Electrochemical cell assembly with surface-reduced gaskets

Abstract

The invention relates to an electrochemical cell assembly (10) comprising first and second end plates (14) and a stack of cell units (22) being arranged between said first and second end plates, wherein at least one fluid channel (78) is provided for supplying fluid to the cell units, wherein a plurality of gaskets (26, 28) is provided around said fluid channel, said plurality of gaskets (26, 28) comprising first gaskets (26) interposed between the cell units and one or more second gaskets (28), each second gasket being interposed between one of the end plates and the stack, wherein at least one of the one or more second gaskets is a surface-reduced gasket (80), said surface-reduced gasket being characterized in that a total surface area of its sealing surfaces is smaller than a total surface area of the sealing surfaces of a first gasket (26).

Description

[0001] Title: Electrochemical cell assembly with surface- reduced gaskets

[0002] Specification

[0003] The invention relates to the field of electrochemical cell stacks, in particular, fuel cell stacks and electrolyser cell stacks. More specifically, the invention relates to an electrochemical cell assembly.

[0004] 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 fuel (e.g. H20) into its constituent parts (e.g. H2and 02) . 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 fuel into its constituent parts using electricity (electrolyser cells ) .

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

[0006] Typically, multiple of such cell units are stacked upon one another to form a " stack" of cell units , also referred to as ' cell repeat units ' . Said stack is commonly arranged between two end plates provided on opposite sides of the stack, thus forming an electrochemical cell assembly . The end plates typically serve as access points for supplying the cell stack with fluid, particular fuel . For this , at least one of the end plates may comprise at least one through-hole formed therein to form a fluid port for supplying fluid from the outside of the electrochemical cell assembly to the stack of cell units .

[0007] In electrochemical cell assemblies , sealing gaskets are interposed between the end plates and the stack of cell units and typically also between the individual cell units to achieve a fluid-tight , in particular gas-tight , seal of the cell stack .

[0008] It is an obj ect of the present invention to improve sealing in an electrochemical cell assembly .

[0009] According to the invention there is provided an electrochemical cell assembly according to claim 1 . The electrochemical cell assembly comprises a first end plate assembly having a first end plate , a second end plate assembly having a second end plate , and a stack of cell units . The stack of cell units comprises a plurality of cell units stacked upon one another along a stacking direction . The stack of cell units is arranged, preferably held in compression, between the first end plate and the second end plate . The first and second end plates are preferably provided on opposite sides of the stack such that , when seen in the stacking direction, one of the end plates is located in front of the stack of cell units and the other one of the end plates is located behind the stack of cell units .

[0010] At least one fluid channel ( or internal fluid mani fold / chimney) is provided in said electrochemical cell assembly for supplying fluid to the cell units . Said fluid channel extends through the stack of cell units along the stacking direction, preferably from the first end plate to the second end plate . A plurality of gaskets is provided around said fluid channel to prevent loss of fluid . Preferably, each gasket , or group of gaskets , delimits a section of the fluid channel .

[0011] Said plurality of gaskets comprises first gaskets and one or more second gaskets . Said first gaskets are gaskets that are interposed between the cell units . Preferably, said first gaskets are configured to prevent loss of fluid between two neighbouring cell units . Preferably, at least one first gasket is located between two adj acent cell units . Preferably, the first gaskets are configured identically . Each of the one or more second gaskets is interposed between one of the end plates and the stack of cell units . That is to say, a second gasket is a gasket that is arranged between the first end plate and the stack of cell units or a gasket that is arranged between the second end plate and the stack of cell units . Preferably, said second gasket or gaskets are configured to prevent loss of fluid between the respective end plate and the stack of cell units .

[0012] Said first and second gaskets each have sealing surfaces that radially extend in a plane perpendicular to the stacking direction . Thus , the sealing surfaces face along the stacking direction . Preferably, said first and second gaskets each have a first and an opposite second sealing surface , said first and second sealing surfaces each extending in a plane perpendicular to the stacking direction .

[0013] According to the invention, at least one of the one or more second gaskets is a surface-reduced gasket , said surface- reduced gasket being characteri zed ( and thus distinguished from the first gaskets ) in that a total surface area of its sealing surfaces is smaller than a total surface area of the sealing surfaces of a respective first gasket .

[0014] The proposed configuration allows for improved sealing in the electrochemical cell assembly . More speci fically, reducing the surface area of the sealing surfaces increases a sealing stress at the surface-reduced gasket when the stack is compressed ( e . g . by displacing the first and the second end plate towards each other along the stacking direction) . Providing such a surface-reduced gasket between the end plate and the stack of cell units makes it possible to selectively enhance sealing performance at the interface between the end plate and the stack. This proves advantageous, for example, with regards to possible end plate deformation during use of the electrochemical cell assembly. In addition, by enhancing the sealing stress of one or more of the gaskets arranged between the end plates and the stack (second gaskets) over the gaskets arranged between the individual cell units (first gaskets) allows to compensate for different contact geometries. For example, the cell units may comprise local protrusions at the part contacting the gasket, leading to a different contact geometry (in particular smaller contact area) compared to the flat end plate (see below) .

[0015] Preferably, the difference in total surface area of the sealing surfaces of a first gasket and the sealing surfaces of a surface-reduced gasket is minimum 5%, preferably minimum 10%. More preferably, the difference in total surface area of the sealing surfaces of a first gasket and the sealing surfaces of a surface-reduced gasket is minimum 5% and maximum 40%, preferably minimum 10% and maximum 40%, preferably minimum 15% and maximum 40%, preferably minimum 20% and maximum 40%. This range has proven advantageous with regards to enhanced sealing stress and thus improved sealing performance.

[0016] The first gaskets and / or the second gaskets may be sealing rings, i.e. ring-shaped. The first gaskets and / or the second gaskets may be annular rings . Preferably, the first and the second gaskets are sealing rings . The sealing rings may each have an outer diameter and an inner diameter . The inner diameter may be a diameter of a central opening of the sealing ring . The central opening of a gasket preferably forms a section of the fluid channel .

[0017] In some embodiments , a surface-reduced gasket is characteri zed in that its outer diameter is smaller than the outer diameter of a respective first gasket . In some embodiments , the inner diameter of a surface-reduced gasket and the inner diameter of a first gasket are the same . As set out above , the gaskets preferably delimit the fluid channel . Thus , providing gaskets with the same inner diameter allows for a constant diameter of the fluid channel , which has a favourable ef fect on the fluid flow .

[0018] Preferably, the outer diameter of a surface-reduced gasket is smaller than the outer diameter of a respective first gasket , wherein the inner diameter of a surface-reduced gasket and the inner diameter of a respective first gasket are the same . This results in a reduced total surface area of the sealing surfaces .

[0019] The gaskets may be formed from an exfoliated vermiculite material . The exfoliated vermiculite material may comprise exfoliated vermiculite or consist of exfoliated vermiculite . Vermiculite is a layered silicate with the chemical sum formula (K, Mg, Fe ) ( Si , Al ) 4O10 (OH)2• The exfoliated vermiculite material may be thermally or chemically exfoliated . The exfoliated vermiculate material may comprise a diluent filler, an elastomer and / or steatite . Examples for an exfoliated vermiculite material comprising a diluent filler and an elastomer are the materials Thermiculite 815 , Thermiculite 835 and Thermiculite 715 ( registered trademarks of the Flexitallic group ) . An example for an exfoliated vermiculite material comprising steatite is the material Thermiculite 866 ( registered trademark of the Flexitallic group ) .

[0020] In some embodiments , the one or more second gaskets comprise one gasket that is located, preferably directly, adj acent to an end plate , preferably contacting the end plate . Preferably, said gasket is a surface-reduced gasket . This allows the sealing performance to be enhanced at the end plate , thus reducing the risk of fuel leakage between the end plate and the stack of cell units .

[0021] In some embodiments , the electrochemical cell assembly comprises at least one sealing device located between the first end plate and the stack of cell units and / or at least one sealing device located between the second end plate and the stack of cell units . Preferably, said sealing device defines a section of the fluid channel . In particular, the sealing device may be configured to guide fluid, particularly fuel , from the end plate , preferably from a through-hole formed in the end plate ( see below) , to the stack of cell units . That is to say, the sealing device may provide a fluid guiding function . Furthermore , the sealing device preferably is configured to prevent loss of fluid between the end plate and the stack of cell units . Thus , the sealing device may provide a sealing function .

[0022] Preferably, the sealing device at least comprises a sleeve , preferably spacer sleeve , and at least one gasket . The sealing device may comprise at least one bottom gasket provided on a bottom face of the sleeve , said bottom face facing the end plate . Alternatively or in addition, the sealing device may comprise at least one top gasket , said at least one top gasket being provided on a top face of the sleeve , said top face facing the stack of cell units . Preferably, said at least one bottom gasket and / or said at least one top gasket is a surface-reduced gasket . The design of the sealing device comprising a sleeve and at least one surface-reduced gasket allows to enhance sealing performance between the end plate and the stack of cell units . In addition, such a sealing device allows to enhance load applied via the sealing device over load trans ferred to other regions of the stack, thus ensuring fluid-tight sealing, while avoiding damage to other parts of the cell unit ( e . g . to electrochemically active layers of the cell units ) .

[0023] Preferably, the sleeve is a disk having a central ( axial ) opening or through-hole .

[0024] Preferably, the sleeve is formed from a ceramic material .

[0025] More preferably, the sleeve is formed from aluminium oxide ( alumina ) . Ceramic materials have the advantage of high mechanical sti f fness and superior creep stability, thus improving long-time sealing function .

[0026] Preferably, the bottom gasket or one of the bottom gaskets of the sealing device is in contact with the end plate . Preferably, said bottom gasket that is in contact with the end plate is a surface-reduced gasket . This allows to enhance sealing performance at the end plate . In particular, it allows to compensate for possible deformations of the end plate , thus ensuring a fluid-tight seal .

[0027] In some embodiments , the first end plate and / or the second end plate each have at least one through-hole formed therein . Said through-hole preferably forms a fluid port for transporting fluid between the outside of the electrochemical cell assembly and the stack of cell units . Transporting fluid between the outside of the electrochemical cell assembly and the stack of cell units may mean supplying fluid from the outside of the electrochemical cell assembly to the stack of cell units or may mean removing fluid from the stack of cell units to the outside of the electrochemical cell assembly . Preferably, the through-hole extends through the end plate concerned in the stacking direction .

[0028] Preferably, the first end plate and the second end plate each comprise more than one , preferably four, through- holes . Preferably, each through-hole in the first end plate is assigned a corresponding through-hole in the second end plate. Preferably, said associated through-holes are aligned with each other along the stacking direction. In an alternative embodiment, the first end plate or the second end plate is devoid of a through-hole. That is, only the second end plate or the first end plate comprises at least one through-hole formed therein.

[0029] Preferably, said at least one through-hole (that is each of said one or more through-holes) is associated with a sealing device described above. This, however, does not exclude that the first end plate and / or the second end plate comprise additional through-holes fulfilling different functions (e.g. for mounting) . The sealing device preferably is located at a position locally corresponding to said through-hole. The sealing device preferably is configured to guide fluid, particularly fuel, from the associated through-hole in the end plate to the stack of cell units.

[0030] In some embodiments, the electrochemical cell assembly further comprises a current collector plate (e.g. monopole plate) . Preferably, said current collector plate is located between the first end plate and the stack of cell units.

[0031] In some embodiments, the one or more second gaskets comprise a gasket that is located directly adjacent to said current collector plate on the side of the current collector plate that is facing the end plate, said gasket being a surface-reduced gasket. This allows to enhance sealing performance at the current collector plate. In embodiments with sealing device , the top gasket or one of the top gaskets of the sealing device may be in contact with the current collector plate , said top gasket (which is in contact with the current collector plate ) being a surface-reduced gasket .

[0032] In some embodiments , the first end plate assembly and / or the second end plate assembly may further comprise an insulation plate located between the end plate and the stack of cell units . The insulation plate is configured to electrically insulate end plate and the stack of cell units . The insulation plate may be formed from an electrically insulating material . The insulation plate may be formed from mica . The insulation plate may be formed from alumina .

[0033] In embodiments having a sealing device and an insulation plate , the sealing device may be received in a through-hole formed in the insulation plate . Thus , compression forces introduced into the sealing device by the end plate are trans ferred directly to the stack of cell units , preferably without trans ferring load to the insulation plate . Thus , a load path via the sealing inserts may be decoupled from a load path via the insulation plate , which allows for applying location-dependent compression forces .

[0034] In some embodiments , the cell units each comprise a fluid port , preferably in the form of a through-hole , said fluid port forming a section of the fluid channel . Preferably, said fluid port is in fluid communication with the active layers of the cell units allowing for fluid entering and exiting the cell units (e.g. via respective fluid channels) . Preferably, in the stack, the column of fluid ports of the stacked cell units and the gaskets (and the optional sealing device) together form the fluid channel or a section of the fluid channel.

[0035] In some embodiments, each cell unit has a plurality of protrusions (shaped port features) formed around its fluid port (e.g. by pressing) . Preferably, said protrusions extend along the stacking direction. Preferably, said protrusions are spaced from each other. Preferably, each first gasket contacts the protrusions of a neighbouring cell unit with a sealing surface. The protrusions may be dimples. The protrusions may be formed by pressing. Suitable configurations of such protrusions are described e.g. in applicant's earlier WO 2020 / 126486A1 (see projections 30 as shown e.g. in Fig. 5, 17 and 36 and as described e.g. on page 17, lines 18-24 and page 19, lines 12-21) , which is hereby incorporated by reference.

[0036] In embodiments having such protrusions, it is preferable, if the (second) gasket abutting the end plate (e.g. a bottom gasket of the sealing device) is a surface-reduced gasket. This allows to compensate for the different contact geometries arising when contacting the protrusions compared to when contacting the flat end plate. The concept of surface-reduced gaskets described above is applicable to various types of cell units. Preferably, the cell units are solid oxide cell units, more preferably solid oxide fuel cell units (SOFC) or solid oxide electrolyser cell units (SOEC) . Most preferably, the cell units are metal-supported solid oxide fuel cell units.

[0037] The cell units each may comprise multiple layers, including a mechanical support plate, electrochemically active layers, and, optionally, a spacer or interconnector plate. The electrochemically active layers may comprise a fuel electrode layer, an electrolyte layer and an air or oxidant electrode layer. The electrochemically active layers may be deposited (e.g. as thin coatings or films) on and supported by the mechanical support plate, e.g. by a metal support plate, such as a metal foil.

[0038] Further embodiments are derivable from the following description and the drawings.

[0039] In the drawings :

[0040] Fig. 1 shows a perspective view of an embodiment of an electrochemical cell assembly;

[0041] Fig. 2 shows a perspective section of the electrochemical cell assembly according to Fig. 1;

[0042] Fig. 3 shows a cross-sectional view of the electrochemical cell assembly according to Fig. 1; Fig . 4 shows a cross-sectional view of a detail of the electrochemical cell assembly; and

[0043] Fig . 5A shows a schematic top view of an example of a gasket and Fig 5B shows a cross-sectional view of the gasket according to Fig . 5A.

[0044] Repeat use of reference symbols in the present speci fication and drawings is intended to represent the same or analogous features or elements .

[0045] Figure 1 schematically shows an exemplary embodiment of an electrochemical cell assembly 10 . The electrochemical cell assembly 10 comprises a first end plate assembly 12 having a first end plate 14 , a second end plate assembly 16 having a second end plate 18 , and a stack 20 of cell units 22 (herein referred to as ' cell repeat units ' ) . Figures 1 to 3 are intended to primarily provide an overview of the electrochemical cell assembly 10 and its components in general by way of example . The invention, however, is not limited to this speci fic design .

[0046] As shown in Figure 1 , the stack 20 is arranged between the first end plate assembly 12 and the second end plate assembly 16 . In the assembled state , the stack 20 is preferably held in a compressed state between the first end plate assembly 12 and the second end plate assembly 16 . For this , the electrochemical cell assembly 10 may comprise additional compression means known in the art (not shown) , such as tension rods, compression springs or bolts.

[0047] Referring to Fig. 2, the stack 20 comprises a plurality of cell repeat units 22, said cell repeat units 22 being stacked upon each other along a stacking direction 24. As set out above, the cell repeat units 22 may be fuel cell units, electrolyser cell units or reversible cell units comprising electrochemically active layers (not shown) . In the example, the cell repeat units 22 are metal-supported solid oxide fuel cells or solid oxide electrolyser cells (SOFC or SOEC) .

[0048] As can be seen from Fig. 3, the electrochemical cell assembly 10 further comprises first gaskets 26 that are interposed between the cell repeat units 22 and second gaskets 28 that are interposed between the respective end plate 14, 18 and the stack 20 of cell repeat units 22 (further details below) .

[0049] Exemplarily, the gaskets 26, 28 are annular sealing rings each having a central opening 30 (see Fig. 5A) . Thus, the gaskets 26, 28 are defined by an inner diameter 32 (= diameter of the central opening 30) and an outer diameter 34 (see Fig. 5A) . As shown in Fig. 5B, each gasket 26, 28 has a first sealing surface 36 (first end face) and an opposite second sealing surface 38 (second end face) , see Fig. 5B . The gaskets 26 , 28 may be formed from an exfoliated vermiculite material .

[0050] In the following, the structure of the end plate assemblies 12 , 16 is described by way of example using the first end plate assembly 12 . Unless stated otherwise , the second end plate assembly 16 is configured identically .

[0051] As set out above , the first end plate assembly 12 comprises the first end plate 14 ( see Fig . 2 ) . The first end plate 14 has at least one through-hole 40 formed therein, in the example four through-holes 40 ( see also Fig . 2 for the second end plate 18 ) . The through-holes 40 extend along the stacking direction 24 and form respective fluid ports 42 for transporting fluid between the outside of the electrochemical cell assembly 10 and the stack 20 of cell repeat units 22 ( further details see below) .

[0052] In the example shown, each through-hole 40 formed in the first end plate 14 is associated with a respective sealing device 44 ( in Fig . 3 only schematically shown) . Preferably, all sealing devices 44 are configured identically .

[0053] As shown in Fig . 4 for one of the sealing devices 44 , each sealing device 44 comprises a sleeve 46 . The sleeve 46 is preferably disk-shaped having a central opening 48 ( see Fig . 4 ) . The sleeve 46 comprises a bottom face 50 and a top face 52 opposite the bottom face 50 . In the assembled electrochemical cell assembly 10 , the bottom face 50 is facing the end plate 14 with the associated through-hole 40 formed therein . The top face 52 is facing the stack 20 of cell repeat units 22 .

[0054] Preferably, the sleeve 46 is formed from a ceramic material , e . g . from alumina .

[0055] In the embodiment shown, each sealing device 44 further comprises a bottom gasket 54 ( second gasket 28 ) provided at the bottom face 50 of the sleeve 46 and a top gasket 56 ( second gasket 28 ) provided at the top face 52 of the sleeve 46 . The bottom gasket 54 abuts the end plate 14 with its second sealing surface 38 and abuts the sleeve 46 with its first sealing surface 36 .

[0056] In the example shown in Fig . 4 , the first end plate assembly 12 further comprises an optional current collector plate 58 (not shown in Figures 1 to 3 ) . The second end plate assembly 16 may not comprise such a current collector plate 58 . The current collector plate 58 is located between the sealing device 44 and the stack 20 of cell repeat units 22 (more speci fically, between the top gasket 56 and the lowest gasket of the stack 20 ) . The current collector plate 58 comprises a through-hole 60 formed therein, said through-hole 60 being arranged coaxially to the central openings 30 of the gaskets 28 , 26 and the central opening 48 of the sleeve 46 .

[0057] In the example of Figures 1 to 3 , the first end plate assembly 12 further comprises an optional insulation plate 62 (not shown in Fig . 4 ) . In the electrochemical cell assembly 10, the insulation plate 62 is located between the first end plate 14 and the stack 20 of cell repeat units 22 (see e.g. Fig. 2a) . Accordingly, an insulation plate 62 of the second end plate assembly 16 is located between the second end plate 18 and the stack 20 of cell repeat units 22 (see Fig. 3) . Preferably, the insulation plate 62 is formed from an electrically insulating material, e.g. from mica or alumina.

[0058] Exemplarily, the insulation plate 62 comprises at least one through-hole 64 formed therein, in this example four through-holes 64 (see Figs. 2 and 3) . The through-holes 64 are arranged at positions locally corresponding to the positions of the through-holes 40 in the first end plate 14 (see Fig. 3) . Preferably, the through-holes 64 in the insulation plate 62 are arranged coaxially to the through- holes 40 in the first end plate 14. In the specific example, each sealing device 44 is arranged in a respective through-hole 64 of the optional insulation plate 62.

[0059] Referring to Fig. 4, it can be seen that in the example each cell repeat unit 22 exemplarily comprises an interconnector plate 66 and a support plate 68 (only schematically shown) , which are stacked upon one another along the stacking direction 24. The support plate 68 typically carries the electrochemically active layers (not shown) . The interconnector plate 66 and the support plate 68 enclose a fluid volume 70 therebetween (see Fig. 4) . Preferably, the interconnector plate 66 and the support plate 68 are attached to each other, e.g. by welding. In order to supply fluid, e.g. fuel, to the fluid volume 70 (and thus to the electrochemically active layers) or to remove fluid from the fluid volume 70, each of the cell repeat units 22 has at least one, in the specific example four, through-holes 72 formed therein, said through-holes 72 being in fluid communication with the active layers of the cell unit 22 via the fluid volume 70. Thus, the through-holes 72 form fluid ports 74 of the respective cell repeat unit 22.

[0060] As can be seen from Fig. 4, in the example, each cell repeat unit 22 has a plurality of optional protrusions 76 (shaped port features) formed around its fluid port 74 (through-hole 72) . In the example, the protrusions 76 are provided by the interconnector plate 66. For example, the protrusions 76 may be formed by pressing the interconnector plate 66. As set out above, the protrusions 76 may, for example, take the form of dimples extending along the stacking direction 24.

[0061] In the stack 20, each of the first gaskets 26 that is located between two adjacent cell repeat units 22 contacts the protrusions 76 of one of the two cell repeat units 22 with its first sealing surface 36 and the support plate 68 of the respective other cell repeat unit 22 with its second sealing surface 38 (see Fig. 4) . Preferably, the first gaskets 26 are arranged coaxially to the through-holes 72 (fluid ports 74) in the cell repeat units 22. As shown in Figures 3 and 4, an aligned column of the central openings 30 of the gaskets 28, 26, the central opening 48 of the sleeve 46, the through-hole 60 of the current collector plate 58 and the through-holes 72 (fluid ports 74) of the cell repeat units 22 form a fluid channel 78 or chimney extending throughout the electrochemical cell assembly 10 along the stacking direction 24. This fluid channel 78 is in fluid communication with, preferably coaxially to, an assigned through-hole 40 in the first end plate 14 and a corresponding through-hole 40 in the second end plate 18 (see Fig. 3) .

[0062] Referring to Fig. 4, it can be seen that in the example the bottom gasket 54 (second gasket 28) has the same inner diameter 32 as the other gaskets (i.e. the top gasket 56 and the first gaskets 26) , but has a smaller outer diameter 34 than the other gaskets (i.e. the top gasket 56 and the first gaskets 26) . Thus, a total surface area of the sealing surfaces 36, 38 of the bottom gaskets 54 is smaller than the total surface area of the respective sealing surfaces 36, 38 of the other gaskets 26, 56. As such, the bottom gasket 54 forms a surface-reduced gasket 80. Preferably, the surface area of the first sealing surface 36 of the surface-reduced gasket 80 (bottom gasket 54) equals a contact area of a respective first gasket 26 with the protrusions 76.

[0063] In embodiments not shown, alternatively or in addition, the top gasket 56 may be a surface-reduced gasket 80.

Claims

Claims1. An electrochemical cell assembly (10) comprising a first end plate assembly (12) having a first end plate ( 14 ) , a second end plate assembly (16) having a second end plate (18) , and a stack (20) of cell units (22) , comprising a plurality of cell units (22) stacked upon one another along a stacking direction (24) , said stack (20) of cell units (22) being arranged between said first end plate (14) and said second end plate (18) , wherein at least one fluid channel (78) is provided in said electrochemical cell assembly (10) for supplying fluid to the cell units (22) , said fluid channel (78) extending through the stack (20) of cell units (22) along the stacking direction (24) , wherein a plurality of gaskets (26, 28) is provided around said fluid channel (78) to prevent loss of fluid, said plurality of gaskets (26, 28) comprising first gaskets (26) interposed between the cell units (22) and one or more second gaskets (28) , each second gasket (28) being interposed between one of the end plates (14, 18) and the stack (20) of cell units ( 22 ) , said first and second gaskets (26, 28) each having sealing surfaces (36, 38) extending in a planeperpendicular to the stacking direction (24) , wherein at least one of the one or more second gaskets (28) is a surface-reduced gasket (80) , said surface-reduced gasket (80) being characterized in that a total surface area of its sealing surfaces (36, 38) is smaller than a total surface area of the sealing surfaces (36, 38) of a first gasket (26) .

2. The electrochemical cell assembly (10) according to claim 1, wherein the difference in total surface area of the sealing surfaces (36, 38) of a first gasket (26) and the sealing surfaces (36, 38) of a surface- reduced gasket (80) is minimum 5%, preferably minimum 5% and maximum 40%.

3. The electrochemical cell assembly (10) according to claim 1 or 2, wherein the first and second gaskets (26, 28) are sealing rings.

4. The electrochemical cell assembly (10) according to the preceding claim, said sealing rings each having an outer diameter (34) and an inner diameter (32) , wherein the outer diameter (34) of a surface-reduced gasket (80) is smaller than the outer diameter (34) of a first gasket (26) .

5. The electrochemical cell assembly (10) according to the preceding claim, wherein the inner diameter (32) of a surface-reduced gasket (80) and the inner diameter (32) of a first gasket (26) are the same.

6. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the one or more second gaskets comprise one gasket that is located adjacent to the respective end plate, preferably contacting the respective end plate, said gasket being a surface-reduced gasket.

7. The electrochemical cell assembly (10) according to any one of the preceding claims, further comprising a sealing device (44) located between the first end plate (14) and the stack (20) of cell units (22) , said sealing device (44) defining a section of the fluid channel (78) and comprising a sleeve (46) , at least one bottom gasket (54) provided on a bottom face (50) of the sleeve (46) , said bottom face (50) facing the end plate (14) , and / or at least one top gasket (56) provided on a top face (52) of the sleeve (46) , said top face (52) facing the stack (20) of cell units (22) , wherein said at least one bottom gasket (54) and / or said at least one top gasket (56) is a surface-reduced gasket (80) .

8. The electrochemical cell assembly (10) according to the preceding claim, wherein the bottom gasket (54) or one of the bottom gaskets (54) is in contact with the end plate (14) , said bottom gasket (54) being a surface-reduced gasket (80) .

9. The electrochemical cell assembly (10) according to any of claims 7 or 8, wherein the first end plate (14) has a through-hole (40) formed therein, said through- hole (40) being in fluid communication with the fluid channel (78) , wherein the sealing device (44) is located at a position locally corresponding to said through-hole (40) .

10. The electrochemical cell assembly (10) according to any one of the preceding claims, further comprising a current collector plate (58) , said current collector plate (58) being located between the first end plate (14) and the stack (20) of cell units (22) , wherein the one or more second gaskets (28) comprise a gasket (56) that is located directly adjacent to said current collector plate (58) on the side of the current collector plate (58) that is facing the end plate (14) , said gasket being a surface-reduced gasket (80) .

11. The electrochemical cell assembly (10) according to any of claims 7 to 9, further comprising a current collector plate (58) , said current collector plate (58) being located between the sealing device (44) and the stack (20) of cell units (22) , wherein the top gasket (56) or one of the top gaskets (56) of the sealing device (44) is in contact with the current collector plate (58) , said top gasket being a surface- reduced gasket (80) .

12. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the cellunits (22) each comprise a fluid port (74) , preferably in the form of a through-hole (72) , said fluid port (74) forming a section of the fluid channel (78) , wherein each cell unit (22) has a plurality of protrusions (76) formed around its fluid port (74) , said protrusions (76) extending along the stacking direction (24) and preferably being spaced from each other, wherein each first gasket (26) contacts the protrusions (76) of a neighbouring cell unit (22) .

13. The electrochemical cell assembly (10) according to the preceding claim, wherein the protrusions (76) are dimples .

14. The electrochemical cell assembly (10) according to any one of the preceding claims, wherein the cell units (22) are solid oxide cell units, preferably solid oxide fuel cell units (SOFC) or solid oxide electrolyser cell units (SOEC) .

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