Solid-state electrochemical cell stack

Abstract

The disclosure set forth relates to an electrochemical cell stack comprising a solid-state electrochemical cell (20), a conductive separator plate (30), and a sealing element (40). The separator plate comprises a relatively recessed support surface (32) for supporting the solid-state electrochemical cell, a contact surface (34) opposite the recessed support surface for contacting an adjacent solid-state electrochemical cell, a central portion (31), and a boundary portion (36) providing a relatively raised top (37) and upstanding sidewalls (38). The sealing element (40) extends between the raised top of the boundary portion and the opposing support surface (39) of the adjacent separator plate. The separation distance between the recessed support surface and the contact surface of the adjacent separator plate, defined by the combined height of the sealing element and the upstanding sidewalls, corresponds to the thickness of the solid-state electrochemical cell.

Description

[Technical Field]

[0001] The present disclosure relates to electrochemical stacks and electrochemical devices including solid-state electrochemical cells, kits of parts for assembly with solid-state electrochemical cells to form electrochemical stacks, methods of manufacturing the parts, and uses of electrochemical stacks. [Background technology]

[0002] Solid oxide cells (SOCs) are electrochemical conversion devices that can generate electricity directly from oxidizing fuels, as in solid oxide fuel cells (SOFCs), or can use electricity and / or heat to generate fuels such as hydrogen (H), carbon monoxide (CO), and / or syngas (a mixture of H and CO) from water (H O) and carbon dioxide (CO), as in solid oxide electrolyzer cells (SOECs). SOCs can be characterized by ceramic-based electrolyte materials that can operate at high temperatures, e.g., 500°C to 850°C. A single SOC can include a fuel electrode layer formed within a porous ceramic to allow fuel to flow toward the electrolyte; an air electrode formed as a thin, porous layer where oxidation and reduction occur; and an electrolyte, a dense layer of ceramic that conducts oxygen ions and is located between the fuel and air electrode. A current collecting layer can be located adjacent to the fuel electrode. SOC stacks can be composed of multiple (typically hundreds) cells, and different SOCs can be connected together in a stack configuration. In a conventional configuration, a repeating unit of a stack configuration may include two separator plates, an SOC cell positioned between the separator plates, a gas manifold for fuel and gas to enter / exit the cell, and a combination of multiple seals and a manifold frame to seal the SOC cell and separator plates together. Unfortunately, the multiple components that make up an SOC stack can make assembly complex and / or cost-ineffective. Furthermore, operating an SOC stack under pressure can be difficult, requiring, for example, the use of a pressure vessel.

[0003] WO 2022 / 043087 A1 describes a stack of so-called metal support cells, which in combination with an external skirt form part of a manifold.

[0004] EP 3846265 A1 describes a fuel cell interconnect assembly. The disclosed stack configuration comprises interconnect plates that are connected via joints with both the cathode and anode interfaces and require seals on each side.

[0005] However, there remains a need for SOC stacks with reduced complexity, reduced number of parts per repeating unit, and / or improved flexibility in terms of operation under pressurized conditions. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to eliminate or at least partially alleviate the limitations associated with known stack assemblies. Alternatively or additionally, the present invention aims to provide an assembly having a reduced number of parts per repeating unit and / or having an internal manifold and / or being operable without the need for an external pressure vessel. [Means for solving the problem]

[0007] An embodiment of the present disclosure relates to an electrochemical stack. The stack is composed of a cell unit disposed between a first adjacent cell unit and a second adjacent cell unit. The stack can be used for particular advantages in electrochemical devices. During use, the stacked units are typically held in compression, for example, by applying opposing forces to the end plates of the stack.

[0008] Each cell unit comprises at least one solid-state electrochemical cell, a conductive separator plate, and an electrically insulating sealing element. As used herein, a solid-state electrochemical cell can be an electrochemical cell having a layered solid electrolyte between opposing solid or semi-solid (e.g., gel) electrode layers. A solid-state electrochemical cell can be an electrochemical cell having a layered solid electrolyte between opposing porous solid electrolyte layers. As will become apparent from the following specification, each cell unit typically comprises only one of a separator plate and a sealing element. This greatly simplifies manufacturing and assembly while providing sufficient sealing in terms of both electrical insulation and process gas restriction.

[0009] Preferably, the stack includes electrode-supported cells that rely on the electrode material for structural support. Typically, the electrolyte is relatively thin and is deposited on the electrodes. The electrodes may be porous and may provide mechanical support for the cell structure, and the electrolyte layer may assist in ionic conduction between the two electrodes.

[0010] The solid-state electrochemical cell may be a solid oxide cell. The solid-state electrochemical cell is provided as a layer stack, preferably a self-supporting layer stack, including a first electrode layer and a second counter-electrode layer separated by a solid electrolyte layer. A solid-state electrochemical cell, e.g., a solid oxide cell, can be understood as an electrochemical conversion device. The device can be used to generate electricity in a so-called fuel cell mode or to chemically convert a feedstock into a product in a so-called electrolyzer mode. The first electrode layer, also called the fuel electrode, is typically contained in a porous ceramic, allowing the fuel (reagent) to flow toward the electrolyte. The second electrode (counter electrode), also called the air electrode or oxygen electrode, is generally deposited as a porous layer where oxygen reduction occurs. The electrolyte is located between the fuel and air electrode layers and generally consists of a dense layer of ceramic that conducts oxygen ions. Advantageously, a solid-state electrochemical cell (e.g., a solid oxide cell) can be a free-standing, self-supporting cell element. Alternatively, or in addition, the layer stack may be provided on a porous carrier, preferably a conductive porous substrate, for example a current collector such as a metal or other conductive mesh.

[0011] The conductive separator plate extends between a solid electrochemical cell (e.g., a solid oxide cell) of a first adjacent cell unit. The separator plate comprises a central portion and a boundary portion extending around the central portion. The central portion includes: i) a relatively recessed bottom surface; and ii) an outward-facing surface opposite the recessed bottom surface. The recessed bottom surface defines a contact surface that supports the solid electrochemical cell (e.g., a solid oxide cell). The outward-facing surface contacts the solid electrochemical cell (e.g., a solid oxide cell) of the first adjacent cell unit. The boundary portion provides upstanding sidewalls that extend circumferentially from the recessed bottom surface and terminate at a relatively raised top surface.

[0012] The sealing element extends between the conductive separator plates of the second adjacent cell units, and in particular, the sealing portion is dimensioned to extend between the raised top surface of the interface portion and the opposing bottom surface of the interface portion of the separator plate of the second adjacent cell unit.

[0013] The separation distance between the recessed bottom surface of a separator plate and the outward facing surface of a second adjacent separator plate, as defined by the combined height of the sealing element and the upstanding sidewall, corresponds to the thickness of the solid electrochemical cell (solid oxide cell).

[0014] Thus, the present disclosure provides stacks and corresponding devices in which each cell is bounded by a cavity bounded longitudinally by the contact surfaces of adjacent separator plates and laterally by upstanding sidewalls of relatively raised boundaries in combination with sealing elements. By matching the stack dimensions with the cell size, sufficient sealing can be achieved both in terms of providing sufficient confinement of process gases within the stack and electrical insulation between adjacent separator plates, allowing operation of the electrochemical device without the need to place the cells / stack in an external pressure vessel.

[0015] In a preferred embodiment, the sealing element extends inward from the raised upper surface of the boundary portion, through the upstanding sidewall, and forms an overlap with the free upper surface of the solid electrolyte layer. Having the sealing element overlap the solid electrolyte advantageously mitigates leakage of ingredients (e.g., fuel to air) through the gap between the sidewall and the solid oxide cell, i.e., from the "fuel" side or compartment to the "air" side or compartment, or vice versa, thereby improving overall efficiency and / or safety during use. The sealing element preferably forms a circumferential overlap with the solid electrolyte layer. The overlap advantageously reduces the need for manufacturing precision to match the recess and cell shapes and / or for auxiliary lateral sealing between the sidewall and the cell. It will be appreciated that at least one of the fuel and air electrode layers is configured to leave a peripheral edge portion of the electrolyte layer uncovered for direct contact with the sealing element. The overlap with the free upper surface of the solid electrolyte can be achieved in several ways, for example, by providing a sealing element with a correspondingly sized protruding or recessed portion. In a preferred embodiment, the overlay is achieved by aligning the free upper surface of the solid electrolyte layer with the upper surface of the boundary portion. The thickness of the sealing element can cover the remaining distance to the adjacent separator plate. The height of the upright sidewall (depth of the recess) can be matched to the thickness of the cell up to and including the solid electrolyte layer, simplifying the manufacturing of the part.

[0016] In a highly preferred embodiment, the central and border portions of each separator plate are part of a monolithic metal plate. Preferably, each cell unit includes no more than a single separator plate and sealing element. Forming the plating from a single monolithic body and / or using only a single sealing element further mitigates potential leaks of process supplies and simplifies stack assembly by limiting the number of contact interfaces between components.

[0017] In another or additional preferred embodiment, the electrochemical stack further comprises means for providing fluid (e.g., gas) access to a fuel on opposite sides of the solid oxide electrochemical cell, respectively. For example, the electrochemical stack may comprise a first channel structure and a second channel structure, the additional first channel structure. The first channel structure is configured to provide fluid access (e.g., fuel feedstock) to an electrode or counter-electrode layer of a solid electrochemical cell (e.g., a solid oxide cell). The second channel structure is configured to provide fluid access (e.g., air supply) to the other of the electrode and counter-electrode layer. The channel structures may be provided by any method known in the art, such as holes or conduits extending through the sidewalls and opening at positions within the cavity corresponding to the positions of the respective porous anode or cathode layers. Thus, in one embodiment, the second channel structure provides fluid access (e.g., fuel) between the separator plate and the electrode layer of the solid oxide cell, while the first channel structure provides fluid access (e.g., air) between the counter electrode layer of the solid oxide cell and the adjacent separator plate, or vice versa (e.g., when the solid oxide cells are oriented in opposite directions).

[0018] Preferably, the first and second channel structures extend between the first pair and the respective second pair of openings at the interface, spanning the thickness of the interface. Advantageously, the openings extend longitudinally along the stack and are aligned with openings in adjacent plates that form internal inlet / outlet headers providing fluid (oxidant-fuel) access to / from the anode / cathode sides of each solid oxide cell.

[0019] In another or further preferred embodiment, the first and second channel structures comprise a first groove structure formed in the recessed bottom surface and extending between the first pair of openings, and a second groove structure formed in the outward-facing surface extending between the second pair of openings, respectively. The groove structure forms a plurality of open channels between the ridges, whereby the upper surfaces of the ridges form contact surfaces for supporting the solid oxide cells, thereby allowing fluid transport to and from the cells. The open channels on the opposing faces of each plate can be oriented as known in the art. In a preferred embodiment, the channels are oriented approximately parallel. Parallel channels allow the device to operate with fuel and oxidant flows in countercurrent or cocurrent operation. When aligning the channels, it may be preferable for the ridges on the opposing faces of each plate to be offset relative to each other. Alternatively, or in addition, the channels may be configured for crossflow (e.g., perpendicular). An offset or cross configuration may advantageously mitigate the formation of stress fields / lines within the cells.

[0020] In some preferred embodiments, the electrochemical stack further comprises an inlay plate disposed at a targeted location over the groove structure along a portion of its path between the opening and the region supporting the cell, the inlay preferably having a thickness that matches the height level of the raised top surface to within ±5%, preferably ±1%. The provision of the inlay advantageously reduces the gap between the plate and the seal, mitigating the formation of areas of increased stress when a compressive force is applied to the stack.

[0021] As described in more detail herein, the recesses, rims, openings, and groove structures can all be formed by machining a single plate, including, but not limited to, drilling and milling, cutting a metal plate. If provided, the inlay can be machined, for example, to be flush with the plate when placed at the target location.

[0022] In some embodiments, at least a portion of the top of the ridges in contact with the solid oxide cell is rounded. Rounding the top of the ridges increases the rate of gas transfer to and from the cell.

[0023] The sealing element is preferably provided as a compressible seal, preferably a ceramic compressible seal capable of withstanding operating temperatures in the range of at least 500-700°C, preferably up to 850°C or 900°C. The compressible seal provides a thickness under operating compression to seal the space between adjacent plates and a larger transient thickness. Suitable materials for compressible seals are generally known in the art. In a preferred embodiment, the seal is a ceramic compressible seal, preferably a vermiculite-based seal. Preferably, the seal is embodied as a multi-layer seal having a rigid core, preferably a metal core, sandwiched between electrically insulating compressible seal layers. The metal core advantageously provides increased rigidity / structural stiffness to the sealing element, for example, during its manufacture, storage, and / or stack assembly.

[0024] In some embodiments, the electrochemical stack further comprises a porous current collector layer disposed along the outer surface of one or more of the electrode and counter-electrode layers. The current collector, e.g., a metal mesh, can improve current transfer between the plate and the electrode. The porous current collector layer may also be a carrier substrate for the stack of functional layers of the cell. When provided on the fuel side, the porous current collector layer may be a metal grid / mesh structure, e.g., Ni-based, or otherwise made of a conductive material (e.g., carbon-based). When provided on the oxidant (e.g., air) side, the structure is preferably formed of a composition that is resistant / inert to oxidation by oxygen under process conditions (e.g., Au, Pt, or a protective layer-coated structure, e.g., a coated ferritic steel mesh).

[0025] The present disclosure further relates to an electrochemical device, comprising a stack according to any one of the preceding claims and end plates disposed along opposite ends of the stack. During use, a compressive force can be applied to the end plates. As mentioned above, a pressure vessel surrounding the stack is not required, but may be provided. For example, raw materials may be provided directly from respective connectors provided in the end plates to an internal gas header consisting of aligned openings.

[0026] In a preferred embodiment, one or more, preferably all, cell units comprise at least two solid oxide cells, e.g., two, three, four, or more solid oxide cells. The cells may be arranged in an array (e.g., a 2x2 array). It should be understood that the separator plates are adjusted accordingly, e.g., to include corresponding recessed areas for accommodating the cells. A plurality, e.g., an array, can advantageously cover a larger surface area than a single cell. The use of multiple cells, as opposed to a single, larger cell having the same area, simplifies cell fabrication. The use of multiple cells can further limit the total height of the stack assembly for a given application (at the expense of a relatively limited increase in lateral dimensions). The use of multiple cells can further improve conversion (of fuel and / or oxidant) within the layers of the stack.

[0027] The present disclosure further relates to methods of manufacturing the electrochemical stacks disclosed herein. 1. A method comprising: providing: a) a solid electrolyte cell comprising an electrode layer and a counter electrode layer separated by a solid electrolyte layer; b) an electrically conductive separator plate as disclosed herein for extending between the solid oxide cell and the solid oxide cell of a first adjacent cell unit, the separator plate comprising: i) a relatively recessed bottom surface for contacting the solid oxide cell; and ii) a central portion providing, opposite the inwardly facing surface, an outwardly facing surface for contacting the solid oxide cell of the first adjacent cell unit, and a border portion providing a relatively raised top surface and upright sidewalls extending circumferentially from the recessed bottom surface; and c) a sealing element as disclosed herein configured to extend between a top surface of the border portion and a bottom surface of the border portion of the electrically conductive separator plate of a second adjacent cell unit, the combined height of the sealing element and the sidewalls corresponding to a thickness of the solid oxide cell;

[0028] It will be appreciated that the method employs a relatively simple pick and place step to assemble the stack from prefabricated parts. To facilitate alignment, each part may be provided with alignment means, such as drilling, pins, etc. Because the parts are held in compression, no separate welding or gluing steps are required. The stack can therefore be relatively easily disassembled, for example for maintenance purposes.

[0029] The present disclosure further relates to components for assembly of stacks / devices comprising stacks. In one embodiment, a kit of components for assembly of an electrochemical stack as disclosed herein is provided. The kit includes an electrically conductive separator plate and a sealing element as disclosed herein.

[0030] The separator plate comprises at least: i) a relatively recessed bottom surface with a first cell support area configured to receive solid oxide cells; and ii) a central portion opposite the recessed bottom surface providing an outwardly facing surface with a second cell support area configured to contact the solid oxide cells of a first adjacent cell unit; and a border central portion providing a relatively raised top surface and upstanding sidewalls extending circumferentially from the recessed bottom surface. A correspondingly configured sealing element extends at least between the raised top surface of the border portion and the recessed bottom surface of the border portion of the conductive separator plate of a second adjacent cell unit, wherein the sealing element and upstanding sidewalls are configured to provide a separation distance corresponding to the thickness of the solid oxide cells between the first cell support area of ​​the separator plate and the second cell support area of ​​the second adjacent separator plate. In a preferred embodiment, the kit further comprises an inlay plate as disclosed herein. The sealing element may be a multi-layer seal as disclosed herein.

[0031] It will be understood that the kit may include a plurality of these components, e.g., 10, 100, or more. Similarly, it will be understood that the kit may further include one or more of the half end plates disclosed herein and / or a manual containing instructions for assembling / disassembling the stack. The kit may further include a corresponding number of solid-state electrochemical cells, e.g., solid oxide cells disclosed herein.

[0032] The present disclosure further relates to a method of manufacturing a separator plate as defined herein. The method includes machining (e.g., milling) a central portion of an essentially flat metal base plate to form a recessed bottom surface configured to receive solid oxide cells, leaving a relatively raised border portion around the central portion. The method may further include machining, preferably with the same tool, a first groove structure in the recessed bottom surface to form a first channel structure extending between a first pair of openings in the border portion, and providing (e.g., carving or otherwise machining) a second groove structure formed in an outward-facing surface of the separator plate opposite the recessed bottom surface to form a second channel structure extending between a second pair of openings in the border portion. It will be understood that the method may also include providing an inlay plate as disclosed herein.

[0033] The present disclosure further relates to the use of the electrochemical stacks or devices disclosed herein for the generation of electrical power or for the production of hydrogen and / or syngas and carbon monoxide. [Brief explanation of the drawings]

[0034] These and other features, aspects, and advantages of the devices, systems, and methods of the present disclosure will become better understood from the following specification, appended claims, and accompanying drawings. [Figure 1A] 1 provides a schematic diagram of operating a solid oxide cell. [Figure 1B] 1 provides a schematic diagram of operating a solid oxide cell. [Figure 2] 1 provides a cross-sectional side view of a stack repeat unit including a solid oxide cell, a separator plate, and a seal. [Figure 3] 1 illustrates an embodiment of a solid oxide cell. [Figure 4A] 1 provides an exploded perspective top view of an electrochemical stack. [Figure 4B] 1 provides an exploded perspective bottom view of an electrochemical stack. [Figure 5A] 1 provides a perspective view of an electrochemical stack. [Figure 5B] 1 provides a top view of the electrochemical stack. [Figure 6] 6A, 6B, and 6C provide cross-sectional side detail views of the electrochemical stack in the header region. [Figure 7] 7A and 7B provide cross-sectional side views of the electrochemical stack in the active area. [Figure 8A] 1 illustrates an embodiment of a sealing element. [Figure 8B] 1 illustrates an embodiment of an electrochemical device. [Figure 8C] 1 provides a top view of an electrochemical device. [Figure 9A] Provides photographs of electrochemical device components. [Figure 9B] Provides photographs of electrochemical device components. [Figure 9C] 1 provides a photograph of the assembled electrochemical device in use. [Figure 10] 1 illustrates an embodiment of an assembly of an electrochemical device. [Figure 11] 1 illustrates an embodiment of an assembly of an electrochemical device. [Figure 12A] 1 provides a perspective view of a plate configured to receive a plurality of solid oxide cells and a plate partially populated with corresponding cells. [Figure 12B] 1 provides a perspective view of a plate configured to receive a plurality of solid oxide cells and a plate partially populated with corresponding cells. DETAILED DESCRIPTION OF THE INVENTION

[0035] The terminology used to describe particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. The term "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and / or "comprising" specify the presence of the stated features but do not exclude the presence or addition of one or more other features. Unless otherwise specified, it will be further understood that when a particular step of a method is referred to as following another step, it may directly follow the other step described above, or that one or more intermediate steps may be performed prior to performing the particular step. Similarly, when a connection between structures or components is described, it will be understood that this connection may be established directly or through intermediate structures or components, unless otherwise specified.

[0036] The present invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic illustrations and / or cross-sectional views of possibly idealized embodiments and intermediate structures of the invention. In the specification and drawings, like numerals refer to like elements throughout. Relative terms, and derivatives thereof, should be construed to refer to an orientation as described below or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation, unless specifically specified.

[0037] An SOC operated in fuel cell mode is also called a solid oxide fuel cell (SOFC). An SOC operated in electrolyzer mode is also called a solid oxide electrolyzer cell (SOEC). The cathode is the electrode of the electrochemical cell where the reduction takes place. The cathode can be negative, as when the cell is electrolytic (where electrical energy provided to the cell is used to decompose chemical compounds), or positive, as when the cell is galvanic (where chemical reactions are used to generate electrical energy).

[0038] A solid oxide cell (or SOC) is an electrochemical conversion device that either produces electricity directly from the oxidation of fuel in a fuel cell mode, or produces hydrogen, syngas, and CO from H2O and CO2 in an electrolyzer mode. Solid oxide cells are characterized by ceramic-based electrolyte materials that can operate at high temperatures (600°C-850°C).

[0039] FIG. 1 schematically illustrates an exemplary SOC 20 during operation, with FIG. 1A illustrating use in fuel cell mode 200 and FIG. 1B illustrating use in electrolyzer mode 300. The solid oxide cell 20 comprises an air electrode 21 (positive in SOFCs, negative in SOECs) and a fuel electrode 22 (negative in SOFCs, positive in SOECs) separated by a solid electrolyte layer 23. The electrolyte layer transports oxide ions (O 2- ), but is impermeable to the flow of fuel and oxidant. The remaining components are not depicted for clarity. For example, typical oxygen-ion conducting electrolytes include yttrium-doped zirconia, scandium-doped zirconia, cerium-doped zirconia, e.g., ZrO2 having a fluorite structure, or a mixture of two or more of these.

[0040] It will be understood that the inventions disclosed herein are equally applicable to solid-state electrochemical cells having a layered solid electrolyte between opposing solid or semi-solid (e.g., gel) electrode layers, such as cells including a proton-conducting solid electrolyte sandwiched between corresponding electrode layers. Exemplary proton-conducting electrolytes include oxides having the perovskite structure ABO3, for example, with the compositions BaZr1-xYxO3, BaCe1-xYxO3, or mixtures of two or more of these compositions.

[0041] Returning to Figure 1, an oxidant stream (O2) is provided to the air side of the cell. A reagent stream is provided to the fuel side of the cell. In SOFC mode, oxygen ions are formed at the air electrode, transported across the electrolyte, and react with the fuel. In SOEC mode, the reagent is reduced at the fuel electrode. The formed oxide ions are transported to the air electrode and released as oxygen. In fuel mode, the fuel X may be hydrogen (H2) or carbon monoxide (CO), which are oxidized (XO) to water (H2O(g)), carbon dioxide (CO2), etc., respectively. In electrolysis mode, an oxidized fuel (XO), such as steam or carbon dioxide, is provided, which is reduced to hydrogen, CO, etc. This process is typically carried out at high temperatures (500°C to 900°C). Pressures can be atmospheric or above.

[0042] In particular, the devices disclosed herein can advantageously be operated at overpressure, e.g., mbar overpressure, e.g., up to 500 mbar overpressure, or even 1 bar or more overpressure without the use of an external pressure vessel.

[0043] 2 provides a cross-sectional side view of an electrochemical stack 100 comprising a cell unit 10, a first adjacent cell unit 10-1, and a second adjacent cell unit 10-2. Note that during use, the cell unit 10 is in direct contact with and sandwiched between the adjacent cell units.

[0044] Each cell unit includes a solid oxide cell 20, 20-1, or 20-2, a separator plate 30, 30-1, or 30-2, and a sealing element 40, 40-1, or 40-2. The separator plate 30 is electrically conductive, e.g., metallic, preferably made of ferritic stainless steel, e.g., CROFER® 22H and / or CROFER® APU. The sealing element 40 is electrically insulating and can thus provide electrical insulation between adjacent conductive separator plates. The solid oxide cell 20 is held in a cavity or recess. Each cell includes at least an electrode layer 21, a counter electrode layer 22, and a solid electrolyte layer 23. In some embodiments, a porous current collector layer 25, e.g., a Ni mesh, is provided extending along the anode or cathode side of the cell, as shown. Typically, this is the cathode side in SOEC mode and the anode side in SOFC mode.

[0045] As described herein, separator plate 30 includes a central portion 31 that forms a cavity or recess for receiving electrochemical cell 20, and a protruding boundary portion 36 that circumferentially surrounds electrochemical cell 20 received by the recess. The cavity or recess is preferably provided on one side of the separator plate, e.g., the upper side. Most preferably, as shown, the recess in central portion 31 of separator plate 30 is configured to receive electrochemical cell 20 such that sealing portion 40 covers both upper surfaces 37 of protruding boundary portion 36 of separator plate 30 and may partially overlap solid electrolyte layer 23 of electrochemical cell 20. In other words, raised upper surface 37 of protruding boundary portion 36 is preferably flush with solid electrolyte layer 23. For example, the height of the upstanding sidewalls 38, i.e., the difference in height between the (raised) bottom contact surface 32 of the central portion 31 and the raised upper surface 37 of the protruding boundary portion 36, is the same as the total thickness of the electrochemical cell 20 minus the top electrode layer 21, i.e., the combined thickness of the bottom electrode layer 22, the optional porous current collecting layer 25, and the solid electrolyte layer 23. Furthermore, the thickness of the (compressed) sealing element 40 is preferably the same as the thickness of the electrode layer 21, which may protrude above the solid electrolyte layer 23 and the upper surface 37 of the protruding boundary portion 36. In this way, the electrochemical cell 20 can fit precisely between adjacent separator plates 30, 30-2 and form electrical connections at the top and bottom.

[0046] In one embodiment, for example, as shown, the cavity or recess is defined by a recessed bottom surface 32 in a central portion 31 of the plate. In other words, the central portion 31 may be lower than the surrounding boundary portion 36. For example, surrounding the recess is a boundary portion 36 having upstanding sidewalls 38 extending upward in a direction along the stack. Of course, the separator plate 30 shown could also be flipped upside down, so that the cavity or recess would be defined by the central portion 31 being elevated relative to the surrounding boundary portion 36.

[0047] As described herein, the sealing element 40 extends between the top surface 37 and bottom surface 39 of each of the protruding boundary portions 36 of the separator plate 30 and the opposing faces of the respective boundary portions of each adjacent cell unit 10-1, 10-2. Preferably, the sealing element 40 includes an opening 49 (best seen in FIG. 4A ) at the location of the electrode layer 21, extending between the raised top surface 37 of the boundary portion 36 of the sealing element 40 and the bottom surface 39 of the adjacent separator plate 30-2.

[0048] As described herein, the central portion 31 has a bottom contact surface 32 that makes electrical contact with the bottom side of the electrochemical cell 20 and a top contact surface 34 opposite the bottom contact surface 32 that makes electrical contact with the top side of the adjacent electrochemical cell 20 of the respective bottom side adjacent cell unit 10-1. For example, as shown, in one preferred embodiment, the bottom contact surface 32 forms a bottom ridge and bottom groove structure. Advantageously, the bottom ridge can provide electrical contact with the bottom side of the electrochemical cell 20, and the bottom groove can provide fluid access to the bottom side of the electrochemical cell 20. In another or further preferred embodiment, for example, as shown, the top contact surface 34 comprises an top ridge and top groove structure. Advantageously, the top ridge can provide electrical contact with the top side of the adjacent electrochemical cell 20-1, and the top groove can provide fluid access to the top side of the adjacent electrochemical cell 20. Preferably, a periodic structure of a plurality of grooves and ridges is formed on the bottom contact surface 32 and / or the top contact surface 34. Most preferably, the grooves comprise an array of parallel channels covering each electrode layer 21 and / or 22. For example, at least five, at least ten, or more (separate) parallel channels may be formed with ridges between them. In this way, fluid may be distributed / flow evenly over each electrode layer via the many channels / grooves, while sufficient electrical contact may be provided by the many ridges.

[0049] Preferably, the combined height of the thickness of the sealing element 40 (minus the depth of the optional seal-receiving recess, as shown in FIG. 7B ) and the height of the cavity or recess formed in the central portion 31 matches the thickness of the electrochemical cell 20 (including the optional porous current collecting layer 25). In this manner, the electrochemical cell 20 may be electrically contacted from both sides by respective separator plates. For example, in the embodiment shown, the separation distance between the recessed bottom surface 32 and the opposing outward-facing surface, as defined by the combined height of the seal and sidewalls, matches the thickness of the solid oxide cell 20.

[0050] In a preferred embodiment, the SOC stack configuration is embodied as a so-called electrode-supported cell, where one of the electrodes provides mechanical integrity on top of which sits a thin (e.g., less than 10 microns) electrolyte layer.

[0051] FIG. 3 provides a cross-sectional side view of the solid oxide cell 20 used in FIG. 2. The cell generally comprises a porous electrode layer 21 including an active oxide electrode layer and a barrier layer. In a preferred embodiment, for example, as shown, the oxide electrode layer is embodied as an LSCF layer and the barrier layer is embodied as a GCO layer. The LSCF layer may have an overall composition of La0.6Sr0.4Fe0.8Co0.2O3 and allows conversion between oxygen and oxygen ions (depending on the mode of operation). The barrier layer prevents reaction between components of the active layer and the electrolyte layer but allows the passage of oxygen ions and electrons. In the embodiment shown, the barrier has an overall composition of Ce0.8Gd0.2O2. The cell further comprises an electrolyte layer. The electrolyte layer allows the passage of oxygen ions but not electrons, typically embodied as a dense ceramic layer. In the embodiment shown, the solid electrolyte layer 23 is an yttria-stabilized zirconia layer (e.g., 8YSZ). The cell further comprises an electrolyte layer and a counter electrode layer 22 (also referred to as a functional fuel electrode layer). In a preferred embodiment, for example, as shown, the fuel electrode layer is embodied as a NiO-8YSZ layer (ZrO fully stabilized with 8 mol% Y2O3). The support layer is shown as a TZ3Y-NiO layer and supports the electrolyte and functional electrode layer. A contact layer may be provided to improve current collection. In the embodiment shown, the contact layer is a NiO-based layer. TEM image showing the porosity of the stack. Note that the electrode layer 21 does not extend over the entire area of ​​the solid electrolyte layer 23; the boundary portion of the solid electrolyte layer 23 remains free. In some embodiments, the free top surface 23t is in direct contact with the sealing element 40 (see, for example, FIGS. 2 and 7B).

[0052] Note that the cells shown are not drawn to scale. The thickness of the solid oxide cell 20 is generally on the order of several hundred microns (e.g., 0.1-2 mm), typically in the range of 0.3-0.6 mm, e.g., about 400 or 500 microns, while the surface area is generally several hundred square centimeters (e.g., 50-1000 cm). 2) or greater. For example, if the SOC is embodied in an overall square shape, the side length will generally be in the range of 10 to 40 cm, e.g., 15±5 cm, or greater. Larger cells may be preferred, but may be increasingly difficult to manufacture. Of course, other shapes and thicknesses are also contemplated. The cavity provided by the sealing and opposing plates is sized accordingly. The separator plate may be relatively thick, preferably 1 mm or greater, e.g., about 2 to 4 mm, and may be machined to provide mechanical stability even when acting as a support for the SOC.

[0053] Of course, the present disclosure should not be construed as being limited to what may be a solid oxide cell 20 as shown in Figure 2. It will be understood that the present invention may be advantageously used with other solid oxide cells 20 known in the art. For further details and exemplary cells, see "Status of Solid Oxide Cell development at TNO" by Van Berkel et al. in EFCF 2022: 15th European SOFC & SOE Forum, 8 July 2022, Lucerne Switzerland, A1206 pp. 1-10; G. Tao et al. "II.A.2 A Reversible Planar Solid Oxide Fuel-Assisted Electrolysis Cell and Solid Oxide Fuel Cell for Hydrogen and Electricity Production Operating on Natural Gas / Biogas" in DOE Hydrogen Program, FY 2006 Annual Progress Report, pages 24-28; and "Review of Progress in High Temperature Solid Oxide Fuel Cells". Journal of the Australian Ceramics Society. 50(1), all of which are incorporated herein by reference in their entirety.

[0054] In some preferred embodiments, the sealing portion overlaps (L) with the free upper surface of the solid electrolyte layer 23, as shown in Figures 2, 4A, 4B, and 7B. The overlap with the solid electrolyte layer 23 prevents fluid movement (e.g., air or fuel) between opposing sides of the cell. The length of overlap L along the free upper surface 23t of the electrolyte layer is typically 1 mm or greater, preferably even greater, e.g., 0.5 to 1 cm, or even up to 2 cm. In practice, the sealing portion extends across the vertical wall a distance of up to 1 to 2 cm. This range provides relaxed manufacturing conditions, allowing for tolerance of small gaps between the sidewalls of the recess and the SOC, and has been found to result in relatively minimal loss of active electrode area.

[0055] 4A and 4B provide exploded perspective views illustrating the construction of an electrochemical stack. FIG. 4A provides a top perspective view of a cell unit 10 covered by an adjacent unit 10-1. FIG. 4B provides a bottom perspective view of the cell unit 10 covered by an adjacent unit. The units include the elements described in connection with FIG. 2. As shown in the top view, the electrode layer 21 of the solid oxide cell 20 leaves the upper surface 23t of the solid electrolyte layer 23 free. According to a preferred embodiment, each of the separator plates 30, 30-1 is formed from a single monolithic metal plate having a recessed central portion leaving a relatively raised border portion 36 (see also FIG. 2). The border portion is provided with pairs of openings 53-1, 53-2, 54-1, 54-2. The recessed bottom surface includes a support area for supporting the SOC and is provided with a first channel structure 51. The first channel structure 51 extends between the first pair of openings. A second channel structure 52 is provided along the outward surface of the plate, opposite the recessed surface. The second channel structure, running along the second support, is intended to support an adjacent SOC. The second channel structure 52 extends between a pair of second openings 54-1, 54-2. The sealing element 40 is sized to extend along the raised upper surface 37 of the plate and the adjacent plate. The sealing portion has openings that provide access to the solid oxide cell 20, so that the sealing portion is sized to extend inward along the free upper surface 23t of the solid electrolyte layer 23. The sealing portion also has openings corresponding to the openings in the plate's interface. Together with adjacent units, these openings form a head that provides fluid access to and from each unit. As illustrated in FIG. 4B, during use, the fuel side of each SOC is exposed to a first fluid flow F1 (e.g., fuel) that moves from openings 54-1 to 54-2 through the second channel structure 52. The corresponding air electrode side of each SOC may, during use, be exposed to a second fluid flow F2 (e.g., air) moving from openings 53-1 to 53-2 through first channel structure 51. Alignment openings 81 are provided to facilitate alignment of the plates and seals. Inlay plates 57-1 and 57-2 are provided.Inlay plate 57-1 covers groove structure 51 along a portion of its path between the opening and the cell support area. Inlay plate 57-2 covers groove structure 52 along a portion of its path between the opening and the cell support area. Inlay plate 57-1 has a thickness such that the plate is flush with the raised top surface 37 of the plate. Inlay plate 57-2 has a thickness such that the plate is flush with the bottom surface 39 of the plate (see FIG. 2).

[0056] 5A and 5B further illustrate an embodiment of stack 1 in an assembled state, with FIG. 5A providing a perspective view of the electrochemical stack and FIG. 5B providing a top view of the electrochemical stack. As shown more clearly in FIGS. 5A and 5B, the boundaries with aligned openings can be seen to form zones A1 and A2 with gas headers that provide fluid access to each cell. A groove structure distributes the respective flows F1 and F2 over the active cell area.

[0057] Figures 6A, 6B, and 6C provide cross-sectional side detail views of the electrochemical stack in header region A2, where Figure 6A is a cross-sectional side view taken along line AA in Figure 5B, and Figures 6B and 6C are detail views of the portion shown in Figure 6A. As shown most clearly in Figures 6B and 6C, inlays 57-1 and 57-2 ensure that seals 40 experience flat contact surfaces at locations between corresponding openings and active cell areas, thereby spreading contact forces and reducing localized stress buildup between adjacent plates.

[0058] 7A and 7B provide cross-sectional side views of the electrochemical stack in the active area, where FIG. 7A is a cross-sectional side view taken along line BB in FIG. 5B and FIG. 7B is a detailed view of the portion shown in FIG. 7A. As best seen in FIG. 7B, the seal 40 overlaps the free top surface 23t of the SOC 20 over a distance L. In some embodiments, for example, as shown, the border portion of the bottom surface 39 of the plate 30-2, opposite the recess, may be recessed. In particular, as shown, the bottom surface 39 of the adjacent separator plate 30-2 may have a seal-receiving recess that may at least partially accommodate the seal element 40 in the area of ​​the partially uncovered edge 23t of the solid electrolyte layer 23 and / or the border portion 36 of the adjacent separator plate 30-2. Advantageously, the thickness 40t of the compressed seal element 40 may correspond to the sum of the thickness 21t of the top electrode layer 21 of the electrochemical cell 20 and the depth 30-2t of the seal-receiving recess. Thus, the electrode layer can be in electrical contact with the bottom ridge 51r of the adjacent separator plate 30-2. This seal-receiving recess can also facilitate the positioning of the seal element 40.

[0059] 8A provides a cross-sectional side view of an embodiment that differs from the embodiment shown in FIG. 7 in that the sealing element 40 is embodied as a multi-layer stack. The seal comprises three layers: two sealing layers 42, 43, preferably compression seals, most preferably vermiculite-based, with a metal foil 41 (preferably ferritic steel) in between, which was found to further ensure a hermetic seal between the fuel and air compartments.

[0060] FIG. 8B is a schematic side view illustrating an embodiment of an electrochemical device 100 comprising a stack disclosed herein. FIG. 8C provides a top view of the device. As shown, the device comprises end plates 60, 61 disposed along opposite ends of the stack. During use, the stack is held in compression, for example, by applying opposing forces to the end plates of the stack. In some embodiments, the device may comprise one or more means for measuring, and preferably regulating, one or more of the following: the temperature of one or more of the plates and end plates, the temperature of the stream, and / or the pressure applied between the opposite ends of the stack. Additionally, the device is preferably configured to measure / regulate the potential V or current I between the opposite ends of the electrochemical stack 1 and / or between individual ones of the separator plates comprised in the stack. In the illustrated embodiment, the end plates are provided with sensors 62-1 and 62-2 in the form of sensors that measure the temperature of the end plates. Additionally, the device is configured with sensors 62-3, 62-4, 62-5, 62-6 for measuring the temperature of the retained stream at corresponding openings. Additionally, the device is provided with multiple terminals T1, T2, Tn for measuring / applying potentials and / or currents during device operation. Note that the stack may also include so-called half-plates 30a and 30b between the stack and the end plates. These half-plates differ from the separator plates in that they are unpatterned and flat on the side that contacts the end plates.

[0061] As illustrated in FIG. 12 , each repeating unit in the stack may include at least two solid oxide cells. FIG. 12A illustrates a separator plate 30 that differs from the described plate in that it is configured to receive four solid oxide electrochemical cells in a 2×2 array. Of course, other configurations having a different number of cells or alternative relative positioning are also contemplated. In the embodiment shown, the plate includes four relatively recessed bottom surfaces 32-1, 32-2, 32-3, and 32-4. As shown, the plate is configured to place the solid oxide electrochemical cells in two rows (R1, R2), whereby adjacent cells in each row are connected in series. Note that the raised sidewalls extend circumferentially around the array and header. Advantageously, adjacent rows may share a common header. Note that the plate also preferably includes a raised separator wall 36a between adjacent rows. The plate also preferably includes a separator wall between adjacent cells within a row. To allow the passage of gas, the plate preferably comprises a groove structure and an inlay plate 57 as described herein above in relation to Figures 4-6.

[0062] 12B illustrates the same plate holding three of the four solid-state electrochemical cells 20. After placing the fourth cell, a sealing element (not shown) is provided. It will be appreciated that the sealing portion includes openings corresponding to the locations of the solid-state electrochemical cells and gas headers.

[0063] The present disclosure further relates to a method for manufacturing an electrochemical stack. In a preferred embodiment, the method includes providing at least a) a solid oxide cell as disclosed herein, b) a conductive separator plate as disclosed herein and a solid oxide cell of a first adjacent cell unit, and c) a sealing element as disclosed herein. The method further includes an assembly process including placing the solid oxide cell on the recessed bottom surface of the separator plate and placing the sealing element on the raised top surface of the interface. The provided components may preferably include one or more, or even all, of the aspects discussed herein above with respect to Figures 1-8.

[0064] According to a further aspect, components may be provided as a kit of parts for assembly with solid oxide cells to form an electrochemical stack as disclosed herein. The kit includes at least an electrically conductive separator plate 30 for assembly between adjacent solid oxide cells and a sealing element 40 for assembly between the adjacent electrically conductive separator plates, the separator plate including: i) a relatively recessed bottom surface 32 with a first cell support area 33 configured to receive a solid oxide cell 20; and ii) a central portion 31 providing an outwardly facing surface 34 opposite the recessed bottom surface 32 with a second cell support area 35 configured to contact a solid oxide cell of a first adjacent cell unit 10-1, and a boundary central portion 31 providing a relatively raised top surface 37 and upstanding sidewalls 38 extending circumferentially from the recessed bottom surface 32. Of course, the kit may also include one or more of the solid oxide cells 20 disclosed herein and / or other components discussed herein, such as an inlay plate.

[0065] 9A and 9B provide photographs of the components of the electrochemical device during assembly. FIG. 9C provides a photograph of the assembled electrochemical device 100. In particular, FIG. 9A depicts a partial stack assembled on a bottom end plate 61. The boundary portion 36 of the top separator plate allows the solid oxide cell 20 to be seen. FIG. 9B depicts two separator plates with boundary portions 36 having openings and recessed bottom surfaces 32 having patterned groove structures. The assembled electrochemical device 100 depicted in FIG. 9C includes the complete stack. Also shown are top and bottom pressure cylinders that apply contact pressure P to the stack 100. A controller 101 measures and regulates the temperature at the separator plate level.

[0066] 10 and 11 illustrate an embodiment of the assembly of an electrochemical device. Stage A illustrates the bottom end plate 61. In Stage B, an end seal element 40a is provided on the end plate 61. In Stage C, a first half separator plate 30a is placed on the end seal element 40a. The half separator plate 30a is in electrical contact with the end plate 61. In Stage D, a porous nickel mesh current collector layer 25 is placed on the recessed bottom surface of the first half separator plate 30a. In Stage E, a solid oxide cell 20, as discussed in connection with FIG. 3, is placed on the porous current collector layer 25. In Stage F, a first seal element 40 is placed on the border of the half separator plate. The seal overlaps the free upper surface of the solid electrolyte layer of the solid oxide cell 20. In Stage G, a first complete separator plate 30 having an inlay as disclosed herein is placed on top of the partial stack formed below Stage F. Note that only the upper inlay plate 61 is visible. At H, I, J, and K, additional porous current collector layers 25, solid oxide cells, separators, and seals are provided. This process can be repeated until the stack contains the desired number of cell units, e.g., 100. At L, the fully formed stack is illustrated. At M, the top and bottom pressure cylinders 63 are shown.

[0067] The present disclosure also provides a method for manufacturing a separator plate, which includes machining (e.g., milling, drilling, or otherwise removing material) a central portion of an essentially flat metal base plate to form a recessed bottom surface configured to receive solid oxide cells, and leaving a relatively raised border portion around the central portion. In a preferred embodiment, the method further includes providing a first groove structure in the recessed bottom surface 32 to form a first channel structure extending between a first pair of openings in the border portion, and providing a second groove structure formed in the separator plate's outward-facing surface 34 opposite the recessed bottom surface 32 to form a second channel structure 52 extending between a second pair of openings 54-1, 54-2 in the border portion 36. Advantageously, the groove structure and / or the openings may be provided by the same tool as the recesses.

[0068] Although features are described herein as part of the same or separate embodiments for purposes of clarity and conciseness, it will be understood that the scope of the present invention may include embodiments having all or any combination of the described features. In interpreting the appended claims, the word "comprising" does not exclude the presence of other elements or acts than those recited in a given claim, the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements, any reference signs in the claims do not limit their scope, and it should be understood that several "means" may be represented by the same or different items or implemented structures or functions, and that the disclosed devices or portions thereof may be combined together or separated into further parts unless otherwise specified. When one claim refers to another claim, this may indicate synergistic advantages achieved by the combination of their respective features. However, the mere fact that certain criteria are recited in mutually different claims does not indicate that a combination of these criteria cannot also be used advantageously. Thus, the present embodiments may include all functional combinations of the claims, and each claim may in principle refer to any preceding claim unless clearly excluded by the context. [Explanation of symbols]

[0069] 1. Electrochemical Stack 10 cell units 10-1 Bottom adjacent cell unit 10-2 Upper adjacent cell unit 20 Electrochemical Cell 20-1 Solid oxide cell 20-2 Solid oxide cell 21 Electrode layer 22 Bottom electrode layer 23 Solid electrolyte layer 23t edge 25 Porous current collecting layer 30 Separator Plate 30-1 Separator plate 30-2 Separator plate 30a half plate 30b Half Plate 31 Central part 32 Bottom surface, bottom contact surface 32-1 Bottom 32-2 Bottom 32-3 Bottom 32-4 Bottom 33 first cell support region 34 Upper contact surface 36 Protruding boundary part 36a Separator wall 37 Top 38 Upright sidewall 39 bottom 40 sealing element 40-1 Sealed part 40-2 Sealed part 40a End sealing element 41 Metal foil, rigid core 42 Electrically insulating compressible sealing layer 43 Electrically insulating compressible sealing layer 49 Opening 51 First channel structure 51g bottom groove 51r bottom ridge 52 Second channel structure 52g upper groove 52r upper ridge 53-1 Opening 53-2 Opening 54-1 Opening 54-2 Opening 57 Upper groove 57-1 Inlay Plate 57-2 Inlay Plate 60 End Plate 61 End plate 62-1 Sensor 62-2 Sensor 62-3 Sensor 62-4 Sensor 62-5 Sensor 62-6 Sensor 63 Bottom Pressure Cylinder 81 Alignment opening 101 Controller

Claims

1. An electrochemical stack (100) comprising at least one intervening cell unit (10) disposed between each bottom adjacent cell unit (10-1) and each top adjacent cell unit (10-2), wherein each intervening cell unit (10) comprises: a solid-state electrochemical cell (20); an electrically conductive separator plate (30); an electrically insulating sealing element (40); the separator plate (30) comprises a central portion (31) forming a recess for accommodating the electrochemical cell (20), and a protruding boundary portion (36) circumferentially surrounding the electrochemical cell (20) accommodated by the recess; the sealing elements (40) extend between the top and bottom surfaces (37, 39) of each of the protruding boundary portions (36) of the separator plate (30) and the opposing surfaces of the boundary portions of each of the adjacent cell units (10-1, 10-2); the central portion (31) has a bottom contact surface (32) that is in electrical contact with the bottom side of the electrochemical cell (20), and a top contact surface (34) opposite the bottom contact surface (32) that is in electrical contact with the top side of the adjacent electrochemical cell (20-1) of each bottom-side adjacent cell unit (10-1); the bottom contact surface (32) forms a structure of bottom ridges (51r) and bottom grooves (51g), the bottom ridges (51r) providing electrical contact with the bottom side of the electrochemical cell (20) and the bottom grooves (51g) providing fluid access to the bottom side of the electrochemical cell (20); The electrochemical stack (100) includes an upper contact surface (34) having a structure of upper ridges (52r) and upper grooves (52g), the upper ridges (52r) providing electrical contact with the upper side of the adjacent electrochemical cell (20-1), and the upper grooves (52g) providing fluid access to the upper side of the adjacent electrochemical cell (20).

2. 2. The electrochemical stack of claim 1, wherein the electrochemical cell comprises a solid electrolyte layer disposed between a bottom electrode layer and a top electrode layer, the solid electrolyte layer being partially covered by the top electrode layer and having a partially uncovered edge, the sealing element extending inward from a raised upper surface of the boundary portion to form an overlap with the uncovered edge of the solid electrolyte layer, and a thickness of the sealing element compressed between the separator plate and an adjacent separator plate of the upper adjacent cell unit is configured to place the electrode layer in electrical contact with a bottom raised portion of the adjacent separator plate.

3. 3. The electrochemical stack of claim 1, wherein the bottom surface of the adjacent separator plate has a seal receiving recess that at least partially receives the sealing element, including an area at the partially uncovered edge of the solid electrolyte layer, and wherein a thickness of the compressed sealing element corresponds to a sum of a thickness of the upper electrode layer and a depth of the seal receiving recess.

4. 4. The electrochemical stack (100) of claim 1, wherein the central portion (31) and the boundary portion (36) are part of a monolithic metal plate, and each intervening cell unit (10) comprises only one of the separator plate and the sealing element.

5. the bottom groove forms part of a first channel structure (51) extending between a pair of first openings (53-1, 53-2) provided through the boundary portion (36); 5. The electrochemical stack (1) according to claim 1, wherein the upper groove (57) forms part of a second channel structure (52) extending between a pair of second openings (54-1, 54-2) provided through the boundary portion (36).

6. 6. The electrochemical stack of claim 1, further comprising an inlay plate between the opening and the cell support area, the inlay plate covering the bottom groove along a portion of its track, the inlay having a thickness that matches the height level of the raised top surface (37).

7. 7. The electrochemical stack of any one of claims 1 to 6, wherein the sealing element (40) is a multi-layer seal having a rigid core (41) sandwiched between electrically insulating compressible sealing layers (42, 43).

8. Electrochemical stack according to any one of claims 1 to 7, wherein the rigid core (41) is a metal core.

9. 9. The electrochemical stack of claim 1, further comprising a porous current collecting layer disposed between the electrochemical cell and the bottom contact surface, the porous current collecting layer configured to provide electrical contact between the bottom ridge and a bottom electrode layer of the electrochemical cell, and to provide fluid access therethrough between the bottom groove and the bottom electrode layer.

10. The electrochemical stack of any one of claims 1 to 9, wherein the electrochemical cell (20) is an electrode-supported cell.

11. An electrochemical device (100) comprising the stack of any one of claims 1 to 10 and respective end plates (60, 61) disposed along opposite ends of the stack.

12. the temperature of one or more of the separator plates (30) and the end plates provided in the stack; a pressure (P) applied between the opposing ends of the stack; the temperature of the first fluid (F1) stream and / or the second fluid (F2) stream, and 12. The electrochemical device (100) of claim 11, further comprising a controller (101) configured to regulate one or more, preferably all, of the electrical potential (V) or the current (I) between opposite ends of the electrochemical stack (100) and / or between individual ones of the separator plates included in the stack.

13. An electrically conductive separator plate (30) for assembly between adjacent solid-state electrochemical cells (20) to form part of an electrochemical stack (1) or electrochemical device according to any one of claims 1 to 12, comprising: the separator plate (30) comprises a central portion (31) forming a recess for receiving each electrochemical cell (20) and a protruding border portion (36) circumferentially surrounding the central portion (31); the central portion (31) has a bottom contact surface (32) for making electrical contact with the bottom side of the electrochemical cell (20) accommodated in the recess, and an upper contact surface (34) opposite the bottom contact surface (32) for making electrical contact with the upper side of an adjacent electrochemical cell (20-1); the bottom contact surface (32) forms a structure of bottom ridges and bottom grooves, the bottom ridges providing electrical contact with a bottom side of the electrochemical cell (20) and the bottom grooves providing fluid access to the bottom side of the electrochemical cell (20); The conductive separator plate (30) has an upper contact surface (34) comprising an upper ridge and upper groove structure, the upper ridge providing electrical contact with the upper side of the adjacent electrochemical cell (20-1), and the upper groove providing fluid access to the upper side of the adjacent electrochemical cell (20).

14. 11. A method of manufacturing a separator plate (30) for an electrochemical stack (100) according to any one of claims 1 to 10, the method comprising: machining a central portion (31) of an essentially flat metal base plate to form recesses in the central portion (31), the recesses being configured to accommodate solid-state electrochemical cells (20), the remainder of the metal plate forming a protruding boundary portion (36) circumferentially surrounding the central portion (31), respective sets of ridges and grooves being formed on either side of the central portion, each set of ridges being configured to be in electrical contact with a respective electrochemical cell (20) on either side of the central portion (31), and each set of grooves forming a respective channel structure providing fluid access to a respective electrochemical cell (20) on either side of the central portion (31).

15. Use (200) of an electrochemical stack, device, separator plate or method according to any one of claims 1 to 14 for the generation of electricity (SOFC) or for the production of hydrogen, syngas and / or carbon monoxide (SOEC).

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