Electrochemical cell assembly

Abstract

The invention relates to an electrochemical cell assembly (10), comprising a stack (16) of stacking units (17), said stacking units comprising cell units (18), wherein each cell unit extends in a first direction and in a second direction, the plurality of cell units comprises electrochemically active cell units (98) and electrochemically inactive dummy cell units (100), adjacent stacking units define a respective fluid flow path between them for fluid to flow in the first direction (26), between a dummy cell unit and an adjacent stacking unit there is provided a flow restriction device (108) comprising at least one flow restriction member (110), said flow restriction device (108) being configured to reduce or prevent fluid flow along said fluid flow path.

Description

[0001] Description

[0002] Title

[0003] Electrochemical cell assembly

[0004] State of the Art

[0005] The invention relates to the field of electrochemical cell stacks, in particular, fuel cell stacks and electrolyser cell stacks. More specifically, the invention relates to an electrochemical cell assembly.

[0006] Fuel cells and electrolyser cells are examples of electrochemical cells. Fuel cells are energy conversion devices that allow for conversion of electrochemical fuel (e.g. hydrogen) to electricity. Electrolyser cells can be considered fuel cells running in reverse mode, i.e. using electricity to decompose a fuel into its constituent parts, for example water into hydrogen and oxygen. Reversible cells are capable of operating in both modes. Such electrochemical cells typically comprise cell chemistry layers that may be configured to allow for conversion of electrochemical fuel to electricity (fuel cells) or for decomposing a fuel into its constituent parts using electricity (electrolyser cells).

[0007] The present invention specifically relates to solid oxide cells (SOCs). Such solid oxide cells (SOCs) typically comprise an electrolyte layer formed from a solid oxide, e.g. from Yttria-stabilized zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO). SOCs can be run as solid oxide fuel cell (SOFC) or as solid oxide electrolyser cell (SOEC).

[0008] Typically, multiple of such cell units are stacked upon one another to form a “stack” of cell units, also referred to as ‘cell repeat units’. Said stack is commonly arranged between two end plates provided on opposite sides of the stack, thus forming an electrochemical cell assembly.

[0009] As described, for example, in WO 2015 / 136295 A1, the stack of cell units may comprise electrochemically active cell units and electrochemically inactive cell units, also referred to as dummy cell units. Said dummy cell units typically are provided at one or both ends of the stack.

[0010] It is an object of the present invention to increase performance and stability of an electrochemical cell assembly. Description of the Invention

[0011] According to the invention, there is provided an electrochemical cell assembly according to claim 1. The electrochemical cell assembly comprises a stack of stacking units. The stack of stacking units comprises a plurality of stacking units that are stacked upon one another along a stacking direction. The stacking units comprise electrochemical cell units. Thus, at least a subset of the stacking units or all stacking units are electrochemical cell units. Each cell unit extends in a cell plane perpendicular to the stacking direction in a first direction, preferably longitudinal direction, and in a second direction, preferably width direction, perpendicular to the first direction. Preferably, each cell unit has a periphery and a central portion surrounded by the periphery. The central portion preferably carries cell chemistry layers (also referred to as electrochemically active layers). The cell chemistry layers preferably comprise a fuel electrode layer, an electrolyte layer and an air or oxidant electrode layer. The plurality of cell units comprises electrochemically active cell units (hereinafter referred to as active cell units) and at least one electrochemically inactive dummy cell unit (hereinafter referred to as dummy cell unit). Adjacent stacking units define a respective fluid flow path, preferably air or oxidant flow path, between them for fluid, preferably air or oxidant, to flow in the first direction, preferably from a fluid inlet port to a fluid outlet port of the electrochemical cell assembly. Thus, the stacking units, in particular the cell units, are configured such that between adjacent stacking units, in particular cell units, a fluid flow path, preferably air or oxidant flow path, is provided for fluid, preferably air or oxidant, to flow in the first direction, preferably from a fluid inlet port to a fluid outlet port of the electrochemical cell assembly. The fluid flow path may comprise multiple flow paths, and they may be straight or convoluted dependent upon the design of cell units, with a net flow direction in the first direction. Preferably, adjacent stacking units define fluid passageways between them for fluid to flow in the first direction. Between a dummy cell unit, preferably each dummy cell unit, and an adjacent stacking unit (can be a cell unit (can be an active cell unit or a further dummy cell unit) or a stacking unit other than a cell unit), preferably between two adjacent dummy cell units, there is provided a flow restriction device, preferably air blocking device, said flow restriction device being configured to reduce or prevent fluid flow along said fluid flow path between a dummy cell unit and an adjacent stacking unit. The flow restriction device comprises at least one flow restriction member, preferably fluid blocking member, more preferably air blocking member, said at least one flow restriction member preferably being located between the dummy cell unit and the adjacent stacking unit. The proposed configuration allows for enhanced performance of the electrochemical cell assembly since air or oxidant flow to the active regions of the cell assembly, i.e. the active cell units, is enhanced. Specifically, by reducing or blocking air or oxidant flow to the electrochemically inactive regions, i.e. the dummy cell units (which do not require air or oxidant supply since they are electrochemically inactive), air or oxidant is predominantly guided to the active cell unit, thus ensuring sufficient and homogeneous air or oxidant supply to the active regions of the cell assembly. This has further proven advantageous with regards to a thermal management of the active cell units. Specifically, increasing air or oxidant flow over the electrochemically active areas helps to homogenise a temperature distribution inside the active cell units, which further increases performance of the cell assembly and helps to avoid damaging of the cell chemistry layers.

[0012] The stack of stacking units may consist of cell units. Thus, the stack of stacking units may be a stack of cell units. Alternatively, the stack of stacking units may comprise stacking units other than cell units. In some preferred embodiments, the stacking units may comprise one or more current transmission plates and / or one or more insulation plates. Preferably, the one ore more insulation plates and / or the one or more current transmission plates are located at an end of the stack of stacking units in the stacking direction.

[0013] In some embodiments, a flow restriction device is provided between a dummy cell unit and an adjacent cell unit (can be active cell unit or inactive dummy cell unit), preferably between each dummy cell unit and an adjacent cell unit. Alternatively or additionally, a flow restriction device may be provided between a dummy cell unit and an adjacent stacking unit other than a cell unit. For example, in some embodiments, the stacking units may comprise a current transmission plate located adjacent to a dummy cell unit. In such embodiments, a flow restriction device may be provided between the dummy cell unit and the current transmission plate. Alternatively or additionally, a dummy cell unit may be located adjacent to an insulation plate. In such embodiments, a flow restriction device may be provided between the dummy cell unit and the insulation plate.

[0014] In some embodiments, the stack of stacking units comprises, preferably in a central portion thereof, a stack of active cell units and at least one dummy cell unit positioned at one or both ends of said stack of active cell units. Adjacent to a top-most dummy cell unit, there may be provided a current transmission plate or an insulation plate. In such embodiments, preferably, there is provided a flow restriction device between the top-most dummy cell unit and the current transmission plate or an insulation plate. Alternatively or in addition, adjacent to a bottom-most dummy cell unit, there may be provided a current transmission plate or an insulation plate. In such embodiments, preferably, there is provided a flow restriction device between the bottom-most dummy cell unit and the current transmission plate or an insulation plate.

[0015] In some preferred embodiments, the stack of stacking units comprises - in that order along the stacking direction from bottom to top - a first current transmission plate, at least one dummy cell unit, a stack of active cell units comprising a plurality of active cell units stacked upon one another along the stacking direction, at least one dummy cell unit, and a second current transmission plate. In such embodiments, there may be provided a flow restriction device between the bottom-most dummy cell unit and the current transmission plate.

[0016] In some embodiments, the cell units are solid oxide fuel cell units (SOFCs). In some embodiments, the cell units are solid oxide electrolyser cell units (SOECs). Preferably, the cell units are metal-supported solid oxide fuel cell units.

[0017] The cell units may be flat or planar. The cell units may each comprise multiple layers or plates overlying each other. In preferred embodiments, each cell unit (active or inactive) comprises an interconnector plate (also referred to as interconnect or separator plate) and a support plate (also referred to as substrate), which are stacked upon each other along the stacking direction. Preferably, the interconnector plate and the support plate are attached to each other, preferably by welding, and enclose a cell volume (fluid or air volume) therebetween. Preferably, the interconnector plate and the support plate are formed from metal, preferably stainless steel. Preferably, the support plate carries cell chemistry layers in its central portion. The support plate may comprise a porous region in its central portion, said porous region carrying the cell chemistry layers. The cell volume may be in fluid communication with the cell chemistry layers via said porous region. As described below, dummy cell units may comprise cell chemistry layers, but may be devoid of such a porous region.

[0018] In preferred embodiments, the support plate has a periphery and a central portion surrounded by the periphery, wherein the central portion of the support plate has a porous region and the cell chemistry layers are disposed on a surface of said porous region that is facing away from the interconnector plate, wherein the interconnector plate has a periphery and a central portion surrounded by the periphery, wherein the support plate and the interconnector plate are stacked upon one another along the stacking direction, wherein the periphery of the support plate is sealingly attached to the periphery of the interconnector plate, wherein the central portion of the support plate and the central portion of the interconnector plate enclose a cell volume (fluid volume) therebetween. The cell chemistry layers preferably comprise a fuel electrode layer, an electrolyte layer and an air or oxidant electrode layer. The cell chemistry layers may be deposited as thin coatings or films on a support plate of the cell unit. The cell chemistry layers may be identical for both active cell units and dummy cell units. It is also possible that the cell chemistry layers of the dummy cell units and the active cell units are different. For example, the dummy cell units may have only a subset of the cell chemistry layer of an active cell unit, e.g. only an air or oxidant electrode layer.

[0019] In some embodiments, at least one fuel port is provided in each of the cell units. In some embodiments, each cell unit has at least one fuel inlet port and at least one fuel outlet port, the cell unit preferably extending between said at least one fuel inlet port and said at least one fuel outlet port in the first direction. Preferably, the respective fuel ports of adjacent cell units are aligned to form a fuel manifold or chimney extending through the stack along the stacking direction. Thus, fuel may enter the stack at its bottom and pass through said manifold to the individual cell units. In active cell units, preferably the at least one fuel port is in fluid communication with the cell chemistry layers, in particular via the cell volume and the porous region mentioned above.

[0020] As used herein, the term "electrochemically inactive cell unit" or "dummy cell unit" refers to a cell unit that is adapted such that it is incapable of performing an electrochemical function. By "incapable of performing an electrochemical function" (in the context of the electrochemically inactive dummy cell units) is meant that each electrochemically inactive cell unit is incapable of performing a designed electrochemical reaction (in particular fuel cell or electrolyser cell reaction) during operation of the electrochemical cell assembly. Preferably, it is incapable of producing electricity directly from oxidizing a fuel by electrochemical conversion. Thus, the dummy cell units may be described as being configured or adapted to be electrochemically inactive, i.e. adapted or configured to be incapable of performing an electrochemical function. The electrochemically inactive cell unit" or "dummy cell unit", however, are electrically conductive so they can carry electrical current in stacking direction.

[0021] In some embodiments, the at least one dummy cell unit may be configured to block fuel flow across the cell chemistry layers, in particular across a fuel electrode side of said cell chemistry layers. This may be caused (i.e. effected) by a blockage in a fuel path across the dummy cell from a fuel inlet port to a fuel outlet port. That is to say, a dummy cell unit may comprise a fuel inlet port and / or a fuel outlet port, but flow from that inlet and / or outlet across the cell chemistry layers is blocked. For example, such a blockage may exist at or immediately adjacent a fuel inlet port. Similarly, such a blockage may exist at or immediately adjacent a fuel outlet port of the dummy cell unit. In such embodiments, preferably fuel may pass through the dummy cell unit to an adjacent active cell unit. As set out above, in embodiments comprising a support plate and an interconnector plate, a fuel blockage may, alternatively or in addition, be caused (i.e. effected) by closing the pores of the porous region carrying the cell chemistry layers or by omitting said porous region during manufacture of the support plate.

[0022] In some embodiments, the electrochemical cell assembly comprises at least one end plate, preferably a first end plate and a second end plate. In such embodiments, the stack of stacking units may be arranged on said at least one end plate, preferably arranged between said first end plate and said second end plate. The first end plate may be a base plate of the electrochemical cell assembly. The second end plate may be a top plate of the electrochemical cell assembly.

[0023] In some embodiments, the stack of cell units comprises a stack of active cell units, and one or both of (a) at least one dummy cell unit positioned between the first end plate and said stack of active cell units, and (b) at least one dummy cell unit positioned between the second end plate and the stack of active cell units.

[0024] The cell units may define first fluid passageways, preferably air or oxidant passageways, between them and an adjacent stack unit, said first fluid passageways contributing to or forming said fluid flow path. In addition to said first fluid passageways, each cell units may define second fluid passageways, preferably fuel passageways, internal of the cell units, e.g. between upper and lower plates (preferably support plate and interconnector plate) of each cell unit. The second fluid passageways may be in communication with fuel ports of the cell units.

[0025] The stack of stacking units may further comprise gaskets, preferably in the form of sealing rings, that are interposed between the cell units. Preferably, the gaskets surround respective fuel ports of the cell units. In such embodiments, the flow restriction member or at least one of the flow restriction members preferably is provided in the same plane as the gaskets.

[0026] In some embodiments, the electrochemical cell assembly comprises a housing surrounding the stack of stacking units around the stacking direction. The housing may be a stack enclosure defining a fluid volume containing the stack of stacking units. The housing may be welded to the first and second plates. The housing, the optional first end plate and the optional second end plate together may form a stack enclosure defining a fluid volume containing the stack of stacking units. The housing may be single piece. The housing may be formed of at least two parts, joined together at their seams, for example by welding. The housing may comprise or consist of a skirt around the cell units.

[0027] In embodiments comprising a housing, the electrochemical cell assembly preferably comprises a fluid inlet port for supplying fluid, preferably air or oxidant, from the exterior of the electrochemical cell assembly to the fluid volume enclosed by the housing, and a fluid outlet port for removing fluid, preferably exhaust air or oxidant, from the fluid volume. Preferably, the electrochemical cell assembly comprises an air or oxidant inlet port and an air or oxidant outlet port. Thus, preferably, the fluid flow path provided between adjacent stacking units, preferably cell units, is a fluid flow path, preferably air or oxidant flow path, for fluid, preferably air or oxidant, to flow from the fluid inlet port to the fluid outlet port. Accordingly, there is provided a fluid flow path from the fluid inlet port to the fluid outlet port through the stack. The fluid inlet port and the fluid outlet port may be formed by a respective through-hole formed in the first or second end plate.

[0028] In preferred embodiments, the cell units extend between the fluid inlet port and the fluid outlet port in the first direction perpendicular to the stacking direction. Thus, the first direction may be a main net flow direction for fluid to flow from the fluid inlet port to the fluid outlet port.

[0029] Reducing fluid flow along the fluid flow path between adjacent stacking units may comprise reducing a cross-section of said fluid flow path, i.e. reducing a cross-sectional area through which fluid, in particular air or oxidant, can flow. In some embodiments, the flow restriction device, preferably the or each flow restriction member, is configured to reduce a cross-section of the fluid flow path by at least 50%, preferably at least 60% more preferably at least 70%, more preferably at least 90%.

[0030] Preferably, the at least one flow restriction member is arranged between the dummy cell unit and the adjacent stacking unit.

[0031] In some embodiments, the flow restriction member or at least one of the flow restriction members abuts the dummy cell unit and the adjacent stacking unit along the stacking direction. That is to say, the flow restriction member or at least one of the flow restriction members spans a distance between the dummy cell unit and the adjacent stacking unit, e.g. a distance defined by outward projections provided in a structured area of the dummy cell unit (see below) and a layer thickness of the cell chemistry layers. In embodiments, wherein the cell units each comprise a support plate and an interconnector plate, and a flow restriction member is provided between a dummy cell unit and an adjacent cell unit, preferably the flow restriction member or at least one of the flow restriction members abuts both the support plate of one of the dummy cell unit and the adjacent a cell unit and the interconnector plate of the other one of the dummy cell unit and the adjacent cell unit.

[0032] Preferably, the at least one flow restriction member extends over at least 50%, preferably at least 70%, more preferably at least 80%, more preferably at least 90%, of the extent of the dummy cell unit in the second direction, preferably along the second direction. In embodiments, wherein a dummy cell unit comprises cell chemistry layers, preferably the at least one flow restriction member extends over at least a portion of the extent, preferably over at least 80%, more preferably at least 90%, more preferably over the full extent, of the cell chemistry layers in the second direction.

[0033] In some embodiments, the flow restriction member or at least one of the flow restriction members is located within the periphery of the dummy cell unit, i.e. surrounded by the periphery. In this way, stack space can be reduced, which has a positive effect on power density of the cell assembly. In some embodiments, the at least one dummy cell unit, preferably each cell unit, may each have flange portions around part or its entire periphery. In such embodiments, the flow restriction member or at least one of the flow restriction members may be located with said flange portions. The flow restriction member or at least one of the flow restriction members may be located on a flange portion. In embodiments of the cell units having a support plate and an interconnector plate, said flange portions may be provided by a periphery of the interconnector plate. The flange portions may be formed by pressing the interconnector plate to a concave configuration (tub-shape), such that the flange portions lie in a plane offset from the plane of the original plate.

[0034] In some embodiments, the flow restriction member or one of the flow restriction members may be formed by a strip, preferably of sealing material. Preferably, said strip extends over at least a portion of the extent, preferably the full extent, of the cell units in the second direction.

[0035] Preferably, the sealing material is a, in particular elastically, deformable material that is capable of compensating for changes in distance between adjacent cell units in stacking direction, e.g. due to compression of the stack and / or thermal expansion. In preferred examples, the sealing material comprises or consists of a vermiculite material, preferably an exfoliated vermiculite material. Vermiculite material has proven particularly advantageous with regards to sealing performance at elevated temperatures and mechanical compliance. The exfoliated vermiculite material may comprise exfoliated vermiculite or consist of exfoliated vermiculite. The exfoliated vermiculite material may be thermally or chemically exfoliated. The exfoliated vermiculate material may comprise a diluent filler made of steatite and an elastomer added as a binder.

[0036] In preferred embodiments, the at least one dummy cell units, preferably each cell unit, has a periphery and a central portion surrounded by the periphery, wherein the central portion of the at least one dummy cell unit, preferably of each cell unit, has a structured area having a plurality of outward projections extending towards an adjacent stacking unit along the stacking direction. Said projections are configured to define, preferably delimit, fluid passageways for fluid to flow between the adjacent stacking units. Said fluid passageways contribute to or form the fluid flow path. In such embodiments, preferably the flow restriction member or at least one of the flow restriction members extends over at least 80%, preferably over at least 90%, of the length of said structured area in the second direction, more preferably at least the full length of said structured area in the second direction.

[0037] Preferably, the flow restriction member or at least one of the flow restriction members is located immediately next to or adjacent to the structured area, preferably extending along an edge of said structured area. Preferably, the structured area extends in the first direction and in the second direction. The structured area may be rectangular, particularly square-shaped. Preferably, said structured area overlies an area covered by the cell chemistry layers. Preferably, the outward projections of a first cell unit engage at their ends against an outer surface of a cell chemistry layer (preferably an outer surface of the air or oxidant electrode layer) of an adjacent cell unit, thus forming fluid passageways therebetween. The shaped outward projection may be configured for partially separating adjacent cell units.

[0038] Preferably, the flow restriction member or at least one of the flow restriction members spans a height of said projections along the stacking direction. Thus, preferably a thickness of the flow restriction member equals or exceeds an extent of said projections along the stacking direction. This further improves efficient fluid blockage through the fluid passageways defined by said projections. In some embodiments, the at least one dummy cell unit, preferably each cell unit (active or inactive), comprises a support plate and an interconnector plate, wherein the support plate and the interconnector plate overlie one another along the stacking direction and are, preferably sealingly, attached to each other to enclose a cell volume, preferably fuel volume, therebetween.

[0039] In such embodiments, preferably the interconnector plate provides the structured area. That is to say, the interconnector plate may comprise outward projections formed in a structured area of its central portion.

[0040] In embodiments comprising a support plate and an interconnector plate, the flow restriction member or at least one of the flow restriction members may be attached, for example by gluing, to the interconnector plate or to the support plate, preferably on a side that faces away from the respective other one of the interconnector plate and the support plate.

[0041] Preferably, the flow restriction member or at least one of the flow restriction members is attached to the interconnector plate on a side that faces away from the support plate. Preferably, the flow restriction member or at least one of the flow restriction members is attached on the side of the interconnector plate, which the outward projections project from. Preferably, the flow restriction member or at least one of the flow restriction members is attached adjacent to the structured area, preferably extending along an edge of said structured area.

[0042] As mentioned above, each cell unit may have at least one fuel port for supplying fuel to the cell unit or for removing exhaust fuel from the cell unit. At least for the active cell units, preferably the at least one fuel port is in communication with an inner fuel volume (cell volume) of the cell unit, said fuel volume e.g. being defined between a support plate and an interconnector plate (see above). The at least one fuel port may be formed by a through-hole extending through the cell (in embodiments comprising a support plate and an interconnector plate through both plates) along the stacking direction.

[0043] In embodiments, wherein the cell units comprise at least one fuel port and a structured area, preferably the flow restriction member or at least one of the flow restriction members is arranged between the at least one fuel port and the structured area. In preferred examples, the flow restriction member or at least one of the flow restriction members is a strip of sealing material (see above), said strip being arranged between the at least one fuel port and the structured area, preferably extending the full length of the structured area in the second direction.

[0044] In some embodiments, each cell unit has at least one fuel inlet port for supplying fuel to the cell unit, in particular to the cell volume, and at least one fuel outlet port for removing fuel from the cell unit, in particular from the cell volume. Preferably, the fuel inlet ports of adjacent cell units are aligned such that they overly along the stacking direction and fuel outlet ports of adjacent cell units are aligned such that they overly along the stacking direction. Preferably, the cell unit extends between said at least one fuel inlet port and said at least one fuel outlet port in the first direction. Thus, the at least one fuel inlet port and the at least one fluid outlet port may be spaced apart from each other along the first direction. Preferably, the at least one fuel inlet port and the at least one fuel outlet port are located at opposite ends of the cell unit with respect to the first direction. In such embodiments, it may be advantageous, if the flow restriction member or at least one of the flow restriction members is located between the at least one fuel inlet port and the at least one fuel outlet port.

[0045] In preferred embodiments, at least one flow restriction member is located between the at least one fuel inlet port and the structured area, and, additionally, at least one flow restriction member is located between the at least one fuel outlet port and the structured area. Preferably, said flow restriction members each take the form of a strip of sealing material (see above), said strip preferably extending adjacent to the structured area, most preferably along the full length of the structured area in the second direction.

[0046] In embodiments, wherein the at least one dummy cell units, preferably each cell unit, comprises at least one fuel port, a gasket, e.g. in the form of a sealing ring, may be provided around each fuel port. In such embodiments, the flow restriction member or at least one of the flow restriction members may be provided in addition to said gasket(s) surrounding the fuel port(s). In this case, preferably, the flow restriction member or at least one of the flow restriction members is provided in the same plane as said gasket(s).

[0047] Alternatively, the flow restriction member or at least one of the flow restriction members may be provided by such a gasket surrounding the at least one fuel port. Thus, the sealing of the fuel port and the blocking of the fluid flow along the fluid flow path may be provided by the same member, which reduces complexity and eases manufacturing due to reduced part count. Preferably, said gasket extends over at least 50% of an extension of the cell unit in the second direction. In some embodiments comprising such gasket(s) around the fuel port(s), said gasket has a main body surrounding the associated fuel port and at least one protrusion that protrudes from said main body, preferably at least in sections in the second direction. The at least one protrusion of the extended gasket may have a curved end portion, preferably extending in the first direction. The at least one protrusion may have a smaller thickness along the stacking direction than the main body of the gasket. This helps to improve reliable sealing of the fuel ports.

[0048] In some embodiments, the at least one dummy cell unit, preferably each cell unit, comprises a first fuel port and a second fuel port (preferably first and second fuel inlet ports and / or first and second fuel outlet ports), said first and second fuel ports being spaced from each other along the second direction. In such embodiments, the fluid flow path may extend between those two fuel ports. Preferably, the flow restriction member or one of the flow restriction members extends between the first fuel port and the second fuel port, preferably from the first fuel port to the second fuel port.

[0049] In preferred embodiments having first and second fuel ports, the flow restriction member or one of the flow restriction members is provided by an extended gasket, said extended gasket having a main body that extends between the first fuel port and the second fuel port, and preferably surrounds both the first fuel port and the second fuel port. Thus, instead of providing two distinct gaskets one around each fuel port there may be provided a single gasket surrounding both fuel ports.

[0050] In preferred embodiments, said extended gasket further comprises at least one protrusion that protrudes from said main body, preferably at least in sections in the second direction. Preferably, said extended gasket has two opposite protrusions (extended portions), said protrusions protruding from the main body in opposite directions, preferably at least on sections along the second direction.

[0051] Preferably, said extended gasket (including the main body and the two protrusions) extends over at least 80% of the extent of a cell unit along the second direction, preferably over at least 90% of the extent, more preferably the full extent (i.e. the full width of a cell unit).

[0052] Preferably, the at least one protrusion of the extended gasket has a curved end portion, preferably extending in the first direction. Preferably, the at least one protrusion of the extended gasket has a smaller thickness along the stacking direction than the main body of the extended gasket. This helps to improve reliable sealing of the fuel ports. In embodiments, wherein the cell units each comprise a structured area having outward projections, said extended gasket preferably spans a height of said projections in stacking direction. In embodiments, wherein the interconnector plate has a flange portion around part or all of its perimeter, preferably said extended gasket is located on said flange portion.

[0053] Preferably, the at least one extended gasket is formed from a vermiculite material.

[0054] Further embodiments are derivable from the following description and the drawings. In the drawings:

[0055] Figure 1 shows a perspective view of an exemplary electrochemical cell assembly;

[0056] Figure 2 shows a top view of the electrochemical cell assembly of Figure 1 ;

[0057] Figure 3 shows a cross-sectional view of the electrochemical cell assembly of Figure 1;

[0058] Figure 4 shows an exploded view of an exemplary cell unit;

[0059] Figure 5 shows a bottom view of a cell unit with a flow restriction device according to a first embodiment;

[0060] Figure 6 shows a bottom view of a cell unit with a flow restriction device according to a second embodiment; and

[0061] Figure 7 shows a bottom view of a cell unit with a flow restriction device according to a third embodiment.

[0062] Repeat use of reference symbols in the present specification and drawings is intended to represent the same or analogous features or elements.

[0063] Referring to Figures 1 to 3, there is shown an exemplary configuration of an electrochemical cell assembly 10. The electrochemical cell assembly 10 comprises a first end plate 12, a second end plate 14 (see Fig. 3, not shown in Fig. 1), and a stack 16 of stacking units 17 arranged between the first end plate 12 and the second end plate 14. Preferably, the stack 16 is held in a compressed state between the first end plate 12 and the second end plate 14.

[0064] In other embodiments, the cell assembly 10 may include only one of the first and second end plates 12, 14.

[0065] Figures 1 to 3 are intended to primarily provide an overview of the electrochemical cell assembly 10 and its components in general by way of example. The invention, however, is not limited to this specific design. The stack 16 comprises a plurality of stacking units 17 that are stacked upon each other along a stacking direction 20. The stacking units 17 comprise electrochemical cell units 18. The cell units 18 may be fuel cell units, electrolyser cell units or reversible cell units. In the example, the cell units 18 are metal-supported solid oxide fuel cells (details see below). As described in detail below, the stack 16 comprises electrochemically active cell units 98 and electrochemically inactive dummy cell units 100.

[0066] In the example shown, the stacking units 17 further comprise current transmission plates 126, 128 that are located at opposing ends of the stack 16, in particular between the end plates 12, 14 and the stacked cell units 18 (see Fig. 3).

[0067] Specifically, the electrochemical cell assembly 10 comprises a current transmission (i.e. current collection or delivery) system 124 for electrically contacting the stack of cell units 18. In the example, the current transmission system 124 comprises a first current transmission plate 126 that is interposed between the bottom-most cell unit 18 (here: dummy cell unit 100, see below) and the first end plate 12. The first current transmission plate 126 is in electrical contact, preferably direct contact, with the bottom-most cell unit 18.

[0068] The current transmission system 124 further comprises a second current transmission plate 128 that is interposed between the top-most cell unit 18 (here: dummy cell unit 100, see below) and the second end plate 14. The second current transmission plate 128 is in electrical contact, preferably in direct contact, with the top-most cell unit 18.

[0069] In the example, a first insulating plate 130 is interposed between the first end plate 12 and the first current transmission plate 126, and a second insulating plate 132 is interposed between the second end plate 12 and the second current transmission plate 128. Preferably, the first and the second insulating plates 130, 132 are formed from a mica material.

[0070] The current transmission plates 126, 128 may be electrically connected by electrical connection members, such as busbars, to electrically connect the cell units 18 to an external device such as an electrical energy storage device or a work machine to be driven by the stack of cell units 18.

[0071] Referring to Figure 3, it can be seen that the stack 16 further comprises gaskets 22 that are interposed between the stacking units 17. Exemplarily, the gaskets 22 are annular sealing rings having a central opening 24. The gaskets 22 surround respective fluid ports 76 of the cell units 18 (details see below).

[0072] As shown in Figure 1 , each cell unit 18 extends in a respective cell plane perpendicular to the stacking direction 20 in a first direction 26 and in a second direction 28 perpendicular to the first direction 26. Each cell unit 18 has a periphery 30 and a central portion 32 surrounded by the periphery 30 (see Figure 2). The central portion 32 carries cell chemistry layers 34.

[0073] In the example shown, the cell units 18 are generally rectangular, albeit with shaped corners 36. Specifically, each cell unit 18 has two opposed long, preferably straight, sides 38-1 , 38-2 that extend along the first direction 26, and two opposed short, preferably shaped, sides 40-1 , 40-2 that extend along the second direction 28 (see Fig. 1).

[0074] In the example shown in Figure 1 , in each of said shaped corners 36, an optional electrically insulating beam 42 is provided. In embodiments not shown, there may be beams 42 provided only on two of the shaped corners 36. In further embodiments not shown there may be no beams 42 provided. In example, the electrically insulating beams 42 take the form of a circular shaped or tubular shaped beam, such as the pipe or tube as shown - with a central opening 44 (may carry an electrical connection member of the current delivery system 124). In the preferred examples, the beams 42 will be made of mica, although other electrically insulating materials, including many ceramics, can also be used; preferably non-frangible electrically insulating materials are used.

[0075] The electrochemical cell assembly 10 further comprises a housing 48 circumscribing the stack 16 around the stacking direction 20. In the example, the housing 48 is a skirt formed in two halves 50-1 , 50-2, which are joined together at a joint line 52, preferably by welding. In preferred examples, the housing 48 is formed from metal, preferably steel. The housing 48 may be welded to the end plates 12, 14. The housing 48 and the end plates 12, 14 together enclose a fluid volume 54 around the stack 16, said fluid volume 54 being an air or oxidant volume.

[0076] In order to supply fluid, preferably air or oxidant, to said fluid volume 54, the electrochemical cell assembly 10 further comprises a fluid inlet port 56 (hereinafter referred to as air inlet port 56) and an opposite fluid outlet port 58 (hereinafter referred to as air outlet port 58), see Fig. 2. In the example, the air inlet port 56 and the air outlet port 58 are each provided by a respective through-hole 60, 62 formed in the first end plate 12. Referring to Figure 2, it can be seen that the cell units 18 extend between the air inlet port 56 and the air outlet port 58 in the first direction 26. As described in detail below, the cell units 18 define a fluid flow path 64 (hereinafter referred to as air flow path 64) for air to flow from the air inlet port 56 to the air outlet port 58 through the stack 16.

[0077] In the example shown in Figures 1 and 2, the electrochemical cell assembly 10 further comprises two optional electrically insulating boards 66 located on opposite sides of the stack 16. Specifically, each board 66 is located in a respective gap 68 provided between the housing 48 and the long sides 38-1, 38-2 of the cell units 18. The boards 66 extend along the long sides 38-1, 38-2 of the cell units 18 in the first direction 26 and in the stacking direction 20. In the preferred examples, the boards 66 will be made of mica, although other electrically insulating materials, including many ceramics, can also be used; preferably non-frangible electrically insulating materials are used.

[0078] In the following, an exemplary configuration of the cell units 18 will be described by reference to Figures 3 and 4.

[0079] As set out above, in the example, the cell units 18 are metal-supported solid oxide fuel cells. Each cell unit 18 exemplarily comprises an interconnector plate 70 (also referred to as interconnect or separator plate) and a support plate 72 (also referred to as substrate), which are stacked upon each other along the stacking direction 20. The support plate 72 and the interconnector plate 70 are formed from metal, preferably stainless steel.

[0080] The support plate 72, in its central portion 32, carries the cell chemistry layers 34 - at least for the active cell units 98 over a porous region (see below). The porous region may be formed by laser-drilled holes formed in the support plate 72.

[0081] As shown in Figure 4, the interconnector plate 70 comprises a structured area 90 in its central portion 32, said structured area 90 having a plurality of shaped outward projections 92. Referring to Figure 3, it can be seen that in the stack 16 said outward projections 92 engage at their ends against an outer surface of an adjacent stacking unit 17 (e.g. the first current transmission plate 126 or the cell chemistry layer 34 of an adjacent cell unit 18), thus defining fluid passageways 94 therebetween. Said fluid passageways 94 contribute to the aforementioned fluid flow path 64 between adjacent stacking units 17 (see also Fig. 2).

[0082] In the example shown, each cell unit 18, more specifically each interconnector plate 70, comprises a flange portion 96 (also referred to as flanged perimeter features) around its periphery 30. The flange portion 96 is preferably formed by pressing the interconnector plate 70 to a concave configuration (tub-shape), such that the flange portion 96 lies in a plane offset from the plane of the original plate (see also Fig. 3).

[0083] The interconnector plate 70 and the support plate 72 are attached to each other at the flange portions 96, preferably by welding. Thus, the interconnector plate 70 and the support plate 72 enclose a cell volume between their central portions 32 due to the tubshape of the interconnector plate 71.

[0084] As shown in Figures 3 and 4, each cell unit 18 has at least one, in the specific example four, through-holes 76 formed therein, said through-holes 76 extending through the cell unit 18 along the stacking direction. Specifically, both the support plate 72 and the interconnector plate 70 have respective through-holes 76. Said through-holes form the above-mentioned fluid ports 78 of the cell unit 18. In the specific example, each cell unit 18 comprises two fuel inlet ports 80 and two fuel outlet ports 82 (see Fig. 2).

[0085] At least for the active cell units 98 (see below), fuel flows from the two fuel inlet ports 80 to the two fuel outlet ports 82 through the cell volume enclosed between the interconnector plate 70 and the support plate 72, wherein a net fuel flow direction 83 extends along the first direction 22. In practice, there will be multiple fuel flow paths through the cell volume, and they may be straight or convoluted, dependent upon the design of cell units 18.

[0086] Referring to Figure 3, it can be seen that an aligned column of the central openings 24 of the gaskets 22 and the through-holes 76 (fluid ports 78) of the cell units 18 forms a fluid manifold 84 extending throughout the stack 16 along the stacking direction 20. In the example, the stack 16 comprises two fluid manifolds 84 serving as fuel inlet manifolds and two fluid manifolds 84 serving as fuel outlet manifolds (exhaust) manifolds. In order to transport fuel between the exterior of the electrochemical cell assembly 10 and the fluid manifolds 84, the first end plate 12 comprises respective through-holes 86 arranged at a position corresponding to the assigned fluid manifold (see Figure 3). Thus, the through- holes 86 form fuel access ports 88 of the cell assembly 10.

[0087] As set out above, the stack 16 comprises electrochemically active cell units 98 and electrochemically inactive dummy cell units 100 (hereinafter referred to as dummy cell units). In the specific example, the stack 16 comprises - in that order in stacking direction 20 - a first insulation plate 130, a first current transmission plate 126, a first stack 102 of dummy cell units 100, a stack 104 of active cell units 98, a second stack 106 of dummy cell units 100, a second current transmission plate 128, and a second insulation plate 132 (see Figure 3). Thus, the stack 16 comprises a stack of active cell units 104 sandwiched between two stacks of dummy cell units 102, 106.

[0088] The active cell units 98 and the dummy cell units 100 may have the same configuration as described above in connection with Figure 4, except that for the dummy cell units 100 a fuel flow path between the fuel inlet and / or outlet ports 80, 82 and the cell chemistry layers 34 is blocked. This may be caused by adding a fuel blocking member in the cell volume formed between the support plate 72 and the interconnector plate. Alternatively or in addition, the porous region in the support plate 72 may be omitted for the dummy cell units 100.

[0089] The cell chemistry layers 34 may be identical for both, active and inactive cell units 98, 100. It is also possible, that the cell chemistry layers 34 of the dummy cell units 100 and the active cell units 98 are different. For example, the dummy cell units 100 may have only a subset of the cell chemistry layer 34 of an active cell unit 98, e.g. only an air or oxidant electrode layer.

[0090] Referring to Figure 3, it can be seen that between a dummy cell unit 100 and an adjacent cell unit 18 (can be dummy cell unit 100 or active cell unit 98), there is provided a flow restriction device 108 comprising at least one flow restriction member 110 for reducing or preventing fluid flow, preferably air flow, between said dummy cell unit 100 and the adjacent cell unit 18, i.e. along the fluid flow path 64 provided between those cell units 18. In the example, there is also provided a flow restriction device 108 between the bottommost dummy cell unit 100 and the first current transmission plate 126. Optionally, there may be provided a flow restriction device 108 between the top-most dummy cell unit 100 and the second current transmission plate 128.

[0091] Figure 5 shows a first example, wherein the flow restriction device 108 comprises two strips 112-1, 112-2 of a flow restriction material, said strips 112-1, 112-2 each forming a respective flow restriction member 110. The flow restriction material preferably is a vermiculite material.

[0092] Specifically, there is provided a first strip 112-1 located between the two fuel inlet ports 80 and the structured area 90, and a second strip 112-1 located between structured area 90 and the two fuel outlet ports 82. In the example of Figure 5, the fuel ports 80, 82 are each surrounded by a respective gasket 22 in the form of an annular sealing ring. As can be seen from Figure 5, each strip 112-1 , 112-2 extends along the second direction, preferably the full extent of the structured area 90 in the second direction 28, such that fluid flow along the fluid flow path 64 is blocked (illustrated in Figure 5 by the arrow 114). Exemplarily, the strips 112-1, 112-2 are each located within the flange portions 96 of the interconnector plate 70. The strips 112-1 , 112-2 preferably each span a height of the outward projections 92 in stacking direction.

[0093] In further embodiments not shown, there may be provided only the first strip 112-1 or only the second strip 112-2, preferably only the first strip 112-1.

[0094] Figure 6 shows a further example, wherein flow restriction members 110 are provided by extended gaskets 116-1 , 116-2 located around the fuel ports 80, 82. Specifically, there is provided a first extended gasket 116-1 that is associated with the fuel inlet ports 80 and a second extended gasket 116-2 that is associated with the fuel outlet ports 82. As shown in Figure 6, each extended gasket 116-1, 116-2 comprises a main body 118 extending between the associated fluid ports 80, 82 and surrounding them, thus blocking fluid to flow through the fluid flow path 64 between the cell units 18 (illustrated by arrow 114 in Figure 6). That is, the main body 118 of the first extended gasket 116-1 extends between the fuel inlet ports 80 and surrounds them, and the main body 118 of the second extended gasket 116-2 extend between the fuel outlet ports 82 and surrounds them. Each extended gasket 116-1 , 116-2 further comprises two protrusion 120, said protrusions 120 protruding from the respective main body 118 in opposite direction along the second direction 28. The protrusions 120 each comprise a shaped end portion 122 that extends up to the flange portions 96 at the long sides 38-1, 38-2 of the interconnector plate 72.

[0095] In preferred examples, the main body 118 of a respective extended gasket 116-1, 116-2 has a larger thickness in stacking direction 20 than the protrusions 120. In preferred examples, the extended gaskets 116-1, 116-2 are formed from a vermiculite material.

[0096] In further embodiments not shown, there may be provided only the first extended gasket 116-1 or only the second extended gasket 116-2, preferably only the first extended gasket 116-1.

[0097] Figure 7 shows a further example, wherein the flow restriction device 108 comprises both, strips 112-1, 112-2 and extended gaskets 116-1 , 116-2. In other words, the example of Figure 7 is a combination of the examples of Figures 5 and 6. To avoid repetition, aspects of Figures 5 and 6 that are generally the same as shown in Figure 7 will not be described again (like reference numerals are used to describe like features).

Claims

Claims1. An electrochemical cell assembly (10), preferably fuel cell assembly, comprising a stack (16) of stacking units (17) that are stacked upon one another along a stacking direction (20), said stacking units (17) comprising electrochemical cell units (18), wherein: each cell unit (18) extends in a cell plane perpendicular to the stacking direction (20) in a first direction (26) and in a second direction (28) perpendicular to the first direction (26), the cell units (18) comprise electrochemically active cell units (98) and at least one electrochemically inactive dummy cell unit (100), adjacent stacking units (17) define a respective fluid flow path (64), preferably oxidant flow path, between them for fluid, preferably oxidant, to flow in the first direction (26), between a dummy cell unit (100) and an adjacent stacking unit (17) there is provided a flow restriction device (108), preferably air blocking device, comprising at least one flow restriction member (110), preferably air blocking member, said flow restriction device (108) being configured to reduce or prevent fluid flow along said fluid flow path (64).

2. The electrochemical cell assembly (10) according to claim 1, wherein the flow restriction device (108), preferably the or each flow restriction member (110), is configured to reduce a cross-section of the fluid flow path (64) by at least 50%, preferably at least 60% more preferably at least 70%, more preferably at least 90%.

3. The electrochemical cell assembly (10) according to claim 1 or 2, wherein the at least one flow restriction member (110) extends over at least 50%, preferably at least 70%, more preferably at least 80%, more preferably at least 90%, of the extent of the dummy cell unit (100) in the second direction (28).

4. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the flow restriction member (110) or at least one of the flow restriction members (110) is located within the periphery (30) of the dummy cell unit (100).

5. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the at least one dummy cell unit (100), preferably each cell unit (18), has a periphery (30) and a central portion (32) surrounded by the periphery (30), the central portion (32) preferably carrying cell chemistry layers (34), wherein the central portion (32) has a structured area (90) having a plurality of outward projections (92) extending towards an adjacent cell unit (18), said projections (92) defining fluid passageways (94) therebetween for fluid to flow between the dummy cell unit (100) and an adjacent stacking unit (17), wherein the flow restriction member (110) or at least one of the flow restriction members (110) extends over at least 80% of the length of said structured area (90) in the second direction (28), preferably over at least 90%, more preferably the full length.

6. The electrochemical cell assembly (10) according to the preceding claim, wherein the flow restriction member (110) or at least one of the flow restriction members (110) spans a height of said projections (92) along the stacking direction (20).

7. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the at least one dummy cell unit (100), preferably each cell unit (18), comprises a support plate (72), preferably carrying cell chemistry layers (34), and an interconnector plate (70), wherein the support plate (72) and the interconnector plate (70) overlie one another along the stacking direction (20) and are, preferably sealingly, attached to each other to enclose a cell volume therebetween.

8. The electrochemical cell assembly (10) according to the preceding claim when referring to claim 5, wherein the interconnector plate (70) provides the structured area (90).

9. The electrochemical cell assembly (10) according to claim 7 or 8, wherein the flow restriction member (110) or at least one of the flow restriction members (110) is attached to the interconnector plate (70) or the support plate (72), preferably on a side of the interconnector plate (70) that faces away from the support plate (72).

10. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the flow restriction member (110) or one of the flow restrictionmembers (100) is formed by a strip (112-1, 112-2) of sealing material, said strip (112-1 , 112-2) extending over at least a portion of the extent of the dummy cell unit (100) in the second direction (28), preferably over the full extent of the structured area (90) in the second direction.

11. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the at least one dummy cell unit (100), preferably each cell unit (18), has at least one fuel port (78), preferably in the form of a through-hole (76) extending along the stacking direction (20).

12. The electrochemical cell assembly (10) according to the preceding claim when referring to claim 5, wherein the flow restriction member (110) or at least one of the flow restriction members (110) is arranged between the at least one fuel port (78) and the structured area (90).

13. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the at least one dummy cell unit (100), preferably each cell unit (18), has at least one fuel inlet port (80) and at least one fuel outlet port (82), wherein the at least one fuel inlet port (80) and the at least one fuel outlet port (82) are located at opposite ends of the dummy cell unit (100) with respect to the first direction (26), wherein the flow restriction member (110) or at least one of the flow restriction members (110) is located between the at least one fuel inlet port (80) and the at least one fuel outlet port (82).

14. The electrochemical cell assembly (10) according to the preceding claim when referring to claim 5, wherein at least one flow restriction member (110) is located between the at least one fuel inlet port (80) and the structured area (90) and / or at least one flow restriction member (110) is located between the at least one fuel outlet port (82) and the structured area (90).

15. The electrochemical cell assembly (10) according to any of claims 11 to 14, wherein the flow restriction member (110) or at least one of the flow restriction members (110) is provided by a gasket (116-1 , 116-2), said gasket (116-1 , 116- 2) surrounding the at least one fuel port (78).

16. The electrochemical cell assembly (10) according to the preceding claim, said gasket having at least one protrusion that protrudes from a main body of said gasket along the second direction (28).

17. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the at least one dummy cell unit (100), preferably each cell unit (18), comprises a first fuel port (78) and a second fluid port (78), said first and second fuel ports (78) being spaced from each other along the second direction (28), wherein the flow restriction member (110) or one of the flow restriction members (110) extends between said first fuel port (78) and said second fuel port (78).

18. The electrochemical cell assembly (10) according to the preceding claim, said flow restriction member (110) being provided by an extended gasket (116-1,116-2), said extended gasket having a main body (118) that extends between and preferably surrounds the first and second fuel ports (78).

19. The electrochemical cell assembly (10) according to the preceding claim, said extended gasket further having at least one protrusion protruding from said main body (118) along the second direction (28), preferably two opposite protrusions (120) protruding from said main body (118) in opposite directions, preferably along the second direction (28).

20. The electrochemical cell assembly (10) according to claim 16 or claim 19, wherein the at least one protrusion (120) has a curved end portion (122), preferably extending in the first direction (26).

21. The electrochemical cell assembly according to claim 16, 19 or 20, wherein the at least one protrusion (120) has a smaller thickness along the stacking direction (20) than the main body (118).

22. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein a flow restriction device (108) is provided between a dummy cell unit (100) and an adjacent cell unit (18).

23. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the stacking units (17) further comprise a current transmission plate (126, 128) located adjacent to a dummy cell unit (100), wherein between the dummy cell unit (100) and the adjacent current transmission plate (126, 128) there is provided a flow restriction device (108).

24. The electrochemical cell assembly (10) according to any one of the preceding claims, further comprisinga housing (48) surrounding the stack (16) of stacking units (17) to define or enclose a fluid volume (54); a fluid inlet port (56), preferably air or oxidant inlet port, for supplying fluid, preferably air or oxidant, from the exterior of the electrochemical cell assembly (10) to the fluid volume (54); a fluid outlet port (58), preferably air or oxidant outlet port, for removing fluid, preferably exhaust air or oxidant, from the fluid volume (54), wherein the cell units (18) extend between the fluid inlet port (56) and the fluid outlet port (58) in the first direction (26).

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