Cell unit and method of manufacturing a cell unit, cell stack and method of manufacturing a cell stack

Abstract

The invention relates to a cell unit (14) comprising: a cell layer (52) comprising electrochemically active layers (54), and an interconnector plate (62), wherein a periphery (56) of the cell layer (52) is attached to a periphery (64) of the interconnector plate (62), wherein a central portion (58) of the cell layer (52) and a central portion (66) of the interconnector plate (62) define a cell volume (50) therebetween, and wherein the interconnector plate (62) has a rounded shape in the central portion (66) forming a bulge (70) that protrudes away from the cell layer (52), said bulge (70) having a peak portion (74) that is arranged to initiate a touch-contact with a cell layer (52) of an adjacent cell unit (14).

Description

[0001] Title: Cell unit and method of manufacturing a cell unit, cell stack and method of manufacturing a cell stack

[0002] Specification

[0003] The invention relates to the field of electrochemical cell stacks, in particular, fuel cell stacks and electrolysis cell stacks. More specifically, the invention relates to cell units, to cell stacks, to methods of manufacturing cell units or cell stacks and to interconnector plates for use in cell units.

[0004] Fuel cell units and electrolysis cell units are examples of electrochemical cell units. Fuel cell units are energy conversion devices that allow for conversion of electrochemical fuel to electricity. Electrolysis cell units may be considered fuel cell units running in reverse mode, i.e. using electricity to decompose a compound into its constituent parts, for example H2O into hydrogen and oxygen. Reversible cell units are capable of operating in both modes.

[0005] Electrochemical cell units often comprise a cell layer having electrochemically active layers and an interconnector plate. The cell layer and the interconnector plate may be sealingly attached to one another and define a cell volume therebetween. An electrochemical cell unit of this type is disclosed in WO 2020 / 126486 Al, for example.

[0006] The electrochemically active layers of the cell layer may be configured to allow for conversion of electrochemical fuel to electricity (fuel cells) or for decomposing a compound into its constituent parts using electricity (electrolysis cells).

[0007] The present invention specifically relates to solid oxide cell units (SOCs). Solid oxide cell units (SOCs) typically comprise an electrolyte layer formed from a solid oxide, e.g. from Yttria-stabilised Zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO). SOCs can be run as solid oxide fuel cell units (SOFC) or as solid oxide electrolysis cell units (SOEC). Typical ly, multiple of such electrochemical cell units are stacked upon one another to form a stack of cell units, also referred to as "cell repeat units". In the stack of cell units, the interconnector plate of one cell unit is in touch-contact with the cell layer of an adjacent cell unit. The touch-contact between adjacent cell units may provide an electrical connection between the cell units.

[0008] It is an object of the invention to improve the performance of a stack of electrochemical cell units.

[0009] According to the invention, there is provided a cell unit with the features of claim 1. The cell unit comprises a cell layer having electrochemically active layers (also referred to as cell chemistry layers). The cell layer comprises a periphery and a central portion surrounded by the periphery. The cell unit further comprises an interconnector plate having a periphery and a central portion surrounded by the periphery. The cell layer and the interconnector plate are stacked upon one another (e.g., along a stacking direction). The periphery of the cell layer is attached, preferably sealingly attached, to the periphery of the interconnector plate. Preferably, the peripheries are sealingly attached to one another by a welded connection. The central portion of the cell layer and the central portion of the interconnector plate define or enclose a cell volume therebetween. That is to say, the central portions of the cell layer and the interconnector plate are spaced apart from each other at least in certain areas. The peripheries of the cell layer and the interconnector plate may surround the cell volume circumferentially. The central portion of the interconnector plate has a rounded shape forming a bulge that protrudes away from the cell layer. Said bulge has a peak portion that is arranged to initiate a touch-contact with a cell layer of an adjacent cell unit (e.g., when stacked in a stack of cell units).

[0010] The inventors have found that the proposed shape of the interconnector plate, i.e. the rounded bulge having the peak portion, may improve the touch-contact between adjacent cell units in a stack of cell units (e.g., controlling a position of initial touch-contact so as to reduce overall force applied in achieving contact across an extent of electrochemically active layers). Particularly, the position at which the touchcontact is initiated can be precisely controlled, e.g. by the location of the peak portion. This may result in the contact area between adjacent cell units being even across the extent of the cell unit and aligned along a direction (e.g., the stacking direction) that is perpendicular to the interconnector plate or to a cell plane defined by the cell unit throughout a stack comprising such cell units. The position of the touch-contact between the cell units is important with respect to the performance of the stack of cell units, as it influences the electrical connection between the cell units and / or the transmission of compression forces between the cell units. The rounded shape of the bulge further has the advantage that it allows for a uniform flattening of the bulge when pressed against the cell layer of an adjacent cell unit.

[0011] As used herein, the cell layer is a self-supporting layer or component comprising electrochemically active layers. It may be formed from said electrochemically active layers, e.g., in the case of an anodesupported or electrolyte-supported electrochemically active layers. Alternatively or additionally the electrochemically active layers may be supported by a support plate to form the cell layer.

[0012] As used herein, the terms "periphery of the cell layer" and "periphery of the interconnector plate" refer to the parts of the cell layer and the interconnector plate that are attached, preferably sealingly attached, to one another. Preferably, the periphery of the cell layer and the periphery of the interconnector plate are planar and parallel to a cell plane defined by the cell unit.

[0013] As used herein, the term "central portion of the cell layer" refers to a portion of the cell layer that is surrounded by the periphery of the cell layer.

[0014] As used herein, the term "central portion of the interconnector plate" refers to a portion of the interconnector plate that is surrounded by the periphery of the interconnector plate.

[0015] The peripheries may be in direct touch-contact with each other. That is to say, in some embodiments, no additional component is arranged between the peripheries. Alternatively, a further component, e.g. a spacer, may be arranged between the peripheries. Accordingly, the peripheries may be in indirect contact with each other, i.e. via the component arranged between the peripheries.

[0016] The bulge is formed by a rounded (i.e. curved) shape of the central portion of the interconnector plate. Thus, the surface of the bulge is rounded at least in areas. The surface of the bulge may be convex when viewed from outwith the cell unit. Said surface may be smoothly curved. In other words, the bulge may not have a wavy profile. Particularly, the bulge may be in the shape of a spherical cap (i.e., a portion of a sphere). However, the rounded shape of the bulge may also differ from that. Particularly, the bulge may be in the shape of an ellipsoid cap, i.e. having a non-circular shape when seen along a viewing direction that is perpendicular to the interconnector plate. The bulge may ensure that, when cell units are stacked upon each other, the interconnector plate contacts the cell layer of the adjacent cell unit in the stack across the central portion of the interconnector plate and cell layer (e.g., over a greater proportion of the central portion than can be the case for interconnector plates without the bulge).

[0017] The peak portion of the bulge may be located in the center of the interconnector plate and / or the center of the central portion of the interconnector plate. However, in other embodiments, this may not be the case. For example, in some embodiments, the peak portion may be positioned off-center within the central portion. This may be deliberately chosen.

[0018] Preferably, when seen along a viewing direction that is perpendicular to the interconnector plate, a surface area delimited by the outer perimeter of the interconnector plate is at least 5 times larger than a surface area of the peak portion, more preferably at least 10 times larger.

[0019] Preferably, the cell unit is a fuel cell unit or an electrolysis cell unit. The cell unit may be a solid oxide cell unit, e.g. solid oxide fuel cell unit or solid oxide electrolysis cell units. The cell unit may be a metal- supported solid oxide cell unit, e.g. metal-supported solid oxide fuel cell unit or metal supported solid oxide electrolysis cell unit.

[0020] Preferably, the cell unit is configured flat and extends in a cell plane. Said cell plane is preferably perpendicular to the stacking direction, i.e. the direction along which the cell layer and the interconnector plate are stacked upon one another.

[0021] In some preferred embodiments, the bulge is configured to be deformable such that it flattens out when pressed against the cell layer of the adjacent cell unit. Flattening the bulge may result in the touchcontact being established in a part of the bulge outside the peak portion, e.g. a part surrounding the peak portion. This may reduce the electrical resistance of the electrical connection between the cell units by ensuring that the extent of the central portion of the interconnector plate contacts (optionally via protrusions discussed below) the cell layer of the neighboring cell unit.

[0022] Preferably, the bulge is configured to be elastically deformable. This allows the bulge to act as a spring member. For example, when being deformed by a compression force acting along a direction that is perpendicular to the interconnector plate, the bulge may build up a spring force that is opposed to the compression force. The spring force build up in the bulge may help to maintain the compression force at an essentially constant level over the lifetime of the stack of cell units. Furthermore, an elastic deformation of the bulge may also promote an even distribution of the compression force in the contact area.

[0023] In some embodiments, the bulge may be configured to be plastically deformable.

[0024] In some preferred embodiments, the peak portion is configured to initiate a point contact with the cell layer of the adjacent cell unit. In these embodiments, the peak portion may be configured punctiform. A point contact allows a particularly precise control of the location at which the touch-contact is initiated. Furthermore, in case of a point contact, the contact area may spread starting from the point contact in a particularly uniform manner upon deformation of the bulge.

[0025] In some preferred embodiments, the peak portion is configured to initiate a line contact with the cell layer of the adjacent cell unit. In these embodiments, the peak portion may be configured elongate. Preferably, the peak portion extends in a plane that is parallel to the interconnector plate. A line contact may have the advantage that the maximum compression force acting on one spot of the interconnector plate and / or the cell layer may be reduced. This may protect the interconnector plate and / or the cell layer from being damaged.

[0026] In some preferred embodiments, the peak portion comprises a flat top, wherein a surface area delimited by the outer perimeter of the interconnector plate is at least 5 times larger than a surface area of the flat top (e.g., when seen in plan view - along a viewing direction that is perpendicular to the plane of interconnector plate (and perpendicular to the above-mentioned cell plane defined by the cell unit)). In these embodiments, preferably, the peak portion, particularly the flat top, is configured to initiate an area contact with the cell layer of the adjacent cell unit. Preferably, the surface area delimited by the outer perimeter of the interconnector plate is at least 10 times larger than the surface area of the flat top. A flat top may also reduce the maximum compression force acting on one spot of the interconnector plate and / or the cell layer and, thus, protect the interconnector plate and / or the cell layer from being damaged. In some preferred embodiments, the cell layer comprises a support plate, the support plate carrying the electrochemically active layers. In these embodiments, the periphery of the cell layer may be the periphery of the support plate and the central portion of the cell layer may be the central portion of the support plate. A support plate has the advantage that it may resist high compression forces acting in the assembled electrochemical cell assembly between the cell units. Preferably, the support plate is configured flat. Preferably, the electrochemically active layers are coated or deposited on the support plate.

[0027] In some embodiments, the support plate carries the electrochemically active layers on a side that is facing away from the cell volume, i.e. the electrochemically active layers are positioned outside the cell volume of the cell unit. In these embodiments, the peak portion of the bulge of an adjacent cell unit may be arranged to contact (an outermost layer of) the electrochemically active layers.

[0028] In some other embodiments, the support plate carries the electrochemically active layers on a side that is facing towards the cell volume, i.e. the electrochemically active layers are positioned in the cell volume.

[0029] In some embodiments, the electrochemically active layers are carried by a porous area of the support plate such that a fluid may be supplied to and exhausted from a layer of the electrochemically active layers which is closest to the support plate. For example a fuel, may leave the cell volume through pores formed in the porous area.

[0030] In some preferred embodiments, the cell unit extends in a first direction, said peak portion being arranged centrally with respect to the extent of the cell unit along the first direction. This arrangement of the peak portion may be advantageous with respect to the resulting touch-contact to the adjacent cell unit. The first direction may correspond to a longitudinal extent of the cell unit. Preferably, the first direction is parallel to the above-mentioned cell plane.

[0031] In some preferred embodiments the cell unit extends in a second direction that is perpendicular to the first direction (and so also perpendicular to the longitudinal direction), said peak portion being arranged centrally with respect to the extent of the cell unit along the second direction. Consequently, when seen in plan view the peak portion is arranged in the center of the cell unit (i.e., along a viewing direction that is perpendicular to the plane of the interconnector plate (and perpendicular to the above-mentioned cell plane defined by the cell unit)). This arrangement of the peak portion may be advantageous with respect to the resulting touch-contact to the adjacent cell unit. The second direction may correspond to a width extent of the cell unit.

[0032] In some preferred embodiments, the maximum extent (i.e., plan view extent) of the bulge across the interconnector plate is equal to or more than 3.0 cm (i.e., when viewed in plan, i.e., from a plane that is parallel to the interconnector plate). This maximum extent of the bulge may result in a large contact area upon flattening of the bulge. Furthermore, this maximum extent may result in a more uniform deformation of the bulge. Typically, the bulge will have the maximum extent at its base. Preferably, the maximum extent of the bulge across the interconnector plate is equal to or more than 5.0 cm. More preferably, the extent of the bulge in the plane across the interconnector plate is equal to or more than 25%, preferably 50%, more preferably 75% of the extent of the central portion of the interconnector plate.

[0033] As used herein, the term "base of the bulge" refers to the part of the bulge at which the bulge originates from the central portion. Preferably, the central portion comprises the rounded shaped between the base of the bulge and the peak portion of the bulge. That is to say, the central portion has a rounded extent between the base of the bulge and the peak portion of the bulge.

[0034] Preferably, a section of the central portion surrounding the base of the bulge is flat. That is to say, the bulge preferably originates from a flat part of the central portion.

[0035] In some preferred embodiments, a height offset between the base of the bulge and the peak portion of the bulge is equal to or more than 0.5 mm and equal to or less than 5.0 mm (the height offset of the bulge, i.e. the height extent of the bulge, being viewed along a direction that is perpendicular to the (plane of the) interconnector plate. This may secure that the contact between the interconnector plate and the cell layer of an adjacent cell unit is indeed initiated by the peak portion of the bulge. Preferably, the height offset between the base of the bulge and the peak portion is equal to or more than 0.5 mm and equal to or less than 2.0 mm. Most preferably, the height offset between the base of the bulge and the peak portion is approximately 1.0 mm. In some preferred embodiments, the base of the bulge and the periphery of the interconnector plate are on the same level (i.e., in height, or height level, e.g, with regard to the direction that is perpendicular to the (plane of the) interconnector plate). In these embodiments, the interconnector plate may be configured flat apart from the bulge.

[0036] In some other preferred embodiments, the base of the bulge and the periphery of the interconnector plate are offset in height (i.e., offset in the height level or dimension, e.g., with regard to the direction that is perpendicular to the interconnector plate).

[0037] In some preferred embodiments, the interconnector plate is tub-shaped and comprises a circumferential wall surrounding a bottom of the tub-shaped interconnector plate, wherein said bottom comprises the bulge. In these embodiments, the bottom of the tub-shaped interconnector plate may be configured flat apart from the bulge, the base of the bulge being the flat part of the bottom of the interconnector plate. The circumferential wall may be perpendicular or inclined to the periphery of the interconnector plate.

[0038] In some preferred embodiments, at least a part of the central portion of the interconnector plate has a structured area, said structured area being structured by a plurality of first protrusions extending towards the cell layer and / or by a plurality of second protrusions extending away from the cell layer. The first protrusions may serve to space the interconnector plate from the cell layer of the same cell unit, thereby providing the cell volume. In this case, it is the second protrusions that form the touchcontact with the adjacent (or neighboring) cell unit. Specifically, peaks of the second protrusions form the touch-contact with the adjacent cell unit (touch-contact by one such protrusion initiating the point contact, touch-contact by two or more such protrusions in a line initiating the line contact, and touchcontact by three or more such protrusions in a flat plane initiating the area contact).

[0039] The first and second protrusions may have a cross-section having an aspect ratio of less than 10, preferably less than 5, more preferably less than 2. They may have a circular, elliptical, rectangular, or hexagonal (etc.) cross section. In this way, the protrusions may be referred to as dimples, and do not restrict flow of fluid (first protrusions do not restrict flow of fluid in the cell volume, second protrusions do not restrict flow of fluid outside the cell volume). Specifically, the first and second protrusions may define a network of interconnected fluid channels therebetween. The first and second protrusions may be pressed or formed in the interconnector plate, and so a protrusion on one side of the interconnector plate is a depression on the opposite side of the interconnector plate.

[0040] In a stack of cell units, the first protrusions of a given cell unit may contact the cell layer of that cell unit, and the second protrusions of that cell unit may contact the cell layer of the adjacent / neighboring cell unit. In this way, the protrusions may transfer compression force through the stack, while maintaining the fluid volumes either side of the interconnector plate. That compression force serves to flatten out the bulge of the interconnector plate in each cell unit.

[0041] The first and second protrusions constitute a recurring pattern of the central portion. As such the protrusions are not considered to influence the overall shape of the central portion. That is to say, the protrusions do not influence whether a part of the central portion is to be considered flat or rounded, for example. In other words, the protrusions protrude out of the plane of the interconnector plate (they are superimposed upon the at least partly curved plane of the central portion of the interconnector plate). The protrusions protrude out of that plane by a constant amount across the extent of the interconnector plate (in other words, peaks of the protrusions follow a plane of the same shape, but offset from, the plane of the interconnector plate. It will be understood that "plane" as used herein means the surface of the interconnector plate excluding the protrusions, and so the "plane" itself may have a flat portion (outwith the bulge) and a curved portion (the bulge).

[0042] In some preferred embodiments, the bulge of the interconnector plate has said structured surface.

[0043] According to the invention there is also provided an interconnector plate for use in a cell unit with the features of claim 16.

[0044] The interconnector plate comprises a periphery for attaching the interconnector plate to a periphery of a cell layer. The interconnector plate further comprises a central portion surrounded by the periphery. The central portion of the interconnector plate has a rounded shape forming a bulge. Said bulge has a peak portion that is arranged to initiate a touch contact with a cell layer of an adjacent cell unit (e.g., when the interconnector plate forms part of a stack of cell units). Additional preferred features of the interconnector plate may be realised as described above.

[0045] According to the invention, there is also provided a stack of cell units with the features of claim 17.

[0046] The stack of cell units comprises a plurality of cell units that are stacked upon one another along a stacking direction. Each of the cell units comprises: a cell layer comprising electrochemically active layers, the cell layer having a periphery and a central portion surrounded by the periphery, and an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein the cell layer and the interconnector plate are stacked upon one another (e.g., along the stacking direction), wherein the periphery of the cell layer is attached, preferably sealingly attached, to the periphery of the interconnector plate, wherein the central portion of the cell layer and the central portion of the interconnector plate define a cell volume therebetween, and wherein the central portion of the interconnector plate has a rounded shape forming a bulge that protrudes away from the cell layer, said bulge having a peak portion that is in touch-contact with a cell layer of an adjacent cell unit. The bulge of the interconnector plates may be flattened out in the stack of cell units, compared to the cell units when present as separate units.

[0047] In some preferred embodiments, the stack of cell units is held under compression and the bulge of the interconnector plates is flattened by said compression. Preferably, the bulge of the interconnector plates is configured to be elastically deformable. Flattening of the bulge by a compression force thus results in a spring force building up in the bulge, said spring force being opposed to the compression force. The bulge may be flattened in the stack of cell units such that it is completely leveled out. Thus, the bulge is not visible in the stack of cell units. Alternatively, the bulge may be flattened such that it is only reduced in its height. Thus, the bulge is still visible in the stack of cell units as such.

[0048] Additional preferred features, e.g. regarding the cell layer or the interconnector plate, may be realised as described above.

[0049] According to the invention there is also provided a method of manufacturing a cell unit with the features of claim 19. The method comprises providing a cell layer comprising electrochemically active layers, the cell layer having a periphery and a central portion surrounded by the periphery.

[0050] The method further comprises providing an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein the central portion of the interconnector plate has a rounded shape forming a bulge, said bulge having a contact peak.

[0051] The method further comprises stacking the cell layer and the interconnector plate upon one another (e.g., along a stacking direction) such that the central portion of the cell layer and the central portion of the interconnector plate define a cell volume therebetween and the bulge protrudes away from the cell layer, the peak portion being arranged to initiate a touch-contact with a cell layer of an adjacent cell unit.

[0052] The method further comprises attaching (directly or indirectly), preferably sealingly attaching, the periphery of the cell layer to the periphery of the interconnector plate. Preferably, the peripheries of the cell layer and the interconnector plate are attached to one another by welding.

[0053] Additional preferred features, e.g. regarding the cell layer or the interconnector plate, may be realised as described above.

[0054] According to the invention, there is also provided a method of manufacturing a stack of cell units with the features of claim 20.

[0055] The method comprises providing a plurality of cell units that are configured as described above.

[0056] The method further comprises stacking the cell units upon one another along the stacking direction, wherein a touch-contact between the interconnector plates of the cell units with the cell layer of a respective adjacent cell unit is initiated by the peak portion of the bulge of the interconnector plate touching the cell layer of the respective adjacent cell unit.

[0057] In some preferred embodiments, the method further comprises compressing the stacked cell units in a direction parallel to the stacking direction, whereby the bulge of the interconnector plate is flattened. That is to say, a compression force acting in a direction parallel to the stacking direction is applied on the stacked cell units, i.e. the stack of cell units. Said compression force results in the bulge of the interconnector plates being flattened. Preferably, the bulge of the interconnector plates is configured to be elastically deformable. Thus, deformation of the bulge results in a spring force building up in the bulge, said spring force being opposed to the compression force.

[0058] Additional preferred features, e.g. regarding the cell layer or the interconnector plate, may be realised as described above.

[0059] Further embodiments are derivable from the following description and the drawings:

[0060] Figure 1 shows a cross-sectional view of an embodiment of an electrochemical cell assembly comprising a stack of cell units;

[0061] Figure 2 shows an exploded view of a cell unit of the stack of cell units of Figure 1;

[0062] Figure 3 shows a bottom view of an assembled cell unit of the stack of cell units of Figure 1;

[0063] Figure 4 shows a cross-sectional view of the cell unit of Figure 3;

[0064] Figure 5 shows a method of manufacturing a stack of cell units;

[0065] Figure 6 shows a bottom view of a cell unit according to a second embodiment;

[0066] Figure 7 shows a bottom view of a cell unit according to a third embodiment; and

[0067] Figure 8 shows a cross-sectional view of a cell unit according to a fourth embodiment.

[0068] Referring to Figure 1, there is shown an exemplary configuration of an electrochemical cell assembly 10.

[0069] The electrochemical cell assembly 10 comprises a stack 12, the stack 12 comprising a plurality of electrochemical cell units 14 that are stacked upon one another along a stacking direction 16. It should be noted that Figure 1 only shows a schematic representation of the cell units 14. The structure of the cell units 14 will be described in more detail below in connection with Figures 2 to 4.

[0070] The cell units 14 are configured flat and extend in a respective cell plane that is perpendicular to the stacking direction 16. Adjacent cell units 14 are in touch-contact with each other, said touch-contact providing an electrical connection between the cell units 14.

[0071] The stack 12 further comprises a plurality of gaskets 18. The gaskets 18 are interposed between adjacent cell units 14. In this example, the gaskets 18 are configured as annular sealing rings having a central opening 20. The gaskets 18 may be formed from a vermiculite material, for example.

[0072] The electrochemical cell assembly 10 further comprises a base plate assembly 22 having a base plate 24. The stack 12 of cell units 14 is arranged upon the base plate 24.

[0073] In this example, the base plate assembly 22 further comprises a first insulating plate 26 that is interposed between the base plate 24 and the stack 12 of cell units 14. The first insulating plate 26 electrically insulates the stack 12 of cell units 14 from the base plate 24 that is preferably formed from a metal material. The first insulating plate 26 may be formed from a mica material, for example.

[0074] The electrochemical cell assembly 10 further comprises an end plate assembly 28 having an end plate 30 that is arranged upon the stack 12 of cell units 14.

[0075] In this example, the end plate assembly 28 further comprises a second insulating plate 32 that is interposed between the end plate 30 and the stack 12 of cell units 14. The second insulating plate 32 electrically insulates the stack 12 of cell units 14 from the end plate 30 that is preferably formed from a metal material. The second insulating plate 32 may be formed from a mica material, for example.

[0076] In this example, the electrochemical cell assembly 10 further comprises a housing 34 that surrounds the stack 12 of cell units 14. The housing 34 extends around the outer perimeters 35 of the cell units 14. In this specific example, the housing 34 is fixedly attached to the end plate 30 and to the base plate 24. The end plate 30 and the base plate 24 may be biased towards each other such that the stack 12 of cell units 14 is compressed between the end plate 30 and the base plate 24. That is to say, a compression force acting along the stacking direction 16 may be applied to the stack 12 of cell units 14. In this case the housing 34, fixedly attached to the base plate 24 and end plate 30 biases said plates towards one another to apply compression to the stack 12 of cell units 14 (i.e., the housing 34 is in tension).

[0077] The base plate 24, the end plate 30 and the housing 34 together define or enclose a fluid volume 36. The stack 12 of cell units 14 is arranged within said fluid volume 36.

[0078] In this example, the base plate 24 comprises at least one fluid inlet port 38 for first fluid, e.g., fuel. The fluid inlet port 38 is provided by a through-hole 40 formed in the base plate 24 (and / or a fluid inlet port in the end plate 30). The fluid inlet port 38 is fluidically connected with cell volumes 50 of the cell units 14 (see e.g. Figure 4) via an inlet manifold 42 that extends through the stack 12 of cell units 14 along the stacking direction 16. The inlet manifold 42 is defined by the gasket openings 20 and through-holes 43 that are formed in the cell units 14 and aligned with the openings 20. During operation of the electrochemical cell assembly 10, the fluid inlet port 38 may be used to provide a fluid, e.g. fuel such as hydrogen, to the cell units 14, i.e. to their cell volume 50.

[0079] In this example, the base plate 24 comprises at least one fluid outlet port 44 for first fluid, e.g. fuel. The fluid outlet port 44 is provided by a through-hole 46 formed in the base plate 24 (and / or a fluid outlet port in the end plate 30). The fluid outlet port 44 is fluidically connected with the cell volumes 50 of the cell units 14 via an outlet manifold 48 that extends through the stack 12 of cell units 14 along the stacking direction 16. The outlet manifold 48 is provided by the gasket openings 20 and through-holes 49 that are formed in the cell units 14 and aligned with the openings 20. During operation of the electrochemical cell assembly 10, the fluid outlet port 44 may be used to remove fluid, e.g. a consumed or partly consumed fuel, from the cell units 14 to the exterior.

[0080] The base plate 24 may further comprise at least one second fluid inlet port for second fluid, e.g. oxidant / air (not visible in the Figures). The second fluid inlet port may be fluidically connected with a first portion of the fluid volume 36 between the housing 34 and the stack 12 of cell units 14. During operation of the electrochemical cell assembly 10, the second fluid inlet port may be used to supply second fluid, e.g. oxidant such as air or oxygen, to the first portion of the fluid volume 36. The base plate 24 may further comprise at least one second fluid outlet port for second fluid, e.g., oxidant / air (not visible in the Figures). The second fluid outlet port may be fluidically connected with a second portion of the fluid volume 36 between the housing 34 and the stack 12 of cell units 14. The first and second portions of the fluid volume may be on opposite sides of the stack 12 of cell units 14. During operation of the electrochemical cell assembly 10, the second fluid outlet port may be used to remove fluid, e.g. a consumed or partly consumed oxidant, from the fluid volume 36.

[0081] In the following, the configuration of the cell units 14 will be explained with additional reference to Figures 2 to 4. It should be noted that Figure 4 shows the standalone cell unit 14 prior to integration into the stack 12 of cell units 14. Figure 4 is a cross-sectional view of the cell unit 14 along the sectional plane A-A' shown in Figure 3.

[0082] The cell unit 14 comprises a cell layer 52 comprising electrochemically active layers 54. The cell layer 52 comprises a periphery 56 and a central portion 58 surrounded by the periphery 56. In this example, the periphery 56 and the central portion 58 are formed by a support plate 60 of the cell layer 52. The electrochemically active layers 54 are carried by the central portion 58 of the support plate 60 or cell layer 52.

[0083] In this example, the electrochemically active layers 54 are arranged on a side of the central portion 58 that is facing away from the cell volume 50 of the assembled cell unit 14 (see Figure 4).

[0084] The electrochemically active layers 54 may be carried by a porous area of the central portion 58 such that during operation a fluid, e.g. a fuel, may exit the cell volume 50 through pores formed in the porous area and reach to a layer of the electrochemically active layers 54 which is closest to the support plate 60. For the sake of simplicity, the porous area and the pores are not visible in the Figures.

[0085] The cell unit 14 further comprises an interconnector plate 62 having a periphery 64 and a central portion 66 surrounded by the periphery 64.

[0086] In the assembled cell unit 14 (see Figure 4), the cell layer 52 and the interconnector plate 62 are stacked upon one another along the stacking direction 16. The periphery 56 of the cell layer 52 is sealingly attached to the periphery 64 of the interconnector plate 62 (in this case, directly attached), preferably by welding.

[0087] The central portion 58 of the cell layer 52 and the central portion 66 of the interconnector plate 62 define or enclose the cell volume 50 therebetween.

[0088] In this example, the central portion 66 of the interconnector plate 62 comprises a structured area 68. Said structured area 68 is structured by a plurality of first protrusions 68a protruding towards the cell layer 52 and a plurality of second protrusions 68b protruding away from the cell layer 52, i.e. in the opposite direction. A reduced number of protrusions are depicted in Fig. 4 for clarity of the figure (and are not shown in subsequent Figures for the same reason). It will be understood that there will typically be many more protrusions than those depicted. Further, the protrusions are typically pressed or formed in the sheet forming the interconnector plate. For example, a second protrusion 68b on one side of the interconnector plate, facing away from the cell layer 52, typically forms a depression on the other side of the interconnector plate, facing towards the cell layer 52 (and similarly for first protrusions 68a).

[0089] The first protrusions 68a serve to space the interconnector plate from the cell layer of the same cell unit (when the cell unit is under compression, e.g., in a stack, and the bulge is flattened out), thereby providing the cell volume. The second protrusions 68b form the touch-contact with the adjacent (or neighboring) cell unit. Specifically, peaks of the second protrusions 68b form the touch-contact with the adjacent cell unit (touch-contact by one such protrusion initiating the point contact, touch-contact by two or more such protrusions in a line initiating the line contact, and touch-contact by three or more such protrusions in a flat plane initiating the area contact).

[0090] The first and second protrusions 68a, b typically have a circular cross section. In this way, the protrusions 68a, b may be referred to as dimples, and do not restrict flow of fluid (first protrusions 68a do not restrict flow of fluid in the cell volume, second protrusions 68b do not restrict flow of fluid outside the cell volume). The first and second protrusions 68a, b may define a network of interconnected fluid channels on each side of the interconnector plate. The first and second protrusions 68a, b may be pressed or formed in the interconnector plate, and so a protrusion on one side of the interconnector plate is a depression on the opposite side of the interconnector plate.

[0091] In a stack of cell units, the first protrusions 68a of a given cell unit contacts the cell layer of that cell unit, and the second protrusions 68b of that cell unit contact the cell layer of the adjacent / neighboring cell unit. In this way, the protrusions transfer compression force through the stack, while maintaining the fluid volumes either side of the interconnector plate. That compression force also serves to flatten out the bulge of the interconnector plate in each cell unit (in doing so, bringing the first protrusions into contact with the cell layer, specifically the support plate thereof).

[0092] The protrusions 68a, 68b are exemplary. Other means for maintaining the spacing between interconnector plate and cell layer (to provide the fluid volumes therebetween) may be used in combination with the interconnector plate described herein.

[0093] The interconnector plate 62 has a (partially) rounded shape in its central portion 66 (see Figure 4). Said rounded shape forms a bulge 70 that protrudes away from the cell layer 52. It should be noted that Figure 4 is a schematic representation and that the bulge 70 is shown significantly enlarged in its height for clarification.

[0094] The bulge 70 has a base 72. The base 72 is the part of the bulge 70 at which the bulge 70 originates from the surrounding part of the central portion 66. In this example, the surrounding part of the central portion 66 is configured flat and planar.

[0095] The bulge 70 comprises a peak portion 74. The peak portion 74 is the highest part of the bulge 70, i.e. the part of the bulge 70 that is furthest away from the cell layer 52 of the cell unit 14. In the example of Figures 2 to 4, the peak portion 74 is punctiform.

[0096] As can be seen in Figure 3, the structured area 68 and the bulge 70 overlap in this example. In other words, the part of the central portion 66 that is having the rounded shape and is thus forming the bulge 70 is also structured. In this specific example, the structured area 68 extends beyond the rounded shape forming the bulge 70 (see Figures 3 and 4). In this example, when seen along a viewing direction that is parallel to the stacking direction 16, the bulge 70 has a circular shape (see Figure 3) which in this case is centred with the centre of the structured area 68 and / or central portion 66 of the interconnector plate 62. Overall, the bulge 70 is thus in the shape of a spherical or elliptical cap. However, other shapes of the bulge 70 are conceivable, for example, a spherical or ellipsoidal cap with the circular shape off-centre with respect to the centre of the structured area 68 and / or central portion 66 of the interconnector plate 62.

[0097] An offset between the base 72 of the bulge 70 and the peak portion 74 of the bulge 70 along the stacking direction 16, i.e. the height of the bulge 70, is equal to or more than 0.5 mm and equal to or less than 5.0 mm. In this specific example, the offset is approximately 1.0 mm. Due to this height of the bulge 70, the bulge 70 is not visible in the more realistic representation of Figure 2.

[0098] The assembled cell unit 14 extends in a first direction 90 that is perpendicular to the stacking direction 16 and in a second direction 92 that is perpendicular to the stacking direction 16 and to the first direction 90.

[0099] In this example, the peak portion 74 is arranged centrally with respect to the extent of the cell unit 14 along the first direction 90.

[0100] In this example, the peak portion 74 is also arranged centrally with respect to the extent of the cell unit 14 along the second direction 92.

[0101] Thus, in this specific example, the peak portion 74 is arranged in the center of the cell unit 14, when seen along a viewing direction that is parallel to the stacking direction 16.

[0102] The maximum extent of the bulge 70 in a plane that is perpendicular to the stacking direction 16, e.g. the extent of the bulge along the first direction 90 or along the second direction 92, is preferably equal to or more than 3.0 cm, more preferably equal to or more than 5.0 cm. In some cases, the extent of the bulge in the plane that is perpendicular to the stacking direction is equal to or more than 25%, preferably 50%, more preferably 75% of the extent of the structured area 68 and / or central portion of the interconnector plate 62. Figure 5 shows a method of manufacturing the stack 12 of cell units 14. Exemplarily, the cell units 14 shown in Figures 2 to 4 are used for visualisation.

[0103] In a first step 201, a plurality of cell units 14 are stacked upon one another along the stacking direction 16. As can be seen in the box representing the first step 201, a touch-contact between adjacent cell units 14 is initiated by the peak portions 74 of the bulges 70 (in examples comprising second protrusions 68b, the touch-contact is initiated by the one of the second protrusions 68b which is closest to the peak portion 74). In this example, the peak portions 74 contact the electrochemically active layers 54 of the adjacent cell unit 14. In view of the punctiform shape of the peak portions 74, the bulges 70 initiate a point contact with the electrochemically active layers 54 of the adjacent cell unit 14.

[0104] The cell units 14 may be stacked upon the base plate 24 or separate from the base plate 24.

[0105] In a second step 203, the stacked cell units 14, i.e. the stack 12 of cell units 14, are compressed along the stacking direction 16. The cell units 14 may be compressed by biasing the end plate 30 towards the base plate 24. This results in a compression force being applied to the stack 12 of cell units 14.

[0106] As can be seen in the box representing the second step 203, compressing the stacked cell units 14 results in flattening of the bulges 70. As a consequence, the extent of the cell units 14 along the stacking direction 16 is reduced and the contact surface between the interconnector plate 62 of one cell unit 14 and the cell layer 52 of the adjacent cell unit 14 is increased, i.e. the touch-contact is established in an area of the bulge 70 outside the peak portion 74. Preferably, the bulges are flattened so that the central area of the interconnector plate resembles a flat plane.

[0107] In cases having protrusions 68a, b, each (at least 90% thereof) of the protrusions are brought into contact with a cell layer (first protrusions 68a with the cell layer (e.g., support plate) of the same cell unit and second protrusions 68b with the cell layer of an adjacent cell unit).

[0108] In this example, the bulges 70 of the interconnector plates 62 are configured to be elastically deformable. Consequently, the bulges 70 store energy during compression. Consequently, the bulges 70 exert a spring force along the stacking direction 16 that is opposite the compression force. Thereby, the bulges 70 secure a substantially constant contact pressure between the cell units 14 over the lifetime of the electrochemical cell assembly 10.

[0109] Figure 6 shows a bottom view of a cell unit 14 according to another embodiment. In the cell unit 14 shown in Figure 6, the peak portion 74 of the bulge 70 is configured to initiate a line contact with the adjacent cell unit 14 (in examples having second protrusions 68b, the line contact is via touch-contact by two or more second protrusions 68b disposed along line 74). For this, the bulge 70 comprises an elongate peak portion 74.

[0110] Figure 7 shows a bottom view of a cell unit 14 according to yet another embodiment. In the cell unit 14 shown in Figure 7, the peak portion 74 of the bulge 70 is configured to initiate a surface contact with the adjacent cell unit 14. For this, the peak portion 74 comprises a flat top (in examples having second protrusions 68b, the surface contact along the flat top is via touch-contact by three or more second protrusions 68b disposed on the flat top). The peak portion 74 having the flat top is dimensioned such that, when seen along a viewing direction that is parallel to the stacking direction 16, a surface area delimited by the outer perimeter 76 of the cell unit 14 is at least 5 times larger than a surface area of the flat top.

[0111] In the embodiments shown in Figures 1 to 7, the interconnector plate 62 is tub-shaped. The interconnector plate 62 thus comprises a circumferential wall 78 surrounding a bottom 80 of the interconnector plate 62. The bottom 80 comprises the bulge 70. That is to say, the bulge 70 originates from the bottom 80 of the interconnector plate 62. The circumferential wall 78 may be perpendicular or inclined to the periphery 64 of the interconnector plate 62. Consequently, the bottom 80 of the interconnector plate 62 and, thus, the base 72 of the bulge 70 are offset from the periphery 64 of the interconnector plate 62 along the stacking direction 16.

[0112] In the embodiment of Figure 8, the interconnector plate 62 is planar apart from the bulge 70. Consequently, the base 72 of the bulge 70 and the periphery 64 of the interconnector plate 62 are on the same level with regard to the stacking direction 16. In example of Figure 8, a spacer 82 is arranged between the periphery 56 of the cell layer 52 and the periphery 64 of the interconnector plate 62. Thus, the peripheries 56 and 64 are indirectly attached to one another, namely via the spacer 82, for example by welding through cell layer 52, the interconnector plate 62 (peripheries 56, 64 thereof, respectively) and the spacer 82. The spacer may be a further plate in the form of a window frame (having a periphery and a hollow centre) specifically to space the cell layer 52 and interconnector plate 62 to form the cell volume therebetween.

Claims

Claims1. A cell unit (14), preferably a fuel cell unit or an electrolysis cell unit, comprising: a cell layer (52) comprising electrochemically active layers (54), the cell layer (52) having a periphery (56) and a central portion (58) surrounded by the periphery (56) and an interconnector plate (62) having a periphery (64) and a central portion (66) surrounded by the periphery (64), wherein: the cell layer (52) and the interconnector plate (62) are stacked upon one another, the periphery (56) of the cell layer (52) is attached to the periphery (64) of the interconnector plate (62), the central portion (58) of the cell layer (52) and the central portion (66) of the interconnector plate (62) define a cell volume (50) therebetween, and the interconnector plate (62) has a rounded shape in the central portion (66) forming a bulge (70) that protrudes away from the cell layer (52), said bulge (70) having a peak portion (74) that is arranged to initiate a touch-contact with a cell layer (52) of an adjacent cell unit (14).

2. The cell unit (14) according to claim 1, wherein the bulge (70) is configured to be deformable such that it flattens out when pressed against the cell layer (52) of the adjacent cell unit (14).

3. The cell unit (14) according to any one of the preceding claims, wherein the peak portion (74) is configured to initiate a point contact with the cell layer (52) of the adjacent cell unit (14).

4. The cell unit (14) according to any one of claims 1 and 2, wherein the peak portion (74) is configured to initiate a line contact with the cell layer (52) of the adjacent cell unit (14).

5. The cell unit (14) according to any one of claims 1 and 2, wherein the peak portion (74) comprises a flat top to initiate an area contact with the cell layer (52) of the adjacent cell unit (14), and wherein a surface area delimited by the outer perimeter (76) of the interconnector plate (62) is at least 5 times larger than a surface area of the flat top.

6. The cell unit (14) according to any one of the preceding claims, wherein the cell layer (52) comprises a support plate (60), the support plate (60) carrying the electrochemically active layers (54).

7. The cell unit (14) according to any one of the preceding claims, wherein the cell unit (14) extends in a first direction (90), said peak portion (74) being arranged centrally with respect to the extent of the cell unit (14) along the first direction (90).

8. The cell unit (14) according to the preceding claim, wherein the cell unit (14) extends in a second direction (92) that is perpendicular to the first direction (90), said peak portion (74) being arranged centrally with respect to the extent of the cell unit (14) along the second direction (92).

9. The cell unit (14) according to any one of the preceding claims, wherein the maximum extent of the bulge (70) across the interconnector plate (62) is equal to or more than 3.0 cm, preferably equal to or less than 5.0 cm.

10. The cell unit (14) according to any one of the preceding claims, wherein the bulge (70) has a base (72), and wherein a height offset between the base (72) of the bulge (70) and the peak portion (74) of the bulge (70) is equal to or more than 0.5 mm and equal to or less than 5.0 mm.

11. The cell unit (14) according to the preceding claim, wherein the base (72) of the bulge (70) and the periphery (64) of the interconnector plate (62) are on the same level.

12. The cell unit (14) according to claim 10, wherein the base (72) of the bulge (70) and the periphery (64) of the interconnector plate (62) are offset in height.

13. The cell unit (14) according to claim 12, wherein the interconnector plate (62) is tub-shaped and comprises a circumferential wall (78) surrounding a bottom (80) of the tub-shaped interconnector plate (62), and wherein said bottom (80) comprises the bulge (70).

14. The cell unit (14) according to any one of the preceding claims, wherein the central portion (66) of the interconnector plate (62) has a structured area (68), said structured area (68) being structured by a plurality of first protrusions extending towards the cell layer (52) and / or by a plurality of second protrusions extending away from the cell layer (52).

15. The cell unit (14) according to claim 14, wherein the bulge (70) of the interconnector plate (62) has said structured area (68).

16. An interconnector plate (62) for use in a cell unit (14), comprising:a periphery (64), and a central portion (66) surrounded by the periphery (64), wherein: the central portion (66) of the interconnector plate (62) has a rounded shape forming a bulge (70), said bulge (70) having a peak portion (74) that is arranged to initiate a touch contact with a cell layer (52) of an adjacent cell unit (14).

17. A stack (12) of cell units (14), comprising a plurality of cell units (14) that are stacked upon one another along a stacking direction (16), the cell units (14) each comprising: a cell layer (52) comprising electrochemically active layers (54), the cell layer (52) having a periphery (56) and a central portion (58) surrounded by the periphery (56), and an interconnector plate (62) having a periphery (64) and a central portion (66) surrounded by the periphery (64), wherein: the cell layer (52) and the interconnector plate (62) are stacked upon one another, the periphery (56) of the cell layer (52) is attached to the periphery (64) of the interconnector plate (62), the central portion (58) of the cell layer (52) and the central portion (66) of the interconnector plate (62) define a cell volume (50) therebetween, and the central portion (66) of the interconnector plate (62) has a rounded shape forming a bulge (70) that protrudes away from the cell layer (52), said bulge (70) having a peak portion (74) that is in touch-contact with a cell layer (52) of an adjacent cell unit (14).

18. The stack (12) of cell units (14) according to claim 17, wherein the stack (12) of cell units (14) is held under compression and the bulge (70) of the interconnector plates (62) is flattened by said compression.

19. A method of manufacturing a cell unit (14), comprising: a. providing a cell layer (52) comprising electrochemically active layers (54), the cell layer (52) having a periphery (56) and a central portion (58) surrounded by the periphery (56), b. providing an interconnector plate (62) having a periphery (64) and a central portion (66) surrounded by the periphery (64), wherein the central portion (66) of theinterconnector plate (62) has a rounded shape forming a bulge (70), said bulge (70) having a peak portion (74), c. stacking the cell layer (52) and the interconnector plate (62) upon one another such that the central portion (58) of the cell layer (52) and the central portion (66) of the interconnector plate (62) define a cell volume (50) therebetween and the bulge (70) protrudes away from the cell layer (52), the peak portion (74) being arranged to initiate a touch-contact with a cell layer (52) of an adjacent cell unit (14), and d. attaching the periphery (56) of the cell layer (52) to the periphery (64) of the interconnector plate (62).

20. A method of manufacturing a stack (12) of cell units (14), comprising: a. providing a plurality of cell units (14) that are configured according to any one of claims1 to 15, b. stacking the cell units (14) upon one another along the stacking direction (16), wherein a touch-contact between the interconnector plates (62) of the cell units (14) with the cell layer (52) of a respective adjacent cell unit (14) is initiated by the peak portion (74) of the bulge (70) of the interconnector plates (62) touching the cell layer (52).

21. The method according to claim 20, wherein the stacked cell units (14) are compressed in a direction parallel to the stacking direction (16), whereby the bulge (70) of the interconnector plates (62) is flattened.

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