Electrochemical cell unit with flat separator

Abstract

The present invention relates to a method of operating a cell stack of cell units, each cell unit in the cell stack including a cell layer having an electrochemically active cell area and a first side and a second side, and a separator plate electrically connected to the cell layer, the separator plate having a first side and a second side, the second side of the separator plate extending across and spaced apart from the first side of the cell layer to form a first fluid volume, and the first side of the separator plate having a protrusion oriented away from the first side of the cell layer and toward the second side of the cell layer of an adjacent cell unit to form a second fluid volume, the method including supplying a first fluid to the first fluid volume, supplying a second fluid to the second fluid volume, and adjusting a pressure difference between the first fluid volume and the second fluid volume to maintain the spaced apart arrangement that forms the first fluid volume.

Description

[Technical Field]

[0001] The present invention relates to electrochemical cell units, particularly fuel cell units and electrolysis cell units, with flat separators, stacks containing such cell units, methods for manufacturing separator plates (interconnects) for use in such cell units, separator plates so formed, and uses of such cell units. Cell units of the present invention include solid oxide, polymer electrolyte membrane, and molten carbonate cells. More specifically, the present invention relates to solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) units, which may include metal-supported solid oxide fuel cell (MS-SOFC) or electrolysis cell (MS-SOEC) units. [Background technology]

[0002] Some fuel cell units can generate electricity by using an electrochemical conversion process to oxidize a fuel to produce electricity. Some electrochemical cell units can also, or instead, operate as regenerative fuel cell (or reverse fuel cell) units, often known as electrolyzer cell units, to produce, for example, hydrogen and oxygen from water or carbon monoxide and oxygen from carbon dioxide. They can be tubular or planar. Planar electrochemical cell units can be arranged on top of each other in a stack configuration, e.g., 100-200 electrochemical cell units in a stack, with the individual electrochemical cell units arranged, for example, electrically in series.

[0003] Electricity-generating solid oxide fuel cells (SOFCs) are based on a solid oxide electrolyte, which conducts negative oxygen ions from a cathode to an anode, located on the opposite side of the electrolyte. Therefore, fuel or reformate contacts the anode (fuel electrode), and an oxidant, such as air or an oxygen-rich fluid, contacts the cathode (air electrode). Conventional ceramic-supported (e.g., anode-supported) SOFCs have low mechanical strength and are prone to breakage. Therefore, metal-supported SOFCs have been developed, with active fuel cell component layers supported on a metal substrate. In these cells, the ceramic layers perform only electrochemical functions and can be very thin; that is, they are not self-supporting but rather a thin coating / film laid on and supported by a metal substrate. Such metal-supported SOFC stacks are more robust and cost-effective than ceramic-supported SOFCs, have superior thermal properties, and can be fabricated using conventional metal welding techniques.

[0004] A solid oxide electrolysis cell (SOEC) can have the same structure as a SOFC, but essentially operates the SOFC in a reverse rotation, or regenerative, mode, where the input of electrical energy achieves the electrolysis of water and / or carbon dioxide to produce hydrogen gas and / or carbon monoxide and oxygen using a solid oxide electrolyte.

[0005] The present invention is directed to electrochemical cell units and the design of their separator plates. It is therefore applicable to various types of fuel cells and electrolysis cells, for example, based on solid oxide electrolytes, polymer electrolyte membranes, and molten electrolytes. For convenience, "cell unit" will be used to refer to an "electrochemical cell unit," which includes a fuel cell or an electrolysis cell unit.

[0006] Each cell unit in the stack of cell units typically includes a cell layer that includes an electrochemically active cell area (e.g., a metal-supported electrochemically active cell area) and a separator plate. The separator plate typically contacts one side of the cell layer of the cell unit and may also contact the opposite side of the cell layer of an adjacent cell unit in the stack of cell units. In the stack of cell units, the separator plate that contacts one side of the cell layer of the cell unit and the opposite side of the cell layer of an adjacent cell unit is sometimes referred to as an "interconnect."

[0007] FIG. 1 shows an exploded perspective view of a cell unit with two gaskets, taken from applicant's earlier application GB 2603665 A, which describes an electrochemical cell unit and a stack including a plurality of such electrochemical cell units with raised elements. The cell unit 10 of FIG. 1 includes a flat (i.e., planar) metal support plate 14 stacked adjacent to a separator plate 12. The separator plate 12 is shown to have a flanged periphery 18 around its periphery. The flanged periphery 18 extends outward from the major plane of the sheet, as seen in the central fluid volume area, creating a recess in the separator plate (and a protrusion on the outer surface). The recess defines a fluid volume within the cell unit upon assembly.

[0008] 1, the cell units 10 have rounded edges and parallel sides, with both the separator plates 12 and the metal support plates 14 provided with fluid ports 22 toward each end. Other shapes, sizes, and numbers of individual cell features are possible, depending on the power requirements and dimensions of the final stack assembly.

[0009] Molded port features 24 are provided around the fluid ports of separator plate 12. The molded port features 24 are provided as multiple elements in the shape of round indentations having a common height and extending a distance from the plane of the bottom of the fluid volume corresponding to the height of flanged periphery 18. This is so that, when cell unit 10 is assembled, the molded port features 24 will contact the opposing surface of metal support plate 14, just like flanged periphery 18. As a result, when flanged periphery 18 is joined to metal support plate 14 by, for example, welding, the molded port features 24 will also contact metal support plate 14.

[0010] In the center of the cell unit 10 is an electrochemically active layer 50 on a metal support plate, which in this example is located outside the enclosed fluid volume.

[0011] The electrochemically active area 50 includes an anode, a cathode, and an electrolyte (not shown) disposed between the anode and cathode. The anode, electrolyte, and cathode may collectively be referred to as the electrochemically active layer 50, the active electrochemical cell layers, or the electrochemically active region. The electrolyte conducts negative oxygen ions or positive hydrogen ions between the anode and cathode. The stack 20 may include a stack of cell units based on a solid oxide electrolyte, a polymer electrolyte membrane, a molten electrolyte, or any other modification capable of electrochemical reactions.

[0012] The concave configuration can give the associated plate the appearance of a rimmed tray, with a correspondingly convex profile (outwardly relative to the cell unit) and typically a planar bottom surface, the recess thus defining (e.g., a portion of) the fluid volume within the assembled cell unit. In this concave configuration, the flanged periphery extends from the plane of the original sheet of separator plate and / or the plane of the metal support plate toward the opposing surface of the other of the separator plate and metal support plate, respectively.

[0013] The fluid volume is thus bordered by a flanged periphery formed by die pressing, hydroforming, stamping, etc. These are simple processes already used to form the central protrusion (described below) of the fluid volume to support and electrically connect adjacent cells via the electrochemically active layer, as in prior art separator plates.

[0014] Figure 2 is an exploded perspective view of the underside of the cell unit of Figure 1. The metal support plate 14 (e.g., a metal foil) is provided with a plurality of small holes or pores 48 that allow fluid within the fluid volume to contact the side of the electrochemical layers closest to the metal support plate 14. These form a porous region surrounded by a non-porous region. The anode (fuel electrode) layer is located adjacent to the small holes / pores, and the (enclosed) fluid volume within the cell unit includes a fuel flow volume that is supplied by fuel entering and exiting through the fluid ports 22, and thus the fuel port 22. The cathode (air electrode) layer is on the opposite, or outer, side of the electrochemically active layer 50 and is exposed to air flowing across it during use of the cell unit 10.

[0015] In the cell unit shown in Figures 1 and 2, only two layers (components) are required: a metal support plate and a separator plate.

[0016] Also provided are central upward projections 32 and central downward projections 36, which include inward and outward projections (upward and downward as shown) extending between the opposing inner surfaces of the two plates and the outer surfaces of the electrochemically active layers of the cell units adjacent to the outward projections. The central upward projections 32 define a fluid path therebetween for fuel, which passes through the enclosed fluid volume between the fluid ports at both ends of the cell units. The central downward projections 36 define a fluid path therebetween for oxidant (such as air), which passes through the fluid volume defined between the downward projections and the outer surfaces of the electrochemically active layers of the cell units adjacent to the downward projections.

[0017] Each gasket, such as gasket 34 (also called a "seal"), provides the primary sealing function and is typically a compressible gasket that is subject to high compressive forces near the port.

[0018] The gasket may be sized to cover all molded port features 24 of each fluid port 22, thereby preventing fluids (e.g., fuel) that may pass through the fluid ports 22 in the stack from leaking between the outside of the cell unit 10 and the gasket (e.g., gasket 34) into the area outside the cell unit, i.e., into the fluid (e.g., oxidant) surrounding the cell unit 10, or vice versa, i.e., fluid outside the fluid port from leaking into the fluid port. This is important to prevent any mixing of fluids inside the cell unit 10 with fluids outside the cell unit 10, i.e., fuel and oxidant. The polarity of the electrochemically active layer 50 determines which orientation this is.

[0019] The gasket may also provide electrical insulation to prevent short circuits between the first cell unit 10 and the adjacent fluid cell unit 10. The gasket may be any suitable cell gasket (sealing ring), such as, for example, a vermiculite-based gasket, e.g., Thermiculite™.

[0020] There are various sources of internal resistance in a cell stack. One such source is the contact resistance between the separator plates and adjacent cell layers.

[0021] The cell stack may have upper and lower compression plates connected to one another by means such as bolts to compress the cell units therebetween, and the compressive force applied to the stack is sufficient to form a seal to prevent leakage from the cell units and / or fluids external to the fluid ports from leaking into the fluid ports.

[0022] Compressive forces within the stack within the planar area of ​​the electrochemically active regions are necessary for good electrical contact and, therefore, good conductivity throughout the stack. The central upward projections 32 and central downward projections 36 provide the necessary electrical contact between the cell units and also support the cell units in the central region, extending upward to the underside of the metal support plate 14 in the area of ​​the small holes or perforations 48 and downward to the opposing surface of the electrochemically active layer of the underlying cell. Furthermore, molded port features 24 around the ports 22 assist in transmitting compressive forces within the stack at the peripheral edges of each unit cell, providing the compressive force necessary to create a seal. Maintaining pressure between the separator plate and the adjacent cell layer is necessary to minimize contact resistance between the separator plate and the adjacent cell layer. This is the function of the upward projections 32. However, including such upward projections 32 has its own drawbacks. For example, the upward protrusions 32 may block holes or pores 48 in the metal support plate 14, obstructing fuel flow to the electrochemically active cell area. In effect, these protrusions reduce the efficiency and power density of the cell unit by reducing fluid access to (and product evacuation from) the electrochemically active cell area through the pores 48. Those skilled in the art will appreciate that because the electrodes supplied by the pores 48 are themselves adapted to transport reactants to the electrolyte, a pore blocked by a protrusion 32 reduces the supply to (and evacuation from) the electrochemically active cell area, but does not render the portion of the electrochemically active cell area adjacent to the blocked pore inoperable. The upward protrusions 32 may also impede the flow of fluids (such as fuel) across the cell unit, reducing the volume available for such fluid flow.

[0023] SUMMARY OF THE INVENTION The present invention seeks to address, overcome or mitigate at least one of the disadvantages of the prior art. Summary of the Invention

[0024] In a first embodiment, an electrochemical cell unit is provided, comprising: a cell layer including an electrochemically active cell area and having a first side (e.g., a lower side) and a second side (e.g., an upper side); and a separator plate (e.g., below the cell layer) including a metal sheet and having a first side (e.g., a lower side) and a second side (e.g., an upper side), the separator plate having a first side (e.g., a lower side) and a second side (e.g., an upper side) extending across and facing the first side of the cell layer to form a first fluid volume therebetween for a first fluid. The separator plate has a region extending across (e.g., below) at least the electrochemically active cell area, the region being free or substantially free of protrusions toward the first surface of the cell layer (i.e., free of protrusions protruding into the first fluid volume). The region is substantially free (preferably completely free) of other components separating the separator plate from the cell layer. The separator plates are adapted to be subjected to a pressure differential between the first and second sides of the separator plates to maintain a spaced apart arrangement that defines a first fluid volume. Preferably, the pressure differential is a fluid pressure differential, more particularly a gas pressure differential.

[0025] The second side of the separator plate extends across the first side of the cell layer in an underside / overside arrangement, with the latter overlying the former.

[0026] The region extending across the electrochemically active cell area is completely or nearly completely flat and is largely, nearly completely, or completely free of protrusions or raised features directed toward the first side of the cell layer (of the cell unit of which the separator is a component). Such protrusions include channels, ridges, or dimples, and may typically be formed by stamping, etching, or machining. The first volume is free of support structures to maintain its volume.

[0027] The region extending across the electrochemically active cell area may coincide with the planar area (i.e., extent) of the electrochemically active cell area, i.e., the second side of the separator does not contact the first side of the cell layer within the planar area (i.e., extent) of the electrochemically active cell area, and no other components are present in this region to separate the separator plate from the cell layer.

[0028] In an operating mode of the electrochemical cell unit, a pressure differential between the first and second sides of the separator plate (i.e., a positive pressure differential between the first and second fluid volumes) maintains or increases the separation between the second side of the separator plate and the first side of the cell layer. In a non-operating mode, when the pressures on the first and second sides of the separator plate are the same, the separation may decrease.

[0029] Preferably, the architecture of the cell layer is selected from either a metal-supported, anode-supported, electrolyte-supported, or cathode-supported architecture, i.e., the cell layer is either a metal-supported cell layer, an anode-supported cell layer, an electrolyte-supported cell layer, or a cathode-supported cell layer.

[0030] More preferably, the cell layer is a metal-supported cell layer, wherein the first side of the cell layer is a first side of a metal support plate and the second side of the cell layer is a second side of the metal support plate opposite the first side of the metal support plate, the second side carrying the electrochemically active cell area. Furthermore, any reference throughout this specification to a cell layer is interchangeable with a cell layer supported by a metal support plate, or a "metal plate-supported cell layer," etc.

[0031] The electrochemical cell unit further comprises an inlet and an outlet to a first fluid volume, preferably disposed toward opposite edges of the cell unit, with the electrochemically active cell area disposed therebetween. The inlet to the first fluid volume may be a type of port for the inflow of a fluid (e.g., reformate) into the first fluid volume formed by the spacing arrangement between the cell layer and the separator plate. The outlet from the first fluid volume may also be a type of port for the inflow of a fluid (e.g., reformate) into the first fluid volume formed by the spacing arrangement between the cell layer and the separator plate.

[0032] The electrochemical cell unit preferably includes a first plurality of protrusions extending outward from a first side of the separator plate, away from the cell layer. The protrusions are raised features or components of the separator plate that are attached to or integrally formed with the separator plate. When the protrusions are integrally formed with the separator plate, they can be formed by pressing the separator plate. Preferably, the first plurality of protrusions are provided in a region that overlies at least the electrochemically active cell area of ​​the cell unit.

[0033] The protrusions may have a cross-sectional shape that is circular, square, cross-shaped, pentagonal, or hexagonal, or may be oval or irregular polygonal, but ideally have a transverse to longitudinal aspect ratio of less than 10, preferably less than 5, and more preferably less than 2. Alternatively or additionally, the length of the protrusions may be less than half the characteristic transverse dimension (e.g., length, width, or diameter) of the electrochemically active cell area.

[0034] One or both of the separator plate and cell layer of the electrochemical cell unit may include a second plurality of protrusions (raised features or components) extending outward toward and contacting the other of the separator plate and cell layer at a plurality of contact points on the cell layer that surround the inlets and outlets for fluid flow to and from the first fluid volume.

[0035] The electrochemical cell unit may further include a flanged periphery on at least one of the separator plate and the cell layer. The flanged periphery may be attached to the separator plate and the cell layer or may be integrally formed with the separator plate and the cell layer by pressing the separator plate and / or the cell layer. The flanged periphery may be used to join the separator plate and the cell layer together. For example, the separator plate and the cell layer may be directly joined at the flanged periphery to form a first fluid volume therebetween. The flanged peripheries of the separator plate and the cell layer may optionally be welded or directly joined by other means.

[0036] The electrochemical cell unit may alternatively include a spacer plate sandwiched between the separator plate and the metal support plate. The spacer plate may provide separation between the metal support plate and the separator plate. For example, the spacer plate may be sandwiched between the separator plate and the metal support plate to form a first fluid volume therebetween. The three plates may be hermetically secured to one another, for example, by welding their peripheries.

[0037] A separator plate of an electrochemical cell unit may be configured or adapted such that a pressure on a first side of the separator plate is lower than a pressure on a second side of the separator plate. In other words, the separator plate may be configured to withstand a dual-pressure environment without irreversible damage or deformation. A dual-pressure environment can be provided to the separator plate by supplying fluids at different pressures to different sides of the separator plate and creating a pressure differential between them. When installed in a stack of cell units, the separator plate may be configured or adapted such that a first fluid volume formed between the separator plate and the cell layer is maintained when a pressure differential exists between the first and second sides of the separator plate.

[0038] For example, the pressure of the first fluid at the second side of the separator plate can be higher than the pressure of the second fluid at the first side of the separator plate, the first fluid being, for example, a fuel and the second fluid being, for example, an oxidizer.

[0039] The pressure difference between the first and second sides of the separator plate may be controlled by any number of means known to those skilled in the art. For example, a pressure difference may be established by using pumps to pump fluids at different rates and pressures. Alternatively, or additionally, the piping or flow paths of the first and second fluids may be provided with mechanisms such as valves and chokes to control the pressure difference therebetween. The pressure difference therebetween may range from 50 mbar to 2 bar, preferably from 100 mbar to 1.5 bar, and more preferably from 200 mbar to 800 mbar. Those skilled in the art will understand that the pressure difference used can be adjusted to maintain the spacing between the separator plate and the cell layer, and may depend on the flexibility of the cell layer and the separator plate (its metal sheet).

[0040] By providing mechanisms in the flow paths of the first and second fluids, the initial pressure at the inlets of the first and second fluid volumes can be controlled, and the pressure differential between the first and second fluid volumes can be controlled (as is the case in fuel cell operation; in electrolysis cell operation, only the first fluid may be supplied and its initial pressure controlled). Additionally or alternatively, the pressure at the outlets of the first and second fluid volumes can be controlled, and a pressure differential between the first and second fluid volumes can be established.

[0041] The separator plate may be configured or adapted to deflect inward when a pressure differential is applied between the first side and the second side. In other words, the pressure differential experienced by the separator plate may be such that the separator plate deflects away from or toward the cell layer. Preferably, the separator plate may be configured to deflect away from the cell layer as a positive function of the pressure differential when exposed to the pressure differential. Deflecting away from the cell layer may maintain (or increase) the spacing between the separator and the cell layer, thereby maintaining (maintaining or increasing) the fluid volume therebetween and improving contact with adjacent cell units.

[0042] A cell stack is provided comprising a plurality of cell units as described above, wherein the second side (e.g., upper side) of the separator plate of a first cell unit is positioned opposite and spaced apart from the first side (e.g., lower side) of the cell layer of the first cell unit to form a first fluid volume for a first fluid therebetween, and the first side (e.g., lower side) of the separator plate of the first cell unit is positioned opposite the electrochemically active cell area of ​​a second adjacent cell unit in the stack of cell units to define a second fluid volume therebetween.

[0043] A cell stack is provided that includes a plurality of cell units, each cell unit including an electrochemically active cell area, a cell layer having a first side and a second side, the second side supporting the electrochemically active cell area, and a separator plate having a first side and a second side, the separator plate comprising a metal sheet, the second side (e.g., an upper side) of the separator plate being positioned below and facing the first side (e.g., a lower side) of the cell layer to form a first fluid volume therebetween for a first fluid. The first side of the separator plate extends across and facing the electrochemically active cell area of ​​an adjacent cell unit in the cell stack to form a second fluid volume therebetween for a second fluid. The separator plate has a region that extends across at least the electrochemically active cell area, the region being free of protrusions toward the cell layer or other components separating the separator plate from a metal support plate. The separator plates are adapted to be subjected to a pressure differential between first and second sides of the separator plates to maintain a spaced apart arrangement that forms a first fluid volume.

[0044] When operating as a fuel cell, the cell stack is configured such that a first fluid volume is for fuel and a second fluid volume is for oxidant. For example, the fuel may be a hydrogen-rich reformate stream (e.g., converted from a hydrocarbon fuel stream such as natural gas). The oxidant may be air or oxygen. When operating as an electrolysis cell, the first fluid volume is for steam.

[0045] The cell stack may be configured such that a first side of a separator plate contacts the outermost layer of the electrochemically active cell area of ​​an adjacent cell unit, providing electrical contact therebetween, and the contact resistance decreases as the pressure difference between the first and second sides of the separator plate increases. For example, as described above, the pressure difference experienced by the separator plate may be caused by the pressure difference between the pressure of a first fluid in a first fluid volume and the pressure of an oxidant, such as air or oxygen, in a second fluid volume on the opposite side of the separator plate.

[0046] In other words, by introducing a pressure differential across the separator plate of one cell unit, the separator plate is forced to deflect toward the electrochemically active area of ​​the adjacent cell unit, resulting in the downward protrusions (or dimples) of the separator plate contacting the electrochemically active area of ​​the adjacent cell unit. This deflection can be achieved across the entire active area without requiring a large protrusion on the opposite side of the separator plate to exert a force in that direction. By contacting the downward protrusions with the electrochemically active area of ​​the adjacent cell unit, contact resistance is reduced, i.e., conductivity is improved throughout the stack.

[0047] In this manner, the separator plate is adapted to be subjected to a pressure differential between the first and second sides of the separator plate to maintain a spaced apart arrangement that forms a first fluid volume.

[0048] (To the extent that there may be protrusions on the second side of the separator plate (over a portion of the area, e.g., 10% or 20%), such protrusions will separate from the first side of the metal support plate under pressure and lift off through holes / pores therein, allowing fuel access to the porous areas of the support plate. It should also be noted that even if there are a few protrusions on the second side of the separator plate, there will be fewer of them than on the first side. Since the fluid pressure applies uniform pressure across the entire plate, there is no need to have protrusions across the entire active area of ​​the second side.)

[0049] A method for manufacturing a cell unit is provided, comprising: providing a planar metal sheet for a separator plate having a first side and a second side, the planar metal sheet having a protrusion; providing a cell layer including an electrochemically active cell area and having the first side and the second side; and overlaying the separator plate and the cell layer such that the separator plate is spaced apart from and faces the first side of the cell layer to form a first fluid volume therebetween, the separator plate having an area extending across at least the electrochemically active cell area, the area being free of protrusions toward the cell layer or other components separating the separator plate from the cell layer.

[0050] The method may include providing a metal support plate with a cell layer including electrochemically active cell areas, a first side of the cell layer being a first side of the metal support plate, a second side of the cell layer being a second side of the metal support plate opposite the first side of the metal support plate, the second side carrying the electrochemically active cell areas. The method may include stamping a planar metal sheet to provide planar protrusions extending from a surface of the planar metal sheet.

[0051] At least one of the separator plate and the cell layer (or the metal support plate supporting the cell layer) can be machined to form a flanged periphery. The flanged periphery of the separator plate and / or the cell layer (or the metal support plate supporting the cell layer) can be integrally formed with the separator plate and / or the cell layer (or the metal support plate supporting the cell layer) by pressing. During manufacture, the separator plate and the cell layer can be directly joined at the flanged periphery, optionally by welding, to form a first fluid volume therebetween.

[0052] As an alternative to (or in addition to) a flanged perimeter, a spacer plate may be provided between the separator plate and the metal support plate. The spacer plate may extend along the perimeter of the separator plate and / or cell layer. The spacer plate may serve to space the plates and define the first fluid volume.

[0053] A method for manufacturing a cell unit stack is provided, the method including providing a plurality of cell units, each manufactured as described above, and positioning one of the plurality of cell units above / below another of the plurality of cell units such that a protrusion of a separator plate of the one of the plurality of cell units extends to and contacts an electrochemically active cell area of ​​another of the plurality of cell units. The positioning above / below further includes providing a gasket between the one of the plurality of cell units and the other of the plurality of cell units.

[0054] A method of operating a cell stack of cell units is provided, the cell stack being as described above, the method including supplying a first fluid to a first fluid volume, supplying a second fluid to a second fluid volume, and adjusting a pressure differential between the first fluid volume and the second fluid volume to maintain a spaced apart configuration that forms the first fluid volume.

[0055] In one aspect of the present invention, a method for operating a cell stack of cell units is provided, wherein each cell unit in the cell stack comprises: a cell layer including an electrochemically active cell area and having a first side and a second side; and a separator plate electrically connected to the cell layer, the separator plate having a first side and a second side, the second side of the separator plate extending across and spaced apart from the first side of the cell layer to form a first fluid volume; and the first side of the separator plate comprises a protrusion oriented away from the first side of the cell layer and toward the second side of the cell layer of an adjacent cell unit to form a second fluid volume. The method includes supplying a first fluid to the first fluid volume, supplying a second fluid to the second fluid volume, and adjusting a pressure difference between the first fluid volume and the second fluid volume to maintain the spaced apart arrangement that forms the first fluid volume. In this way, the electrical connection between the protrusion and the second side of the cell layer of the adjacent cell unit can be controlled by the pressure difference.

[0056] In another aspect of the present invention, an electrochemical cell unit is provided, the electrochemical cell unit comprising: a cell layer including electrochemically active cell areas and having a first side and a second side; and a separator plate electrically connected to the cell layer, the separator plate having a first side and a second side, the second side of the separator plate extending across and spaced apart from the first side of the cell layer to form a first fluid volume, the first side of the separator plate comprising a protrusion oriented away from the first side of the cell layer and toward the second side of the cell layer of an adjacent cell unit, the separator plate being adapted to be subjected to a pressure differential between the first side and the second side of the separator plate to urge the protrusion toward the second side of the cell layer of an adjacent cell unit to maintain the spaced apart arrangement that forms the first fluid volume. In this manner, electrical connection between the protrusion and the second side of the cell layer of an adjacent cell unit can be controlled by the pressure differential.

[0057] In another aspect of the present invention, a method for manufacturing a cell stack including a plurality of electrochemical cell units is provided, the method comprising: providing a plurality of cell units, each cell unit comprising an electrochemically active cell area; a cell layer having a first side and a second side; and a separator plate electrically connected to the cell layer, the separator plate having the first side and the second side, the second side of the separator plate extending across and disposed opposite to and spaced apart from the first side of the cell layer to form a first fluid volume, the first side of the separator plate comprising a protrusion oriented in a direction away from the first side of the cell layer; and stacking the plurality of cell units on top of each other such that the first side of the separator plate of a first cell unit faces the second side of a second, adjacent cell unit in the stack of cell units to define a second fluid volume therebetween. The protrusion of the separator plate of the first cell unit is directed toward a second side of the cell layer of an adjacent cell unit, and the separator plate of the first cell unit is adapted to be exposed to a pressure difference between the first and second sides of the separator plate to maintain an arrangement having a gap that forms a first fluid volume, thereby urging the protrusion toward the second side of the cell layer of the adjacent cell unit.

[0058] Note that if the cell unit is an electrolytic cell unit, the second fluid is produced by a reaction. In other words, the supplying step includes supplying the initial reactants (from a source external to the cell unit) and supplying (or producing by) the products of the electrochemical reaction in the cell unit. For example, in the operation of an electrolytic cell, the first fluid volume of the cell unit is supplied with fuel (in the form of steam from a source external to the cell unit) and the products of the electrolysis reaction, which are hydrogen if the electrolyte is oxygen ion conductive, or oxygen if the electrolyte is proton conductive. Correspondingly, the second fluid volume of the cell unit may be supplied with only the products of the electrolysis reaction, which are oxygen if the electrolyte is oxygen ion conductive (if the fuel is steam) or hydrogen if the electrolyte is proton conductive. Optionally, a sweep gas (e.g., oxygen or air) may be supplied to the second fluid volume from a source external to the cell unit. Such a sweep gas may help evacuate the products of the electrolysis reaction from the second fluid volume.

[0059] A method of operating a cell stack may include supplying fuel (e.g., reformed hydrocarbon fuel or hydrogen in the case of fuel cell operation, or steam and products of the reaction in the case of electrolytic cell operation) to a fuel volume of each cell unit of the cell stack, where the fuel volume of each cell unit is formed between a respective separator plate and a respective cell layer of each cell unit; supplying air or oxygen (from a source external to the cell unit in the case of fuel cell operation, and as a product of the reaction or sweep gas in the case of electrolytic cell operation) to an oxidant fluid volume of each cell unit of the cell stack, where the oxidant fluid volume of each cell unit is formed between the cell units of the cell stack; and adjusting the pressure difference between the fuel volume and the oxidant volume by adjusting the pressure of the reformed hydrocarbon fuel and the pressure of the air or oxygen, respectively.

[0060] The pressure difference between the first and second fluid volumes may be adjusted in the range of 50 mbar to 2 bar, preferably 100 mbar to 1.5 bar, more preferably 200 mbar to 800 mbar.

[0061] The pressure differential is preferably adjusted to reduce the electrical contact resistance between the separator plate and the electrochemically active cell area of ​​a second, adjacent cell unit in the stack of cell units. By increasing the pressure differential, the electrical contact resistance can be reduced, thereby increasing the efficiency of the stack.

[0062] The pressure differential can be regulated, for example, by i) using pumps to pump the first and second fluids at different rates, ii) chokes such as valves or converging-diverging nozzles (e.g., De Laval nozzles) in the piping or flow paths supplying fluids to the first and second fluid inlets of the cell units and / or the entire cell stack, or iii) orifice plates in the piping or flow paths to help regulate the pressure differential between the first and second fluids. Other methods and devices that can be used to establish a pressure differential between the first and second fluids will be readily apparent to those skilled in the art. [Brief explanation of the drawings]

[0063] [Figure 1] FIG. 2 is an exploded perspective view of a fuel cell unit and two gaskets. [Figure 2] FIG. 2 is a second perspective view of the configuration of FIG. 1, viewed from a different angle. [Figure 3] FIG. 1 is a first exploded perspective view of a first configuration including a stack of two cell units separated by a gasket, each cell having two fluid ports. [Figure 4] FIG. 4 is an exploded perspective view of the underside of the configuration of FIG. 3. [Figure 5] FIG. 4 is a cross-sectional view of the configuration of FIG. 3. [Figure 6] FIG. 10 is a first exploded perspective view of a second configuration comprising a stack of two cell units separated by a gasket, with each cell having four fluid ports. [Figure 7] FIG. 7 is an exploded perspective view of the underside of the configuration of FIG. 6. [Figure 8] FIG. 10 is a first exploded perspective view of a third configuration comprising a stack of two cell units separated by a gasket, with each cell having four fluid ports and a spacer plate. [Figure 9] FIG. 9 is an exploded perspective view of the underside of the configuration of FIG. 8. [Figure 10] FIG. 9 is a cross-sectional view of the configuration of FIG. 8. [Figure 11] 1 illustrates a method for manufacturing a cell unit according to the present invention. [Figure 12] 1 illustrates a method for operating a cell stack in steady state according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0064] The figures show only two electrochemical cell units (hereinafter simply referred to as "cell units") in the stack for illustrative purposes only. In various embodiments, multiple cells are provided. In further embodiments (not shown), multiple electrochemical cell stacks are provided, and in still further embodiments, multiple electrochemical cell stacks are provided, each containing multiple electrochemical cells. It will be understood that the anode and cathode inlets, outlets (off-gas), ducts, manifolds, and their configurations are appropriately modified to accommodate such embodiments, as would be readily apparent to one skilled in the art.

[0065] Referring to FIG. 3 , cell unit 300 comprises a flat (i.e., planar) metal support plate 314 stacked adjacent to separator plate 312. Metal support plate 314 is shown with a flanged peripheral feature 318 around its periphery. The flanged peripheral feature 318 extends outward from the sheet's major plane as seen in the central fluid volume area, creating a recess in metal support plate 314 (and a protrusion on the outer surface). The recess forms a first fluid volume 360 ​​within the cell unit upon assembly. The separator plate comprises a metal sheet having a first side and a second side. The second side of the separator plate extends across and faces the first side of the cell layer. The two plates are sealed (e.g., welded) around their peripheries to enclose / seal the enclosed first fluid volume.

[0066] The cell unit 300 has rounded edges and parallel sides, with one fluid port 322 towards each end on both the separator plate 312 and the metal support plate 314. Other shapes, sizes, and numbers of each cell feature are possible depending on the power requirements and dimensions of the final stack assembly.

[0067] The cell unit 300 has an electrochemically active layer 350 provided on a cell layer (shown here as a metal support plate with the cell layer) in the center thereof. In this embodiment, the active layer 350 is disposed outside the first fluid volume 360.

[0068] The electrochemically active area 350 includes an anode, a cathode, and an electrolyte (not shown) disposed between the anode and cathode. The anode, electrolyte, and cathode may be collectively referred to as the electrochemically active layer 350, the active electrochemical cell layer, or the electrochemically active region. The electrochemically active region may be a continuous, generally rectangular region, generally uninterrupted. Alternatively, the electrochemically active cell region may be wrapped around a fluid port to increase the proportion of the cell unit area that is electrochemically active, thereby increasing the power density of the stack of cell units. In other words, near the port, the edges of the active cell region are shaped to conform to the shape of the port. The edges of the active cell region form a partial circle concentric with the port. The edges of the active cell region are spaced from the edges of the port to provide space for formed port features and / or gaskets disposed around the port.

[0069] The electrolyte conducts negative oxygen ions or positive hydrogen ions between the anode and cathode.

[0070] The stack may include a stack of cell units based on solid oxide electrolyte, polymer electrolyte membrane, molten electrolyte, or any other variant capable of electrochemical reaction.

[0071] Figure 4 shows the same cell unit 300 as Figure 3 from a different perspective. Figure 5 shows a cross-section of Figure 3, taken from the rear left to the front right and toward the rear center. Molded port features 324 are provided around the fluid ports of the metal support 314. The molded port features 324 are provided as multiple elements in the form of protrusions with a common height, extending from the plane of the bottom of the fluid volume a distance corresponding to the height of the flanged periphery 318. This is so that, when the cell unit 300 is assembled, the molded port features, like the flanged periphery 318, contact the opposing surface of the separator plate 312. As a result, when the flanged periphery 318 is joined to the separator plate 312, for example by welding, the molded port features 324 also contact the separator plate 312. The protrusions may have a circular, square, cross, pentagonal, or hexagonal cross-sectional shape. They may also have an elliptical or irregular polygonal cross-section.

[0072] The concave configuration can give the associated plate the appearance of a rimmed tray, with a correspondingly convex profile (outwardly relative to the cell unit) and a typically planar bottom surface, thus defining (e.g., a portion of) a first fluid volume 360 ​​within the assembled cell unit. In this concave configuration, the flanged periphery 318 extends from the plane of the original sheet of separator plate and / or the plane of the metal support plate toward the opposing surface of the other of the separator plate and metal support plate, respectively.

[0073] As such, the first fluid volume 360 ​​is bounded by a flanged perimeter 318 formed by a pressing operation such as die pressing, hydroforming, stamping, or the like.

[0074] The metal support plate 314 (e.g., a metal foil) is provided with a plurality of small holes or pores 348 that allow a first fluid in a first fluid volume 360 ​​to be in fluid communication with the cell layer / electrochemical layer supported by the second side (top side as shown) of the metal support plate. These holes or pores form a porous region surrounded by a non-porous region. The anode (fuel electrode) layer is disposed adjacent to the small holes / pores, and the (enclosed) fluid volume 360 ​​within the cell unit includes a first fluid volume 360 ​​that is supplied by the first fuel entering and leaving through the fluid port 22.

[0075] The first fluid may be a fuel (a (reformed) hydrocarbon or other fuel (e.g., ammonia) when operating as a fuel cell, or steam when operating as an electrolysis cell), in which case the fluid port 322 is a fuel port 322. The anode (fuel electrode) layer may be coated or otherwise deposited on the metal support plate 314. The cathode (air electrode) layer is on the opposite, or outer, surface of the electrochemically active layer 350 and is exposed to air flowing across it during use of the cell unit.

[0076] In the cell units shown in Figures 3, 4 and 5, only two layers (components) are required: a metal support plate and a separator plate.

[0077] The separator plate 312 also includes protrusions 336 extending from the separator plate 312 toward adjacent cell units (i.e., away from the metal support plate 314 of the cell unit of which the separator plate is a component). These downward protrusions 336 (in the plan view area of ​​the electrochemically active layers) include outward (downward as shown) protrusions that extend from the separator plate 312 to contact the outer surfaces of the electrochemically active layers of the cell units adjacent to the separator plate in the stack of cell units. The central downward protrusions 336 define a fluid path for an oxidant (such as air) between or within them, through a second fluid volume 365 defined between the downward protrusions and the outer surfaces of the electrochemically active layers of the adjacent cell units.

[0078] When formed into a stack of cell units, the second side of the separator plate of a first cell unit faces the first side of the cell layer of the first cell unit, spaced apart, to form a first fluid volume therebetween for a first fluid, and the first side of the separator plate of the first cell unit faces the electrochemically active cell area of ​​a second adjacent cell unit in the stack of cell units, to define a second fluid volume therebetween. The first fluid volume is for a first fluid (such as a fuel in the form of a reformed hydrocarbon fuel or other fuel (e.g., ammonia) during fuel cell operation, or steam during electrolysis cell operation), and the second fluid volume is for a second fluid (such as an oxidant during fuel cell operation, or produced oxygen during electrolysis cell operation). Two or more gaskets 334 are provided on the underside of each cell unit between each cell unit in the stack (one surrounding each port, but there may be more than two), i.e., gaskets are disposed between adjacent cell units in the stack. There may be multiple inlet and outlet ports.

[0079] Each gasket 334 (also referred to as a "seal") provides a primary sealing function and is preferably compressible. To achieve its sealing function, the gasket is subjected to a compressive force near the port, e.g., by a means capable of applying a compressive force. The gasket is sized to fully cover the molded port feature 324 of each fluid port 322, preventing leakage of a first fluid that may pass through the fluid port 322 (e.g., fuel in the form of a (reformed) hydrocarbon fuel or other fuel (e.g., ammonia) during fuel cell operation, or steam during electrolysis cell operation) from between the outside of the cell unit 300 and the gasket 334 into an area external to the cell unit 300, i.e., a second fluid volume surrounding the cell unit 300 (e.g., oxidant during fuel cell operation, or produced oxygen during electrolysis cell operation), and preventing fluid outside the fluid port from leaking in the reverse direction, i.e., back into the fluid port. This may help prevent mixing of fluids within the cell unit 300, which may be fuel and oxidant, with fluids outside the cell unit 300, and the polarity of the electrochemically active layer 350 determines which way this is oriented.

[0080] The gasket may also provide electrical insulation between the first cell unit and the adjacent fluid cell unit to prevent short circuits. The gasket may be any suitable cell gasket (sealing ring), such as, for example, Thermiculite™.

[0081] Compressive forces within the stack near the electrochemically active layers are typically necessary for good electrical contact between the cell units in the stack and, therefore, good conductivity throughout the stack. The central downward projection 336 creates the necessary electrical contact between the cell units (and the joining, preferably welding, of the separator and cell layers electrically connects these components). For example, in a stack configuration, the central downward projection 336 on the first side of the separator plate 312 of the first cell unit in the stack contacts the outermost layer of the electrochemically active cell area of ​​the adjacent cell unit in the stack, providing electrical contact therebetween.

[0082] 1 and 2, the first configuration does not have a central protrusion, i.e., a protrusion extending between the interior facing surfaces of the two plates (i.e., the separator plate and the cell layer / metal support plate). Thus, fuel enters the first fluid volume 360 ​​through fluid port 322 and can flow freely across the entire surface of separator plate 312 and throughout the first fluid volume.

[0083] Furthermore, as shown in Figures 3, 4 and 5, the area of ​​the separator plate 312 located below the electrochemically active layer 350 of the cell is free of any other components that may serve to separate the separator plate 312 from the metal support plate 314.

[0084] Also, unlike the prior art shown in Figures 1 and 2, the first configuration does not have a central upward protrusion extending between the inner facing surfaces of the two plates, and therefore there is no mechanism within the cell unit that provides support to the cell unit in a central region that extends toward the metal support plate (or, as shown in Figures 3, 4, and 5) in the area of ​​the small holes (also called the porous region, which corresponds to the plan view extent of the electrochemically active layer).

[0085] In conventional designs (e.g., Figures 1 and 2), cell units are stacked with gaskets 34 between each repeating unit. Before compression, the gaskets 34 are thicker than the height of the protrusions 36, and the protrusions do not contact the next unit. When the stack is compressed, initially, the compression force acts only through the gaskets (because the protrusions are not in contact). At some point, the gaskets 34 are compressed enough that the protrusions come into contact. As the stack is further compressed, the compression force acts through the gaskets 34 and the protrusions 36. This can lead to the problems described above.

[0086] In this new concept, the absence of protrusions directed toward the cell layer 348 allows the gasket 334 to compress as needed without compressive forces acting through protrusions or other structures near the active cell area (though some substrate / interconnect movement may occur depending on plate stiffness, etc., but such movement is minimal). Thus, compression in the active cell area is decoupled from gasket compression and can be controlled by a pressure differential, which acts to push apart the cell layer (its metal support plate 314) and interconnect 312 of a cell unit (of which the cell layer and interconnect are components). As a result, the interconnect of that cell unit is forced toward and contacts the adjacent cell unit (usually the electrochemically active layer of the cell layer of the adjacent cell unit), thereby creating the necessary electrical contact between the adjacent cell units. This new configuration significantly reduces the force transmitted by the protrusions 316. The net force through the protrusions and active area is achieved by the pressure differential.

[0087] 6 and 7, cell unit 600 is similar to cell unit 300 of FIGS. 3, 4, and 5, except that separator plate 612 of cell unit 600 has a flanged periphery 618 instead of a metal support plate 614, and separator plate 618 is provided with molded porting and a different configuration of fluid ports. Flanged periphery 618 extends outward from the major plane of the sheet, as seen in the central fluid volume area, creating a recess in the separator plate (and a protrusion on the outer surface). The recess forms a first fluid volume 660 within the cell unit upon assembly.

[0088] It should be noted that the configurations of Figures 6 and 7 can be modified in the manner already described with respect to the configurations of Figures 3, 4, and 5. For example, the first fluid volume can be formed by a flanged periphery of either or both the separator and the metal support plate. If both have flanges, the total height of the molded port feature can be the same as the sum of both flanges. One plate may have a flange and the other plate may have a port feature. More than two ports may be provided.

[0089] The cell unit 600 has rounded edges and parallel sides, with one fluid port 622 toward each corner of both the separator plate 612 and the metal support plate 622, for a total of four fluid ports 622. Other shapes, sizes, and numbers of each cell feature are possible, depending on the power requirements and dimensions of the final stack assembly.

[0090] The separator plate 612 is provided with molded port features around the fluid port 622, similar to the molded port features of the cell unit 300. The molded port features are provided as multiple elements in the form of protrusions having a common height, extending from the plane of the bottom of the fluid volume 660 a distance corresponding to the height of the flanged perimeter 618. This is so that, when the cell unit 600 is assembled, the molded port features, like the flanged perimeter 618, contact the opposing surface of the metal support plate 614. As a result, when the flanged perimeter 618 is joined to the metal support plate 614, for example by welding, the molded port features also contact the metal support plate 614. The protrusions may have a circular, square, cross, pentagonal, or hexagonal cross-sectional shape. They may also have an elliptical or irregular polygonal cross-section.

[0091] 8, 9, and 10, cell unit 800 is similar to (and shown from a similar perspective as) cell units 300 and 600 described above, except that neither separator plate 812 nor metal support plate 814 of cell unit 800 has a flanged periphery. A spacer plate 816 is provided between separator plate 812 and metal support plate 814 of cell unit 800 to form a first enclosed fluid volume 860 between separator plate 812 and metal support plate 814.

[0092] The cell unit 800 has rounded edges and parallel sides, with one fluid port 822 toward each corner of the separator plate 812, metal support plate 814, and spacer plate 816, for a total of four fluid ports 822. Other shapes, sizes, and numbers of each cell feature are possible depending on the power requirements and dimensions of the final stack assembly.

[0093] When the spacer plate 816 is in place within the cell unit, it is positioned above / below the periphery of the separator plate 812 and below / above the periphery of the metal support plate 814. A central hollow portion 817 of the spacer plate 816 is positioned above / below the central downward protrusion 836 that extends between the separator plate 812 and the area of ​​the electrochemically active layer of the cell unit adjacent the outward protrusion. The hollow central portion 817 is also positioned below / above the porous region (multiple small holes) in the metal support plate 812, allowing fluid in the first fluid volume to fluidly communicate with the side of the electrochemical layer closest to the metal support plate 814. When sandwiched between the separator plate 812 and the metal support plate 814, the hollow portion 817 of the spacer plate 816 defines a fluid volume for fuel between the separator plate 812 and the metal support plate 814.

[0094] Unlike the first and second configurations, the third configuration does not include molded porting around the fluid ports in the separator plate. The spacer plate serves to provide separation between the metal support plate of the cell unit and the separator plate. The throat in the spacer plate allows fluid communication between the ports and the first fluid volume.

[0095] In each of the above-described configurations, there is no central upward protrusion extending between the inner facing surfaces of the two plates (i.e., the separator plate and the cell layer / metal support plate), so a means is provided for establishing and maintaining a first fluid volume 360, 660, 860 between the metal support plate 314, 614, 814 and the separator plate 312, 612, 812 during operation of the cell unit.

[0096] When the cell unit 300, 600, 800 is a fuel cell unit (or stack of fuel cell units), fuel (i.e., anode inlet gas, e.g., hydrocarbon fuel, reformed hydrocarbon fuel, H, ammonia) is routed to the anode inlet of the cell unit and flows through port 332, 632, 832 into a first fluid volume (fuel volume) between the separator plate 312, 612, 812 and the cell layer (or metal support plate 314, 614, 814). Simultaneously, oxidant (i.e., cathode inlet gas) is routed to the cathode inlet of the cell unit and flows on both sides of the separator plate 312, 612, 812 and the cell layer (or metal support plate 314, 614, 814). The fuel and oxidant may flow in the same direction on each side of the cell unit, in a co-flow configuration. Alternatively, the fuel and oxidant may flow in a counter-flow or cross-flow configuration.

[0097] When the cell unit 300, 600, 800 is a fuel cell unit, the fuel and oxidant are supplied to the fuel cell unit at different pressures, creating a pressure difference between the fuel and oxidant as they pass through the fuel cell unit. This results in a pressure difference between the first side (close to the oxidant) and the second side (close to the fuel) of the separator plate 312, 612, 812. By creating a pressure difference between the first and second sides, the separation between the separator plate (the second side) and the cell layer (the first side) (or the first side of the metal support plate 314, 614, 814) can be controlled. For example, maintaining or expanding the separation can create and maintain a first fluid volume.

[0098] To enable the separation between the separator plate 312, 612, 812 and the cell layer (or metal support plate 314, 614, 814) to be maintained or increased by establishing a pressure differential between the first side and the second side, the separator plate may be adapted or configured to deflect when exposed to a pressure differential. For example, when exposed to a pressure differential, the separator plate may deflect away from the cell layer (or metal support plate) of a cell unit (toward an adjacent cell unit) as the pressure differential increases; i.e., the separator plate is adapted to deflect away from the cell layer (or metal support plate) as a positive function of the pressure differential when exposed to a pressure differential.

[0099] In a stack configuration, a central downward projection 336, 636, 836 on a first side of the separator plate 312, 612, 812 of a first cell unit in the stack contacts the outermost layer of the electrochemically active cell area of ​​an adjacent cell unit in the stack, providing electrical contact therebetween.

[0100] When each separator plate 312, 612, 812 is subjected to a pressure differential that causes it to deflect away from the cell layer (or metal support plate 314, 614, 814) of the corresponding cell unit, the contact resistance between the central downward protrusion 336, 636, 836 and the outermost layer of the electrochemically active cell area of ​​the adjacent cell unit decreases. In other words, as the pressure differential between the first and second sides of the separator plate increases, the contact resistance between the central downward protrusion 336, 636, 836 and the outermost layer of the electrochemically active cell area of ​​the adjacent cell unit decreases.

[0101] During operation, the pressure differential between the first and second sides of the separator plate can be controlled in the range of 50 mbar to 2 bar, preferably 100 mbar to 1.5 bar, and more preferably 200 mbar to 800 mbar.

[0102] The method for manufacturing any of the cell units described in any of the above embodiments includes multiple steps / operations. The method includes the following steps:

[0103] In step 1110, a separator plate having a first side and a second side is provided, for example, by cutting or punching. The separator plate may be, for example, a non-porous planar metal sheet or other non-porous planar sheet, and serves to separate one cell unit from adjacent cell units in the stack. The separator plate may be provided with a protrusion extending therefrom, which may be provided by pressing / forming in the same step as the cutting / punching.

[0104] In step 1120, a cell layer is provided, including an electrochemically active cell area, including an anode, a cathode, and an electrolyte (not shown) disposed between the anode and cathode. The cell layer has a first side and a second side and can preferably be a metal-supported cell layer. Adding the cell layer can involve depositing or coating the cell layer on a planar metal sheet, for example, by printing the electrochemically active cell area onto the cell layer, thereby forming a metal-supported cell layer with porous regions (pores) that provide fluid communication from the first side to the electrodes supported by the metal support plate on the second side. Alternatively, the cell layer can be self-supporting. For example, the cell layer can have an anode-supported, electrolyte-supported, or cathode-supported architecture. For purposes of explanation only, the term "metal support plate" is used below, but may be interchangeable with "cell layer" or "metal plate-supported cell layer."

[0105] Step 1110 or step 1120 preferably involves providing a cell layer (or metal plate support cell layer) having a flanged perimeter 318, or providing a separator plate having a flanged perimeter 618. The flanged perimeter 318 or 618 extends outwardly from a major planar surface of the metal plate support plate 314 or separator plate 618, respectively.

[0106] The flanged periphery 318 forms a recess in (and a protrusion relative to the outer surface of) the metal support plate 314. The recess forms a first fluid volume 360 ​​within the cell unit when the cell unit is assembled.

[0107] The flanged periphery 618 forms a recess in the separator plate (and a protrusion relative to the outer surface) that forms a fluid volume within the cell unit when the cell unit is assembled.

[0108] The flanged periphery of either the separator plate or the metal support plate may be manufactured by pressing the separator plate or the metal support plate (of the cell layer), respectively.

[0109] Instead of a flanged perimeter, a spacer plate may be provided and sandwiched between the separator plate and the metal support plate to form a first fluid volume therebetween.

[0110] Steps 1110 and 1120 also include providing multiple fluid ports 322, 622, 822 in both the separator plate and the metal support plate to enable the flow of fluid (e.g., reformed fuel) through the cell units (and ultimately the stack of cell units) and to supply fuel to each cell unit, and in particular to supply fuel to the first fluid volume of each cell unit.

[0111] In step 1130, the separator plate and the metal support plate are stacked in a spaced-apart arrangement to form a first fluid volume therebetween. Thus, the separator plate has a region extending across at least the electrochemically active cell area. In step 1130, the separator plate and the metal support plate are stacked together, and when the cell units are placed in a stacked configuration, the separator plate's protrusions extending out of its plane are oriented away from the first fluid volume toward the adjacent cell units. In other words, the separator plate has a continuous region extending across at least the electrochemically active cell area that does not have any protrusions toward the metal support plate. Furthermore, this region is devoid of any other components configured to resist the compressive force of the stack and transmit that force to the protrusions connecting the adjacent cell units. Thus, within the first fluid volume between the separator plate and the metal support plate, there are no components that aid in their physical separation (especially during operation).

[0112] In step 1130, the separator plate and the metal support plate are directly (and hermetically) joined at the flanged periphery to form a first fluid volume therebetween. The separator plate and the metal support plate may optionally be directly joined by welding.

[0113] In an alternative arrangement without a flanged periphery, a spacer plate is sandwiched between the separator plate and the metal support plate to form a first fluid volume therebetween, and at 1130 the three plates are hermetically secured together, for example by welding the periphery.

[0114] The method can continue by forming a stack of cell units, with the second side of the separator plate of a first cell unit (formed as described above) positioned above / below a second cell unit, with the first side of the separator plate of the first cell unit facing the electrochemically active cell area of ​​a second adjacent cell unit in the stack of cell units to seal a second fluid volume therebetween. When forming the stack, multiple gaskets are provided corresponding to the multiple fluid ports of the cell units. Each gasket is positioned around the fluid port of an adjacent cell unit in the stack. The function of the gaskets has already been described above.

[0115] The method for operating the cell stack of cell units described in the above embodiment includes several steps / operations as follows.

[0116] In step 1210, a first fluid is provided to a first fluid volume formed between the separator plate and the metal support plate. The first fluid may be a fuel. When operating as a fuel cell, the first fluid may be a hydrocarbon fuel, a reformed hydrocarbon fuel, ammonia, H2, methanol, etc. When operating as an electrolysis cell, the first fluid is typically steam.

[0117] In step 1220, a second fluid is supplied to a second fluid volume formed between the separator plate of a first cell unit in the stack and the electrochemically active cell area of ​​a second adjacent cell unit in the stack. The second fluid may be an oxidant fluid. When operating as a fuel cell, the second fluid may be an oxidant fluid, such as air or oxygen, supplied to the second fluid volume via an inlet. When operating as an electrolysis cell, the second fluid is typically oxygen produced in the electrolysis reaction.

[0118] In step 1230, a pressure difference between the first fluid volume and the second fluid volume is adjusted to maintain the spacing arrangement forming the first fluid volume. For example, the pressure between the first fluid (e.g., fuel) and the second fluid (e.g., air / oxygen) can be adjusted to create a pressure difference between the two fluids. This pressure difference deflects the separator plate, expanding the spacing between the separator plate and the metal support plate, thereby creating and maintaining the spacing arrangement forming the first fluid volume. The pressure difference between the first fluid volume and the second fluid volume can be in the range of 50 mbar to 2 bar, preferably 100 mbar to 1.5 bar, and more preferably 200 mbar to 800 mbar. Adjusting the pressure difference can also be performed to reduce electrical contact resistance between the separator plate and the electrochemically active cell area of ​​a second adjacent cell unit in the stack (the pressure in the first fluid volume is controlled to be higher than the pressure in the second fluid volume, and the contact resistance decreases as the pressure difference increases).

[0119] The pressure difference may be adjusted by using pressure pumps to pump the first and second fluids at different rates. Alternatively or additionally, the flow of the first and / or second fluids may be blocked by providing valves or converging-diverging nozzles (e.g., Laval nozzles) in the piping or channels supplying the fluids to the cell units of the stack. Alternatively or additionally, orifice plates may be provided in the piping or channels to assist in adjusting the pressure difference. Other methods and devices that may be used to establish the pressure difference will be readily apparent to those skilled in the art.

[0120] The present invention is not limited to the above examples, and other embodiments will be readily apparent to those skilled in the art without departing from the scope of the appended claims.

[0121] These and other features of the invention have been described above purely by way of example, and modifications of the invention in detail may be made within the scope of the appended claims.

Claims

1. 1. A method of operating a cell stack of cell units, comprising the steps of: a cell layer including an electrochemically active cell area and having a first side and a second side; a separator plate electrically connected to the cell layer, the separator plate having a first side and a second side, the second side of the separator plate extending across and spaced apart from the first side of the cell layer to define a first fluid volume; the first side of the separator plate includes a protrusion oriented away from the first side of the cell layer and toward a second side of the cell layer of an adjacent cell unit to form a second fluid volume; The method comprises: supplying a first fluid to the first fluid volume; supplying a second fluid to the second fluid volume; adjusting a pressure differential between the first fluid volume and the second fluid volume to maintain a spacing arrangement that defines the first fluid volume; A method comprising:

2. 2. The method of claim 1, wherein the pressure difference between the first fluid volume and the second fluid volume is adjusted to a range of 50 mbar to 2 bar, preferably 100 mbar to 1.5 bar, more preferably 200 mbar to 800 mbar.

3. 3. The method of claim 1, wherein the pressure difference between the first fluid volume and the second fluid volume is adjusted to reduce electrical contact resistance between the separator plate and the second side of the adjacent cell unit in the stack of cell units.

4. An electrochemical cell unit, a cell layer including an electrochemically active cell area and having a first side and a second side; a separator plate electrically connected to the cell layer, the separator plate having a first side and a second side, the second side of the separator plate extending across and spaced apart from the first side of the cell layer to define a first fluid volume; the first side of the separator plate includes a protrusion oriented in a direction away from the first side of the cell layer and toward a second side of the cell layer of an adjacent cell unit; the separator plate is adapted to be subjected to a pressure differential between the first side and the second side of the separator plate to urge the protrusions toward the second side of the cell layer of the adjacent cell unit to maintain the spacing arrangement that forms the first fluid volume. Electrochemical cell unit.

5. 5. The electrochemical cell unit of claim 4, wherein the cell layer architecture is selected from any of metal-supported, anode-supported, electrolyte-supported, or cathode-supported architectures.

6. 6. The electrochemical cell unit of claim 4 or 5, wherein the cell layer is a metal-supported cell layer, the first side of the cell layer is a first side of a metal support plate, the second side of the cell layer is a second side of the metal support plate located opposite the first side of the metal support plate, and the second side carries the electrochemically active cell area.

7. the separator plate has an area extending across at least the electrochemically active cell area; the region is free of protrusions toward the cell layer or other components for separating the separator plate from the cell layer; The electrochemical cell unit according to any one of claims 4 to 6.

8. 8. The electrochemical cell unit according to claim 4, wherein the protrusion is in the region that overlaps at least the electrochemically active cell area of ​​the adjacent cell unit.

9. 9. The electrochemical cell unit according to claim 4, wherein the separator plates are made of metal.

10. 10. The electrochemical cell unit according to claim 4, wherein the protrusions are formed by pressing the separator plates.

11. an inlet and an outlet to and from the first fluid volume disposed towards opposite edges of the cell unit, with an electrochemically active cell area disposed therebetween; The electrochemical cell unit according to any one of claims 4 to 10, further comprising:

12. 12. The electrochemical cell unit of claim 11 , wherein one or both of the separator plate and the cell layer comprises a second plurality of protrusions extending outward toward and contacting the other of the separator plate and the cell layer at a plurality of contact points surrounding the inlet to and the outlet from the first fluid volume.

13. 13. The electrochemical cell unit of claim 4, wherein at least one of the separator plate and the cell layer comprises a flanged periphery, and the separator plate and the cell layer are directly joined, optionally by welding, at the flanged periphery to form the first fluid volume therebetween.

14. 14. The electrochemical cell unit according to claim 4, wherein the separator plates are adapted to deflect away from the cell layer when exposed to the pressure difference.

15. the second side of the separator plate of a first cell unit is disposed opposite and spaced from the first side of the cell layer of the first cell unit to form a first fluid volume therebetween for a first fluid; the first side of the separator plate of the first cell unit faces the second side of a second, adjacent cell unit in the stack of cell units to define a second fluid volume therebetween; A cell stack comprising a plurality of electrochemical cell units according to any one of claims 4 to 14.

16. The cell stack of claim 15, wherein the protrusion of the separator plate of the first cell unit contacts the second side of the second cell unit in the stack of cell units, preferably contacts the outermost layer of the electrochemically active cell area of ​​the second cell unit in the stack of cell units.

17. 17. The cell stack of claim 15 or 16, wherein the first fluid volume is for fuel and the second fluid volume is for oxidant.

18. 1. A method for manufacturing a cell stack including a plurality of electrochemical cell units, comprising: providing a plurality of cell units, each cell unit comprising: a cell layer including an electrochemically active cell area and having a first side and a second side; and a separator plate electrically connected to the cell layer, the separator plate having a first side and a second side, the second side of the separator plate extending across and positioned opposite the first side of the cell layer in a spaced relationship to form a first fluid volume, the first side of the separator plate comprising a protrusion directed away from the first side of the cell layer; stacking the plurality of cell units one on top of the other such that the first side of the separator plate of a first cell unit faces the second side of a second, adjacent cell unit in the stack of cell units to define a second fluid volume therebetween; the protrusion of the separator plate of the first cell unit is directed toward a second side surface of the cell layer of an adjacent cell unit; the separator plate of the first cell unit is adapted to be subjected to a pressure differential between the first side and the second side of the separator plate to urge the protrusions toward the second side of the cell layer of the adjacent cell unit to maintain the spacing arrangement that forms the first fluid volume; method.

19. The method according to claim 18, wherein the plurality of cell units are those according to any one of claims 4 to 14.

20. Each of the plurality of cell units providing a separator plate having a first side and a second side and having a protrusion; providing a cell layer including an electrochemically active cell area and having a first side and a second side; overlaying the separator plate and the cell layer such that the separator plate extends across and is spaced apart from the first side of the cell layer to define a first fluid volume therebetween, the separator plate having an area extending across at least the electrochemically active cell area; 20. The method of claim 18 or 19, provided by

21. 21. The method of claim 20, wherein the region is free of protrusions toward the cell layer or other components for separating the separator plate from the cell layer.

22. The method according to any one of claims 18 to 21, wherein the protrusions are formed by pressing the separator plate.

23. at least one of the separator plate and the cell layer is processed to form a flanged periphery; the separator plate and the cell layer are directly joined, optionally by welding, at the flanged periphery to form a first fluid volume therebetween; The method according to any one of claims 18 to 22.

24. 24. The method of claim 23, wherein the flanged periphery is formed by pressing at least one of the separator plate and the cell layer.

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