Electrochemical cell unit, stack of cell units, and method of assembly of an electrochemical cell unit

Abstract

The invention relates to an electrochemical cell unit (12), comprising a support plate (20) having a periphery (22) and a central portion (24) surrounded by the periphery and carrying electrochemically active layers (26), and an interconnector plate (30) having a periphery (32) and a central portion (34) surrounded by the periphery, wherein the support plate and the interconnector plate are stacked upon one another along a stacking direction (14), such that the central portion of the support plate and the central portion of the interconnector plate (30) overlap, wherein the central portion of the support plate and the central portion of the interconnector plate are electrically connected to each other in at least one connection area (60) within said central portions. The invention also relates to a stack comprising a plurality of such cell units. The invention also relates to a method of assembly of such a cell unit.

Description

[0001] Description

[0002] Title

[0003] Electrochemical cell unit, stack of cell units, and method of assembly of an electrochemical cell unit

[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 unit, a stack of electrochemical cell units, and to a method of assembly of an electrochemical cell unit.

[0006] Fuel cell units and electrolyser cell units are examples of electrochemical cell units. Fuel cell units are energy conversion devices that allow for conversion of electrochemical fuel to electricity. Electrolyser 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 water into hydrogen and oxygen. Reversible cell units are capable of operating in both modes.

[0007] The present invention specifically relates to electrochemical cell units comprising a support plate having electrochemically active layers thereon, and an interconnector plate. The support plate and the interconnector plate may be welded together along their peripheries to provide for electrical connection between the plates and to seal a fluid volume enclosed between the plates. An electrochemical cell unit of this type is disclosed in WO 2020 / 126486 A1, for example.

[0008] 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 (electrolyser cells). 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 electrolyser cell units (SOEC). WO 20231047 101 A1 describes an electrochemical cell unit comprising a separator plate and a metal support plate on which an electrochemically active cell region is deposited. The separator plate and the metal support plate are welded around their perimeter to form a single metal-supported repeat cell unit. The separator plate has central upward projections and central downward projections which create electrical contact between cell units and also provide a support function for the cell unit in the central region, extending upwardly to the underside of the metal support plate at the area of small holes, and downwardly to the opposing surface of the electrochemically active layer of a cell unit below. The upward projections may contact the metal support plate, thus providing electrical contact between the separator plate and the metal support plate. However, electron flow between the separator plate and the metal support plate is described to be primarily via the weld path around their perimeter.

[0009] EP 3 432 395 B1 describes a stack of electrochemical cell units where wavy current collection plates having upper and lower tips are stacked in an alternative arrangement with cell units. Each cell unit has a plurality of distinct electrochemical elements deposited on it. The upper tips of the current collection plate are electrically conductively joined to a lower side of one metal substrate at positions between said electrochemical elements and the lower tips electrically conductively joined to an electrochemical element of an adjacent cell unit. In such a way, the wavy current collector forms a series electrical connection between adjacent cell units and forms a parallel electrical connection between the plurality of electrical elements on each cell unit.

[0010] It is an object of the invention to improve the performance of an electrochemical cell unit, specifically improving the current density across the electrochemically active region.

[0011] Description of the Invention

[0012] According to a first aspect, there is provided an electrochemical cell unit comprising a support plate and an interconnector plate. The support plate has a periphery and a central portion surrounded by the periphery. The interconnector plate has a periphery and a central portion surrounded by the periphery. The support plate and the interconnector plate are stacked upon one another along a stacking direction, such that, seen along the stacking direction, the central portion of the support plate and the central portion of the interconnector plate at least partially overlap, i.e. overlay one another. Thus, the electrochemical cell unit may have a periphery and a central portion surrounded by the periphery. The central portion of the support plate carries electrochemically active layers, preferably on a side that faces away from the interconnector plate. Thus, the central portion may form an "active" area of the cell unit. The periphery on the other hand may be a "non-active" area of the cell unit.The central portion of the support plate and the central portion of the interconnector plate are electrically connected to each other at one or more connection areas, said one or more connection areas being located within said central portions. That is, when viewed along the stacking direction, said at least one connection area is at least in sections within a perimeter of the central portion of the support plate and the central portion of the interconnector plate.

[0013] Preferably, an electrical connection element is provided at the connection area. The electrical connection element may comprise a weld between the central portion of the support plate and the central portion of the interconnector plate. Alternatively or additionally, the electrical connection element may comprise at least one contact feature provided between the central portions.

[0014] The proposed cell unit having electrical connection areas within a perimeter of the central portions, i.e. within a perimeter of the active area of the cell unit, has improved performance and is less prone to degradation effects . Specifically, it was found that providing a connection element between the central portions (e.g. by fusing the central portions of the plates together at selected areas or by providing a contact feature therebetween) results in the electron flow between the interconnector plate and the support plate occuring primarily via said connection areas (and not via the peripheries). Advantageously, this significantly increases a current density across the electrochemically active region and thus performance of the cell unit. By adjusting the size, number and position of the connection areas, variations in current density, e.g. due to different flow characteristics over the active area, can be compensated, thus leading to a particularly homogeneous current distribution over the active area. In addition to the aforementioned effects, embodiments having weld seams in the central portions further exhibit improved stiffness and flatness of the cell unit, which is beneficial for reliable electrical contact between adjacent cell units, thus leading to enhanced performance of a cell stack. Embodiments comprising contact features additionally allow an electrical pathway and / or resistance between the support plate and the interconnector plate to be flexibly adjusted (e.g. by adjusting the size, material and / or position of the contact feature), which has proven beneficial to achieve a homogeneous current density distribution within the cell unit. In some preferred embodiments, a perimeter of the at least one connection area is at least in sections within a perimeter of the electrochemically active layers, when seen along the stacking direction. Thus, seen along the stacking direction, the at least one connection area may at least in sections be surrounded by the electrochemically active layers, i.e. , the electrochemically active layers preferably extend past the perimeter of the at least one connection area. This further improves performance of the cell unit.

[0015] Preferably, the central portion of the support plate is defined as the area covered by the electrochemically active layers.

[0016] The electrochemically active layers may be formed (e.g. coated or deposited) directly onto the support plate, preferably over a porous region formed in the central portion of the support plate. In other embodiments the electrochemically active layers may be formed on a separate plate (e.g. metal foil), preferably over a porous region formed in said plate, and the separate plate (carrying the fuel cell chemistry layers) is provided over a window (e.g. a frame) on the support plate.

[0017] The electrochemically active layers (also referred to as cell chemistry layers) preferably comprise a fuel electrode (anode in fuel cell mode), an electrolyte and an air electrode (cathode in fuel cell mode). Preferably, the electrochemically active layers comprise an anode layer deposited onto the support plate (preferably onto the porous region), an electrolyte layer deposited over the anode layer, and a cathode layer deposited over the electrolyte layer. However, in some cell arrangements that order may be reversed (such that the cathode layer is closest to the support plate).

[0018] The electrochemical cell unit may be a fuel cell unit. In this case, the electrochemically active layers may be configured for conversion of electrochemical fuel, e.g. hydrogen, to electricity. In fuel cell units, the anode may be a fuel electrode, and the cathode may be an air or oxidant electrode. Alternatively, the electrochemical cell unit may be an electrolyser cell unit. In this case, the electrochemically active layers may be configured for decomposing a compound into its constituent parts using electricity. More preferably, the cell unit is a solid oxide cell unit, in particular solid oxide fuel cell unit or solid oxide electrolyser cell units.

[0019] The present invention specifically relates to solid oxide cell units (SOCs). Thus, the electrochemically active layers may comprise an electrolyte layer formed from a solid oxide, e.g. from Yttria-stabilised Zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO).

[0020] Preferably, the central portion of the interconnector plate comprises a structured area having a plurality of (inward) protrusions, preferably in the form of dimples, wherein said (inward) protrusions protrude in a direction towards the support plate. In such embodiments, preferably, the support plate and the interconnector plate are stacked upon one another along the stacking such that the structured area of the interconnector plate and the area of the support plate covered by the electrochemically active layers overlap. In embodiments comprising such a structured area, preferably, a perimeter of the at least one connection area is at least in sections within a perimeter of said structured area. Preferably, the structured area defines the central portion of the interconnector plate. Thus, the interconnector plate may have a periphery and a structured area surrounded by the periphery. In addition to the (inward) protrusions, the structured area may have (outward) protrusions protruding in a direction away from the support plate.

[0021] The inward protrusions (and preferably the optional outward protrusions) may have a crosssection 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. The inward protrusions and the optional outward protrusions may take the form of dimples. The 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. The protrusions may define a network of interconnected fluid channels therebetween.

[0022] Preferably, the electrochemical cell unit comprises at least one fluid inlet port and at least one fluid outlet port, preferably in the form of through-holes extending through the cell units along the stacking direction. Preferably, the at least one fluid inlet port and the at least one fluid outlet port are located at opposite ends of the cell unit with respect to a first direction, preferably longitudinal direction, of the cell unit. In such embodiments, preferably, the central portions of the plates are located between the at least one fluid inlet port and the at least one fluid outlet port. Preferably, each fluid port is formed by a pair of a through-hole formed in the interconnector plate and a through-hole formed in the support plate, said through-holes being aligned along the stacking direction, preferably flush with one another. Preferably, the support plate and the interconnector plate are stacked upon one another along the stacking direction, such that, seen along the stacking direction, the periphery of the support plate and the periphery of the interconnector plate overlay one another.

[0023] Preferably, the periphery of the support plate is attached, preferably welded, to the periphery of the interconnector plate. Thus, the peripheries of the plates may form an (outer) electrical connection between the support plate and the interconnector plate, in addition to the at least one connection area within the central portions.

[0024] Preferably, the periphery of the support plate is attached to the periphery of the interconnector plate such that the central portion of the support plate and the central portion of the interconnector plate define a fluid volume, preferably for fuel, therebetween.

[0025] Preferably, said fluid volume is in fluid communication with the electrochemically active layers, for example via a porous region in the central portion of the support plate. The optional at least one fluid inlet port and the optional at least one fluid outlet port may be in fluid communication with said fluid volume.

[0026] Preferably, at least one of the support plate and the interconnector plate comprises flanged perimeter features around part or all of its periphery, wherein the support plate and the interconnector plate are, preferably directly, attached at said flanged perimeter features, preferably by welding. In this regard, the periphery of respective plate is also referred to as "flanged perimeter". Preferably, the flanged perimeter features are only provided on the interconnector plate, and the support plate is substantially flat.

[0027] Preferably, the support plate is a metallic support plate, i.e. , formed from metal or metal alloy. Preferably, the interconnector plate is a metallic support plate, i.e., formed from metal or metal alloy. More preferably, the support plate is a steel support plate, i.e. formed from steel and / or the interconnector plate is a steel interconnector plate, i.e. formed from steel.

[0028] In some preferred embodiments, the connection area or at least one of the connection areas is elongate extending in a longitudinal direction. As used herein, the term 'elongate' refers to a component having a length which is greater than both its width and thickness, for example twice as great. Preferably, the connection area or at least one of the connection areas extends along at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90%, preferably the full length, of the electrochemically active layers in the longitudinal direction. Advantageously, this provides for improved electrical contact between the support plate and the interconnector plate.

[0029] In embodiments having at least one fluid inlet port and at least one fluid outlet port, preferably, the longitudinal direction is parallel to the first direction. This has proven advantageous with respect to an efficient current transmission between the support plate and the interconnector plate, while at the same time providing for efficient fluid transport from the fluid inlet port to the fluid outlet port.

[0030] In some embodiments, there is provided a single connection area. In such embodiments, preferably, the single connection area is located centrally with respect to the electrochemically active layers. The single connection area may be elongate extending in a longitudinal direction, preferably along at least 80%, preferably at least 90%, preferably the full length, of the electrochemically active layers in the longitudinal direction.

[0031] In some embodiments, there are plural spatially separated connection areas. The plural connection areas may be distributed over the central portion of the support plate. The plural connection areas may be arranged in one or more rows, said one or more rows preferably extending in the first direction.

[0032] The electrical connection between the support plate and the interconnector plate in said at least one connection area may be provided in different ways. For example, the support plate and the interconnector plate may be directly joined at said at least one connection area to form an electrical connection. As such, the at least one connection area may be a contact area, in which the support plate and the interconnector plate are joined. Alternatively or additionally, there may be provided an additional component interposed between the central portion of the support plate and the central portion of the interconnector plate, said additional component being electrically connected to both the central portion of the support plate and the central portion of the interconnector plate.

[0033] In some preferred embodiments, the electrical connection element comprises a weld between the central portion of the support plate and the central portion of the interconnector plate. In other words, the central portion of the support plate my be welded to the central portion of the interconnector plate, preferably only, at one or more selected areas of said central portions to form said electrical connection in said at least one connection area. That is, said connection area or at least one of said connection areas may be formed by a weld seam connecting the support plate and the interconnector plate at a selected area of the central portions.

[0034] Thus, according to a second aspect, there is provided an electrochemical cell unit, preferably fuel cell unit or electrolyser cell unit, comprising a support plate having a periphery and a central portion surrounded by the periphery, the central portion of the support plate carrying electrochemically active layers, and an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein: the support plate and the interconnector plate are stacked upon one another along a stacking direction, such that the central portion of the support plate and the central portion of the interconnector plate overlap, the central portion of the support plate is welded to the central portion of the interconnector plate at one or more selected areas of said central portions to form an electrical connection between the support plate and the interconnector plate.

[0035] In some embodiments, the electrical connection element may comprise at least one contact feature provided between the central portions. In other words, there may be provided at least one contact feature at selected areas between the central portion of the support plate and the central portion of the interconnector plate. The at least one contact feature preferably is electrically connected to the central portion of the support plate and the central portion of the interconnector plate to form said at least one connection area. Thus, an electrical connection between the support plate and the interconnector plate may be provided via an additional component interposed between the support plate and the interconnector plate.

[0036] Advantageously, this allows to selectively tune an electrical connection between the support plate and the interconnector plate, and may reduce thermal impact during manufacturing.

[0037] The contact feature may be a contact paste, e.g. metal paste. The contact feature may be a contact structure, e.g. in the form of an insert or inlay.

[0038] In some preferred embodiments, the contact feature is formed by a contact inlay that is interposed between the central portion of the support plate and the central portion of the interconnector plate. Thus, at least one contact inlay (also referred to as contact insert) may be interposed between the central portion of the support plate and the central portion of the interconnector plate, preferably within said fluid volume, to form said at least one connection area. In other words, a respective connection area or at least one of the connection areas may be defined by a contact inlay, said contact inlay being arranged between the central portion of the support plate and the central portion of the interconnector plate and electrically connected to both the central portion of the support plate and the central portion of the interconnector plate.

[0039] Thus, according to a third aspect, there is provided an electrochemical cell unit, preferably fuel cell unit or electrolyser cell unit, comprising a support plate having a periphery and a central portion surrounded by the periphery, the central portion of the support plate carrying electrochemically active layers, and an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein: the support plate and the interconnector plate are stacked upon one another along a stacking direction, such that the central portion of the support plate and the central portion of the interconnector plate overlap, the central portion of the support plate and the central portion of the interconnector plate are electrically connected to each other via one or more contact inlays, said one or more contact inlays being interposed between the central portion of the support plate and the central portion of the interconnector plate.

[0040] Advantageously, such a configuration comprising contact inlays has shown to increase current density at the electrochemically active layers and to improve homogeneous current density distribution within the cell unit.

[0041] Preferably, the at least one contact inlay bridges the above-mentioned fluid volume defined between the support plate and the interconnector plate. Preferably, the at least one contact inlay abuts the support plate on a side of the support plate facing the interconnector plate, and abuts the interconnector plate on a side of the interconnector plate facing the support plate.

[0042] The at least one contact inlay may be loosely interposed between the support plate and the interconnector plate. For example, the at least one contact inlay may be held in compression between the support plate and the interconnector plate by attaching the periphery of the interconnector plate to the periphery of the support plate. Preferably, the at least one contact inlay is welded to one of the interconnector plate and the support plate, i.e. is connected to one of the interconnector plate or the support plate by a weld seam. Advantageously, this allows for a reliable electrical connection. Preferably, the at least one contact inlay is welded to the respective plate prior to assembling the cell unit. As such, the at least one contact inlay and the respective plate may be handled as single-piece during assembly, thus facilitating manufacturing of the cell unit.

[0043] Preferably, the at least one contact inlay is welded only to the interconnector plate. As such, thermal impact on the electrochemically active layers, e.g. by welding the contact inlay to the support plate, is reduced. In such embodiments, preferably, the respective contact inlay, preferably loosely, abuts the support plate on a side of the support plate that faces the interconnector plate.

[0044] The interconnector plate may comprise an electrically insulating coating on the side facing the support plate. In such embodiments, advantageously, the weld seam connecting the at least one contact inlay to the interconnector plate bridges the electrically insulating coating to form an electrical connection between the interconnector plate and the contact inlay.

[0045] The electrically insulating coating may be a single-layered coating. Alternatively, the electrically insulating coating may be a multi-layered coating, i.e. comprising several layers that are provided on top of each other. The electrically insulating coating may comprise a catalyst layer and / or an anti-corrosion layer. For example, the catalyst layer may comprise a reforming catalyst, for example configured to catalyse the reformation of a hydrocarbon fuel (e.g., methane) to hydrogen.

[0046] The contact inlay may take various shapes. The contact inlay or at least one of the contact inlays may be round-shaped. The contact inlay or at least one of the contact inlays may be square-shaped. The contact inlay or at least one of the contact inlays may be elongate extending in a longitudinal direction, preferably along at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90%, preferably the full length of the electrochemically active layers and / or the optional structured area of the interconnector plate in the longitudinal direction.

[0047] There may be provided a single contact inlay. There may be provided a plurality of contact inlays, said contact inlays being distributed over the central portion. There may be provided at least two contact inlays arranged in a row, preferably along the first direction. The contact inlay may be formed from different materials. Preferably, the contact inlay is formed from a metallic material, i.e. from metal or metal alloy, more preferably from steel, most preferably from chrome steel.

[0048] Preferably, the contact inlay is formed from a porous material. Advantageously, this improves fluid transport between the support plate and the interconnector plate, i.e., in the fluid volume.

[0049] More preferably, the at least one contact inlay is formed from metal foam, a perforated metal plate, or an expanded metal mesh.

[0050] In some preferred embodiments, the connection element, in particular the contact feature, is formed by a contact protrusion, preferably contact pin, connected to or integrally formed with the central portion of the support plate. Thus, the central portion of the support plate may comprise at least one, preferably elongated, contact protrusion, preferably in the form of a contact pin, said contact protrusion extending in a direction towards the interconnector plate. The at least one contact protrusion may be integrally formed with the support plate. Alternatively, the at least one contact protrusion may be attached to the support plate, preferably prior to attaching the support plate the interconnector plate, more preferably prior to forming the electrochemically active layers on the support plate. The at least one contact protrusion may be welded to the interconnector plate to form said at least one connection area. The at least one contact protrusion may be configured to bridge said fluid volume optionally formed between the central portion of the support plate and the central portion of the interconnector plate.

[0051] As set out above, in some embodiments, the central portion of the interconnector plate comprises a structured area having a plurality of (inward) protrusions, preferably in the form of dimples, protruding in a direction towards the support plate.

[0052] In some embodiments comprising such protrusions, at least a subset of said protrusions is electrically connected to the support plate to form said at least one connection area. Preferably, a connection element is provided between at least a subset of said protrusions and the support plate Thus, a contact feature, e.g. the aforementioned contact inlay, may be provided between said protrusions and the support plate to form said electrical connection. Alternatively, said protrusions may be welded to the support plate to form said electrical connection.

[0053] Thus, according to a fourth aspect, there is provided an electrochemical cell unit, preferably fuel cell unit or electrolyser cell unit, comprising a support plate having a periphery and a central portion surrounded by the periphery, the central portion of the support plate carrying electrochemically active layers, and an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein: the support plate and the interconnector plate are stacked upon one another along a stacking direction, such that the central portion of the support plate and the central portion of the interconnector plate overlay, the central portion of the interconnector plate comprises a structured area having a plurality of (inward) protrusions, preferably in the form of dimples, protruding in a direction towards the support plate, at least a subset of said protrusions is welded to the central portion of the support plate.

[0054] In addition, a different subset of protrusions may be electrically connected to the support plate merely by contacting the support plate, i.e. without being welded to the support plate or being electrically connected by an additional contact feature. Such electrical connection between the protrusions and the support plate is not considered a connection area within the meaning of the present disclosure.

[0055] In embodiments, in which the interconnector plate comprises an electrically insulating coating on the protrusions, the peaks of the protrusions or at least of a subset of said protrusions may be devoid of said coating. In this case, said protrusions or subset of protrusions may be electrically connected to the support plate at said peaks. For example, said peaks may be welded to the support plate. Alternatively, a contact medium, in particular, contact paste may be provided between said peaks and the support plate to form an electrical connection.

[0056] In some embodiments, the central portion, preferably the structured area, of the interconnector plate comprises one or more contact portions, said one or more contact portions being surrounded by said protrusions and having a different shape to said protrusions. In such embodiments, said one or more contact portions may be welded to the central portion of the support plate to form said electrical connection in said at least one connection area.

[0057] Thus, according to a fourth aspect, there is provided an electrochemical cell unit, preferably fuel cell unit or electrolyser cell unit, comprising a support plate having a periphery and a central portion surrounded by the periphery, the central portion of the support plate carrying electrochemically active layers, and an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein: the support plate and the interconnector plate are stacked upon one another along a stacking direction, such that the central portion of the support plate and the central portion of the interconnector plate overlap, the central portion of the interconnector plate comprises a structured area having a plurality of (inward) protrusions, preferably in the form of dimples, protruding in a direction towards the support plate, the central portion, preferably the structured area, of the interconnector plate additionally comprises at least one contact portion, said at least one contact portion being surrounded by said protrusions and having a different shape to said protrusions, said at least one contact portion is welded to the central portion of the support plate.

[0058] Advantageously, such a configuration allows for reliable electrical contact between the plates. In particular, adjusting a position of said at least one contact portion allows adjusting a current density distribution in the cell unit.

[0059] Preferably, said at least one contact portion has a flat profile compared to the protrusions. For example, the contact portion may be formed by a section of the interconnector plate that has not been processed to form protrusions. Preferably, a respective contact portion has a lateral extent perpendicular to the stacking direction larger than the lateral extent of a respective protrusion.

[0060] Advantageously, according to a general aspect applicable to all aspects, the electrochemically active layers may be interrupted, preferably have local cut-outs, at the connection areas (not shown in the figures). Thus, the support plate may be devoid of the electrochemically active layers at areas locally corresponding to the connection areas. This has proven particularly advantageous with regards to easy manufacturing of cell units, in which the connection areas are formed by welding the interconnector plate to the support plate. Furthermore, this enables that the active area is evenly utilized, which is especially beneficial with respect to growing cell size.

[0061] The invention also relates to a stack of cell units, comprising a plurality of electrochemical cell units as described above, said plurality of cell units being stacked upon one another along a (stack) stacking direction. The (stack) stacking direction corresponds to said (cell unit) stacking direction along which the support plate and the interconnector plate are stacked.

[0062] The advantages and optional features set out above in connection with the cell units are also applicable to the stack of cell units.

[0063] The invention also relates to a method of assembly of an electrochemical cell unit, preferably an electrochemical cell unit as described above. The method comprises the following steps, preferably in the order given below: providing a substrate unit comprising a support plate having a periphery and a central portion surrounded by the periphery, the central portion of the support plate preferably carrying electrochemically active layers, and providing an interconnector unit comprising an interconnector plate having a periphery and a central portion surrounded by the periphery, overlaying the substrate unit and the interconnector unit such that the central portion of the support plate and the central portion of the interconnector plate, and preferably the periphery of the support plate and the periphery of the interconnector plate, overlap; electrically connecting the central portion of the support plate to the interconnector plate at selected areas within said central portions, preferably by welding.

[0064] The advantages and optional features set out above in connection with the cell units are also applicable to the stack of cell units.

[0065] Preferably, the method further comprises, preferably prior to or simultaneously with electrically connecting the central portion of the support plate to the interconnector plate, attaching, preferably by welding, the periphery of the support plate to the periphery of the interconnector plate, preferably such that a fluid volume is enclosed between the central portion of the support plate and the central portion of the interconnector plate. In some embodiments, the substrate unit comprises one or more contact protrusions, preferably in the form of contact pins, said one or more contact protrusions being attached to the support plate on a side opposite the electrochemically active layers. In such embodiments, electrically connecting the central portion of the support plate to the interconnector plate may comprise welding said contact protrusions to the interconnector plate.

[0066] As set out above, said contact protrusions may be integrally formed with the support plate. Alternatively, providing the substrate unit may comprise attaching said contact protrusions, preferably contact pins, to the support plate and / or interconnector plate, e.g. by welding, and, preferably thereafter, forming (e.g. depositing or coating) the electrochemically active layers on the support plate.

[0067] In some embodiments, providing the interconnector unit comprises providing one or more contact inlays and attaching, preferably by welding said one or more contact inlays to the central portion of the interconnector plate.

[0068] Further embodiments are derivable from the following description and the drawings:

[0069] Figure 1 shows a perspective view of a stack of electrochemical cell units;

[0070] Figure 2 shows an exploded perspective top view of a cell unit of the stack of Figure 1 ;

[0071] Figure 3 shows an exploded perspective bottom view of the cell unit;

[0072] Figures 4A-D show schematic bottom views of a cell unit to illustrate different exemplary configurations of connection areas;

[0073] Figure 5 shows a schematic top view to illustrate an exemplary configuration of the electrochemically active layers;

[0074] Figure 6 shows a cross-sectional view of a cell unit according to a first embodiment;

[0075] Figure 7 shows a cross-sectional view of a cell unit according to a second embodiment;

[0076] Figure 8 shows a cross-sectional view of a cell unit according to a third embodiment;

[0077] Figure 9 shows a cross-sectional view of a cell unit according to a fourth embodiment.

[0078] Referring to Figure 1, there is shown an exemplary configuration of a stack 10 of cell units 12. The stack 10 comprises a plurality of electrochemical cell units 12 that are stacked upon one another along a stacking direction 14. The electrochemical cell units 12 may be fuel cell units or electrolyser cell units. Each cell unit 12 extends in a respective cell plane perpendicular to the stacking direction 14. Specifically, the cell units 12 extend in a respective first direction 16 (length direction) and a respective second direction 18 (width direction) that is perpendicular to the first direction 16.

[0079] In the following, an exemplary configuration of a cell unit 12 will be explained in more detail with reference to Figures 2 and 3.

[0080] The cell unit 12 comprises a support plate 20 having a periphery 22 and a central portion 24 surrounded by the periphery 22. The central portion 24 of the support plate 20 carries electrochemically active layers 26. In the example, the central portion 24 has a porous area 28 (see Fig. 3), and the electrochemically active layers 20 are deposited on said porous area 28.

[0081] The cell unit 12 further comprises an interconnector plate 30 having a periphery 32 and a central portion 34 surrounded by the periphery 32. The central portion 34 of the interconnector plate 30 comprises a structured area 36. The structured area 36 comprises a plurality of first (inward) protrusions 38 protruding towards the support plate 20 (see Fig. 2). In the example, the structured area 36 further comprises a plurality of optional second (outward) protrusions 40 protruding away from the support plate 20, i.e. in the opposite direction (see Fig. 3).

[0082] Figures 2 and 3 depict only a reduced number of protrusions 38, 40 for clarity of the Figures. It will be understood that there will typically be many more protrusions 38, 40 than those depicted.

[0083] The protrusions 38, 40 are typically pressed or formed in the sheet forming the interconnector plate 30. For example, a second protrusion 40 on one side of the interconnector plate 30, facing away from the support plate 20, typically forms a depression on the other side of the interconnector plate 30, facing towards the support plate 20 (and similarly for first protrusions 38). The first and second protrusions 38, 40 typically have a circular cross section. In this way, the protrusions 38, 40 may be referred to as dimples.

[0084] In the stack 10 of cell units 12, the second protrusions 40 of a given cell unit 12 typically contact the electrochemically active layers 26 of an adjacent / neighboring cell unit 12. In this way, electrical contact is provided between adjacent cell units 12 in the stack, while maintaining fluid passageways between the cell units 12 (i.e. between the protrusions 40). In the specific example, the interconnector plate 30 is configured tub-shaped. Thus, the interconnector plate 30 comprises a bottom 42 and a circumferential wall 44 between the bottom 42 and the periphery 32. In this example, the bottom 42 is configured flat and extends parallel to the cell plane. The circumferential wall 44 is angled with respect to the cell plane and with respect to the stacking direction 14. Thus, as shown in Fig. 2, the periphery 32 of the interconnector plate 30 is elevated with respect to the central portion 32 of the interconnector plate 30. In this regard, the periphery 32 of the interconnector plate 30 is also referred to as "flanged perimeter". It should be noted that instead of (or in addition to) the interconnector being tub-shaped, a spacer could be provided between the interconnector plate 30 and the support plate 20 to generate a fluid volume.

[0085] In the assembled cell unit 12 (see Figures 6 to 8), the support plate 20 and the interconnector plate 30 are stacked upon one another along the stacking direction 14 such that their central portions 24, 34, specifically the porous area 28 of the support plate 20 carrying the electrochemically active layers 26 and the structured area 36 of the interconnector plate 30, overlap.

[0086] The periphery 22 of the support plate 20 is preferably sealingly attached to the periphery 32 of the interconnector plate 30. Preferably, the periphery 22 of the support plate 20 is welded to the periphery 32 of the interconnector plate 30 around part or all of their perimeter. An exemplary configuration of such a weld seam 46 is schematically depicted in Figures 4A-D.

[0087] The central portion 24 of the support plate 20 and the central portion 34 of the interconnector plate 30 define or enclose a fluid volume 48 (internal cell volume, see Fig. 6) therebetween. The fluid volume 48 is in fluid communication with the electrochemically active layers 26 via said porous region 28. Thus, during operation of the cell unit 12 a fluid, e.g. a fuel, may exit the fluid volume 48 through pores formed in the porous area 28 and reach to a layer of the electrochemically active layers 26 that is closest to the support plate 20 (e.g. an anode layer, see above).

[0088] To transport fluid between the fluid volume 48 and the exterior of the cell unit 12, the cell unit 12 further comprises at least one fluid port. In the example, each cell unit 12 comprises one fluid inlet port 50 and one fluid outlet port 52 (see Fig. 1). The fluid inlet port 50 and the fluid outlet port 52 are formed by respective through-holes 54, 56 that extend through the cell unit 12 along the stacking direction 14 (in the example through the support plate 20 and the interconnector plate 30).

[0089] In the assembled stack 10 of cell units 12, the fluid inlet ports 50 and the fluid outlet ports 52 of the cell units 12 are aligned with each other along the stacking direction 14, thus forming a fluid inlet manifold or a fluid outlet manifold, respectively.

[0090] Referring to Figure 1 , it can be seen that the fluid inlet port 50 and the fluid outlet port 52 are located at opposite ends of the cell unit 12 with respect to the first direction 16. The central portion 241 porous area 28 of the support plate 20 and the central portion 341 structured area 36 of the interconnector plate 30 are located between the fluid inlet port 50 and the fluid outlet port 52. Thus, a fluid, e.g. a fuel, that flows from the fluid inlet port 50 to the fluid outlet port 52 through the fluid volume 38 may pass through the structured area 36 and reach to the electrochemically active layers 20 through the porous area 28.

[0091] In the stack 10, each fluid port 50, 52 preferably is associated with a respective gasket 58. In the assembled stack 10 of cell units 12, the gaskets 58 contribute to forming the fluid inlet manifold and the fluid outlet manifold and prevent loss of fluid between adjacent / neighbouring cell units 12.

[0092] As schematically depicted in Figure 4A, the support plate 20 and the interconnector plate 30 are electrically connected to each other in at least one connection area 60 within their central portions 24, 34 - in addition to an electrical connection via the weld seam(s) 46 connecting the peripheries 22, 32. The connection areas 60 are configured such that, seen along the stacking direction, a perimeter of a respective connection area 60 is within the perimeter of the electrochemically active layers 26 and the perimeter of the structured area 36.

[0093] Figures 4A-D depict several exemplary arrangements of such connection areas 60. For example, as shown in Figure 4A, there may be provided a plurality of round or oval-shaped connection areas 60 that are distributed over the central portion 34 of the interconnector plate 30.

[0094] Alternatively, as shown in Fig. 4B, there may be provided a single elongate connection area 60 that extends in a longitudinal direction 62 over about the length of the structured area 36 of the interconnector plate 30. Alternatively, as shown in Fig. 4C, there may be a single connection area 60 located in a center of the cell unit 12.

[0095] Alternatively, as shown in Fig. 4D, there may be provided two or more spatially separated connection areas 60 aligned in the first direction 16.

[0096] The invention, however, is not limited to those exemplary configurations. In other embodiments, various other configurations are conceivable.

[0097] As schematically shown in Figure 5, in some embodiments, the electrochemically active layers 26 may have local cut-outs 64 at the positions of the connection areas 60. The size of the cut-outs 64 may be slightly smaller or larger than the perimeter of the connection areas 60.

[0098] The or each connection area 60 may be formed in different ways. In the following, preferred examples will be described with reference to Figures 6 to 9.

[0099] Figure 6 schematically depicts a first embodiment, according to which a respective connection area 60 is formed by electrically connecting a respective peak 66 of one or more of the inward protrusions 38 to the central portion 24 of the support plate 20.

[0100] In the example shown, the peaks 66 of the protrusions 38 are welded to the support plate 20 to form said electrical connection (schematically illustrated by weld seams 68 in Figure 6). Alternatively, the peaks 66 of the protrusions 38 may be connected to the support plate 20 by a contact medium, e.g. an electrically conductive contact paste, provided between the peaks 66 and the support plate 20.

[0101] As set out above, the protrusions 38 may be coated with an electrically insulating coating (not shown), e.g. a catalytic coating for catalysing fuel decomposition. In such cases, preferably, the peaks of the protrusions are devoid of said coating, thus allowing for an electrically conductive path between the support plate 20 and the protrusions 38. For example, the electrically insulating coating may selectively be applied to the 'valleys' between adjacent protrusions 38 (i.e. the backsides of the outward protrusions 40).

[0102] Figure 7 schematically depicts a second embodiment, according to which the interconnector plate 30 comprises one or more flat contact portions 70 between the protrusions 38. In the example shown, the contact portion 70 is welded to the central portion 24 of the support plate 20 to form a connection area 60 (schematically illustrated by the weld seam 68 in Figure 7). Preferably, if an electrically insulating coating is provided on the side of the interconnector plate 30 facing the support plate 20, the contact portions 70 are devoid of such a coating. Alternatively, the weld seam 68 connecting the contact portion 70 and the support plate 20 may bridge the electrically insulating coating to form an electrical connection.

[0103] Figure 8 schematically depicts a third embodiment, according to which there are provided one or more contact inlays 72 in the fluid volume 48 between the central portion 24 of the support plate 20 and the central portion 34 of the interconnector plate 30, said one or more contact inlays 72 being electrically connected to both the central portion 24 of the support plate 20 and the central portion 34 of the interconnector plate 30. Thus, the contact inlay 72 defines a connection area 60.

[0104] Preferably, the contact inlay 72 is fixedly attached to the interconnector plate 30. More preferably, the contact inlay 72 is welded to the interconnector plate 39 (schematically illustrated in Fig. 8 by the weld seams 68), thus providing for electrical connection between the contact inlay 72 and the interconnector plate 30.

[0105] As shown in Fig. 8, the contact inlay 72 abuts the support plate 20, specifically the porous region 28, on a side facing the interconnector plate 30. The contact inlay, however, is not necessarily fixedly attached to the support plate 20.

[0106] In the example shown, the interconnector plate 30 comprises a flat portion 74 for receiving the contact inlay 72. In other embodiments, the contact inlay 72 may be interposed between the peaks 66 of the protrusions 38 and the support plate 20. In this case, the contact inlay 72 may be welded to the protrusions 38.

[0107] The contact inlay 72 may be formed from a metallic material, preferably from stainless steel. The contact inlay 72 may be formed from a porous material, e.g., such as a metal foam, a metal mesh or an expanded metal sheet.

[0108] The configuration as shown in Figure 8 is only exemplary. It will be understood that typically there are much more protrusions 38 and / or the contact inlay 72 has a lateral extent much larger than shown in Fig. 8. Figure 9 schematically depicts a fourth embodiment, according to which the support plate 20 comprises several contact protrusions 76 in the form of contact pins 78. The contact pins 78 extend elongate in the stacking direction 14 towards the interconnector plate 30. As shown in Figure 9, the contact pins 78 bridge the fluid volume 48 in the stacking direction 14.

[0109] As set out above, the contact pins 78 may be integrally formed with the support plate 20 or fixedly attached to the support plate 20, e.g. by welding. To provide for electrical connection with the interconnector plate 30, the contact pins 78 may be welded to the interconnector plate 30 (schematically illustrated in Fig. 8 by the weld seams 68), thus forming a connection area 60.

[0110] For the sake of clarity of the Figures, the contact pins 78 are depicted at positions locally corresponding to the peaks 66 of the protrusions 38. However, typically, there are much more protrusions 38 than contact pins 78. As such, typically, only a subset of the protrusions 38 is connected to a contact pin 78. In particular, the contact pins 78 may be much larger than the protrusions 38 in a lateral dimension.

Claims

Claims1. An electrochemical cell unit (12), preferably fuel cell unit or electrolyser cell unit, comprising a support plate (20) having a periphery (22) and a central portion (24) surrounded by the periphery (22), the central portion (24) of the support plate (20) carrying electrochemically active layers (26), and an interconnector plate (30) having a periphery (32) and a central portion (34) surrounded by the periphery (32), wherein: the support plate (20) and the interconnector plate (30) are stacked upon one another along a stacking direction (14), such that the central portion (24) of the support plate (20) and the central portion (34) of the interconnector plate (30) overlap, the central portion (24) of the support plate (20) and the central portion (34) of the interconnector plate (30) are electrically connected to each other in at least one connection area (60) within said central portions (24, 34), wherein an electrical connection element is provided at the connection area (60).

2. The electrochemical cell unit (12) according to claim 1, wherein, seen in the stacking direction (14), the at least one connection area (60) is at least in sections within a perimeter of the electrochemically active layers (26).

3. The electrochemical cell unit (12) according to claim 1 or 2, wherein the connection area (60) or at least one of the connection areas (60) is elongated extending in a longitudinal direction (62), preferably along at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90%, preferably the full length, of the electrochemically active layers (26) in the longitudinal direction (62).

4. The electrochemical cell unit (12) according to any preceding claim, wherein the electrical connection element comprises a weld (68) between the central portion (24) of the support plate (20) and the central portion (34) of the interconnector plate (30).

5. The electrochemical cell unit (12) according to any preceding claim, wherein the electrical connection element comprises at least one contact feature (72, 76) provided between the central portions (24, 34).

6. The electrochemical cell unit (12) according to claim 5, wherein said contact feature is formed by a contact inlay (72) that is interposed between and electrically connected to the central portion (24) of the support plate (20) and the central portion (34) of the interconnector plate (30).

7. The electrochemical cell unit (12) according to the preceding claim, wherein the at least one contact inlay (72) is connected to the interconnector plate (30) by a weld seam (68).

8. The electrochemical cell unit according to the preceding claim, wherein the interconnector plate (30) comprises an electrically insulating coating on the side facing the support plate (20), wherein the weld seam (68) bridges the electrically insulating coating to form an electrical connection between the interconnector plate (30) and the contact inlay (72).

9. The electrochemical cell unit (12) according to any one of claims 6 to 8, wherein the at least one contact inlay (72) is formed from a metallic material, preferably from a chrome steel.

10. The electrochemical cell unit (12) according to any one of claims 6 to 9, wherein the at least one contact inlay (72) is formed from a porous material.

11. The electrochemical cell unit (12) according to any one of claims 6 to 10, wherein the at least one contact inlay (72) is formed from metal foam, from a perforated metal plate, or from an expanded metal mesh.

12. The electrochemical cell unit (12) according to any one of the preceding claims, wherein the electrical connection element is formed by a contact protrusion (76), preferably contact pin (78), connected to or integrally formed with the central portion (24) of the support plate (20), said contact protrusion (76) extending in a direction towards the interconnector plate (30) and being welded to the interconnector plate (30).

13. The electrochemical cell unit (12) according to any one of the preceding claims, wherein the central portion (34) of the interconnector plate (30) comprises a structured area (36) having a plurality of protrusions (38), preferably in the form of dimples, protruding in a direction towards the support plate (20).

14. The electrochemical cell unit (12) according to the preceding claim, wherein at least some of said protrusions (38) are electrically connected to the support plate (20).

15. The electrochemical cell unit (12) according to claim 13 or 14, wherein at least some of said protrusions (38) are welded to the support plate (20) to form said electrical connection in said at least one connection area (60).

16. The electrochemical cell unit (12) according to any one of claims 13 to 15, wherein a contact inlay is provided between at least some of said protrusions (38) and the support plate (20) to form said electrical connection in said at least one connection area (60).

17. The electrochemical cell unit (12) according to any one of claims 13 to 16, wherein the interconnector plate (30) comprises an electrically insulating coating on the side facing the support plate (20), wherein the peaks (66) of at least some of the protrusions (38) are devoid of said coating, wherein said protrusions (38) are electrically connected to the support plate (20) at said peaks (66).

18. The electrochemical cell unit (12) according to any one of claims 13 to 17, wherein the central portion (34) of the interconnector plate (30) comprises at least one contact portion (70), said at least one contact portion (70) being surrounded by said protrusions (38) and being of different shape to said protrusions (38), wherein said at least one contact portion (70) is welded to the support plate (20).

19. The electrochemical cell unit (12) according to the preceding claim, wherein said at least one contact portion (70) has a flat extension compared to the protrusions20. The electrochemical cell unit (12) according to claim 18 or 19, wherein said protrusions (38) are formed by processing an original plate of the interconnector plate (30), wherein the at least one contact portion (70) is formed by an unprocessed portion of said original plate.

21. The electrochemical cell unit (12) according to any one of the preceding claims, wherein the electrochemically active layers (26) are interrupted, preferably have local cut-outs, at positions locally corresponding to the at least one connection area (60).

22. The electrochemical cell unit (12) according to any one of the preceding claims, wherein the cell unit (12) comprises at least one fluid inlet port (50) and at least one fluid outlet port (52), preferably in the form of through-holes (54, 56), wherein the at least one fluid inlet port (50) and the at least one fluid outlet port (52) are located at opposite ends of the cell unit (12) with respect to a first direction (16), wherein the central portions (24, 34) of the plates (20, 30) are located between the at least one fluid inlet port (50) and the at least one fluid outlet port (52).

23. A stack (10) of cell units, comprising a plurality of cell units (12) according to any one of the preceding claims, said plurality of cell units (12) being stacked upon one another along the stacking direction (14).

24. Method of assembly of an electrochemical cell unit (12), comprising: providing a substrate unit comprising a support plate (20) having a periphery (22) and a central portion (24) surrounded by the periphery (22), the central portion (24) of the support plate (20) preferably carrying electrochemically active layers (26), and an interconnector unit comprising an interconnector plate (30) having a periphery (32) and a central portion (34) surrounded by the periphery (32), overlaying the substrate unit and the interconnector unit such that the central portion (24) of the support plate (20) and the central portion (34) of the interconnector plate (30), and preferably the periphery (22) of the support plate (20) and the periphery (32) of the interconnector plate (30), overlap;electrically connecting the central portion (24) of the support plate (20) to the interconnector plate (30) at selected areas within said central portions (24, 34), preferably by welding.

25. The method according to the preceding claim, further comprising attaching, preferably by welding, the periphery (22) of the support plate (20) to the periphery (24) of the interconnector plate (30), preferably such that a fluid volume (48) is enclosed between the central portion (24) of the support plate (20) and the central portion (34) of the interconnector plate (30).

26. The method according to the preceding claim, wherein the substrate unit comprises one or more contact protrusions (76), preferably contact pins (78), attached to the support plate (20) on a side opposite the electrochemically active layers (26), wherein connecting the central portion (24) of the support plate (20) to the interconnector plate (30) comprises welding said contact protrusions (76) to the interconnector plate (30).

27. The method according to the preceding claim, wherein providing the substrate unit comprises attaching said contact protrusions (76) to the support plate (20) and, preferably thereafter, depositing the electrochemically active layers (26) on the support plate (20).

28. The method according to any one of claims 24 to 27, wherein providing the interconnector unit comprises providing one or more contact inlays (72) and welding said one or more contact inlays (72) to the central portion (34) of the interconnector plate (30).

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