Electrochemical cell with flat separator

Abstract

The present invention relates to a method of operating a battery stack of battery cells, each battery cell in the battery stack comprising: a battery layer comprising an electrochemically active battery region, the battery layer having a first side and a second side; a separator plate electrically connected to the battery layer, the separator plate having a first side and a second side, the second side of the separator plate extending through and facing the first side of the battery layer in a spaced arrangement to form a first fluid volume, and the first side of the separator plate comprising a protrusion, the protrusion is directed away from a first side of the battery layer and toward a second side of the battery layer adjacent a battery cell to form a second fluid volume, the method comprising: providing a first fluid to the first fluid volume; providing 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 a spaced arrangement forming the first fluid volume.

Description

Technical Field

[0001] The present invention relates to an electrochemical cell unit having a flat separator, and in particular, to fuel cell units and electrolytic cell units, stacks comprising such cell units, methods for manufacturing separator plates (interconnects) used in such cell units, separator plates thus formed, and the use of such cell units. The cell units of the present invention include solid oxide, polymer electrolyte membrane, and molten carbonate types of cells. The present invention more particularly relates to solid oxide fuel cells (SOFCs) and solid oxide electrolytic cell (SOEC) units, and these may include metal-supported solid oxide fuel cells (MS-SOFCs) or electrolytic cell (MS-SOEC) units. Background Art

[0002] Some electrochemical cell units can generate electricity by an electrochemical conversion process that uses an oxidizing fuel to generate electricity. Some electrochemical cell units can also or alternatively operate as regenerative fuel cell (or reverse fuel cell) units (often referred to as electrolytic cell units), for example, to produce hydrogen and oxygen from water, or carbon monoxide and oxygen from carbon dioxide. Their construction can be tubular or planar. Planar electrochemical cell units can be arranged stacked on top of each other in a stacked arrangement, for example, in stacks of 100 to 200 electrochemical cell units, where the individual electrochemical cell units are arranged, for example, in electrical series.

[0003] The electricity-generating solid oxide fuel cell (SOFC) is based on a solid oxide electrolyte that conducts negative oxygen ions from the cathode to the anode located on the opposite side of the electrolyte. For this purpose, fuel or reformed fuel 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 fracture. Thus, metal-supported SOFCs have been developed, which have an active fuel cell component layer supported on a metal substrate. In these cells, the ceramic layer can be very thin because they only perform an electrochemical function: that is, the ceramic layer is not self-supporting, but is a thin coating / membrane placed on and supported by the metal substrate. Such metal-supported SOFC stacks are stronger, less costly, have better thermal performance, and can be manufactured using conventional metal welding techniques compared to ceramic-supported SOFCs.

[0004] A solid oxide electrolytic cell (SOEC) can have the same structure as an SOFC, but basically operates as an SOFC in reverse or in a regenerative mode to achieve the electrolysis of water and / or carbon dioxide by inputting electrical energy and using a solid oxide electrolyte to produce hydrogen and / or carbon monoxide and oxygen.

[0005] The present invention relates to an electrochemical cell unit and to the design of separator plates for them. It is thus applicable to various types of fuel and electrolytic cells, for example cells based on solid oxide electrolytes, polymer electrolyte membranes or molten electrolytes. For convenience, the term "cell unit" is used to refer to an "electrochemical cell unit", including fuel cell units or electrolytic cell units.

[0006] Each cell unit in a stack of cell units typically includes a cell layer that includes an electrochemically active cell region (such as a metal-supported electrochemically active cell region) and a separator plate. The separator plate typically contacts one side of the cell layer of a cell unit, and in a stack of cell units, the separator plate can also contact the opposite side of the cell layer of an adjacent cell unit. In a stack of cell units, a separator plate that contacts one side of the cell layer of its cell unit and the opposite side of the cell layer of an adjacent cell unit can be referred to as an "interconnect".

[0007] Figure 1 shows an exploded perspective view of a cell unit with two gaskets from the applicant's previous application GB 2603665 A, which discussed electrochemical cell units and a stack including a plurality of such electrochemical cell units and raised elements. The cell unit 10 of Figure 1 includes a flat (i.e., planar) metal support plate 14 stacked beside a separator plate 12. The separator plate 12 is shown as having a flanged perimeter 18 around its perimeter. The flanged perimeter 18 extends out of the main plane of the sheet, as found in the central fluid volume region, to form a concave surface in the separator plate (and a convex surface on the outer surface). When the cell unit is assembled, the concave surface will form a fluid volume within the cell unit.

[0008] In the arrangement shown in Figure 1, the cell unit 10 has circular ends and parallel sides, where fluid ports 22 face each end in both the separator plate 12 and the metal support plate 14. Other shapes and sizes and numbers of corresponding cell features are possible, depending on the power and size required for the final stack assembly.

[0009] Formed port features 24 are provided around the fluid ports of the separator plate 12. The formed port features 24 are provided as a plurality of elements in the form of circular pits that extend a distance corresponding to the height of the flanged perimeter 18 from the plane of the base of the fluid volume to have a common height therewith. This causes them to contact the opposite surface of the metal support plate 14 when the cell unit 10 is assembled, just like the flanged perimeter 18. Thus, when the flanged perimeter 18 is joined to the metal support plate 14, for example by welding, the formed port features 24 will likewise contact the metal support plate 14.

[0010] In the middle part of the battery cell 10, the electrochemically active layer 50 is disposed on a metal support plate. In this example, it is located outside the enclosed fluid volume.

[0011] The electrochemically active region 50 includes an anode, a cathode, and an electrolyte (not shown) located between the anode and the cathode. The anode, electrolyte, and cathode may be collectively referred to as the electrochemically active layer 50, the active electrochemical cell layer, or the electrochemically active region. The electrolyte conducts negative oxygen ions or positive hydrogen ions between the anode and the cathode. The stack 20 may include a stack of battery cells based on one of a solid oxide electrolyte, a polymer electrolyte membrane, or a molten electrolyte, or any other variant having electrochemical capabilities.

[0012] The concave configuration can give the associated plate the appearance of a framed tray, with a corresponding convex outer shape (relative to the exterior of the battery cell) and a generally planar base, so that the concave surface defines a fluid volume (e.g., a portion thereof) in the assembled battery cell. In such a concave configuration, a flanged perimeter extends outwardly from the plane of the original sheet of the separator plate and / or the metal support plate toward the respective opposing surface of the other of the separator plate and the metal support plate.

[0013] Thus, the fluid volume is bounded by the flanged perimeter, which is formed by pressing (such as by using a die press), hydroforming, or stamping. These are simple processes that have been carried out when forming a central protrusion (described below) in the fluid volume, as are also found in separator plates in the prior art, and these central protrusions are used to support and electrically connect adjacent cells via the electrochemically active layer.

[0014] Figure 2 shows an exploded perspective bottom view of the battery cell of Figure 1. The metal support plate 14 (e.g., a metal foil) is provided with a plurality of small holes or pores 48 to enable the fluid in the fluid volume to contact the side of the electrochemically active layer closest to the metal support plate 14. These form a porous region bounded by a non-porous region. The anode (fuel electrode) layer is positioned adjacent to the small holes / pores, where the (enclosed) fluid volume within the battery cell includes a fuel flow volume supplied with fuel that enters and exits via the fluid port 22, so the fluid port is the fuel port 22. The cathode (air electrode) layer is located on the opposite side of the electrochemically active layer 50, i.e., on its outer side, and is exposed to air flowing through the layer during use of the battery cell 10.

[0015] In the battery cell depicted in Figures 1 and 2, only two layers (components) are required, namely, the metal support plate and the separator plate.

[0016] There are also provided a central upward protrusion 32 and a central downward protrusion 36, which protrusions include inlet and outlet protrusions (up and down as shown) extending between the opposing inner surfaces of the two plates and the outer surfaces of the electrochemical active layers of the battery cells adjacent to the outward protrusions. The central upward protrusions 32 define fluid passages for fuel therebetween or therein, which fluid passages traverse a closed fluid volume between the fluid ports at each end of the battery cell. The central downward protrusions 36 define fluid passages for an oxidant (such as air) therebetween or therein, which fluid passages traverse a fluid volume defined between the outer surfaces of the electrochemical active layers of the battery cells adjacent to the downward protrusions.

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

[0018] The size of the gasket can be determined to cover all of the formed port features 24 of each fluid port 22 to prevent fluid (such as fuel) that may travel through the fluid port 22 in the stack from infiltrating into the area outside the battery cell between the gasket (e.g., gasket 34) and the outside of the battery cell 10, i.e., into the fluid (such as an oxidant) surrounding the battery cell 10, or to prevent fluid outside the fluid port from infiltrating into the fluid port in the other direction. This is important for preventing any mixing of the fluid inside the battery cell 10 and the fluid outside the battery cell 10, which would be fuel and an oxidant. The polarity of the electrochemical active layer 50 determines which case this will be.

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

[0020] The battery stack has various sources of internal resistance. One such source is the contact resistance between the separator plate and the adjacent battery layer.

[0021] The battery stack can have a top compression plate and a bottom compression plate connected together by bolts or other means to allow the battery cells therebetween to be compressed together. The compressive force applied to the stack is sufficient to form a seal to prevent leakage from the battery cells and / or to prevent fluid outside the fluid port from infiltrating into the fluid port.

[0022] For good electrical contact and thus good conductivity through the stack, a compressive force is required within the planar area of the electrochemically active region in the stack. The central upward protrusion 32 and the central downward protrusion 36 form the required electrical contact between the battery cells and also provide a support function for the battery cells in the central region, extending upward to the lower side of the metal support plate 14 and downward to the opposite surface of the electrochemically active layer of the battery below it in the region of the small holes or pores 48. Additionally, the shaped port feature 24 around the port 22 helps to transfer the compressive force in the stack at the peripheral ends of each unit cell to provide the compressive force required to form a seal. It is necessary to maintain pressure between the separator and the adjacent battery layer to minimize the contact impedance between the separator and the adjacent battery layer. This is the function of the upward protrusion 32. However, including such an upward protrusion 32 also has its own drawbacks. For example, the upward protrusion 32 may block the holes or pores 48 in the metal support plate 14 and hinder the flow of fuel to the electrochemically active battery region. In fact, they reduce the efficiency and power density of the battery cells by reducing the entry of fluid (and the discharge of products therefrom) via the pores 48 into the electrochemically active battery region. Those skilled in the art will understand that the electrodes supplied by the pores 48 are themselves adapted to transfer reactants to the electrolyte, and thus the pores blocked by the protrusions 32 reduce the supply to (and discharge from) the electrochemically active battery region, but do not render inoperable the portion of the electrochemically active battery region close to the blocked pores. The upward protrusion 32 may also hinder the flow of fluid, such as fuel, through the battery cell and reduce the capacity of the flow volume of said fluid.

[0023] The present invention seeks to solve, overcome or mitigate at least one of the disadvantages of the prior art. Summary of the Invention

[0024] In a first aspect, there is provided an electrochemical cell unit comprising: a cell layer including an electrochemically active cell region, the cell layer having a first side (e.g., a lower side) and a second side (e.g., an upper side); and a separator (e.g., below the cell layer) having a first side (e.g., a lower side) and a second side (e.g., an upper side), the separator comprising a metal sheet, the second side of the separator extending in a spaced arrangement past and facing the first side of the cell layer to form a first fluid volume for a first fluid between the second side of the separator and the first side of the cell layer. The separator has a region that at least extends past (e.g., below) the electrochemically active cell region, and this region has no or substantially no protrusions (i.e., no protrusions projecting into the first fluid volume) pointing towards the first side of the cell layer. This region is substantially free (preferably completely free) of other components for separating the separator from the cell layer. The separator is adapted to be exposed to a pressure difference between the first side and the second side of the separator to maintain the spaced arrangement forming the first fluid volume. Preferably, the pressure difference is a fluid pressure difference, more specifically a gas pressure difference.

[0025] The second side of the separator extends past the first side of the cell layer in an arrangement located below / above. In the figure, the first side of the cell layer is located above the second side of the separator.

[0026] The region extending past the electrochemically active cell region is completely or almost completely flat and largely, almost completely or completely free of protrusions or raised features pointing towards the first side of the cell layer (of the cell unit of which the separator is a part). Such protrusions can include channels, ridges or pits and can generally be formed by pressing, etching or machining. There is no support structure in the first volume to maintain this volume.

[0027] The region extending past the electrochemically active cell region can coincide with the plan view area (i.e., extent) of the electrochemically active cell region. In other words, within the plan view area (i.e., extent) of the electrochemically active cell region, the second side of the separator does not contact the first side of the cell layer and this region is free of other components for separating the separator from the cell layer.

[0028] In the operating mode of the electrochemical cell unit, the pressure difference between the first side and the second side of the separator (i.e., the positive pressure difference between the first fluid volume and the second fluid volume) maintains or increases the separation between the second side of the separator and the first side of the cell layer. In the non-operating mode, when the pressures on each of the first side and the second side of the separator are the same, the separation can be reduced.

[0029] Preferably, the architecture of the cell layer is selected from one of the following: a metal-supported architecture, an anode-supported architecture, an electrolyte-supported architecture, or a cathode-supported architecture. That is, the cell layer is one of 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, and the first side of the cell layer is the first side of the metal support plate, and the second side of the cell layer is the second side of the metal support plate opposite to the first side of the metal support plate, and the second side bears the electrochemically active cell region. In addition, any reference to the cell layer throughout the specification may be 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 includes an inlet into the first fluid volume and an outlet out of the first fluid volume, and the inlet and the outlet are preferably located towards opposite edges of the cell unit, wherein the electrochemically active cell region is located between the inlet and the outlet. The inlet into the first fluid volume can be a type of port for a fluid (such as reformate fuel) to flow into the first fluid volume formed by the spaced arrangement between the cell layer and the separator plate. The outlet out of the first fluid volume can also be a type of port for a fluid (such as reformate fuel) to flow into the first fluid volume formed by the spaced arrangement between the cell layer and the separator plate.

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

[0033] The protrusions can have a cross-section in the shape of a circle, a square, a cross, a pentagon, or a hexagon. The cross-section of the protrusions can also be an ellipse or an irregular polygon, but ideally, it should 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 any protrusion can be less than half of the characteristic transverse dimension (e.g., length, width, or diameter) of the electrochemically active cell region.

[0034] One or both of the separator plate and the cell layer of the electrochemical cell unit can also be provided with a second plurality of protrusions (raised features or components) that extend outwardly towards the other of the separator plate and the cell layer and contact the other at a plurality of contact points on the cell layer that surround the inlet for fluid to flow into the first fluid volume and the outlet for fluid to flow out of the first fluid volume.

[0035] The electrochemical cell unit may also include a flanged perimeter on at least one of the separator plate and the cell layer. The flanged perimeter 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 plate and / or the cell layer. The flanged perimeter may be used to bond the separator plate and the cell layer together. For example, the separator plate and the cell layer may directly abut at the flanged perimeter to form a first fluid volume between the separator plate and the cell layer. The flanged perimeters of the separator plate and the cell layer may optionally be welded together or directly abut in some other manner.

[0036] The electrochemical cell unit may optionally include a spacer plate that is disposed and sandwiched between the separator plate and the metal support plate. The spacer plate may provide a separation between the metal support plate and the separator plate. For example, a spacer plate may be disposed and sandwiched between the separator plate and the metal support plate to form a first fluid volume between the separator plate and the metal support plate. The three plates may be hermetically fixed to each other, for example, by welding around their perimeters.

[0037] The separator plate of the electrochemical cell unit may be configured or otherwise adapted to be exposed to a pressure at a first side of the separator plate that is less than the pressure at a second side of the separator plate. In other words, the separator plate may be configured to be able to exist in a dual-pressure environment without being irreparably damaged or deformed. A dual-pressure environment may be supplied to the separator plate by providing fluids at different pressures on different sides of the separator plate to provide a pressure difference between the different sides. When in situ in a stack of cell units, the separator plate may be configured or otherwise adapted such that a first fluid volume formed between the separator plate and the cell layer is maintained in the presence of a pressure difference between its first side and its second side.

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

[0039] The pressure difference between the first side and the second side 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 pumping fluids at different rates and pressures using pumps. Alternatively or additionally, features such as valves and flow restrictors may be provided in the pipes or flow paths of the first fluid and the second fluid, respectively, to control the pressure difference between them. The pressure difference between them may be in the range of 50 mbar to 2 bar, preferably between 100 mbar and 1.5 bar, more preferably between 200 mbar and 800 mbar. Those skilled in the art will understand that the pressure difference used may be customized to maintain the spacing between the separator plate and the cell layer, and the pressure difference may depend on the flexibility of the cell layer and the separator plate (its metal sheet).

[0040] By providing features in the flow paths of the first fluid and the second fluid, the initial pressures at the inlets of the first fluid volume and the second fluid volume can be controlled to control the pressure difference between the first fluid volume and the second fluid volume (which is for fuel cell operation, and for electrolytic cell operation, only the first fluid can be provided and its initial pressure can be controlled). Additionally or alternatively, the pressures at the respective outlets of the first fluid volume and the second fluid volume can be controlled to provide a pressure difference between the first fluid volume and the second fluid volume.

[0041] The separator plate can also be constructed or otherwise adapted to bend when experiencing a pressure difference between its first side and its second side. In other words, the pressure difference experienced by the separator plate may cause the separator plate to bend away from or towards the cell layer. Preferably, the separator plate can be constructed to bend away from the cell layer in response to the positive action of the pressure difference when exposed to the pressure difference. By bending away from the cell layer, the spaced arrangement between the separator plate and the cell layer can be maintained (or increased), and thus the fluid volume therebetween can be maintained (or its height increased), and the contact with adjacent neighboring cell units can be improved.

[0042] A cell stack is provided that includes a plurality of cell units as described above, wherein the second side (e.g., the upper side) of the separator plate of the first cell unit faces the first side (e.g., the lower side) of the cell layer of the first cell unit in a spaced arrangement to form a first fluid volume for the first fluid between the second side of the separator plate and the first side of the cell layer, and the first side (e.g., the lower side) of the separator plate of the first cell unit faces the electrochemically active cell region of the second neighboring cell unit in the stack of cell units and defines a second fluid volume between the first side of the separator plate and the electrochemically active cell region of the second neighboring cell unit.

[0043] A battery stack is provided, the battery stack comprising: a plurality of battery cells, each battery cell comprising: a battery layer comprising an electrochemically active battery region, the battery layer having a first side and a second side, the second side carrying the electrochemically active battery region; and a separator having a first side and a second side, the separator comprising a metal sheet, the second (e.g., upper) side of the separator being spaced and disposed below and facing the first (e.g., lower) side of the battery layer to form a first fluid volume for a first fluid between the second side of the separator and the first side of the battery layer. The first side of the separator extends spaced and passes by and faces the electrochemically active battery region of an adjacent battery cell in the battery stack to form a second fluid volume for a second fluid between the first side of the separator and the electrochemically active battery region of the adjacent battery cell. The separator has a region that at least extends through the electrochemically active battery region, wherein the region has no protrusions pointing towards the battery layer or other components for separating the separator from a metal support plate. The separator is adapted to be exposed to a pressure difference between the first side and the second side of the separator to maintain the spaced arrangement forming the first fluid volume.

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

[0045] The battery stack can also be configured such that the first side of the separator contacts the outermost layer of the electrochemically active battery region of an adjacent battery cell, thereby providing electrical contact between the first side of the separator and the outermost layer and having a contact impedance that decreases as the pressure difference between the first side and the second side of the separator increases. For example, as described above, the pressure difference experienced by the separator can be provided by the pressure difference between the pressure of the first fluid in the first fluid volume and the pressure of the oxidant (such as air or oxygen) on the opposite side of the separator (i.e., the second fluid volume).

[0046] In other words, by introducing a pressure difference on either side of the separator in one battery cell, the separator can be forced to bend towards the electrochemically active region of an adjacent neighboring battery cell, thereby forcing the downward protrusions (or pits) of the separator to contact the electrochemically active region of the adjacent neighboring battery cell. This bending can be achieved over the entire active region without a large number of protrusions on the other side of the separator that would otherwise provide a force in that direction. By bringing the downward protrusions into contact with the electrochemically active region of the adjacent neighboring battery cell, the contact impedance is reduced, i.e., the conductivity through the stack is improved.

[0047] In this way, the separator is adapted to be exposed to the pressure difference between the first side and the second side of the separator to maintain the spaced arrangement forming the first fluid volume.

[0048] (In the case where there may be protrusions on the second side of the separator (in its minority regions, such as 10% or 20%), such protrusions can be separated under the pressure from the first side of the metal support plate, lifted from the holes / pores therein and allowed the fuel to enter the porous region of the support plate. It should also be noted that even if several protrusions are provided on the second side of the separator, their number is less than that on the first side. The fluid pressure will generate a uniform pressure on the plate, thus avoiding the need for protrusions on the second side throughout the active region).

[0049] A method of manufacturing a battery cell is provided. The method includes: providing a planar metal sheet having protrusions for a separator having a first side and a second side; providing a battery layer including an electrochemically active battery region, the battery layer having a first side and a second side; and stacking the separator and the battery layer such that the separator faces the first side of the battery layer in a spaced arrangement to form a first fluid volume between the separator and the first side of the battery layer, and the separator has a region that at least extends through the electrochemically active battery region. This region has no protrusions pointing towards the battery layer or other components for separating the separator from the battery layer.

[0050] The method may include: providing a metal support plate having a battery layer including an electrochemically active battery region, wherein the first side of the battery layer is the first side of the metal support plate, and the second side of the battery layer is the second side of the metal support plate opposite to the first side of the metal support plate, and the second side bears the electrochemically active battery region. The method may include pressing the planar metal sheet to provide planar protrusions extending from the surface of the planar metal sheet.

[0051] At least one of the separator and the battery layer (or the metal support plate supporting the battery layer) may be processed to form a flanged perimeter. The flanged perimeter of the separator and / or the battery layer (or the metal support plate supporting the battery layer) may be integrally formed with the separator and (or the metal support plate supporting the battery layer) by pressing. During manufacturing, the separator and the battery layer may be directly adjacent at the flanged perimeter to optionally form a first fluid volume between the separator and the battery layer by welding.

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

[0053] A method of fabricating a stack of battery cells is provided. The method includes: providing a plurality of battery cells, each battery cell fabricated as described above; and positioning one of the plurality of battery cells above / below another of the plurality of battery cells such that a protrusion of a separator of one of the plurality of battery cells extends through and contacts an electrochemically active cell region of another of the plurality of battery cells. Positioning above / below also includes providing a gasket between one of the plurality of battery cells and another of the plurality of battery cells.

[0054] A method of operating a battery stack of battery cells is provided. The battery stack is as described above, and the method includes: providing a first fluid to a first fluid volume; providing a second fluid to a second fluid volume; and adjusting a pressure difference between the first fluid volume and the second fluid volume to maintain a spaced-apart arrangement forming the first fluid volume.

[0055] In one aspect of the present invention, a method of operating a battery stack of battery cells is provided. In the method, each battery cell in the battery stack includes: a cell layer including an electrochemically active cell region, the cell layer having a first side and a second side; a separator electrically connected to the cell layer, the separator having a first side and a second side, the second side of the separator extending through and facing the first side of the cell layer in a spaced-apart arrangement to form a first fluid volume, and the first side of the separator including protrusions that point away from the first side of the cell layer and toward the second side of the cell layer of an adjacent battery cell to form a second fluid volume. The method includes: providing a first fluid to the first fluid volume; providing 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 a spaced-apart arrangement forming the first fluid volume. In this way, the electrical connection between the protrusions and the second side of the cell layer of an adjacent battery cell can be controlled by the pressure difference.

[0056] In another aspect of the present invention, an electrochemical battery cell is provided. The electrochemical battery cell includes: a cell layer including an electrochemically active cell region, the cell layer having a first side and a second side; a separator electrically connected to the cell layer, the separator having a first side and a second side, the second side of the separator extending through and facing the first side of the cell layer in a spaced-apart arrangement to form a first fluid volume, and the first side of the separator including protrusions that point away from the first side of the cell layer and toward the second side of the cell layer of an adjacent battery cell, wherein the separator is adapted to be exposed to a pressure difference between the first side and the second side of the separator to maintain a spaced-apart arrangement forming the first fluid volume and to bias the protrusions toward the second side of the cell layer of an adjacent battery cell. In this way, the electrical connection between the protrusions and the second side of the cell layer of an adjacent battery cell can be controlled by the pressure difference.

[0057] In another aspect of the present invention, there is provided a method for manufacturing a battery stack including a plurality of electrochemical cell units, the method comprising: providing a plurality of cell units, each cell unit including: a cell layer including an electrochemically active cell region, the cell layer having a first side and a second side; and a separator electrically connected to the cell layer, the separator having a first side and a second side surface, the second side of the separator extending in a spaced-apart arrangement past and facing the first side of the cell layer to form a first fluid volume, the first side of the separator including a protrusion pointing 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 of a first cell unit faces the second side of a second adjacent cell unit in the stack of cell units and defining a second fluid volume between the first side of the separator of the first cell unit and the second side of the second adjacent cell unit, wherein the protrusion in the separator of the first cell unit points towards the second side of the cell layer of the adjacent cell unit, and wherein the separator of the first cell unit is adapted to be exposed to a pressure difference between the first side and the second side of the separator to maintain the spaced-apart arrangement forming the first fluid volume and bias the protrusion towards the second side of the cell layer of the adjacent cell unit.

[0058] It should be noted that when the cell unit is an electrolytic cell unit, a second fluid is produced during the reaction. In other words, the providing step includes providing (from a source external to the cell unit) an initial reactant and providing (or generating at the cell unit) the product of the electrochemical reaction at the cell unit. For example, in an electrolytic cell operation, a fuel (in the form of steam from a source external to the cell unit) and the product of the electrolysis reaction are provided to the first fluid volume of the cell unit, which is hydrogen if the electrolyte is oxygen ion conducting or oxygen if the electrolyte is hydrogen ion conducting. Correspondingly, only the product of the electrolysis reaction can be provided to the second fluid volume of the cell unit, which is oxygen (in the example where steam is the fuel) if the electrolyte is oxygen ion conducting or hydrogen if the electrolyte is hydrogen ion conducting. A purge gas (e.g., oxygen or air) can optionally be provided to the second fluid volume from a source external to the cell unit. Such a purge gas can assist in expelling the product of the electrolysis reaction from the second fluid volume.

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

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

[0061] Preferably, the pressure difference is adjusted to reduce the electrical contact impedance between the separator plate and the electrochemically active cell region of the second adjacent cell in the stack of cells. By increasing the pressure difference, the electrical contact impedance can be reduced, thereby improving the efficiency of the stack.

[0062] For example, the pressure difference can be adjusted by: i) using pumps to pump the first fluid and the second fluid at different rates; ii) flow restrictors in the pipes or flow paths supplying the first fluid inlet and the second fluid inlet of the cell and / or the entire battery stack, such as valves or convergent-divergent nozzles (such as a de Laval nozzle); iii) orifice plates in the pipes or flow channels to assist in adjusting the pressure difference between the first fluid and the second fluid. Those skilled in the art will readily know other ways and devices that can be used to establish the pressure difference between the first fluid and the second fluid. Description of the Drawings

[0063] Figure 1 is an exploded perspective view of a fuel cell unit and two gaskets;

[0064] Figure 2 is a second perspective view of the arrangement in Figure 1 shown from a different angle;

[0065] Figure 3 is a first exploded perspective view of a first arrangement of a stack including two cells separated by gaskets, each cell having two fluid ports.

[0066] Figure 4 is Figure 3 a bottom-side exploded perspective view of the arrangement in

[0067] Figure 5Is Figure 3 A cross-sectional view of the arrangement in

[0068] Figure 6 Is a first exploded perspective view of a second arrangement including a stack of two battery cells separated by a gasket, each battery having four fluid ports;

[0069] Figure 7 Is Figure 6 An exploded perspective view of the underside of the arrangement in

[0070] Figure 8 Is a first exploded perspective view of a third arrangement including a stack of two battery cells separated by a gasket, each battery having four fluid ports and a spacer.

[0071] Figure 9 Is Figure 8 An exploded perspective view of the underside of the arrangement in

[0072] Figure 10 Is Figure 8 A cross-sectional view of the arrangement in

[0073] Figure 11 Shows a method of manufacturing a battery cell according to the present invention.

[0074] Figure 12 Shows a method of operating a battery stack in a steady state according to the present invention. Detailed Description

[0075] For illustrative purposes only, the drawings only show two electrochemical battery cells in the stack (each hereinafter simply referred to as a "battery cell"). In various embodiments, a plurality of batteries are provided. In additional embodiments (not shown), a plurality of electrochemical battery stacks are provided, and in yet additional embodiments, a plurality of electrochemical battery stacks each including a plurality of electrochemical cells are provided. It should be understood that the anode and cathode inlets, outlets (exhaust gases), pipes and manifolds and their configurations are appropriately modified for these embodiments and will be apparent to those of ordinary skill in the art.

[0076] Reference Figure 3, the battery cell 300 includes a flat (i.e., planar) metal support plate 314 stacked beside the separator plate 312. The metal support plate 314 is shown having a flanged peripheral feature 318 around its perimeter. The flanged perimeter 318 extends out of the main plane of the sheet, as found in the central fluid volume region, to form a concave surface in the metal support plate 314 (and a convex surface on the outer surface). When assembling the battery cell, the concave surface will form a first fluid volume 360 within the battery cell. The separator plate has a first side and a second side and includes a metal sheet. The second side of the separator plate extends past and faces the first side of the battery layer. The two plates are sealed (e.g., welded) around their perimeters to enclose / seal the enclosed first fluid volume.

[0077] The battery cell 300 has circular ends and parallel sides, where in both the separator plate 312 and the metal support plate 314, one fluid port 322 faces each end. Other shapes, sizes, and numbers of corresponding battery features are possible, depending on the power and size required for the final stacked assembly.

[0078] In the middle portion of the battery cell 300, an electrochemically active layer 350 is disposed on the battery layer (here the metal support plate with the battery layer is shown). In this embodiment, it is located outside the first fluid volume 360.

[0079] The electrochemically active region 350 includes an anode, a cathode, and an electrolyte (not shown) located between the anode and the cathode. The anode, electrolyte, and cathode can be collectively referred to as the electrochemically active layer 350, the active electrochemistry cell layer, or the electrochemically active region. The electrochemically active region can be a continuous and generally rectangular region, which can generally be uninterrupted. Alternatively, the electrochemically active cell region can wrap around the fluid port to increase the proportion of the battery cell region that is electrochemically active and thereby increase the power density of the stack of battery cells. In other words, near the port, the edge of the active cell region is shaped to match the shape of the port. The edge of the active cell region forms a partial circle concentric with the port. The edge of the active cell region is spaced from the edge of the port to leave room for the formed port feature and / or the gasket disposed around the port.

[0080] The electrolyte conducts negative oxygen ions or positive hydrogen ions between the anode and the cathode.

[0081] The stack can include a stack of battery cells based on one of a solid oxide electrolyte, a polymer electrolyte membrane, or a molten electrolyte, or any other variant having electrochemical capabilities.

[0082] Figure 4 The same battery cell 300 is shown from different perspectives. Figure 3 as the Figure 5 is shownFigure 3 Cross-sectional view. The section is taken from the left rear to the right front and then to the center rear. A formed port feature 324 is provided around the fluid port of the metal support 314. The formed port feature 324 is provided as a plurality of elements in the form of protrusions that extend a distance corresponding to the height of the flanged perimeter 318 from the plane of the base of the fluid volume to have a common height therewith. This causes them to contact the opposite surface of the separator 312 when the battery cell 300 is assembled, just like the flanged perimeter 318. Thus, when the flanged perimeter 318 is joined to the separator 312, for example by welding, the formed port feature 324 will likewise contact the separator 312. The protrusions may have a cross-section in the shape of a circle, square, cross, pentagon or hexagon. Their cross-section may also be oval or an irregular polygon.

[0083] The concave configuration can give the associated plate the appearance of a framed tray, having a corresponding convex outer shape (relative to the outside of the battery cell) and a generally planar base, so that the concave surface defines a first fluid volume 360 (e.g., a portion thereof) in the assembled battery cell. In such a concave configuration, the flanged perimeter 318 extends outwardly from the plane of the original sheet of the separator and / or the metal support plate towards the corresponding opposite surface of the other of the separator and the metal support plate.

[0084] Thus, the first fluid volume 360 is defined by the flanged perimeter 318, which is formed by pressing (such as by using a press), hydroforming or stamping.

[0085] The metal support plate 314 (e.g., metal foil) is provided with a plurality of small holes or pores 348 to enable the first fluid in the first fluid volume 360 to be in fluid communication with the electrochemical layer supported on the second side (the upper side as shown) of the battery layer / metal support plate. These holes or pores form a porous region bounded by a non-porous region. The anode (fuel electrode) layer is positioned adjacent to the small holes / pores, wherein the (enclosed) fluid volume 360 within the battery cell includes the first fluid volume 360 supplied with the first fluid entering and leaving via the fluid port 322.

[0086] The first fluid may be a fuel ((reformed) hydrocarbon or other fuel (e.g., ammonia) when operating as a fuel cell and steam when operating as an electrolytic 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 located on the opposite side of the electrochemically active layer 350, i.e., on its outer side, and is exposed to air flowing through the layer during use of the battery cell.

[0087] InFigure 3 and Figure 4 and Figure 5 In the battery cell depicted, only two layers (components) are required, namely, a metal support plate and a separator plate.

[0088] The separator plate 312 is also provided with protrusions 336 that extend from the separator plate 312 towards adjacent battery cells (in other words, away from the metal support plate 314 of the battery cell of which the separator plate is a part). Those downward protrusions 336 that include outward (downward as shown) protrusions extend from the separator plate 312 to contact the outer surface of the electrochemically active layer of the battery cell adjacent to the separator plate in the stack of battery cells. The central downward protrusions 336 define fluid passages for an oxidant (such as air) therebetween or therein, and these fluid passages pass through a second fluid volume 365 defined between the outer surfaces of the electrochemically active layers of the battery cells adjacent to the downward protrusions.

[0089] When forming a stack of battery cells, the second side of the separator plate of the first battery cell faces the first side of the battery layer of the first battery cell to be spaced apart to form a first fluid volume for a first fluid therebetween, and the first side of the separator plate of the first battery cell faces the electrochemically active cell region of the second adjacent battery cell in the stack of battery cells and defines 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) in fuel cell operation, or steam in electrolytic cell operation), and the second fluid volume is for a second fluid (such as an oxidant in fuel cell operation, or oxygen generated in electrolytic cell operation). Between each battery cell in the stack, two or more gaskets 334 are provided below each battery cell (one around each port, and there may be more than 2 ports), that is, the gaskets are located between adjacent battery cells in the stack. There may be multiple inlet ports and multiple outlet ports.

[0090] Each gasket 334 (also referred to as a "seal") provides the primary sealing function and is preferably compressible. The gasket is compressed near the port to achieve the sealing function. For example, by a means capable of applying a compressive force. The size of the gasket can be determined to cover all of the formed port features 324 of each fluid port 322 to prevent a first fluid (such as a (reformed) hydrocarbon fuel or other fuel (e.g., ammonia) in fuel cell operation, or steam in electrolytic cell operation) that may travel through the fluid port 322 from infiltrating into the area outside the cell unit 300 between the gasket 334 and the outside of the cell unit, i.e., infiltrating into the second fluid volume (such as an oxidant in fuel cell operation, or oxygen generated in electrolytic cell operation) surrounding the cell unit 300, or preventing fluid outside the fluid port from infiltrating into the fluid port in the other direction. This helps prevent any mixing of the fluid inside the cell unit 300 and the fluid outside the cell unit 300, which may be fuel and oxidant, and the polarity of the electrochemically active layer 350 determines which case this will be.

[0091] The gasket can also provide electrical insulation between the first cell unit and an adjacent fluid cell unit to prevent short circuits. The gasket can be any suitable cell gasket (sealing ring), for example, such as Thermiculite (trademark).

[0092] For good electrical contact between the cell units in the stack and thus good conductivity through the stack, a compressive force near the electrochemically active layer in the stack is typically required. The central downward protrusion 336 forms the required electrical contact between the cell units (and the adjacency of the separator and the cell layer, preferably fixed by welding means that these components are electrically connected). For example, when in a stacked arrangement, the central downward protrusion 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 region of the adjacent cell unit in the stack, thereby providing electrical contact between them.

[0093] Different from the prior art shown in FIGS. 1 and 2, the first arrangement does not have a central protrusion, i.e., a protrusion extending between the opposing inner surfaces of two plates (i.e., the separator plate and the cell layer / metal support plate). Therefore, fuel can enter the first fluid volume 360 through the fluid port 322 and freely flow over the entire surface of the separator plate 312 and through the entire first fluid volume.

[0094] In addition, as Figure 3 and Figure 4 as well as Figure 5 shown, there are no other components in the area of the separator plate 312 below the cell electrochemically active layer 350 that can separate the separator plate 312 from the metal support plate 314.

[0095] In addition, different from the prior art shown in FIGS. 1 and 2, since the first arrangement does not have a central upward protrusion extending between the opposite inner surfaces of the two plates, there is no feature in the battery cell that extends (or as shown in Figure 3 and Figure 4 and Figure 5 shown, extends upward to the lower side of the metal support plate) in the small hole region (also known as the porous region and corresponding to the planar range of the electrochemically active layer) to provide a supporting function for the battery cell in the central region.

[0096] In the previous designs (e.g., FIGS. 1 and 2), the battery cells are stacked with a gasket 34 between each repeating unit. Before compression, the gasket 34 is thicker than the height of the protrusion 36, and the protrusion does not contact the next unit. When the stack is compressed, initially the compression force acts only through the gasket (since the protrusion does not contact). At a certain point, the gasket 34 will be fully compressed, and then the protrusion will contact. As the stack is further compressed, the compression force acts through both the gasket 34 and the protrusion 36. This may cause the above problems.

[0097] In the new concept, since there is no protrusion pointing to the battery layer 348, the gasket 334 can be compressed as needed, and the compression force does not act through the protrusion or other structures near the active battery region (depending on the stiffness of the plate, etc., there may be some movement of the base / interconnect, but this movement is small). Therefore, the compression in the active battery region is independent of the gasket compression and can be controlled by the pressure difference used to push apart the battery layer (its metal support plate 314) and the interconnect 312 of this battery cell (the battery layer and the interconnect are its components). Furthermore, the interconnect of this battery cell is pushed towards an adjacent battery cell (usually the electrochemically active layer of the battery layer of the adjacent battery cell) and contacts this adjacent battery cell, and thereby the required electrical contact is generated between the adjacent battery cells. In the new arrangement, the force transmitted by the protrusion 316 can be greatly reduced. The final force through the protrusion and the active region is achieved by the pressure difference.

[0098] Referring to Figure 6 and Figure 7 , the battery cell 600 is similar to Figure 3 , Figure 4 and Figure 5The battery cell 300, except that the separator 612 of the battery cell 600 is shown as having a flanged perimeter 618 instead of the metal support plate 614, with formed port features provided in the separator 618 and a different arrangement of fluid ports. The flanged perimeter 618 extends out of the main plane of the sheet, as found in the central fluid volume region, to form a concave surface in the separator (and a convex surface on the outer surface). When assembling the battery cell, the concave surface will form a first fluid volume 660 within the battery cell.

[0099] It should be noted that Figure 6 and Figure 7 the arrangement of Figure 3 、 Figure 4 and Figure 5 can be modified in the manner already discussed with respect to the arrangement of

[0100] The battery cell 600 has circular ends and parallel sides, where fluid ports 622 face each corner of both the separator 612 and the metal support plate 614, thus there are a total of four fluid ports 622. Other shapes, sizes, and quantities of corresponding battery features are possible, depending on the power and size required for the final stacked assembly.

[0101] Around the fluid ports 622 of the separator 612, formed port features similar to the formed port features 324 of the battery cell 300 are provided. The formed port features are provided as a plurality of elements in the form of protrusions that extend a distance corresponding to the height of the flanged perimeter 618 from the plane of the base of the fluid volume 660 to have a common height therewith. This causes them to contact the opposite surface of the metal support plate 614 when the battery cell 600 is assembled, just like the flanged perimeter 618. Thus, when the flanged perimeter 618 is joined to the metal support plate 614, for example by welding, the formed port features will likewise contact the metal support plate 614. The protrusions can have a cross-section in the shape of a circle, square, cross, pentagon, or hexagon. Their cross-section can also be elliptical or an irregular polygon.

[0102] Refer to Figure 8 、 Figure 9 and Figure 10, the battery cell 800 is similar to the above-described battery cells 300 and 600 (and is shown in a similar view), except that neither the separator plate 812 nor the metal support plate 814 of the battery cell has a flanged perimeter. To form a first enclosed fluid volume 860 between the separator plate 812 and the metal support plate 814 of the battery cell 800, a spacer plate 816 is disposed between the separator plate 812 and the metal support plate 814.

[0103] The battery cell 800 has rounded ends and parallel sides, with fluid ports 822 facing each corner of the separator plate 812, the metal support plate 814, and the spacer plate 816, such that there are a total of four fluid ports 822. Other shapes, sizes, and numbers of corresponding battery features are possible, depending on the power and size required for the final stacked assembly.

[0104] When in place within the battery cell, the spacer plate 816 is located above / below the perimeter of the separator plate 812 and below / above the perimeter of the metal support plate 814. The central hollow portion 817 of the spacer plate 816 is located at least above / below the central downward protrusion 836 that extends between the separator plate 812 and the region of the electrochemically active layer of the battery cell adjacent to the outward protrusion. The hollow central portion 817 is also located at least below / above the porous region (multiple small holes) provided in the metal support plate 812, such that the fluid in the first fluid volume can be in fluid communication 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 forms a fluid volume for fuel between the separator plate 812 and the metal support plate 814.

[0105] Unlike the first and second arrangements, the third arrangement does not have a shaped port feature around the fluid ports of the separator plate. The spacer plate is used to provide a separation between the metal support plate and the separator plate of the battery cell. The throat in the spacer plate allows fluid communication between the port and the first fluid volume.

[0106] In each of the above arrangements, since there is no central upward protrusion extending between the opposing inner surfaces of the two plates (i.e., the separator plate and the battery layer / metal support plate), a way is provided to establish and maintain a first fluid volume 360; 660; 860 between the metal support plates 314; 614; 814 and the separator plates 312; 612; 812 during operation of the battery cell.

[0107] In the case where the battery cells 300; 600; 800 are fuel cell units (or stacks of fuel cell units), fuel (i.e., anode inlet gas, e.g., hydrocarbon fuel, reformed hydrocarbon fuel, H2, ammonia) is delivered to the anode inlet of the battery cell and enters the first fluid volume (fuel volume) between the separator plate 312; 612; 812 and the battery layer (or metal support plate 314; 614; 814) via the ports 332; 632; 832. At the same time, an oxidant (i.e., cathode inlet gas) is delivered to the cathode inlet of the battery cell to flow on either side of the separator plate 312; 612; 812 and the battery layer (or metal support plate 314; 614; 814). The fuel and the oxidant can flow in a co-flow configuration such that the fuel and the oxidizer flow past the respective sides of the battery cell in the same direction. Alternatively, the fuel and the oxidant can flow in a counter-flow or cross-flow configuration.

[0108] In the case where the battery cells 300; 600; 800 are fuel cell units, the fuel and the oxidant are supplied to the fuel cell unit at different pressures to provide a pressure difference between them as they pass through the fuel cell unit. This in turn results in a pressure difference between the first side (near the oxidant) and the second side (near the fuel) of the separator plate 312; 612; 812. By providing a pressure difference between the first side and the second side, the separation between the separator plate (the second side) and the battery layer (the first side) (or the first side of the metal support plate 314; 614; 814) can be controlled. For example, the separation can be maintained or increased to create and maintain the first fluid volume.

[0109] In order to enable the separation between the separator plate 312; 612; 812 and the battery layer (or metal support plate 314; 614; 814) to be maintained or increased by providing a pressure difference between the first side and the second side, the separator plate can be adapted or constructed to bend when exposed to the pressure difference. For example, when exposed to the pressure difference, the separator plate can bend away from the battery layer (or metal support plate) of the battery cell (and towards the adjacent battery cell) as the pressure difference increases, i.e., the separator plate is adapted to bend away from the battery layer (or metal support plate) according to the positive action of the pressure difference when exposed to the pressure difference.

[0110] When in a stacked arrangement, the central downward protrusions 336; 636; 836 on the first side of the separator plate 312; 612; 812 of the first battery cell in the stack contact the outermost layer of the electrochemically active cell region of the adjacent battery cell in the stack, thereby providing electrical contact between them.

[0111] When each of the separator plates 312; 612; 812 is exposed to a pressure difference such that it bends away from the cell layer (or the metal support plate 314; 614; 814) of its corresponding cell unit, the contact impedance between the central downward protrusions 336; 636; 836 and the outermost layer of the electrochemically active cell region of the adjacent cell unit is reduced. In other words, the contact impedance between the central downward protrusions 336; 636; 836 and the outermost layer of the electrochemically active cell region of the adjacent cell unit decreases as the pressure difference between the first and second sides of the separator plate increases.

[0112] During operation, the pressure difference between the first and second sides of the separator plate can be controlled in the range of 50 mbar to 2 bar, preferably between 100 mbar and 1.5 bar, more preferably between 200 mbar and 800 mbar.

[0113] The method of manufacturing any of the cell units described in any of the above embodiments includes a plurality of steps / operations. The method includes the following steps.

[0114] At step 1110, a separator plate having a first side and a second side is provided, for example, by cutting or stamping. For example, the separator plate can be a planar metal sheet that is not porous, or any other planar sheet that is not porous, and is used to separate one cell unit in the stack from an adjacent cell unit. The separator plate can be provided with protrusions extending from the plate of the separator plate, and these protrusions can be provided by pressing / molding in the same step as the cutting / stamping.

[0115] At step 1120, a cell layer including an electrochemically active cell region is provided, the electrochemically active cell region including an anode, a cathode, and an electrolyte (not shown) located between the anode and the 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 include depositing or coating the cell layer on a planar metal sheet, for example, by printing the electrochemically active cell region on the cell layer, thus forming a metal-supported cell layer, where the porous region (holes) provides fluid communication from the first side to the electrode supported by the metal support plate on its second side. Alternatively, the cell layer can be self-supporting. For example, the cell layer has an anode-supported architecture, an electrolyte-supported architecture, or a cathode-supported architecture. For illustrative purposes only, the term "metal support plate" is used in the following paragraphs, but can be interchanged with "cell layer" or "metal-plate-supported cell layer".

[0116] Step 1110 or step 1120 preferably involves providing a cell layer (or a metal-plate-supported cell layer) having a peripherally flanged 318 or a separator plate having a peripherally flanged 618. The peripherally flanged 318 or 618 extends out of the main plane of the metal plate support 314 or the separator plate 618, respectively.

[0117] The flanged perimeter 318 forms a concave surface in the metal support plate 314 (and a convex surface on the outer surface). When assembling the battery cell, the concave surface forms a first fluid volume 360 within the battery cell.

[0118] The flanged perimeter 618 forms a concave surface in the separator plate (and a convex surface on the outer surface). When assembling the battery cell, the concave surface forms a fluid volume within the battery cell.

[0119] The flanged perimeter in the separator plate or the metal support plate can be made by pressing the separator plate or the metal support plate (of the battery layer) respectively.

[0120] As an alternative to the flanged perimeter, a spacer can be provided and sandwiched between the separator plate and the metal support plate to form a first fluid volume therebetween.

[0121] Steps 1110 and 1120 also include providing a plurality of fluid ports 322; 622; 822 in both the separator plate and the metal support plate to allow a fluid (such as reformate fuel) to flow through the battery cell (and ultimately through a stack of battery cells) to supply fuel to each battery cell, particularly to the first fluid volume of each battery cell.

[0122] At 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 that at least extends through the electrochemically active cell region. At step 1130, the separator plate and the metal support plate are stacked such that when the battery cells are placed in a stacked arrangement, the protrusions extending out of the plane of the separator plate are oriented away from the first fluid volume and towards an adjacent battery cell. In other words, there is a continuous region that at least extends through the electrochemically active cell region and that has no protrusions pointing towards the metal support plate. There are no other components that are configured to resist the stacking compressive force and transfer such force to the protrusions connecting adjacent battery cells. Thus, there are no components within the first fluid volume between the separator plate and the metal support plate to help (particularly during operation) physically separate them from each other.

[0123] At step 1130, the separator plate and the metal support plate can be directly adjacent (and sealingly adjacent) at the above-mentioned flanged perimeter to form a first fluid volume therebetween. The separator plate and the metal support plate can optionally be directly adjacent by welding.

[0124] In an alternative arrangement without a flanged perimeter, a spacer is provided and sandwiched between the separator plate and the metal support plate to form a first fluid volume therebetween, and at 1130, the three plates are fixedly sealed to each other, for example, by welding around their perimeters.

[0125] When forming a stack of battery cells, the method can continue, where the second side of the separator plate of the first battery cell (formed as described above) is arranged to be located above / below the second battery cell, such that the first side of the separator plate of the first battery cell faces the electrochemical active cell regions of the second adjacent battery cells in the stack of battery cells and encloses a second fluid volume therebetween. When forming the stack, a plurality of gaskets are provided, the plurality of gaskets corresponding to the plurality of fluid ports of the battery cells. Each gasket is located around the fluid ports of adjacent battery cells in the stack. The function of the gasket has been described above.

[0126] A method of operating a battery stack of battery cells as described in the above embodiments includes a plurality of steps / operations, as follows.

[0127] At step 1210, a first fluid is provided to the first fluid volume formed between the separator plate and the metal support plate. The first fluid can be a fuel. For operation as a fuel cell, the first fluid can be a hydrocarbon fuel, a reformed hydrocarbon fuel, ammonia, H2, methanol, etc. For operation as an electrolytic cell, the first fluid is typically steam.

[0128] At step 1220, a second fluid is provided to the second fluid volume formed between the separator plate of the first battery cell in the stack and the electrochemical active cell region of the second adjacent battery cell in the stack. The second fluid can be an oxidant fluid. For operation as a fuel cell, the second fluid can be an oxidant fluid, e.g., air or oxygen provided to the second fluid volume via an inlet. For operation as an electrolytic cell, the second fluid is typically oxygen generated in the electrolysis reaction.

[0129] At step 1230, the pressure difference between the first fluid volume and the second fluid volume is adjusted to maintain the spaced arrangement forming the first fluid volume. For example, the pressures of the first fluid (such as fuel) and the second fluid (such as air / oxygen) can be adjusted to create a pressure difference between the two fluids. This pressure difference can in turn cause the separator plate to bend, and the separation between the separator plate and the metal support plate can increase to form and maintain the spaced 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 between 100 mbar and 1.5 bar, more preferably between 200 mbar and 800 mbar. The adjustment of the pressure difference can also be to reduce the electrical contact impedance between the separator plate and the electrochemical active cell region of the second adjacent battery cell in the stack (the pressure in the first fluid volume is controlled to be greater than the pressure of the second fluid volume, and as this pressure difference increases, the contact impedance decreases).

[0130] The pressure difference can be adjusted by pumping the first fluid and the second fluid at different rates using a pressure pump. Alternatively or additionally, the flow of the first fluid and / or the second fluid can be blocked by setting a valve or a convergent-divergent nozzle (such as a de Laval nozzle) in the pipeline or flow path for supplying fluid to the stacked battery cells. Alternatively or additionally, an orifice plate can be set in the pipeline or flow path to help adjust the pressure difference. Other ways and devices that can be used to establish the pressure difference will be readily known to those skilled in the art.

[0131] The present invention is not limited to the above examples, and other examples will be apparent to those of ordinary skill in the art without departing from the scope of the appended claims.

[0132] These and other features of the present invention have been described above only by way of example. Detailed modifications can be made to the present invention within the scope of the claims.

Claims

1. A method of operating a battery stack of battery cells, each battery cell in the battery stack comprising: a battery layer including an electrochemically active battery region, the battery layer having a first side and a second side; a separator electrically connected to the battery layer, the separator having a first side and a second side, the second side of the separator extending past and facing the first side of the battery layer at spaced intervals to form a first fluid volume, and the first side of the separator includes a protrusion that points away from the first side of the battery layer and towards the second side of the battery layer of an adjacent battery cell to form a second fluid volume, the method comprising: providing a first fluid to the first fluid volume; providing 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 arrangement forming the first fluid volume.

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

3. The method according to claim 1 or 2, wherein the pressure difference between the first fluid volume and the second fluid volume is adjusted to reduce an electrical contact impedance between the separator and the second side of the adjacent battery cell in the stack of battery cells.

4. An electrochemical battery cell, comprising: a battery layer including an electrochemically active battery region, the battery layer having a first side and a second side; a separator electrically connected to the battery layer, the separator having a first side and a second side, the second side of the separator extending past and facing the first side of the battery layer at spaced intervals to form a first fluid volume, and the first side of the separator includes a protrusion that points away from the first side of the battery layer and towards the second side of the battery layer of an adjacent battery cell, wherein the separator is adapted to be exposed to a pressure difference between the first side and the second side of the separator to maintain the spaced arrangement forming the first fluid volume and to bias the protrusion towards the second side of the battery layer of the adjacent battery cell.

5. The electrochemical battery cell according to claim 4, wherein the architecture of the battery layer is selected from one of the following: a metal-supported architecture, an anode-supported architecture, an electrolyte-supported architecture, or a cathode-supported architecture.

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

7. The electrochemical battery cell according to any one of claims 4 to 6, wherein the separator has a region that at least extends past the electrochemically active battery region, and wherein said zone has no protrusions directed towards the battery layer or other components for separating the separator from the battery layer.

8. The electrochemical cell unit according to any one of claims 4 to 7, wherein the protrusions are in a zone at least above the electrochemically active cell region of the adjacent cell unit.

9. The electrochemical cell unit according to any one of claims 4 to 8, wherein the separator is metal.

10. The electrochemical cell unit according to any one of claims 4 to 9, wherein the protrusions are formed by pressing the separator.

11. The electrochemical cell unit according to any one of claims 4 to 10, further comprising: an inlet for entering the first fluid volume and an outlet for leaving the first fluid volume, the inlet and the outlet being located towards opposite edges of the cell unit, wherein the electrochemically active cell region is between the inlet and the outlet.

12. The electrochemical cell unit according to claim 11, wherein one or both of the separator and the battery layer are provided with a second plurality of protrusions that extend outwardly towards the other of the separator and the battery layer and contact the other at a plurality of contact points surrounding the inlet for entering the first fluid volume and the outlet for leaving the first fluid volume.

13. The electrochemical cell unit according to any one of claims 4 to 12, wherein at least one of the separator and the battery layer includes a flanged perimeter, and the separator and the battery layer are directly adjacent at the flanged perimeter to optionally form the first fluid volume between the separator and the battery layer by welding.

14. The electrochemical cell unit according to any one of claims 4 to 13, wherein the separator is adapted to bend away from the battery layer when exposed to the pressure difference.

15. A battery stack comprising a plurality of electrochemical cell units according to any one of claims 4 to 14, wherein, the second side of the separator of the first cell unit faces the first side of the battery layer of the first cell unit at an interval arrangement to form a first fluid volume for a first fluid between the second side of the separator and the first side of the battery layer, and the first side of the separator of the first cell unit faces the second side of a second adjacent cell unit in the stack of cell units and defines a second fluid volume between the first side of the separator and the second side of the second adjacent cell unit.

16. The battery stack according to claim 15, wherein the protrusions of the separator of the first cell unit contact the second side of the second cell unit in the stack of cell units, preferably contact the outermost layer of the electrochemically active cell region of the second cell unit in the stack of cell units.

17. The battery stack according to claim 15 or 16, wherein the first fluid volume is for fuel and the second fluid volume is for an oxidant.

18. A method for manufacturing a battery stack including a plurality of electrochemical cell units, comprising: providing a plurality of cell units, each cell unit including: a cell layer including an electrochemically active cell region, the cell layer having a first side and a second side; and a separator electrically connected to the cell layer, the separator having a first side and a second side, the second side of the separator extending past and facing the first side of the cell layer at spaced intervals to form a first fluid volume, the first side of the separator including a protrusion pointing 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 of a first cell unit faces the second side of a second adjacent cell unit in the stack of cell units and defining a second fluid volume between the first side of the separator and the second side of the second adjacent cell unit, wherein the protrusion in the separator of the first cell unit points towards the second side of the cell layer of the adjacent cell unit, and wherein the separator of the first cell unit is adapted to be exposed to a pressure difference between the first side and the second side of the separator to maintain the spaced arrangement forming the first fluid volume and bias the protrusion towards the second side of the cell layer of the adjacent cell unit.

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

20. The method according to claim 18 or 19, wherein each of the plurality of cell units is provided by: providing a separator having a first side and a second side, the separator having a protrusion; providing a cell layer including an electrochemically active cell region, the cell layer having a first side and a second side; and stacking the separator and the cell layer such that the separator extends past and faces the first side of the cell layer at spaced intervals to form a first fluid volume between the first side of the separator and the first side of the cell layer, and the separator has a region extending at least past the electrochemically active cell region.

21. The method according to claim 20, wherein the region has no protrusion pointing towards the cell layer or other components for separating the separator from the cell layer.

22. The method according to any one of claims 18 to 21, wherein the protrusion is formed by pressing the separator.

23. The method according to any one of claims 18 to 22, wherein at least one of the separator and the cell layer is processed to form a flanged perimeter, and the separator and the cell layer are directly adjacent at the flanged perimeter to optionally form the first fluid volume between the separator and the cell layer by welding.

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

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