Method of assembly of an electrochemical cell unit and electrochemical cell unit

Abstract

The invention relates to methods of assembly of an electrochemical cell unit as well as to electrochemical cell units. The invention also relates to a stack of cell units.

Description

[0001] Title : Method of assembly of an electrochemical cell unit and electrochemical cell unit

[0002] Specification

[0003] The invention relates to the field of electrochemical cell units , in particular, fuel cell units and electrolyser cell units . More speci fically, the invention relates to a method of assembly of an electrochemical cell unit and an electrochemical cell unit .

[0004] Fuel cells and electrolyser cells are examples of electrochemical cells . Fuel cells are energy conversion devices that allow for conversion of fuel to electricity . Electrolyser cells may be considered fuels cells running in reverse mode , i . e . using electricity to decompose a compound into its constituent parts , for example H2O 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 ) . 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) .

[0005] The electrochemical layers may be arranged in layers on a mechanical support plate, e.g. on a metal plate (so-called "metal-supported electrochemical cells") . Such cells typically also comprise an interconnector plate overlying the support plate on a side that is facing away from the electrochemical layers, such that an inner fluid volume (cell space) is enclosed between the support plate and the interconnector plate. The fluid volume serves to supply operating fluid (e.g. fuel in case of fuel cells) to the electrochemically active layers. For this, the support plate may have a porous region below the electrochemical layers such that fluid (e.g. fuel in case of fuel cells) may pass through the pores from the fluid volume to the electrochemical layers. In order to supply fluid to the cell space, the cell unit may comprise one or more fluid ports, e.g. in the form of through-holes.

[0006] Examples of such electrochemical cell units are known e.g. from WO 2020 / 126486 Al or WO 2021 / 110539 Al.

[0007] Typically, multiple of such cell units are stacked upon one another to form a "stack" of cell units, also referred to as ' cell repeat units ' . A housing may be provided around said electrochemical cell stack to form a stack enclosure defining a second fluid volume , e . g . for air or oxidant in case of fuel cell operation .

[0008] The present invention seeks to ease manufacture and increase performance of an electrochemical cell unit .

[0009] According to the invention, there is provided a method of assembly of an electrochemical cell unit , preferably of a fuel cell unit or electrolyser cell unit , according to claim 1 . The method comprises , preferably in the order as stated : a) providing a support plate ( also referred to as substrate ) , preferably metal support plate , and an interconnector plate ( also referred to as separator plate or interconnect ) , preferably metal interconnector plate . Each of the support plate and the interconnector plate has a periphery and a central portion surrounded by the periphery . At least one of the support plate and the interconnector plate has a weakening line formed therein that extends around part or all of its periphery, preferably through the periphery in a circumferential direction . Said weakening line defines a border section between the weakening line and an external perimeter of the respective plate . Thus , the weakening line divides the periphery of the respective plate into a radially inner section and a radially outer section (border section) . That is , the weakening line is spaced apart from the external perimeter of the respective plate . The peripheries and, in particular, the border section may form a clamping section for clamping the plate or plates during assembly, preferably during attaching the plates ; b) overlying the interconnector plate and the support plate over one another, preferably such that the periphery of the interconnector plate and the periphery of the support plate overly one another . Preferably, the interconnector plate and the support plate are overlaid in a stacking direction, wherein the plates extend perpendicular to said stacking direction . c) attaching ( directly or indirectly) the support plate and the interconnector plate to each other, preferably at their peripheries . During attaching, the support plate and / or the interconnector plate may be clamped, e . g . by a holding bracket , to keep the plates in place .

[0010] Preferably, the plate or plates having the weakening line is clamped at the border section during attaching . ; d) removing the border section of the plate or plates having the wakening line . Thus , the border section is detached from the respective plate .

[0011] The proposed method facilitates a j oining process of the two plates as it allows for larger handling portion, in particular clamping portion, during the attaching step, while - after removing the border section - keeping a footprint of the cell unit , e . g . in a stack of cell units , low . This results in a larger power density . Preferably, the support plate carries cell chemistry layers ( also referred to as electrochemically active layers ) in its central portion, preferably over a porous region ( see below) . Thus , the central portion may form an " active" area of the cell units . The periphery on the other hand may be a "non-active" area of the cell unit . Thus , removing the border section, i . e . part of the periphery, reduces a footprint of "non-active" area resulting in a higher power density .

[0012] The weakening line facilitates removal of the border section ( e . g . clamping part ) after the j oining process and allows for a clean cut . Preferably, the weakening line forms a predetermined breaking point for removing the border section .

[0013] Removing the border section may be performed in di f ferent ways . Preferably, removing the border section comprises breaking, punching or stamping the border section along the weakening line . These are simple processes that require low investment and can be run at low operation costs . Removing the border section may also be performed by laser cutting

[0014] Preferably, the support plate and the interconnector plate are attached to each other at their peripheries , preferably around part or all of their peripheries .

[0015] The support plate and the interconnector may be attached to each other in di f ferent ways . Preferably, the support plate and the interconnector plate are attached to each other by welding. Thus, attaching the interconnector plate and the support plate to each other may comprise welding the support plate to the interconnector plate. Alternatively or in addition, the support plate and the interconnector plate may be attached to each other by brazing.

[0016] The support plate and the interconnector plate may be attached, preferably welded, at points. In preferred embodiments, the support plate is attached to the interconnector plate (in the step c) of attaching) along a joint line. Preferably, the joint line extends around part or all of their peripheries, more preferably around the entire perimeter. The support plate and the interconnector plate may be joined by multiple, spatially separated, joining points along the trace of the joint line. Alternatively, the support plate and the interconnector plate may be attached continuously along the trace of the joint line. In embodiments, in which welding is used to attach the support plate and the interconnector plate, the joint line may be a weld line (line weld seam) .

[0017] Preferably, the support plate is attached to the interconnector plate, such that the weakening line is located between the joint line, preferably line weld seam, and the external perimeter of the plate or plates having the weakening line. Thus, preferably the support plate is attached to the interconnector plate such that the joint line is located between the weakening line and the central portion of the respective plate. In preferred embodiments , the support plate is attached to the interconnector plate such that the j oint line is within 1 mm, more preferably within 0 , 5 mm, of the weakening line . This allows for a particularly small footprint ( and therefore improved power density of the cell unit ) while maintaining the stability of the j oint line .

[0018] In some embodiments , only one of the support plate and the interconnector plate has a weakening line formed therein . For example , only the support plate may have a weakening line . Thus , only the support plate may have a border section that is removed after attaching the support plate to the interconnector plate .

[0019] Alternatively, only the interconnector plate may have a weakening line . Thus , only the interconnector plate may have a border section that is removed after attaching the support plate to the interconnector plate .

[0020] Alternatively, each of the support plate and the interconnector plate ( and optionally the spacer plate , see below) has a weakening line formed therein . Thus , each plate may have a border section . In such embodiments , step d) described above may comprise removing the border section of the interconnector plate and removing the border section of the support plate ( and optionally removing the border section of the spacer plate ) .

[0021] In embodiments , in which both the support plate and the interconnector plate have a weakening line , preferably, the support plate and the interconnector plate ( in step b ) ) are overlaid over one another such that the weakening line of the support plate and the weakening of the interconnector plate overlap, in particular overlie one another ( similarly in cases where there is provided a spacer between the interconnector plate and the support plate ) . This facilitates removal of the border sections and allows for a clean cut , resulting in a smooth edge portion after removal .

[0022] The weakening line may be formed in di f ferent ways .

[0023] Preferably, the support plate and / or the interconnector plate has a material weakening extending along the trace of the weakening line .

[0024] In some embodiments , the weakening line is formed by a plurality of perforations formed in the respective plate ( i . e . in the support plate and / or in the interconnector plate ) along the trace of the weakening line . The perforations may be formed by laser-drilling . The perforations may be formed by through-holes . The perforations may be formed by blind holes .

[0025] Alternatively, the weakening line may be formed by a notch or groove formed in a surface of the respective plate along the trace of the weakening line . The notch may be formed by pressing the respective plate . The notch may be V-shaped .

[0026] Alternatively, the weakening line may be formed by the respective plate having a locally reduced material thickness along the trace of the weakening line . The locally reduced material thickness may be formed by pressing or embossing the respective plate .

[0027] In some embodiments , providing the at least one of the support plate and the interconnector plate having the weakening line ( step a ) ) comprises processing the respective plate to form the weakening line . In other words , providing the at least one of the support plate and the interconnector plate having the weakening line ( step a) ) comprises forming the weakening line in the respective plate or plate .

[0028] The type of processing may vary depending on the desired configuration of the weakening line . In some embodiments , processing the plate to form the weakening line may comprise laser-drilling the plate . Alternatively or in addition, processing the plate to form the weakening line may comprise pressing the plate . Alternatively or in addition, processing the plate to form the weakening line may comprise embossing the plate .

[0029] In some embodiments , the support plate is directly attached to the interconnector plate , preferably by welding . Thus , the interconnector plate and the support plate may be directly adj oined . In such embodiments , the support plate and the interconnector plate may abut ( i . e . are in touchcontact with) one another . Preferably, the support plate and the interconnector plate are directly attached to each other at their peripheries , in particular along a j oint line extending along part or all of their peripheries. Thus, the support plate and the interconnector plate may abut (i.e. are in tough-contact with) one another at their peripheries .

[0030] Alternatively, the support plate may be indirectly attached to the interconnector plate, e.g. via an additional component sandwiched between the interconnector plate and the support plate (e.g. by a spacer or spacer plate described below) . Thus, the support plate and the interconnector plate may not be in tough-contact with one another. For example, a weld line around the perimeter of the cell unit may pass through a component (e.g. gasket or spacer, see below) disposed between the support plate and the interconnector plate.

[0031] In some embodiments, the support plate and / or the interconnector plate, preferably only the interconnector plate, comprises inherent shaped features (for example, flanged perimeter features) that create a fluid volume in the cell unit. As set out above, in the assembled cell unit, the fluid volume may be in fluid communication with cell chemistry layers, e.g. via a porous region formed in the support plate.

[0032] In preferred embodiments, at least one of the support plate and the interconnector plate, preferably only the interconnector plate, comprises flanged perimeter features around part or all of its periphery. Preferably, the periphery of at least one of the support plate and the interconnector plate is formed by a circumferential flange portion .

[0033] Preferably, the flanged perimeter features extend out of a predominant plane of the respective plate (support plate and / or interconnector plate) . Thus, in the assembled state, preferably the flanged perimeter features formed in one of the plates extend toward the other plate (and vice versa if both plates, support plate and interconnector plate, are provided with a flanged perimeter feature) .

[0034] In particular, the flanged perimeter features extend out of a predominant plane of the respective plate such that a concavity (and a convexity to the outside surface) is formed, said concavity forming a fluid volume. Thus, the flanged perimeter features may be configured such that a fluid volume is bordered by the flanged perimeter features.

[0035] In the assembled state of the cell units, the fluid volume bordered by the flanged perimeter features may be enclosed between the support plate and the interconnector plate. In fuel cell operation mode, the fluid volume may be a fuel volume to guide fuel (e.g. hydrogen) or oxidant, to the cell chemistry layers, e.g. via the porous region formed in the support plate. In electrolyser operation mode, the fluid volume may be an oxidant volume to guide oxidant to the cell chemistry layers, e.g. via the porous region formed in the support plate. The flanged perimeter features may be formed by processing, preferably pressing, an original sheet , preferably planar sheet , of the respective plate . In some embodiments , providing the at least one of the support plate and the interconnector plate having the flanged perimeter features comprises processing the respective plate or plates to form the flanged perimeter features .

[0036] Preferably, the flanged perimeter features are formed by pressing, such as by use of a die press , hydroforming or stamping the respective plate or plates . These are simple processes that can be easily implemented into a manufacturing line at low investment costs .

[0037] In preferred embodiments , the flanged perimeter features are formed by processing, preferably pressing, the support plate and / or the interconnector plate to a concave configuration . The concave configuration can give the relevant plate the appearance of a rimmed tray, with a correspondingly convex outside shape ( outside relative to the cell unit ) and usually a planar base , the concavity thus defining ( e . g . part of ) the fluid volume in the assembled cell unit .

[0038] In embodiments having flanged perimeter features , preferably the support plate and the interconnector plate are , preferably directly, attached at said flanged perimeter features , preferably around the entire perimeter . Thus , attaching the support plate to the interconnector plate ( step c ) may comprise j oining the interconnector plate and the support plate at the flanged perimeter features , preferably by welding, preferably around the entire perimeter of the plates . Preferably, the interconnector plate and the support plate are sealed together, preferably welded together, around said flanged perimeter features to form a fluid volume between the support plate and the interconnector plate .

[0039] Preferably, at least the plate having the flanged perimeter features has a weakening line .

[0040] Preferably, the weakening line at least partially, preferably fully, extends along the flanged perimeter features in circumferential direction .

[0041] Preferably, the support plate and the interconnector plate are directly attached at said flanged perimeter features , preferably by welding . Thus , attaching the support plate and the interconnector plate ( step c ) may comprise directly j oining the interconnector plate and the support plate at the flanged perimeter features , preferably by welding . Preferably, the support plate and the interconnector plate abut ( i . e . are in touch-contact with) one another around the flanged perimeter features .

[0042] As set out above , the cell unit may comprise additional components . In some embodiments , the cell unit comprises a spacer or spacer plate that is disposed between the support plate and the interconnector plate . Thus , the step a ) of providing the support plate and the interconnector plate may additionally comprise providing a spacer, preferably spacer plate , having a periphery and a central portion surrounded by the periphery . The spacer (plate ) optionally comprises a weakening line around part or all of its periphery defining a border section between the weakening line and the external perimeter of the spacer plate . In such embodiments , step b ) may comprise overlying the interconnector plate , the spacer plate and the support plate over one another such that the spacer plate is disposed between the interconnector plate and the support plate . The step c ) of attaching may then comprise attaching the interconnector plate , the spacer (plate ) and the support plate together, preferably along a j oint line . Preferably, the interconnector plate , the spacer (plate ) and the support plate are j oined by welding through all three plates .

[0043] According to the invention, there is also provided a method of assembly of an electrochemical cell unit , comprising, preferably in the order as stated : a) providing a support plate , preferably metal support plate , having a periphery and a central portion surrounded by the periphery, providing a spacer plate having a periphery and a central portion surrounded by the periphery, and providing an interconnector plate ( also referred to as separator plate or interconnect ) having a periphery and a central portion surrounded by the periphery, wherein at least one of the support plate , the spacer plate , and the interconnector plate has a weakening line extending around part or all of its periphery, said weakening line defining a border section between the weakening line and an external perimeter of the respective plate . ; b) overlying the interconnector plate , the spacer plate and the support plate over one another such that the spacer plate is sandwiched between the interconnector plate and the support plate , preferably such that the peripheries of the interconnector plate , the spacer plate and the support plate overlie one another ; c) attaching the interconnector plate , the spacer plate and the support plate together, preferably at their peripheries , preferably by welding through all three plates . d) removing the border section or border sections .

[0044] In such embodiments , the cell unit may have a three layer / component design .

[0045] Preferably, the spacer or spacer plate has an open space provided in its central portion and surrounded by the periphery . Thus , the spacer may be a frame-like component . With spacer sandwiched between support plate and interconnector plate , a fluid volume ( fuel volume or oxidant volume ) corresponding to the open space is thus defined between the interconnector plate and the support plate . In other words , the spacer (plate ) may be shaped to define a fluid volume between the interconnector plate and substrate plate . Thus , the spacer configuration may be an alternative configuration to the two layer design described above , in which at least one of the support plate and the interconnector plate have flanged perimeter features .

[0046] The spacer may also be provided in addition to the flanged perimeter features . Thus , the fluid volume enclosed in the assembled cell unit may be defined by the open space of the spacer and the concavity bounded by the flanged perimeter features .

[0047] According to the invention, there is further provided an electrochemical cell unit according to claim 18 .

[0048] Preferably, the electrochemical cell units is a fuel cell unit or an electrolyser cell unit , more preferably a solid oxide fuel cell unit or a solid oxide electrolyser cell units . The electrochemical cell unit comprises a support plate having a periphery and a central portion surrounded by the periphery, and an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein : the support plate and the interconnector plate overlay one another to form the cell unit , the support plate is , preferably sealingly, attached to the interconnector plate , at least part of an external perimeter of the interconnector plate and / or the support plate is formed by a break edge , preferably obtained by removing an outer section of the interconnector plate or the support plate . Preferably, the cell unit is assembled by one of the abovedescribed methods . Thus , the break edge may be obtained by removing the border section or border sections ( step d) above ) .

[0049] According to the invention, there is further provided an electrochemical cell unit according to claim 19 . Preferably, the electrochemical cell unit is a fuel cell unit or electrolyser cell unit , more preferably metal- supported solid oxide fuel cell unit or metal-supported solid oxide electrolyser cell unit . The electrochemical cell assembly comprises a support plate having a periphery and a central portion surrounded by the periphery, and an interconnector plate having a periphery and a central portion surrounded by the periphery, wherein : the support plate and the interconnector plate overlay one another to form the cell unit , the support plate is , preferably sealingly, attached to the interconnector plate , preferably by welding, at least one of the support plate and the interconnector plate has a weakening line extending around part or all of its periphery, said weakening line defining a border section between the weakening line and an external perimeter of the respective plate .

[0050] Preferably, the cell unit according to claim 19 is an intermediate product that is further processed before its final use , e . g . in a stack of cell units . The advantages and optional features of the electrochemical cell unit or its components described above in connection with the method of assembly are also applicable to the electrochemical cell units according to claims 18 and 19. Thus, reference is made to the above disclosure. Equivalently, advantages and optional features of the electrochemical cell unit or its components described below are also applicable to the methods described above.

[0051] In some embodiments, the interconnector plate and the support plate are attached together along a joint line, preferably around part or all of their periphery. Preferably, the weakening line is disposed between the external perimeter of the respective plate and the joint line. The joint line may be a line weld seam.

[0052] In some embodiments, the support plate and the interconnector plate are directly attached to each other, preferably at their peripheries. Thus, the support plate and the interconnector plate may abut (i.e. be in toughcontact with) one another.

[0053] Alternatively, the support plate and the interconnector plate are indirectly attached to each other, preferably at their peripheries, e.g. via an additional component (e.g. spacer or gasket) sandwiched between the support plate and the interconnector plate.

[0054] In some embodiments, the weakening line is closer to the joint line than to the external perimeter of the plate. In some embodiments, the joint line is within 2 mm, more preferably within 1 mm, more preferably within 0,5 mm, of the weakening line.

[0055] In some embodiments, a minimal distance between the weakening line and the external perimeter is at least 1 mm and preferably at most 20 mm.

[0056] In some embodiments, the weakening line is provided in each of the support plate and the interconnector plate (and optionally the spacer plate, see below) . In such embodiments, the weakening line of the support plate and the weakening line of the interconnector plate may overlie one another.

[0057] Alternatively, the weakening line may be provided in only one of the support plate and the interconnector plate, i.e. only one of the support plate and the interconnector plate may comprise a weakening line. In such embodiments, advantageously, the respective other plate (i.e. the plate that does not comprise the weakening line) is configured such that an external (outer) perimeter of said other plate does not extend beyond the weakening line in an extension plane of the plate.

[0058] Preferably, the interconnector plate and the support plate enclose a fluid volume (cell volume or cell space) therebetween. Preferably, the interconnector plate and the support plate are sealingly attached to each other to enclose the fluid volume therebetween. The fluid volume may be in fluid communication with cell chemistry layers provided (e.g. deposited or coated) on the support plate on a side that is facing away from the interconnector plate. For example, as set out above, the support plate may have a porous region formed in its central portion, wherein the cell chemistry layers are deposited over said porous region .

[0059] In some embodiments, a support structure may be provided within the fluid volume in order to help maintain a spacing between the support plate and the interconnector plate. For example, the interconnector plate may comprise inward projections, preferably dimples, in its central portions, said projections extending toward the support plate. Said inward projections may define first fluid passageways (e.g., fuel passageways if the first fluid is fuel) , internal of the cell unit, i.e. between the support plate and the interconnector plate. The first fluid passageways may be in communication with the fluid ports of the cell units .

[0060] In some embodiments, the interconnector plate may comprise shaped outward projection in its central portion. Preferably, said outward projections extend away from the support plate. In a cell stack comprising a plurality of cell units stacked upon one another, the outward projections may form contact portions to contact an adjacent cell unit in the stack. Preferably, the shaped outward projections are configured for partially separating adjacent cell units in a stack of cell units. The cell units may define second fluid passageways (e.g., air or oxidant passageways if the second fluid is air or oxidant) , between the central portions of adjacent cell units. In some embodiments, the outward projections of a first cell unit engage at their ends against an outer surface of an electrochemically active layer of an adjacent cell unit, thus forming fluid passageways therebetween.

[0061] Such (inward and / or outward) projections may be formed by processing, preferably pressing, an original sheet of the support plate or the interconnector plate. In embodiments having flanged perimeter features, the projections may be formed either before or after the flanged perimeter features are formed, but more preferably at the same time.

[0062] In order to supply fluid to the fluid volume enclosed between the support plate and the interconnector plate, at least one fluid port, preferably fuel port, may be provided in the cell unit. Preferably, the at least one fluid port is in communication with a first fluid passageway in the cell unit. The fluid port(s) may be provided as an opening (through-hole) through the cell unit (i.e. through each of the support plate and the interconnector plate of each cell unit) .

[0063] In some embodiments, the cell unit may have at least one fuel inlet port and at least one fuel outlet port, wherein the cell unit extends between said at least one fuel inlet port and said at least one fuel outlet port in a first direction . In a stack of cell units , preferably the respective fluid ports of adj acent cell units are aligned along the stacking direction to form an internal fluid mani fold of the stack .

[0064] As set out above in detail , at least one of the support plate and the interconnector plate , preferably only the interconnector plate , may comprise 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 . The flanged perimeter features may define a fluid volume .

[0065] Preferably, at least the plate having the flanged perimeter features has a weakening line .

[0066] Preferably, the weakening line at least partially, preferably fully, extends along the flanged perimeter features in circumferential direction .

[0067] As set out above in detail , in some embodiments , the cell unit further comprises a spacer or spacer plate that is sandwiched between the support plate and the interconnector plate . In such embodiments , the interconnector plate and the support plate may be attached together indirectly, preferably along a j oint line , via the spacer plate , preferably by welding through all three plates . Thus , the interconnector plate , the spacer plate and the substrate plate may be j oined around part or all of their peripheries. In some embodiments, the interconnector plate is, preferably sealingly, attached to the spacer plate on a first side of the spacer plate, preferably along a first joint line, and the spacer plate is, preferably sealingly, attached to the support plate on its opposite side, preferably along a second joint line. The joint lines attaching the interconnector plate to the spacer plate and the spacer plate to the substrate plate may not overlap.

[0068] As set out above, preferably the support plate carries cell chemistry layers. The cell chemistry layers may be deposited as thin coatings or films on the support plate.

[0069] Preferably, the support plate carries cell chemistry layers over a porous region formed in the central portion of the support plate. The porous region may be formed by holes drilled into the support plate - usually laser drilled.

[0070] In some embodiments the (active) cell chemistry layers take the form of an electrochemically active layer formed (e.g. coated or deposited) directly onto and / or carried by the support plate over the porous region. This arrangement with the (non self-supporting, thin) chemistry layers provided directly on the support plate requires the minimum number of components.

[0071] In other embodiments the porous region is provided on a separate plate (e.g. metal foil) over which the cell chemistry layers are formed (e.g. coated or deposited) , and the separate plate (carrying the fuel cell chemistry layers ) is provided over a window ( e . g . a frame ) on the support plate .

[0072] There can be multiple areas of cell chemistry layers . For example , there can be multiple areas of small holes in the support plate covered by separate , respective electrochemically active layers . Alternatively, there can be multiple windows in the support plate and multiple separate plates onto ( over ) which the cell chemistry layers are formed located above those windows . The or each separate plate may be welded onto the support plate over a window in the support plate .

[0073] The cell chemistry layers ( also referred to as electrochemically active layers ) preferably comprise an anode , an electrolyte and a cathode . In fuel cells , the anode may be a fuel electrode , and the cathode may be an air or oxidant electrode .

[0074] Preferably, the cell chemistry 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 ) .

[0075] In some embodiments , each plate is generally rectangular, having two opposed long sides extending in a first direction ( longitudinal direction) and two opposed short sides extending in a second direction (width direction) .

[0076] In some embodiments the periphery of each plate has two opposed straight sides extending in the first direction and shaped ends .

[0077] In some embodiments , the cell units are solid oxide fuel cell units ( SOFCs ) . In some embodiments , the cell units are solid oxide electrolyser cell units ( SOECs ) . Preferably, the cell units are metal-supported solid oxide fuel cell units .

[0078] Preferably, the interconnector plate and the support plate are formed from metal , more preferably stainless steel , most preferably ferritic stainless steel .

[0079] According to the invention, there is further provided a stack of cell units comprising a plurality of cell units as described above , said cell units being stacked upon one another along a stacking direction .

[0080] According to the invention, there is further provided a method of assembly of an electrochemical cell unit , comprising : a) providing a support plate , preferably carrying cell chemistry layers over a porous region, and an interconnector plate , b) attaching, preferably by welding, the support plate to the interconnector plate along a j oint line , preferably around the entire perimeter, such that between the j oint line and an external perimeter of the support plate and / or the interconnector plate an outer section is defined, c) removing at least part of the outer section of the interconnector plate and / or the support plate .

[0081] The advantages and optional features set out above are also applicable to this method . Thus , reference is made to the above disclosure .

[0082] Further embodiments are derivable from the following description and the drawings .

[0083] In the drawings :

[0084] Figure 1 shows an exploded view of an exemplary electrochemical cell unit ;

[0085] Figure 2 shows a simpli fied schematic cross-sectional view of the cell unit according to Figure 1 ;

[0086] Figure 3 shows a simpli fied schematic cross-sectional view of a cell stack comprising a plurality of cell units according to Figure 1 ;

[0087] Figure 4 shows a simpli fied schematic cross-sectional of two cell units stacked upon one another ; Figures 5 and 6 show flow diagrams to illustrate an exemplary method of assembly of an electrochemical cell unit ;

[0088] Figures 7 to 12 show di f ferent variants of a weakening line ;

[0089] Figure 13 shows an exploded view of a further exemplary embodiment of an electrochemical cell unit having a spacer plate ; and

[0090] Figure 14 shows a simpli fied schematic cross-sectional view of the cell unit according to Figure 13 .

[0091] Repeat use of reference symbols in the present speci fication and drawings is intended to represent the same or analogous features or elements .

[0092] Referring to Figure 1 and 2 , there is shown an exemplary configuration of an electrochemical cell unit 10 (hereinafter referred to as cell unit ) .

[0093] In the example , the cell unit 10 takes the form of a metal- supported solid oxide ( fuel or electrolyser ) cell . The cell unit 10 comprises an interconnector plate 12 ( also referred to as interconnect or separator plate ) and a support plate 14 ( also referred to as substrate ) . In the assembled state , the interconnector plate 12 and the support plate 14 overlie one other along a stacking direction 16 and are sealingly attached to each other, preferably by welding or brazing (see Figure 2, details see below) .

[0094] In the example shown, the plates 12, 14 are generally rectangular, albeit with shaped corners 18. Specifically, the cell unit 10 has two opposed long sides 20-1, 20-2, preferably straight sides, that extend along a first direction 22, and two opposed short sides 24-1, 24-2 that extend along a second direction 26 (see Fig. 1) . In other examples, the plates 12, 14 may have a different geometry.

[0095] The interconnector plate 12 and the support plate 14 are formed from metal, preferably stainless steel, more preferably ferritic stainless steel. The support plate 14 may be a metal foil.

[0096] The interconnector plate 12 and the support plate 14 each have a periphery 28, 30 and a central portion 32, 34 surrounded by the periphery 28, 30.

[0097] The support plate 14, in its central portion 34, carries cell chemistry layers 36 (also referred to as electrochemically active layers) over a porous region 38 (see Fig. 2) . Preferably, the cell chemistry layers 36 are deposited or coated directly upon the metal support plate 14.

[0098] In the example, the porous region 38 comprises an array of through-holes 40 formed by drilling (or other means, for example etching) extending through the support plate 14 and surrounded by a non-porous region forming the periphery 30 (see Figure 2 ) .

[0099] Alternatively, the cell chemistry layers 36 may be formed on a separate porous metal substrate which may be attached to a window-framed support plate (not shown) .

[0100] The cell chemistry layers 36 typically comprise an anode layer, an electrolyte layer and a cathode layer. Depending on the type of cell unit 10, the anode layer (e.g. fuel electrode) or the cathode layer (e.g. oxidant electrode) may be closest, preferably deposited directly onto, the support plate 14.

[0101] In the example, the interconnector plate 12 is tub-shaped having having flanged perimeter features 42 around its periphery 28, preferably formed by pressing the interconnector plate 12 to a concave configuration. As can be seen from Figure 2, the flanged perimeter features 42 extend out of the predominant plane of the interconnector plate 12 to create a concavity 44 (and a convexity to the outside surface) in the interconnector plate 12.

[0102] As set out above, in the assembled state of the cell unit 10, the concavity 44 forms a (first) fluid volume 46 enclosed between the interconnector plate 12 and the support plate 14. The fluid volume 46 is in fluid communication with the cell chemistry layers 36 via said porous region 38. The flanged perimeter features 42 may be formed by pressing the interconnector plate 12 to the concave configuration.

[0103] As schematically shown in Figure 2, the interconnector plate 12 and the support plate 14 are joined at said flanged perimeter features 42 along a joint line 48. Preferably, the interconnector plate 12 and the support plate 14 are attached to each other by welding. Thus, the joint line 48 may be a weld line 50 (The joint line 48 is shown in plan as a dashed-dotted line in subsequent figures, and in cross section as triangles representing welds.) ) . Alternatively, the plates 12, 14 may be joined by brazing .

[0104] In the example, the interconnector plate 12 has a structured area 52 in its central portion 30. As shown in Figure 2, the structure area 52 comprises shaped outward projections 54 extending along the stacking direction 16. Said outward projections 54 form contact portions of the cell unit 10 for contacting an adjacent cell unit 10 in a stack of cell units 10 (see Figure 4, further details below) .

[0105] In the example, the structured area 52 further comprises optional inward protrusions 56 extending into the fluid volume 46. The inwards projections 56 form a supporting structure helping to maintain the fluid volume 46 (cell space) open. The inward projections 56 define first fluid passageways 58 internal of the cell unit 10. The inward projections may have an aspect ratio (length : width) of less than 4, preferably less than 2, preferably circular in cross-section such that fluid in said volume may flow in a tortuous path, the passageways 58 being the space around the projections. Alternatively, the projections, and therefore the passageways, may take the form of channels.

[0106] The projections 54, 56 are - for simplicity - shown as cubes in Figure 2, but may have other cross-sectional shapes such as pyramids, flat-topped pyramids, cones, domes or bumps. The outward projections 54 and the inward protrusions 56 may be formed by dimples.

[0107] The inward and outward projection 54, 56 may be formed in the interconnector plate 12 by pressing or forming the outward projections 54 in a first direction and by pressing or forming the inward projection 56 in a second direction.

[0108] In order to supply fluid (for fuel cells fuel or oxidant, for electrolyser cells sweep gas or oxidant) to the (first) fluid volume 46 between the support plate 14 and the interconnector plate 45 (and thus to the cell chemistry layers 36) or to remove fluid from said fluid volume 46, the cell unit 10 has at least one, in the specific example four fluid ports 60. The fluid port(s) 60 are provided as openings through the cell unit 10. Specifically, both the support plate 14 and the interconnector plate 12 have respective through-holes 62 formed therein, said through- holes 62 being aligned to form a fluid port 60 of the cell unit 10. In the specific example, each cell unit 10 comprises two inlet ports 64 and two outlet ports 66 to the first fluid volume (see Fig. 2) .

[0109] As shown in Figure 3, typically multiple of such cell units 10 are stacked upon one another along the stacking direction 16 to form a stack 100 of cell units 10.

[0110] In the stack, the fluid ports 60, of adjacent cell units 10 are aligned along the stacking direction 16.

[0111] In the example, the stack 100 further comprises gaskets 68 that are interposed between the cell units 10 and surround the fluid ports 64, 66 of the cell units 10. Specifically, each fluid port 64, 66 is associated with a gasket 68 on both sides of the cell unit 10. Preferably, the gaskets 68 are annular sealing rings having a central opening 70. The gaskets 68 may be formed from a vermiculite material.

[0112] As shown in Figure 3, an aligned column of the gasket openings 70 of the gaskets 78 and the fluid ports 64, 66 of the cell units 10 forms a respective fluid manifold 72, 74. Specifically, in the example of Figure 3, the stack 100 of cell units 10 comprises a fluid inlet manifold 72 and a fluid outlet manifold 74. The fluid inlet manifold 72 is configured to supply fluid, preferably fuel, to the cell units 10 in an inflow direction. The fluid outlet manifold 74 is configured to remove exhaust fluid, preferably exhaust fuel, from the cell units 10 in an outflow direction . The stack 100 of cell units 10 may be arranged between two end plates 76 , 78 provided on opposite sides of the stack 100 , thus forming an electrochemical cell assembly 200 . As shown in Figure 3 , the first end plate 76 (bottom plate ) may comprise a fluid access port 80 for supplying fluid from an exterior of the cell assembly 10 to the fluid inlet mani fold 72 , and a fluid exhaust port 82 for discharging exhaust fluid from the fluid outlet mani fold 74 to the exterior . In the example , the fluid access port 80 and the fluid exhaust port 82 are each formed by a respective through-hole 84 formed in the first end plate 76 .

[0113] The electrochemical cell assembly 200 may further comprise a housing 86 circumscribing the stack 100 of cell units 10 around the stacking direction 16 . In preferred examples , the housing 86 is formed from metal , preferably steel . The housing 86 may be welded to the end plates 76 , 78 .

[0114] The housing 86 and the end plates 76 , 78 together enclose a ( second) fluid volume 88 for second fluid, preferably air or oxidant , around the stack 100 of cell units 10 .

[0115] In order to supply fluid, preferably air or oxidant , to said fluid volume 88 enclosed by the housing 86 , the electrochemical cell assembly 200 may further comprise a fluid inlet port and an opposite fluid outlet port (not shown) . The fluid inlet port and the fluid outlet port may each be provided by a respective through-hole formed in the first end plate 76 and / or second end plate 78 . Referring to Figure 4, it can be seen that in the stacked configuration, the outward projections 54 formed in the interconnector plate 12 engage at their ends against an outer surface of the electrochemically active layer 36 of an adjacent cell unit 10, thus defining (second) fluid passageways 90 between adjacent cell units 10. During operation, said fluid passageways 90 may transport (second) fluid ( (e.g., air or oxidant) to the cell chemistry layers 36.

[0116] Thus, in operation of the cell stack 100 in a fuel cell mode, fuel (e.g. hydrogen, hydrocarbon, or other fuel) may be supplied to the anode layer of the cell chemistry layers 36 via the fluid inlet manifold(s) 72, the fluid inlet port(s) 64, the (first) fluid volume 46 (first fluid passageways 58) and the porous region 38, whereas air or oxidant is supplied to the cathode layer (in the Figures top layer) of the cell chemistry layers 36 via the (second) fluid volume 88 enclosed by the housing 86 and the (second) fluid passageways 90 formed between the outwards projections 54.

[0117] In addition to the second fluid passageways 90, fluid (in particular air or oxidant) may flow in a gap 92 formed between the flanged perimeter features 42 of adjacent cell units 10 leading to an undesired fluid 'bypass', bypassing the 'active' area in the central portion of the cell unit 10. Thus, it is desired to keep a width of the flanged perimeter features 42 small. The electrochemical cell assembly 10 preferably also comprises a current collection or delivery system, known in the art (not shown) . For example , the electrochemical cell assembly 200 may comprise one or more current collector plates , e . g . provided between the end plates 76 , 78 and the stack 100 of cell units 10 . In addition, the current collection or delivery system may comprise one or more electrical connection members , such as busbars , for electrically connecting said current collector or delivery plates . In addition, the electrochemical cell assembly 10 may comprise insulation members , such as insulation plates 94 ( see Figure 3 ) or insulation sleeves (not shown) .

[0118] In the following, an exemplary method of assembly of an electrochemical cell unit 10 will be described with reference to Figures 5 and 6 . The insets in Figure 5 show the cell unit 10 in simpli fied cross-section . The insets in Figure 6 show the cell unit 10 in a bottom view .

[0119] In a first step (block 300 in Figures 5 and 6 ) , the interconnector plate 12 and the support plate 14 are provided . In this initial configuration, the interconnector plate 12 and the support plate 14 preferably each have an extended flange portion 96 along the long sides 20- 1 , 20-2 of the plates 12 , 14 (but said extended flange portion may additionally or alternatively be along sides 24- 1 , 24-2 ) . Said extended flange portion 96 may serve as a clamping portion for clamping the plates 12 , 14 during subsequent processing steps . Additionally, there is a weakening line 98 provided along said extended flange portion 96 (The weakening line 98 is shown in plan as a dashed line, and in cross-section as rectangles for through-holes, see below) . The weakening line 98 divides the flange portion 96 into an inner section 102 located closest to the respective central portion 32, 34 and an outer section 104 (border section 106) defining the external perimeter 108 of the plates 12, 14.

[0120] The weakening line 98 forms a predetermined breaking point for removing the border section 106 (see below) .

[0121] In other examples, the extended flange portion 96 may be provided at a different section of the flanged perimeter features 42, e.g. at one or both of the short sides 24-1, 24-2. In even further examples, the flanged perimeter features 42 may have the same width around the entire perimeter of the respective plates 12, 14.

[0122] In the specific example shown in Figure 7, the weakening line 98 is formed by an array of perforations 110, e.g. in the form of through-holes 112, that extend through the respective plates 12, 14.

[0123] The weakening line 98, however, may have different configurations. For example, the weakening line 98 may by formed by a notch 114 formed in the respective plates 12, 14 (see Figure 8 ) . Alternatively, the weakening line 98 may, for example, be formed by the respective plates 12, 14 having a locally reduced material thickness 116 (see Figure 9) .

[0124] Figures 7-9 show weakening lines 98 in both plates 12, 14. However, in some embodiments, only one of the plates 12, 14 may have a weakening line 98, as exemplified in Figures 10 and 11, which are otherwise similar to Figure 7. In some such embodiments, only the plate having the weakening line may have the extended portion - the other plate may terminate between the joint line 48 and the weakening line 98 - as exemplified in Figure 12, which is otherwise similar to Figure 11. The examples of Figures 10 to 12 are similar to that of Figure 7 utilizing perforations 110 (e.g. in the form of through-holes 112) . However, it will be understood that said examples may instead be similar to that of Figures 8 and 9 utilizing notch 114 or locally reduced material thickness 116.

[0125] As set out above, the interconnector plate 12 may initially be provided as a planar sheet, which is then formed, preferably pressed, into the concave configuration to form the flanged perimeter features 42. The weakening line 98 may be formed in the same pressing step.

[0126] In a further step (block 302 in Figures 5 and 6) , the interconnector plate 12 and the support plate 14 are stacked upon one another such that the peripheries 28, 30 of the plates 12, 14, in particular also the weakening lines 98, overlie (where the weakening line is present in both plates) .

[0127] In a further step (block 304 in Figures 5 and 6) , the interconnector plate 12 and the support plate 14 are, preferably sealingly, attached to each other at their peripheries 28, 30. In the example, the interconnector plate 12 and the support plate 14 are joined at a joint line 48 extending along the flanged perimeter features 42. Preferably, the joint line 48 extends around the entire perimeter of the cell unit 10.

[0128] As set out above, preferably, the interconnector plate 12 and the support plate 14 are welded together. Thus, the joint line 48 may be a weld line 50. Alternatively, the plates 12, 14 may be joined by brazing.

[0129] During said step of attaching the interconnector plate 12 to the support plate 14, the plates 12, 14 may be held in position by a holding bracket that clamps the border section 106 of the plates 12, 14.

[0130] After finishing the joining process, preferably welding process, the border sections 106 are removed (illustrated in block 306 in Figures 5 and 6) . This may be accomplished by breaking off the border sections 106 along the weakening lines 98, e.g. by punching or stamping. Thus , after removing the border section 106 , the external perimeter 108 of the cell unit 10 is formed by a break edge 118 .

[0131] The cell units 10 may then be stacked upon each other to form a stack 100 of cell units 10 , as set out above in connection with Figure 3 .

[0132] The proposed concept - i . e . having border sections 106 serving as a clamping portions during attachment , which are removed afterwards - improves precision and reliability of the attaching step, while reducing a footprint of " inactive" areas in the final cell unit 10 .

[0133] Figure 13 and 14 show a further exemplary embodiment of a cell unit 10 comprising a spacer or spacer plate 120 sandwiched between the interconnector plate 12 and the support plate 14 .

[0134] The cell unit 10 shown in Figures 13 and 14 is similar in construction and operation to the cell unit 10 shown in Figures 1 and 2 . Thus , to avoid repetition, aspects of Figures 13 and 14 that are generally the same as shown in Figure 1 will not be described again, except where relevant to explain the particular features of Figures 13 and 14 . Where the same or analogous features are present , like reference numerals have been used .

[0135] As shown in Figure 13 , the spacer plate 120 is a framelike component having an open space 122 in its central portion 124, said open space 122 being surrounded by a periphery

[0136] 126 of the spacer plate 122. In the assembled state of the cell unit 10, the open space 122 defines the (first) fluid volume 46 enclosed between the interconnector plate 12 and the support plate 14 (see Figure 14, in which protrusions in the interconnector plate are not shown for clarity) .

[0137] Thus, the spacer concept may be an alternative concept to the flanged perimeter features 42 to provide an inner fluid volume 46 in the cell unit 10.

[0138] In the example, the interconnector 12 and the support plate 14 are planar (flat) components. In particular, the interconnector plate 12 does not comprise the flanged perimeter features 42.

[0139] As shown in Figure 14, in embodiments having a spacer plate 120, the joint line 48 (weld line 50) may extend through all three plates 12, 14, 120. In other examples, the spacer plate 120 may be joined to the interconnector plate 12 and the support plate 14 by separate joint lines.

[0140] Preferably, each of the interconnector plate 12, the spacer plate 120 and the support plate 14 has a weakening line 98 formed therein (see Figure 14) . The weakening line 98 in the spacer plate 120 may be configured as discussed above in connection with Figures 7 to 9. The weakening line may be present in only one or two of the plates in a similar manner to that discussed above with reference to Figures 10 to 12.

Claims

Claims1. Method of assembly of an electrochemical cell unit (10) , comprising: a) providing a support plate (14) having a periphery (30) and a central portion (34) surrounded by the periphery (30) and an interconnector plate (12) having a periphery(28) and a central portion (32) surrounded by the periphery (28) , wherein at least one of the support plate (14) and the interconnector plate (12) has a weakening line (98) extending around part or all of its periphery (28, 30) , said weakening line (98) defining a border section (106) between the weakening line (98) and an external perimeter (108) of the respective plate (12, 14) , b) overlying the interconnector plate (12) and the support plate (14) over one another, c) attaching the support plate (14) to the interconnector plate (12) , and d) removing the border section (106) .

2. The method according to claim 1, wherein attaching the support plate (14) to the interconnector plate (12) comprises clamping the plate or plates (12, 14) having the weakening line (98) at the border section (106) to hold the support plate (14) and the interconnector plate (12) in place.

3. The method according to claim 1 or 2, wherein removing the border section (106) comprises detaching the border section (106) along the weakening line (98) , preferably by breaking, punching, stamping or laser cutting .

4. The method according to any one of the preceding claims, wherein attaching the support plate (14) to the interconnector plate (12) comprises welding or brazing the support plate (14) to the interconnector plate ( 12 ) .

5. The method according to any one of the preceding claims, wherein the support plate (14) is attached to the interconnector plate (12) along a joint line (48) , preferably around part or all of their peripheries (28, 30) , such that the weakening line (98) is located between said joint line (48) and the external perimeter (108) of the plate or plates (12, 14) having the weakening line (98) .

6. The method according to the preceding claim, wherein the support plate (14) is attached to the interconnector plate (12) such that the joint line (48) is within 1 mm, more preferably within 0,5 mm, of the weakening line (98) .

7. The method according to any one of the preceding claims, wherein each of the support plate (14) and the interconnector plate (12) has a weakening line (98) , wherein the support plate (14) and the interconnectorplate (12) are overlaid over one another such that the weakening line (98) of the support plate (14) and the weakening line (98) of the interconnector plate (12) overlie one another.

8. The method according to any of the preceding claims, wherein the weakening line (98) is formed by a plurality of perforations (110) formed in the respective plate (12, 14) along the trace of the weakening line (98) .

9. The method according to any one of claims 1 to 7, wherein the weakening line (98) is formed by a notch (114) formed in a surface of the respective plate (12, 14) along the trace of the weakening line (98) .

10. The method accosting to any of claims 1 to 7, wherein the weakening line (98) is formed by the respective plate (12, 14) having a locally reduced material thickness (116) extending along the trace of the weakening line (98) .

11. The method according to any one of the preceding claims, wherein providing the at least one of the support plate (14) and the interconnector plate (14) having the weakening line (98) comprises processing the respective plate (12, 14) to form the weakening line (98) .

12. The method according to any one of the preceding claims, wherein the support plate (14) is directlyattached to the interconnector plate (12) , preferably by welding.

13. The method according to any one of the preceding claims, wherein at least one of the support plate (14) and the interconnector plate (12) comprises flanged perimeter features (42) around part or all of its periphery (28, 30) , wherein the support plate (14) and the interconnector plate (12) are, preferably directly, attached at said flanged perimeter features (42) .

14. The method according to the preceding claim, wherein providing the at least one of the support plate (14) and the interconnector plate (12) having the flanged perimeter features (42) comprises processing, preferably pressing of, the respective plate or plates (12, 14) to form the flanged perimeter features (42) .

15. The method according to claim 13 or 14, wherein at least the plate (12, 14) having the flanged perimeter features (42) has a weakening line (98) .

16. The method according to any one of claims 13 to 15, wherein the weakening line (98) at least partially extends along the flanged perimeter features (42) .

17. The method according to any of claims 1 to 11, further comprising : al) providing a spacer (120) , preferably spacer plate, having a periphery (126) and a central portion (124) surrounded by the periphery (126) ,wherein the spacer (120) optionally comprises a weakening line (98) around part or all of its periphery (126) defining a border section (106) between the weakening line (98) and the external perimeter (108) of the spacer; b' ) overlying the interconnector plate (12) , the spacer (120) and the support plate (14) over one another such that the spacer (120) is sandwiched between the interconnector plate (12) and the support plate (14) ; and c' ) attaching the interconnector plate (12) , the spacer (120) and the support plate (14) together, preferably along a joint line (48) , preferably by welding through all three components.

18. An electrochemical cell unit (10) , preferably assembled by a method according to any one of the preceding claims, comprising: a support plate (14) having a periphery (30) and a central portion (34) surrounded by the periphery (30) , and an interconnector plate (12) having a periphery (28) and a central portion (32) surrounded by the periphery (28) , wherein : the support plate (14) and the interconnector plate (12) overlay one another, the support plate (14) is attached to the interconnector plate (12) ,at least part of an external perimeter (108) of the interconnector plate (12) and / or the support plate (14) is formed by a break edge (118) obtained by removing an outer section (104) of the periphery (28, 30) of the interconnector plate (12) and / or the support plate (14) .

19. An electrochemical cell unit, preferably metal- supported solid oxide fuel cell unit or solid oxide electrolyser cell unit, comprising: a support plate (14) having a periphery (30) and a central portion (34) surrounded by the periphery (30) , and an interconnector plate (12) having a periphery (28) and a central portion (32) surrounded by the periphery (28) , wherein : the support plate (14) and the interconnector plate (12) overlay one another, the support plate (14) is attached to the interconnector plate (12) , at least one of the support plate (14) and the interconnector plate (12) has a weakening line (98) around part or all of its periphery (28, 30) , said weakening line (98) defining a border section (106) between the weakening line (98) and an external perimeter (108) of the respective plate (12, 14) .

20. The electrochemical cell unit according to the preceding claim, wherein the interconnector plate (12)and the support plate (14) are attached together along a joint line (48) , preferably around part or all of their peripheries (28, 30) , wherein the weakening line (98) is disposed between the external perimeter (108) of the respective plate (12, 14) and the joint line (48) .

21. The electrochemical cell unit according to the preceding claim, wherein the weakening line (98) is closer to the joint line (48) than to the external perimeter (108) .

22. The electrochemical cell unit according to claim 20 or 21, wherein the joint line (48) is within 1 mm, more preferably within 0,5 mm, of the weakening line (98) .

23. The electrochemical cell unit according to any of claims 20 to 22, wherein a minimal distance between the weakening line (98) and the external perimeter (108) is at least 1 mm, and preferably at most 20 mm.

24. The electrochemical cell unit according to any one of claims 20 to 23, wherein the weakening line (98) is provided in each of the support plate (14) and the interconnector plate (12) , wherein the weakening line (98) of the support plate (14) and the weakening line (98) of the interconnector plate (12) overlie one another .

25. The electrochemical cell unit according to any one of claims 20 to 23, wherein the weakening line (98) is provided in only one of the support plate (14) and theinterconnector plate (12) , and wherein an external perimeter (108) of the respective other plate (12, 14) does not extend beyond said weakening line (98) .

26. The electrochemical cell unit according to any one of claims 19 to 25, wherein the weakening line (98) is formed by a plurality of perforations (110) formed in the respective plate (12, 14) along the trace of the weakening line (98) .

27. The electrochemical cell unit according to any one of claims 19 to 25, wherein the weakening line (98) is formed by a notch (114) formed in a surface of the respective plate (12, 14) along the trace of the weakening line (98) .

28. The electrochemical cell unit accosting to any of claims 19 to 25, wherein the weakening line (98) is formed by the respective plate (12, 14) having a locally reduced material thickness (116) extending along the trace of the weakening line (98) .

29. The electrochemical cell unit according to any one of claim 18 to 28, wherein at least one of the support plate (14) and the interconnector plate (12) comprises flanged perimeter features (42) around part or all of its periphery (28, 30) , wherein the support plate (14) and the interconnector plate (12) are, preferably directly, attached at said flanged perimeter features (42) , preferably by welding.

30. The electrochemical cell unit according to the preceding claim, wherein the flanged perimeter features (42) are only provided on the interconnector plate ( 12 ) .

31. The electrochemical cell unit according to claim 29 or 30 when referring to claim 19, wherein the weakening line (98) at least partially extends along the flanged perimeter features (42) .

32. The electrochemical cell unit according to any one of claim 18 to 31, wherein the support plate (14) is directly attached to the interconnector plate (12) , preferably by welding.

33. The electrochemical cell unit according to any one of claims 18 to 32, further comprising a spacer (120) , preferably spacer plate, sandwiched between the support plate (14) and the interconnector plate (12) , wherein the interconnector plate (12) and the support plate (14) are attached together indirectly, preferably along a joint line (48) , via the spacer (120) , preferably by welding through all three components .

34. A stack (100) of cell units, comprising a plurality of cell units (10) according to any one of claims 18 to 33, said plurality of cell units (10) being stacked upon one another along a stacking direction (16) .

35. Method of assembly of an electrochemical cell unit(10) , comprising:a) providing a support plate (14) , preferably carrying cell chemistry layers (36) over a porous region (38) , and an interconnector plate (12) , b) attaching, preferably by welding, the support plate (14) to the interconnector plate (12) along a joint line (48) , preferably around the entire perimeter, such that between the joint line (48) and an external perimeter (108) of the support plate (14) and / or the interconnector plate (12) an outer section (104) is defined; c) removing at least part of the outer section (104) of the support plate (14) and / or the interconnector plate ( 12 ) .

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