Electrochemical cell interconnect with insulation

Abstract

An interconnect for electrically connecting cells of an electrochemical cell stack is disclosed. The interconnect comprises a first side and a second side; the first side is adapted to face a cell layer comprising an electrochemically active cell region, and a portion of the first side of the interconnect is provided with an electrically insulating layer.

Description

[0001] ELECTROCHEMICAL CELL INTERCONNECT WITH INSULATION

[0002] Field of the Invention

[0003] The present invention relates to an interconnect for use in electrochemical cell units, in particular fuel cell units and electrolyser cell units, cell units comprising said interconnect, stacks containing such cell units, methods for manufacturing said interconnects, cell units, and stacks thereof, and the use of such cell units. The cell units of the present invention include cells of solid oxide, polymer electrolyte membrane, and molten carbonate types. The present invention more specifically relates to solid oxide fuel cell (SOFC) and solid oxide electrolyser cell (SOEC) units, and these may include metal-supported solid oxide fuel cell (MS-SOFC) or electrolyser cell (MS-SOEC) units.

[0004] Background to the Invention

[0005] Some electrochemical cell units can produce electricity by using an electrochemical conversion process that oxidises fuel to produce electricity. Some electrochemical cell units can also, or instead, operate as regenerative fuel cells (or reverse fuel cells) units, often known as electrolyser cell units, for example to produce hydrogen and oxygen from water, or carbon monoxide and oxygen from carbon dioxide. They may be tubular or planar in configuration. Planar electrochemical cell units may be arranged overlying one another in a stack arrangement, for example 100 to 200 or more electrochemical cell units in a stack, with the individual electrochemical cell units arranged, for example, electrically in series.

[0006] A solid oxide fuel cell (SOFC) that produces electricity is based upon a solid oxide electrolyte that conducts negative oxygen ions from a cathode to an anode located on opposite sides of the electrolyte. For this, a 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 vulnerable to fracture. Hence, metal-supported SOFCs have been developed which have the active fuel cell component layer supported on a metal substrate. In these cells, the ceramic layers can be very thin since they only perform an electrochemical function: that is to say, the ceramic layers are not self- supporting but rather are thin coatings / films laid down on and supported by the metal substrate. Such metal supported SOFC stacks are more robust, lower-cost, have better thermal properties than ceramic-supported SOFCs, and can be manufactured using conventional metal welding techniques.

[0007] A solid oxide electrolyser cell (SOEC) may have the same structure as an SOFC but is essentially that SOFC operating in reverse, or in a regenerative mode, to achieve the electrolysis of water and / or carbon dioxide by input of electrical energy and using the solid oxide electrolyte (or other electrolytes as listed above) to produce hydrogen gas and / or carbon monoxide and oxygen.

[0008] The present invention is directed at an electrochemical cell unit and concerns the design of interconnects for them (also known as interconnector plates or separator plates). It is thus applicable to various types of fuel and electrolyser cells, for example, based on solid oxide electrolytes, polymer electrolyte membranes, or molten electrolytes. For convenience, "cell units" is used to refer to "electrochemical cell units" including fuel or electrolyser cell units. Each cell unit in a stack of cell units typically includes a cell layer comprising an electrochemically active cell region (such as a metal-supported or anode-supported electrochemically active cell region) and an interconnect. An interconnect typically contacts one side of the cell layer of a cell unit and, in a stack of cell units, and may also contact an opposite side of a cell layer of an adjacent cell unit. Some interconnects are also configured to separate fluid volumes disposed to opposite sides of said interconnect (e.g. a fuel volume and an oxidant volume).

[0009] Figure 1 shows an exploded perspective view of a cell unit with two gaskets, taken from the Applicant's earlier application GB 2603665 A, which discusses an electrochemical cell unit and a stack comprising a plurality of such electrochemical cell units with raised elements. The cell unit 10 of Figure 1 comprises a flat (i.e. planar) metal support plate 14 stacked next to an interconnect 12. The interconnect 12 is shown to have flanged perimeter 18 around its perimeter. The flanged perimeter 18 extends out of the predominant plane of the sheet, as found at a central fluid volume area, to create a concavity in the interconnect (and a convexity to the outside surface). The concavity will form a fluid volume within this cell unit upon assembly of the cell unit.

[0010] In the illustrated arrangement in Figure 1 the cell unit 10 has rounded ends and parallel sides, with a fluid port 22 towards each end in both the interconnect 12 and the metal support plate 14. Other shapes and sizes and numbers of the respective cell features are possible depending upon the required power and dimensions of the final stack assembly.

[0011] Around the fluid ports of the separator plate 12, shaped port features 24 are provided. The shaped port features 24 are provided as multiple elements in the form of round dimples extending out of the plane of the base of the fluid volume a distance corresponding to that of the height of the flanged perimeter 18 - to have a common height therewith. This is so that they will mechanically contact the opposing surface of the metal support plate 14, just like the flanged perimeter 18, when the cell unit 10 is assembled. As a result, when the flanged perimeter 18 is joined to the metal support plate 14, for example by welding, the shaped port features 24 will likewise contact the metal support plate 14. Said joining may electrically connect the metal support plate and the interconnect.

[0012] In a middle portion of the cell unit 10, an electrochemically active layer 50 is provided on the metal support plate. In this example it is located outside of the enclosed fluid volume.

[0013] The electrochemically active area 50 includes an anode, a cathode, and an electrolyte positioned between the anode and cathode (not explicitly shown). The anode, electrolyte, and cathode may together be referred to as the electrochemically active layer 50, active electrochemical cell layer, or electrochemically active region. The electrolyte conducts either negative oxygen ions or positive hydrogen ions between the anode and cathode. The stack 20 may comprise a stack of cell units that are based on one of solid oxide electrolytes, polymer electrolyte membranes, or molten electrolytes or any other variant capable of electrochemistry.

[0014] The concave configuration can give the relevant plate the appearance of a rimmed tray, with a correspondingly convex outside shape (outside relative to the cell unit) and usually a planar base, the concavity thus defining (e.g. part of) the fluid volume in the assembled cell unit. In this concave configuration, the flanged perimeter extends out of a plane of the original sheet of the interconnect, and / or of the metal support plate, toward a respective opposed surface of the other of the separator plate and the metal support plate.

[0015] The fluid volume is thus bordered by a flanged perimeter, which is formed by pressing, such as by use of a die press, hydroforming or stamping. These are simple processes that are already being undertaken in the formation of central protrusions in the fluid volume (described below), as found likewise on the interconnect, for supporting and electrically connecting adjacent cells via the electrochemically active layers.

[0016] Figure 2 shows an exploded perspective underside view of the cell unit of Figure 1. The metal support plate 14 (e.g. metal foil) is provided with multiple small holes or pores 48 to enable fluid in the fluid volume to be in contact with the side of the electrochemical layers that is closest to the metal support plate 14. These form a porous region bounded by a non-porous region. The anode (fuel electrode) layer is located adjacent the small holes / pores with the (enclosed) fluid volume within the cell unit comprising a fuel flow volume supplied by fuel entering and exiting via the fluid ports 22, which are thus fuel ports 22. The cathode (air electrode) layer is on the opposite side of electrochemically active layer 50, i.e. on its outer face, and is exposed to air flowing across that layer during use of the cell unit 10. Figure 2a shows a simplified cross-section of the arrangement shown in Figures 1 and 2.

[0017] The interconnect may be provided with central area having upward protrusions 32 and downward protrusions 36 which include in and out protrusions (up and down as shown), extending between the internal opposed surfaces of the two plates and an outer surface of the electrochemically active layer of the cell unit adjacent to the outward protrusions. The upward protrusions 32 define fluid pathways between them for fuel, the pathways being through the enclosed fluid volume between fluid ports at each end of the cell unit. The downward protrusions 36 define fluid pathways between them for oxidant (such as air) through the fluid volume defined between the outer surface of the electrochemically active layer of the cell unit adjacent to the downward protrusions.

[0018] Each gasket, for example gasket 34 (also referred to as a "seal"), provides a primary sealing function and will usually be a compressible gasket that is subjected to compressive forces in the vicinity of the ports.

[0019] These gaskets, each of which typically surrounds a respective fluid port and is thus typically annular in shape, may also provide electrical insulation between a first cell unit 10 and an adjacent fluid cell unit 10, so as to prevent a short circuit. The gaskets may be any suitable material such as, for example, vermiculite-based gaskets, e.g. Thermiculite (trade mark).

[0020] The gaskets 34 may be relatively thick, for example approximately 0.5 mm in thickness when compressed, in situ. Relatively thick gaskets, along with downward dimples / protrusions 36, are advantageous in spacing apart neighbouring cell units. However, alternative cell unit designs are possible, such as ones with smaller / lower dimples, protrusions and / or gaskets. As mentioned, it is the function of the interconnect layer to make electrical contact with the active area of the metal support plate below; however, no other electrical contact should be made between the interconnect and the metal support plate.

[0021] There is a risk that deformation (e.g. flexing) of the interconnect and / or the metal support plate may occur, causing unintended and unwanted contact between the interconnect and the non-active-area portions of the metal support plate, resulting in short circuiting of the cell (whether SOEC or SOFC).

[0022] The present invention seeks to address, overcome or mitigate at least one of the prior art disadvantages.

[0023] Summary of the Invention

[0024] It is herein disclosed, to improve the reliable functioning of an electrochemical cell unit and the corresponding cell stack (for electrolysis or fuel cell operation), the introduction of an insulation means, such as at least one insulating layer, on the interconnect (preferably on the air side) in one or more area(s) that correspond to area(s) that are outside of the active cell area (e.g., that face the metal support plate).

[0025] This advantageously prevents or reduces the risk of short circuiting of a cell. This is especially useful in interconnect designs which have lower dimples, particularly relevant to low-airflow thermoneutral (or close-to-thermoneutral) electrolysis cells, for example. However, it is also advantageous in e.g. large fuel cells with potential large deformations with possibility for adjacent cells touching. Insulation makes such designs more feasible and / or practical.

[0026] The insulation means is provided in or on the interconnect, rather than the metal support plate which supports the active cell area, so that it does not interfere with other aspects of cell design / arrangement.

[0027] Another potential advantage is with the provision of a dedicated insulation means, there is no requirement or less necessity for the gasket(s) to be electrically insulating, so the range of possible materials for the gasket(s) is wider.

[0028] In a first aspect, there is provided an interconnect for electrically connecting cells of an electrochemical cell stack, the interconnect having a first side and a second side, the first side being adapted to face a cell layer comprising an electrochemically active cell region, and a portion of the first side of the interconnect is provided with an electrically insulating layer.

[0029] The interconnect is also known as interconnector plate or separator plate. The cell layer may comprise an anode-supported, electrolyte-supported, or metal-supported electrochemically active cell region. The electrochemically active cell region may be the region of the cell layer in which there is provided an air electrode, electrolyte, and fuel electrode. The remainder of the cell layer may not be provided with at least one of the air electrode, electrolyte, and fuel electrode, and so may be described as an electrochemically inactive (cell) region. The electrically insulating coating may face said electrochemically inactive region. The electrochemical cell stack is preferably an electrolysis cell stack, and more preferably a solid oxide electrolyser cell stack.

[0030] Preferably, the first side of the interconnect is adapted to face a cell layer, said cell layer comprising, in a central area, the electrochemically active cell region. Preferably, the portion of the first side of the interconnect that is provided with an electrically insulating layer is a portion that is adapted to face the electrochemically active cell layer outside the central area.

[0031] Preferably, the first side of the interconnect is electrically conductive in an area that is adapted to face the electrochemically active cell region. Preferably, this is a central area of the interconnect, excluding the portion provided with the electrically insulating layer.

[0032] Preferably, the area comprises conductive features, such as conductive protrusions, adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

[0033] Preferably, the protrusions comprise dimples which are pressed or formed in the interconnect, said dimples adapted to contact the electrochemically active cell region. Such pressing or forming is relatively cost-effective and may be executed at the same time as pressing or forming other features of the interconnect. Alternatively or additionally, the protrusions comprise features printed or deposited on - and / or machined or etched into a printed or deposited layer on - the first side of the interconnect. The height of such features may be easy to control, and may be manufactured with relative ease. Alternatively, said area comprises a porous layer (of a given thickness across the area of the electrochemically active cell region) adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

[0034] Preferably, the (first side of the) interconnect has a central area and a periphery between the central area and a perimeter of the interconnect, and the electrically insulating layer is provided on at least a portion of the periphery. In such cases, the central area is the area which is electrically conductive. The electrically insulating layer prevents electrical contact between the periphery of the interconnect and a cell layer in order to prevent electrical shorting of cell units. In such cases, in a stack, the central area of the interconnect is aligned with a or the central area of the cell layer in which the electrochemically active cell region is provided.

[0035] Preferably, the interconnect further comprises at least one fluid port provided in the periphery, and the electrically insulating layer is provided between at least one of: (a) the at least one fluid port and the central area; and (b) the at least one fluid port and the perimeter of the interconnect.

[0036] Preferably, the electrically insulating layer surrounds the at least one fluid port.

[0037] Preferably, the second side of the interconnect is adapted to be exposed to a first fluid volume for a first fluid (e.g. fuel, for example hydrocarbon or H2for a fuel cell, steam for an electrolyser cell), and the first side of the interconnect is adapted to be exposed to a second fluid volume for a second fluid (e.g. oxidant / oxygen / sweep gas) that is different to the first fluid. Preferably, the interconnect is adapted to separate said fluids. Preferably, the electrically insulating layer comprises a dielectric layer (e.g. made of glass ceramic).

[0038] Preferably, the electrically insulating layer comprises at least one of zirconia and hafnium.

[0039] Preferably, the electrically insulating layer has a thickness of between 0.001 mm and 0.5 mm, more preferably between 0.001 mm and 0.1 mm, more preferably between 0.001 mm and 0.05 mm, more preferably between 0.005 mm and 0.02 mm.

[0040] Preferably, the interconnect is for use in a (e.g. metal-supported solid oxide) electrolysis cell unit or (e.g. metal supported) electrolysis cell stack.

[0041] In a second aspect, there is provided an electrochemical cell unit for an electrochemical cell stack comprising the interconnect described above and a cell layer comprising an electrochemically active cell region, the cell layer and the interconnect overlay one another to form the electrochemical cell unit.

[0042] More specifically, the second aspect may provide an electrochemical cell unit for an electrochemical cell stack comprising: a cell layer comprising a metal support plate having a first side and a second side, an electrochemically active cell region, and an electrochemically inactive region which surrounds a central area in which the electrochemically active cell region is provided, wherein the second side of the metal support plate carries the electrochemically active cell region provided over a porous region of the metal support plate; and an interconnect, the interconnect having a first side and a second side, the first side being adapted to face the cell layer, and wherein a portion of the first side of the interconnect is provided (preferably coated, but could be a self-supporting component) with an electrically insulating layer, wherein the cell layer and the interconnect overlay one another to form the electrochemical cell unit (i.e., the first side of the interconnect facing the second side of the metal support plate (e.g., also facing the electrochemically active cell region) or the second side of the interconnect facing the first side of the metal support plate), and the portion of the first side of the interconnect provided with the electrically insulating layer is aligned with or faces the electrochemically inactive region.

[0043] The interconnect of the second aspect may be according to the first aspect.

[0044] Preferably, the cell layer and the interconnect overlie each other in a spaced relationship to form a fluid volume for the first fluid therebetween; the first fluid volume provides a volume for delivery to and exhaust from one side of the electrochemically active cell region.

[0045] Preferably, the electrochemical cell unit is configured to constrain the first fluid in a first fluid volume (e.g., between the second side of the interconnect and the first side of the cell layer / support plate, preferably enclosed by the interconnect and cell layer (support plate) of a cell unit) and to constrain the second fluid in a second fluid volume (e.g., between the first side of the interconnect and the second side of the cell layer / support plate), wherein a cross-sectional area of the second fluid volume is smaller than a cross-sectional area of the first fluid volume. Preferably, the cell layer has a central area carrying the electrochemically active cell region. Preferably, it also comprises a periphery between the electrochemically active cell region and a perimeter of the cell layer, and the portion of the first side of the interconnect upon which the electrically insulating layer is provided is aligned with or faces a portion of the periphery of the cell layer. In this way, the electrically insulating coating may prevent electrical contact, and therefore electrical shorting between the first side of the interconnect and the cell layer (of said cell, or an adjacent cell in a stack of cell units) around the periphery.

[0046] Preferably, the cell layer further comprises an electrochemically inactive region which surrounds a central area, the central area being where the electrochemically active cell region is provided, and the portion of the first side of the interconnect provided with the electrically insulating layer is aligned with or faces the electrochemically inactive region. In this way, the electrically insulating coating may prevent electrical contact, and therefore electrical shorting between the first side of the interconnect and the electrochemically inactive region of the cell layer (of said cell, or an adjacent cell in a stack of cell units). In cases where the electrochemically active cell region is supported by a (metal) support plate, the electrochemically active cell region may coincide with the porous region of the support plate, and the electrochemically inactive cell region may coincide with the non- porous region of the support plate. Alternatively or additionally, the electrochemically active cell region is the area of the support plate covered by the fuel electrode, electrolyte and oxygen electrode.

[0047] Preferably, an outermost layer of the electrochemically active cell region is provided with protrusions adapted to face a first side of the interconnect.

[0048] Preferably, the electrochemically active cell region comprises a solid oxide electrolyte.

[0049] Preferably, the electrochemical cell unit is an electrolysis cell unit, more preferably a solid oxide electrolysis cell (SOEC) unit. Electrolysis cell units may have a lower oxidant flow rate requirement than fuel cell units, and so the height of an oxidant side (e.g., the fluid volume disposed to the first side of the interconnect) of an interconnect for an electrolysis cell unit may be reduced relative to the height of an oxidant side of an interconnect for a fuel cell unit. Such lower heights may increase the chance that the first side of the interconnect contacts the cell layer in undesirable locations (e.g., outside the electrochemically active cell area, causing a short circuit). The electrically insulating coating may prevent such contact.

[0050] Preferably, the cell layer further comprises a metal support plate carrying the electrochemically active cell region provided over (e.g. coated or deposited upon) a (e.g., central) porous region of the metal support plate.

[0051] Preferably, the (central) porous region of the metal support plate is surrounded by a periphery between the (central) porous region and a perimeter of the metal support plate, and the portion of the first side of the interconnect upon which the electrically insulating layer is provided is aligned with or faces a portion of the periphery of the metal support plate; preferably, the porous region provides fluidic communication between the first side and the second side of the metal support plate. In this way, the electrically insulating coating may prevent electrical contact, and therefore electrical shorting between the first side of the interconnect and the periphery of the metal support plate.

[0052] Preferably, the metal support plate has a first side and a second side, the second side of the metal support plate carrying the electrochemically active cell region and the first side of the metal support plate facing the second side of the interconnect.

[0053] Preferably, the second side of the interconnect and the cell layer (in some cases, the first side of the metal support plate) are spaced from one another to provide a first fluid volume therebetween and are joined around their periphery or perimeter and is electrically connected thereto. Protrusions or features on the second side of the interconnect may contact the cell layer to maintain the spacing between the interconnect and cell layer, and thus said fluid volume. Alternatively, the first side of the interconnect and the cell layer are spaced from one another to provide a first fluid volume therebetween, and having at least one gasket provided therebetween. Said gasket may be electrically insulating, albeit that it need not be electrically insulating if said gasket is provided upon the electrically insulating layer. Protrusions or features on the first side of the interconnect may contact the cell layer to maintain the spacing between the interconnect and cell layer, and thus said fluid volume.

[0054] Preferably, the interconnect has at least one bridge dimple that forms a protrusion on the first side of the interconnect and a corresponding depression on the second side of the interconnect, the depression for fluid guidance on the second side of the interconnect and the electrically insulating layer is provided on (i.e., at least on) the at least one bridge dimple. In other words, the electrically insulating layer may be on the protrusion formed by the at least one bridge dimple (a convex side of the bridge dimple) since the electrically insulating layer is on the first side of the interconnect. The depression may be for fluid delivery to and / or exhaust from the porous region. The depression (a volume formed thereby) may be in fluidic communication with the at least one port and / or a first fluid volume enclosed between the (second side of the) interconnect and the (first side of the) cell layer (substrate). The depression (a volume formed thereby) may allow fluidic communication between the at least one port and the first fluid volume and / or porous region.

[0055] Preferably, the at least one fluid port is in fluidic communication with a first fluid volume provided between the interconnect and the metal support plate, the electrochemical cell unit further comprising a fluid guidance insert disposed in the first fluid volume, said fluid guidance insert comprising a plurality of elongate slots formed therein, said elongate slots defining a fluid channel system for conveying fluid between the at least one fluid port and the first fluid volume via the at least one bridge dimple (I.E., the second side of the interconnect, via the depression (volume formed by the depression) of the at least one bridge dimple).

[0056] Preferably, the elongate slots each have a distal end section wherein the distal end section of at least one of the elongate slots is closed by a web of the fluid guidance insert, and wherein the at least one bridge dimple extends away from the fluid guidance insert and spans said web to form a fluid bypass around the web (i.e., for conveying fluid between the at least one fluid port and the first fluid volume via the at least one bridge dimple). In other words, the second side of interconnect faces the fluid guidance insert and so the depression of the at least one bridge dimple faces the insert.

[0057] In other words the bridge dimple allows fluidic communication between the slot and the first fluid volume. The proximal end section may be proximal to the fluidic port and in fluidic communication therewith (it may be referred to as being open or not closed by the web). The distal end section may be distal from the proximal end section (and port).

[0058] Preferably, the at least one fluid port is provided by a through-hole extending through the interconnect, the fluid guidance insert and the metal support plate (i.e., said ports outside the central, electrochemically active area - between said area and periphery).

[0059] Preferably, the distal end section of at least one of the elongate slots is open (in other words, it is not closed by a web).

[0060] In a third aspect, there is provided a stack of electrochemical cell units in accordance with the abovedescribed electrochemical cell unit, comprising a plurality of electrochemical cell units overlaying one another in a stacking direction, the first side of an interconnect of a first cell unit facing an outermost layer of the electrochemically active cell region of a neighbouring cell unit in a spaced relationship to form a second fluid volume for second fluid therebetween. The electrically insulating coating prevents electrical contact with the neighbouring cell unit outside the electrochemically active cell region of that neighbouring cell unit.

[0061] Preferably, in the stack, the electrochemical cell unit is configured to constrain the first fluid in a first fluid volume (e.g., between the second side of the interconnect and the first side of the cell layer / support plate, preferably enclosed by the interconnect and cell layer (support plate) of a given cell unit) and to constrain the second fluid in a second fluid volume (e.g., between the first side of the interconnect and the second side of the cell layer / support plate, preferably between interconnect and cell layer of neighboring cell units), wherein a cross-sectional area of the second fluid volume is smaller than a cross-sectional area of the first fluid volume.

[0062] In a fourth aspect, there is provided an interconnect for electrically connecting cells of a metal- supported solid oxide electrolysis cell (SOEC), comprising a first side and a second side, wherein the first side comprises a first area adapted to face an active region of a metal-supported SOEC cell, and a second area comprising at least one electrically insulating region, wherein the second area is outside of the first area.

[0063] In a fifth aspect, there is provided a method for manufacture of an interconnect for electrically connecting cells of an electrochemical cell stack (preferably an electrolysis cell unit), the method comprising providing an interconnect having a first side and a second side, the first side being adapted to face a cell layer comprising an electrochemically active cell region, and providing an electrically insulating layer on a portion of the first side of the interconnect. Preferably, the first side of the interconnect is electrically conductive in an area that is adapted to face the electrochemically active cell region. Preferably, providing an interconnect comprises providing, in the area, conductive protrusions adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region. Preferably, providing the conductive protrusions comprises pressing or forming the interconnect to provide dimples on the first side of the interconnect, said dimples adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region; alternatively or additionally, providing the conductive protrusions comprises printing or depositing conductive features on the first side of the interconnect, said conductive features adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region. Alternatively, providing the interconnect comprises providing, in the area, a porous layer on the first side of the interconnect, said porous layer adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

[0064] Preferably, providing an electrically insulating layer comprising using at least one of: (a) a wet deposition method such as screen printing, (b) a physical or chemical vapour deposition method, and (c) a wet spraying or plasma spraying method, to deposit the electrically insulating layer on a portion of the first side of the interconnect.

[0065] Preferably, providing the electrically insulating layer further comprises heating the interconnect subsequent to depositing the electrically insulating layer. This may densify the layer and / or may improve adhesion of the layer to the interconnect. Said heating may involve heating the interconnect to a temperature of at least 300°C, preferably at least 500°C, more preferably at least 800°C and at a temperature of less than 1200°C, preferably less than 1000°C, more preferably less than 900°C. Said heating step may be executed in an oxidising environment in order to coat the remainder of the interconnect (i.e. parts not coated with the electrically insulating layer or other layers) with a layer of thermally grown oxide.

[0066] Preferably, the electrically insulating layer is provided on at least a portion of the peripheral area between a central area and a perimeter of the interconnect.

[0067] Preferably, providing the interconnect comprises providing at least one fluid port in the periphery, and the electrically insulating layer is provided between at least one of: (a) the at least one fluid port and the central area, and (b) the at least one fluid port and the perimeter of the interconnect. Preferably, the electrically insulating layer surrounds the at least one fluid port.

[0068] Preferably, the second side of the interconnect is adapted to be exposed to a first fluid, and first side of the interconnect is adapted to be exposed to a second fluid different to the first fluid.

[0069] Preferably, the electrically insulating layer comprises a dielectric layer.

[0070] Preferably, the electrically insulating layer comprises at least one of zirconia and hafnium. Preferably, the electrically insulating layer has a thickness of between 0.001 mm and 0.5 mm, more preferably between 0.001 mm and 0.1 mm, more preferably between 0.001 mm and 0.05 mm, more preferably between 0.005 mm and 0.02 mm.

[0071] Preferably, the interconnect is for use in an electrolysis cell unit or electrolysis cell stack. In a sixth aspect, there is provided a method for manufacture of an electrochemical cell unit, the method comprising: providing, by the method described above, an interconnect having a first side and a second side, the first side being adapted to face a cell layer comprising an electrochemically active cell region, the interconnect provided with an electrically insulating layer on a portion of the first side of the interconnect; providing a cell layer comprising an electrochemically active cell region; and overlying the cell layer and the interconnect to form the electrochemical cell unit.

[0072] More specifically, the sixth aspect may provide an electrochemical cell unit for an electrochemical cell stack comprising: providing a cell layer comprising a metal support plate having a first side and a second side, an electrochemically active cell region and an electrochemically inactive region which surrounds a central area in which the electrochemically active cell region is provided, wherein the second side of the metal support plate carries the electrochemically active cell region provided over a porous region of the metal support plate; providing an interconnect having a first side and a second side, the first side being adapted to face a cell layer and wherein a portion of the first side of the interconnect is provided (e.g., coated) with an electrically insulating layer, wherein an electrically insulating layer is provided on a portion of the first side of the interconnect; and overlying the cell layer and the interconnect to form the electrolysis cell unit (i.e., the first side of the interconnect facing the second side of the metal support plate (in other words, also facing the electrochemically active cell region) or the second side of the interconnect facing the first side of the metal support plate), and the portion of the first side of the interconnect provided with the electrically insulating layer is aligned with or faces the electrochemically inactive region.

[0073] The interconnect of the sixth aspect may be provided according to the fifth aspect. The interconnect and / or cell layer of the sixth aspect may be according to the first or second aspect.

[0074] Preferably, the cell layer has a central area carrying the electrochemically active cell region and a periphery between the electrochemically active cell region and a perimeter of the cell layer, the portion of the first side of the interconnect upon which the electrically insulating layer is provided is aligned with or faces a portion of the periphery of the cell layer.

[0075] Preferably, the cell layer further comprises an electrochemically inactive region which surrounds a central area in which the electrochemically active cell region is provided, and the portion of the first side of the interconnect provided with the electrically insulating layer is aligned with or faces the electrochemically inactive region.

[0076] Preferably, an outermost layer of the electrochemically active cell region is provided with protrusions adapted to face a first side of the interconnect.

[0077] Preferably, the electrochemically active cell region comprises a solid oxide electrolyte.

[0078] Preferably, the electrochemical cell unit is an electrolysis cell unit.

[0079] Preferably, the cell layer further comprises a metal support plate carrying the electrochemically active cell region provided over a central porous region of the metal support plate. Preferably, the central porous region of the metal support plate is surrounded by a periphery between the central porous region and a perimeter of the metal support plate, and the portion of the first side of the interconnect upon which the electrically insulating layer is provided is aligned with or faces a portion of the periphery of the metal support plate.

[0080] Preferably, the metal support plate has a first side and a second side, the second side of the metal support plate carrying the electrochemically active cell region and the first side of the metal support plate facing the second side of the interconnect.

[0081] Preferably, the second side of the interconnect and the cell layer are spaced from one another to provide the fluid volume therebetween and joined around their periphery or perimeter and electrically connected thereto. Alternatively, the first side of the interconnect and the cell layer are spaced from one another to provide the fluid volume with at least one electrically insulating gasket provided therebetween.

[0082] In a seventh aspect, there is provided a method for manufacture of a stack of electrochemical cell units, the method comprising: providing, by the above-described method, a plurality of electrochemical cell units, each of the plurality of cell units having an electrically insulating coating provided on a portion of the first side of the interconnect; and overlaying the plurality of electrochemical cell units over one another in a stacking direction, wherein a first side of an interconnect of a first cell unit faces an outermost layer of an electrochemically active cell region of a neighbouring cell unit in a spaced relationship to form a second fluid volume for second fluid therebetween.

[0083] In order that the present invention be more readily understood, various aspects of specific embodiments will now be described in conjunction with the attached drawings.

[0084] Brief Description of the Drawings

[0085] Figure 1 is an exploded perspective view of a fuel cell unit and two gaskets.

[0086] Figure 2 is a second perspective view of the arrangement in Figure 1, shown from a different angle.

[0087] Figure 2a is a simplified cross-section of the arrangement of Figures 1 and 2.

[0088] Figure 3 is a schematic cross-sectional view of a cell unit.

[0089] Figure 4 is a schematic plan view of an interconnect of a cell unit.

[0090] Figure 5 is an exploded perspective view of a cell unit and two gaskets.

[0091] Figure 6A is a plan view of one exemplary arrangement of an interconnect of a cell unit.

[0092] Figure 6B is an exploded perspective view of an arrangement comprising a stack of two cell units each including an interconnect corresponding to Figure 6A.

[0093] Figure 7A is a plan view of another exemplary arrangement of an interconnect of a cell unit.

[0094] Figure 7B is an exploded perspective view of an arrangement comprising a stack of two cell units each including an interconnect corresponding to Figure 7A.

[0095] Figure 7C shows two cross-sectional views of the arrangement of Figure 7B.

[0096] Figure 8A is a plan view of yet another exemplary arrangement of an interconnect of a cell unit.

[0097] Figure 8B is an exploded perspective view of an arrangement comprising a stack of two cell units each including an interconnect corresponding to Figure 8A. Figure 8C shows two cross-sectional views of the arrangement of Figure 8B.

[0098] Figure 9 is a plan view of an exemplary arrangement of an interconnect of a cell unit.

[0099] Figure 10 is a plan view of another exemplary arrangement of an interconnect of a cell unit.

[0100] Figure 11 illustrates a method of manufacturing an interconnect for electrically connecting cells of an electrochemical cell stack.

[0101] Figures 12A and 12B are perspective, plan, and cross-sectional views of another exemplary arrangement of an interconnect and cell unit comprising a fluid guidance insert.

[0102] Detailed Description

[0103] The drawings are included for illustrative purposes only. Some of the figures only indicate one or two electrochemical cell units (each hereafter referred to simply as a "cell unit") in a stack. 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 each comprising multiple electrochemical cells are provided. It will be appreciated that the anode and cathode inlets, outlets (off-gas), ducting, and manifolding, and their configuration are modified as appropriate for such embodiments, and will be readily apparent to a person of ordinary skill in the art.

[0104] The cell units described with reference to Figures 3 to 12 may be fuel cell units, such as SOFC units, or electrolyser cell units, such as SOEC units.

[0105] Figure 3 shows a simplified schematic of a cell unit. It depicts a cell layer 314 and two adjacent separator plates 312a and 312b. It will be appreciated that these three components are merely exemplary, that a cell unit (i.e. a repeat unit) is constructed from one cell layer 314 and one separator plate (a.k.a. interconnect) 312 - whether a cell layer with an interconnect above or below it - and that plural cell units may be stacked one upon the next to form a stack of cell units.

[0106] The cell layer includes an electrochemically active cell area 350. That electrochemically active cell area 350 may be self-supporting (e.g., fuel electrode-supported or electrolyte-supported) or may be supported by a support plate (that support plate having a porous region 355 for fluidic communication between the electrochemically active cell area 350 and the first fluid flow region).

[0107] The cell layer 314 and the separator plates 312a, 312b each have a first side and a second side. The first side 313a of each separator plate 312 faces the second side 315b of each cell layer 314. The second side 313b of each separator plate 312 faces the first side 315a of each cell layer 314.

[0108] A first fluid volume (or flow region) 360 is defined between the first side 315a of the cell layer 314 and the second side 313b of the separator plate 312. A second fluid volume (flow region) 365 is defined between the second side 315b of the cell layer 314 and the first side 313a of the separator plate 312.

[0109] The first fluid volume (flow region) 360 may be for delivery of first fluid (e.g., fuel) to the first side of the cell layer 314 (i.e. to a layer of the electrochemically active cell area 350 which is in fluidic communication with the first fluid flow region 360, optionally via the porous region 355 of a support plate in cases where the cell layer 314 comprises a support plate supporting the electrochemically active cell area 350). The first fluid volume (flow region) 360 may also exhaust a product of an electrochemical reaction at the electrochemically active cell area 350 (and exhausts any unused fuel).

[0110] The second fluid volume (flow region) 365 may be for delivery of second fluid (e.g., oxidant or sweep gas) and / or for exhaust of a product of the electrochemical reaction at the electrochemically active cell area 350. In the case of electrolysis cell operation, only a sweep gas may be supplied (and exhausted) via the second fluid volume (flow region), to assist in product of the electrochemical cell reaction. The sweep gas may, for example, be oxygen, oxidant, air, or another suitable gas.

[0111] Figure 3 depicts the cross-sectional of the second fluid volume (flow region) 365 as being smaller than the cross-sectional area of the first fluid volume (flow region) 360. This cross-sectional area difference may be defined by the height h2 366 of the second fluid volume (flow region) 365 being smaller than the height hl 361 of the first fluid volume (flow region) 360.

[0112] A cell unit (i.e. a repeat unit, plural units form a stack) comprises one cell layer 314 and one separator plate 312. In an example, cell units 300 are formed from the cell layer 314 and the separator plate 312a, such that said components enclose the first fluid volume (flow region) 360 between the second side 313b of the separator plate and the first side of the cell layer 315a. When two cell units 300 are stacked, the second fluid flow volume 365 is bounded between the second side 315b of the cell layer 314 of a first cell unit 300 and the first side 313a of the separator plate 312b of a second, neighbouring (i.e. adjacent) cell unit 300, and may be referred to as the second fluid volume.

[0113] In an example, cell units 370 are formed from the cell layer 314 and the separator plate 312b, such that said components enclose the second fluid volume (flow region) 365 between the first side 313a of the separator plate 312b and the second side 315b of the cell layer 314. When two cell units 370 are stacked, the first fluid volume (flow region) 360 is bounded between the first side 315a of the cell layer 314 of a first cell unit 300 and the second side 313b of the separator plate 312a of a second, neighbouring (i.e. adjacent) cell unit 370.

[0114] The cell layer is typically (substantially) planar, at least within the plan view area of the electrochemically active cell area 350. The separator plate is typically formed from a planar sheet, for example a metal sheet.

[0115] Conductive features are preferably formed on the first side 313a of the separator plate 312. For example, they are conductive protrusions. Such protrusions may be printed features, or features formed by pressing a metal sheet, for example. Protrusions may take the form of discrete dimples; alternatively, they may take the form of ribs or otherwise. They protrude into the corresponding fluid volume 365, and conductively contact the electrochemically active cell region 350 of the cell layer 314 (the second side 315b thereof) while at the same time performing the role of spacing the cell layer 314 from the separator plate 312b above.

[0116] Instead of protrusions (e.g. dimples), the conductive features may comprise a porous layer formed (e.g. deposited or coated) on the first side of 313a of the separator plate. Alternatively or additionally, a porous layer may be formed (e.g. deposited coated) on the second side 315b of the cell layer 314, specifically on the electrochemically active cell area 350. Such a porous layer may also be provided as a component in its own right (e.g. an expanded metal sheet or mesh) in the stack. Protrusions or other features may be provided on the second side 313b of the separator plate 312, as can be seen in some illustrated examples below.

[0117] Protrusions or porous layers may also serve the purpose of transferring compression force through or between cell units in a stack.

[0118] Figure 4 shows a simplified schematic plan view of an interconnect 400 in its full extent, as seen from the first side of the interconnect 400, corresponding to first side 313a of Figure 3. Said first side of the interconnect may be exposed to (form a boundary of) the second fluid volume, which may be for air or oxidant.

[0119] In this example, four first fluid ports 440 (described further below) are shown on the interconnect, which has an outer perimeter 430, although other numbers (at least one) of ports are possible. Also shown is an area 410 on the interconnect, which contains electrical contact features that faces the electrochemically active cell region of the cell layer below, in situ. This is an electrically conductive area 410. The electrical contact features may comprise conductive protrusions or dimples, for example, adapted to contact said electrochemically active cell region and space the interconnect therefrom. This area 410 is preferably a central area of the interconnect, and may be referred to as a central area 410.

[0120] The area 420 on the interconnect outside the central area 410 is shaded in Figure 4; they are exclusive of each other. In other words, this area 420 is between the central area 410 and the perimeter 430 of the interconnect, and may be described as a periphery 420 of the interconnect. The ports 440 are formed in the periphery 420.

[0121] Referring back to schematic Figure 3, the central area 410 of Figure 4 corresponds to the portion of the first side 313a of interconnect 312b that directly faces the electrochemically active cell area 350 of the cell layer 314, and the periphery 420 corresponds to the remainder of said first side 313a of the interconnect 312b which faces the cell layer 314 but does not correspond to the electrochemically active cell area 350 of the cell layer 314.

[0122] As above mentioned, it is undesirable for any part of the interconnect to get into electrical contact with the cell layer except where such electrical contact is intended, namely between the electrochemically active cell area of the cell layer and the central part of the interconnect. Such undesirable contact may happen if the interconnect undergoes deformation or flexing for any reason during operation, or if the height 366 of the second fluid volume is particularly small, resulting in a short circuit.

[0123] It is herein disclosed that at least one electrically insulating means, such as an insulating layer, may be provided on the interconnect, on at least a portion of the first side 313a, for example in the periphery 420 that does not face the electrochemically active area (of the second side 315b) of the cell layer.

[0124] This is advantageous in electrically insolating the interconnect from the cell layer (except at the active area), particularly if spacing between is small. This is particularly the case for electrolyser cells (e.g. SOECs), in which the first side of the interconnect is adapted to be exposed to oxidant / oxygen volume, in which case oxidant volume may be reduced in size compared to fuel cell (e.g. SOFC) operation. The oxidant volume may be smaller compared to fuel side of fuel cells because the only fluid in the oxidant volume may be that produced by the electrolysis cell reaction (plus, optionally, a sweep gas).

[0125] The insulation layer may be, but is not limited to, a dielectric layer. It is preferably an insulating material with a relative permittivity less than 25, preferably less than 20, more preferably less than 15, more preferably less than 10, more preferably less than 5. It may comprise, for example, a glass ceramic. Further examples for the material of the insulation layer or coating include alumina, hafnium oxide, silica, zirconia, ceria, aluminium silicate (or magnesium silicate) based glasses.

[0126] The insulation layer may have a thickness of between approximately 1 micrometer and 500 micrometers, for example. A smaller range of between preferably between 1 micrometer and 100 micrometers may be preferred, more preferably between 1 micrometer and 50 micrometers, more preferably between 5 micrometers and 20 micrometers. For example, an alumina coating that is approximately 1 micron (e.g. 0.5 to 2 micron) thick on steel has insulating effect. The upper limit of the thickness of the insulation layer may correspond to the applicable cell unit design, for example, to correspond to the height of a dimple on an interconnect.

[0127] It is noted that such insulation means is provided on / in the interconnect rather than the cell layer, so that it does not interfere with cell layer design. Although applying an insulating or dielectric layer on the interconnect airside incurs additional manufacturing costs, it provides an effective way of preventing or reducing the risk of shorting of cells and cell stacks.

[0128] Insulating layers can be deposited using various methods, such as:

[0129] • wet deposition methods, such as screen printing, tape casting, transfer printing of inks;

[0130] • physical or chemical vapour deposition methods (e.g. CVD, PVD, sputtering);

[0131] • wet spraying or plasma spraying methods.

[0132] Screen printing may be a particularly preferred route, because of ease of use.

[0133] After deposition, further heat treatment may be needed. For example, a firing process / oxidation heat treatment may be carried out, to increase the density of the insulating layer and enhance its adhesion to the steel of the interconnect. Said heating may involve heating the interconnect to a temperature of at least 300°C, preferably at least 500°C, more preferably at least 800°C and at a temperature of less than 1200°C, preferably less than 1000°C, more preferably less than 900°C. Said heating step may be executed in an oxidising environment in order to coat the remainder of the interconnect (i.e. parts not coated with the electrically insulating layer or other layers) with a layer of thermally grown oxide. It is appreciated that some dielectric materials such as a glass ceramic layer may not need firing to a high temperature to increase its density, making it more suitable for use on the interconnect.

[0134] The conductive protrusions in the central area 410 may comprise dimples which are pressed or formed in the interconnect, said dimples adapted to contact the electrochemically active cell region. Alternatively or additionally, they may comprise features printed or deposited on this first side of the interconnect. Preferably, the protrusions do not confine fluid flow, i.e. they are not or do not form channels. In such cases, each protrusion preferably has an aspect ratio (length-width in plan view) of less than 5, more preferably less than 2, and are preferably oval or circular in (plan view) cross section.

[0135] Preferably, the at least one port(s) 440 or through-hole(s), are disposed to each side of the electrically conductive area 410. They may be for fluid delivery of a first fluid or second fluid, typically to a first or second fluid volume enclosed by the interconnect and cell layer.

[0136] An electrically insulating layer (or a section thereof) may be provided between the port(s) 440 and the central area 410. Additionally or alternatively, it may be provided between the port(s) 440 and the perimeter 430 of the interconnect. Additionally or alternatively, it may be provided in another location of the interconnect as long as it is away from the central area 410. In principle an insulating layer may be provided to location(s) where there is a risk of unwanted contact happening. Note that an insulating layer can be provided under a gasket (i.e. between the interconnect and a gasket). This can be seen in the following examples.

[0137] The second side of the interconnect may be electrically conductive. However, the second side of the interconnect is often electrically insulating, with the exception that current flows through segments (e.g. welded segments) at the perimeter or edge of the interconnect where it is joined to the cell layer to form the cell unit. For example, there may be an insulating coating on the second side of the interconnect, such as an alumina coating. Protrusions or dimples thereon, which contact the cell layer (on its first side / substrate), are thus electrically insulating.

[0138] The interconnect is adapted to be provided with a gasket to surround a respective each of the at least one port, to be positioned between cell units of the electrochemical cell stack. The gasket(s) are provided on the first side of the interconnect (and thus contact the second side of the cell layer). In cases where the interconnect is provided with an electrically insulating coating surrounding the port(s), the gasket(s) contact the electrically insulating coating. This advantageously helps to prevent corrosion at the interface between the gaskets and interconnect. Further, in such cases, the gasket(s) do not need to be electrically insulating thereby allowing a greater range of choice of gasket materials.

[0139] Figure 5, included as a simple pictorial illustration only to assist understanding, is a modified version of Figure 2, where an exemplary insulating layer 90 is shown (illustrated as a hatched area), positioned between the port 22 and the central area comprising protrusions / dimples 32 / 36. Only one such insulating section is shown here for simplicity; preferably, other sections of the interconnect will be also provided with an insulating layer or coating.

[0140] Aspects of the present disclosure are now described with reference to several examples of cell units and respective cell layers and interconnects (separator plates).

[0141] Figure 6A is a plan view of an interconnect 600, with perimeter 630, viewed from the air side. This interconnect design comprises protrusions on both sides (dimples which are pressed or formed). Protrusions in the central area 610 (which faces the electrochemically active cell area of a corresponding cell layer, not shown), and four fluid ports 640 in the periphery 620, are shown. The periphery may also be referred to as a peripheral area.

[0142] As mentioned, an electrically insulating layer 690 (e.g. in the form of a coating) may be provided in the periphery 620 outside the central area 610 (in which a series of dimples are provided, said dimples protruding into and out of the plane of the image, those dimples protruding out of the plane (protrusions on the first side of the interconnect) adapted to contact an electrochemically active cell area of a cell layer). This layer 690 may be in one continuous area, or provided in several discrete portions or sections. For example:

[0143] • a coating 690a may be provided in the peripheral area 620 between two ports 640;

[0144] • a coating 690b may be provided in the peripheral area 620 between a port 640 and the perimeter 630;

[0145] • a coating 690c (not hashed, for clarity) may be provided in the peripheral area 620 to surround and / or cover a port 640;

[0146] • a coating 690d may be provided in the peripheral area 620 between a port 640 and the central area 610;

[0147] • a coating 690e may be provided in the peripheral area 620 between the central area 610 and the perimeter 630.

[0148] It is appreciated that all of these coatings, or sections thereof, can be included, or only one or some of them, in an interconnect in accordance with the present disclosure. In other words, the above individually described areas with insulation means may be provided alternative or additional to one other in one interconnect. In cases where multiple of the coatings 690a to 690e are provided, it will be appreciated that they are preferably continuous (gaps between areas indicated for coatings 690a to 690e being shown for clarity) and are preferably deposited or formed in the same step. It is preferable that corners of the interconnect, and / or areas distal from support by gaskets and dimples are provided with the insulation means.

[0149] Figure 6B is an exploded perspective view corresponding to Figure 6A, comprising two cell units, each comprising an interconnect 600 and a cell layer 650, in a stacked arrangement. Gaskets 670 may be provided between an interconnect and a neighbouring cell layer, on the first side of the interconnect. Each of the above-described "types" of insulating coating portion 690 is illustrated (for clarity, only one of each type 690a-e is illustrated). It will be noted that the dimples surrounding the port(s) 640 form protrusions on the second side of the interconnect, directed towards the cell layer 650. The coating 690c surrounds the port(s) and concave side of the dimples surrounding the ports, and the gasket(s) 670 contact the planar part of the interconnect surrounding the ports.

[0150] The cell layer 650 in this case comprises a metal support plate. A second side of the metal support plate carries, or has deposited / coated thereon, the electrochemically active cell region (not shown in Figure 6B). A porous region 648, similar to porous region 48 previously described, is provided in the metal support plate to allow communication between a first side of the metal support plate (which faces the second side of the interconnect) and the electrochemically active cell region - specifically an electrode, typically the fuel electrode, which is carried by, coated on or deposited on the second side of the metal support plate. An outermost face of the outermost electrode, typically oxidant electrode, of the electrochemically active cell region and the second side of the metal support plate together form the second side of the cell layer 650. The electrochemically active cell region is provided in a central area of the cell layer 650 (corresponding to the porous region 648), which is surrounded by a periphery of the cell layer which is electrochemically inactive. The electrically insulating coating on the first side of the interconnect faces (e.g., aligns with when seen in plan view) at least a portion of the electrochemically inactive part of the second side of the cell layer, for example faces the (periphery of the) metal support plate where it is not covered by the electrochemically active cell region. In this way, the electrically insulating coating prevents electrical contact (and associated short circuit) between the first side of the interconnect and the second side of the cell layer - more specifically in this case between the periphery of the first side of the interconnect and the periphery of the second side of the cell layer.

[0151] Dimples which form protrusions on the first side of the interconnect protrude towards (and, in a stack of cell units, contact) the second side of a cell layer, to space said components thereby providing a (second) fluid volume, typically for oxidant. Dimples which form protrusions on the second side of the interconnect protrude towards (and, in a stack of cell units, contact) the first side of a cell layer - in the case of Figure 6b, the metal support plate - to space said components thereby providing a (first) fluid volume, typically for fuel. The ports through the interconnect and cell layer typically supply and exhaust (first) fluid from this (first) fluid volume. Said dimples are provided in a central area of the interconnect, surrounded by a periphery between the central area and the perimeter of the interconnect. Said central area of the interconnect corresponds to (e.g., aligns with in plan view) the electrochemically active cell region of the cell layer. Said dimples of Figure 6, like those of Figure 5, take the form of pressed or formed features in the interconnect (i.e., an original plane of the interconnect has been bent to provide the dimples).

[0152] Note that these protrusions may also comprise at least one of: a plurality of ribs extending from the second side of the interconnect toward the first side of the cell layer, a plurality of discrete protrusions extending from the second side of the interconnect toward the first side of the cell layer, or a porous layer.

[0153] Figure 7A is a plan view of another interconnect 700, with perimeter 730, viewed from the first side of the interconnect. This interconnect design comprises protrusions which are deposited or printed on the first side of the interconnect (which includes protrusions formed by selective removal - e.g. by machining or etching - of parts of a homogeneously deposited or printed layer) as can be seen, in the central area 710, to face the second side of the cell layer. Said protrusions are provided instead of the corresponding formed or pressed dimples (which form an outward protrusion on the first side of the interconnect) but provide a similar function (of spacing the first side of the interconnect from the second side of the cell layer, to provide the (second) fluid volume) to the formed or pressed dimples. Four ports 740 in the peripheral area 720 are provided, but it will be appreciated that a greater or lesser number of ports may be provided.

[0154] Similar to Figures 5 and 6B, the interconnect of Figure 7 has a flanged edge / perimeter, and the cell layer (e.g., metal support plate) and interconnect are (sealingly) joined around the flanged perimeter, for example by welding, such that the second side of the interconnect contacts the first side of the cell layer (metal support plate) around the perimeter. It will be understood that the metal support plate may instead have a flanged perimeter. Alternatively, both the metal support plate and the interconnect may have flanged perimeters extending towards and contacting one another to provide the full height of the volume enclosed between the second side of the interconnect and first side of the cell layer. It will be noted that the electrically insulating layer 690 is depicted as not covering the flanged perimeter - indeed it often need not do so since the flanged perimeter results in a relatively greater spacing between the second side of the cell layer and the first side of the interconnect at the flanged perimeter.

[0155] Similar to in Figure 6, an electrically insulating layer 790 (e.g. in the form of a coating) is provided in the periphery 720 outside the central area 710. This layer 790 may be in one continuous area, or provided in several discrete portions or sections. For example:

[0156] • a coating 790a may be provided in the peripheral area 720 between two ports 740;

[0157] • a coating 790b may be provided in the peripheral area 720 between a port 740 and the perimeter 730;

[0158] • a coating 790c (not hashed, for clarity) may be provided in the peripheral area 720 to surround and / or cover a port 740;

[0159] • a coating 790d may be provided in the peripheral area 720 between a port 740 and the central area 710;

[0160] • a coating 790e may be provided in the peripheral area 720 between the central area 710 and the perimeter 730.

[0161] Figure 7B is an exploded perspective view corresponding to Figure 7A, comprising two cell units, each comprising an interconnect 700 and a cell layer 750, in a stacked arrangement. Gaskets 770 may be provided between an interconnect and a neighbouring cell layer, on the first side of the interconnect. Each of the above-described "types" of insulating coating portion 790 is illustrated (for clarity, only one of each type 790b-d is illustrated).

[0162] Figure 7C provides two cross-sectional views of the cell units of Figure 7B. The upper cross-section is taken along line A-A of Figure 7B, and the lower cross-section is taken along line B-B of Figure 7B. Said cell units are shown in a stacked arrangement, merely to assist understanding of the structure of the cell units according to this example. The electrochemically active area 752 on the cell layer 750 can be seen. Thick hashed areas show where insulating layer portions 790a, 790e are included. Other layer portions such as 790b / c / d may be additionally or alternatively included, but not shown in the cross-sections of Figure 7C. Downward protrusions 794 (e.g. printed or deposited) on the first side of the interconnect and upward protrusions 792 (dimples, pressed or formed in the interconnect) in the second side of the interconnect are also shown.

[0163] Figure 8A is a plan view of another interconnect 800, with perimeter 830, viewed from the air side. This interconnect design comprises protrusions (downward) as can be seen, in the central area 810, facing the cell layer. Four ports 840 in the peripheral area 820 are provided. The interconnect does not have a flanged edge / perimeter, instead there is provided a spacer plate 880 as shown in Figure 8B. Similar to in Figures 6 and 7, an electrically insulating layer 890 (e.g. in the form of a coating) may be provided in the periphery 820 outside the central area 810. This layer 890 may be in one continuous area, or provided in several discrete portions or sections. For example:

[0164] • a coating 890a may be provided in the peripheral area 820 between two ports 840;

[0165] • a coating 890b may be provided in the peripheral area 820 between a port 840 and the perimeter 830;

[0166] • a coating 890c (not hashed, for clarity) may be provided in the peripheral area 820 to surround and / or cover a port 840;

[0167] • a coating 890d may be provided in the peripheral area 820 between a port 840 and the central area 810;

[0168] • a coating 890e may be provided in the peripheral area 820 between the central area 810 and the perimeter 830.

[0169] Figure 8B is an exploded perspective view corresponding to Figure 8A, comprising two cell units, each comprising an interconnect 800 and a cell layer 850, in a stacked arrangement. It can be seen that, instead of the interconnect having a flanged perimeter, a spacer plate 880 is provided in each cell unit, to help space the plates apart and define a fluid volume therebetween. The interconnect, spacer, and cell layer (metal support plate) are (sealingly) joined around their perimeter, for example by welding through the three plates. In this case the second side of the interconnect faces and is spaced from (except for the protrusions which contact) the first side of the cell later (metal support plate), said spacing provided by the spacer plate which contacts the second side of the interconnect and the first side of the cell layer (metal support plate). Gaskets 870 may be provided between an interconnect and a neighbouring cell layer, on the first side of the interconnect. Each of the abovedescribed "types" of insulating coating portion 890 is illustrated (for clarity, only one of each type 890a-e is illustrated).

[0170] Figure 8C provides two cross-sectional views of the cell units of Figure 8B. The upper cross-section is taken along line A-A of Figure 8B, and the lower cross-section is taken along line B-B of Figure 8B. Said cell units are shown in a stacked arrangement, merely to assist understanding of the structure of the cell unit according to this example. The electrochemically active area 852 on the cell layer 850 can be seen. Thick hashed areas show where insulating layer portions 890a, 890e are included. Other layer portions such as 890b / c / d may be additionally or alternatively included, but not present in the cross-sections of Figure 8C.

[0171] Figures 7 and 8 show protrusions on the first side of the interconnect which are printed or deposited. It will be understood that such printed or deposited protrusions may additionally or alternatively be provided on the second side of the cell layer (specifically, on the outermost layer of the electrochemically active cell region). Similarly to the protrusions of Figures 7 and 8, said protrusions on the second side of the cell layer may be provided by selective removal - e.g. by machining or etching - of parts of a homogeneously deposited or printed layer, or of parts of the outermost electrode (for example, air electrode) of the electrochemically active cell region. These protrusions serve to space the first side of the interconnect from the second side of the cell layer to form a (second) fluid volume therebetween. Figures 9 and 10 show further variants.

[0172] Figure 9 illustrates an interconnect 900 with a perimeter 930 and six fluid ports 940 (which may be for supplying to and exhausting from the first fluid volume, enclosed between the second side of the interconnect and first side of the cell layer, for example for fuel). Similar to the previous examples, in the peripheral region 920 outside of the central region 910, one or more insulating layer portions 990 are provided. Portions 990a / b / c / d / e each corresponds (in terms of their locations relative to other interconnect features) to 590a / b / c / d / e, 790a / b / c / d / e and 890a / b / c / d / e, respectively, and are not again described in detail here.

[0173] Figure 10 illustrates an interconnect 1000 with a perimeter 1030 and two fuel / fluid ports 1040; unlike the other examples, the ports 1040 are not provided at corners of the interconnect, but instead towards the centre of the width of the interconnect (similar to Figure 5). Similar to the previous examples, in the peripheral region 1020 outside of the central region 1010, one or more insulating layer portions 1090 are provided. Portions 1090b / c / d / e each corresponds (in terms of their locations relative to other interconnect features) to 690b / c / d / e, 790b / c / d / e and 890b / c / d / e, respectively, and are not again described in detail here.

[0174] The interconnects (also known as separator plates) as described in the examples above, each comprising an electrically insulating layer (as integral layer, or as a plurality of disconnected portions i.e. islands), form electrochemical cell units with corresponding cell layers. Multiple electrochemical cell units are stacked one atop another along a stacking direction to form an electrochemical stack such as those shown, in part, in Figures 7B and 8B.

[0175] An electrochemical cell unit, and an electrochemical cell stack, according to aspects of the present disclosure, are hereby described further.

[0176] An electrochemical cell unit for an electrochemical cell stack comprises an interconnect as described above along with a cell layer comprising an electrochemically active cell region. The cell layer and the interconnect overlie one another to form the electrochemical cell unit, in a spaced relationship to form a fluid volume for a first fluid therebetween. The cell layer may have a central area carrying the electrochemically active cell region. It also comprises a periphery between the electrochemically active cell region and a perimeter of the cell layer, which may be described as a region outside of the active cell region or an electrochemically inactive region. The portion of the first side of the interconnect upon which the electrically insulating layer is provided is aligned with (a portion of) the peripheral area of the cell layer (e.g. faces (a portion of) the peripheral area of the cell layer of a neighbouring cell unit).

[0177] The cell layer can also be described to comprise an electrochemically inactive region that is outside of (e.g. surrounds) a central area in which the electrochemically active cell region is provided. This electrochemically inactive region may correspond to the aforementioned periphery of the cell layer.

[0178] The electrochemically active cell region of the cell layer may comprise a solid oxide electrolyte. For example, the electrochemical cell unit is a solid oxide electrolysis cell (SOEC) unit. The cell layer may further comprise a metal support plate carrying the electrochemically active cell region provided (e.g. coated or deposited upon) over a central porous region of the metal support plate. The central porous region of the metal support plate may be surrounded by a periphery between the central porous region and a perimeter of the metal support plate, wherein the portion of the first side of the interconnect upon which the electrically insulating layer is provided is aligned with or faces a portion of the periphery of the metal support plate.

[0179] The metal support plate has a first side and a second side. The second side carries the electrochemically active cell region, and the first side faces the second side of an interconnect. The porous region provides fluidic communication between the first side and the second side of the metal support plate.

[0180] Preferably, the second side of the interconnect and the cell layer (the first side of the metal support plate) are spaced from one another to provide, and preferably enclose, a (first) volume therebetween, preferably a fluid volume for fuel; they are also directly or indirectly, e.g. via a flanged perimeter or a spacer plate, respectively, joined around their periphery or perimeter (e.g. by welding around the perimeter) and are electrically connected thereto.

[0181] The first side of the interconnect and the cell layer (the second side of the metal support plate) are spaced from one another to provide a (second) volume with at least one electrically insulating gasket provided therebetween. This fluid volume may be for fuel.

[0182] An electrochemical cell unit stack may comprise a plurality of electrochemical cell units overlaying one another in a stacking direction. The first side of an interconnect of a first cell unit faces an outermost layer of the electrochemically active cell region (e.g. the second side of a metal support plate) of a neighbouring cell unit in a spaced relationship, to form a (second) fluid volume for a (second) fluid therebetween. This second fluid may be oxidant and / or oxygen.

[0183] The stack of cell units may further comprise one or more gaskets between neighbouring cell units, said gasket(s) contacting the first side of the interconnect and (the second side of) the cell layer (second side of the metal support plate), preferably the gasket(s) contact the electrically insulating layer on said first side of the interconnect.

[0184] The interconnect and cell layer / metal support plate may be provided with ports / through-holes for delivery of fluid to and exhaust from the first fluid volume. These ports are preferably aligned in the stacking direction and surrounded by respective gaskets.

[0185] Figure 12 shows a further example cell unit comprising an interconnect provided with an electrically insulating layer. Fig. 12A shows a lower and an upper exploded perspective view. Fig. 12B shows a plan view of the first side of an interconnect and a cross section (Z-Z as depicted in the plan view) of one cell unit. In this example each cell unit has two fluid ports, similar to Fig. 5, but may have other numbers of fluid ports (e.g., 1, 3, 4, 6 etc) . However, in contrast to Fig. 5 a fluid guidance insert 1253 surrounds a respective fluid port and is provided with at least one elongate slot 1254 (also referred to as a channel, and in this case three slots or channels but there may be more or fewer, e.g., 2, 4, 5) for fluidic communication with the (first) fluid volume enclosed between the second side of the interconnect and the first side of the cell layer. One fluid guidance insert 1253 is associated with a fluid inlet port. This fluid guidance insert 1253 is arranged such that the hole 1256 contributes to forming a through-hole through the cell unit, i.e. the fluid inlet port. The fluid guidance insert 1253 associated with the fluid inlet port is configured to convey a fluid from the fluid inlet port to the fluid volume. Specifically, a fluid may reach from the fluid inlet port through the elongate slots 1254 of the insert 1253 to the enclosed fluid volume. The fluid guidance insert 1253 may spread the fluid along a direction perpendicular to that between inlet and exhaust ports. Thus, the fluid guidance insert 1253 associated with the fluid inlet port may support a uniform distribution of the fluid in the fluid volume, i.e. the width extent of the cell unit. A second fluid guidance insert 1253 is associated with a fluid exhaust port (also referred to as an outlet port). It will be understood that multiple ports for inlet and exhaust may be provided, each of which may be associated with a fluid guidance insert or multiple ports may be associated with a single fluid guidance insert (e.g., one fluid guidance insert for multiple inlet ports and a second fluid guidance insert for multiple exhaust ports).

[0186] The fluid guidance insert 1253 is configured flat (e.g., as a separate plate or component). In the assembled cell unit, a first surface of the fluid guidance insert 1253 is in direct contact with an opposed surface (first side) of the cell layer, i.e. the support plate 14. A second surface of the fluid guidance insert 1253 is in direct contact with an opposed surface (second side) of the interconnect 12. Thus, the fluid guidance inserts 1253 may transfer compression forces (represented by arrows in Fig. 12) between the cell layer and the interconnector plate 12. This may increase the mechanical stability of the cell unit. Specifically, the fluid guidance inserts 1253 may prevent a deformation of the cell layer and the interconnect 12.

[0187] In this example, the proximal end sections of the elongate slots 1254 are open. That is to say, the proximal end sections open into the hole 1256. In this example the distal end sections of the elongate slots 1254 are closed by a respective web 1262. This increases the mechanical stability of the fluid guidance insert 1253. The interconnect 12 comprises several bridge dimples 1268 that extend away from the fluid guidance insert 1253 and that span a respective one of the webs 1262 to form a fluid bypass around that web 1262. Thus, the bridge dimples 1268 fluidically connect the respective elongate slot 1254 with the enclosed fluid volume around the respective web 1262. In this example, each one of the elongate slots 1254 is associated with a respective bridge dimple 1268. Alternatively, several webs 1262 may be associated with a common bridge dimple 1268 or several bridge dimples 1268 may be associated with a common web 1262. It will be understood that one elongate slot may be open at the distal end without compromising structural integrity of the fluid guidance insert 1253. In such cases no bridge dimple is needed for fluid communication between the port and the enclosed fluid volume via an elongate slot with an open distal end.

[0188] In this example, the bridge dimples 1268 are formed or pressed in the interconnect 12. Preferably, the bridge dimples 1268 are formed or pressed at the same step as the upward protrusions 32 and downward protrusions 36 of the interconnect 12 and / or the flanged perimeter of the tub-shaped interconnect 12. Alternatively, the bridge dimples may be formed or pressed in the support plate 14.

[0189] On the first side of the interconnector plate 12 (that is facing away from the enclosed fluid volume), the bridge dimples 1268 form protrusions that extend away from the enclosed fluid volume. The gaskets 34 are positioned directly adjacent to the protrusions of the bridge dimples 1268. The outer perimeter of the gaskets 34 is in direct contact with the protrusions. Thus, the protrusions restrict movement of the gaskets 34.

[0190] On the first side of the interconnector plate 12 (that is the side facing away from the fluid guidance insert), the bridge dimples 1268 form protrusions that extend away from the fluid guidance insert and towards the second side of the cell layer, specifically in this example the second side of the support plate 14. The bridge dimples 1268 are provided with an insulating layer 1290 on the first side of the interconnect and bridge dimples 1268 (the outwardly protruding, i.e., convex side of the bridge dimples). In some cases only the bridge dimples may be coated with the insulating layer 1290 (provided in islands, one island covering each bridge dimple) because the convex side of the bridge dimples (i.e., first side of the interconnect) are the closest part of the interconnect, outside of the down protrusions 36, to the second side of the cell layer. However, an insulating layer may also be provided on other parts (that are aligned with or face the electrochemically inactive region) of the first side of the interconnect as described with reference to previous Figures.

[0191] In accordance with an aspect of the present disclosure, a method of manufacturing an interconnect for electrically connecting cells of an electrochemical cell stack (preferably a SOEC stack) is hereby described, with reference to Figure 11. The method 1100 comprises providing an interconnect having a first side and a second side, the first side being adapted to face a cell layer comprising, preferably in a central area, an electrochemically active cell region (step 1110). The method further comprises providing an electrically insulating layer on a portion, outside said central area, of the first side of the interconnect (step 1120); the insulating layer may be provided by coating or depositing it on said portion.

[0192] Additional steps or preferable aspects in this method may include one or more of:

[0193] • Providing an interconnect may comprise providing, in the area that is adapted to face the electrochemically active cell region, conductive protrusions adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region. Providing the conductive protrusions may comprise pressing or forming the interconnect to provide dimples on the first side of the interconnect, and / or printing or depositing conductive features on the first side of the interconnect. Providing the interconnect may additionally or alternatively comprise providing a porous layer on the first side of the interconnect.

[0194] • Providing an electrically insulating layer may comprise using at least one of: (a) a wet deposition method such as screen printing, (b) a physical or chemical vapour deposition method, and (c) a wet spraying or plasma spraying method, to deposit the electrically insulating layer on a portion of the first side of the interconnect.

[0195] • Providing the electrically insulating layer may comprise heating the interconnect subsequent to depositing the electrically insulating layer. Said heating may involve heating the interconnect to a temperature of at least 300°C, preferably at least 500°C, more preferably at least 800°C and at a temperature of less than 1200°C, preferably less than 1000°C, more preferably less than 900°C. Said heating step may be executed in an oxidising environment in order to coat the remainder of the interconnect (i.e. parts not coated with the electrically insulating or other layers) with a layer of thermally grown oxide. • The electrically insulating layer may be provided on at least a portion of the peripheral area between a central area and a perimeter of the interconnect.

[0196] • Providing the interconnect may comprise providing at least one port in the periphery, wherein the electrically insulating layer is provided between at least one of: (a) the at least one port and the central area, and (b) the at least one port and the perimeter of the interconnect. The electrically insulating surround the at least one port.

[0197] • The second side of the interconnect may be adapted to be exposed to a first fluid, and first side of the interconnect is adapted to be exposed to a second fluid different to the first fluid.

[0198] • The electrically insulating layer may comprise a dielectric layer.

[0199] • The electrically insulating layer may have a thickness of between 1 micrometer and 500 micrometers, preferably between 1 micrometer and 50 micrometers, more preferably between 5 micrometers and 20 micrometers.

[0200] • The interconnect may be meant for use in an electrolysis cell unit or electrolysis cell stack.

[0201] In accordance with an aspect of the present disclosure, a method of manufacturing an electrochemical cell unit is hereby described. The method comprises providing, by the abovedescribed method or by providing an interconnect wherein an electrically insulating layer is provided on a portion of the first side of the interconnect, an interconnect having a first side and a second side, the first side being adapted to face a cell layer comprising an electrochemically active cell region, the interconnect provided with an electrically insulating layer on a portion of the first side of the interconnect. The method further comprises providing a cell layer comprising an electrochemically active cell region. The method further comprises overlying the cell layer and the interconnect to form the electrochemical cell unit.

[0202] Additional steps or preferable aspects in this method may include one or more of:

[0203] • The cell layer may have a central area carrying the electrochemically active cell region and a periphery between the electrochemically active cell region and a perimeter of the cell layer, the portion of the first side of the interconnect upon which the electrically insulating layer is provided is aligned with or faces a portion of the periphery of the cell layer.

[0204] • The cell layer may further comprise an electrochemically inactive region which surrounds a central area in which the electrochemically active cell region is provided, and the portion of the first side of the interconnect provided with the electrically insulating layer may be aligned with or faces the electrochemically inactive region.

[0205] • An outermost layer of the electrochemically active cell region may be provided with protrusions adapted to face a first side of the interconnect.

[0206] • The electrochemically active cell region may comprise a solid oxide electrolyte.

[0207] • The electrochemical cell unit may be an electrolysis cell unit.

[0208] • The cell layer may further comprise a metal support plate carrying the electrochemically active cell region provided over a central porous region of the metal support plate.

[0209] • The central porous region of the metal support plate may be surrounded by a periphery between the central porous region and a perimeter of the metal support plate, and the portion of the first side of the interconnect upon which the electrically insulating layer is provided may be aligned with or face a portion of the periphery of the metal support plate. • The metal support plate may have a first side and a second side, the second side of the metal support plate carrying the electrochemically active cell region and the first side of the metal support plate facing the second side of the interconnect.

[0210] • The second side of the interconnect and the cell layer may be spaced from one another to provide the fluid volume therebetween and joined around their periphery or perimeter and is electrically connected thereto.

[0211] • The first side of the interconnect and the cell layer may be spaced from one another to provide the fluid volume with at least one electrically insulating gasket provided therebetween.

[0212] In accordance with an aspect of the present disclosure, a method of manufacturing a stack of electrochemical cell units is herein described. The method comprises providing, by the method described above, a plurality of electrochemical cell units, each of the plurality of cell units having an electrically insulating coating provided on a portion of the first side of the interconnect. The method further comprises overlaying the plurality of electrochemical cell units over one another in a stacking direction, wherein a first side of an interconnect of a first cell unit faces an outermost layer of an electrochemically active cell region of a neighbouring cell unit in a spaced relationship to form a second fluid volume for second fluid therebetween.

[0213] The present invention is not to be limited by the above-described aspects and embodiments, and that many variations are within the scope of the appended claims. The various aspects and embodiments may be combined if necessary and appropriate. The drawings serve as exemplary illustrations of the invention only, to aid understanding of the invention.

Claims

CLAIMS1. An electrochemical cell unit for an electrochemical cell stack comprising: a cell layer comprising a metal support plate having a first side and a second side, an electrochemically active cell region, and an electrochemically inactive region which surrounds a central area in which the electrochemically active cell region is provided, wherein the second side of the metal support plate carries the electrochemically active cell region provided over a porous region of the metal support plate; and an interconnect , the interconnect having a first side and a second side, the first side being adapted to face the cell layer, and wherein a portion of the first side of the interconnect is provided with an electrically insulating layer, wherein the cell layer and the interconnect overlay one another to form the electrochemical cell unit, and the portion of the first side of the interconnect provided with the electrically insulating layer is aligned with or faces the electrochemically inactive region.

2. The electrochemical cell unit of claim 1, wherein the first side of the interconnect is electrically conductive in an area that is adapted to face the electrochemically active cell region.

3. The electrochemical cell unit of claim 2, wherein the area comprises conductive protrusions adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

4. The electrochemical cell unit of claim 3, wherein the protrusions comprise dimples which are pressed or formed in the interconnect, said dimples adapted to contact the electrochemically active cell region.

5. The electrochemical cell unit of claim 3, wherein the protrusions comprise features printed or deposited on the first side of the interconnect.

6. The electrochemical cell unit of claim 2, wherein said area comprises a porous layer adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

7. The electrochemical cell unit of any preceding claim, wherein an outermost layer of the electrochemically active cell region is provided with protrusions adapted to face a first side of the interconnect.

8. The electrochemical cell unit of any preceding claim, wherein the interconnect has a central area and a periphery between the central area and a perimeter of the interconnect, and wherein the electrically insulating layer is provided on at least a portion of the periphery.

9. The electrochemical cell unit of claim 8, further comprising at least one fluid port provided in the periphery, wherein the electrically insulating layer is provided between at least one of: (a) the at least one fluid port and the central area, and (b) the at least one fluid port and the perimeter of the interconnect.

10. The electrochemical cell unit of claim 9, wherein the electrically insulating layer surrounds the at least one fluid port.

11. The electrochemical cell unit of any preceding claim, wherein the interconnect has at least one bridge dimple that forms a protrusion on the first side of the interconnect and a corresponding depression on the second side of the interconnect, the depression for fluid guidance on the second side of the interconnect and the electrically insulating layer is provided on the at least one bridge dimple.

12. The electrochemical cell unit of claim 11 when dependent on claim 9 or 10, wherein the at least one fluid port is in fluidic communication with a first fluid volume provided between the interconnect and the metal support plate, the electrochemical cell unit further comprising a fluid guidance insert disposed in the first fluid volume, said fluid guidance insert comprising a plurality of elongate slots formed therein, said elongate slots defining a fluid channel system for conveying fluid between the at least one fluid port and the first fluid volume via the at least one bridge dimple.

13. The electrochemical cell unit of claim 12, wherein the elongate slots each have a distal end section wherein the distal end section of at least one of the elongate slots is closed by a web of the fluid guidance insert, and wherein the at least one bridge dimple extends away from the fluid guidance insert and spans said web to form a fluid bypass around the web.

14. The electrochemical cell unit of claim 13, wherein the distal end section of at least one of the elongate slots is open.

15. The electrochemical cell unit of any preceding claim, wherein the second side of the interconnect is adapted to be exposed to a first fluid, and first side of the interconnect is adapted to be exposed to a second fluid different to the first fluid.

16. The electrochemical cell unit of claim 15 being configured to constrain the first fluid in a first fluid volume and to constrain the second fluid in a second fluid volume, wherein a cross-sectional area of the second fluid volume is smaller than a cross-sectional area of the first fluid volume.

17. The electrochemical cell unit of any preceding claim, wherein the electrically insulating layer comprises a dielectric layer.

18. The electrochemical cell unit of any preceding claim, wherein the electrically insulating layer has a thickness of between 1 micrometer and 500 micrometers, preferably between 1 micrometer and 50 micrometers.

19. The electrochemical cell unit of any preceding claim, wherein the electrochemically active cell region comprises a solid oxide electrolyte.

20. The electrochemical cell unit of any preceding claim, wherein the electrochemical cell unit is an electrolysis cell unit.

21. The electrochemical cell unit of any preceding claim, wherein the porous region of the metal support plate is surrounded by a periphery between the central porous region and a perimeter of the metal support plate, and wherein the portion of the first side of the interconnect upon which the electrically insulating layer is provided is aligned with or faces a portion of the periphery of the metal support plate.

22. The electrochemical cell unit of any preceding claim, wherein the metal support plate has a first side and a second side, the second side of the metal support plate carrying the electrochemically active cell region and the first side of the metal support plate facing the second side of the interconnect.

23. The electrochemical cell unit of any preceding claim, wherein the second side of the interconnect and the cell layer are spaced from one another to provide a or the first fluid volume therebetween and are joined around their periphery or perimeter and is electrically connected thereto.

24. The electrochemical cell unit of any one of claims 1 to 22, wherein the first side of the interconnect and the cell layer are spaced from one another to provide a or the first fluid volume therebetween, and having at least one gasket provided therebetween.

25. A stack of electrochemical cell units according to any one of claims 1 to 23, comprising a plurality of electrochemical cell units overlaying one another in a stacking direction, the first side of an interconnect of a first cell unit facing an outermost layer of the electrochemically active cell region of a neighbouring cell unit in a spaced relationship to form a second fluid volume for second fluid therebetween.

26. An interconnect for electrically connecting cells of a metal-supported solid oxide electrolysis cell (SOEC), comprising a first side and a second side, wherein the first side comprises: a first area adapted to face an active region of a metal-supported SOEC cell, and a second area comprising at least one electrically insulating region, wherein the second area is outside of the first area.

27. A method for manufacture of an electrochemical cell unit, the method comprising: providing a cell layer comprising a metal support plate having a first side and a second side, an electrochemically active cell region and an electrochemically inactive region which surrounds a central area in which the electrochemically active cell region is provided, wherein the second side of the metal support plate carries the electrochemically active cell region provided over a porous region of the metal support plate; providing an interconnect having a first side and a second side, the first side being adapted to face a cell layer and wherein a portion of the first side of the interconnect is provided with an electrically insulating layer, wherein an electrically insulating layer is provided on a portion of the first side of the interconnect; and overlying the cell layer and the interconnect to form the electrochemical cell unit, and the portion of the first side of the interconnect provided with the electrically insulating layer is aligned with or faces the electrochemically inactive region.

28. The method of claim 27, wherein the first side of the interconnect is electrically conductive in an area that is adapted to face the electrochemically active cell region.

29. The method of claim 28, wherein providing an interconnect comprises providing, in the area, conductive protrusions adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

30. The method of claim 29, wherein providing the conductive protrusions comprises pressing or forming the interconnect to provide dimples on the first side of the interconnect, said dimples adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

31. The method of claim 29, wherein providing the conductive protrusions comprises printing or depositing conductive features on the first side of the interconnect, said conductive features adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

32. The method of claim 28, wherein providing the interconnect comprises providing, in the area, a porous layer on the first side of the interconnect, said porous layer adapted to contact the electrochemically active cell region and space the interconnect from the electrochemically active cell region.

33. The method of any one of claims 27 to 32, wherein the electrically insulating layer is provided by using at least one of: (a) a wet deposition method such as screen printing, (b) a physical or chemical vapour deposition method, and (c) a wet spraying or plasma spraying method, to deposit the electrically insulating portion of the first side of the interconnect.

34. The method of claim 33, wherein further comprises heating the interconnect subsequent to depositing the electrically insulating layer.

35. The method of any one of claims 27 to 34, wherein the interconnect and / or the cell layer is according to any one of claims 1 to 24.

36. A method for manufacture of a stack of electrochemical cell units, the method comprising: providing, by the method of any one of claims 27 to 35, a plurality of electrochemical cell units, each of the plurality of cell units having an electrically insulating coating provided on a portion of the first side of the interconnect; overlaying the plurality of electrochemical cell units over one another in a stacking direction, wherein a first side of an interconnect of a first cell unit faces an outermost layer of an electrochemically active cell region of a neighbouring electrochemical cell unit in a spaced relationship to form a second fluid volume for second fluid therebetween.

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