Electrochemical cell assembly

Abstract

The invention relates to an electrochemical cell assembly (10) comprising an end plate (14, 18), a stack (20) comprising a plurality of cell units (22) that are stacked upon one another along a stacking direction (24), and an insulating plate (32) that is interposed between the end plate and the stack, wherein the cell units each comprise a periphery (52) and a central portion (54), wherein at least one cut-out (76) is provided in the insulating plate, said cut-out extending through the insulating plate along the stacking direction, and wherein at least one inset (78) is positioned in said cut-out such that, seen along the stacking direction, the inset and the central portion overlap each other, said inset being formed from a ceramic material.

Description

[0001] Description

[0002] Title

[0003] Electrochemical cell assembly

[0004] State of the Art

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

[0006] Fuel cells and electrolyser cells are examples of electrochemical cells. Fuel cells are energy conversion devices that allow for conversion of electrochemical fuel (e.g. H2) to electricity. Electrolyser cells are fuels cells running in reverse mode, i.e. using electricity to decompose a chemical (e.g. H2O) into its constituent parts (e.g. H2 and O2). Reversible cells are capable of operating in both modes. Such electrochemical cells typically comprise cell chemistry layers that may be configured to allow for conversion of electrochemical fuel to electricity (fuel cells) or for decomposing a chemical into its constituent parts using electricity (electrolyser cells).

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

[0008] Typically, multiple of such cell units are stacked upon one another to form a “stack” of cell units, also referred to as ‘cell repeat units’. Said stack of cell units is commonly arranged between a first end plate and a second end plate provided on opposite sides of the stack, thus forming an electrochemical cell assembly. It is an object of the present invention to increase performance and stability of an electrochemical cell assembly.

[0009] Description of the Invention

[0010] According to the invention, there is provided an electrochemical cell assembly with the features of claim 1. The electrochemical cell assembly comprises at least one end plate assembly having an end plate. The electrochemical cell assembly further comprises a stack of cell units, comprising a plurality of cell units that are stacked upon one another along a stacking direction. The electrochemical cell assembly further comprises an insulating plate that is formed from an electrically insulating material, said insulating plate being interposed between the end plate and the stack of cell units. The insulating plate is configured to electrically insulate the stack of cell units from the end plate which is typically formed from an electrically conductive metal material. An undesired electrical contact between the stack of cell units and the end plate might otherwise result in an electrical short circuit. The cell units each comprise a periphery and a central portion surrounded by the periphery. At least one cut-out is provided in the insulating plate, said cut-out extending through the insulating plate along the stacking direction. That is to say, the cut-out is open along the stacking direction both towards the end plate and towards the stack of cell units. At least one inset formed from a ceramic material is positioned in said cut-out. That is to say, at least one ceramic inset is positioned in said-cut out. The at least one inset is positioned in the cut-out provided in the insulating plate such that, when seen along the stacking direction, the inset and the central portion of the cell units overlap each other at least partially.

[0011] Over the lifespan of an electrochemical cell assembly, the insulating plate may be affected by a thickness reduction, i.e. a shrinkage along the stacking direction. Such thickness reduction may be effected by high compressive forces acting on the insulating plate along the stacking direction and / or by a material loss of the insulating plate under high operating temperatures. The thickness reduction may in turn impair a contact between adjacent cell units and, thus, the overall performance of the electrochemical cell assembly. The proposed configuration allows for enhanced performance since the inset stabilises the contact between adjacent cell units, particularly in the central portion of the cell units. Being formed from a stiff ceramic material, the inset displays a high resistance against compressive forces and is, thus, not or only slightly affected by shrinkage. Since the costs for the ceramic material of the inset are high compared to the costs of the electrically insulating material of the insulating plate, the use of an inset (instead of forming the whole insulating plate from the ceramic material) has the advantage that the manufacturing costs can be reduced.

[0012] In this context, the term "inset" relates to a member that is positioned in a cut-out of the insulating plate, formed from a ceramic material and at least partially overlaps with the central portion of the cell units. A member that satisfies only some of the above criteria is not considered as an inset. For example, a member that is positioned in a cut-out of the insulating plate and formed from a ceramic material, but does not at least partially overlap with the central portion of the cell units, is not considered an inset.

[0013] Preferably, the end plate is a base plate of the electrochemical cell assembly. That is to say, during a use of the electrochemical cell assembly as intended, the end plate is a lower end plate of the electrochemical cell assembly and positioned under the stack of cell units. Alternatively, the end plate is an upper end plate of the electrochemical cell assembly. That is to say, during a use of the electrochemical cell assembly as intended, the end plate is postioned on top of the stack of cell units.

[0014] In some embodiments, the electrochemical cell assembly comprises a first end plate assembly having a first end plate and a second end plate assembly having a second end plate, wherein the stack of cell units is arranged between the first end plate and the second end plate. Thus, the electrochemical cell assembly comprises two end plates that are arranged on opposite sides of the stack of cell units. Preferably, the stack of cell units is held in compression between the first and second end plates.

[0015] The cut-out may be provided in different ways. Preferably, the cut-out is configured as a through-hole extending through the insulating plate. A through- hole is fully surrounded by the insulating plate in the lateral directions, i.e. directions that are perpendicular to the stacking direction. Thus, the cut-out may be spaced apart from an outer edge of the insulating plate. Alternatively, the cut- out may only partially be surrounded by the insulating plate in the lateral directions. Thus, the cut-out may be located at the outer edge of the insulating plate.

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

[0017] The cell units may be configured flat or planar. Each cell unit may extend in a cell plane perpendicular to the stacking direction. Thus, each cell unit may extend in a first direction, preferably a length direction, and in a second direction, preferably a width direction, that is perpendicular to the first direction. The first and second directions define said cell plane and are perpendicular to the stacking direction.

[0018] Preferably, the central portions each comprise a structured area. Said structured area may define a plurality of fluid channels in a respective cell volume of the cell units. During operation of the electrochemical cell assembly said fluid channels may serve to distribute or spread a fluid, e.g. a fuel, in the cell volume of the cell units. Preferably, the structured area comprises a plurality of protrusions formed therein, said protrusions extending along the stacking direction, preferably into the cell volume. The protrusions may define a network of fluidical ly interconnected fluid channels therebetween.

[0019] In some embodiments, the structured area is a contact area of the cell units. Thus, the structured area of one cell unit may be in direct contact with an adjacent cell unit.

[0020] Where the central portion comprises the structured area it is preferred that, seen along the stacking direction, the inset and the structured area overlap each other at least partially. Thus, in some preferred embodiments, the central portions each comprise a structured area, said structured area preferably having a plurality of protrusions formed therein, wherein the inset is positioned in the cut-out such that, seen along the stacking direction, the inset and the structured area of the cell units overlap each other at least partially. Preferably, seen along the stacking direction, at least 10% of the structured area overlap with the inset or one of several insets. That is to say, 90% or less of the structured area do not overlap with an inset, i.e. are offset to an inset. Preferably, at least 20% of the structured area overlap with the inset or one of several insets, more preferably at least 30% of the structured area.

[0021] Preferably, the cell units carry electrochemically active layers (also referred to as cell chemistry layers) in their central portion. The electrochemically active layers and the structured area may be provided on opposite sides of the cell units. The electrochemically active layers preferably comprise a fuel electrode layer, an electrolyte layer and an air or oxidant electrode layer. The electrochemically active layers may be deposited as thin coatings or films on the cell unit. The cell unit may comprise a porous area in its central portion, said porous area carrying the electrochemically active layers.

[0022] As mentioned above, the structured area of the cell units may be a contact area of the cell units. Preferably, the structured area of one cell unit is in direct contact with the electrochemically active layers of an adjacent cell unit.

[0023] In preferred embodiments, each cell unit comprises an interconnector plate (also referred to as interconnect or separator plate) and a support plate (also referred to as substrate), which are stacked upon each other along the stacking direction. The interconnector plate and the support plate may both comprise a periphery and a central portion surrounded by the periphery. The peripheries of the interconnector plate and the support plate constitute the periphery of the cell unit. The central portions of the interconnector plate and the support plate constitute the central portion of the cell unit. Preferably, the peripheries of the interconnector plate and the support plate are sealingly attached to each other, preferably by welding, and the central portions enclose the cell volume (fluid or air volume) therebetween. The cell volume may be in fluid communication with the electrochemically active layers via the above-mentioned porous area. Preferably, the interconnector plate and the support plate are formed from a metal material, preferably stainless steel. Preferably, the structured area is provided in the central portion of the interconnector plate. The porous area carrying the electrochemically active layers is preferably provided in the central portion of the support plate.

[0024] The electrochemical cell assembly may comprise one inset or several insets. In some embodiments having several insets, the insets may be configured identical, i.e. having the same dimensions. In alternative embodimentshaving several insets, the insets or a subset of the insets are different from each other.

[0025] In some preferred embodiments, the extent of the inset along the stacking direction is greater than or equal to the extent of the insulating plate along the stacking direction. This has the advantage that the inset can reliably transmit compressive forces between the end plate and the stack of cell units. Preferably, a first surface of the inset that is facing towards the stack of cell units is flush with a first surface of the insulating plate that is facing towards the stack of cell units.

[0026] In some preferred embodiments, the inset is in direct contact with the end plate. Hence, no additional element that may be affected by shrinkage is positioned between the end plate and the inset. This has the advantage that the inset can reliably stabilise the contact between adjacent cell units, particularly in the structured area of the cell units.

[0027] In some preferred embodiments, the ceramic material, i.e. the material of the inset, comprises alumina or consists of alumina. Alumina is especially suitable as a ceramic material for the inset due to its high stiffness and its high stability under typical operating temperatures of the electrochemical cell assembly such as 600 °C and more. In case that the ceramic material comprises alumina, the mass concentration of alumina in the ceramic material is preferably 70% or more, more preferably 80% or more, most preferably 90% or more. Preferably, the ceramic material is a homogeneous material.

[0028] In some preferred embodiments, the electrically insulating material, i.e. the material of the insulating plate, comprises at least one mica group mineral. Mica group minerals are especially suitable as an electrically insulating material for the insulating plate due to their high electrical resistance value and their low thermal conductivity. Furthermore, mica group minerals are cost-effective compared to the ceramic material of the inset. Preferably, the electrically insulating material comprises muscovite and / or phogopite as the at least one mica group mineral. The electrically insulating material may be a laminated material comprising a plurality of sheets, said sheets comprising the at least one mica group mineral and being bonded together by a silicon binder.

[0029] In some preferred embodiments, the insulating plate comprises at least one inlet through-hole forming a fluid inlet port for supplying a fluid, e.g. a fuel, from the exterior to the stack of cell units and at least one outlet through-hole forming a fluid outlet port for removing a fluid, i.e. a consumed or partially consumed fuel, from the stack of cell units to the exterior, wherein the inlet through-hole and the outlet through-hole are located on opposite sides of the inset (i.e. the inset is located between the inlet through-hole and the outlet through-hole). This configuration is particularly advantageous regarding the guidance of fluid, e.g. a fuel, through the electrochemical cell assembly. That is, the fluid may be supplied to the cell units, i.e. to their cell volumes, through the inlet through-hole and removed from the cell units through the outlet through-hole. Between the inlet through-hole and the outlet through-hole, the fluid traverses the central portion of the cell units which are supported by the at least one inset.

[0030] In some preferred embodiments, the insulating plate is elongate, wherein the inlet through-hole and the outlet through-hole are positioned at opposite longitudinal end portions of the insulating plate.

[0031] In some preferred embodiments, a sealing device is arranged in the inlet through- hole, said sealing device defining a fluid channel for guiding fluid from the exterior to the stack of cell units and preventing loss of fluid between the end plate and the stack of cell units. In some preferred embodiments, a sealing device is arranged in the outlet through-hole, said sealing device defining a fluid channel for guiding fluid from the stack of cell units to the exterior and preventing loss of fluid between the stack of cell units and the end plate. Thus, the sealing device or sealing devices provide a fluid guiding function and a sealing function. Preferably, the sealing device or sealing devices each comprise a sleeve-shaped member that is formed from a ceramic material. Preferably, the sleeve-shaped member and the inset are formed from the same ceramic material. A gasket may be provided on each end face of the sleeve-shaped member or sleeve-shaped members.

[0032] The inset may be configured in different shapes. In some preferred embodiments, the inset is plate-shaped. A plate-shaped inset has the advantage that the inset can reliably stabilise the contact between adjacent cell units in a wide area. Furthermore, a large plate-shaped inset has the advantage that the assembly time is low (compared with several smaller insets). In some embodiments, the inset is sleeve-shaped, elongate or cylindrical. A sleeveshaped inset goes along with a reduction of manufacturing costs. Owing to the central through-hole provided in a sleeve-shaped member, the amount of material required for a sleeve-shaped member is reduced (compared with the amount of material required for a cylindrical member having the same outer contour).

[0033] In some preferred embodiments, the inset is plate-shaped, wherein, seen along the stacking direction, an outer perimeter of the inset surrounds an outer perimeter of the structured area of the cell units. This has the advantage that the entire structured area is reliably stabilised by the plate-shaped inset. Particularly, the plate-shaped inset may extend beyond the structured area along a length direction of the insulating plate by 0.1 mm to 10 mm. Particularly, the plateshaped inset may extend beyond the structured area along a width direction of the insulating plate by 0.1 mm to 10 mm.

[0034] In some preferred embodiments, at least two insets are arranged next to one another in the same cut-out. Providing several smaller insets that are arranged next to one another in the same cut-out may result in a reduction of manufacturing costs (compared to providing one larger inset with the same outer contour).

[0035] In some preferred embodiments, at least two cut-outs are provided in the insulating plate, wherein at least one inset is arranged in each of said cut-outs. This has the advantage that sections of the central portion can be stabilised in a targeted manner without impairing the structural integrity of the insulating plate. Particularly, the insulating plate comprises several elongate cut-outs that extend along a width direction of the insulating plate and are spaced apart from one another along a length direction of the insulating plate. Alternatively, the insulating plate may comprise several circular cut-outs that are positioned in the insulating plate in a matrix-like manner.

[0036] In some preferred embodiments, a recess is formed in the end plate, wherein the inset is positioned in said recess and held aligned in the recess by the end plate in a plane perpendicular to the stacking direction. This configuration prevents a dislocation of the inset relative to the end plate in said plane. Preferably, the inset is held aligned in the recess by a form-fit connection acting between the end plate and the inset. Most preferably, the form-fit connection is provided by a circumferential wall of the recess.

[0037] In some preferred embodiments, a depression is formed in the end plate, wherein the inset extends over said depression such that the inset is spaced apart from a bottom of the depression along the stacking direction. This configuration has the advantage that a contact area between the inset and the end plate is reduced. Even though the ceramic material has electrically insulating properties, it is desirable to reduce the contact area between the inset and the end plate to further increase the resistance value between the stack of cell units and the end plate. Owing to the high stability of the ceramic material, the inset can reliably stabilise the central portion of the cell units even though the above-mentioned depression is provided in the end plate. The depression may be provided in the end plate in addition to the above-mentioned recess in the end plate or as an alternative to the above-mentioned recess in the end plate. If both the recess and the depression are provided, the depression is preferably provided in a bottom of the recess, i.e. the bottom of the recess comprises the depression.

[0038] In some preferred embodiments, the inset is integrally formed with the end plate. This has the advantage that the position of the inset relative to the end plate is fixed. Particularly, no structures, e.g. a recess or the like, are required in the end plate to hold the inset aligned with the end plate. Furthermore, the assembly of the electrochemical cell assembly is facilitated since the inset and the end plate are securely held together.

[0039] In some preferred embodiments, the inset is provided on the end plate by an additive manufacturing process, e.g. by a 3D printing process. This has the advantage that a desired shape of the inset can be precisely realised. An inset that is provided by an additive manufacturing process can be recognized in that it is composed of a plurality of joint voxels.

[0040] In some preferred embodiments, the inset comprises at least one first surface facing towards the stack of cell units and at least one second surface facing towards the end plate.

[0041] In some preferred embodiments, the inset comprises several first surfaces that are positioned in a common plane and spatially isolated from each other. This has the advantage that the resistance value of the electrical connection between the stack of cell units and the end plate is reduced. Owing to the high stability of the ceramic material, the inset can reliably stabilise the central portions regardless of the provision of the first surfaces that are spatially isolated from each other. In other words, a clearance between the first surfaces does not result in a structural weakening of the inset that might impair the stabilisation of the central portions. In some preferred embodiments, the inset comprises several second surfaces that are positioned in a common plane and spatially isolated from each other.

[0042] In some preferred embodiments, the spatially isolated first surfaces are provided by a respective protrusion of the inset protruding towards the stack of cell units along the stacking direction. In some preferred embodiments, the spatially isolated second surfaces are provided by a respective protrusion of the inset protruding towards the end plate along the stacking direction.

[0043] In some preferred embodiments, seen along the stacking direction, the first surface or first surfaces and the second surface or second surfaces are positioned offset from each other in a plane perpendicular to the stacking direction. In other words, seen along the stacking direction, no first surface overlaps with a second surface. That is to say, if the inset comprises one first surface and one second surface, the first surface and the second surface are offset from each other in a plane perpendicular to the stacking direction. In case that the inset comprises one first surface and several second surfaces, the first surface is offset from each of the second surfaces, i.e. does not overlap with any one of the first surfaces. In case that the inset comprises one second surface and several first surfaces, the second surface is offset from each first surface, i.e. does not overlap with any one of the first surfaces. In case that the inset comprises several first surfaces and several second surfaces, each first surface is offset from each second surface. These configurations effectively increases the resistance value between the stack of cell units and the end plate. This is due to the fact that every path from a first surface of the inset to a second surface of the inset is at an angle to, i.e. oblique to, the stacking direction. In consequence, every path from a first surface of the inset to a second surface of the inset is longer than the thickness of the inset, i.e. the extent of the inset along the stacking direction. Owing to the high stability of the ceramic material, the inset can reliably stabilise the central portions regardless of the above-described configuration (offset first and second surfaces).

[0044] In some preferred embodiments, an electrically conductive power transmission plate is interposed between the insulating plate and the stack of cell units.

[0045] Further embodiments are derivable from the following description and the drawings.

[0046] In the drawings:

[0047] Figure 1 shows a cross-sectional view of an electrochemical cell assembly according to a first embodiment;

[0048] Figure 2 shows a top-view of an insulating plate and a first end plate of the electrochemical cell assembly shown in Figure 1;

[0049] Figure 3 shows a perspective view of an interconnector plate and a support plate of the electrochemical cell assembly shown in Figure 1 ;

[0050] Figure 4 shows a top-view of the interconnector plate shown in Figure 3;

[0051] Figure 5 shows a top-view of an insulating plate and a first end plate according to a second embodiment; Figure 6 shows a top-view of an insulating plate and a first end plate according to a third embodiments;

[0052] Figure 7 shows a cross-sectional view of an insulating plate and a first end plate according to a fourth embodiment;

[0053] Figure 8 shows a cross-sectional view of an insulating plate and a first end plate according to a fifth embodiment; and

[0054] Figure 9 shows a cross-sectional view of an insulating plate and a first end plate according to a sixth embodiment.

[0055] Referring to Figures 1 and 2, there is shown an exemplary configuration of an electrochemical cell assembly 10 that is configured as a solid oxide cell assembly.

[0056] The cell assembly 10 comprises a first end plate assembly 12 having a first end plate 14 and a second end plate assembly 16 having a second end plate 18.

[0057] The cell assembly 10 further comprises a stack 20 having a plurality of cell units 22 that are stacked upon one another along a stacking direction 24. The cell units 22 extend in a respective cell plane that is perpendicular to the stacking direction 24. The cell units 22 are electrically connected in series. In this example, the cell units 22 are configured flat. An electrical connection between adjacent cell units 22 is established by a direct contact between the cell units 22.

[0058] The stack 20 further comprises gaskets 26 that are interposed between adjacent cell units 22. In this example, the gaskets 26 are configured as annular sealing rings having a central opening 28.

[0059] The stack 20 is arranged between the first end plate 14 and the second end plate 18. That is to say, the first end plate 14 and the second end plate 18 are arranged on opposite sides of the stack 20 and the stack 20 is arranged in a receiving volume defined between the first end plate 14 and the second end plate 18. In this example, the first end plate 14 forms a lower end plate or base plate of the cell assembly 10. The second end plate 18 forms an upper end plate of the cell assembly 10.

[0060] Preferably, the stack 20 is held in compression between the first end plate 14 and the second end plate 18. That is to say, the end plates 14 and 18 are biased towards each other and a compressive force is acting on the stack 20 of cell units 22 along the stacking direction 24. This improves the sealing effect of the gaskets 26 and secures the direct contact between adjacent cell units 22.

[0061] The cell assembly 10 further comprises an insulating plate 32 that is interposed between the first end plate 14 and the stack 20 of cell units 22. In this example, the insulating plate 32 is in direct contact with the first end plate 14. The insulating plate 32 is formed from an electrically insulating material. Preferably, the electrically insulating material comprises at least one mica group mineral such as muscovite or phlogopite.

[0062] In this example, an electrically conductive first power transmission plate 34 is interposed between the stack 20 of cell units 22 and the insulating plate 32. The first power transmission plate 34 is in direct contact with the insulating plate 32 and the stack 20 of cell units 22, i.e. the lowermost cell unit 22.

[0063] In this example, an electrically conductive second power transmission plate 36 is interposed between the stack 20 of cell units 22 and the second end plate 18. The second power transmission plate 36 is in direct contact with the stack 20 of cell units 22, i.e. the uppermost cell unit 22.

[0064] In this example, a second insulating plate 38 is interposed between the second power transmission plate 36 and the second end plate 18. The second insulating plate 38 is in direct contact with the second power transmission plate 36.

[0065] Preferably, the insulating plate 32 and the second insulating plate 38 are formed from the same electrically insulating material, e.g. the material comprising at least one mica group mineral.

[0066] In this example, an electrically conductive third power transmission plate 40 is interposed between the second insulating plate 38 and the second end plate 18. The third power transmission plate 40 is in direct contact with the second insulating plate 38.

[0067] In this example, a third insulating plate 42 is interposed between the third power transmission plate 40 and the second end plate 18. The third insulating plate 42 is in direct contact with the third power transmission plate 40 and the second end plate 18. Preferably, the insulating plate 32 and the third insulating plate 42 are formed from the same electrically insulating material, e.g. the material comprising at least one mica group mineral.

[0068] Preferably, the third power transmission plate 40 is electrically connected to the first power transmission plate 34 by means of one or more bus bars (not visible) that span the stack 20 of cell units 22 along the stacking direction 24. In consequence, the third power transmission plate 40, the bus bar or bus bars, the first power transmission plate 34, the stack 20 of cell units 22 and the second power transmission plate 36 are electrically connected in series in this order.

[0069] In the following, the configuration of the cell units 22 will be explained with additional reference to Figures 3 and 4.

[0070] Each cell unit 22 comprises an interconnector plate 46 having a periphery 48 and a central portion 50 surrounded by the periphery 48. Each cell unit 22 further comprises a support plate 44 having a periphery 45 and a central portion 47 surrounded by the periphery 45. The periphery 48 of the interconnector plate 46 of one cell unit 22 is sealingly attached to the periphery 45 of the suport plate 46 of the same cell unit 22, preferably by welding. The peripheries 45 and 48 of the interconnector plate 46 and the support plate 44 together constitute a periphery 52 of the cell unit 22. The central portions 47 and 50 of the interconnector plate 46 and the support plate 44 define a fluid volume therebetween. The central portions 47 and 50 of the interconnector plate 46 and the support plate 44 together constitute a central portion 54 of the cell unit 22.

[0071] The central portion 47 of the support plate 44 carries electrochemically active layers 49 on a side of the central portion 47 that is facing away from the fluid volume. The electrochemically active layers 49 are provided on a porous area of the central portion 47 of the support plate 44 such that a fluid, e.g. a fuel such as hydrogen, can exit the fluid volume through the porous area and reach the electrochemically active layers 49.

[0072] The central portion 50 of the interconnector plates 46 comprises a structured area 56 having a plurality of protrusions 58, e.g. dimples, protruding along the stacking direction 24. The protrusions 58 define a network 60 of fl uidical ly connected fluid channels therebetween. Said network 60 of fluid channels may serve for distributing a fluid, e.g. a fuel, within the fluid volume of the cell unit 22 during use of the cell assembly 10.

[0073] In the stack 22 of cell units 20, the structured area 56 of one cell unit 22 is in direct contact with the electrochemically active layers 49 of an adjacent cell unit 22.

[0074] With reference to Figure 1, the cell assembly 10 comprises at least one fluid inlet manifold 62 and at least one fluid outlet manifold 64 extending along the stacking direction 24. The manifolds 62 and 64 are provided by overlapping through-holes that are formed in the plates constituting the cell assembly 10. The fluid volume of the cell units 22 is fluidically connected to the fluid inlet manifold 62 and the fluid outlet manifold 64. As can be seen in Figure 2, two fluid inlet manifolds 62 and two fluid outlet manifolds 64 are provided in this example.

[0075] The insulating plate 32 comprises two inlet through-holes 66 and two outlet through-holes 68, said inlet through-holes 66 forming a part of the fluid inlet manifolds 62 and said outlet through-holes 68 forming a part of the fluid outlet manifolds 64. In this example, the insulating plate 32 is configured elongate. The inlet through-holes 66 are positioned at opposite longitudinal end portions of the insulating plate 32.

[0076] The inlet through-holes 66 and the outlet through-holes 68 are provided with a respective sealing device 70 or 72. The sealing devices 70 provided in the inlet through-holes 66 define a fluid channel for guiding fluid from the exterior to the stack 20 of cell units 22 and preventing loss of fluid between the first end plate 14 and the stack 20 of cell units 22. The sealing devices 72 provided in the outlet through-holes 68 define a fluid channel for guiding fluid from the stack 20 of cell units 22 to the exterior and preventing loss of fluid between the stack 20 of cell units 22 and the first end plate 14.

[0077] The sealing devices 70 and 72 each comprise a sleeve-shaped member 74 that is formed from a ceramic material. A respective gasket 26 is provided on each end face of the sealing devices 70 and 72.

[0078] During use of the cell assembly 10, a fuel can be provided to the fluid volume of the cell units 22 through the fluid inlet manifolds 62. The fuel may then flow through the fluid volume of the cell units 22, particularly through the network 60 of channels defined between the protrusions 58 of the structured area 56.

[0079] Consumed or partially consumed fuel can be removed from the cell assembly 10 through the fluid outlet manifolds 64.

[0080] With reference to Figures 1 and 2, the insulating plate 32 comprises a cut-out 76 extending through the insulating plate 32 along the stacking direction 24. The cutout 76 is positioned between the inlet through-holes 66 and the outlet through- holes 68. In this example, the cut-out 76 is provided in the insulating plate 32 as a rectangular through-hole.

[0081] An inset 78 is positioned in the cut-out 76. In this example, the inset 78 is in direct contact with the first end plate 14. Exemplarily, the extent of the inset 78 along the stacking direction 24 is equal to the extent of the insulating plate 32, i.e. a surface of the inset 78 facing towards the stack 20 of cell units 22 is flush with a surface of the insulating plate 32 facing towards the stack 20 of cell units 22.

[0082] The inset 78 is formed from a stiff ceramic material. Preferably, the ceramic material comprises alumina or consists of alumina. The sleeve-shaped members 74 of the sealing devices 70 and 72 may be formed from the same ceramic material.

[0083] Seen along the stacking direction 24, the inset 78 and the structured area 56 of the interconnector plates 46 overlap each other at least partially. This is visible in Figure 2 where the outer perimeter of the structured area 56 is indicated by dashed lines. Owing to its configuration and positioning, the inset 78 securely stabilises the direct contact between adjacent cell units 22 over the lifespan of the cell assembly 10, particularly in the structured area 56 of the cell units 22. Particularly, the compressive force acting on the cell units 22 is supplied to the structured area 56 by the inset 78. This may improve the overall performance of the cell assembly 10 over its lifespan.

[0084] In the example shown in Figures 1 and 2, the inset 78 is configured plate-shaped. Seen along the stacking direction 24, an outer perimeter of the inset 78 surrounds an outer perimeter of the structured area 56. In other words, the whole structured area 56 of the interconnector plates 46 overlaps with the inset 78. This configuration of the inset 78 has the advantage that the entire structured area 56 is stabilised by the inset 78.

[0085] With reference to Figures 5 to 9, further embodiments of the cell assembly 10 will be explained. For the sake of simplicity, certain elements of the cell assembly 10 are not shown in Figures 5 to 9, e.g. the stack 20 of cell units 22, the first connector plate 34 and the second end plate 18.

[0086] The embodiment shown in Figure 5 differs from the embodiment shown in Figures 1 and 2 in that the insulating plate 32 comprises several elongate cutouts 76 that extend along a width direction of the insulating plate 32 and are spaced apart from each other along a length direction of the insulating plate 32. Two elongate insets 78 are arranged next to one another in each of the cut-outs 76. This configuration has the advantage that the amount of ceramic material is reduced compared to the embodiment shown in Figures 1 and 2.

[0087] The embodiment shown in Figure 6 differs from the embodiment shown in Figures 1 and 2 in that the insulating plate 32 comprises several circular cut-outs 76 that are arranged in a matrix-like manner. In this example, nine cut-outs 76 are provided. The cut-outs 76 are arranged in three columns 80, each column 80 having three cut-outs 76. A respective sleeve-shaped inset 78 is provided in each cut-out 76. The configuration shown in Figure 6 has the advantage that the amount of ceramic material is further reduced.

[0088] The embodiment shown in Figure 7 differs from the embodiment shown in Figures 1 and 2 in that a recess 82 is formed in the first end plate 14. The inset 78 is positioned in said recess 82 and held aligned in the recess 82 by the first end plate 14 in a plane perpendicular to the stacking direction 24. In this example, the inset 78 is held aligned by a circumferential wall defining the recess 82. The configuration of Figure 7 has the advantage that a lateral dislocation of the inset 78 relative to the first end plate 14 is reliably prevented.

[0089] In the embodiment shown in Figure 7, the inset 78 is configured plate-shaped. However, the recess 82 may also be combined with an inset 78 having a different shape. Further to that, the first end plate 14 may have several recesses 82 formed therein, a respective inset 78 being positioned in each recess 82.

[0090] The embodiment shown in Figure 8 differs from the embodiment shown in Figures 1 and 2 in that a depression 84 is formed in the first end plate 14. The inset 78 extends over the depression 84 such that the inset 78 is spaced apart from a bottom 85 of the depression 84 along the stacking direction 24. The configuration of Figure 8 has the advantage that a contact area between the first end plate 14 and the inset 78 is reduced. This goes along with an increase of the electrical resistance value between the stack 20 of cell units 22 and the first end plate 14.

[0091] In the embodiments shown in Figures 1 , 2, 5, 6, 7 and 8, the inset 78 or each inset 78 comprises a connected first surface 86 facing towards the stack 20 of cell units 22 and a connected second surface 88 facing towards the first end plate 14.

[0092] The embodiment shown in Figure 9 differs from the embodiment shown in Figures 1 and 2 in that the inset 78 comprises several first surfaces 86 that are positioned in a common plane and spatially isolated from each other. The first surfaces 86 are provided by a respective protrusion 90 of the inset 78 extending along the stacking direction 24 towards the stack 20 of cell units 22. This configuration reduces the contact area between the inset 78 and the first power transmission plate 34 and, thus, increases the electrical resistance value between the stack 20 of cell units 22 and the first end plate 14.

[0093] In the embodiment shown in Figure 9, the inset 78 further comprises several second surfaces 88 that are positioned in a common plane and spatially isolated from each other. The second surfaces 88 are provided by a respective protrusion 92 of the inset 78 extending along the stacking direction 24 towards the first end plate 14. This configuration reduces the contact area between the inset 78 and the first end plate 14 and, thus, increases the electrical resistance value between the stack 20 of cell units 22 and the first end plate 14.

[0094] In the embodiment shown in Figure 9, the first surfaces 86 and the second surfaces 88 are positioned offset from each other. Accordingly, the shortest direct connection from one of the first surfaces 86 to one of the second surfaces 88 is larger than the thickness of the inset 78. This leads to a further increase in the electrical resistance value between the stack 20 of cell units 22 and the first end plate 14.

[0095] In the embodiments shown in Figures 1 , 2, 5, 6, 7, 8 and 9, the inset 78 or insets 78 are provided in the insulating plate 32 that is interposed between the first end plate 14 and the stack 20 of cell units 22. Additionally or alternatively, at least one inset may be provided in a cut-out formed in the second insulating plate 38 and / or the third insulating plate 42, i.e. in one of the insulating plates that are interposed between the upper second end plate 18 and the stack 20 of cell units 22.

[0096] In the embodiments shown in Figures 1 , 2, 5, 6, 7, 8 and 9, the inset 78 or insets 78 are configured as elements that are separate from the first end plate 14. Alternatively, the inset 78 or insets 78 may be integrally formed with the first end plate 14, e.g. by means of an additive manufacturing process.

Claims

Claims1. An electrochemical cell assembly (10), preferably solid oxide fuel cell assembly or solid oxide electrolyser cell assembly, comprising an end plate assembly (12) having an end plate (14, 18), a stack (20) of cell units (22), comprising a plurality of cell units (22) that are stacked upon one another along a stacking direction (24), and an insulating plate (32) that is formed from an electrically insulating material, said insulating plate (32) being interposed between the end plate (14, 18) and the stack (20) of cell units (22), wherein: the cell units (22) each comprise a periphery (52) and a central portion (54) surrounded by the periphery (52), at least one cut-out (76) is provided in the insulating plate (32), said cut-out (76) extending through the insulating plate (32) along the stacking direction (24), and at least one inset (78) is positioned in said cut-out (76) such that, seen along the stacking direction (24), the inset (78) and the central portion (54) of the cell units (22) overlap each other at least partially, said inset (78) being formed from a ceramic material.

2. The electrochemical cell assembly (10) according to claim 1 , wherein the extent of the inset (78) along the stacking direction (24) is greater than or equal to the extent of the insulating plate (32) along the stacking direction (24).

3. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the inset (78) is in direct contact with the end plate (14, 18).

4. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the ceramic material comprises alumina or consists of alumina.

5. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the electrically insulating material comprises at least one mica group mineral.

6. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the insulating plate (32) comprises at least one inlet through-hole (66) forming a fluid inlet port for supplying a fluid from the exterior to the stack (20) of cell units (22) and at least one outlet through- hole (68) forming a fluid outlet port for removing a fluid from the stack (20) of cell units (22) to the exterior, and wherein the inlet through-hole (66) and the outlet through-hole (68) are located on opposite sides of the inset (78).

7. The electrochemical cell assembly (10) according to the preceding claim, wherein the insulating plate (32) is elongate, and wherein the inlet through- hole (66) and the outlet through-hole (68) are positioned at opposite longitudinal end portions of the insulating plate (32).

8. The electrochemical cell assembly (10) according to any one of claims 6 and 7, wherein a sealing device (70) is arranged in the inlet through-hole (66), said sealing device (70) defining a fluid channel for guiding fluid from the exterior to the stack (20) of cell units (22) and preventing loss of fluid between the end plate (14) and the stack (20) of cell units (22), and / or wherein a sealing device (70) is arranged in the outlet through-hole (68), said sealing device (70) defining a fluid channel for guiding fluid from the stack (20) of cell units (22) to the exterior and preventing loss of fluid between the stack (20) of cell units (22) and the end plate (14).

9. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the inset (78) is plate-shaped, sleeve-shaped, elongate or cylindrical.

10. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the central portions (54) of the cell units (22) each comprise a structured area (58), and wherein, seen along the stackingdirection (24), the inset (78) and the structured area (58) overlap each other at least partially.

11. The electrochemical cell assembly (10) according to the preceding claim, wherein the inset (78) is plate-shaped, and wherein, seen along the stacking direction (24), an outer perimeter of the inset (78) surrounds an outer perimeter of the structured area (56) of the cell units (22).

12. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein at least two insets (78) are arranged next to one another in the same cut-out (76).

13. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein at least two cut-outs (76) are provided in the insulating plate (32), and wherein at least one inset (78) is arranged in each of said cut-outs (76).

14. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein a recess (82) is formed in the end plate (14, 18), and wherein the inset (78) is positioned in said recess (82) and held aligned in the recess (82) by the end plate (14, 18) in a plane perpendicular to the stacking direction (24).

15. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein a depression (84) is formed in the end plate (14, 18), and wherein the inset (78) extends over said depression (84) such that the inset (78) is spaced apart from a bottom (85) of the depression (84) along the stacking direction (24).

16. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the inset (78) is integrally formed with the end plate (14, 18).

17. The electrochemical cell assembly (10) according to the preceding claim, wherein the inset (78) is provided on the end plate (14, 18) by an additive manufacturing process.

18. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the inset (78) comprises at least one first surface(86) facing towards the stack (20) of cell units (22) and at least one second surface (88) facing towards the end plate (14, 18).

19. The electrochemical cell assembly (10) according to the preceding claim, wherein the inset (78) comprises several first surfaces (86) that are positioned in a common plane and spatially isolated from each other, and / or wherein the inset (78) comprises several second surfaces (88) that are positioned in a common plane and spatially isolated from each other.

20. The electrochemical cell assembly (10) according to the preceding claim, wherein the spatially isolated first surfaces (86) are provided by a respective protrusion (90) of the inset (78) protruding towards the stack (20) of cell units (22) along the stacking direction (24), and / or wherein the spatially isolated second surfaces (88) are provided by a respective protrusion (92) of the inset (78) protruding towards the end plate (14, 18) along the stacking direction (24).

21. The electrochemical cell assembly (10) according to any one of claims 18 to 20, wherein, seen along the stacking direction (24), the first surface (86) or first surfaces (86) and the second surface (88) or second surfaces (88) are positioned offset from each other.

22. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein an electrically conductive power transmission plate (34) is interposed between the insulating plate (32) and the stack (20) of cell units (22).

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