Method of preparing a cell repeat unit for use in an electrochemical cell stack

Abstract

The invention relates to a method of preparing a cell repeat unit (18) for use in an electrochemical cell stack (10), the method comprising providing an electrochemical cell unit (28), said cell unit (28) having an inner fluid volume (44) and a cell opening (60) for transporting fluid between said inner fluid volume (44) and the exterior of the cell unit, providing a gasket being configured to surround the cell opening, and attaching said gasket to said cell unit by a hot melt adhesive dose (80). The invention also relates to a cell repeat unit and an electrochemical cell stack.

Description

[0001] Title: Method of preparing a cell repeat unit for use in an electrochemical cell stack

[0002] Specification

[0003] 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 a method of preparing a cell repeat unit for use in an electrochemical cell stack, a method of preparing an electrochemical cell stack, a cell repeat unit, and an electrochemical cell stack.

[0004] Fuel cells and electrolyser cells are examples of electrochemical cells. Fuel cells are energy conversion devices that allow for conversion of electrochemical fuel to electricity. Electrolyser cells are fuels cells running in reverse mode, i.e. using electricity to decompose a compound into its constituent parts, for example water into hydrogen and oxygen. Reversible cells are capable of operating in both modes. Such electrochemical cells typically comprise electrochemically active layers that 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).

[0005] The present invention specifically relates to solid oxide cells (SOCs). Such solid oxide cells (SOCs) typically comprise an electrolyte layer formed from a solid oxide, e.g. from Yttria-stabilized zirconia (YSZ), Gadolinia-doped Ceria, or Cerium Gadolinium Oxide (CGO). SOCs can be run as solid oxide fuel cell (SOFC) or as solid oxide electrolyser cell (SOEC).

[0006] Typically, multiple of such cell units are stacked upon one another in a stacking direction to form a "stack" of cell units, with gaskets being interposed between adjacent cell units to avoid loss of fluid. Such electrochemical cell stacks are known, for example, from WO 2020 / 126486 or WO 2022 / 175679.

[0007] It is an object of the present invention to facilitate and improve manufacture and stacking of the cell units. It is a further object of the invention to improve gasket sealing in the electrochemical cell stack.

[0008] According to the invention, there is provided a method of preparing a cell repeat unit. The cell repeat unit is configured for use in an electrochemical cell stack comprising a plurality of cell repeat units stacked upon one another in a stacking direction. The cell repeat unit comprises an electrochemical cell unit, preferably solid oxide fuel cell unit or solid oxide electrolyser cell unit, and a gasket attached to said cell unit.

[0009] The method comprises providing an electrochemical cell unit, preferably solid oxide fuel cell unit or solid oxide electrolyser cell unit. The electrochemical cell unit has an inner fluid volume (i.e., a fluid volume enclosed within the cell unit), and at least one cell opening for transporting fluid between said inner fluid volume and the exterior of the cell unit. Thus, the cell opening forms a fluid port of the cell unit. The method further comprises providing a gasket that is configured to surround said cell opening of the cell unit. The method further comprises attaching said gasket to said cell unit to form a cell repeat unit. The gasket is attached such that the gasket surrounds the cell opening of the cell unit. The step of attaching said gasket to said cell unit comprises applying, in particular dispensing, a hot melt adhesive dose to the gasket and / or to cell unit, and bonding the gasket to the cell unit by said hot melt adhesive dose.

[0010] As used herein, the term "dose" refers to a defined volume of the hot melt adhesive. The hot melt adhesive dose may be applied as a single portion (e.g., as a single glue bead) or as a plurality of portions (e.g., in the form of a plurality of glue beads). The plurality of portions (glue beads) may be spatially separated from each other.

[0011] A hot melt adhesive is also referred to as hot melt, hot glue, hot melt glue, or hot glue adhesive. Such hot melt adhesives are typically applied at elevated temperatures in a molten or liquefied state. During cooling, the hot melt adhesive solidifies, thus building strong cohesive forces between the objects to be bonded. Hot melt adhesives may include one or more of polymers, tackifying agents, plasticizers and waxes. Preferably, the hot melt adhesive is a thermoplastic adhesive.

[0012] The proposed method facilitates manufacturing of a cell repeat unit, and thus aids efficient manufacturing of electrochemical cell stacks. By attaching the gasket to the cell unit to form a cell repeat unit, stacking of the cell units and the gaskets to form an electrochemical cell stack is facilitated since the gasket and the cell unit may be handled as single piece. Specifically, the use of the hot melt adhesive has proven advantageous as it exhibits adhesive properties due to its tack, thus immediately forming a bond between the gasket. This has a great advantage over other glues (e.g. using UV-curable glues) which require an additional curing step before adhesion is secured. Nevertheless, hot melt adhesives allow for repositioning of the gasket due to its relatively large open time (time that it remains sticky). Furthermore, hot melt adhesives exhibit a relatively large pot life stability (i.e., the degree of stability in the molten state), which allows a reliable application of the hot glue even if a manufacturing process is stopped.

[0013] The cell unit may take various configurations. Preferably, the cell unit is a fuel cell unit or electrolyser cell unit. More preferably, the cell unit is a solid oxide cell unit, in particular solid oxide fuel cell unit or solid oxide electrolyser cell unit.

[0014] The cell unit may be configured flat or planar. The cell unit may have an elongated, preferably rectangular, footprint in the plane of its extent with opposing transversal sides and opposing longitudinal sides. In such embodiments, at least one, preferably at least two, cell opening may located at each transversal side.

[0015] The cell unit may comprise two or more layers, wherein the fluid volume is enclosed between said layers. In some examples, the cell unit may comprise a first plate, and a second plate, said first and second plates overlying one another and being, preferably sealingly, attached to each other to enclose a fluid volume (i.e. the inner fluid volume) therebetween. One or both of the first and second plates may be shaped to a concave configuration delimiting a concavity.

[0016] The cell opening may take various shapes. The cell opening may be a circular opening, i.e. having a circular footprint. The cell opening may be a rectangular or square opening, i.e. having a rectangular or square footprint. Preferably, the cell opening takes the form of a through-hole. The through-hole may extend from one side of the cell unit to an opposite side of the cell units. The through-hole may extend along a stacking direction of the cell repeat units. In embodiments, in which the cell unit comprises one or more layers or plates (e.g., a first and a second plate as set out above), the through-hole may extend through one or both, preferably through both, of said layers or plates.

[0017] The cell unit may have more than one cell opening, preferably a plurality of cell openings, for transporting fluid between the inner fluid volume and the exterior of the cell unit. The cell unit may have at least one inlet cell opening for supplying fluid to the inner fluid volume, and at least one outlet cell opening for removing fluid from the inner fluid volume.

[0018] In embodiments having more than one cell opening, the gasket may be configured to surround each of said cell openings. Thus, the gasket may be configured to surround several cell openings. Preferably, each cell opening is associated with its own gasket. Thus, in embodiments comprising more than one cell opening, the method may comprise providing a plurality of gaskets (preferably one for each cell opening in the cell unit), each gasket being configured to surround one of said cell openings. The step of attaching said gaskets to the cell unit may comprise - for each pair of associated cell opening and gasket - applying a hot melt adhesive dose and bonding the gasket to the cell unit such that the gasket surrounds the associated cell opening. The gasket may be bonded to a face (an external face) of the cell unit, said face not forming part of the inner fluid volume (e.g., said face is an opposite face of one of the layers or plates to a face which encloses the inner fluid volume).

[0019] The gasket(s) may take various shapes. Preferably, the gasket(s) comprises a gasket opening. In such embodiments, the gasket may be attached to the cell unit such that the cell opening of the cell unit and the gasket opening are aligned, preferably coaxially with each other. The gasket may be a sealing sheet comprising one or more gasket openings. Preferably, the gasket(s) takes the form of a sealing ring. The sealing ring comprises a gasket opening. The gasket opening and the cell opening in the cell unit may have the same footprint, in particular the same diameter. The gasket opening may be larger than the cell opening in the cell unit.

[0020] In some embodiments, the hot melt adhesive dose may be applied onto the gasket (prior to bonding the gasket to the cell unit). Alternatively, the hot melt adhesive dose may be applied onto the cell unit (prior to bonding the gasket to the cell unit). In even further embodiments, a first portion of the hot melt adhesive dose may be applied onto the gasket and a second portion of the hot melt adhesive dose may be applied onto the cell unit. In preferred embodiments, the hot melt adhesive dose is applied onto the cell unit and after that, the gasket is positioned on said hot melt adhesive dose. This eases manufacturing as it allows to apply hot melt adhesive to bond several gaskets in a single step. In other embodiments, the hot melt adhesive dose is applied onto the gasket, and, after that, the gasket with the hot melt adhesive applied thereon is placed onto the cell unit. The hot melt adhesive may be applied in different ways. For example, the holt melt adhesive may be jetted or sprayed onto the gasket and / or the cell unit. Preferably, the hot melt adhesive is applied using a dispenser, more preferably a microdispenser. Such a microdispenser allows for precise positioning of individual glue beads on the cell unit or gasket. The dispenser, preferably microdispenser, may be mounted to a manipulator, e.g. an x-y-(z)-stage.

[0021] The dispenser, preferably microdispenser, may comprise a heating zone (e.g. heating chamber or hot melt tank) for heating - and thus melting or liquefying - the hot melt adhesive, and a nozzle for dispensing the molten or liquefied hot melt adhesive. The dispenser may further comprise a conveyor device, e.g. pump, for conveying the molten or liquefied hot melt adhesive from the heating zone to the nozzle.

[0022] Preferably, the hot melt adhesive dose is applied in the form of at least one glue bead, preferably two or more spatially separated glue beads. This allows precise control of the bonding points between the gasket and the cell unit. In addition, material costs may be reduced. As used herein, the term "glue bead" refers to a defined volume of hot melt adhesive, wherein the volumes of the individual glue beads correspond in total to the hot melt adhesive dose. Thus, each glue bead may be a portion of the hot melt adhesive dose.

[0023] In embodiments, in which the hot melt adhesive dose is applied in the form of plural glue beads, each glue bead may have the same volume. Alternatively, the volume of the individual glue beads may vary between the plural glue beads.

[0024] Preferably, the or each glue bead has a volume of at least 0.02 cubic millimeters and / or at most 2.0 cubic millimeters. This range has proven advantageous with regards to reliable bonding between the gasket and the cell unit while keeping the overall amount of adhesive material low. In addition, the proposed volumes facilitate removal of the hot melt adhesive in the final electrochemical cell stack (see below).

[0025] Advantageously, the or each glue bead has a volume of at least 0.02 cubic millimeters, preferably at least 0.04 cubic millimeters, preferably at least 0.05 cubic millimeters, preferably at least 0.06 cubic millimeters, preferably at least 0.07 cubic millimeters, and / or at most 1.5 cubic millimeters, preferably at most 1.2 cubic millimeters, preferably at most 1.0 cubic millimeter, preferably at most 0.8 cubic millimeters.

[0026] The glue beads may be applied at different positions on the cell unit, in particular relative to the cell opening, and / or the gasket.

[0027] In some embodiments, the hot melt adhesive dose is applied in the form of at least two glue beads that are placed at opposite sides of the cell opening and the gasket is attached via said at least two glue beads. This symmetric arrangement allows for homogeneous pressure distribution in the gasket in the final electrochemical cell stack and thus improved sealing.

[0028] In other embodiments, the hot melt adhesive dose is applied in the form of at least three glue beads that are, preferably evenly, distributed around the cell opening, and the gasket is attached via said at least three glue beads.

[0029] Preferably, the or each glue bead is applied with an elongated shape. For example, the or each glue bead may take the form of an elongate strip of hot melt adhesive. Advantageously, the or each glue beads is applied with an elongate shape extending in a radially outward direction from the opening, and the gasket is attached via said at least one bead. This allows for an increased bonding area between the cell unit and the gasket, while keeping an amount of hot melt adhesive in close proximity to the cell opening small. As used herein "extending in a radially outward direction from the opening" may mean that the glue bead extend radially outwards from an edge of the cell opening or from a radially-spaced distance away from there (see also below).

[0030] In preferred implementations, the or each, preferably elongate, glue bead is applied such that it has a length of at least 1.0 millimeter, preferably at least 1.1 millimeters, preferably at least 1.2 millimeters, preferably at least 1.3 millimeters and / or at most 3.0 millimeters, preferably at most 2.5 millimeters, preferably at most 2.25 millimeters, preferably at most 2.0 millimeters.

[0031] In preferred implementations, the or each, preferably elongate, glue bead is applied such that it has a width of at least 0.2 millimeters, preferably at least 0.25 millimeters, preferably at least 0.3 millimeters and / or at most 0.8 millimeter, preferably at most 0.7 millimeters, preferably at most 0.6 millimeters, preferably at most 0.5 millimeters.

[0032] In preferred implementations, the or each, preferably elongate, glue bead is applied such that it has a height extending in the stacking direction of at least 0.1 millimeters, preferably at least 0.15 millimeters, preferably at least 0.2 millimeters and / or at most 0.7 millimeters, preferably at most 0.6 millimeters, preferably at most 0.5 millimeters, preferably at most 0.4 millimeters.

[0033] The or each glue bead may be applied such that an outer perimeter of the glue bead is flush with an edge of the cell opening. Preferably, however, the or each a glue bead is placed at a radial distance from an edge of the cell opening. This has proven advantageous with regards to reliable sealing since potential leaking paths due to the hot melt adhesive may be avoided. The "edge" of the cell opening may refer to the circumference of the cell opening.

[0034] In some embodiments, the hot melt adhesive dose, preferably the or each glue bead, may be applied onto the cell unit and / or to the gasket, such that when viewed onto the gasket fully covers the glue bead.

[0035] In preferred embodiments, the hot melt adhesive dose, preferably the or each glue bead, is applied to the cell unit and the gasket is positioned onto said glue bead such that the at glue bead extends past an outer perimeter of the gasket. Thus, in the attached configuration, the or each glue bead may comprise a protruding section that extends past the outer perimeter of the gasket. Preferably, the or each glue bead is applied such that it does not extend past an inner perimeter of the gasket. The inner and outer perimeter may also referred to as the inner and outer diameter of the gasket.

[0036] In preferred embodiments, the or each glue bead is placed around the cell opening maximizing a distance between the glue bead or glue beads and electrochemically active layers of the cell repeat unit. For example, in the case of one glue bead, the glue bead is positioned to an opposite side of the cell opening to the electrochemically active layers. For example, in the case of two glue beads, the glue beads are positioned to opposite sides of the cell opening (e.g., 180 degrees apart around the opening) and equidistant from the electrochemically active layers. Such positioning minimizes any possible spreading of the glue to the electrochemically active layers. According to a general aspect, the method may further comprise attaching additional components (additional to the gasket) to the cell unit using a hot melt adhesive. For example, the method may comprise attaching a flow restriction element to the cell unit. Specifically, the method may comprise providing a flow restriction element, and attaching said flow restriction element by hot melt adhesive. Thus, the hot melt adhesive may also be used to attach a flow restriction element to the cell unit. The advantages and optional features discussed above with respect to the attaching of the gasket (e.g. the application of the hot melt adhesive dose in the form of at least one glue bead as well as its shape and position) are also applicable for attaching the further components, e.g. such as the flow restriction element.

[0037] The flow restriction element may be configured to reduce or prevent fluid flow between adjacent cell units in an electrochemical cell stack. The flow restriction element may take the form of a strip. The flow restriction element may be formed from a vermiculite material or a fibre material.

[0038] According to a further general aspect, preferably, the cell unit comprises a support plate and an interconnector plate, said support plate and said interconnector plate overlying one another and being, preferably sealingly, attached to each other and enclose the inner fluid volume between them. Preferably, the support plate and the interconnector are formed from metal, preferably stainless steel. Preferably, the support plate carries electrochemically active layers. In preferred implementations, the support plate carries electrochemically active layers over a porous region such that the a layer of electrochemically active layers closest to the support plate is in fluidic communication with the inner fluid volume via said porous region.

[0039] In embodiments comprising a support plate and an interconnector plate, the cell opening may be formed by a through-hole extending through the support plate and the interconnector plate.

[0040] In embodiments comprising a support plate and an interconnector plate, the gasket may be attached to the support plate, preferably to a side (or face) of the support plate that faces away from the interconnector plate. Preferably, the hot melt adhesive dose is applied to the support plate, and the gasket is bonded to the support plate by said hot melt adhesive dose. Preferably, the hot melt adhesive dose is applied to a side of the support plate that is facing away from the interconnector plate. Alternatively, the gasket may be attached to the interconnector plate, preferably to a side of the interconnector plate that faces away from the support plate. Thus, the hot melt adhesive dose may be applied to the interconnector plate, preferably to a side of the interconnector plate that faces away from the support plate, and the gasket may be bonded to the interconnector plate by said hot melt adhesive dose.

[0041] The invention also relates to a method of manufacturing an electrochemical cell stack. The method comprises providing a plurality of cell repeat units prepared as described above, and overlying said cell repeat units along a stacking direction to form a stack of cell repeat units. Preferably, the cell repeat units are stacked upon one another such that the cell openings of adjacent cell units are aligned along the stacking direction. Preferably, the cell openings and the gasket openings align with each other and form a fluid manifold. Preferably, the gasket attached to one cell unit is in contact with the adjacent cell unit.

[0042] The method may further comprise providing a first end plate and a second end plate disposed to opposing ends of the stack of cell repeat units. Thus, the electrochemical cell stack may comprise a first end plate, a second end plate and a stack of cell repeat units arranged between the first end plate and the second end plate.

[0043] Preferably, the method further comprises compressing said stack of cell repeat units, preferably between the first end plate and the second end plate.

[0044] In some embodiments, the method may further comprise providing a housing around said stack of cell repeat units, such that the stack of cell repeat units is held in a compressed state. In embodiments comprising first and second end plates, the method may comprise connecting a housing to the first end plate and the second end plate (e.g., by welding) such that the stack of cell repeat units is held in a compressed state between the first end plate and the second end plate.

[0045] In some embodiments, the hot melt adhesive may at least partially be removed after stacking the cell repeat units. Removing the hot melt adhesive may comprise decomposing the hot melt adhesive.

[0046] Preferably, the step of removing the hot melt adhesive comprises heat-treating the stack of cell repeat units, e.g. by a hot conditioning or baking step, or in use of the stack. Such heat treatment may be at a temperature of at least 200 degrees C, preferably at least 300 degrees C, more preferably at least 400 degrees C. Thus, the hot melt adhesive may be "burned off" after stacking the cell repeat units. This further improves sealing of the cell stack. Preferably, the step of at least partially removing the hot melt adhesive is performed after compressing the stack of cell repeat units. In embodiments, in which a housing is provided around the stack of cell repeat units, the step of at least partially removing the hot melt adhesive preferably is performed prior to providing said housing.

[0047] The advantages and optional features described above in connection with the method of preparing the cell repeat unit apply equally to the method of preparing the electrochemical cell stack. Thus, in order to avoid unnecessary repetition, reference is made to the above disclosure.

[0048] The invention also relates to a cell repeat unit for use in an electrochemical cell stack. The cell repeat unit comprises an electrochemical cell unit, and a gasket attached to said cell units. Specifically, the cell unit has an inner fluid volume and a cell opening for transporting fluid between said inner fluid volume and the exterior of the cell unit. The gasket is attached to said cell unit via a hot melt adhesive dose such that the gasket surrounds said cell opening of the cell unit.

[0049] Preferably, the hot melt adhesive dose takes the form of at least one glue bead, preferably two or more spatially separated glue beads, and the gasket is attached to the cell unit via said at least one glue bead.

[0050] Preferably, the or each glue bead has a volume of at least 0.02 cubic millimeters and / or at most 2.0 cubic millimeters.

[0051] Preferably, the or each glue bead has a radial distance to an edge, i.e. a circumference, of the cell opening. Preferably, the at least one glue bead extends past an outer perimeter of the gasket.

[0052] Preferably, the hot melt adhesive dose takes the form of at least two glue beads placed at opposite sides of the cell opening. Thus, preferably, the gasket is attached to the cell unit via at least two glue beads placed at opposite sides of the cell opening. Preferably, the or each glue bead has an elongated shape. More preferably, the or each glue bead has an elongated shape extending in a radially outward direction from the opening.

[0053] Advantageously, the or each glue bead has a length of at least 1.0 millimeter and / or at most 3.0 millimeters and / or a width of at least 0.2 millimeters and / or at most 0.8 millimeters and / or a height extending in the stacking direction of at least 0.1 millimeters and / or at most 0.7 millimeters.

[0054] Preferably, the cell unit comprises a support plate and an interconnector plate, said support plate and said interconnector plate being connected to each other and enclosing the inner fluid volume between them. In such embodiments, the cell opening may be formed by a through-hole extending through the support plate and the interconnector plate. The gasket may be attached to the interconnector plate. The gasket may be attached to the support plate.

[0055] In some embodiments, the cell repeat unit may further comprise at least one flow restriction element, said at least one flow restriction element being attached to the cell unit via hot melt adhesive.

[0056] The additional advantages and optional features described above in connection with the method of preparing the cell repeat unit apply equally to the cell repeat unit. Thus, in order to avoid unnecessary repetition, reference is made to the above disclosure. Preferably, the cell repeat unit is prepared according to a method described above.

[0057] The invention also relates to an electrochemical cell stack comprising a plurality of cell repeat units as described above, said cell repeat units being stacked upon one another along a stacking direction such that the gaskets of the cell repeat units are positioned between neighboring cell unit.

[0058] Preferably, the cell stack is prepared according to the method described above. The optional features and advantages described in connection with the method of preparing an electrochemical cell stack apply equally to the electrochemical cell stack, such that reference is made to the above disclosure.

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

[0060] In the drawings: Fig. 1 shows a schematic perspective view of an example implementation of an electrochemical cell stack;

[0061] Fig. 2 shows a cross-sectional view of the electrochemical cell stack according to Figure 1;

[0062] Fig. 3 shows an exploded perspective view of an example implementation of a cell repeat unit;

[0063] Figure 4 shows a top view of the cell unit of Figure 3 to illustrate the bonding of the gaskets via hot melt adhesive;

[0064] Figure 5 shows a detail of Figure 4 in the region V;

[0065] Figure 6 shows a top view of an exemplary cell unit with a fluid blocking element; and

[0066] Figure 7 shows a flow chart illustrating a method of preparing an electrochemical cell stack.

[0067] Repeat use of reference symbols in the present specification and drawings is intended to represent the same or analogous features or elements.

[0068] Figures 1 and 2 show an example implementation of an electrochemical cell stack 10. The electrochemical cell stack 10 comprises a first end plate 12, a second end plate 14, and a stack 16 of cell repeat units 18 (hereinafter referred to as 'stack 16') arranged between the first end plate 12 and the second end plate 14. In particular, the stack 16 is held in a compressed state between the first end plate 12 and the second end plate 14.

[0069] Figures 1 and 2 are intended to primarily provide an overview of the electrochemical cell stack 10 and its components in general by way of example. The invention, however, is not limited to this specific design of the electrochemical cell stack 10.

[0070] In the example, the electrochemical cell stack 10 further comprises optional insulation plates 20 located between the end plates 12, 14 and the stack 16. The electrochemical cell stack 10 may further comprise one or more current transmission plates (not shown). The current transmission plates may be located between the insulation plates 20 and the stack 16.

[0071] The electrochemical cell stack may further comprise a housing 22 surrounding the stack 16 (see Figure 2, not shown in Figure 1). The housing 22 may be attached (e.g., by welding) to the end plates 12,14 and configured to maintain the stack 16 in a compressed state between the end plates 12, 14. The housing 22 and the end plates 12, 14 together may enclose a fluid volume 24 for first fluid around the stack 16. In fuel cell operation mode, preferably the first fluid is air or oxidant. During operation of the electrochemical cell stack 10, the fluid volume 24 may be supplied with first fluid via respective fluid ports provided in one of the end plates 12, 14 or in the housing 22 (not shown).

[0072] The stack 16 comprises a plurality of cell repeat units 18, which are stacked upon one another along a stacking direction 26. Each cell repeat unit 18 comprises an electrochemical cell unit 28, and at least one gasket 30 attached to the cell unit 28.

[0073] As set out above, the electrochemical cell units 28 may be fuel cell units, electrolyser cell units or reversible cell units comprising electrochemically active layers. A preferred configuration of an electrochemical cell unit 28 will be described below with respect to Figures 2 and 3.

[0074] As shown in Figure 3, the electrochemical cell unit 28 comprises a support plate 32 (also referred to as substrate) and an interconnector plate 34 (also referred to as interconnect or separator plate), which are stacked upon each other along the stacking direction 26. Preferably, the support plate 32 and the interconnector plate 34 are formed from metal, more preferably stainless steel.

[0075] The support plate 32 and the interconnector plate 34 each have a periphery 36, 38 and a central portion 40, 42 surrounded by the periphery 36, 38. The support plate 32 and the interconnector plate 34 are attached to each other at their peripheries 36, 38, preferably by welding, to enclose an inner fluid volume 44 therebetween.

[0076] In the example, the support plate 32 is a flat component. The support plate 32, in its central portion 40, carries electrochemically active layers 46 over a porous region (not visible in Figure 3). The electrochemically active layers 46 (specifically, a layer of the electrochemically active layers 46 which is closest to the support plate 32) are in fluidic communication with the inner fluid volume 44 via said porous region.

[0077] In the specific example, the interconnector plate 34 is tub-shaped having flanged perimeter features 50 around its periphery 38, preferably formed by pressing the interconnector plate 34 to a concave configuration. As can be seen from Figure 3, the flanged perimeter features 50 extend out of the predominant plane of the interconnector plate 34 to create a concavity (and a convexity to the outside surface) in the interconnector plate 34. In the assembled state of the cell unit 28, said concavity forms the fluid volume 44 enclosed between the interconnector plate 34 and the support plate 32.

[0078] In the specific example, the interconnector plate 34 has a structured area 52 in its central portion 42. Specifically, the interconnector plate 34 has optional shaped inward protrusions 54 extending into the fluid volume 44. The inward protrusions 54 form a supporting structure helping to maintain the fluid volume 44 (cell space) open. The inward protrusions 54 define fluid passageways therebetween. Preferably, the inward protrusions 54 abut the support plate 32.

[0079] In the example, the interconnector plate 34, in its structured area 52, further comprises shaped outward projections 56 (see also Figure 2). Said outward projections 56 form contact portions of the cell unit 28 for contacting an adjacent cell unit 28, specifically (an outermost layer of) the electrochemically active layers 46 of an adjacent cell unit 28. More specifically, the outward projections 56 engage at their ends against an outer surface of the electrochemically active layer 46 of an adjacent cell unit 28. The outward projections 56 define fluid passageways 58 for first fluid (e.g., air or oxidant) to flow between adjacent cell units 28 (see Figure 2).

[0080] In order to supply (second) fluid (e.g., fuel) to the inner fluid volume 44 between the support plate 32 and the interconnector plate 34 (and thus to the electrochemically active layers 46) or to remove fluid from said fluid volume 44, each cell unit 28 has at least one, in the specific example four, cell openings 60 in the form of through-holes 62 formed therein. The cell openings 60 form fluid ports for transporting (second) fluid between the inner fluid volume 44 and the exterior of the cell unit 28.

[0081] In the specific example, the interconnector plate 34 and the support plate 32 each have four through- holes 62 formed therein, wherein each through-hole 62 in the interconnector plate 34 is associated with a through-hole 62 in the support plate 32, said associated through-hole being aligned with the stacking direction 26. As set out above, each cell repeat unit 18 comprises at least one gasket 30. In the illustrated example, each cell opening 60 is associated with one gasket 30 surrounding it.

[0082] Preferably, the gaskets 30 are annular sealing rings having an outer perimeter 70 and an inner perimeter 72, said inner perimeter 72 defining a gasket opening 68. In other embodiments, the gasket 30 may take different shapes.

[0083] In the example, the gaskets 30 are attached to the support plate 32 on the side (or face) carrying the electrochemically active layers 46 (i.e., on the side facing away from the interconnector plate 34). In other examples, the gaskets 30 may be attached to the interconnector plate 34.

[0084] As shown in Figure 4, the gaskets 30 preferably are attached to the support plate 32 such that the gasket opening 68 and the associated cell opening 60 (through-hole 62 formed in the support plate 32) are aligned, preferably coaxially with each other.

[0085] The gaskets 30 may be made of various materials. Preferable, the gasket are formed from a vermiculite material or a rubber material.

[0086] Referring to Figure 2, it can be seen that an aligned column of the gasket openings 68 and the cell openings 60 (through-holes 62) of the stacked cell units 28 forms a fluid manifold 74 extending throughout the stack 16 along the stacking direction 26. In the illustrated example, the stack 16 comprises two fluid manifolds 74 serving as fluid inlet manifolds and two fluid manifolds 74 serving as fluid outlet manifolds 54 (exhaust manifolds).

[0087] Each fluid manifold 74 may be in fluidic communication with an associated fluid access port 76 formed in at least one of the end plates 12, 14 for transporting second fluid between the fluid channel 74 and an exterior of the cell stack 10. In the example, the first end plate 14 comprises the fluid access ports 76, each being formed by a respective through-hole 78 formed in the end plate 12 (see Figure 2). In the example, the fluid access ports 76 in the end plate 12 are in fluidic communication with the associated fluid channel 74 via a flow path extending through the neighbouring insulation plate 20. As schematically illustrated in Figures 3 to 5, the gaskets 30 are attached to the cell unit 28 by a hot melt adhesive 80 applied in the form of a plurality of glue beads 82.

[0088] In the specific example, each of the gaskets 30 is attached to the cell unit 28 (specifically, the support plate 32) via two glue beads 82 that are applied at opposite sides of the associated cell opening 60. In other examples, each of the gaskets 30 may be attached by more or less glue beads 82.

[0089] Advantageously, the glue beads 82 are applied with an elongated shape. In particular, the glue beads 82 are applied with an elongated shape extending in a radially outward direction 84 (see Figure 4) from the cell opening 60. In other examples, the glue beads 82 may take a different shape, e.g. a dot or a square.

[0090] Advantageously, each glue beads 82 may be applied with a volume of at least 0.02 cubic millimeters. Preferably, each glue bead 82 has a length 86 of at least 1 millimeter and at most 3 millimeters, a width 88 of at least 0.2 millimeters and at most 0.8 millimeters, and a height of at least 0.1 millimeters and at most 0.7 millimeters.

[0091] As can be seen from Figure 5, preferably, each glue bead 82 is placed at a distance 90 to an edge 92 of the cell opening 60 (viewed in radial direction 84 from the center of the cell opening 60). In the example, each glue bead 82 is applied such that it extends in the radial direction 84 past the outer perimeter 70 of the associated gasket 30 with a protruding section 94. In other examples, the gasket 30 may fully cover the associated glue beads 82.

[0092] As set out above, the hot melt adhesive dose 80, specifically the plurality of glued beads 82, may be applied using a microdispenser.

[0093] Preferably, the glue beads 82 are applied onto the support plate 32, and the gaskets 30 are then placed onto the glue beads 82. In other examples, the hot melt adhesive 80 may be applied to the gaskets 30 and the gaskets 30 may then be placed onto the support plate 32.

[0094] In a similar way, further components may be attached to the cell unit 28 by hot melt adhesive 80. Figure 6 shows an example implementation, in which two flow restriction elements 96 are attached to the support plate 32 by hot melt adhesive 80. In the specific example, each flow restriction element 96 takes the form of a strip of a fluid blocking material attached to the periphery 36 of the support plate 32 and extending along long sides 64-1, 64-2 of the cell unit.

[0095] As described above in connection with the gaskets 30, the hot melt adhesive 80 may be applied in the form of several spatially separated glue beads 82.

[0096] When the corresponding cell repeat units 18 are stacked on top of each other, the gaskets 30 and the flow restriction elements 96 of one cell repeat unit 18 preferably contact the neighboring cell repeat unit 18.

[0097] Figure 7 shows a flow chart of a method to prepare an electrochemical cell stack 10. The method comprises a step 100 of providing a plurality of cell repeat units 18 as described above. The method further comprises a step 102 of overlying the said cell repeat units 28 along a stacking direction 26 to form a stack 16 of cell repeat units 28, such that the cell openings 60 of the adjacent cell repeat units 18 align with each other and - together with the gasket openings 68 - form the above-described fluid manifolds 74.

[0098] Optionally, the method further comprises a step 104 of compressing said cell stack 16, in particular between a first end plate 12 and a second end plate 14;

[0099] Optionally, the method further comprises a step 106 of at least partially removing the hot melt adhesive, e.g. by heat-treating the stack 16 of cell repeat units 28.

[0100] Optionally, the method further comprises a step 108 of proving a housing 22 around the stack of cell repeat units 18. The housing 22 may be connected to the first end plate 12 and the second end plate 14, if provided, such that the stack 16 of cell units 18 is maintained in its compressed state.

Claims

Claims1. Method of preparing a cell repeat unit (18) for use in an electrochemical cell stack (10), the method comprising:- providing an electrochemical cell unit (28), preferably fuel cell unit or electrolyser cell unit, said cell unit (28) having an inner fluid volume (44) and a cell opening (60) for transporting fluid between said inner fluid volume (44) and the exterior of the cell unit (28);- providing a gasket (30), said gasket (30) being configured to surround the cell opening (60) of the cell unit (28),- attaching said gasket (30) to said cell unit (28) such that the gasket (30) surrounds the cell opening (60), wherein attaching said gasket (30) to said cell unit (18) comprises applying a hot melt adhesive dose (80) to the gasket (30) and / or to cell unit (28), and bonding the gasket (30) to the cell unit (28) by said hot melt adhesive dose (80).

2. The method according to claim 1, wherein the hot melt adhesive dose (80) is applied onto the cell unit (28) and after that, the gasket (30) is positioned on said hot melt adhesive dose (80).

3. The method according to any one of the preceding claims, wherein the hot melt adhesive dose (80) is applied using a microdispenser.

4. The method according to any one of the preceding claims, wherein the hot melt adhesive dose (80) is applied in the form of at least one glue bead (82), preferably two or several spatially separated glue beads (82).

5. The method according to the preceding claim, wherein the or each glue bead (82) has a volume of at least 0.02 cubic millimeters and / or at most 2.0 cubic millimeters.

6. The method according to claim 4 or 5, wherein the hot melt adhesive dose (80) is applied in the form of at least two glue beads (82) that are placed at opposite sides of the cell opening (60).

7. The method according to any one of claims 4 to 6, wherein the hot melt adhesive dose (80) is applied in the form of at least three glue beads (82) that are evenly distributed around the cell opening (60).

8. The method according to any one of claims 4 to 7, wherein the or each glue bead (82) is applied with an elongated shape, preferably extending in a radially outward direction (84) from the cell opening (60).

9. The method according to any one of claims 4 to 8, wherein the or each glue bead (82) has a length (86) of at least 1.0 millimeter and / or at most 3.0 millimeters and / or a width (88) of at least 0.2 millimeters and / or at most 0.8 millimeters and / or a height extending in the stacking direction (20) of at least 0.1 millimeters and / or at most 0.7 millimeters.

10. The method according to any one of claims 4 to 9, wherein the or each a glue bead (82) is placed at a distance (90) from an edge (92) of the cell opening (60).

11. The method according to any one of claims 4 to 10, wherein the at least one glue bead (82) is applied to the cell unit (28), and the gasket (30) is positioned onto said at least one glue bead (82) such that the at least one glue bead extends past an outer perimeter (70) of the gasket (30).

12. The method according to any one of claims 4 to 11, wherein the or each glue bead is placed around the cell opening maximizing a distance between the glue bead or glue beads and electrochemically active layers of the cell repeat unit.

13. The method according to any one of the preceding claims, further comprising:- providing a flow restriction element (96);- attaching said flow restriction element (96) by hot melt adhesive.

14. The method according to any one of the preceding claims, wherein the cell unit (28) comprises a support plate (32) and an interconnector plate (34), said support plate (32) and said interconnector plate (34) being connected to each other and enclosing the fluid volume (44)between them, wherein the gasket (30) is attached to the support plate (32), preferably to a side of the support plate (32) that is facing away from the interconnector plate (34).

15. Method of manufacturing an electrochemical cell stack (10), comprising:- providing a plurality of cell repeat units (18) prepared according to a method according to any one of the preceding claims;- overlying said cell repeat units (18) along a stacking direction (26) to form a stack (16) of cell repeat units (18), such that the cell openings (60) of adjacent cell units (28) are aligned along the stacking direction (26).

16. The method according to the preceding claim, further comprising: compressing said cell stack (10), preferably between a first end plate (12) and a second end plate (14).

17. The method according to claim 15 or 16, further comprising: at least partially removing, preferably decomposing, the hot melt adhesive (80), preferably by heat-treating the stack (16) of cell repeat units (18).

18. A cell repeat unit (18) for use in an electrochemical cell stack (10), comprising:- an electrochemical cell unit (28), said cell unit (28) comprising an inner fluid volume (44) and a cell opening (60) for transporting fluid between said inner fluid volume (44) and the exterior of the cell unit (28);- a gasket (30) attached to said cell unit (28) such that the gasket (30) surrounds the cell opening (60) of the cell unit (28), wherein, the gasket (30) is attached to said cell unit (28) via a hot melt adhesive dose (80).

19. The cell repeat unit (18) according to the preceding claim, wherein the hot melt adhesive dose (80) takes the form of at least one glue bead (82), preferably two or more spatially separated glue beads (82).

20. The cell repeat unit (18) according to the preceding claim, wherein the or each glue bead (82) has a volume of at least 0.02 cubic millimeters and / or at most 2.0 cubic millimeters.

21. The cell repeat unit (18) according to claim 19 or 20, wherein the or each glue bead (82) has a radial distance (90) to an edge (92) of the cell opening (60).

22. The cell repeat unit (18) according to any one of claims 19 to 21, wherein the at least one glue bead (82) extends past an outer perimeter (70) of the gasket (30).

23. The cell repeat unit (18) according to any one of claims 19 to 22, wherein the hot melt adhesive dose (80) takes the form of at least two glue beads (82) placed at opposite sides of the cell opening (60).

24. The cell repeat unit (18) according to any one of claims 19 to 23, wherein the or each glue bead (82) has an elongated shape, preferably extending in a radially outward direction (84) from the cell opening (60).

25. The cell repeat unit (18) according to any one of claims 19 to 24, wherein the or each glue bead (82) has: a length (86) of at least 1.0 millimeter and / or at most 3.0 millimeters and / or a width (88) of at least 0.2 millimeters and / or at most 0.8 millimeters and / or a height extending in the stacking direction (26) of at least 0.1 millimeters and / or at most 0.7 millimeters.

26. The cell repeat unit (18) according to any one of claims 18 to 25, wherein the cell unit (28) comprises a support plate (32) and an interconnector plate (34), said support plate (32) and said interconnector plate (34) being connected to each other and enclosing the cell volume (44) between them.

27. The cell repeat unit (18) according to the preceding claim, wherein the gasket (30) is attached to the support plate (32).

28. The cell repeat unit (18) according to any one of claims 18 to 27, further comprising at least one flow restriction element (96), said at least one flow restriction element (96) being attached to the cell unit (18) via hot melt adhesive (80).

29. The cell repeat unit (18) according to any of claims 18 to 28, wherein the cell repeat unit (18) is prepared according to any one of claims 1 to 14.

30. An electrochemical cell stack (10) comprising a plurality of cell repeat units (18) according to any one of claims 18 to 29, said cell repeat units (18) being stacked upon one another along a stacking direction (26).

31. The electrochemical cell stack (10) according to the preceding claim, wherein the cell stack (10) is prepared according to any of claims 15 to 17.

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