Interconnect with cell nests, and method for assembling an electrochemical cell stack with interconnects.

Abstract

The present invention provides low-cost interconnects, unit cells, and methods for forming unit cells. [Solution] The interconnect of the electrochemical cell stack includes reactant holes penetrating the interconnect. The reactant side includes a reactant field having reactant channels and reactant ribs extending between the reactant holes, a peripheral sealing surface surrounding the reactant field and reactant holes, recessed sealing surfaces positioned on the opposing sides of the reactant field inside the peripheral sealing surface and concave relative to the peripheral sealing surface, and a nest sidewall connecting the recessed sealing surface to the peripheral sealing surface. The nest sidewall extends substantially perpendicular to the peripheral sealing surface and the recessed sealing surface. The nest sidewall, recessed sealing surface, and the tops of the reactant ribs define at least partially a cell nest configured to house the electrochemical cell. The air side includes an air field positioned between the reactant holes and an annular sealing surface positioned around the reactant holes.

Description

Technical Field

[0001] Aspects of the present disclosure generally relate to interconnects for an electrochemical cell stack, and more particularly to interconnects having cell nests.

Background Art

[0002] A typical solid oxide electrochemical cell stack includes ceramic electrochemical cells (e.g., fuel cells or electrolysis cells) disposed between conductive metal interconnects. Interconnects of conventional solid oxide electrochemical cells are typically formed by a powder metallurgy process. However, interconnects by powder metallurgy are costly to manufacture.

Summary of the Invention

[0003] According to various embodiments, an interconnect for an electrochemical cell stack includes reactant holes extending through the interconnect, a reactant field on a reactant side having reactant channels and reactant ribs extending between the reactant holes, a peripheral seal surface extending across a peripheral portion of the interconnect, a recessed seal surface disposed on opposite sides of the reactant field inside the peripheral seal surface and recessed with respect to the peripheral seal surface, and a nest sidewall connecting the recessed seal surface to the peripheral seal surface. The nest sidewall extends substantially perpendicular to the peripheral seal surface and the recessed seal surface. The top of the nest sidewall, the recessed seal surface, and the reactant ribs at least partially define a cell nest configured to house an electrochemical cell. An air side opposite the reactant side of the interconnect includes an air field disposed between the reactant holes and an annular seal surface disposed around the reactant holes.

[0004] According to various embodiments, a method for forming a unit cell of an electrochemical cell stack is to apply a sealant to a reactant-side peripheral sealant surface of a first interconnect such that the sealant at least partially surrounds the reactant holes and reactant fields of the first interconnect; to apply a sealant to a recessed sealant surface positioned on the opposing sides of the reactant field inside the peripheral sealant surface and concave with respect to the peripheral sealant surface; and to apply a sealant to a nest sidewall connecting the recessed sealant surface to the peripheral sealant surface, wherein the nest sidewall extends substantially perpendicular to the peripheral sealant surface and the recessed sealant surface, and the nest sidewall, recessed sealant surface, and reactant field The tops of the reactant ribs of the world include at least partially defining a cell nest, arranging a contact layer within the cell nest such that the compliant contact layer contacts the tops of the reactant ribs in the reactant field, arranging cells on the compliant contact layer within the cell nest such that the opposing ends of the electrochemical cells contact the sealant applied to the recessed seal surface and the nest sidewall, applying the sealant to the air-side annular seal surface of the second interconnect, and arranging the second interconnect on the first interconnect such that the air ribs in the air field of the second interconnect contact the electrochemical cells.

[0005] The accompanying drawings, included to provide a further understanding of the present invention and incorporated herein, and forming part thereof, illustrate exemplary embodiments of the present invention and, together with the specification, illustrate the principles of the present invention. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a perspective view of an electrochemical stack according to various embodiments of this disclosure. [Figure 2A] Figure 2A is a cross-sectional view of an anode-supported electrochemical cell according to various embodiments of the present disclosure. [Figure 2B] Figure 2B is a cross-sectional view of an electrolyte-supported electrochemical cell according to various embodiments of the present disclosure. [Figure 3]Figure 3 is a partial cross-sectional view of a unit cell including an interconnect and an electrochemical cell according to a comparative embodiment. [Figure 4A] Figure 4A is a reactant-side perspective view of an interconnect according to various embodiments of this disclosure. [Figure 4B] Figure 4B is an enlarged view of section P of Figure 4A. [Figure 4C] Figure 4C is a perspective view of the air side of the interconnect shown in Figure 4A. [Figure 5A] Figure 5A is a plan view showing the steps in the assembly of a unit cell of an electrochemical cell stack according to various embodiments of the present disclosure. [Figure 5B] Figure 5B is a plan view showing the steps in the assembly of a unit cell of an electrochemical cell stack according to various embodiments of the present disclosure. [Figure 5C] Figure 5C is a plan view showing the steps in the assembly of a unit cell of an electrochemical cell stack according to various embodiments of the present disclosure. [Figure 5D] Figure 5D is a plan view showing the steps in the assembly of a unit cell of an electrochemical cell stack according to various embodiments of the present disclosure. [Figure 6A] Figure 6A is a perspective view of part P in Figure 5D. [Figure 6B] Figure 6B is a cross-sectional view along line L1 in Figure 5D. [Figure 6C] Figure 6C is a cross-sectional view along line L2 in Figure 5D. [Figure 7] Figure 7 shows the air side of an alternative interconnect according to an alternative embodiment of the present disclosure. [Figure 8A] Figure 8A is a plan view showing the steps in the assembly of a unit cell of an electrochemical cell stack according to an alternative embodiment of the present disclosure. [Figure 8B] Figure 8B is a plan view showing the steps in the assembly of a unit cell of an electrochemical cell stack according to an alternative embodiment of the present disclosure. [Figure 8C]Figure 8C is a plan view showing the steps in the assembly of a unit cell of an electrochemical cell stack according to an alternative embodiment of the present disclosure. [Figure 8D] Figure 8D is a plan view showing the steps in the assembly of a unit cell of an electrochemical cell stack according to an alternative embodiment of the present disclosure. [Figure 8E] Figure 8E is a cross-sectional view along line L1 in Figure 8D. [Figure 9A] Figure 9A is a cross-sectional view showing an alternative method for sealing unit cells using metal foil, according to an alternative embodiment of the present disclosure. [Figure 9B] Figure 9B is a cross-sectional view showing an alternative method for sealing unit cells using metal foil, according to an alternative embodiment of the present disclosure. [Figure 10A] Figure 10A is a reactant-side plan view of an alternative interconnect according to another alternative embodiment of the present disclosure. [Figure 10B] Figure 10B is a cross-sectional view along line L1 in Figure 10A. [Figure 10C] Figure 10C is a side cross-sectional view of an alternative unit cell, including an electrochemical cell and the alternative interconnects shown in Figures 10A and 10B. [Figure 10D] Figure 10D is a side cross-sectional view of an alternative unit cell, including an electrochemical cell and the alternative interconnects shown in Figures 10A and 10B. [Figure 11A] Figure 11A is a reactant-side plan view of an alternative interconnect according to another alternative embodiment of the present disclosure. [Figure 11B] Figure 11B is a plan view of the air side of the interconnect. [Figure 11C] Figure 11C is a plan view showing a unit cell including an electrochemical cell and alternative interconnects as shown in Figures 11A and 11B. [Figure 12A] Figure 12A is a perspective view showing the reactant-side (e.g., fuel-side) sheet of an alternative interconnect according to various embodiments of the present disclosure. [Figure 12B]FIG. 12B is a perspective view showing an air side sheet of an alternative interconnect according to various embodiments of the present disclosure. [Figure 12C] FIG. 12C is a perspective view during the process of forming an alternative interconnect using the sheets of FIGS. 12A and 12B. [Figure 12D] FIG. 12D is a perspective view of a part of the completed alternative interconnect. [Figure 13] FIG. 13 is an enlarged perspective view of a unit cell including the alternative interconnects of FIGS. 12A - 12D. **DETAILED DESCRIPTION**

[0007] The present disclosure is fully described herein with reference to the accompanying drawings that illustrate exemplary embodiments of the invention. However, the invention can be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to make the present disclosure thorough and to fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements.

[0008] When an element or layer is referred to as being "on" or "connected to" another element or layer, it can be directly on or directly connected to the other element or layer, or intervening elements or layers may be present. On the other hand, when an element is referred to as being "directly on" or "directly connected to" another element or layer, no intervening elements or layers are present. For the purposes of the present disclosure, it will be understood that "at least one of X, Y, and Z" can be construed as only X, only Y, only Z, or any combination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ, ZZ).

[0009] Electrochemical cell systems include fuel cells and electrolytic cell systems. In high-temperature fuel cell systems such as solid oxide fuel cell (SOFC) systems, the oxidation flow is directed towards the cathode side of the fuel cell, and the fuel flow is directed towards the anode side of the fuel cell. The oxidation flow is usually air, and the fuel flow can be hydrogen (H2), ammonia, or hydrogen-containing gases including hydrocarbon fuels such as methane, natural gas, pentane, ethanol, or methanol. When a fuel cell operates at temperatures typically between 650°C and 950°C, it is possible to transfer negatively charged oxygen ions from the cathode flow to the anode flow, where the oxygen ions combine with free hydrogen or hydrogen in hydrocarbon molecules to form water vapor, and / or with carbon monoxide to form carbon dioxide. Excess electrons from the negatively charged ions are guided back to the cathode side of the fuel cell through the completed electrical circuit between the anode and cathode, resulting in a current flow through the circuit. In electrolytic cell systems such as solid oxide electrolytic cell systems, water (e.g., vapor) is separated into hydrogen and oxygen by applying a voltage to the electrolytic cell.

[0010] Figure 1 is a perspective view of an electrochemical cell stack 10 according to various embodiments of the present disclosure. In the following embodiments, the stack 10 is described as operating as a solid oxide fuel cell (SOFC) stack 10. However, it should be noted that the stack 10 can also operate as an electrolytic cell (e.g., a solid oxide electrolytic cell (SOEC) stack). Referring to Figure 1, the stack 10 includes an electrochemical cell 100, such as a fuel cell (e.g., SOFC) or an electrolytic cell (e.g., SOEC), separated by an interconnect 200. The cell 100 comprises a reactant electrode and an air electrode separated by a solid oxide electrolyte. In the case of an SOFC 100, the reactant includes at least one of the fuels described above, the reactant electrode includes an anode electrode, and the air electrode includes a cathode electrode. In the case of an SOEC 100, the reactant includes vapor, the reactant electrode includes a cathode electrode, and the air electrode includes an anode electrode.

[0011] Stack 10 also comprises a top plate 20 and a bottom plate 22 on the opposite side. In some embodiments, the top plate 20 and the bottom plate 22 may be an interconnect modified to have neither reactant channels nor air channels. In other embodiments, the top plate 20 and / or the bottom plate 22 may have the same design as the interconnect 200. The electrochemical cell system may comprise an electrochemical cell column comprising one or more stacks 10. In the embodiment shown in Figure 1, the column comprises a single stack 10. In alternative embodiments, however, the column may comprise multiple stacks 10 stacked on top of each other.

[0012] The interconnect 200 electrically connects adjacent cells 100 within the stack 10. In particular, the interconnect 200 can electrically connect the reactant electrode of one fuel cell 100 to the air electrode of an adjacent fuel cell 100. The interconnect 200 may be electrically connected to the reactant electrode using an optional Ni mesh or another three-dimensional conductive structure.

[0013] The stack 10 can be placed on a manifold 30 configured to supply reactants to the stack 10. In particular, as will be discussed in detail below, the stack 10 can reduce pressure loss and increase the flow rate of reactants by internally manifolding for the reactants. For example, in an SOFC stack configuration, the manifold 30 can supply fuel to the stack 10 and receive fuel exhaust (e.g., steam, carbon dioxide, unreacted fuel, etc.) from the stack 10. In an SOEC stack configuration, the manifold 30 can supply steam and / or carbon dioxide to the stack 10 and receive hydrogen and unreacted steam from the stack 10.

[0014] Electrochemical cells 100, such as SOFCs and SOECs, are typically supported to increase mechanical stability and reliability. For example, supported cells include electrode-supported cells, electrolyte-supported cells, and co-supported cells. Electrolyte-supported cells have a relatively thick electrolyte, on which a relatively thin electrode is formed. Electrode-supported cells have a relatively thick support electrode (e.g., a reactant electrode) to provide structural support, and co-supported cells may have a relatively thick support electrode and a relatively thick electrolyte.

[0015] Electrolyte-supported cells offer numerous advantages, including improved sealing due to the high density surrounding the electrolyte and reduced stability due to the thin reactant electrode. However, because electrolytes typically exhibit lower conductivity than the anode or cathode material, electrolyte-supported cells often have higher area resistivity (e.g., ohmic resistance) than electrode-supported cells. For example, in an electrolyte-supported solid oxide fuel cell, the ohmic resistance of the electrolyte may contribute most significantly to the total area resistivity of the cell at typical operating temperatures (e.g., around 800°C to 850°C).

[0016] Electrode-supported SOFCs and SOECs are typically manufactured by co-sintering a coating of support electrode material and electrolyte material. Electrode-supported cells include anode-supported cells with a relatively thick anode and cathode-supported cells with a relatively thick cathode. Reactor-supported cells (e.g., anode-supported fuel cells or cathode-supported electrolytic cells) have the advantage of offering a higher CTE and lower operating temperature compared to electrolyte-supported cells. Therefore, reactant-supported cells may be particularly suitable for use with interconnects formed from ferritic or martensitic stainless steel sheet metal.

[0017] Figure 2A is a cross-sectional view of a reactant electrode supported electrochemical (RESE) cell (e.g., an anode-supported fuel cell or a cathode-supported electrolytic cell) 100 according to various embodiments of the present disclosure, and Figure 2B is a cross-sectional view of an electrolyte-supported electrochemical cell 100A according to various embodiments of the present disclosure.

[0018] Referring to Figures 2A and 2B, the electrochemical cells 100 and 100A may comprise an electrolyte 120, a reactant electrode 130 positioned on a first side (e.g., the reactant side) of the electrolyte 120, and an air electrode 140 positioned on a second side (e.g., the air side) of the electrolyte 120. The electrolyte 120 may be formed from an ion-conducting ceramic material such as a doped zirconia material or a doped ceria material. For example, the electrolyte 120 may include scandia-stabilized zirconia (SSZ), yttria-stabilized zirconia (YSZ), yttria-ceria-stabilized zirconia (YCSZ), ytterbia-ceria-scandia-stabilized zirconia (YbCSSZ), or mixtures thereof.

[0019] Preferably, the electrolyte may include YbCSSZ, as disclosed in U.S. Patent No. 8,580,456, incorporated herein by reference, in an amount equal to 9 mol% to 11 mol%, for example 10 mol%, ceria may be present in an amount greater than 0 mol% and less than or equal to 3 mol%, for example 0.5 mol% to 2.5 mol%, for example 1 mol%, and ytterbia may be present in an amount greater than 0 mol% and less than or equal to 2.5 mol%, for example 0.5 mol% to 2 mol%, for example 1 mol%.

[0020] The electrolyte 120 may optionally include a barrier layer 122 positioned on the air side. The barrier layer 122 can be configured to prevent the air electrode material from diffusing into the electrolyte 120. For example, the barrier layer 122 can be formed from a dense ceria material doped with gadolinium or samaria, having a thickness in the range of about 200 nm to about 800 nm.

[0021] The air electrode 140 can be placed on the barrier layer 122. The air electrode 140 can have a single-layer or multi-layer structure. For example, the air electrode 140 may comprise an air-side functional layer 142 and an air-side contact layer 144. The functional layer 142 may include a catalyst such as lanthanum strontium manganate, lanthanum strontium cobaltite, lanthanum strontium cobalt ferrite, or lanthanum nickel ferrite. The contact layer 144 may include a conductive material such as lanthanum strontium manganate configured to reduce the electrical resistance between the air electrode 140 and adjacent components, such as an interconnect.

[0022] The reactant electrode 130 may comprise a catalyst electrode 132 positioned on the reactant side of the electrolyte 120 and a support 138 positioned on the catalyst electrode 132. The catalyst electrode 132 may include a nickel-containing phase and an ion-conducting ceramic phase, such as SSZ, YSZ, YbCSSZ, or doped ceria, such as gadolinia, yttria, and / or samaria-doped ceria, such as samaria-doped ceria (SDC). The catalyst electrode 132 preferably comprises a Ni-SDC cermet or a Ni-YbCSSZ cermet. In some embodiments, the Ni phase may contain additional dopants to improve phase stability and / or redox resistance.

[0023] The catalyst electrode 132 can have a single-layer or multi-layer structure. For example, in SOFC 100, the catalyst electrode 132 may comprise a first functionally graded anode (FGA) layer 134 and a second FGA layer 136. The first FGA layer 134 may have a lower ratio of nickel-containing phase to ionic conductive phase than the second FGA layer 136.

[0024] The first FGA layer 134 may have a thickness T1 in the range of about 7 μm to about 17 μm, for example, about 10 μm to about 14 μm, or about 11 μm to about 13 μm. The second FGA layer 136 may have a thickness T2 in the range of about 2 μm to about 10 μm, for example, about 4 μm to about 8 μm, or about 5 μm to about 6 μm. However, this disclosure is not limited to specific FGA layer thicknesses.

[0025] The support 138 can be formed from a cermet material having a metallic phase and a ceramic phase. For example, the support 138 may include a nickel-containing phase (e.g., a nickel phase) and a ceramic phase. The nickel phase may include nickel and / or nickel alloys and may optionally include other additional metal dopants to improve phase stability and / or redox resistance. A compliant contact layer 150, such as a nickel mesh, can be placed below the reactant electrode 130.

[0026] The ceramic phase may include stabilized zirconia, yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (SSZ), yttria-scandia-stabilized zirconia (YSSZ), and / or doped ceria materials, such as ceria doped with gadolinia, yttria, and / or samaria. The ceramic phase may optionally be doped with additional phase stabilizers, as will be discussed in detail below. The ceramic phase of the support 138 preferably contains (3-10)-YSZ, which is YSZ containing about 3 mol% to about 10 mol% yttria. The ceramic phase (e.g., (3-10)-YSZ) may contain additional dopants (e.g., phase stabilizers) to improve phase stability.

[0027] As shown in Figure 2A, in the RESE cell 100, the support 138 can have a thickness T3 of approximately 200 μm to approximately 600 μm, for example, in the range of approximately 300 μm to approximately 500 μm, approximately 350 μm to approximately 450 μm, or approximately 400 μm. The electrolyte 120 can have a thickness T4 of approximately 5 μm to approximately 15 μm, for example, in the range of approximately 8 μm to approximately 12 μm, or approximately 10 μm. Therefore, a relatively thick support 138 can support a relatively thin electrolyte 120.

[0028] As shown in Figure 2B, the electrolyte-supported electrochemical cell 100A may be equipped with a relatively thick electrolyte 120. In particular, the electrolyte 120 may have a thickness T6 of about 50 μm to about 200 μm, for example, in the range of about 75 μm to about 125 μm, about 85 μm to about 115 μm, or about 100 μm. The relatively thick electrolyte 120 may be self-supporting.

[0029] In some embodiments, the electrochemical cell 100A may optionally include a relatively thin support 138. For example, the support 138 can have a thickness T5 in the range of about 20 μm to about 100 μm, for example, about 25 μm to about 75 μm, or about 40 μm to about 60 μm. Thus, the thickness of the support 138 can be reduced compared to the support 138 of cell 100, or the support 138 can be omitted, without impairing the cell strength.

[0030] Figure 3 is a partial cross-sectional view of a unit cell including an interconnect and an electrochemical cell according to a comparative embodiment. The unit cell of the comparative embodiment includes a RESE cell 100 positioned between two interconnects 201 of the comparative embodiment and sealed by a peripheral seal 203. The interconnect 201 may include a protective coating 201A on the air side, such as a lanthanum strontium manganite and / or manganese cobalt oxide spinel coating.

[0031] The inventors have found that the exposure of the opposing edges of the cell 100 creates a leakage path for the reactant. In particular, the reactant supplied to the upper surface of the cell 100 diffuses to the reactant electrode 130, passes under the peripheral seal 203, and exits from the opposing edges of the reactant electrode 130. This leakage of the reactant may cause combustion if the reactant is a fuel such as hydrogen (H2) or hydrocarbon gas. Furthermore, the exposure of the edges of the reactant electrode may cause a porous nickel oxide phase to form within the reactant electrode 130. This porous nickel oxide phase may cause the reactant electrode 130 to expand, which may apply tension to the adjacent electrolyte 120, potentially causing cracks in the electrolyte 120.

[0032] Therefore, various embodiments provide improved interconnects that include features that enable the prevention or reduction of reactant leakage by "nesting" electrochemical cells between interconnects.

[0033] Figure 4A is a perspective view of the reactant side (e.g., fuel side) of the interconnect 200 according to various embodiments of the present disclosure. Figure 4B is an enlarged view of a portion P of Figure 4A. Figure 4C is a perspective view of the air side of the interconnect 200.

[0034] Referring to Figures 4A and 4B, the interconnect 200 can be formed from ferritic stainless steel, for example, SS430 steel containing 16% to 18% by weight of Cr, less than 0.12% by weight of C, 0% to 0.75% by weight of Ni, 0% to 1% by weight of Si and / or Mn, respectively, with the remainder being iron and various impurities (e.g., unavoidable impurities, e.g., 0% to less than 0.1% by weight of Mo), or VDM® Crofer 22 APU alloy containing 20% ​​to 24% by weight of Cr, 0.3% to 0.8% by weight of Mn, 0.04% to 0.2% by weight of La, 0.03% to 0.2% by weight of Ti, with the remainder being iron and various impurities (e.g., unavoidable impurities). Therefore, the interconnect 200 may include a ferritic stainless steel interconnect containing at least 15 wt% Cr and at least 50 wt% Fe, for example, 16 wt% to 24 wt% Cr and 76 wt% to 84 wt% Fe.

[0035] The interconnect 200 can be formed by any preferred method. For example, the interconnect 200 can be formed by machining, laser cutting, stamp cutting, powder pressing, laser powder bed melting, sand casting, binder jet 3D printing, etc. In some embodiments, the interconnect 200 can be formed by stamping and brazing processes, as will be discussed below with reference to Figures 11A, 11B, and 12A to 12D.

[0036] The interconnect 200 may include a frame 202 extending along the periphery of the interconnect 200. In particular, the frame 202 may be a rectangular structure forming the periphery of the interconnect 200. The interconnect 200 may include reactant holes 210 located inside the frame 202 and adjacent to the opposing first and second peripheral sides of the frame 202. The reactant holes 210 may be through holes penetrating the interconnect 200 in the thickness direction. While one embodiment is shown in which only one reactant hole 210 is located along each of the first and second peripheral sides of the frame 202, in alternative embodiments, a plurality of reactant holes 210, for example, two, three, or four reactant holes, may be located along each of the first and second peripheral sides of the frame 202. Thus, the interconnect 200 is internally manifolded for the reactants (e.g., fuel or vapor).

[0037] The reactant side of the interconnect 200 may comprise a reactant field (i.e., a fuel or vapor flow field) 220 extending between reactant holes 210 on the opposing first and second peripheral sides of the frame 202. The reactant field 220 may comprise reactant channels 222 and reactant ribs 224 separating and defining the reactant channels 222. The reactant (e.g., fuel or vapor) can flow through the reactant channels 222, across the reactant field 220, from one reactant hole (e.g., an inlet hole) 210 located on the first peripheral side of the frame 202 to the other reactant hole (e.g., an outlet hole) 210 on the opposite second peripheral side of the frame 202.

[0038] As shown in Figure 4B, the reactant-side upper surface of the frame 202 includes a planar peripheral sealing surface 204 extending over the periphery of the interconnect 200, and a recessed sealing surface 206 extending along the mutually opposing third and fourth peripheral edges of the interconnect 200 between the reactant field 220 and the peripheral sealing surface 204. In particular, the peripheral sealing surface 204 can be a planar surface surrounding the reactant hole 210 and the reactant field 220. The recessed sealing surface 206 can be a surface that is on the same plane as the peripheral sealing surface 204 and is concave relative to the peripheral sealing surface 204. For example, the recessed sealing surface 206 can be a recess with a depth of approximately 0.2 mm to approximately 1 mm, for example, approximately 0.3 mm to approximately 0.7 mm, or approximately 0.4 mm to approximately 0.6 mm relative to the plane of the peripheral sealing surface 204. In other words, the height of the side walls 205 (e.g., nest side walls 205) of the frame 202 that extends vertically to connect to the recessed sealing surface 206 and the peripheral sealing surface 204 can be within the above range. The side walls 205, the recessed sealing surface 206, and the tops of the ribs 224 can at least partially define a cell nest 208 configured to house an electrochemical cell. This will be described later in relation to Figures 6A and 6B.

[0039] Referring to Figure 4C, the air side of the interconnect 200 may comprise an air field (i.e., an airflow field) 230 positioned between the reactant holes 210. The air field 230 may comprise an air channel 232, an air rib 234 separating the air channel 232, and an air-side recess 236. The air-side recess 236 may be positioned on the third and fourth peripheral edges of the interconnect 200 and may extend between the reactant holes 210. Thus, the interconnect 200 is manifolded externally for air.

[0040] The air side of the interconnect 200 may also include an annular sealing surface 212 surrounding the reactant hole 210. The annular sealing surface 212 may be coplanar with the top of the rib 234. The air-side recess 236 may be coplanar with the bottom end of the air channel 232. In various embodiments, the width of the air-side recess 236 (e.g., the distance between the end of the air rib 234 and the adjacent edge of the interconnect 200) may range from about 5 mm to about 15 mm, for example, about 5 mm to about 12 mm, or about 8 mm to 10 mm.

[0041] Air can flow through the air channel 232 from one air-side recess 236 to the other air-side recess 236. Thus, air and reactants can flow across the interconnect 200 in a substantially perpendicular direction. As used herein, substantially perpendicular includes not only perpendicular but also a range of ±15 degrees from perpendicular. Thus, the interconnect 200 can be referred to as having a cross-flow configuration.

[0042] When the air field 230 is used in a solid oxide type electrochemical cell stack, it may be exposed to high-temperature air. Therefore, the air field 230 may include a conductive protective coating to protect the air field 230 of the interconnect 200 from corrosion and / or oxidation. In some embodiments, the protective coating may include lanthanum strontium manganate and / or manganese cobalt oxide spinel material. In other embodiments, the protective coating includes a metal oxide layer formed in situ on the interconnect 200 by oxidation.

[0043] Figures 5A to 5D are plan views showing the assembly of unit cells in an electrochemical cell stack according to various embodiments of the present disclosure. Figure 6A is a perspective view of a portion P of Figure 5D, Figure 6B is a cross-sectional view along line L1 in Figure 5D, and Figure 6C is a cross-sectional view along line L2 in Figure 5D.

[0044] Referring to Figures 4A and 5A, the edge seal 250 and the recess seal 252 can be formed by distributing a glass or glass-ceramic sealing material on the reactant side of the first interconnect 200. In particular, the sealing material can be distributed on the peripheral sealing surface 204 around the peripheral edge of the reactant hole 210 to form a generally C-shaped edge seal 250, and the sealing material can be distributed on the recess sealing surface 206 to form a generally linear recess seal 252.

[0045] Referring to Figures 4A, 5A, and 5B, the compliant contact layer 150 is positioned on the reactant ribs 224 of the reactant field 220 within the cell nest 208. An electrochemical cell 100, such as a RESE cell, is then positioned at least partially on the compliant contact layer 150 within the cell nest 208 of the first interconnect 200. In particular, the cell 100 can be positioned such that the reactant electrode 130 faces the compliant contact layer 150 and the reactant field 220, while the air electrode 140 does not face the reactant field 220. Opposing edges of the cell 100 can be positioned on the recessed seal 252. The cell 100 can be positioned on the first interconnect 200 before the seals 250, 252 are cured and / or sintered (e.g., while the sealant is in a "wet" state). The resulting structure can be compressed by applying pressure to the cell 100, thereby causing the recessed seal 252 to flow between the side of the cell 100 and the side wall 205 of the cell nest 208 extending from the recessed sealing surface 206. In some embodiments, the sealing material can be cured after compression, for example, using heat and / or ultraviolet irradiation.

[0046] Referring to Figures 4C and 5C, the annular seal 254 can be formed by distributing a glass or glass-ceramic sealing material on the air side of the second interconnect 200'. In particular, the sealing material can be distributed on the annular sealing surface 212 of the interconnect 200' such that the annular seal 254 surrounds the reactant hole 210.

[0047] Referring to Figures 5D and 6A, the second interconnect 200' can be positioned with the air side down on the structure of the first interconnect 200 and cell 100 shown in Figure 5B to form a unit cell 300 (see Figures 6B and 6C). The annular seal 254 may overlap the edge seal 250 and a portion of the reactant electrode 130. The annular seal 254 may also extend over a portion of the recess seal 252. In some embodiments, the edge seal 250 and the annular seal 254 can be fused to increase the thickness of the portion of the annular seal 254 that overlaps the peripheral sealing surface 204.

[0048] As shown in Figures 6A to 6C, the recessed seal 252 can bring the recessed sealing surface 206 into contact with the side wall 205 that extends vertically from the horizontal recessed sealing surface 206. A compliant contact layer 150 can be placed between the cell 100 and the first interconnect 200. In particular, the contact layer 150 can be a nickel mesh that brings the tops of the reactant ribs 224 into contact with the reactant electrodes 130. The reactant holes 210 can be aligned to form a stacked reactant manifold 218.

[0049] The top of the reactant rib 224, the recessed sealing surface 206, and the side wall 205 of the frame 202 connecting the recessed sealing surface 206 to the peripheral sealing surface 204 can define the cell nest 208 at least partially. The cell nest 208 can be configured to accommodate the recessed seal 252, the contact layer 150, and at least a portion of the cell 100. Thus, the cell 100 can be located at least partially (e.g., partially or completely) within the cell nest 208 of the interconnect 200, and the overall thickness of the unit cell 300 can be reduced compared to when the bottom of the cell 100 is located on the peripheral sealing surface 204.

[0050] As shown in Figure 6B, the horizontal portion 252H of the recessed seal 252 can be located between the cell 100 and the recessed seal surface 206 of the interconnect 200, and the vertical portion 252V of the recessed seal can be located between the edge of the cell 100 and the side wall 205 of the cell nest 208. The horizontal portion 252H of the recessed seal 252 can have a thickness within ±20 percent of the thickness of the compliant contact layer 150, for example, 80 percent to 120 percent, in particular 95 percent to 105 percent, so that the top of the electrolyte 120 of the cell is at or slightly above the height of the peripheral seal surface 204, ensuring contact between the air electrode 140 and the air rib 234. This configuration improves the flatness of the unit cell 300 and the sealing of the reactants, preventing the reactants from flowing from the reactant field 220 to the air electrode 140 of the cell 100.

[0051] In some embodiments, after assembling the unit cells 300 as a stack, the sealing material can be sintered, reflowed, and / or cured. For example, the overlapping portions of the annular seal 254 and the edge seal 250 can be integrated to form a single, undivided seal structure.

[0052] Figure 7 shows the air side of an alternative interconnect 200a according to an alternative embodiment of the present disclosure. Interconnect 200a may be similar to interconnect 200. Therefore, only the differences from interconnect 200 will be discussed in detail.

[0053] Referring to Figure 7, the air ribs 234 of interconnect 200a extend into the air-side recess 236. However, the height of the air ribs 234 is reduced within the air-side recess 236 compared to the height of the air ribs 234 in the rest of the air field 230. The air-side recess 236 can also extend into the annular seal surface 212 by passing the air ribs 234 laterally in a direction substantially perpendicular to the longitudinal direction of the air ribs 234, thereby reducing the area of ​​the annular seal surface 212. The reduction in the height of the air ribs 234 can be 50 to 250 microns, for example, 100 to 200 microns. The recess depth of the air-side recess 236 can be 100 to 500 microns, for example, 200 to 400 microns. The reactant side of interconnect 200a may be the same as the reactant side of interconnect 200.

[0054] Figures 8A to 8D are plan views showing the assembly of unit cell 302 of an electrochemical cell stack according to an alternative embodiment of the present disclosure, and Figure 8E is a cross-sectional view along line L1 in Figure 8D. Unit cell 302 may be similar to unit cell 300. Therefore, only the differences from unit cell 300 will be discussed in detail.

[0055] Referring to Figure 8A, the structure shown in Figure 5D can be formed by arranging the electrochemical cell 100 and the sealing material on the first interconnect 200a. Referring to Figures 7 and 8B, the metal foil 260 can be placed on the air-side recess 236 of the second interconnect 200a'. The metal foil 260 can be formed from a metal or a metal alloy, which may be oxidized during high-temperature annealing in an oxidizing atmosphere to form a dielectric film such as an alumina film on its surface. For example, the metal foil 260 can be formed from an alumina-forming material that forms an alumina surface film (i.e., a dielectric film during high-temperature annealing in an oxidizing atmosphere). In one embodiment, the metal foil 260 includes an FeCrAlY alloy. For example, one suitable FeCrAlY alloy is available from Engineered Materials Solutions under the trademark name DuraFoil®. The FeCrAlY alloy may contain 19% to 22% by weight of Cr, 5% to 6% by weight of Al, 0.05% to 0.15% by weight of Y, and the remainder being Fe and unavoidable impurities. Optionally, the FeCrAlY alloy may additionally contain 0.03% to 0.1% by weight of Zr. By converting the surface of the FeCrAlY alloy foil 260 to an alumina surface film, electrical short circuits can be beneficially reduced and / or prevented, and the amount of chromium evaporated when exposed to air during cell operation can be greatly reduced. However, any other suitable foil material may be used.

[0056] Referring to Figure 8C, a glass or glass-ceramic sealing material can be positioned on the air side of the second interconnect 200a' to form the annular seal 254 and the foil seal 256. In particular, the sealing material used to form the foil seal 256 can extend across the metal foil 260 to connect the annular seal 254. The foil seal 256 is located on the reactant side of the metal foil 260.

[0057] As shown in Figures 8D and 8E, the second interconnect 200a' can be positioned with its air side down on the structure of the first interconnect 200a and cell 100 shown in Figure 8A to form a unit cell 302. For clarity, the second interconnect 200a' is transparent in Figure 8D. The annular seal 254 may overlap the edge seal 250 and may overlap a portion of the cell 100. The annular seal 254 may also extend over a portion of the recess seal 252. The metal foil 260 may be located within the air-side recess 236 of the second interconnect 200a'.

[0058] The sealing material can be redistributed by applying heat and / or pressure to the unit cell 302. In particular, by reflowing the foil seal 256, the metal foil 260 can be sealed to the peripheral sealing surface 204 of the first interconnect 200a, the recessed seal 252, and the upper surface of the cell 100 (for example, the upper surface of the reactant electrode 130).

[0059] In alternative embodiments, the sealing material may not be applied to the metal foil 260, as shown in Figure 8C. For example, Figures 9A and 9B are cross-sectional views illustrating alternative methods for sealing the metal foil 260 according to various embodiments of the present disclosure.

[0060] As shown in Figure 9A, a larger amount of sealant can be used to form the recessed seal 252 applied to the cell nest sidewall 205. When the cell 100 is assembled onto the first interconnect 200a, a bulge 252B may be formed in the sealant that extends beyond the cell 100.

[0061] As shown in Figure 9B, when heat and / or pressure is applied to the metal foil 260, the sealing material can be compressed between the metal foil 260 and the interconnect 200a, thereby the resulting recessed seal 252 bonds the metal foil 260 to the peripheral sealing surface 204 of the interconnect 200a and the upper surface of the cell 100.

[0062] Figure 10A is a reactant-side plan view of an alternative interconnect 200b according to another alternative embodiment of the present disclosure, and Figure 10B is a cross-sectional view along line L1 in Figure 10A. Interconnect 200b may be similar to interconnects 200 and 200a. Therefore, only the differences from interconnects 200 and 200a will be discussed in detail.

[0063] Referring to Figures 10A and 10B, instead of forming a recessed sealing surface 206 by making a portion of the frame 202 concave, a flexible gasket 270 can be placed on the reactant side of the frame 202 to form the recessed sealing surface 206. The side walls 275 of the gasket 270, the recessed sealing surface 206, and the tops of the ribs 224 can at least partially define a cell nest 208 configured to house an electrochemical cell. The interconnect 200b may have an air side as shown in Figure 4C or Figure 7.

[0064] Gasket 270 can be formed from any suitable compliant material. For example, gasket 270 can be formed from a compliant metallic silicate clay material such as Thermiculite® 866 or 870, available from Flexitallic US LLC. Thermiculite® is a high-temperature sealant designed for SOFC applications. This material is based on the mineral vermiculite and contains no organic binders or any other organic components. Vermiculite is a naturally occurring layered silicate mineral formed by hydrothermal metamorphism of biotite and phlogopite mica. This mineral retains the thermal and chemical durability of mica and maintains electrical insulation. Like mica, vermiculite arises as plate-like particles consisting of thousands of individual platelets stacked together, each having a thickness in the nanometer range. When these particles are exfoliated, they can produce dispersions of individual platelets that are separated from each other. These platelets are highly flexible and conform to the surfaces of other particles, binding them together. This bonding action makes it possible to manufacture sheet materials without organic binders. Therefore, Thermiculite consists only of chemically exfoliated vermiculite and a second filler material. The second filler material is talc, also known as steatite or soapstone. The second filler material is relatively soft. Thus, by combining chemically exfoliated vermiculite and steatite, a very soft and flexible material is obtained while retaining all the chemical and thermal durability typically associated with mica. Due to the softness of the material and the orientation of the platelets, the material can be compressed with very little load, resulting in a compressible material that provides a very intricate, impedimentary pathway for gases permeating the material in the plane of the sheet or perpendicular to that plane. Therefore, this material has sealing properties.

[0065] Gasket 270 can have a thickness of approximately 0.20 mm to 0.90 mm, for example, in the range of approximately 0.28 mm to 0.68 mm, approximately 0.38 mm to 0.58 mm, or approximately 0.48 mm. By using a flexible gasket, the overall thickness of interconnect 200b can be reduced compared to interconnects 200 and 200a. Therefore, interconnect 200b can be manufactured more easily.

[0066] Figure 10C is a side cross-sectional view of unit cell 300a of an electrochemical cell stack including interconnect 200b and a second interconnect 200b'. Both interconnect 200b and the second interconnect 200b' include a flexible gasket 270. Unit cell 300a differs from unit cell 300 shown in Figure 6B in the presence of the flexible gasket 270. Therefore, interconnect 200b can be used in conjunction with any of the seals described above.

[0067] Figure 10D is a side cross-sectional view of unit cell 302a of an electrochemical cell stack including interconnect 200b and a second interconnect 200b'. Both interconnect 200b and the second interconnect 200b' include a flexible gasket 270. Unit cell 302a differs from unit cell 302 shown in Figure 8E in that it includes the flexible gasket 270. Therefore, interconnect 200b can be used in conjunction with metal foil 260.

[0068] Figure 11A is a reactant-side plan view of an alternative interconnect 400 according to various embodiments of the present disclosure, Figure 11B is an air-side plan view of the interconnect 400, and Figure 11C is a plan view showing a unit cell including an alternative interconnect 400 and an electrochemical cell 100.

[0069] Referring to Figure 11A, the alternative interconnect 400 may include a counterflow or coflow interconnect in which reactant ribs 424 and air ribs 434 extend parallel to each other. The reactant side of the interconnect 400 may include a frame 402 extending over the periphery of the interconnect 400. In one embodiment, the frame 402 may be an integral part of the interconnect 400, similar to the frame 202 described above. In another embodiment, the frame 402 may be a flexible gasket positioned on the interconnect 400, as described above with reference to Figures 10A and 10B.

[0070] The interconnect 400 may include reactant holes 410 positioned adjacent to the first and second opposing peripheral edges of the interconnect 400. The reactant holes 410 may be through holes penetrating the interconnect 400 in the thickness direction. The reactant side of the interconnect 400 may include a reactant manifold 411 which includes a flat and concave portion of the interconnect 400 that is concave relative to the reactant ribs 424 and the frame 402.

[0071] The reactant field 420 extends between the reactant manifold 411 and the reactant holes 410. The reactant field 420 may comprise reactant channels 422 and reactant ribs 424 separating the reactant channels 422. The reactant (e.g., fuel or vapor) can flow through the reactant channels 422, across the reactant field 420, from one reactant hole (e.g., inlet hole) 410 to the other reactant hole (e.g., outlet hole) 410.

[0072] The cell nest 408 can be defined at least partially by the side walls of the frame 402 and the tops of the reactant ribs 424. The cell nest 408 is configured to house the electrochemical cell 100. An edge seal 450, including glass or glass-ceramic material, can be placed inside the frame 402. The edge seal 450 can surround the reactant manifold 411 and the reactant field 420.

[0073] Referring to Figure 11B, the air side of the interconnect 400 may include an air field 430. The air field 430 may include an air channel 432 and an air rib 434 separating the air channel 432. The air side of the interconnect 400 may also include a raised annular sealing surface 412 surrounding the reactant hole 410 and a raised strip sealing surface 446 located on the opposing sides of the air field 430 (i.e., the third and fourth edges of the interconnect 400). The annular seal 454 is located on the annular sealing surface 412 and surrounds the reactant hole 410. The strip seal 456 may be located on the strip sealing surface 446.

[0074] Air can flow through the air channels 432 from the opposing peripheral edges of the interconnect 400 (e.g., the first edge and the second edge). Thus, the air and reactants can flow substantially parallel or in opposing directions on the opposing sides of the interconnect 400.

[0075] Referring to Figure 11C, the unit cell 500 may include an electrochemical cell 100, such as a RESE cell, located between the first interconnect 400 and the second interconnect 400' within the cell nest 408. The reactant side of cell 100 can be sealed to the reactant side of the first interconnect 400 by an edge seal 450. The strip seal surface 446 of the second interconnect 400' can be sealed to the frame 402 of the first interconnect 400 by a strip seal 456. Thus, the opposing ends of the air field 430 of the second interconnect 400' are exposed to the ambient air in the electrochemical cell system, supplying airflow to cell 100.

[0076] Figure 12A is a perspective view showing the reactant-side (e.g., fuel-side) sheet 200rs of an alternative interconnect 200c according to various embodiments of the present disclosure; Figure 12B is a perspective view showing the air-side sheet 200as of an alternative interconnect 200c according to various embodiments of the present disclosure; Figure 12C shows the process of forming an alternative interconnect 200c using the sheets 200rs and 200as of Figures 12A and 12B; and Figure 12D is a perspective view of the completed alternative interconnect 200c.

[0077] Referring to Figures 12A and 12B, sheets 200rs and 200as can be formed by any suitable sheet metal forming method. For example, sheets 200rs and 200as can be formed by stamping sheet metal such as ferritic stainless steel sheets using a stamping process or another similar process. Sheets 200rs and 200as are provided with the reactant holes 210 described above. The reactant holes 210 can be formed by cutting, punching, or any other suitable sheet metal patterning method. The reactant-side sheet 200rs may have a first surface comprising a reactant-side interconnect structure, a reactant field 220, and a cell nest 208, and a substantially flat second surface on the opposite side. The air-side sheet 200as may have a first surface comprising an air-side interconnect structure such as an air field 230, and a substantially flat second surface on the opposite side.

[0078] Referring to Figure 12C, the sheets 200rs and 200as can be joined to each other using any suitable metal joining method such as brazing, welding, or bonding. In one embodiment, the sheets 200rs and 200as can be located on opposite sides of the brazing material 205. The sheets 200rs and 200as can be positioned so that their substantially flat second surfaces are in contact with the brazing material 205. The brazing material 205 can be in the form of a substantially flat sheet having openings 207 corresponding to the reactant holes 210 of the sheets 200rs and 200as. The brazing material 205 can contain any suitable brazing metal or alloy, such as an alloy containing nickel and / or precious metals. The resulting structure can be heated so that the brazing material 205 forms an airtight joint between the reactant-side sheet 200rs and the air-side sheet 200as, thereby producing a completed cross-flow interconnect 200c as shown in Figure 12D. The brazing material 205 remains between the two sheets 200rs and 200as in the completed interconnect.

[0079] In an alternative embodiment, the brazing material 205 may be omitted, and the sheets 200rs and 200as may be directly welded to each other, for example, by laser welding. In another embodiment, the above sheet joining method can also be used to form a counterflow or coflow interconnect 400 as shown in Figures 11A and 11B.

[0080] Figure 13 is an enlarged perspective view showing elements of unit cell 304 of an electrochemical cell stack according to an alternative embodiment of the present disclosure. Unit cell 304 may be similar to unit cells 300 and 302. Therefore, only the differences from unit cells 300 and 302 will be discussed in detail.

[0081] The unit cell 304 may include the joined sheet interconnect 200c shown in Figures 12A to 12D. Furthermore, in this embodiment, instead of the generally C-shaped edge seal 250, the edge seal 250a has a hollow rectangular shape, similar to the gasket 270 shown in Figures 10A and 10B, and can completely enclose the periphery of the reactant-side sheet 200rs of the interconnect 200c. Thus, the edge seal 250a encloses the region including the reactant field 220, the reactant hole 210, and the recess seal 252.

[0082] According to various embodiments, forming an interconnect by joining (e.g., bonding, brazing, welding, etc.) a reactant-side sheet and an air-side sheet significantly reduces the manufacturing cost of the interconnect compared to using more expensive processes such as computer numerical control (CNC) machining, electrical discharge machining (EDM), or 3D printing. In addition, when the interconnect is formed from two sheets, the sheets are not exposed to both fuel and air when used in an electrochemical cell stack. Therefore, corrosion of the interconnect due to the dual atmospheric effect can be reduced and / or prevented.

[0083] The fuel cell and electrolytic cell systems of the embodiments of this disclosure are designed to reduce greenhouse gas emissions and have a positive impact on the climate.

[0084] Any one or more features from any one or more embodiments may be used in any preferred combination with any one or more features from one or more other embodiments. While the foregoing describes particularly preferred embodiments, it will be understood that the present invention is not limited thereto. Those skilled in the art will notice that various modifications can be made to the disclosed embodiments, and that such modifications are intended to be within the scope of the present invention. All publications, patent applications, and patents cited herein are incorporated herein by reference in their entirety.

Claims

1. An interconnect for an electrochemical cell stack, The reactant holes penetrating the interconnect, On the reactant side, A reactant field comprising reactant channels and reactant ribs extending between the reactant holes, A peripheral sealing surface extending over the peripheral edge of the interconnect, A recessed sealing surface is provided, which is positioned on the inner portion of the peripheral sealing surface and on the opposing sides of the reactant field, and is concave relative to the peripheral sealing surface. A nest sidewall connecting the recessed sealing surface to the peripheral sealing surface, wherein the nest sidewall extends substantially perpendicular to the peripheral sealing surface and the recessed sealing surface, and the nest sidewall, the recessed sealing surface, and the top of the reactant rib at least partially define a cell nest configured to house an electrochemical cell, The reactant side comprises, On the opposite side, the air side, An air field is placed between the reactant holes, An annular sealing surface arranged around the reactant hole, The air side comprises, The interconnect comprising the above.

2. The aforementioned air field The air channels between the reactant holes, Air ribs adjacent to the aforementioned air channel, The interconnect according to claim 1, comprising:

3. The interconnect according to claim 2, further comprising air-side recesses disposed on the opposing sides of the air field, wherein the height of the air ribs in the air-side recesses is lower than that in the air field.

4. The interconnect according to claim 2, further comprising air-side recesses disposed on the opposing sides of the air field, wherein the air-side recesses are free from the air ribs, and the air-side recesses are coplanar with the bottom of the air channel in the air field.

5. The interconnect according to claim 2, wherein the reactant channel and the air channel extend in a substantially vertical direction.

6. The interconnect according to claim 2, wherein the reactant channel and the air channel extend substantially parallel to each other.

7. The interconnect according to claim 1, wherein the nest side wall has a height of 0.2 mm to 1 mm.

8. The interconnect according to claim 1, wherein the interconnect comprises a ferritic stainless steel material.

9. The interconnect according to claim 1, wherein the recessed sealing surface is on the same plane as the top of the reactant rib.

10. The interconnect according to claim 1, further comprising a flexible gasket disposed on the reactant side, wherein the gasket forms the peripheral sealing surface and the nest side wall.

11. A unit cell of an electrochemical cell stack, The first interconnect described in claim 1, An electrochemical cell located within the cell nest of the first interconnect, The first interconnect and the second interconnect according to claim 1, which are arranged on the electrochemical cell with the air side facing downwards, The unit cell comprising the above.

12. At least one reactant seal disposed on the peripheral sealing surface, A recessed seal is disposed between the electrochemical cell and both the nest side wall and the recessed sealing surface of the first interconnect, An annular seal disposed between the electrochemical cell and the annular sealing surface of the second interconnect, The unit cell according to claim 11, further comprising the following:

13. The unit cell according to claim 12, further comprising a foil disposed between the second interconnect and the recessed seal.

14. The foil comprises an FeCrAlY alloy having an alumina surface film. The unit cell according to claim 13, wherein the foil overlaps with the air field of the second interconnect and a portion of the electrochemical cell.

15. The unit cell according to claim 11, wherein the first interconnect further comprises a flexible gasket disposed on the reactant side and forming the peripheral sealing surface and the nest side wall.

16. The compliant contact layer is positioned below the electrochemical cell within the cell nest so as to contact the top of the reactant rib and the bottom of the electrochemical cell. The at least one reactant seal, the recess seal, and the annular seal include glass or glass ceramic material. The unit cell according to claim 11, wherein the electrochemical cell includes a solid oxide fuel cell or a solid oxide electrolytic cell.

17. A method for forming unit cells of an electrochemical cell stack, The sealing material is applied to the reactant-side peripheral sealing surface of the first interconnect such that the sealing material at least partially surrounds the reactant holes and reactant field of the first interconnect, The sealing material is placed on the sides of the reactant field that are opposite to each other on the inside of the peripheral sealing surface and applied to a recessed sealing surface that is concave relative to the peripheral sealing surface. The sealing material is applied to a nest sidewall connecting the recessed sealing surface to the peripheral sealing surface, wherein the nest sidewall extends substantially perpendicular to the peripheral sealing surface and the recessed sealing surface, and the nest sidewall, the recessed sealing surface, and the tops of the reactant ribs of the reactant field define the cell nest at least partially. The contact layer is positioned within the cell nest such that the compliant contact layer contacts the tops of the reactant ribs in the reactant field. The cells are arranged on the compliant contact layer within the cell nest such that the opposing ends of the electrochemical cells are in contact with the recessed sealing surface and the sealing material applied to the side wall of the nest, The sealing material is applied to the air-side annular sealing surface of the second interconnect, The second interconnect is positioned on the first interconnect such that the air ribs in the air field of the second interconnect are in contact with the electrochemical cell, Methods that include...

18. The method according to claim 17, wherein the sealing material applied to the annular sealing surface of the second interconnect is in contact with the sealing material applied to the peripheral sealing surface of the first interconnect.

19. Before placing the second interconnect on the first interconnect, The foil is placed on the air-side recess on the air side of the second interconnect, The foil is pressed against the bulging portion of the sealing material applied to the nest side wall that extends beyond the electrochemical cell, compressing the sealing material between the metal foil and the electrochemical cell, and joining the foil to the upper surface of the electrochemical cell. The method according to claim 17, further comprising:

20. Before placing the second interconnect on the first interconnect, The foil is placed on the air-side recess on the air side of the second interconnect, The sealing material is applied to the foil such that the sealing material seals the foil to the electrochemical cell, The method according to claim 17, further comprising:

21. To form at least one of the first interconnect and the second interconnect, A metal sheet is stamped to form a reactant-side sheet having a first surface with a reactant-side structure and a substantially flat second surface on the opposite side. A metal sheet is stamped to form an air-side sheet having a first surface with an air-side structure and a substantially flat second surface on the opposite side. The second surface of the reactant-side sheet and the second surface of the air-side sheet are joined using a brazing or welding process to form the first interconnect or the second interconnect. The method according to claim 17, further comprising being carried out by

22. The aforementioned interconnect is, A reactant-side sheet having a first surface with a reactant-side structure and a substantially flat second surface on the opposite side, An air-side sheet comprising a first surface having an air-side structure and a substantially flat second surface on the opposite side, wherein the second surface of the reactant-side sheet is joined to the second surface of the air-side sheet, The interconnect according to claim 1, comprising:

23. The interconnect according to claim 22, further comprising a brazing material positioned between the second surface of the reactant-side sheet and the second surface of the air-side sheet, wherein the second surface of the reactant-side sheet is brazed to the second surface of the air-side sheet.

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