been no subsequent reports on this technology.

[0017] The fact that most currently commercially available SOC stacks still employ flat cells, with gas distribution channels fabricated in the (typically metallic) interconnects, confirms that such obstacles have not been overcome and that the described patterning techniques are not yet mature enough to be used in industrial-scale manufacturing.

[0018] US Patent Application Publication No. 2008 / 003478 discloses a high-temperature solid oxide fuel cell including a porous conductive support structure. This document refers to a "tubular concept" and defines the fuel cell structure as including a corrugated structure and a folded form of the corrugated structure, resulting in a porous conductive structure with gas line hollow structures and gas line channels integrated into the support structure surface (see Figure 1 of the document).

[0019] To overcome the above-mentioned drawbacks, the inventors have developed a novel and advantageous SRU design, preferably fabricated by modern 3D printing technology. 3D printing advantageously allows for easy mass production. Unlike standard configurations, this design includes corrugated ceramic cells and flat interconnects. This design offers significant improvements in volumetric power density (VPD) due to both a reduction in SRU thickness and an increase in current density due to the cell's corrugated active area. In addition, the disclosed design exhibits improved mechanical strength, which is beneficial for stack durability. This design also advantageously simplifies the fabrication of interconnect plates, which no longer require distribution channels. Summary of the Invention [Means for solving the problem]

[0020] In a first aspect, the present invention relates to a solid oxide cell (SOC) stack made of single repeating units (SRU), each of which comprises: a ceramic cell having a corrugated membrane and a sealing frame with gas distribution holes and channels; and a planar metal interconnect. [Brief explanation of the drawings]

[0021] [Figure 1] 1 depicts a typical shape of an SRU known in the art. [Figure 2] Compared to FIG. 1, an SRU according to the present invention is shown, which has cylindrical corrugated cells and flat interconnects, with channel cross-section and membrane thickness maintained. [Figure 3] 1 shows the geometry of a SOFC / SOEC cell according to one embodiment of the present invention, the basic layout of the cell consists of a corrugated membrane and frame forming a single body. [Figure 4] 1 shows the cells with electrodes and seals and the corresponding interconnects with protective layers and seals. [Figure 5] The parameters of the corrugated cell membrane are shown. [Figure 6] 1 shows a top view of the ceramic solid oxide cell, revealing the membrane channel, sealing frame, gas channels, and inlets / outlets. DETAILED DESCRIPTION OF THE INVENTION

[0022] product The present invention relates to a solid oxide cell (SOC) stack made of single repeating units (SRU), each of which comprises: a ceramic cell having a corrugated membrane and a sealing frame with gas distribution holes and channels; a planar metal interconnect; the ceramic cells and flat metal interconnects are stacked on top of each other; The corrugated membrane is functionalized on both sides with electronically conductive ceramic layers that are the fuel and oxygen electrodes.

[0023] In a preferred embodiment, the multiple single repeating units (SRUs) are connected in series.

[0024] In another preferred embodiment, the cells and interconnects have a rectangular, circular, or square shape.

[0025] The ceramic cell comprises a membrane with two sets of channels (hereinafter referred to as "membrane channels") resulting from its corrugated shape, and a sealing frame with gas distribution holes and channels (hereinafter referred to as "frame channels") for each of these sets. The corrugated structure of this cell membrane is the ceramic electrolyte. As mentioned above, the electrodes are deposited on top of the electrolyte, so they follow the corrugations on both sides of the electrolyte. The stack structure allows the corrugated membrane to contact flat metal interconnects (see Figure 2).

[0026] In contrast to prior art (e.g., U.S. Patent Application Publication No. 2008 / 003478), the cells and corresponding corrugated membranes of the present invention do not define "tubes" or "chambers." Indeed, gas distribution between and within the cells occurs through channels confined by the corrugations defined in the cells and interconnects. U.S. Patent Application Publication No. 2008 / 003478 discloses in paragraph

[0010] that a corrugated structure with hollow channels is applied to a planar, flat body. This does not fit the present invention because no hollow structure or channels are defined. The corrugated structure defines gas distribution channels that contact the flat metal interconnects, but is not itself a hollow structure. In addition, paragraph

[0015] refers to the "planar rear surface of the cell," but the present invention is based on a corrugated membrane, which, as described above, defines corrugations on both sides that contact the flat metal interconnects on both sides. Finally, U.S. Patent Application Publication No. 2008 / 003478 mentions contact between individual cells by flexible metal moldings through the interconnect layer in paragraph

[0019] . In the present invention, the flat metal interconnects are inflexible to ensure contact to the active cells by the corrugation peaks without requiring flexibility or molding of the interconnect layer.

[0027] The interconnect is flat and acts as a lid for the membrane channel, in contrast to traditional flat cell designs where the interconnect has a channel and the flat cell is the lid (see Figure 1). As mentioned above, this flat interconnect is metallic, i.e., fabricated from a metal sheet.

[0028] In principle, the stack of the present invention can operate reversibly in SOFC and SOEC modes; that is, the solid oxide cell (SOC) stack of any of the embodiments of the present invention can be a solid oxide fuel cell (SOFC) or a solid oxide electrolysis cell (SOEC). In one embodiment, the SOC stack of the present invention is a solid oxide fuel cell (SOFC). In a preferred embodiment, the SOC stack of the present invention is a solid oxide electrolysis cell (SOEC). While SOFC / SOEC systems can operate with a variety of gases, typically hydrogen is used as fuel in power generation mode, steam is used in electrolysis mode, and a mixture of hydrogen and CO2 can also be used in co-electrolysis mode. In the former case, hydrogen passes through one set of membrane channels, while oxygen supplied to the other set of channels diffuses across the membrane in the form of oxygen ions and oxidizes the hydrogen, resulting in steam collected at the fuel-side outlet hole. In the latter case, steam (optionally mixed with hydrogen) is supplied to the first set of channels, and air or oxygen is supplied to the second set of channels, with the produced hydrogen collected at the fuel-side outlet hole. Therefore, for simplicity, hereinafter the gases corresponding to the two sides of the cell will be referred to as "fuel" and "oxygen", and the corresponding cell surfaces will be referred to as the "fuel side" and "oxygen side".

[0029] The advantages of the present invention largely stem from the use of corrugated cell membranes. There are many possible corrugation profiles. In a preferred embodiment of the present invention, the cell membrane corrugations have an elliptical geometry, meaning that the tube channels are made of elliptical half-tubes connected in alternating up-down orientation. This geometry can be described by only three parameters: membrane thickness (d), inner diameter of the ellipse (D), and aspect ratio of the ellipse (K=2R1 / D) (see Figure 5).

[0030] According to a preferred embodiment of the present invention, the membrane thickness is d=0.10-0.40 mm, more preferably 0.20-0.30 mm, and even more preferably 0.20 mm, with an aspect ratio K=1, corresponding to a cylinder. In another preferred embodiment, the inner diameter of the corrugation is D=0.70-1.20 mm, more preferably 0.80-1.00 mm, and even more preferably 1.00 mm. These values ​​are consistent with low electrolytic resistance and a conventional flat cell stack (approximately 1.0-1.5 mm). 2 ) The height of such a membrane is 1.2 to 1.6 mm, and the height of the cell frame, and therefore the height of the cell, is preferably the same.

[0031] It can be shown that by reducing the aspect ratio, the internal width of the corrugations, or the membrane thickness, a larger area increase and therefore a larger power density can be achieved. However, it should be noted that there are factors that limit the reduction of these parameters. For example, the internal diameter of the membrane channel should not be reduced too much, as this would cause a significant pressure drop within the cell and consequently a loss of performance at the system level. On the other hand, a reduction in channel size leads to a reduction in the cell thickness, which, as also occurs with membrane thickness, can cause manufacturing problems related to mechanical strength.

[0032] In another preferred embodiment, the present invention includes an input frame channel at one end of a membrane-channel set and an output frame channel at the opposite end (see FIG. 3). Furthermore, there is preferably one input hole in the input frame channel and one output hole in the output frame channel. In yet another preferred embodiment, the input and output holes are positioned adjacent to the ends of a cell diagonal, while the holes corresponding to the other set of membrane channels are positioned adjacent to the ends of the other cell diagonal (see FIG. 3).

[0033] In this configuration, one of the gases, e.g., fuel, is fed through the input holes into the input frame channel, from which it is distributed to all membrane channels on the fuel side of the cell. After electrochemical reactions on the membrane channel surfaces, the exhaust is collected in the output frame channel, from which it is collected in the output holes. The geometry of the oxygen side channels is the same.

[0034] The shape of the frame channels can be optimized based on flow simulations to provide a uniform distribution of gas velocity across each set of membrane channels. In particular, a tapered shape with narrow straight segments corresponding to the three or four channels closest to the input and output holes has been found to be particularly suitable in this regard (see Figures 3 and 6).

[0035] The power density of prior art SOFC / SOEC devices is severely limited by the presence of electrochemically inactive surfaces and volumes in their construction. For example, the area surrounding the electrodes can amount to more than 40% of the total area of ​​some conventional cell designs. Typical metal interconnects occupy even more volume, and their thickness is more than an order of magnitude greater than the thickness of the cell itself (see Figures 1 and 2).

[0036] The present invention reduces both the unused area surrounding the cell and the volume of the interconnects. The volumetric power density (VPD) of the SRU is also improved due to the increased active area of ​​the cell, which effectively increases the current density. In Figure 2, a conventional SRU geometry is compared to an SRU according to the present invention, which has cylindrical corrugated cells and flat interconnects, where the channel cross-section and film thickness are maintained.

[0037] While minimizing interconnect thickness is desirable to maximize power density, oxidation of some metal alloys used for this purpose is known to accelerate below a certain thickness, especially when both sides of the metal are exposed to an oxidizing atmosphere (Zhenguo Yang, Matthew S. Walker, Prabhakar Singh, Jeffry W. Stevenson, and Truls Norby, Oxidation Behavior of Ferritic Stainless Steels under SOFC Interconnect Exposure Conditions, Journal of the Electrochemical Society, 151(12) B669-B678 (2004)). Therefore, according to a preferred embodiment of the present invention, the interconnect thickness is limited to 0.2-0.5 mm. Figure 4 shows such an interconnect, having the same size as the cell, and gas distribution holes whose size and location match those of the cell.

[0038] The total cell+interconnect+seal (SRU) thickness of the preferred embodiment with 0.2 mm interconnects can be less than 2 mm, compared to typical values ​​of about 3 mm or more for conventional flat cell designs.

[0039] Materials and Technology The advantages of the present invention arise primarily from its geometric configuration, while known materials and techniques are used for its manufacture. Thus, in a preferred embodiment, the ceramic cell is made from an ion-conducting material, preferably doped zirconia or doped ceria, more preferably doped zirconia, and even more preferably yttria-stabilized zirconia (YSZ).

[0040] In a preferred embodiment, the fuel electrode is made of a cermet. In the particular embodiment where YSZ is used as the electrolyte, the preferred material for the fuel electrode is Ni-YSZ cermet, which is typically obtained by reducing a NiO-YSZ ceramic composite during the first start-up of the stack.

[0041] In another preferred embodiment, an electronically conductive metal coating is present on the fuel electrode, preferably the metal is nickel. This conductive metal coating can be applied by standard deposition techniques such as brushing, screen printing, etc.

[0042] In another preferred embodiment, the oxygen electrode is made from a highly electronically conductive material, preferably a lanthanum-manganese based mixed oxide such as lanthanum-strontium-manganese oxide (LSM) or lanthanum-strontium-cobalt-manganese oxide (LSCM), more preferably a composite of LSM and YSZ (LSM / YSZ) that is compatible with the YSZ electrolyte.

[0043] In another preferred embodiment, an electronically conductive coating of an oxidation-resistant metal is present on the oxygen electrode, preferably the oxidation-resistant metal is gold or silver. This conductive coating can be applied by standard deposition techniques such as brushing, screen printing, etc.

[0044] In another preferred embodiment, the interconnect material preferably has high oxidation resistance at the operating temperatures of the stack, sufficiently low electrical resistance, and a coefficient of thermal expansion (CTE) that matches that of the cell materials to avoid the buildup of thermal stresses. In a further preferred embodiment, the interconnects have a coefficient of thermal expansion (CTE) of 10-14×10 -6 °C -1 Thermal expansion in the range of 1 to 10 × 10 3 Ccm -1 Preferably, the interconnects are made of stainless steel or alloys having a conductivity in the range of 0.1 to 1.0.

[0045] In another preferred embodiment, to avoid its oxidation while maintaining electrical conductivity, the flat metal interconnect has an electronically conductive and oxidation-resistant coating on its surface in contact with oxygen. Preferably, the coating is made of manganese cobalt oxide (MCO). The interconnect coating can be applied by a simple deposition technique such as screen printing. After the coating is applied and dried, it is sintered, preferably in a reducing atmosphere.

[0046] In another preferred embodiment, a metal mesh or foam is present between the flat metal interconnect and the ceramic cell on both the fuel and oxygen sides to improve current collection / delivery without compromising gas distribution. Preferably, the metal mesh or foam is made from nickel, gold, silver, or platinum. More preferably, a nickel mesh is used on the fuel side and a silver or gold mesh is used on the oxygen side of the cell.

[0047] As noted elsewhere in this application, the fabrication of the complex cell shapes that are the subject of this invention is now possible due to the availability of relatively inexpensive, commercially available 3D printing technologies, which further have the advantage that the designs can be easily modified to meet different technical requirements and different applications.

[0048] A particularly suitable 3D printing technique for fabricating the cell configuration that is the subject of this application is stereolithography (SLA). In this case, the cell is printed using a photopolymerizable paste containing a high concentration of electrolyte particles along with other, primarily organic, components. After washing and drying, the cell is subjected to a heat treatment to burn off the organic components and sinter the ceramic particles, resulting in a dense compact.

[0049] The cell is then functionalized using standard techniques with catalytically active, electronically conducting ceramic layers that act as electrodes.

[0050] To ensure gas tightness, seals must be applied between the end plates, interconnects, and cells before assembling the stack. Therefore, the cell design must include a certain margin around the frame channels and gas inlet and outlet holes to allow for the application of the seal. In a preferred embodiment, the seal is compressible (typically based on mica or alumina) or, more preferably, glass. The latter should have good adhesion to both the cell and interconnect materials and a thermal expansion coefficient compatible with both. A suitable technique for applying such seals is robocasting. To apply the material using this method, a paste must be prepared by mixing glass powder with a suitable vehicle.

[0051] The present invention will now be illustrated by a number of examples which should not be construed as limiting the scope of the invention.

[0052] Example Example 1 (prior art) Figure 1 shows a typical geometry for a state-of-the-art SRU, with proportions corresponding to those of an actual commercial cell. As can be seen, the sets of channels (0.45 mm deep) for the cathode and anode gases are on top of each other and supported by a flat, relatively thick plate, resulting in an interconnect that is much thicker than the cell (1.25 vs. 0.2 mm). The cross section of each channel in this example is 0.54 mm. 2 It has a relatively small area of ​​.

[0053] Example 2 In Figure 2, the SRU geometry from Figure 1 is maintained with the channel cross section and membrane thickness (0.54 mm each). 2and 0.2 mm), compared to one embodiment of the present invention consisting of an SRU with a cylindrical corrugated cell and flat interconnects. As shown, in this case, the interconnects can be as thin as a conventional cell, while the cell can be thinner than a conventional interconnect because the cathode and anode channel sets are no longer on top of each other but are intercalated. The total SRU thickness for this configuration is 1.2 mm, compared to 1.45 mm for the conventional one, representing a 1.2-fold improvement in VPD. Furthermore, in this particular example of the present invention, there is an increase in area and current density equal to the ratio of the circumference to the diameter of a semicircle, i.e., π / 2 = 1.57. Thus, the combined VPD enhancement is nearly two-fold (1.2 × 1.57).

[0054] Example 3 Figure 3 shows the integration of the SRU geometry of the present invention in an actual stack. The basic layout of the cell consists of a corrugated membrane and frame forming a single body. This body should be made of an ionically conductive ceramic material such as stabilized zirconia, preferably zirconia doped with 8 mol% yttria (YSZ). The cell membrane is functionalized on both sides with an electronically conductive ceramic layer. Typical materials known in the art are Ni-YSZ cermet for the fuel electrode and LSM or LSCM for the oxygen electrode, but many more options exist. These coatings can be applied, for example, by 3D printing, spraying, or brushing.

[0055] Example 4 For example, the SOFC power densities required for automotive applications (range extenders and APUs) are of the order of 1.0 kW / l and 0.25 kW / kg, values ​​that can be easily exceeded using the proposed technology. A particular embodiment of the invention based on a membrane with cylindrical corrugations provides an increase in surface area by a factor of π / 2 = 1.57 (ratio of the diameter of a circle to half the circumference) over a flat configuration. The channel size of such corrugations does not affect the area increase, and therefore the channel cross section can be easily adjusted to ensure a sufficiently low pressure drop.

[0056] A cell with a 200-300 μm electrolyte with 0.9 mm inner diameter corrugations is 1.5-1.6 mm thick, while the interconnects can be thinned to 0.2 mm, representing a reduction in SRU thickness of about 2x over most state-of-the-art commercial stacks while maintaining the cross section of the distribution channels. The overall volumetric power density improvement is therefore about 3x.

[0057] The gain in gravimetric power density is even greater because the density of typical ceramic electrolyte and electrode materials is less than that of common interconnect alloys, and both the interconnect thickness and the solid volume fraction of the cell are significantly reduced. Thus, typical surface power densities (0.6 W / cm) 2 ) and stabilized zirconia electrolyte and ferritic steel interconnect densities (approximately 6.0 and 7.7 g / cm, respectively). 2 ), a gravimetric power density of over 1.1 kW / kg is estimated for this embodiment.

[0058] Another advantage of the corrugated shape mentioned earlier is its enhanced mechanical strength, which also has a positive effect on thermal shock resistance, which is important for achieving fast start-up times and good thermal cycling behavior. The strength improvement due to corrugation of a flat membrane can be easily estimated from the stress-strain distribution obtained by the finite element method. This was done for the corrugated membrane described above versus a flat membrane, both of which have a square shape and are surrounded by a rigid frame. Simulations were set up to emulate membrane bending by applying a force to a small spot in the membrane's center. As a result, an eight-fold improvement in stiffness (applied force divided by displacement in the direction of the force) and a two-fold improvement in maximum allowable stress (using the so-called Mohr-Coulomb safety factor) were estimated.

Claims

1. 1. A solid oxide cell stack made of single repeating units, each of the single repeating units comprising: a ceramic cell having a corrugated membrane and a sealing frame with gas distribution holes and channels; a planar metal interconnect; the ceramic cells and flat metal interconnects are stacked on top of each other; The corrugated membrane is functionalized on both sides with electronically conductive ceramic layers that are the fuel and oxygen electrodes, a solid oxide cell stack.

2. 2. The solid oxide cell stack of claim 1, wherein the membrane thickness is 0.10 to 0.40 mm.

3. 3. The solid oxide cell stack according to claim 1, wherein the inner diameter of the corrugations is 0.7 to 1.2 mm.

4. The solid oxide cell stack according to any one of claims 1 to 3, wherein the ceramic cells are made of an ion-conducting material.

5. The solid oxide cell stack according to any one of claims 1 to 4, wherein the fuel electrode is made of cermet.

6. The solid oxide cell stack according to any one of claims 1 to 5, wherein the oxygen electrode is made of an electronically conductive material.

7. The solid oxide cell stack of any one of claims 1 to 6, wherein an electronically conductive metal coating is present on the fuel electrode.

8. 8. The solid oxide cell stack of claim 1, wherein an electronically conductive coating of an oxidation-resistant metal is present on the oxygen electrode.

9. The solid oxide cell stack of any one of claims 1 to 8, wherein the flat metal interconnects are made of stainless steel.

10. The solid oxide cell stack of any one of claims 1 to 9, wherein the planar metal interconnects have an electronically conductive and oxidation-resistant coating on the surfaces in contact with the oxygen.

11. The solid oxide cell stack of claim 10 , wherein the coating is made of manganese cobalt oxide.

12. The solid oxide cell stack according to any one of claims 1 to 11, wherein the SOC is a solid oxide fuel cell.

13. The solid oxide cell stack of any one of claims 1 to 11, wherein the SOC is a solid oxide electrolyzer cell.

14. 14. The solid oxide cell stack of any one of claims 1 to 13, wherein a metal mesh or foam is present between the ceramic cells and the flat metal interconnects.

15. 15. The solid oxide cell stack of claim 14, wherein the metal mesh or foam is made of nickel, gold, silver, or platinum.

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