WO2025244916A1

WO2025244916A1 - Porous metal substrate for metal-supported electrochemical cell

Info

Publication number: WO2025244916A1
Application number: PCT/US2025/029524
Authority: WO
Inventors: Toshio Suzuki; Hongpeng HE; Christian Junaedi; Subir Roychoudhury
Original assignee: Precision Combustion Inc
Current assignee: Precision Combustion Inc
Priority date: 2024-05-20
Filing date: 2025-05-15
Publication date: 2025-11-27
Anticipated expiration: 2026-11-20

Abstract

A porous metal substrate useful in a metal-supported electrochemical cell, wherein a porous metal support layer is covered with a first clad layer disposed on a bottom side and a second clad layer disposed on a top side adjacent a fuel electrode. Specifically, the firsts clad layer is configured with a plurality of perforations, which may also extend through the porous metal support layer and the second clad layer. A metal-supported electrochemical cell is described in addition to methods of making the porous metal substrate and the electrochemical cell.

Description

POROUS METAL SUBSTRATE

FOR METAL-SUPPORTED ELECTROCHEMICAL CELL

GOVERNMENT RIGHTS

[0001] This invention was made with support from the U.S. Government under Contract no. DE-AR0001350 sponsored by the Department of Energy. The government has certain rights in this invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims benefit of U.S. provisional application no. 63/649,579, filed May 20, 2024, the contents of which in their entirety are incorporated herein by reference.

FIELD OF THE INVENTION

[0003] This invention pertains in one aspect to a metal substrate for use in a metal- supported electrochemical cell. In another aspect, this invention pertains to the metal -supported electrochemical cell. Components described herein are useful in fabricating and operating, for example, a solid oxide fuel cell (SOFC), a solid oxide electrolysis cell (SOEC), or a solid oxide electrochemical sensor.

BACKGROUND OF THE INVENTION

[0004] An electrochemical cell is comprised of three essential components disposed in a layered configuration: an oxygen electrode, an electrolyte, and a fuel electrode. More particularly, in a solid oxide fuel cell (SOFC) operating in forward power production mode, the oxygen electrode functions to reduce molecular oxygen with a source of electrons to form oxide ions. The electrolyte functions as a medium to transport the oxide ions from the oxygen electrode to the fuel electrode. The fuel electrode functions to oxidize a fuel feed, such as hydrogen, carbon monoxide, or a mixture thereof, with the oxide ions so as to produce water, carbon dioxide, or a product mixture thereof, respectively, with concomitant production of electrons. Methane is another suitable fuel feed. The electrodes are connected via an external electrical circuit, such that the electrons produced at the fuel electrode traverse the external circuit to the oxygen electrode while being available to do electrical work. The voltage achieved from one electrochemical cell is typically small; therefore, a plurality of such cells are connected in series to form a stack of higher power output.

[0005] When operating in electrolysis mode, the electrochemical process is reversed. Water and carbon dioxide are reduced with electrons at the fuel electrode to form hydrogen and carbon monoxide, respectively, with concomitant production of oxide ions. The oxide ions migrate through the electrolyte to the oxygen electrode, where they are oxidized to form oxygen with release of electrons that then traverse the external circuit for use at the fuel electrode.

[0006] In order to provide structural support and strength to an electrochemical cell, a porous substrate has been used to anchor either the fuel electrode, the electrolyte, or the oxygen electrode. Among various kinds of substrate materials, a porous metal has been shown to be a desirable substrate for improved cell performance. Powder metallurgy can be used to prepare the porous metal substrate with varying porosity and pore sizes. Metal substrates typically require significant porosity (greater than 20 volume percent) and have pores in a size range larger than 10 pm. These pore sizes, however, are larger than the particle sizes of conventional fuel electrode and electrolyte materials, which are usually in a submicron range. Moreover, the pore sizes of conventional metal substrates are larger than the typical thickness of the individual fuel electrode and electrolyte layers.

[0007] Accordingly, the skilled person will appreciate that the porosity and pore size of the metal substrate play an important role in avoiding defects during cell manufacture and operation. Substrates having the required porosity level and pores larger than 10 pm are prone disadvantageously to cave-in of electrode and electrolyte layers. Moreover, the porosity and large pores may cause unacceptable shrinkage of the substrate during fabrication of the cell, leading to warpage, cracks and other defects that reduce cell performance. As a further disadvantage, large pores reduce the contact area between the metal substrate and the anode, resulting in higher contact resistance. Diffusion of fuel cell constituents is another problem. As an illustrative example, under operating conditions chromium in a substrate comprising a ferritic alloy can diffuse into a nickel/yttria-stabilized zirconia (Ni-YSZ) fuel electrode forming an undesirable nickel -chromium alloy.

[0008] One challenge has been to maintain the pore sizes in the metal substrate in a range smaller than 10 pm to ensure that the pore sizes are smaller than the typical thickness (5- 20 pm) of conventional fuel electrode and electrolyte layers applied on top of the metal substrate. Metal substrates with pores smaller than 10 pm, however, are difficult to realize in practical terms of reliable fabrication.

[0009] More to the point, providing efficient fuel transport into and out of the porous metal substrate so as to facilitate improved fuel utilization and cell performance is a challenge. Porous metal substrates comprising fine particles of less than 20 microns in size are limited with respect to gas transport when operating the electrochemical cell at high fuel utilizations.

[0010] One other desirable criterion of a high-performance fuel cell is its ability to achieve a high specific power in units of watts per kilogram (W/kg), which desirably is greater than about 1,000 W/kg, more desirably greater than about 2,000 W/kg. This power output requires a fuel cell operable at a current density of greater than about 1 Amp per square centimeter (1 A/cm²) while maintaining an acceptably thin and lightweight cell substrate.

[0011] In view of the above, it would be desirable to discover an improved porous metal substrate for use in an electrochemical cell, such that the substrate provides structural integrity in addition to being thin and lightweight so as to optimize specific power output. It would be desirable if such a substrate were substantially flat and defect-free in a thickness of less than about 1.1 millimeter (1.1 mm), preferably, less than about 0.5 mm, and with planar dimensions of typically up to about 10 centimeters by 10 centimeters (10 cm x 10 cm) or greater, depending upon its intended application. It would also be desirable for the porous metal substrate to resist electrode cave-in and diffusion of electrode and electrolyte materials into the substrate. To achieve these ends, it would be desirable to provide components that control shrinkage of layers so as to minimize warpage, mismatched layers, and defect formation. Additionally, it would be desirable to ensure efficient fuel flow transport through the substrate at high fuel utilizations. SUMMARY OF THE INVENTION

[0012] In one aspect, this invention provides for a porous metal substrate for use in a metal-supported electrochemical cell, comprising in a layered configuration:

[0013] (a) a first clad layer comprised of submicron to micron size grains of a first metal oxide and configured with a plurality of perforations disposed from one surface to another surface through a first thickness of the first clad layer;

[0014] (b) a porous metal support layer having a porosity ranging from 20 volume percent to 50 volume percent; and

[0015] (c) a second clad layer comprising submicron to micron size grains of a second metal oxide.

[0016] In yet another aspect, this invention provides for a method of making the porous metal substrate of this invention, comprising:

[0017] (a) providing a green first clad tape comprising submicron size grains of a first metal oxide;

[0018] (b) applying a green metal support tape over the green first clad tape, the green metal support tape comprising particles of a metal or alloy and optionally a pore former;

[0019] (c) applying a green second clad tape comprising submicron size grains of a second metal oxide over the green metal support tape to form a green three-layer substrate;

[0020] (d) heating the green three-layer substrate under pressure so as to form a green laminated substrate;

[0021] (e) machining a plurality of perforations into at least the first clad layer of the green laminated substrate so as to form a green perforated substrate;

[0022] (f) co-sintering the green perforated substrate under conditions sufficient to prepare the porous metal substrate of this invention. [0023] In yet another aspect, this invention provides for a novel metal -supported electrochemical cell comprising in a layered configuration:

[0024] (a) a first clad layer comprised of submicron to micron size grains of a first metal oxide and configured with a plurality of perforations disposed from one surface to another surface through a first thickness of the first clad layers;

[0025] (b) a porous metal support layer having a porosity ranging from 20 volume percent to 50 volume percent;

[0026] (c) a second clad layer comprising micron to submicron size grains of a second metal oxide;

[0027] (d) a first electrode layer;

[0028] (e) an electrolyte layer; and

[0029] (f) a second electrode layer having a polarity opposite that of the first electrode layer.

[0030] In yet another aspect, this invention provides for a method of making the aforementioned metal-supported electrochemical cell, comprising:

[0031] (a) providing a green first clad tape comprising submicron size grains of a first metal oxide;

[0032] (b) applying a green metal support tape over the green first clad tape, the green metal support tape comprising particles of a metal or alloy and optionally a pore former;

[0033] (c) applying a green second clad tape comprising submicron size grains of a second metal oxide over the green metal support tape to form a green three-layer substrate;

[0034] (d) heating the green three-layer substrate under pressure so as to form a green laminated substrate;

[0035] (e) machining a plurality of perforations into at least the first clad layer of the green laminated substrate so as to form a green perforated substrate; [0036] (f) applying a green first electrode layer over the green second clad tape of the green perforated substrate;

[0037] (g) applying a green electrolyte layer over the green first electrode layer to form a green half-cell;

[0038] (h) debinding and co-sintering the green half-cell;

[0039] (j) applying a second electrode layer over the electrolyte layer of the half-cell;

[0040] (1) debinding and sintering a resulting green electrochemical cell under conditions sufficient to prepare the electrochemical cell of this invention.

[004 1] The porous metal substrate of this invention finds utility in a metal-supported solid oxide fuel cell (MS-SOFC), a solid oxide electrolysis cell (SOEC), or a solid oxide electrochemical sensor. As one technical advantage, the porous metal substrate is configured as an essentially flat, layered composite with acceptable shrinkage, and as such is essentially free of warpage and other defects. As another technical advantage, the porous metal substrate is disposed in a thickness of less than about 1.1 millimeter (<1.1 mm), preferably, less than about 0.5 mm. Using the porous metal substrate of this invention to fabricate an electrochemical cell advantageously realizes metal -supported cells having well-matched and substantially flat and defect-free surfaces with planar dimensions of up to about 10 cm by 10 cm or greater. Minimizing cell thickness while maintaining a substantially flat surface essentially free of defects and warpage is important to permit lower cell weight and a higher cell specific power, desirably, greater than about 1,000 W/kg, and more desirably, greater than about 2,000 W/kg.

[0042] As another technical advantage, the porosity of the substrate of this invention provides for efficient gas transportation into and out of the electrochemical cell, thereby allowing for improved higher fuel utilizations. Implementation of the novel MS-SOFC of this invention offers improved power density and faster response and provides for durable fuel cell generators for many applications, including aerospace, defense and energy sector applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 illustrates in a transverse cross-sectional view an embodiment 10 of a prior art porous metal substrate.

[0044] FIG. 2 illustrates in a transverse cross-sectional view an embodiment 20 of the porous metal substrate of this invention.

[0045] FIG. 3 illustrates the embodiment 20 of the porous metal substrate of FIG. 2 as viewed from the bottom first clad layer.

[0046] FIG. 4 depicts in a transverse cross-sectional view another embodiment 30 of the porous metal substrate of this invention.

[0047] FIG. 5 depicts in a transverse cross-sectional view yet another embodiment 40 of the porous metal substrate of this invention.

[0048] FIG. 6 depicts an embodiment 50 of the electrochemical cell of this invention.

[0049] FIG. 7 depicts another embodiment 60 of the electrochemical cell of this invention.

[0050] FIG. 8 depicts yet another embodiment 70 of the electrochemical cell of this invention.

[0051] FIG. 9 depicts a process chart for a method of making the electrochemical cell of this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0052] For the purposes of this invention, the word “layer” refers to a quasi-two- dimensional structure wherein length and width are significantly larger than thickness. Also, a layer can be considered a plane or sheet of one thickness of a first material that covers all or a portion of the surface of a second material. The term as used herein does not limit the layer to any particular shape; for example, the layer can be in the form of a square, rectangle, hexagon, circle, ellipse, or any other shape as dictated by design. Generally, all layers in the electrochemical cell have the same shape so that they can be matched, sealed, and secured on edges and comers. [0053] As used herein, the term “grain” or “grains” refers to crystallites or particles of varying and randomly distributed small sizes as specified herein.

[0054] With reference to the porous metal support, the term “porous” or “porosity” refers to a plurality of void spaces of any type or kind within the metal support. The term “pores” specifically refers to void spaces formed when a pore former is chemically burned out of a greenware. The term “perforations” specifically refers to void spaces or apertures that are machined, cut, punched, stamped or otherwise mechanically introduced into a layer, preferably, laser machining or cutting. Pores tend to cover a smaller size range as compared with those of perforations, although there is some overlap in size as detailed hereinafter. The term “size” as used to define the perforations and pores refers to a diameter if circular in shape or a critical cross-sectional dimension if non-circular in shape.

[0055] Where a range is set forth, the word “about” is placed before the lower limit of the range. Unless otherwise noted, the word is intended to modify both the lower and upper limits of the range and allows for an acceptable variance in both lower and upper limits as would be reasonable to an ordinary person skilled in the art.

[0056] As one technical advantage, the porous metal substrate of this invention is substantially flat allowing for a secure and tight-fitting application of an electrode layer thereupon. The term “flat” refers to a level surface characterized by lines or tracings without substantial peaks and valleys. An acceptable level of flatness can be determined by visual inspection of the layer without magnification or by visual inspection under an optical microscope of about 10 to 20 times magnification.

[0057] As another technical advantage, the porous metal substrate of this invention is substantially defect-free, which means that the layer does not contain an unacceptable number of cracks, pinholes, and other disadvantageous imperfections in surface uniformity. Defects can be identified by visual inspection of the layer without magnification or by visual inspection under an optical microscope of about 10 to 100 times magnification.

[0058] As yet another technical advantage, the porous metal substrate of this invention is thin and lightweight; the term “substrate” collectively defining the first clad layer, the porous metal support layer, and the second clad layer. [0059] As yet another advantage, the porous metal substrate of this invention provides for improved gas transport into and out of the electrochemical cell thereby resulting in improved fuel utilizations especially at high flow rates.

[0060] Accordingly, in some illustrative embodiments, this invention provides for a porous metal substrate for use in a metal-supported electrochemical cell, comprising in a layered configuration:

[0061 ] (a) a first clad layer comprised of submicron to micron size grains of a first metal oxide selected from the group consisting of oxides of cerium, lanthanum, chromium, strontium, titanium, and mixtures thereof; and further wherein the first clad layer is configured with a plurality of perforations disposed from one surface to another surface through a first thickness of the first clad layer; the plurality of perforations having a size greater than about 10 microns;

[0062] (b) a porous metal support layer having a porosity ranging from about 20 to 50 volume percent; and

[0063] (c) a second clad layer comprising micron to submicron size grains of a second metal oxide selected from the group consisting of oxides of zirconium, cerium, lanthanum, chromium, strontium, titanium, and mixtures thereof.

[0064] In yet another illustrative embodiment, this invention provides for a metal- supported electrochemical cell comprising in a layered configuration:

[0065] (a) a first clad layer comprised of micron to submicron size grains of a first metal oxide selected from the group consisting of oxides of zirconium, cerium, lanthanum, chromium, strontium, titanium, and mixtures thereof; and further wherein the first clad layer is configured with a plurality of perforations disposed from one surface to another surface through a first thickness of the first clad layer, the plurality of perforations having a size greater than about 10 microns;

[0066] (b) a porous metal support layer having a porosity ranging from about 20 to 50 volume percent; [0067] (c) a second clad layer comprising micron to submicron size grains of a second metal oxide selected from the group consisting of oxides of zirconium, cerium, lanthanum, chromium, strontium, titanium, and mixtures thereof;

[0068] (d) a first electrode layer;

[0069] (e) an electrolyte layer; and

[0070] (f) a second electrode layer having a polarity opposite that of the first electrode layer.

[0071] In some illustrative embodiments of any one of the aforementioned embodiments, (a) the first clad layer, (b) the porous metal support layer, and (c) the second clad layer are co-sintered layers.

[0072] In some illustrative embodiments of any one of the aforementioned embodiments, the plurality of perforations extend through a second thickness of the porous metal support layer.

[0073] In some illustrative embodiments of any one of the aforementioned embodiments, the plurality of perforations extend through a second thickness of the porous metal support layer and a third thickness of the second clad layer.

[0074] In some illustrative embodiments of any one of the aforementioned embodiments, the plurality of perforations have a size greater than about 10 microns and less than 5 millimeters (<5 mm), preferably, greater than about 75 pm (0.075 mm) and less than about 3 mm, more preferably, greater than about 100 pm (0.1 mm) and less than about 2 mm.

[0075] In some illustrative embodiments of any one of the aforementioned embodiments, a spacing between a pair of adjacent perforations, as measured from center to center along a flow direction, ranges from about 1 mm to 10 mm, and preferably from about 2 mm to 6 mm.

[0076] In some illustrative embodiments of any one of the aforementioned embodiments, a percentage of open area of the perforations of the first clad layer ranges from about 2 percent to 40 percent. [0077] In some illustrative embodiments of any one of the aforementioned embodiments, the submicron to micron size grains of the first and second metal oxides each independently range from greater than about 0.1 micron (pm) to less than 1.5 micron (pm).

[0078] In some illustrative embodiments of any one of the aforementioned embodiments, the first and second clad layers each independently have a thickness ranging from about 1 micron (1 pm) to 30 microns (30 pm).

[0079] In some illustrative embodiments of any one of the aforementioned embodiments, the first clad layer further comprises a first metal having a submicron to micron grain size, preferably, ranging from greater than about 0.1 micron (pm) to less than 20 microns (pm). Preferably, the first metal is selected from the group consisting of nickel, iron, cobalt, chromium, copper, manganese, and mixtures thereof; more preferably, selected from nickel, copper, or iron.

[0080] In some illustrative embodiments of any one of the aforementioned embodiments, the second clad layer further comprises a second metal having a submicron to micron grain size, preferably, ranging from greater than about 0.1 micron (pm) to less than 20 microns (pm). Preferably, the second metal is selected from the group consisting of nickel, iron, cobalt, chromium, copper, manganese, and mixtures thereof; more preferably, selected from nickel, copper, or iron.

[0081] In some illustrative embodiments of any one of the aforementioned embodiments, the first metal or second metal content in the first or second clad layer, respectively, ranges from 0 to 60 percent by weight, preferably, from 1 to 60 percent, and more preferably, from 30 percent to 60 percent by weight, based on the total weight of the first or second clad layer as the case may be.

[0082] In some illustrative embodiments of any one of the aforementioned embodiments, the porous metal support layer comprises a ferritic alloy, preferably, a ferritic alloy containing chromium in an amount greater than about 15 weight percent. In some embodiments, the porous metal support layer has a thickness less than about 1.1 millimeters (<1.1 mm), and typically between about 80 microns (80 pm) and 1,000 pm. [0083] In yet other illustrative embodiments of any of the aforementioned embodiments, the porous metal support comprises a plurality of pores of a size (diameter or critical cross-sectional dimension) ranging from about 3 to 75 microns, or a plurality of perforations having a size greater than about 10 microns to less than 5 millimeters, or a combination of both a plurality of pores and a plurality of perforations. It should be appreciated that the overall planar dimensions of the clad layers and the support layer typically extend up to 10 cm by 10 cm or larger.

[0084] In one illustrative embodiment of any one of the foregoing embodiments, the first and second metal oxides are each independently selected from ceria or a divalent or trivalent cation-doped ceria. In an alternative embodiment, the first and second metal oxides are each independently selected from lanthanum chromite or a divalent or trivalent cation-doped lanthanum chromite. In another illustrative embodiment, the first and second metal oxides are each independently selected from strontium titanate or a divalent or trivalent cation-doped strontium titanate. In another illustrative embodiment, the first and second metal oxides are each independently selected from yttrium-stabilized zirconia.

[0085] In yet other illustrative embodiments of any one of the foregoing embodiments, the aforementioned electrochemical cell comprises a metal -supported solid oxide fuel cell or a metal-supported solid oxide electrolysis cell, wherein the first electrode layer is a fuel electrode (anode) layer and the second electrode layer is an oxygen or air electrode (cathode) layer. In other illustrative embodiments of any one of the foregoing embodiments, the fuel electrode layer has a thickness between about 3 microns and 20 microns. In other illustrative embodiments of any one of the foregoing embodiments, the electrolyte layer has a thickness between about 1 micron and 20 microns. In other illustrative embodiments of any one of the foregoing embodiments the oxygen electrode layer has a thickness between about 10 microns and 30 microns.

[0086] In some other illustrative embodiments of any one of the foregoing embodiments, the fuel electrode layer is a composite comprising nickel or nickel oxide and a metal oxide selected from the group consisting of the oxides of zirconium, yttrium, cerium, scandium, gadolinium, samarium, calcium, lanthanum, strontium, magnesium, gallium, barium, and mixtures thereof. In one preferred embodiment the fuel electrode layer comprises nickel oxide-yttria stabilized zirconia, NiO-YSZ.

[0087] In further illustrative embodiments of any one of the foregoing embodiments, the electrolyte layer comprises a metal oxide selected from the group consisting of the oxides of zirconium, yttrium, cerium, scandium, gadolinium, samarium, lanthanum, strontium, magnesium, gallium, barium, calcium and mixtures thereof. In one preferred embodiment, the electrolyte layer comprises yttria-stabilized zirconia.

[0088] In yet further illustrative embodiments of any one of the foregoing embodiments, the oxygen electrode layer is selected from compositions of formula ABO3, wherein A is selected from the group consisting of barium, strontium, lanthanum, samarium, praseodymium, and combinations thereof, and B is selected from the group consisting of iron, cobalt, nickel and manganese. In a preferred embodiment, the ABO3 is lanthanum strontium cobalt ferrite (LaSrCoFeCh).

[0089] In even more illustrative examples of any one of the foregoing embodiments, an interlayer is disposed in between the electrolyte layer and the oxygen electrode layer, optionally further wherein the interlayer has a thickness between about 1 micron and 20 microns. The interlayer functions to retard reaction between the electrolyte and the oxygen electrode or cathode materials. Typically, the interlayer comprises one or more divalent or trivalent cation elements doped with one or more metals selected from Group IIA elements. In some embodiments, the divalent or trivalent cation elements are selected from lanthanum, samarium, yttrium, gadolinium, and combinations thereof. In some embodiments, the interlayer is comprised of a divalent or trivalent cation-doped ceria.

[0090] The electrochemical cell of this invention can be better envisioned from consideration of the Drawings. Similar layers and elements in the Drawings are labeled with the same numerical reference. Attention is directed to FIG. 1, which illustrates in transverse cross-sectional view an embodiment 10 of a prior art porous metal substrate. As seen in FIG. 1, the porous metal substrate 10 comprises three layers: a first clad layer 1, a porous metal support layer 3, and a second clad layer 5. FIG. 2 illustrates in transverse cross-sectional view an embodiment 20 of the porous metal substrate of this invention. Embodiment 20 consists of a first clad layer 1, a porous metal support layer 3, and a second clad layer 5; further wherein a plurality of perforations 7 are disposed from a bottom surface 15 to a top surface 17 through a first thickness 19 of the first clad layer 1. FIG. 3 depicts embodiment 20 of FIG. 2 as viewed from the bottom surface 15 of the first clad layer 1, wherein it is seen that the bottom clad layer

1 is fabricated with a plurality of perforations 7 regularly spaced apart throughout the layer.

[0091] FIG. 4 depicts in transverse cross-sectional view an embodiment 30 of the porous metal substrate of this invention, which is similar in all respects to the embodiment 20 of FIG. 2 with the exception that the plurality of perforations 7 penetrate both the first thickness 19 of the first clad layer 1 and a second thickness 21 of the porous metal support 3.

[0092] FIG 5 depicts in transverse cross-sectional view an embodiment 40 of the porous metal substrate of this invention, which is similar in all respects to the embodiment 20 of FIG.

2 with the exception that the plurality of perforations 7 penetrate through the first thickness 19 of the first clad layer 1, through the second thickness 21 of the porous metal support layer 3, and through a third thickness 23 of the second clad layer 5.

[0093] FIGS. 6-8 illustrate in transverse cross-sectional view embodiments 50-70, respectively, of the metal-supported electrochemical cell of this invention. As depicted in FIG. 6, embodiment 50, the cell comprises in a layered configuration the following components: the first clad layer 1 disposed with a plurality of perforations 7 from a bottom surface 15 through a first thickness 19 to a top surface 17, the porous metal support layer 3, the second clad layer 5, a first electrode layer 9 (e.g., fuel electrode or anode), an electrolyte layer 11, and a second electrode layer 13 having a polarity opposite that of the first electrode, e.g., an oxygen electrode or cathode.

[0094] FIG. 7 illustrates another embodiment 60 of the metal -supported electrochemical cell of this invention, which is similar in all respects to embodiment 50 with the exception that the plurality of perforations 7 penetrate both the first thickness 19 of the first clad layer 1 and the second thickness 21 of the porous metal support layer 3.

[0095] FIG. 8 illustrates another embodiment 70 of the metal -supported electrochemical cell of this invention, which is similar in all respects to embodiment 50 with the exception that the plurality of perforations 7 penetrate the first thickness 19 of the first clad layer 1, the second thickness 21 of the porous metal support layer 3, and the third thickness 23 of the second clad layer 5.

[0096] The first and second metal oxides of the respective first and second clad layers are generally obtained from metal oxides providing for acceptable porosity and oxide ion (O² ) conductivity for use in an electrochemical cell. (The second clad layer adjacent the first electrode layer is also known as a “barrier layer”.) In some embodiments, the first and second metal oxides are each independently selected from the group consisting of oxides of zirconium, cerium, lanthanum, chromium, strontium, titanium, and mixtures thereof. In one preferred embodiment, the first and second metal oxides of the respective first and second clad layers are each independently selected from ceria or a divalent or trivalent cation-doped ceria, for example, gadolinium-doped ceria. In another preferred embodiment, the first and second metal oxides are each independently selected from yttria-stabilized zirconia. In another preferred embodiment, the first and second metal oxides are each independently selected from lanthanum chromite or a divalent or trivalent cation-doped lanthanum chromite. In yet another preferred embodiment, the first and second metal oxides are each independently selected from strontium titanate or a divalent or trivalent cation-doped strontium titanate. The clad layers function to fill-in gaps within the porous metal support and along the interface between the porous metal support and adjoining layers. Typically, the submicron to micron size grains of the first and second clad layers independently range from greater than about 0.1 micron to less than 1.5 microns.

[0097] In the clad layers the first and second metals, if employed, are provided as submicron to micron size grains and are generally obtained from metals providing for acceptable electrical conductivity. This is especially true for the second metal of the second clad layer upon which the first electrode layer is applied. In this instance, the second metal is selected to match or closely match the conductive metal in the electrode selected in order to reduce resistance and facilitate electrical conductivity. In some embodiments, the first and second metals of the first and second clad layers, respectively, are each independently selected from the group consisting of nickel iron, cobalt, chromium, copper, manganese, and mixtures thereof. Among these, nickel or copper is an advantageous embodiment. [0098] In an exemplary embodiment the metal content of the first or second metal in the first or second clad layer, respectively, ranges from about 0 percent to 60 percent, based on the total weight of the relevant clad layer. In one preferred embodiment the first or second metal content of the first or second clad layer, respectively, ranges from about 1 percent to 60 percent, more preferably from about 30 percent to 60 percent by weight, based on the total weight of the relevant clad layer.

[0099] In one exemplary embodiment, the first clad layer is a cermet comprising a first metal oxide and a first metal. In yet another exemplary embodiment the second clad layer is a cermet comprising a second metal oxide and a second metal.

[0100] Generally, the porous metal support comprises any metallic material of suitable strength and conductivity for use in an electrochemical cell. The metal of the porous support can be provided as a pure metallic element or a combination of metallic elements as in an alloy. Non-limiting examples of suitable metal supports include ferritic alloys predominantly comprising iron and an amount of chromium greater than about 15 weight percent as well as smaller amounts of other metallic elements. The metal support is required to be “porous,” meaning that a plurality of pores, channels, and/or open cells are present throughout and within the support so as to facilitate diffusion of gaseous components there through. The porosity of the metal support is typically greater than about 20 volume percent. Desirably, the porosity of the metal support ranges from about 20 to 50 volume percent, based on the total volume of the metal support. In some embodiments, the porosity of the metal support is derived from pores of a diameter (or critical dimension) ranging from about 3 to 75 microns, which are typically introduced into a greenware precursor via a pore former as described hereinafter. In some other embodiments, the porosity of the metal support is derived from perforations of a diameter or cross-sectional dimension ranging from greater than about 10 microns to less than 5 millimeters, which are typically introduced into a greenware precursor via laser cutting, stamping, machining and the like. In yet another embodiments both pores and perforations are present.

[0101] The porous metal support typically is formed into a thin sheet with a thickness ranging from about 80 microns (80 pm) to 1,000 microns (1 millimeter), preferably, from about 100 microns (0.1 millimeter) to 500 microns (0.5 millimeter). Porous metal supports in the shape of a sheet or layer at the upper end of the thickness range (800 - 1,000 pm) are available from commercial suppliers. Below about 500 pm, the porous metal support can be fabricated by tape-casting from powders of the metal component(s). See, for example, US 2008/0096079, incorporated herein by reference, on the subject of preparing thin-porous metal layers from metal powders.

[0102] The skilled person will appreciate that there are various means and methods of preparing the porous metal substrate and electrochemical cell described herein. Typical methods include combining a number of steps that are typically selected from tape-casting, ink printing, ink screening, vapor deposition, lamination, and machining, such as punching, stamping, etching and laser cutting, with subsequent debinding and finally sintering or cosintering. These steps and others can be combined in numerous ways to achieve the electrochemical cell of the invention.

[0103] In one preferred but non-limiting method, as depicted in FIG. 9, the metal- supported electrochemical cell is prepared by the following steps: In step (1) a green tape of a first clad layer is provided comprising a first metal oxide of submicron grain size and optionally a first metal. In step (2) a green metal support tape comprising particles of a metal or alloy and optionally particles of a pore former are applied over the top surface of the green first clad tape. Next in step (3), a green second clad tape comprising a second metal oxide of a submicron grain size and optionally a second metal is applied over the green metal support tape. In step (4) the green three-layer composite is subjected to heating under pressure to obtain a green laminated three-layer substrate. Thereafter, in step (5) a plurality of perforations are machined into at least the green first clad layer. The perforations extend from the bottom surface to the top surface through the first thickness of the green first clad layer. If desired, the perforations can be drilled through a second thickness of the green metal support layer and as well through a third thickness of the green second clad layer, in any case resulting in a green perforated substrate, which if desired may be debound and co-sintered to form the porous metal substrate of this invention. In other embodiments, however, which may be preferred as shown in FIG. 9, in a step (6) a green first electrode layer is applied over the green second clad layer of the green perforated substrate. Next, in step (7) a green electrolyte layer is applied over the green first electrode. Then, in step (8) the resulting green five-layer composite is debound and co-sintered to form the electrochemical half-cell. The full cell is realized by applying in step (9) a green second electrode layer over the electrolyte layer of the half-cell to form a green full cell. In step (10) the green full cell composite is debound and sintered to yield the electrochemical cell of this invention, which includes a metal substrate comprising the metal support layer having a porosity from 20 to 50 volume percent.

[0104] In one illustrative embodiment, the substrate is prepared by tape-casting individually a green first clad layer, a green metal support layer, and a green second clad layer. In another illustrative embodiment, the first and second green clad layers are prepared from one tape-cast green clad layer that is cut into two pieces. The green metal support layer can be tapecast from metal powders and optionally a pore former. The three tapes are stacked to form a sandwich in which the green metal support layer is disposed in between the green first and second clad layers, and all are laminated together. The desired plurality of perforations are introduced into the first clad layer and optionally into the metal support layer and second clad layer as desired.

[0105] Tape-casting involves preparing a slurry comprising a solvent, a binder, powdered forms of the desired metal components and/or ceramic components as appropriate, and optionally, at least one of a plasticizer and a dispersant. The thusly prepared slurry is cast into a sheet or green layer in a selected thickness. With respect to the porous metal support, the slurry typically comprises a solvent, a binder, a powdered form of the appropriate support metal, alloy or precursor thereto, optionally a pore former, and optionally at least one of a plasticizer and dispersant. The solvent employed is selected typically from common organic solvents removable at a temperature between about 50°C and 120°C. Such solvents are generally selected from the group consisting of alcohols, esters, and ketones and are supplied in an amount ranging from about 5 to 20 wt. percent, based on the total weight of the tape. The binder is selected from commercial binder formulations, for example, alcohol and polyvinyl-based binders in an amount ranging from about 5 to 20 wt. percent. Suitable plasticizers include those from phthalate and glycol groups, added typically in an amount ranging from about 1 to 10 wt. percent. Suitable dispersants include fish oil and amine groups provided in an amount ranging from about 1 to 10 wt. percent. The pore former, if used, is exemplified by starch and polymethylmethacrylate (PMMA), and employed in an amount and a particle size able to provide for the pore volume and pore size (range 3-75 microns) selected. After thoroughly mixing all components, the resulting slurry is cast into a green metal support tape. As an alternative green metal support tapes may be obtained commercially.

[0106] The green first and second clad tapes are prepared from submicron size grains of the first and second metal oxide, respectively, or precursors thereof, and a solvent, a binder, and optionally at least one of a plasticizer and dispersant. The organic components are similar in composition and quantity to those mentioned hereinabove. As an illustrative example, the first clad ink may comprise submicron-size powder particles of the first metal oxide and optionally micron to submicron-size powder particles of the first metal precursor. The micron to submicron-size particles of the first metal or its precursor range from greater than 0.1 micron (0.1 pm) to less than 20.0 micron (<20.0 pm) with respect to the first metal or its precursor and from greater than 0.1 micron (0.1 pm) to less than 1 micron (<1 pm) with respect to the first metal oxide. The quantity of first metal or first metal precursor in the first clad ink ranges from about 0 to 60 wt. percent, based on the total weight of the first clad ink. The quantity of first metal oxide in the first clad layer ink ranges from about 40 to 100 wt. percent, based on the total weight of the first clad layer ink.

[0107] The three-layer composite is assembled such that the green metal support layer is sandwiched in between the green first and second clad layers. The resulting green composite is laminated by heating to a temperature up to about 100°C at a pressure between about 100 psi (68.9 kPa) and 1,000 psi (6,895 kPa).

[0108] The plurality of perforations are machined into the green first clad layer, and optionally into the green support layer, and further optionally into the green second clad layer, as desired. The perforations are made using any suitable means including laser cutting, knife cutting, punching, stamping, or otherwise machining, preferably, by laser cutting. The perforations are not limited to any cross-sectional shape. Circular, oval, square, rectangular, triangular, pentagonal, and hexagonal shapes are all suitable design choices. In some embodiments, the perforations are circular. Typically, the perforations range in size from greater than about 10 microns (>10 pm) to less than 5 millimeters (< 5 mm), and preferably, from greater than about 75 pm to less than 3 mm; and more preferably, from greater than about 100 pm to less than 2 mm. Typically, the distance between an adjacent pair of perforations, measured from center to center, ranges from about 1 mm to 10 mm, and preferably, from about 2 mm to 6 mm. The perforations can be uniform in size and density across the layer or, alternatively, can vary in size and/or density across the layer. The perforations can be provided in a regular periodic pattern across the layer or, alternatively, can vary in a non-uniform pattern across the layer.

[0109] The substrate of this invention can be finalized by laminating, debinding and cosintering the perforated three-layer composite. Under typical circumstances, however, the green electrochemical half-cell is fabricated before proceeding with lamination. Accordingly, in some embodiments a green first electrode layer, such as a green anode or fuel electrode, is applied by any suitable means, such as ink printing or tape casting, on top of the green second clad layer of the three-layer composite, after which a green electrolyte layer is applied on top of the first electrode. The resulting green half-cell is then subjected to lamination (if applicable), debinding and co-sintering under conditions sufficient to form the electrochemical half-cell of this invention. As mentioned above, lamination is effected by heating to a temperature up to about 100°C at a pressure between about 100 psi (68.9 kPa) and 1,000 psi (6,895 kPa). Debinding involves heating the green half-cell under air at a temperature between about 60°C and 700°C. The co-sintering step involves heating the greenware under a reducing mixture of hydrogen and an inert gas, such as helium, nitrogen, or argon, while raising the temperature to between about 900°C and l,400°C. The full electrochemical cell is realized by applying a green second electrode layer, such as a green cathode or oxygen electrode, on top of the electrolyte layer and firing again.

[0110] The second clad layer, also known as a barrier layer, advantageously reduces unacceptable shrinkage and warpage of the porous metal support and prevents cave-in of cell constituents into the pores of the metal support. As a further advantage, the finished substrate is essentially flat without defects, which allows for excellent adherence of the electrode layer applied thereto. The porosity of the metal substrate allows for diffusion of gaseous components into and out of the support. The addition of perforations larger than about 10 microns through the first clad layer and optionally through the porous metal support and the second clad layer further facilitates diffusion of gases into and out of the electrochemical cell.

[0111] Materials useful for the first and second electrodes are illustrated, for example, by fuel and oxygen electrodes respectively. These should be stable at operating temperatures; should have a coefficient of thermal expansion compatible with that of the solid oxide electrolyte; and should be chemically compatible with the solid oxide electrolyte and other materials used during fabrication and operation of the solid oxide cell. In power production mode, the function of the fuel electrode is to combine the oxide ions that diffuse through the electrolyte with the fuel supplied to the fuel electrode to produce water and carbon dioxide as well as to produce a flow of electrons.

[0112] The fuel electrode (or anode) is constructed of a porous layer allowing the fuel, typically a gaseous reformate comprising hydrogen and carbon monoxide, to diffuse inside the electrode. Since the fuel electrode must be electrically and ionically conductive, the fuel electrode comprises a cermet, that is, a combination of ceramic and metal prepared by standard ceramic processing techniques. Suitable fuel electrode layers comprise, for example, nickel or nickel oxide and a metal oxide selected from the group consisting of the oxides of zirconium, yttrium, cerium, scandium, gadolinium, samarium, calcium, lanthanum, strontium, magnesium, gallium, barium, and mixtures thereof. In some embodiments the fuel electrode layer comprises nickel oxide-yttria stabilized zirconia, NiO-YSZ.

[0113] The solid oxide electrolyte comprises a dense layer of ceramic that conducts oxide ions (O²'). Typically, the electrolyte comprises a metal oxide selected from the group consisting of scandium, cerium, zirconium, lanthanum, strontium, magnesium, gallium, barium, yttrium, gadolinium, samarium, calcium, and mixtures thereof. As an example of a material from which the solid oxide electrolyte layer can be made, we include yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ). As newer electrolytes are developed, these may lead to more robust materials and less resistivity problems by improving the conductivity of oxide ions, which in turn may lead to better performing electrolyte layers, any of which may be employed in this invention. [0114] The second electrode, having a different polarity from the first electrode, comprises an oxygen electrode (or cathode) that is also porous in order to provide for a uniform flow of oxygen throughout. The oxygen electrode should also be capable of conducting oxide ions (O² ) to the solid oxide electrolyte. As non-limiting examples of a material from which the oxygen electrode can be formed, lanthanum strontium manganite (LSM), lanthanum strontium ferrite (LSF), (La,Sr)(Co,Fe)O3 and any of the cobalites are included.

[0115] The fuel electrode, electrolyte, and oxygen electrode layers are usually fabricated from appropriate inks or tapes. The ink or tape typically contains a solvent, a binder, the specific metal(s) and ceramic(s) of the particular layer involved, and optionally, at least one of a binder and plasticizer. The solvent, binder, plasticizer and dispersant are suitably sourced from any of those mentioned hereinbefore.

[0116] In some embodiments, an interlayer is disposed between the electrolyte layer and the oxygen electrode layer for the purpose of retarding reaction between the electrolyte and the oxygen electrode or cathode. Typically, the interlayer comprises one or more divalent or trivalent cation elements doped with one or more metals selected from Group IIA. In some embodiments, the divalent or trivalent cation elements are selected from the group consisting of lanthanum, samarium, yttrium, gadolinium, and combinations thereof. In some embodiments, the interlayer is comprised of a divalent or trivalent cation-doped ceria. Typically, the interlayer has a thickness between about 1 micron and 20 microns.

[0117] Any individual electrochemical cell produces less than about 1 V under typical operating conditions, but most applications require higher voltages. Accordingly, for practical applications a plurality of individual electrochemical cells of this invention are connected in series to form a stack so as to obtain a higher voltage required for the application. The stack is constructed by securing each electrochemical cell between two interconnects that provide strength to the stack and separate the cells from each other.

[0118] Since the interconnects are exposed at high temperatures to both oxidizing and reducing sides of the cell, the interconnects should be stable under both circumstances. Accordingly, the interconnects are comprised of an electrically conductive material able to withstand the thermal and chemical environments to which they are exposed. In some embodiments, the interconnects are constructed of metallic plate or foil, for example, a high temperature stainless steel alloy. In another embodiment, the interconnects are constructed from metal oxide providing for acceptable thermal stability and electrical conductivity. This invention is not limited to any specific interconnect material or interconnect layer thickness.

[0119] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description but is only limited by the scope of the appended claims.

Claims

1. A porous metal substrate for a metal-supported electrochemical cell, comprising in a layered configuration:

(a) a first clad layer comprised of submicron to micron size grains of a first metal oxide and further configured with a plurality of perforations disposed from one surface to another surface through a first thickness of the first clad layer;

(b) a porous metal support layer having a porosity ranging from 20 volume percent to 50 volume percent; and

(c) a second clad layer comprising submicron to micron size grains of a second metal oxide.

2. The porous metal substrate of claim 1 wherein the first clad layer, the porous metal support layer, and the second clad layer are co-sintered layers.

3. The porous metal substrate of claim 1 or claim 2 wherein the plurality of perforations extend through a second thickness of the porous metal support layer.

4. The porous metal substrate of any one of claims 1 to 3 wherein the plurality of perforations extend through a second thickness of the porous metal support layer and a third thickness of the second clad layer.

5. The porous metal substrate of any one of claims 1 to 4 wherein the plurality of perforations having a size greater than 10 pm and less than 5 mm, preferably, greater than 75 pm and less than 3 mm, and more preferably, greater than 100 pm and less than 2 mm.

6. The porous metal substrate of any one of claims 1 to 5 wherein a spacing between a pair of adjacent perforations, as measured from center to center, ranges from 1 to 10 mm

7. The porous metal substrate of any one of claims 1 to 6 wherein a percentage of open area of the perforations of the first clad layer ranges from 2 to 40 percent.

8. The porous metal substrate of any one of claims 1 to 7 wherein the submicron to micron size grains of the first and second metal oxides each independently range from greater than 0.1 pm to less than 1.5 pm.

9. The porous metal substrate of any one of claims 1 to 8 wherein the first and second clad layers each independently have a thickness ranging from 1 to 30 pm.

10. The porous metal substrate of any one of claims 1 to 9 wherein the first clad layer further comprises a first metal selected from the group consisting of nickel, iron, cobalt, chromium, copper, manganese, and mixtures thereof; more preferably, selected from nickel, copper, or iron; and wherein the first metal has a submicron to micron grain size ranging from greater than 0.1 pm to less than 20 pm.

11. The porous metal substrate of any one of claims 1 to 10 wherein the second clad layer further comprises a second metal selected from the group consisting of nickel, iron, cobalt, chromium, copper, manganese, and mixtures thereof; more preferably, selected from nickel, copper, or iron; and wherein the second metal has a grain size ranging from greater than 0.1 pm to less than 20 pm.

12. The porous metal substrate of any one of claims 1 or 11 wherein a content of first metal or second metal in the first or second clad layer, respectively, ranges from 1 to 60 percent by weight, preferably from 30 to 60 percent by weight, based on the total weight of the first or second clad layer as the case may be.

13. The porous metal substrate of any one of claims 1 to 12 wherein the porous metal support layer has a thickness less than 1.1 mm, and typically between about 80 and 1,000 pm.

14. The porous metal substrate of any one of claims 1 to 13 wherein the porous metal support comprises a ferritic alloy, preferably, a ferritic alloy containing chromium in an amount greater than 15 weight percent.

15. The porous metal substrate of any one of claims 1 to 14 wherein the porous metal support comprises a plurality of pores of a size ranging from 3 to 75 microns, or a plurality of perforations having a size greater than 10 microns to 5 millimeters, or a combination of both a plurality of pores and a plurality of perforations.

16. The porous metal substrate of any one of claims 1 to 15 wherein the first and second metal oxides are each independently selected from ceria or a divalent or trivalent cation-doped ceria; or selected from lanthanum chromite or a divalent or trivalent cation-doped lanthanum chromite; or selected from strontium titanate or a divalent or trivalent cation-doped strontium titanate; or selected from yttrium-stabilized zirconia.

17. A metal -supported electrochemical cell comprising in a layered configuration:

(a) a first clad layer comprising submicron to micron size grains of a first metal oxide and configured with a plurality of perforations disposed from one surface to another surface through a first thickness of the first clad layer;

(b) a porous metal support configured as a layer having a porosity ranging from 20 volume percent to 50 volume percent;

(c) a second clad layer comprising submicron to micron size grains of a second metal oxide;

(d) a first electrode layer;

(e) an electrolyte layer; and

(f) a second electrode layer having a polarity opposite that of the first electrode layer.

18. The metal -supported electrochemical cell of claim 17 wherein the first clad layer, the porous metal support layer, and the second clad layer are co-sintered layers.

19. The metal -supported electrochemical cell of claim 17 or 18 wherein the plurality of perforations extend through a second thickness of the porous metal support layer.

20. The metal-supported electrochemical cell of any one of claims 17 to 19 wherein the plurality of perforations extend through a second thickness of the porous metal support layer and a third thickness of the second clad layer.

21. The metal-supported electrochemical cell of any one of claims 17 to 20 wherein the plurality of perforations having a size greater than 10 pm and less than 5 mm, preferably, greater than 75 pm and less than 3 mm; and more preferably, greater than 100 pm and less than 2 mm.

22. The metal-supported electrochemical cell of any one of claims 17 to 21 wherein a spacing between a pair of adjacent perforations as measured from center-to-center ranges from 1 to 10 mm.

23. The metal-supported electrochemical cell of any one of claims 17 to 22 wherein a percentage of open area of the perforations of the first clad layer ranges from 2 to 40 percent.

24. The metal-supported electrochemical cell of any one of claims 17 to 23 wherein the submicron to micron size grains of the first and second metal oxides each independently range in size from greater than 0.1 micron to less than 1.5 micron.

25. The metal-supported electrochemical cell of any one of claims 17 to 24 wherein the first and second clad layers each independently have a thickness ranging from 1 micron to 30 microns.

26. The porous metal substrate of any one of claims 17 to 25 wherein the first clad layer further comprises a first metal selected from the group consisting of nickel, iron, cobalt, chromium, copper, manganese, and mixtures thereof; more preferably, selected from nickel, copper, or iron; or wherein the second clad layer further comprises a second metal selected from the group consisting of nickel, iron, cobalt, chromium, copper, manganese, and mixtures thereof; more preferably, selected from nickel, copper, or iron; and wherein a content of the first metal or second metal in the first or second clad layer, respectively, ranges from 1 to 60 percent by weight, preferably from 30 to 60 percent by weight, based on a total weight of the first or second clad layer as the case may be.

27. The metal-supported electrochemical cell of any one of claims 17 to 26 comprising a metal-supported solid oxide fuel cell or a metal-supported solid oxide electrolysis cell, wherein the first electrode layer is a fuel electrode (anode) layer and the second electrode layer is an oxygen or air electrode (cathode) layer.

28. The metal-supported electrochemical cell of any one of claims 17 to 27 wherein the first electrode layer has a thickness between 3 and 20 microns; the electrolyte layer has a thickness between 1 and 20 microns; and the second electrode layer has a thickness between 10 and 30 microns.

29. The metal-supported electrochemical cell of any one of claims 17 to 28, wherein the first electrode layer is a fuel electrode comprising nickel or nickel oxide and a metal oxide selected from the group consisting of the oxides of zirconium, yttrium, cerium, scandium, gadolinium, samarium, calcium, lanthanum, strontium, magnesium, gallium, barium, and mixtures thereof.

30. The metal-supported electrochemical cell of any one of claims 17 to 29 wherein the electrolyte layer comprises a metal oxide selected from the group consisting of the oxides of zirconium, yttrium, cerium, scandium, gadolinium, samarium, lanthanum, strontium, magnesium, gallium, barium, calcium and mixtures thereof.

31. The metal-supported electrochemical cell of any one of claims 17 to 30 wherein the second electrode layer is an oxygen electrode selected from compositions of formula ABO3, wherein A is selected from the group consisting of barium, strontium, lanthanum, samarium, praseodymium, and combinations thereof, and B is selected from the group consisting of iron, cobalt, nickel and manganese.

32. The metal-supported electrochemical cell of any one of claims 17 to 31 wherein an interlayer is disposed in between the electrolyte layer and the second electrode layer (oxygen electrode), optionally further wherein the interlayer has a thickness between about 1 micron and 20 microns.

33. A method of making the porous metal substrate of Claim 1, comprising:

(a) providing a green first clad tape comprising submicron size grains of a first metal oxide;

(b) applying a green metal support tape over the green first clad tape, the green metal support tape comprising particles of a metal or alloy and optionally a pore former;

(c) applying a green second clad tape comprising submicron size grains of a second metal oxide over the green metal support tape to form a green three-layer composite;

(d) heating the green three-layer composite under pressure to form a laminated green substrate;

(e) machining a plurality of perforations into at least the first clad layer of the green laminated substrate to form a green perforated substrate;

(f) co-sintering the green perforated substrate under conditions sufficient to prepare the porous metal substrate of Claim 1.

34. A method of making the metal -supported electrochemical cell of Claim 17, comprising:

(d) heating the green three-layer composite under pressure to form a green laminated substrate; (e) machining a plurality of perforations into at least the first clad layer of the green laminated substrate to from a green perforated substrate;

(f) applying a green first electrode layer over the green second clad tape of the green perforated substrate;

(g) applying a green electrolyte layer over the green first electrode layer to form a green half-cell;

(i) debinding and co-sintering a resulting green five-layer composite to form an electrochemical half-cell;

(j) applying a second electrode layer over the electrolyte layer of the half-cell;

(k) debinding and sintering a resulting green full cell under conditions sufficient to prepare the electrochemical cell of Claim 17.